Simulation of Auger electron emission from nanometer-size gold targets using the Geant4 Monte Carlo simulation toolkit

NASA Astrophysics Data System (ADS)

Incerti, S.; Suerfu, B.; Xu, J.; Ivantchenko, V.; Mantero, A.; Brown, J. M. C.; Bernal, M. A.; Francis, Z.; Karamitros, M.; Tran, H. N.

2016-04-01

A revised atomic deexcitation framework for the Geant4 general purpose Monte Carlo toolkit capable of simulating full Auger deexcitation cascades was implemented in June 2015 release (version 10.2 Beta). An overview of this refined framework and testing of its capabilities is presented for the irradiation of gold nanoparticles (NP) with keV photon and MeV proton beams. The resultant energy spectra of secondary particles created within and that escape the NP are analyzed and discussed. It is anticipated that this new functionality will improve and increase the use of Geant4 in the medical physics, radiobiology, nanomedicine research and other low energy physics fields.

Simulation and experimental verification of prompt gamma-ray emissions during proton irradiation.

PubMed

Schumann, A; Petzoldt, J; Dendooven, P; Enghardt, W; Golnik, C; Hueso-González, F; Kormoll, T; Pausch, G; Roemer, K; Fiedler, F

2015-05-21

Irradiation with protons and light ions offers new possibilities for tumor therapy but has a strong need for novel imaging modalities for treatment verification. The development of new detector systems, which can provide an in vivo range assessment or dosimetry, requires an accurate knowledge of the secondary radiation field and reliable Monte Carlo simulations. This paper presents multiple measurements to characterize the prompt γ-ray emissions during proton irradiation and benchmarks the latest Geant4 code against the experimental findings. Within the scope of this work, the total photon yield for different target materials, the energy spectra as well as the γ-ray depth profile were assessed. Experiments were performed at the superconducting AGOR cyclotron at KVI-CART, University of Groningen. Properties of the γ-ray emissions were experimentally determined. The prompt γ-ray emissions were measured utilizing a conventional HPGe detector system (Clover) and quantitatively compared to simulations. With the selected physics list QGSP_BIC_HP, Geant4 strongly overestimates the photon yield in most cases, sometimes up to 50%. The shape of the spectrum and qualitative occurrence of discrete γ lines is reproduced accurately. A sliced phantom was designed to determine the depth profile of the photons. The position of the distal fall-off in the simulations agrees with the measurements, albeit the peak height is also overestimated. Hence, Geant4 simulations of prompt γ-ray emissions from irradiation with protons are currently far less reliable as compared to simulations of the electromagnetic processes. Deviations from experimental findings were observed and quantified. Although there has been a constant improvement of Geant4 in the hadronic sector, there is still a gap to close.

Low-energy electron dose-point kernel simulations using new physics models implemented in Geant4-DNA

NASA Astrophysics Data System (ADS)

Bordes, Julien; Incerti, Sébastien; Lampe, Nathanael; Bardiès, Manuel; Bordage, Marie-Claude

2017-05-01

When low-energy electrons, such as Auger electrons, interact with liquid water, they induce highly localized ionizing energy depositions over ranges comparable to cell diameters. Monte Carlo track structure (MCTS) codes are suitable tools for performing dosimetry at this level. One of the main MCTS codes, Geant4-DNA, is equipped with only two sets of cross section models for low-energy electron interactions in liquid water (;option 2; and its improved version, ;option 4;). To provide Geant4-DNA users with new alternative physics models, a set of cross sections, extracted from CPA100 MCTS code, have been added to Geant4-DNA. This new version is hereafter referred to as ;Geant4-DNA-CPA100;. In this study, ;Geant4-DNA-CPA100; was used to calculate low-energy electron dose-point kernels (DPKs) between 1 keV and 200 keV. Such kernels represent the radial energy deposited by an isotropic point source, a parameter that is useful for dosimetry calculations in nuclear medicine. In order to assess the influence of different physics models on DPK calculations, DPKs were calculated using the existing Geant4-DNA models (;option 2; and ;option 4;), newly integrated CPA100 models, and the PENELOPE Monte Carlo code used in step-by-step mode for monoenergetic electrons. Additionally, a comparison was performed of two sets of DPKs that were simulated with ;Geant4-DNA-CPA100; - the first set using Geant4‧s default settings, and the second using CPA100‧s original code default settings. A maximum difference of 9.4% was found between the Geant4-DNA-CPA100 and PENELOPE DPKs. Between the two Geant4-DNA existing models, slight differences, between 1 keV and 10 keV were observed. It was highlighted that the DPKs simulated with the two Geant4-DNA's existing models were always broader than those generated with ;Geant4-DNA-CPA100;. The discrepancies observed between the DPKs generated using Geant4-DNA's existing models and ;Geant4-DNA-CPA100; were caused solely by their different cross sections. The different scoring and interpolation methods used in CPA100 and Geant4 to calculate DPKs showed differences close to 3.0% near the source.

Simulation of Auger electron emission from nanometer-size gold targets using the Geant4 Monte Carlo simulation toolkit

DOE PAGES

Incerti, S.; Suerfu, B.; Xu, J.; ...

2016-02-16

We report that a revised atomic deexcitation framework for the Geant4 general purpose Monte Carlo toolkit capable of simulating full Auger deexcitation cascades was implemented in June 2015 release (version 10.2 Beta). An overview of this refined framework and testing of its capabilities is presented for the irradiation of gold nanoparticles (NP) with keV photon and MeV proton beams. The resultant energy spectra of secondary particles created within and that escape the NP are analyzed and discussed. It is anticipated that this new functionality will improve and increase the use of Geant4 in the medical physics, radiobiology, nanomedicine research andmore » other low energy physics fields.« less

Signal pulse emulation for scintillation detectors using Geant4 Monte Carlo with light tracking simulation.

PubMed

Ogawara, R; Ishikawa, M

2016-07-01

The anode pulse of a photomultiplier tube (PMT) coupled with a scintillator is used for pulse shape discrimination (PSD) analysis. We have developed a novel emulation technique for the PMT anode pulse based on optical photon transport and a PMT response function. The photon transport was calculated using Geant4 Monte Carlo code and the response function with a BC408 organic scintillator. The obtained percentage RMS value of the difference between the measured and simulated pulse with suitable scintillation properties using GSO:Ce (0.4, 1.0, 1.5 mol%), LaBr3:Ce and BGO scintillators were 2.41%, 2.58%, 2.16%, 2.01%, and 3.32%, respectively. The proposed technique demonstrates high reproducibility of the measured pulse and can be applied to simulation studies of various radiation measurements.

Integration of g4tools in Geant4

NASA Astrophysics Data System (ADS)

Hřivnáčová, Ivana

2014-06-01

g4tools, that is originally part of the inlib and exlib packages, provides a very light and easy to install set of C++ classes that can be used to perform analysis in a Geant4 batch program. It allows to create and manipulate histograms and ntuples, and write them in supported file formats (ROOT, AIDA XML, CSV and HBOOK). It is integrated in Geant4 through analysis manager classes, thus providing a uniform interface to the g4tools objects and also hiding the differences between the classes for different supported output formats. Moreover, additional features, such as for example histogram activation or support for Geant4 units, are implemented in the analysis classes following users requests. A set of Geant4 user interface commands allows the user to create histograms and set their properties interactively or in Geant4 macros. g4tools was first introduced in the Geant4 9.5 release where its use was demonstrated in one basic example, and it is already used in a majority of the Geant4 examples within the Geant4 9.6 release. In this paper, we will give an overview and the present status of the integration of g4tools in Geant4 and report on upcoming new features.

SU-G-TeP3-04: Evaluation of the Dose Enhancement with Gold Nanoparticle in Microdosimetry Level Using the Geant4-DNA Toolkit

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, C; Chow, J

Purpose: This study investigated the dose enhancement effect of using gold nanoparticles (GNP) as radiation sensitizers radiated by different photon beam energies. Microdosimetry of photon-irradiated GNP was determined by the Geant4-DNA process in the DNA scale. Methods: Monte Carlo simulation was conducted using the Geant4 toolkit (ver. 10.2). A GNP with different sizes (30, 50, and 100nm diameter sphere) and a DNA were placed in a water cube (1µm{sup 3}). The GNP was irradiated by photon beams with different energies (50, 100, and 150keV) and produced secondary electrons to increase the dose to the DNA. Energy depositions were calculated formore » both with and without GNP and to investigate the dose enhancement effect at the DNA. The distance between the GNP and DNA was varied to optimize the best GNP position to the DNA. The photon beam source was set to 200nm from the GNP in each simulation. Results: It is found that GNP had a dose enhancement effect on kV photon radiations. For Monte Carlo results on different GNP sizes, distances between the GNP and DNA, and photon beam energies, enhancement ratio was found increasing as GNP size increased. The distance between the GNP and DNA affected the result that as distance increased while the dose enhancement ratio decreased. However, the effect of changing distance was not as significant as varying the GNP size. In addition, increasing the photon beam energy also increased the dose enhancement ratio. The largest dose enhancement ratio was found to be 3.5, when the GNP (100nm diameter) irradiated by the 150keV photon beam was set to 80nm from the DNA. Conclusion: Dose enhancement was determined in the DNA with GNP in the microdosimetry scale. It is concluded that the dose enhancement varied with the photon beam energy, GNP size and distance between the GNP and DNA.« less

Geant4 simulations of a wide-angle x-ray focusing telescope

NASA Astrophysics Data System (ADS)

Zhao, Donghua; Zhang, Chen; Yuan, Weimin; Zhang, Shuangnan; Willingale, Richard; Ling, Zhixing

2017-06-01

The rapid development of X-ray astronomy has been made possible by widely deploying X-ray focusing telescopes on board many X-ray satellites. Geant4 is a very powerful toolkit for Monte Carlo simulations and has remarkable abilities to model complex geometrical configurations. However, the library of physical processes available in Geant4 lacks a description of the reflection of X-ray photons at a grazing incident angle which is the core physical process in the simulation of X-ray focusing telescopes. The scattering of low-energy charged particles from the mirror surfaces is another noteworthy process which is not yet incorporated into Geant4. Here we describe a Monte Carlo model of a simplified wide-angle X-ray focusing telescope adopting lobster-eye optics and a silicon detector using the Geant4 toolkit. With this model, we simulate the X-ray tracing, proton scattering and background detection. We find that: (1) the effective area obtained using Geant4 is in agreement with that obtained using Q software with an average difference of less than 3%; (2) X-rays are the dominant background source below 10 keV; (3) the sensitivity of the telescope is better by at least one order of magnitude than that of a coded mask telescope with the same physical dimensions; (4) the number of protons passing through the optics and reaching the detector by Firsov scattering is about 2.5 times that of multiple scattering for the lobster-eye telescope.

Comparison of GEANT4 very low energy cross section models with experimental data in water.

PubMed

Incerti, S; Ivanchenko, A; Karamitros, M; Mantero, A; Moretto, P; Tran, H N; Mascialino, B; Champion, C; Ivanchenko, V N; Bernal, M A; Francis, Z; Villagrasa, C; Baldacchin, G; Guèye, P; Capra, R; Nieminen, P; Zacharatou, C

2010-09-01

The GEANT4 general-purpose Monte Carlo simulation toolkit is able to simulate physical interaction processes of electrons, hydrogen and helium atoms with charge states (H0, H+) and (He0, He+, He2+), respectively, in liquid water, the main component of biological systems, down to the electron volt regime and the submicrometer scale, providing GEANT4 users with the so-called "GEANT4-DNA" physics models suitable for microdosimetry simulation applications. The corresponding software has been recently re-engineered in order to provide GEANT4 users with a coherent and unique approach to the simulation of electromagnetic interactions within the GEANT4 toolkit framework (since GEANT4 version 9.3 beta). This work presents a quantitative comparison of these physics models with a collection of experimental data in water collected from the literature. An evaluation of the closeness between the total and differential cross section models available in the GEANT4 toolkit for microdosimetry and experimental reference data is performed using a dedicated statistical toolkit that includes the Kolmogorov-Smirnov statistical test. The authors used experimental data acquired in water vapor as direct measurements in the liquid phase are not yet available in the literature. Comparisons with several recommendations are also presented. The authors have assessed the compatibility of experimental data with GEANT4 microdosimetry models by means of quantitative methods. The results show that microdosimetric measurements in liquid water are necessary to assess quantitatively the validity of the software implementation for the liquid water phase. Nevertheless, a comparison with existing experimental data in water vapor provides a qualitative appreciation of the plausibility of the simulation models. The existing reference data themselves should undergo a critical interpretation and selection, as some of the series exhibit significant deviations from each other. The GEANT4-DNA physics models available in the GEANT4 toolkit have been compared in this article to available experimental data in the water vapor phase as well as to several published recommendations on the mass stopping power. These models represent a first step in the extension of the GEANT4 Monte Carlo toolkit to the simulation of biological effects of ionizing radiation.

A Software Toolkit to Study Systematic Uncertainties of the Physics Models of the Geant4 Simulation Package

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genser, Krzysztof; Hatcher, Robert; Perdue, Gabriel

2016-11-10

The Geant4 toolkit is used to model interactions between particles and matter. Geant4 employs a set of validated physics models that span a wide range of interaction energies. These models are tuned to cover a large variety of possible applications. This raises the critical question of what uncertainties are associated with the Geant4 physics model, or group of models, involved in a simulation project. To address the challenge, we have designed and implemented a comprehen- sive, modular, user-friendly software toolkit that allows the variation of one or more parameters of one or more Geant4 physics models involved in simulation studies.more » It also enables analysis of multiple variants of the resulting physics observables of interest in order to estimate the uncertain- ties associated with the simulation model choices. Key functionalities of the toolkit are presented in this paper and are illustrated with selected results.« less

Signal pulse emulation for scintillation detectors using Geant4 Monte Carlo with light tracking simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ogawara, R.; Ishikawa, M., E-mail: masayori@med.hokudai.ac.jp

The anode pulse of a photomultiplier tube (PMT) coupled with a scintillator is used for pulse shape discrimination (PSD) analysis. We have developed a novel emulation technique for the PMT anode pulse based on optical photon transport and a PMT response function. The photon transport was calculated using Geant4 Monte Carlo code and the response function with a BC408 organic scintillator. The obtained percentage RMS value of the difference between the measured and simulated pulse with suitable scintillation properties using GSO:Ce (0.4, 1.0, 1.5 mol%), LaBr{sub 3}:Ce and BGO scintillators were 2.41%, 2.58%, 2.16%, 2.01%, and 3.32%, respectively. The proposedmore » technique demonstrates high reproducibility of the measured pulse and can be applied to simulation studies of various radiation measurements.« less

An implementation of discrete electron transport models for gold in the Geant4 simulation toolkit

NASA Astrophysics Data System (ADS)

Sakata, D.; Incerti, S.; Bordage, M. C.; Lampe, N.; Okada, S.; Emfietzoglou, D.; Kyriakou, I.; Murakami, K.; Sasaki, T.; Tran, H.; Guatelli, S.; Ivantchenko, V. N.

2016-12-01

Gold nanoparticle (GNP) boosted radiation therapy can enhance the biological effectiveness of radiation treatments by increasing the quantity of direct and indirect radiation-induced cellular damage. As the physical effects of GNP boosted radiotherapy occur across energy scales that descend down to 10 eV, Monte Carlo simulations require discrete physics models down to these very low energies in order to avoid underestimating the absorbed dose and secondary particle generation. Discrete physics models for electron transportation down to 10 eV have been implemented within the Geant4-DNA low energy extension of Geant4. Such models allow the investigation of GNP effects at the nanoscale. At low energies, the new models have better agreement with experimental data on the backscattering coefficient, and they show similar performance for transmission coefficient data as the Livermore and Penelope models already implemented in Geant4. These new models are applicable in simulations focussed towards estimating the relative biological effectiveness of radiation in GNP boosted radiotherapy applications with photon and electron radiation sources.

SU-E-T-22: A Deterministic Solver of the Boltzmann-Fokker-Planck Equation for Dose Calculation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, X; Gao, H; Paganetti, H

2015-06-15

Purpose: The Boltzmann-Fokker-Planck equation (BFPE) accurately models the migration of photons/charged particles in tissues. While the Monte Carlo (MC) method is popular for solving BFPE in a statistical manner, we aim to develop a deterministic BFPE solver based on various state-of-art numerical acceleration techniques for rapid and accurate dose calculation. Methods: Our BFPE solver is based on the structured grid that is maximally parallelizable, with the discretization in energy, angle and space, and its cross section coefficients are derived or directly imported from the Geant4 database. The physical processes that are taken into account are Compton scattering, photoelectric effect, pairmore » production for photons, and elastic scattering, ionization and bremsstrahlung for charged particles.While the spatial discretization is based on the diamond scheme, the angular discretization synergizes finite element method (FEM) and spherical harmonics (SH). Thus, SH is used to globally expand the scattering kernel and FFM is used to locally discretize the angular sphere. As a Result, this hybrid method (FEM-SH) is both accurate in dealing with forward-peaking scattering via FEM, and efficient for multi-energy-group computation via SH. In addition, FEM-SH enables the analytical integration in energy variable of delta scattering kernel for elastic scattering with reduced truncation error from the numerical integration based on the classic SH-based multi-energy-group method. Results: The accuracy of the proposed BFPE solver was benchmarked against Geant4 for photon dose calculation. In particular, FEM-SH had improved accuracy compared to FEM, while both were within 2% of the results obtained with Geant4. Conclusion: A deterministic solver of the Boltzmann-Fokker-Planck equation is developed for dose calculation, and benchmarked against Geant4. Xiang Hong and Hao Gao were partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000) and the Shanghai Pujiang Talent Program (#14PJ1404500)« less

Comparison of GATE/GEANT4 with EGSnrc and MCNP for electron dose calculations at energies between 15 keV and 20 MeV.

PubMed

Maigne, L; Perrot, Y; Schaart, D R; Donnarieix, D; Breton, V

2011-02-07

The GATE Monte Carlo simulation platform based on the GEANT4 toolkit has come into widespread use for simulating positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging devices. Here, we explore its use for calculating electron dose distributions in water. Mono-energetic electron dose point kernels and pencil beam kernels in water are calculated for different energies between 15 keV and 20 MeV by means of GATE 6.0, which makes use of the GEANT4 version 9.2 Standard Electromagnetic Physics Package. The results are compared to the well-validated codes EGSnrc and MCNP4C. It is shown that recent improvements made to the GEANT4/GATE software result in significantly better agreement with the other codes. We furthermore illustrate several issues of general interest to GATE and GEANT4 users who wish to perform accurate simulations involving electrons. Provided that the electron step size is sufficiently restricted, GATE 6.0 and EGSnrc dose point kernels are shown to agree to within less than 3% of the maximum dose between 50 keV and 4 MeV, while pencil beam kernels are found to agree to within less than 4% of the maximum dose between 15 keV and 20 MeV.

Microdosimetry calculations for monoenergetic electrons using Geant4-DNA combined with a weighted track sampling algorithm.

PubMed

Famulari, Gabriel; Pater, Piotr; Enger, Shirin A

2017-07-07

The aim of this study was to calculate microdosimetric distributions for low energy electrons simulated using the Monte Carlo track structure code Geant4-DNA. Tracks for monoenergetic electrons with kinetic energies ranging from 100 eV to 1 MeV were simulated in an infinite spherical water phantom using the Geant4-DNA extension included in Geant4 toolkit version 10.2 (patch 02). The microdosimetric distributions were obtained through random sampling of transfer points and overlaying scoring volumes within the associated volume of the tracks. Relative frequency distributions of energy deposition f(>E)/f(>0) and dose mean lineal energy ([Formula: see text]) values were calculated in nanometer-sized spherical and cylindrical targets. The effects of scoring volume and scoring techniques were examined. The results were compared with published data generated using MOCA8B and KURBUC. Geant4-DNA produces a lower frequency of higher energy deposits than MOCA8B. The [Formula: see text] values calculated with Geant4-DNA are smaller than those calculated using MOCA8B and KURBUC. The differences are mainly due to the lower ionization and excitation cross sections of Geant4-DNA for low energy electrons. To a lesser extent, discrepancies can also be attributed to the implementation in this study of a new and fast scoring technique that differs from that used in previous studies. For the same mean chord length ([Formula: see text]), the [Formula: see text] calculated in cylindrical volumes are larger than those calculated in spherical volumes. The discrepancies due to cross sections and scoring geometries increase with decreasing scoring site dimensions. A new set of [Formula: see text] values has been presented for monoenergetic electrons using a fast track sampling algorithm and the most recent physics models implemented in Geant4-DNA. This dataset can be combined with primary electron spectra to predict the radiation quality of photon and electron beams.

Allowing for crystalline structure effects in Geant4

DOE PAGES

Bagli, Enrico; Asai, Makoto; Dotti, Andrea; ...

2017-03-24

In recent years, the Geant4 toolkit for the Monte Carlo simulation of radiation with matter has seen large growth in its divers user community. A fundamental aspect of a successful physics experiment is the availability of a reliable and precise simulation code. Geant4 currently does not allow for the simulation of particle interactions with anything other than amorphous matter. To overcome this limitation, the GECO (GEant4 Crystal Objects) project developed a general framework for managing solid-state structures in the Geant4 kernel and validate it against experimental data. As a result, accounting for detailed geometrical structures allows, for example, simulation ofmore » diffraction from crystal planes or the channeling of charged particle.« less

Geant4-DNA example applications for track structure simulations in liquid water: a report from the Geant4-DNA Project.

PubMed

Incerti, S; Kyriakou, I; Bernal, M A; Bordage, M C; Francis, Z; Guatelli, S; Ivanchenko, V; Karamitros, M; Lampe, N; Lee, S B; Meylan, S; Min, C H; Shin, W G; Nieminen, P; Sakata, D; Tang, N; Villagrasa, C; Tran, H; Brown, J M C

2018-06-14

This Special Report presents a description of Geant4-DNA user applications dedicated to the simulation of track structures (TS) in liquid water and associated physical quantities (e.g. range, stopping power, mean free path…). These example applications are included in the Geant4 Monte Carlo toolkit and are available in open access. Each application is described and comparisons to recent international recommendations are shown (e.g. ICRU, MIRD), when available. The influence of physics models available in Geant4-DNA for the simulation of electron interactions in liquid water is discussed. Thanks to these applications, the authors show that the most recent sets of physics models available in Geant4-DNA (the so-called "option4″ and "option 6″ sets) enable more accurate simulation of stopping powers, dose point kernels and W-values in liquid water, than the default set of models ("option 2″) initially provided in Geant4-DNA. They also serve as reference applications for Geant4-DNA users interested in TS simulations. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Three-dimensional Image Reconstruction in J-PET Using Filtered Back-projection Method

NASA Astrophysics Data System (ADS)

Shopa, R. Y.; Klimaszewski, K.; Kowalski, P.; Krzemień, W.; Raczyński, L.; Wiślicki, W.; Białas, P.; Curceanu, C.; Czerwiński, E.; Dulski, K.; Gajos, A.; Głowacz, B.; Gorgol, M.; Hiesmayr, B.; Jasińska, B.; Kisielewska-Kamińska, D.; Korcyl, G.; Kozik, T.; Krawczyk, N.; Kubicz, E.; Mohammed, M.; Pawlik-Niedźwiecka, M.; Niedźwiecki, S.; Pałka, M.; Rudy, Z.; Sharma, N. G.; Sharma, S.; Silarski, M.; Skurzok, M.; Wieczorek, A.; Zgardzińska, B.; Zieliński, M.; Moskal, P.

We present a method and preliminary results of the image reconstruction in the Jagiellonian PET tomograph. Using GATE (Geant4 Application for Tomographic Emission), interactions of the 511 keV photons with a cylindrical detector were generated. Pairs of such photons, flying back-to-back, originate from e+e- annihilations inside a 1-mm spherical source. Spatial and temporal coordinates of hits were smeared using experimental resolutions of the detector. We incorporated the algorithm of the 3D Filtered Back Projection, implemented in the STIR and TomoPy software packages, which differ in approximation methods. Consistent results for the Point Spread Functions of ~5/7,mm and ~9/20, mm were obtained, using STIR, for transverse and longitudinal directions, respectively, with no time of flight information included.

A Software Toolkit to Study Systematic Uncertainties of the Physics Models of the Geant4 Simulation Package

DOE Office of Scientific and Technical Information (OSTI.GOV)

Genser, Krzysztof; Hatcher, Robert; Kelsey, Michael

The Geant4 simulation toolkit is used to model interactions between particles and matter. Geant4 employs a set of validated physics models that span a wide range of interaction energies. These models rely on measured cross-sections and phenomenological models with the physically motivated parameters that are tuned to cover many application domains. To study what uncertainties are associated with the Geant4 physics models we have designed and implemented a comprehensive, modular, user-friendly software toolkit that allows the variation of one or more parameters of one or more Geant4 physics models involved in simulation studies. It also enables analysis of multiple variantsmore » of the resulting physics observables of interest in order to estimate the uncertainties associated with the simulation model choices. Based on modern event-processing infrastructure software, the toolkit offers a variety of attractive features, e.g. exible run-time con gurable work ow, comprehensive bookkeeping, easy to expand collection of analytical components. Design, implementation technology, and key functionalities of the toolkit are presented in this paper and illustrated with selected results.« less

A Geant4-based Simulation to Evaluate the Feasibility of Using Nuclear Resonance Fluorescence (NRF) in Determining Atomic Compositions of Body Tissue in Cancer Diagnostics and Irradiation

NASA Astrophysics Data System (ADS)

Gilbo, Yekaterina; Wijesooriya, Krishni; Liyanage, Nilanga

2017-01-01

Customarily applied in homeland security for identifying concealed explosives and chemical weapons, NRF (Nuclear Resonance Fluorescence) may have high potential in determining atomic compositions of body tissue. High energy photons incident on a target excite the target nuclei causing characteristic re-emission of resonance photons. As the nuclei of each isotope have well-defined excitation energies, NRF uniquely indicates the isotopic content of the target. NRF radiation corresponding to nuclear isotopes present in the human body is emitted during radiotherapy based on Bremsstrahlung photons generated in a linear electron accelerator. We have developed a Geant4 simulation in order to help assess NRF capabilities in detecting, mapping, and characterizing tumors. We have imported a digital phantom into the simulation using anatomical data linked to known chemical compositions of various tissues. Work is ongoing to implement the University of Virginia's cancer center treatment setup and patient geometry, and to collect and analyze the simulation's physics quantities to evaluate the potential of NRF for medical imaging applications. Preliminary results will be presented.

Implementation of new physics models for low energy electrons in liquid water in Geant4-DNA.

PubMed

Bordage, M C; Bordes, J; Edel, S; Terrissol, M; Franceries, X; Bardiès, M; Lampe, N; Incerti, S

2016-12-01

A new alternative set of elastic and inelastic cross sections has been added to the very low energy extension of the Geant4 Monte Carlo simulation toolkit, Geant4-DNA, for the simulation of electron interactions in liquid water. These cross sections have been obtained from the CPA100 Monte Carlo track structure code, which has been a reference in the microdosimetry community for many years. They are compared to the default Geant4-DNA cross sections and show better agreement with published data. In order to verify the correct implementation of the CPA100 cross section models in Geant4-DNA, simulations of the number of interactions and ranges were performed using Geant4-DNA with this new set of models, and the results were compared with corresponding results from the original CPA100 code. Good agreement is observed between the implementations, with relative differences lower than 1% regardless of the incident electron energy. Useful quantities related to the deposited energy at the scale of the cell or the organ of interest for internal dosimetry, like dose point kernels, are also calculated using these new physics models. They are compared with results obtained using the well-known Penelope Monte Carlo code. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Track structure modeling in liquid water: A review of the Geant4-DNA very low energy extension of the Geant4 Monte Carlo simulation toolkit.

PubMed

Bernal, M A; Bordage, M C; Brown, J M C; Davídková, M; Delage, E; El Bitar, Z; Enger, S A; Francis, Z; Guatelli, S; Ivanchenko, V N; Karamitros, M; Kyriakou, I; Maigne, L; Meylan, S; Murakami, K; Okada, S; Payno, H; Perrot, Y; Petrovic, I; Pham, Q T; Ristic-Fira, A; Sasaki, T; Štěpán, V; Tran, H N; Villagrasa, C; Incerti, S

2015-12-01

Understanding the fundamental mechanisms involved in the induction of biological damage by ionizing radiation remains a major challenge of today's radiobiology research. The Monte Carlo simulation of physical, physicochemical and chemical processes involved may provide a powerful tool for the simulation of early damage induction. The Geant4-DNA extension of the general purpose Monte Carlo Geant4 simulation toolkit aims to provide the scientific community with an open source access platform for the mechanistic simulation of such early damage. This paper presents the most recent review of the Geant4-DNA extension, as available to Geant4 users since June 2015 (release 10.2 Beta). In particular, the review includes the description of new physical models for the description of electron elastic and inelastic interactions in liquid water, as well as new examples dedicated to the simulation of physicochemical and chemical stages of water radiolysis. Several implementations of geometrical models of biological targets are presented as well, and the list of Geant4-DNA examples is described. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, J; Park, S; Jeong, J

Purpose: In particle therapy and radiobiology, the investigation of mechanisms leading to the death of target cancer cells induced by ionising radiation is an active field of research. Recently, several studies based on Monte Carlo simulation codes have been initiated in order to simulate physical interactions of ionising particles at cellular scale and in DNA. Geant4-DNA is the one of them; it is an extension of the general purpose Geant4 Monte Carlo simulation toolkit for the simulation of physical interactions at sub-micrometre scale. In this study, we present Geant4-DNA Monte Carlo simulations for the prediction of DNA strand breakage usingmore » a geometrical modelling of DNA structure. Methods: For the simulation of DNA strand breakage, we developed a specific DNA geometrical structure. This structure consists of DNA components, such as the deoxynucleotide pairs, the DNA double helix, the nucleosomes and the chromatin fibre. Each component is made of water because the cross sections models currently available in Geant4-DNA for protons apply to liquid water only. Also, at the macroscopic-scale, protons were generated with various energies available for proton therapy at the National Cancer Center, obtained using validated proton beam simulations developed in previous studies. These multi-scale simulations were combined for the validation of Geant4-DNA in radiobiology. Results: In the double helix structure, the deposited energy in a strand allowed to determine direct DNA damage from physical interaction. In other words, the amount of dose and frequency of damage in microscopic geometries was related to direct radiobiological effect. Conclusion: In this report, we calculated the frequency of DNA strand breakage using Geant4- DNA physics processes for liquid water. This study is now on-going in order to develop geometries which use realistic DNA material, instead of liquid water. This will be tested as soon as cross sections for DNA material become available in Geant4-DNA.« less

Analysis on the emission and potential application of Cherenkov radiation in boron neutron capture therapy: A Monte Carlo simulation study.

PubMed

Shu, Di-Yun; Geng, Chang-Ran; Tang, Xiao-Bin; Gong, Chun-Hui; Shao, Wen-Cheng; Ai, Yao

2018-07-01

This paper was aimed to explore the physics of Cherenkov radiation and its potential application in boron neutron capture therapy (BNCT). The Monte Carlo toolkit Geant4 was used to simulate the interaction between the epithermal neutron beam and the phantom containing boron-10. Results showed that Cherenkov photons can only be generated from secondary charged particles of gamma rays in BNCT, in which the 2.223 MeV prompt gamma rays are the main contributor. The number of Cherenkov photons per unit mass generated in the measurement region decreases linearly with the increase of boron concentration in both water and tissue phantom. The work presented the fundamental basis for applications of Cherenkov radiation in BNCT. Copyright © 2018 Elsevier Ltd. All rights reserved.

Application of TDCR-Geant4 modeling to standardization of 63Ni.

PubMed

Thiam, C; Bobin, C; Chauvenet, B; Bouchard, J

2012-09-01

As an alternative to the classical TDCR model applied to liquid scintillation (LS) counting, a stochastic approach based on the Geant4 toolkit is presented for the simulation of light emission inside the dedicated three-photomultiplier detection system. To this end, the Geant4 modeling includes a comprehensive description of optical properties associated with each material constituting the optical chamber. The objective is to simulate the propagation of optical photons from their creation in the LS cocktail to the production of photoelectrons in the photomultipliers. First validated for the case of radionuclide standardization based on Cerenkov emission, the scintillation process has been added to a TDCR-Geant4 modeling using the Birks expression in order to account for the light-emission nonlinearity owing to ionization quenching. The scintillation yield of the commercial Ultima Gold LS cocktail has been determined from double-coincidence detection efficiencies obtained for (60)Co and (54)Mn with the 4π(LS)β-γ coincidence method. In this paper, the stochastic TDCR modeling is applied for the case of the standardization of (63)Ni (pure β(-)-emitter; E(max)=66.98 keV) and the activity concentration is compared with the result given by the classical model. Copyright © 2012 Elsevier Ltd. All rights reserved.

SU-E-T-565: RAdiation Resistance of Cancer CElls Using GEANT4 DNA: RACE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perrot, Y; Payno, H; Delage, E

2014-06-01

Purpose: The objective of the RACE project is to develop a comparison between Monte Carlo simulation using the Geant4-DNA toolkit and measurements of radiation damage on 3D melanoma and chondrosarcoma culture cells coupled with gadolinium nanoparticles. We currently expose the status of the developments regarding simulations. Methods: Monte Carlo studies are driven using the Geant4 toolkit and the Geant4-DNA extension. In order to model the geometry of a cell population, the opensource CPOP++ program is being developed for the geometrical representation of 3D cell populations including a specific cell mesh coupled with a multi-agent system. Each cell includes cytoplasm andmore » nucleus. The correct modeling of the cell population has been validated with confocal microscopy images of spheroids. The Geant4 Livermore physics models are used to simulate the interactions of a 250 keV X-ray beam and the production of secondaries from gadolinium nanoparticles supposed to be fixed on the cell membranes. Geant4-DNA processes are used to simulate the interactions of charged particles with the cells. An atomistic description of the DNA molecule, from PDB (Protein Data Bank) files, is provided by the so-called PDB4DNA Geant4 user application we developed to score energy depositions in DNA base pairs and sugar-phosphate groups. Results: At the microscopic level, our simulations enable assessing microscopic energy distribution in each cell compartment of a realistic 3D cell population. Dose enhancement factors due to the presence of gadolinium nanoparticles can be estimated. At the nanometer scale, direct damages on nuclear DNA are also estimated. Conclusion: We successfully simulated the impact of direct radiations on a realistic 3D cell population model compatible with microdosimetry calculations using the Geant4-DNA toolkit. Upcoming validation and the future integration of the radiochemistry module of Geant4-DNA will propose to correlate clusters of ionizations with in vitro experiments. All those developments will be released publicly. This work was supported by grants from Plan Cancer 2009-2013 French national initiative managed by INSERM (Institut National de la Sante et de la Recherche Medicale)« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lau, A; Chen, Y; Ahmad, S

Purpose: Proton therapy exhibits several advantages over photon therapy due to depth-dose distributions from proton interactions within the target material. However, uncertainties associated with protons beam range in the patient limit the advantage of proton therapy applications. To quantify beam range, positron-emitting nuclei (PEN) and prompt gamma (PG) techniques have been developed. These techniques use de-excitation photons to describe the location of the beam in the patient. To develop a detector system for implementing the PG technique for range verification applications in proton therapy, we studied the yields, energy and angular distributions of the secondary particles emitted from a PMMAmore » phantom. Methods: Proton pencil beams of various energies incident onto a PMMA phantom with dimensions of 5 x 5 x 50 cm3 were used for simulation with the Geant4 toolkit using the standard electromagnetic packages as well as the packages based on the binary-cascade nuclear model. The emitted secondary particles are analyzed . Results: For 160 MeV incident protons, the yields of secondary neutrons and photons per 100 incident protons were ~6 and ~15 respectively. Secondary photon energy spectrum showed several energy peaks in the range between 0 and 10 MeV. The energy peaks located between 4 and 6 MeV were attributed to originate from direct proton interactions with 12C (~ 4.4 MeV) and 16O (~ 6 MeV), respectively. Most of the escaping secondary neutrons were found to have energies between 10 and 100 MeV. Isotropic emissions were found for lower energy neutrons (<10 MeV) and photons for all energies, while higher energy neutrons were emitted predominantly in the forward direction. The yields of emitted photons and neutrons increased with the increase of incident proton energies. Conclusions: A detector system is currently being developed incorporating the yields, energy and angular distributions of secondary particles from proton interactions obtained from this study.« less

A Toolkit to Study Sensitivity of the Geant4 Predictions to the Variations of the Physics Model Parameters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fields, Laura; Genser, Krzysztof; Hatcher, Robert

Geant4 is the leading detector simulation toolkit used in high energy physics to design detectors and to optimize calibration and reconstruction software. It employs a set of carefully validated physics models to simulate interactions of particles with matter across a wide range of interaction energies. These models, especially the hadronic ones, rely largely on directly measured cross-sections and phenomenological predictions with physically motivated parameters estimated by theoretical calculation or measurement. Because these models are tuned to cover a very wide range of possible simulation tasks, they may not always be optimized for a given process or a given material. Thismore » raises several critical questions, e.g. how sensitive Geant4 predictions are to the variations of the model parameters, or what uncertainties are associated with a particular tune of a Geant4 physics model, or a group of models, or how to consistently derive guidance for Geant4 model development and improvement from a wide range of available experimental data. We have designed and implemented a comprehensive, modular, user-friendly software toolkit to study and address such questions. It allows one to easily modify parameters of one or several Geant4 physics models involved in the simulation, and to perform collective analysis of multiple variants of the resulting physics observables of interest and comparison against a variety of corresponding experimental data. Based on modern event-processing infrastructure software, the toolkit offers a variety of attractive features, e.g. flexible run-time configurable workflow, comprehensive bookkeeping, easy to expand collection of analytical components. Design, implementation technology, and key functionalities of the toolkit are presented and illustrated with results obtained with Geant4 key hadronic models.« less

The effects of nuclear data library processing on Geant4 and MCNP simulations of the thermal neutron scattering law

NASA Astrophysics Data System (ADS)

Hartling, K.; Ciungu, B.; Li, G.; Bentoumi, G.; Sur, B.

2018-05-01

Monte Carlo codes such as MCNP and Geant4 rely on a combination of physics models and evaluated nuclear data files (ENDF) to simulate the transport of neutrons through various materials and geometries. The grid representation used to represent the final-state scattering energies and angles associated with neutron scattering interactions can significantly affect the predictions of these codes. In particular, the default thermal scattering libraries used by MCNP6.1 and Geant4.10.3 do not accurately reproduce the ENDF/B-VII.1 model in simulations of the double-differential cross section for thermal neutrons interacting with hydrogen nuclei in a thin layer of water. However, agreement between model and simulation can be achieved within the statistical error by re-processing ENDF/B-VII.I thermal scattering libraries with the NJOY code. The structure of the thermal scattering libraries and sampling algorithms in MCNP and Geant4 are also reviewed.

Simulation of orientational coherent effects via Geant4

NASA Astrophysics Data System (ADS)

Bagli, E.; Asai, M.; Brandt, D.; Dotti, A.; Guidi, V.; Verderi, M.; Wright, D.

2017-10-01

Simulation of orientational coherent effects via Geant4 beam manipulation of high-and very-high-energy particle beams is a hot topic in accelerator physics. Coherent effects of ultra-relativistic particles in bent crystals allow the steering of particle trajectories thanks to the strong electrical field generated between atomic planes. Recently, a collimation experiment with bent crystals was carried out at the CERN-LHC, paving the way to the usage of such technology in current and future accelerators. Geant4 is a widely used object-oriented tool-kit for the Monte Carlo simulation of the interaction of particles with matter in high-energy physics. Moreover, its areas of application include also nuclear and accelerator physics, as well as studies in medical and space science. We present the first Geant4 extension for the simulation of orientational effects in straight and bent crystals for high energy charged particles. The model allows the manipulation of particle trajectories by means of straight and bent crystals and the scaling of the cross sections of hadronic and electromagnetic processes for channeled particles. Based on such a model, an extension of the Geant4 toolkit has been developed. The code and the model have been validated by comparison with published experimental data regarding the deflection efficiency via channeling and the variation of the rate of inelastic nuclear interactions.

Studying the response of a plastic scintillator to gamma rays using the Geant4 Monte Carlo code.

PubMed

Ghadiri, Rasoul; Khorsandi, Jamshid

2015-05-01

To determine the gamma ray response function of an NE-102 scintillator and to investigate the gamma spectra due to the transport of optical photons, we simulated an NE-102 scintillator using Geant4 code. The results of the simulation were compared with experimental data. Good consistency between the simulation and data was observed. In addition, the time and spatial distributions, along with the energy distribution and surface treatments of scintillation detectors, were calculated. This simulation makes us capable of optimizing the photomultiplier tube (or photodiodes) position to yield the best coupling to the detector. Copyright © 2015 Elsevier Ltd. All rights reserved.

Comparison of modeled and measured performance of a GSO crystal as gamma detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parno, Diana Syemour; Friend, Megan Lynn; Mamyan, Vahe

2013-11-01

We have modeled, tested, and installed a large, cerium-activated Gd{sub 2}SiO{sub 5} crystal scintillator for use as a detector of gamma rays. We present the measured detector response to two types of incident photons: nearly monochromatic photons up to 40 MeV, and photons from a continuous Compton backscattering spectrum up to 200 MeV. Our GEANT4 simulations, developed to determine the analyzing power of the Compton polarimeter in Hall A of Jefferson Lab, reproduce the measured spectra well.

Abstract ID: 103 GAMOS: Implementation of a graphical user interface for dosimetry calculation in radiotherapy.

PubMed

Abdalaoui Slimani, Faical Alaoui; Bentourkia, M'hamed

2018-01-01

There are several computer programs or combination of programs for radiation tracking and other information in tissues by using Monte Carlo simulation [1]. Among these are GEANT4 [2] programs provided as classes that can be incorporated in C++ codes to achieve different tasks in radiation interactions with matter. GEANT4 made the physics easier but requires often a long learning-curve that implies a good knowledge of C++ and the Geant4 architecture. GAMOS [3], the Geant4-based Architecture for Medicine-Oriented Simulations, facilitates the use of Geant4 by providing a script language that covers almost all the needs of a radiotherapy simulation but it is obviously out of reach of biological researchers. The aim of the present work was to report the design and development of a Graphical User Interface (GUI) for absorbed dose calculation and for particle tracking in humans, small animals and phantoms. The GUI is based on the open source GEANT4 for the physics of particle interactions, on the QT cross-platform application for combining programming commands and for display. The calculation of the absorbed dose can be performed based on 3D CT images in DICOM format, from images of phantoms or from solid volumes that can be made from any pure or composite material to be specified by its molecular formulas. The GUI has several menus relative to the emitting source which can have different shapes, positions, energy as mono- or poly-energy such as X-ray spectra; the types of particles and particle interactions; energy deposition and absorbed dose; and the output results as histograms. In conclusion, the GUI we developed can be easily used by any researcher without the need to be familiar with computer programming, and it will be freely proposed as an open source. Copyright © 2017.

GEANT4 Simulation of Hadronic Interactions at 8-GeV/C to 10-GeV/C: Response to the HARP-CDP Group

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uzhinsky, V.; /Dubna, JINR /CERN; Apostolakis, J.

2011-11-21

The results of the HARP-CDP group on the comparison of GEANT4 Monte Carlo predictions versus experimental data are discussed. It is shown that the problems observed by the group are caused by an incorrect implementation of old features at the programming level, and by a lack of the nucleon Fermi motion in the simulation of quasielastic scattering. These drawbacks are not due to the physical models used. They do not manifest themselves in the most important applications of the GEANT4 toolkit.

Validation of a virtual source model of medical linac for Monte Carlo dose calculation using multi-threaded Geant4

NASA Astrophysics Data System (ADS)

Aboulbanine, Zakaria; El Khayati, Naïma

2018-04-01

The use of phase space in medical linear accelerator Monte Carlo (MC) simulations significantly improves the execution time and leads to results comparable to those obtained from full calculations. The classical representation of phase space stores directly the information of millions of particles, producing bulky files. This paper presents a virtual source model (VSM) based on a reconstruction algorithm, taking as input a compressed file of roughly 800 kb derived from phase space data freely available in the International Atomic Energy Agency (IAEA) database. This VSM includes two main components; primary and scattered particle sources, with a specific reconstruction method developed for each. Energy spectra and other relevant variables were extracted from IAEA phase space and stored in the input description data file for both sources. The VSM was validated for three photon beams: Elekta Precise 6 MV/10 MV and a Varian TrueBeam 6 MV. Extensive calculations in water and comparisons between dose distributions of the VSM and IAEA phase space were performed to estimate the VSM precision. The Geant4 MC toolkit in multi-threaded mode (Geant4-[mt]) was used for fast dose calculations and optimized memory use. Four field configurations were chosen for dose calculation validation to test field size and symmetry effects, , , and for squared fields, and for an asymmetric rectangular field. Good agreement in terms of formalism, for 3%/3 mm and 2%/3 mm criteria, for each evaluated radiation field and photon beam was obtained within a computation time of 60 h on a single WorkStation for a 3 mm voxel matrix. Analyzing the VSM’s precision in high dose gradient regions, using the distance to agreement concept (DTA), showed also satisfactory results. In all investigated cases, the mean DTA was less than 1 mm in build-up and penumbra regions. In regards to calculation efficiency, the event processing speed is six times faster using Geant4-[mt] compared to sequential Geant4, when running the same simulation code for both. The developed VSM for 6 MV/10 MV beams widely used, is a general concept easy to adapt in order to reconstruct comparable beam qualities for various linac configurations, facilitating its integration for MC treatment planning purposes.

Geant4 models for simulation of hadron/ion nuclear interactions at moderate and low energies.

NASA Astrophysics Data System (ADS)

Ivantchenko, Anton; Ivanchenko, Vladimir; Quesada, Jose-Manuel; Wright, Dennis

The Geant4 toolkit is intended for Monte Carlo simulation of particle transport in media. It was initially designed for High Energy Physics purposes such as experiments at the Large Hadron Collider (LHC) at CERN. The toolkit offers a set of models allowing effective simulation of cosmic ray interactions with different materials. For moderate and low energy hadron/ion interactions with nuclei there are a number of competitive models: Binary and Bertini intra-nuclear cascade models, quantum molecular dynamic model (QMD), INCL/ABLA cascade model, and Chiral Invariant Phase Space Decay model (CHIPS). We report the status of these models for the recent version of Geant4 (release 9.3, December 2009). The Bertini cascade in-ternal cross sections were upgraded. The native Geant4 precompound and deexcitation models were used in the Binary cascade and QMD. They were significantly improved including emis-sion of light fragments, the Fermi break-up model, the General Evaporation Model (GEM), the multi-fragmentation model, and the fission model. Comparisons between model predictions and data for thin target experiments for neutron, proton, light ions, and isotope production are presented and discussed. The focus of these validations is concentrated on target materials important for space missions.

Calculation of electron Dose Point Kernel in water with GEANT4 for medical application

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guimaraes, C. C.; Sene, F. F.; Martinelli, J. R.

2009-06-03

The rapid insertion of new technologies in medical physics in the last years, especially in nuclear medicine, has been followed by a great development of faster Monte Carlo algorithms. GEANT4 is a Monte Carlo toolkit that contains the tools to simulate the problems of particle transport through matter. In this work, GEANT4 was used to calculate the dose-point-kernel (DPK) for monoenergetic electrons in water, which is an important reference medium for nuclear medicine. The three different physical models of electromagnetic interactions provided by GEANT4 - Low Energy, Penelope and Standard - were employed. To verify the adequacy of these models,more » the results were compared with references from the literature. For all energies and physical models, the agreement between calculated DPKs and reported values is satisfactory.« less

Electron backscattering simulation in Geant4

NASA Astrophysics Data System (ADS)

Dondero, Paolo; Mantero, Alfonso; Ivanchencko, Vladimir; Lotti, Simone; Mineo, Teresa; Fioretti, Valentina

2018-06-01

The backscattering of electrons is a key phenomenon in several physics applications which range from medical therapy to space including AREMBES, the new ESA simulation framework for radiation background effects. The importance of properly reproducing this complex interaction has grown considerably in the last years and the Geant4 Monte Carlo simulation toolkit, recently upgraded to the version 10.3, is able to comply with the AREMBES requirements in a wide energy range. In this study a validation of the electron Geant4 backscattering models is performed with respect to several experimental data. In addition a selection of the most recent validation results on the electron scattering processes is also presented. Results of our analysis show a good agreement between simulations and data from several experiments, confirming the Geant4 electron backscattering models to be robust and reliable up to a few tens of electronvolts.

Comparison of experimental proton-induced fluorescence spectra for a selection of thin high-Z samples with Geant4 Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Incerti, S.; Barberet, Ph.; Dévès, G.; Michelet, C.; Francis, Z.; Ivantchenko, V.; Mantero, A.; El Bitar, Z.; Bernal, M. A.; Tran, H. N.; Karamitros, M.; Seznec, H.

2015-09-01

The general purpose Geant4 Monte Carlo simulation toolkit is able to simulate radiative and non-radiative atomic de-excitation processes such as fluorescence and Auger electron emission, occurring after interaction of incident ionising radiation with target atomic electrons. In this paper, we evaluate the Geant4 modelling capability for the simulation of fluorescence spectra induced by 1.5 MeV proton irradiation of thin high-Z foils (Fe, GdF3, Pt, Au) with potential interest for nanotechnologies and life sciences. Simulation results are compared to measurements performed at the Centre d'Etudes Nucléaires de Bordeaux-Gradignan AIFIRA nanobeam line irradiation facility in France. Simulation and experimental conditions are described and the influence of Geant4 electromagnetic physics models is discussed.

Investigation of neutron interactions with Ge detectors

NASA Astrophysics Data System (ADS)

Baginova, Miloslava; Vojtyla, Pavol; Povinec, Pavel P.

2018-07-01

Interactions of neutrons with a high-purity germanium detector were studied experimentally and by simulations using the GEANT4 tool. Elastic and inelastic scattering of fast neutrons as well as neutron capture on Ge nuclei were observed. Peaks induced by inelastic scattering of neutrons on 70Ge, 72Ge, 73Ge, 74Ge and 76Ge were well visible in the γ-ray spectra. In addition, peaks due to inelastic scattering of neutrons on copper and lead nuclei, including the well-known peak of 208Pb at 2614.51 keV, were detected. The GEANT4 simulations showed that the simulated spectrum was in a good agreement with the experimental one. Differences between the simulated and the measured spectra were due to the high γ-ray intensity of the used neutron source, physics implemented in GEANT4 and contamination of the neutron source.

Geant4-DNA track-structure simulations for gold nanoparticles: The importance of electron discrete models in nanometer volumes.

PubMed

Sakata, Dousatsu; Kyriakou, Ioanna; Okada, Shogo; Tran, Hoang N; Lampe, Nathanael; Guatelli, Susanna; Bordage, Marie-Claude; Ivanchenko, Vladimir; Murakami, Koichi; Sasaki, Takashi; Emfietzoglou, Dimitris; Incerti, Sebastien

2018-05-01

Gold nanoparticles (GNPs) are known to enhance the absorbed dose in their vicinity following photon-based irradiation. To investigate the therapeutic effectiveness of GNPs, previous Monte Carlo simulation studies have explored GNP dose enhancement using mostly condensed-history models. However, in general, such models are suitable for macroscopic volumes and for electron energies above a few hundred electron volts. We have recently developed, for the Geant4-DNA extension of the Geant4 Monte Carlo simulation toolkit, discrete physics models for electron transport in gold which include the description of the full atomic de-excitation cascade. These models allow event-by-event simulation of electron tracks in gold down to 10 eV. The present work describes how such specialized physics models impact simulation-based studies on GNP-radioenhancement in a context of x-ray radiotherapy. The new discrete physics models are compared to the Geant4 Penelope and Livermore condensed-history models, which are being widely used for simulation-based NP radioenhancement studies. An ad hoc Geant4 simulation application has been developed to calculate the absorbed dose in liquid water around a GNP and its radioenhancement, caused by secondary particles emitted from the GNP itself, when irradiated with a monoenergetic electron beam. The effect of the new physics models is also quantified in the calculation of secondary particle spectra, when originating in the GNP and when exiting from it. The new physics models show similar backscattering coefficients with the existing Geant4 Livermore and Penelope models in large volumes for 100 keV incident electrons. However, in submicron sized volumes, only the discrete models describe the high backscattering that should still be present around GNPs at these length scales. Sizeable differences (mostly above a factor of 2) are also found in the radial distribution of absorbed dose and secondary particles between the new and the existing Geant4 models. The degree to which these differences are due to intrinsic limitations of the condensed-history models or to differences in the underling scattering cross sections requires further investigation. Improved physics models for gold are necessary to better model the impact of GNPs in radiotherapy via Monte Carlo simulations. We implemented discrete electron transport models for gold in Geant4 that is applicable down to 10 eV including the modeling of the full de-excitation cascade. It is demonstrated that the new model has a significant positive impact on particle transport simulations in gold volumes with submicron dimensions compared to the existing Livermore and Penelope condensed-history models of Geant4. © 2018 American Association of Physicists in Medicine.

Improvements in simulation of multiple scattering effects in ATLAS fast simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Basalaev, A. E., E-mail: artem.basalaev@cern.ch

Fast ATLAS Tracking Simulation (Fatras) package was verified on single layer geometry with respect to full simulation with GEANT4. Fatras hadronic interactions and multiple scattering simulation were studied in comparison with GEANT4. Disagreement was found in multiple scattering distributions of primary charged particles (μ, π, e). A new model for multiple scattering simulation was implemented in Fatras. The model was based on R. Frühwirth’s mixture models. New model was tested on single layer geometry and a good agreement with GEANT4 was achieved. Also a comparison of reconstructed tracks’ parameters was performed for Inner Detector geometry, and Fatras with new multiplemore » scattering model proved to have better agreement with GEANT4. New model of multiple scattering was added as a part of Fatras package in the development release of ATLAS software—ATHENA.« less

Addition of luminescence process in Monte Carlo simulation to precisely estimate the light emitted from water during proton and carbon-ion irradiation.

PubMed

Yabe, Takuya; Sasano, Makoto; Hirano, Yoshiyuki; Toshito, Toshiyuki; Akagi, Takashi; Yamashita, Tomohiro; Hayashi, Masateru; Azuma, Tetsushi; Sakamoto, Yusuku; Komori, Masataka; Yamamoto, Seiichi

2018-06-20

Although luminescence of water lower in energy than the Cerenkov-light threshold during proton and carbon-ion irradiation has been found, the phenomenon has not yet been implemented for Monte Carlo simulations. The results provided by the simulations lead to misunderstandings of the physical phenomenon in optical imaging of water during proton and carbon-ion irradiation. To solve the problems, as well as to clarify the light production of the luminescence of water, we modified a Monte Carlo simulation code to include the light production from the luminescence of water and compared them with the experimental results of luminescence imaging of water. We used GEANT4 for the simulation of emitted light from water during proton and carbon-ion irradiation. We used the light production from the luminescence of water using the scintillation process in GEANT4 while those of Cerenkov light from the secondary electrons and prompt gamma photons in water were also included in the simulation. The modified simulation results showed similar depth profiles to those of the measured data for both proton and carbon-ion. When the light production of 0.1 photons/MeV was used for the luminescence of water in the simulation, the simulated depth profiles showed the best match to those of the measured results for both the proton and carbon-ion compared with those used for smaller and larger numbers of photons/MeV. We could successively obtain the simulated depth profiles that were basically the same as the experimental data by using GEANT4 when we assumed the light production by the luminescence of water. Our results confirmed that the inclusion of the luminescence of water in Monte Carlo simulation is indispensable to calculate the precise light distribution in water during irradiation of proton and carbon-ion.

Enhanced photon traps for Hyper-Kamiokande

NASA Astrophysics Data System (ADS)

Rott, Carsten; In, Seongjin; Retière, Fabrice; Gumplinger, Peter

2017-11-01

Hyper-Kamiokande, the next generation large water Cherenkov detector in Japan, is planning to use approximately 80,000 20-inch photomultiplier tubes (PMTs). They are one of the major cost factors of the experiment. We propose a novel enhanced photon trap design based on a smaller and more economical PMT in combination with wavelength shifters, dichroic mirrors, and broadband mirrors. GEANT4 is utilized to obtain photon collection efficiencies and timing resolution of the photon traps. We compare the performance of different trap configurations and sizes. Our simulations indicate an enhanced photon trap with a 12-inch PMT can match a 20-inch PMT's collection efficiency, however at a cost of reduced timing resolution. The photon trap might be suitable as detection module for the outer detector with large photo coverage area.

The impact of new Geant4-DNA cross section models on electron track structure simulations in liquid water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kyriakou, I., E-mail: ikyriak@cc.uoi.gr; Šefl, M.; Department of Dosimetry and Application of Ionizing Radiation, Faculty of Nuclear Sciences and Physical Engineering, Czech Technical University in Prague, 115 19 Prague

The most recent release of the open source and general purpose Geant4 Monte Carlo simulation toolkit (Geant4 10.2 release) contains a new set of physics models in the Geant4-DNA extension for improving the modelling of low-energy electron transport in liquid water (<10 keV). This includes updated electron cross sections for excitation, ionization, and elastic scattering. In the present work, the impact of these developments to track-structure calculations is examined for providing the first comprehensive comparison against the default physics models of Geant4-DNA. Significant differences with the default models are found for the average path length and penetration distance, as well asmore » for dose-point-kernels for electron energies below a few hundred eV. On the other hand, self-irradiation absorbed fractions for tissue-like volumes and low-energy electron sources (including some Auger emitters) reveal rather small differences (up to 15%) between these new and default Geant4-DNA models. The above findings indicate that the impact of the new developments will mainly affect those applications where the spatial pattern of interactions and energy deposition of very-low energy electrons play an important role such as, for example, the modelling of the chemical and biophysical stage of radiation damage to cells.« less

Accelerated GPU based SPECT Monte Carlo simulations.

PubMed

Garcia, Marie-Paule; Bert, Julien; Benoit, Didier; Bardiès, Manuel; Visvikis, Dimitris

2016-06-07

Monte Carlo (MC) modelling is widely used in the field of single photon emission computed tomography (SPECT) as it is a reliable technique to simulate very high quality scans. This technique provides very accurate modelling of the radiation transport and particle interactions in a heterogeneous medium. Various MC codes exist for nuclear medicine imaging simulations. Recently, new strategies exploiting the computing capabilities of graphical processing units (GPU) have been proposed. This work aims at evaluating the accuracy of such GPU implementation strategies in comparison to standard MC codes in the context of SPECT imaging. GATE was considered the reference MC toolkit and used to evaluate the performance of newly developed GPU Geant4-based Monte Carlo simulation (GGEMS) modules for SPECT imaging. Radioisotopes with different photon energies were used with these various CPU and GPU Geant4-based MC codes in order to assess the best strategy for each configuration. Three different isotopes were considered: (99m) Tc, (111)In and (131)I, using a low energy high resolution (LEHR) collimator, a medium energy general purpose (MEGP) collimator and a high energy general purpose (HEGP) collimator respectively. Point source, uniform source, cylindrical phantom and anthropomorphic phantom acquisitions were simulated using a model of the GE infinia II 3/8" gamma camera. Both simulation platforms yielded a similar system sensitivity and image statistical quality for the various combinations. The overall acceleration factor between GATE and GGEMS platform derived from the same cylindrical phantom acquisition was between 18 and 27 for the different radioisotopes. Besides, a full MC simulation using an anthropomorphic phantom showed the full potential of the GGEMS platform, with a resulting acceleration factor up to 71. The good agreement with reference codes and the acceleration factors obtained support the use of GPU implementation strategies for improving computational efficiency of SPECT imaging simulations.

Validation of a virtual source model of medical linac for Monte Carlo dose calculation using multi-threaded Geant4.

PubMed

Aboulbanine, Zakaria; El Khayati, Naïma

2018-04-13

The use of phase space in medical linear accelerator Monte Carlo (MC) simulations significantly improves the execution time and leads to results comparable to those obtained from full calculations. The classical representation of phase space stores directly the information of millions of particles, producing bulky files. This paper presents a virtual source model (VSM) based on a reconstruction algorithm, taking as input a compressed file of roughly 800 kb derived from phase space data freely available in the International Atomic Energy Agency (IAEA) database. This VSM includes two main components; primary and scattered particle sources, with a specific reconstruction method developed for each. Energy spectra and other relevant variables were extracted from IAEA phase space and stored in the input description data file for both sources. The VSM was validated for three photon beams: Elekta Precise 6 MV/10 MV and a Varian TrueBeam 6 MV. Extensive calculations in water and comparisons between dose distributions of the VSM and IAEA phase space were performed to estimate the VSM precision. The Geant4 MC toolkit in multi-threaded mode (Geant4-[mt]) was used for fast dose calculations and optimized memory use. Four field configurations were chosen for dose calculation validation to test field size and symmetry effects, [Formula: see text] [Formula: see text], [Formula: see text] [Formula: see text], and [Formula: see text] [Formula: see text] for squared fields, and [Formula: see text] [Formula: see text] for an asymmetric rectangular field. Good agreement in terms of [Formula: see text] formalism, for 3%/3 mm and 2%/3 mm criteria, for each evaluated radiation field and photon beam was obtained within a computation time of 60 h on a single WorkStation for a 3 mm voxel matrix. Analyzing the VSM's precision in high dose gradient regions, using the distance to agreement concept (DTA), showed also satisfactory results. In all investigated cases, the mean DTA was less than 1 mm in build-up and penumbra regions. In regards to calculation efficiency, the event processing speed is six times faster using Geant4-[mt] compared to sequential Geant4, when running the same simulation code for both. The developed VSM for 6 MV/10 MV beams widely used, is a general concept easy to adapt in order to reconstruct comparable beam qualities for various linac configurations, facilitating its integration for MC treatment planning purposes.

Extension of PENELOPE to protons: simulation of nuclear reactions and benchmark with Geant4.

PubMed

Sterpin, E; Sorriaux, J; Vynckier, S

2013-11-01

Describing the implementation of nuclear reactions in the extension of the Monte Carlo code (MC) PENELOPE to protons (PENH) and benchmarking with Geant4. PENH is based on mixed-simulation mechanics for both elastic and inelastic electromagnetic collisions (EM). The adopted differential cross sections for EM elastic collisions are calculated using the eikonal approximation with the Dirac-Hartree-Fock-Slater atomic potential. Cross sections for EM inelastic collisions are computed within the relativistic Born approximation, using the Sternheimer-Liljequist model of the generalized oscillator strength. Nuclear elastic and inelastic collisions were simulated using explicitly the scattering analysis interactive dialin database for (1)H and ICRU 63 data for (12)C, (14)N, (16)O, (31)P, and (40)Ca. Secondary protons, alphas, and deuterons were all simulated as protons, with the energy adapted to ensure consistent range. Prompt gamma emission can also be simulated upon user request. Simulations were performed in a water phantom with nuclear interactions switched off or on and integral depth-dose distributions were compared. Binary-cascade and precompound models were used for Geant4. Initial energies of 100 and 250 MeV were considered. For cases with no nuclear interactions simulated, additional simulations in a water phantom with tight resolution (1 mm in all directions) were performed with FLUKA. Finally, integral depth-dose distributions for a 250 MeV energy were computed with Geant4 and PENH in a homogeneous phantom with, first, ICRU striated muscle and, second, ICRU compact bone. For simulations with EM collisions only, integral depth-dose distributions were within 1%/1 mm for doses higher than 10% of the Bragg-peak dose. For central-axis depth-dose and lateral profiles in a phantom with tight resolution, there are significant deviations between Geant4 and PENH (up to 60%/1 cm for depth-dose distributions). The agreement is much better with FLUKA, with deviations within 3%/3 mm. When nuclear interactions were turned on, agreement (within 6% before the Bragg-peak) between PENH and Geant4 was consistent with uncertainties on nuclear models and cross sections, whatever the material simulated (water, muscle, or bone). A detailed and flexible description of nuclear reactions has been implemented in the PENH extension of PENELOPE to protons, which utilizes a mixed-simulation scheme for both elastic and inelastic EM collisions, analogous to the well-established algorithm for electrons/positrons. PENH is compatible with all current main programs that use PENELOPE as the MC engine. The nuclear model of PENH is realistic enough to give dose distributions in fair agreement with those computed by Geant4.

Extension of PENELOPE to protons: Simulation of nuclear reactions and benchmark with Geant4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sterpin, E.; Sorriaux, J.; Vynckier, S.

2013-11-15

Purpose: Describing the implementation of nuclear reactions in the extension of the Monte Carlo code (MC) PENELOPE to protons (PENH) and benchmarking with Geant4.Methods: PENH is based on mixed-simulation mechanics for both elastic and inelastic electromagnetic collisions (EM). The adopted differential cross sections for EM elastic collisions are calculated using the eikonal approximation with the Dirac–Hartree–Fock–Slater atomic potential. Cross sections for EM inelastic collisions are computed within the relativistic Born approximation, using the Sternheimer–Liljequist model of the generalized oscillator strength. Nuclear elastic and inelastic collisions were simulated using explicitly the scattering analysis interactive dialin database for {sup 1}H and ICRUmore » 63 data for {sup 12}C, {sup 14}N, {sup 16}O, {sup 31}P, and {sup 40}Ca. Secondary protons, alphas, and deuterons were all simulated as protons, with the energy adapted to ensure consistent range. Prompt gamma emission can also be simulated upon user request. Simulations were performed in a water phantom with nuclear interactions switched off or on and integral depth–dose distributions were compared. Binary-cascade and precompound models were used for Geant4. Initial energies of 100 and 250 MeV were considered. For cases with no nuclear interactions simulated, additional simulations in a water phantom with tight resolution (1 mm in all directions) were performed with FLUKA. Finally, integral depth–dose distributions for a 250 MeV energy were computed with Geant4 and PENH in a homogeneous phantom with, first, ICRU striated muscle and, second, ICRU compact bone.Results: For simulations with EM collisions only, integral depth–dose distributions were within 1%/1 mm for doses higher than 10% of the Bragg-peak dose. For central-axis depth–dose and lateral profiles in a phantom with tight resolution, there are significant deviations between Geant4 and PENH (up to 60%/1 cm for depth–dose distributions). The agreement is much better with FLUKA, with deviations within 3%/3 mm. When nuclear interactions were turned on, agreement (within 6% before the Bragg-peak) between PENH and Geant4 was consistent with uncertainties on nuclear models and cross sections, whatever the material simulated (water, muscle, or bone).Conclusions: A detailed and flexible description of nuclear reactions has been implemented in the PENH extension of PENELOPE to protons, which utilizes a mixed-simulation scheme for both elastic and inelastic EM collisions, analogous to the well-established algorithm for electrons/positrons. PENH is compatible with all current main programs that use PENELOPE as the MC engine. The nuclear model of PENH is realistic enough to give dose distributions in fair agreement with those computed by Geant4.« less

Geant4 Monte Carlo simulation of energy loss and transmission and ranges for electrons, protons and ions

NASA Astrophysics Data System (ADS)

Ivantchenko, Vladimir

Geant4 is a toolkit for Monte Carlo simulation of particle transport originally developed for applications in high-energy physics with the focus on experiments at the Large Hadron Collider (CERN, Geneva). The transparency and flexibility of the code has spread its use to other fields of research, e.g. radiotherapy and space science. The tool provides possibility to simulate complex geometry, transportation in electric and magnetic fields and variety of physics models of interaction of particles with media. Geant4 has been used for simulation of radiation effects for number of space missions. Recent upgrades of the toolkit released in December 2009 include new model for ion electronic stopping power based on the revised version of ICRU'73 Report increasing accuracy of simulation of ion transport. In the current work we present the status of Geant4 electromagnetic package for simulation of particle energy loss, ranges and transmission. This has a direct implication for simulation of ground testing setups at existing European facilities and for simulation of radiation effects in space. A number of improvements were introduced for electron and proton transport, followed by a thorough validation. It was the aim of the present study to validate the range against reference data from the United States National Institute of Standards and Technologies (NIST) ESTAR, PSTAR and ASTAR databases. We compared Geant4 and NIST ranges of electrons using different Geant4 models. The best agreement was found for Penelope, except at very low energies in heavy materials, where the Standard package gave better results. Geant4 proton ranges in water agreed with NIST within 1 The validation of the new ion model is performed against recent data on Bragg peak position in water. The data from transmission of carbon ions via various absorbers following Bragg peak in water demonstrate that the new Geant4 model significantly improves precision of ion range. The absolute accuracy of ion range achieved is on level of 1

Geant4-DNA: overview and recent developments

NASA Astrophysics Data System (ADS)

Štěpán, Václav

Space travel and high altitude flights are inherently associated with prolonged exposure to cosmic and solar radiation. Understanding and simulation of radiation action on cellular and subcellular level contributes to precise assessment of the associated health risks and remains a challenge of today’s radiobiology research. The Geant4-DNA project (http://geant4-dna.org) aims at developing an experimentally validated simulation platform for modelling of the damage induced by ionizing radiation at DNA level. The platform is based on the Geant4 Monte Carlo simulation toolkit. This project extends specific functionalities of Geant4 in following areas: The step-by-step single scattering modelling of elementary physical interactions of electrons, protons, alpha particles and light ions with liquid water and DNA bases, for the so-called “physical” stage. The modelling of the “physico-chemical and chemical” stages corresponding to the production, the diffusion, the chemical reactions occurring between chemical species produced by water radiolysis, and to the radical attack on the biological targets. Physical and chemical stage simulations are combined with biological target models on several scales, from DNA double helix, through nucleosome, to chromatin segments and cell geometries. In addition, data mining clustering algorithms have been developed and optimised for the purpose of DNA damage scoring in simulated tracks. Experimental measurements on pBR322 plasmid DNA are being carried out in order to validate the Geant4-DNA models. The plasmid DNA has been irradiated in dry conditions by protons with energies from 100 keV to 30 MeV and in aqueous conditions, with and without scavengers, by 30 MeV protons, 290 MeV/u carbon and 500 MeV/u iron ions. Agarose gel electrophoresis combined with enzymatic treatment has been used to measure the resulting DNA damage. An overview of the developments undertaken by the Geant4-DNA collaboration including a description of software already available for download, as well as future perspectives, will be presented, on behalf of the Geant4-DNA Collaboration.

Simulation, optimization and testing of a novel high spatial resolution X-ray imager based on Zinc Oxide nanowires in Anodic Aluminium Oxide membrane using Geant4

NASA Astrophysics Data System (ADS)

Esfandi, F.; Saramad, S.

2015-07-01

In this work, a new generation of scintillator based X-ray imagers based on ZnO nanowires in Anodized Aluminum Oxide (AAO) nanoporous template is characterized. The optical response of ordered ZnO nanowire arrays in porous AAO template under low energy X-ray illumination is simulated by the Geant4 Monte Carlo code and compared with experimental results. The results show that for 10 keV X-ray photons, by considering the light guiding properties of zinc oxide inside the AAO template and suitable selection of detector thickness and pore diameter, the spatial resolution less than one micrometer and the detector detection efficiency of 66% are accessible. This novel nano scintillator detector can have many advantages for medical applications in the future.

The NOvA simulation chain

NASA Astrophysics Data System (ADS)

Aurisano, A.; Backhouse, C.; Hatcher, R.; Mayer, N.; Musser, J.; Patterson, R.; Schroeter, R.; Sousa, A.

2015-12-01

The NOνA experiment is a two-detector, long-baseline neutrino experiment operating in the recently upgraded NuMI muon neutrino beam. Simulating neutrino interactions and backgrounds requires many steps including: the simulation of the neutrino beam flux using FLUKA and the FLUGG interface; cosmic ray generation using CRY; neutrino interaction modeling using GENIE; and a simulation of the energy deposited in the detector using GEANT4. To shorten generation time, the modeling of detector-specific aspects, such as photon transport, detector and electronics noise, and readout electronics, employs custom, parameterized simulation applications. We will describe the NOνA simulation chain, and present details on the techniques used in modeling photon transport near the ends of cells, and in developing a novel data-driven noise simulation. Due to the high intensity of the NuMI beam, the Near Detector samples a high rate of muons originating in the surrounding rock. In addition, due to its location on the surface at Ash River, MN, the Far Detector collects a large rate (˜ 140 kHz) of cosmic muons. We will discuss the methods used in NOνA for overlaying rock muons and cosmic ray muons with simulated neutrino interactions and show how realistically the final simulation reproduces the preliminary NOνA data.

The NO vA simulation chain

DOE PAGES

Aurisano, A.; Backhouse, C.; Hatcher, R.; ...

2015-12-23

The NO vA experiment is a two-detector, long-baseline neutrino experiment operating in the recently upgraded NuMI muon neutrino beam. Simulating neutrino interactions and backgrounds requires many steps including: the simulation of the neutrino beam flux using FLUKA and the FLUGG interface, cosmic ray generation using CRY, neutrino interaction modeling using GENIE, and a simulation of the energy deposited in the detector using GEANT4. To shorten generation time, the modeling of detector-specific aspects, such as photon transport, detector and electronics noise, and readout electronics, employs custom, parameterized simulation applications. We will describe the NO vA simulation chain, and present details onmore » the techniques used in modeling photon transport near the ends of cells, and in developing a novel data-driven noise simulation. Due to the high intensity of the NuMI beam, the Near Detector samples a high rate of muons originating in the surrounding rock. In addition, due to its location on the surface at Ash River, MN, the Far Detector collects a large rate ((˜) 140 kHz) of cosmic muons. Furthermore, we will discuss the methods used in NO vA for overlaying rock muons and cosmic ray muons with simulated neutrino interactions and show how realistically the final simulation reproduces the preliminary NO vA data.« less

Evaluation of the dose perturbation around gold and steel fiducial markers in a medical linac through Geant4 Monte Carlo simulation.

PubMed

Pontoriero, Antonio; Amato, Ernesto; Iatí, Giuseppe; De Renzis, Costantino; Pergolizzi, Stefano

2015-01-01

Purpose of this work was to study the dose perturbation within the target volume of a external MV radiation therapy when using metal fiducials. We developed a Monte Carlo simulation in Geant4 of a cylindrical fiducial made either of gold or of steel and simulated the photon irradiation beam originating from a medical Linac operating at 6, 10 or 15 MV. For each energy, two different irradiation schemes were simulated: a single 5 × 5-cm square field in the -x direction, and five 5 × 5-cm fields at 0°, 80°, 165°, 195° and 280°. In a single beam irradiation scheme, we observed a dose reduction behind fiducials varying from -20% for gold at 6 MV to -5% for steel at 15 MV, and a dose increment in front of the fiducial ranging from +33% for gold at 15 MV to +10% for steel at 6 MV. When five beams were employed, a dose increment ranging from +28% to +46% has been found around gold. Around a steel fiducial, an average increment of +17% was found, irrespective of the photon energy. When using a single beam, the decrement of dose behind both steel and gold markers increases with the photon energy. This effect vanishes when a multifield treatment is delivered; in this instance there is a dose increment around fiducials, according to both fiducial material and photon energy, with lower values for steel and 6 MV. This energy represents the best choice when fiducial markers are present inside the irradiated volume.

Design Study of the Absorber Detector of a Compton Camera for On-Line Control in Ion Beam Therapy

NASA Astrophysics Data System (ADS)

Richard, M.-H.; Dahoumane, M.; Dauvergne, D.; De Rydt, M.; Dedes, G.; Freud, N.; Krimmer, J.; Letang, J. M.; Lojacono, X.; Maxim, V.; Montarou, G.; Ray, C.; Roellinghoff, F.; Testa, E.; Walenta, A. H.

2012-10-01

The goal of this study is to tune the design of the absorber detector of a Compton camera for prompt γ-ray imaging during ion beam therapy. The response of the Compton camera to a photon point source with a realistic energy spectrum (corresponding to the prompt γ-ray spectrum emitted during the carbon irradiation of a water phantom) is studied by means of Geant4 simulations. Our Compton camera consists of a stack of 2 mm thick silicon strip detectors as a scatter detector and of a scintillator plate as an absorber detector. Four scintillators are considered: LYSO, NaI, LaBr3 and BGO. LYSO and BGO appear as the most suitable materials, due to their high photo-electric cross-sections, which leads to a high percentage of fully absorbed photons. Depth-of-interaction measurements are shown to have limited influence on the spatial resolution of the camera. In our case, the thickness which gives the best compromise between a high percentage of photons that are fully absorbed and a low parallax error is about 4 cm for the LYSO detector and 4.5 cm for the BGO detector. The influence of the width of the absorber detector on the spatial resolution is not very pronounced as long as it is lower than 30 cm.

CP violating anomalous top-quark coupling in p$$\\bar{p}$$ collision at $$\\sqrt{s}=1.96$$ TeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Sehwook

2011-01-01

We conduct the first study of the T-odd correlations in tt events produced in pmore » $$\\bar{p}$$ collision at the Fermilab Tevatron collider that can be used to search for CP violation. We select events which have lepton+jets final states to identify t$$\\bar{t}$$ events and measure counting asymmetries of several physics observables. Based on the result, we search the top quark anomalous couplings at the production vertex at the Tevatron. In addition, Geant4 development, photon identification, the discrimination of a single photon and a photon doublet from π 0 decay are discussed in this thesis.« less

Use of SRIM and Garfield with Geant4 for the characterization of a hybrid 10B/3He neutron detector

NASA Astrophysics Data System (ADS)

van der Ende, B. M.; Rand, E. T.; Erlandson, A.; Li, L.

2018-06-01

This paper describes a method for more complete neutron detector characterization using Geant4's Monte Carlo methods for characterizing overall detector response rate and Garfield interfaced with SRIM for the simulation of the detector's raw pulses, as applied to a hybrid 10B/3He detector. The Geant4 models characterizing the detector's interaction with a 252Cf point source and parallel beams of mono-energetic neutrons (assuming ISO 8529 reference energy values) compare and agree well with calibrated 252Cf measurements to within 6.4%. Validated Geant4 model outputs serve as input to Garfield+SRIM calculations to provide meaningful pulse height spectra. Modifications to Garfield for this work were necessary to account for simultaneous tracking of electrons resulting from proton and triton reaction products from a single 3He neutron capture event, and it was further necessary to interface Garfield with the energy loss, range, and straggling calculations provided by SRIM. Individual raw pulses generated by Garfield+SRIM are also observed to agree well with experimentally measured raw pulses from the detector.

Evaluation on Geant4 Hadronic Models for Pion Minus, Pion Plus and Neutron Particles as Major Antiproton Annihilation Products

PubMed Central

Tavakoli, Mohammad Bagher; Mohammadi, Mohammad Mehdi; Reiazi, Reza; Jabbari, Keyvan

2015-01-01

Geant4 is an open source simulation toolkit based on C++, which its advantages progressively lead to applications in research domains especially modeling the biological effects of ionizing radiation at the sub-cellular scale. However, it was shown that Geant4 does not give a reasonable result in the prediction of antiproton dose especially in Bragg peak. One of the reasons could be lack of reliable physic model to predict the final states of annihilation products like pions. Considering the fact that most of the antiproton deposited dose is resulted from high-LET nuclear fragments following pion interaction in surrounding nucleons, we reproduced depth dose curves of most probable energy range of pions and neutron particle using Geant4. We consider this work one of the steps to understand the origin of the error and finally verification of Geant4 for antiproton tracking. Geant4 toolkit version 9.4.6.p01 and Fluka version 2006.3 were used to reproduce the depth dose curves of 220 MeV pions (both negative and positive) and 70 MeV neutrons. The geometry applied in the simulations consist a 20 × 20 × 20 cm3 water tank, similar to that used in CERN for antiproton relative dose measurements. Different physic lists including Quark-Gluon String Precompound (QGSP)_Binary Cascade (BIC)_HP, the recommended setting for hadron therapy, were used. In the case of pions, Geant4 resulted in at least 5% dose discrepancy between different physic lists at depth close to the entrance point. Even up to 15% discrepancy was found in some cases like QBBC compared to QGSP_BIC_HP. A significant difference was observed in dose profiles of different Geant4 physic list at small depths for a beam of pions. In the case of neutrons, large dose discrepancy was observed when LHEP or LHEP_EMV lists were applied. The magnitude of this dose discrepancy could be even 50% greater than the dose calculated by LHEP (or LHEP_EMV) at larger depths. We found that effect different Geant4 physic list in reproducing depth dose profile of the beam of pions was not negligible. Because the discrepancies were pronounced in smaller depth and also regarding the contribution of pions in deposited dose of a beam of antiproton, further investigation on choosing most suitable and accurate physic list for this purpose should be done. Furthermore, this study showed careful attention must be paid to choose the appropriate Geant4 physic list for neutron tracking depending to the applications criteria. We failed to find any agreement between results from Geant4 and Fluka to reproduce depth dose profile of pion with the energy range used in this study. PMID:26120569

Cosmogenic activation of germanium used for tonne-scale rare event search experiments

NASA Astrophysics Data System (ADS)

Wei, W.-Z.; Mei, D.-M.; Zhang, C.

2017-11-01

We report a comprehensive study of cosmogenic activation of germanium used for tonne-scale rare event search experiments. The germanium exposure to cosmic rays on the Earth's surface are simulated with and without a shielding container using Geant4 for a given cosmic muon, neutron, and proton energy spectrum. The production rates of various radioactive isotopes are obtained for different sources separately. We find that fast neutron induced interactions dominate the production rate of cosmogenic activation. Geant4-based simulation results are compared with the calculation of ACTIVIA and the available experimental data. A reasonable agreement between Geant4 simulations and several experimental data sets is presented. We predict that cosmogenic activation of germanium can set limits to the sensitivity of the next generation of tonne-scale experiments.

Review on Monte-Carlo Tools for Simulating Relativistic Runaway Electron Avalanches and the Propagation of TerretrialTerrestrial-Gamma Ray Flashes in the Atmosphere

NASA Astrophysics Data System (ADS)

Sarria, D.

2016-12-01

The field of High Energy Atmospheric Physics (HEAP) includes the study of energetic events related to thunderstorms, such as Terrestrial Gamma-ray Flashes (TGF), associated electron-positron beams (TEB), gamma-ray glows and Thunderstorm Ground Enhancements (TGE). Understanding these phenomena requires accurate models for the interaction of particles with atmospheric air and electro-magnetic fields in the <100 MeV energy range. This study is the next step of the work presented in [C. Rutjes et al., 2016] that compared the performances of various codes in the absence of electro-magnetic fields. In the first part, we quantify simple but informative test cases of electrons in various electric field profiles. We will compare the avalanche length (of the Relativistic Runaway Electron Avalanche (RREA) process), the photon/electron spectra and spatial scattering. In particular, we test the effect of the low-energy threshold, that was found to be very important [Skeltved et al., 2014]. Note that even without a field, it was found to be important because of the straggling effect [C. Rutjes et al., 2016]. For this first part, we will be comparing GEANT4 (different flavours), FLUKA and the custom made code GRRR. In the second part, we test the propagation of these high energy particles in the atmosphere, from production altitude (around 10 km to 18 km) to satellite altitude (600 km). We use a simple and clearly fixed set-up for the atmospheric density, the geomagnetic field, the initial conditions, and the detection conditions of the particles. For this second part, we will be comparing GEANT4 (different flavours), FLUKA/CORSIKA and the custom made code MC-PEPTITA. References : C. Rutjes et al., 2016. Evaluation of Monte Carlo tools for high energy atmospheric physics. Geosci. Model Dev. Under review. Skeltved, A. B. et al., 2014. Modelling the relativistic runaway electron avalanche and the feedback mechanism with geant4. JGRA, doi :10.1002/2014JA020504.

Development and validation of a GEANT4 radiation transport code for CT dosimetry

PubMed Central

Carver, DE; Kost, SD; Fernald, MJ; Lewis, KG; Fraser, ND; Pickens, DR; Price, RR; Stabin, MG

2014-01-01

We have created a radiation transport code using the GEANT4 Monte Carlo toolkit to simulate pediatric patients undergoing CT examinations. The focus of this paper is to validate our simulation with real-world physical dosimetry measurements using two independent techniques. Exposure measurements were made with a standard 100-mm CT pencil ionization chamber, and absorbed doses were also measured using optically stimulated luminescent (OSL) dosimeters. Measurements were made in air, a standard 16-cm acrylic head phantom, and a standard 32-cm acrylic body phantom. Physical dose measurements determined from the ionization chamber in air for 100 and 120 kVp beam energies were used to derive photon-fluence calibration factors. Both ion chamber and OSL measurement results provide useful comparisons in the validation of our Monte Carlo simulations. We found that simulated and measured CTDI values were within an overall average of 6% of each other. PMID:25706135

Development and validation of a GEANT4 radiation transport code for CT dosimetry.

PubMed

Carver, D E; Kost, S D; Fernald, M J; Lewis, K G; Fraser, N D; Pickens, D R; Price, R R; Stabin, M G

2015-04-01

The authors have created a radiation transport code using the GEANT4 Monte Carlo toolkit to simulate pediatric patients undergoing CT examinations. The focus of this paper is to validate their simulation with real-world physical dosimetry measurements using two independent techniques. Exposure measurements were made with a standard 100-mm CT pencil ionization chamber, and absorbed doses were also measured using optically stimulated luminescent (OSL) dosimeters. Measurements were made in air with a standard 16-cm acrylic head phantom and with a standard 32-cm acrylic body phantom. Physical dose measurements determined from the ionization chamber in air for 100 and 120 kVp beam energies were used to derive photon-fluence calibration factors. Both ion chamber and OSL measurement results provide useful comparisons in the validation of the Monte Carlo simulations. It was found that simulated and measured CTDI values were within an overall average of 6% of each other.

Multi-threading performance of Geant4, MCNP6, and PHITS Monte Carlo codes for tetrahedral-mesh geometry.

PubMed

Han, Min Cheol; Yeom, Yeon Soo; Lee, Hyun Su; Shin, Bangho; Kim, Chan Hyeong; Furuta, Takuya

2018-05-04

In this study, the multi-threading performance of the Geant4, MCNP6, and PHITS codes was evaluated as a function of the number of threads (N) and the complexity of the tetrahedral-mesh phantom. For this, three tetrahedral-mesh phantoms of varying complexity (simple, moderately complex, and highly complex) were prepared and implemented in the three different Monte Carlo codes, in photon and neutron transport simulations. Subsequently, for each case, the initialization time, calculation time, and memory usage were measured as a function of the number of threads used in the simulation. It was found that for all codes, the initialization time significantly increased with the complexity of the phantom, but not with the number of threads. Geant4 exhibited much longer initialization time than the other codes, especially for the complex phantom (MRCP). The improvement of computation speed due to the use of a multi-threaded code was calculated as the speed-up factor, the ratio of the computation speed on a multi-threaded code to the computation speed on a single-threaded code. Geant4 showed the best multi-threading performance among the codes considered in this study, with the speed-up factor almost linearly increasing with the number of threads, reaching ~30 when N  =  40. PHITS and MCNP6 showed a much smaller increase of the speed-up factor with the number of threads. For PHITS, the speed-up factors were low when N  =  40. For MCNP6, the increase of the speed-up factors was better, but they were still less than ~10 when N  =  40. As for memory usage, Geant4 was found to use more memory than the other codes. In addition, compared to that of the other codes, the memory usage of Geant4 more rapidly increased with the number of threads, reaching as high as ~74 GB when N  =  40 for the complex phantom (MRCP). It is notable that compared to that of the other codes, the memory usage of PHITS was much lower, regardless of both the complexity of the phantom and the number of threads, hardly increasing with the number of threads for the MRCP.

Searching for dark photon with positrons at Jefferson lab

NASA Astrophysics Data System (ADS)

Marsicano, Luca

2018-05-01

The interest in the Dark Photon (A' or U) has recently grown, since it could act as a light mediator to a new sector of Dark Matter particles. In this paradigm, the electron-positron annihilation can rarely produce a γA' pair. Various experiments (e.g. PADME@LNF [1], VEPP-3 [2]) have been proposed to detect this process using positron beams impinging on fixed targets. In such experiments, the energy of the photon from the e+e-→ γA' process is measured with an electromagnetic calorimeter and the missing mass is computed (the A' interacts weakly with Standard Model matter so it can't be detected). However, the A' mass range that can be explored with this technique is limited by the accessible energy in the center of mass frame, which goes as the square root of the beam energy. The realization of a 11 GeV positron beam at Jefferson Lab would allow to search for A' masses up to ˜ 100 MeV, reaching unexplored regions of the A' parameter space. A preliminary study on the feasibility of a PADME-like experiment at Jefferson Lab has been carried out, assuming a 11 GeV positron beam with a ˜ 100 nA current. The achievable sensitivity was estimated, studying the main sources of background (positron bremsstrahlung, annihilation into 2 gammas) using CALCHEP [3] and GEANT4 [4] simulations.

Analysis Tools in Geant4 10.2 and 10.3

NASA Astrophysics Data System (ADS)

Hřivnáčová, I.; Barrand, G.

2017-10-01

A new analysis category based on g4tools was added in Geant4 release 9.5 (2011). The aim was to provide users with a lightweight analysis tool available as part of the Geant4 installation without the need to link to an external analysis package. It has progressively been included in all Geant4 examples. Frequent questions in the Geant4 users forum show its increasing popularity in the Geant4 users community. In this presentation, we will give a brief overview of g4tools and the analysis category. We report on new developments since our CHEP 2013 contribution as well as mention upcoming new features.

Physical models, cross sections, and numerical approximations used in MCNP and GEANT4 Monte Carlo codes for photon and electron absorbed fraction calculation.

PubMed

Yoriyaz, Hélio; Moralles, Maurício; Siqueira, Paulo de Tarso Dalledone; Guimarães, Carla da Costa; Cintra, Felipe Belonsi; dos Santos, Adimir

2009-11-01

Radiopharmaceutical applications in nuclear medicine require a detailed dosimetry estimate of the radiation energy delivered to the human tissues. Over the past years, several publications addressed the problem of internal dose estimate in volumes of several sizes considering photon and electron sources. Most of them used Monte Carlo radiation transport codes. Despite the widespread use of these codes due to the variety of resources and potentials they offered to carry out dose calculations, several aspects like physical models, cross sections, and numerical approximations used in the simulations still remain an object of study. Accurate dose estimate depends on the correct selection of a set of simulation options that should be carefully chosen. This article presents an analysis of several simulation options provided by two of the most used codes worldwide: MCNP and GEANT4. For this purpose, comparisons of absorbed fraction estimates obtained with different physical models, cross sections, and numerical approximations are presented for spheres of several sizes and composed as five different biological tissues. Considerable discrepancies have been found in some cases not only between the different codes but also between different cross sections and algorithms in the same code. Maximum differences found between the two codes are 5.0% and 10%, respectively, for photons and electrons. Even for simple problems as spheres and uniform radiation sources, the set of parameters chosen by any Monte Carlo code significantly affects the final results of a simulation, demonstrating the importance of the correct choice of parameters in the simulation.

Optimization of {sup 6}LiF:ZnS(Ag) Scintillator Light Yield Using Geant4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yehuda-Zada, Y.; Ben-Gurion University; Pritchard, K.

2015-07-01

Neutrons provide an effective tool to probe materials structure. Neutron diffraction is a method to determine the atomic and magnetic structure of a material based on neutron scattering. By this method a collimated incident beam of thermal neutrons heat the examined sample and based on the obtained diffraction pattern information on the structure of the material is provided. Research for developing a novel cold neutron detector for Chromatic Analysis Neutron Diffractometer Or Reflectometer (CANDOR) is underway at the NIST center for neutron research. The system unique design is aimed to provide over ten times fold faster analysis of materials thanmore » conventional system. In order to achieve the fast analysis a large number of neutron detectors is required. A key design constraint for this detector is the thickness of the neutron sensitive element. This is met using {sup 6}LiF:ZnS(Ag) scintillation material with embedded wavelength shifting (WLS) fibers conducting scintillation light to silicon photomultiplier photo-sensors. The detector sensitivity is determined by both the neutron capture probability ({sup 6}Li density) and the detectable light output produced by the ZnS(Ag) ionization, the latter of which is hindered by the fluorescence absorption of the scintillation light by the ZnS. Tradeoffs between the neutron capture probability, stimulated light production and light attenuation for determining the optimal stoichiometry of the {sup 6}LiF and ZnS(Ag) as well as the volume ratio of scintillator and fiber. Simulations performed using the GEANT4 Monte Carlo package were made in order to optimize the detector design. GEANT4 enables the investigation of the neutron interaction with the detector, the ionization process and the light transfer process following the nuclear process. The series of conversions required for this detector were modelled: - A cold neutron enters the sensor and is captured by {sup 6}Li in the scintillator mixture ({sup 6}Li (n,α) {sup 3}H reaction). The study of investigating the capture process probability for neutron energy of 5.1 meV to 2.27 meV (4 - 6 A) is presented. - Alpha particles and tritons travel for a few microns in the scintillation material (α ∼0.007 mm, T ∼0.04 mm) losing energy and ionizing the ZnS. The mean free path of the two particles in each of the component materials and the complete compound was investigated. - The ionization of the ZnS(Ag) scintillation material produces blue light photons with luminescence wavelength of 450 nm. The amount of light output produced for different grain sizes of ZnS is discussed. - A large portion of the scintillation photons are reabsorbed during their passage through the scintillation material. - The blue photons that reach the WLS fibers are absorbed by fluorescent dye and are re-emitted as green photons, conducted by the fiber to the SiPM photo-sensor. This work presents the CANDOR unique design and its design constrains, the results measured by the ultra-thin {sup 6}LiF:ZnS(Ag)-based neutron detector versus the simulation results for several binder concentrations. The light measurement attenuation results along with the measured stopping power were utilized to predict the sensitivity results of configuration with different ZnS grain size, weight ratios and fibers geometry (number and location). The simulations enable to optimize the final sensor design. This design successfully achieved both the high gamma rejection with a sensitive and accurate neutron event detection of 80 percent. (authors)« less

Determination of the temperature of bremsstrahlung photon generated by ultraintense laser using various thickness attenuators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hasegawa, Shuichi; Takashima, Ryuta; Todoriki, Masaru

2011-03-15

We evaluate the simplified method using the Lambert-Beer law to measure the temperature of bremsstrahlung photon generated by an ultraintense laser. Analytical values are compared to the results of the Monte Carlo calculation of GEANT4 and they agreed very well on the condition of the appropriate distance between the attenuator and the detector. We performed the experiment to measure the temperature of bremsstrahlung x-ray emitted from a metal target irradiated by a Ti:sapphire laser with 76 mJ, 72 fs, 2.2 x 10{sup 18} W/cm{sup 2}. For a Cu target of 30 {mu}m thick, the photon temperature was reasonably determined tomore » be 0.18 MeV, which is in good agreement with previous studies.« less

Comparison of simulations with PHITS and HIBRAC with experimental data in the context of particle therapy monitoring

PubMed Central

Rohling, Heide; Sihver, Lembit; Priegnitz, Marlen; Enghardt, Wolfgang; Fiedler, Fine

2014-01-01

Therapeutic irradiation with protons and ions is advantageous over radiotherapy with photons due to its favorable dose deposition. Additionally, ion beams provide a higher relative biological effectiveness than photons. For this reason, an improved treatment of deep-seated tumors is achieved and normal tissue is spared. However, small deviations from the treatment plan can have a large impact on the dose distribution. Therefore, a monitoring is required to assure the quality of the treatment. Particle therapy positron emission tomography (PT-PET) is the only clinically proven method which provides a non-invasive monitoring of dose delivery. It makes use of the β+-activity produced by nuclear fragmentation during irradiation. In order to evaluate these PT-PET measurements, simulations of the β+-activity are necessary. Therefore, it is essential to know the yields of the β+-emitting nuclides at every position of the beam path as exact as possible. We evaluated the three-dimensional Monte-Carlo simulation tool PHITS (version 2.30) [ 1] and the 1D deterministic simulation tool HIBRAC [ 2] with respect to the production of β+-emitting nuclides. The yields of the most important β+-emitting nuclides for carbon, lithium, helium and proton beams have been calculated. The results were then compared with experimental data obtained at GSI Helmholtzzentrum für Schwerionenforschung Darmstadt, Germany. GEANT4 simulations provide an additional benchmark [ 3]. For PHITS, the impact of different nuclear reaction models, total cross-section models and evaporation models on the β+-emitter production has been studied. In general, PHITS underestimates the yields of positron-emitters and cannot compete with GEANT4 so far. The β+-emitters calculated with an extended HIBRAC code were in good agreement with the experimental data for carbon and proton beams and comparable to the GEANT4 results, see [ 4] and Fig. 1. Considering the simulation results and its speed compared with three-dimensional Monte-Carlo tools, HIBRAC is a good candidate for the implementation in clinical routine PT-PET. Fig 1.Depth-dependent yields of the production of 11C and 15O during proton irradiation of a PMMA target with 140 MeV [ 4].

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verbeke, J. M.; Randrup, J.; Vogt, R.

The purpose of this paper is to present the main differences between FREYA versions 1.0 and 2.0.2. FREYA (Fission Reaction Event Yield Algorithm) is a fission event generator which models complete fission events. As such, it automatically includes fluctuations as well as correlations between observables, resulting from conservation of energy and momentum. The main differences between the two versions are: additional fissionable isotopes, angular momentum conservation, Giant Dipole Resonance form factor for the statistical emission of photons, improved treatment of fission photon emission using RIPL database, and dependence on the incident neutron direction. FREYA 2.0.2 has been integrated into themore » LLNL Fission Library 2.0.2, which has itself been integrated into MCNP6.2, TRIPOLI-4.10, and can be called from Geant4.10.« less

A macroscopic and microscopic study of radon exposure using Geant4 and MCNPX to estimate dose rates and DNA damage

NASA Astrophysics Data System (ADS)

van den Akker, Mary Evelyn

Radon is considered the second-leading cause of lung cancer after smoking. Epidemiological studies have been conducted in miner cohorts as well as general populations to estimate the risks associated with high and low dose exposures. There are problems with extrapolating risk estimates to low dose exposures, mainly that the dose-response curve at low doses is not well understood. Calculated dosimetric quantities give average energy depositions in an organ or a whole body, but morphological features of an individual can affect these values. As opposed to human phantom models, Computed Tomography (CT) scans provide unique, patient-specific geometries that are valuable in modeling the radiological effects of the short-lived radon progeny sources. Monte Carlo particle transport code Geant4 was used with the CT scan data to model radon inhalation in the main bronchial bifurcation. The equivalent dose rates are near the lower bounds of estimates found in the literature, depending on source volume. To complement the macroscopic study, simulations were run in a small tissue volume in Geant4-DNA toolkit. As an expansion of Geant4 meant to simulate direct physical interactions at the cellular level, the particle track structure of the radon progeny alphas can be analyzed to estimate the damage that can occur in sensitive cellular structures like the DNA molecule. These estimates of DNA double strand breaks are lower than those found in Geant4-DNA studies. Further refinements of the microscopic model are at the cutting edge of nanodosimetry research.

GEANT4 Tuning For pCT Development

NASA Astrophysics Data System (ADS)

Yevseyeva, Olga; de Assis, Joaquim T.; Evseev, Ivan; Schelin, Hugo R.; Paschuk, Sergei A.; Milhoretto, Edney; Setti, João A. P.; Díaz, Katherin S.; Hormaza, Joel M.; Lopes, Ricardo T.

2011-08-01

Proton beams in medical applications deal with relatively thick targets like the human head or trunk. Thus, the fidelity of proton computed tomography (pCT) simulations as a tool for proton therapy planning depends in the general case on the accuracy of results obtained for the proton interaction with thick absorbers. GEANT4 simulations of proton energy spectra after passing thick absorbers do not agree well with existing experimental data, as showed previously. Moreover, the spectra simulated for the Bethe-Bloch domain showed an unexpected sensitivity to the choice of low-energy electromagnetic models during the code execution. These observations were done with the GEANT4 version 8.2 during our simulations for pCT. This work describes in more details the simulations of the proton passage through aluminum absorbers with varied thickness. The simulations were done by modifying only the geometry in the Hadrontherapy Example, and for all available choices of the Electromagnetic Physics Models. As the most probable reasons for these effects is some specific feature in the code, or some specific implicit parameters in the GEANT4 manual, we continued our study with version 9.2 of the code. Some improvements in comparison with our previous results were obtained. The simulations were performed considering further applications for pCT development.

Effect of Electron Seeding on Experimentally Measured Multipactor Discharge Threshold

NASA Astrophysics Data System (ADS)

Noland, Jonathan; Graves, Timothy; Lemon, Colby; Looper, Mark; Farkas, Alex

2012-10-01

Multipactor is a vacuum phenomenon in which electrons, moving in resonance with an externally applied electric field, impact material surfaces. If the number of secondary electrons created per primary electron impact averages more than unity, the resonant interaction can lead to an electron avalanche. Multipactor is a generally undesirable phenomenon, as it can cause local heating, absorb power, or cause detuning of RF circuits. In order to increase the probability of multipactor initiation, test facilities often employ various seeding sources such as radioactive sources (Cesium 137, Strontium 90), electron guns, or photon sources. Even with these sources, the voltage for multipactor initiation is not certain as parameters such as material type, RF pulse length, and device wall thickness can all affect seed electron flux and energy in critical gap regions, and hence the measured voltage threshold. This study investigates the effects of seed electron source type (e.g., photons versus beta particles), material type, gap size, and RF pulse length variation on multipactor threshold. In addition to the experimental work, GEANT4 simulations will be used to estimate the production rate of low energy electrons (< 5 keV) by high energy electrons and photons. A comparison of the experimental fluxes to the typical energetic photon and particle fluxes experienced by spacecraft in various orbits will also be made. Initial results indicate that for a simple, parallel plate device made of aluminum, there is no threshold variation (with seed electrons versus with no seed electrons) under continuous-wave RF exposure.

Particle flow oriented electromagnetic calorimeter optimization for the circular electron positron collider

NASA Astrophysics Data System (ADS)

Zhao, H.; Fu, C.; Yu, D.; Wang, Z.; Hu, T.; Ruan, M.

2018-03-01

The design and optimization of the Electromagnetic Calorimeter (ECAL) are crucial for the Circular Electron Positron Collider (CEPC) project, a proposed future Higgs/Z factory. Following the reference design of the International Large Detector (ILD), a set of silicon-tungsten sampling ECAL geometries are implemented into the Geant4 simulation, whose performance is then scanned using Arbor algorithm. The photon energy response at different ECAL longitudinal structures is analyzed, and the separation performance between nearby photon showers with different ECAL transverse cell sizes is investigated and parametrized. The overall performance is characterized by a set of physics benchmarks, including νν H events where Higgs boson decays into a pair of photons (EM objects) or gluons (jets) and Z→τ+τ- events. Based on these results, we propose an optimized ECAL geometry for the CEPC project.

Impact of Non-Uniformity in Light Collection on the Energy Resolution of the PANDA Electromagnetic Calorimeter at Photon Energies Below 1 GeV

NASA Astrophysics Data System (ADS)

Diehl, Stefan; Brinkmann, Kai-Thomas; Drexler, Peter; Dormenev, Valery; Novotny, Rainer W.; Rosenbaum, Christoph; Zaunick, Hans-Georg; PANDA-Collaboration

2017-11-01

The electromagnetic calorimeter (EMC) of the PANDA detector at the future FAIR facility comprises more than 15,000 lead tungstate (PWO) crystals. The barrel part will consist of 11 crystal geometries with different degree of tapering, which causes a non-uniformity in light collection as an interplay between the focusing and the internal absorption of the light. For the most tapered crystals the detected light is enhanced by 40%, if the scintillation process is created in the front part of the crystal. Due to the shower development and its fluctuations the non-uniformity leads to a reduction of the energy resolution. To reduce this effect, one lateral crystal side face has been de-polished to a roughness of 0.3 μm. Measurements confirm an increase of the light yield in the rear part of the crystal. In contrast, only a slight decrease can be observed in the front part. The overall non-uniformity is significantly reduced below 5%. This paper will discuss the experimental studies based on GEANT4 and optical simulations to understand the impact of a de-polished side face on the light collection. For consequences on the future performance, a 3×3 sub-array of de-polished crystals was directly studied using a tagged photon beam in the energy range from 50 MeV up to 800 MeV, respectively, performed at the tagged photon facility at MAMI, Mainz. The comparison to an array composed of polished crystals confirms a significant improvement of the constant term of the energy resolution from above 2 % down to 0.5 % and only a small increase of the statistical term. The results can be reproduced in GEANT4 simulations.

TH-A-19A-08: Intel Xeon Phi Implementation of a Fast Multi-Purpose Monte Carlo Simulation for Proton Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Souris, K; Lee, J; Sterpin, E

2014-06-15

Purpose: Recent studies have demonstrated the capability of graphics processing units (GPUs) to compute dose distributions using Monte Carlo (MC) methods within clinical time constraints. However, GPUs have a rigid vectorial architecture that favors the implementation of simplified particle transport algorithms, adapted to specific tasks. Our new, fast, and multipurpose MC code, named MCsquare, runs on Intel Xeon Phi coprocessors. This technology offers 60 independent cores, and therefore more flexibility to implement fast and yet generic MC functionalities, such as prompt gamma simulations. Methods: MCsquare implements several models and hence allows users to make their own tradeoff between speed andmore » accuracy. A 200 MeV proton beam is simulated in a heterogeneous phantom using Geant4 and two configurations of MCsquare. The first one is the most conservative and accurate. The method of fictitious interactions handles the interfaces and secondary charged particles emitted in nuclear interactions are fully simulated. The second, faster configuration simplifies interface crossings and simulates only secondary protons after nuclear interaction events. Integral depth-dose and transversal profiles are compared to those of Geant4. Moreover, the production profile of prompt gammas is compared to PENH results. Results: Integral depth dose and transversal profiles computed by MCsquare and Geant4 are within 3%. The production of secondaries from nuclear interactions is slightly inaccurate at interfaces for the fastest configuration of MCsquare but this is unlikely to have any clinical impact. The computation time varies between 90 seconds for the most conservative settings to merely 59 seconds in the fastest configuration. Finally prompt gamma profiles are also in very good agreement with PENH results. Conclusion: Our new, fast, and multi-purpose Monte Carlo code simulates prompt gammas and calculates dose distributions in less than a minute, which complies with clinical time constraints. It has been successfully validated with Geant4. This work has been financialy supported by InVivoIGT, a public/private partnership between UCL and IBA.« less

Fission Reaction Event Yield Algorithm FREYA 2.0.2

DOE PAGES

Verbeke, J. M.; Randrup, J.; Vogt, R.

2017-09-01

The purpose of this paper is to present the main differences between FREYA versions 1.0 and 2.0.2. FREYA (Fission Reaction Event Yield Algorithm) is a fission event generator which models complete fission events. As such, it automatically includes fluctuations as well as correlations between observables, resulting from conservation of energy and momentum. The main differences between the two versions are: additional fissionable isotopes, angular momentum conservation, Giant Dipole Resonance form factor for the statistical emission of photons, improved treatment of fission photon emission using RIPL database, and dependence on the incident neutron direction. FREYA 2.0.2 has been integrated into themore » LLNL Fission Library 2.0.2, which has itself been integrated into MCNP6.2, TRIPOLI-4.10, and can be called from Geant4.10.« less

The Geant4 physics validation repository

NASA Astrophysics Data System (ADS)

Wenzel, H.; Yarba, J.; Dotti, A.

2015-12-01

The Geant4 collaboration regularly performs validation and regression tests. The results are stored in a central repository and can be easily accessed via a web application. In this article we describe the Geant4 physics validation repository which consists of a relational database storing experimental data and Geant4 test results, a java API and a web application. The functionality of these components and the technology choices we made are also described.

Measurement of angularly dependent spectra of betatron gamma-rays from a laser plasma accelerator with quadrant-sectored range filters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeon, Jong Ho, E-mail: jhjeon07@ibs.re.kr; Nakajima, Kazuhisa, E-mail: naka115@dia-net.ne.jp; Rhee, Yong Joo

Measurement of angularly dependent spectra of betatron gamma-rays radiated by GeV electron beams from laser wakefield accelerators (LWFAs) are presented. The angle-resolved spectrum of betatron radiation was deconvolved from the position dependent data measured for a single laser shot with a broadband gamma-ray spectrometer comprising four-quadrant sectored range filters and an unfolding algorithm, based on the Monte Carlo code GEANT4. The unfolded gamma-ray spectra in the photon energy range of 0.1–10 MeV revealed an approximately isotropic angular dependence of the peak photon energy and photon energy-integrated fluence. As expected by the analysis of betatron radiation from LWFAs, the results indicate thatmore » unpolarized gamma-rays are emitted by electrons undergoing betatron motion in isotropically distributed orbit planes.« less

The Geant4 physics validation repository

DOE PAGES

Wenzel, H.; Yarba, J.; Dotti, A.

2015-12-23

The Geant4 collaboration regularly performs validation and regression tests. The results are stored in a central repository and can be easily accessed via a web application. In this article we describe the Geant4 physics validation repository which consists of a relational database storing experimental data and Geant4 test results, a java API and a web application. Lastly, the functionality of these components and the technology choices we made are also described

A new concept of pencil beam dose calculation for 40-200 keV photons using analytical dose kernels.

PubMed

Bartzsch, Stefan; Oelfke, Uwe

2013-11-01

The advent of widespread kV-cone beam computer tomography in image guided radiation therapy and special therapeutic application of keV photons, e.g., in microbeam radiation therapy (MRT) require accurate and fast dose calculations for photon beams with energies between 40 and 200 keV. Multiple photon scattering originating from Compton scattering and the strong dependence of the photoelectric cross section on the atomic number of the interacting tissue render these dose calculations by far more challenging than the ones established for corresponding MeV beams. That is why so far developed analytical models of kV photon dose calculations fail to provide the required accuracy and one has to rely on time consuming Monte Carlo simulation techniques. In this paper, the authors introduce a novel analytical approach for kV photon dose calculations with an accuracy that is almost comparable to the one of Monte Carlo simulations. First, analytical point dose and pencil beam kernels are derived for homogeneous media and compared to Monte Carlo simulations performed with the Geant4 toolkit. The dose contributions are systematically separated into contributions from the relevant orders of multiple photon scattering. Moreover, approximate scaling laws for the extension of the algorithm to inhomogeneous media are derived. The comparison of the analytically derived dose kernels in water showed an excellent agreement with the Monte Carlo method. Calculated values deviate less than 5% from Monte Carlo derived dose values, for doses above 1% of the maximum dose. The analytical structure of the kernels allows adaption to arbitrary materials and photon spectra in the given energy range of 40-200 keV. The presented analytical methods can be employed in a fast treatment planning system for MRT. In convolution based algorithms dose calculation times can be reduced to a few minutes.

Modeling of the Very Low Frequency (VLF) radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry

NASA Astrophysics Data System (ADS)

Palit, S.; Basak, T.; Mondal, S. K.; Pal, S.; Chakrabarti, S. K.

2013-03-01

X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~ 60 to 100 km) in excess of what is expected from a quiet sun. Very Low Frequency (VLF) radio wave signals reflected from the D region are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the lower ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the VLF signal change. We did the modeling of the VLF signal along the NWC (Australia) to IERC/ICSP (India) propagation path and compared the results with observations. The agreement is found to be very satisfactory.

Monte Carlo investigation of the increased radiation deposition due to gold nanoparticles using kilovoltage and megavoltage photons in a 3D randomized cell model.

PubMed

Douglass, Michael; Bezak, Eva; Penfold, Scott

2013-07-01

Investigation of increased radiation dose deposition due to gold nanoparticles (GNPs) using a 3D computational cell model during x-ray radiotherapy. Two GNP simulation scenarios were set up in Geant4; a single 400 nm diameter gold cluster randomly positioned in the cytoplasm and a 300 nm gold layer around the nucleus of the cell. Using an 80 kVp photon beam, the effect of GNP on the dose deposition in five modeled regions of the cell including cytoplasm, membrane, and nucleus was simulated. Two Geant4 physics lists were tested: the default Livermore and custom built Livermore/DNA hybrid physics list. 10(6) particles were simulated at 840 cells in the simulation. Each cell was randomly placed with random orientation and a diameter varying between 9 and 13 μm. A mathematical algorithm was used to ensure that none of the 840 cells overlapped. The energy dependence of the GNP physical dose enhancement effect was calculated by simulating the dose deposition in the cells with two energy spectra of 80 kVp and 6 MV. The contribution from Auger electrons was investigated by comparing the two GNP simulation scenarios while activating and deactivating atomic de-excitation processes in Geant4. The physical dose enhancement ratio (DER) of GNP was calculated using the Monte Carlo model. The model has demonstrated that the DER depends on the amount of gold and the position of the gold cluster within the cell. Individual cell regions experienced statistically significant (p < 0.05) change in absorbed dose (DER between 1 and 10) depending on the type of gold geometry used. The DER resulting from gold clusters attached to the cell nucleus had the more significant effect of the two cases (DER ≈ 55). The DER value calculated at 6 MV was shown to be at least an order of magnitude smaller than the DER values calculated for the 80 kVp spectrum. Based on simulations, when 80 kVp photons are used, Auger electrons have a statistically insignificant (p < 0.05) effect on the overall dose increase in the cell. The low energy of the Auger electrons produced prevents them from propagating more than 250-500 nm from the gold cluster and, therefore, has a negligible effect on the overall dose increase due to GNP. The results presented in the current work show that the primary dose enhancement is due to the production of additional photoelectrons.

Evaluation of clustering algorithms at the < 1 GeV energy scale for the electromagnetic calorimeter of the PADME experiment

NASA Astrophysics Data System (ADS)

Leonardi, E.; Piperno, G.; Raggi, M.

2017-10-01

A possible solution to the Dark Matter problem postulates that it interacts with Standard Model particles through a new force mediated by a “portal”. If the new force has a U(1) gauge structure, the “portal” is a massive photon-like vector particle, called dark photon or A’. The PADME experiment at the DAΦNE Beam-Test Facility (BTF) in Frascati is designed to detect dark photons produced in positron on fixed target annihilations decaying to dark matter (e+e-→γA‧) by measuring the final state missing mass. One of the key roles of the experiment will be played by the electromagnetic calorimeter, which will be used to measure the properties of the final state recoil γ. The calorimeter will be composed by 616 21×21×230 mm3 BGO crystals oriented with the long axis parallel to the beam direction and disposed in a roughly circular shape with a central hole to avoid the pile up due to the large number of low angle Bremsstrahlung photons. The total energy and position of the electromagnetic shower generated by a photon impacting on the calorimeter can be reconstructed by collecting the energy deposits in the cluster of crystals interested by the shower. In PADME we are testing two different clustering algorithms, PADME-Radius and PADME-Island, based on two complementary strategies. In this paper we will describe the two algorithms, with the respective implementations, and report on the results obtained with them at the PADME energy scale (< 1 GeV), both with a GEANT4 based simulation and with an existing 5×5 matrix of BGO crystals tested at the DAΦNE BTF.

137 Ba Double Gamma Decay Measurement with GAMMASPHERE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merchán, E.; Moran, K.; Lister, C. J.

2015-05-28

The study of the electromagnetic moments (EM), and decay probability, provides detailed information about nuclear wave functions. The well-know properties of EM interactions are good for extracting information about the motion of nucleons. Higher order EM processes always occur, but are usually too weak to be measured. In the case of a 0 + → 0 + transitions, where a single gamma transition is forbidden, the simultaneous emission of two γ-rays has been studied. An interesting opportunity to further investigate 2-photon emission phenomena is by using a standard 137Cs source populating, via β-decay, the J π = 11/2 - isomericmore » state at 662 keV in 137Ba. In this case, two photon process can have contributions from quadrupole-quadrupole or dipole-octupole multipolarities in direct competition with the high multipolarity M4 decay. Since the yield of the double gamma decay is around six orders of magnitude less than the first order transition, very good statistics are needed in order to observe the phenomena and great care must be taken to suppress the first-order decay. The Gammasphere array is ideal since its configuration allows a good coverage of the angular distribution and the Compton events can be suppressed. Nevertheless the process to understand and eliminate the Compton background is a challenge. Geant4 simulations were carried out to help understand and correct for those factors.« less

GEANT4 and Secondary Particle Production

NASA Technical Reports Server (NTRS)

Patterson, Jeff

2004-01-01

GEANT 4 is a Monte Carlo tool set developed by the High Energy Physics Community (CERN, SLAC, etc) to perform simulations of complex particle detectors. GEANT4 is the ideal tool to study radiation transport and should be applied to space environments and the complex geometries of modern day spacecraft.

Hadronic vs. electromagnetic pulse shape discrimination in CsI(Tl) for high energy physics experiments

NASA Astrophysics Data System (ADS)

Longo, S.; Roney, J. M.

2018-03-01

Pulse shape discrimination using CsI(Tl) scintillators to perform neutral hadron particle identification is explored with emphasis towards application at high energy electron-positron collider experiments. Through the analysis of the pulse shape differences between scintillation pulses from photon and hadronic energy deposits using neutron and proton data collected at TRIUMF, it is shown that the pulse shape variations observed for hadrons can be modelled using a third scintillation component for CsI(Tl), in addition to the standard fast and slow components. Techniques for computing the hadronic pulse amplitudes and shape variations are developed and it is shown that the intensity of the additional scintillation component can be computed from the ionization energy loss of the interacting particles. These pulse modelling and simulation methods are integrated with GEANT4 simulation libraries and the predicted pulse shape for CsI(Tl) crystals in a 5 × 5 array of 5 × 5 × 30 cm3 crystals is studied for hadronic showers from 0.5 and 1 GeV/c KL0 and neutron particles. Using a crystal level and cluster level approach for photon vs. hadron cluster separation we demonstrate proof-of-concept for neutral hadron detection using CsI(Tl) pulse shape discrimination in high energy electron-positron collider experiments.

Multi-layer plastic scintillation detector for intermediate- and high-energy neutrons with n- γ discrimination capability

NASA Astrophysics Data System (ADS)

Yu, L.; Terashima, S.; Ong, H. J.; Chan, P. Y.; Tanihata, I.; Iwamoto, C.; Tran, D. T.; Tamii, A.; Aoi, N.; Fujioka, H.; Gey, G.; Sakaguchi, H.; Sakaue, A.; Sun, B. H.; Tang, T. L.; Wang, T. F.; Watanabe, Y. N.; Zhang, G. X.

2017-09-01

A new type of neutron detector, named Stack Structure Solid organic Scintillator (S4), consisting of multi-layer plastic scintillators with capability to suppress low-energy γ rays under high-counting rate has been constructed and tested. To achieve n- γ discrimination, we exploit the difference in the ranges of the secondary charged particles produced by the interactions of neutrons and γ rays in the scintillator material. The thickness of a plastic scintillator layer was determined based on the results of Monte Carlo simulations using the Geant4 toolkit. With layer thicknesses of 5 mm, we have achieved a good separation between neutrons and γ rays at 5 MeVee threshold setting. We have also determined the detection efficiencies using monoenergetic neutrons at two energies produced by the d + d → n+3He reaction. The results agree well with the Geant4 simulations implementing the Li e ̀ge Intranuclear Cascade hadronic model (INCL++) and the high-precision model of low-energy neutron interactions (NeutronHP).

Calibration of the radiation monitor onboard Akebono using Geant4

NASA Astrophysics Data System (ADS)

Asai, Keiko; Takashima, Takeshi; Koi, Tatsumi; Nagai, Tsugunobu

Natural high-energy electrons and protons (keV-MeV) in the space contaminate the data re-ciprocally. In order to calibrate the energy ranges and to remove data contamination on the radiation monitor (RDM) onboard the Japanese satellite, Akebono (EXOS-D), the detector is investigated using the Geant4 simulation toolkit of computational particle tracing. The semi-polar orbiting Akebono, launched in February 1989, is active now. This satellite has been observed the space environment at altitudes of several thousands km. The RDM instrument onboard Akebono monitors energetic particles in the Earth's radiation belt and gives important data accumulated for about two solar cycles. The data from RDM are for electrons in three energy channels of 0.3 MeV, protons in three energy channels of ¿ 30 MeV, and alpha particles in one energy channels of 15-45 MeV. The energy ranges are however based on information of about 20 years ago so that the data seem to include some errors actuary. In addition, these data include contamination of electrons and protons reciprocally. Actuary it is noticed that the electron data are contaminated by the solar protons but unknown quantitative amount of the contamination. Therefore we need data calibration in order to correct the energy ranges and to remove data contamination. The Geant4 simulation gives information of trajectories of incident and secondary particles whose are interacted with materials. We examine the RDM monitor using the Geant4 simulation. We find from the results that relativistic electrons of MeV behave quite complicatedly because of particle-material interaction in the instrument. The results indicate that efficiencies of detection and contamination are dependent on energy. This study compares the electron data from Akebono RDM with the simultaneous observation of CRRES and tries to lead the values of correction for each of the energy channels.

KASCADE-Grande energy reconstruction based on the lateral density distribution using the QGSJet-II.04 interaction model

NASA Astrophysics Data System (ADS)

Gherghel-Lascu, A.; Apel, W. D.; Arteaga-Velázquez, J. C.; Bekk, K.; Bertania, M.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Fuhrmann, D.; Gils, H. J.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Huber, D.; Huege, T.; Kampert, K.-H.; Kang, D.; Klages, H. O.; Link, K.; Łuczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Oehlschläger, J.; Ostapchenko, S.; Palmieri, N.; Pierog, T.; Rebel, H.; Roth, M.; Schieler, H.; Schoo, S.; Schröder, F. G.; Sima, O.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Zabierowski, J.

2017-06-01

The charged particle densities obtained from CORSIKA simulated EAS, using the QGSJet-II.04 hadronic interaction model are used for primary energy reconstruction. Simulated data are reconstructed by using Lateral Energy Correction Functions computed with a new realistic model of the Grande stations implemented in Geant4.10.

Extraction of the photon beam asymmetry Sigma in pi 0 photoproduction off the proton using the CBELSA/TAPS experiment

NASA Astrophysics Data System (ADS)

Sparks, Nathan Andrew

The CBELSA/TAPS experiment at the electron accelerator ELSA, in Bonn, Germany, was used in order to study the photoproduction of neutral pions off the proton with a linearly polarized photon beam; Neutral pions were reconstructed through their dominant decay mode into two photons. The photons were detected in a barrel/forward electromagnetic calorimeter system which covered 99% of the 4pi solid angle. The Crystal Barrel CsI(Tl) calorimeter detected photons at polar angles from 30° to 168°, while TAPS, a BaF2 spectrometer, covered forward polar angles from 5.8° to 30° and served as a fast trigger; Both calorimeters had complete azimuthal angular coverage. Coherent bremsstrahlung of electrons in a diamond radiator was used to produce a linearly polarized beam of photons with a coherent peak at 1305 or 1610 MeV. The analysis of these two datasets allowed for the measurement of the photon beam asymmetry in the beam photon energy range of 920 to 1680 MeV. For the first time, these results cover the very forward polar angles of the neutral pion. The measurements are compared to the SAID, MAID, and BnGa models and to previous measurements. These new measurements of the photon beam asymmetry contribute to the ongoing experimentally-driven exploration of the N and Delta resonances. The study of strange baryons provides a link between the strong interaction physics of the excited nucleons and the heavy flavor baryons. The upcoming GlueX experiment at Jefferson Lab is expected to provide an opportunity to examine strange baryons in much greater detail than ever before. GEANT-based Monte Carlo simulations of Cascade baryons at the GlueX experiment were conducted in order to better understand the capabilities of this experiment. A proposal, "An initial study of mesons and baryons containing strange quarks with GlueX", was submitted to the 40th Jefferson Lab Program Advisory Committee (PAC), in part, supported by these Cascade baryon simulations. 200 days of additional beam time were approved, with the proposal receiving an A scientific rating.

Modeling of very low frequency (VLF) radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry

NASA Astrophysics Data System (ADS)

Palit, S.; Basak, T.; Mondal, S. K.; Pal, S.; Chakrabarti, S. K.

2013-09-01

X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~60 to 100 km) in excess of what is expected to occur due to a quiet sun. Very low frequency (VLF) radio wave signals reflected from the D-region of the ionosphere are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class flare and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the D-region of the ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the change in VLF signal. We did the modeling of the VLF signal along the NWC (Australia) to IERC/ICSP (India) propagation path and compared the results with observations. The agreement is found to be very satisfactory.

Monte Carlo calculations of thermal neutron capture in gadolinium: a comparison of GEANT4 and MCNP with measurements.

PubMed

Enger, Shirin A; Munck af Rosenschöld, Per; Rezaei, Arash; Lundqvist, Hans

2006-02-01

GEANT4 is a Monte Carlo code originally implemented for high-energy physics applications and is well known for particle transport at high energies. The capacity of GEANT4 to simulate neutron transport in the thermal energy region is not equally well known. The aim of this article is to compare MCNP, a code commonly used in low energy neutron transport calculations and GEANT4 with experimental results and select the suitable code for gadolinium neutron capture applications. To account for the thermal neutron scattering from chemically bound atoms [S(alpha,beta)] in biological materials a comparison of thermal neutron fluence in tissue-like poly(methylmethacrylate) phantom is made with MCNP4B, GEANT4 6.0 patch1, and measurements from the neutron capture therapy (NCT) facility at the Studsvik, Sweden. The fluence measurements agreed with MCNP calculated results considering S(alpha,beta). The location of the thermal neutron peak calculated with MCNP without S(alpha,beta) and GEANT4 is shifted by about 0.5 cm towards a shallower depth and is 25%-30% lower in amplitude. Dose distribution from the gadolinium neutron capture reaction is then simulated by MCNP and compared with measured data. The simulations made by MCNP agree well with experimental results. As long as thermal neutron scattering from chemically bound atoms are not included in GEANT4 it is not suitable for NCT applications.

Characterisation and comparison of event generators for pair conversion: A crucial step for future low energy gamma telescope

NASA Astrophysics Data System (ADS)

Gros, P.; Bernard, D.

2017-05-01

Gamma ray astronomy suffers from a sensitivity gap between 0.1 and 100Mev. With high angular resolution for the electrons, it will also be possible to probe the linear polarisation of the photons. An accurate simulation is necessary to correctly design and compare these detectors. We establish baseline distributions of key kinematic variables as simulated by a 5D, exact down to threshold, and polarised event generator. We compare them to simulations with the low energy electromagnetic models available in Geant4 and in EGS5. We show that different generators give a different picture of the optimal angular resolution of pair telescopes. We also show that, of all the simulations we used, only the full 5D generator describes accurately the angular asymmetry in the case of polarised photons.

A tool to convert CAD models for importation into Geant4

NASA Astrophysics Data System (ADS)

Vuosalo, C.; Carlsmith, D.; Dasu, S.; Palladino, K.; LUX-ZEPLIN Collaboration

2017-10-01

The engineering design of a particle detector is usually performed in a Computer Aided Design (CAD) program, and simulation of the detector’s performance can be done with a Geant4-based program. However, transferring the detector design from the CAD program to Geant4 can be laborious and error-prone. SW2GDML is a tool that reads a design in the popular SOLIDWORKS CAD program and outputs Geometry Description Markup Language (GDML), used by Geant4 for importing and exporting detector geometries. Other methods for outputting CAD designs are available, such as the STEP format, and tools exist to convert these formats into GDML. However, these conversion methods produce very large and unwieldy designs composed of tessellated solids that can reduce Geant4 performance. In contrast, SW2GDML produces compact, human-readable GDML that employs standard geometric shapes rather than tessellated solids. This paper will describe the development and current capabilities of SW2GDML and plans for its enhancement. The aim of this tool is to automate importation of detector engineering models into Geant4-based simulation programs to support rapid, iterative cycles of detector design, simulation, and optimization.

Nuclear reaction measurements on tissue-equivalent materials and GEANT4 Monte Carlo simulations for hadrontherapy

NASA Astrophysics Data System (ADS)

De Napoli, M.; Romano, F.; D'Urso, D.; Licciardello, T.; Agodi, C.; Candiano, G.; Cappuzzello, F.; Cirrone, G. A. P.; Cuttone, G.; Musumarra, A.; Pandola, L.; Scuderi, V.

2014-12-01

When a carbon beam interacts with human tissues, many secondary fragments are produced into the tumor region and the surrounding healthy tissues. Therefore, in hadrontherapy precise dose calculations require Monte Carlo tools equipped with complex nuclear reaction models. To get realistic predictions, however, simulation codes must be validated against experimental results; the wider the dataset is, the more the models are finely tuned. Since no fragmentation data for tissue-equivalent materials at Fermi energies are available in literature, we measured secondary fragments produced by the interaction of a 55.6 MeV u-1 12C beam with thick muscle and cortical bone targets. Three reaction models used by the Geant4 Monte Carlo code, the Binary Light Ions Cascade, the Quantum Molecular Dynamic and the Liege Intranuclear Cascade, have been benchmarked against the collected data. In this work we present the experimental results and we discuss the predictive power of the above mentioned models.

Modernizing the ATLAS simulation infrastructure

NASA Astrophysics Data System (ADS)

Di Simone, A.; CollaborationAlbert-Ludwigs-Universitt Freiburg, ATLAS; Institut, Physikalisches; Br., 79104 Freiburg i.; Germany

2017-10-01

The ATLAS Simulation infrastructure has been used to produce upwards of 50 billion proton-proton collision events for analyses ranging from detailed Standard Model measurements to searches for exotic new phenomena. In the last several years, the infrastructure has been heavily revised to allow intuitive multithreading and significantly improved maintainability. Such a massive update of a legacy code base requires careful choices about what pieces of code to completely rewrite and what to wrap or revise. The initialization of the complex geometry was generalized to allow new tools and geometry description languages, popular in some detector groups. The addition of multithreading requires Geant4-MT and GaudiHive, two frameworks with fundamentally different approaches to multithreading, to work together. It also required enforcing thread safety throughout a large code base, which required the redesign of several aspects of the simulation, including truth, the record of particle interactions with the detector during the simulation. These advances were possible thanks to close interactions with the Geant4 developers.

Comparison of CdZnTe neutron detector models using MCNP6 and Geant4

NASA Astrophysics Data System (ADS)

Wilson, Emma; Anderson, Mike; Prendergasty, David; Cheneler, David

2018-01-01

The production of accurate detector models is of high importance in the development and use of detectors. Initially, MCNP and Geant were developed to specialise in neutral particle models and accelerator models, respectively; there is now a greater overlap of the capabilities of both, and it is therefore useful to produce comparative models to evaluate detector characteristics. In a collaboration between Lancaster University, UK, and Innovative Physics Ltd., UK, models have been developed in both MCNP6 and Geant4 of Cadmium Zinc Telluride (CdZnTe) detectors developed by Innovative Physics Ltd. Herein, a comparison is made of the relative strengths of MCNP6 and Geant4 for modelling neutron flux and secondary γ-ray emission. Given the increasing overlap of the modelling capabilities of MCNP6 and Geant4, it is worthwhile to comment on differences in results for simulations which have similarities in terms of geometries and source configurations.

A Virtual Geant4 Environment

NASA Astrophysics Data System (ADS)

Iwai, Go

2015-12-01

We describe the development of an environment for Geant4 consisting of an application and data that provide users with a more efficient way to access Geant4 applications without having to download and build the software locally. The environment is platform neutral and offers the users near-real time performance. In addition, the environment consists of data and Geant4 libraries built using low-level virtual machine (LLVM) tools which can produce bitcode that can be embedded in HTML and accessed via a browser. The bitcode is downloaded to the local machine via the browser and can then be configured by the user. This approach provides a way of minimising the risk of leaking potentially sensitive data used to construct the Geant4 model and application in the medical domain for treatment planning. We describe several applications that have used this approach and compare their performance with that of native applications. We also describe potential user communities that could benefit from this approach.

CPU time optimization and precise adjustment of the Geant4 physics parameters for a VARIAN 2100 C/D gamma radiotherapy linear accelerator simulation using GAMOS.

PubMed

Arce, Pedro; Lagares, Juan Ignacio

2018-01-25

We have verified the GAMOS/Geant4 simulation model of a 6 MV VARIAN Clinac 2100 C/D linear accelerator by the procedure of adjusting the initial beam parameters to fit the percentage depth dose and cross-profile dose experimental data at different depths in a water phantom. Thanks to the use of a wide range of field sizes, from 2  ×  2 cm 2 to 40  ×  40 cm 2 , a small phantom voxel size and high statistics, fine precision in the determination of the beam parameters has been achieved. This precision has allowed us to make a thorough study of the different physics models and parameters that Geant4 offers. The three Geant4 electromagnetic physics sets of models, i.e. Standard, Livermore and Penelope, have been compared to the experiment, testing the four different models of angular bremsstrahlung distributions as well as the three available multiple-scattering models, and optimizing the most relevant Geant4 electromagnetic physics parameters. Before the fitting, a comprehensive CPU time optimization has been done, using several of the Geant4 efficiency improvement techniques plus a few more developed in GAMOS.

Energy resolution experiments of conical organic scintillators and a comparison with Geant4 simulations

NASA Astrophysics Data System (ADS)

Sosa, C. S.; Thompson, S. J.; Chichester, D. L.; Clarke, S. D.; Di Fulvio, A.; Pozzi, S. A.

2018-08-01

An increase in light-collection efficiency (LCE) improves the energy resolution of scintillator-based detection systems. An improvement in energy resolution can benefit detector performance, for example by lowering the measurement threshold and achieving greater accuracy in light-output calibration. This work shows that LCE can be increased by modifying the scintillator shape to reduce optical-photon reflections, thereby decreasing transmission and absorption likelihood at the reflector boundary. The energy resolution of four organic scintillators (EJ200) were compared: two cones and two right-circular cylinders, all with equal base diameter and height (50 mm). The sides of each shape had two surface conditions: one was polished and the other was ground. Each scintillator was coupled to the center of four photomultiplier tube (PMT) configurations of different diameters. The photocathode response of all PMTs was assessed as a function of position using a small cube (5 mm height) of EJ200. The worst configuration, a highly polished conical scintillator mated to a PMT of equal base diameter, produced a smeared energy spectrum. The cause of spectrum smearing is explored in detail. Results demonstrate that a ground cone had the greatest improvement in energy resolution over a ground cylinder by approximately 16.2% at 478 keVee, when using the largest diameter (127 mm) PMT. This result is attributed to the greater LCE of the cone, its ground surface, and the uniform photocathode response near center of the largest PMT. Optical-photon transport simulations in Geant4 of the cone and cylinder assuming a diffuse reflector and a uniform photocathode were compared to the best experimental configuration and agreed well. If a detector application requires excellent energy resolution above all other considerations, a ground cone on a large PMT is recommended over a cylinder.

GEANT4 simulation of cyclotron radioisotope production in a solid target.

PubMed

Poignant, F; Penfold, S; Asp, J; Takhar, P; Jackson, P

2016-05-01

The use of radioisotopes in nuclear medicine is essential for diagnosing and treating cancer. The optimization of their production is a key factor in maximizing the production yield and minimizing the associated costs. An efficient approach to this problem is the use of Monte Carlo simulations prior to experimentation. By predicting isotopes yields, one can study the isotope of interest expected activity for different energy ranges. One can also study the target contamination with other radioisotopes, especially undesired radioisotopes of the wanted chemical element which are difficult to separate from the irradiated target and might result in increasing the dose when delivering the radiopharmaceutical product to the patient. The aim of this work is to build and validate a Monte Carlo simulation platform using the GEANT4 toolkit to model the solid target system of the South Australian Health and Medical Research Institute (SAHMRI) GE Healthcare PETtrace cyclotron. It includes a GEANT4 Graphical User Interface (GUI) where the user can modify simulation parameters such as the energy, shape and current of the proton beam, the target geometry and material, the foil geometry and material and the time of irradiation. The paper describes the simulation and presents a comparison of simulated and experimental/theoretical yields for various nuclear reactions on an enriched nickel 64 target using the GEANT4 physics model QGSP_BIC_AllHP, a model recently developed to evaluate with high precision the interaction of protons with energies below 200MeV available in Geant4 version 10.1. The simulation yield of the (64)Ni(p,n)(64)Cu reaction was found to be 7.67±0.074 mCi·μA(-1) for a target energy range of 9-12MeV. Szelecsenyi et al. (1993) gives a theoretical yield of 6.71mCi·μA(-1) and an experimental yield of 6.38mCi·μA(-1). The (64)Ni(p,n)(64)Cu cross section obtained with the simulation was also verified against the yield predicted from the nuclear database TENDL and compared to experimental yield obtained from literature. Copyright © 2016 Associazione Italiana di Fisica Medica. All rights reserved.

A large surface neutron and photon detector for civil security applications

NASA Astrophysics Data System (ADS)

De Vita, R.; Ambi, F.; Battaglieri, M.; Osipenko, M.; Piombo, D.; Ricco, G.; Ripani, M.; Taiuti, M.

2010-05-01

The security of ports and transportation is of utmost importance for the development of economy and the security of a nation. Among the necessary actions to ensure the security of ports and borders, the inspection of containers is one of the most time consuming and expensive procedures. Potential threats are the illegal traffic of radioactive materials that could be employed for the construction of weapons, as uranium and plutonium. New techniques for the inspections of containers should be fast, allow the detection and identification of dangerous materials, and be non-invasive, to reduce costs and delays. We propose to build a large surface photon and neutron detector based on plastic scintillator to identify the presence of fissile or fertile material inside a container. The detector consists of scintillator bars, wrapped in thin foils of reflecting material containing gadolinium for neutron capture and arranged in planes separated by few-millimeter-thick lead sheets. The total instrumented surface is a few squared meters. Neutrons emitted by fissile materials are identified by gadolinium capture, which results in a high multiplicity gamma flash with total energy of 8 MeV. Photons emitted by the same source are detected via their Compton interaction in the scintillating material. The discrimination between photons and neutrons is achieved by measuring the number of bars of the detector that measured a signal above threshold. The resulting multiplicity is a clear signature of the particle type. First simulations of the detector response with GEANT4 have shown that a detection efficiency of 20-30% for neutrons emitted by fissile materials and a photon/neutron rejection ratio of more than two orders of magnitude can be achieved. Based on these simulations, the sensitivity of the detector to known amounts of plutonium and uranium was estimated. In this contribution, the conceptual design of the detector will be reviewed, the results of the simulations will be presented and the plan of measurements to be performed on a prototype will be discussed.

GEANT4 distributed computing for compact clusters

NASA Astrophysics Data System (ADS)

Harrawood, Brian P.; Agasthya, Greeshma A.; Lakshmanan, Manu N.; Raterman, Gretchen; Kapadia, Anuj J.

2014-11-01

A new technique for distribution of GEANT4 processes is introduced to simplify running a simulation in a parallel environment such as a tightly coupled computer cluster. Using a new C++ class derived from the GEANT4 toolkit, multiple runs forming a single simulation are managed across a local network of computers with a simple inter-node communication protocol. The class is integrated with the GEANT4 toolkit and is designed to scale from a single symmetric multiprocessing (SMP) machine to compact clusters ranging in size from tens to thousands of nodes. User designed 'work tickets' are distributed to clients using a client-server work flow model to specify the parameters for each individual run of the simulation. The new g4DistributedRunManager class was developed and well tested in the course of our Neutron Stimulated Emission Computed Tomography (NSECT) experiments. It will be useful for anyone running GEANT4 for large discrete data sets such as covering a range of angles in computed tomography, calculating dose delivery with multiple fractions or simply speeding the through-put of a single model.

The PANDA DIRC detectors at FAIR

NASA Astrophysics Data System (ADS)

Schwarz, C.; Ali, A.; Belias, A.; Dzhygadlo, R.; Gerhardt, A.; Götzen, K.; Kalicy, G.; Krebs, M.; Lehmann, D.; Nerling, F.; Patsyuk, M.; Peters, K.; Schepers, G.; Schmitt, L.; Schwiening, J.; Traxler, M.; Zühlsdorf, M.; Böhm, M.; Britting, A.; Eyrich, W.; Lehmann, A.; Pfaffinger, M.; Uhlig, F.; Düren, M.; Etzelmüller, E.; Föhl, K.; Hayrapetyan, A.; Kreutzfeld, K.; Kröck, B.; Merle, O.; Rieke, J.; Schmidt, M.; Wasem, T.; Achenbach, P.; Cardinali, M.; Hoek, M.; Lauth, W.; Schlimme, S.; Sfienti, C.; Thiel, M.; Allison, L.; Hyde, C.

2017-07-01

The PANDA detector at the international accelerator Facility for Antiproton and Ion Research in Europe (FAIR) addresses fundamental questions of hadron physics. An excellent hadronic particle identification (PID) will be accomplished by two DIRC (Detection of Internally Reflected Cherenkov light) counters in the target spectrometer. The design for the barrel region covering polar angles between 22o to 140o is based on the successful BABAR DIRC with several key improvements, such as fast photon timing and a compact imaging region. The novel Endcap Disc DIRC will cover the smaller forward angles between 5o (10o) to 22o in the vertical (horizontal) direction. Both DIRC counters will use lifetime-enhanced microchannel plate PMTs for photon detection in combination with fast readout electronics. Geant4 simulations and tests with several prototypes at various beam facilities have been used to evaluate the designs and validate the expected PID performance of both PANDA DIRC counters.

Relation between lineal energy distribution and relative biological effectiveness for photon beams according to the microdosimetric kinetic model.

PubMed

Okamoto, Hiroyuki; Kanai, Tatsuaki; Kase, Yuki; Matsumoto, Yoshitaka; Furusawa, Yoshiya; Fujita, Yukio; Saitoh, Hidetoshi; Itami, Jun; Kohno, Toshiyuki

2011-01-01

Our cell survival data showed the obvious dependence of RBE on photon energy: The RBE value for 200 kV X-rays was approximately 10% greater than those for mega-voltage photon beams. In radiation therapy using mega-voltage photon beams, the photon energy distribution outside the field is different with that in the radiation field because of a large number of low energy scattering photons. Hence, the RBE values outside the field become greater. To evaluate the increase in RBE, the method of deriving the RBE using the Microdosimetric Kinetic model (MK model) was proposed in this study. The MK model has two kinds of the parameters, tissue-specific parameters and the dose-mean lineal energy derived from the lineal energy distributions measured with a Tissue-Equivalent Proportional Counter (TEPC). The lineal energy distributions with the same geometries of the cell irradiations for 200 kV X-rays, (60)Co γ-rays, and 6 MV X-rays were obtained with the TEPC and Monte Carlo code GEANT4. The measured lineal energy distribution for 200 kV X-rays was quite different from those for mega-voltage photon beams. The dose-mean lineal energy of 200 kV X-rays showed the greatest value, 4.51 keV/µm, comparing with 2.34 and 2.36 keV/µm for (60)Co γ-rays and 6 MV X-rays, respectively. By using the results of the TEPC and cell irradiations, the tissue-specific parameters in the MK model were determined. As a result, the RBE of the photon beams (y(D): 2~5 keV/µm) in arbitrary conditions can be derived by the measurements only or the calculations only of the dose-mean lineal energy.

GEANT4 and PHITS simulations of the shielding of neutrons from the 252Cf source

NASA Astrophysics Data System (ADS)

Shin, Jae Won; Hong, Seung-Woo; Bak, Sang-In; Kim, Do Yoon; Kim, Chong Yeal

2014-09-01

Monte Carlo simulations are performed by using the GEANT4 and the PHITS for studying the neutron-shielding abilities of several materials, such as graphite, iron, polyethylene, NS-4-FR and KRAFTON-HB. As a neutron source, 252Cf is considered. For the Monte Carlo simulations by using the GEANT4, high precision (G4HP) models with the G4NDL 4.2 based on ENDF/B-VII data are used. For the simulations by using the PHITS, the JENDL-4.0 library is used. The neutron-dose-equivalent rates with or without five different shielding materials are estimated and compared with the experimental values. The differences between the shielding abilities calculated by using the GEANT4 with the G4NDL 4.2 and the PHITS with the JENDL-4.0 are found not to be significant for all the cases considered in this work. The neutron-dose-equivalent rates obtained by using the GEANT4 and the PHITS are compared with experimental data and other simulation results. Our neutron-dose-equivalent rates agree well with the experimental dose-equivalent rates, within 20% errors, except for polyethylene. For polyethylene, the discrepancies between our calculations and the experiments are less than 40%, as observed in other simulation results.

Geant4 Modifications for Accurate Fission Simulations

NASA Astrophysics Data System (ADS)

Tan, Jiawei; Bendahan, Joseph

Monte Carlo is one of the methods to simulate the generation and transport of radiation through matter. The most widely used radiation simulation codes are MCNP and Geant4. The simulation of fission production and transport by MCNP has been thoroughly benchmarked. There is an increasing number of users that prefer using Geant4 due to the flexibility of adding features. However, it has been found that Geant4 does not have the proper fission-production cross sections and does not produce the correct fission products. To achieve accurate results for studies in fissionable material applications, Geant4 was modified to correct these inaccuracies and to add new capabilities. The fission model developed by the Lawrence Livermore National Laboratory was integrated into the neutron-fission modeling package. The photofission simulation capability was enabled using the same neutron-fission library under the assumption that nuclei fission in the same way, independent of the excitation source. The modified fission code provides the correct multiplicity of prompt neutrons and gamma rays, and produces delayed gamma rays and neutrons with time and energy dependencies that are consistent with ENDF/B-VII. The delayed neutrons are now directly produced by a custom package that bypasses the fragment cascade model. The modifications were made for U-235, U-238 and Pu-239 isotopes; however, the new framework allows adding new isotopes easily. The SLAC nuclear data library is used for simulation of isotopes with an atomic number above 92 because it is not available in Geant4. Results of the modified Geant4.10.1 package of neutron-fission and photofission for prompt and delayed radiation are compared with ENDFB-VII and with results produced with the original package.

Consistency evaluation between EGSnrc and Geant4 charged particle transport in an equilibrium magnetic field.

PubMed

Yang, Y M; Bednarz, B

2013-02-21

Following the proposal by several groups to integrate magnetic resonance imaging (MRI) with radiation therapy, much attention has been afforded to examining the impact of strong (on the order of a Tesla) transverse magnetic fields on photon dose distributions. The effect of the magnetic field on dose distributions must be considered in order to take full advantage of the benefits of real-time intra-fraction imaging. In this investigation, we compared the handling of particle transport in magnetic fields between two Monte Carlo codes, EGSnrc and Geant4, to analyze various aspects of their electromagnetic transport algorithms; both codes are well-benchmarked for medical physics applications in the absence of magnetic fields. A water-air-water slab phantom and a water-lung-water slab phantom were used to highlight dose perturbations near high- and low-density interfaces. We have implemented a method of calculating the Lorentz force in EGSnrc based on theoretical models in literature, and show very good consistency between the two Monte Carlo codes. This investigation further demonstrates the importance of accurate dosimetry for MRI-guided radiation therapy (MRIgRT), and facilitates the integration of a ViewRay MRIgRT system in the University of Wisconsin-Madison's Radiation Oncology Department.

Consistency evaluation between EGSnrc and Geant4 charged particle transport in an equilibrium magnetic field

NASA Astrophysics Data System (ADS)

Yang, Y. M.; Bednarz, B.

2013-02-01

Following the proposal by several groups to integrate magnetic resonance imaging (MRI) with radiation therapy, much attention has been afforded to examining the impact of strong (on the order of a Tesla) transverse magnetic fields on photon dose distributions. The effect of the magnetic field on dose distributions must be considered in order to take full advantage of the benefits of real-time intra-fraction imaging. In this investigation, we compared the handling of particle transport in magnetic fields between two Monte Carlo codes, EGSnrc and Geant4, to analyze various aspects of their electromagnetic transport algorithms; both codes are well-benchmarked for medical physics applications in the absence of magnetic fields. A water-air-water slab phantom and a water-lung-water slab phantom were used to highlight dose perturbations near high- and low-density interfaces. We have implemented a method of calculating the Lorentz force in EGSnrc based on theoretical models in literature, and show very good consistency between the two Monte Carlo codes. This investigation further demonstrates the importance of accurate dosimetry for MRI-guided radiation therapy (MRIgRT), and facilitates the integration of a ViewRay MRIgRT system in the University of Wisconsin-Madison's Radiation Oncology Department.

Geant4 simulation of clinical proton and carbon ion beams for the treatment of ocular melanomas with the full 3-D pencil beam scanning system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farina, Edoardo; Riccardi, Cristina; Rimoldi, Adele

This work investigates the possibility to use carbon ion beams delivered with active scanning modality, for the treatment of ocular melanomas at the Centro Nazionale di Adroterapia Oncologica (CNAO) in Pavia. The radiotherapy with carbon ions offers many advantages with respect to the radiotherapy with protons or photons, such as a higher relative radio-biological effectiveness (RBE) and a dose release better localized to the tumor. The Monte Carlo (MC) Geant4 10.00 patch-03 toolkit is used to reproduce the complete CNAO extraction beam line, including all the active and passive components characterizing it. The simulation of proton and carbon ion beamsmore » and radiation scanned field is validated against CNAO experimental data. For the irradiation study of the ocular melanoma an eye-detector, representing a model of a human eye, is implemented in the simulation. Each element of the eye is reproduced with its chemical and physical properties. Inside the eye-detector a realistic tumor volume is placed and used as the irradiation target. A comparison between protons and carbon ions eye irradiations allows to study possible treatment benefits if carbon ions are used instead of protons. (authors)« less

High-Resolution and -Efficiency Gamma-Ray Detection for the FRIB Decay Station

NASA Astrophysics Data System (ADS)

Grover, Hannah; Leach, Kyle; Natzke, Connor; FRIB Decay Station Collaboration Collaboration

2017-09-01

As we push our knowledge of nuclear structure to the frontier of the unknown with FRIB, a new high-efficiency, -resolution, and -sensitivity photon-detection device is critical. The FRIB Decay Station Collaboration is working to create a new detector array that meets the needs of the exploratory nature of FRIB by minimizing cost and maximizing efficiency. GEANT4 simulations are being utilized to combine detectors in various configurations to test their feasibility. I will discuss these simulations and how they compare to existing simulations of past-generation decay-spectroscopy equipment. This work has been funded by the DOE Office of Science, Office of Nuclear Physics.

Geomega: MEGAlib's Uniform Geometry and Detector Description Tool for Geant3, MGGPOD, and Geant4

NASA Astrophysics Data System (ADS)

Zoglauer, Andreas C.; Andritschke, R.; Schopper, F.; Wunderer, C. B.

2006-09-01

The Medium Energy Gamma-ray Astronomy library MEGAlib is a set of software tools for the analysis of low to medium energy gamma-ray telescopes, especially Compton telescopes. It comprises all necessary data analysis steps from simulation/measurements via event reconstruction to image reconstruction and enables detailed performance assessments. In the energy range of Compton telescopes (with energy deposits from a few keV up to hundreds of MeV), the Geant Monte-Carlo software packages (Geant3 with its MGGPOD extension as well as Geant4) are widely used. Since each tool has its unique advantages, MEGAlib contains a geometry and detector description library, called Geomega, which allows to use those tools in a uniform way. It incorporates the versatile 3D display facilities available within the ROOT libraries. The same geometry, material, trigger, and detector description can be used for all simulation tools as well as for the later event analysis in the MEGAlib framework. This is done by converting the MEGAlib geometry into the Geant3 or MGGPOD format or directly linking the Geomega library into Geant4. The geometry description can handle most (and can be extended to handle all) volumes common to Geant3, Geant4 and ROOT. In Geomega a list of features is implemented which are especially useful for optimizing detector geometries: It allows to define constants, can handle mathematical operations, enables volume scaling, checks for overlaps of detector volumes, does mass calculations, etc. Used in combination with MEGAlib, Geomega enables discretization, application of detector noise, thresholds, various trigger conditions, defective pixels, etc. The highly modular and completely object-oriented library is written in C++ and based on ROOT. It has been originally developed for the tracking Compton scattering and Pair creation telescope MEGA and has been successfully applied to a wide variety of telescopes, such as ACT, NuSTAR, or GRI.

Intrinsic limits on resolutions in muon- and electron-neutrino charged-current events in the KM3NeT/ORCA detector

NASA Astrophysics Data System (ADS)

Adrián-Martínez, S.; Ageron, M.; Aiello, S.; Albert, A.; Ameli, F.; Anassontzis, E. G.; Andre, M.; Androulakis, G.; Anghinolfi, M.; Anton, G.; Ardid, M.; Avgitas, T.; Barbarino, G.; Barbarito, E.; Baret, B.; Barrios-Mart, J.; Belias, A.; Berbee, E.; van den Berg, A.; Bertin, V.; Beurthey, S.; van Beveren, V.; Beverini, N.; Biagi, S.; Biagioni, A.; Billault, M.; Bondì, M.; Bormuth, R.; Bouhadef, B.; Bourlis, G.; Bourret, S.; Boutonnet, C.; Bouwhuis, M.; Bozza, C.; Bruijn, R.; Brunner, J.; Buis, E.; Buompane, R.; Busto, J.; Cacopardo, G.; Caillat, L.; Calamai, M.; Calvo, D.; Capone, A.; Caramete, L.; Cecchini, S.; Celli, S.; Champion, C.; Cherubini, S.; Chiarella, V.; Chiarelli, L.; Chiarusi, T.; Circella, M.; Classen, L.; Cobas, D.; Cocimano, R.; Coelho, J. A. B.; Coleiro, A.; Colonges, S.; Coniglione, R.; Cordelli, M.; Cosquer, A.; Coyle, P.; Creusot, A.; Cuttone, G.; D'Amato, C.; D'Amico, A.; D'Onofrio, A.; De Bonis, G.; De Sio, C.; Di Palma, I.; Díaz, A. F.; Distefano, C.; Donzaud, C.; Dornic, D.; Dorosti-Hasankiadeh, Q.; Drakopoulou, E.; Drouhin, D.; Durocher, M.; Eberl, T.; Eichie, S.; van Eijk, D.; El Bojaddaini, I.; Elsaesser, D.; Enzenhöfer, A.; Favaro, M.; Fermani, P.; Ferrara, G.; Frascadore, G.; Furini, M.; Fusco, L. A.; Gal, T.; Galatà, S.; Garufi, F.; Gay, P.; Gebyehu, M.; Giacomini, F.; Gialanella, L.; Giordano, V.; Gizani, N.; Gracia, R.; Graf, K.; Grégoire, T.; Grella, G.; Grmek, A.; Guerzoni, M.; Habel, R.; Hallmann, S.; van Haren, H.; Harissopulos, S.; Heid, T.; Heijboer, A.; Heine, E.; Henry, S.; Hernández-Rey, J. J.; Hevinga, M.; Hofestädt, J.; Hugon, C. M. F.; Illuminati, G.; James, C. W.; Jansweijerf, P.; Jongen, M.; de Jong, M.; Kadler, M.; Kalekin, O.; Kappes, A.; Katz, U. F.; Keller, P.; Kieft, G.; Kießling, D.; Koffeman, E. N.; Kooijman, P.; Kouchner, A.; Kreter, M.; Kulikovskiy, V.; Lahmann, R.; Lamare, P.; Larosa, G.; Leisos, A.; Leone, F.; Leonora, E.; Lindsey Clark, M.; Liolios, A.; Llorens Alvarez, C. D.; Lo Presti, D.; Löhner, H.; Lonardo, A.; Lotze, M.; Loucatos, S.; Maccioni, E.; Mannheim, K.; Manzali, M.; Margiotta, A.; Margotti, A.; Marinelli, A.; Maris, O.; Markou, C.; Martínez-Mora, J. A.; Martini, A.; Marzaioli, F.; Mele, R.; Melis, K. W.; Michael, T.; Migliozzi, P.; Migneco, E.; Mijakowski, P.; Miraglia, A.; Mollo, C. M.; Mongelli, M.; Morganti, M.; Moussa, A.; Musico, P.; Musumeci, M.; Navas, S.; Nicolau, C. A.; Olcina, I.; Olivetto, C.; Orlando, A.; Orzelli, A.; Pancaldi, G.; Papaikonomou, A.; Papaleo, R.; Păvălas, G. E.; Peek, H.; Pellegrini, G.; Pellegrino, C.; Perrina, C.; Pfutzner, M.; Piattelli, P.; Pikounis, K.; Pleinert, M.-O.; Poma, G. E.; Popa, V.; Pradier, T.; Pratolongo, F.; Pühlhofer, G.; Pulvirenti, S.; Quinn, L.; Racca, C.; Raffaelli, F.; Randazzo, N.; Rauch, T.; Real, D.; Resvanis, L.; Reubelt, J.; Riccobene, G.; Rossi, C.; Rovelli, A.; Saldaña, M.; Salvadori, I.; Samtleben, D. F. E.; Sánchez García, A.; Sánchez Losa, A.; Sanguineti, M.; Santangelo, A.; Santonocito, D.; Sapienza, P.; Schimmel, F.; Schmelling, J.; Schnabel, J.; Sciacca, V.; Sedita, M.; Seitz, T.; Sgura, I.; Simeone, F.; Sipala, V.; Spisso, B.; Spurio, M.; Stavropoulos, G.; Steijger, J.; Stellacci, S. M.; Stransky, D.; Taiuti, M.; Tayalati, Y.; Terrasi, F.; Tézier, D.; Theraube, S.; Timmer, P.; Tönnis, C.; Trasatti, L.; Travaglini, R.; Trovato, A.; Tsirigotis, A.; Tzamarias, S.; Tzamariudaki, E.; Vallage, B.; Van Elewyck, V.; Vermeulen, J.; Versari, F.; Vicini, P.; Viola, S.; Vivolo, D.; Volkert, M.; Wiggers, L.; Wilms, J.; de Wolf, E.; Zachariadou, K.; Zani, S.; Zornoza, J. D.; Zúñiga, J.

2017-05-01

Studying atmospheric neutrino oscillations in the few-GeV range with a multi-megaton detector promises to determine the neutrino mass hierarchy. This is the main science goal pursued by the future KM3NeT/ORCA water Cherenkov detector in the Mediterranean Sea. In this paper, the processes that limit the obtainable resolution in both energy and direction in charged-current neutrino events in the ORCA detector are investigated. These processes include the composition of the hadronic fragmentation products, the subsequent particle propagation and the photon-sampling fraction of the detector. GEANT simulations of neutrino interactions in seawater produced by GENIE are used to study the effects in the 1-20 GeV range. It is found that fluctuations in the hadronic cascade in conjunction with the variation of the inelasticity y are most detrimental to the resolutions. The effect of limited photon sampling in the detector is of significantly less importance. These results will therefore also be applicable to similar detectors/media, such as those in ice. [Figure not available: see fulltext.

A fast GPU-based Monte Carlo simulation of proton transport with detailed modeling of nonelastic interactions.

PubMed

Wan Chan Tseung, H; Ma, J; Beltran, C

2015-06-01

Very fast Monte Carlo (MC) simulations of proton transport have been implemented recently on graphics processing units (GPUs). However, these MCs usually use simplified models for nonelastic proton-nucleus interactions. Our primary goal is to build a GPU-based proton transport MC with detailed modeling of elastic and nonelastic proton-nucleus collisions. Using the cuda framework, the authors implemented GPU kernels for the following tasks: (1) simulation of beam spots from our possible scanning nozzle configurations, (2) proton propagation through CT geometry, taking into account nuclear elastic scattering, multiple scattering, and energy loss straggling, (3) modeling of the intranuclear cascade stage of nonelastic interactions when they occur, (4) simulation of nuclear evaporation, and (5) statistical error estimates on the dose. To validate our MC, the authors performed (1) secondary particle yield calculations in proton collisions with therapeutically relevant nuclei, (2) dose calculations in homogeneous phantoms, (3) recalculations of complex head and neck treatment plans from a commercially available treatment planning system, and compared with (GEANT)4.9.6p2/TOPAS. Yields, energy, and angular distributions of secondaries from nonelastic collisions on various nuclei are in good agreement with the (GEANT)4.9.6p2 Bertini and Binary cascade models. The 3D-gamma pass rate at 2%-2 mm for treatment plan simulations is typically 98%. The net computational time on a NVIDIA GTX680 card, including all CPU-GPU data transfers, is ∼ 20 s for 1 × 10(7) proton histories. Our GPU-based MC is the first of its kind to include a detailed nuclear model to handle nonelastic interactions of protons with any nucleus. Dosimetric calculations are in very good agreement with (GEANT)4.9.6p2/TOPAS. Our MC is being integrated into a framework to perform fast routine clinical QA of pencil-beam based treatment plans, and is being used as the dose calculation engine in a clinically applicable MC-based IMPT treatment planning system. The detailed nuclear modeling will allow us to perform very fast linear energy transfer and neutron dose estimates on the GPU.

Multiple scattering of 13 and 20 MeV electrons by thin foils: a Monte Carlo study with GEANT, Geant4, and PENELOPE.

PubMed

Vilches, M; García-Pareja, S; Guerrero, R; Anguiano, M; Lallena, A M

2009-09-01

In this work, recent results from experiments and simulations (with EGSnrc) performed by Ross et al. [Med. Phys. 35, 4121-4131 (2008)] on electron scattering by foils of different materials and thicknesses are compared to those obtained using several Monte Carlo codes. Three codes have been used: GEANT (version 3.21), Geant4 (version 9.1, patch03), and PENELOPE (version 2006). In the case of PENELOPE, mixed and fully detailed simulations have been carried out. Transverse dose distributions in air have been obtained in order to compare with measurements. The detailed PENELOPE simulations show excellent agreement with experiment. The calculations performed with GEANT and PENELOPE (mixed) agree with experiment within 3% except for the Be foil. In the case of Geant4, the distributions are 5% narrower compared to the experimental ones, though the agreement is very good for the Be foil. Transverse dose distribution in water obtained with PENELOPE (mixed) is 4% wider than those calculated by Ross et al. using EGSnrc and is 1% narrower than the transverse dose distributions in air, as considered in the experiment. All the codes give a reasonable agreement (within 5%) with the experimental results for all the material and thicknesses studied.

A design of a PET detector using micro-channel plate photomultipliers with transmission-line readout

NASA Astrophysics Data System (ADS)

Kim, H.; Frisch, H.; Chen, C.-T.; Genat, J.-F.; Tang, F.; Moses, W. W.; Choong, W. S.; Kao, C.-M.

2010-10-01

A computer simulation study has been conducted to investigate the feasibility of a positron emission tomography (PET) detector design by using micro-channel plate (MCP) photomultiplier tubes (PMT) with transmission-line (TL) readout and waveform sampling. The detector unit consisted of a 24×24 array of pixelated LSO crystals, each of which was 4×4×25 mm 3 in size, and two 102×102 mm 2 MCP-PMTs coupled to both sides of the scintillator array. The crystal (and TL) pitch was 4.25 mm and reflective medium was inserted between the crystals. The transport of the optical photons inside the scintillator were simulated by using the Geant4 package. The output pulses of the MCP-PMT/TL unit were formed by applying the measured single photo-electron response of the MCP-PMT/TL unit to each individual photon that interacts with the photo-cathode of the MCP-PMT. The waveforms of the pulses at both ends of the TL strips were measured and analyzed to produce energy and timing information for the detected event. An experimental setup was developed by employing a Photonis Planacon MCP-PMT (XP85022) and a prototype TL board for measuring the single photo-electron response of the MCP-PMT/TL. The simulation was validated by comparing the predicted output pulses to measurements obtained with a single MCP-PMT/TL coupled to an LSO crystal exposed to 511 keV gamma rays. The validated simulation was then used to investigate the performance of the proposed new detector design. Our simulation result indicates an energy resolution of ˜11% at 511 keV. When using a 400-600 keV energy window, we obtain a coincidence timing resolution of ˜323 ps FWHM and a coincidence detection efficiency of ˜40% for normally incident 511 keV photons. For the positioning accuracy, it is determined by the pitch of the TLs (and crystals) in the direction normal to the TLs and measured to be ˜2.5 mm in the direction parallel to the TLs. The energy and timing obtained at the front- and back-end of the scintillator array also show differences that are correlated with the depth of interaction of the event.

A Design of a PET Detector Using Micro-Channel Plate Photomultipliers with Transmission-Line Readout.

PubMed

Kim, H; Frisch, H; Chen, C-T; Genat, J-F; Tang, F; Moses, W W; Choong, W S; Kao, C-M

2010-01-01

A computer simulation study has been conducted to investigate the feasibility of a positron emission tomography (PET) detector design by using micro-channel plate (MCP) photomultiplier tubes (PMT) with transmission-line (TL) read-out and waveform sampling. The detector unit consisted of a 24×24 array of pixelated LSO crystals, each of which was 4×4×25 mm(3) in size, and two 102×102 mm(2) MCP-PMTs coupled to both sides of the scintillator array. The crystal (and TL) pitch was 4.25 mm and reflective medium was inserted between the crystals. The transport of the optical photons inside the scintillator were simulated by using the Geant4 package. The output pulses of the MCP-PMT/TL unit were formed by applying the measured single photo-electron response of the MCP-PMT/TL unit to each individual photon that interacts with the photo-cathode of the MCP-PMT. The waveforms of the pulses at both ends of the TL strips were measured and analyzed to produce energy and timing information for the detected event. An experimental setup was developed by employing a Photonis Planacon MCP-PMT (XP85022) and a prototype TL board for measuring the single photo-electron response of the MCP-PMT/TL. The simulation was validated by comparing the predicted output pulses to measurements obtained with a single MCP-PMT/TL coupled to an LSO crystal exposed to 511 keV gamma rays. The validated simulation was then used to investigate the performance of the proposed new detector design. Our simulation result indicates an energy resolution of ~11% at 511 keV. When using a 400-600 keV energy window, we obtain a coincidence timing resolution of ~323 ps FWHM and a coincidence detection efficiency of ~40% for normally-incident 511keV photons. For the positioning accuracy, it is determined by the pitch of the TLs (and crystals) in the direction normal to the TLs and measured to be ~2.5 mm in the direction parallel to the TLs. The energy and timing obtained at the front- and back-end of the scintillator array also show differences that are correlated with the depth of interaction of the event.

Muon Telescope (MuTe): A first study using Geant4

NASA Astrophysics Data System (ADS)

Asorey, H.; Balaguera-Rojas, A.; Calderon-Ardila, R.; Núñez, L. A.; Sanabria-Gómez, J. D.; Súarez-Durán, M.; Tapia, A.

2017-07-01

Muon tomography is based on recording the difference of absorption of muons by matter, as ordinary radiography does for using X-rays. The interaction of cosmic rays with the atmosphere produces extensive air showers which provides an abundant source for atmospheric muons, benefiting various applications of muon tomography, particularly the study of the inner structure of volcanoes. The MuTe (for Muon Telescope) is a hybrid detector composed of scintillation bars and a water Cherenkov detector designed to measure cosmic muon flux crossing volcanic edifices. This detector consists of two scintillator plates (1.44 m2 with 30 x 30 pixels), with a maximum distance of 2.0m of separation. In this work we report the first simulation of the MuTe using GEANT4 -set of simulation tools, based in C++ - that provides information about the interaction between radiation and matter. This computational tool allows us to know the energy deposited by the muons and modeling the response of the scintillators and the water cherenkov detector to the passage of radiation which is crucial to compare to our data analysis.

Timing performance of the silicon PET insert probe

PubMed Central

Studen, A.; Burdette, D.; Chesi, E.; Cindro, V.; Clinthorne, N. H.; Cochran, E.; Grošičar, B.; Kagan, H.; Lacasta, C.; Linhart, V.; Mikuž, M.; Stankova, V.; Weilhammer, P.; Žontar, D.

2010-01-01

Simulation indicates that PET image could be improved by upgrading a conventional ring with a probe placed close to the imaged object. In this paper, timing issues related to a PET probe using high-resistivity silicon as a detector material are addressed. The final probe will consist of several (four to eight) 1-mm thick layers of silicon detectors, segmented into 1 × 1 mm2 pads, each pad equivalent to an independent p + nn+ diode. A proper matching of events in silicon with events of the external ring can be achieved with a good timing resolution. To estimate the timing performance, measurements were performed on a simplified model probe, consisting of a single 1-mm thick detector with 256 square pads (1.4 mm side), coupled with two VATAGP7s, application-specific integrated circuits. The detector material and electronics are the same that will be used for the final probe. The model was exposed to 511 keV annihilation photons from an 22Na source, and a scintillator (LYSO)–PMT assembly was used as a timing reference. Results were compared with the simulation, consisting of four parts: (i) GEANT4 implemented realistic tracking of electrons excited by annihilation photon interactions in silicon, (ii) calculation of propagation of secondary ionisation (electron–hole pairs) in the sensor, (iii) estimation of the shape of the current pulse induced on surface electrodes and (iv) simulation of the first electronics stage. A very good agreement between the simulation and the measurements were found. Both indicate reliable performance of the final probe at timing windows down to 20 ns. PMID:20215445

Timing performance of the silicon PET insert probe.

PubMed

Studen, A; Burdette, D; Chesi, E; Cindro, V; Clinthorne, N H; Cochran, E; Grosicar, B; Kagan, H; Lacasta, C; Linhart, V; Mikuz, M; Stankova, V; Weilhammer, P; Zontar, D

2010-01-01

Simulation indicates that PET image could be improved by upgrading a conventional ring with a probe placed close to the imaged object. In this paper, timing issues related to a PET probe using high-resistivity silicon as a detector material are addressed. The final probe will consist of several (four to eight) 1-mm thick layers of silicon detectors, segmented into 1 x 1 mm(2) pads, each pad equivalent to an independent p + nn+ diode. A proper matching of events in silicon with events of the external ring can be achieved with a good timing resolution. To estimate the timing performance, measurements were performed on a simplified model probe, consisting of a single 1-mm thick detector with 256 square pads (1.4 mm side), coupled with two VATAGP7s, application-specific integrated circuits. The detector material and electronics are the same that will be used for the final probe. The model was exposed to 511 keV annihilation photons from an (22)Na source, and a scintillator (LYSO)-PMT assembly was used as a timing reference. Results were compared with the simulation, consisting of four parts: (i) GEANT4 implemented realistic tracking of electrons excited by annihilation photon interactions in silicon, (ii) calculation of propagation of secondary ionisation (electron-hole pairs) in the sensor, (iii) estimation of the shape of the current pulse induced on surface electrodes and (iv) simulation of the first electronics stage. A very good agreement between the simulation and the measurements were found. Both indicate reliable performance of the final probe at timing windows down to 20 ns.

SU-F-T-507: Modeling Cerenkov Emissions From Medical Linear Accelerators: A Monte Carlo Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shrock, Z; Oldham, M; Adamson, J

2016-06-15

Purpose: Cerenkov emissions are a natural byproduct of MV radiotherapy but are typically ignored as inconsequential. However, Cerenkov photons may be useful for activation of drugs such as psoralen. Here, we investigate Cerenkov radiation from common radiotherapy beams using Monte Carlo simulations. Methods: GAMOS, a GEANT4-based framework for Monte Carlo simulations, was used to model 6 and 18MV photon beams from a Varian medical linac. Simulations were run to track Cerenkov production from these beams when irradiating a 50cm radius sphere of water. Electron contamination was neglected. 2 million primary photon histories were run for each energy, and values scoredmore » included integral dose and total track length of Cerenkov photons between 100 and 400 nm wavelength. By lowering process energy thresholds, simulations included low energy Bremsstrahlung photons to ensure comprehensive evaluation of UV production in the medium. Results: For the same number of primary photons, UV Cerenkov production for 18MV was greater than 6MV by a factor of 3.72 as determined by total track length. The total integral dose was a factor of 2.31 greater for the 18MV beam. Bremsstrahlung photons were a negligibly small component of photons in the wavelength range of interest, comprising 0.02% of such photons. Conclusion: Cerenkov emissions in water are 1.6x greater for 18MV than 6MV for the same integral dose. Future work will expand the analysis to include optical properties of tissues, and to investigate strategies to maximize Cerenkov emission per unit dose for MV radiotherapy.« less

A Novel Method for gamma - text{photons} Depth-of-Interaction Detection in Monolithic Scintillation Crystals

NASA Astrophysics Data System (ADS)

Pani, Roberto; Bettiol, Marco; Preziosi, Enrico; Borrazzo, Cristian; Pellegrini, Rosanna; González, Antonio J.; Conde, Pablo; Cinti, Maria Nerina; Fabbri, Andrea; Di Castro, Elisabetta; Majewski, Stan

2016-10-01

Achieved spatial resolution of the PET systems is often limited by the parallax error due to the lack of information about the Depth of Interaction (DoI) inside the crystal of the incoming 511 keV annihilation photons. The smaller the diameter of the PET ring and the thicker the scintillator are, the more this error affects imaging performance. In this work, a DoI calculator suitable for monolithic scintillation crystals and based on the shape of the scintillation light distribution at the photodetector surface has been proposed. To test the estimator performance, a test PET module with a 50 × 50 × 20 mm monolithic LYSO crystal coupled to a 12 × 12 SiPM array has been employed. In addition, for calibration and validation of the method, Geant4 simulations have been also used. The key result of the application of the proposed DoI estimator is obtaining a continuous DoI estimation with an average DoI resolution of about 5 mm in the 20 mm-thick crystal. Benefiting from the DoI estimation capabilities of the method, it has been also possible to achieve additional important goals, first of all reducing the parallax error. First, because the scintillation light collection varies as a function of the 3D position of the interaction of the annihilation photon inside the crystal, a method to correct this response variation via a proper 3D look-up-table is proposed. This has led to an improvement of about 35% in energy resolution. Moreover, a DoI-dependent position algorithm has been proposed, allowing an improvement of both planar (X-Y) position linearity and planar spatial resolution. This algorithm is specifically developed for the rows/columns multi-channel readout logic, that reduces the number of independent channels from N × N to N + N, where N is the number of SiPM photodetection elements (12 in our case) in each row and column. This development was performed in the framework of the MindView PET/MilI brain imaging project.

Geant4 hadronic physics validation with ATLAS Tile Calorimeter test-beam data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alexa, C.; Constantinescu, S.; Dita, S.

We present comparison studies between Geant4 shower packages and ATLAS Tile Calorimeter test-beam data collected at CERN in H8 beam line at the SPS. Emphasis is put on hadronic physics lists and data concerning differences between Tilecal response to pions and protons of same energy. The ratio between the pure hadronic fraction of pion and the pure hadronic fraction of proton F{sub h}{sup {pi}}/F{sub h}{sup p} was estimated with Tilecal test-beam data and compared with Geant4 simulations.

Analysis of GEANT4 Physics List Properties in the 12 GeV MOLLER Simulation Framework

NASA Astrophysics Data System (ADS)

Haufe, Christopher; Moller Collaboration

2013-10-01

To determine the validity of new physics beyond the scope of the electroweak theory, nuclear physicists across the globe have been collaborating on future endeavors that will provide the precision needed to confirm these speculations. One of these is the MOLLER experiment - a low-energy particle experiment that will utilize the 12 GeV upgrade of Jefferson Lab's CEBAF accelerator. The motivation of this experiment is to measure the parity-violating asymmetry of scattered polarized electrons off unpolarized electrons in a liquid hydrogen target. This measurement would allow for a more precise determination of the electron's weak charge and weak mixing angle. While still in its planning stages, the MOLLER experiment requires a detailed simulation framework in order to determine how the project should be run in the future. The simulation framework for MOLLER, called ``remoll'', is written in GEANT4 code. As a result, the simulation can utilize a number of GEANT4 coded physics lists that provide the simulation with a number of particle interaction constraints based off of different particle physics models. By comparing these lists with one another using the data-analysis application ROOT, the most optimal physics list for the MOLLER simulation can be determined and implemented. This material is based upon work supported by the National Science Foundation under Grant No. 714001.

Real-time, ray casting-based scatter dose estimation for c-arm x-ray system.

PubMed

Alnewaini, Zaid; Langer, Eric; Schaber, Philipp; David, Matthias; Kretz, Dominik; Steil, Volker; Hesser, Jürgen

2017-03-01

Dosimetric control of staff exposure during interventional procedures under fluoroscopy is of high relevance. In this paper, a novel ray casting approximation of radiation transport is presented and the potential and limitation vs. a full Monte Carlo transport and dose measurements are discussed. The x-ray source of a Siemens Axiom Artix C-arm is modeled by a virtual source model using single Gaussian-shaped source. A Geant4-based Monte Carlo simulation determines the radiation transport from the source to compute scatter from the patient, the table, the ceiling and the floor. A phase space around these scatterers stores all photon information. Only those photons are traced that hit a surface of phantom that represents medical staff in the treatment room, no indirect scattering is considered; and a complete dose deposition on the surface is calculated. To evaluate the accuracy of the approximation, both experimental measurements using Thermoluminescent dosimeters (TLDs) and a Geant4-based Monte Carlo simulation of dose depositing for different tube angulations of the C-arm from cranial-caudal angle 0° and from LAO (Left Anterior Oblique) 0°-90° are realized. Since the measurements were performed on both sides of the table, using the symmetry of the setup, RAO (Right Anterior Oblique) measurements were not necessary. The Geant4-Monte Carlo simulation agreed within 3% with the measured data, which is within the accuracy of measurement and simulation. The ray casting approximation has been compared to TLD measurements and the achieved percentage difference was -7% for data from tube angulations 45°-90° and -29% from tube angulations 0°-45° on the side of the x-ray source, whereas on the opposite side of the x-ray source, the difference was -83.8% and -75%, respectively. Ray casting approximation for only LAO 90° was compared to a Monte Carlo simulation, where the percentage differences were between 0.5-3% on the side of the x-ray source where the highest dose usually detected was mainly from primary scattering (photons), whereas percentage differences between 2.8-20% are found on the side opposite to the x-ray source, where the lowest doses were detected. Dose calculation time of our approach was 0.85 seconds. The proposed approach yields a fast scatter dose estimation where we could run the Monte Carlo simulation only once for each x-ray tube angulation to get the Phase Space Files (PSF) for being used later by our ray casting approach to calculate the dose from only photons which will hit an movable elliptical cylinder shaped phantom and getting an output file for the positions of those hits to be used for visualizing the scatter dose propagation on the phantom surface. With dose calculation times of less than one second, we are saving much time compared to using a Monte Carlo simulation instead. With our approach, larger deviations occur only in regions with very low doses, whereas it provides a high precision in high-dose regions. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Photon small-field measurements with a CMOS active pixel sensor.

PubMed

Spang, F Jiménez; Rosenberg, I; Hedin, E; Royle, G

2015-06-07

In this work the dosimetric performance of CMOS active pixel sensors for the measurement of small photon beams is presented. The detector used consisted of an array of 520  × 520 pixels on a 25 µm pitch. Dosimetric parameters measured with this sensor were compared with data collected with an ionization chamber, a film detector and GEANT4 Monte Carlo simulations. The sensor performance for beam profiles measurements was evaluated for field sizes of 0.5  × 0.5 cm(2). The high spatial resolution achieved with this sensor allowed the accurate measurement of profiles, beam penumbrae and field size under lateral electronic disequilibrium. Field size and penumbrae agreed within 5.4% and 2.2% respectively with film measurements. Agreements with ionization chambers better than 1.0% were obtained when measuring tissue-phantom ratios. Output factor measurements were in good agreement with ionization chamber and Monte Carlo simulation. The data obtained from this imaging sensor can be easily analyzed to extract dosimetric information. The results presented in this work are promising for the development and implementation of CMOS active pixel sensors for dosimetry applications.

Particle radiation transport and effects models from research to space weather operations

NASA Astrophysics Data System (ADS)

Santin, Giovanni; Nieminen, Petteri; Rivera, Angela; Ibarmia, Sergio; Truscott, Pete; Lei, Fan; Desorgher, Laurent; Ivanchenko, Vladimir; Kruglanski, Michel; Messios, Neophytos

Assessment of risk from potential radiation-induced effects to space systems requires knowledge of both the conditions of the radiation environment and of the impact of radiation on sensi-tive spacecraft elements. During sensitivity analyses, test data are complemented by models to predict how external radiation fields are transported and modified in spacecraft materials. Radiation transport is still itself a subject of research and models are continuously improved to describe the physical interactions that take place when particles pass through shielding materi-als or hit electronic systems or astronauts, sometimes down to nanometre-scale interactions of single particles with deep sub-micron technologies or DNA structures. In recent years, though, such radiation transport models are transitioning from being a research subject by itself, to being widely used in the space engineering domain and finally being directly applied in the context of operation of space weather services. A significant "research to operations" (R2O) case is offered by Geant4, an open source toolkit initially developed and used in the context of fundamental research in high energy physics. Geant4 is also being used in the space domain, e.g. for modelling detector responses in science payloads, but also for studying the radiation environment itself, with subjects ranging from cosmic rays, to solar energetic particles in the heliosphere, to geomagnetic shielding. Geant4-based tools are now becoming more and more integrated in spacecraft design procedures, also through user friendly interfaces such as SPEN-VIS. Some examples are given by MULASSIS, offering multi-layered shielding analysis capa-bilities in realistic spacecraft materials, or GEMAT, focused on micro-dosimetry in electronics, or PLANETOCOSMICS, describing the interaction of the space environment with planetary magneto-and atmospheres, or GRAS, providing a modular and easy to use interface to various analysis types in simple or complex and realistic 3D geometry models. GRAS will also be part of the space weather SEISOP system for supplying near-real-time detailed information on the interaction of the space radiation environment with selected spacecraft elements.

CAD-based Automatic Modeling Method for Geant4 geometry model Through MCAM

NASA Astrophysics Data System (ADS)

Wang, Dong; Nie, Fanzhi; Wang, Guozhong; Long, Pengcheng; LV, Zhongliang; LV, Zhongliang

2014-06-01

Geant4 is a widely used Monte Carlo transport simulation package. Before calculating using Geant4, the calculation model need be established which could be described by using Geometry Description Markup Language (GDML) or C++ language. However, it is time-consuming and error-prone to manually describe the models by GDML. Automatic modeling methods have been developed recently, but there are some problem existed in most of present modeling programs, specially some of them were not accurate or adapted to specifically CAD format. To convert the GDML format models to CAD format accurately, a Geant4 Computer Aided Design (CAD) based modeling method was developed for automatically converting complex CAD geometry model into GDML geometry model. The essence of this method was dealing with CAD model represented with boundary representation (B-REP) and GDML model represented with constructive solid geometry (CSG). At first, CAD model was decomposed to several simple solids which had only one close shell. And then the simple solid was decomposed to convex shell set. Then corresponding GDML convex basic solids were generated by the boundary surfaces getting from the topological characteristic of a convex shell. After the generation of these solids, GDML model was accomplished with series boolean operations. This method was adopted in CAD/Image-based Automatic Modeling Program for Neutronics & Radiation Transport (MCAM), and tested with several models including the examples in Geant4 install package. The results showed that this method could convert standard CAD model accurately, and can be used for Geant4 automatic modeling.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Constantin, M; Sawkey, D; Johnsen, S

Purpose: To validate the physics parameters of a Monte Carlo model for patient plane leakage calculations on the 6MV Unique linac by comparing the simulations against IEC patient plane leakage measurements. The benchmarked model can further be used for shielding design optimization, to predict leakage in the proximity of intended treatment fields, reduce the system weight and cost, and improve components reliability. Methods: The treatment head geometry of the Unique linac was simulated in Geant4 (v9.4.p02 with “Opt3” standard electromagnetic physics list) based on CAD drawings of all collimation and shielding components projected from the target to the area withinmore » 2m from isocenter. A 4×4m2 scorer was inserted 1m from the target in the patient plane and multiple phase space files were recorded by performing a 40-node computing cluster simulation on the EC2 cloud. The photon energy fluence was calculated relative to the value at isocenter for a 10×10cm2 field using 10×10mm2 bins. Tungsten blocks were parked accordingly to represent MLC120. The secondary particle contamination to patient plane was eliminated by “killing” those particles prior to the primary collimator entrance using a “kill-plane”, which represented the upper head shielding components not being modeled. Both IEC patient-plane leakage and X/Y-jaws transmission were simulated. Results: The contribution of photons to energy fluence was 0.064% on average, in excellent agreement with the experimental data available at 0.5, 1.0, and 1.5m from isocenter, characterized by an average leakage of 0.045% and a maximum leakage of 0.085%. X- and Y-jaws transmissions of 0.43% and 0.44% were found in good agreement with measurements of 0.48% and 0.43%, respectively. Conclusion: A Geant4 model based on energy fluence calculations for the 6MV Unique linac was created and validated using IEC patient plane leakage measurements. The “kill-plane” has effectively eliminated electron contamination to patient plane in these simulations.« less

Initial development of goCMC: a GPU-oriented fast cross-platform Monte Carlo engine for carbon ion therapy

PubMed Central

Qin, Nan; Pinto, Marco; Tian, Zhen; Dedes, Georgios; Pompos, Arnold; Jiang, Steve B.; Parodi, Katia; Jia, Xun

2017-01-01

Monte Carlo (MC) simulation is considered as the most accurate method for calculation of absorbed dose and fundamental physics quantities related to biological effects in carbon ion therapy. To improve its computational efficiency, we have developed a GPU-oriented fast MC package named goCMC, for carbon therapy. goCMC simulates particle transport in voxelized geometry with kinetic energy up to 450 MeV/u. Class II condensed history simulation scheme with a continuous slowing down approximation was employed. Energy straggling and multiple scattering were modeled. δ-electrons were terminated with their energy locally deposited. Four types of nuclear interactions were implemented in goCMC, i.e., carbon-hydrogen, carbon-carbon, carbon-oxygen and carbon-calcium inelastic collisions. Total cross section data from Geant4 were used. Secondary particles produced in these interactions were sampled according to particle yield with energy and directional distribution data derived from Geant4 simulation results. Secondary charged particles were transported following the condensed history scheme, whereas secondary neutral particles were ignored. goCMC was developed under OpenCL framework and is executable on different platforms, e.g. GPU and multi-core CPU. We have validated goCMC with Geant4 in cases with different beam energy and phantoms including four homogeneous phantoms, one heterogeneous half-slab phantom, and one patient case. For each case 3 × 107 carbon ions were simulated, such that in the region with dose greater than 10% of maximum dose, the mean relative statistical uncertainty was less than 1%. Good agreements for dose distributions and range estimations between goCMC and Geant4 were observed. 3D gamma passing rates with 1%/1 mm criterion were over 90% within 10%) isodose line except in two extreme cases, and those with 2%/1 mm criterion were all over 96%. Efficiency and code portability were tested with different GPUs and CPUs. Depending on the beam energy and voxel size, the computation time to simulate 107 carbons was 9.9–125 sec, 2.5–50 sec and 60–612 sec on an AMD Radeon GPU card, an NVidia GeForce GTX 1080 GPU card and an Intel Xeon E5-2640 CPU, respectively. The combined accuracy, efficiency and portability make goCMC attractive for research and clinical applications in carbon ion therapy. PMID:28140352

Initial development of goCMC: a GPU-oriented fast cross-platform Monte Carlo engine for carbon ion therapy

NASA Astrophysics Data System (ADS)

Qin, Nan; Pinto, Marco; Tian, Zhen; Dedes, Georgios; Pompos, Arnold; Jiang, Steve B.; Parodi, Katia; Jia, Xun

2017-05-01

Monte Carlo (MC) simulation is considered as the most accurate method for calculation of absorbed dose and fundamental physics quantities related to biological effects in carbon ion therapy. To improve its computational efficiency, we have developed a GPU-oriented fast MC package named goCMC, for carbon therapy. goCMC simulates particle transport in voxelized geometry with kinetic energy up to 450 MeV u-1. Class II condensed history simulation scheme with a continuous slowing down approximation was employed. Energy straggling and multiple scattering were modeled. δ-electrons were terminated with their energy locally deposited. Four types of nuclear interactions were implemented in goCMC, i.e. carbon-hydrogen, carbon-carbon, carbon-oxygen and carbon-calcium inelastic collisions. Total cross section data from Geant4 were used. Secondary particles produced in these interactions were sampled according to particle yield with energy and directional distribution data derived from Geant4 simulation results. Secondary charged particles were transported following the condensed history scheme, whereas secondary neutral particles were ignored. goCMC was developed under OpenCL framework and is executable on different platforms, e.g. GPU and multi-core CPU. We have validated goCMC with Geant4 in cases with different beam energy and phantoms including four homogeneous phantoms, one heterogeneous half-slab phantom, and one patient case. For each case 3× {{10}7} carbon ions were simulated, such that in the region with dose greater than 10% of maximum dose, the mean relative statistical uncertainty was less than 1%. Good agreements for dose distributions and range estimations between goCMC and Geant4 were observed. 3D gamma passing rates with 1%/1 mm criterion were over 90% within 10% isodose line except in two extreme cases, and those with 2%/1 mm criterion were all over 96%. Efficiency and code portability were tested with different GPUs and CPUs. Depending on the beam energy and voxel size, the computation time to simulate {{10}7} carbons was 9.9-125 s, 2.5-50 s and 60-612 s on an AMD Radeon GPU card, an NVidia GeForce GTX 1080 GPU card and an Intel Xeon E5-2640 CPU, respectively. The combined accuracy, efficiency and portability make goCMC attractive for research and clinical applications in carbon ion therapy.

Initial development of goCMC: a GPU-oriented fast cross-platform Monte Carlo engine for carbon ion therapy.

PubMed

Qin, Nan; Pinto, Marco; Tian, Zhen; Dedes, Georgios; Pompos, Arnold; Jiang, Steve B; Parodi, Katia; Jia, Xun

2017-05-07

Monte Carlo (MC) simulation is considered as the most accurate method for calculation of absorbed dose and fundamental physics quantities related to biological effects in carbon ion therapy. To improve its computational efficiency, we have developed a GPU-oriented fast MC package named goCMC, for carbon therapy. goCMC simulates particle transport in voxelized geometry with kinetic energy up to 450 MeV u -1 . Class II condensed history simulation scheme with a continuous slowing down approximation was employed. Energy straggling and multiple scattering were modeled. δ-electrons were terminated with their energy locally deposited. Four types of nuclear interactions were implemented in goCMC, i.e. carbon-hydrogen, carbon-carbon, carbon-oxygen and carbon-calcium inelastic collisions. Total cross section data from Geant4 were used. Secondary particles produced in these interactions were sampled according to particle yield with energy and directional distribution data derived from Geant4 simulation results. Secondary charged particles were transported following the condensed history scheme, whereas secondary neutral particles were ignored. goCMC was developed under OpenCL framework and is executable on different platforms, e.g. GPU and multi-core CPU. We have validated goCMC with Geant4 in cases with different beam energy and phantoms including four homogeneous phantoms, one heterogeneous half-slab phantom, and one patient case. For each case [Formula: see text] carbon ions were simulated, such that in the region with dose greater than 10% of maximum dose, the mean relative statistical uncertainty was less than 1%. Good agreements for dose distributions and range estimations between goCMC and Geant4 were observed. 3D gamma passing rates with 1%/1 mm criterion were over 90% within 10% isodose line except in two extreme cases, and those with 2%/1 mm criterion were all over 96%. Efficiency and code portability were tested with different GPUs and CPUs. Depending on the beam energy and voxel size, the computation time to simulate [Formula: see text] carbons was 9.9-125 s, 2.5-50 s and 60-612 s on an AMD Radeon GPU card, an NVidia GeForce GTX 1080 GPU card and an Intel Xeon E5-2640 CPU, respectively. The combined accuracy, efficiency and portability make goCMC attractive for research and clinical applications in carbon ion therapy.

Monte carlo study of MOSFET packaging, optimised for improved energy response: single MOSFET filtration.

PubMed

Othman, M A R; Cutajar, D L; Hardcastle, N; Guatelli, S; Rosenfeld, A B

2010-09-01

Monte Carlo simulations of the energy response of a conventionally packaged single metal-oxide field effect transistors (MOSFET) detector were performed with the goal of improving MOSFET energy dependence for personal accident or military dosimetry. The MOSFET detector packaging was optimised. Two different 'drop-in' design packages for a single MOSFET detector were modelled and optimised using the GEANT4 Monte Carlo toolkit. Absorbed photon dose simulations of the MOSFET dosemeter placed in free-air response, corresponding to the absorbed doses at depths of 0.07 mm (D(w)(0.07)) and 10 mm (D(w)(10)) in a water equivalent phantom of size 30 x 30 x 30 cm(3) for photon energies of 0.015-2 MeV were performed. Energy dependence was reduced to within + or - 60 % for photon energies 0.06-2 MeV for both D(w)(0.07) and D(w)(10). Variations in the response for photon energies of 15-60 keV were 200 and 330 % for D(w)(0.07) and D(w)(10), respectively. The obtained energy dependence was reduced compared with that for conventionally packaged MOSFET detectors, which usually exhibit a 500-700 % over-response when used in free-air geometry.

Technical Note: On maximizing Cherenkov emissions from medical linear accelerators.

PubMed

Shrock, Zachary; Yoon, Suk W; Gunasingha, Rathnayaka; Oldham, Mark; Adamson, Justus

2018-04-19

Cherenkov light during MV radiotherapy has recently found imaging and therapeutic applications but is challenged by relatively low fluence. Our purpose is to investigate the feasibility of increasing Cherenkov light production during MV radiotherapy by increasing photon energy and applying specialized beam-hardening filtration. GAMOS 5.0.0, a GEANT4-based framework for Monte Carlo simulations, was used to model standard clinical linear accelerator primary photon beams. The photon source was incident upon a 17.8 cm 3 cubic water phantom with a 94 cm source to surface distance. Dose and Cherenkov production was determined at depths of 3-9 cm. Filtration was simulated 15 cm below the photon beam source. Filter materials included aluminum, iron, and copper with thicknesses of 2-20 cm. Histories used depended on the level of attenuation from the filter, ranging from 100 million to 2 billion. Comparing average dose per history also allowed for evaluation of dose-rate reduction for different filters. Overall, increasing photon beam energy is more effective at improving Cherenkov production per unit dose than is filtration, with a standard 18 MV beam yielding 3.3-4.0× more photons than 6 MV. Introducing an aluminum filter into an unfiltered 2400 cGy/min 10 MV beam increases the Cherenkov production by 1.6-1.7×, while maintaining a clinical dose rate of 300 cGy/min, compared to increases of ~1.5× for iron and copper. Aluminum was also more effective than the standard flattening filter, with the increase over the unfiltered beam being 1.4-1.5× (maintaining 600 cGy/min dose rate) vs 1.3-1.4× for the standard flattening filter. Applying a 10 cm aluminum filter to a standard 18 MV, photon beam increased the Cherenkov production per unit dose to 3.9-4.3× beyond that of 6 MV (vs 3.3-4.0× for 18 MV with no aluminum filter). Through a combination of increasing photon energy and applying specialized beam-hardening filtration, the amount of Cherenkov photons per unit radiotherapy dose can be increased substantially. © 2018 American Association of Physicists in Medicine.

Geant4 Computing Performance Benchmarking and Monitoring

DOE PAGES

Dotti, Andrea; Elvira, V. Daniel; Folger, Gunter; ...

2015-12-23

Performance evaluation and analysis of large scale computing applications is essential for optimal use of resources. As detector simulation is one of the most compute intensive tasks and Geant4 is the simulation toolkit most widely used in contemporary high energy physics (HEP) experiments, it is important to monitor Geant4 through its development cycle for changes in computing performance and to identify problems and opportunities for code improvements. All Geant4 development and public releases are being profiled with a set of applications that utilize different input event samples, physics parameters, and detector configurations. Results from multiple benchmarking runs are compared tomore » previous public and development reference releases to monitor CPU and memory usage. Observed changes are evaluated and correlated with code modifications. Besides the full summary of call stack and memory footprint, a detailed call graph analysis is available to Geant4 developers for further analysis. The set of software tools used in the performance evaluation procedure, both in sequential and multi-threaded modes, include FAST, IgProf and Open|Speedshop. In conclusion, the scalability of the CPU time and memory performance in multi-threaded application is evaluated by measuring event throughput and memory gain as a function of the number of threads for selected event samples.« less

The simulation of the LANFOS-H food radiation contamination detector using Geant4 package

NASA Astrophysics Data System (ADS)

Piotrowski, Lech Wiktor; Casolino, Marco; Ebisuzaki, Toshikazu; Higashide, Kazuhiro

2015-02-01

Recent incident in the Fukushima power plant caused a growing concern about the radiation contamination and resulted in lowering the Japanese limits for the permitted amount of 137Cs in food to 100 Bq/kg. To increase safety and ease the concern we are developing LANFOS (Large Food Non-destructive Area Sampler)-a compact, easy to use detector for assessment of radiation in food. Described in this paper LANFOS-H has a 4 π coverage to assess the amount of 137Cs present, separating it from the possible 40K food contamination. Therefore, food samples do not have to be pre-processed prior to a test and can be consumed after measurements. It is designed for use by non-professionals in homes and small institutions such as schools, showing safety of the samples, but can be also utilized by specialists providing radiation spectrum. Proper assessment of radiation in food in the apparatus requires estimation of the γ conversion factor of the detectors-how many γ photons will produce a signal. In this paper we show results of the Monte Carlo estimation of this factor for various approximated shapes of fish, vegetables and amounts of rice, performed with Geant4 package. We find that the conversion factor combined from all the detectors is similar for all food types and is around 37%, varying maximally by 5% with sample length, much less than for individual detectors. The different inclinations and positions of samples in the detector introduce uncertainty of 1.4%. This small uncertainty validates the concept of a 4 π non-destructive apparatus.

Collimation study for LCLS

DOE PAGES

Marin, E.; Raubenhaimer, T.; Welch, J.; ...

2017-06-13

In this study we investigate the power deposition along the undulator section of the SLAC Linac Coherent Light Source (LCLS) due to the primary e¯ -beam but also due to potential secondary particles. The expected beam distribution after the LCLS injector is deliberately broadened as an approximated representation of the beam halo. Secondary particles, as e +, e¯ and photons, are generated as a result of tracking the intercepted beam through a dense material. This process is carried out by means of GEANT-4, which has been convoluted into our main tracking engine, LUCRETIA. Simulations show no losses along the undulatormore » section when assuming the nominal primary beam and collimator gaps. However when opening the gaps of collimators located at the first collimator section, by 25%, the fattened beam is partially intercepted by the second collimator section, which is aligned to the undulators. Secondary particles, mostly photons generated at the second collimator section, deposit their energy along the undulator section, at a rate of the order of a milliwatt.« less

Collimation study for LCLS

NASA Astrophysics Data System (ADS)

Marin, E.; Raubenhaimer, T.; Welch, J.; White, G.

2017-09-01

In this paper we investigate the power deposition along the undulator section of the SLAC Linac Coherent Light Source (LCLS) due to the primary e--beam but also due to potential secondary particles. The expected beam distribution after the LCLS injector is deliberately broadened as an approximated representation of the beam halo. Secondary particles, as e+, e- and photons, are generated as a result of tracking the intercepted beam through a dense material. This process is carried out by means of GEANT-4, which has been convoluted into our main tracking engine, LUCRETIA. Simulations show no losses along the undulator section when assuming the nominal primary beam and collimator gaps. However when opening the gaps of collimators located at the first collimator section, by 25%, the fattened beam is partially intercepted by the second collimator section, which is aligned to the undulators. Secondary particles, mostly photons generated at the second collimator section, deposit their energy along the undulator section, at a rate of the order of a milliwatt.

The radiation environment on the Moon from galactic cosmic rays in a lunar habitat.

PubMed

Jia, Y; Lin, Z W

2010-02-01

We calculated how the radiation environment in a habitat on the surface of the Moon would have depended on the thickness of the habitat in the 1977 galactic cosmic-ray environment. The Geant4 Monte Carlo transport code was used, and a hemispherical dome made of lunar regolith was used to simulate the lunar habitat. We investigated the effective dose from primary and secondary particles including nuclei from protons up to nickel, neutrons, charged pions, photons, electrons and positrons. The total effective dose showed a strong decrease with the thickness of the habitat dome. However, the effective dose values from secondary neutrons, charged pions, photons, electrons and positrons all showed a strong increase followed by a gradual decrease with the habitat thickness. The fraction of the summed effective dose from these secondary particles in the total effective dose increased with the habitat thickness, from approximately 5% for the no-habitat case to about 47% for the habitat with an areal thickness of 100 g/cm(2).

SU-F-T-672: A Novel Kernel-Based Dose Engine for KeV Photon Beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reinhart, M; Fast, M F; Nill, S

2016-06-15

Purpose: Mimicking state-of-the-art patient radiotherapy with high precision irradiators for small animals allows advanced dose-effect studies and radiobiological investigations. One example is the implementation of pre-clinical IMRT-like irradiations, which requires the development of inverse planning for keV photon beams. As a first step, we present a novel kernel-based dose calculation engine for keV x-rays with explicit consideration of energy and material dependencies. Methods: We follow a superposition-convolution approach adapted to keV x-rays, based on previously published work on micro-beam therapy. In small animal radiotherapy, we assume local energy deposition at the photon interaction point, since the electron ranges in tissuemore » are of the same order of magnitude as the voxel size. This allows us to use photon-only kernel sets generated by MC simulations, which are pre-calculated for six energy windows and ten base materials. We validate our stand-alone dose engine against Geant4 MC simulations for various beam configurations in water, slab phantoms with bone and lung inserts, and on a mouse CT with (0.275mm)3 voxels. Results: We observe good agreement for all cases. For field sizes of 1mm{sup 2} to 1cm{sup 2} in water, the depth dose curves agree within 1% (mean), with the largest deviations in the first voxel (4%) and at depths>5cm (<2.5%). The out-of-field doses at 1cm depth agree within 8% (mean) for all but the smallest field size. In slab geometries, the mean agreement was within 3%, with maximum deviations of 8% at water-bone interfaces. The γ-index (1mm/1%) passing rate for a single-field mouse irradiation is 71%. Conclusion: The presented dose engine yields an accurate representation of keV-photon doses suitable for inverse treatment planning for IMRT. It has the potential to become a significantly faster yet sufficiently accurate alternative to full MC simulations. Further investigations will focus on energy sampling as well as calculation times. Research at ICR is also supported by Cancer Research UK under Programme C33589/A19727 and NHS funding to the NIHR Biomedical Research Centre at RMH and ICR. MFF is supported by Cancer Research UK under Programme C33589/A19908.« less

Nuclear spectroscopy with Geant4. The superheavy challenge

NASA Astrophysics Data System (ADS)

Sarmiento, Luis G.

2016-12-01

The simulation toolkit Geant4 was originally developed at CERN for high-energy physics. Over the years it has been established as a swiss army knife not only in particle physics but it has seen an accelerated expansion towards nuclear physics and more recently to medical imaging and γ- and ion- therapy to mention but a handful of new applications. The validity of Geant4 is vast and large across many particles, ions, materials, and physical processes with typically various different models to choose from. Unfortunately, atomic nuclei with atomic number Z > 100 are not properly supported. This is likely due to the rather novelty of the field, its comparably small user base, and scarce evaluated experimental data. To circumvent this situation different workarounds have been used over the years. In this work the simulation toolkit Geant4 will be introduced with its different components and the effort to bring the software to the heavy and superheavy region will be described.

Modeling proton and alpha elastic scattering in liquid water in Geant4-DNA

NASA Astrophysics Data System (ADS)

Tran, H. N.; El Bitar, Z.; Champion, C.; Karamitros, M.; Bernal, M. A.; Francis, Z.; Ivantchenko, V.; Lee, S. B.; Shin, J. I.; Incerti, S.

2015-01-01

Elastic scattering of protons and alpha (α) particles by water molecules cannot be neglected at low incident energies. However, this physical process is currently not available in the "Geant4-DNA" extension of the Geant4 Monte Carlo simulation toolkit. In this work, we report on theoretical differential and integral cross sections of the elastic scattering process for 100 eV-1 MeV incident protons and for 100 eV-10 MeV incident α particles in liquid water. The calculations are performed within the classical framework described by Everhart et al., Ziegler et al. and by the ICRU 49 Report. Then, we propose an implementation of the corresponding classes into the Geant4-DNA toolkit for modeling the elastic scattering of protons and α particles. Stopping powers as well as ranges are also reported. Then, it clearly appears that the account of the elastic scattering process in the slowing-down of the charged particle improves the agreement with the existing data in particular with the ICRU recommendations.

Performance of Geant4 in simulating semiconductor particle detector response in the energy range below 1 MeV

NASA Astrophysics Data System (ADS)

Soti, G.; Wauters, F.; Breitenfeldt, M.; Finlay, P.; Kraev, I. S.; Knecht, A.; Porobić, T.; Zákoucký, D.; Severijns, N.

2013-11-01

Geant4 simulations play a crucial role in the analysis and interpretation of experiments providing low energy precision tests of the Standard Model. This paper focuses on the accuracy of the description of the electron processes in the energy range between 100 and 1000 keV. The effect of the different simulation parameters and multiple scattering models on the backscattering coefficients is investigated. Simulations of the response of HPGe and passivated implanted planar Si detectors to β particles are compared to experimental results. An overall good agreement is found between Geant4 simulations and experimental data.

Geant4 Developments for the Radon Electric Dipole Moment Search at TRIUMF

NASA Astrophysics Data System (ADS)

Rand, E. T.; Bangay, J. C.; Bianco, L.; Dunlop, R.; Finlay, P.; Garrett, P. E.; Leach, K. G.; Phillips, A. A.; Sumithrarachchi, C. S.; Svensson, C. E.; Wong, J.

2011-09-01

An experiment is being developed at TRIUMF to search for a time-reversal violating electric dipole moment (EDM) in odd-A isotopes of Rn. Extensive simulations of the experiment are being performed with GEANT4 to study the backgrounds and sensitivity of the proposed measurement technique involving the detection of γ rays emitted following the β decay of polarized Rn nuclei. GEANT4 developments for the RnEDM experiment include both realistic modelling of the detector geometry and full tracking of the radioactive β, γ, internal conversion, and x-ray processes, including the γ-ray angular distributions essential for measuring an atomic EDM.

Development of an ideal observer that incorporates nuisance parameters and processes list-mode data

DOE PAGES

MacGahan, Christopher Jonathan; Kupinski, Matthew Alan; Hilton, Nathan R.; ...

2016-02-01

Observer models were developed to process data in list-mode format in order to perform binary discrimination tasks for use in an arms-control-treaty context. Data used in this study was generated using GEANT4 Monte Carlo simulations for photons using custom models of plutonium inspection objects and a radiation imaging system. We evaluated observer model performance and then presented using the area under the receiver operating characteristic curve. Lastly, we studied the ideal observer under both signal-known-exactly conditions and in the presence of unknowns such as object orientation and absolute count-rate variability; when these additional sources of randomness were present, their incorporationmore » into the observer yielded superior performance.« less

γ-ray telescopes using conversions to e+e- pairs: event generators, angular resolution and polarimetry

NASA Astrophysics Data System (ADS)

Gros, P.; Bernard, D.

2017-02-01

We benchmark various available event generators in Geant4 and EGS5 in the light of ongoing projects for high angular-resolution pair-conversion telescopes at low energy. We compare the distributions of key kinematic variables extracted from the geometry of the three final state particles. We validate and use as reference an exact generator using the full 5D differential cross-section of the conversion process. We focus in particular on the effect of the unmeasured recoiling nucleus on the angular resolution. We show that for high resolution trackers, the choice of the generator affects the estimated resolution of the telescope. We also show that the current available generator are unable to describe accurately a linearly polarised photon source.

The radiation environment on the surface of Mars - Numerical calculations of the galactic component with GEANT4/PLANETOCOSMICS.

PubMed

Matthiä, Daniel; Berger, Thomas

2017-08-01

Galactic cosmic radiation and secondary particles produced in the interaction with the atmosphere lead to a complex radiation field on the Martian surface. A workshop ("1st Mars Space Radiation Modeling Workshop") organized by the MSL-RAD science team was held in June 2016 in Boulder with the goal to compare models capable to predict this radiation field with each other and measurements from the RAD instrument onboard the curiosity rover taken between November 15, 2015 and January 15, 2016. In this work the results of PLANETOCOSMICS/GEANT4 contributed to the workshop are presented. Calculated secondary particle spectra on the Martian surface are investigated and the radiation field's directionality of the different particles in dependence on the energy is discussed. Omnidirectional particle fluxes are used in combination with fluence to dose conversion factors to calculate absorbed dose rates and dose equivalent rates in a slab of tissue. Copyright © 2017. Published by Elsevier Ltd.

Simulations of GCR interactions within planetary bodies using GEANT4

NASA Astrophysics Data System (ADS)

Mesick, K.; Feldman, W. C.; Stonehill, L. C.; Coupland, D. D. S.

2017-12-01

On planetary bodies with little to no atmosphere, Galactic Cosmic Rays (GCRs) can hit the body and produce neutrons primarily through nuclear spallation within the top few meters of the surfaces. These neutrons undergo further nuclear interactions with elements near the planetary surface and some will escape the surface and can be detected by landed or orbiting neutron radiation detector instruments. The neutron leakage signal at fast neutron energies provides a measure of average atomic mass of the near-surface material and in the epithermal and thermal energy ranges is highly sensitive to the presence of hydrogen. Gamma-rays can also escape the surface, produced at characteristic energies depending on surface composition, and can be detected by gamma-ray instruments. The intra-nuclear cascade (INC) that occurs when high-energy GCRs interact with elements within a planetary surface to produce the leakage neutron and gamma-ray signals is highly complex, and therefore Monte Carlo based radiation transport simulations are commonly used for predicting and interpreting measurements from planetary neutron and gamma-ray spectroscopy instruments. In the past, the simulation code that has been widely used for this type of analysis is MCNPX [1], which was benchmarked against data from the Lunar Neutron Probe Experiment (LPNE) on Apollo 17 [2]. In this work, we consider the validity of the radiation transport code GEANT4 [3], another widely used but open-source code, by benchmarking simulated predictions of the LPNE experiment to the Apollo 17 data. We consider the impact of different physics model options on the results, and show which models best describe the INC based on agreement with the Apollo 17 data. The success of this validation then gives us confidence in using GEANT4 to simulate GCR-induced neutron leakage signals on Mars in relevance to a re-analysis of Mars Odyssey Neutron Spectrometer data. References [1] D.B. Pelowitz, Los Alamos National Laboratory, LA-CP-05-0369, 2005. [2] G.W. McKinney et al, Journal of Geophysics Research, 111, E06004, 2006. [3] S. Agostinelli et al, Nuclear Instrumentation and Methods A, 506, 2003.

Sci—Fri PM: Topics — 01: A monte carlo model of a miniature low-energy x-ray tube using EGSnrc

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watson, P; Seuntjens, J

The INTRABEAM system (Carl Zeiss, Oberkochen, Germany) is a miniature x-ray generator for use in intraoperative radiotherapy and brachytherapy. The device accelerates electrons to up to 50 keV, which are then steered down an evacuated needle probe to strike a thin gold target. For accurate dosimetry of the INTRABEAM system, it is important that the photon spectrum be well understood. Measurements based on air-kerma are heavily impacted by photon spectra, particularly for low photon energies due to the large photoelectric contribution in air mass energy absorption coefficient. While low energy photons have little clinical significance at treatment depths, they maymore » have a large effect on air-kerma measurements. In this work, we have developed an EGSnrc-based monte carlo (MC) model of the Zeiss INTRABEAM system to study the source photon spectra and half-value layers (HVLs) of the bare probe and with various spherical applicators. HVLs were calculated using the analytical attenuation of air-kerma spectra. The calculated bare probe spectrum was compared with simulated and measured results taken from literature. Differences in the L-line energies of gold were found between the spectra predicted by EGSnrc and Geant4. This is due to M and N shell averaging during atomic transitions in EGSnrc. The calculated HVLs of the bare probe and spherical applicators are consistent with literature reported measured values.« less

A Linear Accelerator for TA-FD calibration

NASA Astrophysics Data System (ADS)

Shibata, T.; Ikeda, D.; Ikeda, M.; Enomoto, A.; Ohsawa, S.; Kakiha, K.; Kakihara, K.; Sagawa, H.; Satoh, M.; Shidara, T.; Sugimura, T.; Fukushima, M.; Fukuda, S.; Furukawa, K.; Yoshida, M.

The energy of the primary cosmic ray can be calculated from fluorescence photons detected by fluorescence telescope. However, since we can not know the true energy of primary cosmic ray, it is difficult to calibrate between number of photons and energy directly. In TA project, we will create pseudo- cosmic ray events by using accelerated electron beam which is injected in the air. The injected electron beam creates an air shower and fluorescence photons are emitted. We can calibate between electron beam energy which is known exactry and detected photons. We are developping a small linear accelerator (Linac) at High Energy Accelerator Research Organization (KEK) in Japan. The maximum energy is 40MeV, the typical current is 0.16nC, and the intensity per pulse is 6.4mJ. The accuracy of beam energy is less than 1%. The Linac consists of a -100kV pulse type electron gun, a 1.5m pre-buncher and buncher tube, a 2m S-band accelerator tube, a quadrupole magnet, a 90 degree bending magnet, and a S-Band(2856MHz) 50MW high power klystron as RF source. We chekced the performance of the electron beam, energy resolution, beam spread, beam current, and beam loss by PARMELA simulation, and checked the air shower by electron beam and number of the detected photons by detector simulation which are made by GEANT4. In this Spring, we will do the full beam test in KEK. The beam operation in Utah will be started from this Autumn. In this talk, we will report about the results of the beam test and calibration method by this Linac.

Comparison of hadron shower data in the PAMELA experiment with Geant 4 simulations

NASA Astrophysics Data System (ADS)

Alekseev, V. V.; Dunaeva, O. A.; Bogomolov, Yu V.; Lukyanov, A. D.; Malakhov, V. V.; Mayorov, A. G.; Rodenko, S. A.

2017-01-01

The sampling imaging electromagnetic calorimeter of ≈ 16.3 radiation lengths and ≈ 0.6 nuclear interaction length designed and constructed by the PAMELA collaboration as a part of the large magnetic spectrometer PAMELA. Calorimeter consists of 44 single-sided silicon sensor planes interleaved with 22 plates of tungsten absorber (thickness of each tungsten layer 0.26 cm). Silicon planes are composed of a 3 × 3 matrix of silicon detectors, each segmented into 32 read-out strips with a pitch of 2.4 mm. The orientation of the strips of two consecutive layers is orthogonal and therefore provides two-dimensional spatial information. Due to the high granularity, the development of hadronic showers can be study with a good precision. In this work a Monte Carlo simulations (based on Geant4) performed using different available models, and including detector and physical effects, compared with the experimental data obtained on the near Earth orbit. Response of the PAMELA calorimeter to hadronic showers investigated including total energy release in calorimeter and transverse shower profile characteristics.

Modeling the Martian neutron and gamma-ray leakage fluxes using Geant4

NASA Astrophysics Data System (ADS)

Pirard, Benoit; Desorgher, Laurent; Diez, Benedicte; Gasnault, Olivier

A new evaluation of the Martian neutron and gamma-ray (continuum and line) leakage fluxes has been performed using the Geant4 code. Even if numerous studies have recently been carried out with Monte Carlo methods to characterize planetary radiation environments, only a few however have been able to reproduce in detail the neutron and gamma-ray spectra observed in orbit. We report on the efforts performed to adapt and validate the Geant4-based PLAN- ETOCOSMICS code for use in planetary neutron and gamma-ray spectroscopy data analysis. Beside the advantage of high transparency and modularity common to Geant4 applications, the new code uses reviewed nuclear cross section data, realistic atmospheric profiles and soil layering, as well as specific effects such as gravity acceleration for low energy neutrons. Results from first simulations are presented for some Martian reference compositions and show a high consistency with corresponding neutron and gamma-ray spectra measured on board Mars Odyssey. Finally we discuss the advantages and perspectives of the improved code for precise simulation of planetary radiation environments.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnes, P.; Albuquerque, I. F. M.; Alexander, T.

Geant4-based Monte Carlo package named G4DS has been developed to simulate the response of DarkSide-50, an experiment operating since 2013 at LNGS, designed to detect WIMP interactions in liquid argon. In the process of WIMP searches, DarkSide-50 has achieved two fundamental milestones: the rejection of electron recoil background with a power of ~10^7, using the pulse shape discrimination technique, and the measurement of the residual 39Ar contamination in underground argon, ~3 orders of magnitude lower with respect to atmospheric argon.

Software aspects of the Geant4 validation repository

NASA Astrophysics Data System (ADS)

Dotti, Andrea; Wenzel, Hans; Elvira, Daniel; Genser, Krzysztof; Yarba, Julia; Carminati, Federico; Folger, Gunter; Konstantinov, Dmitri; Pokorski, Witold; Ribon, Alberto

2017-10-01

The Geant4, GeantV and GENIE collaborations regularly perform validation and regression tests for simulation results. DoSSiER (Database of Scientific Simulation and Experimental Results) is being developed as a central repository to store the simulation results as well as the experimental data used for validation. DoSSiER is easily accessible via a web application. In addition, a web service allows for programmatic access to the repository to extract records in JSON or XML exchange formats. In this article, we describe the functionality and the current status of various components of DoSSiER as well as the technology choices we made.

Software Aspects of the Geant4 Validation Repository

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dotti, Andrea; Wenzel, Hans; Elvira, Daniel

2016-01-01

The Geant4, GeantV and GENIE collaborations regularly perform validation and regression tests for simulation results. DoSSiER (Database of Scientic Simulation and Experimental Results) is being developed as a central repository to store the simulation results as well as the experimental data used for validation. DoSSiER is easily accessible via a web application. In addition, a web service allows for programmatic access to the repository to extract records in JSON or XML exchange formats. In this article, we describe the functionality and the current status of various components of DoSSiER as well as the technology choices we made.

Dosimetric evaluation of radionuclides for VCAM-1-targeted radionuclide therapy of early brain metastases.

PubMed

Falzone, Nadia; Ackerman, Nicole L; Rosales, Liset de la Fuente; Bernal, Mario A; Liu, Xiaoxuan; Peeters, Sarah Gja; Soto, Manuel Sarmiento; Corroyer-Dulmont, Aurélien; Bernaudin, Myriam; Grimoin, Elisa; Touzani, Omar; Sibson, Nicola R; Vallis, Katherine A

2018-01-01

Brain metastases develop frequently in patients with breast cancer, and present a pressing therapeutic challenge. Expression of vascular cell adhesion molecule 1 (VCAM-1) is upregulated on brain endothelial cells during the early stages of metastasis and provides a target for the detection and treatment of early brain metastases. The aim of this study was to use a model of early brain metastasis to evaluate the efficacy of α-emitting radionuclides, 149 Tb, 211 At, 212 Pb, 213 Bi and 225 Ac; β-emitting radionuclides, 90 Y, 161 Tb and 177 Lu; and Auger electron (AE)-emitters 67 Ga, 89 Zr, 111 In and 124 I, for targeted radionuclide therapy (TRT). Histologic sections and two photon microscopy of mouse brain parenchyma were used to inform a cylindrical vessel geometry using the Geant4 general purpose Monte Carlo (MC) toolkit with the Geant4-DNA low energy physics models. Energy deposition was evaluated as a radial function and the resulting phase spaces were superimposed on a DNA model to estimate double-strand break (DSB) yields for representative β- and α-emitters, 177 Lu and 212 Pb. Relative biological effectiveness (RBE) values were determined by only evaluating DNA damage due to physical interactions. 177 Lu produced 2.69 ± 0.08 DSB per GbpGy, without significant variation from the lumen of the vessel to a radius of 100 µm. The DSB yield of 212 Pb included two local maxima produced by the 6.1 MeV and 8.8 MeV α-emissions from decay products, 212 Bi and 212 Po, with yields of 7.64 ± 0.12 and 9.15 ± 0.24 per GbpGy, respectively. Given its higher DSB yield 212 Pb may be more effective for short range targeting of early micrometastatic lesions than 177 Lu. MC simulation of a model of early brain metastases provides invaluable insight into the potential efficacy of α-, β- and AE-emitting radionuclides for TRT. 212 Pb, which has the attributes of a theranostic radionuclide since it can be used for SPECT imaging, showed a favorable dose profile and RBE.

Low dose out-of-field radiotherapy, part 2: Calculating the mean photon energy values for the out-of-field photon energy spectrum from scattered radiation using Monte Carlo methods.

PubMed

Skrobala, A; Adamczyk, S; Kruszyna-Mochalska, M; Skórska, M; Konefał, A; Suchorska, W; Zaleska, K; Kowalik, A; Jackowiak, W; Malicki, J

2017-08-01

During radiotherapy, leakage from the machine head and collimator expose patients to out-of-field irradiation doses, which may cause secondary cancers. To quantify the risks of secondary cancers due to out-of-field doses, it is first necessary to measure these doses. Since most dosimeters are energy-dependent, it is essential to first determine the type of photon energy spectrum in the out-of-field area. The aim of this study was to determine the mean photon energy values for the out-of-field photon energy spectrum for a 6 MV photon beam using the GEANT 4-Monte Carlo method. A specially-designed large water phantom was simulated with a static field at gantry 0°. The source-to-surface distance was 92cm for an open field size of 10×10cm2. The photon energy spectra were calculated at five unique positions (at depths of 0.5, 1.6, 4, 6, 8, and 10cm) along the central beam axis and at six different off-axis distances. Monte Carlo simulations showed that mean radiation energy levels drop rapidly beyond the edge of the 6 MV photon beam field: at a distance of 10cm, the mean energy level is close to 0.3MeV versus 1.5MeV at the central beam axis. In some cases, the energy level actually increased even as the distance from the field edge increased: at a depth of 1.6cm and 15cm off-axis, the mean energy level was 0.205MeV versus 0.252MeV at 20cm off-axis. The out-of-field energy spectra and dose distribution data obtained in this study with Monte Carlo methods can be used to calibrate dosimeters to measure out-of-field radiation from 6MV photons. Copyright © 2017 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

Recent developments in Geant4

DOE PAGES

Allison, J.; Amako, K.; Apostolakis, J.; ...

2016-07-01

Geant4 is a software toolkit for the simulation of the passage of particles through matter. It is used by a large number of experiments and projects in a variety of application domains, including high energy physics, astrophysics and space science, medical physics and radiation protection. Over the past several years, major changes have been made to the toolkit in order to accommodate the needs of these user communities, and to efficiently exploit the growth of computing power made available by advances in technology. In conclusion, the adaptation of Geant4 to multithreading, advances in physics, detector modeling and visualization, extensions tomore » the toolkit, including biasing and reverse Monte Carlo, and tools for physics and release validation are discussed here.« less

A Geant4 simulation of the depth dose percentage in brain tumors treatments using protons and carbon ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diaz, José A. M., E-mail: joadiazme@unal.edu.co; Torres, D. A., E-mail: datorresg@unal.edu.co

2016-07-07

The deposited energy and dose distribution of beams of protons and carbon over a head are simulated using the free tool package Geant4 and the data analysis package ROOT-C++. The present work shows a methodology to understand the microscopical process occurring in a session of hadron-therapy using advance simulation tools.

Transmission of ˜ 10 keV electron beams through thin ceramic foils: Measurements and Monte Carlo simulations of electron energy distribution functions

NASA Astrophysics Data System (ADS)

Morozov, A.; Heindl, T.; Skrobol, C.; Wieser, J.; Krücken, R.; Ulrich, A.

2008-07-01

Electron beams with particle energy of ~10 keV were sent through 300 nm thick ceramic (Si3N4 + SiO2) foils and the resulting electron energy distribution functions were recorded using a retarding grid technique. The results are compared with Monte Carlo simulations performed with two publicly available packages, Geant4 and Casino v2.42. It is demonstrated that Geant4, unlike Casino, provides electron energy distribution functions very similar to the experimental distributions. Both simulation packages provide a quite precise average energy of transmitted electrons: we demonstrate that the maximum uncertainty of the calculated values of the average energy is 6% for Geant4 and 8% for Casino, taking into account all systematic uncertainties and the discrepancies in the experimental and simulated data.

Comparison of Geant4-DNA simulation of S-values with other Monte Carlo codes

NASA Astrophysics Data System (ADS)

André, T.; Morini, F.; Karamitros, M.; Delorme, R.; Le Loirec, C.; Campos, L.; Champion, C.; Groetz, J.-E.; Fromm, M.; Bordage, M.-C.; Perrot, Y.; Barberet, Ph.; Bernal, M. A.; Brown, J. M. C.; Deleuze, M. S.; Francis, Z.; Ivanchenko, V.; Mascialino, B.; Zacharatou, C.; Bardiès, M.; Incerti, S.

2014-01-01

Monte Carlo simulations of S-values have been carried out with the Geant4-DNA extension of the Geant4 toolkit. The S-values have been simulated for monoenergetic electrons with energies ranging from 0.1 keV up to 20 keV, in liquid water spheres (for four radii, chosen between 10 nm and 1 μm), and for electrons emitted by five isotopes of iodine (131, 132, 133, 134 and 135), in liquid water spheres of varying radius (from 15 μm up to 250 μm). The results have been compared to those obtained from other Monte Carlo codes and from other published data. The use of the Kolmogorov-Smirnov test has allowed confirming the statistical compatibility of all simulation results.

Study of low energy neutron beam formation based on GEANT4 simulations

NASA Astrophysics Data System (ADS)

Avagyan, R.; Avetisyan, R.; Ivanyan, V.; Kerobyan, I.

2017-07-01

The possibility of obtaining thermal/epithermal energy neutron beams using external protons from cyclotron C18/18 is studied based on GEANT4 simulations. This study will be the basis of the Beam Shaped Assembly (BSA) development for future Boron Neutron Capture Therapy (BNCT). Proton induced reactions on 9Be target are considered as a neutron source, and dependence of neutron yield on target thickness is investigated. The problem of reducing the ratio of gamma to neutron yields by inserting a lead sheet after the beryllium target is studied as well. By GEANT4 modeling the optimal thicknesses of 9Be target and lead absorber are determined and the design characteristics of beam shaping assembly, including the materials and thicknesses of reflector and moderator are considered.

Simulation of Radiation Damage to Neural Cells with the Geant4-DNA Toolkit

NASA Astrophysics Data System (ADS)

Bayarchimeg, Lkhagvaa; Batmunkh, Munkhbaatar; Belov, Oleg; Lkhagva, Oidov

2018-02-01

To help in understanding the physical and biological mechanisms underlying effects of cosmic and therapeutic types of radiation on the central nervous system (CNS), we have developed an original neuron application based on the Geant4 Monte Carlo simulation toolkit, in particular on its biophysical extension Geant4-DNA. The applied simulation technique provides a tool for the simulation of physical, physico-chemical and chemical processes (e.g. production of water radiolysis species in the vicinity of neurons) in realistic geometrical model of neural cells exposed to ionizing radiation. The present study evaluates the microscopic energy depositions and water radiolysis species yields within a detailed structure of a selected neuron taking into account its soma, dendrites, axon and spines following irradiation with carbon and iron ions.

Monte carlo simulations of the n_TOF lead spallation target with the Geant4 toolkit: A benchmark study

NASA Astrophysics Data System (ADS)

Lerendegui-Marco, J.; Cortés-Giraldo, M. A.; Guerrero, C.; Quesada, J. M.; Meo, S. Lo; Massimi, C.; Barbagallo, M.; Colonna, N.; Mancussi, D.; Mingrone, F.; Sabaté-Gilarte, M.; Vannini, G.; Vlachoudis, V.; Aberle, O.; Andrzejewski, J.; Audouin, L.; Bacak, M.; Balibrea, J.; Bečvář, F.; Berthoumieux, E.; Billowes, J.; Bosnar, D.; Brown, A.; Caamaño, M.; Calviño, F.; Calviani, M.; Cano-Ott, D.; Cardella, R.; Casanovas, A.; Cerutti, F.; Chen, Y. H.; Chiaveri, E.; Cortés, G.; Cosentino, L.; Damone, L. A.; Diakaki, M.; Domingo-Pardo, C.; Dressler, R.; Dupont, E.; Durán, I.; Fernández-Domínguez, B.; Ferrari, A.; Ferreira, P.; Finocchiaro, P.; Göbel, K.; Gómez-Hornillos, M. B.; García, A. R.; Gawlik, A.; Gilardoni, S.; Glodariu, T.; Gonçalves, I. F.; González, E.; Griesmayer, E.; Gunsing, F.; Harada, H.; Heinitz, S.; Heyse, J.; Jenkins, D. G.; Jericha, E.; Käppeler, F.; Kadi, Y.; Kalamara, A.; Kavrigin, P.; Kimura, A.; Kivel, N.; Kokkoris, M.; Krtička, M.; Kurtulgil, D.; Leal-Cidoncha, E.; Lederer, C.; Leeb, H.; Lonsdale, S. J.; Macina, D.; Marganiec, J.; Martínez, T.; Masi, A.; Mastinu, P.; Mastromarco, M.; Maugeri, E. A.; Mazzone, A.; Mendoza, E.; Mengoni, A.; Milazzo, P. M.; Musumarra, A.; Negret, A.; Nolte, R.; Oprea, A.; Patronis, N.; Pavlik, A.; Perkowski, J.; Porras, I.; Praena, J.; Radeck, D.; Rauscher, T.; Reifarth, R.; Rout, P. C.; Rubbia, C.; Ryan, J. A.; Saxena, A.; Schillebeeckx, P.; Schumann, D.; Smith, A. G.; Sosnin, N. V.; Stamatopoulos, A.; Tagliente, G.; Tain, J. L.; Tarifeño-Saldivia, A.; Tassan-Got, L.; Valenta, S.; Variale, V.; Vaz, P.; Ventura, A.; Vlastou, R.; Wallner, A.; Warren, S.; Woods, P. J.; Wright, T.; Žugec, P.

2017-09-01

Monte Carlo (MC) simulations are an essential tool to determine fundamental features of a neutron beam, such as the neutron flux or the γ-ray background, that sometimes can not be measured or at least not in every position or energy range. Until recently, the most widely used MC codes in this field had been MCNPX and FLUKA. However, the Geant4 toolkit has also become a competitive code for the transport of neutrons after the development of the native Geant4 format for neutron data libraries, G4NDL. In this context, we present the Geant4 simulations of the neutron spallation target of the n_TOF facility at CERN, done with version 10.1.1 of the toolkit. The first goal was the validation of the intra-nuclear cascade models implemented in the code using, as benchmark, the characteristics of the neutron beam measured at the first experimental area (EAR1), especially the neutron flux and energy distribution, and the time distribution of neutrons of equal kinetic energy, the so-called Resolution Function. The second goal was the development of a Monte Carlo tool aimed to provide useful calculations for both the analysis and planning of the upcoming measurements at the new experimental area (EAR2) of the facility.

Modeling the tagged-neutron UXO identification technique using the Geant4 toolkit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou Y.; Mitra S.; Zhu X.

2011-10-16

It is proposed to use 14 MeV neutrons tagged by the associated particle neutron time-of-flight technique (APnTOF) to identify the fillers of unexploded ordnances (UXO) by characterizing their carbon, nitrogen and oxygen contents. To facilitate the design and construction of a prototype system, a preliminary simulation model was developed, using the Geant4 toolkit. This work established the toolkit environment for (a) generating tagged neutrons, (b) their transport and interactions within a sample to induce emission and detection of characteristic gamma-rays, and (c) 2D and 3D-image reconstruction of the interrogated object using the neutron and gamma-ray time-of-flight information. Using the modeling,more » this article demonstrates the novelty of the tagged-neutron approach for extracting useful signals with high signal-to-background discrimination of an object-of-interest from that of its environment. Simulations indicated that an UXO filled with the RDX explosive, hexogen (C{sub 3}H{sub 6}O{sub 6}N{sub 6}), can be identified to a depth of 20 cm when buried in soil.« less

Modeling of microporous silicon betaelectric converter with 63Ni plating in GEANT4 toolkit*

NASA Astrophysics Data System (ADS)

Zelenkov, P. V.; Sidorov, V. G.; Lelekov, E. T.; Khoroshko, A. Y.; Bogdanov, S. V.; Lelekov, A. T.

2016-04-01

The model of electron-hole pairs generation rate distribution in semiconductor is needed to optimize the parameters of microporous silicon betaelectric converter, which uses 63Ni isotope radiation. By using Monte-Carlo methods of GEANT4 software with ultra-low energy electron physics models this distribution in silicon was calculated and approximated with exponential function. Optimal pore configuration was estimated.

SU-E-T-531: Performance Evaluation of Multithreaded Geant4 for Proton Therapy Dose Calculations in a High Performance Computing Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, J; Coss, D; McMurry, J

Purpose: To evaluate the efficiency of multithreaded Geant4 (Geant4-MT, version 10.0) for proton Monte Carlo dose calculations using a high performance computing facility. Methods: Geant4-MT was used to calculate 3D dose distributions in 1×1×1 mm3 voxels in a water phantom and patient's head with a 150 MeV proton beam covering approximately 5×5 cm2 in the water phantom. Three timestamps were measured on the fly to separately analyze the required time for initialization (which cannot be parallelized), processing time of individual threads, and completion time. Scalability of averaged processing time per thread was calculated as a function of thread number (1,more » 100, 150, and 200) for both 1M and 50 M histories. The total memory usage was recorded. Results: Simulations with 50 M histories were fastest with 100 threads, taking approximately 1.3 hours and 6 hours for the water phantom and the CT data, respectively with better than 1.0 % statistical uncertainty. The calculations show 1/N scalability in the event loops for both cases. The gains from parallel calculations started to decrease with 150 threads. The memory usage increases linearly with number of threads. No critical failures were observed during the simulations. Conclusion: Multithreading in Geant4-MT decreased simulation time in proton dose distribution calculations by a factor of 64 and 54 at a near optimal 100 threads for water phantom and patient's data respectively. Further simulations will be done to determine the efficiency at the optimal thread number. Considering the trend of computer architecture development, utilizing Geant4-MT for radiotherapy simulations is an excellent cost-effective alternative for a distributed batch queuing system. However, because the scalability depends highly on simulation details, i.e., the ratio of the processing time of one event versus waiting time to access for the shared event queue, a performance evaluation as described is recommended.« less

Testing hadronic interaction models using a highly granular silicon-tungsten calorimeter

NASA Astrophysics Data System (ADS)

Bilki, B.; Repond, J.; Schlereth, J.; Xia, L.; Deng, Z.; Li, Y.; Wang, Y.; Yue, Q.; Yang, Z.; Eigen, G.; Mikami, Y.; Price, T.; Watson, N. K.; Thomson, M. A.; Ward, D. R.; Benchekroun, D.; Hoummada, A.; Khoulaki, Y.; Cârloganu, C.; Chang, S.; Khan, A.; Kim, D. H.; Kong, D. J.; Oh, Y. D.; Blazey, G. C.; Dyshkant, A.; Francis, K.; Lima, J. G. R.; Salcido, P.; Zutshi, V.; Boisvert, V.; Green, B.; Misiejuk, A.; Salvatore, F.; Kawagoe, K.; Miyazaki, Y.; Sudo, Y.; Suehara, T.; Tomita, T.; Ueno, H.; Yoshioka, T.; Apostolakis, J.; Folger, G.; Ivantchenko, V.; Ribon, A.; Uzhinskiy, V.; Cauwenbergh, S.; Tytgat, M.; Zaganidis, N.; Hostachy, J.-Y.; Morin, L.; Gadow, K.; Göttlicher, P.; Günter, C.; Krüger, K.; Lutz, B.; Reinecke, M.; Sefkow, F.; Feege, N.; Garutti, E.; Laurien, S.; Lu, S.; Marchesini, I.; Matysek, M.; Ramilli, M.; Kaplan, A.; Norbeck, E.; Northacker, D.; Onel, Y.; Kim, E. J.; van Doren, B.; Wilson, G. W.; Wing, M.; Bobchenko, B.; Chadeeva, M.; Chistov, R.; Danilov, M.; Drutskoy, A.; Epifantsev, A.; Markin, O.; Mizuk, R.; Novikov, E.; Popov, V.; Rusinov, V.; Tarkovsky, E.; Besson, D.; Popova, E.; Gabriel, M.; Kiesling, C.; Simon, F.; Soldner, C.; Szalay, M.; Tesar, M.; Weuste, L.; Amjad, M. S.; Bonis, J.; Callier, S.; Conforti di Lorenzo, S.; Cornebise, P.; Doublet, Ph.; Dulucq, F.; Faucci-Giannelli, M.; Fleury, J.; Frisson, T.; Kégl, B.; van der Kolk, N.; Li, H.; Martin-Chassard, G.; Richard, F.; de La Taille, Ch.; Pöschl, R.; Raux, L.; Rouëné, J.; Seguin-Moreau, N.; Anduze, M.; Balagura, V.; Becheva, E.; Boudry, V.; Brient, J.-C.; Cornat, R.; Frotin, M.; Gastaldi, F.; Magniette, F.; Matthieu, A.; Mora de Freitas, P.; Videau, H.; Augustin, J.-E.; David, J.; Ghislain, P.; Lacour, D.; Lavergne, L.; Zacek, J.; Cvach, J.; Gallus, P.; Havranek, M.; Janata, M.; Kvasnicka, J.; Lednicky, D.; Marcisovsky, M.; Polak, I.; Popule, J.; Tomasek, L.; Tomasek, M.; Ruzicka, P.; Sicho, P.; Smolik, J.; Vrba, V.; Zalesak, J.; Jeans, D.; Götze, M.; Calice Collaboration

2015-09-01

A detailed study of hadronic interactions is presented using data recorded with the highly granular CALICE silicon-tungsten electromagnetic calorimeter. Approximately 350,000 selected π- events at energies between 2 and 10 GeV have been studied. The predictions of several physics models available within the GEANT4 simulation tool kit are compared to this data. A reasonable overall description of the data is observed; the Monte Carlo predictions are within 20% of the data, and for many observables much closer. The largest quantitative discrepancies are found in the longitudinal and transverse distributions of reconstructed energy.

SU-F-T-149: Development of the Monte Carlo Simulation Platform Using Geant4 for Designing Heavy Ion Therapy Beam Nozzle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Jae-ik; Yoo, SeungHoon; Cho, Sungho

Purpose: The significant issue of particle therapy such as proton and carbon ion was a accurate dose delivery from beam line to patient. For designing the complex delivery system, Monte Carlo simulation can be used for the simulation of various physical interaction in scatters and filters. In this report, we present the development of Monte Carlo simulation platform to help design the prototype of particle therapy nozzle and performed the Monte Carlo simulation using Geant4. Also we show the prototype design of particle therapy beam nozzle for Korea Heavy Ion Medical Accelerator (KHIMA) project in Korea Institute of Radiological andmore » Medical Science(KIRAMS) at Republic of Korea. Methods: We developed a simulation platform for particle therapy beam nozzle using Geant4. In this platform, the prototype nozzle design of Scanning system for carbon was simply designed. For comparison with theoretic beam optics, the beam profile on lateral distribution at isocenter is compared with Mont Carlo simulation result. From the result of this analysis, we can expected the beam spot property of KHIMA system and implement the spot size optimization for our spot scanning system. Results: For characteristics study of scanning system, various combination of the spot size from accerlator with ridge filter and beam monitor was tested as simple design for KHIMA dose delivery system. Conclusion: In this report, we presented the part of simulation platform and the characteristics study. This study is now on-going in order to develop the simulation platform including the beam nozzle and the dose verification tool with treatment planning system. This will be presented as soon as it is become available.« less

Assessment and improvements of Geant4 hadronic models in the context of prompt-gamma hadrontherapy monitoring

NASA Astrophysics Data System (ADS)

Dedes, G.; Pinto, M.; Dauvergne, D.; Freud, N.; Krimmer, J.; Létang, J. M.; Ray, C.; Testa, E.

2014-04-01

Monte Carlo simulations are nowadays essential tools for a wide range of research topics in the field of radiotherapy. They also play an important role in the effort to develop a real-time monitoring system for quality assurance in proton and carbon ion therapy, by means of prompt-gamma detection. The internal theoretical nuclear models of Monte Carlo simulation toolkits are of decisive importance for the accurate description of neutral or charged particle emission, produced by nuclear interactions between beam particles and target nuclei. We assess the performance of Geant4 nuclear models in the context of prompt-gamma emission, comparing them with experimental data from proton and carbon ion beams. As has been shown in the past and further indicated in our study, the prompt-gamma yields are consistently overestimated by Geant4 by a factor of about 100% to 200% over an energy range from 80 to 310 MeV/u for the case of 12C, and to a lesser extent for 160 MeV protons. Furthermore, we focus on the quantum molecular dynamics (QMD) modeling of ion-ion collisions, in order to optimize its description of light nuclei, which are abundant in the human body and mainly anticipated in hadrontherapy applications. The optimization has been performed by benchmarking QMD free parameters with well established nuclear properties. In addition, we study the effect of this optimization on charged particle emission. With the usage of the proposed parameter values, discrepancies reduce to less than 70%, with the highest values being attributed to the nucleon-ion induced prompt-gammas. This conclusion, also confirmed by the disagreement we observe in the case of proton beams, indicates the need for further investigation on nuclear models which describe proton and neutron induced nuclear reactions.

Impact of fluorescence emission from gold atoms on surrounding biological tissue-implications for nanoparticle radio-enhancement.

PubMed

Byrne, H L; Gholami, Y; Kuncic, Z

2017-04-21

The addition of gold nanoparticles within target tissue (i.e. a tumour) to enhance the delivered radiation dose is a well studied radiotherapy treatment strategy, despite not yet having been translated into standard clinical practice. While several studies have used Monte Carlo simulations to investigate radiation dose enhancement by Auger electrons emitted from irradiated gold nanoparticles, none have yet considered the effects due to escaping fluorescence photons. Geant4 was used to simulate a water phantom containing 10 mg ml -1 uniformly dispersed gold (1% by mass) at 5 cm depth. Incident monoenergetic photons with energies either side of the gold K-edge at 73 keV and 139.5 keV were chosen to give the same attenuation contrast against water, where water is used as a surrogate for biological tissue. For 73 keV incident photons, adding 1% gold into the water phantom enhances the energy deposited in the phantom by a factor of  ≈1.9 while 139.5 keV incident photons give a lower enhancement ratio of  ≈1.5. This difference in enhancement ratio, despite the equivalent attenuation ratios, can be attributed to energy carried from the target into the surrounding volume by fluorescence photons for the higher incident photon energy. The energy de-localisation is maximal just above the K-edge with 36% of the initial energy deposit in the phantom lost to escaping fluorescence photons. Conversely we find that the absorption of more photons by gold in the phantom reduces the number of scattered photons and hence energy deposited in the surrounding volume by up to 6% for incident photons below the K-edge. For incident photons above the K-edge this is somewhat offset by fluorescence. Our results give new insight into the previously unstudied centimetre scale energy deposition outside a target, which will be valuable for the future development of treatment plans using gold nanoparticles. From these results, we can conclude that gold nanoparticles delivered to a target tumour are capable of increasing dose to the tumour whilst simultaneously decreasing scatter dose to surrounding healthy tissue.

BRDF profile of Tyvek and its implementation in the Geant4 simulation toolkit.

PubMed

Nozka, Libor; Pech, Miroslav; Hiklova, Helena; Mandat, Dusan; Hrabovsky, Miroslav; Schovanek, Petr; Palatka, Miroslav

2011-02-28

Diffuse and specular characteristics of the Tyvek 1025-BL material are reported with respect to their implementation in the Geant4 Monte Carlo simulation toolkit. This toolkit incorporates the UNIFIED model. Coefficients defined by the UNIFIED model were calculated from the bidirectional reflectance distribution function (BRDF) profiles measured with a scatterometer for several angles of incidence. Results were amended with profile measurements made by a profilometer.

Comparison of PHITS, GEANT4, and HIBRAC simulations of depth-dependent yields of β(+)-emitting nuclei during therapeutic particle irradiation to measured data.

PubMed

Rohling, Heide; Sihver, Lembit; Priegnitz, Marlen; Enghardt, Wolfgang; Fiedler, Fine

2013-09-21

For quality assurance in particle therapy, a non-invasive, in vivo range verification is highly desired. Particle therapy positron-emission-tomography (PT-PET) is the only clinically proven method up to now for this purpose. It makes use of the β(+)-activity produced during the irradiation by the nuclear fragmentation processes between the therapeutic beam and the irradiated tissue. Since a direct comparison of β(+)-activity and dose is not feasible, a simulation of the expected β(+)-activity distribution is required. For this reason it is essential to have a quantitatively reliable code for the simulation of the yields of the β(+)-emitting nuclei at every position of the beam path. In this paper results of the three-dimensional Monte-Carlo simulation codes PHITS, GEANT4, and the one-dimensional deterministic simulation code HIBRAC are compared to measurements of the yields of the most abundant β(+)-emitting nuclei for carbon, lithium, helium, and proton beams. In general, PHITS underestimates the yields of positron-emitters. With GEANT4 the overall most accurate results are obtained. HIBRAC and GEANT4 provide comparable results for carbon and proton beams. HIBRAC is considered as a good candidate for the implementation to clinical routine PT-PET.

Comparison of PHITS, GEANT4, and HIBRAC simulations of depth-dependent yields of β+-emitting nuclei during therapeutic particle irradiation to measured data

NASA Astrophysics Data System (ADS)

Rohling, Heide; Sihver, Lembit; Priegnitz, Marlen; Enghardt, Wolfgang; Fiedler, Fine

2013-09-01

For quality assurance in particle therapy, a non-invasive, in vivo range verification is highly desired. Particle therapy positron-emission-tomography (PT-PET) is the only clinically proven method up to now for this purpose. It makes use of the β+-activity produced during the irradiation by the nuclear fragmentation processes between the therapeutic beam and the irradiated tissue. Since a direct comparison of β+-activity and dose is not feasible, a simulation of the expected β+-activity distribution is required. For this reason it is essential to have a quantitatively reliable code for the simulation of the yields of the β+-emitting nuclei at every position of the beam path. In this paper results of the three-dimensional Monte-Carlo simulation codes PHITS, GEANT4, and the one-dimensional deterministic simulation code HIBRAC are compared to measurements of the yields of the most abundant β+-emitting nuclei for carbon, lithium, helium, and proton beams. In general, PHITS underestimates the yields of positron-emitters. With GEANT4 the overall most accurate results are obtained. HIBRAC and GEANT4 provide comparable results for carbon and proton beams. HIBRAC is considered as a good candidate for the implementation to clinical routine PT-PET.

Guiding the Design of Radiation Imagers with Experimentally Benchmarked Geant4 Simulations for Electron-Tracking Compton Imaging

NASA Astrophysics Data System (ADS)

Coffer, Amy Beth

Radiation imagers are import tools in the modern world for a wide range of applications. They span the use-cases of fundamental sciences, astrophysics, medical imaging, all the way to national security, nuclear safeguards, and non-proliferation verification. The type of radiation imagers studied in this thesis were gamma-ray imagers that detect emissions from radioactive materials. Gamma-ray imagers goal is to localize and map the distribution of radiation within their specific field-of-view despite the fact of complicating background radiation that can be terrestrial, astronomical, and temporal. Compton imaging systems are one type of gamma-ray imager that can map the radiation around the system without the use of collimation. Lack of collimation enables the imaging system to be able to detect radiation from all-directions, while at the same time, enables increased detection efficiency by not absorbing incident radiation in non-sensing materials. Each Compton-scatter events within an imaging system generated a possible cone-surface in space that the radiation could have originated from. Compton imaging is limited in its reconstructed image signal-to-background due to these source Compton-cones overlapping with background radiation Compton-cones. These overlapping cones limit Compton imaging's detection-sensitivity in image space. Electron-tracking Compton imaging (ETCI) can improve the detection-sensitivity by measuring the Compton-scattered electron's initial trajectory. With an estimate of the scattered electron's trajectory, one can reduce the Compton-back-projected cone to a cone-arc, thus enabling faster radiation source detection and localization. However, the ability to measure the Compton-scattered electron-trajectories adds another layer of complexity to an already complex methodology. For a real-world imaging applications, improvements are needed in electron-track detection efficiency and in electron-track reconstruction. One way of measuring Compton-scattered electron-trajectories is with high-resolution Charged-Coupled Devices (CCDs). The proof-of-principle CCD-based ETCI experiment demonstrated the CCDs' ability to measure the Compton-scattered electron-tracks as a 2-dimensional image. Electron-track-imaging algorithms using the electron-track-image are able to determine the 3-dimensional electron-track trajectory within +/- 20 degrees. The work presented here is the physics simulations developed along side the experimental proof-of-principle experiment. The development of accurate physics modeling for multiple-layer CCDs based ETCI systems allow for the accurate prediction of future ETCI system performance. The simulations also enable quick development insights for system design, and they guide the development of electron-track reconstruction methods. The physics simulation efforts for this project looked closely at the accuracy of the Geant4 Monte Carlo methods for medium energy electron transport. In older version of Geant4 there were some discrepancies between the electron-tracking experimental measurements and the simulation results. It was determined that when comparing the electron dynamics of electrons at very high resolutions, Geant4 simulations must be fine tuned with careful choices for physics production cuts and electron physics stepping sizes. One result of this work is a CCDs Monte Carlo model that has been benchmarked to experimental findings and fully characterized for both photon and electron transport. The CCDs physics model now match to within 1 percent error of experimental results for scattered-electron energies below 500 keV. Following the improvements of the CCDs simulations, the performance of a realistic two-layer CCD-stack system was characterized. The realistic CCD-stack system looked at the effect of thin passive-layers on the CCDs' front face and back-contact. The photon interaction efficiency was calculated for the two-layer CCD-stack, and we found that there is a 90 percent probability of scattered-electrons from a 662 keV source to stay within a single active layer. This demonstrates the improved detection efficiency, which is one of the strengths of the CCDs' implementation as a ETCI system. The CCD-stack simulations also established that electron-tracks scattering from one CCDs layer to another could be reconstructed. The passive-regions on the CCD-stack mean that these inter-layer scattered-electron-tracks will always loose both angular information and energy information. Looking at the angular changes of these electrons scattering between the CCDs layers showed us there is not a strong energy dependence on the angular changes due to the passive-regions of the CCDs. The angular changes of the electron track are, for the most part, a function of the thickness of the thin back-layer of the CCDs. Lastly, an approach using CCD-stack simulations was developed to reconstruct the energy transport across dead-layers and its feasibility was demonstrated. Adding back this lost energy will limit the loss of energy resolution of the scatter-interactions. Energy resolution losses would negatively impacted the achievable image resolution from image reconstruction algorithms. Returning some of the energy back to the reconstructed electron-track will help retain the expected performance of the electron-track trajectory determination algorithm.

Simulations of neutron transport at low energy: a comparison between GEANT and MCNP.

PubMed

Colonna, N; Altieri, S

2002-06-01

The use of the simulation tool GEANT for neutron transport at energies below 20 MeV is discussed, in particular with regard to shielding and dose calculations. The reliability of the GEANT/MICAP package for neutron transport in a wide energy range has been verified by comparing the results of simulations performed with this package in a wide energy range with the prediction of MCNP-4B, a code commonly used for neutron transport at low energy. A reasonable agreement between the results of the two codes is found for the neutron flux through a slab of material (iron and ordinary concrete), as well as for the dose released in soft tissue by neutrons. These results justify the use of the GEANT/MICAP code for neutron transport in a wide range of applications, including health physics problems.

Refined lateral energy correction functions for the KASCADE-Grande experiment based on Geant4 simulations

NASA Astrophysics Data System (ADS)

Gherghel-Lascu, A.; Apel, W. D.; Arteaga-Velázquez, J. C.; Bekk, K.; Bertaina, M.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Engler, J.; Fuchs, B.; Fuhrmann, D.; Gils, H. J.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Huber, D.; Huege, T.; Kampert, K.-H.; Kang, D.; Klages, H. O.; Link, K.; Łuczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Oehlschläger, J.; Ostapchenko, S.; Palmieri, N.; Petcu, M.; Pierog, T.; Rebel, H.; Roth, M.; Schieler, H.; Schoo, S.; Schröder, F. G.; Sima, O.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Zabierowski, J.

2015-02-01

In previous studies of KASCADE-Grande data, a Monte Carlo simulation code based on the GEANT3 program has been developed to describe the energy deposited by EAS particles in the detector stations. In an attempt to decrease the simulation time and ensure compatibility with the geometry description in standard KASCADE-Grande analysis software, several structural elements have been neglected in the implementation of the Grande station geometry. To improve the agreement between experimental and simulated data, a more accurate simulation of the response of the KASCADE-Grande detector is necessary. A new simulation code has been developed based on the GEANT4 program, including a realistic geometry of the detector station with structural elements that have not been considered in previous studies. The new code is used to study the influence of a realistic detector geometry on the energy deposited in the Grande detector stations by particles from EAS events simulated by CORSIKA. Lateral Energy Correction Functions are determined and compared with previous results based on GEANT3.

Electron-hole pairs generation rate estimation irradiated by isotope Nickel-63 in silicone using GEANT4

NASA Astrophysics Data System (ADS)

Kovalev, I. V.; Sidorov, V. G.; Zelenkov, P. V.; Khoroshko, A. Y.; Lelekov, A. T.

2015-10-01

To optimize parameters of beta-electrical converter of isotope Nickel-63 radiation, model of the distribution of EHP generation rate in semiconductor must be derived. By using Monte-Carlo methods in GEANT4 system with ultra-low energy electron physics models this distribution in silicon calculated and approximated with Gauss function. Maximal efficient isotope layer thickness and maximal energy efficiency of EHP generation were estimated.

Monte Carlo simulation of a photodisintegration of 3 H experiment in Geant4

NASA Astrophysics Data System (ADS)

Gray, Isaiah

2013-10-01

An upcoming experiment involving photodisintegration of 3 H at the High Intensity Gamma-Ray Source facility at Duke University has been simulated in the software package Geant4. CAD models of silicon detectors and wire chambers were imported from Autodesk Inventor using the program FastRad and the Geant4 GDML importer. Sensitive detectors were associated with the appropriate logical volumes in the exported GDML file so that changes in detector geometry will be easily manifested in the simulation. Probability distribution functions for the energy and direction of outgoing protons were generated using numerical tables from previous theory, and energies and directions were sampled from these distributions using a rejection sampling algorithm. The simulation will be a useful tool to optimize detector geometry, estimate background rates, and test data analysis algorithms. This work was supported by the Triangle Universities Nuclear Laboratory REU program at Duke University.

Calculation of Coincidence Summing Correction Factors for an HPGe detector using GEANT4.

PubMed

Giubrone, G; Ortiz, J; Gallardo, S; Martorell, S; Bas, M C

2016-07-01

The aim of this paper was to calculate the True Coincidence Summing Correction Factors (TSCFs) for an HPGe coaxial detector in order to correct the summing effect as a result of the presence of (88)Y and (60)Co in a multigamma source used to obtain a calibration efficiency curve. Results were obtained for three volumetric sources using the Monte Carlo toolkit, GEANT4. The first part of this paper deals with modeling the detector in order to obtain a simulated full energy peak efficiency curve. A quantitative comparison between the measured and simulated values was made across the entire energy range under study. The True Summing Correction Factors were calculated for (88)Y and (60)Co using the full peak efficiencies obtained with GEANT4. This methodology was subsequently applied to (134)Cs, and presented a complex decay scheme. Copyright © 2016 Elsevier Ltd. All rights reserved.

Analysis of the track- and dose-averaged LET and LET spectra in proton therapy using the geant4 Monte Carlo code

PubMed Central

Guan, Fada; Peeler, Christopher; Bronk, Lawrence; Geng, Changran; Taleei, Reza; Randeniya, Sharmalee; Ge, Shuaiping; Mirkovic, Dragan; Grosshans, David; Mohan, Radhe; Titt, Uwe

2015-01-01

Purpose: The motivation of this study was to find and eliminate the cause of errors in dose-averaged linear energy transfer (LET) calculations from therapeutic protons in small targets, such as biological cell layers, calculated using the geant 4 Monte Carlo code. Furthermore, the purpose was also to provide a recommendation to select an appropriate LET quantity from geant 4 simulations to correlate with biological effectiveness of therapeutic protons. Methods: The authors developed a particle tracking step based strategy to calculate the average LET quantities (track-averaged LET, LETt and dose-averaged LET, LETd) using geant 4 for different tracking step size limits. A step size limit refers to the maximally allowable tracking step length. The authors investigated how the tracking step size limit influenced the calculated LETt and LETd of protons with six different step limits ranging from 1 to 500 μm in a water phantom irradiated by a 79.7-MeV clinical proton beam. In addition, the authors analyzed the detailed stochastic energy deposition information including fluence spectra and dose spectra of the energy-deposition-per-step of protons. As a reference, the authors also calculated the averaged LET and analyzed the LET spectra combining the Monte Carlo method and the deterministic method. Relative biological effectiveness (RBE) calculations were performed to illustrate the impact of different LET calculation methods on the RBE-weighted dose. Results: Simulation results showed that the step limit effect was small for LETt but significant for LETd. This resulted from differences in the energy-deposition-per-step between the fluence spectra and dose spectra at different depths in the phantom. Using the Monte Carlo particle tracking method in geant 4 can result in incorrect LETd calculation results in the dose plateau region for small step limits. The erroneous LETd results can be attributed to the algorithm to determine fluctuations in energy deposition along the tracking step in geant 4. The incorrect LETd values lead to substantial differences in the calculated RBE. Conclusions: When the geant 4 particle tracking method is used to calculate the average LET values within targets with a small step limit, such as smaller than 500 μm, the authors recommend the use of LETt in the dose plateau region and LETd around the Bragg peak. For a large step limit, i.e., 500 μm, LETd is recommended along the whole Bragg curve. The transition point depends on beam parameters and can be found by determining the location where the gradient of the ratio of LETd and LETt becomes positive. PMID:26520716

SU-E-QI-15: Single Point Dosimetry by Means of Cerenkov Radiation Energy Transfer (CRET)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volotskova, O; Jenkins, C; Xing, L

2014-06-15

Purpose: Cerenkov light is generated when a charged particles with energy greater then 250 keV, moves faster than the speed of light in a given medium. Both x-ray photons and electrons produce optical Cerenkov photons during the static megavoltage linear accelerator (LINAC) operational mode. Recently, Cerenkov radiation gained considerable interest as possible candidate as a new imaging modality. Optical signals generated by Cerenkov radiation may act as a surrogate for the absorbed superficial radiation dose. We demonstrated a novel single point dosimetry method for megavoltage photon and electron therapy utilizing down conversion of Cerenkov photons. Methods: The custom build signalmore » characterization system was used: a sample holder (probe) with adjacent light tight compartments was connected via fiber-optic cables to a photon counting photomultiplier tube (PMT). One compartment contains a medium only while the other contains medium and red-shifting nano-particles (Q-dots, nanoclusters). By taking the difference between the two signals (Cerenkov photons and CRET photons) we obtain a measure of the down-converted light, which we expect to be proportional to dose as measured with an adjacent ion chamber. Experimental results are compared to Monte Carlo simulations performed using the GEANT4 code. Results: The signal correlation between CR signal, CRET readings and dose produced by LINAC at a single point were investigated. The experimental results were compared with simulations. The dose linearity, signal to noise ratio and dose rate dependence were tested with custom build CRET based probe. Conclusion: Performance characteristics of the proposed single point CRET based probe were evaluated. The direct use of the induced Cerenkov emission and CRET in an irradiated single point volume as an indirect surrogate for the imparted dose was investigated. We conclude that CRET is a promising optical based dosimetry method that offers advantages over those already proposed.« less

Energy response calibration of photon-counting detectors using x-ray fluorescence: a feasibility study.

PubMed

Cho, H-M; Ding, H; Ziemer, B P; Molloi, S

2014-12-07

Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using x-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for x-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm(2) in detection area. The angular dependence of x-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded x-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of x-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of x-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic x-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the x-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory.

Energy response calibration of photon-counting detectors using x-ray fluorescence: a feasibility study

NASA Astrophysics Data System (ADS)

Cho, H.-M.; Ding, H.; Ziemer, BP; Molloi, S.

2014-12-01

Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using x-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for x-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3  ×  3 mm2 in detection area. The angular dependence of x-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded x-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of x-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of x-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic x-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the x-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory.

Energy response calibration of photon-counting detectors using X-ray fluorescence: a feasibility study

PubMed Central

Cho, H-M; Ding, H; Ziemer, BP; Molloi, S

2014-01-01

Accurate energy calibration is critical for the application of energy-resolved photon-counting detectors in spectral imaging. The aim of this study is to investigate the feasibility of energy response calibration and characterization of a photon-counting detector using X-ray fluorescence. A comprehensive Monte Carlo simulation study was performed using Geant4 Application for Tomographic Emission (GATE) to investigate the optimal technique for X-ray fluorescence calibration. Simulations were conducted using a 100 kVp tungsten-anode spectra with 2.7 mm Al filter for a single pixel cadmium telluride (CdTe) detector with 3 × 3 mm2 in detection area. The angular dependence of X-ray fluorescence and scatter background was investigated by varying the detection angle from 20° to 170° with respect to the beam direction. The effects of the detector material, shape, and size on the recorded X-ray fluorescence were investigated. The fluorescent material size effect was considered with and without the container for the fluorescent material. In order to provide validation for the simulation result, the angular dependence of X-ray fluorescence from five fluorescent materials was experimentally measured using a spectrometer. Finally, eleven of the fluorescent materials were used for energy calibration of a CZT-based photon-counting detector. The optimal detection angle was determined to be approximately at 120° with respect to the beam direction, which showed the highest fluorescence to scatter ratio (FSR) with a weak dependence on the fluorescent material size. The feasibility of X-ray fluorescence for energy calibration of photon-counting detectors in the diagnostic X-ray energy range was verified by successfully calibrating the energy response of a CZT-based photon-counting detector. The results of this study can be used as a guideline to implement the X-ray fluorescence calibration method for photon-counting detectors in a typical imaging laboratory. PMID:25369288

Probing Jupiter's Radiation Environment with Juno-UVS

NASA Astrophysics Data System (ADS)

Kammer, J.; Gladstone, R.; Greathouse, T. K.; Hue, V.; Versteeg, M. H.; Davis, M. W.; Santos-Costa, D.; Becker, H. N.; Bolton, S. J.; Connerney, J. E. P.; Levin, S.

2017-12-01

While primarily designed to observe photon emission from the Jovian aurora, Juno's Ultraviolet Spectrograph (Juno-UVS) has also measured background count rates associated with penetrating high-energy radiation. These background counts are distinguishable from photon events, as they are generally spread evenly across the entire array of the Juno-UVS detector, and as the spacecraft spins, they set a baseline count rate higher than the sky background rate. During eight perijove passes, this background radiation signature has varied significantly on both short (spin-modulated) timescales, as well as longer timescales ( minutes to hours). We present comparisons of the Juno-UVS data across each of the eight perijove passes, with a focus on the count rate that can be clearly attributed to radiation effects rather than photon events. Once calibrated to determine the relationship between count rate and penetrating high-energy radiation (e.g., using existing GEANT models), these in situ measurements by Juno-UVS will provide additional constraints to radiation belt models close to the planet.

Time Resolved Phonon Spectroscopy, Version 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goett, Johnny; Zhu, Brian

TRPS code was developed for the project "Time Resolved Phonon Spectroscopy". Routines contained in this piece of software were specially created to model phonon generation and tracking within materials that interact with ionizing radiation, particularly applicable to the modeling of cryogenic radiation detectors for dark matter and neutrino research. These routines were created to link seamlessly with the open source Geant4 framework for the modeling of radiation transport in matter, with the explicit intent of open sourcing them for eventual integration into that code base.

Simulation of Light Collection for Neutron Electrical Dipole Moment measurement

NASA Astrophysics Data System (ADS)

Ji, Pan; nEDM Collaboration

2017-09-01

nEDM (Neutron Electrical Dipole moment) measurement addresses a critical topic in particle physics and Standard Model, that is CPT violation in neutron electrical dipole moment if detected in which the Time reversal violation is connected to the matter/antimatter imparity of the universe. The neutron electric dipole moment was first measured in 1950 by Smith, Purcell, and Ramsey at the Oak Ridge Reactor - the first intense neutron source. This measurement showed that the neutron was very nearly round (to better than one part in a million). The goal of the nEDM experiment is to further improve the precision of this measurement by another factor of 100. The signal from the experiment is detected by collecting the photons generated when neutron beams were captured by liquid helium 3. The Geant4 simulation project that I participate simulates the process of light collection to improve the design for higher capture efficiency. The simulated geometry includes light source, reflector, wavelength shifting fibers, wavelength shifting TPB and acrylic as in real experiment. The UV photons exiting from Helium go through two wavelength-shifting processes in TPB and fibers to be finally captured. Oak Ridge National Laboratory Neutron Electric Dipole Moment measurement project.

Space Earthquake Perturbation Simulation (SEPS) an application based on Geant4 tools to model and simulate the interaction between the Earthquake and the particle trapped on the Van Allen belt

NASA Astrophysics Data System (ADS)

Ambroglini, Filippo; Jerome Burger, William; Battiston, Roberto; Vitale, Vincenzo; Zhang, Yu

2014-05-01

During last decades, few space experiments revealed anomalous bursts of charged particles, mainly electrons with energy larger than few MeV. A possible source of these bursts are the low-frequency seismo-electromagnetic emissions, which can cause the precipitation of the electrons from the lower boundary of their inner belt. Studies of these bursts reported also a short-term pre-seismic excess. Starting from simulation tools traditionally used on high energy physics we developed a dedicated application SEPS (Space Perturbation Earthquake Simulation), based on the Geant4 tool and PLANETOCOSMICS program, able to model and simulate the electromagnetic interaction between the earthquake and the particles trapped in the inner Van Allen belt. With SEPS one can study the transport of particles trapped in the Van Allen belts through the Earth's magnetic field also taking into account possible interactions with the Earth's atmosphere. SEPS provides the possibility of: testing different models of interaction between electromagnetic waves and trapped particles, defining the mechanism of interaction as also shaping the area in which this takes place,assessing the effects of perturbations in the magnetic field on the particles path, performing back-tracking analysis and also modelling the interaction with electric fields. SEPS is in advanced development stage, so that it could be already exploited to test in details the results of correlation analysis between particle bursts and earthquakes based on NOAA and SAMPEX data. The test was performed both with a full simulation analysis, (tracing from the position of the earthquake and going to see if there were paths compatible with the burst revealed) and with a back-tracking analysis (tracing from the burst detection point and checking the compatibility with the position of associated earthquake).

Photon Quenching of the Paranormal (Time) Channel: A Brief Note,

DTIC Science & Technology

1977-04-20

The photon interaction constitutes a time-differentiating operation imposed upon nonobjective, ’ paranormal ’, 4-dimensional spacetime reality...physically materialize a mental phenomenon if the paranormal channel (time channel) is intact and not squelched by photon interaction. Tulpas may then be

Simulations of Si-PIN photodiode based detectors for underground explosives enhanced by ammonium nitrate

NASA Astrophysics Data System (ADS)

Yücel, Mete; Bayrak, Ahmet; Yücel, Esra Barlas; Ozben, Cenap S.

2018-02-01

Massive Ammonium Nitrate (NH4-NO3) based explosives buried underground are commonly used in terror attacks. These explosives can be detected using neutron scattering method with some limitations. Simulations are very useful tools for designing a possible detection system for these kind of explosives. Geant4 simulations were used for generating neutrons at 14 MeV energy and tracking them through the scattering off the explosive embedded in soil. Si-PIN photodiodes were used as detector elements in the design for their low costs and simplicity for signal readout electronics. Various neutron-charge particle converters were applied on to the surface of the photodiodes to increase the detection efficiency. Si-PIN photodiodes coated with 6LiF provided the best result for a certain energy interval. Energy depositions in silicon detector from all secondary particles generated including photons were taken into account to generate a realistic background. Humidity of soil, one of the most important parameter for limiting the detection, was also studied.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanehira, T; Sutherland, K; Matsuura, T

Purpose: To evaluate density inhomogeneities which can effect dose distributions for real-time image gated spot-scanning proton therapy (RGPT), a dose calculation system, using treatment planning system VQA (Hitachi Ltd., Tokyo) spot position data, was developed based on Geant4. Methods: A Geant4 application was developed to simulate spot-scanned proton beams at Hokkaido University Hospital. A CT scan (0.98 × 0.98 × 1.25 mm) was performed for prostate cancer treatment with three or four inserted gold markers (diameter 1.5 mm, volume 1.77 mm3) in or near the target tumor. The CT data was read into VQA. A spot scanning plan was generatedmore » and exported to text files, specifying the beam energy and position of each spot. The text files were converted and read into our Geant4-based software. The spot position was converted into steering magnet field strength (in Tesla) for our beam nozzle. Individual protons were tracked from the vacuum chamber, through the helium chamber, steering magnets, dose monitors, etc., in a straight, horizontal line. The patient CT data was converted into materials with variable density and placed in a parametrized volume at the isocenter. Gold fiducial markers were represented in the CT data by two adjacent voxels (volume 2.38 mm3). 600,000 proton histories were tracked for each target spot. As one beam contained about 1,000 spots, approximately 600 million histories were recorded for each beam on a blade server. Two plans were considered: two beam horizontal opposed (90 and 270 degree) and three beam (0, 90 and 270 degree). Results: We are able to convert spot scanning plans from VQA and simulate them with our Geant4-based code. Our system can be used to evaluate the effect of dose reduction caused by gold markers used for RGPT. Conclusion: Our Geant4 application is able to calculate dose distributions for spot scanned proton therapy.« less

MONTE CARLO STUDY OF THE CARDIAC ABSORBED DOSE DURING X-RAY EXAMINATION OF AN ADULT PATIENT.

PubMed

Kadri, O; Manai, K; Alfuraih, A

2016-12-01

The computational voxel phantom 'High-Definition Reference Korean-Man (HDRK-Man)' was implemented into the Monte Carlo transport toolkit Geant4. The voxel model, adjusted to the Reference Korean Man, is 171 cm in height and 68 kg in weight and composed of ∼30 million voxels whose size is 1.981 × 1.981 × 2.0854 mm 3 The Geant4 code is then utilised to compute the dose conversion coefficients (DCCs) expressed in absorbed dose per air kerma free in air for >30 tissues and organs, including almost all organs required in the new recommendation of the ICRP 103, due to a broad parallel beam of monoenergetic photons impinging in antero-postero direction with energy ranging from 10 to 150 keV. The computed DCCs of different organs are found to be in good agreement with data published using other simulation codes. Also, the influence of patient size on DCC values was investigated for a representative body size of the adult Korean patient population. The study was performed using five different sizes covering the range of 0.8-1.2 magnification order of the original HDRK-Man. It focussed on the computation of DCC for the human heart. Moreover, the provided DCCs were used to present an analytical parameterisation for the calculation of the cardiac absorbed dose for any arbitrary X-ray spectrum and for those patient sizes. Thus, the present work can be considered as an enhancement of the continuous studies performed by medical physicist as part of quality control tests and radiation protection dosimetry. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Optimization of 6LiF:ZnS(Ag) scintillator light yield using GEANT4

NASA Astrophysics Data System (ADS)

Yehuda-Zada, Y.; Pritchard, K.; Ziegler, J. B.; Cooksey, C.; Siebein, K.; Jackson, M.; Hurlbut, C.; Kadmon, Y.; Cohen, Y.; Ibberson, R. M.; Majkrzak, C. F.; Maliszewskyj, N. C.; Orion, I.; Osovizky, A.

2018-06-01

A new cold neutron detector has been developed at the NIST Center for Neutron Research (NCNR) for the CANDoR (Chromatic Analysis Neutron Diffractometer or Reflectometer) project. Geometric and performance constraints dictate that this detector be exceptionally thin (∼ 2 mm). For this reason, the design of the detector consists of a 6LiF:ZnS(Ag) scintillator with embedded wavelength shifting (WLS) fibers. We used the GEANT4 package to simulate neutron capture and light transport in the detector to optimize the composition and arrangement of materials to satisfy the competing requirements of high neutron capture probability and light production and transport. In the process, we have developed a method for predicting light collection and total neutron detection efficiency for different detector configurations. The simulation was performed by adjusting crucial parameters such as the scintillator stoichiometry, light yield, component grain size, WLS fiber geometry, and reflectors at the outside edges of the scintillator volume. Three different detector configurations were fabricated and their test results were correlated with the simulations. Through this correlation we have managed to find a common photon threshold for the different detector configurations which was then used to simulate and predict the efficiencies for many other detector configurations. New detectors that have been fabricated based on simulation results yielding the desired sensitivity of 90% for 3.27 meV (5 Å) cold neutrons. The simulation has proven to be a useful tool by dramatically reducing the development period and the required number of detector prototypes. It can be used to test new designs with different thicknesses and different target neutron energies.

BC404 scintillators as gamma locators studied via Geant4 simulations

NASA Astrophysics Data System (ADS)

Cortés, M. L.; Hoischen, R.; Eisenhauer, K.; Gerl, J.; Pietralla, N.

2014-05-01

In many applications in industry and academia, an accurate determination of the direction from where gamma rays are emitted is either needed or desirable. Ion-beam therapy treatments, the search for orphan sources, and homeland security applications are examples of fields that can benefit from directional sensitivity to gamma-radiation. Scintillation detectors are a good option for these types of applications as they have relatively low cost, are easy to handle and can be produced in a large range of different sizes. In this work a Geant4 simulation was developed to study the directional sensitivity of different BC404 scintillator geometries and arrangements. The simulation includes all the physical processes relevant for gamma detection in a scintillator. In particular, the creation and propagation of optical photons inside the scintillator was included. A simplified photomultiplier tube model was also simulated. The physical principle exploited is the angular dependence of the shape of the energy spectrum obtained from thin scintillator layers when irradiated from different angles. After an experimental confirmation of the working principle of the device and a check of the simulation, the possibilities and limitations of directional sensitivity to gamma radiation using scintillator layers was tested. For this purpose, point-like sources of typical energies expected in ion-beam therapy were used. Optimal scintillator thicknesses for different energies were determined and the setup efficiencies calculated. The use of arrays of scintillators to reconstruct the direction of incoming gamma rays was also studied. For this case, a spherical source emitting Bremsstrahlung radiation was used together with a setup consisting of scintillator layers. The capability of this setup to identify the center of the extended source was studied together with its angular resolution.

Calculation of self–shielding factor for neutron activation experiments using GEANT4 and MCNP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Romero–Barrientos, Jaime, E-mail: jaromero@ing.uchile.cl; Universidad de Chile, DFI, Facultad de Ciencias Físicas Y Matemáticas, Avenida Blanco Encalada 2008, Santiago; Molina, F.

2016-07-07

The neutron self–shielding factor G as a function of the neutron energy was obtained for 14 pure metallic samples in 1000 isolethargic energy bins from 1·10{sup −5}eV to 2·10{sup 7}eV using Monte Carlo simulations in GEANT4 and MCNP6. The comparison of these two Monte Carlo codes shows small differences in the final self–shielding factor mostly due to the different cross section databases that each program uses.

Monte Carlo simulation of chemistry following radiolysis with TOPAS-nBio

NASA Astrophysics Data System (ADS)

Ramos-Méndez, J.; Perl, J.; Schuemann, J.; McNamara, A.; Paganetti, H.; Faddegon, B.

2018-05-01

Simulation of water radiolysis and the subsequent chemistry provides important information on the effect of ionizing radiation on biological material. The Geant4 Monte Carlo toolkit has added chemical processes via the Geant4-DNA project. The TOPAS tool simplifies the modeling of complex radiotherapy applications with Geant4 without requiring advanced computational skills, extending the pool of users. Thus, a new extension to TOPAS, TOPAS-nBio, is under development to facilitate the configuration of track-structure simulations as well as water radiolysis simulations with Geant4-DNA for radiobiological studies. In this work, radiolysis simulations were implemented in TOPAS-nBio. Users may now easily add chemical species and their reactions, and set parameters including branching ratios, dissociation schemes, diffusion coefficients, and reaction rates. In addition, parameters for the chemical stage were re-evaluated and updated from those used by default in Geant4-DNA to improve the accuracy of chemical yields. Simulation results of time-dependent and LET-dependent primary yields Gx (chemical species per 100 eV deposited) produced at neutral pH and 25 °C by short track-segments of charged particles were compared to published measurements. The LET range was 0.05–230 keV µm‑1. The calculated Gx values for electrons satisfied the material balance equation within 0.3%, similar for protons albeit with long calculation time. A smaller geometry was used to speed up proton and alpha simulations, with an acceptable difference in the balance equation of 1.3%. Available experimental data of time-dependent G-values for agreed with simulated results within 7%  ±  8% over the entire time range; for over the full time range within 3%  ±  4% for H2O2 from 49%  ±  7% at earliest stages and 3%  ±  12% at saturation. For the LET-dependent Gx, the mean ratios to the experimental data were 1.11  ±  0.98, 1.21  ±  1.11, 1.05  ±  0.52, 1.23  ±  0.59 and 1.49  ±  0.63 (1 standard deviation) for , , H2, H2O2 and , respectively. In conclusion, radiolysis and subsequent chemistry with Geant4-DNA has been successfully incorporated in TOPAS-nBio. Results are in reasonable agreement with published measured and simulated data.

Analysis of the track- and dose-averaged LET and LET spectra in proton therapy using the GEANT4 Monte Carlo code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guan, Fada; Peeler, Christopher; Taleei, Reza

Purpose: The motivation of this study was to find and eliminate the cause of errors in dose-averaged linear energy transfer (LET) calculations from therapeutic protons in small targets, such as biological cell layers, calculated using the GEANT 4 Monte Carlo code. Furthermore, the purpose was also to provide a recommendation to select an appropriate LET quantity from GEANT 4 simulations to correlate with biological effectiveness of therapeutic protons. Methods: The authors developed a particle tracking step based strategy to calculate the average LET quantities (track-averaged LET, LET{sub t} and dose-averaged LET, LET{sub d}) using GEANT 4 for different tracking stepmore » size limits. A step size limit refers to the maximally allowable tracking step length. The authors investigated how the tracking step size limit influenced the calculated LET{sub t} and LET{sub d} of protons with six different step limits ranging from 1 to 500 μm in a water phantom irradiated by a 79.7-MeV clinical proton beam. In addition, the authors analyzed the detailed stochastic energy deposition information including fluence spectra and dose spectra of the energy-deposition-per-step of protons. As a reference, the authors also calculated the averaged LET and analyzed the LET spectra combining the Monte Carlo method and the deterministic method. Relative biological effectiveness (RBE) calculations were performed to illustrate the impact of different LET calculation methods on the RBE-weighted dose. Results: Simulation results showed that the step limit effect was small for LET{sub t} but significant for LET{sub d}. This resulted from differences in the energy-deposition-per-step between the fluence spectra and dose spectra at different depths in the phantom. Using the Monte Carlo particle tracking method in GEANT 4 can result in incorrect LET{sub d} calculation results in the dose plateau region for small step limits. The erroneous LET{sub d} results can be attributed to the algorithm to determine fluctuations in energy deposition along the tracking step in GEANT 4. The incorrect LET{sub d} values lead to substantial differences in the calculated RBE. Conclusions: When the GEANT 4 particle tracking method is used to calculate the average LET values within targets with a small step limit, such as smaller than 500 μm, the authors recommend the use of LET{sub t} in the dose plateau region and LET{sub d} around the Bragg peak. For a large step limit, i.e., 500 μm, LET{sub d} is recommended along the whole Bragg curve. The transition point depends on beam parameters and can be found by determining the location where the gradient of the ratio of LET{sub d} and LET{sub t} becomes positive.« less

Measuring and interpreting X-ray fluorescence from planetary surfaces.

PubMed

Owens, Alan; Beckhoff, Burkhard; Fraser, George; Kolbe, Michael; Krumrey, Michael; Mantero, Alfonso; Mantler, Michael; Peacock, Anthony; Pia, Maria-Grazia; Pullan, Derek; Schneider, Uwe G; Ulm, Gerhard

2008-11-15

As part of a comprehensive study of X-ray emission from planetary surfaces and in particular the planet Mercury, we have measured fluorescent radiation from a number of planetary analog rock samples using monochromatized synchrotron radiation provided by the BESSY II electron storage ring. The experiments were carried out using a purpose built X-ray fluorescence (XRF) spectrometer chamber developed by the Physikalisch-Technische Bundesanstalt, Germany's national metrology institute. The XRF instrumentation is absolutely calibrated and allows for reference-free quantitation of rock sample composition, taking into account secondary photon- and electron-induced enhancement effects. The fluorescence data, in turn, have been used to validate a planetary fluorescence simulation tool based on the GEANT4 transport code. This simulation can be used as a mission analysis tool to predict the time-dependent orbital XRF spectral distributions from planetary surfaces throughout the mapping phase.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Selvi, Marco

For all experiments dealing with the rare event searches (neutrino, dark matter, neutrino-less double-beta decay), the reduction of the radioactive background is one of the most important and difficult tasks. There are basically two types of background, electron recoils and nuclear recoils. The electron recoil background is mostly from the gamma rays through the radioactive decay. The nuclear recoil background is from neutrons from spontaneous fission, (α, n) reactions and muoninduced interactions (spallations, photo-nuclear and hadronic interaction). The external gammas and neutrons from the muons and laboratory environment, can be reduced by operating the detector at deep underground laboratories andmore » by placing active or passive shield materials around the detector. The radioactivity of the detector materials also contributes to the background; in order to reduce it a careful screening campaign is mandatory to select highly radio-pure materials. In this review I present the status of current Monte Carlo simulations aimed to estimate and reproduce the background induced by gamma and neutron radioactivity of the materials and the shield of rare event search experiment. For the electromagnetic background a good level of agreement between the data and the MC simulation has been reached by the XENON100 and EDELWEISS experiments, using the GEANT4 toolkit. For the neutron background, a comparison between the yield of neutrons from spontaneous fission and (α, n) obtained with two dedicated softwares, SOURCES-4A and the one developed by Mei-Zhang-Hime, show a good overall agreement, with total yields within a factor 2 difference. The energy spectra from SOURCES-4A are in general smoother, while those from MZH presents sharp peaks. The neutron propagation through various materials has been studied with two MC codes, GEANT4 and MCNPX, showing a reasonably good agreement, inside 50% discrepancy.« less

Review of Monte Carlo simulations for backgrounds from radioactivity

NASA Astrophysics Data System (ADS)

Selvi, Marco

2013-08-01

For all experiments dealing with the rare event searches (neutrino, dark matter, neutrino-less double-beta decay), the reduction of the radioactive background is one of the most important and difficult tasks. There are basically two types of background, electron recoils and nuclear recoils. The electron recoil background is mostly from the gamma rays through the radioactive decay. The nuclear recoil background is from neutrons from spontaneous fission, (α, n) reactions and muoninduced interactions (spallations, photo-nuclear and hadronic interaction). The external gammas and neutrons from the muons and laboratory environment, can be reduced by operating the detector at deep underground laboratories and by placing active or passive shield materials around the detector. The radioactivity of the detector materials also contributes to the background; in order to reduce it a careful screening campaign is mandatory to select highly radio-pure materials. In this review I present the status of current Monte Carlo simulations aimed to estimate and reproduce the background induced by gamma and neutron radioactivity of the materials and the shield of rare event search experiment. For the electromagnetic background a good level of agreement between the data and the MC simulation has been reached by the XENON100 and EDELWEISS experiments, using the GEANT4 toolkit. For the neutron background, a comparison between the yield of neutrons from spontaneous fission and (α, n) obtained with two dedicated softwares, SOURCES-4A and the one developed by Mei-Zhang-Hime, show a good overall agreement, with total yields within a factor 2 difference. The energy spectra from SOURCES-4A are in general smoother, while those from MZH presents sharp peaks. The neutron propagation through various materials has been studied with two MC codes, GEANT4 and MCNPX, showing a reasonably good agreement, inside 50% discrepancy.

Development of a Geant4 application to characterise a prototype neutron detector based on three orthogonal 3He tubes inside an HDPE sphere.

PubMed

Gracanin, V; Guatelli, S; Prokopovich, D; Rosenfeld, A B; Berry, A

2017-01-01

The Bonner Sphere Spectrometer (BSS) system is a well-established technique for neutron dosimetry that involves detection of thermal neutrons within a range of hydrogenous moderators. BSS detectors are often used to perform neutron field surveys in order to determine the ambient dose equivalent H*(10) and estimate health risk to personnel. There is a potential limitation of existing neutron survey techniques, since some detectors do not consider the direction of the neutron field, which can result in overly conservative estimates of dose in neutron fields. This paper shows the development of a Geant4 simulation application to characterise a prototype neutron detector based on three orthogonal 3 He tubes inside a single HDPE sphere built at the Australian Nuclear Science and Technology Organisation (ANSTO). The Geant4 simulation has been validated with respect to experimental measurements performed with an Am-Be source. Crown Copyright © 2016. Published by Elsevier Ltd. All rights reserved.

A mathematical deconvolution formulation for superficial dose distribution measurement by Cerenkov light dosimetry.

PubMed

Brost, Eric Edward; Watanabe, Yoichi

2018-06-01

Cerenkov photons are created by high-energy radiation beams used for radiation therapy. In this study, we developed a Cerenkov light dosimetry technique to obtain a two-dimensional dose distribution in a superficial region of medium from the images of Cerenkov photons by using a deconvolution method. An integral equation was derived to represent the Cerenkov photon image acquired by a camera for a given incident high-energy photon beam by using convolution kernels. Subsequently, an equation relating the planar dose at a depth to a Cerenkov photon image using the well-known relationship between the incident beam fluence and the dose distribution in a medium was obtained. The final equation contained a convolution kernel called the Cerenkov dose scatter function (CDSF). The CDSF function was obtained by deconvolving the Cerenkov scatter function (CSF) with the dose scatter function (DSF). The GAMOS (Geant4-based Architecture for Medicine-Oriented Simulations) Monte Carlo particle simulation software was used to obtain the CSF and DSF. The dose distribution was calculated from the Cerenkov photon intensity data using an iterative deconvolution method with the CDSF. The theoretical formulation was experimentally evaluated by using an optical phantom irradiated by high-energy photon beams. The intensity of the deconvolved Cerenkov photon image showed linear dependence on the dose rate and the photon beam energy. The relative intensity showed a field size dependence similar to the beam output factor. Deconvolved Cerenkov images showed improvement in dose profiles compared with the raw image data. In particular, the deconvolution significantly improved the agreement in the high dose gradient region, such as in the penumbra. Deconvolution with a single iteration was found to provide the most accurate solution of the dose. Two-dimensional dose distributions of the deconvolved Cerenkov images agreed well with the reference distributions for both square fields and a multileaf collimator (MLC) defined, irregularly shaped field. The proposed technique improved the accuracy of the Cerenkov photon dosimetry in the penumbra region. The results of this study showed initial validation of the deconvolution method for beam profile measurements in a homogeneous media. The new formulation accounted for the physical processes of Cerenkov photon transport in the medium more accurately than previously published methods. © 2018 American Association of Physicists in Medicine.

An analytical method for computing voxel S values for electrons and photons.

PubMed

Amato, Ernesto; Minutoli, Fabio; Pacilio, Massimiliano; Campenni, Alfredo; Baldari, Sergio

2012-11-01

The use of voxel S values (VSVs) is perhaps the most common approach to radiation dosimetry for nonuniform distributions of activity within organs or tumors. However, VSVs are currently available only for a limited number of voxel sizes and radionuclides. The objective of this study was to develop a general method to evaluate them for any spectrum of electrons and photons in any cubic voxel dimension of practical interest for clinical dosimetry in targeted radionuclide therapy. The authors developed a Monte Carlo simulation in Geant4 in order to evaluate the energy deposited per disintegration (E(dep)) in a voxelized region of soft tissue from monoenergetic electrons (10-2000 keV) or photons (10-1000 keV) homogeneously distributed in the central voxel, considering voxel dimensions ranging from 3 mm to 10 mm. E(dep) was represented as a function of a dimensionless quantity termed the "normalized radius," R(n) = R∕l, where l is the voxel size and R is the distance from the origin. The authors introduced two parametric functions in order to fit the electron and photon results, and they interpolated the parameters to derive VSVs for any energy and voxel side within the ranges mentioned above. In order to validate the results, the authors determined VSV for two radionuclides ((131)I and (89)Sr) and two voxel dimensions and they compared them with reference data. A validation study in a simple sphere model, accounting for tissue inhomogeneities, is presented. The E(dep)(R(n)) for both monoenergetic electrons and photons exhibit a smooth variation with energy and voxel size, implying that VSVs for monoenergetic electrons or photons may be derived by interpolation over the range of energies and dimensions considered. By integration, S values for continuous emission spectra from β(-) decay may be derived as well. The approach allows the determination of VSVs for monoenergetic (Auger or conversion) electrons and (x-ray or gamma-ray) photons by means of two functions whose parameters can be interpolated from tabular data provided. Through integration, it is possible to generalize the method to any continuous (beta) spectrum, allowing to calculate VSVs for any electron and photon emitter in a voxelized structure.

SU-C-BRC-06: OpenCL-Based Cross-Platform Monte Carlo Simulation Package for Carbon Ion Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, N; Tian, Z; Pompos, A

2016-06-15

Purpose: Monte Carlo (MC) simulation is considered to be the most accurate method for calculation of absorbed dose and fundamental physical quantities related to biological effects in carbon ion therapy. Its long computation time impedes clinical and research applications. We have developed an MC package, goCMC, on parallel processing platforms, aiming at achieving accurate and efficient simulations for carbon therapy. Methods: goCMC was developed under OpenCL framework. It supported transport simulation in voxelized geometry with kinetic energy up to 450 MeV/u. Class II condensed history algorithm was employed for charged particle transport with stopping power computed via Bethe-Bloch equation. Secondarymore » electrons were not transported with their energy locally deposited. Energy straggling and multiple scattering were modeled. Production of secondary charged particles from nuclear interactions was implemented based on cross section and yield data from Geant4. They were transported via the condensed history scheme. goCMC supported scoring various quantities of interest e.g. physical dose, particle fluence, spectrum, linear energy transfer, and positron emitting nuclei. Results: goCMC has been benchmarked against Geant4 with different phantoms and beam energies. For 100 MeV/u, 250 MeV/u and 400 MeV/u beams impinging to a water phantom, range difference was 0.03 mm, 0.20 mm and 0.53 mm, and mean dose difference was 0.47%, 0.72% and 0.79%, respectively. goCMC can run on various computing devices. Depending on the beam energy and voxel size, it took 20∼100 seconds to simulate 10{sup 7} carbons on an AMD Radeon GPU card. The corresponding CPU time for Geant4 with the same setup was 60∼100 hours. Conclusion: We have developed an OpenCL-based cross-platform carbon MC simulation package, goCMC. Its accuracy, efficiency and portability make goCMC attractive for research and clinical applications in carbon therapy.« less

Interaction of Solar-Flare-Accelerated Nuclei with the Solar Photosphere and the Isotopic Composition of the Solar Wind

NASA Astrophysics Data System (ADS)

Vasil'ev, G. I.; Ostryakov, V. M.; Pavlov, A. K.; Chakchurina, M. E.

2017-12-01

The nuclear interactions of solar-flare-accelerated protons and ions with the solar atmosphere and the deeper layers of the Sun lead to the formation of several stable and radioactive isotopes. This article examines the GEANT4 depth profiles of 2H, 3H, 3He, 6Li, 7Li, 10Be, and 14C. When accelerated particles pass through a layer of 0.1-2 g cm-2, 6Li, 7Li, 10Be, and 14C isotopes form in sufficient amounts to explain their anomalous abundances in lunar soil samples. It is assumed that they escape into interplanetary space with coronal mass ejections immediately after the flare.

Monte Carlo simulations support non-Cerenkov radioluminescence production in tissue

NASA Astrophysics Data System (ADS)

Ackerman, Nicole L.; Boschi, Federico; Spinelli, Antonello E.

2017-08-01

There is experimental evidence for the production of non-Cerenkov radioluminescence in a variety of materials, including tissue. We constructed a Geant4 Monte Carlo simulation of the radiation from P32 and Tc99m interacting in chicken breast and used experimental imaging data to model a scintillation-like emission. The same radioluminescence spectrum is visible from both isotopes and cannot otherwise be explained through fluorescence or filter miscalibration. We conclude that chicken breast has a near-infrared scintillation-like response with a light yield three orders of magnitude smaller than BGO.

Evaluating average and atypical response in radiation effects simulations

NASA Astrophysics Data System (ADS)

Weller, R. A.; Sternberg, A. L.; Massengill, L. W.; Schrimpf, R. D.; Fleetwood, D. M.

2003-12-01

We examine the limits of performing single-event simulations using pre-averaged radiation events. Geant4 simulations show the necessity, for future devices, to supplement current methods with ensemble averaging of device-level responses to physically realistic radiation events. Initial Monte Carlo simulations have generated a significant number of extremal events in local energy deposition. These simulations strongly suggest that proton strikes of sufficient energy, even those that initiate purely electronic interactions, can initiate device response capable in principle of producing single event upset or microdose damage in highly scaled devices.

Monte-Carlo Estimation of the Inflight Performance of the GEMS Satellite X-Ray Polarimeter

NASA Technical Reports Server (NTRS)

Kitaguchi, Takao; Tamagawa, Toru; Hayato, Asami; Enoto, Teruaki; Yoshikawa, Akifumi; Kaneko, Kenta; Takeuchi, Yoko; Black, Kevin; Hill, Joanne; Jahoda, Keith;

Monte-Carlo estimation of the inflight performance of the GEMS satellite x-ray polarimeter

NASA Astrophysics Data System (ADS)

Kitaguchi, Takao; Tamagawa, Toru; Hayato, Asami; Enoto, Teruaki; Yoshikawa, Akifumi; Kaneko, Kenta; Takeuchi, Yoko; Black, Kevin; Hill, Joanne; Jahoda, Keith; Krizmanic, John; Sturner, Steven; Griffiths, Scott; Kaaret, Philip; Marlowe, Hannah

2014-07-01

We report a Monte-Carlo estimation of the in-orbit performance of a cosmic X-ray polarimeter designed to be installed on the focal plane of a small satellite. The simulation uses GEANT for the transport of photons and energetic particles and results from Magboltz for the transport of secondary electrons in the detector gas. We validated the simulation by comparing spectra and modulation curves with actual data taken with radioactive sources and an X-ray generator. We also estimated the in-orbit background induced by cosmic radiation in low Earth orbit.

Geant4 simulation of ion chambers response to 60Co spectrum of LNMRI/IRD Shepherd 81-14D Radiator

NASA Astrophysics Data System (ADS)

Queiroz Filho, P. P.; Da Silva, C. N. M.

2018-03-01

The National Ionizing Radiation Metrology Laboratory of the Radioprotection and Dosimetry Institute (LNMRI / IRD) has recently acquired a Shepherd 81-14D Radiator. In this work we simulate, using Geant4, the behavior with the inverse square law radiation for 3 models of PTW spherical chambers used in radioprotection, a relevant information to planning the measurements. We did the corrections for the attenuation and scattering in the air for each distance, where we used the 60Co spectrum simulated previously.

The GeantV project: Preparing the future of simulation

DOE PAGES

Amadio, G.; J. Apostolakis; Bandieramonte, M.; ...

2015-12-23

Detector simulation is consuming at least half of the HEP computing cycles, and even so, experiments have to take hard decisions on what to simulate, as their needs greatly surpass the availability of computing resources. New experiments still in the design phase such as FCC, CLIC and ILC as well as upgraded versions of the existing LHC detectors will push further the simulation requirements. Since the increase in computing resources is not likely to keep pace with our needs, it is therefore necessary to explore innovative ways of speeding up simulation in order to sustain the progress of High Energymore » Physics. The GeantV project aims at developing a high performance detector simulation system integrating fast and full simulation that can be ported on different computing architectures, including CPU accelerators. After more than two years of R&D the project has produced a prototype capable of transporting particles in complex geometries exploiting micro-parallelism, SIMD and multithreading. Portability is obtained via C++ template techniques that allow the development of machine- independent computational kernels. Furthermore, a set of tables derived from Geant4 for cross sections and final states provides a realistic shower development and, having been ported into a Geant4 physics list, can be used as a basis for a direct performance comparison.« less

Average stopping powers for electron and photon sources for radiobiological modeling and microdosimetric applications

NASA Astrophysics Data System (ADS)

Vassiliev, Oleg N.; Kry, Stephen F.; Grosshans, David R.; Mohan, Radhe

2018-03-01

This study concerns calculation of the average electronic stopping power for photon and electron sources. It addresses two problems that have not yet been fully resolved. The first is defining the electron spectrum used for averaging in a way that is most suitable for radiobiological modeling. We define it as the spectrum of electrons entering the sensitive to radiation volume (SV) within the cell nucleus, at the moment they enter the SV. For this spectrum we derive a formula that combines linearly the fluence spectrum and the source spectrum. The latter is the distribution of initial energies of electrons produced by a source. Previous studies used either the fluence or source spectra, but not both, thereby neglecting a part of the complete spectrum. Our derived formula reduces to these two prior methods in the case of high and low energy sources, respectively. The second problem is extending electron spectra to low energies. Previous studies used an energy cut-off on the order of 1 keV. However, as we show, even for high energy sources, such as 60Co, electrons with energies below 1 keV contribute about 30% to the dose. In this study all the spectra were calculated with Geant4-DNA code and a cut-off energy of only 11 eV. We present formulas for calculating frequency- and dose-average stopping powers, numerical results for several important electron and photon sources, and tables with all the data needed to use our formulas for arbitrary electron and photon sources producing electrons with initial energies up to  ∼1 MeV.

Monte Carlo investigation of positron annihilation in medical positron emission tomography

NASA Astrophysics Data System (ADS)

Chin, P. W.; Spyrou, N. M.

2007-09-01

A number of Monte Carlo codes are available for simulating positron emission tomography (PET), however, physics approximations differ. A number of radiation processes are deemed negligible, some without rigorous investigation. Some PET literature quantify approximations to be valid, without citing the data source. The radiation source is the first step in Monte Carlo simulations, for some codes this is 511 keV photons 180° apart, not polyenergetic positrons with radiation histories of their own. Without prior assumptions, we investigated electron-positron annihilation under clinical PET conditions. Just before annihilation, we tallied the positron energy and position. Right after annihilation, we tallied the energy and separation angle of photon pairs. When comparing PET textbooks with theory, PENELOPE and EGSnrc, only the latter three agreed. From 10 6 radiation histories, a positron source of 15O in a chest phantom annihilated at as high as 1.58 MeV, producing photons with energies 0.30-2.20 MeV, 79-180° apart. From 10 6 radiation histories, an 18F positron source in a head phantom annihilated at energies as high as 0.56 MeV, producing 0.33-1.18 MeV photons 109-180° apart. 2.5% and 0.8% annihilation events occurred inflight in the chest and the head phantoms, respectively. PET textbooks typically either do not mention any deviation from 180°, or state a deviation of 0.25° or 0.5°. Our findings are founded on the well-established Heitler cross-sections and relativistic kinematics, both adopted unanimously by PENELOPE, EGSnrc and GEANT4. Our results highlight the effects of annihilation in-flight, a process sometimes forgotten within the PET community.

Influence of photon energy cuts on PET Monte Carlo simulation results.

PubMed

Mitev, Krasimir; Gerganov, Georgi; Kirov, Assen S; Schmidtlein, C Ross; Madzhunkov, Yordan; Kawrakow, Iwan

2012-07-01

The purpose of this work is to study the influence of photon energy cuts on the results of positron emission tomography (PET) Monte Carlo (MC) simulations. MC simulations of PET scans of a box phantom and the NEMA image quality phantom are performed for 32 photon energy cut values in the interval 0.3-350 keV using a well-validated numerical model of a PET scanner. The simulations are performed with two MC codes, egs_pet and GEANT4 Application for Tomographic Emission (GATE). The effect of photon energy cuts on the recorded number of singles, primary, scattered, random, and total coincidences as well as on the simulation time and noise-equivalent count rate is evaluated by comparing the results for higher cuts to those for 1 keV cut. To evaluate the effect of cuts on the quality of reconstructed images, MC generated sinograms of PET scans of the NEMA image quality phantom are reconstructed with iterative statistical reconstruction. The effects of photon cuts on the contrast recovery coefficients and on the comparison of images by means of commonly used similarity measures are studied. For the scanner investigated in this study, which uses bismuth germanate crystals, the transport of Bi X(K) rays must be simulated in order to obtain unbiased estimates for the number of singles, true, scattered, and random coincidences as well as for an unbiased estimate of the noise-equivalent count rate. Photon energy cuts higher than 170 keV lead to absorption of Compton scattered photons and strongly increase the number of recorded coincidences of all types and the noise-equivalent count rate. The effect of photon cuts on the reconstructed images and the similarity measures used for their comparison is statistically significant for very high cuts (e.g., 350 keV). The simulation time decreases slowly with the increase of the photon cut. The simulation of the transport of characteristic x rays plays an important role, if an accurate modeling of a PET scanner system is to be achieved. The simulation time decreases slowly with the increase of the cut which, combined with the accuracy loss at high cuts, means that the usage of high photon energy cuts is not recommended for the acceleration of MC simulations.

TOPAS/Geant4 configuration for ionization chamber calculations in proton beams

NASA Astrophysics Data System (ADS)

Wulff, Jörg; Baumann, Kilian-Simon; Verbeek, Nico; Bäumer, Christian; Timmermann, Beate; Zink, Klemens

2018-06-01

Monte Carlo (MC) calculations are a fundamental tool for the investigation of ionization chambers (ICs) in radiation fields, and for calculations in the scope of IC reference dosimetry. Geant4, as used for the toolkit TOPAS, is a major general purpose code, generally suitable for investigating ICs in primary proton beams. To provide reliable results, the impact of parameter settings and the limitations of the underlying condensed history (CH) algorithm need to be known. A Fano cavity test was implemented in Geant4 (10.03.p1) for protons, based on the existing version for electrons distributed with the Geant4 release. This self-consistent test allows the calculation to be compared with the expected result for the typical IC-like geometry of an air-filled cavity surrounded by a higher density material. Various user-selectable parameters of the CH implementation in the EMStandardOpt4 physics-list were tested for incident proton energies between 30 and 250 MeV. Using TOPAS (3.1.p1) the influence of production cuts was investigated for bare air-cavities in water, irradiated by primary protons. Detailed IC geometries for an NACP-02 plane-parallel chamber and an NE2571 Farmer-chamber were created. The overall factor f Q as a ratio between the dose-to-water and dose to the sensitive air-volume was calculated for incident proton energies between 70 and 250 MeV. The Fano test demonstrated the EMStandardOpt4 physics-list with the WentzelIV multiple scattering model as appropriate for IC calculations. If protons start perpendicular to the air cavity, no further step-size limitations are required to pass the test within 0.1%. For an isotropic source, limitations of the maximum step length within the air cavity and its surrounding as well as a limitation of the maximum fractional energy loss per step were required to pass within 0.2%. A production cut of  ⩽5 μm or  ∼15 keV for all particles yielded a constant result for f Q of bare air-filled cavities. The overall factor f Q for the detailed NACP-02 and NE2571 chamber models calculated with TOPAS agreed with the values of Gomà et al (2016 Phys. Med. Biol. 61 2389) within statistical uncertainties (1σ) of  <0.3% for almost all energies with a maximum deviation of 0.6% at 250 MeV for the NE2571. The selection of hadronic scattering models (QGSP_BIC versus QGSP_BERT) in TOPAS impacted the results at the highest energies by 0.3%  ±  0.1%. Based on the Fano cavity test, the Geant4/TOPAS Monte Carlo code, in its investigated version, can provide reliable results for IC calculations. Agreement with the detailed IC models and the published values of Gomà et al can be achieved when production cuts are reduced from the TOPAS default values. The calculations confirm the reported agreement of Gomà et al for with IAEA-TRS398 values within the given uncertainties. An additional uncertainty for the MC-calculated of  ∼0.3% by hadronic interaction models should be considered.

TOPAS/Geant4 configuration for ionization chamber calculations in proton beams.

PubMed

Wulff, Jörg; Baumann, Kilian-Simon; Verbeek, Nico; Bäumer, Christian; Timmermann, Beate; Zink, Klemens

2018-06-07

Monte Carlo (MC) calculations are a fundamental tool for the investigation of ionization chambers (ICs) in radiation fields, and for calculations in the scope of IC reference dosimetry. Geant4, as used for the toolkit TOPAS, is a major general purpose code, generally suitable for investigating ICs in primary proton beams. To provide reliable results, the impact of parameter settings and the limitations of the underlying condensed history (CH) algorithm need to be known. A Fano cavity test was implemented in Geant4 (10.03.p1) for protons, based on the existing version for electrons distributed with the Geant4 release. This self-consistent test allows the calculation to be compared with the expected result for the typical IC-like geometry of an air-filled cavity surrounded by a higher density material. Various user-selectable parameters of the CH implementation in the EMStandardOpt4 physics-list were tested for incident proton energies between 30 and 250 MeV. Using TOPAS (3.1.p1) the influence of production cuts was investigated for bare air-cavities in water, irradiated by primary protons. Detailed IC geometries for an NACP-02 plane-parallel chamber and an NE2571 Farmer-chamber were created. The overall factor f Q as a ratio between the dose-to-water and dose to the sensitive air-volume was calculated for incident proton energies between 70 and 250 MeV. The Fano test demonstrated the EMStandardOpt4 physics-list with the WentzelIV multiple scattering model as appropriate for IC calculations. If protons start perpendicular to the air cavity, no further step-size limitations are required to pass the test within 0.1%. For an isotropic source, limitations of the maximum step length within the air cavity and its surrounding as well as a limitation of the maximum fractional energy loss per step were required to pass within 0.2%. A production cut of  ⩽5 μm or  ∼15 keV for all particles yielded a constant result for f Q of bare air-filled cavities. The overall factor f Q for the detailed NACP-02 and NE2571 chamber models calculated with TOPAS agreed with the values of Gomà et al (2016 Phys. Med. Biol. 61 2389) within statistical uncertainties (1σ) of  <0.3% for almost all energies with a maximum deviation of 0.6% at 250 MeV for the NE2571. The selection of hadronic scattering models (QGSP_BIC versus QGSP_BERT) in TOPAS impacted the results at the highest energies by 0.3%  ±  0.1%. Based on the Fano cavity test, the Geant4/TOPAS Monte Carlo code, in its investigated version, can provide reliable results for IC calculations. Agreement with the detailed IC models and the published values of Gomà et al can be achieved when production cuts are reduced from the TOPAS default values. The calculations confirm the reported agreement of Gomà et al for [Formula: see text] with IAEA-TRS398 values within the given uncertainties. An additional uncertainty for the MC-calculated [Formula: see text] of  ∼0.3% by hadronic interaction models should be considered.

Monte Carlo simulation of chemistry following radiolysis with TOPAS-nBio.

PubMed

Ramos-Méndez, J; Perl, J; Schuemann, J; McNamara, A; Paganetti, H; Faddegon, B

2018-05-17

Simulation of water radiolysis and the subsequent chemistry provides important information on the effect of ionizing radiation on biological material. The Geant4 Monte Carlo toolkit has added chemical processes via the Geant4-DNA project. The TOPAS tool simplifies the modeling of complex radiotherapy applications with Geant4 without requiring advanced computational skills, extending the pool of users. Thus, a new extension to TOPAS, TOPAS-nBio, is under development to facilitate the configuration of track-structure simulations as well as water radiolysis simulations with Geant4-DNA for radiobiological studies. In this work, radiolysis simulations were implemented in TOPAS-nBio. Users may now easily add chemical species and their reactions, and set parameters including branching ratios, dissociation schemes, diffusion coefficients, and reaction rates. In addition, parameters for the chemical stage were re-evaluated and updated from those used by default in Geant4-DNA to improve the accuracy of chemical yields. Simulation results of time-dependent and LET-dependent primary yields G x (chemical species per 100 eV deposited) produced at neutral pH and 25 °C by short track-segments of charged particles were compared to published measurements. The LET range was 0.05-230 keV µm -1 . The calculated G x values for electrons satisfied the material balance equation within 0.3%, similar for protons albeit with long calculation time. A smaller geometry was used to speed up proton and alpha simulations, with an acceptable difference in the balance equation of 1.3%. Available experimental data of time-dependent G-values for [Formula: see text] agreed with simulated results within 7%  ±  8% over the entire time range; for [Formula: see text] over the full time range within 3%  ±  4%; for H 2 O 2 from 49%  ±  7% at earliest stages and 3%  ±  12% at saturation. For the LET-dependent G x , the mean ratios to the experimental data were 1.11  ±  0.98, 1.21  ±  1.11, 1.05  ±  0.52, 1.23  ±  0.59 and 1.49  ±  0.63 (1 standard deviation) for [Formula: see text], [Formula: see text], H 2 , H 2 O 2 and [Formula: see text], respectively. In conclusion, radiolysis and subsequent chemistry with Geant4-DNA has been successfully incorporated in TOPAS-nBio. Results are in reasonable agreement with published measured and simulated data.

Stochastic optimization of GeantV code by use of genetic algorithms

DOE PAGES

Amadio, G.; Apostolakis, J.; Bandieramonte, M.; ...

2017-10-01

GeantV is a complex system based on the interaction of different modules needed for detector simulation, which include transport of particles in fields, physics models simulating their interactions with matter and a geometrical modeler library for describing the detector and locating the particles and computing the path length to the current volume boundary. The GeantV project is recasting the classical simulation approach to get maximum benefit from SIMD/MIMD computational architectures and highly massive parallel systems. This involves finding the appropriate balance between several aspects influencing computational performance (floating-point performance, usage of off-chip memory bandwidth, specification of cache hierarchy, etc.) andmore » handling a large number of program parameters that have to be optimized to achieve the best simulation throughput. This optimization task can be treated as a black-box optimization problem, which requires searching the optimum set of parameters using only point-wise function evaluations. Here, the goal of this study is to provide a mechanism for optimizing complex systems (high energy physics particle transport simulations) with the help of genetic algorithms and evolution strategies as tuning procedures for massive parallel simulations. One of the described approaches is based on introducing a specific multivariate analysis operator that could be used in case of resource expensive or time consuming evaluations of fitness functions, in order to speed-up the convergence of the black-box optimization problem.« less

Stochastic optimization of GeantV code by use of genetic algorithms

NASA Astrophysics Data System (ADS)

Amadio, G.; Apostolakis, J.; Bandieramonte, M.; Behera, S. P.; Brun, R.; Canal, P.; Carminati, F.; Cosmo, G.; Duhem, L.; Elvira, D.; Folger, G.; Gheata, A.; Gheata, M.; Goulas, I.; Hariri, F.; Jun, S. Y.; Konstantinov, D.; Kumawat, H.; Ivantchenko, V.; Lima, G.; Nikitina, T.; Novak, M.; Pokorski, W.; Ribon, A.; Seghal, R.; Shadura, O.; Vallecorsa, S.; Wenzel, S.

2017-10-01

GeantV is a complex system based on the interaction of different modules needed for detector simulation, which include transport of particles in fields, physics models simulating their interactions with matter and a geometrical modeler library for describing the detector and locating the particles and computing the path length to the current volume boundary. The GeantV project is recasting the classical simulation approach to get maximum benefit from SIMD/MIMD computational architectures and highly massive parallel systems. This involves finding the appropriate balance between several aspects influencing computational performance (floating-point performance, usage of off-chip memory bandwidth, specification of cache hierarchy, etc.) and handling a large number of program parameters that have to be optimized to achieve the best simulation throughput. This optimization task can be treated as a black-box optimization problem, which requires searching the optimum set of parameters using only point-wise function evaluations. The goal of this study is to provide a mechanism for optimizing complex systems (high energy physics particle transport simulations) with the help of genetic algorithms and evolution strategies as tuning procedures for massive parallel simulations. One of the described approaches is based on introducing a specific multivariate analysis operator that could be used in case of resource expensive or time consuming evaluations of fitness functions, in order to speed-up the convergence of the black-box optimization problem.

Stochastic optimization of GeantV code by use of genetic algorithms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amadio, G.; Apostolakis, J.; Bandieramonte, M.

GeantV is a complex system based on the interaction of different modules needed for detector simulation, which include transport of particles in fields, physics models simulating their interactions with matter and a geometrical modeler library for describing the detector and locating the particles and computing the path length to the current volume boundary. The GeantV project is recasting the classical simulation approach to get maximum benefit from SIMD/MIMD computational architectures and highly massive parallel systems. This involves finding the appropriate balance between several aspects influencing computational performance (floating-point performance, usage of off-chip memory bandwidth, specification of cache hierarchy, etc.) andmore » handling a large number of program parameters that have to be optimized to achieve the best simulation throughput. This optimization task can be treated as a black-box optimization problem, which requires searching the optimum set of parameters using only point-wise function evaluations. Here, the goal of this study is to provide a mechanism for optimizing complex systems (high energy physics particle transport simulations) with the help of genetic algorithms and evolution strategies as tuning procedures for massive parallel simulations. One of the described approaches is based on introducing a specific multivariate analysis operator that could be used in case of resource expensive or time consuming evaluations of fitness functions, in order to speed-up the convergence of the black-box optimization problem.« less

Designing an upgrade of the Medley setup for light-ion production and fission cross-section measurements

NASA Astrophysics Data System (ADS)

Jansson, K.; Gustavsson, C.; Al-Adili, A.; Hjalmarsson, A.; Andersson-Sundén, E.; Prokofiev, A. V.; Tarrío, D.; Pomp, S.

2015-09-01

Measurements of neutron-induced fission cross-sections and light-ion production are planned in the energy range 1-40 MeV at the upcoming Neutrons For Science (NFS) facility. In order to prepare our detector setup for the neutron beam with continuous energy spectrum, a simulation software was written using the Geant4 toolkit for both measurement situations. The neutron energy range around 20 MeV is troublesome when it comes to the cross-sections used by Geant4 since data-driven cross-sections are only available below 20 MeV but not above, where they are based on semi-empirical models. Several customisations were made to the standard classes in Geant4 in order to produce consistent results over the whole simulated energy range. Expected uncertainties are reported for both types of measurements. The simulations have shown that a simultaneous precision measurement of the three standard cross-sections H(n,n), 235U(n,f) and 238U(n,f) relative to each other is feasible using a triple layered target. As high resolution timing detectors for fission fragments we plan to use Parallel Plate Avalanche Counters (PPACs). The simulation results have put some restrictions on the design of these detectors as well as on the target design. This study suggests a fissile target no thicker than 2 μm (1.7 mg/cm2) and a PPAC foil thickness preferably less than 1 μm. We also comment on the usability of Geant4 for simulation studies of neutron reactions in this energy range.

Comparison of electromagnetic and hadronic models generated using Geant 4 with antiproton dose measured in CERN.

PubMed

Tavakoli, Mohammad Bagher; Reiazi, Reza; Mohammadi, Mohammad Mehdi; Jabbari, Keyvan

2015-01-01

After proposing the idea of antiproton cancer treatment in 1984 many experiments were launched to investigate different aspects of physical and radiobiological properties of antiproton, which came from its annihilation reactions. One of these experiments has been done at the European Organization for Nuclear Research known as CERN using the antiproton decelerator. The ultimate goal of this experiment was to assess the dosimetric and radiobiological properties of beams of antiprotons in order to estimate the suitability of antiprotons for radiotherapy. One difficulty on this way was the unavailability of antiproton beam in CERN for a long time, so the verification of Monte Carlo codes to simulate antiproton depth dose could be useful. Among available simulation codes, Geant4 provides acceptable flexibility and extensibility, which progressively lead to the development of novel Geant4 applications in research domains, especially modeling the biological effects of ionizing radiation at the sub-cellular scale. In this study, the depth dose corresponding to CERN antiproton beam energy by Geant4 recruiting all the standard physics lists currently available and benchmarked for other use cases were calculated. Overall, none of the standard physics lists was able to draw the antiproton percentage depth dose. Although, with some models our results were promising, the Bragg peak level remained as the point of concern for our study. It is concluded that the Bertini model with high precision neutron tracking (QGSP_BERT_HP) is the best to match the experimental data though it is also the slowest model to simulate events among the physics lists.

Comparison of the thermal neutron scattering treatment in MCNP6 and GEANT4 codes

NASA Astrophysics Data System (ADS)

Tran, H. N.; Marchix, A.; Letourneau, A.; Darpentigny, J.; Menelle, A.; Ott, F.; Schwindling, J.; Chauvin, N.

2018-06-01

To ensure the reliability of simulation tools, verification and comparison should be made regularly. This paper describes the work performed in order to compare the neutron transport treatment in MCNP6.1 and GEANT4-10.3 in the thermal energy range. This work focuses on the thermal neutron scattering processes for several potential materials which would be involved in the neutron source designs of Compact Accelerator-based Neutrons Sources (CANS), such as beryllium metal, beryllium oxide, polyethylene, graphite, para-hydrogen, light water, heavy water, aluminium and iron. Both thermal scattering law and free gas model, coming from the evaluated data library ENDF/B-VII, were considered. It was observed that the GEANT4.10.03-patch2 version was not able to account properly the coherent elastic process occurring in crystal lattice. This bug is treated in this work and it should be included in the next release of the code. Cross section sampling and integral tests have been performed for both simulation codes showing a fair agreement between the two codes for most of the materials except for iron and aluminium.

Abstract ID: 176 Geant4 implementation of inter-atomic interference effect in small-angle coherent X-ray scattering for materials of medical interest.

PubMed

Paternò, Gianfranco; Cardarelli, Paolo; Contillo, Adriano; Gambaccini, Mauro; Taibi, Angelo

2018-01-01

Advanced applications of digital mammography such as dual-energy and tomosynthesis require multiple exposures and thus deliver higher dose compared to standard mammograms. A straightforward manner to reduce patient dose without affecting image quality would be removal of the anti-scatter grid, provided that the involved reconstruction algorithms are able to take the scatter figure into account [1]. Monte Carlo simulations are very well suited for the calculation of X-ray scatter distribution and can be used to integrate such information within the reconstruction software. Geant4 is an open source C++ particle tracking code widely used in several physical fields, including medical physics [2,3]. However, the coherent scattering cross section used by the standard Geant4 code does not take into account the influence of molecular interference. According to the independent atomic scattering approximation (the so-called free-atom model), coherent radiation is indistinguishable from primary radiation because its angular distribution is peaked in the forward direction. Since interference effects occur between x-rays scattered by neighbouring atoms in matter, it was shown experimentally that the scatter distribution is affected by the molecular structure of the target, even in amorphous materials. The most important consequence is that the coherent scatter distribution is not peaked in the forward direction, and the position of the maximum is strongly material-dependent [4]. In this contribution, we present the implementation of a method to take into account inter-atomic interference in small-angle coherent scattering in Geant4, including a dedicated data set of suitable molecular form factor values for several materials of clinical interest. Furthermore, we present scatter images of simple geometric phantoms in which the Rayleigh contribution is rigorously evaluated. Copyright © 2017.

Verification of Electromagnetic Physics Models for Parallel Computing Architectures in the GeantV Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amadio, G.; et al.

An intensive R&D and programming effort is required to accomplish new challenges posed by future experimental high-energy particle physics (HEP) programs. The GeantV project aims to narrow the gap between the performance of the existing HEP detector simulation software and the ideal performance achievable, exploiting latest advances in computing technology. The project has developed a particle detector simulation prototype capable of transporting in parallel particles in complex geometries exploiting instruction level microparallelism (SIMD and SIMT), task-level parallelism (multithreading) and high-level parallelism (MPI), leveraging both the multi-core and the many-core opportunities. We present preliminary verification results concerning the electromagnetic (EM) physicsmore » models developed for parallel computing architectures within the GeantV project. In order to exploit the potential of vectorization and accelerators and to make the physics model effectively parallelizable, advanced sampling techniques have been implemented and tested. In this paper we introduce a set of automated statistical tests in order to verify the vectorized models by checking their consistency with the corresponding Geant4 models and to validate them against experimental data.« less

Diffusion-controlled reactions modeling in Geant4-DNA

NASA Astrophysics Data System (ADS)

Karamitros, M.; Luan, S.; Bernal, M. A.; Allison, J.; Baldacchino, G.; Davidkova, M.; Francis, Z.; Friedland, W.; Ivantchenko, V.; Ivantchenko, A.; Mantero, A.; Nieminem, P.; Santin, G.; Tran, H. N.; Stepan, V.; Incerti, S.

2014-10-01

Context Under irradiation, a biological system undergoes a cascade of chemical reactions that can lead to an alteration of its normal operation. There are different types of radiation and many competing reactions. As a result the kinetics of chemical species is extremely complex. The simulation becomes then a powerful tool which, by describing the basic principles of chemical reactions, can reveal the dynamics of the macroscopic system. To understand the dynamics of biological systems under radiation, since the 80s there have been on-going efforts carried out by several research groups to establish a mechanistic model that consists in describing all the physical, chemical and biological phenomena following the irradiation of single cells. This approach is generally divided into a succession of stages that follow each other in time: (1) the physical stage, where the ionizing particles interact directly with the biological material; (2) the physico-chemical stage, where the targeted molecules release their energy by dissociating, creating new chemical species; (3) the chemical stage, where the new chemical species interact with each other or with the biomolecules; (4) the biological stage, where the repairing mechanisms of the cell come into play. This article focuses on the modeling of the chemical stage. Method This article presents a general method of speeding-up chemical reaction simulations in fluids based on the Smoluchowski equation and Monte-Carlo methods, where all molecules are explicitly simulated and the solvent is treated as a continuum. The model describes diffusion-controlled reactions. This method has been implemented in Geant4-DNA. The keys to the new algorithm include: (1) the combination of a method to compute time steps dynamically with a Brownian bridge process to account for chemical reactions, which avoids costly fixed time step simulations; (2) a k-d tree data structure for quickly locating, for a given molecule, its closest reactants. The performance advantage is presented in terms of complexity, and the accuracy of the new algorithm is demonstrated by simulating radiation chemistry in the context of the Geant4-DNA project. Application The time-dependent radiolytic yields of the main chemical species formed after irradiation are computed for incident protons at different energies (from 50 MeV to 500 keV). Both the time-evolution and energy dependency of the yields are discussed. The evolution, at one microsecond, of the yields of hydroxyls and solvated electrons with respect to the linear energy transfer is compared to theoretical and experimental data. According to our results, at high linear energy transfer, modeling radiation chemistry in the trading compartment representation might be adopted.

Modelling PET radionuclide production in tissue and external targets using Geant4

NASA Astrophysics Data System (ADS)

Amin, T.; Infantino, A.; Lindsay, C.; Barlow, R.; Hoehr, C.

2017-07-01

The Proton Therapy Facility in TRIUMF provides 74 MeV protons extracted from a 500 MeV H- cyclotron for ocular melanoma treatments. During treatment, positron emitting radionuclides such as 1C, 15O and 13N are produced in patient tissue. Using PET scanners, the isotopic activity distribution can be measured for in-vivo range verification. A second cyclotron, the TR13, provides 13 MeV protons onto liquid targets for the production of PET radionuclides such as 18F, 13N or 68Ga, for medical applications. The aim of this work was to validate Geant4 against FLUKA and experimental measurements for production of the above-mentioned isotopes using the two cyclotrons. The results show variable degrees of agreement. For proton therapy, the proton-range agreement was within 2 mm for 11C activity, whereas 13N disagreed. For liquid targets at the TR13 the average absolute deviation ratio between FLUKA and experiment was 1.9±2.7, whereas the average absolute deviation ratio between Geant4 and experiment was 0. 6±0.4. This is due to the uncertainties present in experimentally determined reaction cross sections.

GEANT4 benchmark with MCNPX and PHITS for activation of concrete

NASA Astrophysics Data System (ADS)

Tesse, Robin; Stichelbaut, Frédéric; Pauly, Nicolas; Dubus, Alain; Derrien, Jonathan

2018-02-01

The activation of concrete is a real problem from the point of view of waste management. Because of the complexity of the issue, Monte Carlo (MC) codes have become an essential tool to its study. But various codes or even nuclear models exist in MC. MCNPX and PHITS have already been validated for shielding studies but GEANT4 is also a suitable solution. In these codes, different models can be considered for a concrete activation study. The Bertini model is not the best model for spallation while BIC and INCL model agrees well with previous results in literature.

Fast Simulation of the Impact Parameter Calculation of Electrons through Pair Production

NASA Astrophysics Data System (ADS)

Bang, Hyesun; Kweon, MinJung; Huh, Kyoung Bum; Pachmayer, Yvonne

2018-05-01

A fast simulation method is introduced that reduces tremendously the time required for the impact parameter calculation, a key observable in physics analyses of high energy physics experiments and detector optimisation studies. The impact parameter of electrons produced through pair production was calculated considering key related processes using the Bethe-Heitler formula, the Tsai formula and a simple geometric model. The calculations were performed at various conditions and the results were compared with those from full GEANT4 simulations. The computation time using this fast simulation method is 104 times shorter than that of the full GEANT4 simulation.

Detailed measurements of shower properties in a high granularity digital electromagnetic calorimeter

NASA Astrophysics Data System (ADS)

van der Kolk, N.

2018-03-01

The MAPS (Monolithic Active Pixel Sensors) prototype of the proposed ALICE Forward Calorimeter (FoCal) is the highest granularity electromagnetic calorimeter, with 39 million pixels with a size of 30 × 30 μm2. Particle showers can be studied with unprecedented detail with this prototype. Electromagnetic showers at energies between 2 GeV and 244 GeV have been studied and compared with GEANT4 simulations. Simulation models can be tested in more detail than ever before and the differences observed between FoCal data and GEANT4 simulations illustrate that improvements in electromagnetic models are still possible.

Superconducting Qubit Optical Transducer (SQOT)

DTIC Science & Technology

2015-08-05

2 2.2 Qubit- Photon Entanglement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2.1 System...and a high Q will make this challenging. 3 2.2 QUBIT- PHOTON ENTANGLEMENT The parametric interaction enables interconversion between the microwave and...to observe entanglement between a qubit and optical photon and similar to experiments demonstrated solely in the microwave domain [4]: 1. Start with

Development of MCNPX-ESUT computer code for simulation of neutron/gamma pulse height distribution

NASA Astrophysics Data System (ADS)

Abolfazl Hosseini, Seyed; Vosoughi, Naser; Zangian, Mehdi

2015-05-01

In this paper, the development of the MCNPX-ESUT (MCNPX-Energy Engineering of Sharif University of Technology) computer code for simulation of neutron/gamma pulse height distribution is reported. Since liquid organic scintillators like NE-213 are well suited and routinely used for spectrometry in mixed neutron/gamma fields, this type of detectors is selected for simulation in the present study. The proposed algorithm for simulation includes four main steps. The first step is the modeling of the neutron/gamma particle transport and their interactions with the materials in the environment and detector volume. In the second step, the number of scintillation photons due to charged particles such as electrons, alphas, protons and carbon nuclei in the scintillator material is calculated. In the third step, the transport of scintillation photons in the scintillator and lightguide is simulated. Finally, the resolution corresponding to the experiment is considered in the last step of the simulation. Unlike the similar computer codes like SCINFUL, NRESP7 and PHRESP, the developed computer code is applicable to both neutron and gamma sources. Hence, the discrimination of neutron and gamma in the mixed fields may be performed using the MCNPX-ESUT computer code. The main feature of MCNPX-ESUT computer code is that the neutron/gamma pulse height simulation may be performed without needing any sort of post processing. In the present study, the pulse height distributions due to a monoenergetic neutron/gamma source in NE-213 detector using MCNPX-ESUT computer code is simulated. The simulated neutron pulse height distributions are validated through comparing with experimental data (Gohil et al. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 664 (2012) 304-309.) and the results obtained from similar computer codes like SCINFUL, NRESP7 and Geant4. The simulated gamma pulse height distribution for a 137Cs source is also compared with the experimental data.

Monte Carlo calculation of dose rate conversion factors for external exposure to photon emitters in soil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clovas, A.; Zanthos, S.; Antonopoulos-Domis, M.

2000-03-01

The dose rate conversion factors {dot D}{sub CF} (absorbed dose rate in air per unit activity per unit of soil mass, nGy h{sup {minus}1} per Bq kg{sup {minus}1}) are calculated 1 m above ground for photon emitters of natural radionuclides uniformly distributed in the soil. Three Monte Carlo codes are used: (1) The MCNP code of Los Alamos; (2) The GEANT code of CERN; and (3) a Monte Carlo code developed in the Nuclear Technology Laboratory of the Aristotle University of Thessaloniki. The accuracy of the Monte Carlo results is tested by the comparison of the unscattered flux obtained bymore » the three Monte Carlo codes with an independent straightforward calculation. All codes and particularly the MCNP calculate accurately the absorbed dose rate in air due to the unscattered radiation. For the total radiation (unscattered plus scattered) the {dot D}{sub CF} values calculated from the three codes are in very good agreement between them. The comparison between these results and the results deduced previously by other authors indicates a good agreement (less than 15% of difference) for photon energies above 1,500 keV. Antithetically, the agreement is not as good (difference of 20--30%) for the low energy photons.« less

Development of a silicon diode detector for skin dosimetry in radiotherapy.

PubMed

Vicoroski, Nikolina; Espinoza, Anthony; Duncan, Mitchell; Oborn, Bradley M; Carolan, Martin; Metcalfe, Peter; Menichelli, David; Perevertaylo, Vladimir L; Lerch, Michael L F; Rosenfeld, Anatoly B; Petasecca, Marco

2017-10-01

The aim of in vivo skin dosimetry was to measure the absorbed dose to the skin during radiotherapy, when treatment planning calculations cannot be relied on. It is of particularly importance in hypo-fractionated stereotactic modalities, where excessive dose can lead to severe skin toxicity. Currently, commercial diodes for such applications are with water equivalent depths ranging from 0.5 to 0.8 mm. In this study, we investigate a new detector for skin dosimetry based on a silicon epitaxial diode, referred to as the skin diode. The skin diode is manufactured on a thin epitaxial layer and packaged using the "drop-in" technology. It was characterized in terms of percentage depth dose, dose linearity, and dose rate dependence, and benchmarked against the Attix ionization chamber. The response of the skin diode in the build-up region of the percentage depth dose (PDD) curve of a 6 MV clinical photon beam was investigated. Geant4 radiation transport simulations were used to model the PDD in order to estimate the water equivalent measurement depth (WED) of the skin diode. Measured output factors using the skin diode were compared with the MOSkin detector and EBT3 film at 10 cm depth and at surface at isocenter of a water equivalent phantom. The intrinsic angular response of the skin diode was also quantified in charge particle equilibrium conditions (CPE) and at the surface of a solid water phantom. Finally, the radiation hardness of the skin diode up to an accumulated dose of 80 kGy using photons from a Co-60 gamma source was evaluated. The PDD curve measured with the skin diode was within 0.5% agreement of the equivalent Geant4 simulated curve. When placed at the phantom surface, the WED of the skin diode was estimated to be 0.075 ± 0.005 mm from Geant4 simulations and was confirmed using the response of a corrected Attix ionization chamber placed at water equivalent depth of 0.075 mm, with the measurement agreement to within 0.3%. The output factor measurements at 10 cm depth were within 2% of those measured with film and the MOSkin detector down to a field size of 2 × 2 cm 2 . The dose-response for all detector samples was linear and with a repeatability within 0.2%. The skin diode intrinsic angular response showed a maximum deviation of 8% at 90 degrees and from 0 to 60 degree is less than 5%. The radiation sensitivity reduced by 25% after an accumulated dose of 20 kGy but after was found to stabilize. At 60 kGy total accumulated dose the response was within 2% of that measured at 20 kGy total accumulated dose. This work characterizes an innovative detector for in vivo and real-time skin dose measurements that is based on an epitaxial silicon diode combined with the Centre for Medical Radiation Physics (CMRP) "drop-in" packaging technology. The skin diode proved to have a water equivalent depth of measurement of 0.075 ± 0.005 mm and the ability to measure doses accurately relative to reference detectors. © 2017 American Association of Physicists in Medicine.

Effect of the multiple scattering of electrons in Monte Carlo simulation of LINACS.

PubMed

Vilches, Manuel; García-Pareja, Salvador; Guerrero, Rafael; Anguiano, Marta; Lallena, Antonio M

2008-01-01

Results obtained from Monte Carlo simulations of the transport of electrons in thin slabs of dense material media and air slabs with different widths are analyzed. Various general purpose Monte Carlo codes have been used: PENELOPE, GEANT3, GEANT4, EGSNRC, MCNPX. Non-negligible differences between the angular and radial distributions after the slabs have been found. The effects of these differences on the depth doses measured in water are also discussed.

A Prototype Scintillating-Fibre Tracker for the Cosmic-ray Muon Tomography of Legacy Nuclear Waste Containers

NASA Astrophysics Data System (ADS)

Kaiser, R.; Clarkson, A.; Hamilton, D. J.; Hoek, M.; Ireland, D. G.; Johnston, J. R.; Keri, T.; Lumsden, S.; Mahon, D. F.; McKinnon, B.; Murray, M.; Nutbeam-Tuffs, S.; Shearer, C.; Staines, C.; Yang, G.; Zimmerman, C.

2014-03-01

Cosmic-ray muons are highly-penetrative charged particles observed at sea level with a flux of approximately 1 cm-2 min-1. They interact with matter primarily through Coulomb scattering which can be exploited in muon tomography to image objects within industrial nuclear waste containers. This paper presents the prototype scintillating-fibre detector developed for this application at the University of Glasgow. Experimental results taken with test objects are shown in comparison to results from GEANT4 simulations. These results verify the simulation and show discrimination between the low, medium and high-Z materials imaged.

Monte-Carlo Application for Nondestructive Nuclear Waste Analysis

NASA Astrophysics Data System (ADS)

Carasco, C.; Engels, R.; Frank, M.; Furletov, S.; Furletova, J.; Genreith, C.; Havenith, A.; Kemmerling, G.; Kettler, J.; Krings, T.; Ma, J.-L.; Mauerhofer, E.; Neike, D.; Payan, E.; Perot, B.; Rossbach, M.; Schitthelm, O.; Schumann, M.; Vasquez, R.

2014-06-01

Radioactive waste has to undergo a process of quality checking in order to check its conformance with national regulations prior to its transport, intermediate storage and final disposal. Within the quality checking of radioactive waste packages non-destructive assays are required to characterize their radio-toxic and chemo-toxic contents. The Institute of Energy and Climate Research - Nuclear Waste Management and Reactor Safety of the Forschungszentrum Jülich develops in the framework of cooperation nondestructive analytical techniques for the routine characterization of radioactive waste packages at industrial-scale. During the phase of research and development Monte Carlo techniques are used to simulate the transport of particle, especially photons, electrons and neutrons, through matter and to obtain the response of detection systems. The radiological characterization of low and intermediate level radioactive waste drums is performed by segmented γ-scanning (SGS). To precisely and accurately reconstruct the isotope specific activity content in waste drums by SGS measurement, an innovative method called SGSreco was developed. The Geant4 code was used to simulate the response of the collimated detection system for waste drums with different activity and matrix configurations. These simulations allow a far more detailed optimization, validation and benchmark of SGSreco, since the construction of test drums covering a broad range of activity and matrix properties is time consuming and cost intensive. The MEDINA (Multi Element Detection based on Instrumental Neutron Activation) test facility was developed to identify and quantify non-radioactive elements and substances in radioactive waste drums. MEDINA is based on prompt and delayed gamma neutron activation analysis (P&DGNAA) using a 14 MeV neutron generator. MCNP simulations were carried out to study the response of the MEDINA facility in terms of gamma spectra, time dependence of the neutron energy spectrum, neutron flux distribution. The validation of the measurements simulations with Mont-Carlo transport codes for the design, optimization and data analysis of further P&DGNAA facilities is performed in collaboration with LMN CEA Cadarache. The performance of the prompt gamma neutron activation analysis (PGNAA) for the nondestructive determination of actinides in small samples is investigated. The quantitative determination of actinides relies on the precise knowledge of partial neutron capture cross sections. Up to today these cross sections are not very accurate for analytical purpose. The goal of the TANDEM (Trans-uranium Actinides' Nuclear Data - Evaluation and Measurement) Collaboration is the evaluation of these cross sections. Cross sections are measured using prompt gamma activation analysis facilities in Budapest and Munich. Geant4 is used to optimally design the detection system with Compton suppression. Furthermore, for the evaluation of the cross sections it is strongly needed to correct the results to the self-attenuation of the prompt gammas within the sample. In the framework of cooperation RWTH Aachen University, Forschungszentrum Jülich and the Siemens AG will study the feasibility of a compact Neutron Imaging System for Radioactive waste Analysis (NISRA). The system is based on a 14 MeV neutron source and an advanced detector system (a-Si flat panel) linked to an exclusive converter/scintillator for fast neutrons. For shielding and radioprotection studies the codes MCNPX and Geant4 were used. The two codes were benchmarked in processing time and accuracy in the neutron and gamma fluxes. Also the detector response was simulated with Geant4 to optimize components of the system.

GePEToS: A Geant4 Monte Carlo Simulation Package for Positron Emission Tomography

NASA Astrophysics Data System (ADS)

Jan, S.; Collot, J.; Gallin-Martel, M.-L.; Martin, P.; Mayet, F.; Tournefier, E.

2005-02-01

GePEToS is a simulation framework developed over the last few years for assessing the instrumental performance of future positron emission tomography (PET) scanners. It is based on Geant4, written in object-oriented C++ and runs on Linux platforms. The validity of GePEToS has been tested on the well-known Siemens ECAT EXACT HR+ camera. The results of two application examples are presented: the design optimization of a liquid Xe /spl mu/PET camera dedicated to small animal imaging as well as the evaluation of the effect of a strong axial magnetic field on the image resolution of a Concorde P4 /spl mu/PET camera.

Characterizing and simulation the scintillation properties of zinc oxide nanowires in AAO membrane for medical imaging applications

NASA Astrophysics Data System (ADS)

Esfandi, F.; Saramad, S.; Rezaei Shahmirzadi, M.

2017-07-01

In this work, a new method is proposed for extracting some X-ray detection properties of ZnO nanowires electrodeposited on Anodized Aluminum Oxide (AAO) nanoporous template. The results show that the detection efficiency for 12μm thickness of zinc oxide nano scintillator at an energy of 9.8 keV, near the K-edge of ZnO (9.65 keV), is 24%. The X-rays that interact with AAO can also generate electrons that reach the nano scintillator. The scintillation events of these electrons are seen as a low energy tail in the spectrum. In addition, it is found that all the X-rays that are absorbed in 300 nm thickness of the gold layer on the top of the zinc oxide nanowires can participate in the scintillation process with an efficiency of 6%. Hence, the scintillation detection efficiency of the whole detector for 9.8 keV X-ray energy is 30%. The simulation results from Geant4 and the experimental detected photons per MeV energy deposition are also used to extract the light yield of the zinc oxide nano scintillator. The results show that the light yield of the zinc oxide nanowires deposited by the electrochemical method is approximately the same as for single crystal zinc oxide scintillator (9000). Much better spatial resolution of this nano scintillator in comparison to the bulk ones is an advantage which candidates this nano scintillator for medical imaging applications.

Modeling of a cyclotron target for the production of 11C with Geant4.

PubMed

Chiappiniello, Andrea; Zagni, Federico; Infantino, Angelo; Vichi, Sara; Cicoria, Gianfranco; Morigi, Maria Pia; Marengo, Mario

2018-04-12

In medical cyclotron facilities, 11C is produced according to the 14N(p,α)11C reaction and widely employed in studies of prostate and brain cancers by Positron Emission Tomography. It is known from literature [1] that the 11C-target assembly shows a reduction in efficiency during time, meaning a decrease of activity produced at the end of bombardment. This effect might depend on aspects still not completely known. Possible causes of the loss of performance of the 11C-target assembly were addressed by Monte Carlo simulations. Geant4 was used to model the 11C-target assembly of a GE PETtrace cyclotron. The physical and transport parameters to be used in the energy range of medical applications were extracted from literature data and 11C routine productions. The Monte Carlo assessment of 11C saturation yield was performed varying several parameters such as the proton energy and the angle of the target assembly with respect to the proton beam. The estimated 11C saturation yield is in agreement with IAEA data at the energy of interest, while is about the 35% greater than experimental value. A more comprehensive modeling of the target system, including thermodynamic effect, is required. The energy absorbed in the inner layer of the target chamber was up to 46.5 J/mm2 under typical irradiation conditions. This study shows that Geant4 is potentially a useful tool to design and optimize targetry for PET radionuclide productions. Tests to choose the Geant4 physics libraries should be performed before using this tool with different energies and materials. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

Dose calculations at high altitudes and in deep space with GEANT4 using BIC and JQMD models for nucleus nucleus reactions

NASA Astrophysics Data System (ADS)

Sihver, L.; Matthiä, D.; Koi, T.; Mancusi, D.

2008-10-01

Radiation exposure of aircrew is more and more recognized as an occupational hazard. The ionizing environment at standard commercial aircraft flight altitudes consists mainly of secondary particles, of which the neutrons give a major contribution to the dose equivalent. Accurate estimations of neutron spectra in the atmosphere are therefore essential for correct calculations of aircrew doses. Energetic solar particle events (SPE) could also lead to significantly increased dose rates, especially at routes close to the North Pole, e.g. for flights between Europe and USA. It is also well known that the radiation environment encountered by personnel aboard low Earth orbit (LEO) spacecraft or aboard a spacecraft traveling outside the Earth's protective magnetosphere is much harsher compared with that within the atmosphere since the personnel are exposed to radiation from both galactic cosmic rays (GCR) and SPE. The relative contribution to the dose from GCR when traveling outside the Earth's magnetosphere, e.g. to the Moon or Mars, is even greater, and reliable and accurate particle and heavy ion transport codes are essential to calculate the radiation risks for both aircrew and personnel on spacecraft. We have therefore performed calculations of neutron distributions in the atmosphere, total dose equivalents, and quality factors at different depths in a water sphere in an imaginary spacecraft during solar minimum in a geosynchronous orbit. The calculations were performed with the GEANT4 Monte Carlo (MC) code using both the binary cascade (BIC) model, which is part of the standard GEANT4 package, and the JQMD model, which is used in the particle and heavy ion transport code PHITS GEANT4.

Simulation of the Mg(Ar) ionization chamber currents by different Monte Carlo codes in benchmark gamma fields

NASA Astrophysics Data System (ADS)

Lin, Yi-Chun; Liu, Yuan-Hao; Nievaart, Sander; Chen, Yen-Fu; Wu, Shu-Wei; Chou, Wen-Tsae; Jiang, Shiang-Huei

2011-10-01

High energy photon (over 10 MeV) and neutron beams adopted in radiobiology and radiotherapy always produce mixed neutron/gamma-ray fields. The Mg(Ar) ionization chambers are commonly applied to determine the gamma-ray dose because of its neutron insensitive characteristic. Nowadays, many perturbation corrections for accurate dose estimation and lots of treatment planning systems are based on Monte Carlo technique. The Monte Carlo codes EGSnrc, FLUKA, GEANT4, MCNP5, and MCNPX were used to evaluate energy dependent response functions of the Exradin M2 Mg(Ar) ionization chamber to a parallel photon beam with mono-energies from 20 keV to 20 MeV. For the sake of validation, measurements were carefully performed in well-defined (a) primary M-100 X-ray calibration field, (b) primary 60Co calibration beam, (c) 6-MV, and (d) 10-MV therapeutic beams in hospital. At energy region below 100 keV, MCNP5 and MCNPX both had lower responses than other codes. For energies above 1 MeV, the MCNP ITS-mode greatly resembled other three codes and the differences were within 5%. Comparing to the measured currents, MCNP5 and MCNPX using ITS-mode had perfect agreement with the 60Co, and 10-MV beams. But at X-ray energy region, the derivations reached 17%. This work shows us a better insight into the performance of different Monte Carlo codes in photon-electron transport calculation. Regarding the application of the mixed field dosimetry like BNCT, MCNP with ITS-mode is recognized as the most suitable tool by this work.

Monte Carlo simulations and benchmark measurements on the response of TE(TE) and Mg(Ar) ionization chambers in photon, electron and neutron beams

NASA Astrophysics Data System (ADS)

Lin, Yi-Chun; Huang, Tseng-Te; Liu, Yuan-Hao; Chen, Wei-Lin; Chen, Yen-Fu; Wu, Shu-Wei; Nievaart, Sander; Jiang, Shiang-Huei

2015-06-01

The paired ionization chambers (ICs) technique is commonly employed to determine neutron and photon doses in radiology or radiotherapy neutron beams, where neutron dose shows very strong dependence on the accuracy of accompanying high energy photon dose. During the dose derivation, it is an important issue to evaluate the photon and electron response functions of two commercially available ionization chambers, denoted as TE(TE) and Mg(Ar), used in our reactor based epithermal neutron beam. Nowadays, most perturbation corrections for accurate dose determination and many treatment planning systems are based on the Monte Carlo technique. We used general purposed Monte Carlo codes, MCNP5, EGSnrc, FLUKA or GEANT4 for benchmark verifications among them and carefully measured values for a precise estimation of chamber current from absorbed dose rate of cavity gas. Also, energy dependent response functions of two chambers were calculated in a parallel beam with mono-energies from 20 keV to 20 MeV photons and electrons by using the optimal simple spherical and detailed IC models. The measurements were performed in the well-defined (a) four primary M-80, M-100, M120 and M150 X-ray calibration fields, (b) primary 60Co calibration beam, (c) 6 MV and 10 MV photon, (d) 6 MeV and 18 MeV electron LINACs in hospital and (e) BNCT clinical trials neutron beam. For the TE(TE) chamber, all codes were almost identical over the whole photon energy range. In the Mg(Ar) chamber, MCNP5 showed lower response than other codes for photon energy region below 0.1 MeV and presented similar response above 0.2 MeV (agreed within 5% in the simple spherical model). With the increase of electron energy, the response difference between MCNP5 and other codes became larger in both chambers. Compared with the measured currents, MCNP5 had the difference from the measurement data within 5% for the 60Co, 6 MV, 10 MV, 6 MeV and 18 MeV LINACs beams. But for the Mg(Ar) chamber, the derivations reached 7.8-16.5% below 120 kVp X-ray beams. In this study, we were especially interested in BNCT doses where low energy photon contribution is less to ignore, MCNP model is recognized as the most suitable to simulate wide photon-electron and neutron energy distributed responses of the paired ICs. Also, MCNP provides the best prediction of BNCT source adjustment by the detector's neutron and photon responses.

Accelerating navigation in the VecGeom geometry modeller

NASA Astrophysics Data System (ADS)

Wenzel, Sandro; Zhang, Yang; pre="for the"> VecGeom Developers,

2017-10-01

The VecGeom geometry library is a relatively recent effort aiming to provide a modern and high performance geometry service for particle detector simulation in hierarchical detector geometries common to HEP experiments. One of its principal targets is the efficient use of vector SIMD hardware instructions to accelerate geometry calculations for single track as well as multi-track queries. Previously, excellent performance improvements compared to Geant4/ROOT could be reported for elementary geometry algorithms at the level of single shape queries. In this contribution, we will focus on the higher level navigation algorithms in VecGeom, which are the most important components as seen from the simulation engines. We will first report on our R&D effort and developments to implement SIMD enhanced data structures to speed up the well-known “voxelised” navigation algorithms, ubiquitously used for particle tracing in complex detector modules consisting of many daughter parts. Second, we will discuss complementary new approaches to improve navigation algorithms in HEP. These ideas are based on a systematic exploitation of static properties of the detector layout as well as automatic code generation and specialisation of the C++ navigator classes. Such specialisations reduce the overhead of generic- or virtual function based algorithms and enhance the effectiveness of the SIMD vector units. These novel approaches go well beyond the existing solutions available in Geant4 or TGeo/ROOT, achieve a significantly superior performance, and might be of interest for a wide range of simulation backends (GeantV, Geant4). We exemplify this with concrete benchmarks for the CMS and ALICE detectors.

Calibration of the Large Area X-Ray Proportional Counter (LAXPC) Instrument on board AstroSat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antia, H. M.; Yadav, J. S.; Chauhan, Jai Verdhan

We present the calibration and background model for the Large Area X-ray Proportional Counter (LAXPC) detectors on board AstroSat . The LAXPC instrument has three nominally identical detectors to achieve a large collecting area. These detectors are independent of each other, and in the event analysis mode they record the arrival time and energy of each photon that is detected. The detectors have a time resolution of 10 μ s and a dead-time of about 42 μ s. This makes LAXPC ideal for timing studies. The energy resolution and peak channel-to-energy mapping were obtained from calibration on the ground usingmore » radioactive sources coupled with GEANT4 simulations of the detectors. The response matrix was further refined from observations of the Crab after launch. At around 20 keV the energy resolution of the detectors is 10%–15%, while the combined effective area of the three detectors is about 6000 cm{sup 2}.« less

Performance of the Versatile Array of Neutron Detectors at Low Energy (VANDLE)

DOE PAGES

Peters, W. A.; Ilyushkin, S.; Madurga, M.; ...

2016-08-26

The Versatile Array of Neutron Detectors at Low Energy (VANDLE) is a new, highly efficient plastic-scintillator array constructed for decay and transfer reaction experimental setups that require neutron detection. The versatile and modular design allows for customizable experimental setups including beta-delayed neutron spectroscopy and (d,n) transfer reactions in normal and inverse kinematics. The neutron energy and prompt-photon discrimination is determined through the time of flight technique. Fully digital data acquisition electronics and integrated triggering logic enables some VANDLE modules to achieve an intrinsic efficiency over 70% for 300-keV neutrons, measured through two different methods. A custom Geant4 simulation models aspectsmore » of the detector array and the experimental setups to determine efficiency and detector response. Lastly, a low detection threshold, due to the trigger logic and digitizing data acquisition, allowed us to measure the light-yield response curve from elastically scattered carbon nuclei inside the scintillating plastic from incident neutrons with kinetic energies below 2 MeV.« less

Creation of a Geant4 Muon Tomography Package for Imaging of Nuclear Fuel in Dry Cask Storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsoukalas, Lefteri H.

2016-03-01

This is the final report of the NEUP project “Creation of a Geant4 Muon Tomography Package for Imaging of Nuclear Fuel in Dry Cask Storage”, DE-NE0000695. The project started on December 1, 2013 and this report covers the period December 1, 2013 through November 30, 2015. The project was successfully completed and this report provides an overview of the main achievements, results and findings throughout the duration of the project. Additional details can be found in the main body of this report and on the individual Quarterly Reports and associated Deliverables of the project, uploaded in PICS-NE.

Simulation and Digitization of a Gas Electron Multiplier Detector Using Geant4 and an Object-Oriented Digitization Program

NASA Astrophysics Data System (ADS)

McMullen, Timothy; Liyanage, Nilanga; Xiong, Weizhi; Zhao, Zhiwen

2017-01-01

Our research has focused on simulating the response of a Gas Electron Multiplier (GEM) detector using computational methods. GEM detectors provide a cost effective solution for radiation detection in high rate environments. A detailed simulation of GEM detector response to radiation is essential for the successful adaption of these detectors to different applications. Using Geant4 Monte Carlo (GEMC), a wrapper around Geant4 which has been successfully used to simulate the Solenoidal Large Intensity Device (SoLID) at Jefferson Lab, we are developing a simulation of a GEM chamber similar to the detectors currently used in our lab. We are also refining an object-oriented digitization program, which translates energy deposition information from GEMC into electronic readout which resembles the readout from our physical detectors. We have run the simulation with beta particles produced by the simulated decay of a 90Sr source, as well as with a simulated bremsstrahlung spectrum. Comparing the simulation data with real GEM data taken under similar conditions is used to refine the simulation parameters. Comparisons between results from the simulations and results from detector tests will be presented.

High-performing simulations of the space radiation environment for the International Space Station and Apollo Missions

NASA Astrophysics Data System (ADS)

Lund, Matthew Lawrence

The space radiation environment is a significant challenge to future manned and unmanned space travels. Future missions will rely more on accurate simulations of radiation transport in space through spacecraft to predict astronaut dose and energy deposition within spacecraft electronics. The International Space Station provides long-term measurements of the radiation environment in Low Earth Orbit (LEO); however, only the Apollo missions provided dosimetry data beyond LEO. Thus dosimetry analysis for deep space missions is poorly supported with currently available data, and there is a need to develop dosimetry-predicting models for extended deep space missions. GEANT4, a Monte Carlo Method, provides a powerful toolkit in C++ for simulation of radiation transport in arbitrary media, thus including the spacecraft and space travels. The newest version of GEANT4 supports multithreading and MPI, resulting in faster distributive processing of simulations in high-performance computing clusters. This thesis introduces a new application based on GEANT4 that greatly reduces computational time using Kingspeak and Ember computational clusters at the Center for High Performance Computing (CHPC) to simulate radiation transport through full spacecraft geometry, reducing simulation time to hours instead of weeks without post simulation processing. Additionally, this thesis introduces a new set of detectors besides the historically used International Commission of Radiation Units (ICRU) spheres for calculating dose distribution, including a Thermoluminescent Detector (TLD), Tissue Equivalent Proportional Counter (TEPC), and human phantom combined with a series of new primitive scorers in GEANT4 to calculate dose equivalence based on the International Commission of Radiation Protection (ICRP) standards. The developed models in this thesis predict dose depositions in the International Space Station and during the Apollo missions showing good agreement with experimental measurements. From these models the greatest contributor to radiation dose for the Apollo missions was from Galactic Cosmic Rays due to the short time within the radiation belts. The Apollo 14 dose measurements were an order of magnitude higher compared to other Apollo missions. The GEANT4 model of the Apollo Command Module shows consistent doses due to Galactic Cosmic Rays and Radiation Belts for all missions, with a small variation in dose distribution across the capsule. The model also predicts well the dose depositions and equivalent dose values in various human organs for the International Space Station or Apollo Command Module.

Depth dose distribution study within a phantom torso after irradiation with a simulated Solar Particle Event at NSRL

NASA Astrophysics Data System (ADS)

Berger, Thomas; Matthiä, Daniel; Koerner, Christine; George, Kerry; Rhone, Jordan; Cucinotta, Francis A.; Reitz, Guenther

The adequate knowledge of the radiation environment and the doses incurred during a space mission is essential for estimating an astronaut's health risk. The space radiation environment is complex and variable, and exposures inside the spacecraft and the astronaut's body are com-pounded by the interactions of the primary particles with the atoms of the structural materials and with the body itself. Astronauts' radiation exposures are measured by means of personal dosimetry, but there remains substantial uncertainty associated with the computational extrap-olation of skin dose to organ dose, which can lead to over-or under-estimation of the health risk. Comparisons of models to data showed that the astronaut's Effective dose (E) can be pre-dicted to within about a +10In the research experiment "Depth dose distribution study within a phantom torso" at the NASA Space Radiation Laboratory (NSRL) at BNL, Brookhaven, USA the large 1972 SPE spectrum was simulated using seven different proton energies from 50 up to 450 MeV. A phantom torso constructed of natural bones and realistic distributions of human tissue equivalent materials, which is comparable to the torso of the MATROSHKA phantom currently on the ISS, was equipped with a comprehensive set of thermoluminescence detectors and human cells. The detectors are applied to assess the depth dose distribution and radiation transport codes (e.g. GEANT4) are used to assess the radiation field and interactions of the radiation field with the phantom torso. Lymphocyte cells are strategically embedded at selected locations at the skin and internal organs and are processed after irradiation to assess the effects of shielding on the yield of chromosome damage. The first focus of the pre-sented experiment is to correlate biological results with physical dosimetry measurements in the phantom torso. Further on the results of the passive dosimetry using the anthropomorphic phantoms represent the best tool to generate reliable to benchmark computational radiation transport models in a radiation field of interest. The presentation will give first results of the physical dose distribution, the comparison with GEANT4 computer simulations, based on a Voxel model of the phantom, and a comparison with the data from the chromosome aberration study. The help and support of Adam Russek and Michael Sivertz of the NASA Space Radiation Laboratory (NSRL), Brookhaven, USA during the setup and the irradiation of the phantom are highly appreciated. The Voxel model describing the human phantom used for the GEANT4 simulations was kindly provided by Monika Puchalska (CHALMERS, Gothenburg, Sweden).

Including Delbrück scattering in GEANT4

NASA Astrophysics Data System (ADS)

Omer, Mohamed; Hajima, Ryoichi

2017-08-01

Elastic scattering of γ-rays is a significant interaction among γ-ray interactions with matter. Therefore, the planning of experiments involving measurements of γ-rays using Monte Carlo simulations usually includes elastic scattering. However, current simulation tools do not provide a complete picture of elastic scattering. The majority of these tools assume Rayleigh scattering is the primary contributor to elastic scattering and neglect other elastic scattering processes, such as nuclear Thomson and Delbrück scattering. Here, we develop a tabulation-based method to simulate elastic scattering in one of the most common open-source Monte Carlo simulation toolkits, GEANT4. We collectively include three processes, Rayleigh scattering, nuclear Thomson scattering, and Delbrück scattering. Our simulation more appropriately uses differential cross sections based on the second-order scattering matrix instead of current data, which are based on the form factor approximation. Moreover, the superposition of these processes is carefully taken into account emphasizing the complex nature of the scattering amplitudes. The simulation covers an energy range of 0.01 MeV ≤ E ≤ 3 MeV and all elements with atomic numbers of 1 ≤ Z ≤ 99. In addition, we validated our simulation by comparing the differential cross sections measured in earlier experiments with those extracted from the simulations. We find that the simulations are in good agreement with the experimental measurements. Differences between the experiments and the simulations are 21% for uranium, 24% for lead, 3% for tantalum, and 8% for cerium at 2.754 MeV. Coulomb corrections to the Delbrück amplitudes may account for the relatively large differences that appear at higher Z values.

Compton camera study for high efficiency SPECT and benchmark with Anger system

NASA Astrophysics Data System (ADS)

Fontana, M.; Dauvergne, D.; Létang, J. M.; Ley, J.-L.; Testa, É.

2017-12-01

Single photon emission computed tomography (SPECT) is at present one of the major techniques for non-invasive diagnostics in nuclear medicine. The clinical routine is mostly based on collimated cameras, originally proposed by Hal Anger. Due to the presence of mechanical collimation, detection efficiency and energy acceptance are limited and fixed by the system’s geometrical features. In order to overcome these limitations, the application of Compton cameras for SPECT has been investigated for several years. In this study we compare a commercial SPECT-Anger device, the General Electric HealthCare Infinia system with a High Energy General Purpose (HEGP) collimator, and the Compton camera prototype under development by the French collaboration CLaRyS, through Monte Carlo simulations (GATE—GEANT4 Application for Tomographic Emission—version 7.1 and GEANT4 version 9.6, respectively). Given the possible introduction of new radio-emitters at higher energies intrinsically allowed by the Compton camera detection principle, the two detectors are exposed to point-like sources at increasing primary gamma energies, from actual isotopes already suggested for nuclear medicine applications. The Compton camera prototype is first characterized for SPECT application by studying the main parameters affecting its imaging performance: detector energy resolution and random coincidence rate. The two detector performances are then compared in terms of radial event distribution, detection efficiency and final image, obtained by gamma transmission analysis for the Anger system, and with an iterative List Mode-Maximum Likelihood Expectation Maximization (LM-MLEM) algorithm for the Compton reconstruction. The results show for the Compton camera a detection efficiency increased by a factor larger than an order of magnitude with respect to the Anger camera, associated with an enhanced spatial resolution for energies beyond 500 keV. We discuss the advantages of Compton camera application for SPECT if compared to present commercial Anger systems, with particular focus on dose delivered to the patient, examination time, and spatial uncertainties.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wroe, A; Slater, J; McAuley, G

Purpose: To design, implement and evaluate a shielding system that will reduce out-of-field dose experienced by the patient and associated electronic systems in passively scattered proton therapy treatment. Methods: A multi-stage neutron shielding system was retrofitted to the Gantry 1 treatment nozzle at Loma Linda University Medical Center. The system uses multiple borated polyethylene plates staged after the primary beam modifying devices to attenuate and absorb neutrons produced by such devices. This arrangement locates increasing levels of shielding between the sources of secondary particles in the nozzle and the patient. Additionally, the design of this shielding structure allows it tomore » be easily retrofitted to an existing proton nozzle system without impacting design or treatment beam characteristics. The effectiveness of the shielding was evaluated both through experimental measurements and Geant4 Monte Carlo simulations. Results: Measurements were completed with Landauer Luxel+ dosimeters that use optically stimulated luminescence and CR-39 to detect fast neutrons, thermal neutrons, protons, photons and beta particles. Measurements of a 250 MeV proton beam indicated that the shielding system reduced out-of-field dose to the patient by almost half with dose equivalent values at 50 and 40 cm from the field edge decreasing from 0.965 and 1.262 mSv/Gy to 0.596 and 0.777 mSv/Gy respectively. The installation of the multi-stage shielding system also reduced dose equivalent experienced by electronic systems installed in the treatment room by up to 80%. Geant4 simulations were also used to evaluate the neutron fluence at various positions in the treatment room as well as provide information on microdosimetry spectra within the patient and treatment room. Conclusion: The shielding system described above proved to be an effective an inexpensive method of reducing out-of-field doses to the patient and electronic systems and can be easily retrofitted to existing passive scattering nozzles.« less

geant4 hadronic cascade models analysis of proton and charged pion transverse momentum spectra from p + Cu and Pb collisions at 3, 8, and 15 GeV/c

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdel-Waged, Khaled; Benha University, Faculty of Science, Physics Department; Felemban, Nuha

2011-07-15

We describe how various hadronic cascade models, which are implemented in the geant4 toolkit, describe proton and charged pion transverse momentum spectra from p + Cu and Pb collisions at 3, 8, and 15 GeV/c, recently measured in the hadron production (HARP) experiment at CERN. The Binary, ultrarelativistic quantum molecular dynamics (UrQMD) and modified FRITIOF (FTF) hadronic cascade models are chosen for investigation. The first two models are based on limited (Binary) and branched (UrQMD) binary scattering between cascade particles which can be either a baryon or meson, in the three-dimensional space of the nucleus, while the latter (FTF) considersmore » collective interactions between nucleons only, on the plane of impact parameter. It is found that the slow (p{sub T}{<=}0.3 GeV/c) proton spectra are quite sensitive to the different treatments of cascade pictures, while the fast (p{sub T}>0.3 GeV/c) proton spectra are not strongly affected by the differences between the FTF and UrQMD models. It is also shown that the UrQMD and FTF combined with Binary (FTFB) models could reproduce both proton and charged pion spectra from p + Cu and Pb collisions at 3, 8, and 15 GeV/c with the same accuracy.« less

Geant4-DNA simulation of DNA damage caused by direct and indirect radiation effects and comparison with biological data.

NASA Astrophysics Data System (ADS)

Villagrasa, Carmen; Meylan, Sylvain; Gonon, Geraldine; Gruel, Gaëtan; Giesen, Ulrich; Bueno, Marta; Rabus, Hans

2017-09-01

In this work we present results obtained in the frame of the BioQuaRT project. The objective of the study was the correlation between the number of radiation-induced double strand breaks (DSB) of the DNA molecule and the probability of detecting nuclear foci after targeted microbeam irradiation of cells with protons and alpha particles of different LET. The former were obtained by simulation with new methods integrated into Geant4-DNA that permit calculating the number of DSB in a DNA target model induced by direct and indirect radiation effects. A particular focus was laid in this work on evaluating the influence of different criteria applied to the simulated results for predicting the formation of a direct SSB. Indeed, these criteria have an important impact on the predicted number of DSB per particle track and its dependence with LET. Among the criteria tested in this work, the case that a direct radiation interaction leads to a strand break if the cumulative energy deposited in the backbone part of one nucleotide exceeds a threshold of 17.5 eV leads to the best agreement with the relative LET dependence of number of radiation induced foci. Further calculations and experimental data are nevertheless needed in order to fix the simulation parameters and to help interpreting the biological experimental data observed by immunofluorescence in terms of the DSB complexity.

Modeling spallation reactions in tungsten and uranium targets with the Geant4 toolkit

NASA Astrophysics Data System (ADS)

Malyshkin, Yury; Pshenichnov, Igor; Mishustin, Igor; Greiner, Walter

2012-02-01

We study primary and secondary reactions induced by 600 MeV proton beams in monolithic cylindrical targets made of natural tungsten and uranium by using Monte Carlo simulations with the Geant4 toolkit [1-3]. Bertini intranuclear cascade model, Binary cascade model and IntraNuclear Cascade Liège (INCL) with ABLA model [4] were used as calculational options to describe nuclear reactions. Fission cross sections, neutron multiplicity and mass distributions of fragments for 238U fission induced by 25.6 and 62.9 MeV protons are calculated and compared to recent experimental data [5]. Time distributions of neutron leakage from the targets and heat depositions are calculated. This project is supported by Siemens Corporate Technology.

The Gamma Ray Imaging Detector of the AGILE satellite: A novel application of silicon trackers for detection of astrophysics high-energy photons

NASA Astrophysics Data System (ADS)

Rappoldi, Andrea; AGILE Collaboration

2009-10-01

AGILE is a project of the Italian Space Agency (ASI) Scientific Program dedicated to Gamma ray astrophysics. It is designed to be a very light and compact instrument, capable of photon detections and imaging in both the 30 MeV-50 GeV and 18-60 keV energy ranges, with a large field of view (FOV is ˜3 and ˜1 sr, respectively). The core of the instrument (launched on April 23, 2007 from the Indian Space Research Organization's launch facility) is represented by the Gamma Ray Imaging Detector (GRID), which is a silicon tracker developed by the Italian National Institute of Nuclear Physics (INFN), with a spatial resolution of ˜40 μm. The GRID performances have been studied by means of a GEANT Montecarlo, and tested with a dedicated calibration campaign using the tagged gamma beam available at Beam Test Facility (BTF) of INFN Frascati Laboratory.

A new tool for radiation exposure calculations in aircraft flights during disturbed solar activity periods

NASA Astrophysics Data System (ADS)

Paschalis, Pavlos; Tezari, Anastasia; Gerontidou, Maria; Mavromichalaki, Helen

2016-04-01

Galactic cosmic rays and solar energetic particles can penetrate the Earth's atmosphere and interact with its molecules, which can cause atmospheric showers of secondary particles that are detected by ground based neutron monitor detectors. The cascades are of great importance for the study of the radiation exposure of aircraft crews. A new Geant4 software application is presented based on DYASTIMA (Dynamic Atmospheric Shower Tracking Interactive Model Application), which calculates the effective dose that aviators may receive in different flight scenarios characterized by different altitudes and different flight routes, during quiet and disturbed solar and cosmic ray activity. The concept is based on Monte Carlo simulations by using phantoms for the aircraft and the aviator and experimenting with different shielding materials.

Development of a facility for high-precision irradiation of cells with carbon ions.

PubMed

van Goethem, Marc-Jan; Niemantsverdriet, Maarten; Brandenburg, Sytze; Langendijk, Johannes A; Coppes, Robert P; van Luijk, Peter

2011-01-01

Compared to photons, using particle radiation in radiotherapy reduces the dose and irradiated volume of normal tissues, potentially reducing side effects. The biological effect of dose deposited by particles such as carbon ions, however, differs from that of dose deposited by photons. The inaccuracy in models to estimate the biological effects of particle radiation remains the most important source of uncertainties in particle therapy. Improving this requires high-precision studies on biological effects of particle radiation. Therefore, the authors aimed to develop a facility for reproducible and high-precision carbon-ion irradiation of cells in culture. The combined dose nonuniformity in the lateral and longitudinal direction should not exceed +/-1.5%. Dose to the cells from particles than other carbon ions should not exceed 5%. A uniform lateral dose distribution was realized using a single scatter foil and quadrupole magnets. A modulator wheel was used to create a uniform longitudinal dose distribution. The choice of beam energy and the optimal design of these components was determined using GEANT4 and SRIM Monte Carlo simulations. Verification of the uniformity of the dose distribution was performed using a scintillating screen (lateral) and a water phantom (longitudinal). The reproducibility of dose delivery between experiments was assessed by repeated measurements of the spatial dose distribution. Moreover, the reproducibility of dose-response measurements was tested by measuring the survival of irradiated HEK293 cells in three independent experiments. The relative contribution of dose from nuclear reaction fragments to the sample was found to be <5% when using 90 MeV/u carbon ions. This energy still allows accurate dosimetry conforming to the IAEA Report TRS-398, facilitating comparison to dose-effect data obtained with other radiation qualities. A 1.3 mm long spread-out Bragg peak with a diameter of 30 mm was created, allowing the irradiation of cell samples with the specified accuracy. Measurements of the transverse and longitudinal dose distribution showed that the dose variation over the sample volume was +/-0.8% and +/-0.7% in the lateral and longitudinal directions, respectively. The track-averaged LET of 132 +/- 10 keV/microm and dose-averaged LET of 189 +/- 15 keV/microm at the position of the sample were obtained from a GEANT4 simulation, which was validated experimentally. Three separately measured cell-survival curves yielded nearly identical results. With the new facility, high-precision carbon-ion irradiations of biological samples can be performed with highly reproducible results.

Measurement of LYSO Intrinsic Light Yield Using Electron Excitation

NASA Astrophysics Data System (ADS)

Turtos, Rosana Martinez; Gundacker, Stefan; Pizzichemi, Marco; Ghezzi, Alessio; Pauwels, Kristof; Auffray, Etiennette; Lecoq, Paul; Paganoni, Marco

2016-04-01

The determination of the intrinsic light yield (LYint) of scintillating crystals, i.e. number of optical photons created per amount of energy deposited, constitutes a key factor in order to characterize and optimize their energy and time resolution. However, until now measurements of this quantity are affected by large uncertainties and often rely on corrections for bulk absorption and surface/edge state. The novel idea presented in this contribution is based on the confinement of the scintillation emission in the central upper part of a 10 mm cubic crystal using a 1.5 MeV electron beam with diameter of 1 mm. A black non-reflective pinhole aligned with the excitation point is used to fix the light extraction solid angle (narrower than total reflection angle), which then sets a light cone travel path through the crystal. The final number of photoelectrons detected using a Hamamatsu R2059 photomultiplier tube (PMT) was corrected for the extraction solid angle, the Fresnel reflection coefficient and quantum efficiency (QE) of the PMT. The total number of optical photons produced per energy deposited was found to be 40000 ph/MeV ± 9% (syst) ±3% (stat) for LYSO. Simulations using Geant4 were successfully compared to light output measurements of 2 × 2 mm2 section crystals with lengths of 5-30 mm, in order to validate the light transport model and set a limit on Light Transfer Efficiency estimations.

Calculation of conversion coefficients using Chinese adult reference phantoms for air submersion and ground contamination.

PubMed

Lu, Wei; Qiu, Rui; Wu, Zhen; Li, Chunyan; Yang, Bo; Liu, Huan; Ren, Li; Li, Junli

2017-03-21

The effective and organ equivalent dose coefficients have been widely used to provide assessment of doses received by adult members of the public and by workers exposed to environmental radiation from nuclear facilities under normal or accidental situations. Advancements in phantom types, weighting factors, decay data, etc, have led to the publication of newer results in this regard. This paper presents a new set of conversion coefficients for air submersion and ground contamination (with the use of Geant4) for photons from 15 keV to 10 MeV using the Chinese and International Commission on Radiological Protection (ICRP) adult reference male and female phantoms. The radiation fields, except for energy spectrum at low energies, were validated by the data obtained from the Monte Carlo code YURI. The effective dose coefficients of monoenergetic photons, obtained for the ICRP adult reference phantoms, agree well with recently published data for air submersion and ground contamination with a plane source at a depth of 0.5 g cm -2 in soil, but an average difference of 36.5% is observed for ground surface contamination with the abovementioned radiation field. The average differences in organ equivalent dose coefficients between the Chinese and the ICRP adult reference phantoms are within 6% for most organs, but noticeable differences of up to 70% or even higher are found at photon energies below 30 keV under air submersion. The effective dose coefficients obtained with the Chinese adult reference phantoms are greater than those of the ICRP adult reference phantoms above 30 keV and 0.5 MeV for ground contamination and air submersion, respectively; the average differences from the Chinese adult reference phantoms are about 3.6% and 0.4% in the whole energy range with maximum differences of 31.8% and 27.6% at 15 keV for air submersion and ground contamination respectively. These differences are attributed to anatomical discrepancies in overlying tissue mass of an individual organ and the body mass between the Chinese and the ICRP adult reference phantoms. These monoenergetic photon conversion coefficients are subsequently used to evaluate radionuclides with decay data from ICRP publication 107.

Calculation of conversion coefficients using Chinese adult reference phantoms for air submersion and ground contamination

NASA Astrophysics Data System (ADS)

Lu, Wei; Qiu, Rui; Wu, Zhen; Li, Chunyan; Yang, Bo; Liu, Huan; Ren, Li; Li, Junli

2017-03-01

The effective and organ equivalent dose coefficients have been widely used to provide assessment of doses received by adult members of the public and by workers exposed to environmental radiation from nuclear facilities under normal or accidental situations. Advancements in phantom types, weighting factors, decay data, etc, have led to the publication of newer results in this regard. This paper presents a new set of conversion coefficients for air submersion and ground contamination (with the use of Geant4) for photons from 15 keV to 10 MeV using the Chinese and International Commission on Radiological Protection (ICRP) adult reference male and female phantoms. The radiation fields, except for energy spectrum at low energies, were validated by the data obtained from the Monte Carlo code YURI. The effective dose coefficients of monoenergetic photons, obtained for the ICRP adult reference phantoms, agree well with recently published data for air submersion and ground contamination with a plane source at a depth of 0.5 g cm-2 in soil, but an average difference of 36.5% is observed for ground surface contamination with the abovementioned radiation field. The average differences in organ equivalent dose coefficients between the Chinese and the ICRP adult reference phantoms are within 6% for most organs, but noticeable differences of up to 70% or even higher are found at photon energies below 30 keV under air submersion. The effective dose coefficients obtained with the Chinese adult reference phantoms are greater than those of the ICRP adult reference phantoms above 30 keV and 0.5 MeV for ground contamination and air submersion, respectively; the average differences from the Chinese adult reference phantoms are about 3.6% and 0.4% in the whole energy range with maximum differences of 31.8% and 27.6% at 15 keV for air submersion and ground contamination respectively. These differences are attributed to anatomical discrepancies in overlying tissue mass of an individual organ and the body mass between the Chinese and the ICRP adult reference phantoms. These monoenergetic photon conversion coefficients are subsequently used to evaluate radionuclides with decay data from ICRP publication 107.

Simulating Terrestrial Gamma-ray Flashes using SWORD (Invited)

NASA Astrophysics Data System (ADS)

Gwon, C.; Grove, J.; Dwyer, J. R.; Mattson, K.; Polaski, D.; Jackson, L.

2013-12-01

We report on simulations of the relativistic feedback discharges involved with the production of terrestrial gamma-ray flashes (TGFs). The simulations were conducted using Geant4 using the SoftWare for the Optimization of Radiation Detectors (SWORD) framework. SWORD provides a graphical interface for setting up simulations in select high-energy radiation transport engines. Using Geant4, we determine avalanche length, the energy spectrum of the electrons and gamma-rays as they leave the field region, and the feedback factor describing the degree to which the production of energetic particles is self-sustaining. We validate our simulations against previous work in order to determine the reliability of our results. This work is funded by the Office of Naval Research.

Monte-Carlo Geant4 numerical simulation of experiments at 247-MeV proton microscope

NASA Astrophysics Data System (ADS)

Kantsyrev, A. V.; Skoblyakov, A. V.; Bogdanov, A. V.; Golubev, A. A.; Shilkin, N. S.; Yuriev, D. S.; Mintsev, V. B.

2018-01-01

A radiographic facility for an investigation of fast dynamic processes with areal density of targets up to 5 g/cm2 is under development on the basis of high-current proton linear accelerator at the Institute for Nuclear Research (Troitsk, Russia). A virtual model of the proton microscope developed in a software toolkit Geant4 is presented in the article. Fullscale Monte-Carlo numerical simulation of static radiographic experiments at energy of a proton beam 247 MeV was performed. The results of simulation of proton radiography experiments with static model of shock-compressed xenon are presented. The results of visualization of copper and polymethyl methacrylate step wedges static targets also described.

DHCAL with minimal absorber: measurements with positrons

NASA Astrophysics Data System (ADS)

Freund, B.; Neubüser, C.; Repond, J.; Schlereth, J.; Xia, L.; Dotti, A.; Grefe, C.; Ivantchenko, V.; Berenguer Antequera, J.; Calvo Alamillo, E.; Fouz, M.-C.; Marin, J.; Puerta-Pelayo, J.; Verdugo, A.; Brianne, E.; Ebrahimi, A.; Gadow, K.; Göttlicher, P.; Günter, C.; Hartbrich, O.; Hermberg, B.; Irles, A.; Krivan, F.; Krüger, K.; Kvasnicka, J.; Lu, S.; Lutz, B.; Morgunov, V.; Provenza, A.; Reinecke, M.; Sefkow, F.; Schuwalow, S.; Tran, H. L.; Garutti, E.; Laurien, S.; Matysek, M.; Ramilli, M.; Schroeder, S.; Bilki, B.; Norbeck, E.; Northacker, D.; Onel, Y.; Cvach, J.; Gallus, P.; Havranek, M.; Janata, M.; Kovalcuk, M.; Kvasnicka, J.; Lednicky, D.; Marcisovsky, M.; Polak, I.; Popule, J.; Tomasek, L.; Tomasek, M.; Sicho, P.; Smolik, J.; Vrba, V.; Zalesak, J.; van Doren, B.; Wilson, G. W.; Kawagoe, K.; Hirai, H.; Sudo, Y.; Suehara, T.; Sumida, H.; Takada, S.; Tomita, T.; Yoshioka, T.; Bilokin, S.; Bonis, J.; Cornebise, P.; Pöschl, R.; Richard, F.; Thiebault, A.; Zerwas, D.; Hostachy, J.-Y.; Morin, L.; Besson, D.; Chadeeva, M.; Danilov, M.; Markin, O.; Popova, E.; Gabriel, M.; Goecke, P.; Kiesling, C.; van der Kolk, N.; Simon, F.; Szalay, M.; Corriveau, F.; Blazey, G. C.; Dyshkant, A.; Francis, K.; Zutshi, V.; Kotera, K.; Ono, H.; Takeshita, T.; Ieki, S.; Kamiya, Y.; Ootani, W.; Shibata, N.; Jeans, D.; Komamiya, S.; Nakanishi, H.

2016-05-01

In special tests, the active layers of the CALICE Digital Hadron Calorimeter prototype, the DHCAL, were exposed to low energy particle beams, without being interleaved by absorber plates. The thickness of each layer corresponded approximately to 0.29 radiation lengths or 0.034 nuclear interaction lengths, defined mostly by the copper and steel skins of the detector cassettes. This paper reports on measurements performed with this device in the Fermilab test beam with positrons in the energy range of 1 to 10 GeV. The measurements are compared to simulations based on GEANT4 and a standalone program to emulate the detailed response of the active elements.

Efficient voxel navigation for proton therapy dose calculation in TOPAS and Geant4

NASA Astrophysics Data System (ADS)

Schümann, J.; Paganetti, H.; Shin, J.; Faddegon, B.; Perl, J.

2012-06-01

A key task within all Monte Carlo particle transport codes is ‘navigation’, the calculation to determine at each particle step what volume the particle may be leaving and what volume the particle may be entering. Navigation should be optimized to the specific geometry at hand. For patient dose calculation, this geometry generally involves voxelized computed tomography (CT) data. We investigated the efficiency of navigation algorithms on currently available voxel geometry parameterizations in the Monte Carlo simulation package Geant4: G4VPVParameterisation, G4VNestedParameterisation and G4PhantomParameterisation, the last with and without boundary skipping, a method where neighboring voxels with the same Hounsfield unit are combined into one larger voxel. A fourth parameterization approach (MGHParameterization), developed in-house before the latter two parameterizations became available in Geant4, was also included in this study. All simulations were performed using TOPAS, a tool for particle simulations layered on top of Geant4. Runtime comparisons were made on three distinct patient CT data sets: a head and neck, a liver and a prostate patient. We included an additional version of these three patients where all voxels, including the air voxels outside of the patient, were uniformly set to water in the runtime study. The G4VPVParameterisation offers two optimization options. One option has a 60-150 times slower simulation speed. The other is compatible in speed but requires 15-19 times more memory compared to the other parameterizations. We found the average CPU time used for the simulation relative to G4VNestedParameterisation to be 1.014 for G4PhantomParameterisation without boundary skipping and 1.015 for MGHParameterization. The average runtime ratio for G4PhantomParameterisation with and without boundary skipping for our heterogeneous data was equal to 0.97: 1. The calculated dose distributions agreed with the reference distribution for all but the G4PhantomParameterisation with boundary skipping for the head and neck patient. The maximum memory usage ranged from 0.8 to 1.8 GB depending on the CT volume independent of parameterizations, except for the 15-19 times greater memory usage with the G4VPVParameterisation when using the option with a higher simulation speed. The G4VNestedParameterisation was selected as the preferred choice for the patient geometries and treatment plans studied.

Diffusion-controlled reactions modeling in Geant4-DNA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karamitros, M., E-mail: matkara@gmail.com; CNRS, INCIA, UMR 5287, F-33400 Talence; Luan, S.

2014-10-01

Context Under irradiation, a biological system undergoes a cascade of chemical reactions that can lead to an alteration of its normal operation. There are different types of radiation and many competing reactions. As a result the kinetics of chemical species is extremely complex. The simulation becomes then a powerful tool which, by describing the basic principles of chemical reactions, can reveal the dynamics of the macroscopic system. To understand the dynamics of biological systems under radiation, since the 80s there have been on-going efforts carried out by several research groups to establish a mechanistic model that consists in describing allmore » the physical, chemical and biological phenomena following the irradiation of single cells. This approach is generally divided into a succession of stages that follow each other in time: (1) the physical stage, where the ionizing particles interact directly with the biological material; (2) the physico-chemical stage, where the targeted molecules release their energy by dissociating, creating new chemical species; (3) the chemical stage, where the new chemical species interact with each other or with the biomolecules; (4) the biological stage, where the repairing mechanisms of the cell come into play. This article focuses on the modeling of the chemical stage. Method This article presents a general method of speeding-up chemical reaction simulations in fluids based on the Smoluchowski equation and Monte-Carlo methods, where all molecules are explicitly simulated and the solvent is treated as a continuum. The model describes diffusion-controlled reactions. This method has been implemented in Geant4-DNA. The keys to the new algorithm include: (1) the combination of a method to compute time steps dynamically with a Brownian bridge process to account for chemical reactions, which avoids costly fixed time step simulations; (2) a k–d tree data structure for quickly locating, for a given molecule, its closest reactants. The performance advantage is presented in terms of complexity, and the accuracy of the new algorithm is demonstrated by simulating radiation chemistry in the context of the Geant4-DNA project. Application The time-dependent radiolytic yields of the main chemical species formed after irradiation are computed for incident protons at different energies (from 50 MeV to 500 keV). Both the time-evolution and energy dependency of the yields are discussed. The evolution, at one microsecond, of the yields of hydroxyls and solvated electrons with respect to the linear energy transfer is compared to theoretical and experimental data. According to our results, at high linear energy transfer, modeling radiation chemistry in the trading compartment representation might be adopted.« less

WE-AB-204-11: Development of a Nuclear Medicine Dosimetry Module for the GPU-Based Monte Carlo Code ARCHER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, T; Lin, H; Xu, X

Purpose: To develop a nuclear medicine dosimetry module for the GPU-based Monte Carlo code ARCHER. Methods: We have developed a nuclear medicine dosimetry module for the fast Monte Carlo code ARCHER. The coupled electron-photon Monte Carlo transport kernel included in ARCHER is built upon the Dose Planning Method code (DPM). The developed module manages the radioactive decay simulation by consecutively tracking several types of radiation on a per disintegration basis using the statistical sampling method. Optimization techniques such as persistent threads and prefetching are studied and implemented. The developed module is verified against the VIDA code, which is based onmore » Geant4 toolkit and has previously been verified against OLINDA/EXM. A voxelized geometry is used in the preliminary test: a sphere made of ICRP soft tissue is surrounded by a box filled with water. Uniform activity distribution of I-131 is assumed in the sphere. Results: The self-absorption dose factors (mGy/MBqs) of the sphere with varying diameters are calculated by ARCHER and VIDA respectively. ARCHER’s result is in agreement with VIDA’s that are obtained from a previous publication. VIDA takes hours of CPU time to finish the computation, while it takes ARCHER 4.31 seconds for the 12.4-cm uniform activity sphere case. For a fairer CPU-GPU comparison, more effort will be made to eliminate the algorithmic differences. Conclusion: The coupled electron-photon Monte Carlo code ARCHER has been extended to radioactive decay simulation for nuclear medicine dosimetry. The developed code exhibits good performance in our preliminary test. The GPU-based Monte Carlo code is developed with grant support from the National Institute of Biomedical Imaging and Bioengineering through an R01 grant (R01EB015478)« less

TU-E-BRA-05: Reverse Geometry Imaging with MV Detector for Improved Image Resolution.

PubMed

Ganguly, A; Abel, E; Sun, M; Fahrig, R; Virshup, G; Star-Lack, J

2012-06-01

Thick pixilated scintillators can offer significant improvements in quantum efficiency over phosphor screen megavoltage (MV) detectors. However spatial resolution can be compromised due to the spreading of light across pixels within septa. Of particular interest are the lower energy x-ray photons and associated light photons that produce higher image contrast but are stopped near the scintillator entrance surface. They suffer the most scattering in the scintillator prior to detection in the photodiodes. Reversing the detector geometry, so that the incident x-ray beam passes through the photodiode array into the scintillator, allows the light to scatter less prior to detection. This also reduces the Swank noise since now higher and lower energy x-ray photons tend to produce similar electronic signals. In this work, we present simulations and measurements of detector MTF for the conventional/forward and reverse geometries to demonstrate this phenomenon. A tabletop system consisting of a Varian CX1 1MeV linear accelerator and a modified Varian Paxscan4030 with the readout electronics moved away from the incident the beam was used. A special holder was used to press a 2.5W×5.0L×2.0Hcm 3 pixellated Cesium Iodide (CsI:Tl) scintillator array on to the detector glass. The CsI array had a pitch of 0.784mm with plastic septa between pixels and the photodiode array pitch was 0.192 mm. The MTF in the forward and reverse geometries was measured using a 0.5mm thick Tantalum slanted edge. Geant4-based Monte Carlo simulations were performed for comparison. The measured and simulated MTFs matched to within 3.4(±3.7)% in the forward and 4.4(±1.5)% in reverse geometries. The reverse geometry MTF was higher than the forward geometry MTF at all spatial frequencies and doubled to .25 at 0.3lp/mm. A novel method of improving the image resolution at MV energies was demonstrated. The improvements should be more pronounced with increased scintillator thickness. Funding support provided by NIH (grant number NIH R01 CA138426). © 2012 American Association of Physicists in Medicine.

Detector Simulations with DD4hep

NASA Astrophysics Data System (ADS)

Petrič, M.; Frank, M.; Gaede, F.; Lu, S.; Nikiforou, N.; Sailer, A.

2017-10-01

Detector description is a key component of detector design studies, test beam analyses, and most of particle physics experiments that require the simulation of more and more different detector geometries and event types. This paper describes DD4hep, which is an easy-to-use yet flexible and powerful detector description framework that can be used for detector simulation and also extended to specific needs for a particular working environment. Linear collider detector concepts ILD, SiD and CLICdp as well as detector development collaborations CALICE and FCal have chosen to adopt the DD4hep geometry framework and its DDG4 pathway to Geant4 as its core simulation and reconstruction tools. The DDG4 plugins suite includes a wide variety of input formats, provides access to the Geant4 particle gun or general particles source and allows for handling of Monte Carlo truth information, eg. by linking hits and the primary particle that caused them, which is indispensable for performance and efficiency studies. An extendable array of segmentations and sensitive detectors allows the simulation of a wide variety of detector technologies. This paper shows how DD4hep allows to perform complex Geant4 detector simulations without compiling a single line of additional code by providing a palette of sub-detector components that can be combined and configured via compact XML files. Simulation is controlled either completely via the command line or via simple Python steering files interpreted by a Python executable. It also discusses how additional plugins and extensions can be created to increase the functionality.

A Geant4 evaluation of the Hornyak button and two candidate detectors for the TREAT hodoscope

NASA Astrophysics Data System (ADS)

Fu, Wenkai; Ghosh, Priyarshini; Harrison, Mark J.; McGregor, Douglas S.; Roberts, Jeremy A.

2018-05-01

The performance of traditional Hornyak buttons and two proposed variants for fast-neutron hodoscope applications was evaluated using Geant4. The Hornyak button is a ZnS(Ag)-based device previously deployed at the Idaho National Laboratory's TRansient REActor Test Facility (better known as TREAT) for monitoring fast neutrons emitted during pulsing of fissile fuel samples. Past use of these devices relied on pulse-shape discrimination to reduce the significant levels of background Cherenkov radiation. Proposed are two simple designs that reduce the overall light guide mass (here, polymethyl methacrylate or PMMA), employ silicon photomultipliers (SiPMs), and can be operated using pulse-height discrimination alone to eliminate background noise to acceptable levels. Geant4 was first used to model a traditional Hornyak button, and for assumed, hodoscope-like conditions, an intrinsic efficiency of 0.35% for mono-directional fission neutrons was predicted. The predicted efficiency is in reasonably good agreement with experimental data from the literature and, hence, served to validate the physics models and approximations employed. Geant4 models were then developed to optimize the materials and geometries of two alternatives to the Hornyak button, one based on a homogeneous mixture of ZnS(Ag) and PMMA, and one based on alternating layers of ZnS(Ag) and PMMA oriented perpendicular to the incident neutron beam. For the same radiation environment, optimized, 5-cm long (along the beam path) devices of the homogeneous and layered designs were predicted to have efficiencies of approximately 1.3% and 3.3%, respectively. For longer devices, i.e., lengths larger than 25 cm, these efficiencies were shown to peak at approximately 2.2% and 5.9%, respectively. Moreover, both designs were shown to discriminate Cherenkov noise intrinsically by using an appropriate pulse-height discriminator level, i.e., pulse-shape discrimination is not needed for these devices.

TOPAS Tool for Particle Simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perl, Joseph

2013-05-30

TOPAS lets users simulate the passage of subatomic particles moving through any kind of radiation therapy treatment system, can import a patient geometry, can record dose and other quantities, has advanced graphics, and is fully four-dimensional (3D plus time) to handle the most challenging time-dependent aspects of modern cancer treatments.TOPAS unlocks the power of the most accurate particle transport simulation technique, the Monte Carlo (MC) method, while removing the painstaking coding work such methods used to require. Research physicists can use TOPAS to improve delivery systems towards safer and more effective radiation therapy treatments, easily setting up and running complexmore » simulations that previously used to take months of preparation. Clinical physicists can use TOPAS to increase accuracy while reducing side effects, simulating patient-specific treatment plans at the touch of a button. TOPAS is designed as a “user code” layered on top of the Geant4 Simulation Toolkit. TOPAS includes the standard Geant4 toolkit, plus additional code to make Geant4 easier to control and to extend Geant4 functionality. TOPAS aims to make proton simulation both “reliable” and “repeatable.” “Reliable” means both accurate physics and a high likelihood to simulate precisely what the user intended to simulate, reducing issues of wrong units, wrong materials, wrong scoring locations, etc. “Repeatable” means not just getting the same result from one simulation to another, but being able to easily restore a previously used setup and reducing sources of error when a setup is passed from one user to another. TOPAS control system incorporates key lessons from safety management, proactively removing possible sources of user error such as line-ordering mistakes In control files. TOPAS has been used to model proton therapy treatment examples including the UCSF eye treatment head, the MGH stereotactic alignment in radiosurgery treatment head and the MGH gantry treatment heads in passive scattering and scanning modes, and has demonstrated dose calculation based on patient-specific CT data.« less

A Geant4 evaluation of the Hornyak button and two candidate detectors for the TREAT hodoscope

DOE PAGES

Fu, Wenkai; Ghosh, Priyarshini; Harrison, Mark; ...

2018-02-05

The performance of traditional Hornyak buttons and two proposed variants for fast-neutron hodoscope applications was evaluated using Geant4. The Hornyak button is a ZnS(Ag)-based device previously deployed at the Idaho National Laboratory's TRansient REActor Test Facility (better known as TREAT) for monitoring fast neutrons emitted during pulsing of fissile fuel samples. Past use of these devices relied on pulse-shape discrimination to reduce the significant levels of background Cherenkov radiation. Proposed are two simple designs that reduce the overall light guide mass (here, polymethyl methacrylate or PMMA), employ silicon photomultipliers (SiPMs), and can be operated using pulse-height discrimination alone to eliminatemore » background noise to acceptable levels. Geant4 was first used to model a traditional Hornyak button, and for assumed, hodoscope-like conditions, an intrinsic efficiency of 0.35% for mono-directional fission neutrons was predicted. The predicted efficiency is in reasonably good agreement with experimental data from the literature and, hence, served to validate the physics models and approximations employed. Geant4 models were then developed to optimize the materials and geometries of two alternatives to the Hornyak button, one based on a homogeneous mixture of ZnS(Ag) and PMMA, and one based on alternating layers of ZnS(Ag) and PMMA oriented perpendicular to the incident neutron beam. For the same radiation environment, optimized, 5-cm long (along the beam path) devices of the homogeneous and layered designs were predicted to have efficiencies of approximately 1.3% and 3.3%, respectively. For longer devices, i.e., lengths larger than 25 cm, these efficiencies were shown to peak at approximately 2.2% and 5.9%, respectively. Furthermore, both designs were shown to discriminate Cherenkov noise intrinsically by using an appropriate pulse-height discriminator level, i.e., pulse-shape discrimination is not needed for these devices.« less

New estimates of extensive-air-shower energies on the basis of signals in scintillation detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anyutin, N. V.; Dedenko, L. G., E-mail: ddn@dec1.sinp.msu.ru; Roganova, T. M.

New formulas for estimating the energy of inclined extensive air showers (EASs) on the basis of signals in detectors by means of an original method and detailed tables of signals induced in scintillation detectors by photons, electrons, positrons, and muons and calculated with the aid of the GEANT4 code package were proposed in terms of the QGSJETII-04, EPOS LHC, and GHEISHA models. The parameters appearing in the proposed formulas were calculated by employing the CORSIKA code package. It is shown that, for showers of zenith angles in the range of 20◦–45◦, the standard constant-intensity-cut method, which is used to interpretmore » data from the Yakutsk EAS array, overestimates the shower energy by a factor of 1.2 to 1.5. It is proposed to employ the calculated VEM (Vertical Equivalent Muon) signal units of 10.8 and 11.4 MeV for, respectively, ground-based and underground scintillation detectors and to take into account the dependence of signals on the azimuthal angle of the detector position and fluctuations in the development of showers.« less

Design and characterization of a small muon tomography system

NASA Astrophysics Data System (ADS)

Jo, Woo Jin; An, Su Jung; Kim, Hyun-Il; Lee, Chae Young; Chung, Heejun; Chung, Yong Hyun

2015-02-01

Muon tomography is a useful method for monitoring special nuclear materials (SNMs) because it can provide effective information on the presence of high-Z materials, has a high enough energy to deeply penetrate large amounts of shielding, and does not lead to any health risks and danger above background. We developed a 2-D muon detector and designed a muon tomography system employing four detector modules. Two top and two bottom detectors are, respectively, employed to record the incident and the scattered muon trajectories. The detector module for the muon tomography system consists of a plastic scintillator, wavelength-shifting (WLS) fiber arrays placed orthogonally on the top and the bottom of the scintillator, and a position-sensitive photomultiplier (PSPMT). The WLS fiber arrays absorb light photons emitted by the plastic scintillator and re-emit green lights guided to the PSPMT. The light distribution among the WLS fiber arrays determines the position of the muon interaction; consequently, 3-D tomographic images can be obtained by extracting the crossing points of the individual muon trajectories by using a point-of-closest-approach algorithm. The goal of this study is to optimize the design parameters of a muon tomography system by using the Geant4 code and to experimentally evaluate the performance of the prototype detector. Images obtained by the prototype detector with a 420-nm laser light source showed good agreement with the simulation results. This indicates that the proposed detector is feasible for use in a muon tomography system and can be used to verify the Z-discrimination capability of the muon tomography system.

Radiation Environment Inside Spacecraft

NASA Technical Reports Server (NTRS)

O'Neill, Patrick

2015-01-01

Dr. Patrick O'Neill, NASA Johnson Space Center, will present a detailed description of the radiation environment inside spacecraft. The free space (outside) solar and galactic cosmic ray and trapped Van Allen belt proton spectra are significantly modified as these ions propagate through various thicknesses of spacecraft structure and shielding material. In addition to energy loss, secondary ions are created as the ions interact with the structure materials. Nuclear interaction codes (FLUKA, GEANT4, HZTRAN, MCNPX, CEM03, and PHITS) transport free space spectra through different thicknesses of various materials. These "inside" energy spectra are then converted to Linear Energy Transfer (LET) spectra and dose rate - that's what's needed by electronics systems designers. Model predictions are compared to radiation measurements made by instruments such as the Intra-Vehicular Charged Particle Directional Spectrometer (IV-CPDS) used inside the Space Station, Orion, and Space Shuttle.

Nuclear spectroscopy with Geant4: Proton and neutron emission & radioactivity

NASA Astrophysics Data System (ADS)

Sarmiento, L. G.; Rudolph, D.

2016-07-01

With the aid of a novel combination of existing equipment - JYFLTRAP and the TASISpec decay station - it is possible to perform very clean quantum-state selective, high-resolution particle-γ decay spectroscopy. We intend to study the determination of the branching ratio of the ℓ = 9 proton emission from the Iπ = 19/2-, 3174-keV isomer in the N = Z - 1 nucleus 53Co. The study aims to initiate a series of similar experiments along the proton dripline, thereby providing unique insights into "open quantum systems". The technique has been pioneered in case studies using SHIPTRAP and TASISpec at GSI. Newly available radioactive decay modes in Geant4 simulations are going to corroborate the anticipated experimental results.

GEANT4 simulations of a novel 3He-free thermalization neutron detector

NASA Astrophysics Data System (ADS)

Mazzone, A.; Finocchiaro, P.; Lo Meo, S.; Colonna, N.

2018-05-01

A novel concept for 3He-free thermalization detector is here investigated by means of GEANT4 simulations. The detector is based on strips of solid-state detectors with 6Li deposit for neutron conversion. Various geometrical configurations have been investigated in order to find the optimal solution, in terms of value and energy dependence of the efficiency for neutron energies up to 10 MeV. The expected performance of the new detector are compared with those of an optimized thermalization detector based on standard 3He tubes. Although an 3He-based detector is superior in terms of performance and simplicity, the proposed solution may become more appealing in terms of costs in case of shortage of 3He supply.

Fast Simulation of Electromagnetic Showers in the ATLAS Calorimeter: Frozen Showers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barberio, E.; /Melbourne U.; Boudreau, J.

2011-11-29

One of the most time consuming process simulating pp interactions in the ATLAS detector at LHC is the simulation of electromagnetic showers in the calorimeter. In order to speed up the event simulation several parametrisation methods are available in ATLAS. In this paper we present a short description of a frozen shower technique, together with some recent benchmarks and comparison with full simulation. An expected high rate of proton-proton collisions in ATLAS detector at LHC requires large samples of simulated events (Monte Carlo) to study various physics processes. A detailed simulation of particle reactions ('full simulation') in the ATLAS detectormore » is based on GEANT4 and is very accurate. However, due to complexity of the detector, high particle multiplicity and GEANT4 itself, the average CPU time spend to simulate typical QCD event in pp collision is 20 or more minutes for modern computers. During detector simulation the largest time is spend in the calorimeters (up to 70%) most of which is required for electromagnetic particles in the electromagnetic (EM) part of the calorimeters. This is the motivation for fast simulation approaches which reduce the simulation time without affecting the accuracy. Several of fast simulation methods available within the ATLAS simulation framework (standard Athena based simulation program) are discussed here with the focus on the novel frozen shower library (FS) technique. The results obtained with FS are presented here as well.« less

Study of electrode pattern design for a CZT-based PET detector.

PubMed

Gu, Y; Levin, C S

2014-06-07

We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3D positioning cadmium zinc telluride photon detectors comprising 40 mm × 40 mm × 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (~26 to ~127.5 ns full width at half maximum (FWHM) for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (~34 to ~83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode strips' weighting functions, which indicated a stronger 'small pixel' effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 to -80 V w.r.t. the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 versus 100 µm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns.

Study of electrode pattern design for a CZT-based PET detector

PubMed Central

Gu, Y; Levin, C S

2014-01-01

We are developing a 1 mm resolution small animal positron emission tomography (PET) system using 3-D positioning Cadmium Zinc Telluride (CZT) photon detectors comprising 40 mm × 40 mm × 5 mm crystals metalized with a cross-strip electrode pattern with a 1 mm anode strip pitch. We optimized the electrode pattern design for intrinsic sensitivity and spatial, energy and time resolution performance using a test detector comprising cathode and steering electrode strips of varying dimensions. The study found 3 mm and 5 mm width cathode strips locate charge-shared photon interactions near cathode strip boundaries with equal precision. 3 mm width cathode strips exhibited large time resolution variability as a function of photon interaction location between the anode and cathode planes (~26 ns to ~127.5 ns FWHM for 0.5 mm and 4.2 mm depths, respectively). 5 mm width cathode strips by contrast exhibited more stable time resolution for the same interaction locations (~34 ns to ~83 ns FWHM), provided more linear spatial positioning in the direction orthogonal to the electrode planes, and as much as 68.4% improvement in photon sensitivity over the 3 mm wide cathode strips. The results were understood by analyzing the cathode strips’ weighting functions, which indicated a stronger “small pixel” effect in the 3 mm wide cathode strips. Photon sensitivity and anode energy resolution were seen to improve with decreasing steering electrode bias from 0 V to −80 V w.r.t the anode potential. A slight improvement in energy resolution was seen for wider steering electrode strips (400 μm vs. 100 μm) for charge-shared photon interactions. Although this study successfully focused on electrode pattern features for PET performance, the results are generally applicable to semiconductor photon detectors employing cross-trip electrode patterns. PMID:24786208

High-energy radiographic imaging performance of LYSO

DOE PAGES

Smalley, Duane; Duke, Dana; Webb, Timothy; ...

2018-05-23

Here, a comprehensive comparison of the dominant sources of radiation-induced blur for radiographic imaging system performance is made. End-point energies of 6, 10, 15, and 20 MeV bremsstrahlung photon radiation produced at the Los Alamos National Laboratory Microtron facility were used to examine the performance of large-panel cerium-doped lutetium yttrium silicon oxide (LYSO:Ce) scintillators 3, 5 and 10 mm thick. The system resolution was measured and compared between the various end-point energies and scintillator thicknesses. Contrary to expectations, it is found that there was only a minor dependence of system resolution on scintillator thickness or beam end-point energy. This indicatesmore » that increased scintillator thickness does not have a dramatic effect on system performance. The data are then compared to Geant4 simulations to assess contributions to the system performance through the examination of modulation transfer functions. It was determined that the low-frequency response of the system is dominated by the radiation-induced signal, while the higher-frequency response of the system is dominated by the optical imaging of the scintillation emission.« less

Simulation the spatial resolution of an X-ray imager based on zinc oxide nanowires in anodic aluminium oxide membrane by using MCNP and OPTICS Codes

NASA Astrophysics Data System (ADS)

Samarin, S. N.; Saramad, S.

2018-05-01

The spatial resolution of a detector is a very important parameter for x-ray imaging. A bulk scintillation detector because of spreading of light inside the scintillator does't have a good spatial resolution. The nanowire scintillators because of their wave guiding behavior can prevent the spreading of light and can improve the spatial resolution of traditional scintillation detectors. The zinc oxide (ZnO) scintillator nanowire, with its simple construction by electrochemical deposition in regular hexagonal structure of Aluminum oxide membrane has many advantages. The three dimensional absorption of X-ray energy in ZnO scintillator is simulated by a Monte Carlo transport code (MCNP). The transport, attenuation and scattering of the generated photons are simulated by a general-purpose scintillator light response simulation code (OPTICS). The results are compared with a previous publication which used a simulation code of the passage of particles through matter (Geant4). The results verify that this scintillator nanowire structure has a spatial resolution less than one micrometer.

Gamma ray measurements at OMEGA with the newest gas Cherenkov Detector “GCD-3”

DOE Office of Scientific and Technical Information (OSTI.GOV)

McEvoy, A. M.; Herrmann, H. W.; Kim, Y.

Initial results from the newest Gas Cherenkov Detector (GCD-3) are reported demonstrating improved performance over previous GCD iterations. Increased shielding and lengthening of the Cherenkov photon optical path have resulted in a diminished precursor signal with increased temporal separation between the precursor and the primary DT Cherenkov signal. Design changes resulted in a measured GCD-3 sensitivity comparable to GCD-1 at identical 100 psia CO 2 operation. All metal gasket seals and pressure vessel certification to 400 psia operation allow for a GCD-3 lower Cherenkov threshold of 1.8 MeV using the fluorinated gas C 2F 6 as compared to the 6.3more » MeV lower limit of GCD-1 and GCD-2. Calibration data will be used to benchmark GEANT4 and ACCEPT detector models. Lastly, the GCD-3 acts as a prototype for the Super GCD being fielded at the National Ignition Facility (NIF) as part of the National Diagnostics Plan and will be installed at NIF in early 2016.« less

Gamma ray measurements at OMEGA with the newest gas Cherenkov Detector “GCD-3”

DOE PAGES

McEvoy, A. M.; Herrmann, H. W.; Kim, Y.; ...

2016-05-26

Initial results from the newest Gas Cherenkov Detector (GCD-3) are reported demonstrating improved performance over previous GCD iterations. Increased shielding and lengthening of the Cherenkov photon optical path have resulted in a diminished precursor signal with increased temporal separation between the precursor and the primary DT Cherenkov signal. Design changes resulted in a measured GCD-3 sensitivity comparable to GCD-1 at identical 100 psia CO 2 operation. All metal gasket seals and pressure vessel certification to 400 psia operation allow for a GCD-3 lower Cherenkov threshold of 1.8 MeV using the fluorinated gas C 2F 6 as compared to the 6.3more » MeV lower limit of GCD-1 and GCD-2. Calibration data will be used to benchmark GEANT4 and ACCEPT detector models. Lastly, the GCD-3 acts as a prototype for the Super GCD being fielded at the National Ignition Facility (NIF) as part of the National Diagnostics Plan and will be installed at NIF in early 2016.« less

Recent development on the realization of a 1-inch VSiPMT prototype

NASA Astrophysics Data System (ADS)

Barbato, F. C. T.; Barbarino, G.; Campajola, L.; Di Capua, F.; Mollo, C. M.; Valentini, A.; Vivolo, D.

2017-03-01

The VSiPMT (Vacuum Silicon PhotoMultiplier Tube) is an innovative design for a revolutionary hybrid photodetector. The idea, born with the purpose to use a SiPM for large detection volumes, consists in replacing the classical dynode chain with a SiPM. In this configuration, we match the large sensitive area of a photocathode with the performances of the SiPM technology, which therefore acts like an electron detector and so like a current amplifier. The excellent photon counting capability, fast response, low power consumption and great stability are among the most attractive features of the VSiPMT. In order to realize such a device we first studied the feasibility of this detector both from theoretical and experimental point of view, by implementing a Geant4-based simulation and studying the response of a special non-windowed MPPC by Hamamatsu with an electron beam. Thanks to this result Hamamatsu realized two VSiPMT industrial prototypes with a photocathode of 3mm diameter. We present the progress on the realization of a 1-inch prototype and the preliminary tests we are performing on it.

High-energy radiographic imaging performance of LYSO

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smalley, Duane; Duke, Dana; Webb, Timothy

Here, a comprehensive comparison of the dominant sources of radiation-induced blur for radiographic imaging system performance is made. End-point energies of 6, 10, 15, and 20 MeV bremsstrahlung photon radiation produced at the Los Alamos National Laboratory Microtron facility were used to examine the performance of large-panel cerium-doped lutetium yttrium silicon oxide (LYSO:Ce) scintillators 3, 5 and 10 mm thick. The system resolution was measured and compared between the various end-point energies and scintillator thicknesses. Contrary to expectations, it is found that there was only a minor dependence of system resolution on scintillator thickness or beam end-point energy. This indicatesmore » that increased scintillator thickness does not have a dramatic effect on system performance. The data are then compared to Geant4 simulations to assess contributions to the system performance through the examination of modulation transfer functions. It was determined that the low-frequency response of the system is dominated by the radiation-induced signal, while the higher-frequency response of the system is dominated by the optical imaging of the scintillation emission.« less

Modeling the biophysical effects in a carbon beam delivery line by using Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Cho, Ilsung; Yoo, SeungHoon; Cho, Sungho; Kim, Eun Ho; Song, Yongkeun; Shin, Jae-ik; Jung, Won-Gyun

2016-09-01

The Relative biological effectiveness (RBE) plays an important role in designing a uniform dose response for ion-beam therapy. In this study, the biological effectiveness of a carbon-ion beam delivery system was investigated using Monte Carlo simulations. A carbon-ion beam delivery line was designed for the Korea Heavy Ion Medical Accelerator (KHIMA) project. The GEANT4 simulation tool kit was used to simulate carbon-ion beam transport into media. An incident energy carbon-ion beam with energy in the range between 220 MeV/u and 290 MeV/u was chosen to generate secondary particles. The microdosimetric-kinetic (MK) model was applied to describe the RBE of 10% survival in human salivary-gland (HSG) cells. The RBE weighted dose was estimated as a function of the penetration depth in the water phantom along the incident beam's direction. A biologically photon-equivalent Spread Out Bragg Peak (SOBP) was designed using the RBE-weighted absorbed dose. Finally, the RBE of mixed beams was predicted as a function of the depth in the water phantom.

Muon-Induced Neutrons Do Not Explain the DAMA Data

NASA Astrophysics Data System (ADS)

Klinger, J.; Kudryavtsev, V. A.

2015-04-01

We present an accurate model of the muon-induced background in the DAMA/LIBRA experiment. Our work challenges proposed mechanisms which seek to explain the observed DAMA signal modulation with muon-induced backgrounds. Muon generation and transport are performed using the MUSIC /MUSUN code, and subsequent interactions in the vicinity of the DAMA detector cavern are simulated with Geant4. We estimate the total muon-induced neutron flux in the detector cavern to be Φnν=1.0 ×10-9 cm-2 s-1 . We predict 3.49 ×10-5 counts /day /kg /keV , which accounts for less than 0.3% of the DAMA signal modulation amplitude.

MO-FG-BRA-03: A Monte-Carlo Study of Cellular Dosimetry of Radioactive Gold-Palladium Nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Y; Michaud, F; Fortin, M

Purpose: Radioactive gold-palladium nanoparticles ({sup 103}Pd:Pd@Au NPs) are being developed for prostate cancer brachytherapy. Photons emitted by the radioisotope palladium (photon energy: 20.1 and 23.0 keV), interacting with gold-coating of NPs, lead to enhanced energy distribution in nucleus. Here, a simple cellular model was studied using detailed track-structure method. Methods: Geant4-DNA was used with auger electrons enabled. Biological cell was modeled as a sphere of radius r=5 µm that were immersed in a fluid containing large number of NPs at different concentrations (S=1, 2.15, 5.1, 17.2 mg-Au/g-H2O). Nucleus was modeled as a concentric sphere (r=3µm). Thickness of gold-coating on {supmore » 103}Pd core was 15nm, 20nm and 25nm, respectively. A scenario of NP diffusion was investigated, where S=5.1 mg-Au/g-H2O outside cell and S=1 mg-Au/g-H2O in cytoplasm. 10{sup 10} {sup 103}Pd decays were simulated for each combination of NP concentration and gold-coating. Results: A uniform increase in energy deposition (Edep) is observed in cell nucleus and the energy enhancement ratio (EER) is 1.16, 1.22 and 1.3 for 15nm, 20nm and 25nm of gold -coatings, respectively. Edep at the center of nucleus is increased by a factor of 1.47, 2.51 and 5.54 when the NP concentration in the cytoplasm increases from 1 mg-Au/g-H2O to 2.15, 5.10 and 17.2 mg-Au/g-H2O, respectively. When NPs diffuse into cytoplasm, the mean value of Edep in nucleus increases from 0.42 to 1.13 MeV per 10{sup 9} decays (GBq-Second) of {sup 103}Pd and the maximum value increases from 0.54 to 2.5 MeV per GBq-Second. Conclusion: These results suggest that {sup 103}Pd:Pd@Au NPs constitute a promising nanotherapeutic agent. Ongoing studies use transmission electron microscopy (TEM) images of prostate cancer.« less

Monte Carlo studies on photon interactions in radiobiological experiments

PubMed Central

Shahmohammadi Beni, Mehrdad; Krstic, D.; Nikezic, D.

2018-01-01

X-ray and γ-ray photons have been widely used for studying radiobiological effects of ionizing radiations. Photons are indirectly ionizing radiations so they need to set in motion electrons (which are a directly ionizing radiation) to perform the ionizations. When the photon dose decreases to below a certain limit, the number of electrons set in motion will become so small that not all cells in an “exposed” cell population can get at least one electron hit. When some cells in a cell population are not hit by a directly ionizing radiation (in other words not irradiated), there will be rescue effect between the irradiated cells and non-irradiated cells, and the resultant radiobiological effect observed for the “exposed” cell population will be different. In the present paper, the mechanisms underlying photon interactions in radiobiological experiments were studied using our developed NRUphoton computer code, which was benchmarked against the MCNP5 code by comparing the photon dose delivered to the cell layer underneath the water medium. The following conclusions were reached: (1) The interaction fractions decreased in the following order: 16O > 12C > 14N > 1H. Bulges in the interaction fractions (versus water medium thickness) were observed, which reflected changes in the energies of the propagating photons due to traversals of different amount of water medium as well as changes in the energy-dependent photon interaction cross-sections. (2) Photoelectric interaction and incoherent scattering dominated for lower-energy (10 keV) and high-energy (100 keV and 1 MeV) incident photons. (3) The fractions of electron ejection from different nuclei were mainly governed by the photoelectric effect cross-sections, and the fractions from the 1s subshell were the largest. (4) The penetration fractions in general decreased with increasing medium thickness, and increased with increasing incident photon energy, the latter being explained by the corresponding reduction in interaction cross-sections. (5) The areas under the angular distribution curves of photons exiting the medium layer and subsequently undergoing interactions within the cell layer became smaller for larger incident photon energies. (6) The number of cells suffering at least one electron hit increased with the administered dose. For larger incident photon energies, the numbers of cells suffering at least one electron hit became smaller, which was attributed to the reduction in the photon interaction cross-section. These results highlighted the importance of the administered dose in radiobiological experiments. In particular, the threshold administered doses at which all cells in the exposed cell array suffered at least one electron hit might provide hints on explaining the intriguing observation that radiation-induced cancers can be statistically detected only above the threshold value of ~100 mSv, and thus on reconciling controversies over the linear no-threshold model. PMID:29561871

Calculation of DNA strand breaks due to direct and indirect effects of Auger electrons from incorporated 123I and 125I radionuclides using the Geant4 computer code.

PubMed

Raisali, Gholamreza; Mirzakhanian, Lalageh; Masoudi, Seyed Farhad; Semsarha, Farid

2013-01-01

In this work the number of DNA single-strand breaks (SSB) and double-strand breaks (DSB) due to direct and indirect effects of Auger electrons from incorporated (123)I and (125)I have been calculated by using the Geant4-DNA toolkit. We have performed and compared the calculations for several cases: (125)I versus (123)I, source positions and direct versus indirect breaks to study the capability of the Geant4-DNA in calculations of DNA damage yields. Two different simple geometries of a 41 base pair of B-DNA have been simulated. The location of (123)I has been considered to be in (123)IdUrd and three different locations for (125)I. The results showed that the simpler geometry is sufficient for direct break calculations while indirect damage yield is more sensitive to the helical shape of DNA. For (123)I Auger electrons, the average number of DSB due to the direct hits is almost twice the DSB due to the indirect hits. Furthermore, a comparison between the average number of SSB or DSB caused by Auger electrons of (125)I and (123)I in (125)IdUrd and (123)IdUrd shows that (125)I is 1.5 times more effective than (123)I per decay. The results are in reasonable agreement with previous experimental and theoretical results which shows the applicability of the Geant-DNA toolkit in nanodosimetry calculations which benefits from the open-source accessibility with the advantage that the DNA models used in this work enable us to save the computational time. Also, the results showed that the simpler geometry is suitable for direct break calculations, while for the indirect damage yield, the more precise model is preferred.

Geant4 calculations for space radiation shielding material Al2O3

NASA Astrophysics Data System (ADS)

Capali, Veli; Acar Yesil, Tolga; Kaya, Gokhan; Kaplan, Abdullah; Yavuz, Mustafa; Tilki, Tahir

2015-07-01

Aluminium Oxide, Al2O3 is the most widely used material in the engineering applications. It is significant aluminium metal, because of its hardness and as a refractory material owing to its high melting point. This material has several engineering applications in diverse fields such as, ballistic armour systems, wear components, electrical and electronic substrates, automotive parts, components for electric industry and aero-engine. As well, it is used as a dosimeter for radiation protection and therapy applications for its optically stimulated luminescence properties. In this study, stopping powers and penetrating distances have been calculated for the alpha, proton, electron and gamma particles in space radiation shielding material Al2O3 for incident energies 1 keV - 1 GeV using GEANT4 calculation code.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Y M; Bush, K; Han, B

Purpose: Accurate and fast dose calculation is a prerequisite of precision radiation therapy in modern photon and particle therapy. While Monte Carlo (MC) dose calculation provides high dosimetric accuracy, the drastically increased computational time hinders its routine use. Deterministic dose calculation methods are fast, but problematic in the presence of tissue density inhomogeneity. We leverage the useful features of deterministic methods and MC to develop a hybrid dose calculation platform with autonomous utilization of MC and deterministic calculation depending on the local geometry, for optimal accuracy and speed. Methods: Our platform utilizes a Geant4 based “localized Monte Carlo” (LMC) methodmore » that isolates MC dose calculations only to volumes that have potential for dosimetric inaccuracy. In our approach, additional structures are created encompassing heterogeneous volumes. Deterministic methods calculate dose and energy fluence up to the volume surfaces, where the energy fluence distribution is sampled into discrete histories and transported using MC. Histories exiting the volume are converted back into energy fluence, and transported deterministically. By matching boundary conditions at both interfaces, deterministic dose calculation account for dose perturbations “downstream” of localized heterogeneities. Hybrid dose calculation was performed for water and anthropomorphic phantoms. Results: We achieved <1% agreement between deterministic and MC calculations in the water benchmark for photon and proton beams, and dose differences of 2%–15% could be observed in heterogeneous phantoms. The saving in computational time (a factor ∼4–7 compared to a full Monte Carlo dose calculation) was found to be approximately proportional to the volume of the heterogeneous region. Conclusion: Our hybrid dose calculation approach takes advantage of the computational efficiency of deterministic method and accuracy of MC, providing a practical tool for high performance dose calculation in modern RT. The approach is generalizable to all modalities where heterogeneities play a large role, notably particle therapy.« less

DoSSiER: Database of scientific simulation and experimental results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wenzel, Hans; Yarba, Julia; Genser, Krzystof

The Geant4, GeantV and GENIE collaborations regularly perform validation and regression tests for simulation results. DoSSiER (Database of Scientific Simulation and Experimental Results) is being developed as a central repository to store the simulation results as well as the experimental data used for validation. DoSSiER can be easily accessed via a web application. In addition, a web service allows for programmatic access to the repository to extract records in json or xml exchange formats. In this paper, we describe the functionality and the current status of various components of DoSSiER as well as the technology choices we made.

DoSSiER: Database of scientific simulation and experimental results

DOE PAGES

Wenzel, Hans; Yarba, Julia; Genser, Krzystof; ...

2016-08-01

The Geant4, GeantV and GENIE collaborations regularly perform validation and regression tests for simulation results. DoSSiER (Database of Scientific Simulation and Experimental Results) is being developed as a central repository to store the simulation results as well as the experimental data used for validation. DoSSiER can be easily accessed via a web application. In addition, a web service allows for programmatic access to the repository to extract records in json or xml exchange formats. In this paper, we describe the functionality and the current status of various components of DoSSiER as well as the technology choices we made.

Comparing Geant4 hadronic models for the WENDI-II rem meter response function.

PubMed

Vanaudenhove, T; Dubus, A; Pauly, N

2013-01-01

The WENDI-II rem meter is one of the most popular neutron dosemeters used to assess a useful quantity of radiation protection, namely the ambient dose equivalent. This is due to its high sensitivity and its energy response that approximately follows the conversion function between neutron fluence and ambient dose equivalent in the range of thermal to 5 GeV. The simulation of the WENDI-II response function with the Geant4 toolkit is then perfectly suited to compare low- and high-energy hadronic models provided by this Monte Carlo code. The results showed that the thermal treatment of hydrogen in polyethylene for neutron <4 eV has a great influence over the whole detector range. Above 19 MeV, both Bertini Cascade and Binary Cascade models show a good correlation with the results found in the literature, while low-energy parameterised models are not suitable for this application.

Monte Carlo based approach to the LS-NaI 4πβ-γ anticoincidence extrapolation and uncertainty

PubMed Central

Fitzgerald, R.

2016-01-01

The 4πβ-γ anticoincidence method is used for the primary standardization of β−, β+, electron capture (EC), α, and mixed-mode radionuclides. Efficiency extrapolation using one or more γ ray coincidence gates is typically carried out by a low-order polynomial fit. The approach presented here is to use a Geant4-based Monte Carlo simulation of the detector system to analyze the efficiency extrapolation. New code was developed to account for detector resolution, direct γ ray interaction with the PMT, and implementation of experimental β-decay shape factors. The simulation was tuned to 57Co and 60Co data, then tested with 99mTc data, and used in measurements of 18F, 129I, and 124I. The analysis method described here offers a more realistic activity value and uncertainty than those indicated from a least-squares fit alone. PMID:27358944

WE-H-BRA-04: Biological Geometries for the Monte Carlo Simulation Toolkit TOPASNBio

DOE Office of Scientific and Technical Information (OSTI.GOV)

McNamara, A; Held, K; Paganetti, H

2016-06-15

Purpose: New advances in radiation therapy are most likely to come from the complex interface of physics, chemistry and biology. Computational simulations offer a powerful tool for quantitatively investigating radiation interactions with biological tissue and can thus help bridge the gap between physics and biology. The aim of TOPAS-nBio is to provide a comprehensive tool to generate advanced radiobiology simulations. Methods: TOPAS wraps and extends the Geant4 Monte Carlo (MC) simulation toolkit. TOPAS-nBio is an extension to TOPAS which utilizes the physics processes in Geant4-DNA to model biological damage from very low energy secondary electrons. Specialized cell, organelle and molecularmore » geometries were designed for the toolkit. Results: TOPAS-nBio gives the user the capability of simulating biological geometries, ranging from the micron-scale (e.g. cells and organelles) to complex nano-scale geometries (e.g. DNA and proteins). The user interacts with TOPAS-nBio through easy-to-use input parameter files. For example, in a simple cell simulation the user can specify the cell type and size as well as the type, number and size of included organelles. For more detailed nuclear simulations, the user can specify chromosome territories containing chromatin fiber loops, the later comprised of nucleosomes on a double helix. The chromatin fibers can be arranged in simple rigid geometries or within factual globules, mimicking realistic chromosome territories. TOPAS-nBio also provides users with the capability of reading protein data bank 3D structural files to simulate radiation damage to proteins or nucleic acids e.g. histones or RNA. TOPAS-nBio has been validated by comparing results to other track structure simulation software and published experimental measurements. Conclusion: TOPAS-nBio provides users with a comprehensive MC simulation tool for radiobiological simulations, giving users without advanced programming skills the ability to design and run complex simulations.« less

Two-photon fluorescence and fluorescence imaging of two styryl heterocyclic dyes combined with DNA

NASA Astrophysics Data System (ADS)

Gao, Chao; Liu, Shu-yao; Zhang, Xian; Liu, Ying-kai; Qiao, Cong-de; Liu, Zhao-e.

2016-03-01

Two new styryl heterocyclic two-photon (TP) materials, 4-[4-(N-methyl)styrene]-imidazo [4,5-f][1,10] phenanthroline-benzene iodated salt (probe-1) and 4,4- [4-(N-methyl)styrene] -benzene iodated salt (probe-2) were successfully synthesized and studied as potential fluorescent probes of DNA detection. The linear and nonlinear photophysical properties of two compounds in different solvents were investigated. The absorption, one- and two-photon fluorescent spectra of the free dye and dye-DNA complex were also examined to evaluate their photophysical properties. The binding constants of dye-DNA were obtained according to Scatchard equation with good values. The results showed that two probes could be used as fluorescent DNA probes by two-photon excitation, and TP fluorescent properties of probe-1 are superior to that of probe-2. The fluorescent method date indicated that the mechanisms of dye-DNA complex interaction may be groove binding for probe-1 and electrostatic interaction for probe-2, respectively. The MTT assay experiments showed two probes are low toxicity. Moreover, the TP fluorescence imaging of DNA detection in living cells at 800 nm indicated that the ability to locate in cell nuclei of probe-1 is better than that of probe-2.

Two-photon fluorescence and fluorescence imaging of two styryl heterocyclic dyes combined with DNA.

PubMed

Gao, Chao; Liu, Shu-yao; Zhang, Xian; Liu, Ying-kai; Qiao, Cong-de; Liu, Zhao-e

2016-03-05

Two new styryl heterocyclic two-photon (TP) materials, 4-[4-(N-methyl)styrene]-imidazo [4,5-f][1,10] phenanthroline-benzene iodated salt (probe-1) and 4,4-[4-(N-methyl)styrene]-benzene iodated salt (probe-2) were successfully synthesized and studied as potential fluorescent probes of DNA detection. The linear and nonlinear photophysical properties of two compounds in different solvents were investigated. The absorption, one- and two-photon fluorescent spectra of the free dye and dye-DNA complex were also examined to evaluate their photophysical properties. The binding constants of dye-DNA were obtained according to Scatchard equation with good values. The results showed that two probes could be used as fluorescent DNA probes by two-photon excitation, and TP fluorescent properties of probe-1 are superior to that of probe-2. The fluorescent method date indicated that the mechanisms of dye-DNA complex interaction may be groove binding for probe-1 and electrostatic interaction for probe-2, respectively. The MTT assay experiments showed two probes are low toxicity. Moreover, the TP fluorescence imaging of DNA detection in living cells at 800 nm indicated that the ability to locate in cell nuclei of probe-1 is better than that of probe-2. Copyright © 2015 Elsevier B.V. All rights reserved.

A strongly interacting polaritonic quantum dot

NASA Astrophysics Data System (ADS)

Jia, Ningyuan; Schine, Nathan; Georgakopoulos, Alexandros; Ryou, Albert; Clark, Logan W.; Sommer, Ariel; Simon, Jonathan

2018-06-01

Polaritons are promising constituents of both synthetic quantum matter1 and quantum information processors2, whose properties emerge from their components: from light, polaritons draw fast dynamics and ease of transport; from matter, they inherit the ability to collide with one another. Cavity polaritons are particularly promising as they may be confined and subjected to synthetic magnetic fields controlled by cavity geometry3, and furthermore they benefit from increased robustness due to the cavity enhancement in light-matter coupling. Nonetheless, until now, cavity polaritons have operated only in a weakly interacting mean-field regime4,5. Here we demonstrate strong interactions between individual cavity polaritons enabled by employing highly excited Rydberg atoms as the matter component of the polaritons. We assemble a quantum dot composed of approximately 150 strongly interacting Rydberg-dressed 87Rb atoms in a cavity, and observe blockaded transport of photons through it. We further observe coherent photon tunnelling oscillations, demonstrating that the dot is zero-dimensional. This work establishes the cavity Rydberg polariton as a candidate qubit in a photonic information processor and, by employing multiple resonator modes as the spatial degrees of freedom of a photonic particle, the primary ingredient to form photonic quantum matter6.

SU-E-T-764: Track Repeating Algorithm for Proton Therapy Applied to Intensity Modulated Proton Therapy for Head-And-Neck Patients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yepes, P; Mirkovic, D; Mohan, R

Purpose: To determine the suitability of fast Monte Carlo techniques for dose calculation in particle therapy based on track-repeating algorithm for Intensity Modulated Proton Therapy, IMPT. The application of this technique will make possible detailed retrospective studies of large cohort of patients, which may lead to a better determination of Relative Biological Effects from the analysis of patient data. Methods: A cohort of six head-and-neck patients treated at the University of Texas MD Anderson Cancer Center with IMPT were utilized. The dose distributions were calculated with the standard Treatment Plan System, TPS, MCNPX, GEANT4 and FDC, a fast track-repeating algorithmmore » for proton therapy for the verification and the patient plans. FDC is based on a GEANT4 database of trajectories of protons in a water. The obtained dose distributions were compared to each other utilizing the g-index criteria for 3mm-3% and 2mm-2%, for the maximum spatial and dose differences. The γ-index was calculated for voxels with a dose at least 10% of the maximum delivered dose. Dose Volume Histograms are also calculated for the various dose distributions. Results: Good agreement between GEANT4 and FDC is found with less than 1% of the voxels with a γ-index larger than 1 for 2 mm-2%. The agreement between MCNPX with FDC is within the requirements of clinical standards, even though it is slightly worse than the comparison with GEANT4.The comparison with TPS yielded larger differences, what is also to be expected because pencil beam algorithm do not always performed well in highly inhomogeneous areas like head-and-neck. Conclusion: The good agreement between a track-repeating algorithm and a full Monte Carlo for a large cohort of patients and a challenging, site like head-and-neck, opens the path to systematic and detailed studies of large cohorts, which may yield better understanding of biological effects.« less

SU-F-T-217: A Comprehensive Monte-Carlo Study of Out-Of-Field Secondary Neutron Spectra in a Scanned-Beam Proton Therapy Treatment Room

DOE Office of Scientific and Technical Information (OSTI.GOV)

Englbrecht, F; Parodi, K; Trinkl, S

2016-06-15

Purpose: To simulate secondary neutron radiation-fields produced at different positions during phantom irradiation inside a scanning proton therapy gantry treatment room. Further, to identify origin, energy distribution and angular emission as function of proton beam energy. Methods: GEANT4 and FLUKA Monte-Carlo codes were used to model the relevant parts of the treatment room in a gantry-equipped pencil beam scanning proton therapy facility including walls, floor, metallic gantry-components, patient table and the homogeneous PMMA target. The proton beams were modeled based on experimental beam ranges in water and spot shapes in air. Neutron energy spectra were simulated at 0°, 45°, 90°more » and 135° relative to the beam axis at 2m distance from isocenter, as well as 11×11 cm2 fields for 75MeV, 140MeV, 200MeV and for 118MeV with 5cm PMMA range-shifter. The total neutron energy distribution was recorded for these four positions and proton energies. Additionally, the room-components generating secondary neutrons in the room and their contributions to the total spectrum were identified and quantified. Results: FLUKA and GEANT4 simulated neutron spectra showed good general agreement in the whole energy range of 10{sup −}9 to 10{sup 2} MeV. Comparison of measured spectra with the simulated contributions of the various room components helped to limit the complexity of the room model, by identifying the dominant contributions to the secondary neutron spectrum. The iron of the bending magnet and counterweight were identified as sources of secondary evaporation-neutrons, which were lacking in simplified room models. Conclusion: Thorough Monte-Carlo simulations have been performed to complement Bonner-sphere spectrometry measurements of secondary neutrons in a clinical proton therapy treatment room. Such calculations helped disentangling the origin of secondary neutrons and their dominant contributions to measured spectra, besides providing a useful validation of widely used Monte-Carlo packages in comparison to experimental data. Cluster of Excellence of the German Research Foundation (DFG) “Munich-Centre for Advanced Photonics (MAP)”.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnes, P.; et al.

A Geant4-based Monte Carlo package named G4DS has been developed to simulate the response of DarkSide-50, an experiment operating since 2013 at LNGS, designed to detect WIMP interactions in liquid argon. In the process of WIMP searches, DarkSide-50 has achieved two fundamental milestones: the rejection of electron recoil background with a power of ~10^7, using the pulse shape discrimination technique, and the measurement of the residual 39Ar contamination in underground argon, ~3 orders of magnitude lower with respect to atmospheric argon. These results rely on the accurate simulation of the detector response to the liquid argon scintillation, its ionization, andmore » electron-ion recombination processes. This work provides a complete overview of the DarkSide Monte Carlo and of its performance, with a particular focus on PARIS, the custom-made liquid argon response model.« less

The difference of scoring dose to water or tissues in Monte Carlo dose calculations for low energy brachytherapy photon sources.

PubMed

Landry, Guillaume; Reniers, Brigitte; Pignol, Jean-Philippe; Beaulieu, Luc; Verhaegen, Frank

2011-03-01

The goal of this work is to compare D(m,m) (radiation transported in medium; dose scored in medium) and D(w,m) (radiation transported in medium; dose scored in water) obtained from Monte Carlo (MC) simulations for a subset of human tissues of interest in low energy photon brachytherapy. Using low dose rate seeds and an electronic brachytherapy source (EBS), the authors quantify the large cavity theory conversion factors required. The authors also assess whether ap plying large cavity theory utilizing the sources' initial photon spectra and average photon energy induces errors related to spatial spectral variations. First, ideal spherical geometries were investigated, followed by clinical brachytherapy LDR seed implants for breast and prostate cancer patients. Two types of dose calculations are performed with the GEANT4 MC code. (1) For several human tissues, dose profiles are obtained in spherical geometries centered on four types of low energy brachytherapy sources: 125I, 103Pd, and 131Cs seeds, as well as an EBS operating at 50 kV. Ratios of D(w,m) over D(m,m) are evaluated in the 0-6 cm range. In addition to mean tissue composition, compositions corresponding to one standard deviation from the mean are also studied. (2) Four clinical breast (using 103Pd) and prostate (using 125I) brachytherapy seed implants are considered. MC dose calculations are performed based on postimplant CT scans using prostate and breast tissue compositions. PTV D90 values are compared for D(w,m) and D(m,m). (1) Differences (D(w,m)/D(m,m)-1) of -3% to 70% are observed for the investigated tissues. For a given tissue, D(w,m)/D(m,m) is similar for all sources within 4% and does not vary more than 2% with distance due to very moderate spectral shifts. Variations of tissue composition about the assumed mean composition influence the conversion factors up to 38%. (2) The ratio of D90(w,m) over D90(m,m) for clinical implants matches D(w,m)/D(m,m) at 1 cm from the single point sources, Given the small variation with distance, using conversion factors based on the emitted photon spectrum (or its mean energy) of a given source introduces minimal error. The large differences observed between scoring schemes underline the need for guidelines on choice of media for dose reporting. Providing such guidelines is beyond the scope of this work.

The GEANT4 toolkit capability in the hadron therapy field: simulation of a transport beam line

NASA Astrophysics Data System (ADS)

Cirrone, G. A. P.; Cuttone, G.; Di Rosa, F.; Raffaele, L.; Russo, G.; Guatelli, S.; Pia, M. G.

2006-01-01

At Laboratori Nazionali del Sud of the Instituto Nazionale di Fisica Nucleare of Catania (Sicily, Italy), the first Italian hadron therapy facility named CATANA (Centro di AdroTerapia ed Applicazioni Nucleari Avanzate) has been realized. Inside CATANA 62 MeV proton beams, accelerated by a superconducting cyclotron, are used for the radiotherapeutic treatments of some types of ocular tumours. Therapy with hadron beams still represents a pioneer technique, and only a few centers worldwide can provide this advanced specialized cancer treatment. On the basis of the experience so far gained, and considering the future hadron-therapy facilities to be developed (Rinecker, Munich Germany, Heidelberg/GSI, Darmstadt, Germany, PSI Villigen, Switzerland, CNAO, Pavia, Italy, Centro di Adroterapia, Catania, Italy) we decided to develop a Monte Carlo application based on the GEANT4 toolkit, for the design, the realization and the optimization of a proton-therapy beam line. Another feature of our project is to provide a general tool able to study the interactions of hadrons with the human tissue and to test the analytical-based treatment planning systems actually used in the routine practice. All the typical elements of a hadron-therapy line, such as diffusers, range shifters, collimators and detectors were modelled. In particular, we simulated the Markus type ionization chamber and a Gaf Chromic film as dosimeters to reconstruct the depth (Bragg peak and Spread Out Bragg Peak) and lateral dose distributions, respectively. We validated our simulated detectors comparing the results with the experimental data available in our facility.

Geant4 beam model for boron neutron capture therapy: investigation of neutron dose components.

PubMed

Moghaddasi, Leyla; Bezak, Eva

2018-03-01

Boron neutron capture therapy (BNCT) is a biochemically-targeted type of radiotherapy, selectively delivering localized dose to tumour cells diffused in normal tissue, while minimizing normal tissue toxicity. BNCT is based on thermal neutron capture by stable [Formula: see text]B nuclei resulting in emission of short-ranged alpha particles and recoil [Formula: see text]Li nuclei. The purpose of the current work was to develop and validate a Monte Carlo BNCT beam model and to investigate contribution of individual dose components resulting of neutron interactions. A neutron beam model was developed in Geant4 and validated against published data. The neutron beam spectrum, obtained from literature for a cyclotron-produced beam, was irradiated to a water phantom with boron concentrations of 100 μg/g. The calculated percentage depth dose curves (PDDs) in the phantom were compared with published data to validate the beam model in terms of total and boron depth dose deposition. Subsequently, two sensitivity studies were conducted to quantify the impact of: (1) neutron beam spectrum, and (2) various boron concentrations on the boron dose component. Good agreement was achieved between the calculated and measured neutron beam PDDs (within 1%). The resulting boron depth dose deposition was also in agreement with measured data. The sensitivity study of several boron concentrations showed that the calculated boron dose gradually converged beyond 100 μg/g boron concentration. This results suggest that 100μg/g tumour boron concentration may be optimal and above this value limited increase in boron dose is expected for a given neutron flux.

GEANT4 simulation of a scintillating-fibre tracker for the cosmic-ray muon tomography of legacy nuclear waste containers

NASA Astrophysics Data System (ADS)

Clarkson, A.; Hamilton, D. J.; Hoek, M.; Ireland, D. G.; Johnstone, J. R.; Kaiser, R.; Keri, T.; Lumsden, S.; Mahon, D. F.; McKinnon, B.; Murray, M.; Nutbeam-Tuffs, S.; Shearer, C.; Staines, C.; Yang, G.; Zimmerman, C.

2014-05-01

Cosmic-ray muons are highly penetrative charged particles that are observed at the sea level with a flux of approximately one per square centimetre per minute. They interact with matter primarily through Coulomb scattering, which is exploited in the field of muon tomography to image shielded objects in a wide range of applications. In this paper, simulation studies are presented that assess the feasibility of a scintillating-fibre tracker system for use in the identification and characterisation of nuclear materials stored within industrial legacy waste containers. A system consisting of a pair of tracking modules above and a pair below the volume to be assayed is simulated within the GEANT4 framework using a range of potential fibre pitches and module separations. Each module comprises two orthogonal planes of fibres that allow the reconstruction of the initial and Coulomb-scattered muon trajectories. A likelihood-based image reconstruction algorithm has been developed that allows the container content to be determined with respect to the scattering density λ, a parameter which is related to the atomic number Z of the scattering material. Images reconstructed from this simulation are presented for a range of anticipated scenarios that highlight the expected image resolution and the potential of this system for the identification of high-Z materials within a shielded, concrete-filled container. First results from a constructed prototype system are presented in comparison with those from a detailed simulation. Excellent agreement between experimental data and simulation is observed showing clear discrimination between the different materials assayed throughout.

Investigation of OPET Performance Using GATE, a Geant4-Based Simulation Software.

PubMed

Rannou, Fernando R; Kohli, Vandana; Prout, David L; Chatziioannou, Arion F

2004-10-01

A combined optical positron emission tomography (OPET) system is capable of both optical and PET imaging in the same setting, and it can provide information/interpretation not possible in single-mode imaging. The scintillator array here serves the dual function of coupling the optical signal from bioluminescence/fluorescence to the photodetector and also of channeling optical scintillations from the gamma rays. We report simulation results of the PET part of OPET using GATE, a Geant4 simulation package. The purpose of this investigation is the definition of the geometric parameters of the OPET tomograph. OPET is composed of six detector blocks arranged in a hexagonal ring-shaped pattern with an inner radius of 15.6 mm. Each detector consists of a two-dimensional array of 8 × 8 scintillator crystals each measuring 2 × 2 × 10 mm(3). Monte Carlo simulations were performed using the GATE software to measure absolute sensitivity, depth of interaction, and spatial resolution for two ring configurations, with and without gantry rotations, two crystal materials, and several crystal lengths. Images were reconstructed with filtered backprojection after angular interleaving and transverse one-dimensional interpolation of the sinogram. We report absolute sensitivities nearly seven times that of the prototype microPET at the center of field of view and 2.0 mm tangential and 2.3 mm radial resolutions with gantry rotations up to an 8.0 mm radial offset. These performance parameters indicate that the imaging spatial resolution and sensitivity of the OPET system will be suitable for high-resolution and high-sensitivity small-animal PET imaging.

Approach to calculation of mass spectra and two-photon decays of c c¯ mesons in the framework of Bethe-Salpeter equation

NASA Astrophysics Data System (ADS)

Bhatnagar, Shashank; Alemu, Lmenew

2018-02-01

In this work we calculate the mass spectra of charmonium for 1 P ,…,4 P states of 0++ and 1++, for 1 S ,…,5 S states of 0-+, and for 1 S ,…,4 D states of 1- along with the two-photon decay widths of the ground and first excited states of 0++ quarkonia for the process O++→γ γ in the framework of a QCD-motivated Bethe-Salpeter equation (BSE). In this 4 ×4 BSE framework, the coupled Salpeter equations are first shown to decouple for the confining part of the interaction (under the heavy-quark approximation) and are analytically solved, and later the one-gluon-exchange interaction is perturbatively incorporated, leading to mass spectral equations for various quarkonia. The analytic forms of wave functions obtained are used for the calculation of the two-photon decay widths of χc 0. Our results are in reasonable agreement with data (where available) and other models.

Importance Sampling Variance Reduction in GRESS ATMOSIM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wakeford, Daniel Tyler

This document is intended to introduce the importance sampling method of variance reduction to a Geant4 user for application to neutral particle Monte Carlo transport through the atmosphere, as implemented in GRESS ATMOSIM.

Modeling VLF signal modulation during solar flares with GEANT4 Monte Carlo simulation, a simple chemical model and LWPC

NASA Astrophysics Data System (ADS)

Palit, Sourav; Chakrabarti, Sandip Kumar; Pal, Sujay; Basak, Tamal

Extra ionization by X-rays during solar flares affects VLF signal propagation through D-region ionosphere. Ionization produced in the lower ionosphere due to X-ray spectra of solar flares are simulated with an efficient detector simulation program, GEANT4. The balancing between the ionization and loss processes, causing the lower ionosphere to settle back to its undisturbed state is handled with a simple chemical model consisting of four broad species of ion densities. Using the electron densities, modified VLF signal amplitude is then computed with LWPC code. VLF signal along NWC (Australia) to IERC/ICSP (India) propagation path is examined during a M and a X-type solar flares and observational deviations are compared with simulated results. The agreement is found to be excellent.

Geant4 Predictions of Energy Spectra in Typical Space Radiation Environment

NASA Technical Reports Server (NTRS)

Sabra, M. S.; Barghouty, A. F.

2014-01-01

Accurate knowledge of energy spectra inside spacecraft is important for protecting astronauts as well as sensitive electronics from the harmful effects of space radiation. Such knowledge allows one to confidently map the radiation environment inside the vehicle. The purpose of this talk is to present preliminary calculations for energy spectra inside a spherical shell shielding and behind a slab in typical space radiation environment using the 3D Monte-Carlo transport code Geant4. We have simulated proton and iron isotropic sources and beams impinging on Aluminum and Gallium arsenide (GaAs) targets at energies of 0.2, 0.6, 1, and 10 GeV/u. If time permits, other radiation sources and beams (_, C, O) and targets (C, Si, Ge, water) will be presented. The results are compared to ground-based measurements where available.

A Geant4 model of backscatter security imaging systems

NASA Astrophysics Data System (ADS)

Leboffe, Eric Matthew

The operating characteristics of x ray security scanner systems that utilize backscatter signal in order to distinguish person borne threats have never been made fully available to the general public. By designing a model using Geant4, studies can be performed which will shed light on systems such as security scanners and allow for analysis of the performance and safety of the system without access to any system data. Despite the fact that the systems are no longer in use at airports in the United States, the ability to design and validate detector models and phenomena is an important capability that can be applied to many current real world applications. The model presented provides estimates for absorbed dose, effective dose and dose depth distribution that are comparable to previously published work and explores imaging capabilities for the system embodiment modeled.

Performance profiling for brachytherapy applications

NASA Astrophysics Data System (ADS)

Choi, Wonqook; Cho, Kihyeon; Yeo, Insung

2018-05-01

In many physics applications, a significant amount of software (e.g. R, ROOT and Geant4) is developed on novel computing architectures, and much effort is expended to ensure the software is efficient in terms of central processing unit (CPU) time and memory usage. Profiling tools are used during the evaluation process to evaluate the efficiency; however, few such tools are able to accommodate low-energy physics regions. To address this limitation, we developed a low-energy physics profiling system in Geant4 to profile the CPU time and memory of software applications in brachytherapy applications. This paper describes and evaluates specific models that are applied to brachytherapy applications in Geant4, such as QGSP_BIC_LIV, QGSP_BIC_EMZ, and QGSP_BIC_EMY. The physics range in this tool allows it to be used to generate low energy profiles in brachytherapy applications. This was a limitation in previous studies, which caused us to develop a new profiling tool that supports profiling in the MeV range, in contrast to the TeV range that is supported by existing high-energy profiling tools. In order to easily compare the profiling results between low-energy and high-energy modes, we employed the same software architecture as that in the SimpliCarlo tool developed at the Fermilab National Accelerator Laboratory (FNAL) for the Large Hadron Collider (LHC). The results show that the newly developed profiling system for low-energy physics (less than MeV) complements the current profiling system used for high-energy physics (greater than TeV) applications.

A methodology for efficiency optimization of betavoltaic cell design using an isotropic planar source having an energy dependent beta particle distribution.

PubMed

Theirrattanakul, Sirichai; Prelas, Mark

2017-09-01

Nuclear batteries based on silicon carbide betavoltaic cells have been studied extensively in the literature. This paper describes an analysis of design parameters, which can be applied to a variety of materials, but is specific to silicon carbide. In order to optimize the interface between a beta source and silicon carbide p-n junction, it is important to account for the specific isotope, angular distribution of the beta particles from the source, the energy distribution of the source as well as the geometrical aspects of the interface between the source and the transducer. In this work, both the angular distribution and energy distribution of the beta particles are modeled using a thin planar beta source (e.g., H-3, Ni-63, S-35, Pm-147, Sr-90, and Y-90) with GEANT4. Previous studies of betavoltaics with various source isotopes have shown that Monte Carlo based codes such as MCNPX, GEANT4 and Penelope generate similar results. GEANT4 is chosen because it has important strengths for the treatment of electron energies below one keV and it is widely available. The model demonstrates the effects of angular distribution, the maximum energy of the beta particle and energy distribution of the beta source on the betavoltaic and it is useful in determining the spatial profile of the power deposition in the cell. Copyright © 2017. Published by Elsevier Ltd.

Pion and electromagnetic contribution to dose: Comparisons of HZETRN to Monte Carlo results and ISS data

NASA Astrophysics Data System (ADS)

Slaba, Tony C.; Blattnig, Steve R.; Reddell, Brandon; Bahadori, Amir; Norman, Ryan B.; Badavi, Francis F.

2013-07-01

Recent work has indicated that pion production and the associated electromagnetic (EM) cascade may be an important contribution to the total astronaut exposure in space. Recent extensions to the deterministic space radiation transport code, HZETRN, allow the production and transport of pions, muons, electrons, positrons, and photons. In this paper, the extended code is compared to the Monte Carlo codes, Geant4, PHITS, and FLUKA, in slab geometries exposed to galactic cosmic ray (GCR) boundary conditions. While improvements in the HZETRN transport formalism for the new particles are needed, it is shown that reasonable agreement on dose is found at larger shielding thicknesses commonly found on the International Space Station (ISS). Finally, the extended code is compared to ISS data on a minute-by-minute basis over a seven day period in 2001. The impact of pion/EM production on exposure estimates and validation results is clearly shown. The Badhwar-O'Neill (BO) 2004 and 2010 models are used to generate the GCR boundary condition at each time-step allowing the impact of environmental model improvements on validation results to be quantified as well. It is found that the updated BO2010 model noticeably reduces overall exposure estimates from the BO2004 model, and the additional production mechanisms in HZETRN provide some compensation. It is shown that the overestimates provided by the BO2004 GCR model in previous validation studies led to deflated uncertainty estimates for environmental, physics, and transport models, and allowed an important physical interaction (π/EM) to be overlooked in model development. Despite the additional π/EM production mechanisms in HZETRN, a systematic under-prediction of total dose is observed in comparison to Monte Carlo results and measured data.

Application of artificial neural network in 3D imaging with lanthanum bromide calorimeter

NASA Astrophysics Data System (ADS)

Gostojic, A.; Tatischeff, V.; Kiener, J.; Hamadache, C.; Karkour, N.; Linget, D.; Grave, X.; Gibelin, L.; Travers, B.; Blin, S.; Barrillon, P.

2015-07-01

Gamma-ray astronomy in the energy range from 0.1 up to 100 MeV holds many understudied questions connected with e.g. stellar nucleosynthesis, the active Sun, neutron stars and black holes. To access the physics behind, a significant improvement in detection sensitivity is needed compared to previous missions, e.g. CGRO and INTEGRAL. One of the promising concepts for a future gamma-ray mission is an Advanced Compton Telescope. Under the project of creating a prototype of such instrument, we study the perspectives of using a novel inorganic scintillator as a calorimeter part. Modern inorganic crystal or ceramics scintillators are constantly improving on qualities such as energy resolution and radiation hardness, and this makes them a smart choice for a new space-borne telescope. At CSNSM Orsay, we have assembled a detection module from a 5 × 5cm2 area and 1 cm thick, cerium-doped lanthanum (III) bromide (LaBr3:Ce) inorganic scintillator coupled to a 64 channel multi-anode photomultiplier. The readout of the PMT signals is carried out with the ASIC MAROC, used previously for the luminometer of the ATLAS detector (CERN). Characterization, thorough measurements with various radioactive sources, as well as, single photoelectron detection have been done. Furthermore, we made a comparison of measurements with a detailed GEANT4-based simulation which includes tracking of the optical photons. Finally, we have studied the 3D reconstruction of the first interaction point of incident gamma rays, utilizing a neural network algorithm. This spatial position resolution plays a crucial part in the future implementations and, together with the other measured properties, it makes our detector module very interesting for the next generation of space telescopes operating in the MeV range.

Study of spatial resolution of coordinate detectors based on Gas Electron Multipliers

NASA Astrophysics Data System (ADS)

Kudryavtsev, V. N.; Maltsev, T. V.; Shekhtman, L. I.

2017-02-01

Spatial resolution of GEM-based tracking detectors is determined in the simulation and measured in the experiments. The simulation includes GEANT4 implemented transport of high energy electrons with careful accounting of atomic relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing with accounting of diffusion, gas amplification fluctuations, distribution of signals on readout electrodes, electronics noise and particular algorithm of final coordinate calculation (center of gravity). The simulation demonstrates that the minimum of spatial resolution of about 10 μm can be achieved with a gas mixture of Ar -CO2 (75-25 %) at a strips pitch from 250 μm to 300 μm. At a larger pitch the resolution quickly degrades reaching 80-100 μm at a pitch of 460-500 μm. Spatial resolution of low-material triple-GEM detectors for the DEUTERON facility at the VEPP-3 storage ring is measured at the extracted beam facility of the VEPP-4 M collider. One-coordinate resolution of the DEUTERON detector is measured with electron beam of 500 MeV, 1 GeV and 3.5 GeV energies. The determined value of spatial resolution varies in the range from approximately 35 μm to 50 μm for orthogonal tracks in the experiments.

Validation of the Monte Carlo simulator GATE for indium-111 imaging.

PubMed

Assié, K; Gardin, I; Véra, P; Buvat, I

2005-07-07

Monte Carlo simulations are useful for optimizing and assessing single photon emission computed tomography (SPECT) protocols, especially when aiming at measuring quantitative parameters from SPECT images. Before Monte Carlo simulated data can be trusted, the simulation model must be validated. The purpose of this work was to validate the use of GATE, a new Monte Carlo simulation platform based on GEANT4, for modelling indium-111 SPECT data, the quantification of which is of foremost importance for dosimetric studies. To that end, acquisitions of (111)In line sources in air and in water and of a cylindrical phantom were performed, together with the corresponding simulations. The simulation model included Monte Carlo modelling of the camera collimator and of a back-compartment accounting for photomultiplier tubes and associated electronics. Energy spectra, spatial resolution, sensitivity values, images and count profiles obtained for experimental and simulated data were compared. An excellent agreement was found between experimental and simulated energy spectra. For source-to-collimator distances varying from 0 to 20 cm, simulated and experimental spatial resolution differed by less than 2% in air, while the simulated sensitivity values were within 4% of the experimental values. The simulation of the cylindrical phantom closely reproduced the experimental data. These results suggest that GATE enables accurate simulation of (111)In SPECT acquisitions.

Controlling Photons, Qubits and their Interactions in Superconducting Electronic Circuits

NASA Astrophysics Data System (ADS)

Wallraff, Andreas

2009-03-01

A combination of ideas from atomic physics, quantum optics and solid state physics allows us to investigate the fundamental interaction of matter and light on the level of single quanta in electronic circuits. In an approach known as circuit quantum electrodynamics, we coherently couple individual photons stored in a high quality microwave frequency resonator to a fully controllable superconducting two-level system (qubit) realized in a macroscopic electronic circuit [1]. In particular, we have recently observed the simultaneous interaction of one, two and three photons with a single qubit. In these experiments, we have probed the quantum nonlinearity of the qubit/light interaction governed by the Jaynes-Cummings hamiltonian, clearly demonstrating the quantization of the radiation field in the on-chip cavity. We have also performed quantum optics experiments with no photons at all. In this situation, i.e. in pure vacuum, we have resolved the renormalization of the qubit transition frequency - known as the Lamb shift - due to its non-resonant interaction with the cavity vacuum fluctuations [3].[4pt] [1] A. Wallraff et al., Nature (London) 431, 162 (2004)[0pt] [2] J. Fink et al., Nature (London) 454, 315 (2008)[0pt] [3] A. Fragner et al., Science 322, 1357 (2008)

SU-E-T-26: A Study On the Influence of Photonuclear Reactions On the Biological Effectiveness of Therapeutic High Energy X-Ray Beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wakita, A; National Cancer Center Hospital, Chuo-ku, Tokyo; Matsufuji, N

2014-06-01

Purpose: Photons from a modern high-energy therapeutic linear accelerator used in X-ray radiotherapy causes photonuclear reactions in an accelerator or patient's body. The aim of this study is to evaluate the biological effectiveness including these particles by Microdosimetric Kinetic Model (MKM) based on microdosimetry. Methods: A linear accelerator operating at 15 MV was used. CR-39 was used to obtain LET spectra of secondary ions selectively, as CR-39 is regarded insensitive to photons. CR-39 was put on the central axis of the X-ray beam at depths of 0, 5 and 10 cm in plastic phantom at a source to detector distancemore » of 100 cm. Pits formed by the traversal of ions were etched then analyzed to obtain restricted LET distribution. Frequency-mean and dose-mean lineal energy was evaluated from the relationship between the restricted LET and the lineal energy required to evaluate the biological effectiveness by MKM. The relationship was calculated by Monte Carlo simulations with GEANT4. Results: Restricted LET distributions of secondary particles showed broad distributions that decreases exponentially with increasing LET. Frequency-mean and dose-mean lineal energy were determined uniquely within the scope of the energies of secondary particles generated from photons of 15 MeV. The frequency-mean lineal energies at the depth of 0, 5 and 10 cm were 15.1, 16.0 and 19.7 keV/μm respectively, and the dose-mean lineal energies were 18.6, 20.5 and 19.6 keV/μm, respectively. RBE of secondary particles for HSG cell evaluated by MKM was about 2.0 at all depths, and RBE of all particles including photons was evaluated 1.0. Conclusion: We investigated the biological effectiveness of secondary particles by photonuclear reactions. The method to evaluate RBE by MKM was established with measurements and simulations. However, the influence of these secondary ions on RBE was found negligible in the entire biological effectiveness of the high-energy X-ray. This study has been supported by JSPS KAKENHI Grant Number 25861144.« less

Observation of three-photon bound states in a quantum nonlinear medium

NASA Astrophysics Data System (ADS)

Liang, Qi-Yu; Venkatramani, Aditya V.; Cantu, Sergio H.; Nicholson, Travis L.; Gullans, Michael J.; Gorshkov, Alexey V.; Thompson, Jeff D.; Chin, Cheng; Lukin, Mikhail D.; Vuletić, Vladan

2018-02-01

Bound states of massive particles, such as nuclei, atoms, or molecules, constitute the bulk of the visible world around us. By contrast, photons typically only interact weakly. We report the observation of traveling three-photon bound states in a quantum nonlinear medium where the interactions between photons are mediated by atomic Rydberg states. Photon correlation and conditional phase measurements reveal the distinct bunching and phase features associated with three-photon and two-photon bound states. Such photonic trimers and dimers possess shape-preserving wave functions that depend on the constituent photon number. The observed bunching and strongly nonlinear optical phase are described by an effective field theory of Rydberg-induced photon-photon interactions. These observations demonstrate the ability to realize and control strongly interacting quantum many-body states of light.

Corrected Position Estimation in PET Detector Modules With Multi-Anode PMTs Using Neural Networks

NASA Astrophysics Data System (ADS)

Aliaga, R. J.; Martinez, J. D.; Gadea, R.; Sebastia, A.; Benlloch, J. M.; Sanchez, F.; Pavon, N.; Lerche, Ch.

2006-06-01

This paper studies the use of Neural Networks (NNs) for estimating the position of impinging photons in gamma ray detector modules for PET cameras based on continuous scintillators and Multi-Anode Photomultiplier Tubes (MA-PMTs). The detector under study is composed of a 49/spl times/49/spl times/10 mm/sup 3/ continuous slab of LSO coupled to a flat panel H8500 MA-PMT. Four digitized signals from a charge division circuit, which collects currents from the 8/spl times/8 anode matrix of the photomultiplier, are used as inputs to the NN, thus reducing drastically the number of electronic channels required. We have simulated the computation of the position for 511 keV gamma photons impacting perpendicularly to the detector surface. Thus, we have performed a thorough analysis of the NN architecture and training procedures in order to achieve the best results in terms of spatial resolution and bias correction. Results obtained using GEANT4 simulation toolkit show a resolution of 1.3 mm/1.9 mm FWHM at the center/edge of the detector and less than 1 mm of systematic error in the position near the edges of the scintillator. The results confirm that NNs can partially model and correct the non-uniform detector response using only the position-weighted signals from a simple 2D DPC circuit. Linearity degradation for oblique incidence is also investigated. Finally, the NN can be implemented in hardware for parallel real time corrected Line-of-Response (LOR) estimation. Results on resources occupancy and throughput in FPGA are presented.

A model for the Global Quantum Efficiency for a TPB-based wavelength-shifting system used with photomultiplier tubes in liquid argon in MicroBooNE

NASA Astrophysics Data System (ADS)

Pate, S. F.; Wester, T.; Bugel, L.; Conrad, J.; Henderson, E.; Jones, B. J. P.; McLean, A. I. L.; Moon, J. S.; Toups, M.; Wongjirad, T.

2018-02-01

We present a model for the Global Quantum Efficiency (GQE) of the MicroBooNE optical units. An optical unit consists of a flat, circular acrylic plate, coated with tetraphenyl butadiene (TPB), positioned near the photocathode of a 20.2-cm diameter photomultiplier tube. The plate converts the ultra-violet scintillation photons from liquid argon into visible-spectrum photons to which the cryogenic phototubes are sensitive. The GQE is the convolution of the efficiency of the plates that convert the 128 nm scintillation light from liquid argon to visible light, the efficiency of the shifted light to reach the photocathode, and the efficiency of the cryogenic photomultiplier tube. We develop a GEANT4-based model of the optical unit, based on first principles, and obtain the range of probable values for the expected number of detected photoelectrons (NPE) given the known systematic errors on the simulation parameters. We compare results from four measurements of the NPE determined using alpha-particle sources placed at two distances from a TPB-coated plate in a liquid argon cryostat test stand. We also directly measured the radial dependence of the quantum efficiency, and find that this has the same shape as predicted by our model. Our model results in a GQE of 0.0055±0.0009 for the MicroBooNE optical units. While the information shown here is MicroBooNE specific, the approach to the model and the collection of simulation parameters will be widely applicable to many liquid-argon-based light collection systems.

GeantV: from CPU to accelerators

NASA Astrophysics Data System (ADS)

Amadio, G.; Ananya, A.; Apostolakis, J.; Arora, A.; Bandieramonte, M.; Bhattacharyya, A.; Bianchini, C.; Brun, R.; Canal, P.; Carminati, F.; Duhem, L.; Elvira, D.; Gheata, A.; Gheata, M.; Goulas, I.; Iope, R.; Jun, S.; Lima, G.; Mohanty, A.; Nikitina, T.; Novak, M.; Pokorski, W.; Ribon, A.; Sehgal, R.; Shadura, O.; Vallecorsa, S.; Wenzel, S.; Zhang, Y.

2016-10-01

The GeantV project aims to research and develop the next-generation simulation software describing the passage of particles through matter. While the modern CPU architectures are being targeted first, resources such as GPGPU, Intel© Xeon Phi, Atom or ARM cannot be ignored anymore by HEP CPU-bound applications. The proof of concept GeantV prototype has been mainly engineered for CPU's having vector units but we have foreseen from early stages a bridge to arbitrary accelerators. A software layer consisting of architecture/technology specific backends supports currently this concept. This approach allows to abstract out the basic types such as scalar/vector but also to formalize generic computation kernels using transparently library or device specific constructs based on Vc, CUDA, Cilk+ or Intel intrinsics. While the main goal of this approach is portable performance, as a bonus, it comes with the insulation of the core application and algorithms from the technology layer. This allows our application to be long term maintainable and versatile to changes at the backend side. The paper presents the first results of basket-based GeantV geometry navigation on the Intel© Xeon Phi KNC architecture. We present the scalability and vectorization study, conducted using Intel performance tools, as well as our preliminary conclusions on the use of accelerators for GeantV transport. We also describe the current work and preliminary results for using the GeantV transport kernel on GPUs.

Measurements and Monte-Carlo simulations of the particle self-shielding effect of B4C grains in neutron shielding concrete

NASA Astrophysics Data System (ADS)

DiJulio, D. D.; Cooper-Jensen, C. P.; Llamas-Jansa, I.; Kazi, S.; Bentley, P. M.

2018-06-01

A combined measurement and Monte-Carlo simulation study was carried out in order to characterize the particle self-shielding effect of B4C grains in neutron shielding concrete. Several batches of a specialized neutron shielding concrete, with varying B4C grain sizes, were exposed to a 2 Å neutron beam at the R2D2 test beamline at the Institute for Energy Technology located in Kjeller, Norway. The direct and scattered neutrons were detected with a neutron detector placed behind the concrete blocks and the results were compared to Geant4 simulations. The particle self-shielding effect was included in the Geant4 simulations by calculating effective neutron cross-sections during the Monte-Carlo simulation process. It is shown that this method well reproduces the measured results. Our results show that shielding calculations for low-energy neutrons using such materials would lead to an underestimate of the shielding required for a certain design scenario if the particle self-shielding effect is not included in the calculations.

Spectral identification of a 90Sr source in the presence of masking nuclides using Maximum-Likelihood deconvolution

NASA Astrophysics Data System (ADS)

Neuer, Marcus J.

2013-11-01

A technique for the spectral identification of strontium-90 is shown, utilising a Maximum-Likelihood deconvolution. Different deconvolution approaches are discussed and summarised. Based on the intensity distribution of the beta emission and Geant4 simulations, a combined response matrix is derived, tailored to the β- detection process in sodium iodide detectors. It includes scattering effects and attenuation by applying a base material decomposition extracted from Geant4 simulations with a CAD model for a realistic detector system. Inversion results of measurements show the agreement between deconvolution and reconstruction. A detailed investigation with additional masking sources like 40K, 226Ra and 131I shows that a contamination of strontium can be found in the presence of these nuisance sources. Identification algorithms for strontium are presented based on the derived technique. For the implementation of blind identification, an exemplary masking ratio is calculated.

Simulation of nanoparticle-mediated near-infrared thermal therapy using GATE

PubMed Central

Cuplov, Vesna; Pain, Frédéric; Jan, Sébastien

2017-01-01

Application of nanotechnology for biomedicine in cancer therapy allows for direct delivery of anticancer agents to tumors. An example of such therapies is the nanoparticle-mediated near-infrared hyperthermia treatment. In order to investigate the influence of nanoparticle properties on the spatial distribution of heat in the tumor and healthy tissues, accurate simulations are required. The Geant4 Application for Emission Tomography (GATE) open-source simulation platform, based on the Geant4 toolkit, is widely used by the research community involved in molecular imaging, radiotherapy and optical imaging. We present an extension of GATE that can model nanoparticle-mediated hyperthermal therapy as well as simple heat diffusion in biological tissues. This new feature of GATE combined with optical imaging allows for the simulation of a theranostic scenario in which the patient is injected with theranostic nanosystems that can simultaneously deliver therapeutic (i.e. hyperthermia therapy) and imaging agents (i.e. fluorescence imaging). PMID:28663855

Validation of GEANT4 Monte Carlo models with a highly granular scintillator-steel hadron calorimeter

NASA Astrophysics Data System (ADS)

Adloff, C.; Blaha, J.; Blaising, J.-J.; Drancourt, C.; Espargilière, A.; Gaglione, R.; Geffroy, N.; Karyotakis, Y.; Prast, J.; Vouters, G.; Francis, K.; Repond, J.; Schlereth, J.; Smith, J.; Xia, L.; Baldolemar, E.; Li, J.; Park, S. T.; Sosebee, M.; White, A. P.; Yu, J.; Buanes, T.; Eigen, G.; Mikami, Y.; Watson, N. K.; Mavromanolakis, G.; Thomson, M. A.; Ward, D. R.; Yan, W.; Benchekroun, D.; Hoummada, A.; Khoulaki, Y.; Apostolakis, J.; Dotti, A.; Folger, G.; Ivantchenko, V.; Uzhinskiy, V.; Benyamna, M.; Cârloganu, C.; Fehr, F.; Gay, P.; Manen, S.; Royer, L.; Blazey, G. C.; Dyshkant, A.; Lima, J. G. R.; Zutshi, V.; Hostachy, J.-Y.; Morin, L.; Cornett, U.; David, D.; Falley, G.; Gadow, K.; Göttlicher, P.; Günter, C.; Hermberg, B.; Karstensen, S.; Krivan, F.; Lucaci-Timoce, A.-I.; Lu, S.; Lutz, B.; Morozov, S.; Morgunov, V.; Reinecke, M.; Sefkow, F.; Smirnov, P.; Terwort, M.; Vargas-Trevino, A.; Feege, N.; Garutti, E.; Marchesini, I.; Ramilli, M.; Eckert, P.; Harion, T.; Kaplan, A.; Schultz-Coulon, H.-Ch; Shen, W.; Stamen, R.; Bilki, B.; Norbeck, E.; Onel, Y.; Wilson, G. W.; Kawagoe, K.; Dauncey, P. D.; Magnan, A.-M.; Bartsch, V.; Wing, M.; Salvatore, F.; Calvo Alamillo, E.; Fouz, M.-C.; Puerta-Pelayo, J.; Bobchenko, B.; Chadeeva, M.; Danilov, M.; Epifantsev, A.; Markin, O.; Mizuk, R.; Novikov, E.; Popov, V.; Rusinov, V.; Tarkovsky, E.; Kirikova, N.; Kozlov, V.; Smirnov, P.; Soloviev, Y.; Buzhan, P.; Ilyin, A.; Kantserov, V.; Kaplin, V.; Karakash, A.; Popova, E.; Tikhomirov, V.; Kiesling, C.; Seidel, K.; Simon, F.; Soldner, C.; Szalay, M.; Tesar, M.; Weuste, L.; Amjad, M. S.; Bonis, J.; Callier, S.; Conforti di Lorenzo, S.; Cornebise, P.; Doublet, Ph; Dulucq, F.; Fleury, J.; Frisson, T.; van der Kolk, N.; Li, H.; Martin-Chassard, G.; Richard, F.; de la Taille, Ch; Pöschl, R.; Raux, L.; Rouëné, J.; Seguin-Moreau, N.; Anduze, M.; Boudry, V.; Brient, J.-C.; Jeans, D.; Mora de Freitas, P.; Musat, G.; Reinhard, M.; Ruan, M.; Videau, H.; Bulanek, B.; Zacek, J.; Cvach, J.; Gallus, P.; Havranek, M.; Janata, M.; Kvasnicka, J.; Lednicky, D.; Marcisovsky, M.; Polak, I.; Popule, J.; Tomasek, L.; Tomasek, M.; Ruzicka, P.; Sicho, P.; Smolik, J.; Vrba, V.; Zalesak, J.; Belhorma, B.; Ghazlane, H.; Takeshita, T.; Uozumi, S.; Götze, M.; Hartbrich, O.; Sauer, J.; Weber, S.; Zeitnitz, C.

2013-07-01

Calorimeters with a high granularity are a fundamental requirement of the Particle Flow paradigm. This paper focuses on the prototype of a hadron calorimeter with analog readout, consisting of thirty-eight scintillator layers alternating with steel absorber planes. The scintillator plates are finely segmented into tiles individually read out via Silicon Photomultipliers. The presented results are based on data collected with pion beams in the energy range from 8 GeV to 100 GeV. The fine segmentation of the sensitive layers and the high sampling frequency allow for an excellent reconstruction of the spatial development of hadronic showers. A comparison between data and Monte Carlo simulations is presented, concerning both the longitudinal and lateral development of hadronic showers and the global response of the calorimeter. The performance of several GEANT4 physics lists with respect to these observables is evaluated.

Quantum-state-selective decay spectroscopy of 213Ra

NASA Astrophysics Data System (ADS)

Lorenz, Ch.; Sarmiento, L. G.; Rudolph, D.; Ward, D. E.; Block, M.; Heßberger, F. P.; Ackermann, D.; Andersson, L.-L.; Cortés, M. L.; Droese, C.; Dworschak, M.; Eibach, M.; Forsberg, U.; Golubev, P.; Hoischen, R.; Kojouharov, I.; Khuyagbaatar, J.; Nesterenko, D.; Ragnarsson, I.; Schaffner, H.; Schweikhard, L.; Stolze, S.; Wenzl, J.

2017-09-01

An experimental scheme combining the mass resolving power of a Penning trap with contemporary decay spectroscopy has been established at GSI Darmstadt. The Universal Linear Accelerator (UNILAC) at GSI Darmstadt provided a 48Ca beam impinging on a thin 170Er target foil. Subsequent to velocity filtering of reaction products in the Separator for Heavy Ion reaction Products (SHIP), the nuclear ground state of the 5 n evaporation channel 213Ra was mass-selected in SHIPTRAP, and the 213Ra ions were finally transferred into an array of silicon strip detectors surrounded by large composite germanium detectors. Based on comprehensive geant4 simulations and supported by theoretical calculations, the spectroscopic results call for a revision of the decay path of 213Ra, thereby exemplifying the potential of a combination of a mass-selective Penning trap device with a dedicated nuclear decay station and contemporary geant4 simulations.

Development and application of CATIA-GDML geometry builder

NASA Astrophysics Data System (ADS)

Belogurov, S.; Berchun, Yu; Chernogorov, A.; Malzacher, P.; Ovcharenko, E.; Schetinin, V.

2014-06-01

Due to conceptual difference between geometry descriptions in Computer-Aided Design (CAD) systems and particle transport Monte Carlo (MC) codes direct conversion of detector geometry in either direction is not feasible. The paper presents an update on functionality and application practice of the CATIA-GDML geometry builder first introduced at CHEP2010. This set of CATIAv5 tools has been developed for building a MC optimized GEANT4/ROOT compatible geometry based on the existing CAD model. The model can be exported via Geometry Description Markup Language (GDML). The builder allows also import and visualization of GEANT4/ROOT geometries in CATIA. The structure of a GDML file, including replicated volumes, volume assemblies and variables, is mapped into a part specification tree. A dedicated file template, a wide range of primitives, tools for measurement and implicit calculation of parameters, different types of multiple volume instantiation, mirroring, positioning and quality check have been implemented. Several use cases are discussed.

Upgrades for the CMS simulation

DOE PAGES

Lange, D. J.; Hildreth, M.; Ivantchenko, V. N.; ...

2015-05-22

Over the past several years, the CMS experiment has made significant changes to its detector simulation application. The geometry has been generalized to include modifications being made to the CMS detector for 2015 operations, as well as model improvements to the simulation geometry of the current CMS detector and the implementation of a number of approved and possible future detector configurations. These include both completely new tracker and calorimetry systems. We have completed the transition to Geant4 version 10, we have made significant progress in reducing the CPU resources required to run our Geant4 simulation. These have been achieved throughmore » both technical improvements and through numerical techniques. Substantial speed improvements have been achieved without changing the physics validation benchmarks that the experiment uses to validate our simulation application for use in production. As a result, we will discuss the methods that we implemented and the corresponding demonstrated performance improvements deployed for our 2015 simulation application.« less

ALGEBRA: ALgorithm for the heterogeneous dosimetry based on GEANT4 for BRAchytherapy.

PubMed

Afsharpour, H; Landry, G; D'Amours, M; Enger, S; Reniers, B; Poon, E; Carrier, J-F; Verhaegen, F; Beaulieu, L

2012-06-07

Task group 43 (TG43)-based dosimetry algorithms are efficient for brachytherapy dose calculation in water. However, human tissues have chemical compositions and densities different than water. Moreover, the mutual shielding effect of seeds on each other (interseed attenuation) is neglected in the TG43-based dosimetry platforms. The scientific community has expressed the need for an accurate dosimetry platform in brachytherapy. The purpose of this paper is to present ALGEBRA, a Monte Carlo platform for dosimetry in brachytherapy which is sufficiently fast and accurate for clinical and research purposes. ALGEBRA is based on the GEANT4 Monte Carlo code and is capable of handling the DICOM RT standard to recreate a virtual model of the treated site. Here, the performance of ALGEBRA is presented for the special case of LDR brachytherapy in permanent prostate and breast seed implants. However, the algorithm is also capable of handling other treatments such as HDR brachytherapy.

Simulation of argon response and light detection in the DarkSide-50 dual phase TPC

NASA Astrophysics Data System (ADS)

Agnes, P.; Albuquerque, I. F. M.; Alexander, T.; Alton, A. K.; Asner, D. M.; Back, H. O.; Biery, K.; Bocci, V.; Bonfini, G.; Bonivento, W.; Bossa, M.; Bottino, B.; Budano, F.; Bussino, S.; Cadeddu, M.; Cadoni, M.; Calaprice, F.; Canci, N.; Candela, A.; Caravati, M.; Cariello, M.; Carlini, M.; Catalanotti, S.; Cataudella, V.; Cavalcante, P.; Chepurnov, A.; Cicalò, C.; Cocco, A. G.; Covone, G.; D'Angelo, D.; D'Incecco, M.; Davini, S.; de Candia, A.; De Cecco, S.; De Deo, M.; De Filippis, G.; De Vincenzi, M.; Derbin, A. V.; De Rosa, G.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Dionisi, C.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Franco, D.; Gabriele, F.; Galbiati, C.; Giagu, S.; Giganti, C.; Giovanetti, G. K.; Goretti, A. M.; Granato, F.; Gromov, M.; Guan, M.; Guardincerri, Y.; Hackett, B. R.; Herner, K.; Hughes, D.; Humble, P.; Hungerford, E. V.; Ianni, An.; James, I.; Johnson, T. N.; Keeter, K.; Kendziora, C. L.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, A.; Li, X.; Lissia, M.; Loer, B.; Longo, G.; Ma, Y.; Machado, A. A.; Machulin, I. N.; Mandarano, A.; Mari, S. M.; Maricic, J.; Martoff, C. J.; Meyers, P. D.; Milincic, R.; Monte, A.; Mount, B. J.; Muratova, V. N.; Musico, P.; Napolitano, J.; Navrer Agasson, A.; Oleinik, A.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Pantic, E.; Pelczar, K.; Pelliccia, N.; Pocar, A.; Pordes, S.; Pugachev, D. A.; Qian, H.; Randle, K.; Razeti, M.; Razeto, A.; Reinhold, B.; Renshaw, A. L.; Rescigno, M.; Riffard, Q.; Romani, A.; Rossi, B.; Rossi, N.; Sablone, D.; Sands, W.; Sanfilippo, S.; Savarese, C.; Schlitzer, B.; Segreto, E.; Semenov, D. A.; Singh, P. N.; Skorokhvatov, M. D.; Smirnov, O.; Sotnikov, A.; Stanford, C.; Suvorov, Y.; Tartaglia, R.; Testera, G.; Tonazzo, A.; Trinchese, P.; Unzhakov, E. V.; Verducci, M.; Vishneva, A.; Vogelaar, B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A. W.; Westerdale, S.; Wilhelmi, J.; Wojcik, M. M.; Xiang, X.; Xiao, X.; Yang, C.; Ye, Z.; Zhu, C.; Zuzel, G.

2017-10-01

A Geant4-based Monte Carlo package named G4DS has been developed to simulate the response of DarkSide-50, an experiment operating since 2013 at LNGS, designed to detect WIMP interactions in liquid argon. In the process of WIMP searches, DarkSide-50 has achieved two fundamental milestones: the rejection of electron recoil background with a power of ~107, using the pulse shape discrimination technique, and the measurement of the residual 39Ar contamination in underground argon, ~3 orders of magnitude lower with respect to atmospheric argon. These results rely on the accurate simulation of the detector response to the liquid argon scintillation, its ionization, and electron-ion recombination processes. This work provides a complete overview of the DarkSide Monte Carlo and of its performance, with a particular focus on PARIS, the custom-made liquid argon response model.

Full Geant4 and FLUKA simulations of an e-LINAC for its use in particle detectors performance tests

NASA Astrophysics Data System (ADS)

Alpat, B.; Pilicer, E.; Servoli, L.; Menichelli, M.; Tucceri, P.; Italiani, M.; Buono, E.; Di Capua, F.

2012-03-01

In this work we present the results of full Geant4 and FLUKA simulations and comparison with dosimetry data of an electron LINAC of St. Maria Hospital located in Terni, Italy. The facility is being used primarily for radiotherapy and the goal of the present study is the detailed investigation of electron beam parameters to evaluate the possibility to use the e-LINAC (during time slots when it is not used for radiotherapy) to test the performance of detector systems, in particular those designed to operate in space. The critical beam parameters are electron energy, profile and flux available at the surface of device to be tested. The present work aims to extract these parameters from dosimetry calibration data available at the e-LINAC. The electron energy ranges from 4 MeV to 20 MeV. The dose measurements have been performed by using an Advanced Markus Chamber which has a small sensitive volume.

Characterization benches for neutrino telescope Optical Modules at the APC laboratory

NASA Astrophysics Data System (ADS)

Avgitas, Theodore; Creusot, Alexandre; Kouchner, Antoine

2016-04-01

As has been demonstrated by the first generation of neutrino telescopes Antares and IceCube, precise knowledge of the photon detection efficiency of optical modules is of fundamental importance for the understanding of the instrument and accurate event reconstruction. Dedicated test benches have been developed to measure all related quantities for the Digital Optical Modules of the KM3NeT neutrino telescope being currently deployed in the Mediterranean sea. The first bench is a black box with robotic arms equipped with a calibrated single photon source or laser which enable a precise mapping of the detection efficiency at arbitrary incident angles as well as precise measurements of the time delays induced by the photodetection chain. These measurement can be incorporated and compared to full GEANT MonteCarlo simulations of the optical modules. The second bench is a 2 m×2 m ×2 m water tank equipped with muon hodoscopes on top and bottom. It enables to study and measure the angular dependence of the DOM's detection efficiency of the Cherenkov light produced in water by relativistic muons, thus reproducing in situ detection conditions. We describe these two benches and present their first results and status.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ortiz-Ramírez, Pablo, E-mail: rapeitor@ug.uchile.cl; Ruiz, Andrés

The Monte Carlo simulation of the gamma spectroscopy systems is a common practice in these days. The most popular softwares to do this are MCNP and Geant4 codes. The intrinsic spatial efficiency method is a general and absolute method to determine the absolute efficiency of a spectroscopy system for any extended sources, but this was only demonstrated experimentally for cylindrical sources. Due to the difficulty that the preparation of sources with any shape represents, the simplest way to do this is by the simulation of the spectroscopy system and the source. In this work we present the validation of themore » intrinsic spatial efficiency method for sources with different geometries and for photons with an energy of 661.65 keV. In the simulation the matrix effects (the auto-attenuation effect) are not considered, therefore these results are only preliminaries. The MC simulation is carried out using the FLUKA code and the absolute efficiency of the detector is determined using two methods: the statistical count of Full Energy Peak (FEP) area (traditional method) and the intrinsic spatial efficiency method. The obtained results show total agreement between the absolute efficiencies determined by the traditional method and the intrinsic spatial efficiency method. The relative bias is lesser than 1% in all cases.« less

Validation of modelled imaging plates sensitivity to 1-100 keV x-rays and spatial resolution characterisation for diagnostics for the "PETawatt Aquitaine Laser".

PubMed

Boutoux, G; Batani, D; Burgy, F; Ducret, J-E; Forestier-Colleoni, P; Hulin, S; Rabhi, N; Duval, A; Lecherbourg, L; Reverdin, C; Jakubowska, K; Szabo, C I; Bastiani-Ceccotti, S; Consoli, F; Curcio, A; De Angelis, R; Ingenito, F; Baggio, J; Raffestin, D

2016-04-01

Thanks to their high dynamic range and ability to withstand electromagnetic pulse, imaging plates (IPs) are commonly used as passive detectors in laser-plasma experiments. In the framework of the development of the diagnostics for the Petawatt Aquitaine Laser facility, we present an absolute calibration and spatial resolution study of five different available types of IP (namely, MS-SR-TR-MP-ND) performed by using laser-induced K-shell X-rays emitted by a solid silver target irradiated by the laser ECLIPSE at CEntre Lasers Intenses et Applications. In addition, IP sensitivity measurements were performed with a 160 kV X-ray generator at CEA DAM DIF, where the absolute response of IP SR and TR has been calibrated to X-rays in the energy range 8-75 keV with uncertainties of about 15%. Finally, the response functions have been modeled in Monte Carlo GEANT4 simulations in order to reproduce experimental data. Simulations enable extrapolation of the IP response functions to photon energies from 1 keV to 1 GeV, of interest, e.g., for laser-driven radiography.

Micro-scale characterization of a CMOS-based neutron detector for in-phantom measurements in radiation therapy

NASA Astrophysics Data System (ADS)

Arbor, Nicolas; Higueret, Stephane; Husson, Daniel

2018-04-01

The CMOS sensor AlphaRad has been designed at the IPHC Strasbourg for real-time monitoring of fast and thermal neutrons over a full energy spectrum. Completely integrated, highly transparent to photons and optimized for low power consumption, this sensor offers very interesting characteristics for the study of internal neutrons in radiation therapy with anthropomorphic phantoms. However, specific effects related to the CMOS metal substructure and to the charge collection process of low energy particles must be carefully estimated before being used for medical applications. We present a detailed characterization of the AlphaRad chip in the MeV energy range using proton and alpha micro-beam experiments performed at the AIFIRA facility (CENBG, Bordeaux). Two-dimensional maps of the charge collection were carried out on a micro-metric scale to be integrated into a Geant4 Monte Carlo simulation of the system. The gamma rejection, as well as the fast and thermal neutrons separation, were studied using both simulation and experimental data. The results highlight the potential of a future system based on CMOS sensor for in-phantom neutron detection in radiation therapies.

Validation of modelled imaging plates sensitivity to 1-100 keV x-rays and spatial resolution characterisation for diagnostics for the "PETawatt Aquitaine Laser"

NASA Astrophysics Data System (ADS)

Boutoux, G.; Batani, D.; Burgy, F.; Ducret, J.-E.; Forestier-Colleoni, P.; Hulin, S.; Rabhi, N.; Duval, A.; Lecherbourg, L.; Reverdin, C.; Jakubowska, K.; Szabo, C. I.; Bastiani-Ceccotti, S.; Consoli, F.; Curcio, A.; De Angelis, R.; Ingenito, F.; Baggio, J.; Raffestin, D.

2016-04-01

Thanks to their high dynamic range and ability to withstand electromagnetic pulse, imaging plates (IPs) are commonly used as passive detectors in laser-plasma experiments. In the framework of the development of the diagnostics for the Petawatt Aquitaine Laser facility, we present an absolute calibration and spatial resolution study of five different available types of IP (namely, MS-SR-TR-MP-ND) performed by using laser-induced K-shell X-rays emitted by a solid silver target irradiated by the laser ECLIPSE at CEntre Lasers Intenses et Applications. In addition, IP sensitivity measurements were performed with a 160 kV X-ray generator at CEA DAM DIF, where the absolute response of IP SR and TR has been calibrated to X-rays in the energy range 8-75 keV with uncertainties of about 15%. Finally, the response functions have been modeled in Monte Carlo GEANT4 simulations in order to reproduce experimental data. Simulations enable extrapolation of the IP response functions to photon energies from 1 keV to 1 GeV, of interest, e.g., for laser-driven radiography.

Utilizing Machine Learning for Analysis of Tiara for Texas

NASA Astrophysics Data System (ADS)

van Slycke, Jacqueline; Christian, Greg, , Dr.

2017-09-01

The Tiara for Texas detector at Texas A&M University consists of a target chamber housing an array of silicon detectors and surrounded by four high purity germanium clovers that generate voltage pulses proportional to detected gamma ray energies. While some radiation is fully absorbed in one photopeak, others undergo Compton scattering between detectors. This process is thoroughly simulated in GEANT4. Machine learning with scikit-learn allows for the reconstruction of scattered photons to the original energy of the incident gamma ray. In a given simulation, a defined number of rays are emitted from the source. Each ray is marked as an event and its path is tracked. Scikit-learn uses the events' paths to train an algorithm, which recognizes which events should be summed to reconstruct the full gamma ray energy and additional events to test the algorithm. These predictions are not exact, but were analyzed to further understand any discrepancies and increase the effectiveness of the simulation. The results from this research project compare various machine learning techniques to determine which methods should be expanded on in the future. National Science Foundation Grant PHY-1659847 and United States Department of Energy Grant DE-FG02-93ER40773.

Validation of modelled imaging plates sensitivity to 1-100 keV x-rays and spatial resolution characterisation for diagnostics for the “PETawatt Aquitaine Laser”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boutoux, G., E-mail: boutoux@celia.u-bordeaux1.fr; Batani, D.; Burgy, F.

2016-04-15

Thanks to their high dynamic range and ability to withstand electromagnetic pulse, imaging plates (IPs) are commonly used as passive detectors in laser-plasma experiments. In the framework of the development of the diagnostics for the Petawatt Aquitaine Laser facility, we present an absolute calibration and spatial resolution study of five different available types of IP (namely, MS-SR-TR-MP-ND) performed by using laser-induced K-shell X-rays emitted by a solid silver target irradiated by the laser ECLIPSE at CEntre Lasers Intenses et Applications. In addition, IP sensitivity measurements were performed with a 160 kV X-ray generator at CEA DAM DIF, where the absolutemore » response of IP SR and TR has been calibrated to X-rays in the energy range 8-75 keV with uncertainties of about 15%. Finally, the response functions have been modeled in Monte Carlo GEANT4 simulations in order to reproduce experimental data. Simulations enable extrapolation of the IP response functions to photon energies from 1 keV to 1 GeV, of interest, e.g., for laser-driven radiography.« less

Acuros CTS: A fast, linear Boltzmann transport equation solver for computed tomography scatter - Part I: Core algorithms and validation.

PubMed

Maslowski, Alexander; Wang, Adam; Sun, Mingshan; Wareing, Todd; Davis, Ian; Star-Lack, Josh

2018-05-01

To describe Acuros ® CTS, a new software tool for rapidly and accurately estimating scatter in x-ray projection images by deterministically solving the linear Boltzmann transport equation (LBTE). The LBTE describes the behavior of particles as they interact with an object across spatial, energy, and directional (propagation) domains. Acuros CTS deterministically solves the LBTE by modeling photon transport associated with an x-ray projection in three main steps: (a) Ray tracing photons from the x-ray source into the object where they experience their first scattering event and form scattering sources. (b) Propagating photons from their first scattering sources across the object in all directions to form second scattering sources, then repeating this process until all high-order scattering sources are computed using the source iteration method. (c) Ray-tracing photons from scattering sources within the object to the detector, accounting for the detector's energy and anti-scatter grid responses. To make this process computationally tractable, a combination of analytical and discrete methods is applied. The three domains are discretized using the Linear Discontinuous Finite Elements, Multigroup, and Discrete Ordinates methods, respectively, which confer the ability to maintain the accuracy of a continuous solution. Furthermore, through the implementation in CUDA, we sought to exploit the parallel computing capabilities of graphics processing units (GPUs) to achieve the speeds required for clinical utilization. Acuros CTS was validated against Geant4 Monte Carlo simulations using two digital phantoms: (a) a water phantom containing lung, air, and bone inserts (WLAB phantom) and (b) a pelvis phantom derived from a clinical CT dataset. For these studies, we modeled the TrueBeam ® (Varian Medical Systems, Palo Alto, CA) kV imaging system with a source energy of 125 kVp. The imager comprised a 600 μm-thick Cesium Iodide (CsI) scintillator and a 10:1 one-dimensional anti-scatter grid. For the WLAB studies, the full-fan geometry without a bowtie filter was used (with and without the anti-scatter grid). For the pelvis phantom studies, a half-fan geometry with bowtie was used (with the anti-scatter grid). Scattered and primary photon fluences and energies deposited in the detector were recorded. The Acuros CTS and Monte Carlo results demonstrated excellent agreement. For the WLAB studies, the average percent difference between the Monte Carlo- and Acuros-generated scattered photon fluences at the face of the detector was -0.7%. After including the detector response, the average percent differences between the Monte Carlo- and Acuros-generated scatter fractions (SF) were -0.1% without the grid and 0.6% with the grid. For the digital pelvis simulation, the Monte Carlo- and Acuros-generated SFs agreed to within 0.1% on average, despite the scatter-to-primary ratios (SPRs) being as high as 5.5. The Acuros CTS computation time for each scatter image was ~1 s using a single GPU. Acuros CTS enables a fast and accurate calculation of scatter images by deterministically solving the LBTE thus offering a computationally attractive alternative to Monte Carlo methods. Part II describes the application of Acuros CTS to scatter correction of CBCT scans on the TrueBeam system. © 2018 American Association of Physicists in Medicine.

Application of dynamic Monte Carlo technique in proton beam radiotherapy using Geant4 simulation toolkit

NASA Astrophysics Data System (ADS)

Guan, Fada

Monte Carlo method has been successfully applied in simulating the particles transport problems. Most of the Monte Carlo simulation tools are static and they can only be used to perform the static simulations for the problems with fixed physics and geometry settings. Proton therapy is a dynamic treatment technique in the clinical application. In this research, we developed a method to perform the dynamic Monte Carlo simulation of proton therapy using Geant4 simulation toolkit. A passive-scattering treatment nozzle equipped with a rotating range modulation wheel was modeled in this research. One important application of the Monte Carlo simulation is to predict the spatial dose distribution in the target geometry. For simplification, a mathematical model of a human body is usually used as the target, but only the average dose over the whole organ or tissue can be obtained rather than the accurate spatial dose distribution. In this research, we developed a method using MATLAB to convert the medical images of a patient from CT scanning into the patient voxel geometry. Hence, if the patient voxel geometry is used as the target in the Monte Carlo simulation, the accurate spatial dose distribution in the target can be obtained. A data analysis tool---root was used to score the simulation results during a Geant4 simulation and to analyze the data and plot results after simulation. Finally, we successfully obtained the accurate spatial dose distribution in part of a human body after treating a patient with prostate cancer using proton therapy.

Energy deposition and neutron flux study in a gravity-driven dense granular target (DGT) with GEANT4 toolkit

NASA Astrophysics Data System (ADS)

Zhao, Qiang; Cui, Wenjuan; He, Zhiyong; Zhang, Xueying; Ma, Wenjing

2018-07-01

China initiative Accelerator Driven System (CiADS) has been approved as a strategic plan to build an ADS demonstration facility in the next few years. It proposed a new concept for a high-power spallation target: the gravity-driven dense granular target (DGT). As the same with a monolithic target (MT), both solid and liquid target, energy deposition and neutron flux are two critical issues. In this paper, we focus on these two issues and long for some valuable results for the project. Unlike a solid target, the internal geometry structure of a DGT is very complicated. To be as much as closer with the reality, we designed an algorithm and firstly packed the grains randomly in a cylindrical container in GEANT4 software. The packing result was in great agreement with the experimentally measured results. It shows that the algorithm is practicable. In the next step, all the simulations about energy deposition and neutron flux of a DGT were performed with the GEANT4 codes, and the results were compared with the data of a MT. Compared to a MT, a DGT has inarguable advantages in both terms of energy deposition and neutron flux. In addition, the simulations with different radius of grains were also performed. Finally, we found that both the energy deposition and neutron flux are nearly irrelevant to the radius of the grains in the range of 0.5 mm-5 mm when the packing density is same by analyzing the results meticulously.

GATE - Geant4 Application for Tomographic Emission: a simulation toolkit for PET and SPECT

PubMed Central

Jan, S.; Santin, G.; Strul, D.; Staelens, S.; Assié, K.; Autret, D.; Avner, S.; Barbier, R.; Bardiès, M.; Bloomfield, P. M.; Brasse, D.; Breton, V.; Bruyndonckx, P.; Buvat, I.; Chatziioannou, A. F.; Choi, Y.; Chung, Y. H.; Comtat, C.; Donnarieix, D.; Ferrer, L.; Glick, S. J.; Groiselle, C. J.; Guez, D.; Honore, P.-F.; Kerhoas-Cavata, S.; Kirov, A. S.; Kohli, V.; Koole, M.; Krieguer, M.; van der Laan, D. J.; Lamare, F.; Largeron, G.; Lartizien, C.; Lazaro, D.; Maas, M. C.; Maigne, L.; Mayet, F.; Melot, F.; Merheb, C.; Pennacchio, E.; Perez, J.; Pietrzyk, U.; Rannou, F. R.; Rey, M.; Schaart, D. R.; Schmidtlein, C. R.; Simon, L.; Song, T. Y.; Vieira, J.-M.; Visvikis, D.; Van de Walle, R.; Wieërs, E.; Morel, C.

2012-01-01

Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols, and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. This paper gives a detailed description of the design and development of GATE by the OpenGATE collaboration, whose continuing objective is to improve, document, and validate GATE by simulating commercially available imaging systems for PET and SPECT. Large effort is also invested in the ability and the flexibility to model novel detection systems or systems still under design. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at the address http://www-lphe.ep.ch/GATE/. Two benchmarks developed for PET and SPECT to test the installation of GATE and to serve as a tutorial for the users are presented. Extensive validation of the GATE simulation platform has been started, comparing simulations and measurements on commercially available acquisition systems. References to those results are listed. The future prospects toward the gridification of GATE and its extension to other domains such as dosimetry are also discussed. PMID:15552416

Geant4 simulations of soft proton scattering in X-ray optics. A tentative validation using laboratory measurements

NASA Astrophysics Data System (ADS)

Fioretti, Valentina; Mineo, Teresa; Bulgarelli, Andrea; Dondero, Paolo; Ivanchenko, Vladimir; Lei, Fan; Lotti, Simone; Macculi, Claudio; Mantero, Alfonso

2017-12-01

Low energy protons (< 300 keV) can enter the field of view of X-ray telescopes, scatter on their mirror surfaces at small incident angles, and deposit energy on the detector. This phenomenon can cause intense background flares at the focal plane decreasing the mission observing time (e.g. the XMM-Newton mission) or in the most extreme cases, damaging the X-ray detector. A correct modelization of the physics process responsible for the grazing angle scattering processes is mandatory to evaluate the impact of such events on the performance (e.g. observation time, sensitivity) of future X-ray telescopes as the ESA ATHENA mission. The Remizovich model describes particles reflected by solids at glancing angles in terms of the Boltzmann transport equation using the diffuse approximation and the model of continuous slowing down in energy. For the first time this solution, in the approximation of no energy losses, is implemented, verified, and qualitatively validated on top of the Geant4 release 10.2, with the possibility to add a constant energy loss to each interaction. This implementation is verified by comparing the simulated proton distribution to both the theoretical probability distribution and with independent ray-tracing simulations. Both the new scattering physics and the Coulomb scattering already built in the official Geant4 distribution are used to reproduce the latest experimental results on grazing angle proton scattering. At 250 keV multiple scattering delivers large proton angles and it is not consistent with the observation. Among the tested models, the single scattering seems to better reproduce the scattering efficiency at the three energies but energy loss obtained at small scattering angles is significantly lower than the experimental values. In general, the energy losses obtained in the experiment are higher than what obtained by the simulation. The experimental data are not completely representative of the soft proton scattering experienced by current X-ray telescopes because of the lack of measurements at low energies (< 200 keV) and small reflection angles, so we are not able to address any of the tested models as the one that can certainly reproduce the scattering behavior of low energy protons expected for the ATHENA mission. We can, however, discard multiple scattering as the model able to reproduce soft proton funnelling, and affirm that Coulomb single scattering can represent, until further measurements at lower energies are available, the best approximation of the proton scattered angular distribution at the exit of X-ray optics.

Discrete Chromatic Aberrations Arising from Photoinduced Electron-Photon Interactions in Ultrafast Electron Microscopy.

PubMed

Plemmons, Dayne A; Flannigan, David J

2016-05-26

In femtosecond ultrafast electron microscopy (UEM) experiments, the initial excitation period is composed of spatiotemporal overlap of the temporally commensurate pump photon pulse and probe photoelectron packet. Generation of evanescent near-fields at the nanostructure specimens produces a dispersion relation that enables coupling of the photons (ℏω = 2.4 eV, for example) and freely propagating electrons (200 keV, for example) in the near-field. Typically, this manifests as discrete peaks occurring at integer multiples (n) of the photon energy in the low-loss/gain region of electron-energy spectra (i.e., at 200 keV ± nℏω eV). Here, we examine the UEM imaging resolution implications of the strong inelastic near-field interactions between the photons employed in optical excitation and the probe photoelectrons. We find that the additional photoinduced energy dispersion occurring when swift electrons pass through intense evanescent near-fields results in a discrete chromatic aberration that limits the spatial resolving power to several angstroms during the excitation period.

Estimation and correction of produced light from prompt gamma photons on luminescence imaging of water for proton therapy dosimetry

NASA Astrophysics Data System (ADS)

Yabe, Takuya; Komori, Masataka; Toshito, Toshiyuki; Yamaguchi, Mitsutaka; Kawachi, Naoki; Yamamoto, Seiichi

2018-02-01

Although the luminescence images of water during proton-beam irradiation using a cooled charge-coupled device camera showed almost the same ranges of proton beams as those measured by an ionization chamber, the depth profiles showed lower Bragg peak intensities than those measured by an ionization chamber. In addition, a broad optical baseline signal was observed in depths that exceed the depth of the Bragg peak. We hypothesize that this broad baseline signal originates from the interaction of proton-induced prompt gamma photons with water. These prompt gamma photons interact with water to form high-energy Compton electrons, which may cause luminescence or Cherenkov emission from depths exceeding the location of the Bragg peak. To clarify this idea, we measured the luminescence images of water during the irradiations of protons in water with minimized parallax errors, and also simulated the produced light by the interactions of prompt gamma photons with water. We corrected the measured depth profiles of the luminescence images by subtracting the simulated distributions of the produced light by the interactions of prompt gamma photons in water. Corrections were also conducted using the estimated depth profiles of the light of the prompt gamma photons, as obtained from the off-beam areas of the luminescence images of water. With these corrections, we successfully obtained depth profiles that have almost identical distributions as the simulated dose distributions for protons. The percentage relative height of the Bragg peak with corrections to that of the simulation data increased to 94% from 80% without correction. Also, the percentage relative offset heights of the deeper part of the Bragg peak with corrections decreased to 0.2%-0.4% from 4% without correction. These results indicate that the luminescence imaging of water has potential for the dose distribution measurements for proton therapy dosimetry.

GeantV: From CPU to accelerators

DOE PAGES

Amadio, G.; Ananya, A.; Apostolakis, J.; ...

2016-01-01

The GeantV project aims to research and develop the next-generation simulation software describing the passage of particles through matter. While the modern CPU architectures are being targeted first, resources such as GPGPU, Intel© Xeon Phi, Atom or ARM cannot be ignored anymore by HEP CPU-bound applications. The proof of concept GeantV prototype has been mainly engineered for CPU's having vector units but we have foreseen from early stages a bridge to arbitrary accelerators. A software layer consisting of architecture/technology specific backends supports currently this concept. This approach allows to abstract out the basic types such as scalar/vector but also tomore » formalize generic computation kernels using transparently library or device specific constructs based on Vc, CUDA, Cilk+ or Intel intrinsics. While the main goal of this approach is portable performance, as a bonus, it comes with the insulation of the core application and algorithms from the technology layer. This allows our application to be long term maintainable and versatile to changes at the backend side. The paper presents the first results of basket-based GeantV geometry navigation on the Intel© Xeon Phi KNC architecture. We present the scalability and vectorization study, conducted using Intel performance tools, as well as our preliminary conclusions on the use of accelerators for GeantV transport. Lastly, we also describe the current work and preliminary results for using the GeantV transport kernel on GPUs.« less

Use of the GEANT4 Monte Carlo to determine three-dimensional dose factors for radionuclide dosimetry

NASA Astrophysics Data System (ADS)

Amato, Ernesto; Italiano, Antonio; Minutoli, Fabio; Baldari, Sergio

2013-04-01

The voxel-level dosimetry is the most simple and common approach to internal dosimetry of nonuniform distributions of activity within the human body. Aim of this work was to obtain the dose "S" factors (mGy/MBqs) at the voxel level for eight beta and beta-gamma emitting radionuclides commonly used in nuclear medicine diagnostic and therapeutic procedures. We developed a Monte Carlo simulation in GEANT4 of a region of soft tissue as defined by the ICRP, divided into 11×11×11 cubic voxels, 3 mm in side. The simulation used the parameterizations of the electromagnetic interaction optimized for low energy (EEDL, EPDL). The decay of each radionuclide (32P, 90Y, 99mTc, 177Lu, 131I, 153Sm, 186Re, 188Re) were simulated homogeneously distributed within the central voxel (0,0,0), and the energy deposited in the surrounding voxels was mediated on the 8 octants of the three dimensional space, for reasons of symmetry. The results obtained were compared with those available in the literature. While the iodine deviations remain within 16%, for phosphorus, a pure beta emitter, the agreement is very good for self-dose (0,0,0) and good for the dose to first neighbors, while differences are observed ranging from -60% to +100% for voxels far distant from the source. The existence of significant differences in the percentage calculation of the voxel S factors, especially for pure beta emitters such as 32P or 90Y, has already been highlighted by other authors. These data can usefully extend the dosimetric approach based on the voxel to other radionuclides not covered in the available literature.

Fast multipurpose Monte Carlo simulation for proton therapy using multi- and many-core CPU architectures.

PubMed

Souris, Kevin; Lee, John Aldo; Sterpin, Edmond

2016-04-01

Accuracy in proton therapy treatment planning can be improved using Monte Carlo (MC) simulations. However the long computation time of such methods hinders their use in clinical routine. This work aims to develop a fast multipurpose Monte Carlo simulation tool for proton therapy using massively parallel central processing unit (CPU) architectures. A new Monte Carlo, called MCsquare (many-core Monte Carlo), has been designed and optimized for the last generation of Intel Xeon processors and Intel Xeon Phi coprocessors. These massively parallel architectures offer the flexibility and the computational power suitable to MC methods. The class-II condensed history algorithm of MCsquare provides a fast and yet accurate method of simulating heavy charged particles such as protons, deuterons, and alphas inside voxelized geometries. Hard ionizations, with energy losses above a user-specified threshold, are simulated individually while soft events are regrouped in a multiple scattering theory. Elastic and inelastic nuclear interactions are sampled from ICRU 63 differential cross sections, thereby allowing for the computation of prompt gamma emission profiles. MCsquare has been benchmarked with the gate/geant4 Monte Carlo application for homogeneous and heterogeneous geometries. Comparisons with gate/geant4 for various geometries show deviations within 2%-1 mm. In spite of the limited memory bandwidth of the coprocessor simulation time is below 25 s for 10(7) primary 200 MeV protons in average soft tissues using all Xeon Phi and CPU resources embedded in a single desktop unit. MCsquare exploits the flexibility of CPU architectures to provide a multipurpose MC simulation tool. Optimized code enables the use of accurate MC calculation within a reasonable computation time, adequate for clinical practice. MCsquare also simulates prompt gamma emission and can thus be used also for in vivo range verification.

Simulation study of neutron production in thick beryllium targets by 35 MeV and 50.5 MeV proton beams

NASA Astrophysics Data System (ADS)

Shin, Jae Won; Park, Tae-Sun

2017-09-01

A data-driven nuclear model dedicated to an accurate description of neutron productions in beryllium targets bombarded by proton beams is developed as a custom development that can be used as an add-on to GEANT4 code. The developed model, G4Data(Endf7.1), takes as inputs the total and differential cross section data of ENDF/B-VII.1 for not only the charge-exchange 9Be(p,n)9B reaction which produces discrete neutrons but also the nuclear reactions relevant for the production of continuum neutrons such as 9Be(p,pn)8Be and 9Be(p,n α) 5Li . In our benchmarking simulations for two experiments with 35 MeV and 50.5 MeV proton beams impinged on 1.16 and 1.05 cm thick beryllium targets, respectively, we find that the G4Data(Endf7.1) model can reproduce both the total amounts and the spectral shapes of the measured neutron yield data in a satisfactory manner, while all the considered hadronic models of GEANT4 cannot.

Effect of Photon Hormesis on Dose Responses to Alpha Particles in Zebrafish Embryos.

PubMed

Ng, Candy Yuen Ping; Cheng, Shuk Han; Yu, Kwan Ngok

2017-02-11

Photon hormesis refers to the phenomenon where the biological effect of ionizing radiation with a high linear energy transfer (LET) value is diminished by photons with a low LET value. The present paper studied the effect of photon hormesis from X-rays on dose responses to alpha particles using embryos of the zebrafish ( Danio rerio ) as the in vivo vertebrate model. The toxicity of these ionizing radiations in the zebrafish embryos was assessed using the apoptotic counts at 20, 24, or 30 h post fertilization (hpf) revealed through acridine orange (AO) staining. For alpha-particle doses ≥ 4.4 mGy, the additional X-ray dose of 10 mGy significantly reduced the number of apoptotic cells at 24 hpf, which proved the presence of photon hormesis. Smaller alpha-particle doses might not have inflicted sufficient aggregate damages to trigger photon hormesis. The time gap T between the X-ray (10 mGy) and alpha-particle (4.4 mGy) exposures was also studied. Photon hormesis was present when T ≤ 30 min, but was absent when T = 60 min, at which time repair of damage induced by alpha particles would have completed to prevent their interactions with those induced by X-rays. Finally, the drop in the apoptotic counts at 24 hpf due to photon hormesis was explained by bringing the apoptotic events earlier to 20 hpf, which strongly supported the removal of aberrant cells through apoptosis as an underlying mechanism for photon hormesis.

Geant4 simulations of NIST beam neutron lifetime experiment

NASA Astrophysics Data System (ADS)

Valete, Daniel; Crawford, Bret; BL2 Collaboration Collaboration

2017-09-01

A free neutron is unstable and its decay is described by the Standard Model as the transformation of a down quark into an up quark through the weak interaction. Precise measurements of the neutron lifetime test the validity of the theory of the weak interaction and provide useful information for the predictions of the theory of Big Bang nucleosynthesis of the primordial helium abundance in the universe and the number of different types of light neutrinos Nν. The predominant experimental methods for determination of the neutron lifetime are commonly called `beam' and `bottle' methods, and the most recent uses of each method do not agree with each other within their stated uncertainties. An improved experiment of the beam technique, which uses magnetic and electric fields to trap and guide the decay protons of a beam of cold neutrons to a detector, is in progress at the National Institute of Standards and Technology, Gaithersburg, MD with a precision goal of 0.1. I acknowledge the support of the Cross-Diciplinary Institute at Gettysburg College.

Thermo-optical interactions in a dye-microcavity photon Bose-Einstein condensate

NASA Astrophysics Data System (ADS)

Alaeian, Hadiseh; Schedensack, Mira; Bartels, Clara; Peterseim, Daniel; Weitz, Martin

2017-11-01

Superfluidity and Bose-Einstein condensation are usually considered as two closely related phenomena. Indeed, in most macroscopic quantum systems, like liquid helium, ultracold atomic Bose gases, and exciton-polaritons, condensation and superfluidity occur in parallel. In photon Bose-Einstein condensates realized in the dye microcavity system, thermalization does not occur by direct interaction of the condensate particles as in the above described systems, i.e. photon-photon interactions, but by absorption and re-emission processes on the dye molecules, which act as a heat reservoir. Currently, there is no experimental evidence for superfluidity in the dye microcavity system, though effective photon interactions have been observed from thermo-optic effects in the dye medium. In this work, we theoretically investigate the implications of effective thermo-optic photon interactions, a temporally delayed and spatially non-local effect, on the photon condensate, and derive the resulting Bogoliubov excitation spectrum. The calculations suggest a linear photon dispersion at low momenta, fulfilling the Landau’s criterion of superfluidity. We envision that the temporally delayed and long-range nature of the thermo-optic photon interaction offer perspectives for novel quantum fluid phenomena.

Engineering Photon-Photon Interactions within Rubidium-Filled Waveguides

NASA Astrophysics Data System (ADS)

Perrella, C.; Light, P. S.; Vahid, S. Afshar; Benabid, F.; Luiten, A. N.

2018-04-01

Strong photon-photon interactions are a required ingredient for deterministic two-photon optical quantum logic gates. Multiphoton transitions in dense atomic vapors have been shown to be a promising avenue for producing such interactions. The strength of a multiphoton interaction can be enhanced by conducting the interaction in highly confined geometries such as small-cross-section optical waveguides. We demonstrate, both experimentally and theoretically, that the strength of such interactions scale only with the optical mode diameter, d , not d2 as might be initially expected. This weakening of the interaction arises from atomic motion inside the waveguides. We create an interaction between two optical signals, at 780 and 776 nm, using the 5 S1 /2→5 D5 /2 two-photon transition in rubidium vapor within a range of hollow-core fibers with different core sizes. The interaction strength is characterized by observing the absorption and phase shift induced on the 780-nm beam, which is in close agreement with theoretical modeling that accounts for the atomic motion inside the fibers. These observations demonstrate that transit-time effects upon multiphoton transitions are of key importance when engineering photon-photon interactions within small-cross-section waveguides that might otherwise be thought to lead to enhanced optical nonlinearity through increased intensities.

Enhancing a slow and weak optomechanical nonlinearity with delayed quantum feedback

NASA Astrophysics Data System (ADS)

Wang, Zhaoyou; Safavi-Naeini, Amir H.

2017-07-01

A central goal of quantum optics is to generate large interactions between single photons so that one photon can strongly modify the state of another one. In cavity optomechanics, photons interact with the motional degrees of freedom of an optical resonator, for example, by imparting radiation pressure forces on a movable mirror or sensing minute fluctuations in the position of the mirror. Here, we show that the optical nonlinearity arising from these effects, typically too small to operate on single photons, can be sufficiently enhanced with feedback to generate large interactions between single photons. We propose a protocol that allows photons propagating in a waveguide to interact with each other through multiple bounces off an optomechanical system. The protocol is analysed by evolving the full many-body quantum state of the waveguide-coupled system, illustrating that large photon-photon interactions mediated by mechanical motion may be within experimental reach.

A superhigh-frequency optoelectromechanical system based on a slotted photonic crystal cavity

NASA Astrophysics Data System (ADS)

Sun, Xiankai; Zhang, Xufeng; Poot, Menno; Xiong, Chi; Tang, Hong X.

2012-11-01

We develop an all-integrated optoelectromechanical system that operates in the superhigh frequency band. This system is based on an ultrahigh-Q slotted photonic crystal (PhC) nanocavity formed by two PhC membranes, one of which is patterned with electrode and capacitively driven. The strong simultaneous electromechanical and optomechanical interactions yield efficient electrical excitation and sensitive optical transduction of the bulk acoustic modes of the PhC membrane. These modes are identified up to a frequency of 4.20 GHz, with their mechanical Q factors ranging from 240 to 1730. Directly linking signals in microwave and optical domains, such optoelectromechanical systems will find applications in microwave photonics in addition to those that utilize the electromechanical and optomechanical interactions separately.

A new low-energy bremsstrahlung generator for GEANT4.

PubMed

Peralta, L; Rodrigues, P; Trindade, A; Pia, M G

2005-01-01

The 2BN bremsstrahlung cross section is a well-adapted distribution to describe the radiative processes at low-electron kinetic energy (E(k) < 500 keV). In this work a method to implement this distribution in a Monte Carlo generator is developed.

Proceedings of the Eleventh International Conference on Calorimetry in Particle Physics

NASA Astrophysics Data System (ADS)

Cecchi, Claudia

The Pamela silicon tungsten calorimeter / G. Zampa -- Design and development of a dense, fine grained silicon tungsten calorimeter with integrated electronics / D. Strom -- High resolution silicon detector for 1.2-3.1 eV (400-1000 nm) photons / D. Groom -- The KLEM high energy cosmic rays collector for the NUCLEON satellite mission / M. Merkin (contribution not received) -- The electromagnetic calorimeter of the Hera-b experiment / I. Matchikhilian -- The status of the ATLAS tile calorimeter / J. Mendes Saraiva -- Design and mass production of Scintillator Pad Detector (SPD) / Preshower (PS) detector for LHC-b experiment / E. Gushchin -- Study of new FNAL-NICADD extruded scintillator as active media of large EMCal of ALICE at LHC / O. Grachov -- The CMS hadron calorimeter / D. Karmgard (contribution not received) -- Test beam study of the KOPIO Shashlyk calorimeter prototype / A. Poblaguev -- The Shashlik electro-magnetic calorimeter for the LHCb experiment / S. Barsuk -- Quality of mass produced lead-tungstate crystals / R. Zhu -- Status of the CMS electromagnetic calorimeter / J. Fay -- Scintillation detectors for radiation-hard electromagnetic calorimeters / H. Loehner -- Energy, timing and two-photon invariant mass resolution of a 256-channel PBWO[symbol] calorimeter / M. Ippolitov -- A high performance hybrid electromagnetic calorimeter at Jefferson Lab / A. Gasparian -- CsI(Tl) calorimetry on BESHI / T. Hu (contribution not received) -- The crystal ball and TAPS detectors at the MAMI electron beam facility / D. Watts -- Front-end electronics of the ATLAS tile calorimeter / R. Teuscher -- The ATLAS tilecal detector control system / A. Gomes -- Performance of the liquid argon final calibration board / C. de la Taille -- Overview of the LHCb calorimeter electronics / F. Machefert -- LHCb preshower photodetector and electronics / S. Monteil -- The CMS ECAL readout architecture and the clock and control system / K. Kloukinas -- Test of the CMS-ECAL trigger primitive generation / N. Regnault -- Optical data links for the CMS ECAL / J. Grahl (contribution not received) -- CMS ECAL off-detector electronics / R. Alemany Fernandez -- Performance of a low noise readout ASIC for the W-Si calorimeter physics prototype for the future linear collider / C. de la Taille -- Properties of a sampling calorimeter with warm-liquid ionization chambers / S. Plewnia -- Calorimetry and the DO experiment / R. Zitoun (contribution not received) -- Data quality monitoring for the DØ calorimeter / V. Shary -- Status of the construction of the ATLAS electromagnetic liquid argon calorimeter, overview of beam test performance studies / L. Serin -- Uniformity of response of ATLAS liquid argon EM calorimeter / O. Gaunter -- Status of the ATLAS liquid argon hadronic endcap calorimeter construction / M. Vincter -- Results from particle beam tests of the ATLAS liquid argon endcap calorimeters / M. Lefebvre -- First results of the DREAM project / R. Wigmans -- Electron and muon detection with a dual-readout (DREAM) calorimeter / N. Akchurin -- The neutron zero degree calorimeter for the ALICE experiment / M. Gallio -- The liquid xenon scintillation calorimeter of the MEG experiment: operation of a large prototype / G. Signorelli -- Detection of high energy particles using radio frequency signals / C. Hebert -- Hadronic shower simulation / J.-P. Wellisch -- E.M. and hadronic shower simulation with FLUKA / G. Battistoni -- Simulation of the LHCb electromagnetic calorimeter response with GEANT4 / P. Robbe -- Comparison of beam test results of the combined ATLAS liquid argon endcap calorimeters with GEANT3 and GEANT4 simulations / D. Salihagić -- GEANT4 hadronic physics validation with LHC test-beam data / C. Alexa -- The full simulation of the GLAST LAT high energy gamma ray telescope / F. Longo -- Response of the KLOE electromagnetic calorimeter to low-energy particles / T. Spadaro -- Calorimeter algorithms for DØ; / S. Trincaz-Duvoid -- Identification of low P[symbol] muon with the ATLAS tile calorimeter / G. Usai -- Electron and photon reconstruction with fully simulated events in the CMS experiment / G. Daskalakis -- Expected performance of Jet, [symbol] and [symbol] reconstruction in ATLAS / I. Vivarelli -- LHCb calorimeter from trigger to physics / O. Deschamps -- The calibration strategy of CMS electromagnetic calorimeter / P. Meridiani -- Energy and impact point reconstruction in the CMS ECAL (testbeam results from 2003) / I. B. van Vulpen -- The jet energy scale and resolution in the DO calorimeter / A. Kupco (contribution not received) -- Precision linearity studies of the ATLAS liquid argon EM calorimeter / G. Graziani -- Calibration of the ATLAS tile calorimeter / F. Sarri -- Performance of the CMS ECAL laser monitoring source in the test beam / A. Bornheim -- Energy reconstruction algorithms and their influence on the ATLAS tile calorimeter / E. Fullana -- Study of the biological effectiveness of ionizing radiations for a more realistic evaluation of the radiation quality in hadrontherapy / R. Cherubini (contribution not received) -- New dosimetry technologies for IMRT (Intensity Modulated Radio Therapy) / A. Piermattei -- Photon neutron radiotherapy / G. Giannini (contribution not received) -- Recent developments in molecular imaging / G. Zavattini (contribution not received) -- Performance goals and design considerations for a linear collider calorimeter / F. Sefkow -- Improving the jet reconstruction with the particle flow method; an introduction / J.-C. Brient -- Fine grained SiW ECAL for a linear collider detector / D. Strom (in the silicon session) -- Silicon-tungsten sampling electromagnetic calorimeter for the TeV electron-positron linear collider / J.-C. Brient -- LCCAL: a calorimeter prototype for future linear colliders / S. Miscetti -- Analog vs digital hadron calorimetry at a future electron-positron linear collider / S. Magill -- Toward a scintillator based heal and tail catcher for the LC calorimeter / M. Martin (contribution not received) -- Minical options, description in MC, calibration, plans for test beam prototype / G. Eigen (contribution not received) -- Photodetector options for a scintillator heal / E. Popova (contribution not received) -- Very low background scintillators in DAMA project: results and perspectives / R. Bernabei -- EDELWEISS Ge cryogenics detectors: main performance and physics results / X. Navick (contribution not received) -- Review of massive underground detectors / A. Rubbia -- Review of neutrino telescopes underwater and under ice / A. Capone (contribution not received) -- The fluorescence detector of the Pierre Auger Observatory / R. Caruso -- The EUSO mission for the observation of ultra high energy cosmic rays from space / A. Petrolini -- Performance of a 3D imaging electromagnetic calorimeter for the AMSO2 space experiment / C. Adloff -- Beam test calibration of the balloon borne imaging calorimeter for the CREAM experiment / P. Maestro.

Measurement and optimization of the light collection uniformity in strongly tapered PWO crystals of the PANDA detector

NASA Astrophysics Data System (ADS)

Diehl, Stefan; Bremer, Daniel; Brinkmann, Kai-Thomas; Dormenev, Valery; Eissner, Tobias; Novotny, Rainer W.; Rosenbaum, Christoph; Zaunick, Hans-Georg; PANDA Collaboration

2017-06-01

The uniformity of the light collection is a crucial parameter for detectors based on inorganic scintillation crystals to guarantee a response proportional to the deposited energy. Especially in case of tapered crystals, like they are widely used to realize a 4π geometry of electromagnetic calorimeters (EMC) in high energy physics experiments, a strong non-uniformity is introduced by an additional focusing of the scintillation light due to the tapered geometry. The paper will discuss the determination and the reduction of the non-uniformity in strongly tapered lead tungstate crystals as used for the construction of the electromagnetic calorimeter of the PANDA detector at the future Facility for Antiproton and Ion Research (FAIR). Among different concepts for an uniformization a single de-polished lateral side face provided the optimum result with a remaining non-uniformity below 5% in good agreement with similar studies for the CMS ECAL at LHC. The impact on the achievable energy resolution in the energy regime of photons below 800 MeV is discussed in detail in comparison to GEANT4 simulations. The comparison of the response of two arrays with polished and de-polished crystals, respectively, shows in the latter case a significant improvement of the constant term of the parametrization of the energy resolution down to 0.5% accompanied by only very slight increase of the statistical term.

STIC: Photonic Quantum Computation through Cavity Assisted Interaction

DTIC Science & Technology

2007-12-28

PRA ; available as quant-ph/06060791. Report for the grant “Photonic Quantum Computation through Cavity Assisted Interaction” from DTO Luming Duan...cavity •B. Wang, L.-M. Duan, PRA 72 (in press, 2005) Single-photon source Photonic Quantum Computation through Cavity-Assisted Interaction H. Jeff Kimble...interaction [Duan, Wang, Kimble, PRA 05] • “Investigate more efficient methods for combating noise in photonic quantum computation ” • Partial progress

Accurate and efficient modeling of the detector response in small animal multi-head PET systems.

PubMed

Cecchetti, Matteo; Moehrs, Sascha; Belcari, Nicola; Del Guerra, Alberto

2013-10-07

In fully three-dimensional PET imaging, iterative image reconstruction techniques usually outperform analytical algorithms in terms of image quality provided that an appropriate system model is used. In this study we concentrate on the calculation of an accurate system model for the YAP-(S)PET II small animal scanner, with the aim to obtain fully resolution- and contrast-recovered images at low levels of image roughness. For this purpose we calculate the system model by decomposing it into a product of five matrices: (1) a detector response component obtained via Monte Carlo simulations, (2) a geometric component which describes the scanner geometry and which is calculated via a multi-ray method, (3) a detector normalization component derived from the acquisition of a planar source, (4) a photon attenuation component calculated from x-ray computed tomography data, and finally, (5) a positron range component is formally included. This system model factorization allows the optimization of each component in terms of computation time, storage requirements and accuracy. The main contribution of this work is a new, efficient way to calculate the detector response component for rotating, planar detectors, that consists of a GEANT4 based simulation of a subset of lines of flight (LOFs) for a single detector head whereas the missing LOFs are obtained by using intrinsic detector symmetries. Additionally, we introduce and analyze a probability threshold for matrix elements of the detector component to optimize the trade-off between the matrix size in terms of non-zero elements and the resulting quality of the reconstructed images. In order to evaluate our proposed system model we reconstructed various images of objects, acquired according to the NEMA NU 4-2008 standard, and we compared them to the images reconstructed with two other system models: a model that does not include any detector response component and a model that approximates analytically the depth of interaction as detector response component. The comparisons confirm previous research results, showing that the usage of an accurate system model with a realistic detector response leads to reconstructed images with better resolution and contrast recovery at low levels of image roughness.

Accurate and efficient modeling of the detector response in small animal multi-head PET systems

NASA Astrophysics Data System (ADS)

Cecchetti, Matteo; Moehrs, Sascha; Belcari, Nicola; Del Guerra, Alberto

2013-10-01

In fully three-dimensional PET imaging, iterative image reconstruction techniques usually outperform analytical algorithms in terms of image quality provided that an appropriate system model is used. In this study we concentrate on the calculation of an accurate system model for the YAP-(S)PET II small animal scanner, with the aim to obtain fully resolution- and contrast-recovered images at low levels of image roughness. For this purpose we calculate the system model by decomposing it into a product of five matrices: (1) a detector response component obtained via Monte Carlo simulations, (2) a geometric component which describes the scanner geometry and which is calculated via a multi-ray method, (3) a detector normalization component derived from the acquisition of a planar source, (4) a photon attenuation component calculated from x-ray computed tomography data, and finally, (5) a positron range component is formally included. This system model factorization allows the optimization of each component in terms of computation time, storage requirements and accuracy. The main contribution of this work is a new, efficient way to calculate the detector response component for rotating, planar detectors, that consists of a GEANT4 based simulation of a subset of lines of flight (LOFs) for a single detector head whereas the missing LOFs are obtained by using intrinsic detector symmetries. Additionally, we introduce and analyze a probability threshold for matrix elements of the detector component to optimize the trade-off between the matrix size in terms of non-zero elements and the resulting quality of the reconstructed images. In order to evaluate our proposed system model we reconstructed various images of objects, acquired according to the NEMA NU 4-2008 standard, and we compared them to the images reconstructed with two other system models: a model that does not include any detector response component and a model that approximates analytically the depth of interaction as detector response component. The comparisons confirm previous research results, showing that the usage of an accurate system model with a realistic detector response leads to reconstructed images with better resolution and contrast recovery at low levels of image roughness.

Silicon photonics cloud (SiCloud)

NASA Astrophysics Data System (ADS)

DeVore, Peter T. S.; Jiang, Yunshan; Lynch, Michael; Miyatake, Taira; Carmona, Christopher; Chan, Andrew C.; Muniam, Kuhan; Jalali, Bahram

2015-02-01

We present SiCloud (Silicon Photonics Cloud), the first free, instructional web-based research and education tool for silicon photonics. SiCloud's vision is to provide a host of instructional and research web-based tools. Such interactive learning tools enhance traditional teaching methods by extending access to a very large audience, resulting in very high impact. Interactive tools engage the brain in a way different from merely reading, and so enhance and reinforce the learning experience. Understanding silicon photonics is challenging as the topic involves a wide range of disciplines, including material science, semiconductor physics, electronics and waveguide optics. This web-based calculator is an interactive analysis tool for optical properties of silicon and related material (SiO2, Si3N4, Al2O3, etc.). It is designed to be a one stop resource for students, researchers and design engineers. The first and most basic aspect of Silicon Photonics is the Material Parameters, which provides the foundation for the Device, Sub-System and System levels. SiCloud includes the common dielectrics and semiconductors for waveguide core, cladding, and photodetection, as well as metals for electrical contacts. SiCloud is a work in progress and its capability is being expanded. SiCloud is being developed at UCLA with funding from the National Science Foundation's Center for Integrated Access Networks (CIAN) Engineering Research Center.

Comparison of TG-43 dosimetric parameters of brachytherapy sources obtained by three different versions of MCNP codes.

PubMed

Zaker, Neda; Zehtabian, Mehdi; Sina, Sedigheh; Koontz, Craig; Meigooni, Ali S

2016-03-08

Monte Carlo simulations are widely used for calculation of the dosimetric parameters of brachytherapy sources. MCNP4C2, MCNP5, MCNPX, EGS4, EGSnrc, PTRAN, and GEANT4 are among the most commonly used codes in this field. Each of these codes utilizes a cross-sectional library for the purpose of simulating different elements and materials with complex chemical compositions. The accuracies of the final outcomes of these simulations are very sensitive to the accuracies of the cross-sectional libraries. Several investigators have shown that inaccuracies of some of the cross section files have led to errors in 125I and 103Pd parameters. The purpose of this study is to compare the dosimetric parameters of sample brachytherapy sources, calculated with three different versions of the MCNP code - MCNP4C, MCNP5, and MCNPX. In these simulations for each source type, the source and phantom geometries, as well as the number of the photons, were kept identical, thus eliminating the possible uncertainties. The results of these investigations indicate that for low-energy sources such as 125I and 103Pd there are discrepancies in gL(r) values. Discrepancies up to 21.7% and 28% are observed between MCNP4C and other codes at a distance of 6 cm for 103Pd and 10 cm for 125I from the source, respectively. However, for higher energy sources, the discrepancies in gL(r) values are less than 1.1% for 192Ir and less than 1.2% for 137Cs between the three codes.

MO-FG-CAMPUS-IeP1-01: Alternative K-Edge Filters for Low-Energy Image Acquisition in Contrast Enhanced Spectral Mammography

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shrestha, S; Vedantham, S; Karellas, A

Purpose: In Contrast Enhanced Spectral Mammography (CESM), Rh filter is often used during low-energy image acquisition. The potential for using Ag, In and Sn filters, which exhibit K-edge closer to, and just below that of Iodine, instead of the Rh filter, was investigated for the low-energy image acquisition. Methods: Analytical computations of the half-value thickness (HVT) and the photon fluence per mAs (photons/mm2/mAs) for 50µm Rh were compared with other potential K-edge filters (Ag, In and Sn), all with K-absorption edge below that of Iodine. Two strategies were investigated: fixed kVp and filter thickness (50µm for all filters) resulting inmore » HVT variation, and fixed kVp and HVT resulting in variation in Ag, In and Sn thickness. Monte Carlo simulations (GEANT4) were conducted to determine if the scatter-to-primary ratio (SPR) and the point spread function of scatter (scatter PSF) differed between Rh and other K-edge filters. Results: Ag, In and Sn filters (50µm thick) increased photon fluence/mAs by 1.3–1.4, 1.8–2, and 1.7–2 at 28-32 kVp compared to 50µm Rh, which could decrease exposure time. Additionally, the fraction of spectra closer to and just below Iodine’s K-edge increased with these filters, which could improve post-subtraction image contrast. For HVT matched to 50µm Rh filtered spectra, the thickness range for Ag, In, and Sn were (41,44)µm, (49,55)µm and (45,53)µm, and increased photon fluence/mAs by 1.5–1.7, 1.6–2, and 1.6–2.2, respectively. Monte Carlo simulations showed that neither the SPR nor the scatter PSF of Ag, In and Sn differed from Rh, indicating no additional detriment due to x-ray scatter. Conclusion: The use of Ag, In and Sn filters for low-energy image acquisition in CESM is potentially feasible and could decrease exposure time and may improve post-subtraction image contrast. Effect of these filters on radiation dose, contrast, noise and associated metrics are being investigated. Funding Support: Supported in part by NIH R01CA195512. The contents are solely the responsibility of the authors and do not reflect the official views of the NIH or NCI.« less

SU-E-T-161: SOBP Beam Analysis Using Light Output of Scintillation Plate Acquired by CCD Camera.

PubMed

Cho, S; Lee, S; Shin, J; Min, B; Chung, K; Shin, D; Lim, Y; Park, S

2012-06-01

To analyze Bragg-peak beams in SOBP (spread-out Bragg-peak) beam using CCD (charge-coupled device) camera - scintillation screen system. We separated each Bragg-peak beam using light output of high sensitivity scintillation material acquired by CCD camera and compared with Bragg-peak beams calculated by Monte Carlo simulation. In this study, CCD camera - scintillation screen system was constructed with a high sensitivity scintillation plate (Gd2O2S:Tb) and a right-angled prismatic PMMA phantom, and a Marlin F-201B, EEE-1394 CCD camera. SOBP beam irradiated by the double scattering mode of a PROTEUS 235 proton therapy machine in NCC is 8 cm width, 13 g/cm 2 range. The gain, dose rate and current of this beam is 50, 2 Gy/min and 70 nA, respectively. Also, we simulated the light output of scintillation plate for SOBP beam using Geant4 toolkit. We evaluated the light output of high sensitivity scintillation plate according to intergration time (0.1 - 1.0 sec). The images of CCD camera during the shortest intergration time (0.1 sec) were acquired automatically and randomly, respectively. Bragg-peak beams in SOBP beam were analyzed by the acquired images. Then, the SOBP beam used in this study was calculated by Geant4 toolkit and Bragg-peak beams in SOBP beam were obtained by ROOT program. The SOBP beam consists of 13 Bragg-peak beams. The results of experiment were compared with that of simulation. We analyzed Bragg-peak beams in SOBP beam using light output of scintillation plate acquired by CCD camera and compared with that of Geant4 simulation. We are going to study SOBP beam analysis using more effective the image acquisition technique. © 2012 American Association of Physicists in Medicine.

GGEMS-Brachy: GPU GEant4-based Monte Carlo simulation for brachytherapy applications

NASA Astrophysics Data System (ADS)

Lemaréchal, Yannick; Bert, Julien; Falconnet, Claire; Després, Philippe; Valeri, Antoine; Schick, Ulrike; Pradier, Olivier; Garcia, Marie-Paule; Boussion, Nicolas; Visvikis, Dimitris

2015-07-01

In brachytherapy, plans are routinely calculated using the AAPM TG43 formalism which considers the patient as a simple water object. An accurate modeling of the physical processes considering patient heterogeneity using Monte Carlo simulation (MCS) methods is currently too time-consuming and computationally demanding to be routinely used. In this work we implemented and evaluated an accurate and fast MCS on Graphics Processing Units (GPU) for brachytherapy low dose rate (LDR) applications. A previously proposed Geant4 based MCS framework implemented on GPU (GGEMS) was extended to include a hybrid GPU navigator, allowing navigation within voxelized patient specific images and analytically modeled 125I seeds used in LDR brachytherapy. In addition, dose scoring based on track length estimator including uncertainty calculations was incorporated. The implemented GGEMS-brachy platform was validated using a comparison with Geant4 simulations and reference datasets. Finally, a comparative dosimetry study based on the current clinical standard (TG43) and the proposed platform was performed on twelve prostate cancer patients undergoing LDR brachytherapy. Considering patient 3D CT volumes of 400  × 250  × 65 voxels and an average of 58 implanted seeds, the mean patient dosimetry study run time for a 2% dose uncertainty was 9.35 s (≈500 ms 10-6 simulated particles) and 2.5 s when using one and four GPUs, respectively. The performance of the proposed GGEMS-brachy platform allows envisaging the use of Monte Carlo simulation based dosimetry studies in brachytherapy compatible with clinical practice. Although the proposed platform was evaluated for prostate cancer, it is equally applicable to other LDR brachytherapy clinical applications. Future extensions will allow its application in high dose rate brachytherapy applications.

The Vertical Distribution of Buried Volatiles at the Moon revealed by Thermal and Epithermal Neutron Fluxes from LEND Observations

NASA Astrophysics Data System (ADS)

Chin, G.; Sagdeev, R.; Su, J. J.; Murray, J.; Livengood, T. A.

2015-12-01

Determining the quantity and vertical distribution of volatile species on and below the surface of planetary bodies is vital to understand the primordial chemical inventory and subsequent evolution of planets. Volatiles may provide resources to support future human exploration. This is particularly true for the Moon, which is well observed by many methods from ground-based, lunar orbit, and in situ, and is an accessible destination or way station for human exploration. We present Geant4 models of relative fluxes of Fast, Epithermal, and Thermal neutron emission generated in a planetary regolith by galactic cosmic rays to reveal the first 1-2 meters vertical structure of embedded hydrogen or water. Varying ratios of Thermal versus Epithermal, low-energy-Epithermal versus high-energy-Epithermal, and Thermal versus Fast neutron emissions are diagnostics of the depth in which hydrogen/water layers are buried within the top 1-2 meters of the regolith. In addition, we apply model calculations to Lunar Exploration Neutron Detector (LEND) thermal and epithermal data, acquired on the Lunar Reconnaissance Orbiter (LRO), in specific regions of the Moon to retrieve the vertical distribution of buried ice from the remote sensing information. GEANT4 is a set of particle physics transport simulation codes that exploits object-oriented software methods to deliver a comprehensive and flexible toolkit that is modular and extensible, based on a free open-source development model. GEANT4 has become a standard tool to simulate applications as diverse as particle telescope and detector response, space radiation shielding and optimization, total ionizing dose in spacecraft components, and biological effects of radiation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fu, Wenkai; Ghosh, Priyarshini; Harrison, Mark

The performance of traditional Hornyak buttons and two proposed variants for fast-neutron hodoscope applications was evaluated using Geant4. The Hornyak button is a ZnS(Ag)-based device previously deployed at the Idaho National Laboratory's TRansient REActor Test Facility (better known as TREAT) for monitoring fast neutrons emitted during pulsing of fissile fuel samples. Past use of these devices relied on pulse-shape discrimination to reduce the significant levels of background Cherenkov radiation. Proposed are two simple designs that reduce the overall light guide mass (here, polymethyl methacrylate or PMMA), employ silicon photomultipliers (SiPMs), and can be operated using pulse-height discrimination alone to eliminatemore » background noise to acceptable levels. Geant4 was first used to model a traditional Hornyak button, and for assumed, hodoscope-like conditions, an intrinsic efficiency of 0.35% for mono-directional fission neutrons was predicted. The predicted efficiency is in reasonably good agreement with experimental data from the literature and, hence, served to validate the physics models and approximations employed. Geant4 models were then developed to optimize the materials and geometries of two alternatives to the Hornyak button, one based on a homogeneous mixture of ZnS(Ag) and PMMA, and one based on alternating layers of ZnS(Ag) and PMMA oriented perpendicular to the incident neutron beam. For the same radiation environment, optimized, 5-cm long (along the beam path) devices of the homogeneous and layered designs were predicted to have efficiencies of approximately 1.3% and 3.3%, respectively. For longer devices, i.e., lengths larger than 25 cm, these efficiencies were shown to peak at approximately 2.2% and 5.9%, respectively. Furthermore, both designs were shown to discriminate Cherenkov noise intrinsically by using an appropriate pulse-height discriminator level, i.e., pulse-shape discrimination is not needed for these devices.« less

Quality assurance in proton beam therapy using a plastic scintillator and a commercially available digital camera.

PubMed

Almurayshid, Mansour; Helo, Yusuf; Kacperek, Andrzej; Griffiths, Jennifer; Hebden, Jem; Gibson, Adam

2017-09-01

In this article, we evaluate a plastic scintillation detector system for quality assurance in proton therapy using a BC-408 plastic scintillator, a commercial camera, and a computer. The basic characteristics of the system were assessed in a series of proton irradiations. The reproducibility and response to changes of dose, dose-rate, and proton energy were determined. Photographs of the scintillation light distributions were acquired, and compared with Geant4 Monte Carlo simulations and with depth-dose curves measured with an ionization chamber. A quenching effect was observed at the Bragg peak of the 60 MeV proton beam where less light was produced than expected. We developed an approach using Birks equation to correct for this quenching. We simulated the linear energy transfer (LET) as a function of depth in Geant4 and found Birks constant by comparing the calculated LET and measured scintillation light distribution. We then used the derived value of Birks constant to correct the measured scintillation light distribution for quenching using Geant4. The corrected light output from the scintillator increased linearly with dose. The system is stable and offers short-term reproducibility to within 0.80%. No dose rate dependency was observed in this work. This approach offers an effective way to correct for quenching, and could provide a method for rapid, convenient, routine quality assurance for clinical proton beams. Furthermore, the system has the advantage of providing 2D visualization of individual radiation fields, with potential application for quality assurance of complex, time-varying fields. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Efficiency transfer using the GEANT4 code of CERN for HPGe gamma spectrometry.

PubMed

Chagren, S; Tekaya, M Ben; Reguigui, N; Gharbi, F

2016-01-01

In this work we apply the GEANT4 code of CERN to calculate the peak efficiency in High Pure Germanium (HPGe) gamma spectrometry using three different procedures. The first is a direct calculation. The second corresponds to the usual case of efficiency transfer between two different configurations at constant emission energy assuming a reference point detection configuration and the third, a new procedure, consists on the transfer of the peak efficiency between two detection configurations emitting the gamma ray in different energies assuming a "virtual" reference point detection configuration. No pre-optimization of the detector geometrical characteristics was performed before the transfer to test the ability of the efficiency transfer to reduce the effect of the ignorance on their real magnitude on the quality of the transferred efficiency. The obtained and measured efficiencies were found in good agreement for the two investigated methods of efficiency transfer. The obtained agreement proves that Monte Carlo method and especially the GEANT4 code constitute an efficient tool to obtain accurate detection efficiency values. The second investigated efficiency transfer procedure is useful to calibrate the HPGe gamma detector for any emission energy value for a voluminous source using one point source detection efficiency emitting in a different energy as a reference efficiency. The calculations preformed in this work were applied to the measurement exercise of the EUROMET428 project. A measurement exercise where an evaluation of the full energy peak efficiencies in the energy range 60-2000 keV for a typical coaxial p-type HpGe detector and several types of source configuration: point sources located at various distances from the detector and a cylindrical box containing three matrices was performed. Copyright © 2015 Elsevier Ltd. All rights reserved.

Enhancing a slow and weak optomechanical nonlinearity with delayed quantum feedback

PubMed Central

Wang, Zhaoyou; Safavi-Naeini, Amir H.

2017-01-01

A central goal of quantum optics is to generate large interactions between single photons so that one photon can strongly modify the state of another one. In cavity optomechanics, photons interact with the motional degrees of freedom of an optical resonator, for example, by imparting radiation pressure forces on a movable mirror or sensing minute fluctuations in the position of the mirror. Here, we show that the optical nonlinearity arising from these effects, typically too small to operate on single photons, can be sufficiently enhanced with feedback to generate large interactions between single photons. We propose a protocol that allows photons propagating in a waveguide to interact with each other through multiple bounces off an optomechanical system. The protocol is analysed by evolving the full many-body quantum state of the waveguide-coupled system, illustrating that large photon–photon interactions mediated by mechanical motion may be within experimental reach. PMID:28677674

TU-EF-304-09: Quantifying the Biological Effects of Therapeutic Protons by LET Spectrum Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guan, F; Bronk, L; Kerr, M

2015-06-15

Purpose: To correlate in vitro cell kill with linear energy transfer (LET) spectra using Monte Carlo simulations and knowledge obtained from previous high-throughput in vitro proton relative biological effectiveness (RBE) measurements. Methods: The Monte Carlo simulation toolkit Geant4 was used to design the experimental setups and perform the dose, dose-averaged LET, and LET spectra calculations. The clonogenic assay was performed using the H460 lung cancer cell line in standard 6-well plates. Using two different experimental setups, the same dose and dose-averaged LET (12.6 keV/µm) was delivered to the cell layer; however, each respective energy or LET spectrum was different. Wemore » quantified the dose contributions from high-LET (≥10 keV/µm, threshold determined by previous RBE measurements) events in the LET spectra separately for these two setups as 39% and 53%. 8 dose levels with 1 Gy increments were delivered. The photon reference irradiation was performed using 6 MV x-rays from a LINAC. Results: The survival curves showed that both proton irradiations demonstrated an increased RBE compared to the reference photon irradiation. Within the proton-irradiated cells, the setup with 53% dose contribution from high-LET events exhibited the higher biological effectiveness. Conclusion: The experimental results indicate that the dose-averaged LET may not be an appropriate indicator to quantify the biological effects of protons when the LET spectrum is broad enough to contain both low- and high-LET events. Incorporating the LET spectrum distribution into robust intensity-modulated proton therapy optimization planning may provide more accurate biological dose distribution than using the dose-averaged LET. NIH Program Project Grant 2U19CA021239-35.« less

A model for the Global Quantum Efficiency for a TPB-based wavelength-shifting system used with photomultiplier tubes in liquid argon in MicroBooNE

DOE PAGES

Pate, S. F.; Wester, T.; Bugel, L.; ...

2018-02-28

We present a model for the Global Quantum Efficiency (GQE) of the MicroBooNE optical units. An optical unit consists of a flat, circular acrylic plate, coated with tetraphenyl butadiene (TPB), positioned near the photocathode of a 20.2-cm diameter photomultiplier tube. The plate converts the ultra-violet scintillation photons from liquid argon into visible-spectrum photons to which the cryogenic phototubes are sensitive. The GQE is the convolution of the efficiency of the plates that convert the 128 nm scintillation light from liquid argon to visible light, the efficiency of the shifted light to reach the photocathode, and the efficiency of the cryogenic photomultiplier tube. We develop a GEANT4-based model of the optical unit, based on first principles, and obtain the range of probable values for the expected number of detected photoelectrons (more » $$N_{\\rm PE}$$) given the known systematic errors on the simulation parameters. We compare results from four measurements of the $$N_{\\rm PE}$$ determined using alpha-particle sources placed at two distances from a TPB-coated plate in a liquid argon cryostat test stand. We also directly measured the radial dependence of the quantum efficiency, and find that this has the same shape as predicted by our model. Our model results in a GQE of $$0.0055\\pm0.0009$$ for the MicroBooNE optical units. While the information shown here is MicroBooNE specific, the approach to the model and the collection of simulation parameters will be widely applicable to many liquid-argon-based light collection systems.« less

Dose distribution of secondary radiation in a water phantom for a proton pencil beam-EURADOS WG9 intercomparison exercise.

PubMed

Stolarczyk, L; Trinkl, S; Romero-Expósito, M; Mojżeszek, N; Ambrozova, I; Domingo, C; Davídková, M; Farah, J; Kłodowska, M; Knežević, Ž; Liszka, M; Majer, M; Miljanić, S; Ploc, O; Schwarz, M; Harrison, R M; Olko, P

2018-04-19

Systematic 3D mapping of out-of-field doses induced by a therapeutic proton pencil scanning beam in a 300  ×  300  ×  600 mm 3 water phantom was performed using a set of thermoluminescence detectors (TLDs): MTS-7 ( 7 LiF:Mg,Ti), MTS-6 ( 6 LiF:Mg,Ti), MTS-N ( nat LiF:Mg,Ti) and TLD-700 ( 7 LiF:Mg,Ti), radiophotoluminescent (RPL) detectors GD-352M and GD-302M, and polyallyldiglycol carbonate (PADC)-based (C 12 H 18 O 7 ) track-etched detectors. Neutron and gamma-ray doses, as well as linear energy transfer distributions, were experimentally determined at 200 points within the phantom. In parallel, the Geant4 Monte Carlo code was applied to calculate neutron and gamma radiation spectra at the position of each detector. For the cubic proton target volume of 100  ×  100  ×  100 mm 3 (spread out Bragg peak with a modulation of 100 mm) the scattered photon doses along the main axis of the phantom perpendicular to the primary beam were approximately 0.5 mGy Gy -1 at a distance of 100 mm and 0.02 mGy Gy -1 at 300 mm from the center of the target. For the neutrons, the corresponding values of dose equivalent were found to be ~0.7 and ~0.06 mSv Gy -1 , respectively. The measured neutron doses were comparable with the out-of-field neutron doses from a similar experiment with 20 MV x-rays, whereas photon doses for the scanning proton beam were up to three orders of magnitude lower.

The Mapping X-Ray Fluorescence Spectrometer (MAPX)

NASA Technical Reports Server (NTRS)

Blake, David; Sarrazin, Philippe; Bristow, Thomas; Downs, Robert; Gailhanou, Marc; Marchis, Franck; Ming, Douglas; Morris, Richard; Sole, Vincente Armando; Thompson, Kathleen;

A model for the Global Quantum Efficiency for a TPB-based wavelength-shifting system used with photomultiplier tubes in liquid argon in MicroBooNE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pate, S. F.; Wester, T.; Bugel, L.

We present a model for the Global Quantum Efficiency (GQE) of the MicroBooNE optical units. An optical unit consists of a flat, circular acrylic plate, coated with tetraphenyl butadiene (TPB), positioned near the photocathode of a 20.2-cm diameter photomultiplier tube. The plate converts the ultra-violet scintillation photons from liquid argon into visible-spectrum photons to which the cryogenic phototubes are sensitive. The GQE is the convolution of the efficiency of the plates that convert the 128 nm scintillation light from liquid argon to visible light, the efficiency of the shifted light to reach the photocathode, and the efficiency of the cryogenic photomultiplier tube. We develop a GEANT4-based model of the optical unit, based on first principles, and obtain the range of probable values for the expected number of detected photoelectrons (more » $$N_{\\rm PE}$$) given the known systematic errors on the simulation parameters. We compare results from four measurements of the $$N_{\\rm PE}$$ determined using alpha-particle sources placed at two distances from a TPB-coated plate in a liquid argon cryostat test stand. We also directly measured the radial dependence of the quantum efficiency, and find that this has the same shape as predicted by our model. Our model results in a GQE of $$0.0055\\pm0.0009$$ for the MicroBooNE optical units. While the information shown here is MicroBooNE specific, the approach to the model and the collection of simulation parameters will be widely applicable to many liquid-argon-based light collection systems.« less

Dose distribution of secondary radiation in a water phantom for a proton pencil beam—EURADOS WG9 intercomparison exercise

NASA Astrophysics Data System (ADS)

Stolarczyk, L.; Trinkl, S.; Romero-Expósito, M.; Mojżeszek, N.; Ambrozova, I.; Domingo, C.; Davídková, M.; Farah, J.; Kłodowska, M.; Knežević, Ž.; Liszka, M.; Majer, M.; Miljanić, S.; Ploc, O.; Schwarz, M.; Harrison, R. M.; Olko, P.

2018-04-01

Systematic 3D mapping of out-of-field doses induced by a therapeutic proton pencil scanning beam in a 300  ×  300  ×  600 mm3 water phantom was performed using a set of thermoluminescence detectors (TLDs): MTS-7 (7LiF:Mg,Ti), MTS-6 (6LiF:Mg,Ti), MTS-N (natLiF:Mg,Ti) and TLD-700 (7LiF:Mg,Ti), radiophotoluminescent (RPL) detectors GD-352M and GD-302M, and polyallyldiglycol carbonate (PADC)-based (C12H18O7) track-etched detectors. Neutron and gamma-ray doses, as well as linear energy transfer distributions, were experimentally determined at 200 points within the phantom. In parallel, the Geant4 Monte Carlo code was applied to calculate neutron and gamma radiation spectra at the position of each detector. For the cubic proton target volume of 100  ×  100  ×  100 mm3 (spread out Bragg peak with a modulation of 100 mm) the scattered photon doses along the main axis of the phantom perpendicular to the primary beam were approximately 0.5 mGy Gy‑1 at a distance of 100 mm and 0.02 mGy Gy‑1 at 300 mm from the center of the target. For the neutrons, the corresponding values of dose equivalent were found to be ~0.7 and ~0.06 mSv Gy‑1, respectively. The measured neutron doses were comparable with the out-of-field neutron doses from a similar experiment with 20 MV x-rays, whereas photon doses for the scanning proton beam were up to three orders of magnitude lower.

Fast GPU-based Monte Carlo simulations for LDR prostate brachytherapy.

PubMed

Bonenfant, Éric; Magnoux, Vincent; Hissoiny, Sami; Ozell, Benoît; Beaulieu, Luc; Després, Philippe

2015-07-07

The aim of this study was to evaluate the potential of bGPUMCD, a Monte Carlo algorithm executed on Graphics Processing Units (GPUs), for fast dose calculations in permanent prostate implant dosimetry. It also aimed to validate a low dose rate brachytherapy source in terms of TG-43 metrics and to use this source to compute dose distributions for permanent prostate implant in very short times. The physics of bGPUMCD was reviewed and extended to include Rayleigh scattering and fluorescence from photoelectric interactions for all materials involved. The radial and anisotropy functions were obtained for the Nucletron SelectSeed in TG-43 conditions. These functions were compared to those found in the MD Anderson Imaging and Radiation Oncology Core brachytherapy source registry which are considered the TG-43 reference values. After appropriate calibration of the source, permanent prostate implant dose distributions were calculated for four patients and compared to an already validated Geant4 algorithm. The radial function calculated from bGPUMCD showed excellent agreement (differences within 1.3%) with TG-43 accepted values. The anisotropy functions at r = 1 cm and r = 4 cm were within 2% of TG-43 values for angles over 17.5°. For permanent prostate implants, Monte Carlo-based dose distributions with a statistical uncertainty of 1% or less for the target volume were obtained in 30 s or less for 1 × 1 × 1 mm(3) calculation grids. Dosimetric indices were very similar (within 2.7%) to those obtained with a validated, independent Monte Carlo code (Geant4) performing the calculations for the same cases in a much longer time (tens of minutes to more than a hour). bGPUMCD is a promising code that lets envision the use of Monte Carlo techniques in a clinical environment, with sub-minute execution times on a standard workstation. Future work will explore the use of this code with an inverse planning method to provide a complete Monte Carlo-based planning solution.

Fast GPU-based Monte Carlo simulations for LDR prostate brachytherapy

NASA Astrophysics Data System (ADS)

Bonenfant, Éric; Magnoux, Vincent; Hissoiny, Sami; Ozell, Benoît; Beaulieu, Luc; Després, Philippe

2015-07-01

The aim of this study was to evaluate the potential of bGPUMCD, a Monte Carlo algorithm executed on Graphics Processing Units (GPUs), for fast dose calculations in permanent prostate implant dosimetry. It also aimed to validate a low dose rate brachytherapy source in terms of TG-43 metrics and to use this source to compute dose distributions for permanent prostate implant in very short times. The physics of bGPUMCD was reviewed and extended to include Rayleigh scattering and fluorescence from photoelectric interactions for all materials involved. The radial and anisotropy functions were obtained for the Nucletron SelectSeed in TG-43 conditions. These functions were compared to those found in the MD Anderson Imaging and Radiation Oncology Core brachytherapy source registry which are considered the TG-43 reference values. After appropriate calibration of the source, permanent prostate implant dose distributions were calculated for four patients and compared to an already validated Geant4 algorithm. The radial function calculated from bGPUMCD showed excellent agreement (differences within 1.3%) with TG-43 accepted values. The anisotropy functions at r = 1 cm and r = 4 cm were within 2% of TG-43 values for angles over 17.5°. For permanent prostate implants, Monte Carlo-based dose distributions with a statistical uncertainty of 1% or less for the target volume were obtained in 30 s or less for 1 × 1 × 1 mm3 calculation grids. Dosimetric indices were very similar (within 2.7%) to those obtained with a validated, independent Monte Carlo code (Geant4) performing the calculations for the same cases in a much longer time (tens of minutes to more than a hour). bGPUMCD is a promising code that lets envision the use of Monte Carlo techniques in a clinical environment, with sub-minute execution times on a standard workstation. Future work will explore the use of this code with an inverse planning method to provide a complete Monte Carlo-based planning solution.

A Monte Carlo Library Least Square approach in the Neutron Inelastic-scattering and Thermal-capture Analysis (NISTA) process in bulk coal samples

NASA Astrophysics Data System (ADS)

Reyhancan, Iskender Atilla; Ebrahimi, Alborz; Çolak, Üner; Erduran, M. Nizamettin; Angin, Nergis

2017-01-01

A new Monte-Carlo Library Least Square (MCLLS) approach for treating non-linear radiation analysis problem in Neutron Inelastic-scattering and Thermal-capture Analysis (NISTA) was developed. 14 MeV neutrons were produced by a neutron generator via the 3H (2H , n) 4He reaction. The prompt gamma ray spectra from bulk samples of seven different materials were measured by a Bismuth Germanate (BGO) gamma detection system. Polyethylene was used as neutron moderator along with iron and lead as neutron and gamma ray shielding, respectively. The gamma detection system was equipped with a list mode data acquisition system which streams spectroscopy data directly to the computer, event-by-event. A GEANT4 simulation toolkit was used for generating the single-element libraries of all the elements of interest. These libraries were then used in a Linear Library Least Square (LLLS) approach with an unknown experimental sample spectrum to fit it with the calculated elemental libraries. GEANT4 simulation results were also used for the selection of the neutron shielding material.

Monte Carlo simulation of the dose response of a novel 2D silicon diode array for use in hybrid MRI-LINAC systems.

PubMed

Gargett, Maegan; Oborn, Brad; Metcalfe, Peter; Rosenfeld, Anatoly

2015-02-01

MRI-guided radiation therapy systems (MRIgRT) are being developed to improve online imaging during treatment delivery. At present, the operation of single point dosimeters and an ionization chamber array have been characterized in such systems. This work investigates a novel 2D diode array, named "magic plate," for both single point calibration and 2D positional performance, the latter being a key element of modern radiotherapy techniques that will be delivered by these systems. geant4 Monte Carlo methods have been employed to study the dose response of a silicon diode array to 6 MV photon beams, in the presence of in-line and perpendicularly aligned uniform magnetic fields. The array consists of 121 silicon diodes (dimensions 1.5 × 1.5 × 0.38 mm(3)) embedded in kapton substrate with 1 cm pitch, spanning a 10 × 10 cm(2) area in total. A geometrically identical, water equivalent volume was simulated concurrently for comparison. The dose response of the silicon diode array was assessed for various photon beam field shapes and sizes, including an IMRT field, at 1 T. The dose response was further investigated at larger magnetic field strengths (1.5 and 3 T) for a 4 × 4 cm(2) photon field size. The magic plate diode array shows excellent correspondence (< ± 1%) to water dose in the in-line orientation, for all beam arrangements and magnetic field strengths investigated. The perpendicular orientation, however, exhibits a dose shift with respect to water at the high-dose-gradient beam edge of jaw-defined fields [maximum (4.3 ± 0.8)% over-response, maximum (1.8 ± 0.8)% under-response on opposing side for 1 T, uncertainty 1σ]. The trend is not evident in areas with in-field dose gradients typical of IMRT dose maps. A novel 121 pixel silicon diode array detector has been characterized by Monte Carlo simulation for its performance inside magnetic fields representative of current prototype and proposed MRI-linear accelerator systems. In the in-line orientation, the silicon dose is directly proportional to the water dose. In the perpendicular orientation, there is a shift in dose response relative to water in the highest dose gradient regions, at the edge of jaw-defined and single-segment MLC fields. The trend was not observed in-field for an IMRT beam. The array is expected to be a valuable tool in MRIgRT dosimetry.

Monte Carlo simulation of the dose response of a novel 2D silicon diode array for use in hybrid MRI–LINAC systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gargett, Maegan, E-mail: mg406@uowmail.edu.au; Rosenfeld, Anatoly; Oborn, Brad

2015-02-15

Purpose: MRI-guided radiation therapy systems (MRIgRT) are being developed to improve online imaging during treatment delivery. At present, the operation of single point dosimeters and an ionization chamber array have been characterized in such systems. This work investigates a novel 2D diode array, named “magic plate,” for both single point calibration and 2D positional performance, the latter being a key element of modern radiotherapy techniques that will be delivered by these systems. Methods: GEANT4 Monte Carlo methods have been employed to study the dose response of a silicon diode array to 6 MV photon beams, in the presence of in-linemore » and perpendicularly aligned uniform magnetic fields. The array consists of 121 silicon diodes (dimensions 1.5 × 1.5 × 0.38 mm{sup 3}) embedded in kapton substrate with 1 cm pitch, spanning a 10 × 10 cm{sup 2} area in total. A geometrically identical, water equivalent volume was simulated concurrently for comparison. The dose response of the silicon diode array was assessed for various photon beam field shapes and sizes, including an IMRT field, at 1 T. The dose response was further investigated at larger magnetic field strengths (1.5 and 3 T) for a 4 × 4 cm{sup 2} photon field size. Results: The magic plate diode array shows excellent correspondence (< ± 1%) to water dose in the in-line orientation, for all beam arrangements and magnetic field strengths investigated. The perpendicular orientation, however, exhibits a dose shift with respect to water at the high-dose-gradient beam edge of jaw-defined fields [maximum (4.3 ± 0.8)% over-response, maximum (1.8 ± 0.8)% under-response on opposing side for 1 T, uncertainty 1σ]. The trend is not evident in areas with in-field dose gradients typical of IMRT dose maps. Conclusions: A novel 121 pixel silicon diode array detector has been characterized by Monte Carlo simulation for its performance inside magnetic fields representative of current prototype and proposed MRI–linear accelerator systems. In the in-line orientation, the silicon dose is directly proportional to the water dose. In the perpendicular orientation, there is a shift in dose response relative to water in the highest dose gradient regions, at the edge of jaw-defined and single-segment MLC fields. The trend was not observed in-field for an IMRT beam. The array is expected to be a valuable tool in MRIgRT dosimetry.« less

Modeling the truebeam linac using a CAD to Geant4 geometry implementation: dose and IAEA-compliant phase space calculations.

PubMed

Constantin, Magdalena; Perl, Joseph; LoSasso, Tom; Salop, Arthur; Whittum, David; Narula, Anisha; Svatos, Michelle; Keall, Paul J

2011-07-01

To create an accurate 6 MV Monte Carlo simulation phase space for the Varian TrueBeam treatment head geometry imported from CAD (computer aided design) without adjusting the input electron phase space parameters. GEANT4 v4.9.2.p01 was employed to simulate the 6 MV beam treatment head geometry of the Varian TrueBeam linac. The electron tracks in the linear accelerator were simulated with Parmela, and the obtained electron phase space was used as an input to the Monte Carlo beam transport and dose calculations. The geometry components are tessellated solids included in GEANT4 as GDML (generalized dynamic markup language) files obtained via STEP (standard for the exchange of product) export from Pro/Engineering, followed by STEP import in Fastrad, a STEP-GDML converter. The linac has a compact treatment head and the small space between the shielding collimator and the divergent are of the upper jaws forbids the implementation of a plane for storing the phase space. Instead, an IAEA (International Atomic Energy Agency) compliant phase space writer was implemented on a cylindrical surface. The simulation was run in parallel on a 1200 node Linux cluster. The 6 MV dose calculations were performed for field sizes varying from 4 x 4 to 40 x 40 cm2. The voxel size for the 60 x 60 x 40 cm3 water phantom was 4 x 4 x 4 mm3. For the 10 x 10 cm2 field, surface buildup calculations were performed using 4 x 4 x 2 mm3 voxels within 20 mm of the surface. For the depth dose curves, 98% of the calculated data points agree within 2% with the experimental measurements for depths between 2 and 40 cm. For depths between 5 and 30 cm, agreement within 1% is obtained for 99% (4 x 4), 95% (10 x 10), 94% (20 x 20 and 30 x 30), and 89% (40 x 40) of the data points, respectively. In the buildup region, the agreement is within 2%, except at 1 mm depth where the deviation is 5% for the 10 x 10 cm2 open field. For the lateral dose profiles, within the field size for fields up to 30 x 30 cm2, the agreement is within 2% for depths up to 10 cm. At 20 cm depth, the in-field maximum dose difference for the 30 x 30 cm2 open field is within 4%, while the smaller field sizes agree within 2%. Outside the field size, agreement within 1% of the maximum dose difference is obtained for all fields. The calculated output factors varied from 0.938 +/- 0.015 for the 4 x 4 cm2 field to 1.088 +/- 0.024 for the 40 x 40 cm2 field. Their agreement with the experimental output factors is within 1%. The authors have validated a GEANT4 simulated IAEA-compliant phase space of the TrueBeam linac for the 6 MV beam obtained using a high accuracy geometry implementation from CAD. These files are publicly available and can be used for further research.

Generation of circular polarization in CMB radiation via nonlinear photon-photon interaction

NASA Astrophysics Data System (ADS)

Sadegh, Mahdi; Mohammadi, Rohoollah; Motie, Iman

2018-01-01

Standard cosmological models do predict a measurable amount of anisotropies in the intensity and linear polarization of the cosmic microwave background radiation (CMB) via Thomson scattering, even though these theoretical models do not predict circular polarization for CMB radiation. In other hand, the circular polarization of CMB has not been excluded in observational evidences. Here we estimate the circular polarization power spectrum ClV (S ) in CMB radiation due to Compton scattering and nonlinear photon-photon forward scattering via Euler-Heisenberg effective Lagrangian. We have estimated the average value of circular power spectrum is l (l +1 )ClV (S )/(2 π )˜10-4 (μ K) 2 for l ˜300 at present time which is smaller than recently reported data for upper limit of circular polarization (SPIDER collaboration). As a result to test our results, the ability to detect nano-Kelvin level signals of CMB circular polarization requires. We also show that the generation of B-mode polarization for CMB photons in the presence of the primordial scalar perturbation via Euler-Heisenberg interaction is possible however this contribution for B-mode polarization is not remarkable.

Comparison of Space Radiation Calculations from Deterministic and Monte Carlo Transport Codes

NASA Technical Reports Server (NTRS)

Adams, J. H.; Lin, Z. W.; Nasser, A. F.; Randeniya, S.; Tripathi, r. K.; Watts, J. W.; Yepes, P.

2010-01-01

The presentation outline includes motivation, radiation transport codes being considered, space radiation cases being considered, results for slab geometry, results from spherical geometry, and summary. ///////// main physics in radiation transport codes hzetrn uprop fluka geant4, slab geometry, spe, gcr,

Simulation loop between cad systems, GEANT-4 and GeoModel: Implementation and results

NASA Astrophysics Data System (ADS)

Sharmazanashvili, A.; Tsutskiridze, Niko

2016-09-01

Compare analysis of simulation and as-built geometry descriptions of detector is important field of study for data_vs_Monte-Carlo discrepancies. Shapes consistency and detalization is not important while adequateness of volumes and weights of detector components are essential for tracking. There are 2 main reasons of faults of geometry descriptions in simulation: (1) Difference between simulated and as-built geometry descriptions; (2) Internal inaccuracies of geometry transformations added by simulation software infrastructure itself. Georgian Engineering team developed hub on the base of CATIA platform and several tools enabling to read in CATIA different descriptions used by simulation packages, like XML->CATIA; VP1->CATIA; Geo-Model->CATIA; Geant4->CATIA. As a result it becomes possible to compare different descriptions with each other using the full power of CATIA and investigate both classes of reasons of faults of geometry descriptions. Paper represents results of case studies of ATLAS Coils and End-Cap toroid structures.

Proton Linear Energy Transfer measurement using Emulsion Cloud Chamber

NASA Astrophysics Data System (ADS)

Shin, Jae-ik; Park, Seyjoon; Kim, Haksoo; Kim, Meyoung; Jeong, Chiyoung; Cho, Sungkoo; Lim, Young Kyung; Shin, Dongho; Lee, Se Byeong; Morishima, Kunihiro; Naganawa, Naotaka; Sato, Osamu; Kwak, Jungwon; Kim, Sung Hyun; Cho, Jung Sook; Ahn, Jung Keun; Kim, Ji Hyun; Yoon, Chun Sil; Incerti, Sebastien

2015-04-01

This study proposes to determine the correlation between the Volume Pulse Height (VPH) measured by nuclear emulsion and Linear Energy Transfer (LET) calculated by Monte Carlo simulation based on Geant4. The nuclear emulsion was irradiated at the National Cancer Center (NCC) with a therapeutic proton beam and was installed at 5.2 m distance from the beam nozzle structure with various thicknesses of water-equivalent material (PMMA) blocks to position with specific positions along the Bragg curve. After the beam exposure and development of the emulsion films, the films were scanned by S-UTS developed in Nagoya University. The proton tracks in the scanned films were reconstructed using the 'NETSCAN' method. Through this procedure, the VPH can be derived from each reconstructed proton track at each position along the Bragg curve. The VPH value indicates the magnitude of energy loss in proton track. By comparison with the simulation results obtained using Geant4, we found the correlation between the LET calculated by Monte Carlo simulation and the VPH measured by the nuclear emulsion.

Monte Carlo Simulation of Massive Absorbers for Cryogenic Calorimeters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brandt, D.; Asai, M.; Brink, P.L.

There is a growing interest in cryogenic calorimeters with macroscopic absorbers for applications such as dark matter direct detection and rare event search experiments. The physics of energy transport in calorimeters with absorber masses exceeding several grams is made complex by the anisotropic nature of the absorber crystals as well as the changing mean free paths as phonons decay to progressively lower energies. We present a Monte Carlo model capable of simulating anisotropic phonon transport in cryogenic crystals. We have initiated the validation process and discuss the level of agreement between our simulation and experimental results reported in the literature,more » focusing on heat pulse propagation in germanium. The simulation framework is implemented using Geant4, a toolkit originally developed for high-energy physics Monte Carlo simulations. Geant4 has also been used for nuclear and accelerator physics, and applications in medical and space sciences. We believe that our current work may open up new avenues for applications in material science and condensed matter physics.« less

Background and imaging simulations for the hard X-ray camera of the MIRAX mission

NASA Astrophysics Data System (ADS)

Castro, M.; Braga, J.; Penacchioni, A.; D'Amico, F.; Sacahui, R.

2016-07-01

We report the results of detailed Monte Carlo simulations of the performance expected both at balloon altitudes and at the probable satellite orbit of a hard X-ray coded-aperture camera being developed for the Monitor e Imageador de RAios X (MIRAX) mission. Based on a thorough mass model of the instrument and detailed specifications of the spectra and angular dependence of the various relevant radiation fields at both the stratospheric and orbital environments, we have used the well-known package GEANT4 to simulate the instrumental background of the camera. We also show simulated images of source fields to be observed and calculated the detailed sensitivity of the instrument in both situations. The results reported here are especially important to researchers in this field considering that we provide important information, not easily found in the literature, on how to prepare input files and calculate crucial instrumental parameters to perform GEANT4 simulations for high-energy astrophysics space experiments.

Design and optimization of an energy degrader with a multi-wedge scheme based on Geant4

NASA Astrophysics Data System (ADS)

Liang, Zhikai; Liu, Kaifeng; Qin, Bin; Chen, Wei; Liu, Xu; Li, Dong; Xiong, Yongqian

2018-05-01

A proton therapy facility based on an isochronous superconducting cyclotron is under construction in Huazhong University of Science and Technology (HUST). To meet the clinical requirements, an energy degrader is essential in the beamline to modulate the fixed beam energy extracted from the cyclotron. Because of the multiple Coulomb scattering in the degrader, the beam emittance and the energy spread will be considerably increased during the energy degradation process. Therefore, a set of collimators is designed to restrict the increase in beam emittance after the energy degradation. The energy spread will be reduced in the following beam line which is not discussed in this paper. In this paper, the design considerations of an energy degrader and collimators are introduced, and the properties of the degrader material, degrader structure and the initial beam parameters are discussed using the Geant4 Monte-Carlo toolkit, with the main purpose of improving the overall performance of the degrader by multiple parameter optimization.

Geant4 simulation of the CERN-EU high-energy reference field (CERF) facility.

PubMed

Prokopovich, D A; Reinhard, M I; Cornelius, I M; Rosenfeld, A B

2010-09-01

The CERN-EU high-energy reference field facility is used for testing and calibrating both active and passive radiation dosemeters for radiation protection applications in space and aviation. Through a combination of a primary particle beam, target and a suitable designed shielding configuration, the facility is able to reproduce the neutron component of the high altitude radiation field relevant to the jet aviation industry. Simulations of the facility using the GEANT4 (GEometry ANd Tracking) toolkit provide an improved understanding of the neutron particle fluence as well as the particle fluence of other radiation components present. The secondary particle fluence as a function of the primary particle fluence incident on the target and the associated dose equivalent rates were determined at the 20 designated irradiation positions available at the facility. Comparisons of the simulated results with previously published simulations obtained using the FLUKA Monte Carlo code, as well as with experimental results of the neutron fluence obtained with a Bonner sphere spectrometer, are made.

Highly retrievable spin-wave-photon entanglement source.

PubMed

Yang, Sheng-Jun; Wang, Xu-Jie; Li, Jun; Rui, Jun; Bao, Xiao-Hui; Pan, Jian-Wei

2015-05-29

Entanglement between a single photon and a quantum memory forms the building blocks for a quantum repeater and quantum network. Previous entanglement sources are typically with low retrieval efficiency, which limits future larger-scale applications. Here, we report a source of highly retrievable spin-wave-photon entanglement. Polarization entanglement is created through interaction of a single photon with an ensemble of atoms inside a low-finesse ring cavity. The cavity is engineered to be resonant for dual spin-wave modes, which thus enables efficient retrieval of the spin-wave qubit. An intrinsic retrieval efficiency up to 76(4)% has been observed. Such a highly retrievable atom-photon entanglement source will be very useful in future larger-scale quantum repeater and quantum network applications.

Single-photon non-linear optics with a quantum dot in a waveguide

NASA Astrophysics Data System (ADS)

Javadi, A.; Söllner, I.; Arcari, M.; Hansen, S. Lindskov; Midolo, L.; Mahmoodian, S.; Kiršanskė, G.; Pregnolato, T.; Lee, E. H.; Song, J. D.; Stobbe, S.; Lodahl, P.

2015-10-01

Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon-photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures.

Stochastic analog neutron transport with TRIPOLI-4 and FREYA: Bayesian uncertainty quantification for neutron multiplicity counting

DOE PAGES

Verbeke, J. M.; Petit, O.

2016-06-01

From nuclear safeguards to homeland security applications, the need for the better modeling of nuclear interactions has grown over the past decades. Current Monte Carlo radiation transport codes compute average quantities with great accuracy and performance; however, performance and averaging come at the price of limited interaction-by-interaction modeling. These codes often lack the capability of modeling interactions exactly: for a given collision, energy is not conserved, energies of emitted particles are uncorrelated, and multiplicities of prompt fission neutrons and photons are uncorrelated. Many modern applications require more exclusive quantities than averages, such as the fluctuations in certain observables (e.g., themore » neutron multiplicity) and correlations between neutrons and photons. In an effort to meet this need, the radiation transport Monte Carlo code TRIPOLI-4® was modified to provide a specific mode that models nuclear interactions in a full analog way, replicating as much as possible the underlying physical process. Furthermore, the computational model FREYA (Fission Reaction Event Yield Algorithm) was coupled with TRIPOLI-4 to model complete fission events. As a result, FREYA automatically includes fluctuations as well as correlations resulting from conservation of energy and momentum.« less

Background estimation of cosmic-ray induced neutrons in Chooz site water veto tank for possible future Ricochet Deployment

NASA Astrophysics Data System (ADS)

Silva, James

2017-09-01

The Ricochet experiment seeks to measure Coherent (neutral-current) Elastic Neutrino-Nucleus Scattering (CE νNS) using metallic superconducting and germanium semi-conducting detectors with sub-keV thresholds placed near a neutrino source such as the Chooz Nuclear Reactor Complex. In this poster, we present an estimate of the flux of cosmic-ray induced neutrons, which represent an important background in any (CE νNS) search, based on reconstructed cosmic ray data from the Chooz Site. We have simulated a possible Ricochet deployment at the Chooz site in GEANT4 focusing on the spallation neutrons generated when cosmic rays interact with the water tank veto that would surround our detector. We further simulate and discuss the effectiveness of various shielding configurations for optimizing the background levels for a future Ricochet deployment.

Efficiency of the High Efficiency Total Absorption Spectrometer (HECTOR)

NASA Astrophysics Data System (ADS)

Sprowal, Zaire; Simon, Anna; Reingold, Craig; Spyrou, Artemis; Naqvi, Farheen; Dombos, Alexander; Palmisano, Alicia; Anderson, Tyler; Anderson, Samuel; Moylan, Shane; Seymour, Christopher; Skulski, Michael; Smith, Mallory K.; Strauss, Sabrina; Kolk, Byant Vande

2016-09-01

The p-process is a nucleosynthesis process that occurs in explosive environments such as type II and Ia supernovae and is responsible for production of heavy proton rich nuclei. Gamma rays emitted during these explosions induce several photo-disintegration reactions: (γ,n), (γ,p), and (γ , α). To study these interactions, the inverse of these reactions are measured experimentally. The High Efficiency TOtal absorption spectrometeR (HECTOR) at the University of Notre Dame was built for measuring these reactions. Standard gamma sources 60Co and 137Cs and known resonances in 27Al(p, γ)28Si reaction were used to experimentally determine HECTOR's summing efficiency. Here, the preliminary analysis will be presented and the results will be compared to the Geant4 simulation of the array. This work was supported by the National Science Foundation under the Grant Number PHYS-1614442.

Characterization of emergent leakage neutrons from multiple layers of hydrogen/water in the lunar regolith by Monte Carlo simulation

NASA Astrophysics Data System (ADS)

SU, J.; Sagdeev, R.; Usikov, D.; Chin, G.; Boyer, L.; Livengood, T. A.; McClanahan, T. P.; Murray, J.; Starr, R. D.

2013-12-01

Introduction: The leakage flux of lunar neutrons produced by precipitation of galactic cosmic ray (GCR) particles in the upper layer of the lunar regolith and measured by orbital instruments such as the Lunar Exploration Neutron Detector (LEND) is investigated by Monte Carlo simulation. Previous Monte Carlo (MC) simulations have been used to investigate neutron production and leakage from the lunar surface to assess the elemental composition of lunar soil [1-6] and its effect on the leakage neutron flux. We investigate effects on the emergent flux that depend on the physical distribution of hydrogen within the regolith. We use the software package GEANT4 [7] to calculate neutron production from spallation by GCR particles [8,9] in the lunar soil. Multiple layers of differing hydrogen/water at different depths in the lunar regolith model are introduced to examine enhancement or suppression of leakage neutron flux. We find that the majority of leakage thermal and epithermal neutrons are produced in 25 cm to 75 cm deep from the lunar surface. Neutrons produced in the shallow top layer retain more of their original energy due to fewer scattering interactions and escape from the lunar surface mostly as fast neutrons. This provides a diagnostic tool in interpreting leakage neutron flux enhancement or suppression due to hydrogen concentration distribution in lunar regolith. We also find that the emitting angular distribution of thermal and epithermal leakage neutrons can be described by cos3/2(theta) where the fast neutrons emitting angular distribution is cos(theta). The energy sensitivity and angular response of the LEND detectors SETN and CSETN are investigated using the leakage neutron spectrum from GEANT4 simulations. A simplified LRO model is used to benchmark MCNPX[10] and GEANT4 on CSETN absolute count rate corresponding to neutron flux from bombardment of 120MV solar potential GCR particles on FAN lunar soil. We are able to interpret the count rates of SETN and CSETN from the leakage neutron spectrum, emission angle, detector energy sensitivity and angular response. Reference: [1] W. C. Feldman, et al., Science 4 September 1998: Vol. 281 no. 5382 pp. 1496-1500. [2] Gasnault, O., et al., (2000) J. Geophys. Res., 105(E2), 4263-4271. [3] Little, R. C., et al. (2003), J. Geophys. Res., 108(E5), 5046. [4] McKinney et al., (2006), J. Geophys. Res., 111, E06004. [5] Lawrence et al., (2006), J. Geophys. Res., 111, E08001. [6] Looper et al, (2013), Space Weather, VOL. 11, 142-152. [7] J. Allison, et al, (2006) IEEE TRANS. ON NUCL SCI, VOL. 53, NO. 1. [8] J. Masarik and R. Reedy (1996), J. Geophys. Res., 101, 18,891-18,912. [9] P. O'Neil (2010) IEEE Trans. Nucl. Sci., 57(6), 3148-3153. [10] D. Pelowitz, (2005), Rep. LA-CP-05-0369, LANL, Los Alamos, NM.

Feasibility of using Geant4 Monte Carlo simulation for IMRT dose calculations for the Novalis Tx with a HD-120 multi-leaf collimator

NASA Astrophysics Data System (ADS)

Jung, Hyunuk; Shin, Jungsuk; Chung, Kwangzoo; Han, Youngyih; Kim, Jinsung; Choi, Doo Ho

2015-05-01

The aim of this study was to develop an independent dose verification system by using a Monte Carlo (MC) calculation method for intensity modulated radiation therapy (IMRT) conducted by using a Varian Novalis Tx (Varian Medical Systems, Palo Alto, CA, USA) equipped with a highdefinition multi-leaf collimator (HD-120 MLC). The Geant4 framework was used to implement a dose calculation system that accurately predicted the delivered dose. For this purpose, the Novalis Tx Linac head was modeled according to the specifications acquired from the manufacturer. Subsequently, MC simulations were performed by varying the mean energy, energy spread, and electron spot radius to determine optimum values of irradiation with 6-MV X-ray beams by using the Novalis Tx system. Computed percentage depth dose curves (PDDs) and lateral profiles were compared to the measurements obtained by using an ionization chamber (CC13). To validate the IMRT simulation by using the MC model we developed, we calculated a simple IMRT field and compared the result with the EBT3 film measurements in a water-equivalent solid phantom. Clinical cases, such as prostate cancer treatment plans, were then selected, and MC simulations were performed. The accuracy of the simulation was assessed against the EBT3 film measurements by using a gamma-index criterion. The optimal MC model parameters to specify the beam characteristics were a 6.8-MeV mean energy, a 0.5-MeV energy spread, and a 3-mm electron radius. The accuracy of these parameters was determined by comparison of MC simulations with measurements. The PDDs and the lateral profiles of the MC simulation deviated from the measurements by 1% and 2%, respectively, on average. The computed simple MLC fields agreed with the EBT3 measurements with a 95% passing rate with 3%/3-mm gamma-index criterion. Additionally, in applying our model to clinical IMRT plans, we found that the MC calculations and the EBT3 measurements agreed well with a passing rate of greater than 95% on average with a 3%/3-mm gamma-index criterion. In summary, the Novalis Tx Linac head equipped with a HD-120 MLC was successfully modeled by using a Geant4 platform, and the accuracy of the Geant4 platform was successfully validated by comparisons with measurements. The MC model we have developed can be a useful tool for pretreatment quality assurance of IMRT plans and for commissioning of radiotherapy treatment planning.

Cosmic Ray Interactions in Shielding Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aguayo Navarrete, Estanislao; Kouzes, Richard T.; Ankney, Austin S.

2011-09-08

This document provides a detailed study of materials used to shield against the hadronic particles from cosmic ray showers at Earth’s surface. This work was motivated by the need for a shield that minimizes activation of the enriched germanium during transport for the MAJORANA collaboration. The materials suitable for cosmic-ray shield design are materials such as lead and iron that will stop the primary protons, and materials like polyethylene, borated polyethylene, concrete and water that will stop the induced neutrons. The interaction of the different cosmic-ray components at ground level (protons, neutrons, muons) with their wide energy range (from kilo-electronmore » volts to giga-electron volts) is a complex calculation. Monte Carlo calculations have proven to be a suitable tool for the simulation of nucleon transport, including hadron interactions and radioactive isotope production. The industry standard Monte Carlo simulation tool, Geant4, was used for this study. The result of this study is the assertion that activation at Earth’s surface is a result of the neutronic and protonic components of the cosmic-ray shower. The best material to shield against these cosmic-ray components is iron, which has the best combination of primary shielding and minimal secondary neutron production.« less

Validation of GATE Monte Carlo simulations of the GE Advance/Discovery LS PET scanners.

PubMed

Schmidtlein, C Ross; Kirov, Assen S; Nehmeh, Sadek A; Erdi, Yusuf E; Humm, John L; Amols, Howard I; Bidaut, Luc M; Ganin, Alex; Stearns, Charles W; McDaniel, David L; Hamacher, Klaus A

2006-01-01

The recently developed GATE (GEANT4 application for tomographic emission) Monte Carlo package, designed to simulate positron emission tomography (PET) and single photon emission computed tomography (SPECT) scanners, provides the ability to model and account for the effects of photon noncollinearity, off-axis detector penetration, detector size and response, positron range, photon scatter, and patient motion on the resolution and quality of PET images. The objective of this study is to validate a model within GATE of the General Electric (GE) Advance/Discovery Light Speed (LS) PET scanner. Our three-dimensional PET simulation model of the scanner consists of 12 096 detectors grouped into blocks, which are grouped into modules as per the vendor's specifications. The GATE results are compared to experimental data obtained in accordance with the National Electrical Manufactures Association/Society of Nuclear Medicine (NEMA/SNM), NEMA NU 2-1994, and NEMA NU 2-2001 protocols. The respective phantoms are also accurately modeled thus allowing us to simulate the sensitivity, scatter fraction, count rate performance, and spatial resolution. In-house software was developed to produce and analyze sinograms from the simulated data. With our model of the GE Advance/Discovery LS PET scanner, the ratio of the sensitivities with sources radially offset 0 and 10 cm from the scanner's main axis are reproduced to within 1% of measurements. Similarly, the simulated scatter fraction for the NEMA NU 2-2001 phantom agrees to within less than 3% of measured values (the measured scatter fractions are 44.8% and 40.9 +/- 1.4% and the simulated scatter fraction is 43.5 +/- 0.3%). The simulated count rate curves were made to match the experimental curves by using deadtimes as fit parameters. This resulted in deadtime values of 625 and 332 ns at the Block and Coincidence levels, respectively. The experimental peak true count rate of 139.0 kcps and the peak activity concentration of 21.5 kBq/cc were matched by the simulated results to within 0.5% and 0.1% respectively. The simulated count rate curves also resulted in a peak NECR of 35.2 kcps at 10.8 kBq/cc compared to 37.6 kcps at 10.0 kBq/cc from averaged experimental values. The spatial resolution of the simulated scanner matched the experimental results to within 0.2 mm.

A Monte Carlo Simulation for Understanding Energy Measurements of Beta Particles Detected by the UCNb Experiment

NASA Astrophysics Data System (ADS)

Feng, Chi; UCNb Collaboration

2011-10-01

It is theorized that contributions to the Fierz interference term from scalar interaction beyond the Standard Model could be detectable in the spectrum of neutron beta-decay. The UCNb experiment run at the Los Alamos Neutron Science Center aims to accurately measure the neutron beta-decay energy spectrum to detect a nonzero interference term. The instrument consists of a cubic ``integrating sphere'' calorimeter attached with up to 4 photomultiplier tubes. The inside of the calorimeter is coated with white paint and a thin UV scintillating layer made of deuterated polystyrene to contain the ultracold neutrons. A Monte Carlo simulation using the Geant4 toolkit is developed in order to provide an accurate method of energy reconstruction. Offline calibration with the Kellogg Radiation Laboratory 140 keV electron gun and conversion electron sources will be used to validate the Monte Carlo simulation to give confidence in the energy reconstruction methods and to better understand systematics in the experiment data.

MINERvA neutrino detector response measured with test beam data

DOE PAGES

Aliaga, L.; Altinok, O.; Araujo Del Castillo, C.; ...

2015-04-11

The MINERvA collaboration operated a scaled-down replica of thesolid scintillator tracking and sampling calorimeter regions of the MINERvA detector in a hadron test beam at the Fermilab Test Beam Facility. This paper reports measurements with samples of protons, pions, and electrons from 0.35 to 2.0 GeV/c momentum. The calorimetric response to protons, pions, and electrons is obtained from these data. A measurement of the parameter in Birks' law and an estimate of the tracking efficiency are extracted from the proton sample. Overall the data are well described by a Geant4-based Monte Carlo simulation of the detector and particle interactions withmore » agreements better than 4% for the calorimetric response, though some features of the data are not precisely modeled. Furthermore, these measurements are used to tune the MINERvA detector simulation and evaluate systematic uncertainties in support of the MINERvA neutrino cross-section measurement program.« less

Physics process level discrimination of detections for GATE: assessment of contamination in SPECT and spurious activity in PET.

PubMed

De Beenhouwer, Jan; Staelens, Steven; Vandenberghe, Stefaan; Verhaeghe, Jeroen; Van Holen, Roel; Rault, Erwann; Lemahieu, Ignace

2009-04-01

The GEANT4 application for tomographic emission (GATE) is one of the most detailed Monte Carlo simulation tools for SPECT and PET. It allows for realistic phantoms, complex decay schemes, and a large variety of detector geometries. However, only a fraction of the information in each particle history is available for postprocessing. In order to extend the analysis capabilities of GATE, a flexible framework was developed. This framework allows all detected events to be subdivided according to their type: In PET, true coincidences from others, and in SPECT, geometrically collimated photons from others. The framework of the authors can be applied to any isotope, phantom, and detector geometry available in GATE. It is designed to enhance the usability of GATE for the study of contamination and for the investigation of the properties of current and future prototype detectors. The authors apply the framework to a case study of Bexxar, first assuming labeling with 124I, then with 131I. It is shown that with 124I PET, results with an optimized window improve upon those with the standard window but achieve less than half of the ideal improvement. Nevertheless, 124I PET shows improved resolution compared to 131I SPECT with triple-energy-window scatter correction.

NEURAL NETWORK MODELLING OF CARDIAC DOSE CONVERSION COEFFICIENT FOR ARBITRARY X-RAY SPECTRA.

PubMed

Kadri, O; Manai, K

2016-12-01

In this article, an approach to compute the dose conversion coefficients (DCCs) is described for the computational voxel phantom 'High-Definition Reference Korean-Man' (HDRK-Man) using artificial neural networks (ANN). For this purpose, the voxel phantom was implemented into the Monte Carlo (MC) transport toolkit GEANT4, and the DCCs for more than 30 tissues and organs, due to a broad parallel beam of monoenergetic photons with energy ranging from 15 to 150 keV by a step of 5 keV, were calculated. To study the influence of patient size on DCC values, DCC calculation was performed, for a representative body size population, using five different sizes covering the range of 80-120 % magnification of the original HDRK-Man. The focus of the present study was on the computation of DCC for the human heart. ANN calculation and MC simulation results were compared, and good agreement was observed showing that ANNs can be used as an efficient tool for modelling DCCs for the computational voxel phantom. ANN approach appears to be a significant advance over the time-consuming MC methods for DCC calculation. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Discharge rate measurements for Micromegas detectors in the presence of a longitudinal magnetic field

NASA Astrophysics Data System (ADS)

Moreno, B.; Aune, S.; Ball, J.; Charles, G.; Giganon, A.; Konczykowski, P.; Lahonde-Hamdoun, C.; Moutarde, H.; Procureur, S.; Sabatié, F.

2011-10-01

We present first discharge rate measurements for Micromegas detectors in the presence of a high longitudinal magnetic field in the GeV kinematical region. Measurements were performed by using two Micromegas detectors and a photon beam impinging a CH 2 target in the Hall B of the Jefferson Laboratory. One detector was equipped with an additional GEM foil, and a reduction of the discharge probability by two orders of magnitude compared to the stand-alone Micromegas was observed. The detectors were placed in the FROST solenoid providing a longitudinal magnetic field up to 5 T. It allowed for precise measurements of the discharge probability dependence with a diffusion-reducing magnetic field. Between 0 and 5 T, the discharge probability increased by a factor of 10 for polar angles between 19° and 34°. A GEANT4-based simulation developed for sparking rate calculation was calibrated against these data in order to predict the sparking rate in a high longitudinal magnetic field environment. This simulation is then used to investigate the possible use of Micromegas in the Forward Vertex Tracker (FVT) of the future CLAS12 spectrometer. In the case of the FVT a sparking rate of 1 Hz per detector was obtained at the anticipated CLAS12 luminosity.

Application of Geant4 simulation for analysis of soil carbon inelastic neutron scattering measurements

USDA-ARS?s Scientific Manuscript database

Inelastic neutron scattering (INS) was applied to determine soil carbon content. Due to non-uniform soil carbon depth distribution, the correlation between INS signals with some soil carbon content parameter is not obvious; however, a proportionality between INS signals and average carbon weight per...

Applying Monte-Carlo simulations to optimize an inelastic neutron scattering system for soil carbon analysis

USDA-ARS?s Scientific Manuscript database

Computer Monte-Carlo (MC) simulations (Geant4) of neutron propagation and acquisition of gamma response from soil samples was applied to evaluate INS system performance characteristic [sensitivity, minimal detectable level (MDL)] for soil carbon measurement. The INS system model with best performanc...

Qudit-Basis Universal Quantum Computation Using χ^{(2)} Interactions.

PubMed

Niu, Murphy Yuezhen; Chuang, Isaac L; Shapiro, Jeffrey H

2018-04-20

We prove that universal quantum computation can be realized-using only linear optics and χ^{(2)} (three-wave mixing) interactions-in any (n+1)-dimensional qudit basis of the n-pump-photon subspace. First, we exhibit a strictly universal gate set for the qubit basis in the one-pump-photon subspace. Next, we demonstrate qutrit-basis universality by proving that χ^{(2)} Hamiltonians and photon-number operators generate the full u(3) Lie algebra in the two-pump-photon subspace, and showing how the qutrit controlled-Z gate can be implemented with only linear optics and χ^{(2)} interactions. We then use proof by induction to obtain our general qudit result. Our induction proof relies on coherent photon injection or subtraction, a technique enabled by χ^{(2)} interaction between the encoding modes and ancillary modes. Finally, we show that coherent photon injection is more than a conceptual tool, in that it offers a route to preparing high-photon-number Fock states from single-photon Fock states.

Measurement of inclusive radiative B-meson decay B decaying to X(S) meson-gamma

NASA Astrophysics Data System (ADS)

Ozcan, Veysi Erkcan

Radiative decays of the B meson, B→ Xsgamma, proceed via virtual flavor changing neutral current processes that are sensitive to contributions from high mass scales, either within the Standard Model of electroweak interactions or beyond. In the Standard Model, these transitions are sensitive to the weak interactions of the top quark, and relatively robust predictions of the inclusive decay rate exist. Significant deviation from these predictions could be interpreted as indications for processes not included in the minimal Standard Model, like interactions of charged Higgs or SUSY particles. The analysis of the inclusive photon spectrum from B→ Xsgamma decays is rather challenging due to high backgrounds from photons emitted in the decay of mesons in B decays as well as e+e- annihilation to low mass quark and lepton pairs. Based on 88.5 million BB events collected by the BABAR detector, the photon spectrum above 1.9 GeV is presented. By comparison of the first and second moments of the photon spectrum with QCD predictions (calculated in the kinetic scheme), QCD parameters describing the bound state of the b quark in the B meson are extracted: mb=4.45+/-0.16 GeV/c2m2 p=0.65+/-0.29 GeV2 These parameters are useful input to non-perturbative QCD corrections to the semileptonic B decay rate and the determination of the CKM parameter Vub. Based on these parameters and heavy quark expansion, the full branching fraction is obtained as: BRB→X sgEg >1.6GeV=4.050.32 stat+/-0.38syst +/-0.29model x10-4. This result is in good agreement with previous measurements, the statistical and systematic errors are comparable. It is also in good agreement with the theoretical Standard Model predictions, and thus within the present errors there is no indication of any interactions not accounted for in the Standard Model. This finding implies strong constraints on physics beyond the Standard Model.

Search for a dark photon in e(+)e(-) collisions at BABAR.

PubMed

Lees, J P; Poireau, V; Tisserand, V; Grauges, E; Palano, A; Eigen, G; Stugu, B; Brown, D N; Feng, M; Kerth, L T; Kolomensky, Yu G; Lee, M J; Lynch, G; Koch, H; Schroeder, T; Hearty, C; Mattison, T S; McKenna, J A; So, R Y; Khan, A; Blinov, V E; Buzykaev, A R; Druzhinin, V P; Golubev, V B; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Todyshev, K Yu; Lankford, A J; Mandelkern, M; Dey, B; Gary, J W; Long, O; Campagnari, C; Franco Sevilla, M; Hong, T M; Kovalskyi, D; Richman, J D; West, C A; Eisner, A M; Lockman, W S; Panduro Vazquez, W; Schumm, B A; Seiden, A; Chao, D S; Cheng, C H; Echenard, B; Flood, K T; Hitlin, D G; Miyashita, T S; Ongmongkolkul, P; Porter, F C; Andreassen, R; Huard, Z; Meadows, B T; Pushpawela, B G; Sokoloff, M D; Sun, L; Bloom, P C; Ford, W T; Gaz, A; Smith, J G; Wagner, S R; Ayad, R; Toki, W H; Spaan, B; Bernard, D; Verderi, M; Playfer, S; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Fioravanti, E; Garzia, I; Luppi, E; Piemontese, L; Santoro, V; Calcaterra, A; de Sangro, R; Finocchiaro, G; Martellotti, S; Patteri, P; Peruzzi, I M; Piccolo, M; Rama, M; Zallo, A; Contri, R; Lo Vetere, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Bhuyan, B; Prasad, V; Adametz, A; Uwer, U; Lacker, H M; Dauncey, P D; Mallik, U; Chen, C; Cochran, J; Prell, S; Ahmed, H; Gritsan, A V; Arnaud, N; Davier, M; Derkach, D; Grosdidier, G; Le Diberder, F; Lutz, A M; Malaescu, B; Roudeau, P; Stocchi, A; Wormser, G; Lange, D J; Wright, D M; Coleman, J P; Fry, J R; Gabathuler, E; Hutchcroft, D E; Payne, D J; Touramanis, C; Bevan, A J; Di Lodovico, F; Sacco, R; Cowan, G; Bougher, J; Brown, D N; Davis, C L; Denig, A G; Fritsch, M; Gradl, W; Griessinger, K; Hafner, A; Schubert, K R; Barlow, R J; Lafferty, G D; Cenci, R; Hamilton, B; Jawahery, A; Roberts, D A; Cowan, R; Sciolla, G; Cheaib, R; Patel, P M; Robertson, S H; Neri, N; Palombo, F; Cremaldi, L; Godang, R; Sonnek, P; Summers, D J; Simard, M; Taras, P; De Nardo, G; Onorato, G; Sciacca, C; Martinelli, M; Raven, G; Jessop, C P; LoSecco, J M; Honscheid, K; Kass, R; Feltresi, E; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simi, G; Simonetto, F; Stroili, R; Akar, S; Ben-Haim, E; Bomben, M; Bonneaud, G R; Briand, H; Calderini, G; Chauveau, J; Leruste, Ph; Marchiori, G; Ocariz, J; Biasini, M; Manoni, E; Pacetti, S; Rossi, A; Angelini, C; Batignani, G; Bettarini, S; Carpinelli, M; Casarosa, G; Cervelli, A; Chrzaszcz, M; Forti, F; Giorgi, M A; Lusiani, A; Oberhof, B; Paoloni, E; Perez, A; Rizzo, G; Walsh, J J; Lopes Pegna, D; Olsen, J; Smith, A J S; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Li Gioi, L; Pilloni, A; Piredda, G; Bünger, C; Dittrich, S; Grünberg, O; Hartmann, T; Hess, M; Leddig, T; Voß, C; Waldi, R; Adye, T; Olaiya, E O; Wilson, F F; Emery, S; Vasseur, G; Anulli, F; Aston, D; Bard, D J; Cartaro, C; Convery, M R; Dorfan, J; Dubois-Felsmann, G P; Dunwoodie, W; Ebert, M; Field, R C; Fulsom, B G; Graham, M T; Hast, C; Innes, W R; Kim, P; Leith, D W G S; Lewis, P; Lindemann, D; Luitz, S; Luth, V; Lynch, H L; MacFarlane, D B; Muller, D R; Neal, H; Perl, M; Pulliam, T; Ratcliff, B N; Roodman, A; Salnikov, A A; Schindler, R H; Snyder, A; Su, D; Sullivan, M K; Va'vra, J; Wisniewski, W J; Wulsin, H W; Purohit, M V; White, R M; Wilson, J R; Randle-Conde, A; Sekula, S J; Bellis, M; Burchat, P R; Puccio, E M T; Alam, M S; Ernst, J A; Gorodeisky, R; Guttman, N; Peimer, D R; Soffer, A; Spanier, S M; Ritchie, J L; Ruland, A M; Schwitters, R F; Wray, B C; Izen, J M; Lou, X C; Bianchi, F; De Mori, F; Filippi, A; Gamba, D; Lanceri, L; Vitale, L; Martinez-Vidal, F; Oyanguren, A; Villanueva-Perez, P; Albert, J; Banerjee, Sw; Beaulieu, A; Bernlochner, F U; Choi, H H F; King, G J; Kowalewski, R; Lewczuk, M J; Lueck, T; Nugent, I M; Roney, J M; Sobie, R J; Tasneem, N; Gershon, T J; Harrison, P F; Latham, T E; Band, H R; Dasu, S; Pan, Y; Prepost, R; Wu, S L

2014-11-14

Dark sectors charged under a new Abelian interaction have recently received much attention in the context of dark matter models. These models introduce a light new mediator, the so-called dark photon (A^{'}), connecting the dark sector to the standard model. We present a search for a dark photon in the reaction e^{+}e^{-}→γA^{'}, A^{'}→e^{+}e^{-}, μ^{+}μ^{-} using 514  fb^{-1} of data collected with the BABAR detector. We observe no statistically significant deviations from the standard model predictions, and we set 90% confidence level upper limits on the mixing strength between the photon and dark photon at the level of 10^{-4}-10^{-3} for dark photon masses in the range 0.02-10.2  GeV. We further constrain the range of the parameter space favored by interpretations of the discrepancy between the calculated and measured anomalous magnetic moment of the muon.

Quantum state detection and state preparation based on cavity-enhanced nonlinear interaction of atoms with single photon

NASA Astrophysics Data System (ADS)

Hosseini, Mahdi

Our ability to engineer quantum states of light and matter has significantly advanced over the past two decades, resulting in the production of both Gaussian and non-Gaussian optical states. The resulting tailored quantum states enable quantum technologies such as quantum optical communication, quantum sensing as well as quantum photonic computation. The strong nonlinear light-atom interaction is the key to deterministic quantum state preparation and quantum photonic processing. One route to enhancing the usually weak nonlinear light-atom interactions is to approach the regime of cavity quantum electrodynamics (cQED) interaction by means of high finesse optical resonators. I present results from the MIT experiment of large conditional cross-phase modulation between a signal photon, stored inside an atomic quantum memory, and a control photon that traverses a high-finesse optical cavity containing the atomic memory. I also present a scheme to probabilistically change the amplitude and phase of a signal photon qubit to, in principle, arbitrary values by postselection on a control photon that has interacted with that state. Notably, small changes of the control photon polarization measurement basis by few degrees can substantially change the amplitude and phase of the signal state. Finally, I present our ongoing effort at Purdue to realize similar peculiar quantum phenomena at the single photon level on chip scale photonic systems.

SU-F-T-684: Analysis of Cherenkov Excitation in Tissue and the Feasibility of Cherenkov Excited Photodynamic Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saunders, Sara L; Andreozzi, Jacqueline M; Pogue, Brian W

Purpose: The irradiation of photodynamic agents with radiotherapy beams has been demonstrated to enhance tumor killing in various studies, and one proposed mechanism is the optical fluence of Cherenkov emission activating the photosensitizer. This mechanism is explored in Monte Carlo simulations of fluence as well as laboratory measurements of fluence and radical oxygen species. Methods: Simulations were completed using GAMOS/GEANT4 with a 6 MV photon beam in tissue. The effects of blood vessel diameter, blood oxygen saturation, and beam size were examined, recording spectral fluence. Experiments were carried out in solutions of photosensitizer and phantoms. Results: Cherenkov produced by amore » 100×100um{sup 2} 6 MV beam resulted in fluence of less than 1 nJ/cm{sup 2}/Gy per 1 nm wavelength. At this microscopic level, differences in absorption of blood and water in the tissue affected the fluence spectrum, but variation in blood oxygenation had little effect. Light in tissue resulting from larger (10mm ×10mm) 6 MV beams had greater fluence due to light transport and elastic scattering of optical photons, but this transport process also resulted in higher absorption shifts. Therefore, the spectrum produced by a microscopic beam was weighted more heavily in UV/blue wavelengths than the spectrum at the macroscopic level. At the macroscopic level, the total fluence available for absorption by Verteporfin (BPD) in tissue approached uJ/cm{sup 2} for a high radiation dose, indicating that photodynamic activation seems unlikely. Tissue phantom confirmation of these light levels supported this observation, and photosensitization measurements with a radical oxygen species reporter are ongoing. Conclusion: Simulations demonstrated that fluence produced by Cherenkov in tissue by 6 MV photon beams at typical radiotherapy doses appears insufficient to activate photosensitizers to the level required for threshold effects, yet this disagrees with published biological experiments. Experimental validation in tissue phantoms and cell studies are ongoing to clarify this discrepancy. Funding from NIH grant R01CA109558.« less

SU-E-I-85: Absorbed Dose Estimation for a Commercially Available MicroCT Scanner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lau, A; Ahmad, S; Chen, Y

2015-06-15

Purpose: To quantify the simulated absorbed dose delivered for a typical scan from a commercially available microCT scanner in order to aid in the dose estimation. Methods: The simulations were conducted using the Geant4 Monte Carlo Toolkit (version 10) with the standard electromagnetic classes. The Quantum FX microCT scanner (PerkinElmer, Waltham, MA) was modeled incorporating the energy fluence and angular distributions of generated photons, spatial dimensions of nominal source-to-object and source-to-detector distances. The energy distribution was measured using a spectrometer (X-123CdTe, Amptek Inc., Bedford, USA) with a 300 angular spread from the source for the 90 kVp X-ray beams withmore » no additional filtration. The nominal distances from the source to object consisted of three setups: 154.0 mm, 104.0 mm, and 51.96 mm. Our simulations recorded the dose absorbed in a cylindrical phantom of PMMA with a fixed length of 2 cm and varying radii (10, 20, 30 and 40 mm) using 100 million incident photons. The averaged absorbed dose in the object was then quantified for all setups. An exposure measurement of 417 mR was taken using a Radcal 9095 system utilizing 10×9–180 ion chamber with the given technique of 90 kVp, 63 μA, and 12 s. The exposure rate was also simulated with same setup to calculate the conversion factor of the beam current and the number of incident photons. Results: For a typical cone-beam scan with non-filtered 90kVp, the dose coefficients (the absorbed dose per mAs) were 2.614, 2.549 and 2.467 μGy/mAs under source to object distance of 104 mm for the object diameters of 10 mm, 20 mm and 30 mm, respectively. Conclusion: A look-up table was developed where an investigator can estimate the delivered dose using this particular microCT given the scanning protocol (kVp and mAs) as well as the size of the scanned object.« less

Photonic Microresonators from Charge Transfer in Polymer Particles: Toward Enhanced and Tunable Two-Photon Emission.

PubMed

Vattikunta, Radhika; Venkatakrishnarao, Dasari; Sahoo, Chakradhar; Naraharisetty, Sri Ram Gopal; Narayana Rao, Desai; Müllen, Klaus; Chandrasekar, Rajadurai

2018-05-16

Novel photonic microresonators with enhanced nonlinear optical (NLO) intensity are fabricated from polymer particles. As an additional advantage, they offer band gap tunability from the visible to near-infrared regions. A special protocol including (i) copolymerization of 4-(1-pyrenyl)-styrene, styrene, and 1,4-divinylbenzene, (ii) extraction of a dispersible and partly dissolvable, lightly cross-linked polymer network (PN), and (iii) treatment of the blue-emitting PN with electron acceptor (A) molecules such as 1,2,4,5-tetracyanobenzene (TCNB) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) furnishes orange- and red-emitting D-A charge-transfer (CT) complexes with the pendant pyrene units. These complexes, here named PN-TCNB and PN-TCNQ, respectively, precipitate as microparticles upon the addition of water and subsequent ultrasonication. Upon electronic excitation, these spherical microparticles act as whispering-gallery-mode resonators by displaying optical resonances in the photoluminescence (PL) spectra because of light confinement. Further, the trapped incident light increases the light-matter interaction and thereby enhances the PL intensity, including the two-photon luminescence. The described protocol for polymer-based CT microresonators with tunable NLO emissions holds promise for a myriad of photonic applications.

Photonic Aharonov–Bohm effect in photon–phonon interactions

PubMed Central

Li, Enbang; Eggleton, Benjamin J.; Fang, Kejie; Fan, Shanhui

2014-01-01

The Aharonov–Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov–Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov–Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon–phonon interactions to demonstrate that photonic Aharonov–Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon–phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov–Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential. PMID:24476790

Performance of GeantV EM Physics Models

NASA Astrophysics Data System (ADS)

Amadio, G.; Ananya, A.; Apostolakis, J.; Aurora, A.; Bandieramonte, M.; Bhattacharyya, A.; Bianchini, C.; Brun, R.; Canal, P.; Carminati, F.; Cosmo, G.; Duhem, L.; Elvira, D.; Folger, G.; Gheata, A.; Gheata, M.; Goulas, I.; Iope, R.; Jun, S. Y.; Lima, G.; Mohanty, A.; Nikitina, T.; Novak, M.; Pokorski, W.; Ribon, A.; Seghal, R.; Shadura, O.; Vallecorsa, S.; Wenzel, S.; Zhang, Y.

2017-10-01

The recent progress in parallel hardware architectures with deeper vector pipelines or many-cores technologies brings opportunities for HEP experiments to take advantage of SIMD and SIMT computing models. Launched in 2013, the GeantV project studies performance gains in propagating multiple particles in parallel, improving instruction throughput and data locality in HEP event simulation on modern parallel hardware architecture. Due to the complexity of geometry description and physics algorithms of a typical HEP application, performance analysis is indispensable in identifying factors limiting parallel execution. In this report, we will present design considerations and preliminary computing performance of GeantV physics models on coprocessors (Intel Xeon Phi and NVidia GPUs) as well as on mainstream CPUs.

Shielding implications for secondary neutrons and photons produced within the patient during IMPT.

PubMed

DeMarco, J; Kupelian, P; Santhanam, A; Low, D

2013-07-01

Intensity modulated proton therapy (IMPT) uses a combination of computer controlled spot scanning and spot-weight optimized planning to irradiate the tumor volume uniformly. In contrast to passive scattering systems, secondary neutrons and photons produced from inelastic proton interactions within the patient represent the major source of emitted radiation during IMPT delivery. Various published studies evaluated the shielding considerations for passive scattering systems but did not directly address secondary neutron production from IMPT and the ambient dose equivalent on surrounding occupational and nonoccupational work areas. Thus, the purpose of this study was to utilize Monte Carlo simulations to evaluate the energy and angular distributions of secondary neutrons and photons following inelastic proton interactions within a tissue-equivalent phantom for incident proton spot energies between 70 and 250 MeV. Monte Carlo simulation methods were used to calculate the ambient dose equivalent of secondary neutrons and photons produced from inelastic proton interactions in a tissue-equivalent phantom. The angular distribution of emitted neutrons and photons were scored as a function of incident proton energy throughout a spherical annulus at 1, 2, 3, 4, and 5 m from the phantom center. Appropriate dose equivalent conversion factors were applied to estimate the total ambient dose equivalent from secondary neutrons and photons. A reference distance of 1 m from the center of the patient was used to evaluate the mean energy distribution of secondary neutrons and photons and the resulting ambient dose equivalent. For an incident proton spot energy of 250 MeV, the total ambient dose equivalent (3.6 × 10(-3) mSv per proton Gy) was greatest along the direction of the incident proton spot (0°-10°) with a mean secondary neutron energy of 71.3 MeV. The dose equivalent decreased by a factor of 5 in the backward direction (170°-180°) with a mean energy of 4.4 MeV. An 8 × 8 × 8 cm(3) volumetric spot distribution (5 mm FWHM spot size, 4 mm spot spacing) optimized to produce a uniform dose distribution results in an ambient dose equivalent of 4.5 × 10(-2) mSv per proton Gy in the forward direction. This work evaluated the secondary neutron and photon emission due to monoenergetic proton spots between 70 and 250 MeV, incident on a tissue equivalent phantom. Example calculations were performed to estimate concrete shield thickness based upon appropriate workload and shielding design assumptions. Although lower than traditional passive scattered proton therapy systems, the ambient dose equivalent from secondary neutrons produced by the patient during IMPT can be significant relative to occupational and nonoccupational workers in the vicinity of the treatment vault. This work demonstrates that Monte Carlo simulations are useful as an initial planning tool for studying the impact of the treatment room and maze design on surrounding occupational and nonoccupational work areas.

Deterministic photon-emitter coupling in chiral photonic circuits.

PubMed

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Deterministic photon-emitter coupling in chiral photonic circuits

NASA Astrophysics Data System (ADS)

Söllner, Immo; Mahmoodian, Sahand; Hansen, Sofie Lindskov; Midolo, Leonardo; Javadi, Alisa; Kiršanskė, Gabija; Pregnolato, Tommaso; El-Ella, Haitham; Lee, Eun Hye; Song, Jin Dong; Stobbe, Søren; Lodahl, Peter

2015-09-01

Engineering photon emission and scattering is central to modern photonics applications ranging from light harvesting to quantum-information processing. To this end, nanophotonic waveguides are well suited as they confine photons to a one-dimensional geometry and thereby increase the light-matter interaction. In a regular waveguide, a quantum emitter interacts equally with photons in either of the two propagation directions. This symmetry is violated in nanophotonic structures in which non-transversal local electric-field components imply that photon emission and scattering may become directional. Here we show that the helicity of the optical transition of a quantum emitter determines the direction of single-photon emission in a specially engineered photonic-crystal waveguide. We observe single-photon emission into the waveguide with a directionality that exceeds 90% under conditions in which practically all the emitted photons are coupled to the waveguide. The chiral light-matter interaction enables deterministic and highly directional photon emission for experimentally achievable on-chip non-reciprocal photonic elements. These may serve as key building blocks for single-photon optical diodes, transistors and deterministic quantum gates. Furthermore, chiral photonic circuits allow the dissipative preparation of entangled states of multiple emitters for experimentally achievable parameters, may lead to novel topological photon states and could be applied for directional steering of light.

Modeling the TrueBeam linac using a CAD to Geant4 geometry implementation: Dose and IAEA-compliant phase space calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Constantin, Magdalena; Perl, Joseph; LoSasso, Tom

2011-07-15

Purpose: To create an accurate 6 MV Monte Carlo simulation phase space for the Varian TrueBeam treatment head geometry imported from cad (computer aided design) without adjusting the input electron phase space parameters. Methods: geant4 v4.9.2.p01 was employed to simulate the 6 MV beam treatment head geometry of the Varian TrueBeam linac. The electron tracks in the linear accelerator were simulated with Parmela, and the obtained electron phase space was used as an input to the Monte Carlo beam transport and dose calculations. The geometry components are tessellated solids included in geant4 as gdml (generalized dynamic markup language) files obtainedmore » via STEP (standard for the exchange of product) export from Pro/Engineering, followed by STEP import in Fastrad, a STEP-gdml converter. The linac has a compact treatment head and the small space between the shielding collimator and the divergent arc of the upper jaws forbids the implementation of a plane for storing the phase space. Instead, an IAEA (International Atomic Energy Agency) compliant phase space writer was implemented on a cylindrical surface. The simulation was run in parallel on a 1200 node Linux cluster. The 6 MV dose calculations were performed for field sizes varying from 4 x 4 to 40 x 40 cm{sup 2}. The voxel size for the 60x60x40 cm{sup 3} water phantom was 4x4x4 mm{sup 3}. For the 10x10 cm{sup 2} field, surface buildup calculations were performed using 4x4x2 mm{sup 3} voxels within 20 mm of the surface. Results: For the depth dose curves, 98% of the calculated data points agree within 2% with the experimental measurements for depths between 2 and 40 cm. For depths between 5 and 30 cm, agreement within 1% is obtained for 99% (4x4), 95% (10x10), 94% (20x20 and 30x30), and 89% (40x40) of the data points, respectively. In the buildup region, the agreement is within 2%, except at 1 mm depth where the deviation is 5% for the 10x10 cm{sup 2} open field. For the lateral dose profiles, within the field size for fields up to 30x30 cm{sup 2}, the agreement is within 2% for depths up to 10 cm. At 20 cm depth, the in-field maximum dose difference for the 30x30 cm{sup 2} open field is within 4%, while the smaller field sizes agree within 2%. Outside the field size, agreement within 1% of the maximum dose difference is obtained for all fields. The calculated output factors varied from 0.938{+-}0.015 for the 4x4 cm{sup 2} field to 1.088{+-}0.024 for the 40x40 cm{sup 2} field. Their agreement with the experimental output factors is within 1%. Conclusions: The authors have validated a geant4 simulated IAEA-compliant phase space of the TrueBeam linac for the 6 MV beam obtained using a high accuracy geometry implementation from cad. These files are publicly available and can be used for further research.« less

Changing optical band structure with single photons

NASA Astrophysics Data System (ADS)

Albrecht, Andreas; Caneva, Tommaso; Chang, Darrick E.

2017-11-01

Achieving strong interactions between individual photons enables a wide variety of exciting possibilities in quantum information science and many-body physics. Cold atoms interfaced with nanophotonic structures have emerged as a platform to realize novel forms of nonlinear interactions. In particular, when atoms are coupled to a photonic crystal waveguide, long-range atomic interactions can arise that are mediated by localized atom-photon bound states. We theoretically show that in such a system, the absorption of a single photon can change the band structure for a subsequent photon. This occurs because the first photon affects the atoms in the chain in an alternating fashion, thus leading to an effective period doubling of the system and a new optical band structure for the composite atom-nanophotonic system. We demonstrate how this mechanism can be engineered to realize a single-photon switch, where the first incoming photon switches the system from being highly transmissive to highly reflective, and analyze how signatures can be observed via non-classical correlations of the outgoing photon field.

Coupled-resonator waveguide perfect transport single-photon by interatomic dipole-dipole interaction

NASA Astrophysics Data System (ADS)

Yan, Guo-an; Lu, Hua; Qiao, Hao-xue; Chen, Ai-xi; Wu, Wan-qing

2018-06-01

We theoretically investigate single-photon coherent transport in a one-dimensional coupled-resonator waveguide coupled to two quantum emitters with dipole-dipole interactions. The numerical simulations demonstrate that the transmission spectrum of the photon depends on the two atoms dipole-dipole interactions and the photon-atom couplings. The dipole-dipole interactions may change the dip positions in the spectra and the coupling strength may broaden the frequency band width in the transmission spectrum. We further demonstrate that the typical transmission spectra split into two dips due to the dipole-dipole interactions. This phenomenon may be used to manufacture new quantum waveguide devices.

Backscatter dose effects for high atomic number materials being irradiated in the presence of a magnetic field: A Monte Carlo study for the MRI linac

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmad, Syed Bilal

Purpose: To quantify and explain the backscatter dose effects for clinically relevant high atomic number materials being irradiated in the presence of a 1.5 T transverse magnetic field. Methods: Interface effects were investigated using Monte Carlo simulation techniques. We used GPUMCD (v5.1) and GEANT4 (v10.1) for this purpose. GPUMCD is a commercial software written for the Elekta AB, MRI linac. Dose was scored using GPUMCD in cubic voxels of side 1 and 0.5 mm, in two different virtual phantoms of dimensions 20 × 20 × 20 cm and 5 × 5 × 13.3 cm, respectively. A photon beam was generatedmore » from a point 143.5 cm away from the isocenter with energy distribution sampled from a histogram representing the true Elekta, MRI linac photon spectrum. A slab of variable thickness and position containing either bone, aluminum, titanium, stainless steel, or one of the two different dental filling materials was inserted as an inhomogeneity in the 20 × 20 × 20 cm phantom. The 5 × 5 × 13.3 cm phantom was used as a clinical test case in order to explain the dose perturbation effects for a head and neck cancer patient. The back scatter dose factor (BSDF) was defined as the ratio of the doses at a given depth with and without the presence of the inhomogeneity. Backscattered electron fluence was calculated at the inhomogeneity interface using GEANT4. A 1.5 T magnetic field was applied perpendicular to the direction of the beam in both phantoms, identical to the geometry in the Elekta MRI linac. Results: With the application of a 1.5 T magnetic field, all the BSDF’s were reduced by 12%–47%, compared to the no magnetic field case. The corresponding backscattered electron fluence at the interface was also reduced by 45%–64%. The reduction in the BSDF at the interface, due to the application of the magnetic field, is manifested in a different manner for each material. In the case of bone, the dose drops at the interface contrary to the expected increase when no magnetic field is applied. In the case of aluminum, the dose at the interface is the same with and without the presence of the aluminum. For all of the other materials the dose increases at the interface. Conclusions: The reduction in dose at the interface, in the presence of the magnetic field, is directly related to the reduction in backscattered electron fluence. This reduction occurs due to two different reasons. First, the electron spectrum hitting the interface is changed when the magnetic field is turned on, which results in changes in the electron scattering probability. Second, some electrons that have curved trajectories due to the presence of the magnetic field are absorbed by the higher density side of the interface and no longer contribute to the backscattered electron fluence.« less

Comparison of TG‐43 dosimetric parameters of brachytherapy sources obtained by three different versions of MCNP codes

PubMed Central

Zaker, Neda; Sina, Sedigheh; Koontz, Craig; Meigooni1, Ali S.

2016-01-01

Monte Carlo simulations are widely used for calculation of the dosimetric parameters of brachytherapy sources. MCNP4C2, MCNP5, MCNPX, EGS4, EGSnrc, PTRAN, and GEANT4 are among the most commonly used codes in this field. Each of these codes utilizes a cross‐sectional library for the purpose of simulating different elements and materials with complex chemical compositions. The accuracies of the final outcomes of these simulations are very sensitive to the accuracies of the cross‐sectional libraries. Several investigators have shown that inaccuracies of some of the cross section files have led to errors in  125I and  103Pd parameters. The purpose of this study is to compare the dosimetric parameters of sample brachytherapy sources, calculated with three different versions of the MCNP code — MCNP4C, MCNP5, and MCNPX. In these simulations for each source type, the source and phantom geometries, as well as the number of the photons, were kept identical, thus eliminating the possible uncertainties. The results of these investigations indicate that for low‐energy sources such as  125I and  103Pd there are discrepancies in gL(r) values. Discrepancies up to 21.7% and 28% are observed between MCNP4C and other codes at a distance of 6 cm for  103Pd and 10 cm for  125I from the source, respectively. However, for higher energy sources, the discrepancies in gL(r) values are less than 1.1% for  192Ir and less than 1.2% for  137Cs between the three codes. PACS number(s): 87.56.bg PMID:27074460

Proton deflectometry of laser-driven relativistic electron jet from thin foil target

NASA Astrophysics Data System (ADS)

Huang, Chengkun; Palaniyappan, S.; Gautier, D. C.; Johnson, R. P.; Shimada, T.; Fernandez, J. C.; Tsung, F. S.; Mori, W. B.

2017-10-01

Near critical density relativistic electron jets from laser solid interaction carry currents approaching the Alfvén-limit and tens of kilo-Tesla magnetic fields. Such jets are often found in kinetic simulations with low areal density targets, but have not been confirmed experimentally. They may be used for X/gamma-ray generation and is also important for the understanding of post-transparency plasma dynamics. With a short-pulse probe beam at the Trident laser facility, we employed proton deflectometry to infer the jet's properties, structure and the long-time dynamics. We develop corresponding GEANT4 simulation model of the proton deflectometry, with input from the kinetic PIC simulations in 2D and quasi-3D geometry, to compare with the experimental radiography images. Detail comparison of the experimental and simulation features in the deflectometry will be discussed. Work supported by the LDRD program at LANL.

Development of CANDLES low background HPGe detector and half-life measurement of 180Tam

NASA Astrophysics Data System (ADS)

Chan, W. M.; Kishimoto, T.; Umehara, S.; Matsuoka, K.; Suzuki, K.; Yoshida, S.; Nakajima, K.; Iida, T.; Fushimi, K.; Nomachi, M.; Ogawa, I.; Tamagawa, Y.; Hazama, R.; Takemoto, Y.; Nakatani, N.; Takihira, Y.; Tozawa, M.; Kakubata, H.; Trang, V. T. T.; Ohata, T.; Tetsuno, K.; Maeda, T.; Khai, B. T.; Li, X. L.; Batpurev, T.

2018-01-01

A low background HPGe detector system was developed at CANDLES Experimental Hall for multipurpose use. Various low background techniques were employed, including hermatic shield design, radon gas suppression, and background reduction analysis. A new pulse shape discrimination (PSD) method was specially created for coaxial Ge detector. Using this PSD method, microphonics noise and background event at low energy region less than 200 keV can be rejected effectively. Monte Carlo simulation by GEANT4 was performed to acquire the detection efficiency and study the interaction of gamma-rays with detector system. For rare decay measurement, the detector was utilized to detect the nature's most stable isomer tantalum-180m (180Tam) decay. Two phases of tantalum physics run were completed with total livetime of 358.2 days, which Phase II has upgraded shield configuration. The world most stringent half-life limit of 180Tam has been successfully achieved.

Can muon-induced backgrounds explain the DAMA data?

NASA Astrophysics Data System (ADS)

Klinger, Joel; Kudryavtsev, Vitaly A.

2016-05-01

We present an accurate simulation of the muon-induced background in the DAMA/LIBRA experiment. Muon sampling underground has been performed using the MUSIC/MUSUN codes and subsequent interactions in the rock around the DAMA/LIBRA detector cavern and the experimental setup including shielding, have been simulated with GEANT4.9.6. In total we simulate the equivalent of 20 years of muon data. We have calculated the total muon-induced neutron flux in the DAMA/LIBRA detector cavern as Φμ n = 1.0 × 10-9 cm-2s-1, which is consistent with other simulations. After selecting events which satisfy the DAMA/LIBRA signal criteria, our simulation predicts 3.49 × 10-5 cpd/kg/keV which accounts for less than 0.3% of the DAMA/LIBRA modulation amplitude. We conclude from our work that muon-induced backgrounds are unable to contribute to the observed signal modulation.

Large-Angle Scattering of Multi-GeV Muons on Thin Lead Targets

NASA Astrophysics Data System (ADS)

Longhin, A.; Paoloni, A.; Pupilli, F.

2015-10-01

The probability of large-angle scattering for multi-GeV muons in lead targets with a thickness of O(10 - 1) radiation lengths is studied. The new estimates presented here are based both on simulation programs (GEANT4 libraries) and theoretical calculations. In order to validate the results provided by simulation, a comparison is drawn with experimental data from the literature. This study is particularly relevant when applied to muons originating from νμ CC interactions of CNGS beam neutrinos. In that circumstance the process under study represents the dominant background for the νμ → ντ search in the τ→ μ channel for the OPERA experiment at LNGS. Finally we also investigate, in the CNGS context, possible contributions from the muon photo-nuclear process which might in principle also produce a large-angle muon scattering signature in the detector.

2D dose distribution images of a hybrid low field MRI-γ detector

NASA Astrophysics Data System (ADS)

Abril, A.; Agulles-Pedrós, L.

2016-07-01

The proposed hybrid system is a combination of a low field MRI and dosimetric gel as a γ detector. The readout system is based on the polymerization process induced by the gel radiation. A gel dose map is obtained which represents the functional part of hybrid image alongside with the anatomical MRI one. Both images should be taken while the patient with a radiopharmaceutical is located inside the MRI system with a gel detector matrix. A relevant aspect of this proposal is that the dosimetric gel has never been used to acquire medical images. The results presented show the interaction of the 99mTc source with the dosimetric gel simulated in Geant4. The purpose was to obtain the planar γ 2D-image. The different source configurations are studied to explore the ability of the gel as radiation detector through the following parameters; resolution, shape definition and radio-pharmaceutical concentration.

Thick-foils activation technique for neutron spectrum unfolding with the MINUIT routine-Comparison with GEANT4 simulations

NASA Astrophysics Data System (ADS)

Vagena, E.; Theodorou, K.; Stoulos, S.

2018-04-01

Neutron activation technique has been applied using a proposed set of twelve thick metal foils (Au, As, Cd, In, Ir, Er, Mn, Ni, Se, Sm, W, Zn) for off-site measurements to obtain the neutron spectrum over a wide energy range (from thermal up to a few MeV) in intense neutron-gamma mixed fields such as around medical Linacs. The unfolding procedure takes into account the activation rates measured using thirteen (n , γ) and two (n , p) reactions without imposing a guess solution-spectrum. The MINUIT minimization routine unfolds a neutron spectrum that is dominated by fast neutrons (70%) peaking at 0.3 MeV, while the thermal peak corresponds to the 15% of the total neutron fluence equal to the epithermal-resonances area. The comparison of the unfolded neutron spectrum against the simulated one with the GEANT4 Monte-Carlo code shows a reasonable agreement within the measurement uncertainties. Therefore, the proposed set of activation thick-foils could be a useful tool in order to determine low flux neutrons spectrum in intense mixed field.

Internal dosimetry through GATE simulations of preclinical radiotherapy using a melanin-targeting ligand

NASA Astrophysics Data System (ADS)

Perrot, Y.; Degoul, F.; Auzeloux, P.; Bonnet, M.; Cachin, F.; Chezal, J. M.; Donnarieix, D.; Labarre, P.; Moins, N.; Papon, J.; Rbah-Vidal, L.; Vidal, A.; Miot-Noirault, E.; Maigne, L.

2014-05-01

The GATE Monte Carlo simulation platform based on the Geant4 toolkit is under constant improvement for dosimetric calculations. In this study, we explore its use for the dosimetry of the preclinical targeted radiotherapy of melanoma using a new specific melanin-targeting radiotracer labeled with iodine 131. Calculated absorbed fractions and S values for spheres and murine models (digital and CT-scan-based mouse phantoms) are compared between GATE and EGSnrc Monte Carlo codes considering monoenergetic electrons and the detailed energy spectrum of iodine 131. The behavior of Geant4 standard and low energy models is also tested. Following the different authors’ guidelines concerning the parameterization of electron physics models, this study demonstrates an agreement of 1.2% and 1.5% with EGSnrc, respectively, for the calculation of S values for small spheres and mouse phantoms. S values calculated with GATE are then used to compute the dose distribution in organs of interest using the activity distribution in mouse phantoms. This study gives the dosimetric data required for the translation of the new treatment to the clinic.

A fast and complete GEANT4 and ROOT Object-Oriented Toolkit: GROOT

NASA Astrophysics Data System (ADS)

Lattuada, D.; Balabanski, D. L.; Chesnevskaya, S.; Costa, M.; Crucillà, V.; Guardo, G. L.; La Cognata, M.; Matei, C.; Pizzone, R. G.; Romano, S.; Spitaleri, C.; Tumino, A.; Xu, Y.

2018-01-01

Present and future gamma-beam facilities represent a great opportunity to validate and evaluate the cross-sections of many photonuclear reactions at near-threshold energies. Monte Carlo (MC) simulations are very important to evaluate the reaction rates and to maximize the detection efficiency but, unfortunately, they can be very cputime-consuming and in some cases very hard to reproduce, especially when exploring near-threshold cross-section. We developed a software that makes use of the validated tracking GEANT4 libraries and the n-body event generator of ROOT in order to provide a fast, realiable and complete MC tool to be used for nuclear physics experiments. This tool is indeed intended to be used for photonuclear reactions at γ-beam facilities with ELISSA (ELI Silicon Strip Array), a new detector array under development at the Extreme Light Infrastructure - Nuclear Physics (ELI-NP). We discuss the results of MC simulations performed to evaluate the effects of the electromagnetic induced background, of the straggling due to the target thickness and of the resolution of the silicon detectors.

Calibration and GEANT4 Simulations of the Phase II Proton Compute Tomography (pCT) Range Stack Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uzunyan, S. A.; Blazey, G.; Boi, S.

Northern Illinois University in collaboration with Fermi National Accelerator Laboratory (FNAL) and Delhi University has been designing and building a proton CT scanner for applications in proton treatment planning. The Phase II proton CT scanner consists of eight planes of tracking detectors with two X and two Y coordinate measurements both before and after the patient. In addition, a range stack detector consisting of a stack of thin scintillator tiles, arranged in twelve eight-tile frames, is used to determine the water equivalent path length (WEPL) of each track through the patient. The X-Y coordinates and WEPL are required input formore » image reconstruction software to find the relative (proton) stopping powers (RSP) value of each voxel in the patient and generate a corresponding 3D image. In this Note we describe tests conducted in 2015 at the proton beam at the Central DuPage Hospital in Warrenville, IL, focusing on the range stack calibration procedure and comparisons with the GEANT~4 range stack simulation.« less

Radiation Damage to Nervous System: Designing Optimal Models for Realistic Neuron Morphology in Hippocampus

NASA Astrophysics Data System (ADS)

Batmunkh, Munkhbaatar; Bugay, Alexander; Bayarchimeg, Lkhagvaa; Lkhagva, Oidov

2018-02-01

The present study is focused on the development of optimal models of neuron morphology for Monte Carlo microdosimetry simulations of initial radiation-induced events of heavy charged particles in the specific types of cells of the hippocampus, which is the most radiation-sensitive structure of the central nervous system. The neuron geometry and particles track structures were simulated by the Geant4/Geant4-DNA Monte Carlo toolkits. The calculations were made for beams of protons and heavy ions with different energies and doses corresponding to real fluxes of galactic cosmic rays. A simple compartmental model and a complex model with realistic morphology extracted from experimental data were constructed and compared. We estimated the distribution of the energy deposition events and the production of reactive chemical species within the developed models of CA3/CA1 pyramidal neurons and DG granule cells of the rat hippocampus under exposure to different particles with the same dose. Similar distributions of the energy deposition events and concentration of some oxidative radical species were obtained in both the simplified and realistic neuron models.

Comparison of Geant4 multiple Coulomb scattering models with theory for radiotherapy protons

NASA Astrophysics Data System (ADS)

Makarova, Anastasia; Gottschalk, Bernard; Sauerwein, Wolfgang

2017-08-01

Usually, Monte Carlo models are validated against experimental data. However, models of multiple Coulomb scattering (MCS) in the Gaussian approximation are exceptional in that we have theories which are probably more accurate than the experiments which have, so far, been done to test them. In problems directly sensitive to the distribution of angles leaving the target, the relevant theory is the Molière/Fano/Hanson variant of Molière theory (Gottschalk et al 1993 Nucl. Instrum. Methods Phys. Res. B 74 467-90). For transverse spreading of the beam in the target itself, the theory of Preston and Koehler (Gottschalk (2012 arXiv:1204.4470)) holds. Therefore, in this paper we compare Geant4 simulations, using the Urban and Wentzel models of MCS, with theory rather than experiment, revealing trends which would otherwise be obscured by experimental scatter. For medium-energy (radiotherapy) protons, and low-Z (water-like) target materials, Wentzel appears to be better than Urban in simulating the distribution of outgoing angles. For beam spreading in the target itself, the two models are essentially equal.

Exclusive data-based modeling of neutron-nuclear reactions below 20 MeV

NASA Astrophysics Data System (ADS)

Savin, Dmitry; Kosov, Mikhail

2017-09-01

We are developing CHIPS-TPT physics library for exclusive simulation of neutron-nuclear reactions below 20 MeV. Exclusive modeling reproduces each separate scattering and thus requires conservation of energy, momentum and quantum numbers in each reaction. Inclusive modeling reproduces only selected values while averaging over the others and imposes no such constraints. Therefore the exclusive modeling allows to simulate additional quantities like secondary particle correlations and gamma-lines broadening and avoid artificial fluctuations. CHIPS-TPT is based on the formerly included in Geant4 CHIPS library, which follows the exclusive approach, and extends it to incident neutrons with the energy below 20 MeV. The NeutronHP model for neutrons below 20 MeV included in Geant4 follows the inclusive approach like the well known MCNP code. Unfortunately, the available data in this energy region is mostly presented in ENDF-6 format and semi-inclusive. Imposing additional constraints on secondary particles complicates modeling but also allows to detect inconsistencies in the input data and to avoid errors that may remain unnoticed in inclusive modeling.

The simulation library of the Belle II software system

NASA Astrophysics Data System (ADS)

Kim, D. Y.; Ritter, M.; Bilka, T.; Bobrov, A.; Casarosa, G.; Chilikin, K.; Ferber, T.; Godang, R.; Jaegle, I.; Kandra, J.; Kodys, P.; Kuhr, T.; Kvasnicka, P.; Nakayama, H.; Piilonen, L.; Pulvermacher, C.; Santelj, L.; Schwenker, B.; Sibidanov, A.; Soloviev, Y.; Starič, M.; Uglov, T.

2017-10-01

SuperKEKB, the next generation B factory, has been constructed in Japan as an upgrade of KEKB. This brand new e+ e- collider is expected to deliver a very large data set for the Belle II experiment, which will be 50 times larger than the previous Belle sample. Both the triggered physics event rate and the background event rate will be increased by at least 10 times than the previous ones, and will create a challenging data taking environment for the Belle II detector. The software system of the Belle II experiment is designed to execute this ambitious plan. A full detector simulation library, which is a part of the Belle II software system, is created based on Geant4 and has been tested thoroughly. Recently the library has been upgraded with Geant4 version 10.1. The library is behaving as expected and it is utilized actively in producing Monte Carlo data sets for various studies. In this paper, we will explain the structure of the simulation library and the various interfaces to other packages including geometry and beam background simulation.

Designing a new type of neutron detector for neutron and gamma-ray discrimination via GEANT4.

PubMed

Shan, Qing; Chu, Shengnan; Ling, Yongsheng; Cai, Pingkun; Jia, Wenbao

2016-04-01

Design of a new type of neutron detector, consisting of a fast neutron converter, plastic scintillator, and Cherenkov detector, to discriminate 14-MeV fast neutrons and gamma rays in a pulsed n-γ mixed field and monitor their neutron fluxes is reported in this study. Both neutrons and gamma rays can produce fluorescence in the scintillator when they are incident on the detector. However, only the secondary charged particles of the gamma rays can produce Cherenkov light in the Cherenkov detector. The neutron and gamma-ray fluxes can be calculated by measuring the fluorescence and Cherenkov light. The GEANT4 Monte Carlo simulation toolkit is used to simulate the whole process occurring in the detector, whose optimum parameters are known. Analysis of the simulation results leads to a calculation method of neutron flux. This method is verified by calculating the neutron fluxes using pulsed n-γ mixed fields with different n/γ ratios, and the results show that the relative errors of all calculations are <5%. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparison of Geant4 multiple Coulomb scattering models with theory for radiotherapy protons.

PubMed

Makarova, Anastasia; Gottschalk, Bernard; Sauerwein, Wolfgang

2017-07-06

Usually, Monte Carlo models are validated against experimental data. However, models of multiple Coulomb scattering (MCS) in the Gaussian approximation are exceptional in that we have theories which are probably more accurate than the experiments which have, so far, been done to test them. In problems directly sensitive to the distribution of angles leaving the target, the relevant theory is the Molière/Fano/Hanson variant of Molière theory (Gottschalk et al 1993 Nucl. Instrum. Methods Phys. Res. B 74 467-90). For transverse spreading of the beam in the target itself, the theory of Preston and Koehler (Gottschalk (2012 arXiv:1204.4470)) holds. Therefore, in this paper we compare Geant4 simulations, using the Urban and Wentzel models of MCS, with theory rather than experiment, revealing trends which would otherwise be obscured by experimental scatter. For medium-energy (radiotherapy) protons, and low-Z (water-like) target materials, Wentzel appears to be better than Urban in simulating the distribution of outgoing angles. For beam spreading in the target itself, the two models are essentially equal.

Signatures of single-photon interaction between two quantum dots located in different cavities of a weakly coupled double microdisk structure

NASA Astrophysics Data System (ADS)

Seyfferle, S.; Hargart, F.; Jetter, M.; Hu, E.; Michler, P.

2018-01-01

We report on the radiative interaction of two single quantum dots (QDs) each in a separate InP/GaInP-based microdisk cavity via resonant whispering gallery modes. The investigations are based on as-fabricated coupled disk modes. We apply optical spectroscopy involving a 4 f setup, as well as mode-selective real-space imaging and photoluminescence mapping to discern single QDs coupled to a resonant microdisk mode. Excitation of one disk of the double cavity structure and detecting photoluminescence from the other yields proof of single-photon emission of a QD excited by incoherent energy transfer from one disk to the other via a mode in the weak-coupling regime. Finally, we present evidence of photons emitted by a QD in one disk that are transferred to the other disk by a resonant mode and are subsequently resonantly scattered by another QD.

Study of the spatial resolution of low-material GEM tracking detectors

NASA Astrophysics Data System (ADS)

Kudryavtsev, V. N.; Maltsev, T. V.; Shekhtman, L. I.

2018-02-01

The spatial resolution of GEM based tracking detectors has been simulated and measured. The simulation includes the GEANT4 based transport of high energy electrons with careful accounting for atomic relaxation processes including emission of fluorescent photons and Auger electrons and custom post-processing, including accounting for diffusion, gas amplification fluctuations, the distribution of signals on readout electrodes, electronics noise and a particular algorithm of the final coordinate calculation (center of gravity). The simulation demonstrates that a minimum of the spatial resolution of about 10 μm can be achieved with strip pitches from 250 μm to 300 μm. For larger pitches the resolution is quickly degrading reaching 80-100 μm at a pitch of 500 μm. The spatial resolution of low-material triple-GEM detectors for the DEUTRON facility at the VEPP-3 storage ring is measured at the extracted beam facility of the VEPP-4M collider. The amount of material in these detectors is reduced by etching the copper of the GEMs electrodes and using a readout structure on a thin kapton foil rather than on a glass fibre plate. The exact amount of material in one DEUTRON detector is measured by studying multiple scattering of 100 MeV electrons in it. The result of these measurements is X/X0 = 2.4×10-3 corresponding to a thickness of the copper layers of the GEM foils of 3 μm. The spatial resolution of one DEUTRON detector is measured with 500 MeV electrons and the measured value is equal to 35 ± 1 μm for orthogonal tracks.

Constructions of secure entanglement channels assisted by quantum dots inside single-sided optical cavities

NASA Astrophysics Data System (ADS)

Heo, Jino; Kang, Min-Sung; Hong, Chang-Ho; Choi, Seong-Gon; Hong, Jong-Phil

2017-08-01

We propose quantum information processing schemes to generate and swap entangled states based on the interactions between flying photons and quantum dots (QDs) confined within optical cavities for quantum communication. To produce and distribute entangled states (Bell and Greenberger-Horne-Zeilinger [GHZ] states) between the photonic qubits of flying photons of consumers (Alice and Bob) and electron-spin qubits of a provider (trust center, or TC), the TC employs the interactions of the QD-cavity system, which is composed of a charged QD (negatively charged exciton) inside a single-sided cavity. Subsequently, the TC constructs an entanglement channel (Bell state and 4-qubit GHZ state) to link one consumer with another through entanglement swapping, which can be realized to exploit a probe photon with interactions of the QD-cavity systems and single-qubit measurements without Bell state measurement, for quantum communication between consumers. Consequently, the TC, which has quantum nodes (QD-cavity systems), can accomplish constructing the entanglement channel (authenticated channel) between two separated consumers from the distributions of entangled states and entanglement swapping. Furthermore, our schemes using QD-cavity systems, which are feasible with a certain probability of success and high fidelity, can be experimentally implemented with technology currently in use.

Probing different regimes of strong field light-matter interaction with semiconductor quantum dots and few cavity photons

NASA Astrophysics Data System (ADS)

Hargart, F.; Roy-Choudhury, K.; John, T.; Portalupi, S. L.; Schneider, C.; Höfling, S.; Kamp, M.; Hughes, S.; Michler, P.

2016-12-01

In this work we present an extensive experimental and theoretical investigation of different regimes of strong field light-matter interaction for cavity-driven quantum dot (QD) cavity systems. The electric field enhancement inside a high-Q micropillar cavity facilitates exceptionally strong interaction with few cavity photons, enabling the simultaneous investigation for a wide range of QD-laser detuning. In case of a resonant drive, the formation of dressed states and a Mollow triplet sideband splitting of up to 45 μeV is measured for a mean cavity photon number < {n}c> ≤slant 1. In the asymptotic limit of the linear AC Stark effect we systematically investigate the power and detuning dependence of more than 400 QDs. Some QD-cavity systems exhibit an unexpected anomalous Stark shift, which can be explained by an extended dressed 4-level QD model. We provide a detailed analysis of the QD-cavity systems properties enabling this novel effect. The experimental results are successfully reproduced using a polaron master equation approach for the QD-cavity system, which includes the driving laser field, exciton-cavity and exciton-phonon interactions.

Electromagnetic cascade in high-energy electron, positron, and photon interactions with intense laser pulses

NASA Astrophysics Data System (ADS)

Bulanov, S. S.; Schroeder, C. B.; Esarey, E.; Leemans, W. P.

2013-06-01

The interaction of high-energy electrons, positrons, and photons with intense laser pulses is studied in head-on collision geometry. It is shown that electrons and/or positrons undergo a cascade-type process involving multiple emissions of photons. These photons can consequently convert into electron-positron pairs. As a result charged particles quickly lose their energy developing an exponentially decaying energy distribution, which suppresses the emission of high-energy photons, thus reducing the number of electron-positron pairs being generated. Therefore, this type of interaction suppresses the development of the electromagnetic avalanche-type discharge, i.e., the exponential growth of the number of electrons, positrons, and photons does not occur in the course of interaction. The suppression will occur when three-dimensional effects can be neglected in the transverse particle orbits, i.e., for sufficiently broad laser pulses with intensities that are not too extreme. The final distributions of electrons, positrons, and photons are calculated for the case of a high-energy e-beam interacting with a counterstreaming, short intense laser pulse. The energy loss of the e-beam, which requires a self-consistent quantum description, plays an important role in this process, as well as provides a clear experimental observable for the transition from the classical to quantum regime of interaction.

The Application of SNiPER to the JUNO Simulation

NASA Astrophysics Data System (ADS)

Lin, Tao; Zou, Jiaheng; Li, Weidong; Deng, Ziyan; Fang, Xiao; Cao, Guofu; Huang, Xingtao; You, Zhengyun; JUNO Collaboration

2017-10-01

The JUNO (Jiangmen Underground Neutrino Observatory) is a multipurpose neutrino experiment which is designed to determine neutrino mass hierarchy and precisely measure oscillation parameters. As one of the important systems, the JUNO offline software is being developed using the SNiPER software. In this proceeding, we focus on the requirements of JUNO simulation and present the working solution based on the SNiPER. The JUNO simulation framework is in charge of managing event data, detector geometries and materials, physics processes, simulation truth information etc. It glues physics generator, detector simulation and electronics simulation modules together to achieve a full simulation chain. In the implementation of the framework, many attractive characteristics of the SNiPER have been used, such as dynamic loading, flexible flow control, multiple event management and Python binding. Furthermore, additional efforts have been made to make both detector and electronics simulation flexible enough to accommodate and optimize different detector designs. For the Geant4-based detector simulation, each sub-detector component is implemented as a SNiPER tool which is a dynamically loadable and configurable plugin. So it is possible to select the detector configuration at runtime. The framework provides the event loop to drive the detector simulation and interacts with the Geant4 which is implemented as a passive service. All levels of user actions are wrapped into different customizable tools, so that user functions can be easily extended by just adding new tools. The electronics simulation has been implemented by following an event driven scheme. The SNiPER task component is used to simulate data processing steps in the electronics modules. The electronics and trigger are synchronized by triggered events containing possible physics signals. The JUNO simulation software has been released and is being used by the JUNO collaboration to do detector design optimization, event reconstruction algorithm development and physics sensitivity studies.

Fast multipurpose Monte Carlo simulation for proton therapy using multi- and many-core CPU architectures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Souris, Kevin, E-mail: kevin.souris@uclouvain.be; Lee, John Aldo; Sterpin, Edmond

2016-04-15

Purpose: Accuracy in proton therapy treatment planning can be improved using Monte Carlo (MC) simulations. However the long computation time of such methods hinders their use in clinical routine. This work aims to develop a fast multipurpose Monte Carlo simulation tool for proton therapy using massively parallel central processing unit (CPU) architectures. Methods: A new Monte Carlo, called MCsquare (many-core Monte Carlo), has been designed and optimized for the last generation of Intel Xeon processors and Intel Xeon Phi coprocessors. These massively parallel architectures offer the flexibility and the computational power suitable to MC methods. The class-II condensed history algorithmmore » of MCsquare provides a fast and yet accurate method of simulating heavy charged particles such as protons, deuterons, and alphas inside voxelized geometries. Hard ionizations, with energy losses above a user-specified threshold, are simulated individually while soft events are regrouped in a multiple scattering theory. Elastic and inelastic nuclear interactions are sampled from ICRU 63 differential cross sections, thereby allowing for the computation of prompt gamma emission profiles. MCsquare has been benchmarked with the GATE/GEANT4 Monte Carlo application for homogeneous and heterogeneous geometries. Results: Comparisons with GATE/GEANT4 for various geometries show deviations within 2%–1 mm. In spite of the limited memory bandwidth of the coprocessor simulation time is below 25 s for 10{sup 7} primary 200 MeV protons in average soft tissues using all Xeon Phi and CPU resources embedded in a single desktop unit. Conclusions: MCsquare exploits the flexibility of CPU architectures to provide a multipurpose MC simulation tool. Optimized code enables the use of accurate MC calculation within a reasonable computation time, adequate for clinical practice. MCsquare also simulates prompt gamma emission and can thus be used also for in vivo range verification.« less

Monitoring molecular interactions using photon arrival-time interval distribution analysis

DOEpatents

Laurence, Ted A [Livermore, CA; Weiss, Shimon [Los Angels, CA

2009-10-06

A method for analyzing/monitoring the properties of species that are labeled with fluorophores. A detector is used to detect photons emitted from species that are labeled with one or more fluorophores and located in a confocal detection volume. The arrival time of each of the photons is determined. The interval of time between various photon pairs is then determined to provide photon pair intervals. The number of photons that have arrival times within the photon pair intervals is also determined. The photon pair intervals are then used in combination with the corresponding counts of intervening photons to analyze properties and interactions of the molecules including brightness, concentration, coincidence and transit time. The method can be used for analyzing single photon streams and multiple photon streams.

WE-D-BRF-01: FEATURED PRESENTATION - Investigating Particle Track Structures Using Fluorescent Nuclear Track Detectors and Monte Carlo Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dowdell, S; Paganetti, H; Schuemann, J

Purpose: To report on the efforts funded by the AAPM seed funding grant to develop the basis for fluorescent nuclear track detector (FNTD) based radiobiological experiments in combination with dedicated Monte Carlo simulations (MCS) on the nanometer scale. Methods: Two confocal microscopes were utilized in this study. Two FNTD samples were used to find the optimal microscope settings, one FNTD irradiated with 11.1 MeV/u Gold ions and one irradiated with 428.77 MeV/u Carbon ions. The first sample provided a brightly luminescent central track while the latter is used to test the capabilities to observe secondary electrons. MCS were performed usingmore » TOPAS beta9 version, layered on top of Geant4.9.6p02. Two sets of simulations were performed, one with the Geant4-DNA physics list and approximating the FNTDs by water, a second set using the Penelope physics list in a water-approximated FNTD and a aluminum-oxide FNTD. Results: Within the first half of the funding period, we have successfully established readout capabilities of FNTDs at our institute. Due to technical limitations, our microscope setup is significantly different from the approach implemented at the DKFZ, Germany. However, we can clearly reconstruct Carbon tracks in 3D with electron track resolution of 200 nm. A second microscope with superior readout capabilities will be tested in the second half of the funding period, we expect an improvement in signal to background ratio with the same the resolution.We have successfully simulated tracks in FNTDs. The more accurate Geant4-DNA track simulations can be used to reconstruct the track energy from the size and brightness of the observed tracks. Conclusion: We have achieved the goals set in the seed funding proposal: the setup of FNTD readout and simulation capabilities. We will work on improving the readout resolution to validate our MCS track structures down to the nanometer scales.« less

The use of tetrahedral mesh geometries in Monte Carlo simulation of applicator based brachytherapy dose distributions

NASA Astrophysics Data System (ADS)

Paiva Fonseca, Gabriel; Landry, Guillaume; White, Shane; D'Amours, Michel; Yoriyaz, Hélio; Beaulieu, Luc; Reniers, Brigitte; Verhaegen, Frank

2014-10-01

Accounting for brachytherapy applicator attenuation is part of the recommendations from the recent report of AAPM Task Group 186. To do so, model based dose calculation algorithms require accurate modelling of the applicator geometry. This can be non-trivial in the case of irregularly shaped applicators such as the Fletcher Williamson gynaecological applicator or balloon applicators with possibly irregular shapes employed in accelerated partial breast irradiation (APBI) performed using electronic brachytherapy sources (EBS). While many of these applicators can be modelled using constructive solid geometry (CSG), the latter may be difficult and time-consuming. Alternatively, these complex geometries can be modelled using tessellated geometries such as tetrahedral meshes (mesh geometries (MG)). Recent versions of Monte Carlo (MC) codes Geant4 and MCNP6 allow for the use of MG. The goal of this work was to model a series of applicators relevant to brachytherapy using MG. Applicators designed for 192Ir sources and 50 kV EBS were studied; a shielded vaginal applicator, a shielded Fletcher Williamson applicator and an APBI balloon applicator. All applicators were modelled in Geant4 and MCNP6 using MG and CSG for dose calculations. CSG derived dose distributions were considered as reference and used to validate MG models by comparing dose distribution ratios. In general agreement within 1% for the dose calculations was observed for all applicators between MG and CSG and between codes when considering volumes inside the 25% isodose surface. When compared to CSG, MG required longer computation times by a factor of at least 2 for MC simulations using the same code. MCNP6 calculation times were more than ten times shorter than Geant4 in some cases. In conclusion we presented methods allowing for high fidelity modelling with results equivalent to CSG. To the best of our knowledge MG offers the most accurate representation of an irregular APBI balloon applicator.

Two photon excitation of atomic oxygen

NASA Technical Reports Server (NTRS)

Pindzola, M. S.

1977-01-01

A standard perturbation expansion in the atom-radiation field interaction is used to calculate the two photon excitation cross section for 1s(2) 2s(2) 2p(4) p3 to 1s(2) 2s(2) 2p(3) (s4) 3p p3 transition in atomic oxygen. The summation over bound and continuum intermediate states is handled by solving the equivalent inhomogeneous differential equation. Exact summation results differ by a factor of 2 from a rough estimate obtained by limiting the intermediate state summation to one bound state. Higher order electron correlation effects are also examined.

Geant4 simulation for a study of a possible use of carbon ions pencil beam for the treatment of ocular melanomas with the active scanning system at CNAO Centre

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farina, E.; Piersimoni, P.; Riccardi, C.

The aim of this work is to validate the Geant4 application reproducing the CNAO (National Centre for Oncological Hadrontherapy) beamline and to study of a possible use of carbon ion pencil beams for the treatment of ocular melanomas at the CNAO Centre. The promising aspect of carbon ions radiotherapy for the treatment of this disease lies in its superior relative radiobiological effectiveness (RBE). The Monte Carlo Geant4 toolkit is used to simulate the complete CNAO extraction beamline, with the active and passive components along it. A human eye modeled detector, including a realistic target tumor volume, is used as target.more » Cross check with previous studies at CNAO using protons allows comparisons on possible benefits on using such a technique with respect to proton beams. Before the eye-detector irradiation a validation of the Geant4 simulation with CNAO experimental data is carried out with both carbon ions and protons. Important beam parameters such as the transverse FWHM and scanned radiation field 's uniformity are tested within the simulation and compared with experimental measurements at CNAO Centre. The physical processes involved in secondary particles generation by carbon ions and protons in the eye-detector are reproduced to take into account the additional dose to the primary beam given to irradiated eye's tissues. A study of beam shaping is carried out to produce a uniform 3D dose distribution (shaped on the tumor) by the use of a spread out Bragg peak. The eye-detector is then irradiated through a two dimensional transverse beam scan at different depths. In the use case the eye-detector is rotated of an angle of 40 deg. in the vertical direction, in order to mis-align the tumor from healthy tissues in front of it. The treatment uniformity on the tumor in the eye-detector is tested. For a more quantitative description of the deposited dose in the eye-detector and for the evaluation of the ratio between the dose deposited in the tumor and the other eye components, proton and carbon DVHs (Dose Volume Histograms) are compared. A high statistics simulated sample is used to minimize statistical errors. In the simulation a new particle generation method is developed in order to reproduce the experimental treatment plan by importing the DICOM RT-PLAN file, which contains all the information on the irradiation geometries and sequences (treatment plan parameters). Conclusions Even further validations must be done, the good results so far obtained by this work point out and confirm the possibility of using carbon ions delivered with active scanning beams to treat the ocular melanoma.« less

The interactive optical fiber fabrics for smart interior environment

NASA Astrophysics Data System (ADS)

Bai, Z. Q.; Dong, A. H.; Du, Z. Y.; Tan, J.

2017-10-01

Comparing to conventional textiles, interactive photonic textiles can emit light, present different colors, change the surface pattern and can interact with users. They are particularly suitable for decorative purpose. Home furniture is one possible application [1]. With attractive illumination and color effect, the photonic textiles can also be used in hotels, exhibition halls, restaurants and many other circumstances to enhance the interior environment. However, the functionality of the interactive photonic textile for interior purpose is still underdeveloped, since there are still sever challenges about how to improve the usability and functionality of the interactive textile. This project aims to study how to improve the interactive function of photonic textiles, which can enhance the well-being of the end-user. In the end, a color-changeable interactive cushion which can detect the main primary particulate matter (PM) 2.5 was developed.

Inner-shell photodetachment of transition metal negative ions

NASA Astrophysics Data System (ADS)

Dumitriu, Ileana

This thesis focuses on the study of inner-shell photodetachment of transition metal negative ions, specifically Fe- and Ru- . Experimental investigations have been performed with the aim of gaining new insights into the physics of negative atomic ions and providing valuable absolute cross section data for astrophysics. The experiments were performed using the X-ray radiation from the Advanced Light Source, Lawrence Berkeley National Laboratory, and the merged-beam technique for photoion spectroscopy. Negative ions are a special class of atomic systems very different from neutral atoms and positive ions. The fundamental physics of the interaction of transition metal negative ions with photons is interesting but difficult to analyze in detail because the angular momentum coupling generates a large number of possible terms resulting from the open d shell. Our work reports on the first inner-shell photodetachment studies and absolute cross section measurements for Fe- and Ru -. In the case of Fe-, an important astrophysical abundant element, the inner-shell photodetachment cross section was obtained by measuring the Fe+ and Fe2+ ion production over the photon energy range of 48--72 eV. The absolute cross sections for the production of Fe+ and Fe2+ were measured at four photon energies. Strong shape resonances due to the 3p→3d photoexcitation were measured above the 3p detachment threshold. The production of Ru+, Ru2+, and Ru3+ from Ru- was measured over 30--90 eV photon energy range The absolute photodetachment cross sections of Ru - ([Kr] 4d75s 2) leading to Ru+, Ru2+, and Ru 3+ ion production were measured at three photon energies. Resonance effects were observed due to interference between transitions of the 4 p-electrons to the quasi-bound 4p54d85s 2 states and the 4d→epsilonf continuum. The role of many-particle effects, intershell interaction, and polarization seems much more significant in Ru- than in Fe- photodetachment.

RPCs in biomedical applications

NASA Astrophysics Data System (ADS)

Belli, G.; De Vecchi, C.; Giroletti, E.; Guida, R.; Musitelli, G.; Nardò, R.; Necchi, M. M.; Pagano, D.; Ratti, S. P.; Sani, G.; Vicini, A.; Vitulo, P.; Viviani, C.

2006-08-01

We are studying possible applications of Resistive Plate Chambers (RPCs) in the biomedical domain such as Positron Emission Tomography (PET). The use of RPCs in PET can provide several improvements on the usual scintillation-based detectors. The most striking features are the extremely good spatial and time resolutions. They can be as low as 50 μm and 25 ps respectively, to be compared to the much higher intrinsic limits in bulk detectors. Much efforts have been made to investigate suitable materials to make RPCs sensitive to 511 keV photons. For this reason, we are studying different types of coating employing high Z materials with proper electrical resistivity. Later investigations explored the possibility of coating glass electrodes by mean of serigraphy techniques, employing oxide based mixtures with a high density of high Z materials; the efficiency is strongly dependent on its thickness and it reaches a maximum for a characteristic value that is a function of the compound (usually a few hundred microns). The most promising mixtures seem to be PbO, Bi 2O 3 and Tl 2O. Preliminary gamma efficiency measurements for a Multigap RPC prototype (MRPC) are presented as well as simulations using GEANT4-based framework. The MRPC has 5 gas gaps; their spacings are kept by 0.3 mm diameter nylon fishing line, electrodes are made of thin glasses (1 mm for the outer electrodes, 0.15-0.4 mm for the inner ones). The detector is enclosed in a metallic gas-tight box, filled with a C 2H 2F 4 92.5%, SF 6 2.5%, C 4H 10 5% mixture. Different gas mixtures are being studied increasing the SF6 percentage and results of efficiency as a function of the new mixtures will be presented.

Qudit-Basis Universal Quantum Computation Using χ(2 ) Interactions

NASA Astrophysics Data System (ADS)

Niu, Murphy Yuezhen; Chuang, Isaac L.; Shapiro, Jeffrey H.

2018-04-01

We prove that universal quantum computation can be realized—using only linear optics and χ(2 ) (three-wave mixing) interactions—in any (n +1 )-dimensional qudit basis of the n -pump-photon subspace. First, we exhibit a strictly universal gate set for the qubit basis in the one-pump-photon subspace. Next, we demonstrate qutrit-basis universality by proving that χ(2 ) Hamiltonians and photon-number operators generate the full u (3 ) Lie algebra in the two-pump-photon subspace, and showing how the qutrit controlled-Z gate can be implemented with only linear optics and χ(2 ) interactions. We then use proof by induction to obtain our general qudit result. Our induction proof relies on coherent photon injection or subtraction, a technique enabled by χ(2 ) interaction between the encoding modes and ancillary modes. Finally, we show that coherent photon injection is more than a conceptual tool, in that it offers a route to preparing high-photon-number Fock states from single-photon Fock states.

Design and Construction of a Positron Emission Tomography (PET) Unit and Medical Applications with GEANT Detector Simulation Package

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karagoz, Muge

1998-01-01

In order to investigate the possibility of the construction of a sample PET coincidence unit in our HEP laboratory, a setup with two face to face PMTs and two 2x8 Csi(Tl) scintillator matrices has been constructed. In this setup, 1-D projections of a pointlike 22 Na positron source at different angles have been measured. Using these projections a 2-D image has been formed. Monte Carlo studies of this setup have been implemented using the detector simulation tool in CERN program library, GEANT. Again with GEANT a sample human body is created to study the effects of proton therapy. Utilization ofmore » the simulation as a pretherapy tool is also investigated.« less

Behavior of light polarization in photon-scalar interaction

NASA Astrophysics Data System (ADS)

Azizi, Azizollah; Nasirimoghadam, Soudabe

2017-11-01

Quantum theories of gravity help us to improve our insight into the gravitational interactions. Motivated by the interesting effect of gravity on the photon trajectory, we treat a quantum recipe concluding a classical interaction of light and a massive object such as the sun. We use the linear quantum gravity to compute the classical potential of a photon interacting with a massive scalar. The leading terms have a traditional 1/r subordinate and demonstrate a polarization-dependent behavior. This result challenges the equivalence principle; attractive and/or repulsive interactions are admissible.

Interaction-free measurement as quantum channel discrimination

NASA Astrophysics Data System (ADS)

Zhou, You; Yung, Man-Hong

2017-12-01

Interaction-free measurement is a quantum process where, in the ideal situation, an object can be detected as if no interaction took place with the probing photon. Here we show that the problem of interaction-free measurement can be regarded as a problem of quantum-channel discrimination. In particular, we look for the optimal photonic states that can minimize the detection error and the photon loss in detecting the presence or absence of the object, which is taken to be semitransparent, and the number of the interrogation cycle is assumed to be finite. Furthermore, we also investigated the possibility of minimizing the detection error through the use of entangled photons, which is essentially a setting of quantum illumination. However, our results indicate that entanglement does not exhibit a clear advantage; the same performance can be achieved with unentangled photonic states.

Sub-poissonian photon statistics in the coherent state Jaynes-Cummings model in non-resonance

NASA Astrophysics Data System (ADS)

Zhang, Jia-tai; Fan, An-fu

1992-03-01

We study a model with a two-level atom (TLA) non-resonance interacting with a single-mode quantized cavity field (QCF). The photon number probability function, the mean photon number and Mandel's fluctuation parameter are calculated. The sub-Poissonian distributions of the photon statistics are obtained in non-resonance interaction. This statistical properties are strongly dependent on the detuning parameters.

WE-H-207A-01: Computational Evaluation of High-Resolution 18F Positron Imaging Using Radioluminescence Microscopy with Lu2O3: Eu Thin-Film Scintillator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Q; Sengupta, D; Pratx, G

2016-06-15

Purpose: Radioluminescence microscopy, an emerging and powerful tool for high resolution beta imaging, has been applied to molecular imaging of cellular metabolism to understand tumor biology. A novel thin-film (10 µm thickness) scintillator made of Lu{sub 2}O{sub 3}: Eu has been developed to enhance the system performance. However the advances of radioluminescence imaging with Lu{sub 2}O{sub 3}scintillator compared with that using conventional scintillator have not been explored theoretically to date. To validate the advantages of the thin-film scintillator, this study uses a novel computational simulation framework to evaluate the performance of radioluminescence microscopy using both conventional and thin-film scintillators. Methods:more » Numerical models for different stages of positron imaging are established. Positron from {sup 18}F passing through the scintillator and its neighbor structures are modeled by Monte-Carlo simulation using Geant4. The propagation and focus of photons by the microscope are modeled by convolution with a depth-varying point spread function generated by the Gibson-Lanni model. Photons focused on the detector plane are then captured and converted into electronic signals by an electron multiplication (EM) CCD camera, which is described by a photosensor model considering various noises and charge amplification. Results: The performance metrics of radioluminescence imaging with a thin-film Lu{sub 2}O{sub 3} and conventional CdWO{sub 4} scintillator are compared, including spatial resolution, sensitivity, positron track area and intensity. The spatial resolution of Lu{sub 2}O{sub 3} system can achieve 10 µm maximally, a 12 µm enhancement from that obtained from CdWO{sub 4} system. Meanwhile, the system with Lu{sub 2}O{sub 3} scintillator can provide a higher mean sensitivity: 40% compared with that (21.5%) obtained from CdWO{sub 4} system. Moreover, the simulation results are in good agreement with previous experimental measurements. Conclusion: This study provides a new theoretical understanding of our imaging system and has the potential to promote the development of radioluminescence microscopy for more reliable and robust application on the functional imaging of delicate biological structures. The authors acknowledge funding from NIH grant R01CA186275 and SBIR grant 1R43GM110888-01.« less

Monte Carlo calculation of the sensitivity of a commercial dose calibrator to gamma and beta radiation.

PubMed

Laedermann, Jean-Pascal; Valley, Jean-François; Bulling, Shelley; Bochud, François O

2004-06-01

The detection process used in a commercial dose calibrator was modeled using the GEANT 3 Monte Carlo code. Dose calibrator efficiency for gamma and beta emitters, and the response to monoenergetic photons and electrons was calculated. The model shows that beta emitters below 2.5 MeV deposit energy indirectly in the detector through bremsstrahlung produced in the chamber wall or in the source itself. Higher energy beta emitters (E > 2.5 MeV) deposit energy directly in the chamber sensitive volume, and dose calibrator sensitivity increases abruptly for these radionuclides. The Monte Carlo calculations were compared with gamma and beta emitter measurements. The calculations show that the variation in dose calibrator efficiency with measuring conditions (source volume, container diameter, container wall thickness and material, position of the source within the calibrator) is relatively small and can be considered insignificant for routine measurement applications. However, dose calibrator efficiency depends strongly on the inner-wall thickness of the detector.

SU-E-T-554: Monte Carlo Calculation of Source Terms and Attenuation Lengths for Neutrons Produced by 50–200 MeV Protons On Brass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramos-Mendez, J; Faddegon, B; Paganetti, H

2015-06-15

Purpose: We used TOPAS (TOPAS wraps and extends Geant4 for medical physicists) to compare Geant4 physics models with published data for neutron shielding calculations. Subsequently, we calculated the source terms and attenuation lengths (shielding data) of the total ambient dose equivalent (TADE) in concrete for neutrons produced by protons in brass. Methods: Stage1: The Bertini and Binary nuclear models available in Geant4 were compared with published attenuation at depth of the TADE in concrete and iron. Stage2: Shielding data of the TADE in concrete was calculated for 50– 200 MeV proton beams on brass. Stage3: Shielding data from Stage2 wasmore » extrapolated for 235 MeV proton beams. This data was used in a point-line-source analytical model to calculate the ambient dose per unit therapeutic dose at two locations inside one treatment room at the Francis H Burr Proton Therapy Center. Finally, we compared these results with experimental data and full TOPAS simulations. Results: At larger angles (∼130o) the TADE in concrete calculated with the Bertini model was about 9 times larger than that calculated with the Binary model. The attenuation length in concrete calculated with the Binary model agreed with published data within 7%±0.4% (statistical uncertainty) for the deepest regions and 5%±0.1% for shallower regions. For iron the agreement was within 3%±0.1%. The ambient dose per therapeutic dose calculated with the Binary model, relative to the experimental data, was a ratio of 0.93±0.16 and 1.23±0.24 for two locations. The analytical model overestimated the dose by four orders of magnitude. These differences are attributed to the complexity of the geometry. Conclusion: The Binary and Bertini models gave comparable results, with the Binary model giving the best agreement with published data at large angle. Shielding data we calculated using the Binary model is useful for fast shielding calculations with other analytical models. This work was supported by National Cancer Institute Grant R01CA140735.« less

Polarization Transfer in Proton Compton Scattering at High Momentum Transfer

NASA Astrophysics Data System (ADS)

Hamilton, D. J.; Mamyan, V. H.; Aniol, K. A.; Annand, J. R.; Bertin, P. Y.; Bimbot, L.; Bosted, P.; Calarco, J. R.; Camsonne, A.; Chang, G. C.; Chang, T.-H.; Chen, J.-P.; Choi, Seonho; Chudakov, E.; Danagoulian, A.; Degtyarenko, P.; de Jager, C. W.; Deur, A.; Dutta, D.; Egiyan, K.; Gao, H.; Garibaldi, F.; Gayou, O.; Gilman, R.; Glamazdin, A.; Glashausser, C.; Gomez, J.; Hansen, J.-O.; Hayes, D.; Higinbotham, D.; Hinton, W.; Horn, T.; Howell, C.; Hunyady, T.; Hyde-Wright, C. E.; Jiang, X.; Jones, M. K.; Khandaker, M.; Ketikyan, A.; Kubarovsky, V.; Kramer, K.; Kumbartzki, G.; Laveissière, G.; Lerose, J.; Lindgren, R. A.; Margaziotis, D. J.; Markowitz, P.; McCormick, K.; Meziani, Z.-E.; Michaels, R.; Moussiegt, P.; Nanda, S.; Nathan, A. M.; Nikolenko, D. M.; Nelyubin, V.; Norum, B. E.; Paschke, K.; Pentchev, L.; Perdrisat, C. F.; Piasetzky, E.; Pomatsalyuk, R.; Punjabi, V. A.; Rachek, I.; Radyushkin, A.; Reitz, B.; Roche, R.; Roedelbronn, M.; Ron, G.; Sabatie, F.; Saha, A.; Savvinov, N.; Shahinyan, A.; Shestakov, Y.; Širca, S.; Slifer, K.; Solvignon, P.; Stoler, P.; Tajima, S.; Sulkosky, V.; Todor, L.; Vlahovic, B.; Weinstein, L. B.; Wang, K.; Wojtsekhowski, B.; Voskanyan, H.; Xiang, H.; Zheng, X.; Zhu, L.

2005-06-01

Compton scattering from the proton was investigated at s=6.9 GeV2 and t=-4.0 GeV2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in disagreement with a prediction of perturbative QCD based on a two-gluon exchange mechanism, but agree well with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton.

Time-dependent photon heat transport through a mesoscopic Josephson device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Wen-Ting; Zhao, Hong-Kang, E-mail: zhaohonk@bit.edu.cn

The time-oscillating photon heat current through a dc voltage biased mesoscopic Josephson Junction (MJJ) has been investigated by employing the nonequilibrium Green’s function approach. The Landauer-like formula of photon heat current has been derived in both of the Fourier space and its time-oscillating versions, where Coulomb interaction, self inductance, and magnetic flux take effective roles. Nonlinear behaviors are exhibited in the photon heat current due to the quantum nature of MJJ and applied external dc voltage. The magnitude of heat current decreases with increasing the external bias voltage, and subtle oscillation structures appear as the superposition of different photon heatmore » branches. The overall period of heat current with respect to time is not affected by Coulomb interaction, however, the magnitude and phase of it vary considerably by changing the Coulomb interaction. - Highlights: • The time-oscillating photon heat current through a mesoscopic Josephson Junction has been investigated. • The Landauer-like formula of photon heat current has been derived by the nonequilibrium Green’s function approach. • Nonlinear behaviors are exhibited in the photon heat current resulting from the self inductance and Coulomb interaction. • The oscillation structure of heat current is composed of the superposition of oscillations with different periods.« less

Continuous energy adjoint transport for photons in PHITS

NASA Astrophysics Data System (ADS)

Malins, Alex; Machida, Masahiko; Niita, Koji

2017-09-01

Adjoint Monte Carlo can be an effcient algorithm for solving photon transport problems where the size of the tally is relatively small compared to the source. Such problems are typical in environmental radioactivity calculations, where natural or fallout radionuclides spread over a large area contribute to the air dose rate at a particular location. Moreover photon transport with continuous energy representation is vital for accurately calculating radiation protection quantities. Here we describe the incorporation of an adjoint Monte Carlo capability for continuous energy photon transport into the Particle and Heavy Ion Transport code System (PHITS). An adjoint cross section library for photon interactions was developed based on the JENDL- 4.0 library, by adding cross sections for adjoint incoherent scattering and pair production. PHITS reads in the library and implements the adjoint transport algorithm by Hoogenboom. Adjoint pseudo-photons are spawned within the forward tally volume and transported through space. Currently pseudo-photons can undergo coherent and incoherent scattering within the PHITS adjoint function. Photoelectric absorption is treated implicitly. The calculation result is recovered from the pseudo-photon flux calculated over the true source volume. A new adjoint tally function facilitates this conversion. This paper gives an overview of the new function and discusses potential future developments.

Quantum Optics with Near-Lifetime-Limited Quantum-Dot Transitions in a Nanophotonic Waveguide.

PubMed

Thyrrestrup, Henri; Kiršanskė, Gabija; Le Jeannic, Hanna; Pregnolato, Tommaso; Zhai, Liang; Raahauge, Laust; Midolo, Leonardo; Rotenberg, Nir; Javadi, Alisa; Schott, Rüdiger; Wieck, Andreas D; Ludwig, Arne; Löbl, Matthias C; Söllner, Immo; Warburton, Richard J; Lodahl, Peter

2018-03-14

Establishing a highly efficient photon-emitter interface where the intrinsic linewidth broadening is limited solely by spontaneous emission is a key step in quantum optics. It opens a pathway to coherent light-matter interaction for, e.g., the generation of highly indistinguishable photons, few-photon optical nonlinearities, and photon-emitter quantum gates. However, residual broadening mechanisms are ubiquitous and need to be combated. For solid-state emitters charge and nuclear spin noise are of importance, and the influence of photonic nanostructures on the broadening has not been clarified. We present near-lifetime-limited linewidths for quantum dots embedded in nanophotonic waveguides through a resonant transmission experiment. It is found that the scattering of single photons from the quantum dot can be obtained with an extinction of 66 ± 4%, which is limited by the coupling of the quantum dot to the nanostructure rather than the linewidth broadening. This is obtained by embedding the quantum dot in an electrically contacted nanophotonic membrane. A clear pathway to obtaining even larger single-photon extinction is laid out; i.e., the approach enables a fully deterministic and coherent photon-emitter interface in the solid state that is operated at optical frequencies.

Validation of Monte Carlo simulation of mammography with TLD measurement and depth dose calculation with a detailed breast model

NASA Astrophysics Data System (ADS)

Wang, Wenjing; Qiu, Rui; Ren, Li; Liu, Huan; Wu, Zhen; Li, Chunyan; Li, Junli

2017-09-01

Mean glandular dose (MGD) is not only determined by the compressed breast thickness (CBT) and the glandular content, but also by the distribution of glandular tissues in breast. Depth dose inside the breast in mammography has been widely concerned as glandular dose decreases rapidly with increasing depth. In this study, an experiment using thermo luminescent dosimeters (TLDs) was carried out to validate Monte Carlo simulations of mammography. Percent depth doses (PDDs) at different depth values were measured inside simple breast phantoms of different thicknesses. The experimental values were well consistent with the values calculated by Geant4. Then a detailed breast model with a CBT of 4 cm and a glandular content of 50%, which has been constructed in previous work, was used to study the effects of the distribution of glandular tissues in breast with Geant4. The breast model was reversed in direction of compression to get a reverse model with a different distribution of glandular tissues. Depth dose distributions and glandular tissue dose conversion coefficients were calculated. It revealed that the conversion coefficients were about 10% larger when the breast model was reversed, for glandular tissues in the reverse model are concentrated in the upper part of the model.

A Thomson-type mass and energy spectrometer for characterizing ion energy distributions in a coaxial plasma gun operating in a gas-puff mode

PubMed Central

Rieker, G. B.; Poehlmann, F. R.; Cappelli, M. A.

2013-01-01

Measurements of ion energy distribution are performed in the accelerated plasma of a coaxial electromagnetic plasma gun operating in a gas-puff mode at relatively low discharge energy (900 J) and discharge potential (4 kV). The measurements are made using a Thomson-type mass and energy spectrometer with a gated microchannel plate and phosphor screen as the ion sensor. The parabolic ion trajectories are captured from the sensor screen with an intensified charge-coupled detector camera. The spectrometer was designed and calibrated using the Geant4 toolkit, accounting for the effects on the ion trajectories of spatial non-uniformities in the spectrometer magnetic and electric fields. Results for hydrogen gas puffs indicate the existence of a class of accelerated protons with energies well above the coaxial discharge potential (up to 24 keV). The Thomson analyzer confirms the presence of impurities of copper and iron, also of relatively high energies, which are likely erosion or sputter products from plasma-electrode interactions. PMID:23983449

A Thomson-type mass and energy spectrometer for characterizing ion energy distributions in a coaxial plasma gun operating in a gas-puff mode

NASA Astrophysics Data System (ADS)

Rieker, G. B.; Poehlmann, F. R.; Cappelli, M. A.

2013-07-01

Measurements of ion energy distribution are performed in the accelerated plasma of a coaxial electromagnetic plasma gun operating in a gas-puff mode at relatively low discharge energy (900 J) and discharge potential (4 kV). The measurements are made using a Thomson-type mass and energy spectrometer with a gated microchannel plate and phosphor screen as the ion sensor. The parabolic ion trajectories are captured from the sensor screen with an intensified charge-coupled detector camera. The spectrometer was designed and calibrated using the Geant4 toolkit, accounting for the effects on the ion trajectories of spatial non-uniformities in the spectrometer magnetic and electric fields. Results for hydrogen gas puffs indicate the existence of a class of accelerated protons with energies well above the coaxial discharge potential (up to 24 keV). The Thomson analyzer confirms the presence of impurities of copper and iron, also of relatively high energies, which are likely erosion or sputter products from plasma-electrode interactions.

A Thomson-type mass and energy spectrometer for characterizing ion energy distributions in a coaxial plasma gun operating in a gas-puff mode.

PubMed

Rieker, G B; Poehlmann, F R; Cappelli, M A

2013-07-01

Measurements of ion energy distribution are performed in the accelerated plasma of a coaxial electromagnetic plasma gun operating in a gas-puff mode at relatively low discharge energy (900 J) and discharge potential (4 kV). The measurements are made using a Thomson-type mass and energy spectrometer with a gated microchannel plate and phosphor screen as the ion sensor. The parabolic ion trajectories are captured from the sensor screen with an intensified charge-coupled detector camera. The spectrometer was designed and calibrated using the Geant4 toolkit, accounting for the effects on the ion trajectories of spatial non-uniformities in the spectrometer magnetic and electric fields. Results for hydrogen gas puffs indicate the existence of a class of accelerated protons with energies well above the coaxial discharge potential (up to 24 keV). The Thomson analyzer confirms the presence of impurities of copper and iron, also of relatively high energies, which are likely erosion or sputter products from plasma-electrode interactions.

The Liquid Argon Software Toolkit (LArSoft): Goals, Status and Plan

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pordes, Rush; Snider, Erica

LArSoft is a toolkit that provides a software infrastructure and algorithms for the simulation, reconstruction and analysis of events in Liquid Argon Time Projection Chambers (LArTPCs). It is used by the ArgoNeuT, LArIAT, MicroBooNE, DUNE (including 35ton prototype and ProtoDUNE) and SBND experiments. The LArSoft collaboration provides an environment for the development, use, and sharing of code across experiments. The ultimate goal is to develop fully automatic processes for reconstruction and analysis of LArTPC events. The toolkit is based on the art framework and has a well-defined architecture to interface to other packages, including to GEANT4 and GENIE simulation softwaremore » and the Pandora software development kit for pattern recognition. It is designed to facilitate and support the evolution of algorithms including their transition to new computing platforms. The development of the toolkit is driven by the scientific stakeholders involved. The core infrastructure includes standard definitions of types and constants, means to input experiment geometries as well as meta and event- data in several formats, and relevant general utilities. Examples of algorithms experiments have contributed to date are: photon-propagation; particle identification; hit finding, track finding and fitting; electromagnetic shower identification and reconstruction. We report on the status of the toolkit and plans for future work.« less