The uniformity and imaging properties of some new ceramic scintillators

NASA Astrophysics Data System (ADS)

Chac, George T. L.; Miller, Brian W.; Shah, Kanai; Baldoni, Gary; Domanik, Kenneth J.; Bora, Vaibhav; Cherepy, Nerine J.; Seeley, Zachary; Barber, H. Bradford

2012-10-01

Results are presented of investigations into the composition, uniformity and gamma-ray imaging performance of new ceramic scintillators with synthetic garnet structure. The ceramic scintillators were produced by a process that uses flame pyrolysis to make nanoparticles which are sintered into a ceramic and then compacted by hot isostatic compression into a transparent material. There is concern that the resulting ceramic scintillator might not have the uniformity of composition necessary for use in gamma-ray spectroscopy and gamma-ray imaging. The compositional uniformity of four samples of three ceramic scintillator types (GYGAG:Ce, GLuGAG:Ce and LuAG:Pr) was tested using an electron microprobe. It was found that all samples were uniform in elemental composition to the limit of sensitivity of the microprobe (few tenths of a percent atomic) over distance scales from ~ 1 cm to ~ 1 um. The light yield and energy resolution of all ceramic scintillator samples were mapped with a highly collimated 57Co source (122 keV) and performance was uniform at mapping scale of 0.25 mm. Good imaging performance with single gamma-ray photon detection was demonstrated for all samples using a BazookaSPECT system, and the imaging spatial resolution, measured as the FWHM of a LSF was 150 um.

Imaging model for the scintillator and its application to digital radiography image enhancement.

PubMed

Wang, Qian; Zhu, Yining; Li, Hongwei

2015-12-28

Digital Radiography (DR) images obtained by OCD-based (optical coupling detector) Micro-CT system usually suffer from low contrast. In this paper, a mathematical model is proposed to describe the image formation process in scintillator. By solving the correlative inverse problem, the quality of DR images is improved, i.e. higher contrast and spatial resolution. By analyzing the radiative transfer process of visible light in scintillator, scattering is recognized as the main factor leading to low contrast. Moreover, involved blurring effect is also concerned and described as point spread function (PSF). Based on these physical processes, the scintillator imaging model is then established. When solving the inverse problem, pre-correction to the intensity of x-rays, dark channel prior based haze removing technique, and an effective blind deblurring approach are employed. Experiments on a variety of DR images show that the proposed approach could improve the contrast of DR images dramatically as well as eliminate the blurring vision effectively. Compared with traditional contrast enhancement methods, such as CLAHE, our method could preserve the relative absorption values well.

Distributed imaging for liquid scintillation detectors

NASA Astrophysics Data System (ADS)

Dalmasson, J.; Gratta, G.; Jamil, A.; Kravitz, S.; Malek, M.; Wells, K.; Bentley, J.; Steven, S.; Su, J.

2018-03-01

We discuss a novel paradigm in the optical readout of scintillation radiation detectors. In one common configuration, such detectors are homogeneous and the scintillation light is collected and recorded by external photodetectors. It is usually assumed that imaging in such a photon-starved and large-emittance regime is not possible. Here we show that the appropriate optics, matched with highly segmented photodetector coverage and dedicated reconstruction software, can be used to produce images of the radiation-induced events. In particular, such a "distributed imaging" system can discriminate between events produced as a single cluster and those resulting from more delocalized energy depositions. This is crucial in discriminating many common backgrounds at MeV energies. With the use of simulation, we demonstrate the performance of a detector augmented with a practical, if preliminary, set of optics. Finally, we remark that this new technique lends itself to be adapted to different detector sizes and briefly discuss the implications for a number of common applications in science and technology.

Ultrahigh resolution radiation imaging system using an optical fiber structure scintillator plate.

PubMed

Yamamoto, Seiichi; Kamada, Kei; Yoshikawa, Akira

2018-02-16

High resolution imaging of radiation is required for such radioisotope distribution measurements as alpha particle detection in nuclear facilities or high energy physics experiments. For this purpose, we developed an ultrahigh resolution radiation imaging system using an optical fiber structure scintillator plate. We used a ~1-μm diameter fiber structured GdAlO 3 :Ce (GAP) /α-Al 2 O 3 scintillator plate to reduce the light spread. The fiber structured scintillator plate was optically coupled to a tapered optical fiber plate to magnify the image and combined with a lens-based high sensitivity CCD camera. We observed the images of alpha particles with a spatial resolution of ~25 μm. For the beta particles, the images had various shapes, and the trajectories of the electrons were clearly observed in the images. For the gamma photons, the images also had various shapes, and the trajectories of the secondary electrons were observed in some of the images. These results show that combining an optical fiber structure scintillator plate with a tapered optical fiber plate and a high sensitivity CCD camera achieved ultrahigh resolution and is a promising method to observe the images of the interactions of radiation in a scintillator.

High density scintillating glass proton imaging detector

NASA Astrophysics Data System (ADS)

Wilkinson, C. J.; Goranson, K.; Turney, A.; Xie, Q.; Tillman, I. J.; Thune, Z. L.; Dong, A.; Pritchett, D.; McInally, W.; Potter, A.; Wang, D.; Akgun, U.

2017-03-01

In recent years, proton therapy has achieved remarkable precision in delivering doses to cancerous cells while avoiding healthy tissue. However, in order to utilize this high precision treatment, greater accuracy in patient positioning is needed. An accepted approximate uncertainty of +/-3% exists in the current practice of proton therapy due to conversions between x-ray and proton stopping power. The use of protons in imaging would eliminate this source of error and lessen the radiation exposure of the patient. To this end, this study focuses on developing a novel proton-imaging detector built with high-density glass scintillator. The model described herein contains a compact homogeneous proton calorimeter composed of scintillating, high density glass as the active medium. The unique geometry of this detector allows for the measurement of both the position and residual energy of protons, eliminating the need for a separate set of position trackers in the system. Average position and energy of a pencil beam of 106 protons is used to reconstruct the image rather than by analyzing individual proton data. Simplicity and efficiency were major objectives in this model in order to present an imaging technique that is compact, cost-effective, and precise, as well as practical for a clinical setting with pencil-beam scanning proton therapy equipment. In this work, the development of novel high-density glass scintillator and the unique conceptual design of the imager are discussed; a proof-of-principle Monte Carlo simulation study is performed; preliminary two-dimensional images reconstructed from the Geant4 simulation are presented.

Demonstration of neutron detection utilizing open cell foam and noble gas scintillation

NASA Astrophysics Data System (ADS)

Lavelle, C. M.; Coplan, M.; Miller, E. C.; Thompson, Alan K.; Kowler, A. L.; Vest, Robert E.; Yue, A. T.; Koeth, T.; Al-Sheikhly, M.; Clark, Charles W.

2015-03-01

We present results demonstrating neutron detection via a closely spaced converter structure coupled to low pressure noble gas scintillation instrumented by a single photo-multiplier tube (PMT). The converter is dispersed throughout the gas volume using a reticulated vitreous carbon foam coated with boron carbide (B4C). A calibrated cold neutron beam is used to measure the neutron detection properties, using a thin film of enriched 10B as a reference standard. Monte Carlo computations of the ion energy deposition are discussed, including treatment of the foam random network. Results from this study indicate that the foam shadows a significant portion of the scintillation light from the PMT. The high scintillation yield of Xe appears to overcome the light loss, facilitating neutron detection and presenting interesting opportunities for neutron detector design.

Scintillating Quantum Dots for Imaging X-Rays (SQDIX) for Aircraft Inspection

NASA Technical Reports Server (NTRS)

Burke, E. R.; DeHaven, S. L.; Williams, P. A.

2015-01-01

Scintillation is the process currently employed by conventional X-ray detectors to create X-ray images. Scintillating quantum dots (StQDs) or nano-crystals are novel, nanometer-scale materials that upon excitation by X-rays, re-emit the absorbed energy as visible light. StQDs theoretically have higher output efficiency than conventional scintillating materials and are more environmentally friendly. This paper will present the characterization of several critical elements in the use of StQDs that have been performed along a path to the use of this technology in wide spread X-ray imaging. Initial work on the scintillating quantum dots for imaging X-rays (SQDIX) system has shown great promise to create state-of-the-art sensors using StQDs as a sensor material. In addition, this work also demonstrates a high degree of promise using StQDs in microstructured fiber optics. Using the microstructured fiber as a light guide could greatly increase the capture efficiency of a StQDs based imaging sensor.

Characterization of scintillator-based detectors for few-ten-keV high-spatial-resolution x-ray imaging

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

Larsson, Jakob C., E-mail: jakob.larsson@biox.kth.se; Lundström, Ulf; Hertz, Hans M.

2016-06-15

Purpose: High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scintillator-based detectors for this energy range and at high spatial frequencies. Methods: The authors determine the modulation transfer function, noise power spectrum (NPS), and detective quantum efficiency for Gadox, needle CsI, and structured CsI scintillators of different thicknesses and at different photon energies. An extended analysis of the NPS allows for direct measurements of the scintillator effective absorption efficiency andmore » effective light yield as well as providing an alternative method to assess the underlying factors behind the detector properties. Results: There is a substantial difference in performance between the scintillators depending on the imaging task but in general, the CsI based scintillators perform better than the Gadox scintillators. At low energies (16 keV), a thin needle CsI scintillator has the best performance at all frequencies. At higher energies (28–38 keV), the thicker needle CsI scintillators and the structured CsI scintillator all have very good performance. The needle CsI scintillators have higher absorption efficiencies but the structured CsI scintillator has higher resolution. Conclusions: The choice of scintillator is greatly dependent on the imaging task. The presented comparison and methodology will assist the imaging scientist in optimizing their high-resolution few-ten-keV imaging system for best performance.« less

Characterization of scintillator-based detectors for few-ten-keV high-spatial-resolution x-ray imaging.

PubMed

Larsson, Jakob C; Lundström, Ulf; Hertz, Hans M

2016-06-01

High-spatial-resolution x-ray imaging in the few-ten-keV range is becoming increasingly important in several applications, such as small-animal imaging and phase-contrast imaging. The detector properties critically influence the quality of such imaging. Here the authors present a quantitative comparison of scintillator-based detectors for this energy range and at high spatial frequencies. The authors determine the modulation transfer function, noise power spectrum (NPS), and detective quantum efficiency for Gadox, needle CsI, and structured CsI scintillators of different thicknesses and at different photon energies. An extended analysis of the NPS allows for direct measurements of the scintillator effective absorption efficiency and effective light yield as well as providing an alternative method to assess the underlying factors behind the detector properties. There is a substantial difference in performance between the scintillators depending on the imaging task but in general, the CsI based scintillators perform better than the Gadox scintillators. At low energies (16 keV), a thin needle CsI scintillator has the best performance at all frequencies. At higher energies (28-38 keV), the thicker needle CsI scintillators and the structured CsI scintillator all have very good performance. The needle CsI scintillators have higher absorption efficiencies but the structured CsI scintillator has higher resolution. The choice of scintillator is greatly dependent on the imaging task. The presented comparison and methodology will assist the imaging scientist in optimizing their high-resolution few-ten-keV imaging system for best performance.

Demonstration of neutron detection utilizing open cell foam and noble gas scintillation

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

Lavelle, C. M., E-mail: christopher.lavelle@jhuapl.edu; Miller, E. C.; Coplan, M.

2015-03-02

We present results demonstrating neutron detection via a closely spaced converter structure coupled to low pressure noble gas scintillation instrumented by a single photo-multiplier tube (PMT). The converter is dispersed throughout the gas volume using a reticulated vitreous carbon foam coated with boron carbide (B{sub 4}C). A calibrated cold neutron beam is used to measure the neutron detection properties, using a thin film of enriched {sup 10}B as a reference standard. Monte Carlo computations of the ion energy deposition are discussed, including treatment of the foam random network. Results from this study indicate that the foam shadows a significant portionmore » of the scintillation light from the PMT. The high scintillation yield of Xe appears to overcome the light loss, facilitating neutron detection and presenting interesting opportunities for neutron detector design.« less

A fast microchannel plate-scintillator detector for velocity map imaging and imaging mass spectrometry

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

Winter, B.; King, S. J.; Vallance, C., E-mail: claire.vallance@chem.ox.ac.uk

2014-02-15

The time resolution achievable using standard position-sensitive ion detectors, consisting of a chevron pair of microchannel plates coupled to a phosphor screen, is primarily limited by the emission lifetime of the phosphor, around 70 ns for the most commonly used P47 phosphor. We demonstrate that poly-para-phenylene laser dyes may be employed extremely effectively as scintillators, exhibiting higher brightness and much shorter decay lifetimes than P47. We provide an extensive characterisation of the properties of such scintillators, with a particular emphasis on applications in velocity-map imaging and microscope-mode imaging mass spectrometry. The most promising of the new scintillators exhibits an electron-to-photonmore » conversion efficiency double that of P47, with an emission lifetime an order of magnitude shorter. The new scintillator screens are vacuum stable and show no signs of signal degradation even over longer periods of operation.« less

A comparative study of scintillator combining methods for flat-panel X-ray image sensors

NASA Astrophysics Data System (ADS)

Kim, M. S.; Lim, K. T.; Kim, G.; Cho, G.

2018-02-01

An X-ray transmission imaging based on scintillation detection method is the most widely used radiation technique particularly in the medical and industrial areas. As the name suggests, scintillation detection uses a scintillator as an intermediate material to convert incoming radiation into visible-light particles. Among different types of scintillators, CsI(Tl) in a columnar configuration is the most popular type used for applications that require an energy less than 150 keV due to its capability in obtaining a high spatial resolution with a reduced light spreading effect. In this study, different methods in combining a scintillator with a light-receiving unit are investigated and their relationships are given in terms of the image quality. Three different methods of combining a scintillator with a light-receiving unit are selected to investigate their performance in X-ray imaging: upward or downward oriented needles structure of CsI(Tl), coating layer deposition around CsI(Tl), and insertion of FOP. A charge-coupled device was chosen to serve as the light-receiving unit for the proposed system. From the result, the difference of needle directions in CsI(Tl) had no significant effects in the X-ray image. In contrast, deposition of the coating material around CsI(Tl) showed 17.3% reduction in the DQE. Insertion of the FOP increased the spatial resolution by 38%, however, it decreased the light yield in the acquired image by 56%. In order to have the maximum scintillation performance in X-ray imaging, not only the reflection material but also the bonding method must be considered when combining the scintillator with the light-receiving unit. In addition, the use of FOP should be carefully decided based on the purpose of X-ray imaging, e.g., image sharpness or SNR.

Scintillator for low accelerating voltage scanning electron microscopy imaging

NASA Astrophysics Data System (ADS)

Bowser, Christopher; Tzolov, Marian; Barbi, Nicholas

Scintillators are essential in detecting electrons in SEM. The conventional scintillators such as YAP and YAG have poor response at low accelerating voltages due to a top conductive layer of ITO or Al. We have developed a thin film ZnWO4 scintillator with high photoluminescence quantum efficiency of 60% with enough electrical conductivity to prevent charging. We are showing that the ZnWO4 films are effective in detecting electrons at low accelerating voltages. This makes it a good option for a top layer on crystalline scintillators and we have integrated ZnWO4 with YAP to explore the high response of YAP at high electron energies and the effective response of ZnWO4 at low electron energies. We will compare the spectral intensities over a range of accelerating voltages between 1 and 30kV between the conventional and coupled thin film scintillator. The results are interpreted using a simulation of the depth profile of the electron penetration in the scintillator using CASINO. We have verified the absence of charging by measuring the sum of the secondary and backscattered electron coefficients. We have built detectors with the combined scintillators and we will compare SEM images recorded simultaneously by conventional and ZnWO4-based scintillators.

Scintillation Reduction using Conjugate-Plane Imaging (Abstract)

NASA Astrophysics Data System (ADS)

Vander Haagen, G. A.

2017-12-01

(Abstract only) All observatories are plagued by atmospheric turbulence exhibited as star scintillation or "twinkle" whether a high altitude adaptive optics research or a 30-cm amateur telescope. It is well known that these disturbances are caused by wind and temperature-driven refractive gradients in the atmosphere and limit the ultimate photometric resolution of land-based facilities. One approach identified by Fuchs (1998) for scintillation noise reduction was to create a conjugate image space at the telescope and focus on the dominant conjugate turbulent layer within that space. When focused on the turbulent layer little or no scintillation exists. This technique is described whereby noise reductions of 6 to 11/1 have been experienced with mathematical and optical bench simulations. Discussed is a proof-of-principle conjugate optical train design for an 80-mm, f7 telescope.

Comparison of polystyrene scintillator fiber array and monolithic polystyrene for neutron imaging and radiography.

PubMed

Simpson, R; Cutler, T E; Danly, C R; Espy, M A; Goglio, J H; Hunter, J F; Madden, A C; Mayo, D R; Merrill, F E; Nelson, R O; Swift, A L; Wilde, C H; Zocco, T G

2016-11-01

The neutron imaging diagnostic at the National Ignition Facility has been operating since 2011 generating neutron images of deuterium-tritium (DT) implosions at peak compression. The current design features a scintillating fiber array, which allows for high imaging resolution to discern small-scale structure within the implosion. In recent years, it has become clear that additional neutron imaging systems need to be constructed in order to provide 3D reconstructions of the DT source and these additional views need to be on a shorter line of sight. As a result, there has been increased effort to identify new image collection techniques that improve upon imaging resolution for these next generation neutron imaging systems, such as monolithic deuterated scintillators. This work details measurements performed at the Weapons Neutron Research Facility at Los Alamos National Laboratory that compares the radiographic abilities of the fiber scintillator with a monolithic scintillator, which may be featured in a future short line of sight neutron imaging systems.

Comparison of polystyrene scintillator fiber array and monolithic polystyrene for neutron imaging and radiography

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

Simpson, R., E-mail: raspberry@lanl.gov; Cutler, T. E.; Danly, C. R.

The neutron imaging diagnostic at the National Ignition Facility has been operating since 2011 generating neutron images of deuterium-tritium (DT) implosions at peak compression. The current design features a scintillating fiber array, which allows for high imaging resolution to discern small-scale structure within the implosion. In recent years, it has become clear that additional neutron imaging systems need to be constructed in order to provide 3D reconstructions of the DT source and these additional views need to be on a shorter line of sight. As a result, there has been increased effort to identify new image collection techniques that improvemore » upon imaging resolution for these next generation neutron imaging systems, such as monolithic deuterated scintillators. This work details measurements performed at the Weapons Neutron Research Facility at Los Alamos National Laboratory that compares the radiographic abilities of the fiber scintillator with a monolithic scintillator, which may be featured in a future short line of sight neutron imaging systems.« less

Comparison of polystyrene scintillator fiber array and monolithic polystyrene for neutron imaging and radiography

NASA Astrophysics Data System (ADS)

Simpson, R.; Cutler, T. E.; Danly, C. R.; Espy, M. A.; Goglio, J. H.; Hunter, J. F.; Madden, A. C.; Mayo, D. R.; Merrill, F. E.; Nelson, R. O.; Swift, A. L.; Wilde, C. H.; Zocco, T. G.

2016-11-01

The neutron imaging diagnostic at the National Ignition Facility has been operating since 2011 generating neutron images of deuterium-tritium (DT) implosions at peak compression. The current design features a scintillating fiber array, which allows for high imaging resolution to discern small-scale structure within the implosion. In recent years, it has become clear that additional neutron imaging systems need to be constructed in order to provide 3D reconstructions of the DT source and these additional views need to be on a shorter line of sight. As a result, there has been increased effort to identify new image collection techniques that improve upon imaging resolution for these next generation neutron imaging systems, such as monolithic deuterated scintillators. This work details measurements performed at the Weapons Neutron Research Facility at Los Alamos National Laboratory that compares the radiographic abilities of the fiber scintillator with a monolithic scintillator, which may be featured in a future short line of sight neutron imaging systems.

Use and imaging performance of CMOS flat panel imager with LiF/ZnS(Ag) and Gadox scintillation screens for neutron radiography

NASA Astrophysics Data System (ADS)

Cha, B. K.; kim, J. Y.; Kim, T. J.; Sim, C.; Cho, G.; Lee, D. H.; Seo, C.-W.; Jeon, S.; Huh, Y.

2011-01-01

In digital neutron radiography system, a thermal neutron imaging detector based on neutron-sensitive scintillating screens with CMOS(complementary metal oxide semiconductor) flat panel imager is introduced for non-destructive testing (NDT) application. Recently, large area CMOS APS (active-pixel sensor) in conjunction with scintillation films has been widely used in many digital X-ray imaging applications. Instead of typical imaging detectors such as image plates, cooled-CCD cameras and amorphous silicon flat panel detectors in combination with scintillation screens, we tried to apply a scintillator-based CMOS APS to neutron imaging detection systems for high resolution neutron radiography. In this work, two major Gd2O2S:Tb and 6LiF/ZnS:Ag scintillation screens with various thickness were fabricated by a screen printing method. These neutron converter screens consist of a dispersion of Gd2O2S:Tb and 6LiF/ZnS:Ag scintillating particles in acrylic binder. These scintillating screens coupled-CMOS flat panel imager with 25x50mm2 active area and 48μm pixel pitch was used for neutron radiography. Thermal neutron flux with 6x106n/cm2/s was utilized at the NRF facility of HANARO in KAERI. The neutron imaging characterization of the used detector was investigated in terms of relative light output, linearity and spatial resolution in detail. The experimental results of scintillating screen-based CMOS flat panel detectors demonstrate possibility of high sensitive and high spatial resolution imaging in neutron radiography system.

Gas Scintillation Proportional Counters for High-Energy X-ray Astronomy

NASA Technical Reports Server (NTRS)

Gubarev, Mikhail; Ramsey, Brian; Apple, Jeffery

2003-01-01

A focal plane array of high-pressure gas scintillation proportional counters (GSPC) for a balloon-borne hard-x-ray telescope is under development at the Marshall Space Flight Center. These detectors have an active area of approx. 20 sq cm, and are filled with a high pressure (10(exp 6) Pa) xenon-helium mixture. Imaging is via crossed-grid position-sensitive phototubes sensitive in the UV region. The performance of the GSPC is well matched to that of the telescopes x-ray optics which have response to 75 keV and a focal spot size of approx. 500 microns. The detector s energy resolution, 4% FWHM at 60 keV, is adequate for resolving the broad spectral lines of astrophysical importance and for accurate continuum measurements. Full details of the instrument and its performance will be provided.

Characterisation of LSO:Tb scintillator films for high resolution X-ray imaging applications

NASA Astrophysics Data System (ADS)

Cecilia, A.; Rack, A.; Douissard, P.-A.; Martin, T.; Dos Santos Rolo, T.; Vagovič, P.; Pelliccia, D.; Couchaud, M.; Dupré, K.; Baumbach, T.

2011-05-01

Within the framework of an FP6 project (SCINTAX)1The Project SCINTAX is funded by the European Community (STRP 033 427), . we developed a new thin film single crystal scintillator for high resolution X-ray imaging based on a layer of modified LSO (Lu2SiO5) grown by liquid phase epitaxy (LPE) on a dedicated substrate. In this work we present the characterisation of the scintillating LSO films in terms of optical and scintillation properties as well as spatial resolution performances. The obtained results are discussed and compared with the performances of the thin scintillating films commonly used in synchrotron-based micro-imaging applications.

Evaluation of dual γ-ray imager with active collimator using various types of scintillators.

PubMed

Lee, Wonho; Lee, Taewoong; Jeong, Manhee; Kim, Ho Kyung

2011-10-01

The performance of a specialized dual γ-ray imager using both mechanical and electronic collimation was evaluated by Monte Carlo simulation (MCNP5). The dual imager consisted of an active collimator and a planar detector that were made from scintillators. The active collimator served not only as a coded aperture for mechanical collimation but also as a first detector for electronic collimation. Therefore, a single system contained both mechanical and electronic collimation. Various types of scintillators were tested and compared with each other in terms of their angular resolution, efficiency, and background noise. In general, a BGO active collimator had the best mechanical collimation performance, and an LaCl₃(Ce) active collimator provided the best electronic collimation performance. However, for low radiation energies, the mechanical collimation images made from both scintillators showed the same quality, and, for high radiation energies, electronic collimation images made from both scintillators also show similar quality. Therefore, if mechanical collimation is used to detect low-energy radiation and electronic collimation is applied to reconstruct a high-energy source, either LaCl₃(Ce) or BGO would be appropriate for the active collimator of a dual γ-ray imager. These results broaden the choice of scintillators for the active collimator of the dual γ-ray imager, which makes it possible to consider other factors, such as machinability and cost, in making the imager. As a planar detector, BGO showed better performance than other scintillators since its radiation detection efficiency was highest of all. Copyright © 2011 Elsevier Ltd. All rights reserved.

Hexagonal Uniformly Redundant Arrays (HURAs) for scintillator based coded aperture neutron imaging

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

Gamage, K.A.A.; Zhou, Q.

2015-07-01

A series of Monte Carlo simulations have been conducted, making use of the EJ-426 neutron scintillator detector, to investigate the potential of using hexagonal uniformly redundant arrays (HURAs) for scintillator based coded aperture neutron imaging. This type of scintillator material has a low sensitivity to gamma rays, therefore, is of particular use in a system with a source that emits both neutrons and gamma rays. The simulations used an AmBe source, neutron images have been produced using different coded-aperture materials (boron- 10, cadmium-113 and gadolinium-157) and location error has also been estimated. In each case the neutron image clearly showsmore » the location of the source with a relatively small location error. Neutron images with high resolution can be easily used to identify and locate nuclear materials precisely in nuclear security and nuclear decommissioning applications. (authors)« less

Scintillating Quantum Dots for Imaging X-rays (SQDIX) for Aircraft Inspection

NASA Technical Reports Server (NTRS)

Burke, Eric (Principal Investigator); Williams, Phillip (Principal Investigator); Dehaven, Stan

2015-01-01

Scintillation is the process currently employed by conventional x-ray detectors to create x-ray images. Scintillating quantum dots or nano-crystals (StQDs) are a novel, nanometer-scale material that upon excitation by x-rays, re-emit the absorbed energy as visible light. StQDs theoretically have higher output efficiency than conventional scintillating materials and are more environmental friendly. This paper will present the characterization of several critical elements in the use of StQDs that have been performed along a path to the use of this technology in wide spread x-ray imaging. Initial work on the SQDIX system has shown great promise to create state-of-the-art sensors using StQDs as a sensor material. In addition, this work also demonstrates a high degree of promise using StQDs in microstructured fiber optics. Using the microstructured fiber as a light guide could greatly increase the capture efficiency a StQDs based imaging sensor.

Building a multi-cathode-gas-filled scintillator detector for fission fragments

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

Mahgoub, M., E-mail: mmahgoub@jazanu.edu.sa; Physics department, Technical University of Munich, D-85748 Garching

2016-06-10

Radiation cannot be detected directly by human senses, indeed detecting and identifying the fission products or decay yield with high accuracy is a great challenge for experimental physicist. In this work we are building a Multi-Cathode-Gas-filled Scintillator MCGS detector. The detector consists of two parts. First: anode-wire proportional chamber and cathode strip foil, which measure the energy loss of the particles in the gas, due to the ionization, and identifies the position of the products on the detector plane depending on their energy with the presence of a magnetic field. Second: a 7 mm thick scintillator attached to a photomultipliermore » tube in the back end of the detector. This part measures the rest energy of the particles. A data acquisition system records the events and the particles infonnation. The yields are identified from the energy loss to rest energy ratio.« less

Comparison of the imaging performances for recently developed monolithic scintillators: CRY018 and CRY019 for dual isotope gamma ray imaging applications

NASA Astrophysics Data System (ADS)

Polito, C.; Pani, R.; Trigila, C.; Cinti, M. N.; Fabbri, A.; Frantellizzi, V.; De Vincentis, G.; Pellegrini, R.; Pani, R.

2017-01-01

The growing interest for new scintillation crystals with outstanding imaging performances (i.e. resolution and efficiency) has suggested the study of recently discovered scintillators named CRY018 and CRY019. The crystals under investigation are monolithic and have shown enhanced characteristics both for gamma ray spectrometry and for Nuclear Medicine imaging applications such as the dual isotope imaging. Moreover, the non-hygroscopic nature and the absence of afterglow make these scintillators even more attractive for the potential improvement in a wide range of applications. These scintillation crystals show a high energy resolution in the energy range involved in Nuclear Medicine, allowing the discrimination between very close energy values. Moreover, in order to prove their suitability of being powerful imaging systems, the imaging performances like the position linearity and the intrinsic spatial resolution have been evaluated obtaining satisfactory results thanks to the implementation of an optimized algorithm for the images reconstruction.

Inorganic scintillating materials and scintillation detectors

PubMed Central

YANAGIDA, Takayuki

2018-01-01

Scintillation materials and detectors that are used in many applications, such as medical imaging, security, oil-logging, high energy physics and non-destructive inspection, are reviewed. The fundamental physics understood today is explained, and common scintillators and scintillation detectors are introduced. The properties explained here are light yield, energy non-proportionality, emission wavelength, energy resolution, decay time, effective atomic number and timing resolution. For further understanding, the emission mechanisms of scintillator materials are also introduced. Furthermore, unresolved problems in scintillation phenomenon are considered, and my recent interpretations are discussed. These topics include positive hysteresis, the co-doping of non-luminescent ions, the introduction of an aimed impurity phase, the excitation density effect and the complementary relationship between scintillators and storage phosphors. PMID:29434081

Lithium indium diselenide: A new scintillator for neutron imaging

DOE PAGES

Lukosi, Eric; Herrera, Elan; Hamm, Daniel; ...

2016-05-20

Lithium indium diselenide, 6LiInSe 2 or LISe, is a newly developed neutron detection material that shows both semiconducting and scintillating properties. The 24% atomic density of 6Li yields a thermal neutron mean free path of only 920 μm. This paper reports on the performance of LISe crystals in scintillation mode for its potential use as a converter screen for thermal/cold neutron imaging. The spatial resolution of LISe, determined using a 10% value of the Modulation Transfer Function (MTF), was found to not scale linearly with thickness. Crystals having a thickness of 450 μm or larger resulted in an average spatialmore » resolution of 67 μm, and the thinner crystals exhibited an increase in spatial resolution down to the Nyquist frequency of the CCD. The highest measured spatial resolution of 198 μm thick LISe (27 μm) outperforms a commercial 50 μm thick ZnS(Cu): 6LiF scintillation screen (100 μm) by more than a factor of three. For the thicknesses considered in this study, it has been found that the light yield of LISe did not scale with its thickness, suggesting the need for optimizing the synthesis to enhance the scintillation mechanism. Absorption measurements indicate that the 6Li concentration is uniform throughout the samples and its absorption efficiency as a function of thickness follows general nuclear theory, indicating that the variation in apparent brightness is likely due to a combination of particle escape, light transport, and activation of the scintillation mechanisms. As a result, the presence of 115In and its long-lived 116In activation product did not result in ghosting (memory of past neutron exposure), demonstrating potential for using LISe for imaging transient systems.« less

Advanced Scintillator Detectors for Neutron Imaging in Inertial Confinement Fusion

NASA Astrophysics Data System (ADS)

Geppert-Kleinrath, Verena; Danly, Christopher; Merrill, Frank; Simpson, Raspberry; Volegov, Petr; Wilde, Carl

2016-10-01

The neutron imaging team at Los Alamos National Laboratory (LANL) has been providing two-dimensional neutron imaging of the inertial confinement fusion process at the National Ignition Facility (NIF) for over five years. Neutron imaging is a powerful tool in which position-sensitive detectors register neutrons emitted in the fusion reactions, producing a picture of the burning fuel. Recent images have revealed possible multi-dimensional asymmetries, calling for additional views to facilitate three-dimensional imaging. These will be along shorter lines of sight to stay within the existing facility at NIF. In order to field imaging capabilities equivalent to the existing system several technological challenges have to be met: high spatial resolution, high light output, and fast scintillator response to capture lower-energy neutrons, which have scattered from non-burning regions of fuel. Deuterated scintillators are a promising candidate to achieve the timing and resolution required; a systematic study of deuterated and non-deuterated polystyrene and liquid samples is currently ongoing. A test stand has been implemented to measure the response function, and preliminary data on resolution and light output have been obtained at the LANL Weapons Neutrons Research facility.

Scintillating Balloon-Enabled Fiber-Optic System for Radionuclide Imaging of Atherosclerotic Plaques

PubMed Central

Zaman, Raiyan T.; Kosuge, Hisanori; Carpenter, Colin; Sun, Conroy; McConnell, Michael V.; Xing, Lei

2015-01-01

Atherosclerosis underlies coronary artery disease, the leading cause of death in the United States and worldwide. Detection of coronary plaque inflammation remains challenging. In this study, we developed a scintillating balloon-enabled fiber-optic radio-nuclide imaging (SBRI) system to improve the sensitivity and resolution of plaque imaging using 18F-FDG, a marker of vascular inflammation, and tested it in a murine model. Methods The fiber-optic system uses a Complementary Metal-Oxide Silicon (CMOS) camera with a distal ferrule terminated with a wide-angle lens. The novelty of this system is a scintillating balloon in the front of the wide-angle lens to image light from the decay of 18F-FDG emission signal. To identify the optimal scintillating materials with respect to resolution, we calculated the modulation transfer function of yttrium–aluminum–garnet doped with cerium, anthracene, and calcium fluoride doped with europium (CaF2:Eu) phosphors using an edge pattern and a thin-line optical phantom. The scintillating balloon was then fabricated from 10 mL of silicone RTV catalyst mixed with 1 mL of base and 50 mg of CaF2:Eu per mL. The addition of a lutetium oxyorthosilicate scintillating crystal (500 μm thick) to the balloon was also investigated. The SBRI system was tested in a murine atherosclerosis model: carotid-ligated mice (n = 5) were injected with 18F-FDG, followed by ex vivo imaging of the macrophage-rich carotid plaques and nonligated controls. Confirmatory imaging of carotid plaques and controls was also performed by an external optical imaging system and autoradiography. Results Analyses of the different phosphors showed that CaF2:Eu enabled the best resolution of 1.2 μm. The SBRI system detected almost a 4-fold-higher radioluminescence signal from the ligated left carotid artery than the nonligated right carotid: 1.63 × 102 ± 4.01 × 101 vs. 4.21 × 101 ± 2.09 × 100 (photon counts), P = 0.006. We found no significant benefit to adding a

Development and characterization of a scintillating cell imaging dish for radioluminescence microscopy.

PubMed

Sengupta, Debanti; Kim, Tae Jin; Almasi, Sepideh; Miller, Stuart; Marton, Zsolt; Nagarkar, Vivek; Pratx, Guillem

2018-04-16

Radioluminescence microscopy is an emerging modality that can be used to image radionuclide probes with micron-scale resolution. This technique is particularly useful as a way to probe the metabolic behavior of single cells and to screen and characterize radiopharmaceuticals, but the quality of the images is critically dependent on the scintillator material used to image the cells. In this paper, we detail the development of a microscopy dish made of a thin-film scintillating material, Lu2O3:Eu, that could be used as the blueprint for a future consumable product. After developing a simple quality control method based on long-lived alpha and beta sources, we characterize the radioluminescence properties of various thin-film scintillator samples. We find consistent performance for most samples, but also identify a few samples that do not meet the specifications, thus stressing the need for routine quality control prior to biological experiments. In addition, we test and quantify the transparency of the material, and demonstrate that transparency correlates with thickness. Finally, we evaluate the biocompatibility of the material and show that the microscopy dish can produce radioluminescent images of live single cells.

LPE grown LSO:Tb scintillator films for high-resolution X-ray imaging applications at synchrotron light sources

NASA Astrophysics Data System (ADS)

Cecilia, A.; Rack, A.; Douissard, P.-A.; Martin, T.; Dos Santos Rolo, T.; Vagovič, P.; Hamann, E.; van de Kamp, T.; Riedel, A.; Fiederle, M.; Baumbach, T.

2011-08-01

Within the project ScinTAX of the 6th framework program (FP6) of the European Commission (SCINTAX—STRP 033 427) we have developed a new thin single crystal scintillator for high-resolution X-ray imaging. The scintillator is based on a Tb-doped Lu2SiO5 (LSO) film epitaxially grown on an adapted substrate. The high density, effective atomic number and light yield of the scintillating LSO significantly improves the efficiency of the X-ray imaging detectors currently used in synchrotron micro-imaging applications. In this work we present the characterization of the scintillating LSO films in terms of their spatial resolution performance and we provide two examples of high spatial and high temporal resolution applications.

Imaging properties of pixellated scintillators with deep pixels

NASA Astrophysics Data System (ADS)

Barber, H. Bradford; Fastje, David; Lemieux, Daniel; Grim, Gary P.; Furenlid, Lars R.; Miller, Brian W.; Parkhurst, Philip; Nagarkar, Vivek V.

2014-09-01

We have investigated the light-transport properties of scintillator arrays with long, thin pixels (deep pixels) for use in high-energy gamma-ray imaging. We compared 10x10 pixel arrays of YSO:Ce, LYSO:Ce and BGO (1mm x 1mm x 20 mm pixels) made by Proteus, Inc. with similar 10x10 arrays of LSO:Ce and BGO (1mm x 1mm x 15mm pixels) loaned to us by Saint-Gobain. The imaging and spectroscopic behaviors of these scintillator arrays are strongly affected by the choice of a reflector used as an inter-pixel spacer (3M ESR in the case of the Proteus arrays and white, diffuse-reflector for the Saint-Gobain arrays). We have constructed a 3700-pixel LYSO:Ce Prototype NIF Gamma-Ray Imager for use in diagnosing target compression in inertial confinement fusion. This system was tested at the OMEGA Laser and exhibited significant optical, inter-pixel cross-talk that was traced to the use of a single-layer of ESR film as an inter-pixel spacer. We show how the optical cross-talk can be mapped, and discuss correction procedures. We demonstrate a 10x10 YSO:Ce array as part of an iQID (formerly BazookaSPECT) imager and discuss issues related to the internal activity of 176Lu in LSO:Ce and LYSO:Ce detectors.

Imaging properties of pixellated scintillators with deep pixels

PubMed Central

Barber, H. Bradford; Fastje, David; Lemieux, Daniel; Grim, Gary P.; Furenlid, Lars R.; Miller, Brian W.; Parkhurst, Philip; Nagarkar, Vivek V.

2015-01-01

We have investigated the light-transport properties of scintillator arrays with long, thin pixels (deep pixels) for use in high-energy gamma-ray imaging. We compared 10×10 pixel arrays of YSO:Ce, LYSO:Ce and BGO (1mm × 1mm × 20 mm pixels) made by Proteus, Inc. with similar 10×10 arrays of LSO:Ce and BGO (1mm × 1mm × 15mm pixels) loaned to us by Saint-Gobain. The imaging and spectroscopic behaviors of these scintillator arrays are strongly affected by the choice of a reflector used as an inter-pixel spacer (3M ESR in the case of the Proteus arrays and white, diffuse-reflector for the Saint-Gobain arrays). We have constructed a 3700-pixel LYSO:Ce Prototype NIF Gamma-Ray Imager for use in diagnosing target compression in inertial confinement fusion. This system was tested at the OMEGA Laser and exhibited significant optical, inter-pixel cross-talk that was traced to the use of a single-layer of ESR film as an inter-pixel spacer. We show how the optical cross-talk can be mapped, and discuss correction procedures. We demonstrate a 10×10 YSO:Ce array as part of an iQID (formerly BazookaSPECT) imager and discuss issues related to the internal activity of 176Lu in LSO:Ce and LYSO:Ce detectors. PMID:26236070

A novel design for scintillator-based neutron and gamma imaging in inertial confinement fusion

NASA Astrophysics Data System (ADS)

Geppert-Kleinrath, Verena; Cutler, Theresa; Danly, Chris; Madden, Amanda; Merrill, Frank; Tybo, Josh; Volegov, Petr; Wilde, Carl

2017-10-01

The LANL Advanced Imaging team has been providing reliable 2D neutron imaging of the burning fusion fuel at NIF for years, revealing possible multi-dimensional asymmetries in the fuel shape, and therefore calling for additional views. Adding a passive imaging system using image plate techniques along a new polar line of sight has recently demonstrated the merit of 3D neutron image reconstruction. Now, the team is in the process of designing a new active neutron imaging system for an additional equatorial view. The design will include a gamma imaging system as well, to allow for the imaging of carbon in the ablator of the NIF fuel capsules, constraining the burning fuel shape even further. The selection of ideal scintillator materials for a position-sensitive detector system is the key component for the new design. A comprehensive study of advanced scintillators has been carried out at the Los Alamos Neutron Science Center and the OMEGA Laser Facility in Rochester, NY. Neutron radiography using a fast-gated CCD camera system delivers measurements of resolution, light output and noise characteristics. The measured performance parameters inform the novel design, for which we conclude the feasibility of monolithic scintillators over pixelated counterparts.

A high resolution gas scintillation proportional counter for studying low energy cosmic X-ray sources

NASA Technical Reports Server (NTRS)

Hamilton, T. T.; Hailey, C. J.; Ku, W. H.-M.; Novick, R.

1980-01-01

In recent years much effort has been devoted to the development of large area gas scintillation proportional counters (GSPCs) suitable for use in X-ray astronomy. The paper deals with a low-energy GSPC for use in detecting sub-keV X-rays from cosmic sources. This instrument has a measured energy resolution of 85 eV (FWHM) at 149 eV over a sensitive area of 5 sq cm. The development of imaging capability for this instrument is discussed. Tests are performed on the feasibility of using an arrangement of several phototubes placed adjacent to one another to determine event locations in a large flat counter. A simple prototype has been constructed and successfully operated.

Optical imaging of airglow structure in equatorial plasma bubbles at radio scintillation scales

NASA Astrophysics Data System (ADS)

Holmes, J. M.; Pedersen, T.; Parris, R. T.; Stephens, B.; Caton, R. G.; Dao, E. V.; Kratochvil, S.; Morton, Y.; Xu, D.; Jiao, Y.; Taylor, S.; Carrano, C. S.

2015-12-01

Imagery of optical emissions from F-region plasma is one of the few means available todetermine plasma density structure in two dimensions. However, the smallest spatial scalesobservable with this technique are typically limited not by magnification of the lens or resolutionof the detector but rather by the optical throughput of the system, which drives the integrationtime, which in turn causes smearing of the features that are typically moving at speeds of 100m/s or more. In this paper we present high spatio-temporal imagery of equatorial plasma bubbles(EPBs) from an imaging system called the Large Aperture Ionospheric Structure Imager(LAISI), which was specifically designed to capture short-integration, high-resolution images ofF-region recombination airglow at λ557.7 nm. The imager features 8-inch diameter entranceoptics comprised of a unique F/0.87 lens, combined with a monolithic 8-inch diameterinterference filter and a 2x2-inch CCD detector. The LAISI field of view is approximately 30degrees. Filtered all-sky images at common airglow wavelengths are combined with magneticfield-aligned LAISI images, GNSS scintillation, and VHF scintillation data obtained atAscension Island (7.98S, 14.41W geographic). A custom-built, multi-constellation GNSS datacollection system was employed that sampled GPS L1, L2C, L5, GLONASS L1 and L2, BeidouB1, and Galileo E1 and E5a signals. Sophisticated processing software was able to maintainlock of all signals during strong scintillation, providing unprecedented spatial observability ofL band scintillation. The smallest-resolvable scale sizes above the noise floor in the EPBs, as viewed byLAISI, are illustrated for integration times of 1, 5 and 10 seconds, with concurrentzonal irregularity drift speeds from both spaced-receiver VHF measurements and single-stationGNSS measurements of S4 and σφ. These observable optical scale sizes are placed in thecontext of those that give rise to radio scintillation in VHF and L band signals.

Countering Beam Divergence Effects with Focused Segmented Scintillators for High DQE Megavoltage Active Matrix Imagers

PubMed Central

Liu, Langechuan; Antonuk, Larry E; Zhao, Qihua; El-Mohri, Youcef; Jiang, Hao

2012-01-01

The imaging performance of active matrix flat-panel imagers designed for megavoltage imaging (MV AMFPIs) is severely constrained by relatively low x-ray detection efficiency, which leads to a detective quantum efficiency (DQE) of only ~1%. Previous theoretical and empirical studies by our group have demonstrated the potential for addressing this constraint through utilization of thick, two-dimensional, segmented scintillators with optically isolated crystals. However, this strategy is constrained by degradation of high-frequency DQE resulting from spatial resolution loss at locations away from the central beam axis due to oblique incidence of radiation. To address this challenge, segmented scintillators constructed so that the crystals are individually focused toward the radiation source are proposed and theoretically investigated. The study was performed using Monte Carlo simulations of radiation transport to examine the modulation transfer function and DQE of focused segmented scintillators with thicknesses ranging from 5 to 60 mm. The results demonstrate that, independent of scintillator thickness, the introduction of focusing largely restores spatial resolution and DQE performance otherwise lost in thick, unfocused segmented scintillators. For the case of a 60 mm thick BGO scintillator and at a location 20 cm off the central beam axis, use of focusing improves DQE by up to a factor of ~130 at non-zero spatial frequencies. The results also indicate relatively robust tolerance of such scintillators to positional displacements, of up to 10 cm in the source-to-detector direction and 2 cm in the lateral direction, from their optimal focusing position, which could potentially enhance practical clinical use of focused segmented scintillators in MV AMFPIs. PMID:22854009

X-ray imaging performance of scintillator-filled silicon pore arrays

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

Simon, Matthias; Engel, Klaus Juergen; Menser, Bernd

2008-03-15

The need for fine detail visibility in various applications such as dental imaging, mammography, but also neurology and cardiology, is the driver for intensive efforts in the development of new x-ray detectors. The spatial resolution of current scintillator layers is limited by optical diffusion. This limitation can be overcome by a pixelation, which prevents optical photons from crossing the interface between two neighboring pixels. In this work, an array of pores was etched in a silicon wafer with a pixel pitch of 50 {mu}m. A very high aspect ratio was achieved with wall thicknesses of 4-7 {mu}m and pore depthsmore » of about 400 {mu}m. Subsequently, the pores were filled with Tl-doped cesium iodide (CsI:Tl) as a scintillator in a special process, which includes powder melting and solidification of the CsI. From the sample geometry and x-ray absorption measurement the pore fill grade was determined to be 75%. The scintillator-filled samples have a circular active area of 16 mm diameter. They are coupled with an optical sensor binned to the same pixel pitch in order to measure the x-ray imaging performance. The x-ray sensitivity, i.e., the light output per absorbed x-ray dose, is found to be only 2.5%-4.5% of a commercial CsI-layer of similar thickness, thus very low. The efficiency of the pores to transport the generated light to the photodiode is estimated to be in the best case 6.5%. The modulation transfer function is 40% at 4 lp/mm and 10%-20% at 8 lp/mm. It is limited most likely by the optical gap between scintillator and sensor and by K-escape quanta. The detective quantum efficiency (DQE) is determined at different beam qualities and dose settings. The maximum DQE(0) is 0.28, while the x-ray absorption with the given thickness and fill factor is 0.57. High Swank noise is suspected to be the reason, mainly caused by optical scatter inside the CsI-filled pores. The results are compared to Monte Carlo simulations of the photon transport inside the pore

Radiation imaging with a new scintillator and a CMOS camera

NASA Astrophysics Data System (ADS)

Kurosawa, S.; Shoji, Y.; Pejchal, J.; Yokota, Y.; Yoshikawa, A.

2014-07-01

A new imaging system consisting of a high-sensitivity complementary metal-oxide semiconductor (CMOS) sensor, a microscope and a new scintillator, Ce-doped Gd3(Al,Ga)5O12 (Ce:GAGG) grown by the Czochralski process, has been developed. The noise, the dark current and the sensitivity of the CMOS camera (ORCA-Flash4.0, Hamamatsu) was revised and compared to a conventional CMOS, whose sensitivity is at the same level as that of a charge coupled device (CCD) camera. Without the scintillator, this system had a good position resolution of 2.1 ± 0.4 μm and we succeeded in obtaining the alpha-ray images using 1-mm thick Ce:GAGG crystal. This system can be applied for example to high energy X-ray beam profile monitor, etc.

Time-gated scintillator imaging for real-time optical surface dosimetry in total skin electron therapy.

PubMed

Bruza, Petr; Gollub, Sarah L; Andreozzi, Jacqueline M; Tendler, Irwin I; Williams, Benjamin B; Jarvis, Lesley A; Gladstone, David J; Pogue, Brian W

2018-05-02

The purpose of this study was to measure surface dose by remote time-gated imaging of plastic scintillators. A novel technique for time-gated, intensified camera imaging of scintillator emission was demonstrated, and key parameters influencing the signal were analyzed, including distance, angle and thickness. A set of scintillator samples was calibrated by using thermo-luminescence detector response as reference. Examples of use in total skin electron therapy are described. The data showed excellent room light rejection (signal-to-noise ratio of scintillation SNR  ≈  470), ideal scintillation dose response linearity, and 2% dose rate error. Individual sample scintillation response varied by 7% due to sample preparation. Inverse square distance dependence correction and lens throughput error (8% per meter) correction were needed. At scintillator-to-source angle and observation angle  <50°, the radiant energy fluence error was smaller than 1%. The achieved standard error of the scintillator cumulative dose measurement compared to the TLD dose was 5%. The results from this proof-of-concept study documented the first use of small scintillator targets for remote surface dosimetry in ambient room lighting. The measured dose accuracy renders our method to be comparable to thermo-luminescent detector dosimetry, with the ultimate realization of accuracy likely to be better than shown here. Once optimized, this approach to remote dosimetry may substantially reduce the time and effort required for surface dosimetry.

Time-gated scintillator imaging for real-time optical surface dosimetry in total skin electron therapy

NASA Astrophysics Data System (ADS)

Bruza, Petr; Gollub, Sarah L.; Andreozzi, Jacqueline M.; Tendler, Irwin I.; Williams, Benjamin B.; Jarvis, Lesley A.; Gladstone, David J.; Pogue, Brian W.

2018-05-01

The purpose of this study was to measure surface dose by remote time-gated imaging of plastic scintillators. A novel technique for time-gated, intensified camera imaging of scintillator emission was demonstrated, and key parameters influencing the signal were analyzed, including distance, angle and thickness. A set of scintillator samples was calibrated by using thermo-luminescence detector response as reference. Examples of use in total skin electron therapy are described. The data showed excellent room light rejection (signal-to-noise ratio of scintillation SNR  ≈  470), ideal scintillation dose response linearity, and 2% dose rate error. Individual sample scintillation response varied by 7% due to sample preparation. Inverse square distance dependence correction and lens throughput error (8% per meter) correction were needed. At scintillator-to-source angle and observation angle  <50°, the radiant energy fluence error was smaller than 1%. The achieved standard error of the scintillator cumulative dose measurement compared to the TLD dose was 5%. The results from this proof-of-concept study documented the first use of small scintillator targets for remote surface dosimetry in ambient room lighting. The measured dose accuracy renders our method to be comparable to thermo-luminescent detector dosimetry, with the ultimate realization of accuracy likely to be better than shown here. Once optimized, this approach to remote dosimetry may substantially reduce the time and effort required for surface dosimetry.

Laser pixelation of thick scintillators for medical imaging applications: x-ray studies

NASA Astrophysics Data System (ADS)

Sabet, Hamid; Kudrolli, Haris; Marton, Zsolt; Singh, Bipin; Nagarkar, Vivek V.

2013-09-01

To achieve high spatial resolution required in nuclear imaging, scintillation light spread has to be controlled. This has been traditionally achieved by introducing structures in the bulk of scintillation materials; typically by mechanical pixelation of scintillators and fill the resultant inter-pixel gaps by reflecting materials. Mechanical pixelation however, is accompanied by various cost and complexity issues especially for hard, brittle and hygroscopic materials. For example LSO and LYSO, hard and brittle scintillators of interest to medical imaging community, are known to crack under thermal and mechanical stress; the material yield drops quickly with large arrays with high aspect ratio pixels and therefore the pixelation process cost increases. We are utilizing a novel technique named Laser Induced Optical Barriers (LIOB) for pixelation of scintillators that overcomes the issues associated with mechanical pixelation. In this technique, we can introduce optical barriers within the bulk of scintillator crystals to form pixelated arrays with small pixel size and large thickness. We applied LIOB to LYSO using a high-frequency solid-state laser. Arrays with different crystal thickness (5 to 20 mm thick), and pixel size (0.8×0.8 to 1.5×1.5 mm2) were fabricated and tested. The width of the optical barriers were controlled by fine-tuning key parameters such as lens focal spot size and laser energy density. Here we report on LIOB process, its optimization, and the optical crosstalk measurements using X-rays. There are many applications that can potentially benefit from LIOB including but not limited to clinical/pre-clinical PET and SPECT systems, and photon counting CT detectors.

Ultra-fast LuI{sub 3}:Ce scintillators for hard x-ray imaging

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

Marton, Zsolt, E-mail: zmarton@rmdinc.com; Miller, Stuart R.; Ovechkina, Elena

We have developed ultra-fast cerium-coped lutetium-iodide (LuI{sub 3}:Ce) films thermally evaporated as polycrystalline, structured scintillator using hot wall epitaxy (HWE) method. The films have shown a 13 ns decay compared to the 28 ns reported for crystals. The fast speed coupled with its high density (∼5.6 g/cm{sup 3}), high effective atomic number (59.7), and the fact that it can be vapor deposited in a columnar form makes LuI{sub 3}:Ce an attractive candidate for high frame rate, high-resolution, hard X-ray imaging. In crystal form, LuI{sub 3}:Ce has demonstrated bright (>100,000 photons/MeV) green (540 nm) emission, which is well matched to commercialmore » CCD/CMOS sensors and is critical for maintaining high signal to noise ratio in light starved applications. Here, we report on the scintillation properties of films and those for corresponding crystalline material. The vapor grown films were integrated into a high-speed CMOS imager to demonstrate high-speed radiography capability. The films were also tested at Advanced Photon Source, Argonne National Laboratory beamline 1-ID under hard X-ray irradiation. The data show a factor of four higher efficiency than the reference LuAG:Ce scintillators, high image quality, and linearity of scintillation response over a wide energy range. The films were employed to perform hard X-ray microtomography, the results of which will also be discussed.« less

Performance of Gas Scintillation Proportional Counter Array for High-Energy X-Ray Observatory

NASA Technical Reports Server (NTRS)

Gubarev, Mikhail; Ramsey, Brian; Apple, Jeffery

2004-01-01

A focal plane array of high-pressure gas scintillation proportional counters (GSPC) for a High Energy X-Ray Observatory (HERO) is developed at the Marshall Space Flight Center. The array is consisted from eight GSPCs and is a part of balloon born payload scheduled to flight in May 2004. These detectors have an active area of approximately 20 square centimeters, and are filled with a high pressure (10(exp 6) Pa) xenon-helium mixture. Imaging is via crossed-grid position-sensitive phototubes sensitive in the UV region. The performance of the GSPC is well matched to that of the telescopes x-ray optics which have response to 75 keV and a focal spot size of approximately 500 microns. The detector's energy resolution, 4% FWHM at 60 keV, is adequate for resolving the broad spectral lines of astrophysical importance and for accurate continuum measurements. Results of the on-earth detector calibration will be presented and in-flight detector performance will be provided, as available.

Extruded plastic scintillator including inorganic powders

DOEpatents

Bross, Alan D.; Mellott, Kerry L.; Pla-Dalmau, Anna

2006-06-27

A method for producing a plastic scintillator is disclosed. A plurality of nano-sized particles and one or more dopants can be combined with a plastic material for the formation of a plastic scintillator thereof. The nano-sized particles, the dopant and the plastic material can be combined within the dry inert atmosphere of an extruder to produce a reaction that results in the formation of a plastic scintillator thereof and the deposition of energy within the plastic scintillator, such that the plastic scintillator produces light signifying the detection of a radiative element. The nano-sized particles can be treated with an inert gas prior to processing the nano-sized particles, the dopant and the plastic material utilizing the extruder. The plastic scintillator can be a neutron-sensitive scintillator, x-ray sensitive scintillator and/or a scintillator for the detection of minimum ionizing particles.

A method of extending the depth of focus of the high-resolution X-ray imaging system employing optical lens and scintillator: a phantom study.

PubMed

Li, Guang; Luo, Shouhua; Yan, Yuling; Gu, Ning

2015-01-01

The high-resolution X-ray imaging system employing synchrotron radiation source, thin scintillator, optical lens and advanced CCD camera can achieve a resolution in the range of tens of nanometers to sub-micrometer. Based on this advantage, it can effectively image tissues, cells and many other small samples, especially the calcification in the vascular or in the glomerulus. In general, the thickness of the scintillator should be several micrometers or even within nanometers because it has a big relationship with the resolution. However, it is difficult to make the scintillator so thin, and additionally thin scintillator may greatly reduce the efficiency of collecting photons. In this paper, we propose an approach to extend the depth of focus (DOF) to solve these problems. We develop equation sets by deducing the relationship between the high-resolution image generated by the scintillator and the degraded blur image due to defect of focus first, and then we adopt projection onto convex sets (POCS) and total variation algorithm to get the solution of the equation sets and to recover the blur image. By using a 20 μm thick unmatching scintillator to replace the 1 μm thick matching one, we simulated a high-resolution X-ray imaging system and got a degraded blur image. Based on the algorithm proposed, we recovered the blur image and the result in the experiment showed that the proposed algorithm has good performance on the recovery of image blur caused by unmatching thickness of scintillator. The method proposed is testified to be able to efficiently recover the degraded image due to defect of focus. But, the quality of the recovery image especially of the low contrast image depends on the noise level of the degraded blur image, so there is room for improving and the corresponding denoising algorithm is worthy for further study and discussion.

A High-Energy Focal-Plane Gas Scintillation Proportional Counter

NASA Technical Reports Server (NTRS)

Ramsey, B. D.; Austin, R. A.; Apple, J. A.; Dietz, K. L.

1999-01-01

We have developed a high-pressure Gas Scintillation Proportional Counter (GSPC) for the focus of a hard-x-ray telescope. It features an absorption region 50 mm in diameter and 50 mm deep, filled with Xenon + 4% He at 10(exp 6) Pa total pressure, which gives useful response (greater than 75% efficiency) up to the mirror cut-off of 70 keV. Tests with a prototype unit show an energy resolution of 3.5% at 60 keV and a spatial resolution of 0.35 mm from 30-50 keV. Two flight units are currently under construction for a balloon flight in September 1999. Full details of their design and performance will be presented together with available quick-look background data from the flight.

Monte Carlo simulation of a novel water-equivalent electronic portal imaging device using plastic scintillating fibers.

PubMed

Teymurazyan, A; Pang, G

2012-03-01

Most electronic portal imaging devices (EPIDs) developed so far use a thin Cu plate/phosphor screen to convert x-ray energies into light photons, while maintaining a high spatial resolution. This results in a low x-ray absorption and thus a low quantum efficiency (QE) of approximately 2-4% for megavoltage (MV) x-rays. A significant increase of QE is desirable for applications such as MV cone-beam computed tomography (MV-CBCT). Furthermore, the Cu plate/phosphor screen contains high atomic number (high-Z) materials, resulting in an undesirable over-response to low energy x-rays (due to photoelectric effect) as well as high energy x-rays (due to pair production) when used for dosimetric verification. Our goal is to develop a new MV x-ray detector that has a high QE and uses low-Z materials to overcome the obstacles faced by current MV x-ray imaging technologies. A new high QE and low-Z EPID is proposed. It consists of a matrix of plastic scintillating fibers embedded in a water-equivalent medium and coupled to an optically sensitive 2D active matrix flat panel imager (AMFPI) for image readout. It differs from the previous approach that uses segmented crystalline scintillators made of higher density and higher atomic number materials to detect MV x-rays. The plastic scintillating fibers are focused toward the x-ray source to avoid image blurring due to oblique incidence of off-axis x-rays. When MV x-rays interact with the scintillating fibers in the detector, scintillation light will be produced. The light photons produced in a fiber core and emitted within the acceptance angle of the fiber will be guided toward the AMFPI by total internal reflection. A Monte Carlo simulation has been used to investigate imaging and dosimetric characteristics of the proposed detector under irradiation of MV x-rays. Properties, such as detection efficiency, modulation transfer function, detective quantum efficiency (DQE), energy dependence of detector response, and water-equivalence of

A method of extending the depth of focus of the high-resolution X-ray imaging system employing optical lens and scintillator: a phantom study

PubMed Central

2015-01-01

Background The high-resolution X-ray imaging system employing synchrotron radiation source, thin scintillator, optical lens and advanced CCD camera can achieve a resolution in the range of tens of nanometers to sub-micrometer. Based on this advantage, it can effectively image tissues, cells and many other small samples, especially the calcification in the vascular or in the glomerulus. In general, the thickness of the scintillator should be several micrometers or even within nanometers because it has a big relationship with the resolution. However, it is difficult to make the scintillator so thin, and additionally thin scintillator may greatly reduce the efficiency of collecting photons. Methods In this paper, we propose an approach to extend the depth of focus (DOF) to solve these problems. We develop equation sets by deducing the relationship between the high-resolution image generated by the scintillator and the degraded blur image due to defect of focus first, and then we adopt projection onto convex sets (POCS) and total variation algorithm to get the solution of the equation sets and to recover the blur image. Results By using a 20 μm thick unmatching scintillator to replace the 1 μm thick matching one, we simulated a high-resolution X-ray imaging system and got a degraded blur image. Based on the algorithm proposed, we recovered the blur image and the result in the experiment showed that the proposed algorithm has good performance on the recovery of image blur caused by unmatching thickness of scintillator. Conclusions The method proposed is testified to be able to efficiently recover the degraded image due to defect of focus. But, the quality of the recovery image especially of the low contrast image depends on the noise level of the degraded blur image, so there is room for improving and the corresponding denoising algorithm is worthy for further study and discussion. PMID:25602532

Searching for Galactic hidden gas through interstellar scintillation: results from a test with the NTT-SOFI detector

NASA Astrophysics Data System (ADS)

Habibi, F.; Moniez, M.; Ansari, R.; Rahvar, S.

2011-01-01

Aims: Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected at a longer time scale when the light of remote stars crosses an interstellar molecular cloud, but it has never been observed at optical wavelength. In a favorable case, the light of a background star can be subject to stochastic fluctuations on the order of a few percent at a characteristic time scale of a few minutes. Our ultimate aim is to discover or exclude these scintillation effects to estimate the contribution of molecular hydrogen to the Galactic baryonic hidden mass. This feasibility study is a pathfinder toward an observational strategy to search for scintillation, probing the sensitivity of future surveys and estimating the background level. Methods: We searched for scintillation induced by molecular gas in visible dark nebulae as well as by hypothetical halo clumpuscules of cool molecular hydrogen (H2-He) during two nights. We took long series of 10 s infrared exposures with the ESO-NTT telescope toward stellar populations located behind visible nebulae and toward the Small Magellanic Cloud (SMC). We therefore searched for stars exhibiting stochastic flux variations similar to what is expected from the scintillation effect. According to our simulations of the scintillation process, this search should allow one to detect (stochastic) transverse gradients of column density in cool Galactic molecular clouds of order of ~ 3 × 10-5 g/cm2/10 000 km. Results: We found one light-curve that is compatible with a strong scintillation effect through a turbulent structure characterized by a diffusion radius Rdiff < 100 km in the B68 nebula. Complementary observations are needed to clarify the status of this candidate, and no firm conclusion can be established from this single observation. We can also infer limits on the existence of turbulent dense cores (of number density n > 109 cm-3) within the dark nebulae. Because no candidate is found toward the SMC, we

Methods for the continuous production of plastic scintillator materials

DOEpatents

Bross, Alan; Pla-Dalmau, Anna; Mellott, Kerry

1999-10-19

Methods for producing plastic scintillating material employing either two major steps (tumble-mix) or a single major step (inline-coloring or inline-doping). Using the two step method, the polymer pellets are mixed with silicone oil, and the mixture is then tumble mixed with the dopants necessary to yield the proper response from the scintillator material. The mixture is then placed in a compounder and compounded in an inert gas atmosphere. The resultant scintillator material is then extruded and pelletized or formed. When only a single step is employed, the polymer pellets and dopants are metered into an inline-coloring extruding system. The mixture is then processed under a inert gas atmosphere, usually argon or nitrogen, to form plastic scintillator material in the form of either scintillator pellets, for subsequent processing, or as material in the direct formation of the final scintillator shape or form.

A new large area scintillator screen for X-ray imaging

NASA Astrophysics Data System (ADS)

Nagarkar, V. V.; Miller, S. R.; Tipnis, S. V.; Lempicki, A.; Brecher, C.; Lingertat, H.

2004-01-01

We report on the development of a new, large area, powdered scintillator screen based on Lu 2O 3(Eu). As reported earlier, the transparent ceramic form of this material has a very high density of 9.4 g/cm 3, a high light output comparable to that of CsI(Tl), and emits in a narrow spectral band centered at about 610 nm. Research into fabrication of this ceramic scintillator in a large area format is currently underway, however the process is not yet practical for large scale production. Here we have explored fabrication of large area screens using precursor powders from which the ceramics are fabricated. To date we have produced up to 16 × 16 cm 2 area screens with thickness in the range of 18 mg/cm 2. This paper outlines the screen fabrication technique and presents its imaging performance in comparison with a commercial Gd 2O 2S:Tb (GOS) screen.

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.

SU-C-207A-03: Development of Proton CT Imaging System Using Thick Scintillator and CCD Camera

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

Tanaka, S; Uesaka, M; Nishio, T

2016-06-15

Purpose: In the treatment planning of proton therapy, Water Equivalent Length (WEL), which is the parameter for the calculation of dose and the range of proton, is derived by X-ray CT (xCT) image and xCT-WEL conversion. However, about a few percent error in the accuracy of proton range calculation through this conversion has been reported. The purpose of this study is to construct a proton CT (pCT) imaging system for an evaluation of the error. Methods: The pCT imaging system was constructed with a thick scintillator and a cooled CCD camera, which acquires the two-dimensional image of integrated value ofmore » the scintillation light toward the beam direction. The pCT image is reconstructed by FBP method using a correction between the light intensity and residual range of proton beam. An experiment for the demonstration of this system was performed with 70-MeV proton beam provided by NIRS cyclotron. The pCT image of several objects reconstructed from the experimental data was evaluated quantitatively. Results: Three-dimensional pCT images of several objects were reconstructed experimentally. A finestructure of approximately 1 mm was clearly observed. The position resolution of pCT image was almost the same as that of xCT image. And the error of proton CT pixel value was up to 4%. The deterioration of image quality was caused mainly by the effect of multiple Coulomb scattering. Conclusion: We designed and constructed the pCT imaging system using a thick scintillator and a CCD camera. And the system was evaluated with the experiment by use of 70-MeV proton beam. Three-dimensional pCT images of several objects were acquired by the system. This work was supported by JST SENTAN Grant Number 13A1101 and JSPS KAKENHI Grant Number 15H04912.« less

Transitioning glass-ceramic scintillators for diagnostic x-ray imaging from the laboratory to commercial scale

NASA Astrophysics Data System (ADS)

Beckert, M. Brooke; Gallego, Sabrina; Elder, Eric; Nadler, Jason

2016-10-01

This study sought to mitigate risk in transitioning newly developed glass-ceramic scintillator technology from a laboratory concept to commercial product by identifying the most significant hurdles to increased scale. These included selection of cost effective raw material sources, investigation of process parameters with the most significant impact on performance, and synthesis steps that could see the greatest benefit from participation of an industry partner that specializes in glass or optical component manufacturing. Efforts focused on enhancing the performance of glass-ceramic nanocomposite scintillators developed specifically for medical imaging via composition and process modifications that ensured efficient capture of incident X-ray energy and emission of scintillation light. The use of cost effective raw materials and existing manufacturing methods demonstrated proof-of-concept for economical viable alternatives to existing benchmark materials, as well as possible disruptive applications afforded by novel geometries and comparatively lower cost per volume. The authors now seek the expertise of industry to effectively navigate the transition from laboratory demonstrations to pilot scale production and testing to evince the industry of the viability and usefulness of composite-based scintillators.

Optimization of the Performance of Segmented Scintillators for Radiotherapy Imaging through Novel Binning Techniques

PubMed Central

El-Mohri, Youcef; Antonuk, Larry E.; Choroszucha, Richard B.; Zhao, Qihua; Jiang, Hao; Liu, Langechuan

2014-01-01

Thick, segmented crystalline scintillators have shown increasing promise as replacement x-ray converters for the phosphor screens currently used in active matrix flat-panel imagers (AMFPIs) in radiotherapy, by virtue of providing over an order of magnitude improvement in the DQE. However, element-to-element misalignment in current segmented scintillator prototypes creates a challenge for optimal registration with underlying AMFPI arrays, resulting in degradation of spatial resolution. To overcome this challenge, a methodology involving the use of a relatively high resolution AMFPI array in combination with novel binning techniques is presented. The array, which has a pixel pitch of 0.127 mm, was coupled to prototype segmented scintillators based on BGO, LYSO and CsI:Tl materials, each having a nominal element-to-element pitch of 1.016 mm and thickness of ~1 cm. The AMFPI systems incorporating these prototypes were characterized at a radiotherapy energy of 6 MV in terms of MTF, NPS, DQE, and reconstructed images of a resolution phantom acquired using a cone-beam CT geometry. For each prototype, the application of 8×8 pixel binning to achieve a sampling pitch of 1.016 mm was optimized through use of an alignment metric which minimized misregistration and thereby improved spatial resolution. In addition, the application of alternative binning techniques that exclude the collection of signal near septal walls resulted in further significant improvement in spatial resolution for the BGO and LYSO prototypes, though not for the CsI:Tl prototype due to the large amount of optical cross-talk resulting from significant light spread between scintillator elements in that device. The efficacy of these techniques for improving spatial resolution appears to be enhanced for scintillator materials that exhibit mechanical hardness, high density and high refractive index, such as BGO. Moreover, materials that exhibit these properties as well as offer significantly higher light

Study of equatorial plasma bubbles using all sky imager and scintillation technique from Kolhapur station: a case study

NASA Astrophysics Data System (ADS)

Sharma, A. K.; Gurav, O. B.; Gaikwad, H. P.; Chavan, G. A.; Nade, D. P.; Nikte, S. S.; Ghodpage, R. N.; Patil, P. T.

2018-04-01

The nightglow observations of OI 630.0 nm emission carried out from low latitude station Kolhapur using All Sky Imager (ASI) with 140° field of view (FOV) for the month of April 2011 are used. The images were processed to study the field aligned irregularities often called as equatorial plasma bubbles (EPBs). The present study focuses on the occurrence of scintillation during the traversal of EPBs over ionospheric pierce point (IPP). Here we dealt with the depletion level (depth) of the EPB structures and its effect on VHF signals. We compared VHF scintillation data with airglow intensities at Ionospheric pierce point (IPP) from the same location and found that the largely depleted EPBs make stronger scintillation. From previous literature, it is believed that the small scale structures are present near the steeper walls of EPBs which often degrades the communication, the analysis presented in this paper confirms this belief.

A broad band X-ray imaging spectrophotometer for astrophysical studies

NASA Technical Reports Server (NTRS)

Lum, Kenneth S. K.; Lee, Dong Hwan; Ku, William H.-M.

1988-01-01

A broadband X-ray imaging spectrophotometer (BBXRIS) has been built for astrophysical studies. The BBXRIS is based on a large-imaging gas scintillation proportional counter (LIGSPC), a combination of a gas scintillation proportional counter and a multiwire proportional counter, which achieves 8 percent (FWHM) energy resolution and 1.5-mm (FWHM) spatial resolution at 5.9 keV. The LIGSPC can be integrated with a grazing incidence mirror and a coded aperture mask to provide imaging over a broad range of X-ray energies. The results of tests involving the LIGSPC and a coded aperture mask are presented, and possible applications of the BBXRIS are discussed.

Seeing the invisible: direct visualization of therapeutic radiation beams using air scintillation.

PubMed

Fahimian, Benjamin; Ceballos, Andrew; Türkcan, Silvan; Kapp, Daniel S; Pratx, Guillem

2014-01-01

To assess whether air scintillation produced during standard radiation treatments can be visualized and used to monitor a beam in a nonperturbing manner. Air scintillation is caused by the excitation of nitrogen gas by ionizing radiation. This weak emission occurs predominantly in the 300-430 nm range. An electron-multiplication charge-coupled device camera, outfitted with an f/0.95 lens, was used to capture air scintillation produced by kilovoltage photon beams and megavoltage electron beams used in radiation therapy. The treatment rooms were prepared to block background light and a short-pass filter was utilized to block light above 440 nm. Air scintillation from an orthovoltage unit (50 kVp, 30 mA) was visualized with a relatively short exposure time (10 s) and showed an inverse falloff (r(2) = 0.89). Electron beams were also imaged. For a fixed exposure time (100 s), air scintillation was proportional to dose rate (r(2) = 0.9998). As energy increased, the divergence of the electron beam decreased and the penumbra improved. By irradiating a transparent phantom, the authors also showed that Cherenkov luminescence did not interfere with the detection of air scintillation. In a final illustration of the capabilities of this new technique, the authors visualized air scintillation produced during a total skin irradiation treatment. Air scintillation can be measured to monitor a radiation beam in an inexpensive and nonperturbing manner. This physical phenomenon could be useful for dosimetry of therapeutic radiation beams or for online detection of gross errors during fractionated treatments.

Light output measurements and computational models of microcolumnar CsI scintillators for x-ray imaging.

PubMed

Nillius, Peter; Klamra, Wlodek; Sibczynski, Pawel; Sharma, Diksha; Danielsson, Mats; Badano, Aldo

2015-02-01

The authors report on measurements of light output and spatial resolution of microcolumnar CsI:Tl scintillator detectors for x-ray imaging. In addition, the authors discuss the results of simulations aimed at analyzing the results of synchrotron and sealed-source exposures with respect to the contributions of light transport to the total light output. The authors measured light output from a 490-μm CsI:Tl scintillator screen using two setups. First, the authors used a photomultiplier tube (PMT) to measure the response of the scintillator to sealed-source exposures. Second, the authors performed imaging experiments with a 27-keV monoenergetic synchrotron beam and a slit to calculate the total signal generated in terms of optical photons per keV. The results of both methods are compared to simulations obtained with hybridmantis, a coupled x-ray, electron, and optical photon Monte Carlo transport package. The authors report line response (LR) and light output for a range of linear absorption coefficients and describe a model that fits at the same time the light output and the blur measurements. Comparing the experimental results with the simulations, the authors obtained an estimate of the absorption coefficient for the model that provides good agreement with the experimentally measured LR. Finally, the authors report light output simulation results and their dependence on scintillator thickness and reflectivity of the backing surface. The slit images from the synchrotron were analyzed to obtain a total light output of 48 keV -1 while measurements using the fast PMT instrument setup and sealed-sources reported a light output of 28 keV -1 . The authors attribute the difference in light output estimates between the two methods to the difference in time constants between the camera and PMT measurements. Simulation structures were designed to match the light output measured with the camera while providing good agreement with the measured LR resulting in a bulk absorption

Light output measurements and computational models of microcolumnar CsI scintillators for x-ray imaging.

PubMed

Nillius, Peter; Klamra, Wlodek; Sibczynski, Pawel; Sharma, Diksha; Danielsson, Mats; Badano, Aldo

2015-02-01

The authors report on measurements of light output and spatial resolution of microcolumnar CsI:Tl scintillator detectors for x-ray imaging. In addition, the authors discuss the results of simulations aimed at analyzing the results of synchrotron and sealed-source exposures with respect to the contributions of light transport to the total light output. The authors measured light output from a 490-μm CsI:Tl scintillator screen using two setups. First, the authors used a photomultiplier tube (PMT) to measure the response of the scintillator to sealed-source exposures. Second, the authors performed imaging experiments with a 27-keV monoenergetic synchrotron beam and a slit to calculate the total signal generated in terms of optical photons per keV. The results of both methods are compared to simulations obtained with hybridmantis, a coupled x-ray, electron, and optical photon Monte Carlo transport package. The authors report line response (LR) and light output for a range of linear absorption coefficients and describe a model that fits at the same time the light output and the blur measurements. Comparing the experimental results with the simulations, the authors obtained an estimate of the absorption coefficient for the model that provides good agreement with the experimentally measured LR. Finally, the authors report light output simulation results and their dependence on scintillator thickness and reflectivity of the backing surface. The slit images from the synchrotron were analyzed to obtain a total light output of 48 keV−1 while measurements using the fast PMT instrument setup and sealed-sources reported a light output of 28 keV−1. The authors attribute the difference in light output estimates between the two methods to the difference in time constants between the camera and PMT measurements. Simulation structures were designed to match the light output measured with the camera while providing good agreement with the measured LR resulting in a bulk

Transparent ceramic scintillators for gamma spectroscopy and MeV imaging

NASA Astrophysics Data System (ADS)

Cherepy, N. J.; Seeley, Z. M.; Payne, S. A.; Swanberg, E. L.; Beck, P. R.; Schneberk, D. J.; Stone, G.; Perry, R.; Wihl, B.; Fisher, S. E.; Hunter, S. L.; Thelin, P. A.; Thompson, R. R.; Harvey, N. M.; Stefanik, T.; Kindem, J.

2015-09-01

We report on the development of two new mechanically rugged, high light yield transparent ceramic scintillators: (1) Ce-doped Gd-garnet for gamma spectroscopy, and (2) Eu-doped Gd-Lu-bixbyite for radiography. GYGAG(Ce) garnet transparent ceramics offer ρ = 5.8g/cm3, Zeff = 48, principal decay of <100 ns, and light yield of 50,000 Ph/MeV. Gdgarnet ceramic scintillators offer the best energy resolution of any oxide scintillator, as good as R(662 keV) = 3% (Si-PD readout) for small sizes and typically R(662 keV) < 5% for cubic inch sizes. For radiography, the bixbyite transparent ceramic scintillator, (Gd,Lu,Eu)2O3, or "GLO," offers excellent x-ray stopping, with ρ = 9.1 g/cm3 and Zeff = 68. Several 10" diameter by 0.1" thickness GLO scintillators have been fabricated. GLO outperforms scintillator glass for high energy radiography, due to higher light yield (55,000 Ph/MeV) and better stopping, while providing spatial resolution of >8 lp/mm.

The SNO+ Scintillator Purification Plant and Projected Sensitivity to Solar Neutrinos in the Pure Scintillator Phase

NASA Astrophysics Data System (ADS)

Pershing, Teal; SNO+ Collaboration

2016-03-01

The SNO+ detector is a neutrino and neutrinoless double-beta decay experiment utilizing the renovated SNO detector. In the second phase of operation, the SNO+ detector will contain 780 tons of organic liquid scintillator composed of 2 g/L 2,5-diphenyloxazole (PPO) in linear alkylbenzene (LAB). In this phase, SNO+ will strive to detect solar neutrinos in the sub-MeV range, including CNO production neutrinos and pp production neutrinos. To achieve the necessary detector sensitivity, a four-part scintillator purification plant has been constructed in SNOLAB for the removal of ionic and radioactive impurities. We present an overview of the SNO+ scintillator purification plant stages, including distillation, water extraction, gas stripping, and metal scavenger columns. We also give the projected SNO+ sensitivities to various solar-produced neutrinos based on the scintillator plant's projected purification efficiency.

Bright Lu2O3:Eu thin-film scintillators for high-resolution radioluminescence microscopy

PubMed Central

Sengupta, Debanti; Miller, Stuart; Marton, Zsolt; Chin, Frederick; Nagarkar, Vivek

2015-01-01

We investigate the performance of a new thin-film Lu2O3:Eu scintillator for single-cell radionuclide imaging. Imaging the metabolic properties of heterogeneous cell populations in real time is an important challenge with clinical implications. We have developed an innovative technique called radioluminescence microscopy, to quantitatively and sensitively measure radionuclide uptake in single cells. The most important component of this technique is the scintillator, which converts the energy released during radioactive decay into luminescent signals. The sensitivity and spatial resolution of the imaging system depend critically on the characteristics of the scintillator, i.e. the material used and its geometrical configuration. Scintillators fabricated using conventional methods are relatively thick, and therefore do not provide optimal spatial resolution. We compare a thin-film Lu2O3:Eu scintillator to a conventional 500 μm thick CdWO4 scintillator for radioluminescence imaging. Despite its thinness, the unique scintillation properties of the Lu2O3:Eu scintillator allow us to capture single positron decays with over fourfold higher sensitivity, a significant achievement. The thin-film Lu2O3:Eu scintillators also yield radioluminescence images where individual cells appear smaller and better resolved on average than with the CdWO4 scintillators. Coupled with the thin-film scintillator technology, radioluminescence microscopy can yield valuable and clinically relevant data on the metabolism of single cells. PMID:26183115

Hard x-ray and gamma-ray imaging and spectroscopy using scintillators coupled to silicon drift detectors

NASA Astrophysics Data System (ADS)

Lechner, P.; Eckhard, R.; Fiorini, C.; Gola, A.; Longoni, A.; Niculae, A.; Peloso, R.; Soltau, H.; Strüder, L.

2008-07-01

Silicon Drift Detectors (SDDs) are used as low-capacitance photon detectors for the optical light emitted by scintillators. The scintillator crystal is directly coupled to the SDD entrance window. The entrance window's transmittance can be optimized for the scintillator characteristic by deposition of a wavelength-selective anti-reflective coating. Compared to conventional photomultiplier tubes the SDD readout offers improved energy resolution and avoids the practical problems of incompatibility with magnetic fields, instrument volume and requirement of high voltage. A compact imaging spectrometer for hard X-rays and γ-rays has been developed by coupling a large area (29 × 26 mm2) monolithic SDD array with 77 hexagonal cells to a single non-structured CsI-scintillator of equal size. The scintillation light generated by the absorption of an energetic photon is seen by a number of detector cells and the position of the photon interaction is reconstructed by the centroid method. The measured spatial resolution of the system (<= 500 μm) is considerably smaller than the SDD cell size (3.2 mm) and in the order required at the focal plane of high energy missions. The energy information is obtained by summing the detector cell signals. Compared to direct converting pixelated detectors, e.g. CdTe with equal position resolution the scintillator-SDD combination requires a considerably lower number of readout channels. In addition it has the advantages of comprehensive material experience, existing technologies, proven long term stability, and practically unlimited availability of high quality material.

Cosmic-ray cascades photographed in scintillator

NASA Technical Reports Server (NTRS)

Barrowes, S. C.; Huggett, R. W.; Levit, L. B.; Porter, L. G.

1974-01-01

Light produced by nuclear-electromagnetic cascades in a plastic scintillator can be photographed, and the resulting images on film used to measure both the energy content of the cascades and also the positions at which the cascades passed through the scintillator. The energy content of a cascade can be measured to 20% and its position determined to plus or minus 0.8 cm in each scintillator. Techniques for photographing the cascades and analyzing the film are described. Sample data are presented and discussed.

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

Photon statistics in scintillation crystals

NASA Astrophysics Data System (ADS)

Bora, Vaibhav Joga Singh

Scintillation based gamma-ray detectors are widely used in medical imaging, high-energy physics, astronomy and national security. Scintillation gamma-ray detectors are eld-tested, relatively inexpensive, and have good detection eciency. Semi-conductor detectors are gaining popularity because of their superior capability to resolve gamma-ray energies. However, they are relatively hard to manufacture and therefore, at this time, not available in as large formats and much more expensive than scintillation gamma-ray detectors. Scintillation gamma-ray detectors consist of: a scintillator, a material that emits optical (scintillation) photons when it interacts with ionization radiation, and an optical detector that detects the emitted scintillation photons and converts them into an electrical signal. Compared to semiconductor gamma-ray detectors, scintillation gamma-ray detectors have relatively poor capability to resolve gamma-ray energies. This is in large part attributed to the "statistical limit" on the number of scintillation photons. The origin of this statistical limit is the assumption that scintillation photons are either Poisson distributed or super-Poisson distributed. This statistical limit is often dened by the Fano factor. The Fano factor of an integer-valued random process is dened as the ratio of its variance to its mean. Therefore, a Poisson process has a Fano factor of one. The classical theory of light limits the Fano factor of the number of photons to a value greater than or equal to one (Poisson case). However, the quantum theory of light allows for Fano factors to be less than one. We used two methods to look at the correlations between two detectors looking at same scintillation pulse to estimate the Fano factor of the scintillation photons. The relationship between the Fano factor and the correlation between the integral of the two signals detected was analytically derived, and the Fano factor was estimated using the measurements for SrI2:Eu, YAP

Imaging characterization of a new gamma ray detector based on CRY019 scintillation crystal for PET and SPECT applications

NASA Astrophysics Data System (ADS)

Polito, C.; Pani, R.; Trigila, C.; Cinti, M. N.; Fabbri, A.; Frantellizzi, V.; De Vincentis, G.; Pellegrini, R.; Pani, R.

2017-02-01

In the last 40 years, in the field of Molecular Medicine imaging there has been a huge growth in the employment and in the improvement of detectors for PET and SPECT applications in order to reach accurate diagnosis of the diseases. The most important feature required to these detectors is an high quality of images that is usually obtained benefitting from the development of a wide number of new scintillation crystals with high imaging performances. In this contest, features like high detection efficiency, short decay time, great spectral match with photodetectors, absence of afterglow and low costs are surely attractive. However, there are other factors playing an important role in the realization of high quality images such as energy and spatial resolutions, position linearity and contrast resolution. With the aim to realize an high performace gamma ray detector for PET and SPECT applications, this work is focused on the evaluation of the imaging characteristics of a recently developed scintillation crystal, CRY019.

Backscatter absorption gas imaging system

DOEpatents

McRae, Jr., Thomas G.

1985-01-01

A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

Backscatter absorption gas imaging system

DOEpatents

McRae, T.G. Jr.

A video imaging system for detecting hazardous gas leaks. Visual displays of invisible gas clouds are produced by radiation augmentation of the field of view of an imaging device by radiation corresponding to an absorption line of the gas to be detected. The field of view of an imager is irradiated by a laser. The imager receives both backscattered laser light and background radiation. When a detectable gas is present, the backscattered laser light is highly attenuated, producing a region of contrast or shadow on the image. A flying spot imaging system is utilized to synchronously irradiate and scan the area to lower laser power requirements. The imager signal is processed to produce a video display.

Plastic fiber scintillator response to fast neutrons

NASA Astrophysics Data System (ADS)

Danly, C. R.; Sjue, S.; Wilde, C. H.; Merrill, F. E.; Haight, R. C.

2014-11-01

The Neutron Imaging System at NIF uses an array of plastic scintillator fibers in conjunction with a time-gated imaging system to form an image of the neutron emission from the imploded capsule. By gating on neutrons that have scattered from the 14.1 MeV DT energy to lower energy ranges, an image of the dense, cold fuel around the hotspot is also obtained. An unmoderated spallation neutron beamline at the Weapons Neutron Research facility at Los Alamos was used in conjunction with a time-gated imaging system to measure the yield of a scintillating fiber array over several energy bands ranging from 1 to 15 MeV. The results and comparison to simulation are presented.

Plastic fiber scintillator response to fast neutrons.

PubMed

Danly, C R; Sjue, S; Wilde, C H; Merrill, F E; Haight, R C

2014-11-01

The Neutron Imaging System at NIF uses an array of plastic scintillator fibers in conjunction with a time-gated imaging system to form an image of the neutron emission from the imploded capsule. By gating on neutrons that have scattered from the 14.1 MeV DT energy to lower energy ranges, an image of the dense, cold fuel around the hotspot is also obtained. An unmoderated spallation neutron beamline at the Weapons Neutron Research facility at Los Alamos was used in conjunction with a time-gated imaging system to measure the yield of a scintillating fiber array over several energy bands ranging from 1 to 15 MeV. The results and comparison to simulation are presented.

Velocimetry using scintillation of a laser beam for a laser-based gas-flux monitor

NASA Astrophysics Data System (ADS)

Kagawa, Naoki; Wada, Osami; Koga, Ryuji

1999-05-01

This paper describes a velocimetry system using scintillation of a laser-beam with spatial filters based on sensor arrays for a laser- based gas flux monitor. In the eddy correlation method, gas flux is obtained by mutual relation between the gas density and the flow velocity. The velocimetry system is developed to support the flow velocity monitor portion of the laser-based gas flux monitor with a long span for measurement. In order to sense not only the flow velocity but also the flow direction, two photo diode arrays are arranged with difference of a quarter period of the weighting function between them; the two output signals from the sensor arrays have phase difference of either (pi) /2 or -(pi) /2 depending on the sense of flow direction. In order to obtain the flow velocity and the flow direction instantly, an electronic apparatus built by the authors extracts frequency and phase from crude outputs of the pair of sensors. A feasibility of the velocimetry was confirmed indoors by measurement of the flow- velocity vector of the convection. Measured flow-velocity vector of the upward flow agreed comparatively with results of an ultrasonic anemometer.

Synthesis and characterization of a BaGdF5:Tb glass ceramic as a nanocomposite scintillator for x-ray imaging.

PubMed

Lee, Gyuhyon; Struebing, Christian; Wagner, Brent; Summers, Christopher; Ding, Yong; Bryant, Alex; Thadhani, Naresh; Shedlock, Daniel; Star-Lack, Josh; Kang, Zhitao

2016-05-20

Transparent glass ceramics with embedded light-emitting nanocrystals show great potential as low-cost nanocomposite scintillators in comparison to single crystal and transparent ceramic scintillators. In this study, cubic structure BaGdF5:Tb nanocrystals embedded in an aluminosilicate glass matrix are reported for potential high performance MeV imaging applications. Scintillator samples with systematically varied compositions were prepared by a simple conventional melt-quenching method followed by annealing. Optical, structural and scintillation properties were characterized to guide the design and optimization of selected material systems, aiming at the development of a system with higher crystal volume and larger crystal size for improved luminosity. It is observed that enhanced scintillation performance was achieved by tuning the glass matrix composition and using GdF3 in the raw materials, which served as a nucleation agent. A 26% improvement in light output was observed from a BaGdF5:Tb glass ceramic with addition of GdF3.

A comparative study of the luminescence properties of LYSO:Ce, LSO:Ce, GSO:Ce and BGO single crystal scintillators for use in medical X-ray imaging.

PubMed

Valais, I; Michail, C; David, S; Nomicos, C D; Panayiotakis, G S; Kandarakis, I

2008-06-01

The present study is a comparative investigation of the luminescence properties of (Lu,Y)(2)SiO(5):Ce (LYSO:Ce), Lu(2)SiO(5):Ce (LSO:Ce), Gd(2)SiO(5):Ce (GSO:Ce) and (Bi(4)Ge(3)O(12)) BGO single crystal scintillators under medical X-ray excitation. All scintillating crystals have dimensions of 10 x 10 x 10 mm(3) are non-hygroscopic exhibiting high radiation absorption efficiency in the energy range used in medical imaging applications. The comparative investigation was performed by determining the absolute luminescence efficiency (emitted light flux over incident X-ray exposure) in X-ray energies employed in general X-ray imaging (40-140 kV) and in mammographic X-ray imaging (22-49 kV). Additionally, light emission spectra of crystals at various X-ray energies were measured, in order to determine the spectral compatibility to optical photon detectors incorporated in medical imaging systems and the overall efficiency (effective efficiency) of a scintillator-optical detector combination. The light emission performance of LYSO:Ce and LSO:Ce scintillators studied was found very high for X-ray imaging.

Position and time resolution measurements with a microchannel plate image intensifier: A comparison of monolithic and pixelated CeBr3 scintillators

NASA Astrophysics Data System (ADS)

Ackermann, Ulrich; Eschbaumer, Stephan; Bergmaier, Andreas; Egger, Werner; Sperr, Peter; Greubel, Christoph; Löwe, Benjamin; Schotanus, Paul; Dollinger, Günther

2016-07-01

To perform Four Dimensional Age Momentum Correlation measurements in the near future, where one obtains the positron lifetime in coincidence with the three dimensional momentum of the electron annihilating with the positron, we have investigated the time and position resolution of two CeBr3 scintillators (monolithic and an array of pixels) using a Photek IPD340/Q/BI/RS microchannel plate image intensifier. The microchannel plate image intensifier has an active diameter of 40 mm and a stack of two microchannel plates in chevron configuration. The monolithic CeBr3 scintillator was cylindrically shaped with a diameter of 40 mm and a height of 5 mm. The pixelated scintillator array covered the whole active area of the microchannel plate image intensifier and the shape of each pixel was 2.5·2.5·8 mm3 with a pixel pitch of 3.3 mm. For the monolithic setup the measured mean single time resolution was 330 ps (FWHM) at a gamma energy of 511 keV. No significant dependence on the position was detected. The position resolution at the center of the monolithic scintillator was about 2.5 mm (FWHM) at a gamma energy of 662 keV. The single time resolution of the pixelated crystal setup reached 320 ps (FWHM) in the region of the center of the active area of the microchannel plate image intensifier. The position resolution was limited by the cross-section of the pixels. The gamma energy for the pixel setup measurements was 511 keV.

Optimisation of the imaging and dosimetric characteristics of an electronic portal imaging device employing plastic scintillating fibres using Monte Carlo simulations.

PubMed

Blake, S J; McNamara, A L; Vial, P; Holloway, L; Kuncic, Z

2014-11-21

A Monte Carlo model of a novel electronic portal imaging device (EPID) has been developed using Geant4 and its performance for imaging and dosimetry applications in radiotherapy has been characterised. The EPID geometry is based on a physical prototype under ongoing investigation and comprises an array of plastic scintillating fibres in place of the metal plate/phosphor screen in standard EPIDs. Geometrical and optical transport parameters were varied to investigate their impact on imaging and dosimetry performance. Detection efficiency was most sensitive to variations in fibre length, achieving a peak value of 36% at 50 mm using 400 keV x-rays for the lengths considered. Increases in efficiency for longer fibres were partially offset by reductions in sensitivity. Removing the extra-mural absorber surrounding individual fibres severely decreased the modulation transfer function (MTF), highlighting its importance in maximising spatial resolution. Field size response and relative dose profile simulations demonstrated a water-equivalent dose response and thus the prototype's suitability for dosimetry applications. Element-to-element mismatch between scintillating fibres and underlying photodiode pixels resulted in a reduced MTF for high spatial frequencies and quasi-periodic variations in dose profile response. This effect is eliminated when fibres are precisely matched to underlying pixels. Simulations strongly suggest that with further optimisation, this prototype EPID may be capable of simultaneous imaging and dosimetry in radiotherapy.

Development of proton CT imaging system using plastic scintillator and CCD camera

NASA Astrophysics Data System (ADS)

Tanaka, Sodai; Nishio, Teiji; Matsushita, Keiichiro; Tsuneda, Masato; Kabuki, Shigeto; Uesaka, Mitsuru

2016-06-01

A proton computed tomography (pCT) imaging system was constructed for evaluation of the error of an x-ray CT (xCT)-to-WEL (water-equivalent length) conversion in treatment planning for proton therapy. In this system, the scintillation light integrated along the beam direction is obtained by photography using the CCD camera, which enables fast and easy data acquisition. The light intensity is converted to the range of the proton beam using a light-to-range conversion table made beforehand, and a pCT image is reconstructed. An experiment for demonstration of the pCT system was performed using a 70 MeV proton beam provided by the AVF930 cyclotron at the National Institute of Radiological Sciences. Three-dimensional pCT images were reconstructed from the experimental data. A thin structure of approximately 1 mm was clearly observed, with spatial resolution of pCT images at the same level as that of xCT images. The pCT images of various substances were reconstructed to evaluate the pixel value of pCT images. The image quality was investigated with regard to deterioration including multiple Coulomb scattering.

In situ diagnostics of the crystal-growth process through neutron imaging: application to scintillators

DOE PAGES

Tremsin, Anton S.; Makowska, Małgorzata G.; Perrodin, Didier; ...

2016-04-12

Neutrons are known to be unique probes in situations where other types of radiation fail to penetrate samples and their surrounding structures. In this paper it is demonstrated how thermal and cold neutron radiography can provide time-resolved imaging of materials while they are being processed (e.g.while growing single crystals). The processing equipment, in this case furnaces, and the scintillator materials are opaque to conventional X-ray interrogation techniques. The distribution of the europium activator within a BaBrCl:Eu scintillator (0.1 and 0.5% nominal doping concentrations per mole) is studiedin situduring the melting and solidification processes with a temporal resolution of 5–7 s.more » The strong tendency of the Eu dopant to segregate during the solidification process is observed in repeated cycles, with Eu forming clusters on multiple length scales (only for clusters larger than ~50 µm, as limited by the resolution of the present experiments). It is also demonstrated that the dopant concentration can be quantified even for very low concentration levels (~0.1%) in 10 mm thick samples. The interface between the solid and liquid phases can also be imaged, provided there is a sufficient change in concentration of one of the elements with a sufficient neutron attenuation cross section. Tomographic imaging of the BaBrCl:0.1%Eu sample reveals a strong correlation between crystal fractures and Eu-deficient clusters. The results of these experiments demonstrate the unique capabilities of neutron imaging forin situdiagnostics and the optimization of crystal-growth procedures.« less

Near-infrared scintillation of xenon by 63Ni beta decay

NASA Astrophysics Data System (ADS)

Yoshimizu, Norimasa; Lal, Amit; Pollock, Clifford R.

2006-07-01

The near-infrared scintillation of xenon gas by the β decay of 37MBq of Ni63 was studied, in the interest of its use in integrated devices for applications such as optical beacons and wavelength calibration. The emission was imaged and analyzed using Spencer's theory of electron penetration using xenon scattering cross sections derived from Thomas-Fermi theory. The total emission was approximately 2×105photons/s at 20kPa and 1×105photons/s at 100kPa. Spectral data show three dominant peaks at 823, 828, and 882nm as well as the formation of metastable states.

Experimental comparison of high-density scintillators for EMCCD-based gamma ray imaging

NASA Astrophysics Data System (ADS)

Heemskerk, Jan W. T.; Kreuger, Rob; Goorden, Marlies C.; Korevaar, Marc A. N.; Salvador, Samuel; Seeley, Zachary M.; Cherepy, Nerine J.; van der Kolk, Erik; Payne, Stephen A.; Dorenbos, Pieter; Beekman, Freek J.

2012-07-01

Detection of x-rays and gamma rays with high spatial resolution can be achieved with scintillators that are optically coupled to electron-multiplying charge-coupled devices (EMCCDs). These can be operated at typical frame rates of 50 Hz with low noise. In such a set-up, scintillation light within each frame is integrated after which the frame is analyzed for the presence of scintillation events. This method allows for the use of scintillator materials with relatively long decay times of a few milliseconds, not previously considered for use in photon-counting gamma cameras, opening up an unexplored range of dense scintillators. In this paper, we test CdWO4 and transparent polycrystalline ceramics of Lu2O3:Eu and (Gd,Lu)2O3:Eu as alternatives to currently used CsI:Tl in order to improve the performance of EMCCD-based gamma cameras. The tested scintillators were selected for their significantly larger cross-sections at 140 keV (99mTc) compared to CsI:Tl combined with moderate to good light yield. A performance comparison based on gamma camera spatial and energy resolution was done with all tested scintillators having equal (66%) interaction probability at 140 keV. CdWO4, Lu2O3:Eu and (Gd,Lu)2O3:Eu all result in a significantly improved spatial resolution over CsI:Tl, albeit at the cost of reduced energy resolution. Lu2O3:Eu transparent ceramic gives the best spatial resolution: 65 µm full-width-at-half-maximum (FWHM) compared to 147 µm FWHM for CsI:Tl. In conclusion, these ‘slow’ dense scintillators open up new possibilities for improving the spatial resolution of EMCCD-based scintillation cameras.

Efficient high-resolution hard x-ray imaging with transparent Lu2O3:Eu scintillator thin films

NASA Astrophysics Data System (ADS)

Marton, Zsolt; Miller, Stuart R.; Brecher, Charles; Kenesei, Peter; Moore, Matthew D.; Woods, Russell; Almer, Jonathan D.; Miceli, Antonino; Nagarkar, Vivek V.

2015-09-01

We have developed microstructured Lu2O3:Eu scintillator films that provide spatial resolution on the order of micrometers for hard X-ray imaging. In addition to their outstanding resolution, Lu2O3:Eu films also exhibits both high absorption efficiency for 20 to 100 keV X-rays, and bright 610 nm emission whose intensity rivals that of the brightest known scintillators. At present, high spatial resolution of such a magnitude is achieved using ultra-thin scintillators measuring only about 1 to 5 μm in thickness, which limits absorption efficiency to ~3% for 12 keV X-rays and less than 0.1% for 20 to 100 keV X-rays; this results in excessive measurement time and exposure to the specimen. But the absorption efficiency of Lu2O3:Eu (99.9% @12 keV and 30% @ 70 keV) is much greater, significantly decreasing measurement time and radiation exposure. Our Lu2O3:Eu scintillator material, fabricated by our electron-beam physical vapor deposition (EB-PVD) process, combines superior density of 9.5 g/cm3, a microcolumnar structure for higher spatial resolution, and a bright emission (48000 photons/MeV) whose wavelength is an ideal match for the underlying CCD detector array. We grew thin films of this material on a variety of matching substrates, measuring some 5-10μm in thickness and covering areas up to 1 x 1 cm2, which can be a suitable basis for microtomography, digital radiography as well as CT and hard X-ray Micro-Tomography (XMT). The microstructure and optical transparency of such screens was optimized, and their imaging performance was evaluated in the Argonne National Laboratory's Advanced Photon Source. Spatial resolution and efficiency were also characterized.

Combined FDTD-Monte Carlo analysis and a novel design for ZnO scintillator rods in polycarbonate membrane for X-ray imaging

NASA Astrophysics Data System (ADS)

Mohammadian-Behbahani, Mohammad-Reza; Saramad, Shahyar; Mohammadi, Mohammad

2017-05-01

A combination of Finite Difference Time Domain (FDTD) and Monte Carlo (MC) methods is proposed for simulation and analysis of ZnO microscintillators grown in polycarbonate membrane. A planar 10 keV X-ray source irradiating the detector is simulated by MC method, which provides the amount of absorbed X-ray energy in the assembly. The transport of generated UV scintillation light and its propagation in the detector was studied by the FDTD method. Detector responses to different probable scintillation sites and under different energies of X-ray source from 10 to 25 keV are reported. Finally, the tapered geometry for the scintillators is proposed, which shows enhanced spatial resolution in comparison to cylindrical geometry for imaging applications.

Characterization of a scintillating fibre detector for small animal imaging and irradiation dosimetry

PubMed Central

Frelin-Labalme, Anne-Marie; Ledoux, Xavier

2017-01-01

Objective: Small animal image-guided irradiators have recently been developed to mimic the delivery techniques of clinical radiotherapy. A dosemeter adapted to millimetric beams of medium-energy X-rays is then required. This work presents the characterization of a dosemeter prototype for this particular application. Methods: A scintillating optical fibre dosemeter (called DosiRat) has been implemented to perform real-time dose measurements with the dedicated small animal X-RAD® 225Cx (Precision X-Ray, Inc., North Branford, CT) irradiator. Its sensitivity, stem effect, stability, linearity and measurement precision were determined in large field conditions for three different beam qualities, consistent with small animal irradiation and imaging parameters. Results: DosiRat demonstrates good sensitivity and stability; excellent air kerma and air kerma rate linearity; and a good repeatability for air kerma rates >1 mGy s−1. The stem effect was found to be negligible. DosiRat showed limited precision for low air kerma rate measurements (<1 mGy s−1), typically for imaging protocols. A positive energy dependence was found that can be accounted for by calibrating the dosemeter at the needed beam qualities. Conclusion: The dosimetric performances of DosiRat are very promising. Extensive studies of DosiRat energy dependence are still required. Further developments will allow to reduce the dosemeter size to ensure millimetric beams dosimetry and perform small animal in vivo dosimetry. Advances in knowledge: Among existing point dosemeters, very few are dedicated to both medium-energy X-rays and millimetric beams. Our work demonstrated that scintillating fibre dosemeters are suitable and promising tools for real-time dose measurements in the small animal field of interest. PMID:27556813

Clinical evaluation of pixellated NaI:Tl and continuous LaBr 3:Ce, compact scintillation cameras for breast tumors imaging

NASA Astrophysics Data System (ADS)

Pani, R.; Pellegrini, R.; Betti, M.; De Vincentis, G.; Cinti, M. N.; Bennati, P.; Vittorini, F.; Casali, V.; Mattioli, M.; Orsolini Cencelli, V.; Navarria, F.; Bollini, D.; Moschini, G.; Iurlaro, G.; Montani, L.; de Notaristefani, F.

2007-02-01

The principal limiting factor in the clinical acceptance of scintimammography is certainly its low sensitivity for cancers sized <1 cm, mainly due to the lack of equipment specifically designed for breast imaging. The National Institute of Nuclear Physics (INFN) has been developing a new scintillation camera based on Lanthanum tri-Bromide Cerium-doped crystal (LaBr 3:Ce), that demonstrating superior imaging performances with respect to the dedicated scintillation γ-camera that was previously developed. The proposed detector consists of continuous LaBr 3:Ce scintillator crystal coupled to a Hamamatsu H8500 Flat Panel PMT. One centimeter thick crystal has been chosen to increase crystal detection efficiency. In this paper, we propose a comparison and evaluation between lanthanum γ-camera and a Multi PSPMT camera, NaI(Tl) discrete pixel based, previously developed under "IMI" Italian project for technological transfer of INFN. A phantom study has been developed to test both the cameras before introducing them in clinical trials. High resolution scans produced by LaBr 3:Ce camera showed higher tumor contrast with a detailed imaging of uptake area than pixellated NaI(Tl) dedicated camera. Furthermore, with the lanthanum camera, the Signal-to-Noise Ratio ( SNR) value was increased for a lesion as small as 5 mm, with a consequent strong improvement in detectability.

SAPHIRE (scintillator avalanche photoconductor with high resolution emitter readout) for low dose x-ray imaging: Spatial resolution

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

Li Dan; Zhao Wei

2008-07-15

An indirect flat panel imager (FPI) with programmable avalanche gain and field emitter array (FEA) readout is being investigated for low-dose and high resolution x-ray imaging. It is made by optically coupling a structured x-ray scintillator, e.g., thallium (Tl) doped cesium iodide (CsI), to an amorphous selenium (a-Se) avalanche photoconductor called high-gain avalanche rushing amorphous photoconductor (HARP). The charge image created by the scintillator/HARP (SHARP) combination is read out by the electron beams emitted from the FEA. The proposed detector is called scintillator avalanche photoconductor with high resolution emitter readout (SAPHIRE). The programmable avalanche gain of HARP can improve themore » low dose performance of indirect FPI while the FEA can be made with pixel sizes down to 50 {mu}m. Because of the avalanche gain, a high resolution type of CsI (Tl), which has not been widely used in indirect FPI due to its lower light output, can be used to improve the high spatial frequency performance. The purpose of the present article is to investigate the factors affecting the spatial resolution of SAPHIRE. Since the resolution performance of the SHARP combination has been well studied, the focus of the present work is on the inherent resolution of the FEA readout method. The lateral spread of the electron beam emitted from a 50 {mu}mx50 {mu}m pixel FEA was investigated with two different electron-optical designs: mesh-electrode-only and electrostatic focusing. Our results showed that electrostatic focusing can limit the lateral spread of electron beams to within the pixel size of down to 50 {mu}m. Since electrostatic focusing is essentially independent of signal intensity, it will provide excellent spatial uniformity.« less

Pulse Shape Analysis and Discrimination for Silicon-Photomultipliers in Helium-4 Gas Scintillation Neutron Detector

NASA Astrophysics Data System (ADS)

Barker, Cathleen; Zhu, Ting; Rolison, Lucas; Kiff, Scott; Jordan, Kelly; Enqvist, Andreas

2018-01-01

Using natural helium (helium-4), the Arktis 180-bar pressurized gas scintillator is capable of detecting and distinguishing fast neutrons and gammas. The detector has a unique design of three optically separated segments in which 12 silicon-photomultiplier (SiPM) pairs are positioned equilaterally across the detector to allow for them to be fully immersed in the helium-4 gas volume; consequently, no additional optical interfaces are necessary. The SiPM signals were amplified, shaped, and readout by an analog board; a 250 MHz, 14-bit digitizer was used to examine the output pulses from each SiPMpair channel. The SiPM over-voltage had to be adjusted in order to reduce pulse clipping and negative overshoot, which was observed for events with high scintillation production. Pulse shaped discrimination (PSD) was conducted by evaluating three different parameters: time over threshold (TOT), pulse amplitude, and pulse integral. In order to differentiate high and low energy events, a 30ns gate window was implemented to group pulses from two SiPM channels or more for the calculation of TOT. It was demonstrated that pulses from a single SiPM channel within the 30ns window corresponded to low-energy gamma events while groups of pulses from two-channels or more were most likely neutron events. Due to gamma pulses having lower pulse amplitude, the percentage of measured gamma also depends on the threshold value in TOT calculations. Similarly, the threshold values were varied for the optimal PSD methods of using pulse amplitude and pulse area parameters. Helium-4 detectors equipped with SiPMs are excellent for in-the-field radiation measurement of nuclear spent fuel casks. With optimized PSD methods, the goal of developing a fuel cask content monitoring and inspection system based on these helium-4 detectors will be achieved.

Scintillator performance considerations for dedicated breast computed tomography

NASA Astrophysics Data System (ADS)

Vedantham, Srinivasan; Shi, Linxi; Karellas, Andrew

2017-09-01

Dedicated breast computed tomography (BCT) is an emerging clinical modality that can eliminate tissue superposition and has the potential for improved sensitivity and specificity for breast cancer detection and diagnosis. It is performed without physical compression of the breast. Most of the dedicated BCT systems use large-area detectors operating in cone-beam geometry and are referred to as cone-beam breast CT (CBBCT) systems. The large-area detectors in CBBCT systems are energy-integrating, indirect-type detectors employing a scintillator that converts x-ray photons to light, followed by detection of optical photons. A key consideration that determines the image quality achieved by such CBBCT systems is the choice of scintillator and its performance characteristics. In this work, a framework for analyzing the impact of the scintillator on CBBCT performance and its use for task-specific optimization of CBBCT imaging performance is described.

Feasibility evaluation of a neutron grating interferometer with an analyzer grating based on a structured scintillator.

PubMed

Kim, Youngju; Kim, Jongyul; Kim, Daeseung; Hussey, Daniel S; Lee, Seung Wook

2018-03-01

We introduce an analyzer grating based on a structured scintillator fabricated by a gadolinium oxysulfide powder filling method for a symmetric Talbot-Lau neutron grating interferometer. This is an alternative way to analyze the Talbot self-image of a grating interferometer without using an absorption grating to block neutrons. Since the structured scintillator analyzer grating itself generates the signal for neutron detection, we do not need an additional scintillator screen as an absorption analyzer grating. We have developed and tested an analyzer grating based on a structured scintillator in our symmetric Talbot-Lau neutron grating interferometer to produce high fidelity absorption, differential phase, and dark-field contrast images. The acquired images have been compared to results of a grating interferometer utilizing a typical absorption analyzer grating with two commercial scintillation screens. The analyzer grating based on the structured scintillator enhances interference fringe visibility and shows a great potential for economical fabrication, compact system design, and so on. We report the performance of the analyzer grating based on a structured scintillator and evaluate its feasibility for the neutron grating interferometer.

Feasibility evaluation of a neutron grating interferometer with an analyzer grating based on a structured scintillator

NASA Astrophysics Data System (ADS)

Kim, Youngju; Kim, Jongyul; Kim, Daeseung; Hussey, Daniel. S.; Lee, Seung Wook

2018-03-01

We introduce an analyzer grating based on a structured scintillator fabricated by a gadolinium oxysulfide powder filling method for a symmetric Talbot-Lau neutron grating interferometer. This is an alternative way to analyze the Talbot self-image of a grating interferometer without using an absorption grating to block neutrons. Since the structured scintillator analyzer grating itself generates the signal for neutron detection, we do not need an additional scintillator screen as an absorption analyzer grating. We have developed and tested an analyzer grating based on a structured scintillator in our symmetric Talbot-Lau neutron grating interferometer to produce high fidelity absorption, differential phase, and dark-field contrast images. The acquired images have been compared to results of a grating interferometer utilizing a typical absorption analyzer grating with two commercial scintillation screens. The analyzer grating based on the structured scintillator enhances interference fringe visibility and shows a great potential for economical fabrication, compact system design, and so on. We report the performance of the analyzer grating based on a structured scintillator and evaluate its feasibility for the neutron grating interferometer.

Maximum likelihood positioning and energy correction for scintillation detectors

NASA Astrophysics Data System (ADS)

Lerche, Christoph W.; Salomon, André; Goldschmidt, Benjamin; Lodomez, Sarah; Weissler, Björn; Solf, Torsten

2016-02-01

An algorithm for determining the crystal pixel and the gamma ray energy with scintillation detectors for PET is presented. The algorithm uses Likelihood Maximisation (ML) and therefore is inherently robust to missing data caused by defect or paralysed photo detector pixels. We tested the algorithm on a highly integrated MRI compatible small animal PET insert. The scintillation detector blocks of the PET gantry were built with the newly developed digital Silicon Photomultiplier (SiPM) technology from Philips Digital Photon Counting and LYSO pixel arrays with a pitch of 1 mm and length of 12 mm. Light sharing was used to readout the scintillation light from the 30× 30 scintillator pixel array with an 8× 8 SiPM array. For the performance evaluation of the proposed algorithm, we measured the scanner’s spatial resolution, energy resolution, singles and prompt count rate performance, and image noise. These values were compared to corresponding values obtained with Center of Gravity (CoG) based positioning methods for different scintillation light trigger thresholds and also for different energy windows. While all positioning algorithms showed similar spatial resolution, a clear advantage for the ML method was observed when comparing the PET scanner’s overall single and prompt detection efficiency, image noise, and energy resolution to the CoG based methods. Further, ML positioning reduces the dependence of image quality on scanner configuration parameters and was the only method that allowed achieving highest energy resolution, count rate performance and spatial resolution at the same time.

Experiment to demonstrate separation of Cherenkov and scintillation signals

NASA Astrophysics Data System (ADS)

Caravaca, J.; Descamps, F. B.; Land, B. J.; Wallig, J.; Yeh, M.; Orebi Gann, G. D.

2017-05-01

The ability to separately identify the Cherenkov and scintillation light components produced in scintillating mediums holds the potential for a major breakthrough in neutrino detection technology, allowing development of a large, low-threshold, directional detector with a broad physics program. The CHESS (CHErenkov/Scintillation Separation) experiment employs an innovative detector design with an array of small, fast photomultiplier tubes and state-of-the-art electronics to demonstrate the reconstruction of a Cherenkov ring in a scintillating medium based on photon hit time and detected photoelectron density. This paper describes the physical properties and calibration of CHESS along with first results. The ability to reconstruct Cherenkov rings is demonstrated in a water target, and a time precision of 338 ±12 ps FWHM is achieved. Monte Carlo-based predictions for the ring imaging sensitivity with a liquid scintillator target predict an efficiency for identifying Cherenkov hits of 94 ±1 % and 81 ±1 % in pure linear alkyl benzene (LAB) and LAB loaded with 2 g/L of a fluor, PPO, respectively, with a scintillation contamination of 12 ±1 % and 26 ±1 % .

Induced radioactivity of a GSO scintillator by secondary fragments in carbon ion therapy and its effects on in-beam OpenPET imaging.

PubMed

Hirano, Yoshiyuki; Nitta, Munetaka; Nishikido, Fumihiko; Yoshida, Eiji; Inadama, Naoko; Yamaya, Taiga

2016-07-07

The accumulation of induced radioactivity within in-beam PET scanner scintillators is of concern for its long-term clinical usage in particle therapy. To estimate the effects on OpenPET which we are developing for in-beam PET based on GSOZ (Zi doped Gd2SiO5), we measured the induced radioactivity of GSO activated by secondary fragments in a water phantom irradiation by a (12)C beam with an energy of 290 MeV u(-1). Radioisotopes of Na, Ce, Eu, Gd, Nd, Pm and Tb including positron emitters were observed in the gamma ray spectra of the activated GSO with a high purity Ge detector and their absolute radioactivities were calculated. We used the Monte Carlo simulation platform, Geant4 in which the observed radioactivity was assigned to the scintillators of a precisely reproduced OpenPET and the single and coincidence rates immediately after one treatment and after one-year usage were estimated for the most severe conditions. Comparing the highest coincidence rate originating from the activated scintillators (background) and the expected coincidence rate from an imaging object (signal), we determined the expected signal-to-noise ratio to be more than 7 within 3 min and more than 10 within 1 min from the scan start time. We concluded the effects of scintillator activation and their accumulation on the OpenPET imaging were small and clinical long-term usage of the OpenPET was feasible.

Induced radioactivity of a GSO scintillator by secondary fragments in carbon ion therapy and its effects on in-beam OpenPET imaging

NASA Astrophysics Data System (ADS)

Hirano, Yoshiyuki; Nitta, Munetaka; Nishikido, Fumihiko; Yoshida, Eiji; Inadama, Naoko; Yamaya, Taiga

2016-07-01

The accumulation of induced radioactivity within in-beam PET scanner scintillators is of concern for its long-term clinical usage in particle therapy. To estimate the effects on OpenPET which we are developing for in-beam PET based on GSOZ (Zi doped Gd2SiO5), we measured the induced radioactivity of GSO activated by secondary fragments in a water phantom irradiation by a 12C beam with an energy of 290 MeV u-1. Radioisotopes of Na, Ce, Eu, Gd, Nd, Pm and Tb including positron emitters were observed in the gamma ray spectra of the activated GSO with a high purity Ge detector and their absolute radioactivities were calculated. We used the Monte Carlo simulation platform, Geant4 in which the observed radioactivity was assigned to the scintillators of a precisely reproduced OpenPET and the single and coincidence rates immediately after one treatment and after one-year usage were estimated for the most severe conditions. Comparing the highest coincidence rate originating from the activated scintillators (background) and the expected coincidence rate from an imaging object (signal), we determined the expected signal-to-noise ratio to be more than 7 within 3 min and more than 10 within 1 min from the scan start time. We concluded the effects of scintillator activation and their accumulation on the OpenPET imaging were small and clinical long-term usage of the OpenPET was feasible.

Scintillation Counters

NASA Astrophysics Data System (ADS)

Bell, Zane W.

Scintillators find wide use in radiation detection as the detecting medium for gamma/X-rays, and charged and neutral particles. Since the first notice in 1895 by Roentgen of the production of light by X-rays on a barium platinocyanide screen, and Thomas Edison's work over the following 2 years resulting in the discovery of calcium tungstate as a superior fluoroscopy screen, much research and experimentation have been undertaken to discover and elucidate the properties of new scintillators. Scintillators with high density and high atomic number are prized for the detection of gamma rays above 1 MeV; lower atomic number, lower-density materials find use for detecting beta particles and heavy charged particles; hydrogenous scintillators find use in fast-neutron detection; and boron-, lithium-, and gadolinium-containing scintillators are used for slow-neutron detection. This chapter provides the practitioner with an overview of the general characteristics of scintillators, including the variation of probability of interaction with density and atomic number, the characteristics of the light pulse, a list and characteristics of commonly available scintillators and their approximate cost, and recommendations regarding the choice of material for a few specific applications. This chapter does not pretend to present an exhaustive list of scintillators and applications.

GAGG:ce single crystalline films: New perspective scintillators for electron detection in SEM.

PubMed

Bok, Jan; Lalinský, Ondřej; Hanuš, Martin; Onderišinová, Zuzana; Kelar, Jakub; Kučera, Miroslav

2016-04-01

Single crystal scintillators are frequently used for electron detection in scanning electron microscopy (SEM). We report gadolinium aluminum gallium garnet (GAGG:Ce) single crystalline films as a new perspective scintillators for the SEM. For the first time, the epitaxial garnet films were used in a practical application: the GAGG:Ce scintillator was incorporated into a SEM scintillation electron detector and it showed improved image quality. In order to prove the GAGG:Ce quality accurately, the scintillation properties were examined using electron beam excitation and compared with frequently used scintillators in the SEM. The results demonstrate excellent emission efficiency of the GAGG:Ce single crystalline films together with their very fast scintillation decay useful for demanding SEM applications. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of a scintillating G-GEM detector for a 6-MeV X-band Linac for medical applications

NASA Astrophysics Data System (ADS)

Fujiwara, T.; Tanaka, S.; Mitsuya, Y.; Takahashi, H.; Tagi, K.; Kusano, J.; Tanabe, E.; Yamamoto, M.; Nakamura, N.; Dobashi, K.; Tomita, H.; Uesaka, M.

2013-12-01

We recently developed glass gas electron multipliers (G-GEMs) with an entirely new process using photo-etchable glass. The photo-etchable glass used for the substrate is called PEG3 (Hoya Corporation). Taking advantage of low outgassing material, we have envisioned a medical application of G-GEMs. A two-dimensional position-sensitive dosimetry system based on a scintillating gas detector is being developed for real-time dose distribution monitoring in X-ray radiation therapy. The dosimetry system consists of a chamber filled with an Ar/CF4 scintillating gas mixture, inside of which G-GEM structures are mounted. Photons produced by the excited Ar/CF4 gas molecules during the gas multiplication in the GEM holes are detected by a mirror-lens-CCD-camera system. We found that the intensity distribution of the measured light spot is proportional to the 2D dose distribution. In this work, we report on the first results from a scintillating G-GEM detector for a position-sensitive X-ray beam dosimeter.

The low-temperature scintillation properties of bismuth germanate and its application to high-energy gamma radiation imaging devices.

PubMed

Piltingsrud, H V

1979-12-01

Bismuth germanate is a scintillation material with very high z, and high density (7.13 g/cm3). It is a rugged, nonhygroscopic, crystalline material with room-temperature scintillation properties described by previous investigators as having a light yield approximately 8% of that of NaI(Tl), emission peak at approximately 480 nm, decay constant of 0.3 microsec, and energy resolution congruent to 15% (FWHM) for Cs-137 gamma radiations. These properties make it an excellent candidate for applications involving the detection of high-energy gamma photons and positron annihilation radiation, particularly when good spatial resolution is desired. At room temperature, however, the application of this material is somewhat limited by low light output and poor energy resolution. This paper presents new data on the scintillation properties of bismuth germanate as a function of temperature from -- 196 degrees C to j0 degrees C. Low-temperature use of the material is shown to greatly improve its light yield and energy resolution. The implications of this work to the design of imaging devices for high-energy radiation in health physics and nuclear medicine are discussed.

Scintillation properties of polycrystalline LaxY1-xO3 ceramic

NASA Astrophysics Data System (ADS)

Sahi, Sunil; Chen, Wei; Kenarangui, Rasool

2015-03-01

Scintillators are the material that absorbs the high-energy photons and emits visible photons. Scintillators are commonly used in radiation detector for security, medical imaging, industrial applications and high energy physics research. Two main types of scintillators are inorganic single crystals and organic (plastic or liquid) scintillators. Inorganic single crystals are expensive and difficult to grow in desire shape and size. Also, some efficient inorganic scintillator such as NaI and CsI are not environmental friendly. But on the other hand, organic scintillators have low density and hence poor energy resolution which limits their use in gamma spectroscopy. Polycrystalline ceramic can be a cost effective alternative to expensive inorganic single crystal scintillators. Here we have fabricated La0.2Y1.8O3 ceramic scintillator and studied their luminescence and scintillation properties. Ceramic scintillators were fabricated by vacuum sintering of La0.2Y1.8O3 nanoparticles at temperature below the melting point. La0.2Y1.8O3 ceramic were characterized structurally using XRD and TEM. Photoluminescence and radioluminescence studies were done using UV and X-ray as an excitation source. We have used gamma isotopes with different energy to studies the scintillation properties of La0.2Y1.8O3 scintillator. Preliminary studies of La0.2Y1.8O3 scintillator shows promising result with energy resolution comparable to that of NaI and CsI.

SU-E-CAMPUS-T-03: Four-Dimensional Dose Distribution Measurement Using Plastic Scintillator

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

Hashimoto, M; Kozuka, T; Oguchi, M

2014-06-15

Purpose: To develop the detector for the four-dimensional dose distribution measurement. Methods: We made the prototype detector for four-dimensional dose distribution measurement using a cylindrical plastic scintillator (5 cm diameter) and a conical reflection grass. The plastic scintillator is used as a phantom. When the plastic scintillator is irradiated, the scintillation light was emitted according to absorbed dose distribution. The conical reflection grass was arranged to surround the plastic scintillator, which project to downstream the projection images of the scintillation light. Then, the projection image was reflected to 45 degree direction by flat reflection grass, and was recorded by camcorder.more » By reconstructing the three-dimensional dose distribution from the projection image recorded in each frame, we could obtain the four-dimensional dose distribution. First, we tested the characteristic according to the amount of emitted light. Then we compared of the light profile and the dose profile calculated with the radiotherapy treatment planning system. Results: The dose dependency of the amount of light showed linearity. The pixel detecting smaller amount of light had high sensitivity than the pixel detecting larger amount of light. However the difference of the sensitivity could be corrected from the amount of light detected in each pixel. Both of the depth light profile through the conical reflection grass and the depth dose profile showed the same attenuation in the region deeper than peak depth. In lateral direction, the difference of the both profiles was shown at outside field and penumbra region. We consider that the difference is occurred due to the scatter of the scintillation light in the plastic scintillator block. Conclusion: It was possible to obtain the amount of light corresponding to the absorbed dose distribution from the prototype detector. Four-dimensional dose distributions can be reconstructed with high accuracy by the

Experiment to demonstrate separation of Cherenkov and scintillation signals

DOE PAGES

Caravaca, J.; Descamps, F. B.; Land, B. J.; ...

2017-05-05

The ability to separately identify the Cherenkov and scintillation light components produced in scintillating mediums holds the potential for a major breakthrough in neutrino detection technology, allowing development of a large, low-threshold, directional detector with a broad physics program. Furthermore, the CHESS (CHErenkov/Scintillation Separation) experiment employs an innovative detector design with an array of small, fast photomultiplier tubes and state-of-the-art electronics to demonstrate the reconstruction of a Cherenkov ring in a scintillating medium based on photon hit time and detected photoelectron density. Our paper describes the physical properties and calibration of CHESS along with first results. The ability to reconstructmore » Cherenkov rings are demonstrated in a water target, and a time precision of 338 ± 12 ps FWHM is achieved. Finally, Monte Carlo–based predictions for the ring imaging sensitivity with a liquid scintillator target predict an efficiency for identifying Cherenkov hits of 94 ± 1 % and 81 ± 1 % in pure linear alkyl benzene (LAB) and LAB loaded with 2 g/L of a fluor, PPO, respectively, with a scintillation contamination of 12 ± 1 % and 26 ± 1 % .« less

Optical artefact characterization and correction in volumetric scintillation dosimetry

PubMed Central

Robertson, Daniel; Hui, Cheukkai; Archambault, Louis; Mohan, Radhe; Beddar, Sam

2014-01-01

The goals of this study were (1) to characterize the optical artefacts affecting measurement accuracy in a volumetric liquid scintillation detector, and (2) to develop methods to correct for these artefacts. The optical artefacts addressed were photon scattering, refraction, camera perspective, vignetting, lens distortion, the lens point spread function, stray radiation, and noise in the camera. These artefacts were evaluated by theoretical and experimental means, and specific correction strategies were developed for each artefact. The effectiveness of the correction methods was evaluated by comparing raw and corrected images of the scintillation light from proton pencil beams against validated Monte Carlo calculations. Blurring due to the lens and refraction at the scintillator tank-air interface were found to have the largest effect on the measured light distribution, and lens aberrations and vignetting were important primarily at the image edges. Photon scatter in the scintillator was not found to be a significant source of artefacts. The correction methods effectively mitigated the artefacts, increasing the average gamma analysis pass rate from 66% to 98% for gamma criteria of 2% dose difference and 2 mm distance to agreement. We conclude that optical artefacts cause clinically meaningful errors in the measured light distribution, and we have demonstrated effective strategies for correcting these optical artefacts. PMID:24321820

SU-E-T-451: Accuracy and Application of the Standard Imaging W1 Scintillator Dosimeter

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

Kowalski, M; McEwen, M

2014-06-01

Purpose: To evaluate the Standard Imaging W1 scintillator dosimeter in a range of clinical radiation beams to determine its range of possible applications. Methods: The W1 scintillator is a small perturbation-free dosimeter which is of interest in absolute and relative clinical dosimetry due to its small size and water equivalence. A single version of this detector was evaluated in Co-60 and linac photon and electron beams to investigate the following: linearity, sensitivity, precision, and dependence on electrometer type. In addition, depth-dose and cross-plane profiles were obtained in both photon and electron beams and compared with data obtained with wellbehaved ionizationmore » chambers. Results: In linac beams the precision and linearity was very impressive, with typical values of 0.3% and 0.1% respectively. Performance in a Co-60 beam was much poorer (approximately three times worse) and it is not clear whether this is due to the lower signal current or the effect of the continuous beam (rather than pulsed beam of the linac measurements). There was no significant difference in the detector reading when using either the recommended SI Supermax electrometer or two independent high-quality electrometers, except for low signal levels, where the Supermax exhibited an apparent threshold effect, preventing the measurement of the bremsstrahlung background in electron depth-dose curves. Comparisons with ion chamber measurements in linac beams were somewhat variable: good agreement was seen for cross-profiles (photon and electron beams) and electron beam depth-dose curves, generally within the 0.3% precision of the scintillator but systematic differences were observed as a function of measurement depth in photon beam depth-dose curves. Conclusion: A first look would suggest that the W1 scintillator has applications beyond small field dosimetry but performance appears to be limited to higher doserate and/or pulsed radiation beams. Further work is required to resolve

Space-Based Three-Dimensional Imaging of Equatorial Plasma Bubbles: Advancing the Understanding of Ionospheric Density Depletions and Scintillation

DTIC Science & Technology

2012-03-28

Scintillation 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Comberiate, Joseph M. 5e. TASK NUMBER 5f. WORK...bubble climatology. A tomographic reconstruction technique was modified and applied to SSUSI data to reconstruct three-dimensional cubes of ionospheric... modified and applied to SSUSI data to reconstruct three-dimensional cubes of ionospheric electron density. These data cubes allowed for 3-D imaging of

Probing Cherenkov and Scintillation Light Separation for Next-Generation Neutrino Detectors

NASA Astrophysics Data System (ADS)

Caravaca, J.; Descamps, F. B.; Land, B. J.; Orebi Gann, G. D.; Wallig, J.; Yeh, M.

2017-09-01

The ability to separate Cherenkov and scintillation signals in liquid scintillator detectors would enable outstanding background rejection for next-generation neutrino experiments. Reconstruction of directional information, ring imaging, and sub-Cherenkov threshold detection all have the potential to substantially improve particle and event identification. The Cherenkov-Scintillation Separation (CHESS) experiment uses an array of small, fast photomultipliers (PMTs) and state-of-the-art electronics to demonstrate the reconstruction of a Cherenkov ring in a scintillation medium based on photon hit times and detected charge. This setup has been used to characterize the ability to detect Cherenkov light in a range of target media. We show results with pure organic scintillator (LAB) and the prospects with scintillators with a secondary fluor (LAB/PPO). There are future plans to deploy the newly developed water-based liquid scintillator, a medium with a higher Cherenkov/Scintillation light yield ratio than conventional pure liquid scintillators, enhancing the visibility of the less abundant Cherenkov light in the presence of scintillation light. These results can inform the development of future large-scale detectors, such as the proposed Theia experiment, or other large detectors at underground laboratories such as the far-site of the new Long Baseline Neutrino Facility at the Sanford Underground Research Facility. CHESS detector calibrations and commissioning will be discussed, and the latest results will be presented.

Measurement of radiation damage of water-based liquid scintillator and liquid scintillator

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

Bignell, L. J.; Diwan, M. V.; Hans, S.

2015-10-19

Liquid scintillating phantoms have been proposed as a means to perform real-time 3D dosimetry for proton therapy treatment plan verification. We have studied what effect radiation damage to the scintillator will have upon this application. We have performed measurements of the degradation of the light yield and optical attenuation length of liquid scintillator and water-based liquid scintillator after irradiation by 201 MeV proton beams that deposited doses of approximately 52 Gy, 300 Gy, and 800 Gy in the scintillator. Liquid scintillator and water-based liquid scintillator (composed of 5% scintillating phase) exhibit light yield reductions of 1.74 ± 0.55 % andmore » 1.31 ± 0.59 % after ≈ 800 Gy of proton dose, respectively. Some increased optical attenuation was observed in the irradiated samples, the measured reduction to the light yield is also due to damage to the scintillation light production. Based on our results and conservative estimates of the expected dose in a clinical context, a scintillating phantom used for proton therapy treatment plan verification would exhibit a systematic light yield reduction of approximately 0.1% after a year of operation.« less

Infrared hyperspectral imaging sensor for gas detection

NASA Astrophysics Data System (ADS)

Hinnrichs, Michele

2000-11-01

A small light weight man portable imaging spectrometer has many applications; gas leak detection, flare analysis, threat warning, chemical agent detection, just to name a few. With support from the US Air Force and Navy, Pacific Advanced Technology has developed a small man portable hyperspectral imaging sensor with an embedded DSP processor for real time processing that is capable of remotely imaging various targets such as gas plums, flames and camouflaged targets. Based upon their spectral signature the species and concentration of gases can be determined. This system has been field tested at numerous places including White Mountain, CA, Edwards AFB, and Vandenberg AFB. Recently evaluation of the system for gas detection has been performed. This paper presents these results. The system uses a conventional infrared camera fitted with a diffractive optic that images as well as disperses the incident radiation to form spectral images that are collected in band sequential mode. Because the diffractive optic performs both imaging and spectral filtering, the lens system consists of only a single element that is small, light weight and robust, thus allowing man portability. The number of spectral bands are programmable such that only those bands of interest need to be collected. The system is entirely passive, therefore, easily used in a covert operation. Currently Pacific Advanced Technology is working on the next generation of this camera system that will have both an embedded processor as well as an embedded digital signal processor in a small hand held camera configuration. This will allow the implementation of signal and image processing algorithms for gas detection and identification in real time. This paper presents field test data on gas detection and identification as well as discuss the signal and image processing used to enhance the gas visibility. Flow rates as low as 0.01 cubic feet per minute have been imaged with this system.

Subnanosecond Scintillation Detector

NASA Technical Reports Server (NTRS)

Hoenk, Michael (Inventor); Hennessy, John (Inventor); Hitlin, David (Inventor)

2017-01-01

A scintillation detector, including a scintillator that emits scintillation; a semiconductor photodetector having a surface area for receiving the scintillation, wherein the surface area has a passivation layer configured to provide a peak quantum efficiency greater than 40% for a first component of the scintillation, and the semiconductor photodetector has built in gain through avalanche multiplication; a coating on the surface area, wherein the coating acts as a bandpass filter that transmits light within a range of wavelengths corresponding to the first component of the scintillation and suppresses transmission of light with wavelengths outside said range of wavelengths; and wherein the surface area, the passivation layer, and the coating are controlled to increase the temporal resolution of the semiconductor photodetector.

A Hybrid Gas Detector/Phoswich for Hard X-ray Astronomy

NASA Technical Reports Server (NTRS)

Ramsey, B. D.; Austin, R. A.; Minamitani, T.; Weisskopf, M. C.; Grindlay, J. E.; Lum, K. S. K.; Manandhar, R. P.

1993-01-01

A hybrid detector, which combines an optical avalanche chamber with a phoswich, is currently under development. The optical avalanche chamber - a proportional counter designed to give large quantities of light photons during charge multiplication, mounts on the front of the scintillator and gives response at low energies, while the solid scintillator takes over at energies where the gas becomes transparent (greater than 90 keV). Both sections of the hybrid will be read out by a common set of photomultipliers under the phoswich. The addition of the gas section to the phoswich improves the energy resolution of the instrument by a factor of 2.5 at 25 keV and the spatial resolution by a factor of 10 at the same energy. The net result is an instrument with broad band coverage and high sensitivity which will be used for coded aperture imaging on long duration balloon flights.

Optical and Scintillation Properties of Polydimethyl-Diphenylsiloxane Based Organic Scintillators

NASA Astrophysics Data System (ADS)

Quaranta, Alberto; Carturan, Sara Maria; Marchi, Tommaso; Kravchuk, Vladimir L.; Gramegna, Fabiana; Maggioni, Gianluigi; Degerlier, Meltem

2010-04-01

Polysiloxane based scintillators with high light yield have been synthesized. The polymer consists in cross-linked polydimethyl-co-diphenylsiloxane with different molar percentages of phenyl units. 2,5-diphenyl oxazole (PPO) and 2,5-bis(5-ter-butyl-2-benzoxazolyl)thiophene (BBOT) have been dispersed in the polymer as dopants. The energy transfer and scintillation capabilities have been investigated, for two different amounts of phenyl groups in the polymer network and for different concentrations of dye molecules, by means of fluorescence spectroscopy, ion beam induced luminescence (IBIL) and scintillation yield measurements with ¿ particles from an 241Am source. The luminescence features and the scintillation yields have been correlated to the composition of the scintillators.

Fast frame rate rodent cardiac x-ray imaging using scintillator lens coupled to CMOS camera

NASA Astrophysics Data System (ADS)

Swathi Lakshmi, B.; Sai Varsha, M. K. N.; Kumar, N. Ashwin; Dixit, Madhulika; Krishnamurthi, Ganapathy

2017-03-01

Micro-Computed Tomography (MCT) systems for small animal imaging plays a critical role for monitoring disease progression and therapy evaluation. In this work, an in-house built micro-CT system equipped with a X-ray scintillator lens coupled to a commercial CMOS camera was used to test the feasibility of its application to Digital Subtraction Angiography (DSA). Literature has reported such studies being done with clinical X-ray tubes that can be pulsed rapidly or with rotating gantry systems, thus increasing the cost and infrastructural requirements.The feasibility of DSA was evaluated by injected Iodinated contrast agent (ICA) through the tail vein of a mouse. Projection images of the heart were acquired pre and post contrast using the high frame rate X-ray detector and processing done to visualize transit of ICA through the heart.

Scintillator material

DOEpatents

Anderson, David F.; Kross, Brian J.

1994-01-01

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography.

Scintillator material

DOEpatents

Anderson, David F.; Kross, Brian J.

1992-01-01

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography.

Scintillator material

DOEpatents

Anderson, D.F.; Kross, B.J.

1994-06-07

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography. 4 figs.

Scintillator material

DOEpatents

Anderson, D.F.; Kross, B.J.

1992-07-28

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography. 4 figs.

Microdome-gooved Gd(2)O(2)S:Tb scintillator for flexible and high resolution digital radiography.

PubMed

Jung, Phill Gu; Lee, Chi Hoon; Bae, Kong Myeong; Lee, Jae Min; Lee, Sang Min; Lim, Chang Hwy; Yun, Seungman; Kim, Ho Kyung; Ko, Jong Soo

2010-07-05

A flexible microdome-grooved Gd(2)O(2)S:Tb scintillator is simulated, fabricated, and characterized for digital radiography applications. According to Monte Carlo simulation results, the dome-grooved structure has a high spatial resolution, which is verified by X-ray image performance of the scintillator. The proposed scintillator has lower X-ray sensitivity than a nonstructured scintillator but almost two times higher spatial resolution at high spatial frequency. Through evaluation of the X-ray performance of the fabricated scintillators, we confirm that the microdome-grooved scintillator can be applied to next-generation flexible digital radiography systems requiring high spatial resolution.

Monte Carlo simulation studies on scintillation detectors and image reconstruction of brain-phantom tumors in TOFPET

PubMed Central

Mondal, Nagendra Nath

2009-01-01

This study presents Monte Carlo Simulation (MCS) results of detection efficiencies, spatial resolutions and resolving powers of a time-of-flight (TOF) PET detector systems. Cerium activated Lutetium Oxyorthosilicate (Lu2SiO5: Ce in short LSO), Barium Fluoride (BaF2) and BriLanCe 380 (Cerium doped Lanthanum tri-Bromide, in short LaBr3) scintillation crystals are studied in view of their good time and energy resolutions and shorter decay times. The results of MCS based on GEANT show that spatial resolution, detection efficiency and resolving power of LSO are better than those of BaF2 and LaBr3, although it possesses inferior time and energy resolutions. Instead of the conventional position reconstruction method, newly established image reconstruction (talked about in the previous work) method is applied to produce high-tech images. Validation is a momentous step to ensure that this imaging method fulfills all purposes of motivation discussed by reconstructing images of two tumors in a brain phantom. PMID:20098551

First light from a kilometer-baseline Scintillation Auroral GPS Array.

PubMed

Datta-Barua, S; Su, Y; Deshpande, K; Miladinovich, D; Bust, G S; Hampton, D; Crowley, G

2015-05-28

We introduce and analyze the first data from an array of closely spaced Global Positioning System (GPS) scintillation receivers established in the auroral zone in late 2013 to measure spatial and temporal variations in L band signals at 100-1000 m and subsecond scales. The seven receivers of the Scintillation Auroral GPS Array (SAGA) are sited at Poker Flat Research Range, Alaska. The receivers produce 100 s scintillation indices and 100 Hz carrier phase and raw in-phase and quadrature-phase samples. SAGA is the largest existing array with baseline lengths of the ionospheric diffractive Fresnel scale at L band. With an initial array of five receivers, we identify a period of simultaneous amplitude and phase scintillation. We compare SAGA power and phase data with collocated 630.0 nm all-sky images of an auroral arc and incoherent scatter radar electron precipitation measurements, to illustrate how SAGA can be used in multi-instrument observations for subkilometer-scale studies. A seven-receiver Scintillation Auroral GPS Array (SAGA) is now at Poker Flat, Alaska SAGA is the largest subkilometer array to enable phase/irregularities studies Simultaneous scintillation, auroral arc, and electron precipitation are observed.

Development of novel UV emitting single crystalline film scintillators

NASA Astrophysics Data System (ADS)

Zorenko, Yu; Gorbenko, V.; Savchyn, V.; Voznyak, T.; Nikl, M.; Mares, J. A.; Martin, T.; Douissard, P.-A.

2011-04-01

The work is dedicated to development of new types of UV -emitting scintillators based on single crystalline films (SCF) of aluminimum perovskites and garnets grown by the liquid phase epitaxy (LPE) method. The development of the following three types of UV SCF scintillators is considered in this work: i) Ce-doped SCF of Y-Lu-Al-perovskites with Ce3+ emission in the 360-370 nm range with a decay time of 16-17 ns; ii) Pr-doped SCF of Y-Lu-Al garnets with Pr3+ emission in the 300-400 nm range with a decay time of 13-17 ns; iii) La3+ and Sc3+ doped SCF of Y-Lu-Al-garnets, emitting in the 290-400 nm range due to formation of the LaY,Lu, ScY,Lu and ScAl centers with decay time of 250-575 ns. The results of testing the several novel UV-emitting SCFs scintillators for visualization of X-ray images at ESFR are presented. It is shown that the UV emission of the LuAG:Sc, LuAG:La and LuAG:Pr SCFs is efficient enough for conversion of X-ray to the UV light and that these scintillators can be used for improvement of the resolution of imaging detectors in synchrotron radiation applications.

Minimum detectable gas concentration performance evaluation method for gas leak infrared imaging detection systems.

PubMed

Zhang, Xu; Jin, Weiqi; Li, Jiakun; Wang, Xia; Li, Shuo

2017-04-01

Thermal imaging technology is an effective means of detecting hazardous gas leaks. Much attention has been paid to evaluation of the performance of gas leak infrared imaging detection systems due to several potential applications. The minimum resolvable temperature difference (MRTD) and the minimum detectable temperature difference (MDTD) are commonly used as the main indicators of thermal imaging system performance. This paper establishes a minimum detectable gas concentration (MDGC) performance evaluation model based on the definition and derivation of MDTD. We proposed the direct calculation and equivalent calculation method of MDGC based on the MDTD measurement system. We build an experimental MDGC measurement system, which indicates the MDGC model can describe the detection performance of a thermal imaging system to typical gases. The direct calculation, equivalent calculation, and direct measurement results are consistent. The MDGC and the minimum resolvable gas concentration (MRGC) model can effectively describe the performance of "detection" and "spatial detail resolution" of thermal imaging systems to gas leak, respectively, and constitute the main performance indicators of gas leak detection systems.

Cargo Container Imaging with Gaseous Detectors

NASA Astrophysics Data System (ADS)

Forest, Tony

2006-10-01

The gas electron multiplier (GEM) , developed at CERN by Fabio Sauli, represents the latest innovation in micropattern gaseous detectors and has been utilized as a preamplification stage in applications ranging from fundamental physics experiments to medical imaging. Although cargo container inspection systems are currently in place using gamma-rays or X-rays, they are predominantly designed with a resolution to detect contraband. Current imaging systems also suffer from false alarms due to naturally radioactive cargo when radiation portal monitors are used for passive detection of nuclear materials. Detection of small shielded radioactive elements is even more problematic. Idaho State University has been developing a system to image cargo containers in order to detect small shielded radioactive cargo. The possible application of an imaging system with gas electron multiplication will be shown along with preliminary images using gaseous detectors instead of the scintillators currently in use.

Novel scintillators and silicon photomultipliers for nuclear physics and applications

NASA Astrophysics Data System (ADS)

Jenkins, David

2015-06-01

Until comparatively recently, scintillator detectors were seen as an old-fashioned tool of nuclear physics with more attention being given to areas such as gamma-ray tracking using high-purity germanium detectors. Next-generation scintillator detectors, such as lanthanum bromide, which were developed for the demands of space science and gamma- ray telescopes, are found to have strong applicability to low energy nuclear physics. Their excellent timing resolution makes them very suitable for fast timing measurements and their much improved energy resolution compared to conventional scintillators promises to open up new avenues in nuclear physics research which were presently hard to access. Such "medium-resolution" spectroscopy has broad interest across several areas of contemporary interest such as the study of nuclear giant resonances. In addition to the connections to space science, it is striking that the demands of contemporary medical imaging have strong overlap with those of experimental nuclear physics. An example is the interest in PET-MRI combined imaging which requires putting scintillator detectors in a high magnetic field environment. This has led to strong advances in the area of silicon photomultipliers, a solid-state replacement for photomultiplier tubes, which are insensitive to magnetic fields. Broad application to nuclear physics of this technology may be foreseen.

Scintillator-based transverse proton beam profiler for laser-plasma ion sources.

PubMed

Dover, N P; Nishiuchi, M; Sakaki, H; Alkhimova, M A; Faenov, A Ya; Fukuda, Y; Kiriyama, H; Kon, A; Kondo, K; Nishitani, K; Ogura, K; Pikuz, T A; Pirozhkov, A S; Sagisaka, A; Kando, M; Kondo, K

2017-07-01

A high repetition rate scintillator-based transverse beam profile diagnostic for laser-plasma accelerated proton beams has been designed and commissioned. The proton beam profiler uses differential filtering to provide coarse energy resolution and a flexible design to allow optimisation for expected beam energy range and trade-off between spatial and energy resolution depending on the application. A plastic scintillator detector, imaged with a standard 12-bit scientific camera, allows data to be taken at a high repetition rate. An algorithm encompassing the scintillator non-linearity is described to estimate the proton spectrum at different spatial locations.

Thin-film-based scintillators for hard x-ray microimaging detectors: the ScinTAX Project

NASA Astrophysics Data System (ADS)

Rack, A.; Cecilia, A.; Douissard, P.-A.; Dupré, K.; Wesemann, V.; Baumbach, T.; Couchaud, M.; Rochet, X.; Riesemeier, H.; Radtke, M.; Martin, T.

2014-09-01

The project ScinTAX developed novel thin scintillating films for the application in high performance X-ray imaging and subsequent introduced new X-ray detectors to the market. To achieve this aim lutetium orthosilicate (LSO) scintillators doped with different activators were grown successfully by liquid phase epitaxy. The high density of LSO (7.4 g/cm3), the effective atomic number (65.2) and the high light yield make this scintillator highly applicable for indirect X-ray detection in which the ionizing radiation is converted into visible light and then registered by a digital detector. A modular indirect detection system has been developed to fully exploit the potential of this thin film scintillator for radiographic and tomographic imaging. The system is compatible for high-resolution imaging with moderate dose as well as adaptable to intense high-dose applications where radiation hard microimaging detectors are required. This proceedings article shall review the achieved performances and technical details on this high-resolution detector system which is now available. A selected example application demonstrates the great potential of the optimized detector system for hard X-ray microimaging, i.e. either to improve image contrast due to the availability of efficient thin crystal films or to reduce the dose to the sample.

Removal of ring artifacts in microtomography by characterization of scintillator variations.

PubMed

Vågberg, William; Larsson, Jakob C; Hertz, Hans M

2017-09-18

Ring artifacts reduce image quality in tomography, and arise from faulty detector calibration. In microtomography, we have identified that ring artifacts can arise due to high-spatial frequency variations in the scintillator thickness. Such variations are normally removed by a flat-field correction. However, as the spectrum changes, e.g. due to beam hardening, the detector response varies non-uniformly introducing ring artifacts that persist after flat-field correction. In this paper, we present a method to correct for ring artifacts from variations in scintillator thickness by using a simple method to characterize the local scintillator response. The method addresses the actual physical cause of the ring artifacts, in contrary to many other ring artifact removal methods which rely only on image post-processing. By applying the technique to an experimental phantom tomography, we show that ring artifacts are strongly reduced compared to only making a flat-field correction.

Radioactive contamination of scintillators

NASA Astrophysics Data System (ADS)

Danevich, F. A.; Tretyak, V. I.

2018-03-01

Low counting experiments (search for double β decay and dark matter particles, measurements of neutrino fluxes from different sources, search for hypothetical nuclear and subnuclear processes, low background α, β, γ spectrometry) require extremely low background of a detector. Scintillators are widely used to search for rare events both as conventional scintillation detectors and as cryogenic scintillating bolometers. Radioactive contamination of a scintillation material plays a key role to reach low level of background. Origin and nature of radioactive contamination of scintillators, experimental methods and results are reviewed. A programme to develop radiopure crystal scintillators for low counting experiments is discussed briefly.

Chloride, bromide and iodide scintillators with europium

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

Zhuravleva, Mariya; Yang, Kan

A halide scintillator material is disclosed where the halide may comprise chloride, bromide or iodide. The material is single-crystalline and has a composition of the general formula ABX.sub.3 where A is an alkali, B is an alkali earth and X is a halide which general composition was investigated. In particular, crystals of the formula ACa.sub.1-yEu.sub.yI.sub.3 where A=K, Rb and Cs were formed as well as crystals of the formula CsA.sub.1-yEu.sub.yX.sub.3 (where A=Ca, Sr, Ba, or a combination thereof and X=Cl, Br or I or a combination thereof) with divalent Europium doping where 0.ltoreq.y.ltoreq.1, and more particularly Eu doping has beenmore » studied at one to ten mol %. The disclosed scintillator materials are suitable for making scintillation detectors used in applications such as medical imaging and homeland security.« less

2D dosimetry in a proton beam with a scintillating GEM detector

NASA Astrophysics Data System (ADS)

Seravalli, E.; de Boer, M. R.; Geurink, F.; Huizenga, J.; Kreuger, R.; Schippers, J. M.; van Eijk, C. W. E.

2009-06-01

A two-dimensional position-sensitive dosimetry system based on a scintillating gas detector is being developed for pre-treatment verification of dose distributions in particle therapy. The dosimetry system consists of a chamber filled with an Ar/CF4 scintillating gas mixture, inside which two gas electron multiplier (GEM) structures are mounted (Seravalli et al 2008b Med. Phys. Biol. 53 4651-65). Photons emitted by the excited Ar/CF4 gas molecules during the gas multiplication in the GEM holes are detected by a mirror-lens-CCD camera system. The intensity distribution of the measured light spot is proportional to the 2D dose distribution. In this work, we report on the characterization of the scintillating GEM detector in terms of those properties that are of particular importance in relative dose measurements, e.g. response reproducibility, dose dependence, dose rate dependence, spatial and time response, field size dependence, response uniformity. The experiments were performed in a 150 MeV proton beam. We found that the detector response is very stable for measurements performed in succession (σ = 0.6%) and its response reproducibility over 2 days is about 5%. The detector response was found to be linear with the dose in the range 0.05-19 Gy. No dose rate effects were observed between 1 and 16 Gy min-1 at the shallow depth of a water phantom and 2 and 38 Gy min-1 at the Bragg peak depth. No field size effects were observed in the range 120-3850 mm2. A signal rise and fall time of 2 µs was recorded and a spatial response of <=1 mm was measured.

On the response of Y 3Al 5O 12: Ce (YAG: Ce) powder scintillating screens to medical imaging X-rays

NASA Astrophysics Data System (ADS)

Kandarakis, I.; Cavouras, D.; Sianoudis, I.; Nikolopoulos, D.; Episkopakis, A.; Linardatos, D.; Margetis, D.; Nirgianaki, E.; Roussou, M.; Melissaropoulos, P.; Kalivas, N.; Kalatzis, I.; Kourkoutas, K.; Dimitropoulos, N.; Louizi, A.; Nomicos, C.; Panayiotakis, G.

2005-02-01

The aim of this study was to examine Y 3Al 5O 12:Ce (also known as YAG:Ce) powder scintillator under X-ray imaging conditions. This material shows a very fast scintillation decay time and it has never been used in X-ray medical imaging. In the present study various scintillator layers (screens) with coating thickness ranging from 13 to 166 mg/cm 2 were prepared in our laboratory by sedimentation of Y 3Al 5O 12: Ce powder. Optical emission spectra and light emission efficiency (spectrum area over X-ray exposure) of the layers were measured under X-ray excitation using X-ray tube voltages (80-120 kVp) often employed in general medical radiography and fluoroscopy. Spectral compatibility with various optical photon detectors (photodiodes, photocathodes, charge coupled devices, films) and intrinsic conversion efficiency values were determined using emission spectrum data. In addition, parameters related to X-ray detection, energy absorption efficiency and K-fluorescence characteristic emission were calculated. A theoretical model describing radiation and light transfer through scattering media was used to fit experimental data. Intrinsic conversion efficiency (η≈0.03-0.05) and light attenuation coefficients (σ≈26.5 cm/g) were derived through this fitting. Y 3Al 5O 12:Ce showed peak emission in the wavelength range 530-550 nm. The light emission efficiency was found to be maximum for the 107 mg/cm 2 layer. Due to its "green" emission spectrum, Y 3Al 5O 12:Ce showed excellent compatibility (of the order of 0.9) with the sensitivity of many currently used photodetectors. Taking into account its very fast response Y 3Al 5O 12:Ce could be considered for application in X-ray imaging especially in various digital detectors.

Nuclear Science Symposium, 21st, Scintillation and Semiconductor Counter Symposium, 14th, and Nuclear Power Systems Symposium, 6th, Washington, D.C., December 11-13, 1974, Proceedings

NASA Technical Reports Server (NTRS)

1975-01-01

Papers are presented dealing with latest advances in the design of scintillation counters, semiconductor radiation detectors, gas and position sensitive radiation detectors, and the application of these detectors in biomedicine, satellite instrumentation, and environmental and reactor instrumentation. Some of the topics covered include entopistic scintillators, neutron spectrometry by diamond detector for nuclear radiation, the spherical drift chamber for X-ray imaging applications, CdTe detectors in radioimmunoassay analysis, CAMAC and NIM systems in the space program, a closed loop threshold calibrator for pulse height discriminators, an oriented graphite X-ray diffraction telescope, design of a continuous digital-output environmental radon monitor, and the optimization of nanosecond fission ion chambers for reactor physics. Individual items are announced in this issue.

A novel liquid-Xenon detector concept for combined fast-neutrons and gamma imaging and spectroscopy

NASA Astrophysics Data System (ADS)

Breskin, A.; Israelashvili, I.; Cortesi, M.; Arazi, L.; Shchemelinin, S.; Chechik, R.; Dangendorf, V.; Bromberger, B.; Vartsky, D.

2012-06-01

A new detector concept is presented for combined imaging and spectroscopy of fast-neutrons and gamma rays. It comprises a liquid-Xenon (LXe) converter and scintillator coupled to a UV-sensitive gaseous imaging photomultiplier (GPM). Radiation imaging is obtained by localization of the scintillation-light from LXe with the position-sensitive GPM. The latter comprises a cascade of Thick Gas Electron Multipliers (THGEM), where the first element is coated with a CsI UV-photocathode. We present the concept and provide first model-simulation results of the processes involved and the expected performances of a detector having a LXe-filled capillaries converter. The new detector concept has potential applications in combined fast-neutron and gamma-ray screening of hidden explosives and fissile materials with pulsed sources.

Plastic Organic Scintillator Chemistry

NASA Astrophysics Data System (ADS)

Brightwell, C. R.; Temanson, E. S.; Febbraro, M. T.

2017-09-01

Due to their high light output, quick decay time, affordability, durability and ability to be molded, plastic organic scintillators are increasingly becoming a more viable method of particle detection. Since the plastic is composed entirely of single molecular chains with repeating units, scintillating properties remain stable despite changes in experimental conditions. Different scintillating plastics can be modified and tailored to suit specific experiments depending on a variety of requirements such as light output, scintillating wavelength, and PMT compatibility. The synthesis chemistry of a recent but well-known scintillating polyester, polyethylene naphthalate (PEN) will be presented to demonstrate how plastic organic scintillators can be modified for different particle detection experiments. PEN has been successfully synthesized at ORNL, and procedures are currently being investigated to modify PEN using different reactants and catalysts. The goal is to achieve a transparent scintillating plastic with an incorporated wavelength shifter in the chain that scintillates with a wavelength around 440 nm. The status of this project will be presented. This research is supported by the U. S. Department of Energy Office of Science.

Flexible scintillator autoradiography for tumor margin inspection using 18F-FDG

NASA Astrophysics Data System (ADS)

Vyas, K. N.; Grootendorst, M.; Mertzanidou, T.; Macholl, S.; Stoyanov, D.; Arridge, S. R.; Tuch, D. S.

2018-03-01

Autoradiography potentially offers high molecular sensitivity and spatial resolution for tumor margin estimation. However, conventional autoradiography requires sectioning the sample which is destructive and labor-intensive. Here we describe a novel autoradiography technique that uses a flexible ultra-thin scintillator which conforms to the sample surface. Imaging with the flexible scintillator enables direct, high-resolution and high-sensitivity imaging of beta particle emissions from targeted radiotracers. The technique has the potential to identify positive tumor margins in fresh unsectioned samples during surgery, eliminating the processing time demands of conventional autoradiography. We demonstrate the feasibility of the flexible autoradiography approach to directly image the beta emissions from radiopharmaceuticals using lab experiments and GEANT-4 simulations to determine i) the specificity for 18F compared to 99mTc-labeled tracers ii) the sensitivity to detect signal from various depths within the tissue. We found that an image resolution of 1.5 mm was achievable with a scattering background and we estimate a minimum detectable activity concentration of 0.9 kBq/ml for 18F. We show that the flexible autoradiography approach has high potential as a technique for molecular imaging of tumor margins using 18F-FDG in a tumor xenograft mouse model imaged with a radiation-shielded EMCCD camera. Due to the advantage of conforming to the specimen, the flexible scintillator showed significantly better image quality in terms of tumor signal to whole-body background noise compared to rigid and optimally thick CaF2:Eu and BC400. The sensitivity of the technique means it is suitable for clinical translation.

First light from a kilometer-baseline Scintillation Auroral GPS Array

PubMed Central

Datta-Barua, S; Su, Y; Deshpande, K; Miladinovich, D; Bust, G S; Hampton, D; Crowley, G

2015-01-01

We introduce and analyze the first data from an array of closely spaced Global Positioning System (GPS) scintillation receivers established in the auroral zone in late 2013 to measure spatial and temporal variations in L band signals at 100–1000 m and subsecond scales. The seven receivers of the Scintillation Auroral GPS Array (SAGA) are sited at Poker Flat Research Range, Alaska. The receivers produce 100 s scintillation indices and 100 Hz carrier phase and raw in-phase and quadrature-phase samples. SAGA is the largest existing array with baseline lengths of the ionospheric diffractive Fresnel scale at L band. With an initial array of five receivers, we identify a period of simultaneous amplitude and phase scintillation. We compare SAGA power and phase data with collocated 630.0 nm all-sky images of an auroral arc and incoherent scatter radar electron precipitation measurements, to illustrate how SAGA can be used in multi-instrument observations for subkilometer-scale studies. Key Points A seven-receiver Scintillation Auroral GPS Array (SAGA) is now at Poker Flat, Alaska SAGA is the largest subkilometer array to enable phase/irregularities studies Simultaneous scintillation, auroral arc, and electron precipitation are observed PMID:26709318

Scintillator-based fast ion loss measurements in the EAST.

PubMed

Chang, J F; Isobe, M; Ogawa, K; Huang, J; Wu, C R; Xu, Z; Jin, Z; Lin, S Y; Hu, L Q

2016-11-01

A new scintillator-based fast ion loss detector (FILD) has been installed on Experimental Advanced Superconducting Tokamak (EAST) to investigate the fast ion loss behavior in high performance plasma with neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH). A two dimensional 40 mm × 40 mm scintillator-coated (ZnS:Ag) stainless plate is mounted in the front of the detector, capturing the escaping fast ions. Photons from the scintillator plate are imaged with a Phantom V2010 CCD camera. The lost fast ions can be measured with the pitch angle from 60° to 120° and the gyroradius from 10 mm to 180 mm. This paper will describe the details of FILD diagnostic on EAST and describe preliminary measurements during NBI and ICRH heating.

High Latitude Scintillations during the ICI-4 Rocket Campaign.

NASA Astrophysics Data System (ADS)

Patra, S.; Moen, J.

2015-12-01

We present the first results from the Norwegian ICI-4 sounding rocket campaign in February 2015. The ICI-4 was launched into F-region auroral blobs from the Andøya Space Center. The multi needle langmuir probe (m-NLP) on board the rocket sampled the ionospheric density structures at a sub-meter spatial resolution. A multi-phase screen model has been developed to estimate the scintillations from the density measurements acquired on-board spacecrafts. The phase screen model is validated and the comparison of the estimated values with scintillations measured by ground receivers during the campaign will be presented. A combination of scintillation receivers in Svalbard and surrounding areas as well as all sky imagers at Ny Ålesund, Longyerbyen, and Skibotn are used to improve the performance of the model.

Synthesis and Luminescence Properties of Transparent Nanocrystalline GdF3:Tb Glass-Ceramic Scintillator.

PubMed

Lee, Gyuhyon; Savage, Nicholas; Wagner, Brent; Zhang, Yuelan; Jacobs, Benjamin; Menkara, Hisham; Summers, Christopher; Kang, Zhitao

2014-03-01

Transparent glass-ceramic containing rare-earth doped halide nanocrystals exhibits enhanced luminescence performance. In this study, a glass-ceramic with Tb doped gadolinium fluoride nanocrystals embedded in an aluminosilicate glass matrix is investigated for X-ray imaging applications. The nanocrystalline glass-ceramic scintillator was prepared by a melt-quench method followed by an anneal. The GdF 3 :Tb nanocrystals precipitated within the oxide glass matrix during the processing and their luminescence and scintillation properties were investigated. In this nanocomposite scintillator system, the incorporation of high atomic number Gd compound into the glass matrix increases the X-ray stopping power of the glass scintillator, and effective energy transfer between Gd 3+ and Tb 3+ ions in the nanocrystals enhances the scintillation efficiency.

Synthesis and Luminescence Properties of Transparent Nanocrystalline GdF3:Tb Glass-Ceramic Scintillator

PubMed Central

Lee, Gyuhyon; Savage, Nicholas; Wagner, Brent; Zhang, Yuelan; Jacobs, Benjamin; Menkara, Hisham; Summers, Christopher; Kang, Zhitao

2014-01-01

Transparent glass-ceramic containing rare-earth doped halide nanocrystals exhibits enhanced luminescence performance. In this study, a glass-ceramic with Tb doped gadolinium fluoride nanocrystals embedded in an aluminosilicate glass matrix is investigated for X-ray imaging applications. The nanocrystalline glass-ceramic scintillator was prepared by a melt-quench method followed by an anneal. The GdF3:Tb nanocrystals precipitated within the oxide glass matrix during the processing and their luminescence and scintillation properties were investigated. In this nanocomposite scintillator system, the incorporation of high atomic number Gd compound into the glass matrix increases the X-ray stopping power of the glass scintillator, and effective energy transfer between Gd3+ and Tb3+ ions in the nanocrystals enhances the scintillation efficiency. PMID:24610960

Synthesis of plastic scintillation microspheres: Evaluation of scintillators

NASA Astrophysics Data System (ADS)

Santiago, L. M.; Bagán, H.; Tarancón, A.; Garcia, J. F.

2013-01-01

The use of plastic scintillation microspheres (PSm) appear to be an alternative to liquid scintillation for the quantification of alpha and beta emitters because it does not generate mixed wastes after the measurement (organic and radioactive). In addition to routine radionuclide determinations, PSm can be used for further applications, e.g. for usage in a continuous monitoring equipment, for measurements of samples with a high salt concentration and for an extractive scintillation support which permits the separation, pre-concentration and measurement of the radionuclides without additional steps of elution and sample preparation. However, only a few manufacturers provide PSm, and the low number of regular suppliers reduces its availability and restricts the compositions and sizes available. In this article, a synthesis method based on the extraction/evaporation methodology has been developed and successfully used for the synthesis of plastic scintillation microspheres. Seven different compositions of plastic scintillation microspheres have been synthesised; PSm1 with polystyrene, PSm2 with 2,5-Diphenyloxazol(PPO), PSm3 with p-terphenyl (pT), PSm4 with PPO and 1,4-bis(5-phenyloxazol-2-yl) (POPOP), PSm5 pT and (1,4-bis [2-methylstyryl] benzene) (Bis-MSB), PSm6 with PPO, POPOP and naphthalene and PSm7 with pT, Bis-MSB and naphthalene. The synthesised plastic scintillation microspheres have been characterised in terms of their morphology, detection capabilities and alpha/beta separation capacity. The microspheres had a median diameter of approximately 130 μm. Maximum detection efficiency values were obtained for the PSm4 composition as follows 1.18% for 3H, 51.2% for 14C, 180.6% for 90Sr/90Y and 76.7% for 241Am. Values of the SQP(E) parameter were approximately 790 for PSm4 and PSm5. These values show that the synthesised PSm exhibit good scintillation properties and that the spectra are at channel numbers higher than in commercial PSm. Finally, the addition of

Impact of Ionospheric Scintillation on Spaceborne SAR Observations Studied Using GNSS

NASA Technical Reports Server (NTRS)

Pi, Xiaoqing; Meyer, Franz J.; Chotoo, Kancham; Freeman, Anthony; Caton, Ronald G.; Bridgewood, Christopher T.

2012-01-01

A survey of artifacts seen in JAXA's Phase Array type L-band synthetic aperture radar (PALSAR) data over South America during a low solar activity year is reported in this paper. A significant impact on the radar data is revealed: about 14% of the surveyed PALSAR images (totally 2779) are affected by the artifacts during a month and the artifacts occur on 74.2% of the surveyed days. The characteristics of the artifacts have led to a consideration that the artifacts are the effects of ionospheric scintillation. This raises not only a concern about scintillation effects on radar but also a question about active scintillation conditions during a low solar activity year. To assess and verify the scintillation conditions, GPS data collected from the constellation of FORMOSAT-3/COSMIC satellites and three ground-based GPS networks are processed and analyzed. The GPS data provides a global context and regional dense converge, respectively, of ionospheric irregularity and scintillation measurements. It is concluded tat even during a low solar activity year, L-band scintillation at low latitudes can occur frequently and affect L-band SAR significantly.

Modelling the transport of optical photons in scintillation detectors for diagnostic and radiotherapy imaging

NASA Astrophysics Data System (ADS)

Roncali, Emilie; Mosleh-Shirazi, Mohammad Amin; Badano, Aldo

2017-10-01

Computational modelling of radiation transport can enhance the understanding of the relative importance of individual processes involved in imaging systems. Modelling is a powerful tool for improving detector designs in ways that are impractical or impossible to achieve through experimental measurements. Modelling of light transport in scintillation detectors used in radiology and radiotherapy imaging that rely on the detection of visible light plays an increasingly important role in detector design. Historically, researchers have invested heavily in modelling the transport of ionizing radiation while light transport is often ignored or coarsely modelled. Due to the complexity of existing light transport simulation tools and the breadth of custom codes developed by users, light transport studies are seldom fully exploited and have not reached their full potential. This topical review aims at providing an overview of the methods employed in freely available and other described optical Monte Carlo packages and analytical models and discussing their respective advantages and limitations. In particular, applications of optical transport modelling in nuclear medicine, diagnostic and radiotherapy imaging are described. A discussion on the evolution of these modelling tools into future developments and applications is presented. The authors declare equal leadership and contribution regarding this review.

Performance of europium-doped strontium iodide, transparent ceramics and bismuth-loaded polymer scintillators

NASA Astrophysics Data System (ADS)

Cherepy, N. J.; Payne, S. A.; Sturm, B. W.; O'Neal, S. P.; Seeley, Z. M.; Drury, O. B.; Haselhorst, L. K.; Rupert, B. L.; Sanner, R. D.; Thelin, P. A.; Fisher, S. E.; Hawrami, R.; Shah, K. S.; Burger, A.; Ramey, J. O.; Boatner, L. A.

2011-09-01

Recently discovered scintillators for gamma ray spectroscopy - single-crystal SrI2(Eu), GYGAG(Ce) transparent ceramic and Bismuth-loaded plastics - offer resolution and fabrication advantages compared to commercial scintillators, such as NaI(Tl) and standard PVT plastic. Energy resolution at 662 keV of 2.7% is obtained with SrI2(Eu), while 4.5% is obtained with GYGAG(Ce). A new transparent ceramic scintillator for radiographic imaging systems, GLO(Eu), offers high light yield of 70,000 Photons/MeV, high stopping, and low radiation damage. Implementation of single-crystal SrI2(Eu), Gd-based transparent ceramics, and Bi-loaded plastic scintillators can advance the state-of-the art in ionizing radiation detection systems.

Study of a prototype high quantum efficiency thick scintillation crystal video-electronic portal imaging device.

PubMed

Samant, Sanjiv S; Gopal, Arun

2006-08-01

Image quality in portal imaging suffers significantly from the loss in contrast and spatial resolution that results from the excessive Compton scatter associated with megavoltage x rays. In addition, portal image quality is further reduced due to the poor quantum efficiency (QE) of current electronic portal imaging devices (EPIDs). Commercial video-camera-based EPIDs or VEPIDs that utilize a thin phosphor screen in conjunction with a metal buildup plate to convert the incident x rays to light suffer from reduced light production due to low QE (<2% for Eastman Kodak Lanex Fast-B). Flat-panel EPIDs that utilize the same luminescent screen along with an a-Si:H photodiode array provide improved image quality compared to VEPIDs, but they are expensive and can be susceptible to radiation damage to the peripheral electronics. In this article, we present a prototype VEPID system for high quality portal imaging at sub-monitor-unit (subMU) exposures based on a thick scintillation crystal (TSC) that acts as a high QE luminescent screen. The prototype TSC system utilizes a 12 mm thick transparent CsI(Tl) (thallium-activated cesium iodide) scintillator for QE=0.24, resulting in significantly higher light production compared to commercial phosphor screens. The 25 X 25 cm2 CsI(Tl) screen is coupled to a high spatial and contrast resolution Video-Optics plumbicon-tube camera system (1240 X 1024 pixels, 250 microm pixel width at isocenter, 12-bit ADC). As a proof-of-principle prototype, the TSC system with user-controlled camera target integration was adapted for use in an existing clinical gantry (Siemens BEAMVIEW(PLUS)) with the capability for online intratreatment fluoroscopy. Measurements of modulation transfer function (MTF) were conducted to characterize the TSC spatial resolution. The measured MTF along with measurements of the TSC noise power spectrum (NPS) were used to determine the system detective quantum efficiency (DQE). A theoretical expression of DQE(0) was developed

Indirect flat-panel detector with avalanche gain: Fundamental feasibility investigation for SHARP-AMFPI (scintillator HARP active matrix flat panel imager)

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

Zhao Wei; Li Dan; Reznik, Alla

2005-09-15

An indirect flat-panel imager (FPI) with avalanche gain is being investigated for low-dose x-ray imaging. It is made by optically coupling a structured x-ray scintillator CsI(Tl) to an amorphous selenium (a-Se) avalanche photoconductor called HARP (high-gain avalanche rushing photoconductor). The final electronic image is read out using an active matrix array of thin film transistors (TFT). We call the proposed detector SHARP-AMFPI (scintillator HARP active matrix flat panel imager). The advantage of the SHARP-AMFPI is its programmable gain, which can be turned on during low dose fluoroscopy to overcome electronic noise, and turned off during high dose radiography to avoidmore » pixel saturation. The purpose of this paper is to investigate the important design considerations for SHARP-AMFPI such as avalanche gain, which depends on both the thickness d{sub Se} and the applied electric field E{sub Se} of the HARP layer. To determine the optimal design parameter and operational conditions for HARP, we measured the E{sub Se} dependence of both avalanche gain and optical quantum efficiency of an 8 {mu}m HARP layer. The results were used in a physical model of HARP as well as a linear cascaded model of the FPI to determine the following x-ray imaging properties in both the avalanche and nonavalanche modes as a function of E{sub Se}: (1) total gain (which is the product of avalanche gain and optical quantum efficiency); (2) linearity; (3) dynamic range; (4) gain nonuniformity resulting from thickness nonuniformity; and (5) effects of direct x-ray interaction in HARP. Our results showed that a HARP layer thickness of 8 {mu}m can provide adequate avalanche gain and sufficient dynamic range for x-ray imaging applications to permit quantum limited operation over the range of exposures needed for radiography and fluoroscopy.« less

SU-D-BRC-07: System Design for a 3D Volumetric Scintillation Detector Using SCMOS Cameras

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

Darne, C; Robertson, D; Alsanea, F

2016-06-15

Purpose: The purpose of this project is to build a volumetric scintillation detector for quantitative imaging of 3D dose distributions of proton beams accurately in near real-time. Methods: The liquid scintillator (LS) detector consists of a transparent acrylic tank (20×20×20 cm{sup 3}) filled with a liquid scintillator that when irradiated with protons generates scintillation light. To track rapid spatial and dose variations in spot scanning proton beams we used three scientific-complementary metal-oxide semiconductor (sCMOS) imagers (2560×2160 pixels). The cameras collect optical signal from three orthogonal projections. To reduce system footprint two mirrors oriented at 45° to the tank surfaces redirectmore » scintillation light to cameras for capturing top and right views. Selection of fixed focal length objective lenses for these cameras was based on their ability to provide large depth of field (DoF) and required field of view (FoV). Multiple cross-hairs imprinted on the tank surfaces allow for image corrections arising from camera perspective and refraction. Results: We determined that by setting sCMOS to 16-bit dynamic range, truncating its FoV (1100×1100 pixels) to image the entire volume of the LS detector, and using 5.6 msec integration time imaging rate can be ramped up to 88 frames per second (fps). 20 mm focal length lens provides a 20 cm imaging DoF and 0.24 mm/pixel resolution. Master-slave camera configuration enable the slaves to initiate image acquisition instantly (within 2 µsec) after receiving a trigger signal. A computer with 128 GB RAM was used for spooling images from the cameras and can sustain a maximum recording time of 2 min per camera at 75 fps. Conclusion: The three sCMOS cameras are capable of high speed imaging. They can therefore be used for quick, high-resolution, and precise mapping of dose distributions from scanned spot proton beams in three dimensions.« less

Functional Imaging of the Lungs with Gas Agents

PubMed Central

Kruger, Stanley J.; Nagle, Scott K.; Couch, Marcus J.; Ohno, Yoshiharu; Albert, Mitchell; Fain, Sean B.

2015-01-01

This review focuses on the state-of-the-art of the three major classes of gas contrast agents used in magnetic resonance imaging (MRI) – hyperpolarized (HP) gas, molecular oxygen, and fluorinated gas – and their application to clinical pulmonary research. During the past several years there has been accelerated development of pulmonary MRI. This has been driven in part by concerns regarding ionizing radiation using multi-detector computed tomography (CT). However, MRI also offers capabilities for fast multi-spectral and functional imaging using gas agents that are not technically feasible with CT. Recent improvements in gradient performance and radial acquisition methods using ultra-short echo time (UTE) have contributed to advances in these functional pulmonary MRI techniques. Relative strengths and weaknesses of the main functional imaging methods and gas agents are compared and applications to measures of ventilation, diffusion, and gas exchange are presented. Functional lung MRI methods using these gas agents are improving our understanding of a wide range of chronic lung diseases, including chronic obstructive pulmonary disease (COPD), asthma, and cystic fibrosis (CF) in both adults and children. PMID:26218920

Transparent garnet ceramic scintillators for gamma-ray detection

NASA Astrophysics Data System (ADS)

Wang, Yimin; Baldoni, Gary; Rhodes, William H.; Brecher, Charles; Shah, Ananya; Shirwadkar, Urmila; Glodo, Jarek; Cherepy, Nerine; Payne, Stephen

2012-10-01

Lanthanide gallium/aluminum-based garnets have a great potential as host structures for scintillation materials for medical imaging. Particularly attractive features are their high density, chemical radiation stability and more importantly, their cubic structure and isotropic optical properties, which allow them to be fabricated into fully transparent, highperformance polycrystalline optical ceramics. Lutetium/gadolinium aluminum/gallium garnets (described by formulas ((Gd,Lu)3(Al,Ga)5O12:Ce, Gd3(Al,Ga)5O12:Ce and Lu3Al5O12:Pr)) feature high effective atomic number and good scintillation properties, which make them particularly attractive for Positron Emission Tomography (PET) and other γ- ray detection applications. The ceramic processing route offers an attractive alternative to single crystal growth for obtaining scintillator materials at relatively low temperatures and at a reasonable cost, with flexibility in dimension control as well as activator concentration adjustment. In this study, optically transparent polycrystalline ceramics mentioned above were prepared by the sintering-HIP approach, employing nano-sized starting powders. The properties and microstructures of the ceramics were controlled by varying the processing parameters during consolidation. Single-phase, high-density, transparent specimens were obtained after sintering followed by a pressure-assisted densification process, i.e. hot-isostatic-pressing. The transparent ceramics displayed high contact and distance transparency as well as high light yield as high as 60,000-65,000 ph/MeV under gamma-ray excitation, which is about 2 times that of a LSO:Ce single crystal. The excellent scintillation and optical properties make these materials promising candidates for medical imaging and γ-ray detection applications.

Scintillator reflective layer coextrusion

DOEpatents

Yun, Jae-Chul; Para, Adam

2001-01-01

A polymeric scintillator has a reflective layer adhered to the exterior surface thereof. The reflective layer comprises a reflective pigment and an adhesive binder. The adhesive binder includes polymeric material from which the scintillator is formed. A method of forming the polymeric scintillator having a reflective layer adhered to the exterior surface thereof is also provided. The method includes the steps of (a) extruding an inner core member from a first amount of polymeric scintillator material, and (b) coextruding an outer reflective layer on the exterior surface of the inner core member. The outer reflective layer comprises a reflective pigment and a second amount of the polymeric scintillator material.

Transparent ceramic scintillators for gamma spectroscopy and radiography

NASA Astrophysics Data System (ADS)

Cherepy, N. J.; Kuntz, J. D.; Seeley, Z. M.; Fisher, S. E.; Drury, O. B.; Sturm, B. W.; Hurst, T. A.; Sanner, R. D.; Roberts, J. J.; Payne, S. A.

2010-08-01

Transparent ceramics combine the scintillation performance of single crystals with the ruggedness and processability of glass. We have developed a versatile, scaleable fabrication method, wherein nanoparticle feedstock is consolidated at temperatures well below melting to form inch-scale phase-pure transparent ceramics with optical scatter of α <0.1 cm-1. We have fabricated Cerium-doped Gadolinium Garnets with light yields of ~50,000 Ph/MeV and energy resolution of <5% at 662 keV. We have also developed methods to form sheets of the high-Z ceramic scintillator, Europium-doped Lutetium Oxide Bixbyite, producing ~75,000 Ph/MeV for radiographic imaging applications.

Molecular origins of scintillation in organic scintillators (Conference Presentation)

NASA Astrophysics Data System (ADS)

Feng, Patrick; Mengesha, Wondwosen; Myllenbeck, Nicholas

2016-09-01

Organic-based scintillators are indispensable materials for radiation detection owing to their high sensitivity to fast neutrons, low cost, and tailorable properties. There has been a recent resurgence of interest in organic scintillators due to exciting discoveries related to neutron discrimination and gamma-ray spectroscopy, which represent capabilities previously thought not possible in these materials. I will discuss our development of crystalline and polymer-based scintillators for these applications. Structure-property relationships related to intermolecular interactions and host-guest electronic exchange will be discussed in the context of energy-transfer pathways relevant to scintillation. An emphasis will be placed on the rational design of these materials, as guided by first principles and DFT calculations. Two related topics will be discussed: 1) Incorporation of organometallic triplet-harvesting additives to plastic scintillator matrices to confer a 'two-state' (singlet and triplet) luminescence signature to different types of ionizing radiation. This approach relies upon energetic and spatial overlap between the donor and acceptor excited states for efficient electronic exchange. Key considerations also include synthetic modification of the luminescence spectra and kinetics, as well as the addition of secondary additives to increase the recombination efficiency. 2) Design of organotin-containing plastic scintillators as a route towards gamma-ray spectroscopy. Organometallic compounds were selected on the basis of distance-dependent quenching relationships, phase compatibility with the polymer matrix, and the gamma-ray cross sections. This approach is guided by molecular modeling and radiation transport modeling to achieve the highest possible detection sensitivity luminescence intensity.

Chloride, bromide and iodide scintillators with europium doping

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

Zhuravleva, Mariya; Yang, Kan

A halide scintillator material is disclosed where the halide may comprise chloride, bromide or iodide. The material is single-crystalline and has a composition of the general formula ABX.sub.3 where A is an alkali, B is an alkali earth and X is a halide which general composition was investigated. In particular, crystals of the formula ACa.sub.1-yEu.sub.yI.sub.3 where A=K, Rb and Cs were formed as well as crystals of the formula CsA.sub.1-yEu.sub.yX.sub.3 (where A=Ca, Sr, Ba, or a combination thereof and X=Cl, Br or I or a combination thereof) with divalent Europium doping where 0.ltoreq.y.ltoreq.1, and more particularly Eu doping has beenmore » studied at one to ten mol %. The disclosed scintillator materials are suitable for making scintillation detectors used in applications such as medical imaging and homeland security.« less

First-principles Electronic Structure Calculations for Scintillation Phosphor Nuclear Detector Materials

NASA Astrophysics Data System (ADS)

Canning, Andrew

2013-03-01

Inorganic scintillation phosphors (scintillators) are extensively employed as radiation detector materials in many fields of applied and fundamental research such as medical imaging, high energy physics, astrophysics, oil exploration and nuclear materials detection for homeland security and other applications. The ideal scintillator for gamma ray detection must have exceptional performance in terms of stopping power, luminosity, proportionality, speed, and cost. Recently, trivalent lanthanide dopants such as Ce and Eu have received greater attention for fast and bright scintillators as the optical 5d to 4f transition is relatively fast. However, crystal growth and production costs remain challenging for these new materials so there is still a need for new higher performing scintillators that meet the needs of the different application areas. First principles calculations can provide a useful insight into the chemical and electronic properties of such materials and hence can aid in the search for better new scintillators. In the past there has been little first-principles work done on scintillator materials in part because it means modeling f electrons in lanthanides as well as complex excited state and scattering processes. In this talk I will give an overview of the scintillation process and show how first-principles calculations can be applied to such systems to gain a better understanding of the physics involved. I will also present work on a high-throughput first principles approach to select new scintillator materials for fabrication as well as present more detailed calculations to study trapping process etc. that can limit their brightness. This work in collaboration with experimental groups has lead to the discovery of some new bright scintillators. Work supported by the U.S. Department of Homeland Security and carried out under U.S. Department of Energy Contract no. DE-AC02-05CH11231 at Lawrence Berkeley National Laboratory.

Performance of Europium-Doped Strontium Iodide, Transparent Ceramics and Bismuth-loaded Polymer Scintillators

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

Cherepy, N J; Payne, S A; Sturm, B W

2011-08-30

Recently discovered scintillators for gamma ray spectroscopy, single crystal SrI{sub 2}(Eu), GYGAG(Ce) transparent ceramic and Bismuth-loaded plastics, offer resolution and fabrication advantages compared to commercial scintillators, such as NaI(Tl) and standard PVT plastic. Energy resolution at 662 keV of 2.7% is obtained with SrI{sub 2}(Eu), while 4.5% is obtained with GYGAG(Ce). A new transparent ceramic scintillator for radiographic imaging systems, GLO(Eu) offers high light yield of 70,000 Photons/MeV, high stopping, and low radiation damage. Implementation of single crystal SrI{sub 2}(Eu), Gd-based transparent ceramics, and Bi-loaded plastic scintillators can advance the state-of-the art in ionizing radiation detection systems.

Optimization of the design of thick, segmented scintillators for megavoltage cone-beam CT using a novel, hybrid modeling technique

PubMed Central

Liu, Langechuan; Antonuk, Larry E.; El-Mohri, Youcef; Zhao, Qihua; Jiang, Hao

2014-01-01

Purpose: Active matrix flat-panel imagers (AMFPIs) incorporating thick, segmented scintillators have demonstrated order-of-magnitude improvements in detective quantum efficiency (DQE) at radiotherapy energies compared to systems based on conventional phosphor screens. Such improved DQE values facilitate megavoltage cone-beam CT (MV CBCT) imaging at clinically practical doses. However, the MV CBCT performance of such AMFPIs is highly dependent on the design parameters of the scintillators. In this paper, optimization of the design of segmented scintillators was explored using a hybrid modeling technique which encompasses both radiation and optical effects. Methods: Imaging performance in terms of the contrast-to-noise ratio (CNR) and spatial resolution of various hypothetical scintillator designs was examined through a hybrid technique involving Monte Carlo simulation of radiation transport in combination with simulation of optical gain distributions and optical point spread functions. The optical simulations employed optical parameters extracted from a best fit to measurement results reported in a previous investigation of a 1.13 cm thick, 1016 μm pitch prototype BGO segmented scintillator. All hypothetical designs employed BGO material with a thickness and element-to-element pitch ranging from 0.5 to 6 cm and from 0.508 to 1.524 mm, respectively. In the CNR study, for each design, full tomographic scans of a contrast phantom incorporating various soft-tissue inserts were simulated at a total dose of 4 cGy. Results: Theoretical values for contrast, noise, and CNR were found to be in close agreement with empirical results from the BGO prototype, strongly supporting the validity of the modeling technique. CNR and spatial resolution for the various scintillator designs demonstrate complex behavior as scintillator thickness and element pitch are varied—with a clear trade-off between these two imaging metrics up to a thickness of ∼3 cm. Based on these results, an

Characterizing Scintillation and Cherenkov Light in Water-Based Liquid Scintillators

NASA Astrophysics Data System (ADS)

Land, Benjamin; Caravaca, Javier; Descamps, Freija; Orebi Gann, Gabriel

2016-09-01

The recent development of Water-based Liquid Scintillator (WbLS) has made it possible to produce scintillating materials with highly tunable light yields and excellent optical clarity. This allows for a straightforward combination of the directional properties of Cherenkov light with the greater energy resolution afforded by the typically brighter scintillation light which lends itself well to a broad program of neutrino physics. Here we explore the light yields and time profiles of WbLS materials in development for Theia (formerly ASDC) as measured in CheSS: our bench-top Cherenkov and scintillation separation R&D project at Berkeley Lab. This work was supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under U.S. Department of Energy Contract No. DE-AC02-05CH11231.

Development of a Scintillation Detector and the Influence on Clinical Imaging

NASA Astrophysics Data System (ADS)

Panetta, Joseph Vincent

measurement uncertainty. This study shows that the improvements in CRC resulting from improved spatial resolution, measured using phantom studies in the simulations, are representative of improvements in quantitative accuracy in patient studies. While unmodified thick continuous detectors hold promise for both improved image quality and quantitation in whole-body imaging, excellent performance requires intensive hardware and computational solutions. Laser induced optical barriers offer the ability to modify the light spread within the scintillator to improve the intrinsic performance of the detector: while measurements with crystals etched with relatively transmissive etchings show a slight improvement in resolution, simulations show that the LIOBs may be fine-tuned to result in improved performance using relatively simple positioning algorithms. For systems in which DOI information is less important, and transverse resolution and sensitivity are paramount, etching thick detectors with this design, fine-tuned to the particular thickness of the crystal and application, is an interesting alternative to the standard detector design. (Abstract shortened by ProQuest.).

Shifting scintillator neutron detector

DOEpatents

Clonts, Lloyd G; Cooper, Ronald G; Crow, Jr., Morris Lowell; Hannah, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A

2014-03-04

Provided are sensors and methods for detecting thermal neutrons. Provided is an apparatus having a scintillator for absorbing a neutron, the scintillator having a back side for discharging a scintillation light of a first wavelength in response to the absorbed neutron, an array of wavelength-shifting fibers proximate to the back side of the scintillator for shifting the scintillation light of the first wavelength to light of a second wavelength, the wavelength-shifting fibers being disposed in a two-dimensional pattern and defining a plurality of scattering plane pixels where the wavelength-shifting fibers overlap, a plurality of photomultiplier tubes, in coded optical communication with the wavelength-shifting fibers, for converting the light of the second wavelength to an electronic signal, and a processor for processing the electronic signal to identify one of the plurality of scattering plane pixels as indicative of a position within the scintillator where the neutron was absorbed.

ANTS — a simulation package for secondary scintillation Anger-camera type detector in thermal neutron imaging

NASA Astrophysics Data System (ADS)

Morozov, A.; Defendi, I.; Engels, R.; Fraga, F. A. F.; Fraga, M. M. F. R.; Guerard, B.; Jurkovic, M.; Kemmerling, G.; Manzin, G.; Margato, L. M. S.; Niko, H.; Pereira, L.; Petrillo, C.; Peyaud, A.; Piscitelli, F.; Raspino, D.; Rhodes, N. J.; Sacchetti, F.; Schooneveld, E. M.; Van Esch, P.; Zeitelhack, K.

2012-08-01

A custom and fully interactive simulation package ANTS (Anger-camera type Neutron detector: Toolkit for Simulations) has been developed to optimize the design and operation conditions of secondary scintillation Anger-camera type gaseous detectors for thermal neutron imaging. The simulation code accounts for all physical processes related to the neutron capture, energy deposition pattern, drift of electrons of the primary ionization and secondary scintillation. The photons are traced considering the wavelength-resolved refraction and transmission of the output window. Photo-detection accounts for the wavelength-resolved quantum efficiency, angular response, area sensitivity, gain and single-photoelectron spectra of the photomultipliers (PMTs). The package allows for several geometrical shapes of the PMT photocathode (round, hexagonal and square) and offers a flexible PMT array configuration: up to 100 PMTs in a custom arrangement with the square or hexagonal packing. Several read-out patterns of the PMT array are implemented. Reconstruction of the neutron capture position (projection on the plane of the light emission) is performed using the center of gravity, maximum likelihood or weighted least squares algorithm. Simulation results reproduce well the preliminary results obtained with a small-scale detector prototype. ANTS executables can be downloaded from http://coimbra.lip.pt/~andrei/.

A New Columnar CsI(Tl) Scintillator for iQID detectors

PubMed Central

Han, Ling; Miller, Brian W.; Barber, H. Bradford; Nagarkar, Vivek V.; Furenlid, Lars R.

2015-01-01

A 1650 μm thick columnar CsI(Tl) scintillator for upgrading iQID detectors, which is a high-resolution photon-counting gamma-ray and x-ray detector recently developed at the Center for Gamma-Ray Imaging (CGRI), has been studied in terms of sensitivity, spatial resolution and depth-of-interaction effects. To facilitate these studies, a new frame-parsing algorithm for processing raw event data is also proposed that has more degrees of freedom in data processing and can discriminate against a special kind of noise present in some low-cost intensifiers. The results show that in comparison with a 450 μm-thickness columnar CsI(Tl) scintillator, the 1650 μm thick CsI(Tl) scintillator provides more than twice the sensitivity at the expense of some spatial resolution degradation. The depth-of-interaction study also shows that event size and amplitude vary with scintillator thickness, which can assist in future detector simulations and 3D-interaction-position estimation. PMID:26146444

A New Columnar CsI(Tl) Scintillator for iQID detectors.

PubMed

Han, Ling; Miller, Brian W; Barber, H Bradford; Nagarkar, Vivek V; Furenlid, Lars R

2014-09-12

A 1650 μm thick columnar CsI(Tl) scintillator for upgrading iQID detectors, which is a high-resolution photon-counting gamma-ray and x-ray detector recently developed at the Center for Gamma-Ray Imaging (CGRI), has been studied in terms of sensitivity, spatial resolution and depth-of-interaction effects. To facilitate these studies, a new frame-parsing algorithm for processing raw event data is also proposed that has more degrees of freedom in data processing and can discriminate against a special kind of noise present in some low-cost intensifiers. The results show that in comparison with a 450 μm-thickness columnar CsI(Tl) scintillator, the 1650 μm thick CsI(Tl) scintillator provides more than twice the sensitivity at the expense of some spatial resolution degradation. The depth-of-interaction study also shows that event size and amplitude vary with scintillator thickness, which can assist in future detector simulations and 3D-interaction-position estimation.

Equatorial scintillation and systems support

NASA Astrophysics Data System (ADS)

Groves, K. M.; Basu, S.; Weber, E. J.; Smitham, M.; Kuenzler, H.; Valladares, C. E.; Sheehan, R.; MacKenzie, E.; Secan, J. A.; Ning, P.; McNeill, W. J.; Moonan, D. W.; Kendra, M. J.

1997-09-01

The need to nowcast and forecast scintillation for the support of operational systems has been recently identified by the interagency National Space Weather Program. This issue is addressed in the present paper in the context of nighttime irregularities in the equatorial ionosphere that cause intense amplitude and phase scintillations of satellite signals in the VHF/UHF range of frequencies and impact satellite communication, Global Positioning System navigation, and radar systems. Multistation and multifrequency satellite scintillation observations have been used to show that even though equatorial scintillations vary in accordance with the solar cycle, the extreme day-to-day variability of unknown origin modulates the scintillation occurrence during all phases of the solar cycle. It is shown that although equatorial scintillation events often show correlation with magnetic activity, the major component of scintillation is observed during magnetically quiet periods. In view of the day-to-day variability of the occurrence and intensity of scintillating regions, their latitude extent, and their zonal motion, a regional specification and short-term forecast system based on real-time measurements has been developed. This system, named the Scintillation Network Decision Aid, consists of two latitudinally dispersed stations, each of which uses spaced antenna scintillation receiving systems to monitor 250-MHz transmissions from two longitudinally separated geostationary satellites. The scintillation index and zonal irregularity drift are processed on-line and are retrieved by a remote operator on the Internet. At the operator terminal the data are combined with an empirical plasma bubble model to generate three-dimensional maps of irregularity structures and two-dimensional outage maps for the region.

Validating the use of scintillation proxies to study ionospheric scintillation over the Ugandan region

NASA Astrophysics Data System (ADS)

Amabayo, Emirant B.; Jurua, Edward; Cilliers, Pierre J.

2015-06-01

In this study, we compare the standard scintillation indices (S4 and σΦ) from a SCINDA receiver with scintillation proxies (S4p and | sDPR |) derived from two IGS GPS receivers. Amplitude (S4) and phase (σΦ) scintillation data were obtained from the SCINDA installed at Makerere University (0.34°N, 32.57°E). The corresponding amplitude (S4p) and phase (| sDPR |) scintillation proxies were derived from data archived by IGS GPS receivers installed at Entebbe (0.04°N, 32.44°E) and Mbarara (0.60°S, 30.74°E). The results show that for most of the cases analysed in this study, σΦ and | sDPR | are in agreement. Amplitude scintillation occurrence estimated using the S4p are fairly consistent with the standard S4, mainly between 17:00 UT and 21:00 UT, despite a few cases of over and under estimation of scintillation levels by S4p. Correlation coefficients between σΦ and the | sDPR | proxy revealed positive correlation. Generally, S4p and S4 exhibits both moderate and strong positive correlation. TEC depletions associated with equatorial plasma bubbles are proposed as the cause of the observed scintillation over the region. These equatorial plasma bubbles were evident along the ray paths to satellites with PRN 2, 15, 27 and 11 as observed from MBAR and EBBE. In addition to equatorial plasma bubbles, atmospheric gravity waves with periods similar to those of large scale traveling ionospheric disturbances were also observed as one of the mechanisms for scintillation occurrence. The outcome of this study implies that GPS derived scintillation proxies can be used to quantify scintillation levels in the absence of standard scintillation data in the equatorial regions.

A high-speed scintillation-based electronic portal imaging device to quantitatively characterize IMRT delivery.

PubMed

Ranade, Manisha K; Lynch, Bart D; Li, Jonathan G; Dempsey, James F

2006-01-01

We have developed an electronic portal imaging device (EPID) employing a fast scintillator and a high-speed camera. The device is designed to accurately and independently characterize the fluence delivered by a linear accelerator during intensity modulated radiation therapy (IMRT) with either step-and-shoot or dynamic multileaf collimator (MLC) delivery. Our aim is to accurately obtain the beam shape and fluence of all segments delivered during IMRT, in order to study the nature of discrepancies between the plan and the delivered doses. A commercial high-speed camera was combined with a terbium-doped gadolinium-oxy-sulfide (Gd2O2S:Tb) scintillator to form an EPID for the unaliased capture of two-dimensional fluence distributions of each beam in an IMRT delivery. The high speed EPID was synchronized to the accelerator pulse-forming network and gated to capture every possible pulse emitted from the accelerator, with an approximate frame rate of 360 frames-per-second (fps). A 62-segment beam from a head-and-neck IMRT treatment plan requiring 68 s to deliver was recorded with our high speed EPID producing approximately 6 Gbytes of imaging data. The EPID data were compared with the MLC instruction files and the MLC controller log files. The frames were binned to provide a frame rate of 72 fps with a signal-to-noise ratio that was sufficient to resolve leaf positions and segment fluence. The fractional fluence from the log files and EPID data agreed well. An ambiguity in the motion of the MLC during beam on was resolved. The log files reported leaf motions at the end of 33 of the 42 segments, while the EPID observed leaf motions in only 7 of the 42 segments. The static IMRT segment shapes observed by the high speed EPID were in good agreement with the shapes reported in the log files. The leaf motions observed during beam-on for step-and-shoot delivery were not temporally resolved by the log files.

Taheri-Saramad x-ray detector (TSXD): a novel high spatial resolution x-ray imager based on ZnO nano scintillator wires in polycarbonate membrane.

PubMed

Taheri, A; Saramad, S; Ghalenoei, S; Setayeshi, S

2014-01-01

A novel x-ray imager based on ZnO nanowires is designed and fabricated. The proposed architecture is based on scintillation properties of ZnO nanostructures in a polycarbonate track-etched membrane. Because of higher refractive index of ZnO nanowire compared to the membrane, the nanowire acts as an optical fiber that prevents the generated optical photons to spread inside the detector. This effect improves the spatial resolution of the imager. The detection quantum efficiency and spatial resolution of the fabricated imager are 11% and <6.8 μm, respectively.

Toward Scintillator High-Gain Avalanche Rushing Photoconductor Active Matrix Flat Panel Imager (SHARP-AMFPI): Initial fabrication and characterization.

PubMed

Scheuermann, James R; Howansky, Adrian; Hansroul, Marc; Léveillé, Sébastien; Tanioka, Kenkichi; Zhao, Wei

2018-02-01

We present the first prototype Scintillator High-Gain Avalanche Rushing Photoconductor Active Matrix Flat Panel Imager (SHARP-AMFPI). This detector includes a layer of avalanche amorphous Selenium (a-Se) (HARP) as the photoconductor in an indirect detector to amplify the signal and reduce the effects of electronic noise to obtain quantum noise-limited images for low-dose applications. It is the first time avalanche a-Se has been used in a solid-state imaging device and poses as a possible solution to eliminate the effects of electronic noise, which is crucial for low-dose imaging performance of AMFPI. We successfully deposited a solid-state HARP structure onto a 24 × 30 cm 2 array of thin-film transistors (TFT array) with a pixel pitch of 85 μm. The HARP layer consists of 16 μm of a-Se with a hole-blocking and electron-blocking layer to prevent charge injection from the high-voltage bias and pixel electrodes, respectively. An electric field (E S e ) up to 105 V μm -1 was applied across the a-Se layer without breakdown. A 150 μm thick-structured CsI:Tl scintillator was used to form SHARP-AMFPI. The x-ray imaging performance is characterized using a 30 kVp Mo/Mo beam. We evaluate the spatial resolution, noise power, and detective quantum efficiency at zero frequency of the system with and without avalanche gain. The results are analyzed using cascaded linear system model (CLSM). An avalanche gain of 76 ± 5 was measured at E S e = 105 V μm -1 . We demonstrate that avalanche gain can amplify the signal to overcome electronic noise. As avalanche gain is increased, image quality improves for a constant (0.76 mR) exposure until electronic noise is overcome. Our system is currently limited by poor optical transparency of our high-voltage electrode and long integrating time which results in dark current noise. These two effects cause high-spatial frequency noise to dominate imaging performance. We demonstrate the feasibility of a solid-state HARP x-ray imager and

Scintillator Design Via Codoping

NASA Astrophysics Data System (ADS)

Melcher, C. L.; Koschan, M.; Zhuravleva, M.; Wu, Y.; Rothfuss, H.; Meng, F.; Tyagi, M.; Donnald, S.; Yang, K.; Hayward, J. P.; Eriksson, L.

Scintillation materials that lack intrinsic luminescence centers must be doped with optically active ions in order to provide luminescent centers that radiatively de-excite as the final step of the scintillation process. Codoping, on the other hand, can be defined as the incorporation of additional specific impurity species usually for the purpose of modifying the scintillation properties, mechanical properties, or the crystal growth behavior. In recent years codoping has become an increasingly popular approach for engineering scintillators with optimal performance for targeted applications. This report reviews several successful examples and its effect on specific properties.

PLASTIC SCINTILLATOR FOR RADIATION DOSIMETRY.

PubMed

Kim, Yewon; Yoo, Hyunjun; Kim, Chankyu; Lim, Kyung Taek; Moon, Myungkook; Kim, Jongyul; Cho, Gyuseong

2016-09-01

Inorganic scintillators, composed of high-atomic-number materials such as the CsI(Tl) scintillator, are commonly used in commercially available a silicon diode and a scintillator embedded indirect-type electronic personal dosimeters because the light yield of the inorganic scintillator is higher than that of an organic scintillator. However, when it comes to tissue-equivalent dose measurements, a plastic scintillator such as polyvinyl toluene (PVT) is a more appropriate material than an inorganic scintillator because of the mass energy absorption coefficient. To verify the difference in the absorbed doses for each scintillator, absorbed doses from the energy spectrum and the calculated absorbed dose were compared. From the results, the absorbed dose of the plastic scintillator was almost the same as that of the tissue for the overall photon energy. However, in the case of CsI, it was similar to that of the tissue only for a photon energy from 500 to 4000 keV. Thus, the values and tendency of the mass energy absorption coefficient of the PVT are much more similar to those of human tissue than those of the CsI. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Timing Characterization of Helium-4 Fast Neutron Detector with EJ-309 Organic Liquid Scintillator

NASA Astrophysics Data System (ADS)

Liang, Yinong; Zhu, Ting; Enqvist, Andreas

2018-01-01

Recently, the Helium-4 gas fast neutron scintillation detectors is being used in time-sensitive measurements, such time-of-flight and multiplicity counting. In this paper, a set of time aligned signals was acquired in a coincidence measurement using the Helium-4 gas detectors and EJ-309 liquid scintillators. The high-speed digitizer system is implanted with a trigger moving average window (MAW) unit combing with its constant fraction discriminator (CFD) feature. It can calculate a "time offset" to the timestamp value to get a higher resolution timestamp (up to 50 ps), which is better than the digitizer's time resolution (4 ns) [1]. The digitized waveforms were saved to the computer hard drive and post processed with digital analysis code to determine the difference of their arrival times. The full-width at half-maximum (FWHM) of the Gaussian fit was used as to examine the resolution. For the cascade decay of Cobalt-60 (1.17 and 1.33 MeV), the first version of the Helium-4 detector with two Hamamatsu R580 photomultipliers (PMT) installed at either end of the cylindrical gas chamber (20 cm in length and 4.4 cm in diameter) has a time resolution which is about 3.139 ns FWHM. With improved knowledge of the timing performance, the Helium-4 scintillation detectors are excellent for neutron energy spectrometry applications requiring high temporal and energy resolutions.

Development of a real-time digital radiography system using a scintillator-type flat-panel detector

NASA Astrophysics Data System (ADS)

Ikeda, Shigeyuki; Suzuki, Katsumi; Ishikawa, Ken; Okajima, Kenichi

2001-06-01

In order to study the advantage and remaining problems of FPD (flat panel detector) for clinical use by the real-time DR (digital radiography) system, we developed a prototype system using a scintillator type FPD and which was compared with previous I.I.-CCD type real-time DR. We replaced the X- ray detector of DR-2000X from I.I.-4M (4 million pixels)-CCD camera to the scintillator type dynamic FPD(7' X 9', 127 micrometers ), which can take both radiographic and fluoroscopic images. We obtained the images of head and stomach phantoms, and discussed about the image quality with medical doctors.

The timing resolution of scintillation-detector systems: Monte Carlo analysis

NASA Astrophysics Data System (ADS)

Choong, Woon-Seng

2009-11-01

Recent advancements in fast scintillating materials and fast photomultiplier tubes (PMTs) have stimulated renewed interest in time-of-flight (TOF) positron emission tomography (PET). It is well known that the improvement in the timing resolution in PET can significantly reduce the noise variance in the reconstructed image resulting in improved image quality. In order to evaluate the timing performance of scintillation detectors used in TOF PET, we use Monte Carlo analysis to model the physical processes (crystal geometry, crystal surface finish, scintillator rise time, scintillator decay time, photoelectron yield, PMT transit time spread, PMT single-electron response, amplifier response and time pick-off method) that can contribute to the timing resolution of scintillation-detector systems. In the Monte Carlo analysis, the photoelectron emissions are modeled by a rate function, which is used to generate the photoelectron time points. The rate function, which is simulated using Geant4, represents the combined intrinsic light emissions of the scintillator and the subsequent light transport through the crystal. The PMT output signal is determined by the superposition of the PMT single-electron response resulting from the photoelectron emissions. The transit time spread and the single-electron gain variation of the PMT are modeled in the analysis. Three practical time pick-off methods are considered in the analysis. Statistically, the best timing resolution is achieved with the first photoelectron timing. The calculated timing resolution suggests that a leading edge discriminator gives better timing performance than a constant fraction discriminator and produces comparable results when a two-threshold or three-threshold discriminator is used. For a typical PMT, the effect of detector noise on the timing resolution is negligible. The calculated timing resolution is found to improve with increasing mean photoelectron yield, decreasing scintillator decay time and

The timing resolution of scintillation-detector systems: Monte Carlo analysis.

PubMed

Choong, Woon-Seng

2009-11-07

Recent advancements in fast scintillating materials and fast photomultiplier tubes (PMTs) have stimulated renewed interest in time-of-flight (TOF) positron emission tomography (PET). It is well known that the improvement in the timing resolution in PET can significantly reduce the noise variance in the reconstructed image resulting in improved image quality. In order to evaluate the timing performance of scintillation detectors used in TOF PET, we use Monte Carlo analysis to model the physical processes (crystal geometry, crystal surface finish, scintillator rise time, scintillator decay time, photoelectron yield, PMT transit time spread, PMT single-electron response, amplifier response and time pick-off method) that can contribute to the timing resolution of scintillation-detector systems. In the Monte Carlo analysis, the photoelectron emissions are modeled by a rate function, which is used to generate the photoelectron time points. The rate function, which is simulated using Geant4, represents the combined intrinsic light emissions of the scintillator and the subsequent light transport through the crystal. The PMT output signal is determined by the superposition of the PMT single-electron response resulting from the photoelectron emissions. The transit time spread and the single-electron gain variation of the PMT are modeled in the analysis. Three practical time pick-off methods are considered in the analysis. Statistically, the best timing resolution is achieved with the first photoelectron timing. The calculated timing resolution suggests that a leading edge discriminator gives better timing performance than a constant fraction discriminator and produces comparable results when a two-threshold or three-threshold discriminator is used. For a typical PMT, the effect of detector noise on the timing resolution is negligible. The calculated timing resolution is found to improve with increasing mean photoelectron yield, decreasing scintillator decay time and

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.

Data Analysis for the Scintillating Optical Fiber Calorimeter (SOFCAL)

NASA Technical Reports Server (NTRS)

Christl, Mark J.

1997-01-01

The scintillating optical fiber calorimeter is a hybrid instrument with both active and passive components for measuring the proton and helium cosmic ray spectra from 0.2 to IO TeV kinetic energy. A thin emulsion/x-ray film chamber is situated between a cerenkov counter and an imaging calorimeter. Scintillating optical fibers sample the electromagnetic showers that develop in the calorimeter and identify the trajectory of cosmic rays that interact in SOFCAL. The emulsion/x-ray film data provide an in flight calibration for SOFCAL. The data reduction techniques used will be discussed and interim results of the analysis from a 20 hour balloon flight will be presented.

Wide-band gas leak imaging detection system using UFPA

NASA Astrophysics Data System (ADS)

Jin, Wei-qi; Li, Jia-kun; Dun, Xiong; Jin, Minglei; Wang, Xia

2014-11-01

The leakage of toxic or hazardous gases not only pollutes the environment, but also threatens people's lives and property safety. Many countries attach great importance to the rapid and effective gas leak detection technology and instrument development. However, the gas leak imaging detection systems currently existing are generally limited to a narrow-band in Medium Wavelength Infrared (MWIR) or Long Wavelength Infrared (LWIR) cooled focal plane imaging, which is difficult to detect the common kinds of the leaking gases. Besides the costly cooled focal plane array is utilized, the application promotion is severely limited. To address this issue, a wide-band gas leak IR imaging detection system using Uncooled Focal Plane Array (UFPA) detector is proposed, which is composed of wide-band IR optical lens, sub-band filters and switching device, wide-band UFPA detector, video processing and system control circuit. A wide-band (3µm~12µm) UFPA detector is obtained by replacing the protection window and optimizing the structural parameters of the detector. A large relative aperture (F#=0.75) wide-band (3μm~12μm) multispectral IR lens is developed by using the focus compensation method, which combining the thickness of the narrow-band filters. The gas leak IR image quality and the detection sensitivity are improved by using the IR image Non-Uniformity Correction (NUC) technology and Digital Detail Enhancement (DDE) technology. The wide-band gas leak IR imaging detection system using UFPA detector takes full advantage of the wide-band (MWIR&LWIR) response characteristic of the UFPA detector and the digital image processing technology to provide the resulting gas leak video easy to be observed for the human eyes. Many kinds of gases, which are not visible to the naked eyes, can be sensitively detected and visualized. The designed system has many commendable advantages, such as scanning a wide range simultaneously, locating the leaking source quickly, visualizing the gas

Using turbulence scintillation to assist object ranging from a single camera viewpoint.

PubMed

Wu, Chensheng; Ko, Jonathan; Coffaro, Joseph; Paulson, Daniel A; Rzasa, John R; Andrews, Larry C; Phillips, Ronald L; Crabbs, Robert; Davis, Christopher C

2018-03-20

Image distortions caused by atmospheric turbulence are often treated as unwanted noise or errors in many image processing studies. Our study, however, shows that in certain scenarios the turbulence distortion can be very helpful in enhancing image processing results. This paper describes a novel approach that uses the scintillation traits recorded on a video clip to perform object ranging with reasonable accuracy from a single camera viewpoint. Conventionally, a single camera would be confused by the perspective viewing problem, where a large object far away looks the same as a small object close by. When the atmospheric turbulence phenomenon is considered, the edge or texture pixels of an object tend to scintillate and vary more with increased distance. This turbulence induced signature can be quantitatively analyzed to achieve object ranging with reasonable accuracy. Despite the inevitable fact that turbulence will cause random blurring and deformation of imaging results, it also offers convenient solutions to some remote sensing and machine vision problems, which would otherwise be difficult.

Scintillator Waveguide For Sensing Radiation

DOEpatents

Bliss, Mary; Craig, Richard A.; Reeder; Paul L.

2003-04-22

The present invention is an apparatus for detecting ionizing radiation, having: a waveguide having a first end and a second end, the waveguide formed of a scintillator material wherein the therapeutic ionizing radiation isotropically generates scintillation light signals within the waveguide. This apparatus provides a measure of radiation dose. The apparatus may be modified to permit making a measure of location of radiation dose. Specifically, the scintillation material is segmented into a plurality of segments; and a connecting cable for each of the plurality of segments is used for conducting scintillation signals to a scintillation detector.

High resolution scintillation detector with semiconductor readout

DOEpatents

Levin, Craig S.; Hoffman, Edward J.

2000-01-01

A novel high resolution scintillation detector array for use in radiation imaging such as high resolution Positron Emission Tomography (PET) which comprises one or more parallelepiped crystals with at least one long surface of each crystal being in intimate contact with a semiconductor photodetector such that photons generated within each crystal by gamma radiation passing therethrough is detected by the photodetector paired therewith.

Transmission environmental scanning electron microscope with scintillation gaseous detection device.

PubMed

Danilatos, Gerasimos; Kollia, Mary; Dracopoulos, Vassileios

2015-03-01

A transmission environmental scanning electron microscope with use of a scintillation gaseous detection device has been implemented. This corresponds to a transmission scanning electron microscope but with addition of a gaseous environment acting both as environmental and detection medium. A commercial type of low vacuum machine has been employed together with appropriate modifications to the detection configuration. This involves controlled screening of various emitted signals in conjunction with a scintillation gaseous detection device already provided with the machine for regular surface imaging. Dark field and bright field imaging has been obtained along with other detection conditions. With a progressive series of modifications and tests, the theory and practice of a novel type of microscopy is briefly shown now ushering further significant improvements and developments in electron microscopy as a whole. Copyright © 2014 Elsevier B.V. All rights reserved.

Assessment of scintillation proxy maps for a scintillation study during geomagnetically quiet and disturbed conditions over Uganda

NASA Astrophysics Data System (ADS)

Amabayo, Emirant B.; Jurua, Edward; Cilliers, Pierre J.

2017-02-01

The objective of this paper is demonstrate the validity and usefulness of scintillation proxies derived from IGS data, through its comparison with data from dedicated scintillation monitors and its application to GNSS scintillation patterns. The paper presents scintillation patterns developed by using data from the dedicated scintillation monitors of the scintillation network decision aid (SCINDA) network, and proxy maps derived from IGS GPS data for 2011 and 2012 over low latitude stations in Uganda. The amplitude and phase scintillation indicies (S4 and σΦ) were obtained from the Novatel GSV4004B ionospheric scintillation and total electron content (TEC) monitor managed by SCINDA at Makerere (0.340N, 32.570E). The corresponding IGS GPS proxy data were obtained from the receivers at Entebbe (0.040N, 32.440E) and Mbarara (0.600S, 30.740E). The derived amplitude (S4p) and phase (sDPR) scintillation proxy maps were compared with maps of S4 and σΦ during geomagnetic storms (moderate and strong) and geomagnetically quiet conditions. The scintillation patterns using S4 and σΦ and their respective proxies revealed similar diurnal and seasonal patterns of strong scintillation occurrence. The peaks of scintillation occurrence with mean values in the range 0.3 < (S4p , sDPR) ≤ 0.6 were observed during nighttime (17:00-22:00 UT) and in the months of March-April and September-October. The results also indicate that high level scintillations occur during geomagnetically disturbed (moderate and strong) and quiet conditions over the Ugandan region. The results show that SCINDA and IGS based scintillation patterns reveal the same nighttime and seasonal occurrence of irregularities over Uganda irrespective of the geomagnetic conditions. Therefore, the amplitude and phase scintillation proxies presented here can be used to fill gaps in low-latitude data where there are no data available from dedicated scintillation receivers, irrespective of the geomagnetic conditions.

Lead carbonate scintillator materials

DOEpatents

Derenzo, Stephen E.; Moses, William W.

1991-01-01

Improved radiation detectors containing lead carbonate or basic lead carbonate as the scintillator element are disclosed. Both of these scintillators have been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to other known scintillator materials. The radiation detectors disclosed are favorably suited for use in general purpose detection and in medical uses.

Cherenkov and scintillation light separation in organic liquid scintillators

NASA Astrophysics Data System (ADS)

Caravaca, J.; Descamps, F. B.; Land, B. J.; Yeh, M.; Orebi Gann, G. D.

2017-12-01

The CHErenkov/Scintillation Separation experiment (CHESS) has been used to demonstrate the separation of Cherenkov and scintillation light in both linear alkylbenzene (LAB) and LAB with 2 g/L of PPO as a fluor (LAB/PPO). This is the first successful demonstration of Cherenkov light detection from the more challenging LAB/PPO cocktail and improves on previous results for LAB. A time resolution of 338± 12 ps FWHM results in an efficiency for identifying Cherenkov photons in LAB/PPO of 70 ± 3 % and 63± 8% for time- and charge-based separation, respectively, with scintillation contamination of 36± 5% and 38± 4%. LAB/PPO data is consistent with a rise time of τ _r=0.72± 0.33 ns.

Performance of SEM scintillation detector evaluated by modulation transfer function and detective quantum efficiency function.

PubMed

Bok, Jan; Schauer, Petr

2014-01-01

In the paper, the SEM detector is evaluated by the modulation transfer function (MTF) which expresses the detector's influence on the SEM image contrast. This is a novel approach, since the MTF was used previously to describe only the area imaging detectors, or whole imaging systems. The measurement technique and calculation of the MTF for the SEM detector are presented. In addition, the measurement and calculation of the detective quantum efficiency (DQE) as a function of the spatial frequency for the SEM detector are described. In this technique, the time modulated e-beam is used in order to create well-defined input signal for the detector. The MTF and DQE measurements are demonstrated on the Everhart-Thornley scintillation detector. This detector was alternated using the YAG:Ce, YAP:Ce, and CRY18 single-crystal scintillators. The presented MTF and DQE characteristics show good imaging properties of the detectors with the YAP:Ce or CRY18 scintillator, especially for a specific type of the e-beam scan. The results demonstrate the great benefit of the description of SEM detectors using the MTF and DQE. In addition, point-by-point and continual-sweep e-beam scans in SEM were discussed and their influence on the image quality was revealed using the MTF. © 2013 Wiley Periodicals, Inc.

Pulsed laser linescanner for a backscatter absorption gas imaging system

DOEpatents

Kulp, Thomas J.; Reichardt, Thomas A.; Schmitt, Randal L.; Bambha, Ray P.

2004-02-10

An active (laser-illuminated) imaging system is described that is suitable for use in backscatter absorption gas imaging (BAGI). A BAGI imager operates by imaging a scene as it is illuminated with radiation that is absorbed by the gas to be detected. Gases become "visible" in the image when they attenuate the illumination creating a shadow in the image. This disclosure describes a BAGI imager that operates in a linescanned manner using a high repetition rate pulsed laser as its illumination source. The format of this system allows differential imaging, in which the scene is illuminated with light at least 2 wavelengths--one or more absorbed by the gas and one or more not absorbed. The system is designed to accomplish imaging in a manner that is insensitive to motion of the camera, so that it can be held in the hand of an operator or operated from a moving vehicle.

Lead carbonate scintillator materials

DOEpatents

Derenzo, S.E.; Moses, W.W.

1991-05-14

Improved radiation detectors containing lead carbonate or basic lead carbonate as the scintillator element are disclosed. Both of these scintillators have been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to other known scintillator materials. The radiation detectors disclosed are favorably suited for use in general purpose detection and in medical uses. 3 figures.

Characteristics of High Latitude Ionosphere Scintillations

NASA Astrophysics Data System (ADS)

Morton, Y.

2012-12-01

As we enter a new solar maximum period, global navigation satellite systems (GNSS) receivers, especially the ones operating in high latitude and equatorial regions, are facing an increasing threat from ionosphere scintillations. The increased solar activities, however, also offer a great opportunity to collect scintillation data to characterize scintillation signal parameters and ionosphere irregularities. While there are numerous GPS receivers deployed around the globe to monitor ionosphere scintillations, most of them are commercial receivers whose signal processing mechanisms are not designed to operate under ionosphere scintillation. As a result, they may distort scintillation signal parameters or lose lock of satellite signals under strong scintillations. Since 2008, we have established and continuously improved a unique GNSS receiver array at HAARP, Alaska. The array contains high ends commercial receivers and custom RF front ends which can be automatically triggered to collect high quality GPS and GLONASS satellite signals during controlled heating experiments and natural scintillation events. Custom designed receiver signal tracking algorithms aim to preserve true scintillation signatures are used to process the raw RF samples. Signal strength, carrier phase, and relative TEC measurements generated by the receiver array since its inception have been analyzed to characterize high latitude scintillation phenomena. Daily, seasonal, and solar events dependency of scintillation occurrence, spectral contents of scintillation activities, and plasma drifts derived from these measurements will be presented. These interesting results demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations and natural disturbances.

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera.

PubMed

Alhassen, Fares; Kudrolli, Haris; Singh, Bipin; Kim, Sangtaek; Seo, Youngho; Gould, Robert G; Nagarkar, Vivek V

2011-06-01

Preclinical SPECT offers a powerful means to understand the molecular pathways of drug interactions in animal models by discovering and testing new pharmaceuticals and therapies for potential clinical applications. A combination of high spatial resolution and sensitivity are required in order to map radiotracer uptake within small animals. Pinhole collimators have been investigated, as they offer high resolution by means of image magnification. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the detection scintillator at steep angles, introducing parallax errors due to variable depth-of-interaction in scintillator material, especially towards the edges of the detector field of view. These parallax errors ultimately limit the resolution of pinhole preclinical SPECT systems, especially for higher energy isotopes that can easily penetrate through millimeters of scintillator material. A pixellated, focused-cut (FC) scintillator, with its pixels laser-cut so that they are collinear with incoming rays, can potentially compensate for these parallax errors and thus improve the system resolution. We performed the first experimental evaluation of a newly developed focused-cut scintillator. We scanned a Tc-99m source across the field of view of pinhole gamma camera with a continuous scintillator, a conventional "straight-cut" (SC) pixellated scintillator, and a focused-cut scintillator, each coupled to an electron-multiplying charge coupled device (EMCCD) detector by a fiber-optic taper, and compared the measured full-width half-maximum (FWHM) values. We show that the FWHMs of the focused-cut scintillator projections are comparable to the FWHMs of the thinner SC scintillator, indicating the effectiveness of the focused-cut scintillator in compensating parallax errors.

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera

PubMed Central

Alhassen, Fares; Kudrolli, Haris; Singh, Bipin; Kim, Sangtaek; Seo, Youngho; Gould, Robert G.; Nagarkar, Vivek V.

2011-01-01

Preclinical SPECT offers a powerful means to understand the molecular pathways of drug interactions in animal models by discovering and testing new pharmaceuticals and therapies for potential clinical applications. A combination of high spatial resolution and sensitivity are required in order to map radiotracer uptake within small animals. Pinhole collimators have been investigated, as they offer high resolution by means of image magnification. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the detection scintillator at steep angles, introducing parallax errors due to variable depth-of-interaction in scintillator material, especially towards the edges of the detector field of view. These parallax errors ultimately limit the resolution of pinhole preclinical SPECT systems, especially for higher energy isotopes that can easily penetrate through millimeters of scintillator material. A pixellated, focused-cut (FC) scintillator, with its pixels laser-cut so that they are collinear with incoming rays, can potentially compensate for these parallax errors and thus improve the system resolution. We performed the first experimental evaluation of a newly developed focused-cut scintillator. We scanned a Tc-99m source across the field of view of pinhole gamma camera with a continuous scintillator, a conventional “straight-cut” (SC) pixellated scintillator, and a focused-cut scintillator, each coupled to an electron-multiplying charge coupled device (EMCCD) detector by a fiber-optic taper, and compared the measured full-width half-maximum (FWHM) values. We show that the FWHMs of the focused-cut scintillator projections are comparable to the FWHMs of the thinner SC scintillator, indicating the effectiveness of the focused-cut scintillator in compensating parallax errors. PMID:21731108

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera

NASA Astrophysics Data System (ADS)

Alhassen, Fares; Kudrolli, Haris; Singh, Bipin; Kim, Sangtaek; Seo, Youngho; Gould, Robert G.; Nagarkar, Vivek V.

2011-06-01

Preclinical SPECT offers a powerful means to understand the molecular pathways of drug interactions in animal models by discovering and testing new pharmaceuticals and therapies for potential clinical applications. A combination of high spatial resolution and sensitivity are required in order to map radiotracer uptake within small animals. Pinhole collimators have been investigated, as they offer high resolution by means of image magnification. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the detection scintillator at steep angles, introducing parallax errors due to variable depth-of-interaction in scintillator material, especially towards the edges of the detector field of view. These parallax errors ultimately limit the resolution of pinhole preclinical SPECT systems, especially for higher energy isotopes that can easily penetrate through millimeters of scintillator material. A pixellated, focused-cut (FC) scintillator, with its pixels laser-cut so that they are collinear with incoming rays, can potentially compensate for these parallax errors and thus improve the system resolution. We performed the first experimental evaluation of a newly developed focused-cut scintillator. We scanned a Tc-99 m source across the field of view of pinhole gamma camera with a continuous scintillator, a conventional “straight-cut” (SC) pixellated scintillator, and a focused-cut scintillator, each coupled to an electron-multiplying charge coupled device (EMCCD) detector by a fiber-optic taper, and compared the measured full-width half-maximum (FWHM) values. We show that the FWHMs of the focused-cut scintillator projections are comparable to the FWHMs of the thinner SC scintillator, indicating the effectiveness of the focused-cut scintillator in compensating parallax errors.

Practical use of a plastic scintillator for quality assurance of electron beam therapy.

PubMed

Yogo, Katsunori; Tatsuno, Yuya; Tsuneda, Masato; Aono, Yuki; Mochizuki, Daiki; Fujisawa, Yoshiki; Matsushita, Akihiro; Ishigami, Minoru; Ishiyama, Hiromichi; Hayakawa, Kazushige

2017-06-07

Quality assurance (QA) of clinical electron beams is essential for performing accurate and safe radiation therapy. However, with advances in radiation therapy, QA has become increasingly labor-intensive and time-consuming. In this paper, we propose a tissue-equivalent plastic scintillator for quick and easy QA of clinical electron beams. The proposed tool comprises a plastic scintillator plate and a charge-coupled device camera that enable the scintillation light by electron beams to be recorded with high sensitivity and high spatial resolution. Further, the Cerenkov image is directly subtracted from the scintillation image to discriminate Cerenkov emissions and accurately measure the dose profiles of electron beams with high spatial resolution. Compared with conventional methods, discrepancies in the depth profile improved from 7% to 2% in the buildup region via subtractive corrections. Further, the output brightness showed good linearity with dose, good reproducibility (deviations below 1%), and dose rate independence (within 0.5%). The depth of 50% dose measured with the tool, an index of electron beam quality, was within  ±0.5 mm of that obtained with an ionization chamber. Lateral brightness profiles agreed with the lateral dose profiles to within 4% and no significant improvement was obtained using Cerenkov corrections. Field size agreed to within 0.5 mm with those obtained with ionization chamber. For clinical QA of electron boost treatment, a disk scintillator that mimics the shape of a patient's breast is applied. The brightness distribution and dose, calculated using a treatment planning system, was generally acceptable for clinical use, except in limited zones. Overall, the proposed plastic scintillator plate tool efficiently performs QA for electron beam therapy and enables simultaneous verification of output constancy, beam quality, depth, and lateral dose profiles during monthly QAs at lower doses of irradiation (small monitor units, MUs).

Cherenkov and scintillation light separation in organic liquid scintillators

DOE PAGES

Caravaca, J.; Descamps, F. B.; Land, B. J.; ...

2017-11-29

The CHErenkov/Scintillation Separation experiment (CHESS) has been used to demonstrate the separation of Cherenkov and scintillation light in both linear alkylbenzene (LAB) and LAB with 2 g/L of PPO as a fluor (LAB/PPO). This is the first successful demonstration of Cherenkov light detection from the more challenging LAB/PPO cocktail and improves on previous results for LAB. A time resolution of 338 ± 12 ps FWHM results in an efficiency for identifying Cherenkov photons in LAB/PPO of 70 ± 3 % and 63 ± 8 % for time- and charge-based separation, respectively, with scintillation contamination of 36 ± 5 % andmore » 38 ± 4 %. LAB/PPO data is consistent with a rise time of τ r = 0.72 ± 0.33 ns.« less

Cherenkov and scintillation light separation in organic liquid scintillators

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

Caravaca, J.; Descamps, F. B.; Land, B. J.

The CHErenkov/Scintillation Separation experiment (CHESS) has been used to demonstrate the separation of Cherenkov and scintillation light in both linear alkylbenzene (LAB) and LAB with 2 g/L of PPO as a fluor (LAB/PPO). This is the first successful demonstration of Cherenkov light detection from the more challenging LAB/PPO cocktail and improves on previous results for LAB. A time resolution of 338 ± 12 ps FWHM results in an efficiency for identifying Cherenkov photons in LAB/PPO of 70 ± 3 % and 63 ± 8 % for time- and charge-based separation, respectively, with scintillation contamination of 36 ± 5 % andmore » 38 ± 4 %. LAB/PPO data is consistent with a rise time of τ r = 0.72 ± 0.33 ns.« less

Design and image-quality performance of high resolution CMOS-based X-ray imaging detectors for digital mammography

NASA Astrophysics Data System (ADS)

Cha, B. K.; Kim, J. Y.; Kim, Y. J.; Yun, S.; Cho, G.; Kim, H. K.; Seo, C.-W.; Jeon, S.; Huh, Y.

2012-04-01

In digital X-ray imaging systems, X-ray imaging detectors based on scintillating screens with electronic devices such as charge-coupled devices (CCDs), thin-film transistors (TFT), complementary metal oxide semiconductor (CMOS) flat panel imagers have been introduced for general radiography, dental, mammography and non-destructive testing (NDT) applications. Recently, a large-area CMOS active-pixel sensor (APS) in combination with scintillation films has been widely used in a variety of digital X-ray imaging applications. We employed a scintillator-based CMOS APS image sensor for high-resolution mammography. In this work, both powder-type Gd2O2S:Tb and a columnar structured CsI:Tl scintillation screens with various thicknesses were fabricated and used as materials to convert X-ray into visible light. These scintillating screens were directly coupled to a CMOS flat panel imager with a 25 × 50 mm2 active area and a 48 μm pixel pitch for high spatial resolution acquisition. We used a W/Al mammographic X-ray source with a 30 kVp energy condition. The imaging characterization of the X-ray detector was measured and analyzed in terms of linearity in incident X-ray dose, modulation transfer function (MTF), noise-power spectrum (NPS) and detective quantum efficiency (DQE).

Real-time imaging of methane gas leaks using a single-pixel camera.

PubMed

Gibson, Graham M; Sun, Baoqing; Edgar, Matthew P; Phillips, David B; Hempler, Nils; Maker, Gareth T; Malcolm, Graeme P A; Padgett, Miles J

2017-02-20

We demonstrate a camera which can image methane gas at video rates, using only a single-pixel detector and structured illumination. The light source is an infrared laser diode operating at 1.651μm tuned to an absorption line of methane gas. The light is structured using an addressable micromirror array to pattern the laser output with a sequence of Hadamard masks. The resulting backscattered light is recorded using a single-pixel InGaAs detector which provides a measure of the correlation between the projected patterns and the gas distribution in the scene. Knowledge of this correlation and the patterns allows an image to be reconstructed of the gas in the scene. For the application of locating gas leaks the frame rate of the camera is of primary importance, which in this case is inversely proportional to the square of the linear resolution. Here we demonstrate gas imaging at ~25 fps while using 256 mask patterns (corresponding to an image resolution of 16×16). To aid the task of locating the source of the gas emission, we overlay an upsampled and smoothed image of the low-resolution gas image onto a high-resolution color image of the scene, recorded using a standard CMOS camera. We demonstrate for an illumination of only 5mW across the field-of-view imaging of a methane gas leak of ~0.2 litres/minute from a distance of ~1 metre.

Calculations and measurements of the scintillator-to-water stopping power ratio of liquid scintillators for use in proton radiotherapy.

PubMed

Ingram, W Scott; Robertson, Daniel; Beddar, Sam

2015-03-11

Liquid scintillators are a promising detector for high-resolution three-dimensional proton therapy dosimetry. Because the scintillator comprises both the active volume of the detector and the phantom material, an ideal scintillator will exhibit water equivalence in its radiological properties. One of the most fundamental of these is the scintillator's stopping power. The objective of this study was to compare calculations and measurements of scintillator-to-water stopping power ratios to evaluate the suitability of the liquid scintillators BC-531 and OptiPhase HiSafe 3 for proton dosimetry. We also measured the relative scintillation output of the two scintillators. Both calculations and measurements show that the linear stopping power of OptiPhase is significantly closer to water than that of BC-531. BC-531 has a somewhat higher scintillation output. OptiPhase can be mixed with water at high concentrations, which further improves its scintillator-to-water stopping power ratio. However, this causes the solution to become cloudy, which has a negative impact on the scintillation output and spatial resolution of the detector. OptiPhase is preferred over BC-531 for proton dosimetry because its density and scintillator-to-water stopping power ratio are more water equivalent.

Physics considerations in MV-CBCT multi-layer imager design.

PubMed

Hu, Yue-Houng; Fueglistaller, Rony; Myronakis, Marios E; Rottmann, Joerg; Wang, Adam; Shedlock, Daniel; Morf, Daniel; Baturin, Paul; Huber, Pascal; Star-Lack, Josh M; Berbeco, Ross I

2018-05-30

Megavoltage (MV) cone-beam computed tomography (CBCT) using an electronic portal imaging (EPID) offers advantageous features, including 3D mapping, treatment beam registration, high-z artifact suppression, and direct radiation dose calculation. Adoption has been slowed by image quality limitations and concerns about imaging dose. Developments in imager design, including pixelated scintillators, structured phosphors, inexpensive scintillation materials, and multi-layer imager (MLI) architecture have been explored to improve EPID image quality and reduce imaging dose. The present study employs a hybrid Monte Carlo and linear systems model to determine the effect of detector design elements, such as multi-layer architecture and scintillation materials. We follow metrics of image quality including modulation transfer function (MTF) and noise power spectrum (NPS) from projection images to 3D reconstructions to in-plane slices and apply a task based figure-of-merit, the ideal observer signal-to-noise ratio (d') to determine the effect of detector design on object detectability. Generally, detectability was limited by detector noise performance. Deploying an MLI imager with a single scintillation material for all layers yields improvement in noise performance and d' linear with the number of layers. In general, improving x-ray absorption using thicker scintillators results in improved DQE(0). However, if light yield is low, performance will be affected by electronic noise at relatively high doses, resulting in rapid image quality degradation. Maximizing image quality in a heterogenous MLI detector (i.e. multiple different scintillation materials) is most affected by limiting imager noise. However, while a second-order effect, maximizing total spatial resolution of the MLI detector is a balance between the intensity contribution of each layer against its individual MTF. So, while a thinner scintillator may yield a maximal individual-layer MTF, its quantum efficiency will

Temperature dependence of alpha-induced scintillation in the 1,1,4,4-tetraphenyl-1,3-butadiene wavelength shifter

NASA Astrophysics Data System (ADS)

Veloce, L. M.; Kuźniak, M.; Di Stefano, P. C. F.; Noble, A. J.; Boulay, M. G.; Nadeau, P.; Pollmann, T.; Clark, M.; Piquemal, M.; Schreiner, K.

2016-06-01

Liquid noble based particle detectors often use the organic wavelength shifter 1,1,4,4-tetraphenyl-1,3-butadiene (TPB) which shifts UV scintillation light to the visible regime, facilitating its detection, but which also can scintillate on its own. Dark matter searches based on this type of detector commonly rely on pulse-shape discrimination (PSD) for background mitigation. Alpha-induced scintillation therefore represents a possible background source in dark matter searches. The timing characteristics of this scintillation determine whether this background can be mitigated through PSD. We have therefore characterized the pulse shape and light yield of alpha induced TPB scintillation at temperatures ranging from 300 K down to 4 K, with special attention given to liquid noble gas temperatures. We find that the pulse shapes and light yield depend strongly on temperature. In addition, the significant contribution of long time constants above ~50 K provides an avenue for discrimination between alpha decay events in TPB and nuclear-recoil events in noble liquid detectors.

Microcolumnar and polycrystalline growth of LaBr3:Ce scintillator

NASA Astrophysics Data System (ADS)

Nagarkar, V. V.; Miller, S.; Sia, R.; Gaysinskiy, V.

2011-05-01

While a wide variety of new scintillators are now available, cerium-doped lanthanide halide scintillators have shown a strong potential toward fulfilling the needs of highly demanding applications such as radioisotope identification at room temperature, homeland security, quantitative molecular imaging for medical diagnostics, and disease staging and research. Despite their extraordinary advantages in terms of light yield and response uniformity over a wide energy range, issues related to reliable, large volume manufacturing of these high-light-yield materials in a rapid and economic manner has not been resolved or purposefully addressed. Here we report on synthesizing LaBr3:Ce scintillator using a thermal evaporation technique, which offers the potential to synthesize large quantities of small-to-large volume, high-quality material in a time-efficient and cost-effective manner. To date we have successfully applied this method to form both microcolumnar films and thick polycrystalline slabs of LaBr3:Ce, and have characterized their light yield, response linearity, decay time and afterglow.

Scintillation Monitoring Using Asymmetry Index

NASA Astrophysics Data System (ADS)

Shaikh, Muhammad Mubasshir; Mahrous, Ayman; Abdallah, Amr; Notarpietro, Riccardo

station in Cairo, Egypt (lat= 29.8641 °, long= 31.3172 °). It was observed that the level of asymmetry was significantly increased during the main phase of the geomagnetic storm. This was due to the changes in ionization, which in turn produced large gradients along occulted ray path in the ionosphere. A very good correlation was found between the evaluated ionospheric asymmetry index and the S4 scintillation index. Additionally, the correlation between evaluated ionospheric asymmetry and errors related to the RO inversion products such as peak electron density (delta NmF2) and Vertical TEC (delta VTEC) estimates also showed promising results. This work is carried out under the framework of the TRANSMIT project (Training Research and Applications Network to Support the Mitigation of Ionospheric Threats - www.transmit-ionosphere.net). [1]Basu Sa. and Basu Su., (1981), ‘Equatorial Scintillation - A Review’, Journal of Atmospheric and Solar-Terrestrial Physics, 43, p. 473. [2]Davies K., (1990), ‘Ionospheric Radio’, IEEE Electromagnetic Waves Series 31, Peter Peregrinus Ltd. [3]Spencer, P., Mitchell, C.N., (2007) ‘Imaging of fast moving electron-density structures in the polar cap’, Annals of Geophysics, vol. 50, no. 3, pp. 427-434. [4]Shaikh, M.M., Notarpietro, R., Nava, B., (2013) ‘The Impact of Spherical Symmetry Assumption on Radio Occultation Data Inversion in the Ionosphere: An Assessment Study’, Advances in Space Research, doi: http://dx.doi.org/10.1016/j.asr.2013.10.025.

Proton recoil scintillator neutron rem meter

DOEpatents

Olsher, Richard H.; Seagraves, David T.

2003-01-01

A neutron rem meter utilizing proton recoil and thermal neutron scintillators to provide neutron detection and dose measurement. In using both fast scintillators and a thermal neutron scintillator the meter provides a wide range of sensitivity, uniform directional response, and uniform dose response. The scintillators output light to a photomultiplier tube that produces an electrical signal to an external neutron counter.

Composite solid-state scintillators for neutron detection

DOEpatents

Dai, Sheng; Im, Hee-Jung; Pawel, Michelle D.

2006-09-12

Applicant's present invention is a composite scintillator for neutron detection comprising a matrix material fabricated from an inorganic sol-gel precursor solution homogeneously doped with a liquid scintillating material and a neutron absorbing material. The neutron absorbing material yields at least one of an electron, a proton, a triton, an alpha particle or a fission fragment when the neutron absorbing material absorbs a neutron. The composite scintillator further comprises a liquid scintillating material in a self-assembled micelle formation homogeneously doped in the matrix material through the formation of surfactant-silica composites. The scintillating material is provided to scintillate when traversed by at least one of an electron, a proton, a triton, an alpha particle or a fission fragment. The scintillating material is configured such that the matrix material surrounds the micelle formation of the scintillating material. The composite scintillator is fabricated and applied as a thin film on substrate surfaces, a coating on optical fibers or as a glass material.

Passive thermal infrared hyperspectral imaging for quantitative imaging of shale gas leaks

NASA Astrophysics Data System (ADS)

Gagnon, Marc-André; Tremblay, Pierre; Savary, Simon; Farley, Vincent; Guyot, Éric; Lagueux, Philippe; Morton, Vince; Giroux, Jean; Chamberland, Martin

2017-10-01

There are many types of natural gas fields including shale formations that are common especially in the St-Lawrence Valley (Canada). Since methane (CH4), the major component of shale gas, is odorless, colorless and highly flammable, in addition to being a greenhouse gas, methane emanations and/or leaks are important to consider for both safety and environmental reasons. Telops recently launched on the market the Hyper-Cam Methane, a field-deployable thermal infrared hyperspectral camera specially tuned for detecting methane infrared spectral features under ambient conditions and over large distances. In order to illustrate the benefits of this novel research instrument for natural gas imaging, the instrument was brought on a site where shale gas leaks unexpectedly happened during a geological survey near the Enfant-Jesus hospital in Quebec City, Canada, during December 2014. Quantitative methane imaging was carried out based on methane's unique infrared spectral signature. Optical flow analysis was also carried out on the data to estimate the methane mass flow rate. The results show how this novel technique could be used for advanced research on shale gases.

Ionospheric Scintillation Effects on GPS

NASA Astrophysics Data System (ADS)

Steenburgh, R. A.; Smithtro, C.; Groves, K.

2007-12-01

. Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active, although not limited to, a belt encircling the earth within 20 degrees of the geomagnetic equator. As GPS applications and users increases, so does the potential for detrimental impacts from scintillation. We examined amplitude scintillation data spanning seven years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/Americas longitudinal sector at as well as data from Parepare, Indonesia; Marak Parak, Malaysia; Pontianak, Indonesia; Guam; and Diego Garcia, U.K.; in the Pacific longitudinal sector. From these data, we calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. Additionally, we determine Dilution of Precision at one minute resolution. We examine diurnal, seasonal and solar cycle characteristics and make spatial comparisons. In general, activity was greatest during the equinoxes and solar maximum, although scintillation at Antofagasta, Chile was higher during 1998 rather than at solar maximum.

A first comparison of the responses of a 4He-based fast-neutron detector and a NE-213 liquid-scintillator reference detector

NASA Astrophysics Data System (ADS)

Jebali, R.; Scherzinger, J.; Annand, J. R. M.; Chandra, R.; Davatz, G.; Fissum, K. G.; Friederich, H.; Gendotti, U.; Hall-Wilton, R.; Håkansson, E.; Kanaki, K.; Lundin, M.; Murer, D.; Nilsson, B.; Rosborg, A.; Svensson, H.

2015-09-01

A first comparison has been made between the pulse-shape discrimination characteristics of a novel 4He-based pressurized scintillation detector and a NE-213 liquid-scintillator reference detector using an Am/Be mixed-field neutron and gamma-ray source and a high-resolution scintillation-pulse digitizer. In particular, the capabilities of the two fast neutron detectors to discriminate between neutrons and gamma-rays were investigated. The NE-213 liquid-scintillator reference cell produced a wide range of scintillation-light yields in response to the gamma-ray field of the source. In stark contrast, due to the size and pressure of the 4He gas volume, the 4He-based detector registered a maximum scintillation-light yield of 750keVee to the same gamma-ray field. Pulse-shape discrimination for particles with scintillation-light yields of more than 750keVee was excellent in the case of the 4He-based detector. Above 750keVee its signal was unambiguously neutron, enabling particle identification based entirely upon the amount of scintillation light produced.

Optical intensity scintillation in the simulated atmospherical environment

NASA Astrophysics Data System (ADS)

Hajek, Lukas; Latal, Jan; Vanderka, Ales; Vitasek, Jan; Bojko, Marian; Bednarek, Lukas; Vasinek, Vladimir

2016-09-01

There are several parameters of the atmospheric environment which have an effect on the optical wireless connection. Effects like fog, snow or rain are ones of the effects which appears tendentiously and which are bound by season, geographic location, etc. One of the effects that appear with various intensity for the whole time is airflow. The airflow changes the local refractive index of the air and areas with lower or higher refractive index form. The light going through these areas refracts and due to the optical intensity scintillates on the detector of the receiver. The airflow forms on the basis of two effects in the atmosphere. The first is wind cut and flowing over barriers. The other is thermal flow when warm air rises to the higher layers of the atmosphere. The heart of this article is creation such an environment that will form airflow and the refractive index will scintillate. For the experiment, we used special laboratory box with high-speed ventilators and heating units to simulate atmospheric turbulence. We monitor the impact of ventilator arrangement and air temperature on the scintillation of the gas laser with wavelength 633 nm/15 mW. In the experiment, there is watched the difference in behavior between real measurement and flow simulation with the same peripheral conditions of the airflow in the area of 500 x 500 cm.

Calculations and measurements of the scintillator-to-water stopping power ratio of liquid scintillators for use in proton radiotherapy

PubMed Central

Ingram, W. Scott; Robertson, Daniel; Beddar, Sam

2015-01-01

Liquid scintillators are a promising detector for high-resolution three-dimensional proton therapy dosimetry. Because the scintillator comprises both the active volume of the detector and the phantom material, an ideal scintillator will exhibit water equivalence in its radiological properties. One of the most fundamental of these is the scintillator’s stopping power. The objective of this study was to compare calculations and measurements of scintillator-to-water stopping power ratios to evaluate the suitability of the liquid scintillators BC-531 and OptiPhase HiSafe 3 for proton dosimetry. We also measured the relative scintillation output of the two scintillators. Both calculations and measurements show that the linear stopping power of OptiPhase is significantly closer to water than that of BC-531. BC-531 has a somewhat higher scintillation output. OptiPhase can be mixed with water at high concentrations, which further improves its scintillator-to-water stopping power ratio. However, this causes the solution to become cloudy, which has a negative impact on the scintillation output and spatial resolution of the detector. OptiPhase is preferred over BC-531 for proton dosimetry because its density and scintillator-to-water stopping power ratio are more water equivalent. PMID:25705066

Method of making a scintillator waveguide

DOEpatents

Bliss, Mary; Craig, Richard A.; Reeder, Paul L.

2000-01-01

The present invention is an apparatus for detecting ionizing radiation, having: a waveguide having a first end and a second end, the waveguide formed of a scintillator material wherein the therapeutic ionizing radiation isotropically generates scintillation light signals within the waveguide. This apparatus provides a measure of radiation dose. The apparatus may be modified to permit making a measure of location of radiation dose. Specifically, the scintillation material is segmented into a plurality of segments; and a connecting cable for each of the plurality of segments is used for conducting scintillation signals to a scintillation detector.

High-resolution extremity cone-beam CT with a CMOS detector: Task-based optimization of scintillator thickness.

PubMed

Cao, Q; Brehler, M; Sisniega, A; Stayman, J W; Yorkston, J; Siewerdsen, J H; Zbijewski, W

2017-03-01

CMOS x-ray detectors offer small pixel sizes and low electronic noise that may support the development of novel high-resolution imaging applications of cone-beam CT (CBCT). We investigate the effects of CsI scintillator thickness on the performance of CMOS detectors in high resolution imaging tasks, in particular in quantitative imaging of bone microstructure in extremity CBCT. A scintillator thickness-dependent cascaded systems model of CMOS x-ray detectors was developed. Detectability in low-, high- and ultra-high resolution imaging tasks (Gaussian with FWHM of ~250 μ m, ~80 μ m and ~40 μ m, respectively) was studied as a function of scintillator thickness using the theoretical model. Experimental studies were performed on a CBCT test bench equipped with DALSA Xineos3030 CMOS detectors (99 μ m pixels) with CsI scintillator thicknesses of 400 μ m and 700 μ m, and a 0.3 FS compact rotating anode x-ray source. The evaluation involved a radiographic resolution gauge (0.6-5.0 lp/mm), a 127 μm tungsten wire for assessment of 3D resolution, a contrast phantom with tissue-mimicking inserts, and an excised fragment of human tibia for visual assessment of fine trabecular detail. Experimental studies show ~35% improvement in the frequency of 50% MTF modulation when using the 400 μ m scintillator compared to the standard nominal CsI thickness of 700 μ m. Even though the high-frequency DQE of the two detectors is comparable, theoretical studies show a 14% to 28% increase in detectability index ( d' 2 ) of high- and ultrahigh resolution tasks, respectively, for the detector with 400 μ m CsI compared to 700 μ m CsI. Experiments confirm the theoretical findings, showing improvements with the adoption of 400 μ m panel in the visibility of the radiographic pattern (2× improvement in peak-to-through distance at 4.6 lp/mm) and a 12.5% decrease in the FWHM of the tungsten wire. Reconstructions of the tibial plateau reveal enhanced visibility of trabecular structures with

High-resolution extremity cone-beam CT with a CMOS detector: Task-based optimization of scintillator thickness

PubMed Central

Cao, Q.; Brehler, M.; Sisniega, A.; Stayman, J. W.; Yorkston, J.; Siewerdsen, J. H.; Zbijewski, W.

2017-01-01

Purpose CMOS x-ray detectors offer small pixel sizes and low electronic noise that may support the development of novel high-resolution imaging applications of cone-beam CT (CBCT). We investigate the effects of CsI scintillator thickness on the performance of CMOS detectors in high resolution imaging tasks, in particular in quantitative imaging of bone microstructure in extremity CBCT. Methods A scintillator thickness-dependent cascaded systems model of CMOS x-ray detectors was developed. Detectability in low-, high- and ultra-high resolution imaging tasks (Gaussian with FWHM of ~250 μm, ~80 μm and ~40 μm, respectively) was studied as a function of scintillator thickness using the theoretical model. Experimental studies were performed on a CBCT test bench equipped with DALSA Xineos3030 CMOS detectors (99 μm pixels) with CsI scintillator thicknesses of 400 μm and 700 μm, and a 0.3 FS compact rotating anode x-ray source. The evaluation involved a radiographic resolution gauge (0.6–5.0 lp/mm), a 127 μm tungsten wire for assessment of 3D resolution, a contrast phantom with tissue-mimicking inserts, and an excised fragment of human tibia for visual assessment of fine trabecular detail. Results Experimental studies show ~35% improvement in the frequency of 50% MTF modulation when using the 400 μm scintillator compared to the standard nominal CsI thickness of 700 μm. Even though the high-frequency DQE of the two detectors is comparable, theoretical studies show a 14% to 28% increase in detectability index (d′2) of high- and ultrahigh resolution tasks, respectively, for the detector with 400 μm CsI compared to 700 μm CsI. Experiments confirm the theoretical findings, showing improvements with the adoption of 400 μm panel in the visibility of the radiographic pattern (2× improvement in peak-to-through distance at 4.6 lp/mm) and a 12.5% decrease in the FWHM of the tungsten wire. Reconstructions of the tibial plateau reveal enhanced visibility of trabecular

Scintillators and applications thereof

DOEpatents

Williams, Richard T.

2015-09-01

Scintillators of various constructions and methods of making and using the same are provided. In some embodiments, a scintillator comprises at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region.

Scintillators and applications thereof

DOEpatents

Williams, Richard T.

2014-07-15

Scintillators of various constructions and methods of making and using the same are provided. In some embodiments, a scintillator comprises at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region.

Accelerated Fractional Ventilation Imaging with Hyperpolarized Gas MRI

PubMed Central

Emami, Kiarash; Xu, Yinan; Hamedani, Hooman; Profka, Harrilla; Kadlecek, Stephen; Xin, Yi; Ishii, Masaru; Rizi, Rahim R.

2013-01-01

PURPOSE To investigate the utility of accelerated imaging to enhance multi-breath fractional ventilation (r) measurement accuracy using HP gas MRI. Undersampling shortens the breath-hold time, thereby reducing the O2-induced signal decay and allows subjects to maintain a more physiologically relevant breathing pattern. Additionally it may improve r estimation accuracy by reducing RF destruction of HP gas. METHODS Image acceleration was achieved by using an 8-channel phased array coil. Undersampled image acquisition was simulated in a series of ventilation images and images were reconstructed for various matrix sizes (48–128) using GRAPPA. Parallel accelerated r imaging was also performed on five mechanically ventilated pigs. RESULTS Optimal acceleration factor was fairly invariable (2.0–2.2×) over the range of simulated resolutions. Estimation accuracy progressively improved with higher resolutions (39–51% error reduction). In vivo r values were not significantly different between the two methods: 0.27±0.09, 0.35±0.06, 0.40±0.04 (standard) versus 0.23±0.05, 0.34±0.03, 0.37±0.02 (accelerated); for anterior, medial and posterior slices, respectively, whereas the corresponding vertical r gradients were significant (P < 0.001): 0.021±0.007 (standard) versus 0.019±0.005 (accelerated) [cm−1]. CONCLUSION Quadruple phased array coil simulations resulted in an optimal acceleration factor of ~2× independent of imaging resolution. Results advocate undersampled image acceleration to improve accuracy of fractional ventilation measurement with HP gas MRI. PMID:23400938

Real-time Scintillation Monitoring in Alaska from a Longitudinal Chain of ASTRA's SM-211 GPS TEC and Scintillation Receivers

NASA Astrophysics Data System (ADS)

Crowley, G.; Azeem, S. I.; Reynolds, A.; Santana, J.; Hampton, D. L.

2013-12-01

Amplitude and phase scintillation can cause serious difficulties for GPS receivers. Intense scintillation can cause loss of lock. High latitude studies generally show that phase scintillation can be severe, but the amplitude scintillation tends to be small. The reason for this is not yet understood. Furthermore, the actual causes of the ionospheric irregularities that produce high latitude scintillation are not well understood. While the gradient drift instability is thought to be important in the F-region, there may be other structures present in either the E- or F-regions. The role of particle precipitation is also not well understood. Four of ASTRA's CASES GPS receivers were deployed in Alaska to demonstrate our ability to map scintillation in realtime, to provide space weather services to GPS users, and to initiate a detailed investigation of these effects. These dual-frequency GPS receivers measure total electron content (TEC) and scintillation. The scintillation monitors were deployed in a longitudinal chain at sites in Kaktovic, Fort Yukon, Poker Flat, and Gakona. Scintillation statistics show phase scintillations to be largest at Kaktovic and smallest at Gakona. We present GPS phase scintillation and auroral emission results from the Alaska chain to characterize the correspondence between scintillation and auroral features, and to investigate the role of high latitude auroral features in driving the phase scintillations. We will also present data showing how phase scintillation can cause other GPS receivers to lose lock. The data and results are particularly valuable because they illustrate some of the challenges of using GPS systems for positioning and navigation in an auroral region like Alaska. These challenges for snowplough drivers were recently highlighted, along with the CASES SM-211 space weather monitor, in a special video in which ASTRA and three other small businesses were presented with an entrepreneurial award from William Shatner (http://youtu.be/bIVKEQH_YPk).

Ionospheric Scintillation Explorer (ISX)

NASA Astrophysics Data System (ADS)

Iuliano, J.; Bahcivan, H.

2015-12-01

NSF has recently selected Ionospheric Scintillation Explorer (ISX), a 3U Cubesat mission to explore the three-dimensional structure of scintillation-scale ionospheric irregularities associated with Equatorial Spread F (ESF). ISX is a collaborative effort between SRI International and Cal Poly. This project addresses the science question: To what distance along a flux tube does an irregularity of certain transverse-scale extend? It has been difficult to measure the magnetic field-alignment of scintillation-scale turbulent structures because of the difficulty of sampling a flux tube at multiple locations within a short time. This measurement is now possible due to the worldwide transition to DTV, which presents unique signals of opportunity for remote sensing of ionospheric irregularities from numerous vantage points. DTV spectra, in various formats, contain phase-stable, narrowband pilot carrier components that are transmitted simultaneously. A 4-channel radar receiver will simultaneously record up to 4 spatially separated transmissions from the ground. Correlations of amplitude and phase scintillation patterns corresponding to multiple points on the same flux tube will be a measure of the spatial extent of the structures along the magnetic field. A subset of geometries where two or more transmitters are aligned with the orbital path will be used to infer the temporal development of the structures. ISX has the following broad impact. Scintillation of space-based radio signals is a space weather problem that is intensively studied. ISX is a step toward a CubeSat constellation to monitor worldwide TEC variations and radio wave distortions on thousands of ionospheric paths. Furthermore, the rapid sampling along spacecraft orbits provides a unique dataset to deterministically reconstruct ionospheric irregularities at scintillation-scale resolution using diffraction radio tomography, a technique that enables prediction of scintillations at other radio frequencies, and

Improved DQE by means of X-ray spectra and scintillator optimization for FFDM

NASA Astrophysics Data System (ADS)

Job, Isaias D.; Taie-Nobraie, Nima; Colbeth, Richard E.; Mollov, Ivan; Gray, Keith D.; Webb, Chris; Pavkovich, John M.; Zoghi, Fred; Tognina, Carlo A.; Roos, Pieter G.

2012-03-01

The focus of this work was to improve the DQE performance of a full-field digital mammography (FFDM) system by means of selecting an optimal X-ray tube anode-filter combination in conjunction with an optimal scintillator configuration. The flat panel detector in this work is a Varian PaxScan 3024M. The detector technology is comprised of a 2816 row × 3584 column amorphous silicon (a-Si) photodiode array with a pixel pitch of 83μm. The scintillator is cesium iodide and is deposited directly onto the photodiode array and available with configurable optical and x-ray properties. Two X-ray beam spectra were generated with the anode/filter combinations, Molybdenum/Molybdenum (Mo/Mo) and Tungsten/Aluminum (W/Al), to evaluate the imaging performance of two types of scintillators, high resolution (HR) type and high light output (HL) type. The results for the HR scintillator with W/Al anode-filter (HRW/ Al) yielded a DQE(0) of 67%, while HR-Mo/Mo was lower with a DQE(0) of 50%. In addition, the DQE(0) of the HR-W/Al configuration was comparable to the DQE(0) of the HL-Mo/Mo configuration. The significance of this result is the HR type scintillator yields about twice the light output with the W/Al spectrum, at about half the dose, as compared to the Mo/Mo spectrum. The light output or sensitivity was measured in analog-to-digital convertor units (ADU) per dose. The sensitivities (ADU/uGy) were 8.6, 16.8 and 25.4 for HR-Mo/Mo, HR-W/Al, HL-Mo/Mo, respectively. The Nyquist frequency for the 83 μm pixel is 6 lp/mm. The MTF at 5 lp/mm for HR-Mo/Mo and HR-W/Al were equivalent at 37%, while the HL-Mo/Mo MTF was 24%. According to the DQE metric, the more favorable anodefilter combination was W/Al with the HR scintillator. Future testing will evaluate the HL-W/Al configuration, as well as other x-ray filters materials and other scintillator optimizations. While higher DQE values were achieved, the more general conclusion is that the imaging performance can be tuned as required by

Organic scintillators with pulse shape discrimination for detection of radiation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Mabe, Andrew; Carman, M. Leslie; Glenn, Andrew M.; Zaitseva, Natalia P.; Payne, Stephen A.

2016-09-01

The detection of neutrons in the presence of gamma-ray fields has important applications in the fields of nuclear physics, homeland security, and medical imaging. Organic scintillators provide several attractive qualities as neutron detection materials including low cost, fast response times, ease of scaling, and the ability to implement pulse shape discrimination (PSD) to discriminate between neutrons and gamma-rays. This talk will focus on amorphous organic scintillators both in plastic form and small-molecule organic glass form. The first section of this talk will describe recent advances and improvements in the performance of PSD-capable plastic scintillators. The primary advances described in regard to modification of the polymer matrix, evaluation of new scintillating dyes, improved fabrication conditions, and implementation of additives which impart superior performance and mechanical properties to PSD-capable plastics as compared to commercially-available plastics and performance comparable to PSD-capable liquids. The second section of this talk will focus on a class of small-molecule organic scintillators based on modified indoles and oligophenylenes which form amorphous glasses as PSD-capable neutron scintillation materials. Though indoles and oligophenylenes have been known for many decades, their PSD properties have not been investigated and their scintillation properties only scantily investigated. Well-developed synthetic methodologies have permitted the synthesis of a library of structural analogs of these compounds as well as the investigation of their scintillation properties. The emission wavelengths of many indoles are in the sensitive region of common photomultiplier tubes, making them appropriate to be used as scintillators in either pure or doped form. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. This work has been supported by the U

Dynamic 3D measurement of modulated radiotherapy: a scintillator-based approach

NASA Astrophysics Data System (ADS)

Archambault, Louis; Rilling, Madison; Roy-Pomerleau, Xavier; Thibault, Simon

2017-05-01

With the rise of high-conformity dynamic radiotherapy, such as volumetric modulated arc therapy and robotic radiosurgery, the temporal dimension of dose measurement is becoming increasingly important. It must be possible to tell both ‘where’ and ‘when’ a discrepancy occurs between the plan and its delivery. A 3D scintillation-based dosimetry system could be ideal for such a thorough, end-to-end verification; however, the challenge lies in retrieving the volumetric information of the light-emitting volume. This paper discusses the motivation, from an optics point of view, of using the images acquired with a plenoptic camera, or light field imager, of an irradiated plastic scintillator volume to reconstruct the delivered 3D dose distribution. Current work focuses on the optimization of the optical design as well as the data processing that is involved in the ongoing development of a clinically viable, second generation dosimetry system.

High-symmetry organic scintillator systems

DOEpatents

Feng, Patrick L.

2018-02-06

An ionizing radiation detector or scintillator system includes a scintillating material comprising an organic crystalline compound selected to generate photons in response to the passage of ionizing radiation. The organic compound has a crystalline symmetry of higher order than monoclinic, for example an orthorhombic, trigonal, tetragonal, hexagonal, or cubic symmetry. A photodetector is optically coupled to the scintillating material, and configured to generate electronic signals having pulse shapes based on the photons generated in the scintillating material. A discriminator is coupled to the photon detector, and configured to discriminate between neutrons and gamma rays in the ionizing radiation based on the pulse shapes of the output signals.

High-symmetry organic scintillator systems

DOEpatents

Feng, Patrick L.

2017-07-18

An ionizing radiation detector or scintillator system includes a scintillating material comprising an organic crystalline compound selected to generate photons in response to the passage of ionizing radiation. The organic compound has a crystalline symmetry of higher order than monoclinic, for example an orthorhombic, trigonal, tetragonal, hexagonal, or cubic symmetry. A photodetector is optically coupled to the scintillating material, and configured to generate electronic signals having pulse shapes based on the photons generated in the scintillating material. A discriminator is coupled to the photon detector, and configured to discriminate between neutrons and gamma rays in the ionizing radiation based on the pulse shapes of the output signals.

High-symmetry organic scintillator systems

DOEpatents

Feng, Patrick L.

2017-06-14

An ionizing radiation detector or scintillator system includes a scintillating material comprising an organic crystalline compound selected to generate photons in response to the passage of ionizing radiation. The organic compound has a crystalline symmetry of higher order than monoclinic, for example an orthorhombic, trigonal, tetragonal, hexagonal, or cubic symmetry. A photodetector is optically coupled to the scintillating material, and configured to generate electronic signals having pulse shapes based on the photons generated in the scintillating material. A discriminator is coupled to the photon detector, and configured to discriminate between neutrons and gamma rays in the ionizing radiation based on the pulse shapes of the output signals.

High-symmetry organic scintillator systems

DOEpatents

Feng, Patrick L.

2017-09-05

An ionizing radiation detector or scintillator system includes a scintillating material comprising an organic crystalline compound selected to generate photons in response to the passage of ionizing radiation. The organic compound has a crystalline symmetry of higher order than monoclinic, for example an orthorhombic, trigonal, tetragonal, hexagonal, or cubic symmetry. A photodetector is optically coupled to the scintillating material, and configured to generate electronic signals having pulse shapes based on the photons generated in the scintillating material. A discriminator is coupled to the photon detector, and configured to discriminate between neutrons and gamma rays in the ionizing radiation based on the pulse shapes of the output signals.

Temperature dependence of plastic scintillators

NASA Astrophysics Data System (ADS)

Peralta, L.

2018-03-01

Plastic scintillator detectors have been studied as dosimeters, since they provide a cost-effective alternative to conventional ionization chambers. Several articles have reported undesired response dependencies on beam energy and temperature, which provides the motivation to determine appropriate correction factors. In this work, we studied the light yield temperature dependency of four plastic scintillators, BCF-10, BCF-60, BC-404, RP-200A and two clear fibers, BCF-98 and SK-80. Measurements were made using a 50 kVp X-ray beam to produce the scintillation and/or radioluminescence signal. The 0 to 40 °C temperature range was scanned for each scintillator, and temperature coefficients were obtained.

Neutron position-sensitive scintillation detector

DOEpatents

Strauss, Michael G.; Brenner, Raul

1984-01-01

A device is provided for mapping one- and two-dimensional distributions of neutron-positions in a scintillation detector. The device consists of a lithium glass scintillator coupled by an air gap and a light coupler to an array of photomultipliers. The air gap concentrates light flashes from the scintillator, whereas the light coupler disperses this concentrated light to a predetermined fraction of the photomultiplier tube array.

Depth-of-interaction estimates in pixelated scintillator sensors using Monte Carlo techniques

NASA Astrophysics Data System (ADS)

Sharma, Diksha; Sze, Christina; Bhandari, Harish; Nagarkar, Vivek; Badano, Aldo

2017-01-01

Image quality in thick scintillator detectors can be improved by minimizing parallax errors through depth-of-interaction (DOI) estimation. A novel sensor for low-energy single photon imaging having a thick, transparent, crystalline pixelated micro-columnar CsI:Tl scintillator structure has been described, with possible future application in small-animal single photon emission computed tomography (SPECT) imaging when using thicker structures under development. In order to understand the fundamental limits of this new structure, we introduce cartesianDETECT2, an open-source optical transport package that uses Monte Carlo methods to obtain estimates of DOI for improving spatial resolution of nuclear imaging applications. Optical photon paths are calculated as a function of varying simulation parameters such as columnar surface roughness, bulk, and top-surface absorption. We use scanning electron microscope images to estimate appropriate surface roughness coefficients. Simulation results are analyzed to model and establish patterns between DOI and photon scattering. The effect of varying starting locations of optical photons on the spatial response is studied. Bulk and top-surface absorption fractions were varied to investigate their effect on spatial response as a function of DOI. We investigated the accuracy of our DOI estimation model for a particular screen with various training and testing sets, and for all cases the percent error between the estimated and actual DOI over the majority of the detector thickness was ±5% with a maximum error of up to ±10% at deeper DOIs. In addition, we found that cartesianDETECT2 is computationally five times more efficient than MANTIS. Findings indicate that DOI estimates can be extracted from a double-Gaussian model of the detector response. We observed that our model predicts DOI in pixelated scintillator detectors reasonably well.

A Review of Ionospheric Scintillation Models.

PubMed

Priyadarshi, S

This is a general review of the existing climatological models of ionospheric radio scintillation for high and equatorial latitudes. Trans-ionospheric communication of radio waves from transmitter to user is affected by the ionosphere which is highly variable and dynamic in both time and space. Scintillation is the term given to irregular amplitude and phase fluctuations of the received signals and related to the electron density irregularities in the ionosphere. Key sources of ionospheric irregularities are plasma instabilities; every irregularities model is based on the theory of radio wave propagation in random media. It is important to understand scintillation phenomena and the approach of different theories. Therefore, we have briefly discussed the theories that are used to interpret ionospheric scintillation data. The global morphology of ionospheric scintillation is also discussed briefly. The most important (in our opinion) analytical and physical models of scintillation are reviewed here.

Segmented scintillation antineutrino detector

DOEpatents

Reyna, David

2017-05-09

The various technologies presented herein relate to incorporating a wavelength-shifting material in a scintillator to facilitate absorption of a first electromagnetic particle (e.g., a first photon) having a first wavelength and subsequent generation and emission of a second electromagnetic particle (e.g., a second photon) having a second wavelength. The second electromagnetic particle can be emitted isotropically, with a high probability that the direction of emission of the second electromagnetic particle is disparate to the direction of travel of the first electromagnetic particle (and according angle of incidence). Isotropic emission of the second electromagnetic particle enables the second electromagnetic particle to be retained in the scintillator owing to internal reflection. Accordingly, longer length scintillators can be constructed, and accordingly, the scintillator array has a greater area (and volume) over which to detect electromagnetic particles (e.g., antineutrinos) being emitted from a nuclear reaction.

Divalent europium doped and un-doped calcium iodide scintillators: Scintillator characterization and single crystal growth

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

Boatner, L. A.; Ramey, J. O.; Kolopus, J. A.

2015-02-21

Initially, the alkaline-earth scintillator, CaI 2:Eu 2+, was discovered around 1964 by Hofstadter, Odell, and Schmidt. Serious practical problems quickly arose, however, that were associated with the growth of large monolithic single crystals of this material due to its lamellar, mica-like structure. As a result of its theoretically higher light yield, CaI 2:Eu 2+ has the potential to exceed the excellent scintillation performance of SrI 2:Eu 2+. In fact, theoretical predictions for the light yield of CaI2:Eu 2+ scintillators suggested that an energy resolution approaching 2% at 662 keV could be achievable. Like the early SrI 2:Eu 2+ scintillator, themore » performance of CaI 2:Eu 2+ scintillators has traditionally suffered due, at least in part, to outdated materials synthesis, component stoichiometry/purity, and single-crystal-growth techniques. Based on our recent work on SrI 2:Eu 2+ scintillators in single-crystal form, we have developed new techniques that are applied here to CaI 2:Eu 2+ and pure CaI 2 with the goal of growing large un-cracked crystals and, potentially, realizing the theoretically predicted performance of the CaI 2:Eu 2+ form of this material. Calcium iodide does not adhere to modern glassy carbon Bridgman crucibles - so there should be no differential thermal-contraction-induced crystal/crucible stresses on cooling that would result in crystal cracking of the lamellar structure of CaI 2. Here we apply glassy carbon crucible Bridgman growth, high-purity growth-charge compounds, our molten salt processing/filtration technique, and extended vacuum-melt-pumping methods to the growth of both CaI 2:Eu 2+ and un-doped CaI 2. Moreover, large scintillating single crystals were obtained, and detailed characterization studies of the scintillation properties of CaI 2:Eu 2+ and pure CaI 2 single crystals are presented that include studies of the effects of plastic deformation of the crystals on the scintillator performance.« less

Real-time neutron imaging of gas turbines

NASA Astrophysics Data System (ADS)

Stewart, P. A. E.

1987-06-01

The current status of real-time neutron radiography imaging is briefly reviewed, and results of tests carried out on cold neutron sources are reported. In particular, attention is given to demonstrations of neutron radiography on a running gas turbine engine. The future role of real-time neutron imaging in engineering diagnostics is briefly discussed.

Dual-energy micro-CT with a dual-layer, dual-color, single-crystal scintillator.

PubMed

Maier, Daniel Simon; Schock, Jonathan; Pfeiffer, Franz

2017-03-20

A wide range of X-ray imaging applications demand micrometer spatial resolution. In material science and biology especially, there is a great interest in material determination and material separation methods. Here we present a new detector design that allows the recording of a low- and a high-energy radiography image simultaneously with micrometer spatial resolution. The detector system is composed of a layered scintillator stack, two CCDs and an optical system to image the scintillator responses onto the CCDs. We used the detector system with a standard laboratory microfocus X-ray tube to prove the working principle of the system and derive important design characteristics. With the recorded and registered dual-energy data set, the material separation and determination could be shown at an X-ray tube peak energy of up to 160 keV with a spatial resolution of 12 μm. The detector design shows a great potential for further development and a wide range of possible applications.

PREFACE: Applications of Novel Scintillators for Research and Industry (ANSRI 2015)

NASA Astrophysics Data System (ADS)

Roberts, O. J.

2015-06-01

Scintillator detectors are used widely in the field of γ- and X-ray spectroscopy, particularly in the mid 1900s when the invention of NaI(Tl) by nobel laureate Robert Hofstadter in 1948, spurred the creation of new scintillator materials. In the development of such new scintillators, important characteristics such as its intrinsic efficiency, position sensitivity, robustness, energy and timing response, light output, etc, need to be addressed. To date, these requirements cannot be met by a single type of scintillator alone and therefore the development of an ''ideal'' scintillator remains the holy grail of nuclear instrumentation. Consequently, the last two decades have seen significant progress in the development of scintillator crystals, driven largely by technological advances. Conventional inorganic scintillators such as NaI(Tl) and BGO are now being replaced with better, novel organic, inorganic, ceramic and plastic scintillators offering a wider variety of options for many applications. The workshop on the Applications of Novel Scintillators in Research and Industry was held at University College Dublin in January 2015 and covered a wide range of topics that characterise modern advances in the field of scintillator technology. This set of proceedings covers areas including the growth, production and characterisation of such contemporary scintillators, along with their applications in various fields, such as; Medical Imaging; Defence/Security; Astrophysics; and Nuclear/Particle Physics. We would like to thank all those who presented their recent results on their research at the workshop. These proceedings atest to the excitement and interest in such a broad field, that pervades the pursuit of the development of novel materials for future applications. We would also like to thank Professor Luigi Piro, for giving an interesting public talk during the conference, and to the Institute of Physics Ireland Group for supporting the event. We thank ORTEC for

Neutron crosstalk between liquid scintillators

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

Verbeke, J. M.; Prasad, M. K.; Snyderman, N. J.

2015-05-01

We propose a method to quantify the fractions of neutrons scattering between liquid scintillators. Using a spontaneous fission source, this method can be utilized to quickly characterize an array of liquid scintillators in terms of crosstalk. The point model theory due to Feynman is corrected to account for these multiple scatterings. Using spectral information measured by the liquid scintillators, fractions of multiple scattering can be estimated, and mass reconstruction of fissile materials under investigation can be improved. Monte Carlo simulations of mono-energetic neutron sources were performed to estimate neutron crosstalk. A californium source in an array of liquid scintillators wasmore » modeled to illustrate the improvement of the mass reconstruction.« less

High-symmetry organic scintillator systems

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

Feng, Patrick L.

An ionizing radiation detector or scintillator system includes a scintillating material comprising an organic crystalline compound selected to generate photons in response to the passage of ionizing radiation. The organic compound has a crystalline symmetry of higher order than monoclinic, for example an orthorhombic, trigonal, tetragonal, hexagonal, or cubic symmetry. A photodetector is optically coupled to the scintillating material, and configured to generate electronic signals having pulse shapes based on the photons generated in the scintillating material. A discriminator is coupled to the photon detector, and configured to discriminate between neutrons and gamma rays in the ionizing radiation based onmore » the pulse shapes of the output signals.« less

Fission gas bubble identification using MATLAB's image processing toolbox

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

Collette, R.

Automated image processing routines have the potential to aid in the fuel performance evaluation process by eliminating bias in human judgment that may vary from person-to-person or sample-to-sample. This study presents several MATLAB based image analysis routines designed for fission gas void identification in post-irradiation examination of uranium molybdenum (U–Mo) monolithic-type plate fuels. Frequency domain filtration, enlisted as a pre-processing technique, can eliminate artifacts from the image without compromising the critical features of interest. This process is coupled with a bilateral filter, an edge-preserving noise removal technique aimed at preparing the image for optimal segmentation. Adaptive thresholding proved to bemore » the most consistent gray-level feature segmentation technique for U–Mo fuel microstructures. The Sauvola adaptive threshold technique segments the image based on histogram weighting factors in stable contrast regions and local statistics in variable contrast regions. Once all processing is complete, the algorithm outputs the total fission gas void count, the mean void size, and the average porosity. The final results demonstrate an ability to extract fission gas void morphological data faster, more consistently, and at least as accurately as manual segmentation methods. - Highlights: •Automated image processing can aid in the fuel qualification process. •Routines are developed to characterize fission gas bubbles in irradiated U–Mo fuel. •Frequency domain filtration effectively eliminates FIB curtaining artifacts. •Adaptive thresholding proved to be the most accurate segmentation method. •The techniques established are ready to be applied to large scale data extraction testing.« less

Probing the regional distribution of pulmonary gas exchange through single-breath gas- and dissolved-phase 129Xe MR imaging.

PubMed

Kaushik, S Sivaram; Freeman, Matthew S; Cleveland, Zackary I; Davies, John; Stiles, Jane; Virgincar, Rohan S; Robertson, Scott H; He, Mu; Kelly, Kevin T; Foster, W Michael; McAdams, H Page; Driehuys, Bastiaan

2013-09-01

Although some central aspects of pulmonary function (ventilation and perfusion) are known to be heterogeneous, the distribution of diffusive gas exchange remains poorly characterized. A solution is offered by hyperpolarized 129Xe magnetic resonance (MR) imaging, because this gas can be separately detected in the lung's air spaces and dissolved in its tissues. Early dissolved-phase 129Xe images exhibited intensity gradients that favored the dependent lung. To quantitatively corroborate this finding, we developed an interleaved, three-dimensional radial sequence to image the gaseous and dissolved 129Xe distributions in the same breath. These images were normalized and divided to calculate "129Xe gas-transfer" maps. We hypothesized that, for healthy volunteers, 129Xe gas-transfer maps would retain the previously observed posture-dependent gradients. This was tested in nine subjects: when the subjects were supine, 129Xe gas transfer exhibited a posterior-anterior gradient of -2.00 ± 0.74%/cm; when the subjects were prone, the gradient reversed to 1.94 ± 1.14%/cm (P < 0.001). The 129Xe gas-transfer maps also exhibited significant heterogeneity, as measured by the coefficient of variation, that correlated with subject total lung capacity (r = 0.77, P = 0.015). Gas-transfer intensity varied nonmonotonically with slice position and increased in slices proximal to the main pulmonary arteries. Despite substantial heterogeneity, the mean gas transfer for all subjects was 1.00 ± 0.01 while supine and 1.01 ± 0.01 while prone (P = 0.25), indicating good "matching" between gas- and dissolved-phase distributions. This study demonstrates that single-breath gas- and dissolved-phase 129Xe MR imaging yields 129Xe gas-transfer maps that are sensitive to altered gas exchange caused by differences in lung inflation and posture.

IR gas cloud imaging in oil and gas applications: immunity to false stimuli

NASA Astrophysics Data System (ADS)

Naranjo, Edward; Baliga, Shakar; Park, John; Bernascolle, Philippe

2011-05-01

Fixed gas detection equipment for the petroleum industries is no ordinary equipment. It is designed for continued unattended surveillance in harsh environments. The equipment must be reliable and require limited field maintenance. An additional requirement is a high resistance to false alarms and interferences, which can potentially reduce the detector's efficacy and the level of protection provided. In recent years, several manufactures of IR imaging devices have launched commercial models that are applicable to a wide range of chemical species and suitable for industrial use. These cameras are rugged and sufficiently sensitive to detect low concentrations of combustible and toxic gases. Nonetheless, as users become acquainted with these imaging systems, questions of resilience to solar and flame radiation and other IR sources, interferences by fog or steam, have begun to emerge. These questions, in fact, reflect similar concerns as those raised with open path IR gas detectors when they first appeared in the market over 20 years ago. This paper examines an IR gas imager's performance when exposed to several false alarm sources. Gas detection sensitivity in the presence of false stimuli and response and recovery times under an uncontrolled outdoor environment were measured. The results show the specific model tested is reasonably immune to false alarms, while response times were unaffected by the presence of these sources.

High-sensitivity gas-mapping 3D imager and method of operation

DOEpatents

Kreitinger, Aaron; Thorpe, Michael

2018-05-15

Measurement apparatuses and methods are disclosed for generating high-precision and -accuracy gas concentration maps that can be overlaid with 3D topographic images by rapidly scanning one or several modulated laser beams with a spatially-encoded transmitter over a scene to build-up imagery. Independent measurements of the topographic target distance and path-integrated gas concentration are combined to yield a map of the path-averaged concentration between the sensor and each point in the image. This type of image is particularly useful for finding localized regions of elevated (or anomalous) gas concentration making it ideal for large-area leak detection and quantification applications including: oil and gas pipeline monitoring, chemical processing facility monitoring, and environmental monitoring.

Novel Scintillating Materials Based on Phenyl-Polysiloxane for Neutron Detection and Monitoring

NASA Astrophysics Data System (ADS)

Degerlier, M.; Carturan, S.; Gramegna, F.; Marchi, T.; Palma, M. Dalla; Cinausero, M.; Maggioni, G.; Quaranta, A.; Collazuol, G.; Bermudez, J.

Neutron detectors are extensively used at many nuclear research facilities across Europe. Their application range covers many topics in basic and applied nuclear research: in nuclear structure and reaction dynamics (reaction reconstruction and decay studies); in nuclear astrophysics (neutron emission probabilities); in nuclear technology (nuclear data measurements and in-core/off-core monitors); in nuclear medicine (radiation monitors, dosimeters); in materials science (neutron imaging techniques); in homeland security applications (fissile materials investigation and cargo inspection). Liquid scintillators, widely used at present, have however some drawbacks given by toxicity, flammability, volatility and sensitivity to oxygen that limit their duration and quality. Even plastic scintillators are not satisfactory because they have low radiation hardness and low thermal stability. Moreover organic solvents may affect their optical properties due to crazing. In order to overcome these problems, phenyl-polysiloxane based scintillators have been recently developed at Legnaro National Laboratory. This new solution showed very good chemical and thermal stability and high radiation hardness. The results on the different samples performance will be presented, paying special attention to a characterization comparison between synthesized phenyl containing polysiloxane resins where a Pt catalyst has been used and a scintillating material obtained by condensation reaction, where tin based compounds are used as catalysts. Different structural arrangements as a result of different substituents on the main chain have been investigated by High Resolution X-Ray Diffraction, while the effect of improved optical transmittance on the scintillation yield has been elucidated by a combination of excitation/fluorescence measurements and scintillation yield under exposure to alpha and γ-rays.

Note: thermal imaging enhancement algorithm for gas turbine aerothermal characterization.

PubMed

Beer, S K; Lawson, S A

2013-08-01

An algorithm was developed to convert radiation intensity images acquired using a black and white CCD camera to thermal images without requiring knowledge of incident background radiation. This unique infrared (IR) thermography method was developed to determine aerothermal characteristics of advanced cooling concepts for gas turbine cooling application. Compared to IR imaging systems traditionally used for gas turbine temperature monitoring, the system developed for the current study is relatively inexpensive and does not require calibration with surface mounted thermocouples.

Plastic scintillator enhancement through Quantum Dot

NASA Astrophysics Data System (ADS)

Tam, Alan; Boyraz, Ozdal; Nilsson, Mikael

2017-08-01

Plastic scintillators such as Polyvinyl Toluene (PVT) are used for radiation detection but due to their poor performance they are not widely implemented. In order to circumnavigate this, dopants are added to enhance scintillation by energy transfer otherwise lost through non-radiative processes. In this work, we exploit the effects of energy transfer through the use of short wavelength emission Cadmium Sulfide Quantum Dots (QD) as the transfer stimulant. Scintillation enhancement was observed as Cadmium Sulfide QD with scintillating dyes are embedded in PVT polymer matrix for beta and gamma radiation. Energy transfer was observed between Quantum Dots, scintillating dye, and the host polymer. Different concentrations of QD and 2,5-diphenyloxazole (PPO) dye are investigated to characterize the energy transfer.

Direct Imaging of Shale Gas Leaks Using Passive Thermal Infrared Hyperspectral Imaging

NASA Astrophysics Data System (ADS)

Marcotte, F.; Chamberland, M.; Morton, V.; Gagnon, M. A.

2017-12-01

Natural gas is an energy resource in great demand worldwide. There are many types of gas fields including shale formations which are common especially in the St-Lawrence Valley (Qc). Regardless of its origin, methane (CH4) is the major component of natural gas. Methane gas is odorless, colorless and highly flammable. It is also an important greenhouse gas. Therefore, dealing efficiently with methane emanations and/or leaks is an important and challenging issue for both safety and environmental considerations. In this regard, passive remote sensing represents an interesting approach since it allows characterization of large areas from a safe location. The high propensity of methane contributing to global warming is mainly because it is a highly infrared-active molecule. For this reason, thermal infrared remote sensing represents one of the best approaches for methane investigations. In order to illustrate the potential of passive thermal infrared hyperspectral imaging for research on natural gas, imaging was carried out on a shale gas leak that unexpectedly happen during a geological survey near Hospital Enfant-Jésus (Québec City) in December 2014. Methane was selectively identified in the scene by its unique infrared signature. The estimated gas column density near the leak source was on the order of 65 000 ppm×m. It was estimated that the methane content in the shale gas is on the order of 6-7 %, which is in good agreement with previous geological surveys carried out in this area. Such leaks represent a very serious situation because such a methane concentration lies within the methane lower/upper explosion limits (LEL-UEL, 5-15 %). The results show how this novel technique could be used for research work dealing with methane gas.

Ionospheric Scintillation Activity Over Ilorin, Nigeria

NASA Astrophysics Data System (ADS)

Oladipo, O. A.; Adeniyi, J. O.; Doherty, P. H.; Radicella, S. M.; Adimula, I. A.; Olawepo, A. O.

2018-02-01

Scintillation of radio waves in the L-band frequency is a regular occurrence at the equatorial and auroral regions at night most especially during high solar activity periods. Scintillation is caused by plasma density irregularities, and this could cause loss of lock of Global Navigation Satellite System (GNSS) signals leading to impairment of the applications that rely on this system. A study on the occurrence of scintillation activity over Ilorin (latitude = 8.48°N, longitude = 4.67°W, and geomagnetic latitude = 1.89°S), Nigeria was done using S4 index data from NovAtel GPStation-2 receiver (2009-2012) and NovAtel GPStation-6 receiver (August 2013 to December 2016) which are both located at this station. The solar maximum period of the solar cycle 24 is located well within the period of this investigation; hence, this study provides opportunity to see the occurrence pattern of scintillation during different seasons as well as the pattern from low solar activity to solar maximum. The results obtained showed that scintillation occurs between 21:00 LT and 04:00 LT at the peak of the occurrence in 2014. The time window of occurrence decreases with decrease in solar activity. Similarly, scintillation activity was observed to be more regular during high solar activity and it has two peaks of occurrence in March and October. A solar activity trend was observed in scintillation occurrence; scintillation activity increases with increase in the level of solar activity.

Compensated gadolinium-loaded plastic scintillators for thermal neutron detection (and counting)

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

Dumazert, Jonathan; Coulon, Romain; Bertrand, Guillaume H. V.

2015-07-01

Plastic scintillator loading with gadolinium-rich organometallic complexes shows a high potential for the deployment of efficient and cost-effective neutron detectors. Due to the low-energy photon and electron signature of thermal neutron capture by gadolinium-155 and gadolinium-157, alternative treatment to Pulse Shape Discrimination has to be proposed in order to display a trustable count rate. This paper discloses the principle of a compensation method applied to a two-scintillator system: a detection scintillator interacts with photon radiation and is loaded with gadolinium organometallic compound to become a thermal neutron absorber, while a non-gadolinium loaded compensation scintillator solely interacts with the photon partmore » of the incident radiation. Posterior to the nonlinear smoothing of the counting signals, a hypothesis test determines whether the resulting count rate after photon response compensation falls into statistical fluctuations or provides a robust image of a neutron activity. A laboratory prototype is tested under both photon and neutron irradiations, allowing us to investigate the performance of the overall compensation system in terms of neutron detection, especially with regards to a commercial helium-3 counter. The study reveals satisfactory results in terms of sensitivity and orientates future investigation toward promising axes. (authors)« less

Tagging radon daughters in low-energy scintillation detectors

NASA Astrophysics Data System (ADS)

McCarty, Kevin B.

2011-12-01

One problematic source of background in scintillator-based low-energy solar neutrino experiments such as Borexino is the presence of radon gas and its daughters. The mean lifetime of the α-emitter 214Po in the radon chain is sufficiently short, 0.24 ms, that its decay, together with that immediately preceding of 214Bi, is easily recognized as a “coincidence event.” This fact, combined with the capability of α/β pulse-shape discrimination, makes it possible to tag decays of 222Rn and its first four daughters via a likelihood-based method.

High-efficiency organic glass scintillators

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

Feng, Patrick L.; Carlson, Joseph S.

A new family of neutron/gamma discriminating scintillators is disclosed that comprises stable organic glasses that may be melt-cast into transparent monoliths. These materials have been shown to provide light yields greater than solution-grown trans-stilbene crystals and efficient PSD capabilities when combined with 0.01 to 0.05% by weight of the total composition of a wavelength-shifting fluorophore. Photoluminescence measurements reveal fluorescence quantum yields that are 2 to 5 times greater than conventional plastic or liquid scintillator matrices, which accounts for the superior light yield of these glasses. The unique combination of high scintillation light-yields, efficient neutron/gamma PSD, and straightforward scale-up via melt-castingmore » distinguishes the developed organic glasses from existing scintillators.« less

Scintillation properties of selected oxide monocrystals activated with Ce and Pr

NASA Astrophysics Data System (ADS)

Wojtowicz, Andrzej J.; Drozdowski, Winicjusz; Wisniewski, Dariusz; Lefaucheur, Jean-Luc; Galazka, Zbigniew; Gou, Zhenhui; Lukasiewicz, Tadeusz; Kisielewski, Jaroslaw

2006-01-01

In the last 10-15 years there has been a significant effort toward development of new, more efficient and faster materials for detection of ionizing radiation. A growing demand for better scintillator crystals for detection of 511 keV gamma particles has been due mostly to recent advances in modern imaging systems employing positron emitting radionuclides for medical diagnostics in neurology, oncology and cardiology. While older imaging systems were almost exclusively based on BGO and NaI:Tl crystals the new systems, e.g., ECAT Accel, developed by Siemens/CTI, are based on recently discovered and developed LSO (Lu 2SiO 5:Ce, Ce-activated lutetium oxyorthosilicate) crystals. Interestingly, despite very good properties of LSO, there still is a strong drive toward development of new scintillator crystals that would show even better performance and characteristics. In this presentation we shall review spectroscopic and scintillator characterization of new complex oxide crystals, namely LSO, LYSO, YAG, LuAP (LuAlO 3, lutetium aluminate perovskite) and LuYAP activated with Ce and Pr. The LSO:Ce crystals have been grown by CTI Inc (USA), LYSO:Ce, LuAP:Ce and LuYAP:Ce crystals have been grown by Photonic Materials Ltd., Scotland (PML is the only company providing large LuAP:Ce crystals on a commercial scale), while YAG:Pr and LuAP:Pr crystals have been grown by Institute of Electronic Materials Technology (Poland). All these crystals have been characterized at Institute of Physics, N. Copernicus University (Poland). We will review and compare results of measurements of radioluminescence, VUV spectroscopy, scintillation light yields, scintillation time profiles and low temperature thermoluminescence performed on these crystals. We will demonstrate that all experiments clearly indicate that there is a significant room for improvement of LuAP, LuYAP and YAG. While both Ce-activated LSO and LYSO perform very well, we also note that LuYAP:Ce, LuAP:Ce and YAG:Pr offer some

Radiation imaging with optically read out GEM-based detectors

NASA Astrophysics Data System (ADS)

Brunbauer, F. M.; Lupberger, M.; Oliveri, E.; Resnati, F.; Ropelewski, L.; Streli, C.; Thuiner, P.; van Stenis, M.

2018-02-01

Modern imaging sensors allow for high granularity optical readout of radiation detectors such as MicroPattern Gaseous Detectors (MPGDs). Taking advantage of the high signal amplification factors achievable by MPGD technologies such as Gaseous Electron Multipliers (GEMs), highly sensitive detectors can be realised and employing gas mixtures with strong scintillation yield in the visible wavelength regime, optical readout of such detectors can provide high-resolution event representations. Applications from X-ray imaging to fluoroscopy and tomography profit from the good spatial resolution of optical readout and the possibility to obtain images without the need for extensive reconstruction. Sensitivity to low-energy X-rays and energy resolution permit energy resolved imaging and material distinction in X-ray fluorescence measurements. Additionally, the low material budget of gaseous detectors and the possibility to couple scintillation light to imaging sensors via fibres or mirrors makes optically read out GEMs an ideal candidate for beam monitoring detectors in high energy physics as well as radiotherapy. We present applications and achievements of optically read out GEM-based detectors including high spatial resolution imaging and X-ray fluorescence measurements as an alternative readout approach for MPGDs. A detector concept for low intensity applications such as X-ray crystallography, which maximises detection efficiency with a thick conversion region but mitigates parallax-induced broadening is presented and beam monitoring capabilities of optical readout are explored. Augmenting high resolution 2D projections of particle tracks obtained with optical readout with timing information from fast photon detectors or transparent anodes for charge readout, 3D reconstruction of particle trajectories can be performed and permits the realisation of optically read out time projection chambers. Combining readily available high performance imaging sensors with compatible

Nanophosphor composite scintillator with a liquid matrix

DOEpatents

McKigney, Edward Allen; Burrell, Anthony Keiran; Bennett, Bryan L.; Cooke, David Wayne; Ott, Kevin Curtis; Bacrania, Minesh Kantilal; Del Sesto, Rico Emilio; Gilbertson, Robert David; Muenchausen, Ross Edward; McCleskey, Thomas Mark

2010-03-16

An improved nanophosphor scintillator liquid comprises nanophosphor particles in a liquid matrix. The nanophosphor particles are optionally surface modified with an organic ligand. The surface modified nanophosphor particle is essentially surface charge neutral, thereby preventing agglomeration of the nanophosphor particles during dispersion in a liquid scintillator matrix. The improved nanophosphor scintillator liquid may be used in any conventional liquid scintillator application, including in a radiation detector.

Spacecraft Radio Scintillation and Solar System Exploration

NASA Technical Reports Server (NTRS)

Woo, Richard

1993-01-01

When a wave propagates through a turbulent medium, scattering by the random refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study. The observed scattering effects include amplitude or intensity scintillation, phase scintillation, angular broadening, and spectral broadening, among others. In this paper, I will refer to these scattering effects collectively as scintillation. Although the most familiar example is probably the twinkling of stars (light wave intensity scintillation by turbulence in the Earth's atmosphere), scintillation has been encountered and investigated in such diverse fields as ionospheric physics, oceanography, radio astronomy, and radio and optical communications. Ever since planetary spacecraft began exploring the solar system, scintillation has appeared during the propagation of spacecraft radio signals through planetary atmospheres, planetary ionospheres, and the solar wind. Early studies of these phenomena were motivated by the potential adverse effects on communications and navigation, and on experiments that use the radio link to conduct scientific investigations. Examples of the latter are radio occultation measurements (described below) of planetary atmospheres to deduce temperature profiles, and the search for gravitational waves. However,these concerns soon gave way to the emergence of spacecraft radio scintillation as a new scientific tool for exploring small-scale dynamics in planetary atmospheres and structure in the solar wind, complementing in situ and other remote sensing spacecraft measurements, as well as scintillation measurements using natural (celestial) radio sources. The purpose of this paper is to briefly describe and review the solar system spacecraft radio scintillation observations, to summarize the salient features of wave propagation analyses employed in interpreting them, to underscore the unique remote sensing capabilities and scientific relevance of

Deriving depth-dependent light escape efficiency and optical Swank factor from measured pulse height spectra of scintillators.

PubMed

Howansky, Adrian; Peng, Boyu; Lubinsky, Anthony R; Zhao, Wei

2017-03-01

Pulse height spectroscopy has been used by investigators to deduce the imaging properties of scintillators. Pulse height spectra (PHS) are used to compute the Swank factor, which describes the variation in scintillator light output per x-ray interaction. The spread in PHS measured below the K-edge is related to the optical component of the Swank factor, i.e., variations in light escape efficiency from different depths of x-ray interaction in the scintillator, denoted ε¯(z). Optimizing scintillators for medical imaging applications requires understanding of these optical properties, as they determine tradeoffs between parameters such as x-ray absorption, light yield, and spatial resolution. This work develops a model for PHS acquisition such that the effect of measurement uncertainty can be removed. This method allows ε¯(z) to be quantified on an absolute scale and permits more accurate estimation of the optical Swank factor of scintillators. The pulse height spectroscopy acquisition chain was modeled as a linear system of stochastic gain stages. Analytical expressions were derived for signal and noise propagation through the PHS chain, accounting for deterministic and stochastic aspects of x-ray absorption, scintillation, and light detection with a photomultiplier tube. The derived expressions were used to calculate PHS of thallium-doped cesium iodide (CsI) scintillators using parameters that were measured, calculated, or known from literature. PHS were measured at 25 and 32 keV of CsI samples designed with an optically reflective or absorptive backing, with or without a fiber-optic faceplate (FOP), and with thicknesses ranging from 150-1000 μm. Measured PHS were compared with calculated PHS, then light escape model parameters were varied until measured and modeled results reached agreement. Resulting estimates of ε¯(z) were used to calculate each scintillator's optical Swank factor. For scintillators of the same optical design, only minor differences in

Time correlated measurements using plastic scintillators with neutron-photon pulse shape discrimination

NASA Astrophysics Data System (ADS)

Richardson, Norman E., IV

Since the beginning of the nuclear age, there has been a strong demand for the development of efficient technologies for the detection of ionizing radiation. According to the United States' Department of Energy, the accurate assessment of fissile materials is essential in achieving the nonproliferation goals of enhancing safety and security of nuclear fuel cycle and nuclear energy facilities. Nuclear materials can be characterized by the measurement of prompt and delayed neutrons and gamma rays emitted in spontaneous or induced fission reactions and neutrons emitted in fission reactions are the distinctive signatures of nuclear materials. Today, the most widely used neutron detection technologies rely on thermal neutron capture reactions using a moderating material to cause the neutron to lose its energy prior to the detection event. This is necessary because as the fission event occurs, neutrons are emitted carrying high amounts of energy, typically on the order of mega electron volts (MeV). These energetic particles are classified as "fast" neutrons. For detecting the thermal neutrons, the Helium-3 (3He) gas-filled counters are arguably the most widely used technology of neutron detection. 3He counters have been the scientific standard for the nuclear engineering community for several decades, and have earned their place as a reliable technique for the detection of neutrons. However, 3He gas-filled counters have several disadvantages. First, gas-filled counters are not rigid and are sensitive to vibrations. Secondly, gas-filled counters are prone to the count rate limitations due to the physical processes of charge multiplication and transport in the gas medium in the electric field. Lastly, 3He gas-filled counters suffer from a supply shortage of the 3He isotope. As it is stated in [3], this shortage is created by the new demand for Helium-3 due to the deployment of neutron detectors at the borders after the 9/11 attack to help secure the nation against smuggled

LEO-ground scintillation measurements with the optical ground station Oberpfaffenhofen and SOTA/OPALS space terminals

NASA Astrophysics Data System (ADS)

Moll, Florian; Kolev, Dimitar; Abrahamson, Matthew; Schmidt, Christopher; Mata Calvo, Ramon; Fuchs, Christian

2016-10-01

The optical satellite-ground channel is turbulent and causes scintillation of the power received by a ground based telescope. Measurements are important to quantify the effect and evaluate common theory. A telescope with 40 cm primary mirror is used to measure the signals from the OPALS terminal on the International Space Station and the SOTA terminal on the SOCRATES satellite. The measurement instrument is a pupil camera from which images are recorded and intensity scintillation index, power scintillation index, probability density function of intensity and intensity correlation width are derived. A preliminary analysis of measurements from three satellite passed is performed, presented and discussed. The intensity scintillation index ranges from 0.25 to 0.03 within elevations of 26 to 66 deg. Power scintillation index varies from 0.08 to 0.006 and correlation width of intensity between 11 and 3 cm. The measurements can be used to estimate the fluctuation dynamics to be expected for a future operational ground receiver. The measurements are compared to model calculations based on the HV5/7-profile. Good agreement is observed to some part in the intensity scintillation index. Agreement is less for the power scintillation index and intensity correlation width. The reason seems to be a reduction of aperture averaging in some sections of the measurements due to increased speckle size. Finally, topics for future work are identified to improve the measurement analysis and deeper investigate the origin of the observed behavior.

Divalent fluoride doped cerium fluoride scintillator

DOEpatents

Anderson, David F.; Sparrow, Robert W.

1991-01-01

The use of divalent fluoride dopants in scintillator materials comprising cerium fluoride is disclosed. The preferred divalent fluoride dopants are calcium fluoride, strontium fluoride, and barium fluoride. The preferred amount of divalent fluoride dopant is less than about two percent by weight of the total scintillator. Cerium fluoride scintillator crystals grown with the addition of a divalent fluoride have exhibited better transmissions and higher light outputs than crystals grown without the addition of such dopants. These scintillators are useful in radiation detection and monitoring applications, and are particularly well suited for high-rate applications such as positron emission tomography (PET).

Preliminary investigations on the determination of three-dimensional dose distributions using scintillator blocks and optical tomography

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

Kroll, Florian; Karsch, Leonhard; Pawelke, Jörg

2013-08-15

Purpose: Clinical QA in teletherapy as well as the characterization of experimental radiation sources for future medical applications requires effective methods for measuring three-dimensional (3D) dose distributions generated in a water-equivalent medium. Current dosimeters based on ionization chambers, diodes, thermoluminescence detectors, radiochromic films, or polymer gels exhibit various drawbacks: High quality 3D dose determination is either very sophisticated and expensive or requires high amounts of effort and time for the preparation or read out. New detectors based on scintillator blocks in combination with optical tomography are studied, since they have the potential to facilitate the desired cost-effective, transportable, and long-termmore » stable dosimetry system that is able to determine 3D dose distributions with high spatial resolution in a short time.Methods: A portable detector prototype was set up based on a plastic scintillator block and four digital cameras. During irradiation the scintillator emits light, which is detected by the fixed cameras. The light distribution is then reconstructed by optical tomography, using maximum-likelihood expectation maximization. The result of the reconstruction approximates the 3D dose distribution. First performance tests of the prototype using laser light were carried out. Irradiation experiments were performed with ionizing radiation, i.e., bremsstrahlung (6 to 21 MV), electrons (6 to 21 MeV), and protons (68 MeV), provided by clinical and research accelerators.Results: Laser experiments show that the current imaging properties differ from the design specifications: The imaging scale of the optical systems is position dependent, ranging from 0.185 mm/pixel to 0.225 mm/pixel. Nevertheless, the developed dosimetry method is proven to be functional for electron and proton beams. Induced radiation doses of 50 mGy or more made 3D dose reconstructions possible. Taking the imaging properties into account

Preliminary investigations on the determination of three-dimensional dose distributions using scintillator blocks and optical tomography.

PubMed

Kroll, Florian; Pawelke, Jörg; Karsch, Leonhard

2013-08-01

Clinical QA in teletherapy as well as the characterization of experimental radiation sources for future medical applications requires effective methods for measuring three-dimensional (3D) dose distributions generated in a water-equivalent medium. Current dosimeters based on ionization chambers, diodes, thermoluminescence detectors, radiochromic films, or polymer gels exhibit various drawbacks: High quality 3D dose determination is either very sophisticated and expensive or requires high amounts of effort and time for the preparation or read out. New detectors based on scintillator blocks in combination with optical tomography are studied, since they have the potential to facilitate the desired cost-effective, transportable, and long-term stable dosimetry system that is able to determine 3D dose distributions with high spatial resolution in a short time. A portable detector prototype was set up based on a plastic scintillator block and four digital cameras. During irradiation the scintillator emits light, which is detected by the fixed cameras. The light distribution is then reconstructed by optical tomography, using maximum-likelihood expectation maximization. The result of the reconstruction approximates the 3D dose distribution. First performance tests of the prototype using laser light were carried out. Irradiation experiments were performed with ionizing radiation, i.e., bremsstrahlung (6 to 21 MV), electrons (6 to 21 MeV), and protons (68 MeV), provided by clinical and research accelerators. Laser experiments show that the current imaging properties differ from the design specifications: The imaging scale of the optical systems is position dependent, ranging from 0.185 mm/pixel to 0.225 mm/pixel. Nevertheless, the developed dosimetry method is proven to be functional for electron and proton beams. Induced radiation doses of 50 mGy or more made 3D dose reconstructions possible. Taking the imaging properties into account, determined dose profiles are in

Fission gas bubble identification using MATLAB's image processing toolbox

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

Collette, R.; King, J.; Keiser, Jr., D.

Automated image processing routines have the potential to aid in the fuel performance evaluation process by eliminating bias in human judgment that may vary from person-to-person or sample-to-sample. In addition, this study presents several MATLAB based image analysis routines designed for fission gas void identification in post-irradiation examination of uranium molybdenum (U–Mo) monolithic-type plate fuels. Frequency domain filtration, enlisted as a pre-processing technique, can eliminate artifacts from the image without compromising the critical features of interest. This process is coupled with a bilateral filter, an edge-preserving noise removal technique aimed at preparing the image for optimal segmentation. Adaptive thresholding provedmore » to be the most consistent gray-level feature segmentation technique for U–Mo fuel microstructures. The Sauvola adaptive threshold technique segments the image based on histogram weighting factors in stable contrast regions and local statistics in variable contrast regions. Once all processing is complete, the algorithm outputs the total fission gas void count, the mean void size, and the average porosity. The final results demonstrate an ability to extract fission gas void morphological data faster, more consistently, and at least as accurately as manual segmentation methods.« less

Fission gas bubble identification using MATLAB's image processing toolbox

DOE PAGES

Collette, R.; King, J.; Keiser, Jr., D.; ...

2016-06-08

Automated image processing routines have the potential to aid in the fuel performance evaluation process by eliminating bias in human judgment that may vary from person-to-person or sample-to-sample. In addition, this study presents several MATLAB based image analysis routines designed for fission gas void identification in post-irradiation examination of uranium molybdenum (U–Mo) monolithic-type plate fuels. Frequency domain filtration, enlisted as a pre-processing technique, can eliminate artifacts from the image without compromising the critical features of interest. This process is coupled with a bilateral filter, an edge-preserving noise removal technique aimed at preparing the image for optimal segmentation. Adaptive thresholding provedmore » to be the most consistent gray-level feature segmentation technique for U–Mo fuel microstructures. The Sauvola adaptive threshold technique segments the image based on histogram weighting factors in stable contrast regions and local statistics in variable contrast regions. Once all processing is complete, the algorithm outputs the total fission gas void count, the mean void size, and the average porosity. The final results demonstrate an ability to extract fission gas void morphological data faster, more consistently, and at least as accurately as manual segmentation methods.« less

Radiopure Metal-Loaded Liquid Scintillator

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

Rosero, Richard; Yeh, Minfang

2015-03-18

Metal-loaded liquid scintillator plays a key role in particle and nuclear physics experiments. The applications of metal ions in various neutrino experiments and the purification methods for different scintillator components are discussed in this paper.

Radiopure metal-loaded liquid scintillator

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

Rosero, Richard; Yeh, Minfang, E-mail: yeh@bnl.gov

2015-08-17

Metal-loaded liquid scintillator plays a key role in particle and nuclear physics experiments. The applications of metal ions in various neutrino experiments and the purification methods for different scintillator components are discussed in this paper.

Measurement of (222)Rn by absorption in plastic scintillators and alpha/beta pulse shape discrimination.

PubMed

Mitev, Krasimir K

2016-04-01

This work demonstrates that common plastic scintillators like BC-400, EJ-200 and SCSF-81 absorb radon and their scintillation pulse decay times are different for alpha- and beta-particles. This allows the application of pulse shape analysis for separation of the pulses of alpha- and beta-particles emitted by the absorbed radon and its progeny. It is shown that after pulse shape discrimination of beta-particles' pulses, the energy resolution of BC-400 and EJ-200 alpha spectra is sufficient to separate the peaks of (222)Rn, (218)Po and (214)Po and allows (222)Rn measurements that are unaffected by the presence of thoron ((220)Rn) in the environment. The alpha energy resolution of SCSF-81 in the experiments degrades due to imperfect collection of the light emitted inside the scintillating fibers. The experiments with plastic scintillation microspheres (PSM) confirm previous findings of other researchers that PSM have alpha-/beta-discrimination properties and show suitability for radon measurements. The diffusion length of radon in BC-400 and EJ-200 is determined. The pilot experiments show that the plastic scintillators are suitable for radon-in-soil-gas measurements. Overall, the results of this work suggest that it is possible to develop a new type of radon measurement instruments which employ absorption in plastic scintillators, pulse-shape discrimination and analysis of the alpha spectra. Such instruments can be very compact and can perform continuous, real-time radon measurements and thoron detection. They can find applications in various fields from radiation protection to earth sciences. Copyright © 2016 Elsevier Ltd. All rights reserved.

Metal-loaded organic scintillators for neutrino physics

DOE PAGES

Buck, Christian; Yeh, Minfang

2016-08-03

Organic liquid scintillators are used in many neutrino physics experiments of the past and present. In particular for low energy neutrinos when realtime and energy information are required, liquid scintillators have several advantages compared to other technologies. In many cases the organic liquid needs to be loaded with metal to enhance the neutrino signal over background events. Several metal loaded scintillators of the past suffered from chemical and optical instabilities, limiting the performance of these neutrino detectors. Different ways of metal loading are described in the article with a focus on recent techniques providing metal loaded scintillators that can bemore » used under stable conditions for many years even in ton scale experiments. Lastly, we review applications of metal loaded scintillators in neutrino experiments and compare the performance as well as the prospects of different scintillator types.« less

Methods for gas detection using stationary hyperspectral imaging sensors

DOEpatents

Conger, James L [San Ramon, CA; Henderson, John R [Castro Valley, CA

2012-04-24

According to one embodiment, a method comprises producing a first hyperspectral imaging (HSI) data cube of a location at a first time using data from a HSI sensor; producing a second HSI data cube of the same location at a second time using data from the HSI sensor; subtracting on a pixel-by-pixel basis the second HSI data cube from the first HSI data cube to produce a raw difference cube; calibrating the raw difference cube to produce a calibrated raw difference cube; selecting at least one desired spectral band based on a gas of interest; producing a detection image based on the at least one selected spectral band and the calibrated raw difference cube; examining the detection image to determine presence of the gas of interest; and outputting a result of the examination. Other methods, systems, and computer program products for detecting the presence of a gas are also described.

Scintillator high-gain avalanche rushing photoconductor active-matrix flat panel imager: Zero-spatial frequency x-ray imaging properties of the solid-state SHARP sensor structure

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

Wronski, M.; Zhao, W.; Tanioka, K.

Purpose: The authors are investigating the feasibility of a new type of solid-state x-ray imaging sensor with programmable avalanche gain: scintillator high-gain avalanche rushing photoconductor active matrix flat panel imager (SHARP-AMFPI). The purpose of the present work is to investigate the inherent x-ray detection properties of SHARP and demonstrate its wide dynamic range through programmable gain. Methods: A distributed resistive layer (DRL) was developed to maintain stable avalanche gain operation in a solid-state HARP. The signal and noise properties of the HARP-DRL for optical photon detection were investigated as a function of avalanche gain both theoretically and experimentally, and themore » results were compared with HARP tube (with electron beam readout) used in previous investigations of zero spatial frequency performance of SHARP. For this new investigation, a solid-state SHARP x-ray image sensor was formed by direct optical coupling of the HARP-DRL with a structured cesium iodide (CsI) scintillator. The x-ray sensitivity of this sensor was measured as a function of avalanche gain and the results were compared with the sensitivity of HARP-DRL measured optically. The dynamic range of HARP-DRL with variable avalanche gain was investigated for the entire exposure range encountered in radiography/fluoroscopy (R/F) applications. Results: The signal from HARP-DRL as a function of electric field showed stable avalanche gain, and the noise associated with the avalanche process agrees well with theory and previous measurements from a HARP tube. This result indicates that when coupled with CsI for x-ray detection, the additional noise associated with avalanche gain in HARP-DRL is negligible. The x-ray sensitivity measurements using the SHARP sensor produced identical avalanche gain dependence on electric field as the optical measurements with HARP-DRL. Adjusting the avalanche multiplication gain in HARP-DRL enabled a very wide dynamic range which

A comparative study via Monte Carlo simulation of new inorganic scintillator Cs2HfCl6 for applications in nuclear medicine, security and defense, and astrophysics

NASA Astrophysics Data System (ADS)

Chen, Henry; Raby, Paul

2016-09-01

Cs2HfCl6 (CHC) is one of the most promising recently discovered new inorganic single crystal scintillator that has high light output, non-hygroscopic, no self-activity, having energy resolution significantly better than NaI(Tl), even approaching that of LaBr3 yet can also potentially be at a much lower cost than LaBr3. This study attempts to use Monte Carlo simulation to examine the great potential offered by this new scintillator. CHC's detector performance is compared via simulation with that of 4 typical existing scintillators of the same size and same PMT readout. Two halide-scintillators: NaI(Tl) and LaBr3 and two oxide-scintillators: GSO and LSO were used in this simulation to compare their 122 keV and 511 keV gamma responses with that of CHC with both spectroscopy application and imaging applications in mind. Initial simulation results are very promising and consistent with reported experimental measurements. Beside detector energy resolution, image-quality measurement parameters commonly used to characterize imaging detectors as in nuclear medicine such as Light Response Function (LRF) which goes in parallel with spatial resolution and simulated position spectra will also be presented and discussed.

Comparing the response of PSD-capable plastic scintillator to standard liquid scintillator

NASA Astrophysics Data System (ADS)

Woolf, Richard S.; Hutcheson, Anthony L.; Gwon, Chul; Phlips, Bernard F.; Wulf, Eric A.

2015-06-01

This work discusses a test campaign to characterize the response of the recently developed plastic scintillator with pulse shape discrimination (PSD) capabilities (EJ-299-33). PSD is a property exhibited by certain types of scintillating material in which incident stimuli (fast neutrons or γ rays) can be separated by exploiting differences in the scintillation light pulse tail. Detector geometries used were: a 10 cm×10 cm×10 cm cube and a 10-cm diameter×10-cm long cylinder. EJ-301 and EJ-309 liquid scintillators with well-known responses were also tested. The work was conducted at the University of Massachusetts Lowell Van De Graaff accelerator. The facility accelerated protons on a thin Li target to yield quasi-monoenergetic neutrons from the 7Li(p,n)7Be reaction (Q-value: -1.644 MeV). Collimated fast neutrons were obtained by placing detectors behind a neutron spectrometer. Rotating the spectrometer, and thus changing the neutron energy, allowed us to achieve 0.5-3.2 MeV neutrons in 200-300 keV steps. Data were acquired through a flash analog-to-digital converter (ADC) capable of performing digital PSD measurements. By using the PSD technique to separate the neutron events from unwanted γ background, we constructed a pulse height spectrum at each energy. Obtaining a relationship of the relative light output versus energy allowed us to construct the response function for the EJ-299-33 and liquid scintillator. The EJ-299-33 response in terms of electron equivalent energy (Ee.e.) vs. proton equivalent energy (Ep.e.), how it compared with the standard xylene-based EJ-301 (or, NE-213/BC-501 A equivalent) and EJ-309 liquid scintillator response, and how the EJ-301 and EJ-309 compared, are presented. We find that the EJ-299-33 demonstrated a lower light output by up to 40% for <1.0 MeV neutrons; and ranging between a 5-35% reduction for 2.5-3.0 MeV neutrons compared to the EJ-301/309, depending on the scintillator and geometry. Monte Carlo modeling techniques were

Isotopic response with small scintillator based gamma-ray spectrometers

DOEpatents

Madden, Norman W [Sparks, NV; Goulding, Frederick S [Lafayette, CA; Asztalos, Stephen J [Oakland, CA

2012-01-24

The intrinsic background of a gamma ray spectrometer is significantly reduced by surrounding the scintillator with a second scintillator. This second (external) scintillator surrounds the first scintillator and has an opening of approximately the same diameter as the smaller central scintillator in the forward direction. The second scintillator is selected to have a higher atomic number, and thus has a larger probability for a Compton scattering interaction than within the inner region. Scattering events that are essentially simultaneous in coincidence to the first and second scintillators, from an electronics perspective, are precluded electronically from the data stream. Thus, only gamma-rays that are wholly contained in the smaller central scintillator are used for analytic purposes.

Ionosphere scintillations associated with features of equatorial ionosphere

NASA Technical Reports Server (NTRS)

Chandra, H.; Vats, H. O.; Sethia, G.; Deshpande, M. R.; Rastogi, R. G.; Sastri, J. H.; Murthy, B. S.

1979-01-01

Amplitude scintillations of radio beacons aboard the ATS-6 satellite on 40 MHz, 140 MHz and 360 MHz recorded during the ATS-6 phase II at an equatorial station Ootacamund (dip 4 deg N) and the ionograms at a nearby station Kodaikanal (dip 3.5 deg N) are examined for scintillation activity. Only sporadic E events, other than Es-q, Es-c or normal E are found to be associated with intense daytime scintillations. Scintillations are also observed during night Es conditions. The amplitude spread is associated with strong scintillations on all frequencies while frequency spread causes weaker scintillations and that mainly at 40 MHz.

Velocity of mist droplets and suspending gas imaged separately

NASA Astrophysics Data System (ADS)

Kuethe, Dean O.; McBride, Amber; Altobelli, Stephen A.

2012-03-01

Nuclear Magnetic Resonance Images (MRIs) of the velocity of water droplets and velocity of the suspending gas, hexafluoroethane, are presented for a vertical and horizontal mist pipe flow. In the vertical flow, the upward velocity of the droplets is clearly slower than the upward velocity of the gas. The average droplet size calculated from the average falling velocity in the upward flow is larger than the average droplet size of mist drawn from the top of the pipe measured with a multi-stage aerosol impactor. Vertical flow concentrates larger particles because they have a longer transit time through the pipe. In the horizontal flow there is a gravity-driven circulation with high-velocity mist in the lower portion of the pipe and low-velocity gas in the upper portion. MRI has the advantages that it can image both phases and that it is unperturbed by optical opacity. A drawback is that the droplet phase of mist is difficult to image because of low average spin density and because the signal from water coalesced on the pipe walls is high. To our knowledge these are the first NMR images of mist.

Scintillation Effects on Space Shuttle GPS Data

NASA Technical Reports Server (NTRS)

Goodman, John L.; Kramer, Leonard

2001-01-01

Irregularities in ionospheric electron density result in variation in amplitude and phase of Global Positioning System (GPS) signals, or scintillation. GPS receivers tracking scintillated signals may lose carrier phase or frequency lock in the case of phase sc intillation. Amplitude scintillation can cause "enhancement" or "fading" of GPS signals and result in loss of lock. Scintillation can occur over the equatorial and polar regions and is a function of location, time of day, season, and solar and geomagnetic activity. Mid latitude regions are affected only very rarely, resulting from highly disturbed auroral events. In the spring of 1998, due to increasing concern about scintillation of GPS signals during the upcoming solar maximum, the Space Shuttle Program began to assess the impact of scintillation on Collins Miniaturized Airborne GPS Receiver (MAGR) units that are to replace Tactical Air Control and Navigation (TACAN) units on the Space Shuttle orbiters. The Shuttle Program must determine if scintillation effects pose a threat to safety of flight and mission success or require procedural and flight rule changes. Flight controllers in Mission Control must understand scintillation effects on GPS to properly diagnose "off nominal" GPS receiver performance. GPS data from recent Space Shuttle missions indicate that the signals tracked by the Shuttle MAGR manifest scintillation. Scintillation is observed as anomalous noise in velocity measurements lasting for up to 20 minutes on Shuttle orbit passes and are not accounted for in the error budget of the MAGR accuracy parameters. These events are typically coincident with latitude and local time occurrence of previously identified equatorial spread F within about 20 degrees of the magnetic equator. The geographic and seasonal history of these events from ground-based observations and a simple theoretical model, which have potential for predicting events for operational purposes, are reviewed.

Scintillation Breakdowns in Chip Tantalum Capacitors

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander

2008-01-01

Scintillations in solid tantalum capacitors are momentarily local breakdowns terminated by a self-healing or conversion to a high-resistive state of the manganese oxide cathode. This conversion effectively caps the defective area of the tantalum pentoxide dielectric and prevents short-circuit failures. Typically, this type of breakdown has no immediate catastrophic consequences and is often considered as nuisance rather than a failure. Scintillation breakdowns likely do not affect failures of parts under surge current conditions, and so-called "proofing" of tantalum chip capacitors, which is a controllable exposure of the part after soldering to voltages slightly higher than the operating voltage to verify that possible scintillations are self-healed, has been shown to improve the quality of the parts. However, no in-depth studies of the effect of scintillations on reliability of tantalum capacitors have been performed so far. KEMET is using scintillation breakdown testing as a tool for assessing process improvements and to compare quality of different manufacturing lots. Nevertheless, the relationship between failures and scintillation breakdowns is not clear, and this test is not considered as suitable for lot acceptance testing. In this work, scintillation breakdowns in different military-graded and commercial tantalum capacitors were characterized and related to the rated voltages and to life test failures. A model for assessment of times to failure, based on distributions of breakdown voltages, and accelerating factors of life testing are discussed.

Deriving depth-dependent light escape efficiency and optical Swank factor from measured pulse height spectra of scintillators

PubMed Central

Howansky, Adrian; Peng, Boyu; Lubinsky, Anthony R.; Zhao, Wei

2017-01-01

Purpose Pulse height spectroscopy has been used by investigators to deduce the imaging properties of scintillators. Pulse height spectra (PHS) are used to compute the Swank factor, which describes the variation in scintillator light output per x-ray interaction. The spread in PHS measured below the K-edge is related to the optical component of the Swank factor, i.e. variations in light escape efficiency from different depths of x-ray interaction in the scintillator, denoted ε̄(z). Optimizing scintillators for medical imaging applications requires understanding of these optical properties, as they determine tradeoffs between parameters such as x-ray absorption, light yield, and spatial resolution. This work develops a model for PHS acquisition such that the effect of measurement uncertainty can be removed. This method allows ε̄(z) to be quantified on an absolute scale and permits more accurate estimation of the optical Swank factor of scintillators. Methods The pulse height spectroscopy acquisition chain was modeled as a linear system of stochastic gain stages. Analytical expressions were derived for signal and noise propagation through the PHS chain, accounting for deterministic and stochastic aspects of x-ray absorption, scintillation, and light detection with a photomultiplier tube. The derived expressions were used to calculate PHS of thallium-doped cesium iodide (CsI) scintillators using parameters that were measured, calculated, or known from literature. PHS were measured at 25 and 32 keV of CsI samples designed with an optically-reflective or absorptive backing, with or without a fiber-optic faceplate (FOP), and with thicknesses ranging from 150–1000 μm. Measured PHS were compared with calculated PHS, then light escape model parameters were varied until measured and modeled results reached agreement. Resulting estimates of ε̄(z) were used to calculate each scintillator’s optical Swank factor. Results For scintillators of the same optical design

Apparatus and methods for determining gas saturation and porosity of a formation penetrated by a gas filled or liquid filled borehole

DOEpatents

Wilson, Robert D.

2001-03-27

Methods and apparatus are disclosed for determining gas saturation, liquid saturation, porosity and density of earth formations penetrated by a well borehole. Determinations are made from measures of fast neutron and inelastic scatter gamma radiation induced by a pulsed, fast neutron source. The system preferably uses two detectors axially spaced from the neutron source. One detector is preferably a scintillation detector responsive to gamma radiation, and a second detector is preferably an organic scintillator responsive to both neutron and gamma radiation. The system can be operated in cased boreholes which are filled with either gas or liquid. Techniques for correcting all measurements for borehole conditions are disclosed.

Preparation of paper scintillator for detecting 3H contaminant.

PubMed

Miyoshi, Hirokazu; Ikeda, Toshiji

2013-09-01

Liquid scintillator (LS)-encapsulated silica was prepared by the sol-gel method and then was added dropwise onto a wipe paper to form a paper scintillator. First, the efficiencies of wipe were determined for both the paper scintillator and the wipe paper using a liquid scintillation counter (LSC). The efficiencies of wipe using the paper scintillator and the wipe paper were 88 and 36 %, respectively. The detection efficiencies were 5.5 % for the paper scintillator, 46 % for the wipe paper using an LS and 0.08 % for the (3)H/(14)C survey meter, respectively, compared with that of a melt-on scintillator of 47 %. Second, an (3)H contaminant on the paper scintillator was successfully detected using a photomultiplier without an LSC or an (3)H/(14)C survey meter. Finally, the paper scintillator was able to detect beta rays of the (3)H contaminant easily without an LS.

Analytical Calculation of the Lower Bound on Timing Resolution for PET Scintillation Detectors Comprising High-Aspect-Ratio Crystal Elements

PubMed Central

Cates, Joshua W.; Vinke, Ruud; Levin, Craig S.

2015-01-01

Excellent timing resolution is required to enhance the signal-to-noise ratio (SNR) gain available from the incorporation of time-of-flight (ToF) information in image reconstruction for positron emission tomography (PET). As the detector’s timing resolution improves, so does SNR, reconstructed image quality, and accuracy. This directly impacts the challenging detection and quantification tasks in the clinic. The recognition of these benefits has spurred efforts within the molecular imaging community to determine to what extent the timing resolution of scintillation detectors can be improved and develop near-term solutions for advancing ToF-PET. Presented in this work, is a method for calculating the Cramér-Rao lower bound (CRLB) on timing resolution for scintillation detectors with long crystal elements, where the influence of the variation in optical path length of scintillation light on achievable timing resolution is non-negligible. The presented formalism incorporates an accurate, analytical probability density function (PDF) of optical transit time within the crystal to obtain a purely mathematical expression of the CRLB with high-aspect-ratio (HAR) scintillation detectors. This approach enables the statistical limit on timing resolution performance to be analytically expressed for clinically-relevant PET scintillation detectors without requiring Monte Carlo simulation-generated photon transport time distributions. The analytically calculated optical transport PDF was compared with detailed light transport simulations, and excellent agreement was found between the two. The coincidence timing resolution (CTR) between two 3×3×20 mm3 LYSO:Ce crystals coupled to analogue SiPMs was experimentally measured to be 162±1 ps FWHM, approaching the analytically calculated lower bound within 6.5%. PMID:26083559

Analytical calculation of the lower bound on timing resolution for PET scintillation detectors comprising high-aspect-ratio crystal elements

NASA Astrophysics Data System (ADS)

Cates, Joshua W.; Vinke, Ruud; Levin, Craig S.

2015-07-01

Excellent timing resolution is required to enhance the signal-to-noise ratio (SNR) gain available from the incorporation of time-of-flight (ToF) information in image reconstruction for positron emission tomography (PET). As the detector’s timing resolution improves, so does SNR, reconstructed image quality, and accuracy. This directly impacts the challenging detection and quantification tasks in the clinic. The recognition of these benefits has spurred efforts within the molecular imaging community to determine to what extent the timing resolution of scintillation detectors can be improved and develop near-term solutions for advancing ToF-PET. Presented in this work, is a method for calculating the Cramér-Rao lower bound (CRLB) on timing resolution for scintillation detectors with long crystal elements, where the influence of the variation in optical path length of scintillation light on achievable timing resolution is non-negligible. The presented formalism incorporates an accurate, analytical probability density function (PDF) of optical transit time within the crystal to obtain a purely mathematical expression of the CRLB with high-aspect-ratio (HAR) scintillation detectors. This approach enables the statistical limit on timing resolution performance to be analytically expressed for clinically-relevant PET scintillation detectors without requiring Monte Carlo simulation-generated photon transport time distributions. The analytically calculated optical transport PDF was compared with detailed light transport simulations, and excellent agreement was found between the two. The coincidence timing resolution (CTR) between two 3× 3× 20 mm3 LYSO:Ce crystals coupled to analogue SiPMs was experimentally measured to be 162+/- 1 ps FWHM, approaching the analytically calculated lower bound within 6.5%.

Progress in Evaluating Quantitative Optical Gas Imaging

EPA Science Inventory

Development of advanced fugitive emission detection and assessment technologies that facilitate cost effective leak and malfunction mitigation strategies is an ongoing goal shared by industry, regulators, and environmental groups. Optical gas imaging (OGI) represents an importan...

Current Status Of The NAVSEA Backscatter Absorption Gas Imaging (BAGI) Development Project

NASA Astrophysics Data System (ADS)

Kulp, Thomas J.; Kennedy, Randall B.; Garvis, Darrel G.; McRae, Thomas G.; Stahovec, Joe

1989-07-01

During the last five years, work has been underway at the Lawrence Livermore National Laboratory (LLNL) to develop a method for imaging gas clouds that are normally invisible to the human eye. The effort was initiated to provide an effective means of locating leaks of hazardous vapors. Although conventional point or line-of-sight detectors are well suited to the measurement of gas concentrations, their utility in identifying the origin and direction of travel of gas plumes is limited. To obtain spatial information from sensors that provide only zero- or one-dimensional readings, either sequential readings at many different locations from a single device, or multiplexed simultaneous measurements from a sensor array must be taken. The former approach is time consuming and, therefore, impractical in emergency situations where rapid action is required. The latter is useful only in cases where the probability of a hazardous release is high enough to warrant the prior installation of a sensor network. Either method demands high measuremental precision and sufficient discrimination against both interfering gases and interfering sources of the target gas. Backscatter Absorption Gas Imaging (BAGI) is a new technique that makes gas clouds and their surroundings "visible" in a real-time video image. It is superior to conventional sensors in characterizing the spatial properties of gas clouds because it provides data that are inherently two-dimensional. Less measuremental precision is required by the BAGI technique because it conveys information as contrasts between different areas in an image rather than as absolute concentration values. Furthermore, the pictorial display of this information allows it to be rapidly assimilated by emergency-response teams. The size and orientation of the plume are evident through comparison with familiar objects that also appear in the image. Subtler evaluations can be made as well, such as the distinction between innocous and hazardous

Morphology of auroral zone radio wave scintillation

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

Rino, C.L.; Matthews, S.J.

1980-08-01

This paper describes the morphology of midnight sector and morning sector auroral zone scintillation observations made over a two-year period using the Wideband satelite, which is in a sun-synchronous, low-altitude orbit. No definitive seasonal variation was found. The nighttime data showed the highest scintillation ocurrence levels, but significant amounts of morning scintillation were observed. For the most part the scintillation activity followed the general pattern of local magnetic activity. The most prominent feature in the nightime data is a localized amplitude and phase scintillation enhancement at the point where the propagation vector lies within an L shell. A geometrical effectmore » due to a dynamic slab of sheetlike structures in the F region is hypothesized as the source of his enhancement. The data have been sorted by magnetic activity, proximity to local midnight, and season. The general features of the data are in agreement with the accepted morphology of auroral zone scintillation.« less

Liquid Scintillator Production for the NOvA Experiment

DOE PAGES

Mufson, S.; Baugh, B.; Bower, C.; ...

2015-04-15

The NOvA collaboration blended and delivered 8.8 kt (2.72M gal) of liquid scintillator as the active detector medium to its near and far detectors. The composition of this scintillator was specifically developed to satisfy NOvA's performance requirements. A rigorous set of quality control procedures was put in place to verify that the incoming components and the blended scintillator met these requirements. The scintillator was blended commercially in Hammond, IN. The scintillator was shipped to the NOvA detectors using dedicated stainless steel tanker trailers cleaned to food grade.

First results of ground-based LWIR hyperspectral imaging remote gas detection

NASA Astrophysics Data System (ADS)

Zheng, Wei-jian; Lei, Zheng-gang; Yu, Chun-chao; Wang, Hai-yang; Fu, Yan-peng; Liao, Ning-fang; Su, Jun-hong

2014-11-01

The new progress of ground-based long-wave infrared remote sensing is presented. The LWIR hyperspectral imaging by using the windowing spatial and temporal modulation Fourier spectroscopy, and the results of outdoor ether gas detection, verify the features of LWIR hyperspectral imaging remote sensing and technical approach. It provides a new technical means for ground-based gas remote sensing.

High energy resolution plastic scintillator

NASA Astrophysics Data System (ADS)

van Loef, Edgar V.; Feng, Patrick; Markosyan, Gary; Shirwadkar, Urmila; Doty, Patrick; Shah, Kanai S.

2016-09-01

In this paper we present results on a novel tin-loaded plastic scintillator. We will show that this particular plastic scintillator has a light output similar to that of BGO, a fast scintillation decay (< 10 ns), exhibits good neutron/gamma PSD with a Figure-of-Merit of 1.3 at 2.5 MeVee cut-off energy, and excellent energy resolution of about 12% (FWHM) at 662 keV. Under X-ray excitation, the radioluminescence spectrum exhibits a broad band between 350 and 500 nm peaking at 420 nm which is well-matched to bialkali photomultiplier tubes and UV-enhanced photodiodes.

Lu1-xI3:Cex--A Scintillator for gamma ray spectroscopy and time-of-flight PET

DOEpatents

Shah, Kanai S [Newton, MA

2009-03-17

The present invention concerns very fast scintillator materials comprising lutetium iodide doped with Cerium Lu.sub.1-xI.sub.3:Ce.sub.x; LuI.sub.3:Ce). The LuI.sub.3 scintillator material has surprisingly good characteristics including high light output, high gamma ray stopping efficiency, fast response, low cost, good proportionality, and minimal afterglow that the material is useful for gamma ray spectroscopy, medical imaging, nuclear and high energy physics research, diffraction, non-destructive testing, nuclear treaty verification and safeguards, and geological exploration. The timing resolution of the scintillators of the present invention provide compositions capable of resolving the position of an annihilation event within a portion of a human body cross-section.

Structural Measurements from Images of Noble Gas Diffusion

NASA Astrophysics Data System (ADS)

Cadman, Robert V.; Kadlecek, Stephen J.; Emami, Kiarash; MacDuffie Woodburn, John; Vahdat, Vahid; Ishii, Masaru; Rizi, Rahim R.

2009-03-01

Magnetic resonance imaging of externally polarized noble gases such as ^3He has been used for pulmonary imaging for more than a decade. Because gas diffusion is impeded by the alveoli, the diffusion coefficient of gas in the lung, measured on a time scale of milliseconds, is reduced compared to that of the same gas mixture in the absence of restrictions. When the alveolar walls decay, as in emphysema, diffusivity in the lung increases. In this paper, the relationship between diffusion measurements and the size of the restricting structures will be discussed. The simple case of diffusion in an impermeable cylinder, a structure similar to the upper respiratory airways in mammals, has been studied. A procedure will be presented by which airways of order 2 mm in diameter may be accurately measured; demonstration experiments with plastic tubes will also be presented. The additional developments needed before this technique becomes practical will be briefly discussed.

High-sensitivity, high-speed continuous imaging system

DOEpatents

Watson, Scott A; Bender, III, Howard A

2014-11-18

A continuous imaging system for recording low levels of light typically extending over small distances with high-frame rates and with a large number of frames is described. Photodiode pixels disposed in an array having a chosen geometry, each pixel having a dedicated amplifier, analog-to-digital convertor, and memory, provide parallel operation of the system. When combined with a plurality of scintillators responsive to a selected source of radiation, in a scintillator array, the light from each scintillator being directed to a single corresponding photodiode in close proximity or lens-coupled thereto, embodiments of the present imaging system may provide images of x-ray, gamma ray, proton, and neutron sources with high efficiency.

Modeling and prediction of ionospheric scintillation

NASA Technical Reports Server (NTRS)

Fremouw, E. J.

1974-01-01

Scintillation modeling performed thus far is based on the theory of diffraction by a weakly modulating phase screen developed by Briggs and Parkin (1963). Shortcomings of the existing empirical model for the scintillation index are discussed together with questions of channel modeling, giving attention to the needs of the communication engineers. It is pointed out that much improved scintillation index models may be available in a matter of a year or so.

Fracture-resistant lanthanide scintillators

DOEpatents

Doty, F Patrick [Livermore, CA

2011-01-04

Lanthanide halide alloys have recently enabled scintillating gamma ray spectrometers comparable to room temperature semiconductors (<3% FWHM energy resolutions at 662 keV). However brittle fracture of these materials upon cooling hinders the growth of large volume crystals. Efforts to improve the strength through non-lanthanide alloy substitution, while preserving scintillation, have been demonstrated. Isovalent alloys having nominal compositions of comprising Al, Ga, Sc, Y, and In dopants as well as aliovalent alloys comprising Ca, Sr, Zr, Hf, Zn, and Pb dopants were prepared. All of these alloys exhibit bright fluorescence under UV excitation, with varying shifts in the spectral peaks and intensities relative to pure CeBr.sub.3. Further, these alloys scintillate when coupled to a photomultiplier tube (PMT) and exposed to .sup.137Cs gamma rays.

Lanthanum halide scintillators for time-of-flight 3-D pet

DOEpatents

Karp, Joel S [Glenside, PA; Surti, Suleman [Philadelphia, PA

2008-06-03

A Lanthanum Halide scintillator (for example LaCl.sub.3 and LaBr.sub.3) with fast decay time and good timing resolution, as well as high light output and good energy resolution, is used in the design of a PET scanner. The PET scanner includes a cavity for accepting a patient and a plurality of PET detector modules arranged in an approximately cylindrical configuration about the cavity. Each PET detector includes a Lanthanum Halide scintillator having a plurality of Lanthanum Halide crystals, a light guide, and a plurality of photomultiplier tubes arranged respectively peripherally around the cavity. The good timing resolution enables a time-of-flight (TOF) PET scanner to be developed that exhibits a reduction in noise propagation during image reconstruction and a gain in the signal-to-noise ratio. Such a PET scanner includes a time stamp circuit that records the time of receipt of gamma rays by respective PET detectors and provides timing data outputs that are provided to a processor that, in turn, calculates time-of-flight (TOF) of gamma rays through a patient in the cavity and uses the TOF of gamma rays in the reconstruction of images of the patient.

Ionospheric scintillation observations over Kenyan region - Preliminary results

NASA Astrophysics Data System (ADS)

Olwendo, O. J.; Xiao, Yu; Ming, Ou

2016-11-01

Ionospheric scintillation refers to the rapid fluctuations in the amplitude and phase of a satellite signal as it passes through small-scale plasma density irregularities in the ionosphere. By analyzing ionospheric scintillation observation datasets from satellite signals such as GPS signals we can study the morphology of ionospheric bubbles. At low latitudes, the diurnal behavior of scintillation is driven by the formation of large-scale equatorial density depletions which form one to two hours after sunset via the Rayleigh-Taylor instability mechanism near the magnetic equator. In this work we present ionospheric scintillation activity over Kenya using data derived from a newly installed scintillation monitor developed by CRIRP at Pwani University (39.78°E, 3.24°S) during the period August to December, 2014. The results reveal the scintillation activity mainly occurs from post-sunset to post-midnight hours, and ceases around 04:00 LT. We also found that the ionospheric scintillation tends to appear at the southwest and northwest of the station. These locations coincide with the southern part of the Equatorial Ionization Anomaly crest over Kenya region. The occurrence of post-midnight L-band scintillation events which are not linked to pre-midnight scintillation observations raises fundamental question on the mechanism and source of electric fields driving the plasma depletion under conditions of very low background electron density.

Ionospheric scintillation effects on single frequency GPS

NASA Astrophysics Data System (ADS)

Steenburgh, R. A.; Smithtro, C. G.; Groves, K. M.

2008-04-01

Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active within, although not limited to, a belt encircling the Earth within 20 degrees of the geomagnetic equator. As GPS applications and users increase, so does the potential for degraded precision and availability from scintillation. We examined amplitude scintillation data spanning 7 years from Ascension Island, U.K.; Ancon, Peru; and Antofagasta, Chile in the Atlantic/American longitudinal sector as well as data from Parepare, Indonesia; Marak Parak, Malaysia; Pontianak, Indonesia; Guam; and Diego Garcia, U.K. in the Pacific longitudinal sector. From these data, we calculate percent probability of occurrence of scintillation at various intensities described by the S4 index. Additionally, we determine Dilution of Precision at 1 min resolution. We examine diurnal, seasonal, and solar cycle characteristics and make spatial comparisons. In general, activity was greatest during the equinoxes and solar maximum, although scintillation at Antofagasta, Chile was higher during 1998 rather than at solar maximum.

Systematic studies of small scintillators for new sampling calorimeter

NASA Astrophysics Data System (ADS)

Jacosalem, E. P.; Iba, S.; Nakajima, N.; Ono, H.; Sanchez, A. L. C.; Bacala, A. M.; Miyata, H.

2007-12-01

A new sampling calorimeter using very thin scintillators and the multi-pixel photon counter (MPPC) has been proposed to produce better position resolution for the international linear collider (ILC) experiment. As part of this R&D study, small plastic scintillators of different sizes, thickness and wrapping reflectors are systematically studied. The scintillation light due to beta rays from a collimated ^{90}Sr source are collected from the scintillator by wavelength-shifting (WLS) fiber and converted into electrical signals at the PMT. The wrapped scintillator that gives the best light yield is determined by comparing the measured pulse height of each 10 × 40 × 2 mm strip scintillator covered with 3M reflective mirror film, teflon, white paint, black tape, gold, aluminum and white paint+teflon. The pulse height dependence on position, length and thickness of the 3M reflective mirror film and teflon wrapped scintillators are measured. Results show that the 3M radiant mirror film-wrapped scintillator has the greatest light yield with an average of 9.2 photoelectrons. It is observed that light yield slightly increases with scintillator length, but increases to about 100% when WLS fiber diameter is increased from 1.0 mm to 1.6 mm. The position dependence measurement along the strip scintillator showed the uniformity of light transmission from the sensor to the PMT. A dip across the strip is observed which is 40% of the maximum pulse height. The block type scintillator pulse height, on the other hand, is found to be almost proportional to scintillator thickness.

Scintillator materials containing lanthanum fluorides

DOEpatents

Moses, William W.

1991-01-01

An improved radiation detector containing a crystalline mixture of LaF.sub.3 and CeF.sub.3 as the scintillator element is disclosed. Scintillators made with from 25% to 99.5% LaF.sub.3 and the remainder CeF.sub.3 have been found to provide a balance of good stopping power, high light yield and short decay constant that is equal to or superior to other known scintillator materials, and which may be processed from natural starting materials containing both rare earth elements. The radiation detectors disclosed are favorably suited for use in general purpose detection and in positron emission tomography.

Scintillator materials containing lanthanum fluorides

DOEpatents

Moses, W.W.

1991-05-14

An improved radiation detector containing a crystalline mixture of LaF[sub 3] and CeF[sub 3] as the scintillator element is disclosed. Scintillators made with from 25% to 99.5% LaF[sub 3] and the remainder CeF[sub 3] have been found to provide a balance of good stopping power, high light yield and short decay constant that is equal to or superior to other known scintillator materials, and which may be processed from natural starting materials containing both rare earth elements. The radiation detectors disclosed are favorably suited for use in general purpose detection and in positron emission tomography. 2 figures.

Photonic crystal scintillators and methods of manufacture

DOEpatents

Torres, Ricardo D.; Sexton, Lindsay T.; Fuentes, Roderick E.; Cortes-Concepcion, Jose

2015-08-11

Photonic crystal scintillators and their methods of manufacture are provided. Exemplary methods of manufacture include using a highly-ordered porous anodic alumina membrane as a pattern transfer mask for either the etching of underlying material or for the deposition of additional material onto the surface of a scintillator. Exemplary detectors utilizing such photonic crystal scintillators are also provided.

Development of Laser-Polarized Noble Gas Magnetic Resonance Imaging (MRI) Technology

NASA Technical Reports Server (NTRS)

Walsworth, Ronald L.

2004-01-01

We are developing technology for laser-polarized noble gas nuclear magnetic resonance (NMR), with the aim of enabling it as a novel biomedical imaging tool for ground-based and eventually space-based application. This emerging multidisciplinary technology enables high-resolution gas-space magnetic resonance imaging (MRI)-e.g., of lung ventilation, perfusion, and gas-exchange. In addition, laser-polarized noble gases (3He and 1BXe) do not require a large magnetic field for sensitive NMR detection, opening the door to practical MRI with novel, open-access magnet designs at very low magnetic fields (and hence in confined spaces). We are pursuing two specific aims in this technology development program. The first aim is to develop an open-access, low-field (less than 0.01 T) instrument for MRI studies of human gas inhalation as a function of subject orientation, and the second aim is to develop functional imaging of the lung using laser-polarized He-3 and Xe-129.

Fiber optic thermal/fast neutron and gamma ray scintillation detector

DOEpatents

Neal, John S.; Mihalczo, John T

2007-10-30

A system for detecting fissile and fissionable material originating external to the system includes: a .sup.6Li loaded glass fiber scintillator for detecting thermal neutrons, x-rays and gamma rays; a fast scintillator for detecting fast neutrons, x-rays and gamma rays, the fast scintillator conjoined with the glass fiber scintillator such that the fast scintillator moderates fast neutrons prior to their detection as thermal neutrons by the glass fiber scintillator; and a coincidence detection system for processing the time distributions of arriving signals from the scintillators.

SU-E-T-641: Proton Range Measurements Using a Geometrically Calibrated Liquid Scintillator Detector

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

Hui, C; Robertson, D; Alsanea, F

2015-06-15

Purpose: The purpose of this work is to develop a geometric calibration method to accurately calculate physical distances within a liquid scintillator detector and to assess the accuracy, consistency, and robustness of proton beam range measurements when using a liquid scintillator detector system with the proposed geometric calibration process. Methods: We developed a geometric calibration procedure to accurately convert pixel locations in the camera frame into physical locations in the scintillator frame. To ensure accuracy, the geometric calibration was performed before each experiment. The liquid scintillator was irradiated with spot scanning proton beams of 94 energies in two deliveries. Amore » CCD camera was used to capture the two-dimensional scintillation light profile of each of the proton energies. An algorithm was developed to automatically calculate the proton range from the acquired images. The measured range was compared to the nominal range to assess the accuracy of the detector. To evaluate the robustness of the detector between each setup, the experiments were repeated on three different days. To evaluate the consistency of the measurements between deliveries, three sets of measurements were acquired for each experiment. Results: Using this geometric calibration procedure, the proton beam ranges measured using the liquid scintillator system were all within 0.3mm of the nominal range. The average difference between the measured and nominal ranges was −0.20mm. The delivery-to-delivery standard deviation of the proton range measurement was 0.04mm, and the setup-to-setup standard deviation of the measurement was 0.10mm. Conclusion: The liquid scintillator system can measure the range of all 94 beams in just two deliveries. With the proposed geometric calibration, it can measure proton range with sub-millimeter accuracy, and the measurements were shown to be consistent between deliveries and setups. Therefore, we conclude that the liquid

Geophysical analysis of coherent satellite scintillation data

NASA Astrophysics Data System (ADS)

Fremouw, E. J.; Lansinger, J. M.; Miller, D. A.

1981-11-01

In May of 1976, Air Force Satellite P76-5 was launched with the Defense Nuclear Agency's Wideband beacon, DNA-002, as its sole payload. Several researchers have employed the resulting data in studies of ionospheric structure and its effect on transionospheric radio communications. In the present work, recordings of amplitude and phase scintillation imposed on Wideband's VHF and UHF signals by the ionosphere have been used to study medium-scale structures in the auroral-zone F layer. Results include quantitative identification of a very close relationship between scintillation and solar/geomagnetic activity, together with lack of a seasonal variation in scintillation activity in the Alaskan sector. A surprisingly high correlation (90%) was found between monthly means of phase-scintillation index, on the one hand, and sunspot number and 10-cm solar radio flux, on the other. The high-latitude scintillation boundary was found to be very similar to the soft-electron precipitation boundary, including similarity in expansion rates with increasing magnetic activity. Interestingly, it is systematically shifted poleward of the precipitation boundary on the day side of the earth and equatorward on the night side. Taken together, the results of this research disclose a rather direct relationship between scintillation and soft-electron precipitation, with plasma convection likely playing an important role in generation of the scintillation-producing irregularities.

Electrokinetic removal of radionuclides contained in scintillation liquids absorbed in soil type Phaeozem.

PubMed

Valdovinos, V; Monroy-Guzmán, F; Bustos, E

2016-10-01

Control samples of scintillation liquids - Phaeozem soil mixtures were prepared with different scintillation liquids as the support electrolyte, Install Gel ® XF, (Ultima Gold AB™ and Ultima Gold XR™), to construct the polarization curves, and to select the cell potential with the highest mass transfer to remove 24 Na (15 h) and 99m Tc (6 h) as radiotracers from polluted Phaeozem soil. During the electrokinetic treatment (EKT), the removal of radionuclides contained in scintillation liquids absorbed in Phaeozem soil, liquid phase was characterized by Gas Chromatography coupled with a Flame Ionization Detector (GC-FID) and Fourier Transform Infrared Spectrometry (FTIR), solids by FTIR, before and after the application of cell potential. In this sense, the support electrolyte was selected based on the highest current generated (1 mA), as in the case of scintillation liquid 50% Ultima Gold XR™ + 50% Water (1:1), which was used for 6 h in the presence of a mesh and a titanium rod, as anode and cathode, respectively. Finally, the removal percentage accumulated in the liquid phase after the EKT of Phaeozem soil polluted by 99m Tc was 61% close to the anode after 4 h. It was also 61% for 24 Na close to cathode after 2 h, and after 4 h it was 71.8%. Copyright © 2016 Elsevier Ltd. All rights reserved.

Composite scintillators for detection of ionizing radiation

DOEpatents

Dai, Sheng [Knoxville, TN; Stephan, Andrew Curtis [Knoxville, TN; Brown, Suree S [Knoxville, TN; Wallace, Steven A [Knoxville, TN; Rondinone, Adam J [Knoxville, TN

2010-12-28

Applicant's present invention is a composite scintillator having enhanced transparency for detecting ionizing radiation comprising a material having optical transparency wherein said material comprises nano-sized objects having a size in at least one dimension that is less than the wavelength of light emitted by the composite scintillator wherein the composite scintillator is designed to have selected properties suitable for a particular application.

Novel scintillating material 2-(4-styrylphenyl)benzoxazole for the fully digital and MRI compatible J-PET tomograph based on plastic scintillators

PubMed Central

Dulski, Kamil; Niedźwiecki, Szymon; Alfs, Dominika; Białas, Piotr; Curceanu, Catalina; Czerwiński, Eryk; Danel, Andrzej; Gajos, Aleksander; Głowacz, Bartosz; Gorgol, Marek; Hiesmayr, Beatrix; Jasińska, Bożena; Kacprzak, Krzysztof; Kamińska, Daria; Kapłon, Łukasz; Kochanowski, Andrzej; Korcyl, Grzegorz; Kowalski, Paweł; Kozik, Tomasz; Krzemień, Wojciech; Kubicz, Ewelina; Kucharek, Mateusz; Mohammed, Muhsin; Pawlik-Niedźwiecka, Monika; Pałka, Marek; Raczyński, Lech; Rudy, Zbigniew; Rundel, Oleksandr; Sharma, Neha G.; Silarski, Michał; Uchacz, Tomasz; Wiślicki, Wojciech; Zgardzińska, Bożena; Zieliński, Marcin; Moskal, Paweł

2017-01-01

A novel plastic scintillator is developed for the application in the digital positron emission tomography (PET). The novelty of the concept lies in application of the 2-(4-styrylphenyl)benzoxazole as a wavelength shifter. The substance has not been used as scintillator dopant before. A dopant shifts the scintillation spectrum towards longer wavelengths making it more suitable for applications in scintillators of long strips geometry and light detection with digital silicon photomultipliers. These features open perspectives for the construction of the cost-effective and MRI-compatible PET scanner with the large field of view. In this article we present the synthesis method and characterize performance of the elaborated scintillator by determining its light emission spectrum, light emission efficiency, rising and decay time of the scintillation pulses and resulting timing resolution when applied in the positron emission tomography. The optimal concentration of the novel wavelength shifter was established by maximizing the light output and it was found to be 0.05 ‰ for cuboidal scintillator with dimensions of 14 mm x 14 mm x 20 mm. PMID:29176834

Novel scintillating material 2-(4-styrylphenyl)benzoxazole for the fully digital and MRI compatible J-PET tomograph based on plastic scintillators.

PubMed

Wieczorek, Anna; Dulski, Kamil; Niedźwiecki, Szymon; Alfs, Dominika; Białas, Piotr; Curceanu, Catalina; Czerwiński, Eryk; Danel, Andrzej; Gajos, Aleksander; Głowacz, Bartosz; Gorgol, Marek; Hiesmayr, Beatrix; Jasińska, Bożena; Kacprzak, Krzysztof; Kamińska, Daria; Kapłon, Łukasz; Kochanowski, Andrzej; Korcyl, Grzegorz; Kowalski, Paweł; Kozik, Tomasz; Krzemień, Wojciech; Kubicz, Ewelina; Kucharek, Mateusz; Mohammed, Muhsin; Pawlik-Niedźwiecka, Monika; Pałka, Marek; Raczyński, Lech; Rudy, Zbigniew; Rundel, Oleksandr; Sharma, Neha G; Silarski, Michał; Uchacz, Tomasz; Wiślicki, Wojciech; Zgardzińska, Bożena; Zieliński, Marcin; Moskal, Paweł

2017-01-01

A novel plastic scintillator is developed for the application in the digital positron emission tomography (PET). The novelty of the concept lies in application of the 2-(4-styrylphenyl)benzoxazole as a wavelength shifter. The substance has not been used as scintillator dopant before. A dopant shifts the scintillation spectrum towards longer wavelengths making it more suitable for applications in scintillators of long strips geometry and light detection with digital silicon photomultipliers. These features open perspectives for the construction of the cost-effective and MRI-compatible PET scanner with the large field of view. In this article we present the synthesis method and characterize performance of the elaborated scintillator by determining its light emission spectrum, light emission efficiency, rising and decay time of the scintillation pulses and resulting timing resolution when applied in the positron emission tomography. The optimal concentration of the novel wavelength shifter was established by maximizing the light output and it was found to be 0.05 ‰ for cuboidal scintillator with dimensions of 14 mm x 14 mm x 20 mm.

Large volume flow-through scintillating detector

DOEpatents

Gritzo, Russ E.; Fowler, Malcolm M.

1995-01-01

A large volume flow through radiation detector for use in large air flow situations such as incinerator stacks or building air systems comprises a plurality of flat plates made of a scintillating material arranged parallel to the air flow. Each scintillating plate has a light guide attached which transfers light generated inside the scintillating plate to an associated photomultiplier tube. The output of the photomultiplier tubes are connected to electronics which can record any radiation and provide an alarm if appropriate for the application.

Upconverting nanoparticles for optimizing scintillator based detection systems

DOEpatents

Kross, Brian; McKisson, John E; McKisson, John; Weisenberger, Andrew; Xi, Wenze; Zom, Carl

2013-09-17

An upconverting device for a scintillation detection system is provided. The detection system comprises a scintillator material, a sensor, a light transmission path between the scintillator material and the sensor, and a plurality of upconverting nanoparticles particles positioned in the light transmission path.

Unitary scintillation detector and system

DOEpatents

McElhaney, Stephanie A.; Chiles, Marion M.

1994-01-01

The invention is a unitary alpha, beta, and gamma scintillation detector and system for sensing the presence of alpha, beta, and gamma radiations selectively or simultaneously. The scintillators are mounted in a light-tight housing provided with an entrance window for admitting alpha, beta, and gamma radiation and excluding ambient light from the housing. Light pulses from each scintillator have different decay constants that are converted by a photosensitive device into corresponding differently shaped electrical pulses. A pulse discrimination system identifies the electrical pulses by their respective pulse shapes which are determined by decay time. The identified electrical pulses are counted in separate channel analyzers to indicate the respective levels of sensed alpha, beta, and gamma radiations.

Unitary scintillation detector and system

DOEpatents

McElhaney, S.A.; Chiles, M.M.

1994-05-31

The invention is a unitary alpha, beta, and gamma scintillation detector and system for sensing the presence of alpha, beta, and gamma radiations selectively or simultaneously. The scintillators are mounted in a light-tight housing provided with an entrance window for admitting alpha, beta, and gamma radiation and excluding ambient light from the housing. Light pulses from each scintillator have different decay constants that are converted by a photosensitive device into corresponding differently shaped electrical pulses. A pulse discrimination system identifies the electrical pulses by their respective pulse shapes which are determined by decay time. The identified electrical pulses are counted in separate channel analyzers to indicate the respective levels of sensed alpha, beta, and gamma radiations. 10 figs.

Liquid scintillator tiles for calorimetry

DOE PAGES

Amouzegar, M.; Belloni, A.; Bilki, B.; ...

2016-11-28

Future experiments in high energy and nuclear physics may require large, inexpensive calorimeters that can continue to operate after receiving doses of 50 Mrad or more. Also, the light output of liquid scintillators suffers little degradation under irradiation. However, many challenges exist before liquids can be used in sampling calorimetry, especially regarding developing a packaging that has sufficient efficiency and uniformity of light collection, as well as suitable mechanical properties. We present the results of a study of a scintillator tile based on the EJ-309 liquid scintillator using cosmic rays and test beam on the light collection efficiency and uniformity,more » and some preliminary results on radiation hardness.« less

Liquid scintillator tiles for calorimetry

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

Amouzegar, M.; Belloni, A.; Bilki, B.

Future experiments in high energy and nuclear physics may require large, inexpensive calorimeters that can continue to operate after receiving doses of 50 Mrad or more. Also, the light output of liquid scintillators suffers little degradation under irradiation. However, many challenges exist before liquids can be used in sampling calorimetry, especially regarding developing a packaging that has sufficient efficiency and uniformity of light collection, as well as suitable mechanical properties. We present the results of a study of a scintillator tile based on the EJ-309 liquid scintillator using cosmic rays and test beam on the light collection efficiency and uniformity,more » and some preliminary results on radiation hardness.« less

On the relation between GNSS phase scintillation and auroral brightness around satellite's IPP

NASA Astrophysics Data System (ADS)

Spanswick, E.; Mushini, S. C.; Skone, S.; Donovan, E.

2017-12-01

Aurora occurs in different well-known morphologies, or types, including arcs and patchy-pulsating aurora (PPA). Previous observational studies have demonstrated that global navigation satellite system (GNSS) signals transiting the ionosphere in regions of aurora can contain varying levels of scintillation. These scintillations are often attributed to the ionospheric disturbances associated with auroral precipitation, which in extreme cases can affect the accuracy of these systems. One question that remains unanswered is whether a satellite's line of sight transmission through the aurora is a sufficient condition for signal scintillation. Previous studies have used "level" or "strength" of auroral emission as a proxy indicator for scintillation using limited datasets. In general, these results are mixed and inconclusive. In this study, we use a large data set (700 Auroral arc events) to statistically study the relationship between aurora and scintillation of GPS signals. This is one of the largest datasets used in this type of studies. We utilize the THEMIS (Time History of Events and Macroscale Interactions during Substorms) All-Sky Imagers (ASIs) located at Fort Smith (59.9 N, 248.1 E geog.) and Gillam (56.5 N, 265.4 E geog.), Canada. Corresponding GPS data were obtained from CHAIN (Canadian High Arctic Ionospheric Network) GPS receivers collocated with the ASIs. These GPS receivers are custom made receivers capable of providing high rate GPS signal power and phase observations as well as scintillation indices. To obtain information how aurora is affecting the signal, brightness around satellite's Ionospheric Pierce Point (IPP) was calculated and correlated with sigma phi from the satellite's signal. A very low correlation of 0.003 was observed between them. Correlation between the rate of change of brightness around the satellite's IPP and sigma phi was also calculated and a correlation coefficient of 0.7 was observed between them. These results indicate that GPS

Scintillation-Hardened GPS Receiver

NASA Technical Reports Server (NTRS)

Stephens, Donald R.

2015-01-01

CommLargo, Inc., has developed a scintillation-hardened Global Positioning System (GPS) receiver that improves reliability for low-orbit missions and complies with NASA's Space Telecommunications Radio System (STRS) architecture standards. A software-defined radio (SDR) implementation allows a single hardware element to function as either a conventional radio or as a GPS receiver, providing backup and redundancy for platforms such as the International Space Station (ISS) and high-value remote sensing platforms. The innovation's flexible SDR implementation reduces cost, weight, and power requirements. Scintillation hardening improves mission reliability and variability. In Phase I, CommLargo refactored an open-source GPS software package with Kalman filter-based tracking loops to improve performance during scintillation and also demonstrated improved navigation during a geomagnetic storm. In Phase II, the company generated a new field-programmable gate array (FPGA)-based GPS waveform to demonstrate on NASA's Space Communication and Navigation (SCaN) test bed.

Light propagation and fluorescence quantum yields in liquid scintillators

NASA Astrophysics Data System (ADS)

Buck, C.; Gramlich, B.; Wagner, S.

2015-09-01

For the simulation of the scintillation and Cherenkov light propagation in large liquid scintillator detectors a detailed knowledge about the absorption and emission spectra of the scintillator molecules is mandatory. Furthermore reemission probabilities and quantum yields of the scintillator components influence the light propagation inside the liquid. Absorption and emission properties are presented for liquid scintillators using 2,5-Diphenyloxazole (PPO) and 4-bis-(2-Methylstyryl)benzene (bis-MSB) as primary and secondary wavelength shifter. New measurements of the quantum yields for various aromatic molecules are shown.

Performance Evaluations and Quality Validation System for Optical Gas Imaging Cameras That Visualize Fugitive Hydrocarbon Gas Emissions

EPA Science Inventory

Optical gas imaging (OGI) cameras have the unique ability to exploit the electromagnetic properties of fugitive chemical vapors to make invisible gases visible. This ability is extremely useful for industrial facilities trying to mitigate product losses from escaping gas and fac...

Imaging of Combustion Species in a Radially-Staged Gas Turbine Combustor

NASA Technical Reports Server (NTRS)

Locke, Randy J.; Hicks, Yolanda R.; Anderson, Robert C.; Ockunzzi, Kelly A.; Schock, Harold J.

1996-01-01

Plannar laser-induced fluorescence (PLIF) is used to characterize the complex flowfield of a unique fuel-lean, radially-staged high pressure gas turbine combustor. PLIF images of OH are presented for two fuel injector configurations. PLIF images of NO, the first acquired at these conditions, are presented and compared with gas sample extraction probe measurements. Flow field imaging of nascent C2 chemiluminescence is also investigated. An examination is made of the interaction between adjoining lean premixed prevaporized (LPP) injectors. Fluorescence interferences at conditions approaching 2000 K and 15 atm are observed and attributed to polycyclic aromatic hydrocarbon (PAH) emissions. All images are acquired at a position immediately downstream of the fuel injectors with combustor burning JP-5 fuel.

Acoustically modulated magnetic resonance imaging of gas-filled protein nanostructures

NASA Astrophysics Data System (ADS)

Lu, George J.; Farhadi, Arash; Szablowski, Jerzy O.; Lee-Gosselin, Audrey; Barnes, Samuel R.; Lakshmanan, Anupama; Bourdeau, Raymond W.; Shapiro, Mikhail G.

2018-05-01

Non-invasive biological imaging requires materials capable of interacting with deeply penetrant forms of energy such as magnetic fields and sound waves. Here, we show that gas vesicles (GVs), a unique class of gas-filled protein nanostructures with differential magnetic susceptibility relative to water, can produce robust contrast in magnetic resonance imaging (MRI) at sub-nanomolar concentrations, and that this contrast can be inactivated with ultrasound in situ to enable background-free imaging. We demonstrate this capability in vitro, in cells expressing these nanostructures as genetically encoded reporters, and in three model in vivo scenarios. Genetic variants of GVs, differing in their magnetic or mechanical phenotypes, allow multiplexed imaging using parametric MRI and differential acoustic sensitivity. Additionally, clustering-induced changes in MRI contrast enable the design of dynamic molecular sensors. By coupling the complementary physics of MRI and ultrasound, this nanomaterial gives rise to a distinct modality for molecular imaging with unique advantages and capabilities.

The occultation of Epsilon Geminorum by Mars - Analysis of McDonald data. [turbulent scintillation in light curves

NASA Technical Reports Server (NTRS)

Africano, J.; De Vaucouleurs, G.; Evans, D. S.; Finkel, B. E.; Nather, R. E.; Palm, C.; Silverberg, E.; Wiant, J.; Hubbard, W. B.; Jokipii, J. R.

1977-01-01

An analysis of observations of the occultation of Epsilon Gem by Mars on April 8, 1976, is presented. The data were obtained by three neighboring telescopes at McDonald Observatory. Intensity fluctuations on time scales of the order of 100 ms were observed simultaneously at the three telescopes. As the observations compare well with predictions of turbulent scintillation theory, it is concluded that such fluctuations were probably largely the effect of stellar scintillations in the Martian atmosphere. The stellar diameter is included as a parameter in the theory but in a way which differs from previously published interpretations of occultations of extended sources by planetary atmospheres. Scintillations govern the experimental uncertainty in the deduction of the scale height of the high Martian atmosphere. A density scale height of 9.9 + or - 2.5 km is obtained at an altitude of 74 + or - 8 km above the mean surface. For CO 2 gas, this result corresponds to a temperature of 190 + or - 50 K.

Kinetic Monte Carlo simulations of scintillation processes in NaI(Tl)

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

Kerisit, Sebastien N.; Wang, Zhiguo; Williams, Richard

2014-04-26

Developing a comprehensive understanding of the processes that govern the scintillation behavior of inorganic scintillators provides a pathway to optimize current scintillators and allows for the science-driven search for new scintillator materials. Recent experimental data on the excitation density dependence of the light yield of inorganic scintillators presents an opportunity to incorporate parameterized interactions between excitations in scintillation models and thus enable more realistic simulations of the nonproportionality of inorganic scintillators. Therefore, a kinetic Monte Carlo (KMC) model of elementary scintillation processes in NaI(Tl) is developed in this work to simulate the kinetics of scintillation for a range of temperaturesmore » and Tl concentrations as well as the scintillation efficiency as a function of excitation density. The ability of the KMC model to reproduce available experimental data allows for elucidating the elementary processes that give rise to the kinetics and efficiency of scintillation observed experimentally for a range of conditions.« less

Kinetic Monte Carlo Simulations of Scintillation Processes in NaI(Tl)

NASA Astrophysics Data System (ADS)

Kerisit, Sebastien; Wang, Zhiguo; Williams, Richard T.; Grim, Joel Q.; Gao, Fei

2014-04-01

Developing a comprehensive understanding of the processes that govern the scintillation behavior of inorganic scintillators provides a pathway to optimize current scintillators and allows for the science-driven search for new scintillator materials. Recent experimental data on the excitation density dependence of the light yield of inorganic scintillators presents an opportunity to incorporate parameterized interactions between excitations in scintillation models and thus enable more realistic simulations of the nonproportionality of inorganic scintillators. Therefore, a kinetic Monte Carlo (KMC) model of elementary scintillation processes in NaI(Tl) is developed in this paper to simulate the kinetics of scintillation for a range of temperatures and Tl concentrations as well as the scintillation efficiency as a function of excitation density. The ability of the KMC model to reproduce available experimental data allows for elucidating the elementary processes that give rise to the kinetics and efficiency of scintillation observed experimentally for a range of conditions.

Plastic scintillators with efficient neutron/gamma pulse shape discrimination

NASA Astrophysics Data System (ADS)

Zaitseva, Natalia; Rupert, Benjamin L.; PaweŁczak, Iwona; Glenn, Andrew; Martinez, H. Paul; Carman, Leslie; Faust, Michelle; Cherepy, Nerine; Payne, Stephen

2012-03-01

A possibility of manufacturing plastic scintillators with efficient neutron/gamma pulse shape discrimination (PSD) is demonstrated using a system of a polyvinyltoluene (PVT) polymer matrix loaded with a scintillating dye, 2,5-diphenyloxazole (PPO). Similarities and differences of conditions leading to the rise of PSD in liquid and solid organic scintillators are discussed based on the classical model of excited state interaction and delayed light formation. First characterization results are presented to show that PSD in plastic scintillators can be of the similar magnitude or even higher than in standard commercial liquid scintillators.

Scintillator Detector Development at Central Michigan University

NASA Astrophysics Data System (ADS)

McClain, David; Estrade, Alfredo; Neupane, Shree

2017-09-01

Experimental nuclear physics relies both on the accuracy and precision of the instruments for radiation detection used in experimental setups. At Central Michigan University we have setup a lab to work with scintillator detectors for radioactive ion beam experiments, using a Picosecond Laser and radioactive sources for testing. We have tested the resolution for prototypes of large area scintillators that could be used for fast timing measurements in the focal plane of spectrometers, such as the future High Rigidity Spectrometer at the Facility for Rare Isotope Beams (FRIB). We measured the resolution as a function of the length of the detector, and also the position of the beam along the scintillator. We have also designed a scintillating detector to veto light ion background in beta-decay experiments with the Advanced Implantation Detector Array (AIDA) at RIKEN in Japan. We tested different configurations of Silicon Photomultipliers and scintillating fiber optics to find the best detection efficiency.

Attenuation of Scintillation of Discrete Cosmic Sources during Nonresonant HF Heating of the Upper Ionosphere

NASA Astrophysics Data System (ADS)

Bezrodny, V. G.; Watkins, B.; Charkina, O. V.; Yampolski, Y. M.

2014-03-01

The aim of the work is to experimentally investigate the response of scintillation spectra and indices of discrete cosmic sources (DCS) to modification of the ionospheric F-region by powerful electromagnetic fields with frequencies exceeding the Langmuir and upper hybrid ones. The results of a special experiment on the scintillations of radiation from DCS Cygnus A observed with using the 64-beam imaging riometer located near the Gakona village (Alaska, USA) are here presented. The ionosphere was artificially disturbed by powerful HAARP heater. Under the studied conditions of nonresonant heating of the ionospheric plasma, an earlier unknown effect of reducing the level of DCS scintillation was discovered. The theoretical interpretation has been given for the discovered effect, which using allowed the proposed technique of solving the inverse problem (recovery deviations of average electron density and temperature in the modified region from their unperturbed values).

Indirect X-ray Detectors Based on Inkjet-Printed Photodetectors with a Screen-Printed Scintillator Layer.

PubMed

Oliveira, Juliana; Correia, Vitor; Sowade, Enrico; Etxebarria, Ikerne; Rodriguez, Raul D; Mitra, Kalyan Y; Baumann, Reinhard R; Lanceros-Mendez, Senentxu

2018-04-18

Organic photodetectors (PDs) based on printing technologies will allow to expand the current field of PD applications toward large-area and flexible applications in areas such as medical imaging, security, and quality control, among others. Inkjet printing is a powerful digital tool for the deposition of smart and functional materials on various substrates, allowing the development of electronic devices such as PDs on various substrates. In this work, inkjet-printed PD arrays, based on the organic thin-film transistor architecture, have been developed and applied for the indirect detection of X-ray radiation using a scintillator ink as an X-ray absorber. The >90% increase of the photocurrent of the PDs under X-ray radiation, from about 53 nA without the scintillator film to about 102 nA with the scintillator located on top of the PD, proves the suitability of the developed printed device for X-ray detection applications.

Hybrid scintillators for neutron discrimination

DOEpatents

Feng, Patrick L; Cordaro, Joseph G; Anstey, Mitchell R; Morales, Alfredo M

2015-05-12

A composition capable of producing a unique scintillation response to neutrons and gamma rays, comprising (i) at least one surfactant; (ii) a polar hydrogen-bonding solvent; and (iii) at least one luminophore. A method including combining at least one surfactant, a polar hydrogen-bonding solvent and at least one luminophore in a scintillation cell under vacuum or an inert atmosphere.

Comparison of multifrequency equatorial scintillation - American and Pacific sectors

NASA Astrophysics Data System (ADS)

Livingston, R. C.

1980-08-01

In this paper we examine the severity of radio wave amplitude scintillation measured at two stations near the equator but far separated in longitude: Kwajelein, Marshall Islands (167 E), and Ancon, Peru (-77 E). The data used are long-term observations of the Defense Nuclear Agency (DNA) Wideband satellite signal intensity at VHF, UHF, and L band frequencies. The seasonal behavior of the scintillation at the two stations is similar; each shows a broad 8- to 9-month disturbed season centered about local summer. There is short-term variability in the scintillation occurrence statistics but no clear equinoctial maxima. Little difference is observed in the occurrence or severity of L band scintillation at the two stations, although a systematic difference in the frequency dependence of the scintillation produces significantly stronger VHF and UHF scintillation at Ancon. The VHF and UHF latitudinal distributions of scintillation are asymmetric about the geomagnetic equator at both stations.

Co-doping effects on luminescence and scintillation properties of Ce doped (Lu,Gd)3(Ga,Al)5O12 scintillator

NASA Astrophysics Data System (ADS)

Yamaguchi, Hiroaki; Kamada, Kei; Kurosawa, Shunsuke; Pejchal, Jan; Shoji, Yasuhiro; Yokota, Yuui; Ohashi, Yuji; Yoshikawa, Akira

2016-11-01

Mg co-doping effects on scintillation properties of Ce:Lu1Gd2(Ga,Al)5O12 (LGGAG) were investigated. Mg 200 ppm co-doped Ce:LGGAG single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of Mg co-doping. Ce4+ charge transfer absorption was observed below 300 nm in Mg,Ce:LGGAG which is in good agreement with previous reports. The scintillation decay times were accelerated by Mg co-doping.

Defect Engineering by Codoping in KCaI3 :Eu2 + Single-Crystalline Scintillators

NASA Astrophysics Data System (ADS)

Wu, Yuntao; Li, Qi; Jones, Steven; Dun, Chaochao; Hu, Sheng; Zhuravleva, Mariya; Lindsey, Adam C.; Stand, Luis; Loyd, Matthew; Koschan, Merry; Auxier, John; Hall, Howard L.; Melcher, Charles L.

2017-09-01

Eu2 + -doped alkali or alkali earth iodide scintillators with energy resolutions ≤3 % at 662 keV promise the excellent discrimination ability for radioactive isotopes required for homeland-security and nuclear-nonproliferation applications. To extend their applications to x-ray imaging, such as computed tomography scans, the intense afterglow which delays the response time of such materials is an obstacle that needs to be overcome. However, a clear understanding of the origin of the afterglow and feasible solutions is still lacking. In this work, we present a combined experimental and theoretical investigation of the physical insights of codoping-based defect engineering which can reduce the afterglow effectively in KCaI3:Eu2 + single-crystal scintillators. We illustrate that Sc3 + codoping greatly suppresses the afterglow, whereas Y3 + , Gd3 + , or La3 + codoping enhances the afterglow. Meanwhile, a light yield of 57 000 photons / MeV and an energy resolution of 3.4% at 662 keV can be maintained with the appropriate concentration of Sc3 + codoping, which makes the material promising for medical-imaging applications. Through our thermoluminescence techniques and density-functional-theory calculations, we are able to identify the defect structures and understand the mechanism by which codoping affects the scintillation performance of KCaI3:Eu2 + crystals. The proposed defect-engineering strategy is further validated by achieving afterglow suppression in Mg2 + codoped KCaI3:Eu2 + single crystals.

Scintillator tiles read out with silicon photomultipliers

NASA Astrophysics Data System (ADS)

Pooth, O.; Radermacher, T.; Weingarten, S.; Weinstock, L.

2015-10-01

A detector prototype based on a fast plastic scintillator read out with silicon photomultipliers is presented. All studies have been done with cosmic muons and focus on parameter optimization such as coupling the SiPM to the scintillator or wrapping the scintillator with reflective material. The prototype shows excellent results regarding the light-yield and offers a detection efficiency of 99.5% with a signal purity of 99.9% for cosmic muons.

Laser micromachining of cadmium tungstate scintillator for high energy X-ray imaging

NASA Astrophysics Data System (ADS)

Richards, Sion Andreas

Pulsed laser ablation has been investigated as a method for the creation of thick segmented scintillator arrays for high-energy X-ray radiography. Thick scintillators are needed to improve the X-ray absorption at high energies, while segmentation is required for spatial resolution. Monte-Carlo simulations predicted that reflections at the inter-segment walls were the greatest source of loss of scintillation photons. As a result of this, fine pitched arrays would be inefficient as the number of reflections would be significantly higher than in large pitch arrays. Nanosecond and femtosecond pulsed laser ablation was investigated as a method to segment cadmium tungstate (CdWO_4). The effect of laser parameters on the ablation mechanisms, laser induced material changes and debris produced were investigated using optical and electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy for both types of lasers. It was determined that nanosecond ablation was unsuitable due to the large amount of cracking and a heat affected zone created during the ablation process. Femtosecond pulsed laser ablation was found to induce less damage. The optimised laser parameters for a 1028 nm laser was found to be a pulse energy of 54 μJ corresponding to a fluence of 5.3 J cm. -2 a pulse duration of 190 fs, a repetition rate of 78.3 kHz and a laser scan speed of 707 mm s. -1 achieving a normalised pulse overlap of 0.8. A serpentine scan pattern was found to minimise damage caused by anisotropic thermal expansion. Femtosecond pulsed ablation was also found to create a layer of tungsten and cadmium sub-oxides on the surface of the crystals. The CdWO_4 could be cleaned by immersing the CdWO_4 in ammonium hydroxide at 45°C for 15 minutes. However, XPS indicated that the ammonium hydroxide formed a thin layer of CdCO_3 and Cd(OH)_2 on the surface. Prototype arrays were shown to be able to resolve features as small as 0.5 mm using keV energy X-rays. The most

SNO+ Scintillator Purification and Assay

NASA Astrophysics Data System (ADS)

Ford, R.; Chen, M.; Chkvorets, O.; Hallman, D.; Vázquez-Jáuregui, E.

2011-04-01

We describe the R&D on the scintillator purification and assay methods and technology for the SNO+ neutrino and double-beta decay experiment. The SNO+ experiment is a replacement of the SNO heavy water with liquid scintillator comprised of 2 g/L PPO in linear alkylbenzene (LAB). During filling the LAB will be transported underground by rail car and purified by multi-stage distillation and steam stripping at a flow rate of 19 LPM. While the detector is operational the scintillator can be recirculated at 150 LPM (full detector volume in 4 days) to provide repurification as necessary by either water extraction (for Ra, K, Bi) or by functional metal scavenger columns (for Pb, Ra, Bi, Ac, Th) followed by steam stripping to remove noble gases and oxygen (Rn, O2, Kr, Ar). The metal scavenger columns also provide a method for scintillator assay for ex-situ measurement of the U and Th chain radioactivity. We have developed "natural" radioactive spikes of Pb and Ra in LAB and use these for purification testing. Lastly, we present the planned operating modes and purification strategies and the plant specifications and design.

Plastic scintillators modifications for a selective radiation detection

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

Hamel, Matthieu; Bertrand, Guillaume H.V.; Carrel, Frederick

2015-07-01

Recent developments of plastic scintillators are reviewed, from January 2000 to June 2015. All examples are distributed into the main application, i.e. how the plastic scintillator was modified to enhance the detection towards a given radiation particle. The main characteristics of these newly created scintillators and their detection properties are given. (authors)

Influence of coma aberration on aperture averaged scintillations in oceanic turbulence

NASA Astrophysics Data System (ADS)

Luo, Yujuan; Ji, Xiaoling; Yu, Hong

2018-01-01

The influence of coma aberration on aperture averaged scintillations in oceanic turbulence is studied in detail by using the numerical simulation method. In general, in weak oceanic turbulence, the aperture averaged scintillation can be effectively suppressed by means of the coma aberration, and the aperture averaged scintillation decreases as the coma aberration coefficient increases. However, in moderate and strong oceanic turbulence the influence of coma aberration on aperture averaged scintillations can be ignored. In addition, the aperture averaged scintillation dominated by salinity-induced turbulence is larger than that dominated by temperature-induced turbulence. In particular, it is shown that for coma-aberrated Gaussian beams, the behavior of aperture averaged scintillation index is quite different from the behavior of point scintillation index, and the aperture averaged scintillation index is more suitable for characterizing scintillations in practice.

Imaging of Combustion Species in a Radially-Staged Gas Turbine Combustor

NASA Technical Reports Server (NTRS)

Locke, Randy J.; Hicks, Yolanda R.; Anderson, Robert C.; Ockunzzi, Kelly A.; Schock, Harold J.

1996-01-01

Planar laser-induced fluorescence (PLIF) is used to characterize the complex flowfield of a unique fuel-lean, radially-staged, high pressure gas turbine combustor. PLIF images of OH are presented for two fuel injector configurations. PLIF images of NO, the first acquired at these conditions, are presented and compared with gas sample extraction probe measurements. Flow field imaging of nascent C2 chemiluminescence is also investigated. An examination is made of the interaction between adjoining lean premixed prevaporized (LPP) injectors. Fluorescence interferences at conditions approaching 2000 K and 15 atm are observed and attributed to polycyclic aromatic hydrocarbon (PAH) emissions. All images are acquired at a position immediately downstream of the fuel injectors with the combustor burning JP-5 fuel.

Characterization of the scintillation anisotropy in crystalline stilbene scintillator detectors

DOE PAGES

Schuster, P.; Brubaker, E.

2016-11-23

This study reports a series of measurements that characterize the directional dependence of the scintillation response of crystalline melt-grown and solution-grown trans-stilbene to incident DT and DD neutrons. These measurements give the amplitude and pulse shape dependence on the proton recoil direction over one hemisphere of the crystal, confirming and extending previous results in the literature for melt-grown stilbene and providing the first measurements for solution-grown stilbene. In similar measurements of liquid and plastic detectors, no directional dependence was observed, confirming the hypothesis that the anisotropy in stilbene and other organic crystal scintillators is a result of internal effects duemore » to the molecular or crystal structure and not an external effect on the measurement system.« less

Visible scintillation photodetector device incorporating chalcopyrite semiconductor crystals

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

Stowe, Ashley C.; Burger, Arnold

2017-04-04

A photodetector device, including: a scintillator material operable for receiving incident radiation and emitting photons in response; a photodetector material coupled to the scintillator material operable for receiving the photons emitted by the scintillator material and generating a current in response, wherein the photodetector material includes a chalcopyrite semiconductor crystal; and a circuit coupled to the photodetector material operable for characterizing the incident radiation based on the current generated by the photodetector material. Optionally, the scintillator material includes a gamma scintillator material and the incident radiation received includes gamma rays. Optionally, the photodetector material is further operable for receiving thermalmore » neutrons and generating a current in response. The circuit is further operable for characterizing the thermal neutrons based on the current generated by the photodetector material.« less

Cherenkov and scintillation light separation on the CheSS experiment

NASA Astrophysics Data System (ADS)

Caravaca, Javier; Land, Benjamin; Descamps, Freija; Orebi Gann, Gabriel D.

2016-09-01

Separation of the scintillation and Cherenkov light produced in liquid scintillators enables outstanding capabilities for future particle detectors, the most relevant being: particle directionality information in a low energy threshold detector and improved particle identification. The CheSS experiment uses an array of small, fast photomultipliers (PMTs) and state-of-the-art electronics to demonstrate the reconstruction of a Cherenkov ring in liquid scintillator using two techniques: based on the photon density and using the photon hit time information. A charged particle ionizing a scintillation medium produces a prompt Cherenkov cone and late isotropic scintillation light, typically delayed by several ns. The fast response of our PMTs and DAQ provides a precision well below the ns level, making possible the time separation. Furthermore, the usage of the new developed water-based liquid scintillators (WbLS) enhances the separation since it allows tuning of the Cherenkov/Scintillation ratio. Latest results on the separation for pure liquid scintillators and WbLS will be presented.

On the Relationship Between Scintillation Anisotropy and Crystal Structure in Pure Crystalline Organic Scintillator Materials

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

Schuster, Patricia; Feng, Patrick; Brubaker, Erik

We report the scintillation anisotropy effect for proton recoil events has been investigated in five pure organic crystalline materials: anthracene, trans-stilbene, p-terphenyl, bibenzyl, and diphenylacetylene. These measurements include characterization of the scintillation response for one hemisphere of proton recoil directions in each crystal. In addition to standard measurements of the total light output and pulse shape at each angle, the prompt and delayed light anisotropies are analyzed, allowing for investigation of the singlet and triplet molecular excitation behaviors independently. This work provides new quantitative and qualitative observations that make progress toward understanding the physical mechanisms behind the scintillation anisotropy. Thesemore » measurements show that the relationship between the prompt and delayed light anisotropies is correlated with crystal structure, as it changes between the pi-stacked crystal structure materials (anthracene and p-terphenyl) and the herringbone crystal structure materials (stilbene, bibenzyl, and diphenylacetylene). The observations are consistent with a model in which there are preferred directions of kinetic processes for the molecular excitations. Finally, these processes and the impact of their directional dependencies on the scintillation anisotropy are discussed.« less

On the Relationship Between Scintillation Anisotropy and Crystal Structure in Pure Crystalline Organic Scintillator Materials

DOE PAGES

Schuster, Patricia; Feng, Patrick; Brubaker, Erik

2018-05-03

We report the scintillation anisotropy effect for proton recoil events has been investigated in five pure organic crystalline materials: anthracene, trans-stilbene, p-terphenyl, bibenzyl, and diphenylacetylene. These measurements include characterization of the scintillation response for one hemisphere of proton recoil directions in each crystal. In addition to standard measurements of the total light output and pulse shape at each angle, the prompt and delayed light anisotropies are analyzed, allowing for investigation of the singlet and triplet molecular excitation behaviors independently. This work provides new quantitative and qualitative observations that make progress toward understanding the physical mechanisms behind the scintillation anisotropy. Thesemore » measurements show that the relationship between the prompt and delayed light anisotropies is correlated with crystal structure, as it changes between the pi-stacked crystal structure materials (anthracene and p-terphenyl) and the herringbone crystal structure materials (stilbene, bibenzyl, and diphenylacetylene). The observations are consistent with a model in which there are preferred directions of kinetic processes for the molecular excitations. Finally, these processes and the impact of their directional dependencies on the scintillation anisotropy are discussed.« less

Robust GPS carrier tracking under ionospheric scintillation

NASA Astrophysics Data System (ADS)

Susi, M.; Andreotti, M.; Aquino, M. H.; Dodson, A.

2013-12-01

Small scale irregularities present in the ionosphere can induce fast and unpredictable fluctuations of Radio Frequency (RF) signal phase and amplitude. This phenomenon, known as scintillation, can degrade the performance of a GPS receiver leading to cycle slips, increasing the tracking error and also producing a complete loss of lock. In the most severe scenarios, if the tracking of multiple satellites links is prevented, outages in the GPS service can also occur. In order to render a GPS receiver more robust under scintillation, particular attention should be dedicated to the design of the carrier tracking stage, that is the receiver's part most sensitive to these types of phenomenon. This paper exploits the reconfigurability and flexibility of a GPS software receiver to develop a tracking algorithm that is more robust under ionospheric scintillation. For this purpose, first of all, the scintillation level is monitored in real time. Indeed the carrier phase and the post correlation terms obtained by the PLL (Phase Locked Loop) are used to estimate phi60 and S4 [1], the scintillation indices traditionally used to quantify the level of phase and amplitude scintillations, as well as p and T, the spectral parameters of the fluctuations PSD. The effectiveness of the scintillation parameter computation is confirmed by comparing the values obtained by the software receiver and the ones provided by a commercial scintillation monitoring, i.e. the Septentrio PolarxS receiver [2]. Then the above scintillation parameters and the signal carrier to noise density are exploited to tune the carrier tracking algorithm. In case of very weak signals the FLL (Frequency Locked Loop) scheme is selected in order to maintain the signal lock. Otherwise an adaptive bandwidth Phase Locked Loop (PLL) scheme is adopted. The optimum bandwidth for the specific scintillation scenario is evaluated in real time by exploiting the Conker formula [1] for the tracking jitter estimation. The performance

Optical Design Considerations for Efficient Light Collection from Liquid Scintillation Counters

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

Bernacki, Bruce E.; Douglas, Matthew; Erchinger, Jennifer L.

2015-01-01

Liquid scintillation counters measure charged particle-emitting radioactive isotopes and are used for environmental studies, nuclear chemistry, and life science. Alpha and beta emissions arising from the material under study interact with the scintillation cocktail to produce light. The prototypical liquid scintillation counter employs low-level photon-counting detectors to measure the arrival of the scintillation light produced as a result of the dissolved material under study interacting with the scintillation cocktail. For reliable operation the counting instrument must convey the scintillation light to the detectors efficiently and predictably. Current best practices employ the use of two or more detectors for coincidence processingmore » to discriminate true scintillation events from background events due to instrumental effects such as photomultiplier tube dark rates, tube flashing, or other light emission not generated in the scintillation cocktail vial. In low background liquid scintillation counters additional attention is paid to shielding the scintillation cocktail from naturally occurring radioactive material (NORM) present in the laboratory and within the instruments construction materials. Low background design is generally at odds with optimal light collection. This study presents the evolution of a light collection design for liquid scintillation counting in a low background shield. The basic approach to achieve both good light collection and a low background measurement is described. The baseline signals arising from the scintillation vial are modeled and methods to efficiently collect scintillation light are presented as part of the development of a customized low-background, high sensitivity liquid scintillation counting system.« less

SIFTER: Scintillating Fiber Telescopes for Energetic Radiation, Gamma-Ray Applications

NASA Technical Reports Server (NTRS)

Paciesas, William S.

2002-01-01

The research project "SIFTER: Scintillating Fiber Telescopes for Energetic Radiation, Gamma-Ray Applications" approved under the NASA High Energy Astrophysics Research Program. The principal investigator of the proposal was Prof. Geoffrey N. Pendleton, who is currently on extended leave from UAH. Prof. William S. Paciesas administered the grant during Dr. Pendleton's absence. The project was originally funded for one year from 6/8/2000 to 6/7/2001. Due to conflicts with other commitments by the PI, the period of performance was extended at no additional cost until 6/30/2002. The goal of this project was to study scintillating fiber pair-tracking gamma-ray telescope configurations specifically designed to perform imaging and spectroscopy in the 5 - 250 MeV energy range. The main efforts were concentrated in two areas: 1) development of tracking techniques and event reconstruction algorithms, with particular emphasis on angular resolution; and 2) investigation of coded apertures as a means to improve the instrument angular resolution at low energies.

Use of internal scintillator radioactivity to calibrate DOI function of a PET detector with a dual-ended-scintillator readout.

PubMed

Bircher, Chad; Shao, Yiping

2012-02-01

Positron emission tomography (PET) detectors that use a dual-ended-scintillator readout to measure depth-of-interaction (DOI) must have an accurate DOI function to provide the relationship between DOI and signal ratios to be used for detector calibration and recalibration. In a previous study, the authors used a novel and simple method to accurately and quickly measure DOI function by irradiating the detector with an external uniform flood source; however, as a practical concern, implementing external uniform flood sources in an assembled PET system is technically challenging and expensive. In the current study, therefore, the authors investigated whether the same method could be used to acquire DOI function from scintillator-generated (i.e., internal) radiation. The authors also developed a method for calibrating the energy scale necessary to select the events within the desired energy window. The authors measured the DOI function of a PET detector with lutetium yttrium orthosilicate (LYSO) scintillators. Radiation events originating from the scintillators' internal Lu-176 beta decay were used to measure DOI functions which were then compared with those measured from both an external uniform flood source and an electronically collimated external point source. The authors conducted these studies with several scintillators of differing geometries (1.5 × 1.5 and 2.0 × 2.0 mm(2) cross-section area and 20, 30, and 40 mm length) and various surface finishes (mirror-finishing, saw-cut rough, and other finishes in between), and in a prototype array. All measured results using internal and external radiation sources showed excellent agreement in DOI function measurement. The mean difference among DOI values for all scintillators measured from internal and external radiation sources was less than 1.0 mm for different scintillator geometries and various surface finishes. The internal radioactivity of LYSO scintillators can be used to accurately measure DOI function

Use of internal scintillator radioactivity to calibrate DOI function of a PET detector with a dual-ended-scintillator readout

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

Bircher, Chad; Shao Yiping

Purpose: Positron emission tomography (PET) detectors that use a dual-ended-scintillator readout to measure depth-of-interaction (DOI) must have an accurate DOI function to provide the relationship between DOI and signal ratios to be used for detector calibration and recalibration. In a previous study, the authors used a novel and simple method to accurately and quickly measure DOI function by irradiating the detector with an external uniform flood source; however, as a practical concern, implementing external uniform flood sources in an assembled PET system is technically challenging and expensive. In the current study, therefore, the authors investigated whether the same method couldmore » be used to acquire DOI function from scintillator-generated (i.e., internal) radiation. The authors also developed a method for calibrating the energy scale necessary to select the events within the desired energy window. Methods: The authors measured the DOI function of a PET detector with lutetium yttrium orthosilicate (LYSO) scintillators. Radiation events originating from the scintillators' internal Lu-176 beta decay were used to measure DOI functions which were then compared with those measured from both an external uniform flood source and an electronically collimated external point source. The authors conducted these studies with several scintillators of differing geometries (1.5 x 1.5 and 2.0 x 2.0 mm{sup 2} cross-section area and 20, 30, and 40 mm length) and various surface finishes (mirror-finishing, saw-cut rough, and other finishes in between), and in a prototype array. Results: All measured results using internal and external radiation sources showed excellent agreement in DOI function measurement. The mean difference among DOI values for all scintillators measured from internal and external radiation sources was less than 1.0 mm for different scintillator geometries and various surface finishes. Conclusions: The internal radioactivity of LYSO scintillators can

Developments of scintillator-based soft x-ray diagnostic in LHD with CsI:Tl and P47 scintillators.

PubMed

Bando, T; Ohdachi, S; Suzuki, Y

2016-11-01

Multi-channel soft x-ray (SX) diagnostic has been used in the large helical device (LHD) to research magnetohydrodynamic equilibria and activities. However, in the coming deuterium plasma experiments of LHD, it will be difficult to use semiconductor systems near LHD. Therefore, a new type of SX diagnostic, a scintillator-based type diagnostic, has been investigated in order to avoid damage from the radiation. A fiber optic plate coated by P47 scintillator will be used to detect SX emission. Scintillation light will be transferred by pure silica core optical fibers and detected by photomultiplier tubes. A vertically elongated section of LHD will be covered by a 13 ch. array. Effects from the Deuterium Deuterium neutrons can be negligible when the scintillator is covered by a Pb plate 4 cm in thickness to avoid gamma-rays.

Developments of scintillator-based soft x-ray diagnostic in LHD with CsI:Tl and P47 scintillators

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

Bando, T., E-mail: bando.takahiro@nifs.ac.jp; Ohdachi, S.; Suzuki, Y.

2016-11-15

Multi-channel soft x-ray (SX) diagnostic has been used in the large helical device (LHD) to research magnetohydrodynamic equilibria and activities. However, in the coming deuterium plasma experiments of LHD, it will be difficult to use semiconductor systems near LHD. Therefore, a new type of SX diagnostic, a scintillator-based type diagnostic, has been investigated in order to avoid damage from the radiation. A fiber optic plate coated by P47 scintillator will be used to detect SX emission. Scintillation light will be transferred by pure silica core optical fibers and detected by photomultiplier tubes. A vertically elongated section of LHD will bemore » covered by a 13 ch. array. Effects from the Deuterium Deuterium neutrons can be negligible when the scintillator is covered by a Pb plate 4 cm in thickness to avoid gamma-rays.« less

Measurement of ortho-positronium properties in liquid scintillators

NASA Astrophysics Data System (ADS)

Perasso, S.; Consolati, G.; Franco, D.; Hans, S.; Jollet, C.; Meregaglia, A.; Tonazzo, A.; Yeh, M.

2013-08-01

Pulse shape discrimination in liquid scintillator detectors is a well-established technique for the discrimination of heavy particles from light particles. Nonetheless, it is not efficient in the separation of electrons and positrons, as they give rise to indistinguishable scintillator responses. This inefficiency can be overtaken through the exploitation of the formation of ortho-Positronium (o-Ps), which alters the time profile of light pulses induced by positrons. We characterized the o-Ps properties in the most commonly used liquid scintillators, i.e. PC, PXE, LAB, OIL and PC + PPO. In addition, we studied the effects of scintillator doping on the o-Ps properties for dopants currently used in neutrino experiments, Gd and Nd. Further measurements for Li-loaded and Tl-loaded liquid scintillators are foreseen. We found that the o-Ps properties are suitable for enhancing the electron-positron discrimination.

Alkali metal hafnium oxide scintillators

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

Bourret-Courchesne, Edith; Derenzo, Stephen E.; Taylor, Scott Edward

The present invention provides for a composition comprising an inorganic scintillator comprising an alkali metal hafnate, optionally cerium-doped, having the formula A 2HfO 3:Ce; wherein A is an alkali metal having a valence of 1, such as Li or Na; and the molar percent of cerium is 0% to 100%. The alkali metal hafnate are scintillators and produce a bright luminescence upon irradiation by a suitable radiation.

YAP:Ce scintillator characteristics for neutron detection

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

Viererbl, L.; Klupak, V.; Vins, M.

2015-07-01

YAP:Ce (YAlO{sub 3}:Ce{sup +}, Yttrium Aluminum Perovskite, Ce{sup +} doped) crystals with appropriate converters seem like prospective scintillators for neutron detection. An important aspect for neutron detection with inorganic scintillators is the ability to discriminate neutron radiation from gamma radiation by pulse height of signals. For a detailed measurement of the aspect, a YAP:Ce crystal scintillator with lithium or hydrogen converters and a photomultiplier was used. A plutonium-beryllium neutron source and horizontal neutron channel beams of the LVR-15 research reactor were used as neutron sources. The measurement confirmed the possibility to use the YAP:Ce scintillator for neutron radiation detection. Themore » degree of discrimination between neutron and gamma radiation for different detection configurations was studied. (authors)« less

Investigation of the unique degradation phenomenon observed in CsSrBr3: Eu 5% scintillator crystals

NASA Astrophysics Data System (ADS)

Gokhale, S. S.; Loyd, M.; Stand, L.; Lindsey, A.; Swider, S.; Zhuravleva, M.; Melcher, C. L.

2016-10-01

CsSrBr3: Eu 5% is a promising compound scintillator for radiation detection and imaging applications. Light output and energy resolution measured for a crystal of volume 5×5×5 mm3 were 55,000±2000 ph/MeV and 5.6% at 662 keV respectively which is a significant improvement over previous reports. The hygroscopicity of the compound and the tendency of the scintillator crystals to degrade when exposed to the atmosphere necessitate the proper encapsulation of the crystals. It was observed that unlike other hygroscopic scintillator crystals CsSrBr3 undergoes a unique degradation while encapsulated in mineral oil. The light output of the crystal decreases over time, but there is no visually observed physical degradation of the crystal. This degradation is a reversible process wherein a degraded crystal can be subjected to annealing in vacuum in order to restore its original performance.

Radar detection during scintillation. Technical report

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

Knepp, D.L.; Reinking, J.T.

1990-04-01

Electromagnetic signals that propagate through a disturbed region of the ionosphere can experience scattering which can cause fluctuations in the received amplitude, phase, and angle-of-arrival. This report considers the performance of a radar that must operate through a disturbed propagation environment such as might occur during strong equatorial scintillation, during a barium release experiment or after a high altitude nuclear detonation. The severity of the channel disturbance is taken to range from weak scattering where the signal quadrature components are uncorrelated Gaussian variates. The detection performance of noncoherent combining is compared to that of double threshold (M out of N)more » combining under various levels of scintillation disturbance. Results are given for detection sensitivity as a function of the scintillation index and the ratio of the radar hopping bandwidth to the channel bandwidth. It is shown that both types of combining can provide mitigation of fading, and that noncoherent combining generally enjoys an advantage in detection sensitivity of about 2 dB. This work serves as a quantitative guideline to the advantages and disadvantages of certain types of detection strategies during scintillation and is, therefore, useful in the radar design process. However, a detailed simulation of the radar detection algorithms is necessary to evaluate a radar design strategy to predict performance under scintillation conditions.« less

The Ionospheric Scintillation Effects on the BeiDou Signal Receiver

PubMed Central

He, Zhijun; Zhao, Hongbo; Feng, Wenquan

2016-01-01

Irregularities in the Earth’s ionosphere can make the amplitude and phase of radio signals fluctuate rapidly, which is known as ionospheric scintillation. Severe ionospheric scintillation could affect the performance of the Global Navigation Satellite System (GNSS). Currently, the Multiple Phase Screen (MPS) technique is widely used in solving problems caused by weak and strong scintillations. Considering that Southern China is mainly located in the area where moderate and intense scintillation occur frequently, this paper built a model based on the MPS technique and discussed the scintillation impacts on China’s BeiDou navigation system. By using the BeiDou B1I signal, this paper analyzed the scintillation effects on the receiver, which includes the acquisition and tracking process. For acquisition process, this paper focused on the correlation peak and acquisition probability. For the tracking process, this paper focused on the carrier tracking loop and the code tracking loop. Simulation results show that under high scintillation intensity, the phase fluctuation could be −1.13 ± 0.087 rad to 1.40 ± 0.087 rad and the relative amplitude fluctuation could be −10 dB to 8 dB. As the scintillation intensity increased, the average correlation peak would decrease more than 8%, which could thus degrade acquisition performance. On the other hand, when the signal-to-noise ratio (SNR) is comparatively lower, the influence of strong scintillation on the phase locked loop (PLL) is much higher than that of weak scintillation. As the scintillation becomes more intense, PLL variance could consequently results in an error of more than 2.02 cm in carrier-phase based ranging. In addition, the delay locked loop (DLL) simulation results indicated that the pseudo-range error caused by strong scintillation could be more than 4 m and the consequent impact on positioning accuracy could be more than 6 m. PMID:27834867

A novel phoswich imaging detector for simultaneous beta and coincidence-gamma imaging of plant leaves.

PubMed

Wu, Heyu; Tai, Yuan-Chuan

2011-09-07

To meet the growing demand for functional imaging technology for use in studying plant biology, we are developing a novel technique that permits simultaneous imaging of escaped positrons and coincidence gammas from annihilation of positrons within an intake leaf. The multi-modality imaging system will include two planar detectors: one is a typical PET detector array and the other is a phoswich imaging detector that detects both beta and gamma. The novel phoswich detector is made of a plastic scintillator, a lutetium oxyorthosilicate (LSO) array, and a position sensitive photomultiplier tube (PS-PMT). The plastic scintillator serves as a beta detector, while the LSO array serves as a gamma detector and light guide that couples scintillation light from the plastic detector to the PMT. In our prototype, the PMT signal was fed into the Siemens QuickSilver electronics to achieve shaping and waveform sampling. Pulse-shape discrimination based on the detectors' decay times (2.1 ns for plastic and 40 ns for LSO) was used to differentiate beta and gamma events using the common PMT signals. Using our prototype phoswich detector, we simultaneously measured a beta image and gamma events (in single mode). The beta image showed a resolution of 1.6 mm full-width-at-half-maximum using F-18 line sources. Because this shows promise for plant-scale imaging, our future plans include development of a fully functional simultaneous beta-and-coincidence-gamma imager with sub-millimeter resolution imaging capability for both modalities.

Automatic detection of recoil-proton tracks and background rejection criteria in liquid scintillator-micro-capillary-array fast neutron spectrometer

NASA Astrophysics Data System (ADS)

Mor, Ilan; Vartsky, David; Dangendorf, Volker; Tittelmeier, Kai.; Weierganz, Mathias; Goldberg, Mark Benjamin; Bar, Doron; Brandis, Michal

2018-06-01

We describe an analysis procedure for automatic unambiguous detection of fast-neutron-induced recoil proton tracks in a micro-capillary array filled with organic liquid scintillator. The detector is viewed by an intensified CCD camera. This imaging neutron detector possesses the capability to perform high position-resolution (few tens of μm), energy-dispersive transmission-imaging using ns-pulsed beams. However, when operated with CW or DC beams, it also features medium-quality spectroscopic capabilities for incident neutrons in the energy range 2-20 MeV. In addition to the recoil proton events which display a continuous extended track structure, the raw images exhibit complex ion-tracks from nuclear interactions of fast-neutrons in the scintillator, capillaries quartz-matrix and CCD. Moreover, as expected, one also observes a multitude of isolated scintillation spots of varying intensity (henceforth denoted "blobs") that originate from several different sources, such as: fragmented proton tracks, gamma-rays, heavy-ion reactions as well as events and noise that occur in the image-intensifier and CCD. In order to identify the continuous-track recoil proton events and distinguish them from all these background events, a rapid, computerized and automatic track-recognition-procedure was developed. Based on an appropriately weighted analysis of track parameters such as: length, width, area and overall light intensity, the method is capable of distinguishing a single continuous-track recoil proton from typically surrounding several thousands of background events that are found in each CCD frame.

Complex Dynamics of Equatorial Scintillation

NASA Astrophysics Data System (ADS)

Piersanti, Mirko; Materassi, Massimo; Forte, Biagio; Cicone, Antonio

2017-04-01

Radio power scintillation, namely highly irregular fluctuations of the power of trans-ionospheric GNSS signals, is the effect of ionospheric plasma turbulence. The scintillation patterns on radio signals crossing the medium inherit the ionospheric turbulence characteristics of inter-scale coupling, local randomness and large time variability. On this basis, the remote sensing of local features of the turbulent plasma is feasible by studying radio scintillation induced by the ionosphere. The distinctive character of intermittent turbulent media depends on the fluctuations on the space- and time-scale statistical properties of the medium. Hence, assessing how the signal fluctuation properties vary under different Helio-Geophysical conditions will help to understand the corresponding dynamics of the turbulent medium crossed by the signal. Data analysis tools, provided by complex system science, appear to be best fitting to study the response of a turbulent medium, as the Earth's equatorial ionosphere, to the non-linear forcing exerted by the Solar Wind (SW). In particular we used the Adaptive Local Iterative Filtering, the Wavelet analysis and the Information theory data analysis tool. We have analysed the radio scintillation and ionospheric fluctuation data at low latitude focusing on the time and space multi-scale variability and on the causal relationship between forcing factors from the SW environment and the ionospheric response.

SU-F-J-51: A Cone-Based Scintillator Detector for IGRT QA for Scattered and Scanning Proton Therapy

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

Oesten, H; Clasie, B; Jee, K

Purpose: IGRT commissioning and QA are critical components for precise delivery of proton treatment beams to patients. In order to ensure high quality IGRT, a new cone-based scintillator detector was evaluated for our QA activities for double-scattered and scanning proton modalities. This allows a routine evaluation of the gantry-angle dependent position offset between the radiation and imaging. Methods: The cone-based scintillator detector (XRV-124, Logos Systems, Int’l CA, USA) features a unique configuration of measuring stereotactic paths of proton and x-ray beams in a single setup with arbitrary gantry angles. For the beams-eye-view (BEV) analysis of x-ray crosshair images, a cylindricalmore » representation of the cone image was newly developed. The calibration accuracy was evaluated using different CT resolutions for a range of 55 – 95mm in patient’s cranial direction and ±9mm in the lateral direction. Energy-dependent spot sizes (σ) of pencil beams were characterized and compared to measurements by the MatriXX detector (IBA, Germany). Iso-centric deviations between radiation and x-ray imaging were characterized as a function of gantry angle. Results: The position calibration of the detector was successfully verified with a reproducible positioning by x-ray imaging. The measurements were reproducible within clinical tolerances (±1mm). The spot size vs. energy at zero gantry angle measured with the scintillating cone detector agreed with the MatriXX detector measurements within 17%. Conclusion: The new approach to investigate the accuracy of IGRT and pencil beam properties could successfully be implemented into the QA program. The system will improve efficiency in our QA activities for proton treatments.« less

Predicting pulsar scintillation from refractive plasma sheets

NASA Astrophysics Data System (ADS)

Simard, Dana; Pen, Ue-Li

2018-07-01

The dynamic and secondary spectra of many pulsars show evidence for long-lived, aligned images of the pulsar that are stationary on a thin scattering sheet. One explanation for this phenomenon considers the effects of wave crests along sheets in the ionized interstellar medium, such as those due to Alfvén waves propagating along current sheets. If these sheets are closely aligned to our line of sight to the pulsar, high bending angles arise at the wave crests and a selection effect causes alignment of images produced at different crests, similar to grazing reflection off of a lake. Using geometric optics, we develop a simple parametrized model of these corrugated sheets that can be constrained with a single observation and that makes observable predictions for variations in the scintillation of the pulsar over time and frequency. This model reveals qualitative differences between lensing from overdense and underdense corrugated sheets: only if the sheet is overdense compared to the surrounding interstellar medium can the lensed images be brighter than the line-of-sight image to the pulsar, and the faint lensed images are closer to the pulsar at higher frequencies if the sheet is underdense, but at lower frequencies if the sheet is overdense.

Predicting Pulsar Scintillation from Refractive Plasma Sheets

NASA Astrophysics Data System (ADS)

Simard, Dana; Pen, Ue-Li

2018-05-01

The dynamic and secondary spectra of many pulsars show evidence for long-lived, aligned images of the pulsar that are stationary on a thin scattering sheet. One explanation for this phenomenon considers the effects of wave crests along sheets in the ionized interstellar medium, such as those due to Alfvén waves propagating along current sheets. If these sheets are closely aligned to our line-of-sight to the pulsar, high bending angles arise at the wave crests and a selection effect causes alignment of images produced at different crests, similar to grazing reflection off of a lake. Using geometric optics, we develop a simple parameterized model of these corrugated sheets that can be constrained with a single observation and that makes observable predictions for variations in the scintillation of the pulsar over time and frequency. This model reveals qualitative differences between lensing from overdense and underdense corrugated sheets: Only if the sheet is overdense compared to the surrounding interstellar medium can the lensed images be brighter than the line-of-sight image to the pulsar, and the faint lensed images are closer to the pulsar at higher frequencies if the sheet is underdense, but at lower frequencies if the sheet is overdense.

Rapid method for determination of 90Sr in seawater by liquid scintillation counting with an extractive scintillator.

PubMed

Uesugi, Masaki; Watanabe, Ryosuke; Sakai, Hiroaki; Yokoyama, Akihiko

2018-02-01

A rapid determination method of 90 Sr is developed for the monitoring of seawater around the Fukushima Daiichi Nuclear Power Plant (FDNPP). Three ideas of chemical separation and measurements to accelerate 90 Sr analysis are investigated. Strontium is co-precipitated in a two-step procedure with hydroxyapatite after the removal of magnesium phosphate in the presence of citric acid. The purification process of strontium is in combination with solid phase extraction disks. One or two sheets of Sr Rad disk and cyclic operations are examined to eliminate interfering substances and secure the exchange capacity. The suitable conditions of adsorption and stripping are determined with a 85 Sr tracer. Seawater samples up to 1L can be analyzed within 4h. Additionally, the appropriate pH conditions to extract strontium to the scintillator are studied, and the 90 Sr activity is assessed via liquid scintillation counting using an extractive scintillator based on the di-(2-etyl hexyl)-phosphoric acid (HDEHP) extraction method. The new scintillation counting method involves a small quenching effect and a low background compared to the conventional emulsion scintillator method. The minimum detectable activity (MDA) is 35mBq/L of 90 Sr in 180min of counting. The proposed method provides analytical results within a day after receipt of the samples. Copyright © 2017 Elsevier B.V. All rights reserved.

MR imaging of apparent 3He gas transport in narrow pipes and rodent airways

NASA Astrophysics Data System (ADS)

Minard, Kevin R.; Jacob, Richard E.; Laicher, Gernot; Einstein, Daniel R.; Kuprat, Andrew P.; Corley, Richard A.

2008-10-01

High sensitivity makes hyperpolarized 3He an attractive signal source for visualizing gas flow with magnetic resonance (MR) imaging. Its rapid Brownian motion, however, can blur observed flow lamina and alter measured diffusion rates when excited nuclei traverse shear-induced velocity gradients during data acquisition. Here, both effects are described analytically, and predicted values for measured transport during laminar flow through a straight, 3.2-mm diameter pipe are validated using two-dimensional (2D) constant-time images of different binary gas mixtures. Results show explicitly how measured transport in narrow conduits is characterized by apparent values that depend on underlying gas dynamics and imaging time. In ventilated rats, this is found to obscure acquired airflow images. Nevertheless, flow splitting at airway branches is still evident and use of 3D vector flow mapping is shown to reveal surprising detail that highlights the correlation between gas dynamics and lung structure.

Development of a simple-material discrimination method with three plastic scintillator strips for visualizing nuclear reactors

NASA Astrophysics Data System (ADS)

Takamatsu, k.; Tanaka, h.; Shoji, d.

2012-04-01

The Fukushima Daiichi nuclear disaster is a series of equipment failures and nuclear meltdowns, following the T¯o hoku earthquake and tsunami on 11 March 2011. We present a new method for visualizing nuclear reactors. Muon radiography based on the multiple Coulomb scattering of cosmic-ray muons has been performed. In this work, we discuss experimental results obtained with a cost-effective simple detection system assembled with three plastic scintillator strips. Actually, we counted the number of muons that were not largely deflected by restricting the zenith angle in one direction to 0.8o. The system could discriminate Fe, Pb and C. Materials lighter than Pb can be also discriminated with this system. This method only resolves the average material distribution along the muon path. Therefore the user must make assumptions or interpretations about the structure, or must use more than one detector to resolve the three dimensional material distribution. By applying this method to time-dependent muon radiography, we can detect changes with time, rendering the method suitable for real-time monitoring applications, possibly providing useful information about the reaction process in a nuclear reactor such as burnup of fuels. In nuclear power technology, burnup (also known as fuel utilization) is a measure of how much energy is extracted from a primary nuclear fuel source. Monitoring the burnup of fuels as a nondestructive inspection technique can contribute to safer operation. In nuclear reactor, the total mass is conserved so that the system cannot be monitored by conventional muon radiography. A plastic scintillator is relatively small and easy to setup compared to a gas or layered scintillation system. Thus, we think this simple radiographic method has the potential to visualize a core directly in cases of normal operations or meltdown accidents. Finally, we considered only three materials as a first step in this work. Further research is required to improve the

Performance study of a PET scanner based on monolithic scintillators for different DoI-dependent methods

NASA Astrophysics Data System (ADS)

Preziosi, E.; Sánchez, S.; González, A. J.; Pani, R.; Borrazzo, C.; Bettiol, M.; Rodriguez-Alvarez, M. J.; González-Montoro, A.; Moliner, L.; Benlloch, J. M.

2016-12-01

One of the technical objectives of the MindView project is developing a brain-dedicated PET insert based on monolithic scintillation crystals. It will be inserted in MRI systems with the purpose to obtain simultaneous PET and MRI brain images. High sensitivity, high image quality performance and accurate detection of the Depth-of-Interaction (DoI) of the 511keV photons are required. We have developed a DoI estimation method, dedicated to monolithic scintillators, allowing continuous DoI estimation and a DoI-dependent algorithm for the estimation of the photon planar impact position, able to improve the single module imaging capabilities. In this work, through experimental measurements, the proposed methods have been used for the estimation of the impact positions within the monolithic crystal block. We have evaluated the PET system performance following the NEMA NU 4-2008 protocol by reconstructing the images using the STIR 3D platform. The results obtained with two different methods, providing discrete and continuous DoI information, are compared with those obtained from an algorithm without DoI capabilities and with the ideal response of the detector. The proposed DoI-dependent imaging methods show clear improvements in the spatial resolution (FWHM) of reconstructed images, allowing to obtain values from 2mm (at the center FoV) to 3mm (at the FoV edges).

New Developments in Scintillators for Security Applications

NASA Astrophysics Data System (ADS)

Glodo, Jarek; Wang, Yimin; Shawgo, Ryan; Brecher, Charles; Hawrami, Rastgo H.; Tower, Joshua; Shah, Kanai S.

Radiation is an important part of security space: It is detected either passively in search of special nuclear materials or actively to monitor or interrogate objects of interest. Systems relying on radiation require adequate detectors. The most common radiation detectors are based on scintillating materials that convert hard (gamma, x-ray or neutron) radiation into visible light registered by a photodetector. The last decade has seen development of new materials driven by various security applications. This included the search for He-3 replacement technologies, which resulted in development of neutron sensing scintillators such as Ce-doped Cs2LiYCl6 (CLYC) or more recently Cs2LiLa(Br,Cl)6 (CLLBC). Since they are also good gamma-ray scintillators, they have also penetrated the detection market for passive dual-mode (gamma and neutron) detection systems, replacing scintillators such as NaI(Tl) or CsI(Tl) and competing with LaBr3(Ce). High-energy Non-Intrusive Inspection is another area where active research is being pursued in order to replace existing scintillator choices such as CdWO4, which is commonly used in simple radiography, and PbWO4, which is being studied for spectroscopic alternatives to radiography. For radiography, in particular, new ceramic scintillators such as Ce-doped GLuGAG (garnet) are considered, and for spectroscopy, Yb doped Lu2O3. In this paper we provide a short overview of these technologies.

Scintillator Development for the PROSPECT Experiment

NASA Astrophysics Data System (ADS)

Yeh, Minfang

2014-03-01

Doped scintillator is the target material of choice for antineutrino detection as it utilizes the time-delayed coincidence signature of the positron annihilation and neutron capture resulting from the Inverse Beta Decay (IBD) interaction. Additionally, the multiple gamma rays or heavy ions emitted after neutron capture on either Gd or 6Li respectively provide a distinct signal for the identification of antineutrino events and therefore significantly enhance accidental background reduction. The choice of scintillator and dopant depends on the detector requirements and scintillator performance criteria. Both Gd and 6Li doped scintillators have been used in past reactor antineutrino experiments such as Double Chooz, Daya Bay, RENO, and Bugey3 and are currently under investigation by the PROSPECT collaboration. Their properties in terms of light yield, optical transparency, chemical stability and background rejection efficiency using Pulse Shape Discrimination (PSD) will be reported. Research sponsored by the U.S. Department of Energy, Office of Nuclear Physics and Office of High Energy Physics, under contract with Brookhaven National Laboratory-Brookhaven Science Associates.

Evaluation of a SiPM array coupled to a Gd3Al2Ga3O12:Ce (GAGG:Ce) discrete scintillator.

PubMed

David, S; Georgiou, M; Fysikopoulos, E; Loudos, G

2015-11-01

In this study, we present the results of the evaluation of the SensL ArraySL-4 photo-detector, coupled to a 6 × 6 GAGG:Ce scintillator array, with 2 × 2 × 5 mm(3) crystal size elements for possible applications in medical imaging detectors with focus in PET applications. Experimental evaluation was carried out with (22)Na and (137)Cs radioactive sources and the parameters studied were energy resolution and peak to valley ratio. ArraySL-4 is a commercially available, 4 × 4 array detector covering an active area of 13.4 mm(2). The GAGG:Ce scintillator array used in this study has 0.1 mm thickness BaSO4 reflector material between the crystal elements. A symmetric resistive voltage division matrix was applied, which reduces the 16 outputs of the array to 4 position signals. A Field Programmable Gate Array was used for triggering and digital processing of the signal pulses acquired using free running Analog to Digital Converters. Raw images and horizontal profiles of the 6 × 6 GAGG:Ce scintillator array produced under 511 keV and 662 keV excitation are illustrated. Moreover, the energy spectra obtained with (22)Na and (137)Cs radioactive sources from a single 2 × 2 × 5 mm(3) GAGG:Ce scintillator are shown. The peak to valley ratio and the mean energy resolution values are reported. The acquired raw image of the GAGG:Ce crystal array under 511 keV excitation shows a clear visualization of all discrete scintillator elements with a mean peak to valley ratio equal to 40. The mean energy resolution was measured equal to 10.5% and 9% respectively under 511 keV and 662 keV irradiation. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Advanced plastic scintillators for fast neutron discrimination

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

Feng, Patrick L; Anstey, Mitchell; Doty, F. Patrick

2014-09-01

The present work addresses the need for solid-state, fast neutron discriminating scintillators that possess higher light yields and faster decay kinetics than existing organic scintillators. These respective attributes are of critical importance for improving the gamma-rejection capabilities and increasing the neutron discrimination performance under high-rate conditions. Two key applications that will benefit from these improvements include large-volume passive detection scenarios as well as active interrogation search for special nuclear materials. Molecular design principles were employed throughout this work, resulting in synthetically tailored materials that possess the targeted scintillation properties.

Multiparametric imaging of brain hemodynamics and function using gas-inhalation MRI

PubMed Central

Liu, Peiying; Welch, Babu G.; Li, Yang; Gu, Hong; King, Darlene; Yang, Yihong; Pinho, Marco; Lu, Hanzhang

2016-01-01

Diagnosis and treatment monitoring of cerebrovascular diseases routinely require hemodynamic imaging of the brain. Current methods either only provide part of the desired information or require the injection of multiple exogenous agents. In this study, we developed a multiparametric imaging scheme for the imaging of brain hemodynamics and function using gas-inhalation MRI. The proposed technique uses a single MRI scan to provide simultaneous measurements of baseline venous cerebral blood volume (vCBV), cerebrovascular reactivity (CVR), bolus arrival time (BAT), and resting-state functional connectivity (fcMRI). This was achieved with a novel, concomitant O2 and CO2 gas inhalation paradigm, rapid MRI image acquisition with a 9.3 min BOLD sequence, and an advanced algorithm to extract multiple hemodynamic information from the same dataset. In healthy subjects, CVR and vCBV values were 0.23±0.03 %/mmHg and 0.0056±0.0006 %/mmHg, respectively, with a strong correlation (r=0.96 for CVR and r=0.91 for vCBV) with more conventional, separate acquisitions that take twice the scan time. In patients with Moyamoya syndrome, CVR in the stenosis-affected flow territories (typically anterior-cerebral-artery, ACA, and middle-cerebral-artery, MCA, territories) was significantly lower than that in posterior-cerebral-artery (PCA), which typically has minimal stenosis, flow territories (0.12±0.06 %/mmHg vs. 0.21±0.05 %/mmHg, p<0.001). BAT of the gas bolus was significantly longer (p=0.008) in ACA/MCA territories, compared to PCA, and the maps were consistent with the conventional contrast-enhanced CT perfusion method. FcMRI networks were robustly identified from the gas-inhalation MRI data after factoring out the influence of CO2 and O2 on the signal time course. The spatial correspondence between the gas-data-derived fcMRI maps and those using a separate, conventional fcMRI scan was excellent, showing a spatial correlation of 0.58±0.17 and 0.64±0.20 for default mode network and

New Organic Scintillators for Neutron Detection

DTIC Science & Technology

2016-03-01

highly enriched uranium and weapons grade plutonium. Neutrons and gamma rays are two signatures of these materials. Gamma ray detection techniques are...New Organic Scintillators for Neutron Detection Distribution Statement A. Approved for public release; distribution is unlimited. March...Title: New Organic Scintillators for Neutron Detection I. Abstract In this project, Radiation Monitoring Devices (RMD) proposes to develop novel

Binderless composite scintillator for neutron detection

DOEpatents

Hodges, Jason P [Knoxville, TN; Crow, Jr; Lowell, M [Oak Ridge, TN; Cooper, Ronald G [Oak Ridge, TN

2009-03-10

Composite scintillator material consisting of a binderless sintered mixture of a Lithium (Li) compound containing .sup.6Li as the neutron converter and Y.sub.2SiO.sub.5:Ce as the scintillation phosphor, and the use of this material as a method for neutron detection. Other embodiments of the invention include various other Li compounds.

Scintillator Non-Proportionality: Present Understanding and Future Challenges

NASA Astrophysics Data System (ADS)

Moses, W. W.; Payne, S. A.; Choong, W.-S.; Hull, G.; Reutter, B. W.

2008-06-01

Scintillator non-proportionality (the fact that the conversion factor between the energy deposited in a scintillator and the number of visible photons produced is not constant) has been studied both experimentally and theoretically for 50 years. Early research centered on the dependence of the conversion factor on the species of the ionizing radiation (gamma, alpha, beta, proton, etc.), and researchers during the 1960s discovered a strong correlation between the scintillation efficiency and the ionization density. In more recent years, non-proportionality has been proposed as the reason why the energy resolution of most scintillators is worse than that predicted by counting statistics. While much progress has been made, there are still major gaps in our understanding of both the fundamental causes of non-proportionality and their quantitative link to scintillator energy resolution. This paper summarizes the present state of knowledge on the nature of the light-yield non-proportionality and its effect on energy resolution.

Interstellar scintillation observations for PSR B0355+54

NASA Astrophysics Data System (ADS)

Xu, Y. H.; Lee, K. J.; Hao, L. F.; Wang, H. G.; Liu, Z. Y.; Yue, Y. L.; Yuan, J. P.; Li, Z. X.; Wang, M.; Dong, J.; Tan, J. J.; Chen, W.; Bai, J. M.

2018-06-01

In this paper, we report our investigation of pulsar scintillation phenomena by monitoring PSR B0355+54 at 2.25 GHz for three successive months using the Kunming 40-m radio telescope. We measured the dynamic spectrum, the two-dimensional correlation function and the secondary spectrum. These observations have a high signal-to-noise ratio (S/N ≥ 100). We detected scintillation arcs, which are rarely observable using such a small telescope. The sub-microsecond scale width of the scintillation arc indicates that the transverse scale of the structures on the scattering screen is as compact as astronomical unit size. Our monitoring shows that the scintillation bandwidth, the time-scale and the arc curvature of PSR B0355+54 were varying temporally. A plausible explanation would need to invoke a multiple-scattering-screen or multiple-scattering-structure scenario, in which different screens or ray paths dominate the scintillation process at different epochs.

Studies on scintillating fiber response

NASA Astrophysics Data System (ADS)

Albers, D.; Bisplinghoff, J.; Bollmann, R.; Büßer, K.; Cloth, P.; Diehl, O.; Dohrmann, F.; Drüke, V.; Engelhardt, H. P.; Ernst, J.; Eversheim, P. D.; Filges, D.; Gasthuber, M.; Gebel, R.; Greiff, J.; Groß, A.; Groß-Hardt, R.; Heine, A.; Heider, S.; Hinterberger, F.; Igelbrink, M.; Jahn, R.; Jeske, M.; Langkau, R.; Lindlein, J.; Maier, R.; Maschuw, R.; Mayer-Kuckuk, T.; Mertler, G.; Metsch, B.; Mosel, F.; Müller, M.; Münstermann, M.; Paetz gen. Schieck, H.; Petry, H. R.; Prasuhn, D.; Rohdjeß, H.; Rosendaal, D.; Roß, U.; von Rossen, P.; Scheid, H.; Schirm, N.; Schulz-Rojahn, M.; Schwandt, F.; Scobel, W.; Steeg, B.; Sterzenbach, G.; Trelle, H. J.; Wellinghausen, A.; Wiedmann, W.; Woller, K.; Ziegler, R.

1996-02-01

Scintillating fibers of type Bicron BCF-12 with 2 × 2 mm 2 cross section, up to 600 mm length, and PMMA cladding have been tested, in conjunction with the multi-channel photomultiplier Hamamatsu R 4760, with minimum ionizing electrons. The impact of cladding, extramural absorbers and/or wrapping on the light attenuation and photoelectron yield is studied in detail. Fibers have been circularly bent with radii of 171 mm and arranged in two layers to bundles forming granulated scintillator rings. Their performance in the EDDA experiment at COSY for detection of high energy protons revealed typically more than 9 (6) photoelectrons per fiber from bundles with (without) mirror on the rear side, guaranteeing detection efficiencies >99% and full compatibility with corresponding solid scintillator rings. The time resolution of 3.4 ns FWHM per fiber read out is essentially due to the R 4760.

Lu.sub.1-xI.sub.3:Ce.sub.x--a scintillator for gamma ray spectroscopy and time-of-flight PET

DOEpatents

Shah, Kanai S.

2007-02-06

The present invention concerns very fast scintillator materials comprising lutetium iodide doped with Cerium (Lu.sub.1-xI.sub.3:Ce.sub.x; LuI.sub.3:Ce). The LuI.sub.3 scintillator material has surprisingly good characteristics including high light output, high gamma ray stopping efficiency, fast response, low cost, good proportionality, and minimal afterglow that the material is useful for gamma ray spectroscopy, medical imaging, nuclear and high energy physics research, diffraction, non-destructive testing, nuclear treaty verification and safeguards, and geological exploration. The timing resolution of the scintillators of the present invention provide compositions capable of resolving the position of an annihilation event within a portion of a human body cross-section.

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

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

Fiber optic thermal/fast neutron and gamma ray scintillation detector

DOEpatents

Neal, John S.; Mihalczo, John T.

2006-11-28

A detector system that combines a .sup.6Li loaded glass fiber scintillation thermal neutron detector with a fast scintillation detector in a single layered structure. Detection of thermal and fast neutrons and ionizing electromagnetic radiation is achieved in the unified detector structure. The fast scintillator replaces the polyethelene moderator layer adjacent the .sup.6Li loaded glass fiber panel of the neutron detector and acts as the moderator for the glass fibers. Fast neutrons, x-rays and gamma rays are detected in the fast scintillator. Thermal neutrons, x-rays and gamma rays are detected in the glass fiber scintillator.

Improved lithium iodide neutron scintillator with Eu 2+ activation: The elimination of Suzuki-Phase precipitates

DOE PAGES

Boatner, Lynn A.; Comer, Eleanor P.; Wright, Gomez W.; ...

2017-02-21

Monovalent alkali halides such as NaI, CsI, and LiI are widely used as inorganic scintillators for radiation detection due to their light yield, the capability for the growth of large single crystals, relatively low cost, and other favorable characteristics. These materials are frequently activated through the addition of small amounts (e.g., a few hundred ppm) of elements such as thallium - or sodium in the case of CsI. The monovalent alkali halide scintillators can also be activated with low concentrations of Eu 2+, however Eu activation has previously not been widely employed due to the non-uniform segregation of the divalentmore » Eu dopant that leads to the formation of unwanted phases during Bridgman or other solidification crystal-growth methods. Specifically, for Eu concentrations near and above ~0.5%, Suzuki Phase precipitates form in the course of the melt-growth process, and these Suzuki Phase particles scatter the scintillation light. This adversely affects the scintillator performance via reduction in the optical transmission of the material, and depending on the crystal thickness and precipitated-particle concentration, this reduction can occur up to the point of opacity. Here we describe a post-growth process for the removal of Suzuki Phase precipitates from single crystals of the neutron scintillator LiI activated with Eu 2+ at concentrations up to and in excess of 3 wt.%, and we correlate the resulting neutron-detection performance with the thermal processing methods used to remove the Suzuki Phase particles. Furthermore, the resulting improved scintillator properties using increased Eu activator levels are applicable to neutron imaging and active interrogation systems, and pulse-height gamma-ray spectroscopy rather than pulse-shape discrimination can be used to discriminate between gamma ray and neutron interaction events.« less

Improved lithium iodide neutron scintillator with Eu2+ activation: The elimination of Suzuki-Phase precipitates

NASA Astrophysics Data System (ADS)

Boatner, L. A.; Comer, E. P.; Wright, G. W.; Ramey, J. O.; Riedel, R. A.; Jellison, G. E.; Kolopus, J. A.

2017-05-01

Monovalent alkali halides such as NaI, CsI, and LiI are widely used as inorganic scintillators for radiation detection due to their light yield, the capability for the growth of large single crystals, relatively low cost, and other favorable characteristics. These materials are frequently activated through the addition of small amounts (e.g., a few hundred ppm) of elements such as thallium - or sodium in the case of CsI. The monovalent alkali halide scintillators can also be activated with low concentrations of Eu2+, however Eu activation has previously not been widely employed due to the non-uniform segregation of the divalent Eu dopant that leads to the formation of unwanted phases during Bridgman or other solidification crystal-growth methods. Specifically, for Eu concentrations near and above 0.5%, Suzuki Phase precipitates form in the course of the melt-growth process, and these Suzuki Phase particles scatter the scintillation light. This adversely affects the scintillator performance via reduction in the optical transmission of the material, and depending on the crystal thickness and precipitated-particle concentration, this reduction can occur up to the point of opacity. Here we describe a post-growth process for the removal of Suzuki Phase precipitates from single crystals of the neutron scintillator LiI activated with Eu2+ at concentrations up to and in excess of 3 wt%, and we correlate the resulting neutron-detection performance with the thermal processing methods used to remove the Suzuki Phase particles. The resulting improved scintillator properties using increased Eu activator levels are applicable to neutron imaging and active interrogation systems, and pulse-height gamma-ray spectroscopy rather than pulse-shape discrimination can be used to discriminate between gamma ray and neutron interaction events.

High energy resolution with transparent ceramic garnet scintillators

NASA Astrophysics Data System (ADS)

Cherepy, N. J.; Seeley, Z. M.; Payne, S. A.; Beck, P. R.; Swanberg, E. L.; Hunter, S.; Ahle, L.; Fisher, S. E.; Melcher, C.; Wei, H.; Stefanik, T.; Chung, Y.-S.; Kindem, J.

2014-09-01

Breakthrough energy resolution, R(662keV) < 4%, has been achieved with an oxide scintillator, Cerium-doped Gadolinium Yttrium Gallium Aluminum Garnet, or GYGAG(Ce). Transparent ceramic GYGAG(Ce), has a peak emission wavelength of 550 nm that is better matched to Silicon photodetectors than to standard PMTs. We are therefore developing a spectrometer based on pixelated GYGAG(Ce) on a Silicon photodiode array that can provide R(662 keV) = 3.6%. In comparison, with large 1-2 in3 size GYGAG(Ce) ceramics we obtain R(662 keV) = 4.6% with PMT readout. We find that ceramic GYGAG(Ce) of a given stoichiometric chemical composition can exhibit very different scintillation properties, depending on sintering conditions and post-anneal treatments. Among the characteristics of transparent ceramic garnet scintillators that can be controlled by fabrication conditions are: scintillation decay components and their amplitudes, intensity and duration of afterglow, thermoluminescence glow curve peak positions and amplitudes, integrated light yield, light yield non-proportionality - as measured in the Scintillator Light Yield Non-Proportionality Characterization Instrument (SLYNCI), and energy resolution for gamma spectroscopy. Garnet samples exhibiting a significant fraction of Cerium dopant in the tetravalent valence also exhibit: faster overall scintillation decay, very low afterglow, high light yield, but poor light yield proportionality and degraded energy resolution.

Radiation damage effects on the optical properties of plastic scintillators

NASA Astrophysics Data System (ADS)

Jivan, H.; Mdhluli, J. E.; Sideras-Haddad, E.; Mellado, B.; Erasmus, R.; Madhuku, M.

2017-10-01

We report on the radiation damage to the optical properties of plastic scintillators following irradiation using a 6 MeV proton beam produced by the 6 MV tandem accelerator of iThemba LABS, Gauteng. A comparative is drawn between polyvinyl toluene based commercial scintillators EJ200, EJ208, EJ260 and BC408 as well as polystyrene based scintillator UPS923A and scintillators manufactured for the Tile Calorimeter. Results on the proton induced damage indicate a reduction in the light output and transmission capability of the plastics. Scintillators containing a larger Stokes shift, i.e. EJ260 and EJ208 exhibit the most radiation hardness. The EJ208 is recommended as a candidate to be considered for the replacement of Gap scintillators in the Tile Calorimeter for the 2018 upgrade.

Secondary scintillation yield from GEM and THGEM gaseous electron multipliers for direct dark matter search

NASA Astrophysics Data System (ADS)

Monteiro, C. M. B.; Fernandes, L. M. P.; Veloso, J. F. C. A.; Oliveira, C. A. B.; dos Santos, J. M. F.

2012-07-01

The search for alternatives to PMTs as photosensors in optical TPCs for rare event detection has significantly increased in the last few years. In particular, in view of the next generation large volume detectors, the use of photosensors with lower natural radioactivity, such as large area APDs or GM-APDs, with the additional possibility of sparse surface coverage, triggered the intense study of secondary scintillation production in micropattern electron multipliers, such as GEMs and THGEMs, as alternatives to the commonly used uniform electric field region between two parallel meshes. The much higher scintillation output obtained from the electron avalanches in such microstructures presents an advantage in those situations. The accurate knowledge of the amount of such scintillation is important for correct detector simulation and optimization. It will also serve as a benchmark for software tools developed and/or under development for the calculation of the amount of such scintillation.The secondary scintillation yield, or electroluminescence yield, in the electron avalanches of GEMs and THGEMs operating in gaseous xenon and argon has been determined for different gas pressures. At 1 bar, THGEMs deliver electroluminescence yields that are more than one order of magnitude higher when compared to those achieved in GEMs and two orders of magnitude when compared to those achieved in a uniform field gap. The THGEM electroluminescence yield presents a faster decrease with pressure when comparing to the GEM electroluminescence yield, reaching similar values to what is achieved in GEMs for xenon pressures of 2.5 bar, but still one order of magnitude higher than that produced in a uniform field gap. Another exception is the GEM operating in argon, which presents an electroluminescence yield similar to that produced in a uniform electric field gap, while the THGEM achieves yields that are more than one order of magnitude higher.

Measurement of Total Scatter Factor for Stereotactic Cones with Plastic Scintillation Detector.

PubMed

Chaudhari, Suresh H; Dobhal, Rishabh; Kinhikar, Rajesh A; Kadam, Sudarshan S; Deshpande, Deepak D

2017-01-01

Advanced radiotherapy modalities such as stereotactic radiosurgery (SRS) and image-guided radiotherapy may employ very small beam apertures for accurate localized high dose to target. Accurate measurement of small radiation fields is a well-known challenge for many dosimeters. The purpose of this study was to measure total scatter factors for stereotactic cones with plastic scintillation detector and its comparison against diode detector and theoretical estimates. Measurements were performed on Novalis Tx ™ linear accelerator for 6MV SRS beam with stereotactic cones of diameter 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm. The advantage of plastic scintillator detector is in its energy dependence. The total scatter factor was measured in water at the depth of dose maximum. Total scatter factor with plastic scintillation detector was determined by normalizing the readings to field size of 10 cm × 10 cm. To overcome energy dependence of diode detector for the determination of scatter factor with diode detector, daisy chaining method was used. The plastic scintillator detector was calibrated against the ionization chamber, and the reproducibility in the measured doses was found to be within ± 1%. Total scatter factor measured with plastic scintillation detector was 0.728 ± 0.3, 0.783 ± 0.05, 0.866 ± 0.55, 0.885 ± 0.5, and 0.910 ± 0.06 for cone sizes of 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. Total scatter factor measured with diode detector was 0.733 ± 0.03, 0.782 ± 0.02, 0.834 ± 0.07, 0.854 ± 0.02, and 0.872 ± 0.02 for cone sizes of 6 mm, 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. The variation in the measurement of total scatter factor with published Monte Carlo data was found to be -1.3%, 1.9%, -0.4%, and 0.4% for cone sizes of 7.5 mm, 10 mm, 12.5 mm, and 15 mm, respectively. We conclude that total scatter factor measurements for stereotactic cones can be adequately carried out with a plastic scintillation detector. Our results show a

Scintillation analysis of truncated Bessel beams via numerical turbulence propagation simulation.

PubMed

Eyyuboğlu, Halil T; Voelz, David; Xiao, Xifeng

2013-11-20

Scintillation aspects of truncated Bessel beams propagated through atmospheric turbulence are investigated using a numerical wave optics random phase screen simulation method. On-axis, aperture averaged scintillation and scintillation relative to a classical Gaussian beam of equal source power and scintillation per unit received power are evaluated. It is found that in almost all circumstances studied, the zeroth-order Bessel beam will deliver the lowest scintillation. Low aperture averaged scintillation levels are also observed for the fourth-order Bessel beam truncated by a narrower source window. When assessed relative to the scintillation of a Gaussian beam of equal source power, Bessel beams generally have less scintillation, particularly at small receiver aperture sizes and small beam orders. Upon including in this relative performance measure the criteria of per unit received power, this advantageous position of Bessel beams mostly disappears, but zeroth- and first-order Bessel beams continue to offer some advantage for relatively smaller aperture sizes, larger source powers, larger source plane dimensions, and intermediate propagation lengths.

Preparations for the Advanced Scintillator Compton Telescope (ASCOT) balloon flight

NASA Astrophysics Data System (ADS)

Sharma, T.; Bloser, P. F.; Legere, J. S.; Bancroft, C. M.; McConnell, M. L.; Ryan, J. M.; Wright, A. M.

2017-08-01

We describe our ongoing work to develop a new medium-energy gamma-ray Compton telescope using advanced scintillator materials combined with silicon photomultiplier readouts and fly it on a scientific balloon. There is a need in high-energy astronomy for a medium-energy gamma-ray mission covering the energy range from approximately 0.4 - 20 MeV to follow the success of the COMPTEL instrument on CGRO. We believe that directly building on the legacy of COMPTEL, using relatively robust, low-cost, off-the-shelf technologies, is the most promising path for such a mission. Fortunately, high-performance scintillators, such as Cerium Bromide (CeBr3) and p-terphenyl, and compact readout devices, such as silicon photomultipliers (SiPMs), are already commercially available and capable of meeting this need. We are now constructing an Advanced Scintillator Compton Telescope (ASCOT) with SiPM readout, with the goal of imaging the Crab Nebula at MeV energies from a high-altitude balloon flight. We expect a 4-sigma detection at 1 MeV in a single transit. We present calibration results of the detector modules, and updated simulations of the balloon instrument sensitivity. If successful, this project will demonstrate that the energy, timing, and position resolution of this technology are sufficient to achieve an order of magnitude improvement in sensitivity in the medium-energy gamma-ray band, were it to be applied to a 1 cubic meter instrument on a long-duration balloon or Explorer platform.

Use of internal scintillator radioactivity to calibrate DOI function of a PET detector with a dual-ended-scintillator readout

PubMed Central

Bircher, Chad; Shao, Yiping

2012-01-01

Purpose: Positron emission tomography (PET) detectors that use a dual-ended-scintillator readout to measure depth-of-interaction (DOI) must have an accurate DOI function to provide the relationship between DOI and signal ratios to be used for detector calibration and recalibration. In a previous study, the authors used a novel and simple method to accurately and quickly measure DOI function by irradiating the detector with an external uniform flood source; however, as a practical concern, implementing external uniform flood sources in an assembled PET system is technically challenging and expensive. In the current study, therefore, the authors investigated whether the same method could be used to acquire DOI function from scintillator-generated (i.e., internal) radiation. The authors also developed a method for calibrating the energy scale necessary to select the events within the desired energy window. Methods: The authors measured the DOI function of a PET detector with lutetium yttrium orthosilicate (LYSO) scintillators. Radiation events originating from the scintillators’ internal Lu-176 beta decay were used to measure DOI functions which were then compared with those measured from both an external uniform flood source and an electronically collimated external point source. The authors conducted these studies with several scintillators of differing geometries (1.5 × 1.5 and 2.0 × 2.0 mm2 cross-section area and 20, 30, and 40 mm length) and various surface finishes (mirror-finishing, saw-cut rough, and other finishes in between), and in a prototype array. Results: All measured results using internal and external radiation sources showed excellent agreement in DOI function measurement. The mean difference among DOI values for all scintillators measured from internal and external radiation sources was less than 1.0 mm for different scintillator geometries and various surface finishes. Conclusions: The internal radioactivity of LYSO scintillators can be

SU-C-201-01: Investigation of the Effects of Scintillator Surface Treatment On Light Output Measurements with SiPM Detectors

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

Valenciaga, Y; Prout, D; Chatziioannou, A

2015-06-15

Purpose: To examine the effect of different scintillator surface treatments (BGO crystals) on the fraction of scintillation photons that exit the crystal and reach the photodetector (SiPM). Methods: Positron Emission Tomography is based on the detection of light that exits scintillator crystals, after annihilation photons deposit energy inside these crystals. A considerable fraction of the scintillation light gets trapped or absorbed after going through multiple internal reflections on the interfaces surrounding the crystals. BGO scintillator crystals generate considerably less scintillation light than crystals made of LSO and its variants. Therefore, it is crucial that the small amount of light producedmore » by BGO exits towards the light detector. The surface treatment of scintillator crystals is among the factors affecting the ability of scintillation light to reach the detectors. In this study, we analyze the effect of different crystal surface treatments on the fraction of scintillation light that is detected by the solid state photodetector (SiPM), once energy is deposited inside a BGO crystal. Simulations were performed by a Monte Carlo based software named GATE, and validated by measurements from individual BGO crystals coupled to Philips digital-SiPM sensor (DPC-3200). Results: The results showed an increment in light collection of about 4 percent when only the exit face of the BGO crystal, is unpolished; compared to when all the faces are polished. However, leaving several faces unpolished caused a reduction of at least 10 percent of light output when the interaction occurs as far from the exit face of the crystal as possible compared to when it occurs very close to the exit face. Conclusion: This work demonstrates the advantages on light collection from leaving unpolished the exit face of BGO crystals. The configuration with best light output will be used to obtain flood images from BGO crystal arrays coupled to SiPM sensors.« less

Seasonal ionospheric scintillation analysis during increasing solar activity at mid-latitude

NASA Astrophysics Data System (ADS)

Ahmed, Wasiu Akande; Wu, Falin; Agbaje, Ganiyu Ishola; Ednofri, Ednofri; Marlia, Dessi; Zhao, Yan

2017-09-01

Monitoring of ionospheric parameters (such as Total Electron Content and scintillation) is of great importance as it affects and contributes to the errors encountered by radio signals. It thus requires constant measurements to avoid disastrous situation for space agencies, parastatals and departments that employ GNSS applications in their daily operations. The research objective is to have a better understanding of the behaviour of ionospheric scintillation at midlatitude as it threatens the performances of satellite communication, navigation systems and military operations. This paper adopts seasonal ionospheric scintillation scenario. The mid-latitude investigation of ionospheric effect of scintillation was conducted during the increasing solar activity from 2011-2015. Ionospheric scintillation data were obtained from four ionospheric monitoring stations located at mid-latitude (i.e Shenzhen North Station, Beijing Changping North Station Branch, Beijing North Station and Beijing Miyun ground Station). The data was collected from January 2011 to December 2015. There were absence of data due to software problem or system failure at some locations. The scintillation phenomenon was computed using Global Ionospheric Scintillation and TEC Monitoring Model. There are four seasons which existed in China namely: Spring, Summer, Autumn and Winter. The relationship between TEC, amplitude and phase scintillation were observed for each of these seasons. The results indicated that the weak amplitude scintillation was observed as against phase scintillation which was high. Phase scintillation was gradually enhanced from 2011 to 2012 and later declined till 2014. TEC was also at peak around 00:00-10:00 UT (08:00-18:00 LT). The seasonal events temporal density characteristics comply with solar cycle prediction as such it ascended from 2011 to 2013 and then scintillation parameters declined significantly afterwards.

Optimizing ZnS/6LiF scintillators for wavelength-shifting-fiber neutron detectors

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

Crow, Lowell; Funk, Loren L; Hannan, Bruce W

2016-01-01

In this paper we compare the performance of grooved and flat ZnS/6LiF scintillators in a wavelength shifting-fiber (WLSF) detector. Flat ZnS/6LiF scintillators with the thickness L=0.2-0.8 mm were characterized using photon counting and pulse-height analysis and compared to a grooved scintillator of approximately 0.8 mm thick. While a grooved scintillator considerably increases the apparent thickness of the scintillator to neutrons for a given coating thickness, we find that the flat scintillators perform better than the grooved scintillators in terms of both light yield and neutron detection efficiency. The flat 0.8-mm-thick scintillator has the highest light output, and it is 52%more » higher compared with a grooved scintillator of same thickness. The lower light output of the grooved scintillator as compared to the flat scintillator is consistent with the greater scintillator-WLSF separation and the much larger average emission angle of the grooved scintillator. We also find that the average light cone width, or photon travel-length as measured using time-of-flight powder diffraction of diamond and vanadium, decreases with increasing L in the range of L=0.6-0.8 mm. This result contrasts with the traditional Swank diffusion model for micro-composite scintillators, and could be explained by a decrease in photon diffusion-coefficient or an increase in micro-particle content in the flat scintillator matrix for the thicker scintillators.« less

Measurement of tritium with high efficiency by using liquid scintillation counter with plastic scintillator.

PubMed

Furuta, Etsuko; Ohyama, Ryu-ichiro; Yokota, Shigeaki; Nakajo, Toshiya; Yamada, Yuka; Kawano, Takao; Uda, Tatsuhiko; Watanabe, Yasuo

2014-11-01

The detection efficiencies of tritium samples by using liquid scintillation counter with hydrophilic plastic scintillator (PS) was approximately 48% when the sample of 20 μL was held between 2 PS sheets treated by plasma. The activity and count rates showed a good relationship between 400 Bq to 410 KBq mL(-1). The calculated detection limit of 2 min measurement by the PS was 13 Bq mL(-1) when a confidence was 95%. The plasma method for PS produces no radioactive waste. Copyright © 2014 Elsevier Ltd. All rights reserved.

Time-resolved imaging of gas phase nanoparticle synthesis by laser ablation

NASA Astrophysics Data System (ADS)

Geohegan, David B.; Puretzky, Alex A.; Duscher, Gerd; Pennycook, Stephen J.

1998-06-01

The dynamics of nanoparticle formation, transport, and deposition by pulsed laser ablation of c-Si into 1-10 Torr He and Ar gases are revealed by imaging laser-induced photoluminescence and Rayleigh-scattered light from gas-suspended 1-10 nm SiOx particles. Two sets of dynamic phenomena are presented for times up to 15 s after KrF-laser ablation. Ablation of Si into heavier Ar results in a uniform, stationary plume of nanoparticles, while Si ablation into lighter He results in a turbulent ring of particles which propagates forward at 10 m/s. Nanoparticles unambiguously formed in the gas phase were collected on transmission electron microscope grids for Z-contrast imaging and electron energy loss spectroscopy analysis. The effects of gas flow on nanoparticle formation, photoluminescence, and collection are described.

Semiconductor quantum dot scintillation under gamma-ray irradiation

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

Letant, S E; Wang, T

2006-08-23

We recently demonstrated the ability of semiconductor quantum dots to convert alpha radiation into visible photons. In this letter, we report on the scintillation of quantum dots under gamma-ray irradiation, and compare the energy resolution of the 59 keV line of Americium 241 obtained with our quantum dot-glass nanocomposite material to that of a standard sodium iodide scintillator. A factor 2 improvement is demonstrated experimentally and interpreted theoretically using a combination of energy-loss and photon transport models. These results demonstrate the potential of quantum dots for room-temperature gamma-ray detection, which has applications in medical imaging, environmental monitoring, as well asmore » security and defense. Present technology in gamma radiation detection suffers from flexibility and scalability issues. For example, bulk Germanium provides fine energy resolution (0.2% energy resolution at 1.33 MeV) but requires operation at liquid nitrogen temperature. On the other hand, Cadmium-Zinc-Telluride is a good room temperature detector ( 1% at 662 keV) but the size of the crystals that can be grown is limited to a few centimeters in each direction. Finally, the most commonly used scintillator, Sodium Iodide (NaI), can be grown as large crystals but suffers from a lack of energy resolution (7% energy resolution at 662 keV). Recent advancements in nanotechnology6-10 have provided the possibility of controlling materials synthesis at the molecular level. Both morphology and chemical composition can now be manipulated, leading to radically new material properties due to a combination of quantum confinement and surface to volume ratio effects. One of the main consequences of reducing the size of semiconductors down to nanometer dimensions is to increase the energy band gap, leading to visible luminescence, which suggests that these materials could be used as scintillators. The visible band gap of quantum dots would also ensure both efficient photon

A fast scintillator Compton telescope for medium-energy gamma-ray astronomy

NASA Astrophysics Data System (ADS)

Bloser, Peter F.; Ryan, James M.; Legere, Jason S.; Julien, Manuel; Bancroft, Christopher M.; McConnell, Mark L.; Wallace, Mark; Kippen, R. Marc; Tornga, Shawn

2010-07-01

The field of medium-energy gamma-ray astronomy urgently needs a new mission to build on the success of the COMPTEL instrument on the Compton Gamma Ray Observatory. This mission must achieve sensitivity significantly greater than that of COMPTEL in order to advance the science of relativistic particle accelerators, nuclear astrophysics, and diffuse backgrounds, and bridge the gap between current and future hard X-ray missions and the high-energy Fermi mission. Such an increase in sensitivity can only come about via a dramatic decrease in the instrumental background. We are currently developing a concept for a low-background Compton telescope that employs modern scintillator technology to achieve this increase in sensitivity. Specifically, by employing LaBr3 scintillators for the calorimeter, one can take advantage of the unique speed and resolving power of this material to improve the instrument sensitivity while simultaneously enhancing its spectroscopic and imaging performance. Also, using deuterated organic scintillator in the scattering detector will reduce internal background from neutron capture. We present calibration results from a laboratory prototype of such an instrument, including time-of-flight, energy, and angular resolution, and compare them to simulation results using a detailed Monte Carlo model. We also describe the balloon payload we have built for a test flight of the instrument in the fall of 2010.

Scintillating plastic fibers as light pipes for a cosmic ray hodoscope: Feasibility calculations and measured attenuation characteristics

NASA Technical Reports Server (NTRS)

1976-01-01

A candidate hodoscope uses arrays of scintillator fibers, followed by an image intensifier and imaging system such as that proposed for the X-ray shadowgraph. A literature search was performed to ascertain the experience of other workers with hodoscopes using this or similar principles. Calculations were performed to determine the feasibility of candidate systems and some laboratory experiments were performed to attempt to check these numbers.

Scintillation of rare earth doped fluoride nanoparticles

NASA Astrophysics Data System (ADS)

Jacobsohn, L. G.; McPherson, C. L.; Sprinkle, K. B.; Yukihara, E. G.; DeVol, T. A.; Ballato, J.

2011-09-01

The scintillation response of rare earth (RE) doped core/undoped (multi-)shell fluoride nanoparticles was investigated under x-ray and alpha particle irradiation. A significant enhancement of the scintillation response was observed with increasing shells due: (i) to the passivation of surface quenching defects together with the activation of the REs on the surface of the core nanoparticle after the growth of a shell, and (ii) to the increase of the volume of the nanoparticles. These results are expected to reflect a general aspect of the scintillation process in nanoparticles, and to impact radiation sensing technologies that make use of nanoparticles.

Detection of gamma-neutron radiation by solid-state scintillation detectors. Detection of gamma-neutron radiation by novel solid-state scintillation detectors

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

Ryzhikov, V.; Grinyov, B.; Piven, L.

It is known that solid-state scintillators can be used for detection of both gamma radiation and neutron flux. In the past, neutron detection efficiencies of such solid-state scintillators did not exceed 5-7%. At the same time it is known that the detection efficiency of the gamma-neutron radiation characteristic of nuclear fissionable materials is by an order of magnitude higher than the efficiency of detection of neutron fluxes alone. Thus, an important objective is the creation of detection systems that are both highly efficient in gamma-neutron detection and also capable of exhibiting high gamma suppression for use in the role ofmore » detection of neutron radiation. In this work, we present the results of our experimental and theoretical studies on the detection efficiency of fast neutrons from a {sup 239}Pu-Be source by the heavy oxide scintillators BGO, GSO, CWO and ZWO, as well as ZnSe(Te, O). The most probable mechanism of fast neutron interaction with nuclei of heavy oxide scintillators is the inelastic scattering (n, n'γ) reaction. In our work, fast neutron detection efficiencies were determined by the method of internal counting of gamma-quanta that emerge in the scintillator from (n, n''γ) reactions on scintillator nuclei with the resulting gamma energies of ∼20-300 keV. The measured efficiency of neutron detection for the scintillation crystals we considered was ∼40-50 %. The present work included a detailed analysis of detection efficiency as a function of detector and area of the working surface, as well as a search for new ways to create larger-sized detectors of lower cost. As a result of our studies, we have found an unusual dependence of fast neutron detection efficiency upon thickness of the oxide scintillators. An explanation for this anomaly may involve the competition of two factors that accompany inelastic scattering on the heavy atomic nuclei. The transformation of the energy spectrum of neutrons involved in the (n, n'γ) reactions

Application of imaging spectrometer in gas analysis by Raman scattering

NASA Astrophysics Data System (ADS)

Zuo, Duluo; Yu, Anlan; Li, Zhe; Wang, Xingbing; Xiong, Youhui

2015-09-01

Spontaneous Raman scattering is an effective technique in gas analysis, but the detection of minor constituents is difficult because of the low signal level and the usually existed background. Imaging spectrometer can provide highly spatial resolved spectra, so it should be much easier to pick up Raman signal of minor constituents from the Raman/fluorescence background of the sample cell and transporting optics compared with the widely used fiber-coupled spectrometers. For this reason, an imaging spectrometer was constructed from transmitting volume phase holographic grating, camera lenses and CCD detector. When it was used to analyze the gas sample in metal-lined capillary, which is a sample cell believed with great enhancement of Raman signal, the background was compressed obviously. When it was used to analyze the gas in a sample cell including a parabolic reflector, only weak background signal was observed, as the wide separation between the collecting zone (the focus point of the parabolic surface) and the wall of sample cell benefitted to the analysis by imaging spectrometer. By using the last sample cell, the signal from CO2 in ambient air was able to be found by an exposure time about 20 sec, and limits of detection for H2, CO2 and CO were estimated as 60 ppm, 100 ppm and 300 ppm respectively by the results of a longer exposure time. These results show that an imaging spectrometer paired with a well-arranged sample cell will lower the detecting limit effectively.