A cost-effective monitoring technique in particle therapy via uncollimated prompt gamma peak integration

NASA Astrophysics Data System (ADS)

Krimmer, J.; Angellier, G.; Balleyguier, L.; Dauvergne, D.; Freud, N.; Hérault, J.; Létang, J. M.; Mathez, H.; Pinto, M.; Testa, E.; Zoccarato, Y.

2017-04-01

For the purpose of detecting deviations from the prescribed treatment during particle therapy, the integrals of uncollimated prompt gamma-ray timing distributions are investigated. The intention is to provide information, with a simple and cost-effective setup, independent from monitoring devices of the beamline. Measurements have been performed with 65 MeV protons at a clinical cyclotron. Prompt gamma-rays emitted from the target are identified by means of time-of-flight. The proton range inside the PMMA target has been varied via a modulator wheel. The measured variation of the prompt gamma peak integrals as a function of the modulator position is consistent with simulations. With detectors covering a solid angle of 25 msr (corresponding to a diameter of 3-4 in. at a distance of 50 cm from the beam axis) and 108 incident protons, deviations of a few per cent in the prompt gamma-ray count rate can be detected. For the present configuration, this change in the count rate corresponds to a 3 mm change in the proton range in a PMMA target. Furthermore, simulation studies show that a combination of the signals from multiple detectors may be used to detect a misplacement of the target. A different combination of these signals results in a precise number of the detected prompt gamma rays, which is independent on the actual target position.

Collimated prompt gamma TOF measurements with multi-slit multi-detector configurations

NASA Astrophysics Data System (ADS)

Krimmer, J.; Chevallier, M.; Constanzo, J.; Dauvergne, D.; De Rydt, M.; Dedes, G.; Freud, N.; Henriquet, P.; La Tessa, C.; Létang, J. M.; Pleskač, R.; Pinto, M.; Ray, C.; Reithinger, V.; Richard, M. H.; Rinaldi, I.; Roellinghoff, F.; Schuy, C.; Testa, E.; Testa, M.

2015-01-01

Longitudinal prompt-gamma ray profiles have been measured with a multi-slit multi-detector configuration at a 75 MeV/u 13C beam and with a PMMA target. Selections in time-of-flight and energy have been applied in order to discriminate prompt-gamma rays produced in the target from background events. The ion ranges which have been extracted from each individual detector module agree amongst each other and are consistent with theoretical expectations. In a separate dedicated experiment with 200 MeV/u 12C ions the fraction of inter-detector scattering has been determined to be on the 10%-level via a combination of experimental results and simulations. At the same experiment different collimator configurations have been tested and the shielding properties of tungsten and lead for prompt-gamma rays have been measured.

Prompt Gamma Imaging for In Vivo Range Verification of Pencil Beam Scanning Proton Therapy.

PubMed

Xie, Yunhe; Bentefour, El Hassane; Janssens, Guillaume; Smeets, Julien; Vander Stappen, François; Hotoiu, Lucian; Yin, Lingshu; Dolney, Derek; Avery, Stephen; O'Grady, Fionnbarr; Prieels, Damien; McDonough, James; Solberg, Timothy D; Lustig, Robert A; Lin, Alexander; Teo, Boon-Keng K

2017-09-01

To report the first clinical results and value assessment of prompt gamma imaging for in vivo proton range verification in pencil beam scanning mode. A stand-alone, trolley-mounted, prototype prompt gamma camera utilizing a knife-edge slit collimator design was used to record the prompt gamma signal emitted along the proton tracks during delivery of proton therapy for a brain cancer patient. The recorded prompt gamma depth detection profiles of individual pencil beam spots were compared with the expected profiles simulated from the treatment plan. In 6 treatment fractions recorded over 3 weeks, the mean (± standard deviation) range shifts aggregated over all spots in 9 energy layers were -0.8 ± 1.3 mm for the lateral field, 1.7 ± 0.7 mm for the right-superior-oblique field, and -0.4 ± 0.9 mm for the vertex field. This study demonstrates the feasibility and illustrates the distinctive benefits of prompt gamma imaging in pencil beam scanning treatment mode. Accuracy in range verification was found in this first clinical case to be better than the range uncertainty margin applied in the treatment plan. These first results lay the foundation for additional work toward tighter integration of the system for in vivo proton range verification and quantification of range uncertainties. Copyright © 2017 Elsevier Inc. All rights reserved.

Fission prompt gamma-ray multiplicity distribution measurements and simulations at DANCE

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

Chyzh, A; Wu, C Y; Ullmann, J

2010-08-24

The nearly energy independence of the DANCE efficiency and multiplicity response to {gamma} rays makes it possible to measure the prompt {gamma}-ray multiplicity distribution in fission. We demonstrate this unique capability of DANCE through the comparison of {gamma}-ray energy and multiplicity distribution between the measurement and numerical simulation for three radioactive sources {sup 22}Na, {sup 60}Co, and {sup 88}Y. The prospect for measuring the {gamma}-ray multiplicity distribution for both spontaneous and neutron-induced fission is discussed.

A Monte Carlo Simulation of Prompt Gamma Emission from Fission Fragments

NASA Astrophysics Data System (ADS)

Regnier, D.; Litaize, O.; Serot, O.

2013-03-01

The prompt fission gamma spectra and multiplicities are investigated through the Monte Carlo code FIFRELIN which is developed at the Cadarache CEA research center. Knowing the fully accelerated fragment properties, their de-excitation is simulated through a cascade of neutron, gamma and/or electron emissions. This paper presents the recent developments in the FIFRELIN code and the results obtained on the spontaneous fission of 252Cf. Concerning the decay cascades simulation, a fully Hauser-Feshbach model is compared with a previous one using a Weisskopf spectrum for neutron emission. A particular attention is paid to the treatment of the neutron/gamma competition. Calculations lead using different level density and gamma strength function models show significant discrepancies of the slope of the gamma spectra at high energy. The underestimation of the prompt gamma spectra obtained regardless our de-excitation cascade modeling choice is discussed. This discrepancy is probably linked to an underestimation of the post-neutron fragments spin in our calculation.

Physics of pure and non-pure positron emitters for PET: a review and a discussion.

PubMed

Conti, Maurizio; Eriksson, Lars

2016-12-01

With the increased interest in new PET tracers, gene-targeted therapy, immunoPET, and theranostics, other radioisotopes will be increasingly used in clinical PET scanners, in addition to (18)F. Some of the most interesting radioisotopes with prospective use in the new fields are not pure short-range β(+) emitters but can be associated with gamma emissions in coincidence with the annihilation radiation (prompt gamma), gamma-gamma cascades, intense Bremsstrahlung radiation, high-energy positrons that may escape out of the patient skin, and high-energy gamma rays that result in some e (+)/e (-) pair production. The high level of sophistication in data correction and excellent quantitative accuracy that has been reached for (18)F in recent years can be questioned by these effects. In this work, we review the physics and the scientific literature and evaluate the effect of these additional phenomena on the PET data for each of a series of radioisotopes: (11)C, (13)N, (15)O, (18)F, (64)Cu, (68)Ga, (76)Br, (82)Rb, (86)Y, (89)Zr, (90)Y, and (124)I. In particular, we discuss the present complications arising from the prompt gammas, and we review the scientific literature on prompt gamma correction. For some of the radioisotopes considered in this work, prompt gamma correction is definitely needed to assure acceptable image quality, and several approaches have been proposed in recent years. Bremsstrahlung photons and (176)Lu background were also evaluated.

Thermal-neutron capture for A=26-35

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

Chunmei, Z.; Firestone, R.B.

2001-06-01

The prompt gamma-ray data of thermal- neutron captures fornuclear mass number A=26-35 had been evaluated and published in "ATOMICDATA AND NUCLEAR DATA TABLES, 26, 511 (1981)". Since that time themanyexperimental data of the thermal-neutron captures have been measuredand published. The update of the evaluated prompt gamma-ray data is verynecessary for use in PGAA of high-resolution analytical prompt gamma-rayspectroscopy. Besides, the evaluation is also very needed in theEvaluated Nuclear Structure Data File, ENSDF, because there are no promptgamma-ray data in ENSDF. The levels, prompt gamma-rays and decay schemesof thermal-neutron captures for nuclides (26Mg, 27Al, 28Si, 29Si, 30Si,31P, 32S, 33S, 34S, andmore » 35Cl) with nuclear mass number A=26-35 have beenevaluated on the basis of all experimental data. The normalizationfactors, from which absolute prompt gamma-ray intensity can be obtained,and necessary comments are given in the text. The ENSDF format has beenadopted in this evaluation. The physical check (intensity balance andenergy balance) of evaluated thermal-neutron capture data has been done.The evaluated data have been put into Evaluated Nuclear Structure DataFile, ENSDF. This evaluation may be considered as an update of the promptgamma-ray from thermal-neutron capture data tables as published in"ATOMIC DATA AND NUCLEAR DATA TABLES, 26, 511 (1981)".« less

Thermal-neutron capture for A=36-44

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

Chunmei, Z.; Firestone, R.B.

2003-01-01

The prompt gamma-ray data of thermal- neutron captures fornuclear mass number A=26-35 had been evaluated and published in "ATOMICDATA AND NUCLEAR DATA TABLES, 26, 511 (1981)". Since that time the manyexperimental data of the thermal-neutron captures have been measured andpublished. The update of the evaluated prompt gamma-ray data is verynecessary for use in PGAA of high-resolution analytical prompt gamma-rayspectroscopy. Besides, the evaluation is also very needed in theEvaluated Nuclear Structure Data File, ENSDF, because there are no promptgamma-ray data in ENSDF. The levels, prompt gamma-rays and decay schemesof thermal-neutron captures fornuclides (26Mg, 27Al, 28Si, 29Si, 30Si,31P, 32S, 33S, 34S, andmore » 35Cl) with nuclear mass number A=26-35 have beenevaluated on the basis of all experimental data. The normalizationfactors, from which absolute prompt gamma-ray intensity can be obtained,and necessary comments are given in the text. The ENSDF format has beenadopted in this evaluation. The physical check (intensity balance andenergy balance) of evaluated thermal-neutron capture data has been done.The evaluated data have been put into Evaluated Nuclear Structure DataFile, ENSDF. This evaluation may be considered as an update of the promptgamma-ray from thermal-neutron capture data tables as published in"ATOMIC DATA AND NUCLEAR DATA TABLES, 26, 511 (1981)".« less

Moisture effect in prompt gamma measurements from soil samples.

PubMed

Naqvi, A A; Khiari, F Z; Liadi, F A; Khateeb-Ur-Rehman; Raashid, M A; Isab, A H

2016-09-01

The variation in intensity of 1.78MeV silicon, 6.13MeV oxygen, and 2.22MeV hydrogen prompt gamma rays from soil samples due to the addition of 5.1, 7.4, 9.7, 11.9 and 14.0wt% water was studied for 14MeV incident neutron beams utilizing a LaBr3:Ce gamma ray detector. The intensities of 1.78MeV and 6.13MeV gamma rays from silicon and oxygen, respectively, decreased with increasing sample moisture. The intensity of 2.22MeV hydrogen gamma rays increases with moisture. The decrease in intensity of silicon and oxygen gamma rays with moisture concentration indicates a loss of 14MeV neutron flux, while the increase in intensity of 2.22MeV gamma rays with moisture indicates an increase in thermal neutron flux due to increasing concentration of moisture. The experimental intensities of silicon, oxygen and hydrogen prompt gamma rays, measured as a function of moisture concentration in the soil samples, are in good agreement with the theoretical results obtained through Monte Carlo calculations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Photospheric Emission in the Joint GBM and Konus Prompt Spectra of GRB 120323A

NASA Technical Reports Server (NTRS)

Guiriec, S.; Gehrels, N.; McEnery, J.; Kouveliotou, C.; Hartmann, D. H.

2017-01-01

GRB 120323A is a very intense short gamma-ray burst (GRB) detected simultaneously during its prompt gamma-ray emission phase with the Gamma-Ray Burst Monitor (GBM) on board the Fermi Gamma-Ray Space Telescope and the Konus experiment on board the Wind satellite. GBM and Konus operate in the kiloelectronvolt - megaelectronvolt regime; however, the GBM range is broader toward both the low and the high parts of the gamma-ray spectrum. Analyses of such bright events provide a unique opportunity to check the consistency of the data analysis as well as cross-calibrate the two instruments. We performed time-integrated and coarse time-resolved spectral analysis of GRB 120323A prompt emission. We conclude that the analyses of GBM and Konus data are only consistent when using a double-hump spectral shape for both data sets; in contrast, the single hump of the empirical Band function, traditionally used to fit GRB prompt emission spectra, leads to significant discrepancies between GBM and Konus analysis results. Our two-hump model is a combination of a thermal-like and a non-thermal component. We interpret the first component as a natural manifestation of the jet photospheric emission.

Prompt gamma-ray imaging for small animals

NASA Astrophysics Data System (ADS)

Xu, Libai

Small animal imaging is recognized as a powerful discovery tool for small animal modeling of human diseases, which is providing an important clue to complete understanding of disease mechanisms and is helping researchers develop and test new treatments. The current small animal imaging techniques include positron emission tomography (PET), single photon emission tomography (SPECT), computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US). A new imaging modality called prompt gamma-ray imaging (PGI) has been identified and investigated primarily by Monte Carlo simulation. Currently it is suggested for use on small animals. This new technique could greatly enhance and extend the present capabilities of PET and SPECT imaging from ingested radioisotopes to the imaging of selected non-radioactive elements, such as Gd, Cd, Hg, and B, and has the great potential to be used in Neutron Cancer Therapy to monitor neutron distribution and neutron-capture agent distribution. This approach consists of irradiating small animals in the thermal neutron beam of a nuclear reactor to produce prompt gamma rays from the elements in the sample by the radiative capture (n, gamma) reaction. These prompt gamma rays are emitted in energies that are characteristic of each element and they are also produced in characteristic coincident chains. After measuring these prompt gamma rays by surrounding spectrometry array, the distribution of each element of interest in the sample is reconstructed from the mapping of each detected signature gamma ray by either electronic collimations or mechanical collimations. In addition, the transmitted neutrons from the beam can be simultaneously used for very sensitive anatomical imaging, which provides the registration for the elemental distributions obtained from PGI. The primary approach is to use Monte Carlo simulation methods either with the specific purpose code CEARCPG, developed at NC State University or with the general purpose codes GEANT4 or MCNP5, to predict results and investigate the feasibility of this new imaging idea. Benchmark experiments have been conducted to test the capability of the code to simulate prompt gamma rays, which are produced by following the nuclear structures of each irradiated isotope, and coincidence counting techniques, which are considered the most important improvement in neutron-related gamma-ray detection applications to reduce gamma background and improve system signal-to-noise ratios. With coincidence prompt gamma rays available, two major imaging techniques, electronic collimations and mechanic collimations, are implemented in the simulation to illustrate the feasibility of imaging elemental distribution by this new technique. The expectation maximization algorithm is employed in electronic collimation to reconstruct images. The common SPECT imaging algorithms are used in mechanical collimation to get an image. Several critical topics concerning practical applications have already been discussed, such as the radiation dose to the mouse and the detection efficiency of high-energy gamma rays. The funding of this work is provided by the Center for Engineering Application of Radioisotopes (CEAR) at North Carolina State University (NCSU) and Nuclear Engineering Education Research.

Prompt fission gamma-ray emission spectral data for 239Pu(n,f) using fast directional neutrons from the LICORNE neutron source

NASA Astrophysics Data System (ADS)

Qi, L.; Wilson, J. N.; Lebois, M.; Al-Adili, A.; Chatillon, A.; Choudhury, D.; Gatera, A.; Georgiev, G.; Göök, A.; Laurent, B.; Maj, A.; Matea, I.; Oberstedt, A.; Oberstedt, S.; Rose, S. J.; Schmitt, C.; Wasilewska, B.; Zeiser, F.

2018-03-01

Prompt fission gamma-ray spectra (PFGS) have been measured for the 239Pu(n,f) reaction using fast neutrons at Ēn=1.81 MeV produced by the LICORNE directional neutron source. The setup makes use of LaBr3 scintillation detectors and PARIS phoswich detectors to measure the emitted prompt fission gamma rays (PFG). The mean multiplicity, average total energy release per fission and average energy of photons are extracted from the unfolded PFGS. These new measurements provide complementary information to other recent work on thermal neutron induced fission of 239Pu and spontaneous fission of 252Cf.

Feasibility study of single photon emission coupled tomography imaging technique based on prompt gamma ray during antiproton therapy using boron particle

NASA Astrophysics Data System (ADS)

Shin, Han-Back; Jung, Joo-Young; Kim, Moo-Sub; Kim, Sunmi; Choi, Yong; Yoon, Do-Kun; Suh, Tae Suk

2018-06-01

In this study, we proposed an absorbed-dose monitoring technique using prompt gamma rays emitted from the reaction between an antiproton and a boron particle, and demonstrated the greater physical effect of the antiproton boron fusion therapy in comparison with proton beam using Monte Carlo simulation. The physical effect of the treatment, which was 3.5 times greater, was confirmed from the antiproton beam irradiation compared to the proton beam irradiation. Moreover, the prompt gamma ray image is acquired successfully during antiproton irradiation to boron regions. The results show the application feasibility of absorbed dose monitoring technique proposed in our study.

Polarization of the prompt gamma-ray emission from the gamma-ray burst of 6 December 2002.

PubMed

Coburn, Wayne; Boggs, Steven E

2003-05-22

Observations of the afterglows of gamma-ray bursts (GRBs) have revealed that they lie at cosmological distances, and so correspond to the release of an enormous amount of energy. The nature of the central engine that powers these events and the prompt gamma-ray emission mechanism itself remain enigmatic because, once a relativistic fireball is created, the physics of the afterglow is insensitive to the nature of the progenitor. Here we report the discovery of linear polarization in the prompt gamma-ray emission from GRB021206, which indicates that it is synchrotron emission from relativistic electrons in a strong magnetic field. The polarization is at the theoretical maximum, which requires a uniform, large-scale magnetic field over the gamma-ray emission region. A large-scale magnetic field constrains possible progenitors to those either having or producing organized fields. We suggest that the large magnetic energy densities in the progenitor environment (comparable to the kinetic energy densities of the fireball), combined with the large-scale structure of the field, indicate that magnetic fields drive the GRB explosion.

Assessment of the associated particle prompt gamma neutron activation technique for total body nitrogen measurement in vivo

USDA-ARS?s Scientific Manuscript database

Total Body Nitrogen (TBN) can be used to estimate Total Body Protein (TBP), an important body composition component at the molecular level. A system using the associated particle technique in conjunction with prompt gamma neutron activation analysis has been developed for the measurement of TBN in ...

Stability evaluation and correction of a pulsed neutron generator prompt gamma activation analysis system

USDA-ARS?s Scientific Manuscript database

Source output stability is important for accurate measurement in prompt gamma neutron activation. This is especially true when measuring low-concentration elements such as in vivo nitrogen (~2.5% of body weight). We evaluated the stability of the compact DT neutron generator within an in vivo nitrog...

Energy input and response from prompt and early optical afterglow emission in gamma-ray bursts.

PubMed

Vestrand, W T; Wren, J A; Wozniak, P R; Aptekar, R; Golentskii, S; Pal'shin, V; Sakamoto, T; White, R R; Evans, S; Casperson, D; Fenimore, E

2006-07-13

The taxonomy of optical emission detected during the critical first few minutes after the onset of a gamma-ray burst (GRB) defines two broad classes: prompt optical emission correlated with prompt gamma-ray emission, and early optical afterglow emission uncorrelated with the gamma-ray emission. The standard theoretical interpretation attributes prompt emission to internal shocks in the ultra-relativistic outflow generated by the internal engine; early afterglow emission is attributed to shocks generated by interaction with the surrounding medium. Here we report on observations of a bright GRB that, for the first time, clearly show the temporal relationship and relative strength of the two optical components. The observations indicate that early afterglow emission can be understood as reverberation of the energy input measured by prompt emission. Measurements of the early afterglow reverberations therefore probe the structure of the environment around the burst, whereas the subsequent response to late-time impulsive energy releases reveals how earlier flaring episodes have altered the jet and environment parameters. Many GRBs are generated by the death of massive stars that were born and died before the Universe was ten per cent of its current age, so GRB afterglow reverberations provide clues about the environments around some of the first stars.

Estimation and correction of produced light from prompt gamma photons on luminescence imaging of water for proton therapy dosimetry

NASA Astrophysics Data System (ADS)

Yabe, Takuya; Komori, Masataka; Toshito, Toshiyuki; Yamaguchi, Mitsutaka; Kawachi, Naoki; Yamamoto, Seiichi

2018-02-01

Although the luminescence images of water during proton-beam irradiation using a cooled charge-coupled device camera showed almost the same ranges of proton beams as those measured by an ionization chamber, the depth profiles showed lower Bragg peak intensities than those measured by an ionization chamber. In addition, a broad optical baseline signal was observed in depths that exceed the depth of the Bragg peak. We hypothesize that this broad baseline signal originates from the interaction of proton-induced prompt gamma photons with water. These prompt gamma photons interact with water to form high-energy Compton electrons, which may cause luminescence or Cherenkov emission from depths exceeding the location of the Bragg peak. To clarify this idea, we measured the luminescence images of water during the irradiations of protons in water with minimized parallax errors, and also simulated the produced light by the interactions of prompt gamma photons with water. We corrected the measured depth profiles of the luminescence images by subtracting the simulated distributions of the produced light by the interactions of prompt gamma photons in water. Corrections were also conducted using the estimated depth profiles of the light of the prompt gamma photons, as obtained from the off-beam areas of the luminescence images of water. With these corrections, we successfully obtained depth profiles that have almost identical distributions as the simulated dose distributions for protons. The percentage relative height of the Bragg peak with corrections to that of the simulation data increased to 94% from 80% without correction. Also, the percentage relative offset heights of the deeper part of the Bragg peak with corrections decreased to 0.2%-0.4% from 4% without correction. These results indicate that the luminescence imaging of water has potential for the dose distribution measurements for proton therapy dosimetry.

SU-C-204-01: A Fast Analytical Approach for Prompt Gamma and PET Predictions in a TPS for Proton Range Verification

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

Kroniger, K; Herzog, M; Landry, G

2015-06-15

Purpose: We describe and demonstrate a fast analytical tool for prompt-gamma emission prediction based on filter functions applied on the depth dose profile. We present the implementation in a treatment planning system (TPS) of the same algorithm for positron emitter distributions. Methods: The prediction of the desired observable is based on the convolution of filter functions with the depth dose profile. For both prompt-gammas and positron emitters, the results of Monte Carlo simulations (MC) are compared with those of the analytical tool. For prompt-gamma emission from inelastic proton-induced reactions, homogeneous and inhomogeneous phantoms alongside with patient data are used asmore » irradiation targets of mono-energetic proton pencil beams. The accuracy of the tool is assessed in terms of the shape of the analytically calculated depth profiles and their absolute yields, compared to MC. For the positron emitters, the method is implemented in a research RayStation TPS and compared to MC predictions. Digital phantoms and patient data are used and positron emitter spatial density distributions are analyzed. Results: Calculated prompt-gamma profiles agree with MC within 3 % in terms of absolute yield and reproduce the correct shape. Based on an arbitrary reference material and by means of 6 filter functions (one per chemical element), profiles in any other material composed of those elements can be predicted. The TPS implemented algorithm is accurate enough to enable, via the analytically calculated positron emitters profiles, detection of range differences between the TPS and MC with errors of the order of 1–2 mm. Conclusion: The proposed analytical method predicts prompt-gamma and positron emitter profiles which generally agree with the distributions obtained by a full MC. The implementation of the tool in a TPS shows that reliable profiles can be obtained directly from the dose calculated by the TPS, without the need of full MC simulation.« less

Prompt gamma and neutron detection in BNCT utilizing a CdTe detector.

PubMed

Winkler, Alexander; Koivunoro, Hanna; Reijonen, Vappu; Auterinen, Iiro; Savolainen, Sauli

2015-12-01

In this work, a novel sensor technology based on CdTe detectors was tested for prompt gamma and neutron detection using boronated targets in (epi)thermal neutron beam at FiR1 research reactor in Espoo, Finland. Dedicated neutron filter structures were omitted to enable simultaneous measurement of both gamma and neutron radiation at low reactor power (2.5 kW). Spectra were collected and analyzed in four different setups in order to study the feasibility of the detector to measure 478 keV prompt gamma photons released from the neutron capture reaction of boron-10. The detector proved to have the required sensitivity to detect and separate the signals from both boron neutron and cadmium neutron capture reactions, which makes it a promising candidate for monitoring the spatial and temporal development of in vivo boron distribution in boron neutron capture therapy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Prompt optical emission from gamma-ray bursts with multiple timescale variability of central engine activities

NASA Astrophysics Data System (ADS)

Xu, Si-Yao; Li, Zhuo

2014-04-01

Complete high-resolution light curves of GRB 080319B observed by Swift present an opportunity for detailed temporal analysis of prompt optical emission. With a two-component distribution of initial Lorentz factors, we simulate the dynamical process of shells being ejected from the central engine in the framework of the internal shock model. The emitted radiations are decomposed into different frequency ranges for a temporal correlation analysis between the light curves in different energy bands. The resulting prompt optical and gamma-ray emissions show similar temporal profiles, with both showing a superposition of a component with slow variability and a component with fast variability, except that the gamma-ray light curve is much more variable than its optical counterpart. The variability in the simulated light curves and the strong correlation with a time lag between the optical and gamma-ray emissions are in good agreement with observations of GRB 080319B. Our simulations suggest that the variations seen in the light curves stem from the temporal structure of the shells injected from the central engine of gamma-ray bursts. Future observations with high temporal resolution of prompt optical emission from GRBs, e.g., by UFFO-Pathfinder and SVOM-GWAC, will provide a useful tool for investigating the central engine activity.

Sensitivity Analysis of Cf-252 (sf) Neutron and Gamma Observables in CGMF

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

Carter, Austin Lewis; Talou, Patrick; Stetcu, Ionel

CGMF is a Monte Carlo code that simulates the decay of primary fission fragments by emission of neutrons and gamma rays, according to the Hauser-Feshbach equations. As the CGMF code was recently integrated into the MCNP6.2 transport code, great emphasis has been placed on providing optimal parameters to CGMF such that many different observables are accurately represented. Of these observables, the prompt neutron spectrum, prompt neutron multiplicity, prompt gamma spectrum, and prompt gamma multiplicity are crucial for accurate transport simulations of criticality and nonproliferation applications. This contribution to the ongoing efforts to improve CGMF presents a study of the sensitivitymore » of various neutron and gamma observables to several input parameters for Californium-252 spontaneous fission. Among the most influential parameters are those that affect the input yield distributions in fragment mass and total kinetic energy (TKE). A new scheme for representing Y(A,TKE) was implemented in CGMF using three fission modes, S1, S2 and SL. The sensitivity profiles were calculated for 17 total parameters, which show that the neutron multiplicity distribution is strongly affected by the TKE distribution of the fragments. The total excitation energy (TXE) of the fragments is shared according to a parameter RT, which is defined as the ratio of the light to heavy initial temperatures. The sensitivity profile of the neutron multiplicity shows a second order effect of RT on the mean neutron multiplicity. A final sensitivity profile was produced for the parameter alpha, which affects the spin of the fragments. Higher values of alpha lead to higher fragment spins, which inhibit the emission of neutrons. Understanding the sensitivity of the prompt neutron and gamma observables to the many CGMF input parameters provides a platform for the optimization of these parameters.« less

Unfolding the fission prompt gamma-ray energy and multiplicity distribution measured by DANCE

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

Chyzh, A; Wu, C Y; Bredeweg, T

2010-10-16

The nearly energy independence of the {gamma}-ray efficiency and multiplicity response for the DANCE array, the unusual characteristic elucidated in our early technical report (LLNL-TR-452298), gives one a unique opportunity to derive the true prompt {gamma}-ray energy and multiplicity distribution in fission from the measurement. This unfolding procedure for the experimental data will be described in details and examples will be given to demonstrate the feasibility of reconstruction of the true distribution.

Simulation of prompt gamma-ray emission during proton radiotherapy.

PubMed

Verburg, Joost M; Shih, Helen A; Seco, Joao

2012-09-07

The measurement of prompt gamma rays emitted from proton-induced nuclear reactions has been proposed as a method to verify in vivo the range of a clinical proton radiotherapy beam. A good understanding of the prompt gamma-ray emission during proton therapy is key to develop a clinically feasible technique, as it can facilitate accurate simulations and uncertainty analysis of gamma detector designs. Also, the gamma production cross-sections may be incorporated as prior knowledge in the reconstruction of the proton range from the measurements. In this work, we performed simulations of proton-induced nuclear reactions with the main elements of human tissue, carbon-12, oxygen-16 and nitrogen-14, using the nuclear reaction models of the GEANT4 and MCNP6 Monte Carlo codes and the dedicated nuclear reaction codes TALYS and EMPIRE. For each code, we made an effort to optimize the input parameters and model selection. The results of the models were compared to available experimental data of discrete gamma line cross-sections. Overall, the dedicated nuclear reaction codes reproduced the experimental data more consistently, while the Monte Carlo codes showed larger discrepancies for a number of gamma lines. The model differences lead to a variation of the total gamma production near the end of the proton range by a factor of about 2. These results indicate a need for additional theoretical and experimental study of proton-induced gamma emission in human tissue.

Prompt-gamma neutron activation analysis system design: Effects of D-T versus D-D neutron generator source selection

USDA-ARS?s Scientific Manuscript database

Prompt-gamma neutron activation (PGNA) analysis is used for the non-invasive measurement of human body composition. Advancements in portable, compact neutron generator design have made those devices attractive as neutron sources. Two distinct generators are available: D-D with 2.5 MeV and D-T with...

Unfolding the prompt gamma ray spectra measured in a Lanthanum Bromide detector using GRAVEL method

NASA Astrophysics Data System (ADS)

De, S.; Thomas, R. G.; Rout, P. C.; Suryanarayana, S. V.; Nayak, B. K.; Saxena, A.

2018-02-01

Prompt fission Upsilon -ray energy spectra in spontaneous fission of 252Cf has been measured using a 6'' LaBr3(Ce) detector. Unfolding of the measured Upsilon -ray energy spectra has been carried out using GRAVEL method. The response matrix of the detector has been simulated using GEANT4 and the unfolding of Upsilon -ray energy spectra for 60Co and 137Cs sources have been validated. This unfolding technique has then been applied to the prompt gamma spectra obtained from the spontaneous fission of 252Cf.

Progress towards a semiconductor Compton camera for prompt gamma imaging during proton beam therapy for range and dose verification

NASA Astrophysics Data System (ADS)

Gutierrez, A.; Baker, C.; Boston, H.; Chung, S.; Judson, D. S.; Kacperek, A.; Le Crom, B.; Moss, R.; Royle, G.; Speller, R.; Boston, A. J.

2018-01-01

The main objective of this work is to test a new semiconductor Compton camera for prompt gamma imaging. Our device is composed of three active layers: a Si(Li) detector as a scatterer and two high purity Germanium detectors as absorbers of high-energy gamma rays. We performed Monte Carlo simulations using the Geant4 toolkit to characterise the expected gamma field during proton beam therapy and have made experimental measurements of the gamma spectrum with a 60 MeV passive scattering beam irradiating a phantom. In this proceeding, we describe the status of the Compton camera and present the first preliminary measurements with radioactive sources and their corresponding reconstructed images.

"Chiron": A Proposed Remote Sensing Prompt Gamma Ray Activation Analysis Instrument for a Nuclear Powered Prometheus Mission

NASA Technical Reports Server (NTRS)

Floyd, Samuel R.; Keller, John W.; Dworkin, Jason P.; Mildner, David F. R.

2004-01-01

Prompt Gamma Ray Activation Analysis (PGAA) from neutron capture is an important experimental method that yields information on the elemental abundance of target materials. Gamma ray analysis has been used in planetary exploration missions by taking advantage of the production of neutrons as a result of Galactic Cosmic Ray interaction within the planetary surfaces. The .gamma ray signal that can be obtained from the GCR production of neutrons is very low, so we seek a superior neutron source. NASA s Project Prometheus and the Dept. of Energy aim to develop a nuclear power system for planetary exploration. This provides us with a tremendous opportunity to harness the reactor as a source of neutrons that can be used for PGAA. We envision a narrow stream of neutrons from the reactor directed toward the surface of an asteroid or comet producing the prompt gamma ray signal for analysis. Under ideal conditions of neutron flux and spacecraft orbit, both the signal strength and the spatial resolution will improved by several orders of magnitude over previously missions.

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

NASA Astrophysics Data System (ADS)

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

2014-04-01

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

Performance tests of a large volume cerium tribromide (CeBr3) scintillation detector.

PubMed

Naqvi, A A; Khiari, F Z; Liadi, F A; Khateeb-Ur-Rehman; Isab, A A

2016-08-01

The response of a large cylindrical 76mm×76mm (height×diameter) cerium tribromide (CeBr3) detector was measured for prompt gamma rays. The total intrinsic activity of the CeBr3 detector, which was measured over 0.33-3.33MeV range, was found to be 0.022±0.001 counts/s/cm(3). The partial intrinsic activity ( due to (227)Ac contamination), was measured over a energy range of 1.22-2.20MeV energy, was found to be 0.007±0.001 counts/s/cm(3). Compared to intrinsic activities of LaBr3:Ce and LaCl3:Ce detectors of equivalent volume, the CeBr3 detector has 7-8 times less total intrinsic activity. The detector response for low energy prompt gamma rays was measured over 0.3-0.6MeVgamma energy range using a portable neutron generator-based Prompt Gamma Neutron Activation Analysis (PGNAA) setup. The experimental yield of boron, cadmium and mercury prompt gamma-rays was measured from water samples contaminated with 0.75-2.5wt% mercury, 0.31-2.50wt% boron, and 0.0625-0.500wt% cadmium, respectively. An excellent agreement has been observed between the calculated and experimental yields of the gamma rays. Also minimum detection limit (MDC) of the CeBr3 detector was measured for boron, cadmium and mercury samples. The CeBr3 detector has 23% smaller value of MDCB and 18% larger value of MDCCd than those of a LaBr3:Ce detector of equivalent size. This study has shown that CeBr3 detector has an excellent response for the low energy prompt gamma-rays with almost an order of magnitude low intrinsic activity as compared to LaCl3:Ce and LaBr3:Ce detectors of equivalent volume. Copyright © 2016 Elsevier Ltd. All rights reserved.

Use of borated polyethylene to improve low energy response of a prompt gamma based neutron dosimeter

NASA Astrophysics Data System (ADS)

Priyada, P.; Ashwini, U.; Sarkar, P. K.

2016-05-01

The feasibility of using a combined sample of borated polyethylene and normal polyethylene to estimate neutron ambient dose equivalent from measured prompt gamma emissions is investigated theoretically to demonstrate improvements in low energy neutron dose response compared to only polyethylene. Monte Carlo simulations have been carried out using the FLUKA code to calculate the response of boron, hydrogen and carbon prompt gamma emissions to mono energetic neutrons. The weighted least square method is employed to arrive at the best linear combination of these responses that approximates the ICRP fluence to dose conversion coefficients well in the energy range of 10-8 MeV to 14 MeV. The configuration of the combined system is optimized through FLUKA simulations. The proposed method is validated theoretically with five different workplace neutron spectra with satisfactory outcome.

Chlorine signal attenuation in concrete.

PubMed

Naqvi, A A; Maslehuddin, M; Ur-Rehman, Khateeb; Al-Amoudi, O S B

2015-11-01

The intensity of prompt gamma-ray was measured at various depths from chlorine-contaminated silica fume (SF) concrete slab concrete specimens using portable neutron generator-based prompt gamma-ray setup. The intensity of 6.11MeV chloride gamma-rays was measured from the chloride contaminated slab at distance of 15.25, 20.25, 25.25, 30.25 and 35.25cm from neutron target in a SF cement concrete slab specimens. Due to attenuation of thermal neutron flux and emitted gamma-ray intensity in SF cement concrete at various depths, the measured intensity of chlorine gamma-rays decreases non-linearly with increasing depth in concrete. A good agreement was noted between the experimental results and the results of Monte Carlo simulation. This study has provided useful experimental data for evaluating the chloride contamination in the SF concrete utilizing gamma-ray attenuation method. Copyright © 2015 Elsevier Ltd. All rights reserved.

Active interrogation using low-energy nuclear reactions

NASA Astrophysics Data System (ADS)

Antolak, Arlyn; Doyle, Barney; Leung, Ka-Ngo; Morse, Daniel; Provencio, Paula

2005-09-01

High-energy photons and neutrons can be used to interrogate for heavily shielded fissile materials inside sealed cargo containers by detecting their prompt and/or delayed fission signatures. The FIND (Fissmat Inspection for Nuclear Detection) active interrogation system is based on a dual neutron+gamma source that uses low-energy (< 500 keV) proton- or deuteron-induced nuclear reactions to produce high intensities of mono-energetic gamma rays and/or neutrons. The source can be operated in either pulsed (e.g., to detect delayed photofission neutrons and gammas) or continuous (e.g., detecting prompt fission signatures) modes. For the gamma-rays, the source target can be segmented to incorporate different (p,γ) isotopes for producing gamma-rays at selective energies, thereby improving the probability of detection. The design parameters for the FIND system are discussed and preliminary accelerator-based measurements of gamma and neutron yields, background levels, and fission signals for several target materials under consideration are presented.

GPU-based prompt gamma ray imaging from boron neutron capture therapy.

PubMed

Yoon, Do-Kun; Jung, Joo-Young; Jo Hong, Key; Sil Lee, Keum; Suk Suh, Tae

2015-01-01

The purpose of this research is to perform the fast reconstruction of a prompt gamma ray image using a graphics processing unit (GPU) computation from boron neutron capture therapy (BNCT) simulations. To evaluate the accuracy of the reconstructed image, a phantom including four boron uptake regions (BURs) was used in the simulation. After the Monte Carlo simulation of the BNCT, the modified ordered subset expectation maximization reconstruction algorithm using the GPU computation was used to reconstruct the images with fewer projections. The computation times for image reconstruction were compared between the GPU and the central processing unit (CPU). Also, the accuracy of the reconstructed image was evaluated by a receiver operating characteristic (ROC) curve analysis. The image reconstruction time using the GPU was 196 times faster than the conventional reconstruction time using the CPU. For the four BURs, the area under curve values from the ROC curve were 0.6726 (A-region), 0.6890 (B-region), 0.7384 (C-region), and 0.8009 (D-region). The tomographic image using the prompt gamma ray event from the BNCT simulation was acquired using the GPU computation in order to perform a fast reconstruction during treatment. The authors verified the feasibility of the prompt gamma ray image reconstruction using the GPU computation for BNCT simulations.

BATSE Observations of Gamma-Ray Burst Tails

NASA Technical Reports Server (NTRS)

Connaughton, Valerie

2002-01-01

With the observation of low-energy radiation coming from the site of gamma-ray bursts in the hours to weeks after the initial gamma ray burst, it appears that astronomers have discovered a cosmological imprint made by the burster on its surroundings. This paper discusses the phenomenon of postburst emission in Burst and Transient Source Experiment (BATSE) gamma-ray bursts at energies usually associated with prompt emission. After summing up the background-subtracted signals from hundreds of bursts, it is found that tails out to hundreds of seconds after the trigger could be a common feature of events of a duration greater than 2 seconds, and perhaps of the shorter bursts at a lower and shorter-lived level. The tail component may be softer and seems independent of the duration (within the long-GRB sample) and brightness of the prompt burst emission. Some individual bursts have visible tails at gamma-ray energies, and the spectrum in a few cases differs from that of the prompt emission. For one of these bursts, GRB 991216, afterglow at lower energies was detected, which raised the possibility of seeing afterglow observations over large energy ranges using the next generation of GRB detectors in addition to sensitive space- or ground-based telescopes.

Thermal Neutron Die-Way-Time Studies for P and DGNAA of Radioactive Waste Drums at the MEDINA Facility

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

Mildenberger, Frank; Mauerhofer, Eric

2015-07-01

In Germany, radioactive waste with negligible heat production has to pass through a process of quality checking in order to check its conformance with national regulations prior to its transport, intermediate storage and final disposal. Additionally to its radioactive components, the waste may contain non-radioactive chemically toxic substances that can adversely affect human health and pollute the environment, especially the ground water. After an adequate decay time, the waste radioactivity will become harmless but the non-radioactive substances will persist over time. In principle, these hazardous substances may be quantified from traceability and quality controls performed during the production of themore » waste packages. As a consequence, a research and development program was initiated in 2007 with the aim to develop a nondestructive analytical technique for radioactive waste packages based on prompt and delayed gamma neutron activation analysis (P and DGNAA) employing a DT-neutron generator in pulsed mode. In a preliminary study it was experimentally demonstrated that P and DGNAA is suitable to determine the chemical composition of large samples. In 2010 a facility called MEDINA (Multi Element Detection based on Instrumental Neutron Activation) was developed for the qualitative and quantitative determination of nonradioactive, toxic elements and substances in 200-l steel drums. The determination of hazardous substances and elements is generally achieved measuring the prompt gamma-rays induced by thermal neutrons. Additional information about the composition of the waste matrix could be derived measuring the delayed gamma-rays from short life activation products. However a sensitive detection of these delayed gamma-rays requires that thermal neutrons have almost vanished. Therefore, the thermal neutron die-away-time has to be known in order to achieve an optimal discrimination between prompt and delayed gamma-ray spectra acquisition. Measurements Thermal neutron die-away times have been determined for the following cases: a) the empty chamber, b ) an empty 200-l steel drum, for a 200-l steel drum filled c) with concrete d) with polyethylene and e) with a mixture of polyethylene and concrete by measuring the prompt-gamma ray count rate of relevant isotopes like of {sup 1}H, {sup 10}B, {sup 12}C, {sup 28}Si, {sup 35}Cl, {sup 40}Ca and {sup 56}Fe which are emitted from different parts of the facility and the sample. Additionally, the average die-away-time was determined from the total detector count rate. The neutron generator was operated with a neutron emission of 8x10{sup 7} n.s{sup -1}, a neutron pulse with a length of 250 μs and a repetition time of 5 ms. The spectra were acquired between the neutron pulses over t{sub c}=500 μs after a pre-defined waiting time t{sub D} (multiple of 500 μs). The thermal neutron die-away time was ranging between 0.9 ms and 5 ms according to the sample composition. As an example the measured thermal neutron die-away-time Λ [μs] of a drum filled with concrete is presented. Detailed results of this study will be presented and discussed. (authors)« less

Measurement of sigma chi c2 B(chi c2-->J/psi gamma)/sigma chi c1 B(chi c1 -->J/psi gamma) in pp collisions at square root s=1.96 TeV.

PubMed

Abulencia, A; Adelman, J; Affolder, T; Akimoto, T; Albrow, M G; Ambrose, D; Amerio, S; Amidei, D; Anastassov, A; Anikeev, K; Annovi, A; Antos, J; Aoki, M; Apollinari, G; Arguin, J-F; Arisawa, T; Artikov, A; Ashmanskas, W; Attal, A; Azfar, F; Azzi-Bacchetta, P; Azzurri, P; Bacchetta, N; Badgett, W; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Bartsch, V; Bauer, G; Bedeschi, F; Behari, S; Belforte, S; Bellettini, G; Bellinger, J; Belloni, A; Benjamin, D; Beretvas, A; Beringer, J; Berry, T; Bhatti, A; Binkley, M; Bisello, D; Blair, R E; Blocker, C; Blumenfeld, B; Bocci, A; Bodek, A; Boisvert, V; Bolla, G; Bolshov, A; Bortoletto, D; Boudreau, J; Boveia, A; Brau, B; Brigliadori, L; Bromberg, C; Brubaker, E; Budagov, J; Budd, H S; Budd, S; Budroni, S; Burkett, K; Busetto, G; Bussey, P; Byrum, K L; Cabrera, S; Campanelli, M; Campbell, M; Canelli, F; Canepa, A; Carillo, S; Carlsmith, D; Carosi, R; Carron, S; Casarsa, M; Castro, A; Catastini, P; Cauz, D; Cavalli-Sforza, M; Cerri, A; Cerrito, L; Chang, S H; Chen, Y C; Chertok, M; Chiarelli, G; Chlachidze, G; Chlebana, F; Cho, I; Cho, K; Chokheli, D; Chou, J P; Choudalakis, G; Chuang, S H; Chung, K; Chung, W H; Chung, Y S; Ciljak, M; Ciobanu, C I; Ciocci, M A; Clark, A; Clark, D; Coca, M; Compostella, G; Convery, M E; Conway, J; Cooper, B; Copic, K; Cordelli, M; Cortiana, G; Crescioli, F; Cuenca Almenar, C; Cuevas, J; Culbertson, R; Cully, J C; Cyr, D; DaRonco, S; Datta, M; D'Auria, S; Davies, T; D'Onofrio, M; Dagenhart, D; de Barbaro, P; De Cecco, S; Deisher, A; De Lentdecker, G; Dell'Orso, M; Delli Paoli, F; Demortier, L; Deng, J; Deninno, M; De Pedis, D; Derwent, P F; Di Giovanni, G P; Dionisi, C; Di Ruzza, B; Dittmann, J R; DiTuro, P; Dörr, C; Donati, S; Donega, M; Dong, P; Donini, J; Dorigo, T; Dube, S; Efron, J; Erbacher, R; Errede, D; Errede, S; Eusebi, R; Fang, H C; Farrington, S; Fedorko, I; Fedorko, W T; Feild, R G; Feindt, M; Fernandez, J P; Field, R; Flanagan, G; Foland, A; Forrester, S; Foster, G W; Franklin, M; Freeman, J C; Furic, I; Gallinaro, M; Galyardt, J; Garcia, J E; Garberson, F; Garfinkel, A F; Gay, C; Gerberich, H; Gerdes, D; Giagu, S; Giannetti, P; Gibson, A; Gibson, K; Gimmell, J L; Ginsburg, C; Giokaris, N; Giordani, M; Giromini, P; Giunta, M; Giurgiu, G; Glagolev, V; Glenzinski, D; Gold, M; Goldschmidt, N; Goldstein, J; Golossanov, A; Gomez, G; Gomez-Ceballos, G; Goncharov, M; González, O; Gorelov, I; Goshaw, A T; Goulianos, K; Gresele, A; Griffiths, M; Grinstein, S; Grosso-Pilcher, C; Group, R C; Grundler, U; Guimaraes da Costa, J; Gunay-Unalan, Z; Haber, C; Hahn, K; Hahn, S R; Halkiadakis, E; Hamilton, A; Han, B-Y; Han, J Y; Handler, R; Happacher, F; Hara, K; Hare, M; Harper, S; Harr, R F; Harris, R M; Hartz, M; Hatakeyama, K; Hauser, J; Heijboer, A; Heinemann, B; Heinrich, J; Henderson, C; Herndon, M; Heuser, J; Hidas, D; Hill, C S; Hirschbuehl, D; Hocker, A; Holloway, A; Hou, S; Houlden, M; Hsu, S-C; Huffman, B T; Hughes, R E; Husemann, U; Huston, J; Incandela, J; Introzzi, G; Iori, M; Ishizawa, Y; Ivanov, A; Iyutin, B; James, E; Jang, D; Jayatilaka, B; Jeans, D; Jensen, H; Jeon, E J; Jindariani, S; Jones, M; Joo, K K; Jun, S Y; Jung, J E; Junk, T R; Kamon, T; Karchin, P E; Kato, Y; Kemp, Y; Kephart, R; Kerzel, U; Khotilovich, V; Kilminster, B; Kim, D H; Kim, H S; Kim, J E; Kim, M J; Kim, S B; Kim, S H; Kim, Y K; Kimura, N; Kirsch, L; Klimenko, S; Klute, M; Knuteson, B; Ko, B R; Kondo, K; Kong, D J; Konigsberg, J; Korytov, A; Kotwal, A V; Kovalev, A; Kraan, A C; Kraus, J; Kravchenko, I; Kreps, M; Kroll, J; Krumnack, N; Kruse, M; Krutelyov, V; Kubo, T; Kuhlmann, S E; Kuhr, T; Kusakabe, Y; Kwang, S; Laasanen, A T; Lai, S; Lami, S; Lammel, S; Lancaster, M; Lander, R L; Lannon, K; Lath, A; Latino, G; Lazzizzera, I; LeCompte, T; Lee, J; Lee, J; Lee, Y J; Lee, S W; Lefèvre, R; Leonardo, N; Leone, S; Levy, S; Lewis, J D; Lin, C; Lin, C S; Lindgren, M; Lipeles, E; Lister, A; Litvintsev, D O; Liu, T; Lockyer, N S; Loginov, A; Loreti, M; Loverre, P; Lu, R-S; Lucchesi, D; Lujan, P; Lukens, P; Lungu, G; Lyons, L; Lys, J; Lysak, R; Lytken, E; Mack, P; MacQueen, D; Madrak, R; Maeshima, K; Makhoul, K; Maki, T; Maksimovic, P; Malde, S; Manca, G; Margaroli, F; Marginean, R; Marino, C; Marino, C P; Martin, A; Martin, M; Martin, V; Martínez, M; Maruyama, T; Mastrandrea, P; Masubuchi, T; Matsunaga, H; Mattson, M E; Mazini, R; Mazzanti, P; McFarland, K S; McIntyre, P; McNulty, R; Mehta, A; Mehtala, P; Menzemer, S; Menzione, A; Merkel, P; Mesropian, C; Messina, A; Miao, T; Miladinovic, N; Miles, J; Miller, R; Mills, C; Milnik, M; Mitra, A; Mitselmakher, G; Miyamoto, A; Moed, S; Moggi, N; Mohr, B; Moore, R; Morello, M; Movilla Fernandez, P; Mülmenstädt, J; Mukherjee, A; Muller, Th; Mumford, R; Murat, P; Nachtman, J; Nagano, A; Naganoma, J; Nakano, I; Napier, A; Necula, V; Neu, C; Neubauer, M S; Nielsen, J; Nigmanov, T; Nodulman, L; Norniella, O; Nurse, E; Oh, S H; Oh, Y D; Oksuzian, I; Okusawa, T; Oldeman, R; Orava, R; Osterberg, K; Pagliarone, C; Palencia, E; Papadimitriou, V; Paramonov, A A; Parks, B; Pashapour, S; Patrick, J; Pauletta, G; Paulini, M; Paus, C; Pellett, D E; Penzo, A; Phillips, T J; Piacentino, G; Piedra, J; Pinera, L; Pitts, K; Plager, C; Pondrom, L; Portell, X; Poukhov, O; Pounder, N; Prakoshyn, F; Pronko, A; Proudfoot, J; Ptohos, F; Punzi, G; Pursley, J; Rademacker, J; Rahaman, A; Ranjan, N; Rappoccio, S; Reisert, B; Rekovic, V; Renton, P; Rescigno, M; Richter, S; Rimondi, F; Ristori, L; Robson, A; Rodrigo, T; Rogers, E; Rolli, S; Roser, R; Rossi, M; Rossin, R; Ruiz, A; Russ, J; Rusu, V; Saarikko, H; Sabik, S; Safonov, A; Sakumoto, W K; Salamanna, G; Saltó, O; Saltzberg, D; Sánchez, C; Santi, L; Sarkar, S; Sartori, L; Sato, K; Savard, P; Savoy-Navarro, A; Scheidle, T; Schlabach, P; Schmidt, E E; Schmidt, M P; Schmitt, M; Schwarz, T; Scodellaro, L; Scott, A L; Scribano, A; Scuri, F; Sedov, A; Seidel, S; Seiya, Y; Semenov, A; Sexton-Kennedy, L; Sfyrla, A; Shapiro, M D; Shears, T; Shepard, P F; Sherman, D; Shimojima, M; Shochet, M; Shon, Y; Shreyber, I; Sidoti, A; Sinervo, P; Sisakyan, A; Sjolin, J; Slaughter, A J; Slaunwhite, J; Sliwa, K; Smith, J R; Snider, F D; Snihur, R; Soderberg, M; Soha, A; Somalwar, S; Sorin, V; Spalding, J; Spinella, F; Spreitzer, T; Squillacioti, P; Stanitzki, M; Staveris-Polykalas, A; St Denis, R; Stelzer, B; Stelzer-Chilton, O; Stentz, D; Strologas, J; Stuart, D; Suh, J S; Sukhanov, A; Sun, H; Suzuki, T; Taffard, A; Takashima, R; Takeuchi, Y; Takikawa, K; Tanaka, M; Tanaka, R; Tecchio, M; Teng, P K; Terashi, K; Thom, J; Thompson, A S; Thomson, E; Tipton, P; Tiwari, V; Tkaczyk, S; Toback, D; Tokar, S; Tollefson, K; Tomura, T; Tonelli, D; Torre, S; Torretta, D; Tourneur, S; Trischuk, W; Tsuchiya, R; Tsuno, S; Turini, N; Ukegawa, F; Unverhau, T; Uozumi, S; Usynin, D; Vallecorsa, S; van Remortel, N; Varganov, A; Vataga, E; Vázquez, F; Velev, G; Veramendi, G; Veszpremi, V; Vidal, R; Vila, I; Vilar, R; Vine, T; Vollrath, I; Volobouev, I; Volpi, G; Würthwein, F; Wagner, P; Wagner, R G; Wagner, R L; Wagner, J; Wagner, W; Wallny, R; Wang, S M; Warburton, A; Waschke, S; Waters, D; Weinberger, M; Wester, W C; Whitehouse, B; Whiteson, D; Wicklund, A B; Wicklund, E; Williams, G; Williams, H H; Wilson, P; Winer, B L; Wittich, P; Wolbers, S; Wolfe, C; Wright, T; Wu, X; Wynne, S M; Yagil, A; Yamamoto, K; Yamaoka, J; Yamashita, T; Yang, C; Yang, U K; Yang, Y C; Yao, W M; Yeh, G P; Yoh, J; Yorita, K; Yoshida, T; Yu, G B; Yu, I; Yu, S S; Yun, J C; Zanello, L; Zanetti, A; Zaw, I; Zhang, X; Zhou, J; Zucchelli, S

2007-06-08

We measure the ratio of cross section times branching fraction, Rp=sigma chi c2 B(chi c2-->J/psi gamma)/sigma chi c1 B(chi c1-->J/psi gamma), in 1.1 fb(-1) of pp collisions at square root s=1.96 TeV. This measurement covers the kinematic range pT(J/psi)>4.0 GeV/c, |eta(J/psi)<1.0, and pT(gamma)>1.0 GeV/c. For events due to prompt processes, we find Rp=0.395+/-0.016(stat)+/-0.015(syst). This result represents a significant improvement in precision over previous measurements of prompt chi c1,2 hadro production.

Broadband observations of the naked-eye gamma-ray burst GRB 080319B.

PubMed

Racusin, J L; Karpov, S V; Sokolowski, M; Granot, J; Wu, X F; Pal'shin, V; Covino, S; van der Horst, A J; Oates, S R; Schady, P; Smith, R J; Cummings, J; Starling, R L C; Piotrowski, L W; Zhang, B; Evans, P A; Holland, S T; Malek, K; Page, M T; Vetere, L; Margutti, R; Guidorzi, C; Kamble, A P; Curran, P A; Beardmore, A; Kouveliotou, C; Mankiewicz, L; Melandri, A; O'Brien, P T; Page, K L; Piran, T; Tanvir, N R; Wrochna, G; Aptekar, R L; Barthelmy, S; Bartolini, C; Beskin, G M; Bondar, S; Bremer, M; Campana, S; Castro-Tirado, A; Cucchiara, A; Cwiok, M; D'Avanzo, P; D'Elia, V; Valle, M Della; de Ugarte Postigo, A; Dominik, W; Falcone, A; Fiore, F; Fox, D B; Frederiks, D D; Fruchter, A S; Fugazza, D; Garrett, M A; Gehrels, N; Golenetskii, S; Gomboc, A; Gorosabel, J; Greco, G; Guarnieri, A; Immler, S; Jelinek, M; Kasprowicz, G; La Parola, V; Levan, A J; Mangano, V; Mazets, E P; Molinari, E; Moretti, A; Nawrocki, K; Oleynik, P P; Osborne, J P; Pagani, C; Pandey, S B; Paragi, Z; Perri, M; Piccioni, A; Ramirez-Ruiz, E; Roming, P W A; Steele, I A; Strom, R G; Testa, V; Tosti, G; Ulanov, M V; Wiersema, K; Wijers, R A M J; Winters, J M; Zarnecki, A F; Zerbi, F; Mészáros, P; Chincarini, G; Burrows, D N

2008-09-11

Long-duration gamma-ray bursts (GRBs) release copious amounts of energy across the entire electromagnetic spectrum, and so provide a window into the process of black hole formation from the collapse of massive stars. Previous early optical observations of even the most exceptional GRBs (990123 and 030329) lacked both the temporal resolution to probe the optical flash in detail and the accuracy needed to trace the transition from the prompt emission within the outflow to external shocks caused by interaction with the progenitor environment. Here we report observations of the extraordinarily bright prompt optical and gamma-ray emission of GRB 080319B that provide diagnostics within seconds of its formation, followed by broadband observations of the afterglow decay that continued for weeks. We show that the prompt emission stems from a single physical region, implying an extremely relativistic outflow that propagates within the narrow inner core of a two-component jet.

The Supercritical Pile Model: Prompt Emission Across the Electromagnetic Spectrum

NASA Technical Reports Server (NTRS)

Kazanas, Demos; Mastichiadis, A.

2008-01-01

The "Supercritical Pile" GRB model is an economical model that provides the dissipation necessary to convert explosively the energy stored in relativistic protons in the blast wave of a GRB into radiation; at the same time it produces spectra whose luminosity peaks at 1 MeV in the lab frame, the result of the kinematics of the proton-photon - pair production reaction that effects the conversion of proton energy to radiation. We outline the fundamental notions behind the "Supercritical Pile" model and discuss the resulting spectra of the prompt emission from optical to gamma-ray energies of order Gamma^2 m_ec^2, (Gamma is the Lorentz factor of the blast wave) present even in the absence of an accelerated particle distribution and compare our results to bursts that cover this entire energy range. Particular emphasis is given on the emission at the GLAST energy range both in the prompt and the afterglow stages of the burst.

Research on the self-absorption corrections for PGNAA of large samples

NASA Astrophysics Data System (ADS)

Yang, Jian-Bo; Liu, Zhi; Chang, Kang; Li, Rui

2017-02-01

When a large sample is analysed with the prompt gamma neutron activation analysis (PGNAA) neutron self-shielding and gamma self-absorption affect the accuracy, the correction method for the detection efficiency of the relative H of each element in a large sample is described. The influences of the thickness and density of the cement samples on the H detection efficiency, as well as the impurities Fe2O3 and SiO2 on the prompt γ ray yield for each element in the cement samples, were studied. The phase functions for Ca, Fe, and Si on H with changes in sample thickness and density were provided to avoid complicated procedures for preparing the corresponding density or thickness scale for measuring samples under each density or thickness value and to present a simplified method for the measurement efficiency scale for prompt-gamma neutron activation analysis.

Development of a technique using MCNPX code for determination of nitrogen content of explosive materials using prompt gamma neutron activation analysis method

NASA Astrophysics Data System (ADS)

Nasrabadi, M. N.; Bakhshi, F.; Jalali, M.; Mohammadi, A.

2011-12-01

Nuclear-based explosive detection methods can detect explosives by identifying their elemental components, especially nitrogen. Thermal neutron capture reactions have been used for detecting prompt gamma 10.8 MeV following radioactive neutron capture by 14N nuclei. We aimed to study the feasibility of using field-portable prompt gamma neutron activation analysis (PGNAA) along with improved nuclear equipment to detect and identify explosives, illicit substances or landmines. A 252Cf radio-isotopic source was embedded in a cylinder made of high-density polyethylene (HDPE) and the cylinder was then placed in another cylindrical container filled with water. Measurements were performed on high nitrogen content compounds such as melamine (C3H6N6). Melamine powder in a HDPE bottle was placed underneath the vessel containing water and the neutron source. Gamma rays were detected using two NaI(Tl) crystals. The results were simulated with MCNP4c code calculations. The theoretical calculations and experimental measurements were in good agreement indicating that this method can be used for detection of explosives and illicit drugs.

GPU-based prompt gamma ray imaging from boron neutron capture therapy

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

Yoon, Do-Kun; Jung, Joo-Young; Suk Suh, Tae, E-mail: suhsanta@catholic.ac.kr

Purpose: The purpose of this research is to perform the fast reconstruction of a prompt gamma ray image using a graphics processing unit (GPU) computation from boron neutron capture therapy (BNCT) simulations. Methods: To evaluate the accuracy of the reconstructed image, a phantom including four boron uptake regions (BURs) was used in the simulation. After the Monte Carlo simulation of the BNCT, the modified ordered subset expectation maximization reconstruction algorithm using the GPU computation was used to reconstruct the images with fewer projections. The computation times for image reconstruction were compared between the GPU and the central processing unit (CPU).more » Also, the accuracy of the reconstructed image was evaluated by a receiver operating characteristic (ROC) curve analysis. Results: The image reconstruction time using the GPU was 196 times faster than the conventional reconstruction time using the CPU. For the four BURs, the area under curve values from the ROC curve were 0.6726 (A-region), 0.6890 (B-region), 0.7384 (C-region), and 0.8009 (D-region). Conclusions: The tomographic image using the prompt gamma ray event from the BNCT simulation was acquired using the GPU computation in order to perform a fast reconstruction during treatment. The authors verified the feasibility of the prompt gamma ray image reconstruction using the GPU computation for BNCT simulations.« less

TU-FG-BRB-07: GPU-Based Prompt Gamma Ray Imaging From Boron Neutron Capture Therapy

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

Kim, S; Suh, T; Yoon, D

Purpose: The purpose of this research is to perform the fast reconstruction of a prompt gamma ray image using a graphics processing unit (GPU) computation from boron neutron capture therapy (BNCT) simulations. Methods: To evaluate the accuracy of the reconstructed image, a phantom including four boron uptake regions (BURs) was used in the simulation. After the Monte Carlo simulation of the BNCT, the modified ordered subset expectation maximization reconstruction algorithm using the GPU computation was used to reconstruct the images with fewer projections. The computation times for image reconstruction were compared between the GPU and the central processing unit (CPU).more » Also, the accuracy of the reconstructed image was evaluated by a receiver operating characteristic (ROC) curve analysis. Results: The image reconstruction time using the GPU was 196 times faster than the conventional reconstruction time using the CPU. For the four BURs, the area under curve values from the ROC curve were 0.6726 (A-region), 0.6890 (B-region), 0.7384 (C-region), and 0.8009 (D-region). Conclusion: The tomographic image using the prompt gamma ray event from the BNCT simulation was acquired using the GPU computation in order to perform a fast reconstruction during treatment. The authors verified the feasibility of the prompt gamma ray reconstruction using the GPU computation for BNCT simulations.« less

Prompt optical emission from gamma-ray bursts

NASA Astrophysics Data System (ADS)

Kehoe, Robert; Akerlof, Karl; Balsano, Richard; Barthelmy, Scott; Bloch, Jeff; Butterworth, Paul; Casperson, Don; Cline, Tom; Fletcher, Sandra; Frontera, Fillippo; Gisler, Galen; Heise, John; Hills, Jack; Hurley, Kevin; Lee, Brian; Marshall, Stuart; McKay, Tim; Pawl, Andrew; Piro, Luigi; Priedhorsky, Bill; Szymanski, John; Wren, Jim

The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure contemporaneous and early afterglow optical emission from gamma-ray bursts (GRBs). The ROTSE-I telescope array has been fully automated and responding to burst alerts from the GRB Coordinates Network since March 1998, taking prompt optical data for 30 bursts in its first year. We will briefly review observations of GRB990123 which revealed the first detection of an optical burst occurring during the gamma-ray emission, reaching 9th magnitude at its peak. In addition, we present here preliminary optical results for seven other gamma-ray bursts. No other optical counterparts were seen in this analysis, and the best limiting senisitivities are mV > 13.0 at 14.7 seconds after the gamma-ray rise, and mmV > 16.4 at 62 minutes. These are the most stringent limits obtained for GRB optical counterpart brightness in the first hour after the burst. This analysis suggests that there is not a strong correlation between optical flux and gamma-ray emission.

A Temporal Correlation in Quiescent Gamma-Ray Burst Prompt Emission: Evidence for Prognitor Memory

NASA Astrophysics Data System (ADS)

Patton, Thomas L.; Giblin, Timothy; Hakkila, Jon E.

2018-06-01

In spite of the insight gained into the nature of the Gamma-Ray Bursts (GRB) from early and late-time X-Ray observations in the Swift era, GRB prompt emission continues to provide clues and new insight into the activity of the central engine. A comprehensive understanding of all emission components observed in GRBs, from the traditional prompt GRB emission to the long lived X-Ray and optical decay super- imposed with late-time flaring activity, currently remains allusive. Using data from the Swift Burst Alert Telescope (BAT), we've identified and measured durations observed in GRBs that exhibit multi-episodic prompt emission behavior. Duration analysis of the burst attributes revealed no significant correlations between emissions and quiet time durations. This variability allows us to extrapolate that the central engine is constantly active.

BATSE Observations of Gamma-Ray Burst Tails

NASA Technical Reports Server (NTRS)

Connaughton, Valerie; Six, N. Frank (Technical Monitor)

2001-01-01

With the discovery of low-energy radiation appearing to come from the site of gamma-ray bursts in the hours to weeks after the initial burst of gamma rays, it would appear that astronomers have seen a cosmological imprint made by the burster on its surroundings. I discuss in this paper the phenomenon of post-burst emission in BATSE (Burst and Transient Source Experiment) gamma-ray bursts at energies traditionally associated with prompt emission. By summing the background-subtracted signals from hundreds of bursts, I find that tails out to hundreds of seconds after the trigger may be a common feature of long events (duration greater than 2s), and perhaps of the shorter bursts at a lower and shorter-lived level. The tail component appears independent of both the duration (within the long GRB sample) and brightness of the prompt burst emission, and may be softer. Some individual bursts have visible tails at gamma-ray energies and the spectrum in at least a few cases is different from that of the prompt emission. Afterglow at lower energies was detected for one of these bursts, GRB-991216, raising the possibility of afterglow observations over large energy ranges using the next generation of GRB detectors in conjunction with sensitive space or ground-based telescopes.

Prompt gamma timing range verification for scattered proton beams

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

Kormoll, T.; Golnik, C.; Hueso Gonzalez, F.

2015-07-01

Range verification is a very important point in order to fully exploit the physical advantages of protons compared to photons in cancer irradiation. Recently, a simple method has been proposed which makes use of the time of fight of protons in tissue and the promptly emitted secondary photons along the proton path (Prompt Gamma Timing, PGT). This has been considered so far for monoenergetic pencil beams only. In this work, it has been studied whether this technique can also be applied in passively formed irradiation fields with a so called spread out Bragg peak. Time correlated profiles could be recorded,more » which show a trend that is consistent with theoretical predictions. (authors)« less

Correlation Analysis of Prompt Emission from Gamma Ray Bursts

NASA Astrophysics Data System (ADS)

Pothapragada, Sriharsha

Prompt emission from gamma-ray bursts (GRBs) exhibits very rapid, complicated temporal and spectral evolution. This diverse variability in the light-curves reflects the complicated nature of the underlying physics, in which inter-penetrating relativistic shells in the outflow are believed to generate strong magnetic fields that vary over very small scales. We use the theory of jitter radiation to model the emission from such regions and the resulting overall prompt gamma ray emission from a series of relativistic collisionless shocks. We present simulated GRB light-curves developed as a series of "pulses" corresponding to instantaneously illuminated "thin-shell" regions emitting via the jitter radiation mechanism. The effects of various geometries, viewing angles, and bulk Lorentz factor profiles of the radiating outflow jets on the spectral features and evolution of these light-curves are explored. Our results demonstrate how an anisotropic jitter radiation pattern, in conjunction with relativistic shock kinematics, can produce certain features observed in the GRB prompt emission spectra, such as the occurrence of hard, synchrotron violating spectra, the "tracking" of observed flux with spectral parameters, and spectral softening below peak energy within individual episodes of the light curve. We highlight predictions in the light of recent advances in the observational sphere of GRBs.

From prompt gamma distribution to dose: a novel approach combining an evolutionary algorithm and filtering based on Gaussian-powerlaw convolutions.

PubMed

Schumann, A; Priegnitz, M; Schoene, S; Enghardt, W; Rohling, H; Fiedler, F

2016-10-07

Range verification and dose monitoring in proton therapy is considered as highly desirable. Different methods have been developed worldwide, like particle therapy positron emission tomography (PT-PET) and prompt gamma imaging (PGI). In general, these methods allow for a verification of the proton range. However, quantification of the dose from these measurements remains challenging. For the first time, we present an approach for estimating the dose from prompt γ-ray emission profiles. It combines a filtering procedure based on Gaussian-powerlaw convolution with an evolutionary algorithm. By means of convolving depth dose profiles with an appropriate filter kernel, prompt γ-ray depth profiles are obtained. In order to reverse this step, the evolutionary algorithm is applied. The feasibility of this approach is demonstrated for a spread-out Bragg-peak in a water target.

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

Verburg, J; Bortfeld, T

Purpose: We present a new system to perform prompt gamma-ray spectroscopy during proton pencil-beam scanning treatments, which enables in vivo verification of the proton range. This system will be used for the first clinical studies of this technology. Methods: After successful pre-clinical testing of prompt gamma-ray spectroscopy, a full scale system for clinical studies is now being assembled. Prompt gamma-rays will be detected during patient treatment using an array of 8 detector modules arranged behind a tungsten collimator. Each detector module consists of a lanthanum(III) bromide scintillator, a photomultiplier tube, and custom electronics for stable high voltage supply and signalmore » amplification. A new real-time data acquisition and control system samples the signals from the detectors with analog-to-digital converters, analyses events of interest, and communicates with the beam delivery systems. The timing of the detected events was synchronized to the cyclotron radiofrequency and the pencil-beam delivery. Range verification is performed by matching measured energy- and timeresolved gamma-ray spectra to nuclear reaction models based on the clinical treatment plan. Experiments in phantoms were performed using clinical beams in order to assess the performance of the systems. Results: The experiments showed reliable real-time analysis of more than 10 million detector events per second. The individual detector modules acquired accurate energy- and time-resolved gamma-ray measurements at a rate of 1 million events per second, which is typical for beams delivered with a clinical dose rate. The data acquisition system successfully tracked the delivery of the scanned pencil-beams to determine the location of range deviations within the treatment field. Conclusion: A clinical system for proton range verification using prompt gamma-ray spectroscopy has been designed and is being prepared for use during patient treatments. We anticipate to start a first clinical study in the near future. This work was supported by the Federal Share of program income earned by Massachusetts; General Hospital on C06-CA059267, Proton Therapy Research and Treatment Center.« less

Material efficiency studies for a Compton camera designed to measure characteristic prompt gamma rays emitted during proton beam radiotherapy

PubMed Central

Robertson, Daniel; Polf, Jerimy C; Peterson, Steve W; Gillin, Michael T; Beddar, Sam

2011-01-01

Prompt gamma rays emitted from biological tissues during proton irradiation carry dosimetric and spectroscopic information that can assist with treatment verification and provide an indication of the biological response of the irradiated tissues. Compton cameras are capable of determining the origin and energy of gamma rays. However, prompt gamma monitoring during proton therapy requires new Compton camera designs that perform well at the high gamma energies produced when tissues are bombarded with therapeutic protons. In this study we optimize the materials and geometry of a three-stage Compton camera for prompt gamma detection and calculate the theoretical efficiency of such a detector. The materials evaluated in this study include germanium, bismuth germanate (BGO), NaI, xenon, silicon and lanthanum bromide (LaBr3). For each material, the dimensions of each detector stage were optimized to produce the maximum number of relevant interactions. These results were used to predict the efficiency of various multi-material cameras. The theoretical detection efficiencies of the most promising multi-material cameras were then calculated for the photons emitted from a tissue-equivalent phantom irradiated by therapeutic proton beams ranging from 50 to 250 MeV. The optimized detector stages had a lateral extent of 10 × 10 cm2 with the thickness of the initial two stages dependent on the detector material. The thickness of the third stage was fixed at 10 cm regardless of material. The most efficient single-material cameras were composed of germanium (3 cm) and BGO (2.5 cm). These cameras exhibited efficiencies of 1.15 × 10−4 and 9.58 × 10−5 per incident proton, respectively. The most efficient multi-material camera design consisted of two initial stages of germanium (3 cm) and a final stage of BGO, resulting in a theoretical efficiency of 1.26 × 10−4 per incident proton. PMID:21508442

Prompt Emission of GRB 121217A from Gamma-Rays to the Near-Infrared

NASA Technical Reports Server (NTRS)

Elliott, J.; Yu, H.-F.; Schmidl, S.; Greiner, J.; Gruber, D.; Oates, S.; Kobayashi, S.; Zhang, B.; Cummings, J. R.; Filgas, R.;

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

Goldstein, Adam; Connaughton, Valerie; Briggs, Michael S.

We present a method to estimate the jet opening angles of long duration gamma-ray bursts (GRBs) using the prompt gamma-ray energetics and an inversion of the Ghirlanda relation, which is a correlation between the time-integrated peak energy of the GRB prompt spectrum and the collimation-corrected energy in gamma-rays. The derived jet opening angles using this method and detailed assumptions match well with the corresponding inferred jet opening angles obtained when a break in the afterglow is observed. Furthermore, using a model of the predicted long GRB redshift probability distribution observable by the Fermi Gamma-ray Burst Monitor (GBM), we estimate themore » probability distributions for the jet opening angle and rest-frame energetics for a large sample of GBM GRBs for which the redshifts have not been observed. Previous studies have only used a handful of GRBs to estimate these properties due to the paucity of observed afterglow jet breaks, spectroscopic redshifts, and comprehensive prompt gamma-ray observations, and we potentially expand the number of GRBs that can be used in this analysis by more than an order of magnitude. In this analysis, we also present an inferred distribution of jet breaks which indicates that a large fraction of jet breaks are not observable with current instrumentation and observing strategies. We present simple parameterizations for the jet angle, energetics, and jet break distributions so that they may be used in future studies.« less

Detection of pulsed bremsstrahlung-induced prompt neutron capture gamma rays with a HPGe detector

NASA Astrophysics Data System (ADS)

Jones, James L.

1997-02-01

The Idaho National Engineering Laboratory (INEL) is developing a novel photoneutron-based nondestructive evaluation technique which uses a pulsed, high-energy electron accelerator and gamma-ray spectrometry. Highly penetrating pulses of bremsstrahlung photons are produced by each pulse of electrons. Interrogating neutrons are generated by the bremsstrahlung photons interacting within a photoneutron source material. The interactions of the neutrons within a target result in the emission of elemental characteristic gamma-rays. Spectrometry is performed by analyzing the photoneutron-induced, prompt gama-rays acquired between accelerator pulses with a unique, high- purity germanium gamma-ray detection system using a modified transistor reset preamplifier. The detection system, the experimental configuration, and the accelerator operation used to characterize the detection systems performance are described. Using a 6.5-MeV electron accelerator and a beryllium metal photoneutron source, gamma-ray spectra were successfully acquired for Al, Cu, polyethylene, NaCl, and depleted uranium targets as soon as 30 microsecond(s) after each bremsstrahlung flash.

Analysis of neutron and gamma-ray streaming along the maze of NRCAM thallium production target room.

PubMed

Raisali, G; Hajiloo, N; Hamidi, S; Aslani, G

2006-08-01

Study of the shield performance of a thallium-203 production target room has been investigated in this work. Neutron and gamma-ray equivalent dose rates at various points of the maze are calculated by simulating the transport of streaming neutrons, and photons using Monte Carlo method. For determination of neutron and gamma-ray source intensities and their energy spectrum, we have applied SRIM 2003 and ALICE91 computer codes to Tl target and its Cu substrate for a 145 microA of 28.5 MeV protons beam. The MCNP/4C code has been applied with neutron source term in mode n p to consider both prompt neutrons and secondary gamma-rays. Then the code is applied for the prompt gamma-rays as the source term. The neutron-flux energy spectrum and equivalent dose rates for neutron and gamma-rays in various positions in the maze have been calculated. It has been found that the deviation between calculated and measured dose values along the maze is less than 20%.

Comment on 'Imaging of prompt gamma rays emitted during delivery of clinical proton beams with a Compton camera: feasibility studies for range verification'.

PubMed

Sitek, Arkadiusz

2016-12-21

The origin ensemble (OE) algorithm is a new method used for image reconstruction from nuclear tomographic data. The main advantage of this algorithm is the ease of implementation for complex tomographic models and the sound statistical theory. In this comment, the author provides the basics of the statistical interpretation of OE and gives suggestions for the improvement of the algorithm in the application to prompt gamma imaging as described in Polf et al (2015 Phys. Med. Biol. 60 7085).

Comment on ‘Imaging of prompt gamma rays emitted during delivery of clinical proton beams with a Compton camera: feasibility studies for range verification’

NASA Astrophysics Data System (ADS)

Sitek, Arkadiusz

2016-12-01

The origin ensemble (OE) algorithm is a new method used for image reconstruction from nuclear tomographic data. The main advantage of this algorithm is the ease of implementation for complex tomographic models and the sound statistical theory. In this comment, the author provides the basics of the statistical interpretation of OE and gives suggestions for the improvement of the algorithm in the application to prompt gamma imaging as described in Polf et al (2015 Phys. Med. Biol. 60 7085).

First demonstration of aerial gamma-ray imaging using drone for prompt radiation survey in Fukushima

NASA Astrophysics Data System (ADS)

Mochizuki, S.; Kataoka, J.; Tagawa, L.; Iwamoto, Y.; Okochi, H.; Katsumi, N.; Kinno, S.; Arimoto, M.; Maruhashi, T.; Fujieda, K.; Kurihara, T.; Ohsuka, S.

2017-11-01

Considerable amounts of radioactive substances (mainly 137Cs and 134Cs) were released into the environment after the Japanese nuclear disaster in 2011. Some restrictions on residence areas were lifted in April 2017, owing to the successive and effective decontamination operations. However, the distribution of radioactive substances in vast areas of mountain, forest and satoyama close to the city is still unknown; thus, decontamination operations in such areas are being hampered. In this paper, we report on the first aerial gamma-ray imaging of a schoolyard in Fukushima using a drone that carries a high sensitivity Compton camera. We show that the distribution of 137Cs in regions with a diameter of several tens to a hundred meters can be imaged with a typical resolution of 2-5 m within a 10-20 min flights duration. The aerial gamma-ray images taken 10 m and 20 m above the ground are qualitatively consistent with a dose map reconstructed from the ground-based measurements using a survey meter. Although further quantification is needed for the distance and air-absorption corrections to derive in situ dose map, such an aerial drone system can reduce measurement time by a factor of ten and is suitable for place where ground-based measurement are difficult.

Photospheric Emission in the Joint GBM and Konus Prompt Spectra of GRB 120323A

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

Guiriec, S.; Kouveliotou, C.; Gehrels, N.

GRB 120323A is a very intense short gamma -ray burst (GRB) detected simultaneously during its prompt γ -ray emission phase with the Gamma-ray Burst Monitor (GBM) on board the Fermi Gamma-ray Space Telescope and the Konus experiment on board the Wind satellite. GBM and Konus operate in the keV–MeV regime; however, the GBM range is broader toward both the low and the high parts of the γ -ray spectrum. Analyses of such bright events provide a unique opportunity to check the consistency of the data analysis as well as cross-calibrate the two instruments. We performed time-integrated and coarse time-resolved spectralmore » analysis of GRB 120323A prompt emission. We conclude that the analyses of GBM and Konus data are only consistent when using a double-hump spectral shape for both data sets; in contrast, the single hump of the empirical Band function, traditionally used to fit GRB prompt emission spectra, leads to significant discrepancies between GBM and Konus analysis results. Our two-hump model is a combination of a thermal-like and a non-thermal component. We interpret the first component as a natural manifestation of the jet photospheric emission.« less

Short GRB Prompt and Afterglow Correlations

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2007-01-01

The Swift data set on short GRBs has now grown large enough to study correlations of key parameters. The goal is to compare long and short bursts to better understand similarities and differences in the burst origins. In this study we consider the both prompt and afterglow fluxes. It is found that the optical, X-ray and gamma-ray emissions are linearly correlated - stronger bursts tend to have brighter afterglows, and bursts with brighter X-ray afterglow tend to have brighter optical afterglow. Both the prompt and afterglow fluxes are, on average, lower for short bursts than for long. Although there are short GRBs with undetected optical emission, there is no evidence for "dark" short bursts with anomalously low opt/X ratios. The weakest short bursts have a low X-ray/gamma-ray ratio.

X-Ray Flare Candidates in Short Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Margutti, R.; Chincarini, G.; Granot, J.; Guidorzi, C.; Berger, E.; Bernardini, M. G.; Geherls, N.; Soderberg, A. M.; Stamatikos, M.; Zaninoni, E.

2012-01-01

We present the first systematic study of X-ray flare candidates in short gamma-ray bursts (SGRBs) exploiting the large 6-year Swift database with the aim to constrain the physical nature of such fluctuations. We find that flare candidates appear in different types of SGRB host galaxy environments and show no clear correlation with the X-ray afterglow lifetime; flare candidates are detected both in SGRBs with a bright extended emission in the soft gamma-rays and in SGRBs which do not show such component. We furthermore show that SGRB X-ray flare candidates only partially share the set of observational properties of long GRB (LGRB) flares. In particular, the main parameter driving the duration evolution of X-ray variability episodes in both classes is found to be the elapsed time from the explosion, with very limited dependence on the different progenitors, environments, central engine life-times, prompt variability time-scales and energy budgets. On the contrary, SGRB flare candidates significantly differ from LGRB flares in terms of peak luminosity, isotropic energy, flare-to-prompt luminosity ratio and relative variability flux. However, these differences disappear when the central engine time-scales and energy budget are accounted for, suggesting that (i) flare candidates and prompt pulses in SGRBs likely have a common origin; (ii) similar dissipation and/or emission mechanisms are responsible for the prompt and flare emission in long and short GRBs, with SGRBs being less energetic albeit faster evolving versions of the long class. Finally, we show that in strict analogy to the SGRB prompt emission, flares candidates fall off the lag-luminosity relation defined by LGRBs, thus strengthening the SGRB flare-prompt pulse connection.

A MAD Model for Gamma-Ray Burst Variability

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

Lloyd-Ronning, Nicole Marie; Dolence, Joshua C.; Fryer, Christopher Lee

Here we present a model for the temporal variability of long gamma-ray bursts during the prompt phase (the highly variable first 100 seconds or so), in the context of a magnet- ically arrested disk (MAD) around a black hole. In this state, sufficient magnetic flux is held on to the black hole such that it stalls the accretion near the inner region of the disk. The system transitions in and out of the MAD state, which we relate to the vari- able luminosity of the GRB during the prompt phase, with a characteristic timescale defined by the free fall timemore » in the region over which the accretion is arrested. We present simple analytic estimates of the relevant energetics and timescales, and com- pare them to gamma-ray burst observations. In particular, we show how this model can reproduce the characteristic one second time scale that emerges from various analyses of the prompt emission light curve. Finally, we also discuss how our model can accommodate the potentially physically important correlation between a burst quiescent time and the duration of its subsequent pulse (Ramirez-Ruiz & Merloni 2001).« less

A MAD Model for Gamma-Ray Burst Variability

DOE PAGES

Lloyd-Ronning, Nicole Marie; Dolence, Joshua C.; Fryer, Christopher Lee

2016-06-09

Here we present a model for the temporal variability of long gamma-ray bursts during the prompt phase (the highly variable first 100 seconds or so), in the context of a magnet- ically arrested disk (MAD) around a black hole. In this state, sufficient magnetic flux is held on to the black hole such that it stalls the accretion near the inner region of the disk. The system transitions in and out of the MAD state, which we relate to the vari- able luminosity of the GRB during the prompt phase, with a characteristic timescale defined by the free fall timemore » in the region over which the accretion is arrested. We present simple analytic estimates of the relevant energetics and timescales, and com- pare them to gamma-ray burst observations. In particular, we show how this model can reproduce the characteristic one second time scale that emerges from various analyses of the prompt emission light curve. Finally, we also discuss how our model can accommodate the potentially physically important correlation between a burst quiescent time and the duration of its subsequent pulse (Ramirez-Ruiz & Merloni 2001).« less

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

Kin, Tadahiro; Oshima, Masumi; Furutaka, Kazuyoshi

We are developing a new method to identify nuclear levels based on neutron capture reactions, named 'TELLA-2.' Measured data of prompt gamma rays from {sup 33}S(n,{gamma}){sup 34}S was used to improve the method. We will show how we obtain candidates of nuclear levels.

Measurement of the Shape of the Optical-IR Spectrum of Prompt Emission from Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Grossan, Bruce; Kistaubayev, M.; Smoot, G.; Scherr, L.

2017-06-01

While the afterglow phase of gamma-ray bursts (GRBs) has been extensively measured, detections of prompt emission (i.e. during bright X-gamma emission) are more limited. Some prompt optical measurements are regularly made, but these are typically in a single wide band, with limited time resolution, and no measurement of spectral shape. Some models predict a synchrotron self-absorption spectral break somewhere in the IR-optical region. Measurement of the absorption frequency would give extensive information on each burst, including the electron Lorentz factor, the radius of emission, and more (Shen & Zhang 2008). Thus far the best prompt observations have been explained invoking a variety of models, but often with a non-unique interpretation. To understand this apparently heterogeneous behavior, and to reduce the number of possible models, it is critical to add data on the optical - IR spectral shape.Long GRB prompt X-gamma emission typically lasts ~40-80 s. The Swift BAT instrument rapidly measures GRB positions to within a few arc minutes and communicates them via the internet within a few seconds. We have measured the time for a fast-moving D=700 mm telescope to point and settle to be less than 9 s anywhere on the observable sky. Therefore, the majority of prompt optical-IR emission can be measured responding to BAT positions with this telescope. In this presentation, we describe our observing and science programs, and give our design for the Burst Simultaneous Three-channel Instrument (BSTI), which uses dichroics to send eparate bands to 3 cameras. Two EMCCD cameras, give high-time resolution in B and V; a third camera with a HgCdTe sensor covers H band, allowing us to study extinguished bursts. For a total exposure time of 10 s, we find a 5 sigma sensitivity of 21.3 and 20.3 mag in B and R for 1" seeing and Kitt Peak sky brightness, much fainter than typical previous prompt detections. We estimate 5 sigma H-band sensitivity for an IR optimized telescope to be ~16.9 mag in 20 s. With three channels broadly separated in wavelength, two separate slopes would be measured, or if present between our bands, the absorption frequency would be determined, a brand-new window into GRB physics.

A Reconnection Switch to Trigger gamma-Ray Burst Jet Dissipation

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

McKinney, Jonathan C.; Uzdensky, Dmitri A.

2012-03-14

Prompt gamma-ray burst (GRB) emission requires some mechanism to dissipate an ultrarelativistic jet. Internal shocks or some form of electromagnetic dissipation are candidate mechanisms. Any mechanism needs to answer basic questions, such as what is the origin of variability, what radius does dissipation occur at, and how does efficient prompt emission occur. These mechanisms also need to be consistent with how ultrarelativistic jets form and stay baryon pure despite turbulence and electromagnetic reconnection near the compact object and despite stellar entrainment within the collapsar model. We use the latest magnetohydrodynamical models of ultrarelativistic jets to explore some of these questionsmore » in the context of electromagnetic dissipation due to the slow collisional and fast collisionless reconnection mechanisms, as often associated with Sweet-Parker and Petschek reconnection, respectively. For a highly magnetized ultrarelativistic jet and typical collapsar parameters, we find that significant electromagnetic dissipation may be avoided until it proceeds catastrophically near the jet photosphere at large radii (r {approx} 10{sup 13}-10{sup 14}cm), by which the jet obtains a high Lorentz factor ({gamma} {approx} 100-1000), has a luminosity of L{sub j} {approx} 10{sup 50}-10{sup 51} erg s{sup -1}, has observer variability timescales of order 1s (ranging from 0.001-10s), achieves {gamma}{theta}{sub j} {approx} 10-20 (for opening half-angle {theta}{sub j}) and so is able to produce jet breaks, and has comparable energy available for both prompt and afterglow emission. A range of model parameters are investigated and simplified scaling laws are derived. This reconnection switch mechanism allows for highly efficient conversion of electromagnetic energy into prompt emission and associates the observed prompt GRB pulse temporal structure with dissipation timescales of some number of reconnecting current sheets embedded in the jet. We hope this work helps motivate the development of self-consistent radiative compressible relativistic reconnection models.« less

Radiation Characterization Summary: ACRR Polyethylene-Lead-Graphite (PLG) Bucket Located in the Central Cavity on the 32-Inch Pedestal at the Core Centerline (ACRR-PLG-CC-32-cl).

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

Parma, Edward J.,; Vehar, David W.; Lippert, Lance L.

2015-06-01

This document presents the facility-recommended characterization of the neutron, prompt gamma-ray, and delayed gamma-ray radiation fields in the Annular Core Research Reactor (ACRR) for the polyethylene-lead-graphite (PLG) bucket in the central cavity on the 32-inch pedestal at the core centerline. The designation for this environment is ACRR-PLG-CC-32-cl. The neutron, prompt gamma-ray, and delayed gamma-ray energy spectra, uncertainties, and covariance matrices are presented as well as radial and axial neutron and gamma-ray fluence profiles within the experiment area of the bucket. Recommended constants are given to facilitate the conversion of various dosimetry readings into radiation metrics desired by experimenters. Representative pulsemore » operations are presented with conversion examples. Acknowledgements The authors wish to thank the Annular Core Research Reactor staff and the Radiation Metrology Laboratory staff for their support of this work. Also thanks to David Ames for his assistance in running MCNP on the Sandia parallel machines.« less

Radiation Characterization Summary: ACRR Central Cavity Free-Field Environment with the 32-Inch Pedestal at the Core Centerline (ACRR-FF-CC-32-cl).

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

Vega, Richard Manuel; Parma, Edward J.; Naranjo, Gerald E.

2015-08-01

This document presents the facilit y - recommended characteri zation o f the neutron, prompt gamma - ray, and delayed gamma - ray radiation fields in the Annular Core Research Reactor ( ACRR ) for the cen tral cavity free - field environment with the 32 - inch pedestal at the core centerline. The designation for this environmen t is ACRR - FF - CC - 32 - cl. The neutron, prompt gamma - ray , and delayed gamma - ray energy spectra , uncertainties, and covariance matrices are presented as well as radial and axial neutron and gamma -more » ray fluence profiles within the experiment area of the cavity . Recommended constants are given to facilitate the conversion of various dosimetry readings into radiation metrics desired by experimenters. Representative pulse operations are presented with conversion examples . Acknowledgements The authors wish to th ank the Annular Core Research Reactor staff and the Radiation Metrology Laboratory staff for their support of this work . Also thanks to David Ames for his assistance in running MCNP on the Sandia parallel machines.« less

Clustering of gamma-ray burst types in the Fermi GBM catalogue: indications of photosphere and synchrotron emissions during the prompt phase

NASA Astrophysics Data System (ADS)

Acuner, Zeynep; Ryde, Felix

2018-04-01

Many different physical processes have been suggested to explain the prompt gamma-ray emission in gamma-ray bursts (GRBs). Although there are examples of both bursts with photospheric and synchrotron emission origins, these distinct spectral appearances have not been generalized to large samples of GRBs. Here, we search for signatures of the different emission mechanisms in the full Fermi Gamma-ray Space Telescope/GBM (Gamma-ray Burst Monitor) catalogue. We use Gaussian Mixture Models to cluster bursts according to their parameters from the Band function (α, β, and Epk) as well as their fluence and T90. We find five distinct clusters. We further argue that these clusters can be divided into bursts of photospheric origin (2/3 of all bursts, divided into three clusters) and bursts of synchrotron origin (1/3 of all bursts, divided into two clusters). For instance, the cluster that contains predominantly short bursts is consistent of photospheric emission origin. We discuss several reasons that can determine which cluster a burst belongs to: jet dissipation pattern and/or the jet content, or viewing angle.

Measurement of Fission Neutron Spectrum and Multiplicity using a Gamma Tag Double Time-of-flight Setup

NASA Astrophysics Data System (ADS)

Blain, E.; Daskalakis, A.; Danon, Y.

2014-05-01

Recent efforts have been made to improve the prompt fission neutron spectrum and nu-bar measurements for Uranium and Plutonium isotopes particularly in the keV region. A system has been designed at Rensselaer Polytechnic Institute (RPI) utilizing an array of EJ-301 liquid scintillators as well as lithium glass and plastic scintillators to experimentally determine these values. An array of BaF2 detectors was recently obtained from Oak Ridge National Laboratory to be used in conjunction with the neutron detectors. The system uses a novel gamma tagging method for fission which can offer an improvement over conventional fission chambers due to increased sample mass. A coincidence requirement on the gamma detectors from prompt fission gammas is used as the fission tag for the system as opposed to fission fragments in a conventional fission chamber. The system utilizes pulse digitization using Acqiris 8 bit digitizer boards which allow for gamma/neutron pulse height discrimination on the liquid scintillators during post processing. Additionally, a 252Cf fission chamber was designed and constructed at RPI which allowed for optimization and testing of the system without the need for an external neutron source. The characteristics of the gamma tagging method such as false detection rate and detection efficiency were determined using this fission chamber and verified using MCNP Polimi modeling. Prompt fission neutron spectrum data has been taken using the fission chamber focusing on the minimum detectable neutron energy for each of the various detectors. Plastic scintillators were found to offer a significant improvement over traditional liquid scintillators allowing energy measurements down to 50 keV. Background was also characterized for all detectors and will be discussed.

New Fermi-LAT event reconstruction reveals more high-energy gamma rays from gamma-ray bursts

DOE PAGES

Atwood, W. B.; Baldini, L.; Bregeon, J.; ...

2013-08-19

Here, based on the experience gained during the four and a half years of the mission, the Fermi-LAT Collaboration has undertaken a comprehensive revision of the event-level analysis going under the name of Pass 8. Although it is not yet finalized, we can test the improvements in the new event reconstruction with the special case of the prompt phase of bright gamma-ray bursts (GRBs), where the signal-to-noise ratio is large enough that loose selection cuts are sufficient to identify gamma rays associated with the source. Using the new event reconstruction, we have re-analyzed 10 GRBs previously detected by the Largemore » Area Telescope (LAT) for which an X-ray/optical follow-up was possible and found four new gamma rays with energies greater than 10 GeV in addition to the seven previously known. Among these four is a 27.4 GeV gamma ray from GRB 080916C, which has a redshift of 4.35, thus making it the gamma ray with the highest intrinsic energy (~147 GeV) detected from a GRB. We present here the salient aspects of the new event reconstruction and discuss the scientific implications of these new high-energy gamma rays, such as constraining extragalactic background light models, Lorentz invariance violation tests, the prompt emission mechanism, and the bulk Lorentz factor of the emitting region.« less

Prompt Gamma Activation Analysis (PGAA): Technique of choice for nondestructive bulk analysis of returned comet samples

NASA Technical Reports Server (NTRS)

Lindstrom, David J.; Lindstrom, Richard M.

1989-01-01

Prompt gamma activation analysis (PGAA) is a well-developed analytical technique. The technique involves irradiation of samples in an external neutron beam from a nuclear reactor, with simultaneous counting of gamma rays produced in the sample by neutron capture. Capture of neutrons leads to excited nuclei which decay immediately with the emission of energetic gamma rays to the ground state. PGAA has several advantages over other techniques for the analysis of cometary materials: (1) It is nondestructive; (2) It can be used to determine abundances of a wide variety of elements, including most major and minor elements (Na, Mg, Al, Si, P, K, Ca, Ti, Cr, Mn, Fe, Co, Ni), volatiles (H, C, N, F, Cl, S), and some trace elements (those with high neutron capture cross sections, including B, Cd, Nd, Sm, and Gd); and (3) It is a true bulk analysis technique. Recent developments should improve the technique's sensitivity and accuracy considerably.

CGRO/BATSE Data Support the New Paradigm For GRB Prompt Emission and the New L-i(nTh)-E-peak,i(nTh,rest) Relation

NASA Technical Reports Server (NTRS)

Guiriec, S.; Gonzalez, M.M.; Sacahui, J.R.; Kouveliotou, C.; Gehrels, N.; McEnery, J.

2016-01-01

The paradigm for gamma-ray burst (GRB) prompt emission is changing. Since early in the Compton Gamma RayObservatory (CGRO) era, the empirical Band function has been considered a good description of the keV-MeV-gamma-ray prompt emission spectra despite the fact that its shape was very often inconsistent with the theoretical predictions, especially those expected in pure synchrotron emission scenarios. We have recently established a new observational model analyzing data of the NASA Fermi Gamma-ray Space Telescope. In this model, GRB prompt emission would be a combination of three main emission components: (i) a thermal-like component that we have interpreted so far as emission from the jet photosphere, (ii) a non-thermal component that we have interpreted so far as either synchrotron radiation from the propagating and accelerated charged particles within the jet or reprocessed jet photospheric emission, and (iii) an additional non-thermal (cutoff) power law (PL) extending from low to high energies in gamma-rays and most likely of inverse Compton origin. In this article we reanalyze some of the bright GRBs, namely GRBs 941017, 970111, and 990123, observed with the Burst And Transient Source Experiment (BATSE) on board CGRO with the new model. We conclude that BATSE data for these three GRBs are fully consistent with the recent results obtained with Fermi: some bright BATSE GRBs exhibit three separate components during the prompt phase with similar spectral parameters as those reported from Fermi data. In addition, the analysis of the BATSE GRBs with the new prompt emission model results in a relation between the time-resolved energy flux of the non-thermal component, F(in)(Th), and its corresponding nuFnu spectral peak energy,Epeak,inTh (i.e., FinThEpeak,inTh ), which has a similar index when fitted to a PL as the one initially derived from Fermi data. For GRBs with known redshifts (z) this results in a possible universal relation between the luminosity of the non-thermal component, LinTh, and its corresponding nuFnu spectral peak energy in the rest frame, Epeak,iNT,rest (i.e.,LinThEpeak,iNT,rest). We estimated the redshifts of GRBs 941017 and 970111 using GRB 990123 with z = 1.61as a reference. The estimated redshift for GRB 941017 is typical for long GRBs and the estimated redshift for GRB970111 is right in the range of the expected values for this burst.

Stopping power and dose calculations with analytical and Monte Carlo methods for protons and prompt gamma range verification

NASA Astrophysics Data System (ADS)

Usta, Metin; Tufan, Mustafa Çağatay; Aydın, Güral; Bozkurt, Ahmet

2018-07-01

In this study, we have performed the calculations stopping power, depth dose, and range verification for proton beams using dielectric and Bethe-Bloch theories and FLUKA, Geant4 and MCNPX Monte Carlo codes. In the framework, as analytical studies, Drude model was applied for dielectric theory and effective charge approach with Roothaan-Hartree-Fock charge densities was used in Bethe theory. In the simulations different setup parameters were selected to evaluate the performance of three distinct Monte Carlo codes. The lung and breast tissues were investigated are considered to be related to the most common types of cancer throughout the world. The results were compared with each other and the available data in literature. In addition, the obtained results were verified with prompt gamma range data. In both stopping power values and depth-dose distributions, it was found that the Monte Carlo values give better results compared with the analytical ones while the results that agree best with ICRU data in terms of stopping power are those of the effective charge approach between the analytical methods and of the FLUKA code among the MC packages. In the depth dose distributions of the examined tissues, although the Bragg curves for Monte Carlo almost overlap, the analytical ones show significant deviations that become more pronounce with increasing energy. Verifications with the results of prompt gamma photons were attempted for 100-200 MeV protons which are regarded important for proton therapy. The analytical results are within 2%-5% and the Monte Carlo values are within 0%-2% as compared with those of the prompt gammas.

The MCNP Simulation of a PGNAA System at TRR-1/M1

NASA Astrophysics Data System (ADS)

Sangaroon, S.; Ratanatongchai, W.; Picha, R.; Khaweerat, S.; Channuie, J.

2017-06-01

The prompt-gamma neutron activation analysis system (PGNAA) has been installed at Thai Research Reactor-1/Modified 1 (TRR-1/M1) since 1999. The purpose of the system is for elemental and isotopic analyses. The system mainly consists of a series of the moderator and collimator, neutron and gamma-ray shielding and the HPGe detector. In this work, the condition of the system is carried out based on the Monte Carlo method using Monte Carlo N-Particle transport code and the experiment. The flux ratios (Φthermal/Φepithermal and Φthermal/Φfast) and thermal neutron flux have been obtained. The simulated prompt gamma rays of the Portland cement sample have been carried out. The simulation provides significant contribution in upgrading the PGNAA station to be available in various applications.

Broadband Study of GRB 091127: A Sub-Energetic Burst at Higher Redshift?

NASA Technical Reports Server (NTRS)

Troja, E.; Sakamoto, T.; Guidorzi, C.; Norris, J. P.; Panaitescu, A.; Kobayashi, S.; Omodei, N.; Brown, J. C.; Burrows, D. N.; Evans, P. A.;

The Impact of Prompted Narrative Writing during Internship on Reflective Practice: A Qualitative Study

ERIC Educational Resources Information Center

Levine, Rachel B.; Kern, David E.; Wright, Scott M.

2008-01-01

Narrative writing has been used to promote reflection and increased self-awareness among physicians. The purpose of this study was to determine the impact of prompted narrative writing on reflection. Thirty-two interns at 9 internal medicine residency programs participated in a year-long qualitative study about personal growth beginning in July of…

Source Correlated Prompt Neutron Activation Analysis for Material Identification and Localization

NASA Astrophysics Data System (ADS)

Canion, Bonnie; McConchie, Seth; Landsberger, Sheldon

2017-07-01

This paper investigates the energy spectrum of photon signatures from an associated particle imaging deuterium tritium (API-DT) neutron generator interrogating shielded uranium. The goal is to investigate if signatures within the energy spectrum could be used to indirectly characterize shielded uranium when the neutron signature is attenuated. By utilizing the correlated neutron cone associated with each pixel of the API-DT neutron generator, certain materials can be identified and located via source correlated spectrometry of prompt neutron activation gamma rays. An investigation is done to determine if fission neutrons induce a significant enough signature within the prompt neutron-induced gamma-ray energy spectrum in shielding material to be useful for indirect nuclear material characterization. The signature deriving from the induced fission neutrons interacting with the shielding material was slightly elevated in polyethylene-shielding depleted uranium (DU), but was more evident in some characteristic peaks from the aluminum shielding surrounding DU.

In-vivo assessment of total body protein in rats by prompt-γ neutron activation analysis

NASA Astrophysics Data System (ADS)

Stamatelatos, Ion E.; Boozer, Carol N.; Ma, Ruimei; Yasumura, Seiichi

1997-02-01

A prompt-(gamma) neutron activation analysis facility for in vivo determination of total body protein (TBP) in rats has been designed. TBP is determined in vivo by assessment of total body nitrogen. The facility is based on a 252Cf radionuclide neutron source within a heavy water moderator assembly and two NaI(Tl) scintillation detectors. The in vivo precision of the technique, as estimated by three repeated measurements of 15 rats is 6 percent, for a radiation dose equivalent of 60 mSv. The radiation dose per measurement is sufficiently low to enable serial measurements on the same animal. MCNP-4A Monte Carlo transport code was utilized to calculate thermal neutron flux correction factors to account for differences in size and shape of the rats and calibration phantoms. Good agrement was observed in comparing body nitrogen assessment by prompt-(gamma) neutron activation and chemical carcass analysis.

Gamma Ray Bursts - Observations

NASA Technical Reports Server (NTRS)

Gehrels, N.; Cannizzo, J. K.

2010-01-01

We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. The Fermi observatory is observing 250 bursts per year with its medium-energy GRB instrument and about 10 bursts per year with its high-energy LAT instrument. In addition, rapid-response telescopes on the ground are providing new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and high energy emission.

Limits on Optical Polarization during the Prompt Phase of GRB 140430A

NASA Astrophysics Data System (ADS)

Kopač, D.; Mundell, C. G.; Japelj, J.; Arnold, D. M.; Steele, I. A.; Guidorzi, C.; Dichiara, S.; Kobayashi, S.; Gomboc, A.; Harrison, R. M.; Lamb, G. P.; Melandri, A.; Smith, R. J.; Virgili, F. J.; Castro-Tirado, A. J.; Gorosabel, J.; Järvinen, A.; Sánchez-Ramírez, R.; Oates, S. R.; Jelínek, M.

2015-11-01

Gamma-ray burst GRB 140430A was detected by the Swift satellite and observed promptly with the imaging polarimeter RINGO3 mounted on the Liverpool Telescope, with observations beginning while the prompt γ-ray emission was still ongoing. In this paper, we present densely sampled (10-s temporal resolution) early optical light curves (LCs) in 3 optical bands and limits to the degree of optical polarization. We compare optical, X-ray, and gamma-ray properties and present an analysis of the optical emission during a period of high-energy flaring. The complex optical LC cannot be explained merely with a combination of forward and reverse shock emission from a standard external shock, implying additional contribution of emission from internal shock dissipation. We estimate an upper limit for time averaged optical polarization during the prompt phase to be as low as P < 12% (1σ). This suggests that the optical flares and early afterglow emission in this GRB are not highly polarized. Alternatively, time averaging could mask the presence of otherwise polarized components of distinct origin at different polarization position angles.

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

PubMed

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

2015-05-21

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

Imaging the Crab nebula when it is flaring in gamma-rays

NASA Astrophysics Data System (ADS)

De Luca, Andrea

2012-10-01

One of the most intriguing results of the gamma-ray instruments currently in orbit has been the detection of powerful flares from the Crab Nebula in September 2010. In April 2011 a similar flare, lasting several days, made the nebula the brightest source in the gamma-ray sky. A critical reassessment of long term behavior of the Crab flux clearly showed that both Agile and Fermi had already detected similar events in October 2007 and February 2009, pointing to a recurrence time of once per year. A HST observing strategy must be set up to react promptly to any possible new brightening of the Crab in gamma rays. In September 2010 we requested a DD observation which was promptly accepted and carried out. However, the lack of a suitable reference image hampered our efforts to pinpoint the sites of possible variability inside the nebula. Thus, while now we ask for a triggered TOO observation of the Crab Nebula with ACS/WFC in case a gamma-ray flare is announced by the Agile and/or Fermi missions, we are also organizing a regular {monthly} monitoring of the source both in X-ray and optical through a joint Chandra-HST proposal.

Radiation Characterization Summary: ACRR Cadmium-Polyethylene (CdPoly) Bucket Located in the Central Cavity on the 32-Inch Pedestal at the Core Centerline

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

Parma, Edward J.; Naranjo, Gerald E.; Kaiser, Krista Irene

This document presents the facility-recommended characterization of the neutron, prompt gamma-ray, and delayed gamma-ray radiation fields in the Annular Core Research Reactor (ACRR) for the cadmium-polyethylene (CdPoly) bucket in the central cavity on the 32-inch pedestal at the core centerline. The designation for this environment is ACRR-CdPoly-CC-32-cl. The neutron, prompt gamma-ray, and delayed gamma-ray energy spectra, uncertainties, and covariance matrices are presented as well as radial and axial neutron and gamma-ray fluence profiles within the experiment area of the bucket. Recommended constants are given to facilitate the conversion of various dosimetry readings into radiation metrics desired by experimenters. Representative pulsemore » operations are presented with conversion examples. Acknowledgements The authors wish to thank the Annular Core Research Reactor staff and the Radiation Metrology Laboratory staff for their support of this work. Also thanks to Drew Tonigan for helping field the activation experiments in ACRR, David Samuel for helping to finalize the drawings and get the parts fabricated, and Elliot Pelfrey for preparing the active dosimetry plots.« less

Database of prompt gamma rays from slow neutron capture forelemental analysis

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

Firestone, R.B.; Choi, H.D.; Lindstrom, R.M.

2004-12-31

The increasing importance of Prompt Gamma-ray ActivationAnalysis (PGAA) in a broad range of applications is evident, and has beenemphasized at many meetings related to this topic (e.g., TechnicalConsultants' Meeting, Use of neutron beams for low- andmedium-fluxresearch reactors: radiography and materialscharacterizations, IAEA Vienna, 4-7 May 1993, IAEA-TECDOC-837, 1993).Furthermore, an Advisory Group Meeting (AGM) for the Coordination of theNuclear Structure and Decay Data Evaluators Network has stated that thereis a need for a complete and consistent library of cold- and thermalneutron capture gammaray and cross-section data (AGM held at Budapest,14-18 October 1996, INDC(NDS)-363); this AGM also recommended theorganization of an IAEA CRPmore » on the subject. The International NuclearData Committee (INDC) is the primary advisory body to the IAEA NuclearData Section on their nuclear data programmes. At a biennial meeting in1997, the INDC strongly recommended that the Nuclear Data Section supportnew measurements andupdate the database on Neutron-induced PromptGamma-ray Activation Analysis (21st INDC meeting, INDC/P(97)-20). As aconsequence of the various recommendations, a CRP on "Development of aDatabase for Prompt Gamma-ray Neutron Activation Analysis (PGAA)" wasinitiated in 1999. Prior to this project, several consultants had definedthe scope, objectives and tasks, as approved subsequently by the IAEA.Each CRP participant assumed responsibility for the execution of specifictasks. The results of their and other research work were discussed andapproved by the participants in research co-ordination meetings (seeSummary reports: INDC(NDS)-411, 2000; INDC(NDS)-424, 2001; andINDC(NDS)-443, 200). PGAA is a non-destructive radioanalytical method,capable of rapid or simultaneous "in-situ" multi-element analyses acrossthe entire Periodic Table, from hydrogen to uranium. However, inaccurateand incomplete data were a significant hindrance in the qualitative andquantitative analysis of complicated capture-gamma spectra by means ofPGAA. Therefore, the main goal of the CRP was to improve the quality andquantity of the required data in order to make possible the reliableapplication of PGAA in fields such as materials science, chemistry,geology, mining, archaeology, environment, food analysis and medicine.This aim wasachieved thanks to the dedicated work and effort of theparticipants. The CD-ROM included with this publication contains thedatabase, the retrieval system, the three CRM reports, and otherimportant electronic documents related to the CRP. The IAEA wishes tothanks all CRP participants who contributed to the success of the CRP andthe formulation of this publication. Special thanks are due to R.B.Firestone for his leading roll in the development of this CRP and hiscomprehensive compilation, analysis and provision of the adopteddatabase, and to V. Zerkin for the software developments associatedwiththe retrieval system. An essential component of this data compilation isthe extensive sets of new measurements of capture gamma-ray energies andintensities undertaken at Budapest by Zs. Revay under the direction ofG.L. Molnar. The extensive participation and assistance of H.D. Choi isalso greatly appreciated. Other participants inthis CRP were: R.M.Lindstrom, S.M. Mughabghab, A.V.R. Reddy, V.H. Tan and C.M. Zhou. Thanksare also due to S.C. Frankle and M.A. Lone for their active participationas consultants at some of the meetings. Finally, the participants wish tothank R. Paviotti-Corcuera (Nuclear Data Section, Division of Physicaland Chemical Sciences), who was the IAEA responsible officer for the CRP,this publication and the resulting database. The participants aregrateful to D.L. Muir and A.L. Nichols, successive Heads of the NuclearData Section, for their active and enthusiastic encouragement infurthering the work of the CRP.« less

Coupled multi-group neutron photon transport for the simulation of high-resolution gamma-ray spectroscopy applications

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

Burns, Kimberly A.

2009-08-01

The accurate and efficient simulation of coupled neutron-photon problems is necessary for several important radiation detection applications. Examples include the detection of nuclear threats concealed in cargo containers and prompt gamma neutron activation analysis for nondestructive determination of elemental composition of unknown samples.

Scientific prospects for spectroscopy of the gamma-ray burst prompt emission with SVOM

NASA Astrophysics Data System (ADS)

Bernardini, M. G.; Xie, F.; Sizun, P.; Piron, F.; Dong, Y.; Atteia, J.-L.; Antier, S.; Daigne, F.; Godet, O.; Cordier, B.; Wei, J.

2017-10-01

SVOM (Space-based multi-band astronomical Variable Objects Monitor) is a Sino-French space mission dedicated to the study of Gamma-Ray Bursts (GRBs) in the next decade, capable to detect and localise the GRB emission, and to follow its evolution in the high-energy and X-ray domains, and in the visible and NIR bands. The satellite carries two wide-field high-energy instruments: a coded-mask gamma-ray imager (ECLAIRs; 4-150 keV), and a gamma-ray spectrometer (GRM; 15-5500 keV) that, together, will characterise the GRB prompt emission spectrum over a wide energy range. In this paper we describe the performances of the ECLAIRs and GRM system with different populations of GRBs from existing catalogues, from the classical ones to those with a possible thermal component superimposed to their non-thermal emission. The combination of ECLAIRs and the GRM will provide new insights also on other GRB properties, as for example the spectral characterisation of the subclass of short GRBs showing an extended emission after the initial spike.

Panchromatic Observations of the Textbook GRB 110205A: Constraining Physical Mechanisms of Prompt Emission and Afterglow

NASA Technical Reports Server (NTRS)

Zheng, W.; Shen, R. F.; Sakamoto, T.; Beardmore, A. P.; De Pasquale, M.; Wu, X. F.; Gorosabel, J.; Urata, Y.; Sugita, S.; Zhang, B.;

Real-time proton beam range monitoring by means of prompt-gamma detection with a collimated camera

NASA Astrophysics Data System (ADS)

Roellinghoff, F.; Benilov, A.; Dauvergne, D.; Dedes, G.; Freud, N.; Janssens, G.; Krimmer, J.; Létang, J. M.; Pinto, M.; Prieels, D.; Ray, C.; Smeets, J.; Stichelbaut, F.; Testa, E.

2014-03-01

Prompt-gamma profile was measured at WPE-Essen using 160 MeV protons impinging a movable PMMA target. A single collimated detector was used with time-of-flight (TOF) to reduce the background due to neutrons. The target entrance rise and the Bragg peak falloff retrieval precision was determined as a function of incident proton number by a fitting procedure using independent data sets. Assuming improved sensitivity of this camera design by using a greater number of detectors, retrieval precisions of 1 to 2 mm (rms) are expected for a clinical pencil beam. TOF improves the contrast-to-noise ratio and the performance of the method significantly.

Laboratory laser acceleration and high energy astrophysics: {gamma}-ray bursts and cosmic rays

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

Tajima, T.; Takahashi, Y.

1998-08-20

Recent experimental progress in laser acceleration of charged particles (electrons) and its associated processes has shown that intense electromagnetic pulses can promptly accelerate charged particles to high energies and that their energy spectrum is quite hard. On the other hand some of the high energy astrophysical phenomena such as extremely high energy cosmic rays and energetic components of {gamma}-ray bursts cry for new physical mechanisms for promptly accelerating particles to high energies. The authors suggest that the basic physics involved in laser acceleration experiments sheds light on some of the underlying mechanisms and their energy spectral characteristics of the promptlymore » accelerated particles in these high energy astrophysical phenomena.« less

Panchromatic Observations of GRB 110205A and Other GRB Optical Prompt Observations Obtained by ROTSE

NASA Astrophysics Data System (ADS)

Zheng, Weikang; with a larger Collaboration

2011-09-01

The leading radiation mechanisms for gamma-ray bursts (GRBs), as predicted by the standard GRB fireball model, include synchrotron radiation, synchrotron self-Compton (SSC), and inverse Compton scattering from thermal photons. Panchromatic observations during GRB prompt emission are important to distinguish the mechanisms. GRB 110205A, triggered by Swift, is also detected by Suzaku, ROTSE-IIIb and BOOTES telescopes when the GRB is still radiating gamma-rays. These panchromatic observations, covering 6 orders of energy range from 1 eV to 5 MeV, will be presented. We clearly discover an interesting two-break energy spectrum for the first time, roughly consistent with the synchrotron spectrum predicted by the standard GRB fireball model. The two break energies can be explained as νc, the synchrotron cooling frequency, and νm, the synchrotron typical frequency. With a sample of GRBs with optical prompt detections from ROTSE observations, one can also constrain the self-absorption frequency, νa. These detailed prompt observations are important to discriminate different mechanisms and thus lead us to a better and deeper understanding of the GRB fireball model. This research is supported by the NASA grant NNX08AV63G and the NSF grant PHY-0801007.

The Second SWIFT Burst Alert Telescope (BAT) Gamma-Ray Burst Catalog

NASA Technical Reports Server (NTRS)

Sakamoto, T.; Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.;

Gamma-ray Burst Prompt Correlations: Selection and Instrumental Effects

NASA Astrophysics Data System (ADS)

Dainotti, M. G.; Amati, L.

2018-05-01

The prompt emission mechanism of gamma-ray bursts (GRB) even after several decades remains a mystery. However, it is believed that correlations between observable GRB properties, given their huge luminosity/radiated energy and redshift distribution extending up to at least z ≈ 9, are promising possible cosmological tools. They also may help to discriminate among the most plausible theoretical models. Nowadays, the objective is to make GRBs standard candles, similar to supernovae (SNe) Ia, through well-established and robust correlations. However, differently from SNe Ia, GRBs span over several order of magnitude in their energetics, hence they cannot yet be considered standard candles. Additionally, being observed at very large distances, their physical properties are affected by selection biases, the so-called Malmquist bias or Eddington effect. We describe the state of the art on how GRB prompt correlations are corrected for these selection biases to employ them as redshift estimators and cosmological tools. We stress that only after an appropriate evaluation and correction for these effects, GRB correlations can be used to discriminate among the theoretical models of prompt emission, to estimate the cosmological parameters and to serve as distance indicators via redshift estimation.

SU-F-J-65: Prediction of Patient Setup Errors and Errors in the Calibration Curve from Prompt Gamma Proton Range Measurements

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

Albert, J; Labarbe, R; Sterpin, E

2016-06-15

Purpose: To understand the extent to which the prompt gamma camera measurements can be used to predict the residual proton range due to setup errors and errors in the calibration curve. Methods: We generated ten variations on a default calibration curve (CC) and ten corresponding range maps (RM). Starting with the default RM, we chose a square array of N beamlets, which were then rotated by a random angle θ and shifted by a random vector s. We added a 5% distal Gaussian noise to each beamlet in order to introduce discrepancies that exist between the ranges predicted from themore » prompt gamma measurements and those simulated with Monte Carlo algorithms. For each RM, s, θ, along with an offset u in the CC, were optimized using a simple Euclidian distance between the default ranges and the ranges produced by the given RM. Results: The application of our method lead to the maximal overrange of 2.0mm and underrange of 0.6mm on average. Compared to the situations where s, θ, and u were ignored, these values were larger: 2.1mm and 4.3mm. In order to quantify the need for setup error corrections, we also performed computations in which u was corrected for, but s and θ were not. This yielded: 3.2mm and 3.2mm. The average computation time for 170 beamlets was 65 seconds. Conclusion: These results emphasize the necessity to correct for setup errors and the errors in the calibration curve. The simplicity and speed of our method makes it a good candidate for being implemented as a tool for in-room adaptive therapy. This work also demonstrates that the Prompt gamma range measurements can indeed be useful in the effort to reduce range errors. Given these results, and barring further refinements, this approach is a promising step towards an adaptive proton radiotherapy.« less

dAcquisition setting optimization and quantitative imaging for 124I studies with the Inveon microPET-CT system.

PubMed

Anizan, Nadège; Carlier, Thomas; Hindorf, Cecilia; Barbet, Jacques; Bardiès, Manuel

2012-02-13

Noninvasive multimodality imaging is essential for preclinical evaluation of the biodistribution and pharmacokinetics of radionuclide therapy and for monitoring tumor response. Imaging with nonstandard positron-emission tomography [PET] isotopes such as 124I is promising in that context but requires accurate activity quantification. The decay scheme of 124I implies an optimization of both acquisition settings and correction processing. The PET scanner investigated in this study was the Inveon PET/CT system dedicated to small animal imaging. The noise equivalent count rate [NECR], the scatter fraction [SF], and the gamma-prompt fraction [GF] were used to determine the best acquisition parameters for mouse- and rat-sized phantoms filled with 124I. An image-quality phantom as specified by the National Electrical Manufacturers Association NU 4-2008 protocol was acquired and reconstructed with two-dimensional filtered back projection, 2D ordered-subset expectation maximization [2DOSEM], and 3DOSEM with maximum a posteriori [3DOSEM/MAP] algorithms, with and without attenuation correction, scatter correction, and gamma-prompt correction (weighted uniform distribution subtraction). Optimal energy windows were established for the rat phantom (390 to 550 keV) and the mouse phantom (400 to 590 keV) by combining the NECR, SF, and GF results. The coincidence time window had no significant impact regarding the NECR curve variation. Activity concentration of 124I measured in the uniform region of an image-quality phantom was underestimated by 9.9% for the 3DOSEM/MAP algorithm with attenuation and scatter corrections, and by 23% with the gamma-prompt correction. Attenuation, scatter, and gamma-prompt corrections decreased the residual signal in the cold insert. The optimal energy windows were chosen with the NECR, SF, and GF evaluation. Nevertheless, an image quality and an activity quantification assessment were required to establish the most suitable reconstruction algorithm and corrections for 124I small animal imaging.

Correlations of Prompt and Afterglow Emission in Swift Long and Short Gamma Ray Bursts

NASA Technical Reports Server (NTRS)

Gehrel, Neil; Barthelmy, S. d.; Burrows, D. N.; Cannizzo, J. K.; Chincarini, G.; Feinmore, E.; Kouveliotou, C.; O'Brien, P.; Palmer, D. M.; Racusin, J.;

Neutron threshold activation detectors (TAD) for the detection of fissions

NASA Astrophysics Data System (ADS)

Gozani, Tsahi; Stevenson, John; King, Michael J.

2011-10-01

Prompt fission neutrons are one of the strongest signatures of the fission process. Depending on the fission inducing radiation, their average number ranges from 2.5 to 4 neutrons per fission. They are more energetic and abundant, by about 2 orders of magnitude, than the delayed neutrons (≈3 vs. ≈0.01) that are commonly used as indicators for the presence of fissionable materials. The detection of fission prompt neutrons, however, has to be done in the presence of extremely intense probing radiation that stimulated them. During irradiation, the fission stimulation radiation, X-rays or neutrons, overwhelms the neutron detectors and temporarily incapacitate them. Consequently, by the time the detectors recover from the source radiation, fission prompt neutrons are no longer emitted. In order to measure the prompt fission signatures under these circumstances, special measures are usually taken with the detectors such as heavy shielding with collimation, use of inefficient geometries, high pulse height bias and gamma-neutron separation via pulse-shape discrimination with an appropriate organic scintillator. These attempts to shield the detector from the flash of radiation result in a major loss of sensitivity. It can lead to a complete inability to detect the fission prompt neutrons. In order to overcome the blinding induced background from the source radiation, the detection of prompt fission neutrons needs to occur long after the fission event and after the detector has fully recovered from the source overload. A new approach to achieve this is to detect the delayed activation induced by the fission neutrons. The approach demonstrates a good sensitivity in adverse overload situations (gamma and neutron "flash") where fission prompt neutrons could normally not be detected. The new approach achieves the required temporal separation between the detection of prompt neutrons and the detector overload by the neutron activation of the detector material. The technique, called Threshold Activation Detection (TAD), is to utilize appropriate substances that can be selectively activated by the fission neutrons and not by the source radiation and then measure the radioactively decaying activation products (typically beta and gamma rays) well after the source pulse. The activation material should possess certain properties: a suitable half-life of the order of seconds; an energy threshold below which the numerous source neutrons will not activate it (e.g., 3 MeV); easily detectable activation products (typically >1 MeV beta and gamma rays) and have a usable cross-section for the selected reaction. Ideally the substance would be a part of the scintillator. There are several good material candidates for the TAD, including fluorine, which is a major constituent of available scintillators such as BaF 2, CaF 2 and hydrogen free liquid fluorocarbon. Thus the fluorine activation products, in particular the beta particles, can be measured with a very high efficiency in the detector. The principles, applications and experimental results obtained with the fluorine based TAD are discussed.

Evaluation of prompt gamma-ray data and nuclear structure of niobium-94 with statistical model calculations

NASA Astrophysics Data System (ADS)

Turkoglu, Danyal

Precise knowledge of prompt gamma-ray intensities following neutron capture is critical for elemental and isotopic analyses, homeland security, modeling nuclear reactors, etc. A recently-developed database of prompt gamma-ray production cross sections and nuclear structure information in the form of a decay scheme, called the Evaluated Gamma-ray Activation File (EGAF), is under revision. Statistical model calculations are useful for checking the consistency of the decay scheme, providing insight on its completeness and accuracy. Furthermore, these statistical model calculations are necessary to estimate the contribution of continuum gamma-rays, which cannot be experimentally resolved due to the high density of excited states in medium- and heavy-mass nuclei. Decay-scheme improvements in EGAF lead to improvements to other databases (Evaluated Nuclear Structure Data File, Reference Input Parameter Library) that are ultimately used in nuclear-reaction models to generate the Evaluated Nuclear Data File (ENDF). Gamma-ray transitions following neutron capture in 93Nb have been studied at the cold-neutron beam facility at the Budapest Research Reactor. Measurements have been performed using a coaxial HPGe detector with Compton suppression. Partial gamma-ray production capture cross sections at a neutron velocity of 2200 m/s have been deduced relative to that of the 255.9-keV transition after cold-neutron capture by 93Nb. With the measurement of a niobium chloride target, this partial cross section was internally standardized to the cross section for the 1951-keV transition after cold-neutron capture by 35Cl. The resulting (0.1377 +/- 0.0018) barn (b) partial cross section produced a calibration factor that was 23% lower than previously measured for the EGAF database. The thermal-neutron cross sections were deduced for the 93Nb(n,gamma ) 94mNb and 93Nb(n,gamma) 94gNb reactions by summing the experimentally-measured partial gamma-ray production cross sections associated with the ground-state transitions below the 396-keV level and combining that summation with the contribution to the ground state from the quasi-continuum above 396 keV, determined with Monte Carlo statistical model calculations using the DICEBOX computer code. These values, sigmam and sigma 0, were (0.83 +/- 0.05) b and (1.16 +/- 0.11) b, respectively, and found to be in agreement with literature values. Comparison of the modeled population and experimental depopulation of individual levels confirmed tentative spin assignments and suggested changes where imbalances existed.

Measurement of the relative prompt production rate of χ c2 and χ c1 in pp collisions at $$\\sqrt{s} = 7\\ \\mathrm{TeV}$$

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

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.

A measurement is presented of the relative prompt production rate of chi(c2) and chi(c1) with 4.6 inverse femtobarns of data collected by the CMS experiment at the LHC in pp collisions at sqrt(s) = 7 TeV. The two states are measured via their radiative decays chi(c) to J/psi + gamma, with the photon converting into a dielectron pair for J/psi rapidity abs(y(J/psi)) < 1.0 and photon transverse momentum pt(gamma) > 0.5 GeV. The measurement is given for six intervals of pt(J/psi) between 7 and 25 GeV. The results are compared to theoretical predictions.

Prompt and delayed NAA techniques for the characterization of specimen bank materials.

PubMed

Rossbach, M; Stoeppler, M; Byrne, A R

1993-11-01

The combined application of instrumental-, radiochemical- and prompt gamma neutron activation analysis to two spruce shoot materials from the German Environmental Specimen Bank (ESB) resulted in information on 50 elements, covering more than 50% of the total mass. Comparison of the element concentrations in the 'fingerprint' mode clearly indicated a different status of heavy metal pollution at the two distinct collecting sites.

Measurement of the inclusive isolated prompt photon cross section in $$p\\bar{p}$$ collisions at $$\\sqrt{s}=$$1.96~TeV, using the full CDF data sample

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

Luca, Alessandra

2016-01-01

The measurement of the cross section for the inclusive production of isolated prompt photons in proton-antiproton collisions atmore » $$\\sqrt{s}$$=1.96~TeV is presented. The data set corresponds to an integrated luminosity of 9.5~fb$$^{-1}$$, collected with the Collider Detector at Fermilab in Run~II. The measurement is performed as a function of the photon transverse energy ($$E_T^{\\gamma}$$) covering the range of 30~GeV$$< E_T^{\\gamma} <$$500~GeV in the pseudorapidity region $$|\\eta^{\\gamma}|<$$1.0. To reduce the background coming from the decays of $$\\pi^0$$'s, $$\\eta$$'s and other hadrons, photons are required to be isolated in the calorimeter. The output distributions of an Artificial Neural Network are exploited to estimate the remaining contamination from jets faking isolated photons. Results are compared to leading-order and next-to-leading-order perturbative QCD calculations.« less

Beyond the Band Function Paradigm : a New Model for GRB Prompt Emission and Possible Impact in Cosmology

NASA Astrophysics Data System (ADS)

Guiriec, Sylvain

Gamma Ray Bursts (GRBs) are the most violent phenomenons in the Universe. They are associated with the birth of stellar mass black holes either from the collapse of hypermassive stars or the merger of compact objects. The Fireball model is the most popular scenario to explain GRBs. In this theoretical framework, GRB central engines release collimated, bipolar and highly relativistic jets mainly composed of electrons, positrons, photons, and a small amount of baryons. During the first phase of the Fireball model, charged particles are accelerated and release non-thermal radiations. The Fireball model also predicts a thermal like component coming from the jet photosphere. This first phase would be responsible for the GRB prompt emission observed by gamma ray telescopes such as Fermi/GBM in the keV-MeV energy range and which is the only phase discussed in this talk. Until now, GRB prompt emission spectra were considered as adequately fitted with the empirical Band function, which is a smoothly broken power law. However, its parameters are very often incompatible with the Fireball model predictions for both the thermal and non-thermal components. We will see that observation with the Fermi Gamma Ray Space Telescope break the paradigm of the Band function and that deviations from this function exists in many GRBs. Those deviations are adequately fitted with an additional thermal-like component -that we consider as the jet photosphere- and/or an additional power law. Importantly, with the three components together, theory and observations are much more in agreement. We will also see how this new model for prompt emission spectra may have an impact beyond the physics of GRBs. Indeed, this work may confirm a relation between the hardness of the GRB prompt emission and its luminosity which may be used to scale GRBs as standard-like candles for use in cosmology.

Simulations of Multi-Gamma Coincidences From Neutron-Induced Fission in Special Nuclear Materials

NASA Astrophysics Data System (ADS)

Kane, Steven; Gozani, Tsahi; King, Michael J.; Kwong, John; Brown, Craig; Gary, Charles; Firestone, Murray I.; Nikkel, James A.; McKinsey, Daniel N.

2013-04-01

A study is presented on the detection of illicit special nuclear materials (SNM) in cargo containers using a conceptual neutron-based inspection system with xenon-doped liquefied argon (LAr(Xe)) scintillation detectors for coincidence gamma-ray detection. For robustness, the system is envisioned to exploit all fission signatures, namely both prompt and delayed neutron and gamma emissions from fission reactions induced in SNM. However, this paper focuses exclusively on the analysis of the prompt gamma ray emissions. The inspection system probes a container using neutrons produced either by (d, D) or (d, T) in pulsed form or from an associated particle neutron generator to exploit the associated particle imaging (API) technique, thereby achieving background reduction and imaging. Simulated signal and background estimates were obtained in MCNPX (2.7) for a 2 kg sphere of enriched uranium positioned at the center of a 1m × 1m × 1m container, which is filled uniformly with wood or iron cargos at 0.1 g/cc or 0.4 g/cc. Detection time estimates are reported assuming probabilities of detection of 95% and false alarm of 0.5%.

Solar gamma rays. [in solar flares

NASA Technical Reports Server (NTRS)

Ramaty, R.; Kozlovsky, B.; Lingenfelter, R. E.

1974-01-01

The theory of gamma ray production in solar flares is treated in detail. Both lines and continuum are produced. Results show that the strongest line predicted at 2.225 MeV with a width of less than 100 eV and detected at 2.24 + or - 2.02 MeV, is due to neutron capture by protons in the photosphere. Its intensity is dependent on the photospheric He-3 abundance. The neutrons are produced in nuclear reactions of flare accelerated particles which also produce positrons and prompt nuclear deexcitation lines. The strongest prompt lines are at 4.43 MeV from c-12 and at approximately 6.2 from 0-16 and N-15. The gamma ray continuum, produced by electron bremsstrahlung, allows the determination of the spectrum and number of accelerated electrons in the MeV region. From the comparison of the line and continuum intensities a proton-to-electron ratio of about 10 to 100 at the same energy for the 1972, August 4 flare. For the same flare the protons above 2.5 MeV which are responsible for the gamma ray emission produce a few percent of the heat generated by the electrons which make the hard X rays above 20 keV.

Rapid response sensor for analyzing Special Nuclear Material

DOE PAGES

Mitra, S. S.; Doron, O.; Chen, A. X.; ...

2015-06-18

Rapid in-situ analytical techniques are attractive for characterizing Special Nuclear Material (SNM). Present techniques are time consuming, and require sample dissolution. Proof-of-principal studies are performed to demonstrate the utility of employing low energy neutrons from a portable pulsed neutron generator for non-destructive isotopic analysis of nuclear material. In particular, time-sequenced data acquisition, operating synchronously with the pulsing of a neutron generator, partitions the characteristic elemental prompt gamma-rays according to the type of the reaction; inelastic neutron scattering reactions during the ON state and thermal neutron capture reactions during the OFF state of the generator. Thus, the key challenge is isolatingmore » these signature gamma- rays from the prompt fission and β-delayed gamma-rays that are also produced during the neutron interrogation. A commercial digital multi-channel analyzer has been specially customized to enable time-resolved gamma-ray spectral data to be acquired in multiple user-defined time bins within each of the ON/OFF gate periods of the neutron generator. Preliminary results on new signatures from depleted uranium as well as modeling and benchmarking of the concept are presented, however this approach should should be applicable for virtually all forms of SNM.« less

Microstructural study of the nickel-base alloy WAZ-20 using qualitative and quantitative electron optical techniques

NASA Technical Reports Server (NTRS)

Young, S. G.

1973-01-01

The NASA nickel-base alloy WAZ-20 was analyzed by advanced metallographic techniques to qualitatively and quantitatively characterize its phases and stability. The as-cast alloy contained primary gamma-prime, a coarse gamma-gamma prime eutectic, a gamma-fine gamma prime matrix, and MC carbides. A specimen aged at 870 C for 1000 hours contained these same constituents and a few widely scattered high W particles. No detrimental phases (such as sigma or mu) were observed. Scanning electron microscope, light metallography, and replica electron microscope methods are compared. The value of quantitative electron microprobe techniques such as spot and area analysis is demonstrated.

GRB 170817A Associated with GW170817: Multi-frequency Observations and Modeling of Prompt Gamma-Ray Emission

NASA Astrophysics Data System (ADS)

Pozanenko, A. S.; Barkov, M. V.; Minaev, P. Yu.; Volnova, A. A.; Mazaeva, E. D.; Moskvitin, A. S.; Krugov, M. A.; Samodurov, V. A.; Loznikov, V. M.; Lyutikov, M.

2018-01-01

We present our observations of electromagnetic transients associated with GW170817/GRB 170817A using optical telescopes of Chilescope observatory and Big Scanning Antenna (BSA) of Pushchino Radio Astronomy Observatory at 110 MHz. The Chilescope observatory detected an optical transient of ∼19m on the third day in the outskirts of the galaxy NGC 4993; we continued observations following its rapid decrease. We put an upper limit of 1.5 × 104 Jy on any radio source with a duration of 10–60 s, which may be associated with GW170817/GRB 170817A. The prompt gamma-ray emission consists of two distinctive components—a hard short pulse delayed by ∼2 s with respect to the LIGO signal and softer thermal pulse with T ∼ 10 keV lasting for another ∼2 s. The appearance of a thermal component at the end of the burst is unusual for short GRBs. Both the hard and the soft components do not satisfy the Amati relation, making GRB 170817A distinctively different from other short GRBs. Based on gamma-ray and optical observations, we develop a model for the prompt high-energy emission associated with GRB 170817A. The merger of two neutron stars creates an accretion torus of ∼10‑2 M ⊙, which supplies the black hole with magnetic flux and confines the Blandford–Znajek-powered jet. We associate the hard prompt spike with the quasispherical breakout of the jet from the disk wind. As the jet plows through the wind with subrelativistic velocity, it creates a radiation-dominated shock that heats the wind material to tens of kiloelectron volts, producing the soft thermal component.

The Supercritical Pile GRB Model: The Prompt to Afterglow Evolution

NASA Technical Reports Server (NTRS)

Kazanas, Demosthenes

2008-01-01

The 'Supercritical Pile' is a very economical gamma ray burst (GRB) model that provides for the efficient conversion of the energy stored in the protons of a Relativistic Blast Wave (RBW) into radiation and at the same time produces - in the prompt GRB phase, even in the absence of any particle acceleration - a spectral peak at an energy sim 1 MeV. We extend this model to include also the evolution of the RBW Lorentz factor Gamma and thus follow the spectral and temporal features of this model into the early GRB afterglow stage. One of the novel features of the present treatment is the inclusion of the feedback of the GRB produced radiation on the evolution of Gamma with radius. This feedback and the presence of kinematic and dynamic thresholds in the model can be the sources of rich time evolution which we have begun to explore. In particular, one can this way obtain afterglow light curves with steep decays followed by the more conventional flatter afterglow slopes, while at the same time preserving the desirable features of the model, i.e. the well defined relativistic electron source and radiative processes that produce the proper peak in the nu F spectra. Furthermore, the existence of a kinematic threshold in this model provides for a operational distinction of the prompt and afterglow GRB stages; in fact, the afterglow stage sets in when the RBW Lorentz factor cannot anymore fulfill the kinematic condition for pair formation in the photon - proton pair production reactions that constitute the fundamental process for the dissipation of the blast wave kinetic energy. We present the results of a specific set of parameters of this model with emphasis on the multiwavelength prompt emission and transition to the early afterglow.

Investigation of Martian H2O and CO2 via orbital gamma ray spectroscopy

NASA Technical Reports Server (NTRS)

Evans, Larry G.; Squyres, Steven W.

1987-01-01

The capability of an orbital gamma ray spectrometer to address presently unanswered questions concerning H2O and CO2 on Mars is investigated. The gamma ray signal produced by the Martian atmosphere and by several simple models of Martian surface materials is calculated. Results are reported for: (1) the production of neutrons in the atmosphere and in the subsurface material by cosmic ray interactions, (2) the scattering of neutrons and the resultant neutron energy spectrum and spatial distributions, (3) the reproduction of gamma rays by neutron prompt capture and nonelastic scatter reactions, (4) the production of gamma rays by natural radionuclides, (5) the attenuation of the gamma ray signal by passage through surface materials and the Martian atmosphere, (6) the production of the gamma ray continuum background, and (7) the uncertainty in gamma ray line strengths that results from the combined signal and background observed by the detector.

EM reconstruction of dual isotope PET using staggered injections and prompt gamma positron emitters

PubMed Central

Andreyev, Andriy; Sitek, Arkadiusz; Celler, Anna

2014-01-01

Purpose: The aim of dual isotope positron emission tomography (DIPET) is to create two separate images of two coinjected PET radiotracers. DIPET shortens the duration of the study, reduces patient discomfort, and produces perfectly coregistered images compared to the case when two radiotracers would be imaged independently (sequential PET studies). Reconstruction of data from such simultaneous acquisition of two PET radiotracers is difficult because positron decay of any isotope creates only 511 keV photons; therefore, the isotopes cannot be differentiated based on the detected energy. Methods: Recently, the authors have proposed a DIPET technique that uses a combination of radiotracer A which is a pure positron emitter (such as 18F or 11C) and radiotracer B in which positron decay is accompanied by the emission of a high-energy (HE) prompt gamma (such as 38K or 60Cu). Events that are detected as triple coincidences of HE gammas with the corresponding two 511 keV photons allow the authors to identify the lines-of-response (LORs) of isotope B. These LORs are used to separate the two intertwined distributions, using a dedicated image reconstruction algorithm. In this work the authors propose a new version of the DIPET EM-based reconstruction algorithm that allows the authors to include an additional, independent estimate of radiotracer A distribution which may be obtained if radioisotopes are administered using a staggered injections method. In this work the method is tested on simple simulations of static PET acquisitions. Results: The authors’ experiments performed using Monte-Carlo simulations with static acquisitions demonstrate that the combined method provides better results (crosstalk errors decrease by up to 50%) than the positron-gamma DIPET method or staggered injections alone. Conclusions: The authors demonstrate that the authors’ new EM algorithm which combines information from triple coincidences with prompt gammas and staggered injections improves the accuracy of DIPET reconstructions for static acquisitions so they reach almost the benchmark level calculated for perfectly separated tracers. PMID:24506645

Improvement of the prompt-gamma neutron activation facility at Brookhaven National Laboratory.

PubMed

Dilmanian, F A; Lidofsky, L J; Stamatelatos, I; Kamen, Y; Yasumura, S; Vartsky, D; Pierson, R N; Weber, D A; Moore, R I; Ma, R

1998-02-01

The prompt-gamma neutron activation facility at Brookhaven National Laboratory was upgraded to improve both the precision and accuracy of its in vivo determinations of total body nitrogen. The upgrade, guided by Monte Carlo simulations, involved elongating and modifying the source collimator and its shielding, repositioning the system's two NaI(Tl) detectors, and improving the neutron and gamma shielding of these detectors. The new source collimator has a graphite reflector around the 238PuBe neutron source to enhance the low-energy region of the neutron spectrum incident on the patient. The gamma detectors have been relocated from positions close to the upward-emerging collimated neutron beam to positions close to and at the sides of the patient. These modifications substantially reduced spurious counts resulting from the capture of small-angle scattered neutrons in the NaI detectors. The pile-up background under the 10.8 MeV 14N(n, gamma)15N spectral peak has been reduced so that the nitrogen peak-to-background ratio has been increased by a factor of 2.8. The resulting reduction in the coefficient of variation of the total body nitrogen measurements from 3% to 2.2% has improved the statistical significance of the results possible for any given number of patient measurements. The new system also has a more uniform composite sensitivity.

Limits on Neutrino Emission from Gamma-Ray Bursts with the 40 String IceCube Detector

NASA Astrophysics Data System (ADS)

Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; Benzvi, S.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blumenthal, J.; Boersma, D. J.; Bohm, C.; Bose, D.; Böser, S.; Botner, O.; Braun, J.; Brown, A. M.; Buitink, S.; Carson, M.; Chirkin, D.; Christy, B.; Clem, J.; Clevermann, F.; Cohen, S.; Colnard, C.; Cowen, D. F.; D'Agostino, M. V.; Danninger, M.; Daughhetee, J.; Davis, J. C.; de Clercq, C.; Demirörs, L.; Depaepe, O.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; Deyoung, T.; Díaz-Vélez, J. C.; Dierckxsens, M.; Dreyer, J.; Dumm, J. P.; Ehrlich, R.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Fedynitch, A.; Feusels, T.; Filimonov, K.; Finley, C.; Fischer-Wasels, T.; Foerster, M. M.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Geisler, M.; Gerhardt, L.; Gladstone, L.; Glüsenkamp, T.; Goldschmidt, A.; Goodman, J. A.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gurtner, M.; Ha, C.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Heinen, D.; Helbing, K.; Herquet, P.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Homeier, A.; Hoshina, K.; Hubert, D.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Ishihara, A.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Joseph, J. M.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kelley, J. L.; Kemming, N.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Köhne, J.-H.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Krings, T.; Kroll, G.; Kuehn, K.; Kuwabara, T.; Labare, M.; Lafebre, S.; Laihem, K.; Landsman, H.; Larson, M. J.; Lauer, R.; Lehmann, R.; Lünemann, J.; Madsen, J.; Majumdar, P.; Marotta, A.; Maruyama, R.; Mase, K.; Matis, H. S.; Meagher, K.; Merck, M.; Mészáros, P.; Meures, T.; Middell, E.; Milke, N.; Miller, J.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Naumann, U.; Nießen, P.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; O'Murchadha, A.; Ono, M.; Panknin, S.; Paul, L.; Pérez de Los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Porrata, R.; Posselt, J.; Price, P. B.; Prikockis, M.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Rizzo, A.; Rodrigues, J. P.; Roth, P.; Rothmaier, F.; Rott, C.; Ruhe, T.; Rutledge, D.; Ruzybayev, B.; Ryckbosch, D.; Sander, H.-G.; Santander, M.; Sarkar, S.; Schatto, K.; Schmidt, T.; Schoenwald, A.; Schukraft, A.; Schultes, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Slipak, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stephens, G.; Stezelberger, T.; Stokstad, R. G.; Stoyanov, S.; Strahler, E. A.; Straszheim, T.; Sullivan, G. W.; Swillens, Q.; Taavola, H.; Taboada, I.; Tamburro, A.; Tarasova, O.; Tepe, A.; Ter-Antonyan, S.; Tilav, S.; Toale, P. A.; Toscano, S.; Tosi, D.; Turčan, D.; van Eijndhoven, N.; Vandenbroucke, J.; van Overloop, A.; van Santen, J.; Vehring, M.; Voge, M.; Voigt, B.; Walck, C.; Waldenmaier, T.; Wallraff, M.; Walter, M.; Weaver, C.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebe, K.; Wiebusch, C. H.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Wolf, M.; Woschnagg, K.; Xu, C.; Xu, X. W.; Yodh, G.; Yoshida, S.; Zarzhitsky, P.

2011-04-01

IceCube has become the first neutrino telescope with a sensitivity below the TeV neutrino flux predicted from gamma-ray bursts if gamma-ray bursts are responsible for the observed cosmic-ray flux above 1018eV. Two separate analyses using the half-complete IceCube detector, one a dedicated search for neutrinos from pγ interactions in the prompt phase of the gamma-ray burst fireball and the other a generic search for any neutrino emission from these sources over a wide range of energies and emission times, produced no evidence for neutrino emission, excluding prevailing models at 90% confidence.

Mycobacterium avium Complex Empyema in a Patient with Interferon Gamma Autoantibodies

PubMed Central

Chung, Heath H; Opal, Steven M; Dworkin, Jonathan D

2014-01-01

Interferon gamma (IFN-γ) autoantibodies are a relatively recently discovered clinical entity, which have been shown to be associated with disseminated non-tuberculous mycobacterial (NTM) infections and other opportunistic infections. Interestingly, isolated NTM infections (without disseminated NTM infection) have not been shown to be a good predictor of the presence of IFN-γ autoantibodies. This case describes an isolated NTM empyema in a patient with IFN-γ autoantibodies and makes the argument that the development of an NTM empyema in a patient with no known immunodeficiency should prompt consideration for IFN-γ testing. Additionally, this case underscores the importance for clinicians to recognize that an unusual infection without the typical cause of impairment in immunity should prompt a more thorough investigation of the patient's immune system. PMID:25285250

The Prompt Gamma Neutron Activation Analysis Facility at ICN—Pitesti

NASA Astrophysics Data System (ADS)

Bǎrbos, D.; Pǎunoiu, C.; Mladin, M.; Cosma, C.

2008-08-01

PGNAA is a very widely applicable technique for determining the presence and amount of many elements simultaneously in samples ranging in size from micrograms to many grams. PGNAA is characterized by its capability for nondestructive multi-elemental analysis and its ability to analyse elements that cannot be determined by INAA. By means of this PGNAA method we are able to increase the performace of INAA method. A facility has been developed at Institute for Nuclear Research—Piteşti so that the unique features of prompt gamma-ray neutron activation analysis can be used to measure trace and major elements in samples. The facility is linked at the radial neutron beam tube at ACPR-TRIGA reactor. During the PGNAA—facility is in use the ACPR reactor will be operated in steady-state mode at 250 KW maximum power. The facility consists of a radial beam-port, external sample position with shielding, and induced prompt gamma-ray counting system. Thermal neutron flux with energy lower than cadmium cut-off at the sample position was measured using thin gold foil is: φscd = 1.106 n/cm2/s with a cadmium ratio of:80. The gamma-ray detection system consist of an HpGe detector of 16% efficiency (detector model GC1518) with 1.85 keV resolution capability. The HpGe is mounted with its axis at 90° with respect to the incident neutron beam at distance about 200mm from the sample position. To establish the performance capabilities of the facility, irradiation of pure element or sample compound standards were performed to identify the gama-ray energies from each element and their count rates.

A MAD model for gamma-ray burst variability

NASA Astrophysics Data System (ADS)

Lloyd-Ronning, Nicole M.; Dolence, Joshua C.; Fryer, Christopher L.

2016-09-01

We present a model for the temporal variability of long gamma-ray bursts (GRBs) during the prompt phase (the highly variable first 100 s or so), in the context of a magnetically arrested disc (MAD) around a black hole. In this state, sufficient magnetic flux is held on to the black hole such that it stalls the accretion near the inner region of the disc. The system transitions in and out of the MAD state, which we relate to the variable luminosity of the GRB during the prompt phase, with a characteristic time-scale defined by the free-fall time in the region over which the accretion is arrested. We present simple analytic estimates of the relevant energetics and time-scales, and compare them to GRB observations. In particular, we show how this model can reproduce the characteristic one second time-scale that emerges from various analyses of the prompt emission light curve. We also discuss how our model can accommodate the potentially physically important correlation between a burst quiescent time and the duration of its subsequent pulse.

Robotic Telescopes

NASA Astrophysics Data System (ADS)

Akerlof, C. W.

2001-05-01

Since the discovery of gamma-ray bursts, a number of groups have attempted to detect correlated optical transients from these elusive objects. Following the flight of the BATSE instrument on the Compton Gamma-Ray Observatory in 1991, a prompt burst coordinate alert service, BACODINE (now GCN) became available to ground-based telescopes. Several instruments were built to take advantage of this facility, culminating in the discovery of a bright optical flash associated with GRB990123. To date, that single observation remains unique - no other prompt flashes have been seen for a dozen or so other bursts observed with comparably short response times. Thus, GRB prompt optical luminosities may be considerably dimmer than observed for the GRB990123 event or even absent altogether. A new generation of instruments is prepared to explore these possibilties using burst coordinates provided by HETE-2, Swift, Ballerina, Agile and other satellite missions. These telescopes have response times as short as a few seconds and reach limiting magnitudes, m_v 20, guaranteeing a sensitivity sufficient to detect the afterglow many hours later. Results from these experiments should provide important new data about the dynamics and locale of GRBs.

A System for Photon-Counting Spectrophotometry of Prompt Optical Emission from Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Vestrand, W. T.; Albright, K.; Casperson, D.; Fenimore, E.; Ho, C.; Priedhorsky, W.; White, R.; Wren, J.

2003-04-01

With the launch of HETE-2 and the coming launch of the Swift satellite, there will be many new opportunities to study the physics of the prompt optical emission with robotic ground-based telescopes. Time-resolved spectrophotometry of the rapidly varying optical emission is likely to be a rich area for discovery. We describe a program to apply state-of-the-art photon-counting imaging technology to the study of prompt optical emission from gamma-ray bursts. The Remote Ultra-Low Light Imaging (RULLI) project at Los Alamos National Laboratory has developed an imaging sensor which employs stacked microchannel plates and a crossed delay line readout with 200 picosecond photon timing to measure the time of arrival and positions for individual optical photons. RULLI detectors, when coupled with a transmission grating having 300 grooves/mm, can make photon-counting spectroscopic observations with spectral resolution that is an order of magnitude greater and temporal resolution three orders of magnitude greater than the most capable photon-counting imaging detectors that have been used for optical astronomy.

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

Xing, Y; Macq, B; Bondar, L

Purpose: To quantify the accuracy in predicting the Bragg peak position using simulated in-room measurements of prompt gamma (PG) emissions for realistic treatment error scenarios that combine several sources of errors. Methods: Prompt gamma measurements by a knife-edge slit camera were simulated using an experimentally validated analytical simulation tool. Simulations were performed, for 143 treatment error scenarios, on an anthropomorphic phantom and a pencil beam scanning plan for nasal cavity. Three types of errors were considered: translation along each axis, rotation around each axis, and CT-calibration errors with magnitude ranging respectively, between −3 and 3 mm, −5 and 5 degrees,more » and between −5 and +5%. We investigated the correlation between the Bragg peak (BP) shift and the horizontal shift of PG profiles. The shifts were calculated between the planned (reference) position and the position by the error scenario. The prediction error for one spot was calculated as the absolute difference between the PG profile shift and the BP shift. Results: The PG shift was significantly and strongly correlated with the BP shift for 92% of the cases (p<0.0001, Pearson correlation coefficient R>0.8). Moderate but significant correlations were obtained for all cases that considered only CT-calibration errors and for 1 case that combined translation and CT-errors (p<0.0001, R ranged between 0.61 and 0.8). The average prediction errors for the simulated scenarios ranged between 0.08±0.07 and 1.67±1.3 mm (grand mean 0.66±0.76 mm). The prediction error was moderately correlated with the value of the BP shift (p=0, R=0.64). For the simulated scenarios the average BP shift ranged between −8±6.5 mm and 3±1.1 mm. Scenarios that considered combinations of the largest treatment errors were associated with large BP shifts. Conclusion: Simulations of in-room measurements demonstrate that prompt gamma profiles provide reliable estimation of the Bragg peak position for complex error scenarios. Yafei Xing and Luiza Bondar are funded by BEWARE grants from the Walloon Region. The work presents simulations results for a prompt gamma camera prototype developed by IBA.« less

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

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

Souris, K; Lee, J; Sterpin, E

2014-06-15

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

A Correlated Optical and Gamma Emission from GRB 081126A

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

Gendre, B.; Klotz, A.; CESR, Observatoire Midi-Pyrenees, CNRS, Universite de Toulouse, BP 4346, F-31028-Toulouse Cedex 04

2010-10-15

We present an analysis of time-resolved optical emissions observed from the gamma-ray burst GRB 081126 during the prompt phase. The analysis employed time-resolved photometry using optical data obtained by the TAROT telescope, BAT data from the Swift spacecraft and time-resolved spectroscopy at high energies from the GBM instrument onboard the Fermi spacecraft. The optical emission of GRB 081126 is found to be compatible with the second gamma emission pulse shifted by a positive time-lag of 8.4{+-}3.9 sec. This is the first well resolved observation of a time lag between optical and gamma emissions during a gamma-ray burst. Our observations couldmore » potentially provide new constraints on the fireball model for gamma ray burst early emissions. Furthermore, observations of time-lags between optical and gamma ray photons provides an exciting opportunity to constrain quantum gravity theories.« less

On the Lack of a Radio Afterglow from Some Gamma-Ray Bursts - Insight into Their Progenitors?

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

Lloyd-Ronning, Nicole Marie; Fryer, Christopher L.

We investigate the intrinsic properties of a sample of bright (with isotropic equivalent energy Eiso > 10 52 erg) gamma-ray bursts (GRBs), comparing those with and without radio afterglow. We find that the sample of bursts with no radio afterglows has a significantly shorter mean intrinsic duration of the prompt gamma-ray radiation, and the distribution of this duration is significantly different from those bursts with a radio afterglow. Although the sample with no radio afterglow has on average lower isotropic energy, the lack of radio afterglow does not appear to be a result of simply energetics of the burst, butmore » a reflection of a separate physical phenomenon likely related to the circumburst density profile. We also find a weak correlation between the isotropic gamma-ray energy and intrinsic duration in the sample with no radio afterglow, but not in the sample that have observed radio afterglows. We give possible explanations for why there may exist a sample of GRBs with no radio afterglow depending on whether the radio emission comes from the forward or reverse shock, and why these bursts appear to have intrinsically shorter prompt emission durations. Lastly, we discuss how our results may have implications for progenitor models of GRBs.« less

On the Lack of a Radio Afterglow from Some Gamma-Ray Bursts - Insight into Their Progenitors?

DOE PAGES

Lloyd-Ronning, Nicole Marie; Fryer, Christopher L.

2017-02-07

We investigate the intrinsic properties of a sample of bright (with isotropic equivalent energy Eiso > 10 52 erg) gamma-ray bursts (GRBs), comparing those with and without radio afterglow. We find that the sample of bursts with no radio afterglows has a significantly shorter mean intrinsic duration of the prompt gamma-ray radiation, and the distribution of this duration is significantly different from those bursts with a radio afterglow. Although the sample with no radio afterglow has on average lower isotropic energy, the lack of radio afterglow does not appear to be a result of simply energetics of the burst, butmore » a reflection of a separate physical phenomenon likely related to the circumburst density profile. We also find a weak correlation between the isotropic gamma-ray energy and intrinsic duration in the sample with no radio afterglow, but not in the sample that have observed radio afterglows. We give possible explanations for why there may exist a sample of GRBs with no radio afterglow depending on whether the radio emission comes from the forward or reverse shock, and why these bursts appear to have intrinsically shorter prompt emission durations. Lastly, we discuss how our results may have implications for progenitor models of GRBs.« less

Prompt gamma neutron activation analysis of toxic elements in radioactive waste packages.

PubMed

Ma, J-L; Carasco, C; Perot, B; Mauerhofer, E; Kettler, J; Havenith, A

2012-07-01

The French Alternative Energies and Atomic Energy Commission (CEA) and National Radioactive Waste Management Agency (ANDRA) are conducting an R&D program to improve the characterization of long-lived and medium activity (LL-MA) radioactive waste packages. In particular, the amount of toxic elements present in radioactive waste packages must be assessed before they can be accepted in repository facilities in order to avoid pollution of underground water reserves. To this aim, the Nuclear Measurement Laboratory of CEA-Cadarache has started to study the performances of Prompt Gamma Neutron Activation Analysis (PGNAA) for elements showing large capture cross sections such as mercury, cadmium, boron, and chromium. This paper reports a comparison between Monte Carlo calculations performed with the MCNPX computer code using the ENDF/B-VII.0 library and experimental gamma rays measured in the REGAIN PGNAA cell with small samples of nickel, lead, cadmium, arsenic, antimony, chromium, magnesium, zinc, boron, and lithium to verify the validity of a numerical model and gamma-ray production data. The measurement of a ∼20kg test sample of concrete containing toxic elements has also been performed, in collaboration with Forschungszentrum Jülich, to validate the model in view of future performance studies for dense and large LL-MA waste packages. Copyright © 2012 Elsevier Ltd. All rights reserved.

GRB 050117: Simultaneous Gamma-ray and X-ray Observations with the Swift Satellite

NASA Technical Reports Server (NTRS)

Hill, J. E.; Morris, D. C.; Sakamoto, T.; Sato, G.; Burrows, D. N.; Angelini, L.; Pagani, C.; Moretti, A.; Abbey, A. F.; Barthelmy, S.

2005-01-01

The Swift Gamma-Ray Burst Explorer performed its first autonomous, X-ray follow-up to a newly detected GRB on 2005 January 17, within 193 seconds of the burst trigger by the Swift Burst Alert Telescope. While the burst was still in progress, the X-ray Telescope obtained a position and an image for an un-catalogued X-ray source; simultaneous with the gamma-ray observation. The XRT observed flux during the prompt emission was 1.1 x 10(exp -8) ergs/sq cm/s in the 0.5-10 keV energy band. The emission in the X-ray band decreased by three orders of magnitude within 700 seconds, following the prompt emission. This is found to be consistent with the gamma-ray decay when extrapolated into the XRT energy band. During the following 6.3 hours, the XRT observed the afterglow in an automated sequence for an additional 947 seconds, until the burst became fully obscured by the Earth limb. A faint, extremely slowly decaying afterglow, alpha=-0.21, was detected. Finally, a break in the lightcurve occurred and the flux decayed with alpha<-1.2. The X-ray position triggered many follow-up observations: no optical afterglow could be confirmed, although a candidate was identified 3 arcsecs from the XRT position.

On the lack of a radio afterglow from some gamma-ray bursts - insight into their progenitors?

NASA Astrophysics Data System (ADS)

Lloyd-Ronning, Nicole M.; Fryer, Christopher L.

2017-05-01

We investigate the intrinsic properties of a sample of bright (with isotropic equivalent energy Eiso > 1052 erg) gamma-ray bursts (GRBs), comparing those with and without radio afterglow. We find that the sample of bursts with no radio afterglows has a significantly shorter mean intrinsic duration of the prompt gamma-ray radiation, and the distribution of this duration is significantly different from those bursts with a radio afterglow. Although the sample with no radio afterglow has on average lower isotropic energy, the lack of radio afterglow does not appear to be a result of simply energetics of the burst, but a reflection of a separate physical phenomenon likely related to the circumburst density profile. We also find a weak correlation between the isotropic gamma-ray energy and intrinsic duration in the sample with no radio afterglow, but not in the sample that have observed radio afterglows. We give possible explanations for why there may exist a sample of GRBs with no radio afterglow depending on whether the radio emission comes from the forward or reverse shock, and why these bursts appear to have intrinsically shorter prompt emission durations. We discuss how our results may have implications for progenitor models of GRBs.

A SIZE-DURATION TREND FOR GAMMA-RAY BURST PROGENITORS

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

Barnacka, Anna; Loeb, Abraham, E-mail: abarnacka@cfa.harvard.edu, E-mail: aloeb@cfa.harvard.edu

2014-10-10

Gamma-ray bursts (GRBs) show a bimodal distribution of durations, separated at a duration of ∼2 s. Observations have confirmed the association of long GRBs with the collapse of massive stars. The origin of short GRBs is still being explored. We examine constraints on the size of emission regions in short and long GRBs detected by Fermi/GBM. We find that the transverse extent of emission regions during the prompt phase, R, and the burst duration, T {sub 90}, are consistent with the relation R ∼ c × T {sub 90}, for both long and short GRBs. We find the characteristic transverse extentmore » for the prompt emission region to be ∼2 × 10{sup 10} cm and ∼4 × 10{sup 11} cm for short and long GRBs, respectively.« less

The Use of Neutron Analysis Techniques for Detecting The Concentration And Distribution of Chloride Ions in Archaeological Iron

PubMed Central

Watkinson, D; Rimmer, M; Kasztovszky, Z; Kis, Z; Maróti, B; Szentmiklósi, L

2014-01-01

Chloride (Cl) ions diffuse into iron objects during burial and drive corrosion after excavation. Located under corrosion layers, Cl is inaccessible to many analytical techniques. Neutron analysis offers non-destructive avenues for determining Cl content and distribution in objects. A pilot study used prompt gamma activation analysis (PGAA) and prompt gamma activation imaging (PGAI) to analyse the bulk concentration and longitudinal distribution of Cl in archaeological iron objects. This correlated with the object corrosion rate measured by oxygen consumption, and compared well with Cl measurement using a specific ion meter. High-Cl areas were linked with visible damage to the corrosion layers and attack of the iron core. Neutron techniques have significant advantages in the analysis of archaeological metals, including penetration depth and low detection limits. PMID:26028670

First test of the prompt gamma ray timing method with heterogeneous targets at a clinical proton therapy facility

NASA Astrophysics Data System (ADS)

Hueso-González, Fernando; Enghardt, Wolfgang; Fiedler, Fine; Golnik, Christian; Janssens, Guillaume; Petzoldt, Johannes; Prieels, Damien; Priegnitz, Marlen; Römer, Katja E.; Smeets, Julien; Vander Stappen, François; Wagner, Andreas; Pausch, Guntram

2015-08-01

Ion beam therapy promises enhanced tumour coverage compared to conventional radiotherapy, but particle range uncertainties significantly blunt the achievable precision. Experimental tools for range verification in real-time are not yet available in clinical routine. The prompt gamma ray timing method has been recently proposed as an alternative to collimated imaging systems. The detection times of prompt gamma rays encode essential information about the depth-dose profile thanks to the measurable transit time of ions through matter. In a collaboration between OncoRay, Helmholtz-Zentrum Dresden-Rossendorf and IBA, the first test at a clinical proton accelerator (Westdeutsches Protonentherapiezentrum Essen, Germany) with several detectors and phantoms is performed. The robustness of the method against background and stability of the beam bunch time profile is explored, and the bunch time spread is characterized for different proton energies. For a beam spot with a hundred million protons and a single detector, range differences of 5 mm in defined heterogeneous targets are identified by numerical comparison of the spectrum shape. For higher statistics, range shifts down to 2 mm are detectable. A proton bunch monitor, higher detector throughput and quantitative range retrieval are the upcoming steps towards a clinically applicable prototype. In conclusion, the experimental results highlight the prospects of this straightforward verification method at a clinical pencil beam and settle this novel approach as a promising alternative in the field of in vivo dosimetry.

Limits on neutrino emission from gamma-ray bursts with the 40 string IceCube detector.

PubMed

Abbasi, R; Abdou, Y; Abu-Zayyad, T; Adams, J; Aguilar, J A; Ahlers, M; Andeen, K; Auffenberg, J; Bai, X; Baker, M; Barwick, S W; Bay, R; Bazo Alba, J L; Beattie, K; Beatty, J J; Bechet, S; Becker, J K; Becker, K-H; Benabderrahmane, M L; BenZvi, S; Berdermann, J; Berghaus, P; Berley, D; Bernardini, E; Bertrand, D; Besson, D Z; Bindig, D; Bissok, M; Blaufuss, E; Blumenthal, J; Boersma, D J; Bohm, C; Bose, D; Böser, S; Botner, O; Braun, J; Brown, A M; Buitink, S; Carson, M; Chirkin, D; Christy, B; Clem, J; Clevermann, F; Cohen, S; Colnard, C; Cowen, D F; D'Agostino, M V; Danninger, M; Daughhetee, J; Davis, J C; De Clercq, C; Demirörs, L; Depaepe, O; Descamps, F; Desiati, P; de Vries-Uiterweerd, G; DeYoung, T; Díaz-Vélez, J C; Dierckxsens, M; Dreyer, J; Dumm, J P; Ehrlich, R; Eisch, J; Ellsworth, R W; Engdegård, O; Euler, S; Evenson, P A; Fadiran, O; Fazely, A R; Fedynitch, A; Feusels, T; Filimonov, K; Finley, C; Fischer-Wasels, T; Foerster, M M; Fox, B D; Franckowiak, A; Franke, R; Gaisser, T K; Gallagher, J; Geisler, M; Gerhardt, L; Gladstone, L; Glüsenkamp, T; Goldschmidt, A; Goodman, J A; Grant, D; Griesel, T; Gross, A; Grullon, S; Gurtner, M; Ha, C; Hallgren, A; Halzen, F; Han, K; Hanson, K; Heinen, D; Helbing, K; Herquet, P; Hickford, S; Hill, G C; Hoffman, K D; Homeier, A; Hoshina, K; Hubert, D; Huelsnitz, W; Hülss, J-P; Hulth, P O; Hultqvist, K; Hussain, S; Ishihara, A; Jacobsen, J; Japaridze, G S; Johansson, H; Joseph, J M; Kampert, K-H; Kappes, A; Karg, T; Karle, A; Kelley, J L; Kemming, N; Kenny, P; Kiryluk, J; Kislat, F; Klein, S R; Köhne, J-H; Kohnen, G; Kolanoski, H; Köpke, L; Kopper, S; Koskinen, D J; Kowalski, M; Kowarik, T; Krasberg, M; Krings, T; Kroll, G; Kuehn, K; Kuwabara, T; Labare, M; Lafebre, S; Laihem, K; Landsman, H; Larson, M J; Lauer, R; Lehmann, R; Lünemann, J; Madsen, J; Majumdar, P; Marotta, A; Maruyama, R; Mase, K; Matis, H S; Meagher, K; Merck, M; Mészáros, P; Meures, T; Middell, E; Milke, N; Miller, J; Montaruli, T; Morse, R; Movit, S M; Nahnhauer, R; Nam, J W; Naumann, U; Niessen, P; Nygren, D R; Odrowski, S; Olivas, A; Olivo, M; O'Murchadha, A; Ono, M; Panknin, S; Paul, L; Pérez de los Heros, C; Petrovic, J; Piegsa, A; Pieloth, D; Porrata, R; Posselt, J; Price, P B; Prikockis, M; Przybylski, G T; Rawlins, K; Redl, P; Resconi, E; Rhode, W; Ribordy, M; Rizzo, A; Rodrigues, J P; Roth, P; Rothmaier, F; Rott, C; Ruhe, T; Rutledge, D; Ruzybayev, B; Ryckbosch, D; Sander, H-G; Santander, M; Sarkar, S; Schatto, K; Schmidt, T; Schoenwald, A; Schukraft, A; Schultes, A; Schulz, O; Schunck, M; Seckel, D; Semburg, B; Seo, S H; Sestayo, Y; Seunarine, S; Silvestri, A; Slipak, A; Spiczak, G M; Spiering, C; Stamatikos, M; Stanev, T; Stephens, G; Stezelberger, T; Stokstad, R G; Stoyanov, S; Strahler, E A; Straszheim, T; Sullivan, G W; Swillens, Q; Taavola, H; Taboada, I; Tamburro, A; Tarasova, O; Tepe, A; Ter-Antonyan, S; Tilav, S; Toale, P A; Toscano, S; Tosi, D; Turčan, D; van Eijndhoven, N; Vandenbroucke, J; Van Overloop, A; van Santen, J; Vehring, M; Voge, M; Voigt, B; Walck, C; Waldenmaier, T; Wallraff, M; Walter, M; Weaver, C; Wendt, C; Westerhoff, S; Whitehorn, N; Wiebe, K; Wiebusch, C H; Williams, D R; Wischnewski, R; Wissing, H; Wolf, M; Woschnagg, K; Xu, C; Xu, X W; Yodh, G; Yoshida, S; Zarzhitsky, P

2011-04-08

IceCube has become the first neutrino telescope with a sensitivity below the TeV neutrino flux predicted from gamma-ray bursts if gamma-ray bursts are responsible for the observed cosmic-ray flux above 10(18)  eV. Two separate analyses using the half-complete IceCube detector, one a dedicated search for neutrinos from pγ interactions in the prompt phase of the gamma-ray burst fireball and the other a generic search for any neutrino emission from these sources over a wide range of energies and emission times, produced no evidence for neutrino emission, excluding prevailing models at 90% confidence.

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

Guiriec, S.; Kouveliotou, C.; Hartmann, D. H.

The origin of prompt emission from gamma-ray bursts (GRBs) remains to be an open question. Correlated prompt optical and γ -ray emission observed in a handful of GRBs strongly suggests a common emission region, but failure to adequately fit the broadband GRB spectrum prompted the hypothesis of different emission mechanisms for the low- and high-energy radiations. We demonstrate that our multi-component model for GRB γ -ray prompt emission provides an excellent fit to GRB 110205A from optical to γ -ray energies. Our results show that the optical and highest γ -ray emissions have the same spatial and spectral origin, whichmore » is different from the bulk of the X- and softest γ -ray radiation. Finally, our accurate redshift estimate for GRB 110205A demonstrates promise for using GRBs as cosmological standard candles.« less

Recent Progress on GRBs with Swift

NASA Technical Reports Server (NTRS)

Gehrels, N.; Cannizzo, J. K.

2010-01-01

We are in an exciting period of discovery for gamma-ray bursts. The Swift observatory is detecting 100 bursts per year, providing arcsecond localizations and sensitive observations of the prompt and afterglow emission. In addition, rapid-response telescopes on the ground have new capabilities to study optical emission during the prompt phase and spectral signatures of the host galaxies. The combined data set is enabling great advances in our understanding of GRBs including afterglow physics, short burst origin, and supernova physics.

Prompt Neutrino Emission of Gamma-ray Bursts in the Dissipative Photospheric Scenario Revisited: Possible Contributions from Cocoons

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

Xiao, Di; Dai, Zi-Gao; Mészáros, Peter, E-mail: dzg@nju.edu.cn

2017-07-01

High-energy neutrinos are expected to originate from different stages in a gamma-ray burst (GRB) event. In this work, we revisit the dissipative photospheric scenario, in which the GRB prompt emission is produced around the photospheric radius. Meanwhile, possible dissipation mechanisms (e.g., internal shocks or magnetic reconnection) could accelerate cosmic-rays (CRs) to ultra-high energies and then produce neutrinos via hadronuclear and photohadronic processes, which are referred to as prompt neutrinos . In this paper, we obtain the prompt neutrino spectrum of a single GRB within a self-consistent analytical framework, in which the jet-cocoon structure and possible collimation effects are included. Wemore » investigate a possible neutrino signal from the cocoon, which has been ignored in the previous studies. We show that if a GRB event happens at a distance of the order of Mpc, there is a great chance to observe the neutrino emission from the cocoon by IceCube, which is even more promising than jet neutrinos, as the opening angle of the cocoon is much larger. We also determine the diffuse neutrino flux of GRB cocoons and find that it could be comparable with that of the jets. Our results are consistent with the latest result reported by the IceCube collaboration that no significant correlation between neutrino events and observed GRBs is seen in the new data.« less

Prompt Optical Observations of Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Akerlof, Carl; Balsano, Richard; Barthelmy, Scott; Bloch, Jeff; Butterworth, Paul; Casperson, Don; Cline, Tom; Fletcher, Sandra; Frontera, Fillippo; Gisler, Galen; Heise, John; Hills, Jack; Hurley, Kevin; Kehoe, Robert; Lee, Brian; Marshall, Stuart; McKay, Tim; Pawl, Andrew; Piro, Luigi; Szymanski, John; Wren, Jim

2000-03-01

The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 deg2 or better produced no detections. The earliest limiting sensitivity is mROTSE>13.1 at 10.85 s (5 s exposure) after the gamma-ray rise, and the best limit is mROTSE>16.0 at 62 minutes (897 s exposure). These are the most stringent limits obtained for the GRB optical counterpart brightness in the first hour after the burst. Consideration of the gamma-ray fluence and peak flux for these bursts and for GRB 990123 indicates that there is not a strong positive correlation between optical flux and gamma-ray emission.

First evidence of γ collectivity close to the doubly magic core Sn 132

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

Urban, W.; Sieja, K.; Rząca-Urban, T.

2016-03-01

The Te-138 and Xe-140 nuclei have been reinvestigated using prompt gamma-ray data from spontaneous fission of Cm-248, collected with the EUROGAM2 Ge array. gamma bands have been identified in both nuclei. The gamma band observed in Te-138, a nucleus with only six valence nucleons, indicates the presence of collectivity very close to the doubly magic Sn-132 core. Such band is even more pronounced in Xe-140, the N = 86 isotone of Te-138. The newly observed bands are interpreted within the shell model, which reproduce well the. collectivity at N = 86.

BOOTES and GTC observations of cosmic gamma-ray bursts and their progenitors

NASA Astrophysics Data System (ADS)

Castro-Tirado, Alberto J.

2016-07-01

We will summarize the follow-up observations of gamma-ray bursts performed worldwide by the BOOTES Network of robotic telescopes (with some of the data being contemporaneous to the prompt emission) leading to the discovery of many afterglows. Complementary data has been also obtained by the 10.4m GTC telescope in La Palma (mainly spectroscopy), with one of them being the highest extinguished afterglow detected to date.

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

Kin, Tadahiro; Oshima, Masumi; Furutaka, Kazuyoshi

We developed a spectrometer for multiple prompt gamma-ray measurements to identify nuclear levels to determine neutron capture cross sections. From a test of finding candidates of {sup 15}N levels with a developing method, we found performance of the spectrometer is sufficient.

EM reconstruction of dual isotope PET using staggered injections and prompt gamma positron emitters

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

Andreyev, Andriy, E-mail: andriy.andreyev-1@philips.com; Sitek, Arkadiusz; Celler, Anna

2014-02-15

Purpose: The aim of dual isotope positron emission tomography (DIPET) is to create two separate images of two coinjected PET radiotracers. DIPET shortens the duration of the study, reduces patient discomfort, and produces perfectly coregistered images compared to the case when two radiotracers would be imaged independently (sequential PET studies). Reconstruction of data from such simultaneous acquisition of two PET radiotracers is difficult because positron decay of any isotope creates only 511 keV photons; therefore, the isotopes cannot be differentiated based on the detected energy. Methods: Recently, the authors have proposed a DIPET technique that uses a combination of radiotracermore » A which is a pure positron emitter (such as{sup 18}F or {sup 11}C) and radiotracer B in which positron decay is accompanied by the emission of a high-energy (HE) prompt gamma (such as {sup 38}K or {sup 60}Cu). Events that are detected as triple coincidences of HE gammas with the corresponding two 511 keV photons allow the authors to identify the lines-of-response (LORs) of isotope B. These LORs are used to separate the two intertwined distributions, using a dedicated image reconstruction algorithm. In this work the authors propose a new version of the DIPET EM-based reconstruction algorithm that allows the authors to include an additional, independent estimate of radiotracer A distribution which may be obtained if radioisotopes are administered using a staggered injections method. In this work the method is tested on simple simulations of static PET acquisitions. Results: The authors’ experiments performed using Monte-Carlo simulations with static acquisitions demonstrate that the combined method provides better results (crosstalk errors decrease by up to 50%) than the positron-gamma DIPET method or staggered injections alone. Conclusions: The authors demonstrate that the authors’ new EM algorithm which combines information from triple coincidences with prompt gammas and staggered injections improves the accuracy of DIPET reconstructions for static acquisitions so they reach almost the benchmark level calculated for perfectly separated tracers.« less

Automated lithology prediction from PGNAA and other geophysical logs.

PubMed

Borsaru, M; Zhou, B; Aizawa, T; Karashima, H; Hashimoto, T

2006-02-01

Different methods of lithology predictions from geophysical data have been developed in the last 15 years. The geophysical logs used for predicting lithology are the conventional logs: sonic, neutron-neutron, gamma (total natural-gamma) and density (backscattered gamma-gamma). The prompt gamma neutron activation analysis (PGNAA) is another established geophysical logging technique for in situ element analysis of rocks in boreholes. The work described in this paper was carried out to investigate the application of PGNAA to the lithology interpretation. The data interpretation was conducted using the automatic interpretation program LogTrans based on statistical analysis. Limited test suggests that PGNAA logging data can be used to predict the lithology. A success rate of 73% for lithology prediction was achieved from PGNAA logging data only. It can also be used in conjunction with the conventional geophysical logs to enhance the lithology prediction.

The Discovery of the Optical Transient For GRB 010222

NASA Astrophysics Data System (ADS)

Henden, Arne A.

2001-04-01

On February 22, 2001, a very bright gamma-ray burst was detected by the Italian BeppoSAX satellite. The localization was posted about 4 hours after the burst. Prompt notification by phone and by the AAVSO Gamma-Ray Burst Network pager alert system resulted in the discovery of the optical afterglow within the first hour after the locatlization posting. This paper gives a brief history of the event and how the AAVSO was essential to the discovery.

Reexamining the role of the ( n , γ f ) process in the low-energy fission of U 235 and Pu 239

DOE PAGES

Lynn, J. E.; Talou, P.; Bouland, O.

2018-06-01

In this paper, themore » $$(n,{\\gamma}f)$$ process is reviewed in light of modern nuclear reaction calculations in both slow and fast neutron-induced fission reactions on $$^{235}\\mathrm{U}$$ and $$^{239}\\mathrm{Pu}$$. Observed fluctuations of the average prompt fission neutron multiplicity and average total $${\\gamma}$$-ray energy below 100-eV incident neutron energy are interpreted in this framework. The surprisingly large contribution of the $M1$ transitions to the prefission $${\\gamma}$$-ray spectrum of $$^{239}\\mathrm{Pu}$$ is explained by the dominant fission probabilities of $${0}^{+}$$ and $${2}^{+}$$ transition states, which can only be accessed from compound nucleus states formed by the interaction of $s$-wave neutrons with the target nucleus in its ground state, and decaying through $M1$ transitions. The impact of an additional low-lying $M1$ scissors mode in the photon strength function is analyzed. We review experimental evidence for fission fragment mass and kinetic-energy fluctuations in the resonance region and their importance in the interpretation of experimental data on prompt neutron data in this region. In conclusion, calculations are extended to the fast energy range where $$(n,{\\gamma}f)$$ corrections can account for up to 3% of the total fission cross section and about 20% of the capture cross section.« less

Improvement of sensitivity in PIGE analysis of steels by neutron-gamma coincidences measurement

NASA Astrophysics Data System (ADS)

Ene, Antoaneta

2004-07-01

In this work the sensitivities of minor elements in a standard steel sample EURONORM-CRM No. 085-1 irradiated with beams of 5.5 MeV protons and 5 MeV deuterons have been determined both by regular proton- (p-PIGE) and deuteron-induced prompt gamma-ray emission (d-PIGE) methods and with the selection of the (p, n) and (d, n) reaction channels, measuring the neutron-gamma coincidences. A check on the elemental composition of the steel standard has also been carried out using combined INAA and PIXE and quantitative determinations have been done for some elements whose concentrations were not specified by the manufacturer, such as Al, As, Cr, Mo, Na, Ni, W. This complex study has resulted in a significant improvement of the sensitivities for some minor elements in steel by reducing the background and increasing the peak-to-background ratio in the coincident prompt gamma-rays spectra as a result of the elimination of the competing nuclear reactions originating from isotopes of the adjacent elements in the periodic table, present in the steel target. This extension of the PIGE method could be adapted by any analyst with the necessary equipment for the analysis of a wide variety of matrices that are refractory enough to withstand the heating effect of the bombarding beam, taking into account that this type of experiment requires longer irradiation times.

Reexamining the role of the ( n , γ f ) process in the low-energy fission of U 235 and Pu 239

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

Lynn, J. E.; Talou, P.; Bouland, O.

In this paper, themore » $$(n,{\\gamma}f)$$ process is reviewed in light of modern nuclear reaction calculations in both slow and fast neutron-induced fission reactions on $$^{235}\\mathrm{U}$$ and $$^{239}\\mathrm{Pu}$$. Observed fluctuations of the average prompt fission neutron multiplicity and average total $${\\gamma}$$-ray energy below 100-eV incident neutron energy are interpreted in this framework. The surprisingly large contribution of the $M1$ transitions to the prefission $${\\gamma}$$-ray spectrum of $$^{239}\\mathrm{Pu}$$ is explained by the dominant fission probabilities of $${0}^{+}$$ and $${2}^{+}$$ transition states, which can only be accessed from compound nucleus states formed by the interaction of $s$-wave neutrons with the target nucleus in its ground state, and decaying through $M1$ transitions. The impact of an additional low-lying $M1$ scissors mode in the photon strength function is analyzed. We review experimental evidence for fission fragment mass and kinetic-energy fluctuations in the resonance region and their importance in the interpretation of experimental data on prompt neutron data in this region. In conclusion, calculations are extended to the fast energy range where $$(n,{\\gamma}f)$$ corrections can account for up to 3% of the total fission cross section and about 20% of the capture cross section.« less

Constraints on millisecond magnetars as the engines of prompt emission in gamma-ray bursts

NASA Astrophysics Data System (ADS)

Beniamini, Paz; Giannios, Dimitrios; Metzger, Brian D.

2017-12-01

We examine millisecond magnetars as central engines of gamma-ray bursts' (GRBs) prompt emission. Using the protomagnetar wind model of Metzger et al., we estimate the temporal evolution of the magnetization and power injection at the base of the GRB jet and apply these to different prompt emission models to make predictions for the GRB energetics, spectra and light curves. We investigate both shock and magnetic reconnection models for the particle acceleration, as well as the effects of energy dissipation across optically thick and thin regions of the jet. The magnetization at the base of the jet, σ0, is the main parameter driving the GRB evolution in the magnetar model and the emission is typically released for 100 ≲σ0 ≲3000. Given the rapid increase in σ0 as the protomagnetar cools and its neutrino-driven mass loss subsides, the GRB duration is typically limited to ≲100 s. This low baryon loading at late times challenges magnetar models for ultralong GRBs, though black hole models likely run into similar difficulties without substantial entrainment from the jet walls. The maximum radiated gamma-ray energy is ≲5 × 1051 erg, significantly less than the magnetar's total initial rotational energy and in strong tension with the high end of the observed GRB energy distribution. However, the gradual magnetic dissipation model applied to a magnetar central engine, naturally explains several key observables of typical GRBs, including energetics, durations, stable peak energies, spectral slopes and a hard to soft evolution during the burst.

Study on detection geometry and detector shielding for portable PGNAA system using PHITS

NASA Astrophysics Data System (ADS)

Ithnin, H.; Dahing, L. N. S.; Lip, N. M.; Rashid, I. Q. Abd; Mohamad, E. J.

2018-01-01

Prompt gamma-ray neutron activation analysis (PGNAA) measurements require efficient detectors for gamma-ray detection. Apart from experimental studies, the Monte Carlo (MC) method has become one of the most popular tools in detector studies. The absolute efficiency for a 2 × 2 inch cylindrical Sodium Iodide (NaI) detector has been modelled using the PHITS software and compared with previous studies in literature. In the present work, PHITS code is used for optimization of portable PGNAA system using the validated NaI detector. The detection geometry is optimized by moving the detector along the sample to find the highest intensity of the prompt gamma generated from the sample. Shielding material for the validated NaI detector is also studied to find the best option for the PGNAA system setup. The result shows the optimum distance for detector is on the surface of the sample and around 15 cm from the source. The results specify that this process can be followed to determine the best setup for PGNAA system for a different sample size and detector type. It can be concluded that data from PHITS code is a strong tool not only for efficiency studies but also for optimization of PGNAA system.

Search for a Signature of Interaction between Relativistic Jet and Progenitor in Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Yoshida, Kazuki; Yoneoku, Daisuke; Sawano, Tatsuya; Ito, Hirotaka; Matsumoto, Jin; Nagataki, Shigehiro

2017-11-01

The time variability of prompt emission in gamma-ray bursts (GRBs) is expected to originate from the temporal behavior of the central engine activity and the jet propagation in the massive stellar envelope. Using a pulse search algorithm for bright GRBs, we investigate the time variability of gamma-ray light curves to search a signature of the interaction between the jet and the inner structure of the progenitor. Since this signature might appear in the earlier phase of prompt emission, we divide the light curves into the initial phase and the late phase by referring to the trigger time and the burst duration of each GRB. We also adopt this algorithm for GRBs associated with supernovae/hypernovae that certainly are accompanied by massive stars. However, there is no difference between each pulse interval distribution described by a lognorma distribution in the two phases. We confirm that this result can be explained by the photospheric emission model if the energy injection of the central engine is not steady or completely periodic but episodic and described by the lognormal distribution with a mean of ˜1 s.

GRAVITATIONAL-WAVE OBSERVATIONS MAY CONSTRAIN GAMMA-RAY BURST MODELS: THE CASE OF GW150914–GBM

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

Veres, P.; Preece, R. D.; Goldstein, A.

The possible short gamma-ray burst (GRB) observed by Fermi /GBM in coincidence with the first gravitational-wave (GW) detection offers new ways to test GRB prompt emission models. GW observations provide previously inaccessible physical parameters for the black hole central engine such as its horizon radius and rotation parameter. Using a minimum jet launching radius from the Advanced LIGO measurement of GW 150914, we calculate photospheric and internal shock models and find that they are marginally inconsistent with the GBM data, but cannot be definitely ruled out. Dissipative photosphere models, however, have no problem explaining the observations. Based on the peakmore » energy and the observed flux, we find that the external shock model gives a natural explanation, suggesting a low interstellar density (∼10{sup −3} cm{sup −3}) and a high Lorentz factor (∼2000). We only speculate on the exact nature of the system producing the gamma-rays, and study the parameter space of a generic Blandford–Znajek model. If future joint observations confirm the GW–short-GRB association we can provide similar but more detailed tests for prompt emission models.« less

Search for a Signature of Interaction between Relativistic Jet and Progenitor in Gamma-Ray Bursts

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

Yoshida, Kazuki; Yoneoku, Daisuke; Sawano, Tatsuya

The time variability of prompt emission in gamma-ray bursts (GRBs) is expected to originate from the temporal behavior of the central engine activity and the jet propagation in the massive stellar envelope. Using a pulse search algorithm for bright GRBs, we investigate the time variability of gamma-ray light curves to search a signature of the interaction between the jet and the inner structure of the progenitor. Since this signature might appear in the earlier phase of prompt emission, we divide the light curves into the initial phase and the late phase by referring to the trigger time and the burstmore » duration of each GRB. We also adopt this algorithm for GRBs associated with supernovae/hypernovae that certainly are accompanied by massive stars. However, there is no difference between each pulse interval distribution described by a lognorma distribution in the two phases. We confirm that this result can be explained by the photospheric emission model if the energy injection of the central engine is not steady or completely periodic but episodic and described by the lognormal distribution with a mean of ∼1 s.« less

FERMI Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission

DOE PAGES

Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

2009-11-03

Here, we report on the observation of the bright, long gamma-ray burst (GRB), GRB 090902B, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board the Fermi observatory. This was one of the brightest GRBs to have been observed by the LAT, which detected several hundred photons during the prompt phase. With a redshift of z = 1.822, this burst is among the most luminous detected by Fermi. Time-resolved spectral analysis reveals a significant power-law component in the LAT data that is distinct from the usual Band model emission that is seen in the sub-MeV energy range.more » This power-law component appears to extrapolate from the GeV range to the lowest energies and is more intense than the Band component, both below ~50 keV and above 100 MeV. The Band component undergoes substantial spectral evolution over the entire course of the burst, while the photon index of the power-law component remains constant for most of the prompt phase, then hardens significantly toward the end. After the prompt phase, power-law emission persists in the LAT data as late as 1 ks post-trigger, with its flux declining as t –1.5. The LAT detected a photon with the highest energy so far measured from a GRB, 33.4 +2.7 –3.5 GeV. This event arrived 82 s after the GBM trigger and ~50 s after the prompt phase emission had ended in the GBM band. In conclusion, we discuss the implications of these results for models of GRB emission and for constraints on models of the extragalactic background light.« less

Quantitative comparison between PGNAA measurements and MCNP calculations in view of the characterization of radioactive wastes in Germany and France

NASA Astrophysics Data System (ADS)

Mauerhofer, E.; Havenith, A.; Carasco, C.; Payan, E.; Kettler, J.; Ma, J. L.; Perot, B.

2013-04-01

The Forschungszentrum Jülich GmbH (FZJ), together with the Aachen University Rheinisch-Westfaelische Technische Hochschule (RWTH) and the French Alternative Energies and Atomic Energy Commission (CEA Cadarache) are involved in a cooperation aiming at characterizing toxic and reactive elements in radioactive waste packages by means of Prompt Gamma Neutron Activation Analysis (PGNAA) [1]. The French and German waste management agencies have indeed defined acceptability limits concerning these elements in view of their projected geological repositories. A first measurement campaign was performed in the new Prompt Gamma Neutron Activation Analysis (PGNAA) facility called MEDINA, at FZJ, to assess the capture gamma-ray signatures of some elements of interest in large samples up to waste drums with a volume of 200 liter. MEDINA is the acronym for Multi Element Detection based on Instrumental Neutron Activation. This paper presents MCNP calculations of the MEDINA facility and quantitative comparison between measurement and simulation. Passive gamma-ray spectra acquired with a high purity germanium detector and calibration sources are used to qualify the numerical model of the crystal. Active PGNAA spectra of a sodium chloride sample measured with MEDINA then allow for qualifying the global numerical model of the measurement cell. Chlorine indeed constitutes a usual reference with reliable capture gamma-ray production data. The goal is to characterize the entire simulation protocol (geometrical model, nuclear data, and postprocessing tools) which will be used for current measurement interpretation, extrapolation of the performances to other types of waste packages or other applications, as well as for the study of future PGNAA facilities.

The Prompt-afterglow Connection in Gamma-ray Bursts: a Comprehensive Statistical Analysis of Swift X-ray Light-curves

NASA Technical Reports Server (NTRS)

Margutti, R.; Zaninoni, E.; Bernardini, M. G.; Chincarini, G.; Pasotti, F.; Guidorzi, C.; Angelini, Lorella; Burrows, D. N.; Capalbi, M.; Evans, P. A.;

The prompt-afterglow connection in gamma-ray bursts: a comprehensive statistical analysis of Swift X-ray light curves

NASA Astrophysics Data System (ADS)

Margutti, R.; Zaninoni, E.; Bernardini, M. G.; Chincarini, G.; Pasotti, F.; Guidorzi, C.; Angelini, L.; Burrows, D. N.; Capalbi, M.; Evans, P. A.; Gehrels, N.; Kennea, J.; Mangano, V.; Moretti, A.; Nousek, J.; Osborne, J. P.; Page, K. L.; Perri, M.; Racusin, J.; Romano, P.; Sbarufatti, B.; Stafford, S.; Stamatikos, M.

2013-01-01

We present a comprehensive statistical analysis of Swift X-ray light curves of gamma-ray bursts (GRBs) collecting data from more than 650 GRBs discovered by Swift and other facilities. The unprecedented sample size allows us to constrain the rest-frame X-ray properties of GRBs from a statistical perspective, with particular reference to intrinsic time-scales and the energetics of the different light-curve phases in a common rest-frame 0.3-30 keV energy band. Temporal variability episodes are also studied and their properties constrained. Two fundamental questions drive this effort: (i) Does the X-ray emission retain any kind of `memory' of the prompt γ-ray phase? (ii) Where is the dividing line between long and short GRB X-ray properties? We show that short GRBs decay faster, are less luminous and less energetic than long GRBs in the X-rays, but are interestingly characterized by similar intrinsic absorption. We furthermore reveal the existence of a number of statistically significant relations that link the X-ray to prompt γ-ray parameters in long GRBs; short GRBs are outliers of the majority of these two-parameter relations. However and more importantly, we report on the existence of a universal three-parameter scaling that links the X-ray and the γ-ray energy to the prompt spectral peak energy of both long and short GRBs: EX, iso∝E1.00 ± 0.06γ, iso/E0.60 ± 0.10pk.

GLAST and Ground-Based Gamma-Ray Astronomy

NASA Technical Reports Server (NTRS)

McEnery, Julie

2008-01-01

The launch of the Gamma-ray Large Area Space Telescope together with the advent of a new generation of ground-based gamma-ray detectors such as VERITAS, HESS, MAGIC and CANGAROO, will usher in a new era of high-energy gamma-ray astrophysics. GLAST and the ground based gamma-ray observatories will provide highly complementary capabilities for spectral, temporal and spatial studies of high energy gamma-ray sources. Joint observations will cover a huge energy range, from 20 MeV to over 20 TeV. The LAT will survey the entire sky every three hours, allowing it both to perform uniform, long-term monitoring of variable sources and to detect flaring sources promptly. Both functions complement the high-sensitivity pointed observations provided by ground-based detectors. Finally, the large field of view of GLAST will allow a study of gamma-ray emission on large angular scales and identify interesting regions of the sky for deeper studies at higher energies. In this poster, we will discuss the science returns that might result from joint GLAST/ground-based gamma-ray observations and illustrate them with detailed source simulations.

Application of new nuclear de-excitation model of PHITS for prediction of isomer yield and prompt gamma-ray production

NASA Astrophysics Data System (ADS)

Ogawa, Tatsuhiko; Hashimoto, Shintaro; Sato, Tatsuhiko; Niita, Koji

2014-06-01

A new nuclear de-excitation model, intended for accurate simulation of isomeric transition of excited nuclei, was incorporated into PHITS and applied to various situations to clarify the impact of the model. The case studies show that precise treatment of gamma de-excitation and consideration for isomer production are important for various applications such as detector performance prediction, radiation shielding calculations and the estimation of radioactive inventory including isomers.

Prompt fission gamma-ray studies at DANCE

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

Jandel, M.; Rusev, G.; Bond, E. M.

2014-11-26

Measurements of correlated data on prompt-fission γ-rays (PFG) have been carried out for various actinide isotopes in recent years using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory (LANL). We have developed a model that conveniently parametrizes the correlated data of γ-ray multiplicity and energy. New results on two- dimensional prompt-fission γ-ray multiplicity versus energy distributions from spontaneous fission on ²⁵²Cf and neutron-induced fission on 242mAm are presented together with previously obtained results on 233,235U and ²³⁹Pu. Correlated PFG data from ²⁵²Cf are also compared to results of the detailed theoretical model developed at LANL,more » for different thresholds of PFG energies. Future plans to measure correlated data on fission fragments, prompt fission neutrons and γ-rays at DANCE are presented.« less

Three years of Transients with Fermi GBM

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.

2012-01-01

The Gamma-ray Burst Monitor (GBM) is an all-sky monitoring instrument, sensitive between 8 keV and 40 MeV, with a primary objective of supporting the Large Area Telescope (LAT) in observations of Gamma-Ray Bursts (GRBs). Both instruments are part of the Fermi Gamma-ray Space Telescope. Together, the GBM and LAT instruments have provided ground-breaking measurements of GRBs that have, after 10 years of focus on GRB afterglows, inspired renewed interest in the prompt emission phase of GRBs and the physical mechanisms that fuel them. In addition to GRB science, GBM has made significant contributions to the astrophysics of galactic transient sources including long-term variations in the Crab nebula, spin state transitions in accretion powered pulsars, state transitions in black hole X-ray binaries, and unprecedented time-resolved spectral studies of soft gamma-ray repeater bursts. Closer to home, GBM also contributes to solar flare and terrestrial gamma flash science.

Stacked search for time shifted high energy neutrinos from gamma ray bursts with the Antares neutrino telescope

NASA Astrophysics Data System (ADS)

Adrián-Martínez, S.; Albert, A.; André, M.; Anghinolfi, M.; Anton, G.; Ardid, M.; Aubert, J.-J.; Baret, B.; Barrios-Marti, J.; Basa, S.; Bertin, V.; Biagi, S.; Bormuth, R.; Bouwhuis, M. C.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Chiarusi, T.; Circella, M.; Coniglione, R.; Costantini, H.; Coyle, P.; Creusot, A.; Dekeyser, I.; Deschamps, A.; De Bonis, G.; Distefano, C.; Donzaud, C.; Dornic, D.; Drouhin, D.; Dumas, A.; Eberl, T.; Elsässer, D.; Enzenhöfer, A.; Fehn, K.; Felis, I.; Fermani, P.; Folger, F.; Fusco, L. A.; Galatà, S.; Gay, P.; Geißelsöder, S.; Geyer, K.; Giordano, V.; Gleixner, A.; Gracia-Ruiz, R.; Graf, K.; Hallmann, S.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Hößl, J.; Hofestädt, J.; Hugon, C.; James, C. W.; de Jong, M.; Kadler, M.; Kalekin, O.; Katz, U.; Kießling, D.; Kooijman, P.; Kouchner, A.; Kreter, M.; Kreykenbohm, I.; Kulikovskiy, V.; Lahmann, R.; Lefèvre, D.; Leonora, E.; Loucatos, S.; Marcelin, M.; Margiotta, A.; Marinelli, A.; Martínez-Mora, J. A.; Mathieu, A.; Michael, T.; Migliozzi, P.; Moussa, A.; Müller, C.; Nezri, E.; Păvălaş, G. E.; Pellegrino, C.; Perrina, C.; Piattelli, P.; Popa, V.; Pradier, T.; Racca, C.; Riccobene, G.; Richter, R.; Roensch, K.; Saldaña, M.; Samtleben, D. F. E.; Sánchez-Losa, A.; Sanguineti, M.; Sapienza, P.; Schmid, J.; Schnabel, J.; Schüssler, F.; Seitz, T.; Sieger, C.; Spurio, M.; Steijger, J. J. M.; Stolarczyk, Th.; Taiuti, M.; Tamburini, C.; Trovato, A.; Tselengidou, M.; Tönnis, C.; Vallage, B.; Vallée, C.; Van Elewyck, V.; Visser, E.; Vivolo, D.; Wagner, S.; Wilms, J.; Zornoza, J. D.; Zúñiga, J.

2017-01-01

A search for high-energy neutrino emission correlated with gamma-ray bursts outside the electromagnetic prompt-emission time window is presented. Using a stacking approach of the time delays between reported gamma-ray burst alerts and spatially coincident muon-neutrino signatures, data from the Antares neutrino telescope recorded between 2007 and 2012 are analysed. One year of public data from the IceCube detector between 2008 and 2009 have been also investigated. The respective timing profiles are scanned for statistically significant accumulations within 40 days of the Gamma Ray Burst, as expected from Lorentz Invariance Violation effects and some astrophysical models. No significant excess over the expected accidental coincidence rate could be found in either of the two data sets. The average strength of the neutrino signal is found to be fainter than one detectable neutrino signal per hundred gamma-ray bursts in the Antares data at 90% confidence level.

Prompt particle acceleration around moving X-point magnetic field during impulsive phase of solar flares

NASA Technical Reports Server (NTRS)

Sakai, Jun-Ichi

1992-01-01

We present a model for high-energy solar flares to explain prompt proton and electron acceleration, which occurs around moving X-point magnetic field during the implosion phase of the current sheet. We derive the electromagnetic fields during the strong implosion phase of the current sheets, which is driven by the converging flow derived from the magnetohydrodynamic equations. It is shown that both protons and electrons can be promptly (within 1 second) accelerated to approximately 70 MeV and approximately 200 MeV, respectively. This acceleration mechanism can be applicable for the impulsive phase of the gradual gamma ray and proton flares (gradual GR/P flare), which have been called two-ribbon flares.

Prompt Emission Observations of Swift BAT Bursts

NASA Technical Reports Server (NTRS)

Barthelmy, Scott

2009-01-01

We review the prompt emission properties of Swift BAT gamma-ray bursts (GRBs). We present the global properties of BAT GRBs based on their spectral and temporal characteristics. The BAT T90 and T50 durations peak at 80 and 20 s, respectively. The peak energy (Epeak) of about 60% of BAT GRBs is very likely to be less than 1.00 keV. We also present the BAT characteristics of GRBs with soft spectra, so called Xray flashes (XRFs). We will compare the BAT GRBs and XRFs parameter distribution to the other missions.

Measurement of high-energy prompt gamma-rays from neutron induced fission of U-235

NASA Astrophysics Data System (ADS)

Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, Riccardo; Léguillon, Romain; Ogawa, Tatsuhiko; Soldner, Torsten; Hambsch, Franz-Josef; Astier, Alain; Pollitt, Andrew; Petrache, Costel; Tsekhanovich, Igor; Mathieu, Ludovic; Aïche, Mourad; Frost, Robert; Czajkowski, Serge; Guo, Song; Köster, Ulli

2017-09-01

We have developed a new setup to measure prompt γ-rays from the 235U(nth,f) reaction. The setup consists of two multi-wire proportional counters (MWPCs) to detect the fission fragments, two LaBr3(Ce) scintillators to measure the γ-rays. The highly efficient setup was installed at the PF1B beam line of the Institut Laue Langevin (ILL). We have successfully measured the γ-ray spectrum up to about 20 MeV for the fist time in neutron-induced fission.

Activation measurement of the 3He(alpha,gamma)7Be cross section at low energy.

PubMed

Bemmerer, D; Confortola, F; Costantini, H; Formicola, A; Gyürky, Gy; Bonetti, R; Broggini, C; Corvisiero, P; Elekes, Z; Fülöp, Zs; Gervino, G; Guglielmetti, A; Gustavino, C; Imbriani, G; Junker, M; Laubenstein, M; Lemut, A; Limata, B; Lozza, V; Marta, M; Menegazzo, R; Prati, P; Roca, V; Rolfs, C; Alvarez, C Rossi; Somorjai, E; Straniero, O; Strieder, F; Terrasi, F; Trautvetter, H P

2006-09-22

The nuclear physics input from the 3He(alpha,gamma)7Be cross section is a major uncertainty in the fluxes of 7Be and 8B neutrinos from the Sun predicted by solar models and in the 7Li abundance obtained in big-bang nucleosynthesis calculations. The present work reports on a new precision experiment using the activation technique at energies directly relevant to big-bang nucleosynthesis. Previously such low energies had been reached experimentally only by the prompt-gamma technique and with inferior precision. Using a windowless gas target, high beam intensity, and low background gamma-counting facilities, the 3He(alpha,gamma)7Be cross section has been determined at 127, 148, and 169 keV center-of-mass energy with a total uncertainty of 4%. The sources of systematic uncertainty are discussed in detail. The present data can be used in big-bang nucleosynthesis calculations and to constrain the extrapolation of the 3He(alpha,gamma)7Be astrophysical S factor to solar energies.

Type of Writing Task and College Students' Meaning Making Following a Romantic Breakup

ERIC Educational Resources Information Center

Primeau, Joanna E.; Servaty-Seib, Heather L.; Enersen, Donna

2013-01-01

In this study, the authors examined the potential effects of type of writing task (loss/gain vs. general prompt) on the narrative content offered by college students (N = 41) who experienced romantic breakup. Qualitative analyses indicated differences based on type of writing task. Students who received the loss/gain prompt exhibited more…

Measurement of the 235U Induced Fission Gamma-ray Spectrum as an Active Non-destructive Assay of Fresh Nucleear Fuel

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

Sarnoski, Sarah E.; Fast, James E.; Fulsom, Bryan G.

2017-07-17

Non-destructive assay is a powerful tool the International Atomic Energy Agency (IAEA) employs to verify adherence to safeguards agreements. Current IAEA veri- cation techniques for fresh nuclear fuel include passive gamma-ray spectroscopy to determine fuel enrichment. This technique suers from self-shielding and lakes the percision to detect diversion of central fuel rods. The aim of this research is to develop a new, more capable non-destructive analysis technique using active neutron interroga- tion of fuel assemblies and determining the yields of short-lived ssion products from high-resolution gamma-ray spectroscopy using high-purity germanium (HPGe). This paper reports results from irradiation of a onemore » meter tall mock fresh fuel assembly with low enriched uranium (LEU) or depleted uranium (DU) rods using a down-scattered deuterium-tritium (D-T) neutron source. Both prompt and delayed gamma-ray spec- tra were collected as time-stamped list-mode data in a coax detector and without list mode data in a planar strip detector. No dierentiating signatures were observed in the prompt spectra in either detector; however, both detectors observed several short-lived ssion product signatures in LEU and not DU fuel, indicating that this technique has potential for determination of enrichment of fresh fuel assemblies. There were eight unique ssion products observed in the LEU spectra with the coax detector spectra, and three ssion products were observed in the LEU spectra with the strip detector.« less

INTEGRAL Observations of GW170104

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

Savchenko, V.; Ferrigno, C.; Bozzo, E.

2017-09-10

We used data from the International Gamma-Ray Astrophysics Laboratory ( INTEGRAL ) to set upper limits on the γ -ray and hard X-ray prompt emission associated with the gravitational-wave event GW170104, discovered by the Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo collaboration. The unique omnidirectional viewing capability of the instruments on board INTEGRAL allowed us to examine the full 90% confidence level localization region of the LIGO trigger. Depending on the particular spectral model assumed and the specific position within this region, the upper limits inferred from the INTEGRAL observations range from F {sub γ} = 1.9 × 10{sup −7} erg cm{supmore » −2} to F {sub γ} = 10{sup −6} erg cm{sup −2} (75 keV–2 MeV energy range). This translates into a ratio between the prompt energy released in γ -rays along the direction to the observer and the gravitational-wave energy of E {sub γ} / E {sub GW} < 2.6 × 10{sup −5}. Using the INTEGRAL results, we cannot confirm the γ -ray proposed counterpart to GW170104 by the Astro—Rivelatore Gamma a Immagini Leggero (AGILE) team with the mini-Calorimeter (MCAL) instrument. The reported flux of the AGILE/MCAL event, E2, is not compatible with the INTEGRAL upper limits within most of the 90% LIGO localization region. There is only a relatively limited portion of the sky where the sensitivity of the INTEGRAL instruments was not optimal and the lowest-allowed fluence estimated for E2 would still be compatible with the INTEGRAL results. This region was also observed independently by Fermi /Gamma-ray Burst Monitor and AstroSAT, from which, as far as we are aware, there are no reports of any significant detection of a prompt high-energy event.« less

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

Shin, H; Yoon, D; Jung, J

Purpose: The purpose of this study is to suggest a tumor monitoring technique using prompt gamma rays emitted during the reaction between an antiproton and a boron particle, and to verify the increase of the therapeutic effectiveness of the antiproton boron fusion therapy using Monte Carlo simulation code. Methods: We acquired the percentage depth dose of the antiproton beam from a water phantom with and without three boron uptake regions (region A, B, and C) using F6 tally of MCNPX. The tomographic image was reconstructed using prompt gamma ray events from the reaction between the antiproton and boron during themore » treatment from 32 projections (reconstruction algorithm: MLEM). For the image reconstruction, we were performed using a 80 × 80 pixel matrix with a pixel size of 5 mm. The energy window was set as a 10 % energy window. Results: The prompt gamma ray peak for imaging was observed at 719 keV in the energy spectrum using the F8 tally fuction (energy deposition tally) of the MCNPX code. The tomographic image shows that the boron uptake regions were successfully identified from the simulation results. In terms of the receiver operating characteristic curve analysis, the area under the curve values were 0.647 (region A), 0.679 (region B), and 0.632 (region C). The SNR values increased as the tumor diameter increased. The CNR indicated the relative signal intensity within different regions. The CNR values also increased as the different of BURs diamter increased. Conclusion: We confirmed the feasibility of tumor monitoring during the antiproton therapy as well as the superior therapeutic effect of the antiproton boron fusion therapy. This result can be beneficial for the development of a more accurate particle therapy.« less

Time resolved analysis of Fermi gamma-ray bursts with fast-and slow-cooled synchrotron photon models

DOE PAGES

Burgess, J. M.; Preece, R. D.; Connaughton, V.; ...

2014-02-27

Time-resolved spectroscopy is performed on eight bright, long gamma-ray bursts (GRBs) dominated by single emission pulses that were observed with the Fermi Gamma-Ray Space Telescope. Fitting the prompt radiation of GRBs by empirical spectral forms such as the Band function leads to ambiguous conclusions about the physical model for the prompt radiation. Moreover, the Band function is often inadequate to fit the data. Therefore, the GRB spectrum is modeled with two emission components consisting of optically thin non-thermal synchrotron radiation from relativistic electrons and, when significant, thermal emission from a jet photosphere, which is represented by a blackbody spectrum. Inmore » order to produce an acceptable fit, the addition of a blackbody component is required in five out of the eight cases. We also find that the low-energy spectral index α is consistent with a synchrotron component with α = –0.81 ± 0.1. This value lies between the limiting values of α = –2/3 and α = –3/2 for electrons in the slow- and fast-cooling regimes, respectively, suggesting ongoing acceleration at the emission site. The blackbody component can be more significant when using a physical synchrotron model instead of the Band function, illustrating that the Band function does not serve as a good proxy for a non-thermal synchrotron emission component. The temperature and characteristic emission-region size of the blackbody component are found to, respectively, decrease and increase as power laws with time during the prompt phase. Additionally, we find that the blackbody and non-thermal components have separate temporal behaviors as far as their respective flux and spectral evolutions.« less

Improvement of Bragg peak shift estimation using dimensionality reduction techniques and predictive linear modeling

NASA Astrophysics Data System (ADS)

Xing, Yafei; Macq, Benoit

2017-11-01

With the emergence of clinical prototypes and first patient acquisitions for proton therapy, the research on prompt gamma imaging is aiming at making most use of the prompt gamma data for in vivo estimation of any shift from expected Bragg peak (BP). The simple problem of matching the measured prompt gamma profile of each pencil beam with a reference simulation from the treatment plan is actually made complex by uncertainties which can translate into distortions during treatment. We will illustrate this challenge and demonstrate the robustness of a predictive linear model we proposed for BP shift estimation based on principal component analysis (PCA) method. It considered the first clinical knife-edge slit camera design in use with anthropomorphic phantom CT data. Particularly, 4115 error scenarios were simulated for the learning model. PCA was applied to the training input randomly chosen from 500 scenarios for eliminating data collinearities. A total variance of 99.95% was used for representing the testing input from 3615 scenarios. This model improved the BP shift estimation by an average of 63+/-19% in a range between -2.5% and 86%, comparing to our previous profile shift (PS) method. The robustness of our method was demonstrated by a comparative study conducted by applying 1000 times Poisson noise to each profile. 67% cases obtained by the learning model had lower prediction errors than those obtained by PS method. The estimation accuracy ranged between 0.31 +/- 0.22 mm and 1.84 +/- 8.98 mm for the learning model, while for PS method it ranged between 0.3 +/- 0.25 mm and 20.71 +/- 8.38 mm.

Dual-isotope PET using positron-gamma emitters.

PubMed

Andreyev, A; Celler, A

2011-07-21

Positron emission tomography (PET) is widely recognized as a highly effective functional imaging modality. Unfortunately, standard PET cannot be used for dual-isotope imaging (which would allow for simultaneous investigation of two different biological processes), because positron-electron annihilation products from different tracers are indistinguishable in terms of energy. Methods that have been proposed for dual-isotope PET rely on differences in half-lives of the participating isotopes; these approaches, however, require making assumptions concerning kinetic behavior of the tracers and may not lead to optimal results. In this paper we propose a novel approach for dual-isotope PET and investigate its performance using GATE simulations. Our method requires one of the two radioactive isotopes to be a pure positron emitter and the second isotope to emit an additional high-energy gamma in a cascade simultaneously with positron emission. Detection of this auxiliary prompt gamma in coincidence with the annihilation event allows us to identify the corresponding 511 keV photon pair as originating from the same isotope. Two list-mode datasets are created: a primary dataset that contains all detected 511 keV photon pairs from both isotopes, and a second, tagged (much smaller) dataset that contains only those PET events for which a coincident prompt gamma has also been detected. An image reconstructed from the tagged dataset reflects the distribution of the second positron-gamma radiotracer and serves as a prior for the reconstruction of the primary dataset. Our preliminary simulation study with partially overlapping (18)F/(22)Na and (18)F/(60)Cu radiotracer distributions showed that in these two cases the dual-isotope PET method allowed for separation of the two activity distributions and recovered total activities with relative errors of about 5%.

Quantitative comparison between PGNAA measurements and MCNP calculations in view of the characterization of radioactive wastes in Germany and France

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

Mauerhofer, E.; Havenith, A.; Kettler, J.

The Forschungszentrum Juelich GmbH (FZJ), together with the Aachen University Rheinisch-Westfaelische Technische Hochschule (RWTH) and the French Alternative Energies and Atomic Energy Commission (CEA Cadarache) are involved in a cooperation aiming at characterizing toxic and reactive elements in radioactive waste packages by means of Prompt Gamma Neutron Activation Analysis (PGNAA). The French and German waste management agencies have indeed defined acceptability limits concerning these elements in view of their projected geological repositories. A first measurement campaign was performed in the new Prompt Gamma Neutron Activation Analysis (PGNAA) facility called MEDINA, at FZJ, to assess the capture gamma-ray signatures of somemore » elements of interest in large samples up to waste drums with a volume of 200 liter. MEDINA is the acronym for Multi Element Detection based on Instrumental Neutron Activation. This paper presents MCNP calculations of the MEDINA facility and quantitative comparison between measurement and simulation. Passive gamma-ray spectra acquired with a high purity germanium detector and calibration sources are used to qualify the numerical model of the crystal. Active PGNAA spectra of a sodium chloride sample measured with MEDINA then allow for qualifying the global numerical model of the measurement cell. Chlorine indeed constitutes a usual reference with reliable capture gamma-ray production data. The goal is to characterize the entire simulation protocol (geometrical model, nuclear data, and postprocessing tools) which will be used for current measurement interpretation, extrapolation of the performances to other types of waste packages or other applications, as well as for the study of future PGNAA facilities.« less

Analysis of sewage sludge using an experimental prompt gamma neutron activation analysis (pgnaa) set-up with an am-be source

NASA Astrophysics Data System (ADS)

Idiri, Z.; Redjem, F.; Beloudah, N.

2016-09-01

An experimental PGNAA set-up using a 1 Ci Am-Be source has been developed and used for analysis of bulk sewage sludge samples issued from a wastewater treatment plant situated in an industrial area of Algiers. The sample dimensions were optimized using thermal neutron flux calculations carried out with the MCNP5 Monte Carlo Code. A methodology is then proposed to perform quantitative analysis using the absolute method. For this, average thermal neutron flux inside the sludge samples is deduced using average thermal neutron flux in reference water samples and thermal flux measurements with the aid of a 3He neutron detector. The average absolute gamma detection efficiency is determined using the prompt gammas emitted by chlorine dissolved in a water sample. The gamma detection efficiency is normalized for sludge samples using gamma attenuation factors calculated with the MCNP5 code for water and sludge. Wet and dehydrated sludge samples were analyzed. Nutritive elements (Ca, N, P, K) and heavy metals elements like Cr and Mn were determined. For some elements, the PGNAA values were compared to those obtained using Atomic Absorption Spectroscopy (AAS) and Inductively Coupled Plasma (ICP) methods. Good agreement is observed between the different values. Heavy element concentrations are very high compared to normal values; this is related to the fact that the wastewater treatment plant is treating not only domestic but also industrial wastewater that is probably rejected by industries without removal of pollutant elements. The detection limits for almost all elements of interest are sufficiently low for the method to be well suited for such analysis.

Apparatus and method for identification of matrix materials in which transuranic elements are embedded using thermal neutron capture gamma-ray emission

DOEpatents

Close, D.A.; Franks, L.A.; Kocimski, S.M.

1984-08-16

An invention is described that enables the quantitative simultaneous identification of the matrix materials in which fertile and fissile nuclides are embedded to be made along with the quantitative assay of the fertile and fissile materials. The invention also enables corrections for any absorption of neutrons by the matrix materials and by the measurement apparatus by the measurement of the prompt and delayed neutron flux emerging from a sample after the sample is interrogated by simultaneously applied neutrons and gamma radiation. High energy electrons are directed at a first target to produce gamma radiation. A second target receives the resulting pulsed gamma radiation and produces neutrons from the interaction with the gamma radiation. These neutrons are slowed by a moderator surrounding the sample and bathe the sample uniformly, generating second gamma radiation in the interaction. The gamma radiation is then resolved and quantitatively detected, providing a spectroscopic signature of the constituent elements contained in the matrix and in the materials within the vicinity of the sample. (LEW)

Thermal-neutron capture gamma-rays. Volume 1

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

Tuli, J.K.

1997-05-01

The energy and photon intensity of gamma rays as seen in thermal-neutron capture are presented in ascending order of gamma energy. All those gamma-rays with intensity of {ge} 2% of the strongest transition are included. The two strongest transitions seen for the target nuclide are indicated in each case. Where the target nuclide mass number is indicated as nat the natural target was used. The gamma energies given are in keV. The gamma intensities given are relative to 100 for the strongest transition. All data for A > 44 are taken from Evaluated Nuclear Structure Data File (4/97), a computermore » file of evaluated nuclear structure data maintained by the National Nuclear Data Center, Brookhaven National Laboratory, on behalf of the Nuclear Structure and Decay and Decay Data network, coordinated by the International Atomic Energy Agency, Vienna. These data are published in Nuclear Data Sheets, Academic Press, San Diego, CA. The data for A {le} 44 is taken from ``Prompt Gamma Rays from Thermal-Neutron Capture,`` M.A. Lone, R.A. Leavitt, D.A. Harrison, Atomic Data and Nuclear Data Tables 26, 511 (1981).« less

Jet or shock breakout? The low-luminosity GRB 060218

NASA Astrophysics Data System (ADS)

Irwin, Christopher M.; Chevalier, Roger A.

2016-08-01

We consider a model for the low-luminosity gamma-ray burst GRB 060218 that plausibly accounts for multiwavelength observations to day 20. The model components are: (1) a long-lived (tj ˜ 3000 s) central engine and accompanying low-luminosity (Lj ˜ 1047 erg s-1), mildly relativistic (γ ˜ 10) jet; (2) a low-mass (˜4 × 10-3 M⊙) envelope surrounding the progenitor star; and (3) a modest amount of dust (AV ˜ 0.1 mag) in the circumstellar or interstellar environment. Blackbody emission from the transparency radius in a low-power jet outflow can fit the prompt thermal X-ray emission, and the non-thermal X-rays and gamma-rays may be produced via Compton scattering of thermal photons from hot leptons in the jet interior or the external shocks. The later mildly relativistic phase of this outflow can produce the radio emission via synchrotron radiation from the forward shock. Meanwhile, interaction of the associated SN 2006aj with a circumstellar envelope extending to ˜1013 cm can explain the early optical emission. The X-ray afterglow can be interpreted as a light echo of the prompt emission from dust at ˜30 pc. Our model is a plausible alternative to that of Nakar, who recently proposed shock breakout of a jet smothered by an extended envelope as the source of prompt emission. Both our results and Nakar's suggest that bursts such as GRB 060218 may originate from unusual progenitors with extended circumstellar envelopes, and that a jet is necessary to decouple the prompt emission from the supernova.

Evidence of the Exponential Decay Emission in the Swift Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Sakamoto, T.; Sato, G.; Hill, J.E.; Krimm, H.A.; Yamazaki, R.; Takami, K.; Swindell, S.; Osborne, J.P.

2007-01-01

We present a systematic study of the steep decay emission of gamma-ray bursts (GRBs) observed by the Swift X-Ray Telescope (XRT). In contrast to the analysis in recent literature, instead of extrapolating the data of Burst Alert Telescope (BAT) down into the XRT energy range, we extrapolated the XRT data up to the BAT energy range, 15-25 keV, to produce the BAT and XRT composite light curve. Based on our composite light curve fitting, we have confirmed the existence of an exponential decay component which smoothly connects the BAT prompt data to the XRT steep decay for several GRBs. We also find that the XRT steep decay for some of the bursts can be well fitted by a combination of a power-law with an exponential decay model. We discuss that this exponential component may be the emission from an external shock and a sign of the deceleration of the outflow during the prompt phase.

Gamma-Ray Burst Prompt Emission Light Curves and Power Density Spectra in the ICMART Model

NASA Astrophysics Data System (ADS)

Zhang, Bo; Zhang, Bing

2014-02-01

In this paper, we simulate the prompt emission light curves of gamma-ray bursts (GRBs) within the framework of the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. This model applies to GRBs with a moderately high magnetization parameter σ in the emission region. We show that this model can produce highly variable light curves with both fast and slow components. The rapid variability is caused by many locally Doppler-boosted mini-emitters due to turbulent magnetic reconnection in a moderately high σ flow. The runaway growth and subsequent depletion of these mini-emitters as a function of time define a broad slow component for each ICMART event. A GRB light curve is usually composed of multiple ICMART events that are fundamentally driven by the erratic GRB central engine activity. Allowing variations of the model parameters, one is able to reproduce a variety of light curves and the power density spectra as observed.

Extending the Search for Muon Neutrinos Coincident with Gamma-Ray Bursts in IceCube Data

NASA Astrophysics Data System (ADS)

Aartsen, M. G.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Samarai, I. Al; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Archinger, M.; Argüelles, C.; Auffenberg, J.; Axani, S.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berley, D.; Bernardini, E.; Besson, D. Z.; Binder, G.; Bindig, D.; Blaufuss, E.; Blot, S.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Braun, J.; Brayeur, L.; Bretz, H.-P.; Bron, S.; Burgman, A.; Carver, T.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cross, R.; Day, M.; de André, J. P. A. M.; De Clercq, C.; del Pino Rosendo, E.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Eller, P.; Euler, S.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Feintzeig, J.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Fösig, C.-C.; Franckowiak, A.; Friedman, E.; Fuchs, T.; Gaisser, T. K.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Gladstone, L.; Glauch, T.; Glüsenkamp, T.; Goldschmidt, A.; Gonzalez, J. G.; Grant, D.; Griffith, Z.; Haack, C.; Hallgren, A.; Halzen, F.; Hansen, E.; Hansmann, T.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Hoshina, K.; Huang, F.; Huber, M.; Hultqvist, K.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Kang, W.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kheirandish, A.; Kim, J.; Kim, M.; Kintscher, T.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Konietz, R.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Krüger, C.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Kyriacou, A.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lauber, F.; Lennarz, D.; Lesiak-Bzdak, M.; Leuermann, M.; Lu, L.; Lünemann, J.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Mandelartz, M.; Maruyama, R.; Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Micallef, J.; Momenté, G.; Montaruli, T.; Moulai, M.; Nahnhauer, R.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; O'Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Peiffer, P.; Penek, Ö.; Pepper, J. A.; Pérez de los Heros, C.; Pieloth, D.; Pinat, E.; Price, P. B.; Przybylski, G. T.; Quinnan, M.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Reimann, R.; Relethford, B.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Riedel, B.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk, D.; Sabbatini, L.; Sanchez Herrera, S. E.; Sandrock, A.; Sandroos, J.; Sarkar, S.; Satalecka, K.; Schlunder, P.; Schmidt, T.; Schoenen, S.; Schöneberg, S.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stachurska, J.; Stanev, T.; Stasik, A.; Stettner, J.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Ström, R.; Strotjohann, N. L.; Sullivan, G. W.; Sutherland, M.; Taavola, H.; Taboada, I.; Tatar, J.; Tenholt, F.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Tung, C. F.; Turcati, A.; Unger, E.; Usner, M.; Vandenbroucke, J.; van Eijndhoven, N.; Vanheule, S.; van Rossem, M.; van Santen, J.; Vehring, M.; Voge, M.; Vogel, E.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandkowsky, N.; Waza, A.; Weaver, Ch.; Weiss, M. J.; Wendt, C.; Westerhoff, S.; Whelan, B. J.; Wickmann, S.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wolf, M.; Wood, T. R.; Woolsey, E.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zoll, M.; IceCube Collaboration

2017-07-01

We present an all-sky search for muon neutrinos produced during the prompt γ-ray emission of 1172 gamma-ray bursts (GRBs) with the IceCube Neutrino Observatory. The detection of these neutrinos would constitute evidence for ultra-high-energy cosmic-ray (UHECR) production in GRBs, as interactions between accelerated protons and the prompt γ-ray field would yield charged pions, which decay to neutrinos. A previously reported search for muon neutrino tracks from northern hemisphere GRBs has been extended to include three additional years of IceCube data. A search for such tracks from southern hemisphere GRBs in five years of IceCube data has been introduced to enhance our sensitivity to the highest energy neutrinos. No significant correlation between neutrino events and observed GRBs is seen in the new data. Combining this result with previous muon neutrino track searches and a search for cascade signature events from all neutrino flavors, we obtain new constraints for single-zone fireball models of GRB neutrino and UHECR production.

Search for electron and gamma-ray decay of the ^238fPu fission

NASA Astrophysics Data System (ADS)

Beausang, C. W.; Gurdal, G.; Ressler, J.; Barton, C. J.; Caprio, M. A.; Casten, R. F.; Cooper, J. R.; Hecht, A. A.; Hutter, C.; Zamfir, N. V.; Hauschild, K.; Korten, W.; Mergel, E.

2002-04-01

The reaction ^9Be + ^232Th arrow ^241Pu, at beam energies of 50 and 55 MeV, was used in an attempt to populate states in the second minimum (fission isomer) of ^238Pu via the 3n evaporation channel. Prompt gamma-rays, detected using YRAST Ball and conversion electrons, detected using ICE Ball, were collected in coincidence with delayed fission events measured using elements of the Yale SCARY array of solar cell detectors. The solar cell detectors were shielded so as not to view the large prompt fission flux from the target. Instead the detectors were located so that they could detect delayed fission events, originating from the 6 ns fission isomer state in ^238Pu, which occur downstream from the target position. Data analysis is in progress and results to date will be presented. This work is partly supported by the U.S. DOE under grant numbers DE-FG02-91ER-40609, DE-FG02-88ER-40417.

Study of near-stability nuclei populated as fission fragments in heavy-ion fusion reactions

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

Fotiadis, Nikolaos; Nelson, Ronald O; Devlin, Matthew

2010-01-01

Examples are presented to illustrate the power of prompt {gamma}-ray spectroscopy of fission fragments from compound nuclei with A {approx} 200 formed in fusion-evaporation reactions in experiments using the Gammasphere Ge-detector array. Complementary methods, such as Coulomb excitation and deep-inelastic processes, are also discussed. In other cases (n, xn{gamma}) reactions on stable isotopes have been used to establish neutron excitation functions for {gamma}-rays using a pulsed 'white'-neutron source, coupled to a high-energy-resolution germanium-detector array. The excitation functions can unambiguously assign {gamma}-rays to a specific reaction product. Results from all these methods bridge the gaps in the systematics of high-spin statesmore » between the neutron-deficient and neutron-rich nuclei. Results near shell closures should motivate new shell model calculations.« less

The neutron-gamma Feynman variance to mean approach: Gamma detection and total neutron-gamma detection (theory and practice)

NASA Astrophysics Data System (ADS)

Chernikova, Dina; Axell, Kåre; Avdic, Senada; Pázsit, Imre; Nordlund, Anders; Allard, Stefan

2015-05-01

Two versions of the neutron-gamma variance to mean (Feynman-alpha method or Feynman-Y function) formula for either gamma detection only or total neutron-gamma detection, respectively, are derived and compared in this paper. The new formulas have particular importance for detectors of either gamma photons or detectors sensitive to both neutron and gamma radiation. If applied to a plastic or liquid scintillation detector, the total neutron-gamma detection Feynman-Y expression corresponds to a situation where no discrimination is made between neutrons and gamma particles. The gamma variance to mean formulas are useful when a detector of only gamma radiation is used or when working with a combined neutron-gamma detector at high count rates. The theoretical derivation is based on the Chapman-Kolmogorov equation with the inclusion of general reactions and corresponding intensities for neutrons and gammas, but with the inclusion of prompt reactions only. A one energy group approximation is considered. The comparison of the two different theories is made by using reaction intensities obtained in MCNPX simulations with a simplified geometry for two scintillation detectors and a 252Cf-source. In addition, the variance to mean ratios, neutron, gamma and total neutron-gamma are evaluated experimentally for a weak 252Cf neutron-gamma source, a 137Cs random gamma source and a 22Na correlated gamma source. Due to the focus being on the possibility of using neutron-gamma variance to mean theories for both reactor and safeguards applications, we limited the present study to the general analytical expressions for Feynman-alpha formulas.

Standardization of the neutron probe for the assessment of masonry deterioration

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

Livingston, R.A.

1992-01-01

The repair of the infrastructure will require nondestructive methods to assess the condition of existing buildings and other structures, many of which are constructed of masonry. One possible technology is the neutron probe, a prompt-gamma neutron activation (PGNA) technique that can perform non- destructive elemental analyses in the field. It is based on a very low intensity [sup 252]Cf neutron source and a high-purity germanium detector for the gamma rays emitted by neutron capture within the material. The thermal neutron capture cross sections for hydrogen and chlorine are very large, and in masonry, these elements are found primarily in moisturemore » and chlorides. These are major causes of deterioration in porous materials such as brick masonry. The moisture damages the material through expansive stresses during freeze-thaw cycles. Chlorides also generate expansive stresses through periodic cycles of dissolution and recrystallization in response to relative humidity cycles in the atmosphere. Similar problems also occur in reinforced concrete, where chlorides cause additional damage through corrosion of the reinforcing steel. The sensitivity of the neutron probe to hydrogen and chlorine thus means it can be used to map the distribution of these agents of deterioration. Preliminary field work at Colonial Williamsburg and Venice, Italy, showed that the technique could yield useful qualitative information. However, to be a quantitative method, the neutron probe had to be standardized in the laboratory on materials of known composition and specified moisture and chloride content.« less

CAFNA{reg{underscore}sign}, coded aperture fast neutron analysis for contraband detection: Preliminary results

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

Zhang, L.; Lanza, R.C.

1999-12-01

The authors have developed a near field coded aperture imaging system for use with fast neutron techniques as a tool for the detection of contraband and hidden explosives through nuclear elemental analysis. The technique relies on the prompt gamma rays produced by fast neutron interactions with the object being examined. The position of the nuclear elements is determined by the location of the gamma emitters. For existing fast neutron techniques, in Pulsed Fast Neutron Analysis (PFNA), neutrons are used with very low efficiency; in Fast Neutron Analysis (FNS), the sensitivity for detection of the signature gamma rays is very low.more » For the Coded Aperture Fast Neutron Analysis (CAFNA{reg{underscore}sign}) the authors have developed, the efficiency for both using the probing fast neutrons and detecting the prompt gamma rays is high. For a probed volume of n{sup 3} volume elements (voxels) in a cube of n resolution elements on a side, they can compare the sensitivity with other neutron probing techniques. As compared to PFNA, the improvement for neutron utilization is n{sup 2}, where the total number of voxels in the object being examined is n{sup 3}. Compared to FNA, the improvement for gamma-ray imaging is proportional to the total open area of the coded aperture plane; a typical value is n{sup 2}/2, where n{sup 2} is the number of total detector resolution elements or the number of pixels in an object layer. It should be noted that the actual signal to noise ratio of a system depends also on the nature and distribution of background events and this comparison may reduce somewhat the effective sensitivity of CAFNA. They have performed analysis, Monte Carlo simulations, and preliminary experiments using low and high energy gamma-ray sources. The results show that a high sensitivity 3-D contraband imaging and detection system can be realized by using CAFNA.« less

Overview of the SVOM Gamma-Ray Burst mission under development with a focus on its Trigger system

NASA Astrophysics Data System (ADS)

Schanne, Stephane

2017-08-01

The SVOM mission (Space-based Variable Objects Monitor) is a Chinese-French satellite mission under development, devoted to collecting a complete sample of Gamma-Ray Bursts (GRBs) observed at multi-wavelengths with a high fraction of redshift determinations. In January 2017 the mission entered Phase C, starting officially construction, and the launch is foreseen in 2021. The SVOM satellite is equipped with 4 instruments, 2 of which cover the prompt GRB phase. The ECLAIRs coded-mask imager surveys a 2-sr large portion of the sky in the 4-150 keV energy range, well suited for the detection of X-ray rich and highly redshifted GRBs. The ECLAIRs trigger system continuously searches for GRBs using two algorithms, a count-rate trigger for short time scales and an image trigger for long time scales. In case of a localized new GRB candidate or a bright outburst of a known source, it promptly requests a satellite slew and sends an alert to ground. The onboard GRM (Gamma-Ray Monitor) extends the prompt energy coverage up to 5 MeV. After slew, 2 more onboard instruments study the GRB afterglow and refine the GRB localization: the MXT (Multi-pore optics X-ray Telescope) and the VT (Visible Telescope). Two types of ground telescopes are dedicated to SVOM. The GFTs (Ground Follow-up Telescopes) repoint autonomously to GRB alerts, refine their localization and provide photometric redshift. The SVOM observing strategy with roughly antisolar pointing combined with Galactic plane avoidance, ensures that most GRBs are quickly visible by the GFTs and large spectroscopic telescopes. The GWAC (Ground Wide Angle Camera) will observe the sky simultaneously with ECLAIRs to detect prompt optical GRB emissions. Today part of the GWAC is already operational. The SVOM GRB program is complemented by pre-planned target observations and ground-commanded targets of opportunity, e.g. to search for electromagnetic counterparts of gravity-wave events. On behalf of the SVOM and ECLAIRs teams, this paper presents an overview of SVOM with a focus on its GRB trigger system.

Gamma Ray Bursts in the Swift-Fermi Era

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Razzaque, Soebur

2013-01-01

Gamma-ray bursts (GRBs) are among the most violent occurrences in the universe. They are powerful explosions, visible to high redshift, and thought to be the signature of black hole birth. They are highly luminous events and provide excellent probes of the distant universe. GRB research has greatly advanced over the past 10 years with the results from Swift, Fermi and an active follow-up community. In this review we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglows.

Evidence for the color-octet mechanism from CERN LEP2 gamma gamma --> J/psi + X Data.

PubMed

Klasen, Michael; Kniehl, Bernd A; Mihaila, Luminiţa N; Steinhauser, Matthias

2002-07-15

We present theoretical predictions for the transverse-momentum distribution of J/psi mesons promptly produced in gammagamma collisions within the factorization formalism of nonrelativistic quantum chromodynamics, including the contributions from both direct and resolved photons, and we perform a conservative error analysis. The fraction of J/psi mesons from decays of bottom-flavored hadrons is estimated to be negligibly small. New data taken by the DELPHI Collaboration at LEP2 nicely confirm these predictions, while they disfavor those obtained within the traditional color-singlet model.

Fermi-LAT Gamma-ray Bursts and Insight from Swift

NASA Technical Reports Server (NTRS)

Racusin, Judith L.

2011-01-01

A new revolution in GRB observation and theory has begun over the last 3 years since the launch of the Fermi gamma-ray space telescope. The new window into high energy gamma-rays opened by the Fermi-LAT is providing insight into prompt emission mechanisms and possibly also afterglow physics. The LAT detected GRBs appear to be a new unique subset of extremely energetic and bright bursts. In this talk I will discuss the context and recent discoveries from these LAT GRBs and the large database of broadband observations collected by Swift over the last 7 years and how through comparisons between the Swift, GBM, and LAT GRB samples, we can learn about the unique characteristics and relationships between each population.

Fusion gamma diagnostics

NASA Astrophysics Data System (ADS)

Medley, S. S.; Cecil, F. E.; Cole, D.; Conway, M. A.; Wilkinson, F. J., III

1985-05-01

Nuclear reactions of interest in fusion research often possess a branch yielding prompt emission of gamma radiation in excess of 15 MeV which can be exploited to provide a new fusion reaction diagnostic having applications similar to conventional neutron emission measurements. Conceptual aspects of fusion gamma diagnostics are discussed with emphasis on application to the Tokamak Fusion Test Reactor (TFTR) during deuterium neutral beam heating of D-T and D-3He plasmas. Recent measurements of the D (T, γ)5He, D(3He, γ)5Li, and D(D, γ)4He branching ratios at low center-of-mass energy (30-100 keV) and of the response of a large volume Ne226 detector for gamma detection in high neutron backgrounds are presented. Using a well-shielded Ne226 detector during 20 MW-120 kV deuterium beam heating of a tritium plasma in TFTR, the D(T, γ)5He gamma signal level is estimated to be 3.5×105 cps.

Interferon-gamma (INF-gamma) release test can detect cutaneous adverse effects to statins.

PubMed

Goldberg, Ilan; Isman, Gila; Shirazi, Idit; Brenner, Sarah

2009-12-01

An increasing number of cutaneous adverse effects are being reported as use of statins becomes more widespread. A study was undertaken to establish the relationship between statin and a cutaneous reaction by the in vitro interferon-gamma (INF-gamma) release test. The lymphocytes of 20 patients with suspected drug-induced skin reaction were incubated with and without the drug. The level of INF-gamma from the supernatant was measured by enzyme-linked immunosorbent assay (ELISA), and the increase calculated. Response was positive in 27 (21.43%) of the 126 drugs. Statin was the only drug with a positive response in 80% of those cases. Nine of 20 patients (45.0%) had complete resolution after discontinuation of the drug; 6 (30.0%) who replaced one drug by another statin had partial or no resolution; and 5 (20.0%) had no resolution despite cessation of statins of all kinds. A positive INF-gamma release test was found in patients who developed skin reactions while taking statins; the test's reliability was strengthened by prompt improvement following elimination of the suspected drug in the majority of patients.

Thermal-neutron capture gamma-rays. Volume 2

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

Tuli, J.K.

1997-05-01

The energy and photon intensity of gamma rays as seen in thermal-neutron capture are presented ordered by Z, A of target nuclei. All gamma-rays with intensity of {ge}2% of the strongest transition are included. The strongest transition is indicated in each case. Where the target nuclide mass number is indicated as nat the natural target was used. The gamma energies given are in keV. The gamma intensities given are relative to 100 for the strongest transition. All data for A > 44 are taken from Evaluated Nuclear Structure Data File (4/97), a computer file of evaluated nuclear structure data maintainedmore » by the National Nuclear Data Center, Brookhaven National Laboratory, on behalf of the Nuclear Structure and Decay and Decay Data network, coordinated by the International Atomic Energy Agency, Vienna. These data are published in Nuclear Data Sheets, Academic Press, San Diego, CA. The data for A {le} 44 is taken from ``Prompt Gamma Rays from Thermal-Neutron Capture,`` M.A. Lone, R.A. Leavitt, D.A. Harrison, Atomic Data and Nuclear Data Tables 26, 511 (1981).« less

The Supercritical Pile GRB Model: The Prompt to Afterglow Evolution

NASA Technical Reports Server (NTRS)

Mastichiadis, A.; Kazanas, D.

2009-01-01

The "Supercritical Pile" is a very economical GRB model that provides for the efficient conversion of the energy stored in the protons of a Relativistic Blast Wave (RBW) into radiation and at the same time produces - in the prompt GRB phase, even in the absence of any particle acceleration - a spectral peak at energy approx. 1 MeV. We extend this model to include the evolution of the RBW Lorentz factor Gamma and thus follow its spectral and temporal features into the early GRB afterglow stage. One of the novel features of the present treatment is the inclusion of the feedback of the GRB produced radiation on the evolution of Gamma with radius. This feedback and the presence of kinematic and dynamic thresholds in the model can be the sources of rich time evolution which we have began to explore. In particular. one can this may obtain afterglow light curves with steep decays followed by the more conventional flatter afterglow slopes, while at the same time preserving the desirable features of the model, i.e. the well defined relativistic electron source and radiative processes that produce the proper peak in the (nu)F(sub nu), spectra. In this note we present the results of a specific set of parameters of this model with emphasis on the multiwavelength prompt emission and transition to the early afterglow.

Search for Muon Neutrinos from Gamma-ray Bursts with the IceCube Neutrino Telescope

NASA Astrophysics Data System (ADS)

Abbasi, R.; Abdou, Y.; Abu-Zayyad, T.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Andeen, K.; Auffenberg, J.; Bai, X.; Baker, M.; Barwick, S. W.; Bay, R.; Bazo Alba, J. L.; Beattie, K.; Beatty, J. J.; Bechet, S.; Becker, J. K.; Becker, K.-H.; Benabderrahmane, M. L.; Berdermann, J.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Bissok, M.; Blaufuss, E.; Boersma, D. J.; Bohm, C.; Bolmont, J.; Botner, O.; Bradley, L.; Braun, J.; Breder, D.; Castermans, T.; Chirkin, D.; Christy, B.; Clem, J.; Cohen, S.; Cowen, D. F.; D'Agostino, M. V.; Danninger, M.; Day, C. T.; De Clercq, C.; Demirörs, L.; Depaepe, O.; Descamps, F.; Desiati, P.; de Vries-Uiterweerd, G.; DeYoung, T.; Diaz-Velez, J. C.; Dreyer, J.; Dumm, J. P.; Duvoort, M. R.; Edwards, W. R.; Ehrlich, R.; Eisch, J.; Ellsworth, R. W.; Engdegård, O.; Euler, S.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Feusels, T.; Filimonov, K.; Finley, C.; Foerster, M. M.; Fox, B. D.; Franckowiak, A.; Franke, R.; Gaisser, T. K.; Gallagher, J.; Ganugapati, R.; Gerhardt, L.; Gladstone, L.; Goldschmidt, A.; Goodman, J. A.; Gozzini, R.; Grant, D.; Griesel, T.; Groß, A.; Grullon, S.; Gunasingha, R. M.; Gurtner, M.; Ha, C.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Hasegawa, Y.; Heise, J.; Helbing, K.; Herquet, P.; Hickford, S.; Hill, G. C.; Hoffman, K. D.; Hoshina, K.; Hubert, D.; Huelsnitz, W.; Hülß, J.-P.; Hulth, P. O.; Hultqvist, K.; Hussain, S.; Imlay, R. L.; Inaba, M.; Ishihara, A.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Joseph, J. M.; Kampert, K.-H.; Kappes, A.; Karg, T.; Karle, A.; Kelley, J. L.; Kenny, P.; Kiryluk, J.; Kislat, F.; Klein, S. R.; Knops, S.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Kuehn, K.; Kuwabara, T.; Labare, M.; Lafebre, S.; Laihem, K.; Landsman, H.; Lauer, R.; Lennarz, D.; Lucke, A.; Lundberg, J.; Lünemann, J.; Madsen, J.; Majumdar, P.; Maruyama, R.; Mase, K.; Matis, H. S.; McParland, C. P.; Meagher, K.; Merck, M.; Mészáros, P.; Middell, E.; Milke, N.; Miyamoto, H.; Mohr, A.; Montaruli, T.; Morse, R.; Movit, S. M.; Nahnhauer, R.; Nam, J. W.; Nießen, P.; Nygren, D. R.; Odrowski, S.; Olivas, A.; Olivo, M.; Ono, M.; Panknin, S.; Patton, S.; Pérez de los Heros, C.; Petrovic, J.; Piegsa, A.; Pieloth, D.; Pohl, A. C.; Porrata, R.; Potthoff, N.; Price, P. B.; Prikockis, M.; Przybylski, G. T.; Rawlins, K.; Redl, P.; Resconi, E.; Rhode, W.; Ribordy, M.; Rizzo, A.; Rodrigues, J. P.; Roth, P.; Rothmaier, F.; Rott, C.; Roucelle, C.; Rutledge, D.; Ryckbosch, D.; Sander, H.-G.; Sarkar, S.; Schlenstedt, S.; Schmidt, T.; Schneider, D.; Schukraft, A.; Schulz, O.; Schunck, M.; Seckel, D.; Semburg, B.; Seo, S. H.; Sestayo, Y.; Seunarine, S.; Silvestri, A.; Slipak, A.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Stephens, G.; Stezelberger, T.; Stokstad, R. G.; Stoufer, M. C.; Stoyanov, S.; Strahler, E. A.; Straszheim, T.; Sulanke, K.-H.; Sullivan, G. W.; Swillens, Q.; Taboada, I.; Tamburro, A.; Tarasova, O.; Tepe, A.; Ter-Antonyan, S.; Terranova, C.; Tilav, S.; Toale, P. A.; Tooker, J.; Tosi, D.; Turčan, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; Voigt, B.; Walck, C.; Waldenmaier, T.; Walter, M.; Wendt, C.; Westerhoff, S.; Whitehorn, N.; Wiebusch, C. H.; Wiedemann, A.; Wikström, G.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Woschnagg, K.; Xu, X. W.; Yodh, G.; Yoshida, S.; IceCube Collaboration

2010-02-01

We present the results of searches for high-energy muon neutrinos from 41 gamma-ray bursts (GRBs) in the northern sky with the IceCube detector in its 22 string configuration active in 2007/2008. The searches cover both the prompt and a possible precursor emission as well as a model-independent, wide time window of -1 hr to +3 hr around each GRB. In contrast to previous searches with a large GRB population, we do not utilize a standard Waxman-Bahcall GRB flux for the prompt emission but calculate individual neutrino spectra for all 41 GRBs from the burst parameters measured by satellites. For all of the three time windows, the best estimate for the number of signal events is zero. Therefore, we place 90% CL upper limits on the fluence from the prompt phase of 3.7 × 10-3 erg cm-2 (72 TeV-6.5 PeV) and on the fluence from the precursor phase of 2.3 × 10-3 erg cm-2 (2.2-55 TeV), where the quoted energy ranges contain 90% of the expected signal events in the detector. The 90% CL upper limit for the wide time window is 2.7 × 10-3 erg cm-2 (3 TeV-2.8 PeV) assuming an E -2 flux.

High-energy non-thermal and thermal emission from GRB 141207A detected by Fermi

DOE PAGES

Arimoto, Makoto; Asano, Katsuaki; Ohno, Masanori; ...

2016-12-13

A bright long gamma-ray burst GRB 141207A was observed by the Fermi Gamma-ray Space Telescope and detected by both instruments onboard. The observations show that the spectrum in the prompt phase is not well described by the canonical empirical Band function alone, and that an additional power-law component is needed. In the early phase of the prompt emission, a modified blackbody with a hard low-energy photon index (α = +0.2 to +0.4) is detected, which suggests a photospheric origin. In a finely time-resolved analysis, the spectra are also well fitted by the modified blackbody combined with a power-law function. Heremore » we discuss the physical parameters of the photosphere such as the bulk Lorentz factor of the relativistic flow and the radius. We also discuss the physical origin of the extra power-law component observed during the prompt phase in the context of different models such as leptonic and hadronic scenarios in the internal shock regime and synchrotron emission in the external forward shock. In the afterglow phase, the temporal and spectral behaviors of the temporally extended high-energy emission and the fading X-ray emission detected by the X-Ray Telescope on-board Swift are consistent with synchrotron emission in a radiative external forward shock.« less

Hadronic Origin of Prompt High-energy Emission of Gamma-ray Bursts Revisited: In the Case of a Limited Maximum Proton Energy

NASA Astrophysics Data System (ADS)

Wang, Kai; Liu, Ruo-Yu; Dai, Zi-Gao; Asano, Katsuaki

2018-04-01

The high-energy (>100 MeV) emission observed by the Fermi Large Area Telescope during the prompt phase of some luminous gamma-ray bursts (GRBs) could arise from the cascade induced by interactions between accelerated protons and the radiation field of GRBs. The photomeson process, which is usually suggested to operate in such a hadronic explanation, requires a rather high proton energy (>1017 eV) for an efficient interaction. However, whether GRBs can accelerate protons to such a high energy is far from guaranteed, although they have been suggested as the candidate source for ultrahigh-energy cosmic rays. In this work, we revisit the hadronic model for the prompt high-energy emission of GRBs with a smaller maximum proton energy than the usually adopted value estimated from the Bohm condition. In this case, the Bethe–Heitler pair production process becomes comparably important or even dominates over the photomeson process. We show that with a relatively low maximum proton energy with a Lorentz factor of 105 in the comoving frame, the cascade emission can still reproduce various types of high-energy spectra of GRBs. For most GRBs without high-energy emission detected, the maximum proton energy could be even lower and relax the constraints on the parameters of the GRB jet resulting from the nondetection of GRB neutrinos by IceCube.

Characterization of high density SiPM non-linearity and energy resolution for prompt gamma imaging applications

NASA Astrophysics Data System (ADS)

Regazzoni, V.; Acerbi, F.; Cozzi, G.; Ferri, A.; Fiorini, C.; Paternoster, G.; Piemonte, C.; Rucatti, D.; Zappalà, G.; Zorzi, N.; Gola, A.

2017-07-01

Fondazione Bruno Kessler (FBK) (Trento, Italy) has recently introduced High Density (HD) and Ultra High-Density (UHD) SiPMs, featuring very small micro-cell pitch. The high cell density is a very important factor to improve the linearity of the SiPM in high-dynamic-range applications, such as the scintillation light readout in high-energy gamma-ray spectroscopy and in prompt gamma imaging for proton therapy. The energy resolution at high energies is a trade-off between the excess noise factor caused by the non-linearity of the SiPM and the photon detection efficiency of the detector. To study these effects, we developed a new setup that simulates the LYSO light emission in response to gamma photons up to 30 MeV, using a pulsed light source. We measured the non-linearity and energy resolution vs. energy of the FBK RGB-HD e RGB-UHD SiPM technologies. We considered five different cell sizes, ranging from 10 μm up to 25 μm. With the UHD technology we were able to observe a remarkable reduction of the SiPM non-linearity, less than 5% at 5 MeV with 10 μm cells, which should be compared to a non-linearity of 50% with 25 μm-cell HD-SiPMs. With the same setup, we also measured the different components of the energy resolution (intrinsic, statistical, detector and electronic noise) vs. cell size, over-voltage and energy and we separated the different sources of excess noise factor.

Composite space charge density functions for the calculation of gamma sensitivity of self-powered neutron detectors, using Warren's model

NASA Astrophysics Data System (ADS)

Mahant, A. K.; Rao, P. S.; Misra, S. C.

1994-07-01

In the calculational model developed by Warren and Shah for the computation of the gamma sensitivity ( Sγ) it has been observed that the computed Sγ value is quite sensitive to the space charge distribution function assumed for the insulator region and the energy of the gamma photons. The Sγ of SPNDs with Pt, Co and V emitters (manufactured by Thermocoax, France) has been measured at 60Co photon energy and a good correlation between the measured and computed values has been obtained using a composite space charge density function (CSCD), the details of which are presented in this paper. The arguments are extended for evaluating the Sγ values of several SPNDs for which Warren and Shah reported the measured values for a prompt fission gamma spectrum obtained in a swimming pool reactor. These results are also discussed.

Classifying threats with a 14-MeV neutron interrogation system.

PubMed

Strellis, Dan; Gozani, Tsahi

2005-01-01

SeaPODDS (Sea Portable Drug Detection System) is a non-intrusive tool for detecting concealed threats in hidden compartments of maritime vessels. This system consists of an electronic neutron generator, a gamma-ray detector, a data acquisition computer, and a laptop computer user-interface. Although initially developed to detect narcotics, recent algorithm developments have shown that the system is capable of correctly classifying a threat into one of four distinct categories: narcotic, explosive, chemical weapon, or radiological dispersion device (RDD). Detection of narcotics, explosives, and chemical weapons is based on gamma-ray signatures unique to the chemical elements. Elements are identified by their characteristic prompt gamma-rays induced by fast and thermal neutrons. Detection of RDD is accomplished by detecting gamma-rays emitted by common radioisotopes and nuclear reactor fission products. The algorithm phenomenology for classifying threats into the proper categories is presented here.

Fast Pb-glass neutron-to-light converter for ICF (Inertial Confinement Fusion) target burn history measurements

NASA Astrophysics Data System (ADS)

Lerche, R. A.; Cable, M. D.; Phillion, D. W.

1990-09-01

We are developing a streak camera based instrument to diagnose the fusion reaction rate (burn history) within laser-driven ICF targets filled with D-T fuel. Recently, we attempted measurements using the 16.7 MeV gamma ray emitted in the T(d,gamma)He(5) fusion reaction. Pb glass which has a large cross section for pair production acts as a gamma-ray-to-light converter. Gamma rays interact within the glass to form electron-positron pairs that produce large amounts (1000 photons/gamma ray) of prompt (less than 10 ps) Cerenkov light as they slow down. In our experimental instrument, an f/10 Cassegrain telescope optically couples light produced within the converter to a streak camera having 20-ps resolution. Experiments using high-yield (10(exp 13) D-T neutrons), direct-drive targets at Nova produced good signals with widths of 200 ps. Time-of-flight measurements show the signals to be induced by neutrons rather than gamma rays. The Pb glass appears to act as a fast neutron-to-light converter. We continue to study the interactions process and the possibility of using the 16.7 MeV gamma rays for burn time measurements.

GRB 120729A: External Shock Origin for Both the Prompt Gamma-Ray Emission and Afterglow

NASA Astrophysics Data System (ADS)

Huang, Li-Ye; Wang, Xiang-Gao; Zheng, WeiKang; Liang, En-Wei; Lin, Da-bin; Zhong, Shu-Qing; Zhang, Hai-Ming; Huang, Xiao-Li; Filippenko, Alexei V.; Zhang, Bing

2018-06-01

Gamma-ray burst (GRB) 120729A was detected by Swift/BAT and Fermi/GBM, and then rapidly observed by Swift/XRT, Swift/UVOT, and ground-based telescopes. It had a single long and smooth γ-ray emission pulse, which extends continuously to the X-rays. We report Lick/KAIT observations of the source, and make temporal and spectral joint fits of the multiwavelength light curves of GRB 120729A. It exhibits achromatic light-curve behavior, consistent with the predictions of the external shock model. The light curves are decomposed into four typical phases: onset bump (Phase I), normal decay (Phase II), shallow decay (Phase III), and post-jet break (Phase IV). The spectral energy distribution (SED) evolves from prompt γ-ray emission to the afterglow with a photon index from Γ γ = 1.36 to Γ ≈ 1.75. There is no obvious evolution of the SED during the afterglow. The multiwavelength light curves from γ-ray to optical can be well modeled with an external shock by considering energy injection, and a time-dependent microphysics model with {ε }B\\propto {t}{α B} for the emission at early times, T< {T}0+157 {{s}}. Therefore, we conclude that both the prompt γ-ray emission and afterglow of GRB 120729A have the same external shock physical origin. Our model indicates that the ɛ B evolution can be described as a broken power-law function with α B,1 = 0.18 ± 0.04 and α B,2 = 0.84 ± 0.04. We also systematically investigate single-pulse GRBs in the Swift era, finding that only a small fraction of GRBs (GRBs 120729A, 051111, and 070318) are likely to originate from an external shock for both the prompt γ-ray emission and afterglow.

Prompt gamma-ray emission of GRB 170817A associated to GW 170817: A consistent picture

NASA Astrophysics Data System (ADS)

Ziaeepour, Houri

2018-05-01

The short GRB 170817A associated to the first detection of gravitation waves from a Binary Neutron Star (BNS) merger was in many ways unusual. Possible explanations are emission from a cocoon or cocoon break out, off-axis view of a structured or uniform jet, and on-axis ultra-relativistic jet with reduced density and Lorentz factor. Here we use a phenomenological model of shock evolution and synchrotron/self-Compton emission to simulate the prompt emission of GRB 170817A and to test above proposals. We find that synchrotron emission from a mildly relativistic cocoon with a Lorentz factor of 2-3, as considered in the literature, generates a too soft, too long, and too bright prompt emission. Off-axis view of an structured jet with a Lorentz factor of about 10 can reproduce observations, but needs a very efficient transfer of kinetic energy to electrons in internal shocks, which is disfavored by particle in cell simulations. We also comment on cocoon breakout as a mechanism for generation of the prompt gamma-ray. A relativistic jet with a Lorentz factor of about 100 and a density lower than typical short GRBs seems to be the most plausible model and we conclude that GRB 170817A was intrinsically faint. Based on this result and findings of relativistic magnetohydrodynamics simulations of BNS merger in the literature we discuss physical and astronomical conditions, which may lead to such faint short GRBs. We identify small mass difference of progenitor neutron stars, their old age and reduced magnetic field, and anti-alignment of spin-orbit angular momentum induced by environmental gravitational disturbances during the lifetime of the BNS as causes for the faintness of GRB 170817A. We predict that BNS mergers at lower redshifts generate on average fainter GRBs.

Prompt and Afterglow Emission from Short GRB Cocoons

NASA Astrophysics Data System (ADS)

Morsony, Brian; Lazzati, Davide; López-Cámara, Diego; Workman, Jared; Moskal, Jeremiah; Cantiello, Matteo; Perna, Rosalba

2018-01-01

We present simulations of short GRB jets that create a wide cocoon of mildly relativistic material surrounding the narrow, highly relativistic jet. We model the prompt and afterglow emission from the jet and cocoon at a range of observer angles relative to the jet axis. Even far off axis, prompt X-ray and gamma-ray emission from the cocoon may be detectable by FERMI GBM out to several 10’s of Mpc. Afterglow emission off-axis is dominated by cocoon material at early times (hours - days). The afterglow should be detectable at a wide range of frequencies (radio, optical, X-ray) for a large fraction of off-axis short GRBs within 200 Mpc, the detection range of aLIGO at design sensitivity. Given recent events, cocoon emission may be very important in the future for localizing LIGO-detected neutron star mergers.

The 235U Prompt Fission Neutron Spectrum in the BR1 Reactor at SCK•CEN

NASA Astrophysics Data System (ADS)

Wagemans, Jan; Malambu, Edouard; Borms, Luc; Fiorito, Luca

2016-02-01

The BR1 research reactor at SCK•CEN has a spherical cavity in the graphite above the reactor core. In this cavity an accurately characterised Maxwellian thermal neutron field is present. Different converters can be loaded in the cavity in order to obtain other types of neutron (and gamma) irradiation fields. Inside the so-called MARK III converter a fast 235U(n,f) prompt fission neutron field can be obtained. With the support of MCNP calculations, irradiations in MARK III can be directly related to the pure 235U(n,f) prompt fission neutron spectrum. For this purpose MARK III spectrum averaged cross sections for the most relevant fluence dosimetry reactions have been determined. A calibration factor for absolute measurements has been determined applying activation dosimetry following ISO/IEC 17025 standards.

Prompt-delayed $$\\gamma$$-ray spectroscopy with AGATA, EXOGAM and VAMOS++

DOE PAGES

Kim, Y. H.; Lemasson, A.; Rejmund, M.; ...

2017-08-10

Here, a new experimental setup to measure prompt-delayed γ-ray coincidences from isotopically identified fission fragments, over a wide time range of 100ns-200μ s, is presented. The fission fragments were isotopically identified, on an event-by-event basis, using the VAMOS++ large acceptance spectrometer. The prompt γ rays emitted at the target position and corresponding delayed γ rays emitted at the focal plane of the spectrometer were detected using, respectively, thirty two crystals of the AGATA γ-ray tracking array and seven EXOGAM HPGe Clover detectors. Finally, fission fragments produced in fusion and transfer-induced fission reactions, using a 238U beam at an energy ofmore » 6.2 MeV/u impinging on a 9Be target, were used to characterize and qualify the performance of the detection system.« less

Gamma-ray irradiation enhanced boron-10 compound accumulation in murine tumors.

PubMed

Liu, Yong; Nagata, Kenji; Masunaga, Shin-ichiro; Suzuki, Minoru; Kashino, Genro; Kinashi, Yuko; Tanaka, Hiroki; Sakurai, Yoshinori; Maruhashi, Akira; Ono, Koji

2009-11-01

Previous studies have demonstrated that X-ray irradiation affects angiogenesis in tumors. Here, we studied the effects of gamma-ray irradiation on boron-10 compound accumulation in a murine tumor model. The mouse squamous cell carcinoma was irradiated with gamma-ray before BSH ((10)B-enriched borocaptate sodium) administration. Then, the boron-10 concentrations in tumor and normal muscle tissues were measured by prompt gamma-ray spectrometry (PGA). A tumor blood flow assay was performed, and cell killing effects of neutron irradiation with various combinations of BSH and gamma-rays were also examined. BSH concentrations of tumor tissues were 16.1 +/- 0.6 microg/g, 16.7 +/- 0.5 microg/g and 17.8 +/- 0.5 microg/g at 72 hours after gamma-ray irradiation at doses of 5, 10, and 20 Gy, compared with 13.1 +/- 0.5 microg/g in unirradiated tumor tissues. The enhancing inhibition of colony formation by neutron irradiation with BSH was also found after gamma-ray irradiation. In addition, increasing Hoechst 33342 perfusion was also observed. In this study, we demonstrated that gamma-ray irradiation enhances BSH accumulation in tumors. The present results suggest that the enhancement of (10)B concentration that occurs after gamma-ray irradiation may be due to the changes in the extracellular microenvironment, including in tumor vessels, induced by gamma-ray irradiation.

GROND coverage of the main peak of gamma-ray burst 130925A

NASA Astrophysics Data System (ADS)

Greiner, J.; Yu, H.-F.; Krühler, T.; Frederiks, D. D.; Beloborodov, A.; Bhat, P. N.; Bolmer, J.; van Eerten, H.; Aptekar, R. L.; Elliott, J.; Golenetskii, S. V.; Graham, J. F.; Hurley, K.; Kann, D. A.; Klose, S.; Nicuesa Guelbenzu, A.; Rau, A.; Schady, P.; Schmidl, S.; Sudilovsky, V.; Svinkin, D. S.; Tanga, M.; Ulanov, M. V.; Varela, K.; von Kienlin, A.; Zhang, X.-L.

2014-08-01

Aims: Prompt or early optical emission in gamma-ray bursts (GRBs) is notoriously difficult to measure, and observations of the dozen cases show a large variety of properties. Yet, such early emission promises to help us achieve a better understanding of the GRB emission process(es). Methods: We performed dedicated observations of the ultra-long duration (T90 about 7000 s) Swift GRB 130925A in the optical/near-infrared with the 7-channel Gamma-Ray burst Optical and Near-infrared Detector (GROND) at the 2.2 m MPG/ESO telescope. Results: We detect an optical/near-infrared flare with an amplitude of nearly 2 mag which is delayed with respect to the keV-MeV prompt emission by about 300-400 s. The decay time of this flare is shorter than the duration of the flare (500 s) or its delay. Conclusions: While we cannot offer a straightforward explanation, we discuss the implications of the flare properties and suggest ways toward understanding it. Partly based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ID 092.A-0231(B).The GROND photometry table is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/568/A75

Searching for high-energy gamma-ray counterparts to gravitational-wave sources with Fermi-LAT: A needle in a haystack

DOE PAGES

Vianello, G.; Omodei, N.; Chiang, J.; ...

2017-05-20

At least a fraction of gravitational-wave (GW) progenitors are expected to emit an electromagnetic (EM) signal in the form of a short gamma-ray burst (sGRB). Discovering such a transient EM counterpart is challenging because the LIGO/VIRGO localization region is much larger (several hundreds of square degrees) than the field of view of X-ray, optical, and radio telescopes. The Fermi Large Area Telescope (LAT) has a wide field of view (~2.4 sr) and detects ~2–3 sGRBs per year above 100 MeV. It can detect them not only during the short prompt phase, but also during their long-lasting high-energy afterglow phase. If other wide-field, high-energy instruments such as Fermi-GBM, Swift-BAT, or INTEGRAL-ISGRI cannot detect or localize with enough precision an EM counterpart during the prompt phase, the LAT can potentially pinpoint it withmore » $$\\lesssim 10$$ arcmin accuracy during the afterglow phase. This routinely happens with gamma-ray bursts. Moreover, the LAT will cover the entire localization region within hours of any triggers during normal operations, allowing the γ-ray flux of any EM counterpart to be measured or constrained. As a result, we illustrate two new ad hoc methods to search for EM counterparts with the LAT and their application to the GW candidate LVT151012.« less

Searching for high-energy gamma-ray counterparts to gravitational-wave sources with Fermi-LAT: A needle in a haystack

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

Vianello, G.; Omodei, N.; Chiang, J.

At least a fraction of gravitational-wave (GW) progenitors are expected to emit an electromagnetic (EM) signal in the form of a short gamma-ray burst (sGRB). Discovering such a transient EM counterpart is challenging because the LIGO/VIRGO localization region is much larger (several hundreds of square degrees) than the field of view of X-ray, optical, and radio telescopes. The Fermi Large Area Telescope (LAT) has a wide field of view (~2.4 sr) and detects ~2–3 sGRBs per year above 100 MeV. It can detect them not only during the short prompt phase, but also during their long-lasting high-energy afterglow phase. If other wide-field, high-energy instruments such as Fermi-GBM, Swift-BAT, or INTEGRAL-ISGRI cannot detect or localize with enough precision an EM counterpart during the prompt phase, the LAT can potentially pinpoint it withmore » $$\\lesssim 10$$ arcmin accuracy during the afterglow phase. This routinely happens with gamma-ray bursts. Moreover, the LAT will cover the entire localization region within hours of any triggers during normal operations, allowing the γ-ray flux of any EM counterpart to be measured or constrained. As a result, we illustrate two new ad hoc methods to search for EM counterparts with the LAT and their application to the GW candidate LVT151012.« less

Experience of Being Gay, Lesbian or Bisexual at an Australian Medical School: A Qualitative Study

ERIC Educational Resources Information Center

Chur-Hansen, Anna

2004-01-01

Six undergraduate students were interviewed in a qualitative study about their experiences as gay, lesbian or bisexual students studying Medicine. Informants, who were identified by snowball sampling, spoke about their experiences both freely and in response to a series of prompt questions derived from previous research. The transcribed interviews…

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

Aaltonen, Timo Antero; et al.

A measurement of the inclusive production cross section of isolated prompt photons in proton-antiproton collisions at center-of-mass energymore » $$\\sqrt{s}$$=1.96TeV is presented. The results are obtained using the full Run II data sample collected with the Collider Detector at the Fermilab Tevatron, which corresponds to an integrated luminosity of 9.5fb$$^{-1}$$. The cross section is measured as a function of photon transverse energy, $$E_T^{\\gamma}$$, in the range 30$$ < E_T^{\\gamma} <$$500GeV and in the pseudorapidity region $$|\\eta^{\\gamma}|<$$1.0. The results are compared with predictions from parton-shower Monte Carlo models at leading order in quantum chromodynamics (QCD) and from next-to-leading order perturbative QCD calculations. The latter show good agreement with the measured cross section.« less

Galactic and extragalactic hydrogen in the X-ray spectra of Gamma Ray Bursts

NASA Astrophysics Data System (ADS)

Rácz, I. I.; Bagoly, Z.; Tóth, L. V.; Balázs, L. G.; Horváth, I.; Pintér, S.

2017-07-01

Two types of emission can be observed from gamma-ray bursts (GRBs): the prompt emission from the central engine which can be observed in gamma or X-ray (as a low energy tail) and the afterglow from the environment in X-ray and at shorter frequencies. We examined the Swift XRT spectra with the XSPEC software. The correct estimation of the galactic interstellar medium is very important because we observe the host emission together with the galactic hydrogen absorption. We found that the estimated intrinsic hydrogen column density and the X-ray flux depend heavily on the redshift and the galactic foreground hydrogen. We also found that the initial parameters of the iteration and the cosmological parameters did not have much effect on the fitting result.

THE ANATOMY OF A LONG GAMMA-RAY BURST: A SIMPLE CLASSIFICATION SCHEME FOR THE EMISSION MECHANISM(S)

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

Bégué, D.; Burgess, J. Michael, E-mail: jamesb@kth.se, E-mail: damienb@kth.se

2016-03-20

Ultra-relativistic motion and efficient conversion of kinetic energy to radiation are required by gamma-ray burst (GRB) observations, yet they are difficult to simultaneously achieve. Three leading mechanisms have been proposed to explain the observed emission emanating from GRB outflows: radiation from either relativistic internal or external shocks, or thermal emission from a photosphere. Previous works were dedicated to independently treating these three mechanisms and arguing for a sole, unique origin of the prompt emission of GRBs. In contrast, herein, we first explain why all three models are valid mechanisms and that a contribution from each of them is expected inmore » the prompt phase. Additionally, we show that a single parameter, the dimensionless entropy of the GRB outflow, determines which mechanism contributes the most to the emission. More specifically, internal shocks dominate for low values of the dimensionless entropy, external shocks for intermediate values, and finally, photospheric emission for large values. We present a unified framework for the emission mechanisms of GRBs with easily testable predictions for each process.« less

Characterisation and optimisation of the new Prompt Gamma-ray Activation Analysis (PGAA) facility at FRM II

NASA Astrophysics Data System (ADS)

Canella, Lea; Kudějová, Petra; Schulze, Ralf; Türler, Andreas; Jolie, Jan

2011-04-01

At the research reactor Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) a new Prompt Gamma-ray Activation Analysis (PGAA) facility was installed. The instrument was originally built and operating at the spallation source at the Paul Scherrer Institute in Switzerland. After a careful re-design in 2004-2006, the new PGAA instrument was ready for operation at FRM II. In this paper the main characteristics and the current operation conditions of the facility are described. The neutron flux at the sample position can reach up 6.07×1010 [cm-2 s-1], thus the optimisation of some parameters, e.g. the beam background, was necessary in order to achieve a satisfactory analytical sensitivity for routine measurements. Once the optimal conditions were reached, detection limits and sensitivities for some elements, like for example H, B, C, Si, or Pb, were calculated and compared with other PGAA facilities. A standard reference material was also measured in order to show the reliability of the analysis under different conditions at this instrument.

Prompt emission from the counter jet of a short gamma-ray burst

NASA Astrophysics Data System (ADS)

Yamazaki, Ryo; Ioka, Kunihito; Nakamura, Takashi

2018-03-01

The counter jet of a short gamma-ray burst (sGRB) has not yet been observed, while recent discoveries of gravitational waves (GWs) from a binary neutron star merger GW170817 and the associated sGRB 170817A have demonstrated that off-axis sGRB jets are detectable. We calculate the prompt emission from the counter jet of an sGRB and show that it is typically 23-26 mag in the optical-infrared band 10-10^3 s after the GWs for an sGRB 170817A-like event, which is brighter than the early macronova (or kilonova) emission and detectable by LSST in the near future. We also propose a new method to constrain the unknown jet properties, such as the Lorentz factor, opening angle, emission radii, and jet launch time, by observing both the forward and counter jets. To scrutinize the counter jets, space GW detectors like DECIGO are powerful in forecasting the merger time (≲ 1 s) and position (≲ 1 arcmin) (˜ a week) before the merger.

Mercury and gold concentrations of highly polluted environmental samples determined using prompt gamma-ray analysis and instrument neutron activation analysis

NASA Astrophysics Data System (ADS)

Osawa, Takahito; Hatsukawa, Yuichi; Appel, Peter W. U.; Matsue, Hideaki

2011-04-01

The authors have established a method of determining mercury and gold in severely polluted environmental samples using prompt gamma-ray analysis (PGA) and instrumental neutron activation analysis (INAA). Since large amounts of mercury are constantly being released into the environment by small-scale gold mining in many developing countries, the mercury concentration in tailings and water has to be determined to mitigate environmental pollution. Cold-vapor atomic absorption analysis, the most pervasive method of mercury analysis, is not suitable because tailings and water around mining facilities have extremely high mercury concentrations. On the other hand, PGA can determine high mercury concentrations in polluted samples as it has an appropriate level of sensitivity. Moreover, gold concentrations can be determined sequentially by using INAA after PGA. In conclusion, the analytical procedure established in this work using PGA and INAA is the best way to evaluate the degree of pollution and the tailing resource value. This method will significantly contribute to mitigating problems in the global environment.

Effects of rotation of fissioning nuclei in the angular distributions of prompt neutrons and gamma rays originating from the polarized-neutron-induced fission of 233U and 235U nuclei

NASA Astrophysics Data System (ADS)

Danilyan, G. V.; Klenke, J.; Kopach, Yu. N.; Krakhotin, V. A.; Novitsky, V. V.; Pavlov, V. S.; Shatalov, P. B.

2014-06-01

The results of an experiment devoted to searches for effects of rotation of fissioning nuclei in the angular distributions of prompt neutrons and gamma rays originating from the polarized-neutron-induced fission of 233U nuclei are presented. The effects discovered in these angular distributions are opposite in sign to their counterparts in the polarized-neutron-induced fission of 235U nuclei. This is at odds with data on the relative signs of respective effects in the angular distribution of alpha particles from the ternary fission of the same nuclei and may be indicative of problems in the model currently used to describe the effect in question. The report on which this article is based was presented at the seminar held at the Institute of Theoretical and Experimental Physics and dedicated to the 90th anniversary of the birth of Yu.G. Abov, corresponding member of Russian Academy of Sciences, Editor in Chief of the journal Physics of Atomic Nuclei.

Predicting diffusion paths and interface motion in gamma/gamma + beta, Ni-Cr-Al diffusion couples

NASA Technical Reports Server (NTRS)

Nesbitt, J. A.; Heckel, R. W.

1987-01-01

A simplified model has been developed to predict Beta recession and diffusion paths in ternary gamma/gamma + beta diffusion couples (gamma:fcc, beta: NiAl structure). The model was tested by predicting beta recession and diffusion paths for four gamma/gamma + beta, Ni-Cr-Al couples annealed for 100 hours at 1200 C. The model predicted beta recession within 20 percent of that measured for each of the couples. The model also predicted shifts in the concentration of the gamma phase at the gamma/gamma + beta interface within 2 at. pct Al and 6 at. pct Cr of that measured in each of the couples. A qualitative explanation based on simple kinetic and mass balance arguments has been given which demonstrates the necessity for diffusion in the two-phase region of certain gamma/gamma + beta, Ni-Cr-Al couples.

Monte-Carlo Application for Nondestructive Nuclear Waste Analysis

NASA Astrophysics Data System (ADS)

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

2014-06-01

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

On the treatment of ill-conditioned cases in the Monte Carlo library least-squares approach for inverse radiation analyzers

NASA Astrophysics Data System (ADS)

Meric, Ilker; Johansen, Geir A.; Holstad, Marie B.; Mattingly, John; Gardner, Robin P.

2012-05-01

Prompt gamma-ray neutron activation analysis (PGNAA) has been and still is one of the major methods of choice for the elemental analysis of various bulk samples. This is mostly due to the fact that PGNAA offers a rapid, non-destructive and on-line means of sample interrogation. The quantitative analysis of the prompt gamma-ray data could, on the other hand, be performed either through the single peak analysis or the so-called Monte Carlo library least-squares (MCLLS) approach, of which the latter has been shown to be more sensitive and more accurate than the former. The MCLLS approach is based on the assumption that the total prompt gamma-ray spectrum of any sample is a linear combination of the contributions from the individual constituents or libraries. This assumption leads to, through the minimization of the chi-square value, a set of linear equations which has to be solved to obtain the library multipliers, a process that involves the inversion of the covariance matrix. The least-squares solution may be extremely uncertain due to the ill-conditioning of the covariance matrix. The covariance matrix will become ill-conditioned whenever, in the subsequent calculations, two or more libraries are highly correlated. The ill-conditioning will also be unavoidable whenever the sample contains trace amounts of certain elements or elements with significantly low thermal neutron capture cross-sections. In this work, a new iterative approach, which can handle the ill-conditioning of the covariance matrix, is proposed and applied to a hydrocarbon multiphase flow problem in which the parameters of interest are the separate amounts of the oil, gas, water and salt phases. The results of the proposed method are also compared with the results obtained through the implementation of a well-known regularization method, the truncated singular value decomposition. Final calculations indicate that the proposed approach would be able to treat ill-conditioned cases appropriately.

Fission Signatures for Nuclear Material Detection

NASA Astrophysics Data System (ADS)

Gozani, Tsahi

2009-06-01

Detection and interdiction of nuclear materials in all forms of transport is one of the most critical security issues facing the United States and the rest of the civilized world. Naturally emitted gamma rays by these materials, while abundant and detectable when unshielded, are low in energy and readily shielded. X-ray radiography is useful in detecting the possible presence of shielding material. Positive detection of concealed nuclear materials requires methods which unequivocally detect specific attributes of the materials. These methods typically involve active interrogation by penetrating radiation of neutrons, photons or other particles. Fortunately, nuclear materials, probed by various types of radiation, yield very unique and often strong signatures. Paramount among them are the detectable fission signatures, namely prompt neutrons and gamma rays, and delayed neutrons gamma rays. Other useful signatures are the nuclear states excited by neutrons, via inelastic scattering, or photons, via nuclear resonance fluorescence and absorption. The signatures are very different in magnitude, level of specificity, ease of excitation and detection, signal to background ratios, etc. For example, delayed neutrons are very unique to the fission process, but are scarce, have low energy, and hence are easily absorbed. Delayed gamma rays are more abundant but "featureless", and have a higher background from natural sources and more importantly, from activation due to the interrogation sources. The prompt fission signatures need to be measured in the presence of the much higher levels of probing radiation. This requires taking special measures to look for the signatures, sometimes leading to a significant sensitivity loss or a complete inability to detect them. Characteristic gamma rays induced in nuclear materials reflecting their nuclear structure, while rather unique, require very high intensity of interrogation radiation and very high resolution in energy and/or time. The trade off of signatures, their means of stimulation, and methods of detection, will be reviewed.

Local ordering and magnetism in Ga{sub 0.9}Fe{sub 3.1}N

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

Burghaus, Jens; Sougrati, Moulay T., E-mail: moulay-tahar.sougrati@univ-montp2.fr; Moechel, Anne

Prior investigations of the ternary nitride series Ga{sub 1-x}Fe{sub 3+x}N (0{<=}x{<=}1) have indicated a transition from ferromagnetic {gamma}'-Fe{sub 4}N to antiferromagnetic 'GaFe{sub 3}N'. The ternary nitride 'GaFe{sub 3}N' has been magnetically and spectroscopically reinvestigated in order to explore the weakening of the ferromagnetic interactions through the gradual incorporation of gallium into {gamma}'-Fe{sub 4}N. A hysteretic loop at RT reveals the presence of a minority phase of only 0.1-0.2 at%, in accord with the sound two-step synthesis. The composition of the gallium-richest phase 'GaFe{sub 3}N' was clarified by Prompt Gamma-ray Activation Analysis and leads to the berthollide formula Ga{sub 0.91(1)}Fe{sub 3.09(10)}N{submore » 1.05(7)}. Magnetic measurements indicate a transition around 8 K, further supported by Moessbauer spectral data. The weakening of the ferromagnetic coupling through an increasing gallium concentration is explained by a simple Stoner argument. In Ga{sub 0.9}Fe{sub 3.1}N, the presence of iron on the gallium site affects the magnetism by the formation of 13-atom iron clusters. - Graphical Abstract: The crystal structure of GaFe{sub 3}N with green nitrogen atoms in the very center, red iron atoms at the face centers, and gray gallium atoms at the corner positions. Highlights: > Almost phase-pure synthesis of Ga{sub 0.9}Fe{sub 3.1}N. > Prompt gamma-ray activation analysis yields precise composition. > Magnetic ordering of the facial Fe atoms at the lowest temperatures. > Moessbauer spectroscopy suggests percolation or RKKY-type interaction. > Fe{sub 13} clusters due to berthollide character.« less

Identification and properties of the photospheric emission in GRB090902B

DOE PAGES

Ryde, F.; Axelsson, M.; Zhang, B. B.; ...

2010-01-14

We observed the Fermi Gamma-ray Space Telescope using the bright and long GRB090902B, lying at a redshift of z = 1.822. Together the Large Area Telescope (LAT) and the Gamma-ray Burst Monitor (GBM) cover the spectral range from 8 keV to >300 GeV. Here we show that the prompt burst spectrum is consistent with emission from the jet photosphere combined with nonthermal emission described by a single power law with photon index –1.9. The photosphere gives rise to a strong quasi-blackbody spectrum which is somewhat broader than a single Planck function and has a characteristic temperature of ~290 keV. Wemore » model the photospheric emission with a multicolor blackbody, and its shape indicates that the photospheric radius increases at higher latitudes. We derive the averaged photospheric radius R ph = (1.1 ± 0.3) × 10 12 Y 1/4 cm and the bulk Lorentz factor of the flow, which is found to vary by a factor of 2 and has a maximal value of Γ = 750 Y 1/4. Here, Y is the ratio between the total fireball energy and the energy emitted in the gamma rays. Here, we find that during the first quarter of the prompt phase the photospheric emission dominates, which explains the delayed onset of the observed flux in the LAT compared to the GBM. We also interpret the broadband emission as synchrotron emission at R ~ 4 × 10 15 cm. Our analysis emphasizes the importance of having high temporal resolution when performing spectral analysis on gamma-ray bursts, since there is strong spectral evolution.« less

Shear rupture of a directionally solidified eutectic gamma/gamma prime - alpha (Mo) alloy

NASA Technical Reports Server (NTRS)

Harf, F. H.

1978-01-01

Directionally solidified Mo alloys are evaluated to determine the shear rupture strength and to possibly improve it by microstructural and heat treatment variations. Bars of the alloy containing nominally 5.7% Al and 33.5% Mo by weight with balance Ni were directionally solidified at rates between 10 and 100 mm per hour in furnaces with thermal gradients at the liquid-solid interface of 250 or 100 C per cm. A limited number of longitudinal shear rupture tests were conducted at 760 C and 207 MPa in the as - solidified and in several heat treated conditions. It is shown that shear rupture failures are partly transgranular and that resistance to failure is prompted by good fiber alignment and a matrix structure consisting mainly of gamma prime. Well aligned as - solidified specimens sustained the shear stress for an average of 81 hours. A simulated coating heat treatment appeared to increase the transformation of gamma to gamma prime and raised the average shear life of aligned specimens to 111 hours. However, heat treatments at 1245 C and especially at 1190 C appeared to be detrimental by causing partial solutioning of the gamma prime, and reducing lives to 47 and 10 hours, respectively.

The Use of the BAT Instrument on SWIFT for the Detection of Prompt Gamma-Ray Emission from Novae

NASA Technical Reports Server (NTRS)

Skinner, Gerry; Senziani, Fabio; Jean, Pierre; Hernanz, Margarita

2007-01-01

Gamma-rays are expected to be emitted during and immediately following a nova explosion due to the annihilation of positrons emitted by freshly produced short-lived radioactive isotopes. The expected gammaray emission is relatively short-lived and as nova explosions are unpredictable, the best chance of detecting the gamma-rays is with n wide field instrument. At the time when the flux is expected to rcach its peak, most of the gamma-ray production is at depths such that the photons suffer several Compton scatterings before escaping, degrading their energy down to the hard X-ray band (10s of keV). SWIFT/BAT is a very wide field coded mask instrument working in the energy band 14-190 keV and so is very well suited to the search for such gamma-rays. A retrospective search is being made in the BAT data for evidence for gamma-ray emission from the direction of novae at around the time of their explosion. So far the only positive detection is of RS Ophiuchi and in this case the emission is probably due to shock heating.

Astrocytes contribute to gamma oscillations and recognition memory.

PubMed

Lee, Hosuk Sean; Ghetti, Andrea; Pinto-Duarte, António; Wang, Xin; Dziewczapolski, Gustavo; Galimi, Francesco; Huitron-Resendiz, Salvador; Piña-Crespo, Juan C; Roberts, Amanda J; Verma, Inder M; Sejnowski, Terrence J; Heinemann, Stephen F

2014-08-12

Glial cells are an integral part of functional communication in the brain. Here we show that astrocytes contribute to the fast dynamics of neural circuits that underlie normal cognitive behaviors. In particular, we found that the selective expression of tetanus neurotoxin (TeNT) in astrocytes significantly reduced the duration of carbachol-induced gamma oscillations in hippocampal slices. These data prompted us to develop a novel transgenic mouse model, specifically with inducible tetanus toxin expression in astrocytes. In this in vivo model, we found evidence of a marked decrease in electroencephalographic (EEG) power in the gamma frequency range in awake-behaving mice, whereas neuronal synaptic activity remained intact. The reduction in cortical gamma oscillations was accompanied by impaired behavioral performance in the novel object recognition test, whereas other forms of memory, including working memory and fear conditioning, remained unchanged. These results support a key role for gamma oscillations in recognition memory. Both EEG alterations and behavioral deficits in novel object recognition were reversed by suppression of tetanus toxin expression. These data reveal an unexpected role for astrocytes as essential contributors to information processing and cognitive behavior.

Off-axis emission of short γ-ray bursts and the detectability of electromagnetic counterparts of gravitational-wave-detected binary mergers

NASA Astrophysics Data System (ADS)

Lazzati, Davide; Deich, Alex; Morsony, Brian J.; Workman, Jared C.

2017-10-01

We present calculations of the wide angle emission of short-duration gamma-ray bursts from compact binary merger progenitors. Such events are expected to be localized by their gravitational wave emission, fairly irrespective of the orientation of the angular momentum vector of the system, along which the gamma-ray burst outflow is expected to propagate. We show that both the prompt and afterglow emission are dim and challenging to detect for observers lying outside the cone within which the relativistic outflow is propagating. If the jet initially propagates through a baryon contaminated region surrounding the merger site, however, a hot cocoon forms around it. The cocoon subsequently expands quasi-isotropically producing its own prompt emission and external shock powered afterglow. We show that the cocoon prompt emission is detectable by Swift BAT and Fermi GBM. We also show that the cocoon afterglow peaks a few hours to a few days after the burst and is detectable for up to a few weeks at all wavelengths. The timing and brightness of the transient are however uncertain due to their dependence on unknown quantities such as the density of the ambient medium surrounding the merger site, the cocoon energy and the cocoon Lorentz factor. For a significant fraction of the gravitationally detected neutron-star-binary mergers, the cocoon afterglow could possibly be the only identifiable electromagnetic counterpart, at least at radio and X-ray frequencies.

Fermi-LAT Gamma-Ray Bursts and Insights from Swift

NASA Technical Reports Server (NTRS)

Racusin, Judith L.

2010-01-01

A new revolution in Gamma-ray Burst (GRB) observations and theory has begun over the last two years since the launch of the Fermi Gamma-ray Space Telescope. The new window into high energy gamma-rays opened by the Fermi-Large Area Telescope (LAT) is providing insight into prompt emission mechanisms and possibly also afterglow physics. The LAT detected GRBs appear to be a new unique subset of extremely energetic and bright bursts compared to the large sample detected by Swift over the last 6 years. In this talk, I will discuss the context and recent discoveries from these LAT GRBs and the large database of broadband observations collected by the Swift X-ray Telescope (XRT) and UV/Optical Telescope (UVOT). Through comparisons between the GRBs detected by Swift-BAT, G8M, and LAT, we can learn about the unique characteristics, physical differences, and the relationships between each population. These population characteristics provide insight into the different physical parameters that contribute to the diversity of observational GRB properties.

In vivo prompt gamma neutron activation analysis for the screening of boron-10 distribution in a rabbit knee: a simulation study

NASA Astrophysics Data System (ADS)

Zhu, X.; Clackdoyle, R.; Shortkroff, S.; Yanch, J.

2008-05-01

Boron neutron capture synovectomy (BNCS) is under development as a potential treatment modality for rheumatoid arthritis (RA). RA is characterized by the inflammation of the synovium (the membrane lining articular joints), which leads to pain and a restricted range of motion. BNCS is a two-part procedure involving the injection of a boronated compound directly into the diseased joint followed by irradiation with a low-energy neutron beam. The neutron capture reactions taking place in the synovium deliver a local, high-linear energy transfer (LET) dose aimed at destroying the inflamed synovial membrane. For successful treatment via BNCS, a boron-labeled compound exhibiting both high synovial uptake and long retention time is necessary. Currently, the in vivo uptake behavior of potentially useful boronated compounds is evaluated in the knee joints of rabbits in which arthritis has been induced. This strategy involves the sacrifice and dissection of a large number of animals. An in vivo 10B screening approach is therefore under investigation with the goal of significantly reducing the number of animals needed for compound evaluation via dissection studies. The 'in vivo prompt gamma neutron activation analysis' (IVPGNAA) approach uses a narrow neutron beam to irradiate the knee from several angular positions following the intra-articular injection of a boronated compound whose uptake characteristics are unknown. A high-purity germanium detector collects the 478 keV gamma photons produced by the 10B capture reactions. The 10B distribution in the knee is then reconstructed by solving a system of simultaneous equations using a weighted least squares algorithm. To study the practical feasibility of IVPGNAA, simulation data were generated with the Monte Carlo N-particle transport code. The boron-containing region of a rabbit knee was partitioned into 8 compartments, and the 10B prompt gamma signals were tallied from 16 angular positions. Results demonstrate that for this level of spatial resolution, an estimate of 10B distribution inside the joint can be obtained to within 10% uncertainty, under ideal conditions. Variations of the anatomic dimensions among individual rabbit knees and potential knee positioning errors will result in an uncertainty of over 20%. IVPGNAA thus provides sufficient resolution and quantification regarding the in vivo uptake characteristics of boronated pharmaceuticals to serve as a useful means of screening new compounds of potential use in BNCS.

Afterglow Observations Shed New Light on the Nature of X-ray Flashes

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

Granot, J

X-ray flashes (XRFs) and X-ray rich gamma-ray bursts (XRGRBs) share many observational characteristics with long duration ({approx}> 2 s) GRBs, but the reason for which the spectral energy distribution of their prompt emission peaks at lower photon energies, E{sub p}, is still a subject of debate. Although many different models have been invoked in order to explain the lower values of E{sub p}, their implications for the afterglow emission were not considered in most cases, mainly because observations of XRF afterglows have become available only recently. Here we examine the predictions of the various XRF models for the afterglow emission,more » and test them against the observations of XRF 030723 and XRGRB 041006, the events with the best monitored afterglow light curves in their respective class. We show that most existing XRF models are hard to reconcile with the observed afterglow light curves, which are very flat at early times. Such light curves are, however, naturally produced by a roughly uniform jet with relatively sharp edges that is viewed off-axis (i.e. from outside of the jet aperture). This type of model self consistently accommodates both the observed prompt emission and the afterglow light curves of XRGRB 041006 and XRF 030723, implying viewing angles {theta}{sub obs} from the jet axis of ({theta}{sub obs}-{theta}{sub 0}) {approx} 0.15 {theta}{sub 0} and ({theta}{sub obs}-{theta}{sub 0}) {approx} {theta}{sub 0}, respectively, where {theta}{sub 0} {approx} 3{sup o} is the half-opening angle of the jet. This suggests that GRBs, XRGRBs and XRFs are intrinsically similar relativistic jets viewed from different angles. It is then natural to identify GRBs with {gamma}({theta}{sub obs} - {theta}{sub 0}) {approx}< 1, XRGRBs with 1 {approx}< ({theta}{sub obs} - {theta}{sub 0}) {approx}< a few, and XRFs with {gamma}({theta}{sub obs} - {theta}{sub 0}) {approx}> a few, where {gamma} is the Lorentz factor of the outflow near the edge of the jet from which most of the observed prompt emission arises. Future observations with Swift could help test this unification scheme in which GRBs, XRGRBs and XRFs share the same basic physics and differ only by their orientation relative to our line of sight.« less

Fermi-LAT View of Bright Flaring Gamma-Ray Blazars

NASA Astrophysics Data System (ADS)

Bastieri, D.; Ciprini, S.; Gasparrini, D.

2011-06-01

The Fermi LAT provides a continuous and uniform monitoring of the Universe in the gamma-ray band. During the first year many gamma-ray blazar flares, some unidentified transients and emission by the Sun while in a quiet state were promptly detected. This is mainly due to the design of the mission, featuring a detector, the LAT with a wide field of view, and to the operation of the spacecraft itself, that can cover every region of the sky every 3 hours. Nevertheless, the scientific exploitation of this monitoring is more fruitful when early information about transients reaches a broader community. In this respect, the indefatigable activity of flare advocates, who worked on weekly shifts to validate the results and quickly broadcast information about flares and new detections, was the key to most scientific results.

The Early Life Of A Gamma-ray Burst

NASA Astrophysics Data System (ADS)

O'Brien, P. T.; Willingale, D.

2006-09-01

We present results for 100 gamma-ray bursts observed promptly by the Swift satellite. Combining the early gamma-ray and X-ray data from the BAT and XRT, we show that although individual GRBs can display complex light curves, including a variety of decay phases and flares, their early emission can be described by a relatively simple combination of central engine activity and the interaction of a relativistic jet with the surrounding environment. We also discuss the later fading, which in the optical/IR has traditionally been explained as a jet-break. The Swift data reveal many bursts have a relatively early break in their X-ray light curves contradicting the standard jet break model derived from optical data. We discuss the implications of this for GRB jet models and for using GRBs as standard candles.

Gamma-Ray Bursts and Fast Transients. Multi-wavelength Observations and Multi-messenger Signals

NASA Astrophysics Data System (ADS)

Willingale, R.; Mészáros, P.

2017-07-01

The current status of observations and theoretical models of gamma-ray bursts and some other related transients, including ultra-long bursts and tidal disruption events, is reviewed. We consider the impact of multi-wavelength data on the formulation and development of theoretical models for the prompt and afterglow emission including the standard fireball model utilizing internal shocks and external shocks, photospheric emission, the role of the magnetic field and hadronic processes. In addition, we discuss some of the prospects for non-photonic multi-messenger detection and for future instrumentation, and comment on some of the outstanding issues in the field.

Enhancing the detector for advanced neutron capture experiments

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

Couture, A.; Mosby, S.; Baramsai, B.

2015-05-28

The Detector for Advanced Neutron Capture Experiments (DANCE) has been used for extensive studies of neutron capture, gamma decay, photon strength functions, and prompt and delayed fission-gamma emission. Despite these successes, the potential measurements have been limited by the data acquisition hardware. We, thus, report on a major upgrade of the DANCE data acquisition that simultaneously enables strait-forward coupling to auxiliary detectors, including high-resolution high-purity germanium detectors and neutron tagging array. Furthermore, the upgrade will enhance the time domain accessible for time-of-flight neutron measurements as well as improve the resolution in the DANCE barium fluoride crystals for photons.

The "Supercritical Pile" Model for GRB: Tapping the Proton Energy and Getting the v F(sub V) Peak at Approx. 1 MeV

NASA Technical Reports Server (NTRS)

Kazanas, D.; Georganopoulos, M.; Mastichladis, A.

2003-01-01

We propose a process by which the kinetic energy of the protons, that carry most of the energy of GRB relativistic blast waves (RBW) of Lorentz factor is converted explosively into relativistic electrons of the same Lorentz factor, which subsequently produce the observed prompt gamma-ray emission of the burst. This conversion is the result of the combined effects of the reflection of photons produced within the flow by upstream located matter, their re-interception and conversion into e(+) e(-) pairs on the RBW by the p gamma (right arrow) p e(+) e(-) reaction.

The Swift/Fermi GRB 080928 from 1 eV to 150 keV

NASA Technical Reports Server (NTRS)

Sonbas, Eda; Rossi, A.; Schulze, S.; Klose, S.; Kann, D. A.; Ferrero, P.; NicuesaGuelbenzu, A.; Rau, A.; Kruehler, T.; Greiner, J.;

Origin of the bright prompt optical emission in the naked eye burst

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

Hascoeet, R.; Daigne, F.; Mochkovitch, R.

The huge optical brightness of GRB 080319B (the 'Naked Eye Burst') makes this event really challenging for models of the prompt GRB emission. In the framework of the internal shock model, we investigate a scenario where the dominant radiative process is synchrotron emission and the high optical flux is due to the dynamical properties of the relativistic outflow : if the initial Lorentz factor distribution in the jet is highly variable, many internal shocks will form within the outflow at various radii. The most violent shocks will produce the main gamma-ray component while the less violent ones will contribute atmore » lower energy, including the optical range.« less

The Nuclear Weapons Effects National Enterprise

DTIC Science & Technology

2010-06-01

dependent on computers and electrical circuitry for effectiveness. The danger from radiation induced upset or burnout of improperly or unshielded...for Unmanned Systems Radiation Effect Thermal mechanical shock - X-ray Prompt X-ray/gamma dose rate - Rail-span collapse - Photoionization burnout ...event upset (SEU) or even single-event burnout . SEU results when enough ionization charge is deposited by a high-energy particle (natural or man

Conceptual design of the gamma-to-electron magnetic spectrometer for the National Ignition Facility

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

Kim, Y., E-mail: yhkim@lanl.gov; Herrmann, H. W.; Jorgenson, H. J.

2014-11-15

The Gamma-to-Electron Magnetic Spectrometer (GEMS) diagnostic is designed to measure the prompt γ-ray energy spectrum during high yield deuterium-tritium (DT) implosions at the National Ignition Facility (NIF). The prompt γ-ray spectrum will provide “burn-averaged” observables, including total DT fusion yield, total areal density (ρR), ablator ρR, and fuel ρR. These burn-averaged observables are unique because they are essentially averaged over 4π, providing a global reference for the line-of-sight-specific measurements typical of x-ray and neutron diagnostics. The GEMS conceptual design meets the physics-based requirements: ΔE/E = 3%–5% can be achieved in the range of 2–25 MeV γ-ray energy. Minimum DT neutronmore » yields required for 15% measurement uncertainty at low-resolution mode are: 5 × 10{sup 14} DT-n for ablator ρR (at 0.2 g/cm{sup 2}); 2 × 10{sup 15} DT-n for total DT yield (at 4.2 × 10{sup −5} γ/n); and 1 × 10{sup 16} DT-n for fuel ρR (at 1 g/cm{sup 2})« less

A Calibration to Predict the Concentrations of Impurities in Plutonium Oxide by Prompt Gamma Analysis Revision 2

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

Narlesky, Joshua Edward; Kelly, Elizabeth J.

2015-09-10

This report documents the new PG calibration regression equation. These calibration equations incorporate new data that have become available since revision 1 of “A Calibration to Predict the Concentrations of Impurities in Plutonium Oxide by Prompt Gamma Analysis” was issued [3] The calibration equations are based on a weighted least squares (WLS) approach for the regression. The WLS method gives each data point its proper amount of influence over the parameter estimates. This gives two big advantages, more precise parameter estimates and better and more defensible estimates of uncertainties. The WLS approach makes sense both statistically and experimentally because themore » variances increase with concentration, and there are physical reasons that the higher measurements are less reliable and should be less influential. The new magnesium calibration includes a correction for sodium and separate calibration equation for items with and without chlorine. These additional calibration equations allow for better predictions and smaller uncertainties for sodium in materials with and without chlorine. Chlorine and sodium have separate equations for RICH materials. Again, these equations give better predictions and smaller uncertainties chlorine and sodium for RICH materials.« less

GRB 080319B: A Naked-Eye Stellar Blast from the Distant Universe

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

Racusin, J. L.; Burrows, D. N.

On behalf of a large international collaboration [1], we present the unprecedented broadband observations of GRB 080319B, whose prompt optical emission peaked at a visual magnitude of 5.3, making it briefly visible with the naked eye. GRB 080319B was discovered by Swift and captured in exquisite detail by ground based wide-field telescopes, imaging the burst location from before the time of the explosion. The combination of these unique optical data with simultaneous {gamma}-ray observations provides powerful diagnostics of the detailed physics of this explosion within seconds of its formation. We show that the prompt optical and {gamma}-ray emissions from thismore » event arise from different spectral components within the same physical region located at a large distance from the source, implying an extremely relativistic outflow. Our observations also provide good evidence for a bright reverse shock component. The chromatic behavior of the broadband afterglow is consistent with viewing the GRB down the very narrow inner core of a two-component jet that is expanding into a wind-like environment consistent with the massive star origin of long GRBs.« less

Conceptual design of the gamma-to-electron magnetic spectrometer for the National Ignition Facility

DOE PAGES

Kim, Y.; Herrmann, H. W.; Jorgenson, H. J.; ...

2014-08-01

The Gamma-to-Electron Magnetic Spectrometer (GEMS) diagnostic is designed to measure the prompt γ-ray energy spectrum during high yield deuterium-tritium (DT) implosions at the National Ignition Facility (NIF). The prompt γ-ray spectrum will provide ‘burn-averaged’ observables, including total DT fusion yield, total areal density (ρR), ablator ρR, and fuel ρR. These burn-averaged observables are unique because they are essentially averaged over 4π, providing a global reference for the line-of-sight-specific measurements typical of x-ray and neutron diagnostics. The GEMS conceptual design meets the physics-based requirements: ΔE/E = 3 - 5% can be achieved in the range of 2 - 25 MeV γ-raymore » energy. Minimum DT neutron yields required for 15% measurement uncertainty at low-resolution mode are: 5×10 14 DT-n for ablator ρR (at 0.2 g/cm 2); 2×10 15 DT-n for total DT yield (at 4.2×10 -5γ /n); and 1×10 16 DT-n for fuel ρR (at 1 g/cm 2).« less

Application of proton boron fusion reaction to radiation therapy: A Monte Carlo simulation study

NASA Astrophysics Data System (ADS)

Yoon, Do-Kun; Jung, Joo-Young; Suh, Tae Suk

2014-12-01

Three alpha particles are emitted from the point of reaction between a proton and boron. The alpha particles are effective in inducing the death of a tumor cell. After boron is accumulated in the tumor region, the emitted from outside the body proton can react with the boron in the tumor region. An increase of the proton's maximum dose level is caused by the boron and only the tumor cell is damaged more critically. In addition, a prompt gamma ray is emitted from the proton boron reaction point. Here, we show that the effectiveness of the proton boron fusion therapy was verified using Monte Carlo simulations. We found that a dramatic increase by more than half of the proton's maximum dose level was induced by the boron in the tumor region. This increase occurred only when the proton's maximum dose point was located within the boron uptake region. In addition, the 719 keV prompt gamma ray peak produced by the proton boron fusion reaction was positively detected. This therapy method features the advantages such as the application of Bragg-peak to the therapy, the accurate targeting of tumor, improved therapy effects, and the monitoring of the therapy region during treatment.

The Ultra-long GRB 111209A. II. Prompt to Afterglow and Afterglow Properties

NASA Astrophysics Data System (ADS)

Stratta, G.; Gendre, B.; Atteia, J. L.; Boër, M.; Coward, D. M.; De Pasquale, M.; Howell, E.; Klotz, A.; Oates, S.; Piro, L.

2013-12-01

The "ultra-long" gamma-ray burst GRB 111209A at redshift z = 0.677 is the longest GRB ever observed thus far, with a rest frame prompt emission duration of ~4 hr. In order to explain the burst exceptional longevity, a low-metallicity blue supergiant progenitor was invoked. In this article we further constrain the phenomenology and progenitor properties of this peculiar GRB by performing a multiband temporal and spectral analysis of both the prompt and the afterglow emission. We use proprietary and publicly available data from Swift, Konus WIND, XMM-Newton, and TAROT, as well as from other ground-based optical and radio telescopes. We find some peculiar properties that are possibly connected to the exceptional nature of this burst, namely: (1) an unprecedented large optical delay of 410 ± 50 s between the peak time in gamma-rays and the peak time in the optical of a marked multiwavelength flare; (2) multiwavelength prompt emission spectral modeling requires a certain amount of dust in the circumburst environment. The dust produces a rest frame visual extinction of AV = 0.3-1.5 mag, and may undergo destruction at late times; and (3) we detect the presence of a hard spectral extra power-law component at the end of the X-ray steep steep decay phase and before the start of the X-ray afterglow, which has never been revealed thus far in past GRBs. The optical afterglow shows more usual properties; it has a flux power-law decay with an index of 1.6 ± 0.1 and a late rebrightening feature observed at ~1.1 the day after the first Burst Alert Telescope trigger. We discuss our findings in the context of several possible interpretations that have been given thus far of the complex multiband GRB phenomenology and propose a binary channel formation for the blue supergiant progenitor.

The bright optical afterglow of the nearby gamma-ray burst of 29 March 2003.

PubMed

Price, P A; Fox, D W; Kulkarni, S R; Peterson, B A; Schmidt, B P; Soderberg, A M; Yost, S A; Berger, E; Djorgovski, S G; Frail, D A; Harrison, F A; Sari, R; Blain, A W; Chapman, S C

2003-06-19

Past studies of cosmological gamma-ray bursts (GRBs) have been hampered by their extreme distances, resulting in faint afterglows. A nearby GRB could potentially shed much light on the origin of these events, but GRBs with a redshift z

Magnetic field and flavor effects on the gamma-ray burst neutrino flux

NASA Astrophysics Data System (ADS)

Baerwald, Philipp; Hümmer, Svenja; Winter, Walter

2011-03-01

We reanalyze the prompt muon neutrino flux from gamma-ray bursts (GRBs) in terms of the particle physics involved, as in the example of the often-used reference Waxman-Bahcall GRB flux. We first reproduce this reference flux explicitly treating synchrotron energy losses of the secondary pions. Then we include additional neutrino production modes, the neutrinos from muon decays, the magnetic field effects on all secondary species, and flavor mixing with the current parameter uncertainties. We demonstrate that the combination of these effects modifies the shape of the original Waxman-Bahcall GRB flux significantly and changes the normalization by a factor of 3 to 4. As a consequence, the gamma-ray burst search strategy of neutrino telescopes may be based on the wrong flux shape, and the constraints derived for the GRB neutrino flux, such as the baryonic loading, may in fact be much stronger than anticipated.

A question prompt list for patients with advanced cancer in the final year of life: development and cross-cultural evaluation.

PubMed

Walczak, Adam; Mazer, Benjamin; Butow, Phyllis N; Tattersall, Martin H N; Clayton, Josephine M; Davidson, Patricia M; Young, Jane; Ladwig, Susan; Epstein, Ronald M

2013-09-01

Clinicians and patients find prognosis and end-of-life care discussions challenging. Misunderstanding one's prognosis can contribute to poor decision-making and end-of-life quality of life. A question prompt list (booklet of questions patients can ask clinicians) targeting these issues may help overcome communication barriers. None exists for end-of-life discussions outside the palliative care setting. To develop/pilot a question prompt list facilitating discussion/planning of end-of-life care for oncology patients with advanced cancer from Australia and the United States and to explore acceptability, perceived benefits/challenges of using the question prompt list, suggestions for improvements and the necessity of country-specific adaptations. An expert panel developed a question prompt list targeting prognosis and end-of-life issues. Australian/US semi-structured interviews and one focus group elicited feedback about the question prompt list. Transcribed data were analysed using qualitative methods. Thirty-four patients with advanced cancer (15 Australian/19 US) and 13 health professionals treating such patients (7 Australian/6 US) from two Australian and one US cancer centre participated. Most endorsed the entire question prompt list, though a minority queried the utility/appropriateness of some questions. Analysis identified four global themes: (1) reinforcement of known benefits of question prompt lists, (2) appraisal of content and suggestions for further developments, (3) perceived benefits and challenges in using the question prompt list and (4) contrasts in Australian/US feedback. These contrasts necessitated distinct Australian/US final versions of the question prompt list. Participants endorsed the question prompt list as acceptable and useful. Feedback resulted in two distinct versions of the question prompt list, accommodating differences between Australian and US approaches to end-of-life discussions, highlighting the appropriateness of tailoring communication aides to individual populations.

Constraints on Short, Hard Gamma-Ray Burst Beaming Angles from Gravitational Wave Observations

NASA Astrophysics Data System (ADS)

Williams, D.; Clark, J. A.; Williamson, A. R.; Heng, I. S.

2018-05-01

The first detection of a binary neutron star merger, GW170817, and an associated short gamma-ray burst confirmed that neutron star mergers are responsible for at least some of these bursts. The prompt gamma-ray emission from these events is thought to be highly relativistically beamed. We present a method for inferring limits on the extent of this beaming by comparing the number of short gamma-ray bursts (SGRBs) observed electromagnetically with the number of neutron star binary mergers detected in gravitational waves. We demonstrate that an observing run comparable to the expected Advanced LIGO (aLIGO) 2016–2017 run would be capable of placing limits on the beaming angle of approximately θ \\in (2\\buildrel{\\circ}\\over{.} 88,14\\buildrel{\\circ}\\over{.} 15), given one binary neutron star detection, under the assumption that all mergers produce a gamma-ray burst, and that SGRBs occur at an illustrative rate of {{ \\mathcal R }}grb}=10 {Gpc}}-3 {yr}}-1. We anticipate that after a year of observations with aLIGO at design sensitivity in 2020, these constraints will improve to θ \\in (8\\buildrel{\\circ}\\over{.} 10,14\\buildrel{\\circ}\\over{.} 95), under the same efficiency and SGRB rate assumptions.

Very fast optical flaring from a possible new Galactic magnetar.

PubMed

Stefanescu, A; Kanbach, G; Słowikowska, A; Greiner, J; McBreen, S; Sala, G

2008-09-25

Highly luminous rapid flares are characteristic of processes around compact objects like white dwarfs, neutron stars and black holes. In the high-energy regime of X-rays and gamma-rays, outbursts with variabilities on timescales of seconds or less are routinely observed, for example in gamma-ray bursts or soft gamma-ray repeaters. At optical wavelengths, flaring activity on such timescales has not been observed, other than from the prompt phase of one exceptional gamma-ray burst. This is mostly due to the fact that outbursts with strong, fast flaring are usually discovered in the high-energy regime; most optical follow-up observations of such transients use instruments with integration times exceeding tens of seconds, which are therefore unable to resolve fast variability. Here we show the observation of extremely bright and rapid optical flaring in the Galactic transient SWIFT J195509.6+261406. Our optical light curves are phenomenologically similar to high-energy light curves of soft gamma-ray repeaters and anomalous X-ray pulsars, which are thought to be neutron stars with extremely high magnetic fields (magnetars). This suggests that similar processes are in operation, but with strong emission in the optical, unlike in the case of other known magnetars.

Imaging the Crab nebula when it is flaring in gamma-rays

NASA Astrophysics Data System (ADS)

De Luca, Andrea

2013-10-01

One of the most intriguing results of the gamma-ray instruments currently in orbit has been the detection of powerful flares from the Crab Nebula. Such events, detected roughly once per year, can be very spectacular. Indeed, in April 2011, for a few days the Crab was by far the brightest source in the gamma-ray sky. Such a dramatic variability challenges our understanding of how pulsar wind nebulae work and defies current astrophysical models for particle acceleration. With the aim of locating the site{s} of the flares, an ad hoc HST strategy must be put in place to be prepared and react promptly in case of a new brightening in gamma rays. We ask here for a triggered TOO observation of the Crab Nebula with ACS/WFC in case a gamma-ray flare is announced by the Agile and/or Fermi missions. This is a crucial part of a multiwavelength program that we are organizing, based on lessons learnt from our follow-up observations of previous flares, including a regular {monthly} monitoring of the source both in X-ray and optical through a joint Chandra-HST proposal.

Imaging the Crab nebula when it is flaring in gamma-rays

NASA Astrophysics Data System (ADS)

De Luca, Andrea

2014-10-01

One of the most intriguing results of the gamma-ray instruments currently in orbit has been the detection of powerful flares from the Crab Nebula. Such events, with a recurrence time of about once per year, can be so dramatic to make the system the brightest source in the gamma-ray sky, as it occurred in April 2011. Such a discovery challenges our understanding of how pulsar wind nebulae work and defies current astrophysical models for particle acceleration. With the aim of locating the site(s) of the flares, an ad hoc HST strategy have been put in place to be prepared and react promptly in case of a new brightening in gamma rays. We ask here for a triggered TOO observation of the Crab Nebula with ACS/WFC in case a gamma-ray flare is announced by the Agile and/or the Fermi missions. This TOO is crucial part of a multiwavelength program that we have organized, based on lessons learnt from our follow-up observations of previous flares, including a regular (quarterly) monitoring of the source both in X-rays and optical through a joint Chandra-HST proposal.

Induction and quantification of gammma-H2AX foci following cx- and gamma-irradiaton

NASA Technical Reports Server (NTRS)

Leatherbarrow, E. L.; Cucinotta, F. A.; O'Neill, Peter

2004-01-01

Following DNA damage the histone H2AX becomes phosphorylated and can be visualised by immunofluorescence as an indicator of DSBs in individual cells. Using a wild type hamster cell line (V79-4) exposed to either a-particles or to Co-60 gamma-rays to induce DNA DSBs at different doses (20-200OmGy), the dose dependent induction of gamma-H2AX foci were scored both manually (by eye) and using image analysis. A linearly dependence on dose was found for both radiations. The number of DSBs determined by image analysis after a post-irradiation period of 30 minutes at 37 C, is 16.6 foci/cell/Gy for alpha-irradiation and 12.2 foci/cell/Gy for gamma-irradiation; the latter being 3-4 times the levels observed by eye and comparable to gamma-radiation-induced levels of prompt DSBs more recently reported using pulse field gel electrophoresis (approx. 16 DSBs/Gy). The average size of the gamma-H2AX foci induced by alpha-irradiation (0.30 square micrometers) is approximately 1.5 times larger than those induced by gamma-irradiation (0.19 square micrometers). The timescale of induction and removal of DSBs up to 24 hours post-irradiation, was investigated with gamma-H2AX foci levels found to remain significantly higher than controls for 4 or 6 hours in gamma-irradiated samples or alpha irradiated samples, respectively. These results demonstrate that not only gamma radiation but also alpha-radiation induce phosphorylation of the H2AX histone in response to DSBs even at low doses (20mGy for gamma-rays, 1 track/cell on average for alpha-particles) and the variation in size and dephosphorylation of the induced foci is dependent on radiation quality (LET).

The Rapid Gamma-ray Burst Response Campaign with ROTSE

NASA Astrophysics Data System (ADS)

Balsano, R.; Bloch, J.; Casperson, D.; Fletcher, S.; Gisler, G.; Hills, J.; Priedhorsky, W.; Szymanski, J.; Wren, J.; Akerlof, C.; Kehoe, R.; McKay, T.; Pawl, A.; Marshall, S.; Lee, B.; Barthelmy, S.; Butterworth, P.; Cline, T.

2000-04-01

The main goal of the Robotic Optical Transient Search Experiment (ROTSE) is to detect optical emission from Gamma-ray Bursts (GRBs) during and immediately following GRBs. The instruments comprising ROTSE consist of wide-field optics on rapidly slewing mounts optimized for quick response to GRBs localized to several degree regions. Thus far, only one prompt optical counterpart to a GRB has been discovered although simple scaling arguments suggest more should be easily detected. This talk will cover ROTSE responses to GRBs detected by the Burst and Transient Source Experiment and the soon-to-be-launched High Energy Transient Experiment. The expansion of ROTSE to a global network of identical telescopes will also be briefly discussed.

NEUTRON PHYSICS DIVISION ANNUAL PROGRESS REPORT. Period Ending September 1, 1962

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

None

1963-01-11

A total of 74 subsections are included in the report. The information in 4 subsections was previously abstracted in NSA. Separate abstracts were prepared for 38 of the subsections. Those sections for which no abstracts were prepared contain information on prompt neutron lifetime, Rover critical experiments, Pu/sup 239/ fission, neutron decay, the O5R code, alpha scattering, 8 and P wavelengths, proton scattering, deuteron scattering, local optical potentials, N. S. Savamah radiation leakage, reactor shielding, cross section data analysis, gamma transport, gamma energy deposition, gaussian integration, data interpolation, neutron scattering, neutron energy deposition, space vehicles, computer analyses, shielding, positron sources, andmore » secondary particles. (J.R.D.)« less

Monte Carlo Simulations of Background Spectra in Integral Imager Detectors

NASA Technical Reports Server (NTRS)

Armstrong, T. W.; Colborn, B. L.; Dietz, K. L.; Ramsey, B. D.; Weisskopf, M. C.

1998-01-01

Predictions of the expected gamma-ray backgrounds in the ISGRI (CdTe) and PiCsIT (Csl) detectors on INTEGRAL due to cosmic-ray interactions and the diffuse gamma-ray background have been made using a coupled set of Monte Carlo radiation transport codes (HETC, FLUKA, EGS4, and MORSE) and a detailed, 3-D mass model of the spacecraft and detector assemblies. The simulations include both the prompt background component from induced hadronic and electromagnetic cascades and the delayed component due to emissions from induced radioactivity. Background spectra have been obtained with and without the use of active (BGO) shielding and charged particle rejection to evaluate the effectiveness of anticoincidence counting on background rejection.

Nuclear EMP simulation for large-scale urban environments. FDTD for electrically large problems.

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

Smith, William S.; Bull, Jeffrey S.; Wilcox, Trevor

2012-08-13

In case of a terrorist nuclear attack in a metropolitan area, EMP measurement could provide: (1) a prompt confirmation of the nature of the explosion (chemical or nuclear) for emergency response; and (2) and characterization parameters of the device (reaction history, yield) for technical forensics. However, urban environment could affect the fidelity of the prompt EMP measurement (as well as all other types of prompt measurement): (1) Nuclear EMP wavefront would no longer be coherent, due to incoherent production, attenuation, and propagation of gamma and electrons; and (2) EMP propagation from source region outward would undergo complicated transmission, reflection, andmore » diffraction processes. EMP simulation for electrically-large urban environment: (1) Coupled MCNP/FDTD (Finite-difference time domain Maxwell solver) approach; and (2) FDTD tends to be limited to problems that are not 'too' large compared to the wavelengths of interest because of numerical dispersion and anisotropy. We use a higher-order low-dispersion, isotropic FDTD algorithm for EMP propagation.« less

Prompting Technology and Persons With Dementia: The Significance of Context and Communication.

PubMed

Braley, Rachel; Fritz, Rochelle; Van Son, Catherine R; Schmitter-Edgecombe, Maureen

2018-06-12

Smart home auto-prompting has the potential to increase the functional independence of persons with dementia (PWDs) and decrease caregiver burden as instrumental activities of daily living (IADLs) are completed at home. To improve prompting technologies, we sought to inductively understand how PWDs responded to auto-prompting while performing IADL tasks. Fifteen PWDs completed eight IADLs in a smart home testbed and received a hierarchy of verbal auto-prompts (indirect, direct, multimodal) as needed for task completion. Two researchers viewed archived videos and recorded the observed behaviors of the PWDs and their reflections watching the PWDs. Using qualitative descriptive methods, an interdisciplinary analytic team reviewed transcripts and organized data into themes using content analysis. Context and Communication emerged as the major themes, suggesting that positive user experiences will require auto-prompting systems to account for a multitude of contextual factors (individual and environmental) such as level of cognitive impairment, previous exposure to task, and familiarity of environment. Communicating with another human rather than an automated prompting system may be important if individuals begin to exhibit signs of stress while completing activities. Additional work is needed to create auto-prompting systems that provide specific, personalized, and flexible prompts. Holistic conceptualization of "successful task completion" is needed and a positive end-user experience will be key to utility. Such systems will benefit from including positive reinforcement, training, and exploration of how, and whether, direct human involvement can be minimized during the provision of in-home care.

Evaluating the Effects of Gamma-Irradiation for Decontamination of Medicinal Cannabis.

PubMed

Hazekamp, Arno

2016-01-01

In several countries with a National medicinal cannabis program, pharmaceutical regulations specify that herbal cannabis products must adhere to strict safety standards regarding microbial contamination. Treatment by gamma irradiation currently seems the only method available to meet these requirements. We evaluated the effects of irradiation treatment of four different cannabis varieties covering different chemical compositions. Samples were compared before and after standard gamma-irradiation treatment by performing quantitative UPLC analysis of major cannabinoids, as well as qualitative GC analysis of full cannabinoid and terpene profiles. In addition, water content and microscopic appearance of the cannabis flowers was evaluated. This study found that treatment did not cause changes in the content of THC and CBD, generally considered as the most important therapeutically active components of medicinal cannabis. Likewise, the water content and the microscopic structure of the dried cannabis flowers were not altered by standard irradiation protocol in the cannabis varieties studied. The effect of gamma-irradiation was limited to a reduction of some terpenes present in the cannabis, but keeping the terpene profile qualitatively the same. Based on the results presented in this report, gamma irradiation of herbal cannabis remains the recommended method of decontamination, at least until other more generally accepted methods have been developed and validated.

Evaluating the Effects of Gamma-Irradiation for Decontamination of Medicinal Cannabis

PubMed Central

Hazekamp, Arno

2016-01-01

In several countries with a National medicinal cannabis program, pharmaceutical regulations specify that herbal cannabis products must adhere to strict safety standards regarding microbial contamination. Treatment by gamma irradiation currently seems the only method available to meet these requirements. We evaluated the effects of irradiation treatment of four different cannabis varieties covering different chemical compositions. Samples were compared before and after standard gamma-irradiation treatment by performing quantitative UPLC analysis of major cannabinoids, as well as qualitative GC analysis of full cannabinoid and terpene profiles. In addition, water content and microscopic appearance of the cannabis flowers was evaluated. This study found that treatment did not cause changes in the content of THC and CBD, generally considered as the most important therapeutically active components of medicinal cannabis. Likewise, the water content and the microscopic structure of the dried cannabis flowers were not altered by standard irradiation protocol in the cannabis varieties studied. The effect of gamma-irradiation was limited to a reduction of some terpenes present in the cannabis, but keeping the terpene profile qualitatively the same. Based on the results presented in this report, gamma irradiation of herbal cannabis remains the recommended method of decontamination, at least until other more generally accepted methods have been developed and validated. PMID:27199751

Broadband Study of GRB 091127: A Sub-energetic Burst at Higher Redshift?

NASA Astrophysics Data System (ADS)

Troja, E.; Sakamoto, T.; Guidorzi, C.; Norris, J. P.; Panaitescu, A.; Kobayashi, S.; Omodei, N.; Brown, J. C.; Burrows, D. N.; Evans, P. A.; Gehrels, N.; Marshall, F. E.; Mawson, N.; Melandri, A.; Mundell, C. G.; Oates, S. R.; Pal'shin, V.; Preece, R. D.; Racusin, J. L.; Steele, I. A.; Tanvir, N. R.; Vasileiou, V.; Wilson-Hodge, C.; Yamaoka, K.

2012-12-01

GRB 091127 is a bright gamma-ray burst (GRB) detected by Swift at a redshift z = 0.49 and associated with SN 2009nz. We present the broadband analysis of the GRB prompt and afterglow emission and study its high-energy properties in the context of the GRB/SN association. While the high luminosity of the prompt emission and standard afterglow behavior are typical of cosmological long GRBs, its low-energy release (E γ < 3 × 1049 erg), soft spectrum, and unusual spectral lag connect this GRB to the class of sub-energetic bursts. We discuss the suppression of high-energy emission in this burst, and investigate whether this behavior could be connected with the sub-energetic nature of the explosion.

Feasibility study of 235U and 239Pu characterization in radioactive waste drums using neutron-induced fission delayed gamma rays

NASA Astrophysics Data System (ADS)

Nicol, T.; Pérot, B.; Carasco, C.; Brackx, E.; Mariani, A.; Passard, C.; Mauerhofer, E.; Collot, J.

2016-10-01

This paper reports a feasibility study of 235U and 239Pu characterization in 225 L bituminized waste drums or 200 L concrete waste drums, by detecting delayed fission gamma rays between the pulses of a deuterium-tritium neutron generator. The delayed gamma yields were first measured with bare samples of 235U and 239Pu in REGAIN, a facility dedicated to the assay of 118 L waste drums by Prompt Gamma Neutron Activation Analysis (PGNAA) at CEA Cadarache, France. Detectability in the waste drums is then assessed using the MCNPX model of MEDINA (Multi Element Detection based on Instrumental Neutron Activation), another PGNAA cell dedicated to 200 L drums at FZJ, Germany. For the bituminized waste drum, performances are severely hampered by the high gamma background due to 137Cs, which requires the use of collimator and shield to avoid electronics saturation, these elements being very penalizing for the detection of the weak delayed gamma signal. However, for lower activity concrete drums, detection limits range from 10 to 290 g of 235U or 239Pu, depending on the delayed gamma rays of interest. These detection limits have been determined by using MCNPX to calculate the delayed gamma useful signal, and by measuring the experimental gamma background in MEDINA with a 200 L concrete drum mock-up. The performances could be significantly improved by using a higher interrogating neutron emission and an optimized experimental setup, which would allow characterizing nuclear materials in a wide range of low and medium activity waste packages.

Structural Origins of Scintillation: Metal Organic Frameworks as a Nanolaboratory

DTIC Science & Technology

2016-06-01

scintillation response and thus the ability to perform neutron/gamma particle discrimination via pulse-shape discrimination ( PSD ). Unfortunately, the...defined an alternative approach towards particle discrimination that addresses the limitations of conventional PSD organic scintillators. This approach...discrimination ( PSD ), for which the prompt component of the scintillation response is quenched for high specific energy loss (dE/dX) particles such as protons

Research program in nuclear and solid state physics

NASA Technical Reports Server (NTRS)

Stronach, C. E.

1973-01-01

The spectra of prompt gamma rays emitted following nuclear pion absorption were studied to determine the states of excited daughter nuclei, and the branching ratios for these states. Studies discussed include the negative pion absorption of C-12, S-32, and N-14; and the positive pion absorption on 0-16. Abstracts of papers submitted to the conference of the American Physical Society are included.

Optically Stimulated Luminescence Analysis Method for High Dose Rate Using an Optical Fiber Type Dosimeter

NASA Astrophysics Data System (ADS)

Ueno, Katsunori; Tominaga, Kazuo; Tadokoro, Takahiro; Ishizawa, Koji; Takahashi, Yoshinori; Kuwabara, Hitoshi

2016-08-01

The investigation of air dose rates at locations in the Fukushima Dai-ichi Nuclear Power Station is necessary for safe removal of the molten nuclear fuel. The target performance for the investigation is to analyze a dose rate in the range of 10-3 Gy/h to 102 Gy/h with a measurement precision of ±4.0% full scale (F.S.) at a measurement interval of 60 s. In order to achieve this target, the authors proposed an optically stimulated luminescence (OSL) analysis method using prompt OSL for a wide dynamic range of dose rates; the OSL is generated using BaFBr:Eu with a fast decay time constant. The luminescence intensity by prompt OSL was formulated by the electron concentration of the trapping state during gamma ray and stimulation light irradiations. The prototype OSL monitor using BaFBr:Eu was manufactured for investigation of prompt OSL and evaluation of the measurement precision. The time dependence of the luminescence intensity by prompt OSL was analyzed by irradiating the OSL sensor in a 60Co irradiation facility. The measured dose rates were obtained in a prompt mode and an accumulating mode with a precision of ±3.3% F.S. for the dose rate range of 9.5 ×10-4 Gy/h to 1.2 ×102 Gy/h.

A Monte Carlo Library Least Square approach in the Neutron Inelastic-scattering and Thermal-capture Analysis (NISTA) process in bulk coal samples

NASA Astrophysics Data System (ADS)

Reyhancan, Iskender Atilla; Ebrahimi, Alborz; Çolak, Üner; Erduran, M. Nizamettin; Angin, Nergis

2017-01-01

A new Monte-Carlo Library Least Square (MCLLS) approach for treating non-linear radiation analysis problem in Neutron Inelastic-scattering and Thermal-capture Analysis (NISTA) was developed. 14 MeV neutrons were produced by a neutron generator via the 3H (2H , n) 4He reaction. The prompt gamma ray spectra from bulk samples of seven different materials were measured by a Bismuth Germanate (BGO) gamma detection system. Polyethylene was used as neutron moderator along with iron and lead as neutron and gamma ray shielding, respectively. The gamma detection system was equipped with a list mode data acquisition system which streams spectroscopy data directly to the computer, event-by-event. A GEANT4 simulation toolkit was used for generating the single-element libraries of all the elements of interest. These libraries were then used in a Linear Library Least Square (LLLS) approach with an unknown experimental sample spectrum to fit it with the calculated elemental libraries. GEANT4 simulation results were also used for the selection of the neutron shielding material.

Development of a high-resolution liquid xenon detector for gamma-ray astrophysics

NASA Astrophysics Data System (ADS)

Mukherjee, Reshmi

It has been shown here that liquid xenon is one of the most promising detector media for future gamma-ray detectors, owing to an excellent combination of physical properties. The feasibility of the construction of a high resolution liquid xenon detector as a gamma-ray detector for astrophysics has been demonstrated. Up to 3.5 liters of liquid xenon has been successfully purified and using both small and large volume prototypes, the charge and the energy resolution response of such detectors to gamma-rays, internal conversion electrons and alpha particles have been measured. The best energy resolution measured was 4.5 percent FWHM at 1 MeV. Cosmic ray tracks have been imaged using a 2-dimensional liquid xenon multiwire imaging chamber. The spatial resolution along the direction of the drifting electrons was 180 microns rms. Experiments have been performed to study the scintillation light in liquid xenon, as the prompt scintillation signal in the liquid is an electron-ion pair in liquid krypton was measured for the first time with a pulsed ionization chamber to be 18.4 plus or minus 0.3 eV.

FAST OPTICAL VARIABILITY OF A NAKED-EYE BURST-MANIFESTATION OF THE PERIODIC ACTIVITY OF AN INTERNAL ENGINE

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

Beskin, G.; Karpov, S.; Bondar, S.

We imaged the position of the naked-eye burst, GRB080319B, before, during, and after its gamma-ray activity with sub-second temporal resolution using the TORTORA wide-field camera. The burst optical prompt emission, which reached 5.3 mag, has been detected, and its periodic optical variability has been discovered in the form of four equidistant flashes with a duration of several seconds. We also detected a strong correlation (r {approx} 0.82) between optical and gamma-ray light curves with a 2 s delay of the optical emission with respect to the gamma-ray emission. The revealed temporal structure of the optical light curve in comparison withmore » the gamma-ray light curve can be interpreted in the framework of the model of shell collisions in the ejecta containing a significant neutron component. All observed emission features reflect the non-stationary behavior of the burst internal engine-supposedly, a hyperaccreting solar-mass black hole formed in the collapse of a massive stellar core.« less

GRB 080503: IMPLICATIONS OF A NAKED SHORT GAMMA-RAY BURST DOMINATED BY EXTENDED EMISSION

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

Perley, D. A.; Metzger, B. D.; Butler, N. R.

We report on observations of GRB 080503, a short gamma-ray burst (GRB) with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike) in conjunction with a thorough comparison to other short Swift events. In spite of the prompt-emission brightness, however, the optical counterpart is extraordinarily faint, never exceeding 25 mag in deep observations starting at {approx}1 hr after the Burst Alert Telescope (BAT) trigger. The optical brightness peaks at {approx}1 day and then falls sharply in a manner similar to the predictions of Li and Paczynski (1998) for supernova-like emission following compact binary mergers. However,more » a shallow spectral index and similar evolution in X-rays inferred from Chandra observations are more consistent with an afterglow interpretation. The extreme faintness of this probable afterglow relative to the bright gamma-ray emission argues for a very low density medium surrounding the burst (a 'naked' GRB), consistent with the lack of a coincident host galaxy down to 28.5 mag in deep Hubble Space Telescope imaging. The late optical and X-ray peak could be explained by a slightly off-axis jet or by a refreshed shock. Our observations reinforce the notion that short GRBs generally occur outside regions of active star formation, but demonstrate that in some cases the luminosity of the extended prompt emission can greatly exceed that of the short spike, which may constrain theoretical interpretation of this class of events. This extended emission is not the onset of an afterglow, and its relative brightness is probably either a viewing-angle effect or intrinsic to the central engine itself. Because most previous BAT short bursts without observed extended emission are too faint for this signature to have been detectable even if it were present at typical level, conclusions based solely on the observed presence or absence of extended emission in the existing Swift sample are premature.« less

Radiation induced currents in mineral-insulated cables and in pick-up coils: model calculations and experimental verification in the BR1 reactor

NASA Astrophysics Data System (ADS)

Vermeeren, Ludo; Leysen, Willem; Brichard, Benoit

2018-01-01

Mineral-insulated (MI) cables and Low-Temperature Co-fired Ceramic (LTCC) magnetic pick-up coils are intended to be installed in various position in ITER. The severe ITER nuclear radiation field is expected to lead to induced currents that could perturb diagnostic measurements. In order to assess this problem and to find mitigation strategies models were developed for the calculation of neutron-and gamma-induced currents in MI cables and in LTCC coils. The models are based on calculations with the MCNPX code, combined with a dedicated model for the drift of electrons stopped in the insulator. The gamma induced currents can be easily calculated with a single coupled photon-electron MCNPX calculation. The prompt neutron induced currents requires only a single coupled neutron-photon-electron MCNPX run. The various delayed neutron contributions require a careful analysis of all possibly relevant neutron-induced reaction paths and a combination of different types of MCNPX calculations. The models were applied for a specific twin-core copper MI cable, for one quad-core copper cable and for silver conductor LTCC coils (one with silver ground plates in order to reduce the currents and one without such silver ground plates). Calculations were performed for irradiation conditions (neutron and gamma spectra and fluxes) in relevant positions in ITER and in the Y3 irradiation channel of the BR1 reactor at SCK•CEN, in which an irradiation test of these four test devices was carried out afterwards. We will present the basic elements of the models and show the results of all relevant partial currents (gamma and neutron induced, prompt and various delayed currents) in BR1-Y3 conditions. Experimental data will be shown and analysed in terms of the respective contributions. The tests were performed at reactor powers of 350 kW and 1 MW, leading to thermal neutron fluxes of 1E11 n/cm2s and 3E11 n/cm2s, respectively. The corresponding total radiation induced currents are ranging from 1 to 7 nA only, putting a challenge on the acquisition system and on the data analysis. The detailed experimental results will be compared with the corresponding values predicted by the model. The overall agreement between the experimental data and the model predictions is fairly good, with very consistent data for the main delayed current components, while the lower amplitude delayed currents and some of the prompt contributions show some minor discrepancies.

Prospective Teachers' Metaphorical Conceptualizations of Learner

ERIC Educational Resources Information Center

Saban, Ahmet

2010-01-01

This study investigated the metaphorical images that prospective teachers in Turkey formulated to describe learners. Participants (N = 2847) completed the prompt "A student is like ... because ..." to indicate their conceptualizations of learner. Data were analyzed both qualitatively and quantitatively. Altogether 98 well-articulated…

DNA EMP Awareness Course Notes. Supplement to Third Edition.

DTIC Science & Technology

1978-07-31

UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) REPORT DOCUMENTATION PAGE READ INSTRUCTIONS BEFORE COMPLETING FORM I REPORT...the environment through system design and testing. FORM 143 E,,N F’NOV 65 IS OBSOLETE DD JAN73 1473 EDITION OF UNCLASSIFIED SECURITY CLASSIFICATION OF...fields generated tems mission and deployment factors by the prompt gammas. Other forms of EMP, where these environments should be con- such as

Compton Camera and Prompt Gamma Ray Timing: Two Methods for In Vivo Range Assessment in Proton Therapy

PubMed Central

Hueso-González, Fernando; Fiedler, Fine; Golnik, Christian; Kormoll, Thomas; Pausch, Guntram; Petzoldt, Johannes; Römer, Katja E.; Enghardt, Wolfgang

2016-01-01

Proton beams are promising means for treating tumors. Such charged particles stop at a defined depth, where the ionization density is maximum. As the dose deposit beyond this distal edge is very low, proton therapy minimizes the damage to normal tissue compared to photon therapy. Nevertheless, inherent range uncertainties cast doubts on the irradiation of tumors close to organs at risk and lead to the application of conservative safety margins. This constrains significantly the potential benefits of protons over photons. In this context, several research groups are developing experimental tools for range verification based on the detection of prompt gammas, a nuclear by-product of the proton irradiation. At OncoRay and Helmholtz-Zentrum Dresden-Rossendorf, detector components have been characterized in realistic radiation environments as a step toward a clinical Compton camera. On the one hand, corresponding experimental methods and results obtained during the ENTERVISION training network are reviewed. On the other hand, a novel method based on timing spectroscopy has been proposed as an alternative to collimated imaging systems. The first tests of the timing method at a clinical proton accelerator are summarized, its applicability in a clinical environment for challenging the current safety margins is assessed, and the factors limiting its precision are discussed. PMID:27148473

A Global Photoionization Response to Prompt Emission and Outliers: Different Origin of Long Gamma-ray Bursts?

NASA Astrophysics Data System (ADS)

Wang, J.; Xin, L. P.; Qiu, Y. L.; Xu, D. W.; Wei, J. Y.

2018-03-01

By using the line ratio C IV λ1549/C II λ1335 as a tracer of the ionization ratio of the interstellar medium (ISM) illuminated by a long gamma-ray burst (LGRB), we identify a global photoionization response of the ionization ratio to the photon luminosity of the prompt emission assessed by either L iso/E peak or {L}iso}/{E}peak}2. The ionization ratio increases with both L iso/E peak and L iso/E 2 peak for a majority of the LGRBs in our sample, although there are a few outliers. The identified dependence of C IV/C II on {L}iso}/{E}peak}2 suggests that the scatter of the widely accepted Amati relation is related to the ionization ratio in the ISM. The outliers tend to have relatively high C IV/C II values as well as relatively high C IV λ1549/Si IV λ1403 ratios, which suggests an existence of Wolf–Rayet stars in the environment of these LGRBs. We finally argue that the outliers and the LGRBs following the identified C IV/C II‑L iso/E peak ({L}iso}/{E}peak}2) correlation might come from different progenitors with different local environments.

Application of proton boron fusion reaction to radiation therapy: A Monte Carlo simulation study

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

Yoon, Do-Kun; Jung, Joo-Young; Suh, Tae Suk, E-mail: suhsanta@catholic.ac.kr

2014-12-01

Three alpha particles are emitted from the point of reaction between a proton and boron. The alpha particles are effective in inducing the death of a tumor cell. After boron is accumulated in the tumor region, the emitted from outside the body proton can react with the boron in the tumor region. An increase of the proton's maximum dose level is caused by the boron and only the tumor cell is damaged more critically. In addition, a prompt gamma ray is emitted from the proton boron reaction point. Here, we show that the effectiveness of the proton boron fusion therapymore » was verified using Monte Carlo simulations. We found that a dramatic increase by more than half of the proton's maximum dose level was induced by the boron in the tumor region. This increase occurred only when the proton's maximum dose point was located within the boron uptake region. In addition, the 719 keV prompt gamma ray peak produced by the proton boron fusion reaction was positively detected. This therapy method features the advantages such as the application of Bragg-peak to the therapy, the accurate targeting of tumor, improved therapy effects, and the monitoring of the therapy region during treatment.« less

SWIFT Discovery of Gamma-ray Bursts without Jet Break Feature in their X-ray Afterglows

NASA Technical Reports Server (NTRS)

Sato, G.; Yamazaki, R.; Sakamoto, T.; Takahashi, T; Nakazawa, K.; Nakamura, T.; Toma, K.; Hullinger, D.; Tashiro, M.; Parsons, A. M.;

A Team Approach to the Development of Gamma Ray and x Ray Remote Sensing and in Situ Spectroscopy for Planetary Exploration Missions

NASA Technical Reports Server (NTRS)

Trombka, J. I.; Floyd, S.; Ruitberg, A.; Evans, L.; Starr, R.; Metzger, A.; Reedy, R.; Drake, D.; Moss, C.; Edwards, B.

1993-01-01

An important part of the investigation of planetary origin and evolution is the determination of the surface composition of planets, comets, and asteroids. Measurements of discrete line X-ray and gamma ray emissions from condensed bodies in space can be used to obtain both qualitative and quantitative elemental composition information. The Planetary Instrumentation Definition and Development Program (PIDDP) X-Ray/Gamma Ray Team has been established to develop remote sensing and in situ technologies for future planetary exploration missions.

HPGe detector shielding optimization with MCNPX for the MEDINA PGNAA cell

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

Nicol, T.; Perot, B.; Carasco, C.

2015-07-01

Radioactive waste repositories must guarantee the non-toxicity of the waste in the long term, not only regarding radioactivity but also regarding other environmental contamination such as toxic chemicals. Analytical methods already exist for chemical characterization (ICP-MS, ICP-AES...) but they are based on test sampling. A possible alternative, for waste packages with an appropriate gamma radiation level, is to use Prompt Gamma Neutron Activation Analysis (PGNAA), a non-destructive measurement technique sensitive to several toxic chemicals. In view of the characterization of radioactive wastes in Germany and France, collaboration between the CEA Cadarache (France) and the Forschungszentrum Juelich (Germany) was initiated amore » few years ago. FZJ holds a PGNAA graphite cell called MEDINA (Multi Element Detection based on Instrumental Neutron Activation), allowing the characterization of 225 L drums. Fast neutrons are emitted from a D-T pulsed 14 MeV neutron generator and thermalized in graphite to induced radiative captures in the waste materials. Prompt capture gamma rays are detected using a 104% relative efficiency n-type HPGe. However, HPGe crystal is sensitive to fast neutron damage and to thermal neutron activation. A thermal neutron shield made of lithium fluorine and lithium carbonate is already used around the detector. In order to further decrease the current of fast and thermal neutrons coming into the crystal without penalizing MEDINA sensitivity (by decreasing the thermal neutron flux and neutron die away time of the cell, the gamma detection efficiency, or increasing the gamma background), some configurations based on easy-to-implement modifications of MEDINA have been simulated with MCNPX with a model of the cell already validated by experiments. Results show that fast and thermal neutron incoming current in the HPGe could easily be reduced by about a factor of 2 by additional quantities of graphite and by replacing lithium carbonate by lithium fluorine with a higher {sup 6}Li concentration. In addition, these modifications slightly increase the thermal neutron flux in the cell without deteriorating the neutron die away time, and reduce the gamma background about a factor of 2 during the neutron pulse but 5 times less after it. More important changes have also been tested, such as the addition of polyethylene and lead between the neutron generator and the HPGe detector, which is more effective regarding neutron shielding but decreases the neutron die away time, partly compensated by a larger initial thermal neutron flux. Concerning gamma background, hydrogen capture gamma ray (2.23 MeV) is increased due to the presence of polyethylene but lead around the HPGe decreases the total gamma background. In conclusion, simple modifications are possible to improve detector shielding and life time before thermal annealing of the crystal, without reducing MEDINA cell performances. Some of these modifications will be tested in the coming months. (authors)« less

Dependence of the prompt fission γ-ray spectrum on the entrance channel of compound nucleus: Spontaneous vs. neutron-induced fission

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

Chyzh, A.; Jaffke, P.; Wu, C. Y.

Prompt γ-ray spectra were measured for the spontaneous fission of 240,242Pu and the neutron-induced fission of 239,241Pu with incident neutron energies ranging from thermal to about 100 keV. Measurements were made using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments using a parallel-plate avalanche counter. The unfolded prompt fission γ-ray energy spectra can be reproduced reasonably well by Monte Carlo Hauser–Feshbach statistical model for the neutron-induced fission channel but not for the spontaneous fission channel. However, this entrance-channel dependence of the prompt fission γ-ray emission can be described qualitatively by themore » model due to the very different fission-fragment mass distributions and a lower average fragment spin for spontaneous fission. The description of measurements and the discussion of results under the framework of a Monte Carlo Hauser–Feshbach statistical approach are presented.« less

Dependence of the prompt fission γ-ray spectrum on the entrance channel of compound nucleus: Spontaneous vs. neutron-induced fission

DOE PAGES

Chyzh, A.; Jaffke, P.; Wu, C. Y.; ...

2018-06-07

Prompt γ-ray spectra were measured for the spontaneous fission of 240,242Pu and the neutron-induced fission of 239,241Pu with incident neutron energies ranging from thermal to about 100 keV. Measurements were made using the Detector for Advanced Neutron Capture Experiments (DANCE) array in coincidence with the detection of fission fragments using a parallel-plate avalanche counter. The unfolded prompt fission γ-ray energy spectra can be reproduced reasonably well by Monte Carlo Hauser–Feshbach statistical model for the neutron-induced fission channel but not for the spontaneous fission channel. However, this entrance-channel dependence of the prompt fission γ-ray emission can be described qualitatively by themore » model due to the very different fission-fragment mass distributions and a lower average fragment spin for spontaneous fission. The description of measurements and the discussion of results under the framework of a Monte Carlo Hauser–Feshbach statistical approach are presented.« less

Broadband Study of GRB 091127: A Sub-Energetic Burst at Higher Redshift?

DOE PAGES

Troja, E.; Sakamoto, T.; Guidorzi, C.; ...

2012-11-21

GRB 091127 is a bright gamma-ray burst (GRB) detected by Swift at a redshift z = 0.49 and associated with SN 2009nz. In this paper, we present the broadband analysis of the GRB prompt and afterglow emission and study its high-energy properties in the context of the GRB/SN association. While the high luminosity of the prompt emission and standard afterglow behavior are typical of cosmological long GRBs, its low-energy release (E γ < 3 x 10 49 erg), soft spectrum, and unusual spectral lag connect this GRB to the class of sub-energetic bursts. Finally, we discuss the suppression of high-energymore » emission in this burst, and investigate whether this behavior could be connected with the sub-energetic nature of the explosion.« less

Current status of SK-Gd project and EGADS

NASA Astrophysics Data System (ADS)

Xu, Chenyuan; Super-Kamiokande Collaboration

2016-05-01

Supernova Relic Neutrino (SRN) has not been observed yet because of its low event rate and high background. By adding gadolinium into water Cherenkov detector, inverse beta decay will have two signals, the prompt one is positron signal and the delayed one is a ~8 MeV gamma cascade from neutron capture on gadolinium. By this way, background for SRN can be largely reduced by detecting prompt and delayed signals coincidently, and Super-K will also have the ability to distinguish neutrino and anti-neutrino. SK-Gd is a R&D project proposed to dissolve gadolinium into Super-K. As a part of it, EGADS, a 200 ton water Cherenkov detector was built in Kamioka mine. Current status of SK-Gd project and the physics work being performed in EGADS will be presented here.

Feasibility study for measurement of insulation compaction in the cryogenic rocket fuel storage tanks at Kennedy Space Center by fast/thermal neutron techniques

NASA Astrophysics Data System (ADS)

Livingston, R. A.; Schweitzer, J. S.; Parsons, A. M.; Arens, E. E.

2014-02-01

The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Some of the perlite may have compacted over time, compromising the thermal performance and also the structural integrity of the tanks. Neutrons can readily penetrate through the 1.75 cm outer steel shell and through the entire 120 cm thick perlite zone. Neutrons interactions with materials produce characteristic gamma rays which are then detected. In compacted perlite the count rates in the individual peaks in the gamma ray spectrum will increase. Portable neutron generators can produce neutron simultaneous fluxes in two energy ranges: fast (14 MeV) and thermal (25 meV). Fast neutrons produce gamma rays by inelastic scattering which is sensitive to Si, Al, Fe and O. Thermal neutrons produce gamma rays by radiative capture in prompt gamma neutron activation (PGNA), which is sensitive to Si, Al, Na, K and H among others. The results of computer simulations using the software MCNP and measurements on a test article suggest that the most promising approach would be to operate the system in time-of-flight mode by pulsing the neutron generator and observing the subsequent die away curve in the PGNA signal.

Effect of Gamma Ray Irradiation on Interlaminar Shear Strength of Glass Fiber Reinforced Plastics at 77 K

NASA Astrophysics Data System (ADS)

Nishimura, A.; Nishijima, S.; Izumi, Y.

2008-03-01

It is known that an organic material is damaged by gamma ray irradiation, and the strength after irradiation has dependence on the gamma ray dose. These issues are important not only to make global understanding of electric insulating performance of glass fiber reinforced plastics (GFRP) under irradiation condition but also to develop new insulation materials. This paper presents the dependence of fracture mode and interlaminar shear strength (ILSS) on the material and the gamma ray irradiation effect on the fracture mode and the ILSS. 6 mm radius loading nose and supports were used to prompt ILS fracture for a short beam test. A 2.5 mm thick small specimen machined out of a 13 mm thick G-10CR GFRP plate (sliced specimen) showed lower ILSS and translaminar shear (TLS) fracture, although the same size specimen prepared from a 2.5 mm G-10CR GFRP plate (non-sliced specimen) showed ILS fracture and the higher ILSS. Both type of specimens showed the degradation of ILSS after gamma ray irradiation. The fracture mode of the non-sliced specimen changed from ILS to TLS fracture and no bending fracture was observed. The resistance to shear deformation of glass cloth/epoxy laminate structure would be damaged by the irradiation.

High and low energy gamma beam dump designs for the gamma beam delivery system at ELI-NP

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

Yasin, Zafar, E-mail: zafar.yasin@eli-np.ro; Matei, Catalin; Ur, Calin A.

The Extreme Light Infrastructure - Nuclear Physics (ELI-NP) is under construction in Magurele, Bucharest, Romania. The facility will use two 10 PW lasers and a high intensity, narrow bandwidth gamma beam for stand-alone and combined laser-gamma experiments. The accurate estimation of particle doses and their restriction within the limits for both personel and general public is very important in the design phase of any nuclear facility. In the present work, Monte Carlo simulations are performed using FLUKA and MCNPX to design 19.4 and 4 MeV gamma beam dumps along with shielding of experimental areas. Dose rate contour plots from both FLUKAmore » and MCNPX along with numerical values of doses in experimental area E8 of the facility are performed. The calculated doses are within the permissible limits. Furthermore, a reasonable agreement between both codes enhances our confidence in using one or both of them for future calculations in beam dump designs, radiation shielding, radioactive inventory, and other calculations releated to radiation protection. Residual dose rates and residual activity calculations are also performed for high-energy beam dump and their effect is negligible in comparison to contributions from prompt radiation.« less

The background model in the energy range from 0.1 MeV up to several MeV for low altitude and high inclination satellites.

NASA Astrophysics Data System (ADS)

Arkhangelskaja, I. V.; Arkhangelskiy, A. I.

2016-02-01

The gamma-ray background physical origin for low altitude orbits defined by: diffuse cosmic gamma-emission, atmospheric gamma-rays, gamma-emission formed in interactions of charged particles (both prompt and activation) and transient events such as electrons precipitations and solar flares. The background conditions in the energy range from 0.1 MeV up to several MeV for low altitude orbits differ due to frequency of Earth Radiation Belts - ERBs (included South Atlantic Anomaly - SAA) passes and cosmic rays rigidity. The detectors and satellite constructive elements are activated by trapped in ERBs and moving along magnetic lines charged particles. In this case we propose simplified polynomial model separately for polar and equatorial orbits parts: background count rate temporal profile approximation by 4-5 order polynomials in equatorial regions, and linear approximations, parabolas or constants in polar caps. The polynomials’ coefficients supposed to be similar for identical spectral channels for each analyzed equatorial part taken into account normalization coefficients defined due to Kp-indexes study within period corresponding to calibration coefficients being approximately constants. The described model was successfully applied for the solar flares hard X-ray and gamma-ray emission characteristic studies by AVS-F apparatus data onboard CORONAS-F satellite.

High-energy Neutrino Emission from Short Gamma-Ray Bursts: Prospects for Coincident Detection with Gravitational Waves

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

Kimura, Shigeo S.; Murase, Kohta; Mészáros, Peter

We investigate current and future prospects for coincident detection of high-energy neutrinos and gravitational waves (GWs). Short gamma-ray bursts (SGRBs) are believed to originate from mergers of compact star binaries involving neutron stars. We estimate high-energy neutrino fluences from prompt emission, extended emission (EE), X-ray flares, and plateau emission, and we show that neutrino signals associated with the EE are the most promising. Assuming that the cosmic-ray loading factor is ∼10 and the Lorentz factor distribution is lognormal, we calculate the probability of neutrino detection from EE by current and future neutrino detectors, and we find that the quasi-simultaneous detectionmore » of high-energy neutrinos, gamma-rays, and GWs is possible with future instruments or even with current instruments for nearby SGRBs having EE. We also discuss stacking analyses that will also be useful with future experiments such as IceCube-Gen2.« less

Gamma neutron assay method and apparatus

DOEpatents

Cole, J.D.; Aryaeinejad, R.; Greenwood, R.C.

1995-01-03

The gamma neutron assay technique is an alternative method to standard safeguards techniques for the identification and assaying of special nuclear materials in a field or laboratory environment, as a tool for dismantlement and destruction of nuclear weapons, and to determine the isotopic ratios for a blend-down program on uranium. It is capable of determining the isotopic ratios of fissionable material from the spontaneous or induced fission of a sample to within approximately 0.5%. This is based upon the prompt coincidence relationships that occur in the fission process and the proton conservation and quasi-conservation of nuclear mass (A) that exists between the two fission fragments. The system is used in both passive (without an external neutron source) and active (with an external neutron source) mode. The apparatus consists of an array of neutron and gamma-ray detectors electronically connected to determine coincident events. The method can also be used to assay radioactive waste which contains fissile material, even in the presence of a high background radiation field. 7 figures.

Gamma neutron assay method and apparatus

DOEpatents

Cole, Jerald D.; Aryaeinejad, Rahmat; Greenwood, Reginald C.

1995-01-01

The gamma neutron assay technique is an alternative method to standard safeguards techniques for the identification and assaying of special nuclear materials in a field or laboratory environment, as a tool for dismantlement and destruction of nuclear weapons, and to determine the isotopic ratios for a blend-down program on uranium. It is capable of determining the isotopic ratios of fissionable material from the spontaneous or induced fission of a sample to within approximately 0.5%. This is based upon the prompt coincidence relationships that occur in the fission process and the proton conservation and quasi-conservation of nuclear mass (A) that exists between the two fission fragments. The system is used in both passive (without an external neutron source and active (with an external neutron source) mode. The apparatus consists of an array of neutron and gamma-ray detectors electronically connected to determine coincident events. The method can also be used to assay radioactive waste which contains fissile material, even in the presence of a high background radiation field.

An infrared flash contemporaneous with the gamma-rays of GRB 041219a.

PubMed

Blake, C H; Bloom, J S; Starr, D L; Falco, E E; Skrutskie, M; Fenimore, E E; Duchêne, G; Szentgyorgyi, A; Hornstein, S; Prochaska, J X; McCabe, C; Ghez, A; Konopacky, Q; Stapelfeldt, K; Hurley, K; Campbell, R; Kassis, M; Chaffee, F; Gehrels, N; Barthelmy, S; Cummings, J R; Hullinger, D; Krimm, H A; Markwardt, C B; Palmer, D; Parsons, A; McLean, K; Tueller, J

2005-05-12

The explosion that results in a cosmic gamma-ray burst (GRB) is thought to produce emission from two physical processes: the central engine gives rise to the high-energy emission of the burst through internal shocking, and the subsequent interaction of the flow with the external environment produces long-wavelength afterglows. Although observations of afterglows continue to refine our understanding of GRB progenitors and relativistic shocks, gamma-ray observations alone have not yielded a clear picture of the origin of the prompt emission nor details of the central engine. Only one concurrent visible-light transient has been found and it was associated with emission from an external shock. Here we report the discovery of infrared emission contemporaneous with a GRB, beginning 7.2 minutes after the onset of GRB 041219a (ref. 8). We acquired 21 images during the active phase of the burst, yielding early multi-colour observations. Our analysis of the initial infrared pulse suggests an origin consistent with internal shocks.

An optical spectrum of the afterglow of a gamma-ray burst at a redshift of z = 6.295.

PubMed

Kawai, N; Kosugi, G; Aoki, K; Yamada, T; Totani, T; Ohta, K; Iye, M; Hattori, T; Aoki, W; Furusawa, H; Hurley, K; Kawabata, K S; Kobayashi, N; Komiyama, Y; Mizumoto, Y; Nomoto, K; Noumaru, J; Ogasawara, R; Sato, R; Sekiguchi, K; Shirasaki, Y; Suzuki, M; Takata, T; Tamagawa, T; Terada, H; Watanabe, J; Yatsu, Y; Yoshida, A

2006-03-09

The prompt gamma-ray emission from gamma-ray bursts (GRBs) should be detectable out to distances of z > 10 (ref. 1), and should therefore provide an excellent probe of the evolution of cosmic star formation, reionization of the intergalactic medium, and the metal enrichment history of the Universe. Hitherto, the highest measured redshift for a GRB has been z = 4.50 (ref. 5). Here we report the optical spectrum of the afterglow of GRB 050904 obtained 3.4 days after the burst; the spectrum shows a clear continuum at the long-wavelength end of the spectrum with a sharp cut-off at around 9,000 A due to Lyman alpha absorption at z approximately 6.3 (with a damping wing). A system of absorption lines of heavy elements at z = 6.295 +/- 0.002 was also detected, yielding the precise measurement of the redshift. The Si ii fine-structure lines suggest a dense, metal-enriched environment around the progenitor of the GRB.

Early X-Ray Flares in GRBs

NASA Astrophysics Data System (ADS)

Ruffini, R.; Wang, Y.; Aimuratov, Y.; Barres de Almeida, U.; Becerra, L.; Bianco, C. L.; Chen, Y. C.; Karlica, M.; Kovacevic, M.; Li, L.; Melon Fuksman, J. D.; Moradi, R.; Muccino, M.; Penacchioni, A. V.; Pisani, G. B.; Primorac, D.; Rueda, J. A.; Shakeri, S.; Vereshchagin, G. V.; Xue, S.-S.

2018-01-01

We analyze the early X-ray flares in the GRB “flare–plateau–afterglow” (FPA) phase observed by Swift-XRT. The FPA occurs only in one of the seven GRB subclasses: the binary-driven hypernovae (BdHNe). This subclass consists of long GRBs with a carbon–oxygen core and a neutron star (NS) binary companion as progenitors. The hypercritical accretion of the supernova (SN) ejecta onto the NS can lead to the gravitational collapse of the NS into a black hole. Consequently, one can observe a GRB emission with isotropic energy {E}{iso}≳ {10}52 erg, as well as the associated GeV emission and the FPA phase. Previous work had shown that gamma-ray spikes in the prompt emission occur at ∼ {10}15{--}{10}17 cm with Lorentz Gamma factors {{Γ }}∼ {10}2{--}{10}3. Using a novel data analysis, we show that the time of occurrence, duration, luminosity, and total energy of the X-ray flares correlate with E iso. A crucial feature is the observation of thermal emission in the X-ray flares that we show occurs at radii ∼1012 cm with {{Γ }}≲ 4. These model-independent observations cannot be explained by the “fireball” model, which postulates synchrotron and inverse-Compton radiation from a single ultrarelativistic jetted emission extending from the prompt to the late afterglow and GeV emission phases. We show that in BdHNe a collision between the GRB and the SN ejecta occurs at ≃1010 cm, reaching transparency at ∼1012 cm with {{Γ }}≲ 4. The agreement between the thermal emission observations and these theoretically derived values validates our model and opens the possibility of testing each BdHN episode with the corresponding Lorentz Gamma factor.

Multi-wavelength Observations of GRB 111228A and Implications for the Fireball and its Environment

NASA Astrophysics Data System (ADS)

Xin, Li-Ping; Wang, Yuan-Zhu; Lin, Ting-Ting; Liang, En-Wei; Lü, Hou-Jun; Zhong, Shu-Qing; Urata, Yuji; Zhao, Xiao-Hong; Wu, Chao; Wei, Jian-Yan; Huang, Kui-Yun; Qiu, Yu-Lei; Deng, Jin-Song

2016-02-01

Observations of very early multi-wavelength afterglows are critical to reveal the properties of the radiating fireball and its environment as well as the central engine of gamma-ray bursts (GRBs). We report our optical observations of GRB 111228A from 95 s to about 50 hr after the burst trigger and investigate its properties of the prompt gamma-rays and the ambient medium using our data and the data from the Swift and Fermi missions. Our joint optical and X-ray spectral fits to the afterglow data show that the ambient medium features a low dust-to-gas ratio. Incorporating the energy injection effect, our best fit to the afterglow light curves with the standard afterglow model via the Markov Chain Monte Carlo technique shows that {ɛ }e=(6.9+/- 0.3)× {10}-2, {ɛ }B=(7.73+/- 0.62)× {10}-6,{E}K=(6.32+/- 0.86)× {10}53 {erg}, n=0.100+/- 0.014 cm-3. The low medium density likely implies that the afterglow jet may be in a halo or in a hot ISM. A chromatic shallow decay segment observed in the optical and X-ray bands is well explained with the long-lasting energy injection from the central engine, which would be a magnetar with a period of about 1.92 ms inferred from the data. The Ep of its time-integrated prompt gamma-ray spectrum is ˜26 KeV. Using the initial Lorentz factor ({{{Γ }}}0={476}-237+225) derived from our afterglow model fit, it is found that GRB 111228A satisfies the {L}{{iso}}-{E}p,z-{{{Γ }}}0 relation and bridges the typical GRBs and low luminosity GRBs in this relation.

New prompt fission gamma-ray spectral data from 239Pu(nth, f) in response to a high priority request from OECD Nuclear Energy Agency

NASA Astrophysics Data System (ADS)

Gatera, Angélique; Belgya, Tamás; Geerts, Wouter; Göök, Alf; Hambsch, Franz-Josef; Lebois, Matthieu; Maróti, Boglárka; Oberstedt, Stephan; Oberstedt, Andreas; Postelt, Frederik; Qi, Liqiang; Szentmiklósi, Laszló; Vidali, Marzio; Zeiser, Fabio

2017-09-01

Benchmark reactor calculations have revealed an underestimation of γ-heat following fission of up to 28%. To improve the modelling of new nuclear reactors, the OECD/NEA initiated a nuclear data High Priority Request List (HPRL) entry for the major isotopes (235U, 239Pu). In response to that HPRL entry, we executed a dedicated measurement program on prompt fission γ-rays employing state-of-the-art lanthanum bromide (LaBr3) detectors with superior timing and good energy resolution. Our new results from 252Cf(sf), 235U(nth,f) and 241Pu(nth,f) provide prompt fission γ-ray spectra characteristics : average number of photons per fission, average total energy per fission and mean photon energy; all within 2% of uncertainty. We present preliminary results on 239Pu(nth,f), recently measured at the Budapest Neutron Centre and supported by the CHANDA Trans-national Access Activity, as well as discussing our different published results in comparison to the historical data and what it says about the discrepancy observed in the benchmark calculations.

Optical polarimetric observations of GRB prompt emissions by MASTER robots-telescopes net.

NASA Astrophysics Data System (ADS)

Gorbovskoy, Evgeny; Lipunov, Vladimir; Kornilov, Victor; Shatskij, Nikolaj; Kuvshi-Nov, Dmitry; Tyurina, Nataly; Belinski, Alexander; Krylov, Alexander; Balanutsa, Pavel; Chazov, Vadim; Kuznetsov, Artem; Zimnuhov, Dmitry; Balanutsa, Pavel; Kortunov, Petr; Sankovich, Anatoly; Tlatov, An-Drey; Parkhomenko, A.; Krushinsky, Vadim; Zalozhnyh, Ivan; Popov, A.; Kopytova, Taisia; Ivanov, Kirill; Yazev, Sergey; Yurkov, Vladimir

The main goal of the MASTER-Net project is to produce a unique fast sky survey with all sky observed over a single night down to a limiting magnitude of 19 -20mag. Such a survey will make it possible to address a number of fundamental problems: search for dark energy via the discovery and photometry of supernovas (including SNIa), search for exoplanets, microlensing effects, discovery of minor bodies in the Solar System and space-junk monitoring. All MASTER telescopes can be guided by alerts, and we plan to observe prompt optical emission from gamma-ray bursts synchronously in several filters and in several polarization planes. Observations on telescopes capable to observ polarisation of GRB prompt emission have been begun in the summer of 2009. Since summer of 2009 an observations of several GRB have been made. In particular for GRB0910 and GRB091127 optical polarisation has been measured. So, for GRB091127 which supervision have begun all through 91 sec polarisation at level of several tens percent has been registered. (GCN 10231, GCN 10052, GCN 10203)

Tests of a Compton imaging prototype in a monoenergetic 4.44 MeV photon field—a benchmark setup for prompt gamma-ray imaging devices

NASA Astrophysics Data System (ADS)

Golnik, C.; Bemmerer, D.; Enghardt, W.; Fiedler, F.; Hueso-González, F.; Pausch, G.; Römer, K.; Rohling, H.; Schöne, S.; Wagner, L.; Kormoll, T.

2016-06-01

The finite range of a proton beam in tissue opens new vistas for the delivery of a highly conformal dose distribution in radiotherapy. However, the actual particle range, and therefore the accurate dose deposition, is sensitive to the tissue composition in the proton path. Range uncertainties, resulting from limited knowledge of this tissue composition or positioning errors, are accounted for in the form of safety margins. Thus, the unverified particle range constrains the principle benefit of proton therapy. Detecting prompt γ-rays, a side product of proton-tissue interaction, aims at an on-line and non-invasive monitoring of the particle range, and therefore towards exploiting the potential of proton therapy. Compton imaging of the spatial prompt γ-ray emission is a promising measurement approach. Prompt γ-rays exhibit emission energies of several MeV. Hence, common radioactive sources cannot provide the energy range a prompt γ-ray imaging device must be designed for. In this work a benchmark measurement-setup for the production of a localized, monoenergetic 4.44 MeV γ-ray source is introduced. At the Tandetron accelerator at the HZDR, the proton-capture resonance reaction 15N(p,α γ4.439)12C is utilized. This reaction provides the same nuclear de-excitation (and γ-ray emission) occurrent as an intense prompt γ-ray line in proton therapy. The emission yield is quantitatively described. A two-stage Compton imaging device, dedicated for prompt γ-ray imaging, is tested at the setup exemplarily. Besides successful imaging tests, the detection efficiency of the prototype at 4.44 MeV is derived from the measured data. Combining this efficiency with the emission yield for prompt γ-rays, the number of valid Compton events, induced by γ-rays in the energy region around 4.44 MeV, is estimated for the prototype being implemented in a therapeutic treatment scenario. As a consequence, the detection efficiency turns out to be a key parameter for prompt γ-rays Compton imaging limiting the applicability of the prototype in its current realization.

X-Ray Fluence and Transmission and Prompt Radiation Fluence or Dose

DTIC Science & Technology

1981-03-01

Application of Gamma Ray Build-up Data to Shield Design. Report Number WAPD -RM-217. Westinghouse Electric Corporation, Atomic Power Division: January 1954. 14...263 91 R/- 459 05 c05 194 21 2𔃻 229 00 0 264 42 STO 160 85. + 195 00 .. 230 00 ,. 265 20 20 i61 43 RC:L 196 05 5 231 "-:" 0 266 02 2 162 06 06 1

Investigation of the i 13 / 2 neutron orbital in the Sn 132 region: New excited levels in Sb 135

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

Korgul, A.; Ba̧czyk, P.; Urban, W.

2015-02-01

Excited states in Sb-135, populated in spontaneous fission of Cm-248, are studied by means of prompt gamma spectroscopy, using the EUROGAM2 detector array. New excited states containing the neutron i(13/2) orbital in their wave functions are proposed. A more accurate value of the i(13/2) neutron single-particle energy in the Sn-132 core potential is determined

The application of PGNAA borehole logging for copper grade estimation at Chuquicamata mine.

PubMed

Charbucinski, J; Duran, O; Freraut, R; Heresi, N; Pineyro, I

2004-05-01

The field trials of a prompt gamma neutron activation (PGNAA) spectrometric logging method and instrumentation (SIROLOG) for copper grade estimation in production holes of a porphyry type copper ore mine, Chuquicamata in Chile, are described. Examples of data analysis, calibration procedures and copper grade profiles are provided. The field tests have proved the suitability of the PGNAA logging system for in situ quality control of copper ore.

Evolution of the polarization of the optical afterglow of the gamma-ray burst GRB030329.

PubMed

Greiner, Jochen; Klose, Sylvio; Reinsch, Klaus; Schmid, Hans Martin; Sari, Re'em; Hartmann, Dieter H; Kouveliotou, Chryssa; Rau, Arne; Palazzi, Eliana; Straubmeier, Christian; Stecklum, Bringfried; Zharikov, Sergej; Tovmassian, Gaghik; Bärnbantner, Otto; Ries, Christoph; Jehin, Emmanuel; Henden, Arne; Kaas, Anlaug A; Grav, Tommy; Hjorth, Jens; Pedersen, Holger; Wijers, Ralph A M J; Kaufer, Andreas; Park, Hye-Sook; Williams, Grant; Reimer, Olaf

2003-11-13

The association of a supernova with GRB030329 strongly supports the 'collapsar' model of gamma-ray bursts, where a relativistic jet forms after the progenitor star collapses. Such jets cannot be spatially resolved because gamma-ray bursts lie at cosmological distances; their existence is instead inferred from 'breaks' in the light curves of the afterglows, and from the theoretical desire to reduce the estimated total energy of the burst by proposing that most of it comes out in narrow beams. Temporal evolution of the polarization of the afterglows may provide independent evidence for the jet structure of the relativistic outflow. Small-level polarization ( approximately 1-3 per cent) has been reported for a few bursts, but its temporal evolution has yet to be established. Here we report polarimetric observations of the afterglow of GRB030329. We establish the polarization light curve, detect sustained polarization at the per cent level, and find significant variability. The data imply that the afterglow magnetic field has a small coherence length and is mostly random, probably generated by turbulence, in contrast with the picture arising from the high polarization detected in the prompt gamma-rays from GRB021206 (ref. 18).

Simultaneous measurement of (n,{gamma}) and (n,fission) cross sections with the DANCE 4{pi} BaF2 array

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

Bredeweg, T. A.; Fowler, M. M.; Bond, E. M.

2006-03-13

Neutron capture cross section measurements on many of the actinides are complicated by low-energy neutron-induced fission, which competes with neutron capture to varying degrees depending on the nuclide of interest. Measurements of neutron capture on 235U using the Detector for Advanced Neutron Capture Experiments (DANCE) have shown that we can partially resolve capture from fission events based on total photon calorimetry (i.e. total {gamma}-ray energy and {gamma}-ray multiplicity per event). The addition of a fission-tagging detector to the DANCE array will greatly improve our ability to separate these two competing processes so that improved neutron capture and (n,{gamma})/(n,fission) cross sectionmore » ratio measurements can be obtained. The addition of a fission-tagging detector to the DANCE array will also provide a means to study several important issues associated with neutron-induced fission, including (n,fission) cross sections as a function of incident neutron energy, and total energy and multiplicity of prompt fission photons. We have focused on two detector designs with complementary capabilities, a parallel-plate avalanche counter and an array of solar cells.« less

Gamma-ray solid laser: variety of work nuclei and host matrixes in Mendeleev Table screened with use of system of criteria based on joint GG&RH theory

NASA Astrophysics Data System (ADS)

Karyagin, Stanislav V.

2001-03-01

The hosts and nuclei-candidates (mass approximately 46 - 243, transition energy approximately 1 - 200 keV, decay's time 10-7 - 10+2 s) for gamma-laser (GL) realization are represented over Mendeleev Table. The choice of active media (nuclei-candidates, hosts) for GL is based on the joint theory of (gamma) -generation and radiation-heat regime which accounts a big complex of hindrances against GL and thus discards many tentative candidates. Nuclei- candidates are screened at the analyzing of data banks for nuclear transitions. Chosen candidates (approximately 20) could be used due to author's method SPTEN (Soft Prompt Transplantation of Excited Nuclei). The discarded tentative nuclei (approximately 80) with the life-times 10-6 - 10+2 are represented too. All analyzed long-lived (approximately 0.5 - 10+2 s) isomers are turned to be not fit for GL without use of very strong multi-wave Borrman effect even at the supposition of natural line's width. The application of the revealed candidates in two different (gamma) -laser's categories (residential and non- residential) is discussed.

Interdisciplinary Entrepreneurial Leadership Education and the Development of Agricultural Innovators

ERIC Educational Resources Information Center

Mars, Matthew M.

2015-01-01

This article qualitatively explores the potential of entrepreneurial leadership curricula to encourage interdisciplinary interest in agricultural issues and prompt diverse student engagement in agricultural leadership and innovation. The study focuses specifically on the activities and perspectives of 15 undergraduate students who completed an…

Swift captures the spectrally evolving prompt emission of GRB070616

NASA Astrophysics Data System (ADS)

Starling, R. L. C.; O'Brien, P. T.; Willingale, R.; Page, K. L.; Osborne, J. P.; de Pasquale, M.; Nakagawa, Y. E.; Kuin, N. P. M.; Onda, K.; Norris, J. P.; Ukwatta, T. N.; Kodaka, N.; Burrows, D. N.; Kennea, J. A.; Page, M. J.; Perri, M.; Markwardt, C. B.

2008-02-01

The origins of gamma-ray burst (GRB) prompt emission are currently not well understood and in this context long, well-observed events are particularly important to study. We present the case of GRB070616, analysing the exceptionally long-duration multipeaked prompt emission, and later afterglow, captured by all the instruments on-board Swift and by Suzaku Wide-Band All-Sky Monitor (WAM). The high-energy light curve remained generally flat for several hundred seconds before going into a steep decline. Spectral evolution from hard to soft is clearly taking place throughout the prompt emission, beginning at 285s after the trigger and extending to 1200s. We track the movement of the spectral peak energy, whilst observing a softening of the low-energy spectral slope. The steep decline in flux may be caused by a combination of this strong spectral evolution and the curvature effect. We investigate origins for the spectral evolution, ruling out a superposition of two power laws and considering instead an additional component dominant during the late prompt emission. We also discuss origins for the early optical emission and the physics of the afterglow. The case of GRB070616 clearly demonstrates that both broad-band coverage and good time resolution are crucial to pin down the origins of the complex prompt emission in GRBs. This paper is dedicated to the memory of Dr Francesca Tamburelli who died during its production. Francesca played a fundamental role within the team which is in charge of the development of the Swift X-Ray Telescope (XRT) data analysis software at the Italian Space Agency's Science Data Centre in Frascati. She is sadly missed. E-mail: rlcs1@star.le.ac.uk

Beta decay of the fission product 125Sb and a new complete evaluation of absolute gamma ray transition intensities

NASA Astrophysics Data System (ADS)

Rajput, M. U.; Ali, N.; Hussain, S.; Mujahid, S. A.; MacMahon, D.

2012-04-01

The radionuclide 125Sb is a long-lived fission product, which decays to 125Te by negative beta emission with a half-life of 1008 day. The beta decay is followed by the emission of several gamma radiations, ranging from low to medium energy, that can suitably be used for high-resolution detector calibrations, decay heat calculations and in many other applications. In this work, the beta decay of 125Sb has been studied in detail. The complete published experimental data of relative gamma ray intensities in the beta decay of the radionuclide 125Sb has been compiled. The consistency analysis was performed and discrepancies found at several gamma ray energies. Evaluation of the discrepant data was carried out using Normalized Residual and RAJEVAL methods. The decay scheme balance was carried out using beta branching ratios, internal conversion coefficients, populating and depopulating gamma transitions to 125Te levels. The work has resulted in the consistent conversion factor equal to 29.59(13) %, and determined a new evaluated set of the absolute gamma ray emission probabilities. The work has also shown 22.99% of the delayed intensity fraction as outgoing from the 58 d isomeric 144 keV energy level and 77.01% of the prompt intensity fraction reaching to the ground state from the other excited states. The results are discussed and compared with previous evaluations. The present work includes additional experimental data sets which were not included in the previous evaluations. A new set of recommended relative and absolute gamma ray emission probabilities is presented.

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

Lane, Taylor; Parma, Edward J.

Delayed fission gamma-rays play an important role in determining the time dependent ioniz- ing dose for experiments in the central irradiation cavity of the Annular Core Research Reactor (ACRR). Delayed gamma-rays are produced from both fission product decay and from acti- vation of materials in the core, such as cladding and support structures. Knowing both the delayed gamma-ray emission rate and the time-dependent gamma-ray energy spectrum is nec- essary in order to properly determine the dose contributions from delayed fission gamma-rays. This information is especially important when attempting to deconvolute the time-dependent neutron, prompt gamma-ray, and delayed gamma-ray contribution tomore » the response of a diamond photo-conducting diode (PCD) or fission chamber in time frames of milliseconds to seconds following a reactor pulse. This work focused on investigating delayed gamma-ray character- istics produced from fission products from thermal, fast, and high energy fission of Th-232, U-233, U-235, U-238, and Pu-239. This work uses a modified version of CINDER2008, a transmutation code developed at Los Alamos National Laboratory, to model time and energy dependent photon characteristics due to fission. This modified code adds the capability to track photon-induced transmutations, photo-fission, and the subsequent radiation caused by fission products due to photo-fission. The data is compared against previous work done with SNL- modified CINDER2008 [ 1 ] and experimental data [ 2 , 3 ] and other published literature, includ- ing ENDF/B-VII.1 [ 4 ]. The ability to produce a high-fidelity (7,428 group) energy-dependent photon fluence at various times post-fission can improve the delayed photon characterization for radiation effects tests at research reactors, as well as other applications.« less

Electron Acceleration and Efficiency in Nonthermal Gamma-Ray Sources

NASA Astrophysics Data System (ADS)

Bykov, A. M.; Meszaros, P.

1996-04-01

In energetic nonthermal sources such as gamma-ray bursts, active galactic nuclei, or galactic jets, etc., one expects both relativistic and transrelativistic shocks accompanied by violent motions of moderately relativistic plasma. We present general considerations indicating that these sites are electron and positron accelerators leading to a modified power-law spectrum. The electron (or e+/-) energy index is very hard, ~ gamma -1 or flatter, up to a comoving frame break energy gamma *, and becomes steeper above that. In the example of gamma-ray bursts, the Lorentz factor reaches gamma * ~ 103 for e+/- accelerated by the internal shock ensemble on subhydrodynamical timescales. For pairs accelerated on hydrodynamical timescales in the external shocks, similar hard spectra are obtained, and the break Lorentz factor can be as high as gamma * <~ 105. Radiation from the nonthermal electrons produces photon spectra with shapes and characteristic energies in qualitative agreement with observed generic gamma-ray burst and blazar spectra. The scenario described here provides a plausible way to solve one of the crucial problems of nonthermal high-energy sources, namely, the efficient transfer of energy from the proton flow to an appropriate nonthermal lepton component.

Prospects for GRB science with the Fermi Large Area Telescope

DOE PAGES

Band, D. L.; Axelsson, M.; Baldini, L.; ...

2009-08-04

The Large Area Telescope (LAT) instrument on the Fermi mission will reveal the rich spectral and temporal gamma-ray burst (GRB) phenomena in the >100 MeV band. The synergy with Fermi's Gamma-ray Burst Monitor detectors will link these observations to those in the well explored 10-1000 keV range; the addition of the >100 MeV band observations will resolve theoretical uncertainties about burst emission in both the prompt and afterglow phases. Trigger algorithms will be applied to the LAT data both onboard the spacecraft and on the ground. Furthermore, the sensitivity of these triggers will differ because of the available computing resourcesmore » onboard and on the ground. Here we present the LAT's burst detection methodologies and the instrument's GRB capabilities.« less

Delayed Gamma Measurements in Different Nuclear Research Reactors Bringing Out the Importance of the Delayed Contribution in Gamma Flux Calculations

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

Fourmentel, D.; Radulovic, V.; Barbot, L.

Neutron and gamma flux levels are key parameters in nuclear research reactors. In Material Testing Reactors, such as the future Jules Horowitz Reactor, under construction at the French Alternative Energies and Atomic Energy Commission (CEA Cadarache, France), the expected gamma flux levels are very high (nuclear heating is of the order of 20 W/g at 100 MWth). As gamma rays deposit their energy in the reactor structures and structural materials it is important to take them into account when designing irradiation devices. There are only a few sensors which allow measurements of the nuclear heating ; a recent development atmore » the CEA Cadarache allows measurements of the gamma flux using a miniature ionization chamber (MIC). The measured MIC response is often compared with calculation using modern Monte Carlo (MC) neutron and photon transport codes, such as TRIPOLI-4 and MCNP6. In these calculations only the production of prompt gamma rays in the reactor is usually modelled thus neglecting the delayed gamma rays. Hence calculations and measurements are usually in better accordance for the neutron flux than for the gamma flux. In this paper we study the contribution of delayed gamma rays to the total MIC signal in order to estimate the systematic error in gamma flux MC calculations. In order to experimentally determine the delayed gamma flux contributions to the MIC response, we performed gamma flux measurements with CEA developed MIC at three different research reactors: the OSIRIS reactor (MTR - 70 MWth at CEA Saclay, France), the TRIGA MARK II reactor (TRIGA - 250 kWth at the Jozef Stefan Institute, Slovenia) and the MARIA reactor (MTR - 30 MWth at the National Center for Nuclear Research, Poland). In order to experimentally assess the delayed gamma flux contribution to the total gamma flux, several reactor shut down (scram) experiments were performed specifically for the purpose of the measurements. Results show that on average about 30 % of the MIC signal is due to the delayed gamma rays. In this paper we describe experiments in each of the three reactors and how we estimate delayed gamma rays with MIC measurements. The results and perspectives are discussed. (authors)« less

Gadolinium as a Neutron Capture Therapy Agent

NASA Astrophysics Data System (ADS)

Shih, Jing-Luen Allen

The clinical results of treating brain tumors with boron neutron capture therapy are very encouraging and researchers around the world are once again making efforts to develop this therapeutic modality. Boron-10 is the agent receiving the most attention for neutron capture therapy but ^{157}Gd is a nuclide that also holds interesting properties of being a neutron capture therapy agent. The objective of this study is to evaluate ^{157}Gd as a neutron capture therapy agent. In this study it is determined that tumor concentrations of about 300 mug ^{157}Gd/g tumor can be achieved in brain tumors with some FDA approved MRI contrast agents such as Gd-DTPA and Gd-DOTA, and up to 628 mug ^{157 }Gd/g tumor can be established in bone tumors with Gd-EDTMP. Monte Carlo calculations show that with only 250 ppm of ^{157}Gd in tumor, neutron capture therapy can deliver 2,000 cGy to a tumor of 2 cm diameter or larger with 5 times 10^{12} n/cm ^2 fluence at the tumor. Dose measurements which were made with films and TLD's in phantoms verified these calculations. More extended Monte Carlo calculations demonstrate that neutron capture therapy with Gd possesses comparable dose distribution to B neutron capture therapy. With 5 times 10^{12 } n/cm^2 thermal neutrons at the tumor, Auger electrons from the Gd produced an optical density enhancement on the films that is similar to the effect caused by about 300 cGy of Gd prompt gamma dose which will further enhance the therapeutic effects. A technique that combines brachytherapy with Gd neutron capture therapy has been evaluated. Monte Carlo calculations show that 5,000 cGy of prompt gamma dose can be delivered to a treatment volume of 40 cm^3 with a 3-plane implant of a total of 9 Gd needles. The tumor to normal tissue advantage of this method is as good as ^{60} Co brachytherapy. Measurements of prompt gamma dose with films and TLD-700's in a lucite phantom verify the Monte Carlo evaluation. A technique which displays the Gd distribution and its relative concentration in samples has been developed. Concentrations of ^{157}Gd in samples range from 20 ppm to 500 ppm can be determined with this technique. The intrinsic spatial resolution of the imaging system in 70 mum.

Trigger design for a gamma ray detector of HIRFL-ETF

NASA Astrophysics Data System (ADS)

Du, Zhong-Wei; Su, Hong; Qian, Yi; Kong, Jie

2013-10-01

The Gamma Ray Array Detector (GRAD) is one subsystem of HIRFL-ETF (the External Target Facility (ETF) of the Heavy Ion Research Facility in Lanzhou (HIRFL)). It is capable of measuring the energy of gamma-rays with 1024 CsI scintillators in in-beam nuclear experiments. The GRAD trigger should select the valid events and reject the data from the scintillators which are not hit by the gamma-ray. The GRAD trigger has been developed based on the Field Programmable Gate Array (FPGAs) and PXI interface. It makes prompt trigger decisions to select valid events by processing the hit signals from the 1024 CsI scintillators. According to the physical requirements, the GRAD trigger module supplies 12-bit trigger information for the global trigger system of ETF and supplies a trigger signal for data acquisition (DAQ) system of GRAD. In addition, the GRAD trigger generates trigger data that are packed and transmitted to the host computer via PXI bus to be saved for off-line analysis. The trigger processing is implemented in the front-end electronics of GRAD and one FPGA of the GRAD trigger module. The logic of PXI transmission and reconfiguration is implemented in another FPGA of the GRAD trigger module. During the gamma-ray experiments, the GRAD trigger performs reliably and efficiently. The function of GRAD trigger is capable of satisfying the physical requirements.

Feasibility study for measurement of insulation compaction in the cryogenic rocket fuel storage tanks at Kennedy Space Center by fast/thermal neutron techniques

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

Livingston, R. A.; Schweitzer, J. S.; Parsons, A. M.

2014-02-18

The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Some of the perlite may have compacted over time, compromising the thermal performance and also the structural integrity of the tanks. Neutrons can readily penetrate through the 1.75 cm outer steel shell and through the entire 120 cm thick perlite zone. Neutrons interactions with materials produce characteristic gamma rays which are then detected. In compacted perlite the count rates in the individual peaks in the gamma ray spectrum will increase. Portable neutron generators can produce neutron simultaneous fluxes inmore » two energy ranges: fast (14 MeV) and thermal (25 meV). Fast neutrons produce gamma rays by inelastic scattering which is sensitive to Si, Al, Fe and O. Thermal neutrons produce gamma rays by radiative capture in prompt gamma neutron activation (PGNA), which is sensitive to Si, Al, Na, K and H among others. The results of computer simulations using the software MCNP and measurements on a test article suggest that the most promising approach would be to operate the system in time-of-flight mode by pulsing the neutron generator and observing the subsequent die away curve in the PGNA signal.« less

CONSTRAINTS ON VERY HIGH ENERGY EMISSION FROM GRB 130427A

DOE PAGES

Aliu, E.; Aune, T.; Barnacka, A.; ...

2014-10-10

In this study, prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-Ray Space Telescope for ~70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is alsomore » evidence that the high-energy emission may instead be an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations of GRB 130427A ~71 ks (~20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB 130427A for E > 100 GeV. In conclusion, the non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission from this burst.« less

Machine learning-based patient specific prompt-gamma dose monitoring in proton therapy

NASA Astrophysics Data System (ADS)

Gueth, P.; Dauvergne, D.; Freud, N.; Létang, J. M.; Ray, C.; Testa, E.; Sarrut, D.

2013-07-01

Online dose monitoring in proton therapy is currently being investigated with prompt-gamma (PG) devices. PG emission was shown to be correlated with dose deposition. This relationship is mostly unknown under real conditions. We propose a machine learning approach based on simulations to create optimized treatment-specific classifiers that detect discrepancies between planned and delivered dose. Simulations were performed with the Monte-Carlo platform Gate/Geant4 for a spot-scanning proton therapy treatment and a PG camera prototype currently under investigation. The method first builds a learning set of perturbed situations corresponding to a range of patient translation. This set is then used to train a combined classifier using distal falloff and registered correlation measures. Classifier performances were evaluated using receiver operating characteristic curves and maximum associated specificity and sensitivity. A leave-one-out study showed that it is possible to detect discrepancies of 5 mm with specificity and sensitivity of 85% whereas using only distal falloff decreases the sensitivity down to 77% on the same data set. The proposed method could help to evaluate performance and to optimize the design of PG monitoring devices. It is generic: other learning sets of deviations, other measures and other types of classifiers could be studied to potentially reach better performance. At the moment, the main limitation lies in the computation time needed to perform the simulations.

SU-D-304-07: Application of Proton Boron Fusion Reaction to Radiation Therapy

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

Jung, J; Yoon, D; Shin, H

Purpose: we present the introduction of a therapy method using the proton boron fusion reaction. The purpose of this study is to verify the theoretical validity of proton boron fusion therapy using Monte Carlo simulations. Methods: After boron is accumulated in the tumor region, the emitted from outside the body proton can react with the boron in the tumor region. An increase of the proton’s maximum dose level is caused by the boron and only the tumor cell is damaged more critically. In addition, a prompt gamma ray is emitted from the proton boron reaction point. Here we show thatmore » the effectiveness of the proton boron fusion therapy (PBFT) was verified using Monte Carlo simulations. Results: We found that a dramatic increase by more than half of the proton’s maximum dose level was induced by the boron in the tumor region. This increase occurred only when the proton’s maximum dose point was located within the boron uptake region (BUR). In addition, the 719 keV prompt gamma ray peak produced by the proton boron fusion reaction was positively detected. Conclusion: This therapy method features the advantages such as the application of Bragg-peak to the therapy, the accurate targeting of tumor, improved therapy effects, and the monitoring of the therapy region during treatment.« less

Explicit awareness supports conditional visual search in the retrieval guidance paradigm.

PubMed

Buttaccio, Daniel R; Lange, Nicholas D; Hahn, Sowon; Thomas, Rick P

2014-01-01

In four experiments we explored whether participants would be able to use probabilistic prompts to simplify perceptually demanding visual search in a task we call the retrieval guidance paradigm. On each trial a memory prompt appeared prior to (and during) the search task and the diagnosticity of the prompt(s) was manipulated to provide complete, partial, or non-diagnostic information regarding the target's color on each trial (Experiments 1-3). In Experiment 1 we found that the more diagnostic prompts was associated with faster visual search performance. However, similar visual search behavior was observed in Experiment 2 when the diagnosticity of the prompts was eliminated, suggesting that participants in Experiment 1 were merely relying on base rate information to guide search and were not utilizing the prompts. In Experiment 3 participants were informed of the relationship between the prompts and the color of the target and this was associated with faster search performance relative to Experiment 1, suggesting that the participants were using the prompts to guide search. Additionally, in Experiment 3 a knowledge test was implemented and performance in this task was associated with qualitative differences in search behavior such that participants that were able to name the color(s) most associated with the prompts were faster to find the target than participants who were unable to do so. However, in Experiments 1-3 diagnosticity of the memory prompt was manipulated via base rate information, making it possible that participants were merely relying on base rate information to inform search in Experiment 3. In Experiment 4 we manipulated diagnosticity of the prompts without manipulating base rate information and found a similar pattern of results as Experiment 3. Together, the results emphasize the importance of base rate and diagnosticity information in visual search behavior. In the General discussion section we explore how a recent computational model of hypothesis generation (HyGene; Thomas, Dougherty, Sprenger, & Harbison, 2008), linking attention with long-term and working memory, accounts for the present results and provides a useful framework of cued recall visual search. Copyright © 2013 Elsevier B.V. All rights reserved.

The Road Less Travelled? Pathways from Passivity to Agency in Student Learning

ERIC Educational Resources Information Center

Frost, Gail; Connolly, Maureen

2015-01-01

This qualitative study examined fourth-year undergraduate students' responses to reflective writing prompts and journal entries related to their practical experiences in two capstone courses, both based in SBL/PBL pedagogies. We examined their "strategic" approaches to learning that make engagement with subject matter and learning…

Staff and Student Emotional Literacy at One Lutheran Church Missouri Synod School

ERIC Educational Resources Information Center

Dresser, Gary J.

2014-01-01

This qualitative case study examined administrators' and teachers' perceptions of personal and student emotional literacy in one Lutheran Church Missouri Synod (LCMS) school. Students attending LCMS schools were struggling with social and emotional issues prompting behavioral difficulties, while teachers were unprepared for the magnitude of…

Qualitative Investigation of Students' Views about Experimental Physics

ERIC Educational Resources Information Center

Hu, Dehui; Zwickl, Benjamin M.; Wilcox, Bethany R.; Lewandowski, H. J.

2017-01-01

This study examines students' reasoning surrounding seemingly contradictory Likert-scale responses within five items in the Colorado Learning Attitudes About Science Survey for Experimental Physics (E-CLASS). We administered the E-CLASS with embedded open-ended prompts, which asked students to provide explanations after making a Likert-scale…

Jet or Shock Breakout? The Low-Luminosity GRB 060218

NASA Astrophysics Data System (ADS)

Irwin, Christopher; Chevalier, Roger

2016-01-01

We consider a model for the long-duration, low-luminosity gamma-ray burst GRB 060218 that plausibly accounts for multiwavelength observations to day 20. The components of our model are: (1) a long-lived (tj ~ 3000 s) central engine and accompanying low-luminosity (Lj ~ 1045 erg s-1), mildly relativistic jet; (2) a low-mass (~ 10-2 Msun) envelope surrounding the progenitor star; and (3) a modest amount of dust (AV ~ 0.1) in the circumstellar or interstellar environment. Blackbody emission from the transparency radius in a low-power jet outflow can fit the prompt thermal X-ray emission, and the prompt nonthermal X-rays and γ-rays may be produced via Compton scattering of thermal photons from hot leptons in the jet interior or the external shocks. The later mildly relativistic phase of this outflow can produce the radio emission via synchrotron radiation from the forward shock. Meanwhile, interaction of the associated SN 2006aj with a circumstellar envelope extending to ~ 1013 cm can explain the early optical peak. The X-ray afterglow can be interpreted as a light echo of the prompt emission from dust at ~ 30 pc. Our model is a plausible alternative to that of Nakar, who recently proposed shock breakout of a jet smothered by an extended envelope as the source of prompt emission. Both our results and Nakar's suggest that ultra-long bursts such as GRB 060218 and GRB 100316D may originate from unusual progenitors with extended circumstellar envelopes, and that a jet is necessary to decouple the prompt high-energy emission from the supernova.

General relativistic magnetohydrodynamics simulations of prompt-collapse neutron star mergers: The absence of jets

NASA Astrophysics Data System (ADS)

Ruiz, Milton; Shapiro, Stuart L.

2017-10-01

Inspiraling and merging binary neutron stars are not only important source of gravitational waves, but also promising candidates for coincident electromagnetic counterparts. These systems are thought to be progenitors of short gamma-ray bursts (sGRBs). We have shown previously that binary neutron star mergers that undergo delayed collapse to a black hole surrounded by a weighty magnetized accretion disk can drive magnetically powered jets. We now perform magnetohydrodynamic simulations in full general relativity of binary neutron stars mergers that undergo prompt collapse to explore the possibility of jet formation from black hole- light accretion disk remnants. We find that after t -tBH˜26 (MNS/1.8 M⊙) ms (MNS is the ADM mass) following prompt black hole formation, there is no evidence of mass outflow or magnetic field collimation. The rapid formation of the black hole following merger prevents magnetic energy from approaching force-free values above the magnetic poles, which is required for the launching of a jet by the usual Blandford-Znajek mechanism. Detection of gravitational waves in coincidence with sGRBs may provide constraints on the nuclear equation of state (EOS): the fate of an NSNS merger-delayed or prompt collapse, and hence the appearance or nonappearance of an sGRB-depends on a critical value of the total mass of the binary, and this value is sensitive to the EOS.

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

Parodi, K; Dauvergne, D; Kruse, J

In this first inaugural joint ESTRO-AAPM session we will attempt to provide some answers to the problems encountered in the clinical application of particle therapy. Indeed the main advantage is that the physical properties of ion beams offer high ballistic accuracy for tightly conformal irradiation of the tumour volume, with excellent sparing of surrounding healthy tissue and critical organs, This also its Achilles' heel calling for an increasing role of imaging to ensure safe application of the intended dose to the targeted area during the entire course of fractionated therapy. We have three distinguished speakers addressing possible solutions. Katia Parodimore » (Ludwig Maximilians University, Munich, Germany) To date, Positron Emission Tomography (PET) is the only technique which has been already clinically investigated for in-vivo visualization of the beam range during or shortly after ion beam delivery. The method exploits the transient amount of β{sup 2}-activity induced in nuclear interactions between the primary beam and the irradiated tissue, depending on the ion beam species, the tissue elemental composition and physiological properties (in terms of biological clearance), as well as the time course of irradiation and imaging. This contribution will review initial results, ongoing methodological developments and remaining challenges related to the clinical usage of viable but often suboptimal instrumentation and workflows of PET-based treatment verification. Moreover, it will present and discuss promising new detector developments towards next-generation dedicated PET scanners relying on full-ring or dual-head designs for in-beam quasi real-time imaging. Denis Dauvergne (Institut de Physique Nucleaire de Lyon, Lyon, France) Prompt gamma radiation monitoring of hadron therapy presents the advantage of real time capability to measure the ion range. Both simulations and experiments show that millimetric verification of the range can be achieved at the pencil beam scale for active proton beam delivery in homogenous targets. The development of gamma cameras, that has been studied by several groups worldwide over the last years, now reaches - for some of them - the stage of being applicable in clinical conditions, with real size prototypes and count rate capability matching the therapeutic beam intensities. We will review the different concepts of gamma cameras, the advantages and limitations of this method, and the main challenges that should still be overcome before the widespread of prompt gamma quality assurance for proton and hadrontherapy. Jon Kruse (Mayo Clinic, Rochester, MN, USA) Treatment simulation images for proton therapy are used to determine proton stopping power and range in the patient. This talk will discuss the careful control of CT numbers and conversion of CT number to stopping power required in proton therapy. Imaging for treatment guidance of proton therapy also presents unique challenges which will be addressed. Among them are the enhanced relationship between internal anatomy changes and dosimetry, the need for imaging to support adaptive planning protocols, and high operational efficiency. Learning Objectives: To learn about the possibilities of using activation products to determine the range of particle beams in a patient treatment setting To be informed on an alternative methodology using prompt gamma detectors To understand the impact of the accuracy of the knowledge of the patient information with respect to the delivered treatment.« less

Gamma-ray burst theory after Swift.

PubMed

Piran, Tsvi; Fan, Yi-Zhong

2007-05-15

Afterglow observations in the pre-Swift era confirmed to a large extend the relativistic blast wave model for gamma-ray bursts (GRBs). Together with the observations of properties of host galaxies and the association with (type Ic) SNe, this has led to the generally accepted collapsar origin of long GRBs. However, most of the afterglow data was collected hours after the burst. The X-ray telescope and the UV/optical telescope onboard Swift are able to slew to the direction of a burst in real time and record the early broadband afterglow light curves. These observations, and in particular the X-ray observations, resulted in many surprises. While we have anticipated a smooth transition from the prompt emission to the afterglow, many observed that early light curves are drastically different. We review here how these observations are changing our understanding of GRBs.

Feasibility study for wax deposition imaging in oil pipelines by PGNAA technique.

PubMed

Cheng, Can; Jia, Wenbao; Hei, Daqian; Wei, Zhiyong; Wang, Hongtao

2017-10-01

Wax deposition in pipelines is a crucial problem in the oil industry. A method based on the prompt gamma-ray neutron activation analysis technique was applied to reconstruct the image of wax deposition in oil pipelines. The 2.223MeV hydrogen capture gamma rays were used to reconstruct the wax deposition image. To validate the method, both MCNP simulation and experiments were performed for wax deposited with a maximum thickness of 20cm. The performance of the method was simulated using the MCNP code. The experiment was conducted with a 252 Cf neutron source and a LaBr 3 : Ce detector. A good correspondence between the simulations and the experiments was observed. The results obtained indicate that the present approach is efficient for wax deposition imaging in oil pipelines. Copyright © 2017 Elsevier Ltd. All rights reserved.

GRB 130427A: A Nearby Ordinary Monster

NASA Technical Reports Server (NTRS)

Maselli, A.; Melandri, A.; Nava, L.; Mundell, C. G.; Kawai, N.; Campana, S.; Covino, S.; Cummings, J. R.; Cusumano, G.; Evans, P. A.;

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

PubMed

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

2018-07-01

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

Radiation response issues for infrared detectors

NASA Technical Reports Server (NTRS)

Kalma, Arne H.

1990-01-01

Researchers describe the most important radiation response issues for infrared detectors. In general, the two key degradation mechanisms in infrared detectors are the noise produced by exposure to a flux of ionizing particles (e.g.; trapped electronics and protons, debris gammas and electrons, radioactive decay of neutron-activated materials) and permanent damage produced by exposure to total dose. Total-dose-induced damage is most often the result of charge trapping in insulators or at interfaces. Exposure to short pulses of ionization (e.g.; prompt x rays or gammas, delayed gammas) will cause detector upset. However, this upset is not important to a sensor unless the recovery time is too long. A few detector technologies are vulnerable to neutron-induced displacement damage, but fortunately most are not. Researchers compare the responses of the new technologies with those of the mainstream technologies of PV HgCdTe and IBC Si:As. One important reason for this comparison is to note where some of the newer technologies have the potential to provide significantly improved radiation hardness compared with that of the mainstream technologies, and thus to provide greater motivation for the pursuit of these technologies.

Gamma-Ray Bursts and Cosmology

NASA Technical Reports Server (NTRS)

Norris, Jay P.

2003-01-01

The unrivalled, extreme luminosities of gamma-ray bursts (GRBs) make them the favored beacons for sampling the high redshift Universe. To employ GRBs to study the cosmic terrain -- e.g., star and galaxy formation history -- GRB luminosities must be calibrated, and the luminosity function versus redshift must be measured or inferred. Several nascent relationships between gamma-ray temporal or spectral indicators and luminosity or total energy have been reported. These measures promise to further our understanding of GRBs once the connections between the luminosity indicators and GRB jets and emission mechanisms are better elucidated. The current distribution of 33 redshifts determined from host galaxies and afterglows peaks near z $\\sim$ 1, whereas for the full BATSE sample of long bursts, the lag-luminosity relation predicts a broad peak z $\\sim$ 1--4 with a tail to z $\\sim$ 20, in rough agreement with theoretical models based on star formation considerations. For some GRB subclasses and apparently related phenomena -- short bursts, long-lag bursts, and X-ray flashes -- the present information on their redshift distributions is sparse or entirely lacking, and progress is expected in Swift era when prompt alerts become numerous.

CONSTRAINTS ON THE EMISSION MODEL OF THE 'NAKED-EYE BURST' GRB 080319B

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

Abdo, A. A.; Abeysekara, A. U.; Linnemann, J. T.

On 2008 March 19, one of the brightest gamma-ray bursts (GRBs) ever recorded was detected by several ground- and space-based instruments spanning the electromagnetic spectrum from radio to gamma rays. With a peak visual magnitude of 5.3, GRB 080319B was dubbed the 'naked-eye' GRB, as an observer under dark skies could have seen the burst without the aid of an instrument. Presented here are results from observations of the prompt phase of GRB 080319B taken with the Milagro TeV observatory. The burst was observed at an elevation angle of 47 Degree-Sign . Analysis of the data is performed using bothmore » the standard air shower method and the scaler or single-particle technique, which results in a sensitive energy range that extends from {approx}5 GeV to >20 TeV. These observations provide the only direct constraints on the properties of the high-energy gamma-ray emission from GRB 080319B at these energies. No evidence for emission is found in the Milagro data, and upper limits on the gamma-ray flux above 10 GeV are derived. The limits on emission between {approx}25 and 200 GeV are incompatible with the synchrotron self-Compton model of gamma-ray production and disfavor a corresponding range (2 eV-16 eV) of assumed synchrotron peak energies. This indicates that the optical photons and soft ({approx}650 keV) gamma rays may not be produced by the same electron population.« less

ON THE LACK OF TIME DILATION SIGNATURES IN GAMMA-RAY BURST LIGHT CURVES

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

Kocevski, Daniel; Petrosian, Vahe

2013-03-10

We examine the effects of time dilation on the temporal profiles of gamma-ray burst (GRB) pulses. By using prescriptions for the shape and evolution of prompt gamma-ray spectra, we can generate a simulated population of single-pulsed GRBs at a variety of redshifts and observe how their light curves would appear to a gamma-ray detector here on Earth. We find that the observer frame duration of individual pulses does not increase with redshift as 1 + z, which one would expect from cosmological expansion. This time dilation is masked by an opposite and often stronger effect: with increasing redshift and decreasingmore » signal-to-noise ratio only the brightest portion of the light curve can be detected. The results of our simulation are consistent with the fact that the simple time dilation of GRB light curves has not materialized in either the Swift or Fermi detected GRBs with known redshift. We show that the measured durations and associated E{sub iso} estimates for GRBs detected near the instrument's detection threshold should be considered lower limits to the true values. Furthermore, we conclude that attempts at distinguishing between long and short GRBs, at even moderate redshifts, cannot be done based on a burst's temporal properties alone.« less

Radio Flares from Gamma-ray Bursts

NASA Astrophysics Data System (ADS)

Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.; Harrison, R.; Japelj, J.; Guidorzi, C.; Melandri, A.; Gomboc, A.

2015-06-01

We present predictions of centimeter and millimeter radio emission from reverse shocks (RSs) in the early afterglows of gamma-ray bursts (GRBs) with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy, and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parameterization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. and Melandri et al. in which the typical frequency of the RS was suggested to lie at radio rather than optical wavelengths at early times, we show that the brightest and most distinct RS radio signatures are detectable up to 0.1-1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects—typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical RS emission, we suggest that detection of polarized radio/millimeter emission will unambiguously confirm the presence of low-frequency RSs at early time.

Techniques for Targeted Fermi-GBM Follow-Up of Gravitational-Wave Events

NASA Technical Reports Server (NTRS)

Blackburn, L.; Camp, J.; Briggs, M. S.; Connaughton, V.; Jenke, P.; Christensen, N.; Veitch, J.

2012-01-01

The Advanced LIGO and Advanced Virgo ground-based gravitational-wave (GW) detectors are projected to come online 2015 2016, reaching a final sensitivity sufficient to observe dozens of binary neutron star mergers per year by 2018. We present a fully-automated, targeted search strategy for prompt gamma-ray counterparts in offline Fermi-GBM data. The multi-detector method makes use of a detailed model response of the instrument, and benefits from time and sky location information derived from the gravitational-wave signal.

The Influence of Self-Efficacy Beliefs and Metacognitive Prompting on Genetics Problem Solving Ability among High School Students in Kenya

NASA Astrophysics Data System (ADS)

Aurah, Catherine Muhonja

Within the framework of social cognitive theory, the influence of self-efficacy beliefs and metacognitive prompting on genetics problem solving ability among high school students in Kenya was examined through a mixed methods research design. A quasi-experimental study, supplemented by focus group interviews, was conducted to investigate both the outcomes and the processes of students' genetics problem-solving ability. Focus group interviews substantiated and supported findings from the quantitative instruments. The study was conducted in 17 high schools in Western Province, Kenya. A total of 2,138 high school students were purposively sampled. A sub-sample of 48 students participated in focus group interviews to understand their perspectives and experiences during the study so as to corroborate the quantitative data. Quantitative data were analyzed through descriptive statistics, zero-order correlations, 2 x 2 factorial ANOVA,, and sequential hierarchical multiple regressions. Qualitative data were transcribed, coded, and reported thematically. Results revealed metacognitive prompts had significant positive effects on student problem-solving ability independent of gender. Self-efficacy and metacognitive prompting significantly predicted genetics problem-solving ability. Gender differences were revealed, with girls outperforming boys on the genetics problem-solving test. Furthermore, self-efficacy moderated the relationship between metacognitive prompting and genetics problem-solving ability. This study established a foundation for instructional methods for biology teachers and recommendations are made for implementing metacognitive prompting in a problem-based learning environment in high schools and science teacher education programs in Kenya.

Polarization of gamma-ray burst afterglows in the synchrotron self-Compton process from a highly relativistic jet

NASA Astrophysics Data System (ADS)

Lin, Hai-Nan; Li, Xin; Chang, Zhe

2017-04-01

Linear polarization has been observed in both the prompt phase and afterglow of some bright gamma-ray bursts (GRBs). Polarization in the prompt phase spans a wide range, and may be as high as ≳ 50%. In the afterglow phase, however, it is usually below 10%. According to the standard fireball model, GRBs are produced by synchrotron radiation and Compton scattering process in a highly relativistic jet ejected from the central engine. It is widely accepted that prompt emissions occur in the internal shock when shells with different velocities collide with each other, and the magnetic field advected by the jet from the central engine can be ordered on a large scale. On the other hand, afterglows are often assumed to occur in the external shock when the jet collides with interstellar medium, and the magnetic field produced by the shock through, for example, Weibel instability, is possibly random. In this paper, we calculate the polarization properties of the synchrotron self-Compton process from a highly relativistic jet, in which the magnetic field is randomly distributed in the shock plane. We also consider the generalized situation where a uniform magnetic component perpendicular to the shock plane is superposed on the random magnetic component. We show that it is difficult for the polarization to be larger than 10% if the seed electrons are isotropic in the jet frame. This may account for the observed upper limit of polarization in the afterglow phase of GRBs. In addition, if the random and uniform magnetic components decay with time at different speeds, then the polarization angle may change 90° during the temporal evolution. Supported by Fundamental Research Funds for the Central Universities (106112016CDJCR301206), National Natural Science Fund of China (11375203, 11603005), and Open Project Program of State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, China (Y5KF181CJ1)

In Search of Progenitors for Supernovaless Gamma-Ray Bursts 060505 and 060614: Re-examination of Their Afterglows

NASA Astrophysics Data System (ADS)

Xu, D.; Starling, R. L. C.; Fynbo, J. P. U.; Sollerman, J.; Yost, S.; Watson, D.; Foley, S.; O'Brien, P. T.; Hjorth, J.

2009-05-01

GRB 060505 and GRB 060614 are nearby long-duration gamma-ray bursts (LGRBs) without accompanying supernovae (SNe) down to very strict limits. They thereby challenge the conventional LGRB-SN connection and naturally give rise to the question: are there other peculiar features in their afterglows which would help shed light on their progenitors? To answer this question, we combine new observational data with published data and investigate the multiband temporal and spectral properties of the two afterglows. We find that both afterglows can be well interpreted within the framework of the jetted standard external shock wave model, and that the afterglow parameters for both bursts fall well within the range observed for other LGRBs. Hence, from the properties of the afterglows there is nothing to suggest that these bursts should have another progenitor than other LGRBs. Recently, Swift-discovered GRB 080503 also has the spike + tail structure during its prompt γ-ray emission seemingly similar to GRB 060614. We analyze the prompt emission of this burst and find that this GRB is actually a hard-spike + hard-tail burst with a spectral lag of 0.8 ± 0.4 s during its tail emission. Thus, the properties of the prompt emission of GRB 060614 and GRB 080503 are clearly different, motivating further thinking of GRB classification (and even identification of faint core-collapse SNe). Finally, we note that, whereas the progenitor of the two SN-less bursts remains uncertain, the core-collapse origin for the SN-less bursts would be quite certain if a windlike environment can be observationally established, e.g., from an optical decay faster than the X-ray decay in the afterglow's slow cooling phase. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile, under programs 077.D-0661 and 177.A-0591.

Hard X-ray spectral investigations of gamma-ray bursts 120521C and 130606A at high-redshift z ˜ 6

NASA Astrophysics Data System (ADS)

Yasuda, T.; Urata, Y.; Enomoto, J.; Tashiro, M. S.

2017-04-01

This study presents a temporal and spectral analysis of the prompt emission of two high-redshift gamma-ray bursts (GRBs), 120521C at z ˜ 6 and 130606A at z ˜ 5.91, using data obtained from the Swift-XRT/BAT and the Suzaku-WAM simultaneously. Based on follow-up XRT observations, the longest durations of the prompt emissions were approximately 80 s (120521C) and 360 s (130606A) in the rest-frames of the two GRBs. These objects are thus categorized as long-duration GRBs; however, the durations are short compared with the predicted duration of GRBs originating from first-generation stars. Because of the wide bandpass of the instruments, covering the ranges 15 keV-5 MeV (BAT-WAM) and 0.3 keV-5.0 MeV (XRT-BAT-WAM), we could successfully determine the νFν peak energies E_peak^src in the rest-frame and isotropic-equivalent radiated energies Eiso; E^src_peak = 682^{+845}_{-207} keV and E_iso = (8. 25^{+2.24}_{-1.96}) × 10^{52} erg for 120521C, and E^src_peak = 1209^{+553}_{-304} keV and E_iso = (2.82^{+0.17}_{-0.71}) × 10^{53} erg for 130606A. These obtained characteristic parameters are in accordance with the well-known relationship between E_peak^src and Eiso (Amati relationship). In addition, we examined the relationships between E_peak^src and the 1-s peak luminosity, Lp, and between E_peak^src and the geometrical corrected radiated energy, Eγ, and confirmed the E_peak^src-Lp (Yonetoku) and E_peak^src-Eγ (Ghirlanda) relationships. The results imply that these high-redshift GRBs at z ˜ 6, which are expected to have radiated during the reionization epoch, have properties similar to those of low-redshift GRBs regarding X-ray prompt emission.

An approach to derive some simple empirical equations to calibrate nuclear and acoustic well logging tools.

PubMed

Mohammad Al Alfy, Ibrahim

2018-01-01

A set of three pads was constructed from primary materials (sand, gravel and cement) to calibrate the gamma-gamma density tool. A simple equation was devised to convert the qualitative cps values to quantitative g/cc values. The neutron-neutron porosity tool measures the qualitative cps porosity values. A direct equation was derived to calculate the porosity percentage from the cps porosity values. Cement-bond log illustrates the cement quantities, which surround well pipes. This log needs a difficult process due to the existence of various parameters, such as: drilling well diameter as well as internal diameter, thickness and type of well pipes. An equation was invented to calculate the cement percentage at standard conditions. This equation can be modified according to varying conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Holistic Growth of College Peer Study Group Participants: Prompting Academic and Personal Development

ERIC Educational Resources Information Center

Arendale, David R.; Hane, Amanda R.

2014-01-01

This qualitative study focused on observed and perceived changes in academic and personal attitudes and behaviors by student participants in the Peer Assisted Learning (PAL) program at the University of Minnesota (UMN). The PAL model employs best practices from national peer learning models including Supplemental Instruction, Peer-led Team…

Special Education Teacher Retention: An Examination of Selected Veteran Teachers

ERIC Educational Resources Information Center

Hogan, Andrea E.

2012-01-01

Special Education Teacher Retention: An Examination of Selected Veteran Teachers is a qualitative study that examined what prompted veteran special education teachers to continue in the critical shortage fields even though they contend with challenging situations that have been a deterrent for others to remain in the classroom (e.g. Nelson, 2001).…

Taking Advantage of Automated Assessment of Student-Constructed Graphs in Science

ERIC Educational Resources Information Center

Vitale, Jonathan M.; Lai, Kevin; Linn, Marcia C.

2015-01-01

We present a new system for automated scoring of graph construction items that address complex science concepts, feature qualitative prompts, and support a range of possible solutions. This system utilizes analysis of spatial features (e.g., slope of a line) to evaluate potential student ideas represented within graphs. Student ideas are then…

A Methodological Self-Study of Quantitizing: Negotiating Meaning and Revealing Multiplicity

ERIC Educational Resources Information Center

Seltzer-Kelly, Deborah; Westwood, Sean J.; Pena-Guzman, David M.

2012-01-01

This inquiry developed during the process of "quantitizing" qualitative data the authors had gathered for a mixed methods curriculum efficacy study. Rather than providing the intended rigor to their data coding process, their use of an intercoder reliability metric prompted their investigation of the multiplicity and messiness that, as they…

Student Perceptions of SocialSim for Simulation-Based Interprofessional Education in Healthcare

ERIC Educational Resources Information Center

Smith, Mary Kathryn

2016-01-01

This descriptive qualitative study investigates perceptions of students regarding the use of SocialSim, a tool designed to deliver simulation in a virtual environment using social media as a platform to facilitate inteprofessional education. There have been exponential changes in U.S. healthcare system in recent years, prompting the need for…

Student Experiences with Writing: Taking the Temperature of the Classroom

ERIC Educational Resources Information Center

Zumbrunn, Sharon; Ekholm, Eric; Stringer, J. K.; McKnight, Kimberly; DeBusk-Lane, Morgan

2017-01-01

This article offers insights into students' perceptions of writing through the use of drawings and written responses. In a descriptive qualitative study of fifth graders across two diverse elementary schools, students were prompted to draw a picture about a recent experience with writing and how that experience made them feel. Students were then…

Exploring Ohio Police Preparedness for Active Shooter Incidents in Public Schools

ERIC Educational Resources Information Center

Pignatelli, Daniel A.

2010-01-01

School shootings, such as Columbine, have prompted police executives to explore response tactics and preparedness efforts for combating active shooters. This qualitative exploratory case study focused on specific preparation initiatives that have been implemented for the purpose of dealing with active shooters. Being prepared is one of the only…

Thinking Statistically in Writing: Journals and Discussion Boards in an Introductory Statistics Course

ERIC Educational Resources Information Center

Theoret, Julie M.; Luna, Andrea

2009-01-01

This action research combined qualitative and quantitative techniques to investigate two different types of writing assignments in an introductory undergraduate statistics course. The assignments were written in response to the same set of prompts but in two different ways: homework journal assignments or initial posts to a computer discussion…

Restorative Practices in the Collegiate Student Conduct Process: A Qualitative Analysis of Student Conduct Administrators' Perspectives

ERIC Educational Resources Information Center

Mikus, Robert L.

2014-01-01

Restorative justice philosophy and practices have been utilized in a variety of settings. Legislative reform prompted their application in the criminal and juvenile justice systems. They have also been utilized in employment, education, civic, human services and community settings. While their integration in elementary, intermediate and secondary…

Time evolution of the spectral break in the high-energy extra component of GRB 090926A

NASA Astrophysics Data System (ADS)

Yassine, M.; Piron, F.; Mochkovitch, R.; Daigne, F.

2017-10-01

Aims: The prompt light curve of the long GRB 090926A reveals a short pulse 10 s after the beginning of the burst emission, which has been observed by the Fermi observatory from the keV to the GeV energy domain. During this bright spike, the high-energy emission from GRB 090926A underwent a sudden hardening above 10 MeV in the form of an additional power-law component exhibiting a spectral attenuation at a few hundreds of MeV. This high-energy break has been previously interpreted in terms of gamma-ray opacity to pair creation and has been used to estimate the bulk Lorentz factor of the outflow. In this article, we report on a new time-resolved analysis of the GRB 090926A broadband spectrum during its prompt phase and on its interpretation in the framework of prompt emission models. Methods: We characterized the emission from GRB 090926A at the highest energies with Pass 8 data from the Fermi Large Area Telescope (LAT), which offer a greater sensitivity than any data set used in previous studies of this burst, particularly in the 30-100 MeV energy band. Then, we combined the LAT data with the Fermi Gamma-ray Burst Monitor (GBM) in joint spectral fits to characterize the time evolution of the broadband spectrum from keV to GeV energies. We paid careful attention to the systematic effects that arise from the uncertainties on the LAT response. Finally, we performed a temporal analysis of the light curves and we computed the variability timescales from keV to GeV energies during and after the bright spike. Results: Our analysis confirms and better constrains the spectral break, which has been previously reported during the bright spike. Furthermore, it reveals that the spectral attenuation persists at later times with an increase of the break characteristic energy up to the GeV domain until the end of the prompt phase. We discuss these results in terms of keV-MeV synchroton radiation of electrons accelerated during the dissipation of the jet energy and inverse Compton emission at higher energies. We interpret the high-energy spectral break as caused by photon opacity to pair creation. Requiring that all emissions are produced above the photosphere of GRB 090926A, we compute the bulk Lorentz factor of the outflow, Γ. The latter decreases from 230 during the spike to 100 at the end of the prompt emission. Assuming, instead, that the spectral break reflects the natural curvature of the inverse Compton spectrum, lower limits corresponding to larger values of Γ are also derived. Combined with the extreme temporal variability of GRB 090926A, these Lorentz factors lead to emission radii R 1014 cm, which are consistent with an internal origin of both the keV-MeV and GeV prompt emissions.

Portraying Reflexivity in Health Services Research.

PubMed

Rae, John; Green, Bill

2016-09-01

A model is proposed for supporting reflexivity in qualitative health research, informed by arguments from Bourdieu and Finlay. Bourdieu refers to mastering the subjective relation to the object at three levels-the overall social space, the field of specialists, and the scholastic universe. The model overlays Bourdieu's levels of objectivation with Finlay's three stages of research (pre-research, data collection, and data analysis). The intersections of these two ways of considering reflexivity, displayed as cells of a matrix, pose questions and offer prompts to productively challenge health researchers' reflexivity. Portraiture is used to show how these challenges and prompts can facilitate such reflexivity, as illustrated in a research project. © The Author(s) 2016.

Modeling X-ray and gamma-ray emission in the intrabinary shock of pulsar binaries

NASA Astrophysics Data System (ADS)

An, H.

2017-10-01

We present broadband SED and light curve, and a wind interaction model for the gamma-ray binary 1FGL J1018.6-5856 (J1018) which exhibits double peaks in the X-ray light curve. Assuming that the X-ray to low-energy gamma-ray emission is produced by synchrotron radiation and high-energy gamma rays by inverse Compton scattering in the intrabinary shock (IBS), we model the broadband SED and light curve of J1018 using a two-component model having slow electrons in the shock and fast bulk-accelerated electrons at the skin of the shock. The model explains the broadband SED and light curve of J1018 qualitatively well. In particular, modeling the synchrotron emission constrains the orbital geometry. We discuss potential use of the model for other pulsar binaries.

Soliciting additional concerns in the primary care consultation and the utility of a brief communication intervention to aid solicitation: A qualitative study.

PubMed

Summers, Rachael H; Moore, Michael; Ekberg, Stuart; Chew-Graham, Carolyn A; Little, Paul; Stevenson, Fiona; Brindle, Lucy; Leydon, Geraldine M

2016-05-01

To investigate the perspectives of general practitioners (GPs) on the practice of soliciting additional concerns (ACs) and the acceptability and utility of two brief interventions (prompts) designed to aid the solicitation. Eighteen GPs participating in a feasibility randomised controlled trial were interviewed. Interviews were semi-structured and audio-recorded. Data were analysed using a Framework Approach. Participants perceived eliciting ACs as important for: reducing the need for multiple visits, identifying serious illness early, and increasing patient and GP satisfaction. GPs found the prompts easy to use and some continued their use after the study had ended to aid time management. Others noted similarities between the intervention and their usual practice. Nevertheless, soliciting ACs in every consultation was not unanimously supported. The prompts were acceptable to GPs within a trial context, but there was disagreement as to whether ACs should be solicited routinely. Some GPs considered the intervention to aid their prioritisation efficiency within consultations. Some GPs will find prompts which encourage ACs to be solicited early in the consultation enable them to better organise priorities and manage time-limited consultations more effectively. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Brain network dynamics in the human articulatory loop.

PubMed

Nishida, Masaaki; Korzeniewska, Anna; Crone, Nathan E; Toyoda, Goichiro; Nakai, Yasuo; Ofen, Noa; Brown, Erik C; Asano, Eishi

2017-08-01

The articulatory loop is a fundamental component of language function, involved in the short-term buffer of auditory information followed by its vocal reproduction. We characterized the network dynamics of the human articulatory loop, using invasive recording and stimulation. We measured high-gamma activity 70-110 Hz recorded intracranially when patients with epilepsy either only listened to, or listened to and then reproduced two successive tones by humming. We also conducted network analyses, and analyzed behavioral responses to cortical stimulation. Presentation of the initial tone elicited high-gamma augmentation bilaterally in the superior-temporal gyrus (STG) within 40ms, and in the precentral and inferior-frontal gyri (PCG and IFG) within 160ms after sound onset. During presentation of the second tone, high-gamma augmentation was reduced in STG but enhanced in IFG. The task requiring tone reproduction further enhanced high-gamma augmentation in PCG during and after sound presentation. Event-related causality (ERC) analysis revealed dominant flows within STG immediately after sound onset, followed by reciprocal interactions involving PCG and IFG. Measurement of cortico-cortical evoked-potentials (CCEPs) confirmed connectivity between distant high-gamma sites in the articulatory loop. High-frequency stimulation of precentral high-gamma sites in either hemisphere induced speech arrest, inability to control vocalization, or forced vocalization. Vocalization of tones was accompanied by high-gamma augmentation over larger extents of PCG. Bilateral PCG rapidly and directly receives feed-forward signals from STG, and may promptly initiate motor planning including sub-vocal rehearsal for short-term buffering of auditory stimuli. Enhanced high-gamma augmentation in IFG during presentation of the second tone may reflect high-order processing of the tone sequence. The articulatory loop employs sustained reciprocal propagation of neural activity across a network of cortical sites with strong neurophysiological connectivity. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

No changes in serum concentrations of interleukin 10 (IL-10) and interferon gamma (IF-gamma) before and after treatment of the thyroid eye disease (TED).

PubMed

Laban-Guceva, Nevenka; Antova, Magdalena; Bogoev, Milco

2007-11-01

TED is a severe eye disease leading in rare cases to decrease of sight, optic nerve compression and blindness. Recently, significant progresses in understanding the disease have been done. Nevertheless, the treatment of the disease, especially in its severe form remains challenging. Glucocorticoids (GC) have been the basis of the treatment for a long time. Orbital irradiation (OI) and optical decompression (OD) are also used in managing the severe forms of TED. Somatostatin, intravenous immunoglobulin have been also used, with conflicting results. Regarding the potential for the treatment of TED with cytokine antagonists, controlled clinical studies are not available. Since cytokines play an important role in the pathogenesis of the TED, they seemed to be logical choice for modern TED treatment. It has been shown that both Th1 (interleukin-2, tumor necrosis factor gamma, interleukin gamma) and Th2 (interleukin -4, -5, -10) profile T cells are activated in the TED. We therefore measured interleukin-gamma, IF-gamma and interleukin -10 (IL-10)(Th1 and Th2 pattern) to assess its relationship to the course of the disease. This paper shows that both Th1 (IL-2) and Th2 (IF-gamma) pathways represented by those two cytokines are not involved (IL-10 before 2.29+/-5.23 and after treatment 3.77+/-8.44; IF gamma before 0.50+/-0.24 and after treatment 0.35+/-0.19). No relationship to the response to treatment was found. GC resulted in positive response in 8/22 patients, OI (12 patients) given after CS therapy, resulted in a response in all patients. Increase in proptosis, loss of visual acuity is spite of CS treatment prompted OD in two patients, who both recovered visual acuity and proptosis fell under 25 mm Hertel.

Fermi Observations of GRB 090510: A Short Hard Gamma-Ray Burst with an Additional, Hard Power-Law Component from 10 keV to GeV Energies

DOE PAGES

Ackermann, M.; Asano, K.; Atwood, W. B.; ...

2010-05-27

We present detailed observations of the bright short-hard gamma-ray burst GRB 090510 made with the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) on board the Fermi observatory. GRB 090510 is the first burst detected by the LAT that shows strong evidence for a deviation from a Band spectral fitting function during the prompt emission phase. The time-integrated spectrum is fit by the sum of a Band function with E peak = 3.9 ± 0.3 MeV, which is the highest yet measured, and a hard power-law component with photon index –1.62 ± 0.03 that dominates the emission below ≈20more » keV and above ≈100 MeV. The onset of the high-energy spectral component appears to be delayed by ~0.1 s with respect to the onset of a component well fit with a single Band function. A faint GBM pulse and a LAT photon are detected 0.5 s before the main pulse. During the prompt phase, the LAT detected a photon with energy 30.5 +5.8 –2.6 GeV, the highest ever measured from a short GRB. Observation of this photon sets a minimum bulk outflow Lorentz factor, Γ≳ 1200, using simple γγ opacity arguments for this GRB at redshift z = 0.903 and a variability timescale on the order of tens of ms for the ≈100 keV-few MeV flux. Stricter high confidence estimates imply Γ ≳ 1000 and still require that the outflows powering short GRBs are at least as highly relativistic as those of long-duration GRBs. Finally, implications of the temporal behavior and power-law shape of the additional component on synchrotron/synchrotron self-Compton, external-shock synchrotron, and hadronic models are considered.« less

Evaluation of learning from Practical Obstetric Multi-Professional Training and its impact on patient outcomes in Australia using Kirkpatrick's framework: a mixed methods study.

PubMed

Kumar, Arunaz; Sturrock, Sam; Wallace, Euan M; Nestel, Debra; Lucey, Donna; Stoyles, Sally; Morgan, Jenny; Neil, Peter; Schlipalius, Michelle; Dekoninck, Philip

2018-02-17

The aim of this study was to evaluate the implementation of the Practical Obstetric Multi-Professional Training (PROMPT) simulation using the Kirkpatrick's framework. We explored participants' acquisition of knowledge and skills, its impact on clinical outcomes and organisational change to integrate the PROMPT programme as a credentialing tool. We also aimed to assess participants' perception of usefulness of PROMPT in their clinical practice. Mixed methods approach with a pre-test/post-test design. Healthcare network providing obstetric care in Victoria, Australia. Medical and midwifery staff attending PROMPT between 2013 and 2015 (n=508); clinical outcomes were evaluated in two cohorts: 2011-2012 (n=15 361 births) and 2014-2015 (n=12 388 births). Attendance of the PROMPT programme, a simulation programme taught in multidisciplinary teams to facilitate teaching emergency obstetric skills. Clinical outcomes compared before and after embedding PROMPT in educational practice. Assessment of knowledge gained by participants through a qualitative analysis and description of process of embedding PROMPT in educational practice. There was a change in the management of postpartum haemorrhage by early recognition and intervention. The key learning themes described by participants were being prepared with a prior understanding of procedures and equipment, communication, leadership and learning in a safe, supportive environment. Participants reported a positive learning experience and increase in confidence in managing emergency obstetric situations through the PROMPT programme, which was perceived as a realistic demonstration of the emergencies. Participants reported an improvement of both clinical and non-technical skills highlighting principles of teamwork, communication, leadership and prioritisation in an emergency situation. An improvement was observed in management of postpartum haemorrhage, but no significant change was noted in clinical outcomes over a 2-year period after PROMPT. However, the skills acquired by medical and midwifery staff justify embedding PROMPT in educational programmes. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Feasibility study of prompt gamma neutron activation for NDT measurement of moisture in stone and brick

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

Livingston, R. A.; Al-Sheikhly, M.; Grissom, C.

2014-02-18

The conservation of stone and brick architecture or sculpture often involves damage caused by moisture. The feasibility of a NDT method based on prompt gamma neutron activation (PGNA) for measuring the element hydrogen as an indication of water is being evaluated. This includes systematic characterization of the lithology and physical properties of seven building stones and one brick type used in the buildings of the Smithsonian Institution in Washington, D.C. To determine the required dynamic range of the NDT method, moisture-related properties were measured by standard methods. Cold neutron PGNA was also used to determine chemically bound water (CBW) content.more » The CBW does not damage porous masonry, but creates an H background that defines the minimum level of detection of damaging moisture. The CBW was on the order of 0.5% for all the stones. This rules out the measurement of hygric processes in all of the stones and hydric processed for the stones with fine scale pore-size distributions The upper bound of moisture content, set by porosity through water immersion, was on the order of 5%. The dynamic range is about 10–20. The H count rates were roughly 1–3 cps. Taking into account differences in neutron energies and fluxes and sample volume between cold PGNA and a portable PGNA instrument, it appears that it is feasible to apply PGNA in the field.« less

Development of a Compton camera for prompt-gamma medical imaging

NASA Astrophysics Data System (ADS)

Aldawood, S.; Thirolf, P. G.; Miani, A.; Böhmer, M.; Dedes, G.; Gernhäuser, R.; Lang, C.; Liprandi, S.; Maier, L.; Marinšek, T.; Mayerhofer, M.; Schaart, D. R.; Lozano, I. Valencia; Parodi, K.

2017-11-01

A Compton camera-based detector system for photon detection from nuclear reactions induced by proton (or heavier ion) beams is under development at LMU Munich, targeting the online range verification of the particle beam in hadron therapy via prompt-gamma imaging. The detector is designed to be capable to reconstruct the photon source origin not only from the Compton scattering kinematics of the primary photon, but also to allow for tracking of the secondary Compton-scattered electrons, thus enabling a γ-source reconstruction also from incompletely absorbed photon events. The Compton camera consists of a monolithic LaBr3:Ce scintillation crystal, read out by a multi-anode PMT acting as absorber, preceded by a stacked array of 6 double-sided silicon strip detectors as scatterers. The detector components have been characterized both under offline and online conditions. The LaBr3:Ce crystal exhibits an excellent time and energy resolution. Using intense collimated 137Cs and 60Co sources, the monolithic scintillator was scanned on a fine 2D grid to generate a reference library of light amplitude distributions that allows for reconstructing the photon interaction position using a k-Nearest Neighbour (k-NN) algorithm. Systematic studies were performed to investigate the performance of the reconstruction algorithm, revealing an improvement of the spatial resolution with increasing photon energy to an optimum value of 3.7(1)mm at 1.33 MeV, achieved with the Categorical Average Pattern (CAP) modification of the k-NN algorithm.

PSF reconstruction for Compton-based prompt gamma imaging

NASA Astrophysics Data System (ADS)

Jan, Meei-Ling; Lee, Ming-Wei; Huang, Hsuan-Ming

2018-02-01

Compton-based prompt gamma (PG) imaging has been proposed for in vivo range verification in proton therapy. However, several factors degrade the image quality of PG images, some of which are due to inherent properties of a Compton camera such as spatial resolution and energy resolution. Moreover, Compton-based PG imaging has a spatially variant resolution loss. In this study, we investigate the performance of the list-mode ordered subset expectation maximization algorithm with a shift-variant point spread function (LM-OSEM-SV-PSF) model. We also evaluate how well the PG images reconstructed using an SV-PSF model reproduce the distal falloff of the proton beam. The SV-PSF parameters were estimated from simulation data of point sources at various positions. Simulated PGs were produced in a water phantom irradiated with a proton beam. Compared to the LM-OSEM algorithm, the LM-OSEM-SV-PSF algorithm improved the quality of the reconstructed PG images and the estimation of PG falloff positions. In addition, the 4.44 and 5.25 MeV PG emissions can be accurately reconstructed using the LM-OSEM-SV-PSF algorithm. However, for the 2.31 and 6.13 MeV PG emissions, the LM-OSEM-SV-PSF reconstruction provides limited improvement. We also found that the LM-OSEM algorithm followed by a shift-variant Richardson-Lucy deconvolution could reconstruct images with quality visually similar to the LM-OSEM-SV-PSF-reconstructed images, while requiring shorter computation time.

A low-count reconstruction algorithm for Compton-based prompt gamma imaging

NASA Astrophysics Data System (ADS)

Huang, Hsuan-Ming; Liu, Chih-Chieh; Jan, Meei-Ling; Lee, Ming-Wei

2018-04-01

The Compton camera is an imaging device which has been proposed to detect prompt gammas (PGs) produced by proton–nuclear interactions within tissue during proton beam irradiation. Compton-based PG imaging has been developed to verify proton ranges because PG rays, particularly characteristic ones, have strong correlations with the distribution of the proton dose. However, accurate image reconstruction from characteristic PGs is challenging because the detector efficiency and resolution are generally low. Our previous study showed that point spread functions can be incorporated into the reconstruction process to improve image resolution. In this study, we proposed a low-count reconstruction algorithm to improve the image quality of a characteristic PG emission by pooling information from other characteristic PG emissions. PGs were simulated from a proton beam irradiated on a water phantom, and a two-stage Compton camera was used for PG detection. The results show that the image quality of the reconstructed characteristic PG emission is improved with our proposed method in contrast to the standard reconstruction method using events from only one characteristic PG emission. For the 4.44 MeV PG rays, both methods can be used to predict the positions of the peak and the distal falloff with a mean accuracy of 2 mm. Moreover, only the proposed method can improve the estimated positions of the peak and the distal falloff of 5.25 MeV PG rays, and a mean accuracy of 2 mm can be reached.

Linac based photofission inspection system employing novel detection concepts

NASA Astrophysics Data System (ADS)

Stevenson, John; Gozani, Tsahi; Elsalim, Mashal; Condron, Cathie; Brown, Craig

2011-10-01

Rapiscan Systems is developing a LINAC based cargo inspection system for detection of special nuclear material (SNM) in cargo containers. The system, called Photofission Based Alarm Resolution (PBAR) is being developed under a DHD/DNDO Advanced Technology Demonstration (ATD) program. The PBAR system is based on the Rapiscan Eagle P9000 X-ray system, which is a portal system with a commercial 9 MeV LINAC X-ray source. For the purposes of the DNDO ATD program, a conveyor system was installed in the portal to allow scanning and precise positioning of 20 ft ISO cargo containers. The system uses a two step inspection process. In the first step, the basic scan, the container is quickly and completely inspected using two independent radiography arrays: the conventional primary array with high spatial resolution and a lower resolution spectroscopic array employing the novel Z-Spec method. The primary array uses cadmium tungstate (CdWO 4) detectors with conventional current mode readouts using photodiodes. The Z-Spec array uses small plastic scintillators capable of performing very fast (up to 10 8 cps) gamma-ray spectroscopy. The two radiography arrays are used to locate high-Z objects in the image such as lead, tungsten, uranium, which could be potential shielding materials as well as SNM itself. In the current system, the Z-Spec works by measuring the energy spectrum of transmitted X-rays. For high-Z materials the higher end of the energy spectrum is more attenuated than for low-Z materials and thus has a lower mean energy and a narrower width than low- and medium-Z materials. The second step in the inspection process is the direct scan or alarm clearing scan. In this step, areas of the container image, which were identified as high Z, are re-inspected. This is done by precisely repositioning the container to the location of the high-Z object and performing a stationary irradiation of the area with X-ray beam. Since there are a large number of photons in the 9 MV Bremsstrahlung spectrum above the photofission "threshold" of about 6 MeV, the X-ray beam induces numerous fissions if nuclear material is present. The PBAR system looks for the two most prolific fission signatures to confirm the presence of special nuclear materials (SNM). These are prompt neutrons and delayed gamma rays. The PBAR system uses arrays of two types of fast and highly efficient gamma ray detectors: plastic and fluorocarbon scintillators. The latter serves as a detector of fission prompt neutrons using the novel threshold activation detector (TAD) concept as well as a very efficient delayed gamma ray detector. The major advantage of TAD for detecting the prompt neutrons is its insensitivity to the intense source related backgrounds. The current status of the system and experimental results will be shown and discussed.

Study of the effect of gamma irradiation on a commercial polycyclooctene I. Thermal and mechanical properties

NASA Astrophysics Data System (ADS)

García-Huete, N.; Laza, J. M.; Cuevas, J. M.; Vilas, J. L.; Bilbao, E.; León, L. M.

2014-09-01

A gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical, chemical and mechanical properties. Gamma irradiation originates free radicals able to induce chain scission or recombination of radicals, which induces annihilation, branching or crosslinking processes. The aim of this work is to research the structural, thermal and mechanical changes induced on a commercial polycyclooctene (PCO) when it is irradiated with a gamma source of 60Co at different doses (25-200 kGy). After gamma irradiation, gel content was determined by Soxhlet extraction in cyclohexane. Furthermore, thermal properties were evaluated before and after Soxhlet extraction by means of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), as well as mechanical properties were measured by Dynamic Mechanical Thermal Analysis (DMTA). The results showed the variations of the properties depending on the irradiation dose. Finally, a first approach to evaluate qualitatively the shape memory behaviour of all irradiated PCO samples was performed by a visually monitoring shape recovery process.

Ethical issues in the reuse of qualitative data: perspectives from literature, practice, and participants.

PubMed

Yardley, Sarah J; Watts, Kate M; Pearson, Jennifer; Richardson, Jane C

2014-01-01

In this article, we explore ethical issues in qualitative secondary analysis through a comparison of the literature with practitioner and participant perspectives. To achieve this, we integrated critical narrative review findings with data from two discussion groups: qualitative researchers and research users/consumers. In the literature, we found that theoretical debate ran parallel to practical action rather than being integrated with it. We identified an important and novel theme of relationships that was emerging from the perspectives of researchers and users. Relationships were significant with respect to trust, sharing data, transparency and clarity, anonymity, permissions, and responsibility. We provide an example of practice development that we hope will prompt researchers to re-examine the issues in their own setting. Informing the research community of research practitioner and user perspectives on ethical issues in the reuse of qualitative data is the first step toward developing mechanisms to better integrate theoretical and empirical work.

Detection of the thermal component in GRB 160107A

NASA Astrophysics Data System (ADS)

Kawakubo, Yuta; Sakamoto, Takanori; Nakahira, Satoshi; Yamaoka, Kazutaka; Serino, Motoko; saoka, Yoichi; Cherry, Michael L.; Matsukawa, Shohei; Mori, Masaki; Nakagawa, Yujin; Ozawa, Shunsuke; Penacchioni, Ana V.; Ricciarini, Sergio B.; Tezuka, Akira; Torii, Shoji; Yamada, Yusuke; Yoshida, Atsumasa

2018-01-01

We present the detection of a blackbody component in gamma-ray burst GRB 160107A emission by using the combined spectral data of the CALET Gamma-ray Burst Monitor (CGBM) and the MAXI Gas Slit Camera (GSC). MAXI/GSC detected the emission ˜45 s prior to the main burst episode observed by the CGBM. The MAXI/GSC and the CGBM spectrum of this prior emission period is fitted well by a blackbody with temperature 1.0^{+0.3}_{-0.2} keV plus a power law with a photon index of -1.6 ± 0.3. We discuss the radius of the photospheric emission and the main burst emission based on the observational properties. We stress the importance of coordinated observations via various instruments collecting high-quality data over a broad energy coverage in order to understand the GRB prompt emission mechanism.

Properties of gamma-ray burst progenitor stars.

PubMed

Kumar, Pawan; Narayan, Ramesh; Johnson, Jarrett L

2008-07-18

We determined some basic properties of stars that produce spectacular gamma-ray bursts at the end of their lives. We assumed that accretion of the outer portion of the stellar core by a central black hole fuels the prompt emission and that fall-back and accretion of the stellar envelope later produce the plateau in the x-ray light curve seen in some bursts. Using x-ray data for three bursts, we estimated the radius of the stellar core to be approximately (1 - 3) x 10(10) cm and that of the stellar envelope to be approximately (1 - 2) x 10(11) cm. The density profile in the envelope is fairly shallow, with rho approximately r(-2) (where rho is density and r is distance from the center of the explosion). The rotation speeds of the core and envelope are approximately 0.05 and approximately 0.2 of the local Keplerian speed, respectively.

Transient Phenomena: Opportunities for New Discoveries

NASA Technical Reports Server (NTRS)

Lazio, T. Joseph W.

2010-01-01

Known classes of radio wavelength transients range from the nearby (stellar flares and radio pulsars) to the distant Universe (gamma-ray burst afterglows). Hypothesized classes of radio transients include analogs of known objects, such as extrasolar planets emitting Jovian-like radio bursts and giant-pulse emitting pulsars in other galaxies, to the exotic, such as prompt emission from gamma-ray bursts, evaporating black holes and transmitters from other civilizations. Time domain astronomy has been recognized internationally as a means of addressing key scientific questions in astronomy and physics, and pathfinders and Precursors to the Square Kilometre Array (SKA) are beginning to offer a combination of wider fields of view and more wavelength agility than has been possible in the past. These improvements will continue when the SKA itself becomes operational. I illustrate the range of transient phenomena and discuss how the detection and study of radio transients will improve immensely.

Correlative Analysis of GRBs detected by Swift, Konus and HETE

NASA Technical Reports Server (NTRS)

Krimm, Hans A.; Barthelmy, S. D.; Gehrels, N.; Hullinger, D.; Sakamoto, T.; Donaghy, T.; Lamb, D. Q.; Pal'shin, V.; Golenetskii, S.; Ricker, G. R.

2005-01-01

Swift has now detected a large enough sample of gamma-ray bursts (GRBs) to allow correlation studies of burst parameters. Such studies of earlier data sets have yielded important results leading to further understanding of burst parameters and classifications. This work focuses on seventeen Swift bursts that have also been detected either by Konus-Wind or HETE-II, providing high energy spectra and fits to E(sub peak). Eight of these bursts have spectroscopic redshifts and for others we can estimate redshifts using the variability/luminosity relationship. We can also compare E(sub peak) with E(sub iso), and for those bursts for which a jet break was observed in the afterglow we can derive E(sub g) and test the relationship between E(peak) and E(sub gamma). For all bursts we can derive durations and hardness ratios from the prompt emission.

N * → Nη ' decays from photoproduction of η ' -mesons off protons

DOE PAGES

Anisovich, A. V.; Burkert, V.; Collins, P. M.; ...

2017-06-27

We presented a study of the partial-wave content of themore » $$\\gamma p\\to \\eta^\\prime p$$ reaction in the fourth resonance region, which has been prompted by new measurements of polarization observables for that process. Using the Bonn-Gatchina partial-wave formalism, the incorporation of new data indicates that the $N(1895)1/2^-$, $N(1900)3/2^+$, $N(2100)1/2^+$, and $N(2120)3/2^-$ are the most significant contributors to the photoproduction process. Some new results for the branching ratios of the decays of these more prominent resonances to $$N\\eta^\\prime$$ final states are provided; such branches have not been indicated in the most recent edition of the Review of Particle Properties. Based on the analysis performed here, predictions for the helicity asymmetry $E$ for the $$\\gamma p\\to \\eta^\\prime p$$ reaction are presented.« less

Simulation of High Energy Emission from Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Ziaeepour, Houri

Gamma-Ray Bursts (GRBs) are the must violent explosions after the Big-Bang. Their high energy radiation can potentially carry information about the most inner part of the accretion disk of a collapsing star, ionize the surrounding material in the host galaxy, and thereby influence the process of star formation specially in the dense environment at high redshifts. They can also have a significant contribution in the formation of high energy cosmic-rays. Here we present new simulations of GRBs according to a dynamically consistent relativistic shock model for the prompt emission, with or without the presence of an magnetic field. They show that the properties of observed bursts are well reproduced by this model up to GeV energies. They help to better understand GRB phenomenon, and provide an insight into characteristics of relativistic jets and particle acceleration which cannot yet be simulated with enough precision from first principles.

Microstructural probing of ferritic/martensitic steels using internal transmutation-based positron source

NASA Astrophysics Data System (ADS)

Krsjak, Vladimir; Dai, Yong

2015-10-01

This paper presents the use of an internal 44Ti/44Sc radioisotope source for a direct microstructural characterization of ferritic/martensitic (f/m) steels after irradiation in targets of spallation neutron sources. Gamma spectroscopy measurements show a production of ∼1MBq of 44Ti per 1 g of f/m steels irradiated at 1 dpa (displaced per atom) in the mixed proton-neutron spectrum at the Swiss spallation neutron source (SINQ). In the decay chain 44Ti → 44Sc → 44Ca, positrons are produced together with prompt gamma rays which enable the application of different positron annihilation spectroscopy (PAS) analyses, including lifetime and Doppler broadening spectroscopy. Due to the high production yield, long half-life and relatively high energy of positrons of 44Ti, this methodology opens up new potential for simple, effective and inexpensive characterization of radiation induced defects in f/m steels irradiated in a spallation target.

Study of fission fragment de-excitation by gamma-ray spectrometry with the EXILL experiment

NASA Astrophysics Data System (ADS)

Materna, Thomas; a, Michal Rapał; Letourneau, Alain; Marchix, Anthony; Litaize, Olivier; Sérot, Olivier; Urban, Waldemar; Blanc, Aurélien; Jentschel, Michael; Köster, Ulli; Mutti, Paolo; Soldner, Torsten; Simpson, Gary; Ur, Călin A.; France, Gilles de

2017-09-01

A large array of Ge detectors installed at ILL, around a 235U target irradiated with cold neutrons, (EXILL) allowed measurement of prompt gamma-ray cascades occurring in fission fragments with an unambiguous determination of fragments. Here we present preliminary results of a systematic comparison between experimental γ-ray intensities and those obtained from the Monte-Carlo simulation code FIFRELIN, which is dedicated to the de-excitation of fission fragments. Major γ-ray intensities in the 142Ba and 92Kr fission products, extracted from EXILL data, were compared to FIFRELIN, as well as to reported values (when available) obtained with EUROGAM2 in the spontaneous fission of 248Cm. The evolution of γ-ray intensities in 92Kr versus the complementary partner in fission (i.e. versus the total number of evaporated neutrons by the fission pair) was then extracted and compared to FIFRELIN.

The effect of pair cascades on the high-energy spectral cut-off in gamma-ray bursts

NASA Astrophysics Data System (ADS)

Gill, Ramandeep; Granot, Jonathan

2018-03-01

The highly luminous and variable prompt emission in gamma-ray bursts (GRBs) arises in an ultra-relativistic outflow. The exact underlying radiative mechanism shaping its non-thermal spectrum is still uncertain, making it hard to determine the outflow's bulk Lorentz factor Γ. GRBs with spectral cut-off due to pair production (γγ → e+e-) at energies Ec ≳ 10 MeV are extremely useful for inferring Γ. We find that when the emission region has a high enough compactness, then as it becomes optically thick to scattering, Compton downscattering by non-relativistic e±-pairs can shift the spectral cut-off energy well below the self-annihilation threshold, Esa = Γmec2/(1 + z). We treat this effect numerically and show that Γ obtained assuming Ec = Esa can underpredict its true value by as much as an order of magnitude.

Qualitative Issues of Planning in a Dutch University. AIR 1985 Annual Forum Paper.

ERIC Educational Resources Information Center

Savenije, Bas; Otten, Christ

Results of changes to the planning process at the University of Utrecht in the Netherlands are described. During the past years, government actions related to retrenchment prompted the Dutch universities to change their planning process in order to increase flexibility and to account for differences in quality. Two important procedures were…

Not on the Same Page: Undergraduates' Information Retrieval in Electronic and Print Books

ERIC Educational Resources Information Center

Berg, Selinda Adelle; Hoffmann, Kristin; Dawson, Diane

2010-01-01

Academic libraries are increasingly collecting e-books, but little research has investigated how students use e-books compared to print texts. This study used a prompted think-aloud method to gain an understanding of the information retrieval behavior of students in both formats. Qualitative analysis identified themes that will inform instruction…

Naming a Personal "Unearned" Privilege: What Pre-Service Teachers Identify after a Critical Multicultural Education Course

ERIC Educational Resources Information Center

Whiting, Erin Feinauer; Cutri, Ramona Maile

2015-01-01

This qualitative study systematically documents pre-service teachers' responses to a writing prompt asking them to name a personal "unearned" privilege on an end-of-term final assessment. Findings suggest that typical White/European heritage pre-service teachers can name privileges that have advantaged their own lives, even after one…

Patient Handoffs between Emergency Department and Inpatient Physicians: A Qualitative Study to Inform Standardization of Practice and Organization Theory

ERIC Educational Resources Information Center

Hilligoss, Phillip Brian

2011-01-01

This dissertation is motivated by two problems. First, existing literature characterizes patient handoff as an information transfer activity in which safety and quality are compromised by practice variation. This has prompted a movement to standardize practice. However, existing research has not closely examined how practice variations may be…

Choice of the Medium of Instruction in Kenyan Preschools: Averting Xenocentrism

ERIC Educational Resources Information Center

Waithaka, Esther N.

2017-01-01

This qualitative study sought to prompt a critical and reflective discourse on the dismal use of mother tongue in Kenyan early childhood education (ECE) institutions in an attempt to detect existence of xenocentrism. Although the Kenyan ECE policy framework sanctions use of the language of the catchment area when teaching and communicating with…

We All as a Family Are Graduating Tonight: A Case for Mathematical Knowledge for Parental Involvement

ERIC Educational Resources Information Center

Knapp, Andrea; Landers, Racheal; Liang, Senfeng; Jefferson, Vetrece

2017-01-01

The researchers in this study investigated the impact of mathematics-focused parental involvement on Kindergarten to Grade 8 children and parents as well as factors prompting that impact. Qualitative analysis consisting of parent, child, and teacher interviews and 3-year quantitative testing showed significant improvements in students' mathematics…

Semantic Structure of Classroom Discourse Concerning Proof and Proving in High School Mathematics

ERIC Educational Resources Information Center

Ugurel, Isikhan; Boz-Yaman, Burcak

2017-01-01

This study tries to identify high school students' knowledge about the concept of proof, based on classroom discussion. The processes of discourses, both natural and prompted, are studied as they occur between students and teachers. The study employs discourse analysis as the qualitative research framework. Participants are 13 Science High School…

Advanced image fusion algorithms for Gamma Knife treatment planning. Evaluation and proposal for clinical use.

PubMed

Apostolou, N; Papazoglou, Th; Koutsouris, D

2006-01-01

Image fusion is a process of combining information from multiple sensors. It is a useful tool implemented in the treatment planning programme of Gamma Knife Radiosurgery. In this paper we evaluate advanced image fusion algorithms for Matlab platform and head images. We develop nine level grayscale image fusion methods: average, principal component analysis (PCA), discrete wavelet transform (DWT) and Laplacian, filter - subtract - decimate (FSD), contrast, gradient, morphological pyramid and a shift invariant discrete wavelet transform (SIDWT) method in Matlab platform. We test these methods qualitatively and quantitatively. The quantitative criteria we use are the Root Mean Square Error (RMSE), the Mutual Information (MI), the Standard Deviation (STD), the Entropy (H), the Difference Entropy (DH) and the Cross Entropy (CEN). The qualitative are: natural appearance, brilliance contrast, presence of complementary features and enhancement of common features. Finally we make clinically useful suggestions.

Technical Note: Experimental carbon ion range verification in inhomogeneous phantoms using prompt gammas

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

Pinto, M.; Dauvergne, D.; Dedes, G.

2015-05-15

Purpose: The purpose of this study was to experimentally assess the possibility to monitor carbon ion range variations—due to tumor shift and/or elongation or shrinking—using prompt-gamma (PG) emission with inhomogeneous phantoms. Such a study is related to the development of PG monitoring techniques to be used in a carbon ion therapy context. Methods: A 95 MeV/u carbon ion beam was used to irradiate phantoms with a variable density along the ion path to mimic the presence of bone and lung in homogeneous humanlike tissue. PG profiles were obtained after a longitudinal scan of the phantoms. A setup comprising a narrowmore » single-slit collimator and two detectors placed at 90° with respect to the beam axis was used. The time of flight technique was applied to allow the selection between PG and background events. Results: Using the positions at 50% entrance and 50% falloff of the PG profiles, a quantity called prompt-gamma profile length (PGPL) is defined. It is possible to observe shifts in the PGPL when there are absolute ion range shifts as small as 1–2 mm. Quantitatively, for an ion range shift of −1.33 ± 0.46 mm (insertion of a Teflon slab), a PGPL difference of −1.93 ± 0.58 mm and −1.84 ± 1.27 mm is obtained using a BaF{sub 2} and a NaI(Tl) detector, respectively. In turn, when an ion range shift of 4.59 ± 0.42 mm (insertion of a lung-equivalent material slab) is considered, the difference is of 4.10 ± 0.54 and 4.39 ± 0.80 mm for the same detectors. Conclusions: Herein, experimental evidence of the usefulness of employing PG to monitor carbon ion range using inhomogeneous phantoms is presented. Considering the homogeneous phantom as reference, the results show that the information provided by the PG emission allows for detecting ion range shifts as small as 1–2 mm. When considering the expected PG emission from an energy slice in a carbon ion therapy scenario, the experimental setup would allow to retrieve the same PGPL as the high statistics of the full experimental dataset in 58% of the times. However, this success rate increases to 93% when using a better optimized setup by means of Monte Carlo simulations.« less

CORONAS-F observation of gamma-ray emission from the solar flare on 2003 October 29

NASA Astrophysics Data System (ADS)

Kurt, Victoria G.; Yushkov, Boris Yu.; Galkin, Vladimir I.; Kudela, Karel; Kashapova, Larisa K.

2017-10-01

Appreciable hard X-ray (HXR) and gamma-ray emissions in the 0.04-150 MeV energy range associated with the 2003 October 29 solar flare (X10/3B) were observed at 20:38-20:58 UT by the SONG instrument onboard the CORONAS-F mission. To restore flare gamma-ray spectra we fitted the SONG energy loss spectra with a three-component model of the incident spectrum: (1) a power law in energy, assumed to be due to electron bremsstrahlung; (2) a broad continuum produced by prompt nuclear de-excitation gamma-lines; and (3) a broad gamma-line generated from pion-decay. We also restored spectra from the RHESSI data, compared them with the SONG spectra and found a reasonable agreement between these spectra in the 0.1-10 MeV energy range. The pion-decay emission was observed from 20:44:20 UT and had its maximum at 20:48-20:51 UT. The power-law spectral index of accelerated protons estimated from the ratio between intensities of different components of gamma rays changed with time. The hardest spectrum with a power-law index S = -3.5 - 3.6 was observed at 20:48-20:51 UT. Time histories of the pion-decay emission and proton spectrum were compared with changes of the locations of flare energy release as shown by RHESSI hard X-ray images and remote and remote Hα brightenings. An apparent temporal correlation between processes of particle acceleration and restructuring of flare magnetic field was found. In particular, the protons were accelerated to subrelativistic energies after radical change of the character of footpoint motion from a converging motion to a separation motion.

Pulse height tests of a large diameter fast LaBr₃:Ce scintillation detector.

PubMed

Naqvi, A A; Khiari, F Z; Maslehuddin, M; Gondal, M A; Al-Amoudi, O S B; Ukashat, M S; Ilyas, A M; Liadi, F A; Isab, A A; Khateeb-ur Rehman; Raashid, M; Dastageer, M A

2015-10-01

The pulse height response of a large diameter fast 100 mm × 100 mm LaBr3:Ce detector was measured for 0.1-10 MeV gamma-rays. The detector has a claimed time resolution of 608 ps for 511 keV gamma rays, but has relatively poor energy resolution due to the characteristics of its fast photomultiplier. The detector pulse height response was measured for gamma rays from cobalt, cesium, and bismuth radioisotope sources as well as prompt gamma rays from thermal neutron capture in water samples contaminated with mercury (3.1 wt%), boron (2.5 wt%), cadmium (0.25 wt%), chromium (52 wt%), and nickel (22 wt%) compounds. The energy resolution of the detector was determined from full width at half maximum (FWHM) of element-characteristic gamma ray peaks in the pulse height spectrum associated with the element present in the contaminated water sample. The measured energy resolution of the 100 mm × 100 mm detector varies from 12.7±0.2% to 1.9±0.1% for 0.1 to 10 MeV gamma rays, respectively. The graph showing the energy resolution ΔE/E(%) versus 1/√Eγ was fitted with a linear function to study the detector light collection from the slope of the curve. The slope of the present 100 mm × 100 mm detector is almost twice as large as the slope of a similar curve of previously published data for a 89 mm × 203 mm LaBr3:Ce detector. This indicates almost two times poorer light collection in the 100 mm × 100 mm detector as compared to the other detector. Copyright © 2015 Elsevier Ltd. All rights reserved.

SU-F-J-189: A Method to Improve the Spatial Resolution of Prompt Gamma Based Compton Imaging for Proton Range Verification

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

Draeger, E; Chen, H; Polf, J

Purpose: To test two new techniques, the distance-of-closest approach (DCA) and Compton line (CL) filters, developed as a means of improving the spatial resolution of Compton camera (CC) imaging. Methods: Gammas emitted from {sup 22}Na, {sup 137}Cs, and {sup 60}Co point sources were measured with a prototype 3-stage CC. The energy deposited and position of each interaction in each stage were recorded and used to calculate a “cone-of-origin” for each gamma that scattered twice in the CC. A DCA filter was developed which finds the shortest distance from the gamma’s cone-of-origin surface to the location of the gamma source. Themore » DCA filter was applied to the data to determine the initial energy of the gamma and to remove “bad” interactions that only contribute noise to the image. Additionally, a CL filter, which removes gamma events that do not follow the theoretical predictions of the Compton scatter equation, was used to further remove “bad” interactions from the measured data. Then images were reconstructed with raw, unfiltered data, DCA filtered data, and DCA+CL filtered data and the achievable image resolution of each dataset was compared. Results: Spatial resolutions of ∼2 mm, and better than 2 mm, were achievable with the DCA and DCA+CL filtered data, respectively, compared to > 5 mm for the raw, unfiltered data. Conclusion: In many special cases in medical imaging where information about the source position may be known, such as proton radiotherapy range verification, the application of the DCA and CL filters can result in considerable improvements in the achievable spatial resolutions of Compton imaging.« less

Optimization and verification of image reconstruction for a Compton camera towards application as an on-line monitor for particle therapy

NASA Astrophysics Data System (ADS)

Taya, T.; Kataoka, J.; Kishimoto, A.; Tagawa, L.; Mochizuki, S.; Toshito, T.; Kimura, M.; Nagao, Y.; Kurita, K.; Yamaguchi, M.; Kawachi, N.

2017-07-01

Particle therapy is an advanced cancer therapy that uses a feature known as the Bragg peak, in which particle beams suddenly lose their energy near the end of their range. The Bragg peak enables particle beams to damage tumors effectively. To achieve precise therapy, the demand for accurate and quantitative imaging of the beam irradiation region or dosage during therapy has increased. The most common method of particle range verification is imaging of annihilation gamma rays by positron emission tomography. Not only 511-keV gamma rays but also prompt gamma rays are generated during therapy; therefore, the Compton camera is expected to be used as an on-line monitor for particle therapy, as it can image these gamma rays in real time. Proton therapy, one of the most common particle therapies, uses a proton beam of approximately 200 MeV, which has a range of ~ 25 cm in water. As gamma rays are emitted along the path of the proton beam, quantitative evaluation of the reconstructed images of diffuse sources becomes crucial, but it is far from being fully developed for Compton camera imaging at present. In this study, we first quantitatively evaluated reconstructed Compton camera images of uniformly distributed diffuse sources, and then confirmed that our Compton camera obtained 3 %(1 σ) and 5 %(1 σ) uniformity for line and plane sources, respectively. Based on this quantitative study, we demonstrated on-line gamma imaging during proton irradiation. Through these studies, we show that the Compton camera is suitable for future use as an on-line monitor for particle therapy.

Effect of fast neutron, gamma-ray and combined radiations on the thermal decomposition of ammonium perchlorate single crystals

NASA Technical Reports Server (NTRS)

Herley, P. J.; Wang, C. S.; Varsi, G.; Levy, P. W.

1974-01-01

The thermal decomposition kinetics have been determined for ammonium perchlorate crystals subjected to a fast neutron irradiation or to a fast neutron irradiation followed by a gamma-ray irradiation. Qualitatively, the radiation induced changes are similar to those obtained in this and in previous studies, with samples exposed only to gamma rays. The induction period is shortened and the rate constants, obtained from an Avrami-Erofeyev kinetic analysis, are modified. The acceleratory period constant increases and the decay period constant decreases. When compared on an equal deposited energy basis, the fast neutron induced changes are appreciably larger than the gamma-ray induced changes. Some, or all, of the fast neutron induced effects might be attributable to the introduction of localized regions of concentrated radiation damage ('spikes') by lattice atom recoils which become thermal decomposition sites when the crystals are heated.

Learning outcomes for communication skills across the health professions: a systematic literature review and qualitative synthesis

PubMed Central

Denniston, Charlotte; Molloy, Elizabeth; Woodward-Kron, Robyn; Keating, Jennifer L

2017-01-01

Objective The aim of this study was to identify and analyse communication skills learning outcomes via a systematic review and present results in a synthesised list. Summarised results inform educators and researchers in communication skills teaching and learning across health professions. Design Systematic review and qualitative synthesis. Methods A systematic search of five databases (MEDLINE, PsycINFO, ERIC, CINAHL plus and Scopus), from first records until August 2016, identified published learning outcomes for communication skills in health professions education. Extracted data were analysed through an iterative process of qualitative synthesis. This process was guided by principles of person centredness and an a priori decision guide. Results 168 papers met the eligibility criteria; 1669 individual learning outcomes were extracted and refined using qualitative synthesis. A final refined set of 205 learning outcomes were constructed and are presented in 4 domains that include: (1) knowledge (eg, describe the importance of communication in healthcare), (2) content skills (eg, explore a healthcare seeker's motivation for seeking healthcare),( 3) process skills (eg, respond promptly to a communication partner's questions) and (4) perceptual skills (eg, reflect on own ways of expressing emotion). Conclusions This study provides a list of 205 communication skills learning outcomes that provide a foundation for further research and educational design in communication education across the health professions. Areas for future investigation include greater patient involvement in communication skills education design and further identification of learning outcomes that target knowledge and perceptual skills. This work may also prompt educators to be cognisant of the quality and scope of the learning outcomes they design and their application as goals for learning. PMID:28389493

Learning outcomes for communication skills across the health professions: a systematic literature review and qualitative synthesis.

PubMed

Denniston, Charlotte; Molloy, Elizabeth; Nestel, Debra; Woodward-Kron, Robyn; Keating, Jennifer L

2017-04-07

The aim of this study was to identify and analyse communication skills learning outcomes via a systematic review and present results in a synthesised list. Summarised results inform educators and researchers in communication skills teaching and learning across health professions. Systematic review and qualitative synthesis. A systematic search of five databases (MEDLINE, PsycINFO, ERIC, CINAHL plus and Scopus), from first records until August 2016, identified published learning outcomes for communication skills in health professions education. Extracted data were analysed through an iterative process of qualitative synthesis. This process was guided by principles of person centredness and an a priori decision guide. 168 papers met the eligibility criteria; 1669 individual learning outcomes were extracted and refined using qualitative synthesis. A final refined set of 205 learning outcomes were constructed and are presented in 4 domains that include: (1) knowledge (eg, describe the importance of communication in healthcare), (2) content skills (eg, explore a healthcare seeker's motivation for seeking healthcare),( 3) process skills (eg, respond promptly to a communication partner's questions) and (4) perceptual skills (eg, reflect on own ways of expressing emotion). This study provides a list of 205 communication skills learning outcomes that provide a foundation for further research and educational design in communication education across the health professions. Areas for future investigation include greater patient involvement in communication skills education design and further identification of learning outcomes that target knowledge and perceptual skills. This work may also prompt educators to be cognisant of the quality and scope of the learning outcomes they design and their application as goals for learning. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Development of a Compton camera for medical applications based on silicon strip and scintillation detectors

NASA Astrophysics Data System (ADS)

Krimmer, J.; Ley, J.-L.; Abellan, C.; Cachemiche, J.-P.; Caponetto, L.; Chen, X.; Dahoumane, M.; Dauvergne, D.; Freud, N.; Joly, B.; Lambert, D.; Lestand, L.; Létang, J. M.; Magne, M.; Mathez, H.; Maxim, V.; Montarou, G.; Morel, C.; Pinto, M.; Ray, C.; Reithinger, V.; Testa, E.; Zoccarato, Y.

2015-07-01

A Compton camera is being developed for the purpose of ion-range monitoring during hadrontherapy via the detection of prompt-gamma rays. The system consists of a scintillating fiber beam tagging hodoscope, a stack of double sided silicon strip detectors (90×90×2 mm3, 2×64 strips) as scatter detectors, as well as bismuth germanate (BGO) scintillation detectors (38×35×30 mm3, 100 blocks) as absorbers. The individual components will be described, together with the status of their characterization.

Transient astronomy with the Gaia satellite.

PubMed

Hodgkin, Simon T; Wyrzykowski, Łukasz; Blagorodnova, Nadejda; Koposov, Sergey

2013-06-13

Gaia is a cornerstone European Space Agency astrometry space mission and a successor to the Hipparcos mission. Gaia will observe the whole sky for 5 years, providing a serendipitous opportunity for the discovery of large numbers of transient and anomalous events, e.g. supernovae, novae and microlensing events, gamma-ray burst afterglows, fallback supernovae, as well as theoretical or unexpected phenomena. In this paper, we discuss our preparations to use Gaia to search for transients at optical wavelengths, and briefly describe the early detection, classification and prompt publication of anomalous sources.

Storage Rings in the Sky: Gamma Ray Bursts and Galactic Gravitational Collapse Stored Energy

NASA Astrophysics Data System (ADS)

Greyber, H. D.

2004-05-01

The recent discovery of almost 100% polarization of the prompt gamma ray emission from GRB021206, (1), confirms my 44 year old ``Strong" Magnetic Field" model (SMF) for galactic dynamics. In SMF, Storage Ring particles were accelerated long ago during the original gravitational collapse of the pregalactic/prequasar plasma cloud that is permeated by an almost uniform primordial magnetic field (2,3) The enormous, intense, slender, relativistic, stable, completely coherent Storage Ring stores a very small fraction of the huge galactic gravitational collapse energy in an almost radiationless state, unless disturbed. The concept of an Astrophysical Storage Ring was introduced by me in l961. At first it was to explain galactic structure, but soon it proved useful to explain active galactic nuclei (AGN) and the dynamics of quasar/AGN jets. AGN and galactic morphology, energetics and dynamics vary as the ratio of magnetic energy to rotational energy in the particular object. Gamma ray bursts (GRB) are due simply to a ``rock". i.e. a white dwarf, ordinary star, neutron sstar, asteroid, planet, etc. falling rapidly through the Storage Ring and being almost instantly vaporized into a hot plasma fireball, causing an electromagnetic shower (2) Then the fireball speeds into the huge organized magnetic field surrounding the current ring, thus generating very highly polarized prompt gamma ray emission (as seen in GRB021206) from the synchrotron radiation process. The timing fits the GRB observations nicely. For instance, a ``rock" racing at 1000 kilometers per second across a 20,000 km. path in the beam would produce a twenty second burst. Other times, a target might track across a short chord for a short burst. Space missions have shown that often typical currents in space plasmas are made up of slender filaments. Thus the puzzling less than one millisecond spikes observed in some GRB are simply describing the structure of that particular ring current at that particular time. 1. W. Coburn and S.E. Boggs, Nature, 423, 415, (2003) 2. H. D. Greyber in a book, After the Dark Ages: When Galaxies Were Young, eds. S.S. Holt and E. P. Smith, AIP Conference Proceedings 470, 388-396. (1998) 3. H. D. Greyber in a Space Telescope Science Institute Report: Poster Papers from their 2001 Spring Symposium, ``The Dark Universe: Matter, Energy and Gravity," ed. Mario Livio, published March 2003, (34-39)

Modeling Gamma Ray Bursts in the Megnetically Dominated Regime

NASA Astrophysics Data System (ADS)

Zhang, Bing

Recent observations of broad-band prompt emission spectra of gamma-ray bursts (GRBs) by the Fermi Gamma-Ray Telescope suggest that they do not comply with the predictions of the standard fireball internal shock model. Several independent observations (including detections of high polarization degree of gamma-ray emission and early optical emission of some GRBs, as well as non-detection of PeV neutrinos from GRBs by IceCube) support or are consistent with the hypothesis that at least some GRBs have magnetically dominated jets. This calls for serious, detailed investigations of GRB models in the magnetically dominated regime, which interpret GRB emission as dissipation of strong magnetic fields entrained in the ejecta. On the other hand, because of their complexity, magnetic models are so far much less developed than the baryonic fireball models. Here we propose to tackle this difficult problem, aiming at making solid progress in this direction through a set of numerical investigations. Specifically, we propose to carry out the following simulations. (1) Using a relativistic MHD code, we will perform a global simulation to investigate whether efficient magnetic dissipation would occur when two high-σ magnetic blobs collide with a relativistic speed. (2) We will perform a local simulation of the relativistic collisions between two high-σ fluids, and track the evolution of magnetic field configuration in the colliding region and the interplay between magnetic reconnection and development of magnetic turbulence. (3) Through injecting test particles in the simulation box, we will study how electrons get accelerated in the turbulent reconnection regions. (4) Built upon the above-mentioned numerical simulation results, along with a Monte Carlo code and a synchrotron radiation code developed in our group before, we will develop a full numerical model to simulate lightcurves, time-dependent spectra, and polarization properties of GRB prompt emission within the framework of magnetically dominated jets. The results of this proposal will greatly advance our understanding of GRB physics in the magnetically dominated regime. The numerical simulations of collision-induced magnetic dissipation will be also relevant to many other astrophysical phenomena, such as active galactic nuclei, X-ray binary ``micro-quasars'', Crab nebula flares, and jets from tidal disruption events. The program conforms to NASA's Strategic Plan, and is highly relevant to the past and current NASA missions, such as CGRO/BATSE, Fermi, and Swift, as well as some future mission concepts, such as POET.

An external shock origin of GRB 141028A

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

Burgess, J. Michael; Bégué, Damien; Ryde, Felix

The prompt emission of the long, smooth, and single-pulsed gamma-ray burst, GRB 141028A, is analyzed under the guise of an external shock model. First, we fit the γ-ray spectrum with a two-component photon model, namely, synchrotron+blackbody, and then fit the recovered evolution of the synchrotron νF ν peak to an analytic model derived considering the emission of a relativistic blast wave expanding into an external medium. The prediction of the model for the νF ν peak evolution matches well with the observations. We observe the blast wave transitioning into the deceleration phase. Furthermore, we assume the expansion of the blastmore » wave to be nearly adiabatic, motivated by the low magnetic field deduced from the observations. This allows us to recover within an order of magnitude the flux density at the νF ν peak, which is remarkable considering the simplicity of the analytic model. Under this scenario we argue that the distinction between prompt and afterglow emission is superfluous as both early-time emission and late-time emission emanate from the same source. In conclusion, while the external shock model is clearly not a universal solution, this analysis opens the possibility that at least some fraction of GRBs can be explained with an external shock origin of their prompt phase.« less

An external shock origin of GRB 141028A

DOE PAGES

Burgess, J. Michael; Bégué, Damien; Ryde, Felix; ...

2016-05-05

The prompt emission of the long, smooth, and single-pulsed gamma-ray burst, GRB 141028A, is analyzed under the guise of an external shock model. First, we fit the γ-ray spectrum with a two-component photon model, namely, synchrotron+blackbody, and then fit the recovered evolution of the synchrotron νF ν peak to an analytic model derived considering the emission of a relativistic blast wave expanding into an external medium. The prediction of the model for the νF ν peak evolution matches well with the observations. We observe the blast wave transitioning into the deceleration phase. Furthermore, we assume the expansion of the blastmore » wave to be nearly adiabatic, motivated by the low magnetic field deduced from the observations. This allows us to recover within an order of magnitude the flux density at the νF ν peak, which is remarkable considering the simplicity of the analytic model. Under this scenario we argue that the distinction between prompt and afterglow emission is superfluous as both early-time emission and late-time emission emanate from the same source. In conclusion, while the external shock model is clearly not a universal solution, this analysis opens the possibility that at least some fraction of GRBs can be explained with an external shock origin of their prompt phase.« less

Multiwavelength Observations of GRB 110731A: GeV Emission From Onset to Afterglow

DOE PAGES

Ackermann, M.; Ajello, M.; Asano, K.; ...

2013-01-09

In this paper, we report on the multiwavelength observations of the bright, long gamma-ray burst GRB 110731A, by the Fermi and Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that GRB 110731A shares many features with bright Large Area Telescope bursts observed by Fermi during the first three years on-orbit: a light curve with short time variability across the whole energy range during the prompt phase, delayed onset of the emission above 100 MeV, extra power-law component and temporally extended high-energy emission. In addition, this is the first GRB for whichmore » simultaneous GeV, X-ray, and optical data are available over multiple epochs beginning just after the trigger time and extending for more than 800 s, allowing temporal and spectral analysis in different epochs that favor emission from the forward shock in a wind-type medium. Lastly, the observed temporally extended GeV emission is most likely part of the high-energy end of the afterglow emission. Both the single-zone pair transparency constraint for the prompt signal and the spectral and temporal analysis of the forward-shock afterglow emission independently lead to an estimate of the bulk Lorentz factor of the jet Γ ~ 500-550.« less

Multiwavelength Observations of GRB 110731A: GeV Emission from Onset to Afterglow

NASA Astrophysics Data System (ADS)

Ackermann, M.; Ajello, M.; Asano, K.; Baldini, L.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bellazzini, R.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Cecchi, C.; Charles, E.; Chaves, R. C. G.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Franckowiak, A.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Granot, J.; Greiner, J.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Hays, E.; Hughes, R. E.; Jackson, M. S.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Knödlseder, J.; Kocevski, D.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Mészáros, P.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Moretti, E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Norris, J. P.; Nuss, E.; Nymark, T.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orienti, M.; Orlando, E.; Paneque, D.; Perkins, J. S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Racusin, J. L.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Romoli, C.; Roth, M.; Ryde, F.; Sanchez, D. A.; Sgrò, C.; Siskind, E. J.; Sonbas, E.; Spinelli, P.; Stamatikos, M.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Tosti, G.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Gruber, D.; Bhat, P. N.; Bissaldi, E.; Briggs, M. S.; Burgess, J. M.; Connaughton, V.; Foley, S.; Kippen, R. M.; Kouveliotou, C.; McBreen, S.; McGlynn, S.; Paciesas, W. S.; Pelassa, V.; Preece, R.; Rau, A.; van der Horst, A. J.; von Kienlin, A.; Kann, D. A.; Filgas, R.; Klose, S.; Krühler, T.; Fukui, A.; Sako, T.; Tristram, P. J.; Oates, S. R.; Ukwatta, T. N.; Littlejohns, O.

2013-02-01

We report on the multiwavelength observations of the bright, long gamma-ray burst GRB 110731A, by the Fermi and Swift observatories, and by the MOA and GROND optical telescopes. The analysis of the prompt phase reveals that GRB 110731A shares many features with bright Large Area Telescope bursts observed by Fermi during the first three years on-orbit: a light curve with short time variability across the whole energy range during the prompt phase, delayed onset of the emission above 100 MeV, extra power-law component and temporally extended high-energy emission. In addition, this is the first GRB for which simultaneous GeV, X-ray, and optical data are available over multiple epochs beginning just after the trigger time and extending for more than 800 s, allowing temporal and spectral analysis in different epochs that favor emission from the forward shock in a wind-type medium. The observed temporally extended GeV emission is most likely part of the high-energy end of the afterglow emission. Both the single-zone pair transparency constraint for the prompt signal and the spectral and temporal analysis of the forward-shock afterglow emission independently lead to an estimate of the bulk Lorentz factor of the jet Γ ~ 500-550.

Decision making processes in people with symptoms of acute myocardial infarction: qualitative study

PubMed Central

Pattenden, Jill; Watt, Ian; Lewin, Robert J P; Stanford, Neil

2002-01-01

Objective To identify the themes that influence decision making processes used by patients with symptoms of acute myocardial infarction. Design Qualitative study using semistructured interviews. Setting Two district hospitals in North Yorkshire. Participants 22 patients admitted to hospital with confirmed second, third, or fourth acute myocardial infarction. Main outcome measure Patients' perceptions of their experience between the onset of symptoms and the decision to seek medical help. Results Six main themes that influence the decision making process were identified: appraisal of symptoms, perceived risk, previous experience, psychological and emotional factors, use of the NHS, and context of the event. Conclusions Knowledge of symptoms may not be enough to promote prompt action in the event of an acute myocardial infarction. Cognitive and emotional processes, individual beliefs and values, and the influence of the context of the event should also be considered in individual interventions designed to reduce delay in the event of symptoms of acute myocardial infarction. What is already known on this topicIndividual sociodemographic and clinical characteristics affect the time to seeking medical care in patients with symptoms of acute myocardial infarctionAppraisal of symptoms is difficult; people with classic and severe symptoms are more likely to take prompt actionWhat this study addsThe decision to seek medical help in patients who have had one or more previous myocardial infarctions is a complex processSimply providing patients with information on symptoms of acute myocardial infarction, and what to do in the event of these symptoms, may not be sufficient to promote prompt action PMID:11976241

Studies on High Energy Radiation Mechanisms and Gamma-Ray Burst Prompt Emissions

NASA Astrophysics Data System (ADS)

Zhang, B.

2014-07-01

Gamma-Ray Bursts (GRBs) are the most violent high-energy explosion in the universe. They are randomly happened, pulse-like phenomena with short durations. Since its discovery in 1960's by Vela satellite, GRBs have become a hot topic for astrophysical research. In 1997 the BeppoSAX satellite discovered afterglows of GRBs, and then helped to measure GRB redshifts. Thus it was found that GRBs are the events occurred at cosmological distances. Now it is widely accepted that the long bursts with durations longer than 2 s are from the collapsing massive stars, while the short bursts with durations less than 2 s are results of the merging compact binaries. By studying GRBs, the physical processes in ultrarelativistic and very high energy conditions can be investigated, and the researches on other fields, including constraining the cosmological models, can also get helped. The goal of this thesis is to present some discussions on possible radiation mechanisms and prompt light curves of GRBs. Since radiation mechanisms and prompt emissions are related to GRB central engines directly, studying these topics can help us to get a better understanding of some properties of the central engine. In Chapter 1, we review the discovery and observations of GRBs, presenting major achievements from major GRB-monitoring satellites including Compton Gamma-ray Observatory, BeppoSAX satellite, Swift satellite, as well as the latest Fermi Gamma-ray Space Telescope. The multi-wavelength properties of prompt emission as well as afterglows of GRBs are also summarized in Chapter 1. In Chapter 2 the current GRB standard model is presented. According to standard model, a fireball is ejected by the central engine. The internal shock is produced by collisions between various shells with different velocities inside the fireball. The directional kinetic energy of the fireball is then converted to internal energy, and finally the non-thermal radiation (the prompt emission) is produced by internal shocks. And the interaction between the fireball and the outer medium gives rise to external forward and reverse shocks, producing the observed afterglow. In the framework of standard model, we introduce the properties of the fireball, the evolution of shocks, some possible radiation mechanisms, as well as some post-standard effects. Also we present a brief introduction of central engines. And since the internal shock model for prompt emission has some problems hard to be solved, we also introduce some possible alternatives, including the electromagnetic model, the turbulent model, as well as the Internal-Collision-induced Magnetic Reconnection and Turbulence (ICMART) model. In Chapter 3, we present the spectrum of synchro-curvature self-Compton (SCSC) radiation of relativistic electrons with a power-law distribution of Lorentz factors. Synchro-curvature radiation from relativistic electrons moving around curved magnetic field lines and its self-Compton radiation are possible radiation mechanisms in the GRB enviroment. We find that the resulting SCSC spectrum is significantly different from that of either synchrotron self-Compton or curvature self-Compton radiation if both the curvature radius of the magnetic field and the cyclotron radius of the electrons are within some proper ranges. The effects of electrons' cooling and drifting, the low-energy self absorption in seed spectra, and the Klein-Nishina cutoff are also discussed, in order to get an accurate picture. We take GRBs as our example environment for discussions. The results would be considered as a universal approach of the self-Compton emission of relativistic electrons moving in curved magnetic fields, and thus could be applied to many astrophysical phenomena, including active galactic nuclei (AGNs), pulsars, as well as GRBs. In Chapter 4, we simulate the prompt emission light curves of GRBs within the framework of the ICMART model. This model is applied to GRBs with a moderately-high magnetization parameter σ in the emission region. We show that this model can produce highly variable light curves with both fast and slow components. The rapid variability is caused by many locally Doppler-boosted mini-emitters due to turbulent magnetic reconnection in a moderately-high-σ ejecta. The run-away growth and subsequent depletion of these mini-emitters as a function of time define a broad slow component for each ICMART event. A GRB light curve is usually composed of multiple ICMART events fundamentally driven by the erratic GRB central engine activity. Allowing variations of model parameters, including initial Lorentz factor, orientation and size distributions of reconnection regions, jet opening angle, radius of emission region, as well as observing energy band, one is able to reproduce a variety of light curves and the power density spectra (PDS) as observed. We also discuss the effects of these parameters on PDS . Finally in Chapter 5 we present our discussions, and list some remaining problems to be solved, as well as observing instruments to be commissioned in the future. We also present calculations of synchro-curvature radiation in Appendix A, and some discussions on ICMART model in Appendix B.

Physics of Gamma Ray Burst Sources

NASA Technical Reports Server (NTRS)

Meszaros, Peter

2004-01-01

During this grant period, the physics of gamma-ray bursts was investigated. A number of new results have emerged. The importance of pair formation in high compactness burst spectra may help explain x-ray flashes; a universal jet shape is a likely explanation for the distribution of jet break times; gravitational waves may be copiously produced both in short bursts from compact mergers and in long bursts arising from collapsars; x-ray iron lines are likely to be due to interaction with the stellar atmosphere of the progenitor; prompt optical flashes from reverse shocks will give diagnostics on the Lorentz factor and the environment; GeV and TeV emission from bursts may be expected in the external shock; etc. The group working with the PI included postdocs Dr. Bing Zhang (now assistant professor at University of Nevada); Dr. Shiho Kobayashi; graduate student Lijun Gou; collaborators Drs. Tim Kallman and Martin Rees. Meszaros shared with Rees and Dr. Bohan Paczynsky the AAS Rossi Prize in 2000 for their work on the theory of gamma ray bursts. The refereed publications and conference proceedings resulting from this research are summarized below. The PI gave a number of invited talks at major conferences, also listed.

A gamma-ray burst with a high-energy spectral component inconsistent with the synchrotron shock model.

PubMed

González, M M; Dingus, B L; Kaneko, Y; Preece, R D; Dermer, C D; Briggs, M S

2003-08-14

Gamma-ray bursts are among the most powerful events in nature. These events release most of their energy as photons with energies in the range from 30 keV to a few MeV, with a smaller fraction of the energy radiated in radio, optical, and soft X-ray afterglows. The data are in general agreement with a relativistic shock model, where the prompt and afterglow emissions correspond to synchrotron radiation from shock-accelerated electrons. Here we report an observation of a high-energy (multi-MeV) spectral component in the burst of 17 October 1994 that is distinct from the previously observed lower-energy gamma-ray component. The flux of the high-energy component decays more slowly and its fluence is greater than the lower-energy component; it is described by a power law of differential photon number index approximately -1 up to about 200 MeV. This observation is difficult to explain with the standard synchrotron shock model, suggesting the presence of new phenomena such as a different non-thermal electron process, or the interaction of relativistic protons with photons at the source.

Constraints from the time lag between gravitational waves and gamma rays: Implications of GW170817 and GRB 170817A

NASA Astrophysics Data System (ADS)

Shoemaker, Ian M.; Murase, Kohta

2018-04-01

The Laser Interferometer Gravitational-Wave Observatory (LIGO) has recently discovered gravitational waves (GWs) from its first neutron star-neutron star merger at a distance of ˜40 Mpc from the Earth. The associated electromagnetic (EM) detection of the event, including the short gamma-ray burst within Δ t ˜2 s after the GW arrival, can be used to test various aspects of sources physics and GW propagation. Using GW170817 as the first GW-EM example, we show that this event provides a stringent direct test that GWs travel at the speed of light. The gravitational potential of the Milky Way provides a potential source of Shapiro time delay difference between the arrival of photons and GWs, and we demonstrate that the nearly coincident detection of the GW and EM signals can yield strong limits on anomalous gravitational time delay, through updating the previous limits taking into account details of Milky Way's gravitational potential. Finally, we also obtain an intriguing limit on the size of the prompt emission region of GRB 170817A, and discuss implications for the emission mechanism of short gamma-ray bursts.

High-Energy Electromagnetic Offline Follow-Up of Ligo-Virgo Gravitational-Wave Binary Coalescence Candidate Events

NASA Technical Reports Server (NTRS)

Blackburn, L.; Briggs, M. S.; Camp, J.; Christensen, N.; Connaughton, V.; Jenke, P.; Remillard, R. A.; Veitch, J.

2015-01-01

We present two different search methods for electromagnetic counterparts to gravitational-wave (GW) events from ground-based detectors using archival NASA high-energy data from the Fermi Gamma-ray Burst Monitor (GBM) and RXTE All-sky Monitor (ASM) instruments. To demonstrate the methods, we use a limited number of representative GW background noise events produced by a search for binary neutron star coalescence over the last two months of the LIGO-Virgo S6/VSR3 joint science run. Time and sky location provided by the GW data trigger a targeted search in the high-energy photon data. We use two custom pipelines: one to search for prompt gamma-ray counterparts in GBM, and the other to search for a variety of X-ray afterglow model signals in ASM. We measure the efficiency of the joint pipelines to weak gamma-ray burst counterparts, and a family of model X-ray afterglows. By requiring a detectable signal in either electromagnetic instrument coincident with a GW event, we are able to reject a large majority of GW candidates. This reduces the signal-to-noise ratio of the loudest surviving GW background event by around 15-20 percent.

The semi-Hooperon: Gamma-ray and anti-proton excesses in the Galactic Center

NASA Astrophysics Data System (ADS)

Arcadi, Giorgio; Queiroz, Farinaldo S.; Siqueira, Clarissa

2017-12-01

A puzzling excess in gamma-rays at GeV energies has been observed in the center of our galaxy using Fermi-LAT data. Its origin is still unknown, but it is well fitted by Weakly Interacting Massive Particles (WIMPs) annihilations into quarks with a cross section around 10-26 cm3s-1 with masses of 20-50 GeV, scenario which is promptly revisited. An excess favoring similar WIMP properties has also been seen in anti-protons with AMS-02 data potentially coming from the Galactic Center as well. In this work, we explore the possibility of fitting these excesses in terms of semi-annihilating dark matter, dubbed as semi-Hooperon, with the process WIMP WIMP → WIMP X being responsible for the gamma-ray excess, where X = h , Z. An interesting feature of semi-annihilations is the change in the relic density prediction compared to the standard case, and the possibility to alleviate stringent limits stemming from direct detection searches. Moreover, we discuss which models might give rise to a successful semi-Hooperon setup in the context of Z3,Z4 and extra "dark" gauge symmetries.

HIGH-ENERGY ELECTROMAGNETIC OFFLINE FOLLOW-UP OF LIGO-VIRGO GRAVITATIONAL-WAVE BINARY COALESCENCE CANDIDATE EVENTS

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

Blackburn, L.; Camp, J.; Briggs, M. S.

2015-03-15

We present two different search methods for electromagnetic counterparts to gravitational-wave (GW) events from ground-based detectors using archival NASA high-energy data from the Fermi Gamma-ray Burst Monitor (GBM) and RXTE All-sky Monitor (ASM) instruments. To demonstrate the methods, we use a limited number of representative GW background noise events produced by a search for binary neutron star coalescence over the last two months of the LIGO-Virgo S6/VSR3 joint science run. Time and sky location provided by the GW data trigger a targeted search in the high-energy photon data. We use two custom pipelines: one to search for prompt gamma-ray counterpartsmore » in GBM, and the other to search for a variety of X-ray afterglow model signals in ASM. We measure the efficiency of the joint pipelines to weak gamma-ray burst counterparts, and a family of model X-ray afterglows. By requiring a detectable signal in either electromagnetic instrument coincident with a GW event, we are able to reject a large majority of GW candidates. This reduces the signal-to-noise ratio of the loudest surviving GW background event by around 15–20%.« less

Preliminary Monte Carlo calculations for the UNCOSS neutron-based explosive detector

NASA Astrophysics Data System (ADS)

Eleon, C.; Perot, B.; Carasco, C.

2010-07-01

The goal of the FP7 UNCOSS project (Underwater Coastal Sea Surveyor) is to develop a non destructive explosive detection system based on the associated particle technique, in view to improve the security of coastal area and naval infrastructures where violent conflicts took place. The end product of the project will be a prototype of a complete coastal survey system, including a neutron-based sensor capable of confirming the presence of explosives on the sea bottom. A 3D analysis of prompt gamma rays induced by 14 MeV neutrons will be performed to identify elements constituting common military explosives, such as C, N and O. This paper presents calculations performed with the MCNPX computer code to support the ongoing design studies performed by the UNCOSS collaboration. Detection efficiencies, time and energy resolutions of the possible gamma-ray detectors are compared, which show NaI(Tl) or LaBr 3(Ce) scintillators will be suitable for this application. The effect of neutron attenuation and scattering in the seawater, influencing the counting statistics and signal-to-noise ratio, are also studied with calculated neutron time-of-flight and gamma-ray spectra for an underwater TNT target.

Wildland fire and organic discourse: Negotiating place and leisure identity in a changing wildland urban inteface

Treesearch

Joseph G. Champ; Daniel R. Williams; Katie Knotek

2009-01-01

A lack of research on the conceptual intersection of leisure, place and wildland fire and its role in identity prompted this exploratory study. The purpose of this research was to gather evidence regarding how people negotiate identities under the threat of wildland fire. Qualitative interviews with 16 homeowners and recreationists who value leisure activities in...

GPs' thoughts on prescribing medication and evidence-based knowledge: the benefit aspect is a strong motivator. A descriptive focus group study.

PubMed

Skoglund, Ingmarie; Segesten, Kerstin; Björkelund, Cecilia

2007-06-01

To describe GPs' thoughts of prescribing medication and evidence-based knowledge (EBM) concerning drug therapy. Tape-recorded focus-group interviews transcribed verbatim and analysed using qualitative methods. GPs from the south-eastern part of Västra Götaland, Sweden. A total of 16 GPs out of 178 from the south-eastern part of the region strategically chosen to represent urban and rural, male and female, long and short GP experience. Transcripts were analysed using a descriptive qualitative method. The categories were: benefits, time and space, and expert knowledge. The benefit was a merge of positive elements, all aspects of the GPs' tasks. Time and space were limitations for GPs' tasks. EBM as a constituent of expert knowledge should be more customer adjusted to be able to be used in practice. Benefit was the most important category, existing in every decision-making situation for the GP. The core category was prompt and pragmatic benefit, which was the utmost benefit. GPs' thoughts on evidence-based medicine and prescribing medication were highly related to reflecting on benefit and results. The interviews indicated that prompt and pragmatic benefit is important for comprehending their thoughts.

GPs’ thoughts on prescribing medication and evidence-based knowledge: The benefit aspect is a strong motivator

PubMed Central

Skoglund, Ingmarie; Segesten, Kerstin; Björkelund, Cecilia

2007-01-01

Objective To describe GPs’ thoughts of prescribing medication and evidence-based knowledge (EBM) concerning drug therapy. Design Tape-recorded focus-group interviews transcribed verbatim and analysed using qualitative methods. Setting GPs from the south-eastern part of Västra Götaland, Sweden. Subjects A total of 16 GPs out of 178 from the south-eastern part of the region strategically chosen to represent urban and rural, male and female, long and short GP experience. Methods Transcripts were analysed using a descriptive qualitative method. Results The categories were: benefits, time and space, and expert knowledge. The benefit was a merge of positive elements, all aspects of the GPs’ tasks. Time and space were limitations for GPs’ tasks. EBM as a constituent of expert knowledge should be more customer adjusted to be able to be used in practice. Benefit was the most important category, existing in every decision-making situation for the GP. The core category was prompt and pragmatic benefit, which was the utmost benefit. Conclusion GPs’ thoughts on evidence-based medicine and prescribing medication were highly related to reflecting on benefit and results. The interviews indicated that prompt and pragmatic benefit is important for comprehending their thoughts. PMID:17497487

Measurement of Insulation Compaction in the Cryogenic Fuel Tanks at Kennedy Space Center by Fast/Thermal Neutron Techniques

NASA Technical Reports Server (NTRS)

Livingston, R. A.; Schweitzer, J. S.; Parsons, Ann M.; Arens, Ellen E.

2010-01-01

The liquid hydrogen and oxygen cryogenic storage tanks at John F. Kennedy Space Center (KSC) use expanded perlite as thermal insulation. Th ere is evidence that some of the perlite has compacted over time, com promising the thermal performance and possibly also structural integr ity of the tanks. Therefore an Non-destructive Testing (NDT) method for measuring the perlite density or void fraction is urgently needed. Methods based on neutrons are good candidates because they can readil y penetrate through the 1.75 cm outer steel shell and through the ent ire 120 cm thickness of the perlite zone. Neutrons interact with the nuclei of materials to produce characteristic gamma rays which are the n detected. The gamma ray signal strength is proportional to the atom ic number density. Consequently, if the perlite is compacted then the count rates in the individual peaks in the gamma ray spectrum will i ncrease. Perlite is a feldspathic volcanic rock made up of the major elements Si, AI, Na, K and 0 along with some water. With commercially available portable neutron generators it is possible to produce simul taneously fluxes of neutrons in two energy ranges: fast (14 MeV) and thermal (25 meV). Fast neutrons produce gamma rays by inelastic scatt ering which is sensitive to Fe and O. Thermal neutrons produce gamma rays by radiative capture in prompt gamma neutron activation (PGNA) and this is sensitive to Si, AI, Na, Kand H. Thus the two energy ranges produce complementary information. The R&D program has three phases: numerical simulations of neutron and gamma ray transport with MCNP s oftware, evaluation of the system in the laboratory on test articles and finally mapping of the perlite density in the cryogenic tanks at KSC. The preliminary MCNP calculations have shown that the fast/therma l neutron NDT method is capable of distinguishing between expanded an d compacted perlite with excellent statistics.

SU-F-J-200: An Improved Method for Event Selection in Compton Camera Imaging for Particle Therapy

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

Mackin, D; Beddar, S; Polf, J

2016-06-15

Purpose: The uncertainty in the beam range in particle therapy limits the conformality of the dose distributions. Compton scatter cameras (CC), which measure the prompt gamma rays produced by nuclear interactions in the patient tissue, can reduce this uncertainty by producing 3D images confirming the particle beam range and dose delivery. However, the high intensity and short time windows of the particle beams limit the number of gammas detected. We attempt to address this problem by developing a method for filtering gamma ray scattering events from the background by applying the known gamma ray spectrum. Methods: We used a 4more » stage Compton camera to record in list mode the energy deposition and scatter positions of gammas from a Co-60 source. Each CC stage contained a 4×4 array of CdZnTe crystal. To produce images, we used a back-projection algorithm and four filtering Methods: basic, energy windowing, delta energy (ΔE), or delta scattering angle (Δθ). Basic filtering requires events to be physically consistent. Energy windowing requires event energy to fall within a defined range. ΔE filtering selects events with the minimum difference between the measured and a known gamma energy (1.17 and 1.33 MeV for Co-60). Δθ filtering selects events with the minimum difference between the measured scattering angle and the angle corresponding to a known gamma energy. Results: Energy window filtering reduced the FWHM from 197.8 mm for basic filtering to 78.3 mm. ΔE and Δθ filtering achieved the best results, FWHMs of 64.3 and 55.6 mm, respectively. In general, Δθ filtering selected events with scattering angles < 40°, while ΔE filtering selected events with angles > 60°. Conclusion: Filtering CC events improved the quality and resolution of the corresponding images. ΔE and Δθ filtering produced similar results but each favored different events.« less

Evidence of Deterministic Components in the Apparent Randomness of GRBs: Clues of a Chaotic Dynamic

PubMed Central

Greco, G.; Rosa, R.; Beskin, G.; Karpov, S.; Romano, L.; Guarnieri, A.; Bartolini, C.; Bedogni, R.

2011-01-01

Prompt γ-ray emissions from gamma-ray bursts (GRBs) exhibit a vast range of extremely complex temporal structures with a typical variability time-scale significantly short – as fast as milliseconds. This work aims to investigate the apparent randomness of the GRB time profiles making extensive use of nonlinear techniques combining the advanced spectral method of the Singular Spectrum Analysis (SSA) with the classical tools provided by the Chaos Theory. Despite their morphological complexity, we detect evidence of a non stochastic short-term variability during the overall burst duration – seemingly consistent with a chaotic behavior. The phase space portrait of such variability shows the existence of a well-defined strange attractor underlying the erratic prompt emission structures. This scenario can shed new light on the ultra-relativistic processes believed to take place in GRB explosions and usually associated with the birth of a fast-spinning magnetar or accretion of matter onto a newly formed black hole. PMID:22355609

Evidence of deterministic components in the apparent randomness of GRBs: clues of a chaotic dynamic.

PubMed

Greco, G; Rosa, R; Beskin, G; Karpov, S; Romano, L; Guarnieri, A; Bartolini, C; Bedogni, R

2011-01-01

Prompt γ-ray emissions from gamma-ray bursts (GRBs) exhibit a vast range of extremely complex temporal structures with a typical variability time-scale significantly short - as fast as milliseconds. This work aims to investigate the apparent randomness of the GRB time profiles making extensive use of nonlinear techniques combining the advanced spectral method of the Singular Spectrum Analysis (SSA) with the classical tools provided by the Chaos Theory. Despite their morphological complexity, we detect evidence of a non stochastic short-term variability during the overall burst duration - seemingly consistent with a chaotic behavior. The phase space portrait of such variability shows the existence of a well-defined strange attractor underlying the erratic prompt emission structures. This scenario can shed new light on the ultra-relativistic processes believed to take place in GRB explosions and usually associated with the birth of a fast-spinning magnetar or accretion of matter onto a newly formed black hole.

NEAR-EXTREMAL BLACK HOLES AS INITIAL CONDITIONS OF LONG GRB SUPERNOVAE AND PROBES OF THEIR GRAVITATIONAL WAVE EMISSION

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

Van Putten, Maurice H. P. M.

2015-09-01

Long gamma-ray bursts (GRBs) associated with supernovae and short GRBs with extended emission (SGRBEE) from mergers are probably powered by black holes as a common inner engine, as their prompt GRB emission satisfies the same Amati correlation in the E{sub p,i}–E{sub iso} plane. We introduce modified Bardeen equations to identify hyper-accretion driving newly formed black holes in core-collapse supernovae to near-extremal spin as a precursor to prompt GRB emission. Subsequent spin-down is observed in the BATSE catalog of long GRBs. Spin-down provides a natural unification of long durations associated with the lifetime of black hole spin for normal long GRBsmore » and SGRBEEs, given the absence of major fallback matter in mergers. The results point to major emissions unseen in high frequency gravitational waves. A novel matched filtering method is described for LIGO–Virgo and KAGRA broadband probes of nearby core-collapse supernovae at essentially maximal sensitivity.« less

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

Aartsen, M. G.; Ackermann, M.; Adams, J.

We present an all-sky search for muon neutrinos produced during the prompt γ -ray emission of 1172 gamma-ray bursts (GRBs) with the IceCube Neutrino Observatory. The detection of these neutrinos would constitute evidence for ultra-high-energy cosmic-ray (UHECR) production in GRBs, as interactions between accelerated protons and the prompt γ -ray field would yield charged pions, which decay to neutrinos. A previously reported search for muon neutrino tracks from northern hemisphere GRBs has been extended to include three additional years of IceCube data. A search for such tracks from southern hemisphere GRBs in five years of IceCube data has been introducedmore » to enhance our sensitivity to the highest energy neutrinos. No significant correlation between neutrino events and observed GRBs is seen in the new data. Combining this result with previous muon neutrino track searches and a search for cascade signature events from all neutrino flavors, we obtain new constraints for single-zone fireball models of GRB neutrino and UHECR production.« less

Confronting GRB prompt emission with a model for subphotospheric dissipation

DOE PAGES

Ahlgren, Björn; Larsson, Josefin; Nymark, Tanja; ...

2015-09-16

The origin of the prompt emission in gamma-ray bursts (GRBs) is still an unsolved problem and several different mechanisms have been suggested. We fit Fermi GRB data with a photospheric emission model which includes dissipation of the jet kinetic energy below the photosphere. The resulting spectra are dominated by Comptonization and contain no significant contribution from synchrotron radiation. In order to fit to the data, we span a physically motivated part of the model's parameter space and create DREAM (Dissipation with Radiative Emission as A table Model), a table model for XSPEC. Here, we show that this model can describemore » different kinds of GRB spectra, including GRB 090618, representing a typical Band function spectrum, and GRB 100724B, illustrating a double peaked spectrum, previously fitted with a Band+blackbody model, suggesting they originate from a similar scenario. We also suggest that the main difference between these two types of bursts is the optical depth at the dissipation site.« less

Current and Future Research at DANCE

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

Jandel, M.; Baramsai, B.; Bredeweg, T. A.

2015-05-28

An overview of the current experimental program on measurements of neutron capture and neutron induced fission at the Detector for Advanced Neutron Capture Experiments (DANCE) is presented. Three major projects are currently under way: 1) high precision measurements of neutron capture cross sections on Uranium isotopes, 2) research aimed at studies of the short-lived actinide isomer production in neutron capture on 235U and 3) measurements of correlated data of fission observables. New projects include developments of auxiliary detectors to improve the capability of DANCE. We are building a compact, segmented NEUtron detector Array at DANCE (NEUANCE), which will be installedmore » in the central cavity of the DANCE array. It will thus provide experimental information on prompt fission neutrons in coincidence with the prompt fission gamma-rays measured by 160 BaF 2 crystals of DANCE. Additionally, unique correlated data will be obtained for neutron capture and neutron-induced fission using the DANCE-NEUANCE experimental set up in the future.« less

Comparative gene expression profiles induced by PPAR{gamma} and PPAR{alpha}/{gamma} agonists in rat hepatocytes

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

Rogue, Alexandra; Universite de Rennes 1, 35065 Rennes Cedex; Biologie Servier, 45520 Gidy

2011-07-01

Species-differential toxic effects have been described with PPAR{alpha} and PPAR{gamma} agonists between rodent and human liver. PPAR{alpha} agonists (fibrates) are potent hypocholesterolemic agents in humans while they induce peroxisome proliferation and tumors in rodent liver. By contrast, PPAR{gamma} agonists (glitazones) and even dual PPAR{alpha}/{gamma} agonists (glitazars) have caused idiosyncratic hepatic and nonhepatic toxicities in human without evidence of any damage in rodent during preclinical studies. The mechanisms involved in such differences remain largely unknown. Several studies have identified the major target genes of PPAR{alpha} agonists in rodent liver while no comprehensive analysis has been performed on gene expression changes inducedmore » by PPAR{gamma} and dual PPAR{alpha}/{gamma} agonists. Here, we investigated transcriptomes of rat hepatocytes after 24 h treatment with two PPAR{gamma} (troglitazone and rosiglitazone) and two PPAR{alpha}/{gamma} (muraglitazar and tesaglitazar) agonists. Although, hierarchical clustering revealed a gene expression profile characteristic of each PPAR agonist class, only a limited number of genes was specifically deregulated by glitazars. Functional analyses showed that many genes known as PPAR{alpha} targets were also modulated by both PPAR{gamma} and PPAR{alpha}/{gamma} agonists and quantitative differences in gene expression profiles were observed between these two classes. Moreover, most major genes modulated in rat hepatocytes were also found to be deregulated in rat liver after tesaglitazar treatment. Taken altogether, these results support the conclusion that differential toxic effects of PPAR{alpha} and PPAR{gamma} agonists in rodent liver do not result from transcriptional deregulation of major PPAR target genes but rather from qualitative and/or quantitative differential responses of a small subset of genes.« less

Preclinical Medical Students' Diverse Educational and Emotional Responses to a Required Hospice Experience.

PubMed

Tse, Chung Sang; Morrison, Laura J; Ellman, Matthew S

2017-09-01

Physicians' lack of comfort and skill in communicating about hospice care results in deficits and delays in hospice referrals. Preclinical exposure to hospice may lay a foundation to improve medical students' knowledge and comfort with hospice care. To understand how preclinical medical student (MS)-2s respond both educationally and emotionally to a required hospice care experience (HCE). Accompanied by hospice clinicians, MS-2s spent 3 hours seeing inpatient or home hospice patients followed by a 1-hour debriefing. Students submitted written reflections to e-mailed educational and emotional prompts. Two hundred and two MS-2s from 2 academic cohorts completed the HCE at 1 of 2 hospice sites. Written reflective responses were analyzed qualitatively, where salient themes extracted and responses were coded. Ninety-two students submitted 175 responses to Prompt #1 (educational impact) and 85 students entered 85 responses to prompt #2 (emotional impact) of the HCE. Eleven themes were identified for prompt #1, most frequently focusing on hospice services and goals and hospice providers' attitudes and skills. Prompt #2 elicited a diverse spectrum of emotional responses, spanning positive and negative emotions. Most often, students reported "no specified emotional reaction," "sad/depressed," "difficult /challenging," "heartened/encouraged," and "mixed emotions." In an HCE, preclinical students reported learning core aspects of hospice care and experiencing a broad spectrum of emotional responses. These findings may assist educators in the planning of HCEs for preclinical students, including debriefing sessions with skilled clinicians and opportunities for triggered reflection.

Multi-messenger Light Curves from Gamma-Ray Bursts in the Internal Shock Model

NASA Astrophysics Data System (ADS)

Bustamante, Mauricio; Heinze, Jonas; Murase, Kohta; Winter, Walter

2017-03-01

Gamma-ray bursts (GRBs) are promising as sources of neutrinos and cosmic rays. In the internal shock scenario, blobs of plasma emitted from a central engine collide within a relativistic jet and form shocks, leading to particle acceleration and emission. Motivated by present experimental constraints and sensitivities, we improve the predictions of particle emission by investigating time-dependent effects from multiple shocks. We produce synthetic light curves with different variability timescales that stem from properties of the central engine. For individual GRBs, qualitative conclusions about model parameters, neutrino production efficiency, and delays in high-energy gamma-rays can be deduced from inspection of the gamma-ray light curves. GRBs with fast time variability without additional prominent pulse structure tend to be efficient neutrino emitters, whereas GRBs with fast variability modulated by a broad pulse structure can be inefficient neutrino emitters and produce delayed high-energy gamma-ray signals. Our results can be applied to quantitative tests of the GRB origin of ultra-high-energy cosmic rays, and have the potential to impact current and future multi-messenger searches.

Neutron energy spectra from the laser-induced Dd,n3He reaction.

PubMed

Hilscher, D; Berndt, O; Enke, M; Jahnke, U; Nickles, P V; Ruhl, H; Sandner, W

2001-07-01

Detailed neutron energy spectra were measured for the D(d,n)3He reaction induced in solid (CD2)(n) targets by irradiation with 50-fs 2 x 10(18) W/cm(2) light pulses from a 10-TW Ti:Sapphire laser. The neutrons were observed at two angles 5 degrees and 112 degrees relative to the incident laser beam. The neutron spectra at the two angles are characterized by peaks with large widths of about 700 keV full width at half maximum and a shift of 300 keV between them. Neutron energies of up to about 4 MeV were observed indicating that deuterons are accelerated up to an energy of 1 MeV in the laser produced plasma. Simulation calculations can describe qualitatively the neutron spectra by assuming isotropic deuteron acceleration and a reduction of the reaction probability by a factor of 1/3 for deuterons emitted from the front of the target. These calculations indicate in particular that it is necessary to assume deuterons moving both into and out of the front of the target in order to describe the neutron energy spectra at the two angles. The highest recorded mean neutron yield was about 10(4) neutrons per pulse. The neutron yield increases with the number of electrons emitted from the front of the target and with the intensity of the prompt gamma flash induced by the bremsstrahlung of energetic electrons.

Evaluation of the radiation hazard for ion-beam analysis with MeV external proton beams (X-IBA)

NASA Astrophysics Data System (ADS)

Hofsäss, Hans

2018-07-01

MeV ion beams which are extracted into air or He atmosphere are used in many labs for proton-induced X-ray emission (PIXE), proton induced gamma ray emission (PIGE) or Rutherford backscattering (RBS) to analyze samples which are difficult or impossible to handle in vacuum. When MeV proton beams are extracted into air through thin Kapton foils or nowadays thin silicon nitride membranes, the protons will interact with air, as well as elements present in the analyzed samples. Typically the range of MeV protons in air is several cm, in Helium atmosphere several 10 cm and in human skin around 100 μm. Besides the severe radiation hazard in case of a direct exposure of skin with protons, there are a manifold of nuclear reactions or inelastic proton scattering processes which may cause activation of air and target materials but also prompt radiation. The radiation hazard associated with the direct and scattered beam, nuclear reaction products and radionuclide production in air have been discussed in a publication by Doyle et al. in 1991 which was used as a reference in several later publications. I have reevaluated the radiation hazards for external proton beams with up to 4.5 MeV using proton reaction cross sections taken from the JANIS book of proton induced cross sections. The radionuclide production in air is about 3 orders of magnitude lower compared to values given in the 1991 publication. Radionuclide production as well as generation of prompt alpha, gamma and neutron radiation in target materials for elements up to molybdenum is also evaluated.

A Study of the Gamma-Ray Burst Fundamental Plane

DOE PAGES

Dainotti, M. G.; Hernandez, X.; Postnikov, S.; ...

2017-10-17

Long gamma-ray bursts (GRBs) with a plateau phase in their X-ray afterglows obey a 3D relation, between the rest-frame time at the end of the plateau, T a, its corresponding X-ray luminosity, L a, and the peak luminosity in the prompt emission, L peak. This 3D relation identifies a GRB fundamental plane whose existence we here confirm. Here we include the most recent GRBs observed by Swift to define a "gold sample" (45 GRBs) and obtain an intrinsic scatter about the plane compatible within 1σ with the previous result. We compare GRB categories, such as short GRBs with extended emissionmore » (SEE), X-ray flashes, GRBs associated with supernovae, a sample of only long-duration GRBs (132), selected from the total sample by excluding GRBs of the previous categories, and the gold sample, composed by GRBs with light curves with good data coverage and relatively flat plateaus. We find that the relation planes for each of these categories are not statistically different from the gold fundamental plane, with the exception of the SSE, which are hence identified as a physically distinct class. The gold fundamental plane has an intrinsic scatter smaller than any plane derived from the other sample categories. Thus, the distance of any particular GRB category from this plane becomes a key parameter. We computed the several category planes with T a as a dependent parameter obtaining for each category smaller intrinsic scatters (reaching a reduction of 24% for the long GRBs). The fundamental plane is independent from several prompt and afterglow parameters.« less

The impact of prompt gamma compensation on myocardial blood flow measurements with rubidium-82 dynamic PET.

PubMed

Armstrong, Ian S; Memmott, Matthew J; Tonge, Christine M; Arumugam, Parthiban

2018-04-01

Rubidium-82 myocardial perfusion imaging is a well-established technique for assessing myocardial ischemia. With continuing interest on myocardial blood flow (MBF) and myocardial flow reserve (MFR) measurements, there is a requirement to fully appreciate the impact of technical aspects of the process. One such factor for rubidium-82 is prompt gamma compensation (PGC). This study aims to assess the impact of PGC on MBF and MFR calculated from dynamic Rb-82 data. Dynamic rest and stress images were acquired on a Siemens Biograph mCT and reconstructed with and without PGC in 50 patients (29 male). MBF and MFR were measured in the three main coronary territories as well as globally. With PGC, statistically significant reductions in MBF were observed in LAD (-6.9%), LCx (-4.8%), and globally (-6.5%) but only in obese patients. Significant increases in MBF were observed in RCA (+6.4%) in only nonobese patients. In very obese patients, differences of up to 40% in MBF were observed between PGC and non-PGC images. In nearly all cases, similar PGC differences were observed at stress and rest so there were no significant differences in MFR; however, in a small number of very obese patients, differences in excess of 20% were observed. PGC results in statistically significant changes in MBF, with the greatest reductions observed in the LAD and LCx territories of obese patients. In most cases, the impact on stress and rest data is of similar relative magnitudes and changes to MFR are small.

Nature versus Nurture: The Origin of Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars

NASA Astrophysics Data System (ADS)

Marsden, D.; Lingenfelter, R. E.; Rothschild, R. E.; Higdon, J. C.

2001-03-01

Soft gamma-ray repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are young and radio-quiet X-ray pulsars that have been rapidly spun-down to slow spin periods clustered in the range 5-12 s. Most of these unusual pulsars also appear to be associated with supernova shell remnants (SNRs) with typical ages less than 30 kyr. By examining the sizes of these remnants versus their ages, we demonstrate that the interstellar media that surrounded the SGR and AXP progenitors and their SNRs were unusually dense compared to the environments around most young radio pulsars and SNRs. We explore the implications of this evidence on magnetar and propeller-based models for the rapid spin-down of SGRs and AXPs. We find that evidence of dense environments is not consistent with the magnetar model unless a causal link can be shown between the development of magnetars and the external interstellar medium. Propeller-driven spin-down by fossil accretion disks for SGRs and AXPs appears to be consistent with dense environments since the environment can facilitate the formation of such a disk. This may occur in two ways: (1) formation of a ``pushback'' disk from the innermost ejecta pushed back by prompt reverse shocks from supernova remnant interactions with massive progenitor wind material stalled in dense surrounding gas or (2) acquisition of disks by a high-velocity neutron stars, which may be able to capture sufficient amounts of comoving outflowing ejecta slowed by the prompt reverse shocks in dense environments.

The Second Swift BAT Gamma-Ray Burst Catalog

NASA Technical Reports Server (NTRS)

Barthelmy, S. D.; Baumgartner, W. H.; Cummings, J. R.; Fenimore, E. E.; Gehrels, N.; Krimm, H. A.; Markwardt, C. B.; Palmer, D. M.; Parsons, A. M.; Sato, G.;

Physics of gamma-ray bursts and multi-messenger signals from double neutron star mergers

NASA Astrophysics Data System (ADS)

Gao, He

My dissertation includes two parts: Physics of Gamma-Ray Bursts (GRBs): Gamma-ray bursts are multi-wavelength transients, with both prompt gamma-ray emission and late time afterglow emission observed by telescopes in different wavelengths. I have carried out three investigations to understand GRB prompt emission and afterglow. Chapter 2 develops a new method, namely, "Stepwise Filter Correlation" method, to decompose the variability components in a light curve. After proving its reliability through simulations, we apply this method to 266 bright GRBs and find that the majority of the bursts have clear evidence of superposition of fast and slow variability components. Chapter 3 gives a complete presentation of the analytical approximations for synchrotron self-compton emission for all possible orders of the characteristic synchrotron spectral breaks (nua, nu m, and nuc). We identify a "strong absorption" regime whennua > nuc, and derive the critical condition for this regime. The external shock theory is an elegant theory to model GRB afterglows. It invokes a limit number of model parameters, and has well predicted spectral and temporal properties. Chapter 4 gives a complete reference of all the analytical synchrotron external shock afterglow models by deriving the temporal and spectral indices of all the models in all spectral regimes. This complete reference will serve as a useful tool for afterglow observers to quickly identify relevant models to interpret their data and identify new physics when the models fail. Milti-messenger signals from double neutron star merger: As the multi-messenger era of astronomy ushers in, the second part of the dissertation studies the possible electromagnetic (EM) and neutrino emission counterparts of double neutron star mergers. Chapter 6 suggests that if double neutron star mergers leave behind a massive magnetar rather than a black hole, the magnetar wind could push the ejecta launched during the merger process, and under certain conditions, accelerates it to a relativistic speed. Such a magnetar-powered ejecta, when interacting with the ambient medium, would develop a bright broad-band afterglow due to external shock synchrotron radiation. We study this physical scenario in detail, and present the predicted X-ray, optical and radio light curves for a range of magnetar and ejecta parameters. Chapter 7 applies the model to interpret one optical transient discovered recently. In chapter 8, we show that protons accelerated in the external shock would interact with photons generated in the dissipating magnetar wind and emit high energy neutrinos and photons. We find that PeV neutrinos could be emitted from the shock front as long as the ejecta could be accelerated to a relativistic speed. These events would contribute to the diffuse Pev neutrino background and sub-Tev gamma-ray background.

Am I a Mathematics Teacher Who Teaches Middle Grades or a Middle Grades Teacher Who Teaches Mathematics? Untangling the Multiple Identities of Preservice Teachers

ERIC Educational Resources Information Center

Kasten, Sarah E.; Austin, Christopher; Jackson, Christa

2014-01-01

This article reports on a qualitative study that investigated the identities of preservice middle grades teachers preparing to teach mathematics as one of their chosen content areas. Data were collected using open response reflective prompts questionnaires with 68 preservice middle grades teachers at 3 south-central universities. Findings indicate…

The Impact of Male Gender Dissonance on Women's Potential Eligibility for Advancement to the Position of Community College Chief Executive Officer

ERIC Educational Resources Information Center

Garzaniti, Sam G., II

2017-01-01

Purpose: The purpose of this qualitative, replication study was to discover what behaviors female administrators exhibit that may prompt male administrators with whom they work in a California community college to demonstrate behaviors associated with gender dissonance and also to determine what impact these dissonant behaviors may have on women's…

Integrating the 6+1 Writing Traits Model with Cross-Age Tutoring: An Investigation of Elementary Students' Writing Development

ERIC Educational Resources Information Center

Paquette, Kelli R.

2009-01-01

A mixed methodological approach was used to examine the effect of a cross-age tutoring writing program among second- and fourth-grade students in a rural elementary school in Delaware. Pre-test and post-test writing prompts were administered and evaluated using the 6+1 traits writing assessment rubric. Students were assessed qualitatively through…

"No One Wants to Be Taught from a Textbook!": Pre-Service Health and Physical Education Teachers' Reflections on Skill Acquisition and a New Curriculum

ERIC Educational Resources Information Center

Olson, Rebecca; Laidlaw, Penelope; Steel, Kylie

2017-01-01

Changes to the purpose and scope of health and physical education (HPE) in schools have prompted revisions in teacher education degrees within Australia. Using a qualitative approach, this study explored HPE teachers' perceptions of these changes. Of particular interest was pre-service HPE teachers' reflections on the importance of skill…

Rural K-8 Special Education Teachers' Perceptions of Their Positional Status as Special Education Teachers Who Co-Teach with Regular Education Teachers

ERIC Educational Resources Information Center

LaPorte, Kristy L.

2010-01-01

This exploratory qualitative case study investigated rural K-8 special education teacher perceptions of their positional status as special education teachers who co-teach with their regular education peers. Four special education teachers participated in journal prompts, one-on-one interviews, and a focus group interview. The conceptual lens for…

How and Why Young Adults Do and Do Not Search for Health Information: Cognitive and Affective Factors

ERIC Educational Resources Information Center

Myrick, Jessica Gall; Willoughby, Jessica Fitts; Verghese, Roshni Susana

2016-01-01

Objective: The goal of this study was to take an in-depth look at why college students do (or do not) seek health information, and how they seek information when they do. Design: Qualitative content analysis of responses to an open-ended prompt embedded in a survey about health information seeking behaviours. Setting: Nearly 700 (N?=?697) college…

Using a smart phone application to measure high-energy radiation from thunderstorms

NASA Astrophysics Data System (ADS)

Bowers, G. S.; Smith, D. M.; Rexroad, W. Z.; Kelley, N. A.; Martinez-Mckinney, F.; Rubenstein, E. P.; Drukier, G.; Benes, G. N.

2013-12-01

Commercial airline flights and developing cell phone technologies present a burgeoning opportunity for the public to help investigate radiation from thunderstorms, including terrestrial gamma-ray flashes (TGFs), longer-lived gamma-ray glows, x-rays from lightning stepped leaders, and possible high-energy radiation, never yet observed, from blue jets, gigantic jets, and blue starters. GammaPix is a smartphone application from Image Insight, Inc. that uses the camera's CCD or CMOS sensor to identify and qualitatively assess threats related to gamma radioactivity, e.g., those caused by accidental exposure to radioactive material, high-altitude air travel, or acts of terrorism. A science-oriented version of the app is under development that will be publicized for use aboard commercial airline flights and on the ground in regions (like Japan in the wintertime) where thunderstorm charge centers come close to the ground. The primary goal of the project is to learn whether TGFs close to passenger aircraft and population centers on the ground occur often enough to create concern about radiation risk.

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

Bustamante, Mauricio; Heinze, Jonas; Winter, Walter

Gamma-ray bursts (GRBs) are promising as sources of neutrinos and cosmic rays. In the internal shock scenario, blobs of plasma emitted from a central engine collide within a relativistic jet and form shocks, leading to particle acceleration and emission. Motivated by present experimental constraints and sensitivities, we improve the predictions of particle emission by investigating time-dependent effects from multiple shocks. We produce synthetic light curves with different variability timescales that stem from properties of the central engine. For individual GRBs, qualitative conclusions about model parameters, neutrino production efficiency, and delays in high-energy gamma-rays can be deduced from inspection of themore » gamma-ray light curves. GRBs with fast time variability without additional prominent pulse structure tend to be efficient neutrino emitters, whereas GRBs with fast variability modulated by a broad pulse structure can be inefficient neutrino emitters and produce delayed high-energy gamma-ray signals. Our results can be applied to quantitative tests of the GRB origin of ultra-high-energy cosmic rays, and have the potential to impact current and future multi-messenger searches.« less

Disruption of Prefrontal Cortex Large Scale Neuronal Activity by Different Classes of Psychotomimetic Drugs

PubMed Central

Wood, Jesse; Kim, Yunbok; Moghaddam, Bita

2012-01-01

In the absence of overt cellular pathology but profound perceptual disorganization and cognitive deficits, schizophrenia is increasingly considered a disorder of neural coordination. Thus, different causal factors can similarly interrupt the dynamic function of neuronal ensembles and networks, in particular in the prefrontal cortex (PFC), leading to behavioral disorganization. The importance of establishing preclinical biomarkers for this aberrant function has prompted investigations into the nature of psychotomimetic drug effects on PFC neuronal activity. The drugs used in this context include serotonergic hallucinogens, amphetamine, and NMDA receptor antagonists. A prominent line of thinking is that these drugs create psychotomimetic states by similarly disinhibiting the activity of PFC pyramidal neurons. In the present study we did not find evidence in support of this mechanism in PFC subregions of freely moving rats. Whereas the NMDA receptor antagonist MK801 increased PFC population activity, the serotonergic hallucinogen DOI dose-dependently decreased population activity. Amphetamine did not strongly affect this measure. Despite different effects on the direction of change in activity, all three drugs caused similar net disruptions of population activity and modulated gamma oscillations. We also observed reduced correlations between spikerate and LFP power selectively in the gamma band suggesting that these drugs disconnect spike-discharge from PFC gamma oscillators. Gamma band oscillations support cognitive functions affected in schizophrenia. These findings provide insight into mechanisms that may lead to cortical processing deficits in schizophrenia and provide a novel electrophysiological approach for phenotypic characterization of animal models of this disease. PMID:22378875

Signs of magnetic acceleration and multizone emission in GRB 080825C

DOE PAGES

Moretti, Elena; Axelsson, Magnus

2016-03-03

One of the major results from the study of gamma-ray bursts with the Fermi Gamma-ray Space Telescope has been the confirmation that several emission components can be present in the energy spectrum. In this paper, we reanalyse the spectrum of GRB 080825C using data from the Fermi-Large Area Telescope (LAT) and Gamma-ray Burst Monitor instruments. Although fairly weak, it is the first gamma-ray burst detected by the Fermi-LAT. We improve on the original analysis by using the LAT Low Energy events covering the 30–100 MeV band. We find evidence of an additional component above the main emission peak (modelled usingmore » a Band function) with a significance of 3.5σ in two out of the four time bins. The component is well fitted by a Planck function, but shows unusual behaviour: the peak energy increases in the prompt emission phase, reaching energies of several MeV. This is the first time such a trend has been seen, and implies that the origin of this component is different from those previously detected. We suggest that the two spectral components likely arise in different regions of the outflow, and that strong constraints can be achieved by assuming one of them originates from the photosphere. Finally, the most promising model appears to be that the high-energy peak is the result of photospheric emission in a Poynting flux dominated outflow where the magnetization increases with time.« less

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

Moretti, Elena; Axelsson, Magnus

One of the major results from the study of gamma-ray bursts with the Fermi Gamma-ray Space Telescope has been the confirmation that several emission components can be present in the energy spectrum. In this paper, we reanalyse the spectrum of GRB 080825C using data from the Fermi-Large Area Telescope (LAT) and Gamma-ray Burst Monitor instruments. Although fairly weak, it is the first gamma-ray burst detected by the Fermi-LAT. We improve on the original analysis by using the LAT Low Energy events covering the 30–100 MeV band. We find evidence of an additional component above the main emission peak (modelled usingmore » a Band function) with a significance of 3.5σ in two out of the four time bins. The component is well fitted by a Planck function, but shows unusual behaviour: the peak energy increases in the prompt emission phase, reaching energies of several MeV. This is the first time such a trend has been seen, and implies that the origin of this component is different from those previously detected. We suggest that the two spectral components likely arise in different regions of the outflow, and that strong constraints can be achieved by assuming one of them originates from the photosphere. Finally, the most promising model appears to be that the high-energy peak is the result of photospheric emission in a Poynting flux dominated outflow where the magnetization increases with time.« less

Neutron radiative capture methods for surface elemental analysis

USGS Publications Warehouse

Trombka, J.I.; Senftle, F.; Schmadebeck, R.

1970-01-01

Both an accelerator and a 252Cf neutron source have been used to induce characteristic gamma radiation from extended soil samples. To demonstrate the method, measurements of the neutron-induced radiative capture and activation gamma rays have been made with both Ge(Li) and NaI(Tl) detectors, Because of the possible application to space flight geochemical analysis, it is believed that NaI(Tl) detectors must be used. Analytical procedures have been developed to obtain both qualitative and semiquantitative results from an interpretation of the measured NaI(Tl) pulse-height spectrum. Experiment results and the analytic procedure are presented. ?? 1970.

High-flux PGAA for milligram-weight samples

NASA Astrophysics Data System (ADS)

Kudejova, P.; Révay, Z.; Kleszcz, K.; Genreith, C.; Rossbach, M.

2015-05-01

With the high-intensity cold neutron flux available at the Prompt Gamma Activation Analysis (PGAA) instrument of the research reactor FRM II at the Heinz Maier-Leibnitz Zentrum (MLZ), samples with a weight of 1 mg or even less can be investigated for their elemental compositions using the (n,γ) capture reaction. In such cases, the typical sample packing material for PGAA experiments made of 25 μm thick PTFE foil (ca. 80 mg) can be orders of magnitude more massive than the sample weight itself. Proper choice of the packing material and measuring conditions are then of the highest importance [1].

Geometry of the diffusive propagation region in the August 14, 1982 solar electron event

NASA Technical Reports Server (NTRS)

Evenson, P. A.

1985-01-01

On August 14, 1982, relativistic electrons arrived promptly after an impulsive gamma ray flare, indicating that very little scattering was taking place in interplanetary space. By ignoring anisotropy data the time profile of the event is well described by interplanetary diffusion except for the derived particle injection time. This discrepancy provides independent evidence that the particles are diffusing in a volume close to the Sun rather than in interplanetary space. The flux at maximum method of determining the number of particles produced is still a good approximation when appropriately applied.

Design of a setup for 252Cf neutron source for storage and analysis purpose

NASA Astrophysics Data System (ADS)

Hei, Daqian; Zhuang, Haocheng; Jia, Wenbao; Cheng, Can; Jiang, Zhou; Wang, Hongtao; Chen, Da

2016-11-01

252Cf is a reliable isotopic neutron source and widely used in the prompt gamma ray neutron activation analysis (PGNAA) technique. A cylindrical barrel made by polymethyl methacrylate contained with the boric acid solution was designed for storage and application of a 5 μg 252Cf neutron source. The size of the setup was optimized with Monte Carlo code. The experiments were performed and the results showed the doses were reduced with the setup and less than the allowable limit. The intensity and collimating radius of the neutron beam could also be adjusted through different collimator.

Constraining the High-Energy Emission from Gamma-Ray Bursts with Fermi

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Harding, A. K.; Hays, E.; Racusin, J. L.; Sonbas, E.; Stamatikos, M.; Guirec, S.

2012-01-01

We examine 288 GRBs detected by the Fermi Gamma-ray Space Telescope's Gamma-ray Burst Monitor (GBM) that fell within the field-of-view of Fermi's Large Area Telescope (LAT) during the first 2.5 years of observations, which showed no evidence for emission above 100 MeV. We report the photon flux upper limits in the 0.1-10 GeV range during the prompt emission phase as well as for fixed 30 s and 100 s integrations starting from the trigger time for each burst. We compare these limits with the fluxes that would be expected from extrapolations of spectral fits presented in the first GBM spectral catalog and infer that roughly half of the GBM-detected bursts either require spectral breaks between the GBM and LAT energy bands or have intrinsically steeper spectra above the peak of the nuF(sub v) spectra (E(sub pk)). In order to distinguish between these two scenarios, we perform joint GBM and LAT spectral fits to the 30 brightest GBM-detected bursts and find that a majority of these bursts are indeed softer above E(sub pk) than would be inferred from fitting the GBM data alone. Approximately 20% of this spectroscopic subsample show statistically significant evidence for a cut-off in their high-energy spectra, which if assumed to be due to gamma gamma attenuation, places limits on the maximum Lorentz factor associated with the relativistic outflow producing this emission. All of these latter bursts have maximum Lorentz factor estimates that are well below the minimum Lorentz factors calculated for LAT-detected GRBs, revealing a wide distribution in the bulk Lorentz factor of GRB outflows and indicating that LAT-detected bursts may represent the high end of this distribution.

Search for TeV Gamma-ray Emission from GRB 100621A, an extremely bright GRB in X-rays, with H.E.S.S.

NASA Astrophysics Data System (ADS)

H.E.S.S. Collaboration; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; O'C. Drury, L.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giebels, B.; Glicenstein, J. F.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Méhault, J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Niemiec, J.; Nolan, S. J.; Oakes, L.; O'Brien, P. T.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tam, P. H. T.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

2014-05-01

The long gamma-ray burst (GRB) 100621A, at the time the brightest X-ray transient ever detected by Swift-XRT in the 0.3-10 keV range, has been observed with the H.E.S.S. imaging air Cherenkov telescope array, sensitive to gamma radiation in the very-high-energy (VHE, >100 GeV) regime. Due to its relatively small redshift of z ~ 0.5, the favourable position in the southern sky and the relatively short follow-up time (<700 s after the satellite trigger) of the H.E.S.S. observations, this GRB could be within the sensitivity reach of the H.E.S.S. instrument. The analysis of the H.E.S.S. data shows no indication of emission and yields an integral flux upper limit above ~380 GeV of 4.2 × 10-12 cm-2 s-1 (95% confidence level), assuming a simple Band function extension model. A comparison to a spectral-temporal model, normalised to the prompt flux at sub-MeV energies, constraints the existence of a temporally extended and strong additional hard power law, as has been observed in the other bright X-ray GRB 130427A. A comparison between the H.E.S.S. upper limit and the contemporaneous energy output in X-rays constrains the ratio between the X-ray and VHE gamma-ray fluxes to be greater than 0.4. This value is an important quantity for modelling the afterglow and can constrain leptonic emission scenarios, where leptons are responsible for the X-ray emission and might produce VHE gamma rays.

Search for GeV and X-Ray Flares Associated with the IceCube Track-like Neutrinos

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

Peng, Fang-Kun; Wang, Xiang-Yu, E-mail: xywang@nju.edu.cn

Dozens of high-energy neutrinos have been detected by the IceCube neutrino telescope, but no clear association with any classes of astrophysical sources has been identified so far. Recently, Kadler et al. reported that a PeV cascade-like neutrino event occurred in positional and temporal coincidence with a giant gamma-ray flare of the blazar PKS B1424-418. Since IceCube track-like events have much better angular resolution, we here search for possible short-term gamma-ray flares that are associated with the IceCube track-like events with Fermi Large Area Telescope (LAT) observations. Among them, three track-like neutrino events occur within the field of view of Fermimore » -LAT at the time of the detection, so searching for the prompt gamma-ray emission associated with neutrinos is possible. Assuming a point source origin and a single power-law spectrum for the possible gamma-ray sources associated with neutrinos, a likelihood analysis of 0.2–100 GeV photons observed by Fermi -LAT on the timescales of ∼12 hr and one year are performed, and for the three special neutrinos, the analyses are also performed on the timescales of thousands of seconds before and after the neutrino detection. No significant GeV excesses over the background are found and upper limit fluxes at the 95% confidence level are obtained for different timescales. We also search for possible the Swift hard X-ray transient sources associated with the IceCube track-like neutrino events, but the search also yields null results. We discuss the implication of the non-detection of gamma-ray flares for the constraints on the neutrino source density.« less

Tripeptidyl peptidase II plays a role in the radiation response of selected primary cell types but not based on nuclear translocation and p53 stabilization.

PubMed

Firat, Elke; Tsurumi, Chizuko; Gaedicke, Simone; Huai, Jisen; Niedermann, Gabriele

2009-04-15

The giant cytosolic protease tripeptidyl peptidase II (TPPII) was recently proposed to play a role in the DNA damage response. Shown were nuclear translocation of TPPII after gamma-irradiation, lack of radiation-induced p53 stabilization in TPPII-siRNA-treated cells, and complete tumor regression in mice after gamma-irradiation when combined with TPPII-siRNA silencing or a protease inhibitor reported to inhibit TPPII. This suggested that TPPII could be a novel target for tumor radiosensitization and prompted us to study radiation responses using TPPII-knockout mice. Neither the sensitivity to total body irradiation nor the radiosensitivity of resting lymphoid cells, which both strongly depend on p53, was altered in the absence of TPPII. Functional integrity of p53 in TPPII-knockout cells is further shown by a proper G(1) arrest and by the accumulation of p53 and its transcriptional targets, p21, Bax, and Fas, on gamma-irradiation. Furthermore, we could not confirm radiation-induced nuclear translocation of TPPII. Nevertheless, after gamma-irradiation, we found slightly increased mitotic catastrophe of TPPII-deficient primary fibroblasts and increased apoptosis of TPPII-deficient activated CD8(+) T cells. The latter was accompanied by delayed resolution of the DNA double-strand break marker gammaH2AX. This could, however, be due to increased apoptotic DNA damage rather than reduced DNA damage repair. Our data do not confirm a role for TPPII in the DNA damage response based on nuclear TPPII translocation and p53 stabilization but nevertheless do show increased radiation-induced cell death of selected nontransformed cell types in the absence of the TPPII protease.

Development of a fast scintillator based beam phase measurement system for compact superconducting cyclotrons

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

Bhattacharjee, Tanushyam; Kanti Dey, Malay; Dhara, Partha

2013-05-15

In an isochronous cyclotron, measurements of central phase of the ion beam with respect to rf and the phase width provide a way to tune the cyclotron for maximum energy gain per turn and efficient extraction. We report here the development of a phase measurement system and the measurements carried out at the Variable Energy Cyclotron Centre's (VECC's) K= 500 superconducting cyclotron. The technique comprises detecting prompt {gamma}-rays resulting from the interaction of cyclotron ion beam with an aluminium target mounted on a radial probe in coincidence with cyclotron rf. An assembly comprising a fast scintillator and a liquid light-guidemore » inserted inside the cyclotron was used to detect the {gamma}-rays and to transfer the light signal outside the cyclotron where a matching photo-multiplier tube was used for light to electrical signal conversion. The typical beam intensity for this measurement was a few times 10{sup 11} pps.« less

PPPC 4 DM ID: a poor particle physicist cookbook for dark matter indirect detection

NASA Astrophysics Data System (ADS)

Cirelli, Marco; Corcella, Gennaro; Hektor, Andi; Hütsi, Gert; Kadastik, Mario; Panci, Paolo; Raidal, Martti; Sala, Filippo; Strumia, Alessandro

2011-03-01

We provide ingredients and recipes for computing signals of TeV-scale Dark Matter annihilations and decays in the Galaxy and beyond. For each DM channel, we present the energy spectra of at production, computed by high-statistics simulations. We estimate the Monte Carlo uncertainty by comparing the results yielded by the Pythia and Herwig event generators. We then provide the propagation functions for charged particles in the Galaxy, for several DM distribution profiles and sets of propagation parameters. Propagation of e± is performed with an improved semi-analytic method that takes into account position-dependent energy losses in the Milky Way. Using such propagation functions, we compute the energy spectra of e±,bar p and bar d at the location of the Earth. We then present the gamma ray fluxes, both from prompt emission and from Inverse Compton scattering in the galactic halo. Finally, we provide the spectra of extragalactic gamma rays. All results are available in numerical form and ready to be consumed.

Fibrinogen storage disease in a Chinese boy with de novo fibrinogen Aguadilla mutation: Incomplete response to carbamazepine and ursodeoxycholic acid.

PubMed

Zhang, Mei-Hong; Knisely, A S; Wang, Neng-Li; Gong, Jing-Yu; Wang, Jian-She

2016-08-12

Fibrinogen storage disease (FSD) is a rare autosomal-dominant disorder caused by mutation in FGG, encoding the fibrinogen gamma chain. Here we report the first Han Chinese patient with FSD, caused by de novo fibrinogen Aguadilla mutation, and his response to pharmacologic management. Epistaxis and persistent clinical-biochemistry test-result abnormalities prompted liver biopsy in a boy, with molecular study of FGG in him and his parents. He was treated with the autophagy enhancer carbamazepine, reportedly effective in FSD, and with ursodeoxycholic acid thereafter. Inclusion bodies in hepatocellular cytoplasm stained immune-histochemically for fibrinogen. Selective analysis of FGG found the heterozygous mutation c.1201C > T (p.Arg401Trp), absent in both parents. Over more than one year's follow-up, transaminase and gamma-glutamyl transpeptidase activities have lessened but not normalized. This report expands the epidemiology of FSD and demonstrates idiosyncrasy in response to oral carbamazepine and/or ursodeoxycholic acid in FSD.

Fermi and Swift Gamma-Ray Burst Afterglow Population Studies

NASA Technical Reports Server (NTRS)

Racusin, J. L.; Oates, S. R.; Schady, P.; Burrows, D. N.; de Pasquale, M.; Donato, D.; Gehrels, N.; Koch, S.; McEnery, J.; Piran, T.;

Fermi and Swift Gamma-Ray Burst Afterglow Population Studies

NASA Technical Reports Server (NTRS)

Racusin, Judith I.

2011-01-01

The new and extreme population of GRBs detected by Fermi-LAT shows several new features in high energy gamma-rays that are providing interesting and unexpected clues into GRB prompt and afterglow emission mechanisms. Over the last 6 years, it has been Swift that has provided the robust data set of UV/optical and X-ray afterglow observations that opened many windows into components of GRB emission structure. The relationship between the LAT GRBs and the well studied, fainter, less energetic GRBs detected by Swift-BAT is only beginning to be explored by multi-wavelength studies. We explore the large sample of GRBs detected by BAT only, BAT and Fermi-GBM, and GBM and LAT, focusing on these samples separately in order to search for statistically significant differences between the populations, using only those GRBs with measured redshifts in order to physically characterize these objects. We disentangle which differences are instrumental selection effects versus intrinsic properties, in order to better understand the nature of the special characteristics of the LAT bursts.

Fermi and Swift Gamma-Ray Burst Afterglow Population Studies

NASA Technical Reports Server (NTRS)

Racusin, Judith L.; Oates, S. R.; Schady, P.; Burrows, D. N.; dePasquale, M.; Donato, D.; Gehrels, N.; Koch, S.; McEnery, J.; Piran, T.;

Gamma-ray bursts and their use as cosmic probes

PubMed Central

2017-01-01

Since the launch of the highly successful and ongoing Swift mission, the field of gamma-ray bursts (GRBs) has undergone a revolution. The arcsecond GRB localizations available within just a few minutes of the GRB alert has signified the continual sampling of the GRB evolution through the prompt to afterglow phases revealing unexpected flaring and plateau phases, the first detection of a kilonova coincident with a short GRB, and the identification of samples of low-luminosity, ultra-long and highly dust-extinguished GRBs. The increased numbers of GRB afterglows, GRB-supernova detections, redshifts and host galaxy associations has greatly improved our understanding of what produces and powers these immense, cosmological explosions. Nevertheless, more high-quality data often also reveal greater complexity. In this review, I summarize some of the milestones made in GRB research during the Swift era, and how previous widely accepted theoretical models have had to adapt to accommodate the new wealth of observational data. PMID:28791158

On the Neutrino Non-detection of GRB 130427A

NASA Astrophysics Data System (ADS)

Gao, Shan; Kashiyama, Kazumi; Mészáros, Peter

2013-07-01

The recent gamma-ray burst GRB 130427A has an isotropic electromagnetic energy E iso ~ 1054 erg, suggesting an ample supply of target photons for photo-hadronic interactions, which at its low redshift of z ~ 0.34 would appear to make it a promising candidate for neutrino detection. However, the IceCube collaboration has reported a null result based on a search during the prompt emission phase. We show that this neutrino non-detection can provide valuable information about this gamma-ray burst's (GRB's) key physical parameters such as the emission radius Rd , the bulk Lorentz factor Γ, and the energy fraction converted into cosmic rays epsilon p . The results are discussed both in a model-independent way and in the specific scenarios of an internal shock (IS) model, a baryonic photospheric (BPH) model, and a magnetic photospheric (MPH) model. We find that the constraints are most stringent for the MPH model considered, but the constraints on the IS and the BPH models are fairly modest.

The feasibility of in vivo quantification of bone-gadolinium in humans by prompt gamma neutron activation analysis (PGNAA) following gadolinium-based contrast-enhanced MRI

NASA Astrophysics Data System (ADS)

Mostafaei, F.; McNeill, F. E.; Chettle, D. R.; Noseworthy, M. D.; Prestwich, W. V.

2015-11-01

The feasibility of using a 238Pu/Be-based in vivo prompt γ-ray neutron activation analysis (IVNAA) system, previously successfully used for measurements of muscle, for the detection of gadolinium (Gd) in bone was presented. Gd is extensively used in contrast agents in MR imaging. We present phantom measurement data for the measurement of Gd in the tibia. Gd has seven naturally occurring isotopes, of which two have extremely large neutron capture cross sections; 155Gd (14.8% natural abundance (NA), σ= 60,900 barns) and 157Gd (15.65% NA, σ= 254,000 barns). Our previous work focused on muscle but this only informs about the short term kinetics of Gd. We studied the possibility of measuring bone, as it may be a long term storage site for Gd. A human simulating bone phantom set was developed. The phantoms were doped with seven concentrations of Gd of concentrations 0.0, 25, 50, 75, 100, 120 and 150 ppm. Additional elements important for neutron activation analysis, Na, Cl and Ca, were also included to create an overall elemental composition consistent with Reference Man. The overall conclusion is that the potential application of this Pu-Be-based prompt in vivo NAA for the monitoring of the storage and retention of Gd in bone is not feasible.

AN EXTERNAL SHOCK ORIGIN OF GRB 141028A

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

Burgess, J. Michael; Bégué, Damien; Ryde, Felix

The prompt emission of the long, smooth, and single-pulsed gamma-ray burst, GRB 141028A, is analyzed under the guise of an external shock model. First, we fit the γ -ray spectrum with a two-component photon model, namely, synchrotron+blackbody, and then fit the recovered evolution of the synchrotron νF{sub ν} peak to an analytic model derived considering the emission of a relativistic blast wave expanding into an external medium. The prediction of the model for the νF{sub ν} peak evolution matches well with the observations. We observe the blast wave transitioning into the deceleration phase. Furthermore, we assume the expansion of themore » blast wave to be nearly adiabatic, motivated by the low magnetic field deduced from the observations. This allows us to recover within an order of magnitude the flux density at the νF{sub ν} peak, which is remarkable considering the simplicity of the analytic model. Under this scenario we argue that the distinction between prompt and afterglow emission is superfluous as both early-time emission and late-time emission emanate from the same source. While the external shock model is clearly not a universal solution, this analysis opens the possibility that at least some fraction of GRBs can be explained with an external shock origin of their prompt phase.« less

A Bulk Comptonization Model for the Prompt GRM Emission

NASA Technical Reports Server (NTRS)

Kazanas, Demos; Mastichiadis, A.

2010-01-01

The "Supercritical Pile" is a very economical GRB model that provides for the efficient conversion of the energy stored in the protons of a Relativistic Blast Wave (RBW) into radiation and at the same time produces - in the prompt GRB phase, even in the absence of any particle acceleration - a spectral peak at energy approximately 1 MeV. We extend this model to include the evolution of the RBW Lorentz factor F and thus follow its spectral and temporal features into the early GRB afterglow stage. One of the novel features of the present treatment is the inclusion of the feedback of the GRB produced radiation on the evolution of Gamma with radius. This feedback and the presence of kinematic and dynamic thresholds in the model are sources of potentially very rich time evolution which we have began to explore. In particular, one can this way obtain afterglow light curves with steep decays followed by the more conventional flatter afterglow slopes, while at the same time preserving the desirable features of the model, i.e. the well defined relativistic electron source and radiative processes that produce the proper peak in the nu F(sub nu) spectra. In this note we present the results of a specific set of parameters of this model with emphasis on the multiwavelength prompt emission and transition to the early afterglow.

Characterization of the microbunch time structure of proton pencil beams at a clinical treatment facility.

PubMed

Petzoldt, J; Roemer, K E; Enghardt, W; Fiedler, F; Golnik, C; Hueso-González, F; Helmbrecht, S; Kormoll, T; Rohling, H; Smeets, J; Werner, T; Pausch, G

2016-03-21

Proton therapy is an advantageous treatment modality compared to conventional radiotherapy. In contrast to photons, charged particles have a finite range and can thus spare organs at risk. Additionally, the increased ionization density in the so-called Bragg peak close to the particle range can be utilized for maximum dose deposition in the tumour volume. Unfortunately, the accuracy of the therapy can be affected by range uncertainties, which have to be covered by additional safety margins around the treatment volume. A real-time range and dose verification is therefore highly desired and would be key to exploit the major advantages of proton therapy. Prompt gamma rays, produced in nuclear reactions between projectile and target nuclei, can be used to measure the proton's range. The prompt gamma-ray timing (PGT) method aims at obtaining this information by determining the gamma-ray emission time along the proton path using a conventional time-of-flight detector setup. First tests at a clinical accelerator have shown the feasibility to observe range shifts of about 5 mm at clinically relevant doses. However, PGT spectra are smeared out by the bunch time spread. Additionally, accelerator related proton bunch drifts against the radio frequency have been detected, preventing a potential range verification. At OncoRay, first experiments using a proton bunch monitor (PBM) at a clinical pencil beam have been conducted. Elastic proton scattering at a hydrogen-containing foil could be utilized to create a coincident proton-proton signal in two identical PBMs. The selection of coincident events helped to suppress uncorrelated background. The PBM setup was used as time reference for a PGT detector to correct for potential bunch drifts. Furthermore, the corrected PGT data were used to image an inhomogeneous phantom. In a further systematic measurement campaign, the bunch time spread and the proton transmission rate were measured for several beam energies between 69 and 225 MeV as well as for variable momentum limiting slit openings. We conclude that the usage of a PBM increases the robustness of the PGT method in clinical conditions and that the obtained data will help to create reliable range verification procedures in clinical routine.

Combined Photoneutron And X Ray Interrogation Of Containers For Nuclear Materials

NASA Astrophysics Data System (ADS)

Gozani, Tsahi; Shaw, Timothy; King, Michael J.; Stevenson, John; Elsalim, Mashal; Brown, Craig; Condron, Cathie

2011-06-01

Effective cargo inspection systems for nuclear material detection require good penetration by the interrogating radiation, generation of a sufficient number of fissions, and strong and penetrating detection signatures. Inspection systems need also to be sensitive over a wide range of cargo types and densities encountered in daily commerce. Thus they need to be effective with highly hydrogenous cargo, where neutron attenuation is a major limitation, as well as with dense metallic cargo, where x-ray penetration is low. A system that interrogates cargo with both neutrons and x-rays can, in principle, achieve high performance over the widest range of cargos. Moreover, utilizing strong prompt-neutron (˜3 per fission) and delayed-gamma ray (˜7 per fission) signatures further strengthens the detection sensitivity across all cargo types. The complementary nature of x-rays and neutrons, used as both probing radiation and detection signatures, alleviates the need to employ exceedingly strong sources, which would otherwise be required to achieve adequate performance across all cargo types, if only one type of radiation probe were employed. A system based on the above principles, employing a commercially-available 9 MV linac was developed and designed. Neutrons are produced simultaneously with x-rays by the photonuclear interaction of the x-ray beam with a suitable converter. A total neutron yield on the order of 1011 n/s is achieved with an average electron beam current of 100 μA. If fissionable material is present, fissions are produced both by the high-energy x-ray beam and by the photoneutrons. Photofission and neutron fission dominate in hydrogenous and metallic cargos, respectively. Neutron-capture gamma rays provide information on the cargo composition. The prompt neutrons resulting from fission are detected by two independent detector systems: by very efficient Differential Die Away Analysis (DDAA) detectors, and by direct detection of neutrons with energies higher than 3 MeV using a recently developed fluorine-based threshold activation detector (TAD). The delayed gamma-ray signals are measured with high efficiency with the same TAD and with additional lower-cost plastic scintillators.

The perpetual search for parsimony: enhancing the epistemological and practical utility of qualitative research findings.

PubMed

Cutcliffe, John R; Harder, Henry G

2009-10-01

While it appears that the term parsimony has been used in the context of qualitative research and qualitative research methodology, there is a distinct absence of writing that actually explores, seeks to define, understand, critique, apply and/or evaluate the concept in qualitative research literature. This paper explores a number of issues pertaining to parsimony in qualitative research. It is the hope of the authors that this paper might raise awareness of the hitherto unexplored issues, stimulate some further interest in these and prompt other qualitative researchers to contribute to the ensuing debate. While there are currently no definitive criteria for determining the parsimony of qualitative research findings, it would be epistemologically inappropriate and philosophically incongruent to import and translate quantitative notions of parsimony. However, the ideas, principles and epistemological functions that parsimony serves can and should be applied to the qualitative paradigm. The authors suggest that more than one type of qualitative parsimony is required. The authors advance the argument that there is a relationship between the degree of parsimony and the elegance, ease of accessibility and straightforwardness (some might say - beauty) of the writing/findings; the level of expertise of the researcher; and the quality of the data collection interview. The authors also assert that there are a number of practices which, when adhered to, can enhance the parsimony of the findings and that here are a number of major implications arising from qualitative findings that lack parsimony.

A burst chasing x-ray polarimeter

NASA Astrophysics Data System (ADS)

Hill, Joanne E.; Barthelmy, Scott; Black, J. Kevin; Deines-Jones, Philip; Jahoda, Keith; Sakamoto, Takanori; Kaaret, Philip; McConnell, Mark L.; Bloser, Peter F.; Macri, John R.; Legere, Jason S.; Ryan, James M.; Smith, Billy R., Jr.; Zhang, Bing

2007-09-01

Gamma-ray bursts are one of the most powerful explosions in the universe and have been detected out to distances of almost 13 billion light years. The exact origin of these energetic explosions is still unknown but the resulting huge release of energy is thought to create a highly relativistic jet of material and a power-law distribution of electrons. There are several theories describing the origin of the prompt GRB emission that currently cannot be distinguished. Measurements of the linear polarization would provide unique and important constraints on the mechanisms thought to drive these powerful explosions. We present the design of a sensitive, and extremely versatile gamma-ray burst polarimeter. The instrument is a photoelectric polarimeter based on a time-projection chamber. The photoelectric time-projection technique combines high sensitivity with broad band-pass and is potentially the most powerful method between 2 and 100 keV where the photoelectric effect is the dominant interaction process. We present measurements of polarized and unpolarized X-rays obtained with a prototype detector and describe the two mission concepts; the Gamma-Ray Burst Polarimeter (GRBP) for the U.S. Naval Academy satellite MidSTAR-2, and the Low Energy Polarimeter (LEP) onboard POET, a broadband polarimetry concept for a small explorer mission.

The Supercritical Pile Model for GRBs

NASA Technical Reports Server (NTRS)

Kazanas, Demos

2006-01-01

We present the spectral and temporal radiative signatures expected within the Supercritical Pile model of Gamma Ray Bursts (GRB). This model is motivated by the need for a process that provides the dissipation necessary in GRB and presents a well defined scheme for converting the energy stored in the relativistic protons of the Relativistic Blast Waves (RBW) associated with GRB into radiation; at the same time it leads to spectra which exhibit a peak in the burst nuF(sub nu) distribution at an energy E(sub p) approximately equal to 1 MeV in the observer s frame, in agreement with observation and largely independent of the Lorentz factor GAMMA of the associated relativistic outflow. Furthermore, this scheme does not require (but does not preclude) acceleration of particles at the shock other than that provided by the isotropization of the flow bulk kinetic energy on the RBW frame. In the present paper we model in detail the evolution of protons, electrons and photons from a RBW to produce detailed spectra of the prompt GRB phase as a function of time from across a very broad range spanning roughly 4 log10 GAMMA decades in frequency. The model spectra are in general agreement with observations and provide a means for the delineating of the model parameters through direct comparison with trends observed in GRB properties.

A Burst Chasing X-ray Polarimeter

NASA Technical Reports Server (NTRS)

Hill, Joanne E.; Barthelmy, Scott; Black, J. kevin; Deines-Jones, Philip; Jahoda, Keith; Sakamoto, Takanori; Kaaret, Philip; McConnell, Mark L.; Bloser, Peter F.; Macri, John R.;

A Burst Chasing X-ray Polarimeter

NASA Technical Reports Server (NTRS)

Hill, Joanne; Hill, Joe; Barthelmy, S.; Black, K.; Deines-Jones, P.; Jahoda, K.; Sakamoto, T.; Kaaret, P.; McConnell, M.; Bloser, P.;

GABA-B Agonist Baclofen Normalizes Auditory-Evoked Neural Oscillations and Behavioral Deficits in the Fmr1 Knockout Mouse Model of Fragile X Syndrome

PubMed Central

Featherstone, R.; Naschek, M.; Nam, J.; Du, A.; Wright, S.; Weger, R.; Akuzawa, S.

2017-01-01

Abstract Fragile X syndrome is a genetic condition resulting from FMR1 gene mutation that leads to intellectual disability, autism-like symptoms, and sensory hypersensitivity. Arbaclofen, a GABA-B agonist, has shown efficacy in some individuals with FXS but has become unavailable after unsuccessful clinical trials, prompting interest in publicly available, racemic baclofen. The present study investigated whether racemic baclofen can remediate abnormalities of neural circuit function, sensory processing, and behavior in Fmr1 knockout mice, a rodent model of fragile X syndrome. Fmr1 knockout mice showed increased baseline and auditory-evoked high-frequency gamma (30–80 Hz) power relative to C57BL/6 controls, as measured by electroencephalography. These deficits were accompanied by decreased T maze spontaneous alternation, decreased social interactions, and increased open field center time, suggestive of diminished working memory, sociability, and anxiety-like behavior, respectively. Abnormal auditory-evoked gamma oscillations, working memory, and anxiety-related behavior were normalized by treatment with baclofen, but impaired sociability was not. Improvements in working memory were evident predominantly in mice whose auditory-evoked gamma oscillations were dampened by baclofen. These findings suggest that racemic baclofen may be useful for targeting sensory and cognitive disturbances in fragile X syndrome. PMID:28451631

Thermal Emissions Spanning the Prompt and the Afterglow Phases of the Ultra-long GRB 130925A

NASA Astrophysics Data System (ADS)

Basak, Rupal; Rao, A. R.

2015-07-01

GRB 130925A is an ultra-long gamma-ray burst (GRB), and it shows clear evidence for thermal emission in the soft X-ray data of the Swift/X-ray Telescope (XRT; ∼0.5 keV), lasting until the X-ray afterglow phase. Due to the long duration of the GRB, the burst could be studied in hard X-rays with high-resolution focusing detectors (NuSTAR). The blackbody temperature, as measured by the Swift/XRT, shows a decreasing trend until the late phase (Piro et al.) whereas the high-energy data reveal a significant blackbody component during the late epochs at an order of magnitude higher temperature (∼5 keV) compared to contemporaneous low energy data (Bellm et al.). We resolve this apparent contradiction by demonstrating that a model with two black bodies and a power law (2BBPL) is consistent with the data right from the late prompt emission to the afterglow phase. Both blackbodies show a similar cooling behavior up to late times. We invoke a structured jet, having a fast spine and a slower sheath layer, to identify the location of these blackbodies. Independent of the physical interpretation, we propose that the 2BBPL model is a generic feature of the prompt emission of all long GRBs, and the thermal emission found in the afterglow phase of different GRBs reflects the lingering thermal component of the prompt emission with different timescales. We strengthen this proposal by pointing out a close similarity between the spectral evolutions of this GRB and GRB 090618, a source with significant wide band data during the early afterglow phase.

INTEGRAL Detection of the First Prompt Gamma-Ray Signal Coincident with the Gravitational-wave Event GW170817

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

Savchenko, V.; Ferrigno, C.; Bozzo, E.

We report the INTernational Gamma-ray Astrophysics Laboratory ( INTEGRAL ) detection of the short gamma-ray burst GRB 170817A (discovered by Fermi -GBM) with a signal-to-noise ratio of 4.6, and, for the first time, its association with the gravitational waves (GWs) from binary neutron star (BNS) merging event GW170817 detected by the LIGO and Virgo observatories. The significance of association between the gamma-ray burst observed by INTEGRAL and GW170817 is 3.2σ, while the association between the Fermi -GBM and INTEGRAL detections is 4.2σ. GRB 170817A was detected by the SPI-ACS instrument about 2 s after the end of the GW event.more » We measure a fluence of (1.4 ± 0.4 ± 0.6) × 10{sup −7} erg cm{sup −2} (75–2000 keV), where, respectively, the statistical error is given at the 1σ confidence level, and the systematic error corresponds to the uncertainty in the spectral model and instrument response. We also report on the pointed follow-up observations carried out by INTEGRAL , starting 19.5 hr after the event, and lasting for 5.4 days. We provide a stringent upper limit on any electromagnetic signal in a very broad energy range, from 3 keV to 8 MeV, constraining the soft gamma-ray afterglow flux to <7.1 × 10{sup −11} erg cm{sup −2} s{sup −1} (80–300 keV). Exploiting the unique capabilities of INTEGRAL , we constrained the gamma-ray line emission from radioactive decays that are expected to be the principal source of the energy behind a kilonova event following a BNS coalescence. Finally, we put a stringent upper limit on any delayed bursting activity, for example, from a newly formed magnetar.« less

Enhanced Analysis Techniques for an Imaging Neutron and Gamma Ray Spectrometer

NASA Astrophysics Data System (ADS)

Madden, Amanda C.

The presence of gamma rays and neutrons is a strong indicator of the presence of Special Nuclear Material (SNM). The imaging Neutron and gamma ray SPECTrometer (NSPECT) developed by the University of New Hampshire and Michigan Aerospace corporation detects the fast neutrons and prompt gamma rays from fissile material, and the gamma rays from radioactive material. The instrument operates as a double scatter device, requiring a neutron or a gamma ray to interact twice in the instrument. While this detection requirement decreases the efficiency of the instrument, it offers superior background rejection and the ability to measure the energy and momentum of the incident particle. These measurements create energy spectra and images of the emitting source for source identification and localization. The dual species instrument provides superior detection than a single species alone. In realistic detection scenarios, few particles are detected from a potential threat due to source shielding, detection at a distance, high background, and weak sources. This contributes to a small signal to noise ratio, and threat detection becomes difficult. To address these difficulties, several enhanced data analysis tools were developed. A Receiver Operating Characteristic Curve (ROC) helps set instrumental alarm thresholds as well as to identify the presence of a source. Analysis of a dual-species ROC curve provides superior detection capabilities. Bayesian analysis helps to detect and identify the presence of a source through model comparisons, and helps create a background corrected count spectra for enhanced spectroscopy. Development of an instrument response using simulations and numerical analyses will help perform spectra and image deconvolution. This thesis will outline the principles of operation of the NSPECT instrument using the double scatter technology, traditional analysis techniques, and enhanced analysis techniques as applied to data from the NSPECT instrument, and an outline of how these techniques can be used to superior detection of radioactive and fissile materials.

Addressing the third gamma problem in PET

NASA Astrophysics Data System (ADS)

Schueller, M. J.; Mulnix, T. L.; Christian, B. T.; Jensen, M.; Holm, S.; Oakes, T. R.; Roberts, A. D.; Dick, D. W.; Martin, C. C.; Nickles, R. J.

2003-02-01

PET brings the promise of quantitative imaging of the in-vivo distribution of any positron emitting nuclide, a list with hundreds of candidates. All but a few of these, the "pure positron" emitters, have isotropic coincident gamma rays that give rise to misrepresented events in the sinogram and in the resulting reconstructed image. Of particular interest are /sup 10/C, /sup 14/O, /sup 38/K, /sup 52m/Mn, /sup 60/Cu, /sup 61/Cu, /sup 94m/Tc, and /sup 124/I, each having high-energy gammas that are Compton-scattered down into the 511 keV window. The problems arising from the "third gamma," and its accommodation by standard scatter correction algorithms, were studied empirically, employing three scanner models (CTI 933/04, CTI HR+ and GE Advance), imaging three phantoms (line source, NEMA scatter and contrast/detail), with /sup 18/F or /sup 38/K and /sup 72/As mimicking /sup 14/O and /sup 10/C, respectively, in 2-D and 3-D modes. Five findings emerge directly from the image analysis. The third gamma: 1) does, obviously, tax the single event rate of the PET scanners, particularly in the absence of septa, from activity outside of the axial field of view; 2) does, therefore, tax the random rate, which is second order in singles, although the gamma is a prompt coincidence partner; 3) does enter the sinogram as an additional flat background, like randoms, but unlike scatter; 4) is not seriously misrepresented by the scatter algorithm which fits the correction to the wings of the sinogram; and 5) does introduce additional statistical noise from the subsequent subtraction, but does not seriously compromise the detectability of lesions as seen in the contrast/detail phantom. As a safeguard against the loss of accuracy in image quantitation, fiducial sources of known activity are included in the field of view alongside of the subject. With this precaution, a much wider selection of imaging agents can enjoy the advantages of positron emission tomography.

Impulsive And Long Duration High-Energy Gamma-Ray Emission From The Very Bright 2012 March 7 Solar Flares

DOE PAGES

Ajello, M.

2014-06-10

The Fermi Large Area Telescope (LAT) observed two bright X-class solar ares on 2012 March 7, and detected gamma-rays up to 4 GeV. We detected gamma-rays both during the impulsive and temporally-extended emission phases, with emission above 100 MeV lasting for approximately 20 hours. Accurate localization of the gamma-ray production site(s) coincide with the solar active region from which X-ray emissions associated with these ares originated. Our analysis of the > 100 MeV gamma-ray emission shows a relatively rapid monotonic decrease in flux during the first hour of the impulsive phase, and a much slower, almost monotonic decrease in fluxmore » for the next 20 hours. The spectra can be adequately described by a power law with a high energy exponential cutoff, or as resulting from the decay of neutral pions produced by accelerated protons and ions with an isotropic power-law energy distribution. The required proton spectrum has a number index 3, with minor variations during the impulsive phase, while during the temporally extended phase the spectrum softens monotonically, starting with index 4. The > 30 MeV proton flux and spectra observed near the Earth by the GOES satellites also show a monotonic flux decrease and spectral softening during the extended phase, but with a harder spectrum, with index 3. Based on the Fermi-LAT and GOES observations of the flux and spectral evolution of these bright ares, we explore the relative merits of prompt and continuous acceleration scenarios, hadronic and leptonic emission processes, and acceleration at the solar corona by the fast Coronal Mass Ejections (CME) as explanations for the observations. We conclude that the most likely scenario is continuous acceleration of protons in the solar corona which penetrate the lower solar atmosphere and produce pions that decay into gamma-rays.« less

Impulsive And Long Duration High-Energy Gamma-Ray Emission From The Very Bright 2012 March 7 Solar Flares

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

Ajello, M.

The Fermi Large Area Telescope (LAT) observed two bright X-class solar ares on 2012 March 7, and detected gamma-rays up to 4 GeV. We detected gamma-rays both during the impulsive and temporally-extended emission phases, with emission above 100 MeV lasting for approximately 20 hours. Accurate localization of the gamma-ray production site(s) coincide with the solar active region from which X-ray emissions associated with these ares originated. Our analysis of the > 100 MeV gamma-ray emission shows a relatively rapid monotonic decrease in flux during the first hour of the impulsive phase, and a much slower, almost monotonic decrease in fluxmore » for the next 20 hours. The spectra can be adequately described by a power law with a high energy exponential cutoff, or as resulting from the decay of neutral pions produced by accelerated protons and ions with an isotropic power-law energy distribution. The required proton spectrum has a number index 3, with minor variations during the impulsive phase, while during the temporally extended phase the spectrum softens monotonically, starting with index 4. The > 30 MeV proton flux and spectra observed near the Earth by the GOES satellites also show a monotonic flux decrease and spectral softening during the extended phase, but with a harder spectrum, with index 3. Based on the Fermi-LAT and GOES observations of the flux and spectral evolution of these bright ares, we explore the relative merits of prompt and continuous acceleration scenarios, hadronic and leptonic emission processes, and acceleration at the solar corona by the fast Coronal Mass Ejections (CME) as explanations for the observations. We conclude that the most likely scenario is continuous acceleration of protons in the solar corona which penetrate the lower solar atmosphere and produce pions that decay into gamma-rays.« less

African American Girls' Perceptions of Their Adjustment from Coeducational Elementary Schools to a Single-Gender Middle School, and How They Believe Educators Can Best Support This Transition: A Case Study

ERIC Educational Resources Information Center

Presley, Christal L.

2009-01-01

his qualitative and quantitative study investigated student perceptions of seventh-grade African American females who transitioned from a coeducational elementary school to a single-gender middle school. This study was conducted by surveying students, having them answer writing prompts, and interviewing them. Data furnished by the respondents was…

A multiwavelength study of Swift GRB 060111B constraining the origin of its prompt optical emission

NASA Astrophysics Data System (ADS)

Stratta, G.; Pozanenko, A.; Atteia, J.-L.; Klotz, A.; Basa, S.; Gendre, B.; Verrecchia, F.; Boër, M.; Cutini, S.; Henze, M.; Holland, S.; Ibrahimov, M.; Ienna, F.; Khamitov, I.; Klose, S.; Rumyantsev, V.; Biryukov, V.; Sharapov, D.; Vachier, F.; Arnouts, S.; Perley, D. A.

2009-09-01

Context: The detection of bright optical emission measured with good temporal resolution during the prompt phase of GRB 060111Bmakes this GRB a rare event that is especially useful for constraining theories of the prompt emission. Aims: For this reason an extended multi-wavelength campaign was performed to further constrain the physical interpretation of the observations. Methods: In this work, we present the results obtained from our multi-wavelength campaign, as well as from the public Swift/BAT, XRT, and UVOT data. Results: We identified the host galaxy at R˜25 mag from deep R-band exposures taken 5 months after the trigger. Its featureless spectrum and brightness, as well as the non-detection of any associated supernova 16 days after the trigger, enabled us to constrain the distance scale of GRB 060111B11 within 0.4≤ z ≤3 in the most conservative case. The host galaxy spectral continuum is best fit with a redshift of z˜2, and other independent estimates converge to z˜1-2. From the analysis of the early afterglow SED, we find that non-negligible host galaxy dust extinction, in addition to the Galactic one, affects the observed flux in the optical regime. The extinction-corrected optical-to-gamma-ray SED during the prompt emission shows a flux density ratio Fγ/F_opt=10-2-10-4 with spectral index βγ,opt > βγ, strongly suggesting a separate origin of the optical and gamma-ray components. This result is supported by the lack of correlated behavior in the prompt emission light curves observed in the two energy domains. The temporal properties of the prompt optical emission observed during GRB 060111B11 and their similarities to other rapidly-observed events favor interpretation of this optical light as radiation from the reverse shock. Observations are in good agreement with theoretical expectations for a thick shell limit in slow cooling regime. The expected peak flux is consistent with the observed one corrected for the host extinction, likely indicating that the starting time of the TAROT observations is very near to or coincident with the peak time. The estimated fireball initial Lorentz factor is Γ≥260-360 at z=1-2, similar to the Lorentz factors obtained from other GRBs. GRB 060111B11 is a rare case of a GRB with both a bright, well-observed optical counterpart and a “canonical” early X-ray light curve, thus providing a good test case of the reverse shock emission mechanism in both energy ranges. Based on observations performed with: TAROT at the Calern observatory. The Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. CFHT, which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the CNRS of France, and the University of Hawaii. The 2.6 m Shajn telescope at the Crimean Astrophysical Observatory. Some of the data presented here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Establishment of Imaging Spectroscopy of Nuclear Gamma-Rays based on Geometrical Optics

PubMed Central

Tanimori, Toru; Mizumura, Yoshitaka; Takada, Atsushi; Miyamoto, Shohei; Takemura, Taito; Kishimoto, Tetsuro; Komura, Shotaro; Kubo, Hidetoshi; Kurosawa, Shunsuke; Matsuoka, Yoshihiro; Miuchi, Kentaro; Mizumoto, Tetsuya; Nakamasu, Yuma; Nakamura, Kiseki; Parker, Joseph D.; Sawano, Tatsuya; Sonoda, Shinya; Tomono, Dai; Yoshikawa, Kei

2017-01-01

Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that “Electron Tracking Compton Camera” (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics. PMID:28155870

Establishment of Imaging Spectroscopy of Nuclear Gamma-Rays based on Geometrical Optics.

PubMed

Tanimori, Toru; Mizumura, Yoshitaka; Takada, Atsushi; Miyamoto, Shohei; Takemura, Taito; Kishimoto, Tetsuro; Komura, Shotaro; Kubo, Hidetoshi; Kurosawa, Shunsuke; Matsuoka, Yoshihiro; Miuchi, Kentaro; Mizumoto, Tetsuya; Nakamasu, Yuma; Nakamura, Kiseki; Parker, Joseph D; Sawano, Tatsuya; Sonoda, Shinya; Tomono, Dai; Yoshikawa, Kei

2017-02-03

Since the discovery of nuclear gamma-rays, its imaging has been limited to pseudo imaging, such as Compton Camera (CC) and coded mask. Pseudo imaging does not keep physical information (intensity, or brightness in Optics) along a ray, and thus is capable of no more than qualitative imaging of bright objects. To attain quantitative imaging, cameras that realize geometrical optics is essential, which would be, for nuclear MeV gammas, only possible via complete reconstruction of the Compton process. Recently we have revealed that "Electron Tracking Compton Camera" (ETCC) provides a well-defined Point Spread Function (PSF). The information of an incoming gamma is kept along a ray with the PSF and that is equivalent to geometrical optics. Here we present an imaging-spectroscopic measurement with the ETCC. Our results highlight the intrinsic difficulty with CCs in performing accurate imaging, and show that the ETCC surmounts this problem. The imaging capability also helps the ETCC suppress the noise level dramatically by ~3 orders of magnitude without a shielding structure. Furthermore, full reconstruction of Compton process with the ETCC provides spectra free of Compton edges. These results mark the first proper imaging of nuclear gammas based on the genuine geometrical optics.

Studies of Gamma-Ray Burst Prompt Emission with RHESSI and NCT

NASA Astrophysics Data System (ADS)

Bellm, Eric Christopher

Gamma-Ray Bursts (GRBs) are the most luminous objects in the universe. They herald a catastrophic energy release which manifests itself in tenths to hundreds of seconds of irregular gamma-ray emission. This initial "prompt" emission is followed by "afterglow" emission at other wavelengths that fades smoothly over hours to years. GRB prompt emission has been observed with ever-increasing sophistication for more than four decades, but many details of its origin remain unknown. While GRBs are under-stood to result from relativistic jets produced by violent reconfigurations of compact objects, the composition of the outflow, the means of energy dissipation, and the radiative processes underlying the observed emission are all uncertain. I review the present understanding of all facets of GRB science in Chapter 1. Gamma-ray spectroscopy and polarimetry provide two channels for testing models of GRB prompt emission with observed data. In Chapters 2--4, I employ the Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) to conduct broad-band time-resolved spectroscopy of bright GRBs. RHESSI is a solar observatory that uses nine coaxial germanium detectors for imaging and spectroscopy of solar flares. Because the detectors are unshielded, RHESSI also records counts from off-axis sources like GRBs. In Chapter 2, I detail the methods I use for analyzing RHESSI GRB data. In Chapter 3, I conduct joint spectral analysis of bursts co-observed by RHESSI and Swift-BAT, enabling spectral modeling over a wide 15 keV--17 MeV band. These results reveal the difficulty of predicting the peak spectral energy of a burst from BAT observations alone. While GRB spectra commonly have been assumed to be non-thermal and have been fit by purely phenomenological models, some authors have proposed that thermal emission from the GRB photosphere may be the source of the GRB spectral peak. In Chapter 4, I perform time-resolved spectroscopy of bright GRBs observed by RHESSI and compare the fit results of several phenomenological and quasi-thermal models. The fit results for the quasi-thermal models are poorer than those reported for fits in more narrow energy bands, and the fit parameters show significant dependence on the fit band. More sophisticated models and additional data are needed to determine the relevance of the photospheric emission. Polarimetric studies of GRBs are in their infancy, but they have the potential to distinguish GRB emission models and probe the structure of the relativistic jet. Observations to date have exploited the polarimetric signatures produced by Compton scattering in gamma-ray observatories. Since these instruments have poor spatial resolution and are not calibrated for polarimetric observations, only a few bright GRBs have been observed, each with significant systematic effects. In Chapters 5--8, I present development work for a balloon-borne Compton telescope, the Nuclear Compton Telescope (NCT), which is capable of measuring GRB polarization. NCT uses planar cross-strip germanium detectors for Compton imaging (200 keV--10 MeV) and polarimetry (200 keV--2 MeV). Chapter 5 describes NCT and its flight history. In Chapter 6, I discuss calibrations of the effective area of NCT during the 2009 New Mexico and 2010 Australia balloon campaigns. By placing radioactive sources of known activity throughout the NCT field of view, it is possible to determine the efficiency of the telescope. I compare these values to those derived from detailed Monte Carlo simulations. The values derived from the real data show a roughly constant deficit relative to those derived from the Monte Carlo simulations which may be related to known deficiencies in the lower-level event calibrations. Chapter 7 assesses NCT's polarimetric performance. I generated partially polarized beams throughout NCT's field of view by scattering photons off of a scintillator slab triggered in coincidence with the NCT detectors. The measured polarimetric modulation showed good agreement with Monte Carlo simulations for some calibrations, although systematic geometric effects are present. NCT's polarimetric performance compares well to that of other Compton telescopes. Finally, in Chapter 8 I calculate NCT's sensitivity to GRBs and expected detection rate. Using single-site and incompletely-absorbed events, NCT has about one-fourth the sensitivity of BATSE LAD. NCT could detect about half of the bursts in the BATSE catalog if they occurred in its field of view. Bursts bright enough for polarimetric analysis are too rare to detect effectively from a balloon platform, however, so a satellite instrument with NCT-like detectors would be needed to perform a useful census of GRB polarization. Better understanding of the GRB prompt emission will clarify the place of GRBs in stellar life cycles, provide new insights into the physics of collisionless shocks and relativistic jets, and facilitate the use of GRBs as probes of the early universe and electromagnetic counterparts to gravitational wave and neutrino signals. The complex phenomenology of GRBs creates both a challenge and a rich opportunity to explain and utilize these enigmatic events.

Maturation of auditory neural processes in autism spectrum disorder - A longitudinal MEG study.

PubMed

Port, Russell G; Edgar, J Christopher; Ku, Matthew; Bloy, Luke; Murray, Rebecca; Blaskey, Lisa; Levy, Susan E; Roberts, Timothy P L

2016-01-01

Individuals with autism spectrum disorder (ASD) show atypical brain activity, perhaps due to delayed maturation. Previous studies examining the maturation of auditory electrophysiological activity have been limited due to their use of cross-sectional designs. The present study took a first step in examining magnetoencephalography (MEG) evidence of abnormal auditory response maturation in ASD via the use of a longitudinal design. Initially recruited for a previous study, 27 children with ASD and nine typically developing (TD) children, aged 6- to 11-years-old, were re-recruited two to five years later. At both timepoints, MEG data were obtained while participants passively listened to sinusoidal pure-tones. Bilateral primary/secondary auditory cortex time domain (100 ms evoked response latency (M100)) and spectrotemporal measures (gamma-band power and inter-trial coherence (ITC)) were examined. MEG measures were also qualitatively examined for five children who exhibited "optimal outcome", participants who were initially on spectrum, but no longer met diagnostic criteria at follow-up. M100 latencies were delayed in ASD versus TD at the initial exam (~ 19 ms) and at follow-up (~ 18 ms). At both exams, M100 latencies were associated with clinical ASD severity. In addition, gamma-band evoked power and ITC were reduced in ASD versus TD. M100 latency and gamma-band maturation rates did not differ between ASD and TD. Of note, the cohort of five children that demonstrated "optimal outcome" additionally exhibited M100 latency and gamma-band activity mean values in-between TD and ASD at both timepoints. Though justifying only qualitative interpretation, these "optimal outcome" related data are presented here to motivate future studies. Children with ASD showed perturbed auditory cortex neural activity, as evidenced by M100 latency delays as well as reduced transient gamma-band activity. Despite evidence for maturation of these responses in ASD, the neural abnormalities in ASD persisted across time. Of note, data from the five children whom demonstrated "optimal outcome" qualitatively suggest that such clinical improvements may be associated with auditory brain responses intermediate between TD and ASD. These "optimal outcome" related results are not statistically significant though, likely due to the low sample size of this cohort, and to be expected as a result of the relatively low proportion of "optimal outcome" in the ASD population. Thus, further investigations with larger cohorts are needed to determine if the above auditory response phenotypes have prognostic utility, predictive of clinical outcome.

Status of the Monte Carlo library least-squares (MCLLS) approach for non-linear radiation analyzer problems

NASA Astrophysics Data System (ADS)

Gardner, Robin P.; Xu, Libai

2009-10-01

The Center for Engineering Applications of Radioisotopes (CEAR) has been working for over a decade on the Monte Carlo library least-squares (MCLLS) approach for treating non-linear radiation analyzer problems including: (1) prompt gamma-ray neutron activation analysis (PGNAA) for bulk analysis, (2) energy-dispersive X-ray fluorescence (EDXRF) analyzers, and (3) carbon/oxygen tool analysis in oil well logging. This approach essentially consists of using Monte Carlo simulation to generate the libraries of all the elements to be analyzed plus any other required background libraries. These libraries are then used in the linear library least-squares (LLS) approach with unknown sample spectra to analyze for all elements in the sample. Iterations of this are used until the LLS values agree with the composition used to generate the libraries. The current status of the methods (and topics) necessary to implement the MCLLS approach is reported. This includes: (1) the Monte Carlo codes such as CEARXRF, CEARCPG, and CEARCO for forward generation of the necessary elemental library spectra for the LLS calculation for X-ray fluorescence, neutron capture prompt gamma-ray analyzers, and carbon/oxygen tools; (2) the correction of spectral pulse pile-up (PPU) distortion by Monte Carlo simulation with the code CEARIPPU; (3) generation of detector response functions (DRF) for detectors with linear and non-linear responses for Monte Carlo simulation of pulse-height spectra; and (4) the use of the differential operator (DO) technique to make the necessary iterations for non-linear responses practical. In addition to commonly analyzed single spectra, coincidence spectra or even two-dimensional (2-D) coincidence spectra can also be used in the MCLLS approach and may provide more accurate results.

Improvements to Nuclear Data and Its Uncertainties by Theoretical Modeling

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

Danon, Yaron; Nazarewicz, Witold; Talou, Patrick

2013-02-18

This project addresses three important gaps in existing evaluated nuclear data libraries that represent a significant hindrance against highly advanced modeling and simulation capabilities for the Advanced Fuel Cycle Initiative (AFCI). This project will: Develop advanced theoretical tools to compute prompt fission neutrons and gamma-ray characteristics well beyond average spectra and multiplicity, and produce new evaluated files of U and Pu isotopes, along with some minor actinides; Perform state-of-the-art fission cross-section modeling and calculations using global and microscopic model input parameters, leading to truly predictive fission cross-sections capabilities. Consistent calculations for a suite of Pu isotopes will be performed; Implementmore » innovative data assimilation tools, which will reflect the nuclear data evaluation process much more accurately, and lead to a new generation of uncertainty quantification files. New covariance matrices will be obtained for Pu isotopes and compared to existing ones. The deployment of a fleet of safe and efficient advanced reactors that minimize radiotoxic waste and are proliferation-resistant is a clear and ambitious goal of AFCI. While in the past the design, construction and operation of a reactor were supported through empirical trials, this new phase in nuclear energy production is expected to rely heavily on advanced modeling and simulation capabilities. To be truly successful, a program for advanced simulations of innovative reactors will have to develop advanced multi-physics capabilities, to be run on massively parallel super- computers, and to incorporate adequate and precise underlying physics. And all these areas have to be developed simultaneously to achieve those ambitious goals. Of particular interest are reliable fission cross-section uncertainty estimates (including important correlations) and evaluations of prompt fission neutrons and gamma-ray spectra and uncertainties.« less

Geant4 Modifications for Accurate Fission Simulations

NASA Astrophysics Data System (ADS)

Tan, Jiawei; Bendahan, Joseph

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

Fast multipurpose Monte Carlo simulation for proton therapy using multi- and many-core CPU architectures.

PubMed

Souris, Kevin; Lee, John Aldo; Sterpin, Edmond

2016-04-01

Accuracy in proton therapy treatment planning can be improved using Monte Carlo (MC) simulations. However the long computation time of such methods hinders their use in clinical routine. This work aims to develop a fast multipurpose Monte Carlo simulation tool for proton therapy using massively parallel central processing unit (CPU) architectures. A new Monte Carlo, called MCsquare (many-core Monte Carlo), has been designed and optimized for the last generation of Intel Xeon processors and Intel Xeon Phi coprocessors. These massively parallel architectures offer the flexibility and the computational power suitable to MC methods. The class-II condensed history algorithm of MCsquare provides a fast and yet accurate method of simulating heavy charged particles such as protons, deuterons, and alphas inside voxelized geometries. Hard ionizations, with energy losses above a user-specified threshold, are simulated individually while soft events are regrouped in a multiple scattering theory. Elastic and inelastic nuclear interactions are sampled from ICRU 63 differential cross sections, thereby allowing for the computation of prompt gamma emission profiles. MCsquare has been benchmarked with the gate/geant4 Monte Carlo application for homogeneous and heterogeneous geometries. Comparisons with gate/geant4 for various geometries show deviations within 2%-1 mm. In spite of the limited memory bandwidth of the coprocessor simulation time is below 25 s for 10(7) primary 200 MeV protons in average soft tissues using all Xeon Phi and CPU resources embedded in a single desktop unit. MCsquare exploits the flexibility of CPU architectures to provide a multipurpose MC simulation tool. Optimized code enables the use of accurate MC calculation within a reasonable computation time, adequate for clinical practice. MCsquare also simulates prompt gamma emission and can thus be used also for in vivo range verification.

Measurement of characteristic prompt gamma rays emitted from oxygen and carbon in tissue-equivalent samples during proton beam irradiation

PubMed Central

Polf, Jerimy C; Panthi, Rajesh; Mackin, Dennis S; McCleskey, Matt; Saastamoinen, Antti; Roeder, Brian T; Beddar, Sam

2013-01-01

The purpose of this work was to characterize how prompt gamma (PG) emission from tissue changes as a function of carbon and oxygen concentration, and to assess the feasibility of determining elemental concentration in tissues irradiated with proton beams. For this study, four tissue-equivalent water-sucrose samples with differing densities and concentrations of carbon, hydrogen, and oxygen were irradiated with a 48 MeV proton pencil beam. The PG spectrum emitted from each sample was measured using a high-purity germanium detector, and the absolute detection efficiency of the detector, average beam current, and delivered dose distribution were also measured. Changes to the total PG emission from 12C (4.44 MeV) and 16O (6.13 MeV) per incident proton and per Gray of absorbed dose were characterized as a function of carbon and oxygen concentration in the sample. The intensity of the 4.44 MeV PG emission per incident proton was found to be nearly constant for all samples regardless of their carbon concentration. However, we found that the 6.13 MeV PG emission increased linearly with the total amount (in grams) of oxygen irradiated in the sample. From the measured PG data, we determined that 1.64 × 107 oxygen PGs were emitted per gram of oxygen irradiated per Gray of absorbed dose delivered with a 48 MeV proton beam. These results indicate that the 6.13 MeV PG emission from 16O is proportional to the concentration of oxygen in tissue irradiated with proton beams, showing that it is possible to determine the concentration of oxygen within tissues irradiated with proton beams by measuring 16O PG emission. PMID:23920051

Experimental Comparison of Knife-Edge and Multi-Parallel Slit Collimators for Prompt Gamma Imaging of Proton Pencil Beams.

PubMed

Smeets, Julien; Roellinghoff, Frauke; Janssens, Guillaume; Perali, Irene; Celani, Andrea; Fiorini, Carlo; Freud, Nicolas; Testa, Etienne; Prieels, Damien

2016-01-01

More and more camera concepts are being investigated to try and seize the opportunity of instantaneous range verification of proton therapy treatments offered by prompt gammas emitted along the proton tracks. Focusing on one-dimensional imaging with a passive collimator, the present study experimentally compared in combination with the first, clinically compatible, dedicated camera device the performances of instances of the two main options: a knife-edge slit (KES) and a multi-parallel slit (MPS) design. These two options were experimentally assessed in this specific context as they were previously demonstrated through analytical and numerical studies to allow similar performances in terms of Bragg peak retrieval precision and spatial resolution in a general context. Both collimators were prototyped according to the conclusions of Monte Carlo optimization studies under constraints of equal weight (40 mm tungsten alloy equivalent thickness) and of the specificities of the camera device under consideration (in particular 4 mm segmentation along beam axis and no time-of-flight discrimination, both of which less favorable to the MPS performance than to the KES one). Acquisitions of proton pencil beams of 100, 160, and 230 MeV in a PMMA target revealed that, in order to reach a given level of statistical precision on Bragg peak depth retrieval, the KES collimator requires only half the dose the present MPS collimator needs, making the KES collimator a preferred option for a compact camera device aimed at imaging only the Bragg peak position. On the other hand, the present MPS collimator proves more effective at retrieving the entrance of the beam in the target in the context of an extended camera device aimed at imaging the whole proton track within the patient.

A comparison of two prompt gamma imaging techniques with collimator-based cameras for range verification in proton therapy

NASA Astrophysics Data System (ADS)

Lin, Hsin-Hon; Chang, Hao-Ting; Chao, Tsi-Chian; Chuang, Keh-Shih

2017-08-01

In vivo range verification plays an important role in proton therapy to fully utilize the benefits of the Bragg peak (BP) for delivering high radiation dose to tumor, while sparing the normal tissue. For accurately locating the position of BP, camera equipped with collimators (multi-slit and knife-edge collimator) to image prompt gamma (PG) emitted along the proton tracks in the patient have been proposed for range verification. The aim of the work is to compare the performance of multi-slit collimator and knife-edge collimator for non-invasive proton beam range verification. PG imaging was simulated by a validated GATE/GEANT4 Monte Carlo code to model the spot-scanning proton therapy and cylindrical PMMA phantom in detail. For each spot, 108 protons were simulated. To investigate the correlation between the acquired PG profile and the proton range, the falloff regions of PG profiles were fitted with a 3-line-segment curve function as the range estimate. Factors including the energy window setting, proton energy, phantom size, and phantom shift that may influence the accuracy of detecting range were studied. Results indicated that both collimator systems achieve reasonable accuracy and good response to the phantom shift. The accuracy of range predicted by multi-slit collimator system is less affected by the proton energy, while knife-edge collimator system can achieve higher detection efficiency that lead to a smaller deviation in predicting range. We conclude that both collimator systems have potentials for accurately range monitoring in proton therapy. It is noted that neutron contamination has a marked impact on range prediction of the two systems, especially in multi-slit system. Therefore, a neutron reduction technique for improving the accuracy of range verification of proton therapy is needed.

A Study of the Gamma-Ray Burst Fundamental Plane

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

Dainotti, M. G.; Hernandez, X.; Postnikov, S.

2017-10-20

Long gamma-ray bursts (GRBs) with a plateau phase in their X-ray afterglows obey a 3D relation, between the rest-frame time at the end of the plateau, T {sub a} , its corresponding X-ray luminosity, L {sub a} , and the peak luminosity in the prompt emission, L {sub peak}. This 3D relation identifies a GRB fundamental plane whose existence we here confirm. Here we include the most recent GRBs observed by Swift to define a “gold sample” (45 GRBs) and obtain an intrinsic scatter about the plane compatible within 1 σ with the previous result. We compare GRB categories, suchmore » as short GRBs with extended emission (SEE), X-ray flashes, GRBs associated with supernovae, a sample of only long-duration GRBs (132), selected from the total sample by excluding GRBs of the previous categories, and the gold sample, composed by GRBs with light curves with good data coverage and relatively flat plateaus. We find that the relation planes for each of these categories are not statistically different from the gold fundamental plane, with the exception of the SSE, which are hence identified as a physically distinct class. The gold fundamental plane has an intrinsic scatter smaller than any plane derived from the other sample categories. Thus, the distance of any particular GRB category from this plane becomes a key parameter. We computed the several category planes with T {sub a} as a dependent parameter obtaining for each category smaller intrinsic scatters (reaching a reduction of 24% for the long GRBs). The fundamental plane is independent from several prompt and afterglow parameters.« less

TU-FG-BRB-05: A 3 Dimensional Prompt Gamma Imaging System for Range Verification in Proton Radiotherapy

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

Draeger, E; Chen, H; Polf, J

2016-06-15

Purpose: To report on the initial developments of a clinical 3-dimensional (3D) prompt gamma (PG) imaging system for proton radiotherapy range verification. Methods: The new imaging system under development consists of a prototype Compton camera to measure PG emission during proton beam irradiation and software to reconstruct, display, and analyze 3D images of the PG emission. For initial test of the system, PGs were measured with a prototype CC during a 200 cGy dose delivery with clinical proton pencil beams (ranging from 100 MeV – 200 MeV) to a water phantom. Measurements were also carried out with the CC placedmore » 15 cm from the phantom for a full range 150 MeV pencil beam and with its range shifted by 2 mm. Reconstructed images of the PG emission were displayed by the clinical PG imaging software and compared to the dose distributions of the proton beams calculated by a commercial treatment planning system. Results: Measurements made with the new PG imaging system showed that a 3D image could be reconstructed from PGs measured during the delivery of 200 cGy of dose, and that shifts in the Bragg peak range of as little as 2 mm could be detected. Conclusion: Initial tests of a new PG imaging system show its potential to provide 3D imaging and range verification for proton radiotherapy. Based on these results, we have begun work to improve the system with the goal that images can be produced from delivery of as little as 20 cGy so that the system could be used for in-vivo proton beam range verification on a daily basis.« less

Current and Future Research at DANCE

NASA Astrophysics Data System (ADS)

Jandel, M.; Baramsai, B.; Bredeweg, T. A.; Couture, A.; Hayes, A.; Kawano, T.; Mosby, S.; Rusev, G.; Stetcu, I.; Taddeucci, T. N.; Talou, P.; Ullmann, J. L.; Walker, C. L.; Wilhelmy, J. B.

2015-05-01

An overview of the current experimental program on measurements of neutron capture and neutron induced fission at the Detector for Advanced Neutron Capture Experiments (DANCE) is presented. Three major projects are currently under way: 1) high precision measurements of neutron capture cross sections on Uranium isotopes, 2) research aimed at studies of the short-lived actinide isomer production in neutron capture on 235U and 3) measurements of correlated data of fission observables. New projects include developments of auxiliary detectors to improve the capability of DANCE. We are building a compact, segmented NEUtron detector Array at DANCE (NEUANCE), which will be installed in the central cavity of the DANCE array. It will provide experimental information on prompt fission neutrons in coincidence with the prompt fission gamma-rays measured by 160 BaF2 crystals of DANCE. Unique correlated data will be obtained for neutron capture and neutron-induced fission using the DANCE-NEUANCE experimental set up in the future.

The Hands with Eyes and Nose in the Palm: As Effective Communication Alternatives for Profoundly Deaf People in Zimbabwe

ERIC Educational Resources Information Center

Mutswanga, Phillipa

2017-01-01

Drawing from the experiences and testimonies of people with profound deafness, the study qualitatively explored the use of the hands with eyes and nose in the palm as communication alternatives in the field of deafness. The study was prompted by the 27 year old lady, Leah Katz-Hernandez who is deaf who got engaged in March 2015 as the 2016…

The SWIFT Gamma-Ray Burst X-Ray Telescope

NASA Technical Reports Server (NTRS)

Hill, J. E.; Burrows, D. N.; Nousek, J. A.; Wells, A.; Chincarini, G.; Abbey, A. F.; Angelini, L.; Beardmore, A.; Brauninger, H. W.; Chang, W.

2006-01-01

The Swift Gamma-Ray Burst Explorer is designed to make prompt multi-wavelength observations of Gamma-Ray Bursts and GRB afterglows. The X-ray Telescope enables Swift to determine GRB positions with a few arcseconds accuracy within 100 seconds of the burst onset. The XRT utilizes a mirror set built for JET-X and an XMM-Newton/ EPIC MOS CCD detector to provide a sensitive broad-band (0.2-10 keV) X-ray imager with an effective area of more than 120 sq cm at 1.5 keV, a field of view of 23.6 x 23.6 arcminutes, and an angular resolution of 18 arcseconds (HPD). The detection sensitivity is 2x10(exp 14) erg/sq cm/s in 10(exp 4) seconds. The instrument provides automated source detection and position reporting within 5 seconds of target acquisition. It can also measure the redshifts of GRBs with Iron line emission or other spectral features. The XRT operates in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return as the source intensity fades. The XRT measures spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and follows each burst for days or weeks. We provide an overview of the X-ray Telescope scientific background from which the systems engineering requirements were derived, with specific emphasis on the design and qualification aspects from conception through to launch. We describe the impact on cleanliness and vacuum requirements for the instrument low energy response and to maintain the high sensitivity to the fading signal of the Gamma-ray Bursts.