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Sample records for hpge gamma rays

  1. Gamma-ray imaging with position-sensitive HPGe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, K. E-mail: kvetter@lbl.gov; Burks, M.; Mihailescu, L

    2004-06-01

    Due to advances in manufacturing large and highly segmented HPGe detectors along with the availability of fast and high-precision digital electronics, it is now possible to build efficient and high-resolution Compton cameras. Two-dimensionally segmented semi-conductor detectors along with pulse-shape analysis allow to obtain three-dimensional positions and energies of individual gamma-ray interactions. By employing gamma-ray tracking procedures it is possible to determine the scattering sequence in the detector and ultimately to deduce the incident direction of gamma rays without the use of a attenuating collimator. These advanced gamma-ray tracking-based Compton cameras are able not only to image gamma-ray sources with higher sensitivity than collimator-based systems but can increase the sensitivity in finding gamma-ray sources over non-imaging detectors, particularly in complex radiation fields. We have implemented a Compton camera built of a single double-sided strip HPGe detector with a strip pitch size of 2 mm. A three-dimensional position resolution of 0.5 mm at 122 keV by using simple pulse-shape analysis is achieved. We have implemented image reconstruction procedures for search scenarios, which are of interest for national security applications. In addition, we have developed reconstruction procedures to optimize image quality which potentially finds applications in other areas as well.

  2. Employing Thin HPGe Detectors for Gamma-Ray Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, K; Mihailescu, L; Ziock, K; Burks, M; Hull, E; Madden, N; Pehl, R

    2002-05-02

    We have evaluated a collimator-less gamma-ray imaging system, which is based on thin layers of double-sided strip HPGe detectors. The positions of individual gamma-ray interactions will be deduced by the strip addresses and the Ge layers which fired. Therefore, high bandwidth pulse processing is not required as in thick Ge detectors. While the drawback of such a device is the increased number of electronics channels to be read out and processed, there are several advantages, which are particularly important for remote applications: the operational voltage can be greatly reduced to fully deplete the detector and no high bandwidth signal processing electronics is required to determine positions. Only a charge sensitive preamplifier, a slow pulse shaping amplifier, and a fast discriminator are required on a per channel basis in order to determine photon energy and interaction position in three dimensions. Therefore, the power consumption and circuit board real estate can be minimized. More importantly, since the high bandwidth signal shapes are not used to determine the depth position, lower energy signals can be processed. The processing of these lower energy signals increases the efficiency for the recovery of small angle scattering. Currently, we are studying systems consisting of up to ten 2mm thick Ge layers with 2mm pitch size. The required electronics of the few hundred channels can be integrated to reduce space and power. We envision applications in nuclear non-proliferation and gamma-ray astronomy where ease of operation and low power consumption, and reliability, are crucial.

  3. Employing Thin HPGe Detectors for Gamma-Ray Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, K; Mihailescu, L; Ziock, K; Burks, M; Hull, E; Madden, N; Pehl, R

    2002-04-15

    We have evaluated a collimator-less gamma-ray imaging system, which is based on thin layers of double-sided strip HPGe detectors. The position of individual gamma-ray interactions will be deduced by the strip addresses and the Ge layers which fired. Therefore, high bandwidth pulse processing is not required as in thick Ge detectors. While the drawback of such a device is the increased number of electronics channels to be read out and processed, there are several advantages, which are particularly important for remote applications: the operational voltage can be greatly reduced to fully deplete the detector and no high bandwidth signal processing electronics is required to determine positions. Only a charge sensitive preamplifier, a slow pulse shaping amplifier, and a fast discriminator are required on a per channel basis in order to determine photon energy and interaction position in three dimensions. Therefore, the power consumption and circuit board real estate can be minimized. More importantly, since the high bandwidth signal shapes are not used to determine the depth position, lower energy signals can be processed. The processing of these lower energy signals increases the efficiency for the recovery of small angle scattering. Currently, we are studying systems consisting of up to ten 2mm thick Ge layers with 2mm pitch size. The required electronics of the few hundred channels can be integrated to reduce space and power. We envision applications in nuclear non-proliferation and gamma-ray astronomy where ease of operation and low power consumption, and reliability, are crucial.

  4. Gamma-ray Full Spectrum Analysis for Environmental Radioactivity by HPGe Detector

    Directory of Open Access Journals (Sweden)

    Meeyoung Jeong

    2014-12-01

    Full Text Available Odyssey, one of the NASA’s Mars exploration program and SELENE (Kaguya, a Japanese lunar orbiting spacecraft have a payload of Gamma-Ray Spectrometer (GRS for analyzing radioactive chemical elements of the atmosphere and the surface. In these days, gamma-ray spectroscopy with a High-Purity Germanium (HPGe detector has been widely used for the activity measurements of natural radionuclides contained in the soil of the Earth. The energy spectra obtained by the HPGe detectors have been generally analyzed by means of the Window Analysis (WA method. In this method, activity concentrations are determined by using the net counts of energy window around individual peaks. Meanwhile, an alternative method, the so-called Full Spectrum Analysis (FSA method uses count numbers not only from full-absorption peaks but from the contributions of Compton scattering due to gamma-rays. Consequently, while it takes a substantial time to obtain a statistically significant result in the WA method, the FSA method requires a much shorter time to reach the same level of the statistical significance. This study shows the validation results of FSA method. We have compared the concentration of radioactivity of 40K, 232Th and 238U in the soil measured by the WA method and the FSA method, respectively. The gamma-ray spectrum of reference materials (RGU and RGTh, KCl and soil samples were measured by the 120% HPGe detector with cosmic muon veto detector. According to the comparison result of activity concentrations between the FSA and the WA, we could conclude that FSA method is validated against the WA method. This study implies that the FSA method can be used in a harsh measurement environment, such as the gamma-ray measurement in the Moon, in which the level of statistical significance is usually required in a much shorter data acquisition time than the WA method.

  5. Detection of pulsed, bremsstrahlung-induced, prompt neutron capture gamma-rays with HPGe detector

    Energy Technology Data Exchange (ETDEWEB)

    Jones, J.L.

    1996-08-01

    The Idaho National Engineering Laboratory (INEL) is developing a novel photoneutron-based nondestructive evaluation technique which uses a pulsed, high-energy (up to 8-MeV) 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 gamma-rays acquired between accelerator pulses with a unique, high-purity germanium (HPGe) 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 system 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, NaC1, and depleted uranium targets as soon as 30 {mu}s after each bremsstrahlung (or x-ray) flash.

  6. Rapid, autonomous analysis of HPGe gamma-ray spectra III: Plutonium identification and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Gosnell, Thomas B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wong, James L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-02-11

    RadID is a gamma-ray spectrum analysis program originally written to assist in the detection of the illicit movement of nuclear material. It is specific to the rapid analysis of HPGe gamma-ray data to reveal the radionuclide signatures of interest that may be present in the spectra. It is an autonomous, rule-based heuristic system that can identify well over 200 radioactive sources in about one second. RadID does not require knowledge of the detector efficiency, the source-todetector distance, or the geometry of the inspected radiation source—including any shielding. In this third of a three-document series we discuss how RadID detects the presence of plutonium isotopes and determines a number of its characteristics, most notably: the spectral characteristics of weapons-grade plutonium, reactor-grade plutonium, and heat-source plutonium used in radioisotope thermoelectric generators.

  7. Qualitative and quantitative validation of the SINBAD code on complex HPGe gamma-ray spectra

    Energy Technology Data Exchange (ETDEWEB)

    Rohee, E.; Coulon, R.; Normand, S.; Carrel, F. [CEA, LIST, Laboratoire Capteurs et Architectures electroniques, F-91191 Gif-sur-Yvette, (France); Dautremer, T.; Barat, E.; Montagu, T. [CEA, LIST, Laboratoire Modelisation, Simulation et Systemes, F-91191 Gif-sur-Yvette, (France); Jammes, C. [CEA/DEN/SPEx/LDCI, Centre de Cadarache, F-13109 Saint-Paul-lez-Durance, (France)

    2015-07-01

    Radionuclides identification and quantification is a serious concern for many applications as safety or security of nuclear power plant or fuel cycle facility, CBRN risk identification, environmental radioprotection and waste measurements. High resolution gamma-ray spectrometry based on HPGe detectors is a performing solution for all these topics. During last decades, a great number of software has been developed to improve gamma spectra analysis. However, some difficulties remain in the analysis when photoelectric peaks are folded together with a high ratio between theirs amplitudes, when the Compton background is much larger compared to the signal of a single peak and when spectra are composed of a great number of peaks. This study deals with the comparison between conventional methods in radionuclides identification and quantification and the code called SINBAD ('Spectrometrie par Inference Non parametrique Bayesienne Deconvolutive'). For many years, SINBAD has been developed by CEA LIST for unfolding complex spectra from HPGe detectors. Contrary to conventional methods using fitting procedures, SINBAD uses a probabilistic approach with Bayesian inference to describe spectrum data. This conventional fitting method founded for example in Genie 2000 is compared with the nonparametric SINBAD approach regarding some key figures of merit as the peak centroid evaluation (identification) and peak surface evaluation (quantification). Unfriendly cases are studied for nuclides detection with closed gamma-rays energies and high photoelectric peak intensity differences. Tests are performed with spectra from the International Atomic Energy Agency (IAEA) for gamma spectra analysis software benchmark and with spectra acquired at the laboratory. Results show that SINBAD and Genie 2000 performances are quite similar with sometimes best results for SINBAD with the important difference that to achieve same performances the nonparametric method is user-friendly compared

  8. Gamma ray evaluation of fast neutron irradiated on topaz from Sri Lanka by HPGe gamma ray spectrometry

    Science.gov (United States)

    Boonsook, K.; Kaewwiset, W.; Limsuwan, P.; Naemchanthara, K.

    2017-09-01

    The purpose of this study was to evaluate the radionuclide concentrations of London blue topaz after fast neutron irradiation. The London blue topaz was obtained from Sri Lanka which classified into dark and light colors in the shape of an oval and rectangle with small, medium and large size. The optical property and radionuclide concentrations of London blue topaz have been examine by UV-Visible spectroscopy and HPGe gamma ray spectrometry, respectively. The UV-absorption spectra of topaz was taken in the range of 300 to 800 nm at room temperature. The results showed that the absorption peak of topaz was observed with only broad peaks in the range of 550 to 700 nm and 630 nm that correlated to the O - center in hydroxyl sites which substitutes for fluorine in topaz structure. The radioactivity of dark and light colors in the shape of an oval and rectangle London blue topaz was in the range of 1.437 ± 0.014 to 21.551 ± 0.037 nCi/g (oval dark), 2.958 ± 0.031 to 6.748 ± 0.054 nCi/g (oval light) and 2.350 ± 0.014 to 43.952 ± 0.088 nCi/g (rectangle dark), 1.442 ± 0.023 to 6.748 ± 0.054 nCi/g (rectangle light), respectively. The decay rates of 46Sc, 182Ta and 54Mn isotopes created by irradiation showed that the decay time of the radioactive element depended on the size of the topaz so increased with decreasing the size of topaz. Moreover, the size of topaz also affect the absorption coefficient. This study is applied to predict time of residue dose of topaz for enhancement colorless topaz by neutron radiation treatment.

  9. Methods for fitting of efficiency curves obtained by means of HPGe gamma rays spectrometers; Metodos de ajuste de curvas de eficiencia obtidas por meio de espectrometros de HPGe

    Energy Technology Data Exchange (ETDEWEB)

    Cardoso, Vanderlei

    2002-07-01

    The present work describes a few methodologies developed for fitting efficiency curves obtained by means of a HPGe gamma-ray spectrometer. The interpolated values were determined by simple polynomial fitting and polynomial fitting between the ratio of experimental peak efficiency and total efficiency, calculated by Monte Carlo technique, as a function of gamma-ray energy. Moreover, non-linear fitting has been performed using a segmented polynomial function and applying the Gauss-Marquardt method. For the peak area obtainment different methodologies were developed in order to estimate the background area under the peak. This information was obtained by numerical integration or by using analytical functions associated to the background. One non-calibrated radioactive source has been included in the curve efficiency in order to provide additional calibration points. As a by-product, it was possible to determine the activity of this non-calibrated source. For all fittings developed in the present work the covariance matrix methodology was used, which is an essential procedure in order to give a complete description of the partial uncertainties involved. (author)

  10. A new HPGe setup at Gelina for measurement of gamma-ray production cross-sections from inelastic neutron scattering

    Energy Technology Data Exchange (ETDEWEB)

    Mihailescu, L.C.; Olah, L.; Borcea, C.; Plompen, A.J.M. E-mail: plompen@irmm.jrc.be

    2004-10-01

    A new setup was developed at the Geel Electron LINear Accelerator (Gelina) pulsed white neutron source for the measurement of continuous energy excitation functions of gamma-ray production cross-sections in neutron-induced inelastic scattering. Characteristic gamma-rays are identified, background-free, using the good pulse height resolution of two large volume High-Purity Germanium (HPGe) detectors. High incident-energy resolution is achieved by the time-of-flight method with a flight-path length of 200 m and a time resolution of 8 ns full-width at half-maximum. A neutron energy resolution of 1.1 keV fwhm is obtained at 1 MeV (36 keV at 10 MeV). Absolute cross-sections are obtained by measuring the neutron flux with a {sup 235}U fission chamber. The setup was successfully applied to the determination of excitation curves of gamma-ray production cross-sections, level inelastic cross-sections and total inelastic cross-sections for {sup 52}Cr and {sup 58}Ni.

  11. Rapid, autonomous analysis of HPGe gamma-ray spectra II: Uranium identification and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Gosnell, Thomas B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wong, Jamess L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-02-11

    RadID is a gamma-ray spectrum analysis program originally written to assist in the detection of the illicit movement of nuclear material. In this second of the three-document series we discuss how RadID detects the presence of uranium isotopes and determines a number of its characteristics, most notably or processed material and enriched estimates.

  12. Gamma-ray impurities of {sup 111}In, {sup 201}Tl, {sup 177}Lu and {sup 99m}Tc determined by means of a HPGE spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Koskinas, Marina F.; Almeida, Jamille da Silveira; Moreira, Denise Simões; Semmler, Renato; Dias, Mauro da Silva, E-mail: koskinas@ipen.br, E-mail: jamillealmeida@gmail.com, E-mail: denise.moreira@ipen.br, E-mail: rsemmler@ipen.br, E-mail: msdias@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2017-11-01

    This work aims to present the radioactive impurities gamma rays emitters detected in some radiopharmaceuticals widely applied to diagnosis and therapy purposes, supplied to nuclear medicine services in Brazil by the Radiopharmaceutical Center(CR) of Nuclear and Energy Research Institute, IPEN, in São Paulo. The analysis was undertaken by means of an HPGe gamma spectrometer. The radiopharmaceuticals analyzed were: {sup 111}In, {sup 201}Tl, {sup 177}Lu and {sup 99m}Tc. (author)

  13. Radiometric analysis of construction materials using HPGe gamma-ray spectrometry.

    Science.gov (United States)

    Khandaker, M U; Jojo, P J; Kassim, H A; Amin, Y M

    2012-11-01

    Concentrations of primordial radionuclides in common construction materials collected from the south-west coastal region of India were determined using a high-purity germanium gamma-ray spectrometer. Average specific activities (Bq kg(-1)) for (238)U((226)Ra) in cement, brick, soil and stone samples were obtained as 54 ± 13, 21 ± 4, 50 ± 12 and 46 ± 8, respectively. Respective values of (232)Th were obtained as 65 ± 10, 21 ± 3, 58 ± 10 and 57 ± 12. Concentrations of (40)K radionuclide in cement, brick, soil and stone samples were found to be 440 ± 91, 290 ± 20, 380 ± 61 and 432 ± 64, respectively. To evaluate the radiological hazards, radium equivalent activity, various hazard indices, absorbed dose rate and annual effective dose have been calculated, and compared with the literature values. Obtained data could be used as reference information to assess any radiological contamination due to construction materials in future.

  14. Gamma-ray multiplicity measurement of the spontaneous fission of {sup 252}Cf in a segmented HPGe/BGO detector array

    Energy Technology Data Exchange (ETDEWEB)

    Bleuel, D.L., E-mail: bleuel1@llnl.go [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Bernstein, L.A.; Burke, J.T. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Gibelin, J. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Heffner, M.D. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Mintz, J. [Nuclear Engineering Department, University of California, Berkeley, CA 94720 (United States); Norman, E.B. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Nuclear Engineering Department, University of California, Berkeley, CA 94720 (United States); Phair, L. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Scielzo, N.D.; Sheets, S.A.; Snyderman, N.J.; Stoyer, M.A. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Wiedeking, M. [Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2010-12-21

    Coincident {gamma} rays from a {sup 252}Cf source were measured using an array of six segmented high-purity germanium (HPGe) Clover detectors each enclosed by 16 bismuth-germanate (BGO) detectors. The detectors were arranged in a cubic pattern around a 1{mu}Ci{sup 252}Cf source to cover a large solid angle for {gamma}-ray measurement with a reasonable reconstruction of the multiplicity. Neutron multiplicity was determined in certain cases by identifying the prompt {gamma} rays from individual fission fragment pairs. Multiplicity distributions from previous experiments and theoretical models were convolved with the response function of the array and compared to the present results. These results suggest a {gamma}-ray multiplicity spectrum broader than previous measurements and models, and provide no evidence of correlation with neutron multiplicity.

  15. Optimization of statistical methods for HpGe gamma-ray spectrometer used in wide count rate ranges

    Energy Technology Data Exchange (ETDEWEB)

    Gervino, G., E-mail: gervino@to.infn.it [UNITO - Università di Torino, Dipartimento di Fisica, Turin (Italy); INFN - Istituto Nazionale di Fisica Nucleare, Sez. Torino, Turin (Italy); Mana, G. [INRIM - Istituto Nazionale di Ricerca Metrologica, Turin (Italy); Palmisano, C. [UNITO - Università di Torino, Dipartimento di Fisica, Turin (Italy); INRIM - Istituto Nazionale di Ricerca Metrologica, Turin (Italy)

    2016-07-11

    The need to perform γ-ray measurements with HpGe detectors is a common technique in many fields such as nuclear physics, radiochemistry, nuclear medicine and neutron activation analysis. The use of HpGe detectors is chosen in situations where isotope identification is needed because of their excellent resolution. Our challenge is to obtain the “best” spectroscopy data possible in every measurement situation. “Best” is a combination of statistical (number of counts) and spectral quality (peak, width and position) over a wide range of counting rates. In this framework, we applied Bayesian methods and the Ellipsoidal Nested Sampling (a multidimensional integration technique) to study the most likely distribution for the shape of HpGe spectra. In treating these experiments, the prior information suggests to model the likelihood function with a product of Poisson distributions. We present the efforts that have been done in order to optimize the statistical methods to HpGe detector outputs with the aim to evaluate to a better order of precision the detector efficiency, the absolute measured activity and the spectra background. Reaching a more precise knowledge of statistical and systematic uncertainties for the measured physical observables is the final goal of this research project.

  16. GRABGAM Analysis of Ultra-Low-Level HPGe Gamma Spectra

    Energy Technology Data Exchange (ETDEWEB)

    Winn, W.G.

    1999-07-28

    The GRABGAM code has been used successfully for ultra-low level HPGe gamma spectrometry analysis since its development in 1985 at Savannah River Technology Center (SRTC). Although numerous gamma analysis codes existed at that time, reviews of institutional and commercial codes indicated that none addressed all features that were desired by SRTC. Furthermore, it was recognized that development of an in-house code would better facilitate future evolution of the code to address SRTC needs based on experience with low-level spectra. GRABGAM derives its name from Gamma Ray Analysis BASIC Generated At MCA/PC.

  17. Digital gamma-gamma coincidence HPGe system for environmental analysis

    DEFF Research Database (Denmark)

    Markovic, Nikola; Roos, Per; Nielsen, Sven Poul

    2017-01-01

    The performance of a new gamma-gamma coincidence spectrometer system for environmental samples analysis at the Center for Nuclear Technologies of the Technical University of Denmark (DTU) is reported. Nutech Coincidence Low Energy Germanium Sandwich (NUCLeGeS) system consists of two HPGe detectors...... in a surface laboratory with a digital acquisition system used to collect the data in time-stamped list mode with 10. ns time resolution. The spectrometer is used in both anticoincidence and coincidence modes....

  18. Detection limit calculations for peak evaluation methods in HPGe gamma-ray spectrometry according to ISO 11929

    Science.gov (United States)

    Kanisch, Günter

    2017-05-01

    Two peak area estimation methods in gamma-ray spectrometry, the total peak area (TPA) and the background step function (BSF) methods are re-considered first. For least-squares (LS) peak fitting then, a new net peak area uncertainty model is established. It results in a new function fB replacing a TPA method internal design factor. This allows applying the TPA-related decision threshold (DT) and detection limit (DL) formulae, based on ISO 11929(2010), also for peak fitting. Linear LS adapted to Poisson counting data is suggested to derive fB values for a single peak and different combinations of background shape components including a fitted BSF. fB is then adapted to penalized non-linear fitting including Poisson maximum likelihood estimation by MC simulations. Within the DL iteration the fB method is much faster than with non-linear re-fitting. The fitted peak area uncertainty can be safely modeled for peak areas up to 10 DT which is sufficient for DL calculations. The extension for peak multiplets is indicated.

  19. Precision measurement of radioactivity in gamma-rays spectrometry using two HPGe detectors (BEGe-6530 and GC0818-7600SL models comparison techniques: Application to the soil measurement

    Directory of Open Access Journals (Sweden)

    Guembou Shouop Cebastien Joel

    2017-01-01

    • Proved that the activity concentration determination in gamma spectrometry depended on the energy range emitted by a radionuclide. This study showed that the standard deviation measurement was less important to the result realized with BEGe-6530 HPGe model. Our findings were demonstrated that the results of the Broad Energy Germanium detector were more reliable.

  20. Coincidence gamma-ray spectrometry

    DEFF Research Database (Denmark)

    Markovic, Nikola; Roos, Per; Nielsen, Sven Poul

    2017-01-01

    events are recorded in a list mode file with their timestamp and energy, enabling coincidence identification and spectrum manipulation in post-processing. When coincidence gamma-spectrometry is used for cascade emitting nuclides, coincident signals can be extracted thus significantly reducing......Gamma-ray spectrometry with high-purity germanium (HPGe) detectors is often the technique of choice in an environmental radioactivity laboratory. When measuring environmental samples associated activities are usually low so an important parameter that describes the performance of the spectrometer...... for a nuclide of interest is the minimum detectable activity (MDA). There are many ways for lowering the MDAs in gamma spectrometry. Recently, developments of fast and compact digital acquisition systems have led to growing number of multiple HPGe detector spectrometers. In these applications all detected...

  1. Gamma ray generator

    Science.gov (United States)

    Firestone, Richard B; Reijonen, Jani

    2014-05-27

    An embodiment of a gamma ray generator includes a neutron generator and a moderator. The moderator is coupled to the neutron generator. The moderator includes a neutron capture material. In operation, the neutron generator produces neutrons and the neutron capture material captures at least some of the neutrons to produces gamma rays. An application of the gamma ray generator is as a source of gamma rays for calibration of gamma ray detectors.

  2. [sup 227]Ac: a suggested long-lived multiple-line gamma-ray calibration standard

    Energy Technology Data Exchange (ETDEWEB)

    Aarle, J. van; Esterlund, R.A.; Patzelt, P. (Philipps Univ., Marburg (Germany)); Westmeier, W. (Gesellschaft fuer Kernspektrometrie mbH, Ebsdorfergrund-Moelln (Germany))

    1994-04-01

    X-ray and gamma-ray lines following the decay of [sup 227]Ac in transient equilibrium with its daughters were assayed via high-purity germanium-crystal (HPGe) spectrometry of a chemically purified [sup 227]Ac gamma-ray source. Relative emission probabilities were determined for 120 lines (I[sub [gamma

  3. Gamma-ray bursts

    National Research Council Canada - National Science Library

    Gehrels, Neil; Mészáros, Péter

    2012-01-01

    Gamma-ray bursts (GRBs) are bright flashes of gamma rays coming from the cosmos. They occur roughly once per day, typically last for tens of seconds, and are the most luminous events in the universe...

  4. GRETA: utilizing new concepts in gamma-ray detection

    CERN Document Server

    Deleplanque, M A; Vetter, K; Schmid, G J; Stephens, F S; Clark, R M; Diamond, R M; Fallon, P; Macchiavelli, A O

    1999-01-01

    We present a new concept for gamma-ray detector arrays. An example, called GRETA (Gamma-Ray Energy Tracking Array), consists of highly segmented HPGe detectors covering 4 pi solid angle. The new feature is the ability to track the scattering sequence of incident gamma-rays and in every event, this potentially allows one to measure with high resolution the energy deposited, the location (incident angle) and the time of each gamma-ray that hits the array. GRETA will be of order of 1000 times more powerful than the best present arrays, such as Gammasphere or Euroball, and will provide access to new physics.

  5. Gamma-ray Astronomy

    OpenAIRE

    Pohl, Martin

    2007-01-01

    This paper summarizes recents results in gamma-ray astronomy, most of which were derived with data from ground-based gamma-ray detectors. Many of the contributions presented at this conference involve multiwavelength studies which combine ground-based gamma-ray measurements with optical data or space-based X-ray and gamma-ray measurements. Besides measurements of the diffuse emission from the Galaxy, observations of blazars, gamma-ray bursts, and supernova remnants this paper also covers theo...

  6. Coincidence Techniques in Gamma-ray Spectroscopy

    Science.gov (United States)

    Bikit, Istvan; Mrdja, Dusan; Veskovic, Miroslav; Krmar, Miodrag; Slivka, Jaroslav; Todorovic, Natasa; Bikit, Kristina

    In many different gamma-ray detection systems, the events are registered in coincidence, i.e. within short time interval, by two or more detectors. Depending on purpose of an experiment, these events can be rejected (anticoincidence counting) or acquired (coincidence counting). The construction, setup and application of several coincidence systems in Laboratory for nuclear physics of Department of Physics in Novi sad are presented. The anti-Compton shield for HPGe detector based on big annular NaI(Tl) detector and corresponding measurement which proved existing of 283 keV level in Ba-137 populating by beta decay of Cs-137, is described. The application of this system (in addition with NaI(Tl) plug detector) where HPGe detector is actively shielded by NaI(Tl) detector for investigation of double beta decay of positron emitters (Cr-50, Zn-64,) is also shown. The improving of detection limit of HPGe detector by the active shield consisting of five plastic scintillation detectors is presented, as well as the measurements of cross sections for X-ray production, induced by interaction of cosmic-ray muons with massive lead shield. We found that the prompt and delayed coincidence events between plastic veto detector and Ge detector can be sharply divided in two groups. Also, the bremsstrahlung and annihilation events can be time resolved from (n,n') events, although all these events belong to the group of delayed events.

  7. Gamma-ray triangles

    DEFF Research Database (Denmark)

    Ibarra, Alejandro; Lopez-Gehler, Sergio; Molinaro, Emiliano

    2016-01-01

    We introduce a new type of gamma-ray spectral feature, which we denominate gamma-ray triangle. This spectral feature arises in scenarios where dark matter self-annihilates via a chiral interaction into two Dirac fermions, which subsequently decay in flight into another fermion and a photon....... The resulting photon spectrum resembles a sharp triangle and can be readily searched for in the gamma-ray sky. Using data from the Fermi-LAT and H.E.S.S. instruments, we find no evidence for such a spectral feature and, therefore, set strong upper bounds on the corresponding annihilation cross section....... A concrete realization of a scenario yielding gamma-ray triangles consists of an asymmetric dark matter model where the dark matter particle carries lepton number. We show explicitly that this class of models can lead to intense gamma-ray spectral features, potentially at the reach of upcoming gamma...

  8. Basics of Gamma Ray Detection

    Energy Technology Data Exchange (ETDEWEB)

    Stinnett, Jacob [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Venkataraman, Ram [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-09-13

    The objective of this training is to explain the origin of x-rays and gamma rays, gamma ray interactions with matter, detectors and electronics used in gamma ray-spectrometry, and features of a gamma-ray spectrum for nuclear material that is safeguarded.

  9. Gamma ray optics

    Science.gov (United States)

    Jentschel, M.; Günther, M. M.; Habs, D.; Thirolf, P. G.

    2012-07-01

    Via refractive or diffractive scattering one can shape γ ray beams in terms of beam divergence, spot size and monochromaticity. These concepts might be particular important in combination with future highly brilliant gamma ray sources and might push the sensibility of planned experiments by several orders of magnitude. We will demonstrate the experimental feasibility of gamma ray monochromatization on a ppm level and the creation of a gamma ray beam with nanoradian divergence. The results are obtained using the inpile target position of the High Flux Reactor of the ILL Grenoble and the crystal spectrometer GAMS. Since the refractive index is believed to vanish to zero with 1/E2, the concept of refractive optics has never been considered for gamma rays. The combination of refractive optics with monochromator crystals is proposed to be a promising design. Using the crystal spectrometer GAMS, we have measured for the first time the refractive index at energies in the energy range of 180 - 2000 keV. The results indicate a deviation from simple 1/E2 extrapolation of X-ray results towards higher energies. A first interpretation of these new results will be presented. We will discuss the consequences of these results on the construction of refractive optics such as lenses or refracting prisms for gamma rays and their combination with single crystal monochromators.

  10. Gamma ray camera

    Science.gov (United States)

    Perez-Mendez, Victor

    1997-01-01

    A gamma ray camera for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image of the radiation therefrom. The photosensor array is adapted to record an integrated amount of charge proportional to the incident gamma rays closest to it, and includes a transparent metallic layer, photodiode consisting of a p-i-n structure formed on one side of the transparent metallic layer, and comprising an upper p-type layer, an intermediate layer and a lower n-type layer. In the preferred mode, the scintillator crystal is composed essentially of a cesium iodide (CsI) crystal preferably doped with a predetermined amount impurity, and the p-type upper intermediate layers and said n-type layer are essentially composed of hydrogenated amorphous silicon (a-Si:H). The gamma ray camera further includes a collimator interposed between the radiation source and the sensor array, and a readout circuit formed on one side of the photosensor array.

  11. Gamma Ray Astronomy

    Science.gov (United States)

    Wu, S. T.

    2000-01-01

    The project has progressed successfully during this period of performance. The highlights of the Gamma Ray Astronomy teams efforts are: (1) Support daily BATSE data operations, including receipt, archival and dissemination of data, quick-look science analysis, rapid gamma-ray burst and transient monitoring and response efforts, instrument state-of-health monitoring, and instrument commanding and configuration; (2) On-going scientific analysis, including production and maintenance of gamma-ray burst, pulsed source and occultation source catalogs, gamma-ray burst spectroscopy, studies of the properties of pulsars and black holes, and long-term monitoring of hard x-ray sources; (3) Maintenance and continuous improvement of BATSE instrument response and calibration data bases; (4) Investigation of the use of solid state detectors for eventual application and instrument to perform all sky monitoring of X-Ray and Gamma sources with high sensitivity; and (5) Support of BATSE outreach activities, including seminars, colloquia and World Wide Web pages. The highlights of this efforts can be summarized in the publications and presentation list.

  12. Gamma-spectrometric module based on HPGe detector for radiation portal monitors

    Directory of Open Access Journals (Sweden)

    Kondratjev Vladimir

    2015-01-01

    Full Text Available The appearance of small-sized and powerful enough electric cryocoolers of various types on the market, has opened the perspective of HPGe detectors application, cooled by such coolers, in radiation portal monitors. The first results of a spectrometric module based on HPGe detector with relative efficiency of 45% cooled by a Stirling-cycle cryocooler, are presented. The spectrometer has provided energy resolutions of less than 0.95 keV and 1.95 keV at energies of 122 keV and 1332 keV, respectively. The deterioration of the energy resolution of HPGe detector cooled by electric cryocooler in comparison to the resolution with liquid nitrogen cooling was about 8% at the energy of 1332 keV. With the use of activated filters to suppress pulses produced by the mechanical vibrations, the energy resolution of the spectrometer was 0.8 keV and 1.8 keV, respectively, however, the detector relative efficiency at the energy of 1332 keV has dropped to 39 %.

  13. Study of function response of a detector HPGe to photons of reaction {sup 19}F(p,{alpha}{gamma}){sup 16}O; Estudo da funcao resposta de um detetor HPGe a fotons da reacao {sup 19}F(p,{alpha}{gamma}){sup 16}O

    Energy Technology Data Exchange (ETDEWEB)

    Tridapalli, D.B

    2006-07-01

    In the {sup 19}F(p,{alpha}{gamma}){sup 16}O reaction, characteristic gamma-rays with energies: 6.1 MeV; 6.9 MeV and 7.1 keV can be observed. These photons can be used in many important applications such as Proton Induced Gamma-ray Emission (PIGE), gamma radiography and calibration purposes. It has another advantage in calibration procedures, which is the observed photon flux is greater than other reactions studied, {sup 27}Al(p,{alpha}{gamma}){sup 28}Si and {sup 23}Na(p,{alpha}{gamma}){sup 24}Mg. In our laboratory, we are studying the efficiency and response function of HPGe detectors for high energy photons, and for this it is necessary a source with a level scheme with few gamma-ray transitions and known relative yields. The {sup 19}F(p,{alpha}{gamma}){sup 16}O reaction satisfies the first condition but in the literature we found relative yields for thick targets or reaction cross section for thin targets. However, we use targets of intermediate thickness, therefore in this work we measure the relative gamma-ray yields for protons with energies between 1.36 MeV and 1.42 MeV. The experiments were performed at the 1.7 MV Pelletron tandem accelerator of the Laboratorio de Analise de Materiais por Feixes Ionicos (LAMFI) located at Instituto de Fisica da Universidade de Sao Paulo, using a reverse-electrode closed-end coaxial HPGe detector with 72.5 mm in diameter and 60.5 mm in length, at 0 deg. The proton irradiation current was 50 nA, and the target consisted of 250 {mu}g/cm{sup 2} CaF{sub 2} evaporated on a 0.1 mm Ta backing. In this reaction the {sup 20}Ne resonant state fissions in flight, and the resulting {sup 16}O excited states have different half-lives; all observed peaks are deformed due to either Doppler broadening from {sup 16}O random velocity direction or Doppler shift from nuclei that leave the target toward the vacuum chamber. Moreover, the peak deformations vary with the proton energy. These deformations were modeled by a Monte Carlo simulation that

  14. Gamma-ray bursts.

    Science.gov (United States)

    Gehrels, Neil; Mészáros, Péter

    2012-08-24

    Gamma-ray bursts (GRBs) are bright flashes of gamma rays coming from the cosmos. They occur roughly once per day, typically last for tens of seconds, and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this Review, we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglow.

  15. X-ray fluorescence analysis in environmental radiological surveillance using HPGe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Herrera Peraza, E. [Department of Environmental Radiological Surveillance, Centro de Investigacion en Materiales Avanzados (CIMAV), P.O. Box 31109, Miguel de Cervantes no. 120, Complejo Industrial Chihuahua, Chihuahua (Mexico)]. E-mail: eduardo.herrera@cimav.edu.mx; Renteria Villalobos, M. [Department of Environmental Radiological Surveillance, Centro de Investigacion en Materiales Avanzados (CIMAV), P.O. Box 31109, Miguel de Cervantes no. 120, Complejo Industrial Chihuahua, Chihuahua (Mexico); Montero Cabrera, M.E. [Department of Environmental Radiological Surveillance, Centro de Investigacion en Materiales Avanzados (CIMAV), P.O. Box 31109, Miguel de Cervantes no. 120, Complejo Industrial Chihuahua, Chihuahua (Mexico); Munoz Romero, A. [Department of Environmental Radiological Surveillance, Centro de Investigacion en Materiales Avanzados (CIMAV), P.O. Box 31109, Miguel de Cervantes no. 120, Complejo Industrial Chihuahua, Chihuahua (Mexico)

    2004-10-08

    X-ray fluorescence (XRF) has been proven to be a valuable tool for determining trace quantities of heavy metals, such as uranium and lead, in different types of samples. The present paper demonstrates the applicability of XRF spectrometry to measure the concentrations of these heavy metals in samples from natural ore and soil. The values of uranium concentrations in rock from the Pena Blanca uranium ore, in Chihuahua, Mexico, were calculated for the purpose of precertifying the rock powders samples. The comparison with other techniques, such as inductively coupled plasma atomic emission spectrometry, atomic absorption spectrometry, alpha spectrometry and electron microscopy, was used to complete the precertification process, so that the sample powders may be used as secondary standards. The source-sample-detector geometry and the incident angle are the most important factors for obtaining low detection limits. The selected system uses a {sup 57}Co source of about 0.1 mCi to excite the K X-rays from uranium and lead. X-rays were recorded on a CANBERRA HPGe coaxial detector. The comparative results for two incident angles (90 deg and 180 deg ) performed previously by other authors show that the best geometry is the backscattering geometry. In the present paper, using EGS4 code system with Monte Carlo simulation, it was possible to determine the location and distribution of background produced by the Compton edge in the optimized geometry. This procedure allowed to find the minimum detectable concentration of uranium and lead, which was experimentally calculated using standards. The possibility of performing in vivo measurements rapidly and easily, as well as the factors affecting accuracy and the minimum detectable concentration in several samples are also discussed.

  16. Gamma rays from Galactic Pulsars

    NARCIS (Netherlands)

    Calore, F.; di Mauro, M.; Donato, F.

    2015-01-01

    Gamma rays from young pulsars and milli-second pulsars are expected to contribute to the diuse gamma-ray emission measured by the Fermi Large Area Telescope (LAT) at high latitudes. We derive the contribution of the pulsars undetected counterpart by using information from radio to gamma rays and we

  17. Gamma-ray bursts

    CERN Document Server

    Wijers, Ralph A M J; Woosley, Stan

    2012-01-01

    Cosmic gamma ray bursts (GRBs) have fascinated scientists and the public alike since their discovery in the late 1960s. Their story is told here by some of the scientists who participated in their discovery and, after many decades of false starts, solved the problem of their origin. Fourteen chapters by active researchers in the field present a detailed history of the discovery, a comprehensive theoretical description of GRB central engine and emission models, a discussion of GRB host galaxies and a guide to how GRBs can be used as cosmological tools. Observations are grouped into three sets from the satellites CGRO, BeppoSAX and Swift, and followed by a discussion of multi-wavelength observations. This is the first edited volume on GRB astrophysics that presents a fully comprehensive review of the subject. Utilizing the latest research, Gamma-ray Bursts is an essential desktop companion for graduate students and researchers in astrophysics.

  18. A prototype High Purity Germanium detector for high resolution gamma-ray spectroscopy at high count rates

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, R.J., E-mail: rjcooper@lbl.gov [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Amman, M.; Luke, P.N. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Vetter, K. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Department of Nuclear Engineering, University of California, Berkeley, CA 94720 (United States)

    2015-09-21

    Where energy resolution is paramount, High Purity Germanium (HPGe) detectors continue to provide the optimum solution for gamma-ray detection and spectroscopy. Conventional large-volume HPGe detectors are typically limited to count rates on the order of ten thousand counts per second, however, limiting their effectiveness for high count rate applications. To address this limitation, we have developed a novel prototype HPGe detector designed to be capable of achieving fine energy resolution and high event throughput at count rates in excess of one million counts per second. We report here on the concept, design, and initial performance of the first prototype device.

  19. Applied gamma-ray spectrometry

    CERN Document Server

    Dams, R; Crouthamel, Carl E

    1970-01-01

    Applied Gamma-Ray Spectrometry covers real life application of the gamma-ray and the devices used in their experimental studies. This book is organized into 9 chapters, and starts with discussions of the various decay processes, the possible interaction mechanisms of gamma radiation with matter, and the intrinsic and extrinsic variables, which affect the observed gamma-ray and X-ray spectra. The subsequent chapters deal with the properties and fabrication of scintillation detectors, semiconductor detectors, and proportional gas counters. These chapters present some of the most widely utilized

  20. Precise determination of HPGe detector efficiency for gamma spectrometry measurements of environmental samples with variable geometry and density

    Directory of Open Access Journals (Sweden)

    Barrera Manuel

    2017-03-01

    Full Text Available A methodology to determine the full energy peak efficiency (FEPE for precise gamma spectrometry measurements of environmental samples with high-purity germanium (HPGe detector, valid when this efficiency depends on the energy of the radiation E, the height of the cylindrical sample H, and its density ρ, is introduced. The methodology consists of an initial calibration as a function of E and H and the application of a self-attenuation factor, depending on the density of the sample ρ, in order to correct for the different attenuation of the generic sample in relation to the measured standard. The obtained efficiency can be used in the whole range of interest studied, E = 120–2000 keV, H = 1–5 cm, and ρ = 0.8–1.7 g/cm3, being its uncertainty below 5%. The efficiency has been checked by the measurement of standards, resulting in a good agreement between experimental and expected activities. The described methodology can be extended to similar situations when samples show geometric and compaction differences.

  1. Airborne gamma-ray spectrometry

    DEFF Research Database (Denmark)

    Hovgaard, Jens

    A new method - Noise Adjusted Singular Value Decomposition, NASVD - for processing gamma-ray spectra has been developed as part of a Ph.D. project. By using this technique one is able to decompose a large set of data - for example from airborne gamma-ray surveys - into a few spectral components...

  2. Gamma-ray spectrometry of LDEF samples

    Energy Technology Data Exchange (ETDEWEB)

    Winn, W.G.

    1991-01-01

    A total of 31 samples from the Long Duration Exposure Facility (LDEF), including materials of aluminum, vanadium, and steel trunnions were analyzed by ultra-low-level gamma spectroscopy. The study quantified particle induced activations of (sup 22)Na, {sup 46}Sc, {sup 51}Cr, {sup 54}Mn, {sup 56}Co, {sup 57}Co, {sup 58}Co, and {sup 60}Co. The samples of trunnion sections exhibited increasing activity toward the outer end of the trunnion and decreasing activity toward its radial center. The trunnion sections did not include end pieces, which have been reported to collect noticeable {sup 7}Be on their leading surfaces. No significant {sup 7}Be was detected in the samples analyzed. The Underground Counting Facility at Savannah River Laboratory (SRL) was used in this work. The facility is 50 ft. underground, constructed with low-background shielding materials, and operated as a clean room. The most sensitive analyses were performed with a 90%-efficient HPGe gamma-ray detector, which is enclosed in a purged active/passive shield. Each sample was counted for one to six days in two orientations to yield more representative average activities for the sample. The non-standard geometries of the LDEF samples prompted the development of a novel calibration method, whereby the efficiency about the samples surfaces (measured with point sources) predicted the efficiency for the bulk sample.

  3. Gamma-ray spectrometry of LDEF samples

    Energy Technology Data Exchange (ETDEWEB)

    Winn, W.G.

    1991-12-31

    A total of 31 samples from the Long Duration Exposure Facility (LDEF), including materials of aluminum, vanadium, and steel trunnions were analyzed by ultra-low-level gamma spectroscopy. The study quantified particle induced activations of (sup 22)Na, {sup 46}Sc, {sup 51}Cr, {sup 54}Mn, {sup 56}Co, {sup 57}Co, {sup 58}Co, and {sup 60}Co. The samples of trunnion sections exhibited increasing activity toward the outer end of the trunnion and decreasing activity toward its radial center. The trunnion sections did not include end pieces, which have been reported to collect noticeable {sup 7}Be on their leading surfaces. No significant {sup 7}Be was detected in the samples analyzed. The Underground Counting Facility at Savannah River Laboratory (SRL) was used in this work. The facility is 50 ft. underground, constructed with low-background shielding materials, and operated as a clean room. The most sensitive analyses were performed with a 90%-efficient HPGe gamma-ray detector, which is enclosed in a purged active/passive shield. Each sample was counted for one to six days in two orientations to yield more representative average activities for the sample. The non-standard geometries of the LDEF samples prompted the development of a novel calibration method, whereby the efficiency about the samples surfaces (measured with point sources) predicted the efficiency for the bulk sample.

  4. Accurate efficiency calibration of a low-energy HPGe detector using a monochromatic x-ray source

    Energy Technology Data Exchange (ETDEWEB)

    Plagnard, Johann; Bobin, Christophe; Lepy, Marie-Christine [Commissariat a l' Energie Atomique, Laboratoire National Henri Becquerel, 91191 Gif-sur-Yvette Cedex (France)

    2007-05-15

    HPGe detector efficiency has been calibrated using complementary methods involving radioactive x-ray standards, reference synchrotron flux (Super ACO, LURE, France) and a monochromatic x-ray source (SOLEX), combined with Monte Carlo simulation. In the study described here, SOLEX was used to determine the thickness of detector components that create absorption sites in front of the active zone of the detector, by energy scanning in the vicinity of their K and L binding energies. The layers of aluminium (infrared shielding), nickel (electrical contact) and germanium (dead layer) have been measured. This approach ensures accurate determination of the thickness of each component and enables the detector efficiency calculation by Monte Carlo simulation. Differences between simulated data and experimental efficiency values are about 1-5% at energies above 1400 eV and reach 20% at lower energies. (authors)

  5. Experimental and simulated efficiency of a HPGe detector with point-like and extended sources

    CERN Document Server

    Karamanis, D; Andriamonje, Samuel A; Barreau, G; Petit, M

    2002-01-01

    The absolute efficiency of a high purity germanium (HPGe) detector was determined with a point-like calibrated sup 1 sup 5 sup 2 Eu source at two distances from the detector and three pure metallic thorium foils of different thicknesses. The experimental values are compared with the ones determined with the simulation codes MCNP4B and GEANT 3.21. A procedure for HPGe absolute efficiency calibration is proposed for gamma-ray energies higher than 200 keV.

  6. About cosmic gamma ray lines

    Science.gov (United States)

    Diehl, Roland

    2017-06-01

    Gamma ray lines from cosmic sources convey the action of nuclear reactions in cosmic sites and their impacts on astrophysical objects. Gamma rays at characteristic energies result from nuclear transitions following radioactive decays or high-energy collisions with excitation of nuclei. The gamma-ray line from the annihilation of positrons at 511 keV falls into the same energy window, although of different origin. We present here the concepts of cosmic gamma ray spectrometry and the corresponding instruments and missions, followed by a discussion of recent results and the challenges and open issues for the future. Among the lessons learned are the diffuse radioactive afterglow of massive-star nucleosynthesis in 26Al and 60Fe gamma rays, which is now being exploited towards the cycle of matter driven by massive stars and their supernovae; large interstellar cavities and superbubbles have been recognised to be of key importance here. Also, constraints on the complex processes making stars explode as either thermonuclear or core-collapse supernovae are being illuminated by gamma-ray lines, in this case from shortlived radioactivities from 56Ni and 44Ti decays. In particular, the three-dimensionality and asphericities that have recently been recognised as important are enlightened in different ways through such gamma-ray line spectroscopy. Finally, the distribution of positron annihilation gamma ray emission with its puzzling bulge-dominated intensity disctribution is measured through spatially-resolved spectra, which indicate that annihilation conditions may differ in different parts of our Galaxy. But it is now understood that a variety of sources may feed positrons into the interstellar medium, and their characteristics largely get lost during slowing down and propagation of positrons before annihilation; a recent microquasar flare was caught as an opportunity to see positrons annihilate at a source.

  7. Directional detector of gamma rays

    Science.gov (United States)

    Cox, Samson A.; Levert, Francis E.

    1979-01-01

    A directional detector of gamma rays comprises a strip of an electrical cuctor of high atomic number backed with a strip of a second electrical conductor of low atomic number. These elements are enclosed within an electrical conductor that establishes an electrical ground, maintains a vacuum enclosure and screens out low-energy gamma rays. The detector exhibits a directional sensitivity marked by an increased output in the favored direction by a factor of ten over the output in the unfavored direction.

  8. Gamma-ray mirror technology for NDA of spent fuel

    Energy Technology Data Exchange (ETDEWEB)

    Descalle, M. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ruz-Armendariz, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Decker, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Alameda, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Brejnholt, N. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Soufli, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Robinson, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dreyer, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pivovaroff, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ziock, K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chichester, D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Watson, S. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Trellue, H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-09-28

    Direct measurements of gamma rays emitted by fissile material have been proposed as an alternative to measurements of the gamma rays from fission products. From a safeguards applications perspective, direct detection of uranium (U) and plutonium (Pu) K-shell fluorescence emission lines and specific lines from some of their isotopes could lead to improved shipper-receiver difference or input accountability at the start of Pu reprocessing. However, these measurements are difficult to implement when the spent fuel is in the line-of-sight of the detector, as the detector is exposed to high rates dominated by fission product emissions. To overcome the combination of high rates and high background, grazing incidence multilayer mirrors have been proposed as a solution to selectively reflect U and Pu hard X-ray and soft gamma rays in the 90 to 420 keV energy into a high-purity germanium (HPGe) detector shielded from the direct line-of-sight of spent fuel. Several groups demonstrated that K-shell fluorescence lines of U and Pu in spent fuel could be detected with Ge detectors. In the field of hard X-ray optics the performance of reflective multilayer coated reflective optics was demonstrated up to 645 keV at the European Synchrotron Radiation Facility. Initial measurements conducted at Oak Ridge National Laboratory with sealed sources and scoping experiments conducted at the ORNL Irradiated Fuels Examination Laboratory (IFEL) with spent nuclear fuel further demonstrated the pass-band properties of multilayer mirrors for reflecting specific emission lines into 1D and 2D HPGe detectors, respectively.

  9. Pulse shape comparison procedure to characterise position sensitive HPGe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Goel, Namita; Pardo, Cesar Domingo; Engert, Tobias; Gerl, Juergen; Kojouharov, Ivan; Schaffner, Henning [GSI Helmholtzzentrum fuer Schwerionenforschung mbH, Darmstadt (Germany)

    2009-07-01

    A new tool to experimentally characterize 3D position sensitive HPGe detector based on pulse shape comparison procedure is proposed and implemented. It is a novel technique for measuring the HPGe detector pulse shapes as a function of the {gamma}-ray interaction position inside the detector volume. The system also utilizes the principles of positron emission tomography to speed up the scanning time. An application of the Na-22 source emitting pairs of 511 keV gammas in back to back directions allows creating a ''collimator-free'' scanner, where pulse shapes for many lines across the detector or even the whole detector can be registered simultaneously. A position sensitive {gamma}-ray scintillator detector (PSD) oriented towards the source is used for registration of 511 keV gammas in coincidence with the HPGe detector. This PSD is based on a crossed-wire anode position sensitive photomultiplier tube (PSPMT).The main difference with respect to similar existing devices is the individual multianode readout (IMAR) approach. The method allows to exploit better the intrinsic characteristics of the PSPMT, thus yielding better position linearity, improved spatial resolution of about 1 mm(FWHM). This position sensitive {gamma}-ray scintillator detector fulfills the requirements for its implementation in our scanning system.

  10. A transportable source of gamma rays with discrete energies and wide range for calibration and on-site testing of gamma-ray detectors

    Energy Technology Data Exchange (ETDEWEB)

    Granja, Carlos, E-mail: carlos.granja@utef.cvut.cz [Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, 12800 Prague 2 (Czech Republic); Slavicek, Tomas; Kroupa, Martin [Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, 12800 Prague 2 (Czech Republic); Owens, Alan [European Space Technology Centre ESTEC, European Space Agency ESA, Keplerlaan 1, 2200AG Noordwijk (Netherlands); Pospisil, Stanislav; Janout, Zdenek [Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, 12800 Prague 2 (Czech Republic); Kralik, Miloslav; Solc, Jaroslav [Czech Metrology Institute, Radiova 3, 102 00 Prague 10 (Czech Republic); Valach, Ondrej [Institute of Experimental and Applied Physics, Czech Technical University in Prague, Horska 3a/22, 12800 Prague 2 (Czech Republic)

    2015-01-21

    We describe a compact and transportable wide energy range, gamma-ray station for the calibration of gamma-ray sensitive devices. The station was specifically designed for the on-site testing and calibration of gamma-ray sensitive spacecraft payloads, intended for space flight on the BepiColombo and SoIar Orbiter missions of the European Space Agency. The source is intended to serve as a calibrated reference for post test center qualification of integrated payload instruments and for preflight evaluation of scientific radiation sensors. Discrete gamma rays in the energy range 100 keV–9 MeV are produced in the station with reasonable intensity using a radionuclide neutron source and 100 l of distilled water with 22 kg salt dissolved. The gamma-rays generated contain many discrete lines conveniently evenly distributed over the entire energy range. The neutron and gamma-ray fields have been simulated by Monte Carlo calculations. Results of the numerical calculations are given in the form of neutron and gamma-ray spectra as well as dose equivalent rate. The dose rate was also determined directly by dedicated dosemetric measurements. The gamma-ray field produced in the station was characterized using a conventional HPGe detector. The application of the station is demonstrated by measurements taken with a flight-qualified LaBr{sub 3}:Ce scintillation detector. Gamma-ray spectra acquired by both detectors are presented. The minimum measuring times for calibration of the flight-version detector, was between 2 and 10 min (up to 6.2 MeV) and 20–30 min (up to 8 MeV), when the detector was placed at a distance 2–5 m from the station. - Highlights: • Transportable station of mono-energetic gamma rays has been built. • Produced neutron and gamma ray field simulated by Monte Carlo calculations. • Discrete gamma rays produced in wide energy range up to 9 MeV. • Produced gamma ray spectra measured by HPGe and scintillating LaBr{sub 3}Ce detectors. • Demonstration of

  11. Extragalactic Gamma-Ray Astrophysics

    CERN Multimedia

    CERN. Geneva

    2016-01-01

    During the last decades, various classes of radio-loud active galactic nuclei have been established as sources of high-energy radiation extending over a very broad range from soft gamma-rays (photon energies E~MeV) up to very-high-energy gamma-rays (E>100 GeV). These include blazars of different types, as well as young and evolved radio galaxies. The observed gamma-ray emission from such implies efficient particle acceleration processes taking place in highly magnetized and relativistic jets produced by supermassive black holes, processes that have yet to be identified and properly understood. In addition, nearby starforming and starburst galaxies, some of which host radio-quiet Seyfert-type nuclei, have been detected in the gamma-ray range as well. In their cases, the observed gamma-ray emission is due to non-thermal activity in the interstellar medium, possibly including also a contribution from accretion disks and nuclear outflows. Finally, the high-energy emission from clusters of galaxies remains elusive...

  12. Hybrid X-ray and {gamma}-ray spectrometer for in-situ planetary science missions

    Energy Technology Data Exchange (ETDEWEB)

    Skidmore, M.S. [Space Research Centre, Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)], E-mail: mss16@star.le.ac.uk; Ambrosi, R.M. [Space Research Centre, Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Simon, H. [Eurorad, 2, rue Ettore Bugatti, 67201 Eckbolsheim (France)

    2009-06-11

    {gamma}-Ray spectroscopy, X-ray spectroscopy and {gamma}-ray backscatter densitometry for planetary science applications are three complementary analytical techniques that can be used to determine surface and sub-surface composition, constrain heat flow through a planetary regolith and hence understand more about the processes that formed planetary bodies. Evaluating different detector types and configurations in order to achieve these scientific objectives is a key enabling step for a successful flight instrument development programme. In this study, we evaluate and compare different detector solutions and configurations including: planar and hemispherical CdTe, a CsI(Tl) scintillator, a LaBr{sub 3}(Ce) scintillator and a HPGe detector. The LaBr{sub 3}(Ce) detector was chosen as the most suitable detector for an in-situ planetary science mission due to its high-radiation tolerance, low mass compared with HPGe detector systems, its comparable resolution ({approx}3.4% at 662 keV) to compound semiconductors (planar CdTe {approx}2.4% at 662 keV) and high efficiency.

  13. The Gamma-ray Sky with Fermi

    Science.gov (United States)

    Thompson, David

    2012-01-01

    Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

  14. Short duration gamma ray bursts

    Indian Academy of Sciences (India)

    Abstract. After a short review of gamma ray bursts (GRBs), we discuss the physical implications of strong statistical correlations seen among some of the parameters of short duration bursts (90 < 2 s). Finally, we conclude with a brief sketch of a new unified model for long and short GRBs.

  15. Short duration gamma ray bursts

    Indian Academy of Sciences (India)

    Gamma ray bursts (GRBs) are transient extragalactic events appearing randomly in the sky as localized flashes of electromagnetic radiation, consisting predominantly of photons with energy in the range of ~0.1–1 MeV. These sporadic bursts, occurring at the rate of ~600 per year, are isotropically distributed in the sky, ...

  16. Practical gamma-ray spectrometry

    National Research Council Canada - National Science Library

    Gilmore, G.R

    2008-01-01

    ... of Photons 1.7.1 Annihilation radiation 1.7.2 Bremsstrahlung 1.7.3 Prompt gammas 1.7.4 X-rays 1.8 The Mathematics of Decay and Growth of Radioactivity 1.8.1 The decay equation 1.8.2 Growth of activity in reac...

  17. Efficiency calibration of an HPGe X-ray detector for quantitative PIXE analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mulware, Stephen J., E-mail: Stephenmulware@my.unt.edu; Baxley, Jacob D., E-mail: jacob.baxley351@topper.wku.edu; Rout, Bibhudutta, E-mail: bibhu@unt.edu; Reinert, Tilo, E-mail: tilo@unt.edu

    2014-08-01

    Particle Induced X-ray Emission (PIXE) is an analytical technique, which provides reliably and accurately quantitative results without the need of standards when the efficiency of the X-ray detection system is calibrated. The ion beam microprobe of the Ion Beam Modification and Analysis Laboratory at the University of North Texas is equipped with a 100 mm{sup 2} high purity germanium X-ray detector (Canberra GUL0110 Ultra-LEGe). In order to calibrate the efficiency of the detector for standard less PIXE analysis we have measured the X-ray yield of a set of commercially available X-ray fluorescence standards. The set contained elements from low atomic number Z = 11 (sodium) to higher atomic numbers to cover the X-ray energy region from 1.25 keV to about 20 keV where the detector is most efficient. The effective charge was obtained from the proton backscattering yield of a calibrated particle detector.

  18. Portable compton gamma-ray detection system

    Science.gov (United States)

    Rowland, Mark S [Alamo, CA; Oldaker, Mark E [Pleasanton, CA

    2008-03-04

    A Compton scattered gamma-ray detector system. The system comprises a gamma-ray spectrometer and an annular array of individual scintillators. The scintillators are positioned so that they are arrayed around the gamma-ray spectrometer. The annular array of individual scintillators includes a first scintillator. A radiation shield is positioned around the first scintillator. A multi-channel analyzer is operatively connected to the gamma-ray spectrometer and the annular array of individual scintillators.

  19. Selective Beta and Gamma-ray Discrimination by CdWO{sub 4} and PlasticScintillator

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Jun Woo; Kim, Hee Reyoung [Dept. of Nuclear Engineering, Ulsan National Institute of Science and Technology, Ulsan (Korea, Republic of)

    2017-04-15

    Radiation monitoring technique has been used for monitoring of decommissioning site of nuclear facility, radioactive waste disposal site, or in case of radioactivity accident. For rapid measurement of gamma-ray and beta-ray, many portable radiation detectors were developed but they are sensitive to specific radiation type. For example, portable detectors using NaI(Tl) or high purity germanium (HPGe) are suitable to detect gamma-ray. Otherwise, Geiger-müller (GM) tube or ionization chamber are suitable to detect all-types of radiation but it is hard to determine which particle is detected in the detector. In this reason, phoswich detectors for discrimination of beta-ray and gamma-ray were developed by using pulse shape discrimination. In this study, another approach to discriminate the beta-ray and gamma-ray is carried out. Two scintillators are used, cadmium tungstate (CdWO{sub 4}) and plastic scintillator. They have huge difference in their effective atomic number and mass density, thus they have huge difference in their gamma-ray sensitivity while the sensitivity of beta-ray is similar. The characterization of beta-ray and gamma-ray discrimination by using this characteristics is include. A technique of discrimination between beta-ray and gamma-ray was suggested. The method was verified by Monte Carlo simulation and experiment. This work showed feasibility on in field measurement of radiation with discrimination of beta-ray and gamma-ray.

  20. A method to estimate a contribution of Ge(n,n′) reaction to the low-energy part of gamma spectra of HPGe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Krmar, M., E-mail: krmar@df.uns.ac.rs [University of Novi Sad, Faculty of Science, Department of Physics, Trg Dositeja Obradovića 4, Novi Sad (Serbia); Hansman, J.; Jovančević, N.; Lalović, N.; Slivka, J. [University of Novi Sad, Faculty of Science, Department of Physics, Trg Dositeja Obradovića 4, Novi Sad (Serbia); Joković, D.; Maletić, D. [Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade (Serbia)

    2013-05-01

    Long-time background spectra of a well-shielded HPGe detector are recorded in order to estimate the contribution of inelastic neutron scattering on Ge nuclei in the low-energy part of the spectra, mainly influenced by elastic neutron collisions. It is shown that using intensities of several asymmetric peaks characteristic of Ge(n,n′) reactions and some properties of detectors (ability for total absorption or total transmission of gamma photons emitted during de-excitation of Ge nuclei) the contribution of Ge(n,n′) reactions to the low-energy part of spectra can be evaluated. The obtained result is in good agreement with results of simulations available in the literature.

  1. A transportable source of gamma rays with discrete energies and wide range for calibration and on-site testing of gamma-ray detectors

    Science.gov (United States)

    Granja, Carlos; Slavicek, Tomas; Kroupa, Martin; Owens, Alan; Pospisil, Stanislav; Janout, Zdenek; Kralik, Miloslav; Solc, Jaroslav; Valach, Ondrej

    2015-01-01

    We describe a compact and transportable wide energy range, gamma-ray station for the calibration of gamma-ray sensitive devices. The station was specifically designed for the on-site testing and calibration of gamma-ray sensitive spacecraft payloads, intended for space flight on the BepiColombo and SoIar Orbiter missions of the European Space Agency. The source is intended to serve as a calibrated reference for post test center qualification of integrated payload instruments and for preflight evaluation of scientific radiation sensors. Discrete gamma rays in the energy range 100 keV-9 MeV are produced in the station with reasonable intensity using a radionuclide neutron source and 100 l of distilled water with 22 kg salt dissolved. The gamma-rays generated contain many discrete lines conveniently evenly distributed over the entire energy range. The neutron and gamma-ray fields have been simulated by Monte Carlo calculations. Results of the numerical calculations are given in the form of neutron and gamma-ray spectra as well as dose equivalent rate. The dose rate was also determined directly by dedicated dosemetric measurements. The gamma-ray field produced in the station was characterized using a conventional HPGe detector. The application of the station is demonstrated by measurements taken with a flight-qualified LaBr3:Ce scintillation detector. Gamma-ray spectra acquired by both detectors are presented. The minimum measuring times for calibration of the flight-version detector, was between 2 and 10 min (up to 6.2 MeV) and 20-30 min (up to 8 MeV), when the detector was placed at a distance 2-5 m from the station.

  2. Gamma-Ray Line Astronomy

    OpenAIRE

    Diehl, Roland

    2004-01-01

    Gamma-ray lines from radioactive isotopes, ejected into interstellar space by cosmic nucleosynthesis events, are observed with new space telescopes. The Compton Observatory had provided a sky survey for the isotopes 56Co, 22Na, 44Ti, and 26Al, detecting supernova radioactivity and the diffuse glow of long-lived radioactivity from massive stars in the Galaxy. High-resolution spectroscopy is now being exploited with Ge detectors: Since 2002, with ESA's INTEGRAL satellite and the RHESSI solar im...

  3. Scene data fusion: Real-time standoff volumetric gamma-ray imaging

    Energy Technology Data Exchange (ETDEWEB)

    Barnowski, Ross [Department of Nuclear Engineering, UC Berkeley, 4155 Etcheverry Hall, MC 1730, Berkeley, CA 94720, United States of America (United States); Haefner, Andrew; Mihailescu, Lucian [Lawrence Berkeley National Lab - Applied Nuclear Physics, 1 Cyclotron Road, Berkeley, CA 94720, United States of America (United States); Vetter, Kai [Department of Nuclear Engineering, UC Berkeley, 4155 Etcheverry Hall, MC 1730, Berkeley, CA 94720, United States of America (United States); Lawrence Berkeley National Lab - Applied Nuclear Physics, 1 Cyclotron Road, Berkeley, CA 94720, United States of America (United States)

    2015-11-11

    An approach to gamma-ray imaging has been developed that enables near real-time volumetric (3D) imaging of unknown environments thus improving the utility of gamma-ray imaging for source-search and radiation mapping applications. The approach, herein dubbed scene data fusion (SDF), is based on integrating mobile radiation imagers with real-time tracking and scene reconstruction algorithms to enable a mobile mode of operation and 3D localization of gamma-ray sources. A 3D model of the scene, provided in real-time by a simultaneous localization and mapping (SLAM) algorithm, is incorporated into the image reconstruction reducing the reconstruction time and improving imaging performance. The SDF concept is demonstrated in this work with a Microsoft Kinect RGB-D sensor, a real-time SLAM solver, and a cart-based Compton imaging platform comprised of two 3D position-sensitive high purity germanium (HPGe) detectors. An iterative algorithm based on Compton kinematics is used to reconstruct the gamma-ray source distribution in all three spatial dimensions. SDF advances the real-world applicability of gamma-ray imaging for many search, mapping, and verification scenarios by improving the tractiblity of the gamma-ray image reconstruction and providing context for the 3D localization of gamma-ray sources within the environment in real-time.

  4. Scene data fusion: Real-time standoff volumetric gamma-ray imaging

    Science.gov (United States)

    Barnowski, Ross; Haefner, Andrew; Mihailescu, Lucian; Vetter, Kai

    2015-11-01

    An approach to gamma-ray imaging has been developed that enables near real-time volumetric (3D) imaging of unknown environments thus improving the utility of gamma-ray imaging for source-search and radiation mapping applications. The approach, herein dubbed scene data fusion (SDF), is based on integrating mobile radiation imagers with real-time tracking and scene reconstruction algorithms to enable a mobile mode of operation and 3D localization of gamma-ray sources. A 3D model of the scene, provided in real-time by a simultaneous localization and mapping (SLAM) algorithm, is incorporated into the image reconstruction reducing the reconstruction time and improving imaging performance. The SDF concept is demonstrated in this work with a Microsoft Kinect RGB-D sensor, a real-time SLAM solver, and a cart-based Compton imaging platform comprised of two 3D position-sensitive high purity germanium (HPGe) detectors. An iterative algorithm based on Compton kinematics is used to reconstruct the gamma-ray source distribution in all three spatial dimensions. SDF advances the real-world applicability of gamma-ray imaging for many search, mapping, and verification scenarios by improving the tractiblity of the gamma-ray image reconstruction and providing context for the 3D localization of gamma-ray sources within the environment in real-time.

  5. The measurement of gamma-emitting radionuclides in beach sand cores of coastal regions of Ramsar, Iran using HPGe detectors.

    Science.gov (United States)

    Tari, Marziyeh; Moussavi Zarandi, Sayyed Ali; Mohammadi, Kheirollah; Zare, Mohammad Reza

    2013-09-15

    Radionuclides which present in different beach sands are sources of external exposure that contribute to the total radiation exposure of human. (226)Ra, (235)U, (232)Th, (40)K and (137)Cs analysis has been carried out in sand samples collected at six depth levels, from eight locations of the northern coast of Iran, Ramsar, using high-resolution gamma-ray spectroscopy. The average Specific activities of natural radionuclides viz., (226)Ra, (235)U, (232)Th, (40)K and (137)Cs, in the 0-36 cm depth sand were found as: 19.2±0.04, 2.67±0.17, 17.9±0.06, 337.5±0.61 and 3.35±0.12 Bq kg(-1), respectively. The effects of organic matter content and pH value of sand samples on the natural radionuclide levels were also investigated. Finally, the measured radionuclide concentrations in the Ramsar beach were compared with the world average values, as reported by UNSCEAR (2000). None of the studied beaches were considered as a radiological risk. Copyright © 2013 Elsevier Ltd. All rights reserved.

  6. Gamma-Ray Interactions for Reachback Analysts

    Energy Technology Data Exchange (ETDEWEB)

    Karpius, Peter Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Myers, Steven Charles [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-02

    This presentation is a part of the DHS LSS spectroscopy training course and presents an overview of the following concepts: identification and measurement of gamma rays; use of gamma counts and energies in research. Understanding the basic physics of how gamma rays interact with matter can clarify how certain features in a spectrum were produced.

  7. Gamma-Ray Astronomy Technology Needs

    Science.gov (United States)

    Gehrels, N.; Cannizzo, J. K.

    2012-01-01

    In recent decades gamma-ray observations have become a valuable tool for studying the universe. Progress made in diverse 8re1lS such as gamma-ray bursts (GRBs), nucleosynthesis, and active galactic nuclei (AGNs) has complimented and enriched our astrophysical understanding in many ways. We present an overview of current and future planned space y-ray missions and discussion technology needs for- the next generation of space gamma-ray instruments.

  8. X-Ray and Gamma-Ray Radiation Detector

    DEFF Research Database (Denmark)

    2015-01-01

    Disclosed is a semiconductor radiation detector for detecting X-ray and / or gamma-ray radiation. The detector comprises a converter element for converting incident X-ray and gamma-ray photons into electron-hole pairs, at least one cathode, a plurality of detector electrodes arranged with a pitch...

  9. Gravitational microlensing of gamma-ray blazars

    DEFF Research Database (Denmark)

    F. Torres, Diego; E. Romero, Gustavo; F. Eiroa, Ernesto

    2003-01-01

    We present a detailed study of the effects of gravitational microlensing on compact and distant $\\gamma$-ray blazars. These objects have $\\gamma$-ray emitting regions which are small enough as to be affected by microlensing effects produced by stars lying in intermediate galaxies. We analyze...... the temporal evolution of the gamma-ray magnification for sources moving in a caustic pattern field, where the combined effects of thousands of stars are taken into account using a numerical technique. We propose that some of the unidentified $\\gamma$-ray sources (particularly some of those lying at high...... galactic latitude whose gamma-ray statistical properties are very similar to detected $\\gamma$-ray blazars) are indeed the result of gravitational lensing magnification of background undetected Active Galactic Nuclei (AGNs)....

  10. Understanding Doppler Broadening of Gamma Rays

    Energy Technology Data Exchange (ETDEWEB)

    Rawool-Sullivan, Mohini [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Sullivan, John P. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-07-03

    Doppler-broadened gamma ray peaks are observed routinely in the collection and analysis of gamma-ray spectra. If not recognized and understood, the appearance of Doppler broadening can complicate the interpretation of a spectrum and the correct identification of the gamma ray-emitting material. We have conducted a study using a simulation code to demonstrate how Doppler broadening arises and provide a real-world example in which Doppler broadening is found. This report describes that study and its results.

  11. Observations of Gamma-Ray Bursts

    Science.gov (United States)

    Fishman, Gerald J.

    1999-01-01

    Gamma-ray bursts are now generally believed to originate from cosmological distances and represent the largest known explosions in the Universe. These lectures will describe the temporal and spectral characteristic of gamma-ray bursts, their intensity and sky distribution, and other observed characteristics in the gamma-ray region, primarily from data obtained with the BATSE experiment on the Compton Observatory. A summary of recent discoveries and observations in other wavelength regions will also be presented, along with their implications for models of the burst emission mechanism. Various possibilities and models for the energy source(s) of gamma-ray bursts will be described.

  12. Determination of photon emission probabilities for the main gamma-rays of ²²³Ra in equilibrium with its progeny.

    Science.gov (United States)

    Pibida, L; Zimmerman, B; Fitzgerald, R; King, L; Cessna, J T; Bergeron, D E

    2015-07-01

    The currently published (223)Ra gamma-ray emission probabilities display a wide variation in the values depending on the source of the data. The National Institute of Standards and Technology performed activity measurements on a (223)Ra solution that was used to prepare several sources that were used to determine the photon emission probabilities for the main gamma-rays of (223)Ra in equilibrium with its progeny. Several high purity germanium (HPGe) detectors were used to perform the gamma-ray spectrometry measurements. Published by Elsevier Ltd.

  13. Characterization of HPGe gamma spectrometric detectors systems for Instrumental Neutron Activation Analysis (INAA) at the Colombian Geological Survey

    Energy Technology Data Exchange (ETDEWEB)

    Sierra, O., E-mail: osierra@sgc.gov.co; Parrado, G., E-mail: gparrado@sgc.gov.co; Cañón, Y.; Porras, A.; Alonso, D.; Herrera, D. C.; Peña, M., E-mail: mlpena@sgc.gov.co; Orozco, J. [Colombian Geological Survey, Nuclear Affairs Technical Division, Neutron Activation Analysis Laboratory, Bogota D. C. (Colombia)

    2016-07-07

    This paper presents the progress made by the Neutron Activation Analysis (NAA) laboratory at the Colombian Geological Survey (SGC in its Spanish acronym), towards the characterization of its gamma spectrometric systems for Instrumental Neutron Activation Analysis (INAA), with the aim of introducing corrections to the measurements by variations in sample geometry. Characterization includes the empirical determination of the interaction point of gamma radiation inside the Germanium crystal, through the application of a linear model and the use of a fast Monte Carlo N-Particle (MCNP) software to estimate correction factors for differences in counting efficiency that arise from variations in sample density between samples and standards.

  14. Gamma rays from hidden millisecond pulsars

    Science.gov (United States)

    Tavani, Marco

    1992-01-01

    The properties were studied of a new class of gamma ray sources consisting of millisecond pulsars totally or partially surrounded by evaporating material from irradiated companion stars. Hidden millisecond pulsars offer a unique possibility to study gamma ray, optical and radio emission from vaporizing binaries. The relevance of this class of binaries for GRO observations and interpretation of COS-B data is emphasized.

  15. Gamma rays from 'hidden' millisecond pulsars

    Science.gov (United States)

    Tavani, M.

    1993-01-01

    The properties were studied of a new class of gamma ray sources consisting of millisecond pulsars totally or partially surrounded by evaporating material from irradiated companion stars. Hidden millisecond pulsars offer a unique possibility to study gamma ray, optical and radio emission from vaporizing binaries. The relevance of this class of binaries for GRO observations and interpretation of COS-B data is emphasized.

  16. Handbook on Mobile Gamma-ray Spectrometry

    DEFF Research Database (Denmark)

    Aage, Helle Karina; Korsbech, Uffe C C

    2003-01-01

    Basic physics and mathematics for Airborne and Car-borne Gamma-ray Spectrometry supplemented with practical examples and methods for advanced data processing......Basic physics and mathematics for Airborne and Car-borne Gamma-ray Spectrometry supplemented with practical examples and methods for advanced data processing...

  17. Prompt gamma-ray activation analysis (PGAA)

    Energy Technology Data Exchange (ETDEWEB)

    Kern, J. [Fribourg Univ. (Switzerland). Inst. de Physique

    1996-11-01

    The paper deals with a brief description of the principles of prompt gamma-ray activation analysis (PGAA), with the detection of gamma-rays, the PGAA project at SINQ and with the expected performances. 8 figs., 3 tabs., 10 refs.

  18. Low-level gamma-ray spectrometry for the determination of 210Pb

    DEFF Research Database (Denmark)

    Markovic, Nikola; Roos, Per; Nielsen, Sven Poul

    2017-01-01

    A well High purity germanium (HPGe) gamma spectrometer with NaI(Tl) Compton anticoincidence shield recently installed at DTU Nutech and specially designed for low-level measurements was used for the 210Pb determination in environmental samples. The system is compared to standard stand-alone HPGe...

  19. Highly accurate determination of relative gamma-ray detection efficiency for Ge detector and its application

    Energy Technology Data Exchange (ETDEWEB)

    Miyahara, H.; Mori, C. [Nagoya Univeristy, Nagoya (Japan). Department of Nuclear Engineering; Ludington, M. [Albion College, Albion, Michigan (United States); Fleming, R.F.; Dewaraja, Y.K. [University of Michigan, An Arbor, Michigan (United States). Phoenix Memorial Laboratory

    1997-10-01

    When quantitative measurements of {gamma}-rays using High-Purity Ge (HPGe) detectors are made for a variety of applications, accurate knowledge of oy-ray detection efficiency is required. The emission rates of {gamma}-rays from sources can be determined quickly in the case that the absolute peak efficiency is calibrated. On the other hand, the relative peak efficiencies can be used for determination of intensity ratios for plural samples and for comparison to the standard source. Thus, both absolute and relative detection efficiencies are important in use of {gamma}-ray detector. The objective of this work is to determine the relative gamma-ray peak detection efficiency for an HPGe detector with the uncertainty approaching 0.1% . We used some nuclides which emit at least two gamma-rays with energies from 700 to 2400 keV for which the relative emission probabilities are known with uncertainties much smaller than 0.1%. The relative peak detection efficiencies were calculated from the measurements of the nuclides, {sup 46}Sc, {sup 48}Sc, {sup 60}Co and {sup 94}Nb, emitting two {gamma}- rays with the emission probabilities of almost unity. It is important that various corrections for the emission probabilities, the cascade summing effect, and the self-absorption are small. A third order polynomial function on both logarithmic scales of energy and efficiency was fitted to the data, and the peak efficiency predicted at certain energy from covariance matrix showed the uncertainty less than 0.5% except for near 700 keV. As an application, the emission probabilities of the 1037.5 and 1212.9 keV {gamma}-rays for {sup 48}Sc were determined using the function of the highly precise relative peak efficiency. Those were 0.9777+0,.00079 and 0.02345+0.00017 for the 1037.5 and 1212.9 keV {gamma}-rays, respectively. The sum of these probabilities is close to unity within the uncertainty which means that the certainties of the results are high and the accuracy has been improved

  20. Thermal neutron capture gamma-rays

    Energy Technology Data Exchange (ETDEWEB)

    Tuli, J.K.

    1983-01-01

    The energy and intensity of gamma rays as seen in thermal neutron capture are presented. Only those (n,..cap alpha..), E = thermal, reactions for which the residual nucleus mass number is greater than or equal to 45 are included. These correspond to evaluations published in Nuclear Data Sheets. The publication source data are contained in the Evaluated Nuclear Structure Data File (ENSDF). The data presented here do not involve any additional evaluation. Appendix I lists all the residual nuclides for which the data are included here. Appendix II gives a cumulated index to A-chain evaluations including the year of publication. The capture gamma ray data are given in two tables - the Table 1 is the list of all gamma rays seen in (n,..gamma..) reaction given in the order of increasing energy; the Table II lists the gamma rays according to the nuclide.

  1. Characterization of uranium bearing material using x-ray fluorescence and direct gamma-rays measurement techniques

    Energy Technology Data Exchange (ETDEWEB)

    Mujaini, M., E-mail: madihah@uniten.edu.my; Chankow, N. [Faculty of Engineering, Chulalongkorn University Phyathai Rd., Wang Mai, Patumwan, Bangkok 10330 (Thailand); Yusoff, M. Z.; Hamid, N. A. [College of Engineering, Universiti Tenaga Nasional 43000 Kajang, Selangor (Malaysia)

    2016-01-22

    Uranium ore can be easily detected due to various gamma-ray energies emitted from uranium daughters particularly from {sup 238}U daughters such as {sup 214}Bi, {sup 214}Pb and {sup 226}Ra. After uranium is extracted from uranium ore, only low energy gamma-rays emitted from {sup 235}U may be detected if the detector is placed in close contact to the specimen. In this research, identification and characterization of uranium bearing materials is experimentally investigated using direct measurement of gamma-rays from {sup 235}U in combination with the x-ray fluorescence (XRF) technique. Measurement of gamma-rays can be conducted by using high purity germanium (HPGe) detector or cadmium telluride (CdTe) detector while a {sup 57}Coradioisotope-excited XRF spectrometer using CdTe detector is used for elemental analysis. The proposed technique was tested with various uranium bearing specimens containing natural, depleted and enriched uranium in both metallic and powder forms.

  2. X-raying a nearby gamma-ray millisecond pulsar

    Science.gov (United States)

    Pavlov, George

    2013-10-01

    We propose an exploratory EPIC observation of a nearby recycled gamma-ray pulsar recently detected in the radio. The radio pulsations were found in a follow-up search at the location of a bright Fermi source. There are few millisecond pulsars whose spectral properties have been studied both in X-rays and gamma-rays. Those for which a multiwavelength analysis has been done show an intriguing connection between the gamma-ray and X-ray spectra. In a modest exposure we will collect enough counts to test the putative link between the the gamma-ray and X-ray spectra. The results will advance our understanding of the inner workings of the pulsar magnetospheres, including pair cascades, particle acceleration, magnetospheric current distribution, and radiation processes in superstrong magnetic fields.

  3. Gamma-ray Spectra of Starburst Galaxies

    Science.gov (United States)

    Moncada, Roberto Jose; Paglione, Timothy

    2018-01-01

    Starburst galaxies offer a unique window into the nature of star formation, its driving forces, and the energetic interactions within the galaxy. Their supernovae enrich the surrounding environment with cosmic rays that interact with the interstellar medium and galactic magnetic fields producing gamma-rays and non-thermal radio emission. We generated gamma-ray spectra for the 7 brightest starburst galaxies using 8.6 years of Pass 8 Large Area Telescope (LAT) data from the Fermi Gamma-ray Space Telescope. In addition to new detections, we will report on the results of simultaneously modeling the gamma-ray and radio spectra. These results confirm prior studies favoring high magnetic field strengths in the starburst regions.

  4. Measurement of effective atomic number of gunshot residues using scattering of gamma rays

    Science.gov (United States)

    Yılmaz, Demet; Turşucu, Ahmet; Uzunoğlu, Zeynep; Korucu, Demet

    2014-09-01

    Better understanding of gunshot residues and the major elemental composition would be valuable to forensic scientists for their analysis work and interpretation of results. In the present work, the effective atomic numbers of gunshot residues (cartridge case, bullet core, bullet jacket and gunpowder) were analyzed using energy dispersive X-ray analysis (EDX). The scattering of 59.54 keV gamma rays is studied using a high-resolution HPGe detector. The experiment is performed on various elements with atomic number in the 4≤Z≤82. The intensity ratio of coherent to Compton scattered peaks, corrected for photo-peak efficiency of gamma detector and absorption of photons in the sample and air, is plotted as a function of atomic number and constituted a best-fit-curve. From this fit-curve, the respective effective atomic numbers of gunshot residues are determined.

  5. Implications of Gamma-Ray Transparency Constraints in Blazars: Minimum Distances and Gamma-Ray Collimation

    Science.gov (United States)

    Becker, Peter A.; Kafatos, Menas

    1995-01-01

    We develop a general expression for the gamma - gamma absorption coefficient, alpha(sub gamma(gamma)) for gamma-rays propagating in an arbitrary direction at an arbitrary point in space above an X-ray-emitting accretion disk. The X-ray intensity is assumed to vary as a power law in energy and radius between the outer disk radius, R(sub 0), and the inner radius, R(sub ms) which is the radius of marginal stability for a Schwarzschild black hole. We use our result for alpha(sub gamma(gamma)) to calculate the gamma - gamma optical depth, tau(sub gamma(gamma)) for gamma - rays created at height z and propagating at angle Phi relative to the disk axis, and we show that for Phi = 0 and z greater than or approx equal to R(sub 0), tau(sub gamma(gamma)) proportional to Epsilon(sup alpha)z(sup -2(alpha) - 3), where alpha is the X-ray spectral index and Epsilon is the gamma - ray energy. As an application, we use our formalism to compute the minimum distance between the central black hole and the site of production of the gamma-rays detected by EGRET during the 1991 June flare of 3C 279. In order to obtain an upper limit, we assume that all of the X-rays observed contemporaneously by Ginga were emitted by the disk. Our results suggest that the observed gamma - rays may have originated within less than or approx equal to 45 GM/sq c from a black hole of mass greater than or approx equal to 10(exp 9) solar mass, perhaps in active plasma located above the central funnel of the accretion disk. This raises the possibility of establishing a direct connection between the production of the observed gamma - rays and the accretion of material onto the black hole. We also consider the variation of the optical depth as a function of the angle of propagation Phi. Our results indicate that the "focusing" of the gamma - rays along the disk axis due to pair production is strong enough to explain the observed degree of alignment in blazar sources. If the gamma - rays are produced isotropically

  6. Gamma rays from star-forming regions

    OpenAIRE

    Gustavo E. Romero

    2008-01-01

    Star-forming regions have been tentatively associated with gamma-ray sources since the early days of the COS B satellite. After the Compton Gamma-Ray Observatory, the statistical evidence for such an association has became overwhelming. Recent results from Cherenkov telescopes indicate that some high-energy sources are produced in regions of active star formation like Cygnus OB2 and Westerlund 2. In this paper I will briefly review what kind of stellar objects can produce gamma-ray emission i...

  7. On Gamma-Ray Bursts

    CERN Document Server

    Ruffini, Remo; Bianco, Carlo Luciano; Caito, Letizia; Chardonnet, Pascal; Cherubini, Christian; Dainotti, Maria Giovanna; Fraschetti, Federico; Geralico, Andrea; Guida, Roberto; Patricelli, Barbara; Rotondo, Michael; Hernandez, Jorge Armando Rueda; Vereshchagin, Gregory; Xue, She-Sheng

    2008-01-01

    (Shortened) We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high energy ion collisions. We then turn to the theory of vacuum polarization around a Kerr-Newman black hole, leading to the extraction of the blackholic energy, to the concept of dyadosphere and dyadotorus, and to the creation of an electron-positron-photon plasma. We then present a new theoretical approach encompassing the physics of neutron stars and heavy nuclei. It is shown that configurations of nuclear matter in bulk with global charge neutrality can exist on macroscopic scales and with electric fields close to the critical value near their surfaces. These configurations may represent an initial condition for the...

  8. INTEGRAL & RXTE View of Gamma-ray Binaries

    OpenAIRE

    Li, Jian; Torres, Diego F.; Zhang, Shu; Wang, Jianmin

    2013-01-01

    Gamma-ray binaries are X-ray binaries with gamma-ray emissions. Their multi-wavelength emissions range from radio, optical, X-ray and to very high energy (TeV). X-ray emissions are crucial to understand the nature of gamma-ray binaries. INTEGRAL and RXTE have covered and monitored most of the gamma-ray binaries in hard and soft X-rays. Here we report the results of several gamma-ray binaries and possible gamma-ray binaries from INTEGRAL and RXTE.

  9. Study of gamma-ray strength functions

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, D.G.; Gardner, M.A.; Dietrich, F.S.

    1980-08-07

    The use of gamma-ray strength function systematics to calculate neutron capture cross sections and capture gamma-ray spectra is discussed. The ratio of the average capture width, GAMMA/sub ..gamma../-bar, to the average level spacing, D/sub obs/, both at the neutron separation energy, can be derived from such systematics with much less uncertainty than from separate systematics for values of GAMMA/sub ..gamma../-bar and D/sub obs/. In particular, the E1 gamma-ray strength function is defined in terms of the giant dipole resonance (GDR). The GDR line shape is modeled with the usual Lorentzian function and also with a new energy-dependent, Breit-Wigner (EDBW) function. This latter form is further parameterized in terms of two overlapping resonances, even for nuclei where photonuclear measurements do not resolve two peaks. In the mass ranges studied, such modeling is successful for all nuclei away from the N = 50 closed neutron shell. Near the N = 50 shell, a one-peak EDBW appears to be more appropriate. Examples of calculated neutron capture excitation functions and capture gamma-ray spectra using the EDBW form are given for target nuclei in the mass-90 region and also in the Ta-Au mass region. 20 figures.

  10. Gamma-Ray Astrophysics NSSTC Fermi GBM

    Data.gov (United States)

    National Aeronautics and Space Administration — The Fermi Gamma-Ray Burst Monitor (GBM) is not a pointed or imaging instrument. To determine fluxes for known sources, we measure the change in the count rate...

  11. POPULATION SYNTHESIS AND GAMMA RAY BURST PROGENITORS

    Energy Technology Data Exchange (ETDEWEB)

    C. L. FREYER

    2000-12-11

    Population synthesis studies of binaries are always limited by a myriad of uncertainties from the poorly understood effects of binary mass transfer and common envelope evolution to the many uncertainties that still remain in stellar evolution. But the importance of these uncertainties depends both upon the objects being studied and the questions asked about these objects. Here I review the most critical uncertainties in the population synthesis of gamma-ray burst progenitors. With a better understanding of these uncertainties, binary population synthesis can become a powerful tool in understanding, and constraining, gamma-ray burst models. In turn, as gamma-ray bursts become more important as cosmological probes, binary population synthesis of gamma-ray burst progenitors becomes an important tool in cosmology.

  12. A software package using a mesh-grid method for simulating HPGe detector efficiencies

    Energy Technology Data Exchange (ETDEWEB)

    Gritzo, Russell E [Los Alamos National Laboratory; Jackman, Kevin R [REMOTE SENSING LAB; Biegalski, Steven R [UT AUSTIN

    2009-01-01

    Traditional ways of determining the absolute full-energy peak efficiencies of high-purity germanium (HPGe) detectors are often time consuming, cost prohibitive, or not feasible. A software package, KMESS (Kevin's Mesh Efficiency Simulator Software), was developed to assist in predicting these efficiencies. It uses a semiempirical mesh-grid method and works for arbitrary source shapes and counting geometries. The model assumes that any gamma-ray source shape can be treated as a large enough collection of point sources. The code is readily adaptable, has a web-based graphical front-end. and could easily be coupled to a 3D scanner. As will be shown. this software can estimate absolute full-energy peak efficiencies with good accuracy in reasonable computation times. It has applications to the field of gamma-ray spectroscopy because it is a quick and accurate way to assist in performing quantitative analyses using HPGe detectors.

  13. Applications of gamma-ray lasers

    Science.gov (United States)

    Balko, B.; Cohen, L.; Hartmann, F. X.

    1985-11-01

    As a result of the IST/IDA Gamma-Ray Laser Workshop held in May 1985, a general picture of the gamma-ray laser has emerged. The characteristics of the radiation from this source are contrasted with those from other coherent sources; these include energy, bandwidth, intensity, and coherence length. Potential nonmilitary applications are listed; and two classes of military applications are suggested. Those characteristics which drive a specific application are spelled out.

  14. Supernovae and gamma-ray bursts connection

    Energy Technology Data Exchange (ETDEWEB)

    Valle, Massimo Della [INAF-Napoli, Capodimonte Observatory, Salita Moiariello, 16, I-80131 Napoli (Italy); International Center for Relativistic Astrophysics Network, Piazzale della Repubblica 10, I-65122, Pescara (Italy)

    2015-12-17

    I’ll review the status of the Supernova/Gamma-Ray Burst connection. Several pieces of evidence suggest that long duration Gamma-ray Bursts are associated with bright SNe-Ic. However recent works suggest that GRBs might be produced in tight binary systems composed of a massive carbon-oxygen cores and a neutron star companion. Current estimates of the SN and GRB rates yield a ratio GRB/SNe-Ibc in the range ∼ 0.4% − 3%.

  15. Polarization measurements of proton capture gamma rays

    NARCIS (Netherlands)

    Suffert, M.; Endt, P.M.; Hoogenboom, A.M.

    1959-01-01

    The linear polarization has been measured of eight different gamma rays of widely differing energies (Eγ = 0.8 - 8.0 MeV) emitted at resonances in the 24Mg(p, γ)25Al, 30Si(p, γ)31P, and 32S(p, γ)33Cl reactions. The gamma rays emitted at 90° to the proton beam were Compton scattered in a 2″ NaI

  16. Gamma-ray constraints on supernova nucleosynthesis

    Science.gov (United States)

    Leising, Mark D.

    1994-01-01

    Gamma-ray spectroscopy holds great promise for probing nucleosynthesis in individual supernova explosions via short-lived radioactivity, and for measuring current global Galactic supernova nucleosynthesis with longer-lived radioactivity. It was somewhat surprising that the former case was realized first for a Type II supernova, when both Co-56 and Co-57 were detected in SN 1987A. These provide unprecedented constraints on models of Type II explosions and nucleosynthesis. Live Al-26 in the Galaxy might come from Type II supernovae, and if it is eventually shown to be so, can constrain massive star evolution, supernova nucleosynthesis, and the Galactic Type II supernova rate. Type Ia supernovae, thought to be thermonuclear explosions, have not yet been detected in gamma-rays. This is somewhat surprising given current models and recent Co-56 detection attempts. Ultimately, gamma-ray measurements can confirm their thermonuclear nature, probe the nuclear burning conditions, and help evaluate their contributions to Galactic nucleosynthesis. Type Ib/c supernovae are poorly understood. Whether they are core collapse or thermonuclear events might be ultimately settled by gamma-ray observations. Depending on details of the nuclear processing, any of these supernova types might contribute to a detectable diffuse glow of Fe-60 gamma-ray lines. Previous attempts at detection have come very close to expected emission levels. Remnants of any type of age less that a few centuries might be detectable as individual spots of Ti-44 gamma-ray line emission. It is in fact quite surprising that previous surveys have not discovered such spots, and the constraints on the combination of nucleosynthesis yields and supernova rates are very interesting. All of these interesting limits and possibilities mean that the next mission, International Gamma-Ray Astrophysics Laboratory (INTEGRAL), if it has sufficient sensitivity, is very likely to lead to the realization of much of the great potential

  17. VHE Gamma-ray Supernova Remnants

    Energy Technology Data Exchange (ETDEWEB)

    Funk, Stefan; /KIPAC, Menlo Park

    2007-01-22

    Increasing observational evidence gathered especially in X-rays and {gamma}-rays during the course of the last few years support the notion that Supernova remnants (SNRs) are Galactic particle accelerators up to energies close to the ''knee'' in the energy spectrum of Cosmic rays. This review summarizes the current status of {gamma}-ray observations of SNRs. Shell-type as well as plerionic type SNRs are addressed and prospect for observations of these two source classes with the upcoming GLAST satellite in the energy regime above 100 MeV are given.

  18. A fitting algorithm based on simulated annealing techniques for efficiency calibration of HPGe detectors using different mathematical functions

    Energy Technology Data Exchange (ETDEWEB)

    Hurtado, S. [Servicio de Radioisotopos, Centro de Investigacion, Tecnologia e Innovacion (CITIUS), Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012 Sevilla (Spain)], E-mail: shurtado@us.es; Garcia-Leon, M. [Departamento de Fisica Atomica, Molecular y Nuclear, Facultad de Fisica, Universidad de Sevilla, Aptd. 1065, 41080 Sevilla (Spain); Garcia-Tenorio, R. [Departamento de Fisica Aplicada II, E.T.S.A. Universidad de Sevilla, Avda, Reina Mercedes 2, 41012 Sevilla (Spain)

    2008-09-11

    In this work several mathematical functions are compared in order to perform the full-energy peak efficiency calibration of HPGe detectors using a 126cm{sup 3} HPGe coaxial detector and gamma-ray energies ranging from 36 to 1460 keV. Statistical tests and Monte Carlo simulations were used to study the performance of the fitting curve equations. Furthermore the fitting procedure of these complex functional forms to experimental data is a non-linear multi-parameter minimization problem. In gamma-ray spectrometry usually non-linear least-squares fitting algorithms (Levenberg-Marquardt method) provide a fast convergence while minimizing {chi}{sub R}{sup 2}, however, sometimes reaching only local minima. In order to overcome that shortcoming a hybrid algorithm based on simulated annealing (HSA) techniques is proposed. Additionally a new function is suggested that models the efficiency curve of germanium detectors in gamma-ray spectrometry.

  19. Supernovae and Gamma-Ray Bursts

    Science.gov (United States)

    Livio, Mario; Panagia, Nino; Sahu, Kailash

    2001-07-01

    Participants; Preface; Gamma-ray burst-supernova relation B. Paczynski; Observations of gamma-ray bursts G. Fishman; Fireballs T. Piran; Gamma-ray mechanisms M. Rees; Prompt optical emission from gamma-ray bursts R. Kehoe, C. Akerlof, R. Balsano, S. Barthelmy, J. Bloch, P. Butterworth, D. Casperson, T. Cline, S. Fletcher, F. Frontera, G. Gisler, J. Heise, J. Hills, K. Hurley, B. Lee, S. Marshall, T. McKay, A. Pawl, L. Piro, B. Priedhorsky, J. Szymanski and J. Wren; X-ray afterglows of gamma-ray bursts L. Piro; The first year of optical-IR observations of SN1998bw I. Danziger, T. Augusteijn, J. Brewer, E. Cappellaro, V. Doublier, T. Galama, J. Gonzalez, O. Hainaut, B. Leibundgut, C. Lidman, P. Mazzali, K. Nomoto, F. Patat, J. Spyromilio, M. Turatto, J. Van Paradijs, P. Vreeswijk and J. Walsh; X-ray emission of Supernova 1998bw in the error box of GRB980425 E. Pian; Direct analysis of spectra of type Ic supernovae D. Branch; The interaction of supernovae and gamma-ray bursts with their surroundings R. Chevalier; Magnetars, soft gamma-ray repeaters and gamma-ray bursts A. Harding; Super-luminous supernova remnants Y. -H. Chu, C. -H. Chen and S. -P. Lai; The properties of hypernovae: SNe Ic 1998bw, 1997ef, and SN IIn 1997cy K. Nomoto, P. Mazzali, T. Nakamura, K. Iwanmoto, K. Maeda, T. Suzuki, M. Turatto, I. Danziger and F. Patat; Collapsars, Gamma-Ray Bursts, and Supernovae S. Woosley, A. MacFadyen and A. Heger; Pre-supernova evolution of massive stars N. Panagia and G. Bono; Radio supernovae and GRB 980425 K. Weiler, N. Panagia, R. Sramek, S. Van Dyk, M. Montes and C. Lacey; Models for Ia supernovae and evolutionary effects P. Hoflich and I. Dominguez; Deflagration to detonation A. Khokhlov; Universality in SN Iae and the Phillips relation D. Arnett; Abundances from supernovae F. -K. Thielemann, F. Brachwitz, C. Freiburghaus, S. Rosswog, K. Iwamoto, T. Nakamura, K. Nomoto, H. Umeda, K. Langanke, G. Martinez-Pinedo, D. Dean, W. Hix and M. Strayer; Sne, GRBs, and the

  20. Analysis of remotely accrued complex gamma ray spectra - proficiency test

    Energy Technology Data Exchange (ETDEWEB)

    Dowdall, M. (Norwegian Radiation Protection Authority (Norway))

    2009-03-15

    This report presents details pertaining to an exercise conducted as part of the NKS-B programme using synthetic gamma ray spectra to simulate the type of data that may be encountered in the early phase of a nuclear accident. The aim of the exercise was to provide participants with an opportunity to exercise in the type of situation and with the type of data that may result after a nuclear accident. Attempting to conduct such exercise internationally using actual samples presents practical and logistical difficulties and a synthetic spectrum was employed to negate some of these problems. A HPGe spectrum was synthesized containing a range of typical fallout isotopes and distributed, along with calibration information, to the participant laboratories. The participants were required to submit results within three hours of receipt and with the option of submitting further results within one week. The results provided by the laboratories indicate that all laboratories were able to identify and quantify some of the isotopes but only some labs were in a position to identify and quantify virtually all the constituents of the spectrum. Results indicate that there remain some problems with aspects such as true coincidence summation and using file formats with which labs may not be familiar with. The exercise provided a useful opportunity in exploring the possibilities of using synthetic spectra for exercise purposes and offered participants the chance to practice with the sort of scenario that may result after an accident. (au)

  1. The Gamma-Ray Imager GRI

    Science.gov (United States)

    Wunderer, Cornelia B.; GRI Collaboration

    2008-03-01

    Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear reactions are synthesizing the basic constituents of our world. Cosmic accelerators and cosmic explosions are major science themes that are addressed in the gamma-ray regime. ESA's INTEGRAL observatory currently provides the astronomical community with a unique tool to investigate the sky up to MeV energies and hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes have been discovered. NASA's GLAST mission will similarly take the next step in surveying the high-energy ( GeV) sky, and NuSTAR will pioneer focusing observations at hard X-ray energies (to 80 keV). There will be clearly a growing need to perform deeper, more focused investigations of gamma-ray sources in the 100-keV to MeV regime. Recent technological advances in the domain of gamma-ray focusing using Laue diffraction and multilayer-coated mirror techniques have paved the way towards a gamma-ray mission, providing major improvements compared to past missions regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow the study of particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

  2. Investigation of cosmic-ray induced background of Germanium gamma spectrometer using GEANT4 simulation.

    Science.gov (United States)

    Hung, Nguyen Quoc; Hai, Vo Hong; Nomachi, Masaharu

    2017-03-01

    In this article, a GEANT4 Monte Carlo simulation toolkit was used to study the response of the cosmic-ray induced background on a High-Purity Germanium (HPGe) gamma spectrometer in the wide energy range, up to 100MeV. The natural radiation background measurements of the spectrometer were carried out in the energy region from 0.04 to 50MeV. The simulated cosmic-ray induced background of the Ge detector was evaluated in comparison with the measured data. The contribution of various cosmic-ray components including muons, neutrons, protons, electrons, positrons and photons was investigated. We also analyzed secondary particle showers induced by the muonic component. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Gamma rays from cosmic radioactivities

    National Research Council Canada - National Science Library

    Diehl, Roland; Hartmann, Dieter H; Prantzos, Nikos

    2007-01-01

    .... Cobalt lines from SN1987A and 44 Ti lines from the Cassiopeia A (Cas A) supernova remnant offer unique constraints on the properties of the innermost regions of core collapse supernovae. Diffuse gamma...

  4. Cosmological Gamma-Ray Bursters

    Science.gov (United States)

    Tamblyn, P.; Melia, F.

    1993-05-01

    The distribution of gamma-ray burst sources detected with BATSE is iso\\-tro\\-pic yet non-uniform. There is a deficit of weak events which is commonly expressed by a \\vvm less than the 0.5 expected for a uniform Eu\\-clid\\-ean distribution. It has been argued (e.g., Mao and Paczynski 1992) that this may be a signature of a Cosmological expansion in a FRW universe with a uniform, co-moving distribution of sources. However, a comparison of the \\vvm and burst detection rates of several experiments presents an apparent paradox: e.g., Konus detected the bursts more frequently than SMM, implying a better sensitivity and larger sampling volume, yet its measured \\vvm was ~ 0.45 compared to SMM's value of ~ 0.40, suggesting instead a lesser deviation from Eu\\-clid\\-ean space. We point out that this apparent conflict stems from the assumption that all bursts have a standard spectrum with a single power law. But realistic spectra often exhibit broken power laws, with a break energy 100;keV ~ lessepsilon_b ~ less 3 MeV. \\ Thus, the flux measured by a particular instrument depends on both the redshift of the source and the energy window of the detector. In other words, for a given energy window, the flux of a more distant burst will be further decreased below the value expected from the Cosmological model due to the red-shifting of epsilon_b across the window. We show that the inclusion of an intrinsic epsilon_b ( ~ 500 keV) and a consideration of the different detector energy responses and sensitivities can self-consistently account for the rates and \\vvm of the Konus, PVO, SMM, and BATSE datasets. Because of the dependence of the observed characteristics on the energy window, a subset of the BATSE catalog, based solely on the burst fluence in the higher energy (i.e., 4{th}) channel, provides an additional ``data'' point in the \\vvm versus rate plane. In particular, Konus's higher rate for a larger value of \\vvm is due to its better sensitivity, but smaller and

  5. Effects of Shielding on Gamma Rays

    Energy Technology Data Exchange (ETDEWEB)

    Karpius, Peter Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-13

    The interaction of gamma rays with matter results in an effect we call attenuation (i.e. ‘shielding’). Attenuation can dramatically alter the appearance of a spectrum. Attenuating materials may actually create features in a spectrum via x-ray fluorescence

  6. GRI: The Gamma-Ray Imager mission

    Science.gov (United States)

    Knödlseder, Jürgen; GRI Consortium

    With the INTEGRAL observatory ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction have paved the way towards a new gamma-ray mission, providing major improvements regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow studies of particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

  7. New insights from cosmic gamma rays

    Science.gov (United States)

    Roland, Diehl

    2016-04-01

    The measurement of gamma rays from cosmic sources at ~MeV energies is one of the key tools for nuclear astrophysics, in its study of nuclear reactions and their impacts on objects and phenomena throughout the universe. Gamma rays trace nuclear processes most directly, as they originate from nuclear transitions following radioactive decays or high-energy collisions with excitation of nuclei. Additionally, the unique gamma-ray signature from the annihilation of positrons falls into this astronomical window and is discussed here: Cosmic positrons are often produced from β-decays, thus also of nuclear physics origins. The nuclear reactions leading to radioactive isotopes occur inside stars and stellar explosions, which therefore constitute the main objects of such studies. In recent years, both thermonuclear and core-collapse supernova radioactivities have been measured though 56Ni, 56Co, and 44Ti lines, and a beginning has thus been made to complement conventional supernova observations with such measurements of the prime energy sources of supernova light created in their deep interiors. The diffuse radioactive afterglow of massive-star nucleosynthesis in gamma rays is now being exploited towards astrophysical studies on how massive stars feed back their energy and ejecta into interstellar gas, as part of the cosmic cycle of matter through generations of stars enriching the interstellar gas and stars with metals. Large interstellar cavities and superbubbles have been recognised to be the dominating structures where new massive-star ejecta are injected, from 26Al gamma-ray spectroscopy. Also, constraints on the complex interiors of stars derive from the ratio of 60Fe/26Al gamma rays. Finally, the puzzling bulge-dominated intensity distribution of positron annihilation gamma rays is measured in greater detail, but still not understood; a recent microquasar flare provided evidence that such objects may be prime sources for positrons in interstellar space, rather than

  8. Characterisation of imperial college reactor centre legacy waste using gamma-ray spectrometry

    Science.gov (United States)

    Shuhaimi, Alif Imran Mohd

    2016-01-01

    Waste characterisation is a principal component in waste management strategy. The characterisation includes identification of chemical, physical and radiochemical parameters of radioactive waste. Failure to determine specific waste properties may result in sentencing waste packages which are not compliant with the regulation of long term storage or disposal. This project involved measurement of intensity and energy of gamma photons which may be emitted by radioactive waste generated during decommissioning of Imperial College Reactor Centre (ICRC). The measurement will use High Purity Germanium (HPGe) as Gamma-ray detector and ISOTOPIC-32 V4.1 as analyser. In order to ensure the measurements provide reliable results, two quality control (QC) measurements using difference matrices have been conducted. The results from QC measurements were used to determine the accuracy of the ISOTOPIC software.

  9. Gamma-ray albedo of the moon

    OpenAIRE

    Moskalenko, Igor V.; Porter, Troy A.

    2007-01-01

    We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma rays from the Moon is very steep with an effective cutoff around 4 GeV (600 MeV for the inner part of the Moon disc). Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalisation;...

  10. Technology Needs for Gamma Ray Astronomy

    Science.gov (United States)

    Gehrels, Neil

    2011-01-01

    Gamma ray astronomy is currently in an exciting period of multiple missions and a wealth of data. Results from INTEGRAL, Fermi, AGILE, Suzaku and Swift are making large contributions to our knowledge of high energy processes in the universe. The advances are due to new detector and imaging technologies. The steps to date have been from scintillators to solid state detectors for sensors and from light buckets to coded aperture masks and pair telescopes for imagers. A key direction for the future is toward focusing telescopes pushing into the hard X-ray regime and Compton telescopes and pair telescopes with fine spatial resolution for medium and high energy gamma rays. These technologies will provide finer imaging of gamma-ray sources. Importantly, they will also enable large steps forward in sensitivity by reducing background.

  11. Localization of Gamma-Ray Bursts Using the Fermi Gamma-Ray Burst Monitor

    NARCIS (Netherlands)

    Connaughton, V.; Briggs, M.S.; Goldstein, A.; Meegan, C.A.; Paciesas, W.S.; Preece, R.D.; Wilson-Hodge, C.A.; Gibby, M.H.; Greiner, J.; Gruber, D.; Jenke, P.; Kippen, R.M.; Pelassa, V.; Xiong, S.; Yu, H-F.; Bhat, P.N.; Burgess, J.M.; Byrne, D.; Fitzpatrick, G.; Foley, S.; Giles, M.M.; Guiriec, S.; van der Horst, A.J.; von Kienlin, A.; McBreen, S.; McGlynn, S.; Tierney, D.; Zhang, B..B.

    2015-01-01

    The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the

  12. Gamma-Ray Lenses for Astrophysics-and the Gamma-Ray Imager Mission GRI

    DEFF Research Database (Denmark)

    Wunderer, C. B.; Ballmoos, P. V.; Barriere, N.

    2009-01-01

    Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are acc...

  13. Neutron and Gamma-ray Measurements

    Science.gov (United States)

    Krasilnikov, Anatoly V.; Sasao, Mamiko; Kaschuck, Yuri A.; Kiptily, Vasily G.; Nishitani, Takeo; Popovichev, Sergey V.; Bertalot, Luciano

    2008-03-01

    Due to high neutron and gamma-ray yields and large size plasmas many future fusion reactor plasma parameters such as fusion power, fusion power density, ion temperature, fuel mixture, fast ion energy and spatial distributions can be well measured by various fusion product diagnostics. Neutron diagnostics provide information on fusion reaction rate, which indicates how close is the plasma to the ultimate goal of nuclear fusion and fusion power distribution in the plasma core, which is crucial for optimization of plasma breakeven and burn. Depending on the plasma conditions neutron and gamma-ray diagnostics can provide important information, namely about dynamics of fast ion energy and spatial distributions during neutral beam injection, ion cyclotron heating and generated by fast ions MHD instabilities. The influence of the fast particle population on the 2-D neutron source profile was clearly demonstrated in JET experiments. 2-D neutron and gamma-ray source measurements could be important for driven plasma heating profile optimization in fusion reactors. To meat the measurement requirements in ITER the planned set of neutron and gamma ray diagnostics includes radial and vertical neutron and gamma cameras, neutron flux monitors, neutron activation systems and neutron spectrometers. The necessity of using massive radiation shielding strongly influences the diagnostic designs in fusion reactor, determines angular fields of view of neutron and gamma-ray cameras and spectrometers and gives rise to unavoidable difficulties in the absolute calibration. The development, testing in existing tokomaks and a possible engineering integration of neuron and gamma-ray diagnostic systems into ITER are presented.

  14. Inverse compton scattering gamma ray source

    Science.gov (United States)

    Boucher, S.; Frigola, P.; Murokh, A.; Ruelas, M.; Jovanovic, I.; Rosenzweig, J. B.; Travish, G.

    2009-09-01

    Special Nuclear Materials (SNM) (e.g. U-235, Pu-239) can be detected by active interrogation with gamma rays (>6 MeV) through photofission. For long-range detection (˜1 km), an intense beam of gamma rays (˜10 14 per second) is required in order to produce measurable number of neutrons. The production of such fluxes of gamma rays, and in the pulse formats useful for detection, presents many technical challenges, and requires novel approaches to the accelerator and laser technology. RadiaBeam is currently designing a gamma ray source based on Inverse Compton Scattering (ICS) from a high-energy electron beam. To achieve this, improvements in photoinjector, linac, final focus, and laser system are planned. These enhanced sub-systems build on parallel work being performed at RadiaBeam, UCLA, and elsewhere. A high-repetition rate photoinjector, a high-gradient S-band linac, and a laser pulse recirculator will be used. The proposed system will be a transportable source of high-flux, high-energy quasi-monochromatic gamma rays for active interrogation of special nuclear materials.

  15. Stellar Photon Archaeology with Gamma-Rays

    Science.gov (United States)

    Stecker, Floyd W.

    2009-01-01

    Ongoing deep surveys of galaxy luminosity distribution functions, spectral energy distributions and backwards evolution models of star formation rates can be used to calculate the past history of intergalactic photon densities and, from them, the present and past optical depth of the Universe to gamma-rays from pair production interactions with these photons. The energy-redshift dependence of the optical depth of the Universe to gamma-rays has become known as the Fazio-Stecker relation (Fazio & Stecker 1970). Stecker, Malkan & Scully have calculated the densities of intergalactic background light (IBL) photons of energies from 0.03 eV to the Lyman limit at 13.6 eV and for 0$ < z < $6, using deep survey galaxy observations from Spitzer, Hubble and GALEX and have consequently predicted spectral absorption features for extragalactic gamma-ray sources. This procedure can also be reversed. Determining the cutoff energies of gamma-ray sources with known redshifts using the recently launched Fermi gamma-ray space telescope may enable a more precise determination of the IBL photon densities in the past, i.e., the "archaeo-IBL.", and therefore allow a better measure of the past history of the total star formation rate, including that from galaxies too faint to be observed.

  16. Fermi Results on Gamma-Ray Pulsars

    Science.gov (United States)

    Razzano, Massimiliano; Guillemot, Lucas

    By detecting pulsed gamma-ray emission from more than 130 young and recycled pulsars since it began operating in 2008, the Large Area Telescope (LAT) on the Fermi satellite has revolutionized our view of the gamma-ray pulsar population. In addition to detecting and characterizing the gamma-ray emission from many more pulsars, the LAT has discovered a large number of new gamma-ray sources whose properties suggest that they harbor unknown gamma-ray pulsars. Radio observations in support of the Fermi mission have provided a vital contribution to the success of LAT pulsar studies. For instance, radio detections or non-detections of LAT-discovered pulsars constrain the ratio of radio-loud to radio-quiet pulsars, and radio searches in LAT unassociated sources have uncovered several tens of new millisecond pulsars. In this presentation I will summarize some of the main results and implications from pulsar observations with the Fermi LAT and supporting multi-wavelength observations, in particular in the radio domain.

  17. On Gamma-Ray Bursts

    Science.gov (United States)

    Ruffini, R.; Bernardini, M. G.; Bianco, C. L.; Caito, L.; Chardonnet, P.; Cherubini, C.; Dainotti, M. G.; Fraschetti, F.; Geralico, A.; Guida, R.; Patricelli, B.; Rotondo, M.; Rueda Hernandez, J. A.; Vereshchagin, G.; Xue, S.-S.

    2008-09-01

    We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high energy ion collisions. We then turn to the theory of vacuum polarization around a Kerr-Newman black hole, leading to the extraction of the blackholic energy, to the concept of dyadosphere and dyadotorus, and to the creation of an electron-positron-photon plasma. We then present a new theoretical approach encompassing the physics of neutron stars and heavy nuclei. It is shown that configurations of nuclear matter in bulk with global charge neutrality can exist on macroscopic scales and with electric fields close to the critical value near their surfaces. These configurations may represent an initial condition for the process of gravitational collapse, leading to the creation of an electron-positron-photon plasma: the basic self-accelerating system explaining both the energetics and the high energy Lorentz factor observed in GRBs. We then turn to recall the two basic interpretational paradigms of our GRB model: 1) the Relative Space-Time Transformation (RSTT) paradigm and 2) the Interpretation of the Burst Structure (IBS) paradigm. These paradigms lead to a "canonical" GRB light curve formed from two different components: a Proper-GRB (P-GRB) and an extended afterglow comprising a raising part, a peak, and a decaying tail. When the P-GRB is energetically predominant we have a "genuine" short GRB, while when the afterglow is energetically predominant we have a so-called long GRB or a "fake" short GRB. We compare and contrast the description of the relativistic expansion of the electron-positron plasma within our approach and within the other ones in the current literature. We then turn

  18. Measurements of gamma rays from keV-neutron resonance capture by odd-Z nuclei in the 2s-1d shell region

    Energy Technology Data Exchange (ETDEWEB)

    Igashira, Masayuki; Lee, Sam Yol; Mizuno, Satoshi; Hori, Jun-ichi [Tokyo Inst. of Tech. (Japan). Research Lab. for Nuclear Reactors; Kitazawa, Hideo

    1998-03-01

    Measurements of gamma rays from keV-neutron resonance capture by {sup 19}F, {sup 23}Na, and {sup 27}Al, which are odd-Z nuclei in the 2s-1d shell region, were performed, using an anti-Compton HPGe spectrometer and a pulsed neutron source by the {sup 7}Li(p,n){sup 7}Be reaction. Capture gamma rays from the 27-, 49-, and 97-keV resonances of {sup 19}F, the 35- and 53-keV resonances of {sup 23}Na, and the 35-keV resonance of {sup 27}Al were observed. Some results are presented. (author)

  19. Gamma-ray Emission from Globular Clusters

    Science.gov (United States)

    Tam, Pak-Hin T.; Hui, Chung Y.; Kong, Albert K. H.

    2016-03-01

    Over the last few years, the data obtained using the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope has provided new insights on high-energy processes in globular clusters, particularly those involving compact objects such as MilliSecond Pulsars (MSPs). Gamma-ray emission in the 100 MeV to 10 GeV range has been detected from more than a dozen globular clusters in our galaxy, including 47 Tucanae and Terzan 5. Based on a sample of known gammaray globular clusters, the empirical relations between gamma-ray luminosity and properties of globular clusters such as their stellar encounter rate, metallicity, and possible optical and infrared photon energy densities, have been derived. The measured gamma-ray spectra are generally described by a power law with a cut-off at a few gigaelectronvolts. Together with the detection of pulsed γ-rays from two MSPs in two different globular clusters, such spectral signature lends support to the hypothesis that γ-rays from globular clusters represent collective curvature emission from magnetospheres of MSPs in the clusters. Alternative models, involving Inverse-Compton (IC) emission of relativistic electrons that are accelerated close to MSPs or pulsar wind nebula shocks, have also been suggested. Observations at >100 GeV by using Fermi/LAT and atmospheric Cherenkov telescopes such as H.E.S.S.-II, MAGIC-II, VERITAS, and CTA will help to settle some questions unanswered by current data.

  20. Gamma-ray Emission from Globular Clusters

    Directory of Open Access Journals (Sweden)

    Pak-Hin T. Tam

    2016-03-01

    Full Text Available Over the last few years, the data obtained using the Large Area Telescope (LAT aboard the Fermi Gamma-ray Space Telescope has provided new insights on high-energy processes in globular clusters, particularly those involving compact objects such as MilliSecond Pulsars (MSPs. Gamma-ray emission in the 100 MeV to 10 GeV range has been detected from more than a dozen globular clusters in our galaxy, including 47 Tucanae and Terzan 5. Based on a sample of known gammaray globular clusters, the empirical relations between gamma-ray luminosity and properties of globular clusters such as their stellar encounter rate, metallicity, and possible optical and infrared photon energy densities, have been derived. The measured gamma-ray spectra are generally described by a power law with a cut-off at a few gigaelectronvolts. Together with the detection of pulsed γ-rays from two MSPs in two different globular clusters, such spectral signature lends support to the hypothesis that γ-rays from globular clusters represent collective curvature emission from magnetospheres of MSPs in the clusters. Alternative models, involving Inverse-Compton (IC emission of relativistic electrons that are accelerated close to MSPs or pulsar wind nebula shocks, have also been suggested. Observations at >100 GeV by using Fermi/LAT and atmospheric Cherenkov telescopes such as H.E.S.S.-II, MAGIC-II, VERITAS, and CTA will help to settle some questions unanswered by current data.

  1. The observation of gamma ray bursts and terrestrial gamma-ray flashes with AGILE

    Science.gov (United States)

    Del Monte, E.; Barbiellini, G.; Fuschino, F.; Giuliani, A.; Longo, F.; Marisaldi, M.; Mereghetti, S.; Moretti, E.; Trifoglio, M.; Vianello, G.; Costa, E.; Donnarumma, I.; Evangelista, Y.; Feroci, M.; Gallil, M.; Lapshov, I.; Lazzarotto, F.; Lipari, P.; Pacciani, L.; Rapisarda, M.; Soffitta, P.; Tavani, M.; Vercellone, S.; Cutini, S.; Boffelli, F.; Bulgarelli, A.; Caraveo, P.; Cattaneo, P. W.; Chen, A.; Di Cocco, G.; Gianotti, F.; Labanti, C.; Morselli, A.; Pellizzoni, A.; Perotti, F.; Piano, G.; Picozza, P.; Pilia, M.; Prest, M.; Pucella, G.; Rappoldi, A.; Sabatini, S.; Striani, E.; Trois, A.; Vallazza, E.; Vittorini, V.; Antonelli, L. A.; Pittori, C.; Preger, B.; Santolamazza, P.; Verrecchia, F.; Giommi, P.; Salotti, L.

    2011-02-01

    Since its early phases of operation, the AGILE mission is successfully observing Gamma Ray Bursts (GRBs) in the hard X-ray band with the SuperAGILE imager and in the MeV range with the Mini-Calorimeter. Up to now, three firm GRB detections were obtained above 25 MeV and some bursts were detected with lower statistical confidence in the same energy band. When a GRB is localized, either by SuperAGILE or Swift/BAT or INTEGRAL/IBIS or Fermi/GBM or IPN, inside the field of view of the Gamma Ray Imager of AGILE, a detection is searched for in the gamma ray band or an upper limit is provided. A promising result of AGILE is the detection of very short gamma ray transients, a few ms in duration and possibly identified with Terrestrial Gamma-ray Flashes. In this paper we show the current status of the observation of Gamma Ray Bursts and Terrestrial Gamma-ray Flashes with AGILE.

  2. Design and Performance of the GAMMA-400 Gamma-Ray Telescope for Dark Matter Searches

    Science.gov (United States)

    Galper, A. M.; Adriani, O.; Aptekar, R. L.; Arkhangelskaja, I. V.; Arkhangelskiy, A. I.; Boezio, M.; Bonvicini, V.; Boyarchuk, K. A.; Fradkin, M. I.; Gusakov, Yu V.; hide

    2012-01-01

    The GAMMA-400 gamma-ray telescope is designed to measure the fluxes of gamma-rays and cosmic-ray electrons (+) positrons, which can be produced by annihilation or decay of the dark matter particles, as well as to survey the celestial sphere in order to study point and extended sources of gamma-rays, measure energy spectra of Galactic and extragalactic diffuse gamma-ray emission, gamma-ray bursts, and gamma-ray emission from the Sun. GAMMA-400 covers the energy range from 100 MeV to 3000 GeV. Its angular resolution is approximately 0.01deg (E(sub gamma) greater than 100 GeV), the energy resolution approximately 1% (E(sub gamma) greater than 10 GeV), and the proton rejection factor approximately 10(exp 6). GAMMA-400 will be installed on the Russian space platform Navigator. The beginning of observations is planned for 2018.

  3. Nuclear forensics using gamma-ray spectroscopy

    CERN Document Server

    Norman, Eric B

    2016-01-01

    Much of George Dracoulis's research career was devoted to utilizing gamma-ray spectroscopy in fundamental studies in nuclear physics. This same technology is useful in a wide range of applications in the area of nuclear forensics. Over the past several years, our research group has made use of both high- and low- resolution gamma ray spectrometers to: identify the first sample of plutonium large enough to be weighed; determine the yield of the Trinity nuclear explosion; measure fission fragment yields as a function of target nucleus and neutron energy; and observe fallout in the U. S. from the Fukushima nuclear reactor accident.

  4. Precise absolute gamma-ray wavelength measurements

    Science.gov (United States)

    Kessler, E. G.; Dewey, M. S.; Greene, G. L.; Deslattes, R. D.; Börner, H.

    1991-10-01

    Gamma-ray wavelengths measured with the joint NIST/ILL GAMS4 facility at the High Flux Reactor, Grenoble, France, are discussed. This primary goal of these measurements is gamma-ray wavelengths which are consistent with the optical wavelength scale and the Rydberg constant with an uncertainty no larger than 0.1 ppm for energies up to 5 MeV. The current status of the Bragg angle and crystal lattice spacing measurements on reference energy values, the neutron mass, and the determination of fundamental constants is reviewed. Measurement of structure factors at high energies is also considered.

  5. Nuclear Forensics using Gamma-ray Spectroscopy

    Directory of Open Access Journals (Sweden)

    Norman E. B.

    2016-01-01

    Full Text Available Much of George Dracoulis’s research career was devoted to utilising gamma-ray spectroscopy in fundamental studies in nuclear physics. This same technology is useful in a wide range of applications in the area of nuclear forensics. Over the last several years, our research group has made use of both high- and low-resolution gamma-ray spectrometers to: identify the first sample of plutonium large enough to be weighed; determine the yield of the Trinity nuclear explosion; measure fission fragment yields as a function of target nucleus and neutron energy; and observe fallout in the U. S. from the Fukushima nuclear reactor accident.

  6. Gamma ray spectroscopy monitoring method and apparatus

    Science.gov (United States)

    Stagg, William R; Policke, Timothy A

    2017-05-16

    The present invention relates generally to the field of gamma ray spectroscopy monitoring and a system for accomplishing same to monitor one or more aspects of various isotope production processes. In one embodiment, the present invention relates to a monitoring system, and method of utilizing same, for monitoring one or more aspects of an isotope production process where the monitoring system comprises: (A) at least one sample cell; (B) at least one measuring port; (C) at least one adjustable collimator device; (D) at least one shutter; and (E) at least one high resolution gamma ray spectrometer.

  7. Radioactivities and gamma-rays from supernovae

    Science.gov (United States)

    Woosley, S. E.

    1991-01-01

    An account is given of the implications of several calculations relevant to the estimation of gamma-ray signals from various explosive astronomical phenomena. After discussing efforts to constrain the amounts of Ni-57 and Ti-44 produced in SN 1987A, attention is given to the production of Al-27 in massive stars and SNs. A 'delayed detonation' model of type Ia SNs is proposed, and the gamma-ray signal which may be expected when a bare white dwarf collapses directly into a neutron star is discussed.

  8. Gamma-ray bursts as cosmological probes

    Science.gov (United States)

    Vergani, S. D.

    2013-11-01

    Gamma-ray bursts (GRBs) are short, intense burstsof gamma-rays which during seconds to minutes outshine all other sources of gamma-ray emission in the sky.Following the prompt gamma-ray emission, an `afterglow' of emission from the X-ray range to radio wavelengthspersists up to months after the initial burst. The association of the class of long GRBs with the explosion of broad-line type Ic SNe GRBs allow galaxies to be selected independently oftheir emission properties (independently of dust obscuration and, uniquely, independently of their brightnesses atany wavelength) and they also permit the study of the gas in the interstellar medium (ISM) systematically and at anyredshift by the absorption lines present in the afterglow spectra. Moreover, the fading nature of GRBs and theprecise localization of the afterglow allow a detailed investigation of the emission properties of the GRB hostgalaxy once the afterglow has vanished. GRBs therefore constitute a unique tool to understand the link between theproperties of the ISM in the galaxy and the star formation activity, and this at any redshift. This is a unique wayto reveal the physical processes that trigger galaxy formation. The SVOM space mission project is designed to improve the use GRBs as cosmological probes.

  9. Field analyses of (238)U and (226)Ra in two uranium mill tailings piles from Niger using portable HPGe detector.

    Science.gov (United States)

    Déjeant, Adrien; Bourva, Ludovic; Sia, Radia; Galoisy, Laurence; Calas, Georges; Phrommavanh, Vannapha; Descostes, Michael

    2014-11-01

    The radioactivities of (238)U and (226)Ra in mill tailings from the U mines of COMINAK and SOMAÏR in Niger were measured and quantified using a portable High-Purity Germanium (HPGe) detector. The (238)U and (226)Ra activities were measured under field conditions on drilling cores with 600s measurements and without any sample preparation. Field results were compared with those obtained by Inductive Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and emanometry techniques. This comparison indicates that gamma-ray absorption by such geological samples does not cause significant deviations. This work shows the feasibility of using portable HPGe detector in the field as a preliminary method to observe variations of radionuclides concentration with the aim of identifying samples of interest. The HPGe is particularly useful for samples with strong secular disequilibrium such as mill tailings. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. A theory of gamma-ray bursts

    NARCIS (Netherlands)

    Brown, G.E.; Lee, C.-H.; Wijers, R.A.M.J.; Lee, H.K.; Israelian, G.; Bethe, H.A.

    2000-01-01

    Recent observations and theoretical considerations have linked gamma-ray bursts with ultra-bright type Ibc supernovae (`hypernovae'). We here work out a specific scenario for this connection. Based on earlier work, we argue that especially the longest bursts must be powered by the Blandford-Znajek

  11. Black Hole Accretion in Gamma Ray Bursts

    Directory of Open Access Journals (Sweden)

    Agnieszka Janiuk

    2017-02-01

    Full Text Available We study the structure and evolution of the hyperaccreting disks and outflows in the gamma ray bursts central engines. The torus around a stellar mass black hole is composed of free nucleons, Helium, electron-positron pairs, and is cooled by neutrino emission. Accretion of matter powers the relativistic jets, responsible for the gamma ray prompt emission. The significant number density of neutrons in the disk and outflowing material will cause subsequent formation of heavier nuclei. We study the process of nucleosynthesis and its possible observational consequences. We also apply our scenario to the recent observation of the gravitational wave signal, detected on 14 September 2015 by the two Advanced LIGO detectors, and related to an inspiral and merger of a binary black hole system. A gamma ray burst that could possibly be related with the GW150914 event was observed by the Fermi satellite. It had a duration of about 1 s and appeared about 0.4 s after the gravitational-wave signal. We propose that a collapsing massive star and a black hole in a close binary could lead to the event. The gamma ray burst was powered by a weak neutrino flux produced in the star remnant’s matter. Low spin and kick velocity of the merged black hole are reproduced in our simulations. Coincident gravitational-wave emission originates from the merger of the collapsed core and the companion black hole.

  12. HYPERNUCLEAR STRUCTURE FROM GAMMA-RAY SPECTROSCOPY.

    Energy Technology Data Exchange (ETDEWEB)

    MILLENER,D.J.

    2003-10-14

    The energies of p-shell hypernuclear {gamma} rays obtained from recent experiments using the Hyperball at BNL and KEK are used to constrain the YN interaction which enters into shell-model calculations which include both {Lambda} and {Sigma} configurations.

  13. Radio Afterglows of Gamma Ray Bursts

    Indian Academy of Sciences (India)

    Lekshmi Resmi

    2017-09-12

    Sep 12, 2017 ... Gamma Ray Bursts (GRBs) were serendipitously discovered in late 1960s by the Vela military satel- lites. In the following years, dedicated scanning instru- ments on-board high energy missions like BeppoSAX1,. CGRO2, HETE3, Swift4 and Fermi5 have increased the number of GRB detections to several ...

  14. Gamma-Ray Telescope and Uncertainty Principle

    Science.gov (United States)

    Shivalingaswamy, T.; Kagali, B. A.

    2012-01-01

    Heisenberg's Uncertainty Principle is one of the important basic principles of quantum mechanics. In most of the books on quantum mechanics, this uncertainty principle is generally illustrated with the help of a gamma ray microscope, wherein neither the image formation criterion nor the lens properties are taken into account. Thus a better…

  15. Gamma Ray Signatures of Neutrons From a Terrestrial Gamma Ray Flash

    Science.gov (United States)

    Bowers, G. S.; Smith, D. M.; Martinez-McKinney, G. F.; Kamogawa, M.; Cummer, S. A.; Dwyer, J. R.; Wang, D.; Stock, M.; Kawasaki, Z.

    2017-10-01

    Following a lightning strike to a wind turbine in Japan, we have observed a large burst of neutrons lasting 100 ms with a ground fluence of 1,000 n cm-2, thousands of times greater than the peak neutron flux associated with the largest ground level solar particle event ever observed. This is the first detection of an unequivocal signature of neutrons from a terrestrial gamma ray flash, consisting of a 2.223 MeV gamma-ray spectral line from a neutron-capture on hydrogen reaction occurring in our detector, and is shown to be consistent with the production of 1012-1013 photoneutrons from a downward terrestrial gamma ray flash (TGF) at 1.0 km, with a gamma ray brightness typical of upward TGFs observed by satellites.

  16. Diagnosing ICF gamma-ray physics

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, Hans W [Los Alamos National Laboratory; Kim, Y H [Los Alamos National Laboratory; Mc Evoy, A [Los Alamos National Laboratory; Young, C S [Los Alamos National Laboratory; Mack, J M [Los Alamos National Laboratory; Hoffman, N [Los Alamos National Laboratory; Wilson, D C [Los Alamos National Laboratory; Langenbrunner, J R [Los Alamos National Laboratory; Evans, S [Los Alamos National Laboratory; Sedillo, T [Los Alamos National Laboratory; Batha, S H [Los Alamos National Laboratory; Dauffy, L [LLNL; Stoeffl, W [LLNL; Malone, R [Los Alamos National Laboratory; Kaufman, M I [Los Alamos National Laboratory; Cox, B C [Los Alamos National Laboratory; Tunnel, T W [Los Alamos National Laboratory; Miller, E K [NSTEC/SB; Ali, Z A [NSREC/LIVERMORE; Horsfield, C J [AWE; Rubery, M [AWE

    2010-01-01

    Gamma rays produced in an ICF environment open up a host of physics opportunities we are just beginning to explore. A branch of the DT fusion reaction, with a branching ratio on the order of 2e-5 {gamma}/n, produces 16.7 MeV {gamma}-rays. These {gamma}-rays provide a direct measure of fusion reaction rate (unlike x-rays) without being compromised by Doppler spreading (unlike neutrons). Reaction-rate history measurements, such as nuclear bang time and burn width, are fundamental quantities that will be used to optimize ignition on the National Ignition Facility (NIF). Gas Cherenkov Detectors (GCD) that convert fusion {gamma}-rays to UV/visible Cherenkov photons for collection by fast optical recording systems established their usefulness in illuminating ICF physics in several experimental campaigns at OMEGA. Demonstrated absolute timing calibrations allow bang time measurements with accuracy better than 30 ps. System impulse response better than 95 ps fwhm have been made possible by the combination of low temporal dispersion GCDs, ultra-fast microchannel-plate photomultiplier tubes (PMT), and high-bandwidth Mach Zehnder fiber optic data links and digitizers, resulting in burn width measurement accuracy better than 10ps. Inherent variable energy-thresholding capability allows use of GCDs as {gamma}-ray spectrometers to explore other interesting nuclear processes. Recent measurements of the 4.44 MeV {sup 12}C(n,n{prime}) {gamma}-rays produced as 14.1 MeV DT fusion neutrons pass through plastic capsules is paving the way for a new CH ablator areal density measurement. Insertion of various neutron target materials near target chamber center (TCC) producing secondary, neutron-induced {gamma}y-rays are being used to study other nuclear interactions and as in-situ sources to calibrate detector response and DT branching ratio. NIF Gamma Reaction History (GRH) diagnostics, based on the GCD concept, are now being developed based on optimization of sensitivity, bandwidth

  17. The Future of Gamma Ray Astrophysics

    CERN Multimedia

    CERN. Geneva

    2016-01-01

    Over the past decade, gamma ray astrophysics has entered the astrophysical mainstream. Extremely successful space-borne (GeV) and ground-based (TeV) detectors, combined with a multitude of partner telescopes, have revealed a fascinating “astroscape" of active galactic nuclei, pulsars, gamma ray bursts, supernova remnants, binary stars, star-forming galaxies, novae much more, exhibiting major pathways along which large energy releases can flow. From  a basic physics perspective, exquisitely sensitive measurements have constrained the nature of dark matter, the cosmological origin of magnetic field and the properties of black holes. These advances have motivated the development of new facilities, including HAWC, DAMPE, CTA and SVOM, which will further our understanding of the high energy universe. Topics that will receive special attention include merging neutron star binaries, clusters of galaxies, galactic cosmic rays and putative, TeV dark matter.

  18. Simultaneous optical/gamma-ray observations of GRBs

    Science.gov (United States)

    Greiner, J.; Wenzel, W.; Hudec, R.; Moskalenko, E. I.; Metlov, V.; Chernych, N. S.; Getman, V. S.; Ziener, Rainer; Birkle, K.; Bade, N.

    1994-01-01

    Details on the project to search for serendipitous time correlated optical photographic observations of Gamma Ray Bursters (GRB's) are presented. The ongoing photographic observations at nine observatories are used to look for plates which were exposed simultaneously with a gamma ray burst detected by the gamma ray instrument team (BATSE) and contain the burst position. The results for the first two years of the gamma ray instrument team operation are presented.

  19. Balloon-borne gamma-ray telescope with nuclear emulsion

    OpenAIRE

    Takahashi, Satoru; Group, for the Emulsion Gamma-ray Telescope

    2010-01-01

    By detecting the beginning of electron pairs with nuclear emulsion, precise gamma-ray direction and gamma-ray polarization can be detected. With recent advancement in emulsion scanning system, emulsion analyzing capability is becoming powerful. Now we are developing the balloon-borne gamma-ray telescope with nuclear emulsion. Overview and status of our telescope is described.

  20. U and Pu: some nuclear data by gamma-ray spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Delgado, Jose U.; Silva, Ronaldo L. da; Poledna, R.; Almeida, Maria Candida M. de, E-mail: delgado@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RH (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI); Estrada, Julio J. da S. [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Secao de Engenharia Nuclear

    2009-07-01

    The precise knowledge of nuclear parameters like energy and emission probability for uranium and plutonium radionuclides is very important for the correct determination of the isotopic ratio or activity determinations. By means of gamma-ray spectrometry it is possible to obtain these parameters, but in the region below 300 keV it is more critical. The published values for their main decay data exhibit significant differences. A new methodology was developed using a nonlinear regression program to fit the calibration curves in energy, resolution and efficiency of a HPGe detector. The results obtained by means new curve fitting software appear to be consistent in that region for energy, and the uncertainties exhibit improvements compared the published data. Consistent results were also obtained in an energy region extended to 1100 keV. (author)

  1. Stellar Photon Archaeology with Gamma-Rays

    Science.gov (United States)

    Stecker, Floyd W.

    2009-01-01

    Ongoing deep surveys of galaxy luminosity distribution functions, spectral energy distributions and backwards evolution models of star formation rates can be used to calculate the past history of intergalactic photon densities and, from them, the present and past optical depth of the Universe to gamma-rays from pair production interactions with these photons. The energy-redshift dependence of the optical depth of the Universe to gamma-rays has become known as the Fazio-Stecker relation (Fazio & Stecker 1970). Stecker, Malkan & Scully have calculated the densities of intergalactic background light (IBL) photons of energies from 0.03 eV to the Lyman limit at 13.6 eV and for 0$ photon densities in the past, i.e., the "archaeo-IBL.", and therefore allow a better measure of the past history of the total star formation rate, including that from galaxies too faint to be observed.

  2. Gamma Ray Bursts Observations and Theoretical Conjectures

    CERN Document Server

    Alagoz, E; Carrillo, C; Golup, G T; Grimes, M; Herrera, Mora C; Gallo, Palomino J L; López, Vega A; Wicht, J

    2008-01-01

    Gamma Ray Bursts (GRBs) are short bursts of very high energy photons which were discovered in the late 1960s. Ever since their discovery, scientists have wondered about their origin. Nowadays it is known that they originate outside the Milky Way because of their high red shift rst measured in the afterglows thanks to the Beppo-SAX satellite and ground-based observations. However, theoreticians still do not agree about the mechanism that generates the bursts, and different competing models are animatedly debated. Current GRB experiments include the Swift satellite and the Pierre Auger Observatory that could detect GRBs with an increase of the background. A forthcoming dedicated experiment is GLAST, a satellite observatory for detecting gamma rays with energies up to 300 GeV, whose launch is scheduled for early 2008.

  3. Real time gamma-ray signature identifier

    Science.gov (United States)

    Rowland, Mark [Alamo, CA; Gosnell, Tom B [Moraga, CA; Ham, Cheryl [Livermore, CA; Perkins, Dwight [Livermore, CA; Wong, James [Dublin, CA

    2012-05-15

    A real time gamma-ray signature/source identification method and system using principal components analysis (PCA) for transforming and substantially reducing one or more comprehensive spectral libraries of nuclear materials types and configurations into a corresponding concise representation/signature(s) representing and indexing each individual predetermined spectrum in principal component (PC) space, wherein an unknown gamma-ray signature may be compared against the representative signature to find a match or at least characterize the unknown signature from among all the entries in the library with a single regression or simple projection into the PC space, so as to substantially reduce processing time and computing resources and enable real-time characterization and/or identification.

  4. The cannonball model of gamma ray bursts

    CERN Document Server

    Dar, Arnon

    2003-01-01

    The cannonball model (CB) of gamma ray bursts (GRBs) is incredibly more successful than the standard blast-wave models (SM) of GRBs, which suffer from profound inadequacies and limited predictive power. The CB model is falsifiable in its hypothesis and results. Its predictions are summarized in simple analytical expressions, derived, in fair approximations, from first principles. It provides a good description on a universal basis of the properties of long-duration GRBs and of their afterglows (AGs).

  5. Nucleosynthesis and gamma-ray lines

    OpenAIRE

    Prantzos, Nikos

    2011-01-01

    Astrophysical gamma-ray spectroscopy is an invaluable tool for studying nuclear astrophysics, supernova structure, recent star formation in the Milky Way and mixing of nucleosynthesis products in the interstellar medium. After a short, historical, introduction to the field, I present a brief review of the most important current issues. Emphasis is given to radioactivities produced by massive stars and associated supernova explosions, and in particular, those related to observations carried ou...

  6. RADIO FLARES FROM GAMMA-RAY BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J. [Astrophysics Research Institute, Liverpool John Moores University, Liverpool, L3 5RF (United Kingdom); Harrison, R. [Department of Astrophysics, School of Physics and Astronomy, Tel Aviv University, 69978 Tel Aviv (Israel); Japelj, J.; Gomboc, A. [Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, 1000 Ljubljana (Slovenia); Guidorzi, C. [Department of Physics and Earth Sciences, University of Ferrara, Via Saragat, 1, I-44122 Ferrara (Italy); Melandri, A., E-mail: D.Kopac@ljmu.ac.uk [INAF/Brera Astronomical Observatory, via Bianchi 46, I-23807, Merate (Italy)

    2015-06-20

    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.

  7. Gamma-Ray Pulsars Models and Predictions

    CERN Document Server

    Harding, A K

    2001-01-01

    Pulsed emission from gamma-ray pulsars originates inside the magnetosphere, from radiation by charged particles accelerated near the magnetic poles or in the outer gaps. In polar cap models, the high energy spectrum is cut off by magnetic pair production above an energy that is dependent on the local magnetic field strength. While most young pulsars with surface fields in the range B = 10^{12} - 10^{13} G are expected to have high energy cutoffs around several GeV, the gamma-ray spectra of old pulsars having lower surface fields may extend to 50 GeV. Although the gamma-ray emission of older pulsars is weaker, detecting pulsed emission at high energies from nearby sources would be an important confirmation of polar cap models. Outer gap models predict more gradual high-energy turnovers at around 10 GeV, but also predict an inverse Compton component extending to TeV energies. Detection of pulsed TeV emission, which would not survive attenuation at the polar caps, is thus an important test of outer gap models. N...

  8. Highlights of GeV Gamma-Ray Astronomy

    Science.gov (United States)

    Thompson, David J.

    2010-01-01

    Because high-energy gamma rays are primarily produced by high-energy particle interactions, the gamma-ray survey of the sky by the Fermi Gamma-ray Space Telescope offers a view of sites of cosmic ray production and interactions. Gamma-ray bursts, pulsars, pulsar wind nebulae, binary sources, and Active Galactic Nuclei are all phenomena that reveal particle acceleration through their gamma-ray emission. Diffuse Galactic gamma radiation, Solar System gamma-ray sources, and energetic radiation from supernova remnants are likely tracers of high-energy particle interactions with matter and photon fields. This paper will present a broad overview of the constantly changing sky seen with the Large Area Telescope (LAT) on the Fermi spacecraft.

  9. A new measurement of the gamma-ray intensities of sup 234m Pa accompanying the decay of sup 238 U

    Energy Technology Data Exchange (ETDEWEB)

    Siemon, K.; Esterlund, R.A.; Aarle, J. van; Knaack, M.; Patzelt, P. (Marburg Univ. (Germany). Inst. fuer Kernchemie); Westmeier, W. (Gesellschaft fuer Kernspektrometrie mbH, Ebsdorfergrund-Moelln (Germany))

    1992-07-01

    Gamma-ray lines following the decay of {sup 234m}Pa were assayed via high-purity germanium-crystal (HPGe) spectrometry of analytical-grade foils of depleted uranium metal. Absolute intensities were determined for the strongest lines (I{sub {gamma}} {>=} 0.002%), with special emphasis on the 1001 keV line, which is often used for either assay or normalization purposes. The I{sub {gamma}} value derived for this latter line was independently confirmed in two further measurements, in which its intensity relative to the 185.7 keV gamma line which accompanies the decay of {sup 235}U was compared. Our new value for the absolute intensity of this line I{sub {gamma}} (1001 keV) is (0.845 {+-} 0.021)%, which is over 1.4 times greater than the currently-accepted value. (author).

  10. Localization of Gamma-Ray Bursts using the Fermi Gamma-Ray Burst Monitor

    OpenAIRE

    Connaughton, V.; Briggs, M. S.; Goldstein, A.; Meegan, C. A.; Paciesas, W. S.; Preece, R. D.; Wilson-Hodge, C.A.; Gibby, M. H.; Greiner, J.; Gruber, D.; Jenke, P.; Kippen, R. M.; Pelassa, V.; Xiong, S.; Yu, H-F

    2014-01-01

    The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 Gamma-Ray Bursts (GRBs) since it began science operations in July, 2008. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the InterPlanetary Network (IPN), to analyze the accuracy of GBM GRB localizations. We find that the reported statistical uncertainties on GBM localizations, which can be as small as 1 degree, underestimat...

  11. Gamma-Ray Bursts and Cosmology

    Science.gov (United States)

    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.

  12. Polarized gamma-rays with laser-Compton backscattering

    Energy Technology Data Exchange (ETDEWEB)

    Ohgaki, H.; Noguchi, T.; Sugiyama, S. [Electrotechnical Lab., Ibaraki (Japan)] [and others

    1995-12-31

    Polarized gamma-rays were generated through laser-Compton backscattering (LCS) of a conventional Nd:YAG laser with electrons circulating in the electron storage ring TERAS at Electrotechnical Laboratory. We measured the energy, the energy spread, and the yield of the gamma-rays to characterize our gamma-ray source. The gamma-ray energy can be varied by changing the energy of the electrons circulating the storage ring. In our case, the energy of electrons in the storage ring were varied its energy from 200 to 750 MeV. Consequently, we observed gamma-ray energies of 1 to 10 MeV with 1064 run laser photons. Furthermore, the gamma-ray energy was extended to 20 MeV by using the 2nd harmonic of the Nd:YAG laser. This shows a good agreement with theoretical calculation. The gamma-ray energy spread was also measured to be 1% FWHM for -1 MeV gamma-rays and to be 4% FWHM for 10 MeV gamma-rays with a narrow collimator that defined the scattering cone. The gamma-ray yield was 47.2 photons/mA/W/s. This value is consistent with a rough estimation of 59.5 photons/mA/W/s derived from theory. Furthermore, we tried to use these gamma-rays for a nuclear fluorescence experiment. If we use a polarized laser beam, we can easily obtain polarized gamma-rays. Elastically scattered photons from {sup 208} Pb were clearly measured with the linearly polarized gamma-rays, and we could assign the parity of J=1 states in the nucleus. We should emphasize that the polarized gamma-ray from LCS is quit useful in this field, because we can use highly, almost completely, polarized gamma-rays. We also use the LCS gamma-rays to measure the photon absorption coefficients. In near future, we will try to generate a circular polarized gamma-ray. We also have a plan to use an FEL, because it can produce intense laser photons in the same geometric configuration as the LCS facility.

  13. Gamma ray constraints on decaying dark matter

    DEFF Research Database (Denmark)

    Cirelli, M.; Moulin, E.; Panci, P.

    2012-01-01

    We derive new bounds on decaying dark matter from the gamma ray measurements of (i) the isotropic residual (extragalactic) background by Fermi and (ii) the Fornax galaxy cluster by H.E.S.S. We find that those from (i) are among the most stringent constraints currently available, for a large range...... of dark matter masses and a variety of decay modes, excluding half-lives up to similar to 10(26) to few 10(27) seconds. In particular, they rule out the interpretation in terms of decaying dark matter of the e(+/-) spectral features in PAMELA, Fermi and H.E.S.S., unless very conservative choices...

  14. Characteristics of Gamma-Ray Line Flares,

    Science.gov (United States)

    1983-10-01

    extended-burst flares (Royng, Brown, and van Beek 1976). The R a classifications of these flares are 3B. The next veill -observed gamma-ray line flare...R.., Kiplinger, A. L., Orwig, L. K., and Frost, K. J. 1983a, Solar Phys. (in press ). Bai, T., Hudson, H. S., Pelling, R. M., Lin, R. P., Schwartz, R...409. 32 112________k__________ ____________1983, Solar Phys. (in press ). Chupp, E. L., Forrest, D. J., Higbie, P. R., Suni, A. N., Tsai, C., and Dunphy

  15. Gamma ray bursts observed with WATCH‐EURECA

    DEFF Research Database (Denmark)

    Brandt, Søren; Lund, Niels; Castro-Tirado, A. J.

    1994-01-01

    The WATCH wide field x‐ray monitor has the capability of independently locating bright Gamma Ray Bursts to 1° accuracy. We report the preliminary positions of 12 Gamma Ray Bursts observed with the WATCH monitor flown on the ES spacecraft EURECA during its 11 month mission. Also the recurrence...

  16. The First Fermi-LAT Gamma-Ray Burst Catalog

    NARCIS (Netherlands)

    Ackermann, M.; et al., [Unknown; van der Horst, A.J.

    2013-01-01

    In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (gsim 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected

  17. Determination of intergalactic magnetic fields from gamma ray data

    NARCIS (Netherlands)

    Essey, W.; Ando, S.; Kusenko, A.

    2011-01-01

    We report a measurement of intergalactic magnetic fields using combined data from Atmospheric Cherenkov Telescopes and Fermi Gamma-Ray Space Telescope, based on the spectral data alone. If blazars are assumed to produce both gamma rays and cosmic rays, the observed spectra are not sensitive to the

  18. Superluminal blazars and the extragalactic gamma ray background

    Energy Technology Data Exchange (ETDEWEB)

    Xinyu Chi; Young, Enoch C.M. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong (China)

    1997-07-01

    The detection of a few dozen extragalactic gamma ray blazars of extremely high luminosity by the EGRET instrument on board the Compton Gamma Ray Observatory appears to suggest that blazars make the overwhelming contribution to the cosmic gamma ray background in the energy range 100 MeV - 10 GeV. In this paper we point out that the superluminal effect which boosts and beams the gamma ray emission in the jets of blazars will flatten the source count in the low flux part. Consequently, the unresolved blazars would not be expected to make much contribution to the gamma ray background. From our direct modelling of the source count, we conclude that the contribution of the unresolved blazars to the gamma ray background is only 10% of the latest estimate of the EGRET data. The implication for the cosmological evolution of the blazars is discussed. (author)

  19. High Energy Gamma-Ray Emission from Gamma-Ray Bursts - Before GLAST

    Energy Technology Data Exchange (ETDEWEB)

    Fan, Yi-Zhong; Piran, Tsvi

    2011-11-29

    Gamma-ray bursts (GRBs) are short and intense emission of soft {gamma}-rays, which have fascinated astronomers and astrophysicists since their unexpected discovery in 1960s. The X-ray/optical/radio afterglow observations confirm the cosmological origin of GRBs, support the fireball model, and imply a long-activity of the central engine. The high-energy {gamma}-ray emission (> 20 MeV) from GRBs is particularly important because they shed some lights on the radiation mechanisms and can help us to constrain the physical processes giving rise to the early afterglows. In this work, we review observational and theoretical studies of the high-energy emission from GRBs. Special attention is given to the expected high-energy emission signatures accompanying the canonical early-time X-ray afterglow that was observed by the Swift X-ray Telescope. We also discuss the detection prospect of the upcoming GLAST satellite and the current ground-based Cerenkov detectors.

  20. SYSTEMATIC STUDY OF GAMMA-RAY-BRIGHT BLAZARS WITH OPTICAL POLARIZATION AND GAMMA-RAY VARIABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Itoh, Ryosuke; Fukazawa, Yasushi; Kanda, Yuka; Shiki, Kensei; Kawabata, Miho; Nakaoka, Tatsuya; Takaki, Katsutoshi; Takata, Koji; Ui, Takahiro [Department of Physical Science, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Nalewajko, Krzysztof; Madejski, Greg M. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road M/S 29, Menlo Park, CA 94025 (United States); Uemura, Makoto; Tanaka, Yasuyuki T.; Kawabata, Koji S.; Akitaya, Hiroshi; Ohsugi, Takashi [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Schinzel, Frank K. [Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131 (United States); Moritani, Yuki [Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo Institutes for Advanced Study, The University of Tokyo, Kashiwa, Chiba 277-8583 (Japan); Sasada, Mahito [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Yamanaka, Masayuki, E-mail: itoh@hep01.hepl.hiroshima-u.ac.jp, E-mail: itoh@hp.phys.titech.ac.jp [Department of Physics, Faculty of Science and Engineering, Konan University, Okamoto, Kobe, Hyogo 658-8501 (Japan); and others

    2016-12-10

    Blazars are highly variable active galactic nuclei that emit radiation at all wavelengths from radio to gamma rays. Polarized radiation from blazars is one key piece of evidence for synchrotron radiation at low energies, and it also varies dramatically. The polarization of blazars is of interest for understanding the origin, confinement, and propagation of jets. However, even though numerous measurements have been performed, the mechanisms behind jet creation, composition, and variability are still debated. We performed simultaneous gamma-ray and optical photopolarimetry observations of 45 blazars between 2008 July and 2014 December to investigate the mechanisms of variability and search for a basic relation between the several subclasses of blazars. We identify a correlation between the maximum degree of optical linear polarization and the gamma-ray luminosity or the ratio of gamma-ray to optical fluxes. Since the maximum polarization degree depends on the condition of the magnetic field (chaotic or ordered), this result implies a systematic difference in the intrinsic alignment of magnetic fields in parsec-scale relativistic jets between different types of blazars (flat-spectrum radio quasars vs. BL Lacs) and consequently between different types of radio galaxies (FR I versus FR II).

  1. The Theory of Gamma-Ray Bursts

    Science.gov (United States)

    Dai, Zigao; Daigne, Frédéric; Mészáros, Peter

    2017-10-01

    This chapter gives a brief review on the theory of gamma-ray bursts (GRBs), including the models of multi-messengers (e.g., prompt multiwavelength electromagnetic emissions, high-energy neutrinos, ultra-high-energy cosmic rays, and gravitational waves) and central engines (in particular, mergers of binary neutron stars for short GRBs). For detailed reviews, please see (Piran in Phys. Rep. 314:575, 1999; Rev. Mod. Phys. 76:1143, 2004; Mészáros in Annu. Rev. Astron. Astrophys. 40:137, 2002; Rep. Prog. Phys. 69:2259, 2006; Zhang and Mészáros in Int. J. Mod. Phys. A 19:2385, 2004; Zhang in Chin. J. Astron. Astrophys. 7:1, 2007; Nakar in Phys. Rep. 442:166, 2007; Kumar and Zhang in Phys. Rep. 561:1, 2015).

  2. EXIST's Gamma-Ray Burst Sensitivity

    Science.gov (United States)

    Band, D. L.; Grindlay, J. E.; Hong, J.; Fishman, G.; Hartmann, D. H.; Garson, A., III; Krawczynski, H.; Barthelmy, S.; Gehrels, N.; Skinner, G.

    2008-02-01

    We use semianalytic techniques to evaluate the burst sensitivity of designs for the EXIST hard X-ray survey mission. Applying these techniques to the mission design proposed for the Beyond Einstein program, we find that with its very large field of view and faint gamma-ray burst detection threshold, EXIST will detect and localize approximately two bursts per day, a large fraction of which may be at high redshift. We estimate that EXIST's maximum sensitivity will be ~4 times greater than that of Swift's Burst Alert Telescope. Bursts will be localized to better than 40'' at threshold, with a burst position as good as a few arcseconds for strong bursts. EXIST's combination of three different detector systems will provide spectra from 3 keV to more than 10 MeV. Thus, EXIST will enable a major leap in the understanding of bursts, their evolution, environment, and utility as cosmological probes.

  3. Lingering Problems in Gamma-Ray Observations of GRBs

    Science.gov (United States)

    Meegan, Charles A.

    2000-01-01

    Although observations of Gamma Ray Bursts (GRBs) in other wavelengths have transformed the field, the gamma-ray region of the spectrum remains important. This talk will summarize a number of unresolved issues specific to gamma-ray observations. For example, the apparent narrowness of the distribution of peak energy is difficult to explain either as an intrinsic characteristic of bursts or as a selection effect. There have also been controversial claims for anisotropy in subgroups of bursts.

  4. News from Cosmic Gamma-ray Line Observations

    OpenAIRE

    Diehl, Roland

    2016-01-01

    The measurement of gamma rays at MeV energies from cosmic radioactivities is one of the key tools for nuclear astrophysics, in its study of nuclear reactions and how they shape objects such as massive stars and supernova explosions. Additionally, the unique gamma-ray signature from the annihilation of positrons falls into this same astronomical window, and positrons are often produced from radioactive beta decays. Nuclear gamma-ray telescopes face instrumental challenges from penetrating gamm...

  5. Fermi Large Area Telescope Bright Gamma-ray Source List

    Energy Technology Data Exchange (ETDEWEB)

    Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /KIPAC, Menlo Park /SLAC; Ajello, M.; /KIPAC, Menlo Park /SLAC; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M.; /Stockholm U., OKC /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Band, D.L.; /NASA, Goddard /NASA, Goddard; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bastieri, Denis; /INFN, Padua /Padua U.; Bechtol, K.; /KIPAC, Menlo Park /SLAC; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /KIPAC, Menlo Park /SLAC; Bignami, G.F.; /Pavia U.; Bloom, Elliott D.; /KIPAC, Menlo Park /SLAC; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /KIPAC, Menlo Park /SLAC; Bregeon, J.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle /Bari U. /INFN, Bari /KIPAC, Menlo Park /SLAC /IASF, Milan /IASF, Milan /DAPNIA, Saclay /ASDC, Frascati /INFN, Perugia /Perugia U. /KIPAC, Menlo Park /SLAC /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /KIPAC, Menlo Park /SLAC /INFN, Perugia /Perugia U. /KIPAC, Menlo Park /SLAC /Montpellier U. /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /KIPAC, Menlo Park /SLAC /ASDC, Frascati /NASA, Goddard /Maryland U. /Naval Research Lab, Wash., D.C. /INFN, Trieste /Pavia U. /Bari U. /INFN, Bari /KIPAC, Menlo Park /SLAC /UC, Santa Cruz /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /KIPAC, Menlo Park /SLAC /Montpellier U. /Bari U. /INFN, Bari /Ecole Polytechnique /NASA, Goddard; /more authors..

    2009-05-15

    Following its launch in 2008 June, the Fermi Gamma-ray Space Telescope (Fermi) began a sky survey in August. The Large Area Telescope (LAT) on Fermi in three months produced a deeper and better resolved map of the {gamma}-ray sky than any previous space mission. We present here initial results for energies above 100 MeV for the 205 most significant (statistical significance greater than {approx}10{sigma}) {gamma}-ray sources in these data. These are the best characterized and best localized point-like (i.e., spatially unresolved) {gamma}-ray sources in the early mission data.

  6. Review of GRANAT observations of gamma-ray bursts

    DEFF Research Database (Denmark)

    Terekhov, O.; Denissenko, D.; Sunyaev, R.

    1995-01-01

    of the observations of the time histories and spectral evolution of the detected events provided by the different instruments in different energy ranges. Short Gamma-Ray Bursts (histories. They have harder energy spectra than the long (> 2 s) events. Evidence of the existence...... of four differently behaving componenents in gamma-ray burst spectra is discussed. Statistical properties of the gamma-ray burst sources based on the 5 years of observations with (∼ 10−6 erg/cm2) sensitivity as well as the results of high sensitivity (∼ 10−8 erg/cm2) search for Gamma-Ray Bursts within...

  7. Gamma-ray burst interaction with dense interstellar medium

    OpenAIRE

    Barkov, Maxim; Bisnovatyi-Kogan, Gennady

    2004-01-01

    Interaction of cosmological gamma ray burst radiation with the dense interstellar medium of host galaxy is considered. Gas dynamical motion of interstellar medium driven by gamma ray burst is investigated in 2D approximation for different initial density distributions of host galaxy matter and different total energy of gamma ray burst. The maximum velocity of motion of interstellar medium is $1.8\\cdot10^4$ km/s. Light curves of gamma ray burst afterglow are calculated for set of non homogeneo...

  8. Mercuric Iodide Anticoincidence Shield for Gamma-Ray Spectrometer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We utilize a new detector material, polycrystalline mercuric iodide, for background suppression by active anticoincidence shielding in gamma-ray spectrometers. Two...

  9. Mercuric Iodide Anticoincidence Shield for Gamma-Ray Spectrometer Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose to utilize a new detector material, polycrystalline mercuric iodide, for background suppression by active anticoincidence shielding in gamma-ray...

  10. Radio and Gamma-ray Emission from Pulsars

    Science.gov (United States)

    Qiao, G. J.; Lee, K. J.; Wang, H. G.; Xu, R. X.

    The radiation of pulsars have been observed for many years. A few pulsars are discovered to have both radio and gamma-ray emission. Many models on pulsar radiation have been developed, but so far we are still lacking an elaborate model which can explain the emission from radio to gamma-rays in detail. In this paper we present a joint model for radio and gamma-ray emission, in which both the dominate emission mechanisms are inverse Compton scattering. The pulse profiles at radio and gamma-ray bands are reproduced for the Crab-like, Vela-like and Geminga-like pulsars, in good agreement with observations.

  11. A gamma-ray tracking algorithm for the GRETA spectrometer

    CERN Document Server

    Schmid, G J; Lee, I Y; Stephens, F S; Vetter, K; Clark, R M; Diamond, R M; Fallon, P; Macchiavelli, A O; MacLeod, R W

    1999-01-01

    We discuss a gamma-ray tracking algorithm that has been developed for the proposed gamma-ray energy tracking array (GRETA). This algorithm has been designed so as to maximize the resolving power for detecting high-multiplicity gamma-ray events. The conceptual basis for this algorithm will be presented. In addition, Monte Carlo simulated data will be used to assess performance over a large range of relevant parameters. A discussion of the potential gamma-ray polarimeter performance of GRETA is also presented.

  12. A new processing technique for airborne gamma-ray data

    DEFF Research Database (Denmark)

    Hovgaard, Jens

    1997-01-01

    The mathematical-statistical background for at new technique for processing gamma-ray spectra is presented. The technique - Noise Adjusted Singular Value Decomposition - decomposes at set of gamma-ray spectra into a few basic spectra - the spectral components. The spectral components can be proce......The mathematical-statistical background for at new technique for processing gamma-ray spectra is presented. The technique - Noise Adjusted Singular Value Decomposition - decomposes at set of gamma-ray spectra into a few basic spectra - the spectral components. The spectral components can...... be processed in different ways aiming at getting new information that cannot be directly extracted from the original spectra....

  13. Fermi Bubbles: an elephant in the gamma-ray sky

    Directory of Open Access Journals (Sweden)

    Malyshev Dmitry

    2017-01-01

    Full Text Available The Fermi bubbles are one of the most remarkable features in the gamma-ray sky revealed by the Fermi Large Area Telescope (LAT. The nature of the gamma-ray emission and the origin of the bubbles are still open questions. In this note, we will review some basic features of leptonic and hadronic modes of gamma-ray production. At the moment, gamma rays are our best method to study the bubbles, but in order to resolve the origin of the bubbles multi-wavelength and multi-messenger observations will be crucial.

  14. Measuring Cosmological Parameters with Gamma Ray Bursts

    Science.gov (United States)

    Amati, Lorenzo; Della Valle, Massimo

    2013-12-01

    In a few dozen seconds, gamma ray bursts (GRBs) emit up to 1054 erg in terms of an equivalent isotropically radiated energy Eiso, so they can be observed up to z 10. Thus, these phenomena appear to be very promising tools to describe the expansion rate history of the universe. Here, we review the use of the Ep,i-Eiso correlation of GRBs to measure the cosmological density parameter ΩM. We show that the present data set of GRBs, coupled with the assumption that we live in a flat universe, can provide independent evidence, from other probes, that ΩM 0.3. We show that current (e.g. Swift, Fermi/GBM, Konus-WIND) and forthcoming gamma ray burst (GRB) experiments (e.g. CALET/GBM, SVOM, Lomonosov/UFFO, LOFT/WFM) will allow us to constrain ΩM with an accuracy comparable to that currently exhibited by Type Ia supernovae (SNe-Ia) and to study the properties of dark energy and their evolution with time.

  15. Gamma-Ray Bursts: Characteristics and Prospects

    Science.gov (United States)

    Azzam, W. J.; Zitouni, H.; Guessoum, N.

    2017-06-01

    Gamma-ray bursts (GRBs) are the most powerful explosions in the universe. They have remained the object of intense research ever since their discovery was declassified in the early 1970s. Several space-borne missions have been dedicated to their study, including the Compton Gamma-Ray Burst Observatory (CGRO) in the 1990s and the current Swift and Fermi satellites. However, despite several decades of focused research, the precise mechanisms behind these enigmatic explosions have not been fully established. In the first part of this paper, we review what is currently known about GRBs. This includes: GRB light-curves and spectra; the different progenitor models, i.e., the "collapsar" and "merger" models; and the afterglow characteristics, including external shocks and the surrounding medium. In the second part of the paper, we present our work, which focuses on utilizing GRBs as cosmological probes. GRBs are ideal cosmological tools, because they have been observed to great distances (redshifts up to z = 9.4) and their radiation is unencumbered by any intervening dust. Although GRBs are not standard candles, the discovery of several energy and luminosity correlations, like the Amati relation which correlates the intrinsic spectral peak energy, Ep,i to the equivalent isotropic energy, Eiso , has ushered in a new era in which GRBs are used to investigate cosmological issues like the star formation rate and the value of the matter-density parameter, ΩM.

  16. The Most Remote Gamma-Ray Burst

    Science.gov (United States)

    2000-10-01

    ESO Telescopes Observe "Lightning" in the Young Universe Summary Observations with telescopes at the ESO La Silla and Paranal observatories (Chile) have enabled an international team of astronomers [1] to measure the distance of a "gamma-ray burst", an extremely violent, cosmic explosion of still unknown physical origin. It turns out to be the most remote gamma-ray burst ever observed . The exceedingly powerful flash of light from this event was emitted when the Universe was very young, less than about 1,500 million years old, or only 10% of its present age. Travelling with the speed of light (300,000 km/sec) during 11,000 million years or more, the signal finally reached the Earth on January 31, 2000. The brightness of the exploding object was enormous, at least 1,000,000,000,000 times that of our Sun, or thousands of times that of the explosion of a single, heavy star (a "supernova"). The ESO Very Large Telescope (VLT) was also involved in trail-blazing observations of another gamma-ray burst in May 1999, cf. ESO PR 08/99. PR Photo 28a/00 : Sky field near GRB 000131 . PR Photo 28b/00 : The fading optical counterpart of GRB 000131 . PR Photo 28c/00 : VLT spectrum of GRB 000131 . What are Gamma-Ray Bursts? One of the currently most active fields of astrophysics is the study of the mysterious events known as "gamma-ray bursts" . They were first detected in the late 1960's by instruments on orbiting satellites. These short flashes of energetic gamma-rays last from less than a second to several minutes. Despite much effort, it is only within the last few years that it has become possible to locate the sites of some of these events (e.g. with the Beppo-Sax satellite ). Since the beginning of 1997, astronomers have identified about twenty optical sources in the sky that are associated with gamma-ray bursts. They have been found to be situated at extremely large (i.e., "cosmological") distances. This implies that the energy release during a gamma-ray burst within a few

  17. A joint model of pulsar radio and gamma ray emission

    Science.gov (United States)

    Qiao, G.

    The radiation of radio pulsars have been observed from radio to gamma -rays for many years. Observations present abundance infor-mation. Theoretical models for radio and gamma-rays are presented separately. Until now we do not found a model can show emission from radio to gamma -rays at the same time detailedly. For a certain pul-sar, the emission from radio to gamma-rays can be observed at the same time (such as Crab pulsar and so on). So a reasonable model should present the emission from radio to gamma - rays at the same time more detailedly. A joint model for emission from radio to gamma -rays is presented in this paper. Which can show emission characters for both radio and gamma -ray emission band. Such as core and cone emis -s i o n beams at radio emission band, and gamma - rays for Geminga-like, Crab-like and Vela - like emission beams can be shown at the same time. First of all, an inverse Compton scattering model(ICS model, partly see ICS I A &A 1998; ICS II A &A 2001; ICS III ApJ 2000) of radio pulsars will be introduced more detailedly. Then a new model for gamma - ray emission will be introduced. In this model both radio and gamma-ray emission mechanisms are jointed, and the emission beams from radio to gamma -rays can be presented. Various kind of pulse profiles and other observational characteristics can be shown and the theory in agreement with observations well.

  18. Heterogeneity in Short Gamma-Ray Bursts

    Science.gov (United States)

    Norris, Jay P.; Gehrels Neil; Scargle, Jeffrey D.

    2011-01-01

    We analyze the Swift/BAT sample of short gamma-ray bursts, using an objective Bayesian Block procedure to extract temporal descriptors of the bursts' initial pulse complexes (IPCs). The sample comprises 12 and 41 bursts with and without extended emission (EE) components, respectively. IPCs of non-EE bursts are dominated by single pulse structures, while EE bursts tend to have two or more pulse structures. The medians of characteristic timescales - durations, pulse structure widths, and peak intervals - for EE bursts are factors of approx 2-3 longer than for non-EE bursts. A trend previously reported by Hakkila and colleagues unifying long and short bursts - the anti-correlation of pulse intensity and width - continues in the two short burst groups, with non-EE bursts extending to more intense, narrower pulses. In addition we find that preceding and succeeding pulse intensities are anti-correlated with pulse interval. We also examine the short burst X-ray afterglows as observed by the Swift/XRT. The median flux of the initial XRT detections for EE bursts (approx 6 X 10(exp -10) erg / sq cm/ s) is approx > 20 x brighter than for non-EE bursts, and the median X-ray afterglow duration for EE bursts (approx 60,000 s) is approx 30 x longer than for non-EE bursts. The tendency for EE bursts toward longer prompt-emission timescales and higher initial X-ray afterglow fluxes implies larger energy injections powering the afterglows. The longer-lasting X-ray afterglows of EE bursts may suggest that a significant fraction explode into more dense environments than non-EE bursts, or that the sometimes-dominant EE component efficiently p()wers the afterglow. Combined, these results favor different progenitors for EE and non-EE short bursts.

  19. Detection of explosive substances by tomographic inspection using neutron and gamma-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Farahmand, M. [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom)]. E-mail: mf@ns.ph.liv.ac.uk; Boston, A.J. [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Grint, A.N. [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Nolan, P.J. [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Joyce, M.J. [Department of Engineering, Lancaster University (United Kingdom); Mackin, R.O. [Department of Engineering, Lancaster University (United Kingdom); D' Mellow, B. [Department of Engineering, Lancaster University (United Kingdom); Aspinall, M. [Department of Engineering, Lancaster University (United Kingdom); Peyton, A.J. [Department of Engineering, University of Manchester (United Kingdom); Silfhout, R. van [Department of Engineering, University of Manchester (United Kingdom)

    2007-08-15

    In recent years the detection and identification of hazardous materials has become increasingly important. This work discusses research and development of a technique which is capable of detecting and imaging hidden explosives. It is proposed to utilise neutron interrogation of the substances under investigation facilitating the detection of emitted gamma radiation and scattered neutrons. Pulsed fast neutron techniques are attractive because they can be used to determine the concentrations of the light elements (hydrogen, carbon, nitrogen, and oxygen) which can be the primary components of explosive materials. Using segmented High Purity Ge (HPGe) detectors and digital pulse processing [R.J. Cooper, G. Turk, A.J. Boston, H.C. Boston, J.R. Cresswell, A.R. Mather, P.J. Nolan, C.J. Hall, I. Lazarus, J. Simpson, A. Berry, T. Beveridge, J. Gillam, R.A. Lewis, in: Proceedings of the 7th International Conference on Position Sensitive Detectors, Nuclear Instruments and Methods A, in press; I. Lazarus, D.E. Appelbe, A. J. Boston, P.J. Coleman-Smith, J.R. Cresswell, M. Descovich, S.A.A. Gros, M. Lauer, J. Norman, C.J. Pearson, V.F.E. Pucknell, J.A. Sampson, G. Turk, J.J. Valiente-Dobon, IEEE Trans. Nucl. Sci., 51 (2004) 1353; R.J. Cooper, A.J. Boston, H.C. Boston, J.R. Cresswell, A.N. Grint, A.R. Mather, P.J. Nolan, D.P. Scraggs, G. Turk, C.J. Hall, I. Lazarus, A. Berry, T. Beveridge, J. Gillam, R.A. Lewis, in: Proceedings of the 11th International Symposium on Radiation Measurements and Application, 2006. ] the scatter path of incident photons can be reconstructed to determine the origin of the gamma-rays without the need for mechanical collimation by applying the Compton camera principle [V. Schonfelder, A. Hirner, K. Schneider, Nucl. Instr. and Meth. 107 (1973) 385; R.W. Todd, J.M. Nightingale, D.B. Everett, Nature 251 (1974) 132. ]. In addition, it is proposed to utilise the scattered neutrons which recoil from the materials being assayed, detecting them with a fast

  20. A review of gamma ray bursts

    CERN Document Server

    Rees, Martin J

    2000-01-01

    Gamma-ray bursts, an enigma for more than 25 years, are now coming into focus. They involve extraordinary power outputs, and highly relativistic dynamics. The 'trigger' involves stellar-mass compact objects. The most plausible progenitors, ranging from neutron star binary mergers to collapsars (sometimes called 'hypernovae') eventually lead to the formation of a black hole with a torus of hot neutron-density material around it, the extractable energy being up to 10 sup 5 sup 4 ergs. Magnetic fields may exceed 10 sup 1 sup 5 G and particles may be accelerated up to > or approx. 10 sup 2 sup 0 eV. Details of the afterglow may be easier to understand than the initial trigger. Bursts at very high redshift can be astronomically-important as probes of the distant universe.

  1. Gamma-Ray Burst Prompt Correlations

    Directory of Open Access Journals (Sweden)

    M. G. Dainotti

    2018-01-01

    Full Text Available The mechanism responsible for the prompt emission of gamma-ray bursts (GRBs is still a debated issue. The prompt phase-related GRB correlations can allow discriminating among the most plausible theoretical models explaining this emission. We present an overview of the observational two-parameter correlations, their physical interpretations, and their use as redshift estimators and possibly as cosmological tools. The nowadays challenge is to make GRBs, the farthest stellar-scaled objects observed (up to redshift z=9.4, standard candles through well established and robust correlations. However, GRBs spanning several orders of magnitude in their energetics are far from being standard candles. We describe the advances in the prompt correlation research in the past decades, with particular focus paid to the discoveries in the last 20 years.

  2. Gamma-Ray Bursts: A Radio Perspective

    Directory of Open Access Journals (Sweden)

    Poonam Chandra

    2016-01-01

    Full Text Available Gamma-ray bursts (GRBs are extremely energetic events at cosmological distances. They provide unique laboratory to investigate fundamental physical processes under extreme conditions. Due to extreme luminosities, GRBs are detectable at very high redshifts and potential tracers of cosmic star formation rate at early epoch. While the launch of Swift and Fermi has increased our understanding of GRBs tremendously, many new questions have opened up. Radio observations of GRBs uniquely probe the energetics and environments of the explosion. However, currently only 30% of the bursts are detected in radio bands. Radio observations with upcoming sensitive telescopes will potentially increase the sample size significantly and allow one to follow the individual bursts for a much longer duration and be able to answer some of the important issues related to true calorimetry, reverse shock emission, and environments around the massive stars exploding as GRBs in the early Universe.

  3. Pulsar gamma rays from polar cap regions

    Science.gov (United States)

    Chiang, James; Romani, Roger W.

    1992-01-01

    The production is studied of pulsar gamma rays by energetic electrons flowing in the open field region above pulsar polar caps. The propagation was followed of curvature radiation from primary electrons, as well as hard synchrotron radiation generated by secondary pairs, through the pulsar magnetosphere for vacuum dipole open field geometries. Using data from radio and optical observations, models were constructed for the specific geometries and viewing angles appropriate to particular pulsars. These detailed models produce normalized spectra above 10 MeV, pulse profiles, beaming fractions and phase resolved spectra appropriate for direct comparison with COS-B and GRO data. Models are given for the Crab, Vela, and other potentially detectable pulsars; general agreement with existing data is good, although perturbations to the simplified models are needed for close matches. The calculations were extended to the millisecond pulsar range, which allows the production of predictions for the flux and spectra of populations of recycled pulsars and search strategies are pointed out.

  4. The Chase to Capture Gamma Ray Bursts

    Science.gov (United States)

    Gehrels, Neil

    2008-01-01

    Gamma-ray bursts are the most powerful explosions in the universe, thought to be the birth cries of black holes. It has taken 40 years of international cooperation and competition to begin to unravel the mystery of their origin. The most recent chapter in this field is being written by the SWIFT mission, a fast-response satellite with 3 power telescopes. An international team from countries all over the world participates in the chase to capture the fading light of bursts detected by SWIFT. This talk will discuss the challenges and excitement of building this space observatory. New results will be presented on our growing understanding of exploding stars and fiery mergers of orbiting stars.

  5. Jet simulations and gamma-ray burst afterglow jet breaks

    NARCIS (Netherlands)

    van Eerten, H. J.; Meliani, Z.; Wijers, Ramj; Keppens, R.

    2011-01-01

    The conventional derivation of the gamma-ray burst afterglow jet break time uses only the blast wave fluid Lorentz factor and therefore leads to an achromatic break. We show that in general gamma-ray burst afterglow jet breaks are chromatic across the self-absorption break. Depending on

  6. Jet simulations and gamma-ray burst afterglow jet breaks

    NARCIS (Netherlands)

    van Eerten, H. J.; Meliani, Z.; Wijers, R.A.M.J.; Keppens, R.

    2010-01-01

    The conventional derivation of the gamma-ray burst afterglow jet break time uses only the blast wave fluid Lorentz factor and therefore leads to an achromatic break. We show that in general gamma-ray burst afterglow jet breaks are chromatic across the self-absorption break. Depending on

  7. Wolf-Rayet stars as gamma-ray burst progenitors

    NARCIS (Netherlands)

    Langer, N.|info:eu-repo/dai/nl/304829498; van Marle, A. -J; Yoon, S.C.|info:eu-repo/dai/nl/266576753

    2010-01-01

    It became clear in the last few years that long gamma-ray bursts are associated with the endpoints of massive star evolution. They occur in star forming regions at cosmological distances (Jakobsson et al., 2005), and are associated with supernova-type energies. The collapsar model explains gamma-ray

  8. Supernova sheds light on gamma-ray bursts

    CERN Multimedia

    2003-01-01

    On 29 March the HETE-II satellite detected the most violent explosion in the universe to date - an enormous burst of gamma rays. Observers across the world recorded and studied the event. It appears to prove that gamma ray bursts originate in supernovae (1 page)

  9. Gammapy: Python toolbox for gamma-ray astronomy

    Science.gov (United States)

    Deil, Christoph; Donath, Axel; Owen, Ellis; Terrier, Regis; Bühler, Rolf; Armstrong, Thomas

    2017-11-01

    Gammapy analyzes gamma-ray data and creates sky images, spectra and lightcurves, from event lists and instrument response information; it can also determine the position, morphology and spectra of gamma-ray sources. It is used to analyze data from H.E.S.S., Fermi-LAT, and the Cherenkov Telescope Array (CTA).

  10. A simple empirical redshift indicator for gamma-ray bursts

    OpenAIRE

    Atteia, J-L

    2003-01-01

    We propose a new empirical redshift indicator for gamma-ray bursts. This indicator is easily computed from the gamma-ray burst spectral parameters, and its duration, and it provides ``pseudo-redshifts'' accurate to a factor two. Possible applications of this redshift indicator are briefly discussed.

  11. Effectiveness of gamma ray irradiation and ethyl methane ...

    African Journals Online (AJOL)

    The experiment was conducted to study the effect of gamma-ray irradiation on the high concentration thidiazuron (TDZ) produced buds. In vitro buds were irradiated with different gamma-ray doses. Akihime cultivar ('Akihime') was irradiated with the doses of 0, 30, 80, 130, 180, and 230 Gy while 'DNKW001 accession' ...

  12. Delayed Gamma-Ray Spectroscopy for Non-Destructive Assay of Nuclear Materials

    Energy Technology Data Exchange (ETDEWEB)

    Ludewigt, Bernhard [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Mozin, Vladimir [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Campbell, Luke [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Favalli, Andrea [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hunt, Alan W. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Reedy, Edward T.E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Seipel, Heather [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-06-01

    was investigated as a potential alternative to HPGe detectors. Modeling capabilities were added to an existing framework and codes were adapted as needed for analyzing experiments and assessing application-­specific assay concepts. A de-­convolution analysis of the delayed gamma-­ray response spectra modeled for spent fuel assemblies was performed using the same method that was applied to the experimental spectra.

  13. Gamma-ray Explosion in Multiple Compton Scattering Regime

    CERN Document Server

    Gong, Z; Shou, Y R; Qiao, B; Bulanov, S V; Esirkepov, T Zh; Bulanov, S S; Chen, C E; He, X T; Yan, X Q

    2016-01-01

    Gamma-ray explosion from near critical density (NCD) target irradiated by four symmetrical imploding laser pulses is numerically investigated. With peak intensities about $10^{23}$ W/cm$^2$, the laser pulses boost electron energy through direct laser acceleration, while pushing them inward with the ponderomotive force. After backscattering with counter-propagating laser, the accelerated electron will be trapped in the optical lattice or the electromagnetic standing waves (SW) created by the coherent overlapping of the laser pulses, and meanwhile emit gamma-ray photon in Multiple Compton Scattering regime, where electron acts as a medium to transfer energy from laser to gamma-ray. The energy conversion rate from laser pulses to gamma-ray can be as high as around 50\\%. It may become one of the most efficient gamma-ray sources in laboratory.

  14. Polarization measurements of gamma ray bursts and axion like particles

    CERN Document Server

    Rubbia, André

    2008-01-01

    A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of axion like particles (ALPs). Based on evidences of polarized gamma ray emission detected in several gamma ray bursts we estimated the level of ALPs induced dichroism, which could take place in the magnetized fireball environment of a GRB. This allows to estimate the sensitivity of polarization measurements of GRBs to the ALP-photon coupling. This sensitivity $\\gag\\le 2.2\\cdot 10^{-11} {\\rm GeV^{-1}}$ calculated for the ALP mass $m_a=10^{-3}~{\\rm eV}$ and MeV energy spread of gamma ray emission is competitive with the sensitivity of CAST and becomes even stronger for lower ALPs masses.

  15. Gamma Ray Burst and Soft Gamma Repeaters. Spinning, Precessing Gamma Jets

    OpenAIRE

    Fargion, Daniele

    1999-01-01

    Gamma Ray Bursts as recent GRB990123 and GRB990510 are observed to occur in cosmic volumes with a corresponding output reaching, for isotropic explosions, energies as large as two solar masses annihilation. These energies are underestimated because of the neglected role of comparable ejected neutrinos bursts. These extreme power cannot be explained with any standard spherically symmetric Fireball model. A too heavy black hole or Star would be unable to coexist with the shortest millisecond ti...

  16. Performance of HPGe detectors in high magnetic fields

    Czech Academy of Sciences Publication Activity Database

    Lorente, A.S.; Achenbach, P.; Agnello, M.; Majling, Lubomír

    2007-01-01

    Roč. 573, č. 3 (2007), s. 410-417 ISSN 0168-9002 R&D Projects: GA ČR GA202/05/2142 Institutional research plan: CEZ:AV0Z10480505 Keywords : hypernuclear gamma-spectroscopy * HPGe detectors Subject RIV: BE - Theoretical Physics Impact factor: 1.114, year: 2007

  17. News from Cosmic Gamma-ray Line Observations

    Science.gov (United States)

    Diehl, Roland

    The measurement of gamma rays at MeV energies from cosmic radioactivities is one of the key tools for nuclear astrophysics, in its study of nuclear reactions and how they shape objects such as massive stars and supernova explosions. Additionally, the unique gamma-ray signature from the annihilation of positrons falls into this same astronomical window, and positrons are often produced from radioactive beta decays. Nuclear gamma-ray telescopes face instrumental challenges from penetrating gamma rays and cosmic-ray induced backgrounds. But the astrophysical benefits of such efforts are underlined by the discoveries of nuclear gamma rays from the brightest of the expected sources. In recent years, both thermonuclear and core-collapse supernova radioactivity gamma rays have been measured in spectral detail, and complement conventional supernova observations with measurements of origins in deep supernova interiors, from the decay of 56Ni, 56Co, and 44Ti . The diffuse afterglow in gamma rays of radioactivity from massive-star nucleosynthesis is analysed on the large (galactic) scale, with findings important for recycling of matter between successive stellar generations: From 26Al gamma-ray line spectroscopy, interstellar cavities and superbubbles have been recognised in their importance for ejecta transport and recycling. Diffuse galactic emissions from radioactivity and positron-annihilation γ rays should be connected to nucleosynthesis sources: Recently new light has been shed on this connection, among others though different measurements of radioactive 60Fe, and through spectroscopy of positron annihilation gamma rays from a flaring microquasar and from different parts of our Galaxy.

  18. Assessment of the suitability of different random number generators for Monte Carlo simulations in gamma-ray spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Cornejo Diaz, N.; Vergara Gil, A. [Centre for Radiological Protection and Higiene, P.O. Box 6195, Habana (Cuba); Jurado Vargas, M. [Physics Department, University of Extremadura, 06071 Badajoz (Spain)], E-mail: mjv@unex.es

    2010-03-15

    The Monte Carlo method has become a valuable numerical laboratory framework in which to simulate complex physical systems. It is based on the generation of pseudo-random number sequences by numerical algorithms called random generators. In this work we assessed the suitability of different well-known random number generators for the simulation of gamma-ray spectrometry systems during efficiency calibrations. The assessment was carried out in two stages. The generators considered (Delphi's linear congruential, mersenne twister, XorShift, multiplier with carry, universal virtual array, and non-periodic logistic map based generator) were first evaluated with different statistical empirical tests, including moments, correlations, uniformity, independence of terms and the DIEHARD battery of tests. In a second step, an application-specific test was conducted by implementing the generators in our Monte Carlo program DETEFF and comparing the results obtained with them. The calculations were performed with two different CPUs, for a typical HpGe detector and a water sample in Marinelli geometry, with gamma-rays between 59 and 1800 keV. For the Non-periodic Logistic Map based generator, dependence of the most significant bits was evident. This explains the bias, in excess of 5%, of the efficiency values obtained with this generator. The results of the application-specific assessment and the statistical performance of the other algorithms studied indicate their suitability for the Monte Carlo simulation of gamma-ray spectrometry systems for efficiency calculations.

  19. Gamma-ray astronomy: From Fermi up to the HAWC high-energy {gamma}-ray observatory in Sierra Negra

    Energy Technology Data Exchange (ETDEWEB)

    Carraminana, Alberto [Instituto Nacional de Astrofisica, Optica y Electronica Luis Enrique Erro 1, Tonantzintla, Puebla 72840 (Mexico); Collaboration: HAWC Collaboration

    2013-06-12

    Gamma-rays represent the most energetic electromagnetic window for the study of the Universe. They are studied both from space at MeV and GeV energies, with instruments like the Fermi{gamma}-ray Space Telescope, and at TeV energies with ground based instruments profiting of particle cascades in the atmosphere and of the Cerenkov radiation of charged particles in the air or in water. The Milagro gamma-ray observatory represented the first instrument to successfully implement the water Cerenkov technique for {gamma}-ray astronomy, opening the ground for the more sensitive HAWC {gamma}-ray observatory, currently under development in the Sierra Negra site and already providing early science results.

  20. HPGe detector shielding optimization with MCNPX for the MEDINA PGNAA cell

    Energy Technology Data Exchange (ETDEWEB)

    Nicol, T.; Perot, B.; Carasco, C. [CEA, DEN, Cadarache, Nuclear Measurement Laboratory, F-13108 Saint-Paul-lez-Durance (France); Mauerhofer, E. [FZJ, Institute for Energy and Climate Research - Nuclear Waste Management and Reactor Safety, Wilhelm-Johnen-Strasse, D-52428 Juelich (Germany); Collot, J. [Laboratoire de Physique Subatomique et de Cosmologie, Universite Grenoble Alpes, CNRS/IN2P3, Grenoble (France)

    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 a 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

  1. Gamma ray lines from a universal extra dimension

    Energy Technology Data Exchange (ETDEWEB)

    Bertone, Gianfranco; Jackson, C. B.; Shaughnessy, Gabe; Tait, Tim M.P.; Vallinotto, Alberto

    2012-03-01

    Indirect Dark Matter searches are based on the observation of secondary particles produced by the annihilation or decay of Dark Matter. Among them, gamma-rays are perhaps the most promising messengers, as they do not suffer deflection or absorption on Galactic scales, so their observation would directly reveal the position and the energy spectrum of the emitting source. Here, we study the detailed gamma-ray energy spectrum of Kaluza--Klein Dark Matter in a theory with 5 Universal Extra Dimensions. We focus in particular on the two body annihilation of Dark Matter particles into a photon and another particle, which produces monochromatic photons, resulting in a line in the energy spectrum of gamma rays. Previous calculations in the context of the five dimensional UED model have computed the line signal from annihilations into \\gamma \\gamma, but we extend these results to include \\gamma Z and \\gamma H final states. We find that these spectral lines are subdominant compared to the predicted \\gamma \\gamma signal, but they would be important as follow-up signals in the event of the observation of the \\gamma \\gamma line, in order to distinguish the 5d UED model from other theoretical scenarios.

  2. Computers in activation analysis and gamma-ray spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Carpenter, B. S.; D' Agostino, M. D.; Yule, H. P. [eds.

    1979-01-01

    Seventy-three papers are included under the following session headings: analytical and mathematical methods for data analysis; software systems for ..gamma..-ray and x-ray spectrometry; ..gamma..-ray spectra treatment, peak evaluation; least squares; IAEA intercomparison of methods for processing spectra; computer and calculator utilization in spectrometer systems; and applications in safeguards, fuel scanning, and environmental monitoring. Separate abstracts were prepared for 72 of those papers. (DLC)

  3. Central Engine Memory of Gamma-Ray Bursts and Soft Gamma-Ray Repeaters

    Science.gov (United States)

    Zhang, Bin-Bin; Zhang, Bing; Castro-Tirado, Alberto J.

    2016-04-01

    Gamma-ray bursts (GRBs) are bursts of γ-rays generated from relativistic jets launched from catastrophic events such as massive star core collapse or binary compact star coalescence. Previous studies suggested that GRB emission is erratic, with no noticeable memory in the central engine. Here we report a discovery that similar light curve patterns exist within individual bursts for at least some GRBs. Applying the Dynamic Time Warping method, we show that similarity of light curve patterns between pulses of a single burst or between the light curves of a GRB and its X-ray flare can be identified. This suggests that the central engine of at least some GRBs carries “memory” of its activities. We also show that the same technique can identify memory-like emission episodes in the flaring emission in soft gamma-ray repeaters (SGRs), which are believed to be Galactic, highly magnetized neutron stars named magnetars. Such a phenomenon challenges the standard black hole central engine models for GRBs, and suggest a common physical mechanism behind GRBs and SGRs, which points toward a magnetar central engine of GRBs.

  4. CENTRAL ENGINE MEMORY OF GAMMA-RAY BURSTS AND SOFT GAMMA-RAY REPEATERS

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bin-Bin; Castro-Tirado, Alberto J. [Instituto de Astrofísica de Andalucá (IAA-CSIC), P.O. Box 03004, E-18080 Granada (Spain); Zhang, Bing, E-mail: zhang.grb@gmail.com [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States)

    2016-04-01

    Gamma-ray bursts (GRBs) are bursts of γ-rays generated from relativistic jets launched from catastrophic events such as massive star core collapse or binary compact star coalescence. Previous studies suggested that GRB emission is erratic, with no noticeable memory in the central engine. Here we report a discovery that similar light curve patterns exist within individual bursts for at least some GRBs. Applying the Dynamic Time Warping method, we show that similarity of light curve patterns between pulses of a single burst or between the light curves of a GRB and its X-ray flare can be identified. This suggests that the central engine of at least some GRBs carries “memory” of its activities. We also show that the same technique can identify memory-like emission episodes in the flaring emission in soft gamma-ray repeaters (SGRs), which are believed to be Galactic, highly magnetized neutron stars named magnetars. Such a phenomenon challenges the standard black hole central engine models for GRBs, and suggest a common physical mechanism behind GRBs and SGRs, which points toward a magnetar central engine of GRBs.

  5. A New View of the High Energy Gamma-Ray Sky with the Ferrni Gamma-Ray Space Telescope

    Science.gov (United States)

    McEnery, Julie

    2009-01-01

    Following its launch in June 2008, high energy gamma-ray observations by the Fermi Gamma-ray Space Telescope have opened a new and important window on a wide variety of phenomena, including pulsars, black holes and active galactic nuclei, gamma-ray bursts, supernova remnants and the origin of cosmic rays, and searches for hypothetical new phenomena such as super symmetric dark matter annihilations. In this talk I will describe the current status of the Fermi observatory and review the science highlights from the first year of observations.

  6. GLAST and Ground-Based Gamma-Ray Astronomy

    Science.gov (United States)

    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.

  7. Gamma-ray line measurements from supernova explosions

    Science.gov (United States)

    Diehl, Roland

    2017-02-01

    Gamma ray lines are expected to be emitted as part of the afterglow of supernova explosions, because radioactive decay of freshly synthesised nuclei occurs. Significant radioactive gamma ray line emission is expected from 56Ni and 44Ti decay on time scales of the initial explosion (56Ni, τ ~days) and the young supernova remnant (44Ti,τ ~90 years). Less specific, and rather informative for the supernova population as a whole, are lessons from longer lived isotopes such as 26Al and 60Fe. From isotopes of elements heavier than iron group elements, any interesting gamma-ray line emission is too faint to be observable. Measurements with space-based gamma-ray telescopes have obtained interesting gamma ray line emissions from two core collapse events, Cas A and SN1987A, and one thermonuclear event, SN2014J. We discuss INTEGRAL data from all above isotopes, including all line and continuum signatures from these two objects, and the surveys for more supernovae, that have been performed by gamma ray spectrometry. Our objective here is to illustrate what can be learned from gamma-ray line emission properties about the explosions and their astrophysics.

  8. INTEGRAL Results on Gamma-Ray Bursts

    Science.gov (United States)

    Hurley, Kevin C.

    2008-03-01

    Prompt, precise localizations of gamma-ray bursts imaged by IBIS are being disseminated at a rate of about 10 per year (49 to date). The INTEGRAL Burst Alert System (IBAS) produces automated alerts within 10's of seconds, giving positions which are accurate to several arcminutes for events as weak as 5.7 x 10-8 erg cm-2. IBIS is also a very sensitive detector of soft gamma repeaters (SGRs). It has detected well over 200 bursts from SGR1806-20, down to a fluence of 7×10-9 erg cm-2. An unexpected discovery is that the quiescent X-ray emission of this source and SGR 1900+14 is considerably harder than previous measurements indicated, and extends to 200 keV, a property which SGRs share with the AXP's. In addition, the SPI anti-coincidence shield (ACS) system is an extremely useful component of the interplanetary network. With its isotropic response, it detects about 66 confirmed bursts/year ( 450 to date) down to a threshold of 4.8×10-8 erg cm-2, many of which can be localized by triangulation. Most of these events are not detected by Swift or IBIS due to their limited fields of view. The triangulation results are currently being used to search for coincident neutrino emission, for gravitational radiation simultaneous with GRBs, and for coincidences between Type Ic supernovae and bursts, among other things. The SPI ACS has recently played a key role in localizing and identifying two events which are believed to be extragalactic giant magnetar flares (EMFs), from M81 and M31. LIGO was operating at the time of one of these events, and their observations support the EMF hypothesis. SPI is also being used as a Compton-scatter polarimeter for GRBs. Kalemci et al. (2007) and McGlynn et al. (2007) studied its response to GRB041219a, and obtained polarizations of 98% +/- 33%, and 63% (+31%,-30%) respectively.

  9. Ultra-high energy cosmic rays and prompt TeV gamma rays from ...

    Indian Academy of Sciences (India)

    Home; Journals; Pramana – Journal of Physics; Volume 62; Issue 3. Ultra-high energy cosmic rays and prompt TeV gamma rays from gamma ray bursts. Pijushpani Bhattacharjee Nayantara Gupta. Cosmology Volume 62 Issue 3 March 2004 pp 789-792 ...

  10. Gamma-Ray Hold-up Measurements and Results for Casa 2 and Casa 3 at TA-18

    Energy Technology Data Exchange (ETDEWEB)

    Desimone, David J. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vo, Duc Ta [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-03-10

    Numerous critical assembly experiments were performed at TA-18 beginning in the 1940’s. Several buildings, Casa 2 and Casa 3, were constructed to house these experiments. All gamma-ray hold-up measurements and analysis were performed for Casa 2 and Casa 3 in November/December 2015 to support decommissioning and demolition of the facilities. A technique called room hold-up was used to measure the nuclear materials. A grid pattern was laid out on the large room floor approximately every 9-10 feet. A three- to five-minute measurement was taken with a high-purity germanium (HPGe) detector at each location. Also, several measurements were taken in two storage vaults of Casa 3. A calibration check of the detectors showed that the efficiency and energy scale were stable. The final results of the hold-up measurements for Casa 2 and 3 are given.

  11. Gamma-rays from pulsar wind nebulae in starburst galaxies

    Science.gov (United States)

    Mannheim, Karl; Elsässer, Dominik; Tibolla, Omar

    2012-07-01

    Recently, gamma-ray emission at TeV energies has been detected from the starburst galaxies NGC253 (Acero et al., 2009) [1] and M82 (Acciari et al., 2009) [2]. It has been claimed that pion production due to cosmic rays accelerated in supernova remnants interacting with the interstellar gas is responsible for the observed gamma rays. Here, we show that the gamma-ray pulsar wind nebulae left behind by the supernovae contribute to the TeV luminosity in a major way. A single pulsar wind nebula produces about ten times the total luminosity of the Sun at energies above 1 TeV during a lifetime of 105 years. A large number of 3 × 104 pulsar wind nebulae expected in a typical starburst galaxy at a distance of 4 Mpc can readily produce the observed TeV gamma rays.

  12. Detection of gamma rays from a starburst galaxy.

    Science.gov (United States)

    Acero, F; Aharonian, F; Akhperjanian, A G; Anton, G; Barres de Almeida, U; Bazer-Bachi, A R; Becherini, Y; Behera, B; Bernlöhr, K; Bochow, A; Boisson, C; Bolmont, J; Borrel, V; Brucker, J; Brun, F; Brun, P; Bühler, R; Bulik, T; Büsching, I; Boutelier, T; Chadwick, P M; Charbonnier, A; Chaves, R C G; Cheesebrough, A; Chounet, L-M; Clapson, A C; Coignet, G; Dalton, M; Daniel, M K; Davids, I D; Degrange, B; Deil, C; Dickinson, H J; Djannati-Ataï, A; Domainko, W; Drury, L O'C; Dubois, F; Dubus, G; Dyks, J; Dyrda, M; Egberts, K; Emmanoulopoulos, D; Espigat, P; Farnier, C; Fegan, S; Feinstein, F; Fiasson, A; Förster, A; Fontaine, G; Füssling, M; Gabici, S; Gallant, Y A; Gérard, L; Gerbig, D; Giebels, B; Glicenstein, J F; Glück, B; Goret, P; Göring, D; Hauser, D; Hauser, M; Heinz, S; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hoffmann, A; Hofmann, W; Hofverberg, P; Hoppe, S; Horns, D; Jacholkowska, A; de Jager, O C; Jahn, C; Jung, I; Katarzyński, K; Katz, U; Kaufmann, S; Kerschhaggl, M; Khangulyan, D; Khélifi, B; Keogh, D; Klochkov, D; Kluźniak, W; Kneiske, T; Komin, Nu; Kosack, K; Kossakowski, R; Lamanna, G; Lenain, J-P; Lohse, T; Marandon, V; Martineau-Huynh, O; Marcowith, A; Masbou, J; Maurin, D; McComb, T J L; Medina, M C; Méhault, J; Moderski, R; Moulin, E; Naumann-Godo, M; de Naurois, M; Nedbal, D; Nekrassov, D; Nicholas, B; Niemiec, J; Nolan, S J; Ohm, S; Olive, J-F; de Oña Wilhelmi, E; Orford, K J; Ostrowski, M; Panter, M; Paz Arribas, M; Pedaletti, G; Pelletier, G; Petrucci, P-O; Pita, S; Pühlhofer, G; Punch, M; Quirrenbach, A; Raubenheimer, B C; Raue, M; Rayner, S M; Reimer, O; Renaud, M; Rieger, F; Ripken, J; Rob, L; Rosier-Lees, S; Rowell, G; Rudak, B; Rulten, C B; Ruppel, J; Sahakian, V; Santangelo, A; Schlickeiser, R; Schöck, F M; Schwanke, U; Schwarzburg, S; Schwemmer, S; Shalchi, A; Sikora, M; Skilton, J L; Sol, H; Stawarz, Ł; Steenkamp, R; Stegmann, C; Stinzing, F; Superina, G; Szostek, A; Tam, P H; Tavernet, J-P; Terrier, R; Tibolla, O; Tluczykont, M; van Eldik, C; Vasileiadis, G; Venter, C; Venter, L; Vialle, J P; Vincent, P; Vivier, M; Völk, H J; Volpe, F; Wagner, S J; Ward, M; Zdziarski, A A; Zech, A

    2009-11-20

    Starburst galaxies exhibit in their central regions a highly increased rate of supernovae, the remnants of which are thought to accelerate energetic cosmic rays up to energies of approximately 10(15) electron volts. We report the detection of gamma rays--tracers of such cosmic rays--from the starburst galaxy NGC 253 using the High Energy Stereoscopic System (H.E.S.S.) array of imaging atmospheric Cherenkov telescopes. The gamma-ray flux above 220 billion electron volts is F = (5.5 +/- 1.0(stat) +/- 2.8(sys)) x 10(-13) cm(-2) s(-1), implying a cosmic-ray density about three orders of magnitude larger than that in the center of the Milky Way. The fraction of cosmic-ray energy channeled into gamma rays in this starburst environment is five times as large as that in our Galaxy.

  13. Early Time Optical Emission from Gamma-Ray Bursts

    Science.gov (United States)

    Kopac, D.; Gomboc, A.; Japelj, J.

    We present the study of a sample of Gamma-Ray Bursts (GRBs) with contemporaneous early time optical and gamma-ray detections. By performing detailed temporal and spectral analysis of 18 GRBs which show optical peaks during prompt gamma-ray emission, we find that in most cases early time optical emission shows sharp and steep behavior, with a rich diversity of GRBs' broadband spectral properties. These observational results, supported by a simple internal shock dissipation model, show that the standard external shock interpretation for early time optical emission is disfavored in most cases where early time optical peaks are sharp (Delta t/t robotic optical telescopes.

  14. gamma-ray anisotropy measurement in coincidence mode

    CERN Document Server

    Zhang Yong; LiuMinLiang; Liu Zhong; He Jian Jun; Guo Ying Xiang; Lei Xiang Guo; Zhang Yu Hu; Luo Wan Ju

    2002-01-01

    In order to assign gamma-ray multipolarity, a method of ADO ratios deduced from coincidence data has been described. The factors affecting the reliability of the ADO ratios have been discussed using an experimental detector configuration. The multipolarities for known gamma rays deduced by the ADO method are consistent with the previous results obtained from gamma-ray angular distribution and DCO ratio measurements. This consistence proves that the ADO method is reliable. The advantages of the ADO method over the traditional DCO ratio measurement have been discussed

  15. Energy sources in gamma-ray burst models

    Science.gov (United States)

    Taam, Ronald E.

    1987-01-01

    The current status of energy sources in models of gamma-ray bursts is examined. Special emphasis is placed on the thermonuclear flash model which has been the most developed model to date. Although there is no generally accepted model, if the site for the gamma-ray burst is on a strongly magnetized neutron star, the thermonuclear model can qualitatively explain the energetics of some, but probably not all burst events. The critical issues that may differentiate between the possible sources of energy for gamma-ray bursts are listed and briefly discussed.

  16. Constraints on emission regions of gamma-ray pulsars

    Science.gov (United States)

    Wang, H. G.; Qiao, G. J.; Lee, K. J.; Xu, R. X.; Liu, Y.

    A geometric method is developed to constrain the 3-D structure of emission regions of pulsars In terms of retarded magnetic dipolar field and with inclusion of aberration and retardation effects the method is endeavored to constrain the geometrical parameters of emission regions via reproducing some multi-wavelength features e g pulse widths phase offsets between different pulses and polarization properties It is applied to six known gamma-ray pulsars with radio profiles and gamma-ray light curves The constrained results of radio and gamma-ray emission regions of these pulsars are reported

  17. Exploration of Galactic {\\gamma}-Ray Supernova Remnants

    OpenAIRE

    Tian, Wenwu; Zhang, Jianli

    2013-01-01

    New generational very-high-energy telescope arrays have been detecting more than 120 TeV {\\gamma}-ray sources. Multi-wavelength observations on these Gamma-ray sources have proven to be robust in shedding light on their nature. The coming radio telescope arrays like ASKAP and FAST may find more faint (extended) radio sources due to their better sensitivities and resolutions, might identify more previously un-identified {\\gamma}-ray sources and set many new targets for future deep surveys by v...

  18. The Lunar Prospector Gamma-Ray Spectrometer

    Science.gov (United States)

    Feldman, W. C.; Binder, A. B.; Hubbard, G. S.; McMurry, R. E., Jr.; Miller, M. C.; Prettyman, T. H.

    1996-03-01

    The third mission in the NASA Discovery series is Lunar Prospector. It is scheduled for launch on 9 October, 1997 into a circular, 100 km altitude lunar polar orbit. The nominal mission lifetime is one year. One of the five components of its experimental payload is a gamma-ray spectrometer (GRS), whose primary scientific objective is to provide global maps of the lunar elemental composition to depths of 20 cm. Scientifically discriminating results are expected for Fe, Ti, U, Th, K, Si, O, and perhaps Al, Ca, and Mg. In combination with a separate neutron spectrometer, also included on Lunar Prospector, a secondary objective of GRS is to search for, and determine the abundance of water ice to depths of 50 cm within permanently shaded craters at the lunar poles. Both experiments will also be used to search for, and determine the abundance of hydrogen implanted by the solar wind into lunar regolith to depths of 50 cm, thereby providing maps of regolith maturity. All Lunar Prospector experiments will be mounted at the ends of three, 1.9-m long booms that define the spin-plane of the satellite. The Lunar Prospector spin axis will be perpendicular to the lunar orbital plane and be flipped by 180deg half way through the mission.

  19. Observations of cosmic gamma ray bursts with WATCH on EURECA

    DEFF Research Database (Denmark)

    Brandt, Søren; Lund, N.; Castro-Tirado, A. J.

    1995-01-01

    19 Cosmic Gamma-Ray Bursts were detected by the WATCH wide field X-ray monitor during the 11 months flight of EURECA. The identification of the bursts were complicated by a high frequency of background of events caused by high energy cosmic ray interactions in the detector and by low energy, trap...

  20. The early X-ray afterglows of optically bright and dark Gamma-Ray Bursts

    OpenAIRE

    Lin, Yi-Qing

    2006-01-01

    A systematical study on the early X-ray afterglows of both optically bright and dark gamma-ray bursts (B-GRBs and D-GRBs) observed by Swift has been presented. Our sample includes 25 GRBs. Among them 13 are B-GRBs and 12 are D-GRBs. Our results show that the distributions of the X-ray afterglow fluxes ($F_{X}$), the gamma-ray fluxes ($S_{\\gamma}$), and the ratio ($R_{\\gamma, X}$) for both the D-GRBs and B-GRBs are similar. The differences of these distributions for the two kinds of GRBs shoul...

  1. Multiwavelength observations of unidentified high energy gamma ray sources

    Science.gov (United States)

    Halpern, Jules P.

    1993-10-01

    As was the case for COS B, the majority of high-energy (greater than 100 MeV) gamma-ray sources detected by the EGRET instrument on GRO are not immediately identifiable with cataloged objects at other wavelengths. These persistent gamma-ray sources are, next to the gamma-ray bursts, the least understood objects in the universe. Even a rudimentary understanding of their nature awaits identifications and follow-up work at other wavelengths to tell us what they are. The as yet unidentified sources are potentially the most interesting, since they may represent unrecognized new classes of astronomical objects, such as radio-quiet pulsars or new types of active galactic nuclei (AGN's). This two-year investigation is intended to support the analysis, correlation, and theoretical interpretation of data that we are obtaining at x ray, optical, and radio wavelengths in order to render the gamma-ray data interpretable. According to plan, in the first year concentration was on the identification and study of Geminga. The second year will be devoted to studies of similar unidentified gamma-ray sources which will become available in the first EGRET catalogs. The results obtained so far are presented in the two papers which are reproduced in the Appendix. In these papers, we discuss the pulse profiles of Geminga, the geometry and efficiency of the magnetospheric accelerator, the distance to Geminga, the implications for theories of polar cap heating, the effect of the magnetic field on the surface emission and environment of the neutron star, and possible interpretations of a radio-quiet Geminga. The implications of the other gamma-ray pulsars which were discovered to have high gamma-ray efficiency are also discussed, and the remaining unidentified COS B sources are attributed to a population of efficient gamma-ray sources, some of which may be radio quiet.

  2. Fermi: The Gamma-Ray Large Area Telescope Mission Status

    Science.gov (United States)

    McEnery, Julie

    2014-01-01

    Following its launch in June 2008, high-energy gamma-ray observations by the Fermi Gamma-ray Space Telescope have unveiled over 1000 new sources and opened an important and previously unexplored window on a wide variety of phenomena. These have included the discovery of an population of pulsars pulsing only in gamma rays; the detection of photons up to 10s of GeV from gamma-ray bursts, enhancing our understanding of the astrophysics of these powerful explosions; the detection of hundreds of active galaxies; a measurement of the high energy cosmic-ray electron spectrum which may imply the presence of nearby astrophysical particle accelerators; the determination of the diffuse gamma-ray emission with unprecedented accuracy and the constraints on phenomena such as supersymmetric dark-matter annihilations and exotic relics from the Big Bang. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from active galaxies and the discovery of transient sources in our galaxy. In this talk I will describe the current status of the Fermi observatory and review the science highlights from Fermi.

  3. Fermi: The Gamma-Ray Large Area Space Telescope

    Science.gov (United States)

    McEnery, Julie

    2014-01-01

    Following its launch in June 2008, high-energy gamma-ray observations by the Fermi Gamma-ray Space Telescope have unveiled over 1000 new sources and opened an important and previously unexplored window on a wide variety of phenomena. These have included the discovery of an population of pulsars pulsing only in gamma rays; the detection of photons up to 10s of GeV from gamma-ray bursts, enhancing our understanding of the astrophysics of these powerful explosions; the detection of hundreds of active galaxies; a measurement of the high energy cosmic-ray electron spectrum which may imply the presence of nearby astrophysical particle accelerators; the determination of the diffuse gamma-ray emission with unprecedented accuracy and the constraints on phenomena such as supersymmetric dark-matter annihilations and exotic relics from the Big Bang. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from active galaxies and the discovery of transient sources in our galaxy. In this talk I will describe the current status of the Fermi observatory and review the science highlights from Fermi.

  4. Fermi: The Gamma-Ray Large Area Telescope

    Science.gov (United States)

    McEnery, Julie

    2015-01-01

    Following its launch in June 2008, high-energy gamma-ray observations by the Fermi Gamma-ray Space Telescope have unveiled over 1000 new sources and opened an important and previously unexplored window on a wide variety of phenomena. These have included the discovery of an population of pulsars pulsing only in gamma rays; the detection of photons up to 10s of GeV from gamma-ray bursts, enhancing our understanding of the astrophysics of these powerful explosions; the detection of hundreds of active galaxies; a measurement of the high energy cosmic-ray electron spectrum which may imply the presence of nearby astrophysical particle accelerators; the determination of the diffuse gamma-ray emission with unprecedented accuracy and the constraints on phenomena such as supersymmetric dark-matter annihilations and exotic relics from the Big Bang. Continuous monitoring of the high-energy gamma-ray sky has uncovered numerous outbursts from active galaxies and the discovery of transient sources in our galaxy. In this talk I will describe the current status of the Fermi observatory and review the science highlights from Fermi.

  5. Synchrotron cooling in energetic gamma-ray bursts observed by the Fermi Gamma-Ray Burst Monitor

    OpenAIRE

    Yu, Hoi Fung; Greiner, Jochen; van Eerten, Hendrik; Burgess, J. Michael; P. Narayana Bhat; Briggs, Michael S.; Connaughton, Valerie; Diehl, Roland; Goldstein, Adam; Gruber, David; Jenke, Peter A.; von Kienlin, Andreas; Kouveliotou, Chryssa; Paciesas, William S.; Pelassa, Veronique

    2015-01-01

    Context. We study the time-resolved spectral properties of energetic gamma-ray bursts (GRBs) with good high-energy photon statistics observed by the Gamma-Ray Burst Monitor (GBM) onboard the Fermi Gamma-Ray Space Telescope. Aims. We aim to constrain in detail the spectral properties of GRB prompt emission on a time-resolved basis and to discuss the theoretical implications of the fitting results in the context of various prompt emission models. Methods. Our sample comprises eight GRBs observe...

  6. Current Trends in Gamma Ray Detection for Radiological Emergency Response

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, S., Guss, P., Maurer, R.

    2011-08-18

    Passive and active detection of gamma rays from shielded radioactive materials, including special nuclear materials, is an important task for any radiological emergency response organization. This article reports on the current trends and status of gamma radiation detection objectives and measurement techniques as applied to nonproliferation and radiological emergencies.

  7. Determination of gamma ray attenuation coefficients of Al–4% Cu ...

    Indian Academy of Sciences (India)

    Gamma ray attenuation coefficients of metal matrix composites have been investigated. For this purpose, the linear attenuation coefficients of composites containing boron carbide (B4C) at different rates have been measured using a gamma spectrometer that contains a NaI(Tl) detector and MCA at 662, 1173 and 1332 keV, ...

  8. Determination of gamma ray attenuation coefficients of Al–4% Cu ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Gamma ray attenuation coefficients of metal matrix composites have been investigated. For this purpose, the linear attenuation coefficients of composites containing boron carbide (B4C) at different rates have been measured using a gamma spectrometer that contains a NaI(Tl) detector and MCA at 662, 1173 and.

  9. Structure and content of the galaxy and galactic gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    1976-01-01

    The conference included papers on ..gamma..-ray pulsars, galactic diffuse flux and surveys, radio surveys of external galaxies, galactic distribution of pulsars, and galactic gamma emission. Galactic structure drawing on all branches of galactic astronomy is discussed. New and unpublished material is included. (JFP)

  10. The new prompt gamma-ray catalogue for PGAA

    Science.gov (United States)

    Molnar; Revay; Belgya; Firestone

    2000-10-01

    A new catalogue of subthermal neutron-induced prompt gamma rays has been created for 79 elements, from hydrogen to uranium (including fission), on the basis of recent measurements at the Budapest guided-neutron PGAA facility. New energy values have been measured using 35Cl neutron-capture gamma rays, while the gamma-ray production cross-sections have been determined with respect to the 1H thermal capture cross-section. The elemental data have been compared with thermal neutron-capture data for individual nuclides from the Evaluated Nuclear Structure Data File, ENSDF, hence isotope identifications could be made. The catalogue contains elemental spectra and a table with nearly 7000 gamma rays with relative intensity over 1% of the strongest line. The average accuracy is about 0.08 keV for energies and about 5% for cross-sections in the whole energy range, from about 40 keV to 11 MeV.

  11. Gamma-ray emission profile measurements during JET ICRH discharges

    Energy Technology Data Exchange (ETDEWEB)

    Jarvis, O.N.; Marcus, F.B.; Sadler, G.; Van Belle, P. [Commission of the European Communities, Abingdon (United Kingdom). JET Joint Undertaking; Howarth, P.J.A. [Birmingham Univ. (United Kingdom); Adams, J.M.; Bond, D.S. [UKAEA Harwell Lab. (United Kingdom). Energy Technology Div.

    1994-07-01

    Gamma-ray emission from plasma-impurity reactions caused by minority ICRH accelerating fuel ions to MeV energies has been measured using the JET neutron profile monitor. A successful data analysis technique has been used to isolate the RF-induced gamma-ray emission that was detected, enabling profiles of gamma-ray emission to be obtained. The 2-d gamma-ray emission profiles show that virtually all the radiation originates from the low field side of the RF resonance layer, as expected from RF-induced pitch angle diffusion. The emission profiles indicate the presence of a small population of resonant {sup 3}He ions that possess orbits lying near the passing-trapped boundary. 6 refs., 4 figs.

  12. Prompt Optical Observations of Gamma-Ray Bursts.

    Science.gov (United States)

    Akerlof; Balsano; Barthelmy; Bloch; Butterworth; Casperson; Cline; Fletcher; Frontera; Gisler; Heise; Hills; Hurley; Kehoe; Lee; Marshall; McKay; Pawl; Piro; Szymanski; Wren

    2000-03-20

    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.

  13. On the energetics and number of gamma-ray pulsars

    Science.gov (United States)

    Dermer, Charles D.; Sturner, Steven J.

    1994-01-01

    We examine a nearly aligned pulsar model with polar cap acceleration in order to explain the energetics and number of the known gamma-ray pulsars. In this model, the efficiency of converting spin-down luminosity to gamma-ray luminosity increases with decreasing spin-down luminosity, a trend recently emphasized by Ulmer. The predicted gamma-ray flux is proportional to dot P(exp 3/4)/P(exp 5/4) d(exp 2), where P is the period, dot P is the period derivative, and d is the distance to the pulsar. For initial spin periods between approximately equals 10 and 30 ms and neutron star polar magnetic fields between approximately equals 1 and 4 TG, this model accounts for the number and age distribution of the five pulsars which have been observed to emit gamma rays at energies greater than 100 MeV. Implications for pulsar studies are considered.

  14. Public List of LAT-Detected Gamma-Ray Pulsars

    Data.gov (United States)

    National Aeronautics and Space Administration — The following is a compilation of all publicly-announced gamma-ray pulsars detected using the Fermi LAT. Each of the detections has been vetted by the LAT team,...

  15. Gamma-Ray Imager Polarimeter for Solar Flares Project

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose here to develop the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS), the next-generation instrument for high-energy solar observations. GRIPS will...

  16. Gamma-ray flares from the Crab Nebula.

    Science.gov (United States)

    Abdo, A A; Ackermann, M; Ajello, M; Allafort, A; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bouvier, A; Brandt, T J; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Cannon, A; Caraveo, P A; Casandjian, J M; Çelik, Ö; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Costamante, L; Cutini, S; D'Ammando, F; Dermer, C D; de Angelis, A; de Luca, A; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Fortin, P; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashi, K; Hayashida, M; Hays, E; Horan, D; Itoh, R; Jóhannesson, G; Johnson, A S; Johnson, T J; Khangulyan, D; Kamae, T; Katagiri, H; Kataoka, J; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Latronico, L; Lee, S-H; Lemoine-Goumard, M; Longo, F; Loparco, F; Lubrano, P; Madejski, G M; Makeev, A; Marelli, M; Mazziotta, M N; McEnery, J E; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Naumann-Godo, M; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Ormes, J F; Ozaki, M; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Pierbattista, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Ray, P S; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Romani, R W; Sadrozinski, H F-W; Sanchez, D; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Sgrò, C; Siskind, E J; Smith, P D; Spandre, G; Spinelli, P; Strickman, M S; Suson, D J; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J B; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Troja, E; Uchiyama, Y; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Wang, P; Wood, K S; Yang, Z; Ziegler, M

    2011-02-11

    A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10(15) electron volts) electrons in a region smaller than 1.4 × 10(-2) parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.

  17. Gamma-ray spectroscopy with relativistic exotic heavy-ions

    Indian Academy of Sciences (India)

    Abstract. Feasibility of gamma-ray spectroscopy at relativistic energies with exotic heavy-ions and new generation of germanium detectors (segmented Clover) is discussed. An experiment with such detector array and radioactive is discussed.

  18. Handheld dual thermal neutron detector and gamma-ray spectrometer

    Science.gov (United States)

    Stowe, Ashley C.; Burger, Arnold; Bhattacharya, Pijush; Tupitsyn, Yevgeniy

    2017-05-02

    A combined thermal neutron detector and gamma-ray spectrometer system, including: a first detection medium including a lithium chalcopyrite crystal operable for detecting neutrons; a gamma ray shielding material disposed adjacent to the first detection medium; a second detection medium including one of a doped metal halide, an elpasolite, and a high Z semiconductor scintillator crystal operable for detecting gamma rays; a neutron shielding material disposed adjacent to the second detection medium; and a photodetector coupled to the second detection medium also operable for detecting the gamma rays; wherein the first detection medium and the second detection medium do not overlap in an orthogonal plane to a radiation flux. Optionally, the first detection medium includes a .sup.6LiInSe.sub.2 crystal. Optionally, the second detection medium includes a SrI.sub.2(Eu) scintillation crystal.

  19. Diagnosing inertial confinement fusion gamma ray physics (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, H. W.; Hoffman, N.; Wilson, D. C.; Kim, Y. H.; McEvoy, A.; Young, C. S.; Mack, J. M. [Los Alamos National Laboratory, P.O. Box 1663, M/S E526, Los Alamos, New Mexico 87545 (United States); Stoeffl, W.; Dauffy, L. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Horsfield, C. J.; Rubery, M. [Atomic Weapons Establishment, Aldermaston, Reading RG7 4PR (United Kingdom); Miller, E. K. [Special Technologies Laboratory, NSTec, Santa Barbara, California 93111 (United States); Ali, Z. A. [Livermore Operations, NSTec, Livermore, California 94550 (United States)

    2010-10-15

    The gamma reaction history (GRH) diagnostic is a multichannel, time-resolved, energy-thresholded {gamma}-ray spectrometer that provides a high-bandwidth, direct-measurement of fusion reaction history in inertial confinement fusion implosion experiments. 16.75 MeV deuterium+tritium (DT) fusion {gamma}-rays, with a branching ratio of the order of 10{sup -5}{gamma}/(14 MeV n), are detected to determine fundamental burn parameters, such as nuclear bang time and burn width, critical to achieving ignition at the National Ignition Facility. During the tritium/hydrogen/deuterium ignition tuning campaign, an additional {gamma}-ray line at 19.8 MeV, produced by hydrogen+tritium fusion with a branching ratio of unity, will increase the available {gamma}-ray signal and may allow measurement of reacting fuel composition or ion temperature. Ablator areal density measurements with the GRH are also made possible by detection of 4.43 MeV {gamma}-rays produced by inelastic scatter of DT fusion neutrons on {sup 12}C nuclei in the ablating plastic capsule material.

  20. Gamma-ray Emission from Millisecond Pulsars - An Outergap Perspective

    OpenAIRE

    Cheng, K. S.

    2013-01-01

    In this review paper we explain the following gamma-ray emission features from the millisecond pulsars. (1)Why is the dipolar field of millisecond pulsars so weak but the magnetic pair creation process may still be able to control the size of the outergap? (2)A sub-GeV pulse component could occur in the vicinity of the radio pulse of millisecond pulsars. (3)Orbital modulated gamma-rays should exist in the black widow systems for large viewing angle.

  1. Gamma-ray tracking method for pet systems

    Energy Technology Data Exchange (ETDEWEB)

    Mihailescu, Lucian; Vetter, Kai M.

    2010-06-08

    Gamma-ray tracking methods for use with granular, position sensitive detectors identify the sequence of the interactions taking place in the detector and, hence, the position of the first interaction. The improved position resolution in finding the first interaction in the detection system determines a better definition of the direction of the gamma-ray photon, and hence, a superior source image resolution. A PET system using such a method will have increased efficiency and position resolution.

  2. GLAST, the Gamma-ray Large Area Space Telescope

    OpenAIRE

    De Angelis, A

    2000-01-01

    GLAST, a detector for cosmic gamma rays in the range from 20 MeV to 300 GeV, will be launched in space in 2005. Breakthroughs are expected in particular in the study of particle acceleration mechanisms in space and of gamma ray bursts, and maybe on the search for cold dark matter; but of course the most exciting discoveries could come from the unexpected.

  3. Development and performance of a gamma-ray imaging detector

    Science.gov (United States)

    Gálvez, J. L.; Hernanz, M.; Álvarez, J. M.; La Torre, M.; Álvarez, L.; Karelin, D.; Lozano, M.; Pellegrini, G.; Ullán, M.; Cabruja, E.; Martínez, R.; Chmeissani, M.; Puigdengoles, C.

    2012-09-01

    In the last few years we have been working on feasibility studies of future instruments in the gamma-ray range, from several keV up to a few MeV. The innovative concept of focusing gamma-ray telescopes in this energy range, should allow reaching unprecedented sensitivities and angular resolution, thanks to the decoupling of collecting area and detector volume. High sensitivities are essential to perform detailed studies of cosmic explosions and cosmic accelerators, e.g., Supernovae, Classical Novae, Supernova Remnants (SNRs), Gamma-Ray Bursts (GRBs), Pulsars, Active Galactic Nuclei (AGN). In order to achieve the needed performance, a gamma-ray imaging detector with mm spatial resolution and large enough efficiency is required. In order to fulfill the combined requirement of high detection efficiency with good spatial and energy resolution, an initial prototype of a gamma-ray imaging detector based on CdTe pixel detectors is being developed. It consists of a stack of several layers of CdTe detectors with increasing thickness, in order to enhance the gamma-ray absorption in the Compton regime. A CdTe module detector lies in a 11 x 11 pixel detector with a pixel pitch of 1mm attached to the readout chip. Each pixel is bump bonded to a fan-out board made of alumina (Al2O3) substrate and routed to the corresponding input channel of the readout ASIC to measure pixel position and pulse height for each incident gamma-ray photon. We will report the main features of the gamma-ray imaging detector performance such as the energy resolution for a set of radiation sources at different operating temperatures.

  4. Cutaway artist concept of Gamma Ray Observatory (GRO) showing instruments

    Science.gov (United States)

    1990-01-01

    Cutaway artist concept drawing shows Gamma Ray Observatory (GRO) and its instrument locations. The high gain antenna (HGA) and solar array (SA) panels are deployed. The four complement instruments are the Burst and Transient Source Experiment (BATSE) (at the four corners of the satellite), the Oriented Scintillation Spectrometer Experiment (OSSE) (left), the Imaging Compton Telescope (COMPTEL) (center), and the Energetic Gamma Ray Experiment Telescope (EGRET) (right). The exterior covering of each of the four instruments is cutaway showing various components.

  5. Gamma-Ray Spectroscopy at the Institut Laue Langevin

    Science.gov (United States)

    Börner, H. G.; Simpson, G. S.; Jentschel, M.; Mutti, P.

    2005-05-01

    Some aspects of neutron-induced gamma-ray spectroscopy studies, as currently carried out at the high-flux reactor of the Institut Laue Langevin (ILL), are discussed. Neutron-induced fission allows us to study very neutron-rich nuclei, using in-pile and external target arrangements, respectively. The use of high-resolution crystal spectrometers allows investigations of gamma rays with ppm resolution.

  6. GLAST, the Gamma-ray Large Area Space Telescope

    CERN Document Server

    De Angelis, A

    2001-01-01

    GLAST, a detector for cosmic gamma rays in the range from 20 MeV to 300 GeV, will be launched in space in 2005. Breakthroughs are expected in particular in the study of particle acceleration mechanisms in space and of gamma ray bursts, and maybe on the search for cold dark matter; but of course the most exciting discoveries could come from the unexpected.

  7. Micro-Slit Collimators for X-ray/Gamma-ray Imaging Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Mikro Systems, Inc. (MSI) will advance the state-of-the-art in high resolution, high-aspect-ratio x-ray/gamma-ray collimator fabrication into the micro-slit regime...

  8. LOCALIZATION OF GAMMA-RAY BURSTS USING THE FERMI GAMMA-RAY BURST MONITOR

    Energy Technology Data Exchange (ETDEWEB)

    Connaughton, V.; Briggs, M. S.; Burgess, J. M. [CSPAR and Physics Department, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Goldstein, A.; Wilson-Hodge, C. A. [Astrophysics Office, ZP12, NASA/Marshall Space Flight Center, Huntsville, AL 35812 (United States); Meegan, C. A.; Jenke, P.; Pelassa, V.; Xiong, S.; Bhat, P. N. [CSPAR, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Paciesas, W. S. [Universities Space Research Association, Huntsville, AL (United States); Preece, R. D. [Department of Space Science, University of Alabama in Huntsville, 320 Sparkman Drive, Huntsville, AL 35899 (United States); Gibby, M. H. [Jacobs Technology, Inc., Huntsville, AL (United States); Greiner, J.; Yu, H.-F. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching (Germany); Gruber, D. [Planetarium Südtirol, Gummer 5, I-39053 Karneid (Italy); Kippen, R. M. [Los Alamos National Laboratory, NM 87545 (United States); Byrne, D.; Fitzpatrick, G.; Foley, S., E-mail: valerie@nasa.gov [School of Physics, University College Dublin, Belfield, Stillorgan Road, Dublin 4 (Ireland); and others

    2015-02-01

    The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the InterPlanetary Network, to analyze the accuracy of GBM GRB localizations. We find that the reported statistical uncertainties on GBM localizations, which can be as small as 1°, underestimate the distance of the GBM positions to the true GRB locations and we attribute this to systematic uncertainties. The distribution of systematic uncertainties is well represented (68% confidence level) by a 3.°7 Gaussian with a non-Gaussian tail that contains about 10% of GBM-detected GRBs and extends to approximately 14°. A more complex model suggests that there is a dependence of the systematic uncertainty on the position of the GRB in spacecraft coordinates, with GRBs in the quadrants on the Y axis better localized than those on the X axis.

  9. Localization of Gamma-Ray Bursts Using the Fermi Gamma-Ray Burst Monitor

    Science.gov (United States)

    Connaughton, V.; Briggs, M. S.; Goldstein, A.; Meegan, C. A.; Paciesas, W. S.; Preece, R. D.; Wilson-Hodge, C. A.; Gibby, M. H.; Greiner, J.; Gruber, D.; Jenke, P.; Kippen, R. M.; Pelassa, V.; Xiong, S.; Yu, H.-F.; Bhat, P. N.; Burgess, J. M.; Byrne, D.; Fitzpatrick, G.; Foley, S.; Giles, M. M.; Guiriec, S.; van der Horst, A. J.; von Kienlin, A.; McBreen, S.; McGlynn, S.; Tierney, D.; Zhang, B.-B.

    2015-02-01

    The Fermi Gamma-ray Burst Monitor (GBM) has detected over 1400 gamma-ray bursts (GRBs) since it began science operations in 2008 July. We use a subset of over 300 GRBs localized by instruments such as Swift, the Fermi Large Area Telescope, INTEGRAL, and MAXI, or through triangulations from the InterPlanetary Network, to analyze the accuracy of GBM GRB localizations. We find that the reported statistical uncertainties on GBM localizations, which can be as small as 1°, underestimate the distance of the GBM positions to the true GRB locations and we attribute this to systematic uncertainties. The distribution of systematic uncertainties is well represented (68% confidence level) by a 3.°7 Gaussian with a non-Gaussian tail that contains about 10% of GBM-detected GRBs and extends to approximately 14°. A more complex model suggests that there is a dependence of the systematic uncertainty on the position of the GRB in spacecraft coordinates, with GRBs in the quadrants on the Y axis better localized than those on the X axis.

  10. Spatial distribution of reflected gamma rays by Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Jehouani, A. [LPTN, Departement de Physique, Faculte des Sciences Semlalia, B.P. 2390, 40000 Marrakech (Morocco)], E-mail: jehouani@ucam.ac.ma; Merzouki, A. [LPTN, Departement de Physique, Faculte des Sciences Semlalia, B.P. 2390, 40000 Marrakech (Morocco); Remote Sensing and Geomatics of the Environment Laboratory, Ottawa-Carleton Geoscience Centre, Marion Hall, 140 Louis Pasteur, Ottawa, ON, KIN 6N5 (Canada); Boutadghart, F.; Ghassoun, J. [LPTN, Departement de Physique, Faculte des Sciences Semlalia, B.P. 2390, 40000 Marrakech (Morocco)

    2007-10-15

    In nuclear facilities, the reflection of gamma rays of the walls and metals constitutes an unknown origin of radiation. These reflected gamma rays must be estimated and determined. This study concerns reflected gamma rays on metal slabs. We evaluated the spatial distribution of the reflected gamma rays spectra by using the Monte Carlo method. An appropriate estimator for the double differential albedo is used to determine the energy spectra and the angular distribution of reflected gamma rays by slabs of iron and aluminium. We took into the account the principal interactions of gamma rays with matter: photoelectric, coherent scattering (Rayleigh), incoherent scattering (Compton) and pair creation. The Klein-Nishina differential cross section was used to select direction and energy of scattered photons after each Compton scattering. The obtained spectra show peaks at 0.511{sup *} MeV for higher source energy. The Results are in good agreement with those obtained by the TRIPOLI code [J.C. Nimal et al., TRIPOLI02: Programme de Monte Carlo Polycinsetique a Trois dimensions, CEA Rapport, Commissariat a l'Energie Atomique. ].

  11. Inactivation of citrus tristeza virus by gamma ray irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ieki, Hiroyuki; Yamaguchi, Akira

    1984-12-01

    The total exposure of gamma ray and the intensity of gamma ray per hour for the inactivation of citrus tristeza virus (CTV) and also the effect on citrus tissues are described. The budwoods of Morita navel orange infected with a severe seedling-yellow strain of CTV were irradiated with gamma ray from a /sup 60/Co source for 20 - 52 hours. The buds or small tissue pieces of the irradiated budwoods were subsequently grafted onto Mexcan lime. CTV was easily inactivated by the irradiation from 10 to 18 kR for from 20 to 52 hours. The higher the total exposure, the higher the rate of inactivation. The CTV in the budwoods was almost inactivated after the irradiation with 20 kR. When the total exposure to gamma ray on budwoods was the same, CTV was more efficiently inactivated by the irradiation for long period with low intensity of gamma ray per hour than that for short period with high intensity per hour. Gamma ray irradiation was effective to eliminate CTV from citrus tissues. (Mori, K.).

  12. Prospects for future very high-energy gamma-ray sky survey: Impact of secondary gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Inoue, Yoshiyuki; Kalashev, Oleg E.; Kusenko, Alexander

    2014-02-01

    Very high-energy gamma-ray measurements of distant blazars can be well explained by secondary gamma rays emitted by cascades induced by ultra-high-energy cosmic rays. The secondary gamma rays will enable one to detect a large number of blazars with future ground based gamma-ray telescopes such as Cherenkov Telescope Array (CTA). We show that the secondary emission process will allow CTA to detect 100, 130, 150, 87, and 8 blazars above 30 GeV, 100 GeV, 300 GeV, 1 TeV, and 10 TeV, respectively, up to z~8 assuming the intergalactic magnetic field (IGMF) strength B=10-17 G and an unbiased all sky survey with 0.5 h exposure at each field of view, where total observing time is ~540 h. These numbers will be 79, 96, 110, 63, and 6 up to z~5 in the case of B=10-15 G. This large statistics of sources will be a clear evidence of the secondary gamma-ray scenarios and a new key to studying the IGMF statistically. We also find that a wider and shallower survey is favored to detect more and higher redshift sources even if we take into account secondary gamma rays.

  13. Airborne Gamma-Ray Survey RISØ 2004

    DEFF Research Database (Denmark)

    Aage, Helle Karina

    The aim of the described survey was to monitor the gamma radiation originating from the waste disposal deposits and the now closed reactor.......The aim of the described survey was to monitor the gamma radiation originating from the waste disposal deposits and the now closed reactor....

  14. An intercomparison of Monte Carlo codes used for in-situ gamma-ray spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Hurtado, S., E-mail: shurtado@us.e [Centro de Investigacion, Tecnologia e Innovacion, CITIUS, Universidad de Sevilla, Av. Reina Mercedes 4B, E41012 Sevilla (Spain); Villa, M. [Centro de Investigacion, Tecnologia e Innovacion, CITIUS, Universidad de Sevilla, Av. Reina Mercedes 4B, E41012 Sevilla (Spain)

    2010-09-15

    In-situ gamma-ray spectrometry is widely used for monitoring of natural as well as man-made radionuclides and corresponding gamma fields in the environment or working places. It finds effective application in the operational and accidental monitoring of nuclear facilities and their vicinity, waste depositories, radioactive contamination measurements and environmental mapping or geological prospecting. In order to determine accurate radionuclide concentrations in these research fields, Monte Carlo codes have recently been used to obtain the efficiency calibration of in-situ gamma-ray detectors. This work presents an inter-comparison between two Monte Carlo codes applied to in-situ gamma-ray spectrometry. On the commercial market, Canberra has its LABSOCS/ISOCS software which is relatively inexpensive. The ISOCS mathematical efficiency calibration software uses a combination of Monte Carlo calculations and discrete ordinate attenuation computations. Efficiencies can be generated in a few minutes in the field and can be modified easily if needed. However, it has been reported in the literature that ISOCS computation method is accurate on average only within 5%, and additionally in order to use LABSOCS/ISOCS it is necessary a previous characterization of the detector by Canberra, which is an expensive process. On the other hand, the multipurpose and open source GEANT4 takes significant computer time and presents a non-friendly but powerful toolkit, independent of the manufacturer of the detector. Different experimental measurements of calibrated sources were performed with a Canberra portable HPGe detector and compared to the results obtained using both Monte Carlo codes. Furthermore, a variety of efficiency calibrations for different radioactive source distributions were calculated and tested, like plane shapes or containers filled with different materials such as soil, water, etc. LabSOCS simulated efficiencies for medium and high energies were given within an

  15. A New View of the High Energy Gamma-ray Sky with the Fermi Gamma-Ray Space Telescope

    Science.gov (United States)

    McEnery, Julie

    2010-01-01

    This slide presentation reviews some of the findings that have been made possible by the use of the Fermi Gamma-ray Space Telescope. It describes the current status of the Fermi Telescope and reviews some of the science highlights.

  16. A new type gamma-ray spectrum monitoring system

    CERN Document Server

    Cheng Bo; Zhou Jian Bin; Zhang Zhi Ming; Tong Yun Fu

    2002-01-01

    This new radiation monitoring system can be used to monitor the radiation of building materials and the radiation of atmosphere, to explore and evaluate rock for building in the field, and this system can be used to monitor the gamma irradiation near the nuclear establishments in the average situation and in the serious situation of the radiation incident have happened. The control core of this monitoring system is SCM-AT89C52, and gamma-ray sensing head consists of scintillator phi 50 mm x 50 mm NaI(Tl) and PMT GDB44. This system can be used to measure the whole gamma-ray spectrum of 256 channels

  17. Gamma-sky.net: Portal to the gamma-ray sky

    Science.gov (United States)

    Voruganti, Arjun; Deil, Christoph; Donath, Axel; King, Johannes

    2017-01-01

    http://gamma-sky.net is a novel interactive website designed for exploring the gamma-ray sky. The Map View portion of the site is powered by the Aladin Lite sky atlas, providing a scalable survey image tesselated onto a three-dimensional sphere. The map allows for interactive pan and zoom navigation as well as search queries by sky position or object name. The default image overlay shows the gamma-ray sky observed by the Fermi-LAT gamma-ray space telescope. Other survey images (e.g. Planck microwave images in low/high frequency bands, ROSAT X-ray image) are available for comparison with the gamma-ray data. Sources from major gamma-ray source catalogs of interest (Fermi-LAT 2FHL, 3FGL and a TeV source catalog) are overlaid over the sky map as markers. Clicking on a given source shows basic information in a popup, and detailed pages for every source are available via the Catalog View component of the website, including information such as source classification, spectrum and light-curve plots, and literature references. We intend for gamma-sky.net to be applicable for both professional astronomers as well as the general public. The website started in early June 2016 and is being developed as an open-source, open data project on GitHub (https://github.com/gammapy/gamma-sky). We plan to extend it to display more gamma-ray and multi-wavelength data. Feedback and contributions are very welcome!

  18. Optical telescope BIRT in ORIGIN for gamma ray burst observing

    DEFF Research Database (Denmark)

    Content, Robert; Content, Robert; Sharples, Ray

    2012-01-01

    The ORIGIN concept is a space mission with a gamma ray, an X-ray and an optical telescope to observe the gamma ray bursts at large Z to determine the composition and density of the intergalactic matter in the line of sight. It was an answer to the ESA M3 call for proposal. The optical telescope i...... length. All 3 instruments use the same 2k x 2k detector simultaneously so that telescope pointing and tip-tilt control of a fold mirror permit to place the gamma ray burst on the desired instrument without any other mechanism. © 2012 SPIE.......The ORIGIN concept is a space mission with a gamma ray, an X-ray and an optical telescope to observe the gamma ray bursts at large Z to determine the composition and density of the intergalactic matter in the line of sight. It was an answer to the ESA M3 call for proposal. The optical telescope....... All instruments fit together in a box of 80 mm x 80 mm x 200 mm. The low resolution spectrograph uses a very compact design including a special triplet. It contains only spherical surfaces except for one tilted cylindrical surface to disperse the light. To reduce the need for a high precision pointing...

  19. Sizing up the population of gamma-ray binaries

    Science.gov (United States)

    Dubus, Guillaume; Guillard, Nicolas; Petrucci, Pierre-Olivier; Martin, Pierrick

    2017-12-01

    Context. Gamma-ray binaries are thought to be composed of a young pulsar in orbit around a massive O or Be star with their gamma-ray emission powered by pulsar spin-down. The number of such systems in our Galaxy is not known. Aims: We aim to estimate the total number of gamma-ray binaries in our Galaxy and to evaluate the prospects for new detections in the GeV and TeV energy range, taking into account that their gamma-ray emission is modulated on the orbital period. Methods: We modelled the population of gamma-ray binaries and evaluated the fraction of detected systems in surveys with the Fermi-LAT (GeV), H.E.S.S., HAWC and CTA (TeV) using observation-based and synthetic template light curves. Results: The detected fraction depends more on the orbit-average flux than on the light-curve shape. Our best estimate for the number of gamma-ray binaries is 101-52+89 systems. A handful of discoveries are expected by pursuing the Fermi-LAT survey. Discoveries in TeV surveys are less likely. However, this depends on the relative amounts of power emitted in GeV and TeV domains. There could be as many as ≈ 200 HESS J0632+057-like systems with a high ratio of TeV to GeV emission compared to other gamma-ray binaries. Statistics allow for as many as three discoveries in five years of HAWC observations and five discoveries in the first two years of the CTA Galactic Plane survey. Conclusions: We favour continued Fermi-LAT observations over ground-based TeV surveys to find new gamma-ray binaries. Gamma-ray observations are most sensitive to short orbital period systems with a high spin-down pulsar power. Radio pulsar surveys (SKA) are likely to be more efficient in detecting long orbital period systems, providing a complementary probe into the gamma-ray binary population.

  20. Air shower detectors in gamma-ray astronomy

    Energy Technology Data Exchange (ETDEWEB)

    Sinnis, Gus [Los Alamos National Laboratory

    2008-01-01

    Extensive air shower (EAS) arrays directly detect the particles in an EAS that reach the observation altitude. This detection technique effectively makes air shower arrays synoptic telescopes -- they are capable of simultaneously and continuously viewing the entire overhead sky. Typical air shower detectors have an effective field-of-view of 2 sr and operate nearly 100% of the time. These two characteristics make them ideal instruments for studying the highest energy gamma rays, extended sources and transient phenomena. Until recently air shower arrays have had insufficient sensitivity to detect gamma-ray sources. Over the past decade, the situation has changed markedly. Milagro, in the US, and the Tibet AS{gamma} array in Tibet, have detected very-high-energy gamma-ray emission from the Crab Nebula and the active galaxy Markarian 421 (both previously known sources). Milagro has discovered TeV diffuse emission from the Milky Way, three unidentified sources of TeV gamma rays, and several candidate sources of TeV gamma rays. Given these successes and the suite of existing and planned instruments in the GeV and TeV regime (AGILE, GLAST, HESS, VERITAS, CTA, AGIS and IceCube) there are strong reasons for pursuing a next generation of EAS detectors. In conjunction with these other instruments the next generation of EAS instruments could answer long-standing problems in astrophysics.

  1. Extragalactic Gamma Ray Excess from Coma Supercluster Direction ...

    Indian Academy of Sciences (India)

    and the experimental data from Compton Gamma Ray Observatory (CGRO) the pre- liminary results of which are given by Osborne et al. (1994), the diffuse γ ray excess from Coma supercluster direction is calculated. 2. Methods. In this research, the model presented by Osborne et al. (1994) was used. They have used the ...

  2. Delayed Gamma-ray Spectroscopy for Safeguards Applications

    Energy Technology Data Exchange (ETDEWEB)

    Mozin, Vladimir [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2017-01-03

    The delayed gamma-ray assay technique utilizes an external neutron source (D-D, D-T, or electron accelerator-driven), and high-resolution gamma-ray spectrometers to perform characterization of SNM materials behind shielding and in complex configurations such as a nuclear fuel assembly. High-energy delayed gamma-rays (2.5 MeV and above) observed following the active interrogation, provide a signature for identification of specific fissionable isotopes in a mixed sample, and determine their relative content. Potential safeguards applications of this method are: 1) characterization of fresh and spent nuclear fuel assemblies in wet or dry storage; 2) analysis of uranium enrichment in shielded or non-characterized containers or in the presence of a strong radioactive background and plutonium contamination; 3) characterization of bulk and waste and product streams at SNM processing plants. Extended applications can include warhead confirmation and warhead dismantlement confirmation in the arms control area, as well as SNM diagnostics for the emergency response needs. In FY16 and prior years, the project has demonstrated the delayed gamma-ray measurement technique as a robust SNM assay concept. A series of empirical and modeling studies were conducted to characterize its response sensitivity, develop analysis methodologies, and analyze applications. Extensive experimental tests involving weapons-grade Pu, HEU and depleted uranium samples were completed at the Idaho Accelerator Center and LLNL Dome facilities for various interrogation time regimes and effects of the neutron source parameters. A dedicated delayed gamma-ray response modeling technique was developed and its elements were benchmarked in representative experimental studies, including highresolution gamma-ray measurements of spent fuel at the CLAB facility in Sweden. The objective of the R&D effort in FY17 is to experimentally demonstrate the feasibility of the delayed gamma-ray interrogation of shielded SNM

  3. The Gamma-ray Albedo of the Moon

    OpenAIRE

    Moskalenko, Igor V.; Porter, Troy A.

    2007-01-01

    We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the a...

  4. Egret observations of the extragalactic gamma-ray emission

    DEFF Research Database (Denmark)

    Sreekumar, P.; Bertsch, D.L.; Dingus, B.L.

    1998-01-01

    . The analysis indicates that the extragalactic emission is well described by a power-law photon spectrum with an index of -(2.10 +/- 0.03) in the 30 MeV to 100 GeV energy range. No large-scale spatial anisotropy or changes in the energy spectrum are observed in the deduced extragalactic emission. The most......The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by EGRET aboard the Compton Gamma Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray emission. The observed diffuse emission has a Galactic component arising from cosmic-ray interactions...... with the local interstellar gas and radiation, as well as an almost uniformly distributed component that is generally believed to originate outside the Galaxy. Through a careful study and removal of the Galactic diffuse emission, the flux, spectrum, and uniformity of the extragalactic emission are deduced...

  5. Constraining axion by polarized prompt emission from gamma ray bursts

    CERN Document Server

    Rubbia, André

    2008-01-01

    A polarized gamma ray emission spread over a sufficiently wide energy band from a strongly magnetized astrophysical object like gamma ray bursts (GRBs) offers an opportunity to test the hypothesis of invisible axion. The axionic induced dichroism of gamma rays at different energies should cause a misalignment of the polarization plane for higher energy events relative to that one for lower energies events resulting in the loss of statistics needed to form a pattern of the polarization signal to be recognized in a detector. According to this, any evidence of polarized gamma rays coming from an object with extended magnetic field could be interpreted as a constraint on the existence of the invisible axion for a certain parameter range. Based on reports of polarized MeV emission detected in several GRBs we derive a constraint on the axion-photon coupling. This constraint $\\g_{a\\gamma\\gamma}\\le 2.2\\cdot 10^{-11} {\\rm GeV^{-1}}$ calculated for the axion mass $m_a=10^{-3} {\\rm eV}$ is competitive with the sensitivi...

  6. Fermi bubble $\\gamma$-rays as a result of diffusive injection of Galactic cosmic rays

    OpenAIRE

    Thoudam, Satyendra

    2013-01-01

    Recently, the {\\it{Fermi}} space telescope has discovered two large $\\gamma$-ray emission regions, the so-called "Fermi bubbles", that extend up to $\\sim 50^\\circ$ above and below the Galactic center. The $\\gamma$-ray emission from the bubbles are found to follow a hard spectrum with no significant spatial variation in intensity and spectral shape. The origin of the emission is still not clearly understood. Suggested explanations include injection of cosmic-ray nuclei from the Galactic center...

  7. Development of ultrashort x-ray/gamma-ray sources using ultrahigh power lasers (Conference Presentation)

    Science.gov (United States)

    Kim, Hyung Taek; Nakajima, Kazuhisa; Hojbota, Calin; Jeon, Jong Ho; Rhee, Yong-Joo; Lee, Kyung Hwan; Lee, Seong Ku; Sung, Jae Hee; Lee, Hwang Woon; Pathak, Vishwa B.; Pae, Ki Hong; Sebban, Stéphane; Tissandier, Fabien; Gautier, Julien; Ta Phuoc, Kim; Malka, Victor; Nam, Chang Hee

    2017-05-01

    Short-pulse x-ray/gamma-ray sources have become indispensable light sources for investigating material science, bio technology, and photo-nuclear physics. In past decades, rapid advancement of high intensity laser technology led extensive progresses in the field of radiation sources based on laser-plasma interactions - x-ray lasers, betatron radiation and Compton gamma-rays. Ever since the installation of a 100-TW laser in 2006, we have pursued the development of ultrashort x-ray/gamma-ray radiations, such as x-ray lasers, relativistic high-order harmonics, betatron radiation and all-optical Compton gamma-rays. With the construction of two PW Ti:Sapphire laser beamlines having peak powers of 1.0 PW and 1.5 PW in 2010 and 2012, respectively [1], we have investigated the generation of multi-GeV electron beams [2] and MeV betatron radiations. We plan to carry out the Compton backscattering to generate MeV gamma-rays from the interaction of a GeV electron beam and a PW laser beam. Here, we present the recent progress in the development of ultrashort x-ray/gamma-ray radiation sources based on laser plasma interactions and the plan for developing Compton gamma-ray sources driven by the PW lasers. In addition, we will present the applications of laser-plasma x-ray lasers to x-ray holography and coherent diffraction imaging. [references] 1. J. H. Sung, S. K. Lee, T. J. Yu, T. M. Jeong, and J. Lee, Opt. Lett. 35, 3021 (2010). 2. H. T. Kim, K. H. Pae, H. J. Cha, I J. Kim, T. J. Yu, J. H. Sung, S. K. Lee, T. M. Jeong, J. Lee, Phys. Rev. Lett. 111, 165002 (2013).

  8. A terrestrial gamma ray flash observed from an aircraft

    Science.gov (United States)

    Smith, D. M.; Dwyer, J. R.; Hazelton, B. J.; Grefenstette, B. W.; Martinez-McKinney, G. F. M.; Zhang, Z. Y.; Lowell, A. W.; Kelley, N. A.; Splitt, M. E.; Lazarus, S. M.; Ulrich, W.; Schaal, M.; Saleh, Z. H.; Cramer, E.; Rassoul, H.; Cummer, S. A.; Lu, G.; Shao, X.-M.; Ho, C.; Hamlin, T.; Blakeslee, R. J.; Heckman, S.

    2011-10-01

    On 21 August 2009, the Airborne Detector for Energetic Lightning Emissions (ADELE), an array of six gamma-ray detectors, detected a brief burst of gamma rays while flying aboard a Gulfstream V jet near two active thunderstorm cells. The duration and spectral characteristics of the event are consistent with the terrestrial gamma ray flashes (TGFs) seen by instruments in low Earth orbit. A long-duration, complex +IC flash was taking place in the nearer cell at the same time, at a distance of ˜10 km from the plane. The sferics that are probably associated with this flash extended over 54 ms and included several ULF pulses corresponding to charge moment changes of up to 30 C km, this value being in the lower half of the range of sferics associated with TGFs seen from space. Monte Carlo simulations of gamma ray propagation in the Earth's atmosphere show that a TGF of normal intensity would, at this distance, have produced a gamma ray signal in ADELE of approximately the size and spectrum that was actually observed. We conclude that this was the first detection of a TGF from an aircraft. We show that because of the distance, ADELE's directional and spectral capabilities could not strongly constrain the source altitude of the TGF but that such constraints would be possible for TGFs detected at closer range.

  9. Gamma Rays from Top-Mediated Dark Matter Annihilations

    CERN Document Server

    Jackson, C B; Shaughnessy, Gabe; Tait, Tim M P; Taoso, Marco

    2013-01-01

    Lines in the energy spectrum of gamma rays are a fascinating experimental signal, which are often considered "smoking gun" evidence of dark matter annihilation. The current generation of gamma ray observatories are currently closing in on parameter space of great interest in the context of dark matter which is a thermal relic. We consider theories in which the dark matter's primary connection to the Standard Model is via the top quark, realizing strong gamma ray lines consistent with a thermal relic through the forbidden channel mechanism proposed in the Higgs in Space Model. We consider realistic UV-completions of the Higgs in Space and related theories, and show that a rich structure of observable gamma ray lines is consistent with a thermal relic as well as constraints from dark matter searches and the LHC. Particular attention is paid to the one loop contributions to the continuum gamma rays, which can easily swamp the line signals in some cases, and have been largely overlooked in previous literature.

  10. On the nature of gamma-ray burst time dilations

    Science.gov (United States)

    Wijers, Ralph A. M. J.; Paczynski, Bohdan

    1994-01-01

    The recent discovery that faint gamma-ray bursts are stretched in time relative to bright ones has been interpreted as support for cosmological distances: faint bursts have their durations redshifted relative to bright ones. It was pointed out, however, that the relative time stretching can also be produced by an intrinsic correlation bewteen duration and luminosity of gamma-ray bursts in a nearby, bounded distribution. While both models can explain the average amount of time stretching, we find a difference between them in the way the duration distribution of faint bursts deviates from that of bright ones, assuming the luminosity function of gamma-ray bursts is independent of distance. This allows us to distinguish between these two broad classes of model on the basis of the duration distributions of gamma-ray bursts, leading perhaps to an unambiguous determination of the distance scale of gamma-ray bursts. We apply our proposed test to the second Burst and Transient Source Experiment (BATSE) catalog and conclude, with some caution, that the data favor a cosmological interpretation of the time dilation.

  11. Sky and Elemental Planetary Mapping Via Gamma Ray Emissions

    Science.gov (United States)

    Roland, John M.

    2011-01-01

    Low-energy gamma ray emissions ((is) approximately 30keV to (is) approximately 30MeV) are significant to astrophysics because many interesting objects emit their primary energy in this regime. As such, there has been increasing demand for a complete map of the gamma ray sky, but many experiments to do so have encountered obstacles. Using an innovative method of applying the Radon Transform to data from BATSE (the Burst And Transient Source Experiment) on NASA's CGRO (Compton Gamma-Ray Observatory) mission, we have circumvented many of these issues and successfully localized many known sources to 0.5 - 1 deg accuracy. Our method, which is based on a simple 2-dimensional planar back-projection approximation of the inverse Radon transform (familiar from medical CAT-scan technology), can thus be used to image the entire sky and locate new gamma ray sources, specifically in energy bands between 200keV and 2MeV which have not been well surveyed to date. Samples of these results will be presented. This same technique can also be applied to elemental planetary surface mapping via gamma ray spectroscopy. Due to our method's simplicity and power, it could potentially improve a current map's resolution by a significant factor.

  12. Simulating Gamma-Ray Emission in Star-forming Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Pfrommer, Christoph [Leibniz-Institut für Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam (Germany); Pakmor, Rüdiger; Simpson, Christine M.; Springel, Volker, E-mail: cpfrommer@aip.de [Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany)

    2017-10-01

    Star-forming galaxies emit GeV and TeV gamma-rays that are thought to originate from hadronic interactions of cosmic-ray (CR) nuclei with the interstellar medium. To understand the emission, we have used the moving-mesh code Arepo to perform magnetohydrodynamical galaxy formation simulations with self-consistent CR physics. Our galaxy models exhibit a first burst of star formation that injects CRs at supernovae. Once CRs have sufficiently accumulated in our Milky Way–like galaxy, their buoyancy force overcomes the magnetic tension of the toroidal disk field. As field lines open up, they enable anisotropically diffusing CRs to escape into the halo and to accelerate a bubble-like, CR-dominated outflow. However, these bubbles are invisible in our simulated gamma-ray maps of hadronic pion-decay and secondary inverse-Compton emission because of low gas density in the outflows. By adopting a phenomenological relation between star formation rate (SFR) and far-infrared emission and assuming that gamma-rays mainly originate from decaying pions, our simulated galaxies can reproduce the observed tight relation between far-infrared and gamma-ray emission, independent of whether we account for anisotropic CR diffusion. This demonstrates that uncertainties in modeling active CR transport processes only play a minor role in predicting gamma-ray emission from galaxies. We find that in starbursts, most of the CR energy is “calorimetrically” lost to hadronic interactions. In contrast, the gamma-ray emission deviates from this calorimetric property at low SFRs due to adiabatic losses, which cannot be identified in traditional one-zone models.

  13. The influence of anisotropic electron drift velocity on the signal shapes of closed-end HPGe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Mihailescu, L. E-mail: l.mihailescu@fz-juelich.de; Gast, W.; Lieder, R.M.; Brands, H.; Jaeger, H

    2000-06-11

    This study is concerned with the anisotropy of the electron drift velocity in germanium crystals at high electric fields and low temperature, and its influence on the charge collection process in n-type, high-purity germanium (HPGe) detectors of closed-end, coaxial geometry. The electron trajectories inside HPGe detectors are simulated using a phenomenological model to calculate the dependence of the drift velocity on the angle between the electric field and the crystal orientation. The resulting induced currents and pulse shapes for a given detector geometry and preamplifier bandwidth are compared to experiment. Experimentally, the dependence of the pulse shapes on the conductivity anisotropy in closed-end HPGe detectors was observed. The experimental data on pulse shapes were obtained by sampling preamplifier signals of an encapsulated, hexaconical EUROBALL detector, which was irradiated by collimated {sup 22}Na and {sup 241}Am sources. The crystal orientation was measured by neutron reflection. Qualitative agreement between the simulated and experimental pulse shapes was found. A variation in the charge collection time of up to 50 ns was observed for different drift directions of the carriers relative to the crystal orientation. Furthermore, a deflection of the trajectories from a straight radial drift direction of about 20 deg. was predicted by the simulations. These two main effects of charge carrier drift velocity anisotropy in coaxial Ge detectors are expected to play an important role in the development of {gamma}-ray tracking detectors.

  14. Support of low-level instrument background for HPGe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, A. D. [Baltic Scientific Instruments, Riga, LV-1005 (Latvia); Starostin, A. S. [Inst. of Theoretical and Experimental Physics, Moscow, 117218 (Russian Federation); Kuzmenko, V. I.; Rozite, A. R. [Baltic Scientific Instruments, Riga, LV-1005 (Latvia)

    2011-07-01

    The development results for the cryostats with the low-level of instrument background supported by special design, the reduction of mass of the materials surrounding detector and application of the materials with very low content of radiation impurities are presented. The development results for HPGe detector with ultra low-level of instrument background for gamma spectrometer under the GEMMA project for investigation of the neutrino magnetic moment are presented. (authors)

  15. Are gamma-ray bursts the sources of ultra-high energy cosmic rays?

    DEFF Research Database (Denmark)

    Baerwald, Philipp; Bustamante, Mauricio; Winter, Walter

    2014-01-01

    We reconsider the possibility that gamma-ray bursts (GRBs) are the sources of the ultra-high energy cosmic rays (UHECRs) within the internal shock model, assuming a pure proton composition of the UHECRs. For the first time, we combine the information from gamma-rays, cosmic rays, prompt neutrinos.......e., that cosmic rays can leak from the sources. We find that the dip model, which describes the ankle in UHECR observations by the pair production dip, is strongly disfavored in combination with the internal shock model because a) unrealistically high baryonic loadings (energy in protons versus energy...... in electrons/gamma-rays) are needed for the individual GRBs and b) the prompt neutrino flux easily overshoots the corresponding neutrino bound. On the other hand, GRBs may account for the UHECRs in the ankle transition model if cosmic rays leak out from the source at the highest energies. In that case, we...

  16. Compensated gamma ray densimeter measures slurry densities in flow

    Energy Technology Data Exchange (ETDEWEB)

    Guest, R.J.; Zimmerman, C.W.

    1973-09-01

    A gamma-ray densitometer has been compensated so that the density of flowing oil-field slurries is measured accurately and independent of slurry composition. Accuracies over the range of densities employed in oil-field applications is within +.25 lb/gal of true density. Normal drilling mud densities are measured while flowing through the rig's standpipe at accuracies of +0.1 lb/gal of true density. Until the compensated gamma-ray densitometer was developed, it was necessary to recalibrate densitometers when slurries containing elements of high atomic numbers were present. Most oil-field cementing slurries contain no significant amounts of high atomic number elements. However, some cement slurries and drilling mud contain barite (atomic number 56) which precluded accurate measurements by earlier gamma-ray densitometers without recalibration for changes in slurry composition.

  17. Gamma ray polarimetry using a position sensitive germanium detector

    CERN Document Server

    Kroeger, R A; Kurfess, J D; Phlips, B F

    1999-01-01

    Imaging gamma-ray detectors make sensitive polarimeters in the Compton energy regime by measuring the scatter direction of gamma rays. The principle is to capitalize on the angular dependence of the Compton scattering cross section to polarized gamma rays and measure the distribution of scatter directions within the detector. This technique is effective in a double-sided germanium detector between roughly 50 keV and 1 MeV. This paper reviews device characteristics important to the optimization of a Compton polarimeter, and summarizes measurements we have made using a device with a 5x5 cm active area, 1 cm thickness, and strip-electrodes on a 2 mm pitch.

  18. Pulsed Photofission Delayed Gamma Ray Detection for Nuclear Material Identification

    Energy Technology Data Exchange (ETDEWEB)

    John Kavouras; Xianfei Wen; Daren R. Norman; Dante R. Nakazawa; Haori Yang

    2012-11-01

    Innovative systems with increased sensitivity and resolution are in great demand to detect diversion and to prevent misuse in support of nuclear materials management for the U.S. fuel cycle. Nuclear fission is the most important multiplicative process involved in non-destructive active interrogation. This process produces the most easily recognizable signature for nuclear materials. High-energy gamma rays can also excite a nucleus and cause fission through a process known as photofission. After photofission reactions, delayed signals are easily distinguishable from the interrogating radiation. Linac-based, advanced inspection techniques utilizing the fission signals after photofission have been extensively studied for homeland security applications. Previous research also showed that a unique delayed gamma ray energy spectrum exists for each fissionable isotope. Isotopic composition measurement methods based on delayed gamma ray spectroscopy will be the primary focus of this work.

  19. The Annular Gap: Gamma-Ray & Radio Emission of Pulsars

    Science.gov (United States)

    Qiao, G. J.; Du, Y. J.; Han, J. L.; Xu, R. X.

    2013-01-01

    Pulsars have been found more than 40 years. Observations from radio to gamma-rays present abundant information. However, the radiation mechanism is still an open question. It is found that the annular gap could be formed in the magnetosphere of pulsars (neutron stars or quark stars), which combines the advantages of the polar cap, slot gap and outer gap models. It is emphasized that observations of some radio pulsars, normal and millisecond gamma-ray pulsars (MSGPs) show that the annular gap would play a very important role. Here we show some observational and theoretical evidences about the annular gap. For example, bi-drifting sub-pulses; radio and gamma-ray millisecond pulsars and so on.

  20. Neutron/Gamma-ray discrimination through measures of fit

    Energy Technology Data Exchange (ETDEWEB)

    Amiri, Moslem [Faculty of Informatics, Masaryk University, Botanicka 68a, 602 00 Brno, (Czech Republic); Prenosil, Vaclav; Cvachovec, Frantisek [Faculty of Military Technology, University of Defence, Kounicova 156/65, 662 10 Brno, (Czech Republic)

    2015-07-01

    Statistical tests and their underlying measures of fit can be utilized to separate neutron/gamma-ray pulses in a mixed radiation field. In this article, first the application of a sample statistical test is explained. Fit measurement-based methods require true pulse shapes to be used as reference for discrimination. This requirement makes practical implementation of these methods difficult; typically another discrimination approach should be employed to capture samples of neutrons and gamma-rays before running the fit-based technique. In this article, we also propose a technique to eliminate this requirement. These approaches are applied to several sets of mixed neutron and gamma-ray pulses obtained through different digitizers using stilbene scintillator in order to analyze them and measure their discrimination quality. (authors)

  1. An optimum analysis sequence for environmental gamma-ray spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    De la Torre, F.; Rios M, C.; Ruvalcaba A, M. G.; Mireles G, F.; Saucedo A, S.; Davila R, I.; Pinedo, J. L., E-mail: fta777@hotmail.co [Universidad Autonoma de Zacatecas, Centro Regional de Estudis Nucleares, Calle Cipres No. 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2010-10-15

    This work aims to obtain an optimum analysis sequence for environmental gamma-ray spectroscopy by means of Genie 2000 (Canberra). Twenty different analysis sequences were customized using different peak area percentages and different algorithms for: 1) peak finding, and 2) peak area determination, and with or without the use of a library -based on evaluated nuclear data- of common gamma-ray emitters in environmental samples. The use of an optimum analysis sequence with certified nuclear information avoids the problems originated by the significant variations in out-of-date nuclear parameters of commercial software libraries. Interference-free gamma ray energies with absolute emission probabilities greater than 3.75% were included in the customized library. The gamma-ray spectroscopy system (based on a Ge Re-3522 Canberra detector) was calibrated both in energy and shape by means of the IAEA-2002 reference spectra for software intercomparison. To test the performance of the analysis sequences, the IAEA-2002 reference spectrum was used. The z-score and the reduced {chi}{sup 2} criteria were used to determine the optimum analysis sequence. The results show an appreciable variation in the peak area determinations and their corresponding uncertainties. Particularly, the combination of second derivative peak locate with simple peak area integration algorithms provides the greater accuracy. Lower accuracy comes from the combination of library directed peak locate algorithm and Genie's Gamma-M peak area determination. (Author)

  2. Gamma ray spectroscopy of {sup 10}{sub {lambda}}B

    Energy Technology Data Exchange (ETDEWEB)

    Ukai, Mifuyu [Tohoku Univ., Sendai (Japan). Faculty of Science

    2003-03-01

    Interaction between {lambda} and N are composed of the central force independent on spins and the spin dependent forces i.e. the spin-spin force, spin-orbit force dependent on nuclear spins, spin-orbit force dependent on {lambda} particle spin and the tensor force. The radially integrated value of the spin-spin force expressed by {delta} can be evaluated from the measurements of the excitation energies of various hypernuclei. For {sup 10}{sub {lambda}}B, {delta} < 0.22 MeV has been reported from the M1 {gamma}-ray transition of the ground state doublet, while {delta}=0.5 MeV from {sup 7}{sub {lambda}}Li M1 transition of ground state doublet. In the course to explore unified description of the p-shell hypernuclei, these contradictory results must be overcome. In this experiment, it was designed to measure {sup 10}{sub {lambda}}B {gamma}-ray spectroscopy with {gamma}-ray yield four times as high as the past experiments to solve the problem. Experiment was performed on D6 line of AGS at BNL using Hyperball detector. Data of the {gamma}-ray spectroscopy measurement of hypernuclei produced by (K{sup -}, {pi}{sup -}) reaction with {sup 10}B target were collected in 48 hours. The preliminary result of the data analysis shows that the energy is less than 80 keV. This result seems to be suggesting that the scheme which has been based on the two-body interaction should be reconsidered. In addition, numbers of {gamma}-rays from hyperfragments produced by the particles emitted from the excited states of {sup 10}{sub {lambda}}B were observed, which opens a new field of hypernuclei {gamma}-ray spectroscopy using hyperfragments. (S. Funahashi)

  3. The Origin of Cosmic Rays and the Diffuse Galactic Gamma-Ray Emission

    OpenAIRE

    Digel, S. W.; Hunter, S. D.; Moskalenko, I. V.; Ormes, J. F.; Pohl, M.

    2001-01-01

    Cosmic-ray interactions with interstellar gas and photons produce diffuse gamma-ray emission. In this talk we will review the current understanding of this diffuse emission and its relationship to the problem of the origin of cosmic rays. We will discuss the open issues and what progress might be possible with GLAST, which is planned for launch in 2006.

  4. Gamma-ray emission from millisecond pulsars - an Outergap perspective

    Directory of Open Access Journals (Sweden)

    Kwong Sang Cheng

    2013-09-01

    Full Text Available In this review paper we explain the following gamma-ray emission features from the millisecond pulsars. (1 Why is the dipolar field of millisecond pulsars so weak but the magnetic pair creation process may still be able to control the size of the outergap? (2 A sub-GeV pulse component could occur in the vicinity of the radio pulse of millisecond pulsars. (3 Orbital modulated gamma-rays should exist in the black widow systems for large viewing angle.

  5. The rarity of terrestrial gamma-ray flashes

    OpenAIRE

    Smith, D. M.; Dwyer, J. R.; Hazelton, B. J.; Grefenstette, B. W.; Martinez-McKinney, G. F. M.; Zhang, Z. Y.; Lowell, A. W.; Kelley, N. A.; Splitt, M. E.; Lazarus, S. M.; Ulrich, W.; Schaal, M.; Saleh, Z. H.; Cramer, E.; Rassoul, H. K.

    2011-01-01

    We report on the first search for Terrestrial Gamma-ray Flashes (TGFs) from altitudes where they are thought to be produced. The Airborne Detector for Energetic Lightning Emissions (ADELE), an array of gamma-ray detectors, was flown near the tops of Florida thunderstorms in August/September 2009. The plane passed within 10 km horizontal distance of 1213 lightning discharges and only once detected a TGF. If these discharges had produced TGFs of the same intensity as those seen from space, ever...

  6. Gravitational Waves, Gamma Ray Bursts, and Black Stars

    CERN Document Server

    Vachaspati, Tanmay

    2016-01-01

    Stars that are collapsing toward forming a black hole but appear frozen near their Schwarzschild horizon are termed "black stars". The collision of two black stars leads to gravitational radiation during the merging phase followed by a delayed gamma ray burst during coalescence. The recent observation of gravitational waves by LIGO, followed by a possible gamma ray counterpart by Fermi, suggests that the source may have been a merger of two black stars with profound implications for quantum gravity and the nature of black holes.

  7. Gamma-Ray Line Studies of Nuclei in the Cosmos

    OpenAIRE

    Leising, M.; Diehl, R.

    2009-01-01

    Gamma-ray line studies are capable of identifying radioactive tracer isotopes generated in cosmic nucleosynthesis events. Pioneering measurements were made 30 years ago with HEAO-C1, detecting the first interstellar gamma-ray line from 26Al, then with SMM and numerous balloon experiments, among their results the detection of radioactivity from supernova SN1987A, and with the Compton Observatory and its OSSE and COMPTEL instruments in 1991-2000, which performed sky surveys in 26Al and 511 keV ...

  8. SWEPP Gamma-Ray Spectrometer System software design description

    Energy Technology Data Exchange (ETDEWEB)

    Femec, D.A.; Killian, E.W.

    1994-08-01

    To assist in the characterization of the radiological contents of contract-handled waste containers at the Stored Waste Examination Pilot Plant (SWEPP), the SWEPP Gamma-Ray Spectrometer (SGRS) System has been developed by the Radiation Measurements and Development Unit of the Idaho National Engineering Laboratory. The SGRS system software controls turntable and detector system activities. In addition to determining the concentrations of gamma-ray-emitting radionuclides, this software also calculates attenuation-corrected isotopic mass ratios of-specific interest. This document describes the software design for the data acquisition and analysis software associated with the SGRS system.

  9. Cross Sections for (gamma)-ray Production in the 191Ir (n,xn(gamma)) Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Fotiades, N; Nelson, R O; Devlin, M; Chadwick, M B; Talou, P; Becker, J A; Garrett, P E; Younes, W

    2005-01-11

    Discrete {gamma}-ray spectra have been measured for nuclei populated in {sup 191}Ir(n{sub 4}xn{gamma}) with x{<=}11, as a function of incident neutron energy using neutrons from the 'white' neutron source at the Los Alamos Neutron Science Center's WNR facility. The energy of the neutrons was determined using the time-of-flight technique. The data were taken using the GEANIE spectrometer. The cross sections for emission of 202 {gamma} rays of {sup 181-191}Ir were determined for neutron energies 0.2 MeV < E{sub n} < 300 MeV. Comparison with model calculations, using the GNASH reaction model, and with GEANIE results from the similar {sup 193}Ir(n{sub 4}xn{gamma}) reactions is made.

  10. Time-of-flight discrimination between gamma-rays and neutrons by neural networks

    OpenAIRE

    Serkan AKKOYUN

    2012-01-01

    In gamma-ray spectroscopy, a number of neutrons are emitted from the nuclei together with the gamma-rays and these neutrons influence gamma-ray spectra. An obvious method of separating between neutrons and gamma-rays is based on the time-of-flight (tof) technique. This work aims obtaining tof distributions of gamma-rays and neutrons by using feed-forward artificial neural network (ANN). It was shown that, ANN can correctly classify gamma-ray and neutron events. Testing of trained networks on ...

  11. The evaluated gamma-ray activation file (EGAF)

    Energy Technology Data Exchange (ETDEWEB)

    Firestone, R.B.; Molnar, G.L.; Revay, Zs.; Belgya, T.; McNabb, D.P.; Sleaford, B.W.

    2004-09-22

    The Evaluated Gamma-ray Activation File (EGAF), a new database of prompt and delayed neutron capture g-ray cross sections, has been prepared as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project to develop a ''Database of Prompt Gamma-rays from Slow Neutron Capture for Elemental Analysis.'' Recent elemental g-ray cross-section measurements performed with the guided neutron beam at the Budapest Reactor have been combined with data from the literature to produce the EGAF database. EGAF contains thermal cross sections for {approx} 35,000 prompt and delayed g-rays from 262 isotopes. New precise total thermal radiative cross sections have been derived for many isotopes from the primary and secondary gamma-ray cross sections and additional level scheme data. An IAEA TECDOC describing the EGAF evaluation and tabulating the most prominent g-rays will be published in 2004. The TECDOC will include a CD-ROM containing the EGAF database in both ENSDF and tabular formats with an interactive viewer for searching and displaying the data. The Isotopes Project, Lawrence Berkeley National Laboratory continues to maintain and update the EGAF file. These data are available on the Internet from both the IAEA and Isotopes Project websites.

  12. The Evaluated Gamma-ray Activation File (EGAF)

    Science.gov (United States)

    Firestone, R. B.; Molnár, G. L.; Révay, Zs.; Belgya, T.; McNabb, D. P.; Sleaford, B. W.

    2006-03-01

    The Evaluated Gamma-ray Activation File (EGAF), a new database of prompt and delayed neutron capture γ ray cross sections, has been prepared as part of an International Atomic Energy Agency (IAEA) Coordinated Research Project to develop a "Database of Prompt Gamma-rays from Slow Neutron Capture for Elemental Analysis". Recent elemental γ-ray cross-section measurements performed with the guided neutron beam at the Budapest Reactor have been combined with data from the literature to produce the EGAF database. EGAF contains thermal cross sections for ≈35,000 prompt and delayed γ-rays from 262 isotopes. New precise total thermal radiative cross sections have been derived for many isotopes from the primary and secondary gamma-ray cross sections and additional level scheme data. An IAEA TECDOC describing the EGAF evaluation and tabulating the most prominent γ-rays will be published in 2004. The TECDOC will include a CD-ROM containing the EGAF database in both ENSDF and tabular formats with an interactive viewer for searching and displaying the data. The Isotopes Project, Lawrence Berkeley National Laboratory continues to maintain and update the EGAF file. These data are available on the Internet from both the IAEA and Isotopes Project websites.

  13. Gamma-Ray Astronomy Across 6 Decades of Energy: Synergy between Fermi, IACTs, and HAWC

    Science.gov (United States)

    Hui, C. Michelle

    2017-01-01

    Gamma Ray Observatories, Gamma-Ray Astrophysics, GeV TeV Sky Survey, Galaxy, Galactic Plane, Source Distribution, The gamma-ray sky is currently well-monitored with good survey coverage. Many instruments from different waveband/messenger (X rays, gamma rays, neutrinos, gravitational waves) available for simultaneous observations. Both wide-field and pointing instruments in development and coming online in the next decade LIGO

  14. Application of mobile gamma-ray spectrometry for soil mapping

    Science.gov (United States)

    Werban, Ulrike; Lein, Claudia; Pohle, Marco; Dietrich, Peter

    2017-04-01

    Gamma-ray measurements have a long tradition for geological surveys and deposit exploration using airborne and borehole logging systems. For these applications, the relationships between the measured physical parameter - the concentration of natural gamma emitters 40K, 238U and 232Th - and geological origin or sedimentary developments are well described. Thus, Gamma-ray spectrometry seems a useful tool for carrying out spatial mapping of physical parameters related to soil properties. The isotope concentration in soils depends on different soil parameters (e.g. geochemical composition, grain size fractions), which are a result of source rock properties and processes during soil geneses. There is a rising interest in the method for application in Digital Soil Mapping or as input data for environmental, ecological or hydrological modelling, e.g. as indicator for clay content. However, the gamma-ray measurement is influenced by endogenous factors and processes like soil moisture variation, erosion and deposition of material or cultivation. We will present results from a time series of car borne gamma-ray measurements to observe heterogeneity of soil on a floodplain area in Central Germany. The study area is characterised by high variations in grain size distribution and occurrence of flooding events. For the survey, we used a 4 l NaI(Tl) detector with GPS connection mounted on a sledge, which is towed across the field sites by a four-wheel-vehicle. The comparison of data from different dates shows similar structures with small variation between the data ranges and shape of structures. We will present our experiences concerning the application of gamma-ray measurements under variable field conditions and their impacts on data quality.

  15. High-precision gamma-ray spectroscopy of 61Cu, an emerging medical isotope used in positron emission tomography

    Science.gov (United States)

    Nelson, N.; Ellison, P.; Nickles, R.; McCutchan, E.; Sonzogni, A.; Smith, S.; Greene, J.; Carpenter, M.; Zhu, S.; Lister, C.; Moran, K.

    2017-09-01

    61Cu (t1 / 2 = 3.339h) is an important medical isotope used in positron emission tomography (PET) tumor hypoxia imaging scans; however, its beta-plus decay and the subsequent gamma decay of 61Ni has not been studied in over 30 years. Therefore, high quality decay data of 61Cu is desired to determine the overall dose delivered to a patient. In this study, 61Cu was produced at the University of Wisconsin - Madison cyclotron and then assayed using the Gammasphere array at Argonne National Laboratory. Consisting of 70 Compton-suppressed high-purity germanium (HPGe) detectors, Gammasphere provides precise decay data that exceeds that of previous 61Cu studies. γ-ray singles and coincident data were recorded and then analyzed using Radware gf3m software. Through γ- γ coincidence techniques, new γ-ray transitions were identified and high precision determination of γ-ray intensities were made. These modifications and additions to the current decay scheme will be presented, and their impact on the resulting does estimates will be discussed. DOE Isotope Program is acknowledged for funding ST5001030. Work supported by the U.S. DOE under Grant No. DE-FG02-94ER40848 and Contract Nos. DE-AC02-98CH10946 and DE-AC02-06CH11357 and by the Science Undergraduate Laboratory Internship Program (SULI).

  16. Fermi Solar Flare X-Ray and Gamma-Ray Observations

    Data.gov (United States)

    National Aeronautics and Space Administration — The Fermi Gamma-ray Space Telescope was launched in June 2008 to explore high-energy phenomena in the Universe. This GI program is targeted specifically at Fermi...

  17. Gamma ray constraints on flavor violating asymmetric dark matter

    DEFF Research Database (Denmark)

    Masina, I.; Panci, P.; Sannino, F.

    2012-01-01

    We show how cosmic gamma rays can be used to constrain models of asymmetric Dark Matter decaying into lepton pairs by violating flavor. First of all we require the models to explain the anomalies in the charged cosmic rays measured by PAMELA, Fermi and H.E.S.S.; performing combined fits we...... determine the allowed values of the Dark Matter mass and lifetime. For these models, we then determine the constraints coming from the measurement of the isotropic gamma-ray background by Fermi for a complete set of lepton flavor violating primary modes and over a range of DM masses from 100 GeV to 10 Te......V. We find that the Fermi constraints rule out the flavor violating asymmetric Dark Matter interpretation of the charged cosmic ray anomalies....

  18. Strategies for Studying the Sources of Gamma Ray Bursts

    Science.gov (United States)

    Cline, T. L.; Norris, J. P.; Hurley, K. C.

    2003-01-01

    The study of gamma ray bursts (GRBs) has rapidly evolved in recent years with the discovery of their cosmological nature and with BATSE, BeppoSAX, HETE and the IPN enabling a wide variety of associated . afterglow measurements. Multiwavelength observations ranging through the radio, optical, soft and hard x-ray, and gamma-ray regimes have exploded the field of GRB interpretation. Also, the Amanda, Milagro and LIGO experiments can search for related neutrino, cosmic-ray photon, and gravitational radiation events, even with the delayed alerts, such as from the IPN. The infrared region, where the optical emissions from sources at the extreme distances may be shifted, will become important but is undersubscribed. The soon-to-be launched Swift mission will greatly broaden the GRB discipline, and a strategy for associated ground-based measurements is outlined. The need for the improved global distribution of all instruments, in particular, robotic infrared detectors, is cited.

  19. Gamma-ray burst afterglow plateaus and gravitational waves

    Energy Technology Data Exchange (ETDEWEB)

    Corsi, Alessandra [Universita di Roma Sapienza and INFN-Roma, Piazzale Aldo Moro 2, 00185-Roma (Italy); Meszaros, Peter, E-mail: alessandra.corsi@roma1.infn.i, E-mail: nnp@astro.psu.ed [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)

    2009-10-21

    The existence of a shallow decay phase in the early x-ray afterglows of gamma-ray bursts is a common feature. We discuss the possibility that such a feature is connected to the formation of a highly magnetized millisecond pulsar, pumping energy into the fireball via magnetic dipole emission, while undergoing a secular bar-mode instability. If this is the case, gravitational wave losses associated with the neutron star's ellipsoidal deformation, would affect the star's spin-down, possibly producing a gravitational wave signal detectable by the advanced LIGO and Virgo. Such a signal, being emitted in association with an observed x-ray light-curve plateau over relatively long timescales, could open a new interesting opportunity for multi-messenger studies to be carried out in coincidence with gamma-ray burst sources. We conclude that the hypothesis proposed here deserves further investigation.

  20. Method and System for Gamma-Ray Localization Induced Spacecraft Navigation Using Celestial Gamma-Ray Sources

    Science.gov (United States)

    Sheikh, Suneel I. (Inventor); Hisamoto, Chuck (Inventor); Arzoumanian, Zaven (Inventor)

    2015-01-01

    A method and system for spacecraft navigation using distant celestial gamma-ray bursts which offer detectable, bright, high-energy events that provide well-defined characteristics conducive to accurate time-alignment among spatially separated spacecraft. Utilizing assemblages of photons from distant gamma-ray bursts, relative range between two spacecraft can be accurately computed along the direction to each burst's source based upon the difference in arrival time of the burst emission at each spacecraft's location. Correlation methods used to time-align the high-energy burst profiles are provided. The spacecraft navigation may be carried out autonomously or in a central control mode of operation.

  1. Well-type HPGe-detector absolute-peak-efficiency calibration and true-coincidence correction

    CERN Document Server

    Wang, T K; Tseng, C L

    1999-01-01

    A personal-computer-based program SWELL has been developed for well-type HPGe detector effective-solid-angle calculation. This program is very useful in constructing the absolute-peak efficiency (epsilon sub p) versus gamma-ray energy (E subgamma) curves for different sample geometries based on a pre-determined epsilon sub p under a reference counting geometry. The validity of using this program for epsilon sub p (E subgamma) conversion was successfully demonstrated for photons in the energy range approx 20 keV-1.5 MeV; the overall uncertainty can be controlled to be within 3%. In addition, a semi-empirical method has been developed to estimate the true-coincidence correction (COI) factor for well-type HPGe detector. Results based on sup 6 sup 0 Co, sup 1 sup 3 sup 9 Ce, sup 1 sup 3 sup 3 Ba and sup 5 sup 9 Fe sources indicated that the estimated COI factors are in good agreement with the experimentally validated COI values.

  2. Radio-quiet Gamma-ray Pulsars

    Directory of Open Access Journals (Sweden)

    Lupin Chun-Che Lin

    2016-09-01

    Full Text Available A radio-quiet γ-ray pulsar is a neutron star that has significant γ-ray pulsation but without observed radio emission or only limited emission detected by high sensitivity radio surveys. The launch of the Fermi spacecraft in 2008 opened a new epoch to study the population of these pulsars. In the 2nd Fermi Large Area Telescope catalog of γ-ray pulsars, there are 35 (30 % of the 117 pulsars in the catalog known samples classified as radio-quiet γ-ray pulsars with radio flux density (S1400 of less than 30 μJy. Accompanying the observations obtained in various wavelengths, astronomers not only have the opportunity to study the emitting nature of radio-quiet γ-ray pulsars but also have proposed different models to explain their radiation mechanism. This article will review the history of the discovery, the emission properties, and the previous efforts to study pulsars in this population. Some particular cases known as Geminga-like pulsars (e.g., PSR J0633+1746, PSR J0007+7303, PSR J2021+4026, and so on are also to specified discuss their common and specific features.

  3. Gamma-ray spectroscopy of the nucleus {sup 139}Ce

    Energy Technology Data Exchange (ETDEWEB)

    Bucurescu, D.; Cata-Danil, G.; Cata-Danil, I.; Ivascu, M.; Marginean, N.; Marginean, R.; Mihailescu, L.C.; Rusu, C.; Suliman, G. [Horia Hulubei National Institute of Physics and Nuclear Engineering, P.O. Box MG-6, Bucharest (Romania)

    2006-03-15

    Gamma-ray coincidence techniques are used to determine new level structures in the N=81 nucleus {sup 139}Ce, at low spins and excitation energies with the {sup 139}La(p,n{gamma}) reaction at 5.0 and 6.0 MeV incident energy, and at high spins with the {sup 130}Te({sup 12}C,3n{gamma}) reaction at 50.5 MeV, respectively. Lifetime determinations are also made in the (p,n{gamma}) reaction with the centroid DSA method. The observed level structures are discussed by comparison with existing calculations and with those in the neighbouring nucleus {sup 140}Ce. (orig.)

  4. Limits for an inverse bremsstrahlung origin of the diffuse Galactic soft gamma-ray emission

    DEFF Research Database (Denmark)

    Pohl, M.

    1998-01-01

    origin of the soft Galactic gamma-ray continuum through inverse bremsstrahlung. A flux of low-energy cosmic rays strong enough to produce the observed spectrum of gamma-rays implies substantial gamma-ray emission at a few MeV through nuclear de-excitation. It is shown that the existing limits on excess 3......-7 MeV emission from the Galactic plane, in concert with the constraints from pi(0)-decay gamma-ray emission at higher energies, are in serious conflict with an inverse bremsstrahlung origin of the Galactic soft gamma-ray emission for any physically plausible low-energy cosmic ray spectrum. While...

  5. Understanding hadronic gamma-ray emission from supernova remnants

    Energy Technology Data Exchange (ETDEWEB)

    Damiano, Caprioli, E-mail: caprioli@arcetri.astro.it [INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, Firenze (Italy)

    2011-05-01

    We aim to test the plausibility of a theoretical framework in which the gamma-ray emission detected from supernova remnants may be of hadronic origin, i.e., due to the decay of neutral pions produced in nuclear collisions involving relativistic nuclei. In particular, we investigate the effects induced by magnetic field amplification on the expected particle spectra, outlining a phenomenological scenario consistent with both the underlying Physics and the larger and larger amount of observational data provided by the present generation of gamma experiments, which seem to indicate rather steep spectra for the accelerated particles. In addition, in order to study to study how pre-supernova winds might affect the expected emission in this class of sources, the time-dependent gamma-ray luminosity of a remnant with a massive progenitor is worked out. Solid points and limitations of the proposed scenario are finally discussed in a critical way.

  6. Detector calibration for in-situ gamma ray spectrometry

    CERN Document Server

    Balea, G

    2002-01-01

    The power in the technique of in-situ spectrometry lies in the fact that a detector placed on ground measures gamma radiation from sources situated over an area of several hundred square meters. The 'field of view' for the detector would be larger for high energy radiation sources and for sources closer to the soil surface. In contrast, a soil sample would represent an area of a few tens of hundreds of square centimeters. In practice, an effective characterization of a site would involve in-situ gamma ray spectrometry in conjunction with soil sampling. As part of an overall program, in-situ gamma ray spectrometry provides a means to assess the degree of contamination in areas during the course of operations in the field, thus guiding the investigator on where to collect samples. It can also substantially reduce the number of samples need to be collected and subsequently analyzed. (author)

  7. gamma-ray tracking in germanium the backtracking method

    CERN Document Server

    Marel, J V D

    2002-01-01

    In the framework of a European TMR network project the concept for a gamma-ray tracking array is being developed for nuclear physics spectroscopy in the energy range of approx 10 keV up to several MeV. The tracking array will consist of a large number of position-sensitive germanium detectors in a spherical geometry around a target. Due to the high segmentation, a Compton scattered gamma-ray will deposit energy in several different segments. A method has been developed to reconstruct the tracks of multiple coincident gamma-rays and to find their initial energies. By starting from the final point the track can be reconstructed backwards to the origin with the help of the photoelectric and Compton cross-sections and the Compton scatter formula. Every reconstructed track is given a figure of merit, thus allowing suppression of wrongly reconstructed tracks and gamma-rays that have scattered out of the detector system. This so-called backtracking method has been tested on simulated events in a shell-like geometry ...

  8. Monte Carlo simulation of gamma ray tomography for image reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Guedes, Karlos A.N.; Moura, Alex; Dantas, Carlos; Melo, Silvio; Lima, Emerson, E-mail: karlosguedes@hotmail.com [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil); Meric, Ilker [University of Bergen (Norway)

    2015-07-01

    The Monte Carlo simulations of known density and shape object was validate with Gamma Ray Tomography in static experiments. An aluminum half-moon piece placed inside a steel pipe was the MC simulation test object that was also measured by means of gamma ray transmission. Wall effect of the steel pipe due to irradiation geometry in a single pair source-detector tomography was evaluated by comparison with theoretical data. MCNPX code requires a defined geometry to each photon trajectory which practically prevents this usage for tomography reconstruction simulation. The solution was found by writing a program in Delphi language to create input files automation code. Simulations of tomography data by automated MNCPX code were carried out and validated by experimental data. Working in this sequence the produced data needed a databank to be stored. Experimental setup used a Cesium-137 isotopic radioactive source (7.4 × 109 Bq), and NaI(Tl) scintillation detector of (51 × 51) × 10−3 m crystal size coupled to a multichannel analyzer. A stainless steel tubes of 0,154 m internal diameter, 0.014 m thickness wall. The results show that the MCNPX simulation code adapted to automated input file is useful for generating a matrix data M(θ,t), of a computerized gamma ray tomography for any known density and regular shape object. Experimental validation used RMSE from gamma ray paths and from attenuation coefficient data. (author)

  9. Is dark matter visible by galactic gamma rays?

    Indian Academy of Sciences (India)

    Abstract. The EGRET excess in the diffuse galactic gamma ray data above 1 GeV shows all features expected from dark matter WIMP annihilation: (a) It is present and has the same spectrum in all sky directions, not just in the galactic plane. (b) The intensity of the excess shows the 1/r2 profile expected for a flat rotation ...

  10. Inverse Compton Gamma Rays from Dark Matter Annihilation in the ...

    Indian Academy of Sciences (India)

    Inverse Compton Gamma Rays from Dark Matter Annihilation in the Dwarf Galaxies. Jayashri Medhi. ∗. , H. L. Duorah, A. G. Barua & K. Duorah. Physics Department, Gauhati University, Gopinath Bardoloi Nagar, Guwahati 781 014, India. ∗ e-mail: jayashri.medhi@rediffmail.com. Received 18 May 2016; accepted 4 July ...

  11. Analysis of hydrogenated zirconium alloys irradiated with gamma - rays

    Directory of Open Access Journals (Sweden)

    Askhatov Askar

    2017-01-01

    Full Text Available The paper represents the investigations concerning the geometrical size effect of hydrogenated zirconium alloys (Zr-1Ni-H during gamma-ray irradiation on the amount of energy absorbed. The results have shown that the less the cross-sectional dimensions of the sample or product is, the less energy is absorbed. The paper provides theoretical calculations. The zirconium sample with a cross-section of 2.8х2.8 cm absorbs 30-35% of the energy of the incident gamma-ray flow. The increase in the cross-section of a product up to 28 cm leads to the increase in the absorbed energy by more than 2 times. At the same time, the thickness of the product is constant. This effect is explained by the multiple scattering of gamma-rays. It leads to the nonuniform distribution of defects which can accumulate hydrogen and should be considered when developing the analysis methods. These edge effects are confirmed by the measurement of the thermal electromotive force for the samples of zirconium alloys before hydrogenation and gamma-ray irradiation, and after irradiation.

  12. The First FERMI-LAT Gamma-Ray Burst Catalog

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Asano, K.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; hide

    2013-01-01

    In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy great than (20 MeV) gamma-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above approximately 20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.

  13. Rossi Prize Lecture: Gamma Ray Bursts: Origins and Consequences

    Science.gov (United States)

    Meszaros, P.

    2000-12-01

    Some of the major stepping stones towards uncovering the mystery of gamma ray bursts will be discussed. This is an unfinished process, new observations being expected in the near future. I will review the current observational status, and discuss the present theoretical understanding of GRB, as well as the possible impact of future missions and experiments.

  14. Japanese VLBI Network Observations of a Gamma-Ray Narrow ...

    Indian Academy of Sciences (India)

    J. Astrophys. Astr. (2014) 35, 215–218 c Indian Academy of Sciences. Japanese VLBI Network Observations of a Gamma-Ray. Narrow-Line Seyfert 1 Galaxy 1H 0323+342. Kiyoaki Wajima1,∗. , Kenta Fujisawa2, Masaaki Hayashida3. & Naoki Isobe4. 1Shanghai Astronomical Observatory, Chinese Academy of Sciences,.

  15. On the time variability of gamma-ray sources

    DEFF Research Database (Denmark)

    F. Torres, Diego; Pessah, Martin Elias; E. Romero, Gustavo

    2001-01-01

    We present a Monte Carlo analysis of the recently introduced variability indices $\\tau$ (Tompkins 1999) and $I$ (Zhang et al. 2000 & Torres et al. 2001) for $\\gamma$-ray sources. We explore different variability criteria and prove that these two indices, despite the very different approaches used...

  16. BATSE Observations of Gamma-Ray Burst Tails

    Science.gov (United States)

    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.

  17. Evolution of gamma-ray burst progenitors at low metallicity

    NARCIS (Netherlands)

    Yoon, S.C.; Langer, N.

    2005-01-01

    Despite the growing evidence that long Gamma-Ray Bursts (GRBs) are associated with deaths of Wolf-Rayet stars, the evolutionary path of massive stars to GRBs and the exact nature of GRB progenitors remain poorly known. However, recent massive star evolutionary models indicate that — for sufficiently

  18. Application of prompt gamma-ray activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Yong Sam; Park, Kwang Won; Moon, Jong Hwa; Kim, Sun Ha; Baek, Sung Ryel [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2002-03-01

    This technical report is written for the promotion to utilization of prompt gamma-ray activation analysis facility to be installed in HANARO reactor. It is described for a practical aspects including experiment and equipments, methodology, current status of the research and development and its applications. 102 refs., 32 figs., 25 tabs. (Author)

  19. Gamma rays spotlight a dark horse for dark matter

    CERN Multimedia

    Seife, C

    2004-01-01

    "Do mysterious gamma rays emanating from the center of the galaxy hold the secret to the missing matter in the universe? A team of physicists suggests that they might. The controversial finding also shows how little is known about most of the mass in the cosmos"(1/2 page)

  20. Gamma-ray spectroscopy with relativistic exotic heavy-ions

    Indian Academy of Sciences (India)

    Vol. 57, No. 1. — journal of. July 2001 physics pp. 161–164. Gamma-ray spectroscopy with relativistic exotic heavy-ions. SAMIT MANDAL, J GERL, H GEISSEL, K HAUSCHILD. ¿. , M HELLSTR ¨OM, ... large [2,3] to perform a meaningful high spin decay spectroscopy of exotic nuclei. At the same time relativistic Coulomb ...

  1. Gamma-ray bursts, galactic nuclei and cosmic evolution

    Science.gov (United States)

    Rees, Martin J.

    2014-12-01

    This lecture summarises some aspects of gamma-ray bursts, a topic to which Bohdan Paczyński made crucial contributions. It then, more briefly, comments on quasars and active galactic nuclei, where the accretion processes studied by Paczyński and his Polish colleagues play a key role. The lecture concludes with some remarks on cosmology and cosmic evolution.

  2. The NuSTAR View of Gamma Ray Bursts

    Science.gov (United States)

    Kouveliotou, C.

    2014-01-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR) mission was launched June 13, 2012. During the next two pears NuSTAR observed two Gamma Ray Bursts, GRBs 130427A and 130925A. I will describe here the NuSTAR GRB results and discuss their implications on the GRB field.

  3. Specification of High Activity Gamma-Ray Sources.

    Science.gov (United States)

    International Commission on Radiation Units and Measurements, Washington, DC.

    The report is concerned with making recommendations for the specifications of gamma ray sources, which relate to the quantity of radioactive material and the radiation emitted. Primary consideration is given to sources in teletherapy and to a lesser extent those used in industrial radiography and in irradiation units used in industry and research.…

  4. Statistical Properties of Gamma-Ray Burst Host Galaxies

    Indian Academy of Sciences (India)

    A statistical analysis of gamma-ray burst host galaxies is presented and a clear metallicity-stellar mass relation is found in our sample. A trend that a more massive host galaxy tends to have a higher star-formation rate is also found. No correlation is found between V and H. GRB host galaxies at a higher redshift also tend ...

  5. Detecting radio afterglows of gamma-ray bursts with FAST

    National Research Council Canada - National Science Library

    Zhi-Bin Zhang Si-Wei Kong Yong-Feng Huang Di Li Long-Biao Li

    2015-01-01

    Using the generic hydrodynamic model of gamma-ray burst (GRB) after- glows, we calculate the radio afterglow light curves of low luminosity, high luminosity, failed and standard GRBs in different observational bands of FAST's energy window...

  6. A search for Gamma Ray Burst Neutrinos in AMANDA

    NARCIS (Netherlands)

    Duvoort, M.R.|info:eu-repo/dai/nl/30483212X

    2009-01-01

    To date, no neutrinos with energies in or above the GeV range have been identified from astrophysical objects. The aim of the two analyses described in this dissertation is to observe high-energy muon neutrinos from Gamma Ray Bursts (GRBs). GRBs are distant sources, which were discovered by

  7. Reducing Statistical Noise in Airborne Gamma-Ray Data

    DEFF Research Database (Denmark)

    Hovgaard, Jens; Grasty, R. L.

    1997-01-01

    By using the Noise Adjusted Singular Value Decomposition (NASVD) technique it is possible to reconstruct the measured airborne gamma-ray spectra with a noise content that is significant smaller than the noise contained in the original measured spectra. The method can be used for improving the out...... the output of the data processing for example mapping of Th, U, and K distribution....

  8. Constraints on relativity violations from gamma-ray bursts.

    Science.gov (United States)

    Kostelecký, V Alan; Mewes, Matthew

    2013-05-17

    Tiny violations of the Lorentz symmetry of relativity and the associated discrete CPT symmetry could emerge in a consistent theory of quantum gravity such as string theory. Recent evidence for linear polarization in gamma-ray bursts improves existing sensitivities to Lorentz and CPT violation involving photons by factors ranging from ten to a million.

  9. Is dark matter visible by galactic gamma rays?

    Indian Academy of Sciences (India)

    The EGRET excess in the diffuse galactic gamma ray data above 1 GeV shows all features expected from dark matter WIMP annihilation: (a) It is present and has the same spectrum in all sky directions, not just in the galactic plane. (b) The intensity of the excess shows the 1/2 profile expected for a flat rotation curve outside ...

  10. Neutron-stimulated gamma ray analysis of soil

    Science.gov (United States)

    The chapter will discuss methods to use gamma rays to measure elements in soil. In regard to land management, there is a need to develop a non-destructive, non-contact, in-situ method of determining soil elements distributed in a soil volume or on soil surface. A unique method having all of above ...

  11. Calculation of Dose Gamma Ray Build up Factor in Some ...

    African Journals Online (AJOL)

    The gamma ray buildup factor was calculated by analyzing the narrow- beam and broad-beam geometry equations using Taylor's formula for isotropic sources and homogeneous materials. The buildup factor was programmed using MATLAB software to operate with any radiation energy (E), atomic number (Z) and the ...

  12. Gamma-ray burst afterglows from transrelativistic blast wave simulations

    NARCIS (Netherlands)

    van Eerten, H. J.; Leventis, K.; Meliani, Z.; Wijers, R.A.M.J.; Keppens, R.

    2010-01-01

    We present a study of the intermediate regime between ultrarelativistic and non-relativistic flow for gamma-ray burst afterglows. The hydrodynamics of spherically symmetric blast waves is numerically calculated using the AMRVAC adaptive mesh refinement code. Spectra and light curves are calculated

  13. Gamma-ray burst afterglows from transrelativistic blast wave simulations

    NARCIS (Netherlands)

    van Eerten, H. J.; Leventis, K.; Meliani, Z.; Wijers, Ramj; Keppens, R.

    2010-01-01

    We present a study of the intermediate regime between ultrarelativistic and non-relativistic flow for gamma-ray burst afterglows. The hydrodynamics of spherically symmetric blast waves is numerically calculated using the amrvac adaptive mesh refinement code. Spectra and light curves are calculated

  14. The width of the gamma-ray burst luminosity function

    NARCIS (Netherlands)

    Ulmer, A.; Wijers, R.A.M.J.

    1995-01-01

    We examine the width of the gamma-ray burst (GRB) luminosity function through the distribution of GRB peak count rates, Cpeak, as detected by Burst and Transient Source Experiment (BATSE) (1993). In the context of Galactic corona spatial distribution models, we attempt to place constaints on the

  15. Radiobiological studies using gamma and x rays.

    Energy Technology Data Exchange (ETDEWEB)

    Potter, Charles Augustus; Longley, Susan W.; Scott, Bobby R.; Lin, Yong; Wilder, Julie; Hutt, Julie A.; Padilla, Mabel T.; Gott, Katherine M.

    2013-02-01

    There are approximately 500 self-shielded research irradiators used in various facilities throughout the U.S. These facilities use radioactive sources containing either 137Cs or 60Co for a variety of biological investigations. A report from the National Academy of Sciences[1] described the issues with security of particular radiation sources and the desire for their replacement. The participants in this effort prepared two peer-reviewed publications to document the results of radiobiological studies performed using photons from 320-kV x rays and 137Cs on cell cultures and mice. The effectiveness of X rays was shown to vary with cell type.

  16. Capture Gamma-Ray Libraries for Nuclear Applications

    Energy Technology Data Exchange (ETDEWEB)

    Sleaford, B.W.; Firestone, Richard B.; Summers, N.; Escher, J.; Hurst, A.; Krticka, M.; Basunia, S.; Molnar, G.; Belgya, T.; Revay, Z.; Choi, H.D.

    2010-05-01

    The neutron capture reaction is useful in identifying and analyzing the gamma-ray spectrum from an unknown assembly as it gives unambiguous information on its composition. This can be done passively or actively where an external neutron source is used to probe an unknown assembly. There are known capture gamma-ray data gaps in the ENDF libraries used by transport codes for various nuclear applications. The Evaluated Gamma-ray Activation file (EGAF) is a new thermal neutron capture database of discrete line spectra and cross sections for over 260 isotopes that was developed as part of an IAEA Coordinated Research Project. EGAF has been used to improve the capture gamma production in ENDF libraries. For medium to heavy nuclei the quasi continuum contribution to the gamma cascades is not experimentally resolved. The continuum contains up to 90percent of all the decay energy an is modeled here with the statistical nuclear structure code DICEBOX. This code also provides a consistency check of the level scheme nuclear structure evaluation. The calculated continuum is of sufficient accuracy to include in the ENDF libraries. This analysis also determines new total thermal capture cross sections and provides an improved RIPL database. For higher energy neutron capture there is less experimental data available making benchmarking of the modeling codes more difficult. We use CASINO, a version of DICEBOX that is modified for this purpose. This can be used to simulate the neutron capture at incident neutron energies up to 20 MeV to improve the gamma-ray spectrum in neutron data libraries used for transport modelling of unknown assemblies.

  17. Neutron Capture Gamma-Ray Libraries for Nuclear Applications

    Energy Technology Data Exchange (ETDEWEB)

    Sleaford, B W; Firestone, R B; Summers, N; Escher, J; Hurst, A; Krticka, M; Basunia, S; Molnar, G; Belgya, T; Revay, Z; Choi, H D

    2010-11-04

    The neutron capture reaction is useful in identifying and analyzing the gamma-ray spectrum from an unknown assembly as it gives unambiguous information on its composition. this can be done passively or actively where an external neutron source is used to probe an unknown assembly. There are known capture gamma-ray data gaps in the ENDF libraries used by transport codes for various nuclear applications. The Evaluated Gamma-ray Activation file (EGAF) is a new thermal neutron capture database of discrete line spectra and cross sections for over 260 isotopes that was developed as part of an IAEA Coordinated Research project. EGAF is being used to improve the capture gamma production in ENDF libraries. For medium to heavy nuclei the quasi continuum contribution to the gamma cascades is not experimentally resolved. The continuum contains up to 90% of all the decay energy and is modeled here with the statistical nuclear structure code DICEBOX. This code also provides a consistency check of the level scheme nuclear structure evaluation. The calculated continuum is of sufficient accuracy to include in the ENDF libraries. This analysis also determines new total thermal capture cross sections and provides an improved RIPL database. For higher energy neutron capture there is less experimental data available making benchmarking of the modeling codes more difficult. They are investigating the capture spectra from higher energy neutrons experimentally using surrogate reactions and modeling this with Hauser-Feshbach codes. This can then be used to benchmark CASINO, a version of DICEBOX modified for neutron capture at higher energy. This can be used to simulate spectra from neutron capture at incident neutron energies up to 20 MeV to improve the gamma-ray spectrum in neutron data libraries used for transport modeling of unknown assemblies.

  18. Long duration gamma-ray emission from thunderclouds

    Science.gov (United States)

    Kelley, Nicole A.

    Gamma-ray glows are long duration emission coming from thunderclouds. They are one example of high-energy atmospheric physics, a relatively new field studying high-energy phenomena from thunderstorms and lightning. Glows arise from sustained relativistic runaway electron avalanches (RREA). Gamma-ray instruments on the ground, balloons and airplanes have detected glows. The Airborne Detector for Energetic Lightning Emissions (ADELE) is an array of gamma-ray detectors, built at the University of California, Santa Cruz. ADELE detected 12 gamma-ray glows during its summer 2009 campaign. ADELE was designed to study another type of high-energy atmospheric physics, terrestrial gamma-ray flashes (TGFs). TGFs are incredibly bright, sub-millisecond bursts of gamma-rays coming from thunderstorms. ADELE was installed on NCAR's Gulfstream V for the summer of 2009. While many glows were detected, only one TGF was observed. In this thesis I present a detailed explanation of the 2009 version of ADELE along with the results of the 2009 campaign. ADELE was modified to become a smaller, autonomous instrument to fly on the NASA drone, a Global Hawk. This was a piggyback to NASA's Hurricane and Severe Storm Sentinel mission. These flights took place during the summer of 2013. The following summer, ADELE flew on an Orion P3 as a piggyback of NOAA's Hurricane Hunters. This newer, modified instrument is discussed in detail in this thesis. The 12 gamma-ray glows from the 2009 campaign are presented, with information about nearby lightning activity. I show that lightning activity is suppressed after a glow. This could be from the glow causing the cloud to discharge and therefore reduce the lightning activity. It is also possible that glows can only occur once lightning activity has diminished. Lightning is also used to find a distance to the glow. Using this distance, it is found that the brightness of glow cannot be explained as a function of distance while the duration of the glow is

  19. Imaging and background in low-energy gamma ray astronomy

    Science.gov (United States)

    Lei, Fan

    The current status of low energy gamma ray astronomy is reviewed and the conclusion drawn that the next generation of low energy gamma ray telescopes will require high sensitivity, good timing, and spectral resolution. High angular resolution imaging capability is also considered essential. The imaging of low energy gamma rays is hampered by the difficulties encountered in developing high resolution position sensitive detectors. To this end, an improved Rotation Modulation Collimator (RMC) imaging technique, the phoswich multi-pitch RMC, is discussed. This imaging method employs currently available detector and pulse-shape discrimination techniques and is capable of producing images with an angular resolution which is comparable with that of the Coded Aperture Mask (CAM) imaging techniques. The imaging property of this new technique is studied. A comparison of three of the main imaging techniques used in low energy gamma ray astronomy, CAM, Fourier Transform Collimator, and RMC, is performed in terms of both theoretical performances and simulated imaging of the Galactic Center region. A realistic assessment of the possible applications of these three techniques to different types of astronomical Observations is also given. The atmospheric gamma ray radiation was measured by a number of balloon and satellite-borne instruments. A model of this radiation is developed based on the data as measured by a Compton telescope designed by the Max-Planck group. Emission spectra, as predicted by the model, are compared with various observed data, both inside and outside the atmosphere. The sources of background noise in low energy gamma ray telescopes are discussed. A comprehensive model of the background sources is developed and a generalized simulation program is presented which uses a combination of Monte Carlo methods and empirical calculations. Photon, proton, and neutron induced backgrounds are all considered as well as the effects of spacecraft and orbit. The model is

  20. ESA's Integral detects closest cosmic gamma-ray burst

    Science.gov (United States)

    2004-08-01

    5 August 2004 A gamma-ray burst detected by ESA's Integral gamma-ray observatory on 3 December 2003 has been thoroughly studied for months by an armada of space and ground-based observatories. Astronomers have now concluded that this event, called GRB 031203, is the closest cosmic gamma-ray burst on record, but also the faintest. This also suggests that an entire population of sub-energetic gamma-ray bursts has so far gone unnoticed... Gamma ray burst model hi-res Size hi-res: 22 KB Credits: CXC/M. Weiss Artist impression of a low-energy gamma-ray burst This illustration describes a model for a gamma-ray burst, like the one detected by Integral on 3 December 2003 (GRB 031203). A jet of high-energy particles from a rapidly rotating black hole interacts with surrounding matter. Observations with Integral on 3 December 2003 and data on its afterglow, collected afterwards with XMM-Newton, Chandra and the Very Large Array telescope, show that GRB 031203 radiated only a fraction of the energy of normal gamma-ray bursts. Like supernovae, gamma-ray bursts are thought to be produced by the collapse of the core of a massive star. However, while the process leading to supernovae is relatively well understood, astronomers still do not know what happens when a core collapses to form a black hole. The discovery of 'under-energetic' gamma-ray bursts, like GRB 031203, should provide valuable clues as to links between supernovae, black holes and gamma-ray bursts. Lo-res JPG (22 Kb) Hi-res TIFF (5800 Kb) Cosmic gamma-ray bursts (GRBs) are flashes of gamma rays that can last from less than a second to a few minutes and occur at random positions in the sky. A large fraction of them is thought to result when a black hole is created from a dying star in a distant galaxy. Astronomers believe that a hot disc surrounding the black hole, made of gas and matter falling onto it, somehow emits an energetic beam parallel to the axis of rotation. According to the simplest picture, all GRBs

  1. The relativistic feedback discharge model of terrestrial gamma ray flashes

    Science.gov (United States)

    Dwyer, Joseph R.

    2012-02-01

    As thunderclouds charge, the large-scale fields may approach the relativistic feedback threshold, above which the production of relativistic runaway electron avalanches becomes self-sustaining through the generation of backward propagating runaway positrons and backscattered X-rays. Positive intracloud (IC) lightning may force the large-scale electric fields inside thunderclouds above the relativistic feedback threshold, causing the number of runaway electrons, and the resulting X-ray and gamma ray emission, to grow exponentially, producing very large fluxes of energetic radiation. As the flux of runaway electrons increases, ionization eventually causes the electric field to discharge, bringing the field below the relativistic feedback threshold again and reducing the flux of runaway electrons. These processes are investigated with a new model that includes the production, propagation, diffusion, and avalanche multiplication of runaway electrons; the production and propagation of X-rays and gamma rays; and the production, propagation, and annihilation of runaway positrons. In this model, referred to as the relativistic feedback discharge model, the large-scale electric fields are calculated self-consistently from the charge motion of the drifting low-energy electrons and ions, produced from the ionization of air by the runaway electrons, including two- and three-body attachment and recombination. Simulation results show that when relativistic feedback is considered, bright gamma ray flashes are a natural consequence of upward +IC lightning propagating in large-scale thundercloud fields. Furthermore, these flashes have the same time structures, including both single and multiple pulses, intensities, angular distributions, current moments, and energy spectra as terrestrial gamma ray flashes, and produce large current moments that should be observable in radio waves.

  2. Modeling X-ray and gamma-ray emission in the intrabinary shock of pulsar binaries

    Science.gov (United States)

    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.

  3. Star formation rates and stellar masses in z ~ 1 gamma-ray burst hosts

    DEFF Research Database (Denmark)

    Castro Cerón, José María; Michalowski, Michal; Hjorth, J.

    2006-01-01

    Cosmology: Observations, ISM: Dust, Extinction, Galaxies: High-Redshift, Galaxies: ISM, Gamma Rays: Bursts, Infrared: Galaxies Udgivelsesdato: Dec. 4......Cosmology: Observations, ISM: Dust, Extinction, Galaxies: High-Redshift, Galaxies: ISM, Gamma Rays: Bursts, Infrared: Galaxies Udgivelsesdato: Dec. 4...

  4. MESSENGER E/V/H GRNS 5 GAMMA RAY SPECTROMETER DAP V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — Abstract ======== The GRS experiment is a gamma-ray spectrometer designed to observe spectra of gamma rays emitted from Mercury's surface in the energy range from...

  5. ODY MARS GAMMA RAY SPECTROMETER 2 EDR V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — The Odyssey Gamma Ray Spectrometer (GRS) Experiment Data Records (EDRs) are raw, uncalibrated spectra and ancillary data acquired by the Gamma Ray Subsystem -- the...

  6. ODY MARS GAMMA RAY SPECTROMETER 5 AND V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — The ODY MARS GAMMA RAY SPECTROMETER 5 AND data set is a table of neutron data from the NS sub-system of the Mars Odyssey Gamma-Ray Spectrometer that have been...

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

    Energy Technology Data Exchange (ETDEWEB)

    Sarnoski, Sarah E.; Fast, James E.; Fulsom, Bryan G.; Gilbert, Andrew J.; Jacomb-Hood, Timothy W.; VanDevender, Brent A.; Wood, Lynn S.

    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 one 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.

  8. Short Hard Gamma Ray Bursts And Their Afterglows

    CERN Document Server

    Dado, Shlomo

    2009-01-01

    Long duration gamma ray bursts (GRBs) and X-ray flashes (XRFs) are produced by highly- relativistic jets ejected in core-collapse supernova explosions. The origin of short hard gamma-ray bursts (SHBs) has not been established. They may be produced by highly relativistic jets ejected in various processes: mergers of compact stellar objects; large-mass accretion episodes onto compact stars in close binaries or onto intermediate-mass black holes in dense stellar regions; phase transition of compact stars. Natural environments of such events are the dense cores of globular clusters, superstar clusters and young supernova remnants. We have used the cannonball model of GRBs to analyze all Swift SHBs with a well-sampled X-ray afterglow. We show that their prompt gamma-ray emission can be explained by inverse Compton scattering (ICS) of the progenitor's glory light, and their extended soft emission component by ICS of high density light or synchrotron radiation (SR) in a high density interstellar medium within the cl...

  9. Illuminating Radio Dim/Gamma-ray Bright Active Galactic Nuclei

    Science.gov (United States)

    Macomb, Daryl J.; Bohney, Amanda; Shrader, Chris R.

    2017-08-01

    A recent survey of high-latitude gamma-ray sources by Schinzel et al. (arXiv:1702.070336), reveals a sample of about 100 objects which are not detected in the 4-10 GHz radio band to a limiting flux of about 2mJy. This apparent lack of radio flux is puzzling, and may indicate either an extreme Compton-dominated sample, or copious gamma-ray emission from a heretofore unknown population such as a subclass of radio-quiet AGN. To further investigate the nature sources, we have undertaken the task of searching for transient or faint steady emission in the ~15-100-keV X-ray band using the Swift/BAT archive. Here we discuss the analysis, detection's (or not) , and any spectral or temporal information that may enable us to assess the nature of these sources.

  10. The x-/gamma-ray camera ECLAIRs for the gamma-ray burst mission SVOM

    Science.gov (United States)

    Godet, O.; Nasser, G.; Atteia, J.-.; Cordier, B.; Mandrou, P.; Barret, D.; Triou, H.; Pons, R.; Amoros, C.; Bordon, S.; Gevin, O.; Gonzalez, F.; Götz, D.; Gros, A.; Houret, B.; Lachaud, C.; Lacombe, K.; Marty, W.; Mercier, K.; Rambaud, D.; Ramon, P.; Rouaix, G.; Schanne, S.; Waegebaert, V.

    2014-07-01

    We present ECLAIRs, the Gamma-ray burst (GRB) trigger camera to fly on-board the Chinese-French mission SVOM. ECLAIRs is a wide-field (~ 2 sr) coded mask camera with a mask transparency of 40% and a 1024 cm2 detection plane coupled to a data processing unit, so-called UGTS, which is in charge of locating GRBs in near real time thanks to image and rate triggers. We present the instrument science requirements and how the design of ECLAIRs has been optimized to increase its sensitivity to high-redshift GRBs and low-luminosity GRBs in the local Universe, by having a low-energy threshold of 4 keV. The total spectral coverage ranges from 4 to 150 keV. ECLAIRs is expected to detect ~ 200 GRBs of all types during the nominal 3 year mission lifetime. To reach a 4 keV low-energy threshold, the ECLAIRs detection plane is paved with 6400 4 × 4 mm2 and 1 mm-thick Schottky CdTe detectors. The detectors are grouped by 32, in 8×4 matrices read by a low-noise ASIC, forming elementary modules called XRDPIX. In this paper, we also present our current efforts to investigate the performance of these modules with their front-end electronics when illuminated by charged particles and/or photons using radioactive sources. All measurements are made in different instrument configurations in vacuum and with a nominal in-flight detector temperature of -20°C. This work will enable us to choose the in-flight configuration that will make the best compromise between the science performance and the in-flight operability of ECLAIRs. We will show some highlights of this work.

  11. Modulated method for efficient, narrow-bandwidth, laser Compton X-ray and gamma-ray sources

    Science.gov (United States)

    Barty, Christopher P. J.

    2017-07-11

    A method of x-ray and gamma-ray generation via laser Compton scattering uses the interaction of a specially-formatted, highly modulated, long duration, laser pulse with a high-frequency train of high-brightness electron bunches to both create narrow bandwidth x-ray and gamma-ray sources and significantly increase the laser to Compton photon conversion efficiency.

  12. Shielding property of natural biomass against gamma rays.

    Science.gov (United States)

    Mavi, B; Gurbuz, L F; Ciftci, H; Akkurt, I

    2014-01-01

    Algae and cyanobacteria are capable living under harsh conditions in the natural environments and can develop peculiar survival processes. In order to evaluate radiation shielding properties of green algae; Chlorella vulgaris, Scenedesmus obliquus, and cyanobacteria; Synechococcus sp., Planktothrix limnetica, Microcystis aeruginosa, Arthrospira maxima, Anabaena affinis, Phormidium articulatum, and Pseudoanabaena sp. were cultured in batch systems. Air dried biomass was tested for its high tolerance to gamma-radiations in terms of linear attenuation coefficients. In the present work, the linear and mass attenuation coefficients were measured at photon energies of 1173 and 1332 keV. Protection capacity of some biomass was observed to be higher than a 1-cm thick lead standard for comparison. Gamma ray related protection depends not only to thickness but also to density (g/cm3). Hence the effect of biomass density also was tested and significantly found the tested biomass absorbed more of the incoming energy on a density basis than lead. This paper discusses the a new approach to environmental protection from gamma ray. The findings suggest that the test samples, especially cyanobacteria, have a potential for reducing gamma ray more significantly than lead and can be used as shielding materials.

  13. A compact gamma ray imager for oncology

    CERN Document Server

    Pani, R; Del Guerra, A; Festinesi, A; Garibaldi, F; Gigliotti, T; Pellegrini, R; Scafe, R; Scopinaro, F; Soluri, A; Tati, A

    2002-01-01

    A variety of new techniques based on radiopharmaceuticals are showing a valid support for cancer detection and interventional procedures. Axillary lymph nodes status is the most important prognostic factor for determining breast cancer prognosis. The use of dedicated gamma cameras characterized by low costs and weight, could be easily transferred to detection for bioptical procedures. To this aim this paper presents a new detection system having two heads with 4 and 25 cm sup 2 Field of View (FOV) and 0.8 and 3.6 kg weight, respectively. This novel scintillation camera is based upon a compact Position Sensitive Photo Multiplier Tube (PSPMT) Hamamatsu R5900-C8 as individual or array assembled. The Hamamatsu R5900-C8 is a metal channel dynode PMT with a crossed wire anode. The overall dimensions are 28x28 mm sup 2 and 20 mm height. It was coupled to a CsI(Tl) array of individual 3x3x3 mm sup 3 crystals. The measured intrinsic spatial resolution proved much better than the pixel size. A clinical image obtained f...

  14. SU-F-I-56: High-Precision Gamma-Ray Analysis of Medical Isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, N; Chillery, T; Chowdhury, P; Lister, C [University of Massachusetts-Lowell, Lowell, MA (United States); McCutchan, E [National Nuclear Data Center, Brookhaven National Laboratory, Upton, NY (United States); Smith, C [BLIP Facility, Brookhaven National Laboratory, Upton, NY (United States)

    2016-06-15

    Purpose: Advanced, time-resolved, Compton-suppressed gamma-ray spectroscopy with germanium detectors is implemented for assaying medical isotopes to study the radioactive decay process leading to a more accurate appraisal of the received dose and treatment planning. Lowell’s Array for Radiological Assay (LARA), a detector array that is comprised of six Compton-suppressed high-purity germanium detectors, is currently under development at UMass-Lowell which combines Compton-suppression and time-and-angle correlations to allow for highly efficient and highly sensitive measurements. Methods: Two isotopes produced Brookhaven Linac Isotope Producer (BLIP) were investigated. {sup 82}Sr which is the parent isotope for producing {sup 82}Rb is often used in cardiac PET. {sup 82}Sr gamma-ray spectrum is dominated by the 511keV photons from positron annihilation which prevent precise measurement of co-produced contaminant isotopes. A second project was to investigate the production of platinum isotopes. Natural platinum was bombarded with protons from 53MeV to 200MeV. The resulting spectrum was complicated due to the large number of stable platinum isotopes in the target, the variety of open reaction channels (p,xn), (p,pxn), (p,axn). Results: By using face-to-face NaI(Tl) counters 90-degrees to the Compton-suppressed germaniums to detect the 511keV photons, a much cleaner and more sensitive measurement of {sup 85}Sr and other contaminants was obtained. For the platinum target, we identified the production of {sup 188–189–191–195}Pt, {sup 191–192–193–194–195–196}Au and {sup 186–188–189–190–192–194–189–190–192–194}Ir. For example, at the lower energies (53 and 65MeV), we measured {sup 191}Pt production cross-sections of 144mb and 157mb. Considerable care was needed in following the process of dissolving and diluting the samples to get consistent results. The new LARA array will help us better ascertain the absolute efficiency of the counting

  15. Explaining the light curves of Gamma-ray Bursts with precessing jets

    OpenAIRE

    Zwart, Simon Portegies

    1999-01-01

    A phenomenological model is presented to explain the light curves of gamma-ray bursts. Gamma-rays are produced in a narrow beam which sweeps through space due to the precession of a slaved accretion disc. The light curve expected from such a precessing luminosity cone can explain the complex temporal behavior of bright gamma-ray bursts.

  16. The pulsar contribution to the diffuse galactic gamma-ray emission

    DEFF Research Database (Denmark)

    Pohl, M.; Kanbach, G.; Hunter, S.D.

    1997-01-01

    There is active interest in the extent to which unresolved gamma-ray pulsars contribute to the Galactic diffuse emission, and in whether unresolved gamma-ray pulsars could be responsible for the excess of diffuse Galactic emission above 1 GeV that has been observed by EGRET. The diffuse gamma-ray...

  17. Airborne Gamma-ray Measurements in the Chernobyl Plume

    DEFF Research Database (Denmark)

    Grasty, R. L.; Hovgaard, Jens; Multala, J.

    1997-01-01

    On 29 April 1986, the Geological Survey of Finland (GSF) survey aircraft with a gamma ray spectrometer flew through a radioactive plume from the Chernobyl nuclear accident. The aircraft became contaminated and the gamma spectrometer measured radioactivity in the plume as well as radioactivity...... on the aircraft. By using simple assumptions on the build-up of contamination it has been possible to separate the signals from contamination and from plume. The analysis further showed that even a detector/spectrometer with low energy resolution is able to identify a contamination with iodine....

  18. A Novel Study Connecting Ultra-High Energy Cosmic Rays, Neutrinos, and Gamma-Rays

    Science.gov (United States)

    Coenders, Stefan; Resconi, Elisa; Padovani, Paolo; Giommi, Paolo; Caccianiga, Lorenzo

    We present a novel study connecting ultra-high energy cosmic rays, neutrinos, and gamma-rays with the objective to identify common counterparts of the three astrophysical messengers. In the test presented here, we first identify potential hadronic sources by filtering gamma-ray emitters that are in spatial coincidence with IceCube neutrinos. Subsequently, these objects are correlated against ultra-high energy cosmic rays detected by the Pierre Auger Observatory and the Telescope Array, scanning in gamma-ray flux and angular separation between sources and cosmic rays. A maximal excess of 80 cosmic rays (41.9 expected) is observed for the second catalog of hard Fermi-LAT objects of blazars of the high synchrotron peak type. This corresponds to a deviation from the null-hypothesis of 2.94σ . No excess is observed for objects not in spatial connection with neutrinos. The gamma-ray sources that make up the excess are blazars of the high synchrotron peak type.

  19. High spatial resolution X-ray and gamma ray imaging system using diffraction crystals

    Science.gov (United States)

    Smither, Robert K [Hinsdale, IL

    2011-05-17

    A method and a device for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation are provided. The device comprises a plurality of arrays, with each array comprising a plurality of elements comprising a first collimator, a diffracting crystal, a second collimator, and a detector.

  20. Ultra-high energy cosmic rays and prompt TeV gamma rays from ...

    Indian Academy of Sciences (India)

    1020 eV. The synchrotron radiation of the highest energy protons accelerated within the GRB source should produce gamma rays up to TeV energies. Here we briefly discuss the implications on the energetics of the GRB from the point of view of the detectability of the prompt TeV 7-rays of proton-synchrotron origin in GRBs ...

  1. Modeling of Pulses in Terrestrial Gamma-ray Flashes

    Science.gov (United States)

    Xu, Wei; Celestin, Sebastien; Pasko, Victor

    2015-04-01

    Terrestrial Gamma-ray Flashes (TGFs) are high-energy photon bursts originating from the Earth's atmosphere that are associated with lightning activities. After their discovery in 1994 by the Burst and Transient Source Experiment (BATSE) detector aboard the Compton Gamma-Ray Observatory [Fishman et al., Science, 264, 1313, 1994], this phenomenon has been further observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) [Smith et al., Science, 307, 1085, 2005], the Fermi Gamma-ray Space Telescope [Briggs et al., JGR, 115, A07323, 2010] and the Astrorivelatore Gamma a Immagini Leggero (AGILE) satellite [Marisaldi et al., JGR, 115, A00E13, 2010]. Photon spectra corresponding to the mechanism of relativistic runaway electron avalanches (RREAs) usually provide a very good agreement with satellite observations [Dwyer and Smith, GRL, 32, L22804, 2005]. On the other hand, Celestin and Pasko [JGR, 116, A03315, 2011] have shown theoretically that the large flux of thermal runaway electrons generated by streamers during the negative corona flash stage of stepping lightning leaders in intracloud lightning flashes could be responsible for TGFs. Recently, based on analysis of the temporal profiles of 278 TGF events observed by the Fermi Gamma-Ray Burst Monitor, Foley et al. [JGR, 119, 5931, 2014] have suggested that 67% of TGF pulses detected are asymmetric and these asymmetric pulses are consistent with the production mechanism of TGFs by relativistic feedback discharges. In the present work, we employ a Monte Carlo model to study the temporal distribution of photons at low-orbit satellite altitudes during TGF events. Using the pulse fitting method described in [Foley et al., 2014], we further investigate the characteristics of TGF pulses. We mainly focus on the effects of Compton scattering on the symmetry properties and the rise and fall times of TGF pulses.

  2. An X-ray perspective on a gamma-ray mission

    DEFF Research Database (Denmark)

    Lund, Niels

    2003-01-01

    The most recent astrophysics mission of ESA is INTEGRAL, a mission dedicated to gamma-ray astronomy (Winkler et al. 2003). INTEGRAL carries two gamma-ray instruments: the imager, IBIS, and the spectrometer, SPI, and in addition an optical monitor, OMC, and an X-ray monitor, JEM-X. INTEGRAL...... is an observatory mission with 70% of the observation time available to the general astronomical community through a peer-reviewed selection process. This paper describes the INTEGRAL mission primarily as seen from the JEM-X perspective....

  3. Parametric normalization for full-energy peak efficiency of HPGe γ-ray spectrometers at different counting positions for bulky sources.

    Science.gov (United States)

    Peng, Nie; Bang-Fa, Ni; Wei-Zhi, Tian

    2013-02-01

    Application of effective interaction depth (EID) principle for parametric normalization of full energy peak efficiencies at different counting positions, originally for quasi-point sources, has been extended to bulky sources (within ∅30 mm×40 mm) with arbitrary matrices. It is also proved that the EID function for quasi-point source can be directly used for cylindrical bulky sources (within ∅30 mm×40 mm) with the geometric center as effective point source for low atomic number (Z) and low density (D) media and high energy γ-rays. It is also found that in general EID for bulky sources is dependent upon Z and D of the medium and the energy of the γ-rays in question. In addition, the EID principle was theoretically verified by MCNP calculations. Copyright © 2012 Elsevier Ltd. All rights reserved.

  4. Time Evolution of Gamma Rays from Supernova Remnants

    Science.gov (United States)

    Gaggero, Daniele; Zandanel, Fabio; Cristofari, Pierre; Gabici, Stefano

    2018-01-01

    We present a systematic phenomenological study focused on the time evolution of the non-thermal radiation - from radio waves to gamma rays - emitted by typical supernova remnants via hadronic and leptonic mechanisms, for two classes of progenitors: thermonuclear and core-collapse. To this aim, we develop a numerical tool designed to model the evolution of the cosmic-ray spectrum inside a supernova remnant, and compute the associated multi-wavelength emission. We demonstrate the potential of this tool in the context of future population studies based on large collection of high-energy gamma-ray data. We discuss and explore the relevant parameter space involved in the problem, and focus in particular on their impact on the maximum energy of accelerated particles, in order to study the effectiveness and duration of the PeVatron phase. We outline the crucial role of the ambient medium through which the shock propagates during the remnant evolution. In particular, we point out the role of dense clumps in creating a significant hardening in the hadronic gamma-ray spectrum.

  5. THE FIRST FERMI-LAT GAMMA-RAY BURST CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Ackermann, M. [Deutsches Elektronen Synchrotron DESY, D-15738 Zeuthen (Germany); Ajello, M. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Asano, K. [Interactive Research Center of Science, Tokyo Institute of Technology, Meguro City, Tokyo 152-8551 (Japan); Axelsson, M. [Department of Astronomy, Stockholm University, SE-106 91 Stockholm (Sweden); Baldini, L. [Università di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, 91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Bechtol, K.; Bloom, E. D. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bhat, P. N. [Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States); Bissaldi, E. [Institut für Astro- und Teilchenphysik and Institut für Theoretische Physik, Leopold-Franzens-Universität Innsbruck, A-6020 Innsbruck (Austria); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Bonnell, J.; Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bouvier, A., E-mail: nicola.omodei@stanford.edu, E-mail: giacomov@slac.stanford.edu [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); and others

    2013-11-01

    In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (∼> 20 MeV) γ-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above ∼20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.

  6. Elemental analysis of a concrete sample by capture gamma rays with a radioisotope neutron source

    Energy Technology Data Exchange (ETDEWEB)

    Collico Savio, D.L. [Ciudad Universitaria, Buenos Aires (Argentina). Lab. de Fisica Nuclear; Mariscotti, M.A.J. [Ciudad Universitaria, Buenos Aires (Argentina). Lab. de Fisica Nuclear; Ribeiro Guevara, S. [Laboratorio Analisis por Activacion Neutronica, Centro Atomico Bariloche, 8400 Bariloche (Argentina)

    1995-03-15

    Gamma radiation from capture of neutrons in concrete has been studied in the energy region from 0.3 to 10.5 MeV with a HPGe spectrometer and an AmBe neutron source. A careful analysis of the Fe, Si, Ca, and Cl peak intensities made it possible to determine their relative concentrations in the sample. A comparison has been made between this nuclear method and chemical techniques, resulting in good agreement. The employment of these nuclear reactions constitutes a promising technique for the bulk analysis of samples in the concrete industry, because of its nondestructive and in-situ nature. ((orig.)).

  7. DAMPE: A gamma and cosmic ray observatory in space

    Science.gov (United States)

    D'Urso, D.; Dampe Collaboration

    2017-05-01

    DAMPE (DArk Matter Particle Explorer) is one of the five satellite missions in the framework of the Strategic Pioneer Research Program in Space Science of the Chinese Academy of Sciences (CAS). Launched on December 17th 2015 at 08:12 Beijing time, it is taking data into a sun-synchronous orbit, at the altitude of 500km. The main scientific objective of DAMPE is to detect electrons and photons in the range 5GeV-10TeV with unprecedented energy resolution, in order to identify possible Dark Matter signatures. It will also measure the flux of nuclei up to 100TeV with excellent energy resolution. The satellite is equipped with a powerful space telescope for high energy gamma-ray, electron and cosmic rays detection. It consists of a plastic scintillator strips detector (PSD) that serves as anti-coincidence detector, a silicon-tungsten tracker (STK), a BGO imaging calorimeter of about 32 radiation lengths, and a neutron detector. With its excellent photon detection capability and its detector performances (at 100GeV energy resolution ˜1% , angular resolution ˜0.1° , the DAMPE mission is well placed to make strong contributions to high-energy gamma-ray observations: it covers the gap between space and ground observation; it will allow to detect a line signature in the gamma-ray spectrum, if present, in the sub-TeV to TeV region; it will allow a high precision gamma-ray astronomy. A report on the mission goals and status will be discussed, together with in-orbit first data coming from space.

  8. The effect of a gamma ray flare on Schumann resonances

    Directory of Open Access Journals (Sweden)

    A. P. Nickolaenko

    2012-09-01

    Full Text Available We describe the ionospheric modification by the SGR 1806-20 gamma flare (27 December 2004 seen in the global electromagnetic (Schumann resonance. The gamma rays lowered the ionosphere over the dayside of the globe and modified the Schumann resonance spectra. We present the extremely low frequency (ELF data monitored at the Moshiri observatory, Japan (44.365° N, 142.24° E. Records are compared with the expected modifications, which facilitate detection of the simultaneous abrupt change in the dynamic resonance pattern of the experimental record. The gamma flare modified the current of the global electric circuit and thus caused the "parametric" ELF transient. Model results are compared with observations enabling evaluation of changes in the global electric circuit.

  9. On the attenuation of x-rays and gamma-rays in dilute solutions

    DEFF Research Database (Denmark)

    Gerward, Leif

    1996-01-01

    The theory of X-ray and gamma-ray attenuation in solutions is developed. The rule of mixture for the calculation of mass and linear attenuation coefficients is elaborated in the general case as well as in the limit of extreme dilution. The validity of the latter approximation is illustrated...... by the attenuation of 17.443 keV X-rays in aqueous solutions of NaCl. Copyright (C) 1996 Elsevier Science Ltd...

  10. Experimental determination of gamma-ray discrimination in pillar-structured thermal neutron detectors under high gamma-ray flux

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Qinghui [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Conway, Adam M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Voss, Lars F. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Radev, Radoslav P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Nikolić, Rebecca J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dar, Mushtaq A. [King Saud Univ., Riyadh (Saudi Arabia); Cheung, Chin L. [Univ. of Nebraska, Lincoln, NE (United States). Dept. of Chemistry

    2015-08-04

    Silicon pillar structures filled with a neutron converter material (10B) are designed to have high thermal neutron detection efficiency with specific dimensions of 50 μm pillar height, 2 μm pillar diameter and 2 μm spacing between adjacent pillars. In this paper, we have demonstrated such a detector has a high neutron-to-gamma discrimination of 106 with a high thermal neutron detection efficiency of 39% when exposed to a high gamma-ray field of 109 photons/cm2s.

  11. Experimental determination of gamma-ray discrimination in pillar-structured thermal neutron detectors under high gamma-ray flux

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Qinghui; Conway, Adam M.; Voss, Lars F.; Radev, Radoslav P. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); Nikolić, Rebecca J., E-mail: nikolic1@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); Dar, Mushtaq A. [King Saud University, Riyadh 11421 (Saudi Arabia); Cheung, Chin L. [Department of Chemistry, University of Nebraska–Lincoln, Lincoln, NE 68588 (United States)

    2015-11-01

    In this paper, we demonstrate a detector that has a high neutron-to-gamma discrimination of 8.5×10{sup 5} with a high thermal neutron detection efficiency of 39% when exposed to a high gamma-ray field of 10{sup 9} photons/cm{sup 2}s. The detector is based on a silicon pillar structure filled with a neutron converter material ({sup 10}B) designed to have high thermal neutron detection efficiency. The pillar dimensions are 50 µm pillar height, 2 µm pillar diameter and 2 µm spacing between adjacent pillars.

  12. Cosmic Forensics Confirms Gamma-Ray Burst And Supernova Connection

    Science.gov (United States)

    2003-03-01

    Scientists announced today that they have used NASA's Chandra X-ray Observatory to confirm that a gamma-ray burst was connected to the death of a massive star. This result is an important step in understanding the origin of gamma-ray bursts, the most violent events in the present-day universe. "If a gamma-ray burst were a crime, then we now have strong circumstantial evidence that a supernova explosion was at the scene," said Nathaniel Butler of Massachusetts Institute of Technology in Cambridge, lead author of a paper presented today at the meeting of the High Energy Division of the American Astronomical Society. Chandra was able to obtain an unusually long observation (approximately 21 hours) of the afterglow of GRB 020813 (so named because the High-Energy Transient Explorer, HETE, discovered it on August 13, 2002.) A grating spectrometer aboard Chandra revealed an overabundance of elements characteristically dispersed in a supernova explosion. Narrow lines, or bumps, due to silicon and sulfur ions (atoms stripped of most of their electrons) were clearly identified in the X-ray spectrum of GRB 020813. "Our observation of GRB 020813 supports two of the most important features of the popular supra-nova model for gamma-ray bursts," said Butler. "An extremely massive star likely exploded less than two months prior to the gamma-ray burst, and the radiation from the gamma-ray burst was beamed into a narrow cone." An analysis of the data showed that the ions were moving away from the site of the gamma-ray burst at a tenth the speed of light, probably as part of a shell of matter ejected in the supernova explosion. The line features were observed to be sharply peaked, indicating that they were coming from a narrow region of the expanding shell. This implies that only a small fraction of the shell was illuminated by the gamma-ray burst, as would be expected if the burst was beamed into a narrow cone. The observed duration of the afterglow suggests a delay of about 60 days

  13. Light Dawns on Dark Gamma-ray Bursts

    Science.gov (United States)

    2010-12-01

    Gamma-ray bursts are among the most energetic events in the Universe, but some appear curiously faint in visible light. The biggest study to date of these so-called dark gamma-ray bursts, using the GROND instrument on the 2.2-metre MPG/ESO telescope at La Silla in Chile, has found that these gigantic explosions don't require exotic explanations. Their faintness is now fully explained by a combination of causes, the most important of which is the presence of dust between the Earth and the explosion. Gamma-ray bursts (GRBs), fleeting events that last from less than a second to several minutes, are detected by orbiting observatories that can pick up their high energy radiation. Thirteen years ago, however, astronomers discovered a longer-lasting stream of less energetic radiation coming from these violent outbursts, which can last for weeks or even years after the initial explosion. Astronomers call this the burst's afterglow. While all gamma-ray bursts [1] have afterglows that give off X-rays, only about half of them were found to give off visible light, with the rest remaining mysteriously dark. Some astronomers suspected that these dark afterglows could be examples of a whole new class of gamma-ray bursts, while others thought that they might all be at very great distances. Previous studies had suggested that obscuring dust between the burst and us might also explain why they were so dim. "Studying afterglows is vital to further our understanding of the objects that become gamma-ray bursts and what they tell us about star formation in the early Universe," says the study's lead author Jochen Greiner from the Max-Planck Institute for Extraterrestrial Physics in Garching bei München, Germany. NASA launched the Swift satellite at the end of 2004. From its orbit above the Earth's atmosphere it can detect gamma-ray bursts and immediately relay their positions to other observatories so that the afterglows could be studied. In the new study, astronomers combined Swift

  14. ESA's new view of the Milky Way - in gamma rays!

    Science.gov (United States)

    2003-11-01

    Integral's gamma-ray map of the galaxy hi-res Size hi-res: 430 kb Credits: ESA/SPI team A portion of Integral's gamma-ray map of the galaxy A portion of Integral's gamma-ray map of the galaxy. This false colour picture was taken by the spectrometer on board Integral (SPI) between December 2002 and March 2003. The yellow dots correspond to bright known gamma-rays sources, whilst blue areas indicate regions of low emission. Data similar to these, but in a higher energy range, have been used to study where aluminium and iron are produced in the Galaxy. Since its formation from a cloud of hydrogen and helium gas, around 12 000 million years ago, the Milky Way has gradually been enriched with heavier chemical elements. This has allowed planets and, indeed, life on Earth to form. Today, one of those heavier elements - radioactive aluminium - is spread throughout the Galaxy and, as it decays into magnesium, gives out gamma rays with a wavelength known as the '1809 keV line'. Integral has been mapping this emission with the aim of understanding exactly what is producing all this aluminium. In particular, Integral is looking at the aluminium 'hot spots' that dot the Galaxy to determine whether these are caused by individual celestial objects or the chance alignment of many objects. Astronomers believe that the most likely sources of the aluminium are supernovae (exploding high-mass stars) and, since the decay time of the aluminium is around one million years, Integral's map shows how many stars have died in recent celestial history. Other possible sources of the aluminium include 'red giant' stars or hot blue stars that give out the element naturally. To decide between these options, Integral is also mapping radioactive iron, which is only produced in supernovae. Theories suggest that, during a supernova blast, aluminium and iron should be produced together in the same region of the exploding star. Thus, if the iron's distribution coincides with that of the aluminium, it

  15. Are gamma-ray bursts the sources of ultra-high energy cosmic rays?

    Energy Technology Data Exchange (ETDEWEB)

    Baerwald, Philipp [Wuerzburg Univ. (Germany). Inst. fuer Theoretische Physik und Astrophysik; Pennsylvania State Univ., University Park, PA (United States). Dept. of Astronomy and Astrophysics; Pennsylvania State Univ., University Park, PA (United States). Dept. of Physics; Pennsylvania State Univ., University Park, PA (United States). Center for Particle and Gravitational Astrophysics; Pennsylvania State Univ., University Park, PA (United States). Inst. for Gravitation and the Cosmos; Bustamante, Mauricio; Winter, Walter [Wuerzburg Univ. (Germany). Inst. fuer Theoretische Physik und Astrophysik; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany)

    2014-07-15

    We reconsider the possibility that gamma-ray bursts (GRBs) are the sources of the ultra-high energy cosmic rays (UHECRs) within the internal shock model, assuming a pure proton composition of the UHECRs. For the first time, we combine the information from gamma-rays, cosmic rays, prompt neutrinos, and cosmogenic neutrinos quantitatively in a joint cosmic ray production and propagation model, and we show that the information on the cosmic energy budget can be obtained as a consequence. In addition to the neutron model, we consider alternative scenarios for the cosmic ray escape from the GRBs, i.e., that cosmic rays can leak from the sources. We find that the dip model, which describes the ankle in UHECR observations by the pair production dip, is strongly disfavored in combination with the internal shock model because (a) unrealistically high baryonic loadings (energy in protons versus energy in electrons/gamma-rays) are needed for the individual GRBs and (b) the prompt neutrino flux easily overshoots the corresponding neutrino bound. On the other hand, GRBs may account for the UHECRs in the ankle transition model if cosmic rays leak out from the source at the highest energies. In that case, we demonstrate that future neutrino observations can efficiently test most of the parameter space - unless the baryonic loading is much larger than previously anticipated.

  16. Production of gamma rays with energies greater than 30 MeV in the atmosphere

    Science.gov (United States)

    Thompson, D.; Fichtel, C.; Kniffen, D.

    1974-01-01

    A three-dimensional study of atmospheric gamma rays with energy greater than 30 MeV has been carried out. Experimental results were obtained from four balloon flights from Palestine, Texas, with a 15 cm by 15 cm digitized wire grid spark chamber. The energy spectrum for downward-moving gamma rays steepens with increasing atmospheric depth. Near the top of the atmosphere, the spectrum steepens with increasing zenith angle. Experimental results compare reasonably well with a three-dimensional Monte Carlo calculation of atmospheric gamma ray production. Inclusion of upward-moving gamma rays makes possible the use of atmospheric secondaries for in-flight calibration of satellite gamma ray detectors.

  17. Gamma Ray Bursts and Their Links With Supernovae and Cosmology

    Science.gov (United States)

    Meszaros, Peter; Gehrels, Neil

    2012-01-01

    Gamma-ray bursts are the most luminous explosions in the Universe, whose origin and mechanism is the focus of intense interest. They appear connected to supernova remnants from massive stars or the merger of their remnants, and their brightness makes them temporarily detectable out to the largest distances yet explored in the Universe. After pioneering breakthroughs from space and ground experiments, their study is entering a new phase with observations from the recently launched Fermi satellite, as well as the prospect of detections or limits from large neutrino and gravitational wave detectors. The interplay between such observations and theoretical models of gamma-ray bursts is reviewed, as well as their connections to supernovae and cosmology.

  18. Special Nuclear Material Gamma-Ray Signatures for Reachback Analysts

    Energy Technology Data Exchange (ETDEWEB)

    Karpius, Peter Joseph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Myers, Steven Charles [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-08-29

    These are slides on special nuclear material gamma-ray signatures for reachback analysts for an LSS Spectroscopy course. The closing thoughts for this presentation are the following: SNM materials have definite spectral signatures that should be readily recognizable to analysts in both bare and shielded configurations. One can estimate burnup of plutonium using certain pairs of peaks that are a few keV apart. In most cases, one cannot reliably estimate uranium enrichment in an analogous way to the estimation of plutonium burnup. The origin of the most intense peaks from some SNM items may be indirect and from ‘associated nuclides.' Indirect SNM signatures sometimes have commonalities with the natural gamma-ray background.

  19. Cosmology and the Subgroups of Gamma-ray Bursts

    Directory of Open Access Journals (Sweden)

    A. Mészáros

    2011-01-01

    Full Text Available Both short and intermediate gamma-ray bursts are distributed anisotropically in the sky (Mészáros, A. et al. ApJ, 539, 98 (2000, Vavrek, R. et al. MNRAS, 391, 1 741 (2008. Hence, in the redshift range, where these bursts take place, the cosmological principle is in doubt. It has already been noted that short bursts should be mainly at redshifts smaller than one (Mészáros, A. et al. Gamma-ray burst: Sixth Huntsville Symp., AIP, Vol. 1 133, 483 (2009; Mészáros, A. et al. Baltic Astron., 18, 293 (2009. Here we show that intermediate bursts should be at redshifts up to three.

  20. Simulating Terrestrial Gamma-ray Flashes using SWORD (Invited)

    Science.gov (United States)

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

    2013-12-01

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

  1. First results from gamma ray diagnostics in EAST Tokamak

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, R. J.; Hu, L. Q.; Zhong, G. Q., E-mail: gqzhong@ipp.ac.cn; Cao, H. R.; Liu, G. Z.; Li, K.; Zhang, Y.; Lin, S. Y.; Zhang, J. Z. [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2016-11-15

    Gamma ray diagnostics has been developed in the EAST tokamak recently. Six BGO scintillator detectors are arranged on the down-half cross-section and pointed at the up-half cross-section of plasma, with space resolution about 15 cm and energy range from 0.3 MeV to 6 MeV. Three main gamma ray peaks in the energy spectra have been observed and are identified as the results of nuclear reactions {sup 207}Pb(n, n′){sup 207m}Pb, H(n, γ) D, and D(p, γ){sup 3}He, respectively. Upgrading of the system is in progress by using LaBr3(Ce) scintillator, fast photo-multiplier tubes, and a fully digital data acquisition system based on high sample frequency digitizers with digital pulse processing algorithms.

  2. Airborne magnetic and gamma-ray data acquisition

    Energy Technology Data Exchange (ETDEWEB)

    Horsfall, K.R. [Australian Geological Survey Organisation, Canberra, ACT (Australia)

    1997-08-01

    Current aeromagnetic data acquisition has benefited from improvements in measurement precision and compensation systems for removing with closer line spacing than previously, and this has stimulated a demand for lower survey altitudes with flight heights of the order of 60-80 m now common. Radiometric recording of 256 channels of gamma-ray data is now virtually standard and in-flight stabilisation of these systems has improved markedly. Digital acquisition systems are now designed to facilitate both in-flight and post-flight verification of the data. This article briefly outlines he history of the acquisition equipment used in the earlier surveys and details the current sate-of-the-art technology and methodology used in airborne magnetic and gamma-ray surveys. 9 refs., 1 tab., 2 figs.

  3. Borehole Logging for Uranium by Gamma-Ray Spectrometry

    DEFF Research Database (Denmark)

    Løvborg, Leif; Nyegaard, P.; Christiansen, E. M.

    1980-01-01

    The resources in a large syngenetic deposit of low-grade uranium (U) ore with thorium at Kvanefjeld, South Greenland, were evaluated by spectrometric gamma-ray logging of 23 boreholes, 46 mm in diameter and 200 m deep. The borehole probe's detector contained 22 cm3 of sodium-iodide, and the photo......The resources in a large syngenetic deposit of low-grade uranium (U) ore with thorium at Kvanefjeld, South Greenland, were evaluated by spectrometric gamma-ray logging of 23 boreholes, 46 mm in diameter and 200 m deep. The borehole probe's detector contained 22 cm3 of sodium...... to another; this variation is believed to be caused by emanation of radon (Rn) from the borehole walls. Block calculations based on individual calibration constants for the boreholes logged made it possible to obtain a reliable estimate of the tonnage of U. This estimate was only slightly different from...

  4. Gamma-ray bursts, a puzzle being resolved

    CERN Multimedia

    Piran, T

    1999-01-01

    Gamma Ray Bursts (GRBs), short and intense bursts of Gamma-Rays, have puzzled astrophysicists since their accidental discovery in the seventies. BATSE, launched in 1991, has established the cosmological origin of GRBs and has shown that they involve energies much higher than previously expected, corresponding to the most powerful explosions known in the Universe. The fireball model, which has been developed during the last ten years, explains most of the observed features of GRBs . According to this model, GRBs are produced in internal collisions of ejected matter flowing at ultra-relativistic energy. This ultra-relativistic motion reaches Lorentz factors of order 100 or more, higher than seen elsewhere in the Universe. The GRB afterglow was discovered in 1997. It was predicted by this model and it takes place when this relativistic flow is slowed down by the surrounding material. This model was confirmed recently with the discovery last January of the predicted prompt optical emission from GRB 990123. Unfort...

  5. Polarized Emission from Gamma-Ray Burst Jets

    Directory of Open Access Journals (Sweden)

    Shiho Kobayashi

    2017-11-01

    Full Text Available I review how polarization signals have been discussed in the research field of Gamma-Ray Bursts (GRBs. I mainly discuss two subjects in which polarimetry enables us to study the nature of relativistic jets. (1 Jet breaks: Gamma-ray bursts are produced in ultra-relativistic jets. Due to the relativistic beaming effect, the emission can be modeled in a spherical model at early times. However, as the jet gradually slows down, we begin to see the edge of the jet together with polarized signals at some point. (2 Optical flash: later time afterglow is known to be insensitive to the properties of the original ejecta from the GRB central engine. However, a short-lived, reverse shock emission would enable us to study the nature of of GRB jets. I also briefly discuss the recent detection of optical circular polarization in GRB afterglow.

  6. Isotopic response with small scintillator based gamma-ray spectrometers

    Science.gov (United States)

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

    2012-01-24

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

  7. A mobile gamma ray spectrometer system for nuclear hazard mapping

    CERN Document Server

    Smethurst, M A

    2000-01-01

    The Geological Survey of Norway has developed a system for mobile gamma ray spectrometer surveying suitable for use in nuclear emergencies where potentially dangerous radioactive materials have been released into the environment. The measuring system has been designed for use with different kinds of transportation platforms. These include fixed-wing aircraft, helicopters and vans. The choice of transportation platform depends on the nature of the nuclear emergency. Widespread fallout from a distant source can be mapped quickly from the air while local sources of radiation can be delineated by a car-borne system. The measuring system processes gamma ray spectra in real time. The operator of the system is therefore able to guide surveying in accordance with meaningful data values and immediately report these values to decision making The operator is presented with a number of different displays suited to different kinds of nuclear emergencies that lead to more efficient surveying. Real time processing of data m...

  8. Further development of IDGS: Isotope dilution gamma-ray spectrometry

    Science.gov (United States)

    Li, T. K.; Parker, J. L.; Kuno, Y.; Sato, S.; Kamata, M.; Akiyama, T.

    The isotope dilution gamma-ray spectrometry (IDGS) technique for determining the plutonium concentration and isotopic composition of highly radioactive spent-fuel dissolver solutions has been further developed. Both the sample preparation and the analysis have been improved. The plutonium isotopic analysis is based on high-resolution, low-energy gamma-ray spectrometry. The plutonium concentration in the dissolver solutions then is calculated from the measured isotopic differences among the spike, the dissolver solution, and the spiked dissolver solution. Plutonium concentrations and isotopic compositions of dissolver solutions analyzed from this study agree well with those obtained by traditional isotope dilution mass spectrometry (IDMS) and are consistent with the first IDGS experimental result. With the current detector efficiency, sample size, and a 100-min count time, the estimated precision is approximately 0.5 percent for Pu-239 and Pu-240 isotopic analyses and approximately 1 percent for the plutonium concentration analysis.

  9. Binary millisecond pulsar discovery via gamma-ray pulsations.

    Science.gov (United States)

    Pletsch, H J; Guillemot, L; Fehrmann, H; Allen, B; Kramer, M; Aulbert, C; Ackermann, M; Ajello, M; de Angelis, A; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Borgland, A W; Bottacini, E; Brandt, T J; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Çelik, Ö; Charles, E; Chaves, R C G; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; D'Ammando, F; Dermer, C D; Digel, S W; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Favuzzi, C; Ferrara, E C; Franckowiak, A; Fukazawa, Y; Fusco, P; Gargano, F; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; den Hartog, P R; Hayashida, M; Hays, E; Hill, A B; Hou, X; Hughes, R E; Jóhannesson, G; Jackson, M S; Jogler, T; Johnson, A S; Johnson, W N; Kataoka, J; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Massaro, F; Mayer, M; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mitthumsiri, W; Mizuno, T; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Nemmen, R; Nuss, E; Ohno, M; Ohsugi, T; Omodei, N; Orienti, M; Orlando, E; de Palma, F; Paneque, D; Perkins, J S; Piron, F; Pivato, G; Porter, T A; Rainò, S; Rando, R; Ray, P S; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Romani, R W; Romoli, C; Sanchez, D A; Saz Parkinson, P M; Schulz, A; Sgrò, C; do Couto e Silva, E; Siskind, E J; Smith, D A; Spandre, G; Spinelli, P; Suson, D J; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Tinivella, M; Troja, E; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Winer, B L; Wood, K S; Wood, M; Yang, Z; Zimmer, S

    2012-12-07

    Millisecond pulsars, old neutron stars spun up by accreting matter from a companion star, can reach high rotation rates of hundreds of revolutions per second. Until now, all such "recycled" rotation-powered pulsars have been detected by their spin-modulated radio emission. In a computing-intensive blind search of gamma-ray data from the Fermi Large Area Telescope (with partial constraints from optical data), we detected a 2.5-millisecond pulsar, PSR J1311-3430. This unambiguously explains a formerly unidentified gamma-ray source that had been a decade-long enigma, confirming previous conjectures. The pulsar is in a circular orbit with an orbital period of only 93 minutes, the shortest of any spin-powered pulsar binary ever found.

  10. Japanese VLBI Network Observations of a Gamma-Ray Narrow ...

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... We made simultaneous single-dish and VLBI observations of a gamma-ray narrow-line Seyfert 1 (NLS1) galaxy 1H 0323+342. We found significant flux variation at 8 GHz on a time scale of one month. The total flux density varied by 5.5% in 32 days, corresponding to a variability brightness temperature of ...

  11. THE ENGINES BEHIND SUPERNOVAE AND GAMMA-RAY BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    FRYER, CHRISTOPHER LEE [Los Alamos National Laboratory

    2007-01-23

    The authors review the different engines behind supernova (SNe) and gamma-ray bursts (GRBs), focusing on those engines driving explosions in massive stars: core-collapse SNe and long-duration GRBs. Convection and rotation play important roles in the engines of both these explosions. They outline the basic physics and discuss the wide variety of ways scientists have proposed that this physics can affect the supernova explosion mechanism, concluding with a review of the current status in these fields.

  12. A pneumatic sample changer for gamma-ray spectroscopy

    Science.gov (United States)

    Massoni, C.J.; Fones, R.V.; Simon, F.O.

    1973-01-01

    A gravity-feed, pneumatic-ejection sample changer has been developed. The changer is suitable for both flat and well-type detectors and permits the continuous use of gamma-ray spectroscopy equipment 24 h a day, 7 days a week. The electronic circuitry has a fail-safe feature which stops the operation of the changer if a malfunction occurs. ?? 1973 The American Institute of Physics.

  13. Is there cosmological time dilation in gamma-ray bursts?

    Science.gov (United States)

    Band, David L.

    1994-01-01

    Norris et al. report that the temporal structure of faint gamma-ray bursts is longer than that of bright bursts, as expected for time dilation in the cosmological models of burst origin. I show that the observed trends can easily be produced by a burst luminosity function and thus may not result from cosmological effects. A cosmological signature may be present, but the tests Norris et al. present are not powerful enough to detect these signatures.

  14. Gamma-Ray Bursts The Brightest Explosions in the Universe

    CERN Document Server

    Vedrenne, Gilbert

    2009-01-01

    Since their discovery was first announced in 1973, gamma-ray bursts (GRBs) have been among the most fascination objects in the universe. While the initial mystery has gone, the fascination continues, sustained by the close connection linking GRBs with some of the most fundamental topics in modern astrophysics and cosmology. Both authors have been active in GRB observations for over two decades and have produced an outstanding account on both the history and the perspectives of GRB research.

  15. A trio of gamma-ray burst supernovae

    DEFF Research Database (Denmark)

    Cano, Z.; Ugarte Postigo, Antonio de; Pozanenko, A.

    2014-01-01

    We present optical and near-infrared (NIR) photometry for three gamma-ray burst supernovae (GRB-SNe): GRB 120729A, GRB 130215A / SN 2013ez and GRB 130831A / SN 2013fu. In the case of GRB 130215A / SN 2013ez, we also present optical spectroscopy at t-t0=16.1 d, which covers rest-frame 3000...

  16. Depth of interaction detection for {gamma}-ray imaging

    Energy Technology Data Exchange (ETDEWEB)

    Lerche, Ch.W. [Instituto de Aplicaciones de las Tecnologias de la Informacion y de las Comunicaciones Avanzadas, (UPV) Camino de Vera s/n, E46022 (Spain)], E-mail: lerche@ific.uv.es; Doering, M. [Institut fuer Kernphysik, Forschungszentrum Juelich GmbH, D52425 Juelich (Germany); Ros, A. [Institute de Fisica Corpuscular (CSIC-UV), 22085, Valencia E46071 (Spain); Herrero, V.; Gadea, R.; Aliaga, R.J.; Colom, R.; Mateo, F.; Monzo, J.M.; Ferrando, N.; Toledo, J.F.; Martinez, J.D.; Sebastia, A. [Instituto de Aplicaciones de las Tecnologias de la Informacion y de las Comunicaciones Avanzadas, (UPV) Camino de Vera s/n, E46022 (Spain); Sanchez, F.; Benlloch, J.M. [Institute de Fisica Corpuscular (CSIC-UV), 22085, Valencia E46071 (Spain)

    2009-03-11

    A novel design for an inexpensive depth of interaction capable detector for {gamma}-ray imaging has been developed. The design takes advantage of the strong correlation between the width of the scintillation light distribution in monolithic crystals and the interaction depth of {gamma}-rays. We present in this work an inexpensive modification of the commonly used charge dividing circuits which enables the instantaneous and simultaneous computation of the second order moment of light distribution. This measure provides a good estimate for the depth of interaction and does not affect the determination of the position centroids and the energy release of {gamma}-ray impact. The method has been tested with a detector consisting of a monolithic LSO block sized 42x42x10mm{sup 3} and a position-sensitive photomultiplier tube H8500 from Hamamatsu. The mean spatial resolution of the detector was found to be 3.4mm for the position centroids and 4.9mm for the DOI. The best spatial resolutions were observed at the center of the detector and yielded 1.4mm for the position centroids and 1.9mm for the DOI.

  17. The resolution of gamma-ray laser dilemma

    Science.gov (United States)

    Kolesov, Roman

    2000-03-01

    The resolution of the gamma-ray laser dilemma is found. As is well-known [1], this dilemma which for four decades prevailed over all the researches on gamma-ray lasers, states that incoherent pump required to produce a population inversion would unavoidable destroy the conditions of the Mossbauer and Borrmann effects which are crucial for realization of the net gain. The suppression of the resonant absorption (which was predicted in [2]) at the operating nuclear transition by means of coherent laser driving of the adjacent electronic transition reduces the requirement for incoherent pump (and accordingly heating of the active sample) by orders of magnitude. This allows to pump active nuclei in the host lattice without destroying the conditions of both Mossbauer and Borrmann effects. Moreover it allows to pump resonantly at the operating transition that increases the efficiency of the incoherent pump and suggests a new pass for solution of gamma-ray laser problem. [1] Baldwin GC, Solem JC. Rev. Mod. Phys., 69(4), 1085 (1997) [2] Kocharovskaya O, Kolesov R, Rostovtsev Yu, PRL, 82(18), 3593 (1999)

  18. Gamma Ray Burst Optical Counterpart Search Experiment (GROCSE)

    Science.gov (United States)

    Park, H. S.; Ables, E.; Bionta, R. M.; Ott, L.; Parker, E.; Akerlof, C.; Lee, B.; Wallace, S.; Barthelmy, S.; Butterworth, P.

    1995-01-01

    GROCSE (Gamma-Ray Optical Counterpart Search Experiments) is a system of automated telescopes that search for simultaneous optical activity associated with gamma ray bursts in response to real-time burst notifications provided by the BATSE/BACODINE network. The first generation system, GROCSE 1, is sensitive down to Mv (approximately) 8.5 and requires an average of 12 seconds to obtain the first images of the gamma ray burst error box defined by the BACODINE trigger. The collaboration is now constructing a second generation system which has a 4 second slewing time and can reach Mv (approximately) 14 with a 5 second exposure. GROCSE 2 consists of 4 cameras on a single mount. Each camera views the night sky through a commercial Canon lens (f/1.8, focal length 200 mm) and utilizes a 2K x 2K Loral CCD. Light weight and low noise custom readout electronics were designed and fabricated for these CCDs. The total field of view of the 4 cameras is 17.6 x 17.6 (degree). GROCSE 2 will be operated by the end of 1995. In this paper, the authors present an overview of the GROCSE system and the results of measurements with a GROCSE 2 prototype unit.

  19. Towards a complete theory of Gamma Ray Bursts

    CERN Document Server

    Dar, Arnon; Dar, Arnon

    2004-01-01

    Gamma Ray Bursts (GRBs) are notorious for their diversity. Yet, they have a series of common features. The typical energy of their $\\gamma$ rays is a fraction of an MeV. The energy distributions are well described by a ``Band spectrum'', with ``peak energies'' spanning a surprisingly narrow range. The time structure of a GRB consists of pulses, superimposed or not, rising and decreasing fast. The number of photons in a pulse, the pulses' widths and their total energy vary within broad but given ranges. Within a pulse, the energy spectrum softens with increasing time. The duration of a pulse decreases at higher energies and its peak intensity shifts to earlier time. Many other correlations between pairs of GRB observables have been identified. Last (and based on one measured event!) the $\\gamma$-ray polarization is very large. A satisfactory theory of GRBs should naturally and very simply explain, among others, all these facts. We show that the "cannonball" (CB) model does it. In the CB model the process leadi...

  20. Constraining decaying dark matter with Fermi LAT gamma-rays

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Le; Sigl, Guenter [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik; Weniger, Christoph; Maccione, Luca [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Redondo, Javier [Max-Planck-Institut fuer Physik, Muenchen (Germany)

    2009-12-15

    High energy electrons and positrons from decaying dark matter can produce a significant flux of gamma rays by inverse Compton off low energy photons in the interstellar radiation field. This possibility is inevitably related with the dark matter interpretation of the observed PAMELA and FERMI excesses. The aim of this paper is providing a simple and universal method to constraint dark matter models which produce electrons and positrons in their decay by using the Fermi LAT gamma-ray observations in the energy range between 0.5 GeV and 300 GeV. We provide a set of universal response functions that, once convolved with a specific dark matter model produce the desired constraint. Our response functions contain all the astrophysical inputs such as the electron propagation in the galaxy, the dark matter profile, the gamma-ray fluxes of known origin, and the Fermi LAT data. We study the uncertainties in the determination of the response functions and apply them to place constraints on some specific dark matter decay models that can well fit the positron and electron fluxes observed by PAMELA and Fermi LAT. To this end we also take into account prompt radiation from the dark matter decay. We find that with the available data decaying dark matter cannot be excluded as source of the PAMELA positron excess. (orig.)

  1. Neutron diagnostics using compton suppression gamma-ray spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Hong, S. P.; Kang, B. S. [Lab. Of Radiation Convergence Science, Dept. of Radiological Science, College of Medical Science, Konyang University, Daejeon (Korea, Republic of); Kim, C. S.; Cheon, M. S.; Cho, S. [National Fusion Research Institute, Daejeon (Korea, Republic of)

    2016-12-15

    Various neutron diagnostic systems such as a fission chamber, stilbene spectrometers, and a neutron activation system (NAS) have been installed at KSTAR for more accurate detection of neutron flux. Among the systems, the NAS is the most reliable and robust tool, and the measurement data of it generally are to be used for calibration of other systems. The Compton suppression gamma-ray spectrometer which can suppress the expected background, noise signal and Compton scattering was used to measure the gamma-rays of neutron activated samples. In this study, the encapsulated indium samples which are installed and irradiated by the neutrons released from the nuclear fusion reactions in the Korea Superconducting Tokamak Advanced Research (KSTAR) was used and measured using Compton suppressed gamma-ray spectrometer to minimize the measurement error. From the experimental results, the statistical error was decreased by Compton suppression system. the statistical error of the measured sample activity in the Compton suppressed system is estimated to be about 2.3 %, and the statistical error of the measured sample activity in the non-suppressed system was estimated to be about 4.9 %. It was found that the system can reduce the measurement error effectively. It is confirmed that this system can be applied to ITER TBM and future nuclear fusion devices.

  2. Prospects for gamma-ray line observations of individual supernovae

    Science.gov (United States)

    Gehrels, Neil; Leventhal, Marvin; Maccallum, Crawford J.

    1987-01-01

    The gamma-ray line emission from individual type I and type II supernovae are studied using numerical simulations and photon propagation codes to predict the flux levels and line shapes. For both types, the gamma ray lines with the highest flux from an individual event are the 0.847 and 1.238 MeV lines from the Ni-56 to Co-56 to Fe-56 decay chain. For type I supernovae, the 0.847 MeV line peaks at about 70 days after event onset. The historical record indicates an approximate discovery rate of once in 10 years for balloon-borne instruments, once in two to three years for the Gamma-Ray Observatory, and once in one to two years for a proposed space mission. The 0.847 MeV line flux from type II supernovae peaks at about 600 days after event onset at a low level which restricts observations to the events in the Galaxy and its nearest neighbors. The expected line shape is narrower than for type I supernovae.

  3. The GRB 060218/SN 2006aj event in the context of other gamma-ray burst supernovae

    DEFF Research Database (Denmark)

    Ferrero, P.; Kann, D. A.; Zeh, A.

    2006-01-01

    Gamma rays: bursts: X-rays: individuals: GRB 060218, supernovae: individual: SN 2006aj Udgivelsesdato: Oct.......Gamma rays: bursts: X-rays: individuals: GRB 060218, supernovae: individual: SN 2006aj Udgivelsesdato: Oct....

  4. New stage in high-energy gamma-ray studies with GAMMA-400 after Fermi-LAT

    Directory of Open Access Journals (Sweden)

    Topchiev N.P.

    2017-01-01

    Full Text Available Fermi-LAT has made a significant contribution to the study of high-energy gamma-ray diffuse emission and the observations of 3000 discrete sources. However, one third of all gamma-ray sources (both galactic and extragalactic are unidentified, the data on the diffuse gamma-ray emission should be clarified, and signatures of dark matter particles in the high-energy gamma-ray range are not observed up to now. GAMMA-400, the currently developing gamma-ray telescope, will have angular (∼0.01∘ at 100 GeV and energy (∼1% at 100 GeV resolutions in the energy range of 10–1000 GeV which are better than Fermi-LAT (as well as ground gamma-ray telescopes by a factor of 5–10. It will observe some regions of the Universe (such as the Galactic Center, Fermi Bubbles, Crab, Cygnus, etc. in a highly elliptic orbit (without shading the telescope by the Earth continuously for a long time. It will allow us to identify many discrete sources, to clarify the structure of extended sources, to specify the data on the diffuse emission, and to resolve gamma rays from dark matter particles.

  5. Attenuation of the gamma rays in tissues; Atenuacion de los rayos gamma en tejidos

    Energy Technology Data Exchange (ETDEWEB)

    Arcos P, A.; Rodriguez N, S.; Pinedo S, A.; Amador V, P.; Chacon R, A.; Vega C, H.R. [Unidad Academica de Estudios Nucleares, Cipres 10, Fracc. La Penuela, 98068 Zacatecas (Mexico)

    2005-07-01

    The mass and lineal attenuation coefficient and of hepatic tissue, muscular, osseous and of brain before gamma rays of 10{sup -3} to 10{sup 5} MeV were calculated. For the case of the osseous tissue the calculation was made for the cartilage, the cortical tissue and the bone marrow. During the calculations the elementary composition of the tissues of human origin was used. The calculations include by separate the Photoelectric effect, the Compton scattering and the Pair production, as well as the total. For to establish a comparison with the attenuation capacities, the coefficients of the water, the aluminum and the lead also were calculated. The study was complemented measuring the attenuation coefficient of hepatic tissue of bovine before gamma rays of 0.662 MeV of a source of {sup 137} Cs. The measurement was made through of an experiment of photons transmission through samples frozen of hepatic tissue and with a Geiger-Mueller detector. (Author)

  6. Designing a Gamma-Ray Telescope on a Budget

    Science.gov (United States)

    Kohler, Susanna

    2017-05-01

    Major space-based observatories are imperative in astronomy, but they take a long time to plan, build, and launch and they arent cheap. A new study examines an interesting compromise: a low-cost, space-based gamma-ray detector that we could use while we wait for the next big observatory to launch.Coverage and sensitivity of past and future missions for the X-ray to gamma-ray energy range (click for a better look!). The only past mission to explore the 1 MeV region was COMPTEL, on board CGRO. e-ASTROGAM is a proposed future space mission that would explore this range. [Lucchetta et al. 2017]A Gap in CoverageIn the last few decades, weve significantly expanded our X-ray and gamma-ray viewof the sky. One part of the electromagnetic spectrum remains poorly explored, however: the approximate transition point between X-rays and gamma rays near 1 MeV.Space-based gamma-ray telescopes have been proposed for the future to better explore this energy range. But these major observatories have costs of around half a billion Euros and will take roughly a decade to build and launch. Is there a way to get eyes on this energy range sooner?Scaling Down with CubeSatA team of scientists led by Giulio Lucchetta (University of Padova and INFN Padova, Italy) has proposed an intriguing solution for the more immediate future: a nano-satellite telescope based on the CubeSat standard.Structure of the proposed gamma-ray detector, in a 2U CubeSat design. [Lucchetta et al. 2017]A CubeSat is a miniaturized satellite design that can be easily deployed in space, either from the International Space Station or by hitching a ride as a secondary payload on a large rocket. The size of a CubeSat is a standardized unit of measurement: a single CubeSat unit, or 1U, is a mere 10x10x10 cm and a maximum of 1.33 kg in weight.The gamma-ray telescope proposed by Lucchetta and collaborators would use a 2U standard for the instrument, so the instrument would be only 10x10x20 cm in size! The design for the

  7. Coded-aperture Compton camera for gamma-ray imaging

    Science.gov (United States)

    Farber, Aaron M.

    This dissertation describes the development of a novel gamma-ray imaging system concept and presents results from Monte Carlo simulations of the new design. Current designs for large field-of-view gamma cameras suitable for homeland security applications implement either a coded aperture or a Compton scattering geometry to image a gamma-ray source. Both of these systems require large, expensive position-sensitive detectors in order to work effectively. By combining characteristics of both of these systems, a new design can be implemented that does not require such expensive detectors and that can be scaled down to a portable size. This new system has significant promise in homeland security, astronomy, botany and other fields, while future iterations may prove useful in medical imaging, other biological sciences and other areas, such as non-destructive testing. A proof-of-principle study of the new gamma-ray imaging system has been performed by Monte Carlo simulation. Various reconstruction methods have been explored and compared. General-Purpose Graphics-Processor-Unit (GPGPU) computation has also been incorporated. The resulting code is a primary design tool for exploring variables such as detector spacing, material selection and thickness and pixel geometry. The advancement of the system from a simple 1-dimensional simulation to a full 3-dimensional model is described. Methods of image reconstruction are discussed and results of simulations consisting of both a 4 x 4 and a 16 x 16 object space mesh have been presented. A discussion of the limitations and potential areas of further study is also presented.

  8. Data acquisition with a fast digitizer for large volume HPGe detectors

    Energy Technology Data Exchange (ETDEWEB)

    Mihailescu, L.C. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, B-2440 Geel (Belgium); ' Horia Hulubei' National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest (Romania); Borcea, C. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, B-2440 Geel (Belgium); ' Horia Hulubei' National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest (Romania); Plompen, A.J.M. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, B-2440 Geel (Belgium)]. E-mail: Arjan.Plompen@ec.europa.eu

    2007-07-21

    A 12-bits and 420MSample/s waveform digitizer was used with large volume High Purity Germanium (HPGe) detectors for measurements of gamma-ray production cross-section from inelastic neutron scattering. For these time-of-flight measurements at the GELINA white neutron source, the use of a fast digitizer significantly increases the efficiency compared with a conventional data acquisition system. First, the pulse processing time required to obtain the amplitude with high resolution is significantly reduced so that pulse pile-up with the prompt gamma-burst is eliminated for neutron-induced events. Second, an improved time response is obtained for which the amplitude and rise time dependence is strongly reduced compared to that of a conventional constant fraction discriminator. Excellent energy and time resolution is obtained with algorithms suitable for on-line signal processing, so that data storage is under control. Bench tests are presented that compare methods of signal processing. For the best method, the data acquisition system based on the fast digitizer was tested during measurements of gamma production cross-sections for Pb206 and Pb208. A direct comparison was made with results obtained with conventional electronics operated in parallel.

  9. Energy spectra of cosmic gamma-ray bursts

    Science.gov (United States)

    Cline, T. L.; Desai, U. D.; Klebesadel, R. W.; Strong, I. B.

    1973-01-01

    Spectral measurements of six cosmic gamma-ray bursts in the energy region of 0.1 to 1.2 MeV, made using a semi-omnidirectional X-ray detector on IMP-6 are reported. These measurements confirm the hard X-ray or gamma-ray nature of the bursts, as inferred from the original observations by Klebesadel et al., (1973), and show that their maximum energy release is in this several hundred keV region. Each burst consists of several 1 or 2-second pulses each with the characteristic spectrum of approximately 150-keV exponential, followed by a softer decay. There is no evidence of line structure in this energy region, or for a marked change in the energy spectrum within a given pulse. Event size spectra are estimated for galactic and extragalactic models; the total emission is consistent with present measurements of the diffuse background, and unlikely to account for any spectral feature in the few-MeV region.

  10. Earth Occultation Monitoring with the Fermi Gamma Ray Burst Monitor

    Science.gov (United States)

    Wilson-Hodge, Colleen A.

    2014-01-01

    Using the Gamma Ray Burst Monitor (GBM) on-board Fermi, we are monitoring the hard X-ray/soft gamma ray sky using the Earth occultation technique (EOT). Each time a source in our catalog is occulted by (or exits occultation by) the Earth, we measure its flux using the change in count rates due to the occultation. Currently we are using CTIME data with 8 energy channels spanning 8 keV to 1 MeV for the GBM NaI detectors for daily monitoring. Light curves, updated daily, are available on our website http://heastro.phys.lsu.edu/gbm. Our software is also capable of performing the Earth occultation monitoring using up to 128 energy bands, or any combination of those bands, using our 128-channel, 4-s CSPEC data. The GBM BGO detectors, sensitive from about 200 keV to 40 keV, can also be used with this technique. In our standard application of the EOT, we use a catalog of sources to drive the measurements. To ensure that our catalog is complete, our team has developed an Earth occultation imaging method. In this talk, I will describe both techniques and the current data products available. I will highlight recent and important results from the GBM EOT, including the current status of our observations of hard X-ray variations in the Crab Nebula.

  11. The specific gamma-ray constant and exposure rate constant of 182Ta.

    Science.gov (United States)

    Glasgow, G P; Dillman, L T

    1982-01-01

    Reported values of the specific gamma-ray constant gamma for 182Ta range from the original value of 6.1 to 7.692 R cm2h-1mCi-1, recommended in NCRP Report No. 41. The original calculation of gamma was based on inadequate nuclear spectroscopy and decay scheme data. The higher value of gamma occurs because of a computational error in the relative intensity of the 1.2575-MeV gamma ray. Using nuclear spectroscopy data from the most recent Evaluated Nuclear Data File (ENSDF), gamma is calculated to be 6.71 +/- 0.06 R cm2h-1mCi-1 and the exposure rate constant gamma gamma is 6.87 +/- 0.06 R cm2h-1mCi-1. These new calculations are presented and previously reported values of gamma and gamma gamma are reviewed.

  12. NRAO Teams With NASA Gamma-Ray Satellite

    Science.gov (United States)

    2007-06-01

    The National Radio Astronomy Observatory (NRAO) is teaming with NASA's upcoming Gamma-ray Large Area Space Telescope (GLAST) to allow astronomers to use both the orbiting facility and ground-based radio telescopes to maximize their scientific payoff. Under the new, streamlined process, astronomers can compete for coordinated observing time and support from both GLAST and NRAO's radio telescopes. GLAST satellite Artist's rendering of the GLAST spacecraft in orbit above the Earth. CREDIT: General Dynamics C4 Systems Click on Image for Larger File Images of NRAO Telescopes Robert C. Byrd Green Bank Telescope Very Long Baseline Array Very Large Array Atacama Large Millimeter/submillimeter Array GLAST is scheduled for launch no earlier than December 14. It will perform a survey of the entire sky at gamma-ray wavelengths every 3 hours using its primary instrument, the Large Area Telescope (LAT). NRAO operates the Very Large Array (VLA) in New Mexico, the continent-wide Very Long Baseline Array (VLBA), and the Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. The NRAO is a research facility of the National Science Foundation (NSF). "Coordinated gamma-ray and radio observations of celestial objects will greatly enhance the ability to fully understand those objects. Astronomy today requires such multiwavelength studies, and this agreement paves the way for exciting, cutting-edge research," said Fred K.Y. Lo, NRAO Director. GLAST will be vastly more capable than previous gamma-ray satellites, and will carry an instrument, the GLAST Burst Monitor, specifically designed to detect gamma-ray bursts. GLAST observers will study objects such as active galaxies, pulsars, and supernova remnants, which are also readily studied with radio telescopes. By working together, NASA's GLAST mission and NSF's NRAO facilities can study flares from blazars over the widest possible range of energies, which is crucial to understanding how black holes, notorious for drawing matter in, can

  13. Why gamma rays are different. Some notes for pedestrians

    Energy Technology Data Exchange (ETDEWEB)

    Lipkin, H.J.

    1987-09-25

    This talk brings the discussion of gamma ray lasers down from the science fiction level to the real world. Flamboyant exciting proposals presented with evangelical zeal obscure the real difficulties to be overcome before a gamma ray laser becomes feasible in the laboratory, and long before any practical applications. Nuclear gamma radiation does not have many of the properties taken for granted in atomic or molecular radiation and necessary for lasers. The basic science and technology underlying these differences and the proposed methods of overcoming difficulties resulting from them are not properly understood. Grandiose proposals for grasers generally presented tend to ignore them. Considerable illumination in this interdisciplinary problem could be provided by some back-of-the-envelope calculations and simple experimental surveys by small groups of students and postdocs with an elementary knowledge of the nuclear and solid state physics which is evidently not familiar these days to laser physicists. However, nobody seems ready to propose or undertake such work. Unfortunately, budgets for unglamorous basic science are being cut across the board, and evangelical glamour seems to be more effective than real physics in obtaining support.

  14. Searches for Particle Dark Matter with gamma-rays.

    CERN Multimedia

    CERN. Geneva

    2012-01-01

    In this contribution I review the present status and discuss some prospects for indirect detection of dark matter with gamma-rays. Thanks to the Fermi Large Area Telescope, searches in gamma-rays have reached sensitivities that allow to probe the most interesting parameter space of the weakly interacting massive particles (WIMP) paradigm. This gain in sensitivity is naturally accompanied by a number of detection claims or indications, the most recent being the claim of a line feature at a dark matter particle mass of ∼ 130 GeV at the Galactic Centre, a claim which requires confirmation from the Fermi-LAT collaboration and other experiments, for example HESS II or the planned Gamma-400 satellite. Predictions for the next generation air Cherenkov telescope, Cherenkov Telescope Array (CTA), together with forecasts on future Fermi-LAT constraints arrive at the exciting possibility that the cosmological benchmark cross-section could be probed from masses of a few GeV to a few TeV. Consequently, non-detection wou...

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

    Science.gov (United States)

    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.

  16. Properties of gamma-ray burst progenitor stars.

    Science.gov (United States)

    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.

  17. The e-astrogam Gamma-Ray Space Mission

    Science.gov (United States)

    Tatischeff, V.; Tavani, M.; Von Ballmoos, P.; Hanlon, L.; Oberlack, U.; Aboudan, A.; Argan, A.; Bernard, D.; Brogna, A.; Bulgarelli, A.; hide

    2016-01-01

    e-ASTROGAM is a gamma-ray space mission to be proposed as the M5 Medium-size mission of the European Space Agency. It is dedicated to the observation of the Universe with unprecedented sensitivity in the energy range 0.2-100 MeV, extending up to GeV energies, together with a groundbreaking polarization capability. It is designed to substantially improve the COMPTEL and Fermi sensitivities in the MeV-GeV energy range and to open new windows of opportunity for astrophysical and fundamental physics space research. e-ASTROGAM will operate as an open astronomical observatory, with a core science focused on (1) the activity from extreme particle accelerators, including gamma-ray bursts and active galactic nuclei and the link of jet astrophysics to the new astronomy of gravitational waves, neutrinos, ultra-high energy cosmic rays, (2) the high-energy mysteries of the Galactic center and inner Galaxy, including the activity of the supermassive black hole, the Fermi Bubbles, the origin of the Galactic positrons, and the search for dark matter signatures in a new energy window; (3) nucleosynthesis and chemical evolution, including the life cycle of elements produced by supernovae in the Milky Way and the Local Group of galaxies. e-ASTROGAM will be ideal for the study of high-energy sources in general, including pulsars and pulsar wind nebulae, accreting neutron stars and black holes, novae, supernova remnants, and magnetars. And it will also provide important contributions to solar and terrestrial physics. The e-ASTROGAM telescope is optimized for the simultaneous detection of Compton and pair-producing gamma-ray events over a large spectral band. It is based on a very high technology readiness level for all subsystems and includes many innovative features for the detectors and associated electronics.

  18. Absolute activity measurement and gamma-ray emission probability for decay of I-126; Medida absoluta da atividade e determinacao da taxa de emissao gama por decaimento do {sup 126} I

    Energy Technology Data Exchange (ETDEWEB)

    Fonseca, Katia Aparecida

    1997-07-01

    The accurate knowledge of the gamma-ray emission probability per decay of radionuclides is important in several applications. In the case of {sup 126} I, its importance lies mainly in fast neutron dosimetry as well as in the production of {sup 125} I where {sup 126} I appears as an impurity. In the present work the gamma-ray emission probabilities per decay for the 388 and 666-KeV transitions of {sup 126} I have been measured. This radionuclide was obtained by means of the {sup 127} I(n, 2n){sup 126} I reaction in a fast neutron flux at the IPEN 2 MW research reactor. The methodology for the primary standardization of {sup 126} I is described. For this purpose, two different coincidence systems were used due to the complex decay scheme of this radionuclide. The {beta}branch measurement was carried out in a 4 {pi}(PC){beta}-{gamma} coincidence system consisting of a proportional counter, coupled to a pair of 3'x3' Na I (Tl) crystal. The electron capture branch was measured in a X-{gamma} coincidence system using two NaI(Tl) crystals. The gamma-ray measurements were performed in a HPGe system, previously calibrated by means of standard sources supplied by the International Atomic Energy Agency. All the uncertainties evolved were treated rigorously, by means of covariance analysis. (author)

  19. Soil Water Estimation with Cosmic-Ray Neutrons and Th/K/U-Gamma Rays

    Science.gov (United States)

    Schrön, Martin; Werban, Ulrike; Köhli, Markus; Zacharias, Steffen; Dietrich, Peter

    2017-04-01

    Soil water content is an important factor for hydrological processes (infiltration and runoff), agriculture (plant water availability), and radiation protection (radon emanation). It is known that neutron radiation as well as gamma radiation from natural sources are sensitive to the water content in the soil. Cosmic-ray neutron detectors above the ground are widely used to measure soil moisture by counting the number of ground-reflected neutrons. On the other hand, gamma-ray spectrometers are typically used to measure the spatial pattern of soil texture in the field. However, few experiments show the temporal dynamics of gamma radiation at a fixed location. In our study, we passively measured cosmic-ray neutrons and gamma radiation at the same location, while other studies are presented where both quantities are measured in a large spatial domain. It is found that both quantities show a significant reponse to rain events. In fact, during periods of soil drying and wetting, both neutrons and K/Th radiation show comparable behaviour. The presentation further describes state-of-the-art Monte Carlo simulations which support the understanding of the neutron response above air, and hypothesizes a direct relation to the natural gamma radiation.

  20. On the attenuation of X-rays and gamma-rays for aqueous solutions of salts

    CERN Document Server

    Teli, M T

    1998-01-01

    Disparities in the linear attenuation coefficients of X-rays and gamma rays for aqueous solutions of soluble salts arising from the nonequality of volume of the solution with the sum of volumes of its components are analysed and the mixture rule is reformulated. The disparities are illustrated for NaCl solution for concentrations c=0 to 1 gm/cm sup 3 which indicates that the mixture rule of Teli et al. works well within generally acceptable limits.

  1. Probing Intrinsic Properties of Short Gamma-Ray Bursts with Gravitational Waves

    Science.gov (United States)

    Fan, Xilong; Messenger, Christopher; Heng, Ik Siong

    2017-11-01

    Progenitors of short gamma-ray bursts are thought to be neutron stars coalescing with their companion black hole or neutron star, which are one of the main gravitational wave sources. We have devised a Bayesian framework for combining gamma-ray burst and gravitational wave information that allows us to probe short gamma-ray burst luminosities. We show that combined short gamma-ray burst and gravitational wave observations not only improve progenitor distance and inclination angle estimates, they also allow the isotropic luminosities of short gamma-ray bursts to be determined without the need for host galaxy or light-curve information. We characterize our approach by simulating 1000 joint short gamma-ray burst and gravitational wave detections by Advanced LIGO and Advanced Virgo. We show that ˜90 % of the simulations have uncertainties on short gamma-ray burst isotropic luminosity estimates that are within a factor of two of the ideal scenario, where the distance is known exactly. Therefore, isotropic luminosities can be confidently determined for short gamma-ray bursts observed jointly with gravitational waves detected by Advanced LIGO and Advanced Virgo. Planned enhancements to Advanced LIGO will extend its range and likely produce several joint detections of short gamma-ray bursts and gravitational waves. Third-generation gravitational wave detectors will allow for isotropic luminosity estimates for the majority of the short gamma-ray burst population within a redshift of z ˜1 .

  2. Pocket PC-based portable gamma-ray spectrometer

    Directory of Open Access Journals (Sweden)

    Kamontip Ploykrachang

    2011-04-01

    Full Text Available A portable gamma-ray spectrometer based on a Pocket PC has been developed. A 12-bit pipeline analog-to-digitalconverter (ADC associated with an implemented pulse height histogram function on field programmable gate array (FPGAoperating at 15 MHz is employed for pulse height analysis from built-in pulse amplifier. The system, which interfaces withthe Pocket PC via an enhanced RS-232 serial port under the microcontroller facilitation, is utilized for spectrum acquisition,display and analysis. The pulse height analysis capability of the system was tested and it was found that the ADC integralnonlinearity of ±0.45% was obtained with the throughput rate at 160 kcps. The overall system performance was tested usinga PIN photodiode-CsI(Tl crystal coupled scintillation detector and gamma standard radioactive sources of Cs-137 andCo-60. Low cost and the compact system size as a result of the implemented logical function are also discussed.

  3. The estimation of background production by cosmic rays in high-energy gamma ray telescopes

    Science.gov (United States)

    Edwards, H. L.; Nolan, P. L.; Lin, Y. C.; Koch, D. G.; Bertsch, D. L.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kniffen, D. A.; Hughes, E. B.

    1991-01-01

    A calculational method of estimating instrumental background in high-energy gamma-ray telescopes, using the hadronic Monte Carlo code FLUKA87, is presented. The method is applied to the SAS-2 and EGRET telescope designs and is also used to explore the level of background to be expected for alternative configurations of the proposed GRITS telescope, which adapts the external fuel tank of a Space Shuttle as a gamma-ray telescope with a very large collecting area. The background produced in proton-beam tests of EGRET is much less than the predicted level. This discrepancy appears to be due to the FLUKA87 inability to transport evaporation nucleons. It is predicted that the background in EGRET will be no more than 4-10 percent of the extragalactic diffuse gamma radiation.

  4. ODY MARS GAMMA RAY SPECTROMETER 5 SGS V1.0

    Data.gov (United States)

    National Aeronautics and Space Administration — The ODY MARS GAMMA RAY SPECTROMETER 5 SGS (SGS) data set is a collection of data tables that contain a gamma spectrum and the associated engineering data that has...

  5. European team gauges a gamma-ray star

    Science.gov (United States)

    1996-03-01

    Italian astrophysicists have pushed the Hubble Space Telescope to the limit of its powers in finding the distance of Geminga, a pointlike object 500 light-years from the Earth. It is the prototype of a novel kind of star, a radio-silent neutron star, which may be much more common in the Universe than previously supposed. Geminga is so weak in visible light that Hubble had to stare at the spot for more than an hour to register it adequately. The object is nevertheless one of the brightest sources of gamma-rays in the sky, and its output of this very energetic form of radiation can now be accurately ganged. Neutron stars, first discovered as radio pulsars in 1967, are fantastic creations of exploding stars, just one step short of a black hole. They are heavier than the Sun yet only about twenty kilometres wide. Made of compressed nuclear matter, they have gravity and magnetic fields many billions of times stronger than on the Earth. With the first direct measurement of the distance of a radio-silent neutron star, astrophysicists can assess Geminga's power and speed of motion. The astronomical task was like judging the width of a one- franc piece in Paris, seen from the distance of Sicily. Geminga's low brightness greatly aggravated the difficulties. Patrizia Caraveo and her colleagues at the Istituto di Fisica Cosmica in Milan arranged for Hubble's wide-field camera (WFPC2) to make its prolonged observations of Geminga three times. Their findings will be published in Astrophysical Journal Letters on 20 April 1996. Caraveo's co-authors are Giovanni Bignami and Roberto Mignani of Milan, and Laurence Taff of Johns Hopkins University, Maryland. The Italians took advantage of the European Space Agency's collaboration with NASA in the Hubble mission, which gives European astronomers privileged access to the Space Telescope. Shifts of millionths of a degree The three sightings of Geminga, made at intervals of six months, revealed small shifts in the position of the faint

  6. COMBINED MEASUREMENTS WITH THREE-DIMENSIONAL DESIGN INFORMATION VERIFICATION SYSTEM AND GAMMA RAY IMAGING - A COLLABORATIVE EFFORT BETWEEN OAK RIDGE NATIONAL LABORATORY, LAWRENCE LIVERMORE NATIONAL LABORATORY, AND THE JOINT RESEARCH CENTER AT ISPRA

    Energy Technology Data Exchange (ETDEWEB)

    Mihailescu, L; Vetter, K; Ruhter, W; Chivers, D; Dreicer, M; Coates, C; Smith, S; Hines, J; Caiado, A R; Sequeira, V; Fiocco, M; Goncalves, J G

    2006-06-14

    Oak Ridge National Laboratory (ORNL) and Lawrence Livermore National Laboratory (LLNL) have jointly performed tests to demonstrate combined measurements with a three-dimensional (3D) design information verification (DIV) system and a gamma-ray imager for potential safeguard applications. The 3D DIV system was made available by the European Commission's Joint Research Center to ORNL under a collaborative project between the U.S. Department of Energy and the European Atomic Energy Community (EURATOM). The system is able to create 3D maps of rooms and objects and of identifying changes in positions and modifications with a precision on the order of millimeters. The gamma ray imaging system consists of a 4{pi} field-of-view Compton imaging system which has two fully operational DSSD (Double-Sided Segment Detector) High-Purity Germanium (HPGe) detectors developed at LLNL. The Compton imaging instrument not only provides imaging capabilities, but provides excellent energy resolution which enables the identification of radioisotopes and nuclear materials. Joint Research Center was responsible to merge gamma-ray images with the 3D range maps. The results of preliminary first measurements performed at LLNL demonstrate, for the first time, mapping of panoramic gamma-ray images into 3D range data.

  7. A detailed investigation of interactions within the shielding to HPGe detector response using MCNP code

    Energy Technology Data Exchange (ETDEWEB)

    Thanh, Tran Thien; Tao, Chau Van; Loan, Truong Thi Hong; Nhon, Mai Van; Chuong, Huynh Dinh; Au, Bui Hai [Vietnam National Univ., Ho Chi Minh City (Viet Nam). Dept. of Nuclear Physics

    2012-12-15

    The accuracy of the coincidence-summing corrections in gamma spectrometry depends on the total efficiency calibration that is hardly obtained over the whole energy as the required experimental conditions are not easily attained. Monte Carlo simulations using MCNP5 code was performed in order to estimate the affect of the shielding to total efficiency. The effect of HPGe response are also shown. (orig.)

  8. Neutrino emission from gamma-ray burst fireballs, revised.

    Science.gov (United States)

    Hümmer, Svenja; Baerwald, Philipp; Winter, Walter

    2012-06-08

    We review the neutrino flux from gamma-ray bursts, which is estimated from gamma-ray observations and used for the interpretation of recent IceCube data, from a particle physics perspective. We numerically calculate the neutrino flux for the same astrophysical assumptions as the analytical fireball neutrino model, including the dominant pion and kaon production modes, flavor mixing, and magnetic field effects on the secondary muons, pions, and kaons. We demonstrate that taking into account the full energy dependencies of all spectra, the normalization of the expected neutrino flux reduces by about one order of magnitude and the spectrum shifts to higher energies, where we can pin down the exact origin of the discrepancies by the recomputation of the analytical models. We also reproduce the IceCube-40 analysis for exactly the same bursts and same assumptions and illustrate the impact of uncertainties. We conclude that the baryonic loading of the fireballs, which is an important control parameter for the emission of cosmic rays, can be constrained significantly with the full-scale experiment after about ten years.

  9. Focusing Soft Gamma-rays: the Challenge and the Promise

    Science.gov (United States)

    Tomsick, John; Barriere, N.; Boggs, S.

    2011-09-01

    Many science themes would greatly benefit from increased sensitivity in the soft gamma-ray domain. Observation of the light curve and the profile of the 847 keV line from the decay chain of 56Ni synthesized in Type Ia supernovae would place severe constraints on the physical processes at work during these events. This is also true for the observation of the 478 keV line originating in the decay of 7Be synthesized in CO classical novae. In both cases, theoretical models are ready but need observational constraints. In addition, sensitive observations of the 511 keV electron-positron annihilation line would bring new constraints on the origin of the positrons from the Galactic bulge. High significance detection also opens the way for polarization analysis, which is especially interesting in the hard X-ray tails of compact objects. Despite improvements in sensitivity at essentially every other wavelength, the soft gamma-ray domain is lagging behind. Our group at UC Berkeley has been developing a Laue lens: an optic based on diffraction in crystals that enables the concentration of a couple of relatively narrow energy bands in the range from 100 keV to 1.5 MeV. Laue lens telescopes hold the promise of providing at least an order of magnitude improvement in sensitivity with respect to existing instruments, enabling much of the science cited above.

  10. High Energy Gamma-rays from FR I Jets

    CERN Document Server

    Sikora, M

    2003-01-01

    Thanks to Hubble and Chandra telescopes, some of the large scale jets in extragalactic radio sources are now being observed at optical and X-ray frequencies. For the FR I objects the synchrotron nature of this emission is surely established, although a lot of uncertainties--connected for example with the particle acceleration processes involved--remain. In this paper we study production of high energy gamma-rays in FR I kiloparsec-scale jets by inverse-Compton emission of the synchrotron-emitting electrons. We consider different origin of seed photons contributing to the inverse-Compton scattering, including nuclear jet radiation as well as ambient, stellar and circumstellar emission of the host galaxies. We discuss how future detections or non-detections of the evaluated gamma-ray fluxes can provide constraints on the unknown large scale jet parameters, i.e. the magnetic field intensity and the jet Doppler factor. For the nearby sources Centaurus A and M 87, we find measurable fluxes of TeV photons resulting...

  11. High Energy Gamma-rays from FR I Jets

    Energy Technology Data Exchange (ETDEWEB)

    Sikora, Marek

    2003-07-22

    Thanks to Hubble and Chandra telescopes, some of the large scale jets in extragalactic radio sources are now being observed at optical and X-ray frequencies. For the FR I objects the synchrotron nature of this emission is surely established, although a lot of uncertainties--connected for example with the particle acceleration processes involved--remain. In this paper we study production of high energy {gamma}-rays in FR I kiloparsec-scale jets by inverse-Compton emission of the synchrotron-emitting electrons. We consider different origin of seed photons contributing to the inverse-Compton scattering, including nuclear jet radiation as well as ambient, stellar and circumstellar emission of the host galaxies. We discuss how future detections or non-detections of the evaluated {gamma}-ray fluxes can provide constraints on the unknown large scale jet parameters, i.e. the magnetic field intensity and the jet Doppler factor. For the nearby sources Centaurus A and M 87, we find measurable fluxes of TeV photons resulting from synchrotron self-Compton process and from comptonization of the galactic photon fields, respectively. In the case of Centaurus A, we also find a relatively strong emission component due to comptonization of the nuclear blazar photons, which could be easily observed by GLAST at energy {approx} 10 GeV, providing important test for the unification of FR I sources with BL Lac objects.

  12. Zinc oxide nanowire gamma ray detector with high spatiotemporal resolution

    Science.gov (United States)

    Mayo, Daniel C.; Nolen, J. Ryan; Cook, Andrew; Mu, Richard R.; Haglund, Richard F.

    2016-03-01

    Conventional scintillation detectors are typically single crystals of heavy-metal oxides or halides doped with rare-earth ions that record the recombination of electron-hole pairs by photon emission in the visible to ultraviolet. However, the light yields are typically low enough to require photomultiplier detection with the attendant instrumental complications. Here we report initial studies of gamma ray detection by zinc oxide (ZnO) nanowires, grown by vapor-solid deposition. The nanowires grow along the c-axis in a wurtzite structure; they are typically 80 nm in diameter and have lengths of 1- 2 μm. The nanowires are single crystals of high quality, with a photoluminescence (PL) yield from band-edge exciton emission in the ultraviolet that is typically one hundred times larger than the PL yield from defect centers in the visible. Nanowire ensembles were irradiated by 662 keV gamma rays from a Cs-137 source for periods of up to ten hours; gamma rays in this energy range interact by Compton scattering, which in ZnO creates F+ centers that relax to form singly-charged positive oxygen vacancies. Following irradiation, we fit the PL spectra of the visible emission with a sum of Gaussians at the energies of the known defects. We find highly efficient PL from the irradiated area, with a figure of merit approaching 106 photons/s/MeV of deposited energy. Over a period of days, the singly charged O+ vacancies relax to the more stable doubly charged O++ vacancies. However, the overall defect PL returns to pre-irradiation values after about a week, as the vacancies diffuse to the surface of these very thin nanowires, indicating that a self-healing process restores the nanowires to their original state.

  13. Gamma-ray-burst beaming and gravitational-wave observations.

    Science.gov (United States)

    Chen, Hsin-Yu; Holz, Daniel E

    2013-11-01

    Using the observed rate of short-duration gamma-ray bursts (GRBs) it is possible to make predictions for the detectable rate of compact binary coalescences in gravitational-wave detectors. We show that the nondetection of mergers in the existing LIGO/Virgo data constrains the beaming angles and progenitor masses of gamma-ray bursts, although these limits are fully consistent with existing expectations. We make predictions for the rate of events in future networks of gravitational-wave observatories, finding that the first detection of a neutron-star-neutron-star binary coalescence associated with the progenitors of short GRBs is likely to happen within the first 16 months of observation, even in the case of only two observatories (e.g., LIGO-Hanford and LIGO-Livingston) operating at intermediate sensitivities (e.g., advanced LIGO design sensitivity, but without signal recycling mirrors), and assuming a conservative distribution of beaming angles (e.g., all GRBs beamed within θ(j) = 30°). Less conservative assumptions reduce the waiting time until first detection to a period of weeks to months, with an event detection rate of >/~10/yr. Alternatively, the compact binary coalescence model of short GRBs can be ruled out if a binary is not seen within the first two years of operation of a LIGO-Hanford, LIGO-Livingston, and Virgo network at advanced design sensitivity. We also demonstrate that the gravitational wave detection rate of GRB triggered sources (i.e., those seen first in gamma rays) is lower than the rate of untriggered events (i.e., those seen only in gravitational waves) if θ(j)≲30°, independent of the noise curve, network configuration, and observed GRB rate. The first detection in gravitational waves of a binary GRB progenitor is therefore unlikely to be associated with the observation of a GRB.

  14. Detection of terrestrial gamma-ray flashes with the AGILE satellite

    Science.gov (United States)

    Ursi, A.; Marisaldi, M.; Tavani, M.; Sanò, P.; Casella, D.; Dietrich, S.

    2017-05-01

    Terrestrial gamma-ray flashes are brief submillisecond gamma-ray emissions, produced during thunderstorms and strictly correlated to lightning and atmospheric electric activity. Serendipitously discovered in 1994 by the Compton Gamma Ray Observatory, these elusive events have been further investigated by several missions and satellites devoted to high-energy astrophysics, such as RHESSI, AGILE and Fermi. Terrestrial gamma-ray flashes are thought to be bremsstrahlung gamma-rays, produced at the top of thunderclouds by avalanches of electrons accelerated within thunderstorm strong electric fields and abruptly braked in the atmosphere. Exhibiting energies ranging from few keV up to several tens of MeV, terrestrial gamma-ray flashes are the most energetic phenomenon naturally occurring on Earth and they can represent a severe risk for airplanes and aircraft transports, both for the crew and the on board electronics, that should be carefully investigated and understood. The AGILE (Astrorivelatore Gamma ad Immagini LEggero) satellite is an entirely Italian mission, launched in 2007 and still operational, aimed at investigating gamma-ray emissions from cosmic sources. The wide energy range and the unique submillisecond trigger logic of its on-board instruments, together with the narrow quasi-equatorial orbit of the spacecraft, make AGILE a very suitable instrument to detect and investigate terrestrial gamma-ray flashes. Recent improvements rose up the terrestrial gamma-ray flashes detection rate and lead to the observation, for the first time, of multiple events occurring within single thunderstorm processes.

  15. Integral's first look at the gamma-ray Universe

    Science.gov (United States)

    2002-12-01

    The high-energy Universe is a violent place of exploding stars and their collapsed remnants such as the ultra-compressed neutron stars and, at the most extreme, all-consuming black holes. These celestial objects create X-rays and gamma rays that are many times more powerful than the optical radiation we can see with our eyes and optical telescopes. Integral’s Principal Investigators - the scientists responsible for the instruments on board - explain the crucial role that high-energy missions like Integral play in astronomy. “X-ray and gamma-ray astronomy is a pathfinder to unusual objects. At optical wavelengths, the number of stars is staggering. At X-ray and gamma-ray wavelengths, there are fewer objects, but the ones that remain are the really peculiar ones.” As a first test, Integral observed the Cygnus region of the sky, looking particularly at that enigmatic object, Cygnus X-1. Since the 1960s, we have known this object to be a constant generator of high-energy radiation. Most scientists believe that Cygnus X-1 is the site of a black hole, containing around five times the mass of our Sun and devouring a nearby star. Observing Cygnus X-1, which is relatively close by in our own Galaxy - ‘only’ 10 000 light years from us - is a very important step towards understanding black holes. This will also help understand the monstrous black hole - three million times the mass of our Sun - at the centre of our Galaxy. During the initial investigations, scientists had a pleasant surprise when Integral captured its first gamma-ray burst. These extraordinary celestial explosions are unpredictable, occurring from random directions about twice a day. Their precise origin is contentious: they could be the result of massive stars collapsing in the distant Universe or alternatively the result of a collision between two neutron stars. Integral promises to provide vital clues to solving this particular celestial mystery. To study these peculiarities, Integral carries two

  16. Carborne Gamma-Ray Spectrometry. Calibration and Applications

    DEFF Research Database (Denmark)

    Aage, Helle Karina; Korsbech, Uffe C C; Bargholz, Kim

    2006-01-01

    Calibration of carborne gamma-ray spectrometry systems for 137Cs is carried out with a source successively placed at 791 positions within an area of 34m  62m. A computer model supplements the measurements. Hereby a sensitivity map for a surface contamination is generated as well as line and area...... sensitivities. Another model converts surface sensitivity to sensitivity for a deep contamination. Use of the sensitivity map for a non-homogeneous distribution of 137Cs is demonstrated. Applications of line sensitivities for special tasks are discussed....

  17. Passive Gamma-Ray Emission for Soil-Disturbance Detection

    Science.gov (United States)

    2016-08-01

    ER D C/ CR RE L TR -1 6- 10 Passive Gamma-Ray Emission for Soil- Disturbance Detection Co ld R eg io ns R es ea rc h an d En gi ne er in g...variations from geology and soil texture are systematic and predictable, one could map spatiotemporal bulk-density changes relative to some standard state...underlying geology in the area and its rela- tionship to 40K content and distribution (Dickson and Scott 1997; Wilford et al. 1997). Field soil

  18. Gamma ray spectrum from gravitino dark matter decay

    Energy Technology Data Exchange (ETDEWEB)

    Ibarra, A.; Tran, D.

    2007-09-15

    Gravitinos are very promising candidates for the cold dark matter of the Universe. Interestingly, to achieve a sufficiently long gravitino lifetime, R-parity conservation is not required, thus preventing any dangerous cosmological influence of the next-to-lightest supersymmetric particle. When R-parity is violated, gravitinos decay into photons and other particles with a lifetime much longer than the age of the Universe, producing a diffuse gamma ray flux with a characteristic spectrum that could be measured in future experiments, like GLAST, AMS-02 or Cherenkov telescopes. In this letter we compute the energy spectrum of photons from gravitino decay and discuss its main qualitative features. (orig.)

  19. INTERPLANETARY NETWORK LOCALIZATIONS OF KONUS SHORT GAMMA-RAY BURSTS

    Energy Technology Data Exchange (ETDEWEB)

    Pal' shin, V. D.; Svinkin, D. S.; Aptekar, R. L.; Golenetskii, S. V.; Frederiks, D. D.; Mazets, E. P.; Oleynik, P. P.; Ulanov, M. V. [Ioffe Physical Technical Institute, St. Petersburg, 194021 (Russian Federation); Hurley, K. [Space Sciences Laboratory, University of California, 7 Gauss Way, Berkeley, CA 94720-7450 (United States); Cline, T.; Trombka, J.; McClanahan, T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mitrofanov, I. G.; Golovin, D. V.; Kozyrev, A. S.; Litvak, M. L.; Sanin, A. B. [Space Research Institute, 84/32, Profsoyuznaya, Moscow 117997 (Russian Federation); Boynton, W.; Fellows, C.; Harshman, K., E-mail: val@mail.ioffe.ru [Department of Planetary Sciences, University of Arizona, Tucson, AZ 85721 (United States); and others

    2013-08-15

    Between the launch of the Global Geospace Science Wind spacecraft in 1994 November and the end of 2010, the Konus-Wind experiment detected 296 short-duration gamma-ray bursts (including 23 bursts which can be classified as short bursts with extended emission). During this period, the Interplanetary Network (IPN) consisted of up to 11 spacecraft, and using triangulation, the localizations of 271 bursts were obtained. We present the most comprehensive IPN localization data on these events. The short burst detection rate, {approx}18 yr{sup -1}, exceeds that of many individual experiments.

  20. A 3rd Class of Gamma Ray Bursts?

    OpenAIRE

    Horvath, I.

    1998-01-01

    Two classes of Gamma Ray Bursts have been identified so far, characterized by T_90 durations shorter and longer than approximately 2 seconds. We show here that the BATSE 3B data allow a good fit with three Gaussian distributions in log T_90. The chi^2 statistic indicates a 40 % probability for two Gaussians, whereas the three-Gaussian fit probability is 98 %. Using another statistical method, it is argued that the probability that the third class is a random fluctuation is less than 0.02 %.

  1. Single-Crystal Bismuth Iodide Gamma-Ray Spectrometers

    Science.gov (United States)

    2012-02-01

    band gap of 1.730 ± 0.005 eV.52-53 Jellison eta/. used two- modulator generalized ellipsometry to determine ordinary and extraordinary band gaps of 1.991...quality is not comparable to the commercial CdTe and CZT crystals. While the material was observed to be sensitive to radiation (alphas, gamma-rays, and...simulation of CdTe vertical Bridgman growth," J. Cryst. Growth, 173 [3-4] 352-366 (1997). 50 16.A. Bachran, P. Reinshaus, and W. Seifert, "Influence

  2. GRO: Black hole models for gamma-ray bursts

    Science.gov (United States)

    Shaham, Jacob

    1994-01-01

    The possibility of creating gamma ray bursts (GRB's) from accretion flows on to black holes is investigated. The mechanism of initial energy release in the form of a burst is not understood yet. The typical time scales involved in this energy release and the initial distribution of photons as a function of energy are studied. As a first step the problem is formulated in the Minkowski spacetime for a homogeneous and isotropic burst. For an arbitrary initial distribution of photons, the equations of relativistic kinetic theory are formulated for nonequilibrium plasmas which can take into account various particle creation and annihilation processes and various scattering processes.

  3. GRO: Black hole models for gamma ray bursts

    Science.gov (United States)

    Shaham, Jacob

    1993-01-01

    This grant deals with the production of gamma-ray bursts (GRB's) close to horizons of black holes (BH's), mainly via accretion of small chunks of matter onto extreme Kerr BH's. In the past year, we laid the ground work for actual calculations close to Kerr BH's. Because of technical reasons, actual work has only started very recently. Following the detailed list of research subprojects as per our original proposal, we have performed research in the following areas: spectrum calculation; burst dynamics; tidal capture and primordial cloud collapse; halo density profile; and capture of other objects.

  4. Gamma-ray bursts and the sociology of science

    CERN Document Server

    De Rujula, Alvaro

    2003-01-01

    I discuss what we have learned about Gamma-Ray Bursts (GRBs) by studying their `afterglows', and how these are interpreted in the generally-accepted `fireball' model of GRBs, as well as in the generally-unaccepted `cannonball' model of the same phenomena. The interpretation of GRBs is a good example around which to frame a discussion of the different approaches to science found in various fields, such as high-energy physics (HEP), high-energy astrophysics, or even the deciphering of ancient languages. I use this example to draw conclusions on `post-academic' science, and on the current status of European HEP.

  5. Observations of Supernovae Associated with Gamma-Ray Burst

    Science.gov (United States)

    Volnova, Alina; Pozanenko, Alexei; Pruzhinskaya, Maria; Blinnikov, Sergei; Mazaeva, Elena; Inasaridze, Raguli; Ayvazyan, Vova; Inasaridze, Gulnazi; Reva, Inna; Burkhonov, Otabek; Ehgamberdiev, Shukhrat; Kvaratskhelia, Otari; Rumyantsev, Vasilij; Krugly, Yuri; Klunko, Evgeny; Molotov, Igor

    In this paper, we present an overview of the observational properties of supernovae (SNe) associated with long-duration gamma- ray bursts (GRBs). We summarise the statistics of GRB-SNe physical properties and consider different modelling methods. We report the results of the numerical modelling of the GRB 130702A/SN 2013dx multicolour light curve using a spherically symmetrical multi-group radiation hydrodynamics code STELLA. We have obtained main bolometric parameters of the SN and compare our results with those of analytical modelling.

  6. Gamma Ray Bursts in the Swift-Fermi Era

    Science.gov (United States)

    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.

  7. Gravitational waves and neutrinos from gamma-ray bursts

    Energy Technology Data Exchange (ETDEWEB)

    Fryer, Christopher Lee [Los Alamos National Laboratory

    2010-01-01

    Gamma-Ray Bursts (GRBs) are not only strong sources of gammaray emission, but also of neutrinos and gravitational waves (GWs). Observat.ions of these particles can provide a good deal of insight into the progenitor and engine behind these outbursts. But to do so, these particles must be detected . Here we review the different phases of GW and neutrino emission from a range of GRB progenitors, outlining the features and detectability of these phases. Unfortunately, except for a few cases, the detection of non-photon emission is very difficult. But the potential gain from any detection make understanding these sources critically important.

  8. Exploding superstars understanding supernovae and gamma-ray bursts

    CERN Document Server

    Mazure, Alain

    2009-01-01

    The exceptional cosmic history and the fabulous destinies of exploding stars – supernovae and gamma-ray bursters – are highly fertile areas of research and are also very special tools to further our understanding of the universe. In this book, cosmologists Dr Alain Mazure and Dr Stéphane Basa throw light on the assemblage of facts, hypotheses and cosmological conclusions and show how these ‘beacons’ illuminate their immediate surroundings and allow us to study the vast cosmos, like searchlights revealing the matter comprising our universe.

  9. Optimum filter-based discrimination of neutrons and gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Amiri, Moslem [Faculty of Informatics, Masaryk University, Botanicka 68a, 602 00 Brno, (Czech Republic); Prenosil, Vaclav; Cvachovec, Frantisek [Faculty of Military Technology, University of Defence, Kounicova 156/65, 662 10 Brno, (Czech Republic)

    2015-07-01

    An optimum filter-based method for discrimination of neutrons and gamma-rays in a mixed radiation field is presented. The existing filter-based implementations of discriminators require sample pulse responses in advance of the experiment run to build the filter coefficients, which makes them less practical. Our novel technique creates the coefficients during the experiment and improves their quality gradually. Applied to several sets of mixed neutron and photon signals obtained through different digitizers using stilbene scintillator, this approach is analyzed and its discrimination quality is measured. (authors)

  10. Conference on physics from large {gamma}-ray detector arrays

    Energy Technology Data Exchange (ETDEWEB)

    The conference on {open_quotes}Physics from Large {gamma}-ray Detector Arrays{close_quotes} is a continuation of the series of conferences that have been organized every two years by the North American Heavy-ion Laboratories. The aim of the conference this year was to encourage discussion of the physics that can be studied with such large arrays. This volume is the collected proceedings from this conference. It discusses properties of nuclear states which can be created in heavy-ion reactions, and which can be observed via such detector systems.

  11. Cosmology with Gamma-Ray Bursts Using k-correction

    Directory of Open Access Journals (Sweden)

    A. Kovács

    2011-01-01

    Full Text Available In the case of Gamma Ray Bursts with measured redshift, we can calculate the k-correction to get the fluence and energy that were actually produced in the comoving system of the GRB. To achieve this we have to use well-fitted parameters of GRB spectrum, available in the GCN database. The output of the calculations is the comoving isotropic energy Eiso, but this is not the endpoint: this data can be useful forestimating the ΩM parameter of the Universe and for making a GRB Hubble diagram usig Amati’s relation.

  12. Gamma-ray spectroscopy: The diffuse galactic glow

    Science.gov (United States)

    Hartmann, Dieter H.

    1991-01-01

    The goal of this project is the development of a numerical code that provides statistical models of the sky distribution of gamma-ray lines due to the production of radioactive isotopes by ongoing Galactic nucleosynthesis. We are particularly interested in quasi-steady emission from novae, supernovae, and stellar winds, but continuum radiation and transient sources must also be considered. We have made significant progress during the first half period of this project and expect the timely completion of a code that can be applied to Oriented Scintillation Spectrometer Experiment (OSSE) Galactic plane survey data.

  13. High-energy gamma-ray and neutrino backgrounds from star-forming galaxies

    NARCIS (Netherlands)

    Tamborra, I.

    2015-01-01

    Star-forming galaxies have been predicted to contribute considerably to the isotropic diffuse gamma-ray background. The hadronic interactions responsible for high-energy gamma rays also produce high-energy neutrinos. Assuming that at least 100 PeV cosmic rays can be produced and confined in

  14. Neutrino and cosmic-ray emission from multiple internal shocks in gamma-ray bursts

    DEFF Research Database (Denmark)

    Bustamante, Mauricio; Baerwald, Philipp; Murase, Kohta

    2014-01-01

    Gamma-ray bursts are short-lived, luminous explosions at cosmological distances, thought to originate from relativistic jets launched at the deaths of massive stars. They are among the prime candidates to produce the observed cosmic rays at the highest energies. Recent neutrino data have, however...... and cosmic-ray emission from multiple emission regions since these internal collisions must occur at very different radii, from below the photosphere all the way out to the circumburst medium, as a consequence of the efficient dissipation of kinetic energy. We demonstrate that the different messengers...

  15. Diagnosing inertial confinement fusion gamma ray physics (invited).

    Science.gov (United States)

    Herrmann, H W; Hoffman, N; Wilson, D C; Stoeffl, W; Dauffy, L; Kim, Y H; McEvoy, A; Young, C S; Mack, J M; Horsfield, C J; Rubery, M; Miller, E K; Ali, Z A

    2010-10-01

    The gamma reaction history (GRH) diagnostic is a multichannel, time-resolved, energy-thresholded γ-ray spectrometer that provides a high-bandwidth, direct-measurement of fusion reaction history in inertial confinement fusion implosion experiments. 16.75 MeV deuterium+tritium (DT) fusion γ-rays, with a branching ratio of the order of 10(-5)γ/(14 MeV n), are detected to determine fundamental burn parameters, such as nuclear bang time and burn width, critical to achieving ignition at the National Ignition Facility. During the tritium/hydrogen/deuterium ignition tuning campaign, an additional γ-ray line at 19.8 MeV, produced by hydrogen+tritium fusion with a branching ratio of unity, will increase the available γ-ray signal and may allow measurement of reacting fuel composition or ion temperature. Ablator areal density measurements with the GRH are also made possible by detection of 4.43 MeV γ-rays produced by inelastic scatter of DT fusion neutrons on (12)C nuclei in the ablating plastic capsule material.

  16. All-optical Compton gamma-ray source

    CERN Document Server

    Phuoc, K Ta; Thaury, C; Malka, V; Tafzi, A; Goddet, J P; Shah, R C; Sebban, S; Rousse, A; 10.1038/nphoton.2012.82

    2013-01-01

    One of the major goals of research for laser-plasma accelerators is the realization of compact sources of femtosecond X-rays. In particular, using the modest electron energies obtained with existing laser systems, Compton scattering a photon beam off a relativistic electron bunch has been proposed as a source of high-energy and high-brightness photons. However, laser-plasma based approaches to Compton scattering have not, to date, produced X-rays above 1 keV. Here, we present a simple and compact scheme for a Compton source based on the combination of a laser-plasma accelerator and a plasma mirror. This approach is used to produce a broadband spectrum of X-rays extending up to hundreds of keV and with a 10,000-fold increase in brightness over Compton X-ray sources based on conventional accelerators. We anticipate that this technique will lead to compact, high-repetition-rate sources of ultrafast (femtosecond), tunable (X- through gamma-ray) and low-divergence (~1 degree) photons from source sizes on the order...

  17. A Model of Pulsar Radio and Gamma-ray Emissions

    Science.gov (United States)

    Qiao, G. J.; Lee, K. J.; Wang, H. G.; Xu, R. X.

    2007-06-01

    A joint model for a pulsar's radio and γ-ray emission is introduced in this paper. This model is informed by two main concepts. One is inverse Compton scattering (ICS) mechanism for radio emission. The other one is an inner annular region for high energy radiation. In the model the geometry of both radio and γ-ray emission beams can be reproduced. Various morphologies of the radio and γ-ray pulse profiles can also be reproduced by this model. At the radio band, the core and conal emission components are natural results. For the γ-ray band the Geminga-like, Crab-like and Vela-like gamma-ray pulse profiles and their phase shifts relative to radio pulse profiles can be reproduced. There are also some observations, which cannot be understood by traditional models, such as the observed ``bi-drifting'' phenomenon of PSR J0815+09 which can be well understand in this model. It is also pointed out that pulsars as neutron stars or alternately as strange stars may be tested through radiation.

  18. Hipparcos pinpoints an amazing gamma-ray clock

    Science.gov (United States)

    1998-01-01

    Following a preliminary report at a symposium on Hipparcos results in Venice in May, the full story of the pinpointing of Geminga is told in a paper to be published in Astronomy and Astrophysics in January 1998. Patrizia Caraveo of the Istituto di Fisica Cosmica in Milan is the lead author, and other astronomers in Milan, Turin, Garching, Copenhagen and Noordwijk contributed to this aspect of the work (see footnote). The result made it possible to to use the observation of gamma-ray pulses to time the rotation of Geminga with extreme accuracy, as described in a paper by John Mattox of Boston University, Jules Halpern of Columbia University, and Patrizia Caraveo. It is due to appear in the Astrophysical Journal in February 1998, and is already accessible on the Internet. Geminga is a unique object: a highly compressed, spinning neutron star which does not emit radio beeps like the well-known pulsars. Yet it is a powerful source of pulsating gamma-rays and X-rays. Geminga is probably the prototype of millions of radio-silent neutron stars in the Milky Way Galaxy, so far unrecognized. "We needed Hipparcos to finish a long and complicated task of tracking down Geminga," Patrizia Caraveo comments. "Never was so faint an object pinpointed so precisely. Now we can say that we have more exact knowledge on the position of Geminga than of any other 'classical' neutron star -- even the famous Crab pulsar." Closing in on Geminga When first observed in a systematic way by COS-B, Geminga's place in the sky was known only to within half a degree -- an uncertainty in position as wide as the Moon. X-ray observations by other satellites narrowed the field and led to the detection of Geminga by visible light, as an extremely faint star. Last year, the same Milan-based Italian team was able to determine the distance of Geminga at 500 light-years, by a succession of observations with the Hubble Space Telescope (see ESA Information Note 04-96). The next task was precisely to situate a

  19. Using gamma-ray emission to measure areal density of inertial confinement fusion capsules.

    Science.gov (United States)

    Hoffman, N M; Wilson, D C; Herrmann, H W; Young, C S

    2010-10-01

    Fusion neutrons streaming from a burning inertial confinement fusion capsule generate gamma rays via inelastic nuclear scattering in the ablator of the capsule. The intensity of gamma-ray emission is proportional to the product of the ablator areal density (ρR) and the yield of fusion neutrons, so by detecting the gamma rays we can infer the ablator areal density, provided we also have a measurement of the capsule's total neutron yield. In plastic-shell capsules, for example, (12)C nuclei emit gamma rays at 4.44 MeV after excitation by 14.1 MeV neutrons from D+T fusion. These gamma rays can be measured by a new gamma-ray detector under development. Analysis of predicted signals is in progress, with results to date indicating that the method promises to be useful for diagnosing imploded capsules.

  20. Fermi Gamma-Ray Space Telescope: Highlights of the GeV Sky

    Science.gov (United States)

    Thomspon, D. J.

    2011-01-01

    Because high-energy gamma rays can be produced by processes that also produce neutrinos. the gamma-ray survey of the sky by the Fermi Gamma-ray Space Telescope offers a view of potenl ial targds for neutrino observations. Gamma-ray bursts. active galactic nuclei, and supernova remnants are all sites where hadronic, neutrino-producing interactions are plausible. Pulsars, pulsar wind nebulae, and binary sources are all phenomena that reveal leptonic particle acceleration through their gamma-ray emission. \\Vhile important to gamma-ray astrophysics. such sources are of less interest to neutrino studies. This talk will present a broad overview of the constantly changing sky seen with the Large Area Telescope (LAT) on the Fermi spacecraft.

  1. Discrimination between natural and other gamma ray sources from environmental gamma ray dose rate monitoring data.

    Science.gov (United States)

    Kumagai, K; Ookubo, H; Kimura, H

    2015-11-01

    In this study, a method to discriminate between natural and other γ-ray sources from environmental γ-ray dose rate monitoring data was developed, and it was successfully applied to actual monitoring data around nuclear facilities. The environmental dose rate is generally monitored by NaI(Tl) detector systems in the low dose rate range. The background dose rate varies mainly as a result of the deposition of (222)Rn progeny in precipitation and shielding of the ground by snow cover. Increments in the environmental dose rate due to radionuclides released from nuclear facilities must be separated from these background variations. The method in the present study corrects for the dose rate variations from natural sources by multiple regression analysis based on the γ-ray counting rates of single-channel analysers opened in the energy ranges of γ-rays emitted by (214)Bi and (208)Tl. Assuming a normal distribution of the results and using the one-sided type I error of 0.01 while ignoring the type II error, the detection limit of the γ-ray dose rate from artificial sources was 0.77 nGy h(-1). © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  2. Performance optimization for hard X-ray/soft gamma-ray detectors

    Science.gov (United States)

    Harrison, Fiona A.; Kahn, Steven M.; Hailey, Charles J.; Ziock, Klaus P.

    1990-01-01

    This paper discusses the optimization of the performance of imaging scintillation detectors used in the hard X-ray/soft gamma-ray (20-300) keV region of the spectrum. In these devices, absorption of an incident gamma-ray within an alkali halide crystal induces a scintillation light distribution which is centroided by an imaging photomultiplier tube mounted to the crystal. The ultimate imaging resolution is strongly affected by the detailed propagation of the scintillation light within the crystal and at the interface between the crystal and the phototube face plate. A number of refined techniques for preparing the scintillation crystals so as to optimize the imaging resolution have been investigated. The results indicate very good agreement with relatively simple models of the light propagation. It is shown that it is possible to achieve resolution consistent with the most optimistic models.

  3. High energy irradiations simulating cosmic-ray-induced planetary gamma ray production. I - Fe target

    Science.gov (United States)

    Metzger, A. E.; Parker, R. H.; Yellin, J.

    1986-01-01

    Two thick Fe targets were bombarded by a series of 6 GeV proton irradiations for the purpose of simulating the cosmic ray bombardment of planetary objects in space. Gamma ray energy spectra were obtained with a germanium solid state detector during the bombardment, and 46 of the gamma ray lines were ascribed to the Fe targets. A comparison between observed and predicted values showed good agreement for Fe lines from neutron inelastic scattering and spallation reactions, and less satisfactory agreement for neutron capture reactions, the latter attributed to the difference in composition between the Fe target and the mean lunar abundance used in the modeling. Through an analysis of the irradiation results together with continuum data obtained in lunar orbit, it was found that 100 hours of measurement with a current instrument should generate a spectrum containing approximately 20 lines due to Fe alone, with a 2-sigma sensitivity for detection of about 0.2 percent.

  4. Observation of annual modulation induced by $\\gamma$ rays from ($\\alpha$, $\\gamma$) reactions at the Soudan Underground Laboratory

    OpenAIRE

    Tiwari, A.; Zhang, C; Mei, D.-M.; Cushman, P.

    2017-01-01

    Annual modulation of $\\gamma$ rays from ($\\alpha$, $\\gamma$) reactions in the Soudan Underground Lab has been observed using a 12-liter scintillation detector. This significant annual modulation, measured over 4 years, can mimic the signature for dark matter and can also generate potential background events for neutrinoless double-$\\beta$ decay experiments. The measured annual modulation of the event rate from ($\\alpha$, $\\gamma$) reactions is strongly correlated with the time-varying radon c...

  5. LORENTZ-FACTOR-ISOTROPIC-LUMINOSITY/ENERGY CORRELATIONS OF GAMMA-RAY BURSTS AND THEIR INTERPRETATION

    Energy Technology Data Exchange (ETDEWEB)

    Lue Jing; Zou Yuanchuan; Lei Weihua; Wu Qingwen; Wang Dingxiong [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China); Zhang Bing; Lue Houjun [Department of Physics and Astronomy, University of Nevada Las Vegas, 4505 Maryland Parkway, Box 454002, Las Vegas, NV 89154-4002 (United States); Liang Enwei, E-mail: zouyc@hust.edu.cn, E-mail: leiwh@hust.edu.cn, E-mail: zhang@physics.unlv.edu [Department of Physics, Guangxi University, Nanning 530004 (China)

    2012-05-20

    The bulk Lorentz factor of the gamma-ray burst (GRB) ejecta ({Gamma}{sub 0}) is a key parameter to understanding GRB physics. Liang et al. have discovered a correlation between {Gamma}{sub 0} and isotropic {gamma}-ray energy: {Gamma}{sub 0}{proportional_to}E{sup 0.25}{sub {gamma},iso,52}. By including more GRBs with updated data and more methods to derive {Gamma}{sub 0}, we confirm this correlation and obtain {Gamma}{sub 0} {approx_equal} 91E{sup 0.29}{sub {gamma},iso,52}. Evaluating the mean isotropic {gamma}-ray luminosities L{sub {gamma},iso} of the GRBs in the same sample, we discover an even tighter correlation {Gamma}{sub 0} {approx_equal} 249L{sup 0.30}{sub {gamma},iso,52}. We propose an interpretation to this later correlation. Invoking a neutrino-cooled hyperaccretion disk around a stellar mass black hole as the central engine of GRBs, we derive jet luminosity powered by neutrino annihilation and baryon loading from a neutrino-driven wind. Applying beaming correction, we finally derive {Gamma}{sub 0}{proportional_to}L{sup 0.22}{sub {gamma},iso}, which is consistent with the data. This suggests that the central engine of long GRBs is likely a stellar mass black hole surrounded by a hyper-accreting disk.

  6. Linear combination reading program for capture gamma rays

    Science.gov (United States)

    Tanner, Allan B.

    1971-01-01

    This program computes a weighting function, Qj, which gives a scalar output value of unity when applied to the spectrum of a desired element and a minimum value (considering statistics) when applied to spectra of materials not containing the desired element. Intermediate values are obtained for materials containing the desired element, in proportion to the amount of the element they contain. The program is written in the BASIC language in a format specific to the Hewlett-Packard 2000A Time-Sharing System, and is an adaptation of an earlier program for linear combination reading for X-ray fluorescence analysis (Tanner and Brinkerhoff, 1971). Following the program is a sample run from a study of the application of the linear combination technique to capture-gamma-ray analysis for calcium (report in preparation).

  7. Gamma Rays from the Inner Milky Way: Dark Matter or Point Sources?

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    Studies of data from the Fermi Gamma-Ray Space Telescope have revealed bright gamma-ray emission from the central regions of our galaxy, with a spatial and spectral profile consistent with annihilating dark matter. I will present a new model-independent analysis that suggests that rather than originating from dark matter, the GeV excess may arise from a surprising new population of as-yet-unresolved gamma-ray point sources in the heart of the Milky Way.

  8. SEARCH FOR GAMMA-RAYS FROM THE UNUSUALLY BRIGHT GRB 130427A WITH THE HAWC GAMMA-RAY OBSERVATORY

    Energy Technology Data Exchange (ETDEWEB)

    Abeysekara, A. U. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI (United States); Alfaro, R. [Instituto de Física, Universidad Nacional Autónoma de México, México D. F. (Mexico); Alvarez, C.; Arceo, R. [CEFyMAP, Universidad Autónoma de Chiapas, Tuxtla Gutiérrez, Chiapas (Mexico); Álvarez, J. D.; Arteaga-Velázquez, J. C.; Cotti, U.; De León, C. [Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán (Mexico); Solares, H. A. Ayala [Department of Physics, Michigan Technological University, Houghton, MI (United States); Barber, A. S. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT (United States); Baughman, B. M.; Braun, J. [Department of Physics, University of Maryland, College Park, MD (United States); Bautista-Elivar, N. [Universidad Politécnica de Pachuca, Municipio de Zempoala, Hidalgo (Mexico); BenZvi, S. Y. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Rosales, M. Bonilla; Carramiñana, A. [Instituto Nacional de Astrofísica, Óptica y Electrónica, Tonantzintla, Puebla (Mexico); Caballero-Mora, K. S. [Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, México D. F. (Mexico); Castillo, M.; Cotzomi, J. [Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de Puebla, Ciudad Universitaria, Puebla (Mexico); De la Fuente, E., E-mail: dirk.lennarz@gatech.edu [Departamento de Física, Centro Universitario de Ciencias Exactas e Ingenierías, Universidad de Guadalajara, Guadalajara (Mexico); Collaboration: HAWC collaboration; and others

    2015-02-20

    The first limits on the prompt emission from the long gamma-ray burst (GRB) 130427A in the >100 GeV energy band are reported. GRB 130427A was the most powerful burst ever detected with a redshift z ≲ 0.5 and featured the longest lasting emission above 100 MeV. The energy spectrum extends at least up to 95 GeV, clearly in the range observable by the High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, a new extensive air shower detector currently under construction in central Mexico. The burst occurred under unfavorable observation conditions, low in the sky and when HAWC was running 10% of the final detector. Based on the observed light curve at MeV-GeV energies, eight different time periods have been searched for prompt and delayed emission from this GRB. In all cases, no statistically significant excess of counts has been found and upper limits have been placed. It is shown that a similar GRB close to zenith would be easily detected by the full HAWC detector, which will be completed soon. The detection rate of the full HAWC detector may be as high as one to two GRBs per year. A detection could provide important information regarding the high energy processes at work and the observation of a possible cut-off beyond the Fermi Large Area Telescope energy range could be the signature of gamma-ray absorption, either in the GRB or along the line of sight due to the extragalactic background light.

  9. Europe's space camera unmasks a cosmic gamma-ray machine

    Science.gov (United States)

    1996-11-01

    The new-found neutron star is the visible counterpart of a pulsating radio source, Pulsar 1055-52. It is a mere 20 kilometres wide. Although the neutron star is very hot, at about a million degrees C, very little of its radiant energy takes the form of visible light. It emits mainly gamma-rays, an extremely energetic form of radiation. By examining it at visible wavelengths, astronomers hope to figure out why Pulsar 1055-52 is the most efficient generator of gamma-rays known so far, anywhere the Universe. The Faint Object Camera found Pulsar 1055-52 in near ultraviolet light at 3400 angstroms, a little shorter in wavelength than the violet light at the extremity of the human visual range. Roberto Mignani, Patrizia Caraveo and Giovanni Bignami of the Istituto di Fisica Cosmica in Milan, Italy, report its optical identification in a forthcoming issue of Astrophysical Journal Letters (1 January 1997). The formal name of the object is PSR 1055-52. Evading the glare of an adjacent star The Italian team had tried since 1988 to spot Pulsar 1055-52 with two of the most powerful ground-based optical telescopes in the Southern Hemisphere. These were the 3.6-metre Telescope and the 3.5-metre New Technology Telescope of the European Southern Observatory at La Silla, Chile. Unfortunately an ordinary star 100,000 times brighter lay in almost the same direction in the sky, separated from the neutron star by only a thousandth of a degree. The Earth's atmosphere defocused the star's light sufficiently to mask the glimmer from Pulsar 1055-52. The astronomers therefore needed an instrument in space. The Faint Object Camera offered the best precision and sensitivity to continue the hunt. Devised by European astronomers to complement the American wide field camera in the Hubble Space Telescope, the Faint Object Camera has a relatively narrow field of view. It intensifies the image of a faint object by repeatedly accelerating electrons from photo-electric films, so as to produce

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

    Energy Technology Data Exchange (ETDEWEB)

    Chyzh, A; Wu, C Y; Ullmann, J; Jandel, M; Bredeweg, T; Couture, A; Norman, E

    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.

  11. Whisker growth on Sn thin film accelerated under gamma-ray induced electric field

    Science.gov (United States)

    Killefer, Morgan; Borra, Vamsi; Al-Bayati, Ahmed; Georgiev, Daniel G.; Karpov, Victor G.; Ishmael Parsai, E.; Shvydka, Diana

    2017-10-01

    We report on the growth of tin metal whiskers significantly accelerated under non-destructive gamma-ray irradiation. Sn thin film, evaporated on glass substrate, was subjected to a total of 60 h of irradiation. The irradiated samples demonstrated enhanced whisker development, in both densities and lengths, resulting in an acceleration factor of  ∼50. We attribute the observed enhancement to gamma-ray induced electrostatic fields, affecting whisker kinetics. These fields are due to the substrate charging under gamma-rays. We propose that gamma-ray irradiation can be a much needed tool for accelerated testing of whisker propensity.

  12. TPASS: a gamma-ray spectrum analysis and isotope identification computer code

    Energy Technology Data Exchange (ETDEWEB)

    Dickens, J.K.

    1981-03-01

    The gamma-ray spectral data-reduction and analysis computer code TPASS is described. This computer code is used to analyze complex Ge(Li) gamma-ray spectra to obtain peak areas corrected for detector efficiencies, from which are determined gamma-ray yields. These yields are compared with an isotope gamma-ray data file to determine the contributions to the observed spectrum from decay of specific radionuclides. A complete FORTRAN listing of the code and a complex test case are given.

  13. A Monte Carlo modeling alternative for the API Gamma Ray Calibration Facility.

    Science.gov (United States)

    Galford, J E

    2017-04-01

    The gamma ray pit at the API Calibration Facility, located on the University of Houston campus, defines the API unit for natural gamma ray logs used throughout the petroleum logging industry. Future use of the facility is uncertain. An alternative method is proposed to preserve the gamma ray API unit definition as an industry standard by using Monte Carlo modeling to obtain accurate counting rate-to-API unit conversion factors for gross-counting and spectral gamma ray tool designs. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. On the origin of gamma-ray bursts.

    Science.gov (United States)

    Ryde, Felix

    2008-12-13

    Gamma-ray bursts are the most energetic explosions in the Universe, occurring at cosmological distances. The initial phase of the emission from these bursts is predominantly of gamma rays and stems from a highly relativistic outflow. The nature of this emission is still under debate. Here, I present the interpretation that the peak in the photon spectrum can be attributed to the black-body emission of the photosphere of the outflow, having a temperature of approximately 109K. An additional non-thermal spectral component can be attributed to additional dissipation of the kinetic energy in the outflow. This two-component model can be well fitted to most instantaneous spectra. Interestingly, the thermal component exhibits a recurring behaviour over emission pulse structures. Both the temperature and the energy flux vary as broken power laws. During the pre-break phase, the temperature is approximately constant while the energy flux rises. Furthermore, the ratio of the observed thermal flux to the emergent flux increases as a power law over the whole pulse. It is argued that these observations hold the key to our understanding of the prompt emission and the properties of the site from which it emanates.

  15. The rarity of terrestrial gamma-ray flashes

    Science.gov (United States)

    Smith, D. M.; Dwyer, J. R.; Hazelton, B. J.; Grefenstette, B. W.; Martinez-McKinney, G. F. M.; Zhang, Z. Y.; Lowell, A. W.; Kelley, N. A.; Splitt, M. E.; Lazarus, S. M.; Ulrich, W.; Schaal, M.; Saleh, Z. H.; Cramer, E.; Rassoul, H. K.; Cummer, S. A.; Lu, G.; Blakeslee, R. J.

    2011-04-01

    We report on the first search for Terrestrial Gamma-ray Flashes (TGFs) from altitudes where they are thought to be produced. The Airborne Detector for Energetic Lightning Emissions (ADELE), an array of gamma-ray detectors, was flown near the tops of Florida thunderstorms in August/September 2009. The plane passed within 10 km horizontal distance of 1213 lightning discharges and only once detected a TGF. If these discharges had produced TGFs of the same intensity as those seen from space, every one should have been seen by ADELE. Separate and significant nondetections are established for intracloud lightning, negative cloud-to-ground lightning, and narrow bipolar events. We conclude that TGFs are not a primary triggering mechanism for lightning. We estimate the TGF-to-flash ratio to be on the order of 10-2 to 10-3 and show that TGF intensities cannot follow the well-known power-law distribution seen in earthquakes and solar flares, due to our limits on the presence of faint events.

  16. Determination of the measurement threshold in gamma-ray spectrometry.

    Science.gov (United States)

    Korun, M; Vodenik, B; Zorko, B

    2017-03-01

    In gamma-ray spectrometry the measurement threshold describes the lover boundary of the interval of peak areas originating in the response of the spectrometer to gamma-rays from the sample measured. In this sense it presents a generalization of the net indication corresponding to the decision threshold, which is the measurement threshold at the quantity value zero for a predetermined probability for making errors of the first kind. Measurement thresholds were determined for peaks appearing in the spectra of radon daughters 214Pb and 214Bi by measuring the spectrum 35 times under repeatable conditions. For the calculation of the measurement threshold the probability for detection of the peaks and the mean relative uncertainty of the peak area were used. The relative measurement thresholds, the ratios between the measurement threshold and the mean peak area uncertainty, were determined for 54 peaks where the probability for detection varied between some percent and about 95% and the relative peak area uncertainty between 30% and 80%. The relative measurement thresholds vary considerably from peak to peak, although the nominal value of the sensitivity parameter defining the sensitivity for locating peaks was equal for all peaks. At the value of the sensitivity parameter used, the peak analysis does not locate peaks corresponding to the decision threshold with the probability in excess of 50%. This implies that peaks in the spectrum may not be located, although the true value of the measurand exceeds the decision threshold. Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Recent progress in single sided gamma-ray tomography

    Energy Technology Data Exchange (ETDEWEB)

    Thoe, R.S.

    1994-04-01

    The use of scattered radiation for radiography has many potential advantages over conventional projection techniques: For high energy photons the scattering process strongly dominates all other processes. The intensity of scattered radiation is due directly to the electron density and highly insensitive to chemical composition. Finally, the use of scattered radiation allows the investigator to position the radiation source-on-the same side of the object as the detector. In this paper I will present some recent results of a set of measurements made with our uncollimated Compton backscattering tomography apparatus. This technique uses the Compton energy shift of scattered gamma rays to determine the scattering site. By measuring the spectrum of these scattered gamma rays it is then possible to determine the electron density of the object being investigated. I will give a brief description of the apparatus and present the results of numerous measurements made on a brass phantom with voids placed at various depths. These results imply that for this crude apparatus occlusions as small as one cubic millimeter may be located to an accuracy of about one millimeter at depths of about 15 millimeters in solid brass.

  18. Galactic-Centre Gamma Rays in CMSSM Dark Matter Scenarios

    CERN Document Server

    Ellis, John; Spanos, Vassilis C

    2011-01-01

    We study the production of gamma rays via LSP annihilations in the core of the Galaxy as a possible experimental signature of the constrained minimal supersymmetric extension of the Standard Model (CMSSM), in which supersymmetry-breaking parameters are assumed to be universal at the GUT scale, assuming also that the LSP is the lightest neutralino chi. The part of the CMSSM parameter space that is compatible with the measured astrophysical density of cold dark matter is known to include a stau_1 - chi coannihilation strip, a focus-point strip where chi has an enhanced Higgsino component, and a funnel at large tanb where the annihilation rate is enhanced by the poles of nearby heavy MSSM Higgs bosons, A/H. We calculate the total annihilation rates, the fractions of annihilations into different Standard Model final states and the resulting fluxes of gamma rays for CMSSM scenarios along these strips. We observe that typical annihilation rates are much smaller in the coannihilation strip for tanb = 10 than along t...

  19. Gamma-ray irradiation of ohmic MEMS switches

    Science.gov (United States)

    Maciel, John J.; Lampen, James L.; Taylor, Edward W.

    2012-10-01

    Radio Frequency (RF) Microelectromechanical System (MEMS) switches are becoming important building blocks for a variety of military and commercial applications including switch matrices, phase shifters, electronically scanned antennas, switched filters, Automatic Test Equipment, instrumentation, cell phones and smart antennas. Low power consumption, large ratio of off-impedance to on-impedance, extreme linearity, low mass, small volume and the ability to be integrated with other electronics makes MEMS switches an attractive alternative to other mechanical and solid-state switches for a variety of space applications. Radant MEMS, Inc. has developed an electrostatically actuated broadband ohmic microswitch that has applications from DC through the microwave region. Despite the extensive earth based testing, little is known about the performance and reliability of these devices in space environments. To help fill this void, we have irradiated our commercial-off-the-shelf SPST, DC to 40 GHz MEMS switches with gamma-rays as an initial step to assessing static impact on RF performance. Results of Co-60 gamma-ray irradiation of the MEMS switches at photon energies ≥ 1.0 MeV to a total dose of ~ 118 krad(Si) did not show a statistically significant post-irradiation change in measured broadband, RF insertion loss, insertion phase, return loss and isolation.

  20. Estimation of NOx Production from Terrestrial Gamma-ray Flashes

    Science.gov (United States)

    Cramer, E. S.; Briggs, M. S.; Liu, N.; Mailyan, B.; Rassoul, H.; Dwyer, J. R.

    2016-12-01

    The motivation of this work is to understand the effects of TGFs on the ozone layer. One of the main ozone-destroying mechanisms is the production of NOx in the stratospheric region. We first review the mechanisms for NOx production in this region, specifically looking at the global rate produced by lightning. Terrestrial Gamma-ray Flashes, with runaway electron avalanches and the subsequent bremsstrahlung gamma rays, produce atmospheric ionization at all altitudes of the atmosphere. TGFs might have a greater impact on the ozone concentration in the stratosphere since they directly produce ionization and thus NOx in the ozone layer. In order to study the effect from TGFs, we use the runaway electron avalanche model (REAM) to simulate a typical TGF. The photons are then transported through Earth's atmosphere, where they deposit some of their energy as ionization in the ozone layer. We then calculate the number of NOx molecules produced by considering the average energy required to produce one electron-ion pair (W = 35 eV). The W factor has been experimentally quantified and is constant for various types of radiation and over large energy ranges and electric fields. Finally, the effect of TGF NOx production is estimated using the global annual rate of TGFs.

  1. Regularity of high energy photon events from gamma ray bursts

    Science.gov (United States)

    Xu, Haowei; Ma, Bo-Qiang

    2018-01-01

    The effect of Quantum Gravity (QG) may bring a tiny light speed variation as v(E)=c(1‑E/ELV), where E is the photon energy and ELV is a Lorentz violation scale. A remarkable regularity was suggested in previous studies to look for the light speed variation from high energy photon events of Gamma Ray Bursts (GRBs). We provide a general analysis on the data of 25 bright GRBs observed by the Fermi Gamma-ray Space Telescope (FGST). Such method allows a completed scan over all possibilities in a more clean and impartial way without any bias compared to previous intuitive analysis. The results show that with the increase in the intrinsic energies of photons, such regularity truly emerges and gradually becomes significant. For photons with intrinsic energies higher than 40 GeV, the regularity exists at a significance of 3–5 σ with ELV=3.6× 1017 GeV determined by the GRB data.

  2. Effects of Goldstone bosons on gamma-ray bursts

    Energy Technology Data Exchange (ETDEWEB)

    Tu, Huitzu; Ng, Kin-Wang, E-mail: huitzu2@gate.sinica.edu.tw, E-mail: nkw@phys.sinica.edu.tw [Institute of Physics, Academia Sinica, 128 Sec. 2, Academia Rd., Nankang, Taipei 11529, Taiwan (China)

    2016-03-01

    Gamma-ray bursts (GRBs) are the most energetic explosion events in the universe. An amount of gravitational energy of the order of the rest-mass energy of the Sun is released from a small region within a short time. This should lead to the formation of a fireball of temperature in the MeV range, consisting of electrons/positrons, photons, and a small fraction of baryons. We exploit the potential of GRB fireballs for being a laboratory for testing particle physics beyond the Standard Model, where we find that Weinberg's Higgs portal model serves as a good candidate for this purpose. Due to the resonance effects, the Goldstone bosons can be rapidly produced by electron-positron annihilation process in the initial fireballs of the gamma-ray bursts. On the other hand, the mean free path of the Goldstone bosons is larger than the size of the GRB initial fireballs, so they are not coupled to the GRB's relativistic flow and can lead to significant energy loss. Using generic values for the GRB initial fireball energy, temperature, radius, expansion rate, and baryon number density, we find that the GRB bounds on the parameters of Weinberg's Higgs portal model are indeed competitive to current laboratory constraints.

  3. Cosmological tests with the FSRQ gamma-ray luminosity function

    Science.gov (United States)

    Zeng, Houdun; Melia, Fulvio; Zhang, Li

    2016-11-01

    The extensive catalogue of gamma-ray selected flat-spectrum radio quasars (FSRQs) produced by Fermi during a four-year survey has generated considerable interest in determining their gamma-ray luminosity function (GLF) and its evolution with cosmic time. In this paper, we introduce the novel idea of using this extensive database to test the differential volume expansion rate predicted by two specific models, the concordance Λ cold dark matter (ΛCDM) and Rh = ct cosmologies. For this purpose, we use two well-studied formulations of the GLF, one based on pure luminosity evolution (PLE) and the other on a luminosity-dependent density evolution (LDDE). Using a Kolmogorov-Smirnov test on one-parameter cumulative distributions (in luminosity, redshift, photon index and source count), we confirm the results of earlier works showing that these data somewhat favour LDDE over PLE; we show that this is the case for both ΛCDM and Rh = ct. Regardless of which GLF one chooses, however, we also show that model selection tools very strongly favour Rh = ct over ΛCDM. We suggest that such population studies, though featuring a strong evolution in redshift, may none the less be used as a valuable independent check of other model comparisons based solely on geometric considerations.

  4. Host galaxies are the obscurers of Gamma-ray bursts

    Science.gov (United States)

    Buchner, Johannes; Schulze, Steve; Bauer, Franz E.

    2017-08-01

    The luminous, high-energy emission of gamma-ray bursts (GRBs) makes them efficient probes of the high-redshift universe. The origin of the obscuration of gamma-ray burst afterglow is still unclear. We study the afterglows metal column densities along the line-of-sight of all Swift-detected long GRBs with an improved hierarchical Bayesian analysis methodology. We characterise follow-up biases and side-step them using SHOALS, an unbiased sub-sample with highly complete follow-up. That survey also measures Spitzer host masses. Overall, the column densities shows little redshift evolution but a significant correlation with host stellar mass. A simple geometrical model explains the width and shape of the column density distribution and the trend with galaxy mass correlation. Our findings implicate the host's galaxy-scale metal gas as the dominant obscurer. From a galaxy evolution perspective, our study places new constraints on the metal gas mass inside galaxies at z=0.5-4. We compare these with modern cosmological simulations (Illustris and EAGLE) and discuss implications for the obscuration of other sources inside high redshift galaxies, such as active galactic nuclei.

  5. GAMMA RAYS FROM TYPE Ia SUPERNOVA SN 2014J

    Energy Technology Data Exchange (ETDEWEB)

    Churazov, E.; Sunyaev, R.; Grebenev, S. [Space Research Institute (IKI), Profsouznaya 84/32, Moscow 117997 (Russian Federation); Isern, J. [Institut for Space Sciences (ICE-CSIC/IEEC), E-08193 Bellaterra (Spain); Bikmaev, I. [Kazan Federal University (KFU), Kremlevskaya Strasse, 18, Kazan (Russian Federation); Bravo, E. [E.T.S.A.V., Univ. Politecnica de Catalunya, Carrer Pere Serra 1-15, E-08173 Sant Cugat del Valles (Spain); Chugai, N. [Institute of Astronomy of the Russian Academy of Sciences, 48 Pyatnitskaya Street, 119017, Moscow (Russian Federation); Jean, P.; Knödlseder, J. [Université de Toulouse, UPS-OMP, IRAP, Toulouse (France); Lebrun, F. [APC, Univ Paris Diderot, CNRS/IN2P3, CEA/Irfu, Obs de Paris, Sorbonne Paris Cité (France); Kuulkers, E. [European Space Astronomy Centre (ESA/ESAC), Science Operations Department, P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain)

    2015-10-10

    The whole set of INTEGRAL observations of Type Ia supernova SN 2014J, covering the period 19–162 days after the explosion, has been analyzed. For spectral fitting the data are split into early and late periods covering days 19–35 and 50–162, respectively, optimized for {sup 56}Ni and {sup 56}Co lines. As expected for the early period, much of the gamma-ray signal is confined to energies below ∼200 keV, while for the late period it is strongest above 400 keV. In particular, in the late period, {sup 56}Co lines at 847 and 1248 keV are detected at 4.7σ and 4.3σ, respectively. The light curves in several representative energy bands are calculated for the entire period. The resulting spectra and light curves are compared with a subset of models. We confirm our previous finding that the gamma-ray data are broadly consistent with the expectations for canonical one-dimensional models, such as delayed detonation or deflagration models for a near-Chandrasekhar mass white dwarf. Late optical spectra (day 136 after the explosion) show rather symmetric Co and Fe line profiles, suggesting that, unless the viewing angle is special, the distribution of radioactive elements is symmetric in the ejecta.

  6. Elemental Composition Variations for Large Dusty and Rocky Regions on Mars Using Gamma-Ray Data from the Mars Odyssey Gamma-Ray Spectrometer

    Science.gov (United States)

    Evans, L. G.; Starr, R. D.; Reedy, R. C.; Boynton, W. V.

    2004-01-01

    The Gamma-Ray Spectrometer (GRS) on the Mars Odyssey spacecraft has been mapping the elemental composition of the surface materials since June 2002. To study elemental composition variations on the martian surface, seven large regions of Mars were selected: three very dusty ones and four mainly rocky ones. Large regions were used to get good counting statistics on as many gamma-ray peaks as possible from spectrum accumulated by the GRS experiment on Mars Odyssey, including elements with poor counting statistics. Data from TES were used to help select these regions. Gamma-ray peaks for several elements were analyzed. Some results and trends are reported.

  7. Search for Cosmic-Ray-Induced Gamma-Ray Emission in Galaxy Clusters

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Albert, A.; Allafort, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; hide

    2014-01-01

    Current theories predict relativistic hadronic particle populations in clusters of galaxies in addition to the already observed relativistic leptons. In these scenarios hadronic interactions give rise to neutral pions which decay into gamma rays that are potentially observable with the Large Area Telescope (LAT) on board the Fermi space telescope. We present a joint likelihood analysis searching for spatially extended gamma-ray emission at the locations of 50 galaxy clusters in four years of Fermi-LAT data under the assumption of the universal cosmic-ray (CR) model proposed by Pinzke & Pfrommer. We find an excess at a significance of 2.7 delta, which upon closer inspection, however, is correlated to individual excess emission toward three galaxy clusters: A400, A1367, and A3112. We discuss these cases in detail and conservatively attribute the emission to unmodeled background systems (for example, radio galaxies within the clusters).Through the combined analysis of 50 clusters, we exclude hadronic injection efficiencies in simple hadronic models above 21% and establish limits on the CR to thermal pressure ratio within the virial radius, R(sub 200), to be below 1.25%-1.4% depending on the morphological classification. In addition, we derive new limits on the gamma-ray flux from individual clusters in our sample.

  8. Statistical Distributions of Optical Flares from Gamma-Ray Bursts

    Science.gov (United States)

    Yi, Shuang-Xi; Yu, Hai; Wang, F. Y.; Dai, Zi-Gao

    2017-07-01

    We statistically study gamma-ray burst (GRB) optical flares from the Swift/UVOT catalog. We compile 119 optical flares, including 77 flares with redshift measurements. Some tight correlations among the timescales of optical flares are found. For example, the rise time is correlated with the decay time, and the duration time is correlated with the peak time of optical flares. These two tight correlations indicate that longer rise times are associated with longer decay times of optical flares and also suggest that broader optical flares peak at later times, which are consistent with the corresponding correlations of X-ray flares. We also study the frequency distributions of optical flare parameters, including the duration time, rise time, decay time, peak time, and waiting time. Similar power-law distributions for optical and X-ray flares are found. Our statistic results imply that GRB optical flares and X-ray flares may share the similar physical origin, and both of them are possibly related to central engine activities.

  9. Gamma-ray blazars: The view from AGILE

    Science.gov (United States)

    D'Ammando, F.; Bulgarelli, A.; Chen, A. W.; Donnarumma, I.; Giuliani, A.; Longo, F.; Pacciani, L.; Pucella, G.; Striani, E.; Tavani, M.; Vercellone, S.; Vittorini, V.; Covino, S.; Krimm, H. A.; Raiteri, C. M.; Romano, P.; Villata, M.

    2011-07-01

    During the first 3 years of operation the Gamma-Ray Imaging Detector onboard the AGILE satellite detected several blazars in a high γ-ray activity: 3C 279, 3C 454.3, PKS 1510-089, S5 0716+714, 3C 273, W Comae, Mrk 421, PKS 0537-441 and 4C +21.35. Thanks to the rapid dissemination of our alerts, we were able to obtain multiwavelength data from other observatories such as Spitzer, Swift, RXTE, Suzaku, INTEGRAL, MAGIC, VERITAS, and ARGO as well as radio-to-optical coverage by means of the GASP Project of the WEBT and the REM Telescope. This large multifrequency coverage gave us the opportunity to study the variability correlations between the emission at different frequencies and to obtain simultaneous Spectral Energy Distributions of these sources from radio to γ-ray energy bands, investigating the different mechanisms responsible for their emission and uncovering in some cases a more complex behavior with respect to the standard models. We present a review of the most interesting AGILE results on these γ-ray blazars and their multifrequency data.

  10. Tidal tearing of circumstellar disks in Be/X-ray and gamma-ray binaries

    Science.gov (United States)

    Okazaki, Atsuo T.

    2017-11-01

    About one half of high-mass X-ray binaries host a Be star [an OB star with a viscous decretion (slowly outflowing) disk]. These Be/X-ray binaries exhibit two types of X-ray outbursts (Stella et al. 1986), normal X-ray outbursts (L X~1036-37 erg s-1) and occasional giant X-ray outbursts (L X > 1037 erg s-1). The origin of giant X-ray outbursts is unknown. On the other hand, a half of gamma-ray binaries have a Be star as the optical counterpart. One of these systems [LS I +61 303 (P orb = 26.5 d)] shows the superorbital (1,667 d) modulation in radio through X-ray bands. No consensus has been obtained for its origin. In this paper, we study a possibility that both phenomena are caused by a long-term, cyclic evolution of a highly misaligned Be disk under the influence of a compact object, by performing 3D hydrodynamic simulations. We find that the Be disk cyclically evolves in mildly eccentric, short-period systems. Each cycle consists of the following stages: 1) As the Be disk grows with time, the initially circular disk becomes eccentric by the Kozai-Lidov mechanism. 2) At some point, the disk is tidally torn off near the base and starts precession. 3) Due to precession, a gap opens between the disk base and mass ejection region, which allows the formation of a new disk in the stellar equatorial plane (see Figure 1). 4) The newly formed disk finally replaces the precessing old disk. Such a cyclic disk evolution has interesting implications for the long-term behavior of high energy emission in Be/X-ray and gamma-ray binaries.

  11. Pulsed high-energy gamma rays from PSR 1055-52

    Science.gov (United States)

    Fierro, J. M.; Bertsch, D. L.; Brazier, K. T.; Chiang, J.; D'Amico, N.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Johnston, S.; Kanbach, G.

    1993-01-01

    The Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory has detected a high-energy gamma-ray source at a position coincident with that of the radio pulsar PSR 1055-52. Analysis of the EGRET data at the radio pulsar period of 197 ms has revealed pulsed gamma-radiation at energies above 300 MeV, making PSR 1055-52 the fifth detected high-energy gamma-ray pulsar. The pulsed radiation from PSR 1055-52 has a very hard photon spectral index of -1.18 +/- 0.16 and a high efficiency for converting its rotational energy into gamma-rays. No unpulsed emission was observed.

  12. A comparative study of LaBr3(Ce(3+)) and CeBr3 based gamma-ray spectrometers for planetary remote sensing applications.

    Science.gov (United States)

    Kozyrev, A; Mitrofanov, I; Owens, A; Quarati, F; Benkhoff, J; Bakhtin, B; Fedosov, F; Golovin, D; Litvak, M; Malakhov, A; Mokrousov, M; Nuzhdin, I; Sanin, A; Tretyakov, V; Vostrukhin, A; Timoshenko, G; Shvetsov, V; Granja, C; Slavicek, T; Pospisil, S

    2016-08-01

    The recent availability of large volume cerium bromide crystals raises the possibility of substantially improving gamma-ray spectrometer limiting flux sensitivities over current systems based on the lanthanum tri-halides, e.g., lanthanum bromide and lanthanum chloride, especially for remote sensing, low-level counting applications or any type of measurement characterized by poor signal to noise ratios. The Russian Space Research Institute has developed and manufactured a highly sensitive gamma-ray spectrometer for remote sensing observations of the planet Mercury from the Mercury Polar Orbiter (MPO), which forms part of ESA's BepiColombo mission. The Flight Model (FM) gamma-ray spectrometer is based on a 3-in. single crystal of LaBr3(Ce(3+)) produced in a separate crystal development programme specifically for this mission. During the spectrometers development, manufacturing, and qualification phases, large crystals of CeBr3 became available in a subsequent phase of the same crystal development programme. Consequently, the Flight Spare Model (FSM) gamma-ray spectrometer was retrofitted with a 3-in. CeBr3 crystal and qualified for space. Except for the crystals, the two systems are essentially identical. In this paper, we report on a comparative assessment of the two systems, in terms of their respective spectral properties, as well as their suitability for use in planetary mission with respect to radiation tolerance and their propensity for activation. We also contrast their performance with a Ge detector representative of that flown on MESSENGER and show that: (a) both LaBr3(Ce(3+)) and CeBr3 provide superior detection systems over HPGe in the context of minimally resourced spacecraft and (b) CeBr3 is a more attractive system than LaBr3(Ce(3+)) in terms of sensitivities at lower gamma fluxes. Based on the tests, the FM has now been replaced by the FSM on the BepiColombo spacecraft. Thus, CeBr3 now forms the central gamma-ray detection element on the MPO spacecraft.

  13. Total and partial cross sections of the $^{112}$Sn($\\alpha,\\gamma$)$^{116}$Te reaction measured via in-beam $\\gamma$-ray spectroscopy

    OpenAIRE

    Netterdon, L.; Mayer, J.; Scholz, P.; Zilges, A.

    2015-01-01

    An extended database of experimental data is needed to address uncertainties of the nuclear-physics input parameters for Hauser-Feshbach calculations. Especially $\\alpha$+nucleus optical model potentials at low energies are not well known. The in-beam technique with an array of high-purity germanium (HPGe) detectors was successfully applied to the measurement of absolute cross sections of an ($\\alpha$,$\\gamma$) reaction on a heavy nucleus at sub-Coulomb energies. The total and partial cross-s...

  14. An upper limit on the cosmic-ray luminosity of individual sources from gamma-ray observations

    Energy Technology Data Exchange (ETDEWEB)

    Supanitsky, A.D. [Instituto de Astronomía y Física del Espacio (IAFE), CONICET-UBA (Argentina); Souza, V. de, E-mail: supanitsky@iafe.uba.ar, E-mail: vitor@ifsc.usp.br [Instituto de Física de São Carlos, Universidade de São Paulo (Brazil)

    2013-12-01

    Different types of extragalactic objects are known to produce TeV gamma-rays. Some of these objects are the most probable candidates to accelerate cosmic rays up to 10{sup 20} eV. It is very well known that gamma-rays can be produced as a result of the cosmic ray propagation through the intergalactic medium. These gamma-rays contribute to the total flux observed in the direction of the source. In this paper we propose a new method to derive an upper limit on the cosmic-ray luminosity of an individual source based on the measured upper limit on the integral flux of GeV-TeV gamma-rays. We show how it is possible to calculate an upper limit on the cosmic-ray luminosity of a particular source and we explore the parameter space in which the current GeV-TeV gamma-ray measurements can offer a useful determination. We study in detail two particular sources, Pictor A and NGC 7469, and we calculate the upper limit on the proton luminosity of each source based on the upper limit on the integral gamma-ray flux measured by the H.E.S.S. telescopes.

  15. Fermi LAT Search for Dark Matter in Gamma-Ray Lines and the Inclusive Photon Spectrum

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Albert, A.; Baldini, L.; Barbiellini, G.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; hide

    2012-01-01

    Dark matter particle annihilation or decay can produce monochromatic gamma-ray lines and contribute to the diffuse gamma-ray background. Flux upper limits are presented for gamma-ray spectral lines from 7 to 200 GeV and for the diffuse gamma-ray background from 4.8 GeV to 264 GeV obtained from two years of Fermi Large Area Telescope data integrated over most of the sky. We give cross section upper limits and decay lifetime lower limits for dark matter models that produce gamma-ray lines or contribute to the diffuse spectrum, including models proposed as explanations of the PAMELA and Fermi cosmic-ray data.

  16. Terrestrial gamma-ray flash production by lightning

    Science.gov (United States)

    Carlson, Brant E.

    Terrestrial gamma-ray flashes (TGFs) are brief flashes of gamma-rays originating in the Earth's atmosphere and observed by satellites. First observed in 1994 by the Burst And Transient Source Experiment on board the Compton Gamma-Ray Observatory, TGFs consist of one or more ˜1 ms pulses of gamma-rays with a total fluence of ˜1/cm2, typically observed when the satellite is near active thunderstorms. TGFs have subsequently been observed by other satellites to have a very hard spectrum (harder than dN/d E ∝ 1/ E ) that extends from below 25 keV to above 20 MeV. When good lightning data exists, TGFs are closely associated with measurable lightning discharge. Such discharges are typically observed to occur within 300 km of the sub-satellite point and within several milliseconds of the TGF observation. The production of these intense energetic bursts of photons is the puzzle addressed herein. The presence of high-energy photons implies a source of bremsstrahlung, while bremsstrahlung implies a source of energetic electrons. As TGFs are associated with lightning, fields produced by lightning are naturally suggested to accelerate these electrons. Initial ideas about TGF production involved electric fields high above thunderstorms as suggested by upper atmospheric lightning research and the extreme energies required for lower-altitude sources. These fields, produced either quasi-statically by charges in the cloud and ionosphere or dynamically by radiation from lightning strokes, can indeed drive TGF production, but the requirements on the source lightning are too extreme and therefore not common enough to account for all existing observations. In this work, studies of satellite data, the physics of energetic electron and photon production, and consideration of lightning physics motivate a new mechanism for TGF production by lightning current pulses. This mechanism is then developed and used to make testable predictions. TGF data from satellite observations are compared

  17. Novel Chalcogenide Materials for X-ray and Gamma-ray Detection

    Science.gov (United States)

    2016-05-01

    Physics ) Mr. Hao Li ( Chemistry ) Ms Maria Sebastian (Materials Science, to graduate Fall 2014) Chris Malliakas ( Chemistry ) Past postdocs: John...native defects in the gamma-ray detector material Cs2Hg6S1, Applied Physics Letters 2012, 101. (4) Li, H.; Peters, J. A.; Liu, Z. F.; Sebastian, M... Applied Physics 2012, 112. (7) Li, H.; Malliakas, C. D.; Peters, J. A.; Liu, Z. F.; Im, J.; Jin, H.; Morris, C. D.; Zhao, L. D.; Wessels, B. W

  18. A Study of the Gamma-Ray Burst Fundamental Plane

    Science.gov (United States)

    Dainotti, Maria; Gilbertson, Christian; Postnikov, Sergey; Nagataki, Shigehiro; Willingale, Richard

    2017-01-01

    A class of long gamma-ray bursts (GRBs) with a plateau phase in their X-ray afterglows obeys a three dimensional (3D) relation (Dainotti et al. 2016), 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, $L_{peak}$, which is an extension of the two dimensional Dainotti relation. This 3D relation identifies a GRB fundamental plane whose existence we confirmed. We extended the original analysis with X-ray data from July 2014 to July 2016 achieving a total sample of 183 {\\it Swift} GRBs with afterglow plateaus and known redshifts. We added the most recent GRBs to the previous `gold sample' (now including 45 GRBs) and obtained an intrinsic scatter compatible within one $\\sigma$ with the previous result. We compared several GRB categories, such as short with extended emission, X-ray Flashes, GRBs associated with SNe, 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 only by GRBs with light curves with good data coverage and relatively flat plateaus. We evaluated the relation planes for each of the mentioned categories and showed that they are not statistically different from the plane derived from the gold sample and that the fundamental plane derived from the gold sample has an intrinsic scatter smaller than any plane derived from the other sample categories. We compared the jet opening angles tabulated in literature with the angles derived using the $E_{iso}-E_{gamma}$ relation of the method in Pescalli et al. (2015) and calculated the relation plane for a sample of long GRBs accounting for the different jet opening angles. We observed that this correction does not significantly reduce the scatter. In an extended analysis, we found that the fundamental plane is independent from several prompt and afterglow parameters, such as the jet opening angle, $\\theta

  19. High energy radiation from black holes gamma rays, cosmic rays, and neutrinos

    CERN Document Server

    Dermer, Charles D

    2009-01-01

    Bright gamma-ray flares observed from sources far beyond our Milky Way Galaxy are best explained if enormous amounts of energy are liberated by black holes. The highest- energy particles in nature--the ultra-high-energy cosmic rays--cannot be confined by the Milky Way's magnetic field, and must originate from sources outside our Galaxy. Understanding these energetic radiations requires an extensive theoretical framework involving the radiation physics and strong-field gravity of black holes. In High Energy Radiation from Black Holes, Charles Dermer and Govind Menon present a systemat

  20. [Study on bamboo treated with gamma rays by X-ray diffraction].

    Science.gov (United States)

    Sun, Feng-Bo; Fei, Ben-Hua; Jiang, Ze-Hui; Yu, Zi-Xuan; Tian, Gen-Lin; Yang, Quan-Wen

    2011-06-01

    The microfibril angle and crystallinity of bamboo treated with gamma rays were tested by X-ray diffraction (XRD). The result indicated that crystallinity in bamboo increased when irradiation dose was less than 100 kGy, while the irradiation dose was raised to about 100 kGy, crystallinity in bamboo reduced. But during the whole irradiation process, the influence on microfibril angle was not obvious, so it was not the dominant factors on variation in physical-mechanical properties of bamboo during the process of irradiation.