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Sample records for absorption gamma-ray spectrometer

  1. Characterization of a new modular decay total absorption gamma-ray spectrometer (DTAS) for FAIR

    Energy Technology Data Exchange (ETDEWEB)

    Montaner Piza, A.; Tain, J. L.; Agramunt, J.; Algora, A.; Guadilla, V.; Marin, E.; Rice, S.; Rubio, B. [Instituto de Fisica Corpuscular, CSIC-Univ. de Valencia, Apdo. Correos 22085, E-46071 Valencia (Spain)

    2013-06-10

    Beta-decay studies are one of the main goals of the DEcay SPECtroscopy experiment (DESPEC) to be installed at the future Facility for Antiproton and Ion Research (FAIR). DESPEC aims at the study of nuclear structure of exotic nuclei. A new modular Decay Total Absorption gamma-ray Spectrometer (DTAS) is being built at IFIC and is specially adapted to studies at fragmentation facilities such as the Super Fragment Separator (Super-FRS) at FAIR. The designed spectrometer is composed of 16 identical NaI(Tl) scintillation crystals. This work focuses on the characterization of these independent modules, as an initial step for the characterization of the full spectrometer. Monte Carlo simulations have been performed in order to understand the detector response.

  2. Studies of the $\\beta$-decay of Kr and Sr nuclei on and near the N=Z line with a Total Absorption $\\gamma$-ray Spectrometer

    CERN Multimedia

    2002-01-01

    It is proposed to measure the Gamow-Teller strength distribution in the decays of $^{71-75}$Kr and $^{75,76}$Sr using a Total Absorption Gamma-ray Spectrometer (TAGS) based on a large NaI(TI) detector. The $\\gamma$-rays emitted in these decays will be detected in the TAGS in coincidence with positrons and X-rays from electron capture. Measurements of $\\beta$-delayed particles will also be performed in coincidence with the TAGS. Comparison with theoretical calculations based on the mean field approach, Tamm-Dancoff and QRPA method should allow a determination of the shapes of the ground states of these nuclei.

  3. Digital Logarithmic Airborne Gamma Ray Spectrometer

    OpenAIRE

    2014-01-01

    A new digital logarithmic airborne gamma ray spectrometer is designed in this study. The spectrometer adopts a high-speed and high-accuracy logarithmic amplifier (LOG114) to amplify the pulse signal logarithmically and to improve the utilization of the ADC dynamic range, because the low-energy pulse signal has a larger gain than the high-energy pulse signal. The spectrometer can clearly distinguish the photopeaks at 239, 352, 583, and 609keV in the low-energy spectral sections after the energ...

  4. Digital Logarithmic Airborne Gamma Ray Spectrometer

    CERN Document Server

    Zeng, GuoQiang; Li, Chen; Tan, ChengJun; Ge, LiangQuan; Gu, Yi; Cheng, Feng

    2014-01-01

    A new digital logarithmic airborne gamma ray spectrometer is designed in this study. The spectrometer adopts a high-speed and high-accuracy logarithmic amplifier (LOG114) to amplify the pulse signal logarithmically and to improve the utilization of the ADC dynamic range, because the low-energy pulse signal has a larger gain than the high-energy pulse signal. The spectrometer can clearly distinguish the photopeaks at 239, 352, 583, and 609keV in the low-energy spectral sections after the energy calibration. The photopeak energy resolution of 137Cs improves to 6.75% from the original 7.8%. Furthermore, the energy resolution of three photopeaks, namely, K, U, and Th, is maintained, and the overall stability of the energy spectrum is increased through potassium peak spectrum stabilization. Thus, effectively measuring energy from 20keV to 10MeV is possible.

  5. Digital logarithmic airborne gamma ray spectrometer

    Science.gov (United States)

    Zeng, Guo-Qiang; Zhang, Qing-Xian; Li, Chen; Tan, Cheng-Jun; Ge, Liang-Quan; Gu, Yi; Cheng, Feng

    2014-07-01

    A new digital logarithmic airborne gamma ray spectrometer is designed in this study. The spectrometer adopts a high-speed and high-accuracy logarithmic amplifier (LOG114) to amplify the pulse signal logarithmically and to improve the utilization of the ADC dynamic range because the low-energy pulse signal has a larger gain than the high-energy pulse signal. After energy calibration, the spectrometer can clearly distinguish photopeaks at 239, 352, 583 and 609 keV in the low-energy spectral sections. The photopeak energy resolution of 137Cs improves to 6.75% from the original 7.8%. Furthermore, the energy resolution of three photopeaks, namely, K, U, and Th, is maintained, and the overall stability of the energy spectrum is increased through potassium peak spectrum stabilization. Thus, it is possible to effectively measure energy from 20 keV to 10 MeV.

  6. Modernization of multichannel gamma-ray spectrometer at the second horizontal channel of reactor WWR-M

    CERN Document Server

    Berko, V J; Lyibman, V A

    2003-01-01

    Fast anti coincidence scheme with one privileged entrance has been developed, made and adjusted for underestimation of background distribution under full absorption peaks of gamma-ray by transformation one track of multichannel pair gamma-ray spectrometer into anticompton spectrometer. Obtained suppression factor of background is from 1,5 to 4, depending on gamma-ray energy.

  7. 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...

  8. Superconducting High Energy Resolution Gamma-ray Spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Chow, D T

    2002-02-22

    We have demonstrated that a bulk absorber coupled to a TES can serve as a good gamma-ray spectrometer. Our measured energy resolution of 70 eV at 60 keV is among the best measurements in this field. We have also shown excellent agreement between the noise predictions and measured noise. Despite this good result, we noted that our detector design has shortcomings with a low count rate and vulnerabilities with the linearity of energy response. We addressed these issues by implementation of an active negative feedback bias. We demonstrated the effects of active bias such as additional pulse shortening, reduction of TES change in temperature during a pulse, and linearization of energy response at low energy. Linearization at higher energy is possible with optimized heat capacities and thermal conductivities of the microcalorimeter. However, the current fabrication process has low control and repeatability over the thermal properties. Thus, optimization of the detector performance is difficult until the fabrication process is improved. Currently, several efforts are underway to better control the fabrication of our gamma-ray spectrometers. We are developing a full-wafer process to produce TES films. We are investigating the thermal conductivity and surface roughness of thicker SiN membranes. We are exploring alternative methods to couple the absorber to the TES film for reproducibility. We are also optimizing the thermal conductivities within the detector to minimize two-element phonon noise. We are experimenting with different absorber materials to optimize absorption efficiency and heat capacity. We are also working on minimizing Johnson noise from the E S shunt and SQUID amplifier noise. We have shown that our performance, noise, and active bias models agree very well with measured data from several microcalorimeters. Once the fabrication improvements have been implemented, we have no doubt that our gamma-ray spectrometer will achieve even more spectacular results.

  9. The AGATA Spectrometer: next generation gamma-ray spectroscopy

    Science.gov (United States)

    Simpson, J.; AGATA Collaboration

    2015-05-01

    The Advanced GAmma Tracking Array (AGATA) is a European project to develop and operate the next generation gamma-ray spectrometer. AGATA is based on the technique of gamma-ray energy tracking in electrically segmented high-purity germanium crystals. The spectrometer will have an unparalleled level of detection power for electromagnetic nuclear radiation. The tracking technique requires the accurate determination of the energy, time and position of every interaction as a gamma ray deposits its energy within the detector volume. Reconstruction of the full interaction path results in a detector with very high efficiency and excellent spectral response. The realisation of gamma-ray tracking and AGATA is a result of many technical advances and the spectrometer is now operational. AGATA has been operated in a series of scientific campaigns at Legnaro National Laboratory in Italy and GSI in Germany and is presently being assembled at GANIL in France. The status of the instrument will be reviewed.

  10. New xenon gamma-ray spectrometer for sorting of radioactive waste

    Science.gov (United States)

    Ulin, Sergey E.; Novikov, Alexander S.; Dmitrenko, Valery V.; Vlasik, Konstantin F.; Uteshev, Ziyaetdin M.; Shustov, Alexander E.; Petrenko, Denis V.

    2016-09-01

    A gamma-ray spectrometer for radioactive waste sorting is presented. The equipment is based on a new "thin-walled" xenon gamma-ray detector with sensitive volume of 4 liters and a digital electronics unit. Use of the thin wall (0.5 mm of stainless steel covered with fiberglass) provides lower absorption of gamma-rays by the detector's walls and expansion of the energy range of radiation being registered. The digital electronics unit makes it possible to use the equipment in unfavorable field conditions such as high levels of acoustic influence.

  11. $\\gamma$-Ray Absorption at High Redshifts and the $\\gamma$-Ray Background

    CERN Document Server

    Stecker, F W

    1997-01-01

    We present results of a calculation of absorption of 10-500 GeV gamma-rays at high redshifts. This calculation requires the determination of the high- redshift evolution of the full spectral energy distribution of the intergalactic photon field. For this, we have primarily followed the recent analysis of Fall, Charlot and Pei. We give our results for the gamma-ray opacity as a function of redshift out to a redshift of 3. We then give predicted gamma-ray spectra for selected blazars and also extend our results on the background from unresolved blazars to an energy of 500 GeV. Absorption effects are predicted to significantly steepen the background spectrum above 20 GeV. Our absorption calculations can be used to place limits on the redshifts of gamma-ray bursts. Our background calculations can be used to determine the observability of multi-GeV lines from dark matter neutralino particles.

  12. 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.

  13. Electronic characterization of mercuric iodide gamma ray spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Gerrish, V.M.

    1993-01-01

    During the past four years the yield of high resolution mercuric iodide (HgI[sub 2]) gamma ray spectrometers produced at EG G/EM has increased dramatically. Data is presented which demonstrates a strong correlation between starting material and spectrometer performance. Improved spectrometer yields are attributed to the method of HgI[sub 2] synthesis and to material purification procedures. Data is presented which shows that spectrometer performance is correlated with hole mobility-lifetime products. In addition, the measurement of Schottky barrier heights on HgI[sub 2] spectrometers has been performed using I-V curves and the photoelectric method. Barrier heights near 1.1 eV have been obtained using various contacts and contact deposition methods. These data suggest the pinning of the Fermi level at midgap at the HgI[sub 2] surface, probably due to surface states formed prior to contact deposition.

  14. Electronic characterization of mercuric iodide gamma ray spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Gerrish, V.M.

    1993-06-01

    During the past four years the yield of high resolution mercuric iodide (HgI{sub 2}) gamma ray spectrometers produced at EG&G/EM has increased dramatically. Data is presented which demonstrates a strong correlation between starting material and spectrometer performance. Improved spectrometer yields are attributed to the method of HgI{sub 2} synthesis and to material purification procedures. Data is presented which shows that spectrometer performance is correlated with hole mobility-lifetime products. In addition, the measurement of Schottky barrier heights on HgI{sub 2} spectrometers has been performed using I-V curves and the photoelectric method. Barrier heights near 1.1 eV have been obtained using various contacts and contact deposition methods. These data suggest the pinning of the Fermi level at midgap at the HgI{sub 2} surface, probably due to surface states formed prior to contact deposition.

  15. A gamma-ray spectrometer system for fusion applications

    CERN Document Server

    Esposito, B; Kaschuck, Y A; Martin-Solis, J R; Portnov, D V

    2002-01-01

    A NaI scintillator spectrometer system for the measurement of gamma-ray spectra in tokamak discharges has been developed and installed on the Frascati Tokamak Upgrade. Two NaI scintillators are viewing the plasma at two different angles with respect to the equatorial plane. The main features of the spectrometer system (energy range: 0.3-23 MeV) and of the unfolding technique used to restore physical spectra from the pulse-height distributions are described: a method of solution with regularisation for matrix equations of large size, allowing to process count distributions with significant statistical noise, has been developed. A dedicated software, portable to any platform, has been written both for the acquisition and the analysis of the spectra. The typical gamma-ray spectra recorded in hydrogen and deuterium discharges, also with additional heating, are presented and discussed; two components have been observed: (a) thick-target Bremsstrahlung gamma-rays produced by runaway electrons hitting the Inconel po...

  16. 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...

  17. Studies of the $\\beta$-decay of Sr nuclei on and near the N=Z Line with a Total Absorption Gamma-ray Spectrometer

    CERN Multimedia

    Marechal, F; Caballero ontanaya, L

    2002-01-01

    In the framework of the investigation of the shapes of the ground states of the parent nucleus, we propose to carry out measurements of the complete Gamow-Teller strength distribution for the $^{76-80}$Sr isotopes, with a new Total Absorption Gamma Spectrometer installed on a new beam line. The results will be compared with theoretical calculations based on the mean field approach. A brief report on the IS370 experiment on $^{72-75}$Kr decay, which was recently performed at ISOLDE, will be given and the performance of the sum spectrometer will be presented.

  18. Gamma-ray spectrometer onboard Chang'E-2

    Science.gov (United States)

    Ma, T.; Chang, J.; Zhang, N.; Jian, W.; Cai, M. S.; Gong, Y. Z.; Tang, H. S.; Zhang, R. J.; Wang, N. S.; Yu, M.; Mao, J. P.; Hu, Y. M.; Xu, A. A.; Zhu, M. H.

    2013-10-01

    Chang'E-2 gamma-ray spectrometer (GRS) is included in the payload of Chinese second lunar mission Chang'E-2 that has been launched in October 2010. Specific objectives of the GRS are to map abundance of O, Si, Fe, Ti, U, Th, K, and, perhaps, Mg, Al, and Ca, to depth of about 20 cm. The energy resolution and detection efficiency were improved compared with Chang'E-1 GRS. We will describe the design of GRS, which used LaBr3 for its main detector, and present its performance in this paper. Moreover, the initial result of Chang'E-2 GRS is reported.

  19. Search for gamma-ray transients using the SMM spectrometer

    Science.gov (United States)

    Share, G. H.; Harris, M. J.; Leising, M. D.; Messina, D. C.

    1993-01-01

    Observations for transient radiation made by the Gamma Ray Spectrometer on the SMM satellite are summarized. Spectra were obtained from 215 solar flares and 177 gamma-ray bursts. No narrow or moderately broadened lines were observed in any of the bursts. The rate of bursts is consistent with a constant over the mission but is weakly correlated with solar activity. No evidence was found for bursts of 511 keV line emission, unaccompanied by a strong continuum, at levels not less than 0.05 gamma/sq cm s for bursts lasting not more than 16 s. No evidence was found for broad features near 1 MeV from Cyg X-1, the Galactic center, or the Crab in 12-d integrations at levels not less than 0.006 gamma/sq cm s. No evidence was found for transient celestial narrow-line emission from 300 keV to 7 MeV on min-to-hrs-long time scales from 1984 to 1989.

  20. Development of the NPL gamma-ray spectrometer NANA for traceable nuclear decay and structure studies.

    Science.gov (United States)

    Lorusso, G; Shearman, R; Regan, P H; Judge, S M; Bell, S; Collins, S M; Larijani, C; Ivanov, P; Jerome, S M; Keightley, J D; Lalkovski, S; Pearce, A K; Podolyak, Zs

    2016-03-01

    We present a brief report on the progress towards the construction of the National Nuclear Array (NANA), a gamma-ray coincidence spectrometer for discrete-line nuclear structure and decay measurements. The proposed spectrometer will combine a gamma-ray energy resolution of approximately 3% at 1MeV with sub-nanosecond timing discrimination between successive gamma rays in mutually coincident decay cascades. We also review a number of recent measurements using coincidence fast-timing gamma-ray spectroscopy for nuclear structure studies, which have helped to inform the design criteria for the NANA spectrometer.

  1. 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.

  2. Design and applications of an anticoincidence shielded low background gamma-ray spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Petri, H. [Forschungszentrum Juelich GmbH (Germany). Zentralabteilung fuer Chemische Analysen

    1997-03-01

    A low background gamma-ray spectrometer has been constructed for measuring artificial and natural radioative isotopes. The design of the spectrometer, its properties and the application to the determination of natural radioactivity of dental ceramics are described. (orig.)

  3. 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...

  4. Strontium iodide gamma ray spectrometers for planetary science (Conference Presentation)

    Science.gov (United States)

    Prettyman, Thomas H.; Rowe, Emmanuel; Butler, Jarrhett; Groza, Michael; Burger, Arnold; Yamashita, Naoyuki; Lambert, James L.; Stassun, Keivan G.; Beck, Patrick R.; Cherepy, Nerine J.; Payne, Stephen A.; Castillo-Rogez, Julie C.; Feldman, Sabrina M.; Raymond, Carol A.

    2016-09-01

    Gamma rays produced passively by cosmic ray interactions and by the decay of radioelements convey information about the elemental makeup of planetary surfaces and atmospheres. Orbital missions mapped the composition of the Moon, Mars, Mercury, Vesta, and now Ceres. Active neutron interrogation will enable and/or enhance in situ measurements (rovers, landers, and sondes). Elemental measurements support planetary science objectives as well as resource utilization and planetary defense initiatives. Strontium iodide, an ultra-bright scintillator with low nonproportionality, offers significantly better energy resolution than most previously flown scintillators, enabling improved accuracy for identification and quantification of key elements. Lanthanum bromide achieves similar resolution; however, radiolanthanum emissions obscure planetary gamma rays from radioelements K, Th, and U. The response of silicon-based optical sensors optimally overlaps the emission spectrum of strontium iodide, enabling the development of compact, low-power sensors required for space applications, including burgeoning microsatellite programs. While crystals of the size needed for planetary measurements (>100 cm3) are on the way, pulse-shape corrections to account for variations in absorption/re-emission of light are needed to achieve maximum resolution. Additional challenges for implementation of large-volume detectors include optimization of light collection using silicon-based sensors and assessment of radiation damage effects and energetic-particle induced backgrounds. Using laboratory experiments, archived planetary data, and modeling, we evaluate the performance of strontium iodide for future missions to small bodies (asteroids and comets) and surfaces of the Moon and Venus. We report progress on instrument design and preliminary assessment of radiation damage effects in comparison to technology with flight heritage.

  5. Absorption of Intergalactic TeV Gamma-Rays

    CERN Document Server

    Stecker, F W

    1997-01-01

    We discuss the problem of the absorption of very high-energy gamma-rays by pair production interactions with extragalactic photons which originate from stellar emission in the near IR-UV and reradiation of starlight in the mid- and far-IR. The absorption of gamma-rays above 1 TeV is dominated by interactions with infrared photons. We make a new determination of the optical depth of the universe to multi-TeV photons as a function of energy and redshift and use the results to compare with recent spectral data of Mrk 421 and Mrk 501, sources that have been observed in the flaring state up to apx. 10 TeV energy. For the optical depth calculations, we have made use of a new, empirically based calculation of the intergalactic radiation field by Malkan & Stecker which we consider to be more accurate than that based on previous theoretical modeling. We also discuss the absorption of sub-TeV gamma-rays by starlight photons at high redshifts.

  6. HEAO C-1 gamma-ray spectrometer. [experimental design

    Science.gov (United States)

    Mahoney, W. A.; Ling, J. C.; Willett, J. B.; Jacobson, A. S.

    1978-01-01

    The gamma-ray spectroscopy experiment to be launched on the third High Energy Astronomy Observatory (HEAO C) will perform a complete sky search for narrow gamma-ray line emission to the level of about 00001 photons/sq cm -sec for steady point sources. The design of this experiment and its performance based on testing and calibration to date are discussed.

  7. Extragalactic Absorption of High Energy $\\gamma$-Rays

    CERN Document Server

    Stecker, F W

    1999-01-01

    The pair-production absorption of high-energy gamma-rays by intergalactic low-energy photons is expected to produce a high-energy cutoff in the spectra of extragalactic sources which is a sensitive function of redshift. We first discuss the expected absorption coefficient as a function of energy and redshift derived by Stecker and De Jager by making use of a new empirically based calculation of the spectral energy distribution of the intergalactic infrared radiation field as given by Malkan and Stecker. We then discuss the fact that new data on the high energy gamma-ray source Mrk 501 appear to show the amount of intergalactic absorption predicted. The implications of this new HEGRA data, should they be confirmed, are significant for the astrophysics of this source, implying that (1) there is no significant intrinsic absorption inside the source, and (2) the physics of the emission produces a power-law spectrum to energies above 20 TeV. As a further test for intergalactic absorption, we give a predicted spect...

  8. Research and development of a gamma-ray imaging spectrometer in the MeV range in Barcelona

    Science.gov (United States)

    Alvarez, José-Manuel; Galvez, José-Luis; Hernanz, Margarita; Isern, Jordi; Lozano, Manuel; Pellegrini, Giulio; Chmeissani, Mokhtar; Cabruja, Enric; Ullán, Miguel

    2010-07-01

    Gamma-ray astrophysics in the MeV energy range plays an important role for the understanding of cosmic explosions and acceleration mechanisms in a variety of galactic and extragalactic sources, e.g., Supernovae, Classical Novae, Supernova Remnants (SNRs), Gamma-Ray Bursts (GRBs), Pulsars, Active Galactic Nuclei (AGN). Through the development of focusing telescopes in the MeV energy range, it will be possible to reach unprecedented sensitivities, compared with those of the currently operating gamma ray telescopes. In order to achieve the needed performance, a detector with mm spatial resolution and very high peak efficiency is required. It will be also desirable that the detector could detect polarization of the source. Our research and development activities in Barcelona aim to study a gamma-ray imaging spectrometer in the MeV range suited for the focal plane of a gamma-ray telescope mission, based on CdTe pixel detectors arranged in multiple layers with increasing thicknesses, to enhance gamma-ray absorption in the Compton regime. We have developed an initial prototype based on several CdTe module detectors, with 11x11 pixels, a pixel pitch of 1mm and a thickness of 2mm. Each pixel is stud-bump bonded to a fanout board and routed to a readout ASIC to measure pixel position, pulse height and rise time information for each incident gamma-ray photon. We will report on the results of an optimization study based on simulations, to select the optimal thickness of each CdTe detector within the module to get the best energy resolution of the spectrometer.

  9. Lunar radiation environment: a study by using Kaguya gamma-ray spectrometer and Monte Carlo simulation

    Science.gov (United States)

    Kobayashi, Shingo; Hayatsu, Kanako; Uchihori, Yukio; Hareyama, Makoto; Hasebe, Nobuyuki; Fujibayashi, Yukari

    2012-07-01

    We have continued to improve the estimation of radiation dose on the Moon based on observation by remote sensing and calculation of the transportation of cosmic-ray particles in the lunar materials in order to provide basic data for a future manned lunar exploration. On the lunar surface, the dose of primary galactic cosmic rays (pGCR) is the most significant and the contributions of neutrons and gamma rays are relatively small and are approximately 10% and 1% of that of pGCR, respectively. However, these percentages are changed by use of thick shieldings and also geographical feature of the lunar surface, such as margin of a huge boulder, bottom of a pit, inside of a possible lava tube. In this case, the dose by pGCRs is moderated and the contributions of neutrons and gamma rays relatively increase. Here, we show the recent estimation of spatial variation of the lunar dose due to gamma ray and neutrons measured by Kaguya gamma-ray spectrometer. The energy spectrum of gamma rays from the lunar surface are precisely measured by a germanium (Ge) gamma-ray spectrometer onboard the Japanese lunar orbiter (Kaguya/SELENE). The flux of fast neutrons from the lunar surface was also measured by detecting the characteristic gamma rays due to the neutron inelastic reaction with the Ge of the spectrometer, that is 72Ge(n, n'g)72Ge. The estimation of radiation dose on the Moon based on Monte Carlo simulation will also be presented.

  10. Frequency spectrum analysis for spectrum stabilization in airborne gamma-ray spectrometer.

    Science.gov (United States)

    Zeng, Guoqiang; Tan, Chengjun; Ge, Liangquan; Zhang, Qingxian; Gu, Yi

    2014-02-01

    Abnormal multi-crystal spectral drifts often can be observed when power on the airborne gamma-ray spectrometer. Currently, these spectral drifts of each crystal are generally eliminated through manual adjustment, which is time-consuming and labor-ineffective. To realize this quick automatic spectrum stabilization of multi-crystal, a frequency spectrum analysis method for natural gamma-ray background spectrum is put forward in this paper to replace traditional spectrum stabilization method used characteristic peak. Based on the polynomial fitting of high harmonics in frequency spectrum and gamma-ray spectral drift, it calculates overall spectral drift of natural gamma-ray spectrum and adjusts the gain of spectrometer by this spectral drift value, thus completing quick spectrum stabilization in the power on stage of spectrometer. This method requires no manual intervention and can obtain the overall spectral drift value automatically under no time-domain pre-processing to the natural gamma-ray spectra. The spectral drift value calculated by this method has an absolute error less than five channels (1024 resolution) and a relative error smaller than 0.80%, which can satisfy the quick automatic spectrum stabilization requirement when power on the airborne gamma-ray spectrometer instead of manual operation.

  11. Definition of the radiation fields for the JET gamma-ray spectrometer diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Zoita, Vasile, E-mail: Vasile.Zoita@jet.efda.org [EFDA-JET CSU Culham, Culham Science Centre, Abingdon (United Kingdom); Association EURATOM-MEdC, National Institute for Laser, Plasma and Radiation Physics, Bucharest (Romania); Soare, Sorin [Association EURATOM-MEdC, National Institute for Cryogenics and Isotope Technologies, Rm. Valcea (Romania); Craciunescu, Teddy [Association EURATOM-MEdC, National Institute for Laser, Plasma and Radiation Physics, Bucharest (Romania); Curuia, Marian [Association EURATOM-MEdC, National Institute for Cryogenics and Isotope Technologies, Rm. Valcea (Romania); Kiptily, Vasily; Balshaw, Nick [Association EURATOM-CCFE, Culham Science Centre, Abingdon (United Kingdom); Blanchard, Patrick [EFDA-JET CSU Culham, Culham Science Centre, Abingdon (United Kingdom); Association EURATOM-CRPP-EPFL, Lausanne (Switzerland); Croft, David [Association EURATOM-CCFE, Culham Science Centre, Abingdon (United Kingdom); Murari, Andrea [EFDA-JET CSU Culham, Culham Science Centre, Abingdon (United Kingdom); Association EURATOM-ENEA, RFX, Padova (Italy); Syme, Brian [Association EURATOM-CCFE, Culham Science Centre, Abingdon (United Kingdom)

    2013-10-15

    The JET gamma-ray diagnostics system provides information on the behaviour of fast particles within the tokamak plasma. Information on the spatial distribution of the interacting fast particles is obtained from the gamma-ray cameras, while energy distribution information is provided by gamma-ray spectrometers. These techniques have been successfully applied so far in fast particle simulation experiments at JET. The extension of these diagnostics to high performance discharges with high neutron yields is not straightforward due to the background gamma-ray emission induced by neutrons. Two gamma-ray diagnostics upgrade projects at JET addressed this issue by developing neutron/gamma radiation filters (“neutron attenuators”) and collimators for a proper definition of the radiation (neutron and gamma) fields along the diagnostics line-of-sight. A pair of neutron/gamma collimators working in a tandem configuration have been designed and constructed for the JET quasi-tangential gamma-ray spectrometer. The tandem collimators were designed to provide shielding factors of about 5 × 10{sup 2} for 2.45 MeV neutrons and about 10{sup 3} for 9 MeV gamma-rays. The devices have been installed on the JET machine and the paper presents the first experimental results. A similar tandem collimator system was designed for deuterium-tritium experiments on JET. The results of neutron-photon transport calculations for 14.1 MeV neutrons are also presented.

  12. Design of a Multi-Channel Ultra-High Resolution Superconducting Gamma-Ray Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Friedrich, S; Terracol, S F; Miyazaki, T; Drury, O B; Ali, Z A; Cunningham, M F; Niedermayr, T R; Barbee Jr., T W; Batteux, J D; Labov, S E

    2004-11-29

    Superconducting Gamma-ray microcalorimeters operated at temperatures around {approx}0.1 K offer an order of magnitude improvement in energy resolution over conventional high-purity Germanium spectrometers. The calorimeters consist of a {approx}1 mm{sup 3} superconducting or insulating absorber and a sensitive thermistor, which are weakly coupled to a cold bath. Gamma-ray capture increases the absorber temperature in proportion to the Gamma-ray energy, this is measured by the thermistor, and both subsequently cool back down to the base temperature through the weak link. We are developing ultra-high-resolution Gamma-ray spectrometers based on Sn absorbers and superconducting Mo/Cu multilayer thermistors for nuclear non-proliferation applications. They have achieved an energy resolution between 60 and 90 eV for Gamma-rays up to 100 keV. We also build two-stage adiabatic demagnetization refrigerators for user-friendly detector operation at 0.1 K. We present recent results on the performance of single pixel Gamma-ray spectrometers, and discuss the design of a large detector array for increased sensitivity.

  13. Gamma ray spectrometer for future Mars mission: design concept and simulation study

    Science.gov (United States)

    Goyal, S. K.; Banerjee, D.; Vadawale, S.; Panda, Dipak K.; Patel, A. R.; Patinge, A.; Ladiya, T.; Sarbadhikari, A. B.

    2016-07-01

    One of the basic keys to understand the evolution and formation of any planet is the knowledge of the elemental composition of its surface. Gamma spectroscopy on Mars orbiter provides a unique opportunity to measure the elemental composition of its surface, with an atmosphere thin enough to allow detection of gamma rays produced from the near surface rock and soil materials. We are developing gamma ray spectrometer using High Purity Germanium (HPGe) detector for future Mars orbiter mission. The scientific objective of the instrument is to map the naturally occurring radioactive elements (Th, U, and K) and other major elements (Fe, Mg, Cl, Al, Si, S, Mg, Cl) over the entire Martian surface with a spatial resolution of better than 250 km. Gamma ray spectrometer will also have Anti - Coincidence Shield (ACS) detector for background subtraction from the surrounding material. This paper gives the details of the GEANT4 simulation, carried out to study the design requirements for a gamma ray spectrometer for a future Mars orbiter mission. This includes the selection of the size of HPGe detector, selection of the detector material and thickness for the ACS detector, and attenuation of gamma rays in the Martian atmosphere. Generation of gamma rays from the Martian surface due to Galactic Cosmic Rays (GCR) particles' interaction has also been simulated. Preliminary results from the standard off the shelf detector are also presented here.

  14. Gamma-ray absorption and the origin of the gamma-ray flare in Cygnus X-1

    CERN Document Server

    Romero, Gustavo E; Orellana, Mariana

    2010-01-01

    The high-mass microquasar Cygnus X-1, the best-established candidate for a stellar-mass black hole in the Galaxy, has been detected in a flaring state at very high energies (VHE), E > 200 GeV, by the Atmospheric Cherenkov Telescope MAGIC. The flare occurred at orbital phase 0.91, where phase 1 is the configuration with the black hole behind the companion high-mass star, when the absorption of gamma-ray photons by photon-photon annihilation with the stellar field is expected to be highest. We aim to set up a model for the high-energy emission and absorption in Cyg X-1 that can explain the nature of the observed gamma-ray flare. We study the gamma-ray opacity due to pair creation along the whole orbit, and for different locations of the emitter. Then we consider a possible mechanism for the production of the VHE emission. We present detailed calculations of the gamma-ray opacity and infer from these calculations the distance from the black hole where the emitting region was located. We suggest that the flare wa...

  15. Gamma ray absorption of cylindrical fissile material with dual shields

    Institute of Scientific and Technical Information of China (English)

    WU Chen-Yan; TIAN Dong-Feng; CHENG Yi-Ying; HUANG Yong-Yi; LU Fu-Quan; YANG Fu-Jia

    2005-01-01

    This work analyzed the gamma ray attenuation effect from the self-absorption and shield attenuation perspectively. An exact mathematical equation was given for the geometric factor of the cylindrical fissile material with dual shields. In addition, several approximation approaches suitable for real situation were discussed, especially in the radial and axial directions of the cylinders, since the G-factors have simple forms. Then the space distribution patterns of the G-factor were analyzed based on numerical result and effective ways to solve the geometric information of the cylindrical fissile material, the radii and the heights, were deduced. This method was checked and verified by numerical calculation. Because of the efficiency of the method, it is ideal for application in real situations, such as nuclear safeguards, which demands speed of detection and accuracy of geometric analysis.

  16. Measurement of natural radionuclides in phosphgypsum using an anti-cosmic gamma-ray spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Ferreux, Laurent [CEA, LIST, Laboratoire National Henri Becquerel, F-91191, Gif-sur-Yvette Cedex (France)], E-mail: laurent.ferreux@cea.fr; Moutard, Gerard; Branger, Thierry [CEA, LIST, Laboratoire National Henri Becquerel, F-91191, Gif-sur-Yvette Cedex (France)

    2009-05-15

    Gamma-ray spectrometry measurements have been carried out to determine the activity of natural radionuclides in a phosphogypsum sample included in a specific tight container. The gamma spectrometer includes an N-type coaxial high-purity germanium (HPGe) detector equipped with an anti-cosmic system. This measurement required the determination of linear attenuation coefficients of phosphogypsum to calculate self-absorption correction between efficiency calibration conditions and measurement ones. The results are given for the three natural chains and for {sup 40}K, in term of specific activity/g of dry material, ranging from a few Bq kg{sup -1} to a few hundreds Bq kg{sup -1}. The equilibrium within the different families and the {sup 235}U/{sup 238}U ratio are discussed.

  17. An in situ gamma ray spectrometer with CsI/p-i-n detector

    Science.gov (United States)

    Xu, Clarke X.; Williams, Ron R.

    1995-03-01

    The development of a portable gamma ray spectrometer based on a CsI(Tl) scintillator (1.8 cm×1.8 cm×4 cm) with integral p-i-n diode (1.8 cm×4 cm) is described. A single board computer containing the MC68HC11 microcontroller, a single-chip self-contained computer system, is used for system control. The total size of the instrument is only 12 in×7 in. including the spectrometer and power supply. The system provides a low cost, low power gamma ray spectrometer as compared to the more common PMT-based devices. Spectra can be collected in daily intervals for up to 1 week. Special software which monitors the proper working of the spectrometer insures long term stability. This spectrometer can be used for routine monitoring and detection of gamma ray emitting radio nuclides. Performance of the spectrometer as well as gamma ray spectra are presented. The qualitative and quantitative reliability have shown its potential as a stand alone field monitoring instrument due to its low power consumption and intelligence.

  18. A least squares procedure for calculating the calibration constants of a portable gamma-ray spectrometer.

    Science.gov (United States)

    Ribeiro, F B; Carlos, D U; Hiodo, F Y; Strobino, E F

    2005-01-01

    In this study, a least squares procedure for calculating the calibration constants of a portable gamma-ray spectrometer using the general inverse matrix method is presented. The procedure weights the model equations fitting to the calibration data, taking into account the variances in the counting rates and in the radioactive standard concentrations. The application of the described procedure is illustrated by calibrating twice the same gamma-ray spectrometer, with two independent data sets collected approximately 18 months apart in the same calibration facility.

  19. Investigation of pixellated HgI sub 2 gamma-ray spectrometers

    CERN Document Server

    He Zhong

    2002-01-01

    HgI sub 2 gamma-ray spectrometers having small pixel anodes and a thickness of 4-5 mm have been investigated. An energy resolution of 2.9% FWHM was obtained on a 4 mm thick detector using the three-dimensional position sensitive single polarity charge sensing technique. Typical phenomena observed on two detectors are reported and their characteristics are discussed. The results indicate that it is possible to construct efficient gamma-ray spectrometers using commercially available HgI sub 2 materials if the three-dimensional position sensitive single polarity charge sensing method is implemented.

  20. A method for determination mass absorption coefficient of gamma rays by Compton scattering.

    Science.gov (United States)

    El Abd, A

    2014-12-01

    A method was proposed for determination mass absorption coefficient of gamma rays for compounds, alloys and mixtures. It is based on simulating interaction processes of gamma rays with target elements having atomic numbers from Z=1 to Z=92 using the MCSHAPE software. Intensities of Compton scattered gamma rays at saturation thicknesses and at a scattering angle of 90° were calculated for incident gamma rays of different energies. The obtained results showed that the intensity of Compton scattered gamma rays at saturations and mass absorption coefficients can be described by mathematical formulas. These were used to determine mass absorption coefficients for compound, alloys and mixtures with the knowledge of their Compton scattered intensities. The method was tested by calculating mass absorption coefficients for some compounds, alloys and mixtures. There is a good agreement between obtained results and calculated ones using WinXom software. The advantages and limitations of the method were discussed.

  1. Direction-Sensitive Hand-Held Gamma-Ray Spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Mukhopadhyay, S.

    2012-10-04

    A novel, light-weight, hand-held gamma-ray detector with directional sensitivity is being designed. The detector uses a set of multiple rings around two cylindrical surfaces, which provides precise location of two interaction points on two concentric cylindrical planes, wherefrom the source location can be traced back by back projection and/or Compton imaging technique. The detectors are 2.0 × 2.0 mm europium-doped strontium iodide (SrI2:Eu2+) crystals, whose light output has been measured to exceed 120,000 photons/MeV, making it one of the brightest scintillators in existence. The crystal’s energy resolution, less than 3% at 662 keV, is also excellent, and the response is highly linear over a wide range of gamma-ray energies. The emission of SrI2:Eu2+ is well matched to both photo-multiplier tubes and blue-enhanced silicon photodiodes. The solid-state photomultipliers used in this design (each 2.0 × 2.0 mm) are arrays of active pixel sensors (avalanche photodiodes driven beyond their breakdown voltage in reverse bias); each pixel acts as a binary photon detector, and their summed output is an analog representation of the total photon energy, while the individual pixel accurately defines the point of interaction. A simple back-projection algorithm involving cone-surface mapping is being modeled. The back projection for an event cone is a conical surface defining the possible location of the source. The cone axis is the straight line passing through the first and second interaction points.

  2. CdZnTe gamma ray spectrometer for orbital planetary missions

    Energy Technology Data Exchange (ETDEWEB)

    Feldman, W. C. (William C.); Storms, S. A. (Steven A.); Fuller, K. R. (Kenneth R.); Moss, C. E. (Calvin E.); Browne, M. C. (Michael C.); Lawrence, David J. (David Jeffery),; Ianakiev, K. D.; Prettyman, T. H. (Thomas H.)

    2001-01-01

    Knowledge of surface elemental composition is needed to understand the formation and evolution of planetary bodies. Gamma rays and neutrons produced by the interaction of galactic cosmic rays with surface materials can be detected from orbit and analyzed to determine composition. Using gamma ray spectroscopy, major rock forming elements such as Fe, Ti, Al, Si, Mg, and Ca can be detected. The accuracy of elemental abundance is limited by the resolution of the spectrometer. For space missions, scintillators such as BGO and NaI(Tl) have been used for gamma ray spectroscopy. New planetary science missions are being planned to explore Mars, Mercury, the asteroid belt, and the outer planets. Significant improvements in the pulse height resolution relative to scintillation detectors can be made using CdZnTe, a new room temperature detector technology. For an orbiting instrument, a CdZnTe detector at least 16 cm{sup 3} in size is needed. A 4 x 4 array of 1-cm{sup 3} coplanar grid detectors can be manufactured that meets requirements for resolution and counting efficiency. The array will shielded from gamma rays produced in the spacecraft by a BGO detector. By improving pulse height resolution by a factor of three at low energy, the CdZnTe detector will be able to make accurate measurements of elements that are currently difficult to measure using scintillation technology. The BGO shield will provide adequate suppression of gamma rays originating in the spacecraft, enabling the gamma ray spectrometer to be mounted on the deck of a spacecraft. To test this concept, we are constructing a flight qualified, prototype CdZnTe detector array. The prototype consists of a 2 x 2 array of coplanar grid detectors. We will present the results of mechanical and electronic testing and radiation damage tests, and the performance of the array for gamma ray spectroscopy.

  3. SWEPP gamma-ray spectrometer system software user`s guide

    Energy Technology Data Exchange (ETDEWEB)

    Femec, D.A.

    1994-08-01

    The SWEPP Gamma-Ray Spectrometer (SGRS) System has been developed by the Radiation Measurement and Development Unit of the Idaho National Engineering Laboratory to assist in the characterization of the radiological contents of contact-handled waste containers at the Stored Waste Examination Pilot Plant (SWEPP). In addition to determining the concentrations of gamma-ray-emitting radionuclides, the software also calculates attenuation-corrected isotopic mass ratios of specific interest, and provides controls for SGRS hardware as required. This document serves as a user`s guide for the data acquisition and analysis software associated with the SGRS system.

  4. Instrumental and atmospheric background lines observed by the SMM gamma-ray spectrometer

    Science.gov (United States)

    Share, G. H.; Kinzer, R. L.; Strickman, M. S.; Letaw, J. R.; Chupp, E. L.

    1989-01-01

    Preliminary identifications of instrumental and atmospheric background lines detected by the gamma-ray spectrometer on NASA's Solar Maximum Mission satellite (SMM) are presented. The long-term and stable operation of this experiment has provided data of high quality for use in this analysis. Methods are described for identifying radioactive isotopes which use their different decay times. Temporal evolution of the features are revealed by spectral comparisons, subtractions, and fits. An understanding of these temporal variations has enabled the data to be used for detecting celestial gamma-ray sources.

  5. A carborne gamma-ray spectrometer system for natural radioactivity mapping and environmental monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Grasty, R.L.; Cox, J.R. [Exploranium Ltd., Mississauga, Ontario (Canada)

    1997-12-31

    This paper summarizes the experience gained in the use of a carborne gamma-ray spectrometer system for mapping both natural and man-made radiation. Particular emphasis is placed on the calibration of the system for converting the gamma-ray measurements to ground concentrations of potassium, uranium and thorium and the activity of {sup 137}Cs. During the Finnish Emergency Response Exercise (Resume95), the carborne system was shown to be effective in mapping both natural and man-made radiation from {sup 137}Cs fallout and in locating radioactive sources. The application of the carborne system for mineral exploration is also demonstrated. (au). 10 refs.

  6. Fine analysis of the calibration curve for a HPGe spectrometer in gamma ray energy measurement

    CERN Document Server

    Liu Yhi Gang; Wei Long; Chang Tian Ba

    1999-01-01

    A computational method is suggested to analyze gamma ray peak position data of a series of closely shifted spectra of sup 1 sup 9 sup 2 Ir measured by a HPGe spectrometer and an iteration program, Recovery-98 has been designed to find the fine curve of the spectrometer nonlinearity for energy calibration. The program is applied to check a previous experiment (measuring the gamma energies of sup 8 sup 5 Sr, etc.), and the revised result has been reported. (author)

  7. Time series data correction for the Chang'E-1 gamma-ray spectrometer

    Institute of Scientific and Technical Information of China (English)

    Li-Yan Zhang; Yong-Liao Zou; Jian-Zhong Liu; Jian-Jun Liu; Ji Shen; Ling-Li Mu; Xin Ren; Wei-Bin Wen; Chun-Lai Li

    2011-01-01

    The main goal of the gamma-ray spectrometer (GRS) onboard Chang'E-l (CE-1) is to acquire global maps of elemental abundances and their distributions on the moon, since such maps will significantly improve our understanding of lunar formation and evolution. To derive the elemental maps and enable research on lunar formation and evolution, raw data that are received directly from the spacecraft must be converted into time series corrected gamma-ray spectra. The data correction procedures for the CE-1 GRS time series data are thoroughly described. The processing procedures to create the time series gamma-ray spectra described here include channel processing, optimal data selection, energy calibration, gain correction, dead time correction, geometric correction, orbit altitude normalization, eliminating unusable data and galactic cosmic ray correction. Finally, descriptions are also given on data measurement uncertainties, which will help the interested scientists to understand and estimate various uncertainties associated with the above data processing.

  8. Resonance capture gamma-ray spectrometry at Lead Slowing-down Neutron Spectrometer

    CERN Document Server

    Pourimani, R; Popov, Y P; Przytula, M; Wojtkiewicz, R

    2002-01-01

    A new method of measurement of the gamma-ray spectra from resonance neutron capture that can be realized at Lead Slowing-down Neutron Spectrometers was proposed and tested experimentally. The specific feature of the method is the shielding of germanium detector by a 'thick' investigated sample that absorbs intensive neutron flux with energies corresponding to sample resonances. In these energy regions the detector response on neutron irradiation is considerably reduced while the sample gamma-ray spectra are greatly strengthened. The detector response gamma-ray spectra are presented and analysed, and the spectra from neutron capture in tantalum resonances at energies 4.28 and 10.36 eV are shown. The obtained results demonstrate the usefulness of the proposed method. Five new excited levels in germanium isotopes are proposed.

  9. Iron Abundances on the Moon as Seen by the Lunar Prospector Gamma-Ray Spectrometer

    Science.gov (United States)

    Lawrence, D. J.; Feldman, W. C.; Barraclough, B. L.; Elphic, R. C.; Maurice, S.; Binder, A. B.; Lucey, P. G.

    1999-01-01

    Measurements of global-Fe abundances on the Moon are important because Fe is a key element that is used in models of lunar formation and evolution. Previous measurements of lunar Fe abundances have been made by the Apollo Gamma-Ray (AGR) experiment and Clementine spectral reflectance (CSR) experiment. The AGR experiment made direct elemental measurements for about 20% of the Moon. However, these measurements had large uncertainties due mostly to low statistics and an absence of thermal neutron data (see below). The CSR-derived Fe data has much better coverage (100% coverage equatorward of +/-70 deg. latitude) and spatial resolution (about 100-m surface resolution vs. about 150-km surface resolution for the AGR data), but there have been questions regarding the accuracy of these data far from the Apollo landing sites. Here we present preliminary estimates of the relative Fe abundances using the Lunar Prospector (LP) gamma-ray spectrometer (GRS). While these data are important and useful by themselves, the ultimate goal of this study is to combine the LP Fe data with the CSR data to obtain a better calibrated and more accurate picture of the Fe abundances on the Moon. To derive Fe abundances, we are using two gamma ray lines near 7.6 MeV. These gamma-rays are produced by thermal neutron capture. Here, Fe nuclei absorb thermal neutrons, become energetically excited, and then de-excite with the production of gamma-rays. Because this process depends upon thermal neutrons, the measured flux of 7.6 MeV gamma-rays is proportional not only to the Fe abundances, but also to the thermal neutron number density. Here, we use measurements from the LP neutron spectrometer (NS) to correct for this thermal neutron effect. As seen elsewhere, this correction is quite large as the thermal neutron count rate varies over the Moon by a factor of 3. Many considerations need to be taken into account to make sure an appropriate correction is applied. These include (1) converting the

  10. Research on CdZnTe and Other Novel Room Temperature Gamma Ray Spectrometer Materials

    Energy Technology Data Exchange (ETDEWEB)

    Arnold Burger; Michael gGoza; Yunlong Cui; Utpal N. Roy; M. Guo

    2007-05-05

    Room temperature gamma-ray spectrometers are being developed for a number of years for national security applications where high sensitivity, low operating power and compactness are indispensable. The technology has matured now to the point where large volume (several cubic centimeters) and high energy resolution (approximately 1% at 660 eV) of gamma photons, are becoming available for their incorporation into portable systems for remote sensing of signatures from nuclear materials.

  11. Defining the IBL and Gamma-Ray Absorption

    Science.gov (United States)

    Stecker, Floyd

    2012-01-01

    We calculate the intensity and photon spectrum of the intergalactic background light (IBL) as a function of redshift using an approach based on observational data obtained in many different wavelength bands from local to deep galaxy surveys. Our empirically based approach allows us, for the first time, to obtain a completely model independent determination of the IBL and to quantify its uncertainties. Using our results on the IBL, we then place 68% confidence upper and lower limits on the opacity of the universe to gamma-rays, independent of previous constraints that were obtained by making theoretical assumptions. We then compare our results with measurements of the extragalactic background light and upper limits obtained from observations made by the Fermi Gamma-ray Space Telescope.

  12. Development of a Gamma-Ray Spectrometer for Korean Pathfinder Lunar Orbiter

    Science.gov (United States)

    Kim, Kyeong Ja; Park, Junghun; Choi, Yire; Lee, Sungsoon; Yeon, Youngkwang; Yi, Eung Seok; Jeong, Meeyoung; Sun, Changwan; van Gasselt, Stephan; Lee, K. B.; Kim, Yongkwon; Min, Kyungwook; Kang, Kyungin; Cho, Jinyeon; Park, Kookjin; Hasebe, Nobuyuki; Elphic, Richard; Englert, Peter; Gasnault, Olivier; Lim, Lucy; Shibamura, Eido; GRS Team

    2016-10-01

    Korea is preparing for a lunar orbiter mission (KPLO) to be developed in no later than 2018. Onboard the spacecraft is a gamma ray spectrometer (KLGRS) allowing to collect low energy gamma-ray signals in order to detect elements by either X-ray fluorescence or by natural radioactive decay in the low as well as higher energy regions of up to 10 MeV. Scientific objectives include lunar resources (water and volatile measurements, rare earth elements and precious metals, energy resources, major elemental distributions for prospective in-situ utilizations), investigation of the lunar geology and studies of the lunar environment (mapping of the global radiation environment from keV to 10 MeV, high energy cosmic ray flux using the plastic scintillator).The Gamma-Ray Spectrometer (GRS) system is a compact low-weight instrument for the chemical analysis of lunar surface materials within a gamma-ray energy range from 10s keV to 10 MeV. The main LaBr3 detector is surrounded by an anti-coincidence counting module of BGO/PS scintillators to reduce both low gamma-ray background from the spacecraft and housing materials and high energy gamma-ray background from cosmic rays. The GRS system will determine the elemental compositions of the near surface of the Moon.The GRS system is a recently developed gamma-ray scintillation based detector which can be used as a replacement for the HPGe GRS sensor with the advantage of being able to operate at a wide range of temperatures with remarkable energy resolution. LaBr3 also has a high photoelectron yield, fast scintillation response, good linearity and thermal stability. With these major advantages, the LaBr3 GRS system will allow us to investigate scientific objectives and assess important research questions on lunar geology and resource exploration.The GRS investigation will help to assess open questions related to the spatial distribution and origin of the elements on the lunar surface and will contribute to unravel geological surface

  13. CdWO sub 4 scintillator as a compact gamma ray spectrometer for planetary lander missions

    CERN Document Server

    Eisen, Y; Starr, R; Trombka, J I

    2002-01-01

    The objective of this work is to develop a gamma ray spectrometer (GRS) suitable for use on planetary rover missions. The main characteristics of this detector are low weight, small volume low power and resistance to cosmic ray radiation over a long period of time. We describe a 3 cm diameter by 3 cm thick CdWO sub 4 cylindrical scintillator coupled to a PMT as a GRS for the energy region 0.662-7.64 MeV. Its spectral performance and efficiency are compared to that of a CsI(Tl) scintillator 2.5 cm diameter by 6 cm thick coupled to a 28 mmx28 mm PIN photodiode. The comparison is made experimentally using sup 1 sup 3 sup 7 Cs, sup 6 sup 0 Co, 6.13 MeV gamma rays from a sup 1 sup 3 C(alpha,gamma n)O sup 1 sup 6 * source, 7.64 MeV thermal neutron capture gamma rays emitted from iron bars using a sup 2 sup 5 sup 2 Cf neutron source, and natural radioactivity 1.46 MeV sup 4 sup 0 K and 2.61 MeV sup 2 sup 3 sup 2 Th gamma rays. We use a Monte Carlo method to calculate the total peak efficiency of these detectors and ...

  14. Enhanced Analysis Techniques for an Imaging Neutron and Gamma Ray Spectrometer

    Science.gov (United States)

    Madden, Amanda C.

    The presence of gamma rays and neutrons is a strong indicator of the presence of Special Nuclear Material (SNM). The imaging Neutron and gamma ray SPECTrometer (NSPECT) developed by the University of New Hampshire and Michigan Aerospace corporation detects the fast neutrons and prompt gamma rays from fissile material, and the gamma rays from radioactive material. The instrument operates as a double scatter device, requiring a neutron or a gamma ray to interact twice in the instrument. While this detection requirement decreases the efficiency of the instrument, it offers superior background rejection and the ability to measure the energy and momentum of the incident particle. These measurements create energy spectra and images of the emitting source for source identification and localization. The dual species instrument provides superior detection than a single species alone. In realistic detection scenarios, few particles are detected from a potential threat due to source shielding, detection at a distance, high background, and weak sources. This contributes to a small signal to noise ratio, and threat detection becomes difficult. To address these difficulties, several enhanced data analysis tools were developed. A Receiver Operating Characteristic Curve (ROC) helps set instrumental alarm thresholds as well as to identify the presence of a source. Analysis of a dual-species ROC curve provides superior detection capabilities. Bayesian analysis helps to detect and identify the presence of a source through model comparisons, and helps create a background corrected count spectra for enhanced spectroscopy. Development of an instrument response using simulations and numerical analyses will help perform spectra and image deconvolution. This thesis will outline the principles of operation of the NSPECT instrument using the double scatter technology, traditional analysis techniques, and enhanced analysis techniques as applied to data from the NSPECT instrument, and an

  15. Characteristics of bursts observed by the SMM Gamma-Ray Spectrometer

    Science.gov (United States)

    Share, G. H.; Messina, D. C.; Iadicicco, A.; Matz, S. M.; Rieger, E.; Forrest, D. J.

    1992-01-01

    The Gamma Ray Spectrometer (GRS) on the SMM completed close to 10 years of highly successful operation when the spacecraft reentered the atmosphere on December 2, 1989. During this period the GRS detected 177 events above 300 keV which have been classified as cosmic gamma-ray bursts. A catalog of these events is in preparation which will include time profiles and spectra for all events. Visual inspection of the spectra indicates that emission typically extends into the MeV range, without any evidence for a high-energy cutoff; 17 of these events are also observed above 10 MeV. We find no convincing evidence for line-like emission features in any of the time-integrated spectra.

  16. The worldwide NORM production and a fully automated gamma-ray spectrometer for their characterization

    CERN Document Server

    Xhixha, G; Broggini, C; Buso, GP; Caciolli, A; Callegari, I; De Bianchi, S; Fiorentini, G; Guastaldi, E; Xhixha, M Kaçeli; Mantovani, F; Massa, G; Menegazzo, R; Mou, L; Pasquini, A; Alvarez, C Rossi; Shyti, M

    2012-01-01

    Materials containing radionuclides of natural origin, which is modified by human made processes and being subject to regulation because of their radioactivity are known as NORM. We present a brief review of the main categories of non-nuclear industries together with the levels of activity concentration in feed raw materials, products and waste, including mechanisms of radioisotope enrichments. The global management of NORM shows a high level of complexity, mainly due to different degrees of radioactivity enhancement and the huge amount of worldwide waste production. The future tendency of guidelines concerning environmental protection will require both a systematic monitoring based on the ever-increasing sampling and high performance of gamma ray spectroscopy. On the ground of these requirements a new low background fully automated high-resolution gamma-ray spectrometer MCA_Rad has been developed. The design of Pb and Cu shielding allowed to reach a background reduction of two order of magnitude with respect ...

  17. The Extragalactic Background Light and Absorption in Gamma Ray Spectra

    Science.gov (United States)

    Gilmore, Rudy C.

    2008-03-01

    Recent state-of-the-art semi-analytic models (SAMs) can now accurately model the history of galaxy formation and evolution. These SAMs utilize a 'forward evolution' approach and include all of the important processes for determining photon emission from galaxies, such as cooling and shock heating of gas, galaxy mergers, star formation and aging, supernova and AGN feedback, and the reprocessing of light by dust. I will be presenting our group's latest prediction of the extra-galactic background light based on this work and will discuss the implications for the attenuation of VHE gamma rays from distant sources due to pair-production. These results will be compared to recent limits placed on the EBL by observations of GeV and TeV blazar spectra by experiments such as H.E.S.S., MAGIC and VERITAS. The implications for reconstructing the intrinsic spectra of distant blazars will be addressed.

  18. Radioactivity observed in the sodium iodide gamma-ray spectrometer returned on the Apollo 17 mission

    Science.gov (United States)

    Dyer, C. S.; Trombka, J. I.; Schmadebeck, R. L.; Eller, E.; Bielefeld, M. J.; Okelley, G. D.; Eldridge, J. S.; Northcutt, K. J.; Metzger, A. E.; Reedy, R. C.

    1975-01-01

    In order to obtain information on radioactive background induced in the Apollo 15 and 16 gamma-ray spectrometers (7 cm x 7 cm NaI) by particle irradiation during spaceflight, and identical detector was flown and returned to earth on the Apollo 17 mission. The induced radioactivity was monitored both internally and externally from one and a half hours after splashdown. When used in conjunction with a computation scheme for estimating induced activation from calculated trapped proton and cosmic-ray fluences, these results show an important contribution resulting from both thermal and energetic neutrons produced in the heavy spacecraft by cosmic-ray interactions.

  19. High performance gamma-ray spectrometer for runaway electron studies on the FT-2 tokamak

    Science.gov (United States)

    Shevelev, A. E.; Khilkevitch, E. M.; Lashkul, S. I.; Rozhdestvensky, V. V.; Altukhov, A. B.; Chugunov, I. N.; Doinikov, D. N.; Esipov, L. A.; Gin, D. B.; Iliasova, M. V.; Naidenov, V. O.; Nersesyan, N. S.; Polunovsky, I. A.; Sidorov, A. V.; Kiptily, V. G.

    2016-09-01

    A gamma-ray spectrometer based on LaBr3(Ce) scintillator has been used for measurements of hard X-ray emission generated by runaway electrons in the FT-2 tokamak plasmas. Using of the fast LaBr3(Ce) has allowed extending count rate range of the spectrometer by a factor of 10. A developed digital processing algorithm of the detector signal recorded with a digitizer sampling rate of 250 MHz has provided a pulse height analysis at count rates up to 107 s-1. A spectrum deconvolution code DeGaSum has been applied for inferring the energy distribution of runaway electrons escaping from the plasma and interacting with materials of the FT-2 limiter in the vacuum chamber. The developed digital signal processing technique for LaBr3(Ce) spectrometer has allowed studying the evolution of runaways energy distribution in the FT-2 plasma discharges with time resolution of 1-5 ms.

  20. Venus Measurements by the MESSENGER Gamma-Ray and X-Ray Spectrometers

    Science.gov (United States)

    Rhodes, E. A.; Starr, R. D.; Goldsten, J. O.; Schlemm, C. E.; Boynton, W. V.

    2007-12-01

    The Gamma-Ray Spectrometer (GRS), which is a part of the Gamma-Ray and Neutron Spectrometer Instrument, and the X-Ray Spectrometer (XRS) on the MESSENGER spacecraft made calibration measurements during the Venus flyby on June 5, 2007. The purpose of these instruments is to determine elemental abundances on the surface of Mercury. The GRS measures gamma-rays emitted from element interactions with cosmic rays impinging on the surface, while the XRS measures X-ray emissions induced on the surface by the incident solar flux. The GRS sensor is a high-resolution high-purity Ge detector cooled by a Stirling cryocooler, surrounded by a borated-plastic anticoincidence shield. The GRS is sensitive to gamma-rays up to ~10 MeV and can identify most major elements, sampling down to depths of about ten centimeters. Only the shield was powered on for this flyby in order to conserve cooler lifetime. Gamma-rays were observed coming from Venus as well as from the spacecraft. Although the Venus gamma-rays originate from its thick atmosphere rather than its surface, the GRS data from this encounter will provide useful calibration data from a source of known composition. In particular, the data will be useful for determining GRS sensitivity and pointing options for the Mercury flybys, the first of which will be in January 2008. The X-ray spectrum of a planetary surface is dominated by a combination of the fluorescence and scattered solar X-rays. The most prominent fluorescent lines are the Kα lines from the major elements Mg, Al, Si, S, Ca, Ti, and Fe (1-10 keV). The sampling depth is less than 100 u m. The XRS is similar in design to experiments flown on Apollo 15 and 16 and the NEAR-Shoemaker mission. Three large-area gas-proportional counters view the planet, and a small Si-PIN detector mounted on the spacecraft sunshade monitors the Sun. The energy resolution of the gas proportional counters (~850 eV at 5.9 keV) is sufficient to resolve the X-ray lines above 2 keV, but Al and Mg

  1. The gamma-ray spectrometer HORUS and its applications for nuclear astrophysics

    CERN Document Server

    Netterdon, L; Endres, J; Fransen, C; Hennig, A; Mayer, J; Müller-Gatermann, C; Sauerwein, A; Scholz, P; Spieker, M; Zilges, A

    2014-01-01

    A dedicated setup for the in-beam measurement of absolute cross sections of astrophysically relevant charged-particle induced reactions is presented. These, usually very low, cross sections at energies of astrophysical interest are important to improve the modeling of the nucleosynthesis processes of heavy nuclei. Particular emphasis is put on the production of the $p$ nuclei during the astrophysical $\\gamma$ process. The recently developed setup utilizes the high-efficiency $\\gamma$-ray spectrometer HORUS, which is located at the 10 MV FN tandem ion accelerator of the Institute for Nuclear Physics in Cologne. The design of this setup will be presented and results of the recently measured $^{89}$Y(p,$\\gamma$)$^{90}$Zr reaction will be discussed. The excellent agreement with existing data shows, that the HORUS spectrometer is a powerful tool to determine total and partial cross sections using the in-beam method with high-purity germanium detectors.

  2. Development of a low-level background gamma-ray spectrometer by KRISS.

    Science.gov (United States)

    Lee, K B; Park, Tae Soon; Lee, Jong Man; Oh, Phil-Je; Lee, Sang-Han

    2008-01-01

    A new low-level background and high-efficiency gamma-ray spectrometric system, to be used mainly for the activity certification of natural-matrix certified reference materials (CRMs) and environmental reference materials (RMs) that has been developed on the grounds of the Korea Research Institute of Standards and Science (KRISS). The spectrometer consists of a low-background high-purity germanium detector with a relative efficiency of 120% and various shielding devices to reduce radiation background. The cabinet-shaped device made of 10ton of shielding materials encloses the germanium detector for protection against background from natural radioactivity and neutrons. Three plates of 50-mm-thick plastic scintillation detectors on top of the passive shielding cabinet suppress cosmogenic background by detecting high-energetic cosmic muons bombarding the germanium detector. The measured background rate of the spectrometer for the energy range 50-3000keV was 1.72s(-1).

  3. HAND-HELD GAMMA-RAY SPECTROMETER BASED ON HIGH-EFFICIENCY FRISCH-RING CdZnTe DETECTORS.

    Energy Technology Data Exchange (ETDEWEB)

    CUI,Y.

    2007-05-01

    Frisch-ring CdZnTe detectors have demonstrated good energy resolution, el% FWHM at 662 keV, and good efficiency for detecting gamma rays. This technique facilitates the application of CdZnTe materials for high efficiency gamma-ray detection. A hand-held gamma-ray spectrometer based on Frisch-ring detectors is being designed at Brookhaven National Laboratory. It employs an 8x8 CdZnTe detector array to achieve a high volume of 19.2 cm3, so that detection efficiency is significantly improved. By using the front-end ASICs developed at BNL, this spectrometer has a small profile and high energy resolution. The spectrometer includes signal processing circuit, digitization and storage circuit, high-voltage module, and USB interface. In this paper, we introduce the details of the system structure and report our test results with it.

  4. ACCURACY OF MEASUREMENT OF NATURAL GAMMA RAY SPECTRA BY HD—8004 NaI(T1) GAMMA SPECTROMETER

    Institute of Scientific and Technical Information of China (English)

    朱国钦; 郑仁淑

    1995-01-01

    The measurement principle and analysis method of natural gammaray spectra using NaI(T1) scintillation spectrometer are briefly described first,then block diagrams of the HD-8004 NaI(T1) gamma-ray spectrometer,Finally,sample measurements are listed and discussed.The results are quite promising.Based on the analysis of these measurements,measures to improve the accuracy of spectrum measurement are proposed.It is well hoped that these measures can contribute to the development and application of gamma-ray spectrum measurement.

  5. Thermal Design and Performance of the Gamma-Ray Spectrometer for the MESSENGER Spacecraft

    Energy Technology Data Exchange (ETDEWEB)

    Burks, M; Cork, C P; Eckels, D; Hull, E; Madden, N W; Miller, W; Goldsten, J; Rhodes, E; Williams, B

    2004-10-13

    A gamma-ray spectrometer (GRS) has been built and delivered to the Mercury MESSENGER spacecraft which launched on August 3, 2004, from Cape Canaveral, Florida. The GRS, a part of seven scientific instruments on board MESSENGER, is based on a coaxial high-purity germanium detector. Gamma-ray detectors based on germanium have the advantage of providing excellent energy resolution, which is critical to achieving the science goals of the mission. However, germanium has the disadvantage that it must operate at cryogenic temperatures (typically {approx}80 K). This requirement is easy to satisfy in the laboratory but difficult near Mercury, which has an extremely hot thermal radiation environment. To cool the detector, a Stirling cycle mechanical cooler is employed. In addition, radiation and conduction techniques a are used to reduce the GRS heat load. Before delivering the flight sensor, a complete thermal prototype was built and tested. The results of these test, including thermal design, radiative and conductive heat loads, and cooler performance are described.

  6. A Liquid-Cryogen-Free Cryostat for Ultrahigh Resolution Gamma-Ray Spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Dreyer, J G; Hertrich, T; Drury, O B; Hohne, J; Friedrich, S

    2008-06-30

    We are developing ultra-high energy resolution gamma-ray detectors based on superconducting transition edge sensors (TESs) for nuclear non-proliferation and fundamental science applications. They use bulk tin absorbers attached to molybdenum-copper multilayer TESs, and have achieved an energy resolution between 50 and 90 eV FWHM for gamma-ray energies below 122 keV. For increased user-friendliness, we have built a cryostat that attains the required detector operating temperature of 0.1 K at the push of a button without the use of cryogenic liquids. It uses a two-stage mechanical pulse tube refrigerator for precooling to {approx}3 K, and a two-stage adiabatic demagnetization refrigerator for cooling to the base temperature. The cryostat is fully automated, attains a base temperature below 30 mK without the use of cryogenic liquids, and has a hold time of {approx}2 days at 0.1 K between 1-hour demagnetization cycles. Here we discuss the performance of the cryostat for operation in a Gamma-spectrometer with 112-pixel arrays of superconducting TES detectors.

  7. A study of radioactive elements of various rocks in Pattani Province with gamma ray spectrometer

    Directory of Open Access Journals (Sweden)

    Kaewtubtim, P.

    2002-01-01

    Full Text Available The radioactivity of the three elements, potassium, uranium and thorium, in rocks of various types in Pattani Province was investigated by using a gamma ray spectrometer. It was found that potassium contents in igneous rocks, sedimentary rocks and metamorphic rocks were 6.29 %, 2.21% and 1.54 % respectively. Uranium equivalent contents in igneous rock, sedimentary rocks and metamorphic rocks were found to be 22.51 ppm, 11.25 ppm and 14.13 ppm, while thorium contents in these rocks were 21.78 ppm, 18.88 ppm and 18.15 ppm respectively. The results obtained were similar to those reported by Pungtip Ranglek (1995 for igneous rock at Liwong Pluton site in Thepha, Na Thawi, Chana and Saba Yoi Districts, Songkhla Province, and were about six times higher than those reported by Kittichai Wattananikorn (1994 for igneous rock in the northern part of Thailand.

  8. Wireless, low-cost, FPGA-based miniature gamma ray spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Becker, E.M., E-mail: beckere@engr.orst.edu; Farsoni, A.T.

    2014-10-11

    A compact, low-cost, wireless gamma-ray spectrometer is a tool sought by a number of different organizations in the field of radiation detection. Such a device has applications in emergency response, battlefield assessment, and personal dosimetry. A prototype device fitting this description has been constructed in the Advanced Radiation Instrumentation Laboratory at Oregon State University. The prototype uses a CsI(Tl) scintillator coupled to a solid-state photomultiplier and a 40 MHz, 12-bit, FPGA-based digital pulse processor to measure gamma radiation, and is able to be accessed wirelessly by mobile phone. The prototype device consumes roughly 420 mW, weighs about 28 g (not including battery), and measures 2.54×3.81 cm{sup 2}. The prototype device is able to achieve 5.9% FWHM energy resolution at 662 keV.

  9. Innovative Gamma Ray Spectrometer Detection Systems for Conducting Scanning Surveys on Challenging Terrain - 13583

    Energy Technology Data Exchange (ETDEWEB)

    Palladino, Carl; Mason, Bryan; Engle, Matt; LeVangie, James [The Palladino Company, Inc., 720 Fillmore St., San Francisco, CA 94117 (United States); Dempsey, Gregg [United States Environmental Protection Agency, P.O. Box 98517, Las Vegas, NV 89193-8517 (United States); Klemovich, Ron [HydroGeoLogic, Inc., 6340 Glenwood, Suite 200, Building No. 7, Overland Park, KS 66202 (United States)

    2013-07-01

    The Santa Susana Field Laboratory located near Simi Valley, California was investigated to determine the nature and extent of gamma radiation anomalies. The primary objective was to conduct gamma scanning surveys over 100 percent of the approximately 1,906,000 square meters (471 acre) project site with the most sensitive detection system possible. The site had challenging topography that was not conducive to traditional gamma scanning detection systems. Terrain slope varied from horizontal to 48 degrees and the ground surface ranged from flat, grassy meadows to steep, rocky hillsides. In addition, the site was home to many protected endangered plant and animal species, and archaeologically significant sites that required minimal to no disturbance of the ground surface. Therefore, four innovative and unique gamma ray spectrometer detection systems were designed and constructed to successfully conduct gamma scanning surveys of approximately 1,076,000 square meters (266 acres) of the site. (authors)

  10. Wireless, low-cost, FPGA-based miniature gamma ray spectrometer

    Science.gov (United States)

    Becker, E. M.; Farsoni, A. T.

    2014-10-01

    A compact, low-cost, wireless gamma-ray spectrometer is a tool sought by a number of different organizations in the field of radiation detection. Such a device has applications in emergency response, battlefield assessment, and personal dosimetry. A prototype device fitting this description has been constructed in the Advanced Radiation Instrumentation Laboratory at Oregon State University. The prototype uses a CsI(Tl) scintillator coupled to a solid-state photomultiplier and a 40 MHz, 12-bit, FPGA-based digital pulse processor to measure gamma radiation, and is able to be accessed wirelessly by mobile phone. The prototype device consumes roughly 420 mW, weighs about 28 g (not including battery), and measures 2.54×3.81 cm2. The prototype device is able to achieve 5.9% FWHM energy resolution at 662 keV.

  11. Absorption of High Energy $\\gamma$ Rays by Interactions With Starlight Photons in Extragalactic Space at High Redshifts and the High Energy $\\gamma$-Ray Background

    CERN Document Server

    Salamon, M H

    1998-01-01

    We calculate the absorption of 10-500 GeV gamma-rays at high redshifts. This calculation requires the determination of the high-redshift evolution of the intergalactic starlight photon field, including its IR-UV spectral energy distribution. To estimate this evolution, we have followed a recent analysis of Fall, Charlot and Pei which gives results consistent with recent data. We give our results for the gamma-ray opacity as a function of redshift out to a redshift of 3. We also give predicted gamma-ray spectra for selected blazars and give an extragalactic unresolved blazar background spectrum up to 500 GeV. Our results indicate that this background should steepen significantly above 20 GeV owing to intergalactic absorption. Future observations of this steepening would provide a test for the blazar background origin hypothesis. We have used our results to discuss upper limits on the redshifts of gamma-ray bursts. We note that the 17 Feb. 1994 burst observed by EGRET must have originated at a redshift less tha...

  12. Calibration of Ge gamma-ray spectrometers for complex sample geometries and matrices

    Energy Technology Data Exchange (ETDEWEB)

    Semkow, T.M., E-mail: thomas.semkow@health.ny.gov [Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12201 (United States); Department of Environmental Health Sciences, School of Public Health, University at Albany, State University of New York, Rensselaer, NY 12144 (United States); Bradt, C.J.; Beach, S.E.; Haines, D.K.; Khan, A.J.; Bari, A.; Torres, M.A.; Marrantino, J.C.; Syed, U.-F. [Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12201 (United States); Kitto, M.E. [Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12201 (United States); Department of Environmental Health Sciences, School of Public Health, University at Albany, State University of New York, Rensselaer, NY 12144 (United States); Hoffman, T.J. [Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, NY 12201 (United States); Curtis, P. [Kiltel Systems, Inc., Clyde Hill, WA 98004 (United States)

    2015-11-01

    A comprehensive study of the efficiency calibration and calibration verification of Ge gamma-ray spectrometers was performed using semi-empirical, computational Monte-Carlo (MC), and transfer methods. The aim of this study was to evaluate the accuracy of the quantification of gamma-emitting radionuclides in complex matrices normally encountered in environmental and food samples. A wide range of gamma energies from 59.5 to 1836.0 keV and geometries from a 10-mL jar to 1.4-L Marinelli beaker were studied on four Ge spectrometers with the relative efficiencies between 102% and 140%. Density and coincidence summing corrections were applied. Innovative techniques were developed for the preparation of artificial complex matrices from materials such as acidified water, polystyrene, ethanol, sugar, and sand, resulting in the densities ranging from 0.3655 to 2.164 g cm{sup −3}. They were spiked with gamma activity traceable to international standards and used for calibration verifications. A quantitative method of tuning MC calculations to experiment was developed based on a multidimensional chi-square paraboloid. - Highlights: • Preparation and spiking of traceable complex matrices in extended geometries. • Calibration of Ge gamma spectrometers for complex matrices. • Verification of gamma calibrations. • Comparison of semi-empirical, computational Monte Carlo, and transfer methods of Ge calibration. • Tuning of Monte Carlo calculations using a multidimensional paraboloid.

  13. Absorption of Very High Energy $\\gamma$-Rays by Intergalactic Infrared Radiation A New Determination

    CERN Document Server

    Stecker, F W

    1998-01-01

    We present a new calculation of the intergalactic gamma-ray absorption coefficient as a function of both energy and redshift. In reexamining this problem, we make use of a new, empirically based calculation (as opposed to previous model calculations) of the intergalactic infrared radiation field. We find smaller opacities than those given previously (Stecker & De Jager 1997). We apply our results to the new observations of the flaring gamma-ray spectra of Mrk421 and Mrk501, both at a redshift of apx. 0.03. Our new calculations indicate that there should be no significant curvature in the spectra of these sources for energies below 10 TeV, as indicated by recent observations. However, the intrinsic spectra of these sources should be harder by apx. 0.2 to 0.45 in the spectral index in the 1 to 10 TeV range with an intergalactic absorption cutoff above apx. 20 TeV.

  14. TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS): a versatile tool for radioactive beam physics

    Energy Technology Data Exchange (ETDEWEB)

    Ball, G.C. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Andreyev, A. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Austin, R.A.E. [Dept. of Astronomy and Physics, St. Mary' s University, Halifax, NS, B3H 3C3 (Canada)] (and others)

    2007-05-01

    TIGRESS is a new generation {gamma}-ray spectrometer designed for use with radioactive beams from ISAC. This paper gives an overview of the project and presents results from the first radioactive beam experiment with TIGRESS, the Coulomb excitation of {sup 20,21}Na.

  15. Absorption of very high energy gamma rays in the Milky Way

    Science.gov (United States)

    Vernetto, Silvia; Lipari, Paolo

    2016-09-01

    Galactic gamma ray astronomy at very high energy (Eγ≳30 TeV ) is a vital tool in the study of the nonthermal universe. The interpretation of the observations in this energy region requires the precise modeling of the attenuation of photons due to pair production interactions (γ γ →e+e- ) where the targets are the radiation fields present in interstellar space. For gamma rays with energy Eγ≳300 TeV the attenuation is mostly due to the photons of the cosmic microwave background radiation. At lower energy the most important targets are infrared photons with wavelengths in the range λ ≃50 - 500 μ m emitted by dust. The evaluation of the attenuation requires a good knowledge of the density, and energy and angular distributions of the target photons for all positions in the Galaxy. In this work we discuss a simple model for the infrared radiation that depends on only few parameters associated to the space and temperature distributions of the emitting dust. The model allows to compute with good accuracy the effects of absorption for any space and energy distribution of the diffuse Galactic gamma ray emission. The absorption probability due to the Galactic infrared radiation is maximum for Eγ≃150 TeV , and can be as large as Pabs≃0.45 for distant sources on lines of sight that pass close to the Galactic center. The systematic uncertainties on the absorption probability are estimated as Δ Pabs≲0.08 .

  16. Search for Doppler-shifted gamma-ray emission from SS 433 using the SMM spectrometer

    Science.gov (United States)

    Geldzahler, B. J.; Share, G. H.; Kinzer, R. L.; Magura, J.; Chupp, E. L.

    1989-01-01

    Data accumulated from 1980 to 1983 with the Gamma Ray Spectrometer aboard NASA's Solar Maximum Mission (SMM) satellite were searched for evidence of red and blue Doppler-shifted 1.37 MeV Mg-24 nuclear lines from SS 433. The SMM data base covers 270 days when SS 433 was in the field of view and includes periods of radio flaring and quiescence. No evidence was found for Doppler-shifted line emission in any of the spectra. The range of 3-sigma upper limits for individual 9 day integration periods was 0.0008-0.0023 photons/sq cm per sec for the blue beam, encompassing the reported about 1.5 MeV line, and 0.0008-0.002 photons/sq cm per sec for the red beam, encompassing the reported about 1.2 MeV line; the average 3-sigma upper limit in each beam for shifted about 1.37 MeV lines is 0.0015 photons/sq cm per sec for single 9 day integrations. The 3-sigma upper limit on 1.37 MeV gamma-ray emission over 23 9-day integration intervals for the red beam and 28 intervals for the blue beam is 0.0002 photons/sq cm per sec. These new limits from SMM can be reconciled with the HEAO 3 results only if SS 433 emits gamma radiation at or above the SMM sensitivity limit on rare occasions due to variable physical conditions in the system.

  17. Lifetime effects for high-resolution gamma-ray spectroscopy at relativistic energies and their implications for the RISING spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Doornenbal, P., E-mail: pieter@ribf.riken.j [Institut fuer Kernphysik, Universitaet zu Koeln, 50937 Koeln (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Reiter, P. [Institut fuer Kernphysik, Universitaet zu Koeln, 50937 Koeln (Germany); Grawe, H.; Saito, T. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Al-Khatib, A. [Helmholtz-Institut fuer Strahlen- und Kernphysik, Universitaet Bonn, 53115 Bonn (Germany); Banu, A.; Beck, T.; Becker, F. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Bednarczyk, P. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, 64291 Darmstadt (Germany); The Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, 31-342 Krakow (Poland); Benzoni, G. [INFN Sezione di Milano, 20133 Milano (Italy); Bracco, A. [INFN Sezione di Milano, 20133 Milano (Italy); Dipartimento di Fisica, Universita di Milano, 20133 Milano (Italy); Buerger, A. [Helmholtz-Institut fuer Strahlen- und Kernphysik, Universitaet Bonn, 53115 Bonn (Germany); Caceres, L. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Departamento de Fisica Teorica, Universidad Autonoma de Madrid, 28049 Madrid (Spain); Camera, F. [INFN Sezione di Milano, 20133 Milano (Italy); Dipartimento di Fisica, Universita di Milano, 20133 Milano (Italy); Chmel, S. [Helmholtz-Institut fuer Strahlen- und Kernphysik, Universitaet Bonn, 53115 Bonn (Germany); Crespi, F.C.L. [INFN Sezione di Milano, 20133 Milano (Italy); Dipartimento di Fisica, Universita di Milano, 20133 Milano (Italy); Geissel, H.; Gerl, J.; Gorska, M. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Grebosz, J. [GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, 64291 Darmstadt (Germany); Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, 31-342 Krakow (Poland)

    2010-02-01

    The lineshapes and peak position of Doppler corrected gamma-ray spectra from in-beam experiments at relativistic energies are investigated with respect to the intrinsic energy resolution of the employed detectors, the particles' velocities, and the photons' emission angle uncertainties at the moment of gamma-ray emission. The uncertainties in velocity and photon emission angle are dependent on the lifetime of the excited state. The impact of these two observables on the lineshape and energy resolution are studied for the RISING gamma-spectrometer by means of simulations and experimental results from a two-step fragmentation experiment at approx200MeV/u. Potential use of the distinct lineshape for lifetime determination is demonstrated for measured gamma-ray transitions.

  18. Performance of the prototype LaBr3 spectrometer developed for the JET gamma-ray camera upgrade

    Science.gov (United States)

    Rigamonti, D.; Muraro, A.; Nocente, M.; Perseo, V.; Boltruczyk, G.; Fernandes, A.; Figueiredo, J.; Giacomelli, L.; Gorini, G.; Gosk, M.; Kiptily, V.; Korolczuk, S.; Mianowski, S.; Murari, A.; Pereira, R. C.; Cippo, E. P.; Zychor, I.; Tardocchi, M.

    2016-11-01

    In this work, we describe the solution developed by the gamma ray camera upgrade enhancement project to improve the spectroscopic properties of the existing JET γ-ray camera. Aim of the project is to enable gamma-ray spectroscopy in JET deuterium-tritium plasmas. A dedicated pilot spectrometer based on a LaBr3 crystal coupled to a silicon photo-multiplier has been developed. A proper pole zero cancellation network able to shorten the output signal to a length of 120 ns has been implemented allowing for spectroscopy at MHz count rates. The system has been characterized in the laboratory and shows an energy resolution of 5.5% at Eγ = 0.662 MeV, which extrapolates favorably in the energy range of interest for gamma-ray emission from fast ions in fusion plasmas.

  19. Gamma-Gamma Absorption in the Broad Line Region Radiation Fields of Gamma-Ray Blazars

    CERN Document Server

    Boettcher, Markus

    2016-01-01

    The expected level of gamma-gamma absorption in the Broad Line Region (BLR) radiation field of gamma-ray loud Flat Spectrum Radio Quasars (FSRQs)is evaluated as a function of the location of the gamma-ray emission region. This is done self-consistently with parameters inferred from the shape of the spectral energy distribution (SED) in a single-zone leptonic EC-BLR model scenario. We take into account all geometrical effects both in the calculation of the gamma-gamma opacity and the normalization of the BLR radiation energy density. As specific examples, we study the FSRQs 3C279 and PKS 1510-089, keeping the BLR radiation energy density at the location of the emission region fixed at the values inferred from the SED. We confirm previous findings that the optical depth due to $\\gamma\\gamma$ absorption in the BLR radiation field exceeds unity for both 3C279 and PKS 1510-089 for locations of the gamma-ray emission region inside the inner boundary of the BLR. It decreases monotonically, with distance from the cen...

  20. Evidence for Intergalactic Absorption in the TeV Gamma-Ray Spectrum of Markarian 501

    CERN Document Server

    Konopelko, A K; Stecker, F W; Mastichiadis, A; Konopelko, Alexander K.; Kirk, John G.; Stecker, Floyd W.; Mastichiadis, Apostolos

    1999-01-01

    The recent HEGRA observations of the blazar Mkn 501 show strong curvature in the very high energy gamma-ray spectrum. Applying the gamma-ray opacity derived from an empirically based model of the intergalactic infrared background radiation field (IIRF), to these observations, we find that the intrinsic spectrum of this source is consistent with a power-law: dN/dE~ E^-alpha with alpha=2.00 +/- 0.03 over the range 500 GeV - 20 TeV. Within current synchrotron self-Compton scenarios, the fact that the TeV spectral energy distribution of Mkn 501 does not vary with luminosity, combined with the correlated, spectrally variable emission in X-rays, as observed by the BeppoSAX and RXTE instruments, also independently implies that the intrinsic spectrum must be close to alpha=2. Thus, the observed curvature in the spectrum is most easily understood as resulting from intergalactic absorption.

  1. Attenuation studies near K-absorption edges using Compton scattered 241Am gamma rays

    Indian Academy of Sciences (India)

    K K Abdullah; N Ramachandran; K Karunakaran Nair; B R S Babu; Antony Josephm; Rajive Thomas; K M Varier

    2008-04-01

    We have carried out photon attenuation measurements at several energies in the range from 49.38 keV to 57.96 keV around the K-absorption edges of the rare earth elements Sm, Eu, Gd, Tb, Dy and Er using 59.54 keV gamma rays from 241Am source after Compton scattering from an aluminium target. Pellets of oxides of the rare earth elements were chosen as mixture absorbers in these investigations. A narrow beam good geometry set-up was used for the attenuation measurements. The scattered gamma rays were detected by an HPGe detector. The results are consistent with theoretical values derived from the XCOM package.

  2. Airborne gamma-ray spectrometer and magnetometer survey: Chico quadrangle, California. Final report

    Energy Technology Data Exchange (ETDEWEB)

    1981-05-01

    An airborne high sensitivity gamma-ray spectrometer and magnetometer survey was conducted over ten (10) areas over northern California and southwestern Oregon. These include the 2/sup 0/ x 1/sup 0/ NTMS quadrangles of Roseburg, Medford, Weed, Alturas, Redding, Susanville, Ukiah, and Chico along with the 1/sup 0/ x 2/sup 0/ areas of the Coos Bay quadrangle and the Crescent City/Eureka areas combined. This report discusses the results obtained over the Chico, California, map area. Traverse lines were flown in an east-west direction at a line spacing of three. Tie lines were flown north-south approximately twelve miles apart. A total of 16,880.5 line miles of geophysical data were acquired, compiled, and interpreted during the survey, of which 3026.4 line miles are in the quadrangle. The purpose of this study is to acquire and compile geologic and other information with which to assess the magnitude and distribution of uranium resources with which to assess the magnitude and distribution of uranium resources and to determine areas favorable for the occurrence of uranium in the United States.

  3. Airborne gamma-ray spectrometer and magnetometer survey Coos Bay, Oregon. Final report

    Energy Technology Data Exchange (ETDEWEB)

    1981-05-01

    During the months of August, September, and October of 1980, Aero Service Division Western Geophysical Company of America conducted an airborne high sensitivity gamma-ray spectrometer and magnetometer survey over ten (10) areas over northern California and southwestern Oregon. These include the 2/sup 0/ x 1/sup 0/ NTMS quadrangles of Roseburg, Medford, Weed, Alturas, Redding, Susanville, Ukiah, and Chico along with the 1/sup 0/ x 2/sup 0/ areas of the Coos Bay quadrangle and the Crescent City/Eureka areas combined. This report discusses the results obtained over the Coos Bay, Oregon, map area. Line spacing was generally six miles for east/west traverses and eighteen miles for north/south tie lines over the northern one-half of the area. Traverses and tie lines were flown at three miles and twelve miles respectively over the southern one-half of the area. A total of 16,880.5 line miles of geophysical data were acquired, compiled, and interpreted during the survey, of which 863.8 line miles are in this quadrangle.

  4. An anticoincidence-shielded gamma-ray spectrometer for analysis of low level environmental radionuclides.

    Science.gov (United States)

    Byun, Jong In; Choi, Yun Ho; Kwak, Seung Im; Hwang, Han-Yull; Chung, Kun-Ho; Choi, Geun Sik; Park, Doo-Won; Lee, Chang Woo

    2003-05-01

    We developed an ultralow-level background gamma-ray spectrometer, using active and passive shield devices at the same time. Cosmic-ray-induced background is suppressed by means of active shield devices consisting of plastic scintillating plates of 50mm thick and anti-coincidence electronic system. The observed background rate was 0.34 s(-1) (=0.12s(-1) per 100 cm(3) Ge volume) for energy regions between 50 and 3000 ke V. The detection efficiency curve for 10(3)ml Marinelli beaker samples is obtained over all the energy regions. The advantages of the method are demonstrated by measuring the activity of 137Cs in powdered milk sample prepared without taking any chemical procedure. The MDA for 137Cs is estimated to be (17+/-1.7)mBq at a confidence level of 95% and it is about a factor of 10 lower than the MDA obtained from the previous cryostat assembly with 10-cm thick lead shielding.

  5. Thorium distribution on the lunar surface observed by Chang'E-2 gamma-ray spectrometer

    Science.gov (United States)

    Wang, Xianmin; Zhang, Xubing; Wu, Ke

    2016-07-01

    The thorium distribution on the lunar surface is critical for understanding the lunar evolution. This work reports a global map of the thorium distribution on the lunar surface observed by Chang'E-2 gamma-ray spectrometer (GRS). Our work exhibits an interesting symmetrical structure of thorium distribution along the two sides of the belt of Th hot spots. Some potential positions of KREEP volcanism are suggested, which are the Fra Mauro region, Montes Carpatus, Aristarchus Plateau and the adjacent regions of Copernicus Crater. Based on the lunar map of thorium distribution, we draw some conclusions on two critical links of lunar evolution: (1) the thorium abundance within the lunar crust and mantle, in the last stage of Lunar Magma Ocean (LMO) crystallization, may have a positive correlation with the depth in the crust, reaches a peak when coming through the transitional zone between the crust and mantle, and decreases sharply toward the inside of the mantle; thus, the Th-enhanced materials originated from the lower crust and the layer between the crust and mantle, (2) in PKT, KREEP volcanism might be the primary mechanism of Th-elevated components to the lunar surface, whereas the Imbrium impact acted as a relatively minor role.

  6. The global elemental composition of 433 Eros: First results from the NEAR gamma-ray spectrometer orbital dataset

    Science.gov (United States)

    Peplowski, Patrick N.

    2016-12-01

    A primary goal of the Near-Earth Asteroid Rendezvous (NEAR) mission was to compare the elemental composition of the S-type asteroid 433 Eros to the chemical compositions of meteorites, with the specific objective of testing the hypothesis that the S-type asteroids are the source of the ordinary chondrite (OC) meteorites. To that end, NEAR carried an X-ray and Gamma-ray Spectrometer (XGRS) to measure the elemental composition of Eros from orbit. To date, no Eros-originating signal had been reported in GRS orbital measurements, a consequence of NEAR's high orbital altitudes about Eros. A reanalysis of the NEAR GRS orbital dataset, particularly data collected during a series of low-altitude flyovers, has finally revealed the first positively identified gamma-ray signals from Eros. This dataset, which amounts to just 10 h of data collection, was used to produce the first GRS-derived global elemental composition values. Results include the first absolute concentrations of Fe and Th, and the first global K concentration. The data confirm prior conclusions that the elemental composition of Eros' surface is inconsistent with achondritic and volatile-rich carbonaceous chondritic compositions. In contrast, ordinary chondrites, volatile-poor carbonaceous chondrites, and enstatite chondrites have compositions that are consistent with Eros' gamma-ray emissions. When placed in the context of other gamma-ray spectrometer investigations, this analysis indicates that successful gamma-ray spectroscopy investigations require extended periods of time (≥10 days) at orbital altitudes less than or equal to the radius of the target body.

  7. Continuous measurement of radionuclide distribution off Fukushima using a towed sea-bed gamma ray spectrometer

    Science.gov (United States)

    Thornton, Blair; Ohnishi, Seiki; Ura, Tamaki; Odano, Naoteru; Fujita, Tsuneo

    2013-09-01

    Instrumentation and data processing methods to continuously map the distribution of radionuclides on the seafloor have been developed and applied to survey radioactive discharge from the Fukushima Dai-ichi Nuclear Power Plant following the M9.0 earthquake and tsunami that struck the east coast of Japan on March 11 2011. The instrument consists of a flexible rubber hose with an integrated gamma ray spectrometer that measures the full gamma spectrum between 0.1 and 1.8 MeV while being towed along the seafloor by a ship. The data processing methods described allow for quantification of 137Cs and 134Cs concentration in marine sediments, and a technique has been developed to optimize the spatial resolution of the measurements for each radioactive species for a given level of statistical uncertainty. The system was deployed during August and November 2012 to measure the distribution of radionuclides along three transects within an 80 km radius of the plant. Increased levels of 137Cs and 134Cs were recorded and their distributions mapped continuously over distances of 1.6, 12.5 and 22 km respectively. The levels of 137Cs and 134Cs were found to vary significantly with location. The in situ measurements show good agreement with laboratory analyzed samples obtained during the surveys. The results demonstrate that the instrument and data processing techniques described enable high resolution, quantitative measurements of 137Cs and 134Cs in marine sediments, and provide an effective solution for rapid, low cost monitoring of radioactive material on the seafloor.

  8. Indirect dark matter search with diffuse gamma rays from the Galactic Center with the Alpha Magnetic Spectrometer

    Science.gov (United States)

    Jacholkowska, A.; Lamanna, G.; Nuss, E.; Bolmont, J.; Adloff, C.; Alcaraz, J.; Battiston, R.; Brun, P.; Burger, W. J.; Choutko, V.; Coignet, G.; Falvard, A.; Fiandrini, E.; Girard, L.; Goy, C.; Jedamzik, K.; Kossakowski, R.; Moultaka, G.; Natale, S.; Pochon, J.; Pohl, M.; Rosier-Lees, S.; Sapinski, M.; Sevilla Noarbe, I.; Vialle, J. P.

    2006-07-01

    The detection of nonbaryonic dark matter through its gamma-ray annihilation in the center of our galaxy has been studied. The gamma fluxes according to different models have been simulated and compared to those expected to be observed with the Alpha Magnetic Spectrometer (AMS), during a long-term mission on board of the international space station. Under the assumption that the dark matter is composed of the lightest, stable supersymmetric particle, the neutralino, the results of the simulations in the framework of minimal supergravity models, show that with a cuspy dark matter halo profile or a clumpy halo, the annihilation gamma-ray signal would be detected by AMS. More optimistic perspectives are obtained with the anomaly mediated supersymmetry breaking (AMSB) model. The latter leads also to a cosmologically important Li2 abundance. Finally, the discovery potential for the massive Kaluza-Klein dark matter candidates has been evaluated and their detection looks feasible.

  9. An indirect dark matter search with diffuse gamma rays from the Galactic Centre: prospects for the Alpha Magnetic Spectrometer

    CERN Document Server

    Jacholkowska, A; Nuss, E; Adloff, C; Alcaraz, J; Battiston, R; Bolmont, J; Brun, P; Burger, W J; Choutko, V; Coignet, G; Falvard, A; Flandrini, E; Girard, L; Goy, C; Jedamzik, K; Kossakowski, R; Moultaka, G; Natale, S; Pochon, J; Pohl, M; Rosier-Lees, S; Sapinski, M; Noarbe, I S; Vialle, J P; Vialle, JP.

    2005-01-01

    The detection of non-baryonic dark matter through its gamma-ray annihilation in the centre of our galaxy has been studied. The gamma fluxes according to different models have been simulated and compared to those expected to be observed with the Alpha Magnetic Spectrometer (AMS), during a long-term mission on board of the International Space Station. Under the assumption that the dark matter halo is composed of the lightest, stable supersymmetric particle, the neutralino, the results of the simulations in the framework of mSUGRA models, show that with a cuspy dark matter halo or a clumpy halo, the annihilation gamma-ray signal would be detected by AMS. More optimistic perspectives are obtained with the Anomaly Mediated Supersymmetry Breaking (AMSB) model. The latter leads also to a cosmologically important 6Li abundance. Finally, the discovery potential for the massive Kaluza-Klein dark matter candidates has been evaluated and their detection looks feasible.

  10. SHARC: Silicon Highly-segmented Array for Reactions and Coulex used in conjunction with the TIGRESS {gamma}-ray spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Diget, C A; Fox, S P; Adsley, P; Fulton, B R [Department of Physics, University of York, York, YO10 5DD (United Kingdom); Smith, A [School of Physics and Astronomy, The University of Manchester, Manchester, M13 9PL (United Kingdom); Williams, S; Ball, G C; Churchman, R M; Dech, J; Valentino, D Di; Djongolov, M [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada); Porter-Peden, M [Department of Physics, Colorado School of Mines, Golden, CO 80401 (United States); Achouri, L [Laboratoire de Physique Corpusculaire, IN2P3-CNRS, ISMRA et Universite de Caen, F-14050 Caen (France); Al-Falou, H; Austin, R A E [Department of Astronomy and Physics, Saint Mary' s University, Halifax, NS, B3H 3C3 (Canada); Blackmon, J C [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Brown, S; Catford, W N [Department of Physics, University of Surrey, Guildford, GU2 5XH (United Kingdom); Chen, A A; Chen, J, E-mail: christian.diget@york.ac.uk [Department of Physics and Astronomy, McMaster University, Hamilton, ON, L8S 4M1 (Canada)

    2011-02-01

    The combination of {gamma}-ray spectroscopy and charged-particle spectroscopy is a powerful tool for the study of nuclear reactions with beams of nuclei far from stability. This paper presents a new silicon detector array, SHARC, the Silicon Highly-segmented Array for Reactions and Coulex. The array is used at the radioactive-ion-beam facility at TRIUMF (Canada), in conjunction with the TIGRESS {gamma}-ray spectrometer, and is built from custom Si-strip detectors utilising a fully digital readout. SHARC has more than 50% efficiency, approximately 1000-strip segmentation, angular resolutions of {Delta}{theta} {approx} 1.3 deg. and {Delta}{phi} {approx} 3.5 deg., 25-30 keV energy resolution, and thresholds of 200 keV for up to 25 MeV particles. SHARC is now complete, and the experimental program in nuclear astrophysics and nuclear structure has commenced.

  11. A simplified spectrometer based on a fast digital oscilloscope for the measurement of high energy $\\gamma$-rays

    CERN Document Server

    Markochev, S S

    2014-01-01

    A simplified digital spectrometer for the study of $\\gamma$-rays with energies up to $\\sim100$ MeV is presented and tested. The spectrometer is only consisted of a fast digital oscilloscope and three scintillation detectors which can work in single or in coincidence modes: two BGO-detectors comprising $\\varnothing\\,7.62\\times7.62$ cm BGO-crystalls and one plastic detector which includes an organic polystyrene-based scintillator. The basic properties of the spectrometer (energy resolution, time resolution, $\\gamma$-rays detection efficiency) were studied exhaustively also using a Geant4-based Monte-Carlo simulation. Several numerical algorithms for processing of waveforms in offline mode were proposed and tested to perform digital timing, pulse area measurement and processing of pile-up events without rejection. As a result, the spectrometer demonstrated $\\sim10\\%$ better energy resolution than was obtained by a common 10-bit CAMAC ADC with the same detectors. And the developed algorithm based on the pulse sha...

  12. The characteristics of a low background germanium gamma ray spectrometer at China JinPing underground Laboratory

    CERN Document Server

    Mi, Yuhao; Zeng, Zhi; Cheng, Jianping; Su, Jian; Yue, Qian

    2014-01-01

    A low background germanium gamma ray spectrometer, GeTHU, has been installed at China JinPing underground Laboratory. The integral background count rate between 40 and 2700 keV was 0.6 cpm, and the origin was studied by Monte Carlo simulation. Detection limits and efficiencies were calculated for selected gamma peaks. Boric acid and silica sand samples were measured and 137Cs contamination was found in boric acid. GeTHU will be mainly used to measure environmental samples and screen materials in dark matter experiments.

  13. Development of a method for activity measurements of {sup 232}Th daughters with a multidetector gamma-ray coincidence spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Antovic, N. [Faculty of Natural Sciences and Mathematics, University of Montenegro, Cetinjski put b.b., 81000 Podgorica (Montenegro)], E-mail: antovicn@yahoo.com; Svrkota, N. [Center for Ecotoxicological Research, Put Radomira Ivanovica 2, 81000 Podgorica (Montenegro)

    2009-06-15

    The method for activity measurements of the {sup 232}Th daughters, developed at the six-crystal gamma-ray coincidence spectrometer PRIPYAT-2M and based on coincidence counting of the 583 and 2615 keV photons from cascade transitions which follow {beta}{sup -}-decay of {sup 208}Tl, as well as on counting the 911 keV photons which follow {beta}{sup -}-decay of {sup 228}Ac in the integral and non-coincidence mode of counting, is presented.

  14. SONGS - A high resolution imaging gamma-ray spectrometer for the Space Station

    Science.gov (United States)

    Nakano, G. H.; Chase, L. F.; Kilner, J. R.; Sandie, W. G.; Fishman, G. J.; Paciesas, W. S.

    1989-11-01

    The overall design and the instrumental features of the Space-Station Observer for Nuclear Gamma-ray Spectroscopy (SONGS) instrument are described. SONGS comprises an array of 19 two-segment n-type Ge detectors, which have the capability of determining the interaction site in either the upper or the lower segment or in both segments. The detectors provide high energy resolution of 1 keV at 100 keV and of 2 keV at 1 MeV. The close-packed Ge sensor array provides a natural sensitivity for the measurement of gamma ray polarization in the 100 keV to 1 MeV energy range, making it possible to obtain information on the structure of the magnetosphere of neutron stars and of the accretion disk of black holes.

  15. Gamma-ray spectrometer measurement of 238U/235U in uranium ore from a natural reactor at Oklo, Gabon

    Science.gov (United States)

    Moxham, Robert M.

    1976-01-01

    About 20 years ago, Kuroda theorized that a high-grade uranium deposit emplaced about 2x109 years ago could achieve criticality and sustain a nuclear chain reaction, given a sufficient thickness of high-grade ore and an appropriate water content. Such a natural reactor was found in 1972 at the Oklo deposit, Gabon. The ore contains as much as 60 percent uranium, but the isotopic abundance of 235U is as little as 0.4 percent in contrast to the normal abundance of 0.7110 percent 235U. A sample from the Oklo deposit containing about 0.51 atom percent 235U (by mass spectrometer) was analyzed by a gamma-ray spectrometer system, using a high-purity planar germanium detector. The 235U was determined from its daughter's (234Th) 63.3 keV photopeak; the 235U was determined from its 143.8 and 163.4 keV photopeaks. The ratios of these photopeaks were compared with that from a standard having normal uranium isotopic content; the resulting calculations give a 235U abundance of 0.54 atom percent in the Oklo sample. The gamma-ray spectrum also contains lines from five other isotopes in the uranium series, which indicate the Oklo sample to be at or near secular equilibrium, as the time elapsed since the nuclear reaction ended was sufficient to permit the daughters to achieve equilibrium.

  16. Gamma ray radiation induced visible light absorption in P-doped silica fibers at low dose levels

    CERN Document Server

    Lu Ping; Kulkarni, N S; Brown, K

    1999-01-01

    A CCD Fiber Optic Spectrometer has been used to monitor the gamma ray radiation induced loss in P-doped fibers at different dopant concentrations (1, 5 and 10 mol%) with a light source (an incandescent bulb with a temperature of 2800-3000 K). The range of dose rates is limited to that used in medical applications (cancer treatments), that is 0.1 to 1.0 Gray per minute (Gy/min). At low integral dose level (<2.0 Gy) four absorption peaks were observed (470, 502, 540 and 600 nm) within the visible region. It has been observed that the radiation induced loss at 470 and 600 nm depends strongly on dose rate. At dose rates of 0.2 and 0.5 Gy/min the induced loss shows nonlinear relation to the total dose. However, at high dose rate (1.0 Gy/min) and low dose rate (0.1 Gy/min) it seems to have a linear dependence with total dose. The conversion from NBOHCs to GeX centers was observed during gamma radiation at low dose rates (0.1-0.5 Gy/min). At the wavelength of 502 and 540 nm, the radiation induced losses show exce...

  17. Influence of the thorium decay series on the background of high-resolution gamma-ray spectrometers.

    Science.gov (United States)

    Bučar, K; Korun, M; Vodenik, B

    2012-06-01

    The background induced by the members of the thorium decay sequence in six high-resolution, gamma-ray spectrometers was analyzed. For the analysis, the count rates in the peaks of the background spectra, normalized to the unit of emission probability and detection probability, were used. The energy dependence of these normalized count rates carries information about the location of the sources of contamination. The contributions of the detector contamination, the contamination of the shielding material and the radiation penetrating the shield were calculated. The comparison of these contributions among the spectrometers pointed to the weaknesses of some shields, making such a comparison a useful tool for assessing the effectiveness of the shields.

  18. Experimental set-up and optimization of a gamma-ray spectrometer for measurement of cosmogenic radionuclides in meteorites

    Energy Technology Data Exchange (ETDEWEB)

    Taricco, C. [Dipartimento di Fisica Generale dell' Universita and Istituto di Fisica dello Spazio Interplanetario - INAF, Turin (Italy)]. E-mail: taricco@ph.unito.it; Bhandari, N. [Basic Sciences Research Institute, Navrangpura, Ahmedabad (India); Colombetti, P. [Dipartimento di Fisica Generale dell' Universita and Istituto di Fisica dello Spazio Interplanetario - INAF, Turin (Italy); Verma, N. [Dipartimento di Fisica Generale dell' Universita and Istituto di Fisica dello Spazio Interplanetario - INAF, Turin (Italy); Vivaldo, G. [Dipartimento di Fisica Generale dell' Universita and Istituto di Fisica dello Spazio Interplanetario - INAF, Turin (Italy)

    2007-03-01

    We have developed a highly efficient and selective gamma-ray spectrometer with extremely low background for activity measurement of gamma emitting cosmogenic radionuclides in meteorites. This spectrometer can operate in specific modes to match decay scheme of a particular radionuclide and is specially suited for measurement of positron emitters. The system consists of a hyperpure Ge detector (3kg, 147% relative efficiency), operating in coincidence with an umbrella of NaI(Tl) scintillator (90kg) in order to achieve low background. The system is tuned such that strong interference due to naturally occurring uranium daughters, e.g. {sup 214}Bi present in the meteorites and in the laboratory environment, is minimized. It enables us to measure {sup 44}Ti (T{sub 1/2}=59.2y) which is ideal for studying centennial scale variations of cosmic ray flux in the interplanetary space with good reliability. The specific configuration of the coincidence system and electronics are described here.

  19. Pair Production Absorption Troughs in $\\gamma$-Ray Burst Spectra A Potential Distance Discriminator

    CERN Document Server

    Baring, M G; Baring, Matthew G.; Harding, Alice K.

    1997-01-01

    Relativistic bulk motion with large Lorentz factors has recently been inferred for gamma-ray bursts regardless of whether they are of galactic or cosmological origin. This conclusion results from calculations of internal pair production transparency in bursts that usually assume an infinite power-law source spectrum for simplicity, an approximation that is quite adequate for some bursts detected by EGRET. However, for a given bulk Lorentz factor sub-MeV photons in such calculations. Hence it is essential to accurately address the spectral curvature in bursts seen by BATSE. In this paper we present the major properties induced in photon-photon opacity considerations by such spectral curvature. The observed spectral breaks around 1 MeV turn out to be irrelevant to opacity in cosmological bursts, but are crucial to estimates of source transparency in the 1 GeV -- 1 TeV range for sources located in the galactic halo. We find that broad absorption troughs can arise at these energies for suitable bulk motion parame...

  20. Neutrino scattering, absorption and annihilation above the accretion discs of gamma ray bursts

    Energy Technology Data Exchange (ETDEWEB)

    Kneller, J P [Department of Physics, North Carolina State University, Raleigh, NC 27695 (United States); School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); McLaughlin, G C [Department of Physics, North Carolina State University, Raleigh, NC 27695 (United States); Surman, R A [Department of Physics, Union College, Schenectady, NY 12308 (United States)

    2006-04-01

    The central engine that drives gamma ray burst (GRB) explosions may derive from the ability of electrons/positrons and nucleons to tap into the momentum and energy from the large neutrino luminosity emitted by an accretion disc surrounding a black hole. This transfer of momentum and energy occurs due to neutrino absorption, scattering and annihilation, and the non-spherical geometry of the source both increases the annihilation efficiency and, close to the black hole, directs the momentum transfer toward the disc axis. We focus on the micro-physical aspects of this system and present annihilation efficiencies and the momentum/energy transfers for a number of accretion disc models. Models in which the neutrinos and antineutrinos become trapped within the disc have noticeably different momentum and energy deposition structure compared to thin disc models that may lead to significant differences in the explosion dynamics. Using these results we make estimates for the critical densities of infalling material below which the transfer of neutrino momentum/energy will lead to an explosion.

  1. Abundance and distribution of radioelements in lunar terranes: Results of Chang'E-1 gamma ray spectrometer data

    Science.gov (United States)

    Chen, Jian; Ling, Zongcheng; Li, Bo; Zhang, Jiang; Sun, Lingzhi; Liu, Jianzhong

    2016-02-01

    The gamma ray spectrometer (GRS) onboard Chang'E-1 has acquired valuable datasets recording the gamma ray intensities from radioelements (Potassium (K), Thorium (Th) and Uranium (U), etc.) on lunar surface. We extracted the elemental concentrations from the GRS data with spectral fitting techniques and mapped the global absolute abundance of radioelements in terms of the ground truths from lunar samples and meteorites. The obtained global concentration maps of these radioelements indicate heterogeneous distribution among three major lunar crustal terranes (i.e., Procellarum KREEP Terrane (PKT), Feldspathic Highlands Terrane (FHT), and South Pole Aitken Terrane (SPAT)) in relation with their origin and distinct geologic history. The majority of radioelements are restricted in PKT, approving the scenario of KREEP (Potassium (K), rare earth elements (REE), Phosphorus (P)) residua concentrating under the Procellarum region. Moreover, we found the consistency of distribution for radioelements and basalts, concluding that the subsequent volcanism might be associated with local concentrations of radioelements in western Oceanus Procellarum and northwestern South Pole Aitken Basin. The prominent and asymmetric radioactive signatures were confirmed in SPAT comparing to FHT dominated by low level radioactivity, while the magnitudes are much lower than that of PKT, indicating a primary geochemical heterogeneity for the Moon.

  2. Selection of new innovation crystal for Mercury Gamma-ray and Neutron Spectrometer on-board MPO/BepiColombo mission.

    Science.gov (United States)

    Kozyrev, Alexander; Mitrofanov, Igor; Benkhoff, Johannes; Litvak, Maxim; McAuliffe, Jonathan; Mokrousov, Maxim; Owens, Alan; Quarati, Francesco; Shvetsov, Valery; Timoshenko, Gennady

    2015-04-01

    The Mercury Gamma-ray and Neutron Spectrometer (MGNS) was developed in Space Research Institute for detection the flux of neutron and gamma-ray from the Mercury subsurface on-board Mercury Polar Orbiter of ESA BepiColombo mission. The instrument consists of 3He proportional counters and organic scintillator for detection of neutron and also gamma-spectrometer based on scintillation crystal for detection of gamma-ray. For the gamma-ray spectrometer the LaBr3 crystal was selected, the best choice at the time of the instrument proposal in 2004. However, quite recently the European industry has developed the new crystal CeBr3, which could be much better than LaBr3 crystal for planetology. Such crystal with the necessary size of 3 inch became available in the stage of manufactory of Flight Spare Module of MGNS instrument. New CeBr3 crystal has much better signal-to-noise ratio than LaBr3 crystal in the energy band up to 3 MeV. Also, in the LaBr3 crystal, the important for planetology gamma-ray line of potassium at 1461 keV is overlapping with the background gamma-ray line of 138La isotope at 1473 keV. This CeBr3 crystal was integrated to MGNS instrument. We present the results of gamma-ray performance and environment tests of MGNS with CeBr3 crystal, and also comparison between LaBr3 and new CeBr3 crystals in context of space application for this instrument.

  3. Detectors for the Gamma-Ray Resonant Absorption (GRA) Method of Explosives Detection in Cargo: A Comparative Study

    CERN Document Server

    Vartsky, D; Engler, G; Shor, A; Goldschmidt, A; Feldman, G; Bar, D; Orion, I; Wielopolski, L; Vartsky, David; Goldberg, Mark B.; Engler, Gideon; Shor, Asher; Goldschmidt, Aharon; Feldman, Gennady; Bar, Doron; Orion, Itzhak; Wielopolski, Lucian

    2004-01-01

    Gamma-Ray Resonant Absorption (GRA) is an automatic-decision radiographic screening technique that combines high radiation penetration with very good sensitivity and specificity to nitrogenous explosives. The method is particularly well-suited to inspection of large, massive objects (since the incident gamma-ray probe is at 9.17 MeV) such as aviation and marine containers, heavy vehicles and railroad cars. Two kinds of gamma-ray detectors have been employed to date in GRA systems: 1) Resonant-response nitrogen-rich liquid scintillators and 2) BGO detectors. This paper analyses and compares the response of these detector-types to the resonant radiation, in terms of single-pixel figures of merit. The latter are sensitive not only to detector response, but also to accelerator-beam quality, via the properties of the nuclear reaction that produces the resonant gamma-rays. Generally, resonant detectors give rise to much higher nitrogen-contrast sensitivity in the radiographic image than their non-resonant detector ...

  4. A portable medium-resolution gamma-ray spectrometer and analysis software

    Energy Technology Data Exchange (ETDEWEB)

    Lavietes, A.D.; McQuaid, J.H.; Ruhter, W.D.; Buckley, W.M.; Clark, D-L. [Lawrence Livermore National Lab., CA (United States); Paulus, T.J. [EG and G ORTEC, Oak Ridge, TN (United States)

    1996-07-01

    There is a strong need for portable radiometric instrumentation that can both accurately confirm the presence of nuclear materials and allow isotopic analysis of radionuclides in the field. To fulfill this need the Safeguards Technology Program at LLNL has developed a hand-held, non-cryogenic, low-power gamma-ray and x-ray measurements and analysis instrument that can both search for and then accurately verify the presence of nuclear materials. We will report on the use of cadmium zinc telluride (CZT) detectors, detector electronics, and the new field-portable instrument being developed. We will also describe the isotopic analysis that allows enrichment measurements to be made accurately in the field. These systems provide capability for safeguards inspection and verification applications and could find application in counter-smuggling operations.

  5. Ground tests with prototype of CeBr3 active gamma ray spectrometer proposed for future venus surface missions

    Science.gov (United States)

    Litvak, M. L.; Sanin, A. B.; Golovin, D. V.; Jun, I.; Mitrofanov, I. G.; Shvetsov, V. N.; Timoshenko, G. N.; Vostrukhin, A. A.

    2017-03-01

    The results of a series of ground tests with a prototype of an active gamma-ray spectrometer based on a new generation of scintillation crystal (CeBr3) are presented together with a consideration to its applicability to future Venus landing missions. We evaluated the instrument's capability to distinguish the subsurface elemental composition of primary rock forming elements such as O, Na, Mg, Al, Si, K and Fe. Our study uses heritage from previous ground and field tests and applies to the analysis of gamma lines from activation reaction products generated by a pulsed neutron generator. We have estimated that the expected accuracies achieved in this approach could be as high as 1-10% for the particular chemical element being studied.

  6. Data Processing for the Near Earth Asteroid Rendezvous (NEAR), X-Ray and Gamma-Ray Spectrometer (XRS) Ground System

    Science.gov (United States)

    McClanahan, Timothy P.; Mikheeva, I.; Trombka, J. I.; Floyd, S. R.; Boynton, W. V.; Bailey, H.; Bhangoo, J.; Starr, R.; Clark, P. E.; Evans, L. G.

    1999-01-01

    An X-ray and Gamma-ray spectrometer (XGRS) is onboard the Near Earth Asteroid Rendezvous (NEAR) spacecraft to determine the elemental composition of the surface of the asteroid 433Eros. The Eros asteroid is highly non-spherical in physical shape and the development of data management and analysis methodologies are in several areas a divergence from traditional remotely sensed geographical information systems techniques. Field of view and asteroid surface geometry must be derived virtually and then combined with real measurements of solar, spectral and instrument calibration information to derive meaningful scientific results. Spatial resolution of planned geochemical maps will be improved from the initial conditions of low statistical significance per integration by repeated surface flyovers and regional spectral accumulation. This paper describes the results of a collaborative effort of design and development of the NEAR XGRS instrument ground system undertaken by participants at the Goddard Space Flight Center, University of Arizona, Cornell University, Applied Physics Laboratory, and Max Plank institute.

  7. Data Processing for the Near Earth Asteroid Rendezvous (NEAR), X-ray and Gamma-ray Spectrometer (XGRS) Ground System

    Science.gov (United States)

    McClanahan, Timothy P.; Mikheeva, I.; Trombka, J. I.; Floyd, S. R.; Boynton, W. V.; Bailey, H.; Bhangoo, J.; Starr, R.; Clark, P. E.; Evans, L. G.

    1999-01-01

    An X-ray and Gamma-ray spectrometer (XGRS) is onboard the Near Earth Asteroid Rendezvous (NEAR) spacecraft to determine the elemental composition of the surface of the asteroid 433Eros. The Eros asteroid is highly non-spherical in physical shape and the development of data management and analysis methodologies are in several areas a divergence from traditional remotely sensed geographical information systems techniques. Field of view and asteroid surface geometry must be derived virtually and then combined with real measurements of solar, spectral and instrument calibration information to derive meaningful scientific results. Spatial resolution of planned geochemical maps will be improved from the initial conditions of low statistical significance per integration by repeated surface flyovers and regional spectral accumulation. This paper describes the results of a collaborative effort of design and development of the NEAR XGRS instrument ground system undertaken by participants at the Goddard Space Flight Center, University of Arizona, Cornell University, Applied Physics Laboratory, and Max Plank institute.

  8. Ge(Li) detector gamma-ray spectrometer system for measurement of the spectra and production cross sections of. gamma. -rays produced by 14 MeV neutron nonelastic interaction with nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Shen Ronglin; Shi Xiamin; Wu Yongshun; Xing Jinjiang; Ding Dazhao

    1982-02-01

    A 42 cm/sup 3/ Ge(Li) detector gamma-ray spectrometer system for measuring the spectra and the production cross sections of ..gamma..-rays produced by fast neutron nonelastic interaction with nuclei is described in this paper. The incident neutrons are produced by T(d,n)/sup 4/He reaction in an high tension set with the incident deuteron energy of 200 keV. The time of flight technique is used to discriminate between the scattered neutrons and gamma-rays resulting from nonelastic interaction. The ..cap alpha..-particles are picked up by a Si(Au) surface barrier detector and the ARC timing discriminaters are used in both Si(Au) and Ge(Li) channels. The overall time resolution (FWHM) of this system is 4.1 ns typically for energy selection threshold at 400keV. The block diagram of spectrometer system is described in detail. The complex complete shielding damage of Ge(Li) detector in this fast neutron field is well discussed.

  9. Charge collection characteristics of Frisch collar CdZnTe gamma-ray spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    Harrison, Mark J. [Kansas State University, Manhattan, KS 66506 (United States)], E-mail: harrison@ksu.edu; Kargar, Alireza; McGregor, Douglas S. [Kansas State University, Manhattan, KS 66506 (United States)

    2007-08-21

    A collimated {sup 198}Au source was used to determine the charge collection efficiency (CCE) at several locations along the length of a 3.4x3.4x5.5 mm{sup 3} CdZnTe bar detector, both in planar configuration and with Frisch collars of varying length. For each configuration, a 0.50-mm-long region spanning the width of the device was irradiated with 411-keV gamma rays produced by a neutron-activated gold foil. Irradiation began at the cathode and stepped in 0.50-mm steps toward the anode, with a spectrum being collected at each location. By observing the channel location of the full-energy peak in each collected spectrum, an average CCE was determined for each irradiated region. The CCE was found to vary nearly linearly along the length of the device in the planar configuration, starting at a peak value of 89% and dropping to a minimum measured value of 26% near the anode. The addition of a Frisch collar covering the entire length of the crystal greatly altered the CCE profile, which remained near 87% for approximately two-thirds of the length, then sharply dropped near the anode. Results were confirmed by theoretical models. Further CCE mapping was also completed for devices with Frisch collars of various lengths. Those results are reported as well.

  10. Calibration of the 4pi gamma-ray spectrometer using a new numerical simulation approach.

    Science.gov (United States)

    Nafee, Sherif S; Badawi, Mohamed S; Abdel-Moneim, Ali M; Mahmoud, Seham A

    2010-09-01

    The 4pi gamma-counting system is well suited for analysis of small environmental samples of low activity because it combines advantages of the low background and the high detection efficiency due to the 4pi solid angle. A new numerical simulation approach is proposed for the HPGe well-type detector geometry to calculate the full-energy peak and the total efficiencies, as well as to correct for the coincidence summing effect. This method depends on a calculation of the solid angle subtended by the source to the detector at the point of entrance, (Abbas, 2006a). The calculations are carried out for non-axial point and cylindrical sources inside the detector cavity. Attenuation of photons within the source itself (self-attenuation), the source container, the detector's end-cap and the detector's dead layer materials is also taken into account. In the Belgium Nuclear Research Center, low-activity aqueous solutions of (60)Co and (88)Y in small vials are routinely used to calibrate a gamma-ray p-type well HPGe detector in the 60-1836keV energy range. Efficiency values measured under such conditions are in good agreement with those obtained by the numerical simulation.

  11. Monitoring of Natural Soil Radioactivity with Portable Gamma-Ray Spectrometers

    DEFF Research Database (Denmark)

    Bøtter-Jensen, Lars; Løvborg, Leif; Kirkegaard, Peter

    1979-01-01

    measurements at sea were carried out in order to estimate the non-terrestrial contributions to the instrument readings. Counts recorded in the three high-energy windows of the spectrometers were converted into radiometrically equivalent concentrations of thorium, uranium, and potassium in the ground. Large...

  12. Extragalactic Gamma-Ray Absorption and the Intrinsic Spectrum of Mkn 501 During the 1977 Flare

    CERN Document Server

    De Jager, O C

    2002-01-01

    Using the recent models of Malkan & Stecker (2001) for the infrared background radiation and extrapolating them into the optical and UV range using recent galaxy count data, we rederive the optical depth of the Universe to high energy gamma-rays as a function of energy and redshift for energies between 50 GeV and 100 TeV and redshifts between 0.03 and 0.3. We then use these results to derive the intrinsic gamma-ray spectrum of Mkn 501 during its 1997 high state. We find that the spectral energy distribution of Mkn 501 while flaring had a broad, flat peak in the 5-10 TeV range which corresponds to the broad, flat peak in the 50-100 keV range observed during the flare. The differential spectral index of our derived intrinsic gamma-ray spectrum at energies below about 2 TeV was found to be about 1.6 to 1.7. This corresponds to a time averaged index of 1.76 found in soft X-rays at energies below the X-ray synchrotron peak. These results appear to favor a synchrotron-self Compton origin for the TeV emission to...

  13. Data management and analysis techniques used in the near X-ray and gamma-ray spectrometer systems

    Science.gov (United States)

    McClanahan, T. P.; Trombka, J. I.; Floyd, S. R.; Boynton, W. V.; Mikheeva, I.; Bailey, H.; Liewicki, C.; Bhangoo, J.; Starr, R.; Clark, P. E.; Evans, L. G.; Squyres, S.; McNutt, R.; Brückner, J.

    1999-02-01

    The NEAR Earth Asteroid Rendezvous (NEAR) spacecraft will encounter the 433Eros asteroid for a one year orbital mission in December 1998. Its on-board remote sensing instrumentation includes X-ray and gamma-ray (XGRS) spectrometers. NEAR is an orbital mission and long integrations over spatially specific asteroid regions are generally not possible. A methodology for simulating longer integrations has been developed for XGRS and uses unique management, correlative and analytical ground systems to render mapping data products. Evaluation of the spatial environment is accomplished through virtual renderings of the asteroid surface giving incidence, emission and surface roughness factors. Extended computer plate modeling information is employed to optimize ground computer systems processing time. Interactive visualization systems have been developed to manage close to a million spectra that will be collected during the encounter. Feedback systems are employed to inspect, tag and calibrate spectral data products. Mission planning, systems development and managerial responsibilities have been distributed to cooperating science organizations at The Goddard Space Flight Center, The University of Arizona, Cornell University, The Applied Physics Laboratory and The Max Plank Institute.

  14. Improvements on Decay Heat Summation Calculations by Means of Total Absorption Gamma-ray Spectroscopy Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Algora, A.; Sonzogni, A.; Algora, A.; Jordan, D.; Tain, J. L.; Rubio, B.; Agramunt, J.; Caballero, L.; Nacher, E.; Perez-Cerdan, A. B.; Molina, F.; Krasznahorkay, A.; Hunyadi, M. D.; Gulyas, J.; Vitez, A.; Csatlos, M.; Csige, L.; Aysto, J.; Penttila, H.; Rinta-Antila, S.; Moore, I.; Eronen, T.; Jokinen, A.; Nieminen, A.; Hakala, J.; Karvonen, P.; Kankainen, A.; Hager, U.; Sonoda, T.; Saastamoinen, A.; Rissanen, J.; Kessler, T.; Weber, C.; Ronkainen, J.; Rahaman, S.; Elomaa, V.; Burkard, K.; Hueller, W.; Batist, L.; Gelletly, W.; Yoshida, T.; Nichols, A. L.; Sonzogni, A.; Perajarvi, K.

    2011-08-01

    The decay heat of fission products plays an important role in predictions of the heat released by nuclear fuel in reactors. In this contribution we present results of the analysis of the measurement of the beta decay of some refractory isotopes that were considered possible important contributors to the decay heat in reactors. The measurements presented here were performed at the IGISOL facility of the University of Jyvaeskylae, Finland. In our measurements we have combined for the first time a Penning trap (JYFLTRAP), which was used as a high resolution isobaric separator, with a total absorption spectrometer. The results of the measurements as well as their consequences for decay heat summation calculations are discussed.

  15. Absorption of Very High Energy Gamma Rays in the Milky Way

    CERN Document Server

    Vernetto, Silvia

    2016-01-01

    Galactic Gamma ray astronomy at very high energy (E > 30 TeV) is a vital tool in the study of the non-thermal universe. The interpretation of the observations in this energy region requires the precise modeling of the attenuation of photons due to pair production interactions, where the targets are the radiation fields present in interstellar space. For gamma rays with energy E > 300 TeV the attenuation is mostly due to the photons of the Cosmic Microwave Background Radiation (CMBR). At lower energy the most important target are infrared photons with wavelengths in the range 50-500 micron emitted by dust. The evaluation of the attenuation requires a good knowledge of the density, and energy and angular distributions of the target photons for all positions in the Galaxy. In this work we discuss a simple model for the infrared radiation that depends on only few parameters associated to the space and temperature distributions of the emitting dust. The model allows to compute with good accuracy the effects of abs...

  16. In-house development of an FPGA-based MCA8K for gamma-ray spectrometer.

    Science.gov (United States)

    Lanh, Dang; Son, Pham Ngoc; Son, Nguyen An

    2014-01-01

    The objective of this work is domestic development of electronics instruments. It used for measuring ionization radiation and practical training at Nuclear Research Institute (NRI), Dalat, Vietnam. The aim of this work is to study and develop a novel MCA8k for Gamma-ray spectrometer concerning experimental nuclear physics. An approach for design and construction of the aforementioned instrument is to apply logic integrating techniques via Field Programmable Gate Arrays (FPGA) under Max + PlusII, Altera. The instrument allows interfacing to PC with self-developed application software. Scientific significance of this work is partly to contribute to opening a research direction in the field of nuclear electronics science for design and construction of radiation measurement instruments with the advanced IC technology in Vietnam. Practical significance of this work is partly to contribute to enhancement of capabilities in developing radiation measurement instruments for experimental research as well as practical training in nuclear physics. The advantages of FPGA: overcoming ballistic deficit, decrement of serial and parallel noise, flexible in programming, control of the system by software without an interfere of hardware. The disadvantages of FPGA: requirement of good knowledge of VHDL and professional tools for development of a expected project. A new electronics module of MCA8k has been achieved. Some main results obtained from the experimental testing are as follows: differential nonlinearity (DNL) of FPGA-MCA8k approximately 1.27%, integral nonlinearity (INL) = 0.607%, time conversion ≈ 2.2 μs, deadtime (DT) is 0.75%. Data Acquisition Program MCANRI written in VC (+ +)6.0, self-executed under Windows XP environment.

  17. The Calibration of GR320 Gamma Ray Spectrometer With Manmade Radionuclide Planar Source%GR320 γ能谱仪人工核素面源刻度

    Institute of Scientific and Technical Information of China (English)

    王景丹; 倪卫冲

    2012-01-01

    This article introduces the method, experiment and application of calibration for GR320 gamma ray spectrometer with manmade nuclide planar source. Efficiency parameter of Cesium-137 and Cobalt-60 manmade nuclide, was obtained by simulating the infinite planar source with finite planar source, and the GR320 gamma ray spectrometer can detect the surface specific activity of Cesium-137 and Cobalt-60 in surveying the gamma ray radiation of environment. By checking "airborne hot-point" in Xinjiang with GR320 gamma ray spectrometer, the airborne anomaly was validated with Cesium-137, and the was cor-respondant to the in-situ tested result of HPGe spectrometer. Therefore the method can be used to calibrate other-type portable gamma ray spectrometer and other manmade nuclide planar source.%介绍了GR320 γ能谱仪人工核素面源刻度原理和方法、刻度实验过程以及对刻度结果的应用.通过人工核素小面源模拟大面源的刻度,得到人工核素137Cs和60Co面源的效率因子,使GR320 γ能谱仪在进行环境放射性γ辐射水平调查中能够定量给出人工核素137Cs和60Co的面活度.对新疆某地航测异常的地面验证测量结果表明,该航测异常地表确实存在人工核素137Cs,且GR320γ能谱仪测量的面活度结果与该异常就地HPGe谱仪的测量结果基本相符.此法可推广到其它型号的便携式γ能谱仪的刻度,也可扩展到其它人工核素面源的刻度.

  18. 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.

  19. A comparative study of LaBr3(Ce3+) 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(Ce3+) 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(Ce3+) 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(Ce3+) 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.

  20. Total Absorption Gamma-Ray Spectroscopy of 87Br, 88Br and 94Rb Beta-Delayed Neutron Emitters

    CERN Document Server

    Valencia, E; Algora, A; Agramunt, J; Rubio, B; Rice, S; Gelletly, W; Regan, P; Zakari-Issoufou, A -A; Fallot, M; Porta, A; Rissanen, J; Eronen, T; Aysto, J; Batist, L; Bowry, M; Bui, V M; Caballero-Folch, R; Cano-Ott, D; Elomaa, V -V; Estevez, E; Farrelly, G F; Garcia, A R; Gomez-Hornillos, B; Gorlychev, V; Hakala, J; Jordan, M D; Jokinen, A; Kolhinen, V S; Kondev, F G; Martinez, T; Mendoza, E; Moore, I; Penttila, H; Podolyak, Zs; Reponen, M; Sonnenschein, V; Sonzogni, A A

    2016-01-01

    We investigate the decay of 87Br, 88Br and 94Rb using total absorption gamma-ray spectroscopy. These important fission products are beta-delayed neutron emitters. Our data show considerable gamma-intensity, so far unobserved in high-resolution gamma-ray spectroscopy, from states at high excitation energy. We also find significant differences with the beta intensity that can be deduced from existing measurements of the beta spectrum. We evaluate the impact of the present data on reactor decay heat using summation calculations. Although the effect is relatively small it helps to reduce the discrepancy between calculations and integral measurements of the photon component for 235U fission at cooling times in the range 1 to 100 s. We also use summation calculations to evaluate the impact of present data on reactor antineutrino spectra. We find a significant effect at antineutrino energies in the range of 5 to 9 MeV. In addition, we observe an unexpected strong probability for gamma emission from neutron unbound s...

  1. Gamma-ray flare and absorption in Crab Nebula: Lovely TeV--PeV astrophysics

    CERN Document Server

    Kohri, Kazunori; Ioka, Kunihito

    2012-01-01

    We spectrally fit the GeV gamma-ray flares recently-observed in the Crab Nebula by considering a small blob Lorentz-boosted towards us. We point out that the corresponding inverse-Compton flare at TeV--PeV region is more enhanced than synchrotron by a Lorentz factor square \\sim \\Gamma^2, which is already excluding \\Gamma \\gtrsim 200 and will be detected by future TeV - PeV observatories, CTA, Tibet AS + MD and LHAASO for \\Gamma \\gtrsim 30. We also show that PeV photons emitted from the Crab Nebula are absorbed by Cosmic Microwave Background radiation through electron-positron pair creation.

  2. NS HEND instrument is the gamma-ray and neutrom spectrome-ter for studing of Phobos surface composition from Russian "Pfobos-Grunt" massion

    Science.gov (United States)

    Kozyrev, Alexander

    The Neutron Spectrometer HEND (NS HEND) has been proposed for studying elemental composition of Phobos (the Mars's moon) regolith by "Phobos-Grunt" mission. NS HEND have been se-lected by the Federal Space Agency of Russia for the Lander of the "Phobos-Grunt" mission scheduled for launch in 2009. The shallow subsurface of Phobos might be studied by obser-vations of induced nuclear gamma-ray lines and neutron emis-sion. Secondary gammarays and neutrons are produced by en-ergetic Galactic Cosmic Rays within 1-2 meter layer of subsur-face. The knowledge of the spectral density of neutrons in addi-tion to measurements of nuclear gamma lines allows to decon-volve concentrations of soil-forming elements. That is why nu-clear instruments include both the segment for detection of gamma ray lines and segment of neutron spectrometer for the measurement of the neutron leakage spectra. Moreover, meas-urements of neutrons and 2.2 MeV line will also allow to study the content of hydrogen within subsurface layer about 1 meter deep. The concept of NS HEND instrument is based on HEND instru-ment onboard NASA's Mars Odyssey mission launched in 2001 year, which is successfully operating on Mars orbit. Additional element of NS HEND instrument in comparison with HEND is gamma-ray spectrometer, which allows to measure gamma-ray lines together with neutrons from the surface of Phobos. NS HEND will be proto-flight instrument for the Mercury Gamma and Neutron Spectrometer MGNS, which is under development now for ESA's BepiColombo mission to Mercury scheduled in 2013. The total mass for this instrument is less then 3.8 kg and the power consumption is less than 8.0 W. Instrument NS HEND includes the set of three 3 He propor-tional counters inside polyethylene and cadmium enclosures for measurements of thermal and epithermal neutrons, scintillation stilben crystal for measurements of fast and high energy neu-trons with energies from 0.5 MeV up 10 MeV and scintillation crystal of LaBr3 for

  3. Applications of LaBr3(Ce) Gamma-ray Spectrometer Arrays for Nuclear Spectroscopy and Radionuclide Assay

    Science.gov (United States)

    Regan, PH; Shearman, R.; Daniel, T.; Lorusso, G.; Collins, SM; Judge, SM; Bell; Pearce, AK; Gurgi, LA; Rudigier, M.; Podolyák, Zs; Mărginean, N.; Mărginean, R.; Kisyov, S.

    2016-10-01

    An overview of the use of discrete energy gamma-ray detectors based on cerium- doped LaBr3 scintillators for use in nuclear spectroscopy is presented. This review includes recent applications of such detectors in mixed, 'hybrid' gamma-ray coincidence detection arrays such ROSPHERE at IFIN-HH, Bucharest; EXILL+FATIMA at ILL Grenoble, France; GAMMASPHERE+FATIMA at Argonne National Laboratory, USA; FATIMA + EURICA, at RIKEN, Japan; and the National Nuclear Array (NANA) at the UK's National Physical Laboratory. This conference paper highlights the capabilities and limitations of using these sub-nanosecond 'fast-timing', medium-resolution gamma-ray detectors for both nuclear structure research and radionuclide standardisation. Potential future application of such coincidence scintillator arrays in measurements of civilian nuclear fuel waste evaluation and assay is demonstrated using coincidence spectroscopy of a mixed 134,7Cs source.

  4. Influence of Gamma-Ray Irradiation on Absorption and Fluorescent Spectra of Nd:YAG and Yb:YAG Laser Crystals

    Institute of Scientific and Technical Information of China (English)

    SUN Dun-Lu; ZHANG Qing-Li; XIAO Jing-Zhong; LUO Jian-Qiao; JIANG Hai-He; YIN Shao-Tang

    2008-01-01

    We investigate the influence of gamma-ray irradiation on the absorption and fluorescent spectra of Nd3+ : Y3Al5O12 (Nd:YAG) and Yb3+ :Y3Al5O12 (Yb:YAG) crystals grown by the Czochralski method. Two additional absorption (AA) bands induced by gamma-ray irradiation appear at 255nm and 340nm. The former is eontributed due to Fe3+ impurity, the latter is due to Fe2+ ions and F-type colour centres. The intensity of the excitation and emission spectra as well as the fluorescent lifetime of Nd:YAG crystal decrease after the irradiation of 100 Mrad gamma-ray. In contrast, the same dose irradiation does not impair the fluorescent properties of Yb: YA G crystal. These results indicate that Yb: YA G crystal possesses the advantage over Nd: YA G crystal that has better reliability for applications in harsh radiant environment.

  5. Multifractal modelling and spectrum analysis: Methods and applications to gamma ray spectrometer data from southwestern Nova Scotia, Canada

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Multifractal spectrum, autocorrelation/semivariogram and power spectrum are three dif- ferent functions characterizing a field or measure from different aspects. These functions are interre- lated in such that the autocorrelation/semivariogram and power spectrum are related to the low order statistical moments (0 to 2 nd) which may determine the local multifractality (τ"(1)) of a multifractal measure. A better understanding of the interrelationships among these three functions is important because, on one hand, the multifractal modelling characterizes a multifractal measure in a more de- tailed manner since it involves moments of all orders. On the other hand, the commonly used semivariogram and power spectrum functions can be used as alternatives to study the dominant mul- tifractal properties around the mean measure. Moreover, semivariogram and power-spectrum func- tions provide spatial and spectral information, which is highly valued in geological applications. A new fractal relation found between area and power-spectrum will be useful for investigation of new meth- ods of spatial-spectral analysis for pattern recognition, anomaly separation, classification, etc. These results have been demonstrated with the case study of modelling gamma ray spectrometer data from the mineral district, southwestern Nova Scotia, Canada. The results have shown that the values of uranium (U), thorium (Th) and potassium (K) may possess monofractal properties whereas the ratios of these values show high multifractality. The values of the ratios U/K and U/Th show relatively large variances and may provide more information for distinguishing the distinct phases of the granites, country rocks as well as possible gold mineralization-associated regional hydrothermal alteration zones. In addition, the power spectra for U, Th, K, U/Th and U/K consistently show two distinct power-law relationships for two ranges of wave number 12≤ω≤160 km and 0≤ω≤12 km. These properties might

  6. Helium in natal HII regions: the origin of the X-ray absorption in gamma-ray burst afterglows

    CERN Document Server

    Watson, Darach; Andersen, Anja C; Fynbo, Johan P U; Gorosabel, Javier; Hjorth, Jens; Jakobsson, Páll; Krühler, Thomas; Laursen, Peter; Leloudas, Giorgos; Malesani, Daniele

    2012-01-01

    Soft X-ray absorption in excess of Galactic is observed in the afterglows of most gamma-ray bursts (GRBs), but the correct solution to its origin has not been arrived at after more than a decade of work, preventing its use as a powerful diagnostic tool. We resolve this long-standing problem and find that He in the GRB's host HII region is responsible for most of the absorption. We show that the X-ray absorbing column density (N_Hx) is correlated with both the neutral gas column density and with the optical afterglow extinction (Av). This correlation explains the connection between dark bursts and bursts with high N_Hx values. From these correlations we exclude an origin of the X-ray absorption which is not related to the host galaxy, i.e. the intergalactic medium or intervening absorbers are not responsible. We find that the correlation with the dust column has a strong redshift evolution, whereas the correlation with the neutral gas does not. From this we conclude that the column density of the X-ray absorpt...

  7. Emission and absorption lines of gamma-ray bursts affected by the relativistic motion of fireball ejecta

    CERN Document Server

    Qin, Y P

    2003-01-01

    We display by numerical calculation how rest frame spectral lines appear in the observed spectrum of gamma-ray bursts due to the Doppler effect in the fireball framework. The analysis shows that: a) in the spectrum of a relativistically expanding fireball, all rest frame lines would shift to higher energy bands and would be significantly smoothed; b) rest frame weak narrow emission lines as well as narrow absorption lines and absorption line forests would be smoothed and would hardly be detectable; c) the features of rest frame broad emission lines as well as both strong and weak broad absorption lines would remain almost unchanged and therefore would be easier to detect; d) deep gaps caused by rest frame broad absorption lines would be significantly filled; e) a rest frame emission line forest would form a single broad line feature; f) the observed relative width of the rest frame very narrow line would approach $ 0.162$; g) when the Lorentz factor $\\Gamma $ is large enough, the observed line frequency $\

  8. Searching for narrow absorption and emission lines in XMM-Newton spectra of gamma-ray bursts

    CERN Document Server

    Campana, S; D'Avanzo, P; Ghirlanda, G; Melandri, A; Pescalli, A; Salafia, O S; Salvaterra, R; Tagliaferri, G; Vergani, S D

    2016-01-01

    We present the results of a spectroscopic search for narrow emission and absorption features in the X-ray spectra of long gamma-ray burst (GRB) afterglows. Using XMM-Newton data, both EPIC and RGS spectra, of six bright (fluence >10^{-7} erg cm^{-2}) and relatively nearby (z=0.54-1.41) GRBs, we performed a blind search for emission or absorption lines that could be related to a high cloud density or metal-rich gas in the environ close to the GRBs. We detected five emission features in four of the six GRBs with an overall statistical significance, assessed through Monte Carlo simulations, of <3.0 sigma. Most of the lines are detected around the observed energy of the oxygen edge at ~0.5 keV, suggesting that they are not related to the GRB environment but are most likely of Galactic origin. No significant absorption features were detected. A spectral fitting with a free Galactic column density (N_H) testing different models for the Galactic absorption confirms this origin because we found an indication of an...

  9. GEANT4 Monte Carlo simulations of sources measured with the GSI total absorption spectrometer

    CERN Document Server

    Algora, A; Taín, J L; Nacher, E; Rubio, B; Cano-Ott, D; Gadea, A

    2003-01-01

    Beta decay experiments are a primary source of information for nuclear structure studies and at the same time complementary to in-beam investigations far from stability. Although both types of experiment are mainly based on gamma-ray spectroscopy, they face different experimental problems. The solution to these experimental problems is to create a device, a Total Absorption Gamma Spectrometer (TAGS), which ideally is sensitive to the beta population of the nuclear levels rather than to the individual gamma rays. A TAGS can be constructed using a big scintillator crystal (4 pi geometry), which acts as a calorimeter for gamma-ray cascades that follow the beta-decay process. (R.P.)

  10. Proof of principle of a high-spatial-resolution, resonant-response gamma-ray detector for Gamma Resonance Absorption in 14N

    CERN Document Server

    Brandis, M; Vartsky, D; Friedman, E; Kreslo, I; Mardor, I; Dangendorf, V; Levi, S; Mor, I; Bar, D

    2011-01-01

    The development of a mm-spatial-resolution, resonant-response detector based on a micrometric glass capillary array filled with liquid scintillator is described. This detector was developed for Gamma Resonance Absorption (GRA) in 14N. GRA is an automatic-decision radiographic screening technique that combines high radiation penetration (the probe is a 9.17 MeV gamma ray) with very good sensitivity and specificity to nitrogenous explosives. Detailed simulation of the detector response to electrons and protons generated by the 9.17 MeV gamma-rays was followed by a proof-of-principle experiment, using a mixed gamma-ray and neutron source. Towards this, a prototype capillary detector was assembled, including the associated filling and readout systems. Simulations and experimental results indeed show that proton tracks are distinguishable from electron tracks at relevant energies, on the basis of a criterion that combines track length and light intensity per unit length.

  11. Time variations of an absorption feature in the spectrum of the gamma-ray burst on 1980 April 19

    Science.gov (United States)

    Dennis, B. R.; Frost, K. J.; Kiplinger, A. L.; Orwig, L. E.; Desai, U.; Cline, T. L.

    1982-01-01

    The photon number spectrum integrated over the impulsive part of the event is shown to fit a thermal bremsstrahlung function with a temperature of 330 + or - 70 keV at energies between 151 and 487 keV. At lower energies, the data points lie considerably below this function, indicating a broad absorption feature extending down to values less than or equal to 28 keV, the lowest energy measured. The upper energy of this absorption feature varies from 100 to 150 keV on a time scale less than or equal to 0.5 s. This event is interpreted as a typical gamma ray burst, even though it is still considered remotely possible that it is of solar origin. The spectral features, together with their variability, are interpreted in terms of electron interactions at the cyclotron resonance frequency in magnetic fields of 10 to the 12th - 10 to the 13th gauss close to the surface of a neutron star.

  12. Monte Carlo simulation of muon-induced background of an anti-Compton gamma-ray spectrometer placed in a surface and underground laboratory

    CERN Document Server

    Vojtyla, P

    2005-01-01

    Simulations of cosmic ray muon induced background of an HPGe detector placed inside an anti-Compton shield on the surface and in shallow underground is described. Investigation of several model set-ups revealed some trends useful for design of low-level gamma-ray spectrometers. It has been found that background spectrum of an HPGe detector can be scaled down with the shielding depth. No important difference is observed when the same set-up of the anti-Compton spectrometer is positioned horizontally or vertically. A cosmic-muon rejection factor of at least 40 (at around 1 MeV) can be reached when the anti-Compton suppression is operational. The cosmicmuon background can be reduced to such a level that other background components prevail, like those from the residual contamination of the detector and shield materials and/or from radon, especially for the underground facilities.

  13. An error budget for digital soil mapping using proximally sensed EM induction and remotely sensed gamma-ray spectrometer data

    Science.gov (United States)

    Huang, Jingyi; Bishop, Thomas; Triantafilis, John

    2016-04-01

    The cation exchange capacity (CEC) of soil is widely used for agricultural assessment because it is a measure of fertility and an indicator of structural stability. However, measurement of CEC is time consuming. Whilst geostatistical methods have been used, a large number of samples must be collected. Using pedometric methods and specifically coupling easy-to-measure ancillary data with CEC have improved efficiency in spatial prediction. The evaluation of mapping uncertainty has not been considered, however. In this study, we use an error budget procedure to quantify the relative contributions that model, input and covariate error make to prediction error of a digital map of CEC using gamma-ray spectrometry and apparent electrical conductivity (ECa) data. The error budget uses empirical best linear unbiased prediction (E-BLUP) and conditional simulation to produce numerous realizations of the data and their underlying errors. Linear mixed models (LMM) estimated by residual maximum likelihood (REML) is used to create the prediction models. Results show that the combined error of model (5.07 cmol(+)/kg) and input error (12.88 cmol(+)/kg) is approximately 12.93 cmol(+)/kg, which is twice as large as the standard deviation of CEC (6.8 cmol(+)/kg). The individual covariate errors caused by the gamma-ray (9.64 cmol(+)/kg) and EM error (8.55 cmol(+)/kg) are also large. To overcome the former, pre-processing techniques to improve the quality of the gamma-ray data could be considered. In terms of the EM error, this could be reduced by the use of a smaller sampling interval and in particular near the edges of the study area and also at Pedoderm boundaries.

  14. Calibration of a 7.6 cm x 7.6 cm (3 inch x 3 inch) Sodium Iodide Gamma Ray Spectrometer for Air Kerma Rate

    Energy Technology Data Exchange (ETDEWEB)

    Grasty, R.L.; Walters, B.R.B.; Hovgaard, J.; LaMarre, J.R

    2001-07-01

    An experimental procedure is described for converting a gamma ray spectral measurement from a 7.6 cm x 7.6 cm (3 inch x 3 inch) sodium iodide (NaI) detector to air kerma rate. The calibration procedure involves measuring the energy deposited in the detector using 10 radioactive sources of known activity covering an energy range from 60 keV to 1836 keV. For each of the 10 sources, gamma ray spectra were measured with the source at different angles to the detector axis. The total energy deposited in the detector for the ten sources was confirmed by Monte Carlo calculations. The spectra measured at different angles were combined to produce a spectrum that would represent a homogeneous semi-infinite source of radiation. The resultant spectrum was then subdivided into 10 energy regions. Based on the known air kerma rates due to the sources, a calibration coefficient was calculated for each of the 10 energy regions. These calibration coefficients could then be used to convert the energy deposited in the 10 regions of an unknown spectrum to air kerma rate. The calibration procedure was confirmed by comparing the results from the detector with those from calibrated collimated beams of {sup 137}Cs and {sup 60}Co. A comparison of measurements using a calibrated pressurised ionisation chamber with those from a similar NaI spectrometer in Finland provided additional confirmation of the calibration procedure. (author)

  15. Cosmic gamma ray detection and discovery potential with the AMS-2 spectrometer; Detection de rayons {gamma} cosmiques et potentiel de decouvertes avec le spectrometre AMS-02

    Energy Technology Data Exchange (ETDEWEB)

    Girard, L

    2004-12-15

    Yet designed to measure charged component of the cosmic rays, the foreseen Alpha Magnetic Spectrometer (AMS-02) could also release {gamma}-ray studies, in the energy range from GeV to TeV, using the tracker system, for {gamma}-rays converted in e{sup +}e{sup -} pair, and the electromagnetic calorimeter. In the first part of the thesis are described the calibrations and the performances of the engineering model of the calorimeter, obtained from the analysis of data taken during a test-beam performed at CERN in July 2002. In the second part of the thesis, the AMS-02 discovery potential for {gamma}-astrophysics is presented. While exposure maps of the {gamma}--sky are computed for one year of data taking with the {gamma}--detectors, the acceptance of the calorimeter is obtained from Monte-Carlo simulations. The AMS-02 potential is then estimated for signals from the Vela pulsar and for some supersymmetric signals from the Galactic Center. (author)

  16. 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)

  17. Environmental measurement-while-drilling-gamma ray spectrometer (EMWD-GRS) system technology demonstration plan for use at the Savannah River Site F-Area Retention Basin

    Energy Technology Data Exchange (ETDEWEB)

    Williams, C.V.; Lockwood, G.J.; Normann, R.A. [Sandia National Labs., Albuquerque, NM (United States); Gruebel, R.D. [Tech Reps, Inc., Albuquerque, NM (United States)

    1996-08-01

    The Environmental Measurement-While-Drilling-Gamma Ray Spectrometer (EMWD-GRS) system represents an innovative blend of new and existing technology that provides the capability of producing real-time environmental and drillbit data during drilling operations. This demonstration plan presents information on the EMWD-GRS technology, demonstration design, Cs-137 contamination at the Savannah River Site F-Area Retention Basin, responsibilities of demonstration participants, and the policies and procedures for the demonstration to be conducted at the Savannah River Site F-Area Retention Basin. The EMWD-GRS technology demonstration will consist of continuously monitoring for gamma-radiation contamination while drilling two horizontal boreholes below the backfilled retention basin. These boreholes will pass near previously sampled vertical borehole locations where concentrations of contaminant levels are known. Contaminant levels continuously recorded by the EMWD-GRS system during drilling will be compared to contaminant levels previously determined through quantitative laboratory analysis of soil samples.

  18. Horizontal Ampoule Growth and Characterization of Mercuric Iodide at Controlled Gas Pressures for X-Ray and Gamma Ray Spectrometers

    Energy Technology Data Exchange (ETDEWEB)

    McGregor, Douglas S. [Kansas State Univ., Manhattan, KS (United States). Semiconductor Materials and Radiological Technologies Lab., Dept. of Nuclear and Mechanical Engineering; Ariesanti, Elsa [Kansas State Univ., Manhattan, KS (United States). Semiconductor Materials and Radiological Technologies Lab., Dept. of Nuclear and Mechanical Engineering; Corcoran, Bridget [Kansas State Univ., Manhattan, KS (United States). Semiconductor Materials and Radiological Technologies Lab., Dept. of Nuclear and Mechanical Engineering

    2004-04-30

    The project developed a new method for producing high quality mercuric iodide crystals of x-ray and gamma spectrometers. Included are characterization of mercuric iodide crystal properties as a function of growth environment and fabrication and demonstration of room-temperature-operated high-resolution mercuric iodide spectrometers.

  19. Gamma-ray burst spectra

    Science.gov (United States)

    Teegarden, B. J.

    1982-01-01

    A review of recent results in gamma-ray burst spectroscopy is given. Particular attention is paid to the recent discovery of emission and absorption features in the burst spectra. These lines represent the strongest evidence to date that gamma-ray bursts originate on or near neutron stars. Line parameters give information on the temperature, magnetic field and possibly the gravitational potential of the neutron star. The behavior of the continuum spectrum is also discussed. A remarkably good fit to nearly all bursts is obtained with a thermal-bremsstrahlung-like continuum. Significant evolution is observed of both the continuum and line features within most events.

  20. New detector array - the HRIBF Modular Total Absorption Spectrometer

    Science.gov (United States)

    Wolinska-Cichocka, Marzena; Rykaczewski, Krzysztof; Karny, Marek; Kuzniak, Aleksandra; Grzywacz, Robert; Rasco, Charlie; Miller, David; Gross, Carl J.; Johnson, Jim

    2011-10-01

    The construction of a new Modular Total Absorption Spectrometer (MTAS) at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory will be presented. The total absorption gamma spectra measured with MTAS will be used to derive a true beta-feeding pattern and resulting beta strength function for fission products. In particular, the measurements of decay heat released by radioactive nuclei produced in nuclear fuels at power reactors will be performed. MTAS is made up of 19 large NaI(Tl) crystals each encapsulated with a 0.8-mm-thick carbon fiber. There are also two 1-mm- thick Silicon Strip Detectors surrounding a moving tape collector that count beta-energy loss signals. The structure is shielded by more than 1-inch of lead around MTAS which reduces background radiation significantly. MTAS efficiency for full energy deposition of gamma ray approaches nearly 90% for 300 keV gammas and over 75% for a 5 MeV gamma transition. Research supported by the DOE Office of Nuclear Physics.

  1. The Radio to Infrared Emission of Very High Redshift Gamma-Ray Bursts: Probing Early Star Formation through Molecular and Atomic Absorption Lines

    CERN Document Server

    Inoue, S; Ciardi, B; Inoue, Susumu; Omukai, Kazuyuki; Ciardi, Benedetta

    2005-01-01

    We evaluate the broadband afterglow emission of very high redshift gamma-ray bursts (GRBs) using standard relativistic blastwave models with both forward and reverse shock components. For a broad range of parameters, a generic property for GRBs at redshifts $z \\sim$ 5--30 is that the emission peaks in the millimeter to far-infrared bands with milli-Jansky flux levels, first at a few hours after the burst due to the reverse shock, and then again for several days afterwards with somewhat lower flux due to the forward shock. The radio, submillimeter and infrared continuum emission should be readily detectable out to $z \\ga 30$ by the Atacama Large Millimeter Array (ALMA), Extended Very Large Array (EVLA), Square Kilometer Array (SKA) and other facilities. For relatively bright bursts, spectroscopic measurements of molecular and atomic absorption lines due to ambient protostellar gas may be possible. Utilizing models of primordial protostellar clouds, we show that under certain conditions, appreciable absorption ...

  2. Measurement of fast neutrons and secondary gamma rays in graphite

    Energy Technology Data Exchange (ETDEWEB)

    Makarious, A.S.; El-Asyd Abdo, A.; Kansouh, W.A. [Atomic Energy Authority, Cairo (Egypt). Nuclear Research Centre; Bashter, I.I. [Zagazig Univ. (Egypt). Faculty of Science

    1996-05-01

    The spatial fluxes and energy distributions of fast neutrons, total gamma rays and secondary gamma rays transmitted through different thicknesses of graphite have been measured. The graphite samples were arranged in front of one of the horizontal channels of the ET-RR-1 reactor. Gamma ray measurements were carried out for bare, cadmium filtered and boron carbide filtered reactor beams. A fast neutron and gamma ray spectrometer with a stilbene crystal was used to measure the spectrum of fast neutrons and gamma rays. Pulse shape discrimination using the zero cross over technique was used to distinguish the proton pulses from the electron pulses. The total fast neutrons macroscopic cross section and the linear attenuation coefficient for gamma rays were derived both for the whole energy range and at different energies. The obtained values were used to calculate the relaxation lengths for fast neutrons and gamma rays. (Author).

  3. Gamma ray camera

    Science.gov (United States)

    Perez-Mendez, V.

    1997-01-21

    A gamma ray camera is disclosed 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. 6 figs.

  4. 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.

  5. Preliminary results from the high resolution gamma-ray and hard x-ray spectrometer (HIREGS) '92-'93 long duration balloon flight in Antarctica

    Energy Technology Data Exchange (ETDEWEB)

    Lin, R.P.; Feffer, P.T.; Slassi, S.; Whiteside, W.; Smith, D.M.; Hurley, K.C.; Kane, S.R.; McBride, S.; Primbsch, J.H.; Youssefi, K.; Zimmer, G. (Univ. of California, Berkeley, CA (United States)); Pelling, R.M. (Univ. of California, San Diego, CA (United States)); Cotin, F.; Lavigne, J.M.; Rouaix, G.; Vedrenne, G.; Pehl, R.; Cork, C.; Luke, P.; Madden, N.; Malone, D.

    1993-01-01

    HIREGS consists of an array of twelve 6.7 cm diameter x 6.1 cm long liquid nitrogen-cooled segmented germanium detectors enclosed in a bismuth germanate (BGO) active anticoincidence shield. A CsI front collimator defines a 24 degree FWHM field-of-view. The energy resolution is one to several keV FWHM over the instrument energy range of 20 keV to 16 MeV. HIREGS was flown on a 10-day (31 Dec 92--10 Jan 93) circumpolar balloon flight from McMurdo Station, Antarctica. 30.5 hours of observation were obtained between 31 Dec 0400-2130 UT and 1 Jan 0600-1900 UT. Because the Sun was inactive during the flight, only one small flare was detected on 31 Dec 1933 UT. Excellent high resolution [open quotes]quiet[close quotes] Sun hard X-ray and gamma-ray spectra were obtained. These provide stringent upper limits for solar gamma-ray line and hard X-ray and gamma-ray continuum emission, which in turn can constrain the storage and/or continuous acceleration of ions and electrons by the Sun.

  6. 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.

  7. 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.

  8. Nuclear Forensics using Gamma-ray Spectroscopy

    Science.gov (United States)

    Norman, E. B.

    2016-09-01

    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.

  9. SVOM gamma ray monitor

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The space-based multi-band astronomical Variable Object Monitor(SVOM) mission is dedicated to the detection,localization and broad-band study of gamma-ray bursts(GRBs) and other high-energy transient phenomena.The gamma ray monitor(GRM) onboard is designed to observe GRBs up to 5 MeV.With this instrument,one of the key GRB parameters,Epeak,can be easily measured in the hard X-ray band.It can achieve a detection rate of 100 GRBs per year which ensures the scientific output of SVOM.

  10. SVOM Gamma Ray Monitor

    CERN Document Server

    Dong, Yongwei; Li, Yanguo; Zhang, Yongjie; Zhang, Shuangnan

    2009-01-01

    The Space-based multi-band astronomical Variable Object Monitor (SVOM) mission is dedicated to the detection, localization and broad-band study of Gamma-Ray Bursts (GRBs) and other high-energy transient phenomena. The Gamma Ray Monitor (GRM) onboard is designed to observe the GRBs up to 5 MeV. With this instrument one of the key GRB parameter, Epeak, can be easily measured in the hard x-ray band. It can achieve a detection rate of 100 GRBs per year which ensures the scientific output of SVOM.

  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. 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.

  13. Gamma rays from Galactic pulsars

    OpenAIRE

    2014-01-01

    Gamma rays from young pulsars and milli-second pulsars are expected to contribute to the diffuse gamma-ray emission measured by the {\\it 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 show that they explain only a small fraction of the isotropic diffuse gamma-ray background.

  14. Development of a pixelated CdTe detector module for a hard-x and gamma-ray imaging spectrometer application

    Science.gov (United States)

    Galvèz, J.-L.; Hernanz, M.; Álvarez, L.; Artigues, B.; Álvarez, J.-M.; Ullán, M.; Lozano, M.; Pellegrini, G.; Cabruja, E.; Martínez, R.; Chmeissani, M.; Puigdengoles, C.

    2016-07-01

    Stellar explosions are relevant and interesting astrophysical phenomena. Since long ago we have been working on the characterization of novae and supernovae in X and gamma-rays, with the use of space missions. We have also been involved in feasibility studies of future instruments in the energy range from several keV up to a few MeV, in collaboration with other research institutes. High sensitivities are essential to perform detailed studies of cosmic explosions and cosmic accelerators, e.g., Supernovae and Classical Novae. In order to fulfil the combined requirement of high detection efficiency with good spatial and energy resolution, an initial module prototype based on CdTe pixel detectors is being developed. The detector dimensions are 12.5mm x 12.5mm x 2mm with a pixel pitch of 1mm x 1mm. Two kinds of CdTe pixel detectors with different contacts have been tested: ohmic and Schottky. Each pixel is bump bonded to a fanout board made of Sapphire substrate and routed to the corresponding input channel of the readout VATAGP7.1 ASIC, to measure pixel position and pulse height for each incident gamma-ray photon. The study is complemented by the simulation of the CdTe module performance using the GEANT 4 and MEGALIB tools, which will help us to optimise the detector design. We will report on the spectroscopy characterisation of the CdTe detector module as well as the study of charge sharing.

  15. 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 circumstance

  16. 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 circumstance

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

    NARCIS (Netherlands)

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

    2012-01-01

    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 circumstance

  18. Production cross sections of discrete gamma-ray resulting from interaction of 14. 2 MeV neutron with Pb and Bi

    Energy Technology Data Exchange (ETDEWEB)

    Wu Youngshun; Shen Ronglin; Shi Xiamin; Xing Jinqiang; Ding Dazhao

    1982-11-01

    The differential cross sections of gamma-rays produced in interation of 14.2 MeV neutron with natural lead and bismuth have been measured at 55/sup 0/ (lab). The complete shield Ge (Li) spectrometer with time-of-flight technique gated by associated particle in T(d,n) reaction was used. The gamma-ray spectra from 14.2 MeV neutron interactions with /sup 238/U and natural Tungsten have been measured as well. For Pb and Bi, tens of discrete gamma-rays were identified. Some of thme have not been reported in previous work. The effects of attenuation and multiple scattering of neutron and the gamma-ray self-absorption in sample are corrected by Monte-Carlo method. The experimental results are compared with others.

  19. 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.

  20. 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.

  1. (60)Co in cast steel matrix: A European interlaboratory comparison for the characterisation of new activity standards for calibration of gamma-ray spectrometers in metallurgy.

    Science.gov (United States)

    Tzika, Faidra; Burda, Oleksiy; Hult, Mikael; Arnold, Dirk; Marroyo, Belén Caro; Dryák, Pavel; Fazio, Aldo; Ferreux, Laurent; García-Toraño, Eduardo; Javornik, Andrej; Klemola, Seppo; Luca, Aurelian; Moser, Hannah; Nečemer, Marijan; Peyrés, Virginia; Reis, Mario; Silva, Lidia; Šolc, Jaroslav; Svec, Anton; Tyminski, Zbigniew; Vodenik, Branko; Wätjen, Uwe

    2016-08-01

    Two series of activity standards of (60)Co in cast steel matrix, developed for the calibration of gamma-ray spectrometry systems in the metallurgical sector, were characterised using a European interlaboratory comparison among twelve National Metrology Institutes and one international organisation. The first standard, consisting of 14 disc shaped samples, was cast from steel contaminated during production ("originally"), and the second, consisting of 15 similar discs, from artificially-contaminated ("spiked") steel. The reference activity concentrations of (60)Co in the cast steel standards were (1.077±0.019) Bqg(-1) on 1 January 2013 12h00 UT and (1.483±0.022) Bqg(-1) on 1 June 2013 12h00 UT, respectively.

  2. 镍合金对γ射线吸收系数的测量与分析%Gamma Ray Absorption Coefficient of Measurement and Analysis on Nickel Alloy

    Institute of Scientific and Technical Information of China (English)

    郑贤利; 王俊霖; 赵焱; 熊绮丽; 汪资深; 杨君

    2013-01-01

    采用BH1324多道及BH1220智能定标器等设备测量了2种型号的镍合金和铅对不同能量γ射线的吸收系数.实验结果表明,镍合金对γ射线的质量吸收系数随能量的增加减少较缓慢,在能量较高的区域质量吸收系数与铅的相近,因此可用镍合金作为γ射线的屏蔽材料.%The absorption coefficients of different energy gamma - ray on the two types of nickel alloy and lead are measured by BH1324 and BH1220 devices. The experimental results show that the mass - absorption coefficient of nickel alloy decreases slowly with the increase of gamma - ray energy, and the values are close to these of lead in the higher energy region. So nickel alloys are suitable to replace lead as the shielding materials for gamma rays.

  3. Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes

    CERN Document Server

    Marisaldi, M; Trois, A; Giuliani, A; Tavani, M; Labanti, C; Fuschino, F; Bulgarelli, A; Longo, F; Barbiellini, G; Del Monte, E; Moretti, E; Trifoglio, M; Costa, E; Caraveo, P; Cattaneo, P W; Chen, A; D'Ammando, F; De Paris, G; Di Cocco, G; Di Persio, G; Donnarumma, I; Evangelista, Y; Feroci, M; Ferrari, A; Fiorini, M; Froysland, T; Galli, M; Gianotti, F; Lapshov, I; Lazzarotto, F; Lipari, P; Mereghetti, S; Morselli, A; Pacciani, L; Pellizzoni, A; Perotti, F; Picozza, P; Piano, G; Pilia, M; Prest, M; Pucella, G; Rapisarda, M; Rappoldi, A; Rubini, A; Sabatini, S; Soffitta, P; Striani, E; Vallazza, E; Vercellone, S; Vittorini, V; Zambra, A; Zanello, D; Antonelli, L A; Colafrancesco, S; Cutini, S; Giommi, P; Lucarelli, F; Pittori, C; Santolamazza, P; Verrecchia, F; Salotti, L; 10.1103/PhysRevLett.105.128501

    2010-01-01

    Terrestrial Gamma-Ray Flashes (TGFs) are very short bursts of high energy photons and electrons originating in Earth's atmosphere. We present here a localization study of TGFs carried out at gamma-ray energies above 20 MeV based on an innovative event selection method. We use the AGILE satellite Silicon Tracker data that for the first time have been correlated with TGFs detected by the AGILE Mini-Calorimeter. We detect 8 TGFs with gamma-ray photons of energies above 20 MeV localized by the AGILE gamma-ray imager with an accuracy of 5-10 degrees at 50 MeV. Remarkably, all TGF-associated gamma rays are compatible with a terrestrial production site closer to the sub-satellite point than 400 km. Considering that our gamma rays reach the AGILE satellite at 540 km altitude with limited scattering or attenuation, our measurements provide the first precise direct localization of TGFs from space.

  4. 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)

  5. Gamma-rays as probes of the Universe

    CERN Document Server

    Horns, Dieter

    2016-01-01

    The propagation of $\\gamma$ rays over very large distances provides new insights on the intergalactic medium and on fundamental physics. On their path to the Earth, $\\gamma$ rays can annihilate with diffuse infrared or optical photons of the intergalactic medium, producing $e^+ \\, e^-$ pairs. The density of these photons is poorly determined by direct measurements due to significant galactic foregrounds. Studying the absorption of $\\gamma$ rays from extragalactic sources at different distances allows the density of low-energy diffuse photons to be measured. Gamma-ray propagation may also be affected by new phenomena predicted by extensions of the Standard Model of particle physics. Lorentz Invariance is violated in some models of Quantum Gravity, leading to an energy-dependent speed of light in vacuum. From differential time-of-flight measurements of the most distant $\\gamma$-ray bursts and of flaring active galactic nuclei, lower bounds have been set on the energy scale of Quantum Gravity. Another effect tha...

  6. Radial position of single-site gamma-ray interactions from a parametric pulse shape analysis of germanium detector signals

    CERN Document Server

    Orrell, J L; Cooper, M W; Kephart, J D; Seifert, C E; Orrell, John L.; Aalseth, Craig E.; Cooper, Matthew W.; Kephart, Jeremy D.; Seifert, Carolyn E.

    2007-01-01

    Pulse shape analysis of germanium gamma-ray spectrometer signals can yield information on the radial position of individual gamma-ray interactions within the germanium crystal. A parametric pulse shape analysis based on calculation of moments of the reconstructed current pulses from a closed-ended coaxial germanium detector is used to preferentially select single-site gamma-ray interactions. The double escape peak events from the 2614.5 keV gamma-ray of 208-Tl are used as a training set to optimize the single-site event selection region in the pulse shape parameter space. A collimated source of 320.1 keV gamma-rays from 51-Cr is used to scan different radial positions of the same semi-coaxial germanium detector. The previously trained single-site selection region is used to preferentially identify the single-site photoelectric absorption events from the 320.1 keV full-energy peak. From the identified events, a comparison of the pulse shape parameter space distributions between different scan positions allows ...

  7. 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. ...

  8. Gamma-ray emission from individual classical novae

    CERN Document Server

    Gómez-Gomar, J; José, J; Isern, J

    1997-01-01

    Classical novae are important producers of radioactive nuclei, such as be7, n13, f18, na22 and al26. The disintegration of these nuclei produces positrons (except for be7) that through annihilation with electrons produce photons of energies 511 keV and below. Furthermore, be7 and na22 decay producing photons with energies of 478 keV and 1275 keV, respectively, well in the gamma-ray domain. Therefore, novae are potential sources of gamma-ray emission. The properties of gamma-ray spectra and gamma-ray light curves (for the continuum and for the lines at 511, 478 and 1275 keV) have been analyzed, with a special emphasis on the difference between carbon-oxygen and oxygen-neon novae. Predictions of detectability of individual novae by the future SPI spectrometer on board the INTEGRAL satellite are made.

  9. 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

  10. Possible distance indicators in gamma-ray pulsars

    Institute of Scientific and Technical Information of China (English)

    Wei Wang

    2011-01-01

    Distance measurement of gamma-ray pulsars is a current challenge in pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 70 gamma-ray pulsars including 24 new gamma-selected pulsars with almost no distance information. We study the relation between gammaray emission efficiency (η = Lγ/E) and pulsar parameters for young radio-selected gamma-ray pulsars with known distance information in the first gamma-ray pulsar catalog reported by Fermi/LAT. We have introduced three generation-order parameters to describe the gamma-ray emission properties of pulsars, and find a strong correlation of rη- ζ3, a generation-order parameter which reflects γ-ray photon generation in the pair cascade processes induced by magnetic field absorption in a pulsar's magnetosphere.A good correlation of η- BLC, the magnetic field at the light cylinder radius, is also found. These correlations are the distance indicators in gamma-ray pulsars used to evaluate distances for gamma-selected pulsars. Distances of 25 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. The physical origin of the correlations may also be interesting for pulsar studies.

  11. Gamma-ray-selected AGN

    Science.gov (United States)

    Giommi, Paolo

    2016-08-01

    The gamma-ray band is the most energetic part of the electromagnetic spectrum. As such it is also where selection effects are most severe, as it can only be reached by the most extreme non-thermal AGN. Blazars, with their emission dominated by non-thermal blue-shifted radiation arising in a relativistic jet pointed in the direction of the observer, naturally satisfy this though requirement. For this reason, albeit these sources are intrisically very rare (orders of magnitude less abundant than radio quiet AGN of the same optical magnitude) they almost completely dominate the extragalactic gamma-ray and very high energy sky. I will discuss the emission of different types of blazars and the selection effects that are at play in the gamma-ray band based on recent results from the current generation of gamma-ray astronomy satellites, ground-based Cherenkov telescopes, and Monte Carlo simulations.

  12. A wide spectral range photoacoustic aerosol absorption spectrometer.

    Science.gov (United States)

    Haisch, C; Menzenbach, P; Bladt, H; Niessner, R

    2012-11-06

    A photoacoustic spectrometer for the measurement of aerosol absorption spectra, based on the excitation of a pulsed nanosecond optical parametrical oscillator (OPO), will be introduced. This spectrometer is working at ambient pressure and can be used to detect and characterize different classes of aerosols. The spectrometer features a spectral range of 410 to 2500 nm and a sensitivity of 2.5 × 10(-7) m(-1) at 550 nm. A full characterization of the system in the visible spectral range is demonstrated, and the potential of the system for near IR measurement is discussed. In the example of different kinds of soot particles, the performance of the spectrometer was assessed. As we demonstrate, it is possible to determine a specific optical absorption per particle by a combination of the new spectrometer with an aerosol particle counter.

  13. Gamma-ray Pulsar Revolution

    CERN Document Server

    Caraveo, Patrizia A

    2013-01-01

    Isolated Neutron Stars (INSs) were the first sources identified in the field of high-energy gamma-ray astronomy. At first, in the 70s, there were only two identified sources, the Crab and Vela pulsars. However, although few in number, these objects were crucial in establishing the very concept of a gamma-ray source. Moreover, they opened up significant discovery space both in the theoretical and phenomenological fronts. The need to explain the copious gamma-ray emission of these pulsars led to breakthrough developments in understanding the structure and physics of neutron star magnetospheres. In parallel, the 20-year-long chase to understand the nature of Geminga unveiled the existence of a radio-quiet, gamma-ray-emitting, INS, adding a new dimension to the INS family. Today we are living through an extraordinary time of discovery. The current generation of gamma-ray detectors has vastly increased the population of known of gamma-ray-emitting neutron stars. The 100 mark was crossed in 2011 and we are now appr...

  14. 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.

  15. 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 ...

  16. Curved crystal study of de-excitation gamma rays in /sup 184/W following neutron capture

    Energy Technology Data Exchange (ETDEWEB)

    Davidson, W.F.; Reich, C.W.; Greenwood, R.C.; Koch, C.W.

    1981-01-01

    The capture ..gamma..-ray spectrum was studied using the curved-crystal ..gamma..-ray spectrometers installed at the High Flux Reactor of the ILL in Grenoble. Approximately 150 ..gamma..-ray transitions, from approx. 85 keV to 2.33 Mev, were assigned to /sup 184/W. A partial level scheme of /sup 184/W, showing the first four excited positive-parity bands and their de-exciting ..gamma..-ray transitions as observed in this study, is shown. (WHK)

  17. Extragalactic Gamma-Ray Astrophysics

    CERN Document Server

    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...

  18. 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.

  19. Terrestrial gamma-ray flashes

    Energy Technology Data Exchange (ETDEWEB)

    Marisaldi, Martino, E-mail: marisaldi@iasfbo.inaf.it [INAF-IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Fuschino, Fabio; Labanti, Claudio [INAF-IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Tavani, Marco [INAF-IASF Roma, Via Fosso del Cavaliere 100, I-00133 Roma (Italy); Argan, Andrea [INAF, Viale del Parco Mellini 84, 00136 Roma (Italy); Del Monte, Ettore [INAF-IASF Roma, Via Fosso del Cavaliere 100, I-00133 Roma (Italy); Longo, Francesco; Barbiellini, Guido [Dipartimento di Fisica Università di Trieste and INFN Trieste, via A. Valerio 2, I-34127 Trieste (Italy); Giuliani, Andrea [INAF-IASF Milano, Via Bassini 15, I-20133 Milano (Italy); Trois, Alessio [INAF Osservatorio Astronomico di Cagliari, loc. Poggio dei Pini, strada 54, I-09012 Capoterra (Italy); Bulgarelli, Andrea; Gianotti, Fulvio; Trifoglio, Massimo [INAF-IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy)

    2013-08-21

    Lightning and thunderstorm systems in general have been recently recognized as powerful particle accelerators, capable of producing electrons, positrons, gamma-rays and neutrons with energies as high as several tens of MeV. In fact, these natural systems turn out to be the highest energy and most efficient natural particle accelerators on Earth. Terrestrial Gamma-ray Flashes (TGFs) are millisecond long, very intense bursts of gamma-rays and are one of the most intriguing manifestation of these natural accelerators. Only three currently operative missions are capable of detecting TGFs from space: the RHESSI, Fermi and AGILE satellites. In this paper we review the characteristics of TGFs, including energy spectrum, timing structure, beam geometry and correlation with lightning, and the basic principles of the associated production models. Then we focus on the recent AGILE discoveries concerning the high energy extension of the TGF spectrum up to 100 MeV, which is difficult to reconcile with current theoretical models.

  20. Zeptosecond $\\gamma$-ray pulses

    CERN Document Server

    Klaiber, Michael; Keitel, Christoph H

    2007-01-01

    High-order harmonic generation (HHG) in the relativistic regime is employed to obtain zeptosecond pulses of $\\gamma$-rays. The harmonics are generated from atomic systems in counterpropagating strong attosecond laser pulse trains of linear polarization. In this setup recollisions of the ionized electrons can be achieved in the highly relativistic regime via a reversal of the commonly deteriorating drift and without instability of the electron dynamics such as in a standing laser wave. As a result, coherent attosecond $\\gamma$-rays in the 10 MeV energy range as well as coherent zeptosecond $\\gamma$-ray pulses of MeV photon energy for time-resolved nuclear spectroscopy become feasible.

  1. 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.

  2. Corrective optics for diffraction of {gamma}-rays

    Energy Technology Data Exchange (ETDEWEB)

    Materna, T. [Nuclear Physics Institute, University of Cologne, Zuelpicher Str. 77, D-50937 Cologne (Germany) and Institut Laue-Langevin, F-38042 Grenoble, Cedex 9 (France)]. E-mail: materna@ill.fr; Bruyneel, B. [Nuclear Physics Institute, University of Cologne, Zuelpicher Str. 77, D-50937 Cologne (Germany); Jolie, J. [Nuclear Physics Institute, University of Cologne, Zuelpicher Str. 77, D-50937 Cologne (Germany); Linnemann, A. [Nuclear Physics Institute, University of Cologne, Zuelpicher Str. 77, D-50937 Cologne (Germany); Warr, N. [Nuclear Physics Institute, University of Cologne, Zuelpicher Str. 77, D-50937 Cologne (Germany); Boerner, H.G. [Institut Laue-Langevin, F-38042 Grenoble, Cedex 9 (France); Jentschel, M. [Institut Laue-Langevin, F-38042 Grenoble, Cedex 9 (France); Mutti, P. [Institut Laue-Langevin, F-38042 Grenoble, Cedex 9 (France); Simpson, G. [Institut Laue-Langevin, F-38042 Grenoble, Cedex 9 (France)

    2006-12-21

    A new method to correct imperfect bending of curved crystals used for {gamma}-ray diffraction spectroscopy is presented. It relies on using position-sensitive segmented Ge-detectors and permits the determination of the emission area of each {gamma}-ray from the crystals and therefore an off-line correction of bending imperfections as if the crystals were divided into independent 2x2 mm{sup 2} bent crystals. A first experiment using the GAMS-5 spectrometer (Institut Laue-Langevin) shows proof of the principle of the method.

  3. Differential optical absorption spectrometer for measurement of tropospheric pollutants.

    Science.gov (United States)

    Evangelisti, F; Baroncelli, A; Bonasoni, P; Giovanelli, G; Ravegnani, F

    1995-05-20

    Our institute has recently developed a differential optical absorption spectrometry system called the gas analyzer spectrometer correlating optical absorption differences (GASCOAD), which features as a detector a linear image sensor that uses an artificial light source for long-path tropospheric-pollution monitoring. The GASCOAD, its method of eliminating interference from background sky light, and subsequent spectral analysis are reported and discussed. The spectrometer was used from 7 to 22 February 1993 in Milan, a heavily polluted metropolitan area, to measure the concentrations of SO(2), NO(2), O(3), and HNO(2) averaged over a 1.7-km horizontal light path. The findings are reported and briefly discussed.

  4. Gamma-ray Imaging Methods

    Energy Technology Data Exchange (ETDEWEB)

    Vetter, K; Mihailescu, L; Nelson, K; Valentine, J; Wright, D

    2006-10-05

    In this document we discuss specific implementations for gamma-ray imaging instruments including the principle of operation and describe systems which have been built and demonstrated as well as systems currently under development. There are several fundamentally different technologies each with specific operational requirements and performance trade offs. We provide an overview of the different gamma-ray imaging techniques and briefly discuss challenges and limitations associated with each modality (in the appendix we give detailed descriptions of specific implementations for many of these technologies). In Section 3 we summarize the performance and operational aspects in tabular form as an aid for comparing technologies and mapping technologies to potential applications.

  5. 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

  6. Novae in gamma-rays

    CERN Document Server

    Hernanz, M

    2013-01-01

    Classical novae produce radioactive nuclei which are emitters of gamma-rays in the MeV range. Some examples are the lines at 478 and 1275 keV (from 7Be and 22Na) and the positron-electron annihilation emission (511 keV line and a continuum below this energy, with a cut-off at 20-30 keV). The analysis of gamma-ray spectra and light curves is a potential unique and powerful tool both to trace the corresponding isotopes and to give insights on the properties of the expanding envelope determining its transparency. Another possible origin of gamma-rays is the acceleration of particles up to very high energies, so that either neutral pions or inverse Compton processes produce gamma-rays of energies larger than 100 MeV. MeV photons during nova explosions have not been detected yet, although several attempts have been made in the last decades; on the other hand, GeV photons from novae have been detected in some particular novae, in symbiotic binaries, where the companion is a red giant with a wind, instead of a main ...

  7. Short duration gamma ray bursts

    Indian Academy of Sciences (India)

    Patrick Das Gupta

    2004-10-01

    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.

  8. 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.

  9. Long-term variations in the gamma-ray background on SMM

    Science.gov (United States)

    Kurfess, J. D.; Share, G. H.; Kinzer, R. L.; Johnson, W. N.; Adams, J. H., Jr.

    1989-01-01

    Long-term temporal variations in the various components of the background radiation detected by the gamma-ray spectrometer on the Solar Maximum Mission are presented. The SMM gamma-ray spectrometer was launched in February, 1980 and continues to operate normally. The extended period of mission operations has provided a large data base in which it is possible to investigate a variety of environmental and instrumental background effects. In particular, several effects associated with orbital precession are introduced and discussed.

  10. The Gamma-ray Sky with Fermi

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, D.J. [NASA Goddard Space Flight Center, Greenbelt, Maryland, 20771 (United States)

    2013-10-15

    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, 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 clusters of galaxies. Some results include a stringent limit on Lorentz invariance violation derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure in the direction of the center of our Galaxy, and strong constraints on some Weakly Interacting Massive Particle (WIMP) models for dark matter.

  11. Cosmic Rays: What Gamma Rays Can Say

    OpenAIRE

    2014-01-01

    We will review the main channels of gamma ray emission due to the acceleration and propagation of cosmic rays, discussing the cases of both galactic and extra-galactic cosmic rays and their connection with gamma rays observations.

  12. The Gamma-ray Universe through Fermi

    Science.gov (United States)

    Thompson, David J.

    2012-01-01

    Gamma rays, the most powerful form of light, reveal extreme conditions in the Universe. The Fermi Gamma-ray Space Telescope and its smaller cousin AGILE have been exploring the gamma-ray sky for several 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 ga.nuna-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.

  13. High-resolution spectroscopy of gamma-ray transients

    Energy Technology Data Exchange (ETDEWEB)

    Cline, T.L.

    1988-09-25

    The first high-resolution spectrometer flown to observe gamma-ray bursts was launched on the ISEE-3 spacecraft over nine years ago. It recorded two events before instrument failure, giving results that were suggestive but marginal. Other studies, with coarser energy resolution, also show evidence for spectral features as well as for spectral evolution on short time scales. Absolute source strength calibration will be possible only with source identification, but understanding of the burst emission processes will surely come only from the measurements having the best spectral and temporal precision. The only high- resolution gamma-ray spectrometer now planned, here or abroad, for space flight is an instrument sequel to the ISEE-3 spectrometer, to be flown on the interplanetary 'GGS Wind' mission. Much larger and higher-sensitivity, high-resolution instruments may have their optimum opportunities in conjunction with studies of solar flares in the time frame of the solar maximum of 2002.

  14. Part I. Development of a concept inventory addressing students' beliefs and reasoning difficulties regarding the greenhouse effect, Part II. Distribution of chlorine measured by the Mars Odyssey Gamma Ray Spectrometer

    Science.gov (United States)

    Keller, John Michael

    chlorine on Mars measured by the Mars Odyssey Gamma Ray Spectrometer (GRS). The distribution of chlorine is heterogeneous across the surface, with a concentration of high chlorine centered over the Medusa Fossae Formation. The distribution of chlorine correlates positively with hydrogen and negatively with silicon and thermal inertia. Four mechanisms (aeolian, volcanic, aqueous, and hydrothermal) are discussed as possible factors influencing the distribution of chlorine measured within the upper few tens of centimeters of the surface.

  15. Distribution of iron and titanium on the lunar surface from lunar prospector gamma ray spectra

    Science.gov (United States)

    Prettyman, T.

    2001-01-01

    Gamma ray pulse height spectra acquired by the Lunar Prospector (LP) Gamma-Ray Spectrometer (GRS) contain information on the abundance of major elements in the lunar surface, including O, Si, Ti, Al, Fe, Mg, Ca, K, and Th. With the exception of Th and K, prompt gamma rays produced by cosmic ray interactions with surface materials are used to determine elemental abundance. Most of these gamma rays are produced by inelastic scattering of fast neutrons and by neutrons and by neutron capture. The production of neutron-induced gamma rays reaches a maximum deep below the surface (e.g. approximately 140g/cm2 for inelastic scattering and approximately 50 g/cm2 for capture). Consequently, gamma rays sense the bulk composition of lunar materials, in contrast to optical methods (e.g. Clementine Spectral Reflectance (CSR)), which only sample the top few microns. Because most of the gamma rays are produced deep beneath the surface, few escape unscattered and the continuum of scattered gamma rays dominates the spectrum. In addition, due to the resolution of the spectrometer, there are few well-isolated peaks and peak fitting algorithms must be used to deconvolve the spectrum on order to determine the contribution of individual elements.

  16. Gamma rays from dark matter

    CERN Document Server

    Bringmann, Torsten

    2011-01-01

    A leading hypothesis for the nature of the elusive dark matter are thermally produced, weakly interacting massive particles that arise in many theories beyond the standard model of particle physics. Their self-annihilation in astrophysical regions of high density provides a potential means of indirectly detecting dark matter through the annihilation products, which nicely complements direct and collider searches. Here, I review the case of gamma rays which are particularly promising in this respect: distinct and unambiguous spectral signatures would not only allow a clear discrimination from astrophysical backgrounds but also to extract important properties of the dark matter particles; powerful observational facilities like the Fermi Gamma-ray Space Telescope or upcoming large, ground-based Cherenkov telescope arrays will be able to probe a considerable part of the underlying, e.g. supersymmetric, parameter space. I conclude with a more detailed comparison of indirect and direct dark matter searches, showing...

  17. Fast Radio Bursts with Extended Gamma-Ray Emission?

    CERN Document Server

    Murase, Kohta; Fox, Derek B

    2016-01-01

    We consider some general implications of bright gamma-ray counterparts to fast radio bursts (FRBs). We show that, even if these manifest in only a fraction of FRBs, gamma-ray detections with current satellites (including Swift) provide stringent constraints on cosmological FRB models. If the energy is drawn from the magnetic energy of a compact object such as a magnetized neutron star, the sources should be nearby and very rare. If the intergalactic medium is responsible for the observed dispersion measure, the required gamma-ray energy is comparable to that of the early afterglow or extended emission of short gamma-ray bursts. While this can be reconciled with the rotation energy of compact objects, as expected in many merger scenarios, the prompt outflow that yields the gamma-rays is too dense for radio waves to escape. Highly-relativistic winds launched in a precursor phase, and forming a wind bubble, may avoid the scattering and absorption limits and could yield FRB emission. Largely independent of source...

  18. Terrestrial implications of cosmological gamma-ray burst models

    CERN Document Server

    Thorsett, S E

    1995-01-01

    The observation by the BATSE instrument on the Compton Gamma Ray Observatory that gamma-ray bursts (GRBs) are distributed isotropically around the Earth but nonuniformly in distance has led to the widespread conclusion that GRBs are most likely to be at cosmological distances, making them the most luminous sources known in the Universe. If bursts arise from events that occur in normal galaxies, such as neutron star binary inspirals, then they will also occur in our Galaxy about every hundred thousand to million years. The gamma-ray flux at the Earth due to a Galactic GRB would far exceed that from even the largest solar flares. The absorption of this radiation in the atmosphere would substantially increase the stratospheric nitric oxide concentration through photodissociation of N_2, greatly reducing the ozone concentration for several years through NO_x catalysis, with important biospheric effects due to increased solar ultraviolet flux. A nearby GRB may also leave traces in anomalous radionuclide abundances...

  19. DUAL Gamma-Ray Mission

    CERN Document Server

    Boggs, S; von Ballmoos, P; Takahashi, T; Gehrels, N; Tueller, J; Baring, M; Beacom, J; Diehl, R; Greiner, J; Grove, E; Hartmann, D; Hernanz, M; Jean, P; Johnson, N; Kanbach, G; Kippen, M; Knödlseder, J; Leising, M; Madejski, G; McConnell, M; Milne, P; Motohide, K; Nakazawa, K; Oberlack, U; Phlips, B; Ryan, J; Skinner, G; Starrfield, S; Tajima, H; Wulf, E; Zoglauer, A; Zych, A

    2010-01-01

    Gamma-ray astronomy presents an extraordinary scientific potential for the study of the most powerful sources and the most violent events in the Universe. In order to take full advantage of this potential, the next generation of instrumentation for this domain will have to achieve an improvement in sensitivity over present technologies of at least an order of magnitude. The DUAL mission concept takes up this challenge in two complementary ways: a very long observation of the entire sky, combined with a large collection area for simultaneous observations of Type Ia SNe. While the Wide-Field Compton Telescope (WCT) accumulates data from the full gamma-ray sky (0.1-10 MeV) over the entire mission lifetime, the Laue-Lens Telescope (LLT) focuses on 56Co emission from SNe Ia (0.8-0.9 MeV), collecting gamma-rays from its large area crystal lens onto the WCT. Two separated spacecraft flying in formation will maintain the DUAL payloads at the lens' focal distance.

  20. 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....

  1. Investigation of (235)U, (226)Ra, (232)Th, (40)K, (137)Cs, and heavy metal concentrations in Anzali international wetland using high-resolution gamma-ray spectrometry and atomic absorption spectroscopy.

    Science.gov (United States)

    Zare, Mohammad Reza; Kamali, Mahdi; Fallahi Kapourchali, Maryam; Bagheri, Hashem; Khoram Bagheri, Mahdi; Abedini, Ali; Pakzad, Hamid Reza

    2016-02-01

    Measurements of natural radioactivity levels and heavy metals in sediment and soil samples of the Anzali international wetland were carried out by two HPGe-gamma ray spectrometry and atomic absorption spectroscopy techniques. The concentrations of (235)U, (226)Ra, (232)Th, (40)K, and (137)Cs in sediment samples ranged between 1.05 ± 0.51-5.81 ± 0.61, 18.06 ± 0.63-33.36 ± .0.34, 17.57 ± 0.38-45.84 ± 6.23, 371.88 ± 6.36-652.28 ± 11.60, and 0.43 ± 0.06-63.35 ± 0.94 Bq/kg, while in the soil samples they vary between 2.36-5.97, 22.71-38.37, 29.27-42.89, 472.66-533, and 1.05-9.60 Bq/kg for (235)U, (226)Ra, (232)Th, (40)K, and (137)Cs, respectively. Present results are compared with the available literature data and also with the world average values. The radium equivalent activity was well below the defined limit of 370 Bq/kg. The external hazard indices were found to be less than 1, indicating a low dose. Heavy metal concentrations were found to decrease in order as Fe > Mn > Sr > Zn > Cu > Cr > Ni > Pb > Co > Cd. These measurements will serve as background reference levels for the Anzali wetland.

  2. Experiment Signal for Gamma-Ray Research of the Sun

    Science.gov (United States)

    Galper, Arkady; Arkhangelskaja, Irene; Arkhangelsky, Andrey; Shustov, Alexander; Ulin, Sergey; Novikov, Alexander; Grachev, Viktor; Uteshev, Ziyaetdin; Petrenko, Denis; Vlasik, Konstantin; Krivova, Kira; Dmitrenko, Valery; Chernysheva, Irina

    Description as well as physical and technical characteristics of Scientific Instrument (SI) “Signal” are presented. This equipment will be installed onboard the spacecraft (SC) “Interhelioprobe” for researching the Sun and Heliosphere at close distance. “Signal” will be developed for study cosmic gamma-rays. It consists of Xenon Gamma-Spectrometer (XeGS), the anticoincidence scintillation system and the digital electronic module. XeGS is based on cylindrical pulse ionization chamber with Frisch grid filled with high pressure xenon. Anticoincidence system will be made of polystyrene organic scintillator and silicon photomultipliers. Digital electronic module provides analyzing and data processing, collecting measured gamma-ray spectra and communication with onboard systems of SC “Interhelioprobe”. Main “Signal” scientific tasks are: begin{itemize} Research of X-ray and gamma emission in lines and continuum in energy range 30 keV - 5 MeV; begin{itemize} Study of gamma-ray bursts with Galactic and Metagalactic origin; begin{itemize} Analysis of gamma-ray lines near the Earth and Venus; begin{itemize} Charged particle fluxes registration along the spacecraft trajectory.

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

    CERN Document Server

    Leising, M

    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 annihilation emission and the detection of the Cas A supernova remnant in 44Ti radioactivity. The SPI high-resolution Ge spectrometer on INTEGRAL was launched in 2002 and continues to collect data on astrophysically-important gamma-ray lines from decays of 44Ti, 26Al, 60Fe, and positron annihilation. 44Ti decay lines from Cas A have been observed with both INTEGRAL telescopes, and constrain the expansion dynamics of the ejecta. The lack of other 44Ti remnants is a mystery. The 26Al gamma-ray line is now measured throughou...

  4. Balloon-borne gamma-ray polarimetry

    CERN Document Server

    Pearce, Mark

    2011-01-01

    The physical processes postulated to explain the high-energy emission mechanisms of compact astrophysical sources often yield polarised soft gamma rays (X-rays). PoGOLite is a balloon-borne polarimeter operating in the 25-80 keV energy band. The polarisation of incident photons is reconstructed using Compton scattering and photoelectric absorption in an array of phoswich detector cells comprising plastic and BGO scintillators, surrounded by a BGO side anticoincidence shield. The polarimeter is aligned to observation targets using a custom attitude control system. The maiden balloon flight is scheduled for summer 2011 from the Esrange Space Centre with the Crab and Cygnus X-1 as the primary observational targets.

  5. Gamma ray bursts and their afterglows

    Science.gov (United States)

    Nicuesa Guelbenzu, A.

    2017-03-01

    Gamma-Ray Bursts (GRBs) were among the greatest mysteries in modern astrophysics. They were first observed 50 years ago but it took three decades before optical counterparts could be found and the underlying physical phenomena studied in detail. GRB research represents currently one of the most rapidly growing areas in extragalactic astronomy. This is due in large part to the numerous connections that GRBs have with other disciplines like cosmology, supernovae, stellar evolution, nuclear physics, astroparticle and gravitational wave astronomy. Therefore, their study is of great importance to understand various astrophysical phenomena such as the formation of the first stars, the chemical evolution and the expansion of the Universe. Since gamma radiation can travel along cosmological distances without being affected by any possible intervening absorption, GRBs can be detected from the most distant universe, reaching redshifts up to z = 10 or more.

  6. Proximal Gamma-Ray Spectroscopy to Predict Soil Properties Using Windows and Full-Spectrum Analysis Methods

    NARCIS (Netherlands)

    Mahmood, H.S.; Hoogmoed, W.B.; Henten, van E.J.

    2013-01-01

    Fine-scale spatial information on soil properties is needed to successfully implement precision agriculture. Proximal gamma-ray spectroscopy has recently emerged as a promising tool to collect fine-scale soil information. The objective of this study was to evaluate a proximal gamma-ray spectrometer

  7. Effect of gamma rays absorbed doses and heat treatment on the optical absorption spectra of silver ion-exchanged silicate glass

    Energy Technology Data Exchange (ETDEWEB)

    Farah, Khaled, E-mail: kafarah@gmail.com [Unité de recherche: Maîtrise et développement des techniques nucléaires à caractère pacifique, Centre National des Sciences et Technologie Nucléaires, 2020 Sidi-Thabet (Tunisia); ISTLS, University of Sousse (Tunisia); Hosni, Faouzi [Unité de recherche: Maîtrise et développement des techniques nucléaires à caractère pacifique, Centre National des Sciences et Technologie Nucléaires, 2020 Sidi-Thabet (Tunisia); Academie Militaire de Fondouk Jedid, 8012 Nabeul (Tunisia); Mejri, Arbi [Unité de recherche: Maîtrise et développement des techniques nucléaires à caractère pacifique, Centre National des Sciences et Technologie Nucléaires, 2020 Sidi-Thabet (Tunisia); Boizot, Bruno [Laboratoire des Solides Irradiés, Ecole Polytechnique, Route de Saclay, 91128 Palaiseau Cedex (France); Hamzaoui, Ahmed Hichem [Centre National de Recherche en Sciences des Matériaux, B.P. 95, Hammam-Lif 2050 (Tunisia); Ben Ouada, Hafedh [Laboratoire des Interfaces et Matériaux Avancés, Faculté des Sciences, University of Monastir, Avenue de l’environnement, 5019 Monastir (Tunisia)

    2014-03-15

    Samples of a commercial silicate glass have been subjected to ion exchange at 320 °C in a molten mixture of AgNO{sub 3} and NaNO{sub 3} with molar ratio of 1:99 and 5:95 for 60 min. The ion exchange process was followed by gamma irradiation in the dose range of 1–250 kGy and heating at the temperature of 550 °C for different time periods ranging from 10 to 582 min. The spectral absorption in UV–Vis range of the Ag–Na ion exchanged glass was measured and used to determine the states of silver prevailing in the glass during the ion exchange, the gamma irradiation and the heat treatment. The gamma irradiation induced holes and electrons in the glass structure leading to the creation of a brown colour, and silver ions trapped electrons to form silver atoms. We observed the first stage of aggregation after irradiation, as well as after heating. The silver atoms diffused and then aggregated to form nanoclusters after heating at 550 °C. A characteristic band at about 430 nm was induced. The surface Plasmon absorption of silver nanoclusters in the glass indicated that the nanoclusters radius grew between 0.9 and 1.43 nm with increasing of annealing time from 10 to 242 min and then saturated. We also found that the size of aggregates depends on the value of gamma radiation absorbed dose. Contrary to what was expected, we found that 20 kGy is the optimal absorbed dose corresponding to the larger size of the aggregates which decreases for absorbed doses above 20 kGy.

  8. Effect of gamma rays absorbed doses and heat treatment on the optical absorption spectra of silver ion-exchanged silicate glass

    Science.gov (United States)

    Farah, Khaled; Hosni, Faouzi; Mejri, Arbi; Boizot, Bruno; Hamzaoui, Ahmed Hichem; Ben Ouada, Hafedh

    2014-03-01

    Samples of a commercial silicate glass have been subjected to ion exchange at 320 °C in a molten mixture of AgNO3 and NaNO3 with molar ratio of 1:99 and 5:95 for 60 min. The ion exchange process was followed by gamma irradiation in the dose range of 1-250 kGy and heating at the temperature of 550 °C for different time periods ranging from 10 to 582 min. The spectral absorption in UV-Vis range of the Ag-Na ion exchanged glass was measured and used to determine the states of silver prevailing in the glass during the ion exchange, the gamma irradiation and the heat treatment. The gamma irradiation induced holes and electrons in the glass structure leading to the creation of a brown colour, and silver ions trapped electrons to form silver atoms. We observed the first stage of aggregation after irradiation, as well as after heating. The silver atoms diffused and then aggregated to form nanoclusters after heating at 550 °C. A characteristic band at about 430 nm was induced. The surface Plasmon absorption of silver nanoclusters in the glass indicated that the nanoclusters radius grew between 0.9 and 1.43 nm with increasing of annealing time from 10 to 242 min and then saturated. We also found that the size of aggregates depends on the value of gamma radiation absorbed dose. Contrary to what was expected, we found that 20 kGy is the optimal absorbed dose corresponding to the larger size of the aggregates which decreases for absorbed doses above 20 kGy.

  9. High Redshift Gamma Ray Bursts

    Science.gov (United States)

    Gehrels, Neil

    2012-01-01

    The Swift Observatory has been detecting 100 gamma-ray bursts per year for 7 years and has greatly stimulated the field with new findings. Observations are made of the X-ray and optical afterglow from 1 minute after the burst, continuing for days. GRBs are providing a new tool to study the high redshift universe. Swift has detected several events at z>5 and one at z=9.4 giving information on metallicity, star formation rate and reionization. The talk will present the latest results.

  10. Measurements of keV-neutron capture {gamma} rays of fission products. 3

    Energy Technology Data Exchange (ETDEWEB)

    Igashira, Masayuki [Tokyo Inst. of Tech. (Japan). Research Lab. for Nuclear Reactors

    1997-03-01

    {gamma} rays from the keV-neutron capture reactions by {sup 143,145}Nd and {sup 153}Eu have been measured in a neutron energy region of 10 to 80 keV, using a large anti-Compton NaI(Tl) {gamma}-ray spectrometer and the {sup 7}Li(p,n){sup 7}Be pulsed neutron source with a 3-MV Pelletron accelerator. The preliminary results for the capture cross sections and {gamma}-ray spectra of those nuclei are presented and discussed. (author)

  11. 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)....

  12. 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.

  13. High energy gamma rays in the decay of 27h Ho166

    DEFF Research Database (Denmark)

    Hansen, P.Gregers; Wilsky, K.; Horen, D.J.;

    1961-01-01

    The gamma-ray spectrum of 27th Ho166 was re-investigated by means of a three-crystal pair-spectrometer and coincidence techniques. Two new gamma rays with energies of 1747 plusmn 5 and 1825 plusmn 5 keV establish a new level at 1826 keV in Er166. The log ft value for the beta-decay to this state...

  14. Magnetars and Gamma Ray Bursts

    CERN Document Server

    Bucciantini, N

    2012-01-01

    In the last few years, evidences for a long-lived and sustained engine in Gamma Ray Bursts (GRBs) have increased the attention to the so called millisecond-magnetar model, as a competitive alternative to the standard collapsar scenario. I will review here the key aspects of the {\\it millisecond magnetar} model for Long Duration Gamma Ray Bursts (LGRBs). I will briefly describe what constraints, present observations put on any engine model, both in term of energetic, outflow properties, and the relation with the associated Supernova (SN). For each of these I will show how the millisecond magnetar model satisfies the requirements, what are the limits of the model, how can it be further tested, and what observations might be used to discriminate against it. I will also discuss numerical results that show the importance of the confinement by the progenitor star in explaining the formation of a collimated outflow, how a detailed model for the evolution of the central engine can be built, and show that a wide varie...

  15. Gamma-ray burst models.

    Science.gov (United States)

    King, Andrew

    2007-05-15

    I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts.

  16. Resonant Absorption Mechanical Spectrometer and Its Applications in Solids

    Institute of Scientific and Technical Information of China (English)

    张进修; 龚康; 熊小敏; 丁喜冬

    2003-01-01

    An improved apparatus is developed from Ke-pendulum. This new apparatus, resonant absorption mechanical spectrometer (RAMS), can measure the internal friction of solids under a forced vibration mode and the measuring frequency can change quasi-continually from a frequency that is much lower than the resonant frequency of the pendulum system, fr, tothe one that is much higher than fr. The internal friction measurement is able to cover the frequency range from 10-3 Hz to kHz. The measurement method and the calculation formula of the internal friction measured by a RAMS in the full frequency range are derived. A series of resonant absorption peaks are observed in copper, aluminium, zinc, iron samples by the RAMS. The resonant absorption characteristics of the copper sample are studied in details. The experimental results indicate that the position (frequency) of the resonant absorption peaks are independent of the resonant frequency of the pendulum system. The reality of resonant absorption mechanical spectra is discussed and an inference based on the experimental results is presented such that the RAMS is able to characterize some feature of solid materials.

  17. Planetary Geochemistry Using Active Neutron and Gamma Ray Instrumentation

    Science.gov (United States)

    Parsons, A.; Bodnarik, J.; Evans, L.; Floyd, S.; Lim, L.; McClanahan, T.; Namkung, M.; Schweitzer, J.; Starr, R.; Trombka, J.

    2010-01-01

    The Pulsed Neutron Generator-Gamma Ray And Neutron Detector (PNG-GRAND) experiment is an innovative application of the active neutron-gamma ray technology so successfully used in oil field well logging and mineral exploration on Earth, The objective of our active neutron-gamma ray technology program at NASA Goddard Space Flight Center (NASA/GSFC) is to bring the PNG-GRAND instrument to the point where it can be flown on a variety of surface lander or rover missions to the Moon, Mars, Venus, asterOIds, comets and the satellites of the outer planets, Gamma-Ray Spectrometers have been incorporated into numerous orbital planetary science missions and, especially in the case of Mars Odyssey, have contributed detailed maps of the elemental composition over the entire surface of Mars, Neutron detectors have also been placed onboard orbital missions such as the Lunar Reconnaissance Orbiter and Lunar Prospector to measure the hydrogen content of the surface of the moon, The DAN in situ experiment on the Mars Science Laboratory not only includes neutron detectors, but also has its own neutron generator, However, no one has ever combined the three into one instrument PNG-GRAND combines a pulsed neutron generator (PNG) with gamma ray and neutron detectors to produce a landed instrument that can determine subsurface elemental composition without drilling. We are testing PNG-GRAND at a unique outdoor neutron instrumentation test facility recently constructed at NASA/GSFC that consists of a 2 m x 2 m x 1 m granite structure in an empty field, We will present data from the operation of PNG-GRAND in various experimental configurations on a known sample in a geometry that is identical to that which can be achieved on a planetary surface. We will also compare the material composition results inferred from our experiments to both an independent laboratory elemental composition analysis and MCNPX computer modeling results,

  18. γ全吸收型探测装置中子束流监视器的Geant4模拟%Geant4 Simulation of Neutron Beam Monitor in Gamma-Ray Total Absorption Facility

    Institute of Scientific and Technical Information of China (English)

    苏明; 仲启平; 郑玉来; 张奇玮; 阮锡超; 周祖英; 孔祥忠

    2009-01-01

    The relative detection efficiency of a lithium glass detector used as a neutron beam monitor in gamma-ray total absorption facility was simulated by Geant4. The neutron detection efficiency of the lithium glass detector was obtained between 10 keV and 1 MeV. Some factors affecting the efficiency were analyzed. The effect of the time delay caused by the elastic scattering upon TOF (time-of-flight) measurement, and the n-γ discrimination in different thickness lithium glass were discussed. The work will be helpful to understand better the neutron time of flight spectrum and energy spectrum from Li-glass detector which is used as a monitor of keV neutron source.%利用Geant4模拟了γ全吸收型探测装置中用于中子束流监视的锂玻璃探测器的相对探测效率,给出了锂玻璃探测器在10 keV~1 MeV区间的中子探测效率,并对影响探测效率的相关因素进行了分析,讨论了弹性散射引起的时间滞后对TOF(time-of-flight)测量的影响和不同厚度锂玻璃探测器的n-γ分辨效果.在未来使用锂玻璃探测器作为keV中子源监视器时,这项工作将为更好地理解相关中子飞行时间谱和能谱提供依据.

  19. Studying the WHIM with Gamma Ray Bursts

    CERN Document Server

    Branchini, E; Corsi, A; Martizzi, D; Amati, L; Herder, J W den; Galeazzi, M; Gendre, B; Kaastra, J; Moscardini, L; Nicastro, F; Ohashi, T; Paerels, F; Piro, L; Roncarelli, M; Takei, Y; Viel, M

    2009-01-01

    We assess the possibility to detect and characterize the physical state of the missing baryons at low redshift by analyzing the X-ray absorption spectra of the Gamma Ray Burst [GRB] afterglows, measured by a micro calorimeters-based detector with 3 eV resolution and 1000 cm2 effective area and capable of fast re-pointing, similar to that on board of the recently proposed X-ray satellites EDGE and XENIA. For this purpose we have analyzed mock absorption spectra extracted from different hydrodynamical simulations used to model the properties of the Warm Hot Intergalactic Medium [WHIM]. These models predict the correct abundance of OVI absorption lines observed in UV and satisfy current X-ray constraints. According to these models space missions like EDGE and XENIA should be able to detect about 60 WHIM absorbers per year through the OVII line. About 45 % of these have at least two more detectable lines in addition to OVII that can be used to determine the density and the temperature of the gas. Systematic error...

  20. Origin of $\\gamma$ Ray Bursters

    CERN Document Server

    Mészáros, P

    1999-01-01

    The successful discovery of X-ray, optical and radio afterglows of GRB hasmade possible the identification of host galaxies at cosmological distances.The energy release inferred in these outbursts place them among the mostenergetic and violent events in the Universe. They are thought to be theoutcome of a cataclysmic stellar collapse or compact stellar merger, leading toa relativistically expanding fireball, in which particles are accelerated atshocks and produce nonthermal radiation. The substantial agreement betweenobservations and the theoretical predictions of the fireball shock modelprovide confirmation of the basic aspects of this scenario. Among recent issuesare the collimation of the outflow and its implications for the energetics, theproduction of prompt bright flashes at wavelenghts much longer than gamma-rays,the time structure of the afterglow, its dependence on the central engine orprogenitor system behavior, and the role of the environment on the afterglow.

  1. 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...... of the spectrometer system were determined by calculating the average number of U and thorium (Th) counts per meter of borehole and comparing these with the U-Th concentrations in 1-m sections of analyzed drill core. The sensitivity and the background count rate in the uranium window varied appreciably from one hole...

  2. 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.

  3. Gamma ray spectroscopy with PPM resolving power

    CERN Document Server

    Börner, H; Mutti, P

    2002-01-01

    Applications of gamma-ray spectroscopy with ppm resolving power are presented. The extraordinary resolution allows via the Gamma Ray Induced Doppler broadening (GRID) technique to determine lifetimes of excited nuclear levels. This has contributed to important nuclear structure information. We report on the current status of the technique

  4. GAMMA-400 gamma-ray observatory

    CERN Document Server

    Topchiev, N P; Bonvicini, V; Adriani, O; Aptekar, R L; Arkhangelskaja, I V; Arkhangelskiy, A I; Bakaldin, A V; Bergstrom, L; Berti, E; Bigongiari, G; Bobkov, S G; Boezio, M; Bogomolov, E A; Bonechi, L; Bongi, M; Bottai, S; Castellini, G; Cattaneo, P W; Cumani, P; Dalkarov, O D; Dedenko, G L; De Donato, C; Dogiel, V A; Finetti, N; Gascon, D; Gorbunov, M S; Gusakov, Yu V; Hnatyk, B I; Kadilin, V V; Kaplin, V A; Kaplun, A A; Kheymits, M D; Korepanov, V E; Larsson, J; Leonov, A A; Loginov, V A; Longo, F; Maestro, P; Marrocchesi, P S; Martinez, M; Menshenin, A L; Mikhailov, V V; Mocchiutti, E; Moiseev, A A; Mori, N; Moskalenko, I V; Naumov, P Yu; Papini, P; Paredes, J M; Pearce, M; Picozza, P; Rappoldi, A; Ricciarini, S; Runtso, M F; Ryde, F; Serdin, O V; Sparvoli, R; Spillantini, P; Stozhkov, Yu I; Suchkov, S I; Taraskin, A A; Tavani, M; Tiberio, A; Tyurin, E M; Ulanov, M V; Vacchi, A; Vannuccini, E; Vasilyev, G I; Ward, J E; Yurkin, Yu T; Zampa, N; Zirakashvili, V N; Zverev, V G

    2015-01-01

    The GAMMA-400 gamma-ray telescope with excellent angular and energy resolutions is designed to search for signatures of dark matter in the fluxes of gamma-ray emission and electrons + positrons. Precision investigations of gamma-ray emission from Galactic Center, Crab, Vela, Cygnus, Geminga, and other regions will be performed, as well as diffuse gamma-ray emission, along with measurements of high-energy electron + positron and nuclei fluxes. Furthermore, it will study gamma-ray bursts and gamma-ray emission from the Sun during periods of solar activity. The energy range of GAMMA-400 is expected to be from ~20 MeV up to TeV energies for gamma rays, up to 20 TeV for electrons + positrons, and up to 10E15 eV for cosmic-ray nuclei. For high-energy gamma rays with energy from 10 to 100 GeV, the GAMMA-400 angular resolution improves from 0.1{\\deg} to ~0.01{\\deg} and energy resolution from 3% to ~1%; the proton rejection factor is ~5x10E5. GAMMA-400 will be installed onboard the Russian space observatory.

  5. 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.

  6. 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...

  7. Instrumentation for gamma-ray astronomy

    Science.gov (United States)

    Bertsch, David L.; Fichtel, Carl E.; Trombka, Jacob I.

    1988-01-01

    The current status of gamma-ray-telescope technology for ground, airborne, and space observations is surveyed and illustrated with drawings, diagrams, and graphs and tables of typical data. For the low- and medium-energy ranges, consideration is given to detectors and detector cooling systems, background-rejection methods, radiation damage, large-area detectors, gamma-ray imaging, data analysis, and the Compton-interaction region. Also discussed are the gamma-ray interaction process at high energies; multilevel automated spark-chamber gamma-ray telescopes; the Soviet Gamma-1 telescope; the EGRET instrument for the NASA Gamma-Ray Observatory; and Cerenkov, air-shower, and particle-detector instruments for the TeV and PeV ranges. Significant improvements in resolution and sensitivity are predicted for the near future.

  8. Gamma-ray pulsars: a gold mine

    CERN Document Server

    Grenier, Isabelle A

    2015-01-01

    The most energetic neutron stars, powered by their rotation, are capable of producing pulsed radiation from the radio up to gamma rays with nearly TeV energies. These pulsars are part of the universe of energetic and powerful particle accelerators, using their uniquely fast rotation and formidable magnetic fields to accelerate particles to ultra-relativistic speed. The extreme properties of these stars provide an excellent testing ground, beyond Earth experience, for nuclear, gravitational, and quantum-electrodynamical physics. A wealth of gamma-ray pulsars has recently been discovered with the Fermi Gamma-Ray Space Telescope. The energetic gamma rays enable us to probe the magnetospheres of neutron stars and particle acceleration in this exotic environment. We review the latest developments in this field, beginning with a brief overview of the properties and mysteries of rotation-powered pulsars, and then discussing gamma-ray observations and magnetospheric models in more detail.

  9. Modeling gamma-ray bursts

    Science.gov (United States)

    Maxham, Amanda

    Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground to those who study them, from relativistic effects such as beaming, jets, shocks and blastwaves to radiation mechanisms such as synchrotron radiation to galatic and stellar populations and history. Through the Swift and Fermi space telescopes dedicated to observing GRBs over a wide range of energies (from keV to GeV), combined with accurate pinpointing that allows ground based follow-up observations in the optical, infrared and radio, a rich tapestry of GRB observations has emerged. The general picture is of a mysterious central engine (CE) probably composed of a black hole or neutron star that ejects relativistic shells of matter into intense magnetic fields. These shells collide and combine, releasing energy in "internal shocks" accounting for the prompt emission and flaring we see and the "external shock" or plowing of the first blastwave into the ambient surrounding medium has well-explained the afterglow radiation. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge and spread, producing prompt emission and X-ray flares. We have also included a blastwave model, which can constrain X-ray flares and explain the origin of high energy (GeV) emission seen by the Fermi telescope. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We pay special attention to the time history of central engine activity, internal shocks, and observed flares. We calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary

  10. Removal cross sections and total mass attenuation coefficients of fast neutrons and gamma rays for steel

    CERN Document Server

    Elsayed, A A

    2003-01-01

    The present work deals with the study of the attenuation properties and determination of the cross sections of fast neutrons and gamma rays for structure steel used in different applications in nuclear power plants, particle accelerators, research reactors and different radiation attenuation fields. Investigation has been performed by measuring the transmitted fast neutron and gamma ray spectra behind cylindrical samples of steel (rho=7.87 gem sup - sup 3) of different thicknesses. A reactor collimated beam and neutron - gamma spectrometer with stiblbene scintillator were used for measurements. The pluse shape disriminate technique based on zero cross over method was used to discriminate between neutron and gamma ray pulses. Effective removal cross-section (sigma sub R) and total mass attenuation coefficient (mu) of neureons and gamma rays have been achieved using the attenuation relations. Microscopic removal cross sections sigma sup 9 sup 8 and mass removal cross sections sigma sub R sub / subrho of fast ne...

  11. Use of microcontroller in gamma-ray spectrometer construction using NaI(Tl) sensor, with emphasis in multichannel analyzer, to applications in nuclear and environmental geophysics; Uso de microcontrolador na construcao de espectrometro gama com sensor de NaI(Tl), com enfase em analisador multicanal, para aplicacao em geofisica nuclear e ambiental

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Nilton

    2005-07-01

    In this work of nuclear geophysical instrumentation the main purpose was the development of a gamma-ray spectrometer prototype with multi channel analyzer, since the spectroscopic amplifier until your firmware. The heart of the digital part was an ATMEL 8 bits microcontroller (AT89S8252). All circuits were made and assembled in the Laboratory of Applied Geophysical Instrumentation (LIGA) of IAG-USP. A microcontroller software was completely developed in C ANSI language using the Small Device C Compiler version 2.4.8, that is a free software distributed under General Public License (GPL). At first, microcontroller was used to change all digital circuit of one classic SCINTREX GAD-6 differential gamma-ray spectrometer. Measurement times with order of 2 days became possible, and it could work in non climate ambient. Then, after this stage, had been started the development of a multichannel analyzer (MCA) working in pulse height analyzer mode with 4096 channels capacity, to use in many kinds of nuclear detection. Besides it, was developed an automatic gain system for photopeak stabilization, by the use of one radioactive source ({sup 133}Ba). This automatic gain system is very important in the case of NaI(Tl) scintillometric detectors, due PMT sensitivity with temperature and aging of some laboratory electronic circuits. Two power supplies with high stability, using pulse width modulation (PWM) techniques were developed, in order to all system became free of electrical line break off. One PWM power polarizes a photo multiplier tube (PMT) with high voltage and another supplies remaining developed circuits. Calibration in energy using standards sources {sup 137}Cs and {sup 60}Co showed that gamma detector developed has a good linearity and low thermal drift, even working in absent of air-conditioned. Concentrations measurements of K, U and Th were made in samples of soils, vegetables, etc. (author)'

  12. Gamma-ray Burst Cosmology

    CERN Document Server

    Wang, F Y; Liang, E W

    2015-01-01

    Gamma-ray bursts (GRBs) are the most luminous electromagnetic explosions in the Universe, which emit up to $8.8\\times10^{54}$ erg isotropic equivalent energy in the hard X-ray band. The high luminosity makes them detectable out to the largest distances yet explored in the Universe. GRBs, as bright beacons in the deep Universe, would be the ideal tool to probe the properties of high-redshift universe: including the cosmic expansion and dark energy, star formation rate, the reionization epoch and the metal enrichment history of the Universe. In this article, we review the luminosity correlations of GRBs, and implications for constraining the cosmological parameters and dark energy. Observations show that the progenitors of long GRBs are massive stars. So it is expected that long GRBs are tracers of star formation rate. We also review the high-redshift star formation rate derived from GRBs, and implications for the cosmic reionization history. The afterglows of GRBs generally have broken power-law spectra, so it...

  13. Gamma-ray burst progenitors

    CERN Document Server

    Levan, Andrew; de Grijs, Richard; Langer, Norbert; Xu, Dong; Yoon, Sung-Chul

    2016-01-01

    We review our current understanding of the progenitors of both long and short duration gamma-ray bursts (GRBs). Constraints can be derived from multiple directions, and we use three distinct strands; i) direct observations of GRBs and their host galaxies, ii) parameters derived from modeling, both via population synthesis and direct numerical simulation and iii) our understanding of plausible analog progenitor systems observed in the local Universe. From these joint constraints, we describe the likely routes that can drive massive stars to the creation of long GRBs, and our best estimates of the scenarios that can create compact object binaries which will ultimately form short GRBs, as well as the associated rates of both long and short GRBs. We further discuss how different the progenitors may be in the case of black hole engine or millisecond-magnetar models for the production of GRBs, and how central engines may provide a unifying theme between many classes of extremely luminous transient, from luminous an...

  14. Gamma-Ray Burst Progenitors

    Science.gov (United States)

    Levan, Andrew; Crowther, Paul; de Grijs, Richard; Langer, Norbert; Xu, Dong; Yoon, Sung-Chul

    2016-12-01

    We review our current understanding of the progenitors of both long and short duration gamma-ray bursts (GRBs). Constraints can be derived from multiple directions, and we use three distinct strands; (i) direct observations of GRBs and their host galaxies, (ii) parameters derived from modelling, both via population synthesis and direct numerical simulation and (iii) our understanding of plausible analog progenitor systems observed in the local Universe. From these joint constraints, we describe the likely routes that can drive massive stars to the creation of long GRBs, and our best estimates of the scenarios that can create compact object binaries which will ultimately form short GRBs, as well as the associated rates of both long and short GRBs. We further discuss how different the progenitors may be in the case of black hole engine or millisecond-magnetar models for the production of GRBs, and how central engines may provide a unifying theme between many classes of extremely luminous transient, from luminous and super-luminous supernovae to long and short GRBs.

  15. Gamma-Ray Burst Early Afterglows

    CERN Document Server

    Zhang, B

    2005-01-01

    The successful launch and operation of NASA's Swift Gamma-Ray Burst Explorer open a new era for the multi-wavelength study of the very early afterglow phase of gamma-ray bursts (GRBs). GRB early afterglow information is essential to explore the unknown physical composition of GRB jets, the link between the prompt gamma-ray emission and the afterglow emission, the GRB central engine activity, as well as the immediate GRB environment. Here I review some of the recent theoretical efforts to address these problems and describe how the latest Swift data give answers to these outstanding questions.

  16. Atmospheric Cherenkov Gamma-ray Telescopes

    CERN Document Server

    Holder, Jamie

    2015-01-01

    The stereoscopic imaging atmospheric Cherenkov technique, developed in the 1980s and 1990s, is now used by a number of existing and planned gamma-ray observatories around the world. It provides the most sensitive view of the very high energy gamma-ray sky (above 30 GeV), coupled with relatively good angular and spectral resolution over a wide field-of-view. This Chapter summarizes the details of the technique, including descriptions of the telescope optical systems and cameras, as well as the most common approaches to data analysis and gamma-ray reconstruction.

  17. Gamma-ray lines from SN2014J

    CERN Document Server

    Siegert, Thomas

    2015-01-01

    On 21 January 2014, SN2014J was discovered in M82 and found to be the closest type Ia supernova (SN Ia) in the last four decades. INTEGRAL observed SN2014J from the end of January until late June for a total exposure time of about 7 Ms. SNe Ia light curves are understood to be powered by the radioactive decay of iron peak elements of which $^{56}$Ni is dominantly synthesized during the thermonuclear disruption of a CO white dwarf (WD). The measurement of $\\gamma$-ray lines from the decay chain $^{56}$Ni$\\rightarrow$$^{56}$Co$\\rightarrow$$^{56}$Fe provides unique information about the explosion in supernovae. Canonical models assume $^{56}$Ni buried deeply in the supernova cloud, absorbing most of the early $\\gamma$-rays, and only the consecutive decay of $^{56}$Co should become directly observable through the overlaying material several weeks after the explosion when the supernova envelope dilutes as it expands. Surprisingly, with the spectrometer on INTEGRAL, SPI, we detected $^{56}$Ni $\\gamma$-ray lines at ...

  18. Monitoring radioactive plumes by airborne gamma-ray spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Grasty, R.L. [Exploranium, Mississauga, Ontario (Canada); Hovgaard, J. [Danish Emergency Management Agency, Birkerod (Germany); Multala, J. [Geological Survey of Finland, Espoo (Finland)

    1996-06-01

    Airborne gamma-ray spectrometer surveys using large volume sodium-iodide detectors are routinely flown throughout the world for mineral exploration and geological mapping. Techniques have now been developed to detect and map man-made sources of radiation. In Canada, airborne gamma-rays surveys have been flown around nuclear reactors to map {sup 41}Ar plumes from nuclear reactors and to calculate the dose rate at ground level. In May 1986, the Finnish Geological survey aircraft flew through a radioactive plume from the Chernobyl nuclear accident. As the aircraft flew through the plume, the aircraft became increasingly contaminated. By measuring the final aircraft contamination, the activity of the plume could be separated from the contamination due to the aircraft. Within 1 h of encountering the plume, the aircraft activity was comparable to the maximum levels found in the plume. From an analysis of the gamma-ray spectra, the concentration of {sup 131}I and {sup 140}La within the plume were calculated as a function of time.

  19. Study of SMM flares in gamma-rays and neutrons

    Science.gov (United States)

    Dunphy, Philip P.; Chupp, Edward L.

    1992-01-01

    This report summarizes the results of the research supported by NASA grant NAGW-2755 and lists the papers and publications produced through the grant. The objective of the work was to study solar flares that produced observable signals from high-energy (greater than 10 MeV) gamma-rays and neutrons in the Solar Maximum Mission (SMM) Gamma-Ray Spectrometer (GRS). In 3 of 4 flares that had been studied previously, most of the neutrons and neutral pions appear to have been produced after the 'main' impulsive phase as determined from hard x-rays and gamma-rays. We, therefore, proposed to analyze the timing of the high-energy radiation, and its implications for the acceleration, trapping, and transport of flare particles. It was equally important to characterize the spectral shapes of the interacting energetic electrons and protons - another key factor in constraining possible particle acceleration mechanisms. In section 2.0, we discuss the goals of the research. In section 3.0, we summarize the results of the research. In section 4.0, we list the papers and publications produced under the grant. Preprints or reprints of the publications are attached as appendices.

  20. GAMMA-RAY AND X-RAY EMISSION FROM GAMMA-RAY-LOUD BLAZARS

    Institute of Scientific and Technical Information of China (English)

    ZHANG XIONG; ZHAO GANG; XIE GUANG-ZHONG; ZHENG GUANG-SHENG; ZHANG LI

    2001-01-01

    We present a strong correlation of the gamma-ray (above 100 MeV) mean spectral indices aγ and X-ray (1 keV)mean spectral indices cX for 34 gamma-ray-loud blazars (16 BL Lac objects and 18 flat spectrum radio quasars). Astrong correlation is also found between the gamma-ray flux densities F-γ and X-ray flux densities Fx in the low state for 47 blazars (17 BL Lac and 30 flat spectrum radio quasars). Possible correlation on the gamma-ray emission mechanism is discussed. We suggest that the main gamma-ray radiation mechanism is probably the synchrotron process. The gamma-ray emission may be somewhat different from that of BL Lac objects and flat spectrum radio quasars.

  1. 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...

  2. Supernova remnants and gamma-ray sources

    CERN Document Server

    Torres, D F; Dame, T M; Combi, J A; Butt, Y M; Torres, Diego F.; Romero, Gustavo E.; Dame, Thomas M.; Combi, Jorge A.; Butt, Yousaf M.

    2003-01-01

    A review of the possible relationship between $\\gamma$-ray sources and supernova remnants (SNRs) is presented. Particular emphasis is given to the analysis of the observational status of the problem of cosmic ray acceleration at SNR shock fronts. All positional coincidences between SNRs and unidentified $\\gamma$-ray sources listed in the Third EGRET Catalog at low Galactic latitudes are discussed on a case by case basis. For several coincidences of particular interest, new CO(J=1-0) and radio continuum maps are shown, and the mass content of the SNR surroundings is determined. The contribution to the $\\gamma$-ray flux observed that might come from cosmic ray particles (particularly nuclei) locally accelerated at the SNR shock fronts is evaluated. We discuss the prospects for future research in this field and remark on the possibilities for observations with forthcoming $\\gamma$-ray instruments.

  3. 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 scint

  4. Soft gamma rays from heavy WIMPs

    Science.gov (United States)

    Krauss, Manuel Ernst; Opferkuch, Toby; Staub, Florian; Winkler, Martin Wolfgang

    2016-12-01

    We propose an explanation of the galactic center gamma ray excess by supersymmetric WIMPs as heavy as 500 GeV. The lightest neutralino annihilates into vector-like leptons or quarks which cascade decay through intermediate Higgs bosons. Due to the long decay chains, the gamma ray spectrum is much softer than naively expected and peaks at GeV energies. The model predicts correlated diboson and dijet signatures to be tested at the LHC.

  5. The HAWC Gamma-Ray Observatory: Sensitivity to Steady and Transient Sources of Gamma Rays

    CERN Document Server

    Abeysekara, A U; Alvarez, C; Álvarez, J D; Arceo, R; Arteaga-Velázquez, J C; Solares, H A Ayala; Barber, A S; Baughman, B M; Bautista-Elivar, N; Belmont, E; BenZvi, S Y; Berley, D; Rosales, M Bonilla; Braun, J; Caballero-Lopez, R A; Caballero-Mora, K S; Carramiñana, A; Castillo, M; Cotti, U; Cotzomi, J; de la Fuente, E; De León, C; DeYoung, T; Hernandez, R Diaz; Díaz-Vélez, J C; Dingus, B L; DuVernois, M A; Ellsworth, R W; Fernandez, A; Fiorino, D W; Fraija, N; Galindo, A; Garfias, F; González, L X; González, M M; Goodman, J A; Grabski, V; Gussert, M; Hampel-Arias, Z; Hui, C M; Hüntemeyer, P; Imran, A; Iriarte, A; Karn, P; Kieda, D; Kunde, G J; Lara, A; Lauer, R J; Lee, W H; Lennarz, D; Vargas, H León; Linares, E C; Linnemann, J T; Longo, M; Luna-GarcIa, R; Marinelli, A; Martinez, H; Martinez, O; Martínez-Castro, J; Matthews, J A J; Miranda-Romagnoli, P; Moreno, E; Mostafá, M; Nava, J; Nellen, L; Newbold, M; Noriega-Papaqui, R; Oceguera-Becerra, T; Patricelli, B; Pelayo, R; Pérez-Pérez, E G; Pretz, J; Rivière, C; Rosa-González, D; Salazar, H; Salesa, F; Sanchez, F E; Sandoval, A; Santos, E; Schneider, M; Silich, S; Sinnis, G; Smith, A J; Sparks, K; Springer, R W; Taboada, I; Toale, P A; Tollefson, K; Torres, I; Ukwatta, T N; Villaseñor, L; Weisgarber, T; Westerhoff, S; Wisher, I G; Wood, J; Yodh, G B; Younk, P W; Zaborov, D; Zepeda, A; Zhou, H

    2013-01-01

    The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is designed to record air showers produced by cosmic rays and gamma rays between 100 GeV and 100 TeV. Because of its large field of view and high livetime, HAWC is well-suited to measure gamma rays from extended sources, diffuse emission, and transient sources. We describe the sensitivity of HAWC to emission from the extended Cygnus region as well as other types of galactic diffuse emission; searches for flares from gamma-ray bursts and active galactic nuclei; and the first measurement of the Crab Nebula with HAWC-30.

  6. The Science of Nuclear Materials Detection using gamma-ray beams: Nuclear Resonance Fluorescence

    Science.gov (United States)

    Ohgaki, Hideaki

    2014-09-01

    An atomic nucleus is excited by absorption of incident photons with an energy the same as the excitation energy of the level, and subsequently a gamma-ray is emitted as it de-excites. This phenomenon is called Nuclear Resonance Fluorescence and mostly used for studies on Nuclear Physics field. By measuring the NRF gamma-rays, we can identify nuclear species in any materials because the energies of the NRF gamma-rays uniquely depend on the nuclear species. For example, 235U has an excitation level at 1733 keV. If we irradiate a material including 235U with a gamma-ray tuned at this excitation level, the material absorbs the gamma-ray and re-emits another gamma-ray immediately to move back towards the ground state. Therefore we can detect the 235U by measuring the re-emitted (NRF) gamma-rays. Several inspection methods using gamma-rays, which can penetrate a thick shielding have been proposed and examined. Bertozzi and Ledoux have proposed an application of nuclear resonance fluorescence (NRF) by using bremsstrahlung radiations. However the signal-to-noise (SN) ratio of the NRF measurement with the bremsstrahlung radiation is, in general, low. Only a part of the incident photons makes NRF with a narrow resonant band (meV-eV) whereas most of incident radiation is scattered by atomic processes in which the reaction rate is higher than that of NRF by several orders of magnitudes and causes a background. Thus, the NRF with a gamma-ray quasi-monochromatic radiation beam is proposed. The monochromatic gamma-rays are generated by using laser Compton scattering (LCS) of electrons and intense laser photons by putting a collimator to restrict the gamma-ray divergence downstream. The LCS gamma-ray, which is energy-tunable and monochromatic, is an optimum apparatus for NRF measurements We have been conducted NRF experiment for nuclear research, especially with high linear polarized gamma-ray generated by LCS, to survey the distribution of M1 strength in MeV region in LCS

  7. 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

  8. Gamma ray attenuation coefficient measurement for neutron-absorbent materials

    Energy Technology Data Exchange (ETDEWEB)

    Jalali, Majid [Isfahan Nuclear Science and Technology Research Institute (NSTRT), Reactor and Accelerators Research and Development School, Atomic Energy Organization (Iran, Islamic Republic of)], E-mail: m_jalali@entc.org.ir; Mohammadi, Ali [Faculty of Science, Department of Physics, University of Kashan, Km. 6, Ravand Road, Kashan (Iran, Islamic Republic of)

    2008-05-15

    The compounds Na{sub 2}B{sub 4}O{sub 7}, H{sub 3}BO{sub 3}, CdCl{sub 2} and NaCl and their solutions attenuate gamma rays in addition to neutron absorption. These compounds are widely used in the shielding of neutron sources, reactor control and neutron converters. Mass attenuation coefficients of gamma related to the four compounds aforementioned, in energies 662, 778.9, 867.38, 964.1, 1085.9, 1173, 1212.9, 1299.1,1332 and 1408 keV, have been determined by the {gamma} rays transmission method in a good geometry setup; also, these coefficients were calculated by MCNP code. A comparison between experiments, simulations and Xcom code has shown that the study has potential application for determining the attenuation coefficient of various compound materials. Experiment and computation show that H{sub 3}BO{sub 3} with the lowest average Z has the highest gamma ray attenuation coefficient among the aforementioned compounds.

  9. 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.

  10. 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

  11. On the difference between gamma-ray-detected and non-gamma-ray-detected pulsars

    CERN Document Server

    Rookyard, Simon C; Johnston, Simon; Kerr, Matthew

    2016-01-01

    We compare radio profile widths of young, energetic gamma-ray-detected and non-gamma-ray-detected pulsars. We find that the latter typically have wider radio profiles, with the boundary between the two samples exhibiting a dependence on the rate of rotational energy loss. We also find that within the sample of gamma-ray-detected pulsars, radio profile width is correlated with both the separation of the main gamma-ray peaks and the presence of narrow gamma-ray components. These findings lead us to propose that these pulsars form a single population where the main factors determining gamma ray detectability are the rate of rotational energy loss and the proximity of the line of sight to the rotation axis. The expected magnetic inclination angle distribution will be different for radio pulsars with and without detectable gamma rays, naturally leading to the observed differences. Our results also suggest that the geometry of existing radio and outer-magnetosphere gamma-ray emission models are at least qualitative...

  12. Gamma-Ray Pulsars Expected in the Outer Gap Model of Gamma-Ray Emission

    Institute of Scientific and Technical Information of China (English)

    张力; 吴杰; 姜泽军; 梅冬成

    2003-01-01

    We study the possibility of high-energy gamma-ray emission from the known 1130 radio pulsars based on the outer gap model of high-energy emission from pulsars. We estimate the fractional size of outer gap, the integrated flux, the gamma-ray luminosity for each known radio pulsar, and find that only 14% of the known radio pulsars are gamma-ray emitters according to the outer gap model. In the sample of possible 156 gamma-ray pulsars, our statistical analysis indicates that the distributions of the spin-down powers and the ages of these pulsars concentrate mainly on 1033.5-1039 erg/s and 103-107 y, respectively. The predictions of gamma-ray pulsars detected by the AGILE and GLAST missions are given.

  13. 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 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. While Fermi will take......, albeit at much more modest sensitivities. 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 Lane diffraction and multilayer-coated mirror techniques...

  14. The Infrared-Gamma-Ray Connection: A WISE View of the Extragalactic Gamma-Ray Sky

    CERN Document Server

    Massaro, F

    2016-01-01

    Using data from the WISE all-sky survey we discovered that the non-thermal infrared (IR) emission of blazars, the largest known population of extragalactic gamma-ray sources, has peculiar spectral properties. In this work, we confirm and strengthen our previous analyses using the latest available releases of both the WISE and the Fermi source catalogs. We also show that there is a tight correlation between the mid-IR colors and the gamma-ray spectral index of Fermi blazars. We name this correlation "the infrared--gamma-ray connection". We discuss how this connection links both the emitted powers and the spectral shapes of particles accelerated in jets arising from blazars over ten decades in energy. Based on this evidence, we argue that the infrared--gamma-ray connection is stronger than the well known radio--gamma-ray connection.

  15. Gamma-Ray Astronomy from the Ground

    CERN Document Server

    Horns, D

    2016-01-01

    The observation of cosmic gamma-rays from the ground is based upon the detection of gamma-ray initiated air showers. At energies between approximately $10^{11}$ eV and $10^{13}$ eV, the imaging air Cherenkov technique is a particularly successful approach to observe gamma-ray sources with energy fluxes as low as $\\approx 10^{-13}$ erg\\,cm$^{-2}\\,$s$^{-1}$. The observations of gamma-rays in this energy band probe particle acceleration in astrophysical plasma conditions and are sensitive to high energy phenomena beyond the standard model of particle physics (e.g., self-annihilating or decaying dark matter, violation of Lorentz invariance, mixing of photons with light pseudo-scalars). The current standing of the field and its major instruments are summarised briefly by presenting selected highlights. A new generation of ground based gamma-ray instruments is currently under development. The perspectives and opportunities of these future facilities will be discussed.

  16. Measurements of radionuclides in coal samples from two provinces of Pakistan and computation of external gamma-ray dose rate in coal mines

    Energy Technology Data Exchange (ETDEWEB)

    Jamil, K.; All, S.; Iqbal, M.; Qureshi, A.A.; Khan, H.A. [Pinstech, Islamabad (Pakistan). Radiation Physics Division

    1998-11-01

    This paper describes research that has been conducted to quantify the radionuclides present in the coal samples from various coal-mines in the Punjab and Balochistan provinces of Pakistan. A high-purity Ge-detector-based gamma-spectrometer was used. The maximum activity concentrations for Ra-226, Th-232 and K-40 were found to be 31.4 {+-} 3.0, 32.7 {+-} 3.2 and 21.4 {+-} 5.0 Bq kg{sup -1}, respectively. A theoretical model to compute external gamma-ray dose rate from a coal-mine surface was developed. The Monte Carlo simulation was employed to compute the required mass attenuation coefficients corresponding to the various gamma-ray energies from Ra-226, Th-232, their progeny and K-40 present in the coal samples. In addition, the effective thickness of coal slab for self-absorption was also computed using the Monte Carlo Neutron Photo (MCNP) transport code. The computed external gamma-ray dose rate has been found to be much below the dose rate limits for occupational persons as well as for the general population.

  17. Abstracts of papers to be presented at the fifth symposium on x- and gamma-ray sources and applications

    Energy Technology Data Exchange (ETDEWEB)

    1981-01-01

    The program and abstracts of papers are presented. Topics include radiation sources, radiation detectors, mathematical models and data analysis, gamma-ray spectroscopy, instrumentation, applications of x-ray fluorescence, PIXE, and x-ray absorption. (ACR)

  18. High resolution spectroscopy from low altitude satellites. [gamma ray astronomy

    Science.gov (United States)

    Nakano, G. H.; Imhof, W. L.

    1978-01-01

    The P 78 1 satellite to be placed in a synchronous polar orbit at an altitude of 550-660 km will carry two identical high resolution spectrometers each consisting of a single (approximately 85 cc) intrinsic germanium IGE detector. The payload also includes a pair of phoswitch scintillators, an array of CdTe detectors and several particle detectors, all of which are mounted on the wheel of the satellite. The intrinsic high purity IGE detectors receive cooling from two Stirling cycle refrigerators and facilitate the assembly of large and complex detector arrays planned for the next generation of high sensitivity instruments such as those planned for the gamma ray observatory. The major subsystems of the spectrometer are discussed as well as its capabilities.

  19. Next Generation Gamma Ray Diagnostics for the National Ignition Facility

    Science.gov (United States)

    Herrmann, Hans; Kim, Y. H.; McEvoy, A. M.; Zylstra, A. B.; Young, C. S.; Lopez, F. E.; Griego, J. R.; Fatherley, V. E.; Oertel, J. A.; Jorgenson, H. J.; Barlow, D. B.; Stoeffl, W.; Church, J. A.; Hernandez, J. E.; Carpenter, A.; Rubery, M. S.; Horsfield, C. J.; Gales, S.; Leatherland, A.; Hilsabeck, T.; Kilkenny, J. D.; Malone, R. M.; Moy, K.; Hares, J. D.; Milnes, J.

    Fusion reaction history and ablator areal density measurements based on gamma ray detection are an essential part of Inertial Confinement Fusion (ICF) experiments on the National Ignition Facility (NIF). Capability improvements are being implemented in sensitivity, temporal and spectral response relative to the existing Gamma Reaction History diagnostic (GRH-6m). The ``Super'' Gas Cherenkov Detector (GCD) will provide 200x more sensitivity, reduce the effective temporal resolution from 100 to 10 ps, and lower the energy threshold from 2.9 to 1.8 MeV, relative to GRH-6m. The Gamma-to-Electron Magnetic Spectrometer (GEMS) - a Compton spectrometer intended to provide true gamma energy resolution (<=5%) for isolation of specific lines such as t(d, γ) , D(n, γ) , 12C(n,n' γ) and energetic charged particle nuclear reactions indicative of ablator/fuel mix

  20. Constraining the Location of Gamma-Ray Flares in Luminous Blazars

    Science.gov (United States)

    Nalewajko, Krzysztof; Begelman, Mitchell C.; Sikora, Marek

    2014-07-01

    Locating the gamma-ray emission sites in blazar jets is a long standing and highly controversial issue. We jointly investigate several constraints on the distance scale r and Lorentz factor Γ of the gamma-ray emitting regions in luminous blazars (primarily flat spectrum radio quasars). Working in the framework of one-zone external radiation Comptonization models, we perform a parameter space study for several representative cases of actual gamma-ray flares in their multiwavelength context. We find a particularly useful combination of three constraints: from an upper limit on the collimation parameter Γθ self-Compton (SSC) luminosity L SSC low accretion disk luminosity L d. The commonly used intrinsic pair-production opacity constraint on Γ is usually much weaker than the SSC constraint. The SSC and cooling constraints provide a robust lower limit on the collimation parameter Γθ >~ 0.1-0.7. Typical values of r corresponding to moderate values of Γ ~ 20 are in the range 0.1-1 pc, and are determined primarily by the observed variability timescale t var, obs. Alternative scenarios motivated by the observed gamma-ray/millimeter connection, in which gamma-ray flares of t var, obs ~ a few days are located at r ~ 10 pc, are in conflict with both the SSC and cooling constraints. Moreover, we use a simple light travel time argument to point out that the gamma-ray/millimeter connection does not provide a significant constraint on the location of gamma-ray flares. We argue that spine-sheath models of the jet structure do not offer a plausible alternative to external radiation fields at large distances; however, an extended broad-line region is an idea worth exploring. We propose that the most definite additional constraint could be provided by determination of the synchrotron self-absorption frequency for correlated synchrotron and gamma-ray flares.

  1. New insights from cosmic gamma rays

    CERN Document Server

    Diehl, Roland

    2016-01-01

    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 beta-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, and complement conventional supernova observations with measurements of their prime energy sources. The diffuse radioactive afterglow of massi...

  2. 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.

  3. TeV Gamma-Ray Astrophysics

    CERN Document Server

    Ribó, M

    2008-01-01

    The window of TeV Gamma-Ray Astrophysics was opened less than two decades ago, when the Crab Nebula was detected for the first time. After several years of development, the technique used by imaging atmospheric Cherenkov telescopes like HESS, MAGIC or VERITAS, is now allowing to conduct sensitive observations in the TeV regime. Water Cherenkov instruments like Milagro are also providing the first results after years of integration time. Different types of extragalactic and galactic sources have been detected, showing a variety of interesting phenomena that are boosting theory in very high energy gamma-ray astrophysics. Here I review some of the most interesting results obtained up to now, making special emphasis in the field of X-ray/gamma-ray binaries.

  4. Interstellar protons in the TeV gamma-ray SNR HESS J1731-347:Possible evidence for the coexistence of hadronic and leptonic gamma-rays

    CERN Document Server

    Fukuda, T; Sano, H; Torii, K; Yamamoto, H; Acero, F; Fukui, Y

    2014-01-01

    HESS J1731-347 (G353.6-0.7) is one of the TeV gamma-ray SNRs which shows the shell-like morphology. We have made a new analysis of the interstellar protons toward the SNR by using both the 12CO(J=1-0) and HI datasets. The results indicate that the TeV gamma-ray shell shows significant spatial correlation with the interstellar protons at a velocity range from -90 km/s to -75 km/s, and the distance corresponding to the velocity range is ~5.2 kpc, a factor of 2 larger than the previous figure 3 kpc. The total mass of the interstellar protons is estimated to be 6.4x10^4 M_sun, 25 % of which is atomic gas. We have identified the cold HI gas observed as self-absorption which shows significant correspondence with the northeastern gamma-ray peak. While the good correspondence between the interstellar protons and TeV gamma-rays in the north of the SNR lends support to the hadronic scenario for the TeV gamma-rays, the southern part of the shell shows a break in the correspondence; in particular, the southwestern rim of...

  5. Gamma-ray bursts and Population III stars

    CERN Document Server

    Toma, Kenji; Bromm, Volker

    2016-01-01

    Gamma-ray bursts (GRBs) are ideal probes of the epoch of the first stars and galaxies. We review the recent theoretical understanding of the formation and evolution of the first (so-called Population III) stars, in light of their viability of providing GRB progenitors. We proceed to discuss possible unique observational signatures of such bursts, based on the current formation scenario of long GRBs. These include signatures related to the prompt emission mechanism, as well as to the afterglow radiation, where the surrounding intergalactic medium might imprint a telltale absorption spectrum. We emphasize important remaining uncertainties in our emerging theoretical framework.

  6. Gamma-Ray Bursts and Population III Stars

    Science.gov (United States)

    Toma, Kenji; Yoon, Sung-Chul; Bromm, Volker

    2016-12-01

    Gamma-ray bursts (GRBs) are ideal probes of the epoch of the first stars and galaxies. We review the recent theoretical understanding of the formation and evolution of the first (so-called Population III) stars, in light of their viability of providing GRB progenitors. We proceed to discuss possible unique observational signatures of such bursts, based on the current formation scenario of long GRBs. These include signatures related to the prompt emission mechanism, as well as to the afterglow radiation, where the surrounding intergalactic medium might imprint a telltale absorption spectrum. We emphasize important remaining uncertainties in our emerging theoretical framework.

  7. Combined in-beam gamma-ray and conversion electron spectroscopy with radioactive ion beams

    Directory of Open Access Journals (Sweden)

    Konki J.

    2013-12-01

    Full Text Available In-beam gamma-ray and electron spectroscopy have been widely used as tools to study the broad variety of phenomena in nuclear structure. The SPEDE spectrometer is a new device to be used in conjunction with the MINIBALL germanium detector array to enable the detection of internal conversion electrons in coincidence with gamma rays from de-exciting nuclei in radioactive ion beam experiments at the upcoming HIE-ISOLDE facility at CERN, Switzerland. Geant4 simulations were carried out in order to optimise the design and segmentation of the silicon detector to achieve good energy resolution and performance.

  8. Low-background gamma-ray spectrometry for the international monitoring system.

    Science.gov (United States)

    Greenwood, L R; Cantaloub, M G; Burnett, J L; Myers, A W; Overman, C T; Forrester, J B; Glasgow, B G; Miley, H S

    2016-12-28

    PNNL has developed two low-background gamma-ray spectrometers in a new shallow underground laboratory, thereby significantly improving its ability to detect low levels of gamma-ray emitting fission or activation products in airborne particulate in samples from the IMS (International Monitoring System). The combination of cosmic veto panels, dry nitrogen gas to reduce radon and low background shielding results in a reduction of the background count rate by about a factor of 100 compared to detectors operating above ground at our laboratory.

  9. Gamma Ray Bursts in the HAWC Era

    CERN Document Server

    Mészáros, Peter; Murase, Kohta; Fox, Derek; Gao, He; Senno, Nicholas

    2015-01-01

    Gamma-Ray Bursts are the most energetic explosions in the Universe, and are among the most promising for detecting multiple non-electromagnetic signals, including cosmic rays, high energy neutrinos and gravitational waves. The multi-GeV to TeV gamma-ray range of GRB could have significant contributions from hadronic interactions, mixed with more conventional leptonic contributions. This energy range is important for probing the source physics, including overall energetics, the shock parameters and the Lorentz factor. We discuss some of the latest observational and theoretical developments in the field.

  10. Status of the Milagro $\\gamma$ Ray Observatory

    CERN Document Server

    Atkins, R; Berley, D; Chen, M L; Coyne, D G; Delay, R S; Dingus, B L; Dorfan, D E; Ellsworth, R W; Evans, D; Falcone, A D; Fleysher, L; Fleysher, R; Gisler, G; Goodman, J A; Haines, T J; Hoffman, C M; Hugenberger, S; Kelley, L A; Leonor, I; Macri, J R; McConnell, M; McCullough, J F; McEnery, J E; Miller, R S; Mincer, A I; Morales, M F; Némethy, P; Ryan, J M; Schneider, M; Shen, B; Shoup, A L; Sinnis, G; Smith, A J; Sullivan, G W; Thompson, T N; Tümer, T O; Wang, K; Wascko, M O; Westerhoff, S; Williams, D A; Yang, T; Yodh, G B

    2001-01-01

    The Milagro Gamma Ray Observatory is the world's first large-area water Cherenkov detector capable of continuously monitoring the sky at TeV energies. Located in northern New Mexico, Milagro will perform an all sky survey of the Northern Hemisphere at energies between ~250 GeV and 50 TeV. With a high duty cycle, large detector area (~5000 square meters), and a wide field-of-view (~1 sr), Milagro is uniquely capable of searching for transient and DC sources of high-energy gamma-ray emission. Milagro has been operating since February, 1999. The current status of the Milagro Observatory and initial results will be discussed.

  11. 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

  12. Relativistic feedback models of terrestrial gamma-ray flashes and gamma-ray glows

    Science.gov (United States)

    Dwyer, J. R.

    2015-12-01

    Relativistic feedback discharges, also known as dark lightning, are capable of explaining many of the observed properties of terrestrial gamma-ray flashes (TGFs) and gamma-ray glows, both created within thunderstorms. During relativistic feedback discharges, the generation of energetic electrons is self-sustained via the production of backward propagating positrons and back-scattered x-rays, resulting in very larges fluxes of energetic radiation. In addition, ionization produces large electric currents that generate LF/VLF radio emissions and eventually discharge the electric field, terminating the gamma-ray production. In this presentation, new relativistic feedback model results will be presented and compared to recent observations.

  13. Gamma-ray bursts at high redshift

    NARCIS (Netherlands)

    R.A.M.J. Wijers

    1999-01-01

    Gamma-ray bursts are much brighter than supernovae, and could therefore possibly probe the Universe to high redshift. The presently established GRB redshifts range from 0.83 to 5, and quite possibly even beyond that. Since most proposed mechanisms for GRB link them closely to deaths of massive stars

  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 emission from nova outbursts

    CERN Document Server

    Hernanz, M

    2013-01-01

    Classical novae produce radioactive nuclei which are emitters of gamma-rays in the MeV range. Some examples are the lines at 478 and 1275 keV (from 7Be and 22Na) and the positron-electron annihilation emission, with the 511 keV line and a continuum. Gamma-ray spectra and light curves are potential unique tools to trace the corresponding isotopes and to give insights on the properties of the expanding envelope. Another possible origin of gamma-rays is the acceleration of particles up to very high energies, so that either neutral pions or inverse Compton processes produce gamma-rays of energies larger than 100 MeV. MeV photons during nova explosions have not been detected yet, although several attempts have been made in the last decades; on the other hand, GeV photons from novae have been detected with the Fermi satellite in V407 Cyg, a nova in a symbiotic binary, where the companion is a red giant with a wind, instead of a main sequence star as in the cataclysmic variables hosting classical novae. Two more nov...

  16. Gamma-Rays from Intergalactic Shocks

    CERN Document Server

    Keshet, U; Loeb, A; Springel, V; Hernquist, L E; Keshet, Uri; Waxman, Eli; Loeb, Abraham; Springel, Volker; Hernquist, Lars

    2003-01-01

    Structure formation in the intergalactic medium (IGM) produces large-scale, collisionless shock waves, where electrons can be accelerated to highly relativistic energies. Such electrons can Compton scatter cosmic microwave background photons up to gamma-ray energies. We study the radiation emitted in this process using a hydrodynamic cosmological simulation of a LCDM universe. The resulting radiation, extending beyond TeV energies, has roughly constant energy flux per decade in photon energy, in agreement with the predictions of Loeb & Waxman (2000). Assuming that a fraction \\xi_e=0.05 of the shock energy is transferred to the relativistic electrons, as inferred from collisionless non-relativistic shocks in the interstellar medium, we find that the radiation energy flux, e^2 (dJ/de) ~ 50-160 eV cm^{-2} s^{-1} sr^{-1}, constitutes ~10% of the extragalactic gamma-ray background flux. The associated gamma-ray point-sources are too faint to account for the ~60 unidentified EGRET gamma-ray sources, but GLAST s...

  17. Gamma ray observations of the solar system

    Science.gov (United States)

    1981-01-01

    Two general categories are discussed concerning the evolution of the solar system: the dualistic view, the planetesimal approach; and the monistic view, the nebular hypothesis. The major points of each view are given and the models that are developed from these views are described. Possible applications of gamma ray astronomical observations to the question of the dynamic evolution of the solar system are discussed.

  18. Gamma Rays From Rotation-Powered Pulsars

    CERN Document Server

    Harding, A K

    2002-01-01

    The seven known gamma-ray pulsars represent a very small fraction of the more than 1000 presently known radio pulsars, yet they can give us valuable information about pulsar particle acceleration and energetics. Although the theory of acceleration and high-energy emission in pulsars has been studied for over 25 years, the origin of the pulsed gamma rays is a question that remains unanswered. Characteristics of the pulsars detected by the Compton Gamma-Ray Observatory could not clearly distinguish between an emission site at the magnetic poles (polar cap models) and emission from the outer magnetosphere (outer gap models). There are also a number of theoretical issues in both type of model which have yet to be resolved. The two types of models make contrasting predictions for the numbers of radio-loud and radio-quiet gamma-ray pulsars and of their spectral characteristics. GLAST will probably detect at least 50 radio-selected pulsars and possibly many more radio-quiet pulsars. With this large sample, it will b...

  19. New shield for gamma-ray spectrometry

    Science.gov (United States)

    Brar, S. S.; Gustafson, P. F.; Nelson, D. M.

    1969-01-01

    Gamma-ray shield that can be evacuated, refilled with a clean gas, and pressurized for exclusion of airborne radioactive contaminants effectively lowers background noise. Under working conditions, repeated evacuation and filling procedures have not adversely affected the sensitivity and resolution of the crystal detector.

  20. 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

  1. 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.

  2. Chandra Imaging of Gamma-Ray Binaries

    CERN Document Server

    Kargaltsev, Oleg; Hare, Jeremy; Pavlov, George G

    2013-01-01

    We review the multiwavelength properties of the few known gamma-ray binaries, focusing on extended emission recently resolved with Chandra. We discuss the implications of these findings for the nature of compact objects and for physical processes operating in these systems.

  3. Gamma-ray Novae: Rare or Nearby?

    CERN Document Server

    Morris, Paul J; Brown, Anthony M; Chadwick, Paula M

    2016-01-01

    Classical Novae were revealed as a surprise source of gamma-rays in Fermi LAT observations. During the first 8 years since the LAT was launched, 6 novae in total have been detected to > 5 sigma in gamma-rays, in contrast to the 69 discovered optically in the same period. We attempt to resolve this discrepancy by assuming all novae are gamma-ray emitters, and assigning peak one-day fluxes based on a flat distribution of the known emitters to a simulated population. To determine optical parameters, the spatial distribution and magnitudes of bulge and disc novae in M31 are scaled to the Milky Way, which we approximate as a disc with a 20 kpc radius and elliptical bulge with semi major axis 3 kpc and axis ratios 2:1 in the xy plane. We approximate Galactic reddening using a double exponential disc with vertical and radial scale heights of r_d = 5 kpc and z_d = 0.2 kpc, and demonstrate that even such a rudimentary model can easily reproduce the observed fraction of gamma-ray novae, implying that these apparently r...

  4. HAWC observatory catches first gamma rays

    Science.gov (United States)

    Frías Villegas, Gabriela

    2013-06-01

    The world's largest and most modern gamma-ray observatory has carried out its first successful observations. Located inside the Pico de Orizaba national park in the Mexican state of Puebla, the High-Altitude Water Cherenkov Observatory (HAWC) is a collaboration between 26 Mexican and US institutions.

  5. Exploring the Edge of the Stellar Universe with Gamma-Ray Observations

    CERN Document Server

    Stecker, F W

    2006-01-01

    The determination of the densities of intergalactic photons from the FIR to the UV produced by stellar emission and dust reradiation at various redshifts can provide an independent measure of the star formation history of the universe. High energy gamma-rays can annihilate with FIR-UV photons to produce electron-positron pairs which result in high-end absorption cutoffs in the gamma-ray spectra of extragalactic sources. Future measurements of such absorption in the spectra of extragalactic high energy gamma-ray sources at higher redshifts from detectors such as the (soon to be launched) GLAST space telescope can be used to determine intergalactic photon densities in the distant past, thereby shedding light on the history of star formation and galaxy evolution. (abridged),

  6. Discrimination of gamma rays due to inelastic neutron scattering in AGATA

    CERN Document Server

    Ataç, A; Akkoyun, S; Şenyiğit, M; Hüyük, T; Kara, S O; Nyberg, J

    2009-01-01

    Possibilities of discriminating neutrons and gamma rays in the AGATA gamma-ray tracking spectrometer have been investigated with the aim of reducing the background due to inelastic scattering of neutrons in the high-purity germanium crystals. This background may become a serious problem especially in experiments with neutron-rich radioactive ion beams. Simulations using the Geant4 toolkit and a tracking program based on the forward tracking algorithm were carried out by emitting neutrons and gamma rays from the center of AGATA. Three different methods were developed and tested in order to find 'fingerprints' of the neutron interaction points in the detectors. In a simulation with simultaneous emission of six neutrons with energies in the range 1-5 MeV and ten gamma rays with energies between 150 and 1450 keV, the peak-to-background ratio at a gamma-ray energy of 1.0 MeV was improved by a factor of 2.4 after neutron rejection with a reduction of the photopeak efficiency at 1.0 MeV of only a factor of 1.25.

  7. Dose Rate and Mass Attenuation Coefficients of Gamma Ray for Concretes

    CERN Document Server

    Abdel-Latif, A A; Kansouh, W A; El-Sayed, F H

    2003-01-01

    This work is concerned with the study of the leakage gamma ray dose and mass attenuation coefficients for ordinary, basalt and dolomite concretes made from local ores. Concretes under investigation were constructed from gravel, basalt and dolomite ores, and then reconstructed with the addition of 3% steel fibers by weight. Measurements were carried out using a collimated beam from sup 6 sup 0 Co gamma ray source and sodium iodide (3x3) crystal with the genie 2000 gamma spectrometer. The obtained fluxes were transformed to gamma ray doses and displayed in the form of gamma ray dose rates distribution. The displayed curves were used to estimate the linear attenuation coefficients (mu), the relaxation lengths (lambda), half value layer (t sub 1 /2) and tenth value layer (t sub 1 /10). Also, The total mass attenuation coefficients of gamma ray have been calculated to the concerned concretes using XCOM (version 3.1) program and database elements cross sections from Z=1 to 100 at energies from 10 keV to 100 MeV. In...

  8. Radium needle used to calibrate germanium gamma-ray detector.

    Science.gov (United States)

    Kamboj, S; Lovett, D; Kahn, B; Walker, D

    1993-03-01

    A standard platinum-iridium needle that contains 374 MBq 226Ra was tested as a source for calibrating a portable germanium detector used with a gamma-ray spectrometer for environmental radioactivity measurements. The counting efficiencies of the 11 most intense gamma rays emitted by 226Ra and its short-lived radioactive progeny at energies between 186 and 2,448 keV were determined, at the full energy peaks, to construct a curve of counting efficiency vs. energy. The curve was compared to another curve between 43 and 1,596 keV obtained with a NIST mixed-radionuclide standard. It was also compared to the results of a Monte Carlo simulation. The 226Ra source results were consistent with the NIST standard between 248 and 1,596 keV. The Monte Carlo simulation gave a curve parallel to the curve for the combined radium and NIST standard data between 250 and 2,000 keV, but at higher efficiency.

  9. SVOM: a new mission for Gamma-Ray Burst Studies

    CERN Document Server

    Gotz, D; Basa, S; Wei, J; Zhang, S N; Atteia, J -L; Barret, D; Cordier, B; Claret, A; Deng, J; Fan, X; Hu, J Y; Huang, M; Mandrou, P; Mereghetti, S; Qiu, Y; Wu, B

    2009-01-01

    We present the SVOM (Space-based multi-band astronomical Variable Object Monitor) mission, that is being developed in cooperation between the Chinese National Space Agency (CNSA), the Chinese Academy of Science (CAS) and the French Space Agency (CNES). Its scientific objectives include the study of the GRB phenomenon, GRB physics and progenitors, cosmology, and fundamental physics. SVOM is designed to detect all known types of Gamma-Ray Bursts (GRBs), to provide fast and reliable GRB positions, to measure the broadband spectral characteristics and temporal properties of the GRB prompt emission. This will be obtained in first place thanks to a set of four space flown instruments. A wide field (~2 sr) coded mask telescope (ECLAIRs), operating in the 4-250 keV energy range, will provide the triggers and localizations, while a gamma-ray non-imaging spectrometer (GRM), sensitive in the 50 keV-5 MeV domain, will extend the prompt emission energy coverage. After a satellite slew, in order to place the GRB direction ...

  10. Systematic Study of Gamma-ray bright Blazars with Optical Polarization and Gamma-ray Variability

    CERN Document Server

    Itoh, Ryosuke; Fukazawa, Yasushi; Uemura, Makoto; Tanaka, Yasuyuki T; Kawabata, Koji S; Madejski, Grzegorz M; Schinzel, Frank K; Kanda, Yuka; Shiki, Kensei; Akitaya, Hiroshi; Kawabata, Miho; Moritani, Yuki; Nakaoka, Tatsuya; Ohsugi, Takashi; Sasada, Mahito; Takaki, Katsutoshi; Takata, Koji; Ui, Takahiro; Yamanaka, Masayuki; Yoshida, Michitoshi

    2016-01-01

    Blazars are highly variable active galactic nuclei which 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 Jul. 2008 and Dec. 2014 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), thi...

  11. Gamma ray spectroscopy in astrophysics: Solar gamma ray astronomy on solar maximum mission. [experimental design

    Science.gov (United States)

    Forrest, D. J.

    1978-01-01

    The SMM gamma ray experiment and the important scientific capabilities of the instrument are discussed. The flare size detectable as a function of spectrum integration time was studied. A preliminary estimate indicates that a solar gamma ray line at 4.4 MeV one-fifth the intensity of that believed to have been emitted on 4 August 1972 can be detected in approximately 1000 sec with a confidence level of 99%.

  12. The new prompt gamma-ray activation facility at the Paul Scherrer Institute, Switzerland

    CERN Document Server

    Crittin, M; Schenker, J L

    2000-01-01

    Since October 1997, a new Prompt Gamma-ray Activation (PGA) facility at the neutron spallation source SINQ of the Paul Scherrer Institute (PSI) in Villigen, Switzerland, is operational. The detection system includes a Compton-suppression spectrometer and a pair spectrometer. An interesting feature of this PGA facility is the capillary-based neutron focusing optics which permits scanning of samples and nuclear spectroscopy of isotopes having small capture cross sections. During the beam periods 1997 and 1998, measurements were undertaken to characterize the PGA facility (gamma-ray background, efficiencies of the two spectrometers, analytical sensitivities and detection limits for several elements, performances of the neutron lens). Elemental analyses of standards were also performed.

  13. Gamma-Ray Telescopes: 400 Years of Astronomical Telescopes

    Science.gov (United States)

    Gehrels, Neil; Cannizzo, John K.

    2010-01-01

    The last half-century has seen dramatic developments in gamma-ray telescopes, from their initial conception and development through to their blossoming into full maturity as a potent research tool in astronomy. Gamma-ray telescopes are leading research in diverse areas such as gamma-ray bursts, blazars, Galactic transients, and the Galactic distribution of Al-26.

  14. NEW GAMMA RAYS FROM DECAY OF 189W

    Institute of Scientific and Technical Information of China (English)

    杨维凡; 赵之正; 等

    1995-01-01

    Radioactivities of 189W are produced through an 192Os(n,α189W reaction.Gamma ray spectroscopy from chemically separated tungsten sources using HPGe detector has revealed the presence of 22 gamma rays assigned to the decay of 189W,of them,18 gamma rays are new ones unreported until now.

  15. BL Lacertae Objects and the Extragalactic Gamma-Ray Background

    CERN Document Server

    Li, Fan

    2011-01-01

    A tight correlation between gamma-ray and radio emission is found for a sample of BL Lacertae (BL Lac) objects detected by Fermi Gamma-ray Space Telescope (Fermi) and the Energetic Gamma-Ray Experiment Telescope (EGRET). The gamma-ray emission of BL Lac objects exhibits strong variability, and the detection rate of gamma-ray BL Lac objects is low, which may be related to the gamma-ray duty cycle of BL Lac objects. We estimate the gamma-ray duty cycle ~ 0.11, for BL Lac objects detected by EGRET and Fermi. Using the empirical relation of gamma-ray emission with radio emission and the estimated gamma-ray duty cycle, we derive the gamma-ray luminosity function (LF) of BL Lac objects from their radio LF. Our derived gamma-ray LF of BL Lac objects can almost reproduce that calculated with the recently released Fermi bright active galactic nuclei (AGN) sample. We find that about 45% of the extragalactic diffuse gamma-ray background (EGRB) is contributed by BL Lac objects. Combining the estimate of the quasar contri...

  16. Gamma-ray Background Spectrum and Annihilation Rate in the Baryon-symmetric Big-bang Cosmology

    Science.gov (United States)

    Puget, J. L.

    1973-01-01

    An attempt was made to acquire experimental information on the problem of baryon symmetry on a large cosmological scale by observing the annihilation products. Data cover absorption cross sections and background radiation due to other sources for the two main products of annihilation, gamma rays and neutrinos. Test results show that the best direct experimental test for the presence of large scale antimatter lies in the gamma ray background spectrum between 1 and 70 MeV.

  17. ESA's Integral solves thirty-year old gamma-ray mystery

    Science.gov (United States)

    sources towards the direction of the Galactic centre. Lebrun's team includes Ubertini and seventeen other European scientists with long-standing experience in high-energy astrophysics. Much to the team's surprise, almost half of these sources do not fall in any class of known gamma-ray objects. They probably represent a new population of gamma-ray emitters. The first clues about a new class of gamma-ray objects came last October, when Integral discovered an intriguing gamma-ray source, known as IGRJ16318-4848. The data from Integral and ESA's other high-energy observatory XMM-Newton suggested that this object is a binary system, probably including a black hole or neutron star, embedded in a thick cocoon of cold gas and dust. When gas from the companion star is accelerated and swallowed by the black hole, energy is released at all wavelengths, mostly in the gamma rays. However, Lebrun is cautious to draw premature conclusions about the sources detected in the Galactic centre. Other interpretations are also possible that do not involve black holes. For instance, these objects could be the remains of exploded stars that are being energised by rapidly rotating celestial 'powerhouses', known as pulsars. Observations with another Integral instrument (SPI, the Spectrometer on Integral) could provide Lebrun and his team with more information on the nature of these sources. SPI measures the energy of incoming gamma rays with extraordinary accuracy and allows scientist to gain a better understanding of the physical mechanisms that generate them. However, regardless of the precise nature of these gamma-ray sources, Integral's observations have convincingly shown that the energy output from these new objects accounts for almost ninety per cent of the soft gamma-ray background coming from the centre of the Galaxy. This result raises the tantalising possibility that objects of this type hide everywhere in the Galaxy, not just in its centre. Again, Lebrun is cautious, saying, "It is

  18. Gamma-Ray Library and Uncertainty Analysis: Passively Emitted Gamma Rays Used in Safeguards Technology

    Energy Technology Data Exchange (ETDEWEB)

    Parker, W

    2009-09-18

    Non-destructive gamma-ray analysis is a fundamental part of nuclear safeguards, including nuclear energy safeguards technology. Developing safeguards capabilities for nuclear energy will certainly benefit from the advanced use of gamma-ray spectroscopy as well as the ability to model various reactor scenarios. There is currently a wide variety of nuclear data that could be used in computer modeling and gamma-ray spectroscopy analysis. The data can be discrepant (with varying uncertainties), and it may difficult for a modeler or software developer to determine the best nuclear data set for a particular situation. To use gamma-ray spectroscopy to determine the relative isotopic composition of nuclear materials, the gamma-ray energies and the branching ratios or intensities of the gamma-rays emitted from the nuclides in the material must be well known. A variety of computer simulation codes will be used during the development of the nuclear energy safeguards, and, to compare the results of various codes, it will be essential to have all the {gamma}-ray libraries agree. Assessing our nuclear data needs allows us to create a prioritized list of desired measurements, and provides uncertainties for energies and especially for branching intensities. Of interest are actinides, fission products, and activation products, and most particularly mixtures of all of these radioactive isotopes, including mixtures of actinides and other products. Recent work includes the development of new detectors with increased energy resolution, and studies of gamma-rays and their lines used in simulation codes. Because new detectors are being developed, there is an increased need for well known nuclear data for radioactive isotopes of some elements. Safeguards technology should take advantage of all types of gamma-ray detectors, including new super cooled detectors, germanium detectors and cadmium zinc telluride detectors. Mixed isotopes, particularly mixed actinides found in nuclear reactor

  19. Dust extinction in high-z galaxies with gamma-ray burst afterglow spectroscopy

    DEFF Research Database (Denmark)

    Elíasdóttir, Á.; Fynbo, J. P. U.; Hjorth, J.

    2009-01-01

    We report the clear detection of the 2175 Å dust absorption feature in the optical afterglow spectrum of the gamma-ray burst (GRB) GRB 070802 at a redshift of z = 2.45. This is the highest redshift for a detected 2175 Å dust bump to date, and it is the first clear detection of the 2175 Å bump in ...

  20. 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.

  1. Single-Grid-Pair Fourier Telescope for Imaging in Hard-X Rays and gamma Rays

    Science.gov (United States)

    Campbell, Jonathan

    2008-01-01

    This instrument, a proposed Fourier telescope for imaging in hard-x rays and gamma rays, would contain only one pair of grids made of an appropriate radiation-absorpting/ scattering material, in contradistinction to multiple pairs of such as grids in prior Fourier x- and gamma-ray telescopes. This instrument would also include a relatively coarse gridlike image detector appropriate to the radiant flux to be imaged. Notwithstanding the smaller number of grids and the relative coarseness of the imaging detector, the images produced by the proposed instrument would be of higher quality.

  2. TeV gamma-ray astronomy

    Institute of Scientific and Technical Information of China (English)

    Wei Cui

    2009-01-01

    The field of ground-based gamma-ray astronomy has enjoyed rapid growth in recent years. As an increasing number of sources are detected at TeV energies, the field has matured and become a viable branch of modern astronomy. Lying at the uppermost end of the electromagnetic rainbow, TeV photons are always preciously few in number but carry essential information about the particle acceleration and radiative processes involved in extreme astronomical settings. Together with observations at longer wavelengths, TeV gamma-ray observations have drastically improved our view of the universe. In this re-view, we briefly describe recent progress in the field. We will conclude by providing a personal perspective on the future of the field, in particular, on the significant roles that China could play in advancing this young but exciting field.

  3. Are gamma-ray bursts cosmological?

    CERN Document Server

    Horvath, I

    2015-01-01

    Gamma-ray burst sources are distributed with a high level of isotropy, which is compatible with either a cosmological origin or an extended Galactic halo origin. The brightness distribution is another indicator used to characterize the spatial distribution in distance. In this paper the author discusses detailed fits of the BATSE gamma-ray burst peak-flux distributions with Friedmann models taking into account possible density evolution and standard candle luminosity functions. A chi-square analysis is used to estimate the goodness of the fits and the author derives the significance level of limits on the density evolution and luminosity function parameters. Cosmological models provide a good fit over a range of parameter space which is physically reasonable

  4. The future of gamma-ray astronomy

    CERN Document Server

    Knödlseder, Jürgen

    2016-01-01

    The field of gamma-ray astronomy has experienced impressive progress over the last decade. Thanks to the advent of a new generation of imaging air Cherenkov telescopes (H.E.S.S., MAGIC, VERITAS) and thanks to the launch of the Fermi-LAT satellite, several thousand gamma-ray sources are known today, revealing an unexpected ubiquity of particle acceleration processes in the Universe. Major scientific challenges are still ahead, such as the identification of the nature of Dark Matter, the discovery and understanding of the sources of cosmic rays, or the comprehension of the particle acceleration processes that are at work in the various objects. This paper presents some of the instruments and mission concepts that will address these challenges over the next decades.

  5. Stirling Colgate and Gamma-Ray Bursts

    Science.gov (United States)

    Lamb, Donald

    2014-10-01

    Even before the discovery of gamma-ray bursts (GRBs), Stirling Colgate proposed that bursts of x rays and gamma rays might be produced by a relativistic shock created in the supernova explosion of a massive star. We trace the scientific story of GRBs from their detection to the present, highlighting along the way Stirling's interest in them and his efforts to understand them. We summarize our current understanding that short, soft, repeating bursts are produced by magnetic neutron stars; short, hard bursts are produced by the mergers of neutron star-neutron star binaries; and long, hard bursts are produced by the core collapse of massive stars that have lost their hydrogen and helium envelopes. We then discuss some important open questions about GRBs and how they might be answered. We conclude by describing the recent serendipitous discovery of an x-ray burst of exactly the kind he proposed, and the insights into core collapse supernovae and GRBs that it provided.

  6. The future of gamma-ray astronomy

    Science.gov (United States)

    Knödlseder, Jürgen

    2016-06-01

    The field of gamma-ray astronomy has experienced impressive progress over the last decade. Thanks to the advent of a new generation of imaging air Cherenkov telescopes (H.E.S.S., MAGIC, VERITAS) and thanks to the launch of the Fermi-LAT satellite, several thousand gamma-ray sources are known today, revealing an unexpected ubiquity of particle acceleration processes in the Universe. Major scientific challenges are still ahead, such as the identification of the nature of Dark Matter, the discovery and understanding of the sources of cosmic rays, or the comprehension of the particle acceleration processes that are at work in the various objects. This paper presents some of the instruments and mission concepts that will address these challenges over the next decades. xml:lang="fr"

  7. 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.

  8. Physics of gamma-ray bursts

    Science.gov (United States)

    Lamb, D. Q.

    1984-01-01

    Attention is given to the accumulating evidence for the view that gamma-ray bursts come from strongly magnetic neutron stars, discussing the physical properties of the emission region and the radiation processes expected in strong magnetic fields, and emphasizing that the observed burst spectra require that the emission region be optically thin. This entails that the energy of the emitting plasma and/or the plasma itself be continuously replenished during a burst, and that the cooling time scale of the emitting plasma be much shorter than the observed duration of the bursts. This characteristic of the cooling time scale implies that the burst intensity and spectrum can vary on extremely short time scales, and that the burst duration must have a separate explanation. It is emphasized that synchrotron emission is favored as the gamma-ray production mechanism; it is the only mechanism capable of satisfying the optical thinness constraint while producing the observed luminosity.

  9. TeV Gamma Ray Astronomy

    CERN Document Server

    Cui, Wei

    2009-01-01

    The field of ground-based gamma ray astronomy has enjoyed rapid growth in recent years. As an increasing number of sources are detected at TeV energies, the field has matured and become a viable branch of modern astronomy. Lying at the uppermost end of the electromagnetic rainbow, TeV photons are always preciously few in number but carry essential information about the particle acceleration and radiative processes involved in extreme astronomical settings. Together with observations at longer wavelengths, TeV gamma-ray observations have drastically improved our view of the universe. In this review, we briefly describe recent progress in the field. We will conclude by providing a personal perspective on the future of the field, in particular, on the significant roles that China could play to advance this young but exciting field.

  10. The Future of Gamma Ray Astrophysics

    CERN Document Server

    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.

  11. 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.

  12. Do Gamma-Ray Burst Sources Repeat?

    OpenAIRE

    Meegan, Charles A.; Hartmann, Dieter H.; Brainerd, J. J.; Briggs, Michael S.; Paciesas, William S.; Pendleton, Geoffrey; Kouveliotou, Chryssa; Fishman, Gerald; Blumenthal, George; Brock, Martin

    1995-01-01

    The demonstration of repeated gamma-ray bursts from an individual source would severely constrain burst source models. Recent reports (Quashnock and Lamb 1993; Wang and Lingenfelter 1993) of evidence for repetition in the first BATSE burst catalog have generated renewed interest in this issue. Here, we analyze the angular distribution of 585 bursts of the second BATSE catalog (Meegan et al. 1994). We search for evidence of burst recurrence using the nearest and farthest neighbor statistic and...

  13. GAMMA-RAY BURSTS, NEW COSMOLOGICAL BEACONS

    Directory of Open Access Journals (Sweden)

    V. Avila-Reese

    2009-01-01

    Full Text Available Long Gamma-Ray Bursts (GRBs are the brightest electromagnetic explosions in the Universe, associated to the death of massive stars. As such, GRBs are potential tracers of the evolution of the cosmic massive star formation, metallicity, and Initial Mass Function. GRBs also proved to be appealing cosmological distance indicators. This opens a unique opportunity to constrain the cosmic expansion history up to redshifts 5-6. A brief review on both subjects is presented here.

  14. Gamma-ray bounds from EAS detectors and heavy decaying dark matter constraints

    CERN Document Server

    Esmaili, Arman

    2015-01-01

    The very high energy Galactic gamma-ray sky is partially opaque in the (0.1-10) PeV energy range. In the light of the recently detected high energy neutrino flux by IceCube, a comparable very high energy gamma-ray flux is expected in any scenario with a sizable Galactic contribution to the neutrino flux. Here we elaborate on the peculiar energy and anisotropy features imposed upon these very high energy gamma-rays by the absorption on the cosmic microwave background photons and Galactic interstellar light. As a notable application of our considerations, we study the prospects of probing the PeV-scale decaying DM scenario, proposed as a possible source of IceCube neutrinos, by extensive air shower (EAS) cosmic ray experiments.

  15. Ambiguity in gamma-ray tracking of 'two-interaction' events

    Energy Technology Data Exchange (ETDEWEB)

    Hammond, N.J. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Duguet, T. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Lister, C.J. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States)]. E-mail: lister@anl.gov

    2005-08-01

    Tracking of gamma-rays in germanium detectors can allow the full reconstruction of interactions, a feature that is useful in many applications. Scrutiny of the kinematics and geometry of gamma-rays which are Compton scattered only once prior to full absorption reveals that there are special cases where even perfect spatial and energy resolution cannot resolve the true interaction sequence and consequently the gamma-ray tracks cannot be unambiguously reconstructed. The photon energy range where this ambiguity exists is from 255 keV to about 700 keV. This is an energy region of importance for nuclear structure research and a domain where two-point interactions are probable.

  16. Gamma ray tracking with the AGATA demonstrator

    Energy Technology Data Exchange (ETDEWEB)

    Birkenbach, Benedikt; Hess, Herbert; Lewandowski, Lars; Reiter, Peter; Steinbach, Tim; Schneiders, David; Vogt, Andreas [IKP, Universitaet zu Koeln (Germany); Collaboration: AGATA-Collaboration

    2014-07-01

    The performance of the AGATA demonstrator will be discussed based on data taken from a multi-nucleon transfer experiment at the AGATA PRISMA setup at LNL (INFN, Italy). A primary {sup 136}Xe beam of 1 GeV hitting a {sup 238}U target was used to produce a multitude of nuclei in the vicinity of {sup 136}Xe and corresponding reaction partners in the actinide region. The obtained results for in-beam gamma-ray spectroscopy allow for a critical assessment of the novel gamma ray tracking technique and comparison with standard procedure. High resolution spectroscopy of both reaction products after multi-nucleon transfer reaction in the presence of a high background from excited fission fragments is based on pulse-shape analysis (PSA) and gamma-ray tracking (GRT). The quality of the position information is crucial for the final energy resolution after Doppler correction. The impact of the calculated PSA libraries and the initial detector characterization for the PSA and GRT are summarized. Details of the achieved position and energy resolution, peak-to-background optimization are presented and illustrated with results from the neutron-transfer products in Xe and U-isotopes.

  17. Gamma Ray Bursts Cook Book I: Formulation

    CERN Document Server

    Ziaeepour, Houri

    2008-01-01

    Since the suggestion of relativistic shocks as the origin of gamma-ray bursts (GRBs) in early 90's, the mathematical formulation of this process has stayed at phenomenological level. One of the reasons for the slow development of theoretical works in this domain has been the simple power-law behaviour of the afterglows hours or days after the prompt gamma-ray emission. Nowadays with the launch of the Swift satellite, gamma-ray bursts can be observed in multi-wavelength from a few tens of seconds after trigger onward. These observations have leaded to the discovery of features unexplainable by the simple formulation of the shocks and emission processes used up to now. But "devil is in details" and some of these features may be explained with a more detailed formulation of phenomena and without adhoc addition of new processes. Such a formulation is the goal of this work. We present a consistent formulation of the collision between two spherical relativistic shells. The model can be applied to both internal and ...

  18. Bremsstrahlung gamma rays from light Dark Matter

    CERN Document Server

    Cirelli, Marco; Zaharijas, Gabrijela

    2013-01-01

    We discuss the often-neglected role of bremsstrahlung processes on the interstellar gas in computing indirect signatures of Dark Matter (DM) annihilation in the Galaxy, particularly for light DM candidates in the phenomenologically interesting O(10) GeV mass range. Especially from directions close to the Galactic Plane, the expected gamma-ray spectrum is altered via two effects: directly, by the photons emitted in the bremsstrahlung process on the interstellar gas by energetic electrons which are among the DM annihilation byproducts; indirectly, by the modification of the same electron spectrum, due to the additional energy loss process in the diffusion-loss equation (e.g. the resulting inverse Compton emission is altered). We quantify the importance of the bremsstrahlung emission in the GeV energy range, showing that it is the dominant component of the gamma-ray spectrum for some cases. We also find that, in regions in which bremsstrahlung dominates energy losses, the related gamma-ray emission is only moder...

  19. Delayed Nickel Decay in Gamma Ray Bursts

    CERN Document Server

    McLaughlin, G C

    2002-01-01

    Recently observed emission lines in the X-ray afterglow of gamma ray bursts suggest that iron group elements are either produced in the gamma ray burst, or are present nearby. If this material is the product of a thermonuclear burn, then such material would be expected to be rich in Nickel-56. If the nickel remains partially ionized, this prevents the electron capture reaction normally associated with the decay of Nickel-56, dramatically increasing the decay timescale. Here we examine the consequences of rapid ejection of a fraction of a solar mass of iron group material from the center of a collapsar/hypernova. The exact rate of decay then depends on the details of the ionization and therefore the ejection process. Future observations of iron, nickel and cobalt lines can be used to diagnose the origin of these elements and to better understand the astrophysical site of gamma ray bursts. In this model, the X-ray lines of these iron-group elements could be detected in suspected hypernovae that did not produce ...

  20. 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...

  1. Afterglow Radiation from Gamma Ray Bursts

    Energy Technology Data Exchange (ETDEWEB)

    Desmond, Hugh; /Leuven U. /SLAC

    2006-08-28

    Gamma-ray bursts (GRB) are huge fluxes of gamma rays that appear randomly in the sky about once a day. It is now commonly accepted that GRBs are caused by a stellar object shooting off a powerful plasma jet along its rotation axis. After the initial outburst of gamma rays, a lower intensity radiation remains, called the afterglow. Using the data from a hydrodynamical numerical simulation that models the dynamics of the jet, we calculated the expected light curve of the afterglow radiation that would be observed on earth. We calculated the light curve and spectrum and compared them to the light curves and spectra predicted by two analytical models of the expansion of the jet (which are based on the Blandford and McKee solution of a relativistic isotropic expansion; see Sari's model [1] and Granot's model [2]). We found that the light curve did not decay as fast as predicted by Sari; the predictions by Granot were largely corroborated. Some results, however, did not match Granot's predictions, and more research is needed to explain these discrepancies.

  2. Hadronic Gamma Rays from Supernova Remnants

    CERN Document Server

    Moskalenko, I V; Malkov, M A; Diamond, P H

    2007-01-01

    A gas cloud near a supernova remnant (SNR) provides a target for pp-collisions leading to subsequent gamma-ray emission through neutral pion decay. The assumption of a power-law ambient spectrum of accelerated particles with index near -2 is usually built into models predicting the spectra of very-high energy (VHE) gamma-ray emission from SNRs. However, if the gas cloud is located at some distance from the SNR shock, this assumption is not necessarily correct. In this case, the particles which interact with the cloud are those leaking from the shock and their spectrum is approximately monoenergetic with the injection energy gradually decreasing as the SNR ages. The gamma-ray spectrum resulting from particle interactions with the gas cloud will be flatter than expected, with the cutoff defined by the pion momentum distribution in the laboratory frame. We evaluate the flux of particles escaping from a SNR shock and apply the results to the VHE diffuse emission detected by the HESS at the Galactic centre.

  3. Probing Massive Stars Around Gamma-Ray Burst Progenitors

    CERN Document Server

    Lu, Wenbin; Smoot, George F

    2015-01-01

    Long Gamma-Ray Bursts (GRBs) are produced by ultra-relativistic jets launched from core collapse of massive stars. Most massive stars form in binaries and/or in star clusters, which means that there may be a significant external photon field (EPF) around the GRB progenitor. We calculate the inverse-Compton scattering of EPF by the hot electrons in the GRB jet. Three possible cases of EPFs are considered: the progenitor is (I) in a massive binary system, (II) surrounded by a Wolf-Rayet-star wind, and (III) in a dense star cluster. Typical luminosities of 10^47 - 10^50 erg/s in the 10 - 100 GeV band are expected, depending on the stellar luminosity, binary separation (I), wind mass loss rate (II), stellar number density (III), etc. We calculate the lightcurve and spectrum in each case, taking fully into account the equal-arrival time surfaces and possible pair-production absorption with the prompt gamma-rays. Observations can put constraints on the existence of such EPFs (and hence on the nature of GRB progenit...

  4. Novel light-weight materials for shielding gamma ray

    Science.gov (United States)

    Chen, Shuo; Bourham, Mohamed; Rabiei, Afsaneh

    2014-03-01

    A comparison of gamma ray attenuation effectiveness of bulk aluminum, close-cell composite metal foams and open-cell aluminum foam infiltrated with variety of second phase materials were investigated and reported in this study. Mass attenuation coefficients for six sets of samples with three different areal densities of 2, 5 and 10 g/cm2 were determined at photon energies of 0.060, 0.662, 1.173, and 1.332 MeV. Theoretical values were calculated using XCOM software package. A complete agreement was observed between experimental and theoretical results. It is observed that close-cell composite metal foams exhibit a better shielding capability compared to open-cell Al foam with fillers. It is also observed that close-cell composite metal foams offer superior shielding effectiveness compared to bulk aluminum for energies below 0.662 MeV, the mass attenuation coefficients of steel-steel composite metal foam and Al-steel composite metal foam were measured 400 and 300% higher than that of aluminum A356. This study indicates the potential of utilizing the light-weight composite metal foams as shielding material replacing current heavy materials used for attenuation of low energy gamma ray with additional advantages such as high energy absorption and excellent heat rejection capabilities.

  5. Gamma-ray Output Spectra from 239Pu Fission

    Directory of Open Access Journals (Sweden)

    Ullmann John

    2015-01-01

    Full Text Available Gamma-ray multiplicities, individual gamma-ray energy spectra, and total gamma energy spectra following neutron-induced fission of 239Pu were measured using the DANCE detector at Los Alamos. Corrections for detector response were made using a forward-modeling technique based on propagating sets of gamma rays generated from a paramaterized model through a GEANT model of the DANCE array and adjusting the parameters for best fit to the measured spectra. The results for the gamma-ray spectrum and multiplicity are in general agreement with previous results, but the measured total gamma-ray energy is about 10% higher. A dependence of the gamma-ray spectrum on the gamma-ray multplicity was also observed. Global model calculations of the multiplicity and gamma energy distributions are in good agreement with the data, but predict a slightly softer total-energy distribution.

  6. News from Cosmic Gamma-ray Line Observations

    CERN Document Server

    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 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 $^{56}$Ni, $^{56}$Co, and $^{44}$Ti. The diffuse afterglow in gamma rays of radioa...

  7. DUVAS (derivative uv-absorption spectrometer): instrument description and operating manual

    Energy Technology Data Exchange (ETDEWEB)

    Hawthorne, A.R.; Dougherty, J.M.; Metcalfe, C.E.

    1980-11-01

    DUVAS is a real-time, field-portable spectrometer capable of monitoring a variety of aromatic organic vapors and inorganic gases at sub-ppM concentrations. The instrument is a prototype, microcomputer-controlled, derivative ultraviolet (UV) absorption spectrometer (DUVAS) developed primarily for area monitoring at coal conversion facilities, although other important occupational and environmental monitoring applications for compounds such as SO/sub 2/, NO/sub x/, NH/sub 3/, and HCHO are also being pursued.

  8. Experimental Investigation of Clay Fly Ash Bricks for Gamma-Ray Shielding

    Directory of Open Access Journals (Sweden)

    Harjinder Singh Mann

    2016-10-01

    Full Text Available This study aims to determine the effect of fly ash with a high replacing ratio of clay on the radiation shielding properties of bricks. Some interaction parameters (mass attenuation coefficients, half value layer, effective atomic number, effective electron density, and absorption efficiency of clay fly ash bricks were measured with a NaI(Tl detector at 661.6 keV, 1,173.2 keV, and 1,332.5 keV. For the investigation of their shielding behavior, fly ash bricks were molded using an admixture to clay. A narrow beam transmission geometry condition was used for the measurements. The measured values of these parameters were found in good agreement with the theoretical calculations. The elemental compositions of the clay fly ash bricks were analyzed by using an energy dispersive X-ray fluorescence spectrometer. At selected energies the values of the effective atomic numbers and effective electron densities showed a very modest variation with the composition of the fly ash. This seems to be due to the similarity of their elemental compositions. The obtained results were also compared with concrete, in order to study the effect of fly ash content on the radiation shielding properties of clay fly ash bricks. The clay fly ash bricks showed good shielding properties for moderate energy gamma rays. Therefore, these bricks are feasible and eco-friendly compared with traditional clay bricks used for construction.

  9. Experimental investigation of clay fly ash bricks for gamma-ray shielding

    Energy Technology Data Exchange (ETDEWEB)

    Mann Harjinder Singh; Mudahar, Gumel Singh [Dept. of Physics, Punjabi University, Patiala (India); Brar, Gurdarshan Singh [Dept. of Higher Education, Additional Project Director, Chandigarh (India); Mann, Kulwinder Singh [Dept. of Applied Sciences, I.K. Gujral Punjab Technical University, Jalandhar (India)

    2016-10-15

    This study aims to determine the effect of fly ash with a high replacing ratio of clay on the radiation shielding properties of bricks. Some interaction parameters (mass attenuation coefficients, half value layer, effective atomic number, effective electron density, and absorption efficiency) of clay fly ash bricks were measured with a NaI(Tl) detector at 661.6 keV, 1,173.2 keV, and 1,332.5 keV. For the investigation of their shielding behavior, fly ash bricks were molded using an admixture to clay. A narrow beam transmission geometry condition was used for the measurements. The measured values of these parameters were found in good agreement with the theoretical calculations. The elemental compositions of the clay fly ash bricks were analyzed by using an energy dispersive X-ray fluorescence spectrometer. At selected energies the values of the effective atomic numbers and effective electron densities showed a very modest variation with the composition of the fly ash. This seems to be due to the similarity of their elemental compositions. The obtained results were also compared with concrete, in order to study the effect of fly ash content on the radiation shielding properties of clay fly ash bricks. The clay fly ash bricks showed good shielding properties for moderate energy gamma rays. Therefore, these bricks are feasible and eco-friendly compared with traditional clay bricks used for construction.

  10. A Fourier transform spectrometer for visible and near ultra-violet measurements of atmospheric absorption

    Science.gov (United States)

    Parsons, C. L.; Gerlach, J. C.; Whitehurst, M.

    1982-01-01

    The development of a prototype, ground-based, Sun-pointed Michelson interferometric spectrometer is described. Its intended use is to measure the atmospheric amount of various gases which absorb in the near-infrared, visible, and near-ultraviolet portions of the electromagnetic spectrum. Preliminary spectra which contain the alpha, 0.8 micrometer, and rho sigma tau water vapor absorption bands in the near-infrared are presented to indicate the present capability of the system. Ultimately, the spectrometer can be used to explore the feasible applications of Fourier transform spectroscopy in the ultraviolet where grating spectrometers were used exclusively.

  11. High energy gamma-ray emission from Gamma-Ray Bursts -- before GLAST

    CERN Document Server

    Fan, Yi-Zhong

    2008-01-01

    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.

  12. GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Storm, Emma M.; Jeltema, Tesla E.; Profumo, Stefano [Department of Physics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2012-08-20

    Star formation in galaxies is observed to be associated with gamma-ray emission, presumably from non-thermal processes connected to the acceleration of cosmic-ray nuclei and electrons. The detection of gamma rays from starburst galaxies by the Fermi Large Area Telescope (LAT) has allowed the determination of a functional relationship between star formation rate and gamma-ray luminosity. Since star formation is known to scale with total infrared (8-1000 {mu}m) and radio (1.4 GHz) luminosity, the observed infrared and radio emission from a star-forming galaxy can be used to quantitatively infer the galaxy's gamma-ray luminosity. Similarly, star-forming galaxies within galaxy clusters allow us to derive lower limits on the gamma-ray emission from clusters, which have not yet been conclusively detected in gamma rays. In this study, we apply the functional relationships between gamma-ray luminosity and radio and IR luminosities of galaxies derived by the Fermi Collaboration to a sample of the best candidate galaxy clusters for detection in gamma rays in order to place lower limits on the gamma-ray emission associated with star formation in galaxy clusters. We find that several clusters have predicted gamma-ray emission from star formation that are within an order of magnitude of the upper limits derived in Ackermann et al. based on non-detection by Fermi-LAT. Given the current gamma-ray limits, star formation likely plays a significant role in the gamma-ray emission in some clusters, especially those with cool cores. We predict that both Fermi-LAT over the course of its lifetime and the future Cerenkov Telescope Array will be able to detect gamma-ray emission from star-forming galaxies in clusters.

  13. Optical microresonators as single-particle absorption spectrometers

    Science.gov (United States)

    Heylman, Kevin D.; Thakkar, Niket; Horak, Erik H.; Quillin, Steven C.; Cherqui, Charles; Knapper, Kassandra A.; Masiello, David J.; Goldsmith, Randall H.

    2016-12-01

    Optical measurements of nanoscale objects offer major insights into fundamental biological, material and photonic properties. In absorption spectroscopy, sensitivity limits applications at the nanoscale. Here, we present a new single-particle double-modulation photothermal absorption spectroscopy method that employs on-chip optical whispering-gallery-mode (WGM) microresonators as ultrasensitive thermometers. Optical excitation of a nanoscale object on the microresonator produces increased local temperatures that are proportional to the absorption cross-section of the object. We resolve photothermal shifts in the resonance frequency of the microresonator that are smaller than 100 Hz, orders of magnitude smaller than previous WGM sensing schemes. The application of our new technique to single gold nanorods reveals a dense array of sharp Fano resonances arising from the coupling between the localized surface plasmon of the gold nanorod and the WGMs of the resonator, allowing for the exploration of plasmonic-photonic hybridization. In terms of the wider applicability, our approach adds label-free spectroscopic identification to microresonator-based detection schemes.

  14. Observing with a space-borne gamma-ray telescope: selected results from INTEGRAL

    CERN Document Server

    Schanne, S

    2006-01-01

    The International Gamma-Ray Astrophysics Laboratory, i.e. the INTEGRAL satellite of ESA, in orbit since about 3 years, performs gamma-ray observations of the sky in the 15 keV to 8 MeV energy range. Thanks to its imager IBIS, and in particular the ISGRI detection plane based on 16384 CdTe pixels, it achieves an excellent angular resolution (12 arcmin) for point source studies with good continuum spectrum sensitivity. Thanks to its spectrometer SPI, based on 19 germanium detectors maintained at 85 K by a cryogenic system, located inside an active BGO veto shield, it achieves excellent spectral resolution of about 2 keV for 1 MeV photons, which permits astrophysical gamma-ray line studies with good narrow-line sensitivity. In this paper we review some goals of gamma-ray astronomy from space and present the INTEGRAL satellite, in particular its instruments ISGRI and SPI. Ground and in-flight calibration results from SPI are presented, before presenting some selected astrophysical results from INTEGRAL. In partic...

  15. Simulation experiments for gamma-ray mapping of planetary surfaces: Scattering of high-energy neutrons

    Science.gov (United States)

    Brueckner, J.; Englert, P.; Reedy, R. C.; Waenke, H.

    1986-01-01

    The concentration and distribution of certain elements in surface layers of planetary objects specify constraints on models of their origin and evolution. This information can be obtained by means of remote sensing gamma-ray spectroscopy, as planned for a number of future space missions, i.e., Mars, Moon, asteroids, and comets. To investigate the gamma-rays made by interactions of neutrons with matter, thin targets of different composition were placed between a neutron-source and a high-resolution germanium spectrometer. Gamma-rays in the range of 0.1 to 8 MeV were accumulated. In one set of experiments a 14-MeV neutron generator using the T(d,n) reaction as neutron-source was placed in a small room. Scattering in surrounding walls produced a spectrum of neutron energies from 14 MeV down to thermal. This complex neutron-source induced mainly neutron-capture lines and only a few scattering lines. As a result of the set-up, there was a considerable background of discrete lines from surrounding materials. A similar situation exists under planetary exploration conditions: gamma-rays are induced in the planetary surface as well as in the spacecraft. To investigate the contribution of neutrons with higher energies, an experiment for the measurement of prompt gamma radiation was set up at the end of a beam-line of an isochronous cyclotron.

  16. Determining the solar-flare photospheric scale height from SMM gamma-ray measurements

    Science.gov (United States)

    Lingenfelter, Richard E.

    1991-01-01

    A connected series of Monte Carlo programs was developed to make systematic calculations of the energy, temporal and angular dependences of the gamma-ray line and neutron emission resulting from such accelerated ion interactions. Comparing the results of these calculations with the Solar Maximum Mission/Gamma Ray Spectrometer (SMM/GRS) measurements of gamma-ray line and neutron fluxes, the total number and energy spectrum of the flare-accelerated ions trapped on magnetic loops at the Sun were determined and the angular distribution, pitch angle scattering, and mirroring of the ions on loop fields were constrained. Comparing the calculations with measurements of the time dependence of the neutron capture line emission, a determination of the He-3/H ratio in the photosphere was also made. The diagnostic capabilities of the SMM/GRS measurements were extended by developing a new technique to directly determine the effective photospheric scale height in solar flares from the neutron capture gamma-ray line measurements, and critically test current atmospheric models in the flare region.

  17. Verification of some building materials as gamma-ray shields.

    Science.gov (United States)

    Mann, Kulwinder Singh; Singla, Jyoti; Kumar, Vipan; Sidhu, G S

    2012-08-01

    The shielding properties for gamma rays of a few low Z materials were investigated. The values of the mass attenuation coefficient, equivalent atomic number, effective atomic number, exposure buildup factor and energy absorption buildup factor were calculated and used to estimate the shielding effectiveness of the samples under investigation. It has been observed that the shielding effectiveness of a sample is directly related to its effective atomic number. The shielding character of any sample is a function of the incident photon energy. Good shielding behaviour has been verified in soil samples in the photon energy region of 0.015-0.30 MeV and of dolomite in 3-15 MeV. The results have been shown graphically with more useful conclusions.

  18. Two classes of gamma-ray bursts

    CERN Document Server

    Katz, J I

    1995-01-01

    Data from the 3B Catalogue suggest that short and long GRB are the results of different classes of events, rather than different parameter values within a single class: Short bursts have harder spectra in the BATSE bands, but chiefly long bursts are detected at photon energies over 1 MeV, implying that their hard photons are radiated by a process not found in short bursts. The values of \\langle V/V_{max} \\rangle for short and long bursts differ by 4.3 \\sigma, implying different spatial distributions. Only the soft gamma-ray radiation mechanisms are the same in both classes.

  19. Material recognition using fission gamma rays

    Energy Technology Data Exchange (ETDEWEB)

    Viesti, G. [Dipartimento di Fisica dell' Universita di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy)], E-mail: giuseppe.viesti@pd.infn.it; Sajo-Bohus, L. [Universidad Simon-Bolivar, Laboratorio Fisica Nuclear, Apartado 8900, 1080 A. Caracas (Venezuela, Bolivarian Republic of); Fabris, D. [INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Lunardon, M.; Moretto, S. [Dipartimento di Fisica dell' Universita di Padova, Via Marzolo 8, I-35131 Padova (Italy); INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy); Nebbia, G.; Pesente, S. [INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova (Italy)

    2009-07-21

    Material recognition is studied by measuring the transmission spectrum of {sup 252}Cf fission gamma rays in the energy range E{sub {gamma}}=0.1-5.5 MeV for 0.1-MeV-wide energy bins through a number of elementary samples. Each transmitted spectrum is compared with a library of reference spectra for different elements providing the possibility of material identification. In case of elemental samples with known thickness, this procedure allows the identification of the sample Z with uncertainty typically lower than 3 Z-units over a wide range of elements. Applications to composite materials are also reported.

  20. 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...

  1. Multiwavelength Studies of gamma-ray Binaries

    Science.gov (United States)

    Aragona, Christina

    2011-01-01

    High mass X-ray binaries (HMXBs) consist of an O or B star orbited by either a neutron star or a black hole. Of the 114 known Galactic HMXBs, a handful of these objects, dubbed gamma-ray binaries, have been observed to produce MeV-TeV emission. The very high energy emission can be produced either by accretion from the stellar wind onto a black hole or a collision between the stellar wind and a relativistic pulsar wind. Both these scenarios make gamma-ray binaries valuable nearby systems for studying the physics of shocks and jets. Currently, the nature of the compact object and the high energy production mechanism is unknown or unconfirmed in over half of these systems. My goal for this dissertation is to constrain the parameters describing two of these systems: LS 5039 and HD 259440. LS 5039 exhibits gamma-ray emission modulated with its orbital period. The system consists of an ON6.5V((f)) star and an unidentified compact companion. Using optical spectra from the CTIO 1.5m telescope, we found LS 5039 to have an orbital period of 3.90608 d and an eccentricity of 0.337. Spectra of the Halpha line observed with SOAR indicate a mass loss rate of ˜ 1.9x10 -8 M yr-1. Observations taken with ATCA at 13 cm, 6 cm, and 3 cm indicate radio fluxes between 10--40 mJy. The measurements show variability with time, indicating a source other than thermal emission from the stellar wind. HD 259440 is a B0pe star that was proposed as the optical counterpart to the gamma-ray source HESS J0632+057. Using optical spectra from the KPNO CF, KPNO 2.1m, and OHP telescopes, we find a best fit stellar effective temperature of 27500--30000 K, a log surface gravity of 3.75--4.0, a mass of 13.2--19.0 Msolar, and a radius of 6.0--9.6 Rsolar. By fitting the spectral energy distribution, we find a distance between 1.1--1.7 kpc. We do not detect any significant radial velocity shifts in our data, ruling out orbital periods shorter than one month. If HD 259440 is a binary, it is likely a long

  2. The Nature of Gamma Ray Burst Supernovae

    OpenAIRE

    Cano, Zach

    2012-01-01

    Gamma Ray Bursts (GRBs) and Supernovae (SNe) are among the brightest and most energetic physical processes in the universe. It is known that core-collapse SNe arise from the gravitational collapse and subsequent explosion of massive stars (the progen- itors of nearby core-collapse SNe have been imaged and unambiguously identified). It is also believed that the progenitors of long-duration GRBs (L-GRBs) are massive stars, mainly due to the occurrence and detection of very energetic core-collap...

  3. Properties of $\\gamma$-Ray Burst Classes

    CERN Document Server

    Hakkila, J; Roiger, R J; Mallozzi, R S; Pendleton, G N; Meegan, C A; Hakkila, Jon; Haglin, David J.; Roiger, Richard J.; Mallozzi, Robert S.; Pendleton, Geoffrey N.; Meegan, Charles A.

    2000-01-01

    The three gamma-ray burst (GRB) classes identified by statistical clustering analysis (Mukherjee et al. 1998) are examined using the pattern recognition algorithm C4.5 (Quinlan 1986). Although the statistical existence of Class 3 (intermediate duration, intermediate fluence, soft) is supported, the properties of this class do not need to arise from a distinct source population. Class 3 properties can easily be produced from Class 1 (long, high fluence, intermediate hardness) by a combination of measurement error, hardness/intensity correlation, and a newly-identified BATSE bias (the fluence duration bias). Class 2 (short, low fluence, hard) does not appear to be related to Class 1.

  4. Nucleosynthetic Yields from Gamma-Ray Bursts

    CERN Document Server

    Rockefeller, Gabriel; Young, Patrick; Bennett, Michael; Diehl, Steven; Herwig, Falk; Hirschi, Raphael; Hungerford, Aimee; Pignatari, Marco; Magkotsios, Georgios; Timmes, Francis X

    2008-01-01

    The "collapsar" engine for gamma-ray bursts invokes as its energy source the failure of a normal supernova and the formation of a black hole. Here we present the results of the first three-dimensional simulation of the collapse of a massive star down to a black hole, including the subsequent accretion and explosion. The explosion differs significantly from the axisymmetric scenario obtained in two-dimensional simulations; this has important consequences for the nucleosynthetic yields. We compare the nucleosynthetic yields to those of hypernovae. Calculating yields from three-dimensional explosions requires new strategies in post-process nucleosynthesis; we discuss NuGrid's plan for three-dimensional yields.

  5. X-ray and gamma-ray response of a 2 '' x 2 '' LaBr3 : Ce scintillation detector

    NARCIS (Netherlands)

    Quarati, F.; Bos, A. J. J.; Brandenburg, S.; Dathy, C.; Dorenbos, P.; Kraft, S.; Ostendorf, R. W.; Ouspenski, V.; Owens, Alan

    2007-01-01

    Advances in material growth techniques have recently made large volume LaBr3:Ce crystals commercially available. These scintillators are currently being assessed by ESA for use as remote sensing gamma-ray spectrometers on future planetary missions. In addition to their superior scintillation propert

  6. Gamma-ray opacity of the anisotropic stratified broad-line regions in blazars

    Science.gov (United States)

    Abolmasov, Pavel; Poutanen, Juri

    2016-09-01

    The GeV-range spectra of blazars are shaped not only by non-thermal emission processes internal to the relativistic jet but also by external pair-production absorption on the thermal emission of the accretion disc and the broad-line region (BLR). For the first time, we compute here the pair-production opacities in the GeV range produced by a realistic BLR accounting for the radial stratification and radiation anisotropy. Using photoionization modelling with the CLOUDY code, we calculate a series of BLR models of different sizes, geometries, cloud densities, column densities and metallicities. The strongest emission features in the model BLR are Lyα and He II Lyα. Contribution of recombination continua is smaller, especially for hydrogen, because Ly continuum is efficiently trapped inside the large optical depth BLR clouds and converted to Lyman emission lines and higher-order recombination continua. The largest effects on the gamma-ray opacity are produced by the BLR geometry and localization of the gamma-ray source. We show that when the gamma-ray source moves further from the central source, all the absorption details move to higher energies and the overall level of absorption drops because of decreasing incidence angles between the gamma-rays and BLR photons. The observed positions of the spectral breaks can be used to measure the geometry and the location of the gamma-ray emitting region relative to the BLR. Strong dependence on geometry means that the soft photons dominating the pair-production opacity may be actually produced by a different population of BLR clouds than the bulk of the observed broad line emission.

  7. Gamma-ray opacity of the anisotropic stratified broad-line regions in blazars

    Science.gov (United States)

    Abolmasov, Pavel; Poutanen, Juri

    2017-01-01

    The GeV-range spectra of blazars are shaped not only by non-thermal emission processes internal to the relativistic jet but also by external pair-production absorption on the thermal emission of the accretion disc and the broad-line region (BLR). For the first time, we compute here the pair-production opacities in the GeV range produced by a realistic BLR accounting for the radial stratification and radiation anisotropy. Using photoionization modelling with the CLOUDY code, we calculate a series of BLR models of different sizes, geometries, cloud densities, column densities and metallicities. The strongest emission features in the model BLR are Ly α and He II Ly α. Contribution of recombination continua is smaller, especially for hydrogen, because Ly continuum is efficiently trapped inside the large optical depth BLR clouds and converted to Lyman emission lines and higher order recombination continua. The largest effects on the gamma-ray opacity are produced by the BLR geometry and localization of the gamma-ray source. We show that when the gamma-ray source moves further from the central source, all the absorption details move to higher energies and the overall level of absorption drops because of decreasing incidence angles between the gamma-rays and BLR photons. The observed positions of the spectral breaks can be used to measure the geometry and the location of the gamma-ray emitting region relative to the BLR. Strong dependence on geometry means that the soft photons dominating the pair-production opacity may be actually produced by a different population of BLR clouds than the bulk of the observed broad line emission.

  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. SAS-2 galactic gamma ray results. 2. Localized sources

    Science.gov (United States)

    Hartman, R. C.; Fichtel, C. E.; Kniffen, D. A.; Lamb, R. C.; Thompson, D. J.; Bignami, G. F.; Oegelman, H.; Oezel, M. E.; Tuemer, T.

    1976-01-01

    Gamma-ray emission was detected from the radio pulsars PSR1818-04 and PSR1747-46, in addition to the previously reported gamma-ray emission from the Crab and Vela pulsars. Since the Crab pulsar is the only one observed in the optical and X-ray bands, these gamma-ray observations suggest a uniquely gamma-ray phenomenon occurring in a fraction of the radio pulsars. Using distance estimates it is found that PSR1818-04 has a gamma-ray luminosity comparable to that of the Crab pulsar, while the luminosities of PSR1747-46 and the Vela pulsar are approximately an order of magnitude lower. This survey of SAS-2 data for pulsar correlations has also yielded upper limits to gamma-ray luminosity for 71 other radio pulsars.

  10. Relation between $\\gamma$-rays and emission lines for the $\\gamma$-ray loud blazars

    CERN Document Server

    Fan, J H

    2000-01-01

    The relation between the $\\gamma$-ray and the emission line luminosities for a sample of 36 $\\gamma$-ray loud blazars is investigated; an apparent correlation between them, $L_{\\gamma} \\propto L_{Line}^{0.69\\pm0.11}$, with a correlation coefficient $r=0.741$ and a chance probability of $p = 1.9\\times10^{-6}$, is found. It is found, however, that there is no intrinsic correlation between them: the apparent correlation is due to the redshift dependence in a flux-limited sample. Thus no evidence is found to support the argument that the up-scattered soft photons are from the broad emission lines. Our analysis does not conflict with the SSC model. The disk-jet symbiosis and radio/$\\gamma$-ray correlation found in the literature are also discussed. The radio/$\\gamma$-ray correlation may be an apparent correlation caused by the boosting effect since both bands are strongly beamed.

  11. Single-Crystal Bismuth Iodide Gamma-Ray Spectrometers

    Science.gov (United States)

    2012-02-01

    grow high quality Bib single crystals (> 1 cm3 in volume) via a high temperature modified Bridgman crystal growth technique. We will then test and...methods to improve Bib crystals. Finally, test structures will be designed and their performance will be assessed using a variety of small, calibrated...characteristics of the test structures (basic material properties for Bib ). While the main objectives of the project have not changed, more emphasis is

  12. Pulse Summing in the gamma-Ray Spectra

    CERN Document Server

    Gromov, K Ya; Samatov, Zh K; Chumin, V G

    2004-01-01

    It was shown that the peaks formed at the summing of the cascade gamma-rays pulses can be used for the determination of gamma-ray source activity and gamma-ray registration efficency. Possible sources of the determined quantities errors have been investigated. Such a method can be useful at the nuclear reaction cross section measurements, at background analysis in looking for rare decays and so on.

  13. AGNs and microquasars as high energy gamma-ray sources

    CERN Document Server

    Paredes, J M

    2004-01-01

    The extragalactic analogs of the microquasars, the quasars, are strong gamma-ray emitters at GeV energies. It is expected that microquasars are also gamma-ray sources, because of the analogy with quasars and because theoretical models predict the high-energy emission. There are two microquasars that appear as the possible counterparts for two unidentified high-energy gamma-ray sources.

  14. Gamma ray bursts, neutron star quakes, and the Casimir effect

    CERN Document Server

    Carlson, C; Pérez-Mercader, J; Carlson, C; Goldman, T; Perez-Mercader, J

    1994-01-01

    We propose that the dynamic Casimir effect is a mechanism that converts the energy of neutron starquakes into \\gamma--rays. This mechanism efficiently produces photons from electromagnetic Casimir energy released by the rapid motion of a dielectric medium into a vacuum. Estimates based on the cutoff energy of the gamma ray bursts and the volume involved in a starquake indicate that the total gamma ray energy emission is consonant with observational requirements.

  15. Spectra of {gamma} rays feeding superdeformed bands

    Energy Technology Data Exchange (ETDEWEB)

    Lauritsen, T.; Khoo, T.L.; Henry, R.G. [and others

    1995-08-01

    The spectrum of {gamma}rays coincident with SD transitions contains the transitions which populate the SD band. This spectrum can provide information on the feeding mechanism and on the properties (moment of inertia, collectivity) of excited SD states. We used a model we developed to explain the feeding of SD bands, to calculate the spectrum of feeding {gamma}rays. The Monte Carlo simulations take into account the trigger conditions present in our Eurogam experiment. Both experimental and theoretical spectra contain a statistical component and a broad E2 peak (from transitions occurring between excited states in the SD well). There is good resemblance between the measured and calculated spectra although the calculated multiplicity of an E2 bump is low by {approximately}30%. Work is continuing to improve the quality of the fits, which will result in a better understanding of excited SD states. In addition, a model for the last steps, which cool the {gamma} cascade into the SD yrast line, needs to be developed. A strong M1/E2 low-energy component, which we believe is responsible for this cooling, was observed.

  16. Long Gamma-Ray Transients from Collapsars

    CERN Document Server

    Woosley, S E

    2011-01-01

    In the collapsar model for common gamma-ray bursts, the formation of a centrifugally supported disk occurs during the first $\\sim$10 seconds following the collapse of the iron core in a massive star. This only occurs in a small fraction of massive stellar deaths, however, and requires unusual conditions. A much more frequent occurrence could be the death of a star that makes a black hole and a weak or absent outgoing shock, but in a progenitor that only has enough angular momentum in its outermost layers to make a disk. We consider several cases where this is likely to occur - blue supergiants with low mass loss rates, tidally-interacting binaries involving either helium stars or giant stars, and the collapse to a black hole of very massive pair-instability supernovae. These events have in common the accretion of a solar mass or so of material through a disk over a period much longer than the duration of a common gamma-ray burst. A broad range of powers is possible, $10^{47}$ to $10^{50}\\,$erg s$^{-1}$, and t...

  17. The Cosmic Gamma-Ray Bursts

    CERN Document Server

    Djorgovski, S G; Kulkarni, S R; Sari, R; Bloom, J S; Galama, T J; Harrison, F A; Price, P A; Fox, D; Reichart, D; Yost, S; Berger, E; Diercks, A H; Goodrich, R; Chaffee, F H

    2001-01-01

    Cosmic gamma-ray bursts are one of the great frontiers of astrophysics today. They are a playground of relativists and observers alike. They may teach us about the death of stars and the birth of black holes, the physics in extreme conditions, and help us probe star formation in the distant and obscured universe. In this review we summarise some of the remarkable progress in this field over the past few years. While the nature of the GRB progenitors is still unsettled, it now appears likely that at least some bursts originate in explosions of very massive stars, or at least occur in or near the regions of massive star formation. The physics of the burst afterglows is reasonably well understood, and has been tested and confirmed very well by the observations. Bursts are found to be beamed, but with a broad range of jet opening angles; the mean gamma-ray energies after the beaming corrections are ~ 10^51 erg. Bursts are associated with faint ~ 25 mag) galaxies at cosmological redshifts, with ~ 1. The host gal...

  18. Gamma-ray binaries: pulsars in disguise ?

    CERN Document Server

    Dubus, G

    2006-01-01

    LS 5039 and LSI +61 303 are unique amongst high-mass X-ray binaries (HMXB) for their spatially-resolved radio emission and their counterpart at >GeV gamma-ray energies, canonically attributed to non-thermal particles in an accretion-powered relativistic jet. The only other HMXB known to emit very high energy (VHE) gamma-rays, PSR B1259-63, harbours a non-accreting millisecond pulsar. I investigate whether the interaction of the relativistic wind from a young pulsar with the wind from its stellar companion, as in PSR B1259-63, constitutes a viable scenario to explain the observations of LS 5039 and LSI +61 303. Emission would arise from the shocked pulsar wind material, which then flows away to large distances in a comet-shape tail, reproducing on a smaller scale what is observed in isolated, high motion pulsars interacting with the ISM. Simple expectations for the SED are derived and are shown to depend on few input parameters. Detailed modelling of the particle evolution is compared to the observations from ...

  19. The interplanetary gamma ray burst network

    Science.gov (United States)

    Cline, T.

    The Interplanetary Gamma-Ray Burst Network (IPN) is providing gamma-ray burst (GRB) alerts and localizations at the maximum rate anticipated before the launch of the Swift mission. The arc-minute source precision of the IPN is again permitting searches for GRB afterglows in the radio and optical regimes with delays of only hours up to 2 days. The successful addition of the Mars Odyssey mission has compensated for the loss of the asteroid mission NEAR, to reconstitute a fully long- baseline interplanetary network, with Ulysses at > 5 AU and Konus-Wind and HETE-2 near the Earth. In addition to making unassisted GRB localizations that enable a renewed supply of counterpart observations, the Mars/Ulysses/Wind IPN is confirming and reinforcing GRB source localizations with HETE-2. It has also confirmed and reinforced localizations with the BeppoSAX mission before the BeppoSAX termination in May and has detected and localized both SGRs and an unusual hard x-ray transient that is neither an SGR nor a GRB. This IPN is expected to operate until at least 2004.

  20. Gamma-ray bursts and collisionless shocks

    CERN Document Server

    Waxman, E

    2006-01-01

    Particle acceleration in collisionless shocks is believed to be responsible for the production of cosmic-rays over a wide range of energies, from few GeV to >10^{20} eV, as well as for the non-thermal emission of radiation from a wide variety of high energy astrophysical sources. A theory of collisionless shocks based on first principles does not, however, exist. Observations of gamma-ray burst (GRB) "afterglows" provide a unique opportunity for diagnosing the physics of relativistic collisionless shocks. Most GRBs are believed to be associated with explosions of massive stars, and their "afterglows," delayed low energy emission following the prompt burst of gamma-rays, are produced by relativistic collisionless shock waves driven by the explosion into the surrounding plasma. Some of the striking characteristics of these shocks include the generation of downstream magnetic fields with energy density exceeding that of the upstream field by ~8 orders of magnitude, the survival of this strong field at distances ...

  1. Radio flares from gamma-ray bursts

    CERN Document Server

    Kopac, D; Kobayashi, S; Virgili, F J; Harrison, R; Japelj, J; Guidorzi, C; Melandri, A; Gomboc, A

    2015-01-01

    We present predictions of centimeter and millimeter radio emission from reverse shocks in the early afterglows of gamma-ray bursts 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 parametrization 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. (2007) and Melandri et al. (2010) in which the typical frequency of the reverse shock was suggested to lie at radio, rather than optical wavelengths at early times, we show that the brightest and most distinct reverse-shock 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 opt...

  2. $\\gamma$-Ray Bursts the Four Crises

    CERN Document Server

    Tavani, M

    1998-01-01

    We discuss some open problems concerning the origin and the emission mechanism of gamma-ray bursts (GRBs) in light of recent developments. If GRBs originate at extragalactic distances, we are facing four crises: (1) an energy crisis, models have to account for more than 10^{53} ergs of energy emitted in the gamma-ray energy band; (2) a spectral crisis, emission models have to account for the surprising `smoothness' of GRB broad-band spectra, with no indication of the predicted spectral `distorsions' caused by inverse Compton scattering in large radiation energy density media, and no evidence for beaming; (3) an afterglow crisis, relativistic shock models have to explain the complexity of the afterglow behavior, the longevity of optical transients detectable up to six months after the burst, the erratic behavior of the radio emission, and the lack of evidence for substantial beaming as indicated by recent searches for GRB afterglows in the X-ray band; (4) a population crisis, from data clearly indicating that ...

  3. Classifying Unidentified Gamma-ray Sources

    CERN Document Server

    Salvetti, David

    2016-01-01

    During its first 2 years of mission the Fermi-LAT instrument discovered more than 1,800 gamma-ray sources in the 100 MeV to 100 GeV range. Despite the application of advanced techniques to identify and associate the Fermi-LAT sources with counterparts at other wavelengths, about 40% of the LAT sources have no a clear identification remaining "unassociated". The purpose of my Ph.D. work has been to pursue a statistical approach to identify the nature of each Fermi-LAT unassociated source. To this aim, we implemented advanced machine learning techniques, such as logistic regression and artificial neural networks, to classify these sources on the basis of all the available gamma-ray information about location, energy spectrum and time variability. These analyses have been used for selecting targets for AGN and pulsar searches and planning multi-wavelength follow-up observations. In particular, we have focused our attention on the search of possible radio-quiet millisecond pulsar (MSP) candidates in the sample of...

  4. Gamma ray tests of Minimal Dark Matter

    Energy Technology Data Exchange (ETDEWEB)

    Cirelli, Marco [Institut de Physique Théorique, Université Paris Saclay, CNRS, CEA, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Hambye, Thomas [Service de Physique Theórique, Université Libre de Bruxelles, Boulevard du Triomphe, CP225, 1050 Brussels (Belgium); Panci, Paolo [Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98 bis Boulevard Arago, Paris 75014 (France); Sala, Filippo; Taoso, Marco [Institut de Physique Théorique, Université Paris Saclay, CNRS, CEA, Orme des Merisiers, F-91191 Gif-sur-Yvette (France)

    2015-10-12

    We reconsider the model of Minimal Dark Matter (a fermionic, hypercharge-less quintuplet of the EW interactions) and compute its gamma ray signatures. We compare them with a number of gamma ray probes: the galactic halo diffuse measurements, the galactic center line searches and recent dwarf galaxies observations. We find that the original minimal model, whose mass is fixed at 9.4 TeV by the relic abundance requirement, is constrained by the line searches from the Galactic Center: it is ruled out if the Milky Way possesses a cuspy profile such as NFW but it is still allowed if it has a cored one. Observations of dwarf spheroidal galaxies are also relevant (in particular searches for lines), and ongoing astrophysical progresses on these systems have the potential to eventually rule out the model. We also explore a wider mass range, which applies to the case in which the relic abundance requirement is relaxed. Most of our results can be safely extended to the larger class of multi-TeV WIMP DM annihilating into massive gauge bosons.

  5. Contribution of a germanium detector in mobile gamma-ray spectrometry. Spectral analysis and performance

    CERN Document Server

    Gutierrez, S; Bourgeois, C

    2002-01-01

    The sensitivity of the germanium semi-conductor detector is 30 times lower than that of the sodium iodide (NaI) detectors frequently used in airborne spectrometry. Its energy resolution however, is 20 times better, giving more accurate identification of radionuclides, especially when complex spectra are involved. The use of the germanium detector in mobile gamma-ray spectrometry provides a large amount of qualitative and quantitative information. In post-accident situations a germanium detector will be sufficient, and should therefore be used in preference to a NaI detector. An algorithm for detecting the total absorption peaks by studying the variations in the spectral profile of germanium gamma-ray spectra has been developed at the CEA. The use of digital filters that take into account the characteristics of the absorption peaks reduces the statistical fluctuations, making possible detection based on the analysis of the first and second derivatives. The absorption peak is then estimated by subtracting the b...

  6. Constraining the location of gamma-ray flares in luminous blazars

    Energy Technology Data Exchange (ETDEWEB)

    Nalewajko, Krzysztof; Begelman, Mitchell C. [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309 (United States); Sikora, Marek, E-mail: knalew@jila.colorado.edu [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland)

    2014-07-10

    provided by determination of the synchrotron self-absorption frequency for correlated synchrotron and gamma-ray flares.

  7. Gamma-ray spectroscopy on irradiated fuel rods

    Energy Technology Data Exchange (ETDEWEB)

    Terremoto, Luis Antonio Albiac [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Engenharia Nuclear], e-mail: laaterre@ipen.br

    2009-07-01

    The recording of gamma-ray spectra along an irradiated fuel rod allows the fission products to be qualitatively and quantitatively examined. Among all nondestructive examinations performed on irradiated fuel rods by gamma-ray spectroscopy, the most comprehensive one is the average burnup measurement, which is quantitative. Moreover, burnup measurements by means of gamma-ray spectroscopy are less time-consuming and waste-generating than burnup measurements by radiochemical, destructive methods. This work presents the theoretical foundations and experimental techniques necessary to measure, using nondestructive gamma-ray spectroscopy, the average burnup of irradiated fuel rods in a laboratory equipped with hot cells. (author)

  8. GRIPS - Gamma-Ray Burst Investigation via Polarimetry and Spectroscopy

    CERN Document Server

    Greiner, J

    2008-01-01

    The primary scientific goal of the GRIPS mission is to revolutionize our understanding of the early universe using gamma-ray bursts. We propose a new generation gamma-ray observatory capable of unprecedented spectroscopy over a wide range of gamma-ray energies (200 keV--50 MeV) and of polarimetry (200--1000 keV). Secondary goals achievable by this mission include direct measurements of supernova interiors through gamma-rays from radioactive decays, nuclear astrophysics with massive stars and novae, and studies of particle acceleration near compact stars, interstellar shocks, and clusters of galaxies.

  9. 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.

  10. Photoacoustic absorption spectrometer for highly transparent dielectrics with parts-per-million sensitivity

    Science.gov (United States)

    Waasem, Niklas; Fieberg, Stephan; Hauser, Janosch; Gomes, Gregory; Haertle, Daniel; Kühnemann, Frank; Buse, Karsten

    2013-02-01

    A sensitive photoacoustic absorption spectrometer for highly transparent solids has been built and tested. As the light source an optical parametrical oscillator pumped by a nanosecond pulse laser with 10 Hz repetition rate is employed, covering the complete wavelength range from 407 to 2600 nm. A second-harmonic-generation unit extends the range of accessible wavelengths down to 212 nm. A lead-zirconate-titanate piezo transducer, directly coupled to the sample, detects the photoacoustically generated sound waves. Absorption spectra of lithium triborate, lithium niobate, and alpha barium borate crystals with absorption coefficients down to 10-5 cm-1 are presented.

  11. Simulations of the HRIBF Modular Total Absorption Spectrometer (MTAS)

    Science.gov (United States)

    Rasco, Charles; Karney, Marek; Rykaczewski, Krzysztof; Kuzniak, Aleksandra; Wolinska-Cichocka, Marzena; Grzywacz, Robert

    2011-10-01

    We will present calculations of the simulated performance of the MTAS detector at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory. The total absorption gamma spectra measured with MTAS will be used to derive improved beta-feeding patterns and the resulting beta strength functions for fission products. In particular, measurements of decay heat released by radioactive nuclei produced in nuclear fuels at power reactors will be performed. The MTAS is made up of 19 large NaI(Tl) hexagonal detectors and this geometry was simulated using the GEANT4 toolkit. The energy resolution depends crucially on the nonlinearity response of the optical light production of the NaI crystals. We developed a light production curve based on the dE/dx of the electrons generated by all incoming particles and this curve was used to generate the amount of light produced independent of the incoming particle type. Simulation results of the energy resolution compared with several measurements will be presented.

  12. Search for molecular absorptions with the Fourier Transform Spectrometer

    Science.gov (United States)

    Knacke, Roger F.

    1995-01-01

    The objective of this research was a search for water molecules in the gas phase in molecular clouds. Water should be among the most abundant gases in the clouds and is of fundamental importance in gas chemistry, cloud cooling, shock wave chemistry, and gas-grain interactions of interstellar dust. Detection of water in Comet Halley in the 2.7 micron v(3) band in 1986 had shown that airborne H2O observations are feasible (ground-based observations of H2O are impossible because of the massive water content of the atmosphere). We planned to observe the v(3) band in interstellar clouds where a number of lines of this band should be in absorption. The search for H2O commenced in 1988 with a two flight program on the KAO. this resulted in a detection of interstellar H2O with S/N of 2-4 in the v(3) 1(01)-2(02) line at 3801.42/cm. A subsequent flight series of two flights in 1989 resulted in confirmation to the 3801.42/cm line detection and the detection of altogether four strong lines in the 000-001 v(3) vibration-rotation band of H2O.

  13. Measurements of radionuclides in coal samples from two provinces of Pakistan and computation of external {gamma} ray dose rate in coal mines

    Energy Technology Data Exchange (ETDEWEB)

    Jamil, K.; Ali, S. [Environmental Radiation Group, Radiation Physics Division, Pinstech, P. O. Nilore, Islamabad (Pakistan); Iqbal, M. [Nuclear Engineering Division, Pinstech, P. O. Nilore, Islamabad (Pakistan); Qureshi, A.A.; Khan, H.A. [Environmental Radiation Group, Radiation Physics Division, Pinstech, P. O. Nilore, Islamabad (Pakistan)

    1998-11-01

    The radionuclides present in coal may not only be a health hazard for the coal miners but also may be a threat to the general population if these radionuclides disperse in the environment. This research has been conducted to quantify the radionuclides present in the coal samples from various coal-mines of two provinces, Punjab and Balochistan of Pakistan. In this regard, a high-purity Ge-detector-based {gamma}-spectrometer was used. The maximum activity concentrations for {sup 226}Ra, {sup 232}Th and {sup 40}K were found to be 31{center_dot}4{+-}3{center_dot}0, 32{center_dot}7{+-}3{center_dot}2 and 21{center_dot}4{+-}5{center_dot}0 Bq kg{sup -1}, respectively. A theoretical model to compute external {gamma}-ray dose rate from a coal-mine surface was developed. The Monte Carlo simulation was employed to compute the required mass attenuation coefficients corresponding to the various {gamma}-ray energies from {sup 226}Ra, {sup 232}Th, their progeny and {sup 40}K present in the coal samples. In addition, the effective thickness of coal slab for self-absorption was also computed using the Monte Carlo Neutron Photon (MCNP) transport code. The computed external {gamma}-ray dose rate has been found to be much below the dose ratelimits for occupational persons as well as for the general population. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  14. In-Situ Measurement of Aerosol Light Absorption Using a Photo Acoustic Spectrometer

    Science.gov (United States)

    Schmid, O.; Andreae, M. O.; Helas, G.; Guyon, P.; Sciare, J.; Arnott, W. P.

    2002-12-01

    A recently developed photo acoustic spectrometer (PAS) (Arnott et al., 1999) has been used for in-situ light absorption measurements on atmospheric aerosol. Measurement campaigns in the Mediterranean and Amazon regions demonstrated the viability of the PAS under field conditions and provided data on the absorption coefficient of atmospheric aerosol generated by anthropogenic pollution and biomass burning, respectively. By operating the PAS in series with a nephelometer the scattering albedo of (dry) atmospheric aerosol was determined. Here we discuss the principle of the PAS, describe the calibration technique, and present some field data. Arnott, W. P., H. Moosmuller, C. F. Rogers, T. Jin, and R. Bruch, Photoacoustic spectrometer for measuring light absorption by aerosol: instrument description, Atmos. Environ, 33, 2845-2852, 1999.

  15. Airborne Carbon Dioxide Laser Absorption Spectrometer for IPDA Measurements of Tropospheric CO2: Recent Results

    Science.gov (United States)

    Spiers, Gary D.; Menzies, Robert T.

    2008-01-01

    The National Research Council's decadal survey on Earth Science and Applications from Space[1] recommended the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission for launch in 2013-2016 as a logical follow-on to the Orbiting Carbon Observatory (OCO) which is scheduled for launch in late 2008 [2]. The use of a laser absorption measurement technique provides the required ability to make day and night measurements of CO2 over all latitudes and seasons. As a demonstrator for an approach to meeting the instrument needs for the ASCENDS mission we have developed the airborne Carbon Dioxide Laser Absorption Spectrometer (CO2LAS) which uses the Integrated Path Differential Absorption (IPDA) Spectrometer [3] technique operating in the 2 micron wavelength region.. During 2006 a short engineering checkout flight of the CO2LAS was conducted and the results presented previously [4]. Several short flight campaigns were conducted during 2007 and we report results from these campaigns.

  16. Gamma-ray spectroscopy of Positron Annihilation in the Milky Way

    CERN Document Server

    Siegert, Thomas; Khachatryan, Gerasim; Krause, Martin G H; Guglielmetti, Fabrizia; Greiner, Jochen; Strong, Andrew W; Zhang, Xiaoling

    2015-01-01

    The annihilation of positrons in the Galaxy's interstellar medium produces characteristic gamma-rays with a line at 511 keV. This emission has been observed with the spectrometer SPI on INTEGRAL, confirming a puzzling morphology with bright emission from an extended bulge-like region, and faint disk emission. Most plausible sources of positrons are believed to be distributed throughout the disk of the Galaxy. We aim to constrain characteristic spectral shapes for different spatial components in the disk and bulge with the high-resolution gamma-ray spectrometer SPI, based on a new instrumental background method and detailed multi-component sky model fitting. We confirm the detection of the main extended components of characteristic annihilation gamma-ray signatures at 58$\\sigma$ significance in the line. The total Galactic line intensity amounts to $(2.7\\pm0.3)\\times10^{-3}~\\mathrm{ph~cm^{-2}~s^{-1}}$ for our assumed spatial model. We derive spectra for the bulge and disk, and a central point-like and at the p...

  17. Is the Universe More Transparent to Gamma Rays than Previously Thought?

    Science.gov (United States)

    Stecker, Floyd W.; Scully, Sean T.

    2009-01-01

    The MAGIC collaboration has recently reported the detection of the strong gamma-ray blazar 3C279 during a 1-2 day flare. They have used their spectral observations to draw conclusions regarding upper limits on the opacity of the Universe to high energy gamma-rays and, by implication, upper limits on the extragalactic mid-infrared background radiation. In this paper we examine the effect of gamma-ray absorption by the extragalactic infrared radiation on intrinsic spectra for this blazar and compare our results with the observational data on 3C279. We find agreement with our previous results, contrary to the recent assertion of the MAGIC group that the Universe is more transparent to gamma-rays than our calculations indicate. Our analysis indicates that in the energy range between approx. 80 and approx. 500 GeV, 3C279 has a best-fit intrinsic spectrum with a spectral index approx. 1.78 using our fast evolution model and approx. 2.19 using our baseline model. However, we also find that spectral indices in the range of 1.0 to 3.0 are almost as equally acceptable as the best fit spectral indices. Assuming the same intrinsic spectral index for this flare as for the 1991 flare from 3C279 observed by EGRET, viz., 2.02, which lies between our best fit indeces, we estimate that the MAGIC flare was approx.3 times brighter than the EGRET flare observed 15 years earlier.

  18. The Gamma Ray Bursts Hubble diagram

    CERN Document Server

    Capozziello, S; Dainotti, M G; De Laurentis, M; Izzo, L; Perillo, M

    2011-01-01

    Thanks to their enormous energy release, Gamma Rays Bursts (GRBs) have recently attracted a lot of interest to probe the Hubble diagram (HD) deep into the matter dominated era and hence complement Type Ia Supernovae (SNeIa). We consider here three different calibration methods based on the use of a fiducial LCDM model, on cosmographic parameters and on the local regression on SNeIa to calibrate the scaling relations proposed as an equivalent to the Phillips law to standardize GRBs finding any significant dependence. We then investigate the evolution of these parameters with the redshift to obtain any statistical improvement. Under this assumption, we then consider possible systematics effects on the HDs introduced by the calibration method, the averaging procedure and the homogeneity of the sample arguing against any significant bias.

  19. Search for Gamma Ray Bursts at Chacaltaya

    CERN Document Server

    Vernetto, S

    2001-01-01

    A search for Gamma Ray Bursts in the GeV-TeV energy range has been performed by INCA, an air shower array working at 5200 m of altitude at the Chacaltaya Laboratory (Bolivia). The altitude of the detector and the use of the "single particle technique" allows to lower the energy threshold up to few GeVs. No significant signals are observed during the occurrence of 125 GRBs detected by BATSE, and the obtained upper limits on the energy fluence in the interval 1-1000(100) GeV range from 3.2(8.6) 10^-5 to 2.6(7.0) 10^-2 erg/cm^2 depending on the zenith angle of the events. These limits, thanks to the extreme altitude of INCA, are the lowest ever obtained in the sub-TeV energy region by a ground based esperiment.

  20. Black Holes, Supernovae and Gamma Ray Bursts

    CERN Document Server

    Ruffini, Remo

    2013-01-01

    We review recent progress in our understanding of the nature of gamma ray bursts (GRBs) and in particular, of the relationship between short GRBs and long GRBs. The first example of a short GRB is described. The coincidental occurrence of a GRB with a supernova (SN) is explained within the induced gravitational collapse (IGC) paradigm, following the sequence: 1) an initial binary system consists of a compact carbon-oxygen (CO) core star and a neutron star (NS); 2) the CO core explodes as a SN, and part of the SN ejecta accretes onto the NS which reaches its critical mass and collapses to a black hole (BH) giving rise to a GRB; 3) a new NS is generated by the SN as a remnant. The observational consequences of this scenario are outlined.

  1. Gamma-ray Production in Supernova Remnants

    CERN Document Server

    Baring, M G

    1997-01-01

    Supernova remnants are widely believed to be a principal source of galactic cosmic rays, produced by diffusive shock acceleration in the environs of the remnant's expanding shock. This review discusses recent modelling of how such energetic particles can produce gamma-rays via interactions with the remnants' ambient interstellar medium, specifically via neutral pion decay, bremsstrahlung and inverse Compton emission. Predictions that relate to the handful of associations between EGRET unidentified sources and known radio/optical/X-ray emitting remnants are summarized. The cessation of acceleration above 1 TeV - 10 TeV energies in young shell-type remnants is critical to model consistency with Whipple's TeV upper limits; these observations provide important diagnostics for theoretical models.

  2. Relativistic Outflows in Gamma-Ray Bursts

    CERN Document Server

    Aloy, M A

    2007-01-01

    The possibility that gamma-ray bursts (GRBs) were not isotropic emissions was devised theoretically as a way to ameliorate the huge energetic budget implied by the standard fireball model for these powerful phenomena. However, the mechanism by which after the quasy-isotropic release of a few $10^{50} $erg yields a collimated ejection of plasma could not be satisfactory explained analytically. The reason being that the collimation of an outflow by its progenitor system depends on a very complex and non-linear dynamics. That has made necessary the use of numerical simulations in order to shed some light on the viability of some likely progenitors of GRBs. In this contribution I will review the most relevant features shown by these numerical simulations and how they have been used to validate the collapsar model (for long GRBs) and the model involving the merger of compact binaries (for short GRBs).

  3. Statistics of gamma ray burst temporal asymmetry

    CERN Document Server

    Link, B; Link, Bennett; Epstein, Richard

    1996-01-01

    We study the temporal asymmetry of over 600 bursts from the BATSE 3B catalog, encompassing a 200-fold range in peak flux. By comparing the rates of rise and fall of the flux near the highest burst peak, we find that about two-thirds of the bursts exhibit a preferred asymmetry in the sense that the flux rises more rapidly than it falls, confirming the conclusions of previous studies employing smaller databases. The statistical significance of the average time asymmetry of the sample is >99.999\\%; therefore, models that predict time symmetry of the burst profile are ruled out. We find no statistically significant correlation between burst temporal asymmetry and peak. This result is consistent with both cosmological and local interpretations of the gamma ray burst phenomenon.

  4. Perspectives on Gamma-Ray Pulsar Emission

    CERN Document Server

    Baring, Matthew G

    2010-01-01

    Pulsars are powerful sources of radiation across the electromagnetic spectrum. This paper highlights some theoretical insights into non-thermal, magnetospheric pulsar gamma-ray radiation. These advances have been driven by NASA's Fermi mission, launched in mid-2008. The Large Area Telescope (LAT) instrument on Fermi has afforded the discrimination between polar cap and slot gap/outer gap acceleration zones in young and middle-aged pulsars. Altitude discernment using the highest energy pulsar photons will be addressed, as will spectroscopic interpretation of the primary radiation mechanism in the LAT band, connecting to both polar cap/slot gap and outer gap scenarios. Focuses will mostly be on curvature radiation and magnetic pair creation, including population trends that may afford probes of the magnetospheric accelerating potential.

  5. Critical Test Of Gamma Ray Burst Theories

    CERN Document Server

    Dado, Shlomo

    2016-01-01

    Long and precise follow-up measurements of the X-ray afterglow (AG) of very intense gamma ray bursts (GRBs) provide a critical test of GRB afterglow theories. Here we show that the power-law decline with time of X-ray AG of GRB 130427A, the longest measured X-ray AG of an intense GRB with the Swift, Chandra and XMM Newton satellites, and of all other well measured late-time X-ray afterglow of intense GRBs, is that predicted by the cannonball (CB) model of GRBs from their measured spectral index, while it disagrees with that predicted by the widely accepted fireball (FB) models of GRBs.

  6. Gamma-ray burst afterglow theory

    CERN Document Server

    van Eerten, Hendrik

    2013-01-01

    It is by now fairly well established that gamma-ray burst afterglows result from initially relativistic outflows interacting with the medium surrounding the burster and emitting non-thermal radiation ranging from radio to X-rays. However, beyond that, many big and small questions remain about afterglows, with the accumulating amount of observational data at the various frequencies raising as many questions as they answer. In this review I highlight a number of current theoretical issues and how they fit or do not fit within our basic theoretical framework. In addition to theoretical progress I will also emphasize the increasing role and usefulness of numerical studies of afterglow blast waves and their radiation.

  7. SAS-2 galactic gamma ray results, 1

    Science.gov (United States)

    Thompson, D. J.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Bignami, G. F.; Lamb, R. C.; Oegelman, H.; Oezel, M. E.; Tuemer, T.

    1976-01-01

    Continuing analysis of the data from the SAS-2 high energy gamma-ray experiment has produced an improved picture of the sky at photon energies above 35 MeV. On a large scale, the diffuse emission from the galactic plane is the dominant feature observed by SAS-2. This galactic plane emission is most intense between galactic longitude 310 and 45 deg, corresponding to a region within 7kpc of the galactic center. Within the high-intensity region, SAS-2 observes peaks around galactic longitudes 315 deg, 330 deg, 345 deg, 0 deg, and 35 deg. These peaks appear to be correlated with such galactic features and components as molecular hydrogen, atomic hydrogen, magnetic fields, cosmic ray concentrations, and photon fields.

  8. 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.

  9. Gamma ray astronomy above 30 TeV and the IceCube results

    Directory of Open Access Journals (Sweden)

    Vernetto Silvia

    2017-01-01

    Full Text Available The study of the diffuse Galactic gamma ray emission is of fundamental importance to understand the properties of cosmic ray propagation in the Milky Way, and extending the measurements to E ≳ 30 TeV is of great interest. In the same energy range the IceCube detector has also recently observed a flux of astrophysical neutrinos, and it is important to test experimentally if the neutrino production is accompanied by a comparable emission of high energy photons. For E ≳ 30 TeV, the absorption effects due to e+e− pair production when the high energy photons interact with radiation fields present in space are not negligible and must be taken into account. Gamma rays, in good approximation, are completely absorbed if they have an extragalactic origin, but the absorption is significant also for Galactic photons. In this case the size and angular dependence of the absorption depends on the space distribution of the emission. In this work we estimate the absorption for different models of the space distribution of the gamma ray emission, and discuss the potential of future detectors.

  10. Generation of attosecond x-ray and gamma-ray via Compton backscattering.

    Science.gov (United States)

    Chung, Sang-Young; Yoon, Moohyun; Kim, Dong Eon

    2009-05-11

    The generation of an isolated attosecond gamma-ray pulse utilizing Compton backscattering of a relativistic electron bunch has been investigated. The energy of the electron bunch is modulated while the electron bunch interacts with a co-propagating few-cycle CEP (carrier envelope phase)-locked laser in a single-period wiggler. The energy-modulated electron bunch interacts with a counter-propagating driver laser, producing Compton back-scattered radiation. The energy modulation of the electron bunch is duplicated to the temporal modulation of the photon energy of Compton back-scattered radiation. The spectral filtering using a crystal spectrometer allows one to obtain an isolated attosecond gamma-ray.

  11. Practical applicability of field gamma-ray scintillation spectrometry in geophysical surveys

    Science.gov (United States)

    Chiozzi; Pasquale; Verdoya; De Felice P

    2000-07-01

    We discuss the problems and calibration procedures for a portable gamma-ray scintillation spectrometer for determinations of potassium, uranium and thorium concentration in rocks. Particular emphasis was given to the evaluation of the background radiation. The apparatus was tested in the field at two selected areas in NW Italy. We found appropriate sites which could be used as reference targets to frequently check the gamma-ray equipment. An area formed by serpentinitic rocks showed such a low measured radioactivity that it could be used as a reference for the local background effect. An anomalously high uranium amount against negligible potassium and thorium concentrations were found in outcrops of dolomitic rocks, which can be used to detect possible changes in the instrument calibration constants.

  12. V/V(max) test applied to SMM gamma-ray bursts

    Science.gov (United States)

    Matz, S. M.; Higdon, J. C.; Share, G. H.; Messina, D. C.; Iadicicco, A.

    1992-01-01

    We have applied the V/V(max) test to candidate gamma-ray bursts detected by the Gamma-Ray Spectrometer (GRS) aboard the SMM satellite to examine quantitatively the uniformity of the burst source population. For a sample of 132 candidate bursts identified in the GRS data by an automated search using a single uniform trigger criterion we find average V/V(max) = 0.40 +/- 0.025. This value is significantly different from 0.5, the average for a uniform distribution in space of the parent population of burst sources; however, the shape of the observed distribution of V/V(max) is unusual and our result conflicts with previous measurements. For these reasons we can currently draw no firm conclusion about the distribution of burst sources.

  13. SMM hard X-ray observations of the soft gamma-ray repeater 1806-20

    Science.gov (United States)

    Kouveliotou, C.; Norris, J. P.; Cline, T. L.; Dennis, B. R.; Desai, U. D.; Orwig, L. E.

    1987-01-01

    Six bursts from the soft gamma-ray repeater (SGR) 1806-20 have been recorded with the SMM Hard X-ray Burst Spectrometer during a highly active phase in 1983. Rise and decay times of less than 5 ns have been detected. Time profiles of these events indicate low-level emission prior to and after the main peaks. The results suggest that SGRs are distinguished from classical gamma-ray bursts by repetition, softer nonvarying spectra, short durations, simple temporal profiles, and a tendency for source locations to correlate with Population I objects. SGR characteristics differ from those of type I X-ray bursts, but they appear to have similarities with the type II bursts from the Rapid Burster.

  14. Classification of lunar terranes using neutron and thorium gamma-ray data

    Energy Technology Data Exchange (ETDEWEB)

    Feldman, W.C.; Lawrence, D.J.; Elphic, R.C.; Barraclough, B.L. [Los Alamos National Lab., NM (United States); Maurice, S. [Observatoire Midi-Pyrenees, Toulouse (France); Binder, A.B. [Lunar Research Inst., Gilroy, CA (United States); Lucey, P.G. [Univ. of Hawaii, Manoa, HI (United States). Hawaii Inst. of Geophysics and Planetology

    1999-04-01

    A major scientific goal of the Lunar Prospector (LP) gamma-ray and neutron spectrometers is to classify all lunar terranes according to composition. A preliminary analysis of early data indicates this goal will be met for the major rock-forming elements on a spatial scale of about 200 km. The low-altitude phase of LP now in progress should allow reduction of this scale by about a factor of 10 for those elements that have sufficiently high measurable fluxes relative to their backgrounds. Most promising are the flux intensities of thermal, epithermal, and fast neutrons (which each average about 300 counts per 50 km of ground track) and 2.6 MeV gamma rays from thorium (which averages about 50 counts per 50 km of ground track). The authors therefore explore the information content of these measurables to classify the various lunar terrane types.

  15. Gamma-Ray Bursts: Pulses and Populations

    Science.gov (United States)

    Loredo, Thomas J.; Hakkila, J. E.; Broadbent, M.; Wasserman, I. M.; Wolpert, R. L.

    2013-04-01

    We describe ongoing work on two projects that are enabling more thorough and accurate use of archival BATSE data for elucidating the nature of GRB sources; the methods and tools we are developing will also be valuable for analyzing data from other missions. The first project addresses modeling the spectro-temporal behavior of prompt gamma ray emission from GRBs by modeling gamma ray count and event data with a population of pulses, with the population drawn from one or more families of single-pulse kernels. Our approach is built on a multilevel nonparametric probabilistic framework we have dubbed "Bayesian droplets," and offers several important advances over previous pulse decomposition approaches: (1) It works in the pulse-confusion regime, quantifying uncertainty in the number, locations, and shapes of pulses, even when there is strong overlap. (2) It can self-consistently model pulse behavior across multiple spectral bands. (3) It readily handles a variety of spatio-temporal kernel shapes. (4) It reifies the idea of a burst as a population of pulses, enabling explicit modeling and estimation of the pulse population distribution. We describe the framework and present analyses of prototypical simple and complex GRB light curves. The second project aims to enable accurate demographic modeling of GRBs using the BATSE catalog. We present new calculations of the BATSE sky exposure, encompassing the full duration of the BATSE catalog for the first time, with many improvements over the currently available exposure map. A similar calculation of the detection efficiency is in progress. We also describe public Python software enabling access and accurate modeling of BATSE GRB data. The software enables demographic studies (e.g., modeling log N - log S distributions) with accurate accounting of both selection effects and measurement errors. It also enables spectro-temporal modeling of detailed data from individual GRBs. These projects are supported by NASA through the AISR

  16. Gamma Rays from Star Formation in Clusters of Galaxies

    CERN Document Server

    Storm, Emma; Profumo, Stefano

    2012-01-01

    Star formation in galaxies is observed to be associated with gamma-ray emission. The detection of gamma rays from star-forming galaxies by the Fermi Large Area Telescope (LAT) has allowed the determination of a functional relationship between star formation rate and gamma-ray luminosity (Ackermann et. al. 2012). Since star formation is known to scale with total infrared (8-1000 micrometers) and radio (1.4 GHz) luminosity, the observed infrared and radio emission from a star-forming galaxy can be used to quantitatively infer the galaxy's gamma-ray luminosity. Similarly, star forming galaxies within galaxy clusters allow us to derive lower limits on the gamma-ray emission from clusters, which have not yet been conclusively detected in gamma rays. In this study we apply the relationships between gamma-ray luminosity and radio and IR luminosities derived in Ackermann et. al. 2012 to a sample of galaxy clusters from Ackermann et. al. 2010 in order to place lower limits on the gamma-ray emission associated with sta...

  17. 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...

  18. 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...... of the Soft Gamma Repeater SGR 1900+14 in 1992 is verified....

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

    NARCIS (Netherlands)

    Langer, N.; van Marle, A. -J; Yoon, S.C.

    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

  20. Gamma-rays from Muon Capture in $^{14}$N

    CERN Document Server

    Stocki, T J; Gete, E; Saliba, M A; Moftah, B A; Gorringe, T P

    2001-01-01

    Many new $\\gamma$-rays have been observed, following muon capture on $^{14}$N. One had been reported before, and the low yield is confirmed, indicating that the nuclear structure of $^{14}$N is still not understood. Gamma-rays from $^{13}$C resulting from the reaction $^{14}$N($\\mu^{-}$,$\

  1. 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)

  2. Enhanced gamma-ray activity from the Crab nebula

    Science.gov (United States)

    Buehler, R.; Ciprini, S.

    2016-01-01

    Preliminary LAT analysis indicates enhanced gamma-ray activity from the Crab nebula. The daily-averaged gamma-ray emission (E > 100 MeV) from the direction of the Crab Nebula has surpassed 4.0 x 10^-6 ph cm^-2 s^-1 five times in the last 12 days.

  3. Very High Energy Gamma Ray Extension of GRO Observations

    Science.gov (United States)

    Weekes, Trevor C.

    1994-01-01

    The membership, progress, and invited talks, publications, and proceedings made by the Whipple Gamma Ray Collaboration is reported for june 1990 through May 1994. Progress was made in the following areas: the May 1994 Markarian Flare at Whipple and EGRET (Energetic Gamma Ray Experiment Telescope) energies; AGN's (Active Galactic Nuclei); bursts; supernova remnants; and simulations and energy spectra.

  4. SAS-2 galactic gamma-ray results. 2: Localized sources

    Science.gov (United States)

    Hartman, R. C.; Fichtel, C. E.; Kniffen, D. A.; Lamb, R. C.; Thompson, D. J.; Bignami, G. F.; Oegelman, H.; Oezel, M. E.; Tuemer, T.

    1977-01-01

    Gamma ray emission was detected from the radio pulsars PSR 1818-04 and PSR 1747-46, in addition to the previously reported gamma ray emission from the Crab and Vela pulsars. Because the Crab pulsar is the only one observed in the optical and X-ray bands, these gamma ray observations suggest a uniquely gamma ray phenomenon occurring in a fraction of the radio pulsars. PSR 1818-04 has a gamma ray luminosity comparable to that of the Crab pulsar, whereas the luminosities of PSR 1747-46 and the Vela pulsar are approximately an order of magnitude lower. SAS-2 data for pulsar correlations yielded upper limits to gamma ray luminosity for 71 other radio pulsars. For five of the closest pulsars, upper limits for gamma ray luminosity are found to be at least three orders of magnitude lower than that of the Crab pulsar. Gamma ray enhancement near the Milky Way satellite galaxy and the galactic plane in the Cygnus region is also discussed.

  5. The First Fermi Gamma-ray Burst Monitor (GBM) Terrestrial Gamma-ray Flash (TGF) Catalog

    Science.gov (United States)

    Briggs, Michael; Connaughton, Valerie; Stanbro, Matthew; Zhang, Binbin; Bhat, Narayana; Fishman, Gerald; Roberts, Oliver; Fitzpatrick, Gerard; McBreen, Shelia; Grove, Eric; Chekhtman, Alexandre

    2015-04-01

    We present summary results from the first catalog of Terrestrial Gamma-ray Flashes (TGFs) detected with the Gamma-ray Burst Monitor (GBM) on the Fermi Space Telescope. The catalog reports parameters for over 2700 TGFs. Since the launch of Fermi in 2008 the TGF detection sensitivity of GBM has been improved several times, both in the flight software and in ground analysis. Starting in 2010 July individual photons were downloaded for portions of the orbits, enabling an off-line search that found weaker and shorter TGFs. Since 2012 November 26 this telemetry mode has been extended to continuous coverage. The TGF sample is reliable, with cosmic rays rejected using data both from Fermi GBM and from the Large Area Telescope on Fermi. The online catalog include times (UTC and solar), spacecraft geographic positions, durations, count intensities and Bayesian Block durations. The catalog includes separate tables for bright TGFs detected by the flight software and for Terrestrial Electron Beams (TEBs).

  6. Attenuation of TeV $\\gamma$-rays by the starlight photon field of the host galaxy

    CERN Document Server

    Zacharias, Michael; Wagner, Stefan J

    2016-01-01

    The absorption of TeV $\\gamma$-ray photons produced in relativistic jets by surrounding soft photon fields is a long-standing problem of jet physics. In some cases the most likely emission site close to the central black hole is ruled out because of the high opacity caused by strong optical and infrared photon sources, such as the broad line region. Mostly neglected for jet modeling is the absorption of $\\gamma$-rays in the starlight photon field of the host galaxy. Analyzing the absorption for arbitrary locations and observation angles of the $\\gamma$-ray emission site within the host galaxy we find that the distance to the galaxy center, the observation angle, and the distribution of starlight in the galaxy are crucial for the amount of absorption. We derive the absorption value for a sample of $20$ TeV detected blazars with a redshift $z_r<0.2$. The absorption value of the $\\gamma$-ray emission located in the galaxy center may be as high as $20\\%$ with an average value of $6\\%$. This is important in ord...

  7. The transparency of the universe for very high energy gamma-rays

    CERN Document Server

    Horns, D

    2016-01-01

    The propagation of very high energy gamma-rays ($E>100$~GeV) over cosmological distances is suppressed by pair-production processes with the ubiquitous extra-galactic soft photon background, mainly in the optical to near infra-red. The detailed spectroscopy of gamma-ray emitting blazars has revealed the signature of this absorption process leading to a meaningful measurement of the background photon field which is linked to the star-forming history of the universe. Deviations from the expected absorption have been claimed in the past. Here the status of the observations is summarized, an update on the search for the persisting anomalous transparency is given and discussed.

  8. First flight of the Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS)

    Science.gov (United States)

    Saint-Hilaire, Pascal; Shih, Albert Y.; Duncan, Nicole; Bain, Hazel; Maruca, Bennett A.; Kelley, Nicole; Godbole, Niharika; Kaufmann, Pierre; Caspi, Amir; Sample, John; Hoberman, Jane; Mochizuki, Brent; Olson, Jerry; Boggs, Steven E.; Zoglauer, Andreas; Hurford, Gordon J.; Smith, David M.; Tajima, Hiroyasu; Amman, Mark

    2016-05-01

    The Gamma-Ray Imager/Polarimeter for Solar flares (GRIPS) high altitude balloon payload was successfully flown in January 2016 from Antarctica (Jan 19 to Jan 30).GRIPS provides a near-optimal combination of high-resolution imaging, spectroscopy, and polarimetry of solar-flare gamma ray/hard X-ray emissions from ~20 keV to >~10 MeV. GRIPS’s goal is to address questions raised by recent solar flare observations regarding particle acceleration and energy release, such as: What causes the spatial separation between energetic electrons producing hard X-rays and energetic ions producing gamma-ray lines? How anisotropic are the relativistic electrons, and why can they dominate in the corona? How do the compositions of accelerated and ambient material vary with space and time, and why? The spectrometer/polarimeter consists of six 3D position-sensitive germanium detectors (3D-GeDs), where each energy deposition is individually recorded with an energy resolution of a few keV FWHM and a spatial resolution gamma-ray energies (12.5 arcsec FWHM), sufficient to separate 2.2 MeV footpoint sources for almost all flares. Polarimetry is accomplished by analyzing the anisotropy of reconstructed Compton scattering in the 3D-GeDs, with an estimated minimum detectable polarization of a few percent at 150-650 keV in an X-class flare. GRIPS was also equipped with active BGO shields, and three piggy-back instruments: a solar terahertz radiometer (Solar-T), a hard X-ray spectrometer (SMASH), and a sonic anemometer (TILDAE).We will present an overview of GRIPS's first flight, the performance of its instruments and subsystems, including the solar pointing and aspect systems, and the current progress of our data analysis.

  9. Star-forming galaxies as the origin of IceCube neutrinos: Reconciliation with Fermi-LAT gamma rays

    CERN Document Server

    Chakraborty, Sovan

    2016-01-01

    Cosmic ray accelerators like supernova and hypernova remnants in star forming galaxies are one of the most plausible sources of the IceCube observed diffuse astrophysical neutrinos. The neutrino producing hadronic processes will also produce a diffuse gamma ray flux, constrained by the Fermi-LAT bounds. The fact that point sources like blazars also contribute to the diffuse gamma ray flux implies large gamma opacity of the neutrino sources. Indeed, for these high redshift star forming galaxies the gamma absorption during the intergalactic propagation can be significant. In addition, large gamma attenuation inside these extreme source galaxies can reduce the cascade component of the diffuse flux. Under the current astrophysical uncertainties affecting these absorptions processes, we find the associated diffuse gamma ray flux can remain compatible with the current Fermi-LAT bounds.

  10. Extragalactic Gamma Ray Excess from Coma Supercluster Direction

    Indian Academy of Sciences (India)

    Pantea Davoudifar; S. Jalil Fatemi

    2011-09-01

    The origin of extragalactic diffuse gamma ray is not accurately known, especially because our suggestions are related to many models that need to be considered either to compute the galactic diffuse gamma ray intensity or to consider the contribution of other extragalactic structures while surveying a specific portion of the sky. More precise analysis of EGRET data however, makes it possible to estimate the diffuse gamma ray in Coma supercluster (i.e., Coma\\A1367 supercluster) direction with a value of ( > 30MeV) ≃ 1.9 × 10-6 cm-2 s-1, which is considered to be an upper limit for the diffuse gamma ray due to Coma supercluster. The related total intensity (on average) is calculated to be ∼ 5% of the actual diffuse extragalactic background. The calculated intensity makes it possible to estimate the origin of extragalactic diffuse gamma ray.

  11. Effect of Conversion Efficiency on Gamma-Ray Burst Energy

    Institute of Scientific and Technical Information of China (English)

    Lei Xu; Zi-Gao Dai

    2004-01-01

    Beaming effect makes it possible that gamma-ray bursts have a standard energy,but the gamma-ray energy release is sensitive to some parameters.Our attention is focused on the effect of the gamma ray conversion efficiency(ηγ),which may range between 0.01 and 0.9,and which probably has a random value for different GRBs under certain conditions.Making use of the afterglow data from the literature,we carried out a complete correction to the conical opening angle formula.Within the framework of the conical jet model,we ran a simple Monte Carlo simulation for random values of ηγ,and found that the gamma-ray energy release is narrowly clustered,whether we use a constant value of ηγ or random values for different gamma-ray bursts.

  12. The supernova-gamma-ray burst-jet connection.

    Science.gov (United States)

    Hjorth, Jens

    2013-06-13

    The observed association between supernovae and gamma-ray bursts represents a cornerstone in our understanding of the nature of gamma-ray bursts. The collapsar model provides a theoretical framework for this connection. A key element is the launch of a bipolar jet (seen as a gamma-ray burst). The resulting hot cocoon disrupts the star, whereas the (56)Ni produced gives rise to radioactive heating of the ejecta, seen as a supernova. In this discussion paper, I summarize the observational status of the supernova-gamma-ray burst connection in the context of the 'engine' picture of jet-driven supernovae and highlight SN 2012bz/GRB 120422A--with its luminous supernova but intermediate high-energy luminosity--as a possible transition object between low-luminosity and jet gamma-ray bursts. The jet channel for supernova explosions may provide new insights into supernova explosions in general.

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

    DEFF Research Database (Denmark)

    Content, Robert; Sharples, Ray; Page, Mathew J.

    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...

  14. Review of GRANAT observations of gamma-ray bursts

    DEFF Research Database (Denmark)

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

    1995-01-01

    The GRANAT observatory was launched into a high apogee orbit on 1 December, 1989. Three instruments onboard GRANAT - PHEBUS, WATCH and SIGMA are able to detect gamma-ray bursts in a very broad energy range from 6 keV up to 100 MeV. Over 250 gamma-ray bursts were detected. We discuss the results...... 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...... the SIGMA telescope field of view are reviewed....

  15. 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.

  16. The Fermi Gamma-ray Burst Monitor (GBM) Terrestrial Gamma-ray Flash (TGF) Catalog

    Science.gov (United States)

    Stanbro, M.; Briggs, M. S.; Roberts, O.; McBreen, S.; Bhat, N.; Fitzpatrick, G.

    2015-12-01

    We present results from the catalog of Terrestrial Gamma-ray Flashes (TGFs) detected with the Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope. The first release, in January 2015, provided data on 2700 TGFs. Updates are extending the catalog at a rate of ~800 TGFs per year. The TGF sample is reliable, with cosmic rays rejected using data both from Fermi GBM and from the Large Area Telescope on Fermi. The online catalog include times (UTC and solar), spacecraft geographic positions, durations, count intensities and other Bayesian Block durations. The catalog includes separate tables for bright TGFs detected by the flight software and for Terrestrial Electron Beams (TEBs). In January 2016 additional data will be released online from correlating these TGFs with sferics detected by the World Wide Lightning Location Network (WWLLN). Maps of sferics in the vicinity of each TGF will be provided, as will the locations and times of sferics found to be associated with TGFs.

  17. 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.

  18. More Gamma-ray Bursts from the Fermi Gamma-ray Burst Monitor

    Science.gov (United States)

    Briggs, Michael; Fermi GBM Team Team

    2017-01-01

    The Fermi Gamma-ray Burst Monitor (GBM) Team has developed an offline search for weak gamma-ray bursts which were not already detected in-orbit as ``triggers''. This search is ``untargeted'', searching all of the GBM data without guidance from other observations. The initial version of the search has been operational from January 2016, finding several likely short GRBs per month that are posted to a webpage. The GBM individual photon data are binned to various timescales, a background model is created and the binned data are searched for significant signals above the background that are coincident in two or more detectors. The current search has a latency of several days because several steps require manual intervention. An improved version will be fully automatic so that the latency in detecting candidates will be dominated by the few hours delay in receiving the data. The new version of the search will also include additional detection algorithms to increase the GRB detection rate and will also detect some long GRBs. We will report the candidates via the Gamma-ray Coordinates Network (GCN). These prompt GRB detections and localization should aid multi-messenger observations, in some cases refining localizations on timescales useful for followup observations.

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

    CERN Document Server

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

    2016-01-01

    Gamma-ray Bursts (GRBs) are bursts of $\\gamma$-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 (DTW) 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, an...

  20. ESA presents INTEGRAL, its space observatory for Gamma-ray astronomy

    Science.gov (United States)

    1998-09-01

    more strange than the energetic radiation coming from the centre of distant galaxies are flashes of extremely powerful radiation that suddenly appear somewhere on the gamma-sky and disappear again after a short time. These gamma-bursts seem to be the biggest observed explosions in the Universe. But nobody knows their source. Integral will help to solve this long-standing mystery. ESA, the pioneer in gamma-ray astronomy The satellite as it can now be seen at ESA's test centre is five meters high and weighs more than four tonnes. Two main instruments observe the gamma-rays. An imager will give the sharpest gamma-ray images. It is provided by a consortium led by an Italian scientist. Gamma-rays ignore lenses and mirror, so INTEGRAL makes its images with so-called coded-masks. A coded-mask telescope is basically a pinhole camera, but with a larger aperture, i.e. many pinholes. A spectrometer will gauge gamma-ray energies extremely precisely. It is developed by a team of scientists under joint French-German leadership and will be a 100 times more sensitive than the previous high spectral resolution space instrument. It is made of a high-purity Germanium detector that has to be cooled down to minus 188 degree Celsius. These two gamma-ray-instruments are supported by two monitor instruments that play a crucial role in the detection and identification of the gamma-ray sources. An X-ray monitor developed in Denmark will observe X-rays, still powerful but less energetic than gamma-rays. An optical telescope provided by Spain will observe the visible light emitted by the energetic objects. Switzerland will host the Integral Science Data Centre which will preprocess and distribute the scientific data. The mission is conceived as an observatory led by ESA with Russia contributing the launcher and NASA providing tracking support with its Deep Space Network. Alenia Aerospazio in Turin, Italy is ESA's prime contractor for building INTEGRAL. Launch by a Russian Proton rocket from

  1. Capillary absorption spectrometer and process for isotopic analysis of small samples

    Science.gov (United States)

    Alexander, M. Lizabeth; Kelly, James F.; Sams, Robert L.; Moran, James J.; Newburn, Matthew K.; Blake, Thomas A.

    2016-03-29

    A capillary absorption spectrometer and process are described that provide highly sensitive and accurate stable absorption measurements of analytes in a sample gas that may include isotopologues of carbon and oxygen obtained from gas and biological samples. It further provides isotopic images of microbial communities that allow tracking of nutrients at the single cell level. It further targets naturally occurring variations in carbon and oxygen isotopes that avoids need for expensive isotopically labeled mixtures which allows study of samples taken from the field without modification. The method also permits sampling in vivo permitting real-time ambient studies of microbial communities.

  2. Development of whole energy absorption spectrometer for decay heat measurement on fusion reactor materials

    Energy Technology Data Exchange (ETDEWEB)

    Maekawa, Fujio; Ikeda, Yujiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-03-01

    To measure decay heat on fusion reactor materials irradiated by D-T neutrons, a Whole Energy Absorption Spectrometer (WEAS) consisting of a pair of large BGO (bismuth-germanate) scintillators was developed. Feasibility of decay heat measurement with WEAS for various materials and for a wide range of half-lives (seconds - years) was demonstrated by experiments at FNS. Features of WEAS, such as high sensitivity, radioactivity identification, and reasonably low experimental uncertainty of {approx} 10 %, were found. (author)

  3. Galactic sources of high energy neutrinos: Expectation from gamma-ray data

    CERN Document Server

    Sahakyan, N

    2015-01-01

    The recent results from ground based $\\gamma$-ray detectors (HESS, MAGIC, VERITAS) provide a population of TeV galactic $\\gamma$-ray sources which are potential sources of High Energy (HE) neutrinos. Since the $\\gamma$-rays and $\

  4. 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.

  5. The Refractive Index of Silicon at Gamma Ray Energies

    CERN Document Server

    Habs, D; Jentschel, M; Urban, W

    2011-01-01

    The index of refraction n(E_{\\gamma})=1+\\delta(E_{\\gamma})+i\\beta(E_{\\gamma}) is split into a real part \\delta and an absorptive part \\beta. The absorptive part has the three well-known contributions to the cross section \\sigma_{abs}: the photo effect, the Compton effect and the pair creation, but there is also the inelastic Delbr\\"uck scattering. Second-order elastic scattering cross sections \\sigma_{sca} with Rayleigh scattering (virtual photo effect), virtual Compton effect and Delbr\\"uck scattering (virtual pair creation) can be calculated by integrals of the Kramers-Kronig dispersion relations from the cross section \\sigma_{abs}. The real elastic scattering amplitudes are proportional to the refractive indices \\delta_{photo}, \\delta_{Compton} and \\delta_{pair}. While for X-rays the negative \\delta_{photo} dominates, we show for the first time experimentally and theoretically that the positive \\delta_{pair} dominates for \\gamma rays, opening a new era of \\gamma optics applications, i.e. of nuclear photoni...

  6. Gamma Ray Burst reverse shock emission in early radio afterglows

    CERN Document Server

    Resmi, Lekshmi

    2016-01-01

    Reverse shock (RS) emission from Gamma Ray Bursts is an important tool in investigating the nature of the ejecta from the central engine. If the ejecta magnetization is not high enough to suppress the RS, a strong RS emission component, usually peaking in the optical/IR band early on, would give important contribution to early afterglow light curves. In the radio band, synchrotron self-absorption may suppress early RS emission, and also delay the RS peak time. In this paper, we calculate the self-absorbed RS emission in the radio band for different dynamical conditions. In particular, we stress that the RS radio emission is subject to self-absorption in both reverse and forward shocks. We calculate the ratio between the reverse to forward shock flux at the RS peak time for different frequencies, which is a measure of the detectability of the RS emission component. We then constrain the range of physical parameters for a detectable RS, in particular the role of magnetization. We notice that unlike optical RS e...

  7. ICF gamma-ray reaction history diagnostics

    Science.gov (United States)

    Herrmann, H. W.; Young, C. S.; Mack, J. M.; Kim, Y. H.; McEvoy, A.; Evans, S.; Sedillo, T.; Batha, S.; Schmitt, M.; Wilson, D. C.; Langenbrunner, J. R.; Malone, R.; Kaufman, M. I.; Cox, B. C.; Frogget, B.; Miller, E. K.; Ali, Z. A.; Tunnell, T. W.; Stoeffl, W.; Horsfield, C. J.; Rubery, M.

    2010-08-01

    Reaction history measurements, such as nuclear bang time and burn width, are fundamental components of diagnosing ICF implosions and will be employed to help steer the National Ignition Facility (NIF) towards ignition. Fusion gammas provide a direct measure of nuclear interaction rate (unlike x-rays) without being compromised by Doppler spreading (unlike neutrons). Gas Cherenkov Detectors that convert fusion gamma rays to UV/visible Cherenkov photons for collection by fast optical recording systems have established their usefulness in illuminating ICF physics in several experimental campaigns at OMEGA. In particular, bang time precision better than 25 ps has been demonstrated, well below the 50 ps accuracy requirement defined by the NIF. NIF Gamma Reaction History (GRH) diagnostics are being developed based on optimization of sensitivity, bandwidth, dynamic range, cost, and NIF-specific logistics, requirements and extreme radiation environment. Implementation will occur in two phases. The first phase consists of four channels mounted to the outside of the target chamber at ~6 m from target chamber center (GRH-6m) coupled to ultra-fast photo-multiplier tubes (PMT). This system is intended to operate in the 1013-1017 neutron yield range expected during the early THD campaign. It will have high enough bandwidth to provide accurate bang times and burn widths for the expected THD reaction histories (> 80 ps fwhm). Successful operation of the first GRH-6m channel has been demonstrated at OMEGA, allowing a verification of instrument sensitivity, timing and EMI/background suppression. The second phase will consist of several channels located just inside the target bay shield wall at 15 m from target chamber center (GRH-15m) with optical paths leading through the cement shield wall to well-shielded streak cameras and PMTs. This system is intended to operate in the 1016-1020 yield range expected during the DT ignition campaign, providing higher temporal resolution for the

  8. X-ray and gamma ray astronomy detectors

    Science.gov (United States)

    Decher, Rudolf; Ramsey, Brian D.; Austin, Robert

    1994-01-01

    X-ray and gamma ray astronomy was made possible by the advent of space flight. Discovery and early observations of celestial x-rays and gamma rays, dating back almost 40 years, were first done with high altitude rockets, followed by Earth-orbiting satellites> once it became possible to carry detectors above the Earth's atmosphere, a new view of the universe in the high-energy part of the electromagnetic spectrum evolved. Many of the detector concepts used for x-ray and gamma ray astronomy were derived from radiation measuring instruments used in atomic physics, nuclear physics, and other fields. However, these instruments, when used in x-ray and gamma ray astronomy, have to meet unique and demanding requirements related to their operation in space and the need to detect and measure extremely weak radiation fluxes from celestial x-ray and gamma ray sources. Their design for x-ray and gamma ray astronomy has, therefore, become a rather specialized and rapidly advancing field in which improved sensitivity, higher energy and spatial resolution, wider spectral coverage, and enhanced imaging capabilities are all sought. This text is intended as an introduction to x-ray and gamma ray astronomy instruments. It provides an overview of detector design and technology and is aimed at scientists, engineers, and technical personnel and managers associated with this field. The discussion is limited to basic principles and design concepts and provides examples of applications in past, present, and future space flight missions.

  9. 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.

  10. The Gamma-ray Albedo of the Moon

    Energy Technology Data Exchange (ETDEWEB)

    Moskalenko, Igor V.; /Stanford U., HEPL; Porter, Troy A.; /UC, Santa Cruz

    2007-09-28

    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 albedo spectrum of the Moon is well understood, including its absolute normalization; this makes it a useful 'standard candle' for {gamma}-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of {gamma}-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo {gamma}-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo {gamma}-rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA.

  11. NDA via gamma-ray active and passive computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Decman, D.J.; Martz, H.E.; Roberson, G.P.; Johansson, E.

    1996-10-01

    Gamma-ray-based computed tomography (CT) requires that two different measurements be made on a closed waste container. [MAR92 and ROB94] When the results from these two measurements are combined, it becomes possible to identify and quantify all detectable gamma-ray emitting radioisotopes within a container. All measurements are made in a tomographic manner, i.e., the container is moved sequentially through well- known and accurately reproducible translation, rotation, and elevation positions in order to obtain gamma-ray data that is reconstructed by computer into images that represent waste contents. [ROB94] The two measurements modes are called active (A) and passive (P) CT. In the ACT mode, a collimated gamma-ray source external to the waste container emits multiple, mono-energetic gamma rays that pass through the container and are detected on the opposite side. The attenuated gamma-rays transmitted are measured as a function of both energy and position of the container. Thus, container contents are `mapped` via the measured amount of attenuation suffered at each gamma-ray energy. In effect, a three dimensional (3D) image of gamma- ray attenuation versus waste content is obtained. In the PCT measurement mode, the external radioactive source is shuttered turned- off, and the waste container, is moved through similar positions used for the ACT measurements. However, this time the radiation detectors record any gamma-rays emitted by radioactive sources on the inside of the waste container. Thus, internal radioactive content is mapped or 3D-imaged in the same tomographic manner as the attenuating matrix materials were in the ACT measurement mode.

  12. Five-Channel Infrared Laser Absorption Spectrometer for Combustion Product Monitoring Aboard Manned Spacecraft

    Science.gov (United States)

    Briggs, Ryan M.; Frez, Clifford; Borgentun, Carl E.; Bagheri, Mahmood; Forouhar, Siamak; May, Randy D.

    2014-01-01

    Continuous combustion product monitoring aboard manned spacecraft can prevent chronic exposure to hazardous compounds and also provides early detection of combustion events. As future missions extend beyond low-Earth orbit, analysis of returned environmental samples becomes impractical and safety monitoring should be performed in situ. Here, we describe initial designs of a five-channel tunable laser absorption spectrometer to continuously monitor combustion products with the goal of minimal maintenance and calibration over long-duration missions. The instrument incorporates dedicated laser channels to simultaneously target strong mid-infrared absorption lines of CO, HCl, HCN, HF, and CO2. The availability of low-power-consumption semiconductor lasers operating in the 2 to 5 micron wavelength range affords the flexibility to select absorption lines for each gas with maximum interaction strength and minimal interference from other gases, which enables the design of a compact and mechanically robust spectrometer with low-level sensitivity. In this paper, we focus primarily on absorption line selection based on the availability of low-power single-mode semiconductor laser sources designed specifically for the target wavelength range.

  13. Photospheric Emission in Gamma-Ray Bursts

    CERN Document Server

    Pe'er, Asaf

    2016-01-01

    A major breakthrough in our understanding of gamma-ray bursts (GRB) prompt emission physics occurred in the last few years, with the realization that a thermal component accompanies the over-all non-thermal prompt spectra. This thermal part is important by itself, as it provides direct probe of the physics in the innermost outflow regions. It further has an indirect importance, as a source of seed photons for inverse-Compton scattering, thereby it contributes to the non-thermal part as well. In this short review, we highlight some key recent developments. Observationally, although so far it was clearly identified only in a minority of bursts, there are indirect evidence that thermal component exists in a very large fraction of GRBs, possibly close to 100%. Theoretically, the existence of thermal component have a large number of implications as a probe of underlying GRB physics. Some surprising implications include its use as a probe of the jet dynamics, geometry and magnetization.

  14. Neutrino astronomy and gamma-ray bursts

    CERN Document Server

    Waxman, E

    2007-01-01

    The construction of large volume detectors of high energy, >1 TeV, neutrinos is mainly driven by the search for extra-Galactic neutrino sources. The existence of such sources is implied by observations of ultra-high energy, >10^{19} eV, cosmic-rays, the origin of which is a mystery. In this lecture I briefly discuss the expected extra-Galactic neutrino signal and the current state of the experimental efforts. Neutrino emission from gamma-ray bursts (GRBs), which are likely sources of both high energy protons and neutrinos, is discussed in some detail. The detection of the predicted GRB neutrino signal, which may become possible in the coming few years, will allow one to identify the sources of ultra-high energy cosmic-rays and to resolve open questions related to the underlying physics of GRB models. Moreover, detection of GRB neutrinos will allow one to test for neutrino properties (e.g. flavor oscillations and coupling to gravity) with an accuracy many orders of magnitude better than is currently possible.

  15. Short-Duration Gamma-Ray Bursts

    CERN Document Server

    Berger, Edo

    2013-01-01

    Gamma-ray bursts (GRBs) display a bimodal duration distribution, with a separation between the short- and long-duration bursts at about 2 sec. The progenitors of long GRBs have been identified as massive stars based on their association with Type Ic core-collapse supernovae, their exclusive location in star-forming galaxies, and their strong correlation with bright ultraviolet regions within their host galaxies. Short GRBs have long been suspected on theoretical grounds to arise from compact object binary mergers (NS-NS or NS-BH). The discovery of short GRB afterglows in 2005, provided the first insight into their energy scale and environments, established a cosmological origin, a mix of host galaxy types, and an absence of associated supernovae. In this review I summarize nearly a decade of short GRB afterglow and host galaxy observations, and use this information to shed light on the nature and properties of their progenitors, the energy scale and collimation of the relativistic outflow, and the properties ...

  16. The SVOM gamma-ray burst mission

    CERN Document Server

    Cordier, B; Atteia, J -L; Basa, S; Claret, A; Daigne, F; Deng, J; Dong, Y; Godet, O; Goldwurm, A; Götz, D; Han, X; Klotz, A; Lachaud, C; Osborne, J; Qiu, Y; Schanne, S; Wu, B; Wang, J; Wu, C; Xin, L; Zhang, B; Zhang, S -N

    2015-01-01

    We briefly present the science capabilities, the instruments, the operations, and the expected performance of the SVOM mission. SVOM (Space-based multiband astronomical Variable Objects Monitor) is a Chinese-French space mission dedicated to the study of Gamma-Ray Bursts (GRBs) in the next decade. The SVOM mission encompasses a satellite carrying four instruments to detect and localize the prompt GRB emission and measure the evolution of the afterglow in the visible band and in X-rays, a VHF communication system enabling the fast transmission of SVOM alerts to the ground, and a ground segment including a wide angle camera and two follow-up telescopes. The pointing strategy of the satellite has been optimized to favor the detection of GRBs located in the night hemisphere. This strategy enables the study of the optical emission in the first minutes after the GRB with robotic observatories and the early spectroscopy of the optical afterglow with large telescopes to measure the redshifts. The study of GRBs in the...

  17. Sensitivity of HAWC to gamma ray bursts

    Science.gov (United States)

    Taboada, Ignacio; HAWC Collaboration

    2012-12-01

    HAWC is a ground based very high-energy gamma ray detector under construction in Mexico at an altitude of 4100 m a.s.l. Higher altitude, improved design and a larger physical size used to reject CR background, make HAWC 10-20 times more sensitive than its predecessor Milagro. HAWC's large field of view, ~2sr, and over 90% duty cycle make it ideal to search for GRBs. We review the sensitivity of HAWC to GRBs with two independent data acquisition systems. We show that some of the brightest GRBs observed by Fermi LAT (e.g. GRB 090510) could result in >5 σ observation by HAWC. The observations (or limits) of GRBs by HAWC will provide information on the high-energy spectra of GRBs. The high-energy spectra will teach us about extra galactic background light, the Lorentz boost factor of the jets tha power GRBs and/or particle acceleration models of GRBs. Finally we present limits on > 10 GeV emission from GRB 111016B, recently studied with HAWC's engineering array VAMOS.

  18. The Nature of Gamma Ray Burst Supernovae

    CERN Document Server

    Cano, Zach

    2012-01-01

    Gamma Ray Bursts (GRBs) and Supernovae (SNe) are among the brightest and most energetic physical processes in the universe. It is known that core-collapse SNe arise from the gravitational collapse and subsequent explosion of massive stars (the progen- itors of nearby core-collapse SNe have been imaged and unambiguously identified). It is also believed that the progenitors of long-duration GRBs (L-GRBs) are massive stars, mainly due to the occurrence and detection of very energetic core-collapse su- pernovae that happen both temporally and spatially coincident with most L-GRBs. However many outstanding questions regarding the nature of these events exist: How massive are the progenitors? What evolutionary stage are they at when they explode? Do they exist as single stars or in binary systems (or both, and to what fractions)? The work presented in this thesis attempts to further our understanding at the types of progenitors that give rise to long-duration GRB supernovae (GRB-SNe). This work is based on optical ...

  19. Gamma-Ray Bursts: Should cosmologists care?

    Science.gov (United States)

    Laros, J. G.

    1996-03-01

    Gamma-Ray Burst (GRB) locations are distributed isotropically on the sky, but the intensity distribution of the bursts seems clearly incompatible with spatial homogeneity. Of the scenarios that attempt to provide an explanation, there are two that enjoy current popularity: (1) GRBs are produced by high-velocity neutron stars that have formed an extended (˜100 kpc) spherical halo or “corona” around our galaxy. (2) The bursters are at cosmological distances, with redshifts near unity for the weaker events. The major evidence used to argue for or against each of these scenarios remains inconclusive. Assuming, not unreasonably, that the cosmological scenario is correct, one can discuss the advantages and disadvantages of studying GRBs as opposed to other objects at moderate redshift. We find that the advantages of GRBs-high intensity, penetrating radiation, rapid variability, and no expected source evolution-are offset by observational difficulties pertaining to the extraction of cosmological information from GRB data. If the cosmological scenario proves to be correct and if the observational difficulties are overcome, then cosmologists certainly should care.

  20. Blueshifting may explain the gamma ray bursts

    CERN Document Server

    Krasiński, Andrzej

    2015-01-01

    It is shown that the basic observed properties of the gamma-ray bursts (GRBs) are accounted for if one assumes that the GRBs arise by blueshifting the emission radiation of hydrogen and helium generated during the last scattering epoch. The blueshift generator for a single GRB is a Lema\\^{\\i}tre -- Tolman (L--T) region with a nonconstant bang-time function $t_B(r)$ matched into a Friedmann background. Blueshift visible to the observer arises \\textit{only on radial rays} that are emitted in the L--T region. The paper presents three L--T models with different Big Bang profiles, adapted for the highest and the lowest end of the GRB frequency range. The models account for: (1) The observed frequency range of the GRBs; (2) Their limited duration; (3) The afterglows; (4) Their hypothetical collimation into narrow jets; (5) The large distances to their sources; (6) The multitude of the observed GRBs. Properties (2), (3) and (6) are accounted for only qualitatively. With a small correction of the parameters of the mo...

  1. Swift observations of gamma-ray bursts.

    Science.gov (United States)

    Gehrels, Neil

    2007-05-15

    Since its launch on 20 November 2004, the Swift mission has been detecting approximately 100 gamma-ray bursts (GRBs) each year, and immediately (within approx. 90s) starting simultaneous X-ray and UV/optical observations of the afterglow. It has already collected an impressive database, including prompt emission to higher sensitivities than BATSE, uniform monitoring of afterglows and a rapid follow-up by other observatories notified through the GCN. Advances in our understanding of short GRBs have been spectacular. The detection of X-ray afterglows has led to accurate localizations and the conclusion that short GRBs can occur in non-star-forming galaxies or regions, whereas long GRBs are strongly concentrated within the star-forming regions. This is consistent with the NS merger model. Swift has greatly increased the redshift range of GRB detection. The highest redshift GRBs, at z approximately 5-6, are approaching the era of reionization. Ground-based deep optical spectroscopy of high redshift bursts is giving metallicity measurements and other information on the source environment to a much greater distance than other techniques. The localization of GRB 060218 to a nearby galaxy, and the association with SN 2006aj, added a valuable member to the class of GRBs with detected supernova.

  2. Validation of gamma-ray detection techniques for safeguards monitoring at natural uranium conversion facilities

    Energy Technology Data Exchange (ETDEWEB)

    Dewji, S.A., E-mail: dewjisa@ornl.gov [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, TN 37831-6335 (United States); Lee, D.L.; Croft, S. [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, TN 37831-6335 (United States); Hertel, N.E. [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, TN 37831-6335 (United States); Nuclear and Radiological Engineering Program, Georgia Institute of Technology, 770 State Street, Atlanta, GA 30332-0745 (United States); Chapman, J.A.; McElroy, R.D.; Cleveland, S. [Oak Ridge National Laboratory, 1 Bethel Valley Road, MS-6335, Oak Ridge, TN 37831-6335 (United States)

    2016-07-01

    Recent IAEA circulars and policy papers have sought to implement safeguards when any purified aqueous uranium solution or uranium oxides suitable for isotopic enrichment or fuel fabrication exists. Under the revised policy, IAEA Policy Paper 18, the starting point for nuclear material under safeguards was reinterpreted, suggesting that purified uranium compounds should be subject to safeguards procedures no later than the first point in the conversion process. In response to this technical need, a combination of simulation models and experimental measurements were employed to develop and validate concepts of nondestructive assay monitoring systems in a natural uranium conversion plant (NUCP). In particular, uranyl nitrate (UO{sub 2}(NO{sub 3}){sub 2}) solution exiting solvent extraction was identified as a key measurement point (KMP), where gamma-ray spectroscopy was selected as the process monitoring tool. The Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility at Oak Ridge National Laboratory was employed to simulate the full-scale operating conditions of a purified uranium-bearing aqueous stream exiting the solvent extraction process in an NUCP. Nondestructive assay techniques using gamma-ray spectroscopy were evaluated to determine their viability as a technical means for drawing safeguards conclusions at NUCPs, and if the IAEA detection requirements of 1 significant quantity (SQ) can be met in a timely way. This work investigated gamma-ray signatures of uranyl nitrate circulating in the UNCLE facility and evaluated various gamma-ray detector sensitivities to uranyl nitrate. These detector validation activities include assessing detector responses to the uranyl nitrate gamma-ray signatures for spectrometers based on sodium iodide, lanthanum bromide, and high-purity germanium detectors. The results of measurements under static and dynamic operating conditions at concentrations ranging from 10–90 g U/L of natural uranyl nitrate are presented. A range of

  3. Validation of gamma-ray detection techniques for safeguards monitoring at natural uranium conversion facilities

    Science.gov (United States)

    Dewji, S. A.; Lee, D. L.; Croft, S.; Hertel, N. E.; Chapman, J. A.; McElroy, R. D.; Cleveland, S.

    2016-07-01

    Recent IAEA circulars and policy papers have sought to implement safeguards when any purified aqueous uranium solution or uranium oxides suitable for isotopic enrichment or fuel fabrication exists. Under the revised policy, IAEA Policy Paper 18, the starting point for nuclear material under safeguards was reinterpreted, suggesting that purified uranium compounds should be subject to safeguards procedures no later than the first point in the conversion process. In response to this technical need, a combination of simulation models and experimental measurements were employed to develop and validate concepts of nondestructive assay monitoring systems in a natural uranium conversion plant (NUCP). In particular, uranyl nitrate (UO2(NO3)2) solution exiting solvent extraction was identified as a key measurement point (KMP), where gamma-ray spectroscopy was selected as the process monitoring tool. The Uranyl Nitrate Calibration Loop Equipment (UNCLE) facility at Oak Ridge National Laboratory was employed to simulate the full-scale operating conditions of a purified uranium-bearing aqueous stream exiting the solvent extraction process in an NUCP. Nondestructive assay techniques using gamma-ray spectroscopy were evaluated to determine their viability as a technical means for drawing safeguards conclusions at NUCPs, and if the IAEA detection requirements of 1 significant quantity (SQ) can be met in a timely way. This work investigated gamma-ray signatures of uranyl nitrate circulating in the UNCLE facility and evaluated various gamma-ray detector sensitivities to uranyl nitrate. These detector validation activities include assessing detector responses to the uranyl nitrate gamma-ray signatures for spectrometers based on sodium iodide, lanthanum bromide, and high-purity germanium detectors. The results of measurements under static and dynamic operating conditions at concentrations ranging from 10-90 g U/L of natural uranyl nitrate are presented. A range of gamma-ray lines is

  4. Novel Features of Gamma Ray from Dark Matter

    CERN Document Server

    Tang, Yong

    2015-01-01

    In this study, we present some general and novel features of gamma ray from dark matter. We find that gamma-ray spectra with sharp features exist in a wide class of dark matter models and mimic the gamma line signals. The generated gamma rays would generally have polynomial-type spectra or power-law with positive index. We illustrate our results in a model-independent framework with generic kinematic analysis. Similar results can also apply for cosmic rays or neutrino cases.

  5. Low permeability asphalt concrete gamma ray shielding properties.

    Science.gov (United States)

    Binney, S E; Sykes, K L

    1997-01-01

    Energy-dependent gamma ray shielding properties were measured as a function of gamma ray energy for a low permeability asphalt concrete that is used as a cap to prevent water infiltration into radioactive waste sites. Experimental data were compared to ISO-PC point kernel shielding calculations. Calculated dose equivalent rates compared well with experimental values, especially considering the poor detector resolution involved. The shielding properties of the asphalt concrete closely resembled those of aluminum. The results presented can be used to determine the asphalt concrete thickness required to reduce dose equivalent rates from several gamma ray emitting radionuclides.

  6. The STACEE-32 Ground Based Gamma-ray Detector

    CERN Document Server

    Hanna, D S; Boone, L M; Chantell, M C; Conner, Z; Covault, C E; Dragovan, M; Fortin, P; Gregorich, D T; Hinton, J A; Mukherjee, R; Ong, R A; Oser, S; Ragan, K; Scalzo, R A; Schütte, D R; Theoret, C G; Tümer, T O; Williams, D A; Zweerink, J A

    2002-01-01

    We describe the design and performance of the Solar Tower Atmospheric Cherenkov Effect Experiment detector in its initial configuration (STACEE-32). STACEE is a new ground-based gamma ray detector using the atmospheric Cherenkov technique. In STACEE, the heliostats of a solar energy research array are used to collect and focus the Cherenkov photons produced in gamma-ray induced air showers. The large Cherenkov photon collection area of STACEE results in a gamma-ray energy threshold below that of previous detectors.

  7. The STACEE Ground-Based Gamma-Ray Detector

    CERN Document Server

    Gingrich, D M; Bramel, D; Carson, J; Covault, C E; Fortin, P; Hanna, D S; Hinton, J A; Jarvis, A; Kildea, J; Lindner, T; Müller, C; Mukherjee, R; Ong, R A; Ragan, K; Scalzo, R A; Theoret, C G; Williams, D A; Zweerink, J A

    2005-01-01

    We describe the design and performance of the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) in its complete configuration. STACEE uses the heliostats of a solar energy research facility to collect and focus the Cherenkov photons produced in gamma-ray induced air showers. The light is concentrated onto an array of photomultiplier tubes located near the top of a tower. The large Cherenkov photon collection area of STACEE results in a gamma-ray energy threshold below that of previous ground-based detectors. STACEE is being used to observe pulsars, supernova remnants, active galactic nuclei, and gamma-ray bursts.

  8. Gamma rays from muon capture in {sup 14}N

    Energy Technology Data Exchange (ETDEWEB)

    Stocki, T.J. E-mail: trevor.stocki@crc.ca; Measday, D.F.; Gete, E.; Saliba, M.A.; Moftah, B.A.; Gorringe, T.P

    2002-01-14

    Many new {gamma}-rays have been observed, following muon capture on {sup 14}N. One had been reported before, and the low yield is confirmed, indicating that the nuclear structure of {sup 14}N is still not understood. Gamma rays from {sup 13}C resulting from the reaction {sup 14}N({mu}{sup -},{nu}n){sup 13}C compare favourably with states observed in the reaction {sup 14}N({gamma}, p){sup 13}C. More precise energies are also given for the 7017 and 6730 keV {gamma}-rays in {sup 14}C.

  9. Fundamental Physics With Cosmic High-Energy Gamma Rays

    CERN Document Server

    De Angelis, Alessandro

    2016-01-01

    High-energy photons (above the MeV) are a powerful probe for astrophysics and for fundamental physics under extreme conditions. During the recent years, our knowledge of the high-energy gamma-ray sky has impressively progressed thanks to the advent of new detectors for cosmic gamma rays, at ground (H.E.S.S., MAGIC, VERITAS, HAWC) and in space (AGILE, Fermi). This presentation reviews the present status of the studies of fundamental physics problems with high-energy gamma rays, and discusses the expected experimental developments.

  10. Constraining gamma-ray propagation on cosmic distances

    CERN Document Server

    Biteau, Jonathan

    2013-01-01

    Studying the propagation of gamma rays on cosmological distances encompasses a variety of scientific fields, focusing on diffuse radiation fields such as the extragalactic background light, on the probe of the magnetism of the Universe on large scales, and on physics beyond the standard models of cosmology and particle physics. The measurements, constraints and hints from observations of gamma-ray blazars by airborne and ground-based instruments are briefly reviewed. These observations point to gamma-ray cosmology as one of the major science cases of the Cherenkov Telescope Array, CTA.

  11. Photon energy conversion efficiency in gamma-ray spectrometry.

    Science.gov (United States)

    Švec, Anton

    2016-01-01

    Photon energy conversion efficiency coefficient is presented as the ratio of total energy registered in the collected spectrum to the emitted photon energy. This parameter is calculated from the conventional gamma-ray histogram and in principle is not affected by coincidence phenomena. This feature makes it particularly useful for calibration and measurement of radionuclide samples at close geometries. It complements the number of efficiency parameters used in gamma-ray spectrometry and can partly change the view as to how the gamma-ray spectra are displayed and processed.

  12. Recent Topics on Very High Energy Gamma-ray Astronomy

    CERN Document Server

    Mori, Masaki

    2008-01-01

    With the advent of imaging atmospheric Cherenkov telescopes in late 1980's, ground-based observation of TeV gamma-rays came into reality after struggling trials by pioneers for twenty years, and the number of gamma-ray sources detected at TeV energies has increased to be over seventy now. In this review, recent findings from ground-based very-high-energy gamma-ray observations are summarized (as of 2008 March), and up-to-date problems in this research field are presented.

  13. The Multiwavelength View of Gamma-Ray Loud AGN

    Science.gov (United States)

    Venters, Tonia

    2011-01-01

    The gamma-ray sky observed by the Fermi Large Area Telescope (Fermi-LAT) encodes much information about the high-energy processes in the universe. Of the extragalactic sources sources resolved by the Fermi-LAT, blazars comprise the class of gamma-ray emitters with the largest number of identified members. Unresolved blazars are expected to contribute significantly to the diffuse extragalactic gamma-ray emission. However, blazars are also broadband emitters (from radio to TeV energies), and as such the multiwavelength study of blazars can provide insight into the high-energy processes of the universe.

  14. Egret observations of the extragalactic gamma-ray emission

    DEFF Research Database (Denmark)

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

    1998-01-01

    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......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...

  15. SN2014J gamma-rays from the 56Ni decay chain

    CERN Document Server

    Diehl, Roland; Hillebrandt, Wolfgang; Krause, Martin; Greiner, Jochen; Maeda, Keiichi; Röpke, Friedrich K; Sim, Stuart A; Wang, Wei; Zhang, Xiaoling

    2014-01-01

    The measurement of gamma-ray lines from the decay chain of 56Ni provides unique information about the explosion in supernovae. The 56Ni freshly-produced in the supernova powers the optical light curve, as it emits gamma-rays upon its radioactive decay to 56Co and then 56Fe. Gamma-ray lines from 56Co decay are expected to become directly visible through the overlying white dwarf material several weeks after the explosion, as they progressively penetrate the overlying material of the supernova envelope, diluted as it expands. The lines are expected to be Doppler-shifted or broadened from the kinematics of the 56Ni ejecta. With the SPI spectrometer on INTEGRAL and using an improved instrumental background method, we detect the two main lines from 56Co decay at 847 and 1238 keV from SN2014J at 3.3 Mpc, significantly Doppler-broadened, and at intensities (3.65+/-1.21)~10^-4 and (2.27+/-0.69)~10^-4 ph~cm^-2s^-1, respectively, at brightness maximum. We measure their rise towards a maximum after about 60-100 days and...

  16. High-resolution observations of gamma-ray line emission from SN 1987A

    Science.gov (United States)

    Sandie, W. G.; Nakano, G. H.; Chase, L. F., Jr.; Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Paciesas, W. S.; Lasche, G. P.

    1988-11-01

    A balloon-borne gamma-ray spectrometer was flown from Alice springs, Australia, 1987 October 29 - 31, nominally 250 days after the supernova event. High-resolution data, typically 2.5 keV at 1.33 MeV, were obtained for two transits of the supernova. A significant net flux of gamma rays with energy 847 keV was observed from the direction of SN 1987A on each transit. No prominent gamma-ray features were seen at other energies. A preliminary estimate of the line flux is (5.1±1.7)×10-4photons cm-2s-1. The net flux observed in the first supernova transit extends from 838 keV to 850 keV and may be evidence of dynamical broadening of the 847 keV line. The total excess flux from 838 keV to 850 keV corresponds to (1.0±0.28)×10-3photons cm-2s-1. This line may be interpreted as emission from the first excited state of 56Fe due to the radioactive decay of 56Co.

  17. Attenuation of X and Gamma Rays in Personal Radiation Shielding Protective Clothing.

    Science.gov (United States)

    Kozlovska, Michaela; Cerny, Radek; Otahal, Petr

    2015-11-01

    A collection of personal radiation shielding protective clothing, suitable for use in case of accidents in nuclear facilities or radiological emergency situations involving radioactive agents, was gathered and tested at the Nuclear Protection Department of the National Institute for Nuclear, Chemical and Biological Protection, Czech Republic. Attenuating qualities of shielding layers in individual protective clothing were tested via spectra measurement of x and gamma rays, penetrating them. The rays originated from different radionuclide point sources, the gamma ray energies of which cover a broad energy range. The spectra were measured by handheld spectrometers, both scintillation and High Purity Germanium. Different narrow beam geometries were adjusted using a special testing bench and a set of various collimators. The main experimentally determined quantity for individual samples of personal radiation shielding protective clothing was x and gamma rays attenuation for significant energies of the spectra. The attenuation was assessed comparing net peak areas (after background subtraction) in spectra, where a tested sample was placed between the source and the detector, and corresponding net peak areas in spectra, measured without the sample. Mass attenuation coefficients, which describe attenuating qualities of shielding layers materials in individual samples, together with corresponding lead equivalents, were determined as well. Experimentally assessed mass attenuation coefficients of the samples were compared to the referred ones for individual heavy metals.

  18. Prompt gamma-ray analysis using cold and thermal guided neutron beams at JAERI.

    Science.gov (United States)

    Yonezawa, C

    1999-01-01

    A highly sensitive neutron-induced prompt gamma-ray analysis (PGA) system, usable at both cold and thermal neutron beam guides of JRR-3M, has been constructed. The system was designed to achieve the lowest gamma-ray background by using lithium fluoride tiles as neutron shielding, by placing the samples in a He atmosphere and by using a Ge-bismuth germanate detector system for Compton suppression. The gamma-ray spectrometer can acquire three modes of spectra simultaneously: single, Compton suppression, and pair modes. Because of the low-energy guided neutron beams and the low-background system, analytical sensitivities and detection limits better than those in usual PGA systems have been achieved. Boron and multielemental determination by a comparative standardization have been investigated, and accuracy, precision, and detection limits for the elements in various materials were evaluated. The system has been applied to the determination of B and multielements in samples of various fields such as medical, environmental, and geological sciences.

  19. Scanning imaging absorption spectrometer for atmospheric chartography carbon monoxide total columns: statistical evaluation and comparison with chemistry transport model results

    NARCIS (Netherlands)

    de Laat, A.T.J.; Gloudemans, A.M.S.; Aben, I.; Krol, M.C.; Meirink, J.F.; van der Werf, G.R.; Schrijver, H.

    2007-01-01

    This paper presents a detailed statistical analysis of one year (September 2003 to August 2004) of global Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) carbon monoxide (CO) total column retrievals from the Iterative Maximum Likelihood Method (IMLM) algorithm, vers

  20. Scanning Imaging Absorption Spectrometer for Atmospheric Chartography carbon monoxide total columns: Statistical evaluation and comparison with chemistry transport model results

    NARCIS (Netherlands)

    Laat, de A.T.J.; Gloudemans, A.M.S.; Aben, I.; Krol, M.C.; Meirink, J.F.; Werf, van der G.R.; Schrijver, H.

    2007-01-01

    This paper presents a detailed statistical analysis of one year (September 2003 to August 2004) of global Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) carbon monoxide (CO) total column retrievals from the Iterative Maximum Likelihood Method (IMLM) algorithm, vers

  1. 基于Gamma全吸收型BaF2探测装置的数据获取系统%Data Acquisition System Based on Gamma-ray Total Absorption Facility

    Institute of Scientific and Technical Information of China (English)

    张奇玮; 贺国珠; 黄兴; 程品晶; 阮锡超; 朱兴华

    2016-01-01

    The data acquisition system based on gamma‐ray total absorption facility was developed for the accurate measurement of neutron capture cross section in the energy range of keV‐MeV .The pulsed signals from the detectors were acquired by FlashADC for data acquisition system on a Linux operation system .The control of program ,store of data ,online monitoring and analysis code were based on the Root framework .The main performances of system were acquired by the measurement of 60Co and 137Cs .The data acquisition system meets the requirement of accurate measurement of neutron cap‐ture cross section by GTAF .%为精确测量keV能区的中子俘获反应截面,研制了一套基于Gamma全吸收型BaF2探测装置的数据获取系统。数据获取系统工作在Linux环境下,应用 FlashADC采集探测器的脉冲信号。程序控制、数据存储、在线监控与分析程序基于Root平台。通过测量60 Co和137 Cs源,得到了数据获取系统主要性能的测试结果,其满足GTAF装置精确测量中子俘获反应截面的要求。

  2. Development of a Small-Sized, Flexible, and Insertable Fiber-Optic Radiation Sensor for Gamma-Ray Spectroscopy

    Directory of Open Access Journals (Sweden)

    Wook Jae Yoo

    2015-08-01

    Full Text Available We fabricated a small-sized, flexible, and insertable fiber-optic radiation sensor (FORS that is composed of a sensing probe, a plastic optical fiber (POF, a photomultiplier tube (PMT-amplifier system, and a multichannel analyzer (MCA to obtain the energy spectra of radioactive isotopes. As an inorganic scintillator for gamma-ray spectroscopy, a cerium-doped lutetium yttrium orthosilicate (LYSO:Ce crystal was used and two solid-disc type radioactive isotopes with the same dimensions, cesium-137 (Cs-137 and cobalt-60 (Co-60, were used as gamma-ray emitters. We first determined the length of the LYSO:Ce crystal considering the absorption of charged particle energy and measured the gamma-ray energy spectra using the FORS. The experimental results demonstrated that the proposed FORS can be used to discriminate species of radioactive isotopes by measuring their inherent energy spectra, even when gamma-ray emitters are mixed. The relationship between the measured photon counts of the FORS and the radioactivity of Cs-137 was subsequently obtained. The amount of scintillating light generated from the FORS increased by increasing the radioactivity of Cs-137. Finally, the performance of the fabricated FORS according to the length and diameter of the POF was also evaluated. Based on the results of this study, it is anticipated that a novel FORS can be developed to accurately measure the gamma-ray energy spectrum in inaccessible locations such as narrow areas and holes.

  3. Detection of significant cm to sub-mm band radio and gamma-ray correlated variability in Fermi bright blazars

    CERN Document Server

    Fuhrmann, L; Chiang, J; Angelakis, E; Zensus, J A; Nestoras, I; Krichbaum, T P; Ungerechts, H; Sievers, A; Pavlidou, V; Readhead, A C S; Max-Moerbeck, W; Pearson, T J

    2014-01-01

    The exact location of the gamma-ray emitting region in blazars is still controversial. In order to attack this problem we present first results of a cross-correlation analysis between radio (11 cm to 0.8 mm wavelength, F-GAMMA program) and gamma-ray (0.1-300 GeV) ~ 3.5 year light curves of 54 Fermi-bright blazars. We perform a source stacking analysis and estimate significances and chance correlations using mixed source correlations. Our results reveal: (i) the first highly significant multi-band radio and gamma-ray correlations (radio lagging gamma rays) when averaging over the whole sample, (ii) average time delays (source frame: 76+/-23 to 7+/-9 days), systematically decreasing from cm to mm/sub-mm bands with a frequency dependence tau_r,gamma (nu) ~ nu^-1, in good agreement with jet opacity dominated by synchrotron self-absorption, (iii) a bulk gamma-ray production region typically located within/upstream of the 3 mm core region (tau_3mm,gamma=12+/-8 days), (iv) mean distances between the region of gamma-...

  4. Analysis of GeV-band gamma-ray emission from SNR RX J1713.7-3946

    CERN Document Server

    Federici, S; Telezhinsky, I; Wilhelm, A; Dwarkadas, V V

    2015-01-01

    RX J1713.7-3946 is the brightest shell-type Supernova remnant (SNR) of the TeV gamma-ray sky. Earlier Fermi-LAT results on low-energy gamma-ray emission suggested that, despite large uncertainties in the background determination, the spectrum is inconsistent with a hadronic origin. We update the GeV-band spectra using improved estimates for the diffuse galactic gamma-ray emission and more than doubled data volume. We further investigate the viability of hadronic emission models for RX J1713.7-3946. We produced a high-resolution map of the diffuse Galactic gamma-ray background corrected for HI self-absorption and used it in the analysis of more than 5~years worth of Fermi-LAT data. We used hydrodynamic scaling relations and a kinetic transport equation to calculate the acceleration and propagation of cosmic-rays in SNR. We then determined spectra of hadronic gamma-ray emission from RX J1713.7-3946, separately for the SNR interior and the cosmic-ray precursor region of the forward shock, and computed flux varia...

  5. Clustering of galaxies around gamma-ray burst sight-lines

    DEFF Research Database (Denmark)

    Sudilovsky, V.; Greiner, J.; Rau, A.

    2013-01-01

    -lines, as strong MgII tends to trace these sources. In this work, we test this expectation by calculating the two point angular correlation function of galaxies within 120'' (~470 h Kpc470h71-1Kpc at z ~ 0.4) of GRB afterglows. We compare the gamma-ray burst optical and near-infrared detector (GROND) GRB afterglow......There is evidence of an overdensity of strong intervening MgII absorption line systems distributed along the lines of sight toward gamma-ray burst (GRB) afterglows relative to quasar sight-lines. If this excess is real, one should also expect an overdensity of field galaxies around GRB sight...

  6. The Imprint of The Extragalactic Background Light in the Gamma-Ray Spectra of Blazars

    CERN Document Server

    ,

    2012-01-01

    The light emitted by stars and accreting compact objects through the history of the Universe is encoded in the intensity of the extragalactic background light (EBL). Knowledge of the EBL is important to understand the nature of star formation and galaxy evolution, but direct measurements of the EBL are lim- ited by Galactic and other foreground emissions. Here we report an absorption feature seen in the combined spectra of a sample of gamma-ray blazars out to a redshift of z$\\sim$1.6. This feature is caused by attenuation of gamma rays by the EBL at optical to UV frequencies, and allowed us to measure the EBL flux density in this frequency band.

  7. Modelling the TeV gamma-ray spectra of two low redshift AGNs Mkn 501 and Mkn 421

    CERN Document Server

    Konopelko, A K; Kirk, J G; De Jager, O C; Stecker, F W; Konopelko, Alexander K.; Mastichiadis, Apostolos; Kirk, John G.; Jager, Ocker C. de; Stecker, Floyd W.

    2003-01-01

    We discuss the results of modelling the TeV gamma-ray spectra of two AGNs, Mkn 501 and Mkn 421 that have almost the same redshifts: z=0.031 and z=0.034, respectively. The effect of intergalactic gamma-ray absorption is treated as an uncertainty in the measurement of the intrinsic spectrum. Although the objects differ, we obtain satisfactory fits for both of them in a synchrotron self-Compton scenario. Compared to previous models, our fits are characterised by higher values of the Doppler factor (>= 50) and an electron injection spectrum extending to higher energies (Gmax = 1.5x10^5). In the case of Mkn 421, the observed difference in spectral slope in X-rays and TeV gamma-rays between the high and low states can be explained as a variation of a single parameter - the maximum energy Gmax mc^2 at which electrons are injected.

  8. Modeling the Production of Beta-Delayed Gamma Rays for the Detection of Special Nuclear Materials

    Energy Technology Data Exchange (ETDEWEB)

    Hall, J M; Pruet, J A; Brown, D A; Descalle, M; Hedstrom, G W; Prussin, S G

    2005-02-14

    The objective of this LDRD project was to develop one or more models for the production of {beta}-delayed {gamma} rays following neutron-induced fission of a special nuclear material (SNM) and to define a standardized formatting scheme which will allow them to be incorporated into some of the modern, general-purpose Monte Carlo transport codes currently being used to simulate inspection techniques proposed for detecting fissionable material hidden in sea-going cargo containers. In this report, we will describe a Monte Carlo model for {beta}-delayed {gamma}-ray emission following the fission of SNM that can accommodate arbitrary time-dependent fission rates and photon collection histories. The model involves direct sampling of the independent fission yield distributions of the system, the branching ratios for decay of individual fission products and spectral distributions representing photon emission from each fission product and for each decay mode. While computationally intensive, it will be shown that this model can provide reasonably detailed estimates of the spectra that would be recorded by an arbitrary spectrometer and may prove quite useful in assessing the quality of evaluated data libraries and identifying gaps in the libraries. The accuracy of the model will be illustrated by comparing calculated and experimental spectra from the decay of short-lived fission products following the reactions {sup 235}U(n{sub th}, f) and {sup 239}Pu(n{sub th}, f). For general-purpose transport calculations, where a detailed consideration of the large number of individual {gamma}-ray transitions in a spectrum may not be necessary, it will be shown that a simple parameterization of the {gamma}-ray source function can be defined which provides high-quality average spectral distributions that should suffice for calculations describing photons being transported through thick attenuating media. Finally, a proposal for ENDF-compatible formats that describe each of the models and

  9. A broadband gamma-ray spectrometry using novel unfolding algorithms for characterization of laser wakefield-generated betatron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Jong Ho, E-mail: jhjeon07@ibs.re.kr; Nakajima, Kazuhisa, E-mail: naka115@dia-net.ne.jp; Pathak, Vishwa Bandhu; Cho, Myung Hoon; Yoo, Byung Ju; Shin, Kang Woo [Center for Relativistic Laser Science, Institute for Basic Science (IBS), Gwangju 500-712 (Korea, Republic of); Kim, Hyung Taek; Sung, Jae Hee; Lee, Seung Ku; Choi, Il Woo [Center for Relativistic Laser Science, Institute for Basic Science (IBS), Gwangju 500-712 (Korea, Republic of); Advanced Photonics Research Institute, GIST, Gwangju 500-712 (Korea, Republic of); Rhee, Yong Joo [Nuclear Data Center, Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Shin, Jung Hun; Jo, Sung Ha [Advanced Photonics Research Institute, GIST, Gwangju 500-712 (Korea, Republic of); Hojbota, Calin; Cho, Byeoung Ick; Nam, Chang Hee [Center for Relativistic Laser Science, Institute for Basic Science (IBS), Gwangju 500-712 (Korea, Republic of); Department of Physics and Photon Science, GIST, Gwangju 500-712 (Korea, Republic of)

    2015-12-15

    We present a high-flux, broadband gamma-ray spectrometry capable of characterizing the betatron radiation spectrum over the photon energy range from 10 keV to 20 MeV with respect to the peak photon energy, spectral bandwidth, and unique discrimination from background radiations, using a differential filtering spectrometer and the unfolding procedure based on the Monte Carlo code GEANT4. These properties are experimentally verified by measuring betatron radiation from a cm-scale laser wakefield accelerator (LWFA) driven by a 1-PW laser, using a differential filtering spectrometer consisting of a 15-filter and image plate stack. The gamma-ray spectra were derived by unfolding the photostimulated luminescence (PSL) values recorded on the image plates, using the spectrometer response matrix modeled with the Monte Carlo code GEANT4. The accuracy of unfolded betatron radiation spectra was assessed by unfolding the test PSL data simulated with GEANT4, showing an ambiguity of less than 20% and clear discrimination from the background radiation with less than 10%. The spectral analysis of betatron radiation from laser wakefield-accelerated electron beams with energies up to 3 GeV revealed radiation spectra characterized by synchrotron radiation with the critical photon energy up to 7 MeV. The gamma-ray spectrometer and unfolding method presented here facilitate an in-depth understanding of betatron radiation from LWFA process and a novel radiation source of high-quality photon beams in the MeV regime.

  10. A broadband gamma-ray spectrometry using novel unfolding algorithms for characterization of laser wakefield-generated betatron radiation.

    Science.gov (United States)

    Jeon, Jong Ho; Nakajima, Kazuhisa; Kim, Hyung Taek; Rhee, Yong Joo; Pathak, Vishwa Bandhu; Cho, Myung Hoon; Shin, Jung Hun; Yoo, Byung Ju; Hojbota, Calin; Jo, Sung Ha; Shin, Kang Woo; Sung, Jae Hee; Lee, Seung Ku; Cho, Byeoung Ick; Choi, Il Woo; Nam, Chang Hee

    2015-12-01

    We present a high-flux, broadband gamma-ray spectrometry capable of characterizing the betatron radiation spectrum over the photon energy range from 10 keV to 20 MeV with respect to the peak photon energy, spectral bandwidth, and unique discrimination from background radiations, using a differential filtering spectrometer and the unfolding procedure based on the Monte Carlo code GEANT4. These properties are experimentally verified by measuring betatron radiation from a cm-scale laser wakefield accelerator (LWFA) driven by a 1-PW laser, using a differential filtering spectrometer consisting of a 15-filter and image plate stack. The gamma-ray spectra were derived by unfolding the photostimulated luminescence (PSL) values recorded on the image plates, using the spectrometer response matrix modeled with the Monte Carlo code GEANT4. The accuracy of unfolded betatron radiation spectra was assessed by unfolding the test PSL data simulated with GEANT4, showing an ambiguity of less than 20% and clear discrimination from the background radiation with less than 10%. The spectral analysis of betatron radiation from laser wakefield-accelerated electron beams with energies up to 3 GeV revealed radiation spectra characterized by synchrotron radiation with the critical photon energy up to 7 MeV. The gamma-ray spectrometer and unfolding method presented here facilitate an in-depth understanding of betatron radiation from LWFA process and a novel radiation source of high-quality photon beams in the MeV regime.

  11. External gamma-ray dose rate and radon concentration in indoor environments covered with Brazilian granites

    Energy Technology Data Exchange (ETDEWEB)

    Anjos, R.M., E-mail: meigikos@if.uff.br [LARA - Laboratorio de Radioecologia, Instituto de Fisica, Universidade Federal Fluminense, Av. Gal Milton Tavares de Souza, s/no, Gragoata, 24210-340 Niteroi, RJ (Brazil); Juri Ayub, J. [LARA - Laboratorio de Radioecologia, Instituto de Fisica, Universidade Federal Fluminense, Av. Gal Milton Tavares de Souza, s/no, Gragoata, 24210-340 Niteroi, RJ (Brazil); GEA-Instituto de Matematica Aplicada San Luis (IMASL), Universidad Nacional de San Luis, Consejo Nacional de Investigaciones Cientificas y Tecnicas, CCT-San Luis, Ej. de los Andes 950, D5700HHW San Luis (Argentina); Cid, A.S.; Cardoso, R.; Lacerda, T. [LARA - Laboratorio de Radioecologia, Instituto de Fisica, Universidade Federal Fluminense, Av. Gal Milton Tavares de Souza, s/no, Gragoata, 24210-340 Niteroi, RJ (Brazil)

    2011-11-15

    Health hazard from natural radioactivity in Brazilian granites, covering the walls and floor in a typical dwelling room, was assessed by indirect methods to predict external gamma-ray dose rates and radon concentrations. The gamma-ray dose rate was estimated by a Monte Carlo simulation method and validated by in-situ measurements with a NaI spectrometer. Activity concentrations of {sup 232}Th, {sup 226}Ra, and {sup 40}K in an extensive selection of Brazilian commercial granite samples measured by using gamma-ray spectrometry were found to be 4.5-450 Bq kg{sup -1}, 4.9-160 Bq kg{sup -1} and 190-2029 Bq kg{sup -1}, respectively. The maximum external gamma-ray dose rate from floor and walls covered with the Brazilian granites in the typical dwelling room (5.0 m x 4.0 m area, 2.8 m height) was found to be 120 nGy h{sup -1}, which is comparable with the average worldwide exposure to external terrestrial radiation of 80 nGy h{sup -1} due to natural sources, proposed by United Nations Scientific Committee on the Effects of Atomic Radiation. Radon concentrations in the room were also estimated by a simple mass balance equation and exhalation rates calculated from the measured values of {sup 226}Ra concentrations and the material properties. The results showed that the radon concentration in the room ventilated adequately (0.5 h{sup -1}) will be lower than 100 Bq m{sup -3}, value recommended as a reference level by the World Health Organization. - Highlights: > We used indirect methods to predict external gamma dose rate and radon concentration. > The gamma-ray dose rate was estimated by a Monte Carlo simulation method. > The results were validated by in-situ measurements with a NaI spectrometer. > Radon concentrations in the room were estimated by a simple mass balance equation. > Radon concentration in the room ventilated adequately will be lower than 100 Bq m{sup -3}.

  12. Combined in-beam electron and gamma-ray spectroscopy of (184,186)Hg

    CERN Document Server

    Scheck, M; Rahkila, P; Butler, P A; Larsen, A C; Sandzelius, M; Scholey, C; Carrol, R J; Papadakis, P; Jakobsson, U; Grahn, T; Joss, D T; Watkins, H V; Juutinen, S; Bree, N; Cox, D; Huyse, M; Uusitalo, J; Leino, M; Ruotsalainen, P; Nieminen, P; Srebrny, J; Van Duppen, P; Herzan, A; Greenlees, P T; Julin, R; Herzberg, R D; Hauschild, K; Pakarinen, J; Page, R D; Peura, P; Gaffney, L P; Kowalczyk, M; Rinta-Antila, S; Saren, J; Lopez-Martens, A; Sorri, J; Ketelhut, S

    2011-01-01

    By exploiting the SAGE spectrometer a simultaneous measurement of conversion electrons and gamma rays emitted in the de-excitation of excited levels in the neutron-deficient nuclei (184,186)Hg was performed. The light Hg isotopes under investigation were produced using the 4n channels of the fusion-evaporation reactions of (40)Ar and (148,150)Sm. The measured K- and L-conversion electron ratios confirmed the stretched E2 nature of several transitions of the yrast bands in (184,186)Hg. Additional information on the E0 component of the 2(2)(+) -> 2(1)(+) transition in (186)Hg was obtained.

  13. Wavelet-Based Techniques for the Gamma-Ray Sky

    CERN Document Server

    McDermott, Samuel D; Cholis, Ilias; Lee, Samuel K

    2015-01-01

    We demonstrate how the image analysis technique of wavelet decomposition can be applied to the gamma-ray sky to separate emission on different angular scales. New structures on scales that differ from the scales of the conventional astrophysical foreground and background uncertainties can be robustly extracted, allowing a model-independent characterization with no presumption of exact signal morphology. As a test case, we generate mock gamma-ray data to demonstrate our ability to extract extended signals without assuming a fixed spatial template. For some point source luminosity functions, our technique also allows us to differentiate a diffuse signal in gamma-rays from dark matter annihilation and extended gamma-ray point source populations in a data-driven way.

  14. 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.

  15. 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,...

  16. Status of space-based gamma-ray astronomy

    CERN Document Server

    Buehler, Rolf

    2015-01-01

    Gamma-ray observations give us a direct view into the most extreme environments of the universe. They help us to study astronomical particle accelerators as supernovae remnants, pulsars, active galaxies or gamma-ray bursts and help us to understand the propagation of cosmic rays through our Milky Way. This article summarizes the status of gamma-ray observations from space; it is the write-up of a rapporteur talk given at the 34th ICRC in The Hague, The Netherlands. The primary instrument used in the presented studies is the Large Area Telescope on-board the Fermi Spacecraft, which images the whole gamma-ray sky at photon energies between 20 MeV and 2 TeV. The Fermi mission is currently in its 8th year of observations. This article will review many of the exciting discoveries made in this time, focusing on the most recent ones.

  17. Fireball and cannonball models of gamma ray bursts confront observations

    OpenAIRE

    Dar, Arnon

    2005-01-01

    The two leading contenders for the theory of gamma-ray bursts (GRBs) and their afterglows, the Fireball and Cannonball models, are compared and their predictions are confronted, within space limitations, with key GRB observations, including recent observations with SWIFT

  18. Prompt Optical Observations of $\\gamma$-ray Bursts

    CERN Document Server

    Akerlof, Carl W; Barthelmy, S D; Bloch, J; Butterworth, P S; Casperson, D E; Cline, T; Fletcher, S; Frontera, F; Gisler, G; Heise, J; Hills, J; Hurley, K; Kehoe, R; Lee, B; Marshall, S; McKay, T; Pawl, A; Piro, L; Szymanski, J J; Wren, J; Akerlof, Carl; Balsano, Richard; Barthelmy, Scott; Bloch, Jeff; Butterworth, Paul; Casperson, Don; Cline, Tom; Fletcher, Sandra; Frontera, Fillippo; Gisler, Galen; Heise, John; Hills, Jack; Hurley, Kevin; Kehoe, Robert; Lee, Brian; Marshall, Stuart; Kay, Tim Mc; Pawl, Andrew; Piro, Luigi; Szymanski, John; Wren, Jim

    2000-01-01

    The Robotic Optical Transient Search Experiment (ROTSE) seeks to measure simultaneous and early afterglow optical emission from gamma-ray bursts (GRBs). A search for optical counterparts to six GRBs with localization errors of 1 square degree or better produced no detections. The earliest limiting sensitivity is m(ROTSE) > 13.1 at 10.85 seconds (5 second exposure) after the gamma-ray rise, and the best limit is m(ROTSE) > 16.0 at 62 minutes (897 second exposure). These are the most stringent limits obtained for 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 GRB990123 indicates that there is not a strong positive correlation between optical flux and gamma-ray emission.

  19. Location and origin of gamma-rays in blazars

    CERN Document Server

    Rani, B; Hodgson, J A; Zensus, J A

    2016-01-01

    One of the most intriguing and challenging quests of current astrophysics is to understand the physical conditions and processes responsible for production of high-energy particles, and emission of \\gamma-rays. A combination of high-resolution Very Long Baseline Interferometry (VLBI) images with broadband flux variability measurements is a unique way to probe the emission mechanisms at the bases of jets. Our analysis of \\gamma-ray flux variability observed by the Fermi-LAT (Large Area Telescope) along with the parsec-scale jet kinematics suggests that the $\\gamma$-ray emission in blazar S5 0716+714 has a significant correlation with the mm-VLBI core flux and the orientation of jet outflow on parsec scales. These results indicate that the inner jet morphology has a tight connection with the observed $\\gamma$-ray flares. An overview of our current understanding on high-energy radiation processes, their origin, and location is presented here.

  20. 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.

  1. 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.

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

    Indian Academy of Sciences (India)

    Samit Mandal; J Gerl; H Geissel; K Hauschild; M Hellström; Z Janas; I Kojouharov; Y Kopatch; R C Lemmon; P Mayet; Z Podolyak; P H Regan; H Schaffner; C Schlegel; J Simpson; H J Wollersheim

    2001-07-01

    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.

  3. 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...

  4. MIRAX sensitivity for Gamma Ray Bursts

    Science.gov (United States)

    Sacahui, J. R.; Penacchioni, A. V.; Braga, J.; Castro, M. A.; D'Amico, F.

    2016-03-01

    In this work we present the detection capability of the MIRAX (Monitor e Imageador de RAios-X) experiment for Gamma-Ray Bursts (GRBs). MIRAX is an X-ray astronomy mission designed to perform a wide band hard X-ray (10-200 keV) survey of the sky, especially in the Galactic plane. With a total detection area of 169 cm2, large field of view (FoV, 20 ° × 20 °), angular resolution of 1°45‧ and good spectral and time resolution (∼8% at 60 keV, 10 μs), MIRAX will be optimized for the detection and study of transient sources, such as accreting neutron stars (NS), black holes (BH), Active Galactic Nuclei (AGNs), and both short and long GRBs. This is especially important because MIRAX is expected to operate in an epoch when probably no other hard X-ray wide-field imager will be active. We have performed detailed simulations of MIRAX GRB observations using the GEANT4 package, including the background spectrum and images of GRB sources in order to provide accurate predictions of the sensitivity for the expected GRB rate to be observed. MIRAX will be capable of detecting ∼44 GRBs per year up to redshifts of ∼4.5. The MIRAX mission will be able to contribute significantly to GRB science by detecting a large number of GRBs per year with wide band spectral response. The observations will contribute mainly to the part of GRB spectra where a thermal emission is predicted by the Fireball model. We also discuss the possibility of detecting GRB afterglows in the X-ray band with MIRAX.

  5. Gamma-Ray Burst Class Properties

    Science.gov (United States)

    Hakkila, Jon; Haglin, David J.; Pendleton, Geoffrey N.; Mallozzi, Robert S.; Meegan, Charles A.; Roiger, Richard J.

    2000-01-01

    Guided by the supervised pattern recognition algorithm C4.5 developed by Quinlan in 1986, we examine the three gamma-ray burst classes identified by Mukherjee et al. in 1998. C4.5 provides strong statistical support for this classification. However, with C4.5 and our knowledge of the Burst and Transient Source Experiment (BATSE) instrument, we demonstrate that class 3 (intermediate fluence, intermediate duration, soft) does not have to be a distinct source population: statistical/systematic errors in measuring burst attributes combined with the well-known hardness/intensity correlation can cause low peak flux class 1 (high fluence, long, intermediate hardness) bursts to take on class 3 characteristics naturally. Based on our hypothesis that the third class is not a distinct one, we provide rules so that future events can be placed in either class 1 or class 2 (low fluence, short, hard). We find that the two classes are relatively distinct on the basis of Band's work in 1993 on spectral parameters alpha, beta, and E (sub peak) alone. Although this does not indicate a better basis for classification, it does suggest that different physical conditions exist for class 1 and class 2 bursts. In the process of studying burst class characteristics, we identify a new bias affecting burst fluence and duration measurements. Using a simple model of how burst duration can be underestimated, we show how this fluence duration bias can affect BATSE measurements and demonstrate the type of effect it can have on the BATSE fluence versus peak flux diagram.

  6. Dark matter properties implied by gamma ray interstellar emission models

    OpenAIRE

    Balázs, Csaba; Li, Tong

    2016-01-01

    We infer dark matter properties from gamma ray residuals extracted using eight different interstellar emission scenarios proposed by the Fermi-LAT Collaboration to explain the Galactic Center gamma ray excess. Adopting the most plausible simplified ansatz, we assume that the dark matter particle is a Majorana fermion interacting with standard fermions via a scalar mediator. Using this theoretical hypothesis and the Fermi residuals we calculate Bayesian evidences, including Fermi-LAT exclusion...

  7. $\\gamma$-rays and neutrinos from dark matter

    CERN Document Server

    Stecker, F W

    1996-01-01

    High energy gamma-rays and neutrinos can be produced both by the annihilation and by the possible slow decay of dark matter particles. We discuss the fluxes and spectra of such secondaries produced by dark matter particles in the universe and their observability in competition with other astrophysical gamma-ray signals and with atmospheric neutrinos. To do this, we work within the assumption that the dark matter particles are neutralinos which are the lightest supersymmetric particles (LSPs) predicted by supersymmetry theory.

  8. Searches for Axionlike Particles Using Gamma-Ray Observations

    CERN Document Server

    Meyer, Manuel

    2016-01-01

    Axionlike particles (ALPs) are a common prediction of theories beyond the Standard Model of particle physics that could explain the entirety of the cold dark matter. These particles could be detected through their mixing with photons in external electromagnetic fields. Here, we provide a short review over ALP searches that utilize astrophysical $\\gamma$-ray observations. We summarize current bounds as well as future sensitivities and discuss the possibility that ALPs alter the $\\gamma$-ray opacity of the Universe.

  9. Constraining gamma-ray propagation on cosmic distances

    OpenAIRE

    Biteau, Jonathan

    2013-01-01

    Studying the propagation of gamma rays on cosmological distances encompasses a variety of scientific fields, focusing on diffuse radiation fields such as the extragalactic background light, on the probe of the magnetism of the Universe on large scales, and on physics beyond the standard models of cosmology and particle physics. The measurements, constraints and hints from observations of gamma-ray blazars by airborne and ground-based instruments are briefly reviewed. These observations point ...

  10. Physics and astrophysics with gamma-ray telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Vandenbroucke, J. [Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2012-08-15

    In the past few years gamma-ray astronomy has entered a golden age. A modern suite of telescopes is now scanning the sky over both hemispheres and over six orders of magnitude in energy. At {approx}TeV energies, only a handful of sources were known a decade ago, but the current generation of ground-based imaging atmospheric Cherenkov telescopes (H.E.S.S., MAGIC, and VERITAS) has increased this number to nearly one hundred. With a large field of view and duty cycle, the Tibet and Milagro air shower detectors have demonstrated the promise of the direct particle detection technique for TeV gamma rays. At {approx}GeV energies, the Fermi Gamma-ray Space Telescope has increased the number of known sources by nearly an order of magnitude in its first year of operation. New classes of sources that were previously theorized to be gamma-ray emitters have now been confirmed observationally. Moreover, there have been surprise discoveries of GeV gamma-ray emission from source classes for which no theory predicted it was possible. In addition to elucidating the processes of high-energy astrophysics, gamma-ray telescopes are making essential contributions to fundamental physics topics including quantum gravity, gravitational waves, and dark matter. I summarize the current census of astrophysical gamma-ray sources, highlight some recent discoveries relevant to fundamental physics, and describe the synergetic connections between gamma-ray and neutrino astronomy. This is a brief overview intended in particular for particle physicists and neutrino astronomers, based on a presentation at the Neutrino 2010 conference in Athens, Greece. I focus in particular on results from Fermi (which was launched soon after Neutrino 2008), and conclude with a description of the next generation of instruments, namely HAWC and the Cherenkov Telescope Array.

  11. Science with the new generation high energy gamma- ray experiments

    CERN Document Server

    Alvarez, M; Agnetta, G; Alberdi, A; Antonelli, A; Argan, A; Assis, P; Baltz, E A; Bambi, C; Barbiellini, G; Bartko, H; Basset, M; Bastieri, D; Belli, P; Benford, G; Bergström, L; Bernabei, R; Bertone, G; Biland, A; Biondo, B; Bocchino, F; Branchini, E; Brigida, M; Bringmann, T; Brogueira, P; Bulgarelli, A; Caballero, J A; Caliandro, G A; Camarri, P; Cappella, F; Caraveo, P; Carbone, R; Carvajal, M; Casanova, S; Castro-Tirado, A J; Catalano, O; Catena, R; Celi, F; Celotti, A; Cerulli, R; Chen, A; Clay, R; Cocco, V; Conrad, J; Costa, E; Cuoco, A; Cusumano, G; Dai, C J; Dawson, B; De Lotto, B; De Paris, G; Postigo, A de Ugarte; Del Monte, E; Delgado, C; Di Ciaccio, A; Di Cocco, G; Di Falco, S; Di Persio, G; Dingus, B L; Dominguez, A; Donato, F; Donnarumma, I; Doro, M; Edsjö, J; Navas, J M Espino; Santo, M C Espirito; Evangelista, Y; Evoli, C; Fargion, D; Favuzzi, C; Feroci, M; Fiorini, M; Foggetta, L; Fornengo, N; Froysland, T; Frutti, M; Fuschino, F; Gómez, J L; Gómez, M; Gaggero, D; Galante, N; Gallardo, M I; Galli, M; García, J E; Garczarczyk, M; Gargano, F; Gaug, M; Gianotti, F; Giarrusso, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Giuliani, A; Glicenstein, J; Gonçalves, P; Grasso, D; Guerriero, M; He, H L; Incicchitti, A; Kirk, J; Kuang, H H; La Barbera, A; La Rosa, G; Labanti, C; Lamanna, G; Lapshov, I; Lazzarotto, F; Liberati, S; Liello, F; Lipari, P; Longo, F; Loparco, F; Lozano, M; De Sanctis, P G Lucentini; Ma, J M; Maccarone, M C; Maccione, L; Malvezzi, V; Mangano, A; Mariotti, M; Marisaldi, M; Martel, I; Masiero, A; Massaro, E; Mastropietro, M; Mattaini, E; Mauri, F; Mazziotta, M N; Mereghetti, S; Mineo, T; Mizobuchi, S; Moiseev, A; Moles, M; Monte, C; Montecchia, F; Morelli, E; Morselli, A; Moskalenko, I; Nozzoli, F; Ormes, J F; Peres-Torres, M A; Pacciani, L; Pellizzoni, A; Pérez-Bernal, F; Perotti, F; Picozza, P; Pieri, L; Pietroni, M; Pimenta, M; Pina, A; Pittori, C; Pontoni, C; Porrovecchio, G; Prada, F; Prest, M; Prosperi, D; Protheroe, R; Pucella, G; Quesada, J M; Quintana, J M; Quintero, J R; Rainó, S; Rapisarda, M; Rissi, M; Rodríguez, J; Rossi, E; Rowell, G; Rubini, A; Russo, F; Sanchez-Conde, M; Sacco, B; Scapin, V; Schelke, M; Segreto, A; Sellerholm, A; Sheng, X D; Smith, A; Soffitta, P; Sparvoli, R; Spinelli, P; Stamatescu, V; Stark, L S; Tavani, M; Thornton, G; Titarchuk, L G; Tomé, B; Traci, A; Trifoglio, M; Trois, A; Vallania, P; Vallazza, E; Vercellone, S; Vernetto, S; Vitale, V; Wild, N; Ye, Z P; Zambra, A; Zandanel, F; Zanello, D

    2007-01-01

    This Conference is the fifth of a series of Workshops on High Energy Gamma- ray Experiments, following the Conferences held in Perugia 2003, Bari 2004, Cividale del Friuli 2005, Elba Island 2006. This year the focus was on the use of gamma-ray to study the Dark Matter component of the Universe, the origin and propagation of Cosmic Rays, Extra Large Spatial Dimensions and Tests of Lorentz Invariance.

  12. Significant gamma-ray lines from dark matter annihilation

    Energy Technology Data Exchange (ETDEWEB)

    Duerr, Michael [DESY, Notkestrasse 85, 22607 Hamburg (Germany); Fileviez Perez, Pavel; Smirnov, Juri [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

    2016-07-01

    Gamma-ray lines from dark matter annihilation are commonly seen as a ''smoking gun'' for the particle nature of dark matter. However, in many dark matter models the continuum background from tree-level annihilations makes such a line invisible. I present two simple extensions of the Standard Model where the continuum contributions are suppressed and the gamma-ray lines are easily visible over the continuum background.

  13. 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.

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

    CERN Document Server

    Connaughton, V; 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

    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, 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 degree Gaussian with a non-Gaussian tail that contains about 10% of GBM-detected GRBs and extends to approximately 14 degrees. 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 l...

  15. 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.

  16. 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.

  17. The CALET Gamma-ray Burst Monitor (CGBM)

    CERN Document Server

    Yamaoka, Kazutaka; Sakamoto, Takanori; Takahashi, Ichiro; Hara, Takumi; Yamamoto, Tatsuma; Kawakubo, Yuta; Inoue, Ry ota; Terazawa, Shunsuke; Fujioka, Rie; Senuma, Kazumasa; Nakahira, Satoshi; Tomida, Hiroshi; Ueno, Shiro; Torii, Shoji; Cherry, Michael L; Ricciarini, Sergio

    2013-01-01

    The CALET Gamma-ray Burst Monitor (CGBM) is the secondary scientific instrument of the CALET mission on the International Space Station (ISS), which is scheduled for launch by H-IIB/HTV in 2014. The CGBM provides a broadband energy coverage from 7 keV to 20 MeV, and simultaneous observations with the primary instrument Calorimeter (CAL) in the GeV - TeV gamma-ray range and Advanced Star Camera (ASC) in the optical for gamma-ray bursts (GRBs) and other X-gamma-ray transients. The CGBM consists of two kinds of scintillators: two LaBr$_3$(Ce) (7 keV - 1 MeV) and one BGO (100 keV - 20 MeV) each read by a single photomultiplier. The LaBr$_3$(Ce) crystal, used in space for the first time here for celestial gamma-ray observations, enables GRB observations over a broad energy range from low energy X-ray emissions to gamma rays. The detector performance and structures have been verified using the bread-board model (BBM) via vibration and thermal vacuum tests. The CALET is currently in the development phase of the prot...

  18. 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.

  19. 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.

  20. 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.