Energy spectrum of extragalactic gamma-ray sources

NASA Technical Reports Server (NTRS)

Protheroe, R. J.

1985-01-01

The result of Monte Carlo electron photon cascade calculations for propagation of gamma rays through regions of extragalactic space containing no magnetic field are given. These calculations then provide upper limits to the expected flux from extragalactic sources. Since gamma rays in the 10 to the 14th power eV to 10 to the 17th power eV energy range are of interest, interactions of electrons and photons with the 3 K microwave background radiation are considered. To obtain an upper limit to the expected gamma ray flux from sources, the intergalactic field is assumed to be so low that it can be ignored. Interactions with photons of the near-infrared background radiation are not considered here although these will have important implications for gamma rays below 10 to the 14th power eV if the near infrared background radiation is universal. Interaction lengths of electrons and photons in the microwave background radiation at a temperature of 2.96 K were calculated and are given.

Hard gamma-ray background from the coding collimator of a gamma-ray telescope during in conditions of a space experiment

NASA Astrophysics Data System (ADS)

Aleksandrov, A. P.; Berezovoj, A. N.; Gal'Per, A. M.; Grachev, V. M.; Dmitrenko, V. V.; Kirillov-Ugryumov, V. G.; Lebedev, V. V.; Lyakhov, V. A.; Moiseev, A. A.; Ulin, S. E.; Shchvets, N. I.

1984-11-01

Coding collimators are used to improve the angular resolution of gamma-ray telescopes at energies above 50 MeV. However, the interaction of cosmic rays with the collimator material can lead to the appearance of a gramma-ray background flux which can have a deleterious effect on measurement efficiency. An experiment was performed on the Salyut-6-Soyuz spacecraft system with the Elena-F small-scale gamma-ray telescope in order to measure the magnitude of this background. It is shown that, even at a zenith angle of approximately zero degrees (the angle at which the gamma-ray observations are made), the coding collimator has only an insignificant effect on the background conditions.

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

DOE PAGES

Greenwood, L. R.; Cantaloub, M. G.; Burnett, J. L.; ...

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). Furthermore, 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.

Radio galaxies dominate the high-energy diffuse gamma-ray background

DOE PAGES

Hooper, Dan; Linden, Tim; Lopez, Alejandro

2016-08-09

It has been suggested that unresolved radio galaxies and radio quasars (sometimes referred to as misaligned active galactic nuclei) could be responsible for a significant fraction of the observed diffuse gamma-ray background. In this study, we use the latest data from the Fermi Gamma-Ray Space Telescope to characterize the gamma-ray emission from a sample of 51 radio galaxies. In addition to those sources that had previously been detected using Fermi data, we report here the first statistically significant detection of gamma-ray emission from the radio galaxies 3C 212, 3C 411, and B3 0309+411B. Combining this information with the radio fluxes,more » radio luminosity function, and redshift distribution of this source class, we find that radio galaxies dominate the diffuse gamma-ray background, generating 77.2(+25.4)(-9.4)% of this emission at energies above ~1 GeV . We discuss the implications of this result and point out that it provides support for scenarios in which IceCube's high-energy astrophysical neutrinos also originate from the same population of radio galaxies.« less

Components of the Extragalactic Gamma-Ray Background

NASA Technical Reports Server (NTRS)

Stecker, Floyd W.; Venters, Tonia M.

2011-01-01

We present new theoretical estimates of the relative contributions of unresolved blazars and star-forming galaxies to the extragalactic gamma-ray background (EGB) and discuss constraints on the contributions from alternative mechanisms such as dark matter annihilation and truly diffuse gamma-ray production. We find that the Fermi source count data do not rule out a scenario in which the EGB is dominated by emission from unresolved blazars, though unresolved star-forming galaxies may also contribute significantly to the background, within order-of-magnitude uncertainties. In addition, we find that the spectrum of the unresolved star-forming galaxy contribution cannot explain the EGB spectrum found by EGRET at energies between 50 and 200 MeV, whereas the spectrum of unresolved flat spectrum radio quasars, when accounting for the energy-dependent effects of source confusion, could be consistent with the combined spectrum of the low-energy EGRET EGB measurements and the Fermi-Large Area Telescope EGB measurements.

Blazar Duty-Cycle at Gamma-Ray Frequecies: Constraints From Extragalactic Background Radiation And Prospects for AGILE And GLAST

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

Pittori, Carlotta; Cavazzuti, Elisabetta; Colafrancesco, Sergio

2011-11-29

We take into account the constraints from the observed extragalactic {gamma}-ray background to estimate the maximum duty cycle allowed for a selected sample of WMAP Blazars, in order to be detectable by AGILE and GLAST {gamma}-ray experiments. For the nominal sensitivity values of both instruments, we identify a subset of sources which can in principle be detectable also in a steady state without over-predicting the extragalactic background. This work is based on the results of a recently derived Blazar radio LogN-LogS obtained by combining several multi-frequency surveys.

Annihilation radiation in cosmic gamma-ray bursts

NASA Technical Reports Server (NTRS)

Aptekar, R. L.; Golenetskii, S. V.; Guryan, Y. A.; Ilyinskii, V. N.; Mazets, E. P.

1985-01-01

The pair annihilation radiation in gamma-ray bursts is seen as broad lines with extended hard wings. This radiation is suggested to escape in a collimated beam from magnetic polar regions of neutron stars.

Instrumental background in balloon-borne gamma-ray spectrometers and techniques for its reduction

NASA Technical Reports Server (NTRS)

Gehrels, N.

1985-01-01

Instrumental background in balloon-borne gamma-ray spectrometers is presented. The calculations are based on newly available interaction cross sections and new analytic techniques, and are the most detailed and accurate published to date. Results compare well with measurements made in the 20 keV to 10 MeV energy range by the Goddard Low Energy Gamma-ray Spectrometer (LEGS). The principal components of the continuum background in spectrometers with GE detectors and thick active shields are: (1) elastic neutron scattering of atmospheric neutrons on the Ge nuclei; (2) aperture flux of atmospheric and cosmic gamma rays; (3) beta decays of unstable nuclides produced by nuclear interactions of atmospheric protons and neutrons with Ge nuclei; and (4) shield leakage of atmospheric gamma rays. The improved understanding of these components leads to several recommended techniques for reducing the background.

The cosmic gamma-ray background from Type Ia supernovae

NASA Technical Reports Server (NTRS)

The, Lih-Sin; Leising, Mark D.; Clayton, Donald D.

1993-01-01

We present an improved calculation of the cumulative gamma-ray spectrum of Type Ia supernovae during the history of the universe. We follow Clayton & Ward (1975) in using a few Friedmann models and two simple histories of the average galaxian nucleosynthesis rate, but we improve their calculation by modeling the gamma-ray scattering in detailed numerical models of SN Ia's. The results confirm that near 1 MeV the SN Ia background may dominate, and that it is potentially observable, with high scientific importance. A very accurate measurement of the cosmic background spectrum between 0.1 and 1.0 MeV may reveal the turn-on time and the evolution of the rate of Type Ia supernova nucleosynthesis in the universe.

Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-Ray Background

NASA Technical Reports Server (NTRS)

Venters, T. M.; Pavlidou, V.

2012-01-01

The intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the extragalactic gamma-ray background, through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thus inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that the two extreme cases (zero IGMF and IGMF strong enough to completely isotropize cascade photons) would be separable by ten years of Fermi observations and reasonable model parameters for the gamma-ray background. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

Constraining the redshift distribution of ultrahigh-energy-cosmic-ray sources by isotropic gamma-ray background

NASA Astrophysics Data System (ADS)

Liu, Ruo-Yu; Taylor, Andrew; Wang, Xiang-Yu; Aharonian, Felix

2017-01-01

By interacting with the cosmic background photons during their propagation through intergalactic space, ultrahigh energy cosmic rays (UHECRs) produce energetic electron/positron pairs and photons which will initiate electromagnetic cascades, contributing to the isotropic gamma-ray background (IGRB). The generated gamma-ray flux level highly depends on the redshift evolution of the UHECR sources. Recently, the Fermi-LAT collaboration reported that 86-14+16 of the total extragalactic gamma-ray flux comes from extragalactic point sources including those unresolved ones. This leaves a limited room for the diffusive gamma ray generated via UHECR propagation, and subsequently constrains their source distribution in the Universe. Normalizing the total cosmic ray energy budget with the observed UHECR flux in the energy band of (1-4)×1018 eV, we calculate the diffuse gamma-ray flux generated through UHECR propagation. We find that in order to not overshoot the new IGRB limit, these sub-ankle UHECRs should be produced mainly by nearby sources, with a possible non-negligible contribution from our Galaxy. The distance for the majority of UHECR sources can be further constrained if a given fraction of the observed IGRB at 820 GeV originates from UHECR. We note that our result should be conservative since there may be various other contributions to the IGRB that is not included here.

Fermi gamma-ray imaging of a radio galaxy.

PubMed

Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cavazzuti, E; Cecchi, C; Celik, O; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Colafrancesco, S; Cominsky, L R; Conrad, J; Costamante, L; Cutini, S; Davis, D S; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Finke, J; Focke, W B; Fortin, P; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Georganopoulos, M; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; Jackson, M S; Jóhannesson, G; Johnson, A S; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Romani, R W; Roth, M; Ryde, F; Sadrozinski, H F-W; Sambruna, R; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Stawarz, Ł; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wallace, E; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M; Hardcastle, M J; Kazanas, D

2010-05-07

The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved gamma-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy gamma-rays, the lobe flux constitutes a considerable portion (greater than one-half) of the total source emission. The gamma-ray emission from the lobes is interpreted as inverse Compton-scattered relic radiation from the cosmic microwave background, with additional contribution at higher energies from the infrared-to-optical extragalactic background light. These measurements provide gamma-ray constraints on the magnetic field and particle energy content in radio galaxy lobes, as well as a promising method to probe the cosmic relic photon fields.

High-energy Emission from Nonrelativistic Radiative Shocks: Application to Gamma-Ray Novae

NASA Astrophysics Data System (ADS)

Vurm, Indrek; Metzger, Brian D.

2018-01-01

The observation of GeV gamma-rays from novae by Fermi/LAT demonstrates that the nonrelativistic radiative shocks in these systems can accelerate particles to energies of at least ∼10 GeV. The low-energy extension of the same nonthermal particle distribution inevitably gives rise to emission in the hard X-ray band. Above ≳ 10 {keV}, this radiation can escape the system without significant absorption/attenuation, and can potentially be detected by NuSTAR. We present theoretical models for hard X-ray and gamma-ray emission from radiative shocks in both leptonic and hadronic scenarios, accounting for the rapid evolution of the downstream properties due to the fast cooling of thermal plasma. We find that due to strong Coulomb losses, only a fraction of {10}-4{--}{10}-3 of the gamma-ray luminosity is radiated in the NuSTAR band; nevertheless, this emission could be detectable simultaneously with the LAT emission in bright gamma-ray novae with a ∼50 ks exposure. The spectral slope in hard X-rays is α ≈ 0 for typical nova parameters, thus serving as a testable prediction of the model. Our work demonstrates how combined hard X-ray and gamma-ray observations can be used to constrain properties of the nova outflow (velocity, density, and mass outflow rate) and particle acceleration at the shock. A very low X-ray to gamma-ray luminosity ratio ({L}{{X}}/{L}γ ≲ 5× {10}-4) would disfavor leptonic models for the gamma-ray emission. Our model can also be applied to other astrophysical environments with radiative shocks, including SNe IIn and colliding winds in massive star binaries.

The origin of the diffuse background gamma radiation

NASA Technical Reports Server (NTRS)

Stecker, F. W.; Puget, J. L.

1974-01-01

Recent observations provided evidence for diffuse background gamma radiation extending to energies beyond 100 MeV, and evidence of isotropy and implied cosmological origin. Significant features in the spectrum of this background radiation were observed which provide evidence for its origin in nuclear processes in the early stages of big-bang cosmology, and connect these processes with the galaxy formation theory. A test of the theory is in future observations of the background radiation in the 100 MeK to 100 GeV energy range which are made with large orbiting spark-chamber satellite detectors. The theoretical interpretations of present data, their connection with baryon-symmetric cosmology and galaxy formation theory, and the need for future observations are discussed.

The Impact of Electromagnetic Cascades of Very-high Energy Gamma Rays on the Extragalactic Gamma-ray Background

NASA Technical Reports Server (NTRS)

Venters, Tonia

2012-01-01

As very high energy (VHE) photons propagate through the extragalactic background light (EBL), they interact with the soft photons of the EBL and initiate electromagnetic cascades of photons and electrons. The collective intensity of a cosmological population emitting at VHEs (such as blazars) will be attenuated at the highest energies through interactions with the EBL and enhanced at lower energies by the resulting cascade. As such, depending on the space density and spectra of the sources and the model of the EBL, cascade radiation can provide a significant contribution to the extragalactic gamma-ray background (EGB). Through deflections of the charged particles of the cascade, an intergalactic magnetic field (IGMF) may leave an imprint on the anisotropy properties of the EGB. The impact of a strong IGMF is to isotropize lower energy cascade photons, inducing a modulation in the anisotropy energy spectrum of the EGB. We discuss the implications of cascade radiation for the origins of the EGB and the nature of the IGMF, as well as insight that will be provided by data from the Fermi Large Area Telescope in the upcoming years.

The Extragalactic Background Light and the Gamma-ray Opacity of the Universe

NASA Technical Reports Server (NTRS)

Dwek, Eli; Krennrich, Frank

2012-01-01

The extragalactic background light (EBL) is one of the fundamental observational quantities in cosmology. All energy releases from resolved and unresolved extragalactic sources, and the light from any truly diffuse background, excluding the cosmic microwave background (CMB), contribute to its intensity and spectral energy distribution. It therefore plays a crucial role in cosmological tests for the formation and evolution of stellar objects and galaxies, and for setting limits on exotic energy releases in the universe. The EBL also plays an important role in the propagation of very high energy gamma-rays which are attenuated en route to Earth by pair producing gamma-gamma interactions with the EBL and CMB. The EBL affects the spectrum of the sources, predominantly blazars, in the approx 10 GeV to 10 TeV energy regime. Knowledge of the EBL intensity and spectrum will allow the determination of the intrinsic blazar spectrum in a crucial energy regime that can be used to test particle acceleration mechanisms and VHE gamma-ray production models. Conversely, knowledge of the intrinsic gamma-ray spectrum and the detection of blazars at increasingly higher redshifts will set strong limits on the EBL and its evolution. This paper reviews the latest developments in the determination of the EBL and its impact on the current understanding of the origin and production mechanisms of gamma-rays in blazars, and on energy releases in the universe. The review concludes with a summary and future directions in Cherenkov Telescope Array techniques and in infrared ground-based and space observatories that will greatly improve our knowledge of the EBL and the origin and production of very high energy gamma-rays.

Enhancement of natural background gamma-radiation dose around uranium microparticles in the human body.

PubMed

Pattison, John E; Hugtenburg, Richard P; Green, Stuart

2010-04-06

Ongoing controversy surrounds the adverse health effects of the use of depleted uranium (DU) munitions. The biological effects of gamma-radiation arise from the direct or indirect interaction between secondary electrons and the DNA of living cells. The probability of the absorption of X-rays and gamma-rays with energies below about 200 keV by particles of high atomic number is proportional to the third to fourth power of the atomic number. In such a case, the more heavily ionizing low-energy recoil electrons are preferentially produced; these cause dose enhancement in the immediate vicinity of the particles. It has been claimed that upon exposure to naturally occurring background gamma-radiation, particles of DU in the human body would produce dose enhancement by a factor of 500-1000, thereby contributing a significant radiation dose in addition to the dose received from the inherent radioactivity of the DU. In this study, we used the Monte Carlo code EGSnrc to accurately estimate the likely maximum dose enhancement arising from the presence of micrometre-sized uranium particles in the body. We found that although the dose enhancement is significant, of the order of 1-10, it is considerably smaller than that suggested previously.

Enhancement of natural background gamma-radiation dose around uranium microparticles in the human body

PubMed Central

Pattison, John E.; Hugtenburg, Richard P.; Green, Stuart

2010-01-01

Ongoing controversy surrounds the adverse health effects of the use of depleted uranium (DU) munitions. The biological effects of gamma-radiation arise from the direct or indirect interaction between secondary electrons and the DNA of living cells. The probability of the absorption of X-rays and gamma-rays with energies below about 200 keV by particles of high atomic number is proportional to the third to fourth power of the atomic number. In such a case, the more heavily ionizing low-energy recoil electrons are preferentially produced; these cause dose enhancement in the immediate vicinity of the particles. It has been claimed that upon exposure to naturally occurring background gamma-radiation, particles of DU in the human body would produce dose enhancement by a factor of 500–1000, thereby contributing a significant radiation dose in addition to the dose received from the inherent radioactivity of the DU. In this study, we used the Monte Carlo code EGSnrc to accurately estimate the likely maximum dose enhancement arising from the presence of micrometre-sized uranium particles in the body. We found that although the dose enhancement is significant, of the order of 1–10, it is considerably smaller than that suggested previously. PMID:19776147

Lunar occultations for gamma-ray source measurements

NASA Technical Reports Server (NTRS)

Koch, David G.; Hughes, E. B.; Nolan, Patrick L.

1990-01-01

The unambiguous association of discrete gamma-ray sources with objects radiating at other wavelengths, the separation of discrete sources from the extended emission within the Galaxy, the mapping of gamma-ray emission from nearby galaxies and the measurement of structure within a discrete source cannot presently be accomplished at gamma-ray energies. In the past, the detection processes used in high-energy gamma-ray astronomy have not allowed for good angular resolution. This problem can be overcome by placing gamma-ray detectors on the moon and using the horizon as an occulting edge to achieve arcsec resolution. For purposes of discussion, this concept is examined for gamma rays above 100 MeV for which pair production dominates the detection process and locally-generated nuclear gamma rays do not contribute to the background.

Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-ray Background

NASA Technical Reports Server (NTRS)

Venters, T. M.; Pavlidou, V.

2013-01-01

The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and the extragalactic background light. A strong IGMF will deflect secondary particles produced in these cascades and will thus tend to isotropize lower energy cascade photons, thereby inducing a modulation in the anisotropy energy spectrum of the gamma-ray background. Here we present a simple, proof-of-concept calculation of the magnitude of this effect and demonstrate that current Fermi data already seem to prefer nonnegligible IGMF values. The anisotropy energy spectrum of the Fermi gamma-ray background could thus be used as a probe of the IGMF strength.

Astrophysical interpretation of the anisotropies in the unresolved gamma-ray background

NASA Astrophysics Data System (ADS)

Ando, Shin'ichiro; Fornasa, Mattia; Fornengo, Nicolao; Regis, Marco; Zechlin, Hannes-S.

2017-06-01

Recently, a new measurement of the auto- and cross-correlation angular power spectrum (APS) of the isotropic gamma-ray background was performed, based on 81 months of data of the Fermi Large-Area Telescope (LAT). Here, we fit, for the first time, the new APS data with a model describing the emission of unresolved blazars. These sources are expected to dominate the anisotropy signal. The model we employ in our analysis reproduces well the blazars resolved by Fermi LAT. When considering the APS obtained by masking the sources listed in the 3FGL catalog, we find that unresolved blazars underproduce the measured APS below ˜1 GeV . Contrary to past results, this suggests the presence of a new contribution to the low-energy APS, with a significance of, at least, 5 σ . The excess can be ascribed to a new class of faint gamma-ray emitters. If we consider the APS obtained by masking the sources in the 2FGL catalog, there is no underproduction of the APS below 1 GeV, but the new source class is still preferred over the blazars-only scenario (with a significance larger than 10 σ ). The properties of the new source class and the level of anisotropies induced in the isotropic gamma-ray background are the same, independent of the APS data used. In particular, the new gamma-ray emitters must have a soft energy spectrum, with a spectral index ranging, approximately, from 2.7 to 3.2. This complicates their interpretation in terms of known sources, since, normally, star-forming and radio galaxies are observed with a harder spectrum. The new source class identified here is also expected to contribute significantly to the intensity of the isotropic gamma-ray background.

Mapping of radiation anomalies using UAV mini-airborne gamma-ray spectrometry.

PubMed

Šálek, Ondřej; Matolín, Milan; Gryc, Lubomír

2018-02-01

Localization of size-limited gamma-ray anomalies plays a fundamental role in uranium prospecting and environmental studies. Possibilities of a newly developed mini-airborne gamma-ray spectrometric equipment were tested on a uranium anomaly near the village of Třebsko, Czech Republic. The measurement equipment was based on a scintillation gamma-ray spectrometer specially developed for unmanned aerial vehicles (UAV) mounted on powerful hexacopter. The gamma-ray spectrometer has two 103 cm 3 BGO scintillation detectors of relatively high sensitivity. The tested anomaly, which is 80 m by 40 m in size, was investigated by ground gamma-ray spectrometric measurement in a detail rectangular measurement grid. Average uranium concentration is 25 mg/kg eU attaining 700 mg/kg eU locally. The mini-airborne measurement across the anomaly was carried out on three 100 m long parallel profiles at eight flight altitudes from 5 to 40 m above the ground. The resulting 1 s 1024 channel gamma-ray spectra, recorded in counts per second (cps), were processed to concentration units of K, U and Th, while total count (TC) was reported in cps. Increased gamma ray intensity of the anomaly was indicated by mini-airborne measurement at all profiles and altitudes, including the highest altitude of 40 m, at which the recorded intensity is close to the natural radiation background. The reported instrument is able to record data with comparable quality as standard airborne survey, due to relative sensitive detector, lower flight altitude and relatively low flight speed of 1 m/s. The presented experiment brings new experience with using unmanned semi-autonomous aerial vehicles and the latest mini-airborne radiometric instrument. The experiment has demonstrated the instrument's ability to localize size-limited uranium anomalies. Copyright © 2017 Elsevier Ltd. All rights reserved.

The origin of the diffuse background gamma-radiation

NASA Technical Reports Server (NTRS)

Stecker, F. W.; Puget, J. L.

1974-01-01

Recent observations have now provided evidence for diffuse background gamma radiation extending to energies beyond 100 MeV. There is some evidence of isotropy and implied cosmological origin. Significant features in the spectrum of this background radiation have been observed which provide evidence for its origin in nuclear processes in the early stages of the big-band cosmology and tie in these processes with galaxy fromation theory. A crucial test of the theory may lie in future observations of the background radiation in the 100 MeV to 100 GeV energy range which may be made with large orbiting spark-chamber satellite detectors. A discussion of the theoretical interpretations of present data, their connection with baryon symmetric cosmology and galaxy formation theory, and the need for future observations are given.

Measurement of background gamma radiation in the northern Marshall Islands.

PubMed

Bordner, Autumn S; Crosswell, Danielle A; Katz, Ainsley O; Shah, Jill T; Zhang, Catherine R; Nikolic-Hughes, Ivana; Hughes, Emlyn W; Ruderman, Malvin A

2016-06-21

We report measurements of background gamma radiation levels on six islands in the northern Marshall Islands (Enewetak, Medren, and Runit onEnewetak Atoll; Bikini and Nam on Bikini Atoll; and Rongelap on Rongelap Atoll). Measurable excess radiation could be expected from the decay of (137)Cs produced by the US nuclear testing program there from 1946 to 1958. These recordings are of relevance to safety of human habitation and resettlement. We find low levels of gamma radiation for the settled island of Enewetak [mean = 7.6 millirem/year (mrem/y) = 0.076 millisievert/year (mSv/y)], larger levels of gamma radiation for the island of Rongelap (mean = 19.8 mrem/y = 0.198 mSv/y), and relatively high gamma radiation on the island of Bikini (mean = 184 mrem/y = 1.84 mSv/y). Distributions of gamma radiation levels are provided, and hot spots are discussed. We provide interpolated maps for four islands (Enewetak, Medren, Bikini, and Rongelap), and make comparisons to control measurements performed on the island of Majuro in the southern Marshall Islands, measurements made in Central Park in New York City, and the standard agreed upon by the United States and the Republic of the Marshall Islands (RMI) governments (100 mrem/y = 1 mSv/y). External gamma radiation levels on Bikini Island significantly exceed this standard (P = <0.01), and external gamma radiation levels on the other islands are below the standard. To determine conclusively whether these islands are safe for habitation, radiation exposure through additional pathways such as food ingestion must be considered.

Measurement of background gamma radiation in the northern Marshall Islands

PubMed Central

Bordner, Autumn S.; Crosswell, Danielle A.; Katz, Ainsley O.; Shah, Jill T.; Zhang, Catherine R.; Nikolic-Hughes, Ivana; Hughes, Emlyn W.; Ruderman, Malvin A.

2016-01-01

We report measurements of background gamma radiation levels on six islands in the northern Marshall Islands (Enewetak, Medren, and Runit onEnewetak Atoll; Bikini and Nam on Bikini Atoll; and Rongelap on Rongelap Atoll). Measurable excess radiation could be expected from the decay of 137Cs produced by the US nuclear testing program there from 1946 to 1958. These recordings are of relevance to safety of human habitation and resettlement. We find low levels of gamma radiation for the settled island of Enewetak [mean = 7.6 millirem/year (mrem/y) = 0.076 millisievert/year (mSv/y)], larger levels of gamma radiation for the island of Rongelap (mean = 19.8 mrem/y = 0.198 mSv/y), and relatively high gamma radiation on the island of Bikini (mean = 184 mrem/y = 1.84 mSv/y). Distributions of gamma radiation levels are provided, and hot spots are discussed. We provide interpolated maps for four islands (Enewetak, Medren, Bikini, and Rongelap), and make comparisons to control measurements performed on the island of Majuro in the southern Marshall Islands, measurements made in Central Park in New York City, and the standard agreed upon by the United States and the Republic of the Marshall Islands (RMI) governments (100 mrem/y = 1 mSv/y). External gamma radiation levels on Bikini Island significantly exceed this standard (P = <<0.01), and external gamma radiation levels on the other islands are below the standard. To determine conclusively whether these islands are safe for habitation, radiation exposure through additional pathways such as food ingestion must be considered. PMID:27274073

Attenuation of X and Gamma Rays in Personal Radiation Shielding Protective Clothing.

PubMed

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.

Apollo-Soyuz pamphlet no. 2: X-rays, gamma-rays. [experimental design

NASA Technical Reports Server (NTRS)

Page, L. W.; From, T. P.

1977-01-01

The nature of high energy radiation and its penetration through earth's atmosphere is examined with emphasis on X-rays, gamma rays, and cosmic radiation and the instruments used in their detection. The history of radio astronomy and the capabilities of the Uhuru satellite are summarized. The ASTP soft X-ray experiment (MA-048) designed to study the spectra in the range from 0.1 to 10 keV and survey the background over a large section of the sky is described, as well as the determination of SMC C-1 as an X-ray pulsar. The crystal activation experiment (MA-151) used to measure the radioactive isotopes created by cosmic rays in crystals used for gamma ray detectors is also discussed.

Gamma and neutrino radiation dose from gamma ray bursts and nearby supernovae.

PubMed

Karam, P Andrew

2002-04-01

Supernovae and gamma ray bursts are exceptionally powerful cosmic events that occur randomly in space and time in our galaxy. Their potential to produce very high radiation levels has been discussed, along with speculation that they may have caused mass extinctions noted from the fossil record. It is far more likely that they have produced radiation levels that, while not lethal, are genetically significant, and these events may have influenced the course of evolution and the manner in which organisms respond to radiation insult. Finally, intense gamma radiation exposure from these events may influence the ability of living organisms to travel through space. Calculations presented in this paper suggest that supernovae and gamma ray bursts are likely to produce sea-level radiation exposures of about I Gy with a mean interval of about five million years and sea-level radiation exposures of about 0.2 Gy every million years. Comets and meteors traveling through space would receive doses in excess of 10 Gy at a depth of 0.02 m at mean intervals of 4 and 156 million years, respectively. This may place some constraints on the ability of life to travel through space either between planets or between planetary systems. Calculations of radiation dose from neutrino radiation are presented and indicate that this is not a significant source of radiation exposure for even extremely close events for the expected neutrino spectrum from these events.

CONSTRAINING THE EMISSIVITY OF ULTRAHIGH ENERGY COSMIC RAYS IN THE DISTANT UNIVERSE WITH THE DIFFUSE GAMMA-RAY EMISSION

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

Wang Xiangyu; Liu Ruoyu; Aharonian, Felix

Ultrahigh cosmic rays (UHECRs) with energies {approx}> 10{sup 19} eV emitted at cosmological distances will be attenuated by cosmic microwave and infrared background radiation through photohadronic processes. Lower energy extragalactic cosmic rays ({approx}10{sup 18}-10{sup 19} eV) can only travel a linear distance smaller than {approx}Gpc in a Hubble time due to the diffusion if the extragalactic magnetic fields are as strong as nano-Gauss. These prevent us from directly observing most of the UHECRs in the universe, and thus the observed UHECR intensity reflects only the emissivity in the nearby universe within hundreds of Mpc. However, UHECRs in the distant universe,more » through interactions with the cosmic background photons, produce UHE electrons and gamma rays that in turn initiate electromagnetic cascades on cosmic background photons. This secondary cascade radiation forms part of the extragalactic diffuse GeV-TeV gamma-ray radiation and, unlike the original UHECRs, is observable. Motivated by new measurements of extragalactic diffuse gamma-ray background radiation by Fermi/Large Area Telescope, we obtained upper limit placed on the UHECR emissivity in the distant universe by requiring that the cascade radiation they produce not exceed the observed levels. By comparison with the gamma-ray emissivity of candidate UHECR sources (such as gamma-ray bursts (GRBs) and active galactic nuclei) at high redshifts, we find that the obtained upper limit for a flat proton spectrum is {approx_equal} 10{sup 1.5} times larger than the gamma-ray emissivity in GRBs and {approx_equal} 10 times smaller than the gamma-ray emissivity in BL Lac objects. In the case of iron nuclei composition, the derived upper limit of UHECR emissivity is a factor of 3-5 times higher. Robust upper limit on the cosmogenic neutrino flux is further obtained, which is marginally reachable by the Icecube detector and the next-generation detector JEM-EUSO.« less

MGGPOD: a Monte Carlo Suite for Modeling Instrumental Line and Continuum Backgrounds in Gamma-Ray Astronomy

NASA Technical Reports Server (NTRS)

Weidenspointner, G.; Harris, M. J.; Sturner, S.; Teegarden, B. J.; Ferguson, C.

2004-01-01

Intense and complex instrumental backgrounds, against which the much smaller signals from celestial sources have to be discerned, are a notorious problem for low and intermediate energy gamma-ray astronomy (approximately 50 keV - 10 MeV). Therefore a detailed qualitative and quantitative understanding of instrumental line and continuum backgrounds is crucial for most stages of gamma-ray astronomy missions, ranging from the design and development of new instrumentation through performance prediction to data reduction. We have developed MGGPOD, a user-friendly suite of Monte Carlo codes built around the widely used GEANT (Version 3.21) package, to simulate ab initio the physical processes relevant for the production of instrumental backgrounds. These include the build-up and delayed decay of radioactive isotopes as well as the prompt de-excitation of excited nuclei, both of which give rise to a plethora of instrumental gamma-ray background lines in addition t o continuum backgrounds. The MGGPOD package and documentation are publicly available for download. We demonstrate the capabilities of the MGGPOD suite by modeling high resolution gamma-ray spectra recorded by the Transient Gamma-Ray Spectrometer (TGRS) on board Wind during 1995. The TGRS is a Ge spectrometer operating in the 40 keV to 8 MeV range. Due to its fine energy resolution, these spectra reveal the complex instrumental background in formidable detail, particularly the many prompt and delayed gamma-ray lines. We evaluate the successes and failures of the MGGPOD package in reproducing TGRS data, and provide identifications for the numerous instrumental lines.

Rat Phantom Depth Dose Studies in Electron, X-ray, Gamma-Ray, and Reactor Radiation Fields

DTIC Science & Technology

1986-12-01

i©™D©/^ ^1[P@^T Rat phantom depth dose studies in electron , Xrayf gamma-ray, and reactor radiation fields M. Dooley D. M. Eagleson G. H. Zeman...energy electrons , bremsstrahlung, and mixed neutron/gamma radiation fields are sometimes used in radiobiological experiments employing rats. This report...have revealed differing sensitivities of experimental animals that have been exposed to cobalt-60 photons, high-energy electrons , high-energy X rays

Radiation measurement above the lunar surface by Kaguya gamma-ray spectrometer

NASA Astrophysics Data System (ADS)

Hasebe, Nobuyuki; Nagaoka, Hiroshi; Kusano, Hiroki; Hareyama, Matoko; Ideguchi, Yusuke; Shimizu, Sota; Shibamura, Eido

The lunar surface is filled with various ionizing radiations such as high energy galactic particles, albedo particles and secondary radiations of neutrons, gamma rays and other elementary particles. A high-resolution Kaguya Gamma-Ray Spectrometer (KGRS) was carried on the Japan’s lunar explorer SELENE (Kaguya), the largest lunar orbiter since the Apollo missions. The KGRS instrument employed, for the first time in lunar exploration, a high-purity Ge crystal to increase the identification capability of elemental gamma-ray lines. The Ge detector is surrounded by BGO and plastic counters as for anticoincidence shields. The KGRS measured gamma rays in the energy range from 200 keV to 13 MeV with high precision to determine the chemical composition of the lunar surface. It provided data on the abundance of major elements over the entire lunar surface. In addition to the gamma-ray observation by the KGRS, it successfully measured the global distribution of fast neutrons. In the energy spectra of gamma-rays observed by the KGRS, several saw-tooth- peaks of Ge are included, which are formed by the collision interaction of lunar fast neutrons with Ge atoms in the Ge crystal. With these saw-tooth-peaks analysis, global distribution of neutrons emitted from the lunara surface was successfully created, which was compared with the previous results obtained by Lunar Prospector neutron maps. Another anticoincidence counter, the plastic counter with 5 mm thickness, was used to veto radiation events mostly generated by charged particles. A single photomultiplier serves to count scintillation light from the plastic scintillation counter. The global map of counting rates observed by the plastic counter was also created, implying that the radiation counting rate implies the geological distribution, in spite that the plastic counter mostly measures high energy charged particles and energetic neutrons. These results are presented and discussed.

Detecting the Attenuation of Blazar Gamma-ray Emission by Extragalactic Background Light with GLAST

NASA Technical Reports Server (NTRS)

Chen, Andrew; Ritz, Steven

1999-01-01

Gamma rays with energy above 10 GeV interact with optical-UV photons resulting in pair production. Therefore, a large sample of high redshift sources of these gamma rays can be used to probe the extragalactic background starlight (EBL) by examining the redshift dependence of the attenuation of the flux above 10 GeV. GLAST, the next generation high-energy gamma-ray telescope, will for the first time have the unique capability to detect thousands of gamma-ray blazars up to redshifts of at least z = 4, with enough angular resolution to allow identification of a large fraction of their optical counterparts. By combining recent determinations of the gamma-ray blazar luminosity function, recent calculations of the high energy gamma-ray opacity due to EBL absorption, and the expected GLAST instrument performance to produce simulated samples of blazars that GLAST would detect, including their redshifts and fluxes, we demonstrate that these blazars have the potential to be a highly effective probe of the EBL.

The cosmic X-ray background. [heao observations

NASA Technical Reports Server (NTRS)

Boldt, E. A.

1980-01-01

The cosmic X-ray experiment carried out with the A2 Instrument on HEAO-1 made systematics-free measurements of the extra-galactic X-ray sky and yielded the broadband spectral characteristics for two extreme aspects of this radiation. For the apparently isotropic radiation of cosmological origin that dominates the extragalactic X-ray flux ( 3 keV), the spectrum over the energy band of maximum intensity is remarkably well described by a thermal model with a temperature of a half-billion degrees. At the other extreme, broadband observations of individual extragalactic X-ray sources with HEAO-1 are restricted to objects within the present epoch. While the non-thermal hard spectral components associated with unevolved X-ray emitting active galaxies could account for most of the gamma-ray background, the contribution of such sources to the X-ray background must be relatively small. In contrast, the 'deep-space' sources detected in soft X-rays with the HEAO-2 telescope probably represent a major portion of the extragalactic soft X-ray ( 3 keV) background.

The lightest supersymmetric particle and the extragalactic gamma-ray background

NASA Technical Reports Server (NTRS)

Gao, Yi-Tian; Stecker, Floyd W.; Cline, David B.

1991-01-01

The possibility that cosmological photino annihilation is caused by the extragalactic gamma-ray background (EGB) is examined with particular attention given to the lightest supersymmetric particle (LSP). The LSP is considered a general type of the best-motivated candidates for cosmic dark matter (CDM). The theoretical analysis employs a corrected assumption for the annihilation cross section, and cosmological integrations are performed through the early phases of the universe. Romberg's method is used for numerical integration, and the total optical depth is developed for the gamma-ray region. The computed LSP-type annihilation fluxes are found to be negligible when compared to the total EGB observed, suggesting that the LSP candidates for CDM are not significant contributors to the EGB.

Gamma ray camera

DOEpatents

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.

Neutron detection in a high gamma-ray background with EJ-301 and EJ-309 liquid scintillators

NASA Astrophysics Data System (ADS)

Stevanato, L.; Cester, D.; Nebbia, G.; Viesti, G.

2012-10-01

Using a fast digitizer, the neutron-gamma discrimination capability of the new liquid scintillator EJ-309 is compared with that obtained using standard EJ-301. Moreover the capability of both the scintillation detectors to identify a weak neutron source in a high gamma-ray background is demonstrated. The probability of neutron detection is PD=95% at 95% confidence level for a gamma-ray background corresponding to a dose rate of 100 μSv/h.

Radiation resistance of a gamma-ray irradiated nonlinear optic chromophore

NASA Astrophysics Data System (ADS)

Zhang, Cheng; Taylor, Edward W.

2009-11-01

The radiation resistance of organic electro-optic and optoelectronic materials for space applications is receiving increased attention. An earlier investigation reported that guest-host poled polymer EO modulator devices composed of a phenyltetraene bridge-type chromophore in amorphous polycarbonate (CLD/APC) did not exhibit a decrease in EO response (i.e., an increase in modulation-switching voltage- Vπ) following irradiation by low dose [10-160 krad(Si)] 60Co gamma-rays. To provide further evidences to the observed radiation stability, the post-irradiation responses of 60Co gamma-rays on CLD1/APC thin films are examined by various chemical and spectroscopic methods including: a solubility test, thin-layer chromatography, proton nuclear magnetic resonance spectroscopy, UV-vis absorption, and infra-red absorption. The results indicate that CLD1 and APC did not decompose under gamma-ray irradiation at dose levels ranging from 66-274 krad(Si) and from 61-154 krad(Si), respectively which support the previously reported data.

Large-scale anisotropy in the extragalactic gamma-ray background as a probe for cosmological antimatter

NASA Technical Reports Server (NTRS)

Gao, Yi-Tian; Stecker, Floyd W.; Gleiser, Marcelo; Cline, David B.

1990-01-01

Intrinsic anisotropies in the extragalactic gamma-ray background (EGB), which should be detectable with the forthcoming Gamma Ray Observatory, can be used to examine some of the mechanisms proposed to explain its origin, one of which, the baryon-symmetric big bang (BSBB) model, is investigated here. In this simulation, large domains containing matter and antimatter galaxies produce gamma rays by annihilation at the domain boundaries. This mechanism can produce mountain-chain-shaped angular fluctuations in the EGB flux.

TeV gamma rays from 3C 279 - A possible probe of origin and intergalactic infrared radiation fields

NASA Technical Reports Server (NTRS)

Stecker, F. W.; De Jager, O. C.; Salamon, M. H.

1992-01-01

The gamma-ray spectrum of 3C 279 during 1991 June exhibited a near-perfect power law between 50 MeV and over 5 GeV with a differential spectral index of -(2.02 +/- 0.07). If extrapolated, the gamma-ray spectrum of 3C 279 should be easily detectable with first-generation air Cerenkov detectors operating above about 0.3 TeV provided there is no intergalactic absorption. However, by using model-dependent lower and upper limits for the extragalactic infrared background radiation field, a sharp cutoff of the 3C 279 spectrum is predicted at between about 0.1 and about 1 TeV. The sensitivity of present air Cerenkov detectors is good enough to measure such a cutoff, which would provide the first opportunity to obtain a measurement of the extragalactic background infrared radiation field.

Gamma ray camera

DOEpatents

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.

Development of an omnidirectional gamma-ray imaging Compton camera for low-radiation-level environmental monitoring

NASA Astrophysics Data System (ADS)

Watanabe, Takara; Enomoto, Ryoji; Muraishi, Hiroshi; Katagiri, Hideaki; Kagaya, Mika; Fukushi, Masahiro; Kano, Daisuke; Satoh, Wataru; Takeda, Tohoru; Tanaka, Manobu M.; Tanaka, Souichi; Uchida, Tomohisa; Wada, Kiyoto; Wakamatsu, Ryo

2018-02-01

We have developed an omnidirectional gamma-ray imaging Compton camera for environmental monitoring at low levels of radiation. The camera consisted of only six CsI(Tl) scintillator cubes of 3.5 cm, each of which was readout by super-bialkali photo-multiplier tubes (PMTs). Our camera enables the visualization of the position of gamma-ray sources in all directions (∼4π sr) over a wide energy range between 300 and 1400 keV. The angular resolution (σ) was found to be ∼11°, which was realized using an image-sharpening technique. A high detection efficiency of 18 cps/(µSv/h) for 511 keV (1.6 cps/MBq at 1 m) was achieved, indicating the capability of this camera to visualize hotspots in areas with low-radiation-level contamination from the order of µSv/h to natural background levels. Our proposed technique can be easily used as a low-radiation-level imaging monitor in radiation control areas, such as medical and accelerator facilities.

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

NASA Technical Reports Server (NTRS)

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.

Gamma-ray pulsars: Radiation processes in the outer magnetosphere

NASA Technical Reports Server (NTRS)

Romani, Roger W.

1996-01-01

We describe an emission model for gamma ray pulsars based on curvature radiation-reaction limited charges in the outer magnetosphere. We show how pair production on thermal surface flux can limit the acceleration zones. Estimates for the efficiency of GeV photon production eta gamma and the gamma-ray beaming fraction are derived, including their dependence on pulsar parameters. In general eta gamma increases with pulsar age, but is decreased for low magnetic fields and for small magnetic inclinations. We argue that this produces GeV pulse profiles, curvature spectra and detection statistics consistent with the observations. We also describe the optical through X-ray pulsar synchrotron spectrum and the spectral variations with pulsar phase. A test computation for Vela-like parameters reproduces phase-resolved GeV spectra consistent with those observed by EGRET. Finally we comment on very high energy pulsed emission and particle production and note extensions needed to allow a more complete pulsar model.

Estimation of radiation doses in TGFs and gamma ray glows

NASA Astrophysics Data System (ADS)

Celestin, S. J.; Pincon, J. L.; Trompier, F.

2017-12-01

Terrestrial gamma-ray flashes (TGFs) are bursts of high-energy photons originating from the Earth's atmosphere in association with thunderstorm activity [e.g., Briggs et al., JGR, 118, 3805, 2013]. TGFs are associated with initial propagation stages of intracloud lightning, which represent the most frequent type of lightning discharges [e.g., Cummer et al., GRL, 42, 7792, 2015, and references therein]. TGFs are known to be produced inside common thunderclouds [e.g., Splitt et al., JGR, 115, A00E38, 2010; Chronis et al., B. Am. Meteorol. Soc., 97, 639, 2016] typically at altitudes ranging from 10 to 14 km [e.g., Cummer et al., GRL, 41, 8586, 2014]. The global TGF occurrence rate is estimated to be 400,000 per year concerning TGFs detectable by Fermi-GBM (Gamma ray Burst Monitor) [Briggs et al., 2013], but detailed analysis of satellite measurements [Østgaard et al., JGR, 117, A03327, 2012] and theoretical studies [Celestin et al., JGR, 120, 10712, 2015] suggest that it cannot be excluded that TGFs represent a part of a regular process taking place during the propagation of lightning discharges. In addition to TGFs, another type of high-energy emissions has been observed inside thunderstorms from balloons [e.g., Eack et al., 101, 29637, 1996] and airplanes [e.g., McCarthy and Parks, 12, 393, 1985; Kelley et al., Nat. Commun., 6, 7845, 2015]. Referred to as gamma ray glows, these events correspond to significant elevations of the background radiation over long time scales that can be abruptly terminated with the occurrence of a lightning discharge. Kelley et al. [2015] estimate that a proportion larger than 8% of electrified storms produce glows. Dwyer et al. [JGR, 115, D09206, 2010] have estimated that if an aircraft were to find itself in the source electron beam giving rise to a TGF, passengers and crews might receive effective radiation doses above the regulatory limit depending on the beam diameter and Tavani et al. [Nat. Hazards Earth Syst. Sci., 13, 1127, 2013

Radiation dose in the high background radiation area in Kerala, India.

PubMed

Christa, E P; Jojo, P J; Vaidyan, V K; Anilkumar, S; Eappen, K P

2012-03-01

A systematic radiological survey has been carried out in the region of high-background radiation area in Kollam district of Kerala to define the natural gamma-radiation levels. One hundred and forty seven soil samples from high-background radiation areas and five samples from normal background region were collected as per standard sampling procedures and were analysed for (238)U, (232)Th and (40)K by gamma-ray spectroscopy. External gamma dose rates at all sampling locations were also measured using a survey meter. The activities of (238)U, (232)Th and (40)K was found to vary from 17 to 3081 Bq kg(-1), 54 to 11976 Bq kg(-1) and BDL (67.4 Bq kg(-1)) to 216 Bq kg(-1), respectively, in the study area. Such heterogeneous distribution of radionuclides in the region may be attributed to the deposition phenomenon of beach sand soil in the region. Radium equivalent activities were found high in several locations. External gamma dose rates estimated from the levels of radionuclides in soil had a range from 49 to 9244 nGy h(-1). The result of gamma dose rate measured at the sampling sites using survey meter showed an excellent correlation with dose rates computed from the natural radionuclides estimated from the soil samples.

Pulse shape discrimination for background rejection in germanium gamma-ray detectors

NASA Technical Reports Server (NTRS)

Feffer, P. T.; Smith, D. M.; Campbell, R. D.; Primbsch, J. H.; Lin, R. P.

1989-01-01

A pulse-shape discrimination (PSD) technique is developed to reject the beta-decay background resulting from activation of Ge gamma-ray detectors by cosmic-ray secondaries. These beta decays are a major source of background at 0.2-2 MeV energies in well shielded Ge detector systems. The technique exploits the difference between the detected current pulse shapes of single- and multiple-site energy depositions within the detector: beta decays are primarily single-site events, while photons at these energies typically Compton scatter before being photoelectrically absorbed to produce multiple-site events. Depending upon the amount of background due to sources other than beta decay, PSD can more than double the detector sensitivity.

Modeling background radiation in Southern Nevada

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

Haber, Daniel A.; Burnley, Pamela C.; Adcock, Christopher T.

Aerial gamma ray surveys are an important tool for national security, scientific, and industrial interests in determining locations of both anthropogenic and natural sources of radioactivity. There is a relationship between radioactivity and geology and in the past this relationship has been used to predict geology from an aerial survey. The purpose of this project is to develop a method to predict the radiologic exposure rate of the geologic materials by creating a high resolution background model. The intention is for this method to be used in an emergency response scenario where the background radiation envi-ronment is unknown. Two studymore » areas in Southern Nevada have been modeled using geologic data, images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), geochemical data, and pre-existing low resolution aerial surveys from the National Uranium Resource Evaluation (NURE) Survey. Using these data, geospatial areas that are homogenous in terms of K, U, and Th, referred to as background radiation units, are defined and the gamma ray exposure rate is predicted. The prediction is compared to data collected via detailed aerial survey by the Department of Energy's Remote Sensing Lab - Nellis, allowing for the refinement of the technique. By using geologic units to define radiation background units of exposed bedrock and ASTER visualizations to subdivide and define radiation background units within alluvium, successful models have been produced for Government Wash, north of Lake Mead, and for the western shore of Lake Mohave, east of Searchlight, NV.« less

Modeling background radiation in Southern Nevada

DOE PAGES

Haber, Daniel A.; Burnley, Pamela C.; Adcock, Christopher T.; ...

2017-02-06

Aerial gamma ray surveys are an important tool for national security, scientific, and industrial interests in determining locations of both anthropogenic and natural sources of radioactivity. There is a relationship between radioactivity and geology and in the past this relationship has been used to predict geology from an aerial survey. The purpose of this project is to develop a method to predict the radiologic exposure rate of the geologic materials by creating a high resolution background model. The intention is for this method to be used in an emergency response scenario where the background radiation envi-ronment is unknown. Two studymore » areas in Southern Nevada have been modeled using geologic data, images from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), geochemical data, and pre-existing low resolution aerial surveys from the National Uranium Resource Evaluation (NURE) Survey. Using these data, geospatial areas that are homogenous in terms of K, U, and Th, referred to as background radiation units, are defined and the gamma ray exposure rate is predicted. The prediction is compared to data collected via detailed aerial survey by the Department of Energy's Remote Sensing Lab - Nellis, allowing for the refinement of the technique. By using geologic units to define radiation background units of exposed bedrock and ASTER visualizations to subdivide and define radiation background units within alluvium, successful models have been produced for Government Wash, north of Lake Mead, and for the western shore of Lake Mohave, east of Searchlight, NV.« less

Galactic plane gamma-radiation

NASA Technical Reports Server (NTRS)

Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Fichtel, C. E.; Ogelman, H. B.; Tumer, T.; Ozel, M. E.

1979-01-01

Analysis of the SAS 2 data together with the COS B results shows that the distribution of galactic gamma-radiation has several similarities to that of other large-scale tracers of galactic structure. The radiation is primarily confined to a thin disc which exhibits offsets from b = 0 degrees similar to warping at radio frequencies. The principal distinction of the gamma-radiation is a stronger contrast in intensity between the region from 310 to 45 degrees in longitude and the regions away from the center that can be attributed to a variation in cosmic-ray density as a function of position in Galaxy. The diffuse galactic gamma-ray energy spectrum shows no significant variation in direction, and the spectrum seen along the plane is the same as that for the galactic component of the gamma-radiation at high altitudes. The uniformity of the galactic gamma-ray spectrum, the smooth decrease in intensity as a function of altitude, and the absence of any galactic gamma-ray sources at high altitudes indicate a diffuse origin for bulk of the galactic gamma-radiation rather than a collection of localized sources.

A NEW RESULT ON THE ORIGIN OF THE EXTRAGALACTIC GAMMA-RAY BACKGROUND

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

Zhou Ming; Wang Jiancheng, E-mail: mzhou@ynao.ac.cn

2013-06-01

In this paper, we repeatedly use the method of image stacking to study the origin of the extragalactic gamma-ray background (EGB) at GeV bands, and find that the Faint Images of the Radio Sky at Twenty centimeters (FIRST) sources undetected by the Large Area Telescope on the Fermi Gamma-ray Space Telescope can contribute about (56 {+-} 6)% of the EGB. Because FIRST is a flux-limited sample of radio sources with incompleteness at the faint limit, we consider that point sources, including blazars, non-blazar active galactic nuclei, and starburst galaxies, could produce a much larger fraction of the EGB.

Radiative striped wind model for gamma-ray bursts

NASA Astrophysics Data System (ADS)

Bégué, D.; Pe'er, A.; Lyubarsky, Y.

2017-05-01

In this paper, we revisit the striped wind model in which the wind is accelerated by magnetic reconnection. In our treatment, radiation is included as an independent component, and two scenarios are considered. In the first one, radiation cannot stream efficiently through the reconnection layer, while the second scenario assumes that radiation is homogeneous in the striped wind. We show how these two assumptions affect the dynamics. In particular, we find that the asymptotic radial evolution of the Lorentz factor is not strongly modified whether radiation can stream through the reconnection layer or not. On the other hand, we show that the width, density and temperature of the reconnection layer are strongly dependent on these assumptions. We then apply the model to the gamma-ray burst context and find that photons cannot diffuse efficiently through the reconnection layer below radius r_D^{Δ } ˜ 10^{10.5} cm, which is about an order of magnitude below the photospheric radius. Above r_D^{Δ }, the dynamics asymptotes to the solution of the scenario in which radiation can stream through the reconnection layer. As a result, the density of the current sheet increases sharply, providing efficient photon production by the Bremsstrahlung process that could have profound influence on the emerging spectrum. This effect might provide a solution to the soft photon problem in gamma-ray bursts.

Gamma-ray astronomy

NASA Technical Reports Server (NTRS)

Ramaty, R.; Lingenfelter, R. E.

1982-01-01

Cosmic gamma rays, the physical processes responsible for their production and the astrophysical sites from which they were seen are reported. The bulk of the observed gamma ray emission is in the photon energy range from about 0.1 MeV to 1 GeV, where observations are carried out above the atmosphere. There are also, however, gamma ray observations at higher energies obtained by detecting the Cerenkov light produced by the high energy photons in the atmosphere. Gamma ray emission was observed from sources as close as the Sun and the Moon and as distant as the quasar 3C273, as well as from various other galactic and extragalactic sites. The radiation processes also range from the well understood, e.g. energetic particle interactions with matter, to the still incompletely researched, such as radiation transfer in optically thick electron positron plasmas in intense neutron star magnetic fields.

A low level of extragalactic background light as revealed by gamma-rays from blazars.

PubMed

Aharonian, F; Akhperjanian, A G; Bazer-Bachi, A R; Beilicke, M; Benbow, W; Berge, D; Bernlöhr, K; Boisson, C; Bolz, O; Borrel, V; Braun, I; Breitling, F; Brown, A M; Chadwick, P M; Chounet, L-M; Cornils, R; Costamante, L; Degrange, B; Dickinson, H J; Djannati-Ataï, A; Drury, L O'C; Dubus, G; Emmanoulopoulos, D; Espigat, P; Feinstein, F; Fontaine, G; Fuchs, Y; Funk, S; Gallant, Y A; Giebels, B; Gillessen, S; Glicenstein, J F; Goret, P; Hadjichristidis, C; Hauser, D; Hauser, M; Heinzelmann, G; Henri, G; Hermann, G; Hinton, J A; Hofmann, W; Holleran, M; Horns, D; Jacholkowska, A; de Jager, O C; Khélifi, B; Klages, S; Komin, Nu; Konopelko, A; Latham, I J; Le Gallou, R; Lemière, A; Lemoine-Goumard, M; Leroy, N; Lohse, T; Martin, J M; Martineau-Huynh, O; Marcowith, A; Masterson, C; McComb, T J L; de Naurois, M; Nolan, S J; Noutsos, A; Orford, K J; Osborne, J L; Ouchrif, M; Panter, M; Pelletier, G; Pita, S; Pühlhofer, G; Punch, M; Raubenheimer, B C; Raue, M; Raux, J; Rayner, S M; Reimer, A; Reimer, O; Ripken, J; Rob, L; Rolland, L; Rowell, G; Sahakian, V; Saugé, L; Schlenker, S; Schlickeiser, R; Schuster, C; Schwanke, U; Siewert, M; Sol, H; Spangler, D; Steenkamp, R; Stegmann, C; Tavernet, J-P; Terrier, R; Théoret, C G; Tluczykont, M; van Eldik, C; Vasileiadis, G; Venter, C; Vincent, P; Völk, H J; Wagner, S J

2006-04-20

The diffuse extragalactic background light consists of the sum of the starlight emitted by galaxies through the history of the Universe, and it could also have an important contribution from the 'first stars', which may have formed before galaxy formation began. Direct measurements are difficult and not yet conclusive, owing to the large uncertainties caused by the bright foreground emission associated with zodiacal light. An alternative approach is to study the absorption features imprinted on the gamma-ray spectra of distant extragalactic objects by interactions of those photons with the background light photons. Here we report the discovery of gamma-ray emission from the blazars H 2356 - 309 and 1ES 1101 - 232, at redshifts z = 0.165 and z = 0.186, respectively. Their unexpectedly hard spectra provide an upper limit on the background light at optical/near-infrared wavelengths that appears to be very close to the lower limit given by the integrated light of resolved galaxies. The background flux at these wavelengths accordingly seems to be strongly dominated by the direct starlight from galaxies, thus excluding a large contribution from other sources-in particular from the first stars formed. This result also indicates that intergalactic space is more transparent to gamma-rays than previously thought.

X-ray and gamma ray astronomy detectors

NASA Technical Reports Server (NTRS)

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.

Modeling background radiation using geochemical data: A case study in and around Cameron, Arizona

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

Marsac, Kara E.; Burnley, Pamela C.; Adcock, Christopher T.

Here, this study compares high-resolution forward models of natural gamma-ray background with that measured by high resolution aerial gamma-ray surveys. The ability to predict variations in natural background radiation levels should prove useful for those engaged in measuring anthropogenic contributions to background radiation for the purpose of emergency response and homeland security operations. The forward models are based on geologic maps and remote sensing multi-spectral imagery combined with two different sources of data: 1) bedrock geochemical data (uranium, potassium and thorium concentrations) collected from national databases, the scientific literature and private companies, and 2) the low spatial resolution NURE (Nationalmore » Uranium Resource Evaluation) aerial gamma-ray survey. The study area near Cameron, Arizona, is located in an arid region with minimal vegetation and, due to the presence of abandoned uranium mines, was the subject of a previous high resolution gamma-ray survey. We found that, in general, geologic map units form a good basis for predicting the geographic distribution of the gamma-ray background. Predictions of background gamma-radiation levels based on bedrock geochemical analyses were not as successful as those based on the NURE aerial survey data sorted by geologic unit. The less successful result of the bedrock geochemical model is most likely due to a number of factors including the need to take into account the evolution of soil geochemistry during chemical weathering and the influence of aeolian addition. Refinements to the forward models were made using ASTER visualizations to create subunits of similar exposure rate within the Chinle Formation, which contains multiple lithologies and by grouping alluvial units by drainage basin rather than age.« less

Modeling background radiation using geochemical data: A case study in and around Cameron, Arizona

DOE PAGES

Marsac, Kara E.; Burnley, Pamela C.; Adcock, Christopher T.; ...

2016-09-16

Here, this study compares high-resolution forward models of natural gamma-ray background with that measured by high resolution aerial gamma-ray surveys. The ability to predict variations in natural background radiation levels should prove useful for those engaged in measuring anthropogenic contributions to background radiation for the purpose of emergency response and homeland security operations. The forward models are based on geologic maps and remote sensing multi-spectral imagery combined with two different sources of data: 1) bedrock geochemical data (uranium, potassium and thorium concentrations) collected from national databases, the scientific literature and private companies, and 2) the low spatial resolution NURE (Nationalmore » Uranium Resource Evaluation) aerial gamma-ray survey. The study area near Cameron, Arizona, is located in an arid region with minimal vegetation and, due to the presence of abandoned uranium mines, was the subject of a previous high resolution gamma-ray survey. We found that, in general, geologic map units form a good basis for predicting the geographic distribution of the gamma-ray background. Predictions of background gamma-radiation levels based on bedrock geochemical analyses were not as successful as those based on the NURE aerial survey data sorted by geologic unit. The less successful result of the bedrock geochemical model is most likely due to a number of factors including the need to take into account the evolution of soil geochemistry during chemical weathering and the influence of aeolian addition. Refinements to the forward models were made using ASTER visualizations to create subunits of similar exposure rate within the Chinle Formation, which contains multiple lithologies and by grouping alluvial units by drainage basin rather than age.« less

Anisotropies in the Diffuse Gamma-Ray Background Measured by the Fermi LAT

NASA Technical Reports Server (NTRS)

Ferrara, E. C.; McEnery, J. E.; Troja, E.

2012-01-01

The contribution of unresolved sources to the diffuse gamma-ray background could induce anisotropies in this emission on small angular scales. We analyze the angular power spectrum of the diffuse emission measured by the Fermi LAT at Galactic latitudes absolute value of b > 30 deg in four energy bins spanning 1 to 50 GeV. At multipoles l >= 155, corresponding to angular scales approx < 2 deg, angular power above the photon noise level is detected at > 99.99% CL in the 1-2 GeV, 2- 5 GeV, and 5- 10 GeV energy bins, and at > 99% CL at 10-50 GeV. Within each energy bin the measured angular power takes approximately the same value at all multipoles l >= 155, suggesting that it originates from the contribution of one or more unclustered source populations. The amplitude of the angular power normalized to the mean intensity in each energy bin is consistent with a constant value at all energies, C(sub p) / (I)(exp 2) = 9.05 +/- 0.84 x 10(exp -6) sr, while the energy dependence of C(sub p) is consistent with the anisotropy arising from one or more source populations with power-law photon spectra with spectral index Gamma (sub s) = 2.40 +/- 0.07. We discuss the implications of the measured angular power for gamma-ray source populations that may provide a contribution to the diffuse gamma-ray background.

Interpretation of various radiation backgrounds observed in the gamma-ray spectrometer experiments carried on the Apollo missions and implications for diffuse gamma-ray measurements

NASA Technical Reports Server (NTRS)

Dyer, C. S.; Trombka, J. I.; Metzger, A. E.; Seltzer, S. M.; Bielefeld, M. J.; Evans, L. G.

1975-01-01

Since the report of a preliminary analysis of cosmic gamma-ray measurements made during the Apollo 15 mission, an improved calculation of the spallation activation contribution has been made including the effects of short-lived spallation fragments, which can extend the correction to 15 MeV. In addition, a difference between Apollo 15 and 16 data enables an electron bremsstrahlung contribution to be calculated. A high level of activation observed in a crystal returned on Apollo 17 indicates a background contribution from secondary neutrons. These calculations and observations enable an improved extraction of spurious components and suggest important improvements for future detectors.

Gamma ray astrophysics. [emphasizing processes and absorption

NASA Technical Reports Server (NTRS)

Stecker, F. W.

1974-01-01

Gamma ray production processes are reviewed, including Compton scattering, synchrotron radiation, bremsstrahlung interactions, meson decay, nucleon-antinucleon annihilations, and pion production. Gamma ray absorption mechanisms through interactions with radiation and with matter are discussed, along with redshifts and gamma ray fluxes.

Use of a solar panel as a directionally sensitive large-area radiation monitor for direct and scattered x-rays and gamma-rays.

PubMed

Abdul-Majid, S

1987-01-01

The characteristics of a 25.4 X 91 cm solar cell panel used as an x-ray and gamma-ray radiation monitor are presented. Applications for monitoring the primary x-ray beam are described at different values of operating currents and voltages as well as for directional dependence of scattered radiation. Other applications in gamma-ray radiography are also given. The detector showed linear response to both x-ray and gamma-ray exposures. The equipment is rigid, easy to use, relatively inexpensive and requires no power supply or any complex electronic equipment.

Can the cosmic x ray and gamma ray background be due to reflection of a steep power law spectrum and Compton scattering by relativistic electrons?

NASA Technical Reports Server (NTRS)

Zycki, Piotr T.; Zdziarski, Andrzej A.; Svensson, Roland

1991-01-01

We reconsider the recent model for the origin in the cosmic X-ray and gamma-ray background by Rogers and Field. The background in the model is due to an unresolved population of AGNs. An individual AGN spectrum contains three components: a power law with the energy index of alpha = 1.1, an enhanced reflection component, and a component from Compton scattering by relativistic electrons with a low energy cutoff at some minimum Lorentz factor, gamma(sub min) much greater than 1. The MeV bump seen in the gamma-ray background is then explained by inverse Compton emission by the electrons. We show that the model does not reproduce the shape of the observed X-ray and gamma-ray background below 10 MeV and that it overproduces the background at larger energies. Furthermore, we find the assumptions made for the Compton component to be physically inconsistent. Relaxing the inconsistent assumptions leads to model spectra even more different from that of the observed cosmic background. Thus, we can reject the hypothesis that the high-energy cosmic background is due to the described model.

Gadolinium-doped water cerenkov-based neutron and high energy gamma-ray detector and radiation portal monitoring system

DOEpatents

Dazeley, Steven A; Svoboda, Robert C; Bernstein, Adam; Bowden, Nathaniel

2013-02-12

A water Cerenkov-based neutron and high energy gamma ray detector and radiation portal monitoring system using water doped with a Gadolinium (Gd)-based compound as the Cerenkov radiator. An optically opaque enclosure is provided surrounding a detection chamber filled with the Cerenkov radiator, and photomultipliers are optically connected to the detect Cerenkov radiation generated by the Cerenkov radiator from incident high energy gamma rays or gamma rays induced by neutron capture on the Gd of incident neutrons from a fission source. The PMT signals are then used to determine time correlations indicative of neutron multiplicity events characteristic of a fission source.

Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries

NASA Astrophysics Data System (ADS)

Madau, Piero; Fragos, Tassos

2017-05-01

We compute the expected X-ray diffuse background and radiative feedback on the intergalactic medium (IGM) from X-ray binaries prior to and during the epoch of reionization. The cosmic evolution of compact binaries is followed using a population synthesis technique that treats separately neutron stars and black hole binaries in different spectral states and is calibrated to reproduce the observed X-ray properties of galaxies at z ≲ 4. Together with an updated empirical determination of the cosmic history of star formation, recent modeling of the stellar mass-metallicity relation, and a scheme for absorption by the IGM that accounts for the presence of ionized H II bubbles during the epoch of reionization, our detailed calculations provide refined predictions of the X-ray volume emissivity and filtered radiation background from “normal” galaxies at z ≳ 6. Radiative transfer effects modulate the background spectrum, which shows a characteristic peak between 1 and 2 keV. Because of the energy dependence of photoabsorption, soft X-ray photons are produced by local sources, while more energetic radiation arrives unattenuated from larger cosmological volumes. While the filtering of X-ray radiation through the IGM slightly increases the mean excess energy per photoionization, it also weakens the radiation intensity below 1 keV, lowering the mean photoionization and heating rates. Numerical integration of the rate and energy equations shows that the contribution of X-ray binaries to the ionization of the bulk IGM is negligible, with the electron fraction never exceeding 1%. Direct He I photoionizations are the main source of IGM heating, and the temperature of the largely neutral medium in between H II cavities increases above the temperature of the cosmic microwave background (CMB) only at z ≲ 10, when the volume filling factor of H II bubbles is already ≳0.1. Therefore, in this scenario, it is only at relatively late epochs that neutral intergalactic hydrogen

Radiation Backgrounds at Cosmic Dawn: X-Rays from Compact Binaries

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

Madau, Piero; Fragos, Tassos

We compute the expected X-ray diffuse background and radiative feedback on the intergalactic medium (IGM) from X-ray binaries prior to and during the epoch of reionization. The cosmic evolution of compact binaries is followed using a population synthesis technique that treats separately neutron stars and black hole binaries in different spectral states and is calibrated to reproduce the observed X-ray properties of galaxies at z ≲ 4. Together with an updated empirical determination of the cosmic history of star formation, recent modeling of the stellar mass–metallicity relation, and a scheme for absorption by the IGM that accounts for the presencemore » of ionized H ii bubbles during the epoch of reionization, our detailed calculations provide refined predictions of the X-ray volume emissivity and filtered radiation background from “normal” galaxies at z ≳ 6. Radiative transfer effects modulate the background spectrum, which shows a characteristic peak between 1 and 2 keV. Because of the energy dependence of photoabsorption, soft X-ray photons are produced by local sources, while more energetic radiation arrives unattenuated from larger cosmological volumes. While the filtering of X-ray radiation through the IGM slightly increases the mean excess energy per photoionization, it also weakens the radiation intensity below 1 keV, lowering the mean photoionization and heating rates. Numerical integration of the rate and energy equations shows that the contribution of X-ray binaries to the ionization of the bulk IGM is negligible, with the electron fraction never exceeding 1%. Direct He i photoionizations are the main source of IGM heating, and the temperature of the largely neutral medium in between H ii cavities increases above the temperature of the cosmic microwave background (CMB) only at z ≲ 10, when the volume filling factor of H ii bubbles is already ≳0.1. Therefore, in this scenario, it is only at relatively late epochs that neutral intergalactic

Can Winds Driven by Active Galactic Nuclei Account for the Extragalactic Gamma-Ray and Neutrino Backgrounds?

NASA Astrophysics Data System (ADS)

Liu, Ruo-Yu; Murase, Kohta; Inoue, Susumu; Ge, Chong; Wang, Xiang-Yu

2018-05-01

Various observations are revealing the widespread occurrence of fast and powerful winds in active galactic nuclei (AGNs) that are distinct from relativistic jets, likely launched from accretion disks and interacting strongly with the gas of their host galaxies. During the interaction, strong shocks are expected to form that can accelerate nonthermal particles to high energies. Such winds have been suggested to be responsible for a large fraction of the observed extragalactic gamma-ray background (EGB) and the diffuse neutrino background, via the decay of neutral and charged pions generated in inelastic pp collisions between protons accelerated by the forward shock and the ambient gas. However, previous studies did not properly account for processes such as adiabatic losses that may reduce the gamma-ray and neutrino fluxes significantly. We evaluate the production of gamma rays and neutrinos by AGN-driven winds in detail by modeling their hydrodynamic and thermal evolution, including the effects of their two-temperature structure. We find that they can only account for less than ∼30% of the EGB flux, as otherwise the model would violate the independent upper limit derived from the diffuse isotropic gamma-ray background. If the neutrino spectral index is steep with Γ ≳ 2.2, a severe tension with the isotropic gamma-ray background would arise as long as the winds contribute more than 20% of the IceCube neutrino flux in the 10–100 TeV range. At energies ≳ 100 TeV, we find that the IceCube neutrino flux may still be accountable by AGN-driven winds if the spectral index is as small as Γ ∼ 2.0–2.1.

Gamma Ray Pulsars: Multiwavelength Observations

NASA Technical Reports Server (NTRS)

Thompson, David J.

2004-01-01

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The seven or more pulsars seen by instruments on the Compton Gamma Ray Observatory (CGRO) show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. For all the known gamma-ray pulsars, multiwavelength observations and theoretical models based on such observations offer the prospect of gaining a broad understanding of these rotating neutron stars. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2006, will provide a major advance in sensitivity, energy range, and sky coverage.

X-ray radiative transfer in protoplanetary disks. The role of dust and X-ray background fields

NASA Astrophysics Data System (ADS)

Rab, Ch.; Güdel, M.; Woitke, P.; Kamp, I.; Thi, W.-F.; Min, M.; Aresu, G.; Meijerink, R.

2018-01-01

Context. The X-ray luminosities of T Tauri stars are about two to four orders of magnitude higher than the luminosity of the contemporary Sun. As these stars are born in clusters, their disks are not only irradiated by their parent star but also by an X-ray background field produced by the cluster members. Aims: We aim to quantify the impact of X-ray background fields produced by young embedded clusters on the chemical structure of disks. Further, we want to investigate the importance of the dust for X-ray radiative transfer in disks. Methods: We present a new X-ray radiative transfer module for the radiation thermo-chemical disk code PRODIMO (PROtoplanetary DIsk MOdel), which includes X-ray scattering and absorption by both the gas and dust component. The X-ray dust opacities can be calculated for various dust compositions and dust-size distributions. For the X-ray radiative transfer we consider irradiation by the star and by X-ray background fields. To study the impact of X-rays on the chemical structure of disks we use the well established disk ionization tracers N2H+ and HCO+. Results: For evolved dust populations (e.g. grain growth), X-ray opacities are mostly dominated by the gas; only for photon energies E ≳ 5-10 keV do dust opacities become relevant. Consequently the local disk X-ray radiation field is only affected in dense regions close to the disk midplane. X-ray background fields can dominate the local X-ray disk ionization rate for disk radii r ≳ 20 au. However, the N2H+ and HCO+ column densities are only significantly affected in cases of low cosmic-ray ionization rates (≲10-19 s-1), or if the background flux is at least a factor of ten higher than the flux level of ≈10-5 erg cm-2 s-1 expected for clusters typical for the solar vicinity. Conclusions: Observable signatures of X-ray background fields in low-mass star-formation regions, like Taurus, are only expected for cluster members experiencing a strong X-ray background field (e.g. due to

Highlights of GeV Gamma-Ray Astronomy

NASA Technical Reports Server (NTRS)

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.

[Shielding effect of clinical X-ray protector and lead glass against annihilation radiation and gamma rays of 99mTc].

PubMed

Fukuda, Atsushi; Koshida, Kichiro; Yamaguchi, Ichiro; Takahashi, Masaaki; Kitabayashi, Keitarou; Matsubara, Kousuke; Noto, Kimiya; Kawabata, Chikako; Nakagawa, Hiroto

2004-12-01

Various pharmaceutical companies in Japan are making radioactive drugs available for positron emission tomography (PET) in hospitals without a cyclotron. With the distribution of these drugs to hospitals, medical check-ups and examinations using PET are expected to increase. However, the safety guidelines for radiation in the new deployment of PET have not been adequately improved. Therefore, we measured the shielding effect of a clinical X-ray protector and lead glass against annihilation radiation and gamma rays of (99m)Tc. We then calculated the shielding effect of a 0.25 mm lead protector, 1 mm lead, and lead glass using the EGS4 (Electron Gamma Shower Version 4) code. The shielding effects of 22-mm lead glass against annihilation radiation and gamma rays of (99m)Tc were approximately 31.5% and 93.3%, respectively. The clinical X-ray protector against annihilation radiation approximately doubled the skin-absorbed dose.

Modeling background radiation using geochemical data: A case study in and around Cameron, Arizona.

PubMed

Marsac, Kara E; Burnley, Pamela C; Adcock, Christopher T; Haber, Daniel A; Malchow, Russell L; Hausrath, Elisabeth M

2016-12-01

This study compares high resolution forward models of natural gamma-ray background with that measured by high resolution aerial gamma-ray surveys. The ability to predict variations in natural background radiation levels should prove useful for those engaged in measuring anthropogenic contributions to background radiation for the purpose of emergency response and homeland security operations. The forward models are based on geologic maps and remote sensing multi-spectral imagery combined with two different sources of data: 1) bedrock geochemical data (uranium, potassium and thorium concentrations) collected from national databases, the scientific literature and private companies, and 2) the low spatial resolution NURE (National Uranium Resource Evaluation) aerial gamma-ray survey. The study area near Cameron, Arizona, is located in an arid region with minimal vegetation and, due to the presence of abandoned uranium mines, was the subject of a previous high resolution gamma-ray survey. We found that, in general, geologic map units form a good basis for predicting the geographic distribution of the gamma-ray background. Predictions of background gamma-radiation levels based on bedrock geochemical analyses were not as successful as those based on the NURE aerial survey data sorted by geologic unit. The less successful result of the bedrock geochemical model is most likely due to a number of factors including the need to take into account the evolution of soil geochemistry during chemical weathering and the influence of aeolian addition. Refinements to the forward models were made using ASTER visualizations to create subunits of similar exposure rate within the Chinle Formation, which contains multiple lithologies and by grouping alluvial units by drainage basin rather than age. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

HOW FAR AWAY ARE THE SOURCES OF ICECUBE NEUTRINOS? CONSTRAINTS FROM THE DIFFUSE TERAELECTRONVOLT GAMMA-RAY BACKGROUND

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

Chang, Xiao-Chuan; Liu, Ruo-Yu; Wang, Xiang-Yu, E-mail: xywang@nju.edu.cn

The nearly isotropic distribution of teraelectronvolt to petaelectronvolt neutrinos recently detected by the IceCube Collaboration suggests that they come from sources at a distance beyond our Galaxy, but how far away they are is largely unknown because of a lack of any associations with known sources. In this paper, we propose that the cumulative TeV gamma-ray emission accompanying the production of neutrinos can be used to constrain the distance of these neutrino sources, since the opacity of TeV gamma rays due to absorption by the extragalactic background light depends on the distance these TeV gamma rays have traveled. As themore » diffuse extragalactic TeV background measured by Fermi is much weaker than the expected cumulative flux associated with IceCube neutrinos, the majority of IceCube neutrinos, if their sources are transparent to TeV gamma rays, must come from distances larger than the horizon of TeV gamma rays. We find that above 80% of the IceCube neutrinos should come from sources at redshift z > 0.5. Thus, the chance of finding nearby sources correlated with IceCube neutrinos would be small. We also find that, to explain the flux of neutrinos under the TeV gamma-ray emission constraint, the redshift evolution of neutrino source density must be at least as fast as the cosmic star formation rate.« less

Assessment of background gamma radiation levels using airborne gamma ray spectrometer data over uranium deposits, Cuddapah Basin, India - A comparative study of dose rates estimated by AGRS and PGRS.

PubMed

Srinivas, D; Ramesh Babu, V; Patra, I; Tripathi, Shailesh; Ramayya, M S; Chaturvedi, A K

2017-02-01

The Atomic Minerals Directorate for Exploration and Research (AMD) has conducted high-resolution airborne gamma ray spectrometer (AGRS), magnetometer and time domain electromagnetic (TDEM) surveys for uranium exploration, along the northern margins of Cuddapah Basin. The survey area includes well known uranium deposits such as Lambapur-Peddagattu, Chitrial and Koppunuru. The AGRS data collected for uranium exploration is utilised for estimating the average absorbed rates in air due to radio-elemental (potassium in %, uranium and thorium in ppm) distribution over these known deposit areas. Further, portable gamma ray spectrometer (PGRS) was used to acquire data over two nearby locations one from Lambapur deposit, and the other from known anomalous zone and subsequently average gamma dose rates were estimated. Representative in-situ rock samples were also collected from these two areas and subjected to radio-elemental concentration analysis by gamma ray spectrometer (GRS) in the laboratory and then dose rates were estimated. Analyses of these three sets of results complement one another, thereby providing a comprehensive picture of the radiation environment over these deposits. The average absorbed area wise dose rate level is estimated to be 130 ± 47 nGy h -1 in Lambapur-Peddagattu, 186 ± 77 nGy h -1 in Chitrial and 63 ± 22 nGy h -1 in Koppunuru. The obtained average dose levels are found to be higher than the world average value of 54 nGy h -1 . The gamma absorbed dose rates in nGy h -1 were converted to annual effective dose rates in mSv y -1 as proposed by the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). The annual average effective dose rates for the entire surveyed area is 0.12 mSv y -1 , which is much lower than the recommended limit of 1 mSv y -1 by International Commission on Radiation protection (ICRP). It may be ascertained here that the present study establishes a reference data set (baseline) in these areas

The diffuse gamma-ray background, light element abundances, and signatures of early massive star formation

NASA Technical Reports Server (NTRS)

Silk, Joseph; Schramm, David N.

1992-01-01

Attention is drawn to a potentially observable flux of diffuse extragalactic gamma rays produced by inelastic cosmic-ray interactions that is inevitably a by-product of spallation-synthesized Be. The epoch of cosmic ray-induced Population II light element nucleosynthesis is constrained to be at redshift greater than 0.5. A spectral feature in the diffuse extragalactic gamma-ray background with amplitude 0.1 above 10 MeV is predicted if the Be is synthesized at z less than 10. The possibility is discussed that the cosmic-ray flux responsible for Population II Be and B synthesis may be associated with a precursor hypothesized Population III.

Toward advanced gamma rays radiation resistance and shielding efficiency with phthalonitrile resins and composites

NASA Astrophysics Data System (ADS)

Derradji, Mehdi; Zegaoui, Abdeldjalil; Xu, Yi-Le; Wang, An-ran; Dayo, Abdul Qadeer; Wang, Jun; Liu, Wen-bin; Liu, Yu-Guang; Khiari, Karim

2018-04-01

The phthalonitrile resins have claimed the leading place in the field of high performance polymers thanks to their combination of outstanding properties. The present work explores for the first time the gamma rays radiation resistance and shielding efficiency of the phthalonitrile resins and its related tungsten-reinforced nanocomposites. The primary goal of this research is to define the basic behavior of the phthalonitrile resins under highly ionizing gamma rays. The obtained results confirmed that the neat phthalonitrile resins can resist absorbed doses as high as 200 kGy. Meanwhile, the remarkable shielding efficiency of the phthalonitrile polymers was confirmed to be easily improved by preparing lead-free nanocomposites. In fact, the gamma rays screening ratio reached the exceptional value of 42% for the nanocomposites of 50 wt% of nano-tungsten loading. Thus, this study confirms that the remarkable performances of the phthalonitrile resins are not limited to the thermal and mechanical properties and can be extended to the gamma rays radiation and shielding resistances.

Sneaky Gamma-Rays: Using Gravitational Lensing to Avoid Gamma-Gamma-Absorption

NASA Astrophysics Data System (ADS)

Boettcher, Markus; Barnacka, Anna

2014-08-01

It has recently been suggested that gravitational lensing studies of gamma-ray blazars might be a promising avenue to probe the location of the gamma-ray emitting region in blazars. Motivated by these prospects, we have investigated potential gamma-gamma absorption signatures of intervening lenses in the very-high-energy gamma-ray emission from lensedblazars. We considered intervening galaxies and individual stars within these galaxies. We find that the collective radiation field of galaxies acting as sources of macrolensing are not expected to lead to significant gamma-gamma absorption. Individual stars within intervening galaxies could, in principle, cause a significant opacity to gamma-gamma absorption for VHE gamma-rays if the impact parameter (the distance of closest approach of the gamma-ray to the center of the star) is small enough. However, we find that the curvature of the photon path due to gravitational lensing will cause gamma-ray photons to maintain a sufficiently large distance from such stars to avoid significant gamma-gamma absorption. This re-inforces the prospect of gravitational-lensing studies of gamma-ray blazars without interference due to gamma-gamma absorption due to the lensing objects.

Very High-Energy Gamma-Ray Sources.

ERIC Educational Resources Information Center

Weekes, Trevor C.

1986-01-01

Discusses topics related to high-energy, gamma-ray astronomy (including cosmic radiation, gamma-ray detectors, high-energy gamma-ray sources, and others). Also considers motivation for the development of this field, the principal results to date, and future prospects. (JN)

Effective gamma-ray doses due to natural radiation from soils of southeastern Brazil

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

Silveira, M. A. G.; Moreira, R. H.; Bellini, B. S.

2010-08-04

We have used gamma-ray spectrometry to study the distribution of natural radiation from soils of southeastern Brazil: Billings reservoir, Sao Bernardo do Campo Parks, Diadema Parks, Interlagos region, Sao Paulo, and soil from Sao Paulo and Rio de Janeiro beaches. In most of the regions studied we have found that the dose due the external exposure to gamma-rays, proceeding from natural terrestrial elements, are between the values 0.3 and 0.6 mSv/year, established by the United Nations Scientific Committee on the Effects of Atomic Radiation.

Low-dose radiation modifies skin response to acute gamma-rays and protons.

PubMed

Mao, Xiao Wen; Pecaut, Michael J; Cao, Jeffrey D; Moldovan, Maria; Gridley, Daila S

2013-01-01

The goal of the present study was to obtain pilot data on the effects of protracted low-dose/low-dose-rate (LDR) γ-rays on the skin, both with and without acute gamma or proton irradiation (IR). Six groups of C57BL/6 mice were examined: a) 0 Gy control, b) LDR, c) Gamma, d) LDR+Gamma, e) Proton, and f) LDR+Proton. LDR radiation was delivered to a total dose of 0.01 Gy (0.03 cGy/h), whereas the Gamma and Proton groups received 2 Gy (0.9 Gy/min and 1.0 Gy/min, respectively). Assays were performed 56 days after exposure. Skin samples from all irradiated groups had activated caspase-3, indicative of apoptosis. The significant (p<0.05) increases in immunoreactivity in the Gamma and Proton groups were not present when LDR pre-exposure was included. However, the terminal deoxynucleotidyl transferase dUTP nick-end labeling assay for DNA fragmentation and histological examination of hematoxylin and eosin-stained sections revealed no significant differences among groups, regardless of radiation regimen. The data demonstrate that caspase-3 activation initially triggered by both forms of acute radiation was greatly elevated in the skin nearly two months after whole-body exposure. In addition, LDR γ-ray priming ameliorated this response.

Gamma ray bursts of black hole universe

NASA Astrophysics Data System (ADS)

Zhang, T. X.

2015-07-01

Slightly modifying the standard big bang theory, Zhang recently developed a new cosmological model called black hole universe, which has only a single postulate but is consistent with Mach's principle, governed by Einstein's general theory of relativity, and able to explain existing observations of the universe. In the previous studies, we have explained the origin, structure, evolution, expansion, cosmic microwave background radiation, quasar, and acceleration of black hole universe, which grew from a star-like black hole with several solar masses through a supermassive black hole with billions of solar masses to the present state with hundred billion-trillions of solar masses by accreting ambient matter and merging with other black holes. This study investigates gamma ray bursts of black hole universe and provides an alternative explanation for the energy and spectrum measurements of gamma ray bursts according to the black hole universe model. The results indicate that gamma ray bursts can be understood as emissions of dynamic star-like black holes. A black hole, when it accretes its star or merges with another black hole, becomes dynamic. A dynamic black hole has a broken event horizon and thus cannot hold the inside hot (or high-frequency) blackbody radiation, which flows or leaks out and produces a GRB. A star when it collapses into its core black hole produces a long GRB and releases the gravitational potential energy of the star as gamma rays. A black hole that merges with another black hole produces a short GRB and releases a part of their blackbody radiation as gamma rays. The amount of energy obtained from the emissions of dynamic star-like black holes are consistent with the measurements of energy from GRBs. The GRB energy spectra derived from this new emission mechanism are also consistent with the measurements.

A gamma-ray testing technique for spacecraft. [considering cosmic radiation effects

NASA Technical Reports Server (NTRS)

Gribov, B. S.; Repin, N. N.; Sakovich, V. A.; Sakharov, V. M.

1977-01-01

The simulated cosmic radiation effect on a spacecraft structure is evaluated by gamma ray testing in relation to structural thickness. A drawing of the test set-up is provided and measurement errors are discussed.

Spectral analysis of paramagnetic centers induced in human tooth enamel by x-rays and gamma radiation

NASA Astrophysics Data System (ADS)

Kirillov, V. A.; Kuchuro, I. I.

2010-03-01

Based on study of spectral and relaxation characteristics, we have established that paramagnetic centers induced in tooth enamel by x-rays and gamma radiation are identical in nature. We show that for the same exposure dose, the intensity of the electron paramagnetic resonance (EPR) signal induced by x-radiation with effective energy 34 keV is about an order of magnitude higher than the amplitude of the signal induced by gamma radiation. We have identified a three-fold attenuation of the EPR signal along the path of the x-radiation from the buccal to the lingual side of a tooth, which is evidence that the individual had undergone diagnostic x-ray examination of the dentition or skull. We have shown that the x-ray exposure doses reconstructed from the EPR spectra are an order of magnitude higher than the applied doses, while the dose loads due to gamma radiation are equal to the applied doses. The data obtained indicate that for adequate reconstruction of individual absorbed doses from EPR spectra of tooth enamel in the population subjected to the combined effect of x-radiation and accidental external gamma radiation as a result of the disaster at the Chernobyl nuclear power plant, we need to take into account the contribution to the dose load from diagnostic x-rays in examination of the teeth, jaw, or skull.

Secondary gamma-ray production in a coded aperture mask

NASA Technical Reports Server (NTRS)

Owens, A.; Frye, G. M., Jr.; Hall, C. J.; Jenkins, T. L.; Pendleton, G. N.; Carter, J. N.; Ramsden, D.; Agrinier, B.; Bonfand, E.; Gouiffes, C.

1985-01-01

The application of the coded aperture mask to high energy gamma-ray astronomy will provide the capability of locating a cosmic gamma-ray point source with a precision of a few arc-minutes above 20 MeV. Recent tests using a mask in conjunction with drift chamber detectors have shown that the expected point spread function is achieved over an acceptance cone of 25 deg. A telescope employing this technique differs from a conventional telescope only in that the presence of the mask modifies the radiation field in the vicinity of the detection plane. In addition to reducing the primary photon flux incident on the detector by absorption in the mask elements, the mask will also be a secondary radiator of gamma-rays. The various background components in a CAMTRAC (Coded Aperture Mask Track Chamber) telescope are considered. Monte-Carlo calculations are compared with recent measurements obtained using a prototype instrument in a tagged photon beam line.

Fiber fed x-ray/gamma ray imaging apparatus

DOEpatents

Hailey, C.J.; Ziock, K.P.

1992-06-02

X-ray/gamma ray imaging apparatus is disclosed for detecting the position, energy, and intensity of x-ray/gamma ray radiation comprising scintillation means disposed in the path of such radiation and capable of generating photons in response to such radiation; first photodetection means optically bonded to the scintillation means and capable of generating an electrical signal indicative of the intensity, and energy of the radiation detected by the scintillation means; second photodetection means capable of generating an electrical signal indicative of the position of the radiation in the radiation pattern; and means for optically coupling the scintillation means to the second photodetection means. The photodetection means are electrically connected to control and storage means which may also be used to screen out noise by rejecting a signal from one photodetection means not synchronized to a signal from the other photodetection means; and also to screen out signals from scattered radiation. 6 figs.

Anisotropies in the diffuse gamma-ray background measured by the Fermi LAT

DOE PAGES

Ackermann, M.; Ajello, M.; Albert, A.; ...

2012-04-23

The contribution of unresolved sources to the diffuse gamma-ray background could induce anisotropies in this emission on small angular scales. Here, we analyze the angular power spectrum of the diffuse emission measured by the Fermi Large Area Telescope at Galactic latitudes | b | > 30 ° in four energy bins spanning 1–50 GeV. At multipoles ℓ ≥ 155 , corresponding to angular scales ≲ 2 ° , angular power above the photon noise level is detected at > 99.99 % confidence level in the 1–2 GeV, 2–5 GeV, and 5–10 GeV energy bins, and at > 99 % confidencemore » level at 10–50 GeV. Within each energy bin the measured angular power takes approximately the same value at all multipoles ℓ ≥ 155 , suggesting that it originates from the contribution of one or more unclustered source populations. Furthermore, the amplitude of the angular power normalized to the mean intensity in each energy bin is consistent with a constant value at all energies, C P / < I > 2 = 9.05 ± 0.84 × 10 - 6 sr , while the energy dependence of C P is consistent with the anisotropy arising from one or more source populations with power-law photon spectra with spectral index Γ s = 2.40 ± 0.07 . We also discuss the implications of the measured angular power for gamma-ray source populations that may provide a contribution to the diffuse gamma-ray background.« less

GAMMA-RAYS FROM THE QUASAR PKS 1441+25: STORY OF AN ESCAPE

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

Abeysekara, A. U.; Archambault, S.; Archer, A.

2015-12-20

Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the universe. The detection of significant emission above 100 GeV from a distant quasar would show that some of the radiated gamma-rays escape pair-production interactions with low-energy photons, be it the extragalactic background light (EBL), or the radiation near the supermassive black hole lying at the jet’s base. VERITAS detected gamma-ray emission up to ∼200 GeV from PKS 1441+25 (z = 0.939) during 2015 April, a period of high activity across all wavelengths. This observation of PKS 1441+25more » suggests that the emission region is located thousands of Schwarzschild radii away from the black hole. The gamma-ray detection also sets a stringent upper limit on the near-ultraviolet to near-infrared EBL intensity, suggesting that galaxy surveys have resolved most, if not all, of the sources of the EBL at these wavelengths.« less

The transient gamma-ray spectrometer

NASA Technical Reports Server (NTRS)

Owens, A.; Baker, R.; Cline, T. L.; Gehrels, N.; Jermakian, J.; Nolan, T.; Ramaty, R.; Smith, G.; Stilwell, D. E.; Teegarden, B. J.

1991-01-01

The authors describe the Transient Gamma-Ray Spectrometer (TGRS) to be flown onboard the WIND spacecraft. This instrument is designed to detect cosmic gamma-ray bursts over the energy range of 20 keV to 10 MeV with an expected spectroscopic resolution of 2 keV at 1 MeV (E/Delta-E = 500). The active detection element is a 215-cu cm high-purity n-type Ge crystal cooled to cryogenic temperatures by a passive radiative cooler. The geometric field of view (FOV) defined by the cooler is 170 deg FWFM. Burst data are stored directly in an onboard 2.75-Mb burst memory with an absolute timing accuracy of +/-1.5 ms. This capacity is sufficient to store the entire spectral data set of all but the largest bursts. In addition to burst measurements, the instrument will also study solar flares, search for possible diffuse background lines, and monitor the 511-keV positron annihilation radiation from the galactic center. The experiment is scheduled to be launched on a Delta II launch vehicle from Cape Canaveral on December 31, 1992.

Gamma ray imager on the DIII-D tokamak

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

Pace, D. C., E-mail: pacedc@fusion.gat.com; Taussig, D.; Eidietis, N. W.

2016-04-15

A gamma ray camera is built for the DIII-D tokamak [J. Luxon, Nucl. Fusion 42, 614 (2002)] that provides spatial localization and energy resolution of gamma flux by combining a lead pinhole camera with custom-built detectors and optimized viewing geometry. This diagnostic system is installed on the outer midplane of the tokamak such that its 123 collimated sightlines extend across the tokamak radius while also covering most of the vertical extent of the plasma volume. A set of 30 bismuth germanate detectors can be secured in any of the available sightlines, allowing for customizable coverage in experiments with runaway electronsmore » in the energy range of 1–60 MeV. Commissioning of the gamma ray imager includes the quantification of electromagnetic noise sources in the tokamak machine hall and a measurement of the energy spectrum of background gamma radiation. First measurements of gamma rays coming from the plasma provide a suitable testbed for implementing pulse height analysis that provides the energy of detected gamma photons.« less

Gamma ray imager on the DIII-D tokamak

DOE PAGES

Pace, D. C.; Cooper, C. M.; Taussig, D.; ...

2016-04-13

A gamma ray camera is built for the DIII-D tokamak [J. Luxon, Nucl. Fusion 42, 614 (2002)] that provides spatial localization and energy resolution of gamma flux by combining a lead pinhole camera with custom-built detectors and optimized viewing geometry. This diagnostic system is installed on the outer midplane of the tokamak such that its 123 collimated sightlines extend across the tokamak radius while also covering most of the vertical extent of the plasma volume. A set of 30 bismuth germanate detectors can be secured in any of the available sightlines, allowing for customizable coverage in experiments with runaway electronsmore » in the energy range of 1- 60 MeV. Commissioning of the gamma ray imager includes the quantification of electromagnetic noise sources in the tokamak machine hall and a measurement of the energy spectrum of background gamma radiation. In conclusion, first measurements of gamma rays coming from the plasma provide a suitable testbed for implementing pulse height analysis that provides the energy of detected gamma photons.« less

Portable compton gamma-ray detection system

DOEpatents

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

2008-03-04

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

Method and system for determining radiation shielding thickness and gamma-ray energy

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

Klann, Raymond T.; Vilim, Richard B.; de la Barrera, Sergio

2015-12-15

A system and method for determining the shielding thickness of a detected radiation source. The gamma ray spectrum of a radiation detector is utilized to estimate the shielding between the detector and the radiation source. The determination of the shielding may be used to adjust the information from known source-localization techniques to provide improved performance and accuracy of locating the source of radiation.

A 3D simulation look-up library for real-time airborne gamma-ray spectroscopy

NASA Astrophysics Data System (ADS)

Kulisek, Jonathan A.; Wittman, Richard S.; Miller, Erin A.; Kernan, Warnick J.; McCall, Jonathon D.; McConn, Ron J.; Schweppe, John E.; Seifert, Carolyn E.; Stave, Sean C.; Stewart, Trevor N.

2018-01-01

A three-dimensional look-up library consisting of simulated gamma-ray spectra was developed to leverage, in real-time, the abundance of data provided by a helicopter-mounted gamma-ray detection system consisting of 92 CsI-based radiation sensors and exhibiting a highly angular-dependent response. We have demonstrated how this library can be used to help effectively estimate the terrestrial gamma-ray background, develop simulated flight scenarios, and to localize radiological sources. Source localization accuracy was significantly improved, particularly for weak sources, by estimating the entire gamma-ray spectra while accounting for scattering in the air, and especially off the ground.

Mercuric iodine room temperature gamma-ray detectors

NASA Technical Reports Server (NTRS)

Patt, Bradley E.; Markakis, Jeffrey M.; Gerrish, Vernon M.; Haymes, Robert C.; Trombka, Jacob I.

1990-01-01

high resolution mercuric iodide room temperature gamma-ray detectors have excellent potential as an essential component of space instruments to be used for high energy astrophysics. Mercuric iodide detectors are being developed both as photodetectors used in combination with scintillation crystals to detect gamma-rays, and as direct gamma-ray detectors. These detectors are highly radiation damage resistant. The list of applications includes gamma-ray burst detection, gamma-ray line astronomy, solar flare studies, and elemental analysis.

Inclusive gamma-ray spectra from psi/3095/ and psi-prime/3684/ decays

NASA Technical Reports Server (NTRS)

Biddick, C. J.; Burnett, T. H.; Masek, G. E.; Miller, E. S.; Smith, J. G.; Stronski, J. P.; Sullivan, M. K.; Vernon, W.; Badtke, D. H.; Barnett, B. A.

1977-01-01

Inclusive gamma-ray experiments were carried out in a e(+)e(-) colliding-beam apparatus with NaI(Tl) arrays as detectors. The inclusive gamma-ray spectra, after cosmic-ray background subtraction, are shown as histograms for the decays of the psi(3095) and psi-prime(3684). The psi spectrum has no significant narrow structure, while the psi-prime spectrum shows at least four peaks. Three major radiative decays of the psi-prime(3684) are found, and their respective branching fractions are computed.

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

NASA Astrophysics Data System (ADS)

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

2017-05-01

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

TRANSISTORIZED RADIATION MEASURING APPARATUS FOR $gamma$-RAYS

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

Beug, L.; Rudack, G.

1961-06-24

It is often necessary to measure the content of containers which for various reasons cannot be opened or inspected visually, but the gamma rays emitted by certain radioisotopes can be used for these measuring purposes because they can penetrate iron walls of from 2 to 100 mm thickness. A level gage is described which consists of a measuring table, a radiation source, a radiation detector, a transformer which converts the incident rays in electric current, a discriminator, a recording device, and an adequate current supply. In principle, there are 2 different measuring methods: one uses 2 counting tubes and determinesmore » the level by the difference method, while the other uses only one tube which has been calibrated with a standard source. Several circuit diagrams used in the construction of the devices are discussed. The use of transistors instead of electron tubes is advantageous because they are more compact, sturdier, less dependent on temperature, have a longer life time, and are more economical. A table shows the characteristic properties of one radiation measuring device: 100 pulses/sec, 200 mu amp, -20 deg -+50 deg C, 500-5000 OMEGA , 12w, counting duration 10/sup 10/ pulses. (OID)« less

Exposure Dose Reconstruction from EPR Spectra of Tooth Enamel Exposed to the Combined Effect of X-rays and Gamma Radiation

NASA Astrophysics Data System (ADS)

Kirillov, V. A.; Kuchuro, J. I.

2014-09-01

We have used EPR dosimetry on tooth enamel to show that the combined effect of x-rays with effective energy 34 keV and gamma radiation with average energy 1250 keV leads to a significant increase in the reconstructed absorbed dose compared with the applied dose from a gamma source or from an x-ray source or from both sources of electromagnetic radiation. In simulation experiments, we develop an approach to estimating the contribution of diagnostic x-rays to the exposure dose formed in the tooth enamel by the combined effect of x-rays and gamma radiation.

Very-high-energy gamma rays from a distant quasar: how transparent is the universe?

PubMed

Albert, J; Aliu, E; Anderhub, H; Antonelli, L A; Antoranz, P; Backes, M; Baixeras, C; Barrio, J A; Bartko, H; Bastieri, D; Becker, J K; Bednarek, W; Berger, K; Bernardini, E; Bigongiari, C; Biland, A; Bock, R K; Bonnoli, G; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Commichau, S; Contreras, J L; Cortina, J; Costado, M T; Covino, S; Curtef, V; Dazzi, F; De Angelis, A; De Cea Del Pozo, E; de Los Reyes, R; De Lotto, B; De Maria, M; De Sabata, F; Mendez, C Delgado; Dominguez, A; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernández, E; Firpo, R; Fonseca, M V; Font, L; Galante, N; López, R J García; Garczarczyk, M; Gaug, M; Goebel, F; Hayashida, M; Herrero, A; Höhne, D; Hose, J; Hsu, C C; Huber, S; Jogler, T; Kneiske, T M; Kranich, D; La Barbera, A; Laille, A; Leonardo, E; Lindfors, E; Lombardi, S; Longo, F; López, M; Lorenz, E; Majumdar, P; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Mizobuchi, S; Moles, M; Moralejo, A; Nieto, D; Nilsson, K; Ninkovic, J; Otte, N; Oya, I; Panniello, M; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pegna, R G; Perez-Torres, M A; Persic, M; Peruzzo, L; Piccioli, A; Prada, F; Prandini, E; Puchades, N; Raymers, A; Rhode, W; Ribó, M; Rico, J; Rissi, M; Robert, A; Rügamer, S; Saggion, A; Saito, T Y; Salvati, M; Sanchez-Conde, M; Sartori, P; Satalecka, K; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Shore, S N; Sidro, N; Sierpowska-Bartosik, A; Sillanpää, A; Sobczynska, D; Spanier, F; Stamerra, A; Stark, L S; Takalo, L; Tavecchio, F; Temnikov, P; Tescaro, D; Teshima, M; Tluczykont, M; Torres, D F; Turini, N; Vankov, H; Venturini, A; Vitale, V; Wagner, R M; Wittek, W; Zabalza, V; Zandanel, F; Zanin, R; Zapatero, J

2008-06-27

The atmospheric Cherenkov gamma-ray telescope MAGIC, designed for a low-energy threshold, has detected very-high-energy gamma rays from a giant flare of the distant Quasi-Stellar Radio Source (in short: radio quasar) 3C 279, at a distance of more than 5 billion light-years (a redshift of 0.536). No quasar has been observed previously in very-high-energy gamma radiation, and this is also the most distant object detected emitting gamma rays above 50 gigaelectron volts. Because high-energy gamma rays may be stopped by interacting with the diffuse background light in the universe, the observations by MAGIC imply a low amount for such light, consistent with that known from galaxy counts.

Gamma rays and the case for baryon symmetric big-bang cosmology

NASA Technical Reports Server (NTRS)

Stecker, F. W.

1977-01-01

The baryon symmetric big-bang cosmologies offer an explanation of the present photon-baryon ratio in the universe, the best present explanation of the diffuse gamma-ray background spectrum in the 1 to 200 MeV range, and a mechanism for galaxy formation. In the context of an open universe model, the value of omega which best fits the present gamma-ray data is omega equals approx. 0.1 which does not conflict with upper limits on Comptonization distortion of the 3K background radiation. In regard to He production, evidence is discussed that nucleosynthesis of He may have taken place after the galaxies were formed.

Gamma ray pulsars

NASA Technical Reports Server (NTRS)

Oegelman, H.; Ayasli, S.; Hacinliyan, A.

1976-01-01

Recent data from the high energy gamma ray experiment have revealed the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields correspond to many radiation lengths which cause electrons to emit photons via magnetic bremsstrahlung and these photons to pair produce. The cascade develops until the mean photon energy drops below the pair production threshold which happens to be in the gamma ray range; at this stage the photons break out from the source.

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

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

Itoh, Ryosuke; Fukazawa, Yasushi; Kanda, Yuka

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

Pulsed high-energy gamma rays from PSR 1055-52

NASA Technical Reports Server (NTRS)

Fierro, J. M.; Bertsch, D. L.; Brazier, K. T.; Chiang, J.; D'Amico, N.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Johnston, S.; Kanbach, G.

1993-01-01

The Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory has detected a high-energy gamma-ray source at a position coincident with that of the radio pulsar PSR 1055-52. Analysis of the EGRET data at the radio pulsar period of 197 ms has revealed pulsed gamma-radiation at energies above 300 MeV, making PSR 1055-52 the fifth detected high-energy gamma-ray pulsar. The pulsed radiation from PSR 1055-52 has a very hard photon spectral index of -1.18 +/- 0.16 and a high efficiency for converting its rotational energy into gamma-rays. No unpulsed emission was observed.

Sensitivity to Antibiotics of Bacteria Exposed to Gamma Radiation Emitted from Hot Soils of the High Background Radiation Areas of Ramsar, Northern Iran.

PubMed

Mortazavi, Seyed Mohammad Javad; Zarei, Samira; Taheri, Mohammad; Tajbakhsh, Saeed; Mortazavi, Seyed Alireza; Ranjbar, Sahar; Momeni, Fatemeh; Masoomi, Samaneh; Ansari, Leila; Movahedi, Mohammad Mehdi; Taeb, Shahram; Zarei, Sina; Haghani, Masood

2017-04-01

Over the past several years our laboratories have investigated different aspects of the challenging issue of the alterations in bacterial susceptibility to antibiotics induced by physical stresses. To explore the bacterial susceptibility to antibiotics in samples of Salmonella enterica subsp. enterica serovar Typhimurium ( S. typhimurium ), Staphylococcus aureus , and Klebsiella pneumoniae after exposure to gamma radiation emitted from the soil samples taken from the high background radiation areas of Ramsar, northern Iran. Standard Kirby-Bauer test, which evaluates the size of the zone of inhibition as an indicator of the susceptibility of different bacteria to antibiotics, was used in this study. The maximum alteration of the diameter of inhibition zone was found for K. pneumoniae when tested for ciprofloxacin. In this case, the mean diameter of no growth zone in non-irradiated control samples of K. pneumoniae was 20.3 (SD 0.6) mm; it was 14.7 (SD 0.6) mm in irradiated samples. On the other hand, the minimum changes in the diameter of inhibition zone were found for S. typhimurium and S. aureus when these bacteria were tested for nitrofurantoin and cephalexin, respectively. Gamma rays were capable of making significant alterations in bacterial susceptibility to antibiotics. It can be hypothesized that high levels of natural background radiation can induce adaptive phenomena that help microorganisms better cope with lethal effects of antibiotics.

The Imprint of the Extragalactic Background Light in the Gamma-Ray Spectra of Blazars

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Allafort, A.; Schady, P.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R; Blandford, R. D.;

Cumulative Neutrino and Gamma-Ray Backgrounds from Halo and Galaxy Mergers

NASA Astrophysics Data System (ADS)

Yuan, Chengchao; Mészáros, Peter; Murase, Kohta; Jeong, Donghui

2018-04-01

The merger of dark matter halos and the gaseous structures embedded in them, such as protogalaxies, galaxies, and groups and clusters of galaxies, results in strong shocks that are capable of accelerating cosmic rays (CRs) to ≳10 PeV. These shocks will produce high-energy neutrinos and γ-rays through inelastic pp collisions. In this work, we study the contributions of these halo mergers to the diffuse neutrino flux and to the nonblazar portion of the extragalactic γ-ray background. We formulate the redshift dependence of the shock velocity, galactic radius, halo gas content, and galactic/intergalactic magnetic fields over the dark matter halo distribution up to a redshift z = 10. We find that high-redshift mergers contribute a significant amount of the CR luminosity density, and the resulting neutrino spectra could explain a large part of the observed diffuse neutrino flux above 0.1 PeV up to several PeV. We also show that our model can somewhat alleviate tensions with the extragalactic γ-ray background. First, since a larger fraction of the CR luminosity density comes from high redshifts, the accompanying γ-rays are more strongly suppressed through γγ annihilations with the cosmic microwave background and the extragalactic background light. Second, mildly radiative-cooled shocks may lead to a harder CR spectrum with spectral indices of 1.5 ≲ s ≲ 2.0. Our study suggests that halo mergers, a fraction of which may also induce starbursts in the merged galaxies, can be promising neutrino emitters without violating the existing Fermi γ-ray constraints on the nonblazar component of the extragalactic γ-ray background.

BATSE Observations of Gamma-Ray Burst Tails

NASA Technical Reports Server (NTRS)

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

2001-01-01

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

BATSE Observations of Gamma-Ray Burst Tails

NASA Technical Reports Server (NTRS)

Connaughton, Valerie

2002-01-01

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

Cosmic-Ray Background Flux Model Baed on a Gamma-Ray Large Area Space Telescope Baloon Flight Engineering

NASA Technical Reports Server (NTRS)

2002-01-01

Cosmic-ray background fluxes were modeled based on existing measurements and theories and are presented here. The model, originally developed for the Gamma-ray Large Area Space Telescope (GLAST) Balloon Experiment, covers the entire solid angle (4(pi) sr), the sensitive energy range of the instrument ((approx) 10 MeV to 100 GeV) and abundant components (proton, alpha, e(sup -), e(sup +), (mu)(sup -), (mu)(sup +) and gamma). It is expressed in analytic functions in which modulations due to the solar activity and the Earth geomagnetism are parameterized. Although the model is intended to be used primarily for the GLAST Balloon Experiment, model functions in low-Earth orbit are also presented and can be used for other high energy astrophysical missions. The model has been validated via comparison with the data of the GLAST Balloon Experiment.

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

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

Carraminana, Alberto; Collaboration: HAWC Collaboration

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 earlymore » science results.« less

The Imprint of the Extragalactic Background Light in the Gamma-Ray Spectra of Blazars

DOE PAGES

Ackermann, M.; Ajello, M.; Allafort, A.; ...

2012-11-30

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 limited by galactic and other foreground emissions. In this paper, we report an absorption feature seen in the combined spectra of a sample of gamma-ray blazars out to a redshift of z ~ 1.6. Finally, this feature is caused by attenuation of gamma rays by the EBL at optical to ultravioletmore » frequencies and allowed us to measure the EBL flux density in this frequency band.« less

A Search Technique for Weak and Long-Duration Gamma-Ray Bursts from Background Model Residuals

NASA Technical Reports Server (NTRS)

Skelton, R. T.; Mahoney, W. A.

1993-01-01

We report on a planned search technique for Gamma-Ray Bursts too weak to trigger the on-board threshold. The technique is to search residuals from a physically based background model used for analysis of point sources by the Earth occultation method.

Unstable matter and the 1-0 MeV gamma-ray background

NASA Technical Reports Server (NTRS)

Daly, Ruth A.

1988-01-01

The spectrum of photons produced by an unstable particle which decayed while the universe was young is calculated. This spectrum is compared to that of the 1-10 MeV shoulder, a feature of the high-energy, extragalactic gamma-ray background, whose origin has not yet been determined. The calculated spectrum contains two parameters which are adjusted to obtain a maximal fit to the observed spectrum; the fit thus obtained is accurate to the 99 percent confidence level. The implications for the mass, lifetime, initial abundance, and branching ratio of the unstable particle are discussed.

Biological radiation dose from secondary particles in a Milky Way gamma-ray burst

NASA Astrophysics Data System (ADS)

Atri, Dimitra; Melott, Adrian L.; Karam, Andrew

2014-07-01

Gamma-ray bursts (GRBs) are a class of highly energetic explosions emitting radiation in a very short timescale of a few seconds and with a very narrow opening angle. Although, all GRBs observed so far are extragalactic in origin, there is a high probability of a GRB of galactic origin beaming towards the Earth in the past ~0.5 Gyr. We define the level of catastrophic damage to the biosphere as approximation 100 kJ m-2, based on Thomas et al. (2005a, b). Using results in Melott & Thomas (2011), we estimate the probability of the Earth receiving this fluence from a GRB of any type, as 87% during the last 500 Myr. Such an intense burst of gamma rays would ionize the atmosphere and deplete the ozone (O3) layer. With depleted O3, there will be an increased flux of Solar UVB on the Earth's surface with potentially harmful biological effects. In addition to the atmospheric damage, secondary particles produced by gamma ray-induced showers will reach the surface. Among all secondary particles, muons dominate the ground-level secondary particle flux (99% of the total number of particles) and are potentially of biological significance. Using the Monte Carlo simulation code CORSIKA, we modelled the air showers produced by gamma-ray primaries up to 100 GeV. We found that the number of muons produced by the electromagnetic component of hypothetical galactic GRBs significantly increases the total muon flux. However, since the muon production efficiency is extremely low for photon energies below 100 GeV, and because GRBs radiate strongly for only a very short time, we find that the biological radiation dose from secondary muons is negligible. The main mechanism of biological damage from GRBs is through Solar UVB irradiation from the loss of O3 in the upper atmosphere.

Fermi Gamma-Ray Imaging of a Radio Galaxy

DOE PAGES

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

2010-04-01

The Fermi Gamma-ray Space Telescope has detected the γ-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved γ-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy γ-rays, the lobe flux constitutes a considerable portion (greater than one-half) of the total source emission. The γ-ray emission from the lobes is interpreted as inverse Compton–scattered relic radiation from the cosmic microwave background, with additional contribution at higher energies from the infrared-to-optical extragalactic background light. In conclusion, these measurements provide γ-raymore » constraints on the magnetic field and particle energy content in radio galaxy lobes, as well as a promising method to probe the cosmic relic photon fields.« less

Spectral evolution of active galactic nuclei: A unified description of the X-ray and gamma

NASA Technical Reports Server (NTRS)

Leiter, D.; Boldt, E.

1982-01-01

A model for spectral evolution is presented whereby active galactic nuclei (AGN) of the type observed individually emerge from an earlier stage at z approx = 4 in which they are the thermal X-ray sources responsible for most of the cosmic X-ray background (CXB). The conjecture is pursued that these precursor objects are initially supermassive Schwarzschild black holes with accretion disks radiating near the Eddington luminosity limit. It is noted that after approx. 10 to the 8th power years these central black holes are spun-up to a canonical Kerr equilibrium state (A/M = 0.998; Thorne 1974) and shown how they then can lead to spectral evolution involving non-thermal emission extending to gamma rays, at the expense of reduced thermal disk radiation. That major portion of the CXB remaining after the contribution of usual AGN are considered, while a superposition of AGN sources at z 1 can account for the gamma ray background. Extensive X-ray measurements carried out with the HEAO 1 and 2 missions as well as gamma ray and optical data are shown to compare favorably with principal features of this model.

Teaching about Natural Background Radiation

ERIC Educational Resources Information Center

Al-Azmi, Darwish; Karunakara, N.; Mustapha, Amidu O.

2013-01-01

Ambient gamma dose rates in air were measured at different locations (indoors and outdoors) to demonstrate the ubiquitous nature of natural background radiation in the environment and to show that levels vary from one location to another, depending on the underlying geology. The effect of a lead shield on a gamma radiation field was also…

Studying the High Energy Gamma Ray Sky with Gamma Ray Large Area Space Telescope (GLAST)

NASA Technical Reports Server (NTRS)

Kamae, T.; Ohsugi, T.; Thompson, D. J.; Watanabe, K.

1998-01-01

Building on the success of the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory, the Gamma Ray Large Area Space Telescope (GLAST) will make a major step in the study of such subjects as blazars, gamma Ray bursts, the search for dark matter, supernova remnants, pulsars, diffuse radiation, and unidentified high energy sources. The instrument will be built on new and mature detector technologies such as silicon strip detectors, low-power low-noise LSI, and a multilevel data acquisition system. GLAST is in the research and development phase, and one full tower (of 25 total) is now being built in collaborating institutes. The prototype tower will be tested thoroughly at Stanford Linear Accelerator Center (SLAC) in the fall of 1999.

High energy gamma ray astronomy

NASA Technical Reports Server (NTRS)

Fichtel, Carl E.

1987-01-01

High energy gamma ray astronomy has evolved with the space age. Nonexistent twenty-five years ago, there is now a general sketch of the gamma ray sky which should develop into a detailed picture with the results expected to be forthcoming over the next decade. The galactic plane is the dominant feature of the gamma ray sky, the longitude and latitude distribution being generally correlated with galactic structural features including the spiral arms. Two molecular clouds were already seen. Two of the three strongest gamma ray sources are pulsars. The highly variable X-ray source Cygnus X-3 was seen at one time, but not another in the 100 MeV region, and it was also observed at very high energies. Beyond the Milky Way Galaxy, there is seen a diffuse radiation, whose origin remains uncertain, as well as at least one quasar, 3C 273. Looking to the future, the satellite opportunities for high energy gamma ray astronomy in the near term are the GAMMA-I planned to be launched in late 1987 and the Gamma Ray Observatory, scheduled for launch in 1990. The Gamma Ray Observatory will carry a total of four instruments covering the entire energy range from 30,000 eV to 3 x 10 to the 10th eV with over an order of magnitude increase in sensitivity relative to previous satellite instruments.

Gamma Ray Astrophysics: New insight into the universe

NASA Technical Reports Server (NTRS)

Fichtel, C. E.; Trombka, J. I.

1981-01-01

Gamma ray observations of the solar system, the galaxy and extragalactic radiation are reported. Topics include: planets, comets, and asteroids; solar observations; interstellar medium and galactic structure; compact objects; cosmology; and diffuse radiation. The instrumentation used in gamma ray astronomy in covered along with techniques for the analysis of observational spectra.

Limits to the radiative decays of neutrinos and axions from gamma-ray observations of SN 1987A

NASA Technical Reports Server (NTRS)

Kolb, Edward W.; Turner, Michael S.

1989-01-01

Gamma-ray observations obtained by the SMM gamma-ray spectrometer in the energy range 4.1-6.4 MeV are used to provide limits on the possible radiative decay of neutrinos and axions emitted by SN 1987A. For branching ratio values for the radiative decay modes of less than about 0.0001, the present limits are more stringent than those based upon the photon flux from decaying relic neutrinos. The data are also used to set an axion mass limit.

Space instrumentation for gamma-ray astronomy

NASA Astrophysics Data System (ADS)

Teegarden, B. J.

1999-02-01

The decade of the 1990s has witnessed a renaissance in the field of gamma-ray astronomy. The seminal event was the launch of the Compton Gamma-Ray Observatory (CGRO) in April 1991. There have been a flood of major discoveries from CGRO including breakthroughs in gamma-ray bursts, annihilation radiation, and blazars. The Italian SAX satellite was launched in April 1996. Although not primarily a gamma-ray mission, it has added a new dimension to our understanding of gamma-ray bursts. Along with these new discoveries a firm groundwork has been laid for missions and new technology development that should maintain a healthy and vigorous field throughout most of the next decade. These include the ESA INTEGRAL mission (INTErnational Gamma-Ray Astrophysics Laboratory, to be launched in mid-2001) and the NASA GLAST mission (Gamma-Ray Large Area Space Telescope) with a likely launch in the middle of the next decade. These two missions will extend the observational capabilities well beyond those of CGRO. New technologies (to gamma-ray astronomy), such as cooled germanium detectors, silicon strip detectors, and CdTe detectors are planned for these new missions. Additional promising new technologies such as CdZnTe strip detectors, scintillator fibers, and a gamma-ray lens for future gamma-ray astronomy missions are under development in laboratories around the world.

Natural Radiation from Soil using Gamma-Ray Spectrometry

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

Silveira, M. A. G.; Moreira, R. H.; Paula, A. L. C. de

2009-06-03

We have studied the distribution of natural radioactivity in the soil of Interlagos, in Sao Paulo city and Billings Reservoir, in Sao Bernardo do Campo, Sao Paulo, Brazil. The main contribution of the effective radiation dose is due to the elements of the {sup 238}Th decay series, with smaller contributions from {sup 40}K and the elements of the series of {sup 238}U. The results indicate the dose in all of the studied areas is around the average international dose due to external exposure to gamma rays (0.48 mSv/yr) proceeding from natural terrestrial elements.

Background radiation in inelastic X-ray scattering and X-ray emission spectroscopy. A study for Johann-type spectrometers

NASA Astrophysics Data System (ADS)

Paredes Mellone, O. A.; Bianco, L. M.; Ceppi, S. A.; Goncalves Honnicke, M.; Stutz, G. E.

2018-06-01

A study of the background radiation in inelastic X-ray scattering (IXS) and X-ray emission spectroscopy (XES) based on an analytical model is presented. The calculation model considers spurious radiation originated from elastic and inelastic scattering processes along the beam paths of a Johann-type spectrometer. The dependence of the background radiation intensity on the medium of the beam paths (air and helium), analysed energy and radius of the Rowland circle was studied. The present study shows that both for IXS and XES experiments the background radiation is dominated by spurious radiation owing to scattering processes along the sample-analyser beam path. For IXS experiments the spectral distribution of the main component of the background radiation shows a weak linear dependence on the energy for the most cases. In the case of XES, a strong non-linear behaviour of the background radiation intensity was predicted for energy analysis very close to the backdiffraction condition, with a rapid increase in intensity as the analyser Bragg angle approaches π / 2. The contribution of the analyser-detector beam path is significantly weaker and resembles the spectral distribution of the measured spectra. Present results show that for usual experimental conditions no appreciable structures are introduced by the background radiation into the measured spectra, both in IXS and XES experiments. The usefulness of properly calculating the background profile is demonstrated in a background subtraction procedure for a real experimental situation. The calculation model was able to simulate with high accuracy the energy dependence of the background radiation intensity measured in a particular XES experiment with air beam paths.

Cosmic-Ray Background Flux Model based on a Gamma-Ray Large-Area Space Telescope Balloon Flight Engineering Model

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

Mizuno, T

2004-09-03

Cosmic-ray background fluxes were modeled based on existing measurements and theories and are presented here. The model, originally developed for the Gamma-ray Large Area Space Telescope (GLAST) Balloon Experiment, covers the entire solid angle (4{pi} sr), the sensitive energy range of the instrument ({approx} 10 MeV to 100 GeV) and abundant components (proton, alpha, e{sup -}, e{sup +}, {mu}{sup -}, {mu}{sup +} and gamma). It is expressed in analytic functions in which modulations due to the solar activity and the Earth geomagnetism are parameterized. Although the model is intended to be used primarily for the GLAST Balloon Experiment, model functionsmore » in low-Earth orbit are also presented and can be used for other high energy astrophysical missions. The model has been validated via comparison with the data of the GLAST Balloon Experiment.« less

Monitoring Energy Calibration Drift Using the Scintillator Background Radiation

NASA Astrophysics Data System (ADS)

Conti, Maurizio; Eriksson, Lars; Hayden, Charles

2011-06-01

Scintillating materials commonly used in nuclear medicine can contain traces of isotopes that naturally emit gamma or beta radiation. Examples of these are 138La contained in LaBr3 and other Lanthanum based scintillators, and 176Lu contained in LSO, LYSO, LuYAP and other Lutetium based scintillators. In particular,176Lu decays into 176Hf and emits a beta particle with maximum energy 589 keV, and a cascade of gamma rays of energies 307 keV, 202 keV and 88 keV. We propose to use the background radiation for monitoring of detector calibration drift and for self-calibration of detectors in complex detector systems. A calibration drift due to random or systematic changes in photomultiplier tube (PMT) gain was studied in a Siemens PET scanner, based on LSO blocks. Both a conventional radioactive source (68Ge, 511 keV photons from electron-positron annihilation) and the LSO background radiation were used for calibration. The difference in the calibration peak shift at 511 keV estimated with the two methods was less than 10%.

RADIATION GENETICS IN WHEAT. VII. COMPARISON OF RADIATION EFFECTS OF BETA- AND GAMMA-RAYS ON DIPLOID WHEAT

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

Matsumura, S.

1962-01-01

Seeds of Triticum monococcum flavescens were soaked in P/sup 32/ and I/ sup 131/solutions for 2 days before sowing, to compare the effects of beta and gamma radiations. Radioactive solutions of pH 6-7 contained 0.05-0.8 mc/gr P/sup 32/ and 0.2--0.8 mc/g I/sup 131/. For comparison, seeds soaked in water for 2 days were exposed to gamma radiation with Co/sup 60/ at the dosages 2.5, 5, 10, and 20 kr. The growth of seedlings, height of mature plants, single-spike fertility, and chromosome aberrations of treated plants in X/sub 1/ and chlorophyll mutations in X/sub 2/ were compared for beta and gammamore » irradiation. The higher the dosage of beta and gamma rays, the more delayed were emergence and growth of seedlings and the lower were survival rate, height of mature plants, and fertility. The relation between the inhibition of seedling growth and dosage of beta and gamma radiations coincides roughly with that between the decrease of survival rate or- fertility and dosage. There was no emergence of seedlings at 20 kr gamma radiation and 0.8 mc/g P/sup 32/ beta radiation. The effects of beta radiation from 0.15-0.2 mc/g P/sup 32/ and 0.8 mc/g I/sup 131/ solutions correspond roughly to those of 2.5 kr gamma radiation. As to chromosome aberrations and chlorophyll mutations, the effects of 2.5 kr gamma radiation coincide roughly with those of 0.1 mc/g P/sup 32/ and 0.6-0.8 mc/g I/sup 131/ solution. If it is assumed that the effects of beta radiation are confined only to the embryo, then a 0.2 mc/g P/sup 32/ solution equals about 2.4 krad. This will account for the present data. (auth)« less

Prompt gamma-ray imaging for small animals

NASA Astrophysics Data System (ADS)

Xu, Libai

codes GEANT4 or MCNP5, to predict results and investigate the feasibility of this new imaging idea. Benchmark experiments have been conducted to test the capability of the code to simulate prompt gamma rays, which are produced by following the nuclear structures of each irradiated isotope, and coincidence counting techniques, which are considered the most important improvement in neutron-related gamma-ray detection applications to reduce gamma background and improve system signal-to-noise ratios. With coincidence prompt gamma rays available, two major imaging techniques, electronic collimations and mechanic collimations, are implemented in the simulation to illustrate the feasibility of imaging elemental distribution by this new technique. The expectation maximization algorithm is employed in electronic collimation to reconstruct images. The common SPECT imaging algorithms are used in mechanical collimation to get an image. Several critical topics concerning practical applications have already been discussed, such as the radiation dose to the mouse and the detection efficiency of high-energy gamma rays. The funding of this work is provided by the Center for Engineering Application of Radioisotopes (CEAR) at North Carolina State University (NCSU) and Nuclear Engineering Education Research.

The Diffuse Gamma-Ray Background from Type Ia Supernovae

NASA Technical Reports Server (NTRS)

Lien, Amy; Fields, Brian D.

2012-01-01

The origin of the diffuse extragalactic gamma-ray background (EGB) has been intensively studied but remains unsettled. Current popular source candidates include unresolved star-forming galaxies, starburst galaxies, and blazars. In this paper we calculate the EGB contribution from the interactions of cosmic rays accelerated by Type Ia supernovae, extending earlier work which only included core-collapse supernovae. We consider Type Ia events in star-forming galaxies, but also in quiescent galaxies that lack star formation. In the case of star-forming galaxies, consistently including Type Ia events makes little change to the star-forming EGB prediction, so long as both supernova types have the same cosmic-ray acceleration efficiencies in star-forming galaxies. Thus our updated EGB estimate continues to show that star-forming galaxies can represent a substantial portion of the signal measured by Fermi. In the case of quiescent galaxies, conversely, we find a wide range of possibilities for the EGB contribution. The dominant uncertainty we investigated comes from the mass in hot gas in these objects, which provides targets for cosmic rays: total gas masses are as yet poorly known, particularly at larger radii. Additionally, the EGB estimation is very sensitive to the cosmic-ray acceleration efficiency and confinement, especially in quiescent galaxies. In the most optimistic allowed scenarios, quiescent galaxies can be an important source of the EGB. In this case, star-forming galaxies and quiescent galaxies together will dominate the EGB and leave little room for other contributions. If other sources, such as blazars, are found to have important contributions to the EGB, then either the gas mass or cosmic-ray content of quiescent galaxies must be significantly lower than in their star-forming counterparts. In any case, improved Fermi EGB measurements will provide important constraints on hot gas and cosmic rays in quiescent galaxies.

Cosmic ray albedo gamma rays from the quiet sun

NASA Technical Reports Server (NTRS)

Seckel, D.; Stanev, T.; Gaisser, T. K.

1992-01-01

We estimate the flux of gamma-rays that result from collisions of high energy galactic cosmic rays with the solar atmosphere. An important aspect of our model is the propagation of cosmic rays through the magnetic fields of the inner solar systems. We use diffusion to model propagation down to the bottom of the corona. Below the corona we trace particle orbits through the photospheric fields to determine the location of cosmic ray interactions in the solar atmosphere and evolve the resultant cascades. For our nominal choice of parameters, we predict an integrated flux of gamma rays (at 1 AU) of F(E(sub gamma) greater than 100 MeV) approximately = 5 x 10(exp -8)/sq cm sec. This can be an order of magnitude above the galactic background and should be observable by the Energetic Gamma Ray experiment telescope (EGRET).

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

NASA Technical Reports Server (NTRS)

Paciesas, William S.

2002-01-01

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

Synchrotron radiation-based quasi-elastic scattering using time-domain interferometry with multi-line gamma rays.

PubMed

Saito, Makina; Masuda, Ryo; Yoda, Yoshitaka; Seto, Makoto

2017-10-02

We developed a multi-line time-domain interferometry (TDI) system using 14.4 keV Mössbauer gamma rays with natural energy widths of 4.66 neV from 57 Fe nuclei excited using synchrotron radiation. Electron density fluctuations can be detected at unique lengths ranging from 0.1 nm to a few nm on time scales from several nanoseconds to the sub-microsecond order by quasi-elastic gamma-ray scattering (QGS) experiments using multi-line TDI. In this report, we generalize the established expression for a time spectrum measured using an identical single-line gamma-ray emitter pair to the case of a nonidentical pair of multi-line gamma-ray emitters by considering the finite energy width of the incident synchrotron radiation. The expression obtained illustrates the unique characteristics of multi-line TDI systems, where the finite incident energy width and use of a nonidentical emitter pair produces further information on faster sub-picosecond-scale dynamics in addition to the nanosecond dynamics; this was demonstrated experimentally. A normalized intermediate scattering function was extracted from the spectrum and its relaxation form was determined for a relaxation time of the order of 1 μs, even for relatively large momentum transfer of ~31 nm -1 . The multi-line TDI method produces a microscopic relaxation picture more rapidly and accurately than conventional single-line TDI.

Novel Chalcogenide Materials for x ray and Gamma ray Detection

DTIC Science & Technology

2016-05-01

REPORT OF PROJECT: Novel chalcogenide materials for x - ray and - ray detection HDTRA1-09-1-0044 Mercouri Kanatzidis , PI Northwestern University...investigated semiconductor for hard radiation detection. The μτ products for electrons however are lower than those of CZT, the leading material for X - ray ...Formation of native defects in the gamma- ray detector material, Cs2Hg6S7 Semiconductor devices detecting hard radiation such as x - rays and

Research in cosmic and gamma ray astrophysics

NASA Technical Reports Server (NTRS)

Stone, E. C.; Davis, L., Jr.; Mewaldt, R. A.; Prince, T. A.

1989-01-01

Research activities in cosmic rays, gamma rays, and astrophysical plasmas are covered. The activities are divided into sections and described, followed by a bibliography. The astrophysical aspects of cosmic rays, gamma rays, and of the radiation and electromagnetic field environment of the Earth and other planets are investigated. These investigations are performed by means of energetic particle and photon detector systems flown on spacecraft and balloons.

Gamma Rays at Very High Energies

NASA Astrophysics Data System (ADS)

Aharonian, Felix

This chapter presents the elaborated lecture notes on Gamma Rays at Very High Energies given by Felix Aharonian at the 40th Saas-Fee Advanced Course on "Astrophysics at Very High Energies". Any coherent description and interpretation of phenomena related to gammarays requires deep knowledge of many disciplines of physics like nuclear and particle physics, quantum and classical electrodynamics, special and general relativity, plasma physics, magnetohydrodynamics, etc. After giving an introduction to gamma-ray astronomy the author discusses the astrophysical potential of ground-based detectors, radiation mechanisms, supernova remnants and origin of the galactic cosmic rays, TeV emission of young supernova remnants, gamma-emission from the Galactic center, pulsars, pulsar winds, pulsar wind nebulae, and gamma-ray loud binaries.

Gamma radiation field intensity meter

DOEpatents

Thacker, Louis H.

1994-01-01

A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

Gamma radiation field intensity meter

DOEpatents

Thacker, Louis H.

1995-01-01

A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode.

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

NASA Astrophysics Data System (ADS)

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

Unidentified Gamma-Ray Sources: Hunting Gamma-Ray Blazars

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

Massaro, F.; D'Abrusco, R.; Tosti, G.

2012-04-02

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified {gamma}-ray sources (UGSs). Despite the large improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one third of the Fermi-detected objects are still not associated to low energy counterparts. Recently, using the Wide-field Infrared Survey Explorer (WISE) survey, we discovered that blazars, the rarest class of Active Galactic Nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Basedmore » on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated to the UGS sample of the second Fermi {gamma}-ray catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated to {gamma}-ray sources in the 2FGL catalog.« less

UNIDENTIFIED {gamma}-RAY SOURCES: HUNTING {gamma}-RAY BLAZARS

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

Massaro, F.; Ajello, M.; D'Abrusco, R.

2012-06-10

One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of unidentified {gamma}-ray sources (UGSs). Despite the major improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one-third of the Fermi-detected objects are still not associated with low-energy counterparts. Recently, using the Wide-field Infrared Survey Explorer survey, we discovered that blazars, the rarest class of active galactic nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, wemore » designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated with the UGS sample of the second Fermi {gamma}-ray LAT catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart to each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated with {gamma}-ray sources in the 2FGL catalog.« less

Science with the Advanced Gamma Ray Imaging System (AGIS)

NASA Astrophysics Data System (ADS)

Coppi, Paolo

2009-05-01

We present the scientific drivers for the Advanced Gamma Ray Imaging System (AGIS), a concept for the next-generation ground- based gamma-ray experiment, comprised of an array of ˜100 imaging atmospheric Cherenkov telescopes. Design requirements for AGIS include achieving a sensitivity an order of magnitude better than the current generation of space or ground-based instruments in the energy range of 40 GeV to ˜100 TeV. We present here an overview of the scientific goals of AGIS, including the prospects for understanding VHE phenomena in the vicinity of accreting black holes, particle acceleration in a variety of astrophysical environments, indirect detection of dark matter, study of cosmological background radiation fields, and particle physics beyond the standard model.

The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-Ray Background

NASA Technical Reports Server (NTRS)

Venters, Tonia M.; Pavlidou, Vasiliki

2011-01-01

The spectral shapes of the contributions of different classes of unresolved gamma-ray emitters can provide insight into their relative contributions to the extragalactic gamma-ray background (EGB) and the natures of their spectra at GeV energies, We calculate the spectral shapes of the contributions to the EGB arising from BL Lacertae type objects (BL Lacs) and flat-spectrum radio quasars (FSRQs) assuming blazar spectra can be described as broken power laws, We fit the resulting total blazar spectral shape to the Fermi Large Area Telescope measurements of the EGB, finding that the best-fit shape reproduces well the shape of the Fermi EGB for various break scenarios. We conclude that a scenario in which the contribution of blazars is dominant cannot be excluded on spectral grounds alone, even if spectral breaks are shown to be common among Fermi blazars. We also find that while the observation of a featureless (within uncertainties) power-law EGB spectrum by Fermi does not necessarily imply a single class of contributing unresolved sources with featureless individual spectra, such an observation and the collective spectra of the separate contributing populations determine the ratios of their contributions. As such, a comparison with studies including blazar gamma-ray luminosity functions could have profound implications for the blazar contribution to the EGB, blazar evolution, and blazar gamma-ray spectra and emission.

Diffuse Gamma Rays Galactic and Extragalactic Diffuse Emission

NASA Technical Reports Server (NTRS)

Moskalenko, Igor V.; Strong, Andrew W.; Reimer, Olaf

2004-01-01

Diffuse gamma rays consist of several components: truly diffuse emission from the interstellar medium, the extragalactic background, whose origin is not firmly established yet, and the contribution from unresolved and faint Galactic point sources. One approach to unravel these components is to study the diffuse emission from the interstellar medium, which traces the interactions of high energy particles with interstellar gas and radiation fields. Because of its origin such emission is potentially able to reveal much about the sources and propagation of cosmic rays. The extragalactic background, if reliably determined, can be used in cosmological and blazar studies. Studying the derived average spectrum of faint Galactic sources may be able to give a clue to the nature of the emitting objects.

Research in particle and gamma-ray astrophysics

NASA Technical Reports Server (NTRS)

Stone, E. C.; Davis, L., Jr.; Mewaldt, R. A.; Prince, T. A.

1988-01-01

Research activities in cosmic rays, gamma rays, and astrophysical plasmas are covered. Each activity is described, followed by a bibliography. The research program is directed toward the investigation of the astrophysical aspects of cosmic rays and gamma rays and of the radiation and electromagnetic field environment of the earth and other planets. These investigations were performed by means of energetic particle and photon detector systems flown on spacecraft and balloons.

Gamma-ray line afterglow from burst environments

NASA Technical Reports Server (NTRS)

Fencl, H. S.; Boyd, R. N.; Hartmann, Dieter

1992-01-01

We consider photoerosion and direct pair production in a medium surrounding a gamma-ray burst. The resulting secondary gamma-rays may provide diagnostic tools of these environments and, in turn, of the nature of the bursters themselves. In some instances short-lived nuclides are formed; the beta-delayed gamma-rays produced from their decays provide the signatures of the photoerosion. In addition, annihilation radiation produced from positrons resulting from direct pair production is related to the plasma conditions in the medium. We investigate the plausibility of detecting the various radiations. Under extremely favorable conditions, the photoerosion afterglow might be detectable with the present generation of detectors. However, the positron annihilation line should be detectable under a fairly wide range in the conditions of the medium.

Gamma radiation field intensity meter

DOEpatents

Thacker, L.H.

1995-10-17

A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

Gamma radiation field intensity meter

DOEpatents

Thacker, L.H.

1994-08-16

A gamma radiation intensity meter measures dose rate of a radiation field. The gamma radiation intensity meter includes a tritium battery emitting beta rays generating a current which is essentially constant. Dose rate is correlated to an amount of movement of an electroscope element charged by the tritium battery. Ionizing radiation decreases the voltage at the element and causes movement. A bleed resistor is coupled between the electroscope support element or electrode and the ionization chamber wall electrode. 4 figs.

Gamma-Ray Dose Measurement with Radio-Photoluminescence Glass Dosimeter in Mixed Radiation Field for BNCT

NASA Astrophysics Data System (ADS)

Hiramatsu, K.; Yoshihashi, S.; Kusaka, S.; Sato, F.; Hoashi, E.; Murata, I.

2017-09-01

Accelerator based neutron sources (ABNS) are being developed as the next generation neutron irradiation system for BNCT. From the ABNS, unnecessary gamma-rays will be generated by neutron capture reactions, as well as fast neutrons. To control the whole-body radiation dose to the patient, measurement of gamma-ray dose in the irradiation room is necessary. In this study, the objective is to establish a method to measure gamma-ray dose separately in a neutron/gamma mixed field by using RPL glass dosimeter. For this purpose, we proposed a lead filter method which uses a pair of RPL glasses with and without a lead filter outside. In order to realize this method, the basic characteristics of glass dosimeter was verified in the gamma-ray field, before adapting it in the mixture field. From the result of the experiment using the lead filter, the simulation result especially for the case with a lead filter overestimated the absorbed does obtained from measurement. We concluded that the reason of the discrepancy is caused by existence of gradient of the dose distribution in the glass, and the difference of sensitivity to low-energy photon between measurement and theory.

Six faint gamma-ray pulsars seen with the Fermi Large Area Telescope: Towards a sample blending into the background

DOE PAGES

Hou, X.; Smith, D. A.; Guillemot, L.; ...

2014-10-14

Context. Here, GeV gamma-ray pulsations from over 140 pulsars have been characterized using the Fermi Large Area Telescope, enabling improved understanding of the emission regions within the neutron star magnetospheres, and the contributions of pulsars to high energy electrons and diffuse gamma rays in the Milky Way. The first gamma-ray pulsars to be detected were the most intense and/or those with narrow pulses. Aims. As the Fermi mission progresses, progressively fainter objects can be studied. In addition to more distant pulsars (thus probing a larger volume of the Galaxy), or ones in high background regions (thus improving the sampling uniformitymore » across the Galactic plane), we detect pulsars with broader pulses or lower luminosity. Adding pulsars to our catalog with inclination angles that are rare in the observed sample, and/or with lower spindown power, will reduce the bias in the currently known gamma-ray pulsar population. Methods. We use rotation ephemerides derived from radio observations to phase-fold gamma rays recorded by the Fermi Large Area Telescope, to then determine the pulse profile properties. Spectral analysis provides the luminosities and, when the signal-to-noise ratio allows, the cutoff energies. We constrain the pulsar distances by different means in order to minimize the luminosity uncertainties. Results. We present six new gamma-ray pulsars with an eclectic mix of properties. Three are young, and three are recycled. They include the farthest, the lowest power, two of the highest duty-cycle pulsars seen, and only the fourth young gamma-ray pulsar with a radio interpulse. Finally, we discuss the biases existing in the current gamma-ray pulsar catalog, and steps to be taken to mitigate the bias.« less

A Three-Dimensional Analysis of the Galactic Gamma-Ray Emission Resulting from Cosmic-Ray Interactions with the Interstellar Gas and Radiation Fields

NASA Technical Reports Server (NTRS)

Sodroski, Thomas J.; Dwek, Eli

2000-01-01

The primary task objective is to construct a 3-D model for the distribution of high-energy (20 MeV - 30 GeV) gamma-ray emission in the Galactic disk. Under this task the contractor will utilize data from the EGRET instrument on the Compton Gamma-Ray Observatory, H I and CO surveys, radio-continuum surveys at 408 MHz, 1420 MHz, 5 GHz, and 19 GHz, the COBE Diffuse Infrared Background Experiment (DIRBE) all-sky maps from 1 to 240 microns, and ground-based B, V, J, H, and K photometry. The respective contributions to the gamma-ray emission from cosmic ray/matter interactions, inverse Compton scattering, and extragalactic emission will be determined.

ON ULTRA-HIGH-ENERGY COSMIC RAYS AND THEIR RESULTANT GAMMA-RAYS

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

Gavish, Eyal; Eichler, David

2016-05-01

The Fermi Large Area Telescope collaboration has recently reported on 50 months of measurements of the isotropic extragalactic gamma-ray background (EGRB) spectrum between 100 MeV and 820 GeV. Ultra-high-energy cosmic ray (UHECR) protons interact with the cosmic microwave background photons and produce cascade photons of energies 10 MeV–1 TeV that contribute to the EGRB flux. We examine seven possible evolution models for UHECRs and find that UHECR sources that evolve as the star formation rate (SFR), medium low luminosity active galactic nuclei type-1 ( L = 10{sup 43.5} erg s{sup −1} in the [0.5–2] KeV band), and BL Lacertae objectsmore » (BL Lacs) are the most acceptable given the constraints imposed by the observed EGRB. Other possibilities produce too much secondary γ -radiation. In all cases, the decaying dark matter (DM) contribution improves the fit at high energy, but the contribution of still unresolved blazars, which would leave the smallest role for decaying DM, may yet provide an alternative improvement. The possibility that the entire EGRB can be fitted with resolvable but not-yet-resolved blazars, as recently claimed by Ajello et al., would leave little room in the EGRB to accommodate γ -rays from extragalactic UHECR production, even for many source evolution rates that would otherwise be acceptable. We find that under the assumption of UHECRs being mostly protons, there is not enough room for producing extragalactic UHECRs with active galactic nucleus, gamma-ray burst, or even SFR source evolution. Sources that evolve as BL Lacs, on the other hand, would produce much less secondary γ -radiation and would remain a viable source of UHECRs, provided that they dominate.« less

A Shallow Underground Laboratory for Low-Background Radiation Measurements and Materials Development

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

Aalseth, Craig E.; Bonicalzi, Ricco; Cantaloub, Michael G.

Abstract: Pacific Northwest National Laboratory recently commissioned a new shallow underground laboratory, located at a depth of approximately 30 meters water-equivalent. This new addition to the small class of radiation measurement laboratories located at modest underground depths worldwide houses the latest generation of custom-made, high-efficiency, low-background gamma-ray spectrometers and gas proportional counters. This manuscript describes the unique capabilities present in the shallow underground laboratory; these include large-scale ultra-pure materials production and a suite of radiation detection systems. Reported data characterize the degree of background reduction achieved through a combination of underground location, graded shielding, and rejection of cosmic-ray events. Wemore » conclude by presenting measurement targets and future opportunities.« less

In-flight observation of long duration gamma-ray glows by aircraft

NASA Astrophysics Data System (ADS)

Kochkin, Pavlo; (Lex) van Deursen, A. P. J.; de Boer, Alte; Bardet, Michiel; Allasia, Cedric; Boissin, Jean Francois; Ostgaard, Nikolai

2017-04-01

The Gamma-Ray Glow is a long-lasting (several seconds to minutes) X- and gamma radiation presumably originated from high-electric field of thunderclouds. Such glows were previously observed by aircraft, balloons, and from the ground. When detected on ground with other particles, i.e. electrons and neutrons, they are usually called Thunderstorm Ground Enhancements (TGEs). Their measured spectra are often consistent with Relativistic Runaway Electron Avalanche (RREA) mechanism. That is why RREA is a commonly accepted explanation for their existence. The gamma-ray glows are observed to be interrupted by lightning discharge, which terminates the high-electric field region. In January 2016 an Airbus A340 factory test aircraft was performing intentional flights through thunderstorms over Northern Australia. The aircraft was equipped with a dedicated in-flight lightning detection system called ILDAS (http://ildas.nlr.nl). The system also contained two scintillation detectors each with 38x38 mm cylinder LaBr3 crystals. While being at 12 km altitude the system detected a gamma-ray flux enhancement 30 times the background counts. It lasted for 20 seconds and was abruptly terminated by a lightning flash. The flash hit the aircraft and its parameters were recorded with 10 ns sampling time including gamma radiation. Ground-based lightning detection network WWLLN detected 4 strikes in the nearby region, all in association with the same flash. The ILDAS system recorded the time-resolved spectrum of the glow. In 6 minutes, after making a U-turn, the aircraft passed the same glow region. Smaller gamma-ray enhancement was again detected. In this presentation we will show the mapped event timeline including airplane, gamma-ray glow, WWLLN, and cloud data. We will discuss the glow's properties, i.e. intensity and differential spectrum, and its possible origin. This result will also be compared to previously reported observations.

Spectral analysis of the gamma-ray background near the dwarf Milky Way satellite Segue 1: Improved limits on the cross section of neutralino dark matter annihilation

DOE PAGES

Baushev, A. N.; Federici, S.; Pohl, M.

2012-09-20

The indirect detection of dark matter requires that dark matter annihilation products be discriminated from conventional astrophysical backgrounds. We re-analyze GeV-band gamma-ray observations of the prominent Milky Way dwarf satellite galaxy Segue 1, for which the expected astrophysical background is minimal. Here, we explicitly account for the angular extent of the conservatively expected gamma-ray signal and keep the uncertainty in the dark-matter profile external to the likelihood analysis of the gamma-ray data.

Fermi Gamma-Ray Space Telescope: Science Highlights for the First 8 Months

NASA Technical Reports Server (NTRS)

Moiseev, Alexander

2010-01-01

The Fermi Gamma-ray Space Telescope was launched on June 11, 2008 and since August 2008 has successfully been conducting routine science observations of high energy phenomena in the gamma-ray sky. A number of exciting discoveries have been made during its first year of operation, including blazar flares, high-energy gamma-ray bursts, and numerous new,gamma-ray sources of different types, among them pulsars and Active Galactic Nuclei (AGN). fermi-LAT also performed accurate mea.<;urement of the diffuse gamma-radiation which clarifies the Ge V excess reported by EGRET almost 10 years ago, high precision measurement of the high energy electron spectrum, and other observations. An overview of the observatory status and recent results as of April 30, 2009, are presented. Key words: gamma-ray astronomy, cosmic rays, gamma-ray burst, pulsar, blazar. diffuse gamma-radiation

Effect of fast neutron, gamma-ray and combined radiations on the thermal decomposition of ammonium perchlorate single crystals

NASA Technical Reports Server (NTRS)

Herley, P. J.; Wang, C. S.; Varsi, G.; Levy, P. W.

1974-01-01

The thermal decomposition kinetics have been determined for ammonium perchlorate crystals subjected to a fast neutron irradiation or to a fast neutron irradiation followed by a gamma-ray irradiation. Qualitatively, the radiation induced changes are similar to those obtained in this and in previous studies, with samples exposed only to gamma rays. The induction period is shortened and the rate constants, obtained from an Avrami-Erofeyev kinetic analysis, are modified. The acceleratory period constant increases and the decay period constant decreases. When compared on an equal deposited energy basis, the fast neutron induced changes are appreciably larger than the gamma-ray induced changes. Some, or all, of the fast neutron induced effects might be attributable to the introduction of localized regions of concentrated radiation damage ('spikes') by lattice atom recoils which become thermal decomposition sites when the crystals are heated.

Very high-energy gamma rays from gamma-ray bursts.

PubMed

Chadwick, Paula M

2007-05-15

Very high-energy (VHE) gamma-ray astronomy has undergone a transformation in the last few years, with telescopes of unprecedented sensitivity having greatly expanded the source catalogue. Such progress makes the detection of a gamma-ray burst at the highest energies much more likely than previously. This paper describes the facilities currently operating and their chances for detecting gamma-ray bursts, and reviews predictions for VHE gamma-ray emission from gamma-ray bursts. Results to date are summarized.

EBL constraints with VERITAS gamma-ray observations

NASA Astrophysics Data System (ADS)

Fernandez Alonso, M.; VERITAS Collaboration

2017-10-01

The extragalactic background light (EBL) contains all the radiation emitted by nuclear and accretion processes since the epoch of recombination. Direct measurements of the EBL in the near-IR to mid-IR waveband are extremely difficult due mainly to the zodiacal light foreground. Instead, gamma-ray astronomy offers the possibility to indirectly set limits to the EBL by studying the effects of gamma-ray absorption in the spectra of detected sources in the very high energy range (VHE: 100 GeV). These effects can be generally seen in the spectra of VHE blazars as a softening (steepening) of the spectrum and/or abrupt changes in the spectral index or breaks. In this work, we use recent VERITAS data of a group of blazars and apply two methods to derive constraints for the EBL spectral properties. We present preliminary results that will be completed with new observations in the near future to enhance the calculated restrictions to the EBL.

Search of the energetic gamma-ray experiment telescope (EGRET) data for high-energy gamma-ray microsecond bursts

NASA Technical Reports Server (NTRS)

Fichtel, C. E.; Bertsch, D. L.; Dingus, B. L.; Esposito, J. A.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mattox, J. R.

1994-01-01

Hawking (1974) and Page & Hawking (1976) investigated theoretically the possibility of detecting high-energy gamma rays produced by the quantum-mechanical decay of a small black hole created in the early universe. They concluded that, at the very end of the life of the small black hole, it would radiate a burst of gamma rays peaked near 250 MeV with a total energy of about 10(exp 34) ergs in the order of a microsecond or less. The characteristics of a black hole are determined by laws of physics beyond the range of current particle accelerators; hence, the search for these short bursts of high-energy gamma rays provides at least the possibility of being the first test of this region of physics. The Compton Observatory Energetic Gamma-Ray Experiment Telescope (EGRET) has the capability of detecting directly the gamma rays from such bursts at a much fainter level than SAS 2, and a search of the EGRET data has led to an upper limit of 5 x 10(exp -2) black hole decays per cu pc per yr, placing constraints on this and other theories predicting microsecond high-energy gamma-ray bursts.

ADP study of gamma-ray bursts

NASA Technical Reports Server (NTRS)

Lamb, Don Q.; Wang, John C. L.; Heuter, Geoffry J.; Graziani, Carlo; Loredo, Tom; Freeman, Peter

1991-01-01

This grant supported study of cyclotron scattering lines in the spectra of gamma-ray bursts through analysis of Ginga and HEAO-1 archival data, and modeling of the results in terms of radiation transfer calculations of cyclotron scattering in a strong magnetic field. A Monte Carlo radiation transfer code with which we are able to calculate the expected properties of cyclotron scattering lines in the spectra of gamma-ray bursts was developed. The extensive software necessary in order to carry out fits of these model spectra to gamma-ray burst spectral data, including folding of the model spectra through the detector response functions was also developed. Fits to Ginga satellite data on burst GB880205 were completed and fits to Ginga satellite data on burst GB870303 are being carried out. These fits have allowed us to test our software, as well as to garner new scientific results. This work has demonstrated that cyclotron resonant scattering successfully accounts for the locations, strengths, and widths of the observed line features in GB870303 and GB880205. The success of the model provides compelling evidence that these gamma-ray bursts come from strongly magnetic neutron stars and are galactic in origin, resolving longstanding controversies about the nature and distance of the burst sources. These results were reported in two papers which are in press in the proceedings of the Taos Workshop on Gamma-Ray Bursts, and in a paper submitted for publication.

Public exposure due to external gamma background radiation in boundary areas of Iran.

PubMed

Pooya, S M Hosseini; Dashtipour, M R; Enferadi, A; Orouji, T

2015-09-01

A monitoring program in boundary areas of a country is an appropriate way to indicate the level of public exposure. In this research, gamma background radiation was measured using TL dosimeters at 12 boundary areas as well as in the capital city of Iran during the period 2010 to 2011. The measurements were carried out in semi-annual time intervals from January to June and July to December in each year. The maximum average dose equivalent value measured was approximately 70 μSv/month for Tehran city. Also, the average dose values obtained were less than 40 μSv/month for all the cities located at the sea level except that of high level natural radiation area of Ramsar, and more than 55 μSv/month for the higher elevation cities. The public exposure due to ambient gamma dose equivalent in Iran is within the levels reported by UNSCEAR. Copyright © 2015 Elsevier Ltd. All rights reserved.

Gamma-400 Science Objectives Built on the Current HE Gamma-Ray and CR Results

NASA Technical Reports Server (NTRS)

Moiseev, Alexander; Mitchell, John; Thompson, David

2012-01-01

The main scientific interest of the Russian Gamma-400 team: Observe gamma-rays above approximately 50 GeV with excellent energy and angular resolution with the goals of: (1) Studying the fine spectral structure of the isotropic high-energy gamma-radiation, (2) Attempting to identify the many still-unidentified Fermi-LAT gamma-ray sources. Gamma-400 will likely be the only space-based gamma-ray observatory operating at the end of the decade. In our proposed Gamma-400-LE version, it will substantially improve upon the capabilities of Fermi LAT and AGILE in both LE and HE energy range. Measuring gamma-rays from approx 20 MeV to approx 1 TeV for at least 7 years, Gamma-400-LE will address the topics of dark matter, cosmic ray origin and propagation, neutron stars, flaring pulsars, black holes, AGNs, GRBs, and actively participate in multiwavelength campaigns.

Gamma-Ray imaging for nuclear security and safety: Towards 3-D gamma-ray vision

NASA Astrophysics Data System (ADS)

Vetter, Kai; Barnowksi, Ross; Haefner, Andrew; Joshi, Tenzing H. Y.; Pavlovsky, Ryan; Quiter, Brian J.

2018-01-01

The development of portable gamma-ray imaging instruments in combination with the recent advances in sensor and related computer vision technologies enable unprecedented capabilities in the detection, localization, and mapping of radiological and nuclear materials in complex environments relevant for nuclear security and safety. Though multi-modal imaging has been established in medicine and biomedical imaging for some time, the potential of multi-modal data fusion for radiological localization and mapping problems in complex indoor and outdoor environments remains to be explored in detail. In contrast to the well-defined settings in medical or biological imaging associated with small field-of-view and well-constrained extension of the radiation field, in many radiological search and mapping scenarios, the radiation fields are not constrained and objects and sources are not necessarily known prior to the measurement. The ability to fuse radiological with contextual or scene data in three dimensions, in analog to radiological and functional imaging with anatomical fusion in medicine, provides new capabilities enhancing image clarity, context, quantitative estimates, and visualization of the data products. We have developed new means to register and fuse gamma-ray imaging with contextual data from portable or moving platforms. These developments enhance detection and mapping capabilities as well as provide unprecedented visualization of complex radiation fields, moving us one step closer to the realization of gamma-ray vision in three dimensions.

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

DOE PAGES

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

2013-08-19

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

Cosmic-ray physics with the milagro gamma-ray observatory

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

Sinnis, Gus

2008-01-01

The Milagro gamma-ray observatory is a water Cherenkov detector with an energy response between 100 GeV and 100 TeV. While the major scientific goals of Milagro were to detect and study cosmic sources of TeV gamma rays, Milagro has made measurements important to furthering our understanding of the cosmic radiation that pervades our Galaxy. Milagro has made the first measurement of the Galactic diffuse emission in the TeV energy band. In the Cygnus Region we measure a flux {approx}2.7 times that predicted by GALPROP. Milagro has also made measurements of the anisotropy of the arrival directions of the local cosmicmore » radiation. On large scales the measurements made by Milagro agree with those previously reported by the Tibet AS{gamma} array. However, we have also discovered a time dependence to this anisotropy, perhaps due to solar modulation. On smaller scales, {approx}10 degrees, we have detected two regions of excess. These excesses have a spectrum that is inconsistent with the local cosmic-ray spectrum.« less

Properties of the Intergalactic Magnetic Field Constrained by Gamma-Ray Observations of Gamma-Ray Bursts

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

Veres, P.; Dermer, C. D.; Dhuga, K. S.

The magnetic field in intergalactic space gives important information about magnetogenesis in the early universe. The properties of this field can be probed by searching for radiation of secondary e {sup +} e {sup −} pairs created by TeV photons that produce GeV range radiation by Compton-scattering cosmic microwave background photons. The arrival times of the GeV “echo” photons depend strongly on the magnetic field strength and coherence length. A Monte Carlo code that accurately treats pair creation is developed to simulate the spectrum and time-dependence of the echo radiation. The extrapolation of the spectrum of powerful gamma-ray bursts (GRBs)more » like GRB 130427A to TeV energies is used to demonstrate how the intergalactic magnetic field can be constrained if it falls in the 10{sup −21}–10{sup −17} G range for a 1 Mpc coherence length.« less

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

NASA Technical Reports Server (NTRS)

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.

Gamma Ray Observatory (GRO) Prelaunch Mission Operations Report (MOR)

NASA Technical Reports Server (NTRS)

1991-01-01

The NASA Astrophysics Program is an endeavor to understand the origin and fate of the universe, to understand the birth and evolution of the large variety of objects in the universe, from the most benign to the most violent, and to probe the fundamental laws of physics by examining their behavior under extreme physical conditions. These goals are pursued by means of observations across the entire electromagnetic spectrum, and through theoretical interpretation of radiations and fields associated with astrophysical systems. Astrophysics orbital flight programs are structured under one of two operational objectives: (1) the establishment of long duration Great Observatories for viewing the universe in four major wavelength regions of the electromagnetic spectrum (radio/infrared/submillimeter, visible/ultraviolet, X-ray, and gamma ray), and (2) obtaining crucial bridging and supporting measurements via missions with directed objectives of intermediate or small scope conducted within the Explorer and Spacelab programs. Under (1) in this context, the Gamma Ray Observatory (GRO) is one of NASA's four Great Observatories. The other three are the Hubble Space Telescope (HST) for the visible and ultraviolet portion of the spectrum, the Advanced X-ray Astrophysics Facility (AXAF) for the X-ray band, and the Space Infrared Telescope Facility (SIRTF) for infrared wavelengths. GRO's specific mission is to study the sources and astrophysical processes that produce the highest energy electromagnetic radiation from the cosmos. The fundamental physical processes that are known to produce gamma radiation in the universe include nuclear reactions, electron bremsstrahlung, matter-antimatter annihilation, elementary particle production and decay, Compton scattering, synchrotron radiation. GRO will address a variety of questions relevant to understanding the universe, such as: the formation of the elements; the structure and dynamics of the Galaxy; the nature of pulsars; the existence

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

NASA Astrophysics Data System (ADS)

1998-09-01

A unique opportunity for journalists and cameramen to view INTEGRAL will be provided at ESA/ESTEC, Noordwijk, the Netherlands on Tuesday 22 September. On show will be the full-size structural thermal model which is now beeing examined in ESA's test centre. Following introductions to the project, the INTEGRAL spacecraft can be seen, filmed and photographed in its special clean room environment.. Media representatives wishing to participate in the visit to ESA's test centre and the presentation of INTEGRAL are kindly requested to return by fax the attached registration form to ESA Public relations, Tel. +33 (0) 1.53.69.71.55 - Fax. +33 (0) 1.53.69.76.90. For details please see the attached programme Gamma-ray astronomy - why ? Gamma-rays cannot be detected from the ground since the earth's atmosphere shields us from high energetic radiation. Only space technology has made gamma-astronomy possible. To avoid background radiation effects INTEGRAL will spend most of its time in the orbit outside earth's radiation belts above an altitude of 40'000 km. Gamma-rays are the highest energy form of electromagnetic radiation. Therefore gamma-ray astronomy explores the most energetic phenomena occurring in nature and addresses some of the most fundamental problems in physics. We know for instance that most of the chemical elements in our bodies come from long-dead stars. But how were these elements formed? INTEGRAL will register gamma-ray evidence of element-making. Gamma-rays also appear when matter squirms in the intense gravity of collapsed stars or black holes. One of the most important scientific objectives of INTEGRAL is to study such compact objects as neutron stars or black holes. Besides stellar black holes there may exist much bigger specimens of these extremely dense objects. Most astronomers believe that in the heart of our Milky Way as in the centre of other galaxies there may lurk giant black holes. INTEGRAL will have to find evidence of these exotic objects. Even

The radiated electromagnetic field from collimated gamma rays and electron beams in air

NASA Astrophysics Data System (ADS)

Tumolillo, T. A.; Wondra, J. P.; Hobbs, W. E.; Smith, K.

1980-12-01

Nuclear weapons effects computer codes are used to study the electromagnetic field produced by gamma rays or by highly relativistic electron beams moving through the air. Consideration is given to large-area electron and gamma beams, small-area electron beams, variation of total beam current, variation of pressure in the beam channel, variation of the beam rise time, variation of beam radius, far-field radiated signals, and induced current on a system from a charged-particle beam. The work has application to system EMP coupling from nuclear weapons or charged-particle-beam weapons.

Secondary production of neutral pi-mesons and the diffuse galactic gamma radiation

NASA Technical Reports Server (NTRS)

Dermer, C. D.

1986-01-01

Isobaric and scaling model predictions of the secondary spectra of neutral pi-mesons produced in proton-proton collisions, at energies between threshold and a few GeV, are compared on the basis of accelerator data and found to show the isobaric model to be superior. This model is accordingly used, in conjuction with a scaling model representation at high energies, in a recalculation of the pi exp (0) gamma-radiation's contribution to the diffuse galactic gamma background; the cosmic ray-induced production of photons (whose energy exceeds 100 MeV) by such radiation occurs at a rate of 1.53 x 10 to the -25 photons/(s-H atom). These results are compared with previous calculations of this process as well as with COS-B observations of the diffuse galactic gamma-radiation.

Soft gamma rays from black holes versus neutron stars

NASA Technical Reports Server (NTRS)

Liang, Edison P.

1992-01-01

The recent launches of GRANAT and GRO provide unprecedented opportunities to study compact collapsed objects from their hard x ray and gamma ray emissions. The spectral range above 100 keV can now be explored with much higher sensitivity and time resolution than before. The soft gamma ray spectral data is reviewed of black holes and neutron stars, radiation, and particle energization mechanisms and potentially distinguishing gamma ray signatures. These may include soft x ray excesses versus deficiencies, thermal versus nonthermal processes, transient gamma ray bumps versus power law tails, lines, and periodicities. Some of the highest priority future observations are outlines which will shed much light on such systems.

Found: A Galaxy's Missing Gamma Rays

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-04-01

Recent reanalysis of data from the Fermi Gamma-ray Space Telescope has resulted in the first detection of high-energy gamma rays emitted from a nearby galaxy. This discovery reveals more about how supernovae interact with their environments.Colliding Supernova RemnantAfter a stellar explosion, the supernovas ejecta expand, eventually encountering the ambient interstellar medium. According to models, this generates a strong shock, and a fraction of the kinetic energy of the ejecta is transferred into cosmic rays high-energy radiation composed primarily of protons and atomic nuclei. Much is still unknown about this process, however. One open question is: what fraction of the supernovas explosion power goes into accelerating these cosmic rays?In theory, one way to answer this is by looking for gamma rays. In a starburst galaxy, the collision of the supernova-accelerated cosmic rays with the dense interstellar medium is predicted to produce high-energy gamma rays. That radiation should then escape the galaxy and be visible to us.Pass 8 to the RescueObservational tests of this model, however, have beenstumped by Arp 220. This nearby ultraluminous infrared galaxy is the product of a galaxy merger ~700 million years ago that fueled a frenzy of starbirth. Due to its dusty interior and extreme levels of star formation, Arp 220 has long been predicted to emit the gamma rays produced by supernova-accelerated cosmic rays. But though weve looked, gamma-ray emission has never been detected from this galaxy until now.In a recent study, a team of scientists led by Fang-Kun Peng (Nanjing University) reprocessed 7.5 years of Fermi observations using the new Pass 8 analysis software. The resulting increase in resolution revealed the first detection of GeV emission from Arp 220!Acceleration EfficiencyGamma-ray luminosity vs. total infrared luminosity for LAT-detected star-forming galaxies and Seyferts. Arp 220s luminosities are consistent with the scaling relation. [Peng et al. 2016

A 3-Dimensional Analysis of the Galactic Gamma-Ray Emission Resulting from Cosmic-Ray Interactions with the Interstellar Gas and Radiation Fields

NASA Technical Reports Server (NTRS)

Sodroski, Thomas J.; Dwek, Eli (Technical Monitor)

2001-01-01

The contractor will provide support for the analysis of data under ADP (NRA 96-ADP- 09; Proposal No . 167-96adp). The primary task objective is to construct a 3-D model for the distribution of high-energy (20 MeV - 30 GeV) gamma-ray emission in the Galactic disk. Under this task the contractor will utilize data from the EGRET instrument on the Compton Gamma-Ray Observatory, H I and CO surveys, radio-continuum surveys at 408 MHz, 1420 MHz, 5 GHz, and 19 GHz, the COBE Diffuse Infrared Background Experiment (DIME) all-sky maps from 1 to 240 p, and ground-based B, V, J, H, and K photometry. The respective contributions to the gamma-ray emission from cosmic ray/matter interactions, inverse Compton scattering, and extragalactic emission will be determined.

Measurement of Cerenkov radiation induced by the gamma-rays of Co-60 therapy units using wavelength shifting fiber.

PubMed

Jang, Kyoung Won; Shin, Sang Hun; Kim, Seon Geun; Kim, Jae Seok; Yoo, Wook Jae; Ji, Young Hoon; Lee, Bongsoo

2014-04-21

In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a plastic optical fiber, spectra and intensities of Cerenkov radiation were measured with a spectrometer. The spectral peaks of light outputs from the wavelength shifting fiber and the plastic optical fiber were measured at wavelengths of 500 and 510 nm, respectively, and the intensity of transmitted light output of the wavelength shifting fiber was 22.2 times higher than that of the plastic optical fiber. Also, electron fluxes and total energy depositions of gamma-ray beams generated from a Co-60 therapy unit were calculated according to water depths using the Monte Carlo N-particle transport code. The relationship between the fluxes of electrons over the Cerenkov threshold energy and the energy depositions of gamma-ray beams from the Co-60 unit is a near-identity function. Finally, percentage depth doses for the gamma-ray beams were obtained using the fiber-optic Cerenkov radiation sensor, and the results were compared with those obtained by an ionization chamber. The average dose difference between the results of the fiber-optic Cerenkov radiation sensor and those of the ionization chamber was about 2.09%.

Diffuse gamma radiation

NASA Technical Reports Server (NTRS)

Fichtel, C. E.; Simpson, G. A.; Thompson, D. J.

1977-01-01

An examination of the intensity, energy spectrum, and spatial distribution of the diffuse gamma-radiation observed by SAS-2 satellite away from the galactic plane in the energy range above 35 MeV has shown that it consists of two components. One component is generally correlated with galactic latitudes, the atomic hydrogen column density was deduced from 21 cm measurements, and the continuum radio emission, believed to be synchrotron emission. It has an energy spectrum similar to that in the plane and joins smoothly to the intense radiation from the plane. It is therefore presumed to be of galactic origin. The other component is apparently isotropic, at least on a coarse scale, and has a steep energy spectrum. No evidence is found for a cosmic ray halo surrounding the galaxy in the shape of a sphere or oblate spheroid with galactic dimensions. Constraints for a halo model with significantly larger dimensions are set on the basis of an upper limit to the gamma-ray anisotropy.

Gamma ray pulsars. [electron-photon cascades

NASA Technical Reports Server (NTRS)

Oegelman, H.; Ayasli, S.; Hacinliyan, A.

1977-01-01

Data from the SAS-2 high-energy gamma-ray experiment reveal the existence of four pulsars emitting photons above 35 MeV. An attempt is made to explain the gamma-ray emission from these pulsars in terms of an electron-photon cascade that develops in the magnetosphere of the pulsar. Although there is very little material above the surface of the pulsar, the very intense magnetic fields (10 to the 12th power gauss) correspond to many radiation lengths which cause electrons to emit photons by magnetic bremsstrahlung and which cause these photons to pair-produce. The cascade develops until the mean photon energy drops below the pair-production threshold which is in the gamma-ray range; at this stage, the photons break out from the source.

Space-Borne Observations of Intense Gamma-Ray Flashes (TGFs) Above Thunderstorms

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

2010-01-01

Intense millisecond flashes of MeV photons are being observed with space-borne detectors. These terrestrial gamma-ray flashes (TGFs) were discovered with the Burst and Transient Source Experiment (BATSE) aboard the Compton Gamma-Ray Observatory (CGRO) in the early 1990s. They are now being observed with several other instruments, including the Gamma-ray Burst Monitor (GBM) detectors on the Fermi Gamma-ray Space Telescope. Although Fermi-GBM was designed and optimized for the observation of cosmic gamma-ray bursts (GRBs), it has unprecedented capabilities for TGF observations. The TGFs usually have extremely hard continuous spectra, typical of highly-Comptonized bremsstrahlung radiation. These spectral are harder than those of GRBs, with photons extending to over 40 MeV. The most likely origin of these high-energy photons is bremsstrahlung radiation produced by a relativistic runaway avalanche electron beam. Such a beam is expected to be produced in an extended, intense electric field in or above thunderstorm regions. The altitude of origin and beaming characteristics of the radiation are quite uncertain. These TGFs may produce an appreciable radiation dose to passengers and crew in nearby aircraft. They have generated considerable observational and theoretical interest in recent years. Instruments are being designed specifically for TGF observations from new spacecraft as well as from airborne platforms.

Technology Needs for Gamma Ray Astronomy

NASA Technical Reports Server (NTRS)

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.

Observation of pulsed hard X-rays/gamma-rays from PSR 1509-58

NASA Astrophysics Data System (ADS)

Gunji, S.; Hirayama, M.; Kamae, T.; Miyazaki, S.; Sekimoto, Y.; Takahashi, T.; Tamura, T.; Tanaka, M.; Yamasaki, N.; Yamagami, T.; Nomachi, M.; Murakami, H.; Braga, J.; Neri, J. A.

1994-06-01

We observed a young rotation-powered pulsar, PSR 1509-58, in the hard X-ray/gamma-ray or the soft gamma-ray band with a balloon-borne detector in Brazil on 1991 November 19 (UT). With a timing analysis we detected pulsations in the energy band 94-240 keV at the 150.687 ms period determined from radio observations. The pulsating flux is (7.1 +/- 1.7) x 10-4 per sq cm per sec in this band, and the energy spectrum follows a power law with photon index alpha = 1.64 +/- 0.4. The averaged pulse profile shows a broad single peak with a sharp rise and has a duty cycle around 50% or higher: these features are similar to what have been observed in the X-ray band by the Ginga satellite. Based on the data available now, the fraction of energy transformed from rotational energy loss to pulsed/nonpulsed soft gamma-ray radiation is estimated. If the solid angle swept by the pulsed beam is about the same as for the Crab pulsar (PSR 0531+21) and the Vela pulsar (PSR 0833-45), PSR 1509-58 turn out to be an extremely efficient pulsar, converting a large fraction of its rotational energy loss to radiation, as the outer gap model predicts. The observed pulsed spectrum, however, is strong in the soft gamma-ray band, in a sharp contrast to what has been observed in the Vela pulsar, a pulsar expected to be similar PSR 1509-58 in the outer gap model. The fact that the pulse profile remains broad and single-peaked in the soft gamma-ray band is also new for Crab-like pulsars. In these regards, PSR 1509-58 may require some alteration to the standard outer gap model or even a new model for gamma-ray emission in pulsars.

High energy gamma ray results from the second small astronomy satellite

NASA Technical Reports Server (NTRS)

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

1974-01-01

A high energy (35 MeV) gamma ray telescope employing a thirty-two level magnetic core spark chamber system was flown on SAS 2. The high energy galactic gamma radiation is observed to dominate over the general diffuse radiation along the entire galactic plane, and when examined in detail, the longitudinal and latitudinal distribution seem generally correlated with galactic structural features, particularly with arm segments. The general high energy gamma radiation from the galactic plane, explained on the basis of its angular distribution and magnitude, probably results primarily from cosmic ray interactions with interstellar matter.

X-Ray Background from Early Binaries

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-11-01

What impact did X-rays from the first binary star systems have on the universe around them? A new study suggests this radiation may have played an important role during the reionization of our universe.Ionizing the UniverseDuring the period of reionization, the universe reverted from being neutral (as it was during recombination, the previous period)to once again being ionized plasma a state it has remained in since then. This transition, which occurred between 150 million and one billion years after the Big Bang (redshift of 6 z 20), was caused by the formation of the first objects energetic enough to reionize the universes neutral hydrogen.ROSAT image of the soft X-ray background throughout the universe. The different colors represent different energy bands: 0.25 keV (red), 0.75 keV (green), 1.5 keV (blue). [NASA/ROSAT Project]Understanding this time period in particular, determining what sources caused the reionization, and what the properties were of the gas strewn throughout the universe during this time is necessary for us to be able to correctly interpret cosmological observations.Conveniently, the universe has provided us with an interesting clue: the large-scale, diffuse X-ray background we observe all around us. What produced these X-rays, and what impact did this radiation have on the intergalactic medium long ago?The First BinariesA team of scientists led by Hao Xu (UC San Diego) has suggested that the very first generation of stars might be an important contributor to these X-rays.This hypothetical first generation, Population III stars, are thought to have formed before and during reionization from large clouds of gas containing virtually no metals. Studies suggest that a large fraction of Pop III stars formed in binaries and when those stars ended their lives as black holes, ensuing accretion from their companions could produceX-ray radiation.The evolution with redshift of the mean X-ray background intensities. Each curve represents a different

Gamma-ray transfer and energy deposition in supernovae

NASA Technical Reports Server (NTRS)

Swartz, Douglas A.; Sutherland, Peter G.; Harkness, Robert P.

1995-01-01

Solutions to the energy-independent (gray) radiative transfer equations are compared to results of Monte Carlo simulations of the Ni-56 and Co-56 decay gamma-ray energy deposition in supernovae. The comparison shows that an effective, purely absorptive, gray opacity, kappa(sub gamma) approximately (0. 06 +/- 0.01)Y(sub e) sq cm/g, where Y is the total number of electrons per baryon, accurately describes the interaction of gamma-rays with the cool supernova gas and the local gamma-ray energy deposition within the gas. The nature of the gamma-ray interaction process (dominated by Compton scattering in the relativistic regime) creates a weak dependence of kappa(sub gamma) on the optical thickness of the (spherically symmetric) supernova atmosphere: The maximum value of kappa(sub gamma) applies during optically thick conditions when individual gamma-rays undergo multiple scattering encounters and the lower bound is reached at the phase characterized by a total Thomson optical depth to the center of the atmosphere tau(sub e) approximately less than 1. Gamma-ray deposition for Type Ia supernova models to within 10% for the epoch from maximum light to t = 1200 days. Our results quantitatively confirm that the quick and efficient solution to the gray transfer problem provides an accurate representation of gamma-ray energy deposition for a broad range of supernova conditions.

Gamma-Ray "Raindrops" from Flaring Blazar

NASA Image and Video Library

2017-12-08

This visualization shows gamma rays detected during 3C 279's big flare by the LAT instrument on NASA's Fermi satellite. Gamma rays are represented as expanding circles reminiscent of raindrops on water. The flare is an abrupt shower of "rain" that trails off toward the end of the movie. Both the maximum size of the circle and its color represent the energy of the gamma ray, with white lowest and magenta highest. In a second version of the visualization, a background map shows how the LAT detects 3C 279 and other sources by accumulating high-energy photons over time (brighter squares reflect higher numbers of gamma rays). The movie starts on June 14 and ends June 17. The area shown is a region of the sky five degrees on a side and centered on the position of 3C 279. Read more: go.nasa.gov/1TqximF Credits: NASA/DOE/Fermi LAT Collaboration

GeV-gamma-ray emission regions

NASA Image and Video Library

2017-12-08

NASA's Fermi Closes on Source of Cosmic Rays New images from NASA's Fermi Gamma-ray Space Telescope show where supernova remnants emit radiation a billion times more energetic than visible light. The images bring astronomers a step closer to understanding the source of some of the universe's most energetic particles -- cosmic rays. Fermi mapped GeV-gamma-ray emission regions (magenta) in the W44 supernova remnant. The features clearly align with filaments detectable in other wavelengths. This composite merges X-rays (blue) from the Germany-led ROSAT mission, infrared (red) from NASA's Spitzer Space Telescope, and radio (orange) from the Very Large Array near Socorro, N.M. Credit: NASA/DOE/Fermi LAT Collaboration, ROSAT, JPL-Caltech, and NRAO/AUI For more information: www.nasa.gov/mission_pages/GLAST/news/cosmic-rays-source....

SAS 2 observations of the earth albedo gamma radiation above 35 MeV

NASA Technical Reports Server (NTRS)

Thompson, D. J.; Simpson, G. A.; Ozel, M. E.

1981-01-01

The earth albedo gamma radiation above 35 MeV in the equatorial region is investigated using observations from the second Small Astronomy Satellite. The zenith angle distribution of the gamma radiation has a peak toward the horizon which is about an order of magnitude more intense than the radiation coming from the nadir, and nearly two orders of magnitude more intense than the gamma radiation from most parts of the sky. The gamma radiation originating from the western horizon is a factor of four more intense than the radiation from the eastern horizon and a factor of three more intense than that from the northern and southern directions. This reflects the geomagnetic effects on the incident cosmic rays whose interactions produce the albedo gamma rays. The variation of the upcoming gamma ray intensity with vertical cutoff rigidity is consistent with the empirical relationship found by Gur'yan et al. (1979).

Characterization and Evolution of the Swift X-ray Telescope Instrumental Background

NASA Technical Reports Server (NTRS)

Hill, Joanne; Pagani, C.; Morris, D. C.; Racusin, J.; Grupe, D.; Vetere, L.; Stroh, M.; Falcone, A.; Kennea, J.; Burrows, D. N.;

Gamma-ray flares from the Crab Nebula.

PubMed

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.

Gamma-Ray Flares from the Crab Nebula

NASA Astrophysics Data System (ADS)

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.; Parkinson, P. M. Saz; 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.

2011-02-01

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 (1015 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.

Dose response and repair kinetics of gamma-H2AX foci induced by in vitro irradiation of whole blood and T-lymphocytes with X- and gamma-radiation.

PubMed

Beels, Laurence; Werbrouck, Joke; Thierens, Hubert

2010-09-01

Dose response and repair kinetics of phosphorylated histone H2A isoform X (gamma-H2AX) foci in T-lymphocytes were investigated in the low-dose range after in vitro irradiation of whole blood and T-lymphocytes with 100 kVp X-rays and (60)Co gamma-rays. Whole blood or isolated T-lymphocytes were irradiated in vitro and gamma-H2AX foci were scored. Dose response was determined in the 0-500 mGy dose range. Foci kinetics were studied at doses of 5 and 200 mGy up to 24 h post-irradiation. After X-irradiation, the dose response for whole blood shows a biphasic behaviour with a low-dose hypersensitivity, which is less pronounced for isolated T-lymphocytes. In contrast, gamma-radiation shows a linear dose response for both irradiation conditions. Concerning repair kinetics, delayed repair was found after X-ray whole blood irradiation (5 and 200 mGy) with 40% of the foci persisting 24 h post-irradiation. This number of foci is reduced to 10% after irradiation of isolated T-lymphocytes with 200 mGy X-rays. On the contrary, gamma-H2AX foci are reduced to background levels 24 h post-irradiation with 200 mGy (60)Co gamma-rays. gamma-H2AX foci response and repair kinetics depend on irradiation conditions and radiation quality, possibly linked to Bystander response.

Cosmic-ray effects on diffuse gamma-ray measurements.

NASA Technical Reports Server (NTRS)

Fishman, G. J.

1972-01-01

Evaluation of calculations and experimental evidence from 600-MeV proton irradiation indicating that cosmic-ray-induced radioactivity in detectors used to measure the diffuse gamma-ray background produces a significant counting rate in the energy region around 1 MeV. It is concluded that these counts may be responsible for the observed flattening of the diffuse photon spectrum at this energy.

Position sensitive detection of neutrons in high radiation background field.

PubMed

Vavrik, D; Jakubek, J; Pospisil, S; Vacik, J

2014-01-01

We present the development of a high-resolution position sensitive device for detection of slow neutrons in the environment of extremely high γ and e(-) radiation background. We make use of a planar silicon pixelated (pixel size: 55 × 55 μm(2)) spectroscopic Timepix detector adapted for neutron detection utilizing very thin (10)B converter placed onto detector surface. We demonstrate that electromagnetic radiation background can be discriminated from the neutron signal utilizing the fact that each particle type produces characteristic ionization tracks in the pixelated detector. Particular tracks can be distinguished by their 2D shape (in the detector plane) and spectroscopic response using single event analysis. A Cd sheet served as thermal neutron stopper as well as intensive source of gamma rays and energetic electrons. Highly efficient discrimination was successful even at very low neutron to electromagnetic background ratio about 10(-4).

The Use of Gamma-Ray Imaging to Improve Portal Monitor Performance

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

Ziock, Klaus-Peter; Collins, Jeff; Fabris, Lorenzo

2008-01-01

We have constructed a prototype, rapid-deployment portal monitor that uses visible-light and gamma-ray imaging to allow simultaneous monitoring of multiple lanes of traffic from the side of a roadway. Our Roadside Tracker uses automated target acquisition and tracking (TAT) software to identify and track vehicles in visible light images. The field of view of the visible camera overlaps with and is calibrated to that of a one-dimensional gamma-ray imager. The TAT code passes information on when vehicles enter and exit the system field of view and when they cross gamma-ray pixel boundaries. Based on this in-formation, the gamma-ray imager "harvests"more » the gamma-ray data specific to each vehicle, integrating its radiation signature for the entire time that it is in the field of view. In this fashion we are able to generate vehicle-specific radiation signatures and avoid source confusion problems that plague nonimaging approaches to the same problem.« less

Novel Chalcogenide Materials for X-ray and Gamma-ray Detection

DTIC Science & Technology

2016-05-01

53 Novel Chalcogenide Materials for x-ray and y-ray Detection Distribution Statement A. Approved for public release; distribution is unlimited. 0...TITLE AND SUBTITLE Sa. CONTRACT NUMBER Novel Chalcogenide Materials for x-ray and y-ray Detection Sb. GRANT NUMBER HDTRA 1-09-1-0044 Sc. PROGRAM...heavy atom chalcogenide family of semiconductors for room temperature gamma radiation detection . Its goal was to accelerate nuclear detector material

Pulsar gamma-rays: Spectra luminosities and efficiencies

NASA Technical Reports Server (NTRS)

Harding, A. K.

1980-01-01

The general characteristics of pulsar gamma ray spectra are presented for a model where the gamma rays are produced by curvature radiation from energetic particles above the polar cap and attenuated by pair production. The shape of the spectrum is found to depend on pulsar period, magnetic field strength, and primary particle energy. By a comparison of numerically calculated spectra with the observed spectra of the Crab and Vela pulsars, it is determined that primary particles must be accelerated to energies of about 3 x 10 to the 7th power mc sq. A genaral formula for pulsar gamma ray luminosity is determined and is found to depend on period and field strength.

Radiation-induced degradation of cyclohexanebutyric acid in aqueous solutions by gamma ray irradiation

NASA Astrophysics Data System (ADS)

Jia, Wenbao; He, Yanquan; Ling, Yongsheng; Hei, Daqian; Shan, Qing; Zhang, Yan; Li, Jiatong

2015-04-01

The radiation-induced degradation of cyclohexanebutyric acid under gamma ray irradiation was investigated. Degradation experiments were performed with 100 mL sealed Pyrex glass vessels loaded with 80 mL of cyclohexanebutyric acid solutions at various initial concentrations of 10, 20, and 40 mg L-1. The absorbed doses were controlled at 0, 0.65, 1.95, 3.25, 6.5, 9.75, and 13 kGy. The results showed that gamma ray irradiation could effectively degrade cyclohexanebutyric acid in aqueous solutions. The removal rate of cyclohexanebutyric acid increased significantly with the increase of absorbed dose and the decrease of its initial concentration. At the same time, the removal of chemical oxygen demand (COD) was as effective as that of cyclohexanebutyric acid. The kinetic studies showed that the degradation of cyclohexanebutyric acid followed pseudo first-order reaction. Above all, the proposed mechanism obtained when NaNO2, NaNO3 and tert-butanol were added showed that the •OH radical played a major role in the gamma degradation process of cyclohexanebutyric acid, while •H and eaq- played a minor role in the gamma degradation process. The degradation products were identified by Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectrometry (GC/MS) during cyclohexanebutyric acid degradation.

Development of a Small-Sized, Flexible, and Insertable Fiber-Optic Radiation Sensor for Gamma-Ray Spectroscopy

PubMed Central

Yoo, Wook Jae; Shin, Sang Hun; Lee, Dong Eun; Jang, Kyoung Won; Cho, Seunghyun; Lee, Bongsoo

2015-01-01

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. PMID:26343667

Gamma Radiation from PSR B1055-52

NASA Technical Reports Server (NTRS)

Thompson, D. J.; Bailes, M.; Bertsch, D. L.; Cordes, J.; DAmico, N. D.; Esposito, J. A.; Finley, J.; Hartman, R. C.; Hermsen, W.; Kanbach, G.;

Gamma Radiation from PSR B1055-52

NASA Technical Reports Server (NTRS)

Thompson, D. J.; Bailes, M.; Bertsch, D. L.; Cordes, J.; DAmico, N.; Esposito, J. A.; Finley, J.; Hartman, R. C.; Hermsen, W.; Kanbach, G.;

Apparatus and method for detecting gamma radiation

DOEpatents

Sigg, R.A.

1994-12-13

A high efficiency radiation detector is disclosed for measuring X-ray and gamma radiation from small-volume, low-activity liquid samples with an overall uncertainty better than 0.7% (one sigma SD). The radiation detector includes a hyperpure germanium well detector, a collimator, and a reference source. The well detector monitors gamma radiation emitted by the reference source and a radioactive isotope or isotopes in a sample source. The radiation from the reference source is collimated to avoid attenuation of reference source gamma radiation by the sample. Signals from the well detector are processed and stored, and the stored data is analyzed to determine the radioactive isotope(s) content of the sample. Minor self-attenuation corrections are calculated from chemical composition data. 4 figures.

Apparatus and method for detecting gamma radiation

DOEpatents

Sigg, Raymond A.

1994-01-01

A high efficiency radiation detector for measuring X-ray and gamma radiation from small-volume, low-activity liquid samples with an overall uncertainty better than 0.7% (one sigma SD). The radiation detector includes a hyperpure germanium well detector, a collimator, and a reference source. The well detector monitors gamma radiation emitted by the reference source and a radioactive isotope or isotopes in a sample source. The radiation from the reference source is collimated to avoid attenuation of reference source gamma radiation by the sample. Signals from the well detector are processed and stored, and the stored data is analyzed to determine the radioactive isotope(s) content of the sample. Minor self-attenuation corrections are calculated from chemical composition data.

Fermi Gamma-Ray Observatory-Science Highlights for the First 8 Months

NASA Technical Reports Server (NTRS)

Moiseev, Alexander

2009-01-01

This viewgraph presentation reviews the science highlights for the first 8 months of the Fermi Gamma-Ray Observatory. Results from pulsars, flaring AGN, gamma ray bursts, diffuse radiation, LMC and electron spectrum are also presented.

Spectral formation in a radiative shock: application to anomalous X-ray pulsars and soft gamma-ray repeaters

NASA Astrophysics Data System (ADS)

Kylafis, N. D.; Trümper, J. E.; Ertan, Ü.

2014-02-01

Context. In the fallback disk model for the persistent emission of anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs), the hard X-ray emission arises from bulk- and thermal Comptonization of bremsstrahlung photons, which are generated in the accretion column. The relatively low X-ray luminosity of these sources implies a moderate transverse optical depth to electron scattering, with photons executing a small number of shock crossings before escaping sideways. Aims: We explore the range of spectral shapes that can be obtained with this model and characterize the most important parameter dependencies. Methods: We use a Monte Carlo code to study the crisscrossing of photons in a radiative shock in an accretion column and compute the resulting spectrum. Results: As expected, high-energy power-law X-ray spectra are produced in radiative shocks with photon-number spectral index Γ ≳ 0.5. We find that the required transverse optical depth is 1 ≲ τ⊥ ≲ 7. Such spectra are observed in low-luminosity X-ray pulsars. Conclusions: We demonstrate here with a simple model that Compton upscattering in the radiative shock in the accretion column can produce hard X-ray spectra similar to those seen in the persistent and transient emission of AXPs and SGRs. In particular, one can obtain a high-energy power-law spectrum, with photon-number spectral-index Γ ~ 1 and a cutoff at 100 - 200 keV, with a transverse Thomson optical depth of ~5, which is shown to be typical in AXPs/SGRs.

Wavelet-based techniques for the gamma-ray sky

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

McDermott, Samuel D.; Fox, Patrick J.; Cholis, Ilias

2016-07-01

Here, 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 darkmore » matter annihilation and extended gamma-ray point source populations in a data-driven way.« less

FERMI-LAT OBSERVATIONS OF THE DIFFUSE {gamma}-RAY EMISSION: IMPLICATIONS FOR COSMIC RAYS AND THE INTERSTELLAR MEDIUM

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

Ackermann, M.; Ajello, M.; Bechtol, K.

The {gamma}-ray sky >100 MeV is dominated by the diffuse emissions from interactions of cosmic rays with the interstellar gas and radiation fields of the Milky Way. Observations of these diffuse emissions provide a tool to study cosmic-ray origin and propagation, and the interstellar medium. We present measurements from the first 21 months of the Fermi Large Area Telescope (Fermi-LAT) mission and compare with models of the diffuse {gamma}-ray emission generated using the GALPROP code. The models are fitted to cosmic-ray data and incorporate astrophysical input for the distribution of cosmic-ray sources, interstellar gas, and radiation fields. To assess uncertaintiesmore » associated with the astrophysical input, a grid of models is created by varying within observational limits the distribution of cosmic-ray sources, the size of the cosmic-ray confinement volume (halo), and the distribution of interstellar gas. An all-sky maximum-likelihood fit is used to determine the X{sub CO} factor, the ratio between integrated CO-line intensity and H{sub 2} column density, the fluxes and spectra of the {gamma}-ray point sources from the first Fermi-LAT catalog, and the intensity and spectrum of the isotropic background including residual cosmic rays that were misclassified as {gamma}-rays, all of which have some dependency on the assumed diffuse emission model. The models are compared on the basis of their maximum-likelihood ratios as well as spectra, longitude, and latitude profiles. We also provide residual maps for the data following subtraction of the diffuse emission models. The models are consistent with the data at high and intermediate latitudes but underpredict the data in the inner Galaxy for energies above a few GeV. Possible explanations for this discrepancy are discussed, including the contribution by undetected point-source populations and spectral variations of cosmic rays throughout the Galaxy. In the outer Galaxy, we find that the data prefer models with a

Extragalactic gamma-ray background from AGN winds and star-forming galaxies in cosmological galaxy-formation models

NASA Astrophysics Data System (ADS)

Lamastra, A.; Menci, N.; Fiore, F.; Antonelli, L. A.; Colafrancesco, S.; Guetta, D.; Stamerra, A.

2017-10-01

We derive the contribution to the extragalactic gamma-ray background (EGB) from active galactic nuclei (AGN) winds and star-forming galaxies by including a physical model for the γ-ray emission produced by relativistic protons accelerated by AGN-driven and supernova-driven shocks into a state-of-the-art semi-analytic model of galaxy formation. This is based on galaxy interactions as triggers of AGN accretion and starburst activity and on expanding blast waves as the mechanism to communicate outwards the energy injected into the interstellar medium by the active nucleus. We compare the model predictions with the latest measurement of the EGB spectrum performed by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope (Fermi) in the range between 100 MeV and 820 GeV. We find that AGN winds can provide 35 ± 15% of the observed EGB in the energy interval Eγ = 0.1-1 GeV, for 73 ± 15% at Eγ = 1-10 GeV, and for 60 ± 20% at Eγ ≳10 GeV. The AGN wind contribution to the EGB is predicted to be larger by a factor of 3-5 than that provided by star-forming galaxies (quiescent plus starburst) in the hierarchical clustering scenario. The cumulative γ-ray emission from AGN winds and blazars can account for the amplitude and spectral shape of the EGB, assuming the standard acceleration theory, and AGN wind parameters that agree with observations. We also compare the model prediction for the cumulative neutrino background from AGN winds with the most recent IceCube data. We find that for AGN winds with accelerated proton spectral index p = 2.2-2.3, and taking into account internal absorption of γ-rays, the Fermi-LAT and IceCube data could be reproduced simultaneously.

Gamma-Ray Flares from the Crab Nebula

DOE PAGES

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

2010-01-06

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 (10more » 15 electron volts) electrons in a region smaller than 1.4 × 10 -2 parsecs. In conclusion, these are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.« less

Primary gamma rays. [resulting from cosmic ray interaction with interstellar matter

NASA Technical Reports Server (NTRS)

Fichtel, C. E.

1974-01-01

Within this galaxy, cosmic rays reveal their presence in interstellar space and probably in source regions by their interactions with interstellar matter which lead to gamma rays with a very characteristic energy spectrum. From the study of the intensity of the high energy gamma radiation as a function of galactic longitude, it is already clear that cosmic rays are almost certainly not uniformly distributed in the galaxy and are not concentrated in the center of the galaxy. The galactic cosmic rays appear to be tied to galactic structural features, presumably by the galactic magnetic fields which are in turn held by the matter in the arm segments and the clouds. On the extragalactic scale, it is now possible to say that cosmic rays are not universal at the density seen near the earth. The diffuse celestial gamma ray spectrum that is observed presents the interesting possibility of cosmological studies and possible evidence for a residual universal cosmic ray density, which is much lower than the present galactic cosmic ray density.

Stellar Photon Archaeology with Gamma-Rays

NASA Technical Reports Server (NTRS)

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.

Cosmic Gamma-Rays

Science.gov Websites

[Argonne Logo] [DOE Logo] Cosmic Gamma-Rays Home Publications Talks People Students Argonne > ; HEP > Cosmic Gamma-Rays Projects VERITAS Past Projects TrICE What's New CTA Cosmic Gamma-Rays The

A review on natural background radiation

PubMed Central

Shahbazi-Gahrouei, Daryoush; Gholami, Mehrdad; Setayandeh, Samaneh

2013-01-01

The world is naturally radioactive and approximately 82% of human-absorbed radiation doses, which are out of control, arise from natural sources such as cosmic, terrestrial, and exposure from inhalation or intake radiation sources. In recent years, several international studies have been carried out, which have reported different values regarding the effect of background radiation on human health. Gamma radiation emitted from natural sources (background radiation) is largely due to primordial radionuclides, mainly 232Th and 238U series, and their decay products, as well as 40K, which exist at trace levels in the earth's crust. Their concentrations in soil, sands, and rocks depend on the local geology of each region in the world. Naturally occurring radioactive materials generally contain terrestrial-origin radionuclides, left over since the creation of the earth. In addition, the existence of some springs and quarries increases the dose rate of background radiation in some regions that are known as high level background radiation regions. The type of building materials used in houses can also affect the dose rate of background radiations. The present review article was carried out to consider all of the natural radiations, including cosmic, terrestrial, and food radiation. PMID:24223380

The Energetic Gamma-Ray Experiment Telescope (EGRET) Science Symposium

NASA Technical Reports Server (NTRS)

Fichtel, Carl E. (Editor); Hunter, Stanley D. (Editor); Sreekumar, Parameswaran (Editor); Stecker, Floyd W. (Editor)

1990-01-01

The principle purpose of this symposium is to provide the EGRET (Energetic Gamma-Ray Experiment Telescope) scientists with an opportunity to study and improve their understanding of high energy gamma ray astronomy. The Symposium began with the galactic diffusion radiation both because of its importance in studying galactic cosmic rays, galactic structure, and dynamic balance, and because an understanding of its characteristics is important in the study of galactic sources. The galactic objects to be reviewed included pulsars, bursts, solar flares, and other galactic sources of several types. The symposium papers then proceeded outward from the Milky Way to normal galaxies, active galaxies, and the extragalactic diffuse radiation.

Position sensitive detection of neutrons in high radiation background field

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

Vavrik, D., E-mail: vavrik@itam.cas.cz; Institute of Theoretical and Applied Mechanics, Academy of Sciences of the Czech Republic, Prosecka 76, 190 00 Prague 9; Jakubek, J.

We present the development of a high-resolution position sensitive device for detection of slow neutrons in the environment of extremely high γ and e{sup −} radiation background. We make use of a planar silicon pixelated (pixel size: 55 × 55 μm{sup 2}) spectroscopic Timepix detector adapted for neutron detection utilizing very thin {sup 10}B converter placed onto detector surface. We demonstrate that electromagnetic radiation background can be discriminated from the neutron signal utilizing the fact that each particle type produces characteristic ionization tracks in the pixelated detector. Particular tracks can be distinguished by their 2D shape (in the detector plane)more » and spectroscopic response using single event analysis. A Cd sheet served as thermal neutron stopper as well as intensive source of gamma rays and energetic electrons. Highly efficient discrimination was successful even at very low neutron to electromagnetic background ratio about 10{sup −4}.« less

Nuclear isomer suitable for gamma ray laser

NASA Technical Reports Server (NTRS)

Jha, S.

1979-01-01

The operation of gamma ray lasers (gasers) are studied. It is assumed that the nuclear isomers mentioned in previously published papers have inherent limitations. It is further assumed that the judicious use of Bormann effect or the application of the total external reflection of low energy gamma radiation at grazing angle of incidence may permit the use of a gaser crystal sufficiently long to achieve observable stimulated emission. It is suggested that a long lived 0(+) isomer decaying by low energy gamma ray emission to a short lived 2(+) excited nuclear state would be an attractive gaser candidate. It is also suggested that the nuclear isomer be incorporated in a matrix of refractory material having an electrostatic field gradient whose principal axis lies along the length of the medium. This results in the preferential transmission of electric quadrupole radiation along the length of the medium.

Levels of naturally occurring gamma radiation measured in British homes and their prediction in particular residences.

PubMed

Kendall, G M; Wakeford, R; Athanson, M; Vincent, T J; Carter, E J; McColl, N P; Little, M P

2016-03-01

Gamma radiation from natural sources (including directly ionising cosmic rays) is an important component of background radiation. In the present paper, indoor measurements of naturally occurring gamma rays that were undertaken as part of the UK Childhood Cancer Study are summarised, and it is shown that these are broadly compatible with an earlier UK National Survey. The distribution of indoor gamma-ray dose rates in Great Britain is approximately normal with mean 96 nGy/h and standard deviation 23 nGy/h. Directly ionising cosmic rays contribute about one-third of the total. The expanded dataset allows a more detailed description than previously of indoor gamma-ray exposures and in particular their geographical variation. Various strategies for predicting indoor natural background gamma-ray dose rates were explored. In the first of these, a geostatistical model was fitted, which assumes an underlying geologically determined spatial variation, superimposed on which is a Gaussian stochastic process with Matérn correlation structure that models the observed tendency of dose rates in neighbouring houses to correlate. In the second approach, a number of dose-rate interpolation measures were first derived, based on averages over geologically or administratively defined areas or using distance-weighted averages of measurements at nearest-neighbour points. Linear regression was then used to derive an optimal linear combination of these interpolation measures. The predictive performances of the two models were compared via cross-validation, using a randomly selected 70 % of the data to fit the models and the remaining 30 % to test them. The mean square error (MSE) of the linear-regression model was lower than that of the Gaussian-Matérn model (MSE 378 and 411, respectively). The predictive performance of the two candidate models was also evaluated via simulation; the OLS model performs significantly better than the Gaussian-Matérn model.

The large area high resolution gamma ray astrophysics facility - HR-GRAF

NASA Astrophysics Data System (ADS)

Fenyves, E. J.; Chaney, R. C.; Hoffman, J. H.; Cline, D. B.; Atac, M.; Park, J.; White, S. R.; Zych, A. D.; Tumer, Q. T.; Hughes, E. B.

1990-03-01

The long-term program is described in terms of its equipment, scientific objectives, and long-range scientific studies. A prototype of a space-based large-area high-resolution gamma-ray facility (HR-GRAF) is being developed to examine pointlike and diffuse gamma-ray sources in the range 1 MeV-100 GeV. The instrument for the facility is proposed to have high angular and energy resolution and very high sensitivity to permit the study of the proposed objects. The primary research targets include the mapping of galactic gamma radiation, observing the angular variations of diffuse gamma rays, and studying the Galactic center with particular emphasis on the hypothetical black hole. Also included in the research plans are obtaining data on gamma-ray bursters, investigating the transmission of gamma rays from cold dark matter, and studying nuclear gamma-ray lines.

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

NASA Astrophysics Data System (ADS)

Integral solves mystery hi-res Size hi-res: 60 kb Credits: Credit: ESA, F. Lebrun (CEA-Saclay). ESA's Integral solves thirty-year old gamma-ray mystery The central regions of our galaxy, the Milky Way, as seen by Integral in gamma rays. With its superior ability to see faint details, Integral correctly reveals the individual sources that comprised the foggy, gamma-ray background seen by previous observatories. The brightest 91 objects seen in this image were classified by Integral as individual sources, while the others appear too faint to be properly characterized at this stage. During the spring and autumn of 2003, Integral observed the central regions of our Galaxy, collecting some of the perpetual glow of diffuse low-energy gamma rays that bathe the entire Galaxy. These gamma rays were first discovered in the mid-1970s by high-flying balloon-borne experiments. Astronomers refer to them as the 'soft' Galactic gamma-ray background, with energies similar to those used in medical X-ray equipment. Initially, astronomers believed that the glow was caused by interactions involving the atoms of the gas that pervades the Galaxy. Whilst this theory could explain the diffuse nature of the emission, since the gas is ubiquitous, it failed to match the observed power of the gamma rays. The gamma rays produced by the proposed mechanisms would be much weaker than those observed. The mystery has remained unanswered for decades. Now Integral's superb gamma-ray telescope IBIS, built for ESA by an international consortium led by Principal Investigator Pietro Ubertini (IAS/CNR, Rome, Italy), has seen clearly that, instead of a fog produced by the interstellar medium, most of the gamma-rays are coming from individual celestial objects. In the view of previous, less sensitive instruments, these objects appeared to merge together. In a paper published today in "Nature", Francois Lebrun (CEA Saclay, Gif sur Yvette, France) and his collaborators report the discovery of 91 gamma-ray

Investigation of Martian H2O and CO2 via orbital gamma ray spectroscopy

NASA Technical Reports Server (NTRS)

Evans, Larry G.; Squyres, Steven W.

1987-01-01

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

Ionizing Organic Compound Based Nanocomposites for Efficient Gamma-Ray Sensor

NASA Technical Reports Server (NTRS)

Singh, N. B.; Dayal, Vishall; Su, Ching-Hua; Arnold, Bradley; Choa, Fow-Sen; Kabandana, Monia G. K.; House, David

2017-01-01

Thin film and nanocrystalline materials of oxides have been very attractive choice as low cost option for gamma-ray detection and have shown great promise. Our studies on pure oxide films indicated that thickness and microstructure have pronounced effect on sensitivity. Since the interaction of gamma-ray with composites involves all three interaction processes; photoelectric effect, Compton scattering, and pair production, composites containing ionic organics have better chance for enhancing sensitivity. In the composites of ionizing organics oxidation effect of unusual oxides changes much faster and hence increases the sensitivity of radiation. In this study, we have used nickel oxide and titanium oxide in ionic organics to develop composite materials for low energy gamma-ray sensing. We prepared composites containing ethylene carbonate and evaluated the effect of commercial Cs-137 radiation source by studying current-voltage relationship at several frequencies. Radiated samples showed higher resistivity compared to as prepared composites.

Spectral properties of blast-wave models of gamma-ray burst sources

NASA Technical Reports Server (NTRS)

Meszaros, P.; Rees, M. J.; Papathanassiou, H.

1994-01-01

We calculate the spectrum of blast-wave models of gamma-ray burst sources, for various assumptions about the magnetic field density and the relativistic particle acceleration efficiency. For a range of physically plausible models we find that the radiation efficiency is high and leads to nonthermal spectra with breaks at various energies comparable to those observed in the gamma-ray range. Radiation is also predicted at other wavebands, in particular at X-ray, optical/UV, and GeV/TeV energies. We discuss the spectra as a function of duration for three basic types of models, and for cosmological, halo, and galactic disk distances. We also evaluate the gamma-ray fluences and the spectral characteristics for a range of external densities. Impulsive burst models at cosmological distances can satisfy the conventional X-ray paucity constraint S(sub x)/S(sub gamma)less than a few percent over a wide range of durations, but galactic models can do so only for bursts shorter than a few seconds, unless additional assumptions are made. The emissivity is generally larger for bursts in a denser external environment, with the efficiency increasing up to the point where all the energy input is radiated away.

Research in cosmic and gamma ray astrophysics

NASA Technical Reports Server (NTRS)

Stone, Edward C.; Mewaldt, Richard A.; Prince, Thomas A.

1992-01-01

Discussed here is research in cosmic ray and gamma ray astrophysics at the Space Radiation Laboratory (SRL) of the California Institute of Technology. The primary activities discussed involve the development of new instrumentation and techniques for future space flight. In many cases these instrumentation developments were tested in balloon flight instruments designed to conduct new investigations in cosmic ray and gamma ray astrophysics. The results of these investigations are briefly summarized. Specific topics include a quantitative investigation of the solar modulation of cosmic ray protons and helium nuclei, a study of cosmic ray positron and electron spectra in interplanetary and interstellar space, the solar modulation of cosmic rays, an investigation of techniques for the measurement and interpretation of cosmic ray isotopic abundances, and a balloon measurement of the isotopic composition of galactic cosmic ray boron, carbon, and nitrogen.

Soft gamma-ray detector for the ASTRO-H Mission

NASA Astrophysics Data System (ADS)

Watanabe, Shin; Tajima, Hiroyasu; Fukazawa, Yasushi; Blandford, Roger; Enoto, Teruaki; Kataoka, Jun; Kawaharada, Madoka; Kokubun, Motohide; Laurent, Philippe; Lebrun, François; Limousin, Olivier; Madejski, Greg; Makishima, Kazuo; Mizuno, Tsunefumi; Nakamori, Takeshi; Nakazawa, Kazuhiro; Mori, Kunishiro; Odaka, Hirokazu; Ohno, Masanori; Ohta, Masayuki; Sato, Goro; Sato, Rie; Takeda, Shin'ichiro; Takahashi, Hiromitsu; Takahashi, Tadayuki; Tanaka, Takaaki; Tashiro, Makoto; Terada, Yukikatsu; Uchiyama, Hideki; Uchiyama, Yasunobu; Yamada, Shinya; Yatsu, Yoichi; Yonetoku, Daisuke; Yuasa, Takayuki

2012-09-01

ASTRO-H is the next generation JAXA X-ray satellite, intended to carry instruments with broad energy coverage and exquisite energy resolution. The Soft Gamma-ray Detector (SGD) is one of ASTRO-H instruments and will feature wide energy band (60-600 keV) at a background level 10 times better than the current instruments on orbit. The SGD is complimentary to ASTRO-H’s Hard X-ray Imager covering the energy range of 5-80 keV. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield where Compton kinematics is utilized to reject backgrounds. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and CdTe (cadmium telluride) sensors. Good energy resolution is afforded by semiconductor sensors, and it results in good background rejection capability due to better constraints on Compton kinematics. Utilization of Compton kinematics also makes the SGD sensitive to the gamma-ray polarization, opening up a new window to study properties of gamma-ray emission processes. In this paper, we will present the detailed design of the SGD and the results of the final prototype developments and evaluations. Moreover, we will also present expected performance based on the measurements with prototypes.

Low energy gamma ray emission from the Cygnus OB2 association

NASA Technical Reports Server (NTRS)

Chen, Wan; White, Richard L.

1992-01-01

According to our newly developed model of gamma-ray emission from chaotic early-type stellar winds, we predict the combined gamma-ray flux from the circumstellar winds of many very luminous early-type stars in the Cyg OB2 association can be detectable by the Energetic Gamma Ray Experiment Telescope (EGRET) (and maybe also by OSSE) on CGRO. Due to different radiation mechanisms, the gamma-ray spectrum from stellar winds can be quite different from that of CYG X-3; this spectral difference and the time-variation of Cyg X-3 flux will help to distinguish the gamma-ray components from different sources in this small region, which is spatially unresolvable by CGRO.

Background sources at PEP

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

Lynch, H.; Schwitters, R.F.; Toner, W.T.

Important sources of background for PEP experiments are studied. Background particles originate from high-energy electrons and positrons which have been lost from stable orbits, ..gamma..-rays emitted by the primary beams through bremsstrahlung in the residual gas, and synchrotron radiation x-rays. The effect of these processes on the beam lifetime are calculated and estimates of background rates at the interaction region are given. Recommendations for the PEP design, aimed at minimizing background are presented. 7 figs., 4 tabs.

Giant collimated gamma-ray flashes

NASA Astrophysics Data System (ADS)

Benedetti, Alberto; Tamburini, Matteo; Keitel, Christoph H.

2018-06-01

Bright sources of high-energy electromagnetic radiation are widely employed in fundamental research, industry and medicine1,2. This motivated the construction of Compton-based facilities planned to yield bright gamma-ray pulses with energies up to3 20 MeV. Here, we demonstrate a novel mechanism based on the strongly amplified synchrotron emission that occurs when a sufficiently dense ultra-relativistic electron beam interacts with a millimetre-thickness conductor. For electron beam densities exceeding approximately 3 × 1019 cm-3, electromagnetic instabilities occur, and the ultra-relativistic electrons travel through self-generated electromagnetic fields as large as 107-108 gauss. This results in the production of a collimated gamma-ray pulse with peak brilliance above 1025 photons s-1 mrad-2 mm-2 per 0.1% bandwidth, photon energies ranging from 200 keV to gigaelectronvolts and up to 60% electron-to-photon energy conversion efficiency. These findings pave the way to compact, high-repetition-rate (kilohertz) sources of short (≲30 fs), collimated (milliradian) and high-flux (>1012 photons s-1) gamma-ray pulses.

Observation of fluctuation of gamma-ray count rate accompanying thunderstorm activity and energy spectrum of gamma rays in the atmosphere up to several kilometers altitude from the ground

NASA Astrophysics Data System (ADS)

Torii, T.; Sanada, Y.; Watanabe, A.

2017-12-01

In the vicinity of the tops of high mountains and in the coastal areas of the Sea of Japan in winter, the generation of high energy photons that lasts more than 100 seconds at the occurrence of thunderclouds has been reported. At the same time, 511 keV gamma rays are also detected. On the other hand, we irradiated a radiosonde equipped with gamma-ray detectors at the time of thunderstorm and observed fluctuation in gamma-ray count-rate. As a result, we found that the gamma-ray count-rate increases significantly near the top of the thundercloud. Therefore, in order to investigate the fluctuation of the energy of the gamma rays, we developed a radiation detector for radiosonde to observe the fluctuation of the low energy gamma-ray spectrum and observed the fluctuation of the gamma-ray spectrum. We will describe the counting rate and spectral fluctuation of gamma-ray detectors for radiosonde observed in the sky in Fukushima prefecture, Japan.

Systems and methods for detecting nuclear radiation in the presence of backgrounds

DOEpatents

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

2005-06-21

Systems and methods for the simultaneous detection and identification of radiation species, including neutrons, gammas/x-rays and minimum ionizing particles (MIPs). A plurality of rectangular and/or triangularly shaped radiation sensitive scintillators can be configured from a plurality of nano-sized particles, dopants and an extruded plastic material. A wavelength-shifting fiber can then be located within a central hole of each extruded scintillator, wherein the wavelength-shifting fiber absorbs scintillation light and re-emits the light at a longer wavelength, thereby piping the light to a photodetector whose response to the light indicates the presence of radiation The resulting method and system can simultaneously detect neutrons, gamma rays, x-rays and cosmic rays (MIPs) and identify each.

Fermi GBM Observations of Terrestrial Gamma-ray Flashes

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

Briggs, Michael S.

2011-09-21

Terrestrial Gamma-ray Flashes are short pulses of energetic radiation associated with thunderstorms and lightning. While the Gamma-ray Burst Monitor (GBM) on Fermi was designed to observe gamma-ray bursts, its large BGO detectors are excellent for observing TGFs. Using GBM, TGF pulses are seen to either be symmetrical or have faster rise time than fall times. Some TGFs are resolved into double, partially overlapping pulses. Using ground-based radio observations of lightning from the World Wide Lightning Location Network (WWLLN), TGFs and their associated lightning are found to be simultaneous to {approx_equal}40 {mu} s. The lightning locations are typically within 300 kmmore » of the sub-spacecraft point.« less

Gamma watermarking

DOEpatents

Ishikawa, Muriel Y.; Wood, Lowell L.; Lougheed, Ronald W.; Moody, Kenton J.; Wang, Tzu-Fang

2004-05-25

A covert, gamma-ray "signature" is used as a "watermark" for property identification. This new watermarking technology is based on a unique steganographic or "hidden writing" digital signature, implemented in tiny quantities of gamma-ray-emitting radioisotopic material combinations, generally covertly emplaced on or within an object. This digital signature may be readily recovered at distant future times, by placing a sensitive, high energy-resolution gamma-ray detecting instrument reasonably precisely over the location of the watermark, which location may be known only to the object's owner; however, the signature is concealed from all ordinary detection means because its exceedingly low level of activity is obscured by the natural radiation background (including the gamma radiation naturally emanating from the object itself, from cosmic radiation and material surroundings, from human bodies, etc.). The "watermark" is used in object-tagging for establishing object identity, history or ownership. It thus may serve as an aid to law enforcement officials in identifying stolen property and prosecuting theft thereof. Highly effective, potentially very low cost identification-on demand of items of most all types is thus made possible.

Fermi LAT Search for Dark Matter in Gamma-Ray Lines and the Inclusive Photon Spectrum

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Albert, A.; Baldini, L.; Barbiellini, G.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.;

Fermi LAT search for dark matter in gamma-ray lines and the inclusive photon spectrum

DOE PAGES

Ackermann, M.

2012-07-05

Dark matter particle annihilation or decay can produce monochromatic gamma-ray lines and contribute to the diffuse gamma-ray background. Furthermore, we present the flux upper limits for gamma-ray spectral lines from 7 to 200 GeV and for the diffuse gamma-ray background from 4.8 GeV to 264 GeV obtained from two years of Fermi Large Area Telescope data integrated over most of the sky. Here, we give cross-section upper limits and decay lifetime lower limits for dark matter models that produce gamma-ray lines or contribute to the diffuse spectrum, including models proposed as explanations of the PAMELA and Fermi cosmic-ray data.

Effect of gamma ray and high-energy oxygen ion radiation on electrical and optical properties of MCT epitaxial layers

NASA Astrophysics Data System (ADS)

Sitharaman, S.; Kanjilal, D.; Arora, S. K.; Ganguly, S. K.; Nagpal, Anjana; Gautam, Madhukar; Raman, R.; Kumar, Shiv; Prakash, V. R.; Gupta, S. C.

1999-11-01

Hg1-xCdxTe epitaxial layers grown from Te-rich solution have been exposed to Gamma ray radiation up to 650 Grey using Co60 and high energy oxygen radiation at 100Mev. The electrical resistivity, carrier density and Hall mobility values at 77K and IR transmission at 300K have been measured in n,p and compensated epilayers both before and after irradiation. These properties are very much affected by these radiations. In the uncompensated p-type epitaxial layers both types of radiation produced an increase in extrinsic carrier density and a corresponding decrease in Hall mobility. It is observed that both types of radiation have significant effect on the compensated layers and the degree of compensation is greatly reduced by the oxygen irradiation. The 100 Mev oxygen irradiation produced an apparent shift in the bandgap towards shorter wavelength and the absorption below the energy gap is reduced as shown by FTIR measurements, whereas Gamma ray radiation up to the dose 650 Grey did not have any effect on optical properties. These results show the ability of oxygen radiation to passivate the activity of residual impurities or defects.

Gamma radiation effects on polydimethylsiloxane rubber foams under different radiation conditions

NASA Astrophysics Data System (ADS)

Sui, H. L.; Liu, X. Y.; Zhong, F. C.; Li, X. Y.; Wang, L.; Ju, X.

2013-07-01

Polydimethylsiloxane rubber foams were irradiated by gamma ray under different radiation conditions designed by orthogonal design method. Compression set measurement, infrared attenuated total reflectance spectroscopy (ATR) and X-ray induced photoelectron spectroscopy (XPS) were used. Three aging factors' influence effects on the mechanical property and chemical structure were studied. It was found that among the three factors and the chosen levels, both properties were affected most by radiation dose, while radiation dose rate had no obvious influence on both properties. The stiffening of the rubber foams was caused by cross-linking reactions in the Si-CH3. At the same radiation dose, the rigidity of the foams irradiated in air was lower than that in nitrogen. When polydimethylsiloxane was irradiated at a high dose in sealed nitrogen atmosphere, carbon element distribution would be changed. Hydrocarbons produced by gamma ray in the sealed tube would make the carbon content in the skin-deep higher than that in the middle, which indicated that polydimethylsiloxane rubber foams storing in a sealed atmosphere filled with enough hydrocarbons should be helpful to extend the service life.

LaCl3:Ce Coincidence Signatures to Calibrate Gamma-ray Detectors

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

McIntyre, Justin I.; Schrom, Brian T.; Cooper, Matthew W.

Abstract Calibrating the gamma-ray detection efficiency of radiation detectors in a field environment is difficult under most circumstances. To counter this problem we have developed a technique that uses a Cerium doped Lanthanum-Tri-Chloride (LaCl3:Ce) scintillation detector to provide gated gammas[ , ]. Exploiting the inherent radioactivity of the LaCl3:Ce due to the long-lived radioactive isotope 138La (t1/2 = 1.06 x 1011 yrs) allows the use of the 788 and 1436-keV gammas as a measure of efficiency. In this paper we explore the effectiveness of using the beta-gamma coincidences radiation LaCl3:Ce detector to calibrate the energy and efficiency of a numbermore » of gamma-ray detectors.« less

Gamma-ray mirror technology for NDA of spent fuel

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

Descalle, M. A.; Ruz-Armendariz, J.; Decker, T.

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

Applying the new gamma ray imager diagnostic to measurements of runaway electron Bremsstrahlung radiation in the DIII-D Tokamak (invited)

NASA Astrophysics Data System (ADS)

Cooper, C. M.; Pace, D. C.; Paz-Soldan, C.; Commaux, N.; Eidietis, N. W.; Hollmann, E. M.; Shiraki, D.

2016-11-01

A new gamma ray imager (GRI) is developed to probe the electron distribution function with 2D spatial resolution during runaway electron (RE) experiments at the DIII-D tokamak. The diagnostic is sensitive to 0.5-100 MeV gamma rays, allowing characterization of the RE distribution function evolution during RE growth and dissipation. The GRI consists of a lead "pinhole camera" mounted on the DIII-D midplane with 123 honeycombed tangential chords 20 cm wide that span the vessel interior. Up to 30 bismuth germanate (BGO) scintillation detectors capture RE bremsstrahlung radiation for Pulse Height Analysis (PHA) capable of discriminating up to 20 000 pulses per second. Digital signal processing routines combining shaping filters are performed during PHA to reject noise and record gamma ray energy. The GRI setup and PHA algorithms will be described and initial data from experiments will be presented. A synthetic diagnostic is developed to generate the gamma ray spectrum of a GRI channel given the plasma information and a prescribed distribution function. Magnetic reconstructions of the plasma are used to calculate the angle between every GRI sightline and orient and discriminate gamma rays emitted by a field-aligned RE distribution function.

Applying the new gamma ray imager diagnostic to measurements of runaway electron Bremsstrahlung radiation in the DIII-D Tokamak (invited).

PubMed

Cooper, C M; Pace, D C; Paz-Soldan, C; Commaux, N; Eidietis, N W; Hollmann, E M; Shiraki, D

2016-11-01

A new gamma ray imager (GRI) is developed to probe the electron distribution function with 2D spatial resolution during runaway electron (RE) experiments at the DIII-D tokamak. The diagnostic is sensitive to 0.5-100 MeV gamma rays, allowing characterization of the RE distribution function evolution during RE growth and dissipation. The GRI consists of a lead "pinhole camera" mounted on the DIII-D midplane with 123 honeycombed tangential chords 20 cm wide that span the vessel interior. Up to 30 bismuth germanate (BGO) scintillation detectors capture RE bremsstrahlung radiation for Pulse Height Analysis (PHA) capable of discriminating up to 20 000 pulses per second. Digital signal processing routines combining shaping filters are performed during PHA to reject noise and record gamma ray energy. The GRI setup and PHA algorithms will be described and initial data from experiments will be presented. A synthetic diagnostic is developed to generate the gamma ray spectrum of a GRI channel given the plasma information and a prescribed distribution function. Magnetic reconstructions of the plasma are used to calculate the angle between every GRI sightline and orient and discriminate gamma rays emitted by a field-aligned RE distribution function.

Arcsec source location measurements in gamma-ray astronomy from a lunar observatory

NASA Astrophysics Data System (ADS)

Koch, D. G.; Hughes, B. E.

1990-03-01

The physical processes typically used in the detection of high energy gamma-rays do not permit good angular resolution, which makes difficult the unambiguous association of discrete gamma-ray sources with objects emitting at other wavelengths. This problem can be overcome by placing gamma-ray detectors on the moon and using the horizon as an occulting edge to achieve arcsec resolution. For the purpose of discussion, this concept is examined for gamma rays above about 20 MeV for which pair production dominates the detection process and locally-generated nuclear gamma rays do not contribute to the background.

AN ORIENTATIONAL RESPONSE TO WEAK GAMMA RADIATION

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

Brown, F.A. Jr.

1963-10-01

The common planarian worm, Duesia dorotocephsla, displays a significant orientational response to increase in Cs/sup 137/ gamma radiation when the increase is no greater than six times background. The worms are able to distinguish the direction of the weak gamma source, turning away from it, whether it is presented on the right or left side. The response sign is, therefore, the same as that of the response of these negatively phototactic worms to visible light. There is a clear compass-directional relationship of the responsiveness to the experimental gamma radiation. A conspicuous negative response is present when the worms are travelingmore » northward or southward in the earth's field with the gamma change in an east-west axis. No statistically significant mean turning response to the gamma radiation is found when the worms are traveling eastward or westward in the earth's field with the gamma change in a north-south axis. The previously observed annual fluctuation in the character of the monthly orientational rhythm of north-directed worms has been confirmed in an additional year of study. During colder months, the rhythm is monthly; during warmer months it is semi-monthly. There is a semi-monthly fluctuation in the response of Dugesia to weak gamma radiation during mid-morning hours, the worms turning away from the source for four days prior to new end full moon, and toward it for two days following new and full moon. The stronger the field strength, up to 9 times backgound, the larger the amplitude of the rhythm. There is a direct relationship between intensities of gamma radiation between that of background and nine times backgound, and the strength of the negative response of the worms. Evidence suggests that the negative response of Dugesia to a gamma source may be modified by experimental alteration of the natural ambient electrostatic field. Some possible biological significances of this remarkable responsiveness to gamma radiation, and its particular

EGRET Diffuse Gamma Ray Maps Between 30 MeV and 10 GeV

NASA Technical Reports Server (NTRS)

Cillis, A, N.; Hartman, R. C.

2004-01-01

This paper presents all-sky maps of diffuse gamma radiation in various energy ranges between 30 MeV and 10 GeV, based on data collected by the EGRET instrument on the Compton Gamma Ray Observatory. Although the maps can be used for a variety of applications. the immediate goal is the generation of diffuse gamma-ray maps which can be used as a diffuse background/foreground for point source analysis of the data to be obtained from new high-energy gamma-ray missions like GLAST and AGILE. To generate the diffuse gamma maps from the raw EGRET maps, the point sources in the Third EGRET Catalog were subtracted out using the appropriate point spread function for each energy range. After that, smoothing was performed to minimize the effects of photon statistical noise. A smoothing length of 1 deg vas used for the Galactic plane maps. For the all-sky maps, a procedure was used which resulted in a smoothing length roughly equivalent to 4 deg. The result of this work is 16 maps of different energy intervals for absolute value of b < or equal to 20 deg, and 32 all-sky maps, 16 in equatorial coordinates (J2000) and 16 in Galactic coordinates.

EGRET Diffuse Gamma Ray Maps Between 30 MeV and 10 GeV

NASA Technical Reports Server (NTRS)

Cillis, A. N.; Hartman, R. C.

2004-01-01

This paper presents all-sky maps of diffuse gamma radiation in various energy ranges between 30 MeV and 10 GeV, based on data collected by the EGRET instrument on the Compton Gamma Ray Observatory. Although the maps can be used for a variety of applications, the immediate goal is the generation of diffuse gamma-ray maps which can be used as a diffuse background/foreground for point source analysis of the data to be obtained from new high-energy gamma-ray missions like GLAST and AGILE. To generate the diffuse gamma maps from the raw EGRET maps, the point sources in the Third EGRET Catalog were subtracted out using the appropriate point spread function for each energy range. After that, smoothing was performed to minimize the effects of photon statistical noise. A smoothing length of 1deg was used for the Galactic plane maps. For the all-sky maps, a procedure was used which resulted in a smoothing length roughly equivalent to 4deg. The result of this work is 16 maps of different energy intervals for [b]less than or equal to 20deg, and 32 all-sky maps, 16 in equatorial coordinates (J2000) and 16 in Galactic coordinates.

Radiation detection system for portable gamma-ray spectroscopy

DOEpatents

Rowland, Mark S [Alamo, CA; Howard, Douglas E [Livermore, CA; Wong, James L [Dublin, CA; Jessup, James L [Tracy, CA; Bianchini, Greg M [Livermore, CA; Miller, Wayne O [Livermore, CA

2006-06-20

A portable gamma ray detection apparatus having a gamma ray detector encapsulated by a compact isolation structure having at least two volumetrically-nested enclosures where at least one is a thermal shield. The enclosures are suspension-mounted to each other to successively encapsulate the detector without structural penetrations through the thermal shields. A low power cooler is also provided capable of cooling the detector to cryogenic temperatures without consuming cryogens, due to the heat load reduction by the isolation structure and the reduction in the power requirements of the cooler. The apparatus also includes a lightweight portable power source for supplying power to the apparatus, including to the cooler and the processing means, and reducing the weight of the apparatus to enable handheld operation or toting on a user's person.

A New Determination of the Extragalactic Diffuse X-Ray Background from EGRET Data

NASA Technical Reports Server (NTRS)

Strong, Andrew W.; Moskalenko, Igor V.; Reimer, Olaf

2004-01-01

We use the GALPROP model for cosmic-ray propagation to obtain a new estimate of the Galactic component of gamma rays, and show that away from the Galactic plane it gives an accurate prediction of the observed EGRET intensities in the energy range 30 MeV - 50 GeV. On this basis we re-evaluate the extragalactic gamma-ray background. We find that for some energies previous work underestimated the Galactic contribution at high latitudes and hence overestimated the background. Our new background spectrum shows a positive curvature similar to that expected for models of the extragalactic emission based on the blazar population.

Simulating Terrestrial Gamma-ray Flashes using SWORD (Invited)

NASA Astrophysics Data System (ADS)

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

2013-12-01

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

Observations of TeV Gamma Rays from Supernova Remnants

NASA Astrophysics Data System (ADS)

Buckley, James H.

1994-12-01

Measurements of the gamma ray flux from a number of supernova remnants (SNRs) at energies above 250 GeV have been made with the Whipple Imaging air \\v Cerenkov detector. Observation of the gamma ray emission of SNRs at energies above 1 GeV should provide a sensitive test of shock acceleration models of particle acceleration in SNRs. Gamma-ray luminosities of supernova remnants are well constrained by the observed supernova rate and the cosmic ray flux if supernovae are indeed the source of cosmic rays. Drury et al. (Astron. Astrophys. 287, 959 (1994)) predict that the luminosity of nearby Sedov-phase SNRs should be observable by the Whipple telescope. In this model, diffusive shock acceleration produces energetic charged particles which interact with the ambient medium forming gamma rays. There is an indication that a number of unidentified EGRET sources may correspond to supernova remnants (G. Kanbach, private communication), although at these energies (>100 MeV) the diffuse background is somewhat uncertain. Measurements of the gamma-ray flux with the Whipple instrument have a similar sensitivity to the EGRET detector for a source spectral index of 2.15, and less sensitivity to diffuse background. A number of observations of SNRs including: Tycho, W66, IC443, and others have been made. Currently for Tycho an upper limit of 9times 10(-12) cm(-2) sec(-1) is obtained. The status of these observations will be presented, and it will be shown that these measurements combined with the EGRET observations are beginning to provide a useful constraint on models of cosmic ray origin. Gamma-ray observations may also be used to constrain models of particle acceleration in SNRs exhibiting pulser-powered synchrotron nebula (plerions). The status of observations of this class of objects, including the Crab nebula, will also be presented. Supported in part by the U.S. Dept. of Energy.

A study of the sensitivity of an imaging telescope (GRITS) for high energy gamma-ray astronomy

NASA Technical Reports Server (NTRS)

Yearian, Mason R.

1990-01-01

When a gamma-ray telescope is placed in Earth orbit, it is bombarded by a flux of cosmic protons much greater than the flux of interesting gammas. These protons can interact in the telescope's thermal shielding to produce detectable gamma rays, most of which are vetoed. Since the proton flux is so high, the unvetoed gamma rays constitute a significant background relative to some weak sources. This background increases the observing time required to pinpoint some sources and entirely obscures other sources. Although recent telescopes have been designed to minimize this background, its strength and spectral characteristics were not previously calculated in detail. Monte Carlo calculations are presented which characterize the strength, spectrum and other features of the cosmic proton background using FLUKA, a hadronic cascade program. Several gamma-ray telescopes, including SAS-2, EGRET and the Gamma Ray Imaging Telescope System (GRITS), are analyzed, and their proton-induced backgrounds are characterized. In all cases, the backgrounds are either shown to be low relative to interesting signals or suggestions are made which would reduce the background sufficiently to leave the telescope unimpaired. In addition, several limiting cases are examined for comparison to previous estimates and calibration measurements.

Gamma-ray Pulsars: Models and Predictions

NASA Technical Reports Server (NTRS)

Harding Alice K.; White, Nicholas E. (Technical Monitor)

2000-01-01

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(exp 12) - 10(exp 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 of the primary curvature emission 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. Next-generation gamma-ray telescopes sensitive to GeV-TeV emission will provide critical tests of pulsar acceleration and emission mechanisms.

Gamma-ray vortices from nonlinear inverse Thomson scattering of circularly polarized light.

PubMed

Taira, Yoshitaka; Hayakawa, Takehito; Katoh, Masahiro

2017-07-10

Inverse Thomson scattering is a well-known radiation process that produces high-energy photons both in nature and in the laboratory. Nonlinear inverse Thomson scattering occurring inside an intense light field is a process which generates higher harmonic photons. In this paper, we theoretically show that the higher harmonic gamma-ray produced by nonlinear inverse Thomson scattering of circularly polarized light is a gamma-ray vortex, which means that it possesses a helical wave front and carries orbital angular momentum. Our work explains a recent experimental result regarding nonlinear inverse Thomson scattering that clearly shows an annular intensity distribution as a remarkable feature of a vortex beam. Our work implies that gamma-ray vortices should be produced in various situations in astrophysics in which high-energy electrons and intense circularly polarized light fields coexist. Nonlinear inverse Thomson scattering is a promising radiation process for realizing a gamma-ray vortex source based on currently available laser and accelerator technologies, which would be an indispensable tool for exploring gamma-ray vortex science.

77 FR 62267 - Proposed Extension of Existing Information Collection; Gamma Radiation Surveys

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-12

... Extension of Existing Information Collection; Gamma Radiation Surveys AGENCY: Mine Safety and Health...-9440 (voice); or 202-693-9441 (facsimile). SUPPLEMENTARY INFORMATION: I. Background Gamma radiation... debilitating occupational diseases. Natural sources include rocks, soils, and ground water. Gamma radiation...

The gamma-ray observatory

NASA Technical Reports Server (NTRS)

1991-01-01

An overview is given of the Gamma Ray Observatory (GRO) mission. Detection of gamma rays and gamma ray sources, operations using the Space Shuttle, and instruments aboard the GRO, including the Burst and Transient Source Experiment (BATSE), the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), and the Energetic Gamma Ray Experiment Telescope (EGRET) are among the topics surveyed.

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

NASA Astrophysics Data System (ADS)

An, H.

2017-10-01

We present broadband SED and light curve, and a wind interaction model for the gamma-ray binary 1FGL J1018.6-5856 (J1018) which exhibits double peaks in the X-ray light curve. Assuming that the X-ray to low-energy gamma-ray emission is produced by synchrotron radiation and high-energy gamma rays by inverse Compton scattering in the intrabinary shock (IBS), we model the broadband SED and light curve of J1018 using a two-component model having slow electrons in the shock and fast bulk-accelerated electrons at the skin of the shock. The model explains the broadband SED and light curve of J1018 qualitatively well. In particular, modeling the synchrotron emission constrains the orbital geometry. We discuss potential use of the model for other pulsar binaries.

Separation of gamma-ray and neutron events with CsI(Tl) pulse shape analysis

NASA Astrophysics Data System (ADS)

Ashida, Y.; Nagata, H.; Koshio, Y.; Nakaya, T.; Wendell, R.

2018-04-01

Fast neutrons are a large background to measurements of gamma-rays emitted from excited nuclei, such that detectors that can efficiently distinguish between the two are essential. In this paper we describe the separation of gamma-rays from neutrons with the pulse shape information of the CsI(Tl) scintillator, using a fast neutron beam and several gamma-ray sources. We find that a figure of merit optimized for this separation takes on large and stable values (nearly 4) between 5 and 10 MeV of electron equivalent deposited energy, the region of most interest to the study of nuclear de-excitation gamma-rays. Accordingly, this work demonstrates the ability of CsI(Tl) scintillators to reject neutron backgrounds to gamma-ray measurements at these energies.

Handheld dual thermal neutron detector and gamma-ray spectrometer

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

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

2017-05-02

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

X-Ray Spectral Diagnostics of Gamma-Ray Burst Environments.

PubMed

Paerels; Kuulkers; Heise; Liedahl

2000-05-20

Recently, detection of discrete features in the X-ray afterglow spectra of GRB 970508 and GRB 970828 was reported. The most natural interpretation of these features is that they are redshifted Fe K emission complexes. The identification of the line emission mechanism has drastic implications for the inferred mass of radiating material and hence the nature of the burst site. X-ray spectroscopy provides a direct observational constraint on these properties of gamma-ray bursters. We briefly discuss how these constraints arise in the context of an application to the spectrum of GRB 970508.

Very high-frequency gravitational waves from magnetars and gamma-ray bursts

NASA Astrophysics Data System (ADS)

Wen, Hao; Li, Fang-Yu; Li, Jin; Fang, Zhen-Yun; Beckwith, Andrew

2017-12-01

Extremely powerful astrophysical electromagnetic (EM) systems could be possible sources of high-frequency gravitational waves (HFGWs). Here, based on properties of magnetars and gamma-ray bursts (GRBs), we address “Gamma-HFGWs” (with very high-frequency around 1020 Hz) caused by ultra-strong EM radiation (in the radiation-dominated phase of GRB fireballs) interacting with super-high magnetar surface magnetic fields (˜1011 T). By certain parameters of distance and power, the Gamma-HFGWs would have far field energy density Ω gw around 10-6, and they would cause perturbed signal EM waves of ˜10-20 W/m2 in a proposed HFGW detection system based on the EM response to GWs. Specially, Gamma-HFGWs would possess distinctive envelopes with characteristic shapes depending on the particular structures of surface magnetic fields of magnetars, which could be exclusive features helpful to distinguish them from background noise. Results obtained suggest that magnetars could be involved in possible astrophysical EM sources of GWs in the very high-frequency band, and Gamma-HFGWs could be potential targets for observations in the future. Supported by National Natural Science Foundation of China (11605015, 11375279, 11205254, 11647307) and the Fundamental Research Funds for the Central Universities (106112017CDJXY300003, 106112017CDJXFLX0014)

Observation of nuclear reactors on satellites with a balloon-borne gamma-ray telescope

NASA Technical Reports Server (NTRS)

O'Neill, Terrence J.; Kerrick, Alan D.; Ait-Ouamer, Farid; Tumer, O. Tumay; Zych, Allen D.

1989-01-01

Four Soviet nuclear-powered satellites flying over a double Compton gamma-ray telescope resulted in the detection of gamma rays with 0.3-8.0 MeV energies on April 15, 1988, as the balloonborne telescope searched, from a 35-km altitude, for celestial gamma-ray sources. The satellites included Cosmos 1900 and 1932. The USSR is the only nation currently employing moderated nuclear reactors for satellite power; reactors in space may cause significant problems for gamma-ray astronomy by increasing backgrounds, especially in the case of gamma-ray bursts.

Gamma ray transients

NASA Technical Reports Server (NTRS)

Cline, Thomas L.

1987-01-01

The discovery of cosmic gamma ray bursts was made with systems designed at Los Alamos Laboratory for the detection of nuclear explosions beyond the atmosphere. HELIOS-2 was the first gamma ray burst instrument launched; its initial results in 1976, seemed to deepen the mystery around gamma ray transients. Interplanetary spacecraft data were reviewed in terms of explaining the behavior and source of the transients.

Angular power spectrum of the diffuse gamma-ray emission as measured by the Fermi Large Area Telescope and constraints on its dark matter interpretation

DOE PAGES

Fornasa, Mattia; Cuoco, Alessandro; Zavala, Jesús; ...

2016-12-09

The isotropic gamma-ray background arises from the contribution of unresolved sources, including members of confirmed source classes and proposed gamma-ray emitters such as the radiation induced by dark matter annihilation and decay. Clues about the properties of the contributing sources are imprinted in the anisotropy characteristics of the gamma-ray background. We use 81 months of Pass 7 Reprocessed data from the Fermi Large Area Telescope to perform a measurement of the anisotropy angular power spectrum of the gamma-ray background. Here, we analyze energies between 0.5 and 500 GeV, extending the range considered in the previous measurement based on 22 monthsmore » of data. We also compute, for the first time, the cross-correlation angular power spectrum between different energy bins. The derived angular spectra are compatible with being Poissonian, i.e. constant in multipole. Furthermore, the energy dependence of the anisotropy suggests that the signal is due to two populations of sources, contributing, respectively, below and above ~ 2 GeV . Finally, using data from state-of-the-art numerical simulations to model the dark matter distribution, we constrain the contribution from dark matter annihilation and decay in Galactic and extra-Galactic structures to the measured anisotropy. These constraints are competitive with those that can be derived from the average intensity of the isotropic gamma-ray background.« less

Recent high energy gamma-ray results from SAS-2

NASA Technical Reports Server (NTRS)

Thompson, D. J.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Bignami, G. F.; Ogelman, H. B.; Ozel, M. E.; Tumer, T.; Lamb, R. C.

1977-01-01

Recent developments in gamma-ray astronomy due to the results from SAS-2 have focused on two areas. First, the emission from the plane of the Galaxy is the dominant feature in the gamma-ray sky. The galactic latitude and longitude distributions are consistent with the concept that the high-energy radiation originates from cosmic rays interacting with interstellar matter, and the measurements support a galactic origin for cosmic rays. Second, searches of the SAS-2 data for emission from localized sources have shown three strong discrete gamma-ray sources: the Crab nebula and PSR 0531 + 21, the Vela supernova remnant and PSR 0833-45, and a source near galactic coordinates 193 deg longitude, +3 deg latitude, which does not appear to be associated with other known celestial objects. Evidence has also been found for pulsed gamma-ray emission from two other radio pulsars, PSR 1818-04 and PSR 1747-46. A localized source near longitudes 76-80 deg may be associated with the X-ray source Cyg X-3.

Stacking Searches for Greater Than 100 MeV Gamma Ray Emission from Radio Galaxies and Seyfert Galaxies

NASA Technical Reports Server (NTRS)

Cillis, A. N.; Hartman, R. C.; Bertsch, D. L.

2003-01-01

The EGRET telescope on CGRO detected more than sixty sources of high-energy gamma radiation associated with active galactic nuclei (AGN). All but one of those belong to the blazar subclass; the only exception is the nearby radio galaxy Centaurus A. Since there is no obvious reason other than proximity to expect Cen A to be the only non-blazar AGN emitting in high-energy gamma rays, we have utilized the "stacking" technique to search for $>100$-MeV emission from two non-blazar AGN subclasses, radio galaxies and Seyfert galaxies. Maps of gamma-ray counts, exposure, and diffuse background have been created, then co-added in varying numbers based on sorts by redshift, 5-GHZ flux density, and optical brightness, and finally tested for gamma-ray emission. No detection significance greater than $2\\sigma$ has been found for any subclass, sorting parameter, or number of objects co-added. Monte Carlo simulations have also been performed, to validate the technique and estimate the significance of the results.

Basics of Gamma Ray Detection

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

Stinnett, Jacob; Venkataraman, Ram

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

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

NASA Technical Reports Server (NTRS)

Becker, Peter A.; Kafatos, Menas

1995-01-01

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

Method of incident low-energy gamma-ray direction reconstruction in the GAMMA-400 gamma-ray space telescope

NASA Astrophysics Data System (ADS)

Kheymits, M. D.; Leonov, A. A.; Zverev, V. G.; Galper, A. M.; Arkhangelskaya, I. V.; Arkhangelskiy, A. I.; Suchkov, S. I.; Topchiev, N. P.; Yurkin, Yu T.; Bakaldin, A. V.; Dalkarov, O. D.

2016-02-01

The GAMMA-400 gamma-ray space-based telescope has as its main goals to measure cosmic γ-ray fluxes and the electron-positron cosmic-ray component produced, theoretically, in dark-matter-particles decay or annihilation processes, to search for discrete γ-ray sources and study them in detail, to examine the energy spectra of diffuse γ-rays — both galactic and extragalactic — and to study gamma-ray bursts (GRBs) and γ-rays from the active Sun. Scientific goals of GAMMA-400 telescope require fine angular resolution. The telescope is of a pair-production type. In the converter-tracker, the incident gamma-ray photon converts into electron-positron pair in the tungsten layer and then the tracks are detected by silicon- strip position-sensitive detectors. Multiple scattering processes become a significant obstacle in the incident-gamma direction reconstruction for energies below several gigaelectronvolts. The method of utilising this process to improve the resolution is proposed in the presented work.

Gamma Ray Astronomy

NASA Technical Reports Server (NTRS)

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.

Radiation anomaly detection algorithms for field-acquired gamma energy spectra

NASA Astrophysics Data System (ADS)

Mukhopadhyay, Sanjoy; Maurer, Richard; Wolff, Ron; Guss, Paul; Mitchell, Stephen

2015-08-01

The Remote Sensing Laboratory (RSL) is developing a tactical, networked radiation detection system that will be agile, reconfigurable, and capable of rapid threat assessment with high degree of fidelity and certainty. Our design is driven by the needs of users such as law enforcement personnel who must make decisions by evaluating threat signatures in urban settings. The most efficient tool available to identify the nature of the threat object is real-time gamma spectroscopic analysis, as it is fast and has a very low probability of producing false positive alarm conditions. Urban radiological searches are inherently challenged by the rapid and large spatial variation of background gamma radiation, the presence of benign radioactive materials in terms of the normally occurring radioactive materials (NORM), and shielded and/or masked threat sources. Multiple spectral anomaly detection algorithms have been developed by national laboratories and commercial vendors. For example, the Gamma Detector Response and Analysis Software (GADRAS) a one-dimensional deterministic radiation transport software capable of calculating gamma ray spectra using physics-based detector response functions was developed at Sandia National Laboratories. The nuisance-rejection spectral comparison ratio anomaly detection algorithm (or NSCRAD), developed at Pacific Northwest National Laboratory, uses spectral comparison ratios to detect deviation from benign medical and NORM radiation source and can work in spite of strong presence of NORM and or medical sources. RSL has developed its own wavelet-based gamma energy spectral anomaly detection algorithm called WAVRAD. Test results and relative merits of these different algorithms will be discussed and demonstrated.

Ground-based very high energy gamma ray astronomy: Observational highlights

NASA Technical Reports Server (NTRS)

Turver, K. E.

1986-01-01

It is now more than 20 years since the first ground based gamma ray experiments involving atmospheric Cerenkov radiation were undertaken. The present highlights in observational ground-based very high energy (VHE) gamma ray astronomy and the optimism about an interesting future for the field follow progress in these areas: (1) the detection at increased levels of confidence of an enlarged number of sources so that at present claims were made for the detection, at the 4 to 5 sd level of significance, of 8 point sources; (2) the replication of the claimed detections with, for the first time, confirmation of the nature and detail of the emission; and (3) the extension of gamma ray astronomy to the ultra high energy (UHE) domain. The pattern, if any, to emerge from the list of sources claimed so far is that X-ray binary sources appear to be copious emitters of gamma rays over at least 4 decades of energy. These X-ray sources which behave as VHE and UHE gamma ray emitters are examined.

The Advanced Gamma-ray Imaging System (AGIS): Simulation Studies

NASA Astrophysics Data System (ADS)

Fegan, Stephen; Buckley, J. H.; Bugaev, S.; Funk, S.; Konopelko, A.; Maier, G.; Vassiliev, V. V.; Simulation Studies Working Group; AGIS Collaboration

2008-03-01

The Advanced Gamma-ray Imaging System (AGIS) is a concept for the next generation instrument in ground-based very high energy gamma-ray astronomy. It has the goal of achieving significant improvement in sensitivity over current experiments. We present the results of simulation studies of various possible designs for AGIS. The primary characteristics of the array performance, collecting area, angular resolution, background rejection, and sensitivity are discussed.

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

NASA Technical Reports Server (NTRS)

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.

Studies of the Low-energy Gamma Background

NASA Astrophysics Data System (ADS)

Bikit, K.; Mrđa, D.; Bikit, I.; Slivka, J.; Veskovic, M.; Knezevic, D.

The investigations of contribution to the low-energy part of background gamma spectrum (below 100 keV) and knowing detection efficiency for this region are important for both, a fundamental, as well as for applied research. In this work, the components contributing to the low-energy region of background gamma spectrum for shielded detector are analyzed, including the production and spectral distribution of muon-induced continuous low-energy radiation in the vicinity of high-purity germanium detector.In addition, the detection efficiency for low energy gamma region is determined using the GEANT 4 simulation package. This technique offers excellent opportunity to predict the detection response in mentioned region. Unfortunately, the frequently weakly known dead layer thickness on the surface of the extended-range detector, as well as some processes which are not incorporated in simulation (e.g. charge collection from detector active volume) may limit the reliability of simulation technique. Thus, the 14, 17, 21, 26, 33, 59.5 keV transitions in the calibrated 241Am point source were used to check the simulated efficiencies.

Limits on dark matter annihilation signals from the Fermi LAT 4-year measurement of the isotropic gamma-ray background

DOE PAGES

Ackermann, M.

2015-09-02

We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months of Fermi Large Area Telescope (LAT) observations. An improved theoretical description of the cosmological DM annihilation signal, based on two complementary techniques and assuming generic weakly interacting massive particle (WIMP) properties, renders more precise predictions compared to previous work. More specifically, we estimate the cosmologically-induced gamma-ray intensity to have an uncertainty of a factor ~ 20 in canonical setups. We consistently include both the Galactic and extragalactic signals under the same theoretical framework, and study the impact of the former onmore » the IGRB spectrum derivation. We find no evidence for a DM signal and we set limits on the DM-induced isotropic gamma-ray signal. Our limits are competitive for DM particle masses up to tens of TeV and, indeed, are the strongest limits derived from Fermi LAT data at TeV energies. This is possible thanks to the new Fermi LAT IGRB measurement, which now extends up to an energy of 820 GeV. As a result, we quantify uncertainties in detail and show the potential this type of search offers for testing the WIMP paradigm with a complementary and truly cosmological probe of DM particle signals.« less

Limits on dark matter annihilation signals from the Fermi LAT 4-year measurement of the isotropic gamma-ray background

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

Collaboration: Fermi LAT Collaboration

2015-09-01

We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months of Fermi Large Area Telescope (LAT) observations. An improved theoretical description of the cosmological DM annihilation signal, based on two complementary techniques and assuming generic weakly interacting massive particle (WIMP) properties, renders more precise predictions compared to previous work. More specifically, we estimate the cosmologically-induced gamma-ray intensity to have an uncertainty of a factor ∼ 20 in canonical setups. We consistently include both the Galactic and extragalactic signals under the same theoretical framework, and study the impact of the former on themore » IGRB spectrum derivation. We find no evidence for a DM signal and we set limits on the DM-induced isotropic gamma-ray signal. Our limits are competitive for DM particle masses up to tens of TeV and, indeed, are the strongest limits derived from Fermi LAT data at TeV energies. This is possible thanks to the new Fermi LAT IGRB measurement, which now extends up to an energy of 820 GeV. We quantify uncertainties in detail and show the potential this type of search offers for testing the WIMP paradigm with a complementary and truly cosmological probe of DM particle signals.« less

Applying the new gamma ray imager diagnostic to measurements of runaway electron Bremsstrahlung radiation in the DIII-D Tokamak (invited)

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

Cooper, C. M., E-mail: coopercm@fusion.gat.com; Pace, D. C.; Paz-Soldan, C.

2016-11-15

A new gamma ray imager (GRI) is developed to probe the electron distribution function with 2D spatial resolution during runaway electron (RE) experiments at the DIII-D tokamak. The diagnostic is sensitive to 0.5–100 MeV gamma rays, allowing characterization of the RE distribution function evolution during RE growth and dissipation. The GRI consists of a lead “pinhole camera” mounted on the DIII-D midplane with 123 honeycombed tangential chords 20 cm wide that span the vessel interior. Up to 30 bismuth germanate (BGO) scintillation detectors capture RE bremsstrahlung radiation for Pulse Height Analysis (PHA) capable of discriminating up to 20 000 pulses permore » second. Digital signal processing routines combining shaping filters are performed during PHA to reject noise and record gamma ray energy. The GRI setup and PHA algorithms will be described and initial data from experiments will be presented. A synthetic diagnostic is developed to generate the gamma ray spectrum of a GRI channel given the plasma information and a prescribed distribution function. Magnetic reconstructions of the plasma are used to calculate the angle between every GRI sightline and orient and discriminate gamma rays emitted by a field-aligned RE distribution function.« less

Applying the new gamma ray imager diagnostic to measurements of runaway electron Bremsstrahlung radiation in the DIII-D Tokamak (invited)

DOE PAGES

Cooper, C. M.; Pace, D. C.; Paz-Soldan, C.; ...

2016-08-30

A new gamma ray imager (GRI) is developed to probe the electron distribution function with 2D spatial resolution during runaway electron (RE) experiments at the DIII-D tokamak. The diagnostic is sensitive to 0.5-100 MeV gamma rays, allowing characterization of the RE distribution function evolution during RE growth and dissipation. The GRI consists of a lead "pinhole camera" mounted on the DIII-D midplane with 123 honeycombed tangential chords 20 cm wide that span the vessel interior. Up to 30 bismuth germanate (BGO) scintillation detectors capture RE bremsstrahlung radiation for Pulse Height Analysis (PHA) capable of discriminating up to 20,000 pulses permore » second. Digital signal processing routines combining shaping filters are performed during PHA to reject noise and record gamma ray energy. The GRI setup and PHA algorithms will be described and initial data from experiments will be presented. A synthetic diagnostic is developed to generate the gamma ray spectrum of a GRI channel given the plasma information and a prescribed distribution function. Furthermore, magnetic reconstructions of the plasma are used to calculate the angle between every GRI sightline and orient and discriminate gamma rays emitted by a field-aligned RE distribution function.« less

Analysis of Data from the Balloon Borne Gamma RAy Polarimeter Experiment (GRAPE)

NASA Astrophysics Data System (ADS)

Wasti, Sambid K.; Bloser, Peter F.; Legere, Jason S.; McConnell, Mark L.; Ryan, James M.

2016-04-01

The Gamma Ray Polarimeter Experiment (GRAPE), a balloon borne polarimeter for 50~300 keV gamma rays, successfully flew in 2011 and 2014. The main goal of these balloon flights was to measure the gamma ray polarization of the Crab Nebula. Analysis of data from the first two balloon flights of GRAPE has been challenging due to significant changes in the background level during each flight. We have developed a technique based on the Principle Component Analysis (PCA) to estimate the background for the Crab observation. We found that the background depended mostly on the atmospheric depth, pointing zenith angle and instrument temperatures. Incorporating Anti-coincidence shield data (which served as a surrogate for the background) was also found to improve the analysis. Here, we present the calibration data and describe the analysis done on the GRAPE 2014 flight data.

Neutron/Gamma-ray discrimination through measures of fit

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

Amiri, Moslem; Prenosil, Vaclav; Cvachovec, Frantisek

2015-07-01

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

Development of a digital method for neutron/gamma-ray discrimination based on matched filtering

NASA Astrophysics Data System (ADS)

Korolczuk, S.; Linczuk, M.; Romaniuk, R.; Zychor, I.

2016-09-01

Neutron/gamma-ray discrimination is crucial for measurements with detectors sensitive to both neutron and gamma-ray radiation. Different techniques to discriminate between neutrons and gamma-rays based on pulse shape analysis are widely used in many applications, e.g., homeland security, radiation dosimetry, environmental monitoring, fusion experiments, nuclear spectroscopy. A common requirement is to improve a radiation detection level with a high detection reliability. Modern electronic components, such as high speed analog to digital converters and powerful programmable digital circuits for signal processing, allow us to develop a fully digital measurement system. With this solution it is possible to optimize digital signal processing algorithms without changing any electronic components in an acquisition signal path. We report on results obtained with a digital acquisition system DNG@NCBJ designed at the National Centre for Nuclear Research. A 2'' × 2'' EJ309 liquid scintillator was used to register mixed neutron and gamma-ray radiation from PuBe sources. A dedicated algorithm for pulse shape discrimination, based on real-time filtering, was developed and implemented in hardware.

Delayed Gamma-ray Spectroscopy for Safeguards Applications

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

Mozin, Vladimir

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 inmore » 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

Direct measurement of 235U in spent fuel rods with Gamma-ray mirrors

NASA Astrophysics Data System (ADS)

Ruz, J.; Brejnholt, N. F.; Alameda, J. B.; Decker, T. A.; Descalle, M. A.; Fernandez-Perea, M.; Hill, R. M.; Kisner, R. A.; Melin, A. M.; Patton, B. W.; Soufli, R.; Ziock, K.; Pivovaroff, M. J.

2015-03-01

Direct measurement of plutonium and uranium X-rays and gamma-rays is a highly desirable non-destructive analysis method for the use in reprocessing fuel environments. The high background and intense radiation from spent fuel make direct measurements difficult to implement since the relatively low activity of uranium and plutonium is masked by the high activity from fission products. To overcome this problem, we make use of a grazing incidence optic to selectively reflect Kα and Kβ fluorescence of Special Nuclear Materials (SNM) into a high-purity position-sensitive germanium detector and obtain their relative ratios.

Effects of gamma radiation on the chromosomes of Gryllidae (orthoptera)

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

Lim, H.C.; Kevan, D.K.; Vickery, V.R.

1972-12-01

BS>Six species if Gryllidae (orthoptera), Gryllus assimilis, G, Bim aculatus, G. pennsylvanicus, Acheta domesticus, Scapipedus marginatus, and Allonemobius allardi, were subjected to gamma radiation treatment (dosages varied from 1000 rads to 2446 rads) in order to induce chromosomal abnormalities. Gamma radiation was found to affect development, survival, and reproduction. Effects of gamma rays were similar in all of the species studied, but sensitivity varied between the different species. (auth)

Exploring atmospheric radon with airborne gamma-ray spectroscopy

NASA Astrophysics Data System (ADS)

Baldoncini, Marica; Albéri, Matteo; Bottardi, Carlo; Minty, Brian; Raptis, Kassandra G. C.; Strati, Virginia; Mantovani, Fabio

2017-12-01

222Rn is a noble radioactive gas produced along the 238U decay chain, which is present in the majority of soils and rocks. As 222Rn is the most relevant source of natural background radiation, understanding its distribution in the environment is of great concern for investigating the health impacts of low-level radioactivity and for supporting regulation of human exposure to ionizing radiation in modern society. At the same time, 222Rn is a widespread atmospheric tracer whose spatial distribution is generally used as a proxy for climate and pollution studies. Airborne gamma-ray spectroscopy (AGRS) always treated 222Rn as a source of background since it affects the indirect estimate of equivalent 238U concentration. In this work the AGRS method is used for the first time for quantifying the presence of 222Rn in the atmosphere and assessing its vertical profile. High statistics radiometric data acquired during an offshore survey are fitted as a superposition of a constant component due to the experimental setup background radioactivity plus a height dependent contribution due to cosmic radiation and atmospheric 222Rn. The refined statistical analysis provides not only a conclusive evidence of AGRS 222Rn detection but also a (0.96 ± 0.07) Bq/m3 222Rn concentration and a (1318 ± 22) m atmospheric layer depth fully compatible with literature data.

Radiation-mediated Shocks in Gamma-Ray Bursts: Pair Creation

NASA Astrophysics Data System (ADS)

Lundman, Christoffer; Beloborodov, Andrei M.; Vurm, Indrek

2018-05-01

Relativistic sub-photospheric shocks are a possible mechanism for producing prompt gamma-ray burst (GRB) emission. Such shocks are mediated by scattering of radiation. We introduce a time-dependent, special relativistic code which dynamically couples Monte Carlo radiative transfer to the flow hydrodynamics. The code also self-consistently follows electron–positron pair production in photon–photon collisions. We use the code to simulate shocks with properties relevant to GRBs. We focus on plane-parallel solutions, which are accurate deep below the photosphere. The shock generates a power-law photon spectrum through the first-order Fermi mechanism, extending upward from the typical upstream photon energy. Strong (high Mach number) shocks produce rising νF ν spectra. We observe that in non-relativistic shocks the spectrum extends to {E}\\max ∼ {m}e{v}2, where v is the speed difference between the upstream and downstream. In relativistic shocks the spectrum extends to energies E> 0.1 {m}e{c}2 where its slope softens due to Klein–Nishina effects. Shocks with Lorentz factors γ > 1.5 are prolific producers of electron–positron pairs, yielding hundreds of pairs per proton. The main effect of pairs is to reduce the shock width by a factor of ∼ {Z}+/- -1. Most pairs annihilate far downstream of the shock, and the radiation spectrum relaxes to a Wien distribution, reaching equilibrium with the plasma at a temperature determined by the shock jump conditions and the photon number per proton. We discuss the implications of our results for observations of radiation generated by sub-photospheric shocks.

New shield for gamma-ray spectrometry

NASA Technical Reports Server (NTRS)

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.

Study on Effects of Gamma-Ray Irradiation on TlBr Semiconductor Detectors

NASA Astrophysics Data System (ADS)

Matsumura, Motohiro; Watanabe, Kenichi; Yamazaki, Atsushi; Uritani, Akira; Kimura, Norihisa; Nagano, Nobumichi; Hitomi, Keitaro

Radiation hardness of thallium bromide (TlBr) semiconductor detectors to 60Co gamma-ray irradiation was evaluated. The energy spectra and μτ products of electrons were measured to evaluate the irradiation effects. No significant degradation of spectroscopic performance of the TlBr detector for 137Cs gamma-rays was observed up to 45 kGy irradiation. Although the μτ products of electrons in the TlBr detector slightly decreased, position of the photo-peak was stable without significant degradation after the gamma-ray irradiation. We confirmed that the TlBr semiconductor detector has a high tolerance for gamma-ray irradiation at least up to 45 kGy.

Recombining plasma in the gamma-ray-emitting mixed-morphology supernova remnant 3C 391

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

Ergin, T.; Sezer, A.; Saha, L.

2014-07-20

A group of middle-aged mixed-morphology (MM) supernova remnants (SNRs) interacting with molecular clouds (MCs) has been discovered to be strong GeV gamma-ray emitters by the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope (Fermi-LAT). The recent observations of the Suzaku X-ray satellite have revealed that some of these interacting gamma-ray-emitting SNRs, such as IC443, W49B, W44, and G359.1-0.5, have overionized plasmas. 3C 391 (G31.9+0.0) is another Galactic MM SNR interacting with MCs. It was observed in GeV gamma rays by Fermi-LAT as well as in the 0.3-10.0 keV X-ray band by Suzaku. In this work, 3C 391more » was detected in GeV gamma rays with a significance of ∼18σ and we showed that the GeV emission is point-like in nature. The GeV gamma-ray spectrum was shown to be best explained by the decay of neutral pions assuming that the protons follow a broken power-law distribution. We revealed radiative recombination structures of silicon and sulfur from 3C 391 using Suzaku data. In this paper, we discuss the possible origin of this type of radiative plasma and hadronic gamma rays.« less

Gamma-Ray Emission in Dissipative Pulsar Magnetospheres: from Theory to Fermi Observations

NASA Technical Reports Server (NTRS)

Kalapotharakos, Konstantinos; Harding, Alice K.; Kazanas, Demosthenes

2014-01-01

We compute the patterns of gamma-ray emission due to curvature radiation in dissipative pulsar magnetospheres. Our ultimate goal is to construct macrophysical models that are able to reproduce the observed gamma-ray light curve phenomenology recently published in the Second Fermi Pulsar Catalog. We apply specific forms of Ohm's law on the open field lines using a broad range for the macroscopic conductivity values that result in solutions ranging, from near-vacuum to near-force-free. Using these solutions, we generate model gamma-ray light curves by calculating realistic trajectories and Lorentz factors of radiating particles under the influence of both the accelerating electric fields and curvature radiation reaction. We further constrain our models using the observed dependence of the phase lags between the radio and gamma-ray emission on the gamma-ray peak separation. We perform a statistical comparison of our model radio-lag versus peak-separation diagram and the one obtained for the Fermi standard pulsars. We find that for models of uniform conductivity over the entire open magnetic field line region, agreement with observations favors higher values of this parameter. We find, however, significant improvement in fitting the data with models that employ a hybrid form of conductivity, specifically, infinite conductivity interior to the light cylinder and high but finite conductivity on the outside. In these models the gamma-ray emission is produced in regions near the equatorial current sheet but modulated by the local physical properties. These models have radio lags near the observed values and statistically best reproduce the observed light curve phenomenology. Additionally, they also produce GeV photon cut-off energies.

High energy gamma-ray astronomy observations of Geminga with the VERITAS array

NASA Astrophysics Data System (ADS)

Finnegan, Gary Marvin

The closest known supernova remnant and pulsar is Geminga. The Geminga pulsar is the first pulsar to have ever been detected initially by gamma rays and the first pulsar in a class of radio-quiet pulsars. In 2007, the Milagro collaboration detected a large angularly extended (˜ 2.6°) emission of high energy gamma rays (˜ 20 TeV ) that was positionally coincident with Geminga. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is a ground- based observatory with four imaging Cherenkov telescopes with an energy range between 100 GeV to more than 30 TeV. The imaging Cherenkov telescopes detect the Cherenkov light from charged particles in electromagnetic air showers initiated by high energy particles such as gamma rays and cosmic rays. Most gamma-ray sources detected by VERITAS are point like sources, which have an angular extension smaller than the angular resolution of the telescopes (˜ 0.1°). For a point source, the background noise can be measured in the same field of view (FOV) as the source. For an angularly extended object, such as Geminga, an external FOV from the source region must be used to estimate the background noise, to avoid contamination from the extended source region. In this dissertation, I describe a new analysis procedure that is designed to increase the observation sensitivity of angularly extended objects like Geminga. I apply this procedure to a known extended gamma-ray source, Boomerang, as well as Geminga. The results indicate the detection of very high energy emission from the Geminga region at the level of 4% of the Crab nebula with a weighted average spectral index of -2.8 ± 0.2. A possible extension less than one degree wide is shown. This detection, however, awaits a confirmation by the VERITAS collaboration. The luminosity of the Geminga extended source, the Vela Nebula, and the Crab nebula was calculated for energies greater than 1 TeV. The data suggest that older pulsars, such as Geminga and Vela, convert the

Millisecond Pulsars at Gamma-Ray Energies: Fermi Detections and Implications

NASA Technical Reports Server (NTRS)

Harding, Alice K.

2011-01-01

The Fermi Gamma-Ray Space Telescope has revolutionized the study of pulsar physics with the discovery of new populations of radio quiet and millisecond gamma-ray pulsars. The Fermi Large Area Telescope has so far discovered approx.20 new gamma-ray millisecond pulsars (MSPs) by both folding at periods of known radio MSPs or by detecting them as gamma-ray sources that are followed up by radio pulsar searches. The second method has resulted in a phenomenally successful synergy, with -30 new radio MSPs (to date) having been discovered at Fermi unidentified source locations and the gamma-ray pulsations having then been detected in a number of these using the radio timing solutions. Many of the newly discovered MSPs may be suitable for addition to the collection of very stable MSPs used for gravitational wave detection. Detection of such a large number of MSPs was surprising, given that most have relatively low spin-down luminosity and surface field strength. I will discuss their properties and the implications for pulsar particle acceleration and emission, as well as their potential contribution to gamma-ray backgrounds and Galactic cosmic rays.

Protracted low-dose radiation priming and response of liver to acute gamma and proton radiation.

PubMed

Gridley, D S; Mao, X W; Cao, J D; Bayeta, E J M; Pecaut, M J

2013-10-01

This study evaluated liver from C57BL/6 mice irradiated with low-dose/low-dose-rate (LDR) γ-rays (0.01 Gy, 0.03 cGy/h), with and without subsequent exposure to acute 2 Gy gamma or proton radiation. Analyses were performed on day 56 post-exposure. Expression patterns of apoptosis-related genes were strikingly different among irradiated groups compared with 0 Gy (p < 0.05). Two genes were affected in the Gamma group, whereas 10 were modified in the LDR + Gamma group. In Proton and LDR + Proton groups, there were six and 12 affected genes, respectively. Expression of genes in the Gamma (Traf3) and Proton (Bak1, Birc2, Birc3, Mcl1) groups was no longer different from 0 Gy control group when mice were pre-exposed to LDR γ-rays. When each combined regimen was compared with the corresponding group that received acute radiation alone, two genes in the LDR + Gamma group and 17 genes in the LDR + Proton group were modified; greatest effect was on Birc2 and Nol3 (> 5-fold up-regulated by LDR + Protons). Oxygen radical production in livers from the LDR + Proton group was higher in LDR, Gamma, and LDR + Gamma groups (p < 0.05 vs. 0 Gy), but there were no differences in phagocytosis of E. coli. Sections stained with hematoxylin and eosin (H&E) suggested more inflammation, with and without necrosis, in some irradiated groups. The data demonstrate that response to acute radiation is dependent on radiation quality and regimen and that some LDR γ-ray-induced modifications in liver response were still evident nearly 2 months after exposure.

Monte Carlo Simulations of Background Spectra in Integral Imager Detectors

NASA Technical Reports Server (NTRS)

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

1998-01-01

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

The structure and content of the galaxy and galactic gamma rays

NASA Technical Reports Server (NTRS)

Fichtel, C. E. (Editor); Stecker, F. W. (Editor)

1977-01-01

Gamma radiation investigations by COS-B and SAS-2 satellite are reported. Data from CO surveys of the galaxy and the galactic distribution of pulsars are analyzed. Theories of galactic gamma ray emission are explored.

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

DOEpatents

Smither, Robert K [Hinsdale, IL

2011-05-17

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

Research in particle and gamma-ray astrophysics

NASA Technical Reports Server (NTRS)

Stone, E. C.; Davis, L., Jr.; Mewaldt, R. A.; Prince, T. A.

1988-01-01

This research program is directed toward the investigation of the astrophysical aspects of cosmic rays and gamma rays and of the radiation and electromagnetic field environment of the Earth and other planets. The emphasis was on precice measurements with high resolution in charge, mass and energy. These investigations were carried out by means of energetic particle and photon detector systems flown on spacecraft and balloons.

The Gamma-ray Sky with Fermi

NASA Technical Reports Server (NTRS)

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.

The 2010 May Flaring Episode of Cygnus X-3 in Radio, X-Rays, and gamma-Rays

NASA Technical Reports Server (NTRS)

Williams, Peter K. G.; Tomsick, John A.; Bodaghee, Arash; Bower, Geoffrey C.; Pooley, Guy G.; Pottschmidt, Katja; Rodriguez, Jerome; Wilms, Joern; Migliari, Simone; Trushkin, Sergei A.

2011-01-01

In 2009, Cygnus X-3 (Cyg X-3) became the first microquasar to be detected in the GeV gamma-ray regime, via the satellites Fermi and AGILE. The addition of this new band to the observational toolbox holds promise for building a more detailed understanding of the relativistic jets of this and other systems. We present a rich dataset of radio, hard and soft X-ray, and gamma-ray observations of Cyg X-3 made during a flaring episode in 2010 May. We detect a approx.3-d softening and recovery of the X-ray emission, followed almost immediately by a approx.1-Jy radio flare at 15 GHz, followed by a 4.3sigma gamma-ray flare (E > 100 MeV) approx.1.5 d later. The radio sampling is sparse, but we use archival data to argue that it is unlikely the gamma-ray flare was followed by any significant unobserved radio flares. In this case, the sequencing of the observed events is difficult to explain in a model in which the gamma-ray emission is due to inverse Compton scattering of the companion star's radiation field. Our observations suggest that other mechanisms may also be responsible for gamma-ray emission from Cyg X-3.

Energetic neutron and gamma-ray spectra under the earth radiation belts according to ``SALUTE-7''-``KOSMOS-1686'' orbital complex and ``CORONAS-I'' satellite data

NASA Astrophysics Data System (ADS)

Bogomolov, A. V.; Dmitriev, A. V.; Myagkova, I. N.; Ryumin, S. P.; Smirnova, O. N.; Sobolevsky, I. M.

The spectra of neutrons > 10 MeV and gamma-rays 1.5-100 MeV under the Earth Radiation Belts, restored from the data, obtained onboard orbital complex ``SALUTE-7''-``KOSMOS-1686'', are presented. The spectra shapes are similar to those for albedo neutrons and gamma-rays, but absolute values of their fluxes (0.2 cm^-2 s^-1 for neutrons, 0.8 cm^-2 s^-1 for gamma-rays at the equator and 1.2 cm^-2 s^-1, 1.9 cm^-2 s^-1, accordingly, at L=1.9) are several times as large. It is possibly explained by the fact that most of the detected particles were produced by the cosmic ray interactions with the orbital complex matter. Neutron and gamma-ray fluxes obtained from ``CORONAS-I'' data are near those for albedo particles.

Modelling Hard Gamma-Ray Emission from Supernova Remnants

NASA Technical Reports Server (NTRS)

Baring, Matthew G.

1999-01-01

The observation by the CANGAROO (Collaboration of Australia and Nippon Gamma Ray Observatory at Outback) experiment of TeV emission from SN 1006, in conjunction with several instances of non-thermal X-ray emission from supernova remnants, has led to inferences of super-TeV electrons in these extended sources. While this is sufficient to propel the theoretical community in their modelling of particle acceleration and associated radiation, the anticipated emergence in the next decade of a number of new experiments probing the TeV and sub-TeV bands provides further substantial motivation for modellers. In particular, the quest for obtaining unambiguous gamma-ray signatures of cosmic ray ion acceleration defines a "Holy Grail" for observers and theorists alike. This review summarizes theoretical developments in the prediction of MeV-TeV gamma-rays from supernova remnants over the last five years, focusing on how global properties of models can impact, and be impacted by, hard gamma-ray observational programs, thereby probing the supernova remnant environment. Properties of central consideration include the maximum energy of accelerated particles, the density of the unshocked interstellar medium, the ambient magnetic field, and the relativistic electron-to-proton ratio. Criteria for determining good candidate remnants for observability in the TeV band are identified.

Intense Gamma-Ray Flashes Above Thunderstorms on the Earth and Other Planets

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

2010-01-01

Intense millisecond flashes of MeV photons have been observed with space-borne detectors in Earth orbit. They are expected to be present on other planets that exhibit lightning. The terrestrial gamma-ray flashes (TGFs) were discovered with the Burst and Transient Source Experiment (BATSE) aboard the Compton Gamma-Ray Observatory (CGRO) in the early 1990s. They are now being observed with several other instruments, including the Gamma-ray Burst Monitor (GBM) detectors on the Fermi Gamma-ray Space Telescope. Although Fermi- GBM was designed and optimized for the observation of cosmic gamma-ray bursts (GRBs), it has unprecedented capabilities for TGF observations. The TGFs usually have extremely hard continuous spectra, typical of highly- Comptonized bremsstrahlung radiation. These spectral are harder than those of GRBs, with photons extending to over 40 MeV. The most likely origin of these high-energy photons is bremsstrahlung radiation produced by a relativistic "runaway avalanche" electron beam. Such a beam is expected to be produced in an extended, intense electric field in or above thunderstorm regions. The altitude of origin and beaming characteristics of the radiation are quite uncertain. They have generated considerable observational and theoretical interest in recent years. This talk will give an overview of the all of the space-borne observations of TGFs that have been made thus far. Instruments are being designed specifically for TGF observations from new spacecraft as well as from airborne platforms

Modeling Background Radiation in our Environment Using Geochemical Data

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

Malchow, Russell L.; Marsac, Kara; Burnley, Pamela

2015-02-01

Radiation occurs naturally in bedrock and soil. Gamma rays are released from the decay of the radioactive isotopes K, U, and Th. Gamma rays observed at the surface come from the first 30 cm of rock and soil. The energy of gamma rays is specific to each isotope, allowing identification. For this research, data was collected from national databases, private companies, scientific literature, and field work. Data points were then evaluated for self-consistency. A model was created by converting concentrations of U, K, and Th for each rock and soil unit into a ground exposure rate using the following equation:more » D=1.32 K+ 0.548 U+ 0.272 Th. The first objective of this research was to compare the original Aerial Measurement System gamma ray survey to results produced by the model. The second objective was to improve the method and learn the constraints of the model. Future work will include sample data analysis from field work with a goal of improving the geochemical model.« less

The Highest-Energy Photons Seen by the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory

NASA Technical Reports Server (NTRS)

Thompson, D. J.; Bertsch, D. L.; ONeal, R. H., Jr.

2005-01-01

During its nine-year lifetime, the Energetic Gamma Ray Experiment Telescope (EGBET) on the Compton Gamma Ray Observatory (CGRO) detected 1506 cosmic photons with measured energy E>10 GeV. Of this number, 187 are found within a 1 deg of sources that are listed in the Third EGRET Catalog and were included in determining the detection likelihood, flux, and spectra of those sources. In particular, five detected EGRET pulsars are found to have events above 10 GeV, and together they account for 37 events. A pulsar not included in the Third EGRET Catalog has 2 events, both with the same phase and in one peak of the lower-energy gamma-ray light-curve. Most of the remaining 1319 events appear to be diffuse Galactic and extragalactic radiation based on the similarity of the their spatial and energy distributions with the diffuse model and in the E>100, MeV emission. No significant time clustering which would suggest a burst was detected.

The gamma ray north-south effect

NASA Technical Reports Server (NTRS)

White, R. S.; O'Neill, T. J.; Tumer, O. T.; Zych, A. D.

1988-01-01

Theoretical calculations are presented that explain the balloon observations by O'Neill et al. (1987) of a strong north-south anisotropy of atmospheric gamma rays over the Southern Hemisphere, and to predict the north-south ratios. It is shown that the gamma rays that originate at the longest distances from the telescopes give the largest north-south ratios. Comparisons are made of the experimental north-south ratios measured on balloons launched from Alice Springs, Australia, and from Palestine, Texas, U.S., and predictions are made for ratios at other geomagnetic latitudes and longitudes. It is pointed out that observers who measure backgrounds for celestial sources may be misled unless they correct for the north-south effect.

Finding Sub-threshold Short Gamma-ray Bursts in Fermi GBM Data

NASA Astrophysics Data System (ADS)

Burns, Eric; Fermi Gamma-ray Burst Monitor Team

2018-01-01

The all-sky monitoring capability of Fermi GBM makes it ideal for finding transients, and the most prolific detector of short gamma-ray bursts with about 40 on-board triggers per year. Because the observed brightness of short gamma-ray bursts has no correlation with redshift, weak short gamma-ray bursts are important during the gravitational wave era. With this in mind, we discuss two searches of GBM data to find short gamma-ray which were below the on-board trigger threshold. The untargeted search looks for significant background-subtracted signals in two or more detectors at various timescales in the continuous data, detecting ~80 additional short GRB candidates per year. The targeted search is the most sensitive search for weak gamma-ray signals in GBM data and is run over limited time intervals around sources of interest like gravitational waves.

Future Hard X-ray and Gamma-Ray Missions

NASA Astrophysics Data System (ADS)

Krawczynski, Henric; Physics of the Cosmos (PCOS) Gamma Ray Science Interest Group (GammaSIG) Team

2017-01-01

With four major NASA and ESA hard X-ray and gamma-ray missions in orbit (Swift, NuSTAR, INTEGRAL, and Fermi) hard X-ray and gamma-ray astronomy is making major contributions to our understanding of the cosmos. In this talk, I will summarize the current and upcoming activities of the Physics of the Cosmos Gamma Ray Science Interest Group and highlight a few of the future hard X-ray and gamma-ray mission discussed by the community. HK thanks NASA for the support through the awards NNX14AD19G and NNX16AC42G and for PCOS travel support.

Determining optical and radiation characteristics of cathode ray tubes' glass to be reused as radiation shielding glass

NASA Astrophysics Data System (ADS)

Zughbi, A.; Kharita, M. H.; Shehada, A. M.

2017-07-01

A new method of recycling glass of Cathode Ray Tubes (CRTs) has been presented in this paper. The glass from CRTs suggested being used as raw materials for the production of radiation shielding glass. Cathode ray tubes glass contains considerable amounts of environmentally hazardous toxic wastes, namely heavy metal oxides such as lead oxide (PbO). This method makes CRTs glass a favorable choice to be used as raw material for Radiation Shielding Glass and concrete. The heavy metal oxides increase its density, which make this type of glass nearly equivalent to commercially available shielding glass. CRTs glass have been characterized to determine heavy oxides content, density, refractive index, and radiation shielding properties for different Gamma-Ray energies. Empirical methods have been used by using the Gamma-Ray source cobalt-60 and computational method by using the code XCOM. Measured and calculated values were in a good compatibility. The effects of irradiation by gamma rays of cobalt-60 on the optical transparency for each part of the CRTs glass have been studied. The Results had shown that some parts of CRTs glass have more resistant to Gamma radiation than others. The study had shown that the glass of cathode ray tubes could be recycled to be used as radiation shielding glass. This proposed use of CRT glass is only limited to the available quantity of CRT world-wide.

A Unified Model for GRB Prompt Emission from Optical to Gamma-Rays; Exploring GRBs as Standard Candles

NASA Technical Reports Server (NTRS)

Guiriec, S.; Kouveliotou, C.; Hartmann, D. H.; Granot, J.; Asano, K.; Meszaros, P.; Gill, R.; Gehrels, N.; McEnery, J.

2016-01-01

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

Fermi-LAT Observations of the Gamma-Ray Burst GRB 130427A

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Asano, K.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.;

Terrestrial Gamma-Ray Flashes (TGFs)

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

2010-01-01

This slide presentation reviews the observation of Terrestrial Gamma Ray Flashes (TGFs) by Gamma-Ray Telescopes. These were: (1) BATSE /Compton Observatory, (2) Solar Spectroscopic Imager, (3) AGILE Gamma-ray Telescope, and (4) Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope. It contains charts which display the counts over time, a map or the TGFs observed by the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). and a map showing the latitude and longitude of 85 of the TGFs observed by the Fermi GBM.

A search for optical counterparts of gamma-ray bursts. Final report

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

Park, Hye-Sook

Gamma Ray Bursts (GRBS) are mysterious flashes of gamma rays lasting several tens to hundreds of seconds that occur approximately once per day. NASA launched the orbiting Compton Gamma Ray Observatory to study GRBs and other gamma ray phenomena. CGRO carries the Burst and Transient Experiment (BATSE) specifically to study GRBS. Although BATSE has collected data on over 600 GRBS, and confirmed that GRBs are localized, high intensity point sources of MeV gamma rays distributed isotropically in the sky, the nature and origin of GRBs remains a fundamental problem in astrophysics. BATSE`s 8 gamma ray sensors located on the comersmore » of the box shaped CGRO can detect the onset of GRBs and record their intensity and energy spectra as a function of time. The position of the burst on the sky can be determined to < {plus_minus}10{degrees} from the BATSE data stream. This position resolution is not sufficient to point a large, optical telescope at the exact position of a GRB which would determine its origin by associating it with a star. Because of their brief duration it is not known if GRBs are accompanied by visible radiation. Their seemingly large energy output suggests thatthis should be. Simply scaling the ratio of visible to gamma ray intensities of the Crab Nebula to the GRB output suggests that GRBs ought to be accompanied by visible flashes of magnitude 10 or so. A few photographs of areas containing a burst location that were coincidentally taken during the burst yield lower limits on visible output of magnitude 4. The detection of visible light during the GRB would provide information on burst physics, provide improved pointing coordinates for precise examination of the field by large telescope and provide the justification for larger dedicated optical counterpart instruments. The purpose of this experiment is to detect or set lower limits on optical counterpart radiation simultaneously accompanying the gamma rays from« less

Constraining the location of gamma-ray flares in luminous blazars

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

Nalewajko, Krzysztof; Begelman, Mitchell C.; Sikora, Marek, E-mail: knalew@jila.colorado.edu

2014-07-10

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 ≲ 1, from an upper limit on the synchrotron self-Compton (SSC)more » luminosity L{sub SSC} ≲ L{sub X}, and from an upper limit on the efficient cooling photon energy E{sub cool,obs} ≲ 100 MeV. These three constraints are particularly strong for sources with low accretion disk luminosity L{sub 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{sub var,obs}. Alternative scenarios motivated by the observed gamma-ray/millimeter connection, in which gamma-ray flares of t{sub 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

Fiber optic thermal/fast neutron and gamma ray scintillation detector

DOEpatents

Neal, John S.; Mihalczo, John T.

2006-11-28

A detector system that combines a .sup.6Li loaded glass fiber scintillation thermal neutron detector with a fast scintillation detector in a single layered structure. Detection of thermal and fast neutrons and ionizing electromagnetic radiation is achieved in the unified detector structure. The fast scintillator replaces the polyethelene moderator layer adjacent the .sup.6Li loaded glass fiber panel of the neutron detector and acts as the moderator for the glass fibers. Fast neutrons, x-rays and gamma rays are detected in the fast scintillator. Thermal neutrons, x-rays and gamma rays are detected in the glass fiber scintillator.

Gamma-ray astrophysics

NASA Technical Reports Server (NTRS)

Stecker, F. W. (Editor); Trombka, J. I. (Editor)

1973-01-01

Conference papers on gamma ray astrophysics are summarized. Data cover the energy region from about 0.3 MeV to a few hundred GeV and theoretical models of production mechanisms that give rise to both galactic and extragalactic gamma rays.

The interaction of natural background gamma radiation with depleted uranium micro-particles in the human body.

PubMed

Pattison, John E

2013-03-01

In this study, some characteristics of the photo-electrons produced when natural background gamma radiation interacts with micron-sized depleted uranium (DU) particles in the human body have been estimated using Monte Carlo simulations. In addition, an estimate has been made of the likelihood of radiological health effects occurring due to such an exposure. Upon exposure to naturally occurring background gamma radiation, DU particles in the body will produce an enhancement of the dose to the tissue in the immediate vicinity of the particles due to the photo-electric absorption of the radiation in the particle. In this study, the photo-electrons produced by a 10 μm-size particle embedded in tissue at the centre of the human torso have been investigated. The mean energies of the photo-electrons in the DU particle and in the two consecutive immediately surrounding 2 μm-wide tissue shells around the particle were found to be 38, 49 and 50 keV, respectively, with corresponding ranges of 1.3, 38 and 39 μm, respectively. The total photo-electron fluence-rates in the two consecutive 2 μm-wide tissue layers were found to be 14% and 7% of the fluence-rate in the DU particle, respectively. The estimated dose enhancement due to one 10 μm-sized DU particle in 1 cm(3) of tissue was less than 2 in 10 million of the dose received by the tissue without a particle being present. The increase in risk of death from cancer due to this effect is consequently insignificant.

The Gamma-ray Universe through Fermi

NASA Technical Reports Server (NTRS)

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.

The SWIFT Gamma-Ray Burst X-Ray Telescope

NASA Technical Reports Server (NTRS)

Hill, J. E.; Burrows, D. N.; Nousek, J. A.; Wells, A.; Chincarini, G.; Abbey, A. F.; Angelini, L.; Beardmore, A.; Brauninger, H. W.; Chang, W.

2006-01-01

The Swift Gamma-Ray Burst Explorer is designed to make prompt multi-wavelength observations of Gamma-Ray Bursts and GRB afterglows. The X-ray Telescope enables Swift to determine GRB positions with a few arcseconds accuracy within 100 seconds of the burst onset. The XRT utilizes a mirror set built for JET-X and an XMM-Newton/ EPIC MOS CCD detector to provide a sensitive broad-band (0.2-10 keV) X-ray imager with an effective area of more than 120 sq cm at 1.5 keV, a field of view of 23.6 x 23.6 arcminutes, and an angular resolution of 18 arcseconds (HPD). The detection sensitivity is 2x10(exp 14) erg/sq cm/s in 10(exp 4) seconds. The instrument provides automated source detection and position reporting within 5 seconds of target acquisition. It can also measure the redshifts of GRBs with Iron line emission or other spectral features. The XRT operates in an auto-exposure mode, adjusting the CCD readout mode automatically to optimize the science return as the source intensity fades. The XRT measures spectra and lightcurves of the GRB afterglow beginning about a minute after the burst and follows each burst for days or weeks. We provide an overview of the X-ray Telescope scientific background from which the systems engineering requirements were derived, with specific emphasis on the design and qualification aspects from conception through to launch. We describe the impact on cleanliness and vacuum requirements for the instrument low energy response and to maintain the high sensitivity to the fading signal of the Gamma-ray Bursts.

Astrophysical gamma-ray production by inverse Compton interactions of relativistic electrons

NASA Technical Reports Server (NTRS)

Schlickeiser, R.

1979-01-01

The inverse Compton scattering of background photon gases by relativistic electrons is a good candidate for the production of high-energy gamma rays in the diffuse interstellar medium as well as in discrete sources. By discussing the special case of the scattering of the diffuse starlight in the interstellar medium by cosmic ray electrons, we demonstrate that previous derivations of the gamma ray source function for this process on the basis of the Thomson limit of the Klein-Nishina cross section lead to incorrect values for gamma-ray energies above 100 MeV. It is shown that the Thomson limit is not applicable for the calculation of gamma-ray source functions in astrophysical circumstances in which target photons with energies greater than 1 eV are scattered by relativistic electrons.

Gamma ray astrophysics and signatures of axion-like particles

NASA Astrophysics Data System (ADS)

Serpico, Pasquale D.

2009-02-01

We propose that axion-like particles (ALPs) with a two-photon vertex, consistent with all astrophysical and laboratory bounds, may lead to effects in the spectra of high-energy gamma-ray sources detectable by satellite or ground-based telescopes. We discuss two kinds of signatures: (i) a peculiar spectral depletion due to gamma rays being converted into ALPs in the magnetic fields of efficient astrophysical accelerators according to the “Hillas criterion”, such as jets of active galactic nuclei or hot spots of radio galaxies; (ii) an appearance of otherwise invisible sources in the GeV or TeV sky due to back-conversion of an ALP flux (associated with gamma-ray emitters suffering some attenuation) in the magnetic field of the Milky Way. These two mechanisms might also provide an exotic way to avoid the exponential cutoff of very high energy gamma-rays expected due to the pair production onto the extragalactic background light.

Neutron-driven gamma-ray laser

DOEpatents

Bowman, Charles D.

1990-01-01

A lasing cylinder emits laser radiation at a gamma-ray wavelength of 0.87 .ANG. when subjected to an intense neutron flux of about 400 eV neutrons. A 250 .ANG. thick layer of Be is provided between two layers of 100 .ANG. thick layer of .sup.57 Co and these layers are supported on a foil substrate. The coated foil is coiled to form the lasing cylinder. Under the neutron flux .sup.57 Co becomes .sup.58 Co by neutron absorption. The .sup.58 Co then decays to .sup.57 Fe by 1.6 MeV proton emission. .sup.57 Fe then transitions by mesne decay to a population inversion for lasing action at 14.4 keV. Recoil from the proton emission separates the .sup.57 Fe from the .sup.57 Co and into the Be, where Mossbauer emission occurs at a gamma-ray wavelength.

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

NASA Astrophysics Data System (ADS)

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

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

Electron Acceleration and Efficiency in Nonthermal Gamma-Ray Sources

NASA Astrophysics Data System (ADS)

Bykov, A. M.; Meszaros, P.

1996-04-01

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

Topics in gamma ray astronomy

NASA Technical Reports Server (NTRS)

Ramaty, R.; Lingenfelter, R. E.

1986-01-01

Observations of gamma rays from solar flares, gamma ray bursts, the Galactic center, galactic nucleosynthesis, SS433, and Cygnus X-3, and their effects on astrophysical problems are discussed. It is observed that gamma ray spectra from solar flares are applicable to the study of particle acceleration and confinement and the determination of chemical abundances in the solar atmosphere. The gamma ray lines from the compact galactic object SS433 are utilized to examine the acceleration of jets, and analysis of the gamma ray lines of Cygnus X-3 reveal that particles can be accelerated in compact sources to ultrahigh energies.

Detection of 16 gamma-ray pulsars through blind frequency searches using the Fermi LAT.

PubMed

Abdo, A A; Ackermann, M; Ajello, M; Anderson, B; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Baring, M G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Bignami, G F; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, O; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; Dermer, C D; de Angelis, A; de Luca, A; de Palma, F; Digel, S W; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Farnier, C; Favuzzi, C; Fegan, S J; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giommi, P; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Gwon, C; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; Jóhannesson, G; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Marelli, M; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Pierbattista, M; Piron, F; Porter, T A; Primack, J R; Rainò, S; Rando, R; Ray, P S; Razzano, M; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Romani, R W; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J G; Thompson, D J; Tibaldo, L; Tibolla, O; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Van Etten, A; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Watters, K; Winer, B L; Wolff, M T; Wood, K S; Ylinen, T; Ziegler, M

2009-08-14

Pulsars are rapidly rotating, highly magnetized neutron stars emitting radiation across the electromagnetic spectrum. Although there are more than 1800 known radio pulsars, until recently only seven were observed to pulse in gamma rays, and these were all discovered at other wavelengths. The Fermi Large Area Telescope (LAT) makes it possible to pinpoint neutron stars through their gamma-ray pulsations. We report the detection of 16 gamma-ray pulsars in blind frequency searches using the LAT. Most of these pulsars are coincident with previously unidentified gamma-ray sources, and many are associated with supernova remnants. Direct detection of gamma-ray pulsars enables studies of emission mechanisms, population statistics, and the energetics of pulsar wind nebulae and supernova remnants.

A luminous gamma-ray binary in the large magellanic cloud

DOE PAGES

Corbet, R. H. D.; Chomiuk, L.; Coe, M. J.; ...

2016-09-27

Gamma-ray binaries consist of a neutron star or a black hole interacting with a normal star to produce gamma-ray emission that dominates the radiative output of the system. Previously, only a handful of such systems have been discovered, all within our Galaxy. We report the discovery of a luminous gamma-ray binary in the Large Magellanic Cloud, found with the Fermi Large Area Telescope (LAT), from a search for periodic modulation in all sources in the third Fermi LAT catalog. This is the first such system to be found outside the Milky Way. Furthermore, the system has an orbital period ofmore » 10.3 days, and is associated with a massive O5III star located in the supernova remnant DEM L241, previously identified as the candidate high-mass X-ray binary (HMXB) CXOU J053600.0–673507. X-ray and radio emission are also modulated on the 10.3 day period, but are in anti-phase with the gamma-ray modulation. Optical radial velocity measurements suggest that the system contains a neutron star. The source is significantly more luminous than similar sources in the Milky Way, at radio, optical, X-ray, and gamma-ray wavelengths. The detection of this extra-galactic system, but no new Galactic systems, raises the possibility that the predicted number of gamma-ray binaries in our Galaxy has been overestimated, and that HMXBs may be born containing relatively slowly rotating neutron stars.« less

The Advanced Gamma-Ray Imaging System (AGIS)

NASA Astrophysics Data System (ADS)

Otte, Nepomuk

The Advanced Gamma-ray Imaging System (AGIS) is a concept for the next generation of imag-ing atmospheric Cherenkov telescope arrays. It has the goal of providing an order of magnitude increase in sensitivity for Very High Energy Gamma-ray ( 100 GeV to 100 TeV) astronomy compared to currently operating arrays such as CANGAROO, HESS, MAGIC, and VERITAS. After an overview of the science such an array would enable, we discuss the development of the components of the telescope system that are required to achieve the sensitivity goal. AGIS stresses improvements in several areas of IACT technology including component reliability as well as exploring cost reduction possibilities in order to achieve its goal. We discuss alterna-tives for the telescopes and positioners: a novel Schwarzschild-Couder telescope offering a wide field of view with a relatively smaller plate scale, and possibilities for rapid slewing in order to address the search for and/or study of Gamma-ray Bursts in the VHE gamma-ray regime. We also discuss options for a high pixel count camera system providing the necessary finer solid angle per pixel and possibilities for a fast topological trigger that would offer improved realtime background rejection and lower energy thresholds.

Rain-induced increase in background radiation detected by Radiation Portal Monitors.

PubMed

Livesay, R J; Blessinger, C S; Guzzardo, T F; Hausladen, P A

2014-11-01

A complete understanding of both the steady state and transient background measured by Radiation Portal Monitors (RPMs) is essential to predictable system performance, as well as maximization of detection sensitivity. To facilitate this understanding, a test bed for the study of natural background in RPMs has been established at the Oak Ridge National Laboratory. This work was performed in support of the Second Line of Defense Program's mission to enhance partner country capability to deter, detect, and interdict the illicit movement of special nuclear material. In the present work, transient increases in gamma-ray counting rates in RPMs due to rain are investigated. The increase in background activity associated with rain, which has been well documented in the field of environmental radioactivity, originates primarily from the wet-deposition of two radioactive daughters of (222)Rn, namely, (214)Pb and (214)Bi. In this study, rainfall rates recorded by a co-located weather station are compared with RPM count rates and high-purity germanium spectra. The data verify that these radionuclides are responsible for the largest environmental background fluctuations in RPMs. Analytical expressions for the detector response function in Poly-Vinyl Toluene have been derived. Effects on system performance and potential mitigation strategies are discussed. Copyright © 2014 Elsevier Ltd. All rights reserved.

Neutron, gamma ray and post-irradiation thermal annealing effects on power semiconductor switches

NASA Technical Reports Server (NTRS)

Schwarze, G. E.; Frasca, A. J.

1991-01-01

The effects of neutron and gamma rays on the electrical and switching characteristics of power semiconductor switches must be known and understood by the designer of the power conditioning, control, and transmission subsystem of space nuclear power systems. The SP-100 radiation requirements at 25 m from the nuclear source are a neutron fluence of 10(exp 13) n/sq cm and a gamma dose of 0.5 Mrads. Experimental data showing the effects of neutrons and gamma rays on the performance characteristics of power-type NPN Bipolar Junction Transistors (BJTs), Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs), and Static Induction Transistors (SITs) are presented. These three types of devices were tested at radiation levels which met or exceeded the SP-100 requirements. For the SP-100 radiation requirements, the BJTs were found to be most sensitive to neutrons, the MOSFETs were most sensitive to gamma rays, and the SITs were only slightly sensitive to neutrons. Post-irradiation thermal anneals at 300 K and up to 425 K were done on these devices and the effectiveness of these anneals are also discussed.

Balloon Borne Instrumentation for Detection of Gamma Ray Glows

NASA Astrophysics Data System (ADS)

Sterpka, C. F.; Bagheri, M.; Dwyer, J. R.; Liu, N.; Morman, K.; Gadbois, J. L.; Bozarth, A.; Boggs, L.; Mailyan, B. G.; Nag, A.; Lazarus, S. M.; Austin, M.; Aguirre, F.; Colvin, J.; Haley, V.; Rassoul, H.

2017-12-01

Gamma-ray glows are emissions of gamma rays that last from seconds to minutes and are produced by runaway electrons in high-field regions of thunderclouds. The lightning group at the University of New Hampshire in collaboration with the Florida Institute of Technology has designed balloon-based instrumentation for flying into thunderstorms with the aim of detecting such radiation. The instrumentation includes two Geiger-Muller tubes, sensitive to both gamma rays and charged particles, and a low-power lightweight electric field mill, designed and calibrated to measure both polarity and amplitude of the vertical electric field inside the thunderstorm region. With the polarity measurement provided by the field mill, the Geiger-Muller tubes should be capable of differentiating energetic electrons from positrons. Additionally, a lead sheet is placed between the Geiger-Muller tubes to differentiate between charged particles and gamma rays. We have conducted several test flights of this system during the summer of 2017. In this study, we will present an overview of the instrumentation and discuss preliminary results from the test flights.

Gamma-ray detector guidance of breast cancer therapy

NASA Astrophysics Data System (ADS)

Ravi, Ananth

2009-12-01

Breast cancer is the most common form of cancer in women. Over 75% of breast cancer patients are eligible for breast conserving therapy. Breast conserving therapy involves a lumpectomy to excise the gross tumour, followed by adjuvant radiation therapy to eradicate residual microscopic disease. Recent advances in the understanding of breast cancer biology and recurrence have presented the opportunity to improve breast conserving therapy techniques. This thesis has explored the potential of gamma-ray detecting technology to improve guidance of both surgical and adjuvant radiation therapy aspects of breast conserving therapy. The task of accurately excising the gross tumour during breast conserving surgery (BCS) is challenging, due to the limited guidance currently available to surgeons. Radioimmuno guided surgery (RIGS) has been investigated to determine its potential to delineate the gross tumour intraoperatively. The effects of varying a set of user controllable parameters on the ability of RIGS to detect and delineate model breast tumours was determined. The parameters studied were: Radioisotope, blood activity concentration, collimator height and energy threshold. The most sensitive combination of parameters was determined to be an 111Indium labelled radiopharmaceutical with a gamma-ray detecting probe collimated to a height of 5 mm and an energy threshold at the Compton backscatter peak. Using these parameters it was found that, for the breast tumour model used, the minimum tumour-to-background ratio required to delineate the tumour edge accurately was 5.2+/-0.4 at a blood activity concentration of 5 kBq/ml. Permanent breast seed implantation (PBSI) is a form of accelerated partial breast irradiation that dramatically reduces the treatment burden of adjuvant radiation therapy on patients. Unfortunately, it is currently difficult to localize the implanted brachytherapy seeds, making it difficult to perform a correction in the event that seeds have been misplaced

Compton Gamma-Ray Observatory

NASA Technical Reports Server (NTRS)

1991-01-01

This photograph shows the Compton Gamma-Ray Observatory (GRO) being deployed by the Remote Manipulator System (RMS) arm aboard the Space Shuttle Atlantis during the STS-37 mission in April 1991. The GRO reentered Earth atmosphere and ended its successful mission in June 2000. For nearly 9 years, the GRO Burst and Transient Source Experiment (BATSE), designed and built by the Marshall Space Flight Center (MSFC), kept an unblinking watch on the universe to alert scientists to the invisible, mysterious gamma-ray bursts that had puzzled them for decades. By studying gamma-rays from objects like black holes, pulsars, quasars, neutron stars, and other exotic objects, scientists could discover clues to the birth, evolution, and death of stars, galaxies, and the universe. The gamma-ray instrument was one of four major science instruments aboard the Compton. It consisted of eight detectors, or modules, located at each corner of the rectangular satellite to simultaneously scan the entire universe for bursts of gamma-rays ranging in duration from fractions of a second to minutes. In January 1999, the instrument, via the Internet, cued a computer-controlled telescope at Las Alamos National Laboratory in Los Alamos, New Mexico, within 20 seconds of registering a burst. With this capability, the gamma-ray experiment came to serve as a gamma-ray burst alert for the Hubble Space Telescope, the Chandra X-Ray Observatory, and major gound-based observatories around the world. Thirty-seven universities, observatories, and NASA centers in 19 states, and 11 more institutions in Europe and Russia, participated in the BATSE science program.

Compton Gamma-Ray Observatory

NASA Technical Reports Server (NTRS)

1991-01-01

This photograph shows the Compton Gamma-Ray Observatory being released from the Remote Manipulator System (RMS) arm aboard the Space Shuttle Atlantis during the STS-35 mission in April 1991. The GRO reentered the Earth's atmosphere and ended its successful mission in June 2000. For nearly 9 years, GRO's Burst and Transient Source Experiment (BATSE), designed and built by the Marshall Space Flight Center, kept an unblinking watch on the universe to alert scientist to the invisible, mysterious gamma-ray bursts that had puzzled them for decades. By studying gamma-rays from objects like black holes, pulsars, quasars, neutron stars, and other exotic objects, scientists could discover clues to the birth, evolution, and death of star, galaxies, and the universe. The gamma-ray instrument was one of four major science instruments aboard the Compton. It consisted of eight detectors, or modules, located at each corner of the rectangular satellite to simultaneously scan the entire universe for bursts of gamma-rays ranging in duration from fractions of a second to minutes. In January 1999, the instrument, via the Internet, cued a computer-controlled telescope at Las Alamos National Laboratory in Los Alamos, New Mexico, within 20 seconds of registering a burst. With this capability, the gamma-ray experiment came to serve as a gamma-ray burst alert for the Hubble Space Telescope, the Chandra X-Ray Observatory, and major gound-based observatories around the world. Thirty-seven universities, observatories, and NASA centers in 19 states, and 11 more institutions in Europe and Russia, participated in BATSE's science program.

Fermi Large Area Telescope Measurements of the Diffuse Gamma-Ray Emission at Intermediate Galactic Latitudes

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

Abdo, A.A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.

The diffuse galactic {gamma}-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess {gamma}-ray emission {ge}1 GeV relative to diffuse galactic {gamma}-ray emission models consistent with directly measured CR spectra (the so-called 'EGRET GeV excess'). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse {gamma}-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10{sup o}more » {le} |b| {le} 20{sup o}. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic {gamma}-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.« less

Fermi large area telescope measurements of the diffuse gamma-ray emission at intermediate galactic latitudes.

PubMed

Abdo, A A; Ackermann, M; Ajello, M; Anderson, B; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Dereli, H; Dermer, C D; de Angelis, A; de Palma, F; Digel, S W; Di Bernardo, G; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gaggero, D; Gargano, F; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kuehn, F; Kuss, M; Lande, J; Latronico, L; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Mazziotta, M N; McConville, W; McEnery, J E; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rodriguez, A Y; Roth, M; Ryde, F; Sadrozinski, H F-W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Sellerholm, A; Sgrò, C; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Starck, J-L; Stecker, F W; Striani, E; Strickman, M S; Strong, A W; Suson, D J; Tajima, H; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Vasileiou, V; Vilchez, N; Vitale, V; Waite, A P; Wang, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

2009-12-18

The diffuse galactic gamma-ray emission is produced by cosmic rays (CRs) interacting with the interstellar gas and radiation field. Measurements by the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma-Ray Observatory indicated excess gamma-ray emission greater, > or approximately equal to 1 GeV relative to diffuse galactic gamma-ray emission models consistent with directly measured CR spectra (the so-called "EGRET GeV excess"). The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse gamma-ray emission with improved sensitivity and resolution compared to EGRET. We report on LAT measurements for energies 100 MeV to 10 GeV and galactic latitudes 10 degrees < or = |b| < or = 20 degrees. The LAT spectrum for this region of the sky is well reproduced by a diffuse galactic gamma-ray emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess.

Characterizing near-surface elemental layering on Mars using gamma-ray spectroscopy: A proof-of-principle experiment

NASA Astrophysics Data System (ADS)

Peplowski, Patrick N.; Wilson, Jack T.; Beck, Andrew W.; Burks, Morgan; Goldsten, John O.; Lawrence, David J.

2018-01-01

Gamma-ray spectroscopy investigations characterize the chemical composition of planetary surfaces by measuring element-characteristic gamma rays with energies of ∼100 keV to ∼9 MeV. Over this energy range, the mean free path of a gamma ray varies from about 1 to 25 cm, therefore gamma-ray measurements sample subsurface composition. Many elements emit gamma rays at multiple, often widely spaced energies, so gamma-ray measurements can in principle also be used to identify depth-dependent variations in subsurface composition. We report results from laboratory measurements and radiation transport modeling designed to demonstrate this capability. The laboratory measurements verified the presence of depth-dependent gamma-ray signatures, and were then used to benchmark radiation transport simulations that were used to model realistic Mars-like scenarios. The models indicate that compositionally distinct subsurface deposits, buried to depths of ∼80 cm (125 g/cm2), can be identified using gamma-ray measurements. Going beyond identification to characterization (burial depth, relative composition of the layers) of the deposits requires knowledge of the vertical and horizontal variability in the water content of the near-surface surface materials, the local Galactic Cosmic Ray environment (magnitude and energy distribution), the depth-dependent neutron flux, gamma-ray production cross sections, and knowledge of the composition and column density of the atmosphere. The results of our experiments and models provided a basis for examining the utility of using orbiter- and lander-based gamma-ray measurements to identify subsurface deposits on Mars.

Development and Evaluation of Real-Time Volumetric Compton Gamma-Ray Imaging

NASA Astrophysics Data System (ADS)

Barnowski, Ross Wegner

An approach to gamma-ray imaging has been developed that enables near real-time volumetric (3D) imaging of unknown environments thus improving the utility of gamma-ray imaging for source-search and radiation mapping applications. The approach, herein dubbed scene data fusion (SDF), is based on integrating mobile radiation imagers with real time tracking and scene reconstruction algorithms to enable a mobile mode of operation and 3D localization of gamma-ray sources. The real-time tracking allows the imager to be moved throughout the environment or around a particular object of interest, obtaining the multiple perspectives necessary for standoff 3D imaging. A 3D model of the scene, provided in real-time by a simultaneous localization and mapping (SLAM) algorithm, can be incorporated into the image reconstruction reducing the reconstruction time and improving imaging performance. The SDF concept is demonstrated in this work with a Microsoft Kinect RGB-D sensor, a real-time SLAM solver, and two different mobile gamma-ray imaging platforms. The first is a cart-based imaging platform known as the Volumetric Compton Imager (VCI), comprising two 3D position-sensitive high purity germanium (HPGe) detectors, exhibiting excellent gamma-ray imaging characteristics, but with limited mobility due to the size and weight of the cart. The second system is the High Efficiency Multimodal Imager (HEMI) a hand-portable gamma-ray imager comprising 96 individual cm3 CdZnTe crystals arranged in a two-plane, active-mask configuration. The HEMI instrument has poorer energy and angular resolution than the VCI, but is truly hand-portable, allowing the SDF concept to be tested in multiple environments and for more challenging imaging scenarios. An iterative algorithm based on Compton kinematics is used to reconstruct the gamma-ray source distribution in all three spatial dimensions. Each of the two mobile imaging systems are used to demonstrate SDF for a variety of scenarios, including

Gamma rays from Centaurus A

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

Gupta, Nayantara, E-mail: nayan@phy.iitb.ac.in

2008-06-15

Centaurus A, the cosmic ray accelerator a few Mpc away from us, is possibly one of the nearest sources of extremely high energy cosmic rays. We investigate whether the gamma ray data currently available from Centaurus A in the GeV-TeV energy band can be explained with only proton-proton interactions. We show that for a single power law proton spectrum, mechanisms of {gamma}-ray production other than proton-proton interactions are needed inside this radio-galaxy to explain the gamma ray flux observed by EGRET, upper limits from HESS/CANGAROO-III and the correlated extremely energetic cosmic ray events observed by the Pierre Auger experiment. Inmore » future, with better {gamma}-ray data, and simultaneous observation with {gamma}-ray and cosmic ray detectors, it will be possible to carry out such studies on different sources in more detail.« less

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

NASA Astrophysics Data System (ADS)

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.

Future prospects for gamma-ray

NASA Technical Reports Server (NTRS)

Fichtel, C.

1980-01-01

Astrophysical phenomena discussed are: the very energetic and nuclear processes associated with compact objects; astrophysical nucleo-synthesis; solar particle acceleration; the chemical composition of the planets and other bodies of the solar system; the structure of our galaxy; the origin and dynamic pressure effects of the cosmic rays; the high energy particles and energetic processes in other galaxies, especially active ones; and the degree of matter antimater symmetry of the universe. The gamma ray results of GAMMA-I, the gamma ray observatory, the gamma ray burst network, solar polar, and very high energy gamma ray telescopes on the ground provide justification for more sophisticated telescopes.

The Advanced Gamma-ray Imaging System (AGIS)-Simulation Studies

NASA Astrophysics Data System (ADS)

Maier, G.; Buckley, J.; Bugaev, V.; Fegan, S.; Funk, S.; Konopelko, A.; Vassiliev, V. V.

2008-12-01

The Advanced Gamma-ray Imaging System (AGIS) is a US-led concept for a next-generation instrument in ground-based very-high-energy gamma-ray astronomy. The most important design requirement for AGIS is a sensitivity of about 10 times greater than current observatories like Veritas, H.E.S.S or MAGIC. We present results of simulation studies of various possible designs for AGIS. The primary characteristics of the array performance, collecting area, angular resolution, background rejection, and sensitivity are discussed.

Gamma ray astrophysics to the year 2000. Report of the NASA Gamma Ray Program Working Group

NASA Technical Reports Server (NTRS)

1988-01-01

Important developments in gamma-ray astrophysics up to energies of 100 GeV during the last decade are reviewed. Also, the report seeks to define the major current scientific goals of the field and proposes a vigorous program to pursue them, extending to the year 2000. The goals of gamma-ray astronomy include the study of gamma rays which provide the most direct means of studying many important problems in high energy astrophysics including explosive nucleosynthesis, accelerated particle interactions and sources, and high-energy processes around compact objects. The current research program in gamma-ray astronomy in the U.S. including the space program, balloon program and foreign programs in gamma-ray astronomy is described. The high priority recommendations for future study include an Explorer-class high resolution gamma-ray spectroscopy mission and a Get Away Special cannister (GAS-can) or Scout class multiwavelength experiment for the study of gamma-ray bursts. Continuing programs include an extended Gamma Ray Observatory mission, continuation of the vigorous program of balloon observations of the nearby Supernova 1987A, augmentation of the balloon program to provide for new instruments and rapid scientific results, and continuation of support for theoretical research. Long term recommendations include new space missions using advanced detectors to better study gamma-ray sources, the development of these detectors, continued study for the assembly of large detectors in space, collaboration with the gamma-ray astronomy missions initiated by other countries, and consideration of the Space Station attached payloads for gamma-ray experiments.

Gamma Radiation Effects on Peanut Skin Antioxidants

PubMed Central

de Camargo, Adriano Costa; de Souza Vieira, Thais Maria Ferreira; Regitano-D’Arce, Marisa Aparecida Bismara; Calori-Domingues, Maria Antonia; Canniatti-Brazaca, Solange Guidolin

2012-01-01

Peanut skin, which is removed in the peanut blanching process, is rich in bioactive compounds with antioxidant properties. The aims of this study were to measure bioactive compounds in peanut skins and evaluate the effect of gamma radiation on their antioxidant activity. Peanut skin samples were treated with 0.0, 5.0, 7.5, or 10.0 kGy gamma rays. Total phenolics, condensed tannins, total flavonoids, and antioxidant activity were evaluated. Extracts obtained from the peanut skins were added to refined-bleached-deodorized (RBD) soybean oil. The oxidative stability of the oil samples was determined using the Oil Stability Index method and compared to a control and synthetic antioxidants (100 mg/kg BHT and 200 mg/kg TBHQ). Gamma radiation changed total phenolic content, total condensed tannins, total flavonoid content, and the antioxidant activity. All extracts, gamma irradiated or not, presented increasing induction period (h), measured by the Oil Stability Index method, when compared with the control. Antioxidant activity of the peanut skins was higher than BHT. The present study confirmed that gamma radiation did not affect the peanut skin extracts’ antioxidative properties when added to soybean oil. PMID:22489142

Time evolution of gamma rays from supernova remnants

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

Gamma ray detector shield

DOEpatents

Ohlinger, R.D.; Humphrey, H.W.

1985-08-26

A gamma ray detector shield comprised of a rigid, lead, cylindrical-shaped vessel having upper and lower portions with an pneumatically driven, sliding top assembly. Disposed inside the lead shield is a gamma ray scintillation crystal detector. Access to the gamma detector is through the sliding top assembly.

High resolution x-ray and gamma ray imaging using diffraction lenses with mechanically bent crystals

DOEpatents

Smither, Robert K [Hinsdale, IL

2008-12-23

A method for high spatial resolution imaging of a plurality of sources of x-ray and gamma-ray radiation is provided. High quality mechanically bent diffracting crystals of 0.1 mm radial width are used for focusing the radiation and directing the radiation to an array of detectors which is used for analyzing their addition to collect data as to the location of the source of radiation. A computer is used for converting the data to an image. The invention also provides for the use of a multi-component high resolution detector array and for narrow source and detector apertures.

The Spectrum of Isotropic Diffuse Gamma-Ray Emission Between 100 Mev and 820 Gev

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Brandt, T. J.; Hays, E.;

Preliminary design and performance of an advanced gamma ray spectrometer for future orbiter missions. [composition and evolution of planets

NASA Technical Reports Server (NTRS)

Metzger, A. E.; Parker, R. H.; Arnold, J. R.; Reedy, R. C.; Trombka, J. I.

1975-01-01

A knowledge of the composition of planets, satellites, and asteroids is of primary importance in understanding the formation and evolution of the solar system. Gamma-ray spectroscopy is capable of measuring the composition of meter-depth surface material from orbit around any body possessing little or no atmosphere. Measurement sensitivity is determined by detector efficiency and resolution, counting time, and the background flux while the effective spatial resolution depends upon the field-of-view and counting time together with the regional contrast in composition. The advantages of using germanium as a detector of gamma rays in space are illustrated experimentally and a compact instrument cooled by passive thermal radiation is described. Calculations of the expected sensitivity of this instrument at the Moon and Mars show that at least a dozen elements will be detected, twice the number which have been isolated in the Apollo gamma-ray data.

Gamma ray spectroscopy with Arduino UNO

NASA Astrophysics Data System (ADS)

Lavelle, C. M.

2018-05-01

We review a simple gamma ray spectrometer constructed on a solderless breadboard. The spectrometer's detector consists of a CsI(Tl) scintillator and silicon photomultiplier (SiPM) and its readout is facilitated by an Arduino UNO. The system is low cost and utilizes a minimum of components while still achieving satisfactory charge linearity and noise levels. This instrument can be used in instructional laboratories to introduce both radiation detection and analog signal processing concepts. We also expect it will be of interest to those seeking to introduce gamma spectroscopy to the expanding ecosystem of Arduino hardware.

Gamma-Ray Bursts: An Overview

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

1995-01-01

A history and overview of the observed properties of gamma-ray bursts are presented. The phenomenon of gamma-ray bursts is without precedent in astronomy, having no observed property that would be a direct indicator of their distance and no counterpart object in another wavelength region. Their brief, random appearance only in the gamma-ray region has made their study difficult. The observed time profiles, spectral properties, and durations of gamma-ray bursts cover a wide range. All proposed models for their origin must be considered speculative. It is humbling to think that even after 25 years since their discovery, the distance scale of gamma-ray bursts is still very much debatable.

Reusable shielding material for neutron- and gamma-radiation

NASA Astrophysics Data System (ADS)

Calzada, Elbio; Grünauer, Florian; Schillinger, Burkhard; Türck, Harald

2011-09-01

At neutron research facilities all around the world radiation shieldings are applied to reduce the background of neutron and gamma radiation as far as possible in order to perform high quality measurements and to fulfill the radiation protection requirements. The current approach with cement-based compounds has a number of shortcomings: "Heavy concrete" contains a high amount of elements, which are not desired to obtain a high attenuation of neutron and/or gamma radiation (e.g. calcium, carbon, oxygen, silicon and aluminum). A shielding material with a high density of desired nuclei such as iron, hydrogen and boron was developed for the redesign of the neutron radiography facility ANTARES at beam tube 4 (located at a cold neutron source) of FRM-II. The composition of the material was optimized by help of the Monte Carlo code MCNP5. With this shielding material a considerable higher attenuation of background radiation can be obtained compared to usual heavy concretes.

Effects of increased shielding on gamma-radiation levels within spacecraft

NASA Astrophysics Data System (ADS)

Haskins, P. S.; McKisson, J. E.; Weisenberger, A. G.; Ely, D. W.; Ballard, T. A.; Dyer, C. S.; Truscott, P. R.; Piercey, R. B.; Ramayya, A. V.; Camp, D. C.

The Shuttle Activation Monitor (SAM) experiment was flown on the Space Shuttle Columbia (STS-28) from 8 - 13 August, 1989 in a 57°, 300 km orbit. One objective of the SAM experiment was to determine the relative effect of different amounts of shielding on the gamma-ray backgrounds measured with similarly configured sodium iodide (NaI) and bismuth germante (BGO) detectors. To achieve this objective twenty-four hours of data were taken with each detector in the middeck of the Shuttle on the ceiling of the airlock (a high-shielding location) as well as on the sleep station wall (a low-shielding location). For the cosmic-ray induced background the results indicate an increased overall count rate in the 0.2 to 10 MeV energy range at the more highly shielded location, while in regions of trapped radiation the low shielding configuration gives higher rates at the low energy end of the spectrum.

Evaluation of the gamma radiation shielding parameters of bismuth modified quaternary glass system

NASA Astrophysics Data System (ADS)

Kaur, Parminder; Singh, K. J.; Thakur, Sonika

2018-05-01

Glasses modified with heavy metal oxides (HMO) are an interesting area of research in the field of gamma-ray shielding. Bismuth modified lithium-zinc-borate glasses have been studied whereby bismuth oxide is added from 0 to 50 mol%. The gamma ray shielding properties of the glasses were evaluated at photon energy 662 keV with the help of XMuDat computer program by using the Hubbell and Seltzer database. Various gamma ray shielding parameters such as attenuation coefficient, shield thickness in terms of half and tenth value layer, effective atomic number have been studied in this work. A useful comparison of this glass system has been made with standard radiation shielding concretes viz. ordinary, barite and iron concrete. The glass samples containing 20 to 50 mol% bismuth oxide have shown better gamma ray shielding properties and hence have the potential to become good radiation absorbers.

Computed radiography as a gamma ray detector—dose response and applications

NASA Astrophysics Data System (ADS)

O'Keeffe, D. S.; McLeod, R. W.

2004-08-01

Computed radiography (CR) can be used for imaging the spatial distribution of photon emissions from radionuclides. Its wide dynamic range and good response to medium energy gamma rays reduces the need for long exposure times. Measurements of small doses can be performed without having to pre-sensitize the computed radiography plates via an x-ray exposure, as required with screen-film systems. Cassette-based Agfa MD30 and Kodak GP25 CR plates were used in applications involving the detection of gamma ray emissions from technetium-99m and iodine-131. Cassette entrance doses as small as 1 µGy (140 keV gamma rays) produce noisy images, but the images are suitable for applications such as the detection of breaks in radiation protection barriers. A consequence of the gamma ray sensitivity of CR plates is the possibility that some nuclear medicine patients may fog their x-rays if the x-ray is taken soon after their radiopharmaceutical injection. The investigation showed that such fogging is likely to be diffuse.

Improved detector for the measurement of gamma radiation

NASA Astrophysics Data System (ADS)

Zelt, F. B.

1985-07-01

The present invention lies in the field of gamma ray spectrometry of geologic deposits and other materials, such as building materials (cement, asphalt, etc.) More specifically, the invention is an improved device for the gamma ray spetcrometery of gelogical deposits as a tool for petroleum exploration, geologic research and monitoring of radio-active materials such as in uranium mill tailings and the like. Improvement consists in enlarging the area of the receptor face and without any necessarily substantial increase in the volume of the receptor crystal over the current cylindrical shapes. The invention also provides, as a corollary of the increase in area receptor crystal face, a reduction in the weight of the amount of material necessary to provide effective shielding of the crystal from atmospheric radiation and radiation from deposits not under examination. The area of the receptor crystal face is increased by forming the crystal as a truncated cone with the shielding shaped as a hollow frustrum of a cone. A photomultiplier device is secured to the smaller face of the crystal. The improved detector shape can also be used in scintillometers which measure total gamma radiation.

Gamma-ray lines from neutron stars as probes of fundamental physics

NASA Technical Reports Server (NTRS)

Brecher, K.

1978-01-01

The detection of gamma-ray lines produced at the surface of neutron stars will serve to test both the strong and gravitational interactions under conditions unavailable in terrestrial laboratories. Observation of a single redshifted gamma-ray line, combined with an estimate of the mass of the star will serve as a strong constraint on allowable equations of state of matter at supernuclear densities. Detection of two redshifted lines arising from different physical processes at the neutron star surface can provide a test of the strong principle of equivalence. Expected fluxes of nuclear gamma-ray lines from accreting neutron stars were calculated, including threshold, radiative transfer and redshift effects. The most promising probes of neutron star structure are the deuterium formation line and the positron annihilation line. Detection of sharp redshifted gamma-ray lines from X-ray sources such as Cyg X-1 would argue strongly in favor of a neutron star rather than black hole identification for the object.

Gamma radiation exposure of accompanying persons due to Lu-177 patients

NASA Astrophysics Data System (ADS)

Kovan, Bilal; Demir, Bayram; Tuncman, Duygu; Capali, Veli; Turkmen, Cuneyt

2015-07-01

Neuroendocrine tumours (NET) are cancers usually observed and arisen in the stomach, intestine, pancreas and breathing system. Recently, radionuclide therapy applications with Lu-177 peptide compound are rapidly growing; especially effective clinical results are obtained in the treatment of well-differentiated and metastatic NET. In this treatment, Lu-177-DOTA, a beta emitter radioisotope in the radiopharmaceutical form, is given to the patient by intravenous way. Lu-177 has also gamma rays apart from beta rays. Gamma rays have 175 keV average energy and these gamma rays should be under the control in terms of radiation protection. In this study, we measured the exposure dose from the Lu-177 patient.

A Monte Carlo simulation to study a design of a gamma-ray detector for neutron resonance densitometry

NASA Astrophysics Data System (ADS)

Tsuchiya, H.; Harada, H.; Koizumi, M.; Kitatani, F.; Takamine, J.; Kureta, M.; Iimura, H.