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

NASA Astrophysics Data System (ADS)

Jones, James L.

1997-02-01

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

Analysis of Nuclear Lifetimes Using the Gamma-ray Induced Doppler Shift Attenuation Method

NASA Astrophysics Data System (ADS)

Crespi, F. C. L.

2018-05-01

Lifetime measurements allow extraction of fundamental information on the nature of the excited states of a nuclear system. Since nuclear lifetimes cover many orders of magnitude, a number of experimental techniques and detection setups have been developed depending on the range of the lifetime of interest. The Gamma-ray Induced Doppler Shift Attenuation (GRIDSA) Method presented here is applied to the measurement of very short lifetimes, in the femtosecond range. It allows determining the nuclear lifetime by measuring the Doppler shift of a gamma ray emitted from the state of interest, in different directions with respect to a coincident preceding gamma ray, populating the same state and inducing a recoil of the nucleus in the target material with velocities of the order of 104-105 m/s. We realized an experiment in order to test the GRIDSA technique for the measurement of fs lifetimes after (n,γ) reactions. The measurement was performed at the Institut Laue-Langevin (ILL) with the 8 Ge-clover detectors of the FIPPS array. Preliminary results are discussed.

Measurement of radon/thoron exhalation rates and gamma-ray dose rate in granite areas in Japan.

PubMed

Prasad, G; Ishikawa, T; Hosoda, M; Sahoo, S K; Kavasi, N; Sorimachi, A; Tokonami, S; Uchida, S

2012-11-01

Radon and thoron exhalation rates and gamma-ray dose rate in different places in Hiroshima Prefecture were measured. Exhalation rates were measured using an accumulation chamber method. The radon exhalation rate was found to vary from 3 to 37 mBq m(-2) s(-1), while the thoron exhalation rate ranged from 40 to 3330 mBq m(-2) s(-1). The highest radon exhalation rate (37 mBq m(-2) s(-1)) and gamma-ray dose rate (92 nGy h(-1)) were found in the same city (Kure City). In Kure City, indoor radon and thoron concentrations were previously measured at nine selected houses using a radon-thoron discriminative detector (Raduet). The indoor radon concentrations varied from 16 to 78 Bq m(-3), which was higher than the average value in Japan (15.5 Bq m(-3)). The indoor thoron concentration ranged from ND (not detected: below a detection limit of approximately 10 Bq m(-3)) to 314 Bq m(-3). The results suggest that radon exhalation rate from the ground is an influential factor for indoor radon concentration.

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.

Ultra-High Rate Measurements of Spent Fuel Gamma-Ray Emissions

NASA Astrophysics Data System (ADS)

Rodriguez, Douglas; Vandevender, Brent; Wood, Lynn; Glasgow, Brian; Taubman, Matthew; Wright, Michael; Dion, Michael; Pitts, Karl; Runkle, Robert; Campbell, Luke; Fast, James

2014-03-01

Presently there are over 200,000 irradiated spent nuclear fuel (SNF) assemblies in the world, each containing a concerning amount of weapons-usable material. Both facility operators and safeguards inspectors want to improve composition determination. Current measurements are expensive and difficult so new methods are developed through models. Passive measurements are limited since a few specific decay products and the associated down-scatter overwhelm the gamma rays of interest. Active interrogation methods produce gamma rays beyond 3 MeV, minimizing the impact of the passive emissions that drop off sharply above this energy. New devices like the Ultra-High Rate Germanium (UHRGe) detector are being developed to advance these novel measurement methods. Designed for reasonable resolution at 106 s-1 output rates (compared to ~ 1 - 10 e 3 s-1 standards), SNF samples were directly measured using UHRGe and compared to models. Model verification further enables using Los Alamos National Laboratory SNF assembly models, developed under the Next Generation Safeguards Initiative, to determine emission and signal expectations. Measurement results and future application requirements for UHRGe will be discussed.

Suppressing effect of low-dose gamma-ray irradiation on collagen-induced arthritis.

PubMed

Nakatsukasa, Hiroko; Tsukimoto, Mitsutoshi; Ohshima, Yasuhiro; Tago, Fumitoshi; Masada, Ayako; Kojima, Shuji

2008-07-01

We previously reported attenuation of autoimmune disease by low-dose gamma-ray irradiation in MRL-lpr/lpr mice. Here, we studied the effect of low-dose gamma-ray irradiation on collagen-induced arthritis (CIA) in DBA/1J mice. Mice were immunized with type II collagen, and exposed to low-dose gamma-rays (0.5 Gy per week for 5 weeks). Paw swelling, redness, and bone degradation were suppressed by irradiation, which also delayed the onset of pathological change and reduced the severity of the arthritis. Production of tumor necrosis factor-alpha, interferon-gamma, and interleukin-6, which play important roles in the onset of CIA, was suppressed by the irradiation. The level of anti-type II collagen antibody, which is essential for the onset of CIA, was also lower in irradiated CIA mice. The population of plasma cells was increased in CIA mice, but irradiation blocked this increase. Since regulatory T cells are known to be involved in suppression of autoimmune disease, the population of CD4(+)CD25(+)Foxp3(+) regulatory T cells was measured. Intriguingly, a significant increase of these regulatory T cells was found in irradiated CIA mice. Overall, our data suggest that low-dose gamma-ray irradiation could attenuate CIA through suppression of pro-inflammatory cytokines and autoantibody production, and induction of regulatory T cells.

Cosmic rays, gamma rays and synchrotron radiation from the Galaxy

DOE PAGES

Orlando, Elena

2012-07-30

Galactic cosmic rays (CR), interstellar gamma-ray emission and synchrotron radiation are related topics. CR electrons propagate in the Galaxy and interact with the interstellar medium, producing inverse-Compton emission measured in gamma rays and synchrotron emission measured in radio. I present an overview of the latest results with Fermi/LAT on the gamma-ray diffuse emission induced by CR nuclei and electrons. Then I focus on the recent complementary studies of the synchrotron emission in the light of the latest gamma-ray results. Relevant observables include spectral indices and their variations, using surveys over a wide range of radio frequencies. As a result, thismore » paper emphasizes the importance of using the parallel study of gamma rays and synchrotron radiation in order to constrain the low-energy interstellar CR electron spectrum, models of propagation of CRs, and magnetic fields.« less

Topics in Astrophysical X-Ray and Gamma Ray Spectroscopy. Ph.D. Thesis - Maryland Univ.

NASA Technical Reports Server (NTRS)

Bussard, R. W.

1978-01-01

A number of topics relating to astrophysical observations that have already been made or are currently planned of spectral features, mostly emission lines, in the X-ray and gamma ray region of the electromagnetic spectrum are investigated. These topics include: the production of characteristic X-ray and gamma ray lines by nonthermal ions, spectral features induced by processes occurring in strong magnetic fields, and the positron annihilation line at 0.5 MeV. The rate of X-ray production at 6.8 keV by the 2p to 1s transition in fast hydrogen- and helium-like iron ions, following both electron capture to excited levels and collisional excitation is calculated. The cross section for electron-ion Coulomb collisions in strong fields is also calculated.

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

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

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

2014-02-01

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

Gamma-ray dose rate surveys help investigating century-scale beach ridge progradation in the wave-dominated Catumbela delta (Angola)

NASA Astrophysics Data System (ADS)

Dinis, Pedro A.; Pereira, Alcides C.; Quinzeca, Domingos; Jombi, Domingos

2017-10-01

A strandplain at the downdrift side of the wave-dominated Catumbela delta (Angola) includes distinguishable deposits with very high natural radioactivity (up to 0.44 microSv/hour). In order to establish the geometry of these sedimentary units and understand their genetic processes, dose rate surveys were performed with the portable equipment Rados RDS-40WE. In addition, grain-size distribution, heavy-mineral composition and gamma-ray mass spectra of the high dose rate deposits were analysed. High dose rate values are found in ribbon units aligned parallel to the shoreline, which are a few tens of meters wide and up to approximately 3 km long. These units reflect the concentration of Th-bearing grains in coastal deposits enriched in heavy minerals. An integrated analysis of the high dose rate ribbons in GIS environment with aerial photography and topographic maps suggests that parts of the high dose rate units formed during the last two centuries may be related with the erosion of older shoreline deposits, due to updrift displacements of the Catumbela river outlet and recycling of shoreline accumulations with downdrift deposition. Simple gamma-ray surveys carried out with a portable detector can unravel depositional units characterised by significant enrichment in heavy-mineral grains that are likely to correspond to key events in the evolution of wave-dominated accumulations. The location of such deposits should be taken into account when planning future work using more expensive or time-consuming techniques.

Note: Operation of gamma-ray microcalorimeters at elevated count rates using filters with constraints

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

Alpert, B. K.; Horansky, R. D.; Bennett, D. A.

Microcalorimeter sensors operated near 0.1 K can measure the energy of individual x- and gamma-ray photons with significantly more precision than conventional semiconductor technologies. Both microcalorimeter arrays and higher per pixel count rates are desirable to increase the total throughput of spectrometers based on these devices. The millisecond recovery time of gamma-ray microcalorimeters and the resulting pulse pileup are significant obstacles to high per pixel count rates. Here, we demonstrate operation of a microcalorimeter detector at elevated count rates by use of convolution filters designed to be orthogonal to the exponential tail of a preceding pulse. These filters allow operationmore » at 50% higher count rates than conventional filters while largely preserving sensor energy resolution.« less

Low-dose gamma-ray irradiation induces translocation of Nrf2 into nuclear in mouse macrophage RAW264.7 cells.

PubMed

Tsukimoto, Mitsutoshi; Tamaishi, Nana; Homma, Takujiro; Kojima, Shuji

2010-01-01

The transcription factor nuclear erythroid-derived 2-related factor 2 (Nrf2) regulates expression of genes encoding antioxidant proteins involved in cellular redox homeostasis, while gamma-ray irradiation is known to induce reactive oxygen species in vivo. Although activation of Nrf2 by various stresses has been studied, it has not yet been determined whether ionizing irradiation induces activation of Nrf2. Therefore, we investigated activation of Nrf2 in response to gamma-irradiation in mouse macrophage RAW264.7 cells. Irradiation of cells with gamma-rays induced an increase of Nrf2 expression. Even 0.1 Gy of gamma-irradiation induced a translocation of Nrf2 from cytoplasm to the nucleus, indicating the activation of Nrf2 by low-dose irradiation. Expression of heme oxygenase-1, which is regulated by Nrf2, was also increased at 24 h after irradiation with more than 0.1 Gy of gamma-rays. Furthermore, the activation of Nrf2 was suppressed by U0126, which is an inhibitor of the extracellular signal regulated protein kinase 1/2 (ERK1/2) pathway, suggesting involvement of ERK1/2-dependent pathway in the irradiation-induced activation of Nrf2. Our results indicate that low-dose gamma-irradiation induces activation of Nrf2 through ERK1/2-dependent pathways.

Gamma-ray Output Spectra from 239 Pu Fission

DOE PAGES

Ullmann, John

2015-05-25

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

Constraints onthe bulk Lorentz factor of gamma-ray burstswith the detection rate by Fermi LAT

NASA Astrophysics Data System (ADS)

Chen, Ye; Liu, Ruo-Yu; Wang, Xiang-Yu

2018-07-01

The bulk Lorentz factor (Γ) of the outflow is an essential parameter for understanding the physics of gamma-ray burst (GRB). Informations about the Lorentz factors of some individual GRBs have been obtained from the spectral features of the high-energy gamma-ray emissions (>100 MeV), assuming that the spectral breaks or cutoffs are due to the pair-production attenuation (i.e. γγ → e+e-). In this paper, we attempt to interpret the dependence of the Large Area Telescope (LAT) detection rate of GRBs on the number of high-energy gamma-rays, taking into account the attenuation effect. We first simulate a long-GRB sample with Monte Carlo method using the luminosity function, rate distribution with redshift, and properties of the GRB spectrum. To characterize the distribution of the Lorentz factors, we assume that the Lorentz factors follow the relation Γ =Γ _0E_{iso, 52}k, where Eiso,52 is the isotropic photon energy in unit of 1052 erg. After taking into account the attenuation effect related with the above Lorentz factor distribution, we are able to reproduce the LAT-detected rate of GRBs as the function of the number of gamma-rays for suitable choice of the values of Γ0 and k. The result suggests that the distribution of the bulk Lorentz factor for the majority of GRBs is in the range of 50-250.

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.

[Protective effects of astaxanthin against oxidative damage induced by 60Co gamma-ray irradiation].

PubMed

Zhao, Wei; Jing, Xuejun; Chen, Chen; Cui, Jie; Yang, Mo; Zhang, Zunzhen

2011-09-01

To investigate the protection effect of haematococcus pluvialis (containing astaxanthin) against the impairment of anti-oxidative system and DNA damage in mice induced by 60Co gamma-rays. Fifty mice were randomly divided into five groups, i.e. three haematococcus pluvialis groups (41.7, 83.3 and 166.7 mg/kg in vegetable oil, respectively), control group and model group (vegetable oil only). All mice except control group were irradiated by 8 Gy 60Co gamma-rays 30 days later, and executed in the 4th day after irradiation. Liver cells were collected for the analysis of the integrity of DNA by comet assay, as well as MDA contents, SOD and GSH-Px activities in liver by commercial kits. Peripheral granulocyte and bone marrow nucleated cells were counted by hematocyte counter. MDA contents of model group were higher than those of control group (P < 0.01), and SOD, GSH-Px activities of model group were lower than those of control group (P < 0.01). Compared with the model group, MDA contents were decreased (P < 0.01), and SOD and GSH-Px activities were increased (P < 0.01) in all haematococcus pluvialis groups, especially in the high haematococcus pluvialis group, and the more haematococcus pluvialis in the diet of mice, the lower rate of comet tail and OTM value were shown (P < 0.01). Furthermore, the counts of peripheral granulocyte and bone marrow nucleated cells of model group were lower than those of the control group, while the counts of peripheral granulocyte and bone marrow nucleated cells of medium and high haematococcus pluvialis groups were increased significantly when compared with the model group (P < 0.01). Astaxanthin might have some protective effect against oxidative impairment and DNA damage induced by 60Co gamma-rays in mice.

Cosmological gamma-ray bursts

NASA Technical Reports Server (NTRS)

Paczynski, Bohdan

1991-01-01

The distribution in angle and flux of gamma-ray bursts indicates that the majority of gamma-ray bursters are at cosmological distances, i.e., at z of about 1. The rate is then about 10 exp -8/yr in a galaxy like the Milky Way, i.e., orders of magnitude lower than the estimated rate for collisions between neutron stars in close binary systems. The energy per burst is about 10 exp 51 ergs, assuming isotropic emission. The events appear to be less energetic and more frequent if their emission is strongly beamed. Some tests for the distance scale are discussed: a correlation between the burst's strength and its spectrum; the absorption by the Galactic gas below about 2 keV; the X-ray tails caused by forward scattering by the Galactic dust; about 1 month recurrence of some bursts caused by gravitational lensing by foreground galaxies; and a search for gamma-ray bursts in M31. The bursts appear to be a manifestation of something exotic, but conventional compact objects can provide an explanation. The best possibility is offered by a decay of a bindary composed of a spinning-stellar-mass black-hole primary and a neutron or a strange-quark star secondary. In the final phase the secondary is tidally disrupted, forms an accretion disk, and up to 10 exp 54 ergs are released. A very small fraction of this energy powers the gamma-ray burst.

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

NASA Technical Reports Server (NTRS)

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

2015-01-01

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

Development of a Watt-level gamma-ray source based on high-repetition-rate inverse Compton scattering

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

Mihalcea, D.; Murokh, A.; Piot, P.

2017-07-01

A high-brilliance (~10 22 photon s -1 mm -2 mrad -2 /0.1%) gamma-ray source experiment is currently being planned at Fermilab (E γ≃1.1 MeV). The source implements a high-repetition-rate inverse Compton scattering by colliding electron bunches formed in a ~300-MeV superconducting linac with a high-intensity laser pulse. This paper describes the design rationale along with some of technical challenges associated to producing high-repetition-rate collision. The expected performances of the gamma-ray source are also presented.

Dose rate estimation around a 60Co gamma-ray irradiation source by means of 115mIn photoactivation.

PubMed

Murataka, Ayanori; Endo, Satoru; Kojima, Yasuaki; Shizuma, Kiyoshi

2010-01-01

Photoactivation of nuclear isomer (115m)In with a halflife of 4.48 h occurs by (60)Co gamma-ray irradiation. This is because the resonance gamma-ray absorption occurs at 1078 keV level for stable (115)In, and that energy gamma-rays are produced by Compton scattering of (60)Co primary gamma-rays. In this work, photoactivation of (115m)In was applied to estimate the dose rate distribution around a (60)Co irradiation source utilizing a standard dose rate taken by alanine dosimeter. The (115m)In photoactivation was measured at 10 to 160 cm from the (60)Co source. The derived dose rate distribution shows a good agreement with both alanine dosimeter data and Monte Carlo simulation. It is found that angular distribution of the dose rate along a circumference at radius 2.8 cm from the central axis shows +/- 10% periodical variation reflecting the radioactive strength of the source rods, but less periodic distribution at radius 10 and 20 cm. The (115m)In photoactivation along the vertical direction in the central irradiation port strongly depends on the height and radius as indicated by Monte Carlo simulation. It is demonstrated that (115m)In photoactivation is a convenient method to estimate the dose rate distribution around a (60)Co source.

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

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.

A comparison of neutron and gamma damage effects on silica glass in a nuclear reactor radiation environment

NASA Astrophysics Data System (ADS)

Holcomb, David E.; Miller, Don W.

1993-08-01

A study of the relative damage effects of neutrons and gamma rays on silica glass in a nuclear reactor radiation environment is reported. The neutron and gamma energy spectra of the Ohio State University Research Reactor beam port #1 were applied to silica glass to obtain primary knock-on charged particle energy spectra. The resultant charged particle spectra were then applied to the polyatomic forms of the Lindhard et al. integrodifferential equation for damage energy and the Parkin and Coulter integrodifferential equation for net atomic displacement. The results show that near a nuclear reactor core the vast majority of the dose to silica is due to gamma rays (factor of roughly 40) and that neutrons cause much more displacement damage than gamma rays (35 times the oxygen displacement rate and 500 times the silicon displacement rate). However, pure silica core optical fibers irradiated in a nuclear reactor's mixed neutron/gamma environment exhibit little difference in transmission loss on an equal dose basis compared to fibers irradiated in a gamma only environment, indicating that atomic displacement is not a significant damage mechanism.

Gamma-Ray Emission from Galaxy Clusters : DARK MATTER AND COSMIC-RAYS

NASA Astrophysics Data System (ADS)

Pinzke, Anders

The quest for the first detection of a galaxy cluster in the high energy gamma-ray regime is ongoing, and even though clusters are observed in several other wave-bands, there is still no firm detection in gamma-rays. To complement the observational efforts we estimate the gamma-ray contributions from both annihilating dark matter and cosmic-ray (CR) proton as well as CR electron induced emission. Using high-resolution simulations of galaxy clusters, we find a universal concave shaped CR proton spectrum independent of the simulated galaxy cluster. Specifically, the gamma-ray spectra from decaying neutral pions, which are produced by CR protons, dominate the cluster emission. Furthermore, based on our derived flux and luminosity functions, we identify the galaxy clusters with the brightest galaxy clusters in gamma-rays. While this emission is challenging to detect using the Fermi satellite, major observations with Cherenkov telescopes in the near future may put important constraints on the CR physics in clusters. To extend these predictions, we use a dark matter model that fits the recent electron and positron data from Fermi, PAMELA, and H.E.S.S. with remarkable precision, and make predictions about the expected gamma-ray flux from nearby clusters. In order to remain consistent with the EGRET upper limit on the gamma-ray emission from Virgo, we constrain the minimum mass of substructures for cold dark matter halos. In addition, we find comparable levels of gamma-ray emission from CR interactions and dark matter annihilations without Sommerfeld enhancement.

Fieldable computer system for determining gamma-ray pulse-height distributions, flux spectra, and dose rates from Little Boy

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

Moss, C.E.; Lucas, M.C.; Tisinger, E.W.

1984-01-01

Our system consists of a LeCroy 3500 data acquisition system with a built-in CAMAC crate and eight bismuth-germanate detectors 7.62 cm in diameter and 7.62 cm long. Gamma-ray pulse-height distributions are acquired simultaneously for up to eight positions. The system was very carefully calibrated and characterized from 0.1 to 8.3 MeV using gamma-ray spectra from a variety of radioactive sources. By fitting the pulse-height distributions from the sources with a function containing 17 parameters, we determined theoretical repsonse functions. We use these response functions to unfold the distributions to obtain flux spectra. A flux-to-dose-rate conversion curve based on the workmore » of Dimbylow and Francis is then used to obtain dose rates. Direct use of measured spectra and flux-to-dose-rate curves to obtain dose rates avoids the errors that can arise from spectrum dependence in simple gamma-ray dosimeter instruments. We present some gamma-ray doses for the Little Boy assembly operated at low power. These results can be used to determine the exposures of the Hiroshima survivors and thus aid in the establishment of radation exposure limits for the nuclear industry.« less

Search for Cosmic-Ray-Induced Gamma-Ray Emission in Galaxy Clusters

NASA Technical Reports Server (NTRS)

Ackermann, M.; Ajello, M.; Albert, A.; Allafort, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.;

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.

Constraints on the bulk Lorentz factor of gamma-ray bursts with the detection rate by Fermi LAT

NASA Astrophysics Data System (ADS)

Chen, Ye; Liu, Ruo-Yu; Wang, Xiang-Yu

2018-05-01

The bulk Lorentz factor(Γ) of the outflow is an essential parameter to understanding the physics of gamma-ray burst (GRB). Informations about the Lorentz factors of some individual GRBs have been obtained from the spectral features of the high-energy gamma-ray emissions (>100 MeV), assuming that the spectral breaks or cutoffs are due to the pair-production attenuation (i.e., γγ → e+e-). In this paper, we attempt to interpret the dependence of the LAT detection rate of GRBs on the number of high-energy gamma-rays, taking into account the attenuation effect. We first simulate a long-GRB sample with Monte Carlo method using the luminosity function, rate distribution with redshift and properties of the GRB spectrum. To characterize the distribution of the Lorentz factors, we assume that the Lorentz factors follow the relation Γ =Γ _0E_iso,52k, where Eiso, 52 is the isotropic photon energy in unit of 1052erg. After taking into account the attenuation effect related with the above Lorentz factor distribution, we are able to reproduce the LAT-detected rate of GRBs as the function of the number of gamma-rays for suitable choice of the values of Γ0 and k. The result suggests that the distribution of the bulk Lorentz factor for the majority of GRBs is in the range of 50 - 250.

Fermi Sees the Gamma Ray Sky

NASA Image and Video Library

2009-10-30

This view of the gamma-ray sky constructed from one year of Fermi LAT observations is the best view of the extreme universe to date. The map shows the rate at which the LAT detects gamma rays with energies above 300 million electron volts -- about 120 million times the energy of visible light -- from different sky directions. Brighter colors equal higher rates. Credit: NASA/DOE/Fermi LAT Collaboration Full story: www.nasa.gov/mission_pages/GLAST/news/first_year.html

Effect of gamma-ray irradiation on the device process-induced defects in 4H-SiC epilayers

NASA Astrophysics Data System (ADS)

Miyazaki, T.; Makino, T.; Takeyama, A.; Onoda, S.; Ohshima, T.; Tanaka, Y.; Kandori, M.; Yoshie, T.; Hijikata, Y.

2016-11-01

We investigated the gamma-ray irradiation effect on 4H-SiC device process-induced defects by photoluminescence (PL) imaging and deep level transient spectroscopy (DLTS). We found that basal plane dislocations (BPDs) that were present before the irradiation were eliminated by gamma-ray irradiation of 1 MGy. The reduction mechanism of BPD was discussed in terms of BPD-threading edge dislocation (TED) transformation and shrinkage of stacking faults. In addition, the entire PL image was gradually darkened with increasing absorbed dose, which is presumably due to the point defects generated by gamma-ray irradiation. We obtained DLTS peaks that could be assigned to complex defects, termed RD series, and found that the peaks increased with absorbed dose.

Found: A Galaxy's Missing Gamma Rays

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-04-01

]Peng and collaborators argue that this emission is due solely to cosmic-ray interactions with interstellar gas. This picture is supported by the lack of variability in the emission, and the fact that Arp 220s gamma-ray luminosity is consistent with the scaling relation between gamma-ray and infrared luminosity for star-forming galaxies. The authors also argue that, due to Arp 220s high gas density, all cosmic rays will interact with the gas before escaping.Under these two assumptions, Peng and collaborators use the gamma-ray luminosity and the known supernova rate in Arp 220 to estimate how efficiently cosmic rays are acceleratedby supernova remnants in the galaxy. They determine that 4.2 2.6% of the supernova remnants kinetic energy is used to accelerate cosmic rays above 1 GeV.This is the first time such a rate has been measured directly from gamma-ray emission, but its consistent with estimates of 3-10% efficiency in the Milky Way. Future analysis of other ultraluminous infrared galaxies like Arp 220 with Fermi (and Pass 8!) will hopefully reveal more about these recent-merger, starburst environments.CitationFang-Kun Peng et al 2016 ApJ 821 L20. doi:10.3847/2041-8205/821/2/L20

Microscopic observations of X-ray and gamma-ray induced decomposition of ammonium perchlorate crystals

NASA Technical Reports Server (NTRS)

Herley, P. J.; Levy, P. W.

1972-01-01

The X-ray and gamma-ray induced decomposition of ammonium perchlorate was studied by optical, transmission, and scanning electron microscopy. This material is a commonly used oxidizer in solid propellents which could be employed in deep-space probes, and where they will be subjected to a variety of radiations for as long as ten years. In some respects the radiation-induced damage closely resembles the effects produced by thermal decomposition, but in other respects the results differ markedly. Similar radiation and thermal effects include the following: (1) irregular or ill-defined circular etch pits are formed in both cases; (2) approximately the same size pits are produced; (3) the pit density is similar; (4) the c face is considerably more reactive than the m face; and (5) most importantly, many of the etch pits are aligned in crystallographic directions which are the same for thermal or radiolytic decomposition. Thus, dislocations play an important role in the radiolytic decomposition process.

Active neutron and gamma-ray imaging of highly enriched uranium for treaty verification

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

Hamel, Michael C.; Polack, J. Kyle; Ruch, Marc L.

The detection and characterization of highly enriched uranium (HEU) presents a large challenge in the non-proliferation field. HEU has a low neutron emission rate and most gamma rays are low energy and easily shielded. To address this challenge, an instrument known as the dual-particle imager (DPI) was used with a portable deuterium-tritium (DT) neutron generator to detect neutrons and gamma rays from induced fission in HEU. We evaluated system response using a 13.7-kg HEU sphere in several configurations with no moderation, high-density polyethylene (HDPE) moderation, and tungsten moderation. A hollow tungsten sphere was interrogated to evaluate the response to amore » possible hoax item. First, localization capabilities were demonstrated by reconstructing neutron and gamma-ray images. Once localized, additional properties such as fast neutron energy spectra and time-dependent neutron count rates were attributed to the items. For the interrogated configurations containing HEU, the reconstructed neutron spectra resembled Watt spectra, which gave confidence that the interrogated items were undergoing induced fission. The time-dependent neutron count rate was also compared for each configuration and shown to be dependent on the neutron multiplication of the item. This result showed that the DPI is a viable tool for localizing and confirming fissile mass and multiplication.« less

Active neutron and gamma-ray imaging of highly enriched uranium for treaty verification

DOE PAGES

Hamel, Michael C.; Polack, J. Kyle; Ruch, Marc L.; ...

2017-08-11

The detection and characterization of highly enriched uranium (HEU) presents a large challenge in the non-proliferation field. HEU has a low neutron emission rate and most gamma rays are low energy and easily shielded. To address this challenge, an instrument known as the dual-particle imager (DPI) was used with a portable deuterium-tritium (DT) neutron generator to detect neutrons and gamma rays from induced fission in HEU. We evaluated system response using a 13.7-kg HEU sphere in several configurations with no moderation, high-density polyethylene (HDPE) moderation, and tungsten moderation. A hollow tungsten sphere was interrogated to evaluate the response to amore » possible hoax item. First, localization capabilities were demonstrated by reconstructing neutron and gamma-ray images. Once localized, additional properties such as fast neutron energy spectra and time-dependent neutron count rates were attributed to the items. For the interrogated configurations containing HEU, the reconstructed neutron spectra resembled Watt spectra, which gave confidence that the interrogated items were undergoing induced fission. The time-dependent neutron count rate was also compared for each configuration and shown to be dependent on the neutron multiplication of the item. This result showed that the DPI is a viable tool for localizing and confirming fissile mass and multiplication.« less

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.

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

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

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

2010-08-24

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

Particle-Induced Gamma-ray Emission Spectroscopy Over a Broad Range of Elements

NASA Astrophysics Data System (ADS)

Olds, Hannah; Wilkinson, John; Tighe, Meghanne; McLallen, Walter; McGuire, Patrick

2017-09-01

Ion beam analysis is a common application of nuclear physics that allows elemental and isotopic information about materials to be determined from accelerated light ion beams One of the best know ion beam analysis techniques is Particle-Induced Gamma-ray Emission (PIGE) spectroscopy, which can be used ex vacuo to identify the elements of interest in almost any solid target. The energies of the gamma-rays emitted by excited nuclei will be unique to each element and depend on its nuclear structure. For the most sensitivity, the accelerated ions should exceed the Coulomb barrier of the target, but many isotopes are known to be accessible to PIGE even below the Coulomb barrier. To explore the sensitivity of PIGE across the periodic table, PIGE measurements were made on elements with Z = 5, 9, 11-15, 17, 19-35, 37, 42, 44-48, 53, 56, 60, 62, 73, and 74 using 3.4 MeV protons. These measurements will be compared with literature values and be used as a basis for comparison with higher-energy proton beams available at the University of Notre Dame's St. Andre accelerator when it comes online this Fall. The beam normalization technique of using atmospheric argon and its 1459 keV gamma-ray to better estimate the integrated beam on target will also be discussed. Funded by the NSF REU program and the University of Notre Dame.

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.

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.

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.

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.

Effects of Correlated and Uncorrelated Gamma Rays on Neutron Multiplicity Counting

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

Cowles, Christian C.; Behling, Richard S.; Imel, George R.

Neutron multiplicity counting relies on time correlation between neutron events to assay the fissile mass, (α,n) to spontaneous fission neutron ratio, and neutron self-multiplication of samples. Gamma-ray sensitive neutron multiplicity counters may misidentify gamma rays as neutrons and therefore miscalculate sample characteristics. Time correlated and uncorrelated gamma-ray-like signals were added into gamma-ray free neutron multiplicity counter data to examine the effects of gamma ray signals being misidentified as neutron signals on assaying sample characteristics. Multiplicity counter measurements with and without gamma-ray-like signals were compared to determine the assay error associated with gamma-ray-like signals at various gamma-ray and neutron rates. Correlatedmore » and uncorrelated gamma-ray signals each produced consistent but different measurement errors. Correlated gamma-ray signals most strongly led to fissile mass overestimates, whereas uncorrelated gamma-ray signals most strongly lead to (α,n) neutron overestimates. Gamma-ray sensitive neutron multiplicity counters may be able to account for the effects of gamma-rays on measurements to mitigate measurement uncertainties.« less

Gamma non-ionizing energy loss: Comparison with the damage factor in silicon devices

NASA Astrophysics Data System (ADS)

El Allam, E.; Inguimbert, C.; Meulenberg, A.; Jorio, A.; Zorkani, I.

2018-03-01

The concept of non-ionizing energy loss (NIEL) has been demonstrated to be a successful approach to describe the displacement damage effects in silicon materials and devices. However, some discrepancies exist in the literature between experimental damage factors and theoretical NIELs. 60Co gamma rays having a low NIEL are an interesting particle source that can be used to validate the NIEL scaling approach. This paper presents different 60Co gamma ray NIEL values for silicon targets. They are compared with the radiation-induced increase in the thermal generation rate of carriers per unit fluence. The differences between the different models, including one using molecular dynamics, are discussed.

Gamma-Ray background spectrum and annihilation rate in the baryon-symmetric big-bang cosmology

NASA Technical Reports Server (NTRS)

Puget, J. L.

1973-01-01

An attempt was made to extract experimental data on baryon symmetry by observing annihilation products. Specifically, gamma rays and neutrons with long mean free paths were analyzed. Data cover absorption cross sections and radiation background of the 0.511 MeV gamma rays from positron annihilations and the 70 MeV gamma rays from neutral pion decay.

Nucleosynthesis, neutrino bursts and gamma-rays from coalescing neutron stars

NASA Technical Reports Server (NTRS)

Eichler, David; Livio, Mario; Piran, Tsvi; Schramm, David N.

1989-01-01

It is pointed out here that neutron-star collisions should synthesize neutron-rich heavy elements, thought to be formed by rapid neutron capture (the r-process). Furthermore, these collisions should produce neutrino bursts and resultant bursts of gamma rays; the latter should comprise a subclass of observable gamma-ray bursts. It is argued that observed r-process abundances and gamma-ray burst rates predict rates for these collisions that are both significant and consistent with other estimates.

Terrestrial Gamma-Ray Flashes (TGFs) Observed with the Fermi-Gamma-Ray Burst Monitor: The First Hundred TGFs

NASA Technical Reports Server (NTRS)

Fishman, G J.; Briggs, M. S.; Connaughton, V.; Bhat, P. N.

2010-01-01

The Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope Observatory (Fermi) is now detecting 2.1 TGFs per week. At this rate, nearly a hundred TGFs will have been detected by the time of this Meeting. This rate has increased by a factor of 8 since new flight software was uploaded to the spacecraft in November 2009 in order to increase the sensitivity of GBM to TGFs. The high time resolution (2 microseconds) allows temporal features to be resolved so that some insight may be gained on the origin and transport of the gamma-ray photons through the atmosphere. The absolute time of the TGFs, known to several microseconds, also allows accurate correlations of TGFs with lightning networks and other lightning-related phenomena. The thick bismuth germanate (BGO) scintillation detectors of the GBM system have observed photon energies from TGFs at energies above 40 MeV. New results on the some temporal aspects of TGFs will be presented.

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.

Very-High-Energy Solar Gamma Rays From Cosmic-Ray Interactions

NASA Astrophysics Data System (ADS)

Zhou, Bei; Ng, Kenny; Beacom, John; Peter, Annika; Rott, Cartsen

2017-01-01

Cosmic-ray induced gamma rays from the Sun has been observed up to 100 GeV. However, there are no theoretical predictions beyond 10 GeV. We provide the first calculation of the hadronic disk component in TeV-PeV, where solar magnetic fields can be ignored. We also consider the leptonic gamma-ray halo, taking into account electrons from local pulsars. With Fermi and soon HAWC & LHAASO observations, our results provide new insights on local cosmic rays, solar magnetic fields, and solar dark matter studies. BZ is supported by OSU Fowler Fellowship. KN and FB are supported by NSF Grant PHY-1404311. AK is supported by NSF GRFP Grant No. DGE-1321846. CR is supported by the Korea Neutrino Research Center. KN is also supported by the OSU Presidential Fellowship.

Characterization of gamma rays existing in the NMIJ standard neutron field.

PubMed

Harano, H; Matsumoto, T; Ito, Y; Uritani, A; Kudo, K

2004-01-01

Our laboratory provides national standards on fast neutron fluence. Neutron fields are always accompanied by gamma rays produced in neutron sources and surroundings. We have characterised these gamma rays in the 5.0 MeV standard neutron field. Gamma ray measurement was performed using an NE213 liquid scintillator. Pulse shape discrimination was incorporated to separate the events induced by gamma rays from those by neutrons. The measured gamma ray spectra were unfolded with the HEPRO program package to obtain the spectral fluences using the response matrix prepared with the EGS4 code. Corrections were made for the gamma rays produced by neutrons in the detector assembly using the MCNP4C code. The effective dose equivalents were estimated to be of the order of 25 microSv at the neutron fluence of 10(7) neutrons cm(-2).

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.

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.

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.

CHANGES IN FLAVONOIDS INDUCED BY $gamma$-RAY IRRADIATION (in Japanese)

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

Mizuno, T.; Kinpyo, T.

1960-07-01

Ethanol or pyridine solutions of five flavonoids, i.e., myricetin, quercetin, quercitrin, rutin, and hesperidin, were irradiated with gamma -rays (source Co/sup 60/). Results show that the decomposition of flavonoids increased with the increase of the total-dose gamma rays (0.5 to 770 k. r.) and that glycosides such as quercitrin and rutin were more stable than aglycons, such as myricetin or quercetin. It was found that monosaccharides and aglycons, which are the components of glycosides, were formed by gamma -ray decomposition of glycosides, such as quercitrin, rutin, or hesperidin, and that by the decomposition of aglycons such as myricetin or quercetinmore » an unknown substance (showing its peak at 297 m mu in ultraviolet absorption spectra) was formed. Infrared absorption spectra of the substances produced by radiolysis from the above-mentioned flavonoids were compared with those of the flavonoids. (auth)« less

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.

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 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.

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.

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.

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

PubMed

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

2009-11-01

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

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.

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

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.

Gamma ray energy tracking in GRETINA

NASA Astrophysics Data System (ADS)

Lee, I. Y.

2011-10-01

The next generation of stable and exotic beam accelerators will provide physics opportunities to study nuclei farther away from the line of stability. However, these experiments will be more demanding on instrumentation performance. These come from the lower production rate for more exotic beams, worse beam impurities, and large beam velocity from the fragmentation and inverse reactions. Gamma-ray spectroscopy will be one of the most effective tools to study exotic nuclei. However, to fully exploit the physics reach provided by these new facilities, better gamma-ray detector will be needed. In the last 10 years, a new concept, gamma-ray energy tracking array, was developed. Tracking arrays will increase the detection sensitivity by factors of several hundred compared to current arrays used in nuclear physics research. Particularly, the capability of reconstructing the position of the interaction with millimeters resolution is needed to correct the Doppler broadening of gamma rays emitted from high velocity nuclei. GRETINA is a gamma-ray tracking array which uses 28 Ge crystals, each with 36 segments, to cover ¼ of the 4 π of the 4 π solid angle. The gamma ray tracking technique requires detailed pulse shape information from each of the segments. These pulses are digitized using 14-bit 100 MHz flash ADCs, and digital signal analysis algorithms implemented in the on-board FPGAs provides energy, time and selection of pulse traces. A digital trigger system, provided flexible trigger functions including a fast trigger output, and also allows complicated trigger decisions to be made up to 20 microseconds. Further analyzed, carried out in a computer cluster, determine the energy, time, and three-dimensional positions of all gamma-ray interactions in the array. This information is then utilized, together with the characteristics of Compton scattering and pair-production processes, to track the scattering sequences of the gamma rays. GRETINA construction is completed in

Characterization of non-CG genomic hypomethylation associated with gamma-ray-induced suppression of CMT3 transcription in Arabidopsis thaliana.

PubMed

Kim, Ji Eun; Lee, Min Hee; Cho, Eun Ju; Kim, Ji Hong; Chung, Byung Yeoup; Kim, Jin-Hong

2013-12-01

Ionizing radiation causes various epigenetic changes, as well as a variety of DNA lesions such as strand breaks, cross-links, oxidative damages, etc., in genomes. However, radiation-induced epigenetic changes have rarely been substantiated in plant genomes. The current study investigates whether DNA methylation of Arabidopsis thaliana genome is altered by gamma rays. We found that genomic DNA methylation decreased in wild-type plants with increasing doses of gamma rays (5, 50 and 200 Gy). Irradiation with 200 Gy significantly increased the expression of transcriptionally inactive centromeric 180-bp (CEN) and transcriptionally silent information (TSI) repeats. This increase suggested that there was a substantial release of transcriptional gene silencing by gamma rays, probably by induction of DNA hypomethylation. High expression of the DNA demethylase ROS1 and low expression of the DNA methyltransferase CMT3 supported this hypothesis. Moreover, Southern blot analysis following digestion of genomic DNA with methylation-sensitive enzymes revealed that the DNA hypomethylation occured preferentially at CHG or CHH sites rather than CG sites, depending on the radiation dose. Unlike CEN and TSI repeats, the number of Ta3, AtSN1 and FWA repeats decreased in transcription but increased in non-CG methylation. In addition, the cmt3-11 mutant showed neither DNA hypomethylation nor transcriptional activation of silenced repeats upon gamma irradiation. Furthermore, profiles of genome-wide transcriptomes in response to gamma rays differed between the wild-type and cmt3-11 mutant. These results suggest that gamma irradiation induced DNA hypomethylation preferentially at non-CG sites of transcriptionally inactive repeats in a locus-specific manner, which depends on CMT3 activity.

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 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.

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.

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.

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.

Simulation of prompt gamma-ray emission during proton radiotherapy.

PubMed

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

2012-09-07

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

The goals of gamma-ray spectroscopy in high energy astrophysics

NASA Technical Reports Server (NTRS)

Lingenfelter, Richard E.; Higdon, James C.; Leventhal, Marvin; Ramaty, Reuven; Woosley, Stanford E.

1990-01-01

The use of high resolution gamma-ray spectroscopy in astrophysics is discussed with specific attention given to the application of the Nuclear Astrophysics Explorer (NAE). The gamma-ray lines from nuclear transitions in radionucleic decay and positron annihilation permits the study of current sites, rates and models of nucleosynthesis, and galactic structure. Diffuse galactic emission is discussed, and the high-resolution observations of gamma-ray lines from discrete sites are also described. Interstellar mixing and elemental abundances can also be inferred from high-resolution gamma-ray spectroscopy of nucleosynthetic products. Compact objects can also be examined by means of gamma-ray emissions, allowing better understanding of neutron stars and the accreting black hole near the galactic center. Solar physics can also be investigated by examining such features as solar-flare particle acceleration and atmospheric abundances.

Mutagenic effects of gamma rays on soybean (Glycine max L.) germination and seedlings

NASA Astrophysics Data System (ADS)

Kusmiyati, F.; Sutarno; Sas, M. G. A.; Herwibawa, B.

2018-01-01

Narrow genetic diversity is a main problem restricting the progress of soybean breeding. One way to improve genetic diversity of plant is through mutation. The purpose of this study was to investigate effect of different dose of gamma rays as induced mutagen on physiological, morphological, and anatomical markers during seed germination and seedling growth of soybean. Seeds of soybean cultivars Dering-1 were irradiated with 11 doses of gamma rays (0, 5, 10, 20, 40, 80, 160, 320, 640, 1280, and 2560 Gy [Gray]. The research design was arranged in a completely randomized block design in three replicates. Results showed that soybean seed exposed at high doses (640, 1280, and 2560 Gy) did not survive more than 20 days, the doses were then removed from anatomical evaluation. Higher doses of gamma rays siginificantly reduced germination percentage at the first count and final count, coefficient of germination velocity, germination rate index, germination index, seedling height and seedling root length, and significantly increased mean germination time, first day of germination, last day of germination, and time spread of germination. However, the effects of gamma rays were varies for density, width, and length of stomata. The LD50 obtained based on survival percentage was 314.78 Gy. It can be concluded that very low and low doses of gamma rays (5-320 Gy) might be used to study the improvement of soybean diversity.

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

NASA Astrophysics Data System (ADS)

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

2017-01-01

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

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.

An improved time of flight gamma-ray telescope to monitor diffuse gamma-ray in the energy range 5 MeV - 50 MeV

NASA Technical Reports Server (NTRS)

Dacostafereiraneri, A.; Bui-Van, A.; Lavigne, J. M.; Sabaud, C.; Vedrenne, G.; Agrinier, B.; Gouiffes, C.

1985-01-01

A time of flight measuring device is the basic triggering system of most of medium and high energy gamma-ray telescopes. A simple gamma-ray telescope has been built in order to check in flight conditions the functioning of an advanced time of flight system. The technical ratings of the system are described. This telescope has been flown twice with stratospheric balloons, its axis being oriented at various Zenital directions. Flight results are presented for diffuse gamma-rays, atmospheric secondaries, and various causes of noise in the 5 MeV-50 MeV energy range.

The First Fermi Large Area Telescope Catalog of Gamma-ray Pulsars

DOE PAGES

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

2010-03-25

The dramatic increase in the number of known gamma-ray pulsars since the launch of the Fermi Gamma-ray Space Telescope (formerly GLAST) offers the first opportunity to study a sizable population of these high-energy objects. This catalog summarizes 46 high-confidence pulsed detections using the first six months of data taken by the Large Area Telescope (LAT), Fermi's main instrument. Sixteen previously unknown pulsars were discovered by searching for pulsed signals at the positions of bright gamma-ray sources seen with the LAT, or at the positions of objects suspected to be neutron stars based on observations at other wavelengths. The dimmest observed flux among these gamma-ray-selected pulsars is 6.0 × 10 –8 ph cm –2 s –1 (for E>100 MeV). Pulsed gamma-ray emission was discovered from 24 known pulsars by using ephemerides (timing solutions) derived from monitoring radio pulsars. Eight of these new gamma-ray pulsars are millisecond pulsars. The dimmest observed flux among the radio-selected pulsars is 1.4 × 10 –8 ph cm –2 s –1 (for E>100 MeV). The remaining six gamma-ray pulsars were known since the Compton Gamma Ray Observatory mission, or before. The limiting flux for pulse detection is non-uniform over the sky owing to different background levels, especially near the Galactic plane. The pulsed energy spectra can be described by a power law with an exponential cutoff, with cutoff energies in the range ~1-5 GeV. The rotational energy-loss rate (more » $$\\dot{E}$$) of these neutron stars spans five decades, from ~3 × 10 33 erg s –1 to 5 × 10 38 erg s –1, and the apparent efficiencies for conversion to gamma-ray emission range from ~0.1% to ~ unity, although distance uncertainties complicate efficiency estimates. The pulse shapes show substantial diversity, but roughly 75% of the gamma-ray pulse profiles have two peaks, separated by ≳0.2 of rotational phase. For most of the pulsars, gamma-ray emission appears to come mainly from the outer

The Gamma-Ray Imager GRI

NASA Astrophysics Data System (ADS)

Wunderer, Cornelia B.; GRI Collaboration

2006-09-01

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear reactions are synthesizing the basic constituents of our world. Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime. With the INTEGRAL observatory, ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer coated mirror techniques have paved the way towards a gamma-ray mission, providing major improvements compared to past missions regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow to study particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

Gamma-ray Emission from Globular Clusters

NASA Astrophysics Data System (ADS)

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

2016-03-01

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

Active Neutron and Gamma-Ray Instrumentation for In Situ Planetary Science Applications

NASA Technical Reports Server (NTRS)

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

On the Induced Gravitational Collapse Scenario of Gamma-ray Bursts Associated with Supernovae

NASA Astrophysics Data System (ADS)

Becerra, L.; Bianco, C. L.; Fryer, C. L.; Rueda, J. A.; Ruffini, R.

2016-12-01

Following the induced gravitational collapse (IGC) paradigm of gamma-ray bursts (GRBs) associated with type Ib/c supernovae, we present numerical simulations of the explosion of a carbon-oxygen (CO) core in a binary system with a neutron-star (NS) companion. The supernova ejecta trigger a hypercritical accretion process onto the NS thanks to a copious neutrino emission and the trapping of photons within the accretion flow. We show that temperatures of 1-10 MeV develop near the NS surface, hence electron-positron annihilation into neutrinos becomes the main cooling channel leading to accretion rates of 10-9-{10}-1 {M}⊙ s-1 and neutrino luminosities of 1043-1052 erg s-1 (the shorter the orbital period the higher the accretion rate). We estimate the maximum orbital period, {P}\\max , as a function of the NS initial mass, up to which the NS companion can reach by hypercritical accretion the critical mass for gravitational collapse leading to black hole formation. We then estimate the effects of the accreting and orbiting NS companion onto a novel geometry of the supernova ejecta density profile. We present the results of a 1.4× {10}7 particle simulation which show that the NS induces accentuated asymmetries in the ejecta density around the orbital plane. We elaborate on the observables associated with the above features of the IGC process. We apply this framework to specific GRBs: we find that X-ray flashes (XRFs) and binary-driven hypernovae are produced in binaries with P\\gt {P}\\max and P\\lt {P}\\max , respectively. We analyze in detail the case of XRF 060218.

Genome-wide survey of artificial mutations induced by ethyl methanesulfonate and gamma rays in tomato.

PubMed

Shirasawa, Kenta; Hirakawa, Hideki; Nunome, Tsukasa; Tabata, Satoshi; Isobe, Sachiko

2016-01-01

Genome-wide mutations induced by ethyl methanesulfonate (EMS) and gamma irradiation in the tomato Micro-Tom genome were identified by a whole-genome shotgun sequencing analysis to estimate the spectrum and distribution of whole-genome DNA mutations and the frequency of deleterious mutations. A total of ~370 Gb of paired-end reads for four EMS-induced mutants and three gamma-ray-irradiated lines as well as a wild-type line were obtained by next-generation sequencing technology. Using bioinformatics analyses, we identified 5920 induced single nucleotide variations and insertion/deletion (indel) mutations. The predominant mutations in the EMS mutants were C/G to T/A transitions, while in the gamma-ray mutants, C/G to T/A transitions, A/T to T/A transversions, A/T to G/C transitions and deletion mutations were equally common. Biases in the base composition flanking mutations differed between the mutagenesis types. Regarding the effects of the mutations on gene function, >90% of the mutations were located in intergenic regions, and only 0.2% were deleterious. In addition, we detected 1,140,687 spontaneous single nucleotide polymorphisms and indel polymorphisms in wild-type Micro-Tom lines. We also found copy number variation, deletions and insertions of chromosomal segments in both the mutant and wild-type lines. The results provide helpful information not only for mutation research, but also for mutant screening methodology with reverse-genetic approaches. © 2015 The Authors. Plant Biotechnology Journal published by Society for Experimental Biology and The Association of Applied Biologists and John Wiley & Sons Ltd.

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.

Lunar elemental analysis obtained from the Apollo gamma-ray and X-ray remote sensing experiment

NASA Technical Reports Server (NTRS)

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

1974-01-01

Gamma ray and X-ray spectrometers carried in the service module of the Apollo 15 and 16 spacecraft were employed for compositional mapping of the lunar surface. The measurements involved the observation of the intensity and characteristics energy distribution of gamma rays and X-rays emitted from the lunar surface. A large scale compositional map of over 10 percent of the lunar surface was obtained from an analysis of the observed spectra. The objective of the X-ray experiment was to measure the K spectral lines from Mg, Al, and Si. Spectra were obtained and the data were reduced to Al/Si and Mg/Si intensity ratios and ultimately to chemical ratios. The objective of the gamma-ray experiment was to measure the natural and cosmic ray induced activity emission spectrum. At this time, the elemental abundances for Th, U, K, Fe, Ti, Si, and O have been determined over a number of major lunar regions.

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.

Gamma-Ray Astronomy Technology Needs

NASA Technical Reports Server (NTRS)

Gehrels, N.; Cannizzo, J. K.

2012-01-01

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

The Andromeda galaxy in gamma-rays

NASA Technical Reports Server (NTRS)

Oezel, M. E.; Berkhuijsen, E. M.

1987-01-01

Implications of high-energy gamma-ray observations of the Andromeda galaxy with the next generation of satellites Gamma-1 and GRO are discussed in the context of the origin of cosmic rays and gamma-ray processes. The present estimate of the total gamma-ray flux of this galaxy at energies above 100 MeV is a factor of about three less than previous estimates.

Gamma-ray burster recurrence timescales

NASA Technical Reports Server (NTRS)

Schaefer, B. E.; Cline, T. L.

1984-01-01

Three optical transients have been found which are associated with gamma-ray bursters (GRBs). The deduced recurrence timescale for these optical transients (tau sub opt) will depend on the minimum brightness for which a flash would be detected. A detailed analysis using all available data of tau sub opt as a function of E(gamma)/E(opt) is given. For flashes similar to those found in the Harvard archives, the best estimate of tau sub opt is 0.74 years, with a 99% confidence interval from 0.23 years to 4.7 years. It is currently unclear whether the optical transients from GRBs also give rise to gamma-ray events. One way to test this association is to measure the recurrence timescale of gamma-ray events tau sub gamma. A total of 210 gamma-ray error boxes were examined and it was found that the number of observed overlaps is not significantly different from the number expected from chance coincidence. This observation can be used to place limits on tau sub gamma for an assumed luminosity function. It was found that tau sub gamma is approx. 10 yr if bursts are monoenergetic. However, if GRBs have a power law luminosity function with a wide dynamic range, then the limit is tau sub gamma 0.5 yr. Hence, the gamma-ray data do not require tau sub gamma and tau sub opt to be different.

GRI: The Gamma-Ray Imager mission

NASA Astrophysics Data System (ADS)

Knödlseder, J.; Gri Consortium

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe While at lower wavebands the observed emission is generally dominated by thermal processes the gamma-ray sky provides us with a view on the non-thermal Universe Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood and nuclear reactions are synthesizing the basic constituents of our world Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime With the INTEGRAL observatory ESA has provided a unique tool to the astronomical community and has put Europe in the lead in the field of gamma-ray astronomy INTEGRAL provides an unprecedented survey of the soft gamma-ray sky revealing hundreds of sources new classes of objects extraordinary views of antimatter annihilation in our Galaxy and fingerprints of recent nucleosynthesis processes While INTEGRAL has provided the global overview over the soft gamma-ray sky there is a growing need to perform deeper more focused investigations of gamma-ray sources In soft X-rays a comparable step was taken going from the Einstein satellite to the XMM Newton observatory Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer-coated mirror techniques have paved the way towards a gamma-ray mission providing major improvements compared to past missions regarding sensitivity and angular resolution Such a

Gamma ray spectroscopy in astrophysics. [conferences

NASA Technical Reports Server (NTRS)

Cline, T. L. (Editor); Ramaty, R. (Editor)

1978-01-01

Experimental and theoretical aspects of gamma ray spectroscopy in high energy astrophysics are discussed. Line spectra from solar, stellar, planetary, and cosmic gamma rays are examined as well as HEAO investigations, the prospects of a gamma ray observatory, and follow-on X-ray experiments in space.

Gamma-ray line astrophysics

NASA Technical Reports Server (NTRS)

Lingenfelter, R. E.; Ramaty, R.

1986-01-01

Recent observations of gamma-ray line emission from solar flares, gamma-ray bursts, the galactic center, the interstellar medium and the jets of SS433 are reviewed. The implications of these observations on high energy processes in these sources are discussed.

A Compton scatter attenuation gamma ray spectrometer

NASA Technical Reports Server (NTRS)

Austin, W. E.

1972-01-01

A Compton scatter attenuation gamma ray spectrometer conceptual design is discussed for performing gamma spectral measurements in monodirectional gamma fields from 100 R per hour to 1,000,000 R per hour. Selectable Compton targets are used to scatter gamma photons onto an otherwise heavily shielded detector with changeable scattering efficiencies such that the count rate is maintained between 500 and 10,000 per second. Use of two sum-Compton coincident detectors, one for energies up to 1.5 MeV and the other for 600 keV to 10 MeV, will allow good peak to tail pulse height ratios to be obtained over the entire spectrum and reduces the neutron recoil background rate.

A Monte Carlo modeling alternative for the API Gamma Ray Calibration Facility.

PubMed

Galford, J E

2017-04-01

The gamma ray pit at the API Calibration Facility, located on the University of Houston campus, defines the API unit for natural gamma ray logs used throughout the petroleum logging industry. Future use of the facility is uncertain. An alternative method is proposed to preserve the gamma ray API unit definition as an industry standard by using Monte Carlo modeling to obtain accurate counting rate-to-API unit conversion factors for gross-counting and spectral gamma ray tool designs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Investigation of natural effective gamma dose rates case study: Ardebil Province in Iran

PubMed Central

2012-01-01

Gamma rays pose enough energy to induce chemical changes that may be biologically important for the normal functioning of body cells. The external exposure of human beings to natural environmental gamma radiation normally exceeds that from all man-made sources combined. In this research natural background gamma dose rates and corresponding annual effective doses were determined for selected cities of Ardebil province. Outdoor gamma dose rates were measured using an Ion Chamber Survey Meter in 105 locations in selected districts. Average absorbed doses for Ardebil, Sar-Ein, Germy, Neer, Shourabil Recreational Lake, and Kosar were determined as 265, 219, 344, 233, 352, and 358 nSv/h, respectively. Although dose rates recorded for Germi and Kosar are comparable with some areas with high natural radiation background, however, the dose rates in other districts are well below the levels reported for such locations. Average annual effective dose due to indoor and outdoor gamma radiation for Ardebil province was estimated as 1.73 (1.35–2.39) mSv, which is on average 2 times higher than the world population weighted average. PMID:23369115

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.

Noiseless coding for the Gamma Ray spectrometer

NASA Technical Reports Server (NTRS)

Rice, R.; Lee, J. J.

1985-01-01

The payload of several future unmanned space missions will include a sophisticated gamma ray spectrometer. Severely constrained data rates during certain portions of these missions could limit the possible science return from this instrument. This report investigates the application of universal noiseless coding techniques to represent gamma ray spectrometer data more efficiently without any loss in data integrity. Performance results demonstrate compression factors from 2.5:1 to 20:1 in comparison to a standard representation. Feasibility was also demonstrated by implementing a microprocessor breadboard coder/decoder using an Intel 8086 processor.

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

NASA Astrophysics Data System (ADS)

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

2007-12-01

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

Benchmark gamma-ray skyshine experiment

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

Nason, R.R.; Shultis, J.K.; Faw, R.E.

1982-01-01

A benchmark gamma-ray skyshine experiment is descibed in which /sup 60/Co sources were either collimated into an upward 150-deg conical beam or shielded vertically by two different thicknesses of concrete. A NaI(Tl) spectrometer and a high pressure ion chamber were used to measure, respectively, the energy spectrum and the 4..pi..-exposure rate of the air-reflected gamma photons up to 700 m from the source. Analyses of the data and comparison to DOT discrete ordinates calculations are presented.

Simulating Gamma-Ray Emission in Star-forming Galaxies

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

Pfrommer, Christoph; Pakmor, Rüdiger; Simpson, Christine M.

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

Simulating Gamma-Ray Emission in Star-forming Galaxies

NASA Astrophysics Data System (ADS)

Pfrommer, Christoph; Pakmor, Rüdiger; Simpson, Christine M.; Springel, Volker

2017-10-01

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

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.

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)

New insight into mitochondrial changes in vascular endothelial cells irradiated by gamma ray.

PubMed

Hu, Shunying; Gao, Yajing; Zhou, Hao; Kong, Fanxuan; Xiao, Fengjun; Zhou, Pingkun; Chen, Yundai

2017-05-01

To investigate alterations of mitochondria in irradiated endothelial cells to further elucidate the mechanism underlying radiation-induced heart disease. Experiments were performed using human umbilical vein endothelial cells (HUVECs). HUVECs were irradiated with single gamma ray dose of 0, 5, 10 and 20 Gy, respectively. Apoptosis was assessed by flow cytometry at 24, 48 and 72 h post-irradiation, respectively. The intracellular reactive oxygen species (ROS) was measured with 2',7'-dichlorofluorescein-diacetate (DCFH-DA) at 24 h post-irradiation. Mitochondrial membrane potential (ΔΨm) by JC-1 and the opening of mitochondrial permeability transition pore (mPTP) by a calcein-cobalt quenching method were detected at 24 h post-irradiation in order to measure changes of mitochondria induced by gamma ray irradiation. Gamma ray irradiation increased HUVECs apoptosis in a dose-dependent and time-dependent manner. Irradiation also promoted ROS production in HUVECs in a dose-dependent manner. At 24 h post-irradiation, the results showed that irradiation decreases ΔΨm, however, paradoxically, flow cytometry showed green fluorescence instensity higher in irradiated HUVECs than in control HUVECs in an irradiation dose-dependent manner which indicated gamma ray irradiation inhibited mPTP opening in HUVECs. Gamma ray irradiation induces apoptosis and ROS production of endothelial cells, and decreases ΔΨm meanwhile contradictorily inhibiting the opening of mPTP.

On the induced gravitational collapse scenario of gamma-ray bursts associated with supernovae

DOE PAGES

Becerra, L.; Bianco, C. L.; Fryer, C. L.; ...

2016-12-10

Following the induced gravitational collapse (IGC) paradigm of gamma-ray bursts (GRBs) associated with type Ib/c supernovae, we present numerical simulations of the explosion of a carbon–oxygen (CO) core in a binary system with a neutron-star (NS) companion. The supernova ejecta trigger a hypercritical accretion process onto the NS thanks to a copious neutrino emission and the trapping of photons within the accretion flow. We show that temperatures of 1–10 MeV develop near the NS surface, hence electron–positron annihilation into neutrinos becomes the main cooling channel leading to accretion rates of 10–9–more » $${10}^{-1}\\,{M}_{\\odot }$$ s–1 and neutrino luminosities of 10 43–10 52 erg s –1 (the shorter the orbital period the higher the accretion rate). We estimate the maximum orbital period, $${P}_{\\max },$$ as a function of the NS initial mass, up to which the NS companion can reach by hypercritical accretion the critical mass for gravitational collapse leading to black hole formation. We then estimate the effects of the accreting and orbiting NS companion onto a novel geometry of the supernova ejecta density profile. We present the results of a $$1.4\\times {10}^{7}$$ particle simulation which show that the NS induces accentuated asymmetries in the ejecta density around the orbital plane. We elaborate on the observables associated with the above features of the IGC process. We apply this framework to specific GRBs: we find that X-ray flashes (XRFs) and binary-driven hypernovae are produced in binaries with $$P\\gt {P}_{\\max }$$ and $$P\\lt {P}_{\\max },$$ respectively. As a result, we analyze in detail the case of XRF 060218.« less

Gamma Ray Bursts-Afterglows and Counterparts

NASA Technical Reports Server (NTRS)

Fishman, Gerald J

1998-01-01

Several breakthrough discoveries were made last year of x-ray, optical and radio afterglows and counterparts to gamma-ray bursts, and a redshift has been associated with at least one of these. These discoveries were made possible by the fast, accurate gamma-ray burst locations of the BeppoSAX satellite. It is now generally believed that the burst sources are at cosmological distances and that they represent the most powerful explosions in the Universe. These observations also open new possibilities for the study of early star formation, the physics of extreme conditions and perhaps even cosmology. This session will concentrate on recent x-ray, optical and radio afterglow observations of gamma-ray bursts, associated redshift measurements, and counterpart observations. Several review and theory talks will also be presented, along with a summary of the astrophysical implications of the observations. There will be additional poster contributions on observations of gamma-ray burst source locations at wavelengths other than gamma rays. Posters are also solicited that describe new observational capabilities for rapid follow-up observations of gamma-ray bursts.

Characteristics of gamma-ray line flares

NASA Technical Reports Server (NTRS)

Bai, T.; Dennis, B.

1983-01-01

Observations of solar gamma rays by the Solar Maximum Mission (SMM) demonstrate that energetic protons and ions are rapidly accelerated during the impulsive phase. To understand the acceleration mechanisms for these particles, the characteristics of the gamma ray line flares observed by SMM were studied. Some very intense hard X-ray flares without detectable gamma ray lines were also investigated. Gamma ray line flares are distinguished from other flares by: (1) intense hard X-ray and microwave emissions; (2) delay of high energy hard X-rays; (3) emission of type 2 and/or type 4 radio bursts; and (4) flat hard X-ray spectra (average power law index: 3.1). The majority of the gamma ray line flares shared all these characteristics, and the remainder shared at least three of them. Positive correlations were found between durations of spike bursts and spatial sizes of flare loops as well as between delay times and durations of spike bursts.

Project-induced displacement, secondary stressors, and health.

PubMed

Cao, Yue; Hwang, Sean-Shong; Xi, Juan

2012-04-01

It has been estimated that about 15 million people are displaced by development projects around the world each year. Despite the magnitude of people affected, research on the health and other impacts of project-induced displacement is rare. This study extends existing knowledge by exploring the short-term health impact of a large scale population displacement resulting from China's Three Gorges Dam Project. The study is theoretically guided by the stress process model, but we supplement it with Cernea's impoverishment risks and reconstruction (IRR) model widely used in displacement literature. Our panel analysis indicates that the displacement is associated positively with relocatees' depression level, and negatively with their self-rated health measured against a control group. In addition, a path analysis suggests that displacement also affects depression and self-rated health indirectly by changing social integration, socioeconomic status, and community resources. The importance of social integration as a protective mechanism, a factor that has been overlooked in past studies of population displacement, is highlighted in this study. Published by Elsevier Ltd.

PROJECT-INDUCED DISPLACEMENT, SECONDARY STRESSORS, AND HEALTH

PubMed Central

Cao, Yue; Hwang, Sean-Shong; Xi, Juan

2012-01-01

It has been estimated that about 15 million people are displaced by development projects around the world each year. Despite the magnitude of people affected, research on the health and other impacts of project-induced displacement is rare. This study extends existing knowledge by exploring the short-term health impact of a large scale population displacement resulting from China’s Three Gorges Dam Project. The study is theoretically guided by the stress process model, but we supplement it with Cernea’s Impoverishment Risks and Reconstruction (IRR) model widely used in displacement literature. Our panel analysis indicates that the displacement is associated positively with relocatees’ depression level, and negatively with their self-rated health measured against a control group. In addition, a path analysis suggests that displacement also affects depression and self-rated health indirectly by changing social integration, socioeconomic status, and community resources. The importance of social integration as a protective mechanism, a factor that has been overlooked in past studies of population displacement, is highlighted in this study. PMID:22341203

About cosmic gamma ray lines

NASA Astrophysics Data System (ADS)

Diehl, Roland

2017-06-01

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

Near-infrared and gamma-ray monitoring of TANAMI gamma-ray bright sources

DOE PAGES

Nesci, R.; Tosti, G.; Pursimo, T.; ...

2013-06-18

Context. We present that spectral energy distribution and its variability are basic tools for understanding the physical processes operating in active galactic nuclei (AGN). Aims. In this paper we report the results of a one-year near-infrared (NIR) and optical monitoring of a sample of 22 AGN known to be gamma-ray emitters, aimed at discovering correlations between optical and gamma-ray emission. Methods. We observed our objects with the Rapid Eye Mount (REM) telescope in J,H,K, and R bands nearly twice every month during their visibility window and derived light curves and spectral indexes. We also analyzed the gamma-ray data from themore » Fermi gamma-ray Space Telescope, making weekly averages. Results. Six sources were never detected during our monitoring, proving to be fainter than their historical Two micron all sky survey (2MASS) level. All of the sixteen detected sources showed marked flux density variability, while the spectral indexes remained unchanged within our sensitivity limits. Steeper sources showed, on average, a larger variability. From the NIR light curves we also computed a variability speed index for each detected source. Only one source (PKS 0208-512) underwent an NIR flare during our monitoring. Half of the sources showed a regular flux density trend on a one-year time scale, but do not show any other peculiar characteristic. The broadband spectral index α ro appears to be a good proxy of the NIR spectral index only for BL Lac objects. No clear correlation between NIR and gamma-ray data is evident in our data, save for PKS 0537-441, PKS 0521-360, PKS 2155-304, and PKS 1424-418. In conclusion, the gamma-ray/NIR flux ratio showed a large spread, QSO being generally gamma-louder than BL Lac, with a marked correlation with the estimated peak frequency (ν peak) of the synchrotron emission.« less

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.

Did A Galactic Gamma-Ray Burst Kill the Dinosaurs?

NASA Astrophysics Data System (ADS)

Brecher, K.

1997-12-01

Gamma-ray bursts now appear to be primarily of extragalactic origin. Statistically, assuming isotropic emission, the observed event rates and fluxes imply that one event occurs per 10(4) \\ - 10(6) \\ years per galaxy, with about 10(51) \\ - 10(53) \\ ergs in gamma-rays emitted per event. Unless the Milky Way is unusual, a gamma-ray burst should occur within 10(2) \\ - 10(3) \\ pc of the Sun in a time span of order 10(8) \\ years. Independent of the underlying cause of the event, it would irradiate the solar system with a brief flash of MeV gamma-rays with a fluence as large as 10(9) - 10(11) \\ erg cm(-2) . What is the effect of such an event on the Earth and objects nearby? Ruderman (\\underbar{Science}, 184, 1079, 1974) and subsequent authors have considered a number of effects of a flash of gamma-rays from a nearby supernova explosion on the Earth's atmosphere, and on its biota. However, with regard to the demise of the dinosaurs, it appears that there was a marked increase in the deposition rate of the rare earth iridium coincident with their extinction. For this reason, an asteroid-Earth impact has been considered the leading contender for the death of the dinosaurs. Here we consider a new mechanism for mass biological extinctions, caused by small comets nudged into the inner solar system by nearby gamma-ray bursts. If comets populate the Oort cloud with a wide distribution of masses, radii and orbital eccentricities, we find that small (< 1 km), low density (10(-2) \\ gm cm(-3) ) objects in highly eccentric orbits can be injected into the inner solar system by a nearby gamma-ray burst. For a relatively brief period of time, the near Earth comet population would increase dramatically. The consequent increased probability of comet-Earth impacts of appropriate energy and material content could account for many of the characteristics of the Cretaceous-Tertiary or other terrestrial mass biological extinctions.

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.

Gamma-Ray Pulsar Candidates for GLAST

NASA Technical Reports Server (NTRS)

Thompson, D. J.

2008-01-01

The Gamma-ray Large Area Space Telescope (GLAST) will be launched this year, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio frequencies, are likely to emit greater than 100 MeV gamma rays with intensities detectable by the LAT. The main figure of merit used to select gamma-ray pulsar candidates is sqrt(E-dot)/d2, where E-dot is the energy loss due to rotational spin-down, and d is the distance to the pulsar. The figure of merit incorporates spin-down flux at earth (proportional to E-dot/d2) times efficiency, assumed proportional to l/sqrt(E-dot). A few individual objects are cited to illustrate the issues. Since large E-dot pulsars also tend to have large timing noise and occasional glitches, their ephemerides can become inaccurate in weeks to months. To detect and study the gamma-ray emission the photons must be accurately tagged with the pulse phase. With hours to days between gamma-ray photon arrival times from a pulsar and months to years of LAT exposure needed for good detections, GLAST will rely on radio and X-ray timing measurements throughout the continuous gamma-ray observations. The poster will describe efforts to coordinate pulsar timing of the candidate gamma-ray pulsars.

Role of NADP+-dependent isocitrate dehydrogenase (NADP+-ICDH) on cellular defence against oxidative injury by gamma-rays.

PubMed

Lee, S H; Jo, S H; Lee, S M; Koh, H J; Song, H; Park, J W; Lee, W H; Huh, T L

2004-09-01

To investigate the regulation of NADPH-producing isocitrate dehydrogenase (ICDH) in cytosol (IDPc) and mitochondria (IDPm) upon gamma-ray irradiation, and the roles of IDPc and IDPm in the protection against cellular damage induced by gamma-ray irradiation. Changes of IDPc and IDPm proteins upon gamma-ray irradiation to NIH3T3 cells were analysed by immunoblotting. To increase or decrease the expression of IDPc or IDPm, NIH3T3 cells were stably transfected with mouse IDPc or IDPm cDNA in either the sense or the antisense direction. The transfected cells with either increased or decreased IDPc or IDPm were exposed to gamma-rays, and the levels of reactive oxygen species generation, protein oxidation and lipid peroxidation were measured. Both IDPc and IDPm activities were induced by gamma-ray in NIH3T3 cells. Cells with decreased expression of IDPc or IDPm had elevated reactive oxygen species generation, lipid peroxidation and protein oxidation. Conversely, overproduction of IDPc or IDPm protein partially protected the cells from oxidative damage induced by gamma-ray irradiation. The protective role of IDPc and IDPm against gamma-ray-induced cellular damage can be attributed to elevated NADPH, reducing equivalents needed for recycling reduced glutathione in the cytosol and mitochondria. Thus, a primary biological function of the ICDHs may be production of NADPH, which is a prerequisite for some cellular defence systems against oxidative damage.

The Gamma-Ray Imager GRI

NASA Astrophysics Data System (ADS)

Wunderer, Cornelia B.; GRI Collaboration

2008-03-01

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

Observation of gamma ray bursts and flares by the EGRET telescope on the Compton Gamma Ray Observatory

NASA Technical Reports Server (NTRS)

Schneid, E. J.; Bertsch, D. L.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kwok, P. W.; Mattox, J. R.; Sreekumar, P.; Thompson, D. J.; Kanbach, G.

1992-01-01

The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory has observed energetic gamma ray bursts and flares. On May 3, 1991, EGRET detected a gamma ray burst both in the energy measuring NaI (Tl) scintillator and independently in the spark chamber imaging assembly. The NaI spectra were accumulated by a special BURST mode of EGRET. The spectra were measured over a range from 1 to 200 MeV, in three sequential spectra of 1,2, and 4 seconds. During the peak of the burst, six individual gamma rays were detected in the spark chamber, allowing a determination of the burst arrival direction. The intense flares of June were also detected. A solar flare on June 4 was observed to last for several minutes and for a brief time, less than a minute, had significant emission of gamma rays exceeding 150 MeV.

Enhanced detection of terrestrial gamma-ray flashes by AGILE.

PubMed

Marisaldi, M; Argan, A; Ursi, A; Gjesteland, T; Fuschino, F; Labanti, C; Galli, M; Tavani, M; Pittori, C; Verrecchia, F; D'Amico, F; Østgaard, N; Mereghetti, S; Campana, R; Cattaneo, P W; Bulgarelli, A; Colafrancesco, S; Dietrich, S; Longo, F; Gianotti, F; Giommi, P; Rappoldi, A; Trifoglio, M; Trois, A

2015-11-16

At the end of March 2015 the onboard software configuration of the Astrorivelatore Gamma a Immagini Leggero (AGILE) satellite was modified in order to disable the veto signal of the anticoincidence shield for the minicalorimeter instrument. The motivation for such a change was the understanding that the dead time induced by the anticoincidence prevented the detection of a large fraction of Terrestrial Gamma-Ray Flashes (TGFs). The configuration change was highly successful resulting in an increase of one order of magnitude in TGF detection rate. As expected, the largest fraction of the new events has short duration (<100 μs), and part of them has simultaneous association with lightning sferics detected by the World Wide Lightning Location Network. The new configuration provides the largest TGF detection rate surface density (TGFs/km 2 /yr) to date, opening prospects for improved correlation studies with lightning and atmospheric parameters on short spatial and temporal scales along the equatorial region.

Terrestrial Gamma-ray Flashes (TGFs) Observed with the Fermi-Gamma-ray Burst Monitor: Temporal and Spectral Properties

NASA Technical Reports Server (NTRS)

Fishman, G. J.; Briggs, M. S.; Connaughton, W.; Wilson-Hodge, C.; Bhat, P. N.

2010-01-01

The Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope Observatory (Fermi) was detecting 2.1 TGFs per week. This rate has increased by a factor of 8 since new flight software was uploaded to the spacecraft in November 2009 in order to increase the sensitivity of GBM to TGFs. Further upgrades to Fermi-GBM to allow observations of weaker TGFs are in progress. The high time resolution (2 s) allows temporal features to be resolved so that some insight may be gained on the origin and transport of the gamma-ray photons through the atmosphere. The absolute time of the TGFs, known to several microseconds, also allows accurate correlations of TGFs with lightning networks and other lightning-related phenomena. The thick bismuth germanate (BGO) scintillation detectors of the GBM system have observed photon energies from TGFs at energies above 40 MeV. New results on the some temporal aspects of TGFs will be presented along with spectral characteristics and properties of several electron-positron TGF events that have been identified.

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

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

Population Synthesis of Radio & Gamma-Ray Millisecond Pulsars

NASA Astrophysics Data System (ADS)

Frederick, Sara; Gonthier, P. L.; Harding, A. K.

2014-01-01

In recent years, the number of known gamma-ray millisecond pulsars (MSPs) in the Galactic disk has risen substantially thanks to confirmed detections by Fermi Gamma-ray Space Telescope (Fermi). We have developed a new population synthesis of gamma-ray and radio MSPs in the galaxy which uses Markov Chain Monte Carlo techniques to explore the large and small worlds of the model parameter space and allows for comparisons of the simulated and detected MSP distributions. The simulation employs empirical radio and gamma-ray luminosity models that are dependent upon the pulsar period and period derivative with freely varying exponents. Parameters associated with the birth distributions are also free to vary. The computer code adjusts the magnitudes of the model luminosities to reproduce the number of MSPs detected by a group of ten radio surveys, thus normalizing the simulation and predicting the MSP birth rates in the Galaxy. Computing many Markov chains leads to preferred sets of model parameters that are further explored through two statistical methods. Marginalized plots define confidence regions in the model parameter space using maximum likelihood methods. A secondary set of confidence regions is determined in parallel using Kuiper statistics calculated from comparisons of cumulative distributions. These two techniques provide feedback to affirm the results and to check for consistency. Radio flux and dispersion measure constraints have been imposed on the simulated gamma-ray distributions in order to reproduce realistic detection conditions. The simulated and detected distributions agree well for both sets of radio and gamma-ray pulsar characteristics, as evidenced by our various comparisons.

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).

A link between prompt optical and prompt gamma-ray emission in gamma-ray bursts.

PubMed

Vestrand, W T; Wozniak, P R; Wren, J A; Fenimore, E E; Sakamoto, T; White, R R; Casperson, D; Davis, H; Evans, S; Galassi, M; McGowan, K E; Schier, J A; Asa, J W; Barthelmy, S D; Cummings, J R; Gehrels, N; Hullinger, D; Krimm, H A; Markwardt, C B; McLean, K; Palmer, D; Parsons, A; Tueller, J

2005-05-12

The prompt optical emission that arrives with the gamma-rays from a cosmic gamma-ray burst (GRB) is a signature of the engine powering the burst, the properties of the ultra-relativistic ejecta of the explosion, and the ejecta's interactions with the surroundings. Until now, only GRB 990123 had been detected at optical wavelengths during the burst phase. Its prompt optical emission was variable and uncorrelated with the prompt gamma-ray emission, suggesting that the optical emission was generated by a reverse shock arising from the ejecta's collision with surrounding material. Here we report prompt optical emission from GRB 041219a. It is variable and correlated with the prompt gamma-rays, indicating a common origin for the optical light and the gamma-rays. Within the context of the standard fireball model of GRBs, we attribute this new optical component to internal shocks driven into the burst ejecta by variations of the inner engine. The correlated optical emission is a direct probe of the jet isolated from the medium. The timing of the uncorrelated optical emission is strongly dependent on the nature of the medium.

The solar gamma ray and neutron capabilities of COMPTEL on the Gamma Ray Observatory

NASA Technical Reports Server (NTRS)

Ryan, James M.; Lockwood, John A.

1989-01-01

The imaging Compton telescope COMPTEL on the Gamma Ray Observatory (GRO) has unusual spectroscopic capabilities for measuring solar gamma-ray and neutron emission. The launch of the GRO is scheduled for June 1990 near the peak of the sunspot cycle. With a 30 to 40 percent probability for the Sun being in the COMPTEL field-of-view during the sunlit part of an orbit, a large number of flares will be observed above the 800 keV gamma-ray threshold of the telescope. The telescope energy range extends to 30 MeV with high time resolution burst spectra available from 0.1 to 10 MeV. Strong Compton tail suppression of instrumental gamma-ray interactions will facilitate improved spectral analysis of solar flare emissions. In addition, the high signal to noise ratio for neutron detection and measurement will provide new neutron spectroscopic capabilities. Specifically, a flare similar to that of 3 June 1982 will provide spectroscopic data on greater than 1500 individual neutrons, enough to construct an unambiguous spectrum in the energy range of 20 to 200 MeV. Details of the instrument and its response to solar gamma-rays and neutrons will be presented.

Gamma-Ray Pulsar Candidates for GLAST

NASA Technical Reports Server (NTRS)

Thompson, David J.; Smith, D. A.; Dumora, D.; Guillemot, L.; Parent, D.; Reposeur, T.; Grove, E.; Romani, R. W.; Thorsett, S. E.

2007-01-01

The Gamma-ray Large Area Space Telescope (GLAST) will be launched less than a year from now, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio Erequencies, are likely to emit greater than l00 MeV gamma rays with intensities detectable by the LAT. The main figure of merit used to select gamma-ray pulsar candidates is sqrt(E-dot)/d^2, where E-dot is the energy loss due to rotational spindown, and d is the distance to the pulsar. The figure of merit incorporates spin-down flux at earth (proportional to E-dot/d^2) times efficiency, assumed proportional to 1/sqrt(E-dot). A few individual objects are cited to illustrate the issues. Since large E-dot pulsars also tend to have large timing noise and occasional glitches, their ephemerides can become inaccurate in weeks to months. To detect and study the gamma-ray emission the photons must be accurately tagged with the pulse phase. With hours to days between gamma-ray photon arrival times from a pulsar and months to years of LAT exposure needed for good detections, GLAST will need timing measurements throughout the continuous gamma-ray observations. The poster will describe efforts to coordinate pulsar timing of the candidate gamma-ray pulsars.

GRI: the gamma-ray imager mission

NASA Astrophysics Data System (ADS)

Knödlseder, Jürgen

2006-06-01

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear reactions are synthesizing the basic constituents of our world. Cosmic accelerators and cosmic explosions are the major science themes that are addressed in the gamma-ray regime. With the INTEGRAL observatory, ESA has provided a unique tool to the astronomical community revealing hundreds of sources, new classes of objects, extraordinary views of antimatter annihilation in our Galaxy, and fingerprints of recent nucleosynthesis processes. While INTEGRAL provides the global overview over the soft gamma-ray sky, there is a growing need to perform deeper, more focused investigations of gamma-ray sources. In soft X-rays a comparable step was taken going from the Einstein and the EXOSAT satellites to the Chandra and XMM/Newton observatories. Technological advances in the past years in the domain of gamma-ray focusing using Laue diffraction and multilayer-coated mirror techniques hav paved the way towards a gamma-ray mission, providing major improvements compared to past missions regarding sensitivity and angular resolution. Such a future Gamma-Ray Imager will allow to study particle acceleration processes and explosion physics in unprecedented detail, providing essential clues on the innermost nature of the most violent and most energetic processes in the Universe.

High energy irradiations simulating cosmic-ray-induced planetary gamma ray production. I - Fe target

NASA Technical Reports Server (NTRS)

Metzger, A. E.; Parker, R. H.; Yellin, J.

1986-01-01

Two thick Fe targets were bombarded by a series of 6 GeV proton irradiations for the purpose of simulating the cosmic ray bombardment of planetary objects in space. Gamma ray energy spectra were obtained with a germanium solid state detector during the bombardment, and 46 of the gamma ray lines were ascribed to the Fe targets. A comparison between observed and predicted values showed good agreement for Fe lines from neutron inelastic scattering and spallation reactions, and less satisfactory agreement for neutron capture reactions, the latter attributed to the difference in composition between the Fe target and the mean lunar abundance used in the modeling. Through an analysis of the irradiation results together with continuum data obtained in lunar orbit, it was found that 100 hours of measurement with a current instrument should generate a spectrum containing approximately 20 lines due to Fe alone, with a 2-sigma sensitivity for detection of about 0.2 percent.

The Mystery of Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

2004-01-01

Gamma-ray bursts remain one of the greatest mysteries in astrophysics. Observations of gamma-ray bursts made by the BATSE experiment on the Compton Gamma-Ray Observatory will be described. Most workers in the field now believe that they originate from cosmological distances. This view has been reinforced by observations this year of several optical afterglow counterparts to gamma-ray bursts. A summary of these recent discoveries will be presented, along with their implications for models of the burst emission mechanism and the energy source of the bursts.

Comparison of Terrestrial Gamma Ray Flash Simulations with Observations by Fermi

DTIC Science & Technology

2016-10-31

allowing a direction comparison between the gamma rays measured in low -Earth orbit and the VLF-LF radio frequency emissions recorded on the ground...directly calculated from X and its time derivative, including the gamma-ray emission rate, the current moment, and the optical power of the TGF. For

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.

Diffuse gamma-ray emission from pulsars in the Large Magellanic Cloud

NASA Technical Reports Server (NTRS)

Hartmann, Dieter H.; Brown, Lawrence E.; Schnepf, Neil

1993-01-01

We investigate the contribution of pulsars to the diffuse gamma-ray emission from the LMC. The pulsar birth rate in the LMC is a factor of about 10 lower than that of the Galaxy and the distance to pulsars in the LMC is about 5-10 times larger than to Galactic pulsars. The resulting total integrated photon flux from LMC pulsars is thus reduced by a factor of about 100 to 1000. However, the surface brightness is not reduced by the same amount because of the much smaller angular extent of the LMC in comparison to the diffuse glow from the Galactic plane. We show that gamma-ray emission due to pulsars born in the LMC could produce gamma-ray fluxes that are larger than the inverse Compton component from relativistic cosmic-ray electrons and a significant fraction of the extragalactic isotropic background or the diffuse Galactic background in that direction. The diffuse pulsar glow above 100 MeV should therefore be included in models of high-energy emission from the LMC. For a gamma-ray beaming fraction of order unity the detected emissions from the LMC constrain the pulsar birth rate to less than one per 50 yr. This limit is about one order of magnitude above the supernova rate inferred from the historic record or from the star-formation rate.

Hard X-ray and low-energy gamma-ray spectrometers

NASA Technical Reports Server (NTRS)

Gehrels, N.; Crannell, C. J.; Orwig, L. E.; Forrest, D. J.; Lin, R. P.; Starr, R.

1988-01-01

Basic principles of operation and characteristics of scintillation and semi-conductor detectors used for solar hard X-ray and gamma-ray spectrometers are presented. Scintillation materials such as NaI offer high stopping power for incident gamma rays, modest energy resolution, and relatively simple operation. They are, to date, the most often used detector in solar gamma-ray spectroscopy. The scintillator BGO has higher stopping power than NaI, but poorer energy resolution. The primary advantage of semi-conductor materials such as Ge is their high-energy resolution. Monte-Carlo simulations of the response of NaI and Ge detectors to model solar flare inputs show the benefit of high resoluton for studying spectral lines. No semi-conductor material besides Ge is currently available with adequate combined size and purity to make general-use hard X-ray and gamma-ray detectors for solar studies.

Fermi Gamma-Ray Space Telescope

NASA Technical Reports Server (NTRS)

McEnery, Julie E.; Michelson, Peter F.; Paclesas, William S.; Ritz, Steven

2012-01-01

The Fermi Gamma-ray Space Telescope, launched in June 2008, is an observatory designed to survey the high-energy gamma-ray sky. The primary instrument, the Large Area Telescope (LAT), provides observations from 20 MeV to greater than 300 GeV. A second instrument, the Gamma-ray Burst Monitor (GBM), provides observations of transients from less than 10 keV to 40 MeV. We describe the design and performance of the instruments and their subsystems, the spacecraft and the ground system.

Radioactivity Levels and Gamma-Ray Dose Rate in Soil Samples from Kohistan (Pakistan) Using Gamma-Ray Spectrometry

NASA Astrophysics Data System (ADS)

Hasan, M. Khan; Ismail, M.; K., Khan; Akhter, P.

2011-01-01

The analysis of naturally occurring radionuclides (226Ra, 232Th and 40K) and an anthropogenic radionuclide 137Cs is carried out in some soil samples collected from Kohistan district of N.W.F.P. (Pakistan), using gamma-ray spectrometry. The gamma spectrometry is operated using a high purity Germanium (HPGe) detector coupled with a computer based high resolution multi channel analyzer. The specific activity in soil ranges from 24.72 to 78.48Bq·kg-1 for 226Ra, 21.73 to 75.28Bq·kg-1 for 232Th, 7.06 to 14.9Bq·kg-1 for 137Cs and 298.46 to 570.77Bq·kg-1 for 40K with the mean values of 42.11, 43.27, 9.5 and 418.27Bq·kg-1, respectively. The radium equivalent activity in all the soil samples is lower than the safe limit set in the OECD report (370Bq·kg-1). Man-made radionuclide 137Cs is also present in detectable amount in all soil samples. Presence of 137Cs indicates that the samples in this remote area also receive some fallout from nuclear accident in Chernobyl power plant in 1986. The internal and external hazard indices have the mean values of 0.48 and 0.37 respectively. Absorbed dose rates and effective dose equivalents are also determined for the samples. The concentration of radionuclides found in the soil samples during the present study is nominal and does not pose any potential health hazard to the general public.

Origin of X-Ray and Gamma-Ray Emission from the Galactic Central Region

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

Chernyshov, D. O.; Dogiel, V. A.; Cheng, K.-S.

We study a possible connection between different non-thermal emissions from the inner few parsecs of the Galaxy. We analyze the origin of the gamma-ray source 2FGL J1745.6−2858 (or 3FGL J1745.6−2859c) in the Galactic Center (GC) and the diffuse hard X-ray component recently found by the Nuclear Spectroscopic Telescope Array , as well as the radio emission and processes of hydrogen ionization from this area. We assume that a source in the GC injected energetic particles with power-law spectrum into the surrounding medium in the past or continues to inject until now. The energetic particles may be protons, electrons, or amore » combination of both. These particles diffuse to the surrounding medium and interact with gas, magnetic field, and background photons to produce non-thermal emissions. We study the spectral and spatial features of the hard X-ray emission and gamma-ray emission by the particles from the central source. Our goal is to examine whether the hard X-ray and gamma-ray emissions have a common origin. Our estimations show that, in the case of pure hadronic models, the expected flux of hard X-ray emission is too low. Despite the fact that protons can produce a non-zero contribution in gamma-ray emission, it is unlikely that they and their secondary electrons can make a significant contribution in hard X-ray flux. In the case of pure leptonic models, it is possible to reproduce both X-ray and gamma-ray emissions for both transient and continuous supply models. However, in the case of the continuous supply model, the ionization rate of molecular hydrogen may significantly exceed the observed value.« less

Development of a Portable Gamma-ray Survey System for the Measurement of Air Dose Rates

NASA Astrophysics Data System (ADS)

Goto, Jun; Shobugawa, Yugo; Kawano, Yoh; Amaya, Yoshihiro; Izumikawa, Takuji; Katsuragi, Yoshinori; Shiiya, Tomohiro; Suzuki, Tsubasa; Takahashi, Takeshi; Takahashi, Toshihiro; Yoshida, Hidenori; Naito, Makoto

BIo-Safety Hybrid Automatic MOnitor-Niigata (BISHAMON), a portable gamma-ray survey system, was developed to support victims of the Fukushima Daiichi nuclear disaster. BISHAMON is capable of constructing a map of the distribution of ambient dose equivalent rates using vehicle-mounted or on-foot survey methods. In this study, we give an overview of BISHAMON and its measurement results including a comparison with those of other systems such as KURAMA.

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

NASA Technical Reports Server (NTRS)

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

Gamma-ray Albedo of the Moon

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

Moskalenko, Igor V.; Porter, Troy A.

2007-06-14

We use the GEANT4 Monte Carlo framework to calculate the gamma-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of gamma-rays from the Moon is very steep with an effective cutoff around 3 GeV (600 MeV for the inner part of the Moon disc). Since it is the only (almost) black spot in the gamma-ray sky, it provides a unique opportunity for calibration of gamma-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST).more » The albedo flux depends on the incident CR spectrum which changes over the solar cycle. Therefore, it is possible to monitor the CR spectrum using the albedo gamma-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo -rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the GLAST LAT to monitor the CR spectrum near the Earth beyond the lifetime of PAMELA.« less

Low-mass X-ray binaries and gamma-ray bursts

NASA Technical Reports Server (NTRS)

Lasota, J. P.; Frank, J.; King, A. R.

1992-01-01

More than twenty years after their discovery, the nature of gamma-ray burst sources (GRBs) remains mysterious. The results from BATSE experiment aboard the Compton Observatory show however that most of the sources of gamma-ray bursts cannot be distributed in the galactic disc. The possibility that a small fraction of sites of gamma-ray bursts is of galactic disc origin cannot however be excluded. We point out that large numbers of neutron-star binaries with orbital periods of 10 hr and M dwarf companions of mass 0.2-0.3 solar mass are a natural result of the evolution of low-mass X-ray binaries (LMXBs). The numbers and physical properties of these systems suggest that some gamma-ray burst sources may be identified with this endpoint of LMXB evolution. We suggest an observational test of this hypothesis.

Energy- and time-resolved detection of prompt gamma-rays for proton range verification.

PubMed

Verburg, Joost M; Riley, Kent; Bortfeld, Thomas; Seco, Joao

2013-10-21

In this work, we present experimental results of a novel prompt gamma-ray detector for proton beam range verification. The detection system features an actively shielded cerium-doped lanthanum(III) bromide scintillator, coupled to a digital data acquisition system. The acquisition was synchronized to the cyclotron radio frequency to separate the prompt gamma-ray signals from the later-arriving neutron-induced background. We designed the detector to provide a high energy resolution and an effective reduction of background events, enabling discrete proton-induced prompt gamma lines to be resolved. Measuring discrete prompt gamma lines has several benefits for range verification. As the discrete energies correspond to specific nuclear transitions, the magnitudes of the different gamma lines have unique correlations with the proton energy and can be directly related to nuclear reaction cross sections. The quantification of discrete gamma lines also enables elemental analysis of tissue in the beam path, providing a better prediction of prompt gamma-ray yields. We present the results of experiments in which a water phantom was irradiated with proton pencil-beams in a clinical proton therapy gantry. A slit collimator was used to collimate the prompt gamma-rays, and measurements were performed at 27 positions along the path of proton beams with ranges of 9, 16 and 23 g cm(-2) in water. The magnitudes of discrete gamma lines at 4.44, 5.2 and 6.13 MeV were quantified. The prompt gamma lines were found to be clearly resolved in dimensions of energy and time, and had a reproducible correlation with the proton depth-dose curve. We conclude that the measurement of discrete prompt gamma-rays for in vivo range verification of clinical proton beams is feasible, and plan to further study methods and detector designs for clinical use.

Accumulation and dissipation of positive charges induced on a PMMA build-up cap of an ionisation chamber by (60)Co gamma-ray irradiation.

PubMed

Morishita, Y; Takata, N

2013-07-01

The signal current from an ionisation chamber with a PMMA build-up cap decreases with irradiation time due to electric fields produced by positive charges induced on the cap. In the present study, it was confirmed that the signal current decreases faster for irradiation using narrower (60)Co gamma-ray beams. This is because the number of secondary electrons that are emitted from surrounding materials and penetrate the build-up cap is smaller in a narrower gamma-ray beam, so that fewer positive charges are neutralised. The ionisation chamber was first subjected to continuous gamma-ray irradiation for 24 h, following which it was irradiated with shorter periodic gamma-ray bursts while measuring the current signal. This allowed the coefficients of positive charge accumulation and dissipation to be determined. It was found that the dissipation coefficient has a large constant value during gamma-ray irradiation and decreases asymptotically to a small value after irradiation is stopped. From the coefficients, the minimum signal current was calculated, which is the value when accumulation and dissipation balance each other under continuous irradiation. The time required for the signal current to recover following irradiation was also calculated.

GRI: The Gamma-Ray Imager mission

NASA Astrophysics Data System (ADS)

Knödlseder, Jürgen; GRI Consortium

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

GRI: The Gamma-Ray Imager mission

NASA Astrophysics Data System (ADS)

Knödlseder, Jürgen; GRI Consortium

2006-06-01

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

Gamma rays induce DNA damage and oxidative stress associated with impaired growth and reproduction in the copepod Tigriopus japonicus.

PubMed

Han, Jeonghoon; Won, Eun-Ji; Lee, Bo-Young; Hwang, Un-Ki; Kim, Il-Chan; Yim, Joung Han; Leung, Kenneth Mei Yee; Lee, Yong Sung; Lee, Jae-Seong

2014-07-01

Nuclear radioisotope accidents are potentially ecologically devastating due to their impact on marine organisms. To examine the effects of exposure of a marine organism to radioisotopes, we irradiated the intertidal copepod Tigriopus japonicus with several doses of gamma radiation and analyzed the effects on mortality, fecundity, and molting by assessing antioxidant enzyme activities and gene expression patterns. No mortality was observed at 96h, even in response to exposure to a high dose (800Gy) of radiation, but mortality rate was significantly increased 120h (5 days) after exposure to 600 or 800Gy gamma ray radiation. We observed a dose-dependent reduction in fecundity of ovigerous females; even the group irradiated with 50Gy showed a significant reduction in fecundity, suggesting that gamma rays are likely to have a population level effect. In addition, we observed growth retardation, particularly at the nauplius stage, in individuals after gamma irradiation. In fact, nauplii irradiated with more than 200Gy, though able to molt to copepodite stage 1, did not develop into adults. Upon gamma radiation, T. japonicus showed a dose-dependent increase in reactive oxygen species (ROS) levels, the activities of several antioxidant enzymes, and expression of double-stranded DNA break damage genes (e.g. DNA-PK, Ku70, Ku80). At a low level (sub-lethal dose) of gamma irradiation, we found dose-dependent upregulation of p53, implying cellular damage in T. japonicus in response to sub-lethal doses of gamma irradiation, suggesting that T. japonicus is not susceptible to sub-lethal doses of gamma irradiation. Additionally, antioxidant genes, phase II enzyme (e.g. GSTs), and cellular chaperone genes (e.g. Hsps) that are involved in cellular defense mechanisms also showed the same expression patterns for sublethal doses of gamma irradiation (50-200Gy). These findings indicate that sublethal doses of gamma radiation can induce oxidative stress-mediated DNA damage and increase

Dose-rate plays a significant role in synchrotron radiation X-ray-induced damage of rodent testes.

PubMed

Chen, Heyu; Wang, Ban; Wang, Caixia; Cao, Wei; Zhang, Jie; Ma, Yingxin; Hong, Yunyi; Fu, Shen; Wu, Fan; Ying, Weihai

2016-01-01

Synchrotron radiation (SR) X-ray has significant potential for applications in medical imaging and cancer treatment. However, the mechanisms underlying SR X-ray-induced tissue damage remain unclear. Previous studies on regular X-ray-induced tissue damage have suggested that dose-rate could affect radiation damage. Because SR X-ray has exceedingly high dose-rate compared to regular X-ray, it remains to be determined if dose-rate may affect SR X-ray-induced tissue damage. We used rodent testes as a model to investigate the role of dose-rate in SR X-ray-induced tissue damage. One day after SR X-ray irradiation, we determined the effects of the irradiation of the same dosage at two different dose-rates, 0.11 Gy/s and 1.1 Gy/s, on TUNEL signals, caspase-3 activation and DNA double-strand breaks (DSBs) of the testes. Compared to those produced by the irradiation at 0.11 Gy/s, irradiation at 1.1 Gy/s produced higher levels of DSBs, TUNEL signals, and caspase-3 activation in the testes. Our study has provided the first evidence suggesting that dose-rate could be a significant factor in SR X-ray-induced tissue damage, which may establish a valuable base for utilizing this factor to manipulate the tissue damage in SR X-ray-based medical applications.

Dose-rate plays a significant role in synchrotron radiation X-ray-induced damage of rodent testes

PubMed Central

Chen, Heyu; Wang, Ban; Wang, Caixia; Cao, Wei; Zhang, Jie; Ma, Yingxin; Hong, Yunyi; Fu, Shen; Wu, Fan; Ying, Weihai

2016-01-01

Synchrotron radiation (SR) X-ray has significant potential for applications in medical imaging and cancer treatment. However, the mechanisms underlying SR X-ray-induced tissue damage remain unclear. Previous studies on regular X-ray-induced tissue damage have suggested that dose-rate could affect radiation damage. Because SR X-ray has exceedingly high dose-rate compared to regular X-ray, it remains to be determined if dose-rate may affect SR X-ray-induced tissue damage. We used rodent testes as a model to investigate the role of dose-rate in SR X-ray-induced tissue damage. One day after SR X-ray irradiation, we determined the effects of the irradiation of the same dosage at two different dose-rates, 0.11 Gy/s and 1.1 Gy/s, on TUNEL signals, caspase-3 activation and DNA double-strand breaks (DSBs) of the testes. Compared to those produced by the irradiation at 0.11 Gy/s, irradiation at 1.1 Gy/s produced higher levels of DSBs, TUNEL signals, and caspase-3 activation in the testes. Our study has provided the first evidence suggesting that dose-rate could be a significant factor in SR X-ray-induced tissue damage, which may establish a valuable base for utilizing this factor to manipulate the tissue damage in SR X-ray-based medical applications. PMID:28078052

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

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

NASA Technical Reports Server (NTRS)

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

Simultaneous optical/gamma-ray observations of GRBs

NASA Technical Reports Server (NTRS)

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

1994-01-01

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

Design and performance of the GAMMA-400 gamma-ray telescope for dark matter searches

NASA Astrophysics Data System (ADS)

Galper, A. M.; Adriani, O.; Aptekar, R. L.; Arkhangelskaja, I. V.; Arkhangelskiy, A. I.; Boezio, M.; Bonvicini, V.; Boyarchuk, K. A.; Fradkin, M. I.; Gusakov, Yu. V.; Kaplin, V. A.; Kachanov, V. A.; Kheymits, M. D.; Leonov, A. A.; Longo, F.; Mazets, E. P.; Maestro, P.; Marrocchesi, P.; Mereminskiy, I. A.; Mikhailov, V. V.; Moiseev, A. A.; Mocchiutti, E.; Mori, N.; Moskalenko, I. V.; Naumov, P. Yu.; Papini, P.; Picozza, P.; Rodin, V. G.; Runtso, M. F.; Sparvoli, R.; Spillantini, P.; Suchkov, S. I.; Tavani, M.; Topchiev, N. P.; Vacchi, A.; Vannuccini, E.; Yurkin, Yu. T.; Zampa, N.; Zverev, V. G.; Zirakashvili, V. N.

2013-02-01

The GAMMA-400 gamma-ray telescope is designed to measure the fluxes of gamma-rays and cosmic-ray electrons + positrons, which can be produced by annihilation or decay of the dark matter particles, as well as to survey the celestial sphere in order to study point and extended sources of gamma-rays, measure energy spectra of Galactic and extragalactic diffuse gamma-ray emission, gamma-ray bursts, and gamma-ray emission from the Sun. GAMMA-400 covers the energy range from 100 MeV to 3000 GeV. Its angular resolution is ~0.01° (Eγ > 100 GeV), the energy resolution ~1% (Eγ > 10 GeV), and the proton rejection factor ~106. GAMMA-400 will be installed on the Russian space platform Navigator. The beginning of observations is planned for 2018.

The Animated Gamma-ray Sky Revealed by the Fermi Gamma-ray Space Telescope

ScienceCinema

Isabelle Grenier

2018-04-17

The Fermi Gamma-ray Space Telescope has been observing the sky in gamma-rays since August 2008.  In addition to breakthrough capabilities in energy coverage (20 MeV-300 GeV) and angular resolution, the wide field of view of the Large Area Telescope enables observations of 20% of the sky at any instant, and of the whole sky every three hours. It has revealed a very animated sky with bright gamma-ray bursts flashing and vanishing in minutes, powerful active galactic nuclei flaring over hours and days, many pulsars twinkling in the Milky Way, and X-ray binaries shimmering along their orbit. Most of these variable sources had not been seen by the Fermi predecessor, EGRET, and the wealth of new data already brings important clues to the origin of the high-energy emission and particles powered by the compact objects. The telescope also brings crisp images of the bright gamma-ray emission produced by cosmic-ray interactions in the interstellar medium, thus allowing to measure the cosmic nuclei and electron spectra across the Galaxy, to weigh interstellar clouds, in particular in the dark-gas phase. The telescope sensitivity at high energy will soon provide useful constraints on dark-matter annihilations in a variety of environments. I will review the current results and future prospects of the Fermi mission.

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

NASA Technical Reports Server (NTRS)

Puget, J. L.

1973-01-01

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

Feasibility study of a low-energy gamma ray system for measuring quantity and flow rate of slush hydrogen

NASA Technical Reports Server (NTRS)

Singh, Jag J.; Shen, Chih-Ping; Sprinkle, Danny R.

1992-01-01

As part of a study to demonstrate the suitability of an X-ray or gamma ray probe for monitoring the quality and flow rate of slush hydrogen, mass attenuation coefficients for Cd-109 X- and gamma radiation in five chemical compounds were measured. The Ag-109 K rays were used for water and acetic acid, whereas E3 transition from the first excited state at 87.7 keV in Ag-109 provided the probe radiation for bromobenzene, alpha (exp 2) chloroisodurene, and cetyl bromide. Measurements were made for a single phase (gas, liquid, solid) as well as mixed phases (liquid plus solid) in all cases. It was shown that the mass attenuation coefficient for the selected radiations is independent of the phase of the test fluids or phase ratios in the case of mixed phase fluids. Described here are the procedure and the results for the five fluid systems investigated.

Gamma-ray lens development status for a European gamma-ray imager

NASA Astrophysics Data System (ADS)

Frontera, F.; Pisa, A.; Carassiti, V.; Evangelisti, F.; Loffredo, G.; Pellicciotta, D.; Andersen, K. H.; Courtois, P.; Amati, L.; Caroli, E.; Franceschini, T.; Landini, G.; Silvestri, S.; Stephen, J. B.

2006-06-01

A breakthrough in the sensitivity level of the hard X-/gamma-ray telescopes, which today are based on detectors that view the sky through (or not) coded masks, is expected when focusing optics will be available also in this energy range. Focusing techniques are now in an advanced stage of development. To date the most efficient technique to focus hard X-rays with energies above 100 keV appears to be the Bragg diffraction from crystals in transmission configuration (Laue lenses). Crystals with mosaic structure appear to be the most suitable to build a Laue lens with a broad passband, even though other alternative structures are being investigated. The goal of our project is the development of a broad band focusing telescope based on gamma-ray lenses for the study of the continuum emission of celestial sources from 60 keV up to >600 keV. We will report details of our project, its development status and results of our assessment study of a lens configuration for the European Gamma Ray Imager (GRI) mission now under study for the ESA plan Cosmic Vision 2015-2025.

Diffuse gamma-ray emission from self-confined cosmic rays around Galactic sources

NASA Astrophysics Data System (ADS)

D'Angelo, Marta; Morlino, Giovanni; Amato, Elena; Blasi, Pasquale

2018-02-01

The propagation of particles accelerated at supernova remnant shocks and escaping the parent remnants is likely to proceed in a strongly non-linear regime, due to the efficient self-generation of Alfvén waves excited through streaming instability near the sources. Depending on the amount of neutral hydrogen present in the regions around the sites of supernova explosions, cosmic rays may accumulate an appreciable grammage in the same regions and get self-confined for non-negligible times, which in turn results in an enhanced rate of production of secondaries. Here we calculate the contribution to the diffuse gamma-ray background due to the overlap along lines of sight of several of these extended haloes as due to pion production induced by self-confined cosmic rays. We find that if the density of neutrals is low, the haloes can account for a substantial fraction of the diffuse emission observed by Fermi-Large Area Telescope (LAT), depending on the orientation of the line of sight with respect to the direction of the Galactic Centre.

Evaluation of the Environmental Gamma-ray Dose Rate by Skyshine Analysis During the Maintenance of an Activated TFC in ITER

NASA Astrophysics Data System (ADS)

Sato, S.; Takatsu, H.; Maki, K.; Yamada, K.; Mori, S.; Iida, H.; Santoro, R. T.

1997-09-01

Gamma-ray exposure dose rates at the ITER site boundary were estimated for the cases of removal of a failed activated Toroidal Field (TF) coil from the torus and removal of a failed activated TF coil together with a sector of the activated Vacuum Vessel (VV). Skyshine analyses were performed using the two-dimensional SN radiation transport code, DOT3.5. The exposure gamma-ray dose rates on the ground at the site boundary (presently assumed to be 1 km from the ITER building), were calculated to be 1.1 and 84 μSv/year for removal of the TF coil without and with a VV sector, respectively. The dose rate level for the latter case is close to the tentative radiation limit of 100 μSv/year so an additional ˜14 cm of concrete is required in the ITER building roof to satisfy the criterion for a safety factor often for the site boundary dose rate.

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.

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.

DEATH LINE OF GAMMA-RAY PULSARS WITH OUTER GAPS

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

Wang, Ren-Bo; Hirotani, Kouichi, E-mail: rbwang1225@gmail.com, E-mail: hirotani@tiara.sinica.edu.tw

2011-08-01

We analytically investigate the condition for a particle accelerator to be active in the outer magnetosphere of a rotation-powered pulsar. Within the accelerator (or the gap), the magnetic-field-aligned electric field accelerates electrons and positrons, which emit copious gamma-rays via the curvature process. If one of the gamma-rays emitted by a single pair materializes as a new pair on average, the gap is self-sustained. However, if the neutron-star spin-down rate decreases below a certain limit, the gap becomes no longer self-sustained and the gamma-ray emission ceases. We explicitly compute the multiplicity of cascading pairs and find that the obtained limit correspondsmore » to a modification of the previously derived outer-gap death line. In addition to this traditional death line, we find another death line, which becomes important for millisecond pulsars, by separately considering the threshold of photon-photon pair production. Combining these traditional and new death lines, we give predictions on the detectability of gamma-ray pulsars with Fermi and AGILE. An implication for X-ray observations of heated polar-cap emission is also discussed.« less

European team gauges a gamma-ray star

NASA Astrophysics Data System (ADS)

1996-03-01

neutron star. The background of a few brighter but more distant stars displayed by Hubble's camera provided a frame of reference. In the course of a year, Geminga moved northeastwards by 0.17 arc-seconds, equivalent to one degree in 21,000 years. That was due to Geminga's high-speed motion through the Galaxy. But the neutron star also seemed to shift to either side of its interstellar track, because of changes in Hubble's viewpoint as the Earth orbited around the Sun. At opposite seasons, spring and autumn in this case, the Earth is on opposite sides of the Sun, at vantage points 300 million kilometres apart. As a result, the bearings of stars change a little, by the effect called parallax. Nearby stars shift more than very distant stars, and astronomers can measure their distances by trigonometry. The sideways displacement measured using the Hubble Space Telescope was 0.00636 arc-seconds, less than two millionths of a degree. From this figure the astronomers calculate that Geminga is 512 light-years away (157 parsecs) with an uncertainty of the order of 100 light-years. The strong gamma-rays and weak light observed today left Geminga around the time that Columbus discovered America. "We are pleased to have measured a parallax for an object at the limit of detection, which was never done before," says Patrizia Caraveo. "But what really matters is that we have pinned down an important object that has puzzled us for more than 20 years." From "it's not there" to "here it is" Geminga has tested the patience of the Milanese astronomers for twenty years. NASA's shortlived SAS-2 satellite (1973) first recorded a mysterious source of gamma-rays in the constellation of Gemini. In 1976 Giovanni Bignami named it Geminga. This is a pun signifying either "Gemini gamma" or "gh'è minga" which in the Milanese argot means "it's not there". Geminga lived up to its name when Bignami and his colleagues looked in vain for radio emissions from it. By 1981, data from ESA's longlived gamma-ray

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.

Fermi Detection of a Luminous gamma-ray Pulsar in a Globular Cluster

NASA Technical Reports Server (NTRS)

Freire, P. C. C.; Abdo, A. A.; Ajello, M.; Allafort, A.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Blandford, R. D.;

RoboPol: the optical polarization of gamma-ray-loud and gamma-ray-quiet blazars

NASA Astrophysics Data System (ADS)

Angelakis, E.; Hovatta, T.; Blinov, D.; Pavlidou, V.; Kiehlmann, S.; Myserlis, I.; Böttcher, M.; Mao, P.; Panopoulou, G. V.; Liodakis, I.; King, O. G.; Baloković, M.; Kus, A.; Kylafis, N.; Mahabal, A.; Marecki, A.; Paleologou, E.; Papadakis, I.; Papamastorakis, I.; Pazderski, E.; Pearson, T. J.; Prabhudesai, S.; Ramaprakash, A. N.; Readhead, A. C. S.; Reig, P.; Tassis, K.; Urry, M.; Zensus, J. A.

2016-12-01

We present average R-band optopolarimetric data, as well as variability parameters, from the first and second RoboPol observing season. We investigate whether gamma-ray-loud and gamma-ray-quiet blazars exhibit systematic differences in their optical polarization properties. We find that gamma-ray-loud blazars have a systematically higher polarization fraction (0.092) than gamma-ray-quiet blazars (0.031), with the hypothesis of the two samples being drawn from the same distribution of polarization fractions being rejected at the 3σ level. We have not found any evidence that this discrepancy is related to differences in the redshift distribution, rest-frame R-band luminosity density, or the source classification. The median polarization fraction versus synchrotron-peak-frequency plot shows an envelope implying that high-synchrotron-peaked sources have a smaller range of median polarization fractions concentrated around lower values. Our gamma-ray-quiet sources show similar median polarization fractions although they are all low-synchrotron-peaked. We also find that the randomness of the polarization angle depends on the synchrotron peak frequency. For high-synchrotron-peaked sources, it tends to concentrate around preferred directions while for low-synchrotron-peaked sources, it is more variable and less likely to have a preferred direction. We propose a scenario which mediates efficient particle acceleration in shocks and increases the helical B-field component immediately downstream of the shock.

Multiwavelength Study of Gamma-Ray Bright Blazars

NASA Astrophysics Data System (ADS)

Morozova, Daria; Larionov, V. M.; Hagen-Thorn, V. A.; Jorstad, S. G.; Marscher, A. P.; Troitskii, I. S.

2011-01-01

We investigate total intensity radio images of 6 gamma-ray bright blazars (BL Lac, 3C 279, 3C 273, W Com, PKS 1510-089, and 3C 66A) and their optical and gamma-ray light curves to study connections between gamma-ray and optical brightness variations and changes in the parsec-scale radio structure. We use high-resolution maps obtained by the BU group at 43 GHz with the VLBA, optical light curves constructed by the St.Petersburg State U. (Russia) team using measurements with the 0.4 m telescope of St.Petersburg State U. (LX200) and the 0.7 m telescope of the Crimean Astrophysical Observatory (AZT-8), and gamma-ray light curves, which we have constructed with data provided by the Fermi Large Area Telescope. Over the period from August 2008 to November 2009, superluminal motion is found in all 6 objects with apparent speed ranging from 2c to 40c. The blazars with faster apparent speeds, 3C 273, 3C 279, PKS 1510-089, and 3C 66A, exhibit stronger variability of the gamma-ray emission. There is a tendency for sources with sharply peaked gamma-ray flares to have faster jet speed than sources with gamma-ray light curves with no sharp peaks. Gamma-ray light curves with sharply peaked gamma-ray flares possess a stronger gamma-ray/optical correlations. The research at St.Petersburg State U. was funded by the Minister of Education and Science of the Russian Federation (state contract N#P123). The research at BU was funded in part by NASA Fermi Guest Investigator grant NNX08AV65G and by NSF grant AST-0907893. The VLBA is an instrument of the National Radio Astronomy Observatory, a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Novel drift structures for silicon and compound semiconductor X-ray and gamma-ray detectors

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

Patt, B.E.; Iwanczyk, J.S.

Recently developed silicon- and compound-semiconductor-based drift detector structures have produced excellent performance for charged particles, X-rays, and gamma rays and for low-signal visible light detection. The silicon drift detector (SDD) structures that the authors discuss relate to direct X-ray detectors and scintillation photon detectors coupled with scintillators for gamma rays. Recent designs include several novel features that ensure very low dark current and hence low noise. In addition, application of thin window technology ensures a very high quantum efficiency entrance window on the drift photodetector. The main features of the silicon drift structures for X rays and light detection aremore » very small anode capacitance independent of the overall detector size, low noise, and high throughput. To take advantage of the small detector capacitance, the first stage of the electronics needs to be integrated into the detector anode. In the gamma-ray application, factors other than electronic noise dominate, and there is no need to integrate the electronics into the anode. Thus, a different drift structure is needed in conjunction with a high-Z material. The main features in this case are large active detector volume and electron-only induced signal.« less

Gamma-ray Astrophysics with AGILE

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

Longo, Francesco; Tavani, M.; Barbiellini, G.

2007-07-12

AGILE will explore the gamma-ray Universe with a very innovative instrument combining for the first time a gamma-ray imager and a hard X-ray imager. AGILE will be operational in spring 2007 and it will provide crucial data for the study of Active Galactic Nuclei, Gamma-Ray Bursts, unidentified gamma-ray sources. Galactic compact objects, supernova remnants, TeV sources, and fundamental physics by microsecond timing. The AGILE instrument is designed to simultaneously detect and image photons in the 30 MeV - 50 GeV and 15 - 45 keV energy bands with excellent imaging and timing capabilities, and a large field of view coveringmore » {approx} 1/5 of the entire sky at energies above 30 MeV. A CsI calorimeter is capable of GRB triggering in the energy band 0.3-50 MeV AGILE is now (March 2007) undergoing launcher integration and testing. The PLSV launch is planned in spring 2007. AGILE is then foreseen to be fully operational during the summer of 2007.« less

Gamma-ray emission from internal shocks in novae

NASA Astrophysics Data System (ADS)

Martin, P.; Dubus, G.; Jean, P.; Tatischeff, V.; Dosne, C.

2018-04-01

Context. Gamma-ray emission at energies ≥100 MeV has been detected from nine novae using the Fermi Large Area Telescope (LAT), and can be explained by particle acceleration at shocks in these systems. Eight out of these nine objects are classical novae in which interaction of the ejecta with a tenuous circumbinary material is not expected to generate detectable gamma-ray emission. Aim. We examine whether particle acceleration at internal shocks can account for the gamma-ray emission from these novae. The shocks result from the interaction of a fast wind radiatively-driven by nuclear burning on the white dwarf with material ejected in the initial runaway stage of the nova outburst. Methods: We present a one-dimensional model for the dynamics of a forward and reverse shock system in a nova ejecta, and for the associated time-dependent particle acceleration and high-energy gamma-ray emission. Non-thermal proton and electron spectra are calculated by solving a time-dependent transport equation for particle injection, acceleration, losses, and escape from the shock region. The predicted emission is compared to LAT observations of V407 Cyg, V1324 Sco, V959 Mon, V339 Del, V1369 Cen, and V5668 Sgr. Results: The ≥100 MeV gamma-ray emission arises predominantly from particles accelerated up to 100 GeV at the reverse shock and undergoing hadronic interactions in the dense cooling layer downstream of the shock. The emission rises within days after the onset of the wind, quickly reaches a maximum, and its subsequent decrease reflects mostly the time evolution of the wind properties. Comparison to gamma-ray data points to a typical scenario where an ejecta of mass 10-5-10-4 M⊙ expands in a homologous way with a maximum velocity of 1000-2000 km s-1, followed within a day by a wind with a velocity <2000 km s-1 and a mass-loss rate of 10-4-10-3 M⊙ yr-1 declining over a time scale of a few days. Because of the large uncertainties in the measurements, many parameters of the

Ultra high energy gamma rays, cosmic rays and neutrinos from accreting degenerate stars

NASA Technical Reports Server (NTRS)

Brecher, K.; Chanmugam, G.

1985-01-01

Super-Eddington accretion for a recently proposed unipolar induction model of cosmic ray acceleration in accreting binary star systems containing magnetic white dwarfs or neutron stars is considered. For sufficiently high accretion rates and low magnetic fields, the model can account for: (1) acceleration of cosmic ray nuclei up to energies of 10 to the 19th power eV; (2) production of more or less normal solar cosmic ray composition; (3) the bulk of cosmic rays observed with energies above 1 TeV, and probably even down to somewhat lower energies as well; and (4) possibly the observed antiproton cosmic ray flux. It can also account for the high ultra high energy (UHE) gamma ray flux observed from several accreting binary systems (including Cygnus X-3), while allowing the possibility of an even higher neutrino flux from these sources, with L sub nu/L sub gamma is approximately 100.

GLAST and Ground-Based Gamma-Ray Astronomy

NASA Technical Reports Server (NTRS)

McEnery, Julie

2008-01-01

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

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

NASA Technical Reports Server (NTRS)

McEnery, Julie

2009-01-01

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

Fermi: The Gamma-Ray Large Area Telescope

NASA Technical Reports Server (NTRS)

McEnery, Julie

2015-01-01

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

Fermi: The Gamma-Ray Large Area Telescope

NASA Technical Reports Server (NTRS)

McEnery, Julie

2014-01-01

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

Gamma Ray Bursts

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Meszaros, Peter

2012-01-01

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

Discoveries by the Fermi Gamma Ray Space Telescope

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2011-01-01

Fermi is a large space gamma-ray mission developed by NASA and the DOE with major contributions from France, Germany, Italy, Japan and Sweden. It was launched in June 2008 and has been performing flawlessly since then. The main instrument is the Large Area Telescope (LAT) operating in the 20 MeV to 300 GeV range and a smaller monitor instrument is the Gamma-ray Burst Monitor (GBM) operating in the 8 keV to 40 MeV range. New findings are occurring every week. Some of the key discoveries are: 1) Discovery of many new gamma-ray pulsars, including gamma-ray only and millisecond pulsars. 2) Detection of high energy gamma-ray emission from globular clusters, most likely due to summed emission from msec pulsars. 3) Discovery of delayed and extended high energy gamma-ray emission from short and long gamma-ray busts. 4) Detection of approximately 250 gamma-ray bursts per year with the GBM instrument. 5) Most accurate measurement of the cosmic ray electron spectrum between 30 GeV and 1 TeV, showing some excess above the conventional diffusion model. The talk will present the new discoveries and their implications.

Lunar elemental analysis obtained from the Apollo gamma-ray and X-ray remote sensing experiment

NASA Technical Reports Server (NTRS)

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

1977-01-01

Gamma-ray and X-ray spectrometers carried in the service modules of the Apollo 15 and Apollo 16 spacecraft were employed for compositional mapping of the lunar surface. The measurements involved the observation of the intensity and characteristic energy distribution of gamma rays and X-rays emitted from the lunar surface. A large-scale compositional map of over 10 percent of the lunar surface was obtained from an analysis of the observed spectra. The objective of the X-ray experiment was to measure the K spectral lines from Mg, Al, and Si. Spectra were obtained and the data were reduced to Al/Si and Mg/Si intensity ratios and ultimately to chemical ratios. Analyses of the results have indicated (1) that the Al/Si ratios are highest in the lunar highlands and considerably lower in the maria, and (2) that the Mg/Si concentrations generally show the opposite relationship. The objective of the gamma-ray experiment was to measure the natural and cosmic-ray-induced activity emission spectrum. At this time, the elemental abundances for Th, U, K, Fe, Ti, Si, and O have been determined over a number of major lunar regions. Regions of relatively high natural radioactivity were found in the Mare Imbrium and Oceanus Procellarum regions.

GBM Observations of Terrestrial Gamma-Ray Flashes

NASA Technical Reports Server (NTRS)

Briggs, M. S.; Fishman, G. J.; Connaughton, V.; Bhat, P. N.; Paciesas, W. S.; Preece, R. D.; Wilson-Hodge, C.; Chaplin, V. L.; Kippen, R. M.; vonKienlin, A.;

Effect of gamma-ray irradiation on structural properties of GaAsN films grown by metal organic vapor phase epitaxy

NASA Astrophysics Data System (ADS)

Klangtakai, Pawinee; Sanorpim, Sakuntam; Wattanawareekul, Atiwat; Suwanyangyaun, Pattana; Srepusharawoot, Pornjuk; Onabe, Kentaro

2015-05-01

The effects of gamma-ray irradiation on the structural properties of GaAs1-xNx films (N concentration=1.9 and 5.1 at%) grown by metal organic vapor phase epitaxy on GaAs (001) substrates were investigated. The GaAs1-xNx films were irradiated by gamma rays with irradiation strength of 0-2.0 MGy. Scanning electron microscopy and atomic force microscopy results showed that a gamma ray with a strength of 0, 0.5, 1.0, 1.5, and 2.0 MGy formed holes with a density of 0.0, 8.8, 9.4, 11.5, and 11.9 μm-2, respectively, on the surface of a GaAs0.981N0.019 film with low N content. On the other hand, the irradiated high-N-content GaAs0.949N0.051 film exhibited a cross-hatch pattern, which was induced by partial strain relaxation at high N levels, with a line density of 0.0, 0.21, 0.37, 0.67, and 0.26 μm-1 corresponding to an irradiation strength of 0, 0.5, 1.0, 1.5, and 2.0 MGy, respectively. The high-resolution X-ray diffraction and Raman scattering results revealed an increase in N incorporation and strain relaxation after irradiation. In addition, the GaAs0.949N0.051 films exhibited phase separation, which took place via N out-diffusion across the interface when the irradiation strength exceeded 1.0 MGy. Based on these results, the main cause of structural change was determined to be the irradiation effects including displacement damage and gamma-ray heating.

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.

Future Facilities for Gamma-Ray Pulsar Studies

NASA Technical Reports Server (NTRS)

Thompson, D. J.

2003-01-01

Pulsars seen at gamma-ray energies offer insight into particle acceleration to very high energies, along with information about the geometry and interaction processes in the magnetospheres of these rotating neutron stars. During the next decade, a number of new gamma-ray facilities will become available for pulsar studies. This brief review describes the motivation for gamma-ray pulsar studies, the opportunities for such studies, and some specific discussion of the capabilities of the Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) for pulsar measurements.

Significance of medium energy gamma ray astronomy in the study of cosmic rays

NASA Technical Reports Server (NTRS)

Fichtel, C. E.; Kniffen, D. A.; Thompson, D. J.; Bignami, G. F.; Cheung, C. Y.

1975-01-01

Medium energy (about 10 to 30 MeV) gamma ray astronomy provides information on the product of the galactic electron cosmic ray intensity and the galactic matter to which the electrons are dynamically coupled by the magnetic field. Because high energy (greater than 100 MeV) gamma ray astronomy provides analogous information for the nucleonic cosmic rays and the relevant matter, a comparison between high energy and medium energy gamma ray intensities provides a direct ratio of the cosmic ray electrons and nucleons throughout the galaxy. A calculation of gamma ray production by electron bremsstrahlung shows that: bremsstrahlung energy loss is probably not negligible over the lifetime of the electrons in the galaxy; and the approximate bremsstrahlung calculation often used previously overestimates the gamma ray intensity by about a factor of two. As a specific example, expected medium energy gamma ray intensities are calculated for the speral arm model.

Measurement of air kerma rates for 6- to 7-MeV high-energy gamma-ray field by ionisation chamber and build-up plate.

PubMed

Kowatari, Munehiko; Tanimura, Yoshihiko; Tsutsumi, Masahiro

2014-12-01

The 6- to 7-MeV high-energy gamma-ray calibration field by the (19)F(p, αγ)(16)O reaction is to be served at the Japan Atomic Energy Agency. For the determination of air kerma rates using an ionisation chamber in the 6- to 7-MeV high-energy gamma-ray field, the establishment of the charged particle equilibrium must be achieved during measurement. In addition to measurement of air kerma rates by the ionisation chamber with a thick build-up cap, measurement using the ionisation chamber and a build-up plate (BUP) was attempted, in order to directly determine air kerma rates under the condition of regular calibration for ordinary survey meters and personal dosemeters. Before measurements, Monte Carlo calculations were made to find the optimum arrangement of BUP in front of the ionisation chamber so that the charged particle equilibrium could be well established. Measured results imply that air kerma rates for the 6- to 7-MeV high-energy gamma-ray field could be directly determined under the appropriate condition using an ionisation chamber coupled with build-up materials. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Repeated irradiations with gamma-rays at a Dose of 0.5 Gy may exacerbate asthma.

PubMed

Fang, Su-ping; Tago, Fumitoshi; Tanaka, Takashi; Simura, Noriko; Muto, Yasuko; Goto, Resuke; Kojima, Shuji

2005-06-01

We previously showed that 0.5 Gy whole-body gamma-ray irradiation with a single or small number of repeated exposures inhibits tumor growth in mice, via elevation of the IFN-gamma/IL-4 ratio concomitantly with a decrease in the percentage of B cells. Here we examined whether repeated 0.5 Gy gamma-rays irradiation can improve asthma in an OVA-induced asthmatic mouse model. We found that repeated irradiation (10 times) with 0.5 Gy of gamma-rays significantly increased total IgE in comparison with the disease-control group. The levels of IL-4 and IL-5 were also significantly higher in the gamma-ray-irradiated group, while that of IFN-gamma was significantly lower, resulting in a further decrease of the IFN-gamma/IL-4 ratio from the normal value. These results indicate that the repeated irradiation with gamma-rays may exacerbate asthma, and may have opposite effects on different immune reactions unlike the irradiation with a single or small number of repeated exposures.

Pulsar timing for the Fermi gamma-ray space telescope

DOE PAGES

Smith, D. A.; Guillemot, L.; Camilo, F.; ...

2008-10-27

Here, we describe a comprehensive pulsar monitoring campaign for the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). The detection and study of pulsars in gamma rays give insights into the populations of neutron stars and supernova rates in the Galaxy, into particle acceleration mechanisms in neutron star magnetospheres, and into the “engines” driving pulsar wind nebulae. LAT's unprecedented sensitivity between 20 MeV and 300 GeV together with its 2.4 sr field-of-view makes detection of many gamma-ray pulsars likely, justifying the monitoring of over two hundred pulsars with large spin-down powers. To search for gamma-ray pulsationsmore » from most of these pulsars requires a set of phase-connected timing solutions spanning a year or more to properly align the sparse photon arrival times. We describe the choice of pulsars and the instruments involved in the campaign. Attention is paid to verifications of the LAT pulsar software, using for example giant radio pulses from the Crab and from PSR B1937+21 recorded at Nançay, and using X-ray data on PSR J0218+4232 from XMM-Newton. We demonstrate accuracy of the pulsar phase calculations at the microsecond level.« less

Monte Carlo simulation to calculate the rate of 137Cs gamma rays dispersion in gallium arsenide compound

NASA Astrophysics Data System (ADS)

Haider, F. A.; Chee, F. P.; Abu Hassan, H.; Saafie, S.

2017-01-01

Radiation effects on Gallium Arsenide (GaAs) have been tested by exposing samples to Cesium-137 (137Cs) gamma rays. Gallium Arsenide is a basic photonic material for most of the space technology communication, and, therefore, lends itself for applications where this is of concern. Monte Carlo simulations of interaction between direct ionizing radiation and GaAs structure have been performed in TRIM software, being part of SRIM 2011 programming package. An adverse results shows that energy dose does not govern the displacement of atoms and is dependent on the changes of incident angles and thickness of the GaAs target element. At certain thickness of GaAs and incident angle of 137Cs ion, the displacement damage is at its highest value. From the simulation result, it is found that if the thickness of the GaAs semiconductor material is small compared to the projected range at that particular incident energy, the energy loss in the target GaAs will be small. Hence, when the depth of semiconductor material is reduced, the range of damage in the target also decreased. However, the other factors such as quantum size effect, the energy gap between the conduction and valence band must also be taken into consideration when the dimension of the device is diminished.

Nuclear gamma rays from energetic particle interactions

NASA Technical Reports Server (NTRS)

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

1978-01-01

Gamma ray line emission from nuclear deexcitation following energetic particle reactions is evaluated. The compiled nuclear data and the calculated gamma ray spectra and intensities can be used for the study of astrophysical sites which contain large fluxes of energetic protons and nuclei. A detailed evaluation of gamma ray line production in the interstellar medium is made.

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.

Dark gamma-ray bursts

NASA Astrophysics Data System (ADS)

Brdar, Vedran; Kopp, Joachim; Liu, Jia

2017-03-01

Many theories of dark matter (DM) predict that DM particles can be captured by stars via scattering on ordinary matter. They subsequently condense into a DM core close to the center of the star and eventually annihilate. In this work, we trace DM capture and annihilation rates throughout the life of a massive star and show that this evolution culminates in an intense annihilation burst coincident with the death of the star in a core collapse supernova. The reason is that, along with the stellar interior, also its DM core heats up and contracts, so that the DM density increases rapidly during the final stages of stellar evolution. We argue that, counterintuitively, the annihilation burst is more intense if DM annihilation is a p -wave process than for s -wave annihilation because in the former case, more DM particles survive until the supernova. If among the DM annihilation products are particles like dark photons that can escape the exploding star and decay to standard model particles later, the annihilation burst results in a flash of gamma rays accompanying the supernova. For a galactic supernova, this "dark gamma-ray burst" may be observable in the Čerenkov Telescope Array.

KASCADE-Grande Limits on the Isotropic Diffuse Gamma-Ray Flux between 100 TeV and 1 EeV

NASA Astrophysics Data System (ADS)

Apel, W. D.; Arteaga-Velázquez, J. C.; Bekk, K.; Bertaina, M.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Feng, Z.; Fuhrmann, D.; Gherghel-Lascu, A.; Gils, H. J.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Huege, T.; Kampert, K.-H.; Kang, D.; Klages, H. O.; Link, K.; Łuczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Oehlschläger, J.; Ostapchenko, S.; Pierog, T.; Rebel, H.; Roth, M.; Schieler, H.; Schoo, S.; Schröder, F. G.; Sima, O.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Zabierowski, J.; KASCADE-Grande Collaboration

2017-10-01

KASCADE and KASCADE-Grande were multi-detector installations to measure individual air showers of cosmic rays at ultra-high energy. Based on data sets measured by KASCADE and KASCADE-Grande, 90% C.L. upper limits to the flux of gamma-rays in the primary cosmic ray flux are determined in an energy range of {10}14{--}{10}18 eV. The analysis is performed by selecting air showers with a low muon content as expected for gamma-ray-induced showers compared to air showers induced by energetic nuclei. The best upper limit of the fraction of gamma-rays to the total cosmic ray flux is obtained at 3.7× {10}15 eV with 1.1× {10}-5. Translated to an absolute gamma-ray flux this sets constraints on some fundamental astrophysical models, such as the distance of sources for at least one of the IceCube neutrino excess models.

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.

The Gamma-Ray Albedo of the Moon

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

Moskalenko, I.V.; /Stanford U., HEPL /KIPAC, Menlo Park; Porter, T.A.

2008-03-25

We use the GEANT4 Monte Carlo framework to calculate the {gamma}-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of {gamma}-rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalization; this makesmore » it a useful 'standard candle' for {gamma}-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of {gamma}-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo {gamma}-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo {gamma}-rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA.« less

The Gamma-ray Albedo of the Moon

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

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

2007-09-28

We use the GEANT4 Monte Carlo framework to calculate the {gamma}-ray albedo of the Moon due to interactions of cosmic ray (CR) nuclei with moon rock. Our calculation of the albedo spectrum agrees with the EGRET data. We show that the spectrum of {gamma}-rays from the Moon is very steep with an effective cutoff around 3-4 GeV (600 MeV for the inner part of the Moon disk) and exhibits a narrow pion-decay line at 67.5 MeV, perhaps unique in astrophysics. Apart from other astrophysical sources, the albedo spectrum of the Moon is well understood, including its absolute normalization; this makesmore » it a useful 'standard candle' for {gamma}-ray telescopes. The steep albedo spectrum also provides a unique opportunity for energy calibration of {gamma}-ray telescopes, such as the forthcoming Gamma Ray Large Area Space Telescope (GLAST). Since the albedo flux depends on the incident CR spectrum which changes over the solar cycle, it is possible to monitor the CR spectrum using the albedo {gamma}-ray flux. Simultaneous measurements of CR proton and helium spectra by the Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics (PAMELA), and observations of the albedo {gamma}-rays by the GLAST Large Area Telescope (LAT), can be used to test the model predictions and will enable the LAT to monitor the CR spectrum near the Earth beyond the lifetime of the PAMELA.« less

Observational techniques for solar flare gamma-rays, hard X-rays, and neutrons

NASA Technical Reports Server (NTRS)

Lin, Robert P.

1989-01-01

The development of new instrumentation and techniques for solar hard X-ray, gamma ray and neutron observations from spacecraft and/or balloon-borne platforms is examined. The principal accomplishments are: (1) the development of a two segment germanium detector which is near ideal for solar hard X-ray and gamma ray spectroscopy; (2) the development of long duration balloon flight techniques and associated instrumentation; and (3) the development of innovative new position sensitive detectors for hard X-ray and gamma rays.

A Correlation Between the Intrinsic Brightness and Average Decay Rate of Gamma-Ray Burst X-Ray Afterglow Light Curves

NASA Technical Reports Server (NTRS)

Racusin, J. L.; Oates, S. R.; De Pasquale, M.; Kocevski, D.

2016-01-01

We present a correlation between the average temporal decay (alpha X,avg, greater than 200 s) and early-time luminosity (LX,200 s) of X-ray afterglows of gamma-ray bursts as observed by the Swift X-ray Telescope. Both quantities are measured relative to a rest-frame time of 200 s after the gamma-ray trigger. The luminosity â€" average decay correlation does not depend on specific temporal behavior and contains one scale-independent quantity minimizing the role of selection effects. This is a complementary correlation to that discovered by Oates et al. in the optical light curves observed by the Swift Ultraviolet Optical Telescope. The correlation indicates that, on average, more luminous X-ray afterglows decay faster than less luminous ones, indicating some relative mechanism for energy dissipation. The X-ray and optical correlations are entirely consistent once corrections are applied and contamination is removed. We explore the possible biases introduced by different light-curve morphologies and observational selection effects, and how either geometrical effects or intrinsic properties of the central engine and jet could explain the observed correlation.

Gamma-ray-burst beaming and gravitational-wave observations.

PubMed

Chen, Hsin-Yu; Holz, Daniel E

2013-11-01

Using the observed rate of short-duration gamma-ray bursts (GRBs) it is possible to make predictions for the detectable rate of compact binary coalescences in gravitational-wave detectors. We show that the nondetection of mergers in the existing LIGO/Virgo data constrains the beaming angles and progenitor masses of gamma-ray bursts, although these limits are fully consistent with existing expectations. We make predictions for the rate of events in future networks of gravitational-wave observatories, finding that the first detection of a neutron-star-neutron-star binary coalescence associated with the progenitors of short GRBs is likely to happen within the first 16 months of observation, even in the case of only two observatories (e.g., LIGO-Hanford and LIGO-Livingston) operating at intermediate sensitivities (e.g., advanced LIGO design sensitivity, but without signal recycling mirrors), and assuming a conservative distribution of beaming angles (e.g., all GRBs beamed within θ(j) = 30°). Less conservative assumptions reduce the waiting time until first detection to a period of weeks to months, with an event detection rate of >/~10/yr. Alternatively, the compact binary coalescence model of short GRBs can be ruled out if a binary is not seen within the first two years of operation of a LIGO-Hanford, LIGO-Livingston, and Virgo network at advanced design sensitivity. We also demonstrate that the gravitational wave detection rate of GRB triggered sources (i.e., those seen first in gamma rays) is lower than the rate of untriggered events (i.e., those seen only in gravitational waves) if θ(j)≲30°, independent of the noise curve, network configuration, and observed GRB rate. The first detection in gravitational waves of a binary GRB progenitor is therefore unlikely to be associated with the observation of a GRB.

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.

NEAR Gamma Ray Spectrometer Characterization and Repair

NASA Technical Reports Server (NTRS)

Groves, Joel Lee; Vajda, Stefan

1998-01-01

This report covers the work completed in the third year of the contract. The principle activities during this period were (1) the characterization of the NEAR 2 Gamma Ray Spectrometer using a neutron generator to generate complex gamma ray spectra and a large Ge Detecter to identify all the major peaks in the spectra; (2) the evaluation and repair of the Engineering Model Unit of the Gamma Ray Spectrometer for the NEAR mission; (3) the investigation of polycapillary x-ray optics for x-ray detection; and (4) technology transfer from NASA to forensic science.

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.

Determination of the optimum-size californium-252 neutron source for borehole capture gamma-ray analysis

USGS Publications Warehouse

Senftle, F.E.; Macy, R.J.; Mikesell, J.L.

1979-01-01

The fast- and thermal-neutron fluence rates from a 3.7 ??g 252Cf neutron source in a simulated borehole have been measured as a function of the source-to-detector distance using air, water, coal, iron ore-concrete mix, and dry sand as borehole media. Gamma-ray intensity measurements were made for specific spectral lines at low and high energies for the same range of source-to-detector distances in the iron ore-concrete mix and in coal. Integral gamma-ray counts across the entire spectrum were also made at each source-to-detector distance. From these data, the specific neutron-damage rate, and the critical count-rate criteria, we show that in an iron ore-concrete mix (low hydrogen concentration), 252Cf neutron sources of 2-40 ??g are suitable. The source size required for optimum gamma-ray sensitivity depends on the energy of the gamma ray being measured. In a hydrogeneous medium such as coal, similar measurements were made. The results show that sources from 2 to 20 ??g are suitable to obtain the highest gamma-ray sensitivity, again depending on the energy of the gamma ray being measured. In a hydrogeneous medium, significant improvement in sensitivity can be achieved by using faster electronics; in iron ore, it cannot. ?? 1979 North-Holland Publishing Co.

Terrestrial gamma-ray flashes

NASA Astrophysics Data System (ADS)

Marisaldi, Martino; Fuschino, Fabio; Labanti, Claudio; Tavani, Marco; Argan, Andrea; Del Monte, Ettore; Longo, Francesco; Barbiellini, Guido; Giuliani, Andrea; Trois, Alessio; Bulgarelli, Andrea; Gianotti, Fulvio; Trifoglio, Massimo

2013-08-01

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

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 supernova-gamma-ray burst-jet connection.

PubMed

Hjorth, Jens

2013-06-13

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

Search for medium-energy gamma-ray pulsars

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

Sweeney, W.E. Jr.

1987-01-01

Results are presented from a search for pulsed gamma rays from four radio pulsars, chosen for their interest to gamma-ray astronomers in previous studies. The data set used for the search consists of gamma-ray events at energies of 1-30 MeV, detected during a 40-hour balloon flight of the UCR double Compton scatter telescope launched at the National Scientific Balloon Facility in Palestine, Texas, USA on September 30, 1978. No statistically significant signals were detected from any of the pulsars. Three sigma upper limits to pulsed 1-30 MeV gamma ray flux from PSR 0950+08, PSR 1822+09, PSR 1929+10, and PSR 1953+29more » are presented. Two complete exposures to PSR 0950+08 were obtained. The reported tentative detection of 1-20 MeV gamma rays from PSR 0950+08 is not confirmed.« less

Gamma Ray Burst Discoveries by the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2006-01-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit after a beautiful launch on November 20, 2004. A new-technology wide-field gamma-ray camera detects more than a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners and calibrated in Germany, are pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. Early results from the mission will be presented. The long-standing mystery of short GRBs has been solved, and the answer is the most interesting possible scenario. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. Observations of magnetars, galactic transients, supernovae, AGN and many other types of sources are also being performed

Gamma Ray Burst Discoveries by the Swift Mission

NASA Astrophysics Data System (ADS)

Gehrels, N.; Swift Team

2005-12-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit after a beautiful launch on November 20, 2004. A new-technology wide-field gamma-ray camera detects more than a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. The long-standing mystery of short GRBs has been solved, and the answer is the most interesting possible scenario. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. These, and other topics, will be discussed.

Gamma Ray Burst Discoveries by the Swift Mission

NASA Astrophysics Data System (ADS)

Gehrels, Neil

2006-04-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit since November 20, 2004 and all hardware is performing well. A new-technology wide-field gamma-ray camera is detecting a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 50-100 sec by an autonomously controlled ``swift'' spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. There has been a break-through in the long-standing mystery of short GRBs; they appear to be caused by merging neutron stars. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow.

Gamma Ray Burst Discoveries by the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2006-01-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit since November 20, 2004 and all hardware is performing well. A new-technology wide-field gamma-ray camera is detecting a hundred bursts per year. sensitive narrow-field X-ray and uv/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 50-100 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. There has been a break-through in the longstanding mystery of short GRBs; they appear to be caused by merging neutron stars. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow.

Gamma Ray Burst Discoveries by the Swift Mission

NASA Technical Reports Server (NTRS)

Gehrels, Neil

2006-01-01

Gamma-ray bursts are among the most fascinating occurrences in the cosmos. They are thought to be the birth cries of black holes throughout the universe. The NASA Swift mission is an innovative new multiwavelength observatory designed to determine the origin of bursts and use them to probe the early Universe. Swift is now in orbit after a beautiful launch on November 20, 2004. A new-technology wide-field gamma-ray camera detects more than a hundred bursts per year. Sensitive narrow-field X-ray and UV/optical telescopes, built in collaboration with UK and Italian partners, are pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, arcsec positions are determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Information is also rapidly sent to the ground to a team of more than 50 observers at telescopes around the world. The first year of findings from the mission will be presented. The long-standing mystery of short GRBs has been solved, and the answer is the most interesting possible scenario. High redshift bursts have been detected leading to a better understanding of star formation rates and distant galaxy environments. GRBs have been found with giant X-ray flares occurring in their afterglow. These, and other topics, will be discussed.

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.

Gamma-Ray Astrophysics: New Insight Into the Universe

NASA Technical Reports Server (NTRS)

Fichtel, Carl E.; Trombka, Jacob I.

1997-01-01

During the 15 years that have passed since the first edition of this book was published, there has been a major increase in our knowledge of gamma-ray astronomy. Much of this advance arises from the extensive results that have been forthcoming from the Compton Gamma-Ray Observatory. There has been the discovery of a new class of gamma-ray objects, namely high-energy gamma- ray-emitting blazars, a special class of Active Galactic Nuclei, whose basic high-energy properties now seem to be understood. A much improved picture of our galaxy now exists in the frequency range of gamma rays. The question of whether cosmic rays are galactic or metagalactic now seems settled with certainty. Significant new information exists on the gamma-ray properties of neutron star pulsars, Seyfert galaxies, and gamma-ray bursts. Substantial new insight has been obtained on solar phenomena through gamma-ray observations. Hence, this seemed to be an appropriate time to write a new edition of this book to add the important scientific implications of these many new findings. The special importance of gamma-ray astrophysics had long been recognized by many physicists and astronomers, and theorists had pursued many aspects of the subject well before the experimental results began to become available. The slower development of the experimental side was not because of a lack of incentive, but due to the substantial experimental difficulties that had to be overcome. Thus, as the gamma-ray results became available in much greater number and detail, it was possible to build upon the theoretical work that already existed and to make substantial progress in the study of many of the phenomena involved. Consequently, a much better understanding of many of the astrophysical phenomena mentioned here and others is now possible. Our principal aims in writing this book are the same as they were for the first edition: to provide a text which describes the significance of gamma-ray astrophysics and to assemble

Measurements of neutron distribution in neutrons-gamma-rays mixed field using imaging plate for neutron capture therapy.

PubMed

Tanaka, Kenichi; Endo, Satoru; Hoshi, Masaharu

2010-01-01

The imaging plate (IP) technique is tried to be used as a handy method to measure the spatial neutron distribution via the (157)Gd(n,gamma)(158)Gd reaction for neutron capture therapy (NCT). For this purpose, IP is set in a water phantom and irradiated in a mixed field of neutrons and gamma-rays. The Hiroshima University Radiobiological Research Accelerator is utilized for this experiment. The neutrons are moderated with 20-cm-thick D(2)O to obtain suitable neutron field for NCT. The signal for IP doped with Gd as a neutron-response enhancer is subtracted with its contribution by gamma-rays, which was estimated using IP without Gd. The gamma-ray response of Gd-doped IP to non-Gd IP is set at 1.34, the value measured for (60)Co gamma-rays, in estimating the gamma-ray contribution to Gd-doped IP signal. Then measured distribution of the (157)Gd(n,gamma)(158)Gd reaction rate agrees within 10% with the calculated value based on the method that has already been validated for its reproducibility of Au activation. However, the evaluated distribution of the (157)Gd(n,gamma)(158)Gd reaction rate is so sensitive to gamma-ray energy, e.g. the discrepancy of the (157)Gd(n,gamma)(158)Gd reaction rate between measurement and calculation becomes 30% for the photon energy change from 33keV to 1.253MeV.

Probing stochastic inter-galactic magnetic fields using blazar-induced gamma ray halo morphology

NASA Astrophysics Data System (ADS)

Duplessis, Francis; Vachaspati, Tanmay

2017-05-01

Inter-galactic magnetic fields can imprint their structure on the morphology of blazar-induced gamma ray halos. We show that the halo morphology arises through the interplay of the source's jet and a two-dimensional surface dictated by the magnetic field. Through extensive numerical simulations, we generate mock halos created by stochastic magnetic fields with and without helicity, and study the dependence of the halo features on the properties of the magnetic field. We propose a sharper version of the Q-statistics and demonstrate its sensitivity to the magnetic field strength, the coherence scale, and the handedness of the helicity. We also identify and explain a new feature of the Q-statistics that can further enhance its power.

Gamma-ray astronomy with a large muon detector in the ARGO-YBJ experiment

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

Di Sciascio, G.; Di Girolamo, T.; Megna, R.

2005-02-21

The ARGO-YBJ experiment, currently under construction at the YangBaJing Laboratory (Tibet, P.R. China, 4300 m a.s.l.), could be upgraded with a large ({approx} 2500 m2) muon detector both to extend the sensitivity to {gamma}-ray sources to energies greater than {approx} 20 TeV and to perform a cosmic ray primary composition study. In this paper we present an evaluation of the rejection power for proton-induced showers achievable with the upgraded ARGO-YBJ detector. Minimum detectable {gamma}-ray fluxes are calculated for different experimental setups.

Possible Detection of Gamma Ray Air Showers in Coincidence with BATSE Gamma Ray Bursts

NASA Astrophysics Data System (ADS)

Lin, Tzu-Fen

1999-08-01

Project GRAND presents the results of a search for coincident high-energy gamma ray events in the direction and at the time of nine Gamma Ray Bursts (GRBs) detected by BATSE. A gamma ray has a non-negligible hadron production cross section; for each gamma ray of energy of 100 GeV, there are 0.015 muons which reach detection level (Fasso & Poirier, 1999). These muons are identified and their angles are measured in stations of eight planes of proportional wire chambers (PWCs). A 50 mm steel plate above the bottom pair of planes is used to distinguish muons from electrons. The mean angular resolution is 0.26o over a ± 61o range in the XZ and YZ planes. The BATSE GRB catalogue is examined for bursts which are near zenith for Project GRAND. The geometrical acceptance is calculated for each of these events. The product is then taken of the GRB flux and GRANDÕs geometrical acceptance. The nine sources with the best combination of detection efficiency and BATSEÕs intensity are selected to be examined in the data. The most significant detection of these nine sources is at a statistical significance of +3.7s; this is also the GRB with the highest product of GRB flux and geometrical acceptance.

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

Solar Gamma Rays Above 8 MeV

NASA Technical Reports Server (NTRS)

Crannell, C. J.; Crannell, H.; Ramaty, R.

1978-01-01

Processes which lead to the production of gamma rays with energy greater than 8 MeV in solar flares are reviewed and evaluated. Excited states produced by inelastic scattering, charge exchange, and spallation reactions in the abundant nuclear species are considered in order to identify nuclear lines which may contribute to the Gamma ray spectrum of solar flares. The flux of 15.11 MeV Gamma rays relative to the flux of 4.44 MeV Gamma rays from the de-excitation of the corresponding states in C12 is calculated for a number of assumed distributions of exciting particles. This flux ratio is a sensitive diagnostic of accelerated particle spectra. Other high energy nuclear levels are not so isolated as the 15.11 MeV state and are not expected to be so strong. The spectrum of Gamma rays from the decay of Pi dey is sensitive to the energy distribution of particles accelerated to energies greater than 100 MeV.

Telescope for x ray and gamma ray studies in astrophysics

NASA Technical Reports Server (NTRS)

Weaver, W. D.; Desai, Upendra D.

1993-01-01

Imaging of x-rays has been achieved by various methods in astrophysics, nuclear physics, medicine, and material science. A new method for imaging x-ray and gamma-ray sources avoids the limitations of previously used imaging devices. Images are formed in optical wavelengths by using mirrors or lenses to reflect and refract the incoming photons. High energy x-ray and gamma-ray photons cannot be reflected except at grazing angles and pass through lenses without being refracted. Therefore, different methods must be used to image x-ray and gamma-ray sources. Techniques using total absorption, or shadow casting, can provide images in x-rays and gamma-rays. This new method uses a coder made of a pair of Fresnel zone plates and a detector consisting of a matrix of CsI scintillators and photodiodes. The Fresnel zone plates produce Moire patterns when illuminated by an off-axis source. These Moire patterns are deconvolved using a stepped sine wave fitting or an inverse Fourier transform. This type of coder provides the capability of an instantaneous image with sub-arcminute resolution while using a detector with only a coarse position-sensitivity. A matrix of the CsI/photodiode detector elements provides the necessary coarse position-sensitivity. The CsI/photodiode detector also allows good energy resolution. This imaging system provides advantages over previously used imaging devices in both performance and efficiency.

Early optical polarization of a gamma-ray burst afterglow.

PubMed

Mundell, Carole G; Steele, Iain A; Smith, Robert J; Kobayashi, Shiho; Melandri, Andrea; Guidorzi, Cristiano; Gomboc, Andreja; Mottram, Chris J; Clarke, David; Monfardini, Alessandro; Carter, David; Bersier, David

2007-03-30

We report the optical polarization of a gamma-ray burst (GRB) afterglow, obtained 203 seconds after the initial burst of gamma-rays from GRB 060418, using a ring polarimeter on the robotic Liverpool Telescope. Our robust (2sigma) upper limit on the percentage of polarization, less than 8%, coincides with the fireball deceleration time at the onset of the afterglow. The combination of the rate of decay of the optical brightness and the low polarization at this critical time constrains standard models of GRB ejecta, ruling out the presence of a large-scale ordered magnetic field in the emitting region.

Boron analysis for neutron capture therapy using particle-induced gamma-ray emission.

PubMed

Nakai, Kei; Yamamoto, Yohei; Okamoto, Emiko; Yamamoto, Tetsuya; Yoshida, Fumiyo; Matsumura, Akira; Yamada, Naoto; Kitamura, Akane; Koka, Masashi; Satoh, Takahiro

2015-12-01

The neutron source of BNCT is currently changing from reactor to accelerator, but peripheral facilities such as a dose-planning system and blood boron analysis have still not been established. To evaluate the potential application of particle-induced gamma-ray emission (PIGE) for boron measurement in clinical boron neutron capture therapy, boronophenylalanine dissolved within a cell culture medium was measured using PIGE. PIGE detected 18 μgB/mL f-BPA in the culture medium, and all measurements of any given sample were taken within 20 min. Two hours of f-BPA exposure was required to create a boron distribution image. However, even though boron remained in the cells, the boron on the cell membrane could not be distinguished from the boron in the cytoplasm. Copyright © 2015 Elsevier Ltd. All rights reserved.

Fermi: The Gamma-Ray Large Area Space Telescope

NASA Technical Reports Server (NTRS)

McEnery, Julie

2014-01-01

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

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.

Gamma ray heating and neutrino cooling rates due to weak interaction processes on sd-shell nuclei in stellar cores

NASA Astrophysics Data System (ADS)

Fayaz, Muhammad; Nabi, Jameel-Un; Majid, Muhammad

2017-07-01

Gamma ray heating and neutrino cooling rates, due to weak interaction processes, on sd-shell nuclei in stellar core are calculated using the proton neutron quasiparticle random phase approximation theory. The recent extensive experimental mass compilation of Wang et al. (Chin. Phys. C 36:1603, 2012), other improved model input parameters including nuclear quadrupole deformation (Raman et al. in At. Data Nucl. Data Tables 78(1):1-128, 2001; Möller et al. in At. Data Nucl. Data Tables 109:1-204, 2016) and physical constants are taken into account in the current calculation. The purpose of this work is two fold, one is to improve the earlier calculation of weak rates performed by Nabi and Klapdor-Kleingrothaus (At. Data Nucl. Data Tables 71:149, 1999a) using the same theory. We further compare our results with previous calculations. The selected sd-shell nuclei, considered in this work, are of special interest for the evolution of O-Ne-Mg core in 8-10 M_{⊙} stars due to competitive gamma ray heating rates and cooling by URCA processes. The outcome of these competitions is to determine, whether the stars end up as a white dwarf (Nabi in Phys. Rev. C 78(4):045801, 2008b), an electron-capture supernova (Jones et al. in Astrophys. J. 772(2):150, 2013) or Fe core-collapse supernova (Suzuki et al. in Astrophys. J. 817(2):163, 2016). The selected sd-shell nuclei for calculation of associated weak-interaction rates include ^{20,23}O, ^{20,23}F, ^{20,23,24}Ne, {}^{20,23-25}Na, and {}^{23-25}Mg. The cooling and heating rates are calculated for density range (10 ≤ ρ (g cm^{-3}) ≤ 10^{11}) and temperature range (0.01× 109≤ T(K)≤ 30× 109). The calculated gamma heating rates are orders of magnitude bigger than the shell model rates (except for ^{25}Mg at low densities). At high temperatures the gamma heating rates are in reasonable agreement. The calculated cooling rates are up to an order of magnitude bigger for odd-A nuclei.

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

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

Ludewigt, Bernhard; Mozin, Vladimir; Campbell, Luke

2015-06-01

High-­energy, beta-delayed gamma-­ray spectroscopy is a potential, non-­destructive assay techniques for the independent verification of declared quantities of special nuclear materials at key stages of the fuel cycle and for directly assaying nuclear material inventories for spent fuel handling, interim storage, reprocessing facilities, repository sites, and final disposal. Other potential applications include determination of MOX fuel composition, characterization of nuclear waste packages, and challenges in homeland security and arms control verification. Experimental measurements were performed to evaluate fission fragment yields, to test methods for determining isotopic fractions, and to benchmark the modeling code package. Experimental measurement campaigns were carried outmore » at the IAC using a photo-­neutron source and at OSU using a thermal neutron beam from the TRIGA reactor to characterize the emission of high-­energy delayed gamma rays from 235U, 239Pu, and 241Pu targets following neutron induced fission. Data were collected for pure and combined targets for several irradiation/spectroscopy cycle times ranging from 10/10 seconds to 15/30 minutes.The delayed gamma-ray signature of 241Pu, a significant fissile constituent in spent fuel, was measured and compared to 239Pu. The 241Pu/ 239Pu ratios varied between 0.5 and 1.2 for ten prominent lines in the 2700-­3600 keV energy range. Such significant differences in relative peak intensities make it possible to determine relative fractions of these isotopes in a mixed sample. A method for determining fission product yields by fitting the energy and time dependence of the delayed gamma-­ray emission was developed and demonstrated on a limited 235U data set. De-­convolution methods for determining fissile fractions were developed and tested on the experimental data. The use of high count-­rate LaBr 3 detectors was investigated as a potential alternative to HPGe detectors. Modeling capabilities

An Overview of the XGAM Code and Related Software for Gamma-ray Analysis

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

Younes, W.

2014-11-13

The XGAM spectrum-fitting code and associated software were developed specifically to analyze the complex gamma-ray spectra that can result from neutron-induced reactions. The XGAM code is designed to fit a spectrum over the entire available gamma-ray energy range as a single entity, in contrast to the more traditional piecewise approaches. This global-fit philosophy enforces background continuity as well as consistency between local and global behavior throughout the spectrum, and in a natural way. This report presents XGAM and the suite of programs built around it with an emphasis on how they fit into an overall analysis methodology for complex gamma-raymore » data. An application to the analysis of time-dependent delayed gamma-ray yields from 235U fission is shown in order to showcase the codes and how they interact.« less

Binary millisecond pulsar discovery via gamma-ray pulsations.

PubMed

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

2012-12-07

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

Gamma-ray luminosity and photon index evolution of FSRQ blazars and contribution to the gamma-ray background

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

Singal, J.; Ko, A.; Petrosian, V., E-mail: jsingal@richmond.edu

We present the redshift evolutions and distributions of the gamma-ray luminosity and photon spectral index of flat spectrum radio quasar (FSRQ) type blazars, using non-parametric methods to obtain the evolutions and distributions directly from the data. The sample we use for analysis consists of almost all FSRQs observed with a greater than approximately 7σ detection threshold in the first-year catalog of the Fermi Gamma-ray Space Telescope's Large Area Telescope, with redshifts as determined from optical spectroscopy by Shaw et al. We find that FSQRs undergo rapid gamma-ray luminosity evolution, but negligible photon index evolution, with redshift. With these evolutions accountedmore » for we determine the density evolution and luminosity function of FSRQs and calculate their total contribution to the extragalactic gamma-ray background radiation, resolved and unresolved, which is found to be 16(+10/–4)%, in agreement with previous studies.« less

The Goddard program of gamma ray transient astronomy

NASA Technical Reports Server (NTRS)

Cline, T. L.; Desai, U. D.; Teegarden, B. J.

1980-01-01

Gamma ray burst studies are reviewed. The past results, present status and future expectations are outlined regarding endeavors using experiments on balloons, IMP-6 and -7, OGO-3, ISEE-1 and -3, Helios-2, Solar Maximum Mission, the Einstein Observatory, Solar Polar and the Gamma Ray Observatory, and with the interplanetary gamma ray burst networks, to which some of these spacecraft sensors contribute. Additional emphasis is given to the recent discovery of a new type of gamma ray transient, detected on 1979 March 5.

The BATSE experiment on the Gamma Ray Observatory: Solar flare hard x ray and gamma-ray capabilities

NASA Technical Reports Server (NTRS)

Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Parnell, T. A.; Paciesas, W. S.; Pendleton, G. N.; Hudson, H. S.; Matteson, J. L.; Peterson, L. E.; Cline, T. L.

1989-01-01

The Burst and Transient Source Experiment (BATSE) for the Gamma Ray Observatory (GRO) consists of eight detector modules that provide full-sky coverage for gamma-ray bursts and other transient phenomena such as solar flares. Each detector module has a thin, large-area scintillation detector (2025 sq cm) for high time-resolution studies, and a thicker spectroscopy detector (125 sq cm) to extend the energy range and provide better spectral resolution. The total energy range of the system is 15 keV to 100 MeV. These 16 detectors and the associated onboard data system should provide unprecedented capabilities for observing rapid spectral changes and gamma-ray lines from solar flares. The presence of a solar flare can be detected in real-time by BATSE; a trigger signal is sent to two other experiments on the GRO. The launch of the GRO is scheduled for June 1990, so that BATSE can be an important component of the Max '91 campaign.

Calculations of the skyshine gamma-ray dose rates from independent spent fuel storage installations (ISFSI) under worst case accident conditions

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

Pace, J.V. III; Cramer, S.N.; Knight, J.R.

1980-09-01

Calculations of the skyshine gamma-ray dose rates from three spent fuel storage pools under worst case accident conditions have been made using the discrete ordinates code DOT-IV and the Monte Carlo code MORSE and have been compared to those of two previous methods. The DNA 37N-21G group cross-section library was utilized in the calculations, together with the Claiborne-Trubey gamma-ray dose factors taken from the same library. Plots of all results are presented. It was found that the dose was a strong function of the iron thickness over the fuel assemblies, the initial angular distribution of the emitted radiation, and themore » photon source near the top of the assemblies. 16 refs., 11 figs., 7 tabs.« less

Prediction of cellular radiosensitivity from DNA damage induced by gamma-rays and carbon ion irradiation in canine tumor cells.

PubMed

Wada, Seiichi; Van Khoa, Tran; Kobayashi, Yasuhiko; Funayama, Tomoo; Ogihara, Kikumi; Ueno, Shunji; Ito, Nobuhiko

2005-11-01

Diseases of companion animals are shifting from infectious diseases to neoplasms (cancer), and since radiation therapy is one of the effective choices available for cancer treatment, the application of radiotherapy in veterinary medicine is likely to increase. However tumor tissues have different radiosensitivities, and therefore it is important to determine the intrinsic radiosensitivity of tumors in individual patients in advance of radiotherapy. We have studied the relationship between the surviving cell fraction measured by a clonogenic assay and DNA double strand breaks detected by a comet assay under neutral conditions in three canine tumor cell lines, after gamma-ray and carbon ion irradiation. In all the cell lines, cell death assessed by the clonogenic assay was much higher following irradiation with carbon ions than with gamma-rays. The initial and residual (4 hr) DNA damage due to gamma-ray and carbon ion irradiation were higher in a radiosensitive cell line than in a radioresistant cell line. The surviving cell fraction at 2 Gy (SF2) showed a tendency for correlation with both the initial and residual DNA damage. In particular, the residual damage per Gy was significantly correlated with SF2, regardless of the type of radiation. This indicates that cellular radiosensitivity can be predicted by detection of radiation-induced residual DNA damage.

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.

Bright x-ray flares in gamma-ray burst afterglows.

PubMed

Burrows, D N; Romano, P; Falcone, A; Kobayashi, S; Zhang, B; Moretti, A; O'brien, P T; Goad, M R; Campana, S; Page, K L; Angelini, L; Barthelmy, S; Beardmore, A P; Capalbi, M; Chincarini, G; Cummings, J; Cusumano, G; Fox, D; Giommi, P; Hill, J E; Kennea, J A; Krimm, H; Mangano, V; Marshall, F; Mészáros, P; Morris, D C; Nousek, J A; Osborne, J P; Pagani, C; Perri, M; Tagliaferri, G; Wells, A A; Woosley, S; Gehrels, N

2005-09-16

Gamma-ray burst (GRB) afterglows have provided important clues to the nature of these massive explosive events, providing direct information on the nearby environment and indirect information on the central engine that powers the burst. We report the discovery of two bright x-ray flares in GRB afterglows, including a giant flare comparable in total energy to the burst itself, each peaking minutes after the burst. These strong, rapid x-ray flares imply that the central engines of the bursts have long periods of activity, with strong internal shocks continuing for hundreds of seconds after the gamma-ray emission has ended.

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

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

PubMed

Coburn, Wayne; Boggs, Steven E

2003-05-22

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

Structural and optical effects induced by gamma irradiation on NdPO{sub 4}: X-ray diffraction, spectroscopic and luminescence study

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

Sadhasivam, S.; Rajesh, N.P., E-mail: rajeshnp@hotmail.com

2016-02-15

Highlights: • Inorganic NdPO{sub 4} crystal was grown first time using potassium polyphosphate (K{sub 6}P{sub 4}O{sub 13}) flux. • NdPO{sub 4} crystal is insoluble in water, non-hygroscopic and high radiation resistance favoring for actinides host. • Actinide immobilization can be made at 1273 K. • High yield of 1061 nm photon emission. - Abstract: Rare earth orthophosphate (NdPO{sub 4}) monazite single crystals were grown using high temperature flux growth method employing K{sub 6}P{sub 4}O{sub 13} (K{sub 6}) as molten solvent. Their structural parameters were studied using single crystal X-ray diffraction (XRD) method. The grown crystals were examined by SEM andmore » EDX techniques for their homogeniousity and inclusion in the crystals. The influence of gamma irradiation in structural and optical absorption properties were studied by the powder XRD, FTIR and reflectance spectroscopy. The effect of gamma irradiation on luminescence properties was recorded. No significant structural change is observed up to 150 kGy gamma dose. The gamma ray induced charge trap in the crystal was saturated to 40 kGy dose. The luminescence intensity decreases with an increase in the irradiation. The emission of luminescence intensity stabilizes above 40 kGy gamma dose.« less

Sizing up the population of gamma-ray binaries

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

CVD-diamond-based position sensitive photoconductive detector for high-flux x-rays and gamma rays.

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

Shu, D.

1999-04-19

A position-sensitive photoconductive detector (PSPCD) using insulating-type CVD diamond as its substrate material has been developed at the Advanced Photon Source (APS). Several different configurations, including a quadrant pattern for a x-ray-transmitting beam position monitor (TBPM) and 1-D and 2-D arrays for PSPCD beam profilers, have been developed. Tests on different PSPCD devices with high-heat-flux undulator white x-ray beam, as well as with gamma-ray beams from {sup 60}Co sources have been done at the APS and National Institute of Standards and Technology (NIST). It was proven that the insulating-type CVD diamond can be used to make a hard x-ray andmore » gamma-ray position-sensitive detector that acts as a solid-state ion chamber. These detectors are based on the photoconductivity principle. A total of eleven of these TBPMs have been installed on the APS front ends for commissioning use. The linear array PSPCD beam profiler has been routinely used for direct measurements of the undulator white beam profile. More tests with hard x-rays and gamma rays are planned for the CVD-diamond 2-D imaging PSPCD. Potential applications include a high-dose-rate beam profiler for fourth-generation synchrotrons radiation facilities, such as free-electron lasers.« less

Analysis of Data from the Energetic Gamma-Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory

NASA Technical Reports Server (NTRS)

Kniffen, Donald A.; Elliott, William W.

1999-01-01

The final report consists of summaries of work proposed, work accomplished, papers and presentations published and continuing work regarding the cooperative agreement. The work under the agreement is based on high energy gamma ray source data analysis collected from the Energetic Gamma-Ray Experiment Telescope (EGRET).

Modeling Photodisintegration-induced TeV Photon Emission from Low-luminosity Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

Liu, Xue-Wen; Wu, Xue-Feng; Lu, Tan

2012-05-01

Ultra-high-energy cosmic-ray heavy nuclei have recently been considered as originating from nearby low-luminosity gamma-ray bursts that are associated with Type Ibc supernovae. Unlike the power-law decay in long duration gamma-ray bursts, the light curve of these bursts exhibits complex UV/optical behavior: shock breakout dominated thermal radiation peaks at about 1 day, and, after that, nearly constant emission sustained by radioactive materials for tens of days. We show that the highly boosted heavy nuclei at PeV energy interacting with the UV/optical photon field will produce considerable TeV photons via the photodisintegration/photo-de-excitation process. It was later predicted that a thermal-like γ-ray spectrum peaks at about a few TeV, which may serve as evidence of nucleus acceleration. The future observations by the space telescope Fermi and by the ground atmospheric Cherenkov telescopes such as H.E.S.S., VERITAS, and MAGIC will shed light on this prediction.

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.

Prompt optical emission from gamma-ray bursts

NASA Astrophysics Data System (ADS)

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

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

IR observations in gamma-ray blazars

NASA Technical Reports Server (NTRS)

Mahoney, W. A.; Gautier, T. N.; Ressler, M. E.; Wallyn, P.; Durouchoux, P.; Higdon, J. C.

1997-01-01

The infrared photometric and spectral observation of five gamma ray blazars in coordination with the energetic gamma ray experiment telescope (EGRET) onboard the Compton Gamma Ray Observatory is reported. The infrared measurements were made with a Cassegrain infrared camera and the mid-infrared large well imager at the Mt. Palomar 5 m telescope. The emphasis is on the three blazars observed simultaneously by EGRET and the ground-based telescope during viewing period 519. In addition to the acquisition of broadband spectral measurements for direct correlation with the 100 MeV EGRET observations, near infrared images were obtained, enabling a search for intra-day variability to be carried out.

Search for gamma-ray transients using the SMM spectrometer

NASA Technical Reports Server (NTRS)

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

1993-01-01

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

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

NASA Technical Reports Server (NTRS)

Forrest, D. J.

1978-01-01

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

In vivo gamma-rays induced initial DNA damage and the effect of famotidine in mouse leukocytes as assayed by the alkaline comet assay.

PubMed

Mozdarani, Hossein; Nasirian, Borzo; Haeri, S Abolghasem

2007-03-01

Ionizing radiation induces a variety of lesions in DNA, each of which can be used as a bio-indicator for biological dosimetry or the study of the radioprotective effects of substances. To assess gamma ray-induced DNA damage in vivo in mouse leukocytes at various doses and the effect of famotidine, blood was collected from Balb/c male mice after irradiation with 4 Gy gamma-rays at different time intervals post-irradiation. To assess the response, mice were irradiated with doses of gamma-rays at 1 to 4 Grays. Famotidine was injected intra-peritoneally (i.p) at a dose of 5 mg/kg at various time intervals before irradiation. Four slides were prepared from each sample and alkaline comet assay was performed using standard protocols. Results obtained show that radiation significantly increases DNA damage in leukocytes in a dose dependent manner (p < 0.01) when using appropriate sampling time after irradiation, because increasing sampling time after irradiation resulted in a time dependent disappearance of DNA damage. Treatment with only 5 mg/kg famotidine before 4 Gy irradiation led to almost 50% reduction in DNA damage when compared with those animals which received radiation alone. The radioprotective capability of famotidine might be attributed to radical scavenging properties and an anti-oxidation mechanism.

LUMINOSITY EVOLUTION OF GAMMA-RAY PULSARS

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

Hirotani, Kouichi, E-mail: hirotani@tiara.sinica.edu.tw

2013-04-01

We investigate the electrodynamic structure of a pulsar outer-magnetospheric particle accelerator and the resulting gamma-ray emission. By considering the condition for the accelerator to be self-sustained, we derive how the trans-magnetic-field thickness of the accelerator evolves with the pulsar age. It is found that the thickness is small but increases steadily if the neutron-star envelope is contaminated by sufficient light elements. For such a light element envelope, the gamma-ray luminosity of the accelerator is kept approximately constant as a function of age in the initial 10,000 yr, forming the lower bound of the observed distribution of the gamma-ray luminosity ofmore » rotation-powered pulsars. If the envelope consists of only heavy elements, on the other hand, the thickness is greater, but it increases less rapidly than a light element envelope. For such a heavy element envelope, the gamma-ray luminosity decreases relatively rapidly, forming the upper bound of the observed distribution. The gamma-ray luminosity of a general pulsar resides between these two extreme cases, reflecting the envelope composition and the magnetic inclination angle with respect to the rotation axis. The cutoff energy of the primary curvature emission is regulated below several GeV even for young pulsars because the gap thickness, and hence the acceleration electric field, is suppressed by the polarization of the produced pairs.« less

Gamma-Ray Telescopes: 400 Years of Astronomical Telescopes

NASA Technical Reports Server (NTRS)

Gehrels, Neil; Cannizzo, John K.

2010-01-01

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

Probing stochastic inter-galactic magnetic fields using blazar-induced gamma ray halo morphology

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

Duplessis, Francis; Vachaspati, Tanmay, E-mail: fdupless@asu.edu, E-mail: tvachasp@asu.edu

Inter-galactic magnetic fields can imprint their structure on the morphology of blazar-induced gamma ray halos. We show that the halo morphology arises through the interplay of the source's jet and a two-dimensional surface dictated by the magnetic field. Through extensive numerical simulations, we generate mock halos created by stochastic magnetic fields with and without helicity, and study the dependence of the halo features on the properties of the magnetic field. We propose a sharper version of the Q-statistics and demonstrate its sensitivity to the magnetic field strength, the coherence scale, and the handedness of the helicity. We also identify andmore » explain a new feature of the Q-statistics that can further enhance its power.« less

Tycho's Star Shines in Gamma Rays

NASA Image and Video Library

2017-12-08

NASA image relase December 13, 2011 Gamma-rays detected by Fermi's LAT show that the remnant of Tycho's supernova shines in the highest-energy form of light. This portrait of the shattered star includes gamma rays (magenta), X-rays (yellow, green, and blue), infrared (red) and optical data. Credit: Gamma ray, NASA/DOE/Fermi LAT Collaboration; X-ray, NASA/CXC/SAO; Infrared, NASA/JPL-Caltech; Optical, MPIA, Calar Alto, O. Krause et al. and DSS To read more go to: www.nasa.gov/mission_pages/GLAST/news/tycho-star.html NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Analysis of high resolution satellite data for cosmic gamma ray bursts

NASA Technical Reports Server (NTRS)

Imhof, W. L.; Nakano, G. H.; Reagan, J. B.

1976-01-01

Cosmic gamma ray bursts detected a germanium spectrometer on the low altitude satellite 1972-076B were surveyed. Several bursts with durations ranging from approximately 0.032 to 15 seconds were found and are tabulated. The frequency of occurrence/intensity distribution of these events was compared with the S to the -3/2 power curve of confirmed events. The longer duration events fall above the S to the -3/2 power curve of confirmed events, suggesting they are perhaps not all true cosmic gamma-ray bursts. The narrow duration events fall closely on the S to the -3/2 power curve. The survey also revealed several counting rate spikes, with durations comparable to confirmed gamma-ray bursts, which were shown to be of magnetospheric origin. Confirmation that energetic electrons were responsible for these bursts was achieved from analysis of all data from the complete payload of gamma-ray and energetic particle detectors on board the satellite. The analyses also revealed that the narrowness of the spikes was primarily spatial rather than temporal in character.

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.

Gamma-Ray Bursts from Neutron Star Kicks

NASA Astrophysics Data System (ADS)

Huang, Y. F.; Dai, Z. G.; Lu, T.; Cheng, K. S.; Wu, X. F.

2003-09-01

The idea that gamma-ray bursts might be a phenomenon associated with neutron star kicks was first proposed by Dar & Plaga. Here we study this mechanism in more detail and point out that the neutron star should be a high-speed one (with proper motion larger than ~1000 km s-1). It is shown that the model agrees well with observations in many aspects, such as the energetics, the event rate, the collimation, the bimodal distribution of durations, the narrowly clustered intrinsic energy, and the association of gamma-ray bursts with supernovae and star-forming regions. We also discuss the implications of this model on the neutron star kick mechanism and suggest that the high kick speed was probably acquired as the result of the electromagnetic rocket effect of a millisecond magnetar with an off-centered magnetic dipole.

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

Sex-dependent Differences in Intestinal Tumorigenesis Induced in Apc1638N/+ Mice by Exposure to {gamma} Rays

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

Trani, Daniela; Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia; Maastricht Radiation Oncology

Purpose: The purpose of the present study was to assess the effect of 1 and 5 Gy radiation doses and to investigate the interplay of gender and radiation with regard to intestinal tumorigenesis in an adenomatous polyposis coli (APC) mutant mouse model. Methods and Materials: Apc1638N/+ female and male mice were exposed whole body to either 1 Gy or 5 Gy of {gamma} rays and euthanized when most of the treated mice became moribund. Small and large intestines were processed to determine tumor burden, distribution, and grade. Expression of proliferation marker Ki-67 and estrogen receptor (ER)-{alpha} were also assessed bymore » immunohistochemistry. Results: We observed that, with both 1 Gy and 5 Gy of {gamma} rays, females displayed reduced susceptibility to radiation-induced intestinal tumorigenesis compared with males. As for radiation effect on small intestinal tumor progression, although no substantial differences were found in the relative frequency and degree of dysplasia of adenomas in irradiated animals compared with controls, invasive carcinomas were found in 1-Gy- and 5-Gy-irradiated animals. Radiation exposure was also shown to induce an increase in protein levels of proliferation marker Ki-67 and sex-hormone receptor ER-{alpha} in both non tumor mucosa and intestinal tumors from irradiated male mice. Conclusions: We observed important sex-dependent differences in susceptibility to radiation-induced intestinal tumorigenesis in Apc1638N/+ mutants. Furthermore, our data provide evidence that exposure to radiation doses as low as 1 Gy can induce a significant increase in intestinal tumor multiplicity as well as enhance tumor progression in vivo.« less

The EGRET high energy gamma ray telescope

NASA Technical Reports Server (NTRS)

Hartman, R. C.; Bertsch, D. L.; Fichtel, C. E.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Kwok, P. W.; Lin, Y. C.; Mattox, J. R.; Mayer-Hasselwander, H. A.

1992-01-01

The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (GRO) is sensitive in the energy range from about 20 MeV to about 30,000 MeV. Electron-positron pair production by incident gamma photons is utilized as the detection mechanism. The pair production occurs in tantalum foils interleaved with the layers of a digital spark chamber system; the spark chamber records the tracks of the electron and positron, allowing the reconstruction of the arrival direction of the gamma ray. If there is no signal from the charged particle anticoincidence detector which surrounds the upper part of the detector, the spark chamber array is triggered by two hodoscopes of plastic scintillators. A time of flight requirement is included to reject events moving backward through the telescope. The energy of the gamma ray is primarily determined by absorption of the energies of the electron and positron in a 20 cm deep NaI(Tl) scintillator.

The EGRET high energy gamma ray telescope

NASA Astrophysics Data System (ADS)

Hartman, R. C.; Bertsch, D. L.; Fichtel, C. E.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Kwok, P. W.; Lin, Y. C.; Mattox, J. R.; Mayer-Hasselwander, H. A.; Michelson, P. F.; von Montigny, C.; Nolan, P. L.; Pinkau, K.; Rothermel, H.; Schneid, E.; Sommer, M.; Sreekumar, P.; Thompson, D. J.

1992-02-01

The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (GRO) is sensitive in the energy range from about 20 MeV to about 30,000 MeV. Electron-positron pair production by incident gamma photons is utilized as the detection mechanism. The pair production occurs in tantalum foils interleaved with the layers of a digital spark chamber system; the spark chamber records the tracks of the electron and positron, allowing the reconstruction of the arrival direction of the gamma ray. If there is no signal from the charged particle anticoincidence detector which surrounds the upper part of the detector, the spark chamber array is triggered by two hodoscopes of plastic scintillators. A time of flight requirement is included to reject events moving backward through the telescope. The energy of the gamma ray is primarily determined by absorption of the energies of the electron and positron in a 20 cm deep NaI(Tl) scintillator.

Prompt Optical Observations of Gamma-Ray Bursts

NASA Astrophysics Data System (ADS)

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

2000-03-01

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

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.

Distinguishing fissions of 232Th, 237Np and 238U with beta-delayed gamma rays

DOE PAGES

Iyengar, A.; Norman, E. B.; Howard, C.; ...

2013-04-08

Measurements of beta-delayed gamma-ray spectra following 14-MeV neutron-induced fissions of 232Th, 238U, and 237Np were conducted at Lawrence Berkeley National Laboratory’s 88-Inch Cyclotron. Spectra were collected for times ranging from 1 minute to 14 hours after irradiation. Lastly, intensity ratios of gamma-ray lines were extracted from the data that allow identification of the fissioning isotope.

Search for TeV gamma ray emission from the Andromeda galaxy

NASA Astrophysics Data System (ADS)

Aharonian, F. A.; Akhperjanian, A. G.; Beilicke, M.; Bernlöhr, K.; Bojahr, H.; Bolz, O.; Börst, H.; Coarasa, T.; Contreras, J. L.; Cortina, J.; Denninghoff, S.; Fonseca, V.; Girma, M.; Götting, N.; Heinzelmann, G.; Hermann, G.; Heusler, A.; Hofmann, W.; Horns, D.; Jung, I.; Kankanyan, R.; Kestel, M.; Kettler, J.; Kohnle, A.; Konopelko, A.; Kornmeyer, H.; Kranich, D.; Krawczynski, H.; Lampeitl, H.; Lopez, M.; Lorenz, E.; Lucarelli, F.; Mang, O.; Meyer, H.; Mirzoyan, R.; Moralejo, A.; Ona, E.; Panter, M.; Plyasheshnikov, A.; Pühlhofer, G.; Rauterberg, G.; Reyes, R.; Rhode, W.; Ripken, J.; Röhring, A.; Rowell, G. P.; Sahakian, V.; Samorski, M.; Schilling, M.; Siems, M.; Sobzynska, D.; Stamm, W.; Tluczykont, M.; Völk, H. J.; Wiedner, C. A.; Wittek, W.

2003-03-01

Using the HEGRA system of imaging atmospheric Cherenkov telescopes, the Andromeda galaxy (M 31) was surveyed for TeV gamma ray emission. Given the large field of view of the HEGRA telescopes, three pointings were sufficient to cover all of M 31, including also M 32 and NGC 205. No indications for point sources of TeV gamma rays were found. Upper limits are given at a level of a few percent of the Crab flux. A specific search for monoenergetic gamma-ray lines from annihilation of supersymmetric dark matter particles accumulating near the center of M 31 resulted in flux limits in the 10-13 cm-2 s-1 range, well above the predicted MSSM flux levels except for models with pronounced dark-matter spikes or strongly enhanced annihilation rates.

A cosmic and solar X-ray and gamma-ray instrument for a scout launch

NASA Technical Reports Server (NTRS)

Forrest, D. J.; Vestrand, W. T.; Chupp, E. L.

1988-01-01

An overview is presented for a set of simple and robust X-ray and gamma ray instruments which have both cosmic and solar objectives. The primary solar scientific objective is the study of the beaming of energetic electrons and ions in solar flares. The instrument will measure spectra and polarization of flare emissions up to 10 MeV. At X-ray energies both the directly emitted flux and the reflected albedo flux will be measured with a complement of six X-ray sensors. Each of these detectors will have a different high Z filter selected to optimize both the energy resolution and high rate capabilities in the energy band 10 to 300 keV. At energies greater than 100 keV seven 7.6 x 7.6 cm NaI and a set of 30 concentric plastic scattering detectors will record the spectra and polarization of electron bremsstrahlung and nuclear gamma rays. All of the components of the instrument are in existence and have passed flight tests for earlier space missions. The instrument will use a spinning solar oriented Scout spacecraft. The NaI detectors will act as a self-modulating gamma ray detector for cosmic sources in a broad angular band which lies at 90 degrees to the Sun-Earth vector and hence will scan the entire sky in 6 months.

mBAND analysis of chromosome aberrations in lymphocytes exposed in vitro to alpha-particles and gamma-rays.

PubMed

Tawn, E Janet; Janet, E; Whitehouse, Caroline A; Holdsworth, Duncan; De Ruyck, Kim; Vandenbulcke, Katia; Thierens, Hubert

2008-06-01

To investigate the profiles of chromosome damage induced in vitro by exposure to alpha-particles and gamma-rays. Human peripheral blood lymphocytes were exposed to three dose regimes: alpha-particle doses of 0.2 and 0.5 Gy and a gamma-ray dose of 1.5 Gy. After culturing for 47 hours, chromosome aberrations involving the number 5 chromosomes were identified using a multi-coloured banding (mBAND) technique. Analysis of the frequencies of chromosome 5 breaks within aberrant cells and within aberrant number 5 chromosomes demonstrated that alpha-particle irradiation is more likely to result in multiple breaks in a chromosome than gamma-irradiation. Additionally, overdispersion was observed for all doses for the distribution of breaks amongst all cells analysed and breaks amongst total number 5 chromosomes, with this being greatest for the 0.2 Gy alpha-particle dose. The ratio of interchanges to intrachanges (F ratio) was 1.4 and 2.4 for 0.2 and 0.5 Gy alpha-particles respectively and 5.5 for 1.5 Gy gamma-rays. Evaluation of simple versus complex exchanges indicated ratios of 1.9 and 2.7 for 0.2 and 0.5 Gy alpha-particles respectively and 10.6 for 1.5 Gy gamma-rays. The majority of the intrachanges involving chromosomes 5 induced by alpha-particle radiation were associated with more complex exchanges. This study has confirmed that exchanges induced by exposure to high linear energy transfer (LET) alpha-particle radiation comprise a greater proportion of intrachanges than those induced by exposure to low LET gamma-rays. However, since the majority of these are associated with complex rearrangements and likely to be non-transmissible, this limits their applicability as a marker of past in vivo exposure.

Solar X-Ray and Gamma-Ray Imaging Spectroscopy

NASA Astrophysics Data System (ADS)

Dennis, B. R.; Christe, S. D.; Shih, A. Y.; Holman, G. D.; Emslie, A. G.; Caspi, A.

2018-02-01

X-ray and gamma-ray Sun observations from a lunar-based observatory would provide unique information on solar atmosphere thermal and nonthermal processes. EUV and energetic neutral atom imaging spectroscopy would augment the scientific value.

Gamma-ray detectors for breast imaging

NASA Astrophysics Data System (ADS)

Williams, Mark B.; Goode, Allen R.; Majewski, Stan; Steinbach, Daniela; Weisenberger, Andrew G.; Wojcik, Randolph F.; Farzanpay, Farzin

1997-07-01

Breast cancer is the most common cancer of American women and is the leading cause of cancer-related death among women aged 15 - 54; however recent years have shown that early detection using x-ray mammography can lead to a high probability of cure. However, because of mammography's low positive predictive value, surgical or core biopsy is typically required for diagnosis. In addition, the low radiographic contrast of many nonpalpable breast masses, particularly among women with radiographically dense breasts, results in an overall rate of 10% to 25% for missed tumors. Nuclear imaging of the breast using single gamma emitters (scintimammography) such as (superscript 99m)Tc, or positron emitters such as F-18- fluorodeoxyglucose (FDG) for positron emission tomography (PET), can provide information on functional or metabolic tumor activity that is complementary to the structural information of x-ray mammography, thereby potentially reducing the number of unnecessary biopsies and missed cancers. This paper summarizes recent data on the efficacy of scintimammography using conventional gamma cameras, and describes the development of dedicated detectors for gamma emission breast imaging. The detectors use new, high density crystal scintillators and large area position sensitive photomultiplier tubes (PSPMTs). Detector design, imaging requirements, and preliminary measured imaging performance are discussed.

Reactivation of Latent Epstein-Barr Virus; A Comparison After Gamma Rays and Proton Treatment

NASA Technical Reports Server (NTRS)

Mehta, Satish K.; Plante, Ianik; Bloom, David C.; Stowe, Raymond; Renner, Ashlie; Wu, Honglu; Crucian, Brian; Pierson, Duane L.

2017-01-01

Among different unique stressors astronauts are exposed to during spaceflight, cosmic radiation constitutes an important one that leads to various health effects. In particular, space radiation may contribute to decreased immunity, which has been observed in astronauts during short and long duration missions, as evidenced by several changes in cellular immunity and plasma cytokines levels. Reactivation of latent herpes viruses, either directly from radiation or resulting from perturbation in the immune system, is also observed in astronauts. While EBV is one of the eight human herpes viruses known to infect more than 90% human adults and stays latent for the life of the host without normally causing adverse effects of reactivation, increased reactivation in astronauts is well-documented, though the mechanism of this increase is not understood. In this work, we have studied the effect of two different types of radiations, Cs-137 gamma and 150-MeV proton on the reactivation rates of the Epstein - Barr virus (EBV) in vitro in EBV latent cell lines at doses of 0.1, 0.5, 1.0 and 2.0 Gy. While we find that both types of radiations reactivated latent EBV in vitro, we observe that at equivalent doses, early response is stronger for protons but with time, the reactivation induced by gamma rays is more persistent. These differences between the protons and gamma rays curves in latent virus reactivation challenge the common paradigm that protons and gamma rays have similar biological effects.

Gamma-Ray Imaging for Explosives Detection

NASA Technical Reports Server (NTRS)

deNolfo, G. A.; Hunter, S. D.; Barbier, L. M.; Link, J. T.; Son, S.; Floyd, S. R.; Guardala, N.; Skopec, M.; Stark, B.

2008-01-01

We describe a gamma-ray imaging camera (GIC) for active interrogation of explosives being developed by NASA/GSFC and NSWCICarderock. The GIC is based on the Three-dimensional Track Imager (3-DTI) technology developed at GSFC for gamma-ray astrophysics. The 3-DTI, a large volume time-projection chamber, provides accurate, approx.0.4 mm resolution, 3-D tracking of charged particles. The incident direction of gamma rays, E, > 6 MeV, are reconstructed from the momenta and energies of the electron-positron pair resulting from interactions in the 3-DTI volume. The optimization of the 3-DTI technology for this specific application and the performance of the GIC from laboratory tests is presented.

The Einstein@Home Gamma-ray Pulsar Survey. II. Source Selection, Spectral Analysis, and Multiwavelength Follow-up

NASA Astrophysics Data System (ADS)

Wu, J.; Clark, C. J.; Pletsch, H. J.; Guillemot, L.; Johnson, T. J.; Torne, P.; Champion, D. J.; Deneva, J.; Ray, P. S.; Salvetti, D.; Kramer, M.; Aulbert, C.; Beer, C.; Bhattacharyya, B.; Bock, O.; Camilo, F.; Cognard, I.; Cuéllar, A.; Eggenstein, H. B.; Fehrmann, H.; Ferrara, E. C.; Kerr, M.; Machenschalk, B.; Ransom, S. M.; Sanpa-Arsa, S.; Wood, K.

2018-02-01

We report on the analysis of 13 gamma-ray pulsars discovered in the Einstein@Home blind search survey using Fermi Large Area Telescope (LAT) Pass 8 data. The 13 new gamma-ray pulsars were discovered by searching 118 unassociated LAT sources from the third LAT source catalog (3FGL), selected using the Gaussian Mixture Model machine-learning algorithm on the basis of their gamma-ray emission properties being suggestive of pulsar magnetospheric emission. The new gamma-ray pulsars have pulse profiles and spectral properties similar to those of previously detected young gamma-ray pulsars. Follow-up radio observations have revealed faint radio pulsations from two of the newly discovered pulsars and enabled us to derive upper limits on the radio emission from the others, demonstrating that they are likely radio-quiet gamma-ray pulsars. We also present results from modeling the gamma-ray pulse profiles and radio profiles, if available, using different geometric emission models of pulsars. The high discovery rate of this survey, despite the increasing difficulty of blind pulsar searches in gamma rays, suggests that new systematic surveys such as presented in this article should be continued when new LAT source catalogs become available.

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

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

PubMed

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

2006-08-01

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

Galactic gamma-ray observations and galactic structure

NASA Technical Reports Server (NTRS)

Stecker, F. W.

1975-01-01

Recent observations of gamma-rays originating in the galactic disk together with radio observations, support an emerging picture of the overall structure of our galaxy with higher interstellar gas densities and star formation rates in a region which corresponds to that of the inner arms. The emerging picture is one where molecular clouds make up the dominant constituent of the interstellar gas in the inner galaxy and play a key role in accounting for the gamma-rays and phenomena associated with the production of young stars and other population 1 objects. In this picture, cosmic rays are associated with supernovae and are primarily of galactic origin. These newly observed phenomena can be understood as consequences of the density wave theories of spiral structure. Based on these new developments, the suggestion is made that a new galactic population class, Population O, be added to the standard Populations 1 and 2 in order to recognize important differences in dynamics and distribution between diffuse galactic H1 and interstellar molecular clouds.

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

NASA Astrophysics Data System (ADS)

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

2016-04-01

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

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.

Fermi GBM Observations of Terrestrial Gamma-Ray Flashes

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Briggs, M. S.; Connaughton, V.; Fishman, G. J.; Bhat, P. N.; Paciesas, W. S.; Preece, R.; Kippen, R. M.; vonKienlin, A.; Dwyer, J. R.;

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.

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.

Directional detector of gamma rays

DOEpatents

Cox, Samson A.; Levert, Francis E.

1979-01-01

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

Air shower detectors in gamma-ray astronomy

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

Sinnis, Gus

2008-01-01

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

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).

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

NASA Astrophysics Data System (ADS)

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

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

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.

The gamma-ray light curves of SN 1987A

NASA Technical Reports Server (NTRS)

Leising, Mark D.; Share, Gerald H.

1990-01-01

Observations of the SN 1987A ejecta in four Co-56-decay gamma-ray lines, obtained using the SMM gamma-ray spectrometer between February 1987 and May 1989, are reported and analyzed. The instrument characteristics and data-reduction procedures are described, and the results are presented in extensive tables and graphs and discussed with reference to theoretical models. Gamma-ray fluxes significantly above possible instrumental levels (as determined from analysis of pre-1987 data) were detected in the second half of 1987 and the first half of 1988. The data are found to favor a model with some Co-56 in regions of low gamma-ray optical depth by 200 d after the SN outburst over models with all Co-56 at one depth within a uniform expanding envelope. Also investigated are the gamma-ray contribution to the total bolometric luminosity and the escape (and potential observability) of Co-57 gamma rays.

Gamma-ray pulsars: Emission zones and viewing geometries

NASA Technical Reports Server (NTRS)

Romani, Roger W.; Yadigaroglu, I.-A.

1995-01-01

There are now a half-dozen young pulsars detected in high-energy photons by the Compton Gamma-Ray Observatory (CGRO), showing a variety of emission efficiencies and pulse profiles. We present here a calculation of the pattern of high-energy emission on the sky in a model which posits gamma-ray production by charge-depleted gaps in the outer magnetosphere. This model accounts for the radio to gamma-ray pulse offsets of the known pulsars, as well as the shape of the high-energy pulse profiles. We also show that about one-third of emitting young radio pulsars will not be detected due to beaming effects, while approximately 2.5 times the number of radio-selected gamma-ray pulsars will be viewed only high energies. Finally we compute the polarization angle variation and find that the previously misunderstood optical polarization sweep of the Crab pulsar arises naturally in this picture. These results strongly support an outer magnetosphere location for the gamma-ray emission.

Gamma rays from hidden millisecond pulsars

NASA Technical Reports Server (NTRS)

Tavani, Marco

1992-01-01

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

Population Studies of Radio and Gamma-Ray Pulsars

NASA Technical Reports Server (NTRS)

Harding, Alice K; Gonthier, Peter; Coltisor, Stefan

2004-01-01

Rotation-powered pulsars are one of the most promising candidates for at least some of the 40-50 EGRET unidentified gamma-ray sources that lie near the Galactic plane. Since the end of the EGRO mission, the more sensitive Parkes Multibeam radio survey has detected mere than two dozen new radio pulsars in or near unidentified EGRET sources, many of which are young and energetic. These results raise an important question about the nature of radio quiescence in gamma-ray pulsars: is the non-detection of radio emission a matter of beaming or of sensitivity? The answer is very dependent on the geometry of the radio and gamma-ray beams. We present results of a population synthesis of pulsars in the Galaxy, including for the first time the full geometry of the radio and gamma-ray beams. We use a recent empirically derived model of the radio emission and luminosity, and a gamma-ray emission geometry and luminosity derived theoretically from pair cascades in the polar slot gap. The simulation includes characteristics of eight radio surveys of the Princeton catalog plus the Parkes MB survey. Our results indicate that EGRET was capable of detecting several dozen pulsars as point sources, with the ratio of radio-loud to radio-quiet gamma-ray pulsars increasing significantly to about ten to one when the Parkes Survey is included. Polar cap models thus predict that many of the unidentified EGRET sources could be radio-loud gamma- ray pulsars, previously undetected as radio pulsars due to distance, large dispersion and lack of sensitivity. If true, this would make gamma-ray telescopes a potentially more sensitive tool for detecting distant young neutron stars in the Galactic plane.

"Short, Hard Gamma-Ray Bursts - Mystery Solved?????"

NASA Technical Reports Server (NTRS)

Parsons, A.

2006-01-01

After over a decade of speculation about the nature of short-duration hard-spectrum gamma-ray bursts (GRBs), the recent detection of afterglow emission from a small number of short bursts has provided the first physical constraints on possible progenitor models. While the discovery of afterglow emission from long GRBs was a real breakthrough linking their origin to star forming galaxies, and hence the death of massive stars, the progenitors, energetics, and environments for short gamma-ray burst events remain elusive despite a few recent localizations. Thus far, the nature of the host galaxies measured indicates that short GRBs arise from an old (> 1 Gyr) stellar population, strengthening earlier suggestions and providing support for coalescing compact object binaries as the progenitors. On the other hand, some of the short burst afterglow observations cannot be easily explained in the coalescence scenario. These observations raise the possibility that short GRBs may have different or multiple progenitors systems. The study of the short-hard GRB afterglows has been made possible by the Swift Gamma-ray Burst Explorer, launched in November of 2004. Swift is equipped with a coded aperture gamma-ray telescope that can observe up to 2 steradians of the sky and can compute the position of a gamma-ray burst to within 2-3 arcmin in less than 10 seconds. The Swift spacecraft can slew on to this burst position without human intervention, allowing its on-board x ray and optical telescopes to study the afterglow within 2 minutes of the original GRB trigger. More Swift short burst detections and afterglow measurements are needed before we can declare that the mystery of short gamma-ray burst is solved.

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.

Fermi: The Gamma-Ray Large Area Telescope Mission Status

NASA Technical Reports Server (NTRS)

McEnery, Julie

2014-01-01

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

Swift Gamma-Ray Burst Explorer: Mission Design for Rapid, Accurate Location of Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Bundas, David J.

2004-01-01

The Swift Gamma-ray Burst Explorer is a NASA Mid-sized Explorer (MIDEX) with the primary mission of determining the origins of Gamma-Ray Bursts (GRBs). It will be the first mission to autonomously respond to newly-discovered GRBs and provide immediate follow-up with narrow field instruments capable of multi-wavelength (UV, Optical, X-ray) observations. The characteristics of GRBs that are the key mission design drivers, are their non-repeating and brief duration bursts of multi-wavelength photons. In addition, rapid notification of the location and characteristics of the GRBs to ground-and-space-based observatories drive the end-to-end data analysis and distribution requirements.

Swift Gamma-ray Burst Explorer: Mission Design for Rapid, Accurate Location of Gamma-ray Bursts

NASA Technical Reports Server (NTRS)

Bundas, David J.

2005-01-01

The Swift Gamma-ray Burst Explorer is a NASA Mid-sized Explorer (MIDEX) with the primary mission of determining the origins of Gamma-Ray Bursts (GRBs). It will be the first mission to autonomously respond to newly-discovered GRBs and provide immediate follow-up with narrow field instruments capable of multi-wavelength (UT, Optical, X-ray) observations. The characteristics of GRBs that are the key mission design drivers, are their non-repeating and brief duration bursts of multi-wavelength photons. In addition, rapid notification of the location and characteristics of the GRBs to ground-and-space-based observatories drive the end-to-end data analysis and distribution requirements.

Early and Late Chromosome Damages in Human Lymphocytes Induced by Gamma Rays and Fe Ions

NASA Technical Reports Server (NTRS)

Sunagawa, Mayumi; Zhang, Ye; Yeshitla, Samrawit; Kadhim, Munira; Wilson, Bobby; Wu, Honglu

2014-01-01

Chromosomal translocations and inversions are considered stable, and cells containing these types of chromosome aberrations can survive multiple cell divisions. An efficient method to detect an inversion is multi-color banding fluorescent in situ hybridization (mBAND) which allows identification of both inter- and intrachromosome aberrations simultaneously. Post irradiation, chromosome aberrations may also arise after multiple cell divisions as a result of genomic instability. To investigate the stable or late-arising chromosome aberrations induced after radiation exposure, we exposed human lymphocytes to gamma rays and Fe ions ex vivo, and cultured the cells for multiple generations. Chromosome aberrations were analyzed in cells collected at first mitosis and at several time intervals during the culture period post irradiation. With gamma irradiation, about half of the damages observed at first mitosis remained after 7 day- and 14 day- culture, suggesting the transmissibility of damages to the surviving progeny. Detailed analysis of chromosome break ends participating in exchanges revealed a greater fraction of break ends involved in intrachromosome aberrations in the 7- and 14-day samples in comparison to the fraction at first mitosis. In particular, simple inversions were found at 7 and 14 days, but not at the first mitosis, suggesting that some of the aberrations might be formed days post irradiation. In contrast, at the doses that produced similar frequencies of gamma-induced chromosome aberrations as observed at first mitosis, a significantly lower yield of aberrations remained at the same population doublings after Fe ion exposure. At these equitoxic doses, more complex type aberrations were observed for Fe ions, indicating that Fe ion-induced initial chromosome damages are more severe and may lead to cell death. Comparison between low and high doses of Fe ion irradiation in the induction of late damages will also be discussed.

Thermal neutron detector and gamma-ray spectrometer utilizing a single material

DOEpatents

Stowe, Ashley; Burger, Arnold; Lukosi, Eric

2017-05-02

A combined thermal neutron detector and gamma-ray spectrometer system, including: a detection medium including a lithium chalcopyrite crystal operable for detecting thermal neutrons in a semiconductor mode and gamma-rays in a scintillator mode; and a photodetector coupled to the detection medium also operable for detecting the gamma rays. Optionally, the detection medium includes a .sup.6LiInSe.sub.2 crystal. Optionally, the detection medium comprises a compound formed by the process of: melting a Group III element; adding a Group I element to the melted Group III element at a rate that allows the Group I and Group III elements to react thereby providing a single phase I-III compound; and adding a Group VI element to the single phase I-III compound and heating; wherein the Group I element includes lithium.

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.

AGIS -- the Advanced Gamma-ray Imaging System

NASA Astrophysics Data System (ADS)

Krennrich, Frank

2009-05-01

The Advanced Gamma-ray Imaging System, AGIS, is envisioned to become the follow-up mission of the current generation of very high energy gamma-ray telescopes, namely, H.E.S.S., MAGIC and VERITAS. These instruments have provided a glimpse of the TeV gamma-ray sky, showing more than 70 sources while their detailed studies constrain a wealth of physics and astrophysics. The particle acceleration, emission and absorption processes in these sources permit the study of extreme physical conditions found in galactic and extragalactic TeV sources. AGIS will dramatically improve the sensitivity and angular resolution of TeV gamma-ray observations and therefore provide unique prospects for particle physics, astrophysics and cosmology. This talk will provide an overview of the science drivers, scientific capabilities and the novel technical approaches that are pursued to maximize the performance of the large array concept of AGIS.

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.

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.

Binary Millisecond Pulsar Discovery via Gamma-Ray Pulsations

DOE PAGES

Pletsch, H. J.; Guillemot, L.; Fehrmann, H.; ...

2012-12-07

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

MAGIC gamma-ray telescopes hunting for neutrinos and their sources

NASA Astrophysics Data System (ADS)

Góra, D.; Bernardini, E.; Satalecka, K.; Noda, K.; Manganaro, M.; López, M.; MAGIC Collaboration

2017-09-01

The discovery of an astrophysical flux of high-energy neutrinos by the IceCube Collaboration marks a major breakthrough in the ongoing search for the origin of cosmic rays. Presumably, the neutrinos, together with gamma rays, result from pion decay, following hadronic interactions of protons accelerated in astrophysical objects to ultra-relativistic energies. So far, the neutrino sky map shows no significant indication of astrophysical sources. Here, we report first results from follow-up observations, of sky regions where IceCube has detected muon tracks from energetic neutrinos, using the MAGIC telescopes which are sensitive to gamma rays at TeV energies. Furthermore, we show that MAGIC has the potential to distinguish air showers induced by tau neutrinos from the background of hadronic showers in the PeV-EeV energy range, employing a novel analysis method to the data obtained with high-zenith angle observations.

Pathology of Serially Sacrificed Female B6C3F1 Mice Continuously Exposed to Very Low-Dose-Rate Gamma Rays.

PubMed

Tanaka, I B; Komura, J; Tanaka, S

2017-03-01

We have previously reported on life span shortening as well as increased incidence rates in several neoplasms in B6C3F1 mice that were continuously exposed to 21 mGy/day of gamma rays for 400 days. To clarify whether the life shortening was due to early appearance of neoplasms (shortened latency) or increased promotion/progression, 8-week-old female specific-pathogen-free B6C3F1 mice were gamma-ray irradiated at a low dose rate of 20 mGy/day for 400 days. At 100 days postirradiation, 60-90 mice were sacrificed, and thereafter every 100 days alongside the age-matched nonirradiated controls, for 700 days. Additional groups were allowed to live out their natural life span. Pathological examination was performed on all mice to identify lesions, non-neoplastic and neoplastic, as well as to determine the cause of death. Body weights were significantly increased in irradiated mice from sacrifice days 200-500. Incidence rates for spontaneously occurring non-neoplastic lesions, such as adrenal subcapsular cell hyperplasia, fatty degeneration of the liver, atrophy and tubulostromal hyperplasia of the ovaries, were significantly increased in irradiated mice. Significantly increased incidence rates with no shortening of latency periods were observed in irradiated mice for malignant lymphomas, hepatocellular adenomas/carcinomas, bronchioloalveolar adenomas, harderian gland adenoma/adenocarcinoma. Shortened latencies with significantly increased incidence rates were observed for adrenal subcapsular cell adenomas and ovarian neoplasms (tubulostromal adenoma, granulosa cell tumors) in irradiated mice. Life span shortening in mice exposed to 20 mGy/day was mostly due to malignant lymphomas. Multiple primary neoplasms were significantly increased in mice exposed to 20 mGy/day from sacrifice days 400-700 and in the life span group. Our results confirm that continuous low-dose-rate gamma-ray irradiation of female B6C3F1 mice causes both cancer induction (shortened latency) and

Cell cycle perturbations and genotoxic effects in human primary fibroblasts induced by low-energy protons and X/gamma-rays.

PubMed

Antoccia, Antonio; Sgura, Antonella; Berardinelli, Francesco; Cavinato, Maria; Cherubini, Roberto; Gerardi, Silvia; Tanzarella, Caterina

2009-09-01

The effect of graded doses of high-linear energy transfer (LET) low-energy protons to induce cycle perturbations and genotoxic damage was investigated in normal human fibroblasts. Furthermore, such effects were compared with those produced by low-LET radiations. HFFF2, human primary fibroblasts were exposed to either protons (LET = 28.5 keV/microm) or X/gamma-rays, and endpoints related to cell cycle kinetics and DNA damage analysed. Following both type of irradiations, unsynchronized cells suffered an inhibition to entry into S-phase for doses of 1-4 Gy and remained arrested in the G(1)-phase for several days. The levels of induction of regulator proteins, such as TP53 and CDKN1A showed a clear LET-dependence. DSB induction and repair as measured by scoring for gamma-H2AX foci indicated that protons, with respect to X-rays, yielded a lower number of DSBs per Gy, which showed a slower kinetics of disappearance. Such result was in agreement with the extent of MN induction in binucleated cells after X-irradiation. No significant differences between the two types of radiations were observed with the clonogenic assay, resulting anyway the slope of gamma-ray curve higher than that the proton one. In conclusion, in normal human primary fibroblasts cell cycle arrest at the G(1)/S transition can be triggered shortly after irradiation and maintained for several hours post-irradiation of both protons and X-rays. DNA damage produced by protons appears less amenable to be repaired and could be transformed in cytogenetic damage in the form of MN.

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.

SAS-2 gamma-ray observations of PSR 1747-46. [radio pulsar

NASA Technical Reports Server (NTRS)

Thompson, D. J.; Fichtel, C. E.; Kniffen, D. A.; Ogelman, H. B.; Lamb, R. C.

1976-01-01

Evidence is reported for the observation of gamma-ray emission from the radio pulsar PSR 1747-46 by the gamma-ray telescope aboard SAS 2. The evidence is based on the presence of both an approximately 3-sigma enhancement of gamma rays at the pulsar's location and an approximately 4-sigma peak in the phase plot of 79 gamma-ray events whose phase was calculated from the pulsar's known period. The gamma-ray pulsation is found to appear at a phase lag of about 0.16 from that predicted by the radio observations. The pulsed gamma-ray fluxes above 35 MeV and 100 MeV are estimated, and it is shown that the gamma-ray pulse width is similar to the radio pulse width. It is concluded that PSR 1747-46 is a most likely candidate for pulsed gamma-ray emission.

LFsGRB: Binary neutron star merger rate via the luminosity function of short gamma-ray bursts

NASA Astrophysics Data System (ADS)

Paul, Debdutta

2018-04-01

LFsGRB models the luminosity function (LF) of short Gamma Ray Bursts (sGRBs) by using the available catalog data of all short GRBs (sGRBs) detected till 2017 October, estimating the luminosities via pseudo-redshifts obtained from the Yonetoku correlation, and then assuming a standard delay distribution between the cosmic star formation rate and the production rate of their progenitors. The data are fit well both by exponential cutoff powerlaw and broken powerlaw models. Using the derived parameters of these models along with conservative values in the jet opening angles seen from afterglow observations, the true rate of short GRBs is derived. Assuming a short GRB is produced from each binary neutron star merger (BNSM), the rate of gravitational wave (GW) detections from these mergers are derived for the past, present and future configurations of the GW detector networks.

ASTRONOMY: Neighborhood Gamma Ray Burst Boosts Theory.

PubMed

Schilling, G

2000-07-07

Titanic explosions that emit powerful flashes of energetic gamma rays are one of astronomy's hottest mysteries. Now an analysis of the nearest gamma ray burst yet detected has added weight to the popular theory that they are expelled during the death throes of supermassive stars.

Gamma-Ray Background Variability in Mobile Detectors

NASA Astrophysics Data System (ADS)

Aucott, Timothy John

Gamma-ray background radiation significantly reduces detection sensitivity when searching for radioactive sources in the field, such as in wide-area searches for homeland security applications. Mobile detector systems in particular must contend with a variable background that is not necessarily known or even measurable a priori. This work will present measurements of the spatial and temporal variability of the background, with the goal of merging gamma-ray detection, spectroscopy, and imaging with contextual information--a "nuclear street view" of the ubiquitous background radiation. The gamma-ray background originates from a variety of sources, both natural and anthropogenic. The dominant sources in the field are the primordial isotopes potassium-40, uranium-238, and thorium-232, as well as their decay daughters. In addition to the natural background, many artificially-created isotopes are used for industrial or medical purposes, and contamination from fission products can be found in many environments. Regardless of origin, these backgrounds will reduce detection sensitivity by adding both statistical as well as systematic uncertainty. In particular, large detector arrays will be limited by the systematic uncertainty in the background and will suffer from a high rate of false alarms. The goal of this work is to provide a comprehensive characterization of the gamma-ray background and its variability in order to improve detection sensitivity and evaluate the performance of mobile detectors in the field. Large quantities of data are measured in order to study their performance at very low false alarm rates. Two different approaches, spectroscopy and imaging, are compared in a controlled study in the presence of this measured background. Furthermore, there is additional information that can be gained by correlating the gamma-ray data with contextual data streams (such as cameras and global positioning systems) in order to reduce the variability in the background

High energy gamma-ray observations of SN 1987A

NASA Technical Reports Server (NTRS)

Sood, R. K.; Thomas, J. A.; Waldron, L.; Manchanda, R. K.; Rochester, G. K.

1988-01-01

Results are presented from observations of SN 1987A made with a combined high energy gamma ray and hard X-ray payload carried on a balloon flight over Alice Springs, Australia on April 5, 1988. The payload instrumentation is described, emphasizing the characteristics of the gamma-ray detector. The gamma-ray emission profile is illustrated and the preliminary results of the observations are summarized.

Detecting Axionlike Particles with Gamma Ray Telescopes

NASA Astrophysics Data System (ADS)

Hooper, Dan; Serpico, Pasquale D.

2007-12-01

We propose that axionlike particles (ALPs) with a two-photon vertex, consistent with all astrophysical and laboratory bounds, may lead to a detectable signature in the spectra of high-energy gamma-ray sources. This occurs as a result of 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. The discovery of such an effect is possible by GLAST in the 1 100 GeV range and by ground-based gamma-ray telescopes in the TeV range.

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.

An Ordinary Gamma-Ray Burst with Extraordinary Consequences

NASA Image and Video Library

2017-10-18

On Aug. 17, the Gamma-ray Burst Monitor on NASA's Fermi Gamma-ray Space Telescope caught a short burst of gamma rays from the spectacular smashup of two neutron stars, setting off a chain of events that marks the first-ever detection of a cosmic event in gravitational waves and different kinds of light. NASA scientists Colleen Wilson-Hodge and Tyson Littenberg explain what happened and what it means for science and discovery.

Characterizing the source properties of terrestrial gamma ray flashes

NASA Astrophysics Data System (ADS)

Dwyer, Joseph R.; Liu, Ningyu; Eric Grove, J.; Rassoul, Hamid; Smith, David M.

2017-08-01

Monte Carlo simulations are used to determine source properties of terrestrial gamma ray flashes (TGFs) as a function of atmospheric column depth and beaming geometry. The total mass per unit area traversed by all the runaway electrons (i.e., the total grammage) during a TGF, Ξ, is introduced, defined to be the total distance traveled by all the runaway electrons along the electric field lines multiplied by the local air mass density along their paths. It is shown that key properties of TGFs may be directly calculated from Ξ and its time derivative, including the gamma ray emission rate, the current moment, and the optical power of the TGF. For the calculations presented in this paper, a standard TGF gamma ray fluence, F0 = 0.1 cm-2 above 100 keV for a spacecraft altitude of 500 km, and a standard total grammage, Ξ0 = 1018 g/cm2, are introduced, and results are presented in terms of these values. In particular, the current moments caused by the runaway electrons and their accompanying ionization are found for a standard TGF fluence, as a function of source altitude and beaming geometry, allowing a direct comparison between the gamma rays measured in low-Earth orbit and the VLF-LF radio frequency emissions recorded on the ground. Such comparisons should help test and constrain TGF models and help identify the roles of lightning leaders and streamers in the production of TGFs.

Fermi Bubbles: an elephant in the gamma-ray sky

NASA Astrophysics Data System (ADS)

Malyshev, Dmitry

2017-03-01

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

A fast forward algorithm for real-time geosteering of azimuthal gamma-ray logging.

PubMed

Qin, Zhen; Pan, Heping; Wang, Zhonghao; Wang, Bintao; Huang, Ke; Liu, Shaohua; Li, Gang; Amara Konaté, Ahmed; Fang, Sinan

2017-05-01

Geosteering is an effective method to increase the reservoir drilling rate in horizontal wells. Based on the features of an azimuthal gamma-ray logging tool and strata spatial location, a fast forward calculation method of azimuthal gamma-ray logging is deduced by using the natural gamma ray distribution equation in formation. The response characteristics of azimuthal gamma-ray logging while drilling in the layered formation models with different thickness and position are simulated and summarized by using the method. The result indicates that the method calculates quickly, and when the tool nears a boundary, the method can be used to identify the boundary and determine the distance from the logging tool to the boundary in time. Additionally, the formation parameters of the algorithm in the field can be determined after a simple method is proposed based on the information of an offset well. Therefore, the forward method can be used for geosteering in the field. A field example validates that the forward method can be used to determine the distance from the azimuthal gamma-ray logging tool to the boundary for geosteering in real-time. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

Prompt gamma-ray imaging for small animals

NASA Astrophysics Data System (ADS)

Xu, Libai

Small animal imaging is recognized as a powerful discovery tool for small animal modeling of human diseases, which is providing an important clue to complete understanding of disease mechanisms and is helping researchers develop and test new treatments. The current small animal imaging techniques include positron emission tomography (PET), single photon emission tomography (SPECT), computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US). A new imaging modality called prompt gamma-ray imaging (PGI) has been identified and investigated primarily by Monte Carlo simulation. Currently it is suggested for use on small animals. This new technique could greatly enhance and extend the present capabilities of PET and SPECT imaging from ingested radioisotopes to the imaging of selected non-radioactive elements, such as Gd, Cd, Hg, and B, and has the great potential to be used in Neutron Cancer Therapy to monitor neutron distribution and neutron-capture agent distribution. This approach consists of irradiating small animals in the thermal neutron beam of a nuclear reactor to produce prompt gamma rays from the elements in the sample by the radiative capture (n, gamma) reaction. These prompt gamma rays are emitted in energies that are characteristic of each element and they are also produced in characteristic coincident chains. After measuring these prompt gamma rays by surrounding spectrometry array, the distribution of each element of interest in the sample is reconstructed from the mapping of each detected signature gamma ray by either electronic collimations or mechanical collimations. In addition, the transmitted neutrons from the beam can be simultaneously used for very sensitive anatomical imaging, which provides the registration for the elemental distributions obtained from PGI. The primary approach is to use Monte Carlo simulation methods either with the specific purpose code CEARCPG, developed at NC State University or with the general purpose

Gamma-ray spectroscopy at MHz counting rates with a compact LaBr3 detector and silicon photomultipliers for fusion plasma applications.

PubMed

Nocente, M; Rigamonti, D; Perseo, V; Tardocchi, M; Boltruczyk, G; Broslawski, A; Cremona, A; Croci, G; Gosk, M; Kiptily, V; Korolczuk, S; Mazzocco, M; Muraro, A; Strano, E; Zychor, I; Gorini, G

2016-11-01

Gamma-ray spectroscopy measurements at MHz counting rates have been carried out, for the first time, with a compact spectrometer based on a LaBr 3 scintillator and silicon photomultipliers. The instrument, which is also insensitive to magnetic fields, has been developed in view of the upgrade of the gamma-ray camera diagnostic for α particle measurements in deuterium-tritium plasmas of the Joint European Torus. Spectra were measured up to 2.9 MHz with a projected energy resolution of 3%-4% in the 3-5 MeV range, of interest for fast ion physics studies in fusion plasmas. The results reported here pave the way to first time measurements of the confined α particle profile in high power plasmas of the next deuterium-tritium campaign at the Joint European Torus.

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

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

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

Zhang, Bin-Bin; Castro-Tirado, Alberto J.; Zhang, Bing, E-mail: zhang.grb@gmail.com

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

Electron trapping in rad-hard RCA IC's irradiated with electrons and gamma rays

NASA Technical Reports Server (NTRS)

Danchenko, V.; Brashears, S. S.; Fang, P. H.

1984-01-01

Enhanced electron trapping has been observed in n-channels of rad-hard CMOS devices due to electron and gamma-ray irradiation. Room-temperature annealing results in a positive shift in the threshold potential far beyond its initial value. The slope of the annealing curve immediately after irradiation was found to depend strongly on the gate bias applied during irradiation. Some dependence was also observed on the electron dose rate. No clear dependence on energy and shielding over a delidded device was observed. The threshold shift is probably due to electron trapping at the radiation-induced interface states and tunneling of electrons through the oxide-silicon energy barrier to fill the radiation-induced electron traps. A mathematical analysis, based on two parallel annealing kinetics, hole annealing and electron trapping, is applied to the data for various electron dose rates.

Predicting supernova associated to gamma-ray burst 130427a

NASA Astrophysics Data System (ADS)

Wang, Y.; Ruffini, R.; Kovacevic, M.; Bianco, C. L.; Enderli, M.; Muccino, M.; Penacchioni, A. V.; Pisani, G. B.; Rueda, J. A.

2015-07-01

Binary systems constituted by a neutron star and a massive star are not rare in the universe. The Induced Gravitational Gamma-ray Burst (IGC) paradigm interprets Gamma-ray bursts as the outcome of a neutron star that collapses into a black hole due to the accretion of the ejecta coming from its companion massive star that underwent a supernova event. GRB 130427A is one of the most luminous GRBs ever observed, of which isotropic energy exceeds 1054 erg. And it is within one of the few GRBs obtained optical, X-ray and GeV spectra simultaneously for hundreds of seconds, which provides an unique opportunity so far to understand the multi-wavelength observation within the IGC paradigm, our data analysis found low Lorentz factor blackbody emission in the Episode 3 and its X-ray light curve overlaps typical IGC Golden Sample, which comply to the IGC mechanisms. We consider these findings as clues of GRB 130427A belonging to the IGC GRBs. We predicted on GCN the emergence of a supernova on May 2, 2013, which was later successfully detected on May 13, 2013.

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....

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.

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.

Method for efficient, narrow-bandwidth, laser compton x-ray and gamma-ray sources

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

Barty, Christopher P. J.

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

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

NASA Astrophysics Data System (ADS)

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

2018-05-01

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

Gamma ray irradiated silicon nanowires: An effective model to investigate defects at the interface of Si/SiOx

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

Yin, Kui; Zhao, Yi; Liu, Liangbin

2014-01-20

The effect of gamma ray irradiation on silicon nanowires was investigated. Here, an additional defect emerged in the gamma-ray-irradiated silicon nanowires and was confirmed with electron spin resonance spectra. {sup 29}Si nuclear magnetic resonance spectroscopy showed that irradiation doses had influence on the Q{sup 4} unit structure. This phenomenon indicated that the unique core/shell structure of silicon nanowires might contribute to induce metastable defects under gamma ray irradiation, which served as a satisfactory model to investigate defects at the interface of Si/SiOx.

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.

Gamma ray astronomy and black hole astrophysics

NASA Technical Reports Server (NTRS)

Liang, Edison P.

1990-01-01

The study of soft gamma emissions from black-hole candidates is identified as an important element in understanding black-hole phenomena ranging from stellar-mass black holes to AGNs. The spectra of Cyg X-1 and observations of the Galactic Center are emphasized, since thermal origins and MeV gamma-ray bumps are evident and suggest a thermal-pair cloud picture. MeV gamma-ray observations are suggested for studying black hole astrophysics such as the theorized escaping pair wind, the anticorrelation between the MeV gamma bump and the soft continuum, and the relationship between source compactness and temperature.

The cAMP signaling system inhibits the repair of {gamma}-ray-induced DNA damage by promoting Epac1-mediated proteasomal degradation of XRCC1 protein in human lung cancer cells

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

Cho, Eun-Ah; Juhnn, Yong-Sung, E-mail: juhnn@snu.ac.kr

2012-06-01

Highlights: Black-Right-Pointing-Pointer cAMP signaling system inhibits repair of {gamma}-ray-induced DNA damage. Black-Right-Pointing-Pointer cAMP signaling system inhibits DNA damage repair by decreasing XRCC1 expression. Black-Right-Pointing-Pointer cAMP signaling system decreases XRCC1 expression by promoting its proteasomal degradation. Black-Right-Pointing-Pointer The promotion of XRCC1 degradation by cAMP signaling system is mediated by Epac1. -- Abstract: Cyclic AMP is involved in the regulation of metabolism, gene expression, cellular growth and proliferation. Recently, the cAMP signaling system was found to modulate DNA-damaging agent-induced apoptosis by regulating the expression of Bcl-2 family proteins and inhibitors of apoptosis. Thus, we hypothesized that the cAMP signaling may modulate DNAmore » repair activity, and we investigated the effects of the cAMP signaling system on {gamma}-ray-induced DNA damage repair in lung cancer cells. Transient expression of a constitutively active mutant of stimulatory G protein (G{alpha}sQL) or treatment with forskolin, an adenylyl cyclase activator, augmented radiation-induced DNA damage and inhibited repair of the damage in H1299 lung cancer cells. Expression of G{alpha}sQL or treatment with forskolin or isoproterenol inhibited the radiation-induced expression of the XRCC1 protein, and exogenous expression of XRCC1 abolished the DNA repair-inhibiting effect of forskolin. Forskolin treatment promoted the ubiquitin and proteasome-dependent degradation of the XRCC1 protein, resulting in a significant decrease in the half-life of the protein after {gamma}-ray irradiation. The effect of forskolin on XRCC1 expression was not inhibited by PKA inhibitor, but 8-pCPT-2 Prime -O-Me-cAMP, an Epac-selective cAMP analog, increased ubiquitination of XRCC1 protein and decreased XRCC1 expression. Knockdown of Epac1 abolished the effect of 8-pCPT-2 Prime -O-Me-cAMP and restored XRCC1 protein level following {gamma}-ray

Search for gamma ray lines from supernovae and supernova remnants

NASA Technical Reports Server (NTRS)

Chupp, E. L.; Forrest, D. J.; Suri, A. N.; Adams, R.; Tsai, C.

1974-01-01

A gamma ray monitor with a NaI crystal shielded with a cup-shaped CsI cover was contained in the rotating wheel compartment of the OSO-7 spacecraft for measuring the gamma ray spectra from 0.3 to 10 MeV in search for gamma ray lines from a possible remnant in the Gum Nebula and the apparent Type I supernovae in NGC5253. A brief analysis of data yielded no positive indications for X-rays, gamma ray lines, or continuum from these sources.

Gammapy: Python toolbox for gamma-ray astronomy

NASA Astrophysics Data System (ADS)

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

2017-11-01

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

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.

Gamma-Ray Bursts: A Mystery Story

NASA Technical Reports Server (NTRS)

Parsons, Ann

2007-01-01

With the success of the Swift Gamma-Ray Burst Explorer currently in orbit, this is quite an exciting time in the history of Gamma Ray Bursts (GRBs). The study of GRBs is a modern astronomical mystery story that began over 30 years ago with the serendipitous discovery of these astronomical events by military satellites in the late 1960's. Until the launch of BATSE on the Compton Gamma-ray Observatory, astronomers had no clue whether GRBs originated at the edge of our solar system, in our own Milky Way Galaxy or incredibly far away near the edge of the observable Universe. Data from BATSE proved that GRBs are distributed isotropically on the sky and thus could not be the related to objects in the disk of our Galaxy. Given the intensity of the gamma-ray emission, an extragalactic origin would require an astounding amount of energy. Without sufficient data to decide the issue, a great debate continued about whether GRBs were located in the halo of our own galaxy or were at extragalactic - even cosmological distances. This debate continued until 1997 when the BeppoSAX mission discovered a fading X-ray afterglow signal in the same location as a GRB. This discovery enabled other telescopes, to observe afterglow emission at optical and radio wavelengths and prove that GRBs were at cosmological distances by measuring large redshifts in the optical spectra. Like BeppoSAX Swift, slews to new GRB locations to measure afterglow emission. In addition to improved GRB sensitivity, a significant advantage of Swift over BeppoSAX and other missions is its ability to slew very quickly, allowing x-ray and optical follow-up measurements to be made as early as a minute after the gamma-ray burst trigger rather than the previous 6-8 hour delay. Swift afterglow measurements along with follow-up ground-based observations, and theoretical work have allowed astronomers to identify two plausible scenarios for the creation of a GRB: either through core collapse of super massive stars or

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

Recommended Priorities for NASA's Gamma Ray Astronomy Program 1999-2013

NASA Technical Reports Server (NTRS)

Carol, Ladd

1999-01-01

The Gamma-Ray Astronomy Program Working Group (GRAPWG) recommends priorities for the NASA Gamma-Ray Astronomy Program. The highest priority science topic is nuclear astrophysics and sites of gamma ray line emission. Other high priority topics are gamma ray bursts, hard x-ray emission from accreting black holes and neutron stars, the Advanced Compton Telescope (ACT), the High-resolution Spectroscopic Imager (HSI), and the Energetic X-ray Imaging Survey Telescope (EXIST). The recommendations include special consideration for technology development, TeV astronomy, the ultra-long duration balloon (ULDB) program, the International Space Station, optical telescope support, and data analysis and theory.

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.

A data acquisition and control system for high-speed gamma-ray tomography

NASA Astrophysics Data System (ADS)

Hjertaker, B. T.; Maad, R.; Schuster, E.; Almås, O. A.; Johansen, G. A.

2008-09-01

A data acquisition and control system (DACS) for high-speed gamma-ray tomography based on the USB (Universal Serial Bus) and Ethernet communication protocols has been designed and implemented. The high-speed gamma-ray tomograph comprises five 500 mCi 241Am gamma-ray sources, each at a principal energy of 59.5 keV, which corresponds to five detector modules, each consisting of 17 CdZnTe detectors. The DACS design is based on Microchip's PIC18F4550 and PIC18F4620 microcontrollers, which facilitates an USB 2.0 interface protocol and an Ethernet (IEEE 802.3) interface protocol, respectively. By implementing the USB- and Ethernet-based DACS, a sufficiently high data acquisition rate is obtained and no dedicated hardware installation is required for the data acquisition computer, assuming that it is already equipped with a standard USB and/or Ethernet port. The API (Application Programming Interface) for the DACS is founded on the National Instrument's LabVIEW® graphical development tool, which provides a simple and robust foundation for further application software developments for the tomograph. The data acquisition interval, i.e. the integration time, of the high-speed gamma-ray tomograph is user selectable and is a function of the statistical measurement accuracy required for the specific application. The bandwidth of the DACS is 85 kBytes s-1 for the USB communication protocol and 28 kBytes s-1 for the Ethernet protocol. When using the iterative least square technique reconstruction algorithm with a 1 ms integration time, the USB-based DACS provides an online image update rate of 38 Hz, i.e. 38 frames per second, whereas 31 Hz for the Ethernet-based DACS. The off-line image update rate (storage to disk) for the USB-based DACS is 278 Hz using a 1 ms integration time. Initial characterization of the high-speed gamma-ray tomograph using the DACS on polypropylene phantoms is presented in the paper.

Probing Intrinsic Properties of Short Gamma-Ray Bursts with Gravitational Waves.

PubMed

Fan, Xilong; Messenger, Christopher; Heng, Ik Siong

2017-11-03

Progenitors of short gamma-ray bursts are thought to be neutron stars coalescing with their companion black hole or neutron star, which are one of the main gravitational wave sources. We have devised a Bayesian framework for combining gamma-ray burst and gravitational wave information that allows us to probe short gamma-ray burst luminosities. We show that combined short gamma-ray burst and gravitational wave observations not only improve progenitor distance and inclination angle estimates, they also allow the isotropic luminosities of short gamma-ray bursts to be determined without the need for host galaxy or light-curve information. We characterize our approach by simulating 1000 joint short gamma-ray burst and gravitational wave detections by Advanced LIGO and Advanced Virgo. We show that ∼90% of the simulations have uncertainties on short gamma-ray burst isotropic luminosity estimates that are within a factor of two of the ideal scenario, where the distance is known exactly. Therefore, isotropic luminosities can be confidently determined for short gamma-ray bursts observed jointly with gravitational waves detected by Advanced LIGO and Advanced Virgo. Planned enhancements to Advanced LIGO will extend its range and likely produce several joint detections of short gamma-ray bursts and gravitational waves. Third-generation gravitational wave detectors will allow for isotropic luminosity estimates for the majority of the short gamma-ray burst population within a redshift of z∼1.

Break Point Distribution on Chromosome 3 of Human Epithelial Cells exposed to Gamma Rays, Neutrons and Fe Ions

NASA Technical Reports Server (NTRS)

Hada, M.; Saganti, P. B.; Gersey, B.; Wilkins, R.; Cucinotta, F. A.; Wu, H.

2007-01-01

Most of the reported studies of break point distribution on the damaged chromosomes from radiation exposure were carried out with the G-banding technique or determined based on the relative length of the broken chromosomal fragments. However, these techniques lack the accuracy in comparison with the later developed multicolor banding in situ hybridization (mBAND) technique that is generally used for analysis of intrachromosomal aberrations such as inversions. Using mBAND, we studied chromosome aberrations in human epithelial cells exposed in vitro to both low or high dose rate gamma rays in Houston, low dose rate secondary neutrons at Los Alamos National Laboratory and high dose rate 600 MeV/u Fe ions at NASA Space Radiation Laboratory. Detailed analysis of the inversion type revealed that all of the three radiation types induced a low incidence of simple inversions. Half of the inversions observed after neutron or Fe ion exposure, and the majority of inversions in gamma-irradiated samples were accompanied by other types of intrachromosomal aberrations. In addition, neutrons and Fe ions induced a significant fraction of inversions that involved complex rearrangements of both inter- and intrachromosome exchanges. We further compared the distribution of break point on chromosome 3 for the three radiation types. The break points were found to be randomly distributed on chromosome 3 after neutrons or Fe ions exposure, whereas non-random distribution with clustering break points was observed for gamma-rays. The break point distribution may serve as a potential fingerprint of high-LET radiation exposure.

M-BAND Study of Radiation-Induced Chromosome Aberrations in Human Epithelial Cells: Radiation Quality and Dose Rate Effects

NASA Technical Reports Server (NTRS)

Hada, Megumi; Cucinotta, Francis; Wu, Honglu

2009-01-01

The advantage of the multicolor banding in situ hybridization (mBAND) technique is its ability to identify both inter- (translocation to unpainted chromosomes) and intra- (inversions and deletions within a single painted chromosome) chromosome aberrations simultaneously. To study the detailed rearrangement of low- and high-LET radiation induced chromosome aberrations in human epithelial cells (CH184B5F5/M10) in vitro, we performed a series of experiments with Cs-137 gamma rays of both low and high dose rates, neutrons of low dose rate and 600 MeV/u Fe ions of high dose rate, with chromosome 3 painted with multi-binding colors. We also compared the chromosome aberrations in both 2- and 3-dimensional cell cultures. Results of these experiments revealed the highest chromosome aberration frequencies after low dose rate neutron exposures. However, detailed analysis of the radiation induced inversions revealed that all three radiation types induced a low incidence of simple inversions. Most of the inversions in gamma-ray irradiated samples were accompanied by other types of intra-chromosomal aberrations but few inversions were accompanied by inter-chromosomal aberrations. In contrast, neutrons and Fe ions induced a significant fraction of inversions that involved complex rearrangements of both inter- and intrachromosomal exchanges. The location of the breaks involved in chromosome exchanges was analyzed along the painted chromosome. The breakpoint distribution was found to be randomly localized on chromosome 3 after neutron or Fe ion exposure, whereas non-random distribution with clustering breakpoints was observed after -ray exposure. Our comparison of chromosome aberration yields between 2- and 3-dimensional cell cultures indicated a significant difference for gamma exposures, but not for Fe ion exposures. These experimental results indicated that the track structure of the radiation and the cellular/chromosome structure can both affect radiation-induced chromosome

High resolution gamma-ray spectroscopy at high count rates with a prototype High Purity Germanium detector

NASA Astrophysics Data System (ADS)

Cooper, R. J.; Amman, M.; Vetter, K.

2018-04-01

High-resolution gamma-ray spectrometers are required for applications in nuclear safeguards, emergency response, and fundamental nuclear physics. To overcome one of the shortcomings of conventional High Purity Germanium (HPGe) detectors, we have developed a prototype device capable of achieving high event throughput and high energy resolution at very high count rates. This device, the design of which we have previously reported on, features a planar HPGe crystal with a reduced-capacitance strip electrode geometry. This design is intended to provide good energy resolution at the short shaping or digital filter times that are required for high rate operation and which are enabled by the fast charge collection afforded by the planar geometry crystal. In this work, we report on the initial performance of the system at count rates up to and including two million counts per second.

The Mystery of Gamma-Ray Bursts

NASA Technical Reports Server (NTRS)

Fishman, Gerald J.

1998-01-01

Gamma-ray bursts remain on of the greatest mysteries in astrophysics in spite of recent observational advances and intense theoretical work. Although some of the basic properties of bursts were known 25 years ago, new and more detailed observations have been made by the BATSE (Burst and Transient Source Experiment) experiment on the Compton Gamma Ray Observatory in the past five years. Recent observations of bursts and some proposed models will be discussed.

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.

Multiwavelength observations of unidentified high energy gamma ray sources

NASA Technical Reports Server (NTRS)

Halpern, Jules P.

1993-01-01

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

High resolution gamma-ray spectrometry of culverts containing transuranic waste at the Savannah River Site

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

Hofstetter, K.J.; Sigg, R.

1990-12-31

A number of concrete culverts used to retrievably store drummed, dry, radioactive waste at the Savannah River Site (SRS), were suspected of containing ambiguous quantities of transuranic (TRU) nuclides. These culverts were assayed in place for Pu-239 content using thermal and fast neutron counting techniques. High resolution gamma-ray spectroscopy on 17 culverts, having neutron emission rates several times higher than expected, showed characteristic gamma-ray signatures of neutron emitters other than Pu-239 (e.g., Pu-238, Pu/Be, or Am/Be neutron sources). This study confirmed the Pu-239 content of the culverts with anomalous neutron rates and established limits on the Pu-239 mass in eachmore » of the 17 suspect culverts by in-field, non-intrusive gamma-ray measurements.« less

High resolution gamma-ray spectrometry of culverts containing transuranic waste at the Savannah River Site

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

Hofstetter, K.J.; Sigg, R.

1990-01-01

A number of concrete culverts used to retrievably store drummed, dry, radioactive waste at the Savannah River Site (SRS), were suspected of containing ambiguous quantities of transuranic (TRU) nuclides. These culverts were assayed in place for Pu-239 content using thermal and fast neutron counting techniques. High resolution gamma-ray spectroscopy on 17 culverts, having neutron emission rates several times higher than expected, showed characteristic gamma-ray signatures of neutron emitters other than Pu-239 (e.g., Pu-238, Pu/Be, or Am/Be neutron sources). This study confirmed the Pu-239 content of the culverts with anomalous neutron rates and established limits on the Pu-239 mass in eachmore » of the 17 suspect culverts by in-field, non-intrusive gamma-ray measurements.« less

Real time method and computer system for identifying radioactive materials from HPGe gamma-ray spectroscopy

DOEpatents

Rowland, Mark S.; Howard, Douglas E.; Wong, James L.; Jessup, James L.; Bianchini, Greg M.; Miller, Wayne O.

2007-10-23

A real-time method and computer system for identifying radioactive materials which collects gamma count rates from a HPGe gamma-radiation detector to produce a high-resolution gamma-ray energy spectrum. A library of nuclear material definitions ("library definitions") is provided, with each uniquely associated with a nuclide or isotope material and each comprising at least one logic condition associated with a spectral parameter of a gamma-ray energy spectrum. The method determines whether the spectral parameters of said high-resolution gamma-ray energy spectrum satisfy all the logic conditions of any one of the library definitions, and subsequently uniquely identifies the material type as that nuclide or isotope material associated with the satisfied library definition. The method is iteratively repeated to update the spectrum and identification in real time.

Investigation of gamma rays from the galactic center

NASA Technical Reports Server (NTRS)

Helmken, H. F.

1973-01-01

Data from Argentine balloon flights made to investigate gamma ray emission from the galactic center are summarized. Data are also summarized from a Palestine, Texas balloon flight to measure gamma rays from NP 0532 and Crab Nebulae.

Fermi Gamma-Ray Space Telescope: Highlights of the GeV Sky

NASA Technical Reports Server (NTRS)

Thomspon, D. J.

2011-01-01

Because high-energy gamma rays can be produced by processes that also produce neutrinos. the gamma-ray survey of the sky by the Fermi Gamma-ray Space Telescope offers a view of potenl ial targds for neutrino observations. Gamma-ray bursts. active galactic nuclei, and supernova remnants are all sites where hadronic, neutrino-producing interactions are plausible. Pulsars, pulsar wind nebulae, and binary sources are all phenomena that reveal leptonic particle acceleration through their gamma-ray emission. \\Vhile important to gamma-ray astrophysics. such sources are of less interest to neutrino studies. This talk will present a broad overview of the constantly changing sky seen with the Large Area Telescope (LAT) on the Fermi spacecraft.

Very high energy gamma ray extension of GRO observations

NASA Technical Reports Server (NTRS)

Weekes, Trevor C.

1992-01-01

This has been an exiciting year for high energy gamma-ray astronomy, both from space and from ground-based observatories. It has been a particularly active period for the Whipple Observatory gamma-ray group. In phase 1 of the Compton Gamma Ray Observatory (GRO), there has not been too much opportunity for overlapping observations with the Energetic Gamma Ray Experiment Telescope (EGRET) and the other GRO telescopes; however, significant progress was made in the development of data analysis techniques and in improving the sensitivity of the technique which will have direct application in correlative observations in phase 2. Progress made during the period 1 Jul. 1991 - 31 Dec. 1991 is presented.

Gamma ray-induced synthesis of hyaluronic acid/chondroitin sulfate-based hydrogels for biomedical applications

NASA Astrophysics Data System (ADS)

Zhao, Linlin; Gwon, Hui-Jeong; Lim, Youn-Mook; Nho, Young-Chang; Kim, So Yeon

2015-01-01

Hyaluronic acid (HA)/chondroitin sulfate (CS)/poly(acrylic acid) (PAAc) hydrogel systems were synthesized by gamma-ray irradiation without the use of additional initiators or crosslinking agents to achieve a biocompatible hydrogel system for skin tissue engineering. HA and CS derivatives with polymerizable residues were synthesized. Then, the hydrogels composed of glycosaminoglycans, HA, CS, and a synthetic ionic polymer, PAAc, were prepared using gamma-ray irradiation through simultaneous free radical copolymerization and crosslinking. The physicochemical properties of the HA/CS/PAAc hydrogels having various compositions were investigated to evaluate their feasibility as artificial skin substitutes. The gel fractions of the HA/CS/PAAc hydrogels increased in absorbed doses up to 15 kGy, and they exhibited 91-93% gel fractions under 15 kGy radiation. All of the HA/CS/PAAc hydrogels exhibited relatively high water contents of over 90% and reached an equilibrium swelling state within 24 h. The enzymatic degradation kinetics of the HA/CS/PAAc hydrogels depended on both the concentration of the hyaluronidase solution and the ratio of HA/CS/PAAc. The in vitro drug release profiles of the HA/CS/PAAc hydrogels were significantly influenced by the interaction between the ionic groups in the hydrogels and the ionic drug molecules as well as the swelling of the hydrogels. From the cytotoxicity results of human keratinocyte (HaCaT) cells cultured with extracts of the HA/CS/PAAc hydrogels, all of the HA/CS/PAAc hydrogel samples tested showed relatively high cell viabilities of more than 82%, and did not induce any significant adverse effects on cell viability.

Thermal-neutron capture gamma-rays. Volume 1

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

Tuli, J.K.

1997-05-01

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

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.

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.

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.

Propagation of Cosmic Rays and Diffuse Galactic Gamma Rays

NASA Technical Reports Server (NTRS)

Moskalenko, Igor V.

2004-01-01

This paper presents an introduction to the astrophysics of cosmic rays and diffuse gamma-rays and discusses some of the puzzles that have emerged recently due to more precise data and improved propagation models: the excesses in Galactic diffuse gamma-ray emission, secondary antiprotons and positrons, and the flatter than expected gradient of cosmic rays in the Galaxy. These also involve the dark matter, a challenge to modern physics, through its indirect searches in cosmic rays. Though the final solutions are yet to be found, I discuss some ideas and results obtained mostly with the numerical propagation model GALPROP. A fleet of spacecraft and balloon experiments targeting these specific issues is set to lift off in a few years, imparting a feeling of optimism that a new era of exciting discoveries is just around the corner. A complete and comprehensive discussion of all the recent results is not attempted here due to the space limitations.

Pulsed Gamma Rays from the Millisecond Pulsar J0030+0451 with the Fermi Large Area Telescope

DOE PAGES

Abdo, A. A.; Ackermann, M.; Atwood, W. B.; ...

2009-06-19

In this paper, we report the discovery of gamma-ray pulsations from the nearby isolated millisecond pulsar (MSP) PSR J0030+0451 with the Large Area Telescope on the Fermi Gamma-ray Space Telescope (formerly GLAST). This discovery makes PSR J0030+0451 the second MSP to be detected in gamma rays after PSR J0218+4232, observed by the EGRET instrument on the Compton Gamma-Ray Observatory. The spin-down power E(dotabove) = 3.5 x 10 33 erg s -1 is an order of magnitude lower than the empirical lower bound of previously known gamma-ray pulsars. The emission profile is characterized by two narrow peaks, 0.07 ± 0.01 andmore » 0.08 ± 0.02 wide, respectively, separated by 0.44 ± 0.02 in phase. The first gamma-ray peak falls 0.15 ± 0.01 after the main radio peak. The pulse shape is similar to that of the "normal" gamma-ray pulsars. An exponentially cutoff power-law fit of the emission spectrum leads to an integral photon flux above 100 MeV of (6.76 ± 1.05 ± 1.35) × 10 –8 cm –2 s –1 with cutoff energy (1.7 ± 0.4 ± 0.5) GeV. Finally, based on its parallax distance of (300 ± 90) pc, we obtain a gamma-ray efficiency L γ/E(dotabove) ≃ 15% for the conversion of spin-down energy rate into gamma-ray radiation, assuming isotropic emission.« less

Computational techniques in gamma-ray skyshine analysis

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

George, D.L.

1988-12-01

Two computer codes were developed to analyze gamma-ray skyshine, the scattering of gamma photons by air molecules. A review of previous gamma-ray skyshine studies discusses several Monte Carlo codes, programs using a single-scatter model, and the MicroSkyshine program for microcomputers. A benchmark gamma-ray skyshine experiment performed at Kansas State University is also described. A single-scatter numerical model was presented which traces photons from the source to their first scatter, then applies a buildup factor along a direct path from the scattering point to a detector. The FORTRAN code SKY, developed with this model before the present study, was modified tomore » use Gauss quadrature, recent photon attenuation data and a more accurate buildup approximation. The resulting code, SILOGP, computes response from a point photon source on the axis of a silo, with and without concrete shielding over the opening. Another program, WALLGP, was developed using the same model to compute response from a point gamma source behind a perfectly absorbing wall, with and without shielding overhead. 29 refs., 48 figs., 13 tabs.« less

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.

Fermi: The Gamma-Ray Large Area Space Telescope Mission Status

NASA Technical Reports Server (NTRS)

McEnery, Julie E

2014-01-01

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

All-Sky Earth Occultation Observations with the Fermi Gamma-Ray Burst Monitor

NASA Technical Reports Server (NTRS)

Wilson-Hodge, C. A.; Beklen, E.; Bhat, P. N.; Briggs, M.; Camero-Arranz, A.; Case, G.; Jenke, P.; Chaplin, V.; Cherry, M.; Connaughton, V.;

Development of the instruments for the Gamma Ray Observatory

NASA Technical Reports Server (NTRS)

Madden, J. J.; Kniffen, D. A.

1986-01-01

The Gamma Ray Observatory (GRO) is to be launched in 1988 by the STS. The GRO will feature four very large instruments: the Oriented Scintillation Spectrometer Experiment (OSSE), the Imaging Compton Telescope (COMPTEL), the Energetic Gamma Ray Experiment Telescope (EGRET) and the Burst and Transient Source Experiment (BATSE). The instruments weigh from 900-1200 kg each, and required the development of specialized lifting and dolly devices to permit their assembly, manipulation and testing. The GRO is intended a{s a tool for studying discrete celestial objects such as black holes, neutron stars and other gamma-ray emitting objects, scanning for nucleosynthesis processes, mapping the Galaxy and other, high energy galaxies in terms of gamma rays, searching for cosmological effects and observing gamma ray bursts. The instruments will be sensitive from the upper end mof X-rya wavelengths to the highest energies possible. Details of the hardware and performance specifications of each of the instruments are discussed.

AGIS: A Next-generation TeV Gamma-ray Observatory

NASA Astrophysics Data System (ADS)

Vandenbroucke, Justin

2010-05-01

The Advanced Gamma-ray Imaging System (AGIS) is a next-generation array of imaging atmospheric Cherenkov telescopes for gamma-ray astronomy in the 100 GeV to 100 TeV band. TeV astronomy has flourished in the last few years. Together with the extremely successful first year of the Fermi LAT telescope for GeV gamma-ray astronomy, we are now in a golden age of gamma-ray astronomy. AGIS seeks to continue the success of gamma-ray astronomy by discovering hundreds of new TeV sources and improving our understanding of known sources, as well as searching for signals from dark matter annihilation. AGIS will feature 36 Schwarzschild-Couder (SC) telescopes spanning 1 km2. The two-mirror SC design allows a wide field of view (8 deg diameter) and high-resolution (0.05 deg diameter) pixellation. I will present the science capabilities of the AGIS observatory as well as the technical design and current status of the project.

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.

Gamma-ray spectrometer experiment, Apollo 17: NaI(T1) detector crystal activation

NASA Technical Reports Server (NTRS)

Trombka, J. I.; Schmadebeck, R. L.; Bielefeld, M.; Okelley, G. D.; Eldridge, J. S.; Northcutt, K. J.; Metzger, A. E.; Schonfeld, E.; Peterson, L. E.; Arnold, J. R.

1973-01-01

An attempt was made to obtain experimental data on proton induced activity and its effect on gamma ray spectral measurements. A NaI(T1) crystal flown in Apollo 17 command module was used for the experiment.

Statistical properties of the time histories of cosmic gamma-ray bursts detected by the BATSE experiment of the Compton gamma-ray observatory

NASA Technical Reports Server (NTRS)

Sagdeev, Roald

1995-01-01

The main scientific objectives of the project were: (1) Calculation of average time history for different subsets of BATSE gamma-ray bursts; (2) Comparison of averaged parameters and averaged time history for different Burst And Transient Source Experiments (BASTE) Gamma Ray Bursts (GRB's) sets; (3) Comparison of results obtained with BATSE data with those obtained with APEX experiment at PHOBOS mission; and (4) Use the results of (1)-(3) to compare current models of gamma-ray bursts sources.

Can comet clouds around neutron stars explain gamma-ray bursts?

NASA Technical Reports Server (NTRS)

Tremaine, S.; Zytkow, A. N.

1986-01-01

The proposal of Harwit and Salpeter (1973) that gamma-ray bursts are due to impacts of comets onto neutron stars is examined further. It is assumed that most stars are formed with comet clouds similar to the Oort comet cloud which surrounds the sun, and it is suggested that there are at least four mechanisms by wich neutron stars may be formed while retaining their comet clouds: a spherically symmetric supernova explosion in an isolated star, accretion-induced collapse of a white dwarf in a cataclysmic variable with a very low mass secondary, accretion-induced collapse of a white dwarf in a wide binary with a low-mass giant companion, and coalescence of a close binary composed of two white dwarfs. Estimates are given of the cometary impact rates for such systems. It is suggested that if the wide binary scenario is correct, optical bursts may arise from the impact of comets onto the white dwarf remnant of the giant companion.

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

Search for Sub-TeV Gamma Rays Coincident with BATSE Gamma Ray Bursts

NASA Astrophysics Data System (ADS)

D'Andrea, C. P.; D'Andrea, Christopher; Gress, Joseph; Race, Doran

2003-07-01

project GRAND is a 100m × 100m air shower array of proportional wire chambers (PWCs). There are 64 stations each with eight 1.29 m2 PWC planes arranged in four orthogonal pairs placed vertically above one another to geometrically measure the angles of charged secondaries. A steel plate above the bottom pair of PWCs differentiates muons (which pass undeflected through the steel) from non-p enetrating particles. FLUKA Monte Carlo studies show that a TeV gamma ray striking the atmosphere at normal incidence produces 0.23 muons which reach ground level where their angles and identities are measured. Thus, paradoxically, secondary muons are used as a signature for gamma ray primaries. The data are examined for possible angular and time coincidences with eight gamma ray bursts (GRBs) detected by BATSE. Seven of the GRBs were selected because of their good acceptance by GRAND and high BATSE fluence. The eighth GRB was added due to its possible coincident detection by Milagrito. For each of the eight candidate GRBs, the number of excess counts during the BATSE T90 time interval and within ±5° of BATSE's direction was obtained. The highest statistical significance reported in this paper (2.7σ ) is for the event that was predicted to be the most likely to be observed (GRB 971110).

Exploring the Extreme Universe with the Fermi Gamma-Ray Space Telescope

NASA Technical Reports Server (NTRS)

Thompson, D. J.

2010-01-01

Because high-energy gamma rays are produced by powerful sources, the Fermi Gamma-ray Space Telescope provides a window on extreme conditions in the Universe. Some key observations of the constantly changing gamma-ray sky include: (1) Gamma-rays from pulsars appear to come from a region well above the surface of the neutron star; (2) Multiwavelength studies of blazars show that simple models of jet emission are not always adequate to explain what is seen; (3) Gamma-ray bursts can constrain models of quantum gravity; (4) Cosmic-ray electrons at energies approaching 1 TeV suggest a local source for some of these particles.

Day-Scale Variability of 3C 279 and Searches for Correlations in Gamma-Ray, X-Ray and Optical Bands

NASA Technical Reports Server (NTRS)

Hartman, R. C.; Villata, M.; Balonek, T. J.; Bertsch, D. L.; Bock, H.; Boettcher, M.; Carini, M. T.; Collmar, W.; DeFrancesco, G.; Ferrera, E. C.;

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.

FERMI Observations of Gamma -Ray Emission From the Moon

NASA Technical Reports Server (NTRS)

Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwoo, W. B.; Baldini, I.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.;

The AGILE Mission and Gamma-Ray Bursts

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

Longo, Francesco; INFN, section of Trieste; Tavani, M.

2007-05-01

The AGILE Mission will explore the gamma-ray Universe with a very innovative instrument combining for the first time a gamma-ray imager and a hard X-ray imager. AGILE will be operational at the beginning of 2007 and it will provide crucial data for the study of Active Galactic Nuclei, Gamma-Ray Bursts, unidentified gamma-ray sources, Galactic compact objects, supernova remnants, TeV sources, and fundamental physics by microsecond timing. The AGILE instrument is designed to simultaneously detect and image photons in the 30 MeV - 50 GeV and 15 - 45 keV energy bands with excellent imaging and timing capabilities, and a largemore » field of view covering {approx} 1/5 of the entire sky at energies above 30 MeV. A CsI calorimeter is capable of GRB triggering in the energy band 0.3-50 MeV. The broadband detection of GRBs and the study of implications for particle acceleration and high energy emission are primary goals of the mission. AGILE can image GRBs with 2-3 arcminute error boxes in the hard X-ray range, and provide broadband photon-by photon detection in the 15-45 keV, 03-50 MeV, and 30 MeV-30 GeV energy ranges. Microsecond on-board photon tagging and a {approx} 100 microsecond gamma-ray detection deadtime will be crucial for fast GRB timing. On-board calculated GRB coordinates and energy fluxes will be quickly transmitted to the ground by an ORBCOMM transceiver. AGILE is now (January 2007) undergoing final satellite integration and testing. The PLS V launch is planned in spring 2007. AGILE is then foreseen to be fully operational during the summer of 2007.« less

Time-resolved Neutron-gamma-ray Data Acquisition for in Situ Subsurface Planetary Geochemistry

NASA Technical Reports Server (NTRS)

Bodnarik, Julie G.; Burger, Dan Michael; Burger, A.; Evans, L. G.; Parsons, A. M.; Schweitzer, J. S.; Starr R. D.; Stassun, K. G.

2013-01-01

The current gamma-ray/neutron instrumentation development effort at NASA Goddard Space Flight Center aims to extend the use of active pulsed neutron interrogation techniques to probe the subsurface elemental composition of planetary bodies in situ. Previous NASA planetary science missions, that used neutron and/or gamma-ray spectroscopy instruments, have relied on neutrons produced from galactic cosmic rays. One of the distinguishing features of this effort is the inclusion of a high intensity 14.1 MeV pulsed neutron generator synchronized with a custom data acquisition system to time each event relative to the pulse. With usually only one opportunity to collect data, it is difficult to set a priori time-gating windows to obtain the best possible results. Acquiring time-tagged, event-by-event data from nuclear induced reactions provides raw data sets containing channel/energy, and event time for each gamma ray or neutron detected. The resulting data set can be plotted as a function of time or energy using optimized analysis windows after the data are acquired. Time windows can now be chosen to produce energy spectra that yield the most statistically significant and accurate elemental composition results that can be derived from the complete data set. The advantages of post-processing gamma-ray time-tagged event-by-event data in experimental tests using our prototype instrument will be demonstrated.

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.

The sensitivity of EGRET to gamma ray polarization