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1

Molecular changes in UV-induced and gamma-ray-induced mutations in human lymphoblastoid cells.  

PubMed

We have characterized the structural changes in the hypoxanthine-guanine phosphoribosyltransferase (HPRT) gene of 14 UV-induced, 15 gamma-ray-induced and 17 spontaneous mutants of human lymphoblastoid cells selected for 6-thioguanine (6TG) resistance. Southern blot analysis using the full-length HPRT cDNA as a probe revealed that 29% (5/17) of the spontaneous mutants contained detectable alterations in their restriction fragment patterns. Among the 15 mutants induced by gamma rays, 7 (47%) had such alterations indicative of large deletions in the HPRT gene. In contrast, all 14 UV-induced mutants exhibited hybridization patterns indistinguishable from those of the wild-type cells. These results suggest that UV is likely to induce point mutations at the HPRT locus on the human chromosome and that the molecular mechanism of UV-induced mutation is quite different from that of ionizing radiation-induced mutation or spontaneous mutation in human cells. PMID:1973821

Tachibana, A; Ohbayashi, T; Takebe, H; Tatsumi, K

1990-06-01

2

Induced mutagenesis in Vicia faba L. 1 Chlorophyll mutations induced by gamma rays, ethyl methane sulphonate and hydrazine.  

PubMed

The seeds of Vicia faba L. (2n = 12) having a moisture content of 9.06% were given individual and combined treatments of gamma rays (5 kR), ethyl methane sulphonate (0.25% and 0.50%, 6 h) and hydrazine (0.25% and 0.50%, 6 h). Chlorophyll mutations were scored in the M2-generation as mutants per 100 M2 plants. The mutation frequency was highest for xantha and lowest for striata. The frequency of chlorophyll mutations was higher due to chemicals than due to gamma rays at the available levels of treatments. Quantitative estimation of chlorophyll pigments was also made in different kinds of chlorophyll mutants and the chlorophyll content was in the following decreasing order: viridoalba > chlorina > xanthoalba > striata > viridis > alboxantha > xantha > albino. The total leaf area in these mutants was similarly found in the following decreasing order: viridoalba > chlorina > xantha > xanthoalba > alboxantha > viridis > striata > albino. PMID:7418451

Vishnoi, A K; Gupta, P K

1980-01-01

3

Molecular analysis of gamma-ray-induced mutations at the hprt locus in primary human skin fibroblasts by multiplex polymerase chain reaction  

SciTech Connect

A total of 153 hprt mutants (23 spontaneous, 130 {gamma}-ray-induced) of primary human skin fibroblasts were isolated and genetic alterations at the locus were studied by multiplex polymerase chain reaction (PCR). The analyses showed that 51% (66/130) of {gamma}-ray-induced genetic changes were large deletions, whereas the majority of spontaneous mutants (21/23) exhibited point mutations. The spectrum of large genetic alterations appeared to be dependent on dose in {gamma}-ray-induced (1-4 Gy) mutations; mutants with complete loss of the hprt locus comprised 21 (3/14) or 39% (15/38) of clones isolated after irradiation with 1 or 4 Gy, respectively. The frequency of partial deletions was found to be higher in the mutants isolated from clones irradiated with 2 Gy (38%) than from those irradiated with 4 Gy (8%). Mapping of all intragenic depletion breakpoints exhibited a nonrandom distribution of breakpoints toward the 3{prime} end of the hprt gene. 46 refs., 4 figs., 2 tabs.

Park, M.S.; Hanks, T.; Jaberaboansari, A.; Chen, D.J. [Los Alamos National Lab., NM (United States)

1995-01-01

4

Prompt gamma-ray coincidences from U-235 induced fission  

NASA Astrophysics Data System (ADS)

An experiment to measure gamma-ray emission from the prompt fission fragments of U-235 was recently performed at the Intense Pulsed Neutron Source facility at Argonne National Laboratory. Ten HPGE detectors were used to observe coincident gamma-rays from the fission fragments. Unlike previous fission studies which focused on the fission fragments populated by beta decay, we have measured the prompt fission yields by inducing fission in the U-235 target. Coincidence information between light and heavy fission fragments permits the assignment of observed gamma-rays to a particular isotope. Preliminary analysis indicates new spectroscopic information for dozens of nuclei, as well as the observation of isotopes for which gamma-ray decays were previously unreported. We will report on the prompt fission yields of the major fission fragments, as well as the new spectroscopic information for select nuclei.

Jewell, J. Keith; Cole, Jerald; Drigert, Mark; Reber, Edward; Aryaeinejad, Rahmat

1999-10-01

5

Elemental concentrations from neutron induced gamma ray spectroscopy  

Microsoft Academic Search

Advances in neutron induced gamma ray spectroscopy techniques provide a means for the evaluation of most of the minerals and fluids found in subsurface petroleum reservoir formations. Specific problems associated with the currently used neutron reaction mechanisms and procedures are reviewed. Examples of the most significant applications of induced spectroscopy measurements are discussed.

R. Hertzog

1988-01-01

6

Induced Background in the Mars Observer Gamma-Ray Spectrometer  

NASA Technical Reports Server (NTRS)

Gamma-Ray Spectrometers in space must necessarily work in an environment of a background of lines due to natural and cosmic-ray induced radioactivity and lines due to prompt emission following nuclear reactions caused by primary and secondary cosmic rays. The Gamma-Ray Spectrometer (GRS) on the Mar Observer mission has provided important data allowing one to estimate for future missions the extent of the background due to cosmic rays. These data will help in the design of instruments and in calculation of realistic background intensities that may effect the sensitivity of determining the intensity of lines of interest.

Boynton, William V.; Evans, Larry G.; Starr, Richard; Bruekner, Johnnes; Bailey, S. H.; Trombka, Jacob I.

1997-01-01

7

WIMP-induced gamma ray spectrum of active Galactic nuclei  

NASA Astrophysics Data System (ADS)

As direct and indirect dark matter detection experiments continue to place stringent constraints on WIMP masses and couplings, it becomes imperative to expand the scope of the search for particle dark matter by looking in new and exotic places. One such place may be the core of active Galactic nuclei (AGN) where the density of dark matter is expected to be extremely high. Recently, several groups have explored the possibility of observing signals of dark matter from its interactions with the high-energy jets emanating from these galaxies. In this work, we build upon these analyses by including the other components of the WIMP-induced gamma ray spectrum of active Galactic nuclei; namely, (i) the continuum from WIMP annihilation into light standard model states which subsequently radiate and/or decay into photons and (ii) the direct (loop-induced) decay into photons. We work in the context of models of universal extra dimensions (in particular, a model with two extra dimensions) and compute all three components of the gamma ray spectrum and compare with current data. We find that the model with two extra dimensions exhibits several interesting features which may be observable with the Fermi gamma ray telescope. We also show that, in conjunction with other measurements, the gamma ray spectrum from AGN can be an invaluable tool for restricting WIMP parameter space.

Gómez, M. A.; Jackson, C. B.; Shaughnessy, G.

2013-07-01

8

Detection of Neutrons Liberated from Beryllium by Gamma Rays: a New Technique for Inducing Radioactivity  

Microsoft Academic Search

We have observed that a radiation emitted from beryllium under the influence of radium gamma rays excites induced radioactivity in iodine, and we conclude that neutrons are liberated from beryllium by gamma rays.

Leo Szilard; T. A. Chalmers

1934-01-01

9

Interferences of Neutron Induced gamma -Ray Emission in Ge(Li) Detectors in Elemental Analysis by Proton Induced gamma -Ray Emission.  

National Technical Information Service (NTIS)

Intensities of low energy gamma -rays induced in Ge(Li) detectors by epithermal and fast neutrons from (p,n) reactions are compared with direct gamma -ray emission during proton bombardment of materials. Interferences of the (n, gamma ) and (n,n' gamma ) ...

F. Bodart G. Demortier

1978-01-01

10

Neutron-induced gamma ray spectroscopy: Simulations for chemical mapping of planetary surfaces  

Microsoft Academic Search

Cosmic rays interact with the surface of a planetary body and produce a cascade of secondary particles, such as neutrons. Neutron-induced scattering and capture reactions play an important role in the production of discrete gamma ray lines that can be measured by a gamma ray spectrometer on board an orbiting spacecraft. These data can be used to determine the concentration

J. Brueckner; H. Waenke; R. C. Reedy

1987-01-01

11

Lymphocytes from wasted mice express enhanced spontaneous and {gamma}-ray-induced apoptosis  

SciTech Connect

Mice bearing the autosomal recessive mutation wasted (wst/wst) display a disease pattern including faulty repair of DNA damage in lymphocytes after radiation exposure, neurologic abnormalities, and immunodeficiency. Many of the features of this mouse model have suggested a premature or increased spontaneous frequency of apoptosis in thymocytes; past work has shown an inability to establish cultured T cell lines, an abnormally high death rate of stimulated T cells in culture, and an increased sensitivity of T cells to the killing effects of ionizing radiations in wst/wst mice relative to controls. The experiments reported here were designed to examine splenic and thymic lymphocytes from wasted and control mice for signs of early apoptosis. Our results revealed enhanced expression of Rp-8 mRNA (associated with apoptosis) in thymic lymphocytes and reduced expression in splenic lymphocytes of wst/wst mice relative to controls; expression of Rp-2 and Td-30 mRNA (induced during apoptosis) were not detectable in spleen or thymus. Higher spontaneous DNA fragmentation was observed in wasted mice than in controls; however, {gamma}-ray-induced DNA fragmentation peaked at a lower dose and occurred to a greater extent in wasted mice relative to controls. These results provide evidence for high spontaneous and {gamma}-ray-induced apoptosis in T cells of wasted mice as a mechanism underlying the observed lymphocyte and DNA repair abnormalities.

Woloschak, G.E. [Argonne National Lab., IL (United States)]|[Loyola Univ. Medical Center, Maywood, IL (United States); Chang-Liu, Chin-Mei [Argonne National Lab., IL (United States); Chung, Jen; Libertin, C.R. [Loyola Univ. Medical Center, Maywood, IL (United States)

1993-09-01

12

Changes in DNA Base Sequence Induced by Gamma-Ray Mutagenesis of Lambda Phage and Prophage  

PubMed Central

Mutations in the cI (repressor) gene were induced by gamma-ray irradiation of lambda phage and of prophage, and 121 mutations were sequenced. Two-thirds of the mutations in irradiated phage assayed in recA host cells (no induction of the SOS response) were G:C to A:T transitions; it is hypothesized that these may arise during DNA replication from adenine mispairing with a cytosine product deaminated by irradiation. For irradiated phage assayed in host cells in which the SOS response had been induced, 85% of the mutations were base substitutions, and in 40 of the 41 base changes, a preexisting base pair had been replaced by an A:T pair; these might come from damaged bases acting as AP (apurinic or apyrimidinic) sites. The remaining mutations were 1 and 2 base deletions. In irradiated prophage, base change mutations involved the substitution of both A:T and of G:C pairs for the preexisting pairs; the substitution of G:C pairs shows that some base substitution mechanism acts on the cell genome but not on the phage. In the irradiated prophage, frameshifts and a significant number of gross rearrangements were also found.

Tindall, K. R.; Stein, J.; Hutchinson, F.

1988-01-01

13

Neutron-induced gamma-ray spectroscopy: simulations for chemical mapping of planetary surfaces  

SciTech Connect

Cosmic rays interact with the surface of a planetary body and produce a cascade of secondary particles, such as neutrons. Neutron-induced scattering and capture reactions play an important role in the production of discrete gamma-ray lines that can be measured by a gamma-ray spectrometer on board of an orbiting spacecraft. These data can be used to determine the concentration of many elements in the surface of a planetary body, which provides clues to its bulk composition and in turn to its origin and evolution. To investigate the gamma rays made by neutron interactions, thin targets were irradiated with neutrons having energies from 14 MeV to 0.025 eV. By means of foil activation technique the ratio of epithermal to thermal neutrons was determined to be similar to that in the Moon. Gamma rays emitted by the targets and the surrounding material were detected by a high-resolution germanium detector in the energy range of 0.1 to 8 MeV. Most of the gamma-ray lines that are expected to be used for planetary gamma-ray spectroscopy were found in the recorded spectra and the principal lines in these spectra are presented. 58 refs., 7 figs., 9 tabs.

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

1986-01-01

14

Detection of SNM by delayed gamma rays from induced fission  

NASA Astrophysics Data System (ADS)

The Pulsed Neutron Interrogation Test Assembly (PUNITA) is an experimental device for research in NDA methods and field applicable instrumentation for nuclear safeguards and security applications. PUNITA incorporates a standard 14-MeV (D-T) pulsed neutron generator inside a large graphite mantle. The generator target is surrounded by a thick tungsten filter with the purpose to increase the neutron output and to tailor the neutron energy spectrum. In this configuration a sample may be exposed to a relatively high average thermal neutron flux of about (2.2±0.1)×10 3 s -1 cm -2 at only 10% of the maximum target neutron emission. The sample cavity is large enough to allow variation of the experimental setup including the fissile sample, neutron and gamma detectors, and shielding materials. The response from SNM samples of different fissile material content was investigated with various field-applicable scintillation gamma detectors such as the 3×2 in. LaBr 3 detector. Shielding in the form of tungsten and cadmium was applied to the detector to improve the signal to background ratio. Gamma and neutron shields surrounding the samples were also tested for the purpose of simulating clandestine conduct. The energy spectra of delayed gamma rays were recorded in the range 100 keV-9 MeV. In addition time spectra of delayed gamma rays in the range 3.3-8 MeV were recorded in the time period of 10 ms-120 s after the 14-MeV neutron burst. The goal of the experiment was to optimize the sample/detector configuration including the energy range and time period for SNM detection. The results show, for example, that a 170 g sample of depleted uranium can be detected with the given setup in less than 3 min of investigation. Samples of higher enrichment or higher mass are detected in much shorter time.

Rennhofer, H.; Crochemore, J.-M.; Roesgen, E.; Pedersen, B.

2011-10-01

15

RADIO PROTECTIVE EFFECTS OF GINSENG EXTRACT IN GAMMA-RAYS INDUCED CHROMOSOMAL DAMAGES OF HUMAN LYMPHOCYTE  

Microsoft Academic Search

RADIOPROTECTIVE EFFECTS OF GINSENG EXTRACT IN GAMMA - RAYS INDUCED CHROMOSOMAL DAMAGES OF HUMAN LYMPHOCYTE. Ginsan, a polysaccharide extracted from Panax ginseng and subsequently referred as ginseng, posses various biological properties as an anticancer and antioxidant agent. Ginseng also approved effective against radiation effects through its immunomodulating actions in whole body irradiated mouse. But its protective effects on radiation induced

M. Syaifudin; Jie-Young Song; Yun-Sil Lee; Chang-Mo Kang

16

DEVELOPMENT OF ADVANCED NEUTRON INDUCED PROMPT GAMMA RAY ANALYSIS SYSTEM FOR SURVEY OF ANTI-PERSONNEL MINES  

Microsoft Academic Search

An advanced neutron induced prompt gamma ray analysis system has been designed for detection and localization of anti-personnel landmines. The system consists of an improved Cockcroft-Walton type accelerator neutron source using DD fusion reaction and multi-functional gamma ray spectrometers combining a compact multi-Compton gamma camera based on stacked BGO scintillators to deduce the incident direction of 10.8 MeV gamma rays

T. Iguchi; J. Kawarabayashi; K. Watanabe; K. Nishimura; T. Handa; H. Sawamura

17

Oscillation Induced Gamma Ray Emission from Dead Pulsars: A Model for Delayed GeV Emission in Gamma Ray Bursts  

NASA Astrophysics Data System (ADS)

The oscillation of a crustal platelet of a neutron star will result in a high potential drop between the magnetic field lines. This potential drop can result in the emission of high energy curvature radiation photons with energy up to a few tens GeV. We consider the radiation processes that take place in the stellar magnetosphere and compute the energy spectrum escaping the magnetosphere. The strain energy available decreases as the star radiates. Thus, the resultant potential drop decreases with time and results in a time delay in the emission of GeV photons. The delay time and the duration of the gamma ray emission process are consistent with the observed behaviour of the high energy gamma ray photons ( ~ 26 GeV) in GRB 940217. These two time scales depend on the stored strain energy, the magnetic field and the period of the star. Our modelling spectrum also provides a good fit to the observed spectrum of the high energy GRB 930131. The radiation processes result in the production of enormous amount of e(+/-) . Line features are expected to be found in some of the gamma ray bursts in our model. In conclusion, if some of the gamma ray bursts do come from the galactic neutron stars, our model provides a good explanation to the time scales and spectral features observed.

Ding, K. Y. Winnis; Cheng, K. S.

1995-03-01

18

Evaluation of gamma-Ray Production Cross Sections from Neutron-Induced Reactions on Tungsten.  

National Technical Information Service (NTIS)

An evaluation of neutron-induced gamma-ray production cross sections and secondary spectra for the major tungsten isotopes has been completed for neutron energies from 10 exp -5 eV to 20 MeV. The evaluation for energies in the keV region is based on calcu...

P. G. Young

1974-01-01

19

Change in Ion Beam Induced Current from Si Metal-Oxide-Semiconductor Capacitors after Gamma-Ray Irradiation  

SciTech Connect

To investigate the effects of gamma-ray irradiation on transient current induced in MOS capacitors by heavy ion incidence, Si MOS capacitors were irradiated with gamma-rays up to 60.9 kGy(SiO2). The change in Transient Ion Beam Induced Current (TIBIC) signals due to gamma-ray irradiation was investigated using 15 MeV-oxygen ion microbeams. After gamma-ray irradiation, the peak current of the TIBIC signal vs. bias voltage curve shifted toward negative voltages. This shift can be interpreted in terms of the charge trapped in the oxide. In this dose range, no significant effects of the interface traps induced by gamma-ray irradiation on the TIBIC signals were observed.

Ohshima, T.; Onoda, S.; Hirao, T. [Japan Atomic Energy Agency, 1233 Watanuki, Takasaki, Gunma 370-1292 (Japan); Takahashi, Y. [College of Science and Technology, Nihon University, Funabashi (Japan); Vizkelethy, G.; Doyle, B. L. [Sandia National Laboratories, PO Box 5800, MS 1056, Albuquerque, NM 87185 (United States)

2009-03-10

20

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

PubMed

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. PMID:18413978

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

2008-07-01

21

Lignocellulolytic mutants of Pleurotus ostreatus induced by gamma-ray radiation and their genetic similarities  

NASA Astrophysics Data System (ADS)

To induce the lignocellulolytic mutants of Pleurotus ostreatus, the mycelia were irradiated by gamma-ray radiation to doses of 1-2 kGy. Five strains were isolated by the criteria of clamp connection, fruiting body formation, growth rate and activities of extracellular enzymes. All isolated strains were able to form the fruiting bodies and grew similarly to the control. The extracellular enzymes activities in liquid media of isolated strains were up to 10 times higher than the control. Genetic similarities of the isolated strains ranged from 64.4% to 93.3% of the control. From these results, it seems that the genetic diversity of P. ostreatus could be changed and useful strains be induced by gamma-ray radiation to recycle or reuse biowastes.

Lee, Y.-K.; Chang, H.-H.; Kim, J.-S.; Kim, J. K.; Lee, K.-S.

2000-02-01

22

ROLE OF CERIUM IN SUPPRESSION OF GAMMA-RAY INDUCED COLORING OF BORATE GLASSES  

Microsoft Academic Search

The role of cerium in the suppression of gamma-ray induced coloration in ; glass was found to depend on the relative concentration of Ce\\/sup 3+\\/ to Ce\\/sup ; 4+\\/ ions as well as on the total cerium content. In a borate glass having high ; ultraviolet transmission, it was found that both Ce\\/sup 3+\\/ and Ce\\/sup 4+\\/ ions ; are

ADLI M. BISHAY

1962-01-01

23

Proton-induced X-ray and gamma ray emission analysis of biological samples  

NASA Astrophysics Data System (ADS)

A 4.1 MeV external proton beam was employed to simultaneously induce X-ray emission (PIXE) and gamma ray emission (PIGE) in biological samples that included human colostrum, spermatozoa, teeth, tree-rings, and follicular fluids. The analytical method was developed to simultaneously determine the elements lithium (Z = 3) through uranium (Z = 92) in the samples. PIXE-PIGE experimental design is described as well as applications in environmental and medical fields.

Hall, Gene S.; Navon, Eliahu

1986-04-01

24

Proton-induced X-ray and gamma ray emission analysis of biological samples  

Microsoft Academic Search

A 4.1 MeV external proton beam was employed to simultaneously induce X-ray emission (PIXE) and gamma ray emission (PIGE) in biological samples that included human colostrum, spermatozoa, teeth, tree-rings, and follicular fluids. The analytical method was developed to simultaneously determine the elements lithium (Z = 3) through uranium (Z = 92) in the samples. PIXE-PIGE experimental design is described as

Gene S. Hall; Eliahu Navon

1986-01-01

25

Search for Neutrino-induced Cascades from Gamma-Ray Bursts with AMANDA  

Microsoft Academic Search

Using the neutrino telescope AMANDA-II, we have conducted two analyses searching for neutrino-induced cascades from gamma-ray bursts. No evidence of astrophysical neutrinos was found, and limits are presented for several models. We also present neutrino effective areas which allow the calculation of limits for any neutrino production model. The first analysis looked for a statistical excess of events within a

A. Achterberg; M. Ackermann; J. Adams; J. Ahrens; K. Andeen; J. Auffenberg; J. N. Bahcall; X. Bai; B. Baret; S. W. Barwick; R. Bay; K. Beattie; T. Becka; J. K. Becker; K.-H. Becker; P. Berghaus; D. Berley; E. Bernardini; D. Bertrand; D. Z. Besson; E. Blaufuss; D. J. Boersma; C. Bohm; J. Bolmont; S. Böser; O. Botner; A. Bouchta; J. Braun; C. Burgess; T. Burgess; T. Castermans; D. Chirkin; B. Christy; J. Clem; D. F. Cowen; M. V. D'Agostino; A. Davour; C. T. Day; C. De Clercq; L. Demirörs; F. Descamps; P. Desiati; T. De Young; J. C. Diaz-Velez; J. Dreyer; J. P. Dumm; M. R. Duvoort; W. R. Edwards; R. Ehrlich; J. Eisch; R. W. Ellsworth; P. A. Evenson; O. Fadiran; A. R. Fazely; K. Filimonov; M. M. Foerster; B. D. Fox; A. Franckowiak; T. K. Gaisser; J. Gallagher; R. Ganugapati; H. Geenen; L. Gerhardt; A. Goldschmidt; J. A. Goodman; R. Gozzini; T. Griesel; S. Grullon; A. Groß; R. M. Gunasingha; M. Gurtner; A. Hallgren; F. Halzen; K. Han; K. Hanson; D. Hardtke; R. Hardtke; J. E. Hart; Y. Hasegawa; T. Hauschildt; D. Hays; J. Heise; K. Helbing; M. Hellwig; P. Herquet; G. C. Hill; J. Hodges; K. D. Hoffman; B. Hommez; K. Hoshina; D. Hubert; B. Hughey; P. O. Hulth; K. Hultqvist; J.-P. Hülß; S. Hundertmark; M. Inaba; A. Ishihara; J. Jacobsen; G. S. Japaridze; H. Johansson; A. Jones; J. M. Joseph; K.-H. Kampert; T. Karg; A. Karle; H. Kawai; J. L. Kelley; N. Kitamura; S. R. Klein; S. Klepser; G. Kohnen; H. Kolanoski; L. Köpke; M. Kowalski; T. Kowarik; M. Krasberg; K. Kuehn; M. Labare; H. Landsman; H. Leich; D. Leier; I. Liubarsky; J. Lundberg; J. Lünemann; J. Madsen; K. Mase; H. S. Matis; T. McCauley; C. P. McParland; A. Meli; T. Messarius; P. Mészáros; H. Miyamoto; A. Mokhtarani; T. Montaruli; A. Morey; R. Morse; S. M. Movit; K. Münich; R. Nahnhauer; J. W. Nam; P. Nießen; D. R. Nygren; H. Ögelman; A. Olivas; S. Patton; C. Peña-Garay; C. Pérez de los Heros; A. Piegsa; D. Pieloth; A. C. Pohl; R. Porrata; J. Pretz; P. B. Price; G. T. Przybylski; K. Rawlins; S. Razzaque; E. Resconi; W. Rhode; M. Ribordy; A. Rizzo; S. Robbins; P. Roth; C. Rott; D. Rutledge; D. Ryckbosch; H.-G. Sander; S. Sarkar; S. Schlenstedt; T. Schmidt; D. Schneider; D. Seckel; B. Semburg; S. H. Seo; S. Seunarine; A. Silvestri; A. J. Smith; M. Solarz; C. Song; J. E. Sopher; G. M. Spiczak; C. Spiering; M. Stamatikos; T. Stanev; P. Steffen; T. Stezelberger; R. G. Stokstad; M. C. Stoufer; S. Stoyanov; E. A. Strahler; T. Straszheim; K.-H. Sulanke; G. W. Sullivan; T. J. Sumner; I. Taboada; O. Tarasova; A. Tepe; L. Thollander; S. Tilav; M. Tluczykont; P. A. Toale; D. Turcan; N. van Eijndhoven; J. Vandenbroucke; A. Van Overloop; V. Viscomi; B. Voigt; W. Wagner; C. Walck; H. Waldmann; M. Walter; Y.-R. Wang; C. Wendt; C. H. Wiebusch; G. Wikström; D. R. Williams; R. Wischnewski; H. Wissing; K. Woschnagg; X. W. Xu; G. Yodh; S. Yoshida; J. D. Zornoza

2007-01-01

26

Induced Radioactivity in Recovered Skylab Materials. [gamma ray spectra  

NASA Technical Reports Server (NTRS)

Four radioactive isotopes found in aluminum and stainless steel samples from Skylab debris were recovered in Australia. The low-level activity was induced by high-energy protons and neutrons in the space environment. Measurements of the specific activities are given.

Fishman, G. J.; Meegan, C. A.

1980-01-01

27

Proton and gamma ray induced gain degradation in bipolar transistor  

NASA Astrophysics Data System (ADS)

This paper describes the results of the effect of 24 MeV proton and (CO)-C-60 gamma-irradiation on the collector characteristic., and forward current gain of commercial bipolar transistor (npn 2N2219A). The transistor has been exposed to these radiations in the biased condition and the collector characteristics and forward current gain have been measured as a function of proton fluence and gamma-dose. The observation is that both the proton and gamma-irradiation induce significant gain degradation in the transistor. The results are discussed in terms of displacement damage produced by energetic protons and gamma-radiation in the bulk of the semiconductor.

Kulkarni, S. R.; Sarma, A.; Joshi, G. R.; Ravindra, M.; Damle, R.

2003-09-01

28

Bayesian methods for inferring soil contamination profiles from neutron-induced gamma-ray spectra  

NASA Astrophysics Data System (ADS)

Prompt-gamma neutron-activation analysis offers a potential for noninvasive characterization of contaminated soil. In this method, neutron irradiation of the surface induces a capture-gamma-ray signature from the contaminant which can be identified in a gamma-ray energy spectrum measured at the surface. The fundamental problem is to infer the contaminant concentration profile from the measured capture-gamma-ray intensities which include gamma-ray contributions from all soil depths. Radiation-transport theory is used to simulate the neutron field and both the uncollided and first-scattered gamma-ray components in uniform soil compositions. Simulated data, generated for any assumed one-dimensional contamination profile, are used to test several methods of profile reconstruction. The methods applied to solve this inverse problem include: linear (Tikhonov) regularization with and without positivity constraints, Backus-Gilbert smoothing, maximum-entropy Bayesian optimization, and a new Bayesian approach that accepts prior information in the form of a multivariate lognormal probability density. A tutorial on inverse theory is provided to relate the seemingly disparate approaches of Bayesian optimization and regularization of a Fredholm integral equation. Particular attention is given to using Shannon-Jaynes configurational entropy as a prior constraint. In the Bayesian context, all methods seek the maximum-a-posteriori (MAP) solution lying at the mode of Bayes' posterior. Comparative inverse MAP solutions are presented for bilinear and step concentration profiles. Maximum-entropy and lognormal-prior methods, which enforce positivity and accept additional prior information, successfully locate bulk concentrations with reasonable peak estimates and minimum computation. Practical depth resolutions are limited to a range of 60 cm in nominal soil by poor neutron penetration. The variance of Bayes' posterior probability distribution is investigated to assess the utility of the MAP concentration profile inferred from a single gamma-ray spectrum. Relative-a-posteriori (RAP) probability contours are sampled to illustrate the range of alternative solutions. Then, maximum-entropy profiles from several RAP contours are used to predict the range of individual MAP solutions that would be computed for replicate data sets. This new method of exploratory variance analysis is referred to as maximum-entropy-relative-a-posteriori (MERAP) analysis. Example problems emphasize proof-of-principle demonstrations rather than development of optimized, robust algorithms.

Letellier, Bruce Clark

1998-11-01

29

Gamma Rays  

MedlinePLUS

... infrared, and ultraviolet light, are part of the electromagnetic spectrum. While gamma rays and x-rays pose the same kind of hazard, they differ in their origin. Gamma rays originate in the nucleus. X-rays originate in the electron fields surrounding the nucleus or are machine-produced. What ...

30

Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses.  

PubMed

High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90° collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF2 scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF2 scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured. PMID:23742543

Taira, Y; Toyokawa, H; Kuroda, R; Yamamoto, N; Adachi, M; Tanaka, S; Katoh, M

2013-05-01

31

Photon-induced positron annihilation lifetime spectroscopy using ultrashort laser-Compton-scattered gamma-ray pulses  

NASA Astrophysics Data System (ADS)

High-energy ultrashort gamma-ray pulses can be generated via laser Compton scattering with 90° collisions at the UVSOR-II electron storage ring. As an applied study of ultrashort gamma-ray pulses, a new photon-induced positron annihilation lifetime spectroscopy approach has been developed. Ultrashort gamma-ray pulses with a maximum energy of 6.6 MeV and pulse width of 2.2 ps created positrons throughout bulk lead via pair production. Annihilation gamma rays were detected by a BaF2 scintillator mounted on a photomultiplier tube. A positron lifetime spectrum was obtained by measuring the time difference between the RF frequency of the electron storage ring and the detection time of the annihilation gamma rays. We calculated the response of the BaF2 scintillator and the time jitter caused by the variation in the total path length of the ultrashort gamma-ray pulses, annihilation gamma rays, and scintillation light using a Monte Carlo simulation code. The positron lifetime for bulk lead was successfully measured.

Taira, Y.; Toyokawa, H.; Kuroda, R.; Yamamoto, N.; Adachi, M.; Tanaka, S.; Katoh, M.

2013-05-01

32

Fermi large area telescope observations of the cosmic-ray induced gamma-ray emission of the Earth's atmosphere  

Microsoft Academic Search

We report on measurements of the cosmic-ray induced gamma-ray emission of Earth's atmosphere by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The Large Area Telescope has observed the Earth during its commissioning phase and with a dedicated Earth limb following observation in September 2008. These measurements yielded ˜6.4×106 photons with energies >100MeV and ˜250 hours total

A. A. Abdo; M. Ackermann; M. Ajello; W. B. Atwood; L. Baldini; J. Ballet; G. Barbiellini; D. Bastieri; B. M. Baughman; K. Bechtol; R. Bellazzini; B. Berenji; E. D. Bloom; E. Bonamente; A. W. Borgland; A. Bouvier; J. Bregeon; A. Brez; M. Brigida; P. Bruel; R. Buehler; T. H. Burnett; S. Buson; G. A. Caliandro; R. A. Cameron; P. A. Caraveo; J. M. Casandjian; C. Cecchi; Ö. Çelik; E. Charles; A. Chekhtman; J. Chiang; S. Ciprini; R. Claus; J. Cohen-Tanugi; J. Conrad; F. de Palma; S. W. Digel; E. Do Couto E Silva; P. S. Drell; R. Dubois; D. Dumora; C. Farnier; C. Favuzzi; S. J. Fegan; W. B. Focke; P. Fortin; M. Frailis; Y. Fukazawa; S. Funk; P. Fusco; F. Gargano; N. Gehrels; S. Germani; B. Giebels; N. Giglietto; F. Giordano; T. Glanzman; G. Godfrey; I. A. Grenier; M.-H. Grondin; J. E. Grove; L. Guillemot; S. Guiriec; E. Hays; D. Horan; R. E. Hughes; G. Jóhannesson; A. S. Johnson; T. J. Johnson; W. N. Johnson; T. Kamae; H. Katagiri; J. Kataoka; N. Kawai; M. Kerr; J. Knödlseder; M. Kuss; J. Lande; L. Latronico; M. Lemoine-Goumard; F. Longo; F. Loparco; B. Lott; M. N. Lovellette; P. Lubrano; A. Makeev; M. N. Mazziotta; J. E. McEnery; C. Meurer; P. F. Michelson; W. Mitthumsiri; T. Mizuno; C. Monte; M. E. Monzani; A. Morselli; I. V. Moskalenko; S. Murgia; P. L. Nolan; J. P. Norris; E. Nuss; T. Ohsugi; A. Okumura; N. Omodei; E. Orlando; J. F. Ormes; D. Paneque; J. H. Panetta; D. Parent; V. Pelassa; M. Pepe; M. Pesce-Rollins; F. Piron; T. A. Porter; S. Rainò; R. Rando; M. Razzano; A. Reimer; O. Reimer; T. Reposeur; L. S. Rochester; A. Y. Rodriguez; M. Roth; H. F.-W. Sadrozinski; A. Sander; P. M. Saz Parkinson; C. Sgrò; G. H. Share; E. J. Siskind; D. A. Smith; P. D. Smith; G. Spandre; P. Spinelli; M. S. Strickman; D. J. Suson; H. Takahashi; T. Tanaka; J. B. Thayer; J. G. Thayer; D. J. Thompson; L. Tibaldo; D. F. Torres; G. Tosti; A. Tramacere; Y. Uchiyama; T. L. Usher; V. Vasileiou; N. Vilchez; V. Vitale; A. P. Waite; P. Wang; B. L. Winer; K. S. Wood; T. Ylinen; M. Ziegler

2009-01-01

33

On the determination of nitrogen in carbon matrix by deuteron induced gamma-ray emission technique  

NASA Astrophysics Data System (ADS)

The systematic study of the experimental conditions affecting the minimum detection limit attainable by the deuteron induced gamma-ray emission (DIGE) method in the case of nitrogen determination in carbon matrix is presented. An optimal experimental set-up has been realized with the use of plate glass linings of the transport tube and chamber close to the target and using copper diaphragms for shaping the beam. The necessity of the reduction of electronic pile-up and the cosmic background is also discussed. The best detection limit obtained was 130 ?g/g. A comparison with other analytical methods has been made.

Sziki, G. Á.; Elekes, Z.; Uzonyi, I.; Kiss, Á. Z.

2002-05-01

34

Magnetic Compton-induced pair cascade model for gamma-ray pulsars  

NASA Technical Reports Server (NTRS)

Electrons accelerated to relativistic energies in pulsar magnetospheres will Compton scatter surface thermal emission and nonthermal optical, UV, and soft X-ray emission to gamma-ray energies, thereby initiating a pair cascade through synchrotron radiation and magnetic pair production. This process is proposed as the origin of the high-energy radiation that has been detected from six isolated pulsars. We construct an analytic model of magnetic Compton scattering near the polar cap of isolated pulsar magnetospheres and present approximate analytic derivations for scattered spectra, electron energy-loss rates, and photon luminosities. A Monte Carlo simulation is used to model the pair cascade induced by relativistic electrons scattering photons through the cyclotron resonance. For simplicity, the primary electrons are assumed to be monoenergetic and the nonresonant emission is omitted. Assuming that the angle phi(sub B) between the magnetic and spin axes is approximately equal to the polar-cap angle theta(sub pc), this model can produce both double-peaked and broad single-peaked pulse profiles and account for the trend of harder gamma-ray spectra observed from older pulsars.

Sturner, Steven J.; Dermer, Charles D.; Michel, F. Curtis

1995-01-01

35

Gamma-ray bursts and cosmic rays from accretion-induced collapse  

NASA Technical Reports Server (NTRS)

It is shown that the birth of naked or nearly naked neutron stars in accretion-induced collapse or in the bare collapse of white dwarfs can produce cosmological gamma-ray bursts and can provide the required injection rate of cosmic rays into the interstellar space. It is estimated that most of the e(+)e(-) pairs annihilate in flight on a short time scale in the vicinity of the neutron star. It is shown that the gamma-ray bursts, the 0.511 MeV Galactic annihilation radiation, and the cosmic rays exclude the possibility that the large uncertainties in the Galactic pulsar birthrate and the Galactic SN II explosion rate would allow a significant contribution to the pulsar birthrate from naked or nearly naked neutron star formation. The upper bound on the Galactic birthrate of naked or nearly naked neutron stars of less than 1 in 1000 yr makes it very unlikely that a neutrino burst unaccompanied by optical emission from the birth of a naked or nearly naked neutron star will be detected in the near future by underground neutrino telescopes.

Dar, Arnon; Kozlovsky, Ben Z.; Nussinov, Shmuel; Ramaty, Reuven

1992-01-01

36

THE INTERNAL-COLLISION-INDUCED MAGNETIC RECONNECTION AND TURBULENCE (ICMART) MODEL OF GAMMA-RAY BURSTS  

SciTech Connect

The recent Fermi observation of GRB 080916C shows that the bright photosphere emission associated with a putative fireball is missing, which suggests that the central engine likely launches a Poynting-flux-dominated (PFD) outflow. We propose a model of gamma-ray burst (GRB) prompt emission in the PFD regime, namely, the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. It is envisaged that the GRB central engine launches an intermittent, magnetically dominated wind, and that in the GRB emission region, the ejecta is still moderately magnetized (e.g., 1 {approx}< {sigma} {approx}< 100). Similar to the internal shock (IS) model, the mini-shells interact internally at the radius R{sub IS} {approx} {Gamma}{sup 2} c{Delta}t. Most of these early collisions, however, have little energy dissipation, but serve to distort the ordered magnetic field lines entrained in the ejecta. At a certain point, the distortion of magnetic field configuration reaches the critical condition to allow fast reconnection seeds to occur, which induce relativistic MHD turbulence in the interaction regions. The turbulence further distorts field lines easing additional magnetic reconnections, resulting in a runway release of the stored magnetic field energy (an ICMART event). Particles are accelerated either directly in the reconnection zone, or stochastically in the turbulent regions, which radiate synchrotron photons that power the observed gamma rays. Each ICMART event corresponds to a broad pulse in the GRB light curve, and a GRB is composed of multiple ICMART events. This model retains the merits of IS and other models, but may overcome several difficulties/issues faced by the IS model (e.g., low efficiency, fast cooling, electron number excess, Amati/Yonetoku relation inconsistency, and missing bright photosphere). Within this model, the observed GRB variability timescales could have two components, one slow component associated with the central engine time history, and another fast component associated with relativistic magnetic turbulence in the emission region. The model predicts a decrease of gamma-ray polarization degree and E{sub p} in each ICMART event (broad pulse) during the prompt GRB phase, as well as a moderately magnetized external reverse shock. The model may be applied to the GRBs that have time-resolved, featureless Band-function spectra, such as GRB 080916C and most GRBs detected by Fermi LAT.

Zhang Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); Yan Huirong [Kavli Institute of Astronomy and Astrophysics, Peking University, Beijing 100871 (China)

2011-01-10

37

The Internal-collision-induced Magnetic Reconnection and Turbulence (ICMART) Model of Gamma-ray Bursts  

NASA Astrophysics Data System (ADS)

The recent Fermi observation of GRB 080916C shows that the bright photosphere emission associated with a putative fireball is missing, which suggests that the central engine likely launches a Poynting-flux-dominated (PFD) outflow. We propose a model of gamma-ray burst (GRB) prompt emission in the PFD regime, namely, the Internal-Collision-induced MAgnetic Reconnection and Turbulence (ICMART) model. It is envisaged that the GRB central engine launches an intermittent, magnetically dominated wind, and that in the GRB emission region, the ejecta is still moderately magnetized (e.g., 1 <~ ? <~ 100). Similar to the internal shock (IS) model, the mini-shells interact internally at the radius R IS ~ ?2 c?t. Most of these early collisions, however, have little energy dissipation, but serve to distort the ordered magnetic field lines entrained in the ejecta. At a certain point, the distortion of magnetic field configuration reaches the critical condition to allow fast reconnection seeds to occur, which induce relativistic MHD turbulence in the interaction regions. The turbulence further distorts field lines easing additional magnetic reconnections, resulting in a runway release of the stored magnetic field energy (an ICMART event). Particles are accelerated either directly in the reconnection zone, or stochastically in the turbulent regions, which radiate synchrotron photons that power the observed gamma rays. Each ICMART event corresponds to a broad pulse in the GRB light curve, and a GRB is composed of multiple ICMART events. This model retains the merits of IS and other models, but may overcome several difficulties/issues faced by the IS model (e.g., low efficiency, fast cooling, electron number excess, Amati/Yonetoku relation inconsistency, and missing bright photosphere). Within this model, the observed GRB variability timescales could have two components, one slow component associated with the central engine time history, and another fast component associated with relativistic magnetic turbulence in the emission region. The model predicts a decrease of gamma-ray polarization degree and Ep in each ICMART event (broad pulse) during the prompt GRB phase, as well as a moderately magnetized external reverse shock. The model may be applied to the GRBs that have time-resolved, featureless Band-function spectra, such as GRB 080916C and most GRBs detected by Fermi LAT.

Zhang, Bing; Yan, Huirong

2011-01-01

38

Development of compact Compton gamma camera for non-destructive detection and location of hidden explosives with neutron induced prompt gamma-ray imaging  

Microsoft Academic Search

As a unique gamma-ray sensor for detection and location of hidden explosives with neutron induced prompt gamma-ray analysis, we are developing a compact and efficient Compton gamma camera based on stacked BGO scintillator rods to deduce the incident direction of characteristic 10.8 MeV gamma-rays produced from nitrogen abundant in explosives through neutron capture reaction. The detector unit consists of 5.4

T. Iguchi; J. Kawarabayashi; K. Watanabe; H. Kenjyo; A. Uritani

2005-01-01

39

Radiation induced changes in electrical conductivity of chemical vapor deposited silicon carbides under fast neutron and gamma-ray irradiations  

Microsoft Academic Search

The radiation-induced changes in the volume electrical conductivities of chemical vapor deposited silicon carbides (CVD-SiCs) were in-site investigated by performing irradiation using 1.17 and 1.33-MeV gamma-ray and 14-MeV fast neutron beams in air and vacuum. Under gamma-ray irradiation at ionization dose rates of 3.6 and 5.9Gy\\/s and irradiation temperature of approximately 300K, the initial rapid increase in electrical conductivity; this

Bun Tsuchiya; Tatsuo Shikama; Shinji Nagata; Kesami Saito; Syunya Yamamoto; Seiki Ohnishi; Takashi Nozawa

2011-01-01

40

Evaluation of the cosmic-ray induced background in coded aperture high energy gamma-ray telescopes  

NASA Technical Reports Server (NTRS)

While the application of coded-aperture techniques to high-energy gamma-ray astronomy offers potential arc-second angular resolution, concerns were raised about the level of secondary radiation produced in a thick high-z mask. A series of Monte-Carlo calculations are conducted to evaluate and quantify the cosmic-ray induced neutral particle background produced in a coded-aperture mask. It is shown that this component may be neglected, being at least a factor of 50 lower in intensity than the cosmic diffuse gamma-rays.

Owens, Alan; Barbier, Loius M.; Frye, Glenn M.; Jenkins, Thomas L.

1991-01-01

41

Benchmarking computer simulations of neutron-induced, gamma-ray spectroscopy for well logging  

Microsoft Academic Search

The spectroscopy of gamma rays created by thermal neutron capture and inelastic scattering of fast neutrons is commonly used in the study of wellbore geophysics. In this type of well logging, a sonde, consisting of a pulsed source of fast neutrons and gamma ray detectors, is pulled through the formations traversed by the borehole. The many geometries, lithologies, reservoir fluids,

Richard C. Odom; Shawn M. Bailey; Robert D. Wilson

1997-01-01

42

Body Composition to Climate Change Studies--the Many Facets of Neutron Induced Prompt Gamma-ray Analysis.  

National Technical Information Service (NTIS)

In-vivo body composition analysis of humans and animals and in-situ analysis of soil using fast neutron inelastic scattering and thermal neutron capture induced prompt-gamma rays have been described. By measuring carbon (C), nitrogen (N) and oxygen (O), p...

S. Mitra

2008-01-01

43

Characterisation of Melanesian Obsidian Sources and Artefacts Using the Proton Induced gamma-Ray Emission (PIGME) Technique.  

National Technical Information Service (NTIS)

Proton induced gamma-ray emission (PIGME) has been used to determine F, Na and Al concentrations in obsidian from known locations in Melanesia and to relate artefacts from this region to such sources. The PIGME technique is a fast, non-destructive, and ac...

J. R. Bird W. R. Ambrose L. H. Russell M. D. Scott

1981-01-01

44

Search for Neutrino-induced Cascades from Gamma-Ray Bursts with AMANDA  

NASA Astrophysics Data System (ADS)

Using the neutrino telescope AMANDA-II, we have conducted two analyses searching for neutrino-induced cascades from gamma-ray bursts. No evidence of astrophysical neutrinos was found, and limits are presented for several models. We also present neutrino effective areas which allow the calculation of limits for any neutrino production model. The first analysis looked for a statistical excess of events within a sliding window of 1 or 100 s (for short and long burst classes, respectively) during the years 2001-2003. The resulting upper limit on the diffuse flux normalization times E2 for the Waxman-Bahcall model at 1 PeV is 1.6×10-6 GeV cm-2 s-1 sr-1 (a factor of 120 above the theoretical prediction). For this search 90% of the neutrinos would fall in the energy range 50 TeV to 7 PeV. The second analysis looked for neutrino-induced cascades in coincidence with 73 bursts detected by BATSE in the year 2000. The resulting upper limit on the diffuse flux normalization times E2, also at 1 PeV, is 1.5×10-6 GeV cm-2 s-1 sr-1 (a factor of 110 above the theoretical prediction) for the same energy range. The neutrino-induced cascade channel is complementary to the up-going muon channel. We comment on its advantages for searches of neutrinos from GRBs and its future use with IceCube.

Achterberg, A.; Ackermann, M.; Adams, J.; Ahrens, J.; Andeen, K.; Auffenberg, J.; Bahcall, J. N.; Bai, X.; Baret, B.; Barwick, S. W.; Bay, R.; Beattie, K.; Becka, T.; Becker, J. K.; Becker, K.-H.; Berghaus, P.; Berley, D.; Bernardini, E.; Bertrand, D.; Besson, D. Z.; Blaufuss, E.; Boersma, D. J.; Bohm, C.; Bolmont, J.; Böser, S.; Botner, O.; Bouchta, A.; Braun, J.; Burgess, C.; Burgess, T.; Castermans, T.; Chirkin, D.; Christy, B.; Clem, J.; Cowen, D. F.; D'Agostino, M. V.; Davour, A.; Day, C. T.; De Clercq, C.; Demirörs, L.; Descamps, F.; Desiati, P.; De Young, T.; Diaz-Velez, J. C.; Dreyer, J.; Dumm, J. P.; Duvoort, M. R.; Edwards, W. R.; Ehrlich, R.; Eisch, J.; Ellsworth, R. W.; Evenson, P. A.; Fadiran, O.; Fazely, A. R.; Filimonov, K.; Foerster, M. M.; Fox, B. D.; Franckowiak, A.; Gaisser, T. K.; Gallagher, J.; Ganugapati, R.; Geenen, H.; Gerhardt, L.; Goldschmidt, A.; Goodman, J. A.; Gozzini, R.; Griesel, T.; Grullon, S.; Groß, A.; Gunasingha, R. M.; Gurtner, M.; Hallgren, A.; Halzen, F.; Han, K.; Hanson, K.; Hardtke, D.; Hardtke, R.; Hart, J. E.; Hasegawa, Y.; Hauschildt, T.; Hays, D.; Heise, J.; Helbing, K.; Hellwig, M.; Herquet, P.; Hill, G. C.; Hodges, J.; Hoffman, K. D.; Hommez, B.; Hoshina, K.; Hubert, D.; Hughey, B.; Hulth, P. O.; Hultqvist, K.; Hülß, J.-P.; Hundertmark, S.; Inaba, M.; Ishihara, A.; Jacobsen, J.; Japaridze, G. S.; Johansson, H.; Jones, A.; Joseph, J. M.; Kampert, K.-H.; Karg, T.; Karle, A.; Kawai, H.; Kelley, J. L.; Kitamura, N.; Klein, S. R.; Klepser, S.; Kohnen, G.; Kolanoski, H.; Köpke, L.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Kuehn, K.; Labare, M.; Landsman, H.; Leich, H.; Leier, D.; Liubarsky, I.; Lundberg, J.; Lünemann, J.; Madsen, J.; Mase, K.; Matis, H. S.; McCauley, T.; McParland, C. P.; Meli, A.; Messarius, T.; Mészáros, P.; Miyamoto, H.; Mokhtarani, A.; Montaruli, T.; Morey, A.; Morse, R.; Movit, S. M.; Münich, K.; Nahnhauer, R.; Nam, J. W.; Nießen, P.; Nygren, D. R.; Ögelman, H.; Olivas, A.; Patton, S.; Peña-Garay, C.; Pérez de los Heros, C.; Piegsa, A.; Pieloth, D.; Pohl, A. C.; Porrata, R.; Pretz, J.; Price, P. B.; Przybylski, G. T.; Rawlins, K.; Razzaque, S.; Resconi, E.; Rhode, W.; Ribordy, M.; Rizzo, A.; Robbins, S.; Roth, P.; Rott, C.; Rutledge, D.; Ryckbosch, D.; Sander, H.-G.; Sarkar, S.; Schlenstedt, S.; Schmidt, T.; Schneider, D.; Seckel, D.; Semburg, B.; Seo, S. H.; Seunarine, S.; Silvestri, A.; Smith, A. J.; Solarz, M.; Song, C.; Sopher, J. E.; Spiczak, G. M.; Spiering, C.; Stamatikos, M.; Stanev, T.; Steffen, P.; Stezelberger, T.; Stokstad, R. G.; Stoufer, M. C.; Stoyanov, S.; Strahler, E. A.; Straszheim, T.; Sulanke, K.-H.; Sullivan, G. W.; Sumner, T. J.; Taboada, I.; Tarasova, O.; Tepe, A.; Thollander, L.; Tilav, S.; Tluczykont, M.; Toale, P. A.; Tur?an, D.; van Eijndhoven, N.; Vandenbroucke, J.; Van Overloop, A.; Viscomi, V.; Voigt, B.; Wagner, W.; Walck, C.; Waldmann, H.; Walter, M.; Wang, Y.-R.; Wendt, C.; Wiebusch, C. H.; Wikström, G.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Woschnagg, K.; Xu, X. W.; Yodh, G.; Yoshida, S.; Zornoza, J. D.

2007-07-01

45

Isotropic Gamma-Ray Background: Cosmic-Ray-Induced Albedo from Debris in the Solar System?  

Microsoft Academic Search

We calculate the gamma-ray albedo due to cosmic-ray interactions with debris (small rocks, dust, and grains) in the Oort Cloud. We show that under reasonable assumptions a significant proportion of what is called the \\

Igor V. Moskalenko; Troy A. Porter

2009-01-01

46

Proton induced. gamma. -ray analysis of atmospheric aerosols for carbon, nitrogen, and sulfur composition  

Microsoft Academic Search

A technique for the simultaneous quantitative determination of carbon, nitrogen, and sulfur using in-beam ..gamma..-ray spectrometry has been developed for use with atmospheric aerosol samples. Samples are collected on quartz filters, and the aerosol composition is determined by analyzing the ..gamma.. rays emitted following the inelastic scattering of 7.0-MeV protons. Samples are nondestructively irradiated for 1000 s in a helium

Edward S. Macias; C. David. Radcliffe; Charles W. Lewis; Carole R. Sawicki

1978-01-01

47

Charged Particle Induced Radiation damage of Germanium Detectors in Space: Two Mars Observer Gamma-Ray Detectors  

NASA Technical Reports Server (NTRS)

The Mars Observer Gamma-Ray Spectrometer (MO GRS) was designed to measure gamma-rays emitted by the Martian surface. This gamma-ray emission is induced by energetic cosmic-ray particles penetrating the Martian surface and producing many secondary particles and gamma rays. The MO GRS consisted of an high-purity germanium (HPGe) detector with a passive cooler. Since radiation damage due to permanent bombardment of energetic cosmic ray particles (with energies up to several GeV) was expected for the MO GRS HPGe crystal, studies on radiation damage effects of HPGe crystals were carried on earth. One of the HPGe crystals (paradoxically called FLIGHT) was similar to the MO GRS crystal. Both detectors, MO GRS and FLIGHT, contained closed-end coaxial n-type HPGe crystals and had the same geometrical dimensions (5.6 x 5.6 cm). Many other parameters, such as HV and operation temperature, differed in space and on earth, which made it somewhat difficult to directly compare the performance of both detector systems. But among other detectors, detector FLIGHT provided many useful data to better understand radiation damage effects.

Bruekner, J.; Koenen, M.; Evans, L. G.; Starr, R.; Bailey, S. H.; Boynton W. V.

1997-01-01

48

Gamma ray astronomy  

NASA Technical Reports Server (NTRS)

Miscellaneous tasks related to mission operations and data analysis for the Burst and Transient Source Experiment on the Gamma Ray Observatory, to collection, analysis, and interpretation of data from the Marshall Space Flight Center Very Low Frequency transient monitoring program, and to compilation and analysis of induced radioactivity data were performed. The results are summarized and relevant references are included.

Paciesas, William S.

1992-01-01

49

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

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

50

Time correlation of cosmic-ray-induced neutrons and gamma rays at sea level  

NASA Astrophysics Data System (ADS)

The neutrons and gamma rays produced by cosmic ray interactions in spallation and evaporation processes of air nuclei are time-correlated. The occurrence of their counts in a fixed time interval is not a random (Poisson) distribution, but rather time-correlated bursts of counts. A computational model is developed to explore time correlations of cosmic-ray-induced background of neutrons and gammas at sea level. Their lifetimes in air showers, multiplicity distributions, coincidence count statistic, and excess variance are analyzed. The effects of latitude and area size on multiplicity and coincidence distributions are also studied. The coincidence count distributions and Feynman-Y statistic are used to reveal the duration of spallation processes and properties of multiplying media. It is found that the coincidence count distribution in fixed time intervals deviates from a Poisson distribution. The Feynman-Y is about an order of magnitude greater for gammas than that for neutrons. For both neutrons and gammas, the duration of time-correlated multiplying processes in air showers is ~250 µs.

Miloshevsky, G.; Hassanein, A.

2014-02-01

51

Development of an intense, pulsed source of combined characteristic-gamma-rays and neutrons to induce fission  

Microsoft Academic Search

The detection of fissile material by passive and active techniques is an area of intense interest. Many active approaches detect the products of fission induced by photon and\\/or neutron irradiation.1 One such approach has focused on using intense, pulsed, beam-target interactions to produce an irradiation source of 6.13-, 6.92-, and 7.13-MeV characteristic gamma rays from the 19F(p, ??)16O reaction.2,3 Initially,

R. J. Commisso; J. W. Schumer; J. P. Apruzese; R. J. Allen; G. Cooperstein; D. D. Hinshelwood; S. L. Jackson; D. Mosher; D. P. Murphy; P. F. Ottinger; D. G. Phipps; S. B. Swanekamp; B. V. Weber; F. C. Young; A. Hunt; M. Gagliardi; H. Seipel

2010-01-01

52

Method and apparatus for neutron induced gamma ray logging for direct porosity identification  

SciTech Connect

In a gamma ray well logging instrument, a neutron generator is pulsed at a predetermined rate. Each neutron burst produces gamma radiation resulting from inelastic scattering and neutron capture. The detected gamma radiations are detected by a detector system within the logging instrument. The detected pulses are transmitted to the surface electronics where pulses occurring in the inelastic interval are directed to one section of a multi-channel analyzer and pulses from the capture interval are directed to another section of the analyzer. The use of address decoders and ratio circuits enables an electrical signal to be obtained which represents the ratio of the total capture gamma ray counts within an energy range to the total inelastic gamma ray counts within the same energy range. This electrical signal is representative of the porosity of the subsurface formations being irradiated by neutrons.

Oliver, D.W.; Chace, D.M.

1984-02-07

53

EMISSION PATTERNS AND LIGHT CURVES OF GAMMA RAYS IN THE PULSAR MAGNETOSPHERE WITH A CURRENT-INDUCED MAGNETIC FIELD  

SciTech Connect

We study the emission patterns and light curves of gamma rays in the pulsar magnetosphere with a current-induced magnetic field perturbation. Based on the solution of a static dipole with the magnetic field induced by some currents (perturbation field), we derive the solutions of a static as well as a retarded dipole with the perturbation field in the Cartesian coordinates. The static (retarded) magnetic field can be expressed as the sum of the pure static (retarded) dipolar magnetic field and the static (retarded) perturbation field. We use the solution of the retarded magnetic field to investigate the influence of the perturbation field on the emission patterns and light curves, and apply the perturbed solutions to calculate the gamma-ray light curves for the case of the Vela pulsar. We find that the perturbation field induced by the currents will change the emission patterns and then the light curves of gamma rays, especially for a larger perturbation field. Our results indicate that the perturbation field created by the outward-flowing (inward-flowing) electrons (positrons) can decrease the rotation effect on the magnetosphere and makes emission pattern appear to be smoother relative to that of the pure retarded dipole, but the perturbation field created by the outward-flowing (inward-flowing) positrons (electrons) can make the emission pattern less smooth.

Li, X.; Zhang, L., E-mail: lizhang@ynu.edu.cn [Department of Physics, Yunnan University, Kunming (China)

2011-12-20

54

Gamma-ray Induced Two and Three-body Breakup of ^3He  

Microsoft Academic Search

Using monoenergetic gamma-ray beams at the High-Intensity Gamma-ray Source (HIGS) at Duke University\\/TUNL and a high-pressure ^3He gas scintillator as both target and detector, the two-body total breakup cross section for the reaction ^3He(gamma,p)d was measured at E_gamma = 10.0, 12.5 and 15 MeV. This is the energy range where large discrepancies exist between different data sets and where the

W. Tornow; J. H. Esterline; C. R. Howell; A. P. Tonchev; H. J. Karwowski; J. H. Kelley; J. Li; S. F. Mikhailov; I. V. Pinayev; J. K. Wu; G. J. Weisel; H. Witala

2004-01-01

55

Gamma-ray induced inhibition of DNA synthesis in ataxia telangiectasia fibroblasts is a function of excision repair capacity  

SciTech Connect

The extent of the deficiency in ..gamma..-ray induced DNA repair synthesis in an ataxia telangiectasia (AT) human fibroblast strain was found to show no oxygen enhancement, consistent with a defect in the repair of base damage. Repair deficiency, but not repair proficiency, in AT cells was accompanied by a lack of inhibition of DNA synthesis by either ..gamma..-rays or the radiomimetic drug bleomycin. Experiments with 4-nitroquinoline 1-oxide indicated that lack of inhibition was specific for radiogenic-type damage. Thus excision repair, perhaps by DNA strand incision or chromatin modification, appears to halt replicon initiation in irradiated repair proficient cells whereas in repair defective AT strains this putatively important biological function is inoperative.

Smith, P.J.; Paterson, M.C.

1980-12-16

56

Multiple fractions of gamma rays induced resistance to cis-dichloro-diammineplatinum (II) and methotrexate in human HeLa cells  

SciTech Connect

Previous irradiation could induce changes in the cell-sensitivity to additional cytotoxic agents. In this study we examined whether the sensitivity to additional cytotoxic agents was affected in cells irradiated with multiple fractions of gamma rays if these agents were given at the time when the lesions induced in DNA by radiation have already been repaired. Human cervix carcinoma HeLa cells were irradiated daily with 0.5 Gy of gamma rays five times a week for 6 weeks. When the fractionation regimen was completed, that is when the cells had accumulated the total dose of 15 Gy of gamma rays, the sensitivity of these cells to gamma rays, UV light, cis-dichlorodiammineplatinum (II) (cis-DDP), methotrexate (MTX), and hydroxyurea (HU) was examined and compared to control cells. Results revealed that preirradiated cells did not change sensitivity to gamma rays and UV light, but that they increased the resistance to cis-DDP, and MTX (especially for higher concentrations of MTX), and increased sensitivity to HU (for lower concentrations of HU). The increased resistance to cis-DDP was also measurable up to 30 days after the last dose of gamma rays. The results indicate that preirradiation of HeLa cells with multiple fractions of gamma rays could change their sensitivity to additional cytotoxic agents, and that this is a relatively long-lasting effect. Our results suggest that caution is needed in medical application of radiation combined with chemical treatment.

Osmak, M.; Perovic, S. (Ruder Boskovic Institute, Croatia (Yugoslavia))

1989-06-01

57

Measuring the correlation length of intergalactic magnetic fields from observations of gamma-ray induced cascades  

NASA Astrophysics Data System (ADS)

Context. The imaging and timing properties of ?-ray emission from electromagnetic cascades initiated by very-high-energy (VHE) ?-rays in the intergalactic medium depend on the strength B and correlation length ?B of intergalactic magnetic fields (IGMF). Aims: We study the possibility of measuring both B and ?B via observations of the cascade emission with ?-ray telescopes. Methods: For each measurement method, we find two characteristics of the cascade signal, which are sensitive to the IGMF B and ?B values in different combinations. For the case of IGMF measurement using the observation of extended emission around extragalactic VHE ?-ray sources, the two characteristics are the slope of the surface brightness profile and the overall size of the cascade source. For the case of IGMF measurement from the time delayed emission, these two characteristics are the initial slope of the cascade emission light curve and the overall duration of the cascade signal. Results: We show that measurement of the slope of the cascade induced extended emission and/or light curve can both potentially provide measure of the IGMF correlation length, provided it lies within the range 10 kpc ? ?B ? 1 Mpc. For correlation lengths outside this range, gamma-ray observations can provide an upper or lower bound on ?B. The latter of the two methods holds great promise in the near future for providing a measurement/constraint using measurements from present/next-generation ?-ray-telescopes. Conclusions: Measurement of the IGMF correlation length will provide an important constraint on its origin. In particular, it will enable to distinguish between an IGMF of galactic wind origin from an IGMF of cosmological origin.

Neronov, A.; Taylor, A. M.; Tchernin, C.; Vovk, I.

2013-06-01

58

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

National Technical Information Service (NTIS)

The Idaho National Engineering Laboratory (INEL) is developing a novel photoneutron-based nondestructive evaluation technique which uses a pulsed, high-energy (up to 8-MeV) electron accelerator and gamma-ray spectrometry. Highly penetrating pulses of brem...

J. L. Jones

1996-01-01

59

Possible effects on avionics induced by Terrestrial Gamma-Ray Flashes  

NASA Astrophysics Data System (ADS)

We address the issue of the possible susceptibility of typical aircraft electronics exposed to particle, gamma-ray and neutron irradiation coming from Terrestrial Gamma-ray Flashes (TGF). We consider possible scenarios regarding the intensity, the duration, and geometry of TGFs influencing a nearby aircraft, and study their effects on electronic equipment. We calculate, for different assumptions, the total dose and the dose-rate, and estimate single-event effects. We find that in addition to the electromagnetic component (electrons/positrons, gamma-rays) also secondary neutrons produced by gamma-ray photoproduction in the aircraft structure substantially contribute to single-event effects in critical semiconductors components. Depending on the physical characteristics and geometry, TGFs may deliver a large flux of neutrons within a few milliseconds on an aircraft. This flux is calculated to be orders of magnitude larger than the natural cosmic-ray background, and may constitute a serious hazard to aircraft electronic equipment. We present a series of numerical simulations supporting our conclusions. Our results suggest the necessity of dedicated measurement campaigns addressing the radiative and particle environment of aircraft near or within thunderstorms.

Tavani, Marco; Argan, Andrea; Paccagnella, Alessandro; Pesoli, Alessandro; Palma, Francesco; Gerardin, Simone; Bagatin, Marta; Trois, Alessio; Picozza, Piergiorgio; Benvenuti, Piero; Flamini, Enrico; Marisaldi, Martino; Pittori, Carlotta; Giommi, Paolo

2013-04-01

60

Possible effects on avionics induced by terrestrial gamma-ray flashes  

NASA Astrophysics Data System (ADS)

Terrestrial gamma-ray flashes (TGFs) are impulsive (intrinsically sub-millisecond) events associated with lightning in powerful thunderstorms. TGFs turn out to be very powerful natural accelerators known to accelerate particles and generate radiation up to hundreds of MeV energies. The number ratio of TGFs over normal lightning has been measured in tropical regions to be near 10-4. We address in this Article the issue of the possible susceptibility of typical aircraft electronics exposed to TGF particle, gamma ray and neutron irradiation. We consider possible scenarios regarding the intensity, the duration, and geometry of TGFs influencing nearby aircraft, and study their effects on electronic equipment. We calculate, for different assumptions, the total dose and the dose-rate, and estimate single-event-effects. We find that in addition to the electromagnetic component (electrons/positrons, gamma rays) also secondary neutrons produced by gamma-ray photo production in the aircraft structure substantially contribute to single-event effects in critical semiconductors components. Depending on the physical characteristics and geometry, TGFs may deliver a large flux of neutrons within a few milliseconds in an aircraft. This flux is calculated to be orders of magnitude larger than the natural cosmic-ray background, and may constitute a serious hazard to aircraft electronic equipment. We present a series of numerical simulations supporting our conclusions. Our results suggest the necessity of dedicated measurement campaigns addressing the radiative and particle environment of aircraft near or within thunderstorms.

Tavani, M.; Argan, A.; Paccagnella, A.; Pesoli, A.; Palma, F.; Gerardin, S.; Bagatin, M.; Trois, A.; Picozza, P.; Benvenuti, P.; Flamini, E.; Marisaldi, M.; Pittori, C.; Giommi, P.

2013-04-01

61

PROTON INDUCED GAMMA-RAY ANALYSIS OF ATMOSPHERIC AEROSOLS FOR CARBON, NITROGEN, AND SULFUR COMPOSITION  

EPA Science Inventory

A technique for the simultaneous quantitative analysis of carbon, nitrogen, and sulfur using in-beam gamma-ray spectrometry has been developed for use with atmospheric aerosol samples. Samples are collected on quartz filters, and the aerosol composition is determined by analyzing...

62

BREEDING EXPERIMENT ON MUTATION INDUCTION BY IRRADIATION. 1. EFFECTS OF X- AND $gamma$RAY IRRADIATION ON CABBAGE SEEDS  

Microsoft Academic Search

Studies were made on the effects of x and gamma irradiation on dry ; cabbage seeds and the utility of artificially induced mutations in plant breeding ; was examined. The radiosensitivity of cabbage in the R⁠generation and the ; phenotypic mutation in the Râ generation are discussed. Two varieties of ; Succession and Fuji Early were used. The seeds

D. W. Kim; Y. C. Kim; C. H. Lee; K. W. Choe

1962-01-01

63

Application of Time-Series Analysis to Induced Gamma Ray Spectroscopy Logs From Two Cold Lake Heavy-Oil Observation Wells  

Microsoft Academic Search

This paper reports on induced gamma ray spectroscopy (IGRS) logs from two cyclic-steam-stimulation observation wells in Cold Lake that were analyzed to determine the vertical resolution and repeatability of data derived from gamma rays of inelastic and capture neutron reactions. Time-series analysis, a technique that uses the Fourier representation of the log data, was used to quantify the vertical resolution

Daniel Georgi

1991-01-01

64

Limits on thunderstorm-induced radioactive chlorine from gamma ray observations  

NASA Astrophysics Data System (ADS)

We present analysis of thunderstorm data collected with a liquid nitrogen-cooled germanium spectrometer with energies between 13 keV-2.6 MeV that was deployed at Langmuir Lab on South Baldy Peak in New Mexico for June through August 2005. The motivation was to search for gamma ray emissions from radioactive chlorine-39 and chlorine-38, as suggested by Greenfield et al. (2003). Based on the observations, we place an upper limit on the rate of chlorine production through such a process (6.8 × 10-17 chlorine atoms per argon atom). This rate is sufficiently low to suggest that the anomalous gamma ray count increases observed by Greenfield et al. (2003) were not caused by radioactive chlorine.

Lundberg, J. L.; Millan, R. M.; Eack, K.

2011-11-01

65

Magnetic Compton-induced pair cascade model for gamma-ray pulsars  

Microsoft Academic Search

Electrons accelerated to relativistic energies in pulsar magnetospheres will Compton scatter surface thermal emission and nonthermal optical, UV, and soft X-ray emission to gamma-ray energies, thereby initiating a pair cascade through synchrotron radiation and magnetic pair production. This process is proposed as the origin of the high-energy radiation that has been detected from six isolated pulsars. We construct an analytic

Steven J. Sturner; Charles D. Dermer; F. Curtis Michel

1995-01-01

66

Gamma Ray-Induced Loss of Expression of HLA and Glyoxalase I Alleles in Lymphoblastoid Cells  

Microsoft Academic Search

Gamma rays from a cesium source were used to generate human lymphoblastoid cell line variants that had lost expression of all major histocompatibility complex antigens coded for by a single haplotype. The cell line was heterozygous at the glyoxalase I locus and had the HLA haplotypes HLA-A1, B8, DRw3, and HLA-A2, B5, DRw1. We selected with anti-HLA-B8 antiserum in a

Paula Kavathas; Fritz H. Bach; Robert Demars

1980-01-01

67

Cosmic-ray induced gamma-ray emission from the starburst galaxy NGC 253  

NASA Astrophysics Data System (ADS)

Cosmic rays in galaxies interact with the interstellar medium and give us a direct view of nuclear and particle interactions in the cosmos. For example, cosmic-ray proton interactions with interstellar hydrogen produce gamma rays via PcrPism??0???. For a "normal" star-forming galaxy like the Milky Way, most cosmic rays escape the Galaxy before such collisions, but in starburst galaxies with dense gas and huge star formation rate, most cosmic rays do suffer these interactions [1,2]. We construct a "thick-target" model for starburst galaxies, in which cosmic rays are accelerated by supernovae, and escape is neglected. This model gives an upper limit to the gamma-ray emission. Only two free parameters are involved in the model: cosmic-ray proton acceleration energy rate from supernova and the proton injection spectral index. The pionic gamma-radiation is calculated from 10 MeV to 10 TeV for the starburst galaxy NGC 253, and compared to Fermi and HESS data. Our model fits NGC 253 well, suggesting that cosmic rays in this starburst are in the thick target limit, and that this galaxy is a gamma-ray calorimeter.

Wang, Xilu; Fields, Brian D.

2014-05-01

68

Deuteron induced gamma-ray emission method applied at a nuclear microprobe for carbon and oxygen content measurements  

NASA Astrophysics Data System (ADS)

The deuteron induced gamma-ray emission (DIGE) method is not usually used for analytical purposes at nuclear microprobes; therefore we show here its capabilities at the microprobe facility of the Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI). In this paper the compositional analysis of magnetic spherules carried out earlier [Nucl. Instr. and Meth B 181 (2001) 557] is combined with the determination of their carbon and oxygen contents, elements which (beside nitrogen and hydrogen) play a relevant role in the study of planetary evolution and in the elucidation of the composition of cosmic parent bodies.

Elekes, Z.; Szö?r, Gy.; Kiss, Á. Z.; Rózsa, P.; Simon, A.; Uzonyi, I.; Simulák, J.

2002-05-01

69

A Study of Venus Surface Elemental Composition From 14MeV Neutron Induced Gamma Ray Spectroscopy: Activation Analysis  

Microsoft Academic Search

The surface elemental composition of Venus can be determined by using an artificially pulsed 14 MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14 MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through

I. Jun; W. Kim; M. Smith; I. Mitrofanov; M. L. Litvak

2010-01-01

70

Gamma ray camera  

Microsoft Academic Search

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

1997-01-01

71

Gamma ray camera  

Microsoft Academic Search

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

Victor

1997-01-01

72

Gamma-ray Induced Two- and Three-body Breakup of ^3He  

NASA Astrophysics Data System (ADS)

Using monoenergetic ?-ray beams at the High-Intensity Gamma-ray Source (HIGS) at Duke University/TUNL and a high-pressure ^3He gas scintillator as both target and detector, the two-body total breakup cross section for the reaction ^3He(?,p)d was measured at E_? = 10.0, 12.5 and 15 MeV. This is the energy range where large discrepancies exist between different data sets and where the calculations are sensitive to three-nucleon force effects. Preliminary results will be presented. The photon analyzing power for the kinematically incomplete three-body breakup of ^3He was measured at ?n = 90^o (lab) using 15 MeV linearly polarized ?-rays. The neutrons were detected with two pairs of liquid scintillators positioned in the horizontal and vertical planes. Our preliminary result is in excellent agreement with rigorous 3N calculations.

Tornow, W.; Esterline, J. H.; Howell, C. R.; Tonchev, A. P.; Karwowski, H. J.; Kelley, J. H.; Li, J.; Mikhailov, S. F.; Pinayev, I. V.; Wu, J. K.; Weisel, G. J.; Witala, H.

2004-10-01

73

Formation and Repair of gamma-Ray Induced Nucleic Acid Base Damage in Bacteria and Mammalian Cells. Final Report, September 1, 1973--August 31, 1976.  

National Technical Information Service (NTIS)

Results are summarized from a three-year study of the formation and repair of gamma -ray induced thymine damage in bacteria and mammalian cells. A systematic study was made of the formation of a specific type of ionizing radiation induced base damage unde...

P. A. Cerutti

1976-01-01

74

Gamma-ray waveguides  

SciTech Connect

We have developed an approach for gamma-ray optics using layered structures acting as planar waveguides. Experiments demonstrating channeling of 122 keV gamma rays in two prototype waveguides validate the feasibility of this technology. Gamma-ray waveguides allow one to control the direction of radiation up to a few MeV. The waveguides are conceptually similar to polycapillary optics, but can function at higher gamma-ray energies. Optics comprised of these waveguides will be able to collect radiation from small solid angles or concentrate radiation into small area detectors. Gamma-ray waveguides may find applications in medical imaging and treatment, astrophysics, and homeland security.

Tournear, D. M.; Hoffbauer, M. A.; Akhadov, E. A.; Chen, A. T.; Pendleton, S. J.; Williamson, T. L.; Cha, K. C.; Epstein, R. I. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2008-04-14

75

A study of Venus surface elemental composition from 14 MeV neutron induced gamma ray spectroscopy: Activation analysis  

Microsoft Academic Search

The surface elemental composition of Venus can be determined using an artificially pulsed 14MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through 3 different neutron

I. Jun; W. Kim; M. Smith; I. Mitrofanov; M. Litvak

2011-01-01

76

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

SciTech Connect

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 by 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.

Trani, Daniela [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States) [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States); Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Maastricht Radiation Oncology (MaastRO) Lab, GROW-School for Oncology and Developmental Biology, University of Maastricht (Netherlands); Moon, Bo-Hyun [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States) [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States); Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Kallakury, Bhaskar; Hartmann, Dan P. [Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States)] [Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Datta, Kamal [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States) [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States); Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Fornace, Albert J., E-mail: af294@georgetown.edu [Department of Biochemistry and Molecular and Cellular Biology, Georgetown University, Washington, District of Columbia (United States); Lombardi Comprehensive Cancer Center, Georgetown University Medical Center, Washington, District of Columbia (United States); Center of Excellence in Genomic Medicine Research (CEGMR), King Abdulaziz University, Jeddah (Saudi Arabia)

2013-01-01

77

Fluorine concentrations in bone biopsy samples determined by proton-induced gamma-ray emission and cyclic neutron activation.  

PubMed

Fluorine concentrations in bone biopsy samples taken from the iliac crest of subjects, divided into four groups depending on the length of dialysis treatment, and aluminium levels in blood and bone pathology, in terms of osteoporosis, were determined by two instrumental methods. Proton-induced gamma-ray emission (PIGE), making use of the resonance reaction of 19F(p, alpha gamma)16O at 872 keV, and cyclic neutron activation analysis (CNAA), using the 19F(n, gamma)20F reaction in a reactor irradiation facility, were employed. Rutherford backscattering (RBS) was used to calculate the volume, and, hence, mass of the sample excited in PIGE by determining the major element composition of the samples in order to express results in terms of concentration. From this preliminary investigation, a relationship is suggested between fluorine concentrations in bone and aluminium levels in the system. PMID:1704715

Spyrou, N M; Altaf, W J; Gill, B S; Jeynes, C; Nicolaou, G; Pietra, R; Sabbioni, E; Surian, M

1990-01-01

78

Determination of total fluorine in five coal reference materials by proton-induced gamma-ray emission spectrometry.  

PubMed

The direct non-destructive proton-induced gamma-ray emission (PIGE) technique with a germanium detector was applied to the determination of total fluorine concentration in five coal reference materials (BCR 40, NIST 1632b, NIST 1635, SARM 20 and USGS CLB-1). Duplicate analyses were made from five randomly selected bottles of each coal. Individual data are presented and some problems (calibration, proton stopping power, effects of sample heating by the proton beam, background estimation) which were encountered during this study are discussed. Sensitivity and reproducibility of the determinations, and homogeneity of the coal samples with respect to fluorine contents by analysis of variance were investigated. The present data are also compared with the few published values for these reference samples, including other PIGE data. The use of synthetic standards and spiked samples in the present study suggested that the PIGE method was more accurate than other techniques. PMID:18966506

Roelandts, I; Robaye, G; Delbrouck-Habaru, J M; Weber, G

1996-03-01

79

Thermal and Gamma-ray induced relaxation in As-S glasses: modeling and experiment  

SciTech Connect

Enthalpy relaxation is measured in a series of As-S glasses irradiated with gamma rays and these samples are compared with a set of identical control samples kept in the dark. It is shown that gamma irradiation lifts the kinetic barrier for relaxation at room temperature and speeds up the enthalpy release. The measured values of thermal relaxation in the dark agree closely with modeling results obtained by fitting differential scanning calorimetry curves with the TNM equations. The measured values of activation energy for enthalpy relaxation are also in close agreement with that predicted by the TNM model therefore lending credence to the fitting results. These measurements permit extraction of the effect of gamma irradiation on the glass structure for a series of As-S glasses with increasing structural coordination, and gamma irradiation is shown to reduce the structural relaxation time. It is also shown that lower coordination glasses exhibit greater radiation sensitivity but also greater thermal relaxation due to their lower Tg. On the other end, over-coordinated glasses show lower relaxation and almost no radiation sensitivity. This behavior is similar to the glass response under sub-bandgap light irradiation.

Lucas, Pierre; King, Ellyn A.; Erdmann, Robert G.; Riley, Brian J.; Sundaram, S. K.; McCloy, John S.

2011-09-09

80

Assessment of gamma ray-induced DNA damage in Lasioderma serricorne using the comet assay  

NASA Astrophysics Data System (ADS)

We attempted a DNA comet assay under alkaline conditions to verify the irradiation treatment of pests. Lasioderma serricorne (Fabricius) were chosen as test insects and irradiated with gamma rays from a 60Co source at 1 kGy. We conducted the comet assay immediately after irradiation and over time for 7 day. Severe DNA fragmentation in L. serricorne cells was observed just after irradiation and the damage was repaired during the post-irradiation period in a time-dependent manner. The parameters of the comet image analysis were calculated, and the degree of DNA damage and repair were evaluated. Values for the Ratio (a percentage determined by fluorescence in the damaged area to overall luminance, including intact DNA and the damaged area of a comet image) of individual cells showed that no cells in the irradiated group were included in the Ratio<0.1 category, the lowest grade. This finding was observed consistently throughout the 7-day post-irradiation period. We suggest that the Ratio values of individual cells can be used as an index of irradiation history and conclude that the DNA comet assay under alkaline conditions, combined with comet image analysis, can be used to identify irradiation history.

Kameya, Hiromi; Miyanoshita, Akihiro; Imamura, Taro; Todoriki, Setsuko

2012-03-01

81

Gamma ray-induced loss of expression of HLA and glyoxalase I alleles in lymphoblastoid cells  

SciTech Connect

Gamma rays from a cesium source were used to generate human lymphoblastoid cell line variants that had lost expression of all major histocompatibility complex antigens coded for by a single haplotype. The cell line was heterozygous at the glyoxalase I locus and had the HLA haplotypes HLA-A1, B8, DRw3, and HLA-A2, B5, DRw1. We selected with anti-HLA-B8 antiserum in a population of cells that had been irradiated with 300R. The incidence of B8-loss variants was 4.1 X 10/sup -5/ on day 5 after irradiation. Analysis of variants showed that expressions of HLA and GLO alleles trans to B8 were retained. However, expression of additional cis-linked HLA and GLO gene products was lost in 12 of 17 variants. Variants that had lost expression of (i) HLA-B8, (ii) HLA-B8, A1, (iii) HLA-B8, A1, DRw3, or (iv) HLA-B8, A1, DRw3 and the cis-linked glyoxalase I allele were obtained. Karyotype analysis was performed on eight variants that had lost expression of two or more cis-linked alleles. Three variants had two normal appearing no. 6 chromosomes, four variants had a deletion that included the region coding for HLA genes on the short arm of one no. 6 chromosome, and one variant had an inversion or translocation involving the short arm of one no. 6.

Kavathas, P.; Bach, F.H.; DeMars, R.

1980-07-01

82

Growth and sedimentation of fine particles produced in aqueous solutions of palladium sulfate and palladium sulfate-silver sulfate induced by gamma-ray irradiation.  

National Technical Information Service (NTIS)

It is known that palladium and palladium-silver fine particles were formed from deaerated aqueous solutions of palladium sulfate and palladium sulfate-silver sulfate induced by gamma-ray irradiation. Changes in particle size and with amount of particles i...

M. Hatada C. D. Jonah

1994-01-01

83

Gamma-Ray Pulsars  

Microsoft Academic Search

Gamma-ray photons from young pulsars allow the deepest insight into the properties and interactions of high-energy particles with magnetic and photon fields in a pulsar magnetosphere. Measurements with the Compton Gamma-Ray Observatory have led to the detection of nearly ten Gamma-ray pulsars. Although quite a variety of individual signatures is found for these pulsars, some general characteristics can be summarized:

Gottfried Kanbach

2002-01-01

84

Gamma ray transients  

NASA Technical Reports Server (NTRS)

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.

Cline, Thomas L.

1987-01-01

85

Freshly induced short-lived gamma-ray activity as a measure of fission rates in lightly re-irradiated spent fuel  

NASA Astrophysics Data System (ADS)

A new measurement technique has been developed to determine fission rates in burnt fuel, following re-irradiation in a zero-power research reactor. The development has been made in the frame of the LIFE@PROTEUS program at the Paul Scherrer Institute, which aims at characterizing the interfaces between fresh and highly burnt fuel assemblies in modern LWRs. To discriminate against the high intrinsic gamma-ray activity of the burnt fuel, the proposed measurement technique uses high-energy gamma-rays, above 2000 keV, emitted by short-lived fission products freshly produced in the fuel. To demonstrate the feasibility of this technique, a fresh UO 2 sample and a 36 GWd/t burnt UO 2 sample were irradiated in the PROTEUS reactor and their gamma-ray activities were recorded directly after irradiation. For both fresh and the burnt fuel samples, relative fission rates were derived for different core positions, based on the short-lived 142La (2542 keV), 89Rb (2570 keV), 138Cs (2640 keV) and 95Y (3576 keV) gamma-ray lines. Uncertainties on the inter-position fission rate ratios were mainly due to the uncertainties on the net-area of the gamma-ray peaks and were about 1-3% for the fresh sample, and 3-6% for the burnt one. Thus, for the first time, it has been shown that the short-lived gamma-ray activity, induced in burnt fuel by irradiation in a zero-power reactor, can be used as a quantitative measure of the fission rate. For both fresh and burnt fuel, the measured results agreed, within the uncertainties, with Monte Carlo (MCNPX) predictions.

Kröhnert, H.; Perret, G.; Murphy, M. F.; Chawla, R.

2010-12-01

86

Nucleosynthesis in Jet-induced Supernovae: Connection between Gamma-Ray Bursts and Extremely Metal-Poor Stars  

NASA Astrophysics Data System (ADS)

Jet-induced supernovae (SNe) have been suggested to take place in gamma-ray bursts (GRBs) and highly-energetic SNe (hypernovae). I summarize hydrodynamical and nucleosynthetic properties of the jet-induced explosion of a population (Pop) III 40 Msolar star. In particular, I present the aspherical effect on nucleosynthetic yield and its dependence on properties of the relativistic jets. Nucleosynthesis in Pop III SNe can be constrained by abundance patterns of extremely metal-poor (EMP) stars which were formed in the early universe. The jet-induced SNe acquire favorable features for EMP stars as follows: (1) the ejection of Fe-peak products and the fallback of unprocessed materials are compatibly realized and (2) the varieties of energy deposition rates in the jet-induced SNe explains a trend of [C/Fe] in the EMP stars. Furthermore, the variation of energy deposition rates lead the variation of ejected 56Ni(Fe) masses, and thus can explain both GRB-associated SNe and GRBs without bright SNe, GRBs 060505 and 060614. Therefore, I propose the analogical origins of GRBs and EMP stars and their connection.

Tominaga, Nozomu

2010-10-01

87

Gamma Ray Bursts.  

National Technical Information Service (NTIS)

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 pion...

N. Gehrels P. Meszaros

2012-01-01

88

Gamma-Ray Pulsars  

NASA Technical Reports Server (NTRS)

The Fermi Gamma-Ray Space Telescope has revolutionized the study of pulsar physics with the detection of over 80 gamma-ray pulsars. Several new populations have been discovered, including 24 radio quiet pulsars found through gamma-ray pulsations alone and about 20 millisecond gamma-ray pulsars. The gamma-ray pulsations from millisecond pulsars were discovered by both folding at periods of known radio millisecond pulsars or by detecting them as gamma-ray sources that are followed up by radio pulsar searches. The second method has resulted in a phenomenally successful synergy, with -35 new radio MSPs (to date) having been discovered at Fermi unidentified source locations and the gamma-ray pulsations having then been detected in a number of these using the radio timing solutions. The higher sensitivity and larger energy range of the Fermi Large Area Telescope has produced detailed energy-dependent light curves and phase-resolved spectroscopy on brighter pulsars, that have ruled out polar cap models as the major source of the emission in favor of outer magnetosphere accelerators. The large number of gamma-ray pulsars now allows for the first time meaningful population and sub-population studies that are revealing surprising properties of these fascinating sources.

Harding, Alice K.

2011-01-01

89

Gamma-ray Bursts  

NASA Astrophysics Data System (ADS)

Prologue C. Kouveliotou, R. A . M. J. Wijers and S. E. Woosley; 1. The discovery of the gamma-ray burst phenomenon R. W. Klebesadel; 2. Instrumental principles E. E. Fenimore; 3. The BATSE era G. J. Fishman and C. A. Meegan; 4. The cosmological era L. Piro and K. Hurley; 5. The Swift era N. Gehrels and D. N. Burrows; 6. Discoveries enabled by multi-wavelength afterglow observations of gamma-ray bursts J. Greiner; 7. Prompt emission from gamma-ray bursts T. Piran, R. Sari and R. Mochkovitch; 8. Basic gamma-ray burst afterglows P. Mészáros and R. A. M. J. Wijers; 9. The GRB-supernova connection J. Hjorth and J. S. Bloom; 10. Models for gamma-ray burst progenitors and central engines S. E. Woosley; 11. Jets and gamma-ray burst unification schemes J. Granot and E. Ramirez-Ruiz; 12. High-energy cosmic rays and neutrinos E. Waxman; 13. Long gamma-ray burst host galaxies and their environments J. P. U. Fynbo, D. Malesani and P. Jakobsson; 14. Gamma-ray burst cosmology V. Bromm and A. Loeb; 15. Epilogue R. D. Blandford; Index.

Kouveliotou, Chryssa; Wijers, Ralph A. M. J.; Woosley, Stan

2012-11-01

90

Gamma ray detector shield  

DOEpatents

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.

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

1985-08-26

91

Photobleaching effect on gamma-ray and 14 MeV fast neutron induced transmission loss of fused silica core optical fiber  

Microsoft Academic Search

A photo-bleaching effect on radiation-induced transmission loss of fused silica core optical fibers was examined under 60Co gamma-ray and 14 MeV fast neutron irradiation. In the visible wavelength range, radiation induced loss could be reduced by the photo-bleaching under the both irradiation. For using optical fibers in visible wavelength range such as a light guide and an image guide, the

K. Toh; T. Shikama; S. Nagata; Bun Tsuchiya; M. Yamauchi; T. Nishitani

2005-01-01

92

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

PubMed

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 the expression of antioxidant enzymes and proteins with chaperone-related functions, thereby significantly affecting life history parameters such as fecundity and molting in the copepod T. japonicus. PMID:24800869

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

93

In vivo investigation of a new 109Cd gamma-ray induced K-XRF bone lead measurement system.  

PubMed

A new 109Cd gamma-ray induced K-XRF bone lead measurement system using an array of four detectors has been developed. Previous results from Monte Carlo (MC) simulations and experiments with phantoms predicted that it would be about three times more sensitive than the conventional system, albeit using a more active source. A dosimetry study has been performed for this system and it demonstrated that the dose delivered to the measured individuals is acceptable even for 5-year-old children. Approval to apply this system to human studies has been received from the Research Ethics Board. In this study, 20 adult volunteers, 10 male, 10 female, were recruited to have their tibia measured with both the conventional system and the new system. The result confirmed the improvement predicted by the MC simulations and the in vitro measurements. Two other interesting points were discovered from the data. One is that the data from the new system showed a significant positive correlation between age and tibia lead concentration, while the data from the conventional system do not. The other is that 85% of the tibia lead concentrations were under the minimum detection limit when measured by the conventional system, and the proportion reduced to 50% when measured by the new system. PMID:16394343

Nie, Huiling; Chettle, David; Luo, Liqiang; O'Meara, Joanne

2006-01-21

94

Formation and conversion of defect centers in low water peak single mode optical fiber induced by gamma rays irradiation  

NASA Astrophysics Data System (ADS)

The formation and conversion processes of defect centers in low water peak single mode optical (LWPSM) fiber irradiated with gamma rays were investigated at room temperature using electron spin resonance. Germanium electron center (GEC) and self-trapped hole center (STH) occur when the fibers are irradiated with 1 and 5 kGy cumulative doses, respectively. With the increase in irradiation doses, the GEC defect centers disappear, and new defect centers such as E' centers (Si and Ge) and nonbridge oxygen hole centers (NBOHCs) generate. The generation of GEC and STH is attributed to the electron transfer, which is completely balanced. This is the main reason that radiation-induced attenuation (RIA) of the LWPSM fiber is only 10 dB/km at communication window. The new defect centers come from the conversion of GEC and STH to E' centers and NBOHC, and the conversion processes cause bond cleavage, which is the root cause that the RIA of the LWPSM fiber significantly increases up to 180 dB/km at working window. Furthermore, the concentration of new defect centers is saturated easily even by increasing cumulative doses.

Wen, J. X.; Luo, W. Y.; Xiao, Z. Y.; Wang, T. Y.; Chen, Z. Y.; Zeng, X. L.

2010-02-01

95

Cascaded Gamma Rays as a Probe of Cosmic Rays  

NASA Astrophysics Data System (ADS)

Very-high-energy (VHE) and ultra-high-energy (UHE) gamma rays from extragalactic sources experience electromagnetic cascades during their propagation in intergalactic space. Recent gamma-ray data on TeV blazars and the diffuse gamma-ray background may have hints of the cascade emission, which are especially interesting if it comes from UHE cosmic rays. I show that cosmic-ray-induced cascades can be discriminated from gamma-ray-induced cascades with detailed gamma-ray spectra. I also discuss roles of structured magnetic fields, which suppress inverse-Compton pair halos/echoes but lead to guaranteed signals - synchrotron pair halos/echoes.

Murase, Kohta

2014-06-01

96

Induced Mutations for Improving Production on Bread and Durum Wheat  

NASA Astrophysics Data System (ADS)

Wheat is a very important crop and has been bred for food and its improvement is continuous from cross-breeding. Radiation and chemically induced mutations have provided variability in selection for novel varieties. Four bread and one durum wheat cultivars were exposed to gamma rays, Cs 137 with doses 10, 15 and 20 krad (2000 seeds of each dose and cultivars). We have isolated mutant plants with height reduced and on cv Progress spike without chaff.

Stamo, Ilirjana; Ylli, Ariana; Dodbiba, Andon

2007-04-01

97

Induced Mutations for Improving Production on Bread and Durum Wheat  

SciTech Connect

Wheat is a very important crop and has been bred for food and its improvement is continuous from cross-breeding. Radiation and chemically induced mutations have provided variability in selection for novel varieties. Four bread and one durum wheat cultivars were exposed to gamma rays, Cs 137 with doses 10, 15 and 20 krad (2000 seeds of each dose and cultivars). We have isolated mutant plants with height reduced and on cv Progress spike without chaff.

Stamo, Ilirjana; Ylli, Ariana; Dodbiba, Andon [Institute of Biological Research, Academy of Sciences, Rruga Sami Frasheri 5, Tirana (Albania); Institute of Nuclear Physics, Academy of Sciences, P.O. Box 85 Tirana (Albania)

2007-04-23

98

Gamma Ray Pulsars: Observations  

NASA Technical Reports Server (NTRS)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET 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. Unless a new pulsed component appears at higher energies, progress in gamma-ray pulsar studies will be greatest in the 1-20 GeV range. Ground-based telescopes whose energy ranges extend downward toward 10 GeV should make important measurements of the spectral cutoffs. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2005, will provide a major advance in sensitivity, energy range, and sky coverage.

Thompson, David J.; White, Nicholas E. (Technical Monitor)

2000-01-01

99

Gamma-Ray Detectors  

NASA Astrophysics Data System (ADS)

The common methods of analyzing gamma-ray spectra obtained from detectors capable of energy discrimination are discussed. Gamma-ray spectra generally are in the form of detector response versus discrete channel number. The methods considered for gamma-ray spectroscopy are somewhat general and can be applied to other types of spectroscopy. The general objective of spectroscopy is to obtain, at a minimum, the qualitative identification of the source (e.g., source energies or nuclides present). However, most spectroscopy applications seek quantitative information also, as expressed by, e.g., the source strength or the nuclide concentration. Various different methods for qualitative and quantitative analysis are summarized, and an illustrative example is provided. A review of detectors used for gamma-ray spectroscopy is included.

Dunn, William L.; McGregor, Douglas S.

100

A GAMMA-RAY INDUCED ABSORPTION BAND IN SOME LEAD BORATE GLASSES  

Microsoft Academic Search

Observations made on some lead borate, lead aluminoberate, and lead ; beroaluminosilicate glasses showed that an absorption band is induced at 1.5 ev ; (825 m mu ) by gamma irradiation. Experimental evidence indicates that this band ; is associated with Pb\\/sup 2+\\/ ions and beron in the structure of these glasses. ; On replacing PbO by TlâO in a

ADLI M. BISHAY

1960-01-01

101

Measurement of Delayed Gamma-Ray and Neutron Emission from Bremsstrahlung-Induced Fission  

Microsoft Academic Search

Recently, there has been an increased interest in applying nuclear physics principles for detection of smuggled nuclear material. One technique being investigated for the detection of fissile materials is called active detection. Active detection consists of irradiating an unknown sample with an intense source of photons to induce photofission in the sample. The radiation emitted by the fission fragments is

Zephne Larsen; Alan Hunt; Stuart Jackson; David Hinshelwood

2010-01-01

102

Gamma ray pulsars: Observations  

Microsoft Academic Search

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO\\/EGRET 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

David J. Thompson

2001-01-01

103

Estrogens decrease {gamma}-ray-induced senescence and maintain cell cycle progression in breast cancer cells independently of p53  

SciTech Connect

Purpose: Sequential administration of radiotherapy and endocrine therapy is considered to be a standard adjuvant treatment of breast cancer. Recent clinical reports suggest that radiotherapy could be more efficient in association with endocrine therapy. The aim of this study was to evaluate the estrogen effects on irradiated breast cancer cells (IR-cells). Methods and Materials: Using functional genomic analysis, we examined the effects of 17-{beta}-estradiol (E{sub 2}, a natural estrogen) on MCF-7 breast cancer cells. Results: Our results showed that E{sub 2} sustained the growth of IR-cells. Specifically, estrogens prevented cell cycle blockade induced by {gamma}-rays, and no modification of apoptotic rate was detected. In IR-cells we observed the induction of genes involved in premature senescence and cell cycle progression and investigated the effects of E{sub 2} on the p53/p21{sup waf1/cip1}/Rb pathways. We found that E{sub 2} did not affect p53 activation but it decreased cyclin E binding to p21{sup waf1/cip1} and sustained downstream Rb hyperphosphorylation by functional inactivation of p21{sup waf1/cip1}. We suggest that Rb inactivation could decrease senescence and allow cell cycle progression in IR-cells. Conclusion: These results may help to elucidate the molecular mechanism underlying the maintenance of breast cancer cell growth by E{sub 2} after irradiation-induced damage. They also offer clinicians a rational basis for the sequential administration of ionizing radiation and endocrine therapies.

Toillon, Robert-Alain [Laboratoire Jean-Claude Heuson de Cancerologie Mammaire, Universite Libre de Bruxelles, Brussels (Belgium)]. E-mail: robert.toillon@univ-lille1.fr; Magne, Nicolas [Radiotherapy Unit, Institut Jules Bordet, Brussels (Belgium); Laios, Ioanna [Laboratoire Jean-Claude Heuson de Cancerologie Mammaire, Universite Libre de Bruxelles, Brussels (Belgium); Castadot, Pierre [Radiotherapy Unit, Institut Jules Bordet, Brussels (Belgium); Kinnaert, Eric [Radiotherapy Unit, Institut Jules Bordet, Brussels (Belgium); Van Houtte, Paul [Radiotherapy Unit, Institut Jules Bordet, Brussels (Belgium); Desmedt, Christine B.Sc. [Microarray Unit, Institut Jules Bordet, Brussels (Belgium); Leclercq, Guy [Laboratoire Jean-Claude Heuson de Cancerologie Mammaire, Universite Libre de Bruxelles, Brussels (Belgium); Lacroix, Marc [Laboratoire Jean-Claude Heuson de Cancerologie Mammaire, Universite Libre de Bruxelles, Brussels (Belgium)

2007-03-15

104

An imaging neutron/gamma-ray spectrometer  

NASA Astrophysics Data System (ADS)

We present the test results of a neutron/gamma-ray imaging spectrometer for the identification and location of radioactive and special nuclear materials. Radioactive materials that could be fashioned into a radiation dispersal device typically emit gamma rays, while fissile materials such as uranium and plutonium emit both neutrons and gamma rays via spontaneous or induced fission. The simultaneous detection of neutrons and gamma rays is a clear indication of the presence of fissile material. The instrument works as a double-scatter telescope, requiring a neutron or gamma ray to undergo an interaction in two detectors to be considered a valid event. While this requirement reduces the detector efficiency, it yields information about the direction and energy of the incident particle, which is then used to reconstruct an image of the emitting source. Because of this imaging capability background events can be rejected, decreasing the number of events required for high confidence detection and thereby greatly improving its sensitivity. The instrument is optimized for the detection of neutrons with energies from 1-20 MeV and gamma rays from 0.4 to 10 MeV. Images and energy spectra for neutron and gamma rays are reported for several sources including depleted uranium and plutonium. In addition, the effect of neutron source shielding is investigated.

Madden, Amanda C.; Bloser, Peter F.; Fourguette, Dominique; Larocque, Liane; Legere, Jason S.; Lewis, Matt; McConnell, Mark L.; Rousseau, Marissa; Ryan, James M.

2013-05-01

105

gamma ray astronomy with muons  

Microsoft Academic Search

Although gamma ray showers are muon poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard gamma ray spectra there is a relative ``enhancement'' of muons from gamma ray primaries as compared to that from nucleon primaries. All shower gamma rays above the

Francis Halzen; Todor Stanev; Gaurang B. Yodh

1997-01-01

106

The gamma-ray observatory  

NASA Technical Reports Server (NTRS)

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.

1991-01-01

107

Modifying effect of vitamins C, E and beta-carotene against gamma-ray-induced DNA damage in mouse cells  

Microsoft Academic Search

The modifying effect of treatment with vitamins C, E and beta-carotene on the clastogenic activity of gamma rays was investigated in mice. Damage in vivo was measured by the micronucleus assay in bone marrow polychromatic erythrocytes and exfoliated bladder cells. The vitamins were administered orally, either for five consecutive days before or immediately after irradiation with 2 Gy of gamma

Maria Konopacka; Maria Widel; Joanna Rzeszowska-Wolny

1998-01-01

108

On the mechanism of UV and gamma-ray-induced intrachromosomal recombination in yeast cells synchronized in different stages of the cell cycle.  

PubMed

A genetic system selecting for deletion events (DEL recombination) due to intrachromosomal recombination has previously been constructed in the yeast Saccharomyces cerevisiae. Intrachromosomal recombination is inducible by chemical and physical carcinogens. We wanted to understand better the mechanism of induced DEL recombination and to attempt to determine in which phase of the cell cycle DEL recombination is inducible. Yeast cells were arrested at specific phases of the cell cycle, irradiated with UV or gamma-rays, and assayed for DEL recombination and interchromosomal recombination. In addition, the contribution of intrachromatid crossing-over to the number of radiation induced DEL recombination events was directly investigated at different phases of the cell cycle. UV irradiation induced DEL recombination preferentially in S phase, while gamma-rays induced DEL recombination in every phase of the cell cycle including G1. UV and gamma-radiation induced intrachromatid crossing over preferentially in G1, but it accounted at the most for only 14% of the induced DEL recombination events. The possibility is discussed that single-strand annealing or one-sided invasion events, which can occur in G1 and may be induced by a double-strand break intermediate, may be responsible for a large proportion of the induced DEL recombination events. PMID:7565592

Galli, A; Schiestl, R H

1995-08-21

109

Choice of detectors for in vivo elemental analysis by counting natural and neutron-induced gamma rays for medical applications  

NASA Astrophysics Data System (ADS)

Body fat is measured by detecting C and O in vivo through fast neutron inelastic scattering. A sealed D?T neutron generator is used for the pulsed (4-10 kHz) production of fast neutrons. Carbon and oxygen are detected by counting the 4.44 and 6.13 MeV gamma rays resulting from the inelastic scattering of the fast neutrons from 12C and 16O. Large Bi 4Ge 3O 12 (BGO) crystal detectors (127 × 76 mm) are used for the gamma ray detection during the 10 ?s neutron burst. BGO detectors improved the signal to background ratio for the carbon detection by a factor of six compared to 152 × 152 mm NaI (Tl) detectors. Exposure to scattered neutrons did not affect the gain stability of the BGOs. Thermal neutrons from a moderated 238Pu?Be source are used for the measurement of total body nitrogen (and thus protein). The resulting high energy prompt gamma rays from nitrogen (10.83 MeV) are detected simultaneously with the irradiation. BGO detectors have superior stability operating in an environment of variable neutron exposure and high counting rates. However, the presence of neutrons creates a 10.2 MeV gamma ray peak from 73Ge in the BGO detector which interferes with the nitrogen peak. Whole body gamma ray counters, consisting of NaI(Tl) crystal detectors in a shielded room, are used to measure the natural radioactivity of the body due to 40K. They are also used to measure body Ca, P, Na and Cl, following total body exposure to thermal neutrons.

Kehayias, Joseph J.; Zhuang, Hong; Dowling, Lisa; Ma, Ruimei; Moore, Robert

1994-12-01

110

A study of Venus surface elemental composition from 14 MeV neutron induced gamma ray spectroscopy: Activation analysis  

NASA Astrophysics Data System (ADS)

The surface elemental composition of Venus can be determined using an artificially pulsed 14 MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14 MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through 3 different neutron interaction mechanisms: capture, inelastic, and activation reactions. Each reaction type has a different neutron energy dependency and different time scale for gamma ray production and transport. Certain elements are more easily identified through one reaction type over the others. Thus, careful analysis of the gamma ray spectra during and after the neutron pulse provides a comprehensive understanding of the surface elemental composition. In this paper, we use a well-tested neutron/gamma transport code, called Monte Carlo N-Particles (MCNP), to investigate the measurement capability of a PNG-GRS detection system through the neutron activation reactions. An activation analysis was performed for a representative soil composition of Venus with a notional operational scenario of PNG and GRS. The analysis shows that the proposed instrument concept can identify most of the modeled surface elements at Venus with sufficient accuracy through the activation mode. Specifically, U, Th, K, Si can be measured to within 1%, Fe within 2%, Al within 10%, Ca within 5%, Mg with 15%, Mn with 20%, and Cl within 6%. Although modeled in the analysis, it is shown that the activation mode alone cannot distinguish the S and Ti peaks.

Jun, I.; Kim, W.; Smith, M.; Mitrofanov, I.; Litvak, M.

2011-02-01

111

A Study of Venus Surface Elemental Composition From 14-MeV Neutron Induced Gamma Ray Spectroscopy: Activation Analysis  

NASA Astrophysics Data System (ADS)

The surface elemental composition of Venus can be determined by using an artificially pulsed 14 MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14 MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through 3 different neutron interaction mechanisms: capture, inelastic, and activation reactions. Each reaction type has a different neutron energy dependency and different time scale for gamma ray production and transport. Certain elements are more easily identified through one reaction type over the others. Thus, careful analysis of the gamma ray spectra during and after the neutron pulse provides a comprehensive understanding of the surface elemental composition. In this paper, we use a well-tested neutron/gamma transport code, called Monte Carlo N-Particles (MCNP), to investigate the measurement capability of a PNG-GRS detection system through the neutron activation reactions. An activation analysis was performed for a representative soil composition of Venus with a notional operational scenario of PNG and GRS. The analysis shows that the proposed instrument concept can identify most of the modeled surface elements at Venus with sufficient accuracy through the activation mode. Specifically, U, Th, K, Si can be measured to within 1%, Fe within 2%, Al within 10%, Ca within 5%, Mg with 15%, Mn with 20%, and Cl within 6%. Although modeled in the analysis, it is shown that the activation mode alone cannot distinguish the S and Ti peaks.

Jun, I.; Kim, W.; Smith, M.; Mitrofanov, I.; Litvak, M. L.

2010-12-01

112

The unified interaction model applied to the gamma ray induced supralinearity and sensitization of peak 5 in LiF:Mg,Ti (TLD-100)  

NASA Astrophysics Data System (ADS)

We describe the development of a comprehensive theory of thermoluminescence (TL) supralinearity and sensitization, the unified interaction model (UNIM), based on both radiation absorption stage and recombination stage mechanisms. The UNIM incorporates both the track interaction model (TIM) for heavy charged particles (HCPs) and the defect interaction model (DIM) for isotropically ionizing gamma rays and electrons, in a unified and self-consistent conceptual and mathematical formalism. The model is applied to explain the unique features of gamma-induced supralinearity and sensitization of peak 5 in LiF:Mg,Ti, especially the strictly linear, then supralinear behaviour and the dependence of the supralinearity on ionization density (gamma ray energy and particle type). Both features arise from a localized trapping entity (the track for HCPs, spatially correlated trapping centres and luminescent centres (TC/LC pairs) for gamma rays and electrons, which dominate the dose response at low dose and are not subject to intra-track competitive processes, thus leading to linear dose response behaviour. The decreasing efficiency of the competitive processes relative to the luminescence recombination processes, as a function of dose, leads to the supralinear behaviour. The decrease of the supralinearity with decreasing gamma ray energy (increasing ionization density) arises from the increasing probability of the TC/LC pair to simultaneously capture an electron - hole pair, leading to geminate recombination not subject to competitive processes. The UNIM is shown to be capable of yielding excellent fits to the experimental data with many of the variable parameters of the model strongly constrained by ancillary optical absorption and sensitization measurements.

Mahajna, S.; Horowitz, Y. S.

1997-09-01

113

Gamma ray optics  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

114

Gamma ray camera  

DOEpatents

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.

Perez-Mendez, Victor (Berkeley, CA)

1997-01-01

115

Gamma ray camera  

DOEpatents

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.

Perez-Mendez, V.

1997-01-21

116

Gamma ray pulsars  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

117

Gamma-ray Polarimetry  

SciTech Connect

An astrophysics application of a low noise Double-sided Silicon Strip Detector (DSSD) is described. A Semiconductor Multiple-Compton Telescope (SMCT) is being developed to explore the gamma-ray universe in the 0.1-20 MeV energy band. Excellent energy resolution and polarization sensitivity are key features of the SMCT. We have developed prototype modules for a low-noise DSSD system, which reached an energy resolution of 1.3 keV (FWHM) for 122 keV at 0 C. Results of a gamma-ray imaging test are also presented.

Tajima, Hiroyasu

2003-02-05

118

Selection and 3D-reconstruction of gamma-ray-induced air showers with H.E.S.S  

SciTech Connect

H.E.S.S. (High Energy Stereoscopic System) is an array of four large imaging Cherenkov telescopes devoted to gamma-ray astronomy above 100 GeV. It has been fully operational since December 2003. Here, we report on a new analysis method based on a simple 3D-modeling of an electromagnetic air shower. This method allows to separate gamma-rays from background events in the field of view without any assumption on the morphology of the source or on the background distribution. This is a crucial point in the study of extended sources (e.g. Supernova Remnants) or in the search for unexpected sources in a sky survey. The performance and results of this method on galactic sources are presented.

Lemoine-Goumard, M.; Degrange, B. [LLR, Ecole Polytechnique, 91128 Palaiseau Cedex (France)

2005-02-21

119

Inelastic cross sections from gamma-ray measurements  

SciTech Connect

Measurements of gamma rays following neutron induced reactions have been studied with the Germanium Array for Neutron-induced Excitations (GEANIE) at the Los Alamos Neutron Science Center (LANSCE) for many years. Gamma-ray excitation functions and coincidence studies provide insight into nuclear reaction mechanisms as well as expanding our knowledge of energy levels and gamma-rays. Samples studied with Ge detectors at LANSCE range from Be to Pu. Fe, Cr and Ti have been considered for use as reference cross sections. An overview of the measurements and efforts to create a reliable neutron-induced gamma-ray reference cross section will be presented.

Nelson, Ronald Owen [Los Alamos National Laboratory

2010-12-06

120

Short Gamma-Ray Bursts with Extended Emission from the Accretion-Induced Collapse of a White Dwarf  

NASA Astrophysics Data System (ADS)

Evidence is growing for a class of gamma-ray bursts (GRBs) characterized by an initial spike hard radiation followed, after a 3-10 s lull in emission, by a softer period of extended emission lasting 10-100 s. These "short GRBs with extended emission" (SGRBEEs) show no evidence for an associated supernova (SN) and, in conflict with compact object merger models, appear to originate exclusively inside the disk of their host galaxies. We argue that SGRBEEs may instead be produced by the accretion-induced collapse (AIC) of a white dwarf (WD) or the merger and collapse of a WD-WD binary, perhaps thus sharing a close relation to the progenitors of Type Ia SNe. In this model, the initial spike of emission is powered by accretion onto the newly-formed proto-neutron star (PNS) from a small disk that is formed in the AIC or merger event. If the PNS is strongly magnetized (a "proto-magnetar"), the extended emission may be produced by a relativistic wind that extracts the PNS's rotational energy on a timescale 10-100 s. We have modeled the extended emission from GRB060614 using spin-down calculations of a cooling proto-magnetar, finding reasonable agreement with observations for a magnetar with a surface field strength B 3e15 G and initial rotation period 1 ms. The 3-10 s delay between the prompt and extended emission is naturally explained by this model as the time required for the proto-magnetar to cool sufficiently that its outflow becomes ultra-relativistic. In the case of WD-WD mergers, extended emission may also be produced by accretion of the disk formed during the merger prior to collapse. We discuss ways to test the AIC/WD-WD merger model for SGRBEEs and to distinguish spin-down and accretion-powered extended emission via late-time radio observations and by searching for off-axis events, which may appear as X-ray flashes with no associated SN.

Metzger, Brian D.; Quataert, E.; Thompson, T. A.

2008-03-01

121

MODELING PHOTODISINTEGRATION-INDUCED TeV PHOTON EMISSION FROM LOW-LUMINOSITY GAMMA-RAY BURSTS  

SciTech Connect

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 {gamma}-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.

Liu Xuewen [Physics Department, Sichuan University, Chengdu 610065 (China); Wu Xuefeng; Lu Tan, E-mail: astrolxw@gmail.com, E-mail: xfwu@pmo.ac.cn, E-mail: t.lu@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2012-05-15

122

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

PubMed

In this study, a wavelength shifting fiber that shifts ultra-violet and blue light to green light was employed as a sensor probe of a fiber-optic Cerenkov radiation sensor. In order to characterize Cerenkov radiation generated in the developed wavelength shifting fiber and a plastic optical fiber, spectra and intensities of Cerenkov radiation were measured with a spectrometer. The spectral peaks of light outputs from the wavelength shifting fiber and the plastic optical fiber were measured at wavelengths of 500 and 510 nm, respectively, and the intensity of transmitted light output of the wavelength shifting fiber was 22.2 times higher than that of the plastic optical fiber. Also, electron fluxes and total energy depositions of gamma-ray beams generated from a Co-60 therapy unit were calculated according to water depths using the Monte Carlo N-particle transport code. The relationship between the fluxes of electrons over the Cerenkov threshold energy and the energy depositions of gamma-ray beams from the Co-60 unit is a near-identity function. Finally, percentage depth doses for the gamma-ray beams were obtained using the fiber-optic Cerenkov radiation sensor, and the results were compared with those obtained by an ionization chamber. The average dose difference between the results of the fiber-optic Cerenkov radiation sensor and those of the ionization chamber was about 2.09%. PMID:24755521

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

2014-01-01

123

Measurement of Cerenkov Radiation Induced by the Gamma-Rays of Co-60 Therapy Units Using Wavelength Shifting Fiber  

PubMed Central

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

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

2014-01-01

124

Gamma-ray telescopes  

Microsoft Academic Search

The last half-century has seen dramatic developments in ??ray telescopes, from their initial conception and development through to their blossoming into full maturity as a potent\\u000a research tool in astronomy. Gamma-ray telescopes are leading research in diverse areas such as ??ray bursts, blazars, Galactic transients, and the Galactic distribution of 26Al.

Neil Gehrels; John K. Cannizzo

2009-01-01

125

Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Gamma-Ray Bursts (GRBs) are now known to be the most powerful explosions in the Universe. I will summarize the history of observations of GRBs, and how we came to know that the sources are so distant. I will also give an overview of the most prominent theories as to the cause of bursts.

Meegan, Charles A.; Six, N. Frank (Technical Monitor)

2002-01-01

126

Gamma-ray Astronomy.  

National Technical Information Service (NTIS)

The Burst and Transient Source Experiment (BATSE) is one of four instruments on the Compton observatory which was launched by the space shuttle Atlantis on April 5, 1991. As of mid-March, 1994, BATSE detected more than 925 cosmic gamma-ray bursts and more...

W. S. Paciesas

1994-01-01

127

Gamma Ray Astronomy  

NASA Technical Reports Server (NTRS)

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.

Wu, S. T.

2000-01-01

128

Liquid xenon gamma ray imager  

US Patent & Trademark Office Database

A gamma ray imager includes a chamber containing a scintillation liquid such as xenon and several mutually optically isolated interaction modules immersed in the scintillation liquid within the chamber. Multiple photodetectors optically coupled to the modules separately detect scintillation light resulting from gamma ray interactions in the modules. Charge readout devices coupled to the modules provide time projection chamber-class detection of ionization charges produced by gamma ray interactions within the modules. A signal processor connected to the multiple photodetectors and charge readout devices analyzes signals produced by gamma ray interactions within the modules and calculates from the signals gamma ray energy and gamma ray angle. The calculations use Compton scattering formula inversion and also use anti-correlation of prompt scintillation light signals from gamma ray interactions and charge signals from gamma ray interactions.

2013-07-02

129

A rapid method for the quantification of C, N and O in biomedical samples by proton-induced gamma-ray emission analysis applied to human placental samples.  

PubMed

A new fast, accurate and simple quantification method for C, N and O in biomedical samples by external-beam proton-induced gamma-ray emission analysis is presented. Concentration values for C, N and O in commercial standards of NBS bovine liver 1577a, IAEA animal muscle H-4 and IAEA horse kidney H-8 were determined using the new method. The concentrations of C, N, O, Na, Mg and P were determined from placental samples of 13 alcoholic mothers and from 16 abstinent controls. The values obtained for C, N, O, Mg and P were the first values ever obtained for human placentas. PMID:3353453

Lapatto, R; Räisänen, J

1988-01-01

130

The new prompt gamma-ray catalogue for PGAA  

Microsoft Academic Search

A new catalogue of subthermal neutron-induced prompt gamma rays has been created for 79 elements, from hydrogen to uranium (including fission), on the basis of recent measurements at the Budapest guided-neutron PGAA facility. New energy values have been measured using 35Cl neutron-capture gamma rays, while the gamma-ray production cross-sections have been determined with respect to the 1H thermal capture cross-section.

G. L. Molnár; Zs. Révay; T. Belgya; R. B. Firestone

2000-01-01

131

Analytical applications of neutron capture gamma-ray spectroscopy  

Microsoft Academic Search

Prompt gamma rays from thermally induced nuclear reactions have been used to estimate the boron, chlorine and phosphorus contents in industrial and reference materials. A neutron capture gamma-ray spectroscopy facility for analytical purposes using 252Cf sources has been designed and calibrated and is described in this paper. The facility is principally designed for measurement of the prompt gamma-ray spectra obtained

A. M. Hassan; E. Gantner; E. Mainka; H. Ruf; U. Kuhnes; M. Mostafa

1983-01-01

132

Benchmark test of 14-MeV neutron-induced gamma-ray production data in JENDL-3.2 and FENDL/E-1.0 through analysis of the OKTAVIAN experiments  

SciTech Connect

Secondary gamma rays play an important role along with neutrons in influencing nuclear design parameters, such as nuclear heating, radiation dose, and material damage on the plasma-facing components, vacuum vessel, and superconducting magnets, of fusion devices. Because evaluated nuclear data libraries are used in the designs, one must examine the accuracy of secondary gamma-ray data in these libraries through benchmark tests of existing experiments. The validity of the data should be confirmed, or problems with the data should be pointed out through these benchmark tests to ensure the quality of the design. Here, gamma-ray production data of carbon, fluorine, aluminum, silicon, titanium, chromium, manganese, cobalt, copper, niobium, molybdenum, tungsten, and lead in JENDL-3.2 and FENDL/E-1.0 induced by 14-MeV neutrons are tested through benchmark analyses of leakage gamma-ray spectrum measurements conducted at the OKTAVIAN deuterium-tritium neutron source facility. The MCNP transport code is used along with the flagging method for detailed analyses of the spectra. As a result, several moderate problems are pointed out for secondary gamma-ray data of titanium, chromium, manganese, and lead in FENDL/E-1.0. Because no fatal errors are found, however, secondary gamma-ray data for the 13 elements in both libraries are reasonably well validated through these benchmark tests as far as 14-MeV neutron incidence is concerned.

Maekawa, F.; Oyama, F. [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Dept. of Reactor Engineering

1996-06-01

133

Determination of Fluorine in Fourteen Microanalytical Geologic Reference Materials using SIMS, EPMA, and Proton Induced Gamma Ray Emission (PIGE) Analysis  

NASA Astrophysics Data System (ADS)

Fluorine (F) is a volatile constituent of magmas and hydrous minerals, and trace amounts of F are incorporated into nominally anhydrous minerals such as olivine and clinopyroxene. Microanalytical techniques are routinely used to measure trace amounts of F at both high sensitivity and high spatial resolution in glasses and crystals. However, there are few well-established F concentrations for the glass standards routinely used in microanalytical laboratories, particularly standards of low silica, basaltic composition. In this study, we determined the F content of fourteen commonly used microanalytical glass standards of basaltic, intermediate, and rhyolitic composition. To serve as calibration standards, five basaltic glasses with ~0.2 to 2.5 wt% F were synthesized and characterized. A natural tholeiite from the East Pacific Rise was mixed with variable amounts of CaF2. The mixture was heated in a 1 atmosphere furnace to 1440 °C at fO2 = NNO for 30 minutes and quenched in water. Portions of the run products were studied by electron probe microanalysis (EPMA) and secondary ion mass spectrometry (SIMS). The EPMA used a 15 µm diameter defocused electron beam with a 15 kV accelerating voltage and a 25 nA primary current, a TAP crystal for detecting FK? X-rays, and Biotite 3 as the F standard. The F contents by EPMA agreed with the F added to the basalts after correction for mass loss during melting. The SIMS analyses used a primary beam of 16O- and detection of low-energy negative ions (-5 kV) at a mass resolution that resolved 18OH. Both microanalytical techniques confirmed homogeneity, and the SIMS calibration defined by EPMA shows an excellent linear trend with backgrounds of 2 ppm or less. Analyses of basaltic glass standards based on our synthesized calibration standards gave the following F contents and 2? errors (ppm): ALV-519 = 83 ± 3; BCR-2G = 359 ± 6; BHVO-2G = 322 ± 15; GSA-1G = 10 ± 1; GSC-1G = 11 ± 1; GSD-1G = 19 ± 2; GSE-1G = 173 ± 1; KL2G (MPI-DING) = 101 ± 1; ML3B-G (MPI-DING) = 49 ± 17. These values are lower than published values for BCR-2 and BHVO-2 (unmelted powders) and the “information values” for the MPI-DING glass standards. Proton Induced Gamma ray Emission (PIGE) was tested for the high silica samples. PIGE analyses (1.7 MeV Tandem Accelerator; reaction type: 19F(p, ??)16O; primary current = 20-30 nA; incident beam voltage = 1.5 MeV) were calibrated with a crystal of fluor-topaz (F = 20.3 wt%) and gave F values of: NIST 610 = 266 ± 14 ppm; NIST 620 = 54 ± 5 ppm; and UTR-2 = 1432 ± 32 ppm. SIMS calibration defined by the PIGE analyses shows an excellent linear trend with low background similar to the basaltic calibration. The F concentrations of intermediate MPI-DING glasses were determined based on SIMS calibration generated from the PIGE analysis above. The F concentrations and 2? errors (ppm) are: T1G = 219.9 ± 6.8; StHs/680-G = 278.0 ± 2.0 ppm. This study revealed a large matrix effect between the high-silica and basaltic glasses, thus requiring the use of appropriate standards and separate SIMS calibrations when analyzing samples of different compositions.

Guggino, S. N.; Hervig, R. L.

2010-12-01

134

Measurement of gamma-ray production cross sections in neutron-induced reactions for Al and Pb  

SciTech Connect

The prompt gamma-radiation from the interaction of fast neutrons with aluminum and lead was measured using the white neutron beam of the WNR facility at the Los Alamos National Laboratory. The samples (Al and isotopically enriched {sup 207}Pb and {sup 208}Pb) were positioned at about 20 m or 41 m distance from the neutron production target. The spectra of the emitted gamma-rays were measured with a high-resolution HPGe detector. The incident neutron energy was determined by the time-of-flight method and the neutron fluence was measured with a U fission chamber. From the aluminum gamma-ray spectra excitation functions for prominent gamma-transitions in various residual nuclei (in the range from O to Al) were derived for neutron energies from 3 MeV to 400 MeV. For lead (n,xn{gamma}) reactions were studied for neutron energies up to 200 MeV by analyzing prominent gamma-transitions in the residual nuclei {sup 200,202,204,206,207,208}Pb. The experimental results were compared with nuclear model calculations using the code GNASH. A good overall agreement was obtained without special parameter adjustments.

Pavlik, A.; Vonach, H.; Hitzenberger, H. [Universitaet Wien (Austria). Institut fuer Radiumforschung und Kernphysik; Nelson, R.O.; Haight, R.C.; Wender, S.A.; Young, P.G.; Chadwick, M.B. [Los Alamos National Lab., NM (United States)

1995-02-01

135

Molecular characterisation of murine acute myeloid leukaemia induced by 56Fe ion and 137Cs gamma ray irradiation  

PubMed Central

Exposure to sparsely ionising gamma- or X-ray irradiation is known to increase the risk of leukaemia in humans. However, heavy ion radiotherapy and extended space exploration will expose humans to densely ionising high linear energy transfer (LET) radiation for which there is currently no understanding of leukaemia risk. Murine models have implicated chromosomal deletion that includes the hematopoietic transcription factor gene, PU.1 (Sfpi1), and point mutation of the second PU.1 allele as the primary cause of low-LET radiation-induced murine acute myeloid leukaemia (rAML). Using array comparative genomic hybridisation, fluorescence in situ hybridisation and high resolution melt analysis, we have confirmed that biallelic PU.1 mutations are common in low-LET rAML, occurring in 88% of samples. Biallelic PU.1 mutations were also detected in the majority of high-LET rAML samples. Microsatellite instability was identified in 42% of all rAML samples, and 89% of samples carried increased microsatellite mutant frequencies at the single-cell level, indicative of ongoing instability. Instability was also observed cytogenetically as a 2-fold increase in chromatid-type aberrations. These data highlight the similarities in molecular characteristics of high-LET and low-LET rAML and confirm the presence of ongoing chromosomal and microsatellite instability in murine rAML.

Bacher, Jeffery W.

2013-01-01

136

Unidentified Gamma-Ray Sources: Hunting Gamma-Ray Blazars  

SciTech Connect

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

Massaro, F.; D'Abrusco, R.; Tosti, G.; Ajello, M.; Gasparrini, A.Paggi.D.

2012-04-02

137

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

SciTech Connect

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

Massaro, F.; Ajello, M. [SLAC National Laboratory and Kavli Institute for Particle Astrophysics and Cosmology, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States); D'Abrusco, R.; Paggi, A. [Harvard-Smithsonian Astrophysical Observatory, 60 Garden Street, Cambridge, MA 02138 (United States); Tosti, G. [Dipartimento di Fisica, Universita degli Studi di Perugia, 06123 Perugia (Italy); Gasparrini, D. [ASI Science Data Center, ESRIN, I-00044 Frascati (Italy)

2012-06-10

138

Repair kinetics of gamma-ray induced DNA damage determined by the single cell gel electrophoresis assay in murine leukocytes in vivo.  

PubMed

The repair kinetics of the gamma rays induced DNA damage was determined in murine peripheral blood leukocytes in vivo by the comet assay. Mice were exposed to 1.0 Gy of gamma rays in a 137Cs source and samples of peripheral blood were taken from their tails at different times. The repair was evaluated per mice in separate experiments by measuring the proportion of cells with tail (comets) in each sample. An average of nearly 80% of comets was obtained at the initial time after the exposure; 2 min later the frequency decreased to 45% and continued diminishing to 22% at 15 min. This evidences the presence of a rapid repair mechanism. For a period of 25 to 40 min after exposure there was a slight but consistent increase of comets from 22 to 38% followed by a second reduction, which could be due to a late repair process that causes strand breaks and then joined them. In summary our results indicated that this system seems to be appropriate for the study of the repair capacity of cells following exposure to ionizing radiation. PMID:10047778

Mendiola-Cruz, M T; Morales-Ramírez, P

1999-01-26

139

Gamma-ray localization of terrestrial gamma-ray flashes.  

PubMed

Terrestrial gamma-ray flashes (TGFs) are very short bursts of high-energy photons and electrons originating in Earth's atmosphere. We present here a localization study of TGFs carried out at gamma-ray energies above 20 MeV based on an innovative event selection method. We use the AGILE satellite Silicon Tracker data that for the first time have been correlated with TGFs detected by the AGILE Mini-Calorimeter. We detect 8 TGFs with gamma-ray photons of energies above 20 MeV localized by the AGILE gamma-ray imager with an accuracy of ?5-10° at 50 MeV. Remarkably, all TGF-associated gamma rays are compatible with a terrestrial production site closer to the subsatellite point than 400 km. Considering that our gamma rays reach the AGILE satellite at 540 km altitude with limited scattering or attenuation, our measurements provide the first precise direct localization of TGFs from space. PMID:20867680

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

2010-09-17

140

Evidence for an Inducible Repair-Recombination System in the Female Germ Line of Drosophila Melanogaster. II. Differential Sensitivity to Gamma Rays  

PubMed Central

In a previous paper, we reported that the reactivity level, which regulates the frequency of transposition of I factor, a LINE element-like retrotransposon, is enhanced by the same agents that induce the SOS response in Escherichia coli. In this report, we describe experimental evidence that, for identical genotypes, the reactivity levels correlate with the sensitivity of oogenesis to gamma rays, measured by the number of eggs laid and by frequency of dominant lethals. This strongly supports the hypothesis that the reactivity level is one manifestation of an inducible DNA repair system taking place in the female germ line of Drosophila melanogaster. The implications of this finding for the understanding of the regulation of I factor are discussed and some other possible biological roles of this system are outlined.

Laurencon, A.; Bregliano, J. C.

1995-01-01

141

Evaluation of a pragmatic approach for the prediction of radiation-induced losses in optical fibers exposed to a gamma-ray environment  

NASA Astrophysics Data System (ADS)

The many advantages of optical fibers for their use in various nuclear environments ushered the respective communities to extensive studies over the last decades. Forecasting the behavior of fiber-optic links exposed to ionizing radiation still remains an important issue. We have developed an industry-aimed pragmatic method based on a simple model for the prediction of radiation induced losses in commercially available optical fibers exposed to 60Co gamma rays. When environmental and measurement conditions are well defined, long-term losses could be predicted with a precision of about 15%, for dose rates ranging between 100 Gy/h and 3 kGy/h and total doses up to MGy levels. Thermally induced effects were also considered, between ambient temperature and 80 degree(s)C. From an interpretation of these results, we discuss its applicability and potential further improvements.

Van Uffelen, Marco; Berghmans, Francis; Decreton, Marc C.; Nowodzinski, Antoine; Lecompte, Jean-Claude

2000-10-01

142

Gamma Ray Pulsars: Multiwavelength Observations  

Microsoft Academic Search

High-energy gamma rays are a valuable tool for studying particle acceleration\\u000aand radiation in the magnetospheres of energetic pulsars. The seven or more\\u000apulsars seen by instruments on the Compton Gamma Ray Observatory (CGRO) show\\u000athat: the light curves usually have double-peak structures (suggesting a broad\\u000acone of emission); gamma rays are frequently the dominant component of the\\u000aradiated power;

David J. Thompson

2003-01-01

143

The Gamma Ray Pulsar Population  

Microsoft Academic Search

We apply a likelihood analysis to pulsar detections, pulsar upper limits, and\\u000adiffuse background measurements from the OSSE and EGRET instruments on the\\u000aCompton Gamma Ray Observatory to constrain the luminosity law for gamma-ray\\u000apulsars and some properties of the gamma-ray pulsar population. We find that\\u000athe dependence of luminosity on spin period and dipole magnetic field is much\\u000asteeper

M. A. McLaughlin; J. M. Cordes

1999-01-01

144

{gamma} ray astronomy with muons  

SciTech Connect

Although {gamma} ray showers are muon poor, they still produce a number of muons sufficient to make the sources observed by GeV and TeV telescopes observable also in muons. For sources with hard {gamma} ray spectra there is a relative {open_quotes}enhancement{close_quotes} of muons from {gamma} ray primaries as compared to that from nucleon primaries. All shower {gamma} rays above the photoproduction threshold contribute to the number of muons N{sub {mu}}, which is thus proportional to the primary {gamma} ray energy. With {gamma} ray energy 50 times higher than the muon energy and a probability of muon production by the {gamma}{close_quote}s of about 1{percent}, muon detectors can match the detection efficiency of a GeV satellite detector if their effective area is larger by 10{sup 4}. The muons must have enough energy for sufficiently accurate reconstruction of their direction for doing astronomy. These conditions are satisfied by relatively shallow neutrino detectors such as AMANDA and Lake Baikal, and by {gamma} ray detectors such as MILAGRO. TeV muons from {gamma} ray primaries, on the other hand, are rare because they are only produced by higher energy {gamma} rays whose flux is suppressed by the decreasing flux at the source and by absorption on interstellar light. We show that there is a window of opportunity for muon astronomy with the AMANDA, Lake Baikal, and MILAGRO detectors. {copyright} {ital 1997} {ital The American Physical Society}

Halzen, F. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States)] [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Stanev, T. [Bartol Research Institute, University of Delaware, Newark, Delaware 19716 (United States)] [Bartol Research Institute, University of Delaware, Newark, Delaware 19716 (United States); Yodh, G.B. [Department of Physics and Astronomy, University of California, Irvine, California 92715 (United States)] [Department of Physics and Astronomy, University of California, Irvine, California 92715 (United States)

1997-04-01

145

Gamma rays produce superior seedless citrus  

SciTech Connect

Using gamma radiation, seedless forms of some varieties of oranges and grapefruit are being produced. Since it has long been known that radiation causes mutations in plants and animals, experiments were conducted to determine if seediness could be altered by exposing seeds or budwood to higher than natural doses of gamma radiation. Orange and grapefruit seeds and cuttings exposed to gamma rays in the early 1970's have produced trees that bear fruit superior to that now on the market.

Pyrah, D.

1984-10-01

146

Digital Pulse Processing and Gamma Ray Tracking  

NSDL National Science Digital Library

Two of the big changes in new generations of Nuclear Physics instrumentation will be the incorporation of digital processing and the use of gamma ray tracking. The Nuclear Physics Group at Daresbury has set up a project to investigate digital pulse processing for gamma ray detectors and how best to implement gamma ray tracking in large Germanium gamma ray detectors. Topics on this site include but are not limited to: gamma ray tracking, overview of the Gamma Ray Tracking Project, pictures of one of the tracking gamma ray detectors (TIGRE), pictures of test experiment, gamma ray tracking project publications, and links to other gamma ray tracking pages.

2010-09-21

147

Intrinsic and dust-induced polarization in gamma-ray burst afterglows: The case of GRB 021004  

NASA Astrophysics Data System (ADS)

Polarization measurements for the optical counterpart to GRB 021004 are presented and discussed. Our observations were performed with the TNG and the VLT-UT3 (Melipal) during the first and fourth night after the gamma-ray burst discovery. We find robust evidence for temporal evolution of the polarization, which is therefore, at least partially, intrinsic to the optical transient. We do not find convincing evidence of wavelength dependence for the intrinsic polarization of the transient, in agreement with current polarization models for optical afterglows. We discuss the role of dust, both in our galaxy and in the host, in modifying the transmitted polarization vector, showing how a sizable fraction of the observed polarized flux is due to Galactic selective extinction, while it is not possible to single out any clear contribution from dust in the host galaxy. We discuss how our data compare to those obtained by different groups showing that a two-component model is required to describe the complete dataset. This is not surprising given the complex lightcurve of GRB 021004. Based on observations made with ESO telescopes at the Paranal Observatory under programme Id 70.D-0111, on data from the ESO/ST-ECF Science Archive Facility and on observations made with the TNG under programme TAC 8_01(47).

Lazzati, D.; Covino, S.; di Serego Alighieri, S.; Ghisellini, G.; Vernet, J.; Le Floc'h, E.; Fugazza, D.; Di Tomaso, S.; Malesani, D.; Masetti, N.; Pian, E.; Oliva, E.; Stella, L.

2003-11-01

148

Gamma-ray bursters  

NASA Technical Reports Server (NTRS)

Current theoretical models developed to explain the observational data (from spaceborne detectors) on gamma-ray bursters are summarized and illustrated with drawings, diagrams, graphs, and photographic images. Although the data are fragmentary and often flawed by instrument defects, models involving neutron stars with strong magnetic fields are generally favored, and it is assumed that most observed bursters lie within the Galaxy. The neutron-star origin of the bursts is suggested by their intensity and rapid variability (implying a very compact high-energy source) and the presence in some burster spectra of a line at 420 keV which is explained by the combination of electron-positron annihilation and gravitational reddening. Consideration is also given to optical flashes observed to occur about once per year in the direction of gamma bursters, and the need for further searches for lower-energy emissions from bursters is stressed.

Schaefer, B. E.

1985-01-01

149

Astrophysical gamma-ray spectroscopy  

NASA Technical Reports Server (NTRS)

Observations of gamma-ray lines from solar flares, the Galactic Center, and transient celestial events are reviewed. The lines observed in each case are identified, and possible emission sources are considered. Future prospects for gamma-ray line astronomy are briefly discussed.

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

1979-01-01

150

Planetary gamma-ray spectroscopy  

NASA Technical Reports Server (NTRS)

The measured intensities of certain gamma rays of specific energies escaping from a planetary surface can be used to determine the abundances of a number of elements. The fluxes of the more intense gamma-ray lines emitted from 32 elements were calculated using current nuclear data and existing models for the source processes. The source strengths for neutron-capture reactions were modified from those previously used. The fluxes emitted form a surface of average lunar composition are reported for 292 gamma-ray lines. These theoretical fluxes were used elsewhere to convert the data from the Apollo gamma-ray spectrometers to elemental abundances and can be used with measurements from future missions to map the concentrations of a number of elements over a planet's surface. Detection sensitivities for these elements are examined and applications of gamma-ray spectroscopy for future orbiters to Mars and other solar-system objects are discussed.

Reedy, R. C.

1978-01-01

151

Induced mutagenesis in Jatropha curcas L. using gamma rays and detection of DNA polymorphism through RAPD marker.  

PubMed

The aim of this study is to examine the effect of different doses (control, 5, 10, 15, 20 and 25 Kr) of gamma irradiation on seed germination, flowering, fruit and seed traits of Jatropha curcas and to identify DNA polymorphism among the mutants through a Randomly Amplified Polymorphic DNA (RAPD) marker analysis. The improved agronomic traits such as flowering, fruits and seeds were recorded in 5 Kr dose and seed germination percentage in 10 Kr dose treated plants, while corresponding parameters were reduced significantly (P>0.05) in 25 Kr dose gamma rays treated plants when compared to that of control. All the twenty-three random primers used except six primers, namely OPAW16, OPAK07, OPAK15, OPS01, OPAK20 and OPAL09 were showed polymorphic bands. The primers: OPAW16, OPAK07, OPAK15, OPS01, OPAK20 and OPAL09 produced only one band each across the six mutants, while the primers: OPU13, OPAB 15, OPF01 and OPAB11 were produced with maximum number of bands (8). The number of amplicons varied from 1 to 8 with an average of 3.9 bands, of which 2.3 were polymorphic. The percentage of polymorphism per primer ranged from 0 to 100 with an average of 55.16%. The Jaccard's coefficients of dissimilarity varied from 0.324 to 0.397, indicative of the level of genetic variation among the mutants studied. The maximum dissimilarity value (0.397) was observed in 5 Kr mutant while the minimum value (0.250) was observed in 20 Kr mutant when compared to that of control. In a dendrogram constructed based on genetic similarity coefficients, the mutants were grouped into three main clusters; (a) control, 10, 15 and 20 Kr dose mutants clustered together, (b) 25 Kr dose grouped alone, (c) 5 Kr dose also grouped alone. The mutants showing the differences in morphological traits showed DNA polymorphism in PCR profile amplified by RAPD marker. It is concluded that DNA polymorphism detected by RAPD analysis offered a useful molecular marker for the identification of mutants in gamma radiation treated plants. PMID:21262483

Dhakshanamoorthy, Dharman; Selvaraj, Radhakrishnan; Chidambaram, A L A

2011-01-01

152

Pulsars as gamma ray sources.  

NASA Astrophysics Data System (ADS)

Aspects of the physics of rotation powered pulsars as gamma ray sources are discussed. The shock excitation of pulsar powered nebulae (plerions) is discussed, based on recent theoretical work on the structure of relativistic, collisionless magnetosonic shock waves. This theory is used to outline a model in which the ?^-2^ injection spectrum of the Crab Nebula is satisfactorily accounted for. The same theory suggests a model of the ``wisp'' features in the Crab Nebula which accounts for these time variable features in the surface bightness as compressions associated with the magnetic overshoots within the shock structure. It is pointed out that this theory suggests observable variability in the high energy gamma rays from the Crab Nebula (?>50MeV.) The energetics of pulsed gamma ray emission from the six known EGRET pulsars are reviewed and shown to fit a simple efficiency {prop.to}{PHI}_open_^-k^ law, where k~0.8 and {PHI}_open_={OMEGA}_*_^2mu/c^2^=10^13^(?(P)_15_ /P^3^)^1/2^ is a measure of the total voltage available on a pulsar's open field lines. Here ?(P)_15_=?(P)/10^-15^. This result is used to define a criterion for cessation of gamma ray emission in voltage-P space, such that empirically pulsars should stop being gamma ray emitters when the total spindown luminosity falls to ~2x10^32^ergs/sec. A simple result of the same form as the empirical gamma ray emission efficency is derived for the acceleration efficiency of particle beams extracted from the polar cap, and for high voltage pulsars, where curvature radiation reaction is important, equated to the gamma ray efficiency. However, it is also argued that since radio emission from the polar caps continues to lower voltages and spin down luminosities than inferred for the gamma ray emission, that this correspondence is a coincidence and that the EGRET gamma rays come from the outer magnetosphere. The most popular of outer magnetosphere models are shown to be unable to simultanously account for gamma ray efficiencies approaching unity and having most of the gamma ray luminosity in sharp pulses, suggesting that the gamma ray emission has something to do with dense return current boundary layers whose physics has yet to be quantified.

Arons, J.

1996-11-01

153

Gamma-Ray Pulsars: Observations  

NASA Technical Reports Server (NTRS)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET 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. Unless a new pulsed component appears at higher energies, progress in gamma-ray pulsar studies will be greatest in the 1-10 GeV range . Ground-based telescopes whose energy ranges extend downward toward 10 GeV should make important measurements of the spectral cutoffs. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a possible launch in 2005, will provide a major advance in sensitivity, energy range, and sky coverage.

Thompson, David J.

2000-01-01

154

Jet Shockwaves Produce Gamma Rays  

NASA Video Gallery

Theorists believe that GRB jets produce gamma rays by two processes involving shock waves. Shells of material within the jet move at different speeds and collide, generating internal shock waves th...

155

Gamma-ray spectrometer experiment  

NASA Technical Reports Server (NTRS)

The experiments in gamma-ray spectrometry to determine the geochemical composition of the lunar surface are reported. The theory is discussed of discrete energy lines of natural radioactivity, and the lines resulting from the bombardment of the lunar surface by high energy cosmic rays. The gamma-ray spectrometer used in lunar orbit and during transearth coast is described, and a preliminary analysis of the results is presented.

Arnold, J. R.; Peterson, L. E.; Metzger, A. E.; Trombka, J. I.

1972-01-01

156

Correlation between radiation-induced defects, and optical properties of pure fused silica-core optical fiber, under gamma-ray irradiation in air at 1273 K  

NASA Astrophysics Data System (ADS)

Radiation-induced effects on optical properties such as thermoluminescence and optical absorption of pure fused silica-core optical fibers were investigated in situ under gamma-ray irradiation at 0.16 mGy/s and 1273 K in air. The intensities of broad optical transmission peaks below 900 nm decreased due to appearances of non-bridging oxygen hole center (NBOHC), oxygen deficiency centers (ODCs), and optical leakage with increasing annealing time. The intensities of optical absorption and luminescence characteristics peaks at 1390 nm were enhanced by the increment of Si-OH concentration due to the reaction of water vapor or hydrogen with NBOHC, ODCs, and SiO 2 glass network. In addition, high resolution-transmission electron microscopy (HR-TEM) showed that SiO 2 crystals approximately 10 nm in diameter were formed in the clad and core of the irradiated optical fiber. The crystallization of the SiO 2 glass network had greater influence on the optical transmission and luminescence properties.

Tsuchiya, B.; Kondo, S.; Tsurui, T.; Toh, K.; Nagata, S.; Shikama, T.

2011-10-01

157

First Quantitative Imaging of Organic Fluorine within Angiogenic Tissues by Particle Induced Gamma-Ray Emission (PIGE) Analysis: First PIGE Organic Fluorine Imaging  

PubMed Central

PET (Positron Emission Tomography) allows imaging of the in vivo distribution of biochemical compounds labeled with a radioactive tracer, mainly 18F-FDG (2-deoxy-2-[18F] fluoro-D-glucose). 18F only allows a relatively poor spatial resolution (2-3 mm) which does not allow imaging of small tumors or specific small size tissues, e.g. vasculature. Unfortunately, angiogenesis is a key process in various physiologic and pathologic processes and is, for instance, involved in modern anticancer approaches. Thus ability to visualize angiogenesis could allow early diagnosis and help to monitor the response of cancer to specific chemotherapies. Therefore, indirect analytical techniques are required to assess the localization of fluorinated compounds at a micrometric scale. Multimodality imaging approaches could provide accurate information on the metabolic activity of the target tissue. In this article, PIGE method (Particle Induced Gamma-ray Emission) was used to determine fluorinated tracers by the nuclear reaction of 19F(p,p??)19F in tissues. The feasibility of this approach was assessed on polyfluorinated model glucose compounds and novel peptide-based tracer designed for angiogenesis imaging. Our results describe the first mapping of the biodistribution of fluorinated compounds in both vascularized normal tissue and tumor tissue.

Lavielle, Sebastien; Gionnet, Karine; Ortega, Richard; Deves, Guillaume; Kilarski, Victor; Wehbe, Katia; Bikfalvi, Andreas; Deleris, Gerard

2011-01-01

158

Study of asymmetries of Cd(Zn)Te devices investigated using photo-induced current transient spectroscopy, Rutherford backscattering, surface photo-voltage spectroscopy, and gamma ray spectroscopies  

SciTech Connect

Despite these recent advancements in preparing the surface of Cd(Zn)Te devices for detector applications, large asymmetries in the electronic properties of planar Cd(Zn)Te detectors are common. Furthermore, for the development of patterned electrode geometries, selection of each electrode surface is crucial for minimizing dark current in the device. This investigation presented here has been carried out with three objectives. Each objective is oriented towards establishing reliable methods for the selection of the anode and cathode surfaces independent of the crystallographic orientation. The objectives of this study are (i) investigate how the asymmetry in I-V characteristics of Cd(Zn)Te devices may be associated with the TeO2 interfacial layer using Rutherford backscattering to study the structure at the Au-Cd(Zn)Te interface, (ii) develop an understanding of how the concentration of the active traps in Cd(Zn)Te varies with the external bias, and (iii) propose non-destructive methods for selection of the anode and cathode which are independent of crystallographic orientation. The spectroscopic methods employed in this investigation include Rutherford backscattering spectroscopy, photo-induced current transient spectroscopy, and surface photo-voltage spectroscopy, as well as gamma ray spectroscopy to demonstrate the influence on detector properties.

Crocco, J.; Bensalah, H.; Zheng, Q.; Dieguez, E. [Crystal Growth Laboratory, Universidad Autonoma de Madrid, Madrid Spain (Spain); Corregidor, V.; Avles, E. [Instituto Tecnologico e Nuclear UFA, Sacavem (Portugal); Castaldini, A.; Fraboni, B.; Cavalcoli, D.; Cavallini, A. [PHoS Laboratory, Department of Physics, University of Bologna, Bologna (Italy); Vela, O. [Centro de Investigacion Energeticas Medioambientales y Tecnologicas (CIEMAT), Madrid (Spain)

2012-10-01

159

Nuclear gamma-rays from energetic particle interactions  

NASA Technical Reports Server (NTRS)

Gamma-ray line emission due to nuclear deexcitation following energetic particle interactions with abundant constituents of cosmic matter is studied. Reactions induced by energetic protons and alpha particles in ambient nuclei (He, C, N, O, Ne, Mg, Al, Si, S, Ca, and Fe) are considered, along with inverse reactions in which energetic nuclei interact with ambient H and He. Line-production cross sections are evaluated by analyzing a large body of laboratory nuclear data. Both prompt gamma rays, produced by direct excitation of nuclear levels and by spallation reactions that leave the secondary nucleus in an excited state, and delayed emission from long-lived radioactive nuclei also produced in the energetic particle reactions are investigated. A line list is provided, and the shapes of the gamma-ray lines are determined. Gamma-ray line production in the interstellar medium is evaluated in detail.

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

1979-01-01

160

Protection of spermatogenesis against gamma ray-induced damage by granulocyte colony-stimulating factor in mice.  

PubMed

The radioprotective effects of granulocyte colony-stimulating factor (GCSF) were further investigated with respect to the testicular system. Recombinant human GCSF (100 ?g kg(-1) body weight/day) was administrated to male C3H/HeN mice by subcutaneous injection for three consecutive days before pelvic irradiation (5 Gy) and histopathological parameters were assessed at 12 h and 21 days post-irradiation (pi). The GCSF protected the germ cells from radiation induced- apoptosis (P < 0.01 vs. irradiated group at 12 h pi). GCSF remarkably attenuated radiation-induced reduction in testis weight, seminiferous tubular diameter, seminiferous epithelial depth and sperm head count in the testes (P < 0.05 versus irradiated group at 21 days pi). Repopulation index and stem cell survival index of the seminiferous tubules were increased in the GCSF-treated group when compared with the radiation group (P < 0.01). The frequency of abnormal sperm in the GCSF group was lower than that in the irradiated group at 21 days pi (P < 0.01). The decrease in the sperm count and in sperm liability in the epididymis caused by irradiation was counteracted by GCSF. The present study suggests that GCSF protects from radiation-induced testicular dysfunction via an anti-apoptotic effect and recovery of spermatogenesis. PMID:21382061

Kim, J; Lee, S; Jeon, B; Jang, W; Moon, C; Kim, S

2011-04-01

161

The Gamma-ray Sky with Fermi  

NASA Technical Reports Server (NTRS)

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.

Thompson, David

2012-01-01

162

Terrestrial gamma-ray flashes  

NASA Astrophysics Data System (ADS)

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.

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

163

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  

SciTech Connect

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 DNA 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 irradiation. From these results, we conclude that the cAMP signaling system inhibits the repair of {gamma}-ray-induced DNA damage by promoting the ubiquitin-proteasome dependent degradation of XRCC1 in an Epac-dependent pathway in lung cancer cells.

Cho, Eun-Ah [Department of Biochemistry and Molecular Biology, Cancer Research Center, Seoul National University College of Medicine, Seoul 110-799 (Korea, Republic of)] [Department of Biochemistry and Molecular Biology, Cancer Research Center, Seoul National University College of Medicine, Seoul 110-799 (Korea, Republic of); Juhnn, Yong-Sung, E-mail: juhnn@snu.ac.kr [Department of Biochemistry and Molecular Biology, Cancer Research Center, Seoul National University College of Medicine, Seoul 110-799 (Korea, Republic of)] [Department of Biochemistry and Molecular Biology, Cancer Research Center, Seoul National University College of Medicine, Seoul 110-799 (Korea, Republic of)

2012-06-01

164

Gamma rays induce a p53-independent mitochondrial biogenesis that is counter-regulated by HIF1?  

PubMed Central

Mitochondrial biogenesis is an orchestrated process that presides to the regulation of the organelles homeostasis within a cell. We show that ?-rays, at doses commonly used in the radiation therapy for cancer treatment, induce an increase in mitochondrial mass and function, in response to a genotoxic stress that pushes cells into senescence, in the presence of a functional p53. Although the main effector of the response to ?-rays is the p53-p21 axis, we demonstrated that mitochondrial biogenesis is only indirectly regulated by p53, whose activation triggers a murine double minute 2 (MDM2)-mediated hypoxia-inducible factor 1? (HIF1?) degradation, leading to the release of peroxisome-proliferator activated receptor gamma co-activator 1? inhibition by HIF1?, thus promoting mitochondrial biogenesis. Mimicking hypoxia by HIF1? stabilization, in fact, blunts the mitochondrial response to ?-rays as well as the induction of p21-mediated cell senescence, indicating prevalence of the hypoxic over the genotoxic response. Finally, we also show in vivo that post-radiotherapy mitochondrial DNA copy number increase well correlates with lack of HIF1? increase in the tissue, concluding this may be a useful molecular tool to infer the trigger of a hypoxic response during radiotherapy, which may lead to failure of activation of cell senescence.

Bartoletti-Stella, A; Mariani, E; Kurelac, I; Maresca, A; Caratozzolo, M F; Iommarini, L; Carelli, V; Eusebi, L H; Guido, A; Cenacchi, G; Fuccio, L; Rugolo, M; Tullo, A; Porcelli, A M; Gasparre, G

2013-01-01

165

Gamma-ray Imaging Methods  

SciTech Connect

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

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

2006-10-05

166

A POSSIBLE APPROACH TO THREE-DIMENSIONAL COSMIC-RAY PROPAGATION IN THE GALAXY. IV. ELECTRONS AND ELECTRON-INDUCED {gamma}-RAYS  

SciTech Connect

Based on the diffusion-halo model for cosmic-ray (CR) propagation, including stochastic reacceleration due to collisions with hydromagnetic turbulence, we study the behavior of the electron component and the diffuse {gamma}-rays (D{gamma}'s) induced by them. The galactic parameters appearing in these studies are essentially the same as those appearing in the hadronic CR components, while we additionally need information on the interstellar radiation field, taking into account dependences on both the photon energy, E{sub ph}, and the position, r. We compare our numerical results with the data on hadrons, electrons, and D{gamma}'s, including the most recent results from Fermi, which gives two remarkable results: (1) the electron spectrum falls with energy as E{sup -3}{sub e} up to 1 TeV, and does not exhibit prominent spectral features around 500 GeV, in contrast to the dramatic excess appearing in both ATIC and PPB-BETS spectra and (2) the EGRET GeV-excess in the D{gamma} spectrum is neither due to an astronomical origin (much harder CR spectrum in the galactic center) nor a cosmological one (dark matter annihilation or decay), but due to an instrumental problem. In the present paper, however, we focus our interest rather conservatively upon the internal relation between these three components, using common galactic parameters. We find that they are in reasonable harmony with each other within both the theoretical and experimental uncertainties, apart from the electron-anomaly problem, while some enhancement of D{gamma}'s appears in the high galactic latitude with |b|>60{sup 0} in the GeV region.

Shibata, T.; Ishikawa, T.; Sekiguchi, S. [Department of Physics and Mathematics, Aoyama-Gakuin University, Kanagawa 252-5258 (Japan)

2011-01-20

167

Radiation-induced terpolymerization of methyl. cap alpha. ,. beta. ,. beta. -trifluoroacrylate with tetrafluoroethylene and. cap alpha. -olefin. [. gamma. rays  

SciTech Connect

Radiation-induced terpolymerizations of methyl ..cap alpha..,..beta..,..beta..-trifluoroacrylate (MTFA) with tetrafluoroethylene (TFE) and ..cap alpha..-olefins, such as ethylene, propylene, and isobutylene, were carried out in bulk at 25/sup 0/C for the purpose of controlling the content of ester group in the MTFA-..cap alpha..-olefin alternating copolymers. These monomers polymerized to form alternating terpolymers which contained 50 mole % ..cap alpha..-olefin in a wide range of monomer composition. The content of MTFA, namely, the ester group in polymer, can be varied without destruction of the alternating structures between fluoroolefins (MTFA, TFE) and ..cap alpha..-olefin by changing the MTFA/TFE ratio in the monomer mixture. The relative reactivities of MTFA and TFE in the terpolymerization were discussed according to kinetic treatments by free propagating and complex mechanisms. The relation between the MTFA/TFE ratio in the monomer mixture and that in terpolymer was explained favorably by the complex mechanism. It was also concluded that the relative reactivity of MTFA is larger than that of TFE in the terpolymerizations.

Matsuda, O.; Watanabe, T.; Tabata, Y.; Machi, S.

1980-04-01

168

Phenotypic and functional changes induced in hematopoietic stem/progenitor cells after gamma-ray radiation exposure.  

PubMed

Ionizing radiation (IR) exposure causes rapid and acute bone marrow (BM) suppression that is reversible for nonlethal doses. Evidence is accumulating that IR can also provoke long-lasting residual hematopoietic injury. To better understand these effects, we analyzed phenotypic and functional changes in the stem/progenitor compartment of irradiated mice over a 10-week period. We found that hematopoietic stem cells (HSCs) identified by their repopulating ability continued to segregate within the Hoechst dye excluding "side population (SP)" early after IR exposure. However, transient phenotypic changes were observed within this cell population: Sca-1 (S) and c-Kit (K) expression levels were increased and severely reduced, respectively, with a concurrent increase in the proportion of SP(SK) cells positive for established indicators of the presence of HSCs: CD150 and CD105. Ten weeks after IR exposure, expression of Sca-1 and c-Kit at the SP cell surface returned to control levels, and BM cellularity of irradiated mice was restored. However, the c-Kit(+)Sca-1(+)Lin(-/low) (KSL) stem/progenitor compartment displayed major phenotypic modifications, including an increase and a severe decrease in the frequencies of CD150(+)Flk2(-) and CD150(-)Flk2(+) cells, respectively. CD150(+) KSL cells also showed impaired reconstituting ability, an increased tendency to apoptosis, and accrued DNA damage. Finally, 15 weeks after exposure, irradiated mice, but not age-matched controls, allowed engraftment and significant hematopoietic contribution from transplanted congenic HSCs without additional host conditioning. These results provide novel insight in our understanding of immediate and delayed IR-induced hematopoietic injury and highlight similarities between HSCs of young irradiated and old mice. PMID:19489102

Simonnet, Arthur J; Nehmé, Johnny; Vaigot, Pierre; Barroca, Vilma; Leboulch, Philippe; Tronik-Le Roux, Diana

2009-06-01

169

Gamma-ray pulsar model  

Microsoft Academic Search

Extremely high energy bursts of pulsed gamma-rays have recently been detected from several binary X-ray pulsars and young radio pulsars. It is proposed that curvature synchrotron radiation from electrons (accelerated along the open magnetic field lines) is a possible origin of this emission. The electric and magnetic fields in the present model are computed in the near zone (close to

Jeffrey M. Cohen; Errol Mustafa

1987-01-01

170

Diffuse galactic gamma ray lines  

NASA Technical Reports Server (NTRS)

The production rate of 4.44-MeV line for a variety of assumed cosmic ray spectra is evaluated. These results are compared with reported galactic gamma-ray line intensities and are consistent with a low energy cosmic ray density which increases toward the galactic center in proportion to the molecular gas density.

Lingenfelter, R. E.; Ramaty, R.

1977-01-01

171

The GRAD gamma ray spectrometer  

SciTech Connect

A gamma-ray spectrometer for an upcoming space shuttle mission is described. Consisting of a 150 cm/sup 3/ n-type germanium detector set inside active shielding of bismuth germanate and plastic scintillator, the instrument will be used in studies of the Orbiter background and the galactic center.

Rester, A.C.; Piercey, R.B.; Eichhorn, G.; Coldwell, R.L.; McKisson, J.M.; Ely, D.W.; Mann, H.M.; Jenkins, D.A.

1986-02-01

172

Gamma-ray camera flyby  

ScienceCinema

Animation based on an actual classroom demonstration of the prototype CCI-2 gamma-ray camera's ability to image a hidden radioactive source, a cesium-137 line source, in three dimensions. For more information see http://newscenter.lbl.gov/feature-stories/2010/06/02/applied-nuclear-physics/.

173

Gamma-ray camera flyby  

SciTech Connect

Animation based on an actual classroom demonstration of the prototype CCI-2 gamma-ray camera's ability to image a hidden radioactive source, a cesium-137 line source, in three dimensions. For more information see http://newscenter.lbl.gov/feature-stories/2010/06/02/applied-nuclear-physics/.

None

2010-01-01

174

Cosmological gamma-ray bursts  

NASA Technical Reports Server (NTRS)

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.

Paczynski, Bohdan

1991-01-01

175

Continuous Energy gamma-Ray Spectrometry.  

National Technical Information Service (NTIS)

Compton recoil gamma-ray spectroscopy provides absolute measurements of continuous gamma-ray spectra. Peaks which possess sufficient intensity above the continuum level can be observed. Since the inception of this spectrometric method, this method has evo...

R. Gold B. J. Kaiser J. P. McNeece

1983-01-01

176

High Altitude Balloons and gamma Ray Astronomy.  

National Technical Information Service (NTIS)

The author's experience with scientific high altitude ballooning will be presented. Usefulness of satellite versus balloon platforms will be contrasted in the context of gamma ray astronomy. General principles of gamma ray astronomy instrumentation will b...

C. J. MacCallum

1988-01-01

177

The Gamma-ray Universe through Fermi  

NASA Technical Reports Server (NTRS)

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.

Thompson, David J.

2012-01-01

178

Portable compton gamma-ray detection system  

SciTech Connect

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.

Rowland, Mark S. (Alamo, CA); Oldaker, Mark E. (Pleasanton, CA)

2008-03-04

179

Gamma-Ray Spectroscopy of 166Er  

Microsoft Academic Search

Relative intensities of gamma rays of 166Er from the decays of 166mHo were precisely measured with a calibrated Ge(Li) detector. Errors of relative gamma-ray intensities are about 0.5% for strong gamma rays. Angular correlations for 11 cascades were measured with Ge(Li) and NaI(T1) detectors. The B(E2) ratios were deduced from the relative gamma-ray intensities and the adopted values of the

Kazuo Kato; Masaharu Hoshi; Yasukazu Yoshizawa

1981-01-01

180

Gamma-radiation-induced mutation spectrum in the episomal lacI gene of Escherichia coli under oxic conditions.  

PubMed

In this study we have determined the mutation spectrum in the complete episomal lacI gene of Escherichia coli induced by gamma-radiation under oxic conditions. Mutants were generated by 60Co gamma-irradiation of an E. coli culture of stationary cells in LB medium, under continuous flushing with oxygen. Oligonucleotide probe analysis showed that 14% of the gamma-ray-induced mutations were located at the lacI gene hot spot at position 620-632, which is characterized by a triple repeat of the 5'-TGGC-3' sequence. Previously it was shown that about 70% of the spontaneous mutations were located at this site due to the loss or the addition of a TGGC sequence. The non-hot spot mutations were further characterized by automated sequence analysis. The results show that base pair (bp) substitutions were the main type of gamma-ray-induced mutations. Although all types of bp substitutions were observed, 74% of the bp substitutions involved C/G base pairs. C/G --> T/A and C/G --> A/T substitutions were predominant, both accounting for 35% of all bp substitutions, whereas A/T --> C/G substitutions were only seldomly observed (3%). A relatively large amount of -1 bp deletions (15% of all mutations) was detected in the gamma-ray-induced mutation spectrum, mainly affecting C/G base pairs, and 10% were deletions, ranging in size from 11 to 532 bp. It can be concluded that under oxic conditions gamma-radiation induces in E. coli mainly bp substitutions of all types but preferentially at C/G base pairs, and that the mutations tend to be randomly distributed within the lacI gene sequence. PMID:8600354

Wijker, C A; Lafleur, M V; van Steeg, H; Mohn, G R; Retèl, J

1996-02-01

181

Gamma ray spectroscopy in astrophysics. [conferences  

NASA Technical Reports Server (NTRS)

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.

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

1978-01-01

182

High altitude balloons and gamma ray astronomy  

Microsoft Academic Search

The author's experience with scientific high altitude ballooning will be presented. Usefulness of satellite versus balloon platforms will be contrasted in the context of gamma ray astronomy. General principles of gamma ray astronomy instrumentation will be discussed and illustrated in terms of our current instrument, the Gamma Ray Imaging Spectrometer (GRIS). Some words about the supernova phenomenon and its necessity

Crawford J. MacCallum

1988-01-01

183

Gamma ray astrophysics. [emphasizing processes and absorption  

NASA Technical Reports Server (NTRS)

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.

Stecker, F. W.

1974-01-01

184

Gamma Ray Spectroscopy of Mn54  

Microsoft Academic Search

Internal conversion electrons of 0.84 Mev gamma ray were measured by a two-directional focusing beta-ray spectrometer, and it was determined that Egamma{=}837.9± 0.3 kev and K\\/L+M{=}8.5± 0.7. Weak gamma rays were searched, using scintillation counters, but no gamma ray was observed.

Toshio Katoh; Masao Nozawa; Yasukazu Yoshizawa; Yujiro Koh

1958-01-01

185

Compton Gamma Ray Observatory Guest Investigator Program  

NASA Technical Reports Server (NTRS)

This paper presents a final report for the Compton Gamma Ray Observatory Guest Investigator Program from 06/01/91-07/31/97. The topics include: 1) Solar Flare Neutron Spectra and Accelerated Ions; 2) Gamma Ray Lines From The Orion Complex; 3) Implications of Nuclear Line Emission From The Orion Complex; 4) Possible Sites of Nuclear Line Emission From Massive OB Associations; 5) Gamma-Ray Burst Repitition and BATSE Position Uncertainties; 6) Effects of Compton Scattering on BATSE Gamma-Ray Burst Spectra; and 7) Selection Biases on the Spectral and Temporal Distribution of Gamma Ray Bursts.

Lingenfelter, Richard E.

1997-01-01

186

Terrestrial Gamma-Ray Flashes (TGFs)  

NASA Technical Reports Server (NTRS)

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.

Fishman, Gerald J.

2010-01-01

187

Neutron-capture gamma-ray data for obtaining elemental abundances from planetary spectra.  

SciTech Connect

Determination of elemental abundances is a top scientific priority of most planetary missions. Gamma-ray spectroscopy is an excellent method to determine elemental abundances using gamma rays made by nuclear reactions induced by cosmic-ray particles and by the decay of radioactive nuclides [Re73,Re78]. Many important planetary gamma rays are made by neutron-capture reactions. However, much of the data for the energies and intensities of neutron-capture gamma rays in the existing literature [e.g. Lo81] are poor [RF99,RF00]. With gamma-ray spectrometers having recently returned data from Lunar Prospector and NEAR and soon to be launch to Mars, there is a need for good data for neutron-capture gamma rays.

Reedy, Robert; Frankle, S. C. (Stephanie C.)

2001-01-01

188

Pinhole imaging of gamma rays  

Microsoft Academic Search

An approximate calculation is made of the effective area of pinhole collimators allowing for penetration of the metal by gamma -rays of two energies (364 and 140 keV). The particular case of normally-incident rays is treated without approximation. At 364 keV the performance even of heavy alloy (90% tungsten) collimators is dominated by penetration. The effective radius may approach twice

D. Paix

1967-01-01

189

Analysis of noise power spectrum of gamma rays camera  

NASA Astrophysics Data System (ADS)

Gamma rays camera is widely used in many studies, including the image diagnostics of the radiation sources, flash photography, and nondestructive assessment (NDA), etc. As a major component of the high sensitivity gamma rays camera, the MCP image intensifier is characterized in the intensified image, tunable shutter time and gain. The gamma rays camera is consisting with rays-fluorescence convertor, the optical imaging system, the MCP image intensifier, CCD and other devices. The performance of the gamma rays camera is mainly dependent on such parameters as the modulation transfer function (MTF), the noise power spectrum (NPS), and the detective quantum efficiency (DQE), etc. All of the parameters are somewhat limited by the noise characteristics of the system. Compared with the standard derivative noise distribution, the NPS, which can reflect the evolution characteristics of the noise of the imaging system with the change of the spatial frequency, could convey more information on the noise distribution in the system. In this paper, theoretical analysis is presented on the major sources of the noise in the gamma rays camera. Based on the analysis, the noise power spectra of the gamma rays camera were calibrated under various radiation dosages respectively with the visible light and gamma rays radiation sources (0.2MeV and 1.25MeV in energy, respectively). As indicated by the experimental results, the noise is majorly induced by the fluctuations of the gain of the MCP image intensifier. And the remarkable noise peak occurs nearby the spatial frequency of about 0.633 Hz/mm. And almost the same phenomena were found with both the 0.2MeV and 1.25MeV radiation energy. Besides, the noise power spectra are in circular symmetrical distribution, whose intensities are rapidly decreased with the increasing spatial frequencies.

Xie, Hongwei; Zhang, Faqiang; Zhang, Jianhua; Chen, Jinchuan; Chen, Dingyang; Li, Linbo

2014-01-01

190

Which unidentified EGRET sources are gamma-ray pulsars?  

Microsoft Academic Search

We consider high energy gamma -ray radiation from the radio pulsars associated with some unidentified EGRET gamma -ray sources. Calculated efficiencies for the conversion of spin-down power to gamma -rays and the energy spectra of the high energy gamma -rays from these possible gamma -ray pulsars in outer gap models are compared with observed results. Of these possible gamma -ray

L. Zhang; K. S. Cheng

1998-01-01

191

Diffuse galactic gamma ray lines  

NASA Technical Reports Server (NTRS)

The origin and observability were studied of diffuse gamma ray line emission from the galaxy. It was found that such lines could be formed by nuclear excitation interactions of low energy cosmic rays with both interstellar gas and dust grains. The gamma ray emission lines from deexcitation of grain nuclei are sharp with Doppler widths of the order of 10 kev or less; the lines from gas nuclei are also relatively sharp with widths of the order of 100 kev for the most intense line; and the lines from cosmic ray nuclei are broad with widths of the order of several hundred kev. A detailed evaluation is presented of the production rate of the 4.44 Mev line for a variety of assumed cosmic ray spectra. Results are compared with reported galactic gamma ray line intensities and it is concluded that the measurements are consistent with a low energy cosmic ray density which increases toward the galactic center in proportion to the molecular gas density.

Lingenfelter, R. E.; Ramaty, R.

1976-01-01

192

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

SciTech Connect

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.

Chyzh, A; Wu, C Y; Ullmann, J; Jandel, M; Bredeweg, T; Couture, A; Norman, E

2010-08-24

193

Cell cycle and LET dependence for radiation-induced mutation: a possible mechanism for reversed dose-rate effect.  

PubMed

A previous study of the mutagenic action of 252Cf radiation in mouse L5178Y cells showed that the mutation frequency was higher when the dose was chronic rather than acute, which was in sharp contrast to the effects reported for gamma-rays (Nakamura and Sawada, 1988). A subsequent study using synchronized cells revealed that the cells at the G2/M stage were uniquely sensitive to mutation induction by 252Cf radiation but not to gamma-rays (Tauchi et al., 1993). A long phase cell population was first subjected to conditioning gamma or 252Cf radiation doses at different dose-rates. The cell cycle distribution of these cells was then observed, and they were then exposed to 252Cf radiation, and the mutation rate was determined. The G2/M fraction increased by 3- to 4-fold when the conditioning doses (2 Gy of gamma or 1 Gy of 252Cf radiation) were delivered chronically over 10 h, but only slightly when the same doses were delivered over a 1 h period or less. Subsequent 252Cf irradiation gave higher mutation frequencies in the cells pre-irradiated with gamma-rays over a protracted period of time than in those exposed with the higher dose-rate gamma-rays. These results suggest that the radiation-induced G2 block could be at least partly (but not totally) responsible for this reverse dose-rate effect (Tauchi et al. 1996). Possible factors which cause the hyper-sensitivity of G2/M cells to mutation induction by neutrons will be discussed. PMID:10804993

Tauchi, H; Endo, S; Eguchi-Kasai, K; Furusawa, Y; Suzuki, M; Matsuura, S; Ando, K; Nakamura, N; Sawada, S; Komatsu, K

1999-12-01

194

Differential radiosensitivity phenotypes of DNA-PKcs mutations affecting NHEJ and HRR systems following irradiation with gamma-rays or very low fluences of alpha particles.  

PubMed

We have examined cell-cycle dependence of chromosomal aberration induction and cell killing after high or low dose-rate ? irradiation in cells bearing DNA-PKcs mutations in the S2056 cluster, the T2609 cluster, or the kinase domain. We also compared sister chromatid exchanges (SCE) production by very low fluences of ?-particles in DNA-PKcs mutant cells, and in homologous recombination repair (HRR) mutant cells including Rad51C, Rad51D, and Fancg/xrcc9. Generally, chromosomal aberrations and cell killing by ?-rays were similarly affected by mutations in DNA-PKcs, and these mutant cells were more sensitive in G1 than in S/G2 phase. In G1-irradiated DNA-PKcs mutant cells, both chromosome- and chromatid-type breaks and exchanges were in excess than wild-type cells. For cells irradiated in late S/G2 phase, mutant cells showed very high yields of chromatid breaks compared to wild-type cells. Few exchanges were seen in DNA-PKcs-null, Ku80-null, or DNA-PKcs kinase dead mutants, but exchanges in excess were detected in the S2506 or T2609 cluster mutants. SCE induction by very low doses of ?-particles is resulted from bystander effects in cells not traversed by ?-particles. SCE seen in wild-type cells was completely abolished in Rad51C- or Rad51D-deficient cells, but near normal in Fancg/xrcc9 cells. In marked contrast, very high levels of SCEs were observed in DNA-PKcs-null, DNA-PKcs kinase-dead and Ku80-null mutants. SCE induction was also abolished in T2609 cluster mutant cells, but was only slightly reduced in the S2056 cluster mutant cells. Since both non-homologous end-joining (NHEJ) and HRR systems utilize initial DNA lesions as a substrate, these results suggest the possibility of a competitive interference phenomenon operating between NHEJ and at least the Rad51C/D components of HRR; the level of interaction between damaged DNA and a particular DNA-PK component may determine the level of interaction of such DNA with a relevant HRR component. PMID:24714417

Lin, Yu-Fen; Nagasawa, Hatsumi; Little, John B; Kato, Takamitsu A; Shih, Hung-Ying; Xie, Xian-Jin; Wilson, Paul F; Brogan, John R; Kurimasa, Akihiro; Chen, David J; Bedford, Joel S; Chen, Benjamin P C

2014-01-01

195

Differential Radiosensitivity Phenotypes of DNA-PKcs Mutations Affecting NHEJ and HRR Systems following Irradiation with Gamma-Rays or Very Low Fluences of Alpha Particles  

PubMed Central

We have examined cell-cycle dependence of chromosomal aberration induction and cell killing after high or low dose-rate ? irradiation in cells bearing DNA-PKcs mutations in the S2056 cluster, the T2609 cluster, or the kinase domain. We also compared sister chromatid exchanges (SCE) production by very low fluences of ?-particles in DNA-PKcs mutant cells, and in homologous recombination repair (HRR) mutant cells including Rad51C, Rad51D, and Fancg/xrcc9. Generally, chromosomal aberrations and cell killing by ?-rays were similarly affected by mutations in DNA-PKcs, and these mutant cells were more sensitive in G1 than in S/G2 phase. In G1-irradiated DNA-PKcs mutant cells, both chromosome- and chromatid-type breaks and exchanges were in excess than wild-type cells. For cells irradiated in late S/G2 phase, mutant cells showed very high yields of chromatid breaks compared to wild-type cells. Few exchanges were seen in DNA-PKcs-null, Ku80-null, or DNA-PKcs kinase dead mutants, but exchanges in excess were detected in the S2506 or T2609 cluster mutants. SCE induction by very low doses of ?-particles is resulted from bystander effects in cells not traversed by ?-particles. SCE seen in wild-type cells was completely abolished in Rad51C- or Rad51D-deficient cells, but near normal in Fancg/xrcc9 cells. In marked contrast, very high levels of SCEs were observed in DNA-PKcs-null, DNA-PKcs kinase-dead and Ku80-null mutants. SCE induction was also abolished in T2609 cluster mutant cells, but was only slightly reduced in the S2056 cluster mutant cells. Since both non-homologous end-joining (NHEJ) and HRR systems utilize initial DNA lesions as a substrate, these results suggest the possibility of a competitive interference phenomenon operating between NHEJ and at least the Rad51C/D components of HRR; the level of interaction between damaged DNA and a particular DNA-PK component may determine the level of interaction of such DNA with a relevant HRR component.

Little, John B.; Kato, Takamitsu A.; Shih, Hung-Ying; Xie, Xian-Jin; Wilson Jr., Paul F.; Brogan, John R.; Kurimasa, Akihiro; Chen, David J.; Bedford, Joel S.; Chen, Benjamin P. C.

2014-01-01

196

Study of the characteristics of high-energy proton-induced gamma ray and neutron emission from materials that imitate surface of planets.  

SciTech Connect

A proposed ISTC Project is discussed in the present paper. The proposal is aimed at experiments to determine the space-energy characteristics of the neutron and gamma ray emission fields generated by 0.2-0.8 GeV proton irradiation of thick targets composed of various elements. At present, reliable data on physical properties of secondary radiation from materials irradiated by intennediate- and high-energy protons for some fundamental and applied researches in astrophysics, space physics, atomic and nuclear physics, as well as for designing and operating the latest accelerators are lacking.

Titarenko, Y. E. (Yury E.); Batyaev, V. F. (Vyacheslav F.); Karpikhin, E. I. (Evgeny I.); Zhivun, V. M. (Valery M.); Koldobsky, A. B. (Aleksander B.); Mulambetov, R. D. (Ruslan D.); Mulambetova, S. V.; Mashnik, S. G. (Stepan G.); Nekrasov, Y. V. (Yu V.); Trebukhovsky, Y. V. (Yury V.); Barashenkov, V. S. (Vladilen Sergeevich); Dmitrenko, V. V.; Ulin, S. E.; Hasebe, N.; Prael, R. E. (Richard E.)

2003-01-01

197

Pulsed neutron gamma-ray logging in archaeological site survey  

NASA Astrophysics Data System (ADS)

An archaeological survey method based on neutron gamma-ray logging is described. The method relies on the measurement of capture gamma radiation induced by neutron irradiation from a pulsed generator. This technique provides elemental information on the irradiated zone by spectroscopic analysis of the gamma-ray data. This approach has been studied with Geant4 Monte Carlo simulations. In particular, irradiation volume for a deuterium-deuterium and deuterium-tritium (D-T) neutron generator and sampling volume for the D-T source were estimated. In addition, a neutron log response, which illustrates the capability of the neutron tool to localize artifacts lying beneath the surface, is shown.

Miceli, A.; Festa, G.; Gorini, G.; Senesi, R.; Andreani, C.

2013-12-01

198

Standoff Performance of HPGe Detectors in Identification of Gamma-Ray Radiation Sources  

Microsoft Academic Search

The detection and identification of radiation sources at distances in the range of 15 meters or more is becoming increasingly important for illicit materials interdiction and the location of lost or orphan sources. In most locations, there is a considerable gamma-ray flux from natural background (NORM) and cosmic- induced nuclides. This gamma-ray flux varies with time, weather conditions, location, and

Ronald M. Keyser; Timothy R. Twomey; Sam Hitch

199

Quasars, blazars, and gamma rays  

NASA Technical Reports Server (NTRS)

The paper discusses the extragalactic sources that have been discovered with the Energetic Gamma Ray Experiment Telescope. All of the sources demonstrate evidence of blazar properties at other wavelengths, including high optical polarization, extreme optical variability, flat-spectrum radio emission associated with a compact core, and apparent superluminal motion. These properties are believed to be produced by those few rare extragalactic quasars and radio galaxies that are favorably aligned to make it possible to observe almost directly down a relativistically outflowing jet of matter expelled from a supermassive black hole.

Dermer, Charles D.; Schlickeiser, Reinhard

1992-01-01

200

Cosmological aspects of gamma ray bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray burst observations provide a great opportunity for cosmography in high redshift. Some tight correlations between different physical properties of GRBs are discovered and used for cosmography. However, data selection, assumptions, systematic uncertainty and some other issues affect most of them. Most importantly, until the physical origin of a relation is understood, one should be cautious to employ the relation to utilize Gamma ray bursts for cosmography. In the first part of this dissertation, I use Liang-Zhang correlation to constrain ? Cold Dark Matter standard cosmology and a particular class of brane cosmology (brane-induced gravity model). With the most probable model being Om = 0.23 and O ? = 0.77 for flat ?CDM cosmology and O m = 0.18 and Wrc = 0.17 for flat brane-induced gravity cosmology, my result for the energy components of these two models is comparable with the result from SNIa observation. With average uncertainty of distance modulus being 0.2771, the two discussed cosmologies are indistinguishable using my current sample of GRB with redshift ranging between 0.1685 and 3.2. I argue that by expanding my sample and adding more low and high redshift GRBs and also with improvement in using GRB for cosmography, we might be able to distinguish between different cosmological models and tighten the most probable model. Looking into correlation and evolution of GRB prompt emission and afterglow has many advantages. It helps to open windows to comprehend the physics of GRBs and examine different GRB models. It is also possible to use GRB correlation as an accurate redshift estimator and more importantly to constrain the cosmological parameters. XRT flares of GRB afterglow are thought to be the result of central engine activity. Studying this component leads us to understand GRB flare and central engine nature. In the next part of this dissertation, I study the correlation and evolution of different prompt emission and afterglow GRB properties and some GRB flare-based quantities. Considering instrument bias and selection effect, I conclude some well-correlated correlations and establish some property evolution. The correlation between average luminosity and isotropic gamma-ray energy, energy of plateau and isotropic gamma-ray energy and luminosity at break time and break time and evolution of plateau energy are well established. It is also realized that the apparent evolution of isotropic gamma-ray energy and average luminosity is due to the instrumental flux threshold. With expanding the sample of GRB and accommodating more GRBs with XRT flares to my sample, I can reevaluate my result more firmly and confirm or rule out some hard to assert results due to limited number of data. In search for physically motivated GRB relation, analyzing the thermal component of GRB prompt emission, I derive two well-correlated relations. They are between calculated and estimated flux of the GRB thermal component for the co-moving bolometric and co-moving detector band-pass range of spectrum. In this study, three samples of Swift, pre-Swift and combined samples are used. The quality of this correlation is comparable with the Ghirlanda relation in terms of Spearman rank correlation parameters (correlation coefficient and correlation significance) and reduced chi2 of best fit. These results for the Swift GRB sample for co-moving bolometric range of spectrum are 0.81, 4.07 x 10-7 and 0.66 respectively. The derived correlations also imply a E gamma,iso - E4peak relation that provides physical insight to Egamma - Epeak Ghirlanda correlation. Three scaling coefficients are employed to study these correlations. Monte Carlo statistics indicates that the existing correlations are independent of these constants. For Swift and combined sample 73%--84.8% successes are recorded. Therefore, it is expected by determining these constants, the tightness of these correlations will further improve.

Behkam, Razieh

201

Gamma-ray pulsar studies with COMPTEL  

Microsoft Academic Search

Since the launch of the Compton Gamma-Ray Observatory (CGRO) the number of detected gamma-ray pulsars increased from two to six. COMPTEL, on-board CGRO and sensitive to gamma-rays with energies between approximately 0.7 and 30 MeV, detected three of these unambiguously. The classical Crab and Vela pulsars have been observed on several occasions and detailed pulse patterns and spectral parameters have

W. Hermsen; L. Kuiper; R. Diehl; G. Lichti; V. Schoenfelder; A. W. Strong; A. Connors; J. Ryan; K. Bennett; M. Busetta; A. Carraminana; R. Buccheri; I. A. Grenier

1994-01-01

202

Gamma-Ray Pulsar Studies with GLAST  

Microsoft Academic Search

Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests

D. J. Thompson; GAMMA-RAY PULSARS

2008-01-01

203

Gamma-Ray Pulsar Studies with GLAST  

NASA Technical Reports Server (NTRS)

This viewgraph presentation reviews the prospects of extending the understanding of gamma ray pulsars, and answering the open questions left from the limited observations that are available from current observatories. There are 2 new gamma ray observatories that are either on orbit or will be shortly launched: (1) Astro-rivelatore Gamma a Immagini LEggero (AGILE), and Gamma-ray Large Area Space Telescope (GLAST). On board GLAST there will be two instruments Large Area Telescope (LAT), and GLAST Burst Monitor (GBM).

Thompson, David J.

2007-01-01

204

Gamma-Ray Pulsar Candidates for GLAST  

Microsoft Academic Search

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 frequencies, are likely to emit >100 MeV gamma rays with intensities detectable by

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

2006-01-01

205

Gamma-Ray Pulsar Candidates for GLAST  

Microsoft Academic Search

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 >100; MeV gamma rays with intensities detectable by the LAT. The main

David John Thompson

2008-01-01

206

Gamma-Ray Astronomy Technology Needs  

NASA Technical Reports Server (NTRS)

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.

Gehrels, N.; Cannizzo, J. K.

2012-01-01

207

Very High Energy Gamma-Ray Astronomy  

Microsoft Academic Search

We present a review of the current status of very high energy gamma-ray astronomy. The development of the atmospheric Cerenkov imaging technique for ground-based gamma-ray astronomy has led to a rapid growth in the number of observatories. The detection of TeV gamma-rays from active galactic nuclei was unexpected and is providing new insights into the emission mechanisms in the jets.

Michael Catanese; Trevor C. Weekes

1999-01-01

208

GAMCIT: A gamma ray burst detector  

NASA Technical Reports Server (NTRS)

The origin of celestial gamma ray bursts remains one of the great mysteries of modern astrophysics. The GAMCIT Get-Away-Special payload is designed to provide new and unique data in the search for the sources of gamma ray bursts. GAMCIT consists of three gamma ray detectors, an optical CCD camera, and an intelligent electronics system. This paper describes the major components of the system, including the electronics and structural designs.

Surka, Derek M.; Grunsfeld, John M.; Warneke, Brett A.

1992-01-01

209

Astrophysical constraints from gamma-ray spectroscopy  

Microsoft Academic Search

Gamma-ray lines from cosmic sources provide unique isotopic information, since they originate from energy level transitions in the atomic nucleus. Gamma-ray telescopes explored this astronomical window in the past three decades, detecting radioactive isotopes that have been ejected in interstellar space by cosmic nucleosynthesis events and nuclei that have been excited through collisions with energetic particles. Astronomical gamma-ray telescopes feature

Roland Diehl; Nikos Prantzos; Peter von Ballmoos

2006-01-01

210

GRETINA: A gamma ray energy tracking array  

NASA Astrophysics Data System (ADS)

A gamma-ray energy tracking array (GRETA) is a new concept for the detection of gamma radiation. In such an array, the individual interactions of all the gamma rays are identified by their energies and positions. Then, using tracking algorithms based on the properties of gamma ray interactions, the scattering sequences are reconstructed. GRETA will give high peak efficiency, peak-to-background ratio, and position resolution. Recent research and development efforts have demonstrated that the construction of a gamma ray tracking array is feasible, and a plan for constructing a US array GRETINA is in place.

Lee, I. Y.; Clark, R. M.; Cromaz, M.; Deleplanque, M. A.; Descovich, M.; Diamond, R. M.; Fallon, P.; Macchiavelli, A. O.; Stephens, F. S.; Ward, D.

2004-12-01

211

BATSE observations of gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are being detected with unprecedented sensitivity by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray observatory since its launch in April, 1991. The experiment is detecting about one gamma-ray burst per day. A brief description is presented of the on-orbit performance of BATSE, the methods of identification of bursts, and examples of the diverse time profiles of the gamma-ray bursts observed. The most significant finding thus far is the apparent isotropy of the bursts together with the observed inhomogeneity of the sources.

Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Horack, J. M.; Brock, M. N.; Paciesas, W. S.; Pendleton, G. N.; Kouveliotou, C.

1991-09-01

212

BATSE observations of gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are being detected with unprecedented sensitivity by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory since its launch in April, 1991. The experiment is detecting about one gamma-ray burst per day. A brief description is presented of the on-orbit performance of BATSE, the methods of identification of bursts, and examples of the diverse time profiles of the gamma-ray bursts observed. The most significant finding thus far is the apparent isotropy of the bursts together with the observed inhomogeneity of the sources.

Fishman, Gerald J.; Meegan, C. A.; Wilson, R. B.; Horack, J. M.; Brock, M. N.; Paciesas, William S.; Pendleton, G. N.; Kouveliotou, C.

213

Radio Observations of Gamma-ray Novae  

NASA Astrophysics Data System (ADS)

Recent detection of gamma-ray emission from classical novae by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope surprised many in the astronomical community. We present results from radio observations, obtained using the Karl G. Jansky Very Large Array (VLA), of three gamma-ray novae: Mon2012, Sco2012, and Del2013. Radio observations allow for the calculation of ejecta masses, place limits on the distances, and provide information about the gamma-ray emission mechanism for these sources.

Linford, Justin D.; Chomiuk, L.; Ribeiro, V.; project, E.-Nova

2014-01-01

214

Low-level gamma-ray spectrometry  

SciTech Connect

Low-level gamma-ray spectrometry generally equates to high-sensitivity gamma-ray spectrometry that can be attained by background reduction, selective signal identification, or some combination of both. Various methods for selectively identifying gamma-ray events and for reducing the background in gamma-ray spectrometers are given. The relative magnitude of each effect on overall sensitivity and the relative cost'' for implementing them are given so that a cost/benefit comparison can be made and a sufficiently sensitive spectrometer system can be designed for any application without going to excessive or unnecessary expense. 10 refs., 8 figs.

Brodzinski, R.L.

1990-10-01

215

Future prospects for gamma-ray  

NASA Technical Reports Server (NTRS)

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.

Fichtel, C.

1980-01-01

216

Gamma-ray burst populations  

NASA Astrophysics Data System (ADS)

Over the last fifty years the field of gamma-ray bursts has shown incredible growth, but the amassing of data has also left observers and theorists alike wondering about some of the basic questions surrounding these phenomena. Additionally, these events show remarkable individuality and extrema, ranging in redshift throughout the observable universe and over ten orders of magnitude in energy. This work focuses on analyzing groups of bursts that are different from the general trend and trying to understand whether these bursts are from different intrinsic populations and if so, what can be said about their progenitors. This is achieved through numerical Monte Carlo simulations and statistical inference in conjunction with current GRB observations. Chapter 1 gives a general introduction of gamma-ray burst theory and observations in a semi-historical context. Chapter 2 provides an introduction to the theory and practical issues surrounding the numerical simulations and statistics. Chapters 3--5 are each dedicated to a specific problem relating to a different type of GRB population: high-luminosity v. low-luminosity bursts, constraints from high-redshift bursts, and Type I v. Type II bursts. Chapter 6 follows with concluding remarks.

Virgili, Francisco Javier

217

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

Microsoft Academic Search

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,

T. F. Lin; J. Carpenter; S. Desch; J. Gress; J. Poirier; A. Roesch

2000-01-01

218

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

Microsoft Academic Search

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,

Tzu-Fen Lin

1999-01-01

219

Gamma rays in a spectrum from the Mars Odyssey gamma-ray spectrometer.  

NASA Astrophysics Data System (ADS)

The gamma-ray spectrum from a long sum over the middle latitudes of Mars measured by the Mars Odyssey Gamma Ray Spectrometer was analyzed. About 250 peaks and features were observed, including many seen during the cruise to Mars. The sources of about 85% of these gamma rays were identified. Most were background lines from the Ge detector or from Ti, Mg, and Zn near the detector. Many gamma rays from Mars are present.

Brückner, J.; Reedy, R. C.; Evans, L. G.; Kim, K. J.; Boynton, W. V.

2003-04-01

220

Similarities between human ataxia fibroblasts and murine SCID cells: high sensitivity to gamma rays and high frequency of methotrexate-induced DHFR gene amplification, but normal radiosensitivity to densely ionizing alpha particles.  

PubMed

Two gamma-ray hypersensitive cell lines, human ataxia telangiectasia (AT) and murine severe combined immune deficiency (SCID) cells, proved to be very competent in amplifying their dihydrofolate reductase (DHFR) gene under methotrexate selection stress. Over a period of months, methotrexate-resistant clones were obtained which were able to grow in progressively increasing methotrexate concentrations up to 1 mM. By then methotrexate-resistant AT and SCID cells had amplified their DHFR gene 6- and 30-fold, respectively, and showed very high DHFR mRNA expression. In contrast, related cells with normal radiosensitivity (human GM637 and mouse BALB/c fibroblasts) did not show DHFR gene amplification under comparable conditions. This correlation of the capacity of DHFR gene amplification and gamma-ray hypersensitivity in AT and SCID cells suggests that gene amplification may have a mechanism(s) in common with those involved in repair of gamma-radiation-induced damage. No difference in cell killing could be observed following exposure to densely ionizing alpha particles: AT and SCID cells exhibited comparable survival rates to GM637 and BALB/c cells, respectively. PMID:7809366

Lücke-Huhle, C

1994-01-01

221

Photofission in uranium by nuclear reaction gamma-rays  

NASA Astrophysics Data System (ADS)

The ideal photon source for active interrogation of fissile materials would use monoenergetic photons to minimize radiation dose to surroundings. The photon energy would be high enough to produce relatively large photofission signals, but below the photoneutron threshold for common cargo materials in order to reduce background levels. To develop such a source, we are investigating the use of low-energy, proton-induced nuclear reactions to generate monochromatic, MeV-energy gamma-rays. Of particular interest are the nuclear resonances at 163 keV for the 11B(p,?) 12C reaction producing 11.7 MeV gamma-rays, 340 keV for the 19F(p,??) 16O reaction producing 6.13 MeV photons, and 441 keV for the 7Li(p,?) 8Be reaction producing 14.8 and 17.7 MeV photons. A 700 keV Van de Graaff ion accelerator was used to test several potential (p,?) materials and the gamma-ray yields from these targets were measured with a 5? × 5? NaI detector. A pulsed proton beam from the accelerator was used to induce prompt (neutron) and delayed (neutron and gamma-ray) photofission signals in uranium which were measured with 3He and NaI detectors. We show that the accelerator data is in good agreement with Monte Carlo radiation transport calculations and published results.

Morse, Daniel H.; Antolak, Arlyn J.; Doyle, Barney L.

2007-08-01

222

Cloaked Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

It is suggested that many gamma-ray bursts (GRBs) are cloaked by an ultrarelativistic baryonic shell that has high optical depth when the photons are manufactured. Such a shell would not fully block photons reflected or emitted from its inner surface, because the radial velocity of the photons can be less than that of the shell. This avoids the standard problem associated with GRBs that the thermal component should be produced where the flow is still obscured by high optical depth. The radiation that escapes high optical depth obeys the Amati relation. Observational implications may include (1) anomalously high ratios of afterglow to prompt emission, such as may have been the case in the recently discovered PTF 11agg, and (2) ultrahigh-energy neutrino pulses that are non-coincident with detectable GRB. It is suggested that GRB 090510, a short, very hard GRB with very little afterglow, was an exposed GRB, in contrast to those cloaked by baryonic shells.

Eichler, David

2014-06-01

223

Gamma rays from 'hidden' millisecond pulsars  

NASA Technical Reports Server (NTRS)

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.

Tavani, M.

1993-01-01

224

Gamma-Ray Pulsar Candidates for GLAST  

NASA Technical Reports Server (NTRS)

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.

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

225

Gamma rays from hidden millisecond pulsars  

NASA Technical Reports Server (NTRS)

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.

Tavani, Marco

1992-01-01

226

Fermi Gamma-Ray Space Telescope.  

National Technical Information Service (NTIS)

The nonthermal nature of high-energy gamma-ray emission almost assures that gamma-ray sources will be radio sources. The VLBA/Fermi cooperative effort has already produced some excellent science, and more is anticipated from ongoing programs. The Fermi Gu...

D. Thompson J. McEnery

2011-01-01

227

Gamma-Ray Pulsar Candidates for GLAST  

NASA Technical Reports Server (NTRS)

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.

Thompson, D. J.

2008-01-01

228

Gamma-ray emission from slow pulsars  

Microsoft Academic Search

The gamma-ray flux to be expected from three slow pulsars is calculated, neglecting the problem of the reliability of the observations. The principal hypothesis here is that since the gamma-ray luminosity is a substantial fraction of the intrinsic energy loss, it should be produced in the vicinity of the speed of light radius. This is from the argument of simultaneous

M. Morini; A. Treves

1981-01-01

229

Gamma-Ray Astronomy Technology Needs.  

National Technical Information Service (NTIS)

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 astrophys...

J. K. Cannizzo N. Gehrels

2012-01-01

230

GAMMA-RAY SPECTROSCOPY IN WELL LOGGING  

Microsoft Academic Search

Thermal neutron capture gamma rays have been observed in boreholes ; drilled in shales, sandstones, and limestones. A capsuled source of neutrons and ; a scintillation crystal detector, connected through 5,000 ft of logging cable to ; a transistorized, multichannel, pulse-height analyzer, were used. Resolved peaks ; were identified on the basis of the known energies of expected gamma rays

Richard L. Caldwell; W. F. Baldwin; J. D. Bargainer; J. E. Berry; G. N. Salaita; R. W. Sloan

1963-01-01

231

SIMULATE Program: a gamma ray spectroscopy tool  

Microsoft Academic Search

A software package which simulates the virtual creation of gamma ray spectra emitted from a combination of radioactive sources, as seen by a semiconductor or scintillation detector, is presented . It partially utilizes Monte Carlo techniques based on the physics of gamma ray spectroscopy. In addition, certain algorithms are used to compensate for the premature termination of the fate of

C. A Kalfas; E. Tsoulou

2003-01-01

232

Neutron Capture gamma-Ray Facility.  

National Technical Information Service (NTIS)

A neutron capture gamma-ray facility was constructed for prompt gamma-ray spectrometry, and its characteristics were measured. In the facility, a neutron beam is extracted from the H-6 horizontal experimental hole of Japan Research Reactor No.3, JAERI, an...

T. Tojo C. Yonezawa S. Koura S. Arai T. Komori

1980-01-01

233

Simulation fidelity issues when using gamma-ray simulators for TREE testing  

NASA Astrophysics Data System (ADS)

Factors that influence the fidelity of gamma-ray TREE testing are investigated. Specifically, package-induced dose enhancement in 256K CMOS static-random-access-memories (SRAMs) and dose enhancement from finite-range electrons produced (by gamma-ray interactions) in materials external to the SRAM packages are studied. Two gamma-ray simulators with significantly different spectra are used in the studies. The spectral differences produced less change in SRAM upset levels than did surrounding materials of equal mass density but differing atomic number. The implication for gamma-ray simulation testing is that individual devices within electronic systems may respond quite differently in gamma-ray TREE testing because of the structural materials within the system than when tests are performed on these individual devices without the system present.

Hartman, E. F.; Browning, J. S.; Drumm, C. R.

1990-12-01

234

Atmospheric gamma-ray and neutron flashes  

SciTech Connect

Gamma-ray pulses are calculated from 2D numerical simulations of an upward atmospheric discharge in a self-consistent electric field using the multigroup approach to the kinetics of relativistic runaway electrons (REs). Computed {gamma}-ray numbers and spectra are consistent with those of terrestrial {gamma}-ray flashes (TGFs) observed aboard spacecrafts. The RE flux is concentrated mainly within the domain of the Blue Jet fluorescence. This confirms that exactly the domain adjacent to a thundercloud is the source of the observed {gamma}-ray flashes. The yield of photonuclear neutrons is calculated. One {gamma}-ray pulse generates {approx}10{sup 14}-10{sup 15} neutrons. The possibility of the direct deposition of REs to the detector readings and the origin of the lightning-advanced TGFs are discussed.

Babich, L. P., E-mail: babich@elph.vniief.ru; Kudryavtsev, A. Yu., E-mail: kay@sar.ru; Kudryavtseva, M. L., E-mail: kay@sar.ru; Kutsyk, I. M. [All-Russian Research Institute of Experimental Physics (VNIIEF), Russian Federal Nuclear Center (Russian Federation)

2008-01-15

235

Instrumentation for gamma-ray astronomy  

NASA Astrophysics Data System (ADS)

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

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

1988-03-01

236

Instrumentation for gamma-ray astronomy  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

237

Gamma-Ray Spectral Calculations for Uranium Borehole Logging.  

National Technical Information Service (NTIS)

Gamma-ray transport calculations were performed to determine the energy distribution of gamma rays inside a borehole introduced into an infinite medium. The gamma rays from the naturally occurring radioactive isotopes of potassium, thorium, and uranium we...

D. A. Close M. L. Evans M. Jain

1980-01-01

238

Dose-dependent changes in the spectrum of mutations induced by ionizing radiation.  

PubMed

We examined the influence of dose on the spectrum of mutations induced at the hypoxanthine guanine phosphoribosyltransferase (Hprt) locus in Chinese hamster ovary (CHO) cells. Independent CHO-K1 cell mutants at the Hprt locus were isolated from cells exposed to 0, 0.5, 1.5, 3.0 and 6.0 Gy (137)Cs gamma rays, and the genetic changes responsible for the mutations were determined by multiplex polymerase chain reaction (PCR)-based exon deletion analysis. We observed dose-dependent changes in mutation spectra. At low doses, the principal radiation-induced mutations were point mutations. With increasing dose, multibase deletion mutations became the predominant mutation type such that by 6.0 Gy, there were almost three times more deletion mutations than point mutations. The dose response for induction of point mutations was linear while that for multibase deletions fit a linear-quadratic response. There was a biphasic distribution of deletion sizes, and different dose responses for small compared to large deletions. The frequency of large (>36 kb) total gene deletions increased exponentially, implying that they develop from the interaction between two independent events. In contrast, the dose response for deletion mutations of less than 10 kb was nearly linear, suggesting that these types of mutations develop mostly from single events and not the interactions between two independently produced lesions. The observation of dose-dependent changes in radiation-induced mutation spectra suggests that the types of alterations and therefore the risks from low-dose radiation exposure cannot be easily extrapolated from high-dose effects. PMID:10669553

Schwartz, J L; Jordan, R; Sun, J; Ma, H; Hsieb, A W

2000-03-01

239

Modeling gamma-ray bursts  

NASA Astrophysics Data System (ADS)

Discovered serendipitously in the late 1960s, gamma-ray bursts (GRBs) are huge explosions of energy that happen at cosmological distances. They provide a grand physical playground to those who study them, from relativistic effects such as beaming, jets, shocks and blastwaves to radiation mechanisms such as synchrotron radiation to galatic and stellar populations and history. Through the Swift and Fermi space telescopes dedicated to observing GRBs over a wide range of energies (from keV to GeV), combined with accurate pinpointing that allows ground based follow-up observations in the optical, infrared and radio, a rich tapestry of GRB observations has emerged. The general picture is of a mysterious central engine (CE) probably composed of a black hole or neutron star that ejects relativistic shells of matter into intense magnetic fields. These shells collide and combine, releasing energy in "internal shocks" accounting for the prompt emission and flaring we see and the "external shock" or plowing of the first blastwave into the ambient surrounding medium has well-explained the afterglow radiation. We have developed a shell model code to address the question of how X-ray flares are produced within the framework of the internal shock model. The shell model creates randomized GRB explosions from a central engine with multiple shells and follows those shells as they collide, merge and spread, producing prompt emission and X-ray flares. We have also included a blastwave model, which can constrain X-ray flares and explain the origin of high energy (GeV) emission seen by the Fermi telescope. Evidence suggests that gamma-ray prompt emission and X-ray flares share a common origin and that at least some flares can only be explained by long-lasting central engine activity. We pay special attention to the time history of central engine activity, internal shocks, and observed flares. We calculate the gamma-ray (Swift/BAT band) and X-ray (Swift/XRT band) lightcurves for arbitrary central engine activity and compare the model results with the observational data. We show that the observed X-ray flare phenomenology can be explained within the internal shock model. The number, width and occurring time of flares are then used to diagnose the central engine activity, putting constraints on the energy, ejection time, width and number of ejected shells. We find that the observed X-ray flare time history generally reflects the time history of the central engine, which reactivates multiple times after the prompt emission phase with progressively reduced energy. This shell model code can be used to constrain broadband observations of GRB 090926A, which showed two flares in both the Swift UVOT and XRT bands. Using the prompt emission fluence to constrain the total energy contained in the blastwave, the internal shock model requires that Lorentz factors of the shells causing flares must be less than the Lorentz factor of the blastwave when the shells are ejected. Recent observations of Gamma-Ray Bursts (GRBs) by the Fermi Large Area Telescope (LAT) revealed a power law decay feature of the high energy emission (above 100 MeV), which led to the suggestion that it originates from an external shock. We analyze four GRBs (080916C, 090510, 090902B and 090926A) jointly detected by Fermi LAT and Gamma-ray Burst Monitor (GBM), which have high quality lightcurves in both instrument energy bands. Using the MeV prompt emission (GBM) data, we can record the energy output from the central engine as a function of time. Assuming a constant radiative efficiency, we are able to track energy accumulation in the external shock using our internal/external shell model code and show that the late time lightcurves fit well within the external shock model, but the early time lightcurves are dominated by the internal shock component which has a shallow decay phase due to the initial pile-up of shells onto the blast wave.

Maxham, Amanda

240

Planetary gamma-ray spectroscopy, a special form of prompt charged particle and prompt neutron activation analysis  

Microsoft Academic Search

Gamma-rays emitted from the surfaces of atmosphere-free extraterrestrial bodies such as asteroids, planets, or moons, can be measured to determine their chemical surface composition. Gamma-rays are emitted from naturally radioactive elements and, in their majority, are induced by the interaction of the energetic galactic cosmic particle radiation. Neutrons of the secondary hadron cascade contribute considerably to the gamma-ray line surface

P. Englert; J. Brückner; H. Wänke

1987-01-01

241

Observations of Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Some basic observed properties of gamma-ray bursts are reviewed. Although some properties were known 25 years ago, new and more detailed observations have been made by the Compton Observatory in the past three years. The new observation with the greatest impact has been the observed isotropic distribution of bursts along with a deficiency of weak bursts which would be expected from a homogeneous burst distribution. This is not compatible with any known Galactic population of objects. Gamma-ray bursts show an enormous variety of burst morphologies and a wide spread in burst durations. The spectra of gamma-ray bursts are characterized by rapid variations and peak power which is almost entirely in the gamma-ray energy range. Delayed gamma-ray burst photons extending to GeV energies have been detected for the first time. A time dilation effect has also been reported to be observed in gamma-ray, bursts. The observation of a gamma-ray burst counterpart in another wavelength region has yet to be made.

Fishman, G. J.

1995-01-01

242

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

NASA Technical Reports Server (NTRS)

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.

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

243

gamma. -ray diagnostic for the CIT  

SciTech Connect

We have examined the feasibility of a fusion ..gamma..-ray diagnostic for the Compact Ignition Tokamak (CIT), which is expected to produce 10/sup 20/ (d, t) fusion reactions per second. Gamma rays at 16.7 MeV are produced by the t(d, ..gamma..)He/sup 5/ fusion reaction. A Monte Carlo coupled neutron--photon transport code is used to model the expected ..gamma..-ray spectrum incident upon a Compton spectrometer backed by a Cerenkov detector. The results indicate that a signal of approx.3 x 10/sup 4/ counts/s and a signal-to-noise ratio of approx.30 can be achieved.

Petrasso, R.D.; Fiore, C.L.; Li, C.

1988-08-01

244

GRETA - Gamma Ray Energy Tracking Array  

NASA Astrophysics Data System (ADS)

Gamma ray energy tracking is a new concept for detecting gamma rays. It can be implemented as a 4? array of highly segmented Ge detector, which would advance detection sensitivity by three orders of magnitude in certain applications. Such an array will provide tremendous discovery potential at current stable and exotic beam facilities, as well as at future facilities. The development of a tracking array for nuclear structure physics has brought together scientists from different areas. Technical advances made in the last 5 years have demonstrated that the construction of a gamma ray energy-tracking array is feasible, and a plan for constructing a US array is in place.

Lee, I.-Yang

2003-03-01

245

NEAR Gamma Ray Spectrometer Characterization and Repair  

NASA Technical Reports Server (NTRS)

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.

Groves, Joel Lee; Vajda, Stefan

1998-01-01

246

IR observations in gamma-ray blazars  

NASA Technical Reports Server (NTRS)

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.

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

1997-01-01

247

Fermi Gamma-Ray Space Telescope  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

248

Gamma-Ray Spectroscopy of 42K  

Microsoft Academic Search

Decay of 42K was investigated by a Ge(Li) detector and a 5''phi× 4'' NaI scintillation counter. Two gamma-ray peaks were newly observed at 0.692 and 1.228 MeV in the gamma-gamma coincidence spectrum. The 0.587 MeV gamma-ray, previously reported by McCullen et al., could not be seen and the upper limit of the intensity of this gamma-ray relative to the 0.900

Kiyoshi Kawade; Hiroshi Yamamoto; Kanzo Yoshikawa; Katsuyuki Iizawa; Isao Kitamura; Susumu Amemiya; Toshio Katoh; Yasukazu Yoshizawa

1970-01-01

249

The AGILE gamma ray satellite  

NASA Astrophysics Data System (ADS)

AGILE (Light Imager for Gamma-ray Astrophysics) will be launched on an equatorial orbit in 2007 by the PSLV Indian launcher. It is a small scientific satellite for the detection of ?-ray cosmic sources in the energy range 50 MeV 30 GeV with a field of view of 15 of the sky, and will become the only detector in that energy range till the launch of GLAST. Three different detectors and an anticoincidence system are the components of the scientific instrument. The main detector is a silicon tungsten tracker. The second detector is a X-ray detector in the range 15 45 keV; its main aim is to highlight the X-ray emission associated to the gamma emissions. The third detector is a small calorimeter made of 30 CsI scintillating bars read out by photodiodes; its energy range is 150 300 keV. The large number of channels (about 37 000, with analog read out), requires very reliable components. Each part of the instrument has undergone several tests during the assembly phase; then the whole instrument has been calibrated on a dedicated photon tagged beam-line developed at the DAPHNE BTF (Beam Test Facility, INFN Frascati) and has been integrated with the satellite.

Basset, M.; AGILE Team

2007-03-01

250

Interpretations and implications of gamma ray lines from solar flares, the galactic center in gamma ray transients  

NASA Technical Reports Server (NTRS)

Observations and theories of astrophysical gamma ray line emission are reviewed and prospects for future observations by the spectroscopy experiments on the planned Gamma Ray Observatory are discussed.

Ramaty, R.; Lingenfelter, R. E.

1980-01-01

251

Geolocation of Terrestrial Gamma Ray Flashes in Gamma Rays Using the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

We derive geolocations of bright Terrestrial Gamma ray Flashes (TGFs) directly in gamma rays using the Fermi Large Area Telescope (LAT) and compare with geolocations derived from LF and VLF (radio) networks. Imaging of the gamma ray direction is made possible by the fine spatial resolution of the LAT instrument, which is intended to make maps of the high-energy gamma ray astrophysical sky. Simulations show that LAT can geolocate very bright TGFs in favorable geometries with accuracies of several tens of km. Recent work by Connaughton et al. (2013) strongly suggests that the broadband radio signal is produced by the same bulk flow of relativistic electrons that create the gamma ray signal through bremsstrahlung interactions in the atmosphere. Our analysis confirms this picture by establishing that the radio and gamma ray signals are both temporally and spatially coincident. This work was performed at NRL and sponsored by NASA DPR S-15633-Y.

Schaal, Meagan; Grove, J. E.; Chekhtman, A.; Xiong, S.; Fitzpatrick, G.; Cummer, S.; Holzworth, R. H.

2014-01-01

252

Geolocation of Terrestrial Gamma Ray Flashes in Gamma Rays Using the Fermi Large Area Telescope  

NASA Astrophysics Data System (ADS)

We derive geolocations of bright Terrestrial Gamma ray Flashes (TGFs) directly in gamma rays using the Fermi Large Area Telescope (LAT) and compare with geolocations derived from LF and VLF (radio) networks. Imaging of the gamma ray direction is made possible by the fine spatial resolution of the LAT instrument, which is intended to make maps of the high-energy gamma ray astrophysical sky. Simulations show that LAT can geolocate very bright TGFs in favorable geometries with accuracies of several tens of km. Recent work by Connaughton et al. (2013) strongly suggests that the broadband radio signal is produced by the same bulk flow of relativistic electrons that create the gamma ray signal through bremsstrahlung interactions in the atmosphere. Our analysis confirms this picture by establishing that the radio and gamma ray signals are both temporally and spatially coincident. This work was performed at NRL and sponsored by NASA DPR S-15633-Y.

Schaal, M.; Grove, J.; Chekhtman, A.; Xiong, S.; Fitzpatrick, G.; Cummer, S. A.; Holzworth, R. H.

2013-12-01

253

Measuring High Energy Gamma Rays at the Homestake Mine for DUSEL Experiments  

NASA Astrophysics Data System (ADS)

Measuring external sources of background is very important to the planned DUSEL experiments. High energy gamma rays induced by muons in rock can range from keV to GeV. Characterizing the high energy gamma rays induced by muons at the Homestake Mine is implemented at different levels with multiple NaI detectors. With over one year data collection, we are able to show a spectrum of the high energy gamma rays induced by muons. A Monte Carlo simulation is also carried out to understand the muon ionization in the NaI detectors and the detection efficiency of high energy gamma-rays. We report the experimental results with the comparison from Monte Carlo simulations.

Zhang, Chao; Mei, Dongming; Thomas, Keenan; Gray, Fred

2011-04-01

254

Extreme energy gamma rays and neutrinos and their observation in JEM-EUSO Mission  

SciTech Connect

The origin of the extreme energy cosmic rays (EECRs) is a mystery in the contemporary astrophysics. The JEM-EUSO Mission that mainly aims establishing astronomy using such EECRs with very high statistics will also have realistic capability of detecting gamma rays and neutrinos with approx10{sup 20} eV energies. Aboard the International Space Station, the JEM-EUSO mission also provides a unique platform to detect and study the air showers from extreme energy gamma rays and neutrinos. In the present paper, we discuss a part of results from our study on properties of gamma ray and neutrino induced air showers and the advantage for space-based observation.

Shinozaki, K. [RIKEN, Wako 351-0198 (Japan)

2010-06-01

255

Gamma-Ray Heating in Power Reactors.  

National Technical Information Service (NTIS)

The objective of this work is to examine gamma ray heating in commercial nuclear power reactors. Design methods, computer codes, data libraries, and experimental data are examined. Some recommendations are made as to extensions of existing methods and cod...

A. P. Olson

1976-01-01

256

Gamma-Ray Pulsar Studies With GLAST  

SciTech Connect

Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

Thompson, D.J.; /NASA, Goddard

2011-11-23

257

Gamma-Ray Burst Smashes a Record  

NSF Publications Database

... the most distant explosion ever seen The Birth of a Gamma-Ray Burst: one scenario Credit and ... via e-mail, Web sites and cell phone. One of the first groups to respond was Reichart's team from ...

258

Positron annihilation gamma rays from novae  

NASA Technical Reports Server (NTRS)

The potential for observing annihilation gamma rays from novae is investigated. These gamma rays, a unique signature of the thermonuclear runaway models of novae, would result from the annihilation of positrons emitted by beta(+)-unstable nuclei produced near the peak of the runaway and carried by rapid convection to the surface of the nova envelope. Simple models, which are extensions of detailed published models, of the expansion of the nova atmospheres are evolved. These models serve as input into investigations of the fate of nearby Galactic fast novae could yield detectable fluxes of electron-positron annihilation gamma rays produced by the decay of N-13 and F-18. Although nuclear gamma-ray lines are produced by other nuclei, it is unlikely that the fluxes at typical nova distances would be detectable to present and near-future instruments.

Leising, Mark D.; Clayton, Donald D.

1987-01-01

259

Gamma-Ray Pulsar Studies with GLAST  

SciTech Connect

Some pulsars have their maximum observable energy output in the gamma-ray band, offering the possibility of using these high-energy photons as probes of the particle acceleration and interaction processes in pulsar magnetospheres. After an extended hiatus between satellite missions, the recently-launched AGILE mission and the upcoming Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) will allow gamma-ray tests of the theoretical models developed based on past discoveries. With its greatly improved sensitivity, better angular resolution, and larger energy reach than older instruments, GLAST LAT should detect dozens to hundreds of new gamma-ray pulsars and measure luminosities, light curves, and phase-resolved spectra with unprecedented resolution. It will also have the potential to find radio-quiet pulsars like Geminga, using blind search techniques. Cooperation with radio and X-ray pulsar astronomers is an important aspect of the LAT team's planning for pulsar studies.

Thompson, D. J. [Astrophysics Science Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2008-02-27

260

Gamma-ray bursts: An overview  

NASA Technical Reports Server (NTRS)

Gamma Ray Bursts were discovered by researchers studying data from gamma ray detectors aboard the Vela satellites. Since the original discovery, over 500 bursts have been observed by more than a dozen experiments on planetary spacecraft, earth orbiters, balloon flights, and even ground based instruments. Unfortunately, a description of the nature of these transient phenomena is no closer today than two decades ago. Part of the problem lies in the large variability in their physical characteristics. This variability has spawned more than 40 gamma ray burst models. Each model claims some subset of the 500 observed bursts that conclusively proves its validity. A very brief overview is presented of the gamma ray burst phenomenon.

Lestrade, John Patrick

1990-01-01

261

The EGRET high energy gamma ray telescope  

NASA Technical Reports Server (NTRS)

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.

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

262

Gamma rays from the magellanic clouds  

NASA Technical Reports Server (NTRS)

Predicted gamma ray fluxes from the Megallanic Clouds, obtained by using updated parameters, are significantly above the values previously determined, and well within the capabilities of observation from COS-B satellite. Concepts relating galactic gamma ray production and other Population 1 phenomena in the Milky Way were used to postulate a factor of four increase in predicted flux, based on the galactic origin hypothesis. The values obtained provide a possible test of two interpretations of gamma ray emission: enhancement in the inner galaxy from gas and cosmic ray sources alone, or increases produced by the trapping of cosmic rays in spiral arms. Because spiral structure is absent in the small cloud, and questionable in the large cloud, and both clouds are classed as irregular galaxies, the predicted enhancement in gamma ray flux may not be as great in the absence of clear spiral structure.

Stecker, F. W.

1977-01-01

263

Thermal neutron capture gamma-rays  

SciTech Connect

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

Tuli, J.K.

1983-01-01

264

Gamma-ray spectroscopy - Requirements and prospects  

NASA Technical Reports Server (NTRS)

The only previous space instrument which had sufficient spectral resolution and directionality for the resolution of astrophysical sources was the Gamma-Ray Spectrometer carried by HEAO-3. A broad variety of astrophysical investigations entail gamma-ray spectroscopy of E/Delta-E resolving power of the order of 500 at 1 MeV; it is presently argued that a sensitivity to narrow gamma-ray lines of a few millionths ph/sq cm, from about 10 keV to about 10 MeV, should typify the gamma-ray spectrometers of prospective missions. This performance is achievable with technology currently under development, and could be applied to the NASA's planned Nuclear Astrophysics Explorer.

Matteson, James L.

1991-01-01

265

The EGRET high energy gamma ray telescope  

NASA Astrophysics Data System (ADS)

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.

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.

1992-02-01

266

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

Microsoft Academic Search

We study the possibility of high-energy gamma-ray emission from the known 1130 radio pulsars based on the outer gap model of high-energy emission from pulsars. We estimate the fractional size of outer gap, the integrated flux, the gamma-ray luminosity for each known radio pulsar, and find that only 14% of the known radio pulsars are gamma-ray emitters according to the

Li Zhang; Jie Wu; Ze-Jun Jiang; Dong-Cheng Mei

2003-01-01

267

Low-State Gamma-Ray Emission from Blazars and the Gamma-Ray Background  

Microsoft Academic Search

We examine the contribution of flat spectrum radio sources (FSRSs), or blazars, to the diffuse gamma-ray background (DGRB), prompted by the association of the extragalactic gamma -ray sources detected by the EGRET instrument aboard the Compton Gamma Ray Observatory (CGRO) with this class of objects by using their well-studied log N--log S distribution. The basic assumption of our study are

Demosthenes Kazanas; Eric Perlman

1997-01-01

268

Comparison of gamma-ray coincidence and low-background gamma-ray singles spectrometry  

Microsoft Academic Search

Aerosol samples have been studied under different background conditions using gamma-ray coincidence and low-background gamma-ray singles spectrometric techniques with High-Purity Germanium detectors. Conventional low-background gamma-ray singles counting is a competitive technique when compared to the gamma–gamma coincidence approach in elevated background conditions. However, measurement of gamma–gamma coincidences can clearly make the identification of different nuclides more reliable and efficient than

J. Konki; P. T. Greenlees; U. Jakobsson; P. Jones; R. Julin; S. Juutinen; S. Ketelhut; K. Hauschild; R. Kontro; A.-P. Leppänen; A. Lopez-Martens; A. Mattila; P. Nieminen; M. Nyman; K. Peräjärvi; P. Peura; P. Rahkila; P. Ruotsalainen; J. Sarén; C. Scholey; J. Sorri; H. Toivonen; J. Turunen; J. Uusitalo

269

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

Microsoft Academic Search

Non-destructive gamma-ray analysis is a fundamental part of nuclear safeguards, including nuclear energy safeguards technology. Developing safeguards capabilities for nuclear energy will certainly benefit from the advanced use of gamma-ray spectroscopy as well as the ability to model various reactor scenarios. There is currently a wide variety of nuclear data that could be used in computer modeling and gamma-ray spectroscopy

2009-01-01

270

First results on terrestrial gamma ray flashes from the Fermi Gamma-ray Burst Monitor  

Microsoft Academic Search

The Gamma-ray Burst Monitor (GBM) on the Fermi Gamma-ray Space Telescope detected 12 intense terrestrial gamma ray flashes (TGFs) during its first year of observation. Typical maximum energies for most of the TGFs are ?30 MeV, with one TGF having a 38 MeV photon; two of the TGFs are softer and longer than the others. After correcting for instrumental effects,

M. S. Briggs; G. J. Fishman; V. Connaughton; P. N. Bhat; W. S. Paciesas; R. D. Preece; C. Wilson-Hodge; V. L. Chaplin; R. M. Kippen; A. von Kienlin; C. A. Meegan; E. Bissaldi; J. R. Dwyer; D. M. Smith; R. H. Holzworth; J. E. Grove; A. Chekhtman

2010-01-01

271

Swift: A gamma ray burst MIDEX  

Microsoft Academic Search

Swift is a first of its kind multiwavelength transient observatory for gamma-ray burst astronomy. It has the optimum capabilities for the next breakthroughs in determining the origin of gamma-ray bursts and their afterglows as well as using bursts to probe the early Universe. Swift will also perform the first sensitive hard X-ray survey of the sky. The mission is being

2001-01-01

272

Swift gamma-ray burst MIDEX  

Microsoft Academic Search

Swift is a first of its kind multiwavelength transient observatory for gamma-ray burst astronomy. It has the optimum capabilities for the next breakthroughs in determining the origin of gamma-ray bursts and their afterglows as well a using bursts to probe the early Universe. Swift will also perform the first sensitive hard X-ray survey of the sky. The mission is being

Neil A. Gehrels

2000-01-01

273

The swift gamma-ray burst MIDEX  

Microsoft Academic Search

Swift is a first of its kind multiwavelength transient observatory for gamma-ray burst astronomy. It has the optimum capabilities for the next breakthroughs in determining the origin of gamma-ray bursts and their afterglows as well as using bursts to probe the early Universe. Swift will also perform the first sensitive hard X-ray survey of the sky. The mission is being

Neil Gehrels

2000-01-01

274

Compton scattering gamma-ray source optimization  

NASA Astrophysics Data System (ADS)

The interaction of a bright relativistic electron beam with an intense laser pulse via Compton scattering can generate tunable gamma-rays for precision nuclear photonics applications. The properties of the gamma-ray phase space will be outlined, in relation with the 6D electron bunch and 6D laser pulse phase space, along with collimation, nonlinear effects and other sources of spectral broadening. Optimization strategies will be outlines within the context of nuclear photonics applications.

Hartemann, Frederic; Wu, Sheldon; Albert, Félicie; Barty, Chris

2012-10-01

275

Research in cosmic and gamma ray astrophysics  

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

276

Very high energy gamma-ray spectroscopy  

Microsoft Academic Search

The cosmic gamma-ray spectrum in the relatively unexplored energy range 1 ⪅ E? ⪅ 103GeV may have several interesting features. It may contain the gamma-ray lines from photino annihilation in the galactic halo, if photinos indeed comprise the unidentified dark matter in typical galaxies. There could also be a detectable diffuse background at E? > 30 GeV. These and other

David Eichler; James H. Adams Jr.

1987-01-01

277

GAMMA-RAY BURSTS AS HYPERNOVAE  

Microsoft Academic Search

The energetics of optical and radio afterglows following BeppoSAX and BATSE gamma-ray bursts (GRBs) suggests that gamma-ray emission is not narrowly collimated, but a moderate beaming is possible, so the total energy of a GRB may be in the range ? 1050 1051 erg. All attempts to generate a fireball powered by neutrino-antineutrino annihilation have failed so far, and a

Bohdan Paczynski

278

Gamma-ray Albedo of the Moon  

SciTech Connect

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). 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.

Moskalenko, Igor V.; Porter, Troy A.

2007-06-14

279

Method and apparatus for gamma ray well logging  

Microsoft Academic Search

A radioactive logging source carried by a logging tool injects gamma rays into the formation. A detector generates a pulse for each gamma ray incident upon the detector having an amplitude proportional to the gamma ray energy. Electrical signals corresponding to each such amplitude are delivered to the surface. These incident gamma rays originate from the formation as well as

Hubner

1985-01-01

280

Analysis of gamma ray displacement damage in Light Water Reactor pressure vessels  

SciTech Connect

In addition to fast neutrons, the copious energetic gamma rays, present in a reactor environment, induce displacement damage in the reactor pressure vessel. The contribution of gamma ray damage to embrittlement is most pronounced in reactors with large water gaps separating the core from the reactor pressure vessel. Water moderates the energies of fast neutrons much more effectively than it attenuates the high energy gamma flux, and thus enhances the high energy gamma flux, incident on the vessel relative to the fast neutron flux. In this paper, an analysis of computer transport calculations is presented which quantifies the relative contribution of gamma ray damage in various pressure vessels. The results indicate that gamma ray damage must be included for accurate predictions of radiation-induced embrittlement.

Alexander, D.E.; Rehn, L.E.

1995-05-01

281

Historical aspects of gamma-ray astronomy  

NASA Astrophysics Data System (ADS)

Over the entire 20th century, Cosmic Rays proved to be the watershed of fundamental knowledge from which poured out several streams that made us familiar with aspects of the universe that could never have been known through optical and radio astronomies alone. Cosmic ray interaction studies opened up the field of elementary particles and high energy physical processes. Gamma-ray astronomy enabled us to study celestial environments characterised by the dominance of high energy particles and their interactions with matter, magnetic and electric fields in the neighbourhood of these special environments. While neutrino astronomy is still in its infancy, it has the potential of becoming the most exciting field of study in the current century. Gamma-ray astronomy has had a chequered career. In the early part of the 20th century, Millikan proposed that cosmic rays are merely gamma rays. This was disproved by Compton, through the establishment of the latitude effect. The soviet astrophysicist Shklovskii pointed out at the III International conference on cosmic rays held at Guanjuato, Mexico, the possibility of supernova remants like the Crab Nebula being sources of TeV gamma rays. This was based on his realisation that the high degree of polarized light from the Crab could be due to Synchrotron emission by TeV energy electrons spiralling round the filamentary magnetic fields of the nebula. He argued that the same mechanism that accelerated electrons could also accelerate the protons which through their interaction with the surrounding matter generate pi-zero measons that would immediately decay into gamma rays. However, the efforts by the soviet experimentalists, who used the night air cerenkov technique for detection of the TeV gamma rays, proved negative; only upper limits could be set on the fluxew of TeV gamma rays from several of the SN-remnants; the negative results were first reported at the 7th ICRC held at Jaipur, India in 1963. High energy gamma ray astronomy had a remarkable revival with the discovery of Pulsars in 1967 and their identification with Neutron stars. The field has thrived since then has been extended even to the PeV range. Beginning with 1965, gamma ray astronomy in the energy range MeV to tens of GeV has also been successfully pursued with ballons, and satellites. The most perplexing in this energy range has been the discovery of the Gamma ray bursts. In the keynote address the historical aspects of this field will be covered with some references to the work in India.

Sreekantan, B. V.

2002-03-01

282

Fission-product gamma-ray line pairs sensitive to fissile material and neutron energy  

NASA Astrophysics Data System (ADS)

The beta-delayed gamma-ray spectra from the fission of 235U, 238U, and 239Pu by thermal and near-14-MeV neutrons have been measured for delay times ranging from 1 min to 14 h. Spectra at all delay times contain sets of prominent gamma-ray lines with intensity ratios that identify the fissile material and distinguish between fission induced by low-energy or high-energy neutrons.

Marrs, R. E.; Norman, E. B.; Burke, J. T.; Macri, R. A.; Shugart, H. A.; Browne, E.; Smith, A. R.

2008-07-01

283

Mercuric iodine room temperature gamma-ray detectors  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

284

Mercuric iodide room temperature gamma-ray detectors  

NASA Astrophysics Data System (ADS)

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.

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

1989-07-01

285

Prompt gamma rays from thermal-neutron capture  

Microsoft Academic Search

A catalog of ..gamma..-rays emitted following thermal-neutron capture in natural elements is presented. In Table I, ..gamma..-rays are arranged in order of increasing energy. Each line contains the ..gamma..-ray energy, intensity, element identification, thermal-neutron radiative-capture cross section, and the energies and intensities of two of the more abundant ..gamma..-rays associated with that element. In Table II, ..gamma..-rays are arranged by

M. A. Lone; R. A. Leavitt; D. A. Harrison

1981-01-01

286

Colour centres formation in CaF2 single crystals by gamma-rays and reactor neutrons  

Microsoft Academic Search

The induced colour in single crystals of calcium fluoride irradiated with gamma-rays and reactor neutrons have been investigated by optical measurements (absorption and photoluminescence). The optical absorption spectrum increases slightly by increasing gamma-rays dose up to 106 Gy and absorption bands centred at about 225, 260, 340, 396 and 580 nm are observed. At higher doses, in the case of

M. Izerrouken; L. Guerbous; A. Meftah

2010-01-01

287

Gamma-ray spectrometry of LDEF samples  

SciTech Connect

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

Winn, W.G.

1991-12-31

288

Gamma-ray spectrometry of LDEF samples  

SciTech Connect

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

Winn, W.G.

1991-01-01

289

Gamma-ray Burst Cosmology  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts (GRBs) are brief flashes of gamma-rays occurring at cosmological distances. GRB was discovered by Vela satellite in 1967. The discovery of afterglows in 1997 made it possible to measure the GRBs' redshifts and confirmed the cosmological origin. GRB cosmology includes utilizing long GRBs as standard candles to constrain the dark energy and cosmological parameters, measuring the high-redshift star formation rate (SFR), probing the metal enrichment history of the universe, dust, quantum gravity, etc. The correlations between GRB observables in the prompt emission and afterglow phases were discovered, so we can use these correlations as standard candles to constrain the cosmological parameters and dark energy, especially at high redshifts. Observations show that long GRBs may be associated with supernovae. So long GRBs are promising tools to measure the high-redshift SFR. GRB afterglows have a smooth continuum, so the extraction of IGM absorption features from the spectrum is very easy. The information of metal enrichment history and reionization can be obtained from the absorption lines. In this thesis, we investigate the high-redshift cosmology using GRBs, called GRB cosmology. This is a new and fast developing field. The structure of this thesis is as follows. In the first chapter, we introduce the progress of GRB studies. First we introduce the progress of GRB studies in various satellite eras, mainly in the Swift and Fermi eras. The fireball model and standard afterglow model are also presented. In chapter 2, we introduce the standard cosmology model, astronomical observations and dark energy models. Then progress on the GRB cosmology studies is introduced. Some of my works including what to be submitted are also introduced in this chapter. In chapter 3, we present our studies on constraining the cosmological parameters and dark energy using latest observations. We use SNe Ia, GRBs, CMB, BAO, the X-ray gas mass fraction in clusters and the linear growth rate of perturbations, and find that the ?CDM is the best fitted model. The transition redshift z_{T} is from 0.40_{-0.08}^{+0.14} to 0.65_{-0.05}^{+0.10}. This is the first time to combine GRBs with other observations to constrain the cosmological parameters, dark energy and transition redshift. In chapter 4, we investigate the early dark energy model using GRBs, SNe Ia, CMB and BAO. The negligible dark energy at high redshift will influence the growth of cosmic structures and leave observable signatures that are different from the standard cosmology. We propose that GRBs are promising tools to study the early dark energy. We find that the fractional dark energy density is less than 0.03 and the linear growth index of perturbations is 0.66. In chapter 5, we use a model-independent method to constrain the dark energy equation of state (EOS) w(z). Among the parameters describing the properties of dark energy, EOS is the most important. Whether and how it evolves with time are crucial in distinguishing different cosmological models. In our analysis, we include high-redshift GRBs. We find that w(z)<0 at z>1.7, and EOS deviates from the cosmological constant at z>0.5 at 95.4% confidence level. In chapter 6, we probe the cosmographic parameters to distinguish between the dark energy and modified gravity models. These two families of models can drive the universe to acclerate. We first derive the expressions of deceleration, jerk and snap parameters in the dark energy and modified gravity models. The snap parameters in these models are different, so they can be used to distinguish between the models. In chapter 7, we measure the high-redshift SFR using long GRBs. Swift observations reveal that the number of high-redshift GRBs is larger than the predication from SFR. We find that the evolving initial mass function can interpret this discrepancy. We study the high-redshift SFR up to z˜ 8.2 considering the Swift GRBs tracing the star formation history and the cosmic metallicity evolution in different background cosmological models. In chapter 8, we

Wang, F. Y.

2011-07-01

290

Gamma Rays in Spectra Measured by the Kaguya Gamma-Ray Spectrometer  

NASA Astrophysics Data System (ADS)

Of 200 peaks observed in spectra measured by the Kaguya Gamma Ray Spectrometer, the sources of 80% have been identified. Most are from the Ge detector, structural Al, and other local matter. Some gamma rays are from several elements in the Moon.

Reedy, R. C.; Hasebe, N.; Yamashita, N.; Karouji, Y.; Hareyama, M.; Kobayashi, S.; Okudaira, O.; Shibamura, E.; Kobayashi, M. N.; Kim, K. J.; D'Uston, C.; Diez, B.; Gasnault, O.; Forni, O.; Kaguya GRS Team

2009-03-01

291

Affaiblissement et taux d'erreur de transmission de fibres optiques multimodes soumises a une irradiation gamma a faible debit de dose. (Low dose rate gamma ray induced loss and data error rate of multimode silica fibre links).  

National Technical Information Service (NTIS)

Fiber optics data transmission from numerous multiplexed sensors, is potentially attractive for nuclear plant applications. Multimode silica fiber behaviour during steady state gamma ray exposure is studied as a joint programme between LETI CE/SACLAY and ...

G. Breuze H. Fanet J. Serre D. Colas E. Garnero

1993-01-01

292

Dose-dependent and gender-related radiation-induced transcription alterations of Gadd45a and Ier5 inhuman lymphocytes exposed to gamma ray emitted by (60)Co.  

PubMed

Growth arrest DNA damage-inducible 45a gene (Gadd45a) and immediate early response gene 5 (Ier5) have been emphasised as ideal radiation biomarkers in several reports. However, some aspects of radiation-induced transcriptional alterations of these genes are unknown. In this study, gender-dependency and dose-dependency as two factors that may affect radiation-induced transcription of Gadd45a and Ier5 genes were investigated. Human lymphocyte cells from six healthy voluntary blood donors (three women and three men) were irradiated in vitro with doses of 0.5-4.0 Gy from a (60)Co source and RNA isolated 4 h later using the High Pure RNA Isolation Kit. Dose and gender dependency of radiation-induced transcriptional alterations of Gadd45a and Ier5 genes were studied by quantitative real-time polymerase chain reaction. The results showed that as a whole, Gadd45a and Ier5 gave responses to gamma rays, while the responses were independent of radiation doses. Therefore, regardless of radiation dose, Gadd45a and Ier5 can be considered potential radiation biomarkers. Besides, although radiation-induced transcriptional alterations of Gadd45a in female and male lymphocyte samples were insignificant at 0.5 Gy, at other doses, their quantities in female samples were at a significantly higher level than in male samples. Radiation-induced transcription of Ier5 of females samples had a reduction in comparison with male samples at 1 and 2 Gy, but at doses of 0.5 and 4 Gy, females were significantly more susceptible to radiation-induced transcriptional alteration of Ier5. PMID:22923252

Tavakoli, Hassan; Manoochehri, Mahdi; Modarres Mosalla, Sayed Mahdi; Ghafori, Mostafa; Karimi, Ali Akbar

2013-04-01

293

Low-state gamma-ray emission from blazars and the gamma-ray background  

NASA Technical Reports Server (NTRS)

The contribution of flat spectrum radio sources (FSRS) or blazars to the diffuse gamma ray background is examined. The basic assumptions of the investigation are: the existence of steady state gamma ray emission at the energetic gamma ray experiment telescope (EGRET) instrument energy band from the entire population of the FSRS; a proportionality between the FSRS' gamma ray luminosities and radio luminosities; and the production of the diffuse gamma ray background by the ensemble of blazars. Under these assumptions, the estimated average value of the proportionality constant in the luminosity relationship (vF(sub v))(sub 100 MeV) = f(vF(sub v))(sub 5 GHz) is approximately 70, compared to a mean observed value of 750. The implications of this result for the active galactic nuclei models are considered.

Kazanas, Demosthenes; Perlman, Eric

1997-01-01

294

Stellar Photon Archaeology with Gamma-Rays  

NASA Technical Reports Server (NTRS)

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.

Stecker, Floyd W.

2009-01-01

295

Measurement of Radionuclide Activities Induced in Target Components of an IBA CYCLONE 18/9 by Gamma-Ray Spectrometry with HPGe and LaBr3: Ce Detectors.  

PubMed

Cyclotrons are used worldwide to produce radiopharmaceuticals by proton irradiation of a suitable target. The intense secondary neutron beam generated by proton interactions with the target induce high radionuclide activities in the target assembly parts that may result in an exposure to high dose levels of the operators during maintenance. The main goal of this work is to evaluate gamma-emitting radionuclide activities induced in Havar foils and titanium windows of a target assembly and carousel stripper forks of an IBA CYCLONE 18/9 cyclotron. The knowledge of radionuclide inventory for each component is required by many companies to assess risk for operators before waste handling and disposal. Gamma-ray spectrometric analyses were carried out with High Purity Germanium (HPGe) and Lanthanum bromide (LaBr3:Ce) scintillation detectors. HPGe is the most used detector for its high energy resolution although it is more suitable for use in a laboratory. The use of LaBr3:Ce can be considered a viable option, particularly in realizing a portable spectrometric system to perform "on-site" measurements and a fast dose rate evaluation before the disposal of activated parts. Due to a high activity of target assembly components replaced after a typical irradiation cycle (about 5000 ?Ah integrated beam current), gamma-ray spectrometric measurements were performed at a large distance from the detector, even more than 100 cm, or by using a purposely realized Lead-walled collimator. The identification of some key-radionuclides allows to evaluate through simple formulations the dose rate behavior for each component as function of decay time from the last irradiation. The knowledge of the dose rate behavior is a significant piece of information to health physicists for waste handling with safety at work. For an Havar™ foil, the dose rate will be reduced to about 1/1,000 of the starting value after a decay period of approximately 4 y (about 1,500 d), with a relatively safety at product disposal work. For a longer time, only long-lived radionuclides Co, Co, and Mn contribute to dose rate. PMID:24949919

Tomarchio, Elio

2014-08-01

296

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

NASA Technical Reports Server (NTRS)

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.

Venters, T. M.; Pavlidou, V.

2012-01-01

297

Digital discrimination of neutrons and gamma-rays in organic scintillation detectors using moment analysis  

NASA Astrophysics Data System (ADS)

Digital discrimination of neutron and gamma-ray events in an organic scintillator has been investigated by moment analysis. Signals induced by an americium-beryllium (Am/Be) isotropic neutron source in a stilbene crystal detector have been sampled with a flash analogue-to-digital converter (ADC) of 1 GSamples/s sampling rate and 10-bit vertical resolution. Neutrons and gamma-rays have been successfully discriminated with a threshold corresponding to gamma-ray energy about 217 keV. Moment analysis has also been verified against the results assessed by a time-of-flight (TOF) measurement. It is shown that the classification of neutrons and gamma-rays afforded by moment analysis is consistent with that achieved by digital TOF measurement. This method has been applied to analyze the data acquired from the stilbene crystal detector in mixed radiation field of the HL-2A tokamak deuterium plasma discharges and the results are described.

Xie, Xufei; Zhang, Xing; Yuan, Xi; Chen, Jinxiang; Li, Xiangqing; Zhang, Guohui; Fan, Tieshuan; Yuan, Guoliang; Yang, Jinwei; Yang, Qingwei

2012-09-01

298

Digital discrimination of neutrons and gamma-rays in organic scintillation detectors using moment analysis.  

PubMed

Digital discrimination of neutron and gamma-ray events in an organic scintillator has been investigated by moment analysis. Signals induced by an americium-beryllium (Am/Be) isotropic neutron source in a stilbene crystal detector have been sampled with a flash analogue-to-digital converter (ADC) of 1 GSamples/s sampling rate and 10-bit vertical resolution. Neutrons and gamma-rays have been successfully discriminated with a threshold corresponding to gamma-ray energy about 217 keV. Moment analysis has also been verified against the results assessed by a time-of-flight (TOF) measurement. It is shown that the classification of neutrons and gamma-rays afforded by moment analysis is consistent with that achieved by digital TOF measurement. This method has been applied to analyze the data acquired from the stilbene crystal detector in mixed radiation field of the HL-2A tokamak deuterium plasma discharges and the results are described. PMID:23020376

Xie, Xufei; Zhang, Xing; Yuan, Xi; Chen, Jinxiang; Li, Xiangqing; Zhang, Guohui; Fan, Tieshuan; Yuan, Guoliang; Yang, Jinwei; Yang, Qingwei

2012-09-01

299

Digital discrimination of neutrons and gamma-rays in organic scintillation detectors using moment analysis  

SciTech Connect

Digital discrimination of neutron and gamma-ray events in an organic scintillator has been investigated by moment analysis. Signals induced by an americium-beryllium (Am/Be) isotropic neutron source in a stilbene crystal detector have been sampled with a flash analogue-to-digital converter (ADC) of 1 GSamples/s sampling rate and 10-bit vertical resolution. Neutrons and gamma-rays have been successfully discriminated with a threshold corresponding to gamma-ray energy about 217 keV. Moment analysis has also been verified against the results assessed by a time-of-flight (TOF) measurement. It is shown that the classification of neutrons and gamma-rays afforded by moment analysis is consistent with that achieved by digital TOF measurement. This method has been applied to analyze the data acquired from the stilbene crystal detector in mixed radiation field of the HL-2A tokamak deuterium plasma discharges and the results are described.

Xie Xufei; Zhang Xing; Yuan Xi; Chen Jinxiang; Li Xiangqing; Zhang Guohui; Fan Tieshuan [School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing (China); Yuan Guoliang; Yang Jinwei; Yang Qingwei [Southwestern Institute of Physics, Chengdu (China)

2012-09-15

300

Photoneutron spectroscopy using monoenergetic gamma rays for bulk explosives detection  

NASA Astrophysics Data System (ADS)

To date, the most successful nuclear methods to confirm the presence of bulk explosives have been radiative thermal neutron capture (thermal neutron activation) and prompt radiative emission following inelastic fast neutron scattering (fast neutron analysis). This paper proposes an alternative: photoneutron spectroscopy using monoenergetic gamma rays. If monoenergetic gamma rays whose energies exceed the threshold for neutron production are incident on a given isotope, the emitted neutrons have a spectrum consisting of one or more discrete energies and the spectrum can be used as a fingerprint to identify the isotope. A prototype compact gamma-ray generator is proposed as a suitable source and a commercially available 3He ionization chamber is proposed as a suitable spectrometer. Advantages of the method with respect to the previously mentioned ones may include simpler spectra and low inherent natural neutron background. Its drawbacks include a present lack of suitable commercially available photon sources, induced neutron backgrounds and low detection rates. This paper describes the method, including kinematics, sources, detectors and geometries. Simulations using a modified Geant4 Monte Carlo modelling code are described and results are presented to support feasibility. Further experiments are recommended.

McFee, J. E.; Faust, A. A.; Pastor, K. A.

2013-03-01

301

Microsecond flares in gamma-ray bursts  

NASA Technical Reports Server (NTRS)

It has been suggested that gamma-ray burst light curves may consist of many superposed flares with a duration shorter than 30/microsec. If true, the implications for the interpretation of burst data are enormous. With the launch of the Compton Gamma-Ray Observatory, four predictions of Mitrofanov's (1989) suggestion can be tested. Our results which contradict this suggestion are (1) the photon arrival times are not correlated between independent detectors, (2) the spectral hardness and intensity does not depend on the detector area, (3) the bursts seen by detectors which measure photon positions do not see microsecond flares, and (4) burst positions deduced from detectors with different projected areas are close to the positions deduced from time-of-flight differences between separated spacecraft. We conclude, therefore, that gamma-ray bursts are not composed of microsecond flares.

Schaefer, Bradley E.; Cohen, Justin; Teegarden, Bonnard J.; Cline, Thomas L.; Fishman, Gerald J.; Meegan, Charles A.; Wilson, Robert B.; Paciesas, William S.; Pendleton, Geoffrey N.; Matteson, James L.

1993-01-01

302

Gamma-Ray Imaging for Explosives Detection  

NASA Technical Reports Server (NTRS)

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.

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

303

Gamma-ray imaging for explosives detection  

NASA Astrophysics Data System (ADS)

We describe a gamma-ray imaging camera (GIC) for active interrogation of explosives being developed by NASA/GSFC and NSWC/Carderock. 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, ~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.

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

2008-05-01

304

Gamma ray pulsars. [electron-photon cascades  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

305

THE fermi gamma-ray burst monitor  

NASA Astrophysics Data System (ADS)

The Gamma-Ray Burst Monitor (GBM) will significantly augment the science return from the Fermi Observatory in the study of gamma-ray bursts (GRBs). The primary objective of GBM is to extend the energy range over which bursts are observed downward from the energy range of the Large Area Telescope (LAT) on Fermi into the hard X-ray range where extensive previous data sets exist. A secondary objective is to compute burst locations onboard to allow re-orienting the spacecraft so that the LAT can observe delayed emission from bright bursts. GBM uses an array of 12 sodium iodide scintillators and two bismuth germanate scintillators to detect gamma rays from ~8 keV to ~40 MeV over the full unocculted sky. The onboard trigger threshold is ~0.7 photons cm-2 s-1 (50-300 keV, 1 s peak). GBM generates onboard triggers for ~250 GRBs per year.

Meegan, Charles; Lichti, Giselher; Bhat, P. N.; Bissaldi, Elisabetta; Briggs, Michael S.; Connaughton, Valerie; Diehl, Roland; Fishman, Gerald; Greiner, Jochen; Hoover, Andrew S.; van der Horst, Alexander J.; von Kienlin, Andreas; Kippen, R. Marc; Kouveliotou, Chryssa; McBreen, Sheila; Paciesas, W. S.; Preece, Robert; Steinle, Helmut; Wallace, Mark S.; Wilson, Robert B.; Wilson-Hodge, Colleen

2009-09-01

306

Technology Needs for Gamma Ray Astronomy  

NASA Technical Reports Server (NTRS)

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.

Gehrels, Neil

2011-01-01

307

Gamma-ray spectroscopy - Status and prospects  

NASA Technical Reports Server (NTRS)

Contemporary gamma-ray spectroscopy instruments and their results are reviewed. Sensitivities of 10 to the -4th to 10 to the -3rd ph/sq cm-sec have been achieved for steady sources and 10 to the -2nd to 1 ph/sq cm-sec for transient sources. This has led to the detection of gamma-ray lines from more than 40 objects representing 6 classes of astrophysical phenomena. The lines carry model-independent information and are of fundamental importance to theoretical modeling and our understanding of the objects. The objectives and anticipated results of future instruments are discussed. Several instruments in development will have a factor of 10 sensitivity improvement to certain phenomena over contemporary instruments. A factor of 100 improvement in sensitivity will allow the full potential of gamma-ray spectroscopy to be realized. Instrument concepts which would achieve this with both present and advanced techniques are discussed.

Matteson, J. L.

1983-01-01

308

Gamma rays from pulsar wind shock acceleration  

NASA Technical Reports Server (NTRS)

A shock forming in the wind of relativistic electron-positron pairs from a pulsar, as a result of confinement by surrounding material, could convert part of the pulsar spin-down luminosity to high energy particles through first order Fermi acceleration. High energy protons could be produced by this mechanism both in supernova remnants and in binary systems containing pulsars. The pion-decay gamma-rays resulting from interaction of accelerated protons with surrounding target material in such sources might be observable above 70 MeV with EGRET (Energetic Gamma-Ray Experimental Telescope) and above 100 GeV with ground-based detectors. Acceleration of protons and expected gamma-ray fluxes from SN1987A, Cyg X-3 type sources and binary pulsars are discussed.

Harding, Alice K.

1990-01-01

309

Neutron and Gamma-ray Measurements  

SciTech Connect

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

Krasilnikov, Anatoly V. [RRC 'Kurchatov Institute', Academician Kurchatov squarel, Moscow, 123182 (Russian Federation); SRC RF TRINITI, Troitsk, 142190 (Russian Federation); Sasao, Mamiko [Tohoku University, Sendai (Japan); Kaschuck, Yuri A. [SRC RF TRINITI, Troitsk, 142190 (Russian Federation); Kiptily, Vasily G.; Popovichev, Sergey V. [UKAEA, Abingdon (United Kingdom); Nishitani, Takeo [Japan Atomic Energy Agency, Tokai (Japan); Bertalot, Luciano [ITER Organization, Cadarach (France)

2008-03-12

310

Neutron and Gamma-ray Measurements  

NASA Astrophysics Data System (ADS)

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

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

2008-03-01

311

Gamma ray pulsars: Models and observations  

NASA Technical Reports Server (NTRS)

The two known gamma ray pulsars, the Crab and Vela, were used as guides for the development of models of high-energy radiation from spinning neutron stars. Two general classes of models were developed: those with the gamma radiation originating in the pulsar magnetosphere far from the neutron star surface (outer gap models) and those with the gamma radiation coming from above the polar cap (polar cap models). The goal is to indicate how EGRET can contribute to understanding gamma-ray pulsars, and especially how it can help distinguish between models for emission.

Thompson, David J.

1990-01-01

312

Gamma-Ray Burst Detection with Icecube  

NASA Astrophysics Data System (ADS)

With their narrow emission window gamma-ray bursts (GRBs) are among the most promising objects for the first identification of high-energy cosmic neutrinos. If a considerable fraction of the ultra-high energy cosmic rays is indeed produced in GRBs, IceCube, which is now more than half-way completed, should be able to detect the associated neutrinos in the next few years. Furthermore, optical follow-up observations of neutrino multiplets will enhance IceCube's sensitivity to choked GRBs which do not produce a gamma-ray signal.

Kappes, Alexander

313

VHE Gamma-ray Supernova Remnants  

SciTech Connect

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

Funk, Stefan; /KIPAC, Menlo Park

2007-01-22

314

Noiseless coding for the Gamma Ray spectrometer  

NASA Technical Reports Server (NTRS)

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.

Rice, R.; Lee, J. J.

1985-01-01

315

Precise absolute gamma-ray wavelength measurements  

NASA Astrophysics Data System (ADS)

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

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

1991-10-01

316

Gamma-ray binaries: pulsars in disguise?  

Microsoft Academic Search

Context: .LS 5039 and LS I+61°303 are unique amongst high-mass X-ray binaries (HMXB) for their spatially-resolved radio emission and their counterpart at >GeV gamma-ray energies, canonically attributed to non-thermal particles in an accretion-powered relativistic jet. The only other HMXB known to emit very high-energy (VHE) gamma-rays, PSR B1259-63, harbours a non-accreting millisecond pulsar. Aims: .The purpose is to investigate whether

Guillaume Dubus; Marie Curie

2006-01-01

317

Gamma ray bursts from magnetospheric plasma oscillations  

NASA Technical Reports Server (NTRS)

Neutron star Magnetospheric Plasma Oscillations (MPO), can account for the energetics, decay time scale, and spectra of typical Gamma Ray Bursts (GRBs). The soft photon source is likely to be due to backwarming of the reprocessing boundary by the incipient gamma rays. It is shown that the observed fraction of bursts displaying low energy absorption features may be understood in the context of an MPO model. Moreover, it is found that GRB spectra should display these cyclotron lines about 18 percent of the time, which is consistent with the KONUS and Ginga sets of data.

Melia, Fulvio

1989-01-01

318

Gamma-ray Burst Skymap Website  

NSDL National Science Digital Library

The Gamma-ray Burst Skymap website automatically updates for each gamma-ray burst as it occurs, whether detected by Swift or other orbiting satellites. For each burst, the location on the sky, star map, constellation and detecting mission are generated automatically. It is then quickly updated by hand to include a written description of the burst properties and scientific significance, as observations continue. Note: In order to view the content of the website, users need to download and install Silverlight on their computers.

319

Radioactivities and gamma-rays from supernovae  

NASA Technical Reports Server (NTRS)

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

Woosley, S. E.

1991-01-01

320

Energy–angle correlation of neutrons and gamma-rays emitted from an HEU source  

NASA Astrophysics Data System (ADS)

Special Nuclear Materials (SNM) yield very unique fission signatures, namely correlated neutrons and gamma-rays. A major challenge is not only to detect, but also to rapidly identify and recognize SNM with certainty. Accounting for particle multiplicity and correlations is one of standard ways to detect SNM. However, many parameter data such as joint distributions of energy, angle, lifetime, and multiplicity of neutrons and gamma-rays can lead to better recognition of SNM signatures in the background radiation noise. These joint distributions are not well understood. The Monte Carlo simulations of the transport of neutrons and gamma-rays produced from spontaneous and interrogation-induced fission of SNM are carried out using the developed MONSOL computer code. The energy spectra of neutrons and gamma-rays from a bare Highly Enriched Uranium (HEU) source are investigated. The energy spectrum of gamma-rays shows spectral lines by which HEU isotopes can be identified, while those of neutrons do not show any characteristic lines. The joint probability density function (JPDF) of the energy–angle association of neutrons and gamma-rays is constructed. Marginal probability density functions (MPDFs) of energy and angle are derived from JPDF. A probabilistic model is developed for the analysis of JPDF and MPDFs. This probabilistic model is used to evaluate mean values, standard deviations, covariance and correlation between the energy and angle of neutrons and gamma-rays emitted from the HEU source. For both neutrons and gamma-rays, it is found that the energy–angle variables are only weakly correlated.

Miloshevsky, G.; Hassanein, A.

2014-06-01

321

The Gamma-Ray Opacity of the Universe & Indirect Measurements of the EBL  

NASA Astrophysics Data System (ADS)

As gamma rays with energies of 20 GeV to 10s of TeV travel over extragalactic distances, their energy-dependent cross section with diffuse photons from the EBL (Extragalactic Background Light) results in electron-positron pair production. Thereby, absorption by the EBL affects the energy spectra of all extragalactic gamma-ray sources, effectively creating an energy dependent gamma-ray horizon.Observations of blazars with current generation satellite- and ground-based telescopes have revealed low gamma-ray opacities, much lower than previously expected. In turn, the energy spectra of blazars at GeV to TeV energies now also provide strong constraints to the EBL in the UV/optical light, the near-IR and the mid-IR.While photons with energies of 1 TeV or larger photons should not reach the observer from a redshift of z ~ 1 or larger, the production of secondary photons via hypothesized new physics (Axion-Like Particles), or cosmic-ray induced cascades could render high-redshift sources observable at TeV energies. Therefore, measurements of the gamma-ray opacity of the universe are also relevant for testing propagation models that are build on physical scenarios beyond gamma-ray absorption via pair production. A completely self-consistent picture, where direct measurements of the EBL or lower limits from galaxy counts, converge with indirect measurements with gamma rays is yet to be achieved with observations.Recent results from gamma-ray observations, their interpretation and caveats will be discussed.

Krennrich, Frank

2014-06-01

322

Trimethylpsoralen induces small deletion mutations in Caenorhabditis elegans.  

PubMed Central

To examine the mutagenic spectrum of 4,5',8-trimethylpsoralen (TMP) in Caenorhabditis elegans, we isolated mutations in the unc-22 and pal-1 genes following TMP mutagenesis and analyzed them for restriction fragment length polymorphisms by Southern blot. Eleven of 21 unc-22 mutations exhibited restriction fragment length polymorphisms, 8 of which were deletions of between 0.10 and 15 kb in length. Both of two pal-1 mutations were also small deletions within this size range. Comparison of our results with previous studies on mutagenesis by gamma-rays and x-rays suggests that the mutagenic spectrum of TMP may be similar. TMP should be useful in generating mutations that cause complete loss of function of single genes and that are likely to result in allele-specific DNA polymorphisms. Images

Yandell, M D; Edgar, L G; Wood, W B

1994-01-01

323

P2Y6 receptors and ADAM17 mediate low-dose gamma-ray-induced focus formation (activation) of EGF receptor.  

PubMed

The EGF receptor (EGFR) is frequently expressed in tumors of epithelial origin. Although it is well known that ionizing radiation induces activation of EGFR, the mechanism remains unknown. Recently, we reported that activation of P2Y receptors is involved in ?-radiation-induced activation of extracellular signal-regulated kinase1/2 (ERK1/2), which is dependent on activation of EGFR. Here we focused on the mechanism of activation of EGFR in response to low-dose ? radiation, mainly in terms of the activation-associated formation of EGFR foci in A549 cells. Irradiation of cells with 0.1 Gy ? rays induced biphasic phosphorylation of EGFR and ERK1/2 as well as biphasic formation of EGFR foci. The radiation-induced focus formation of EGFR was abolished by ecto-nucleotidase, P2Y receptor antagonists and knockdown of P2Y6 receptor, suggesting the involvement of extracellular nucleotides and activation of P2Y6 receptors in this process. Further, a disintegrin and metalloprotease 17 (ADAM17) is expressed in A549 cells and an ADAM17 inhibitor significantly blocked the radiation-induced focus formation of EGFR. We conclude that activation of both P2Y6 receptors and ADAM17 mediates the low-dose ?-radiation-induced activation of EGFR, as evaluated in terms of focus formation, in A549 cells. PMID:21268712

Tamaishi, Nana; Tsukimoto, Mitsutoshi; Kitami, Akihiro; Kojima, Shuji

2011-02-01

324

Mercury Gamma-rays and Neutron Spectrometer for ESA BepiColompo mission: numerical simulation of neutrons and gamma-rays from Mercury subsurface  

NASA Astrophysics Data System (ADS)

The nuclear instrument MGNS is under development for implementation on the MPO of Bepi-Colombo mission, as the contribution of Federal Space Agency of Russia to this project. In com-parison of gamma-rays spectrometer onboard NASA's Messenger interplanetary probe, which will provide mapping data for northern hemisphere of the planet only because of elliptical orbit, the MGNS onboard MPO will provide global mapping of the planet with similar coverage of southern and northern hemispheres of the Mercury. For analyse chemistry composition of Mercury subsurface we will apply method of as-called remote sensing of neutrons. This method can be use for study celestial body of Solar system without thick atmospheres, like Moon, Mars, Phobos, Mercury etc. by the analysis of induced nuclear gamma-rays and neutron emission. These gamma-rays and neutrons are produced by energetic galactic cosmic rays colliding with nuclei of regolith within a 1-2 meter layer of subsurface. This report will also describe result of numerical simulation flux of neutrons and gamma-rays lines from Mercury subsurface. The simulation was done for four different theoretical models of surface composition (model: ChM, EM, RM and VM) and for four different surface temperature (90 , 300 , 500 and 725 ). We simulate spectrum of neutron flux generated by Mercury surface and flax of gamma-rays for two major line (Al: 7.724 MeV and Si: 3.539 MeV) as function of temperature and subsurface composition.

Kozyrev, S. Alexander; Gunko, Natalya; Gurvits, Leonid; Litvak, Maxim; Malakhov, Alexey; Mitrofanov, Igor; Mokrousov, Maxim; Sanin, Anton; Shvetsov, Valery; Timoshenko, Genagy; Tretyakov, Vladislav; Tsygan, Anatoly; Vostrukhin, Andrey

325

Gamma-ray bursts as cosmological probes  

NASA Astrophysics Data System (ADS)

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

Vergani, S. D.

2013-11-01

326

Historical aspects of gamma-ray astronomy  

Microsoft Academic Search

Over the entire 20th century, Cosmic Rays proved to be the watershed of fundamental knowledge from which poured out several streams that made us familiar with aspects of the universe that could never have been known through optical and radio astronomies alone. Cosmic ray interaction studies opened up the field of elementary particles and high energy physical processes. Gamma-ray astronomy

B. V. Sreekantan

2002-01-01

327

Study of gamma-ray strength functions  

SciTech Connect

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

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

1980-08-07

328

Physics of Gamma Ray Emitting AGN  

NASA Astrophysics Data System (ADS)

The TANAMI program has been studying the physics of relativistic jets of gamma-ray emitting AGN since November 2007 and was converted to a 5-year Large Proposal from Oct 2009. We propose to continue VLBI monitoring of these sources contemporaneously with observations at gamma-ray frequencies by the Fermi satellite which is continuously monitoring the full sky for the next 5 to 10 years. TANAMI has met all goals of its first 2.5 years, in particular by producing high-quality dual-frequency images and setting up a baseline for morphological and kinematic studies of Southern-Hemisphere gamma-ray sources/candidates. With its associated optical/UV and X-ray programs and its unique VLBI dual-frequency characteristics, TANAMI has become one of the major multiwavelength resources for the Fermi mission and the only one covering sources south of -30 degrees. The continuation of our program will establish critical jet parameters, including speeds and Doppler factors, which all depend on multi-year VLBI data. Tracking new jet components and associating their ejection epochs with gamma-ray flares will be possible and promises to pin down the origin and nature of the elusive high energy emission from AGN.

Ojha, Roopesh; Lovell, Jim; Edwards, Philip; Kadler, Matthias; Monitoringteam, Gamma Ray Blazar; Tingay, Steven

2010-10-01

329

Current segmented gamma-ray scanner technology  

SciTech Connect

A new generation of segmented gamma-ray scanners has been developed at Los Alamos for scrap and waste measurements at the Savannah River Plant and the Los Alamos Plutonium Facility. The new designs are highly automated and exhibit special features such as good segmentation and thorough shielding to improve performance.

Bjork, C.W.

1987-01-01

330

Observations of Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

Observations of Gamma-ray bursts (GRBs) remain one of the most baffling phenomena in astrophysics. This talk will summarize the observations of GRBs with particular emphasis on those that present the greatest difficulty for theoretical interpretation. These include the short and highly variable temporal structure, the hard non-thermal spectra, and the enormous total energy output.

Meegan, C. A.; Six, N. Frank (Technical Monitor)

2001-01-01

331

Gamma-Ray Pulsars: Models and Predictions  

NASA Technical Reports Server (NTRS)

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.

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

2000-01-01

332

Prompt Signals of Gamma Ray Bursts.  

National Technical Information Service (NTIS)

We introduce a new model of gamma ray burst (GRB) that explains its observed prompt signals, namely, its primary thermal spectrum and high energy tail. This mechanism can be applied to either assumption of GRB pro-genitor: coalescence of compact objects o...

P. Chen

2001-01-01

333

Gamma-ray astronomy comes of age  

NASA Astrophysics Data System (ADS)

The 'spark chamber' detector used for energies greater than 10 MeV in gamma-ray astronomy is a pictorial device in which the ionization trails left by an electron-positron pair can be seen as a series of sparks. Such a detector, although yielding comparatively low angular resolution, has been used in the COS-B satellite observations of pulsars and molecular clouds that began in 1975. Preliminary COS-B analysis results indicate an abundance of cosmic ray protons in the Milky Way 60,000 light years from the galactic center; some of these protons may be of extragalactic origin. Another significant discovery of the COS-B mission has been a population of unidentified gamma-ray objects (UGOs). UGOs are unique in emitting gamma rays preferentially over all other forms of electromagnetic radiation, thereby posing many theoretical problems and compelling efforts toward their identification with objects emitting at other wavelengths. The only probable identification of this type that has thus far been accomplished is of the 'Geminga' gamma-ray source in Gemini; both an X-ray counterpart and possible optical counterparts have been proposed.

Bignami, G. F.

1985-10-01

334

Observations of cosmic gamma ray sources and their contribution to the diffuse gamma ray background  

NASA Astrophysics Data System (ADS)

The objective is to study soft gamma ray emission in the 0.1 to 10 MeV energy band for selected active galactic nuclei and explore how much they contribute to the total diffuse gamma ray background. A series of imaging observations of extragalactic objects in the low energy gamma-ray region were carried out by the Coded Aperture Directional Gamma-ray Telescope (DGT). The DGT was successfully flown at stratospheric balloon altitudes, and observations were made of the Crab, NGC 1275, MKN 421, and NGC 4151. The measured Crab spectrum is consistent with a featureless power-law of the form. Significant emission was detected up to 500 keV from the Seyfert galaxy, NGC 4151. To increase the total sky exposure the extragalactic field images were analyzed, including the 3C 273 region, obtained by the DGT.

Bhattacharya, Debadarshi

335

Investigation of gamma rays from the galactic center  

NASA Technical Reports Server (NTRS)

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.

Helmken, H. F.

1973-01-01

336

Precise gamma-ray Timing and Radio Observations of 17 Fermi gamma-ray Pulsars  

Microsoft Academic Search

We present precise phase-connected pulse timing solutions for 16 gamma-ray-selected pulsars recently discovered using the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope plus one very faint radio pulsar (PSR J1124-5916) that is more effectively timed with the LAT. We describe the analysis techniques including a maximum likelihood method for determining pulse times of arrival from unbinned photon

P. S. Ray; M. Kerr; D. Parent; A. A. Abdo; L. Guillemot; S. M. Ransom; N. Rea; M. T. Wolff; A. Makeev; M. S. E. Roberts; F. Camilo; M. Dormody; P. C. C. Freire; J. E. Grove; C. Gwon; A. K. Harding; S. Johnston; M. Keith; M. Kramer; P. F. Michelson; R. W. Romani; P. M. Saz Parkinson; D. J. Thompson; P. Weltevrede; K. S. Wood; M. Ziegler

2011-01-01

337

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

NASA Technical Reports Server (NTRS)

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%.

Forrest, D. J.

1978-01-01

338

Terrestrial gamma-ray flash production by lightning  

Microsoft Academic Search

Terrestrial gamma-ray flashes (TGFs) are brief flashes of gamma-rays originating in the Earth's atmosphere and observed by satellites. First observed in 1994 by the Burst And Transient Source Experiment on board the Compton Gamma-Ray Observatory, TGFs consist of one or more ˜1 ms pulses of gamma-rays with a total fluence of ˜1\\/cm2, typically observed when the satellite is near active

Brant E. Carlson

2010-01-01

339

Simultaneous optical/gamma-ray observations of GRBs  

NASA Technical Reports Server (NTRS)

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.

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

340

Solar gamma-ray experiment on Astro-A satellite  

Microsoft Academic Search

The instrumentation and performance parameters of the Japanese Astro-A satellite for measuring solar gamma ray lines and continua associated with solar flares are described. A gamma ray spectrometer which is a phoswich scintillator covers the gamma ray range from 0.24-6.48 MeV with a resolution of 10 percent at 662 keV. Techniques to discern gamma ray from particle events are discussed,

K. Okudaira; Y. Hirasima; M. Yoshimori; I. Kondo

1981-01-01

341

Wide energy range gamma-ray calibration source  

Microsoft Academic Search

Calibration source with monoenergetic gamma-ray lines in wide energy range designed for gamma-ray detector energetic calibration and testing has been built. Gamma-rays are obtained from thermal neutron capture, which is a suitable and cost efficient way how to provide discrete gamma-ray lines with energies above 3 MeV with reasonable intensity. With appropriate and interchangeable targets the source can generate different

M Kroupa; C Granja; Z Janout; M Kralik; F Krejci; A Owens; S Pospisil; F Quarati; J Solc; M Vobecky

2011-01-01

342

The origin and implications of gamma rays from solar flares  

NASA Technical Reports Server (NTRS)

Solar flares studied in the gamma ray region provide essential information on accelerated nuclei that can be obtained in no other way. A multitude of physical processes, such as particle acceleration, nuclear reactions, positron and neutron physics, and kinematical line broadening, come into consideration at gamma ray energies. Gamma ray observations are complementary to hard X ray observations, since both provide information on accelerated particles. It appears that only in the gamma ray region do these particles produce distinct spectral lines.

Ramaty, R.

1975-01-01

343

Gamma ray constraints on the Galactic supernova rate  

NASA Technical Reports Server (NTRS)

We perform Monte Carlo simulations of the expected gamma ray signatures of Galactic supernovae of all types to estimate the significance of the lack of a gamma ray signal due to supernovae occurring during the last millenium. Using recent estimates of the nuclear yields, we determine mean Galactic supernova rates consistent with the historic supernova record and the gamma ray limits. Another objective of these calculations of Galactic supernova histories is their application to surveys of diffuse Galactic gamma ray line emission.

Hartmann, D.; The, L.-S.; Clayton, Donald D.; Leising, M.; Mathews, G.; Woosley, S. E.

1991-01-01

344

Calibration of the RLS HPGe spectral gamma ray logging system  

Microsoft Academic Search

Gamma-ray spectral data have been recorded with the Radionuclide Logging System (RLS) high purity germanium (HPGe) system at (1) the American Petroleum Institute (API) spectral gamma-ray calibration center in Houston, Texas; (2) the US Department of Energy (DOE) spectral gamma-ray field calibration facility in Spokane, Washington; and (3) the DOE spectral gamma-ray primary calibration center in Grand Junction, Colorado. Analyses

C. J. Koizumi; J. R. Brodeur; W. H. Ulbricht; R. K. Price

1991-01-01

345

Lunar Elemental Abundances from Gamma-Ray and Neutron Measurements  

NASA Astrophysics Data System (ADS)

The determination of elemental abundances is one of the highest science objectives of most lunar missions. Such multi-element abundances, ratios, or maps should include results for elements that are diagnostic or important in lunar processes, including heat-producing elements (such as K and Th), important incompatible elements (Th and rare earth elements), H (for polar deposits and regolith maturity), and key variable elements in major lunar provinces (such as Fe and Ti in the maria). Both neutron and gamma-ray spectroscopy can be used to infer elemental abundances; the two complement each other. These elemental abundances need to be determined with high accuracy and precision from measurements such as those made by the gamma-ray spectrometer (GRS) and neutron spectrometers (NS) on Lunar Prospector. As presented here, a series of steps, computer codes, and nuclear databases are needed to properly convert the raw gamma-ray and neutron measurements into good elemental abundances, ratios, and/or maps. Lunar Prospector (LP) is the first planetary mission that has measured neutrons escaping from a planet other than the Earth. The neutron spectrometers on Lunar Prospector measured a wide range of neutron energies. The ability to measure neutrons with thermal (E < 0.1 eV), epithermal (E about equal 0.1 - 1000 eV), and fast (E about 0.1-10 MeV) energies maximizes the scientific return, being especially sensitive to both H (using epithermal neutrons) and thermal-neutron-absorbing elements. Neutrons are made in the lunar surface by the interaction of galactic-cosmic-ray (GCR) particles with the atomic nuclei in the surface. Most neutrons are produced with energies above about 0.1 MeV. The flux of fast neutrons in and escaping from the Moon depends on es the intensity of the cosmic rays (which vary with solar activity) and the elemental composition of the surface. Variations in the elemental composition of the lunar surface can affect the flux of fast neutrons by about 25% , with Ti and Fe emitting more fast neutrons than light elements like O and Si. Most elements moderate neutrons to thermal energies at similar rates. The main exception is when neutrons scatter from H, in which case neutrons can be rapidly thermalized. The cross sections for the absorption of thermal neutrons can vary widely among elements, with major elements like Ti and Fe having high-capture cross sections. Some trace elements, such as Sm and Gd, have such large neutron-absorption cross sections that, despite their low abundances, can absorb significant amounts of thermal neutrons in the Moon. Because the processes affecting neutrons are complicated, good modeling is needed to properly extract elemental information from measured neutron fluxes. The LAHET Code System (LCS) can be use to calculate neutron fluxes from GCR interactions in the Moon. Lunar Gamma-Ray Spectroscopy: The main sources of planetary gamma-rays are the decay of the naturally occurring radioactive isotopes of K, Th, and U and the interactions of GCRs with atomic nuclei in the planet's surface. Most "cosmogenic" gamma-rays are produced by fast and thermal neutrons made in the planet's surface by GCRs, and their production rates can vary with time. Over 300 gamma-ray lines have been identified that can be emitted from planetary surfaces by a variety of production mechanisms. There exist nuclear databases that can be used to identify and quantify other gamma-ray lines. Use will be made of gamma-rays from major elements, particularly those from Si and O, that have not been routinely used in the past. The fluxes of gamma-rays from a given element can vary depending on many factors besides the concentration of that element. For example, the fluxes of neutron-capture gamma-rays in the planetary region of interest depend on (1) the total cross section for elements to absorb thermalized neutrons and (2) the H content of the top meter of the surface. The fluxes of the fast neutrons that induce inelastic-scattering and other nonelastic-scattering reactions can vary with the composition of

Reedy, R. C.; Vaniman, D. T.

1999-01-01

346

Investigations in cosmic and gamma ray astronomy and nuclear instruments  

NASA Technical Reports Server (NTRS)

The Nuclear Radiation Monitor (NRM) is flying on the Spacelab 2 vehicle as part of a set of instrumentation designed to measure the ambient physical environment on Spacelab in orbit. The NRM measures the natural and induced gamma ray activity. The instrument is constituted of a 25 sq in (NaI (T1)) crystal viewed with a single phototube and surrounded by a plastic anticoincidence shield. It is mounted on a pedestal and placed, with its electronics, on the Spacelab pallet. The detector head was designed and a development model fabricated and tested. Extensive software studies for on board and GSE microprocessors for use with the NRM were also made.

Gregory, J. C.

1982-01-01

347

Theory and Modeling of Gamma-Ray Pulsars  

Microsoft Academic Search

Newborn neutron stars from supernovae explosions radiate brightly in gamma rays, outshining all other objects in the Galaxy. The gamma rays are emitted in a beam, and a flash of emission is observed at every rotation of the star; hence these objects are called gamma-ray pulsars. A great amount of energy is radiated in this form (~ 1035 erg\\/s), originating

Ion-Alexis George Yadigaroglu

1997-01-01

348

Probing the Radio Emission from Gamma Ray Blazars  

Microsoft Academic Search

The Energetic Gamma Ray Experiment Telescope on the Compton Gammay Ray Observatory discovered nearly 70 blazars with high confidence. The mechanics that results in the detectable gamma ray emission from these sources, is not completely understood, however. We obtained high resolution VLBA polarization imaging of two such gamma ray sources. We present our analysis of the superluminal motions discovered in

R. J. Cool; G. A. Moellenbrock

2003-01-01

349

Chemist's gamma-ray table. [9299 energy entries  

Microsoft Academic Search

An edited listing of gamma-ray information has been prepared. Prominent gamma rays originating from nuclides with half lives long enough to be seen in radiochemical experiments are included. Information is ordered by nuclide in one section and by energy in a second section. This shorter listing facilitates identification of nuclides responsible for gamma rays observed in experiments.

I. Binder; R. Kraus; R. Klein; D. Lee; M. M. Fowler

1977-01-01

350

Gamma-Ray Telescopes: 400 Years of Astronomical Telescopes  

NASA Technical Reports Server (NTRS)

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.

Gehrels, Neil; Cannizzo, John K.

2010-01-01

351

Very High-Energy Gamma-Ray Sources.  

ERIC Educational Resources Information Center

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)

Weekes, Trevor C.

1986-01-01

352

A Search for Gamma-Ray Bursts and Pulsars, and the Application of Kalman Filters to Gamma-Ray Reconstruction  

Microsoft Academic Search

Part I describes the analysis of periodic and transient signals in EGRET data. A method to search for the transient flux from gamma-ray bursts independent of triggers from other gamma-ray instruments is developed. Several known gamma-ray bursts were independently detected, and there is evidence for a previously unknown gamma-ray burst candidate. Statistical methods using maximum likelihood and Bayesian inference are

Brian Jones

2002-01-01

353

A search for gamma-ray bursts and pulsars, and the application of Kalman filters to gamma-ray reconstruction  

Microsoft Academic Search

High-energy gamma-ray astronomy was revolutionized in 1991 with the launch of the Energetic Gamma-Ray Experiment Telescope (EGRET) on board the Compton Gamma-Ray Observatory. In addition to unprecedented instrument effective area and a narrow point-spread function, EGRET provided photon time-tagging to an absolute accuracy of 100 mus. The opportunity to analyze high-quality gamma-ray data requires sophisticated statistical and analytic tools. Part

Brian Butler Jones

1999-01-01

354

Measurement of DNA damage induced by irradiation with gamma-rays from a TRIGA Mark II research reactor in human cells using Fast Micromethod.  

PubMed

The Fast Micromethod is a novel quick and convenient microplate assay for determination of DNA single-strand breaks. This method measures the rate of unwinding of cellular DNA upon exposure to alkaline conditions using a fluorescent dye which preferentially binds to double-stranded DNA. Here we applied this method to determine the levels of DNA single-strand breaks in HeLa cells induced by y-irradiation deriving from fission isotopes and activation products at the TRIGA Mark II research reactor in Mainz. An increased strand scission factor (SSF) value, which is indicative for DNA damage, was found at doses of 1 Gy and higher. A similar increase in SSF value, which further increased in a dose-dependent manner, was found in human peripheral blood mononuclear cells after irradiation with 6 MV X-rays from a linear accelerator to give a total exposure of 0.5 to 10 Gy. PMID:12064446

Hassanein, Hamdy; Müller, Claudia I; Schlösser, Dietmar; Kratz, Karl-Ludwig; Senyuk, Olga F; Schröder, Heinz C

2002-06-01

355

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

SciTech Connect

Non-destructive gamma-ray analysis is a fundamental part of nuclear safeguards, including nuclear energy safeguards technology. Developing safeguards capabilities for nuclear energy will certainly benefit from the advanced use of gamma-ray spectroscopy as well as the ability to model various reactor scenarios. There is currently a wide variety of nuclear data that could be used in computer modeling and gamma-ray spectroscopy analysis. The data can be discrepant (with varying uncertainties), and it may difficult for a modeler or software developer to determine the best nuclear data set for a particular situation. To use gamma-ray spectroscopy to determine the relative isotopic composition of nuclear materials, the gamma-ray energies and the branching ratios or intensities of the gamma-rays emitted from the nuclides in the material must be well known. A variety of computer simulation codes will be used during the development of the nuclear energy safeguards, and, to compare the results of various codes, it will be essential to have all the {gamma}-ray libraries agree. Assessing our nuclear data needs allows us to create a prioritized list of desired measurements, and provides uncertainties for energies and especially for branching intensities. Of interest are actinides, fission products, and activation products, and most particularly mixtures of all of these radioactive isotopes, including mixtures of actinides and other products. Recent work includes the development of new detectors with increased energy resolution, and studies of gamma-rays and their lines used in simulation codes. Because new detectors are being developed, there is an increased need for well known nuclear data for radioactive isotopes of some elements. Safeguards technology should take advantage of all types of gamma-ray detectors, including new super cooled detectors, germanium detectors and cadmium zinc telluride detectors. Mixed isotopes, particularly mixed actinides found in nuclear reactor streams can be especially challenging to identify. The super cooled detectors have a marked improvement in energy resolution, allowing the possibility of deconvolution of mixtures of gamma rays that was unavailable with high purity germanium detectors. Isotopic analysis codes require libraries of gamma rays. In certain situations, isotope identification can be made in the field, sometimes with a short turnaround time, depending on the choice of detector and software analysis package. Sodium iodide and high purity germanium detectors have been successfully used in field scenarios. The newer super cooled detectors offer dramatically increased resolution, but they have lower efficiency and so can require longer collection times. The different peak shapes require software development for the specific detector type and field application. Libraries can be tailored to specific scenarios; by eliminating isotopes that are certainly not present, the analysis time may be shortened and the accuracy may be increased. The intent of this project was to create one accurate library of gamma rays emitted from isotopes of interest to be used as a reliable reference in safeguards work. All simulation and spectroscopy analysis codes can draw upon this best library to improve accuracy and cross-code consistency. Modeling codes may include MCNP and COG. Gamma-ray spectroscopy analysis codes may include MGA, MGAU, U235 and FRAM. The intent is to give developers and users the tools to use in nuclear energy safeguards work. In this project, the library created was limited to a selection of actinide isotopes of immediate interest to reactor technology. These isotopes included {sup 234-238}U, {sup 237}Np, {sup 238-242}Pu, {sup 241,243}Am and {sup 244}Cm. These isotopes were examined, and the best of gamma-ray data, including line energies and relative strengths were selected.

Parker, W

2009-09-18

356

Simulation of prompt gamma-ray emission during proton radiotherapy.  

PubMed

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. PMID:22864267

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

2012-09-01

357

Gamma ray-induced bystander effect in tumour glioblastoma cells: a specific study on cell survival, cytokine release and cytokine receptors.  

PubMed

Recent experimental evidence has challenged the paradigm according to which radiation traversal through the nucleus of a cell is a prerequisite for producing genetic changes or biological responses. Thus, unexposed cells in the vicinity of directly irradiated cells or recipient cells of medium from irradiated cultures can also be affected. The aim of the present study was to evaluate, by means of the medium transfer technique, whether interleukin-8 and its receptor (CXCR1) may play a role in the bystander effect after gamma irradiation of T98G cells in vitro. In fact the cell specificity in inducing the bystander effect and in receiving the secreted signals that has been described suggests that not only the ability to release the cytokines but also the receptor profiles are likely to modulate the cell responses and the final outcome. The dose and time dependence of the cytokine release into the medium, quantified using an enzyme linked immunosorbent assay, showed that radiation causes alteration in the release of interleukin-8 from exposed cells in a dose-independent but time-dependent manner. The relative receptor expression was also affected in exposed and bystander cells. PMID:17251249

Facoetti, A; Ballarini, F; Cherubini, R; Gerardi, S; Nano, R; Ottolenghi, A; Prise, K M; Trott, K R; Zilio, C

2006-01-01

358

Gamma rays and large scale galactic structure  

NASA Technical Reports Server (NTRS)

Gamma ray astronomy is now beginning to provide a new look at the galactic structure and the distribution of cosmic rays, both electrons and nucleons, within the galaxy. The observations are consistent with a galactic spiral-arm model in which the cosmic rays are linearly coupled to the interstellar gas on the scale of the spiral arms. The agreement between the predictions of the model and the observations for regions of the plane where both 21-cm and 2.6-mm CO surveys exist emphasizes the need to extend these observations to include the entire plane. Future gamma-ray observations with more sensitivity and better angular resolutions, combined with these radio surveys, should shed new light on the distribution of cosmic rays, the nature of the galaxy, and the location and intensity of the spiral arms.

Kniffen, D. A.; Fichtel, C. E.; Thompson, D. J.

1977-01-01

359

The GAMCIT gamma ray burst detector  

NASA Technical Reports Server (NTRS)

The GAMCIT payload is a Get-Away-Special payload designed to search for high-energy gamma-ray bursts and any associated optical transients. This paper presents details on the design of the GAMCIT payload, in the areas of battery selection, power processing, electronics design, gamma-ray detection systems, and the optical imaging of the transients. The paper discusses the progress of the construction, testing, and specific design details of the payload. In addition, this paper discusses the unique challenges involved in bringing this payload to completion, as the project has been designed, constructed, and managed entirely by undergraduate students. Our experience will certainly be valuable to other student groups interested in taking on a challenging project such as a Get-Away-Special payload.

Mccall, Benjamin J.; Grunsfeld, John M.; Sobajic, Srdjan D.; Chang, Chinley Leonard; Krum, David M.; Ratner, Albert; Trittschuh, Jennifer E.

1993-01-01

360

Neutron-driven gamma-ray laser  

DOEpatents

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

Bowman, Charles D. (Los Alamos, NM)

1990-01-01

361

Morphological study of short gamma ray bursts  

NASA Astrophysics Data System (ADS)

Gamma Ray Bursts (GRB) of duration less than about 2 s, detected by the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory have been selected for temporal analysis. These bursts constitute nearly 25% of the total and presumably form a separate class. Several parameters to describe the complexity and rapidity based on the burst temporal structure are derived and their dependence on other temporal and spectral properties are explored. A parameter is derived for each burst to characterize its spectral evolution based on its light curves in 4 energy channels. Bursts detected during April 1991 and March 1993 have been analysed yielding a sample size of 51 bursts. It has been found that the burst complexity is independent of its spectral content. The spectral evolution of short bursts is same as that of longer bursts. Also a systematic search for a coherent emission of ?-rays in short bursts yielded a negative result.

Bhat, P. N.; Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Paciesas, W. S.

1996-08-01

362

Spectral evolution in gamma-ray bursts  

NASA Technical Reports Server (NTRS)

The Hard X-ray Burst Spectrometer (HXRBS) and the Gamma-Ray Spectrometer (GRS) on NASA's Solar Maximum Mission satellite have independently monitored cosmic gamma-ray bursts since launch in February 1980. Several bursts with relatively simple pulse structure and sufficient intensity have been analyzed for evidence of spectral variability on time scales shorter than the pulse durations. In many of these bursts pulse structures are found, ranging in duration from 1 to 10 seconds, which exhibit a trend of hard-to-soft spectral evolution. No significant evidence for soft-to-hard evolution has been found. The HXRBS data above 100 keV and the GRS data above 1 MeV indicate that the spectral evolution generally is not due to time-varying absorption features at energies below 100 keV.

Norris, J. P.; Share, G. H.; Messina, D. C.; Matz, M.; Kouveliotou, C.; Dennis, B. R.; Desai, U. D.; Cline, T. L.

1986-01-01

363

Research in cosmic and gamma ray astrophysics  

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

364

Gamma rays, cosmic rays, and galactic structure  

NASA Technical Reports Server (NTRS)

Observations of cosmic and gamma radiation by SAS-2 satellite are summarized and analyzed to determine processes responsible for producing observed galactic radiation. In addition to the production of gamma rays in discrete galactic objects such as pulsars, there are three main mechanisms by which high-energy (greater than 100 MeV) radiation is produced by high-energy interactions involving cosmic rays in interstellar space. These processes, which produce what may be called diffuse galactic gamma-rays, are: (1) the decay of pi mesons produced by interactions of cosmic ray nucleons with interstellar gas nuclei; (2) the bremsstrahlung radiation produced by cosmic ray electrons interacting in the Coulomb fields of nuclei of interstellar gas atoms; and (3) Compton interactions between cosmic ray electrons and low-energy photons in interstellar space.

Stecker, F. W.

1977-01-01

365

Gamma Ray Observatory (GRO): Emergency support  

NASA Technical Reports Server (NTRS)

The Gamma Ray Observatory (GRO) is an Earth orbiting satellite that studies sources of localized, galactic, and extragalactic gamma rays. It will be carried into a near-circular orbit by the Space Shuttle, following which it will be placed in its operational orbit by its on-board hydrazine propulsion system. Formal orbit parameters are 350 km x 450 km x 28.5 degrees with a period of 93 minutes. Deep Space Network coverage will be provided during emergencies that would prevent communications via the normal Tracking and Data Relay Satellite System (TDRSS)-White Sands data link. Emergency support will be provided by the DSN's 26-meter antenna subnetwork. Information is given in tabular form for DSN support, frequency assignments, telemetry, and command.

Schauer, K.; Madden, J.

1991-01-01

366

Gamma-ray multiplicity measurements using STEFF  

NASA Astrophysics Data System (ADS)

An ongoing investigation into the angular momentum generated during the fission of 252Cf is currently under way using the SpecTrometer for Exotic Fission Fragments (STEFF). Measurements have been made of the fold distribution (measured multiplicity) with STEFF. These have been compared to a Monte-carlo simulation to determine a value for the average angular momentum Jrms = 6hslash which is comparable to previous measurements [1]. Measurements of the gamma-ray multiplicity were performed whilst gating on different fragment mass regions. The result was compared with a sum of the lowest 2+ energies from both fragment and complementary in the mass gate. The results support the view that gamma-ray multiplicity is largely determined by the decay of the nucleus through near yrast transitions that follow the statistical decay.

Pollitt, A. J.; Smith, A. G.; Tsekhanovich, I.; Dare, J. A.

2012-09-01

367

Cosmic-Rays and Gamma Ray Bursts  

NASA Astrophysics Data System (ADS)

Cosmic-rays are subatomic particles of energies ranging between a few eV to hundreds of TeV. These particles register a power-law spectrum, and it seems that most of them originate from astrophysical galactic and extragalactic sources. The shock acceleration in superalfvenic astrophysical plasmas, is believed to be the main mechanism responsible for the production of the non-thermal cosmic-rays. Especially, the importance of the very high energy cosmic-ray acceleration, with its consequent gamma-ray radiation and neutrino production in the shocks of the relativistic jets of Gamma Ray Bursts, is a favourable theme of study. I will discuss the cosmic-ray shock acceleration mechanism particularly focusing on simulation studies of cosmic-ray acceleration occurring in the relativistic shocks of GRB jets.

Meli, A.

2013-07-01

368

The gamma ray north-south effect  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

369

Real time gamma-ray signature identifier  

DOEpatents

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

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

2012-05-15

370

Gamma-Ray Burst Progenitors: Merger Model  

NASA Astrophysics Data System (ADS)

The mergers of neutron stars and black holes remain a viable model for gamma-ray burst central engines, at least for the class of short bursts: their time scales, occurrence rates and energy output seem to be consistent with observations. We will present results of our latest simulations showing how the orbit of a neutron star around a black hole shrinks due to gravitational radiation, how the neutron star's matter gets accreted by the black hole, and how the tidal forces of the black hole finally shred the neutron star into a thick disk. In this process, huge amounts of energy are radiated away by gravitational waves and by neutrinos emitted from the hot disk. The neutrino luminosities are so large that an appreciable fraction (some few percent!) of neutrinos annihilate with antineutrinos creating the clean fireball necessary to power gamma-ray bursts.

Ruffert, Maximilian

2002-04-01

371

Gamma-Ray Polarimetry with Compton Telescope  

SciTech Connect

Compton telescope is a promising technology to achieve very high sensitivity in the soft gamma-ray band (0.1-10 MeV) by utilizing Compton kinematics. Compton kinematics also enables polarization measurement which will open new windows to study gamma-ray production mechanism in the universe. CdTe and Si semiconductor technologies are key technologies to realize the Compton telescope in which their high energy resolution is crucial for high angular resolution and background rejection capability. We have assembled a prototype module using a double-sided silicon strip detector and CdTe pixel detectors. In this paper, we present expected polarization performance of a proposed mission (NeXT/SGD). We also report results from polarization measurements using polarized synchrotron light and validation of EGS4 MC simulation.

Tajima, H

2004-07-06

372

Nucleosynthesis and astrophysical gamma ray spectroscopy  

NASA Technical Reports Server (NTRS)

The HEAO-3 gamma ray spectrometer has provided evidence in the quest for the understanding of complex element formation in the universe with the discovery of Al-26 in the interstellar medium. It has demonstrated that the synthesis of intermediate mass nuclei is currently going on in the galaxy. This discovery was confirmed by the Solar Maximum Mission. The flux is peaked near the galactic center and indicates about 3 solar masses of Al-26 in the interstellar medium, with an implied ratio of Al-26/Al-27 = .00001. Several possible distributions were studied but the data gathered thus far do not allow discrimination between them. It is felt that only the spaceflight of a high resolution gamma ray spectrometer with adequate sensitivity will ultimately resolve the issue of the source of this material.

Jacobson, Allan S.

1987-01-01

373

Gamma ray spectroscopic measurements of Mars.  

PubMed

A gamma ray spectrometer placed in orbit around Mars is expected to yield significant compositional data which can be related to the evolution of that planet. Components of the observable gamma ray flux come from the Martian surface, galactic and intergalactic space, and the spacecraft itself. The flux can be detected by a scintillation crystal or solid state detector, either of which combines efficiency of detection with energy resolution, and returns information to the earth as a pulse height distribution in order to detect characteristic energy line structure. The data will be evaluated for evidence of elemental differentiation with reference to terrestrial, meteoritic, solar, and lunar abundances. A lengthy mission will allow the surface of Mars to be mapped in a search for possible correlations between composition and topography or albedo. PMID:20076376

Metzger, A E; Arnold, J R

1970-06-01

374

The gamma-ray telescope Gamma-1  

NASA Astrophysics Data System (ADS)

The telescope 'Gamma-1' is designed to investigate cosmic gamma rays in the energy range from 50 MeV to 5000 MeV. The geometrical sensitive area of the telescope amounts to 1500 cm2, the angular resolution in each direction is equal to 1.2° at the energy 300 MeV and is about 20arcmin when including a coded mask in the telescope, the energy resolution changes from 70% at 100 MeV to 35% at 550 MeV. The characteristics of the telescope and its systems have been determined by the Monte-Carlo method as well as by accelerator calibrations. Discrete sources at the intensity level of 10-7quanta cm-2s-1 may be recorded in a year of observations with the gamma-ray telescope 'Gamma-1' with a source location accuracy of ?10 arc min.

Akimov, V. V.; Balebanov, V. M.; Belousov, A. S.; Blokhintsev, I. D.; Veselova, G. V.

375

Mutations induced in Drosophila during space flight.  

PubMed

To examine the possible effects of space radiation on living organisms, fruit flies Drosophila melanogaster were loaded on the US Space Shuttle Endeavour, and after the flight we have analyzed two types of mutations, sex-linked recessive lethal mutations induced in male reproductive cells and somatic mutations which give rise to morphological changes in hairs growing on the surface of wing epidermal cells. Wild type strains and a radiation-sensitive strain mei-41 were used. The frequencies of sex-linked recessive lethal mutations in flight groups were 2 and 3 times higher for wild type Canton-S and mei-41 strains, respectively, than those in ground control groups. By contrast, the frequencies of wing-hair somatic mutations differed little between flight and control groups. The possibility that the space environment causes mutations in certain types of cells such as male reproductive cells, is discussed. PMID:11541768

Ikenaga, M; Yoshikawa, I; Kojo, M; Ayaki, T; Ryo, H; Ishizaki, K; Kato, T; Yamamoto, H; Hara, R

1997-12-01

376

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

NASA Technical Reports Server (NTRS)

We describe the development of an instrument capable of detailed in situ bulk geochemical analysis of the surface of planets, moons, asteroids, and comets. This instrument technology uses a pulsed neutron generator to excite the solid materials of a planet and measures the resulting neutron and gamma-ray emission with its detector system. These time-resolved neutron and gamma-ray data provide detailed information about the bulk elemental composition, chemical context, and density distribution of the soil within 50 cm of the surface. While active neutron scattering and neutron-induced gamma-ray techniques have been used extensively for terrestrial nuclear well logging applications, our goal is to apply these techniques to surface instruments for use on any solid solar system body. As described, experiments at NASA Goddard Space Flight Center use a prototype neutron-induced gamma-ray instrument and the resulting data presented show the promise of this technique for becoming a versatile, robust, workhorse technology for planetary science, and exploration of any of the solid bodies in the solar system. The detection of neutrons at the surface also provides useful information about the material. This paper focuses on the data provided by the gamma-ray detector.

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

2011-01-01

377

Gamma-ray production cross sections from neutron interactions with iron.  

SciTech Connect

The initial purpose of this experiment was to provide a consistent data base of neutron-induced gamma-ray production cross sections over a large energy range for use in estimating elemental composition of the martian surface by observing gamma rays produced by cosmic ray interactions on the planet's surface [Bo02]. However, these data should be useful for other projects such as oil-well logging, accelerator transmutation of nuclear waste, shielding calculations, gamma-ray heating for nuclear reactors and verification of nuclear model calculations and databases. The goal of the measurements was to collect data on the strongest gamma rays from many samples of interest. Because of the available beam time this meant that many of the measurcments were rather short. Despite the short running time the large samples used and the good beam intensity resulted in very satisfactory results. The samples, chosen mainly as common constituents of rock and soil and measured in the same few week period, include: B&, BN, C, Al, Mg, Si, S, Cay Ti, Cr, Mn, and Fe. Be was also used as a neutron scatterer that only produces one gamma ray (478 keV from 7Li) with appreciable intensity. Thus Be can serve as a measure of neutron-induced backgrounds. In this first paper we present results for Fe.

Nelson, R. O. (Ronald O.); Laymon, C. M. (Charles M.); Wender, S. A. (Stephen A.); Drake, D. M. (Darrell M.); Drosg, Manfred; Bobias, S. G. (S. George); McGrath, C. A. (Christopher A.)

2002-01-01

378

The gamma-ray telescope Gamma1  

Microsoft Academic Search

The telescope ‘Gamma-1’ is designed to investigate cosmic gamma rays in the energy range from 50 MeV to 5000 MeV. The geometrical sensitive area of the telescope amounts to 1500 cm2, the angular resolution in each direction is equal to 1.2° at the energy 300 MeV and is about 20' when including a coded mask in the telescope, the energy

V. V. Akimov; V. M. Balebanov; A. S. Belousov; I. D. Blokhintsev; G. V. Veselova; M. B. Dobrijan; L. F. Kalinkin; S. V. Kovalenko; V. D. Kozlov; N. G. Leikov; N. K. Mordvov; Y. I. Nagornih; V. E. Nesterov; O. F. Prilutsky; V. L. Prohin; V. G. Rodin; S. R. Tabaldiev; V. N. Chuprov; V. I. Fuks; I. A. Gerasimov; V. S. Ovtchinnikov; V. P. Poluektov; A. V. Serov; V. Y. Tugaenko; L. V. Kurnosova; M. A. Rusakovich; N. P. Topchiev; M. I. Fradkin; I. F. Bugakov; G. M. Gorodinsky; E. I. Chuikin; S. A. Voronov; A. M. Galper; V. A. Grigoriev; M. V. Guzenko; V. G. Kirillov-Ugriumov; S. V. Koldashov; M. G. Korotkov; B. I. Luchkov; A. A. Moiseev; Yu. V. Ozerov; A. V. Popov; V. A. Rud'ko; M. F. Runtso; B. Yu. Chesnokov; B. Agrinier; A. Bouere; M. Gros; J. P. Leray; A. Leconte; P. Masse; B. Mougin; P. Keirle; J. Cretolle; J. Paul; A. Raviart; B. Parlier; M. Poiviller; C. Hugot; F. Soroka; G. Serra; A. R. Bazer-Bachi; C. Doulade; J. Ducros; G. Vedrenne; F. Cotin; Y. M. Lavigne; P. Mandrou; E. Orsal; M. Avignon; J. Durand; J. Joli; F. Gardon; J. Mouli; M. Nobileau; D. Fournier

1989-01-01

379

GAMANAL. Interpretation of Gamma-Ray Spectra  

Microsoft Academic Search

GAMANAL provides a complete qualitative and quantitative analysis of mixtures of radioactive species such as fission products by computer interpretation of high-resolution gamma-ray spectra. The program first determines and removes the background or Compton continuum under the peaks in a spectrum to locate the peak regions. This is done by examining the pulse-height spectrum data for background and peak regions

Gunnink

1986-01-01

380

A portable gamma ray spectrometer/computer  

SciTech Connect

A state-of-the-art portable gamma ray spectrometer has been developed commercially. The instrument is available with NaI or hand-held Germanium detectors and can collect and analyze up to 4K channels of PHA or MCS spectra. An integral LCD provides graphic and character readout. Dual microprocessors are operated in a tightly-coupled multi-programming environment providing unique operator interface capability.

Roberts, H.

1984-02-01

381

Gamma-ray energy tracking array: GRETINA  

NASA Astrophysics Data System (ADS)

A Gamma-ray energy tracking array can provide higher efficiency, better peak-to-total ratio and higher position resolution than the current generation of detector arrays. Particularly, the capability of reconstructing the position of the interaction with millimetre resolution is needed to fully exploit the physics opportunities provided by current and next generation radioactive beam facilities. This paper presents the basic concepts of energy tracking, examples of physics opportunities, and the status of the GRETINA/GRETA project.

Lee, I.-Yang

2013-03-01

382

Gamma Ray Observatory over Baja California, Mexico  

NASA Technical Reports Server (NTRS)

In this view of the Gamma Ray Observatory over Baja California, Mexico (31.5N, 113.0W), the Salton Sea and Imperial Valley region of California where the mouth of the Colorado River empties into the Sea of Cortez is clearly visible. The Los Angeles basin is partially visible below the GRO's left solar panel. Looking due east, across Mexico and south Texas, toward the Earth limb, the Texas Gulf coast is faintly visible.

1991-01-01

383

Gamma -ray irradiation head for panoramic irradiation  

SciTech Connect

The invention relates to a gamma -ray irradiation head for panoramic irradiation comprising a tungsten target revolving about an axis, and means for deflecting electrons around the same axis for producing photons in several directions either successively or simultaneously. When the beam of electrons is deflected in its entirety and when the impact zone moves on the target about the axis, the axis of the radiation lobe moves in the same way and permits irradiation according to a variable azimuth.

Azam, G.; Bensussan, A.

1980-10-21

384

Gamma rays from extragalactic radio sources  

NASA Technical Reports Server (NTRS)

It is proposed that the important connection between 3C 273 and 3C 279, the first two extragalactic sources detected at greater than 100 MeV energies, is their superluminal nature. In support of this conjecture, we propose a radiation mechanism that focuses gamma rays in the superluminal direction, due to Compton scattering of accretion-disk photons by relativistic nonthermal electrons in the jet.

Dermer, Charles D.; Schlickeiser, Reinhard; Mastichiadis, Apostolos

1992-01-01

385

Gamma rays from active galactic nuclei  

NASA Technical Reports Server (NTRS)

The general properties of Active Galactic Nuclei (AGN) and quasars are reviewed with emphasis on their continuum spectral emission. Two general classes of models for the continuum are outlined and critically reviewed in view of the impending GRO (Gamma Ray Observatory) launch and observations. The importance of GRO in distinguishing between these models and in general in furthering the understanding of AGN is discussed. The very broad terms the status of the current understanding of AGN are discussed.

Kazanas, Demosthenes

1990-01-01

386

Gamma-ray spectroscopy of 126Ba  

Microsoft Academic Search

States of 126Ba up to spin 36+ were populated in the reaction 96Zr(34S, 4n)126Ba at 155 MeV and up to spin 20+ in the reaction 116Sn(13C, 3n)126Ba at 56 MeV. Gamma-ray spectroscopy was performed with the 8pi spectrometer, an instrument comprising 20 Campton-suppressed HPGe detectors and 71 BGO ball elements. A level scheme organized into fifteen rotational bands is proposed

D. Ward; V. P. Janzen; H. R. Andrews; D. C. Radford; G. C. Ball; D. Horn; J. C. Waddington; J. K. Johansson; F. Banville; J. Gascon; S. Monaro; N. Nadon; S. Pilotte; D. Prevost; P. Taras; R. Wyss

1991-01-01

387

Hypernovae and Gamma-Ray Bursts  

Microsoft Academic Search

Recently, there have been a number of candidates for the gamma-ray burst (GRB)\\/supernova (SN) connection (see Nomoto et al.\\u000a 2001 for references). Among the SNe with a possible GRB counterpart, the Type Ic SNe 1998bw and 1997ef are characterised by\\u000a a very large kinetic explosion energy, EK \\u000a >~1052\\\\gtrsim 10^{52}\\u000a erg. This is more than one order of magnitude larger than

P. Mazzali; K. Nomoto; K. Maeda; T. Nakamura

2001-01-01

388

Gamma-ray bursts as hypernovae  

Microsoft Academic Search

A standard fireball\\/afterglow model of a gamma-ray burst (GRB) relates the event to a merging neutron star binary, or a neutron star-black hole binary, which places the events far away from star-forming regions, and is thought to have an energy of ~1051 erg. A hypernova, the death of a massive and rapidly spinning star, may release ~1054 erg of kinetic

Bohdan Paczynski

1998-01-01

389

Hypernovae and Gamma-Ray Bursts  

Microsoft Academic Search

The nature of very energetic supernovae (hypernovae) is discussed. They are the explosive death of stars more massive than\\u000a ?20–25M?, probably linked to the enigmatic Gamma-Ray Bursts. The optical properties of hypernovae indicate that they are significantly\\u000a aspherical. Synthetic light curves and late-phase spectra of aspherical supernova\\/hypernova models are presented. These models\\u000a can account for the optical observations of SNe

Ken’ichi Nomoto; Keiichi Maeda; Nozomu Tominaga; Takuya Ohkubo; Jinsong Deng; Paolo A. Mazzali

2010-01-01

390

Hypernovae and Gamma-Ray Bursts  

Microsoft Academic Search

The nature of very energetic supernovae (hypernovae) is discussed. They are the explosive death of stars more massive than ~20–25M?, probably linked to the enigmatic Gamma-Ray Bursts. The optical properties of hypernovae indicate that they are significantly aspherical. Synthetic light curves and late-phase spectra of aspherical supernova\\/hypernova models are presented. These models can account for the optical observations of SNe

Ken’ichi Nomoto; Keiichi Maeda; Nozomu Tominaga; Takuya Ohkubo; Jinsong Deng; Paolo A. Mazzali

2005-01-01

391

Cosmic very high-energy gamma rays  

Microsoft Academic Search

The article gives a brief overview, aimed at nonspecialists, about the goals and selected recent results of the detection of very-high energy gamma-rays (energies above 100 GeV) with ground based detectors. The stress is on the physics questions, especially the origin of Galactic Cosmic Rays and the emission of TeV gamma-radiation from active galaxies. Moreover some particle-physics questions which are

R. Plaga

1998-01-01

392

Induction of Supernova-like Explosions by Gamma-Ray Bursts in Close Binary Systems  

NASA Astrophysics Data System (ADS)

We propose that a gamma-ray burst in one member of a binary may induce a supernova-like explosion of a close, white dwarf companion. Such an explosion might be brought about in rather light companions, which cannot undergo the standard accretion-induced explosion. This would give some supernovae associated with gamma-ray bursts an appearance rather unlike that of the typical Type I supernova. GRB 980425, if indeed associated with SN 1998bw, is too weak to have produced the latter through our proposed mechanism.

Milgrom, Mordehai; Usov, Vladimir V.

2000-03-01

393

Afterglow Radiation from Gamma Ray Bursts  

SciTech Connect

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

Desmond, Hugh; /Leuven U. /SLAC

2006-08-28

394

Gamma Ray Burst All-Sky Spectrometer  

NASA Astrophysics Data System (ADS)

The Gamma Ray Burst All-Sky Spectrometer Experiment (GASE) is designed to detect radio emission from gamma ray bursts (GRB's). Radio emission from GRB's could help us better understand the plasma physics of the blast and might also help us measure dark energy. GASE uses short-baseline interferometry with eight dipole antennas located at the MIT Haystack Observatory. These antennas measure the radiofrequency sky at 30 MHz over a 4 MHz bandwidth and are able to collect information from the entire sky. Since the entire sky is surveyed, radio frequency interference occurring at the horizon can be eliminated as a transient source. Along with the SWIFT satellite and the Gamma Ray Burst Coordinate system, we will be able measure blast time, duration and position. We are currently designing techniques to calibrate and image the full sky in radio. In addition to locating and measuring GRB's, GASE may be able to measure dark energy due to the dispersion by the IGM. The pulse of radio emission is delayed as it travels through the intergalactic plasma, with longer wavelengths taking longer to arrive than shorter wavelengths. With the known free electron density (?m) we will use the dispersion measure to calculate the line of sight distance to the GRB and compare to the observed redshift to measure dark energy.

Steger, Arielle

2011-05-01

395

Solar gamma rays. [in solar flares  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

396

Nuclear gamma rays from solar flares  

NASA Technical Reports Server (NTRS)

The theory of gamma ray line emission from solar flares is reviewed and revised. It is shown that the recently observed (Chupp et al., 1972) line emissions at 0.5, 2.2, 4.4 and 6.1 MeV are due to positron annihilation, deuterium deexcitation following neutron capture on hydrogen, and the deexcitation of excited states in carbon and oxygen. From the observed relative line intensities it is possible to determine the spectrum of accelerated protons in the flare region. This spectrum is found to be very similar to that the charged particles from the flare observed near earth. The total numbers of protons at the sun is deduced from the observed absolute line intensities for various interaction models. It is found that if the protons at the sun have a spectrum which is an exponential in rigidity, the total energy in protons is a few times 10 to the 28th power ergs if the gamma rays are produced by protons moving down into the sun; and about 10 to the 30th power ergs if the gamma rays are produced at the site of the acceleration.

Ramaty, R.; Lingenfelter, R. E.

1973-01-01

397

The Properties of Gamma-ray Binaries  

NASA Astrophysics Data System (ADS)

There are a small but growing number of high mass X-ray binaries (HMXBs) that also exhibit emission above 100 MeV. All of these "gamma-ray binaries" exhibit variable emission across the electromagnetic spectrum, from radio to TeV energies, that is modulated with the binary orbital period. The optical stellar companions in these gamma-ray binaries fall into a range of spectral classes: Wolf-Rayet, O main sequence, B supergiant, and Be. Their high energy emission is probably powered by the collision of stellar wind or disk outflows with relativistic pulsar winds in a shock region. These sources present a unique opportunity to study particle acceleration in nearby, Galactic sources. I will review the observed multiwavelength properties of known gamma-ray binaries and discuss the population in the context of the late stages of massive star evolution. I am grateful for support from the Fermi Cycle 4 program through NASA grant NNX11AO41G and from NSF grant AST-1109247.

McSwain, M. Virginia

2013-06-01

398

Neutrino bursts from gamma-ray bursts  

NASA Technical Reports Server (NTRS)

If gamma-ray bursts originate at cosmological distances, as strongly indicated by the results from Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory (CGRO), then ultrarelativistic ejecta are the likely consequence of the highly super-Eddington luminosity of the sources. If the energy injection rate varies with time, then the Lorentz factor of the wind also varies, and the shells of ejected matter collide with each other. The collisions between baryons produce pions which decay into high-energy photons, electrons, electron positron pairs, and neutrino pairs. The bulk Lorentz factor of approximately 300 is required if our model is to be compatible with the observed millisecond variability. The strongest gamma-ray bursts are observed to deliver approximately 10(exp -4) ergs/sq cm in 100-200 keV photons. In our scenario more energy may be delivered in a neutrino burst. Typical neutrinos may be approximately 30 GeV if the protons have a Maxwellian energy distribution, and up to approximately TeV if the protons have a power-law distribution. Such neutrino bursts are close to the detection limit of the DUMAND II experiment.

Paczynski, Bohdan; Xu, Guohong

1994-01-01

399

Distribution of Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

Gamma-Ray Bursts (GRBs) are known to be bright, irregular flashes of gamma rays that typically last just a few seconds, believed to be caused by stellar collapse or the merger of a pair of compact objects. Through previous work, it has been found that GRBs are distributed roughly uniformly over the entire sky, rather than being confined to the relatively narrow band of the Milky Way. Using the Python programming language, we generated a model of GRBs over cosmological distances, based on current empirical GRB distributions. The grbsim python module uses the acceptance-rejection Monte Carlo method to simulate the luminosity and redshift of a large population of GRBs, including cosmological effects such as dark energy and dark matter terms that modify the large-scale structure of space-time. The results of running grbsim are demonstrated to match the distribution of GRBs observed by the Burst Alert Telescope on NASA’s Swift satellite. The grbsim module will subsequently be used to simulate gamma ray and neutrino events for the Astrophysical Multimessenger Observatory Network.

Diaz Rodriguez, Mariangelly; Smith, M.; Tešic, G.

2014-01-01

400

Positron annihilation in gamma-ray bursts  

NASA Technical Reports Server (NTRS)

Emission features appear at energies of 350 to 450 keV in the spectra of a number of gamma ray burst sources. These features were interpreted as electron-positron annihilation lines, redshifted by the gravitational field near the surface of a neutron star. Evidence that gamma ray bursts originate at neutron stars with magnetic field strengths of approx. 10(exp 12) Gauss came from recent observations of cyclotron scattering harmonics in the spectra of two bursts. Positrons could be produced in gamma ray burst sources either by photon-photon pair production or by one-photon pair production in a strong magnetic field. The annihilation of positrons is affected by the presence of a strong neutron star magnetic field in several ways. The relaxation of transverse momentum conservation causes an intrinsic broadening of the two-photon annihilation line and there is a decrease in the annihilation cross section below the free-space value. An additional channel for one-photon annihilation also becomes possible in high magnetic fields. The physics of pair production and annihilation near strongly magnetized neutron stars will be reviewed. Results from a self-consistent model for non-thermal synchrotron radiation and pair annihilation are beginning to identify the conditions required to produce observable annihilation features from strongly magnetized plasmas.

Harding, Alice K.

1990-01-01

401

Physical constraints on models of gamma-ray bursters  

SciTech Connect

This report deals with the constraints that can be placed on models of gamma-ray burst sources based on only the well-established observational facts and physical principles. The premise is developed that the very hard x-ray and gamma-ray continua spectra are well-established aspects of gamma-ray bursts. Recent theoretical work on gamma-ray bursts are summarized with emphasis on the geometrical properties of the models. Constraints on the source models which are implied by the x-ray and gamma-ray spectra are described. The allowed ranges for the luminosity and characteristic dimension for gamma-ray burst sources are shown. Some of the deductions and inferences about the nature of the gamma-ray burst sources are summarized. 67 refs., 3 figs.

Epstein, R.I.

1985-01-01

402

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

DOEpatents

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.

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

2013-02-12

403

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

NASA Technical Reports Server (NTRS)

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 in gamma - ray blazars, then these objects should appear as bright MeV sources when viewed along off-axis lines of sight.

Becker, Peter A.; Kafatos, Menas

1995-01-01

404

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

NASA Technical Reports Server (NTRS)

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.

Ryan, James M.; Lockwood, John A.

1989-01-01

405

Fermi Gamma-ray Space Telescope Observations of Gamma-ray Pulsars  

NASA Astrophysics Data System (ADS)

The Large Area Telescope on the recently launched Fermi Gamma-ray Space Telescope (formerly GLAST), with its large field of view and effective area, combined with its excellent timing capabilities, is poised to revolutionize the field of gamma-ray astrophysics. The large improvement in sensitivity over EGRET is expected to result in the discovery of many new gamma-ray pulsars, which in turn should lead to fundamental advances in our understanding of pulsar physics and the role of neutron stars in the Galaxy. Almost immediately after launch, Fermi clearly detected all previously known gamma-ray pulsars and is producing high precision results on these. An extensive radio and X-ray timing campaign of known (primarily radio) pulsars is being carried out in order to facilitate the discovery of new gamma-ray pulsars. In addition, a highly efficient time-differencing technique is being used to conduct blind searches for radio-quiet pulsars, which has already resulted in new discoveries. I present some recent results from searches for pulsars carried out on Fermi data, both blind searches, and using contemporaneous timing of known radio pulsars.

Saz Parkinson, P. M.

2009-04-01

406

HIGH-ENERGY GAMMA-RAY AFTERGLOWS FROM LOW-LUMINOSITY GAMMA-RAY BURSTS  

SciTech Connect

The observations of gamma-ray bursts (GRBs) such as 980425, 031203 and 060218, with luminosities much lower than those of other classic bursts, lead to the definition of a new class of GRBs-LL-GRBs. The nature of the outflow responsible for them is not yet clear. Two scenarios have been suggested: one is the conventional relativistic outflow with initial Lorentz factor of order of GAMMA{sub 0} approx> 10 and the other is a trans-relativistic outflow with GAMMA{sub 0} approx = 1-2. Here, we compare the high-energy gamma-ray afterglow emission from these two different models, taking into account both synchrotron self-inverse Compton (SSC) scattering and the external inverse Compton scattering due to photons from the cooling supernova or hypernova envelope (SNIC). We find that the conventional relativistic outflow model predicts a relatively high gamma-ray flux from SSC at early times (<10{sup 4} s for typical parameters) with a rapidly decaying light curve, while in the trans-relativistic outflow model, one would expect a much flatter light curve of high-energy gamma-ray emission at early times, which could be dominated by both the SSC emission and the SNIC emission, depending on the properties of the underlying supernova and the shock parameter epsilon{sub e} and epsilon{sub B}. The Fermi Gamma-ray Space Telescope should be able to distinguish between the two models in the future.

He Haoning; Wang Xiangyu; Yu Yunwei [Department of Astronomy, Nanjing University, Nanjing 210093 (China); Meszaros, Peter [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)

2009-12-01

407

EGRET Measurements of Energetic Gamma Rays from the Gamma-Ray Bursts of 1992 June 22 and 1994 March 1  

NASA Astrophysics Data System (ADS)

Energetic gamma-ray emissions from the gamma-ray bursts on 1992 June 22 (GRB 920622) and on 1994 March 1 (GRB 940301) were detected by the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO). Spectral data for both bursts were measured by EGRET's large NaI detector. Gamma rays up to 160 MeV were observed for GRB 94030t with its spark chamber telescope. Time-integrated, high-energy spectra for both bursts were fitted by single-power-law models having spectral indexes of 3.0 and 2.5 for GRB 920622 and GRB 940301, respectively.

Schneid, E. J.; Bertsch, D. L.; Dingus, B. L.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mattox, J. R.; Mayer-Hasselwander, H. A.; Michelson, P. F.; von Montigny, C.; Nolan, P. L.; Sreekumar, P.; Thompson, D. J.

1995-11-01

408

EGRET - The high energy gamma ray telescope for NASA's Gamma Ray Observatory  

NASA Technical Reports Server (NTRS)

The EGRET high energy gamma-ray telescope under development for NASA's Gamma Ray Observatory will have an energy range of approximately 12 to 30,000 MeV, energy resolution of about 15 percent FWHM over most of that range, an effective area of about 2000 sq cm at high energies, and single photon angular accuracy of approximately 2 deg at 100 MeV, less than 0.1 deg above 5 GeV. This instrument can locate strong sources to an accuracy of about 5 arc min. The instrument utilizes a set of digital spark chambers interleaved with tantalum foils for detection and identification of gamma-ray events, and a large NaI(Tl) scintillator for energy determination. The system is triggered by a coincidence matrix using two arrays of plastic scintillation counters and a large plastic scintillator anticoincidence dome that rejects incident charged particles.

Fichtel, C. E.; Bertsch, D. L.; Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.; Hofstadter, R.; Hughes, E. B.; Campbell-Finman, L. E.; Pinkau, K.; Mayer-Hasselwander, H.

1983-01-01

409

CdZnTe gamma ray spectrometer for orbital gamma ray spectroscopy.  

SciTech Connect

We present the design and analysis of a new gamma ray spectrometer for planetary science that uses an array of CdZnTe detectors to achieve the detection efficiency needed for orbital measurements. The use of CdZnTe will provide significantly improved pulse height resolution relative to scintillation-based detectors, with commensurate improvement in the accuracy of elemental abundances determined by gamma ray and neutron spectroscopy. The spectrometer can be flown either on the instrument deck of the spacecraft or on a boom. For deck-mounted systems, a BGO anticoincidence shield is included in the design to suppress the response of the CdZnTe detector to gamma rays that originate in the spacecraft. The BGO shield also serves as a backup spectrometer, providing heritage from earlier planetary science missions and reducing the risk associated with the implementation of new technology.

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

2001-01-01

410

Cosmic gamma-ray background from structure formation in the intergalactic medium  

PubMed

The Universe is filled with a diffuse background of gamma-ray radiation, the origin of which remains one of the unsolved puzzles of cosmology. Less than one-quarter of the gamma-ray flux can be attributed to unresolved discrete sources, such as active galactic nuclei; the remainder appears to constitute a truly diffuse background. Here we show that the shock waves induced by gravity in the gas of the intergalactic medium, during the formation of large-scale structures like filaments and sheets of galaxies, produce a population of highly relativistic electrons. These electrons scatter a small fraction of the cosmic microwave background photons in the local Universe up to gamma-ray energies, thereby providing the gamma-ray background. The predicted diffuse flux agrees with the observed background across more than four orders of magnitude in photon energy, and the model predicts that the gamma-ray background, though generated locally, is isotropic to better than five per cent on angular scales larger than a degree. Moreover, the agreement between the predicted and observed background fluxes implies a mean cosmological density of baryons that is consistent with Big Bang nucleosynthesis. PMID:10821264

Loeb; Waxman

2000-05-11

411

The axion–photon interaction and gamma ray signals of dark matter  

NASA Astrophysics Data System (ADS)

We explore two scenarios where the axion–photon interaction could induce additional astrophysical gamma ray signals for the dark matter. In the first scenario, dark compact objects made of axions, named axion stars, could collide with neutron stars. The whole energy of the axion star can be dissipated in the magnetized conducting medium of the neutron star generating gamma rays. The second scenario is an indirect method for observing self–annihilating dark matter trapped in stars: Gamma rays produced by the self–annihilation of neutralinos in the interior of the Sun can be transformed into axions due to photon–axion conversion. Then, the axion will travel freely in the Sun and be converted into photons again. This process is often referred as 'shine light through walls', in this case, the wall will be the solar interior. Hence, GeV gamma rays might pass through the Sun. We may conclude that observation of GeV photons by gamma-ray observatories like HAWC, coming from the Sun, may be a signal of annihilation of neutralinos in the interior of the Sun.

Barranco, J.; Carrillo Monteverde, A.; Delepine, D.

2014-03-01

412

GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES  

SciTech Connect

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

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

2012-08-20

413

Radioprotection by fullerenols of Stylonychia mytilus exposed to gamma-rays.  

PubMed

The aim was to study the protective effects of fullerenols, C60(OH)x, on Stylonychia mytilus cells exposed to 60Co gamma-rays and the probable mechanisms of fullerenols protection. Ciliated protozoans Smytilus, kept in solutions of fullerenols at different concentrations, were irradiated with 60Co gamma-rays to various dose levels. Surviving cells were counted each day over 5 days after irradiation, and the surviving fraction was calculated. The relations of the surviving fraction to radiation dose and to fullerenols concentration were studied. Superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) and lipofusion (LIP) levels in S. mytilus were also measured. The surviving fraction of S. mytilus decreased with increasing gamma-ray doses from 100 to 2000 Gy. Fullerenols enhanced the surviving fraction, except for the highest gamma-ray dose level. The maximum protection by fullernols occurred at a concentration of 0.10 mg ml(-1). However, fullerenols at concentration of 0.25 mg ml(-1) yielded a surviving fraction lower than that for the control sample. Fullerenols at a concentration of 0.10 mg ml(-1) increased the SOD and CAT activities in the gamma-ray plus fullerenols (gamma + F) group compared with the levels in both the gamma-ray (gamma) group (p < 0.01) and the control group (p < 0.01). The MDA and LIP levels in the gamma + F groups (p < 0.01) were significantly lower than that in both the control group (p < 0.05) and the gamma group (p < 0.01). At a concentration of 0.25 mg ml(-1), fullerenols reduced the SOD and CAT activities, but increased the MDA and LIP level compared with the control. There was no significant difference in SOD and CAT activities between the gamma + F group and gamma group. While the MDA and LIP level in the gamma + F and gamma groups were similar at a dose of 500 Gy, the LIP level in the gamma + F group was significantly higher than that in the gamma group (p < 0.01) at a dose of 2000 Gy. Fullerenols are good radiation protectors for the protozoan S. mytilus exposed to gamma-rays. The effectiveness of radioprotection depends on both fullerenols concentration and gamma-ray dose. The protective effect of fullerenols on damage induced by gamma-rays seems to be mediated, at least in part, through their anti-oxidative and radical scavenging activities. PMID:16019926

Zhao, Q; Li, Y; Xu, J; Liu, R; Li, W

2005-02-01

414

{gamma}-ray spectroscopy of {sup 163}Ta  

SciTech Connect

Excited states in {sup 163}Ta have been identified for the first time using the {sup 106}Cd({sup 60}Ni,3p) fusion evaporation reaction. {gamma} rays were detected using the JUROGAM {gamma}-ray spectrometer and recoil discrimination was achieved using the recoil ion transport unit (RITU) gas-filled separator in conjunction with the GREAT spectrometer situated at the focal plane of the RITU. The yrast states are assigned to a strongly coupled rotational band based on a {pi}h{sub 11/2} configuration. This structure exhibits large signature splitting at low spins that disappears after the paired band crossing because of the alignment of a pair of i{sub 13/2} neutrons. This effect is ascribed to triaxial shape changes induced by the core-polarizing properties of the deformation-aligned h{sub 11/2} proton and the rotation-aligned i{sub 13/2} neutrons. Two additional strongly coupled band structures have been established and are discussed in terms of octupole-vibrational and two-quasiparticle excitations built on the yrast structure. The experimental results are compared with predictions from cranked-shell-model and total-Routhian-surface calculations.

Sandzelius, M. [Department of Physics, Royal Institute of Technology, S-10691 Stockholm (Sweden); Department of Physics, University of Jyvaeskylae, FIN-40014 Jyvaeskylae (Finland); Cederwall, B.; Andgren, K.; Baeck, T.; Hadinia, B.; Johnson, A.; Khaplanov, A.; Wyss, R. [Department of Physics, Royal Institute of Technology, S-10691 Stockholm (Sweden); Ganioglu, E. [Department of Physics, Royal Institute of Technology, S-10691 Stockholm (Sweden); Science Faculty, Physics Department, Istanbul University, 34459 Istanbul (Turkey); Thomson, J.; Bianco, L.; Joss, D. T.; Page, R. D. [Oliver Lodge Laboratory, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Eeckhaudt, S.; Grahn, T.; Greenlees, P. T.; Jones, P. M.; Julin, R.; Juutinen, S.; Ketelhut, S. [Department of Physics, University of Jyvaeskylae, FIN-40014 Jyvaeskylae (Finland)] (and others)

2009-11-15

415

Scientific considerations in the design of the Mars observer gamma-ray spectrometer  

SciTech Connect

Cosmic-ray primary and secondary particles induce characteristic gamma-ray and neutron emissions from condensed bodies in our solar system. These characteristic emissions can be used to obtain qualitative and quantitative elemental analyses of planetary surfaces from orbital altitudes. Remote sensing gamma-ray spectroscopy has been successfully used to obtain elemental composition of the Moon and Mars during United States Apollo 15 and 16 missions and the Soviet Luna and Mars missions. A remote sensing gamma-ray and neutron spectrometer will be included aboard the United States Mars Observer Mission. If proper care is not taken in the design of the spectrometer and choice of materials in the construction of the detector system and spacecraft, the sensitivity of these remote sensing spectrometers can be greatly degraded. A discussion of these design and material selection problems is presented. 16 refs., 5 figs., 3 tabs.

Arnold, J.R.; Boynton, W.V.; Englert, P.; Feldman, W.C.; Metzger, A.E.; Reedy, R.C.; Squyres, S.W.; Trombka, J.I.; Wanke, H.

1987-01-01

416

Cosmic–ray and gamma–ray constraints on dark matter stability  

NASA Astrophysics Data System (ADS)

We examine different constraints on dark matter stability from cosmic–ray and gamma–ray observations and their complementarity through higher–order effects. Two–body and three–body decays of dark matter particles into charged leptons and quarks generically induce decays into monochromatic photons at the quantum level, giving rise to distinct signatures. We also present a general model–independent analysis of hadronic constraints in the mass–lifetime parameter space and compare those constraints to current and projected limits on gamma–ray lines. Furthermore, we discuss how the production of monochromatic photons can be enhanced by kinematic effects, potentially giving rise to observable lines in the gamma–ray sky.

Tran, David

2014-03-01

417

Rapid increase in prescission GDR {gamma}-ray emission with energy  

SciTech Connect

A rapid increase in the emission of prescission giant dipole resonance (GDR) {gamma}-rays with bombarding energy is observed in excited Th and Cf nuclei formed in the reactions {sup 16}O+{sup 20B}Pb and {sup 32}S+{sup nat}W,{sup 208}Pb. This increase begins around E{sub exc} = 40 MeV for the {sup 16}O+{sup 208}Pb reaction and E{sub exc} = 70 MeV for the {sup 32}S-induced reactions. The excess {gamma}-ray yield above these thresholds cannot be described within the standard statistical model. Statistical model calculations which include a temperature dependent nuclear dissipation are able to reproduce simultaneously the observed GDR {gamma}-ray spectra and recently measured evaporation residue across sections.

Hofman, D.J.; Back, B.B. [Argonne National Lab., IL (United States); Paul, P. [State Univ. of New York, Stony Brook, NY (United States). Dept. of Physics

1995-12-31

418

Energy response and dose-rate calibration of a Geiger-Mueller gamma-ray detector  

SciTech Connect

To obtain more precise dose-rate measurements, we have taken a commercial gamma-ray dosimeter that uses a Geiger-Mueller (GM) tube as its detector and, by supplying it with an externally regulated high voltage, counted the gamma-ray-induced pulses with suitable scaling and timing circuits. We have now improved the method of calibration by measuring detector response to 13 different sources, each with an independently verified strength, in the energy range from 60 keV to 2.6 MeV. With the use of computer codes, the resulting response curve can be folded into the spectrum of the source to be measured.

Plassmann, E.A.; Pederson, R.A.; Moss, C.E.

1984-01-01

419

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

SciTech Connect

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.

Di Sciascio, G.; Di Girolamo, T.; Megna, R.; Saggese, L. [INFN, sez. di Napoli (Italy); Dipartimento di Scienze Fisiche dell Universita di Napoli (Italy); Fratini, K. [INFN, sez. di Roma 3 (Italy); Dipartimento di Fisica dell Universita di Roma 3 (Italy)

2005-02-21

420

Studying Mercury subsurface structure composition by Russian Mercury Gamma-ray and Neutron Spectrometer (MGNS) onboard BepiColombo mission  

Microsoft Academic Search

Introduction: Mercury is the celestial body of the Solar system, after Mars and Moon, for which elementary composition of the shallow subsurface might be studied by observations of induced nuclear gamma-ray lines and neutron emission. Secondary gamma-rays and neutrons are produced by energetic galactic cosmic rays colliding with nuclei of regolith within a 1-2 meter layer of subsurface. For detection

A. Kozyrev; I. Mitrofanov; M. Litvak; A. Sanin; V. Tretyakov; M. Mokrousov; A. Malachov; A. Vostruchin; A. Rogozhin; L. Gurvits

2006-01-01

421

Gamma ray emission and solar flares  

NASA Technical Reports Server (NTRS)

Solar gamma ray line and continuum emission provide information about particle acceleration and its temporal behavior; the energy spectrum, composition and directivity of the accelerated particles; and the composition, density and temperatures of the ambient medium. These data, coupled with the comprehensive photon and particle observations available for the sun, give a detailed picture of the particle acceleration and flare energy release processes. Additional information on elemental and isotopic abundances, surface nuclear reactions and coronal heating mechanisms can be obtained. Implications of present observations and the potential return from future observational are discussed.

Lin, R. P.; Ramaty, R.

1978-01-01

422

Multiwavelength Studies of gamma-ray Binaries  

NASA Astrophysics Data System (ADS)

High mass X-ray binaries (HMXBs) consist of an O or B star orbited by either a neutron star or a black hole. Of the 114 known Galactic HMXBs, a handful of these objects, dubbed gamma-ray binaries, have been observed to produce MeV-TeV emission. The very high energy emission can be produced either by accretion from the stellar wind onto a black hole or a collision between the stellar wind and a relativistic pulsar wind. Both these scenarios make gamma-ray binaries valuable nearby systems for studying the physics of shocks and jets. Currently, the nature of the compact object and the high energy production mechanism is unknown or unconfirmed in over half of these systems. My goal for this dissertation is to constrain the parameters describing two of these systems: LS 5039 and HD 259440. LS 5039 exhibits gamma-ray emission modulated with its orbital period. The system consists of an ON6.5V((f)) star and an unidentified compact companion. Using optical spectra from the CTIO 1.5m telescope, we found LS 5039 to have an orbital period of 3.90608 d and an eccentricity of 0.337. Spectra of the Halpha line observed with SOAR indicate a mass loss rate of ˜ 1.9x10 -8 M yr-1. Observations taken with ATCA at 13 cm, 6 cm, and 3 cm indicate radio fluxes between 10--40 mJy. The measurements show variability with time, indicating a source other than thermal emission from the stellar wind. HD 259440 is a B0pe star that was proposed as the optical counterpart to the gamma-ray source HESS J0632+057. Using optical spectra from the KPNO CF, KPNO 2.1m, and OHP telescopes, we find a best fit stellar effective temperature of 27500--30000 K, a log surface gravity of 3.75--4.0, a mass of 13.2--19.0 Msolar, and a radius of 6.0--9.6 Rsolar. By fitting the spectral energy distribution, we find a distance between 1.1--1.7 kpc. We do not detect any significant radial velocity shifts in our data, ruling out orbital periods shorter than one month. If HD 259440 is a binary, it is likely a long period (> 100 d) system.

Aragona, Christina

423

PRECURSORS OF SHORT GAMMA-RAY BURSTS  

SciTech Connect

We carried out a systematic search of precursors on the sample of short gamma-ray bursts (GRBs) observed by Swift. We found that {approx}8%-10% of short GRBs display such early episodes of emission. One burst (GRB 090510) shows two precursor events, the former {approx}13 s and the latter {approx}0.5 s before the GRB. We did not find any substantial difference between the precursor and the main GRB emission, and between short GRBs with and without precursors. We discuss possible mechanisms to reproduce the observed precursor emission within the scenario of compact object mergers. The implications of our results on quantum gravity constraints are also discussed.

Troja, E.; Gehrels, N. [NASA, Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Rosswog, S. [School of Engineering and Science, Jacobs University Bremen, Campus Ring 1, 28759 Bremen (Germany)

2010-11-10

424

Gamma ray lines from interstellar grains  

NASA Technical Reports Server (NTRS)

The existence of very narrow (FWHM or approximately = 5 KeV) gamma ray line emission from interstellar grains is pointed out. The prime candidate for detection is the line at 6.129 Mev from O-16, but other very narrow lines could also be detected at 0.847, 1.369, 1.634, 1.779 and 2.313 Mev from Fe-56, Mg-24, Ne-20, Si-28 and N-14. Measurements of this line emission can provide information on the composition, size and spatial distribution of interstellar grains.

Lingenfelter, R. E.; Ramaty, R.

1976-01-01

425

Comptonization of gamma rays by cold electrons  

NASA Technical Reports Server (NTRS)

An analytic method is developed for calculating the emergent spectrum of gamma-rays and X-rays scattered in a homogeneous medium with low-temperature electrons. The Klein-Nishina corrections of the scattering cross section and absorption processes are taken in account. The wavelength relaxation and the spatial diffusion problems are solved separately, and the emergent spectrum is calculated by convolving the evolution function of the spectrum in an infinite medium with the photon luminosity resulting from the spatial diffusion in a finite sphere. The analytic results are compared with that of Monte Carlo calculations and it is concluded that the analytic result is quite accurate.

Xu, Yueming; Ross, Randy R.; Mccray, Richard

1991-01-01

426

Gamma Ray Bursts: an Enigma Being Unraveled  

SciTech Connect

The best astrophysical accelerators are quasars and the 'progenitors' of GRBs which, after decades of observations and scores of theories, we still do not understand. But, I shall argue, we now know quite well where GRBs come from, and we understand how their 'beams' behave, as they make short pulses of gamma rays and long-duration X-ray, optical and radio 'afterglows'. I shall argue that our understanding of these phenomena, based on the 'Cannonball Model', is unusually simple, precise and successful. The 'sociology' of GRBs is interesting per se and, in this sense, the avatars of the Cannonball Model in confronting the generally accepted 'fireball models' are also quite revealing.

De Rujula, Alvaro (Boston University and CERN) [Boston University and CERN

2003-05-14

427

Gamma-Ray Spectroscopy of 76As  

Microsoft Academic Search

Decay of 76As was investigated by using a Ge(Li) detector and Ge(Li)-NaI(Tl) coincidence methods. Sixteen new gamma-rays were observed and eleven of them were assigned in a proposed decay scheme. Four new levels were found at 2026.4, 2348, 2365.1 and 2514 keV. Spins and parities of levels at 2026.4, 2655.7 and 2669.8 keV were estimated from log ft values of

Katsuyuki Iizawa; Isao Kitamura; Kiyoshi Kawade; Hiroshi Yamamoto; Kanzo Yoshikawa; Susumu Amemiya; Toshio Katoh

1971-01-01

428

Directions in gamma-ray spectroscopy  

NASA Technical Reports Server (NTRS)

Current and future instrumentation for gamma-ray spectroscopy in the spectral range from 10 keV to 10 MeV is described. New technologies for Germanium (Ge) spectrometers and emerging detector technologies are highlighted. Scientific objectives are considered, with emphasis on capabilities beyond those of the Nuclear Astrophysics Explorer (NAE). A list of instrument requirements is given. Technologies under development for an NAE-era spectrometer are presented. Spectrometers beyond NAE and other types of future technologies are discussed, and a partial list of current and future spectrometers is provided.

Gehrels, Neil; Candey, Robert M.

1990-01-01

429

Status of the Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

The Compton Gamma Ray Observatory and three of its four experiment packages continue to function in a nearly flawless manner now well into the eighth year of mission operations. Only the EGRET instrument is operating with reduced capability due mainly to the depleted spark-chamber gas, but it is nonetheless still expected to make significant contributions, notably in the area of Solar flares and AGN variability. We discuss the status of the mission as of mid-1999 as well as the prospects of an extended mission lasting well into the first decade of the next century. .

Gehrels, Neil; Shrader, Chris

2000-04-01

430

Fermi gamma-ray imaging of a radio galaxy.  

PubMed

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. PMID:20360067

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, ?; 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

2010-05-01

431

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

432

A model of the diffuse galactic gamma ray emission  

NASA Technical Reports Server (NTRS)

The galaxy was observed to be a source of high energy gamma rays as shown by the two successful satellite experiments, SAS-2 and COS-B. It is generally understood that these diffuse gamma rays result from interactions between energetic cosmic rays and interstellar gas. This work makes use of the most recent data on the distribution of atomic and molecular hydrogen in the galaxy along with new estimates of gamma ray production functions to model the diffuse galactic gamma ray emission. The model allows various spatial distributions for cosmic rays in the Galaxy including non-axisymmetric ones. In the light of the expected data from EGRET (Energetic Gamma-Ray Experiment Telescope), an improved model of cosmic ray-matter-gamma ray interaction will provide new insights into the distribution of cosmic rays and the strength of its coupling to matter.

Sreekumar, Parameswaran

1990-01-01

433

Highlights of GeV Gamma-Ray Astronomy  

NASA Technical Reports Server (NTRS)

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.

Thompson, David J.

2010-01-01

434

Comparison of activation effects in {gamma}-ray detector materials  

SciTech Connect

Activation induced by cosmic and trapped radiation in {gamma}-ray detector materials represents a significant source of background for space-based detector systems. Selection of detector materials should therefore include consideration of this background source. Results are presented from measurements of induced radioactivity in different scintillators activated either as a result of irradiation by mono-energetic protons at accelerator facilities, or flight on board the Space Shuttle. Radiation transport computer codes are used to help compare the effects observed from the scintillators, by identifying and quantifying the influence on the background spectra from more than one hundred of the radionuclides produced by spallation. For the space experiment data, the simulation results also permit determination of the contributions to detector activation from the different sources of radiation in the Shuttle cabin.

Truscott, P.R.; Evans, H.E.; Dyer, C.S.; Peerless, C.L.; Flatman, J.C.; Cosby, M.; Knight, P. [Defence Research Agency, Farnborough (United Kingdom). Space Dept.] [Defence Research Agency, Farnborough (United Kingdom). Space Dept.; Moss, C.E. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States)

1996-06-01

435