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1

RADIOBIOLOGICAL STUDIES ON PLANTS. IV. GAMMA-RAY-INDUCED CHLOROPHYLL MUTATIONS AND MUTATION FREQUENCIES IN WHEAT AND OATS  

Microsoft Academic Search

Seeds of Triticum vulgare, Avena sativa (monosomic plants), and A. ; strigosa were irradiated with gamma-rays from a Co⁶°-source and induced ; chlorophyll mutations and mutation frequencies were investigated in their X; , X, and X progenies. Chlorophyll mutations were found in two ; species of oats. In A. sativa, four kinds of chlorophyll mutations, yellow, ; cream-I, -ll and

I. Nishiyama; S. Ichikawa

1961-01-01

2

Fingerprinting reveals gamma-ray induced mutations in fungal DNA: implications for identification of patent strains of Trichoderma harzianum.  

PubMed

We have analyzed different patent strains and gamma-ray induced mutants of Trichoderma harzianum by DNA fingerprinting and PCR fingerprinting (RAPD). Applying wild-type phage M13 DNA, with the oligonucleotides (CT)8 and (GTG)5 as probes for hybridization, as well as the oligonucleotides GGCATCGGCC, (GTG)5, (CAC)5 and the M13 sequence GAGGGTGGCGGTTCT as primers in PCR, we were able to obtain different and discriminative fingerprint patterns for all strains and mutants investigated. Irradiation of fungi led to mutations which resulted in new fingerprint patterns. Consequently, irradiation-induced mutants can be clearly distinguished from the original wild-type isolates by genomic fingerprinting which is of importance for the patent protection of fungal strains. Sequencing of the ITS-1 and ITS-2 regions of the rDNA gene complex revealed the same sequence for all mutant strains and the original wild-type strain. PMID:7954899

Schlick, A; Kuhls, K; Meyer, W; Lieckfeldt, E; Brner, T; Messner, K

1994-07-01

3

Fingerprinting reveals gamma-ray induced mutations in fungal DNA: implications for identification of patent strains of Trichoderma harzianum  

Microsoft Academic Search

We have analyzed different patent strains and gamma-ray induced mutants of Trichoderma harzianum by DNA fingerprinting and PCR fingerprinting (RAPD). Applying wild-type phage M13 DNA, with the oligonucleotides (CT)8 and (GTG)5 as probes for hybridization, as well as the oligonucleotides GGCATCGGCC, (GTG)5, (CAC)5 and the M13 sequence GAGGGTGGCGGTTCT as primers in PCR, we were able to obtain different and discriminative

A. Schlick; K. Kuhls; W. Meyer; E. Lieckfeldt; T. Brner; K. Messner

1994-01-01

4

Photoneutron-induced, prompt neutron capture gamma-ray spectroscopy  

SciTech Connect

Many practical radioisotopic-based and accelerator-based nondestructive evaluation (NDE) methods using neutron-induced prompt gamma rays have been successfully developed for various applications during the last several decades. In addition, electron accelerator-based X-ray radiography has been well established for more than 100 yr. Combining the advantages of these two NDE technologies has been limited by the fact that most gamma-ray detectors are rendered ineffective by the intense bremsstrahlung photons (i.e., X-ray flash) associated with each electron accelerator pulse. In support of a U.S. Department of Energy project, the Idaho National Engineering and Environmental Laboratory (INEEL) is developing a prototype high-purity germanium (HPGe)-based NDE system that performs prompt gamma-ray spectroscopy for gamma rays acquired between accelerator-produced bremsstrahlung pulses. Using a 6.5-MeV electron accelerator and a beryllium metal photoneutron source, the acquired gamma-ray spectrum for an interrogated 2.7-kg block of NaCl is presented and compared to one obtained using a {sup 252}Cf neutron source. In addition, the predicted photoneutron source spectrum is compared to a typical {sup 252}Cf neutron source spectrum.

Jones, J.L.; Yoon, W.Y. [Idaho National Engineering and Environmental Lab., Idaho Falls, ID (United States)

1997-12-01

5

The measurement of gamma ray induced heating in a mixed neutron and gamma ray environment  

SciTech Connect

The problem of measuring the gamma heating in a mixed DT neutron and gamma ray environment was explored. A new detector technique was developed to make this measurement. Gamma heating measurements were made in a low-Z assembly irradiated with 14-Mev neutrons and (n, n{prime}) gammas produced by a Texas Nuclear Model 9400 neutron generator. Heating measurements were made in the mid-line of the lattice using a proportional counter operating in the Continuously-varied Bias-voltage Acquisition mode. The neutron-induced signal was separated from the gamma-induced signal by exploiting the signal rise-time differences inherent to radiations of different linear energy transfer coefficient, which are observable in a proportional counter. The operating limits of this measurement technique were explored by varying the counter position in the low-Z lattice, hence changing the irradiation spectrum observed. The experiment was modelled numerically to help interpret the measured results. The transport of neutrons and gamma rays in the assembly was modelled using the one- dimensional radiation transport code ANISN/PC. The cross-section set used for these calculations was derived from the ENDF/B-V library using the code MC{sup 2}-2 for the case of DT neutrons slowing down in a low-Z material. The calculated neutron and gamma spectra in the slab and the relevant mass-stopping powers were used to construct weighting factors which relate the energy deposition in the counter fill-gas to that in the counter wall and in the surrounding material. The gamma energy deposition at various positions in the lattice is estimated by applying these weighting factors to the measured gamma energy deposition in the counter at those locations.

Chiu, H.K.

1991-10-01

6

Identification of Selected Gamma-Ray Induced Deficiencies in Zebrafish Using Multiplex Polymerase Chain Reaction  

PubMed Central

The ease with which mutations can be generated in zebrafish makes this vertebrate an important resource for developmental genetics and genome studies. We have developed a PCR-based screening method that allows the efficient identification of gamma-ray induced deficiencies targeted to selected sequences. We describe three mutants characteristic of our findings and show that these mutations include deletions and translocations that can affect as much as 1% of the genome. These deficiencies provide a basis for analyzing the functions of cloned zebrafish genes using noncomplementation screens for point mutations induced by high-efficiency chemical mutagenesis.

Fritz, A.; Rozowski, M.; Walker, C.; Westerfield, M.

1996-01-01

7

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

8

Characterizing, simulating, and eliminating vibration-induced counts in measurement-while-drilling gamma ray detectors  

Microsoft Academic Search

A measurement-while-drilling (MWD) gamma ray tool will report a higher than actual count rate if its scintillation crystal package produces vibration-induced light pulses. The scintillation crystal is used as a transducer that measures the count rate of gamma rays coming from naturally occurring radioisotopes in downhole shales. Each gamma ray causes the crystal to emit a number of visible light

K. Kimmich; C. Grodsinsky

1997-01-01

9

Gamma-Ray and Neutron-Induced Conductivity in Insulating Materials  

Microsoft Academic Search

Excess conductivities induced by steady-state sources of gamma rays and by pulsed sources of neutrons and gamma rays in polyethylene, polystyrene, polypropylene, Nylon, polyisobutylene (impregnated paper), mylar, Teflon, diallylphthalate, H-film, cellulose acetate, reconstituded mica, tantalum oxide, and an epoxy formulation have been measured. The measurements were made at steady-state gamma-ray dose rates within the interval from 1.0 ?? 10-3 rads(H2O)\\/sec

S. E. Harrison; F. N. Coppage; A. W. Snyder

1963-01-01

10

Neutrino-induced gamma-ray emission from supernovae  

Microsoft Academic Search

During a core-collapse supernova, absorption of nue emitted from the protoneutron star by protons in the hydrogen envelope produces neutrons and positrons. Neutron capture on protons and positron annihilation then produce gamma rays of 2.22 and 0.511 MeV, respectively. We calculate the fluxes of these gamma rays expected from a supernova with an 11M&sun; progenitor. The flux from neutron capture

Yu Lu; Yong-Zhong Qian

2007-01-01

11

Signals induced in semiconductor gamma-ray imaging detectors  

NASA Astrophysics Data System (ADS)

The signal induced in a readout circuit connected to a pixel electrode in a semiconductor gamma-ray imaging array is calculated by solving the Laplace equation. Two approaches are presented that use Green functions in solving the boundary value problem: decomposition into basis functions, and construction of an infinite series of image charges. Another approach is developed based on the Ramo-Shockley theorem, which makes use of weighting potentials. These potentials may be readily calculated in three dimensions using a Fourier-transform propagation technique. An analytic solution is found for the special two-dimensional case of a strip detector. Experiments on CdZnTe square-pixel test structures using alpha radiation confirm the expected trends in pulse shape as a function of pixel size. Signals observed simultaneously on adjacent pixels also follow the predicted division of currents. Trends with pixel size are also confirmed in the shape of pulse-height spectra taken using a 99mTc source.

Eskin, J. D.; Barrett, H. H.; Barber, H. B.

1999-01-01

12

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

13

Changes in DNA base sequence induced by gamma-ray mutagenesis of lambda phage and prophage  

SciTech Connect

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.

1988-04-01

14

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

15

Proton-induced prompt gamma-ray emission for determination of light elements in human bone  

Microsoft Academic Search

Proton-induced prompt gamma-ray emission (PIGE) analysis has been used for the determination of light elements in human dense\\u000a bone samples. Li, B, N, O, F, Na, Mg, Al, P and Ca peaks were detected. Smoothed, freeze-dried samples were irradiated in\\u000a vacuo by 2.4 MeV protons and the induced prompt gamma rays recorded with a 110 cm3 Ge(Li) detector. Absolute concentrations

M. Hyvnen-Dabek

1981-01-01

16

Gamma-ray-induced effects in erbium-doped fiber optic amplifiers  

Microsoft Academic Search

Four Erbium doped fiber optic amplifiers (EDFAs) were irradiated by gamma-rays to dose levels of 40 Krad(Si) and 100 Krad(Si) at dose rates of 0.25 rad(Si) sec-1 and 1.0 rad(Si) sec-1, respectively. All EDFAs were observed to incur radiation induced permanent decreases to their pre-irradiated signal gains. The paper will discuss the influence of gamma-ray irradiations on EDFA parameters such

Edward W. Taylor; Stanley J. McKinney; Anthony D. Sanchez; Alan H. Paxton; Douglas M. Craig; James E. Winter; Roberta M. Ewart; Ken Miller; Tim O'Connor; Robert W. Kaliski

1998-01-01

17

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

18

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 (2.20.1)103 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 32 in. LaBr3 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

19

Preparation of charged polystyrene microlatexes by emulsion polymerization induced by gamma rays  

Microsoft Academic Search

Ionic polymerizable surfactants MOBS and MOTB were synthesized and used as emulsifier to synthesize monodisperse polystyrene microlatexes by emulsion polymerization induced by gamma rays. Transmission electron microscopy and X-ray fluorescence were used to characterize the prepared polystyrene. The results show that ionic polymerizable surfactants are effective in the preparation of monodisperse polystyrene microlatexes, and that emulsion polymerization induced by gamma

Xinbo Wang; Zhicheng Zhang; Jun Chen; Shijie Wang

2007-01-01

20

Effect of Sup 60 Co gamma Rays on Con A and LPS Induced Lymphocytes.  

National Technical Information Service (NTIS)

The effect of /sup 60/Co gamma -rays on lymphocytes induced by Con A and LPS and the relationship between these two groups of cells were investigated by means of /sup 3/H-TdR incorporation. The study showed that in vitro, Con A cells were able to promote ...

Su L. Liu K. Ma X

1987-01-01

21

Co⁶° GAMMA-RAY INDUCED DEGRADATION OF BUTYL RUBBER AND ITS VULCANIZATES  

Microsoft Academic Search

The Co⁶° gamma-ray induced degradation of butyl rubber and of its ; vulcanizates at 25 deg was investigated. Vinylidene groups are formed on ; irradiation in air and vacuum, causing the appearance of 11.25 mu bands in the ; IR spectra. The results may be regarded as further confirmation of the ; similarity in the mechanism of degradation of butyl

V. F. Drozdovskii; I. A. Shokhin; N. A. Klauzen

1961-01-01

22

Simultaneous measurements of DT fusion gamma-ray and neutron-induced secondary gamma-ray using Gas Cherenkov Detector  

Microsoft Academic Search

A Gas Cherenkov Detector (GCD) which captures 16.75 MeV DT fusion gamma-rays has been developed by Los Alamos National Laboratory in collaboration with Lawrence Livermore National Laboratory and Atomic Weapons Establishment. Due to the fast time response, the GCD will be an essential instrument for National Ignition Facility (NIF) fusion reaction history studies. A challenge faced by the GCD is

Y. Kim; H. W. Herrmann; J. R. Langenbrunner; C. S. Young; S. C. Evans; T. J. Sedillo; A. M. McEvoy; W. Stoeffl; C. Horsfield; M. Rubery

2009-01-01

23

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

NASA Astrophysics Data System (ADS)

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

Jones, James L.

1997-02-01

24

Gamma-ray-induced modifications of the chemical structure of an ion exchange resin  

Microsoft Academic Search

Gamma-ray irradiation of ion exchange resins used for processing nuclear effluent may lead to considerable modifications of the molecular structure and macroscopic properties. In the present study, crosslinked poly(4-vinylpyridine) (P4VP), irradiated by a 137Cs ?-source up to an integrated dose of 14400 kGy, has been investigated. The particle-induced desorption-mass spectrometry (PDMS) technique is able to detect the radiation-induced structural degradation

M. Draye; B. Nsouli; H. Allali; M. Lemaire; J.-P. Thomas

1997-01-01

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. Bser; 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. Demirrs; 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. Gro; 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. Hl; 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. Kpke; M. Kowalski; T. Kowarik; M. Krasberg; K. Kuehn; M. Labare; H. Landsman; H. Leich; D. Leier; I. Liubarsky; J. Lundberg; J. Lnemann; J. Madsen; K. Mase; H. S. Matis; T. McCauley; C. P. McParland; A. Meli; T. Messarius; P. Mszros; H. Miyamoto; A. Mokhtarani; T. Montaruli; A. Morey; R. Morse; S. M. Movit; K. Mnich; R. Nahnhauer; J. W. Nam; P. Nieen; D. R. Nygren; H. gelman; A. Olivas; S. Patton; C. Pea-Garay; C. Prez 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. Wikstrm; D. R. Williams; R. Wischnewski; H. Wissing; K. Woschnagg; X. W. Xu; G. Yodh; S. Yoshida; J. D. Zornoza

2007-01-01

26

Quantitative analysis of the fluid inclusions by particle-induced gamma-ray emission  

Microsoft Academic Search

The particle-induced gamma-ray emission (PIGE) method, very sensitive for the light elements Li, Be, B, F, Na, is complementary to the PIXE method for the determination of trace elements in complex materials. The deep penetration (more than 50 mm) of 3 MeV protons in light matrices allows heterogenities situated under the irradiated surface of the target to be revealed. This

M. Volfinger

2002-01-01

27

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

28

Preparation of polystyrene latex particles by gamma-rays-induced emulsifier-free emulsion polymerization  

Microsoft Academic Search

Monodisperse polystyrene latex particles were prepared by 60Co-gamma-ray radiation-induced emulsifier-free emulsion polymerization with the use of surfactant monomer at room temperature. The surfactant monomer 10(9)-hydroxyl-9(10)-allyl ether octadecanoic acid (HAEOA) was synthesized and characterized by FT-IR and 1H-NMR spectra. TEM was used to characterize the polystyrene latex particles. HAEOA acted as not only a comonomer but also a stabilizer to copolymerize

Xinbo Wang; Zhicheng Zhang

2006-01-01

29

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

30

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

31

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

32

Numerical simulations of planetary gamma-ray spectra induced by galactic cosmic rays  

SciTech Connect

The fluxes of cosmic-ray-produced gamma rays escaping from Mars were calculated using the LAHET Code System and basic nuclear data for {gamma}-ray production. Both surface water content and atmospheric thickness strongly affect the fluxes of {gamma}-ray lines escaping from Mars.

Masarik, J.; Reedy, R.C.

1994-07-01

33

Fluorine determination in human and animal bones by particle-induced gamma-ray emission  

Microsoft Academic Search

Fluorine was determined in the iliac crest bones of patients and in ribs collected from post-mortem investigations by particle-induced\\u000a gamma-ray emission based on the 19F(p,p??)19F reaction, using 2.0\\/2.5 MeV protons. The results indicate that for 68% of the human samples the F concentration is in the\\u000a range 5001999 ?g g1. For comparison purposes fluorine was also determined in some animal

Chaturvedula S. Sastri; Venkatesh Iyengar; Gilbert Blondiaux; Yves Tessier; Hermann Petri; Peter Hoffmann; Namik K. Aras; Vladimir Zaichick; Hugo M. Ortner

2001-01-01

34

Fluorine determination in human and animal bones by particle-induced gamma-ray emission.  

PubMed

Fluorine was determined in the iliac crest bones of patients and in ribs collected from post-mortem investigations by particle-induced gamma-ray emission based on the 19F(p,p'gamma)19F reaction, using 2.0/2.5 MeV protons. The results indicate that for 68% of the human samples the F concentration is in the range 500-1999 microg g(-1). For comparison purposes fluorine was also determined in some animal bones; in some animal tissues lateral profiles of fluorine were measured. PMID:11569877

Sastri, C S; Iyengar, V; Blondiaux, G; Tessier, Y; Petri, H; Hoffmann, P; Aras, N K; Zaichick, V; Ortner, H M

2001-08-01

35

Measurements of activation induced by environmental neutrons using ultra low-level gamma-ray spectrometry.  

PubMed

The flux of environmental neutrons is being studied by activation of metal discs of selected elements. Near the earth's surface the total neutron flux is in the order of 10(-2) cm(-2)s(-1), which gives induced activities of a few mBq in the discs. Initial results from this technique, involving activation at ground level for several materials (W, Au, Ta, In, Re, Sm, Dy and Mn) and ultra low-level gamma-ray spectrometry in an underground laboratory located at 500 m.w.e., are presented. Diffusion of environmental neutrons in water is also measured by activation of gold at different depths. PMID:10724430

Martnez Canet, M J; Hult, M; Khler, M; Johnston, P N

2000-03-01

36

Statistical origin of the highest-energy fusion-induced gamma rays  

NASA Astrophysics Data System (ADS)

Mass-separated gamma-ray spectra and energy-dependent gamma multiplicities provide direct support for the statistical emission of giant dipole resonance gamma rays following equilibrium of a fused compound nuclear system. A 4? NaI(Tl) array was employed to measure the gamma-ray spectrum and associated multiplicities following the fusion of 35Cl with 54Fe. Mass separation was achieved using the Rochester Recoil Mass Spectrometer.

Herman, M. G.; Cormier, T. M.; Satteson, M.

1988-03-01

37

Statistical origin of the highest-energy fusion-induced gamma rays  

Microsoft Academic Search

Mass-separated gamma-ray spectra and energy-dependent gamma multiplicities provide direct support for the statistical emission of giant dipole resonance gamma rays following equilibrium of a fused compound nuclear system. A 4pi NaI(Tl) array was employed to measure the gamma-ray spectrum and associated multiplicities following the fusion of 35Cl with 54Fe. Mass separation was achieved using the Rochester Recoil Mass Spectrometer.

M. G. Herman; T. M. Cormier; M. Satteson

1988-01-01

38

COMPTEL observations of the Orion complex: Evidence for cosmic-ray induced gamma-ray lines  

Microsoft Academic Search

We report the detection of gamma-ray emission from the Orion complex in the 3-7 MeV range by the Imaging Compton Telescope (COMPTEL) telescope aboard the Compton Gamma Ray Observatory (CGRO). This emission can be identified with the 4.44 MeV and 6.13 MeV nuclear de-excitation lines of C-12star and O-16star, respectively, which are predicted to be the strongest gamma-ray lines originating

H. Bloemen; R. Wijnands; K. Bennett; R. Diehl; W. Hermsen; G. Lichti; D. Morris; J. Ryan; V. Schonfelder; A. W. Strong; B. N. Swanenburg; C. de Vries; C. Winkler

1994-01-01

39

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

40

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

SciTech Connect

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 {approx}6.4x10{sup 6} photons with energies >100 MeV and {approx}250 hours total live time for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission--often referred to as Earth albedo gamma-ray emission--has a power-law shape up to 500 GeV with spectral index {gamma}=2.79{+-}0.06.

Abdo, A. A. [Space Science Division, Naval Research Laboratory, Washington, D.C. 20375 (United States); National Academy of Sciences, Washington, D.C. 20001 (United States); Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Buehler, R.; Cameron, R. A.; Charles, E.; Chiang, J.; Claus, R.; Digel, S. W.; Couto e Silva, E. do; Drell, P. S.; Dubois, R.; Focke, W. B.; Funk, S.; Glanzman, T. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, California 94305 (United States)] (and others)

2009-12-15

41

Characterization of dark-matter-induced anisotropies in the diffuse gamma-ray background  

NASA Astrophysics Data System (ADS)

The Fermi-LAT collaboration has recently reported the detection of angular power above the photon noise level in the diffuse gamma-ray background between 1 and 50 GeV. Such signal can be used to constrain a possible contribution from dark matter (DM) induced photons. We estimate the intensity and features of the angular power spectrum (APS) of this potential DM signal, for both decaying and annihilating DM candidates, by constructing template all-sky gamma-ray maps for the emission produced in the galactic halo and its substructures, as well as in extragalactic (sub)haloes. The DM distribution is given by state-of-the-art N-body simulations of cosmic structure formation, namely Millennium-II for extragalactic (sub)haloes, and Aquarius for the galactic halo and its subhaloes. We use a hybrid method of extrapolation to account for (sub)structures that are below the resolution limit of the simulations, allowing us to estimate the total emission all the way down to the minimal self-bound halo mass. We describe in detail the features appearing in the APS of our template maps and we estimate the effect of various uncertainties such as the value of the minimal halo mass, the fraction of substructures hosted in a halo and the shape of the DM density profile. Our results indicate that the fluctuation APS of the DM-induced emission is of the same order as the Fermi-LAT APS, suggesting that one can constrain this hypothetical emission from the comparison with the measured anisotropy. We also quantify the uncertainties affecting our results, finding `theoretical error bands' spanning more than two orders of magnitude and dominated (for a given particle physics model) by our lack of knowledge of the abundance of low-mass (sub)haloes.

Fornasa, Mattia; Zavala, Jess; Snchez-Conde, Miguel A.; Siegal-Gaskins, Jennifer M.; Delahaye, Timur; Prada, Francisco; Vogelsberger, Mark; Zandanel, Fabio; Frenk, Carlos S.

2013-02-01

42

DamageRepair Kinetics and Early Adaptive Response Induced by Gamma Rays in Murine Leukocytes in vivo  

Microsoft Academic Search

The kinetics of damage induction and repair at different doses, and the adaptive response induced by gamma ray exposure were determined in murine leukocytes in vivo. The adaptive response was determined after an adaptive dose of 0.01 Gy and a challenge dose of 1.0 Gy administered 60 min later. DNA damage was measured by the single cell gel electrophoresis. Results

M. T. Mendiola-Cruz; P. Morales-Ramrez

1999-01-01

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 1.610-6 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 1.510-6 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.; Bser, 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.; Demirrs, 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.; Gro, 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.; Hl, 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.; Kpke, L.; Kowalski, M.; Kowarik, T.; Krasberg, M.; Kuehn, K.; Labare, M.; Landsman, H.; Leich, H.; Leier, D.; Liubarsky, I.; Lundberg, J.; Lnemann, J.; Madsen, J.; Mase, K.; Matis, H. S.; McCauley, T.; McParland, C. P.; Meli, A.; Messarius, T.; Mszros, P.; Miyamoto, H.; Mokhtarani, A.; Montaruli, T.; Morey, A.; Morse, R.; Movit, S. M.; Mnich, K.; Nahnhauer, R.; Nam, J. W.; Nieen, P.; Nygren, D. R.; gelman, H.; Olivas, A.; Patton, S.; Pea-Garay, C.; Prez 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.; Wikstrm, G.; Williams, D. R.; Wischnewski, R.; Wissing, H.; Woschnagg, K.; Xu, X. W.; Yodh, G.; Yoshida, S.; Zornoza, J. D.

2007-07-01

45

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

Microsoft Academic Search

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,

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

1996-01-01

46

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

Microsoft Academic Search

Fluorine concentrations in bone biopsy samples taken from the iliac crest of subjects, divided into four groups depending\\u000a on the length of dialysis treatment, and aluminium levels in blood and bone pathology, in terms of osteoporosis, were determined\\u000a by two instrumental methods. Proton-induced gamma-ray emission (PIGE), making use of the resonance reaction of19F(p,??)16O at 872 keV, and cyclic neutron activation

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

1990-01-01

47

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

48

INVESTIGATION OF $gamma$-RAYS EMITTED IN THE FISSION OF U²³⁵ INDUCED BY 2.8 AND 14.7 Mev NEUTRONS  

Microsoft Academic Search

The gamma rays coinciding in time with fission fragments were recorded ; with a scintillation counter. It is shown that the gamma -ray spectrum is the ; same for U²³⁵ fission induced by 2.8 and 14.7 Mev neutrons as for fission ; induced by thermal neutrons. It is concluded that the total gamma -quantum ; energy per U²³⁵ fission event

A. N. Protopopov; B. M. Shiryaev

1958-01-01

49

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

50

Comparison of X-ray and gamma-ray dose-response curves for pink somatic mutations in Tradescantia clone 02  

Microsoft Academic Search

Summary Microdosimetric data indicate that the mean specific energy,?, produced by individual charged particles from X rays and gamma rays is different for the two radiation qualities by nearly a factor of two. In order to test whether this influences the initial, linear component in the dose-effect relations, a comparison was made between dose-response curves for pink somatic mutations inTradescantia

A. G. Underbrink; A. M. Kellerer; R. E. Mills; A. H. Sparrowt

1976-01-01

51

Application of induced gamma-ray spectroscopy measurements: characterization of a North Sea reservoir  

Microsoft Academic Search

Implementation of a correct mineral transform model and strategy on elemental chemistry, derived from gamma-ray spectroscopy logging tools, can provide a continuous accurate measurement of mineralogy through a complete reservoir section. Such mineralogy logs are potentially valuable on their own, especially for the identification of clay minerals in petroleum exploration; however, they can also be used for the determination of

J. C. Lofts; P. K. Harvey; M. A. Lovell; J. Locke

1994-01-01

52

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

NASA Astrophysics Data System (ADS)

A series of 6 GeV proton irradiations at the Argonne National Laboratory's Zero Gradient Synchrocyclotron included the bombardment of two thick Fe targets for the purpose of simulating the cosmic ray bombardment of planetary objects in space. Cosmic ray bombardment leads to characteristic gamma ray production, from which, by measuring their energy and intensity, surface composition may be derived.

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

1986-03-01

53

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

54

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

55

Proton induced X-ray emission and proton induced gamma ray emission analysis in geochemical exploration for gold and base metal deposits  

Microsoft Academic Search

Proton induced X-ray emission (PIXE) and proton induced gamma ray emission (PIGME) analysis has been used in geochemical exploration to determine various elements in rocks and regolith in relation to gold and base metal mineralisation. Elements analysed by PIXE include K, Fe, Ca, Ti, Mn, Cl, Ga, Rb, Sr, Zr, Y, Nb, Cu, Zn, Pb, Ni, As, V and Mo,

Aung Pwa; R. Siegele; D. D. Cohen; E. Stelcer; J. C. van Moort

2002-01-01

56

Neutron and Prompt Gamma Ray Emission in the Proton Induced Fission of 239Np and 243Am and Spontaneous Fission of 252Cf  

Microsoft Academic Search

Average prescission < Mnpre > and postscission < Mnpost > neutron multiplicities as well as average gamma-ray multiplicity , average energy emitted by gamma-rays and average energy per one gamma quantum as a function of mass and total kinetic energy (TKE) of fission fragments were measured in proton induced reactions p+242Pu-->243Am, p+238U-->239Np (at proton energy Ep=13, 20 and

L. Krupa; G. N. Kniajeva; J. Kliman; A. A. Bogatchev; G. M. Chubarian; O. Dorvaux; I. M. Itkis; M. G. Itkis; S. Khlebnikov; N. A. Kondratiev; E. M. Kozulin; V. Lyapin; T. Materna; W. Rubchenia; I. V. Pokrovsky; W. Trzaska; D. Vakhtin; V. M. Voskressensky

2005-01-01

57

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

58

Gamma-ray induced cascades and magnetic fields in the intergalactic medium  

SciTech Connect

We present the results of Monte Carlo simulations of three-dimensional electromagnetic cascade initiated by interactions of the multi-TeV {gamma} rays with the cosmological infrared/optical photon background in the intergalactic medium. Secondary electrons in the cascade are deflected by the intergalactic magnetic fields before they scatter on CMB photons. This leads to extended 0.1 deg. -10 deg. scale emission at multi-GeV and TeV energies around extragalactic sources of very high-energy {gamma} rays. The morphology of the extended emission depends, in general, on the properties of magnetic fields in the intergalactic medium. Using Monte Carlo simulated data sets, we demonstrate that the decrease of the size of extended source with the increase of energy allows to measure weak magnetic fields with magnitudes in the range from {<=}10{sup -16} G to 10{sup -12} G if they exist in the voids of the large scale structure.

Elyiv, A.; Neronov, A.; Semikoz, D. V. [Main Astronomical Observatory National Academy of Sciences of Ukraine, 27 Akademika Zabolotnoho Street 03680 Kyiv (Ukraine); ISDC Data Center for Astrophysics, Chemin d'Ecogia 16, 1290 Versoix (Switzerland) and Geneva Observatory, 51 Chemin des Maillettes, CH-1290 Sauverny (Switzerland); APC, 10 rue Alice Domon et Leonie Duquet, F-75205 Paris Cedex 13 (France) and Institute for Nuclear Research RAS, 60th October Anniversary Prospect 7a, Moscow, 117312 (Russian Federation)

2009-07-15

59

In vivo elemental analysis by counting neutron-induced gamma rays for medical and biological applications  

Microsoft Academic Search

Non-invasive in vivo elemental analysis is a technique used to assess human body composition which is indicative of nutritional status and health condition. The in vivo measurement of the body's major elements is used for a variety of medical studies requiring the determination of the body's compartments (protein, fat, water, bone). Whole body gamma-ray counters, consisting of Nal(Tl) crystal detectors

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

1995-01-01

60

Multielement analysis of major and minor elements by thermal neutron induced capture gamma-ray spectrometry  

Microsoft Academic Search

The utility of prompt gamma-rays from thermal neutron capture for the measurement of nine elements (Si, Al, Fe, Na, K, Ca,\\u000a Ti, Mg and P) in major and minor abundance has been investigated. National Bureau of Standards (NBS) and United States Geological\\u000a Survey (USGS) standards were used to demonstrate generally good agreement between experimental measurements and certified\\u000a values. Usually accuracies

E. S. Gladney; D. B. Curtis; E. T. Jurney

1978-01-01

61

The determination of minor elements in steel by proton-induced prompt gamma-ray spectrometry  

Microsoft Academic Search

Pure elemental targets of Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo and W were irradiated with protons from 3.5 to 6.0 MeV,\\u000a interference-free sensitivities were calculated for analysis by prompt gamma-ray spectrometry and sensitivity curves were\\u000a plotted to show the variation of sensitivity with bombarding energy. Appropriate bombarding energies were selected for analysis\\u000a and the extent

M. Peisach; D. Gihwala

1981-01-01

62

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

63

Polymer degradation during radiation-induced emulsion polymerization of styrene. [. gamma. rays  

Microsoft Academic Search

Styrene was polymerized in emulsion with initiation by ..gamma..-rays at a dose rate of 0.6 Mrad\\/hr. Polymerization rates were as expected from previous reports by others. No branching or crosslinking was detectable, and the anti M\\/sub w\\/\\/anti M\\/sub n\\/ ratio of the polystyrene did not change significantly during the course of the polymerization reaction. The molecular weight of the product

K. Sato; A. Rudin; R. Y. M. Huang

1976-01-01

64

Rapid, non-destructive carbon analysis of forest soils using neutron-induced gamma-ray spectroscopy  

SciTech Connect

Forest soils are pivotal to understanding global carbon (C) cycling and evaluating policies for mitigating global change. However, they are very difficult to monitor because of the heterogeneity of soil characteristics, the difficulty of representative sampling, and the slow time scale of response to environmental change. Here we demonstrate that use of gamma-ray spectroscopy facilitates in situ non-destructive analysis of C and other elements in forest soils. In this approach the element-specific gamma-rays are induced by fast and thermal neutrons interacting with the nuclei of the elements present in the soil. Background gamma-rays emanating from naturally occurring radionuclides in the forest are recorded as well. We applied this approach in a mature northern hardwood forest on glacial till soils at the Bartlett Experimental Forest in New Hampshire, USA. The inelastic neutron scattering (INS) system yielded strong signals in gamma-ray counts/h, from C and other elements present in the soil matrix that included silicon, oxygen, hydrogen, iron, aluminum, manganese and potassium. The INS sensitivity for carbon was 20.656 counts h{sup -1} kg{sup -1} C m{sup -2} based on current net C gamma-ray counts and the data for the O horizon and mineral soil to a depth of 30 cm obtained from a nearby quantitative soil pit (7.35 kg C m{sup -2}). We estimate the minimum detectable change to be {approx}0.34 kg C m{sup -2}, which is {approx}5% of the current soil C content, and the minimum detectable limit to be {approx}0.23 kg C m{sup -1}. Eight % reproducibility from 11 measurements was limited, in part, by the large variability in the system counting geometry due to the uneven forest microtopography. The INS approach has the potential to revolutionize belowground monitoring of C and other elements, because the possibility of detecting a 5% change in forest soils has not been possible with destructive sampling methods.

Wielopolski, L.; Mitra, S.; Yanai, R. D.; Levine, C. R.; Vadeboncoeur, M. A.

2010-08-01

65

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

NASA Astrophysics Data System (ADS)

A series of 6 GeV proton irradiations at the Argonne National Laboratory's Zero Gradient Synchrocyclotron included the bombardment of two thick Fe targets for the purpose of simulating the cosmic ray bombardment of planetary objects in space. Cosmic ray bombardment leads to characteristic gamma ray production, from which, by measuring their energy and intensity, surface composition may be derived. In this experiment, gamma ray energy spectra were obtained with a germanium solid state detector during the bombardment. The spectra show much detail, with 46 of the gamma ray lines ascribed to the Fe targets. The background includes recoil-broadened lines due to energetic neutron interactions in the Ge detector. A comparison with values predicted by modeling shows good agreement for Fe lines from neutron inelastic scattering and spallation reactions, and less satisfactory agreement for neutron capture reactions, the latter found to be due primarily to the difference in composition between the Fe target and the mean lunar abundance used in the modeling. Analysis of the irradiation results combined with continuum data obtained in lunar orbit indicates that 100 hours of measurement with a state-of-the-art instrument should generate a spectrum containing approximately 20 lines due to Fe alone, with a 2? sensitivity for detection of about 0.2%.

Metzger, Albert E.; Parker, Richard H.; Yellin, Joseph

1986-09-01

66

Comparison of protein expression profile changes in human fibroblasts induced by low doses of gamma rays and energetic protons  

NASA Astrophysics Data System (ADS)

Extrapolation of known radiation risks to the risks from low dose and low dose-rate exposures of human population, especially prolonged exposure of astronauts in the space radiation environment, relies in part on the mechanistic understanding of radiation induced biological consequences at the molecular level. While some genomic data at the mRNA level are available for cells or animals exposed to radiation, the data at the protein level are still lacking. Here, we studied protein expression profile changes using Panorama antibody microarray chips that contain antibodies to more than 200 proteins (or modified proteins) involved in cell signaling that included mostly apoptosis, cytoskeleton, cell cycle and signal transduction. Normal human fibroblasts were cultured till fully confluent and then exposed to 2 cGy of gamma rays at either low (1 cGy/hr) or high (0.2 Gy/min) dose-rate, or to 2 cGy of 150 MeV protons at high dose-rate. The proteins were isolated at 2 and 6 hours after exposure and labeled with Cy3 for the irradiated cells and with Cy5 for the control samples before loaded onto the protein microarray chips. The intensities of the protein spots were analyzed using ScanAlyze software and normalized by the summed fluorescence intensities and the housekeeping proteins. Comparison of the overall protein expression profiles in gamma-irradiated cells showed significantly higher inductions at the high dose-rate than at the low dose-rate. The protein profile in cells after the proton exposure showed a much earlier induction pattern in comparison to both the high and low dose-rate gamma exposures. The same expression patterns were also found in individual cell signaling cascades. At 6 hours post irradiation, high dose-rate gamma rays induced cellular protein level changes (ratio to control 2) mostly in apoptosis, cell cycle and cytoskeleton, while low dose-rate gamma rays induced similar changes with smaller fold-change values. In comparison, protons induced protein changes mainly in the cell cycle category. Thus, at the total dose of 2 cGy, high dose-rate gamma rays may generate more cellular responses through protein level and modification changes to regulate cell signaling and cell-cell communication. Protons presented the less effect, possibly due to the different track distribution compared with gamma radiation.

Zhang, Ye; Clement, Jade; Gridley, Diala; Rohde, Larry; Wu, Honglu

67

In vivo elemental analysis by counting neutron-induced gamma rays for medical and biological applications  

NASA Astrophysics Data System (ADS)

Non-invasive in vivo elemental analysis is a technique used to assess human body composition which is indicative of nutritional status and health condition. The in vivo measurement of the body's major elements is used for a variety of medical studies requiring the determination of the body's compartments (protein, fat, water, bone). Whole body gamma-ray counters, consisting of Nal(Tl) crystal detectors in a shielded room, are used for measuring in vivo the body's Ca, Cl, Na and P by delayed neutron activation analysis. Thermal neutrons from a moderated 238Pu-Be source are used for the measurement of total body nitrogen (and thus protein) and chlorine at low radiation exposure (0.80 mSv). The resulting high energy prompt gamma-rays from nitrogen (10.83 MeV) and chlorine (6.11 MeV) are detected simultaneously with the irradiation. Body fat (the main energy store) and fat distribution (which relates to risk for cardiovascular disease) are measured by detecting C and O in vivo through fast neutron inelastic scattering. A small sealed D-T neutron generator is used for the pulsed (4 - 8 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 the 12C and 16O nuclei, respectively. One use of this method is the systematic study of the mechanisms driving the age-associated depletion of the metabolizing, oxygen-consuming cellular compartment of the body. The understanding of this catabolism may suggest ways to maintain lean tissue and thus to preserve quality of life for the very old.

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

1995-03-01

68

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

69

Gamma-ray irradiated polymer optical waveguides  

SciTech Connect

Optical waveguides fabricated by gamma-ray irradiation on polymer through a gold mask are presented. The gamma-ray induced index change is found almost linearly dependent on the dose of the irradiation. And the measured propagation losses are low enough for practical application. Due to the high penetrability of gamma ray, uniform refractive index change in depth can be easily achieved. Moreover, due to large-area printing, the uniformity of waveguide made by gamma-ray irradiation is much better than that by e-beam direct writing.

Lai, C.-C.; Wei, T.-Y.; Chang, C.-Y.; Wang, W.-S.; Wei, Y.-Y. [Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, No. 1, Roosevelt Road Sec. 4, Taipei 10617, Taiwan (China); Nuclear Science and Technology Development Center, National Tsing-Hua University, No. 101, Sec. 2, Kuang-Fu Road, Hsin-Chu 30043, Taiwan (China)

2008-01-14

70

High energy gamma ray production in proton-induced reactions at 104, 145, and 195 MeV  

Microsoft Academic Search

Energy spectra and angular distributions have been measured for high energy gamma rays (Egamma>=20 MeV) from proton-nucleus reactions at 104, 145, and 195 MeV on targets of C, Zn, and Pb. Gamma rays were observed with energies up to 170 MeV. The spectra showed differences from the typical exponential shape that is observed in gamma ray production from heavy-ion reactions.

J. Clayton; W. Benenson; M. Cronqvist; R. Fox; D. Krofcheck; R. Pfaff; T. Reposeur; J. D. Stevenson; J. S. Winfield; B. Young; M. F. Mohar; C. Bloch; D. E. Fields

1992-01-01

71

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

PubMed

The signal current from an ionisation chamber with a PMMA build-up cap decreases with irradiation time due to electric fields produced by positive charges induced on the cap. In the present study, it was confirmed that the signal current decreases faster for irradiation using narrower (60)Co gamma-ray beams. This is because the number of secondary electrons that are emitted from surrounding materials and penetrate the build-up cap is smaller in a narrower gamma-ray beam, so that fewer positive charges are neutralised. The ionisation chamber was first subjected to continuous gamma-ray irradiation for 24 h, following which it was irradiated with shorter periodic gamma-ray bursts while measuring the current signal. This allowed the coefficients of positive charge accumulation and dissipation to be determined. It was found that the dissipation coefficient has a large constant value during gamma-ray irradiation and decreases asymptotically to a small value after irradiation is stopped. From the coefficients, the minimum signal current was calculated, which is the value when accumulation and dissipation balance each other under continuous irradiation. The time required for the signal current to recover following irradiation was also calculated. PMID:23390147

Morishita, Y; Takata, N

2013-02-06

72

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

73

Body composition to climate change studies - the many facets of neutron induced prompt gamma-ray analysis  

SciTech Connect

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), protein, fat and water are determined. C determination in soil has become important for understanding below ground carbon sequestration process in the light of climate change studies. Various neutron sources ranging from radio isotopic to compact 14 MeV neutron generators employing the associated particle neutron time-of-flight technique or micro-second pulsing were implemented. Gamma spectroscopy using recently developed digital multi-channel analyzers has also been described.

Mitra,S.

2008-11-17

74

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

75

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

PubMed Central

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 300 R. The incidence of B8-loss variants was 4.1 X 10(-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. Images

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

1980-01-01

76

Thermal and gamma-ray induced relaxation in As-S glasses: modelling and experiment  

NASA Astrophysics Data System (ADS)

Enthalpy relaxation was 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 modelling results obtained by fitting differential scanning calorimetry curves with the Tool-Narayanaswamy-Moynihan (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 behaviour 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.

2011-10-01

77

Determination of fluorine by proton-induced gamma-ray emission (PIGE) spectrometry in igneous and metamorphic charnockitic rocks from Rogaland (S. W. Norway)  

Microsoft Academic Search

More than 200 specimens from different occurrences of the Rogaland igneous complex and surrounding granulite facies metamorphic rocks (S. W. Norway) have been analysed by a direct non-destructive proton induced gamma-ray emission (PIGE) technique. The fluorine contents vary from

I. Roelandts; G. Robaye; G. Weber; J. M. Delbrouck; J. C. Duchesne

1987-01-01

78

Determination of Fluorine in NBS Coal and Coal Fly Ash by Proton Induced Gamma Ray Emission and Spark Source Mass Spectrometry  

Microsoft Academic Search

Fluorine concentrations in US National Bureau of Standards standard reference materials 1632a (coal) and 1633a (coal fly ash) have been determined by proton induced gamma ray emission (PIGME) and spark source mass spectrometry (SSMS) using the method of standard additions. Good agreement was obtained between the two techniques with no significant bias. The mean values for 1632a and 1633a were

E. Clayton; L. S. Dale

1985-01-01

79

2-[(Aminopropyl)amino] ethanethiol-mediated reductions in 60Co gamma-ray and fission-spectrum neutron-induced chromosome damage in V79 cells.  

PubMed

The radioprotector 2-[aminopropyl)amino] ethanethiol (WR1065), which has been reported to reduce the cytotoxic and mutagenic effects of low LET radiation, was investigated for its ability to protect against low LET (60Co gamma ray) and high LET (fission-spectrum neutron)-induced chromosome damage in V79 cells. Cells were irradiated in G2 phase in the presence or absence of 4 mM WR1065 and were harvested and analyzed 2 h later for chromatid-type aberrations. Irradiation of G2-phase V79 cells in the presence of WR1065 resulted in a 30 to 50% reduction in the frequency of gamma-ray and neutron-induced chromatid-type breaks and exchanges. The effects were found only after exposures of greater than 200 cGy gamma-ray or 50 cGy neutron irradiation. The radioprotector was effective at reducing neutron-induced aberrations after exposures at dose rates of both 10 and 43 cGy/min. Thus the radioprotector WR1065 is an effective anti-clastogenic agent in V79 cells, protecting against both 60Co gamma-ray and fission-spectrum neutron-induced aberrations, when present during irradiation. PMID:3340717

Schwartz, J L; Giovanazzi, S M; Karrison, T; Jones, C; Grdina, D J

1988-01-01

80

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

81

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 UO2 sample and a 36 GWd/t burnt UO2 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.

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

2010-12-01

82

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

83

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

84

Compound and precompound gamma-ray entry lines from measured multiplicities and energies in alpha-induced reactions  

Microsoft Academic Search

Multiplicities of quasi-continuum gamma-rays have been measured for the 160Gd(alpha, xngamma) reactions as a function of bombarding energy and for the 4n exit channel also as a function of gamma-ray energy. Increase of beam energy causes initially an increase of the energy and angular momentum of the entry line in the residual nucleus until the neutron ``drip line'' is reached.

W. J. Ockels; M. J. A. de Voigt; Z. Sujkowski

1978-01-01

85

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

86

Effects of (60)Co gamma -rays on PWM and LPS Induced Lymphocytes.  

National Technical Information Service (NTIS)

The relationship between lymphocytes induced by PWM and LPS was investigated by means of (3)H-TdR and (14)C-UR incorporation. The study showed that in vitro, PWM-induced cells were able to promote the stimulating effect of LPS to B lymphocyte. The stimula...

L. Su F. Liu K. Liu C. Xu Yu Zhiying

1987-01-01

87

A gamma ray laser based on induced annihilation of electron-positron pairs  

Microsoft Academic Search

In this paper, the coherent amplification of gamma radiation of a system of parapositronium atoms is proposed. The nonlinear optics of positronium media is suggested. The induced annihilation transitions for the electron-positron plasma are compared with those of the positronium medium. It is suggested that the Bose-Einstein condensation could play a crucial role in the estimation of the induced annihilation

A. Loeb; S. Eliezer

1986-01-01

88

Coincidence method for the analysis of minor elements in steel by deuteron-induced prompt \\/gamma-ray spectrometry (d-PIGE)  

Microsoft Academic Search

The sensitivities of minor elements analysis in a standard steel sample irradiated with 5 MeV deuterons have been determined by the regular deuteron-induced \\/gamma-ray emission (d-PIGE) method and with the selection of the (d,n) reaction channel by measuring \\/gamma-n coincidences. This approach has resulted in a significant improvement of the sensitivity of the analysis. A comparative study with the published

A. Ene; T. Badica; A. Olariu; I. V. Popescu; C. Besliu

2001-01-01

89

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  

Microsoft Academic Search

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,

R. Lapatto; J. Raisanen

1988-01-01

90

Gamma ray optics  

SciTech Connect

Via refractive or diffractive scattering one can shape {gamma} 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/E{sup 2}, 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/E{sup 2} 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.; Guenther, M. M.; Habs, D.; Thirolf, P. G. [Institut Laue-Langevin, F38042 Grenoble (France); Max-Planck-Institut fuer Quantenoptik, D-85748 Garching (Germany); Max-Planck-Institut fuer Quantenoptik, D-85748 Garching, Germany and Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching (Germany); Ludwig-Maximilians-Universitaet Muenchen, D-85748 Garching (Germany)

2012-07-09

91

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

92

Gamma-ray-induced mutagen sensitivity and risk of sporadic breast cancer in young women: a case-control study  

PubMed Central

Hypersensitivity to radiation exposure has been suggested to be a risk factor for the development of breast cancer. In this casecontrol study of 515 young women (?55 years) with newly diagnosed sporadic breast cancer and 402 cancer-free controls, we examined the radiosensitivity as measured by the frequency of chromatid breaks induced by gamma-radiation exposure in the G2 phase of phytohemagglutinin-stimulated and short-term cultured fresh lymphocytes. We found that the average chromatid breaks per cell from 50 well-spread metaphases were statistically significantly higher in 403 non-Hispanic White breast cancer patients (0.52 0.22) than that in 281 non-Hispanic White controls (0.44 0.16) (P value < 0.001), and in 60 Mexican American breast cancer patients (0.52 0.19) than that in 65 Mexican American controls (0.44 0.16) (P value = 0.021), but the difference was not significant in African Americans (52 cases [0.45 0.16] versus 56 controls [0.47 0.16], P = 0.651). The frequency of chromatid breaks per cell above the median of control subjects was associated with two-fold increased risk for breast cancer in non-Hispanic Whites and Mexican Americans. A doseresponse relationship was evident between radiosensitivity and risk for breast cancer (Ptrend < 0.001) in these two ethnic groups. We concluded that gamma-ray-induced mutagen sensitivity may play a role in susceptibility to breast cancer in young non-Hispanic White and Mexican American women.

Han, Chan H.; Xiong, Ping; Bondy, Melissa L.; Yu, Tse-Kuan; Brewster, Abenaa M.; Shete, Sanjay; Arun, Banu K.; Buchholz, Thomas A.; Wei, Qingyi

2012-01-01

93

Proton-induced prompt gamma-ray spectrometry: A survey of its analytical significance and some applications  

Microsoft Academic Search

A survey was carried out of prompt gamma-rays emitted during bombardment of all stable non-gaseous elements with protons from\\u000a 3.5 to 6.0 MeV. Attainable sensitivities were calculated for the 5 most intense gamma-rays as a function of bombarding energy.\\u000a For most elements maximum sensitivity was attainable with protons between 4 and 5 MeV. Applications of the technique to the\\u000a analysis

D. Gihwala; M. Peisach

1982-01-01

94

Benchmark Experiments of Fusion Neutron Induced Gamma-Ray Radioactivity in Various Structural Materials  

Microsoft Academic Search

The fusion reactor inventory code FISPACT, together with the European Activation File EAF, is the European reference software for calculating the neutron-induced activation of fusion reactor relevant materials. Experimental verifications (benchmarks) of the code predictions have been performed at ENEA Frascati by means of an irradiation facility consisting of a D-T neutron generator and a moderator\\/reflector structure which is employed

M. Pillon; M. Angelone; P. Batistoni; R. A. Forrest; J.-Ch. Sublet

2000-01-01

95

Fission-gamma-Ray Coincidence Studies of ^238U Neutron-Induced Fission in the Range 1 < En < 200 MeV  

Microsoft Academic Search

Studies of prompt fission-gamma-ray coincidences are being carried out using the high-resolution gamma-ray detector array GEANIE at the WNR broad-spectrum neutron source at LANSCE. Thin Si solar cells with thin ^238U deposits are used to detect fission products in coincidence with their de-excitation gamma rays. Low-energy gamma rays and x-rays are detected with planar Ge detectors. Higher-energy gamma rays are

R. O. Nelson; T. Ethvignot; T. Granier; P. Casoli; N. Fotiades; M. Devlin; P. E. Garrett; W. Younes; J. A. Becker; L. A. Bernstein

2002-01-01

96

Cotton fabric modification for imparting high water and oil repellency using perfluoroalkyl phosphate acrylate via gamma-ray-induced grafting  

Microsoft Academic Search

The perfluoroalkyl phosphate acrylates were grafted onto a cotton fabric via gamma-ray irradiation to improve the hydrophobic and oleophobic properties. The change in chemical structure of grafted cotton fabric was detected by the Fourier transform infrared spectroscopy and the X-ray photoelectron spectroscopy. The contact angles for water and sunflower oil were determined to be over 150 and 140, respectively, after

Hui Miao; Fenfen Bao; Liangliang Cheng; Wenfang Shi

2010-01-01

97

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.; Gnther, M. M.; Habs, D.; Thirolf, P. G.

2012-07-01

98

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

99

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

100

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 Bi4Ge3O12 (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

101

Hypernuclear gamma rays  

SciTech Connect

The observation of hypernuclear ..gamma.. rays pprovides a method of determining the spin dependence of the ..lambda..-nucleon interaction with a sensitivity not approachable by other means in the forseeable future. The transitions of primary interest are those between states that differ only in the orientation of the spin of the ..lambda.. particle with respect to the angular momentum of the nuclear core. The effective ..lambda..-nucleon interaction can be specified by a small number of ..gamma..-ray measurements. A program of experiments directed at this goal is in progress at Brookhaven National Laboratory. This paper reviews the status of the subject with emphasis on the recent experiment to measure ground state doublet splittings using germanium ..gamma..-ray detectors.

May, M.

1985-01-01

102

Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are the brightest transient sources in the gamma-ray sky. Since their discovery in the late 1960s, the investigation of the astrophysical sys- tems in which these phenomena take place, and the physical mechanisms that drive them, has become a vast and prolific area of modern astrophysics. In this work I will briefly describe the most relevant observations of these sources, and the models that describe their nature, emphasizing on the in- vestigations about the progenitor astrophysical systems. FULL TEXT IN SPANISH

Pellizza, L. J.

103

Gamma-ray bursts.  

PubMed

Gamma-ray bursts (GRBs) are bright flashes of gamma rays coming from the cosmos. They occur roughly once per day, typically last for tens of seconds, and are the most luminous events in the universe. More than three decades after their discovery, and after pioneering advances from space and ground experiments, they still remain mysterious. The launch of the Swift and Fermi satellites in 2004 and 2008 brought in a trove of qualitatively new data. In this Review, we survey the interplay between these recent observations and the theoretical models of the prompt GRB emission and the subsequent afterglow. PMID:22923573

Gehrels, Neil; Mszros, Pter

2012-08-24

104

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

105

Variation in sensitivity to. gamma. -ray-induced chromosomal aberrations during the mitotic cycle of the sea urchin egg  

SciTech Connect

Sea urchin eggs were irradiated with /sup 137/Cs ..gamma.. rays at various stages of the mitotic cycle, and chromosomal aberrations at the first postirradiation mitosis and embryonic abnormalities at later developmental stages were examined. The radiosensitivity of the eggs to both endpoints varied in parallel with the mitotic stage at the time of irradiation, suggesting a possible relationship between chromosomal damage and embryonic abnormalities.

Ejima, Y. (Univ. of Tokyo, Japan); Nakamura, I.; Shiroya, T.

1982-11-01

106

A rapid method for carbon and oxygen determination with external beam proton induced gamma-ray emission analysis  

Microsoft Academic Search

The applicability of the gamma-rays from the reaction 12C(p, p'gamma)12C and 16O(p, p'gamma)16O for carbon and oxygen detection has been investigated. The optimum proton energy region for the analyses was determined. Various system construction materials were tested for obtaining a minimum background. Kapton, Havar and Ni exit foils were tested and the advantages of each are discussed. In the present

J. Risnen

1986-01-01

107

Hard X-Ray and Gamma-Ray Emission Induced by Ultra-High-Energy Protons in Cluster Accretion Shocks  

Microsoft Academic Search

All sufficiently massive clusters of galaxies are expected to be surrounded by strong accretion shocks, where protons can be accelerated to ~1018-1019 eV under plausible conditions. Such protons interact with the cosmic microwave background and efficiently produce very high energy electron-positron pairs, which then radiate synchrotron and inverse Compton emission, peaking respectively at hard X-ray and TeV gamma-ray energies. Characterized

Susumu Inoue; Felix A. Aharonian; Naoshi Sugiyama

2005-01-01

108

Cross sections for the photofission of 232Th, induced by mono-energetic gamma rays of 12 different energies  

Microsoft Academic Search

Thorium-loaded nuclear emulsions have been exposed to mono-energetic gamma-rays obtained from (n, gamma) reactions on the following elements: S, Dy, Y, Ca, Ti, Be, Mn, Pb, Fe, Al, Cu and Ni. The photo-fission cross section of 232Th has been measured at 12 energies in the range 5.4-9 MeV. For the same energies, the ratios of the 232Th cross section with

A. Manfredini; L. Fiore; C. Ramorino; H. G. de Carvalho; W. Woelfli

1969-01-01

109

Gamma Ray Observatory survives  

Microsoft Academic Search

Right now the budgetary position of NASA science projects for fiscal year 1982 is shaky, outside of the Space Shuttle Program. Two scientifically crucial missions being planned are the Gamma Ray Observatory (GRO) and the Venus Orbiting Imaging Radar (VOIR). President Reagan's proposed budgetary cuts have left both programs intact but delayed. For FY 1982, GRO will be able to

Peter M. Bell

1981-01-01

110

Scission gamma rays  

SciTech Connect

Gamma rays probably emitted by the fissioning nucleus {sup 236}U* at the instant of the break of the neck or within the time of about 10{sup -21} s after or before this were discovered in the experiment devoted to searches for the effect of rotation of the fissioning nucleus in the process {sup 235}U(n,{gamma}f) and performed in a polarized beam of cold neutrons from the MEPHISTO Guideline at the FRM II Munich reactor. Detailed investigations revealed that the angular distribution of these gamma rays is compatible with the assumption of the dipole character of the radiation and that their energy spectrum differs substantially from the spectrum of prompt fission gamma rays. In the measured interval 250-600 keV, this spectrum can be described by an exponential function at the exponent value of {alpha} = -5 x 10{sup -3} keV{sup -1}. The mechanism of radiation of such gamma rays is not known at the present time. Theoretical models based on the phenomenon of the electric giant dipole resonance in a strongly deformed fissioning nucleus or in a fission fragment predict harder radiation whose spectrum differs substantially from the spectrum measured in the present study.

Danilyan, G. V., E-mail: danilyan@itep.r [Institute of Theoretical and Experimental Physics (Russian Federation); Klenke, J. [Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) (Germany); Krakhotin, V. A.; Kuznetsov, V. L.; Novitsky, V. V.; Pavlov, V. S.; Shatalov, P. B. [Institute of Theoretical and Experimental Physics (Russian Federation)

2009-11-15

111

Gamma-ray bursts  

Microsoft Academic Search

Gamma-ray bursts are the most luminous explosions in the Universe, and their origin and mechanism are the focus of intense research and debate. More than three decades after their discovery, and after pioneering breakthroughs from space and ground experiments, their study is entering a new phase with the recently launched Swift satellite. The interplay between these observations and theoretical models

P. Mszros

2006-01-01

112

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

113

Delayed gamma Rays from Fission.  

National Technical Information Service (NTIS)

Studies of delayed gamma rays from fission at early times were conducted using the pulsed beams of neutrons and bremsstrahlung x rays from an electron linear accelerator to produce fissions. Measurements of the energy spectrum of isomeric gamma rays from ...

R. B. Walton R. E. Sund

1965-01-01

114

Gamma-Ray Burst Wallsheet  

NSDL National Science Digital Library

The Gamma-ray Burst Wallsheet was developed to illustrate the properties of light emanating from a gamma-ray burst as seen by three distant satellites, including NASA's Swift. The back of the wallsheet has one of the three activities in the accompanying educator guide (Angling for Gamma-ray Bursts).

2005-01-01

115

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; Risnen, J

1988-01-01

116

CaF2:Tm (TLD300) thermoluminescent response and glow curve induced by gamma-rays and ions  

Microsoft Academic Search

The thermoluminescent response of CaF2:Tm after exposure to 60Co gamma-rays at doses from 0.44 Gy to 8.75 kGy and to low fluences (105 108 cm-2) of 25 and 40 MeV 1H, 75 and 120 MeV 3He, 180, 300 and 480 MeV 12C, 400 MeV 16O and 800 MeV 20Ne ion beams, spanning a LET interval up to about 500

G. Massillon-Jl; I. Gamboa-Debuen; A. E. Buenfil; M. A. Monroy-Rodrguez; M. E. Brandan

2008-01-01

117

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 m 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

118

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

NASA Astrophysics Data System (ADS)

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

2012-05-01

119

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

2010-09-14

120

Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes  

SciTech Connect

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 {approx}5-10 deg. 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.

Marisaldi, M.; Labanti, C.; Fuschino, F.; Bulgarelli, A.; Trifoglio, M.; Di Cocco, G.; Gianotti, F. [INAF-IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Argan, A.; De Paris, G. [INAF, Viale del Parco Mellini 84, Roma (Italy); Trois, A.; Del Monte, E.; Costa, E.; Di Persio, G.; Donnarumma, I.; Evangelista, Y.; Feroci, M.; Lazzarotto, F.; Pacciani, L.; Rubini, A.; Sabatini, S. [INAF-IASF Roma, via del Fosso del Cavaliere 100, I-00133 Roma (Italy)

2010-09-17

121

Gamma-ray luminosity properties of gamma-ray pulsars  

Microsoft Academic Search

Based on a new self-consistent outer gap model, we statistically study luminosity properties of gamma-ray pulsars with ages of <=2 107 yr in the Galaxy as well as those with ages of <=5 106 yr in the Gould belt using a Monte Carlo method, where the gamma-ray beaming effect has been included. Generally, the relation between gamma-ray luminosity, Lgamma, and

L. Zhang; Z. X. Han; Z. J. Jiang

2005-01-01

122

Simulation of prompt gamma-ray emission during proton radiotherapy  

Microsoft Academic Search

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

Joost M Verburg; Helen A Shih; Joao Seco

2012-01-01

123

Hydrated electron-induced inactivation of tyrosinase in aqueous solution by exposure to cobalt-60 gamma-rays. II. Catecholase activity.  

PubMed

Tyrosinase (0.2 mg/ml) was irradiated with 60Co gamma-rays. The catecholase activity was measured at varying radiation doses under various atmospheric conditions. D0 was found to be 1.25 kGy and hit number to be 2 in N2-saturated solution. OH radical scavengers, t-BuOH and MeOH, had no effect. O2 which is an enhancer of OH-induced enzyme inactivation had little effect. But N2O as a e aq scavenger and Cu++ markedly protected against the inactivation indicating that e aq was the main species to inactivate the enzymatic activity. By Ultrogel chromatography, it was found that the enzymatic activity was lost when this enzyme dissociated into its subunits. Thus, it was concluded that the radiation-induced inactivation was due to the reduction of Cu++ as the active center and the chelater with e aq followed by the dissociation. PMID:7849641

Terato, H; Yamamoto, O

1994-09-01

124

Hydrated electron-induced inactivation of tyrosinase in aqueous solution by exposure to cobalt-60 gamma-rays. I. Cresolase activity.  

PubMed

Tyrosinase (0.2 mg/ml of 0.1 M phosphate buffer solution, pH 6.5) which has cresolase and catecholase activities was irradiated with 60Co gamma-rays. The cresolase activity was measured at varying radiation doses under various atmospheric conditions. D0 was found to be 350 Gy in N2-saturated solution. The OH radical has been shown to be the main species involved in radiation-induced enzyme inactivation. However, in this study, OH radical scavengers, t-BuOH and MeOH, had no effect. O2 which acts generally as an enhancer of OH-induced enzyme inactivation also had little effect, but N20 ae aq scavenger, and Cu++ markedly inhibited the inactivation indicating that e aq is the main species involved in inactivating the cresolase activity, reducing Cu++ as the active center. PMID:7849640

Terato, H; Yamamoto, O

1994-09-01

125

Cross sections relevant to gamma-ray line emission in solar flares: 3He-induced reactions on 16O nuclei  

Microsoft Academic Search

gamma-ray production cross sections have been measured for gamma-ray lines copiously emitted in the 3He bombardment of 16O nuclei: the 937-, 1042-, and 1081-keV lines of 18F and the 1887-keV line of 18Ne. Four Ge detectors with BGO shielding for Compton suppression were used to measure the angular distributions of the gamma rays. The excitation functions have been obtained for

V. Tatischeff; J. Duprat; J. Kiener; M. Assuno; A. Coc; C. Engrand; M. Gounelle; A. Lefebvre; M.-G. Porquet; N. de Srville; J.-P. Thibaud; C. Bourgeois; M. Chabot; F. Hammache; J.-A. Scarpaci

2003-01-01

126

Extragalactic Gamma-Rays Gamma Ray Bursts and Blazars  

Microsoft Academic Search

The extragalactic gamma-ray sky is dominated by two classes of sources: Gamma-Ray Bursts (GRBs) and radio loud active galactic nuclei whose jets are pointing at us (blazars). We believe that the radiation we receive from them originates from the transformation of bulk relativistic energy into random energy. Although the mechanisms to produce, collimate and accelerate the jets in these sources

Gabriele Ghisellini

2005-01-01

127

Enhanced biodegradation and emulsification of crude oil and hyperproduction of biosurfactants by a gamma ray-induced mutant of Pseudomonas aeruginosa.  

PubMed

A gamma ray-induced mutant of Pseudomonas aeruginosa strain S8, capable of hyperproduction of biosurfactant from hydrocarbons, was isolated and named as EBN-8. The mutant showed 3-4 times more hydrocarbon emulsification/conversion as compared to the parent when grown on Khaskheli crude oil in minimal medium. Enhanced biosurfactant production and hydrocarbon utilization by the mutant was also observed during growth on heptadecane in minimal medium as indicated by emulsion index and surface tension of cell-free culture broth. Using heptadecane as carbon and energy source, time course for the growth (cfu ml-1) and biosurfactant production were compared for both parent and mutant. These studies were carried out for 24 d at 30 +/- 2 degrees C and for 20 d at 37 degrees C. Growth of EBN-8 was much faster compared to the parent as well as being 2-3 times more hyperproductive. PMID:7576503

Iqbal, S; Khalid, Z M; Malik, K A

1995-09-01

128

The Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory Compton) is the second in NASA's series of great Observatories. Launched on 1991 April 5, Compton represents a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made. We describe the capabilities of the four scientific instruments, and the observing program of the first 2 years of the mission. Examples of early discoveries by Compton are enumerated, including the discovery that gamma-ray bursts are isotropic but spatially inhomogeneous in their distribution; the discovery of a new class of high-energy extragalacatic gamma-ray sources, the gamma-ray AGNs; the discovery of emission from SN 1987A in the nuclear line of Co-57; and the mapping of emission from Al-26 in the interstellar medium (ISM) near the Galactic center. Future observations will include deep surveys of selected regions of the sky, long-tem studies of individual objects, correlative studies of objects at gamma-ray and other energies, a Galactic plane survey at intermediate gamma-ray energies, and improved statistics on gamma-ray bursts to search for small anisotropies. After completion of the all-sky survey, a Guest Investigator program is in progress with guest observers' time share increasing from 30% upward for the late mission phases.

Gehrels, N.; Chipman, E.; Kniffen, D.

1994-06-01

129

Delayed gamma Rays from Fission.  

National Technical Information Service (NTIS)

Measurements of the energy spectrum of delayed gamma rays from the neutron fission of PU239 and U235 were performed with a naI detector at a number of time intervals between 2 and 80 microsec. The data showed three new prominent gamma rays with energies o...

R. B. Walton R. E. Sund

1966-01-01

130

The gamma-ray cosmos  

NASA Astrophysics Data System (ADS)

NASA's Compton Observatory spacecraft and the Russian/French Granat satellite have yielded vast new knowledge concerning the gamma-ray universe, which is indicative of the most energetic events in existence. A survey is presently conducted of the state of observational and theoretical understanding of gamma-ray sources in active galaxies and within the Galaxy.

Chupp, Edward L.

1992-12-01

131

Gamma ray astrophysics  

NASA Astrophysics Data System (ADS)

A general review of cosmic energetic gamma particles is given. A discussion on the subject starting with the discovery of the PeV gamma rays by Sammorski and Stamm, passing to the super-nova SN1987A explosion when several groups waited for high energy gamma particles but none has come so far up to the measurements of TeV gamma incoming from the Crab Nebula. The discussion in this paper is a by product of the cosmic ray research done in the Chacaltaya Cosmic Rays Observatory in the past few years. A brief description of the facilities on Mount Chacaltaya (5,200 m above sea level (a.s.l.)) is also given.

Martinic, Nicholas J.

1994-04-01

132

A simple calibration procedure for in-beam gamma-ray spectroscopy  

Microsoft Academic Search

The absolute gamma-ray yields from 2 MeV protons on a 0.3 cm thick, 99.99% pure aluminum target have been determined to an accuracy of about 4%. Such data are useful for in-beam gamma-ray studies as an overall, secondary calibration and in elemental analysis using proton-induced gamma-ray emission (PIGME).

C. E. Laird; Robert L. Hershberger; David S. Flynn

1987-01-01

133

The Highest Energy Gamma Rays from Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts are equally likely to occur from any part of the sky, are detected by satellites about once per day, and emit most of their energy in a few seconds. Consequently, a detector with a large field of view and high duty factor is essential to observe gamma-ray bursts. EGRET was the 1st such detector sensitive enough to detect GeV gamma rays from gamma-ray bursts. While only 4 bursts were detected, these were the brightest bursts, as measured at < 1 MeV, in EGRET's field of view. Therefore, GeV emission may be characteristic of many bursts, and several models even predict emission extending to > TeV energies. Recently, a new TeV gamma-ray observatory, Milagro, has begun observing the Northern hemisphere sky. Milagro has > 1 sr field of view and operates 24 hours/day, 7 days/week. Milagrito, a smaller prototype of Milagro, operated for 15 months and 54 bursts were identified by BATSE, a sub-MeV detector in low Earth orbit, to be within Milagrito's field of view. One of the 54 bursts had marginal evidence of TeV gamma-ray emission. The prospect of observing gamma-ray bursts with Milagro will be discussed.

Dingus, Brenda L.

2000-04-01

134

Elemental mapping of planetary surfaces using gamma-ray spectroscopy  

SciTech Connect

The gamma rays escaping from a planet can be used to map the concentrations of various elements in its surface. In a planet, the high-energy particles in the galactic cosmic rays induce a cascade of particles that includes many neutrons. The {gamma} rays are made by the nuclear excitations induced by these cosmic-ray particles and their secondaries (especially capture or inelastic-scattering reactions induced by neutrons) and decay of the naturally-occurring radioelements. After a short history of planetary {gamma}-ray spectroscopy and its applications, the {gamma}-ray spectrometer planned for the Mars Observer mission is presented. The results of laboratory experiments that simulate the cosmic-ray bombardments of planetary surfaces or measure cross sections for the production of {gamma} rays and the status of the theoretical calculations for the processes that make and transport neutrons and {gamma} rays will be reviewed. The emphasis here is on studies of Mars and on new ideas, concepts, and problems that have arisen over the last decade, such as Doppler broadening and peaks from neutron scattering with germanium nuclei in a high-resolution {gamma}-ray spectrometer. 31 refs., 1 fig., 1 tab.

Reedy, R.C.

1990-01-01

135

Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes  

Microsoft Academic Search

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

M. Marisaldi; C. Labanti; F. Fuschino; A. Bulgarelli; M. Trifoglio; G. Di Cocco; F. Gianotti; A. Argan; G. De Paris; A. Trois; E. Del Monte; E. Costa; G. Di Persio; I. Donnarumma; Y. Evangelista; M. Feroci; F. Lazzarotto; L. Pacciani; A. Rubini; S. Sabatini

2010-01-01

136

The Highest Energy Gamma Rays from Gamma-Ray Bursts  

Microsoft Academic Search

Gamma-ray bursts are equally likely to occur from any part of the sky, are detected by satellites about once per day, and emit most of their energy in a few seconds. Consequently, a detector with a large field of view and high duty factor is essential to observe gamma-ray bursts. EGRET was the 1st such detector sensitive enough to detect

Brenda L. Dingus

2000-01-01

137

Repair of gamma-ray-induced base damage in L5178Y sublines is damage type-dependent and unrelated to radiation sensitivity.  

PubMed

The L5178Y (LY) murine lymphoma sublines LY-R and LY-S are differentially sensitive to ionizing radiation. The high radiation sensitivity of LY-S cells is related to impaired rejoining of DNA double strand breaks. We found previously that the gamma-ray-induced base damage is higher in the more radiosensitive LY-S subline. Here, we examine the role of the repair of ionizing radiation induced base damage in relation to the radiosensitivity difference of these sublines. We used the GS/MS technique to estimate the repair rates of six types of base damage in gamma-irradiated LY cells. All modified DNA bases identified in the course of this study were typical for irradiated chromatin. The total amount of initial base damage was higher in the radiation sensitive LY-S subline than in the radiation resistant LY-R subline. The repair rates of 5-OHMeUra, 5-OHCyt, 8-OHAde were similar in both cell lines, the repair rates of FapyAde and 8-OHGua were higher in the radiosensitive LY-S cell line, whereas the repair of 5-OHUra was faster in its radioresistant counter, the LY-R. Altogether, the repair rates of the y-ray-induced DNA base damage in LY sublines are related neither to the initial amounts of the damaged bases nor to the differential lethal or mutagenic effects of ionizing radiation in these sublines. PMID:11732621

Kruszewski, M; Zastawny, T H; Szumiel, I

2001-01-01

138

The STACEE-32 ground based gamma-ray detector  

NASA Astrophysics Data System (ADS)

We describe the design and performance of the Solar Tower Atmospheric Cherenkov Effect Experiment detector in its initial configuration (STACEE-32). STACEE is a new ground-based gamma-ray detector using the atmospheric Cherenkov technique. In STACEE, the heliostats of a solar energy research array are used to collect and focus the Cherenkov photons produced in gamma-ray induced air showers. The large Cherenkov photon collection area of STACEE results in a gamma-ray energy threshold below that of previous detectors.

Hanna, D. S.; Bhattacharya, D.; Boone, L. M.; Chantell, M. C.; Conner, Z.; Covault, C. E.; Dragovan, M.; Fortin, P.; Gregorich, D. T.; Hinton, J. A.; Mukherjee, R.; Ong, R. A.; Oser, S.; Ragan, K.; Scalzo, R. A.; Schuette, D. R.; Thoret, C. G.; Tmer, T. O.; Williams, D. A.; Zweerink, J. A.

2002-09-01

139

Gamma rays at airplane altitudes  

SciTech Connect

An examination of the gamma ray flux above 1 TeV in the atmosphere is needed to better understand the anomalous showers from point sources. Suggestions are made for future experiments on board airplanes.

Iwai, J.; Koss, T.; Lord, J.; Strausz, S.; Wilkes, J.; Woosley, J. (University of Washington, Seattle, WA 98195 USA (US))

1990-03-20

140

Gamma-ray Burst Cosmology  

Microsoft Academic Search

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

F. Y. Wang

2011-01-01

141

Underground Gamma-Ray Spectrometry  

Microsoft Academic Search

Gamma-ray spectrometry using high purity Ge detectors has made significant advances in recent years because large crystals have become readily available and the importance of very radiopure materials in the construction of detectors has been understood. The combination of these improvements has made it possible to decrease detection limits in special low-background counting systems. Gamma-ray spectrometry systems located underground are

Mikael Hult; Matthias Khler; Nova Gorica

142

Swift: Gamma-Ray Bursts  

NSDL National Science Digital Library

In the late 1960s, scientists accidentally discovered gamma-ray bursts, intense flashes of energy that typically last no more than a few seconds or minutes. For decades after the discovery of these powerful bursts, they remained one of the greatest mysteries in astronomy. This video segment discusses the Swift satellite mission, launched in 2004 to investigate gamma-ray bursts, and presents some theories as to their origins. The segment is four minutes fourteen seconds in length.

143

Gamma-ray burst afterglows  

Microsoft Academic Search

The discovery of counterparts in X-ray and optical to radio wavelengths has revolutionized the study of gamma-ray bursts, until recently the most enigmatic of astrophysical phenomena. We now know that gamma-ray bursts are the biggest explosions in nature, caused by the ejection of ultrarelativistic matter from a powerful energy source and its subsequent collision with its environment. We have just

Paradijs van J. A; Chryssa Kouveliotou; Ralph A. M. J. Wijers

2000-01-01

144

Supernovae and Gamma Ray Bursts  

Microsoft Academic Search

We review the observational status of the Supernova\\/Gamma-Ray Burst connection. Recent (and less recent) observations of long duration Gamma-ray bursts suggest that a significant fraction of them (but not all) are associated with bright SNe of type Ib\\/c. Current estimates of the SN and GRB rates yield a ratio GRB\\/SNe-Ibc in the range ~ 0.4% - 3%. An analysis of

M. Della Valle

2007-01-01

145

Directional detector of gamma rays  

DOEpatents

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

Cox, Samson A. (Downers Grove, IL); Levert, Francis E. (Chicago, IL)

1979-01-01

146

Gamma-Ray Bursts and Particle Acceleration  

Microsoft Academic Search

Gamma-ray bursts (GRBs) are possible sources of ultra-high-energy cosmic rays (UHE-CRs). To test the GRB origin of UHECRs, it is essential to search for characteristic, proton-induced signatures of secondary radiation. In this paper we present our recent results of Monte Carlo simulations that model the broadband prompt emission of GRBs including various processes associated with electrons and protons accelerated to

Katsuaki Asano; Katsuaki

2008-01-01

147

The distance indicators in gamma-ray pulsars  

NASA Astrophysics Data System (ADS)

Distance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars, including 34 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (?=L ?/?) and pulsar parameters, for young radio-selected gamma-ray pulsars with known distance information. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find a strong correlation between ? and ?3, the generation order parameter which reflects ?-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation between ? and B LC, the magnetic field at the light cylinder radius, is also found. These correlations can serve as distance indicators in gamma-ray pulsars, to evaluate distances for gamma-selected pulsars. Distances of 35 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. The physical origin of the correlations may be also interesting for pulsar studies.

Wang, Wei

2013-03-01

148

Unveiling the secrets of gamma ray bursts  

Microsoft Academic Search

Gamma Ray Bursts are unpredictable and brief flashes of gamma rays that occur about once a day in random locations in the sky. Since gamma rays do not penetrate the Earth's atmosphere, they are detected by satellites, which automatically trigger ground-based telescopes for follow-up observations at longer wavelengths. In this introduction to Gamma Ray Bursts we review how building a

Andreja Gomboc

2012-01-01

149

Optical observations of Gamma-Ray Bursts  

Microsoft Academic Search

We briefly review the status and recent progress in the field of optical observations of gamma-ray burst afterglows. We will focus on the fundamental observational evidence for the relationship between gamma-ray bursts and the final evolutionary phases of massive stars. In particular, we will address (i) gamma-ray burst host galaxies, (ii) optically dark gamma-ray burst afterglows, (iii) the gamma-ray burstsupernova

J. Hjorth; E. Pian; J. P. U. Fynbo

2004-01-01

150

Gamma-Ray Burst:. Discoveries with Swift  

NASA Astrophysics Data System (ADS)

Gamma Ray Bursts (GRBs) are bright, brief flashes of high energy photons and are the most powerful explosions since the Big Bang, with typical energies up to around 1051 ergs. Their outbursts persist for durations ranging from milliseconds to tens of seconds or more. In these brief moments the explosions radiate more energy than the Sun will release in its entire 10 billion year lifetime. They come in two classes: long (2 s), softspectrum bursts and short, hard events. Current theories attribute these phenomena to the final collapse of a massive star, or the coalescence of a binary system induced by gravity wave emission. New results from Swift and related programmes offer fresh understanding of the physics of gamma-ray bursts and of the local environments and host galaxies of burst progenitors. Bursts found at very high red-shifts are new tools for exploring the intergalactic medium, the first stars and the earliest stages of galaxy formation.

Wells, Alan

2007-11-01

151

Gamma-Ray Emission from Fission of Heavy Nuclei  

Microsoft Academic Search

Average gamma-ray multiplicity , average energy emitted by gamma-rays and average energy per one gamma quantum as a function of mass and total kinetic energy (TKE) of fission fragments were measured in proton induced reactions p+242Pu->243Am, p+238U->239Np (at proton energy Ep=13, 20 and 55 MeV) and spontaneous fission of 252Cf. Complex structures in , and (as

L. Krupa; G. N. Kniajeva; A. A. Bogatchev; G. M. Chubarian; O. Dorvaux; I. M. Itkis; M. G. Itkis; S. Khlebnikov; J. Kliman; N. A. Kondratiev; E. M. Kozulin; V. Lyapin; T. Materna; W. Rubchenia; I. V. Pokrovsky; W. Trzaska; D. Vakhtin; V. M. Voskresenski

2003-01-01

152

The Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory (Compton) was launched by the Space Shuttle Atlantis on 5 April 1991. The spacecraft and instruments are in good health and returning exciting results. The mission provides nearly six orders of magnitude in spectral coverage, from 30 keV to 30 GeV, with sensitivity over the entire range an order of magnitude better than that of previous observations. The 16,000 kilogram observatory contains four instruments on a stabilized platform. The mission began normal operations on 16 May 1991 and is now over half-way through a full-sky survey. The mission duration is expected to be from six to ten years. A Science Support Center has been established at Goddard Space Flight Center for the purpose of supporting a vigorous Guest Investigator Program. New scientific results to date include: (1) the establishment of the isotropy, combined with spatial inhomogeneity, of the distribution of gamma-ray bursts in the sky; (2) the discovery of intense high energy (100 MeV) gamma-ray emission from 3C 279 and other quasars and BL Lac objects, making these the most distant and luminous gamma-ray sources ever detected; (3) one of the first images of a gamma-ray burst; (4) the observation of intense nuclear and position-annihilation gamma-ray lines and neutrons from several large solar flares; and (5) the detection of a third gamma-ray pulsar, plus several other transient and pulsing hard X-ray sources.

Gehrels, N.; Chipman, E.; Kniffen, D. A.

1993-01-01

153

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

154

Planetary gamma-ray spectroscopy: the effects of hydrogen absorption cross-section of the gamma-ray spectrum  

Microsoft Academic Search

The gamma-ray spectroscopy of planet surfaces is one of several possible methods that are useful in determining the elemental composition of planet surfaces from orbiting spacecraft. This has been demonstrated on the Apollos 15 and 16 missions as well as the Soviet Mars-5 mission. Planetary gamma-ray emission is primarily the result of natural radioactive decay and cosmic-ray and solar-flare-induced nuclear

Lapides

1981-01-01

155

Experimental simulations of planetary gamma-ray spectroscopy using thick targets irradiated by protons  

NASA Astrophysics Data System (ADS)

To simulate planetary gamma-ray spectroscopy, gamma rays were measured during a series of five irradiations of up to 30-ton thick targets with protons beams of 1.5 and 2.5 GeV. The targets were steel (iron), basalt with structural steel, basalt with added S and Cl, and basalt with added H, S, and Cl. The pulsed proton beam was carefully monitored and counted. Spectra were collected with both proton beam on and beam off and with a lead shield both between the target and the germanium detector and with the lead shield removed. This set of four spectra was used to determine the fluxes of prompt gamma rays emitted from the target. Over 200 discrete gamma-ray lines per irradiation were observed and identified. Counting results for the more intense gamma rays were compiled, and gamma-ray fluxes determined for about 25 gamma rays of interest to planetary gamma-ray spectroscopy. The ratios of thermal and fast neutron induced gamma-ray fluxes between irradiations were similar. Thus the relative gamma-ray fluxes can be used in testing model calculations and interpreting planetary gamma-ray spectra.

Brckner, J.; Reedy, R. C.; Englert, P. A. J.; Drake, D. M.

2011-11-01

156

Effect of Gamma-Ray Beaming on the Fluxes of Gamma-Ray Pulsars  

Microsoft Academic Search

We study the effect of gamma-ray beaming on gamma-ray emission of the pulsars in a self-sustained outer gap model. In this model, averaged gamma-ray flux is a function of period, magnetic field, magnetic inclination angle and solid angle of gamma-ray beaming for a gamma-ray pulsar. We generate a sample of gamma-ray pulsars with their ages less than 106 years by

Ze-Jun Jiang; Li Zhang

2005-01-01

157

Environmental corrections for a neutron-induced gamma-ray spectroscopy logging system in an air-filled borehole  

Microsoft Academic Search

When a nuclear explosive is tested underground, rock in the immediate vicinity of the explosion is heated to very high temperatures. If any of that rock contains carbonates (dolomite or calcite), these are dissociated and the carbon may combine with oxygen to form carbon dioxide, increasing the hazard of a delayed leak. We are trying to adapt a commercial neutron-induced

J. R. Hearst; J. G. Conaway; M. A. Mathews; J. W. Barber

1989-01-01

158

Neutron and gamma-ray emission in the proton induced fission of 238U and 242Pu  

Microsoft Academic Search

Average prescission Mpren and postscission Mpostn neutron multiplicities as well as average ?-ray multiplicity ?M??, average energy ?E?? emitted by ?-rays as a function of mass and total kinetic energy (TKE) of fission fragments were measured in proton induced reactions p+242Pu?243Am, p+238U?239Np at proton energy Ep=13, 20 and 55 MeV.

G. N Kniajeva; L. Krupa; A. A. Bogachev; G. G. Chubarian; O. Dorvaux; I. M Itkis; M. G Itkis; J. Kliman; S. Khlebnikov; N. A Kondratiev; E. M Kozulin; V. Lyapin; T. Materna; I. V. Pokrovsky; V. A Rubchenya; W. H Trzaska; D. Vakhtin; V. M Voskressenski

2004-01-01

159

Fluorine in fifteen GSJ geochemical reference samples as determined by proton induced gamma ray emission spectrometry \\/PIGE  

Microsoft Academic Search

Fifteen geochemical reference samples \\/GRS\\/ issued from the Geological Survey of Japan have been analyzed by an automated proton induced -ray emission \\/PIGE\\/ method for fluorine. Results of determinations are reported. Values are given for many GRS that have not previously been analyzed for fluorine.

I. Roelandts; G. Robaye; G. Weber; P. Aloupogiannis; J. M. Delbrouck-Habaru

1987-01-01

160

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

161

Proton elastic scattering and proton induced gamma-ray emission cross-sections on Na from 2 to 5 MeV  

Microsoft Academic Search

Differential cross-sections for proton elastic scattering on sodium and for gamma-ray emission from the reactions 23Na(p,p'gamma)23Na (Egamma = 440 keV and Egamma = 1636 keV) and 23Na(p,alpha'gamma)20Ne (Egamma = 1634 keV) were measured for proton energies from 2.2 to 5.2 MeV using a 63 mug\\/cm2 NaBr target evaporated on a self-supporting thin C film. The gamma-rays were detected by a

A. Caciolli; G. Calzolai; M. Chiari; G. Garcia; F. Lucarelli; S. Nava

2008-01-01

162

Upgrade of the JET Gamma-Ray Cameras  

SciTech Connect

The JET gamma-ray camera diagnostics have already provided valuable information on the gamma-ray imaging of fast ion in JET plasmas /1,2/. The applicability of gamma-ray imaging to high performance deuterium and deuterium-tritium JET discharges is strongly dependent on the fulfilment of rather strict requirements for the characterisation of the neutron and gamma-ray radiation fields. These requirements have to be satisfied within very stringent boundary conditions for the design, such as the requirement of minimum impact on the co-existing neutron camera diagnostics. The JET Gamma-Ray Cameras (GRC) upgrade project deals with these issues with particular emphasis on the design of appropriate neutron/gamma-ray filters ('neutron attenuators'). Several design versions have been developed and evaluated for the JET GRC neutron attenuators at the conceptual design level. The main design parameter was the neutron attenuation factor. The two design solutions, that have been finally chosen and developed at the level of scheme design, consist of: a) one quasi-crescent shaped neutron attenuator (for the horizontal camera) and b) two quasi-trapezoid shaped neutron attenuators (for the vertical one). The second design solution has different attenuation lengths: a short version, to be used together with the horizontal attenuator for deuterium discharges, and a long version to be used for high performance deuterium and DT discharges. Various neutron-attenuating materials have been considered (lithium hydride with natural isotopic composition and {sup 6}Li enriched, light and heavy water, polyethylene). Pure light water was finally chosen as the attenuating material for the JET gamma-ray cameras. The neutron attenuators will be steered in and out of the detector line-of-sight by means of an electro-pneumatic steering and control system. The MCNP code was used for neutron and gamma ray transport in order to evaluate the effect of the neutron attenuators on the neutron field of the JET GRC. The modelling was dedicated to the estimation of neutron and (plasma-emitted) gamma-ray attenuation, neutron-induced gamma-ray background and the neutron in-scattering impact on the neutron detectors due to the attenuator in the parking location. A numerical study of the gamma-ray detector (CsI(Tl)) was done by means of the IST Monte Carlo code. It provided preliminary results on the detector efficiency and response function.

Soare, S.; Curuia, M.; Anghel, M.; Constantin, M.; David, E. [Association EURATOM-MEdC, National Institute for Cryogenics and Isotopic Technologies, Rm. Valcea (Romania); Zoita, V.; Craciunescu, T.; Falie, D.; Pantea, A.; Tiseanu, I. [Association EURATOM-MEdC, National Institute for Laser, Plasma and Radiation Physics, Bucharest (Romania); Kiptily, V.; Prior, P.; Edlington, T.; Griph, S.; Krivchenkov, Y.; Loughlin, M.; Popovichev, S.; Riccardo, V.; Syme, B.; Thompson, V. [Association EURATOM-UKAEA/JOC, Culham Science Centre, Abingdon (United Kingdom)] (and others)

2008-03-12

163

Development of Compact Wide-Angle Imaging Detector for MeV Gamma-Rays using Stacked BGO Scintillator Rods  

Microsoft Academic Search

We are developing a compact wide-angle imaging detector for MeV gamma-rays using stacked BGO scintillator rods to apply to neutron induced prompt gamma-ray analysis (NPGA), which is one of the promising methods for non-destructive detection of hidden explosives by measuring characteristic gamma-rays produced from chemical elements. The gamma-ray imaging in NPGA applications is also necessary to locate them and improve

Kenichi Watanabe; Shinji Mihoya; J. Kawarabayashi; T. Iguchi

2006-01-01

164

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

165

FISSION PRODUCT GAMMA RAY SPECTRA  

Microsoft Academic Search

Uranium-235 fission product gamma spectra were calculated for various ; reactor operating histories. An IBM704 digital computer program was coded to ; compute the gamma energy contributed by each fission product gamma ray and to sum ; these results in energy groups. A representative curve showing the decay of ; various energy groups is presented. Comparisons are made with data

1958-01-01

166

Cosmological gamma-ray bursts  

SciTech Connect

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Gamma-ray bursts are brief events that dominate the emission from all other gamma-ray objects in the sky, flicker for tens of seconds, and then turn off. Their nature remains uncertain despite years of efforts to understand them. One hypothesis is that the bursts arise within our galaxy albeit in an extended halo of neutron stars. Another hypothesis uses the isotropic distribution of gamma-ray bursts to argue that they come from nearly the edge of the universe. If gamma-ray bursts originate from cosmological distances, then the expansion of the universe should cause the dimmer (and presumably further) bursts to last longer. The authors have developed methods for measuring this time stretching, related the time stretching to the distance to the bursts, determined how the detailed physics causes temporal variations, and found the amount of total energy and peak luminosity that the events must be producing.

Fenimore, E.; Epstein, R.; Ho, C.; Intzand, J.

1996-04-01

167

Gamma-Ray Shielding Studies.  

National Technical Information Service (NTIS)

A monoenergetic beam of gamma rays was used to study the deep penetration of 10-MeV gamma radiation in aluminum. Recently a positron annihilation system was developed at General Atomic for the purpose of making shielding measurements in the energy range f...

J. A. Lonergan E. A. Beaver J. Parez D. F. Herring

1967-01-01

168

Periodicities in gamma ray bursts  

SciTech Connect

Gamma ray burst models based on magnetic neutron stars face a problem of account for the scarcity of observed periods. Both this scarcity and the typical period found when any is detected are explained if the neutron stars are accreting in binary systems

Wood, K.S.

1984-05-26

169

Cosmic gamma-ray bursts  

Microsoft Academic Search

The results of the observation of cosmic gamma-ray bursts are discussed and available theoretical models are presented. Emphasis is placed on a cosmological model in which a gamma burst results from a powerful (? 10511053 erg) and very short ( ?10 100 s) energy release which occurs in a compact ( ? 106107 cm) region and gives rise to a

Konstantin A Postnov

1999-01-01

170

On Gamma-Ray Bursts  

Microsoft Academic Search

We show by example how the uncoding of Gamma-Ray Bursts (GRBs) offers unprecedented possibilities to foster new knowledge in fundamental physics and in astrophysics. After recalling some of the classic work on vacuum polarization in uniform electric fields by Klein, Sauter, Heisenberg, Euler and Schwinger, we summarize some of the efforts to observe these effects in heavy ions and high

Remo Ruffini; M. G. Bernardini; C. L. Bianco; Letizia Caito; Pascal Chardonnet; Christian Cherubini; M. G. Dainotti; Federico Fraschetti; Andrea Geralico; Roberto Guida; Barbara Patricelli; Michael Rotondo; J. A. Rueda Hernandez; Gregory Vereshchagin; She-Sheng Xue

2008-01-01

171

The gamma Rays of Uranium  

Microsoft Academic Search

OUR knowledge of the gamma rays of uranium has until now been confined to their discovery by Rutherford (Phys. Zeit., 1902, 517) and to the observations of Eve (ibid., 1907, 185). The latter directed attention to their extraordinary feebleness and to their relatively low penetrating power. Eve found that uranium gives out only about one-tenth as much gamma radiation as

Frederick Soddy; Alexander S. Russell

1909-01-01

172

Striking regression of subcutaneous fibrosis induced by high doses of gamma rays using a combination of pentoxifylline and ?-tocopherol: an experimental study  

Microsoft Academic Search

Purpose: To establish a successful treatment of subcutaneous fibrosis developing after high doses of gamma rays, suitable for use in clinical practice.Methods and Materials: We used an animal model of acute localized gamma irradiation simulating accidental overexposure in humans. Three groups of 5 Large White pigs were irradiated using a collimated 192Ir source to deliver a single dose of 160

Jean-Louis Lefaix; Sylvie Delanian; Marie-Catherine Vozenin; Jean-Jacques Leplat; Yves Tricaud; Michle Martin

1999-01-01

173

VLF Remote Sensing of the Lower Ionosphere with AWESOME Receivers: Solar Flares, Lightning-induced Electron Precipitation, Sudden Ionospheric Disturbances, Sprites, Gravity Waves and Gamma-ray Flares  

Microsoft Academic Search

Stanford University Very Low Frequency (VLF) radio receivers have been used extensively for remote sensing of the ionosphere and the magnetosphere. Among the phenomena that can be uniquely measured via VLF receivers are radio atmospherics, whistlers, electron precipitation, solar flares, sudden ionospheric disturbances, gravity waves, sprites, and cosmic gamma-ray flares. With the use of simple square air-core magnetic loop antennas

M. Cohen; P. Scherrer; D. Scherrer

2006-01-01

174

Apoptosis (cell death) induced in mouse bowel by 1,2-dimethylhydrazine, methylazoxymethanol acetate, and gamma-rays  

SciTech Connect

Apoptosis is a pattern of cell death involving nuclear pyknosis, cytoplasmic condensation, and karyorrhexis. The frequency of apoptosis after treatment with two colon carcinogens and radiation was studied in the crypts of five different portions of mouse bowel. When 1,2-dimethylhydrazine (DMH) was injected s.c., the earliest rise in apoptotic incidence after a high dose (200 mg/kg) was noted at 3 h in small intestine and at 6 h in large bowel. After i.p. administration of methylazoxymethanol (MAM) acetate, apoptotic cells were seen in large bowel after 3 h. When the plateau values attained after high doses of DMH were compared, many apoptotic cells were found in the lower part of the large bowel, whereas few such cells were observed in the small intestine and the upper part of the large bowel. This finding was reversed in the case of radiation-induced apoptosis. In the descending colon, a definite circadian rhythm in the apoptotic incidence was observed 6 h after injection of DMH or MAM acetate. Apoptosis showed a high incidence when these drugs were given between 2400 h and 0900 h, but a low incidence after administration between 1200 h and 2100 h. In the small intestine a rhythm was also noted for MAM acetate, but not significantly for DMH.

Ijiri, K. (Univ. of Tokyo (Japan))

1989-11-15

175

Synchrotron Emission from Very High Energy Gamma-Ray-induced Pair Cascades in Active Galactic Nucleus Environments  

NASA Astrophysics Data System (ADS)

The discovery of very high energy (VHE; E > 100 GeV) ?-ray emission from intermediate- and low-frequency-peaked blazars suggests that ?? absorption and pair cascading might occur in these objects. In previous papers, we investigated the Compton emission from VHE ?-ray-induced pair cascades, deflected by moderate magnetic fields, in a largely model-independent way, and demonstrated that this emission can explain the Fermi fluxes and spectra of the radio galaxies Cen A and NGC 1275. In this paper, we describe a generalization of our Monte Carlo cascade code to include the angle-dependent synchrotron output from the cascades, allowing for the application to situations with non-negligible magnetic fields, leading to potentially observable synchrotron signatures, but still not dominating the radiative energy loss of cascade particles. We confirm that the synchrotron radiation from the cascades in NGC 1275 and Cen A is negligible for the parameters used in our previous works. We demonstrate that the magnetic field cannot be determined from a fit of the cascade emission to the ?-ray spectrum alone, and the degeneracy can only be lifted if the synchrotron emission from the cascades is observed as well. We illustrate this fact with the example of NGC 1275. We point out that the cascade synchrotron emission may produce spectral features in the same energy range in which the big blue bump is observed in the spectral energy distributions of several blazars, and may make a non-negligible contribution to this feature. We illustrate this idea with the example of 3C 279.

Roustazadeh, P.; Bttcher, M.

2012-05-01

176

Portable compton gamma-ray detection system  

DOEpatents

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

177

Low-level gamma-ray spectrometry  

Microsoft Academic Search

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

R L Brodzinski

1991-01-01

178

High energy gamma ray balloon instrument  

Microsoft Academic Search

The High Energy Gamma Ray Balloon Instrument was built in part to verify certain subsystems' performance for the Energetic Gamma Ray Experiment Telescope (EGRET) instrument, the high energy telescope to be carried on the Gamma Ray Observatory. This paper describes the instrument, the performance of some subsystems, and some relevant results.

D. J. Thompson; R. G. Baker; D. L. Bertsch; J. R. Chesney; S. M. Derdeyn; C. H. Ehrmann; C. E. Fichtel; S. D. Hunter; J. S. Jacques; N. A. Laubenthal

1985-01-01

179

Faint Radio Sources and Gamma Ray Bursts  

Microsoft Academic Search

We calculate the number density of faint radio sources that are expected in radio source surveys due to the isotropic emission of Gamma Ray Burst sources. The calculation assumes the beamed supernovae model for gamma ray burst sources detected in gamma rays, x-rays, optical and radio wavelengths. Since the radio wavelength emission is expected to be more isotropically radiated, the

G. I. Langston; A. H. Minter; T. M. Freismuth

2002-01-01

180

Monte Carlo calibration of the SMM gamma ray spectrometer for high energy gamma rays and neutrons  

Microsoft Academic Search

The Gamma Ray Spectrometer (GRS) on the Solar Maximum Mission spacecraft was primarily designed and calibrated for nuclear gamma ray line measurements, but also has a high energy mode which allows the detection of gamma rays at energies above 10 MeV and solar neutrons above 20 MeV. The GRS response has been extrapolated until now for high energy gamma rays

J. F. Cooper; C. Reppin; D. J. Forrest; E. L. Chupp; G. H. Share; R. L. Kinzer

1985-01-01

181

Gamma-ray halos as a measure of intergalactic magnetic fields: A classical moment problem  

Microsoft Academic Search

The presence of weak intergalactic magnetic fields can be studied by their effect on electromagnetic cascades induced by multi-TeV gamma rays in the cosmic radiation background. Small deflections of secondary electrons and positrons as the cascade develops extend the apparent size of the emission region of distant TeV gamma-ray sources. These gamma-ray halos can be resolvable in imaging atmospheric Cherenkov

Markus Ahlers

2011-01-01

182

Background modelling in very-high-energy gamma-ray astronomy  

Microsoft Academic Search

Context: Ground based Cherenkov telescope systems measure astrophysical gamma-ray emission against a background of cosmic-ray induced air showers. The subtraction of this background is a major challenge for the extraction of spectra and morphology of gamma-ray sources. Aims: The unprecedented sensitivity of the new generation of ground based very-high-energy gamma-ray experiments such as HESS has lead to the discovery of

D. Berge; S. Funk; J. Hinton

2007-01-01

183

Background Modelling in Very-High-Energy gamma-ray Astronomy  

Microsoft Academic Search

Ground based Cherenkov telescope systems measure astrophysical gamma-ray emission against a background of cosmic-ray induced air showers. The subtraction of this background is a major challenge for the extraction of spectra and morphology of gamma-ray sources. The unprecedented sensitivity of the new generation of ground based very-high-energy gamma-ray experiments such as H.E.S.S. has lead to the discovery of many previously

David Berge; S. Funk; J. Hinton

2006-01-01

184

Determination of the gamma-ray spectrum in a strong neutron\\/gamma-ray mixed field  

Microsoft Academic Search

The knowledge of gamma-ray spectrum highly affects the accuracy of the correspondingly derived gamma-ray dose and the correctness of calculated neutron dose in the neutron\\/gamma-ray mixed field dosimetry when using the paired ionization chambers technique. It is of our interest to develop a method to determine the gamma-ray spectrum in a strong neutron\\/gamma-ray mixed field. The current type detector, Mg(Ar)

Yuan-Hao Liu; Yi-Chun Lin; Sander Nievaart; Wen-Tsae Chou; Hong-Ming Liu; Shiang-Huei Jiang

2011-01-01

185

High-energy gamma rays from the intense 1993 January 31 gamma-ray burst  

Microsoft Academic Search

The intense gamma-ray burst of 1993 January 31 was detected by the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Observatory. Sixteen gamma rays above 30 MeV were imaged in the telescope when only 0.04 gamma rays were expected by chance. Two of these gamma rays have energies of approximately 1 GeV, and the five bin spectrum of the

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

1994-01-01

186

Monte Carlo approach to sequential {gamma}-ray emission from fission fragments  

SciTech Connect

A Monte Carlo simulation of the fission fragment statistical decay based on a sequential neutron followed by {gamma}-ray emission is proposed. The {gamma}-ray energy spectrum is calculated as a function of the mass of the fission fragments and integrated over the whole mass distribution. The prompt {gamma}-ray multiplicity distribution, both the average number of emitted {gamma} rays and the average {gamma}-ray energy as a function of the mass of the fission fragments [respectively, N{sub {gamma}}(A) and <{epsilon}{sub {gamma}}>(A)], are also assessed. The {gamma}-{gamma} correlations emitted from both light and heavy fragments are calculated as well as correlations between {gamma}-ray energies. Results are reported for the neutron-induced fission of {sup 235}U (at 0.53 MeV neutron energy) and for the spontaneous fission of {sup 252}Cf.

Lemaire, S.; Talou, P.; Kawano, T.; Madland, D.G. [Theoretical Division, Nuclear Physics Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Chadwick, M.B. [PADNWP, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2006-01-15

187

Utilization of freshly induced high-energy gamma-ray activity as a measure of fission rates in re-irradiated burnt UO2 fuel  

Microsoft Academic Search

In the frame of the LIFE@PROTEUS program, a measurement technique is being developed to measure fission rates in burnt fuel, following re-irradiation in a zero-power research reactor. In the presented approach, the fission rates are estimated by measuring high energy gamma-rays (above 2000 keV) emitted by short-lived fission products freshly produced in the fuel. Due to their high energies, these

Hanna Krhnert; Michael F. Murphy; Gregory Perret; Rakesh Chawla

2009-01-01

188

Preparation and properties of the composite coreshell latex of poly(3-methacryloxylpropyltrimethoxylsilane)\\/poly(methyl acrylate) induced by gamma ray radiation  

Microsoft Academic Search

Co-polymerization of 3-methacryloxylpropyltrimethoxylsilane (MPS) and MA and seeded polymerization of MPS in the presence of poly(methyl acrylate) (PMA) seed latex were carried out by 60Co gamma ray irradiation. The morphology of the two kinds of latex particles was observed by transmission electronic microscopy (TEM) and the mechanical, thermal and solvent absorption properties of the latex films were also studied. It

Mingxuan Zou; Zhicheng Zhang; Xuefeng Shen; Jun Nie; Xuewu Ge

2005-01-01

189

Measurement of 14 MeV neutron-induced prompt gamma-ray spectra from 15 elements found in cargo containers  

Microsoft Academic Search

Within the EURopean Illicit TRAfficking Countermeasures Kit (EURITRACK) project, the gamma-ray spectra produced in a series of materials by 14-MeV tagged-neutron beams have been collected in the inspection portal equipped with large volume NaI(Tl) detectors, in order to build a database of signatures for various elements: C, N, O, Na, Al, Si, Cl, K, Ca, Cr, Fe, Ni, Cu, Zn,

B. Perot; C. Carasco; S. Bernard; A. Mariani; J.-L. Szabo; G. Sannie; V. Valkovic; D. Sudac; G. Viesti; M. Lunardon; C. Botosso; G. Nebbia; S. Pesente; S. Moretto; A. Zenoni; A. Donzella; M. Moszynski; M. Gierlik; W. Klamra; P. Le Tourneur; M. Lhuissier; A. Colonna; C. Tintori; P. Peerani; V. Sequeira; M. Salvato

2008-01-01

190

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

Microsoft Academic Search

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

Y. E. Titarenko; V. F. Batyaev; E. I. Karpikhin; V. M. Zhivun; A. B. Koldobsky; R. D. Mulambetov; S. V. Mulambetova; S. G. Mashnik; Y. V. Nekrasov; Y. V. Trebukhovsky; V. S. Barashenkov; V. V. Dmitrenko; S. E. Ulin; N. Hasebe; R. E. Prael

2003-01-01

191

Hard X-ray and Gamma-ray Emission Induced by UltraHigh Energy Protons in Cluster Accretion Shocks and their Detectability  

Microsoft Academic Search

Protons can be plausibly accelerated to $\\\\sim 10^{18}$-$10^{19}$ eV in strong accretion shocks surrounding massive clusters of galaxies. Such protons efficiently produce very high energy pairs through interactions with the CMB, which then radiate synchrotron and inverse Compton emission with hard spectra, peaking respectively in hard X-rays and TeV gamma-rays. We discuss the prospects for detecting this emission from nearby

Susumu Inoue; Felix A. Aharonian; Naoshi Sugiyama

2005-01-01

192

AEC resistant rice mutants induced by gamma-ray irradiation may include both elevated lysine production and increased activity of stress related enzymes  

Microsoft Academic Search

To increase the contents of specific free amino acids in the rice (Oryza sativa L.) cultivar Donganbyeo, mutant cell lines resistant to growth inhibition by S-(2-aminoethyl)-cysteine (AEC) were selected from calli irradiated with gamma-rays through embryo culture. In the four AEC resistant M3 lines, LR369, LR5132, LR72 and LR948, the amino acids contents were 26, 7, 29 and 37%, respectively,

Dong Sub Kim; In Sok Lee; Cheol Seong Jang; Sang Jae Lee; Hi Sup Song; Young Il Lee; Yong Weon Seo

2004-01-01

193

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

194

Probing the gamma-ray sky  

NASA Astrophysics Data System (ADS)

The observational results of the NASA's Compton Gamma Ray Observatory (GRO) are reviewed with attention given to the results from solar flares and gamma-ray bursts. The observatory is described emphasizing the Burst and Transient Source Experiment, the Oriented Scintillation Spectrometer Experiment, and the Energetic Gamma Ray Experiment Telescope. Increases in gamma-ray emission are noted in solar observations, and the pulsar in the Crab nebula was studied extensively. More gamma-ray pulsars were observed, and a total of 261 gamma-ray bursts are recorded as a result of the GRO observations. A gamma-ray galaxy was discovered by the GRO instruments, and the source - 3C 279 - is estimated to be 7 billion light years from earth. The GRO is shown to be of use in the characterization of astronomical phenomena that cannot be observed from earth.

Hurley, Kevin

1992-12-01

195

Proton-induced x-ray emission, proton-induced gamma-ray emission, and x-ray absorption spectroscopy: applications to environmental analysis  

SciTech Connect

Two sample preparation techniques, the single-acid wet-oxidation and the lithium metaborate fusion-dissolution, have been applied to PIXE analysis with acceptable trace-element recoveries. A variety of samples have been prepared, including: white bass organs, deer and elk antlers. NRS standard reference materials, IAEA standard animal bone, USGS standard rock samples, and munitions disposal residues. PIGE analysis has been applied to light-element analysis of environment samples. Thin-and thick-target gamma-ray yields were determined for Li, B, O, F, Na, Mg, and Al. Light-elements in coal and oil fly ash were determined with parts per million sensitivity. Nickel and vanadium compounds have been identified in fly ash collected from vanadium compounds have been identified in fly ash collected from the flue lines of an oil-fired power plant using x-ray absorption spectroscopy. VOSO/sub 4/.3H/sub 2/O was the primary vanadium compound and NiO and NiSO/sub 4/ were the primary nickel compounds. NXRAY was written to control data acquisition on a Canberra Series 90 MCA-PDP 11/23PLUS computer system. This program provides for data to be transferred between individual collection regions of the MCA and the host computer, and spectra to be plotted on a HP 7475A graphics plotter.

Lytle, N.W.

1986-01-01

196

Gamma-Ray Output Spectra from ^239Pu Fission  

NASA Astrophysics Data System (ADS)

A new measurement of the gamma-ray energy spectrum and multiplicity following neutron-induced fission of ^239Pu has been made using DANCE, a highly-segmented, nearly 4? BaF2 array at the Los Alamos Neutron Science Center. The ^239Pu target consisted of an approximately 2 mg/cm^2 deposit mounted in a small parallel-plate avalanche chamber inserted into the DANCE in order to tag fission events. The gamma-ray spectra were measured for several strong neutron resonances below 100 eV. The measured spectra were corrected for detector response by using simple parameterizations of the actual fission gamma-ray emission coupled with a GEANT model of the DANCE array.

Ullmann, John; Jandel, Marian; Bredeweg, Todd; Couture, Aaron; Haight, Robert; O'Donnell, John; Vieira, David; Wu, Ching-Yen; Chyzh, Andrii; Gostic, Julie; Henderson, Roger; Kwan, Elaine

2011-10-01

197

Observations of the Highest Energy Gamma Rays from Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

EGRET has extended the highest energy observations of gamma-ray bursts to GeV gamma rays. Such high energies imply the fireball that is radiating the gamma rays has a bulk Lorentz factor of several hundred. However, EGRET only detected a few gamma-ray bursts. GLAST will likely detect several hundred bursts and extend the maximum energy to a few 100 GeV. Meanwhile new ground based detectors with sensitivity to TeV gamma rays from gamma-ray bursts are beginning operation.

Dingus, Brenda L.

2003-04-01

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

Continued Study of the Parameterization of the El gamma-Ray Strength Function.  

National Technical Information Service (NTIS)

The parameterization of the magnitude and the energy dependence of the E1 gamma-ray strength function for the calculation of neutron- and proton-induced capture cross sections and capture gamma-ray spectra is investigated. The energy-dependent Breit-Wigne...

M. A. Gardner D. G. Gardner

1981-01-01

200

Prompt gamma rays emitted in fission of 226Ra by 12 MeV protons  

Microsoft Academic Search

The total energy associated with the emission of prompt gamma rays in fission of 226Ra induced by 12 MeV protons was measured in correlation with the fragment mass and kinetic energy. The dependence of the average total gamma ray energy on fragment mass and total kinetic energy resembles the corresponding dependence of the average number of neutrons. Using these results

A. Gayer; Z. Fraenkel

1977-01-01

201

Doubled haploidy and induced mutation  

Microsoft Academic Search

Doubled haploid (DH) systems have many attractive features for inducing and fixing mutations. Doubled haploidy provides the\\u000a fastest route to homozygosity with the greatest fidelity. The ability to fix mutations via doubled haploidy is a key factor,\\u000a especially as induced mutations?are predominantly recessive and cannot normally be detected until the M2 generation at the earliest. The DH systems themselves provide

I. Szarejko; B. P. Forster

2007-01-01

202

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

203

Recommended standards for gamma ray intensities  

NASA Astrophysics Data System (ADS)

Gamma ray data are used in more and more areas of application, and so over the years the demand for recommended gamma ray energies and intensities has increased. This paper proposes a list of gamma rays whose intensity is sufficiently well-known and they can be used for the calibration of gamma ray spectrometers and other applications; it is based on studies carried out by an international group of evaluators: the Decay Data Evaluation Project. One goal of this paper is to gather this set of data together in order to facilitate and generalize their use. In the first part, a brief description of the methodology followed throughout the evaluations is given, different methods of gamma ray intensity evaluation are presented, some typical examples of evaluations are shown; in the second part, the list of chosen nuclides is given along with their applications, and finally a list of recommended gamma ray intensities is presented.

B, Marie-Martine; Chechev, Valery P.

2013-11-01

204

Nuclear gamma-rays from energetic particle interactions  

Microsoft Academic Search

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

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

1979-01-01

205

GRETINA: A gamma ray energy tracking array  

Microsoft Academic Search

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,

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

2004-01-01

206

The physics of gamma-ray bursts  

Microsoft Academic Search

Gamma-ray bursts (GRB's), short and intense pulses of low-energy gamma rays, have fascinated astronomers and astrophysicists since their unexpected discovery in the late sixties. During the last decade, several space missions---BATSE (Burst and Transient Source Experiment) on the Compton Gamma-Ray Observatory, BeppoSAX and now HETE II (High-Energy Transient Explorer)---together with ground-based optical, infrared, and radio observatories have revolutionized our understanding

Tsvi Piran

2004-01-01

207

The Supernovae\\/Gamma-Ray Burst Connection  

Microsoft Academic Search

The correlation of SN 1998bw and GRB 980425 shows that some supernovae produce gamma-ray bursts. SN 1998bw resembled previous Type Ic supernovae in terms of its spectral evolution and finite polarization. A check of correlations between the Asiago supernova catalog and the BATSE catalog of gamma-ray bursts suggests that a correlation of gamma-ray bursts with Type Ic supernovae cannot be

J. C. Wheeler; L. Wang; P. Hoflich

1998-01-01

208

Using Gamma Rays as Intergalactic Magnetometers  

NASA Astrophysics Data System (ADS)

Gamma rays from distant blazars interact with the extragalactic background light, creating electron-positron pairs, and reducing the amount of gamma-rays seen by ground-based atmospheric Cherenkov telescopes. These pairs can Compton-scatter the cosmic microwave background, creating a gamma-ray signature observable by the Fermi Large Area Telesope (LAT). The signature is also dependent on the intergalactic magnetic field (IGMF), since it can deflect the pairs from our line of sight, reducing the gamma-ray emission. We present preliminary constraints on the IGMF using Fermi-LAT and Cherenkov telescope observations, ruling out both very large and very small values of the IGMF strength.

Finke, Justin; Reyes, L. C.; Georganopoulos, M.; Fermi-LAT Collaboration

2013-04-01

209

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

210

Gamma rays from compact binary systems  

NASA Astrophysics Data System (ADS)

Some of the very high energy (VHE) gamma-ray sources detected with the modern generation of Cherenkov telescopes have been identified with previously known X-ray binary systems. These detections demonstrate the richness of non-thermal phenomena in compact galactic objects containing relativistic outflows or winds produced near black holes and neutron stars. Recently, the well-known microquasar Cygnus X-3 seems to be associated with a gamma-ray source detected with AGILE. Here I summarise the main observational results on gamma-ray emission from X-ray binaries, as well as some of the proposed scenarios to explain the production of VHE gamma-rays.

Paredes, Josep M.

2008-12-01

211

Gamma ray bursts inner engines  

NASA Astrophysics Data System (ADS)

Long gamma ray bursts (GRBs) are brief durations of intense, highly variable gamma radiation coming from point like sources in the Universe. GRBs have been seen in connection with Type 1c supernovae. Their isotropical equivalent energy released in gamma rays is in some cases above 10 54 erg, but the engine creating this energy is unknown. In this thesis several models for the engine are explored. It is shown that cannonballs can in principle form from hyperaccreting disks, however the cannonball model requires almost all supernovae to create cannonballs, and our finding then implies that a hyperaccreting disk is a natural consequence in most supernovae, a notion which remains to be confirmed. General relativistic magnetohydrodynamic simulations of the collapsar model have been performed. Within our setup we found that the duration of the collapsar is too short to explain GRBs, and the energy output is not sufficient. Also the supernova connection could not be explained. I find that the more likely candidate for the GRB engine is an accreting quark star. A quark star has a maximum mass, if the mass increases above this the star will collapse to a black hole. This allows for a two stage engine that might be able to explain features observed in GRBs.

Staff, Jan Erling

212

Gamma-ray burst models.  

PubMed

I consider various possibilities for making gamma-ray bursts, particularly from close binaries. In addition to the much-studied neutron star+neutron star and black hole+neutron star cases usually considered good candidates for short-duration bursts, there are also other possibilities. In particular, neutron star+massive white dwarf has several desirable features. These systems are likely to produce long-duration gamma-ray bursts (GRBs), in some cases definitely without an accompanying supernova, as observed recently. This class of burst would have a strong correlation with star formation and occur close to the host galaxy. However, rare members of the class need not be near star-forming regions and could have any type of host galaxy. Thus, a long-duration burst far from any star-forming region would also be a signature of this class. Estimates based on the existence of a known progenitor suggest that this type of GRB may be quite common, in agreement with the fact that the absence of a supernova can only be established in nearby bursts. PMID:17293332

King, Andrew

2007-05-15

213

Observations of the Highest Energy Gamma-Rays from Gamma-Ray Bursts  

Microsoft Academic Search

EGRET has extended the highest energy observations of gamma-ray bursts to GeV gamma rays. Such high energies imply the fireball that is radiating the gamma-rays has a bulk Lorentz factor of several hundred. However, EGRET only detected a few gamma-ray bursts. GLAST will likely detect several hundred bursts and may extend the maximum energy to a few 100 GeV. Meanwhile

Brenda L. Dingus

2002-01-01

214

Observations of the Highest Energy Gamma Rays from Gamma-Ray Bursts  

Microsoft Academic Search

EGRET has extended the highest energy observations of gamma-ray bursts to GeV gamma rays. Such high energies imply the fireball that is radiating the gamma rays has a bulk Lorentz factor of several hundred. However, EGRET only detected a few gamma-ray bursts. GLAST will likely detect several hundred bursts and extend the maximum energy to a few 100 GeV. Meanwhile

Brenda L. Dingus

2003-01-01

215

Observations of the highest energy gamma-rays from gamma-ray bursts  

Microsoft Academic Search

EGRET has extended the highest energy observations of gamma-ray bursts to GeV gamma rays. Such high energies imply the fireball that is radiating the gamma-rays has a bulk Lorentz factor of several hundred. However, EGRET only detected a few gamma-ray bursts. GLAST will likely detect several hundred bursts and may extend the maximum energy to a few 100 GeV. Meanwhile

Brenda L. Dingus

2001-01-01

216

Gamma rays from the interactions of reactor fast neutrons ordered by increasing gamma-ray energy  

Microsoft Academic Search

Radioactive material handled in nuclear safeguards often emits both gamma rays and neutrons. The gamma rays emitted by the radioactive isotopes are listed in several compilations, which can be used for identification and quantitative analysis of the radioactive isotopes present. Some of the neutrons are moderated and undergo thermal capture. The capture gamma rays are also listed in several compilations

1982-01-01

217

Black Holes, Supernovae and Gamma Ray Bursts  

NASA Astrophysics Data System (ADS)

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

Ruffini, Remo

2013-09-01

218

Vegetation Density Determinations by Gamma Ray Absorption.  

National Technical Information Service (NTIS)

A method of non-destructive determination of vegetation density in place is presented. This method utilizes a gamma ray absorption technique. The 122 keV gamma rays from Cobalt-57 were used for this work. The determinations are made using the principle of...

C. M. Cialella J. G. Dante

1971-01-01

219

The science of gamma-ray spectroscopy  

Microsoft Academic Search

The explosion mechanism associated with thermonuclear supernovae (SNIa) is still a matter of debate. Nevertheless, there is a wide agreement that high amounts of radioactive nuclei are produced during these events, that are expected to be strong gamma-ray emitters. In this paper we investigate the use of gamma-rays as a diagnostic tool. For this purpose we have performed a complete

J. Isern; E. Bravo; A. Hirschmann

2006-01-01

220

A review of gamma ray bursts  

Microsoft Academic Search

Gamma-ray bursts have continued to puzzle astronomers since their discovery thirty years ago. The sources and emission mechanisms are still uncertain. The instruments on the Compton Gamma Ray Observatory, most notably BATSE, have produced a revolution in our understanding of bursts. BATSE found that the burst spatial distribution was isotropic but inhomogeneous, a result inconsistent with any disk population of

Charles Meegan; Kevin Hurley; Alanna Connors; Brenda Dingus; Steven Matz

1997-01-01

221

On The Origin of Gamma Ray Bursts  

Microsoft Academic Search

We propose that repeated photoexcitation\\/ionization of high Z atoms of highly relativistic flows by star light in dense stellar regions followed by emission of decay\\/recombination photons, which are beamed and boosted to gamma ray energies in the observer frame, produce gamma ray bursts (GRBs). We show that this overlooked mechanism, which is able to convert efficiently baryonic kinetic energy release

Nir J. Shaviv; Arnon Dar

1996-01-01

222

Gamma ray observation with emulsion hybrid telescope  

Microsoft Academic Search

A new gamma ray observation project with balloon borne emulsion chambers is presented. A new technique based on the accelerator emulsion experiments was implemented for studying high energy stellar objects with cosmic gamma rays. This paper provides the aim and concept of this project as well as some results of test experiments.

S. Aoki; K. Kodam; J. Kawada; N. Nonaka; A. Suzuki; T. Hara; Y. Watanabe; H. Rokujyo; A. Ariga; M. Kazuyama; H. Kubota; M. Komatsu; T. Sako; O. Sato; Y. Taira; S. Takahashi; N. Naganawa; T. Nakano; M. Nakamura; K. Niwa; Y. Nonoyama; K. Hamada; T. Fukuda; T. Furukawa; K. Hoshino; M. Miyanishi; S. Miyamoto; K. Morishima; T. Yoshioka; J. Yoshida; A. Iyono; Y. Sato; I. Tezuka

2009-01-01

223

The Supernova-Gamma-Ray Burst Connection  

Microsoft Academic Search

SN 1998bw and its corresponding relativistically expanding radio source are coincident with the gamma -ray burst source GRB 980425. We searched for other possible supernova- gamma -ray burst associations among 101 recent Type Ia and 17 Type Ib\\/c supernovae (SNe) for which the dates of optical maximum are relatively well known. We show that Type Ia SNe can be excluded

Lifan Wang; J. Craig Wheeler

1998-01-01

224

Supernova and Gamma-Ray Burst Remnants  

Microsoft Academic Search

The connection between Supernovae and Gamma-Ray Bursts has provided insights to extend our understanding of both these phenomena beyond what was known from studying them separately. A unique window into the connections between the progenitors and mechanisms of supernova and gamma-ray burst explosions is provided by their remnants. This meeting brings together experts of the remnants of both Supernovae and

Roger Chevalier; Una Hwang; Martin Laming

2006-01-01

225

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

PubMed

Very high-energy (VHE) gamma-ray astronomy has undergone a transformation in the last few years, with telescopes of unprecedented sensitivity having greatly expanded the source catalogue. Such progress makes the detection of a gamma-ray burst at the highest energies much more likely than previously. This paper describes the facilities currently operating and their chances for detecting gamma-ray bursts, and reviews predictions for VHE gamma-ray emission from gamma-ray bursts. Results to date are summarized. PMID:17293337

Chadwick, Paula M

2007-05-15

226

Observations of the highest energy gamma-rays from gamma-ray bursts  

NASA Astrophysics Data System (ADS)

EGRET has extended the highest energy observations of gamma-ray bursts to GeV gamma rays. Such high energies imply the fireball that is radiating the gamma-rays has a bulk Lorentz factor of several hundred. However, EGRET only detected a few gamma-ray bursts. GLAST will likely detect several hundred bursts and may extend the maximum energy to a few 100 GeV. Meanwhile new ground based detectors with sensitivity to gamma-ray bursts are beginning operation, and one recently reported evidence for TeV emission from a burst. .

Dingus, Brenda L.

2001-04-01

227

Observations of the Highest Energy Gamma-Rays from Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

EGRET has extended the highest energy observations of gamma-ray bursts to GeV gamma rays. Such high energies imply the fireball that is radiating the gamma-rays has a bulk Lorentz factor of several hundred. However, EGRET only detected a few gamma-ray bursts. GLAST will likely detect several hundred bursts and may extend the maximum energy to a few 100 GeV. Meanwhile new ground based detectors with sensitivity to gamma-ray bursts are beginning operation, and one recently reported evidence for TeV emission from a burst.

Dingus, Brenda L.

2002-12-01

228

The GLAST Gamma-Ray Telescope Mission  

SciTech Connect

The Gamma-ray Large Area Space Telescope, GLAST, is an orbital mission under construction to measure the cosmic gamma-ray flux in the energy range 20 MeV to >300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. With its launch in 2007, GLAST will open a new and important window on a wide variety of high energy phenomena, including black holes and active galactic nuclei; gamma-ray bursts; the origin of cosmic rays and supernova remnants; and searches for hypothetical new phenomena such as supersymmetric dark-matter annihilations, Lorentz-invariance violation, and exotic relics from the Big Bang. In addition to a short review of the science opportunities, this talk will describe the high-energy gamma-ray telescope and its components and review the mission status.

Johnson, Robert P. [Institute for Particle Physics, University of California, Santa Cruz, CA 95065 (United States)

2006-07-11

229

Planetary Gamma-Ray Spectroscopy: the Effects of Hydrogen and the Macroscopic Thermal-Neutron Absorption Cross-Section on the Gamma-Ray Spectrum  

Microsoft Academic Search

The gamma-ray spectroscopy of planet surfaces is one of several possible methods that are useful in determining the elemental composition of planet surfaces from orbiting spacecraft. This has been demonstrated on the Apollos 15 and 16 missions as well as the Soviet Mars-5 mission. Planetary gamma-ray emission is primarily the result of natural radioactive decay and cosmic-ray and solar-flare-induced nuclear

Jeffrey Rolf Lapides

1981-01-01

230

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

231

Discovery of extended VHE \\\\gamma-ray emission from the vicinity of the young massive stellar cluster Westerlund 1  

Microsoft Academic Search

Results obtained in very-high-energy (VHE; E > 100 GeV) \\\\gamma-ray observations performed with the H.E.S.S. telescope array are used to investigate particle acceleration processes in the vicinity of the young massive stellar cluster Westerlund 1 (Wd 1). Imaging of Cherenkov light from \\\\gamma-ray induced particle cascades in the Earth's atmosphere is used to search for VHE \\\\gamma\\\\ rays from the

A. Abramowski; F. Acero; F. Aharonian; A. G. Akhperjanian; G. Anton; A. Balzer; A. Barnacka; U. Barres de Almeida; Y. Becherini; J. Becker; B. Behera; K. Bernlhr; E. Birsin; J. Biteau; A. Bochow; C. Boisson; J. Bolmont; P. Bordas; J. Brucker; F. Brun; P. Brun; T. Bulik; I. Bsching; S. Carrigan; S. Casanova; M. Cerruti; P. M. Chadwick; A. Charbonnier; R. C. G. Chaves; A. Cheesebrough; L.-M. Chounet; A. C. Clapson; G. Coignet; G. Cologna; J. Conrad; M. Dalton; M. K. Daniel; I. D. Davids; B. Degrange; C. Deil; H. J. Dickinson; A. Djannati-Ata; W. Domainko; L. O'C. Drury; F. Dubois; G. Dubus; K. Dutson; J. Dyks; M. Dyrda; K. Egberts; P. Eger; P. Espigat; L. Fallon; C. Farnier; S. Fegan; F. Feinstein; M. V. Fernandes; A. Fiasson; G. Fontaine; A. Frster; M. Fling; Y. A. Gallant; H. Gast; L. Grard; D. Gerbig; B. Giebels; J. F. Glicenstein; B. Glck; P. Goret; D. Gring; S. Hffner; J. D. Hague; D. Hampf; M. Hauser; S. Heinz; G. Heinzelmann; G. Henri; G. Hermann; J. A. Hinton; A. Hoffmann; W. Hofmann; P. Hofverberg; M. Holler; D. Horns; A. Jacholkowska; O. C. de Jager; C. Jahn; M. Jamrozy; I. Jung; M. A. Kastendieck; K. Katarzynski; U. Katz; S. Kaufmann; D. Keogh; D. Khangulyan; B. Khlifi; D. Klochkov; W. Kluzniak; T. Kneiske; Nu. Komin; K. Kosack; R. Kossakowski; H. Laffon; G. Lamanna; D. Lennarz; T. Lohse; A. Lopatin; C.-C. Lu; V. Marandon; A. Marcowith; J. Masbou; D. Maurin; N. Maxted; M. Mayer; T. J. L. McComb; M. C. Medina; J. Mhault; R. Moderski; E. Moulin; C. L. Naumann; M. Naumann-Godo; M. de Naurois; D. Nedbal; D. Nekrassov; N. Nguyen; B. Nicholas; J. Niemiec; S. J. Nolan; S. Ohm; E. de Ona Wilhelmi; B. Opitz; M. Ostrowski; I. Oya; M. Panter; M. Paz Arribas; G. Pedaletti; G. Pelletier; P.-O. Petrucci; S. Pita; G. Phlhofer; M. Punch; A. Quirrenbach; M. Raue; S. M. Rayner; A. Reimer; O. Reimer; M. Renaud; R. de los Reyes; F. Rieger; J. Ripken; L. Rob; S. Rosier-Lees; G. Rowell; B. Rudak; C. B. Rulten; J. Ruppel; V. Sahakian; D. Sanchez; A. Santangelo; R. Schlickeiser; F. M. Schck; A. Schulz; U. Schwanke; S. Schwarzburg; S. Schwemmer; F. Sheidaei; M. Sikora; J. L. Skilton; H. Sol; G. Spengler; L. Stawarz; R. Steenkamp; C. Stegmann; F. Stinzing; K. Stycz; I. Sushch; A. Szostek; J.-P. Tavernet; R. Terrier; M. Tluczykont; K. Valerius; C. van Eldik; G. Vasileiadis; C. Venter; J. P. Vialle; A. Viana; P. Vincent; H. J. Vlk; F. Volpe; S. Vorobiov; M. Vorster; S. J. Wagner; M. Ward; R. White; A. Wierzcholska; M. Zacharias; A. Zajczyk; A. A. Zdziarski; A. Zech; H.-S. Zechlin

2011-01-01

232

Gamma-Ray Burst Physics with Glast  

NASA Astrophysics Data System (ADS)

The Gamma-ray Large Area Space Telescope (GLAST) is an international space mission that will study the cosmos in the energy range 10 keV-300 GeV, the upper end of which is one of the last poorly observed region of the celestial electromagnetic spectrum. The ancestor of the GLAST/LAT was the Energetic Gamma Ray Experiment Telescope (EGRET) detector, which flew onboard the Compton Gamma Ray Observatory (CGRO). The amount of information and the step forward that the high energy astrophysics made thanks to its 9 years of observations are impressive. Nevertheless, EGRET uncovered the tip of the iceberg, raising many questions, and it is in the light of EGRET's results that the great potential of the next generation gamma-ray telescope can be appreciated. GLAST will have an imaging gamma-ray telescope, the Large Area Telescope (LAT) vastly more capable than instruments flown previously, as well as a secondary instrument, the GLAST Bursts Monitor, or GBM, to augment the study of gamma-ray bursts. Gamma-Ray Bursts (GRBs) science is one of the most exciting challenges for the GLAST mission, exploring the high energy emission of one of the most intense phenomena in the sky, shading light on various problems: from the acceleration of particles to the emission processes, to more exotic physics like Quantum Gravity effect. In this paper we report the work done so far in the simulation development as well as the study of the LAT sensitivity to GRB.

Omodei, N.

2006-04-01

233

Gamma-Ray Burst Physics with GLAST  

SciTech Connect

The Gamma-ray Large Area Space Telescope (GLAST) is an international space mission that will study the cosmos in the energy range 10 keV-300 GeV, the upper end of which is one of the last poorly observed region of the celestial electromagnetic spectrum. The ancestor of the GLAST/LAT was the Energetic Gamma Ray Experiment Telescope (EGRET) detector, which flew onboard the Compton Gamma Ray Observatory (CGRO). The amount of information and the step forward that the high energy astrophysics made thanks to its 9 years of observations are impressive. Nevertheless, EGRET uncovered the tip of the iceberg, raising many questions, and it is in the light of EGRET's results that the great potential of the next generation gamma-ray telescope can be appreciated. GLAST will have an imaging gamma-ray telescope, the Large Area Telescope (LAT) vastly more capable than instruments own previously, as well as a secondary instrument, the GLAST Bursts Monitor, or GBM, to augment the study of gamma-ray bursts. Gamma-Ray Bursts (GRBs) science is one of the most exciting challenges for the GLAST mission, exploring the high energy emission of one of the most intense phenomena in the sky, shading light on various problems: from the acceleration of particles to the emission processes, to more exotic physics like Quantum Gravity effect. In this paper we report the work done so far in the simulation development as well as the study of the LAT sensitivity to GRB.

Omodei, N.; /INFN, Pisa

2006-10-06

234

How to Make a Gamma-ray  

NASA Video Gallery

Animation showing a proton traveling near the speed of light striking a slower-moving proton. The protons survive the collision, but their interaction creates an unstable particle, a pion, with only 14 percent of the proton's mass. In 10 millionths of a billionth of a second, the pion decays into a pair of gamma-ray photons. Years of data collected by NASA's Fermi Gamma-Ray Space Telescope reveal that the shattered remains of a supernova first observed in 1572 shine in high-energy gamma-rays.

Holly Zell

2011-12-12

235

Detecting Axionlike Particles with Gamma Ray Telescopes  

SciTech Connect

We propose that axionlike particles (ALPs) with a two-photon vertex, consistent with all astrophysical and laboratory bounds, may lead to a detectable signature in the spectra of high-energy gamma-ray sources. This occurs as a result of gamma rays being converted into ALPs in the magnetic fields of efficient astrophysical accelerators according to the 'Hillas criterion', such as jets of active galactic nuclei or hot spots of radio galaxies. The discovery of such an effect is possible by GLAST in the 1-100 GeV range and by ground-based gamma-ray telescopes in the TeV range.

Hooper, Dan; Serpico, Pasquale D. [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, Illinois 60510-0500 (United States)

2007-12-07

236

Detecting axionlike particles with gamma ray telescopes.  

PubMed

We propose that axionlike particles (ALPs) with a two-photon vertex, consistent with all astrophysical and laboratory bounds, may lead to a detectable signature in the spectra of high-energy gamma-ray sources. This occurs as a result of gamma rays being converted into ALPs in the magnetic fields of efficient astrophysical accelerators according to the "Hillas criterion", such as jets of active galactic nuclei or hot spots of radio galaxies. The discovery of such an effect is possible by GLAST in the 1-100 GeV range and by ground-based gamma-ray telescopes in the TeV range. PMID:18233353

Hooper, Dan; Serpico, Pasquale D

2007-12-06

237

The MILAGRO Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

MILAGRO will be the first water-\\v{C}erenkov detector specifically built to study extensive air showers. It is being built in an existing man-made pond 60m x 80m by 8m, located in the Jemez mountains near Los Alamos, NM. Unlike conventional air shower detectors, which sample less than 1% of the particles which reach detector level, MILAGRO will be totally sensitive to the electrons, photons, hadrons, and muons in the air shower. The energy threshold of the MILAGRO detector is comparable to atmospheric \\v{C}erenkov detectors, however it has several advantages over these optical detectors. MILAGRO is operational 24 hours a day in all weather conditions and it has an open aperture which allows it to view the entire northern sky every day. These capabilities allow for a systematic all-sky survey to be done for the first time at VHE energies. MILAGRO will measure the Crab spectrum with high significance. In addition, it will detect and measure the spectra from AGN's such as MRK 421. MILAGRO will be the first VHE detector capable of recording Gamma Ray Bursts at energies above 250 GeV. MILAGRO will search for point sources of VHE gamma radiation, both steady and episodic. The scientific merits of this detector together with its design and current status will be discussed.

Shoup, A.; Barwick, S.; Chumney, P.; Yodh, G. B.; Chang, C. Y.; Chen, M. L.; Dion, C.; Goodman, J. A.; Berley, D.; Haines, T. J.; Hoffman, C. M.; Nagle, D. E.; Sandberg, V. D.; Sanders, G.; Schaller, S.; White, D. H.; Schmidt, D. M.; Sinnis, C.; Cavalli-Sforza, M.; Coyne, D.; Dorfan, D.; Kelley, L.; Klein, S.; Schnee, R.; Williams, D. A.; Yang, T.; Mincer, A. I.; Nemethy, P.; Bauer, D.; Caldwell, D.; Lu, A.; Yellin, S.; O'Neill, T. J.; Tumer, O. T.; Zych, A.; Freedman, S. J.; Fujikawa, B. K.; Ellsworth, R. W.; Biller, S.; Dingus, B. L.; Ahulwalia, H. S.

1994-12-01

238

Measurement of the initial levels of DNA damage in human lymphocytes induced by 29 kV X rays (mammography X rays) relative to 220 kV X rays and gamma rays.  

PubMed

Experiments using the alkaline comet assay, which measures all single-strand breaks regardless of their origin, were performed to evaluate the biological effectiveness of photons with different energies in causing these breaks. The aim was to measure human lymphocytes directly for DNA damage and subsequent repair kinetics induced by mammography 29 kV X rays relative to 220 kV X rays, 137Cs gamma rays and 60Co gamma rays. The level of DNA damage, predominantly due to single-strand breaks, was computed as the Olive tail moment or percentage DNA in the tail for different air kerma doses (0.5, 0.75, 1, 1.5, 2 and 3 Gy). Fifty cells were analyzed per slide with a semiautomatic imaging system. Data from five independent experiments were transformed to natural logarithms and fitted using a multiple linear regression analysis. Irradiations with the different photon energies were performed simultaneously for each experiment to minimize interexperimental variation. Blood from only one male and one female was used. The interexperimental variation and the influence of donor gender were negligible. In addition, repair kinetics and residual DNA damage after exposure to a dose of 3 Gy were evaluated in three independent experiments for different repair times (10, 20, 30 and 60 min). Data for the fraction of remaining damage were fitted to the simple function F(d) = A/(t + A), where F(d) is the fraction of remaining damage, t is the time allowed for repair, and A (the only fit parameter) is the repair half-time. It was found that the comet assay data did not indicate any difference in the initial radiation damage produced by 29 kV X rays relative to the reference radiation types, 220 kV X rays and the gamma rays of 137Cs and 60Co, either for the total dose range or in the low-dose range. These results are, with some restrictions, consistent with physical examinations and predictions concerning, for example, the assessment of the possible difference in effectiveness in causing strand breaks between mammography X rays and conventional (150-250 kV) X rays, indicating that differences in biological effects must arise through downstream processing of the damage. PMID:15850412

Gomolka, M; Rssler, U; Hornhardt, S; Walsh, L; Panzer, W; Schmid, E

2005-05-01

239

Identification of fissile materials from fission product gamma-ray spectra  

Microsoft Academic Search

A new activepassive nondestructive assay technique has been developed to identify fissile materials by observing the gamma-ray emissions from induced fission products. This technique entails using a neutron source to induce fissions in unknown containerized fissile materials and to subsequently observe high energy peaks (>800keV) in the fission product gamma-ray spectrum. Ratios of the observed peak intensities are then formed.

D. H Beddingfield; F. E Cecil

1998-01-01

240

Complementary PIGE, PIXE, EDXRF and gamma-ray spectroscopic investigation on natural chromites  

Microsoft Academic Search

Elemental analysis has been carried out on a selected number of natural chromites by using various non-destructive nuclear analytical techniques like simultaneous particle-induced X-ray emission particle-induced gamma-ray emission (PIXE PIGE), energy dispersive X-ray fluorescence (EDXRF) and gamma-ray spectroscopic measurements. For PIXE PIGE investigation, a 3 MeV proton beam from a 3 MV pelletron accelerator was utilized for irradiating the samples,

P. K. Nayak; V. Vijayan

2006-01-01

241

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

242

Spektroskopiya gamma-izlucheniya oskolkov deleniya (sup 239)Pu teplovymi i rezonansnymi nejtronami na impul'snom puchke nejtronov reaktora IBR-30. (Gamma-ray spectroscopy of fragments of (sup 239)Pu fission induced by thermal and resonance neutrons on the pulsed neutron beam of IBR-30 reactor).  

National Technical Information Service (NTIS)

The search for the peculiarities of (sup 239)Pu fission induced by thermal and resonance neutrons on the pulsed neutron beam of IBR-30 reactor in the energy interval from 0.3 up to 220 eV was developed using the prompt gamma-ray spectroscopy method. Relia...

N. A. Gundorin Y. Kopach S. A. Telezhnikov V. I. Furman

1995-01-01

243

Gamma-ray Emission from HMXBs  

NASA Astrophysics Data System (ADS)

During the last ten years, high-mass X-ray binaries (HMXB) have consolidated their status of gamma-ray sources. Even before the first EGRET detection candidates, HMXB seemed to be interesting sources to look for gamma rays, and study the processes giving rise to such an energetic photons. Presently, there is already a well established population of gamma-ray emittings HMXB found or confirmed by the current GeV and TeV instruments. These objects have turned out to be very efficient as accelerators, and also channelling the available energy budget into relativistic particles. Their emission is strongly variable and typically periodical, with a low-energy counterpart that is intimately related to the processes at the highest energies. In this talk, I will review the main processes associated to the production of gamma-rays in high-mass X-ray binaries.

Bosch-Ramon, Valenti

2012-07-01

244

Gamma Ray Bursts from Magnetospheric Plasma Oscillations.  

National Technical Information Service (NTIS)

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 incipien...

F. Melia

1989-01-01

245

Neutron Detection Gamma Ray Sensitivity Criteria  

SciTech Connect

The shortage of 3He has triggered the search for effective alternative neutron detection technologies for national security and safeguards applications. Any new detection technology must satisfy two basic criteria: (1) it must meet a neutron detection efficiency requirement, and (2) it must be insensitive to gamma-ray interference at a prescribed level, while still meeting the neutron detection requirement. It is the purpose of this paper to define measureable gamma ray sensitivity criteria for neutron detectors. Quantitative requirements are specified for: intrinsic gamma ray detection efficiency and gamma ray absolute rejection. The ratio GARRn is defined, and it is proposed that the requirement for neutron detection be 0.9 < GARRn < 1.1 at a 10 mR/h exposure rate. An example of results from a 3He based neutron detector are provided showing that this technology can meet the stated requirements. Results from tests of some alternative technologies are also reported.

Kouzes, Richard T.; Ely, James H.; Lintereur, Azaree T.; Mace, Emily K.; Stephens, Daniel L.; Woodring, Mitchell L.

2011-10-21

246

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

247

GRAPE - The Gamma Ray Polarimeter Experiment  

NASA Astrophysics Data System (ADS)

We have developed a design for a hard X-ray polarimeter operating in the energy range from 50 to 500 keV. This modular design, known as GRAPE (Gamma-Ray Polarimeter Experiment), has been successfully demonstrated in the lab using partially polarized gamma-ray sources and using fully polarized photon beams at Argonne National Laboratory. In June of 2007, a GRAPE engineering model was flown on a high altitude balloon flight to demonstrate the design and to collect background data. We are currently working on the development of a much larger balloon payload that would provide a significant level of sensitivity for gamma-ray bursts on a long-duration balloon flight and, if flown near solar max, would also provide significant sensitivity for solar flare polarization measurements. We shall review the history, status and future potential of the GRAPE project and summarize the potential for making polarization measurements of gamma-ray bursts and solar flares.

McConnell, Mark L.; Bloser, P. F.; Legere, J.; Ryan, J. M.; Connor, T.

2009-01-01

248

Do Gamma-ray Burst Sources Repeat.  

National Technical Information Service (NTIS)

The demonstration of repeated gamma-ray bursts from an individual source would severely constrain burst source models. Recent reports of evidence for repetition in the first BATSE burst catalog have generated renewed interest in this issue. Here, we analy...

C. A. Meegan D. H. Hartmann J. J. Brainerd M. Briggs W. S. Paciesas

1994-01-01

249

Gamma-ray emission from thermonuclear supernovae  

SciTech Connect

The explosion mechanism associated with thermonuclear supernovae (SNIa) is still a matter of debate. Nevertheless, there is a wide agreement that high amounts of radioactive nuclei are produced during these events and that they are expected to be strong {gamma}-ray emitters. In this paper we investigate the use of this {gamma}-rays as a diagnostic tool. For this purpose we have performed a complete study of the {gamma}-ray spectra associated with all the different scenarios currently proposed: detonation, deflagration, delayed detonation, and pulsating delayed detonation. Our study shows that the {gamma}-ray emission from SNIa is, effectively, a promising tool but that has to be carefully used since it can lead to misinterpretations. We also show that 3D effects can be relevant in some circumstances and that they can provide important information about the exploding system and the thermonuclear burning front mechanism if high resolution spectra could be obtained.

Isern, J. [Institut de Ciencies de l'Espai (CSIC - IEEC), Campus UAB, Torre C5-parells 2n, 08193 Bellaterra (Spain); Institut d'Estudis Espacials de Catalunya (Spain); Bravo, E.; Hirschmann, A. [Departament de Fisica i Enginyeria Nuclear UPC (Spain); Diagonal 647, 08028 Barcelona (Spain); Institut d'Estudis Espacials de Catalunya (Spain)

2007-08-21

250

Radio counterparts of gamma-ray pulsars  

NASA Astrophysics Data System (ADS)

Observations of pulsars with the Large Area Telescope (LAT) on the Fermi satellite have revolutionized our view of the gamma-ray pulsar population. For the first time, a large number of young gamma-ray pulsars have been discovered in blind searches of the LAT data. More generally, the LAT has discovered many new gamma-ray sources whose properties suggest that they are powered by unknown pulsars. Radio observations of gamma-ray sources have been key to the success of pulsar studies with the LAT. For example, radio observations of LAT-discovered pulsars provide constraints on the relative beaming fractions, which are crucial for pulsar population studies. Also, radio searches of LAT sources with no known counterparts have been very efficient, with the discovery of over forty millisecond pulsars. I review radio follow-up studies of LAT-discovered pulsars and unidentified sources, and discuss some of the implications of the results.

Guillemot, L.

2013-03-01

251

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

252

Gamma-ray Burst Predictions for the Fermi Gamma Ray Space Telescope  

Microsoft Academic Search

Results of a phenomenological model to estimate the gamma-ray burst (GRB) detection rate by the Fermi Gamma-Ray Space Telescope are reported. This estimate is based on the Burst and Transient Source Experiment (BATSE) 4B GRB fluence distribution, the mean ratio of fluences measured at 100 MeV-5 GeV with Energetic Gamma-Ray Experiment Telescope (EGRET) and at 20 keV-2 MeV with BATSE,

Truong Le; Charles D. Dermer

2009-01-01

253

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

254

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

255

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

Microsoft Academic Search

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

P. M. Saz Parkinson

2009-01-01

256

Pair-Signatures and High-Energy Gamma-Ray Emission from Gamma-Ray Bursts  

Microsoft Academic Search

We discuss high-energy gamma-ray emission from gamma-ray bursts (GRBs). When such high-energy gamma rays are expected, e+\\/- pairs may play an important role both inside and outside the source. e+\\/- pair-signatures inside the source (the pair-annihilation bump and the cutoff due to the pair-creation process) are useful for diagnosing the fireball of GRBs. The recipes for diagnoses are largely model-independent

Kohta Murase; Kunihito Ioka; Shigehiro Nagataki

2008-01-01

257

Constraints on the Luminosity Function of Gamma-Ray Bursts from the Gamma Ray Background  

Microsoft Academic Search

The width of the gamma-ray burst (GRB) luminosity function is presently not well constrained. A wide luminosity function might be expected were GRBs associated with supernovae, for example. The possibility that a large number of undetected GRBs might make a contribution to the diffuse soft gamma-ray background is investigated. If gamma-ray bursts (GRBs) create supernova-like remnants, the width of the

H. Che

1999-01-01

258

Solar Two Gamma-Ray Observatory  

Microsoft Academic Search

The field of high energy gamma-ray astronomy grew tremendously in the last decade due to the launch of the EGRET detector on the Compton Gamma-Ray Observatory in 1991 and the proliferation of ground-based air ?herenkov telescopes (ACTs) such as the Whipple 10 meter reflector. Interestingly, the ground-based telescopes only see 45 of the over 170 objects detected by EGRET. A

T. Tmer; D. Bhattacharya; U. Mohideen; R. Rieben; V. Souchkov; H. Tom; J. Zweerink

1999-01-01

259

GRI: the gamma-ray imager mission  

NASA Astrophysics Data System (ADS)

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

Kndlseder, Jrgen

2006-07-01

260

The Gamma-Ray Imager GRI  

NASA Astrophysics Data System (ADS)

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

Wunderer, Cornelia B.; GRI Collaboration

2006-09-01

261

Gamma-Ray Burst Physics with GLAST  

Microsoft Academic Search

The Gamma-ray Large Area Space Telescope (GLAST), scheduled to be launched in late of 2007, is the next generation satellite for high-energy gamma-ray astronomy. The Large Area Telescope (LAT), the main instrument of GLAST, will survey the sky in the energy range between 20 MeV to more than 300 GeV, shedding light on many issues left open by its highly

Nicola Omodei

2007-01-01

262

A General Gamma-Ray Source Catalog  

NASA Astrophysics Data System (ADS)

The past several years have seen unprecedented growth in the field of gamma-ray astronomy. Highly successful missions such as the Compton Gamma-Ray Observatory (CGRO) have led to both a great increase in the number of detected gamma-ray sources and a more fundamental understanding of the basic physical processes involved for those sources. New ground-based observatories, the Rossi X-Ray Timing Explorer (RXTE), and the SIGMA instrument aboard the GRANAT spacecraft have all contributed to this explosion. Detailed observations of active galaxies, pulsars, accreting binaries, and diffuse emission have had a tremendous impact on our view of the universe. Given that new experiments that will provide a similar increase in source numbers are several years away, it is a good time to take inventory of the state of gamma-ray astronomy. To this end, we have developed a general gamma-ray point-source catalog containing 309 objects that summarize the field. Gamma-ray astronomy, as we define it, includes photon energies from 50 keV to about 1 TeV. While many catalogs concentrate on a single type of astronomical object and/or a very restricted energy range, the nature of this catalog is somewhat different. The large variety of objects and the many orders of magnitude in energy space covered by gamma-ray astronomy presents an organizational challenge. We focus on two main types of information: a general listing of the basic characteristics of each source, and detailed tables of a representative sample of high-energy observations. We also summarize the gamma-ray instruments whose observations are included in the catalog.

Macomb, D. J.; Gehrels, N.

1999-02-01

263

Gamma-Ray Bursts: the Four Crises  

Microsoft Academic Search

We discuss some open problems concerning the origin and the emission\\u000amechanism of gamma-ray bursts (GRBs) in light of recent developments. If GRBs\\u000aoriginate at extragalactic distances, we are facing four crises: (1) an energy\\u000acrisis, models have to account for more than 10^{53} ergs of energy emitted in\\u000athe gamma-ray energy band; (2) a spectral crisis, emission models have

Marco Tavani

1998-01-01

264

Gamma-Ray Bursts: the Four Crises  

Microsoft Academic Search

We discuss some open problems concerning the origin and the emission mechanism of gamma-ray bursts (GRBs) in light of recent developments. If GRBs originate at extragalactic distances, we are facing four crises: (1) an energy crisis, models have to account for more than 10^{53} ergs of energy emitted in the gamma-ray energy band; (2) a spectral crisis, emission models have

M. Tavani

1999-01-01

265

Swift's 500th Gamma Ray Burst  

NASA Video Gallery

On April 13, 2010, NASA's Swift Gamma-ray Burst Explorer satellite discovered its 500th burst. Swift's main job is to quickly localize each gamma-ray burst (GRB), report its position so that others can immediately conduct follow-up observations, and then study the burst using its X-ray and Ultraviolet/Optical telescopes. Some notable bursts are identified in the video.

Katherine Lewis

2010-04-19

266

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

267

Gamma Ray Bursts Cook Book I: Formulation  

Microsoft Academic Search

Since the suggestion of relativistic shocks as the origin of gamma-ray bursts\\u000a(GRBs) in early 90's, the mathematical formulation of this process has stayed\\u000aat phenomenological level. One of the reasons for the slow development of\\u000atheoretical works in this domain has been the simple power-law behaviour of the\\u000aafterglows hours or days after the prompt gamma-ray emission. Nowadays with

Houri Ziaeepour

2008-01-01

268

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

269

Classification of Swift's gamma-ray bursts  

Microsoft Academic Search

Context. Two classes of gamma-ray bursts have been identified in the BATSE catalogs characterized by durations shorter and longer than about 2 s. There are, however, some indications for the existence of a third class. Swift satellite detectors have different spectral sensitivity than pre-Swift ones for gamma-ray bursts. Therefore we reanalyze the durations and their distribution and also the classi-

I. Horvth; L. G. Balzs; Z. Bagoly; P. Veres

2008-01-01

270

First Gamma Ray Burst Observations with Swift  

Microsoft Academic Search

Swift is a NASA Explorer mission that was launched on November 20, 2004. It is a multiwavelength observatory for transient astronomy. The goals of the mission are to determine the origin of gamma-ray bursts and their afterglows and use bursts to probe the early Universe. A wide-field gamma-ray camera will detect more than a hundred GRBs per year to 3

Neil Gehrels

2005-01-01

271

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

272

Gamma-ray bursts and Swift  

Microsoft Academic Search

Discovered by accident using satellites monitoring the nuclear test-ban treaty, gamma-ray bursts (GRBs) are the most powerful explosive events in the Universe. Several GRBs per day occur randomly on the sky, typically lasting a few seconds as a gamma-ray source. This abrupt burst is followed by emission across the entire electromagnetic spectrum which can last for several weeks or more.

Paul O'Brien; Julian Osborne; Keith Mason

2005-01-01

273

GeV gamma-ray sources  

NASA Astrophysics Data System (ADS)

We report on the preliminary extension of our work on cataloging the GeV sky to approximately 7 years of CGRO/EGRET observations with special emphasis on a search for transient sources. The search method and significance levels are presented. Our initial results on 13 possible transients indicate that 3 may be new gamma-ray sources. Sixteen new steady GeV sources are also detected, 3 of which have never been reported as gamma-ray sources. .

Lamb, R. C.; Macomb, D. J.

2000-06-01

274

Mining Gamma-Ray Burst Data  

Microsoft Academic Search

Gamma-ray bursts provide what is probably one of the messiest of all astrophysical data sets. Burst class properties are indistinct,\\u000a as overlapping characteristics of individual bursts are convolved with effects of instrumental and sampling biases. Despite\\u000a these complexities, data mining techniques have allowed new insights to be made about gamma-ray burst data. We demonstrate\\u000a how data mining techniques have simultaneously

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

275

GRI: The Gamma-Ray Imager mission  

Microsoft Academic Search

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe While at lower wavebands the observed emission is generally dominated by thermal processes the gamma-ray sky provides us with a view on the non-thermal Universe Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood and nuclear

Jrgen Kndlseder

2006-01-01

276

The Gamma-Ray Imager GRI  

Microsoft Academic Search

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear

Cornelia B. Wunderer

2008-01-01

277

The Gamma-Ray Imager GRI  

Microsoft Academic Search

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear

Cornelia B. Wunderer

2006-01-01

278

Gamma-Ray Bursts from Minijets  

Microsoft Academic Search

Striking similarities exist between high-energy gamma-ray emission from active galactic nuclei (AGNs) and gamma-ray bursts (GRBs). They suggest that GRBs are generated by inverse Compton scattering from highly relativistic electrons in transient jets. Such jets may be produced along the axis of an accretion disk formed around stellar black holes (BHs) or neutron stars (NSs) in BH-NS and NS-NS mergers

Nir J. Shaviv; Arnon Dar

1995-01-01

279

Cataclysmic Variables and Gamma-Ray Sources  

NASA Astrophysics Data System (ADS)

The cataclysmic variables are associated with high energy events and probably many of them could be potential gamma-ray sources. Up to now Fermi-LAT detected 3 gamma-ray transients, which belong to CVs and related objects: V407 Cyg, N Sco 2012 and N Mon 2012 = V959 Mon. We present the first multicolour observations of the slow classical nova V959 Mon.

Pavlenko, E.; Malanushenko, V.; Shugarov, S.; Chochol, D.

2013-07-01

280

Observing Gamma-ray Bursts with GLAST  

Microsoft Academic Search

The Gamma-ray Large Area Telescope (GLAST) is a satellite-based observatory to study the high-energy gamma-ray sky. The Large Area Telescope, the main instrument, is a pair-conversion telescope which will survey the sky in the energy range 20 MeV to greater than 300 GeV. The LAT's wide field of view (>2; sr), large effective area and low deadtime combine to provide

Julie E. McEnery

2007-01-01

281

gamma rays and neutrinos from a powerful cosmic accelerator  

Microsoft Academic Search

Possibly the powerful radio quasar 3C273 will reveal its nature as an efficient proton accelerator up to energies of order 1011 GeV in the near future. It is shown in this paper that the shock-accelerated protons expected to be present in the quasar's plasma jet induce an unsaturated synchrotron cascade with electromagnetic radiation emerging in the x-ray and gamma-ray ranges.

K. Mannheim

1993-01-01

282

Abnormal pattern of post-gamma-ray DNA replication in radioresistant fibroblast strains from affected members of a cancer-prone family with Li-Fraumeni syndrome.  

PubMed Central

Non-malignant dermal fibroblast strains, cultured from affected members of a Li-Fraumeni syndrome (LFS) family with diverse neoplasms associated with radiation exposure, display a unique increased resistance to the lethal effects of gamma-radiation. In the studies reported here, this radioresistance (RR) trait has been found to correlate strongly with an abnormal pattern of post-gamma-ray DNA replicative synthesis, as monitored by radiolabelled thymidine incorporation and S-phase cell autoradiography. In particular, the time interval between the gamma-ray-induced shutdown of DNA synthesis and its subsequent recovery was greater in all four RR strains examined and the post-recovery replication rate was much higher and was maintained longer than in normal and spousal controls. Alkaline sucrose sedimentation profiles of pulse-labelled cellular DNA indicated that the unusual pattern of DNA replication in irradiated RR strains may be ascribed to anomalies in both replicon initiation and DNA chain elongation processes. Moreover, the RR strain which had previously displayed the highest post-gamma-ray clonogenic survival was found to harbour a somatic (codon 234) mutation (presumably acquired during culture in vitro) in the same conserved region of the p53 tumour-suppressor gene as the germline (codon 245) mutation in the remaining three RR strains from other family members, thus coupling the RR phenotype and abnormal post-gamma-ray DNA synthesis pattern with faulty p53 expression. Significantly, these two aberrant radioresponse end points, along with documented anomalies in c-myc and c-raf-1 proto-oncogenes, are unprecedented among other LFS families carrying p53 germline mutations. We thus speculate that this peculiar cancer-prone family may possess in its germ line a second, as yet unidentified, genetic defect in addition to the p53 mutation. Images Figure 8

Mirzayans, R.; Aubin, R. A.; Bosnich, W.; Blattner, W. A.; Paterson, M. C.

1995-01-01

283

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

284

Observing cosmic nuclei in gamma rays  

NASA Astrophysics Data System (ADS)

Nucleosynthesis events in cosmic objects create new nuclei, admixtures of radioactive isotopes being part of the matter ejected into interstellar space by these events. Gamma rays are emitted in radioactive decays, and can be measured with space-based gamma-ray telescopes. Four mission years of INTEGRAL have led to discoveries of new sources and to detailed astronomical refinements of already-known gamma-ray line emission. As part of the main science objectives of INTEGRAL's spectrometer SPI, diffuse emission from annihilation of positrons has presented a new puzzle, as the Galactic distribution of their presumed sources does not agree with the gamma-ray image. Recent massive-star nucleosynthesis is traced throughout the Galaxy with radioactivites seen in 26Al and now also 60Fe gamma rays; precision line spectroscopy now reveals Doppler shifts for the 26Al line, separately for different parts of the Galaxy. This provides new insights into the dynamics of hot interstellar gas. The processes generating new atomic nuclei in stars and supernovae are reflected in the abundances of the ejected radioactivities. For individual supernovae, measurements of 44Ti with its 85 year decay time probes the symmetry of the supernova interior. Since such gamma-ray measurements probe the generation of new nuclei in cosmic sites through a radiation process which is independent of environmental parameters such as temperature or ionization, it will remain worthwhile to further develop instrumentation in this window to the nuclear-physics universe.

Diehl, Roland

2008-01-01

285

T-odd angular correlations in the emission of prompt gamma rays and neutrons in nuclear fission induced by polarized neutrons  

SciTech Connect

Study of the T-odd three-vector correlation in the emission of prompt neutrons from {sup 235}U fission by polarized cold neutrons has been continued at the facility MEPHISTO of the FRM II reactor (Technical University of Munich). The sought correlation was not found within experimental error of 2.3 Multiplication-Sign 10{sup -5}. The upper limit for the asymmetry coefficient has been set to vertical bar D{sub n} vertical bar < 6 Multiplication-Sign 10{sup -5} at 99% confidence level, whereas for ternary fission correlation coefficient D{sub {alpha}} = (170{+-}20) Multiplication-Sign 10{sup -5}. This limit casts doubt on a model that explains the three-vector correlation in ternary fission by the Coriolis mechanism. At the same time, five-vector correlation in the emission of prompt fission neutrons has been measured, which describes the rotation of the fissioning nucleus at the moment it breaks (ROT effect). At the angle 22.5 Degree-Sign to the fission axis, the correlation coefficient was found to be (1.57 {+-} 0.20) Multiplication-Sign 10{sup -4}, while at the angle of 67.5 Degree-Sign it is zero within the experimental uncertainty. The existence of ROT effect in the emission of prompt fission neutrons can be explained by the anisotropy of neutron emission in the rest frame of the fragment (fission fragments are aligned with respect to the axis of deformation of the fissioning nucleus), similar to the mechanism of ROT effect in the emission of prompt {gamma}-rays.

Danilyan, G. V. [Institute for Theoretical and Experimental Physics (Russian Federation); Klenke, J. [Forschungs-Neutronenquelle Heinz Meier-Leibnitz (FRM II) (Germany); Krakhotin, V. A.; Kopach, Yu. N.; Novitsky, V. V.; Pavlov, V. S.; Shatalov, P. B. [Institute for Theoretical and Experimental Physics (Russian Federation)

2011-05-15

286

Gamma-Ray Bursts and Particle Acceleration  

NASA Astrophysics Data System (ADS)

Gamma-ray bursts (GRBs) are possible sources of ultra-high-energy cosmic rays (UHE-CRs). To test the GRB origin of UHECRs, it is essential to search for characteristic, proton-induced signatures of secondary radiation. In this paper we present our recent results of Monte Carlo simulations that model the broadband prompt emission of GRBs including various processes associated with electrons and protons accelerated to high energies. The most notable effect of accelerated protons on the high-energy spectra is the synchrotron emission from secondary electron-positron pairs injected by photomeson interactions. Secondary photons tend to make the spectra flat, so a spectral flattening in the GeV-TeV bands may serve as a signature of UHECR acceleration. In some cases, the proton-induced photons overwhelm the photon field, resulting in a spectral peak due to inverse Compton emission from secondary pairs located around 107 eV. We can expect to detect synchrotron photons from protons or muons. Observations with GLAST or with atmospheric Cerenkov telescopes can provide useful estimates of the bulk Lorents factor and can constrain the proton acceleration efficiency.

Asano, Katsuaki

2008-08-01

287

Gamma-Ray Bursts and Particle Acceleration  

SciTech Connect

Gamma-ray bursts (GRBs) are possible sources of ultra-high-energy cosmic rays (UHE-CRs). To test the GRB origin of UHECRs, it is essential to search for characteristic, proton-induced signatures of secondary radiation. In this paper we present our recent results of Monte Carlo simulations that model the broadband prompt emission of GRBs including various processes associated with electrons and protons accelerated to high energies. The most notable effect of accelerated protons on the high-energy spectra is the synchrotron emission from secondary electron-positron pairs injected by photomeson interactions. Secondary photons tend to make the spectra flat, so a spectral flattening in the GeV-TeV bands may serve as a signature of UHECR acceleration. In some cases, the proton-induced photons overwhelm the photon field, resulting in a spectral peak due to inverse Compton emission from secondary pairs located around 10{sup 7} eV. We can expect to detect synchrotron photons from protons or muons. Observations with GLAST or with atmospheric Cerenkov telescopes can provide useful estimates of the bulk Lorents factor and can constrain the proton acceleration efficiency.

Asano, Katsuaki [Interactive Research Center for Science, Graduate School of Science, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan)

2008-08-28

288

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

289

Cosmic Gamma-ray from Inverse Compton Process in Unstable Dark Matter Scenario  

SciTech Connect

Motivated by the PAMELA anomaly in the fluxes of cosmic-ray e{sup +} and e{sup -}, we study the cosmic gamma-ray induced by the inverse Compton (IC) scattering process in unstable dark matter scenario assuming that the anomaly is due to the e{sup +}- emission by the decay of dark matter. We calculate the fluxes of IC-induced gamma-ray produced in our Galaxy and that from cosmological distance, and show that both of them are significant. We discuss a possibility that large dark matter mass over TeV scale might be constrained by the gamma-ray observation by Fermi Gamma-ray Space Telescope.

Ishiwata, Koji; Moroi, Takeo [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Matsumoto, Shigeki [Department of Physics, University of Toyama, Toyama 930-8555 (Japan)

2010-03-26

290

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

291

The Supernovae Associated with Gamma-Ray Bursts  

Microsoft Academic Search

Supernovae were long suspected as possible progenitors of gamma-ray bursts. The arguments relied on circumstantial evidence. Several recent gamma-ray bursts, notably GRB 030329, have provided direct, spectroscopic evidence that supernovae and gamma-ray bursts are related. The supernovae associated with gamma-ray bursts are all of Type Ic, implying a compact progenitor, which has implications for gamma-ray burst models. Other peculiar Type

T. Matheson

2005-01-01

292

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

Microsoft Academic Search

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.

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

2008-01-01

293

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

294

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

Microsoft Academic Search

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 1min to 14h. 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.

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

2008-01-01

295

FIGARO: detecting nuclear materials using high-energy gamma-rays  

Microsoft Academic Search

The potential diversion of nuclear materials is a major international concern. Fissile (e.g., U, Pu) and other nuclear materials (e.g., D, Be) can be detected using 67MeV gamma-rays produced in the 19F(p,??) 16O reaction. These gamma-rays can induce neutron emission via photoneutron and photofission processes in nuclear materials. However, they are not energetic enough to generate significant numbers of neutrons

B. J. Micklich; D. L. Smith; T. N. Massey; C. L. Fink; D. Ingram

2003-01-01

296

FIGARO: detecting nuclear materials using high-energy gamma-rays  

Microsoft Academic Search

The potential diversion of nuclear materials is a major international concern. Fissile (e.g., U, Pu) and other nuclear materials (e.g., D, Be) can be detected using 6-7MeV gamma-rays produced in the 19F(p,alphagamma) 16O reaction. These gamma-rays can induce neutron emission via photoneutron and photofission processes in nuclear materials. However, they are not energetic enough to generate significant numbers of neutrons

B. J. Micklich; D. L. Smith; T. N. Massey; C. L. Fink; D. Ingram

2003-01-01

297

FIGARO: Detecting nuclear material using high-energy gamma rays from oxygen  

Microsoft Academic Search

Potential diversion of nuclear materials is a major international concern. Fissile (e.g., U, Pu) and other nuclear materials (e.g., D, Be) can be detected using 6-7 MeV gamma rays produced in the 19F(p,alphagamma)16O reaction. These gamma rays will induce neutron emission via the photoneutron and photofission processes in nuclear materials. However, they are not energetic enough to generate significant numbers

B. J. Micklich; D. L. Smith; T. N. Massey; D. Ingram; A. Fessler

2001-01-01

298

FIGARO : detecting nuclear materials using high-energy gamma rays for oxygen  

Microsoft Academic Search

Potential diversion of nuclear materials is a major international concern. Fissile (e.g., U, Pu) and other nuclear materials (e.g., D, Be) can be detected using 6-7 MeV gamma rays produced in the ¹⁹F(p,αγ)¹⁶O reaction. These gamma rays will induce neutron emission via the photoneutron and photofission processes in nuclear materials. However, they are not energetic enough to generate significant numbers

B. J. Michlich; D. L. Smith; T. N. Massey; D. Ingram; A. Fessler

2000-01-01

299

FIGARO: Detecting nuclear material using high-energy gamma rays from oxygen  

Microsoft Academic Search

Potential diversion of nuclear materials is a major international concern. Fissile (e.g., U, Pu) and other nuclear materials (e.g., D, Be) can be detected using 67 MeV gamma rays produced in the 19F(p,??)16O reaction. These gamma rays will induce neutron emission via the photoneutron and photofission processes in nuclear materials. However, they are not energetic enough to generate significant numbers

B. J. Micklich; D. L. Smitha; T. N. Masseyb; D. Ingramb; A. Fesslera

2001-01-01

300

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

NASA Astrophysics Data System (ADS)

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

Iyengar, A.; Norman, E. B.; Howard, C.; Angell, C.; Kaplan, A.; Ressler, J. J.; Chodash, P.; Swanberg, E.; Czeszumska, A.; Wang, B.; Yee, R.; Shugart, H. A.

2013-06-01

301

Atmospheric gamma rays in the energy region 401000 GeV  

Microsoft Academic Search

A large stack of lead-emulsion sandwich detector assembly was flown over Hyderabad, India. High energy gamma rays at the float\\u000a altitude were unambiguously identified from the cascades they induced, and their energies reliably determined by improved\\u000a methods. From an analysis of 163 gamma rays of energy ? 30 GeV, it is found that the differential energy spectrum is represented\\u000a by

K C Anand; R R Daniel; S A Stephens

1973-01-01

302

The Gamma-Ray Imager GRI  

NASA Astrophysics Data System (ADS)

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

Wunderer, Cornelia B.; GRI Collaboration

2008-03-01

303

VLF Remote -Sensing of the Lower Ionosphere with AWESOME Receivers: Solar Flares, Lightning-induced Electron Precipitation, Sudden Ionospheric Disturbances, Sprites, Gravity Waves and Gamma-ray Flares  

NASA Astrophysics Data System (ADS)

Stanford University Very Low Frequency (VLF) radio receivers have been used extensively for remote sensing of the ionosphere and the magnetosphere. Among the phenomena that can be uniquely measured via VLF receivers are radio atmospherics, whistlers, electron precipitation, solar flares, sudden ionospheric disturbances, gravity waves, sprites, and cosmic gamma-ray flares. With the use of simple square air-core magnetic loop antennas of a couple of meters in size, the sensitivity of these instruments allows the measurement of magnetic fields as low as several tens of femtoTesla per root Hz, in the frequency range of ~300 Hz to 50 kHz. This sensitivity well exceeds that required to detect any event above the ambient atmospheric noise floor, determined by the totality of lightning activity on this planet. In recent years, as cost of production, timing accuracy (due to low cost GPS cards), and data handling flexibility of the systems has improved, it has become possible to distribute many of these instruments in the form of arrays, to perform interferometric and holographic imaging of the lower ionosphere. These goals can be achieved using the newest version of the Stanford VLF receiver, known as AWESOME: Atmospheric Weather Educational System for Observation and Modeling of Electromagnetics. In the context of the IHY/UNBSS program for 2007, the AWESOME receivers can be used extensively as part of the United Nations initiative to place scientific instruments in developing countries. Drawing on the Stanford experiences from setting up arrays of VLF receivers, including an interferometer in Alaska, the Holographic Array for Ionospheric and Lightning research (HAIL) consisting of instruments at 13 different high schools in mid-western United States, a broader set of ELF/VLF receivers in Alaska, and various receivers abroad, including in France, Japan, Greece, Turkey, and India, a global network of ELF/VLF receivers offer possibilities for a wide range of scientific topics, as well as serving as a means for educational outreach. Most recently, AWESOME receivers were placed in several North African countries, including Tunisia, Algeria, and Morocco. The new AWESOME version is substantially lower in cost, and easier to set-up and use. Nevertheless, the receivers offer the same ultimate levels of resolution in time, sensitivity and dynamic range, as well as ease of handling of data that is used by researchers conducting cutting edge ionospheric and Space Weather research. In this context, the placement of these systems at underdeveloped host countries provides an open-ended potential for exploration, limited only by the imagination and drive of the users.

Inan, U. S.; Cohen, M.; Scherrer, P.; Scherrer, D.

2006-11-01

304

The 1979 March 5 gamma-ray transient: Was it a classic gamma-ray burst?  

Microsoft Academic Search

The 1979 March 5 gamma-ray transient has long been thought to be fundamentally different from the classic gamma-ray bursts (GRBs). It had recurrences, pulsations, and a soft spectral component unlike classic GRBs. With the exception of the soft component reported from the KONUS experiment, the unusual characteristics of the March 5 transient were detectable primarily because it was extremely bright.

E. E. Fenimore; R. W. Klebesadel; J. G. Laros

1996-01-01

305

The 1979 March 5 Gamma-Ray Transient: Was It a Classic Gamma-Ray Burst?  

Microsoft Academic Search

The 1979 March 5 gamma-ray transient has long been thought to be fundamentally different from the classic gamma-ray bursts (GRBs). It had recurrences, pulsations, and a soft spectral component unlike classic GRBs. With the exception of the soft component reported from the KONUS experiment, the unusual characteristics of the March 5 transient were detectable primarily because it was extremely bright.

E. E. Fenimore; R. W. Klebesadel; J. G. Laros

1996-01-01

306

Searching for Gamma-ray Pulsars using the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope  

Microsoft Academic Search

The Large Area Telescope (LAT) on the recently launched Fermi Gamma-ray Space Telescope (formerly GLAST) has greatly increased the sensitivity to astrophysical gamma-ray sources over previous gamma-ray telescope missions such as the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma-Ray Observatory (CGRO). The LAT has a much larger effective area and field of view, helping to increase the

Michael Dormody

2009-01-01

307

GRI: The Gamma-Ray Imager mission  

NASA Astrophysics Data System (ADS)

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

Kndlseder, Jrgen

308

Luminosity Evolution of Gamma-Ray Pulsars  

NASA Astrophysics Data System (ADS)

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

Hirotani, Kouichi

2013-04-01

309

Inverse compton scattering gamma ray source  

NASA Astrophysics Data System (ADS)

Special Nuclear Materials (SNM) (e.g. U-235, Pu-239) can be detected by active interrogation with gamma rays (>6 MeV) through photofission. For long-range detection (1 km), an intense beam of gamma rays (1014 per second) is required in order to produce measurable number of neutrons. The production of such fluxes of gamma rays, and in the pulse formats useful for detection, presents many technical challenges, and requires novel approaches to the accelerator and laser technology. RadiaBeam is currently designing a gamma ray source based on Inverse Compton Scattering (ICS) from a high-energy electron beam. To achieve this, improvements in photoinjector, linac, final focus, and laser system are planned. These enhanced sub-systems build on parallel work being performed at RadiaBeam, UCLA, and elsewhere. A high-repetition rate photoinjector, a high-gradient S-band linac, and a laser pulse recirculator will be used. The proposed system will be a transportable source of high-flux, high-energy quasi-monochromatic gamma rays for active interrogation of special nuclear materials.

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

2009-09-01

310

Gamma-ray Emission in GPS Quasars  

NASA Astrophysics Data System (ADS)

In this paper, it is argued that the relativistic jets in gigahertz peaked spectrum (GPS) quasars are oriented at small angle to the line of sight and are powerful gamma-ray sources. Besides luminous hard gamma-ray emission, most of them may have significant soft gamma-ray and X-ray emission due to infrared photons from very dense and dusty nuclear interstellar media in GPS quasars, which is consistent with ASCA X-ray observations. Because Compton cooling in GPS quasars is stronger than in flat spectrum radio quasars (FSRQs), synchrotron emission in GPS quasars may less dominate over thermal emission of the accretion disk and hot dust than in FSRQs, hence most GPS quasars show low optical polarization and small variability. We suggest that it is the significant radio emission of electron/positron pairs produced by the interaction of gamma-rays with the dense gas and dust grains in GPS quasars that makes GPS quasars show steep radio spectra, low radio polarization, and relatively faint VLBI/VLBA cores. The gamma-ray emission in GPS quasars can be tested by the observation of the INTEGRAL and GLAST in the near future.

Bai, Jin-Ming

2005-06-01

311

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

312

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

313

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

314

Shape of the 4.438 MeV gamma-ray line of 12C from proton and alpha-particle induced reactions on 12C and 16O  

Microsoft Academic Search

We calculated in detail the angular distribution of gamma rays and the resulting shape of the gamma-ray line produced by the nuclear deexcitation of the 4.439 MeV state of 12C following proton and alpha-particle interactions with 12C and 16O in the energy range from threshold to 100 MeV per nucleon, making use of available experimental data. In the proton energy

J. Kiener; N. de Srville; V. Tatischeff

2001-01-01

315

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

316

Population genetics of induced mutations.  

PubMed

The contribution of induced mutations to the burden of genetic disease in the context of population genetics is considered. A clear distinction is made between the effects of genetic disease and mutational events. Much of the existing burden of genetic disease is a consequence of mutations that occurred in the past. The problem of distinguishing between spontaneous and induced mutations is discussed. Molecular genetics techniques are blurring the definitions of these terms. Classical population genetics shows that the frequency of affected individuals will reach an equilibrium depending on the mutation rate and the selective pressure against affected individuals. Increasing the mutation rate or reducing the selective pressures would result in a new equilibrium with an increase in the frequency in subsequent generations of affected individuals with dominant and X-linked mutant alleles. The increase in the number of recessive mutant alleles would be much slower and take many generations to reach the new equilibrium level. One assumption behind such equilibria is random mating. Changes in human demography with a rapid increase in population size, the breakup of small, relatively inbred subpopulations, and relaxed selective pressures will lead to a new equilibrium for recessive genes at probably higher frequencies. These factors will be the major contributors to increasing the burden of recessive genetic disease by increasing the total numbers of cases. The proportion of the population with a genetic disease will also continue to grow as a greater proportion of the population survives to late middle age and succumbs to diseases associated with old age, such as cancer, circulatory disease, dementias, and diabetes, each of which is likely to have a genetic component.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7789363

Lovell, D P

1995-01-01

317

Gamma-ray and neutron spectroscopy of planetary surfaces and atmospheres  

SciTech Connect

The neutrons and gamma rays escaping from a planet can be used to map the concentrations of various elements in its surface. In a planet, the high-energy particles in the galactic cosmic rays induce a cascade of particles that includes many neutrons. The ..gamma.. rays are made by the decay of the naturally-occurring radioelements and by nuclear excitations induced by cosmic-ray particles and their secondaries (especially neutron capture or inelastic scattering reactions). After a short history of planetary ..gamma..-ray and neutron spectroscopy, the ..gamma..-ray spectrometer and active neutron detection system planned for the Mars Observer Mission are presented. The results of laboratory experiments that simulate the cosmic-ray bombardments of planetary surfaces and the status of the theoretical calculations for the processes that make and transport neutrons and ..gamma.. rays will be reviewed. Studies of Mars, including its atmosphere, are emphasized, as are new ideas, concepts, and problems that have arisen over the last decade, such as Doppler broadening and peaks from neutron scattering with germanium nuclei in a ..gamma..-ray spectrometer. 23 refs., 1 fig.

Reedy, R.C.

1987-01-01

318

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

319

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

320

Emission region of gamma ray bursts  

SciTech Connect

Within the last few years the rapid accumulation of gamma ray burst spectral data, especially those of KONUS and SMM, has made the confrontation between theories of the gamma ray emission mechanisms and observations much more urgent and challenging. At present the most viable model seems to be some combination of inverse Comptonization and synchrotron emission. In this paper we limit the acceptable parameter space of the emission region by taking into account the maximum set of observational constraints. We then apply these to two specific scenarios: surface emission versus magnetospheric emission and consider some observable predictions based on these scenarios.

Liang, E.P.

1985-05-01

321

Photospheric Emission from Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

In spite of extensive research over the past decades, a complete physical picture of the origin of the prompt gamma-ray burst emission is still lacking. During recent years, evidence has been accumulating that the jet photosphere plays an important role. In this paper we summarize the lessons learned from Fermi observations regarding the behavior of the photosphere and discuss why photospheric emission does not necessarily appear as blackbody radiation. We concentrate on two strong and important bursts, GRB 090902B and GRB 110721A, which serve as examples of the standard appearance photospheric emission may have in gamma-ray burst spectra.

Axelsson, M.

2013-07-01

322

Gamma ray energy tracking in GRETINA  

NASA Astrophysics Data System (ADS)

The next generation of stable and exotic beam accelerators will provide physics opportunities to study nuclei farther away from the line of stability. However, these experiments will be more demanding on instrumentation performance. These come from the lower production rate for more exotic beams, worse beam impurities, and large beam velocity from the fragmentation and inverse reactions. Gamma-ray spectroscopy will be one of the most effective tools to study exotic nuclei. However, to fully exploit the physics reach provided by these new facilities, better gamma-ray detector will be needed. In the last 10 years, a new concept, gamma-ray energy tracking array, was developed. Tracking arrays will increase the detection sensitivity by factors of several hundred compared to current arrays used in nuclear physics research. Particularly, the capability of reconstructing the position of the interaction with millimeters resolution is needed to correct the Doppler broadening of gamma rays emitted from high velocity nuclei. GRETINA is a gamma-ray tracking array which uses 28 Ge crystals, each with 36 segments, to cover .5ex1 -.1em/ -.15em.25ex4 of the 4? solid angle. The gamma ray tracking technique requires detailed pulse shape information from each of the segments. These pulses are digitized using 14-bit 100 MHz flash ADCs, and digital signal analysis algorithms implemented in the on-board FPGAs provides energy, time and selection of pulse traces. A digital trigger system, provided flexible trigger functions including a fast trigger output, and also allows complicated trigger decisions to be made up to 20 microseconds. Further analyzed, carried out in a computer cluster, determine the energy, time, and three-dimensional positions of all gamma-ray interactions in the array. This information is then utilized, together with the characteristics of Compton scattering and pair-production processes, to track the scattering sequences of the gamma rays. GRETINA construction is completed in March 2011, and extensive engineering runs were carried out using radioactive sources, and beams from the 88-Inch Cyclotron at LBNL. The data obtained will be used to optimize its performance. Then the first scientific campaign will start in March 2012 at NSCL MSU.

Lee, I. Y.

2011-10-01

323

Gamma ray sources using imperfect relativistic mirrors  

SciTech Connect

The collective backscattering of intense laser radiation by energetic electron beams is considered. Exact solutions for the radiation field are obtained, for arbitrary electron pulse shapes and laser intensities. The electron beams act as imperfect nonlinear mirrors on the incident laser radiation. This collective backscattering process can lead to the development of new sources of ultrashort pulse radiation in the gamma-ray domain. Numerical examples show that, for plausible experimental conditions, intense pulses of gamma rays, due to the double Doppler shift of the harmonics of the incident laser radiation, can be produced using the available technology, with durations less than one attosecond.

Mendonca, J. T. [GoLP and CFIF, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal); Serbeto, A. [Instituto de Fisica, Universidade Federal Fluminense, 24210-340 Rio de Janeiro (Brazil)

2008-11-15

324

Identifiability of UHE Gamma-ray Air Showers by Neural-Network-Analysis  

NASA Astrophysics Data System (ADS)

The chemical composition of Ultra-High-Energy (UHE) comic rays is one of unsolved mysteries, and its study will give us fruitful information on the origin and acceleration mechanism of UHE cosmic rays. Especially, a detection of UHE gamma-rays by hybrid experiments, such as AUGER and TA, will be a key to solve these questions. The characteristics of UHE gamma-ray showers have been studied on lateral and longitudinal structure of shower particles by AIRES and our own simulation code, so far. There are apparent differences in a slope of lateral distribution (Eta) and a depth of shower maximum (Xmax) between gamma-ray and proton induced showers because UHE gamma-ray showers are affected by the LPM effect and the geomagnetic cascading process in an energy region of > 1019.5eV. Different features between gamma-ray and proton showers are pointed out from the simulation study and an identifiability of gamma-ray showers from proton ones is also discussed by the method of Neural-Network-Analysis.

Wada, Y.; Inoue, N.; Miyazawa, K.; et al.

325

HYPERNUCLEAR STRUCTURE FROM GAMMA-RAY SPECTROSCOPY.  

SciTech Connect

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

MILLENER,D.J.

2003-10-14

326

Nature of Cosmic gamma Ray Bursts.  

National Technical Information Service (NTIS)

The nature of cosmic gamma ray burst is studied. The sources of the observed gamma bursts are supposed to be presented by the two populations of galactic objects, namely: the old neutron stars concentrated in the galactic disk; and the old degenerated dwa...

N. I. Shakura N. N. Shakura

1990-01-01

327

Gamma ray activity of neodymium samples  

NASA Astrophysics Data System (ADS)

The gamma ray activity of three samples of natural neodymium has been measured and the concentration of radioactive elements from uranium and thorium chains as well as that from radioactive isotopes of lantanium and lutetium has been quantitatively determined. All the samples show significant contaminations up to p.p.m.

Arpesella, C.; Bellotti, E.; Miramonti, L.; Sverzellati, P. P.

1996-02-01

328

Gamma ray activity of neodymium samples  

Microsoft Academic Search

The gamma ray activity of three samples of natural neodymium has been measured and the concentration of radioactive elements from uranium and thorium chains as well as that from radioactive isotopes of lantanium and lutetium has been quantitatively determined. All the samples show significant contaminations up to p.p.m.

C. Arpesella; E. Bellotti; L. Miramonti; P. P. Sverzellati

1996-01-01

329

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

330

Glass as a gamma Ray Dosemeter.  

National Technical Information Service (NTIS)

The advantages of glass as a gamma -rays dosemeter are studied. Experiments have shown that ordinary microscope object glass can be used as a dosemeter, which dose range for linear response extends from about 10 exp 4 -10 exp 6 rads. Heat treatment of the...

Sutrisno Puspodikoro

1978-01-01

331

Gamma-ray Burst Educator Guide  

NSDL National Science Digital Library

This guide accompanies an educational wallsheet that uses Gamma-ray Bursts as an engagement to teach selected topics in physical science and mathematics. It features four curriculum enhancement activities, background information, assessment information, student worksheets, extension and transfer activities, and detailed information about the physical science and mathematics content standards for grades 9-12.

2004-01-01

332

Gamma-ray Burst Science with GLAST  

SciTech Connect

The recent observations of Gamma-ray bursts (GRBs) with Swift have provided unprecedented information about nature of GRBs. The launch of GLAST in late 2007 will unveil the final spectral regime of GRB prompt emission and afterglows. Here we briefly review various theoretical suggestions of producing high energy photons from GRB fireballs, and discuss what observatons are expected from the GLAST observatory.

Zhang Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States)

2007-07-12

333

Cosmological aspects of gamma ray bursts  

Microsoft Academic Search

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

Razieh Behkam

2010-01-01

334

Hypernuclear Structure from Gamma-Ray Spectroscopy.  

National Technical Information Service (NTIS)

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

D. J. Millener

2004-01-01

335

Supernovae, hypernovae and gamma ray bursts  

Microsoft Academic Search

Recent observations suggest that gamma ray bursts (GRBs) and their afterglows are produced by highly relativistic jets emitted in core collapse supernova explosions (SNe). The result of the event, probably, is not just a compact object plus a spherical ejecta: within a day, a fraction of the parent star falls back to produce a thick accretion disk around the compact

Arnon Dar

2001-01-01

336

Developments in Mercuric Iodide gamma Ray Imaging.  

National Technical Information Service (NTIS)

A mercuric iodide gamma-ray imaging array and camera system previously described has been characterized for spatial and energy resolution. Based on this data, a new camera is being developed to more fully exploit the potential of the array. Characterizati...

B. E. Patt A. G. Beyerle R. C. Dolin C. Ortale

1987-01-01

337

Gamma-ray Astrophysics with AGILE  

SciTech Connect

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

Longo, Francesco [Department of Physics, University of Trieste (Italy)]|[INFN, Section of Trieste (Italy); Tavani, M.; Barbiellini, G.; Argan, A.; Basset, M.; Boffelli, F.; Bulgarelli, A.; Caraveo, P.; Cattaneo, P.; Chen, A.; Costa, E.; Del Monte, E.; Di Cocco, G.; Di Persio, G.; Donnarumma, I.; Feroci, M.; Fiorini, M.; Foggetta, L.; Froysland, T.; Frutti, M. (and others)

2007-07-12

338

Gamma Ray Burst Detectives (Elementary School)  

NSDL National Science Digital Library

This interactive resource invites students to join NASA to find the source of gamma ray bursts, the single biggest explosions in the Universe since the Big Bang. The web site features an animation, information on three possible star sources, and a check yes or no for each star with feedback.

Wpsu

2010-04-29

339

Accretion Models of Gamma-Ray Bursts  

Microsoft Academic Search

Many models of gamma-ray bursts (GRBs) involve accretion onto a compact object, usually a black hole, at a mass accretion rate on the order of a fraction of a solar mass per second. If the accretion disk is larger than a few tens or hundreds of Schwarzschild radii, the accretion will proceed via a convection-dominated accretion flow (CDAF) in which

Ramesh Narayan; Tsvi Piran; Pawan Kumar

2001-01-01

340

Positron Annihilation in gamma-Ray Bursts.  

National Technical Information Service (NTIS)

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...

A. K. Harding

1990-01-01

341

Gamma-Ray Burst Environments and Progenitors  

Microsoft Academic Search

Likely progenitors for gamma-ray bursts (GRBs) are the mergers of compact objects or the explosions of massive stars. These two cases have distinctive environments for the GRB afterglow: the compact object explosions occur in the interstellar medium (ISM) and those of massive stars occur in the preburst stellar wind. We calculate the expected afterglow for a burst in a Wolf-Rayet

Roger A. Chevalier; Zhi-Yun Li

1999-01-01

342

Gamma-Ray Bursts The Second Revolution  

Microsoft Academic Search

Gamma-ray bursts GRBs are among the most mysterious astronomical phenomenon ever discovered. Unlike most astronomical discoveries which were explained within weeks or months after their initial discovery, GRBs remain a puzzle for more than thirty years. During the last decade our understanding of GRBs has undergone two major revolutions. First, BATSE discovered that GRBs are distributed isotropically over the sky

Tsvi Piran

1998-01-01

343

Three Types of Gamma-Ray Bursts  

Microsoft Academic Search

A multivariate analysis of gamma-ray burst (GRB) bulk properties is presented to discriminate between distinct classes of GRBs. Several variables representing burst duration, fluence, and spectral hardness are considered. Two multivariate clustering procedures are used on a sample of 797 bursts from the Third BATSE Catalog, a nonparametric average linkage hierarchical agglomerative clustering procedure validated with Wilks' Lambda^* and other

Soma Mukherjee; Eric D. Feigelson; Gutti Jogesh Babu; Fionn Murtagh; Chris Fraley; Adrian Raftery

1998-01-01

344

Theories of Gamma-Ray Bursts  

Microsoft Academic Search

The gamma ray burst phenomenon is reviewed from a theoretical point of view, with emphasis on the fireball shock scenario of the prompt emission and the longer wavelength afterglow. Recent progress and issues are discussed, including spectral-temporal evolution, localizations, jets, spectral lines, environmental and cosmological aspects, as well as some prospects for future experiments in both electromagnetic and nonelectromagnetic channels.

P. Mszros

2002-01-01

345

Supernovae and gamma-ray bursts  

Microsoft Academic Search

The observed properties of Supernovae (SNe) and Cosmic Gamma-ray Bursts (GRBs) are briefly summarized. Measurement of SNe distances in cosmology gives important results. It is explained how the acceleration of expansion of Universe was established using SNe. I point out which features of gaseous Supernova Remnants and GRBs (and their afterglows) are common and what is different in those events.

Sergei Blinnikov

2006-01-01

346

The Cosmic Gamma-Ray Bursts  

Microsoft Academic Search

Cosmic gamma-ray bursts are one of the great frontiers of astrophysics today. They are a playground of relativists and observers alike. They may teach us about the death of stars and the birth of black holes, the physics in extreme conditions, and help us probe star formation in the distant and obscured universe. In this review we summarise some of

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

2002-01-01

347

Balloon borne X and gamma ray experiments  

Microsoft Academic Search

A brief history of X and gamma ray astronomy is presented, in order to show the scientific interest in this field of research, and to define the type of work needed for further progress. A general description of the experimental apparatus is given, with a summary of typical detectors and their characteristics. Following this is a discussion of the numerous

K. Hurley

1975-01-01

348

The Supernova Gamma-Ray Burst Connection  

Microsoft Academic Search

There is now clear evidence for Type I supernovae happening in coincidence with two long soft gamma-ray bursts (GRBs) and compelling observations that suggest this may be a common occurrence. At the same time, it is clear that only a small fraction, 1%, of supernovae make GRBs. Why do some stars die one way, and others, another? I will argue

S. E. Woosley

2005-01-01

349

The Supernova Gamma-Ray Burst Connection  

Microsoft Academic Search

This program brought together scientists in both Supernovae and Gamma-Ray Bursts to merge the current progress of both disciplines. We used this combined knowledge to address a range of SN\\/GRB questions such as: Do all long duration GRBs have an underlying SN?, What is special about SNe associated with GRBs?, Where do XRFs, which share several attributes with GRBs, fit

Christopher L. Fryer; Shrinivas R. Kulkarni; Ken'ichi Nomoto; Philip Pinto

2006-01-01

350

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

351

First RHESSI terrestrial gamma ray flash catalog  

Microsoft Academic Search

We present a summary of data from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) terrestrial gamma ray flash (TGF) catalog. We describe the RHESSI search algorithm and discuss its limitations due to its design emphasis on cleanliness rather than completeness. This search algorithm has identified 820 TGFs between March of 2002 and February of 2008. Radiation damage to

B. W. Grefenstette; D. M. Smith; B. J. Hazelton; L. I. Lopez

2009-01-01

352

Gamma Ray Telescope Senses High-Energy Radiation  

NSDL National Science Digital Library

This video from NASA describes the GLAST satellite, which is equipped with a gamma-ray telescope, and shares some background about the kinds of extreme universal phenomena indicated by the presence of gamma rays.

Wnet

2011-11-02

353

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

354

Gamma ray lines from the galactic center and gamma ray transients  

SciTech Connect

The observations and interpretations of cosmic (nonsolar) gamma ray lines are discussed. The most prominent of these lines is the e(+)e(-) annihilation line which was observed from the Galactic Center and from several gamma ray transients. At the Galactic Center the e(+)e(-) pairs are probably produced by an accreting massive black hole (solar mass of approximately one million) and annihilate within the central light year to produce a line at almost exactly 0.511 MeV. In gamma ray transients the annihilation line is redshifted by factors consistent with neutron star surface redshifts. Other observed transient gamma ray lines appear to be due to cyclotron absorption in the strong magnetic fields of neutron stars, and nuclear deexcitations and neutron capture, which could also occur on or around these objects.

Ramaty, R.; Leiter, D.; Lingenfelter, R.E.

1981-04-01

355

Gamma ray lines from the Galactic Center and gamma ray transients  

NASA Astrophysics Data System (ADS)

The observations and interpretations of cosmic (nonsolar) gamma ray lines are discussed. The most prominent of these lines is the e(+)e(-) annihilation line which was observed from the Galactic Center and from several gamma ray transients. At the Galactic Center the e(+)e(-) pairs are probably produced by an accreting massive black hole (solar mass of approximately one million) and annihilate within the central light year to produce a line at almost exactly 0.511 MeV. In gamma ray transients the annihilation line is redshifted by factors consistent with neutron star surface redshifts. Other observed transient gamma ray lines appear to be due to cyclotron absorption in the strong magnetic fields of neutron stars, and nuclear deexcitations and neutron capture, which could also occur on or around these objects.

Ramaty, R.; Leiter, D.; Lingenfelter, R. E.

1981-04-01

356

Muon Detection of TEV Gamma Rays from Gamma-Ray Bursts  

Microsoft Academic Search

Because of the limited size of the satellite-borne instruments, it has not been possible to observe the flux of gamma-ray bursts (GRBs) beyond GeV energy. We here show that it is possible to detect the GRB radiation of TeV energy and above by detecting the muon secondaries produced when the gamma rays shower in Earth's atmosphere. Observation is made possible

J. Alvarez-Muiz; F. Halzen

1999-01-01

357

Gamma-ray Emission from the gamma-ray-loud BL Lac Objects  

Microsoft Academic Search

Using the HST observation data of BL Lac objects by Urry et al. and gamma-ray observation data, we find that there is a correlation between Fgamma and Fnuclei for gamma-ray-loud BL Lac objects (correlation coefficients: gamma=0.63, p=4.0 10-2), but no correlation between Fgamma and FOhost, where FOnuclei and FOhost are the fluxes of nuclei and host galaxy in V-band.

Guang-Zhong Xie; Ben-Zhong Dai; En-Wei Liang; Zhao-Hua Xie

2001-01-01

358

Gamma-Ray Lenses for Astrophysicsand the Gamma-Ray Imager Mission GRI  

Microsoft Academic Search

Observations of the gamma-ray sky reveal the most powerful sources and the most violent events in the Universe. While at lower wavebands the observed emission is generally dominated by thermal processes, the gamma-ray sky provides us with a view on the non-thermal Universe. Here particles are accelerated to extreme relativistic energies by mechanisms which are still poorly understood, and nuclear

Cornelia B. Wunderer; Peter v. Ballmoos; Nicolas Barriere; Angela Bazzano; Steven E. Boggs; Finn Christensen; Filippo Frontera; Margarida Hernanz; Jrgen Knodlseder; Andreas Zoglauer

2009-01-01

359

Medium-Energy Gamma-Ray Astrophysics with the 3DTI Gamma-Ray Telescope  

Microsoft Academic Search

Gamma-ray observations in the medium energy range (0.50-50.0 MeV) are central to unfolding many outstanding questions in astrophysics. The challenges of medium-energy gamma-ray observations, however, are the low photon statistics and large backgrounds. We review these questions, address the telescope technology requirements, and describe our development of the 3-Dimensional Track Imaging (3-DTI) Compton telescope and its performance for a new

Stanley D. Hunter; Robert G. Baker; Louis M. Barbier; Peter F. Bloser; LaVida Cooper; John F. Krizmanic; Jason T. Link; Mark L. McConnell; Georgia A. de Nolfo; James M. Ryan; Satpal Singh; Seunghee Son

2006-01-01

360

The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts  

Microsoft Academic Search

I present an analysis of the gamma-ray and afterglow energies of a complete sample of 16 short-duration GRBs with prompt X-ray follow-up. I find that 80% of the bursts exhibit a linear correlation between their gamma-ray fluence and the afterglow X-ray flux normalized to t=1 day, a proxy for the kinetic energy of the blast wave (FX,1~F1.01+\\/-0.27gamma). An even tighter

E. Berger

2007-01-01

361

A Balloon-Borne Gamma-Ray Polarimeter for Gamma-Ray Bursts  

Microsoft Academic Search

We have developed a design for a hard X-ray polarimeter operating in the energy range from 50 to 500 keV. This modular design, known as GRAPE (Gamma-Ray Polarimeter Experiment), was successfully demonstrated with partially polarized gamma-ray sources in the lab and fully polarized photon beams at Argonne National Laboratory. In June of 2007, a GRAPE engineering model flew on a

M. L. McConnell; C. M. Bancroft; P. F. Bloser; T. P. Connor; J. S. Legere; J. R. Macri; J. M. Ryan

2009-01-01

362

Absorption of gamma-rays in the 5 March 1979 gamma-ray burst source  

Microsoft Academic Search

Absorption of gamma-rays above the source of their burst on March 5, 1979 is considered, in order to measure their distance. The results of a spherical model of the gamma-ray burst shows that unless the photons were collimated during the burst, the gamma-gamma optical thickness above an isotropically emitting burst source would be as high as 10 to the 5th

A. A. Zdziarski

1984-01-01

363

The Gamma-ray Large Area Space Telescope and Gamma-Ray Bursts  

Microsoft Academic Search

The Gamma-ray Large Area Telescope (GLAST) is a satellite-based observatory to study the high energy gamma-ray sky. The main instrument on GLAST, the Large Area Telescope (LAT) is a pair-conversion telescope that will survey the sky from 20 MeV to greater than 300 GeV With the GLAST launch in 2007, the LAT will open a new and important window on

Julie McEnery

2006-01-01

364

Light Curves of Swift Gamma-Ray Bursts  

Microsoft Academic Search

Recent observations from the Swift gamma-ray burst mission indicate that a fraction of gamma-ray bursts are characterized by a canonical behavior of the X-ray afterglows. We present an effective theory that allows us to account for X-ray light curves of both (short\\/long) gamma-ray bursts and X-ray-rich flashes. We propose that gamma-ray bursts originate from massive magnetic-powered pulsars.

Paolo Cea; Via G. Amendola

2007-01-01

365

Gamma-Ray Observatory - The next great observatory in space  

Microsoft Academic Search

The Gamma-Ray Observatory (GRO) which is part of NASA's Great Observatories space program is presented. The GRO is equipped with the Burst and Transient Source Experiment (which detects low-energy gamma-ray photons from 20 keV to 600 keV and locates sources of gamma-ray bursts), the Oriented Scintillation Spectrometer Experiment (which detects celestial gamma rays from 100 keV to 10 MeV and

Valerie Neal; Gerald Fishman; Donald Kniffen

1990-01-01

366

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

367

Cygnus X-3 and EGRET Gamma-Ray Observations  

Microsoft Academic Search

0!rQ1The Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma Ray Observatory observed the Cygnus region in 14 different viewing periods during 1991 May to 1994 July. We present here our results on unpulsed and pulsed emissions of gamma rays at E > 50 MeV from Cyg X-3. While we detect a gamma-ray source consistent with the position of

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

1997-01-01

368

Advanced gamma-ray astronomy telescope experiment: AGATE  

Microsoft Academic Search

In order to continue the achievements in high energy (10 MeV - 100 GeV) gamma-ray astronomy made with the Energetic Gamma-Ray Experiment Telescope (EGRET) instrument on the Compton Gamma Ray Observatory (CGRO), a 'next generation' high energy gamma- ray telescope with a large increase in sensitivity coupled with improved angular resolution will be required. This 'next generation' telescope is envisioned

Brenda L. Dingus; D. L. Bertsch; Rajani Cuddapah; Carl E. Fichtel; Stanley D. Hunter; D. J. Thompson

1993-01-01

369

Observations of GRB 990123 by the Compton Gamma Ray Observatory  

Microsoft Academic Search

GRB 990123 was the first burst from which simultaneous optical, X-ray, and gamma-ray emission was detected; its afterglow has been followed by an extensive set of radio, optical, and X-ray observations. We have studied the gamma-ray burst itself as observed by the Compton Gamma Ray Observatory detectors. We find that gamma-ray fluxes are not correlated with the simultaneous optical observations

M. S. Briggs; D. L. Band; R. M. Kippen; R. D. Preece; C. Kouveliotou; J. van Paradijs; G. H. Share; R. J. Murphy; S. M. Matz; A. Connors; C. Winkler; M. L. McConnell; J. M. Ryan; O. R. Williams; C. A. Young; B. Dingus; J. R. Catelli; R. A. M. J. Wijers

1999-01-01

370

A high energy gamma ray survey of Cygnus and Cassiopeia  

Microsoft Academic Search

A gamma-ray telescope was used to search for celestial sources at energies above several hundred MeV. Upper limits for the gamma ray emission of six strong X-ray sources are given. The atmospheric generation rate of secondary gamma rays was also determined. The gamma ray detector is a large balloon-borne gas Cherenkov detector which has been previously described. It has a

M. F. Campbell

1974-01-01

371

Very High Energy Gamma Ray Extension of GRO Observations.  

National Technical Information Service (NTIS)

This has been an exiciting year for high energy gamma-ray astronomy, both from space and from ground-based observatories. It has been a particularly active period for the Whipple Observatory gamma-ray group. In phase 1 of the Compton Gamma Ray Observatory...

T. C. Weekes

1992-01-01

372

GLAST and Ground-Based gamma-ray Astronomy.  

National Technical Information Service (NTIS)

The launch of the Gamma-ray Large Area Space Telescope (GLAST) in 2007 will open the possibility of combined studies of astrophysical sources with existing ground-based VHE gamma ray experiments such as H.E.S.S., VERITAS and MAGIC. Ground-based gamma ray ...

B. Giebels F. Longo J. E. Carson J. E. McEnery S. Funk

2007-01-01

373

Imaging and background in low-energy gamma ray astronomy  

Microsoft Academic Search

The current status of low energy gamma ray astronomy is reviewed and the conclusion drawn that the next generation of low energy gamma ray telescopes will require high sensitivity, good timing, and spectral resolution. High angular resolution imaging capability is also considered essential. The imaging of low energy gamma rays is hampered by the difficulties encountered in developing high resolution

Fan Lei

1989-01-01

374

The University of Durham Mark 6 Gamma Ray Telescope  

Microsoft Academic Search

The design, construction and operation of the University of Durham ground-based gamma ray telescope is discussed. The telescope has been designed to detect gamma rays in the = 200 GeV region and to achieve good discrimination between gamma ray and hadron initiated showers in the higher energy region (? 300 GeV). The telescope was commissioned in 1995 and a description

P. Armstrong; P. M. Chadwick; P. J. Cottle; J. E. Dickinson; M. R. Dickinson; N. A. Dipper; W. Hogg; J. Holder; T. R. Kendall; T. J. L. McComb; C. M. Moore; K. J. Orford; S. M. Rayner; I. D. Roberts; M. D. Roberts; M. Robertshaw; S. E. Shaw; K. Tindale; S. P. Tummey; K. E. Turver

1999-01-01

375

The University of Durham Mark 6 Gamma Ray Telescope  

Microsoft Academic Search

The design, construction and operation of the University of Durham ground-based gamma ray telescope is discussed. The telescope has been designed to detect gamma rays in the >= 150 GeV region and to achieve good discrimination between gamma ray and hadron initiated showers using conventional imaging and novel fluctuation measures. The telescope was commissioned in 1995 and a description of

P. M. Chadwick; M. R. Dickinson; N. A. Dipper; J. Holder; T. R. Kendall; T. J. L. McComb; K. J. Orford; S. M. Rayner; I. D. Roberts; S. E. Shaw; K. E. Turver; J. E. Dickinson; M. D. Roberts; S. P. Tummey

1997-01-01

376

Gamma-ray burst data from DMSP satellites.  

National Technical Information Service (NTIS)

A number of gamma-ray bursts have been detected by means of gamma-ray detectors aboard three Air Force Defense Meteorological Satellite Program (DMSP) satellites, in polar orbits at 800 km altitude. The gamma-ray data have a 2-second resolving time, and a...

J. Terrell R. W. Klebesadel P. Lee J. W. Griffee

1991-01-01

377

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

378

New Gamma-ray flaring activity from NRAO 676  

NASA Astrophysics Data System (ADS)

The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed a renewed gamma-ray flaring activity from a gamma-ray source not included in any of the Fermi LAT catalogs.

Cutini, Sara

2012-10-01

379

A new analysis method for reconstructing the arrival direction of TeV gamma rays using a single imaging atmospheric Cherenkov telescope  

Microsoft Academic Search

We present a method of atmospheric Cherenkov imaging which reconstructs the unique arrival direction of TeV gamma rays using a single telescope. The method is derived empirically and utilizes several features of gamma-ray-induced air showers which determine, to a precision of \\/0.12, the arrival direction of photons on an event-by-event basis. Data from the Whipple Observatory's 10 m gamma-ray telescope

R. W. Lessard; J. H. Buckley; V. Connaughton; S. Le Bohec

2001-01-01

380

A new analysis method for reconstructing the arrival direction of TeV gamma rays using a single imaging atmospheric Cherenkov telescope  

Microsoft Academic Search

We present a method of atmospheric Cherenkov imaging which reconstructs the unique arrival direction of TeV gamma rays using a single telescope. The method is derived empirically and utilizes several features of gamma-ray-induced air showers which determine, to a precision of 0.12, the arrival direction of photons on an event-by-event basis. Data from the Whipple Observatory's 10 m gamma-ray telescope

R. W. Lessard; J. H. Buckley; V. Connaughton; S. Le Bohec

2001-01-01

381

Intrinsic germanium gamma-ray data from the New American Petroleum Institute spectral gamma-ray calibration models  

Microsoft Academic Search

High-resolution gamma-ray spectra have been recorded at the new American Petroleum Institute (API) spectral gamma-ray logging calibration center with a US Department of Energy passive spectral gamma-ray logging unit. These measurements were completed before gamma-ray source concentrations were assigned to the calibration model zones. Analyses of spectra gathered from five of the calibration zones yielded linear relationships between: (1) tentative

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

1991-01-01

382

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

383

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

384

Detection of high-energy gamma rays from quasar PKS 0528 + 134 by EGRET on the Compton Gamma Ray Observatory  

Microsoft Academic Search

The first several pointing directions of the Compton Gamma Ray Observatory, launched on 1991 April 5, were toward the Galactic anticenter. In addition to the known gamma-ray sources, Crab and Geminga, high-energy gamma-ray emission was observed from the quasar PKS 0528 + 134 by the Energetic Gamma Ray Experiment Telescope (EGRET). A redshift measurement, reported here, of 2.07 confirms the

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

1993-01-01

385

Effects of neutrons and gamma-rays on polymethylmethacrylate plastic optical fiber  

NASA Astrophysics Data System (ADS)

The effects of neutron and gamma-ray irradiation on a polymethylmethacrylate (PMMA) plastic optical fiber (POF) were investigated. An improvement in the optical transmission was observed at the beginning of irradiation, but radiation damage (radiation-induced transmission loss in the visible wavelength range) increased as the irradiation continued. To determine the effects of neutrons and gamma-rays, the amount of energy absorbed in the PMMA POF was calculated using the PHITS codes. Energy deposition in the fiber was calculated considering nuclear reactions listed in the nuclear data file used for the Monte Carlo N-particle transport code. The effects of neutron and gamma radiation were observed to be similar with absorbed energy less than 1.2 kGy. However, the transmission loss induced by neutrons was larger than that induced by gamma-rays when higher energy was deposited.

Toh, K.; Sakasai, K.; Nakamura, T.; Soyama, K.; Shikama, T.

2011-10-01

386

Search on extraterrestrial gamma-ray lines from Southern Hemisphere sources with high energy resolution gamma-ray telescopes  

Microsoft Academic Search

The scope of the GEL 1 and 2 balloon-borne gamma ray telescope experiments is described. The gamma ray spectrometer to be used on GEL 1 is described. It is designed to study the nature of the Galactic center positron annihilation 511 KeV line. The telescope effect is achieved through the aperture angle formed by the gamma ray spectrometer anticoincidence crystals.

J. M. Dacosta; J. O. D. Jardim; F. Gonzalez-Blanco; D. J. R. Nordemann; I. M. Martin; S. L. G. Dutra; F. Albernhe; G. Vedrenne; D. Boclet; P. Durouchoux

1981-01-01

387

Mercuric iodide room temperature gamma-ray detectors  

SciTech Connect

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. 3 refs.

Patt, B.E.; Markakis, J.M.; Gerrish, V.M. (EG and G Energy Measurements, Inc., Goleta, CA (USA)); Haymes, R.C. (National Aeronautics and Space Administration, Washington, DC (USA). Astrophysics Div.); Trombka, J.I. (National Aeronautics and Space Administration, Greenbelt, MD (USA). Goddard Space Flight Center)

1989-01-01

388

Balloon-borne gamma-ray telescope with nuclear emulsion  

Microsoft Academic Search

We are planning to observe cosmic gamma-ray in the energy range 10MeV to 100GeV by balloon-borne gamma-ray telescope with nuclear emulsion. Nuclear emulsion is a precise tracker. By detecting starting point of electron pair, gamma-ray direction can be determined precisely (1.4mrad@1-2GeV). This is much better than Fermi Gamma-ray Space Telescope launched June 2008. Now we are developing the gamma-ray telescope

Satoru Takahashi; Shigeki Aoki; Tsutomu Fukuda; Kaname Hamada; Toshio Hara; Atsushi Iyono; Jiro Kawada; Masashi Kazuyama; Koichi Kodama; Masahiro Komatsu; Shinichiro Koshiba; Hirotaka Kubota; Seigo Miyamoto; Motoaki Miyanishi; Kunihiro Mor-Ishima; Naotaka Naganawa; Tatsuhiro Naka; Mitsuhiro Nakamura; Toshiyuki Nakano; Kimio Niwa; Yoshiaki Nonoyama; Keita Ozaki; Hiroki Rokujo; Takashi Sako; Os-Amu Sato; Yoshihiro Sato; Kazuya Suzuki; Atsumu Suzuki; Ikuo Tezuka; Junya Yoshida; Teppei Yoshioka

2010-01-01

389

Balloon-borne gamma-ray telescope with nuclear emulsion  

NASA Astrophysics Data System (ADS)

We are planning to observe cosmic gamma-ray in the energy range 10MeV to 100GeV by balloon-borne gamma-ray telescope with nuclear emulsion. Nuclear emulsion is a precise tracker. By detecting starting point of electron pair, gamma-ray direction can be determined precisely (1.4mrad@1-2GeV). This is much better than Fermi Gamma-ray Space Telescope launched June 2008. Now we are developing the gamma-ray telescope with nuclear emulsion and are planning to observe by balloon flight. Overview and status of our telescope is introduced in this presentation.

Takahashi, Satoru; Aoki, Shigeki; Fukuda, Tsutomu; Hamada, Kaname; Hara, Toshio; Iyono, Atsushi; Kawada, Jiro; Kazuyama, Masashi; Kodama, Koichi; Komatsu, Masahiro; Koshiba, Shinichiro; Kubota, Hirotaka; Miyamoto, Seigo; Miyanishi, Motoaki; Mor-Ishima, Kunihiro; Naganawa, Naotaka; Naka, Tatsuhiro; Nakamura, Mitsuhiro; Nakano, Toshiyuki; Niwa, Kimio; Nonoyama, Yoshiaki; Ozaki, Keita; Rokujo, Hiroki; Sako, Takashi; Sato, Os-Amu; Sato, Yoshihiro; Suzuki, Kazuya; Suzuki, Atsumu; Takahashi, Satoru; Tezuka, Ikuo; Yoshida, Junya; Yoshioka, Teppei

390

The Calculation of Solar Gamma-rays by TALYS  

NASA Astrophysics Data System (ADS)

Solar gamma-ray lines, produced from nuclear reactions of accelerated particles interacting with solar atmosphere ambient medium, are the most direct diagnosis about the acceleration and transport of electrons and ions in solar flares. Analysis of gamma-ray line spectrum in solar flare has provided information about composition, spectrum and angular distribution of the accelerated ions, as well as elemental abundance of the ambient solar atmosphere. A new gamma-ray calculation program was developed by using an efficient nuclear code - TALYS. The theory of gamma-ray production in solar flares is treated in detail. In addition, the characteristics of gamma-ray spectrum are also presented.

Chen, W.; Gan, W. Q.

2011-05-01

391

The Calculation of Solar Gamma-Rays by TALYS  

NASA Astrophysics Data System (ADS)

Solar gamma-ray lines, produced from nuclear reactions of accelerated particles interacting with the solar atmospheric medium, are the most direct diagnosis for the acceleration and transportation of energetic electrons and ions in solar flares. Much information about composition, spectrum, and angular distribution of the accelerated ions, as well as the elemental abundances of the ambient solar atmosphere can be derived from solar gamma-ray line spectra. A new gamma-ray calculation program has been developed by using an efficient nuclear code - TALYS. The theory of gamma-ray production in solar flares is treated in detail. The characteristics of gamma-ray spectrum are also presented.

Chen, Wei; Gan, Wei-Qun

2012-01-01

392

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

2012-08-03

393

Neutron and Prompt Gamma Ray Emission in the Proton Induced Fission of 239Np and 243Am and Spontaneous Fission of 252Cf  

NASA Astrophysics Data System (ADS)

Average prescission < Mnpre > and postscission < Mnpost > neutron multiplicities as well as average ?-ray multiplicity , average energy emitted by ?-rays and average energy per one gamma quantum as a function of mass and total kinetic energy (TKE) of fission fragments were measured in proton induced reactions p+242Pu?243Am, p+238U?239Np (at proton energy Ep=13, 20 and 55 MeV) and spontaneous fission of 252Cf. The solid angle aberration and the Doppler shift in the laboratory angular distribution of ?-ray emission were utilized to obtain the number and energy of ?-rays as functions of single fragment mass. The results in the case of 252Cf, for both average number and average energy as functions of single fragment mass, are characterized by a sawtooth behavior similar to that which is well known for neutron emission. The similar behavior is seen for proton induced fission of 239Np and 243Am. The fragment mass dependence < Mnpost > (m) and (m) show a clear sawtooth structure that is gradually washed out with increasing proton energy Ep. Using the response matrix techniques we were able to distinguish between the statistical dipole (E1) and collective quadrupole (E2) ?-ray emission of single fission fragments.

Krupa, L.; Kniajeva, G. N.; Kliman, J.; Bogatchev, A. A.; Chubarian, G. M.; Dorvaux, O.; Itkis, I. M.; Itkis, M. G.; Khlebnikov, S.; Kondratiev, N. A.; Kozulin, E. M.; Lyapin, V.; Materna, T.; Rubchenia, W.; Pokrovsky, I. V.; Trzaska, W.; Vakhtin, D.; Voskressensky, V. M.

2005-09-01

394

Real time gamma-ray signature identifier  

SciTech Connect

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

395

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

396

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

397

SUB-LUMINOUS {gamma}-RAY PULSARS  

SciTech Connect

Most pulsars observed by the Fermi Large Area Telescope have {gamma}-ray luminosities scaling with spin-down power E-dot as L{sub {gamma}}{approx}(E-dot x 10{sup 33} erg s{sup -1}){sup 1/2}. However, there exist one detection and several upper limits an order of magnitude or more fainter than this trend. We describe these 'sub-luminous' {gamma}-ray pulsars and discuss the case for this being an orientation effect. Of the 12 known young radio pulsars with E-dot >10{sup 34} erg s{sup -1} and d {<=} 2 kpc several are substantially sub-luminous. The limited available geometrical constraints favor aligned geometries for these pulsars, although no one case for alignment is compelling. In this scenario GeV emission detected from such sub-luminous pulsars can be due to a lower altitude, lower-power accelerator gap.

Romani, R. W.; Kerr, M.; Craig, H. A. [Department of Physics, Stanford University, Stanford, CA 94305 (United States); Johnston, S. [Australia Telescope National Facility, CSIRO, Epping, NSW 1710 (Australia); Cognard, I. [Laboratoire de Physique et Chimie de l'Environnement, LPCE UMR 6115 CNRS, 45071 Orleans Cedex 02 (France); Smith, D. A., E-mail: rwr@astro.stanford.edu [Centre d'Etudes Nucleaires de Bordeaux Gradignan, Universite Bordeaux 1, CNRS/IN2p3, 33175 Gradignan (France)

2011-09-01

398

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

399

Neutron-driven gamma-ray laser  

DOEpatents

A lasing cylinder emits laser radiation at a gamma-ray wavelength of 0.87 {angstrom} when subjected to an intense neutron flux of about 400 eV neutrons. A 250 {angstrom} thick layer of Be is provided between two layers of 100 {angstrom} 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, C.D.

1989-03-28

400

SuperAGILE and Gamma Ray Bursts  

SciTech Connect

The solid-state hard X-ray imager of AGILE gamma-ray mission -- SuperAGILE -- has a six arcmin on-axis angular resolution in the 15-45 keV range, a field of view in excess of 1 steradian. The instrument is very light: 5 kg only. It is equipped with an on-board self triggering logic, image deconvolution, and it is able to transmit the coordinates of a GRB to the ground in real-time through the ORBCOMM constellation of satellites. Photon by photon Scientific Data are sent to the Malindi ground station at every contact. In this paper we review the performance of the SuperAGILE experiment (scheduled for a launch in the middle of 2006), after its first onground calibrations, and show the perspectives for Gamma Ray Bursts.

Pacciani, Luigi; Costa, Enrico; Del Monte, Ettore; Donnarumma, Immacolata; Evangelista, Yuri; Feroci, Marco; Frutti, Massimo; Lazzarotto, Francesco; Lapshov, Igor; Rubini, Alda; Soffitta, Paolo; Tavani, Marco [IASF-INAF Rome (Italy); Barbiellini, Guido [INFN Trieste (Italy); Mastropietro, Marcello [CNR Montelibretti (Italy); Morelli, Ennio [IASF-INAF-Bologna (Italy); Rapisarda, Massimo [ENEA Frascati (Italy)

2006-05-19

401

The Compton Gamma Ray Observatory: mission status.  

NASA Astrophysics Data System (ADS)

The Arthur Holly Compton Gamma Ray Observatory (Compton) is the second in NASA's series of Great Observatories. Compton has now been operating for over two and a half years, and has given a dramatic increase in capability over previous gamma-ray missions. The spacecraft and scientific instruments are all in good health, and many significant discoveries have already been made and continue to be made. The authors describe the capabilities of the four scientific instruments and the observing programs for the first three years of the mission. During Phases 2 and 3 of the mission a Guest Investigator program has been in progress with the Guest Observers' time share increasing from 30% to over 50% for the later mission phases.

Gehrels, N.; Chipman, E.; Kniffen, D. A.

402

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

403

Gamma ray bursts: a 1983 overview  

SciTech Connect

Gamma ray burst observations are reviewed with mention of new gamma-ray and optical transient measurements and with discussions of the controversial, contradictory and unresolved issues that have recently emerged: burst spectra appear to fluctuate in time as rapidly as they are measured, implying that any one spectrum may be incorrect. Energy spectra can be obligingly fitted to practically any desired shape, implying, in effect, that no objective spectral resolution exists at all. Burst fluxes and temporal quantities, including the total event energy, are characterized very differently with differing instruments, implying that even elementary knowledge of their properties is instrumentally subjective. Finally, the log N-log S determinations are deficient in the weak bursts, while there is no detection of a source direction anisotropy, implying that Ptolemy was right or that burst source distance estimates are basically guesswork. These issues may remain unsolved until vastly improved instruments are flown.

Cline, T.L.

1983-10-01

404

Plasma Instabilities in Gamma-Ray Bursts  

SciTech Connect

Magnetic fields are important in a variety of astrophysical scenarios, ranging from possible creation mechanisms of cosmological magnetic fields through relativistic jets such as that from Active Galactic Nuclei and gamma-ray bursts to local phenomena in the solar system. Here, the outstanding importance of plasma instabilities to astrophysics is illustrated by applying the so-called neutral point method to gamma-ray bursts (GRBs), which are assumed to have a homogeneous background magnetic field. It is shown how magnetic turbulence, which is a prerequisite for the creation of dissipation and, subsequently, radiation, is created by the highly relativistic particles in the GRB jet. Using the fact that different particle compositions lead to different instability conditions, conclusions can be drawn about the particle composition of the jet, showing that it is more likely of baryonic nature.

Tautz, Robert C. [Institut fuer Theoretische Physik, Lehrstuhl IV: Weltraum-und Astrophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2008-12-24

405

Gamma-ray polarimetry with Compton Telescope  

NASA Astrophysics Data System (ADS)

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, Hiroyasu; Madejski, Grzegorz; Mitani, Takefumi; Tanaka, Takaaki; Nakamura, Hidehito; Nakazawa, Kazuhiro; Takahashi, Tadayuki; Fukazawa, Yasushi; Kamae, Tuneyoshi; Kokubun, Motohide; Marlow, Daniel; Nomachi, Masaharu; do Couto e Silva, Eduardo

2004-10-01

406

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

407

Accelerated Emission of Gamma Rays from the 31-yr Isomer of {sup 178 }Hf Induced by X-Ray Irradiation  

SciTech Connect

A sample of 6.3{times}10{sup 14} nuclei of the 4-quasiparticle isomer of {sup 178}Hf having a half-life of 31thinspthinspyr and excitation energy of 2.446thinspthinspMeV was irradiated with x-ray pulses from a device typically used in dental medicine. It was operated at 15thinspthinspmA to produce bremsstrahlung radiation with an end point energy set to be 70 or 90thinspthinspkeV. Spectra of the isomeric target were taken with a high purity Ge detector. Intensities of selected transitions in the normal decay cascade of the {sup 178}Hf isomer were found to increase by about 4{percent} . Such an accelerated decay is consistent with an integrated cross section of 1{times}10{sup {minus}21}thinspcm{sup 2}thinspkeV for the resonant absorption of x rays to induce gamma decay. {copyright} {ital 1999} {ital The American Physical Society }

Collins, C.B.; Davanloo, F.; Iosif, M.C.; Dussart, R.; Hicks, J.M. [Center for Quantum Electronics, University of Texas at Dallas, Richardson, Texas 75083 (United States); Karamian, S.A. [Joint Institute for Nuclear Research, Dubna, 141980 (Russia); Ur, C.A.; Popescu, I.I. [H. Hulubei National Institute of Physics and Nuclear Engineering and RC-IGE Foundation, Bucharest (Romania); Kirischuk, V.I. [Scientific Center Institute for Nuclear Research, Kiev (Ukraine); Carroll, J.J. [Center for Photon Induced Processes, Youngstown State University, Youngstown, Ohio 44555 (United States); Roberts, H.E. [System Technology Group, SRS Technologies, Huntsville, Alabama 35812 (United States); McDaniel, P. [Air Force Research Laboratory, DEPA, Kirtland Air Force Base, Albuquerque, New Mexico 87117 (United States); Crist, C.E. [Sandia National Laboratory, Albuquerque, New Mexico 87185 (United States)

1999-01-01

408

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

409

Gamma Ray Bursts, Swift and REM  

Microsoft Academic Search

Relevant information about the physics of Gamma Ray Bursts (GRBs) is hidden in the first phases of the afterglow, i.e. in the multi-wavelength (X-ray to Radio) emission soon after the explosion. Optical and NIR afterglow are particularly important since they allow to measure the redshift of the source and possibly to discover the host galaxies. We present in these pages

G. Chincarini; F. M. Zerbi

2003-01-01

410

Supernova, Hypernova and Gamma Ray Bursts  

Microsoft Academic Search

Recent observations suggest that gamma ray bursts (GRBs) and their afterglows\\u000aare produced by highly relativistic jets emitted in core collapse supernova\\u000aexplosions (SNe). The result of the event, probably, is not just a compact\\u000aobject plus a spherical ejecta: within days, a fraction of the parent star\\u000afalls back to produce a thick accretion disk around the compact object.

Arnon Dar

2001-01-01

411

Gamma ray bursts and cosmic ray origin  

Microsoft Academic Search

This paper presents the theoretical basis of the fireball\\/blast wave model, and some implications of recent results on GRB source models and cosmic-ray production from GRBs. BATSE observations of the prompt gamma-ray luminous phase, and Beppo-SAX and long wavelength afterglow observations of GRBs are briefly summarized. Derivation of spectral and temporal indices of an adiabatic blast wave decelerating in a

C. D. Dermer

2001-01-01

412

Gamma Ray Bursts and Cosmic Ray Origin  

Microsoft Academic Search

This paper presents the theoretical basis of the fireball\\/blast wave model, and some implications of recent results on GRB source models and cosmic-ray production from GRBs. BATSE observations of the prompt gamma-ray luminous phase, and Beppo-SAX and long wavelength afterglow observations of GRBs are briefly summarized. Derivation of spectral and temporal indices of an adiabatic blast wave decelerating in a

C. D. Dermer

2002-01-01

413

Fermi Detects Solar Flare's Gamma Rays  

NASA Video Gallery

During a powerful solar blast in March, NASA's Fermi Gamma-ray Space Telescope detected the highest-energy light ever associated with an eruption on the sun. The discovery heralds Fermi's new role as a solar observatory, a powerful new tool for understanding solar outbursts during the sun's maximum period of activity. Credit: NASA's Goddard Space Flight Center > Related story > Download high-res video

gsfcvideo

2012-06-12

414

Time resolved gamma-ray spectrometry  

Microsoft Academic Search

A new approach is proposed for the measurement of the time-dependent processes in gamma-ray spectrometry. During data acquisition,\\u000a the energy and the detection time of each event are recorded and the data are later analyzed off-line. This separation of\\u000a acquisition and data handling extends the possibilities of the analysis. A series of demonstration experiments was performed\\u000a to show the feasibility

L. Szentmiklsi; T. Belgya; G. L. Molnr; Zs. Rvay

2007-01-01

415

Linssi : Database for gamma-ray spectrometry  

Microsoft Academic Search

Linssi is a Structured Query Language (SQL) database for HPGe gamma-ray spectrometry. It covers the whole production chain from\\u000a sample preparation to final analysis results. Static or mobile sampling and measurement and multiple sample types are supported.\\u000a In addition, each sample can be split or combined any number of times. A sample may be measured multiple times and each measurement

P. A. Aarnio; J. J. Ala-Heikkil; A. Isolankila; A. Kuusi; M. Moring; M. Nikkinen; T. Siiskonen; H. Toivonen; K. Ungar; W. Zhang

2008-01-01

416

Pulsar kicks and gamma-ray burst  

Microsoft Academic Search

Aims:We use the supernova-GRB (gamma-ray burst) association and assume that the GRB asymmetric explosions produce pulsars in order to test the consistency of distributions of modeled and observed pulsar-kick velocities. Methods: The deduced distribution of kick velocity from the model of GRB and the observed kick distribution of radio pulsars are checked by a K-S test. Results: These two distributions

X. H. Cui; H. G. Wang; R. X. Xu; G. J. Qiao

2007-01-01

417

Pulsar's kicks and Gamma-ray bursts  

Microsoft Academic Search

The consistence of the distributions of pulsar's kick velocities from the\\u000amodel of GRB and from the pulsar observations is tested based on the\\u000asupernova-GRB ($\\\\gamma$-ray burst) association and under the assumption that\\u000athe GRB asymmetric explosions produce pulsars. The deduced distribution of kick\\u000avelocity from the model of GRB and the observed kick distribution of radio\\u000apulsars are checked

X. H. Cui; H. G. Wang; R. X. Xu; G. J. Qiao

2007-01-01

418

The Swift Gamma-Ray Burst Mission  

Microsoft Academic Search

The Swift mission, scheduled for launch in 2004, is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is a first-of-its-kind autonomous rapid-slewing satellite for transient astronomy and pioneers the way for future rapid-reaction and multiwavelength missions. It will be far more powerful than any previous GRB mission, observing more than 100 bursts yr-1 and performing detailed X-ray and UV\\/optical

N. Gehrels; G. Chincarini; P. Giommi; K. O. Mason; J. A. Nousek; A. A. Wells; N. E. White; S. D. Barthelmy; D. N. Burrows; L. R. Cominsky; K. C. Hurley; F. E. Marshall; P. Mszros; P. W. A. Roming; L. Angelini; L. M. Barbier; T. Belloni; S. Campana; P. A. Caraveo; M. M. Chester; O. Citterio; T. L. Cline; M. S. Cropper; J. R. Cummings; A. J. Dean; E. D. Feigelson; E. E. Fenimore; D. A. Frail; A. S. Fruchter; G. P. Garmire; K. Gendreau; G. Ghisellini; J. Greiner; J. E. Hill; S. D. Hunsberger; H. A. Krimm; S. R. Kulkarni; P. Kumar; F. Lebrun; N. M. Lloyd-Ronning; C. B. Markwardt; B. J. Mattson; R. F. Mushotzky; J. P. Norris; J. Osborne; B. Paczynski; D. M. Palmer; H.-S. Park; A. M. Parsons; J. Paul; M. J. Rees; C. S. Reynolds; J. E. Rhoads; T. P. Sasseen; B. E. Schaefer; A. T. Short; A. P. Smale; I. A. Smith; L. Stella; G. Tagliaferri; T. Takahashi; M. Tashiro; L. K. Townsley; J. Tueller; M. J. L. Turner; M. Vietri; W. Voges; M. J. Ward; R. Willingale; F. M. Zerbi; W. W. Zhang

2004-01-01

419

Kinetics of proposed gamma-ray lasers  

SciTech Connect

Gamma-ray lasers, although proposed for many years, remain undeveloped because pumping can destroy conditions essential for gain. We review many of the solutions (viz, narrowed-line, explosive neutron pump, two-stage pump, two-step pump) proposed so far, with emphasis on kinetics. The most promising approach requires fast interlevel transfer from a separated isomer to initiate a superradiant Borrmann mode in a solid host. However, suitable nuclear transitions and nondestructive transfer mechanisms have yet to be identified.

Baldwin, G.C.

1985-01-01

420

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

421

Nuclear gamma Rays Following K- Capture  

Microsoft Academic Search

It is suggested that the study of the nuclear deexcitation gamma rays emitted following K- capture may help clarify the nature of the capture mechanism. We consider capture in 208Pb and 16O. Capture rates to the various proton or neutron single-hole states in 207Pb, 207Tl, 15O, and 15N are estimated, and the consequences of capture to the isomeric states in

S. D. Bloom; M. S. Weiss; C. M. Shakin

1972-01-01

422

Status of the Milagro Gamma Ray Observatory  

Microsoft Academic Search

The Milagro Gamma Ray Observatory is the world's first large-area water Cherenkov detector capable of continuously monitoring the sky at TeV energies. Located in the mountains of northern New Mexico, Milagro will perform an all sky survey of the Northern Hemisphere at energies between 250 GeV and 50 TeV. With a high duty-cycle, large detector area, and wide field-of-view

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

1999-01-01

423

Short-hard gamma-ray bursts  

Microsoft Academic Search

Two types of gamma-ray bursts (GRBs) are observed: short-duration hard spectrum GRBs and long-duration soft spectrum GRBs. For many years long GRBs were the focus of intense research while the lack of observational data limited the study of short-hard GRBs (SHBs). In 2005 a breakthrough occurred following the first detections of SHB afterglows, longer wavelength emission that follows the burst

Ehud Nakar

2007-01-01

424

The Cosmic Gamma-Ray Bursts  

Microsoft Academic Search

Cosmic gamma-ray bursts are one of the great frontiers of astrophysics today.\\u000aThey are a playground of relativists and observers alike. They may teach us\\u000aabout the death of stars and the birth of black holes, the physics in extreme\\u000aconditions, and help us probe star formation in the distant and obscured\\u000auniverse. In this review we summarise some of

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

2001-01-01

425

Gamma Ray Bursts and Cosmic Ray Origin  

Microsoft Academic Search

This paper presents the theoretical basis of the fireball\\/blast wave model,\\u000aand some implications of recent results on GRB source models and cosmic-ray\\u000aproduction from GRBs. BATSE observations of the prompt gamma-ray luminous\\u000aphase, and Beppo-SAX and long wavelength afterglow observations of GRBs are\\u000abriefly summarized. Derivation of spectral and temporal indices of an adiabatic\\u000ablast wave decelerating in a

C. D. Dermer

2002-01-01

426

Gamma-ray spectroscopy: An historical perspective  

Microsoft Academic Search

The possibility of MeV-range gamma-rays from extraterrestrial sources had been speculated on by cosmic-ray physicists since the late 1940's. The first definitive detection occurred with balloon-borne cosmic-ray instrumentation during a class 2 solar flare in March 1958, apparently associated with the acceleration of a nonthermal particle population. Following this detection, physicists were motivated to develop instrumentation specific for observation of

Laurence E. Peterson

1988-01-01

427

Gamma-ray spectroscopy: An historical perspective  

Microsoft Academic Search

The possibility of MeV-range gamma-rays from extraterrestrial sources had been speculated on by cosmic-ray physicists since the late 1940s. The first definitive detection occurred with balloon-borne cosmic-ray instrumentation during a class 2 solar flare in March 1958, apparently associated with the acceleration of a nonthermal particle population. Following this detection, physicists were motivated to develop instrumentation specific for observation of

Laurence E. Peterson

1988-01-01

428

The Supernova Gamma-Ray Burst Connection  

Microsoft Academic Search

Observations show that at least some gamma-ray bursts (GRBs) happen simultaneously with core-collapse supernovae (SNe), thus linking by a common thread nature's two grandest explosions. We review here the growing evidence for and theoretical implications of this association, and conclude that most long-duration soft-spectrum GRBs are accompanied by massive stellar explosions (GRB-SNe). The kinetic energy and luminosity of well-studied GRB-SNe

S. E. Woosley; J. S. Bloom

2006-01-01

429

Spectral variations in gamma-ray bursts  

Microsoft Academic Search

We report the initial results of an analysis of 19 gamma-ray burst energy spectra recorded by the Venera-13 and 14 SIGNE experiments. The complete data-base includes some 150 events, with 5 channel energy spectra taken in the 50-700 keV range with 0.5 s time resolution, for 64 s. The observed spectra of each event analyzed were fitted with a power

K. Hurley; V. Kargatis; E. Liang; C. Barat; E. Eveno; M. Niel; V. Sh. Dolidze; A. A. Kozlenkov; I. G. Mitrofanov; A. S. Pozanenko

1991-01-01

430

Gamma-rays from massive protostars  

Microsoft Academic Search

Massive protostars have associated bipolar outflows with velocities of\\u000ahundreds of km\\/s. Such outflows produce strong shocks when interact with the\\u000aambient medium leading to regions of non-thermal radio emission. Under certain\\u000aconditions, the population of relativistic particles accelerated at the\\u000aterminal shocks of the protostellar jets can produce significant gamma-ray\\u000aemission. We estimate the conditions necessary for high-energy emission

Gustavo E. Romero; Anabella T. Araudo; Valenti Bosch-Ramon; Josep M. Paredes

2009-01-01

431

Gamma-Rays from Massive Protostars  

Microsoft Academic Search

Massive protostars have associated bipolar outflows with velocities of hundreds of km s-1. Such outflows produce strong shocks when interact with the ambient medium leading to regions of non-thermal radio emission. Under certain conditions, the population of relativistic particles accelerated at the terminal shocks of the protostellar jets can produce significant gamma-ray emission. We estimate the conditions necessary for high-energy

G. E. Romero; A. T. Araudo; V. Bosch-Ramon; J. M. Paredes

2010-01-01

432

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

PubMed

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. PMID:10688769

Milgrom; Usov

2000-03-10

433

Radio search for gamma-ray pulsar counterparts  

NASA Astrophysics Data System (ADS)

The Fermi gamma-ray satellite, launched in June 2008 is already returning remarkable results. In particular, it has discovered a large number of gamma-ray pulsars without any known radio counterpart (where only 1 was known prior to launch) and has detected unknown sources of gamma-ray radiation in the galactic plane with arcmin positional accuracy. Here we request time to (a) search the gamma-ray pulsars for radio pulsations using very deep integrations at 1.4 GHz and (b) search the unidentified galactic plane sources for radio pulsars. Detecting (or not) pulsars in the former case will help to distinguish between models of gamma-ray emission in pulsars. Detection of radio pulsars in the latter case will enable a search for gamma-ray pulsations to be made and/or determine other causes (such as pulsar wind nebulae) for the gamma-ray emission.

Keith, Michael; Johnston, Simon; Romani, Roger W.; Thompson, David J.; Weltevrede, Patrick; Michelson, Peter

2009-04-01

434

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

435

Solar Two Gamma-Ray Observatory  

NASA Astrophysics Data System (ADS)

The field of high energy gamma-ray astronomy grew tremendously in the last decade due to the launch of the EGRET detector on the Compton Gamma-Ray Observatory in 1991 and the proliferation of ground-based air ?herenkov telescopes (ACTs) such as the Whipple 10 meter reflector. Interestingly, the ground-based telescopes only see 4-5 of the over 170 objects detected by EGRET. A simple extrapolation of the EGRET objects' energy spectra up to the energies which the ACTs are sensitive suggests that many of them should have been detected. The key to resolving this lack of detections is to observe these sources in the previously unobserved 20-250 GeV energy range. The Solar Two Observatory collaboration is developing a secondary optics system on the central tower of the world's largest solar energy pilot plant, Solar Two, to observe gamma-ray sources in this energy range. The progress in building the secondary optics system to be used to image 64 heliostats at Solar Two located in Barstow, California, is presented. We hope to design and build this detector over the next 2 years.

Tmer, T.; Bhattacharya, D.; Mohideen, U.; Rieben, R.; Souchkov, V.; Tom, H.; Zweerink, J.

1999-06-01

436

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

437

Thermonuclear model for. gamma. -ray bursts  

SciTech Connect

The production of ..gamma..-ray bursts by thermonuclear explosions on strongly magnetized nuetron stars is examined. For a neutron star with a magnetic field strength of several times 10/sup 12/ gauss, accretion at approx.10/sup -13/ M/sub sun/ yr/sup -1/ is focused onto kilometer sized regions. The accreted material is confined above the surface by the magnetic field and by a combination of magnetic and crustal stresses below the surface. Stable hydrogen burning leads to a critical helium mass that, depending upon model parameters, explodes either by convective deflagration or detonation, liberating 10/sup 38/--10/sup 40/ ergs km/sup -2/ of thermonuclear energy. Multibillion degree plasma pushed above the surface by the explosion has ..beta..>1 and therefore expands and stresses the magnetic field. Hard emission comes both from the magnetically confined photosphere and from relativistic electrons accelerated by magnetic field recombination. The hard ..gamma..-ray outburst of several seconds is followed by an enduring, softer emission of X-rays, lasting from several minutes to an hour, as the subsurface ashes of the thermonuclear explosion cool. Gamma-ray bursters, at a typical distance of several hundred parsecs, should recur on a time scale of months (low energy) to centuries (high energy). Special attention is given to the spectracular event of 1979 March 5.

Woosley, S.E.; Wallace, R.K.

1982-07-15

438

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

439

Gamma rays as an indicator of nucleosynthesis  

NASA Astrophysics Data System (ADS)

In 1957 the collaboration of E. M. Burbidge, G. R. Burbidge, W. A. Fowler, and F. Hoyle, and the work by A. G. W. Cameron, laid the foundations for understanding the origin of the elements in terms of a few basic processes and astrophysical environments. Half a century after this pioneering work, there is considerable observational evidence for the basic notions of element synthesis during the big-bang, followed by hydrostatic and explosive stellar nucleosynthesis ever since the first population of stars re-illuminated the Universe, and through particle interactions in the turbulent interstellar medium. In 1969 D. D. Clayton, S. A. Colgate, and G. J. Fishman proposed to search for gamma-ray lines from the decay of 56-Ni, freshly synthesized in supernovae. Evidence for these lines was obtained for SN 1987A, and three decades after this pivotal supernova we have ample gamma-ray line evidence for ongoing nucleosynthesis in the Milky Way from surveys for individual sources and unresolved, integrated diffuse emission from an ensemble of such sources. We review the observational evidence for gamma ray lines from various species, and discuss the astrophysical implications of detections and a few puzzles suggested by lack of detections. We reflect on historic developments, assess the accomplishments, and present an outlook on the future of this branch of nuclear astrophysics.

Hartmann, Dieter H.

2007-04-01

440

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

441

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

442

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

PubMed

The prompt optical emission that arrives with the gamma-rays from a cosmic gamma-ray burst (GRB) is a signature of the engine powering the burst, the properties of the ultra-relativistic ejecta of the explosion, and the ejecta's interactions with the surroundings. Until now, only GRB 990123 had been detected at optical wavelengths during the burst phase. Its prompt optical emission was variable and uncorrelated with the prompt gamma-ray emission, suggesting that the optical emission was generated by a reverse shock arising from the ejecta's collision with surrounding material. Here we report prompt optical emission from GRB 041219a. It is variable and correlated with the prompt gamma-rays, indicating a common origin for the optical light and the gamma-rays. Within the context of the standard fireball model of GRBs, we attribute this new optical component to internal shocks driven into the burst ejecta by variations of the inner engine. The correlated optical emission is a direct probe of the jet isolated from the medium. The timing of the uncorrelated optical emission is strongly dependent on the nature of the medium. PMID:15889084

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

2005-05-12

443

Soft Gamma-Ray Repeaters and Magnetars  

NASA Astrophysics Data System (ADS)

The history and observational properties of the soft gamma repeaters are reviewed in this Chapter. Over the past decades, we have gone from viewing these objects as a special class of cosmic gamma-ray burst, to seeing them as one manifestation of magnetars. There is now a solid body of multiwavelength observations, as well as some more controversial properties. There are still a number of fundamental unanswered questions, which will require better theory, more sensitive observations, and many years to answer. The story of the soft gamma repeaters (SGRs) begins in 1979. On January 7th, a short duration, soft spectrum burst was observed from the direction of the Galactic center [28]. At that time, relatively little was known about cosmic gamma-ray bursts (GRBs), but their energy spectra, as observed up to that point, were clearly hard, containing photons up to hundreds of keV and beyond. On the other hand, it was clear that the spectrum of the January 7 event was much softer than that of a GRB, i.e., with little emission beyond 100 keV. The event was called a gamma-ray burst without the gamma-rays. Several months later, the most intense gamma-ray transient which had been observed up to that time, the March 5, 1979 burst, was detected. This event had a hard spectrum and a long duration, with a pulsating tail, and it was localized to the N49 supernova remnant in the Large Magellanic Cloud [3,7]. At the distance of the LMC, the intensity of this burst was >103 times the Eddington luminosity. And in the days that followed, smaller bursts were detected from the source [31]. Many theories were proposed to explain this event, which was generally thought to be an unusual GRB. Several weeks later, another repeating source was discovered when it emitted three short duration, soft spectrum bursts in 3 days [32]. Finally, between July and December 1987, yet another repeater was discovered [2]. This object turned out to be the same as the one which had been detected on January 7, 1979. The source was named SGR1806-20, with SGR standing both for the constellation (Sagittarius) and for Soft Gamma Repeater, to distinguish it from the GRBs.

Hurley, Kevin

444

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

445

A Balloon-Borne Gamma-Ray Polarimeter for Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

We have developed a design for a hard X-ray polarimeter operating in the energy range from 50 to 500 keV. This modular design, known as GRAPE (Gamma-Ray Polarimeter Experiment), was successfully demonstrated with partially polarized gamma-ray sources in the lab and fully polarized photon beams at Argonne National Laboratory. In June of 2007, a GRAPE engineering model flew on a high altitude balloon flight which demonstrated the design and collected background data. A much larger payload is currently under development that will provide a significant level of sensitivity for gamma-ray bursts on a long-duration balloon flight. The first balloon flight of the full GRAPE instrument is currently scheduled to take place in the Fall of 2011 from Ft. Sumner, NM.

McConnell, M. L.; Bancroft, C. M.; Bloser, P. F.; Connor, T. P.; Legere, J. S.; Macri, J. R.; Ryan, J. M.

2009-05-01

446

Pulsed Bremsstrahlung Interrogation with Photoneutron - Gamma-Ray Spectrometry for Nondestructive Evaluation  

NASA Astrophysics Data System (ADS)

A novel photoneutron-based nondestructive evaluation (NDE) technique which does not require a radioactive neutron source is presented. Some unique features of this technique include: 1) pulsed interrogation neutron production within, or very near, an inspected object, 2) spectrum tailoring of the source neutrons, and 3) compatibility with many existing high-energy, commercial x-ray inspection devices. Basic concept feasibility was first established by numerical methods. The pulsed photoneutron inspection technique performs nondestructive elemental analysis using gamma-ray spectrometry. Highly penetrating bremsstrahlung photons are produced by a pulsed electron accelerator capable of producing up to 16-MeV electrons. The photoneutrons are generated by the bremsstrahlung photons interacting with an inspected object and near-by beryllium metal. The interactions of the neutrons within an inspected item result in the emission of elemental characteristic gamma-rays. Spectrometry is performed by analyzing the gamma -rays acquired between accelerator pulses. A unique fast detection and acquisition system, using two 5.08 x 5.08 -cm organic scintillators, acquires gamma-ray emissions within 100 ns of each accelerator pulse. The fast system is capable of processing individual gamma-ray signals at count rates up to 40 MHz between accelerator pulses with a repetition rate up to 1 kHz. The system incorporates a unique x-ray flash recovery method which allows individual gamma-ray detection as soon as 75 ns after the start of each x-ray flash occurring within the detector. Conventional detection and data acquisition systems are used to acquire gamma-ray spectra for the time period between 1000 ns and the next accelerator pulse. Operational tests using a 30-ps pulse width, electron accelerator demonstrated the x-ray flash recovery methodology, gamma-ray detection, and data acquisition. Although, gamma -ray spectrometry performance was limited by x-ray flash -induced gain shifts in the photomultiplier tubes, the basic NDE concept was successfully demonstrated using a modified high-purity germanium detection system.

Jones, James Litton

447

Suppression of gamma-ray sensitivity of liquid scintillators for neutron detection  

NASA Astrophysics Data System (ADS)

Methods to reduce gamma-ray sensitivity of a liquid scintillator EJ309 have been studied. Zero-crossing pulse shape discrimination method was used to separate events generated by neutron and gamma radiation between 60- keVee and 4 MeVee. The measurements were carried out under irradiation from an intense 137Cs source, yielding dose rate of 10 mR/h at the detector. A Pu-Be source was used to establish neutron integration window. Pile-up rejection (PUR) circuit was used to reduce gamma-ray induced events under irradiation from an intense gamma-ray source. Further, application of lead, tin and copper shields was done in order to decrease intrinsic gamma-neutron detection efficiency.

Swiderski, L.; Moszy?ski, M.; Wolski, D.; Iwanowska, J.; Szcz??niak, T.; Schotanus, P.; Hurlbut, C.

2011-10-01

448

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

449

NEUTRON GENERATOR OUTPUT MONITORING FOR NORMALIZATION OF GAMMA-RAY SPECTRA.  

SciTech Connect

Neutron generators (NG) being devices where neutron outputs are accomplished electrically, suffer from fluctuations in their outputs. Of particular importance are the short term variations that may affect individual data acquisition runs. Thus when using NGs for quantitative neutron-induced gamma-ray spectroscopy, the neutron output must be continuously monitored in real time, and normalization procedures subsequently applied to properly evaluate the gamma-ray spectra. Using a plastic scintillator, we developed a scheme for detecting fast neutrons that relies firstly, on recording a spectrum and, secondly, on establishing a region-of-interest (ROI) that may effectively discriminate against gamma rays that are always present in a neutron field. We discuss the optimization of these procedures for a field system to measure carbon in soil.

MITRA,S.; WIELOPOLSKI, L.

2006-05-08

450

Ultra-high Energy Source Contributions to the Extragalactic Gamma-Ray Background  

NASA Astrophysics Data System (ADS)

The ingredients of the extragalactic gamma-ray background (EGB) at GeV-TeV energies must contain contributions from all source classes that are known to emit at these energies, including blazars, radio galaxies, star-forming galaxies, pulsars, and gamma-ray bursts. An uncertain contribution should be provided by cosmic-rays accelerated in cluster formation shocks, as well as from exotic processes, including dark matter annihilation and decay. After presenting an overview, the focus of this talk will be on contributions to the EGB from blazars emitting at >>TeV energies as well as from ultra-high energy cosmic rays. These ultra-high energy sources induce secondary radiations that cascade into the TeV and GeV band. Measurements of the EGB at very high gamma-ray energies can be used to constrain the number and distribution of such sources.

Dermer, Charles D.

2012-05-01

451

Effects of axion-photon mixing on gamma-ray spectra from magnetized astrophysical sources  

SciTech Connect

Astrophysical {gamma}-ray sources come in a variety of sizes and magnetizations. We deduce general conditions under which {gamma}-ray spectra from such sources would be significantly affected by axion-photon mixing. We show that, depending on strength and coherence of the magnetic field, axion couplings down to {approx}(10{sup 13}GeV){sup -1} can give rise to significant axion-photon conversions in the environment of accreting massive black holes. Resonances can occur between the axion mass term and the plasma frequency term as well as between the plasma frequency term and the vacuum Cotton-Mouton shift. Both resonances and nonresonant transitions could induce detectable features or even strong suppressions in finite energy intervals of {gamma}-ray spectra from active galactic nuclei. Such effects can occur at keV to TeV energies for couplings that are currently allowed by all experimental constraints.

Hochmuth, Kathrin A. [Max-Planck-Institut fuer Physik (Werner-Heisenberg-Institut), Foehringer Ring 6, 80805 Munich (Germany); Sigl, Guenter [APC - AstroParticules et Cosmologie, 10, rue Alice Domon et Leonie Duquet, 75205 Paris Cedex 13 (France) and Institut d'Astrophysique de Paris, UMR 7095 CNRS-Universite Pierre and Marie Curie, 98 bis boulevard Arago, F-75014 Paris (France)

2007-12-15

452

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

453

{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

454

Fission Product Gamma-Ray Line Pairs Sensitive to Fissile Material and Neutron Energy  

Microsoft Academic Search

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 minute to 14 hours. 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.

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

2007-01-01

455

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

456

Short Gamma-Ray Bursts and Dark Matter Seeding in Neutron Stars  

NASA Astrophysics Data System (ADS)

We present a mechanism based on internal self-annihilation of dark matter accreted from the galactic halo in the inner regions of neutron stars that may trigger full or partial conversion into a quark star. We explain how this effect may induce a gamma-ray burst (GRB) that could be classified as short, according to the usual definition based on time duration of the prompt gamma-ray emission. This mechanism differs in many aspects from the most discussed scenario associating short GRBs with compact object binary mergers. We list possible observational signatures that should help distinguish between these two possible classes of progenitors.

ngeles Prez-Garca, M.; Daigne, F.; Silk, J.

2013-05-01

457

Novel methodology for the quantitative assay of fissile materials using temporal and spectral beta-delayed gamma-ray signatures  

Microsoft Academic Search

An analytical model for the generation of beta-delayed gamma-ray spectra following thermal-neutron-induced fission of mixed samples of 235UPu is presented. Using an energy-dependent figure-of-merit to designate the spectral regions employed in the assay, the unique temporal beta-delayed gamma-ray signatures are utilized to determine the fraction of 239PuU and 239Pu within a 3 keV energy bin, traditional sources of systematic uncertainty

D. H. Chivers; K. Alfonso; B. L. Goldblum; B. Ludewigt

2011-01-01

458

Radioprotector WR1065 reduces radiation-induced mutations at the hypoxanthine-guanine phosphoribosyl transferase locus in V79 cells  

SciTech Connect

N-(2-mercaptoethyl)-1,3-diaminopropane (WR1065) protects against radiation-induced cell killing and mutagenesis at the hypoxanthine-guanine phosphoribosyl transferase (HGPRT) locus in V79 Chinese hamster lung fibroblast cells. WR1065 (4 mm) was found to be effective in protecting against radiation-induced cell lethality only if present during irradiation. No protective effect was observed if the protector was added within 5 min after irradiation or 3 h later. The effect of WR1065 on radiation-induced mutation, expressed as resistance to the cytotoxic purine analogue 6-thioguanine (HGPRT), was also investigated. This agent was effective in reducing radiation-induced mutations regardless of when it was administered. Following 10 Gy of /sup 60/Co ..gamma..-rays, the mutation frequencies observed per 10/sup 6/ survivors were 77 +- 8, 27 +- 6, 42 +- 7, and 42 +- 7 for radiation only, and WR1065 present during, immediately after, or 3 h after irradiation. These data suggest that although a segment of radiation-induced damage leading to reproductive death cannot be modulated through the postirradiation action of WR1065, processes leading to the fixation of gross genetic damage and mutation induction in surviving cells can be effectively altered and interfered with leading to a marked reduction in mutation frequency.

Grdina, D.J.; Hill, C.K.; Peraino, C. (Argonne National Lab., IL (USA)); Biserka, N. (Central Inst. for Tumors and Allied Diseases, Zagreb (Yugoslavia)); Wells, R.L. (Colorado State Univ., Fort Collins (USA). Dept. of Radiology and Radiation Biology)

1985-06-01

459

Common Gamma-ray Glows above Thunderclouds  

NASA Astrophysics Data System (ADS)

Gamma-ray glows are continuous, long duration gamma- and x-ray emission seen coming from thunderclouds. The Airborne for Energetic Lightning Emissions (ADELE) observed 12 gamma-ray glows during its summer 2009 flight campaign over the areas of Colorado and Florida in the United States. For these glows we shall present their spectra, relationship to lightning activity and how their duration and size changes as a function of distance. Gamma-ray glows follow the relativistic runaway electron avalanche (RREA) spectrum and have been previously measured from the ground and inside the cloud. ADELE measured most glows as it flew above the screening layer of the cloud. During the brightest glow on August 21, 2009, we can show that we are flying directly into a downward facing relativistic runaway avalanche, indicative of flying between the upper positive and negative screening layer of the cloud. In order to explain the brightness of this glow, RREA with an electric field approaching the limit for relativistic feedback must be occurring. Using all 12 glows, we show that lightning activity diminishes during the onset of the glow. Using this along with the fact that glows occur as the field approaches the level necessary for feedback, we attempt to distinguish between two possibilities: that glows are evidence that RREA with feedback, rather than lightning, is sometimes the primary channel for discharging the cloud, or else that the overall discharging is still controlled by lightning, with glows simply appearing during times when a subsidence of lightning allows the field to rise above the threshold for RREA.

Kelley, Nicole; Smith, David; Dwyer, Joseph; Hazelton, Bryna; Grefenstette, Brian; Lowell, Alex; Splitt, Michael; Lazarus, Steven; Rassoul, Hamid

2013-04-01

460

RHESSI as Gamma Ray Burst Polarimeter  

NASA Astrophysics Data System (ADS)

The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) was designed to measure hard X-rays and ?-rays from solar flares. With its big detection area and thin side shielding it also proved to be well suited for studying Gamma Ray Bursts (GRB). Polarization analysis is feasible as well, due to a big modulation factor (MF), though serious constraints on the minimum detectable polarization (MDP) come from detection efficiency of double scattered photons. More constraints are given by background of accidental and real coincidences.

Hajdas, W.; Wigger, C.; Zehnder, A.

2005-07-01

461

High-spin gamma-ray spectroscopy  

SciTech Connect

Nuclei can carry angular momentum by single-particle alignments and by collective motion, as has been well illustrated in discrete-line spectroscopy. From continuum ..gamma..-ray studies in still higher spin regions, it appears that these modes both continue. In favorable cases in rare-earth nuclei, particle alignments from the valence shell separate from proton alignments from the next higher shell. A new generation of Compton-suppressed Ge detector arrays will greatly enhance high-spin studies, both continuum and discrete-line. 17 references.

Diamond, R.M.

1984-03-01

462

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)

2003-05-14

463

Gamma Ray Bursts In Their Historic Context  

NASA Astrophysics Data System (ADS)

Gamma ray bursts remained essentially non-understood or misunderstood from their 1973 discovery (not, I will claim, ``serendipitous'') to the first, 1997, redshift. This is by no means a record. The poster explored some of the examples of longer-standing puzzles and the after-dinner talk some of the details of the GRB case. The most striking feature of the GRB history is probably the unanimity with which ``all we, like sheep, went astray,'' which followed the epoch of ``we have turned everyone to his own way.'' Some of the reasons for this, the range of hypotheses, and how GRBs were presented to the astronomical and larger communities are discussed.

Trimble, Virginia

2004-09-01

464

Gamma Rays from Heavy Neutralino Dark Matter  

SciTech Connect

We consider the gamma-ray spectrum from neutralino dark matter annihilations and show that internal bremsstrahlung of W pair final states gives a previously neglected source of photons at energies near the mass of the neutralino. For masses larger than about 1 TeV, and for present day detector resolutions, this results in a characteristic signal that may dominate not only over the continuous spectrum from W fragmentation, but also over the {gamma}{gamma} and {gamma}Z line signals which are known to give large rates for heavy neutralinos. Observational prospects thus seem promising.

Bergstroem, Lars; Bringmann, Torsten; Eriksson, Martin; Gustafsson, Michael [Department of Physics, Stockholm University, AlbaNova University Center, SE - 106 91 Stockholm (Sweden)

2005-12-09

465

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

466

Gamma rays and matter-antimatter asymmetry.  

NASA Astrophysics Data System (ADS)

It is commonly asserted that although there is a marked asymmetry of matter and antimatter on all scales up to and including clusters of galaxies, on the supercluster scale there could indeed be symmetry, the ensuing annihilation gamma rays being of lower intensity than those observed. The authors argue here that this is not so after making a detailed examination of the manner in which such a supercluster, antisupercluster geometry could be present and allowing for factors which appear not to have been previously considered.

Dudarewicz, A.; Wolfendale, A. W.

467

Material recognition using fission gamma rays  

NASA Astrophysics Data System (ADS)

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

Viesti, G.; Sajo-Bohus, L.; Fabris, D.; Lunardon, M.; Moretto, S.; Nebbia, G.; Pesente, S.

2009-07-01

468

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; Jhannesson, G; Johnson, A S; Johnson, T J; Johnson, W N; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Kndlseder, 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; Rain, 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; Sgr, 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

2010-04-01

469

Superluminal blazars and the extragalactic gamma ray background.  

NASA Astrophysics Data System (ADS)

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

Xinyu, Chi; Young, E. C. M.

1997-07-01

470

Superluminal blazars and the extragalactic gamma ray background  

NASA Astrophysics Data System (ADS)

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

Chi, Xinyu; Young, Enoch C. M.

1997-07-01

471

Colorado School of Mines fusion gamma ray diagnostic project  

NASA Astrophysics Data System (ADS)

The purpose of our fusion gamma ray project continues to be the development of fusion gamma ray spectrometry as a diagnostic of high temperature fusion plasmas. The three broad areas in support of this purpose are: measurement of gamma ray producing reactions at low energies; development of gamma ray spectrometers capable of measuring the gamma ray yields from current and proposed fusion plasma devices; and determination of appropriate plasma parameters from measured fusion gamma ray yields at present fusion plasma devices. This report summarizes the progress made in these three areas. The recently completed measurement of the radiative capture of protons by the nuclei Li-6, Li-7, Be-9, and B-11 is summarized. Preliminary results of the investigation of the radiative capture of deuterons by Li-6 and B-10 as well as additional data taken on the reaction D(d,gamma)He-4 at very low energies are also presented.

Cecil, F. E.

1991-02-01

472

Multiwavelength observations of Gamma-Ray Bright Blazars  

NASA Astrophysics Data System (ADS)

We have investigated total intensity radio images of 6 gamma-ray bright blazars (BL Lac, 3C 279, 3C 273, W Com, PKS 1510-089, and 3C 66A) and their optical and gamma-ray light curves to study connections between gamma-ray and optical brightness variations and changes in the parsec-scale radio structure. The blazars with faster apparent speeds, 3C 273, 3C 279, PKS 1510-089, and 3C 66A, exhibit stronger variability of the gamma-ray emission with higher flux density. Only blazars with faster apparent speeds show simultaneous optical and gamma-ray brightness variations during the flares. Our results are consisted with models in which the gamma-ray emission arises in high-relativistic jets.

Morozova, D. A.; Troitskiy, I. S.

2012-05-01

473

Massive Binaries as VHE Gamma-ray Sources  

NASA Astrophysics Data System (ADS)

Recent progress in gamma-ray astronomy has established Very High Energy (VHE) gamma-ray binaries as a new class of gamma-ray sources. All of them are massive binaries consisting of an OB star and a compact object. The next generation observing fascilities, such as the Cherenkov Telescope Array, will detect many more massive binaries as VHE gamma-ray sources. Studying VHE gamma-ray binaries is important not only to understand physics at work in individual systems, but also to construct a unified dynamical model for the interaction and the origin of high-energy emission in this class of objects. In this talk, we discuss the interaction between the stellar wind and/or circumstellar disk and the compact object, based on 3-D hydrodynamic simulations of a few VHE gamma-ray binaries.

Okazaki, Atsuo

2013-06-01