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1

A compact X-ray to Gamma-ray FEL  

NASA Astrophysics Data System (ADS)

We study the possibility of using the magnetic mode driven by an intense radiation source impinging on a relativistic ionization front as a plasma undulator with periods that can be orders of magnitude smaller than those of conventional undulators, allowing for the generation of ultrashort-wavelength radiation with modest electron-beam energies, and therefore strongly decreasing the size of FEL systems. The effects of the plasma background on the resonance condition and on the growth rate of the generated radiation are investigated, as well as the role of the associated beam-plasma instabilities in the FEL mechanism. In order to check the validity of our theoretical predictions, we have performed simulations both with GENESIS 1.3, for an equivalent magnetic field structure, and with OSIRIS 2.0, in order to also include the plasma effects. The analysis reveals a good agreement between theory and simulation results, illustrating the possibility of using short-period plasma undulators to produce a compact X-ray to Gamma-ray FEL.

Fiuza, Frederico; Silva, Luis

2008-11-01

2

GAMMA-ray diagnostic for the Compact Ignition Tokamak  

SciTech Connect

We have examined the feasibility of a fusion ..gamma..-ray diagnostic for the Compact Ignition Tokamak, which is expected to produce 10/sup 20/ (d,t) fusion reactions per second. Gamma rays at 16.7 MeV are produced by the t(d,..gamma..)He/sup 5/ fusion reaction. A Monte-Carlo coupled neutron-photon transport code is used to model the expected ..gamma..-ray spectrum incident upon a Compton spectrometer backed by a Cerenkov detector. The results indicate that a signal of /approximately/3 x 10/sup 4/cts/s and a signal-to-noise ratio of /approximately/30 can be achieved. 8 refs., 4 figs.

Petrasso, R.D.; Fiore, C.L.; Li, Chi-Kang

1988-04-01

3

Compact Binary Progenitors of Short Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

In recent years, detailed observations and accurate numerical simulations have provided support to the idea that mergers of compact binaries containing either two neutron stars (NSs) or an NS and a black hole (BH) may constitute the central engine of short gamma-ray bursts (SGRBs). The merger is expected to lead to the production of a spinning BH surrounded by an accreting torus. Several mechanisms can extract energy from this system and power the SGRBs. Here we connect observations and numerical simulations of compact binary mergers, and use the current sample of SGRBs with measured energies to constrain the mass of their powering tori. By comparing the masses of the tori with the results of fully general-relativistic simulations, we are able to infer the properties of the binary progenitors which yield SGRBs. We find that most of the tori have masses smaller than 0.01M, favoring ``high-mass'' binary NSs mergers. This has important consequences for the gravitational-wave signals that may be detected in association with SGRBs, since ``high-mass'' systems do not form a long-lived hypermassive NS after the merger. While NS-BH systems cannot be excluded to be the engine of at least some of the SGRBs, the BH would need to have an initial spin of ˜0.9, or higher.

Giacomazzo, Bruno; Perna, Rosalba; Rezzolla, Luciano; Troja, Eleonora; Lazzati, Davide

2013-04-01

4

Compact Binary Progenitors of Short Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

In recent years, detailed observations and accurate numerical simulations have provided support to the idea that mergers of compact binaries containing either two neutron stars (NSs) or an NS and a black hole (BH) may constitute the central engine of short gamma-ray bursts (SGRBs). The merger of such compact binaries is expected to lead to the production of a spinning BH surrounded by an accreting torus. Several mechanisms can extract energy from this system and power the SGRBs. Here we connect observations and numerical simulations of compact binary mergers, and use the current sample of SGRBs with measured energies to constrain the mass of their powering tori. By comparing the masses of the tori with the results of fully general-relativistic simulations, we are able to infer the properties of the binary progenitors that yield SGRBs. By assuming a constant efficiency in converting torus mass into jet energy epsilon(sub jet) = 10%, we find that most of the tori have masses smaller than 0.01 Solar M, favoring "high-mass" binary NSs mergers, i.e., binaries with total masses approx >1.5 the maximum mass of an isolated NS. This has important consequences for the gravitational wave signals that may be detected in association with SGRBs, since "high-mass" systems do not form a long-lived hypermassive NS after the merger. While NS-BH systems cannot be excluded to be the engine of at least some of the SGRBs, the BH would need to have an initial spin of approx. 0.9 or higher.

Giacomazzo, Bruno; Perna, Rosalba; Rezzolla, Luciano; Troja, Eleonora; Lazzati, Davide

2013-01-01

5

Compact Binary Progenitors of Short Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

In recent years, detailed observations and accurate numerical simulations have provided support to the idea that mergers of compact binaries containing either two neutron stars (NSs) or an NS and a black hole (BH) may constitute the central engine of short gamma-ray bursts (SGRBs). The merger of such compact binaries is expected to lead to the production of a spinning BH surrounded by an accreting torus. Several mechanisms can extract energy from this system and power the SGRBs. Here we connect observations and numerical simulations of compact binary mergers, and use the current sample of SGRBs with measured energies to constrain the mass of their powering tori. By comparing the masses of the tori with the results of fully general-relativistic simulations, we are able to infer the properties of the binary progenitors that yield SGRBs. By assuming a constant efficiency in converting torus mass into jet energy, epsilonjet = 10%, we find that most of the tori have masses smaller than 0.01 M ?, favoring "high-mass" binary NSs mergers, i.e., binaries with total masses >~ 1.5 the maximum mass of an isolated NS. This has important consequences for the gravitational wave signals that may be detected in association with SGRBs, since "high-mass" systems do not form a long-lived hypermassive NS after the merger. While NS-BH systems cannot be excluded to be the engine of at least some of the SGRBs, the BH would need to have an initial spin of ~0.9 or higher.

Giacomazzo, Bruno; Perna, Rosalba; Rezzolla, Luciano; Troja, Eleonora; Lazzati, Davide

2013-01-01

6

COMPACT BINARY PROGENITORS OF SHORT GAMMA-RAY BURSTS  

SciTech Connect

In recent years, detailed observations and accurate numerical simulations have provided support to the idea that mergers of compact binaries containing either two neutron stars (NSs) or an NS and a black hole (BH) may constitute the central engine of short gamma-ray bursts (SGRBs). The merger of such compact binaries is expected to lead to the production of a spinning BH surrounded by an accreting torus. Several mechanisms can extract energy from this system and power the SGRBs. Here we connect observations and numerical simulations of compact binary mergers, and use the current sample of SGRBs with measured energies to constrain the mass of their powering tori. By comparing the masses of the tori with the results of fully general-relativistic simulations, we are able to infer the properties of the binary progenitors that yield SGRBs. By assuming a constant efficiency in converting torus mass into jet energy, {epsilon}{sub jet} = 10%, we find that most of the tori have masses smaller than 0.01 M{sub Sun }, favoring 'high-mass' binary NSs mergers, i.e., binaries with total masses {approx}> 1.5 the maximum mass of an isolated NS. This has important consequences for the gravitational wave signals that may be detected in association with SGRBs, since 'high-mass' systems do not form a long-lived hypermassive NS after the merger. While NS-BH systems cannot be excluded to be the engine of at least some of the SGRBs, the BH would need to have an initial spin of {approx}0.9 or higher.

Giacomazzo, Bruno [JILA, University of Colorado and National Institute of Standards and Technology, Boulder, CO 80309 (United States); Perna, Rosalba [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States); Rezzolla, Luciano [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Potsdam D-14476 (Germany); Troja, Eleonora [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Lazzati, Davide [Department of Physics, NC State University, 2401 Stinson Drive, Raleigh, NC 27695-8202 (United States)

2013-01-10

7

Design of a compact spectrometer for high-flux MeV gamma-ray beams.  

PubMed

A novel design for a compact gamma-ray spectrometer is presented. The proposed system allows for spectroscopy of high-flux multi-MeV gamma-ray beams with MeV energy resolution in a compact design. In its basic configuration, the spectrometer exploits conversion of gamma-rays into electrons via Compton scattering in a low-Z material. The scattered electron population is then spectrally resolved using a magnetic spectrometer. The detector is shown to be effective for gamma-ray energies between 3 and 20 MeV. The main properties of the spectrometer are confirmed by Monte Carlo simulations. PMID:24985864

Corvan, D J; Sarri, G; Zepf, M

2014-06-01

8

Compact high-resolution gamma-ray computed tomography system for multiphase flow studies  

SciTech Connect

In this paper, a compact high-resolution gamma-ray Computed Tomography (CompaCT) measurement system for multiphase flow studies and tomographic imaging of technical objects is presented. Its compact and robust design makes it particularly suitable for studies on industrial facilities and outdoor applications. Special care has been given to thermal ruggedness, shock resistance, and radiation protection. Main components of the system are a collimated {sup 137}Cs isotopic source, a thermally stabilised modular high-resolution gamma-ray detector arc with 112 scintillation detector elements, and a transportable rotary unit. The CompaCT allows full CT scans of objects with a diameter of up to 130 mm and can be operated with any tilting angle from 0 Degree-Sign (horizontal) to 90 Degree-Sign (vertical).

Bieberle, A.; Nehring, H.; Berger, R.; Arlit, M.; Haerting, H.-U.; Schubert, M. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics, Bautzner Landstrasse 400, 01328 Dresden (Germany); Hampel, U. [Helmholtz-Zentrum Dresden-Rossendorf, Institute of Fluid Dynamics, Bautzner Landstrasse 400, 01328 Dresden (Germany); Technische Universitaet Dresden, AREVA Endowed Chair of Imaging Techniques in Energy and Process Engineering, 01062 Dresden (Germany)

2013-03-15

9

Searching gamma-ray bursts for gravitational lensing echoes - Implications for compact dark matter  

NASA Technical Reports Server (NTRS)

The first available 44 gamma-ray bursts (GRBs) detected by the Burst and Transient Source Experiment on board the Compton Gamma-Ray Observatory have been inspected for echo signals following shortly after the main signal. No significant echoes have been found. Echoes would have been expected were the GRBs distant enough and the universe populated with a sufficient density of compact objects composing the dark matter. Constraints on dark matter abundance and GRB redshifts from the present data are presented and discussed. Based on these preliminary results, a universe filled to critical density of compact objects between 10 exp 6.5 and 10 exp 8.1 solar masses are now marginally excluded, or the most likely cosmological distance paradigm for GRBs is not correct. We expect future constraints to be able either to test currently popular cosmological dark matter paradigms or to indicate that GRBs do not lie at cosmological distances.

Nemiroff, R. J.; Norris, J. P.; Wickramasinghe, W. A. D. T.; Horack, J. M.; Kouveliotou, C.; Fishman, G. J.; Meegan, C. A.; Wilson, R. B.; Paciesas, W. S.

1993-01-01

10

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

Microsoft Academic Search

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

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

2005-01-01

11

Compact Gamma-Ray Imager for In-Vivo Gene Imaging  

SciTech Connect

A compact, low-cost, gamma-ray imaging system is needed to study gene expression in small animals. State-of-the-art electronic imaging systems have insufficient resolution and animals must be sacrificed for detailed imaging that precludes time evolution studies. With improved electronics radioactive tracers attached to gene markers can be used to track the absorption and mobility of gene therapy medications in live animals. Other instrumentation being developed for medical applications does not have the response to match the radiation source for this work. The objective of this research was to develop thick film (Cd,Zn)Te detectors matched to the gamma ray energy of {sup 129}I. The detector would be a direct readout device using p-i-n diodes formed from the high Z material absorbing the radiation, with separate readout. Higher quality semiconducting material was expected from epitaxial growth on GaAs, a near lattice matched substrate. In practice, it was difficult to obtain material with high resistance and low leakage current. Spire Corporation achieved the goal of fabricating working detectors in (Cd,Zn)Te deposited on GaAs. The spectra of an alpha emitter ({sup 225}Am) was adequately resolved in thin film devices. Thick p-i-n diodes were fabricated but other processing problems prevented full demonstration of a gamma ray detector.

Greenwald, A. C.

2000-06-01

12

Portable gamma-ray monitor composed of a compact electrically cooled Ge detector and a mini-MCA system  

Microsoft Academic Search

A portable gamma-ray monitor composed of a compact electrically cooled germanium detector and a mini-MCA system was developed for in situ gamma-ray monitoring with very fast starting time and easy operation. This detector is suitable for an accident, an emergency, a fast inspection, and an easy analysis since the detector could acquire data after a 51 min cooling time. The

Masaki Katagiri; Atsushi Birumachi; Kaoru Sakasai; Kouji Takahashi

2003-01-01

13

Portable gamma-ray monitor composed of a compact electrically cooled Ge detector and a mini-MCA system  

Microsoft Academic Search

A portable gamma-ray monitor composed of a compact electrically cooled germanium detector and a mini-MCA system was developed for in-situ gamma-ray monitoring with very fast starting time and easy operation. This detector may be used mainly in an accident, an emergency, a fast inspection and an easy analysis because the starting time of the Ge detector is 51 minute. The

Masaki Katagiri; Atsushi Birumachi; Kaoru Sakasai; Kouji Takahashi

2002-01-01

14

ARE ALL SHORT-HARD GAMMA-RAY BURSTS PRODUCED FROM MERGERS OF COMPACT STELLAR OBJECTS?  

SciTech Connect

The origin and progenitors of short-hard gamma-ray bursts (GRBs) remain a puzzle and a highly debated topic. Recent Swift observations suggest that these GRBs may be related to catastrophic explosions in degenerate compact stars, denoted as 'Type I' GRBs. The most popular models include the merger of two compact stellar objects (NS-NS or NS-BH). We utilize a Monte Carlo approach to determine whether a merger progenitor model can self-consistently account for all the observations of short-hard GRBs, including a sample with redshift measurements in the Swift era (z-known sample) and the CGRO/BATSE sample. We apply various merger time delay distributions invoked in compact star merger models to derive the redshift distributions of these Type I GRBs, and then constrain the unknown luminosity function of Type I GRBs using the observed luminosity-redshift (L-z) distributions of the z-known sample. The best luminosity function model, together with the adopted merger delay model, is then applied to confront the peak flux distribution (log N-log P distribution) of the BATSE and Swift samples. We find that for all the merger models invoking a range of merger delay timescales (including those invoking a large fraction of 'prompt mergers'), it is difficult to reconcile the models with all the data. The data are instead statistically consistent with the following two possible scenarios. First, that short/hard GRBs are a superposition of compact-star-merger-origin (Type I) GRBs and a population of GRBs that track the star formation history, which are probably related to the deaths of massive stars (Type II GRBs). Second, the entire short/hard GRB population is consistent with a typical delay of 2 Gyr with respect to the star formation history with modest scatter. This may point toward a different Type I progenitor than the traditional compact star merger models.

Virgili, Francisco J.; Zhang Bing [Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV 89154 (United States); O'Brien, Paul [Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH (United Kingdom); Troja, Eleonora, E-mail: virgilif@physics.unlv.edu, E-mail: zhang@physics.unlv.edu [Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2011-02-01

15

Prospects for compact high-intensity laser synchrotron x-ray and gamma sources  

SciTech Connect

A laser interacting with a relativistic electron beam behaves like a virtual wiggler of an extremely short period equal to half of the laser wavelength. This approach opens a route to relatively compact, high-brightness x-ray sources alternative or complementary to conventional synchrotron light sources. Although not new, the laser synchrotron source (LSS) concept is still waiting for a convincing demonstration. Available at the BNL Accelerator Test Facility (ATF), a high-brightness electron beam and the high-power CO{sub 2} laser may be used as prototype LSS brick stones. In a feasible demonstration experiment, 10-GW, 100-ps CO{sub 2} laser beam will be brought to a head-on collision with a 10-ps, 0.5-nC, 50 MeV electron bunch. Flashes of collimated 4.7 keV (2.6 {angstrom}) x-rays of 10-ps pulse duration, with a flux of {approximately} 10{sup 19} photons/sec, will be produced via linear Compton backscattering. The x-ray spectrum is tunable proportionally to the e-beam energy. A rational short-term extension of the proposed experiment would be further enhancement of the x-ray flux to the 10{sup 22} photons/sec level, after the ongoing ATF CO{sub 2} laser upgrade to 5 TW peak power and electron bunch shortening to 3 ps is realized. In the future, exploiting the promising approach of a high-gradient laser wake field accelerator, a compact ``table-top`` LSS of monochromatic gamma radiation may become feasible.

Pogorelsky, I.V. [Brookhaven National Lab., Upton, NY (United States). Accelerator Test Facility

1996-11-01

16

Prospects for compact high-intensity laser synchrotron x-ray and gamma sources  

SciTech Connect

A laser interacting with a relativistic electron beam behaves like a virtual wiggler of an extremely short period equal to half of the laser wavelength. This approach opens a route to relatively compact, high- brightness x-ray sources alternative or complementary to conventional synchrotron light sources. Although not new, the laser synchrotron source (LSS) concept is still waiting for a convincing demonstration. Available at the BNL Accelerator Test Facility (ATF), a high- brightness electron beam and the high-power C0{sub 2} laser may be used as prototype LSS brick stones. In a feasible demonstration experiment, 10 GW, 100 ps C0{sub 2} laser beam will be brought to a head-on collision with a 10 ps, 0.5 nC, 50 MeV electron bunch. Flashes of collimated 4.7 keV (2.6 A) x-rays of 10-ps pulse duration, with a flux of {approximately}10{sup 19} photons/sec, will be produced via linear Compton backscattering. The x-ray spectra is tunable proportionally to the e- beam energy. A rational short-term extension of the proposed experiment would be further enhancement of the x-ray flux to the 10{sup 22} photon/sec level, after the ongoing ATF C0{sub 2} laser upgrade to 5 TW peak power and electron bunch shortening to 3 ps is realized. In the future, exploiting the promising approach of a high-gradient laser wake field accelerator, a compact ``table- top`` LSS of monochromatic gamma radiation may become feasible.

Pogorelsky, I.V.

1997-01-01

17

Development of a Precision Tunable Gamma-Ray Source Driven by a Compact X-Band LINAC.  

National Technical Information Service (NTIS)

A precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development at LLNL. High-brightness, relativistic electron bunches produced by the linac interact with a Joule-class, 10 ps laser pulse to generate t...

C. W. Siders D. P. McNabb F. V. Hartemann M. Y. Shverdin T. S. Chu

2009-01-01

18

DEVELOPMENT OF A PRECISION TUNABLE GAMMA-RAY SOURCE DRIVEN BY A COMPACT X-BAND LINAC  

Microsoft Academic Search

A precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development at LLNL. High-brightness, relativistic electron bunches produced by the linac interact with a Joule-class, 10 ps laser pulse to generate tunable -rays in the 0.5-2.5 MeV photon energy range via Compton scattering. The source will be used to excite nuclear resonance fluorescence lines in

F V Hartemann; F Albert; G G Anderson; S G Anderson; A J Bayramian; S M Betts; T S Chu; R R Cross; C A Ebbers; S E Fisher; D J Gibson; A S Ladran; M J Messerly; V A Semenov; M Y Shverdin; C W Siders; D P McNabb; C J Barty; A E Vlieks; E N Jongewaard; S G Tantawi

2009-01-01

19

Observations of discrete gamma ray sources with SAS-2. [compact sources centered on Crab nebula and Vela X supernova remnant  

NASA Technical Reports Server (NTRS)

Compact gamma ray sources centered on the Crab nebula and the Vela X supernova remnant are considered. An excess in the galactic radiation was observed in both regions. Data indicate that a large fraction of this flux is pulsed. The excess from the Vela region could reflect either a large-scale galactic feature, such as a superposition of spiral arm segments, or it could be associated with the Vela supernova remnant. Low-energy gamma ray bursts were observed in the SAS-2 anticoincidence shielding.

Thompson, D. J.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Bignami, G. F.

1974-01-01

20

The Locations of Short Gamma-Ray Bursts as Evidence for Compact Object Binary Progenitors  

NASA Astrophysics Data System (ADS)

We present a detailed investigation of Hubble Space Telescope rest-frame UV/optical observations of 22 short gamma-ray burst (GRB) host galaxies and sub-galactic environments. Utilizing the high angular resolution and depth of HST we characterize the host galaxy morphologies, measure precise projected physical and host-normalized offsets between the bursts and host centers, and calculate the locations of the bursts with respect to their host light distributions (rest-frame UV and optical). We calculate a median short GRB projected physical offset of 4.5 kpc, about 3.5 times larger than that for long GRBs, and find that ?25% of short GRBs have offsets of >~ 10 kpc. When compared to their host sizes, the median offset is 1.5 half-light radii (re ), about 1.5 times larger than the values for long GRBs, core-collapse supernovae, and Type Ia supernovae. In addition, ?20% of short GRBs having offsets of >~ 5re , and only ?25% are located within 1re . We further find that short GRBs severely under-represent their hosts' rest-frame optical and UV light, with ?30%-45% of the bursts located in regions of their host galaxies that have no detectable stellar light, and ?55% in the regions with no UV light. Therefore, short GRBs do not occur in regions of star formation or even stellar mass. This demonstrates that the progenitor systems of short GRBs must migrate from their birth sites to their eventual explosion sites, a signature of kicks in compact object binary systems. Utilizing the full sample of offsets, we estimate natal kick velocities of ?20-140 km s-1. These independent lines of evidence provide the strongest support to date that short GRBs result from the merger of compact object binaries (NS-NS/NS-BH).

Fong, W.; Berger, E.

2013-10-01

21

Diversity of Short Gamma-Ray Burst Afterglows from Compact Binary Mergers Hosting Pulsars  

NASA Astrophysics Data System (ADS)

Short-duration gamma-ray bursts (sGRBs) are widely believed to result from the mergers of compact binaries. This model predicts an afterglow that bears the characteristic signatures of a constant, low-density medium, including a smooth prompt-afterglow transition, and a simple temporal evolution. However, these expectations are in conflict with observations for a non-negligible fraction of sGRB afterglows. In particular, the onset of the afterglow phase for some of these events appears to be delayed and, in addition, a few of them exhibit late-time rapid fading in their light curves. We show that these peculiar observations can be explained independently of ongoing central engine activity if some sGRB progenitors are compact binaries hosting at least one pulsar. The Poynting flux emanating from the pulsar companion can excavate a bow-shock cavity surrounding the binary. If this cavity is larger than the shock deceleration length scale in the undisturbed interstellar medium, then the onset of the afterglow will be delayed. Should the deceleration occur entirely within the swept-up thin shell, a rapid fade in the light curve will ensue. We identify two types of pulsar that can achieve the conditions necessary for altering the afterglow: low-field, long-lived pulsars, and high-field pulsars. We find that a sizable fraction (?20%-50%) of low-field pulsars are likely to reside in neutron star binaries based on observations, while their high-field counterparts are not. Hydrodynamical calculations motivated by this model are shown to be in good agreement with observations of sGRB afterglow light curves.

Holcomb, Cole; Ramirez-Ruiz, Enrico; De Colle, Fabio; Montes, Gabriela

2014-07-01

22

Compact LaBr{sub 3}: Ce Gamma Ray Detector with Si-APD Readout  

SciTech Connect

BrilLanCe 380 (LaBr{sub 3}:Ce) crystal scintillators available from Saint-Gobain Crystals have achieved 2.6% FWHM for 662 keV photons. This is accomplished with PMT light sensors. Attempts to have similarly good results with PIN photo-diodes and APDs have not been successful. PIN photodiodes do not have any gain and the signal to noise ratio is poor at room temperature. Similarly, even though APDs have sufficient gain, they have poor signal to noise at room temperature. Recently there have been improvements in APDs decreasing the internal noise and increasing their sensitivity, making them an excellent light sensor. With the improved APD, it is now possible to achieve performance with a solid state light sensor comparable to that of PMTs. We have measured 2.8% for 662 keV gamma rays at room temperature using an APD for a light sensor on a 20 mm long crystal of 1.6 cc volume. APDs have advantages of compactness, inherent ruggedness and minimal sensitivity to magnetic fields. Such a device is very practical for hand held and portable field measurement applications. (Performance reported in SGC literature.)

Flamanc, Jeremy [Saint-Gobain Crystals, 104 Route de Larchant, 77140 St Pierre les Nemours (France); Rozsa, Csaba [Saint-Gobain Crystals, 17900 Great Lakes Parkway, Hiram, OH 44234 (United States)

2009-03-10

23

Gamma Rays  

MedlinePLUS

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

24

A compact radio source in the high-redshift soft gamma-ray blazar IGR J12319-0749  

NASA Astrophysics Data System (ADS)

Context. Blazars are powerful active galactic nuclei (AGNs) radiating prominently in the whole electromagnetic spectrum, from the radio to the X-ray and gamma-ray bands. Their emission is dominated by synchrotron and inverse-Compton radiation from a relativistic jet originating from an accreting central supermassive black hole. The object IGR J12319-0749 has recently been identified as a soft gamma-ray source with the IBIS instrument of the INTEGRAL satellite, coincident with a quasar at high redshift (z = 3.12). Aims: We studied the radio structure of IGR J12319-0749 to strengthen its blazar identification by detecting a compact radio jet on the milli-arcsecond (mas) angular scale, and to measure its astrometric position accurate to mas level. Methods: We used the technique of electronic very long baseline interferometry (e-VLBI) to image IGR J12319-0749 with the European VLBI Network (EVN) at 5 GHz on 2012 June 19. Results: IGR J12319-0749 (J1231-0747) is a compact radio source, practically unresolved on interferometric baselines up to ~136 million wavelengths. The estimated brightness temperature (at least 2 × 1011 K) indicates that the radio emission of its jet is Doppler-boosted. The accurate position of the compact radio source is consistent with the positions measured at higher energies.

Frey, S.; Paragi, Z.; Gabányi, K. É.; An, T.

2013-04-01

25

Compact, high-resolution, gamma ray imaging for scintimammography and other medical diagostic applications  

DOEpatents

A high resolution gamma ray imaging device includes an aluminum housing, a lead screen collimator at an opened end of the housing, a crystal scintillator array mounted behind the lead screen collimator, a foam layer between the lead screen collimator and the crystal scintillator array, a photomultiplier window coupled to the crystal with optical coupling grease, a photomultiplier having a dynode chain body and a base voltage divider with anodes, anode wire amplifiers each connected to four anodes and a multi pin connector having pin connections to each anode wire amplifier. In one embodiment the crystal scintillator array includes a yttrium aluminum perovskite (YAP) crystal array. In an alternate embodiment, the crystal scintillator array includes a gadolinium oxyorthosilicate (GSO) crystal array.

Majewski, Stanislaw (Grafton, VA); Weisenberger, Andrew G. (Grafton, VA); Wojcik, Randolph F. (Yorktown, VA); Steinbach, Daniela (Williamsburg, VA)

1999-01-01

26

Effects of gamma-ray, neutrino, and particle production on the energetics and dynamics of compact extragalactic radio sources  

NASA Technical Reports Server (NTRS)

Consideration is given to particle production and high-energy radiation within apparently superluminal radio components of extragalactic radio sources forming within the apparent region of nuclear activity of a quasar or active galaxy. The physical conditions in compact components observed as radio emitters are derived for the quasars 3C 273 and 3C 345 and extrapolated to those of initial components of sizes on the order of 10 to the 15th cm on the basis of two-dimensional relativistic jet and relativistic three-dimensional models of component expansion. Probabilities that a given particle avoids an inelastic collision in the relativistic plasma are calculated for both cases which show that collisions which produce particles and radiation may be very important during the formation of a compact radio component. The consequences of electron-positron production, bremsstrahlung and proton-proton inelastic collisions ultimately giving rise to neutrinos and gamma rays for the development and energetics of the radio component are then examined, and upper limits to the amount of energy which can be channeled into radio components from an active region without giving rise to a high-energy X-ray source are derived.

Vestrand, W. T.; Scott, J. S.; Marscher, A. P.; Christiansen, W. A.

1981-01-01

27

Limits on the cosmological abundance of supermassive compact objects from a millilensing search in gamma-ray burst data  

NASA Astrophysics Data System (ADS)

A new search for the gravitational lens effects of a significant cosmological density of supermassive compact objects (SCOs) on gamma-ray bursts has yielded a null result. We inspected the timing data of 774 BATSE-triggered GRBs for evidence of millilensing: repeated peaks similar in light-curve shape and spectra. Our null detection leads us to conclude that, in all candidate universes simulated, OmegaSCO < 0.1 is favored for 105 < MSCO/Modot < 109, while in some universes and mass ranges the density limits are as much as 10 times lower. Therefore, a cosmologically significant population of SCOs near globular cluster mass neither came out of the primordial universe, nor condensed at recombination.

Nemiroff, Robert J.; Marani, Gabriela F.; Norris, J. P.; Bonnell, J. T.

2001-01-01

28

A Compact Monitoring System for Recording X-Rays, Gamma Rays and Neutrons Generated By Atmospheric Lightning Discharges and Other Natural Phenomena  

NASA Astrophysics Data System (ADS)

The generation of X-rays, gamma-rays and neutrons by atmospheric lightning discharges has been predicted by different researchers several decades ago. But only within the last 25 years the first experimental evidences of events relating the generation of these radiations with lightning have been made; since then there is a continuing effort to collect more information about this type of phenomenon. In this study we describe a compact monitoring system to detect simultaneously X-rays, gamma-rays and neutrons using rather inexpensive off-the-shelf commercial detectors (Micro Roengten Radiation Monitor, 8-inch gamma tube coupled to a 3x3 inch sodium iodide [Nai(Tl)] crystal, Ludlum He-3 neutron detector) and accompanying computer interfaces. The system is extremely portable and can be powered with small automotive batteries, if necessary. Measurements are performed at ground-level. Preliminary measurements have already yielded positive results, e.g., changes in the neutron flux related to a lightning discharge and varying weather conditions have been observed in the city of Sao Jose dos Campos, Brazil (23° 11? 11?S, 45° 52? 43? W, 600 m above sea level). This a pilot study, in the near future a larger number of these compact monitoring system will be installed in different location in order to increase the area coverage. Although the main objective of the study is to detect high-energy events produced by lightning discharges, the monitoring system will also be able to detect changes in the radiation background produced by other natural phenomena.

Martin, I. M.; Alves, M. A.

2009-12-01

29

Searching for the 511 keV annihilation line from galactic compact objects with the IBIS gamma ray telescope  

NASA Astrophysics Data System (ADS)

Context. The first detection of a gamma ray line with an energy of about 500 keV from the center of our Galaxy dates back to the early seventies. Thanks to the astrophysical application of high spectral resolution detectors, it was soon clear that this radiation was due to the 511 keV photons generated by electron-positron annihilation. Even though the physical process are known, the astrophysical origin of this radiation is still a mystery. Aims: The spectrometer SPI aboard the INTEGRAL gamma-ray satellite has been used to produce the first all-sky map in light of the 511 keV annihilation, but no direct evidence of any 511 keV galactic compact objects has been found. Owing to its moderate angular resolution, these SPI data are still compatible with a distribution of point sources clustered in the bulge of our Galaxy. Thanks to the fine angular resolution and the large field of view, the IBIS imager on the INTEGRAL satellite gives us the unique opportunity to search for a possible 511 keV line from point sources associated to known objects, such as X-ray binaries, or supernovae, or even new ones. Methods: We present the first deep IBIS 511 keV all-sky map, obtained by applying standard analysis to about 5 years of data. Possible 511 keV signals are also searched over hour-day-month timescales. The IBIS sensitivity at 511 keV depends on the detector quantum efficiency at this energy and on the background. Both these quantities were estimated in this work. Results: We find no evidence of Galactic 511 keV point sources. With an exposure of 10 Ms, in the center of the Galaxy, we estimate a 1.6 × 10-4 ph cm-2 s-1 flux 2 sigma upper limit. A similar limit is given in a wide area in the Galactic center region with similar exposures. The IBIS 511 keV flux upper limits for microquasars and supernova remnants detected in the hard X domain (E > 20 keV) are also reported. Conclusions: Our results are consistent with a diffuse e + e - annihilation scenario. If positrons are generated in compact objects, we expect that a significant fraction of them propagate in the interstellar medium before they are annihilated away from their birth places.

De Cesare, G.

2011-07-01

30

Monte-Carlo simulation of a compact gamma-ray detector using wavelength-shifting fibers coupled to a YAP scintillation crystal  

NASA Astrophysics Data System (ADS)

The production and transportation of fluorescent light produced in wavelength-shifting fibers (WSFs) coupled to YAP scintillation crystal is simulated using the GEANT4 codes. An advantage of the wavelength-shifting fiber readout technique over a direct readout with a position-sensitive photo-sensor is the reduced requirement for position sensitive photomultiplier tube photocathode area. With this gamma-ray detector, the gamma camera is small and flexible and has larger effective field of view and low cost. Simulation results show that a) a mean 12 of photons per 59.5 keV gamma ray interaction is produced in the WSF located nearest to the incident gamma ray, and a spatial resolution of 3.6 mm FWHM is obtained, b) a mean 27 of photons per 140 keV gamma ray interaction is produced and a spatial resolution of 3.1 mm FWHM is obtained. Results demonstrate the feasibility of this concept of a compact gamma-ray detector based on wavelength-shifting fibers readout. However, since the very low photoelectron levels, it is very important to use a photon counting device with good single photo-electron response to readout the WSFs. Supported by National Nature Science Foundation of China (10275063)

Zhu, Jie; Ma, Hong-Guang; Ma, Wen-Yan; Zeng, Hui; Wang, Zhao-Min; Xu, Zi-Zong

2008-05-01

31

The Formation and Merger of Compact Objects in the Central Engine of Active Galactic Nuclei and Quasars: Gamma-Ray Burst and Gravitational Radiation  

NASA Astrophysics Data System (ADS)

The production rate of compact objects, i.e., neutron stars (NSs) and black holes (BHs), in active galactic nuclei (AGNs) and quasars (QSOs), where frequent supernova explosions are used to explain the high metallicity, is very high because of the interaction between the accretion disk and main-sequence stars in the nucleus of the quasar. The compact object red giant (RG) star binaries can be easily formed because of the large captured cross section of the RG stars. The (NS/BH, NS/BH) binary can be formed after the supernova explosion of the (NS/BH, RG) binary. Intense transient gamma-ray emission (gamma-ray burst) and gravitational radiation can result from the merger of these two compact objects. Collision between the helium core (Hc) of the RG and the BH may also take place and may also result in long-duration gamma-ray bursts but no gravitational waves. We estimate that the merger rate of (NS/BH, NS/BH) binaries and (Hc, BH) is proportional to the metal abundance N V/C IV and can be as high as 10-3 [(N V/C IV)/0.01] yr-1 per AGN/QSO.

Cheng, K. S.; Wang, Jian-Min

1999-08-01

32

Compact Stellar X-ray Sources  

NASA Astrophysics Data System (ADS)

1. Accreting neutron stars and black holes: a decade of discoveries D. Psaltis; 2. Rapid X-ray variability M. van der Klis; 3. New views of thermonuclear bursts T. Strohmayer and L. Bildsten; 4. Black hole binaries J. McClintock and R. Remillard; 5. Optical, ultraviolet and infrared observations of X-ray binaries P. Charles and M. Coe; 6. Fast X-ray transients and X-ray flashes J. Heise and J. in 't Zand; 7. Isolated neutron stars V. Kaspi, M. Roberts and A. Harding; 8. Globular cluster X-ray sources F. Verbunt and W. Lewin; 9. Jets from X-ray binaries R. Fender; 10. X-Rays from cataclysmic variables E. Kuulkers, A. Norton, A. Schwope and B. Warner; 11. Super soft sources P. Kahabka and E. van den Heuvel; 12. Compact stellar X-ray sources in normal galaxies G. Fabbiano and N. White; 13. Accretion in compact binaries A. King; 14. Soft gamma repeaters and anomalous X-ray pulsars: magnetar candidates P. Woods and C. Thompson; 15. Cosmic gamma-ray bursts, their afterglows, and their host galaxies K. Hurley, R. Sari and S. Djorgovski; 16. Formation and evolution of compact stellar X-ray sources T. Tauris and E. van den Heuvel.

Lewin, Walter; van der Klis, Michiel

2010-11-01

33

Sandstone and shale compaction curves derived from sonic and gamma ray logs in offshore wells, North Slope, Alaska; parameters for basin modeling  

USGS Publications Warehouse

Representative compaction curves for the principle lithologies are essential input for reliable models of basin history. Compaction curves influence estimates of maximum burial and erosion. Different compaction curves may produce significantly different thermal histories. Default compaction curves provided by basin modeling packages may or may not be a good proxy for the compaction properties in a given area. Compaction curves in the published literature span a wide range, even within one lithology, e.g., sandstone (see Panel 3). An abundance of geophysical well data for the North Slope, from both government and private sources, provides us with an unusually good opportunity to develop compaction curves for the Cretaceous-Tertiary Brookian sandstones, siltstones, and shales. We examined the sonic and gamma ray logs from 19 offshore wells (see map), where significant erosion is least likely to have occurred. Our data are primarily from the Cretaceous-Tertiary Brookian sequence and are less complete for older sequences. For each well, the fraction of shale (Vsh) at a given depth was estimated from the gamma ray log, and porosity was computed from sonic travel time. By compositing porosities for the near-pure sand (Vsh99%)from many individual wells we obtained data over sufficient depth intervals to define sandstone and shale 'master' compaction curves. A siltstone curve was defined using the sonic-derived porosities for Vsh values of 50%. These compaction curves generally match most of the sonic porosities with an error of 5% or less. Onshore, the curves are used to estimate the depth of maximum burial at the end of Brookian sedimentation. The depth of sonic-derived porosity profiles is adjusted to give the best match with the 'master' compaction curves. The amount of the depth adjustment is the erosion estimate. Using our compaction curves, erosion estimates on the North Slope range from zero in much of the offshore, to as much as 1500 ft along the coast, and to more than 10,000 ft in the foothills (Panel 3). Compaction curves provide an alternative to vitrinite reflectance for estimating erosion. Vitrinite reflectance data are often very sparse in contrast to well log data and are subject to inconsistencies when measurements are made by different labs. The phenomenon of 'recycling' can also make the reflectance values of dispersed vitrinite problematic for quantifying erosion. Recycling is suspected in dispersed vitrinite in North Slope rocks, particularly in the younger, Cretaceous-Tertiary section. The compaction curves defined here are being integrated into our burial history and thermal models to determine the timing of source rock maturation. An example on Panel 3 shows the results of calculating the maturity of the Shublik Fm. at the Tulaga well using two different sets of shale and siltstone compaction curves. Finally, accurate compaction curves improve a model's ability to realistically simulate the pressure regime during burial, including overpressures.

Rowan, Elisabeth L.; Hayba, Daniel O.; Nelson, Philip H.; Burns, W. Matthew; Houseknecht, David W.

2003-01-01

34

Gamma-ray bursters  

NASA Technical Reports Server (NTRS)

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

Schaefer, B. E.

1985-01-01

35

Gamma ray camera  

Microsoft Academic Search

A gamma ray camera is disclosed for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an

1997-01-01

36

Gamma ray camera  

Microsoft Academic Search

A gamma ray camera for detecting rays emanating from a radiation source such as an isotope. The gamma ray camera includes a sensor array formed of a visible light crystal for converting incident gamma rays to a plurality of corresponding visible light photons, and a photosensor array responsive to the visible light photons in order to form an electronic image

Victor

1997-01-01

37

Future prospects for gamma-ray  

NASA Technical Reports Server (NTRS)

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

Fichtel, C.

1980-01-01

38

Gamma-ray waveguides  

SciTech Connect

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

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

2008-04-14

39

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

40

Last Moments in the Life of a Compact Binary System: Gravitational Waves, Gamma-Ray Bursts and Magnetar Formation  

NASA Astrophysics Data System (ADS)

The first detections of afterglows from short gamma-ray bursts (GRBs) have confirmed the previous suspicion that they are triggered by a different central engine than long bursts. In particular, the recent detections of short GRBs in galaxies without star formation lends support to the idea that an old stellar population is involved. Most prominent are mergers of either double neutron stars or of a neutron star with a stellar-mass black hole companion. Since the final identification of the central engine will only come from an integral view of several properties, we review the observable signatures that can be expected from both double neutron stars and neutron star black hole systems. We discuss the gravitational wave emission, the structure of the neutrino-cooled accretion disks, the resulting neutrino signal and possible mechanisms to launch a GRB. In addition, we address the speculative idea that in some cases a magnetar-like object may be the final outcome of a double neutron star merger. We also discuss possibilities to explain the late-time X-ray activity that has been observed in several bursts.

Rosswog, S.

2007-03-01

41

Gamma-Ray Pulsars  

Microsoft Academic Search

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

Gottfried Kanbach

2002-01-01

42

Gamma ray transients  

NASA Technical Reports Server (NTRS)

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

Cline, Thomas L.

1987-01-01

43

HALO RETENTION AND EVOLUTION OF COALESCING COMPACT BINARIES IN COSMOLOGICAL SIMULATIONS OF STRUCTURE FORMATION: IMPLICATIONS FOR SHORT GAMMA-RAY BURSTS  

SciTech Connect

Merging compact binaries are the one source of gravitational radiation so far identified. Because short-period systems that will merge in less than a Hubble time have already been observed as binary pulsars, they are important both as gravitational wave sources for observatories such as LIGO, but also as progenitors for short gamma-ray bursts (SGRBs). The fact that these systems must have large systemic velocities implies that by the time they merge, they will be far from their formation site. The locations of merging sites depend sensitively on the gravitational potential of the galaxy host, which until now has been assumed to be static. Here we refine such calculations to incorporate the temporal evolution of the host's gravitational potential as well as that of its nearby neighbors using cosmological simulations of structure formation. This results in merger site distributions that are more diffusively distributed with respect to their putative hosts, with locations extending out to distances of a few Mpc for lighter halos. The degree of mixing between neighboring compact binary populations computed in this way is severely enhanced in environments with a high number density of galaxies. We find that SGRB redshift estimates based solely on the nearest galaxy in projection can be very inaccurate, if progenitor systems inhere large systematic kicks at birth.

Zemp, Marcel [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Ramirez-Ruiz, Enrico; Diemand, Juerg, E-mail: mzemp@umich.ed, E-mail: enrico@ucolick.or, E-mail: diemand@ucolick.or [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

2009-11-10

44

Gamma-ray Bursts  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

45

Gamma Ray Bursts.  

National Technical Information Service (NTIS)

Gamma-ray bursts (GRBs) are bright flashes of gamma-rays coming from the cosmos. They occur roughly once per day, last typically lOs of seconds and are the most luminous events in the universe. More than three decades after their discovery, and after pion...

N. Gehrels P. Meszaros

2012-01-01

46

Gamma-Ray Pulsars  

NASA Technical Reports Server (NTRS)

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

Harding, Alice K.

2011-01-01

47

gamma. -ray diagnostic for the CIT  

SciTech Connect

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

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

1988-08-01

48

Cosmological gamma-ray bursts  

NASA Technical Reports Server (NTRS)

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

Paczynski, Bohdan

1991-01-01

49

Gamma-ray telescopes  

Microsoft Academic Search

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

Neil Gehrels; John K. Cannizzo

2009-01-01

50

Gamma Ray Pulsars: Observations  

NASA Technical Reports Server (NTRS)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. Unless a new pulsed component appears at higher energies, progress in gamma-ray pulsar studies will be greatest in the 1-20 GeV range. Ground-based telescopes whose energy ranges extend downward toward 10 GeV should make important measurements of the spectral cutoffs. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2005, will provide a major advance in sensitivity, energy range, and sky coverage.

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

2000-01-01

51

Gamma-Ray Detectors  

NASA Astrophysics Data System (ADS)

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

Dunn, William L.; McGregor, Douglas S.

52

Gamma ray pulsars: Observations  

Microsoft Academic Search

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO\\/EGRET show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of

David J. Thompson

2001-01-01

53

gamma ray astronomy with muons  

Microsoft Academic Search

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

Francis Halzen; Todor Stanev; Gaurang B. Yodh

1997-01-01

54

The gamma-ray observatory  

NASA Technical Reports Server (NTRS)

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

1991-01-01

55

Gamma ray optics  

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

56

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

57

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

58

Gamma Ray Astronomy  

NASA Technical Reports Server (NTRS)

The project has progressed successfully during this period of performance. The highlights of the Gamma Ray Astronomy teams efforts are: (1) Support daily BATSE data operations, including receipt, archival and dissemination of data, quick-look science analysis, rapid gamma-ray burst and transient monitoring and response efforts, instrument state-of-health monitoring, and instrument commanding and configuration; (2) On-going scientific analysis, including production and maintenance of gamma-ray burst, pulsed source and occultation source catalogs, gamma-ray burst spectroscopy, studies of the properties of pulsars and black holes, and long-term monitoring of hard x-ray sources; (3) Maintenance and continuous improvement of BATSE instrument response and calibration data bases; (4) Investigation of the use of solid state detectors for eventual application and instrument to perform all sky monitoring of X-Ray and Gamma sources with high sensitivity; and (5) Support of BATSE outreach activities, including seminars, colloquia and World Wide Web pages. The highlights of this efforts can be summarized in the publications and presentation list.

Wu, S. T.

2000-01-01

59

Quasars, blazars, and gamma rays  

NASA Technical Reports Server (NTRS)

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

Dermer, Charles D.; Schlickeiser, Reinhard

1992-01-01

60

Images obtained with a compact gamma camera  

NASA Astrophysics Data System (ADS)

A design for a compact gamma camera based on the use of a position-sensitive photomultiplier is presented. Tests have been carried out on a prototype detector system, having a sensitive area of 25 cm 2, using both a simple pinhole aperture and a parallel collimator. Images of a thyroid phantom are presented, and after processing to reduce the artefacts introduced by the use of a pinhole aperture, the quality is compared with that obtained using a standard Anger camera.

Bird, A. J.; Ramsden, D.

1990-12-01

61

Gamma ray pulsars  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

62

ACCELERATING COMPACT OBJECT MERGERS IN TRIPLE SYSTEMS WITH THE KOZAI RESONANCE: A MECHANISM FOR 'PROMPT' TYPE Ia SUPERNOVAE, GAMMA-RAY BURSTS, AND OTHER EXOTICA  

SciTech Connect

White dwarf-white dwarf (WD-WD) and neutron star-neutron star (NS-NS) mergers may produce Type Ia supernovae and gamma-ray bursts (GRBs), respectively. A general problem is how to produce binaries with semi-major axes small enough to merge in significantly less than the Hubble time (t{sub H}), and thus accommodate the observation that these events closely follow episodes of star formation. I explore the possibility that such systems are not binaries at all, but actually coeval, or dynamical formed, triple systems. The tertiary induces Kozai oscillations in the inner binary, driving it to high eccentricity, and reducing its gravitational wave (GW) merger timescale. This effect significantly increases the allowed range of binary period P such that the merger time is t{sub merge} < t{sub H}. In principle, Chandrasekhar-mass binaries with P {approx} 300 days can merge in {approx}< t{sub H} if they contain a prograde solar-mass tertiary at high enough inclination. For retrograde tertiaries, the maximum P such that t{sub merge} {approx}< t{sub H} is yet larger. In contrast, P {approx}< 0.3 days is required in the absence of a tertiary. I discuss implications of these findings for the production of transients formed via compact object binary mergers. Based on the statistics of solar-type binaries, I argue that many such binaries should be in triple systems affected by the Kozai resonance. If true, expectations for the mHz GW signal from individual sources, the diffuse background, and the foreground for GW experiments like LISA are modified. This work motivates future studies of triples systems of A, B, and O stars, and new types of searches for WD-WD binaries in triple systems.

Thompson, Todd A., E-mail: thompson@astronomy.ohio-state.edu [Department of Astronomy and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States)

2011-11-10

63

Gamma-ray Polarimetry  

SciTech Connect

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

Tajima, Hiroyasu

2003-02-05

64

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

65

Gamma ray astronomy  

NASA Technical Reports Server (NTRS)

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

Paciesas, William S.

1992-01-01

66

Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

67

Gamma-ray Astronomy.  

National Technical Information Service (NTIS)

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

W. S. Paciesas

1994-01-01

68

Liquid xenon gamma ray imager  

US Patent & Trademark Office Database

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

2013-07-02

69

Soft gamma rays from black holes versus neutron stars  

NASA Technical Reports Server (NTRS)

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

Liang, Edison P.

1992-01-01

70

Unidentified Gamma-Ray Sources: Hunting Gamma-Ray Blazars  

SciTech Connect

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

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

2012-04-02

71

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

SciTech Connect

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

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

2012-06-10

72

Gamma Ray Astrophysics: New insight into the universe  

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

73

Gamma-ray localization of terrestrial gamma-ray flashes.  

PubMed

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

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

2010-09-17

74

Compact x-ray source and panel  

DOEpatents

A compact, self-contained x-ray source, and a compact x-ray source panel having a plurality of such x-ray sources arranged in a preferably broad-area pixelized array. Each x-ray source includes an electron source for producing an electron beam, an x-ray conversion target, and a multilayer insulator separating the electron source and the x-ray conversion target from each other. The multi-layer insulator preferably has a cylindrical configuration with a plurality of alternating insulator and conductor layers surrounding an acceleration channel leading from the electron source to the x-ray conversion target. A power source is connected to each x-ray source of the array to produce an accelerating gradient between the electron source and x-ray conversion target in any one or more of the x-ray sources independent of other x-ray sources in the array, so as to accelerate an electron beam towards the x-ray conversion target. The multilayer insulator enables relatively short separation distances between the electron source and the x-ray conversion target so that a thin panel is possible for compactness. This is due to the ability of the plurality of alternating insulator and conductor layers of the multilayer insulators to resist surface flashover when sufficiently high acceleration energies necessary for x-ray generation are supplied by the power source to the x-ray sources.

Sampayon, Stephen E. (Manteca, CA)

2008-02-12

75

{gamma} ray astronomy with muons  

SciTech Connect

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

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

1997-04-01

76

Gamma Ray Pulsars: Multiwavelength Observations  

Microsoft Academic Search

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

David J. Thompson

2003-01-01

77

The Gamma Ray Pulsar Population  

Microsoft Academic Search

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

M. A. McLaughlin; J. M. Cordes

1999-01-01

78

Digital Pulse Processing and Gamma Ray Tracking  

NSDL National Science Digital Library

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

2010-09-21

79

Astrophysical gamma-ray spectroscopy  

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

80

The gamma-ray telescope Gamma-1  

NASA Astrophysics Data System (ADS)

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

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

81

The gamma-ray telescope Gamma1  

Microsoft Academic Search

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

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

1989-01-01

82

Planetary gamma-ray spectroscopy  

NASA Technical Reports Server (NTRS)

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

Reedy, R. C.

1978-01-01

83

Gamma-ray spectrometer experiment  

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

84

Compact Gamma Camera System for Breast Cancer Imaging.  

National Technical Information Service (NTIS)

The goal of this project is the development of a compact solid-state gamma camera specifically designed to image metabolically active tumors in the breast and axillary nodes with the highest possible detection efficiency and spatial resolution. The compac...

S. E. Derenzo

1999-01-01

85

Compact Gamma Camera System for Breast Cancer Imaging.  

National Technical Information Service (NTIS)

In this project we have developed a compact solid-state gamma camera specifically designed to image metabolically active tumors in the breast and axillary nodes with the highest possible detection efficiency and spatial resolution. We have assembled final...

S. E. Derenzo

2001-01-01

86

Gamma rays, cosmic rays, and galactic structure  

NASA Technical Reports Server (NTRS)

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

Stecker, F. W.

1977-01-01

87

The significance of gamma ray observations for neutrino astronomy  

NASA Technical Reports Server (NTRS)

X-ray, gamma ray and neutrino observations are examined to show, in a general way, the relationship between them. Existing gamma ray measurements are summarized and some examples are used to set ranges or limits for neutrino fluxes for specific types of models. The purpose of this is to show the possibilities for separation between models and to aid in the consideration of neutrino detector designs. Attention is given to exceptional and normal galaxies, as well as to compact objects, and diffuse isotropic radiation. It is noted that the close relationship between gamma rays and neutrino production will be useful for future neutrino astronomy.

Fichtel, C. E.

1979-01-01

88

Pulsars as gamma ray sources.  

NASA Astrophysics Data System (ADS)

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

Arons, J.

1996-11-01

89

Diffuse galactic gamma ray lines  

NASA Technical Reports Server (NTRS)

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

Lingenfelter, R. E.; Ramaty, R.

1977-01-01

90

Compact Five-Gun Cathode Ray Tube.  

National Technical Information Service (NTIS)

The objective of this contract was to develope a compact five-gun cathode ray tube similar to thE JAN-7YP2, but restricted to an overall length of 12 inches. Initial efforts during this period were directed towards design and tooling of a suitable glass e...

G. E. Hassler

1970-01-01

91

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

92

Gamma-Ray Pulsars: Observations  

NASA Technical Reports Server (NTRS)

High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The six or more pulsars seen by CGRO/EGRET show that the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. Unless a new pulsed component appears at higher energies, progress in gamma-ray pulsar studies will be greatest in the 1-10 GeV range . Ground-based telescopes whose energy ranges extend downward toward 10 GeV should make important measurements of the spectral cutoffs. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a possible launch in 2005, will provide a major advance in sensitivity, energy range, and sky coverage.

Thompson, David J.

2000-01-01

93

Jet Shockwaves Produce Gamma Rays  

NASA Video Gallery

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

94

Physics of Gamma Ray Burst Sources  

NASA Technical Reports Server (NTRS)

During this grant period, the physics of gamma-ray bursts was investigated. A number of new results have emerged. The importance of pair formation in high compactness burst spectra may help explain x-ray flashes; a universal jet shape is a likely explanation for the distribution of jet break times; gravitational waves may be copiously produced both in short bursts from compact mergers and in long bursts arising from collapsars; x-ray iron lines are likely to be due to interaction with the stellar atmosphere of the progenitor; prompt optical flashes from reverse shocks will give diagnostics on the Lorentz factor and the environment; GeV and TeV emission from bursts may be expected in the external shock; etc. The group working with the PI included postdocs Dr. Bing Zhang (now assistant professor at University of Nevada); Dr. Shiho Kobayashi; graduate student Lijun Gou; collaborators Drs. Tim Kallman and Martin Rees. Meszaros shared with Rees and Dr. Bohan Paczynsky the AAS Rossi Prize in 2000 for their work on the theory of gamma ray bursts. The refereed publications and conference proceedings resulting from this research are summarized below. The PI gave a number of invited talks at major conferences, also listed.

Meszaros, Peter

2004-01-01

95

Gamma-ray pulsar model  

Microsoft Academic Search

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

Jeffrey M. Cohen; Errol Mustafa

1987-01-01

96

Short Gamma-Ray Burst Formation Rate from BATSE Data Using Ep -Lp Correlation and the Minimum Gravitational-wave Event Rate of a Coalescing Compact Binary  

NASA Astrophysics Data System (ADS)

Using 72 short gamma-ray bursts (SGRBs) with well determined spectral data observed by BATSE, we determine their redshift and luminosity by applying the Ep -Lp correlation for SGRBs found by Tsutsui et al. For 53 SGRBs with an observed flux brighter than 4 × 10–6 erg cm–2 s–1, the cumulative redshift distribution up to z = 1 agrees well with that of 22 Swift SGRBs. This suggests that the redshift determination by the Ep -Lp correlation for SGRBs works well. The minimum event rate at z = 0 is estimated as R_on{-axis}^min = 6.3_{-3.9}^{+3.1} \\times \\, 10^{-10}\\, events\\, Mpc^{-3\\,yr^{-1}}, so that the minimum beaming angle is 0.°6-7.°8 assuming a merging rate of 10–7- 4 × 10–6 events Mpc–3 yr–1 suggested from the binary pulsar data. Interestingly, this angle is consistent with that for SGRB 130603B of ~4°-8°. On the other hand, if we assume a beaming angle of ~6° suggested from four SGRBs with the observed beaming angle value, then the minimum event rate including off-axis SGRBs is estimated as R_all^min=1.15_{-0.66}^{+0.56}\\,\\times \\,10^{-7}\\, events \\,Mpc^{-3\\,yr^{-1}}. If SGRBs are induced by the coalescence of binary neutron stars (NSs) and/or black holes (BHs), then this event rate leads to a minimum gravitational-wave detection rate of 3.8_{-2.2}^{+1.8} \\,(146_{-83}^{+71})\\, events\\, yr^{-1} for an NS-NS (NS-BH) binary, respectively, by a worldwide network with KAGRA, advanced-LIGO, advanced-VIRGO, and GEO.

Yonetoku, Daisuke; Nakamura, Takashi; Sawano, Tatsuya; Takahashi, Keitaro; Toyanago, Asuka

2014-07-01

97

Gamma ray spectrometer experiment  

NASA Technical Reports Server (NTRS)

The transearth coast period of the Apollo 16 mission provided an opportunity to study the astronomical sources of gamma radiation. This experiment was used to aid compositional identification for geochemical mapping of the lunar surface.

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

1972-01-01

98

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

99

ROSAT: X ray survey of compact groups  

NASA Technical Reports Server (NTRS)

This is the final technical report on grant NAG5-1954, which was awarded under the NASA ROSAT Guest Investigator Program to Columbia University. This grant was awarded for a number of projects on two rather different topics: (1) an x-ray survey of compact groups of galaxies; and (2) the fate of gas in merging galaxies. Progress made in these projects is presented.

Vangorkom, Jacqueline

1993-01-01

100

A tandem-based compact dual-energy gamma generator  

NASA Astrophysics Data System (ADS)

A dual-energy tandem-type gamma generator has been developed at E. O. Lawrence Berkeley National Laboratory and Sandia National Laboratories. The tandem accelerator geometry allows higher energy nuclear reactions to be reached, thereby allowing more flexible generation of MeV-energy gammas for active interrogation applications. Both positively charged ions and atoms of hydrogen are created from negative ions via a gas stripper. In this paper, we show first results of the working tandem-based gamma generator and that a gas stripper can be utilized in a compact source design. Preliminary results of monoenergetic gamma production are shown.

Persaud, A.; Kwan, J. W.; Leitner, M.; Leung, K.-N.; Ludewigt, B.; Tanaka, N.; Waldron, W.; Wilde, S.; Antolak, A. J.; Morse, D. H.; Raber, T.

2010-02-01

101

Gamma-ray Emission from X-ray Binaries  

NASA Astrophysics Data System (ADS)

The detection of PSR B1259-63, HESS J0632+057, LS 5039, LS I +61 303 at the TeV energies has established X-ray binaries (XRBs) as a new class of very-high-energy (VHE, >100 GeV) gamma-ray emitters. Among them, PSR B1259-63 is a Be/pulsar system, detected at TeV energies by HESS and Fermi LAT, while HESS J0632+057 is a recently discovered VHE emitter composed of a Be star and a compact object of unknown nature. LS 5039 and LS I +61 303 are possibly microquasars, a sub-class of XRBs that contain a black hole with collimated, relativistic jets. Powered by accretion from the companion stars, microquasars radiate strongly at X-ray and soft gamma-ray energies. Cygnus X-1 and Cygnus X-3 are two famous microquasars as well. Cygnus X-1 has been observed once at TeV energies while Cygnus X-3 is a known GeV emitter. Many theoretical models envision VHE emission when these sources manifest relativistic persistent jets or transient ejections. In light of these considerations, VERITAS has been employed to study two XRBs for possible TeV emission. The first Be/XRB is 1A 0535+262. No GeV or TeV emission was detected over the outburst and orbital period. The gamma-ray and X-ray observations suggest the absence of a significant population of non-thermal particles in the system, which distinguishes 1A 0535+262 from other Be/XRBs such as PSR B1259-63 and LS I +61 303. VERITAS has also been involved in the study of Cygnus X-3 as part of the multi-wavelength study effort in the radio, infra-red, soft x-ray, hard x-ray and gamma-ray (<100 GeV) bands, which has proven very useful in the understanding of the physics of the system, even in the lack of TeV emission. With the aid of VERITAS, it can be possible to cast light on the particular conditions which could trigger VHE emission. This can help us understand the mechanisms that may trigger VHE gamma-ray emission, thus improving our knowledge of particle acceleration and radiative processes in the jets. The implications have far reaching consequences on the understanding of other XRBs and microquasars and also of active galactic nuclei, which are in many ways similar to microquasars and are prominent VHE gamma-ray sources themselves.

Varlotta, Angelo; VERITAS; AGILE

2013-01-01

102

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

ScienceCinema

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

103

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

ScienceCinema

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

Isabelle Grenier

2010-01-08

104

The Gamma-ray Sky with Fermi  

NASA Technical Reports Server (NTRS)

Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

Thompson, David

2012-01-01

105

Terrestrial gamma-ray flashes  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

106

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

107

Gamma ray spectroscopy in astrophysics. [conferences  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

108

Gamma Ray Spectroscopy of Mn54  

Microsoft Academic Search

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

Toshio Katoh; Masao Nozawa; Yasukazu Yoshizawa; Yujiro Koh

1958-01-01

109

Distribution of Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

110

Diffuse galactic gamma ray lines  

NASA Technical Reports Server (NTRS)

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

Lingenfelter, R. E.; Ramaty, R.

1976-01-01

111

The Gamma-ray Universe through Fermi  

NASA Technical Reports Server (NTRS)

Gamma rays, the most powerful form of light, reveal extreme conditions in the Universe. The Fermi Gamma-ray Space Telescope and its smaller cousin AGILE have been exploring the gamma-ray sky for several years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge ga.nuna-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.

Thompson, David J.

2012-01-01

112

Pinhole imaging of gamma rays  

Microsoft Academic Search

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

D. Paix

1967-01-01

113

Compact Gamma Camera System for Breast Cancer Imaging.  

National Technical Information Service (NTIS)

The goal of this project is the development of a compact solid-state gamma camera specifically designed to image metabolically active tumors in the breast and axillary nodes with the highest possible detection efficiency and spatial resolution. We have de...

S. Derenzo

2000-01-01

114

The GRAD gamma ray spectrometer  

SciTech Connect

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

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

1986-02-01

115

Gamma-ray camera flyby  

ScienceCinema

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

116

Gamma-ray camera flyby  

SciTech Connect

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

None

2010-01-01

117

Continuous Energy gamma-Ray Spectrometry.  

National Technical Information Service (NTIS)

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

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

1983-01-01

118

High Altitude Balloons and gamma Ray Astronomy.  

National Technical Information Service (NTIS)

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

C. J. MacCallum

1988-01-01

119

Recent developments in semiconductor gamma-ray detectors  

SciTech Connect

The successful development of lithium-drifted Ge detectors in the 1960's marked the beginning of the significant use of semiconductor crystals for direct detection and spectroscopy of gamma rays. In the 1970's, high-purity Ge became available, which enabled the production of complex detectors and multi-detector systems. In the following decades, the technology of semiconductor gamma-ray detectors continued to advance, with significant developments not only in Ge detectors but also in Si detectors and room-temperature compound-semiconductor detectors. In recent years, our group at Lawrence Berkeley National Laboratory has developed a variety of gamma ray detectors based on these semiconductor materials. Examples include Ge strip detectors, lithium-drifted Si strip detectors, and coplanar-grid CdZnTe detectors. These advances provide new capabilities in the measurement of gamma rays, such as the ability to perform imaging and the realization of highly compact spectroscopy systems.

Luke, Paul N.; Amman, Mark; Tindall, Craig; Lee, Julie S.

2003-10-28

120

Multiwavelength Studies of gamma-ray Binaries  

NASA Astrophysics Data System (ADS)

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

Aragona, Christina

121

Portable compton gamma-ray detection system  

SciTech Connect

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

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

2008-03-04

122

Gamma-Ray Spectroscopy of 166Er  

Microsoft Academic Search

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

Kazuo Kato; Masaharu Hoshi; Yasukazu Yoshizawa

1981-01-01

123

High altitude balloons and gamma ray astronomy  

Microsoft Academic Search

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

Crawford J. MacCallum

1988-01-01

124

Gamma ray astrophysics. [emphasizing processes and absorption  

NASA Technical Reports Server (NTRS)

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

Stecker, F. W.

1974-01-01

125

Cascaded Gamma Rays as a Probe of Cosmic Rays  

NASA Astrophysics Data System (ADS)

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

Murase, Kohta

2014-06-01

126

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

Microsoft Academic Search

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

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

127

Compton Gamma Ray Observatory Guest Investigator Program  

NASA Technical Reports Server (NTRS)

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

Lingenfelter, Richard E.

1997-01-01

128

Terrestrial Gamma-Ray Flashes (TGFs)  

NASA Technical Reports Server (NTRS)

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

Fishman, Gerald J.

2010-01-01

129

Which unidentified EGRET sources are gamma-ray pulsars?  

Microsoft Academic Search

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

L. Zhang; K. S. Cheng

1998-01-01

130

Studies of Cosmic Rays with GeV Gamma Rays.  

National Technical Information Service (NTIS)

We describe the role of GeV gamma-ray observations with GLAST-LAT (Gamma-ray Large Area Space Telescope - Large Area Telescope) in identifying interaction sites of cosmic-ray proton (or hadrons) with interstellar medium (ISM). We expect to detect gamma ra...

H. Tajima J. Chiang J. Cohen-Tanugi S. Finazzi T. Kamae

2007-01-01

131

Gamma-Ray Pulsar Studies with GLAST  

NASA Technical Reports Server (NTRS)

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

Thompson, David J.

2007-01-01

132

X-ray driven gamma emission  

NASA Astrophysics Data System (ADS)

X-ray driven gamma emission describes processes that may release nuclear energy in a 'clean' way, as bursts of incoherent or coherent gamma rays without the production of radioactive by-products. Over the past decade, studies in this area have gained tremendous momentum. X-ray triggered gamma emission from long-lived metastable nuclear excited states has been established since 1987 for one nuclide and it appears likely that triggering in other isotopes will be demonstrated conclusively in the near future. With these experimental results have come new proposals for the creation of collective and avalanche-like incoherent gamma-ray bursts and even for the ultimate light source, a gamma-ray laser. Obviously, many applications would benefit from controlled bursts of gamma radiation, whether coherent or not. This talk reviews the experimental results and concepts for the production of gamma rays, driven by externally produced x rays.

Carroll, James

2002-04-01

133

Special issue on compact x-ray sources  

NASA Astrophysics Data System (ADS)

Journal of Physics B: Atomic, Molecular and Optical Physics is delighted to announce a forthcoming special issue on compact x-ray sources, to appear in the winter of 2014, and invites you to submit a paper. The potential for high-brilliance x- and gamma-ray sources driven by advanced, compact accelerators has gained increasing attention in recent years. These novel sources—sometimes dubbed 'fifth generation sources'—will build on the revolutionary advance of the x-ray free-electron laser (FEL). New radiation sources of this type have widespread applications, including in ultra-fast imaging, diagnostic and therapeutic medicine, and studies of matter under extreme conditions. Rapid advances in compact accelerators and in FEL techniques make this an opportune moment to consider the opportunities which could be realized by bringing these two fields together. Further, the successful development of compact radiation sources driven by compact accelerators will be a significant milestone on the road to the development of high-gradient colliders able to operate at the frontiers of particle physics. Thus the time is right to publish a peer-reviewed collection of contributions concerning the state-of-the-art in: advanced and novel acceleration techniques; sophisticated physics at the frontier of FELs; and the underlying and enabling techniques of high brightness electron beam physics. Interdisciplinary research connecting two or more of these fields is also increasingly represented, as exemplified by entirely new concepts such as plasma based electron beam sources, and coherent imaging with fs-class electron beams. We hope that in producing this special edition of Journal of Physics B: Atomic, Molecular and Optical Physics (iopscience.iop.org/0953-4075/) we may help further a challenging mission and ongoing intellectual adventure: the harnessing of newly emergent, compact advanced accelerators to the creation of new, agile light sources with unprecedented capabilities. New schemes for compact accelerators: laser- and beam-driven plasma accelerators; dielectric laser accelerators; THz accelerators. Latest results for compact accelerators. Target design and staging of advanced accelerators. Advanced injection and phase space manipulation techniques. Novel diagnostics: single-shot measurement of sub-fs bunch duration; measurement of ultra-low emittance. Generation and characterization of incoherent radiation: betatron and undulator radiation; Thomson/Compton scattering sources, novel THz sources. Generation and characterization of coherent radiation. Novel FEL simulation techniques. Advances in simulations of novel accelerators: simulations of injection and acceleration processes; simulations of coherent and incoherent radiation sources; start-to-end simulations of fifth generation light sources. Novel undulator schemes. Novel laser drivers for laser-driven accelerators: high-repetition rate laser systems; high wall-plug efficiency systems. Applications of compact accelerators: imaging; radiography; medical applications; electron diffraction and microscopy. Please submit your article by 15 May 2014 (expected web publication: winter 2014); submissions received after this date will be considered for the journal, but may not be included in the special issue.

Hooker, Simon; Midorikawa, Katsumi; Rosenzweig, James

2014-04-01

134

The AGILE gamma ray satellite  

NASA Astrophysics Data System (ADS)

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

Basset, M.; AGILE Team

2007-03-01

135

Gamma-Ray Astronomy Technology Needs  

NASA Technical Reports Server (NTRS)

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

Gehrels, N.; Cannizzo, J. K.

2012-01-01

136

GRETINA: A gamma ray energy tracking array  

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

137

Gamma-Ray Spectroscopy of 42K  

Microsoft Academic Search

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

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

1970-01-01

138

Gamma-ray pulsar studies with COMPTEL  

Microsoft Academic Search

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

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

1994-01-01

139

Gamma-Ray Pulsar Studies with GLAST  

Microsoft Academic Search

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

D. J. Thompson; GAMMA-RAY PULSARS

2008-01-01

140

Gamma-Ray Pulsar Candidates for GLAST  

Microsoft Academic Search

The Gamma-ray Large Area Space Telescope (GLAST) will be launched less than a year from now, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio frequencies, are likely to emit >100 MeV gamma rays with intensities detectable by

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

2006-01-01

141

Gamma-Ray Pulsar Candidates for GLAST  

Microsoft Academic Search

The Gamma-ray Large Area Space Telescope (GLAST) will be launched this year, and its Large Area Telescope (LAT) is expected to discover scores to hundreds of gamma-ray pulsars. This poster discusses which of the over 1700 known pulsars, mostly visible only at radio frequencies, are likely to emit >100; MeV gamma rays with intensities detectable by the LAT. The main

David John Thompson

2008-01-01

142

Very High Energy Gamma-Ray Astronomy  

Microsoft Academic Search

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

Michael Catanese; Trevor C. Weekes

1999-01-01

143

GAMCIT: A gamma ray burst detector  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

144

Astrophysical constraints from gamma-ray spectroscopy  

Microsoft Academic Search

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

Roland Diehl; Nikos Prantzos; Peter von Ballmoos

2006-01-01

145

Mechanisms and sites for astrophysical gamma ray line production  

NASA Technical Reports Server (NTRS)

The production of gamma ray lines and estimates of line fluxes resulting from nuclear deexcitations, positron annihilation, and electron capture at various astrophysical sites are discussed. Supernova and nova explosions synthesize long-lived radioactive isotopes and eject them into space where they produce observable gamma ray lines by decaying into excited levels of daughter nuclei or by emitting positrons. Energetic charged particles in the interstellar medium, in supernova remants, in solar or stellar flares, and possibly in the vicinity of compact objects, produce gamma-ray lines by inelastic collisions which either excite nuclear levels or produce positrons and neutrons. Energetic particles can result from acceleration in time-varying magnetic fields (solar flares) or from gravitational accretion onto neutron stars and black holes. Electromagnetic processes in the strong magnetic fields of pulsars can produce positron-electron pairs, with line emission resulting from positron annihilation. Deexcitations of quantized states in strong magnetic fields can also produce lines.

Ramaty, R.

1978-01-01

146

BATSE observations of gamma-ray bursts  

NASA Astrophysics Data System (ADS)

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

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

1991-09-01

147

BATSE observations of gamma-ray bursts  

NASA Astrophysics Data System (ADS)

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

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

148

Radio Observations of Gamma-ray Novae  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

149

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

150

Gamma-ray burst populations  

NASA Astrophysics Data System (ADS)

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

Virgili, Francisco Javier

151

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

Microsoft Academic Search

Project GRAND presents the results of a search for coincident high-energy gamma ray events in the direction and at the time of nine Gamma Ray Bursts (GRBs) detected by BATSE. A gamma ray has a non-negligible hadron production cross section; for each gamma ray of energy of 100 GeV, there are 0.015 muons which reach detection level (Fasso & Poirier,

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

2000-01-01

152

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

Microsoft Academic Search

Project GRAND presents the results of a search for coincident high-energy gamma ray events in the direction and at the time of nine Gamma Ray Bursts (GRBs) detected by BATSE. A gamma ray has a non-negligible hadron production cross section; for each gamma ray of energy of 100 GeV, there are 0.015 muons which reach detection level (Fasso & Poirier,

Tzu-Fen Lin

1999-01-01

153

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

NASA Astrophysics Data System (ADS)

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

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

2003-04-01

154

Instrumentation for gamma-ray astronomy  

NASA Astrophysics Data System (ADS)

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

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

1988-03-01

155

Instrumentation for gamma-ray astronomy  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

156

X-ray and gamma ray astronomy detectors  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

157

X-ray and gamma ray astronomy detectors  

NASA Astrophysics Data System (ADS)

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

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

158

Cosmic-ray positrons from mature gamma-ray pulsars  

Microsoft Academic Search

We consider a possible contribution of mature gamma -ray pulsars (with ages of >= 105 yrs) to cosmic ray positrons. Within the framework of the gamma -ray pulsar outer gap model, e+\\/- pairs in the pulsar magnetosphere are produced by the cascade of e+\\/- pairs through synchrotron radiation of the return current from the outer gap. A good fraction of

L. Zhang; K. S. Cheng

2001-01-01

159

THE X-RAY EVOLUTION OF HICKSON COMPACT GROUPS  

SciTech Connect

The Hickson compact groups, displaying regions of high galaxy densities, should provide environments where galaxy evolution occurs rapidly. The repeated galaxy interactions and mergers present in compact groups increase the rate of star formation and increase the number of X-ray binaries. A fraction of the H I gas will also become heated via stirring and shocks, which yields extended diffuse, hot gas halos that can encompass all members of a compact group. Using a sample of 16 Hickson compact groups from the Chandra X-Ray Observatory archives, we report on a correlation between the diffuse X-ray gas and the total X-ray point source population luminosities. The correlation of the X-ray gas and point source luminosities is further examined to establish a general evolutionary trend.

Fuse, C.; Broming, E., E-mail: cfuse@rollins.edu, E-mail: ebroming@rollins.edu [Department of Physics, Rollins College, Winter Park, FL 32789 (United States)

2013-02-20

160

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

161

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

Microsoft Academic Search

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

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

162

NEAR Gamma Ray Spectrometer Characterization and Repair  

NASA Technical Reports Server (NTRS)

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

Groves, Joel Lee; Vajda, Stefan

1998-01-01

163

Gamma-Ray Pulsar Candidates for GLAST  

NASA Technical Reports Server (NTRS)

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

Thompson, D. J.

2008-01-01

164

Internal Energy Dissipation of Gamma-Ray Bursts Observed with Swift: Precursors, Prompt Gamma-Rays, Extended Emission, and Late X-Ray Flares  

NASA Astrophysics Data System (ADS)

We jointly analyze the gamma-ray burst (GRB) data observed with Burst Alert Telescope (BAT) and X-ray Telescope on board the Swift mission to present a global view on the internal energy dissipation processes in GRBs, including precursors, prompt gamma-ray emission, extended soft gamma-ray emission, and late X-ray flares. The Bayesian block method is utilized to analyze the BAT light curves to identify various emission episodes. Our results suggest that these emission components likely share the same physical origin, which is the repeated activation of the GRB central engine. What we observe in the gamma-ray band may be a small part of more extended underlying activities. The precursor emission, which is detected in about 10% of Swift GRBs, is preferably detected in those GRBs that have a massive star core-collapse origin. The soft extended emission tail, on the other hand, is preferably detected in those GRBs that have a compact star merger origin. Bright X-ray emission is detected during the BAT quiescent phases prior to subsequent gamma-ray peaks, implying that X-ray emission may be detectable prior the BAT trigger time. Future GRB alert instruments with soft X-ray capability are essential for revealing the early stages of GRB central engine activities, and shedding light on jet composition and the jet launching mechanism in GRBs.

Hu, You-Dong; Liang, En-Wei; Xi, Shao-Qiang; Peng, Fang-Kun; Lu, Rui-Jing; Lü, Lian-Zhong; Zhang, Bing

2014-07-01

165

Research in cosmic and gamma ray astrophysics  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

166

Development of a Compact Scanning Transmission X-Ray Microscope  

NASA Astrophysics Data System (ADS)

We report a compact scanning transmission X-ray microscope newly designed and developed at the Photon Factory. The microscope has very compact size and is equipped with fully digitized control electronics to realize high stability, precise positioning and fast data acquisition. The hardware design of the microscope is described in detail. Results of measurement using test samples are also presented.

Takeichi, Y.; Inami, N.; Suga, H.; Ueno, T.; Kishimoto, S.; Takahashi, Y.; Ono, K.

2014-04-01

167

Gamma rays from 'hidden' millisecond pulsars  

NASA Technical Reports Server (NTRS)

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

Tavani, M.

1993-01-01

168

Gamma-Ray Pulsar Candidates for GLAST  

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

169

Gamma rays from hidden millisecond pulsars  

NASA Technical Reports Server (NTRS)

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

Tavani, Marco

1992-01-01

170

Fermi Gamma-Ray Space Telescope.  

National Technical Information Service (NTIS)

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

D. Thompson J. McEnery

2011-01-01

171

Gamma-ray emission from slow pulsars  

Microsoft Academic Search

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

M. Morini; A. Treves

1981-01-01

172

Gamma-Ray Astronomy Technology Needs.  

National Technical Information Service (NTIS)

In recent decades gamma-ray observations have become a valuable tool for studying the universe. Progress made in diverse 8re1lS such as gamma-ray bursts (GRBs), nucleosynthesis, and active galactic nuclei (AGNs) has complimented and enriched our astrophys...

J. K. Cannizzo N. Gehrels

2012-01-01

173

GAMMA-RAY SPECTROSCOPY IN WELL LOGGING  

Microsoft Academic Search

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

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

1963-01-01

174

SIMULATE Program: a gamma ray spectroscopy tool  

Microsoft Academic Search

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

C. A Kalfas; E. Tsoulou

2003-01-01

175

Neutron Capture gamma-Ray Facility.  

National Technical Information Service (NTIS)

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

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

1980-01-01

176

Cloaked Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

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

Eichler, David

2014-06-01

177

Chandra imaging of gamma-ray binaries  

NASA Astrophysics Data System (ADS)

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

Kargaltsev, O.; Rangelov, B.; Hare, J.; Pavlov, G. G.

2014-03-01

178

Atmospheric gamma-ray and neutron flashes  

SciTech Connect

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

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

2008-01-15

179

X-ray Flashes and Their Relation to Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

Essentially all missions sensitive to cosmic X-rays have detected intense flashes of X-ray emissions, with typical timescales from seconds to hours. However, the net harvest from 25 years of observation is not much more than 100 flashes, plus another 200 X-ray counterparts of gamma-ray bursts (GRBs). The existing sample is consistent with an isotropic sky distribution of sources. Our best estimate of the log N/log S distribution suggests that the slope of the distribution is significantly flatter than 3/2, ruling out an homogeneous source population. Only a few percent of x-ray flashes can be ascribed to the counterparts of classical gamma-ray bursts. Other candidate sources include magnetic energy release in nearby stars, transient accretion on nearby compact objects, and matter-choked versions of gamma ray bursts. Because the sample is so restricted, our understanding of X-ray flashes is reminiscent of gamma-ray bursts before BATSE. However, a dedicated experiment and modern, real-time follow-up could revolutionize our understanding. A simple non-focusing experiment could detect hundreds of events per year, and a wide-field focusing system based on lobster-eye x-ray optics could catalog thousands.

Priedhorsky, W.; Arefiev, V.; Borozdin, K.

2000-12-01

180

Gamma-Ray Spectral Calculations for Uranium Borehole Logging.  

National Technical Information Service (NTIS)

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

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

1980-01-01

181

Correlated X-Ray and Very High Energy Emission in the Gamma-Ray Binary LS I +61 303  

Microsoft Academic Search

The discovery of very high energy (VHE) gamma-ray emitting X-ray binaries has triggered an intense effort to better understand the particle acceleration, absorption, and emission mechanisms in compact binary systems, which provide variable conditions along eccentric orbits. Despite this, the nature of some of these systems, and of the accelerated particles producing the VHE emission, is unclear. To answer some

H. Anderhub; L. A. Antonelli; P. Antoranz; M. Backes; C. Baixeras; S. Balestra; J. A. Barrio; D. Bastieri; J. Becerra González; J. K. Becker; W. Bednarek; K. Berger; E. Bernardini; A. Biland; O. Blanch Bigas; R. K. Bock; G. Bonnoli; P. Bordas; D. Borla Tridon; V. Bosch-Ramon; D. Bose; I. Braun; T. Bretz; D. Britzger; M. Camara; E. Carmona; A. Carosi; P. Colin; S. Commichau; J. L. Contreras; M. T. Costado; S. Covino; F. Dazzi; A. De Angelis; E. de Cea del Pozo; R. De los Reyes; B. De Lotto; M. De Maria; F. De Sabata; C. Delgado Mendez; A. Domínguez; D. Dominis Prester; D. Dorner; M. Doro; D. Elsaesser; M. Errando; D. Ferenc; E. Fernández; R. Firpo; M. V. Fonseca; N. Galante; R. J. García López; M. Garczarczyk; N. Godinovic; F. Goebel; D. Hadasch; A. Herrero; D. Hildebrand; D. Höhne-Mönch; J. Hose; D. Hrupec; C. C. Hsu; T. Jogler; S. Klepser; D. Kranich; A. La Barbera; A. Laille; E. Leonardo; E. Lindfors; S. Lombardi; F. Longo; M. López; E. Lorenz; P. Majumdar; G. Maneva; N. Mankuzhiyil; K. Mannheim; L. Maraschi; M. Mariotti; M. Martínez; D. Mazin; M. Meucci; J. M. Miranda; R. Mirzoyan; H. Miyamoto; J. Moldón; M. Moles; A. Moralejo; D. Nieto; K. Nilsson; J. Ninkovic; R. Orito; I. Oya; R. Paoletti; J. M. Paredes; M. Pasanen; D. Pascoli; F. Pauss; R. G. Pegna; M. A. Perez-Torres; L. Peruzzo; F. Prada; E. Prandini; N. Puchades; I. Puljak; I. Reichardt; W. Rhode; M. Ribó; J. Rico; M. Rissi; A. Robert; S. Rügamer; A. Saggion; T. Y. Saito; M. Salvati; M. Sánchez-Conde; K. Satalecka; V. Scalzotto; V. Scapin; T. Schweizer; M. Shayduk; S. N. Shore; N. Sidro; A. Sierpowska-Bartosik; J. Sitarek; D. Sobczynska; F. Spanier; S. Spiro; A. Stamerra; L. S. Stark; T. Suric; L. Takalo; F. Tavecchio; P. Temnikov; D. Tescaro; M. Teshima; D. F. Torres; N. Turini; H. Vankov; R. M. Wagner; V. Zabalza; F. Zandanel; R. Zanin; J. Zapatero; A. Falcone; L. Vetere; N. Gehrels; S. Trushkin; V. Dhawan; P. Reig

2009-01-01

182

Gamma rays from the magellanic clouds  

NASA Technical Reports Server (NTRS)

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

Stecker, F. W.

1977-01-01

183

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

184

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

185

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

186

The EGRET high energy gamma ray telescope  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

187

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

188

The EGRET high energy gamma ray telescope  

NASA Astrophysics Data System (ADS)

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

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

1992-02-01

189

An imaging neutron/gamma-ray spectrometer  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

190

Observations of Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

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

Fishman, G. J.

1995-01-01

191

Gamma ray pulsars: Models and observations  

NASA Technical Reports Server (NTRS)

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

Thompson, David J.

1990-01-01

192

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

193

Gamma-Ray Pulsar Studies with GLAST  

SciTech Connect

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

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

2008-02-27

194

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

195

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

NASA Technical Reports Server (NTRS)

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

Becker, Peter A.; Kafatos, Menas

1995-01-01

196

GRETA - Gamma Ray Energy Tracking Array  

NASA Astrophysics Data System (ADS)

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

Lee, I.-Yang

2003-03-01

197

IR observations in gamma-ray blazars  

NASA Technical Reports Server (NTRS)

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

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

1997-01-01

198

Fermi Gamma-Ray Space Telescope  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

199

Historical aspects of gamma-ray astronomy  

Microsoft Academic Search

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

B. V. Sreekantan

2002-01-01

200

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

NASA Technical Reports Server (NTRS)

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

Ramaty, R.; Lingenfelter, R. E.

1980-01-01

201

Possible X-ray counterparts of gamma-ray sources  

NASA Technical Reports Server (NTRS)

The results are presented of a survey regarding the X-ray source positions which fall within the error boxes of 10 unidentified gamma-ray sources observed with the aid of the COS-B satellite. In three cases, including CG 135-1, CG 312-1, and CG 327-0, an X-ray source was found within the gamma-ray error box. However, because of the large uncertainty regarding the gamma-ray source positions, the positional coincidence is not necessarily conclusive. It is, therefore, necessary to take into account additional information on the spectral or temporal characteristics of the X-ray sources. It is found that the X-ray source 4U 02416 plus 1 is a possible candidate as the X-ray-counterpart of CG 135 plus 1 in connection with both spectral hardness characteristics and positional coincidence.

Maraschi, L.; Markert, T.; Apparao, K. M. V.; Bradt, H.; Helmken, H.; Wheaton, W.; Baity, W. A.; Peterson, L. E.

1978-01-01

202

Research in cosmic and gamma ray astrophysics  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

203

X-Ray-Driven Gamma Emission  

NASA Astrophysics Data System (ADS)

X-ray-driven gamma emission describes processes that may release nuclear energy in a ‘clean’ way, as bursts of incoherent or coherent gamma rays without the production of radioactive by-products. Over the past decade, studies in this area, as a part of the larger field of quantum nucleonics, have gained tremendous momentum. Since 1987 it has been established that photons could trigger gamma emission from a long-lived metastable nuclear excited state of one nuclide and it appears likely that triggering in other isotopes will be demonstrated conclusively in the near future. With these experimental results have come new proposals for the creation of collective and avalanche-like incoherent gamma-ray bursts and even for the ultimate light source, a gamma-ray laser. Obviously, many applications would benefit from controlled bursts of gamma radiation, whether coherent or not. This paper reviews the experimental results and concepts for the production of gamma rays, driven by externally produced X-rays.

Carroll, J. J.; Karamian, S. A.; Rivlin, L. A.; Zadernovsky, A. A.

2001-07-01

204

Historical aspects of gamma-ray astronomy  

NASA Astrophysics Data System (ADS)

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

Sreekantan, B. V.

2002-03-01

205

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

206

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

207

Gamma rays produce superior seedless citrus  

SciTech Connect

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

Pyrah, D.

1984-10-01

208

Gamma-Ray Heating in Power Reactors.  

National Technical Information Service (NTIS)

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

A. P. Olson

1976-01-01

209

Gamma-Ray Burst Smashes a Record  

NSF Publications Database

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

210

Positron annihilation gamma rays from novae  

NASA Technical Reports Server (NTRS)

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

Leising, Mark D.; Clayton, Donald D.

1987-01-01

211

Gamma-ray bursts: An overview  

NASA Technical Reports Server (NTRS)

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

Lestrade, John Patrick

1990-01-01

212

Gamma-ray spectroscopy - Requirements and prospects  

NASA Technical Reports Server (NTRS)

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

Matteson, James L.

1991-01-01

213

Compact soft x-ray source using Thomson scattering  

Microsoft Academic Search

A compact soft x-ray source using Thomson scattering, enabled by the combination of a picosecond laser and an electron rf gun, was developed aiming at biological studies such as those using an x-ray microscope. The x-ray source included both a photoinjector system and a picosecond laser system with a tabletop size of 2×2 m2. An infrared laser beam (lambda0=1047 nm)

Shigeru Kashiwagi; Ryunosuke Kuroda; Takashi Oshima; Fumio Nagasawa; Tomoaki Kobuki; Daisuke Ueyama; Yoshimasa Hama; Masakazu Washio; Kiminori Ushida; Hitoshi Hayano; Junji Urakawa

2005-01-01

214

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

215

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

Microsoft Academic Search

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

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

2003-01-01

216

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

217

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

218

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

Microsoft Academic Search

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

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

2010-01-01

219

A compact synchrotron-based transmission X-ray microscope.  

PubMed

A compact transmission X-ray microscope has been designed and implemented based on a cylindrical symmetry around the optical axis that sharply limits the instabilities due to thermal mechanical drift. Identical compact multi-axis closed-loop actuation modules drive different optical components. The design is modular and simplifies the change of individual parts, e.g. the use of different magnification and focusing devices. This compact instrument can be easily transported between laboratory and synchrotron facilities and quickly put into operation. An automated alignment mechanism simplifies the assembly of different modules after transportation. After describing the design details, the results of the first tests are presented. PMID:24562558

Chen, Yu Sheng; Chen, Huang Han; Li, Tsong Tse; Ong, Edwin; Lim, Jun; Margaritondo, Giorgio; Hwu, En-Te; Hwu, Yeukuang

2014-03-01

220

VHE Gamma-ray Supernova Remnants  

SciTech Connect

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

Funk, Stefan; /KIPAC, Menlo Park

2007-01-22

221

Compton scattering gamma-ray source optimization  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

222

Very high energy gamma-ray spectroscopy  

Microsoft Academic Search

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

David Eichler; James H. Adams Jr.

1987-01-01

223

GAMMA-RAY BURSTS AS HYPERNOVAE  

Microsoft Academic Search

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

Bohdan Paczynski

224

Cosmic very high-energy gamma rays  

Microsoft Academic Search

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

R. Plaga

1998-01-01

225

Future directions in X-ray/gamma-ray observations  

NASA Technical Reports Server (NTRS)

Facilities available for X ray and gamma ray astronomical observations in the late 1980s are described, with an emphasis on NASA programs. Current European programs for launching Rosat and Exosat will provide coverage in the 0.4-60 keV energy range. The proposed NASA advanced X ray astrophysics facility is intended to cover the 0.1-8 keV range with higher than 0.5 arcsec resolution. The Japanese Astro-B, scheduled for launch in 1983, observes in the 1-60 keV range. X ray and gamma ray observations are also scheduled for Spacelab flights. The French-Soviet Gamma-1 spark chamber high energy gamma ray telescope is intended for LEO orbit and observations in the energy range above 50 MeV with a 2 deg, 1-5 arcmin resolution. The NASA gamma ray observatory is set for 1988 launch and will feature four instruments to monitor the 60 keV-300 GeV range. Balloon-borne instrumentation will also be launched, with attention given to the medium gamma ray energy range from 1-30 MeV.

Kniffen, D. A.

1982-01-01

226

Colorado School of Mines fusion gamma ray project: Technical progress report  

Microsoft Academic Search

This report summarizes the technical accomplishments of the first year of a contract between the Colorado School of Mines and the US Department of Energy entitled ''Fusion gamma ray diagnostics of alpha particle production and confinement in the Compact Ignition Torus'' No. DE-FG02-88ER53276. The stated goals of the contract were to: develop a high count rate gamma ray spectrometry system;

Cecil

1989-01-01

227

Radiation detection system for portable gamma-ray spectroscopy  

DOEpatents

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

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

2006-06-20

228

Method and apparatus for gamma ray well logging  

Microsoft Academic Search

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

Hubner

1985-01-01

229

The goals of gamma-ray spectroscopy in high energy astrophysics  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

230

Gamma-ray Burst Cosmology  

NASA Astrophysics Data System (ADS)

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

Wang, F. Y.

2011-07-01

231

X-ray emission mechanism for the gamma-ray binary LS 5039  

NASA Astrophysics Data System (ADS)

We address an unsolved issue in the model of the gamma-ray binary LS 5039, which consists of an O star and a compact object not yet identified. In previous studies, the X-ray emission observed with Suzaku has been assumed to be due to the synchrotron emission from high energy electrons, and the inverse Compton (IC) emission from low energy electrons has been neglected. However, this IC emission can affect the X-ray emission. In this study, we calculate the IC emission from low energy electrons (? < 10^4) accelerated near the compact object, including those created by the radiative cooling. We find that the IC emission of the low energy electrons can be responsible for the Suzaku band if the minimum Lorentz factor of injected electrons ?_{min} is around 10^3. In addition, we show that the Suzaku light curve is well reproduced if ?_{min} varies in proportion to the Fermi flux.

Yamaguchi, Masaki

2012-07-01

232

Mercuric iodine room temperature gamma-ray detectors  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

233

Mercuric iodide room temperature gamma-ray detectors  

NASA Astrophysics Data System (ADS)

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

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

1989-07-01

234

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

235

VHE Gamma-Rays from Galactic X-Ray Binary Systems  

NASA Astrophysics Data System (ADS)

The detection of TeV gamma-rays from LS 5039 and the binary pulsar PSR B1259-63 by HESS, and from LS I +61 303 and the stellar-mass black hole Cygnus X-1 by MAGIC, provides clear evidence of very efficient acceleration of particles to multi-TeV energies in X-ray binaries. These observations demonstrate the richness of nonthermal phenomena in compact galactic objects containing relativistic outflows or winds produced near black holes and neutron stars. I review here some of the main observational results on very high energy (VHE) ?-ray emission from X-ray binaries, as well as some of the proposed scenarios to explain the production of VHE ?-rays. I put special emphasis on the flare TeV emission, suggesting that the flaring activity might be a common phenomena in X-ray binaries.

Paredes, J. M.

236

Miniaturization in x ray and gamma ray spectroscopy  

Microsoft Academic Search

The paper presents advances in two new sensor technologies and a miniaturized associated electronics technology which, when combined, can allow for very significant miniaturization and for the reduction of weight and power consumption in x-ray and gamma-ray spectroscopy systems: (1) Mercuric iodide (HgI2) x-ray technology, which allows for the first time the construction of truly portable, high-energy resolution, non-cryogenic x-ray

Jan S. Iwanczyk; Yuzhong J. Wang; James G. Bradley

1993-01-01

237

Gamma-Ray Burst Detection with Icecube  

NASA Astrophysics Data System (ADS)

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

Kappes, Alexander

238

Gamma-ray binaries: pulsars in disguise?  

Microsoft Academic Search

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

Guillaume Dubus; Marie Curie

2006-01-01

239

THE fermi gamma-ray burst monitor  

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

240

Technology Needs for Gamma Ray Astronomy  

NASA Technical Reports Server (NTRS)

Gamma ray astronomy is currently in an exciting period of multiple missions and a wealth of data. Results from INTEGRAL, Fermi, AGILE, Suzaku and Swift are making large contributions to our knowledge of high energy processes in the universe. The advances are due to new detector and imaging technologies. The steps to date have been from scintillators to solid state detectors for sensors and from light buckets to coded aperture masks and pair telescopes for imagers. A key direction for the future is toward focusing telescopes pushing into the hard X-ray regime and Compton telescopes and pair telescopes with fine spatial resolution for medium and high energy gamma rays. These technologies will provide finer imaging of gamma-ray sources. Importantly, they will also enable large steps forward in sensitivity by reducing background.

Gehrels, Neil

2011-01-01

241

PANGU: A High Resolution Gamma-Ray Space Telescope  

NASA Astrophysics Data System (ADS)

We propose a high angular resolution telescope dedicated to the sub-GeV gamma-ray astronomy as a candidate for the CAS-ESA joint small mission. This mission, called PANGU (PAir-productioN Gamma-ray Unit), will open up a unique window of electromagnetic spectrum that has never been explored with great precision. A wide range of topics of both astronomy and fundamental physics can be attacked with a telescope that has an angular resolution about one order of magnitude better than the currently operating Fermi Gamma-ray Space Telescope (Fermi) in the sub-GeV range, covering galactic and extragalactic cosmic-ray physics, extreme physics of a variety of extended (e.g. supernova remnants, galaxies, galaxy clusters) and compact (e.g. black holes, pulsars, gamma-ray bursts) objects, solar and terrestrial gamma-ray phenomena, and searching for Dark Matter (DM) decay and/or annihilation signature etc. The unprecedented resolution can be achieved with a pair-production telescope that, instead of the high-Z converter commonly used, relies on a large number of thin active tracking layers to increase the photon conversion probability, and to precisely reconstruct the pair-produced electron and positron tracks. Scintillating fibers or thin silicon micro-strip detectors are suitable technology for such a tracker. The energy measurement is achieved by measuring the momentum of the electrons and positrons through a magnetic field. The innovated spectrometer approach provides superior photon conversion identification and photon pointing resolution, and is particular suitable in the sub-GeV range, where the opening angle between the electron and positron is relatively large. The level of tracking precision makes it possible to measure the polarization of gamma rays, which would open up a new frontier in gamma-ray astronomy. The sub-GeV full sky survey by PANGU would provides crucial link with GeV to TeV maps from current/future missions including Fermi, DAMPE, HERD, and CTA.

Su, Meng

2014-08-01

242

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

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

243

Telescope for x ray and gamma ray studies in astrophysics  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

244

Hydrogen-poor Disks in Compact X-Ray Binaries  

Microsoft Academic Search

We show that accretion disks in several compact X-ray binaries with hydrogen-depleted donors are likely subject to a thermal ionization instability, unless they are strongly irradiated. These disks are particularly interesting in that their MHD-turbulent properties in the neutral phase may be quite different from those of standard, hydrogen-rich disks.

Kristen Menou; Rosalba Perna; Lars Hernquist

2002-01-01

245

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

NASA Technical Reports Server (NTRS)

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

Kazanas, Demosthenes; Perlman, Eric

1997-01-01

246

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

247

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

248

Development of wide-band X-ray/gamma-ray imagers using reach through APD arrays  

SciTech Connect

It is quite important to obtain wide band spectra of gamma-ray bursts (GRBs) at the same time in order to probe the emission processes or the structure of GRBs. An avalanche photo diode (APD) is a compact photon sensor with an internal gain of 100. We have developed an X-ray/gamma-ray detector using a back-illuminated reach-through APD (5x5 mm{sup 2}) optically coupled with a conventional CsI(Tl) scintillator, which covers typically from 1 keV to 1 MeV. Further, we developed a 1-dimensional array of the 8/16 APDs (net 16x20 mm{sup 2}) for the purpose of an imaging photon detector to be used in future GRB missions. Here we present the current status and performance of our hybrid detector.

Nakamori, T.; Kataoka, J.; Toizumi, T.; Koizumi, M.; Tanaka, S.; Kanai, Y.; Yatsu, Y.; Kawai, N. [Dept. of Physics, Tokyo Institute of Technology, 2-12-1 Ohokayama, Meguro, Tokyo (Japan); Ishikawa, Y.; Kawai, T.; Kawabata, N.; Matsunaga, Y. [Solid State Division, Hamamatsu Photonics K. K., 1126-1, Ichino-cho, Hamamatsu, Shizuoka (Japan)

2009-05-25

249

Stellar Photon Archaeology with Gamma-Rays  

NASA Technical Reports Server (NTRS)

Ongoing deep surveys of galaxy luminosity distribution functions, spectral energy distributions and backwards evolution models of star formation rates can be used to calculate the past history of intergalactic photon densities and, from them, the present and past optical depth of the Universe to gamma-rays from pair production interactions with these photons. The energy-redshift dependence of the optical depth of the Universe to gamma-rays has become known as the Fazio-Stecker relation (Fazio & Stecker 1970). Stecker, Malkan & Scully have calculated the densities of intergalactic background light (IBL) photons of energies from 0.03 eV to the Lyman limit at 13.6 eV and for 0$ < z < $6, using deep survey galaxy observations from Spitzer, Hubble and GALEX and have consequently predicted spectral absorption features for extragalactic gamma-ray sources. This procedure can also be reversed. Determining the cutoff energies of gamma-ray sources with known redshifts using the recently launched Fermi gamma-ray space telescope may enable a more precise determination of the IBL photon densities in the past, i.e., the "archaeo-IBL.", and therefore allow a better measure of the past history of the total star formation rate, including that from galaxies too faint to be observed.

Stecker, Floyd W.

2009-01-01

250

Gravitational Waves versus X-Ray and Gamma-Ray Emission in a Short Gamma-Ray Burst  

NASA Astrophysics Data System (ADS)

Recent progress in the understanding of the physical nature of neutron star equilibrium configurations and the first observational evidence of a genuinely short gamma-ray burst (GRB), GRB 090227B, allows us to give an estimate of the gravitational waves versus the X-ray and gamma-ray emission in a short GRB.

Oliveira, F. G.; Rueda, Jorge A.; Ruffini, R.

2014-06-01

251

Gamma Rays, Cosmic Rays and the Dynamics of the Galaxy.  

National Technical Information Service (NTIS)

The galactic gamma ray emission has recently been observed by the SAS-2 and COS-B satellites; the impact of these results on our knowledge of galactic cosmic rays and the interstellar medium is summarized. Despite the fact that an unknown proportion of th...

C. Cesarsky

1978-01-01

252

X-Ray Observations of gamma-Ray Bursts.  

National Technical Information Service (NTIS)

As of this writing, all existing simultaneous x-ray observations of gamma-ray bursts (that is, observation having useful sensitivity below 30 keV at the time of the burst) have been serendipitous. Otherwise stated, there has never been a true GRB instrume...

J. G. Laros M. Katoh T. Murakami

1984-01-01

253

Gamma rays and large scale galactic structure  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

254

Gamma-ray astronomy comes of age  

NASA Astrophysics Data System (ADS)

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

Bignami, G. F.

1985-10-01

255

Microsecond flares in gamma-ray bursts  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

256

Gamma-Ray Imaging for Explosives Detection  

NASA Technical Reports Server (NTRS)

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

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

2008-01-01

257

Gamma-ray imaging for explosives detection  

NASA Astrophysics Data System (ADS)

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

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

2008-05-01

258

Gamma ray pulsars. [electron-photon cascades  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

259

Gamma-ray spectroscopy - Status and prospects  

NASA Technical Reports Server (NTRS)

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

Matteson, J. L.

1983-01-01

260

Gamma rays from pulsar wind shock acceleration  

NASA Technical Reports Server (NTRS)

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

Harding, Alice K.

1990-01-01

261

Noiseless coding for the Gamma Ray spectrometer  

NASA Technical Reports Server (NTRS)

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

Rice, R.; Lee, J. J.

1985-01-01

262

Precise absolute gamma-ray wavelength measurements  

NASA Astrophysics Data System (ADS)

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

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

1991-10-01

263

Gamma ray bursts from magnetospheric plasma oscillations  

NASA Technical Reports Server (NTRS)

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

Melia, Fulvio

1989-01-01

264

Gamma-ray Burst Skymap Website  

NSDL National Science Digital Library

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

265

Radioactivities and gamma-rays from supernovae  

NASA Technical Reports Server (NTRS)

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

Woosley, S. E.

1991-01-01

266

Observations of Compact X-Ray Binaries with the Chandra X-Ray Observatory  

NASA Technical Reports Server (NTRS)

The Chandra X-Ray Observatory Launched on July 23, 1999. The first X-ray photons were detected on August 12 of that same year. Subsequently observations with the Observatory, which features sub-arcsecond angular resolution, have revolutionized our understanding of the X-ray emitting sky providing hosts of spectacular energy-resolved images and high-resolution spectra. Here we present a brief overview of Chandra X-Ray Observatory observations of compact X-ray binaries.

Weisskopf, Martin C.

2006-01-01

267

Probing the Radio Emission from Gamma Ray Blazars  

Microsoft Academic Search

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

R. J. Cool; G. A. Moellenbrock

2003-01-01

268

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

269

Development of Compton gamma-ray sources at LLNL  

NASA Astrophysics Data System (ADS)

Compact Compton scattering gamma-ray sources offer the potential of studying nuclear photonics with new tools. The optimization of such sources depends on the final application, but generally requires maximizing the spectral density (photons/eV) of the gamma-ray beam while simultaneously reducing the overall bandwidth on target to minimize noise. We have developed an advanced design for one such system, comprising the RF drive, photoinjector, accelerator, and electron-generating and electron-scattering laser systems. This system uses a 120 Hz, 250 pC, 2 ps, 0.35 mm mrad electron beam with 250 MeV maximum energy in an X-band accelerator scattering off a 150 mJ, 10 ps, 532 nm laser to generate 5 × 1010 photons/eV/s/Sr at 0.5 MeV with an overall bandwidth of less than 1%. The source will be able to produce photons up to energies of 2.5 MeV. We also discuss Compton scattering gamma-ray source predictions given by numerical codes.

Albert, F.; Anderson, S. G.; Ebbers, C. A.; Gibson, D. J.; Hartemann, F. V.; Marsh, R. A.; Messerly, M. J.; Prantil, M. A.; Wu, S.; Barty, C. P. J.

2012-12-01

270

Development of Compton gamma-ray sources at LLNL  

SciTech Connect

Compact Compton scattering gamma-ray sources offer the potential of studying nuclear photonics with new tools. The optimization of such sources depends on the final application, but generally requires maximizing the spectral density (photons/eV) of the gamma-ray beam while simultaneously reducing the overall bandwidth on target to minimize noise. We have developed an advanced design for one such system, comprising the RF drive, photoinjector, accelerator, and electron-generating and electron-scattering laser systems. This system uses a 120 Hz, 250 pC, 2 ps, 0.35 mm mrad electron beam with 250 MeV maximum energy in an X-band accelerator scattering off a 150 mJ, 10 ps, 532 nm laser to generate 5 Multiplication-Sign 10{sup 10} photons/eV/s/Sr at 0.5 MeV with an overall bandwidth of less than 1%. The source will be able to produce photons up to energies of 2.5 MeV. We also discuss Compton scattering gamma-ray source predictions given by numerical codes.

Albert, F.; Anderson, S. G.; Ebbers, C. A.; Gibson, D. J.; Hartemann, F. V.; Marsh, R. A.; Messerly, M. J.; Prantil, M. A.; Wu, S.; Barty, C. P. J. [Lawrence Livermore National Laboratory, NIF and Photon Science, 7000 East avenue, Livermore, CA 94550 (United States)

2012-12-21

271

Gamma-ray bursts as cosmological probes  

NASA Astrophysics Data System (ADS)

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

Vergani, S. D.

2013-11-01

272

Physics of Gamma Ray Emitting AGN  

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

273

The origin and implications of gamma rays from solar flares  

NASA Technical Reports Server (NTRS)

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

Ramaty, R.

1975-01-01

274

Cosmic-Ray Production of Low-Energy Gamma Rays  

Microsoft Academic Search

An attempt has been made to detect and measure any vertically incident flux of low- energy (0.25 to 10 Mev) gamma rays that might be present at high altitudes. The experiment con- sisted of a series of balloon flights carrying a phoswitch gamma spectrometer with pulse height recording to altitudes of about 5.5 g\\/cmatmosphere depth. Directional sensitivity was obtained by

Frank C. Jones

1961-01-01

275

Propagation of Cosmic Rays and Diffuse Galactic Gamma Rays  

NASA Technical Reports Server (NTRS)

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

Moskalenko, Igor V.

2004-01-01

276

Gamma-Ray-Burst Beaming and Gravitational-Wave Observations  

NASA Astrophysics Data System (ADS)

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

Chen, Hsin-Yu; Holz, Daniel E.

2013-11-01

277

Gamma-Ray Bursts During Neutron Star Formation. Gamma-Ray Bursts and Transient X-Ray Sources.  

National Technical Information Service (NTIS)

Discussions are presented of the associations between cosmic gamma ray bursts and transient X-ray sources, and the release of gravitational binding energy during the formation of neutron stars. The model for studying the associations is described along wi...

J. M. Cohen U. D. Desai S. S. Holt

1973-01-01

278

Development of wideband X-ray and gamma-ray spectrometer using transmission-type, large-area APD  

Microsoft Academic Search

The avalanche photodiode (APD) is a high-performance and compact light sensor recently applied in various fields of experimental physics. Among several types of APDs, the reach-through APD offers an advantage in direct X-ray detection, thanks to its thick depletion layer (?100?m) in front of the amplification region. This type of APD is also sensitive to weak scintillation light from gamma-ray

S. Tanaka; J. Kataoka; Y. Kanai; Y. Yatsu; M. Arimoto; M. Koizumi; N. Kawai; Y. Ishikawa; S. Kawai; N. Kawabata

2007-01-01

279

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

SciTech Connect

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

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

2007-05-05

280

ATCA Observations of the New Gamma-ray Source PKS 1824-582  

NASA Astrophysics Data System (ADS)

The report of the Fermi-LAT detection of a new gamma ray source positionally coincident with PKS 1824-582 (ATel #6067), has been followed up with observations of this radio source using the Australia Telescope Compact Array (ATCA) between 22:37UT on 2014 April 14 and 00:40UT on 2014 April 15. ...

Edwards, Philip G.; Stevens, Jamie; Ojha, Roopesh

2014-04-01

281

COMPACT CdZnTe-BASED GAMMA CAMERA FOR PROSTATE CANCER IMAGING  

SciTech Connect

In this paper, we discuss the design of a compact gamma camera for high-resolution prostate cancer imaging using Cadmium Zinc Telluride (CdZnTe or CZT) radiation detectors. Prostate cancer is a common disease in men. Nowadays, a blood test measuring the level of prostate specific antigen (PSA) is widely used for screening for the disease in males over 50, followed by (ultrasound) imaging-guided biopsy. However, PSA tests have a high false-positive rate and ultrasound-guided biopsy has a high likelihood of missing small cancerous tissues. Commercial methods of nuclear medical imaging, e.g. PET and SPECT, can functionally image the organs, and potentially find cancer tissues at early stages, but their applications in diagnosing prostate cancer has been limited by the smallness of the prostate gland and the long working distance between the organ and the detectors comprising these imaging systems. CZT is a semiconductor material with wide band-gap and relatively high electron mobility, and thus can operate at room temperature without additional cooling. CZT detectors are photon-electron direct-conversion devices, thus offering high energy-resolution in detecting gamma rays, enabling energy-resolved imaging, and reducing the background of Compton-scattering events. In addition, CZT material has high stopping power for gamma rays; for medical imaging, a few-mm-thick CZT material provides adequate detection efficiency for many SPECT radiotracers. Because of these advantages, CZT detectors are becoming popular for several SPECT medical-imaging applications. Most recently, we designed a compact gamma camera using CZT detectors coupled to an application-specific-integrated-circuit (ASIC). This camera functions as a trans-rectal probe to image the prostate gland from a distance of only 1-5 cm, thus offering higher detection efficiency and higher spatial resolution. Hence, it potentially can detect prostate cancers at their early stages. The performance tests of this camera have been completed. The results show better than 6-mm resolution at a distance of 1 cm. Details of the test results are discussed in this paper.

CUI, Y.; LALL, T.; TSUI, B.; YU, J.; MAHLER, G.; BOLOTNIKOV, A.; VASKA, P.; DeGERONIMO, G.; O'CONNOR, P.; MEINKEN, G.; JOYAL, J.; BARRETT, J.; CAMARDA, G.; HOSSAIN, A.; KIM, K.H.; YANG, G.; POMPER, M.; CHO, S.; WEISMAN, K.; SEO, Y.; BABICH, J.; LaFRANCE, N.; AND JAMES, R.B.

2011-10-23

282

Compact CdZnTe-based gamma camera for prostate cancer imaging  

NASA Astrophysics Data System (ADS)

In this paper, we discuss the design of a compact gamma camera for high-resolution prostate cancer imaging using Cadmium Zinc Telluride (CdZnTe or CZT) radiation detectors. Prostate cancer is a common disease in men. Nowadays, a blood test measuring the level of prostate specific antigen (PSA) is widely used for screening for the disease in males over 50, followed by (ultrasound) imaging-guided biopsy. However, PSA tests have a high falsepositive rate and ultrasound-guided biopsy has a high likelihood of missing small cancerous tissues. Commercial methods of nuclear medical imaging, e.g. PET and SPECT, can functionally image the organs, and potentially find cancer tissues at early stages, but their applications in diagnosing prostate cancer has been limited by the smallness of the prostate gland and the long working distance between the organ and the detectors comprising these imaging systems. CZT is a semiconductor material with wide band-gap and relatively high electron mobility, and thus can operate at room temperature without additional cooling. CZT detectors are photon-electron direct-conversion devices, thus offering high energy-resolution in detecting gamma rays, enabling energy-resolved imaging, and reducing the background of Compton-scattering events. In addition, CZT material has high stopping power for gamma rays; for medical imaging, a few-mm-thick CZT material provides adequate detection efficiency for many SPECT radiotracers. Because of these advantages, CZT detectors are becoming popular for several SPECT medical-imaging applications. Most recently, we designed a compact gamma camera using CZT detectors coupled to an application-specific-integratedcircuit (ASIC). This camera functions as a trans-rectal probe to image the prostate gland from a distance of only 1-5 cm, thus offering higher detection efficiency and higher spatial resolution. Hence, it potentially can detect prostate cancers at their early stages. The performance tests of this camera have been completed. The results show better than 6-mm resolution at a distance of 1 cm. Details of the test results are discussed in this paper.

Cui, Yonggang; Lall, Terry; Tsui, Benjamin; Yu, Jianhua; Mahler, George; Bolotnikov, Aleksey; Vaska, Paul; de Geronimo, Gianluigi; O'Connor, Paul; Meinken, George; Joyal, John; Barrett, John; Camarda, Giuseppe; Hossain, Anwar; Kim, Ki Hyun; Yang, Ge; Pomper, Marty; Cho, Steve; Weisman, Ken; Seo, Youngho; Babich, John; Lafrance, Norman; James, Ralph B.

2011-06-01

283

Current segmented gamma-ray scanner technology  

SciTech Connect

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

Bjork, C.W.

1987-01-01

284

Observations of Gamma-Ray Bursts  

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

285

Gamma-Ray Pulsars: Models and Predictions  

NASA Technical Reports Server (NTRS)

Pulsed emission from gamma-ray pulsars originates inside the magnetosphere, from radiation by charged particles accelerated near the magnetic poles or in the outer gaps. In polar cap models, the high energy spectrum is cut off by magnetic pair production above an energy that is, dependent on the local magnetic field strength. While most young pulsars with surface fields in the range B = 10(exp 12) - 10(exp 13) G are expected to have high energy cutoffs around several GeV, the gamma-ray spectra of old pulsars having lower surface fields may extend to 50 GeV. Although the gamma-ray emission of older pulsars is weaker, detecting pulsed emission at high energies from nearby sources would be an important confirmation of polar cap models. Outer gap models predict more gradual high-energy turnovers of the primary curvature emission around 10 GeV, but also predict an inverse Compton component extending to TeV energies. Detection of pulsed TeV emission, which would not survive attenuation at the polar caps, is thus an important test of outer gap models. Next-generation gamma-ray telescopes sensitive to GeV-TeV emission will provide critical tests of pulsar acceleration and emission mechanisms.

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

2000-01-01

286

Gamma-ray burster recurrence time scales  

NASA Technical Reports Server (NTRS)

In the decade since gamma-ray bursters (GRBs) were discovered by Klebesadel et al. (1973), many models have been proposed to explain the GRB phenomenon. A difficulty is related to the small number of predictions which would make it possible to evaluate the models. One verifiable prediction is the recurrence time scale, tau-gamma. One method to measure tau-gamma is to look for possible cases of recurrence as indicated by overlapping error boxes. The analysis considered in the present investigation is composed of three procedures. One of these involves a search through known error regions for cases where the error regions overlap. In addition, the number of overlaps expected by chance coincidence alone has been determined, and a calculation has been performed regarding the number of overlaps which are expected due to recurrence for various assumed tau-gamma and luminosity functions.

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

1985-01-01

287

Development of a compact high brightness X-ray source  

Microsoft Academic Search

Based on the concept of interacting electron with intense light stored in a supercavity, a compact and high brightness soft X-ray source has been proposed for lithography at ILT\\/ILE. For the purpose of enhancing the collision frequency of electron-photon beams, the idea of a combination of a supercavity pumped by a cw diode laser with an electrostatic dc accelerator has

J. Chen; K. Imasaki; M. Fujita; C. Yamanaka; M. Asakawa; S. Nakai; T. Asakuma

1994-01-01

288

Investigation of gamma rays from the galactic center  

NASA Technical Reports Server (NTRS)

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

Helmken, H. F.

1973-01-01

289

New, room-temperature gamma-ray detector for improved assay of plutonium  

SciTech Connect

Gamma-ray spectroscopy for portable and unattended assay of nuclear materials requires rugged, reliable, room-temperature detectors that are stable in variable environments and detect gamma rays with good efficiency and energy resolution. For portable assays especially, compact detectors address needs for large numbers of measurements performed in rapid succession with heavy shielding and collimation by a user who must carry the spectroscopy equipment. Most measurements are made with compact NaI detectors. The assay of variable-burnup plutonium and other plutonium materials of variable isotopic composition challenges low-resolution gamma-ray spectroscopy in numerous safeguards applications including holdup measurements, safeguards inspections, monitoring, and safeguards close-out in decontamination and decommissioning. A new, commercial-prototype coplanar-grid CdZnTe detector has been evaluated using the assay of variable-burnup plutonium as a metric indicator to show the substantial benefit of its improved performance compared to results of the same measurements performed with the compact NaI detector. Detector performance, spectrum-quality, and assay results as well as gamma-ray spectra of reference sources are compared for the coplanar-grid CdZnTe and compact NaI detectors to illustrate the advantages of the new room-temperature gamma-ray detector. Isotope identification with the coplanar-grid CdZnTe detector is demonstrated. Preliminary calculations (Monte Carlo coupled to simulations of radiation transport and charge collection) of the spectral response of the detector to plutonium indicate promise for the use of the coplanar-grid CdZnTe detector for further improvements in the accuracy of assays and for analysis of gamma-ray isotopic distributions.

Russo, P.A.; Meier, A.P.; Rawool-Sullivan, M. [and others

1997-11-01

290

Miniaturization in x ray and gamma ray spectroscopy  

NASA Technical Reports Server (NTRS)

The paper presents advances in two new sensor technologies and a miniaturized associated electronics technology which, when combined, can allow for very significant miniaturization and for the reduction of weight and power consumption in x-ray and gamma-ray spectroscopy systems: (1) Mercuric iodide (HgI2) x-ray technology, which allows for the first time the construction of truly portable, high-energy resolution, non-cryogenic x-ray fluorescence (XRF) elemental analyzer systems, with parameters approaching those of laboratory quality cryogenic instruments; (2) the silicon avalanche photodiode (APD), which is a solid-state light sensitive device with internal amplification, capable of uniquely replacing the vacuum photomultiplier tube in scintillation gamma-ray spectrometer applications, and offering substantial improvements in size, ruggedness, low power operation and energy resolution; and (3) miniaturized (hybridized) low noise, low power amplification and processing electronics, which take full advantage of the favorable properties of these new sensors and allow for the design and fabrication of advanced, highly miniaturized x-ray and gamma-ray spectroscopy systems. The paper also presents experimental results and examples of spectrometric systems currently under construction. The directions for future developments are discussed.

Iwanczyk, Jan S.; Wang, Yuzhong J.; Bradley, James G.

1993-01-01

291

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

292

Method and apparatus for elemental analysis employing combination of neutron inelastic scattering and gamma ray scattering  

SciTech Connect

The present invention discloses a method and apparatus of elemental analysis which finds particular application in the online analyses of the specific energy (Calorific value) of coal or coke by the determination of carbon content. Analysis is achieved by a comparison of the output of neutron inelastic scatter which produces first gamma rays and of scatter of second gamma rays. Preferably 4.43 mev carbon gamma rays are used and, in addition, one or more of moisture, ash, or hydrogen content of coal or coke can be measured using 2.2 mev hydrogen capture gamma rays. The method and apparatus have the advantage of providing a compensated count rate that is essentially independent of sample compaction.

Sowerby, B.D.

1982-02-02

293

The future of high energy gamma ray astronomy and its potential astrophysical implications  

NASA Technical Reports Server (NTRS)

Future satellites should carry instruments having over an order of magnitude greater sensitivity than those flown thus far as well as improved energy and angular resolution. The information to be obtained from these experiments should greatly enhance knowledge of: the very energetic and nuclear processes associated with compact objects; the structure of our galaxy; the origin and dynamic pressure effects of the cosmic rays; the high energy particles and energetic processes in other galaxies; and the degree of matter-antimatter symmetry of the universe. The relevant aspects of extragalactic gamma ray phenomena are emphasized along with the instruments planned. The high energy gamma ray results of forthcoming programs such as GAMMA-1 and the Gamma Ray Observatory should justify even more sophisticated telescopes. These advanced instruments might be placed on the space station currently being considered by NASA.

Fichtel, C. E.

1982-01-01

294

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

295

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

Microsoft Academic Search

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

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

2011-01-01

296

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

NASA Technical Reports Server (NTRS)

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

Forrest, D. J.

1978-01-01

297

Modeling of a slanted-hole collimator in a compact endo-cavity gamma camera.  

NASA Astrophysics Data System (ADS)

Having the ability to take an accurate 3D image of a tumor greatly helps doctors diagnose it and then create a treatment plan for a patient. One way to accomplish molecular imaging is to inject a radioactive tracer into a patient and then measure the gamma rays emitted from regions with high-uptake of the tracer, viz., the cancerous tissues. In large, expensive PET- or SPECT-imaging systems, the 3D imaging easily is accomplished by rotating the gamma-ray detectors and then employing software to reconstruct the 3D images from the multiple 2D projections at different angles of view. However, this method is impractical in a very compact imaging system due to anatomical considerations, e.g., the transrectal gamma camera under development at Brookhaven National Laboratory (BNL) for detection of intra-prostatic tumors. The camera uses pixilated cadmium zinc telluride (CdZnTe or CZT) detectors with matched parallel-hole collimator. Our research investigated the possibility of using a collimator with slanted holes to create 3D pictures of a radioactive source. The underlying concept is to take 2D projection images at different angles of view by adjusting the slant angle of the collimator, then using the 2D projection images to reconstruct the 3D image. To do this, we first simulated the response of a pixilated CZT detector to radiation sources placed in the field of view of the camera. Then, we formulated an algorithm to use the simulation results as prior knowledge and estimate the distribution of a shaped source from its 2D projection images. From the results of the simulation, we measured the spatial resolution of the camera as ~7-mm at a depth of 13.85-mm when using a detector with 2.46-mm pixel pitch and a collimator with 60° slant angle.

Kamuda, Mark; Cui, Yonggang; Lall, Terry; Ionson, Jim; Camarda, Giuseppe S.; Hossain, Anwar; Yang, Ge; Roy, Utpal N.; James, Ralph B.

2013-09-01

298

Gamma-ray line astrophysics  

NASA Astrophysics Data System (ADS)

The Compton Observatory instruments have measured ?-ray lines from several individual sources and from the diffuse interstellar medium. At this late phase of CGRO's mission, we review the astrophysical achievements by these observations of solar flare spectra, supernova lines from Co and 44Ti isotopes, 511 keV annihilation radiation from Galactic plane and bulge, and diffuse 1809 keV radioactivity emission in the Galaxy from 26Al. We briefly address other candidate lines from 7Be and 22Na nova radioactivities, and nuclear 12C and 16O de-excitation lines from Orion or the inner Galaxy. An astronomy with ?-ray lines has been established, the derived lessons suggest specific observations with the INTEGRAL observatory and other experiments of the future. .

Diehl, Roland

2000-04-01

299

Morphological study of short gamma ray bursts  

NASA Astrophysics Data System (ADS)

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

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

1996-08-01

300

Spectral evolution in gamma-ray bursts  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

301

Terrestrial gamma-ray flash production by lightning  

Microsoft Academic Search

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

Brant E. Carlson

2010-01-01

302

Simultaneous optical/gamma-ray observations of GRBs  

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

303

Solar gamma-ray experiment on Astro-A satellite  

Microsoft Academic Search

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

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

1981-01-01

304

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

305

Gamma ray constraints on the Galactic supernova rate  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

306

Calibration of the RLS HPGe spectral gamma ray logging system  

Microsoft Academic Search

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

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

1991-01-01

307

On gamma-ray astronomy  

Microsoft Academic Search

Summary  Photons in the visible range form the basis of astronomy. They move in straight lines, which preserves source information,\\u000a but they arise only very indirectly from nuclear or high-energy processes. Cosmic-ray particles, on the other hand, arise\\u000a directly from high-energy processes in astronomical objects of various classes, but carry no information about source direction.\\u000a Radio emissions are still more complex

P. Morrison

1958-01-01

308

Fiber fed x-ray/gamma ray imaging apparatus  

DOEpatents

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

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

1992-06-02

309

Fiber fed x-ray/gamma ray imaging apparatus  

DOEpatents

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

Hailey, Charles J. (San Francisco, CA); Ziock, Klaus-Peter (Livermore, CA)

1992-01-01

310

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

311

The gamma ray energy tracking array  

NASA Astrophysics Data System (ADS)

Gamma-ray tracking is a new concept for the detection of ? radiation. One proposed implementation of this concept, called GRETA for Gamma Ray Energy Tracking Array, aims at an improvement in nuclear physics and is based on an array of highly segmented HPGe detectors. We have developed new techniques to determine three-dimensional positions and energies of interactions based on pulse-shape analysis in a two-dimensionally segmented Ge detector and algorithms which use this information to reconstruct the scattering sequence of ? rays, even if many ? rays hit the array at the same time. Such a detector will have a high efficiency and a good peak-to-background ratio, an excellent Doppler-shift correction and high count rate capability, as well as a high polarization sensitivity. However, the concept will not only improve the sensitivity for ? rays in nuclear physics but large potential gain is also possible in other areas, such as ?-ray imaging used in astrophysics or medicine. Only recently we have shown the proof-of-principle of the proposed concept based on the measured position resolution of better than 1 mm in three dimensions in a 36-fold segmented Ge detector at an ?-ray energy of 374 keV. .

Vetter, K.

2001-07-01

312

X-ray scaling relations in Compact Group Galaxies: Compact Object Populations with Chandra  

NASA Astrophysics Data System (ADS)

We report on the latest results from an on-going campaign to understand nuclear and accreting binary activity, as well as diffuse emission, in compact groups (CGs) of galaxies. Using multi-wavelength data for a sample of 19 CGs, we have measured star formation rates (SFRs) and stellar masses (M*). Using Chandra data for this sample, we have detected X-ray point sources (both nuclear and non-nuclear), as well as X-ray diffuse emission. We have thus achieved a detailed characterization of the X-ray data, which allows us, for the first time, to systematically explore the form of the X-ray scaling relations between, on the one hand, point-source X-ray luminosity, Lx, due to X-ray binary populations, and, on the other hand, SFR and M* in this unique extragalactic environment. We compare the Lx-SFR-M* correlation in CGs to (1) the well established correlation for the general extragalactic X-ray binary population, and (2) the Lx vs. SFR results for Ultraviolet-Luminous Galaxies (UVLGs). Both CG galaxies and UVLGs are earlier Universe analogs, allowing us to explore Lx-SFR-M* evolution as a function of environment and cosmic time.

Tzanavaris, Panayiotis; Brandt, W. N.; Johnson, K. E.; Charlton, J. C.; Gallagher, S.; Desjardins, T. D.; Lenkic, L.

2014-01-01

313

Theory and Modeling of Gamma-Ray Pulsars  

Microsoft Academic Search

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

Ion-Alexis George Yadigaroglu

1997-01-01

314

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

Microsoft Academic Search

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

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

1977-01-01

315

Gamma-Ray Telescopes: 400 Years of Astronomical Telescopes  

NASA Technical Reports Server (NTRS)

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

Gehrels, Neil; Cannizzo, John K.

2010-01-01

316

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

317

Gamma-Ray Emission from LS I +61 303  

NASA Astrophysics Data System (ADS)

LS I +61 303 is a high-mass ?-ray binary with known orbital and super-orbital variability in the radio, optical, X-ray, and ?-ray wavelengths. The compact companion is probably a neutron star but remains unconfirmed. Here, we use data from the Fermi Gamma-ray Space Telescope to examine LS I +61 303’s ?-ray emission over both its orbital and its super-orbital period. We find that the emission peaks at orbital phases of 0.3 and 0.5, and that the energy spectrum follows a log parabola model. We also find that there is ?-ray variability in the 1667-day super-orbit, but further investigation will be required to determine the exact parameters of this variability. We interpret these results as possible evidence for a mass stream flowing from the optical star’s circumstellar disk and colliding with a pulsar’s wind, emitting across the electromagnetic spectrum. We are grateful for support provided through NSF grants AST-1109247 and PHY-0849416.

Schaefer, Leigh; McSwain, M. V.

2013-01-01

318

X-ray Polarization And The Physics Of Compact Objects  

NASA Astrophysics Data System (ADS)

The upcoming GEMS mission will enable us, for the first time, to measure soft X-ray polarization of bright astrophysical objects as a function of photon energy. This will give important insights because the X-ray polarization is connected to fundamental emission and radiative transfer processes. Significant and even strong polarization can be induced by scattering processes in the accretion and ejection flow around compact objects. It may further be modified by the structure of non-Newtonian spacetime. When strong magnetic fields are present they also alter the polarization state of an X- ray photon. The information derived from X-ray polarimetry is particularly helpful when combined with simultaneous, multiple waveband spectroscopy and timing results as it thereby helps to break degeneracy in complex modeling. In my talk, I review theoretical methods and predictions relating future X-ray polarimetry observations to the properties of accreting black holes, neutron stars and surrounding outflows or jets. In particular, I show how X-ray polarization will put constraints on the black hole angular momentum in X-ray binaries and on the emission and scattering geometry in active galactic nuclei. I summarize the state-of-the-art observational techniques and discuss prospects as well as useful future directions for X-ray polarimetry.

Goosmann, R.

2011-09-01

319

A model of the diffuse galactic gamma ray emission  

NASA Technical Reports Server (NTRS)

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

Sreekumar, Parameswaran

1990-01-01

320

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

321

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

322

Solar gamma rays. [in solar flares  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

323

The Properties of Gamma-ray Binaries  

NASA Astrophysics Data System (ADS)

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

McSwain, M. Virginia

2013-06-01

324

Gamma-ray and X-ray Observations Towards the Gamma-Cygni Supernova Remnant  

NASA Astrophysics Data System (ADS)

We report on observations of the source VER J2019+407 towards the Gamma-Cygni supernova remnant. Very high energy (> 320 GeV) gamma-ray emission from the source was detected by the VERITAS observatory, an array of four 12-meter imaging atmospheric Cherenkov telescopes based near Tucson, Arizona. The proximity of this source to a diffuse region of gamma-ray emission detected by the Fermi Space Telescope increases its significance, and may suggest a connection between the two. To further investigate the properties of VER J2019+407, we have obtained a 50 ks Chandra observation of this region. Analysis of the Chandra data, and implications for the gamma-ray source, will be presented.

Dwarkadas, Vikram; Weinstein, A.; Theiling, M.; VERITAS Collaboration

2013-04-01

325

Gamma-ray Attenuation in X-ray Binaries: An Application to LSI + 61°303  

NASA Astrophysics Data System (ADS)

The X-ray binary LSI + 61°303 consisting of a main-sequence Be star and a compact object has been detected in the TeV range with MAGIC and VERITAS, and showed a clear intensity modulation as a function of the orbital phase. We describe a gamma-ray attenuation model and apply it to this system. Our first result is that interaction of high energy photons with the background radiation produced by the main-sequence star alone does not account for the observed modulation. We then include interactions between very high energy radiation and matter and are able to constrain fundamental parameters of the system such as the mass of the compact object and the density of circumstellar matter around the Be star. In our analysis of the TeV data, we find that the compact object has mass M 2 > 2.5 M sun at the 99% confidence level, implying it is most likely a black hole. However, we find a column density which conflicts with results from X-ray observations, suggesting that attenuation may not play an important role in the modulation.

Nuñez, Paul D.; LeBohec, Stephan; Vincent, Stephane

2011-04-01

326

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

SciTech Connect

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

Parker, W

2009-09-18

327

Gamma ray emission from radio pulsars  

NASA Technical Reports Server (NTRS)

While the proposed research received partial funding under this grant, during the term of support substantial progress was made on the development of a new model for the emission of gamma-rays from isolated rotation-powered pulsars. In phase one of the work, we showed how a modified version of the 'outer gap' model of pulsar emission could reproduce the double peaked profiles seen in CGRO pulsar observations. This work also demonstrated the spectrum of gap radiation varies significantly with position in the magnetosphere, and produced approximate computations of the emission from outer magnetosphere gap zones, including primary curvature radiation, gamma - gamma pair production and synchrotron radiation and inverse Compton scattering by the resulting secondary particles. This work was followed in phase two by a more complete treatment of the geometry of the radiation zone, and improved connections with observations at other wavelengths.

Romani, Roger W.

1994-01-01

328

Optical telescope BIRT in ORIGIN for gamma ray burst observing  

NASA Astrophysics Data System (ADS)

The ORIGIN concept is a space mission with a gamma ray, an X-ray and an optical telescope to observe the gamma ray bursts at large Z to determine the composition and density of the intergalactic matter in the line of sight. It was an answer to the ESA M3 call for proposal. The optical telescope is a 0.7-m F/1 with a very small instrument box containing 3 instruments: a slitless spectrograph with a resolution of 20, a multi-imager giving images of a field in 4 bands simultaneously, and a cross-dispersed Échelle spectrograph giving a resolution of 1000. The wavelength range is 0.5 ?m to 1.7 ?m. All instruments fit together in a box of 80 mm x 80 mm x 200 mm. The low resolution spectrograph uses a very compact design including a special triplet. It contains only spherical surfaces except for one tilted cylindrical surface to disperse the light. To reduce the need for a high precision pointing, an Advanced Image Slicer was added in front of the high resolution spectrograph. This spectrograph uses a simple design with only one mirror for the collimator and another for the camera. The Imager contains dichroics to separate the bandwidths and glass thicknesses to compensate the differences in path length. All 3 instruments use the same 2k x 2k detector simultaneously so that telescope pointing and tip-tilt control of a fold mirror permit to place the gamma ray burst on the desired instrument without any other mechanism.

Content, Robert; Sharples, Ray; Page, Mathew J.; Cole, Richard; Walton, David M.; Winter, Berend; Pedersen, Kristian; Hjorth, Jens; Andersen, Michael; Hornstrup, Allan; den Herder, Jan-Willem A.; Piro, Luigi

2012-09-01

329

Gamma-rays from cosmic ray interactions in supernova shells  

NASA Technical Reports Server (NTRS)

A model is presented for the transport and interaction of cosmic rays accelerated by a pulsar and confined inside an expanding supernova remnant. Assuming that protons are accelerated at the reverse shock in the confined pulsar wind and convected into the shell via the Rayleigh-Taylor instability, the diffusion and interaction of these protons in the expanding envelope is modeled. The resulting gamma-ray flux is lower than previous estimates due primarily to the inclusion of proton adiabatic losses in the expanding pulsar wind. Energy-dependent diffusion causes the higher energy gamma-ray light curves to decay faster than those at lower energy. The predicted flux from SN1987A, for proton luminosity less than 10 exp 40 erg/s, is below the present detector sensitivities at both GeV and TeV energies, although supernovae occurring within the Galaxy may be detectable.

Harding, A. K.; Mastichiadis, A.; Protheroe, R. J.; Szabo, A. P.

1991-01-01

330

Compact x-ray lasers in the laboratory  

SciTech Connect

Compact x-ray lasers in the laboratory can be produced with ultrahigh gradient rf linacs based on recent advances in linac technology by an SLAC-LLNL-LBL collaboration and on the development of bright, high current electron sources by BNL and LANL. The GeV electron beams generated with such accelerators can be converted to soft x rays in the range of 2--10 nm by passage through short period, high field strength wigglers. Alternatively, the beam can pump a low density dielectric to produce x rays via recombination. Such linear light sources can produce trains of picosecond (or shorter) pulses of extremely high spectral brilliance suitable for flash holography of biological specimens in vivo and for studies of fast chemical reactions. 15 refs., 7 figs., 3 tabs.

Barletta, W.A.

1988-10-03

331

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

NASA Astrophysics Data System (ADS)

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

Saz Parkinson, P. M.

2009-04-01

332

The GAMCIT gamma ray burst detector  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

333

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

334

Gamma Ray Observatory (GRO): Emergency support  

NASA Technical Reports Server (NTRS)

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

Schauer, K.; Madden, J.

1991-01-01

335

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

336

The gamma ray north-south effect  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

337

Real time gamma-ray signature identifier  

DOEpatents

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

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

2012-05-15

338

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

339

Gamma-Ray Polarimetry with Compton Telescope  

SciTech Connect

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

Tajima, H

2004-07-06

340

Nucleosynthesis and astrophysical gamma ray spectroscopy  

NASA Technical Reports Server (NTRS)

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

Jacobson, Allan S.

1987-01-01

341

Gamma ray spectroscopic measurements of Mars.  

PubMed

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

Metzger, A E; Arnold, J R

1970-06-01

342

Wide energy range gamma-ray calibration facility  

Microsoft Academic Search

A number of radiation-related applications in space such as ?-ray detection demands a flexible and wide-range ?-ray source which can serve as calibrating and testing facility for ?-ray detectors and ?-ray sensitive devices. A dedicated wide energy range ?-ray facility with adjustable and modular segments designed for ?-ray detector calibration and testing was built. Gamma rays are obtained from thermal

M. Kroupa; Z. Janout; M. Kralik; F. Krejci; A. Owens; S. Pospisil; F. Quarati; J. Solc

2010-01-01

343

The Comptonization of iron X-ray features in compact X-ray sources  

Microsoft Academic Search

The formation of X-ray spectral features due to iron in a relatively cool cloud of gas with a Thomson depth greater than 1 surrounding a compact source of continuum X-rays is described. Coupled equations are solved for the ionization structure of the cloud and for the radiative transfer of the X-rays. Photoionization suppresses the strength of emission lines and absorption

R. R. Ross; R. Weaver; R. McCray

1978-01-01

344

Comptonization of gamma rays by cold electrons  

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

345

Gamma Ray Bursts: an Enigma Being Unraveled  

SciTech Connect

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

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

2003-05-14

346

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

347

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

348

Gamma-ray energy tracking array: GRETINA  

NASA Astrophysics Data System (ADS)

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

Lee, I.-Yang

2013-03-01

349

Gamma Ray Observatory over Baja California, Mexico  

NASA Technical Reports Server (NTRS)

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

1991-01-01

350

Gamma -ray irradiation head for panoramic irradiation  

SciTech Connect

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

Azam, G.; Bensussan, A.

1980-10-21

351

Gamma rays from extragalactic radio sources  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

352

Gamma rays from active galactic nuclei  

NASA Technical Reports Server (NTRS)

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

Kazanas, Demosthenes

1990-01-01

353

Gamma-ray spectroscopy of 126Ba  

Microsoft Academic Search

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

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

1991-01-01

354

Hypernovae and Gamma-Ray Bursts  

Microsoft Academic Search

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

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

2001-01-01

355

Gamma-ray bursts as hypernovae  

Microsoft Academic Search

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

Bohdan Paczynski

1998-01-01

356

Hypernovae and Gamma-Ray Bursts  

Microsoft Academic Search

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

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

2010-01-01

357

Hypernovae and Gamma-Ray Bursts  

Microsoft Academic Search

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

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

2005-01-01

358

The Swift Gamma-Ray Burst Explorer  

NASA Astrophysics Data System (ADS)

Swift is a NASA gamma-ray burst MIDEX mission that is in development for launch in 2003. It is a multiwavelength transient observatory for GRB astronomy. The goals of the mission are to determine the origin of GRBs and their afterglows and to use bursts to probe the early Universe. Swift will also perform a survey of the hard X-ray sky to a sensitivity level of 0.6 mCrab. A wide-field camera will detect hundreds of GRBs per year to 5 times fainter than BATSE. Sensitive narrow-field X-ray and UV/optical telescopes will be pointed at the burst location in 20 to 70 sec by an autonomously controlled "swift" spacecraft. For each burst, Swift will determine arcsec positions and will perform optical/UV/X-ray/gamma-ray spectrophotometry. Measurements of redshift will be performed for many of the bursts. The instrumentation is a combination of superb existing flight-spare hardware and design from XMM and Spectrum-X/JET-X, and development of a coded-aperture camera with a large-area ( 0.5 square meter) CdZnTe detector array. The spacecraft bus and two of the three instruments have been delivered to NASA and are being integrated at Goddard Space Flight Center, with the final instrument delivery imminent. Key components of the mission are vigorous follow-up and outreach programs to engage the public and astronomical community in Swift.

Burrows, D. N.; Swift Team

2002-12-01

359

Swift: A Gamma Ray Bursts Explorer  

NASA Technical Reports Server (NTRS)

Swift is a NASA gamma-ray burst MIDEX mission that is in development for launch in December 2003. It is a multiwavelength transient observatory for GRB astronomy. The goals of the mission are to determine the origin of GRBs and their afterglows and use bursts to probe the early Universe. It will also.perform a survey of the hard X-ray sky to a sensitivity level of -1 mCrab. A wide-field camera will detect more than a hundred GRBs per year to 5 times fainter than BATSE. Sensitive narrow-field X-ray and UV/optical telescopes will be pointed at the burst location in 20 to 70 sec by an autonomously controlled 'swift' spacecraft. For each burst, arcsec positions will be determined and optical/UV/X-ray/gamma-ray spectrophotometry performed. Measurements of redshift will be made for many of the bursts. The instrumentation is a combination of superb existing flight-spare hardware and design from XMM and Spectrum-X/JET-X contributed by collaborators in the UK and Italy and development of a coded-aperture camera with a large-area (approximately 0.5 square meter) CdZnTe detector array. The hardware is currently in final stages of fabrication and initial stages of integration and test. Key components of the mission are vigorous follow-up and outreach programs to engage the astronomical community and public in Swift.

Gehrels, Neil

2003-01-01

360

Highlights of GeV Gamma-Ray Astronomy  

NASA Technical Reports Server (NTRS)

Because high-energy gamma rays are primarily produced by high-energy particle interactions, the gamma-ray survey of the sky by the Fermi Gamma-ray Space Telescope offers a view of sites of cosmic ray production and interactions. Gamma-ray bursts, pulsars, pulsar wind nebulae, binary sources, and Active Galactic Nuclei are all phenomena that reveal particle acceleration through their gamma-ray emission. Diffuse Galactic gamma radiation, Solar System gamma-ray sources, and energetic radiation from supernova remnants are likely tracers of high-energy particle interactions with matter and photon fields. This paper will present a broad overview of the constantly changing sky seen with the Large Area Telescope (LAT) on the Fermi spacecraft.

Thompson, David J.

2010-01-01

361

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

362

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

363

Nuclear gamma rays from solar flares  

NASA Technical Reports Server (NTRS)

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

Ramaty, R.; Lingenfelter, R. E.

1973-01-01

364

Neutrino bursts from gamma-ray bursts  

NASA Technical Reports Server (NTRS)

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

Paczynski, Bohdan; Xu, Guohong

1994-01-01

365

Positron annihilation in gamma-ray bursts  

NASA Technical Reports Server (NTRS)

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

Harding, Alice K.

1990-01-01

366

Missing High-Energy Gamma-ray Afterglows of Gamma-ray Bursts  

NASA Astrophysics Data System (ADS)

The largest explosions in the Universe, gamma-ray bursts (GRBs), are short-lived signatures of a rare type of end stage stellar evolution. We study the X-ray and gamma-ray emission with the Swift and Fermi observatories. High energy gamma-ray (>100 MeV) emission from these objects is rare, only present in ~8% of GRBs. We investigate whether or not there are bursts in the Swift sample that should have been detectable by Fermi-LAT, assuming the same emission component. By using the well-studied Swift X-ray afterglows, we extrapolate from the soft X-ray energy range (0.3 keV-10 keV) to the LAT energy range (100 MeV-100 GeV), to search for bursts which should have had high-energy afterglows, but must have breaks or cutoffs in their spectra. We compare the extrapolated gamma-ray fluxes to upper limits measured while the GRBs were in the LAT field of view, and find candidates for cutoff spectra requiring full broadband modeling. By characterizing the missing LAT afterglows, we can gain a better understanding of the emission mechanism, environment, and microphysical parameters.

Holt, Carrie; Racusin, J. L.; Kocevski, D.; Fermi Large Area Telescope Collaboration

2014-01-01

367

DESIGN OF A 250 MeV, X-BAND PHOTOINJECTOR LINAC FOR A PRECISION COMPTON-SCATTERING BASED GAMMA-RAY SOURCE  

Microsoft Academic Search

We present a compact, X-band, high-brightness accelerator design suitable for driving a precision gamma-ray source. Future applications of gamma-rays generated by Compton-scattering of laser and relativistic electron beams place stringent demands on the brightness and stability of the incident electron beam. This design identifies the beam parameters required for gamma-ray production, including position, and pointing stability. The design uses an

S G Anderson; F Albert; D J Gibson; D McNabb; M Messerly; B Rusnak; M Shverdin; F V Hartemann; C W Siders; C J Barty; S Tantawi; A Vlieks

2009-01-01

368

COMPACT OPTICAL COUNTERPARTS OF ULTRALUMINOUS X-RAY SOURCES  

SciTech Connect

Using archival Hubble Space Telescope (HST) imaging data, we report the multiband photometric properties of 13 ultraluminous X-ray sources (ULXs) that have a unique compact optical counterpart. Both magnitude and color variation are detected at timescales of days to years. The optical color, variability, and X-ray to optical flux ratio indicate that the optical emission of most ULXs is dominated by X-ray reprocessing on the disk, similar to that of low-mass X-ray binaries. For most sources, the optical spectrum is a power law, F{sub {nu}}{proportional_to}{nu}{sup {alpha}} with {alpha} in the range 1.0-2.0 and the optically emitting region has a size on the order of 10{sup 12} cm. Exceptions are NGC 2403 X-1 and M83 IXO 82, which show optical spectra consistent with direct emission from a standard thin disk, M101 ULX-1 and M81 ULS1, which have X-ray to optical flux ratios more similar to high-mass X-ray binaries, and IC 342 X-1, in which the optical light may be dominated by the companion star. Inconsistent extinction between the optical counterpart of NGC 5204 X-1 and the nearby optical nebulae suggests that they may be unrelated.

Tao Lian; Feng Hua [Department of Engineering Physics and Center for Astrophysics, Tsinghua University, Beijing 100084 (China); Grise, Fabien; Kaaret, Philip [Department of Physics and Astronomy, University of Iowa, Van Allen Hall, Iowa City, IA 52242 (United States)

2011-08-20

369

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

NASA Astrophysics Data System (ADS)

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

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

1995-11-01

370

Development of X-ray/gamma-ray imaging spectrometers using reach-through APD arrays  

NASA Astrophysics Data System (ADS)

We present spectroscopic capability of a position sensitive detector using a large area reach-through avalanche photodiode (APD) array, mainly for astronomical applications. It is quite important to obtain wide band spectra of high energy astrophysical phenomena simultaneously in order to probe emission processes or structures. Especially observations of transient objects, such as gamma-ray bursts of active galactic nuclei, require detectors with wide energy band coverage for the sake of an efficient spectroscopy within limited time windows. An APD is a compact semiconductor photon sensor with an internal gain which is often up to ~ 100. A reach-through type APD has a thicker depletion layer thus higher efficiency for direct X-ray detection compared to a reverse type APD. We have developed 1-dimensional reach-through APD arrays which consist of 8 and 16 segments with a pixel size of 2.2 × 16 and 1.1 × 16 mm2. We demonstrated quite uniform gain and energy resolution for 5.9 keV X-ray over the pixels of these arrays. Subsequently we constructed X-ray/gamma-ray detector using the APD array optically coupled to a conventional CsI(Tl) scintillator which demonstrated energy coverage typically from 1 keV to 1 MeV.

Nakamori, T.; Enomoto, T.; Toizumi, T.; Tokoyoda, K.; Yatsu, Y.; Kawai, N.; Kataoka, J.; Ishikawa, Y.; Kawai, T.; Kawabata, N.; Matsunaga, Y.

2012-03-01

371

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

NASA Technical Reports Server (NTRS)

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

Ryan, James M.; Lockwood, John A.

1989-01-01

372

A NEW CLASSIFICATION METHOD FOR GAMMA-RAY BURSTS  

SciTech Connect

Recent Swift observations suggest that the traditional long versus short gamma-ray burst (GRB) classification scheme does not always associate GRBs to the two physically motivated model types, i.e., Type II (massive star origin) versus Type I (compact star origin). We propose a new phenomenological classification method of GRBs by introducing a new parameter {epsilon} = E{sub {gamma},iso,52}/E {sup 5/3}{sub p,z,2}, where E{sub {gamma},iso} is the isotropic gamma-ray energy (in units of 10{sup 52} erg) and E{sub p,z} is the cosmic rest-frame spectral peak energy (in units of 100 keV). For those short GRBs with 'extended emission', both quantities are defined for the short/hard spike only. With the current complete sample of GRBs with redshift and E{sub p} measurements, the {epsilon} parameter shows a clear bimodal distribution with a separation at {epsilon} {approx} 0.03. The high-{epsilon} region encloses the typical long GRBs with high luminosity, some high-z 'rest-frame-short' GRBs (such as GRB 090423 and GRB 080913), as well as some high-z short GRBs (such as GRB 090426). All these GRBs have been claimed to be of Type II origin based on other observational properties in the literature. All the GRBs that are argued to be of Type I origin are found to be clustered in the low-{epsilon} region. They can be separated from some nearby low-luminosity long GRBs (in 3{sigma}) by an additional T{sub 90} criterion, i.e., T{sub 90,z} {approx}< 5 s in the Swift/BAT band. We suggest that this new classification scheme can better match the physically motivated Type II/I classification scheme.

Lue Houjun; Liang Enwei [Department of Physics, Guangxi University, Nanning 530004 (China); Zhang Binbin; Zhang Bing, E-mail: lew@gxu.edu.c, E-mail: zhang@physics.unlv.ed [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States)

2010-12-20

373

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

NASA Technical Reports Server (NTRS)

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

Moiseev, Alexander; Mitchell, John; Thompson, David

2012-01-01

374

The unusual afterglow of the gamma-ray burst of 26 March 1998 as evidence for a supernova connection  

Microsoft Academic Search

Cosmic gamma-ray bursts have now been firmly established as one of the most powerful phenomena in the Universe, releasing almost the rest-mass energy of a neutron star within the space of a few seconds (ref. 1). The two most popular models to explain gamma-ray bursts are the coalescence of two compact objects such as neutron stars or black holes, or

J. S. Bloom; S. R. Kulkarni; S. G. Djorgovski; A. C. Eichelberger; P. Côté; J. P. Blakeslee; S. C. Odewahn; F. A. Harrison; D. A. Frail; A. V. Filippenko; D. C. Leonard; A. G. Riess; H. Spinrad; D. Stern; A. Bunker; A. Dey; B. Grossan; S. Perlmutter; R. A. Knop; I. M. Hook; M. Feroci

1999-01-01

375

Polarimetry with the Soft Gamma-ray Detector onboard ASTRO-H  

NASA Astrophysics Data System (ADS)

X-ray and gamma-ray polarimetry is a powerful probe to investigate emission mechanisms and geometries of astrophysical sources. It provides vital information on ordered magnetic field and accretion disk around compact objects. The Soft Gamma-ray Detector (SGD) onboard ASTRO-H satellite, scheduled for launch in 2014, is a highly-sensitive spectrometer in the 40-600 keV energy band. Since the SGD employs a Si/CdTe Compton camera surrounded by a thick BGO active shield, it is also sensitive to polarization in the 50-200 keV energy range. We have been developing the SGD through extensive tests in laboratory, detailed Monte-Carlo simulation and verification tests at synchrotron facilities (e.g., Takeda et al. 2010; Tajima et al. 2010). In this contribution, we will present the SGD instrumentation, prototype testing and expected performance as a gamma-ray polarimeter.

Mizuno, Tsunefumi

2012-07-01

376

Supernovae-optical precursors of short gamma-ray bursts  

NASA Astrophysics Data System (ADS)

The probability of observing “supernova-gamma-ray burst” (GRB) pair events and recurrent GRBs from one galaxy in a time interval of several years has been estimated. Supernova explosions in binary systems accompanied by the formation of a short-lived pair of compact objects can be the sources of such events. If a short GRB is generated during the collision of a pair, then approximately each of ˜300 short GRBs with redshift z must have an optical precursor—a supernova in the observer’s time interval <2(1 + z) yr. If the supernova explosion has the pattern of a hypernova, then a successive observation of long and short GRBs is possible. The scenario for the generation of multiple GRBs in collapsing galactic nuclei is also discussed.

Dokuchaev, V. I.; Eroshenko, Yu. N.

2011-02-01

377

Multi-wavelength emission region of gamma-ray pulsars  

Microsoft Academic Search

Recent obserbations by Fermi Gamma-Ray Space Telescope of gamma-ray pulsars have revealed further details of the structure of the emission region. We investigate the emission region for the multi-wavelength light curve using outer gap model. We assume that gamma-ray and non-thermal X-ray photons are emitted from a particle acceleration region in the outer magnetosphere, and UV\\/optical photons originate above that

Shota Kisaka; Yasufumi Kojima

2011-01-01

378

Interpretation of the pulsed gamma ray emission from Vela  

NASA Technical Reports Server (NTRS)

A model is proposed for the Vela pulsar in which the radio emission originates near the surface of the neutron star while the pulsed gamma ray emission is produced by synchrotron radiation near the speed of light cylinder. This model can explain the energy flux, double pulse structure, and phase shift with respect to the radio of the gamma ray emission and offers approximate quantitative predictions for other X-ray and gamma-ray fluxes.

Thompson, D. J.

1975-01-01

379

Planetary gamma-ray spectroscopy of the surface of Mercury  

Microsoft Academic Search

To approach basic scientific questions on the origin and evolution of Mercury one needs data on its chemical composition. Gamma-rays emitted from the surface can be measured by a gamma-ray spectrometer on board an orbiting spacecraft. The gamma-ray flux emitted by the surface of Mercury is simulated by Monte-Carlo codes that calculate the interaction of cosmic-ray particles with the surface

J. Brückner; J. Masarik

1997-01-01

380

High energy gamma-ray observations of SN 1987A  

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

381

Thermal-neutron capture gamma-rays. Volume 1.  

National Technical Information Service (NTIS)

The energy and photon intensity of gamma rays as seen in thermal-neutron capture are presented in ascending order of gamma energy. All those gamma-rays with intensity of (ge) 2% of the strongest transition are included. The two strongest transitions seen ...

J. K. Tuli

1997-01-01

382

Reviews of Topical Problems: the Study of Cosmic gamma Rays  

Microsoft Academic Search

CONTENTS 1. Introduction 630 2. Main Cosmic gamma-ray (CGR) Production Processes. Interaction of CGR with Interstellar and Intergalactic Matter 631 3. Methods of Study of CGR 632 4. Comparability of Experimental Results. Calibration of gamma Detectors 634 5. Conditions of CGR Study. Atmospheric and Local Backgrounds 635 6. Results of Diffuse CGR Measurement in Balloons. The gamma-ray Flux Extrapolated to

A. M. Gal'per; V. G. Kirillov-Ugryumov; B. I. Luchkov; O. F. Prilutskii

1972-01-01

383

Thermal-neutron capture gamma-rays. Volume 1  

Microsoft Academic Search

The energy and photon intensity of gamma rays as seen in thermal-neutron capture are presented in ascending order of gamma energy. All those gamma-rays with intensity of 2% of the strongest transition are included. The two strongest transitions seen for the target nuclide are indicated in each case. Where the target nuclide mass number is indicated as nat the natural

Tuli

1997-01-01

384

Uncovering the Intrinsic Variability of Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

We develop a robust technique to determine the minimum variability timescale for gamma-ray burst (GRB) light curves, utilizing Haar wavelets. Our approach averages over the data for a given GRB, providing an aggregate measure of signal variation while also retaining sensitivity to narrow pulses within complicated time series. In contrast to previous studies using wavelets, which simply define the minimum timescale in reference to the measurement noise floor, our approach identifies the signature of temporally smooth features in the wavelet scaleogram and then additionally identifies a break in the scaleogram on longer timescales as a signature of a true, temporally unsmooth light curve feature or features. We apply our technique to the large sample of Swift GRB gamma-ray light curves and for the first time—due to the presence of a large number of GRBs with measured redshift—determine the distribution of minimum variability timescales in the source frame. We find a median minimum timescale for long-duration GRBs in the source frame of ?t min = 0.5 s, with the shortest timescale found being on the order of 10 ms. This short timescale suggests a compact central engine (3 × 103 km). We discuss further implications for the GRB fireball model and present a tantalizing correlation between the minimum timescale and redshift, which may in part be due to cosmological time dilation.

Golkhou, Vahid Z.; Butler, Nathaniel R.

2014-05-01

385

UNCOVERING THE INTRINSIC VARIABILITY OF GAMMA-RAY BURSTS  

NASA Astrophysics Data System (ADS)

We develop a robust technique to determine the minimum variability timescale for gamma-ray burst (GRB) light curves, utilizing Haar wavelets. Our approach averages over the data for a given GRB, providing an aggregate measure of signal variation while also retaining sensitivity to narrow pulses within complicated time series. In contrast to previous studies using wavelets, which simply define the minimum timescale in reference to the measurement noise floor, our approach identifies the signature of temporally smooth features in the wavelet scaleogram and then additionally identifies a break in the scaleogram on longer timescales as a signature of a true, temporally unsmooth light curve feature or features. We apply our technique to the large sample of Swift GRB gamma-ray light curves and for the first time—due to the presence of a large number of GRBs with measured redshift—determine the distribution of minimum variability timescales in the source frame. We find a median minimum timescale for long-duration GRBs in the source frame of ?tmin = 0.5 s, with the shortest timescale found being on the order of 10 ms. This short timescale suggests a compact central engine (3000 km). We discuss further implications for the GRB fireball model and present a tantalizing correlation between the minimum timescale and redshift, which may in part be due to cosmological time dilation.

Golkhou, V. Zach; Butler, Nathaniel R

2014-08-01

386

GAMMA RAYS FROM STAR FORMATION IN CLUSTERS OF GALAXIES  

SciTech Connect

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

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

2012-08-20

387

The SWIFT Gamma-Ray Burst X-Ray Telescope  

NASA Technical Reports Server (NTRS)

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

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

2006-01-01

388

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

389

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

390

Very high energy gamma ray astronomy  

NASA Technical Reports Server (NTRS)

Recent results in ground based very high energy gamma ray astronomy are reviewed. The various modes of the atmospheric Cerenkov technique are described, and the importance of cosmic ray rejection methods is stressed. The positive detections of the Crab pulsar that suggest a very flat spectrum and time-variable pulse phase are discussed. Observations of other pulsars (particularly Vela) suggest these features may be general. Evidence that a 4.8 hr modulated effect was detected from Cyg X-3 is strengthened in that the exact period originally proposed agrees well with a recent determination of the X-ray period. The southern sky observations are reviewed, and the significance of the detection of an active galaxy (NGC 5128) is considered for source models and future observations.

Grindlay, J. E.

1976-01-01

391

X-ray and Gamma-ray Polarimetry of GRBs  

NASA Astrophysics Data System (ADS)

Polarimetry is expected to play a major role as a diagnostic tool for GRBs. Techniques and methods for X/Gamma ray polarimetry are reviewed including the specific problems related to the transient nature of the sources. Optical data do not encourage optimistic predictions on polarimetry of afterglows. I review some of the existing and proposed experiments for the prompt and discuss the existing results.

Costa, E.

2013-07-01

392

Colorado School of Mines fusion gamma ray project: Technical progress report  

SciTech Connect

This report summarizes the technical accomplishments of the first year of a contract between the Colorado School of Mines and the US Department of Energy entitled ''Fusion gamma ray diagnostics of alpha particle production and confinement in the Compact Ignition Torus'' No. DE-FG02-88ER53276. The stated goals of the contract were to: develop a high count rate gamma ray spectrometry system; install the system on TFTR and carry out measurements of alpha particle production during ICRH d-/sup 3/He plasmas as benchmarks for similar proposed measurements on CIT; and, assess the feasibility of fusion gamma ray diagnostics of alpha particle confinement. We have completed the first objective, are in the process of implementing the second objective and are making some very preliminary progress in the third. In addition to the above stated goals, we have, in connection with a separate contract with the DOE Office of High Energy and Nuclear Physics, completed gamma ray branching ratio measurements of the p-/sup 6/Li and p-/sup 11/B reactions at proton bombarding energies down to 40 keV. These gamma ray branching ratios will provide the basis for gamma ray diagnostics of future ''advanced fuel'' fusion reactor systems and hence are reported in this progress report.

Cecil, F.E.

1989-01-19

393

COMBINED GAMMA-RAY AND NEUTRON DETECTOR FOR MEASURING THE CHEMICAL COMPOSITION OF AIRLESS PLANETARY BODIES.  

SciTech Connect

Galactic cosmic rays (GCR) constant1,y itnpinge all planetary bodies and produce characteristic gamma-ray lines and leakage neutrons as reaction products. Together with gamma-ray lines produced by radioactive decay, these nuclear emissions provide a powerful technique for remotely measuring the chemical composition of airless planetary surfaces. While lunar gamma-ray spectroscopy was first demonstrated with Apollo Gamma-Ray measurements, the full value of combined gamma-ray and neutron spectroscopy was shown for the first time with the Lunar Prospector Gamma-Ray (LP-GRS) and Neutron Spectrometers (LP-NS). Any new planetary mission will likely have the requirement that instrument mass and power be kept to a minimum. To satisfy such requirements, we have been designing a GR/NS instrument which combines all the functionality of the LP-GRS and LP-NS for a fraction of the mass and power. Specifically, our design uses a BGO scintillator crystal to measure gamma-rays from 0.5-10 MeV. A borated plastic scintillator and a lithium gliiss scintillator are used to separately measure thermal, epithermal, and fast neutrons as well as serve as an anticoincidence shield for the BGO. All three scintillators are packaged together in a compact phoswich design. Modifications to this design could include a CdZnTe gamma-ray detector for enhanced energy resolution at low energies (0.5-3 MeV). While care needs to be taken to ensure that an adequate count rate is achieved for specific mission designs, previous mission successes demonstrate that a cornbined GR/NS provides essential information about planetary surfaces.

Lawrence, David J. (David Jeffery),; Barraclough, B. L. (Bruce L.); Feldman, W. C. (William C.); Prettyman, T. H. (Thomas H.); Wiens, R. C. (Roger C.)

2001-01-01

394

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

395

Theoretical Studies in Gamma-Ray Astrophysics  

NASA Technical Reports Server (NTRS)

These studies were stimulated by the reported COMPTEL detection of nuclear gamma ray line emission from the Orion star formation region. Although the observation have very recently been retracted, the detailed analyses that we carried out clearly showed that the low energy cosmic rays that would have been required to explain the reported fluxes were exceedingly restrictive and thus highly improbable. More importantly, these studies proved to be the trigger for very productive new work. In particular, they led us into carefully re-examining the problem of the origin of the light elements, Li, Be and B, where we showed that the light elements could, in fact, be produced primarily by Galactic cosmic rays and did not require an unobserved low energy cosmic ray source , as had been suggested. We further showed that the observed abundances of Be and B in old halo stars contradicted the common belief that the Galactic cosmic rays were accelerated out of the well mixed interstellar medium, and required instead that they be accelerated out of freshly synthesized matter from supernovae. This work, in turn, led us to propose a new origin of Galactic cosmic rays from the refractory grains in supernova enriched core of superbubbles, which is now the subject of our on-going research under a new grant from the Astrophysics Theory Program.

Lingenfelter, Richard E.

1998-01-01

396

Cosmological Cosmic-Ray Contribution to the Extragalactic Gamma-Ray Background  

NASA Astrophysics Data System (ADS)

The extragalactic gamma-ray background measured by The Fermi Gamma-Ray Space Telescope is substantially different from previous measurements. Fermi has clarified that the dominant emission mechanism comes from cosmic-ray interactions with interstellar gas in normal galaxies. We present a constraint of cosmological cosmic-ray contribution to the extragalactic gamma-ray background. Even though normal galaxies seem to be dominant component, they still fall short to explain measured gamma-ray background at highest energies, thus another source has to be taken into consideration. Using models of evolution of cosmic accretion shock, we calculate pionic gamma-ray source-function for cosmological cosmic rays independent of redshift. We show that cosmological cosmic rays could even dominate the extragalactic gamma-ray background at highest energies. We also show that measured background can well be explained by these two cosmic-ray components - normal star-forming galaxies and cosmological cosmic rays.

Ciprijanovic, A.

2012-12-01

397

Development of wideband X-ray and gamma-ray spectrometer using transmission-type, large-area APD  

NASA Astrophysics Data System (ADS)

The avalanche photodiode (APD) is a high-performance and compact light sensor recently applied in various fields of experimental physics. Among several types of APDs, the reach-through APD offers an advantage in direct X-ray detection, thanks to its thick depletion layer (?100 ?m) in front of the amplification region. This type of APD is also sensitive to weak scintillation light from gamma-ray scintillators with a high quantum efficiency of ˜80% (at ??500 nm). In this paper, we propose a novel design of a compact X-ray-to-gamma-ray detector widely applicable between 1 keV and several hundreds of keV. The prototype consists of a reach-through APD (transmission type) optically coupled with a cubic CsI(Tl) crystal 4×4×4 mm3 in size. By applying the pulse shape discrimination technique to the APD output, we successfully discriminated the X-ray signals directly detected within the APD (1-40 keV), and gamma-ray signals absorbed in a CsI(Tl) scintillator (10-800 keV) located immediately behind the APD. Optimum FWHM energy resolutions of 15.1±0.2%, 6.6±0.4%, and 7.6±0.1% were obtained for 5.9 keV X-rays, 32 keV X-rays, and 662 keV gamma rays, respectively, measured at +20C. This stacked configuration is viable for various future applications in space science and nuclear medicine.

Tanaka, S.; Kataoka, J.; Kanai, Y.; Yatsu, Y.; Arimoto, M.; Koizumi, M.; Kawai, N.; Ishikawa, Y.; Kawai, S.; Kawabata, N.

2007-11-01

398

Optical and Gamma Ray Space Observations  

NASA Technical Reports Server (NTRS)

Results of the first year of data acquired from several Earth observatories concerning the optical counterparts gamma ray bursts (GRB) are presented. From the present statistics, it seems to be obvious that typical GRB's have optical emission at the time of the burst at a level at least below 1/(F(sub gamma)/F(sub opt)) approximately equal to 1/0.5 and optical emission a few hours after the burst is lower by a factor of 10 to 200 than the simultaneous emission. Given the fact that GRB spectra are rather broad over the observed energy range of say 20 keV up to 100 MeV, the observations indicate that the broad spectral shape may not continue into the optical range. After the confirmation of the isotropic distribution of GRB's by the BATSE experiment the interpretation now tends to put the sources at cosmological distances.

1992-01-01

399

Very high energy gamma ray astrophysics  

SciTech Connect

The second reflector (project GRANITE) is on schedule. At present (January 1992) it and the 10 m reflector are obtaining stereoscopic views of gamma-ray air showers from the Crab Nebula which verify the expected performance of the twin reflector telescopes. With the additional improvements of the upgrade (a pending DOE proposal) the twin reflectors should reach a limiting intensity of 1% that of the Crab. The astonishing early results from the EGRET detector aboard the Compton Gamma Ray Observatory indicate that distant quasars (powered by supermassive black holes) are active at GeV energies. The Whipple instruments are poised to see if such behavior continues above 100 GeV, as well as perform sensitive observations of previously reported GeV (Geminga) and TeV (Hercules X-1, etc.) sources. In addition to observing sources and identifying their location in the sky to one arcminute, experiments are planned to search for WIMPS in the mass range 0.1 to 1 TeV, and to determine the abundance of anti-protons in the cosmic rays. The successful performance of the stereoscopic reflectors demonstrates the feasibility of the concept of arrays of Cherenkov receivers. Design studies for a much larger array (CASITA) are just beginning.

Lamb, R.C.; Lewis, D.A.

1992-02-01

400

Compact soft x-ray source using Thomson scattering  

SciTech Connect

A compact soft x-ray source using Thomson scattering, enabled by the combination of a picosecond laser and an electron rf gun, was developed aiming at biological studies such as those using an x-ray microscope. The x-ray source included both a photoinjector system and a picosecond laser system with a tabletop size of 2x2 m{sup 2}. An infrared laser beam ({lambda}{sub 0}=1047 nm) was obtained from an all-solid-state mode-locked Nd:YLF laser system and injected into the photocathode of an accelerator system. A 4.2 MeV electron beam was generated from a laser-driven photocathode rf gun system. The residual laser beam was amplified up to about 4.2 mJ/pulse using a flash-lamp-pumped laser amplifier. Upon collision of the electron beam with the amplified laser beam, 300 eV soft x rays were generated by Thomson backscattering. The stable interaction between the two beams was achieved using the same seed laser pulse for irradiating the photocathode and the scattering process with laser photons.

Kashiwagi, Shigeru; Kuroda, Ryunosuke; Oshima, Takashi; Nagasawa, Fumio; Kobuki, Tomoaki; Ueyama, Daisuke; Hama, Yoshimasa; Washio, Masakazu; Ushida, Kiminori; Hayano, Hitoshi; Urakawa, Junji [Advanced Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku-ku, Tokyo, 169-8555 (Japan); RIKEN, Institute of Physical and Chemical Research, 2-1 Hirosawa, Wako, Saitama, 351-0198 (Japan); KEK, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2005-12-15

401

A compact synchrotron X-ray source for X-ray lithography  

Microsoft Academic Search

The Oxford Instruments group is constructing a novel compact electron storage ring intended for use as a powerful source of soft X-rays. The main application foreseen for such a source is in X-ray lithography for future sub-micron semiconductor geometries, but other research applications are also anticipated. At the heart of the source are two 180° superconducting dipole magnets which reduce

D. E. Andrews; J. V. Worth; P. M. Williams; M. N. Wilson

1988-01-01

402

A compact synchrotron X-ray source for X-ray lithography  

Microsoft Academic Search

The Oxford Instruments group is constructing a novel compact electron storage ring intended for use as a powerful source of soft X-rays. The main application foreseen for such a source is in X-ray lithography for future sub-micron semiconductor geometries, but other research applications are also anticipated.At the heart of the source are two 180° superconducting dipole magnets which reduce the

D. E. Andrews; J. V. Worth; P. M. Williams; M. N. Wilson

1988-01-01

403

Phantom experiments on a PSAPD-based compact gamma camera with submillimeter spatial resolution for small animal SPECT.  

PubMed

We demonstrate a position sensitive avalanche photodiode (PSAPD) based compact gamma camera for the application of small animal single photon emission computed tomography (SPECT). The silicon PSAPD with a two-dimensional resistive layer and four readout channels is implemented as a gamma ray detector to record the energy and position of radiation events from a radionuclide source. A 2 mm thick monolithic CsI:Tl scintillator is optically coupled to a PSAPD with a 8mm×8mm active area, providing submillimeter intrinsic spatial resolution, high energy resolution (16% full-width half maximum at 140 keV) and high gain. A mouse heart phantom filled with an aqueous solution of 370 MBq (99m)Tc-pertechnetate (140 keV) was imaged using the PSAPD detector module and a tungsten knife-edge pinhole collimator with a 0.5 mm diameter aperture. The PSAPD detector module was cooled with cold nitrogen gas to suppress dark current shot noise. For each projection image of the mouse heart phantom, a rotated diagonal readout algorithm was used to calculate the position of radiation events and correct for pincushion distortion. The reconstructed image of the mouse heart phantom demonstrated reproducible image quality with submillimeter spatial resolution (0.7 mm), showing the feasibility of using the compact PSAPD-based gamma camera for a small animal SPECT system. PMID:21278833

Kim, Sangtaek; McClish, Mickel; Alhassen, Fares; Seo, Youngho; Shah, Kanai S; Gould, Robert G

2010-10-01

404

Search for VHE gamma rays from SS433/W50 with the CANGAROO-II telescope  

NASA Astrophysics Data System (ADS)

SS433, located at the center of the supernova remnant W50, is a close proximity binary system consisting of a compact star and a normal star. Jets of material are directed outwards from the vicinity of the compact star symmetrically to the east and west. Non-thermal hard X-ray emission is detected from lobes lying on both sides. Shock accelerated electrons are expected to generate VHE gamma rays through the inverse-Compton process in the lobes. Observations of the western X-ray lobe region of SS433/W50 system have been performed to detect VHE gamma rays using the 10 m CANGAROO-II telescope in August and September, 2001, and July and September, 2002. The total observation times are 85.2 h for ON source, and 80.8 h for OFF source data. No significant excess of VHE gamma rays has been found at three regions of the western X-ray lobe of SS433/W50 system. We have derived 99% confidence level upper limits to the fluxes of gamma rays and have set constraints on the strengths of the magnetic fields assuming the synchrotron/inverse-Compton model for the wide energy range of photon spectrum from radio to TeV. The derived lower limits are 4.3?G for the center of the brightest X-ray emission region and 6.3?G for the far end from SS433 in the western X-ray lobe. In addition, we suggest that the spot-like X-ray emission may provide a major contribution to the hardest X-ray spectrum in the lobe.

Hayashi, Sei.; Kajino, F.; Naito, T.; Asahara, A.; Bicknell, G. V.; Clay, R. W.; Doi, Y.; Edwards, P. G.; Enomoto, R.; Gunji, S.; Hara, S.; Hara, T.; Hattori, T.; Itoh, C.; Kabuki, S.; Katagiri, H.; Kawachi, A.; Kifune, T.; Ksenofontov, L. T.; Kubo, H.; Kurihara, T.; Kurosaka, R.; Kushida, J.; Matsubara, Y.; Miyashita, Y.; Mizumoto, Y.; Mori, M.; Mori, H.; Muraishi, H.; Muraki, Y.; Nakase, T.; Nishida, D.; Nishijima, K.; Ohishi, M.; Okumura, K.; Patterson, J. R.; Protheroe, R. J.; Sakamoto, N.; Sakurazawa, K.; Swaby, D. L.; Tanimori, T.; Tanimura, H.; Thornton, G.; Tokanai, F.; Tsuchiya, K.; Uchida, T.; Watanabe, S.; Yamaoka, T.; Yanagita, S.; Yoshida, T.; Yoshikoshi, T.

2009-09-01

405

DETECTION OF VHE {gamma}-RAYS FROM HESS J0632+057 DURING THE 2011 FEBRUARY X-RAY OUTBURST WITH THE MAGIC TELESCOPES  

SciTech Connect

The very high energy (VHE) {gamma}-ray source HESS J0632+057 has recently been confirmed to be a {gamma}-ray binary. The optical counterpart is the Be star MWC 148, and a compact object of unknown nature orbits it every {approx}321 days with a high eccentricity of {approx}0.8. We monitored HESS J0632+057 with the stereoscopic MAGIC telescopes from 2010 October to 2011 March and detected significant VHE {gamma}-ray emission during 2011 February, when the system exhibited an X-ray outburst. We find no {gamma}-ray signal in the other observation periods when the system did not show increased X-ray flux. Thus, HESS J0632+057 exhibits {gamma}-ray variability on timescales of the order of one to two months possibly linked to the X-ray outburst that takes place about 100 days after the periastron passage. Furthermore, our measurements provide for the first time the {gamma}-ray spectrum down to about 140 GeV and indicate no turnover of the spectrum at low energies. We compare the properties of HESS J0632+057 with the similar {gamma}-ray binary LS I +61 Degree-Sign 303 and discuss the possible origin of the multi-wavelength emission of the source.

Aleksic, J.; Blanch, O. [IFAE, Edifici Cn., Campus UAB, E-08193 Bellaterra (Spain); Alvarez, E. A.; Asensio, M.; Barrio, J. A. [Grupo de Fisica Altas Energias, Universidad Complutense, E-28040 Madrid (Spain); Antonelli, L. A.; Bonnoli, G. [INAF National Institute for Astrophysics, I-00136 Rome (Italy); Antoranz, P. [Dipartimento di Fisica, Universita di Siena and INFN Pisa, I-53100 Siena (Italy); Backes, M. [Technische Universitaet Dortmund, D-44221 Dortmund (Germany); Barres de Almeida, U.; Bock, R. K.; Borla Tridon, D. [Max-Planck-Institut fuer Physik, D-80805 Muenchen (Germany); Bastieri, D. [Dipartimento di Fisica, Universita di Padova and INFN, I-35131 Padova (Italy); Becerra Gonzalez, J.; Berger, K. [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Bednarek, W. [Department of Astrophysics, University of Lodz, PL-90236 Lodz (Poland); Bernardini, E. [Deutsches Elektronen-Synchrotron (DESY), D-15738 Zeuthen (Germany); Biland, A.; Boller, A. [ETH Zurich, CH-8093 Zurich (Switzerland); Bosch-Ramon, V., E-mail: jogler@slac.stanford.edu, E-mail: pmunar@am.ub.es [Facultat de Fisica, Universitat de Barcelona (ICC/IEEC), E-08028 Barcelona (Spain); and others

2012-07-20

406

Gamma ray emission and solar flares  

NASA Technical Reports Server (NTRS)

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

Lin, R. P.; Ramaty, R.

1978-01-01

407

Gamma ray lines from interstellar grains  

NASA Technical Reports Server (NTRS)

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

Lingenfelter, R. E.; Ramaty, R.

1976-01-01

408

Gamma-Ray Spectroscopy of 76As  

Microsoft Academic Search

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

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

1971-01-01

409

Directions in gamma-ray spectroscopy  

NASA Technical Reports Server (NTRS)

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

Gehrels, Neil; Candey, Robert M.

1990-01-01

410

Status of the Compton Gamma Ray Observatory  

NASA Astrophysics Data System (ADS)

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

Gehrels, Neil; Shrader, Chris

2000-04-01

411

Fermi gamma-ray imaging of a radio galaxy.  

PubMed

The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from the giant radio lobes of the radio galaxy Centaurus A. The resolved gamma-ray image shows the lobes clearly separated from the central active source. In contrast to all other active galaxies detected so far in high-energy gamma-rays, the lobe flux constitutes a considerable portion (greater than one-half) of the total source emission. The gamma-ray emission from the lobes is interpreted as inverse Compton-scattered relic radiation from the cosmic microwave background, with additional contribution at higher energies from the infrared-to-optical extragalactic background light. These measurements provide gamma-ray constraints on the magnetic field and particle energy content in radio galaxy lobes, as well as a promising method to probe the cosmic relic photon fields. PMID:20360067

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

2010-05-01

412

Cosmological aspects of gamma ray bursts  

NASA Astrophysics Data System (ADS)

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

Behkam, Razieh

413

The Resonant Absorption of gamma-Rays in 14N  

Microsoft Academic Search

Using a nitrogen filled proportional counter the resonant absorption of gamma-rays to the 8.06 MeV level in 14N has been observed by means of the 14N(gamma,p)13C reaction. The inverse reaction 13C(p,gamma)14N at the 554keV resonance was used as the source of gamma-rays. The gamma-ray flux was accurately measured with a scintillation counter and from the results the width of the

G. M. Griffiths

1958-01-01

414

Improved Gamma-Ray Flux Monitoring at the High Intensity Gamma-Ray Source (HIGS)  

NASA Astrophysics Data System (ADS)

An improved gamma-ray beam flux monitor has been built for use at the High Intensity Gamma-Ray Source at the Duke University Free Electron Laser Laboratories. It is important to know precisely the gamma-ray flux of this beam. It is also important to limit beam attenuation to a minimum while making an accurate flux measurement. The improvements from a more accurate gamma-ray intensity monitor will allow for more precise cross-section measurements and will be valuable to many of the experiments conducted at HIGS. The detector consists of a thin scintillator optically coupled to two photomultiplier tubes, a thin foil, and then another thin scintillator attached to two photomultiplier tubes. The front scintillator is used to veto counts from charged particles emitted upstream in the beam-line. The preliminary tests of the monitor show very promising results and after slight adjustments and calibrations, the detector will be ready to acquire accurate beam intensity measurements while contributing very little to beam attenuation.

Reynolds, Robert

2002-10-01

415

Gamma Rays in a Spectrum from the Mars Odyssey Gamma-Ray Spectrometer  

NASA Astrophysics Data System (ADS)

About 250 peaks and broad features were observed in a long spectrum from the Mars Odyssey Gamma-Ray Spectrometer, most of which have been identified. Many are background lines from Ge, Mg, Ti, Zn, and other elements near the GRS.

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

2003-03-01

416

Nuclear gamma rays from stellar flares  

NASA Technical Reports Server (NTRS)

Solar flare observations are consistent with the phenomenological description that a loop of magnetic flux is convected to the surface of the star and twisted. The resulting inductive current parallel to the field is dissipated at an enhanced rate throughout the field volume by current limiting instabilities. The steady state balance between joule heating and thermal conduction along the field lines of force to the denser, cooler surface establishes a temperature distribution. The expansion of heated and ionized surface layers leads to a pressure balance and hence predictable density and X-ray emission measure. The current limitation instabilities result observationally in the parallel current being transferred to run-away ions that reach a kinetic energy of some finite fraction of the inductive potential drop. The nuclear excitation gamma rays produced by such a run-away ion current are calculated for a white dwarf flare.

Colgate, S. A.

1978-01-01

417

The Swift Gamma Ray Burst Mission  

NASA Technical Reports Server (NTRS)

The Swift mission: scheduled for launch in early 2004: is a multiwavelength observatory for gamma-ray burst (GRB) astronomy. It is the 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 per year and performing detailed X-ray and UV/optical afterglow observations spanning timescales from 1 minute to several days after the burst. The objectives are to: 1) determine the origin of GFU3s; 2) classify GRBs and search for new types; 3) study the interaction of the ultra-relativistic outflows of GRBs with their surrounding medium; and 4) use GRBs to study the early universe out to z greater than 10. The mission is being developed by a NASA-led international collaboration. It will carry three instruments: a new-generation wide-field gamma-ray (15-150 keV) detector that will detect bursts, calculate 1-4 arcmin positions: and trigger autonomous spacecraft slews; a narrow-field X-ray telescope that will give 5 arcsec positions and perform spectroscopy in the 0.2 to 10 keV band; and a narrow-field UV/optical telescope that will operate in the 170-600 nm band and provide 0.3 arcsec positions and optical finding charts. Redshift determinations will be made for most bursts. In addition to the primary GRB science, the mission will perform a hard X-ray survey to a sensitivity of approx. 1 mCrab (approx. 2 x l0(exp -11) erg/sq cm s in the 15-150 keV band), more than an order of magnitude better than HEAO A-4. A flexible data and operations system will allow rapid follow-up observations of all types of high-energy transients. with rapid data downlink and uplink available through the NASA TDRSS system. Swift transient data will be rapidly distributed to the astronomical community and all interested observers are encouraged to participate in follow-up measurements. A Guest Investigator program for the mission will provide funding for community involvement. Innovations from the Swift program applicable to the future include: 1) a large-area gamma-ray detector us- ing the new CdZnTe detectors; 2) an autonomous rapid slewing spacecraft; 3) a multiwavelength payload combining optical, X-ray, and gamma-ray instruments; 4) an observing program coordinated with other ground-based and space-based observatories; and 5) immediate multiwavelength data flow to the community. The mission is currently funded for 2 years of operations and the spacecraft will have a lifetime to orbital decay of approx. 8 years.

Gehrels, N.; Chincarini, G.; Giommi, P.; Mason, K. O.; Nousek, J. A.; Wells, A. A.; White, N. E.; Barthelmy, S. D.; Burrows, D. N.; Cominsky, L. R.

2004-01-01

418

SAS-2 galactic gamma ray results, 1  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

419

Wolf-Rayet Stars and Gamma-Ray Bursts  

NASA Astrophysics Data System (ADS)

Observational properties of Gamma-Ray bursts, WR stars and their CO-cores at the end of evolution are analysed. Distribution of Gamma-Ray burst energies N(?E) has a wide range from 7?1051 to 2?1054 ergs. There are some evidences for bimodality of energy distribution N(?E) if we take into account Gamma-Ray burst GRB980425, associated with peculiar Ic-type supernova SN1998bw for which ?E?1048 ergs. These characteristics for Gamma-Ray bursts are in agreement with the distribution of the final masses of CO-cores of WR stars which is wide and continuous: MfCO=(1-2)Msolardiv(20- 44)Msolar. Possible bimodality of distribution of Gamma-Ray burst energies (? E1=1048 ergs; ? E2=7?1051div2?1054 ergs) is in agreement with bimodal distribution of relativistic objects: MNS=(1.35±0.15)Msolar, MBM=(4-15)Msolar. Arguments are given favoring possible connection of Gamma-Ray bursts with core collapses of WR stars. Expected frequency of collapses of CO-cores of WR stars in Galaxy is ~10-3 year-1 which is 3-4 order of magnitude higher than that of Gamma-Ray bursts calculated per one galaxy. WO stars can be considered as most probable candidates for progenitors of Gamma-Ray bursts. For these WR stars the frequency of collapses is ~10-5 years-1. Models of Paczynski (1998) and Gershtein (2000) can be considered as realistic models for Gamma-Ray burst phenomenon. For both models taking into account jet-like structure of Gamma-Ray formation region as well as random outcome of collapse of CO-core of WR star can explain observed Gamma-Ray burst frequencies. Investigation of WR galaxies (Conti, 1991) in connection with Gamma-Ray bursts seems to be very promising.

Cherepashchuk, A. M.

420

EGRET observations of high energy gamma ray pulsars  

Microsoft Academic Search

Observations with the EGRET instrument on CGRO have so far revealed gamma ray emission at E>100 MeV from 6, possibly 7 pulsars: 5 (6) radio pulsars and the radio quiet pulsar Geminga. The observed gamma ray lightcurves show mostly two peaked emission patterns; only PSR B1706-44 has a more complex lightcurve. The gamma ray photon number spectra between 30 MeV

G. Kanbach

1998-01-01

421

Radio search for gamma-ray pulsar counterparts  

Microsoft Academic Search

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

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

2009-01-01

422

On the energetics and number of gamma-ray pulsars  

Microsoft Academic Search

We examine a nearly aligned pulsar model with polar cap acceleration in order to explain the energetics and number of the known gamma-ray pulsars. In this model, the efficiency of converting spin-down luminosity to gamma-ray luminosity increases with decreasing spin-down luminosity, a trend recently emphasized by Ulmer. The predicted gamma-ray flux is proportional to dot P3\\/4\\/P5\\/4 d2, where P is

Charles D. Dermer; Steven J. Sturner

1994-01-01

423

Neutron-Insensitive Proportional Counter for Gamma-Ray Dosimetry  

Microsoft Academic Search

A gamma-ray dosimeter with low sensitivity to neutrons has been developed for radiation dosimetry in mixed fields of neutrons and gamma rays. Neutron sensitivity in a 2.5- to 3-Mev H2(d,n)He3 neutron field has been shown experimentally to be ?1.2% on the basis of first collision dose in tissue. Gamma-ray sensitivity is independent of energy to within ±5% from 1.25 Mev

Randall S. Caswell

1960-01-01

424

Gamma Rays in the Decay of Barium131  

Microsoft Academic Search

Gamma rays accompanying electron capture of 12-day Ba131 have been studied with a single-channel scintillation spectrometer. Relative intensities have been determined for the 122 kev (198), 214 kev (148), 372 kev (100), 496 kev plus satellite (360), and 620 kev (33) gamma-rays. Three new gamma-rays have been found at 823+\\/-20 kev (2.0), 917+\\/-15 kev (7.2), and 1032+\\/-15 kev (11.0), and

William C. Beggs; Berol L. Robinson; Richard W. Fink

1956-01-01

425

The Radio and Gamma-Ray Luminosities of Blazars  

Microsoft Academic Search

Based on the gamma-ray data of blazars in the third EGRET catalog and radio data at 5 GHz, we studied the correlation between the radio and gamma-ray luminosities using two statistical methods. The first method was the partial correlation analysis method, which indicates that there exist correlations between the radio and gamma-ray luminosities in both high and low states as

L. Zhang; K. S. Cheng; J. H. Fan

2001-01-01

426

The Radio and Gamma-Ray Luminosities of Blazars  

Microsoft Academic Search

Based on the $\\\\gamma$-ray data of blazars in the third EGRET catalog and\\u000aradio data at 5 GHz, we studied the correlation between the radio and\\u000a$\\\\gamma$-ray luminosities using two statistical methods. The first method was\\u000athe partial correlation analysis method, which indicates that there exist\\u000acorrelations between the radio and $\\\\gamma$-ray luminosities in both high and\\u000alow states as

L. Zhang; K. S. Cheng; J. H. Fan

2001-01-01

427

Fermi GBM Observations of Terrestrial Gamma-Ray Flashes  

NASA Technical Reports Server (NTRS)

This slide presentation explores the relationship between Terrestrial Gamma-Ray Flashes (TGF) and lightning. Using data from the World-Wide Lightning Location Network (WWLLN), and the gamma ray observations from Fermi's Gamma-ray Burst Monitor (GBM), the study reviews any causal relationship between TGFs and lightning. The conclusion of the study is that the TGF and lightning are simultaneous with out a causal relationship.

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

2010-01-01

428

Interpretation of the pulsed gamma-ray emission from Vela  

NASA Technical Reports Server (NTRS)

A model is proposed for the Vela pulsar in which the radio emission originates near the surface of the neutron star while the pulsed gamma-ray emission is produced by synchrotron radiation near the speed-of-light cylinder. This model can explain the energy flux, double pulse structure, and phase shift (with respect to the radio) of the gamma-ray emission, and offers approximate quantitative predictions for other X- and gamma-ray fluxes.

Thompson, D. J.

1975-01-01

429

The new prompt gamma-ray catalogue for PGAA  

Microsoft Academic Search

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

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

2000-01-01

430

Goddard Contributions to the Workshop on Gamma Ray Transients  

NASA Technical Reports Server (NTRS)

Six articles addressing cosmic and solar gamma ray transients are presented. The topics covered include: gamma ray lines from solar flares and cosmic transients including burst spectra; a review of the 1979 March 5 transient; time variation in the 511 KeV flux observed by the ISEE spectrometer; time variations of an absorption feature in the spectrum of the burst on 1980 April 19; and the theory of gamma ray amplification through stimulated annihilation radiation.

1981-01-01

431

Factors influencing in situ gamma-ray measurements  

Microsoft Academic Search

Introduction In situ passive gamma-ray sensors are very well suitable for mapping physical soil properties. In order to make a qualitative sound soil map, high quality input parameters for calibration are required. This paper will focus on the factors that affect the output of in situ passive gamma-ray sensors, the primary source, soil, not taken into account. Factors The gamma-ray

E. H. Loonstra; F. M. van Egmond

2009-01-01

432

Capture Gamma-ray Spectroscopy Using Cold Neutron Beams  

NASA Astrophysics Data System (ADS)

The availability of cold neutron beams can improve the quality of results obtainable from a capture gamma-ray measurement. Although capture gamma-ray instruments that use cold neutrons are less susceptible to problems that limit the capabilities of thermal instruments, new design parameters become important to consider. We discuss some of the questions that relate to neutron beam handling and present techniques for improving the quality of the capture gamma-ray instrument.

Stone, C. A.; Mildner, D. F. R.; Zeisler, R.; Cranmer, D. C.

1991-10-01

433

Multi-energy gamma-ray automated scanning system  

SciTech Connect

A CAMAC-based gamma-ray scanning system was used to measure the transmission through stacked attenuators for up to 16 different gamma rays. For each measurement, we obtained the transmission for gamma rays ranging in energy from 77 to 2614 keV. These transmission measurements were used to produce a set of linear equations that may be solved for either thickness or density of the discrete attenuators comprising a given stacked assembly.

Hsu, H.H.; Pratt, J.C.; Shunk, E.R.

1981-01-01

434

Analytical applications of neutron capture gamma-ray spectroscopy  

Microsoft Academic Search

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

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

1983-01-01

435

Analysis of fissionable material using delayed gamma rays from photofission  

Microsoft Academic Search

The energetic gamma-ray spectra from the fission products of photofission have been investigated to determine whether photofission can identify heavily shielded fissionable material. Target samples of natural thorium, 93% enriched ²³⁵U, natural uranium, and 93% enriched ²³⁹Pu were irradiated with bremsstrahlung gamma rays produced by 10-MeV electrons from a small linear accelerator. The gamma-ray spectra for each of the four

C. L. Hollas; D. A. Close; C. E. Moss

1986-01-01

436

Analysis of fissionable material using delayed gamma rays from photofission  

Microsoft Academic Search

The energetic gamma-ray spectra from the fission products of photofission have been investigated to determine whether photofission can identify heavily shielded fissionable material. Target samples of natural thorium, 93% enriched 235U, natural uranium, and 93% enriched 239Pu were irradiated with bremsstrahlung gamma rays produced by 10-MeV electrons from a small linear accelerator. The gamma-ray spectra for each of the four

C. L. Hollas; D. A. Close; C. E. Moss

1987-01-01

437

Gamma Rays from Short-Lived Fission-Fragment Isomers  

Microsoft Academic Search

Measurements of the energy spectra of isomeric gamma rays from the neutron fission of U235 and Pu239 at a number of time intervals between 50 and 600 musec showed six prominent gamma rays for both cases of fission. The intensities and half-lives for these gamma rays indicate that there are three fission-fragment isomers, each giving rise to a pair of

R. E. Sund; R. B. Walton

1966-01-01

438

Gamma-ray Spectroscopic Performance of a ˜10 kg Array of High Purity Germanium Crystals  

NASA Astrophysics Data System (ADS)

The gamma-ray spectroscopic performance of a single-cryostat, close-pack array of high purity germanium crystals is presented. The unit design is intended to provide high detection efficiency (˜1000% relative efficiency) for standoff gamma-ray detection in field measurement applications. However, the array design shares much in common with design concepts proposed by the Majorana Collaboration to search for neutrinoless double beta decay of Ge-76. The presentation will focus on those topics of relevance to both the field application and basic scientific research. Specifically this will include array operation, data collection, and data reduction that elucidate the unique features of a ˜10 kg compact array of high purity germanium gamma-ray spectrometers.

Orrell, John; Aalseth, Craig; Bonebrake, Chris; Caggiano, Jac; Day, Tony; Fast, Jim; Fuller, Erin; Hyronimus, Brian; Mullen, Dennis; Runkle, Bob; Smart, Jes; Warren, Glen

2009-10-01

439

Gamma-ray bursts during neutron star formation. Gamma-ray bursts and transient X-ray sources  

NASA Technical Reports Server (NTRS)

Discussions are presented of the associations between cosmic gamma ray bursts and transient X-ray sources, and the release of gravitational binding energy during the formation of neutron stars. The model for studying the associations is described along with the release of neutrinos during the collapse of white dwarfs.

Cohen, J. M.; Desai, U. D.; Holt, S. S.

1973-01-01

440

Future Facilities for Gamma-Ray Pulsar Studies  

NASA Technical Reports Server (NTRS)

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

Thompson, D. J.

2003-01-01

441

A total throughput transient spectrometer for gamma-ray bursters  

NASA Astrophysics Data System (ADS)

The present instrument concept for a high-throughput/high-time/high-energy resolution gamma-ray detector based on an array of 12 high-purity Ge detectors; sensitivities thus obtainable would be sufficient not only to obtain data on the energy spectra of gamma-ray bursts, but also to accomplish polarization measurements. This spectrometer is envisioned as ideally suited for a large platform with substantial telemetry capacity, such as the NASA Space Station. Secondary objectives for the instrument would include solar gamma radiation spectroscopy and the monitoring of X-ray and gamma-ray pulsars, as well as surveying the sky for slow transients.

Hurley, K.

442

Gamma-ray/neutron spectroscopy from the Mars observer  

NASA Technical Reports Server (NTRS)

The Gamma-Ray Spectrometer (GRS) experiment on Mars Observer will measure gamma rays and neutrons that escape from Mars. The intensities of gamma-ray lines and of the thermal and epithermal neutrons can be used to study many problems related to Martian volcanism and volatiles. The results of theoretical calculations for the production and transport of gamma rays and neutrons indicate that the GRS should be able to determine the abundances of many elements and the amounts and stratigraphy of H2O and CO2 on and in the top meter of the Martian surface. Design considerations of the GRS are discussed.

Englert, P.; Reedy, R. C.; Drake, D. M.; Feldman, W. C.; Squyres, S. W.; Evans, L. G.; Boynton, W. V.

1987-01-01

443

Nonrelativistic phase in gamma-ray burst afterglows  

Microsoft Academic Search

The discovery of multiband afterglows definitely shows that most $\\\\gamma$-ray\\u000abursts are of cosmological origin. $\\\\gamma$-ray bursts are found to be one of\\u000athe most violent explosive phenomena in the Universe, in which astonishing\\u000aultra-relativistic motions are involved. In this article, the multiband\\u000aobservational characteristics of $\\\\gamma$-ray bursts and their afterglows are\\u000abriefly reviewed. The standard model of $\\\\gamma$-ray bursts,

HUANG Yongfeng; T. Lu; K. S. Cheng

2007-01-01

444

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

445

Gamma ray constraints on the galactic supernova rate  

NASA Technical Reports Server (NTRS)

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

Ha