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  • Other Sources  (16)
  • 1
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    Solar gamma ray lines observed during the solar activity of August 2 to August 11, 1972. (1973)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Keywords: SPACE RADIATION
    Type: Nature; 241; Feb. 2
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  • 2
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    The LXeCAT instrument for gamma-ray astrophysics (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Liquid Xenon Coded Aperture Telescope (LXeCAT) and its capability to image astrophysical gamma-ray sources in the MeV region is described. The gamma-ray detector is a Liquid Xenon Time Projection Chamber (LXeTPC) triggered by the primary scintillation light. Effective background rejection is a direct consequence of the intrinsic three-dimensional imaging capability of the LXeTPC. Initial results with a 10 liter prototype confirm an energy resolution of 6% FWHM, a position resolution of 1 mm RMS and a light triggering efficiency higher than 90% for 1 MeV gamma-rays.
    Keywords: ASTROPHYSICS
    Type: NASA-CR-199796 , NAS 1.26:199796 , NIPS-95-06474
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  • 3
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    Comparison of backgrounds in OSO-7 and SMM spectrometers and short-term activation in SMM (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The backgrounds in the OSO-7 Gamma-Ray Monitor and the Solar Maximum Mission Gamma-Ray Spectrometer are compared. After scaling to the same volume, the background spectra agree to within 30 percent. This shows that analyses which successfully describe the background in one detector can be applied to similar detectors of different sizes and on different platforms. The background produced in the SMM spectrometer by a single trapped-radiation belt passage is also studied. This background is found to be dominated by a positron-annihilation line and a continuum spectrum with a high energy cutoff at 5 MeV.
    Keywords: SPACE RADIATION
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  • 4
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    A directional gamma-ray telescope using coded aperture techniques (1983)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A directional detector for gamma-ray astronomy has been developed to image sources in the energy range 0.1 to 5 MeV. An array of 35 gain stabilized bismuth germanate detectors, together with a coded aperture mask based on a uniformly redundant array allows imaging in 4 deg square sky bins over a 16 x 24 deg field-of-view. The position of a strong point source, such as the Crab Nebula, can be determined to within not more than about 1 deg. A complementary 'anti-mask' greatly reduces systematic effects arising from nonuniform background rates amongst the detectors. The telescope has an effective area of 190 sq cm and an energy resolution of 19.5 percent FWHM at 662 keV. Results of laboratory tests of the imaging system, including the ability to image multiple sources, uniformity of response over the field-of-view, and the effect of the 'anti-mask', are in good agreement with computer simulations. Features of the flight detector system are described and results of laboratory tests and computer simulations are reviewed. A balloon flight of the telescope is planned for the fall of 1982.
    Keywords: ASTRONOMY
    Type: Advances in Space Research (ISSN 0273-1177); 3; 4 19; 1983
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  • 5
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    Limit on galactic 6.13 MeV gamma-ray line (1981)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The University of New Hampshire large gamma-ray detector observed the galactic center region during a balloon flight from Alice Springs, Australia on 1977 November 21-22. The absence of any observable line at 6.13 MeV or its escape-peak energy makes it possible to place an upper limit of 8.1 x 10 to the -4th photons/(sq cm s) at the 99% confidence level on the 0-16 de-excitation line at this energy from the galactic disk in the direction of the center. This limit restricts the interpretation given by Willett et al. (1979) of the line at 6.13 MeV which they observed while viewing the galactic anticenter. The present results indicate that it is highly unlikely that the line which these authors report is due to dark nebulae or the quiet sun. Possible explanations for their observation are atmospheric background, local production in the detector, a localized cosmic source in the direction of the galactic anticenter, or a statistical fluctuation.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 244
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  • 6
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    Statistical evaluation of gamma-ray line observations (1980)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The statistical reliability of reported positive observations of solar and cosmic gamma-ray lines has been evaluated. The relative probability that each measurement is due to a real source rather than to an accidental fluctuation in the background has been determined, and it is found that the results are statistically compelling in only a small fraction of the reported observations. At present, extreme caution must be exercised in drawing astrophysical conclusions from reports of the detection of cosmic gamma-ray lines.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 242
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  • 7
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    Photofraction of a 5 cm x 2 cm BGO scintillator (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The photofraction of a 5.1 cm x 2.0 cm bismuth germanate (BGO) scintillator was measured over a gamma-ray energy range of 0.2 to 6.1 MeV. Several methods, used to minimize the effect of room scattering on the measurement, are discussed. These include a gamma-gamma coincidence technique, a beta-gamma coincidence technique, and the use of sources calibrated with a standard 7.6 cm x 7.6 cm sodium iodide scintillator.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Transactions on Nuclear Science (ISSN 0018-9499); NS-32; 538-540
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  • 8
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    Analysis of the 0.511 MeV radiation at the OSO-7 satellite (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Observations of the 0.511 MeV positron annihilation, gamma ray on the OSO-7 satellite are presented. Variables which affect the counting rate are discussed. An upper limit flux of .0076 photons/sq cm/sec is obtained for the quiet sun and a positive solar flux of .063(+ or - .0002) photons/sq cm/sec is obtained for the 3B flare of 4 August 1972. The width of this annihilation line gives an upper limit temperature for the annihilation region of approximately 6 million K. An analysis of the line width and position also shows that the contribution to the line from positronium annihilation is less than 100% at the 99% confidence level. An upper limit is also found for an isotropic cosmic flux.
    Keywords: SPACE RADIATION
    Type: NASA-CR-139585
    Format: application/pdf
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  • 9
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    Upper limits to pulsed gamma ray emission from PSR 0833-45, 1747-46, and 1818-04 (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Pulsed gamma ray emission from three pulsars (PSR 0833-45, 1747-46, and 1818-04) have been sought on a balloon flight of the University of New Hampshire Large Gamma Ray Telescope, which incorporates a shielded sodium iodide scintillator array, and was launched from Alice Springs, Australia. Over the energy range 0.1 - 10 MeV, no evidence is found for pulsed gamma rays, and upper limits are set for Vela which are comparable to, or below, the extrapolation to lower energies of the pulsed emission reported by SAS-2 and COS-B.
    Keywords: ASTRONOMY
    Type: International Cosmic Ray Conference; Jul 13, 1981 - Jul 25, 1981; Paris; France
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  • 10
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    Observation of radioactive background in the OSO-7 gamma ray monitor (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The counting rate as measured by the gamma ray monitor on the OSO-7 satellite, covering the energy range 0.3-10 MeV, during a sixteen month period (October 1971-December 1972) was considerably higher than expected from balloon data previously reported. Dyer et al. (1971) have shown the importance of activation in satellites for diffuse gamma flux measurements. The OSO-7 spectra exhibit strong, complex line structure, especially between 400 keV and 900 keV, and several identifications can be made consistent with the model of Dyer et al. The spectral structure and time variations are presented which must be explained by any activation model.
    Keywords: SPACE RADIATION
    Type: International Cosmic Ray Conference; Aug 15, 1975 - Aug 29, 1975; Munich
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