The Cosmic y-RAY Spectrum Between 0.3 and 25 MeV Measured on Apollo 15
1973; IOP Publishing; Volume: 181; Linguagem: Inglês
10.1086/152084
ISSN1538-4357
AutoresJ. I. Trombka, A. E. Metzger, James Arnold, J. L. Matteson, R. C. Reedy, L. E. Peterson,
Tópico(s)Particle Detector Development and Performance
Resumoview Abstract Citations (66) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Cosmic y-RAY Spectrum Between 0.3 and 25 MeV Measured on Apollo 15 Trombka, J. I. ; Metzger, A. E. ; Arnold, J. R. ; Matteson, J. L. ; Reedy, R. C. ; Peterson, L. E. Abstract The spectrum of the total (diffuse and discrete sources) cosmic y-ray background over the 0.3- 27 MeV range has been measured with an uncollimated NaI(Tl) scintillation counter 7.0 cm in diameter x 7.0 cm long located on a boom 7.6 m from the Apollo 15 service module. Data on cosmic y-rays were taken during Trans-Earth coast at various boom extensions, detector gains, and with the plastic anticoincidence scintillator enabled and disabled. The energy-loss spectrum at full extension with the anticoincidence enabled, corrected for monochromatic spacecraft 7-rays, is 0.18 counts (cm2 s MeV) 1 at 1 MeV, in agreement with previous measurements on the Ranger 3 and the ERS-l8. At 5 MeV, the Apollo measurement of 7 >c l0- counts (cm2 s MeV)-1 is about a factor of 5 below that determined from the ERS-18. Corrections for line contributions and spacecraft continuum at higher energies give a steep equivalent photon spectrum with a broad feature in the 1-3 MeV region. This flattening can be reduced (but not eliminated) with an estimated correction for spallation effects in the detector, leaving a spectrum which we interpret as a maximum estimate to the true cosmic photon spectrum in the 0.3-27 MeV range. At 3 MeV this limit is a factor of 3 and at 27 MeV a factor of 10 above a power law which extrapolates from measurements below 1 MeV. We have also measured a flux of 0.03 i 0.015 photons (cm2 s)-' at 0.51 MeV which may be mostly of local origin. Subject headings: cosmic rays - gamma rays Publication: The Astrophysical Journal Pub Date: May 1973 DOI: 10.1086/152084 Bibcode: 1973ApJ...181..737T full text sources ADS |
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