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Spectrum of atmospheric gamma rays to 10 MeV at lambda = 40 degResults of measurements of the differential counting rate spectra due to atmospheric gamma rays as a function of altitude to 3.6 g/sq cm over Texas. Two gain settings and a 128-channel pulse height analyzer were used to cover the range from 0.2 to 10 MeV. The detector was a 7.6 x 7.6 cm NaI crystal, which was surrounded on five sides by a 2-cm-thick plastic anticoincidence shield for charged particle rejection. The system had a nearly isotropic response to photons above 0.2 MeV. The spectrum at ceiling appeared as a steep continuum with a power-law index of about 1.4. The only obvious feature was the 0.51-MeV positron annihilation line. The spectral shape was independent for depths less than 20 g/sq cm, the absolute intensity varying in proportion to the intensity of the cosmic ray secondary charged particles. Also, at depths less than 30 g/sq cm the observed flux variation with altitude can be described in terms of an empirical depth-dependent source function.
Document ID
19740032603
Document Type
Reprint (Version printed in journal)
Authors
Peterson, L. E.
Schwartz, D. A.
Ling, J. C. (California, University La Jolla, Calif., United States)
Date Acquired
August 7, 2013
Publication Date
December 1, 1973
Publication Information
Publication: Journal of Geophysical Research
Volume: 78
Subject Category
SPACE RADIATION
Funding Number(s)
CONTRACT_GRANT: NGR-05-005-003
Distribution Limits
Public
Copyright
Other