Browsing by Author "Glenn, Stephen W"

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    Atmospheric gamma radiation
    (1969) Glenn, Stephen W; Haymes, Robert C.
    During the summer of 1967, a series of balloon flights with a directional gamma-ray detector were made. The detector is collimated to a half-angle of about 12° and measurements are made over gamma-ray energies between 30-570 keV. The energy range is divided into 128 channels. Detailed knowledge of the instrument response allows the actual incident spectrum to be unfolded. The altitude dependence of the gamma-ray count rate is well fit by curves of the form f = A ± Be-p/D where p is the pressure and the plus or minus sign is used for pressures below or above the maximum count rate altitude of about 75 mb. The spectra at different altitudes are presented. The spectrum of the gamma radiation high in the atmosphere (3.5 mb) is analyzed in detail and appears to be proportional to the ionizing radiation which varies as a function of geomagnetic latitude. A small zenith angle dependence may have been observed. The -500 keV feature which has been observed previously appears to be at 490 keV. The results of this experiment indicate that any contribution from a possible 511 keV annihilation energy line must be very small compared to the peak at 490 keV. Line features due to neutrons are present in the spectrum and appear to be of expected magnitude. During one of the flights, the sun was in the field of view and an observed increase may be attributed to enhanced solar emission of gamma radiation. The increase appeared to remain constant for at least twenty minutes and the spectrum of the increase at the top of the atmo- sphere is fit by the curve f(E) = 43.1 E-(1.75 ± .05) photons/cm2-sec (where E is in keV).