Atmospheric neutron and gamma ray fluxes and energy spectra

Abstract

The energy spectra and fluxes of atmospheric neutrons and gamma rays from 8 to 60 MeV and from 2 to 10 MeV, respectively, have been measured with a time‐of‐flight (TOF) system using organic liquid scintillators at balloon altitudes (3–5 g/cm²) over Palestine, Texas (λ=42°N). The TOF detector consisted of two banks of six cylindrical NE213 liquid scintillators, each being 7.5 cm in diameter by 7.5 cm long, separated by 0.75 m. A TOF system was used to measure upward and downward moving neutrons and gamma rays. Pulse shape discrimination is included on each NE213 scintillator to discriminate between neutrons and gamma rays. The measured neutron leakage current is 1.9 × 10−3 from 8 ≤En <18 MeV, 1.5 × 10−3 from 18 ≤En <30 MeV, and 9.5 × 10−4 neutron/cm² s MeV from 30 ≤En ≤60 MeV. The total downward gamma ray flux from 2 to 6 MeV at 3.5 g cm−2 is given by 0.012E−1.5 photon/cm² s sr MeV. The upward moving gamma ray flux at 4 g cm−2 from 2 to 10 MeV is 0.063E−1.8 photon/cm² s sr Mev.

Satellite observation of atmospheric nuclear gamma radiation

“…The continuum was represented as a power law with spectral index -1.4. Ryan et al (1977) and Lockwood et al (1979) report measurements of the upward moving gamma ray background in the Flight Center (Ling 1975) privately communicated measurements of the 2.31 MeV line from 14N, the 4.44 MeV line from 12C and liB, the 6.1MeV line from 160, and the line complex at about 6.7 MeV. Willett et al (1979) have made a further report of the 6.13 MeV line.…”

Event reconstruction in high resolution Compton telescopes

“…The development of Compton telescopes began in the 1970's, with work done at the Max Planck Institut (Schönfelder et al 1973), University of California, Riverside (Herzo et al 1975), and the University of New Hampshire (Lockwood et al 1979), culminating in the design and flight of COMPTEL/CGRO. These historical Compton telescopes consist of two scintillation detector planes -a low atomic number "converter" and a high atomic number "absorber".…”

Instrumental background in balloon-borne gamma-ray spectrometers and techniques for its reduction

“…17 MeV, E > .066 MeV). The elastic scattering component is seen to be important at low energies, exceeding even the aperture flux below 50 keV for the coaxial detectors and below 25 keV for the planar detectors.…”

“…The three points from Lockwood et al [17] have been multiplibad by a factor of 1.15 [18] to correct for a depth of 3.5 g cm-2 . The points from Ryan et al…”