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Atmospheric neutron and gamma ray fluxes and energy spectra at balloon altitude

Thesis/Dissertation ·
OSTI ID:6428048
The energy spectra and fluxes of atmospheric neutrons and gamma-rays have been measured with a time-of-flight (TOF) system using organic liquid scintillators, from two balloon flights at atmospheric depth of about 4.5 g/cm/sup 2/ over Palestine, Texas lambda = 42/sup 0/N). The detector consists of two banks of six NE213 liquid scintillators, each 7.6 cm x 7.6 cm. The two banks are separated by 75 cm with a TOF system between the two banks to measure upward or downward moving particles. Pulse shape discrimination is included on each NE213 scintillator to discriminate between neutrons and gamma-rays. This detector has been calibrated at several neutron energies to determine the efficiency both as function of energy and direction of the incident neutrons. For gamma-rays, both the analytical and the Monte Carlo methods are used to calculate the efficiency. The measured neutron leakage current is 3.3 x 10/sup -3/ from 10 less than or equal to En < 15 MeV, 7.8 x 10/sup -4/ from 15 less than or equal to En < 30 MeV and 4.8 x 10/sup -4/ (neutron/cm/sup 2/-sec-MeV) from 30 less than or equal to En less than or equal to 60 MeV. The total downward gamma-ray flux from 2 MeV to 6 MeV at 3.5 g cm/sup -2/ is given by 0.012E/sup -1/ /sup 5/ (photons/cm/sup 2/-sec-sr-MeV). The upward moving gamma-ray flux at 4 g cm/sup -2/ from 2 MeV to 10 MeV is .063E/sup -1/ /sup 8/ (photons/cm/sup 2/-sec-sr-MeV).
Research Organization:
New Hampshire Univ., Durham (USA)
OSTI ID:
6428048
Country of Publication:
United States
Language:
English