Neutron flux and energy spectrum above the atmosphere

Neutron detectors consisting of B10F3 proportional counters and Li6I(Eu) scintillation counters, surrounded by varying amounts of moderating material, have been flown above the atmosphere in a number of vehicles. The shape of the neutron energy spectrum given by Hess, Canfield, and Lingenfelter has been verified within experimental limitations, and the flux of neutrons at 650-km altitude and 36.5°N geomagnetic latitude has been determined to be 0.28±30 per cent neutrons per cm2 sec, whereas at 320-km altitude and 8.7°S the flux is 012±40 per cent neutrons per cm2 sec. This flux determination gives an absolute neutron flux a factor of 3 lower than previously reported determinations.