A measurement of the atmospheric neutron flux in the energy range 50 < E < 350 MeV

Abstract

A series of telescopes having approximately a 30° half opening angle and responding to neutrons in the energy range 50 to 350 MeV has been flown to the top of the atmosphere on balloons released from an equatorial launching site at Kampala, Uganda, between 1967 and 1970. The downward moving neutron flux has been measured as a function of altitude, and is compared with other results in similar energy ranges. The neutron albedo at a residual atmospheric depth of 3 mb has been measured to be 0.24 ± 0.10 neutrons m −2 sec −1 MeV −1 at approximately 140 MeV. This value is considerably higher than previously accepted theoretical predictions. The implications of this higher value are discussed in relation to the population of the Earth's inner radiation belt by neutron decay protons.