Calculation of low-energy neutron flux in the atmosphere by the<i>S</i>_<i>n</i>method

Abstract

The transport equation pertaining to cosmic-ray neutrons in the atmosphere was solved for neutron flux by means of the numerical multigroup Sn method. Flux values were obtained at geomagnetic latitude 57°N as a function of altitude and energy group in the range from thermal to 20 Mev. These results, and continuous neutron flux distributions over energy determined from them, are presented for several representative altitudes. On the basis of the fluxes and appropriate neutron cross sections, averaged world rates for production of carbon 14 and tritium by neutron absorption processes in the atmosphere were calculated to be 2.1 atoms C14 cm−2 sec−1 and 0.07 atom T cm−2 sec−1. All results obtained are compared with other results.