The slowing down of fission neutrons in an infinite homogeneous medium

Abstract

The slowing down of fast neutrons produced uniformly in an infinite non-capturing homogeneous medium with a fission spectrum energy distribution has been studied. A simple approximate expression for the flux as a function of energy has been obtained and found to give values in error by at most 15 per cent. A correction to this expression is given from which values correct to a few per cent may be obtained. Numerical results for energies above 0·1 MeV are presented for hydrogen, deuterium and carbon. For energies in the range thermal to about 0·1 MeV, the flux for all non-capturing media shows the well-known 1 E dependence.