Diffusion of High Energy Gamma-Rays through Matter. II. Solution of the Diffusion Equation

Abstract

An approximate solution of the diffusion equation derived by Foldy has been obtained for the case in which the total gamma-ray cross section is independent of energy. This is the case for essentially all materials in the energy region in which the derived diffusion equation is valid. For monoenergetic gamma-rays incident normally on a slab of material, the distribution in angle of gamma-rays of a given energy after traversing a large thickness of material is shown to be Gaussian with a breadth depending on the energy in accordance with a theorem derived by Foldy. Some numerical calculations for the case of 17-Mev gamma-rays incident on water are presented to illustrate the nature of the results.