A Study of the Angular and Energy Distributions of Radiation at Small Distances from a Point Source of Gamma Rays or Neutrons

The theoretical expression for the singly scattered angular and energy flux of radiation from a point source is studied in the limit of very small source-detector separation distances (π_Or << 1). It is shown that both the angular and energy distributions are related in a simple way to the scattering kernel. Examples are given for gamma and neutron point sources in air. The applicability of the distributions at separation distances of the order of a mean free path (π₀r ≈ 1) is discussed.