Simulating energy and angle distributions above infinite plane 60Co sources

A combination of a disc and a ring source of appropriate radii can be used to produce gamma-ray energy and angle distributions equivalent to those above an infinite plane, thus avoiding the "far-out" correction usually required for shielding experiments performed in a simulated fallout field. Examination of angle distribution data measured 3 ft above plane 60Co sources led to this concept. Monte Carlo calculations of both the energy and the angle distributions 3 ft and 40 ft above disc, ring, and infinite plane sources substantiate this concept. The degree of simulation is somewhat insensitive to the exact radius of the ring source; large deviations in ring source radii can be tolerated without severe penalty in some shielding studies.