The Diffusion and Absorption of Neutrons in Paraffin Spheres

Measurements are described of the activities imparted to silver and to indium detectors placed in paraffin spheres of various sizes with a radon-beryllium source of neutrons located at the center. The results are discussed with the aid of diffusion theory. Reasonably good quantitative agreement is obtained at distances from the source greater than about 8 cm. Various independent estimates are made of the mean free path of the neutrons in paraffin, their specific absorption rate constant, and the ratio of the latter to the diffusion constant. The mean free path is found as 0.53 cm; the ratio of the specific absorption rate constant to the diffusion constant as 0.026 ${\mathrm{cm}}^{-2\mathrm{}}$.