On the determination of diffusion and slowing-down constants of ordinary water and beryllium oxide, using a pulsed neutron source

Abstract

A method of obtaining the diffusion constants and the age to thermal energy of water and beryllium oxide, using a pulsed neutron source, is described. Such a method has been used by L. J. Haworth et al. (1942) in the measurement of the mean life of thermal neutrons in water and by von Darel (1953) in the measurement of the diffusion length in water and heavy water. The main advantages of this method are that comparatively small quantities of the moderator material are required, and it is possible to determine the absorption mean free path, transport mean free path, and the age to thermal energy directly. In the case of water moderator of infinite dimensions, the interpretation of the decay constants depends very much on the choice of the theory.