Diffusion of Deuterium in Deuteron-Irradiated Copper

Abstract

The rate of diffusion of deuterium in metals can be studied by measuring the counting rate of neutrons from the D (d,n) He3 reaction occurring in metals irradiated with low energy deuterons. A method of analyzing the time-dependence of the observed neutron counting rate is presented and applied to experiments on Cu in the temperature range −46° to +20°C. It is concluded from the results that grain boundary diffusion is primarily responsible for the movement of deuterium in polycrystalline Cu in this temperature range. The apparent activation energy for diffusion of deuterium in polycrystalline 99.999% Cu is found to be 0.12±0.02 ev/atom. Chemical purity appears to play an influential role in deuterium diffusion in Cu, the rate in OFHC Cu being significantly lower than that in the more pure material. A surface resistance effect, independent of the crystallinity of the specimen but proportional to the deuteron beam current, was found to be of major importance in determining the rate of escape of deuterium from the targets.