TRAPPING AND RE-EMISSION OF FAST DEUTERIUM IONS FROM NICKEL

A simple diffusion model is proposed for the re-emission of fast ions during bombardment of a metal surface. Experiments using a nickel target have been conducted in order to make a comparison with this model. Although the experimental results agree qualitatively with the predicted behaviour, the rate of re-emission is much lower than expected on the basis of known diffusion coefficients of deuterium in nickel. Thermal desorption of gas initially trapped in the nickel by bombardment at low temperatures indicates a number of specific activation energies for release, in addition to that associated with diffusion, and these are attributed to radiation damage sites produced during the ion bombardment.