ATOM TRANSPORT UNDER ION IRRADIATION

Diffusion coefficients in nickel single crystals under heavy ion irrad iation were measured near the irradiated surface by using multi-layer specimens. Analysis of the depth dependence of these diffusion, coeffi cients yields information on the effective fraction eta Of the displac ement rate, with which transporting, i.e., 'freely migrating' defects are produced, and on the radiation-induced sink strength. Upper limits of eta = 7% are estimated for a self-ion irradiation at 950 K. By inc reasing the irradiation temperature from 800 to 950 K the effective si nk strength was observed to decrease while eta increases. The relation between swelling rates and the magnitude of the radiation-enhanced di ffusion coefficient is briefly discussed. (C) 1997 Elsevier Science B. V.