Positron Lifetimes in Voids and Other Defects in Annealed, Neutron-Irradiated Aluminum

摘要

Positron lifetimes were measured in neutron-irradiated high-purity aluminum single crystals, and companion small-angle x-ray scattering experiments were performed to determine the radius of gyration and volume fraction of radiation-induced voids. The lifetime data are consistent with a model in which positrons are trapped both in voids and in other defects which are tentatively identified as vacancy clusters bound to transmutation-produced silicon. The lifetime in the latter defects increased from 230 to 430 ps as the voids annealed out (around 306 exp 0 C), suggesting that the clusters grow in size as voids disappear. The lifetime in voids remained constant at (550 +- 30) ps. (ERA citation 02:022892)