Low-dose neutron irradiation damage in copper. I. Vacancy loop production

Abstract

Abstract In this paper vacancy loop production in neutron-irradiated pure copper is described. Single crystals with an [011] orientation have been irradiated at 355K and 523–623 K with doses of up to 2 × 1022nm−2 in the materials test reactor PLUTO. Subsequent observations in the transmission electron microscope of material irradiated at 355 K revealed that the damage structure consists of a uniform distribution of dislocation loops which are predominantly vacancy in nature. An analysis has been carried out to quantify the link between the cascades produced by energetic neutron lattice-atom collisions and the observed vacancy loop population. This has exposed the need to know the threshold energy, E T, required to generate a cascade that collapses to a loop of minimim visible size. Taking 6 keV and 10keV as limiting values for E T, the corresponding values of the recoil spectrum averaged defect yield, Y N, and cascade efficiency, eN, are 0·08 to 0·11 and 0·49 to 0·37, respectively. At irradiation temperat...