Dual Ion Irradiation: Impact of the Conflicting Roles of Helium on Void Nucleation

摘要

It has recently been demonstrated that ion simulations of neutron-induced swelling are strongly affected by the presence of the injected ion acting as an extra interstitial atom. The injected interstitial has been shown to exert a strong influence on both the void nucleation and steady-state regimes of swelling. In dual-ion irradiations where helium and self-ions are injected simultaneously, the helium acts as a nucleation-assisting gas atom once it finds a vacancy cluster. While diffusing to the cluster, however, helium has a high probability of trapping a vacancy and creating an unpaired interstitial. In this latter role, large levels of coinjected helium tend to strongly suppress void nucleation, not only at the lower irradiation temperatures cited by other researchers, but also at higher temperatures. The major consequence of the injected interstitial effect of large helium levels is to increase the duration of the transient regime of swelling. A similar helium-generated interstitial effect also occurs in neutron irradiations, but the impact is negligible under most conditions due to the nonlinearity of the injected interstitial effect and to the absence of the larger influence of injected ions. 6 figures. (ERA citation 10:002613)