Influence of pre-implanted helium on dislocation loop type in tungsten under self-ion irradiation

Transmission electron microscopy with in-situ ion irradiation has been used to examine dislocation loop formation during self-ion irradiation of pristine W and samples pre-implanted with He. Dislocation loops with b = ±½〈111〉 and b = 〈100〉 were observed in both the pristine W and He implanted samples. This contrasts previous works with He/H ion irradiation where no b = 〈100〉 type loops have been observed in W. The b = 〈100〉 dislocation loops form during the cascade and He has no effect on the type of dislocation loop formed, unlike nucleation of b = 〈100〉 type loops in FeCr alloys. Below, figure of W sample pre-implanted with He and irradiated to 3.0 DPA with W ions at 500 °C under different two-beam conditions showing the presence of both b = ±½〈111〉 and b = 〈100〉 dislocation loops.303