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 samples pre-implanted with He. 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 b = <100> type loop nucleation in FeCr alloys.