Structural defect accumulation in tungsten and tungsten-5wt.% tantalum under incremental proton damage

We have performed proton irradiation of W and W-5wt.%Ta materials at 350 °C with a step-wise damage level increase up to 0.7 dpa and using two beam energies, namely 40 keV and 3 MeV, in order to probe the accumulation of radiation-induced lattice damage in these materials. Interstitial-type a/2 dislocation loops are formed under irradiation, and their size increases in W-5Ta up to a loop width of 21 ± 4 nm at 0.3 dpa, where loop saturation takes place. In contrast, the loop length in W increases progressively up to 183 ± 50 nm at 0.7 dpa, whereas the loop width remains relatively constant at 29 ± 7 nm at >0.3 dpa, giving rise to dislocation strings. The dislocation loops and tangles are observed in both materials examined after a 3 MeV proton irradiation at 350 °C. Ta doping delays the evolution of radiation-induced dislocation structures in W, and can consequently impact the hydrogen isotope retention under plasma exposure. [Display omitted] •Interstitial a/2 loops form in proton-irradiated W and W-5Ta at 350 °C.•At 0.3dpa loop length in W-5Ta reaches saturation, whereas it still increases in W.•Dislocation loops in W evolve into dislocation strings above 0.3dpa.•At high damage levels dislocation loops and tangles coexist in both W and W-5Ta.