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 degrees 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 < 111 > dislocation loops are formed under irradiation, and their size increases in W-5Ta up to a loop width of 21 +/- 4 nmat 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 nmat >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 degrees C. Ta doping delays the evolution of radiation-induced dislocation structures in W, and can consequently impact the hydrogen isotope retention under plasma exposure. (c) 2018 Elsevier B.V. All rights reserved.