Fuzz nanostructure and erosion on tungsten-vanadium alloys exposed to helium plasma in the STEP linear plasma device

Tungsten-vanadium (W-V) alloys with 5 and 10 wt.% V made using hot-pressing sintering have been subjected to helium plasma at 1050 K with ion energy of 100 eV for one hour in a linear plasma generator STEP. The W-V alloys consist of three typical phase regions, i.e. the W-enriched region, the W-V solid solute region and the V-enriched region. Slight surface erosion on the W-V solid solute region and severe surface erosion on the V-enriched region are observed on the exposed surface. Sputtering during the He plasma loading contributed to the surface erosion in the W-V solid solute region and the V-enriched region. Slight sputtering on W-V solid solute region is expected given that the lighter alloying element increases the sputtering yield of the W-based material. Moreover, fuzz nanostructure formed on the surface of the W-V alloys under the applied irradiation conditions. The W-V solid solute region exhibits severe fuzz growth in comparison with the W-enriched region when exposed to He plasma, especially in the low flux area. The intense attraction interaction between He and substitutional V atoms aggravates the fuzz growth on the W-V solid solute region. Furthermore, the aggravation effect of V on fuzz nanostructure evolution is mitigated in the high flux area due to the enhanced preferential V sputtering.