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. (paper)