Impacts of helium and hydrogen on the defect evolution in tungsten under high-energy cascades: A molecular dynamics study

Tungsten (W) is widely regarded as one of the primary candidates for plasma-facing materials in fusion reactors. However, during the fusion process, hydrogen (H) and helium (He) are inevitably present in the materials, making it essential to consider their impact on radiation damage. This study employed molecular dynamics simulations to investigate cascade behavior in W under varying H and He concentrations, with primary knock-on atom (PKA) energies ranging from 10 keV to 100 keV. Our results indicate that cascades with higher PKA energies are more likely to exhibit unfragmented configurations. He increases the number of Frenkel pairs (FPs), whereas H has minimal effect. Moreover, both H and He influence cluster size. The variation in FPs counts can be attributed to the vacancy occupancy and threshold displacement energy in W, while changes in cluster size result from their impact on formation energy. Notably, while H and He do not affect the type of dislocation loop, He significantly disrupts the interactions between dislocation loops, promoting the formation of a mixed-dislocation network and inhibiting the development of loops with a single Burgers vector. These findings contribute to a deeper understanding of the influence of H and He on defect evolution in W.