Helium was present in fusion reactor wall materials, and its effect on radiation damage must be taken into account. The effect of He on displacement cascades in tungsten was studied using molecular dynamics simulations. Three different W-W potentials were compared and found to differ, especially for the clustering of the vacancies formed in the cascades. While there were differences in the amounts of damage depending on the potential, the overall effect of He in interstitial positions was to increase the amount of damage, while He in substitutional positions reduces it, due to the effect He has on the recombination of tungsten interstitials.

Simulation of Cascades in Tungsten-Helium. N.Juslin, V.Jansson, K.Nordlund: Philosophical Magazine, 2010, 90[26], 3581-9