Sputtering yields of pure and helium-implanted tungsten under fusion-relevant conditions calculated using molecular dynamics

This study uses atomistic simulations to calculate the sputtering yield of tungsten in the presence and absence of near-surface helium clusters. We find that near-surface helium in the concentrations tested (consistent with 100 eV implantation fluences of 1: 0 and 2: 2 x 10(19) He m(-2) at a flux on the order of 1025 He m(-2) s(-1)) has a negligible effect on the sputtering yield, suggesting that any changes in sputtering that might be observed experimentally are due either to much higher near-surface concentrations of helium or due to other structural changes in the tungsten that would occur only at much higher helium fluences than we are able to probe using molecular dynamics simulation. We do find a dependence on surface orientation and incident helium energy: comparing {0 0 1}, {1 1 0}, and {1 1 1} surfaces, we find that {1 1 0} surfaces at high energy show the most sputtering, while {1 1 1} surfaces at low energy show the least. We attribute these differences in surface orientation to the more closely-packed nature of {1 1 0} surfaces compared to the other two orientations. (C) 2014 Elsevier B.V. All rights reserved.