Suppression of carbon erosion by hydrogen shielding during high-flux hydrogen bombardment

Abstract

The erosion of carbon by intensive hydrogen bombardment has been recently shown to decrease sharply at very high fluxes $(\ensuremath{\sim}{10}^{19}\mathrm{ions}/{\mathrm{cm}}^{2}\mathrm{s}).$ This effect cannot be explained by standard sputtering or erosion models, yet understanding it is central for selection of fusion reactor divertor materials, and formulation of sputtering models for high-flux conditions. Using molecular dynamics computer simulations we now show that the effect is due to the buildup of a high hydrogen content at the surface, leading to a shielding of carbon atoms by the hydrogen.