Molecular dynamics simulation of erosion and surface evolution of tungsten due to bombardment with deuterium and carbon in Tokamak fusion environments

Abstract

The behavior of tungsten as plasma facing material in fusion environment is investigated using molecular dynamics simulation. Tungsten erosion and surface evolution is simulated during irradiation by carbon and deuterium ions. Non-cumulative pure carbon bombardment on crystal tungsten shows that substrate temperature does not affect carbon trapping rate, implantation depth, and tungsten sputtering yield. Carbon induced tungsten physical sputtering yield threshold is predicted to be around ∼25eV. Cumulative carbon irradiation on crystal tungsten reveals that tungsten erosion is enhanced at high substrate temperatures. Cumulative carbon induced tungsten sputtering yield matches experimental data as well as Monte Carlo results. Carbon pre-irradiated tungsten tends to trap more hydrogen and facilitates gas bubble formation. Simultaneous deuterium and carbon bombardment on crystal tungsten indicates that carbon induced tungsten sputtering yield exhibits a maximum value when carbon ratio is around 20%. Higher carbon ratio reduces both the carbon and deuterium trapping rates.