ERO simulation of tungsten erosion and re-deposition for EAST divertor in helium and deuterium discharges including the lithium impurity effect

Tungsten erosion and re-deposition have been simulated by the Monte Carlo code ERO for the EAST upper outer divertor, with a comparative study specifically addressing the effects of carbon and lithium impurities on tungsten target erosion under helium versus deuterium plasma discharge conditions. The simulations indicate that tungsten erosion in helium discharges is significantly higher than in deuterium discharges due to a higher sputtering yield by helium ions. In deuterium discharges, the tungsten gross erosion rate initially rises with increasing carbon concentration in background plasma due to enhanced tungsten sputtering by carbon, and then decreases due to the protective effects of carbon deposition on the tungsten surface. In contrast, in helium discharges, an increase in background carbon concentration leads directly to a lower tungsten gross erosion rate, as helium sputtering dominates the tungsten erosion process. Lithium impurities play a notable protective role against tungsten erosion in both helium and deuterium discharges. Assuming suitable lithium and carbon concentrations, the modelling results align well with experimental data. The simulations offer key insights into tungsten erosion processes in deuterium and helium discharges.