Reduction of erosion yield of graphite materials under high flux beam irradiation

Erosion yield of various graphite materials at elevated temperatures due to high flux beam irradiation was studied. The irradiation was performed by a 5 keV argon beam with a maximum flux of about 1021 Ar·m-2·s-1, about two orders of magnitude higher than that of previous beam experiments. It was found that the total erosion yield of graphite materials at elevated temperatures (1780-1980 K) in high flux regions shows a significant reduction with flux, which was not observed in the previous low flux experiments. The flux dependence of the radiation enhanced sublimation (RES) yield, which is the total yield minus the physical sputtering yield, is consistent with the model based on C self-interstitial diffusion with stable stable defects as sinks of interstitials in both high and low flux regions. According to the experimental data and this model, much less erosion of graphite materials under actual deuterium edge plasma conditions with a high heat flux to the plasma facing components (PFCs) can be expected. (author)