EROSION PROCESSES IN PLASMA-WALL INTERACTIONS

During plasma-wall interactions in fusion experiments large energy and particle fluxes are deposited predominantly onto limiter and divertor structures. Besides good thermomechanical properties, plasma facing materials must exhibit low erosion yields. Under normal operation conditions, the main erosion mechanisms are physical sputtering, chemical sputtering, radiation enhanced sublimation and thermal sublimation. High-Z materials, such as W, show low effective sputtering yields at low plasma temperatures and a favourable redeposition behaviour, and may be suited for divertor plates for these plasma conditions. For higher plasma temperatures low-Z materials such as CFC materials and Ti-doped graphites, which enable high power removal, are preferable. In the other wall areas a low-Z material with reduced chemical erosion, e.g. B4C coatings, could be appropriate.