Impurity release from low-Z materials under light particle bombardment

Recent progress in the understanding of the erosion of low-Z materials under bombardment conditions characteristic of magnetic fusion experiments is reviewed. The role of physical sputtering, chemical sputtering and radiation-enhanced sublimation in tokamaks is considered, and observations are related to laboratory measurements. The role of physical sputtering is largely understood, and tokamak measurements, under conditions where physical sputtering is expected to dominate, can be well predicted, except in the energy range near the sputtering threshold. Chemical erosion and radiation-enhanced sublimation are less-well understood, and predictions of erosion yields under tokamak conditions require assumptions (primarily related to energy and flux density dependence) which do not have a solid experimental basis. Also, only a few quantitative results from tokamaks are available to confirm predictions, and those which are available are not always consistent. (orig.)