THE HYDROGEN SURFACE-CHEMISTRY OF CARBON AS A PLASMA-FACING MATERIAL

Recent progress in plasma performance in experiments on controlled the rmonuclear fusion will lead to next-generation fusion experiments with the ultimate goal to make a power-generating fusion reactor reality. A major issue in the design of fusion experiments is the selection of the first wall material. Due to its outstanding thermal properties and its low Z carbon is and will be a first choice material, either eleme ntal or in compounds and composites. Given the fact that in magnetical ly confined hydrogen plasmas of high density and temperature substanti al wall fluxes of H species occur, the hydrogen/carbon surface chemist ry, in particular chemical erosion and H retention, becomes a concern. Although for more than a decade materials science studies on the H-ca rbon interaction have been performed, the elementary reaction steps of this interaction have become clear only recently. This report reviews work performed on the H/carbon surface chemistry under the aspects of chemical erosion. It presents in detail model studies directed toward s identifying elementary reaction steps. Related fields, e.g. the H/C surface chemistry as relevant for the production of hard a-C:H coating s and low pressure diamond synthesis are covered in the review.