The hydrogen surface chemistry of carbon as a plasma facing material

Recent progress in plasma performance in experiments on controlled thermonuclear 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 elemental or in compounds and composites. Given the fact that in magnetically confined hydrogen plasmas of high density and temperature substantial wall fluxes of H species occur, the hydrogen/carbon surface chemistry, in particular chemical erosion and H retention, becomes a concern. Although for more than a decade materials science studies on the H---carbon 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 towards identifying elementary reaction steps. Related fields, e.g. the H/C surface chemistry as relevant for the production of hard a-C:H coatings and low pressure diamond synthesis are covered in the review.