Chemical erosion of carbon at low temperatures and low ion energies

Investigations of chemical erosion of carbon (EK98) were carried out in hydrogen and deuterium low pressure discharges. Atomic hydrogen fluxes to the surface were obtained From the radiation of the Balmer lines (Gamma (H) = Gamma (D) = 2.6 x 10(21) m(-2) s(-1)). From the diffusion flow onto a surface, the reflection coefficients of graphite for H and D atoms were determined to be 40% and 65%, respectively. Erosion yields were derived from weight loss measurements and emission spectroscopy of the CH and Ct bands at ion energies between 5-40 eV in the substrate temperature range of 300-1100 K. Spectroscopic results indicate the influence of higher hydrocarbons. An isotope effect of 2.5-3 was measured, which vanishes at room temperature and approx. 5 eV ion energy. Here, an erosion yield of 0.1% remains. The measurements were compared with model calculations and were in satisfying agreement.