Erosion and redeposition of graphite by hydrogen plasmas

The results of erosion and redeposition studies of graphite by hydrogen plasma bombardment in the PISCES facility are reviewed. The total erosion yields of several types of graphites have been measured during plasma exposure with ion fluxes of up to 2 x 1018 cm-2 . S-1, ion energies of 50 to 200 eV, and sample temperatures of 50 to 9500C. Hydrogen and deuterium plasmas have been used to bombard Poco, ATJ, and pyrolytic graphites, and a four-directional carbon-carbon (C-C) composite weave. The erosion rates of all the graphites tested are about equal, suggesting that surface damage by the ion bombardment results in similar erosion yields. The C-C composite weave material showed an increased weight loss during initial exposure, and then equal or lower erosion yields compared to the other graphites