INVESTIGATION OF IMPURITY DEPOSITION ON PLASMA-FACING COMPONENT USINGELECTRON-BEAM TECHNIQUE

In experiments in PISCES-B facility we have observed carbon film forma tion on beryllium substrates after hydrogen plasma exposure. The sourc es of the carbon are gaseous impurities in the vacuum system, which al so exist in a fusion reactor such as the International thermonuclear e xperimental reactor (ITER). Thin film formation, resulting from electr on-impurity interactions, is studied using a focused electron beam. In itial results show that carbon films are readily formed on beryllium s urface in a range of power densities from two kilowatts to over one me gawatt per square meter. Electron beam experiments on silicon and tung sten substrates, under the sane conditions, do not result in carbon fi lm formation. Microanalyses using scanning electron microscopy, Energy Dispersive X-ray spectroscopy and Raman are presented. (C) 1997 Elsev ier Science B.V.