IMPLANTED DEUTERIUM RETENTION AND RELEASE IN CARBON-COATED BERYLLIUM

Deuterium implantation experiments have been conducted on samples of c lean and carbon-coated beryllium. These studies entailed preparation a nd characterization of beryllium samples coated with carbon thicknesse s of 100, 500, and 1000 Angstrom. Heat treatment of a beryllium sample coated with carbon to a thickness of approximately 100 Angstrom revea led that exposure to a temperature of 400 degrees C under high vacuum conditions was sufficient to cause substantial diffusion of beryllium through the carbon layer, resulting in more beryllium than carbon at t he surface. Comparable concentrations of carbon and beryllium were obs erved in the bulk of the coating layer. Higher than expected oxygen le vels were observed throughout the coating layer as well. Samples were exposed to deuterium implantation followed by thermal desorption witho ut exposure to air. Differences were observed in deuterium retention a nd postimplantation release behavior in the carbon-coated samples as c ompared with bare samples. For comparable implantation conditions (sam ple temperature of 400 degrees C and an incident deuterium flux of app roximately 6 X 10(19) D/m(2)-s), the quantity of deuterium retained in the bare sample was less than that retained in the carbon-coated samp les. Further, the release of the deuterium took place at lower tempera tures for the bare beryllium surfaces than for carbon-coated beryllium samples.