Thermal desorption measurements of hydrogen--isotope retention in the Alcator-A tokamak

Results are presented for deuterium retention measurements in type 304 stainless steel exposed in the edge plasma of the Alcator-A tokamak. Stainless steel samples, at 300 K, with surface conditions characterized by Auger electron spectroscopy, were introduced into the limiter shadow region for exposure to deuterium plasmas, and then withdrawn into an appended UHV chamber for thermal desorption measurements. For unoxidized samples exposed at the vacuum vessel wall radius, 1 x 1015 D cm-2 was retained after exposure to high density (n-bar/sub e/=3 x 1014 cm-3) discharges. Exposure to consecutive series of N discharges produced retention proportional to N/sup 1/2/