The W-D system was studied by using thermal desorption spectrometry. Impurities (O, He) were introduced by gas exposure and ion implantation. Auger electron spectroscopy was used to monitor the surface coverage of impurities. The release of D from sub-surface defects, including surface recombination to D2, was modelled It was shown that, for D, dissociation enthalpies which were lower than 1.3eV, surface recombination was the rate-determining step. By fitting the experimental data, a D-vacancy dissociation enthalpy of 1.43eV and an attempt frequency of 1013/s was found. Although the O and N coverage of the surface inhibited surface trapping of D from vacuum, no indication was found for an O-induced enthalpy barrier for D de-trapping from the surface. The ion-induced defects ranged from monovacancies to He bubbles and gave rise to D de-trapping with activation enthalpies ranging from 1.2 to 1.8eV.

Deuterium Interaction with Impurities in Tungsten Studied with TDS. H.Eleveld, A.Van Veen.: Journal of Nuclear Materials, 1992, 191-194, 433-8