Deuterium interaction with impurities in tungsten studied with TDS

The deuterium-tungsten system was studied using thermal desorption spectrometry (TDS). Impurities (oxygen and helium) were introduced by gas exposure and ion implantation. Auger electron spectroscopy was used to monitor surface coverage with impurities. The release of deuterium from subsurface defects including surface recombination to D2 has been módelled. It was shown that for deuterium dissociation enthalpies lower than 1.3 eV surface recombination is the rate determining step. By fitting of the experimental data a deuterium vacancy dissociation enthalpy of 1.43 ± 0.02 eV and an attempt frequency of 1 × 1013 s−1 was found. Though oxygen and nitrogen coverage of the surface inhibited surface trapping of deuterium from the vacuum no indication was found of an oxygen induced enthalpy barrier for deuterium detrapping from the surface. Ion induced defects varying from monovacancies to helium bubbles give rise to deuterium detrapping with activation enthalpies varying from 1.2 to 1.8 eV.