Thermal desorption of D2 and CD4 from bulk-boronized graphites

Thermal desorption spectra of D2 and CD4 from bulk-boronized graphites containing 3 to 38 wt% B as well as from pure graphite and stoichiometric B4C were measured. The samples were implanted with 3 keV D3+ ions at temperatures between 130 and 700degC to fluences between 2.3x1016 and 2.3x1019 D/cm2 prior to the desorption. An enhancement of D2 release is observed with increasing boron content, while the CD4 release decreases correspondingly. The desorption peak maximum of D2 is shifted towards lower temperatures with increasing boron concentrations. Apparently, it is the boron in solid solution which mainly influences the trapping and release behaviour of deuterium. The formation of CD4 is suggested to proceed via a precursor state. The formation of the complete CD4 molecule takes place only close to the desorption temperature. The reduction of binding energy for D has only a minor influence on ion-beam-induced detrapping. (orig.)