REEMISSION OF DEUTERIUM ATOMS FROM MO, TA AND W DURING D+-IRRADIATION

The reemission of atoms and molecules from high-Z metal specimens (Mo, Ta, W) during D+-irradiation has been studied by means of line-of-sight quadrupole mass spectrometry. The key result of this study is the experimental evidence for the phenomenon of atom reemission during D+-irradiation of Mo, Ta and W at temperatures > 1200 K. The atom reemission can explain the decreasing trend with increasing temperature observed in previous reemission studies [4-7] where only molecules were detected in the residual gas. The shape of the reemission curves, as a function of temperature, indicates that activated surface processes may be affecting the angular distribution and/or the energy of the desorbing species. For D+-irradiation of the Ta sample, reemission of atoms and molecules was also observed from the back (unirradiated) surface of the specimen, demonstrating D-permeation. Observation of a permeating flux in this manner may be the basis of a technique for measuring hydrogen diffusion coefficients in metals at very high temperatures.