Deuterium in molten lithium: Retention and Release

A study of deuterium retention and release properties of molten lithium is presented for samples exposed to deuterium plasmas in PISCES-B. Using thermal desorption spectrometry (TDS), retained D atom inventory and the surface recombination constant have been determined. Retention was measured for D+ ion fluences in the range 10^20-10^22 cm^-2 with sample temperature in the range 473-773^o K. Results show full absorption of all deuterium ions incident on the liquid lithium surface, until the sample is completely converted to lithium deuteride. In collaboration with SNL, surface recombination constants were inferred from the outgassing rates of selected samples during TDS. These data are Arrhenius in the temperature range 573-873^o K but are lower than predicted by kinetic modeling. Comparison of the level of departure from the model, with that for experimental results in the literature for hydrogen recombination on Nb and Pd, suggests good agreement between our data and the model. The difference is explainable by a fractional surface coverage with contamination.