Plasma interaction with liquid lithium: Measurements of retention and erosion

This paper reports on recent studies of high flux deuterium and helium plasma interaction with liquid lithium in the Pisces–B edge plasma simulator facility. Deuterium retention is explored as a function of plasma ion fluence in the range 6×1019–4×1022 atoms cm−2 and exposure temperatures of 523–673 K. The results are consistent with full uptake of the deuterium ions incident on the liquid metal surface, independent of the temperature of the liquid lithium. Full uptake continues until the sample is volumetrically converted to lithium deuteride. Helium retention is not observed for fluences up to 5×1021 He atoms cm−2. Measurements of the erosion of lithium are found to be consistent with physical sputtering for the lithium solid phase. However, a mechanism that provides an increased evaporative-like yield and is related to ion impact events on the surface, dominates during the liquid phase leading to an enhanced loss rate for liquid lithium that is greater than the expected loss rate due to evaporation at elevated temperatures. Further, the material loss rate is found to depend linearly on the incident ion flux, even at very high temperature.