Measurements and modeling of D, He and Li sputtering of liquid lithium

The absolute sputtering yields of D⁺, He⁺ and Li⁺ on solid lithium have been measured and modeled at low energies in the ion-surface interaction experiment (IIAX). The experiment has been extended to measure physical sputtering from liquid lithium surfaces bombarded by D⁺, He⁺ and Li⁺. A Colutron ion source is used to create and accelerate gaseous or metal ions onto the liquid metal target. A plasma cup removes any oxides and saturates the surface with deuterium. A small high-temperature, HV substrate heater is used to heat the 0.76 g lithium sample past its melting point to 200 °C. Upon melting, a thin oxide layer is formed on the exposed lithium surface, which is cleaved by an in situ arm rotated in front of the target. Results suggest that the absolute sputtering yield of lithium is less than unity. In addition, the behavior of liquid lithium self-sputtering suggests stratification of the top liquid metal surface. This is consistent with VFTRIM-3D modeling, where D atoms migrate into the bulk while the first few monolayers remain mostly lithium.