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 bee n measured and modeled at low energies in the ion-surface interaction exper iment (IIAX). The experiment has been extended to measure physical sputteri ng from liquid lithium surfaces bombarded by D+, He+ and Li+. A Colutron io n source is used to create and accelerate gaseous or metal ions onto the li quid metal target. A plasma cup removes any oxides and saturates the surfac e 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 degreesC. Upon melting, a thin oxide layer is formed on the exposed lithium surface, whic h is cleaved by an in situ arm rotated in front of the target. Results sugg est that the absolute sputtering yield of lithium is less than unity. In ad dition, the behavior of liquid lithium self-sputtering suggests stratificat ion of the top liquid metal surface. This is consistent with VFTRIM-3D mode ling, where D atoms migrate into the bulk while the first few monolayers re main mostly lithium. (C) 2001 Elsevier Science B.V. All rights reserved.