Erosion from Liquid‐Metal Plasma‐Facing Components in Future Fusion Devices

The use of liquid metals as candidate plasma‐facing component (PFC) materials can enhance the performance and heat flux limits of fusion devices. Their applicability however, is strongly dependent on erosion properties including sputtering and evaporation. In this paper, the viability of candidate liquid metals such as lithium, tin and tin‐lithium is considered. Recent experimental results in the (Ion‐surface Interaction Experiment) IIAX at the University of Illinois and PISCES‐B at the University of California, San Diego have demonstrated anomalous erosion properties for liquid lithium and liquid tin‐lithium as the sample temperatures are raised. In IIAX the sputtering yield of liquid lithium and liquid tin‐lithium has been measured for 200–1000 eV bombardment of H⁺, D⁺, He⁺ and Li⁺ at 45‐degree incidence. Experiments in IIAX are carried out for sample temperatures between 200–450 °C. These experiments simulate similar conditions in fusion devices such as deuterium surface treatment, oblique incidence and ion fluence. The secondary ion sputtered fraction from liquid lithium and tin‐lithium has been found to be near 60–70% for temperatures ranging from 200–450 °C. This measurement is important in that the sputtered flux in the ionic state will immediately return to the lithium surface due to the sheath potential in a magnetic confinement device. Erosion from liquid lithium both from evaporation and sputtering is tolerable for temperatures ranging from 200–450 °C. When all mechanisms are considered: sputtering, secondary ion fraction and evaporation, candidate liquid metals such as lithium, show promise as viable PFCs under fusion device conditions.