Collaborative Research and Development on Liquid Metal Plasma Facing Components*

Liquid metal plasma facing components (PFCs) provide the potential to avoid component replacement by continually replenishing the plasma-facing surface. Data during the NSTX liquid lithium divertor (LLD) campaign indicate that impurity accumulation on the static lithium resulted in a mixed-material surface. However, no lithium ejection nor substrate influx was observed during normal operation. This motivates research on flowing systems for near-term machines. Experiments on the Magnum-PSI linear test-stand and EAST tokamak have begun to explore issues related to near-surface lithium transport, surface evolution and coating lifetime for exposures of 5-10s. Technology development for a fully-flowing liquid lithium PFC is being conducted including construction of a liquid lithium flow loop and thermal-hydraulic studies of novel, capillary-restrained lithium PFCs for possible use on EAST and NSTX-U.