Erosion/redeposition analysis of lithium-based liquid surface diverters

A sputtering erosion/redeposition analysis was performed for three candidate tokamak fusion reactor liquid divertor surfaces-lithium, tin-lithium (Sn80Li20), and flibe (LiF + BeF2 salt). The analysis uses coupled edge-plasma, impurity-transport, and sputtering codes (UEDGE/WBC/VFTRIM), and available sputtering data. A pure-lithium surface strongly absorbs impinging D-T ions-this results in a high temperature, low density, (similar to 200 eV, similar to1 x 10(19) m(-3)) low-recycle plasma edge regime. Lithium appears to perform well in this regime. Although overall sputtering is high, self-sputtering is finite. Most (similar to 95%) of the sputtered lithium is confined to the near-surface region and redeposited on the divertor with the remainder (similar to5%) also being redeposited after transport in the scrape-off layer. Lithium core plasma contamination is low (similar to 10(-4) Li/D-T). Tin-lithium and flibe would likely operate in a high-recycle regime (e.g., 30 eV, 3 x 10(20) m(-3)). Erosion/redeposition performance of these materials is also good, with finite self-sputtering and negligible core plasma contamination predicted, but with some concern about changing surface composition due to different constituent element redeposition distances. (C) 2001 Published by Elsevier Science B.V.