Erosion/Redeposition Analysis of Lithium Based Liquid Surface Divertors

J. Nucl. Materials, 290-293, 185-190 (2000).

Brooks, J. N., Rognlien, T., Ruzic, D. N., Allain, J. P.

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, (200 eV, 1×10¹⁹ 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 (95%) of the sputtered lithium is confined to the near-surface region and redeposited on the divertor with the remainder (5%) also being redeposited after transport in the scrape-off layer. Lithium core plasma contamination is low (10⁻⁴ Li/D–T). Tin–lithium and flibe would likely operate in a high-recycle regime (e.g., 30 eV, 3×10²⁰ 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.