Suppressed Gross Erosion of High-temperature Lithium via Rapid Deuterium Implantation
Authors: T. Abrams, M.A. Jaworski, M. Chen, E.A. Carter, R. Kaita, D.P. Stotler, G. De Temmerman, T.W. Morgan, M.A. van den Berg, H.J. van der Meiden
Abstract: Li-coated high-Z substrates are planned for use in the NSTX-U divertor and are a candidate PFC for reactors, but it remained necessary to characterize the gross Li erosion rate under D high plasma fluxes (>1023 m-2 s-1) because large quantities of D are implanted under these conditions. A realistic model for the compositional evolution of a Li/D layer was developed that incorporates MD simulations of D diffusion in liquid Li. Predictions of Li erosion from a mixed Li/D material were also developed that include formation of lithium deuteride (LiD). The erosion rate of Li from LiD was predicted to be significantly lower than from pure Li. This prediction was tested in the Magnum-PSI linear plasma device at ion fluxes of 1023 m-2 s-1 and Li surface temperatures ≤800 ºC. Eroding Li/LiD coatings ranging in thickness from 200 nm to 500 µm were studied. The dynamic D/Li concentration was inferred via 1D diffusion simulations. The pure Li erosion rate remained greater than Langmuir Law evaporation, as expected. For mixedmaterial Li/LiD surfaces the erosion rates were reduced in good agreement with modeling in almost all cases. These results imply that the temperature limit for a Li-coated PFC may be significantly higher than previously imagined.
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Submitted to: Nuclear Fusion
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Download PPPL-5114 (pdf 1.8 MB 28pp)
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