Liquid Lithium Limiter Effects on Tokamak Plasmas and Plasma-Liquid Surface Interactions
Authors: R. Kaita, R. Majeski, R. Doerner, G. Antar, M. Baldwin, R. Conn, P. Efthimion, M. Finkenthal, D. Hoffman, B. Jones, S. Krashenninikov, H. Kugel, S. Luckhardt, R. Maingi, J. Menard, T. Munsat, D. Stutman, G. Taylor, J. Timberlake, V. Soukhanovskii, D. Whyte, R. Woolley, and L. Zakharov
Date of PPPL Report: October 2002
Presented at: the Nineteenth IAEA Fusion Energy Conference, October 14-19, 2002, in Lyon, France.
We present results from the first experiments with a large area liquid lithium limiter in a magnetic fusion device, and its effect on improving plasma performance by reducing particle recycling. Using large area liquid metal surfaces in any major fusion device is unlikely before a test on a smaller scale. This has motivated its demonstration in the CDX-U spherical torus with a unique, fully toroidal lithium limiter. The highest current discharges were obtained with a liquid lithium limiter. There was a reduction in recycling, as indicated by a significant decrease in the deuterium-alpha emission and oxygen radiation. How these results might extrapolate to reactors is suggested in recycling/retention experiments with liquid lithium surfaces under high-flux deuterium and helium plasma bombardment in PISCES-B. Data on deuterium atoms retained in liquid lithium indicate retention of all incident ions until full volumetric conversion to lithium deuteride. The PISCES-B results also show a material loss mechanism that lowers the maximum operating temperature compared to that for the liquid surface equilibrium vapor pressure. This may restrict the lithium temperature in reactors.