The effect of lithium surface coatings on plasma performance in the National Spherical Torus Experiment

Kugel, H. W.; Bell, M. G.; Ahn, J.-W.; Allain, J. P.; Bell, R.; Boedo, J.; Bush, C.; Gates, D.; Gray, T.; Kaye, S.; Kaita, R.; LeBlanc, B.; Maingi, R.; Majeski, R.; Mansfield, D.; Menard, J.; Mueller, D.; Ono, M.; Paul, S.; Raman, R.
May 2008
Physics of Plasmas;May2008, Vol. 15 Issue 5, p056118
Academic Journal
National Spherical Torus Experiment [which M. Ono et al., Nucl. Fusion 40, 557 (2000)] high-power divertor plasma experiments have shown, for the first time, that benefits from lithium coatings applied to plasma facing components found previously in limited plasmas can occur also in high-power diverted configurations. Lithium coatings were applied with pellets injected into helium discharges, and also with an oven that directed a collimated stream of lithium vapor toward the graphite tiles of the lower center stack and divertor. Lithium oven depositions from a few milligrams to 1 g have been applied between discharges. Benefits from the lithium coatings were sometimes, but not always, seen. These benefits sometimes included decreases in plasma density, inductive flux consumption, and edge-localized mode occurrence, and increases in electron temperature, ion temperature, energy confinement, and periods of edge and magnetohydrodynamic quiescence. In addition, reductions in lower divertor D, C, and O luminosity were measured.


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