PPPL-4852

Particle Control and Plasma Performance in the Lithium Tokamak Experiment (LTX)

Authors: Richard Majeski, et. al.

Abstract:
The Lithium Tokamak eXperiment (LTX) is a small, low aspect ratio tokamak,1 which is fitted with a stainless steel-clad copper liner, conformal to the last closed flux surface. The liner can be heated to 350 oC. Several gas fueling systems, including supersonic gas injection, and molecular cluster injection have been studied, and produce fueling efficiencies up to 35%. Discharges are strongly affected by wall conditioning. Discharges without lithium wall coatings are limited to plasma currents of order 10 kA, and discharge durations of order 5 msec. With solid lithium coatings discharge currents exceed 70 kA, and discharge durations exceed 30 msec. Heating the lithium wall coating, however, results in a prompt degradation of the discharge, at the melting point of lithium. These results suggest that the simplest approach to implementing liquid lithium walls in a tokamak - thin, evaporated, liquefied coatings of lithium - does not produce an adequately clean surface.
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Submitted to: Physics of Plasmas, (December 2012)

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