Compatibility of Lithium Plasma-Facing Surfaces with High Edge
Temperatures in the Lithium Tokamak Experiment (LTX)
Authors: R. Majeski, R.E. Bell, D.P. Boyle,
R. Kaita, T. Kozub, B.P. LeBlanc, M. Lucia, R. Maingi, E. Merino,
Y. Raitses, J.C. Schmitt
Abstract: High edge electron temperatures (200 eV or
greater) have been measured at the walllimited plasma boundary in
the Lithium Tokamak Experiment (LTX). Flat electron temperature
profiles are a long-predicted consequence of low recycling
boundary conditions. Plasma density in the outer scrape-off layer
is very low, 2-3 x 1017 m-3, consistent with a low recycling
metallic lithium boundary. Despite the high edge temperature, the
core impurity content is low. Zeff is estimated to be ~ 1.2, with
a very modest contribution (<0.1) from lithium. Experiments are
transient. Gas puffing is used to increase the plasma density.
After gas injection stops, the discharge density is allowed to
drop, and the edge is pumped by the low recycling lithium wall. An
upgrade to LTX - LTX-β - which includes a 35A, 20 kV neutral beam
injector (on loan to LTX from Tri-Alph Energy)to provide core
fueling to maintain constant density, as well as auxiliary
heating, is underway. LTX-β is briefly described.
Submitted to: Physics of Plasmas
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