Liquid Metal Plasma-facing Component Research on the National Spherical Torus Experiment
Authors: Michael A. Jaworski, A. Khodak, R. Kaita
Abstract:
Liquid metal plasma facing components have been proposed as a
means of solving several problems facing the creation of economically viable fusion
power reactors. Liquid metals face critical issues in three key areas: free-surface
stability, material migration and demonstration of integrated scenarios. To date, few
demonstrations exist of this approach in a diverted tokamak and we here provide
an overview of such work on the National Spherical Torus Experiment (NSTX). The
Liquid Lithium Divertor (LLD) was installed and operated for the 2010 run campaign
using evaporated coatings as the filling method. Despite a nominal liquid level
exceeding the capillary structure and peak current densities into the PFCs exceeding
100 [kA/ m2 ], no macroscopic ejection events were observed and can be understood from
a stability analysis of the Raleight-Taylor instability. Capillary restraint and thermalhydraulic
considerations lead to a proposed liquid-metal plasma-facing component
scheme of actively-supplied, capillary-restrained systems. Even with state-of-the-art
cooling techniques, design studies indicate that the surface temperature with divertorrelevant
heat fluxes will still reach temperatures above 700C. At this point, one would
expect significant vapor production from a liquid leading to a continuously vaporshielded
regime. Such high-temperature liquid lithium PFCs may be possible on the
basis of momentum-balance arguments.
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Published in: Plasma Physics and Controlled Fusion Fusion 55 124040 (28 November 2013)
doi:10.1088/0741-3335/55/12/124040
Presented at: 40th EPS, Expoo, Finland, July 20113 (Invited paper)
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