Dependence of recycling and edge profiles on lithium evaporation in high triangularity, high performance NSTX H-mode discharges

NSTX Team

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20 Scopus citations

Abstract

Abstract In this paper, the effects of a pre-discharge lithium evaporation variation on highly shaped discharges in the National Spherical Torus Experiment (NSTX) are documented. Lithium wall conditioning ('dose') was routinely applied onto graphite plasma facing components between discharges in NSTX, partly to reduce recycling. Reduced Dα emission from the lower and upper divertor and center stack was observed, as well as reduced midplane neutral pressure; the magnitude of reduction increased with the pre-discharge lithium dose. Improved energy confinement, both raw τE and H-factor normalized to scalings, with increasing lithium dose was also observed. At the highest doses, we also observed elimination of edge-localized modes. The midplane edge plasma profiles were dramatically altered, comparable to lithium dose scans at lower shaping, where the strike point was farther from the lithium deposition centroid. This indicates that the benefits of lithium conditioning should apply to the highly shaped plasmas planned in NSTX-U.

Original languageEnglish
Article number48581
Pages (from-to)1134-1137
Number of pages4
JournalJournal of Nuclear Materials
Volume463
DOIs
StatePublished - Jul 22 2015

Funding

This research was sponsored in part by U.S. Dept. of Energy under contracts DE-AC02-09CH11466 , DE-AC05-00OR22725 , DE-FC02-04ER54698 , DE-FC02-99ER54512 and DE-AC52-07NA27344 . We gratefully acknowledge the contributions of the NSTX operations staff.

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