Transition to ELM-free Improved H-mode by Lithium Deposition on NSTX Graphite Divertor Surfaces
Authors: D.K. Mansfield, H.W. Kugel, R. Maingi, M.G. Bell, R. Bell, R. Kaita, J. Kallman, S. Kaye, B. LeBlanc, D. Mueller, S. Paul, R. Raman, L. Roquemore, S. Sabbagh, H. Schneider, C.H. Skinner, V. Soukhanovskii, J. Timberlake, J. Wilgen, L. Zakharov
Abstract:
Lithium evaporated onto plasma facing components in the NSTX lower divertor has made dramatic improvements in discharge performance. As lithium accumulated, plasmas previously exhibiting robust Type 1 ELMs gradually transformed into discharges with intermittent ELMs and finally into continuously evolving ELM-free discharges. During this sequence, other discharge parameters changed in a complicated manner. As the ELMs disappeared, energy confinement improved and remarkable changes in edge and scrape-off layer plasma properties were observed. These results demonstrate that active modification of plasma surface interactions can preempt large ELMs.
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Submitted to: Journal of Nuclear Materials
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