Continuous Improvement of H-Mode Discharge Performance with Progressively Increasing Lithium Coatings in the National Spherical Torus Experiment

R. Maingi, S. M. Kaye, C. H. Skinner, D. P. Boyle, J. M. Canik, M. G. Bell, R. E. Bell, T. K. Gray, M. A. Jaworski, R. Kaita, H. W. Kugel, B. P. LeBlanc, D. K. Mansfield, T. H. Osborne, S. A. Sabbagh, and V. A. Soukhanovskii

Phys. Rev. Lett. 107, 145004 – Published 29 September 2011

Abstract

Lithium wall coatings have been shown to reduce recycling, improve energy confinement, and suppress edge localized modes in the National Spherical Torus Experiment. Here, we show that these effects depend continuously on the amount of predischarge lithium evaporation. We observed a nearly monotonic reduction in recycling, decrease in electron transport, and modification of the edge profiles and stability with increasing lithium. These correlations challenge basic expectations, given that even the smallest coatings exceeded that needed for a nominal thickness of the order of the implantation range.

Received 3 June 2011

DOI:https://doi.org/10.1103/PhysRevLett.107.145004

Authors & Affiliations

R. Maingi¹, S. M. Kaye², C. H. Skinner², D. P. Boyle³, J. M. Canik¹, M. G. Bell², R. E. Bell², T. K. Gray¹, M. A. Jaworski², R. Kaita², H. W. Kugel², B. P. LeBlanc², D. K. Mansfield², T. H. Osborne⁴, S. A. Sabbagh⁵, and V. A. Soukhanovskii⁶

¹Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
²Princeton Plasma Physics Laboratory, PO Box 451, Princeton, New Jersey 08543, USA
³Princeton University, Princeton, New Jersey 08543, USA
⁴General Atomics, San Diego, California 92186, USA
⁵Columbia University, New York, New York 10027, USA
⁶Lawrence Livermore National Laboratory, Livermore, California 94550, USA