The effect of progressively increasing lithium coatings on plasma discharge characteristics, transport, edge profiles and ELM stability in the National Spherical Torus Experiment

R. Maingi, D. P. Boyle, J. M. Canik, S. M. Kaye, C. H. Skinner, J. P. Allain, M. G. Bell, R. E. Bell, S. P. Gerhardt, T. K. Gray, M. A. Jaworski, R. Kaita, H. W. Kugel, B. P. Leblanc, J. Manickam, D. K. Mansfield, J. E. Menard, T. H. Osborne, R. Raman, A. L. Roquemore & 3 others S. A. Sabbagh, P. B. Snyder, V. A. Soukhanovskii

Research output: Research - peer-reviewArticle

Abstract

Lithium wall coatings have been shown to reduce recycling, suppress edge-localized modes (ELMs), and improve energy confinement in the National Spherical Torus Experiment (NSTX). Here we document the effect of gradually increasing lithium wall coatings on the discharge characteristics, with the reference ELMy discharges obtained in boronized, i.e. non-lithiated conditions. We observed a continuous but not quite monotonic reduction in recycling and improvement in energy confinement, a gradual alteration of edge plasma profiles, and slowly increasing periods of ELM quiescence. The measured edge plasma profiles during the lithium-coating scan were simulated with the SOLPS code, which quantified the reduction in divertor recycling coefficient from 98% to 90%. The reduction in recycling and fuelling, coupled with a drop in the edge particle transport rate, reduced the average edge density profile gradient, and shifted it radially inwards from the separatrix location. In contrast, the edge electron temperature (T e) profile was unaffected in the H-mode pedestal steep gradient region within the last 5% of normalized poloidal flux, ψ N ; however, the T e gradient became steeper at the top of the H-mode pedestal for 0.8<ψ N<0.94 with lithium coatings. The peak pressure gradients were comparable during ELMy and ELM-free phases, but were shifted away from the separatrix in the ELM-free discharges, which is stabilizing to the current-driven instabilities thought to be responsible for ELMs in NSTX.

LanguageEnglish (US)
Article number083001
JournalNuclear Fusion
Volume52
Issue number8
DOIs
StatePublished - Aug 2012
Externally publishedYes

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plasma jets
lithium
coatings
profiles
recycling
gradients
energy
poloidal flux
refueling
pressure gradients
electron energy
coefficients

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics

Cite this

The effect of progressively increasing lithium coatings on plasma discharge characteristics, transport, edge profiles and ELM stability in the National Spherical Torus Experiment. / Maingi, R.; Boyle, D. P.; Canik, J. M.; Kaye, S. M.; Skinner, C. H.; Allain, J. P.; Bell, M. G.; Bell, R. E.; Gerhardt, S. P.; Gray, T. K.; Jaworski, M. A.; Kaita, R.; Kugel, H. W.; Leblanc, B. P.; Manickam, J.; Mansfield, D. K.; Menard, J. E.; Osborne, T. H.; Raman, R.; Roquemore, A. L.; Sabbagh, S. A.; Snyder, P. B.; Soukhanovskii, V. A.

In: Nuclear Fusion, Vol. 52, No. 8, 083001, 08.2012.

Research output: Research - peer-reviewArticle

Maingi, R, Boyle, DP, Canik, JM, Kaye, SM, Skinner, CH, Allain, JP, Bell, MG, Bell, RE, Gerhardt, SP, Gray, TK, Jaworski, MA, Kaita, R, Kugel, HW, Leblanc, BP, Manickam, J, Mansfield, DK, Menard, JE, Osborne, TH, Raman, R, Roquemore, AL, Sabbagh, SA, Snyder, PB & Soukhanovskii, VA 2012, 'The effect of progressively increasing lithium coatings on plasma discharge characteristics, transport, edge profiles and ELM stability in the National Spherical Torus Experiment' Nuclear Fusion, vol 52, no. 8, 083001. DOI: 10.1088/0029-5515/52/8/083001
Maingi, R. ; Boyle, D. P. ; Canik, J. M. ; Kaye, S. M. ; Skinner, C. H. ; Allain, J. P. ; Bell, M. G. ; Bell, R. E. ; Gerhardt, S. P. ; Gray, T. K. ; Jaworski, M. A. ; Kaita, R. ; Kugel, H. W. ; Leblanc, B. P. ; Manickam, J. ; Mansfield, D. K. ; Menard, J. E. ; Osborne, T. H. ; Raman, R. ; Roquemore, A. L. ; Sabbagh, S. A. ; Snyder, P. B. ; Soukhanovskii, V. A./ The effect of progressively increasing lithium coatings on plasma discharge characteristics, transport, edge profiles and ELM stability in the National Spherical Torus Experiment. In: Nuclear Fusion. 2012 ; Vol. 52, No. 8.
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AU - Osborne,T. H.

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