Ideal magnetohydrodynamic stability of the tokamak high-confinement-mode edge region

H. R. Wilson, J. W. Connor, A. R. Field, S. J. Fielding, R. L. Miller, L. L. Lao, J. R. Ferron, A. D. Turnbull

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88 Scopus citations

Abstract

The ideal magnetohydrodynamic (MHD) stability of the tokamak edge is analyzed, with particular emphasis on radially localized instabilities; it is proposed that these are responsible for edge pressure gradient limits and edge localized modes (ELMS). Data and stability calculations from DIII-D [to appear in Proceedings of the 16th International Conference on Fusion Energy, Yokohama (International Atomic Energy Agency, Vienna, 1998), Paper No. IAEA-F1-CN-69/EX8/ 1] tokamak equilibria indicate that two types of instability are important: the ballooning mode (driven by pressure gradient) and the peeling mode (driven by current density). The characteristics of these instabilities, and their coupling, are described based on a circular cross-section, large aspect ratio model of the tokamak equilibrium. In addition, preliminary results are presented from an edge MHD stability code which is being developed to analyze general geometry tokamak equilibria; an interpretation of the density threshold to access the high-confinement-mode (H-mode), observed on COMPASS-D [Plasma Phys. Controlled Fusion 38, 1091 (1996)] is provided by these results. Experiments on DIII-D and the stability calculations indicate how to control ELMs by plasma shaping.

Original languageEnglish
Pages (from-to)1925-1934
Number of pages10
JournalPhysics of Plasmas
Volume6
Issue number5 I
DOIs
StatePublished - May 1999
Externally publishedYes

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