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

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 ap...

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Bibliographic Details
Published in:Physics of Plasmas 1999-05, Vol.6 (5), p.1925-1934
Main Authors: Wilson, H. R., Connor, J. W., Field, A. R., Fielding, S. J., Miller, R. L., Lao, L. L., Ferron, J. R., Turnbull, A. D.
Format: Article
Language:English
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Summary: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.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.873492