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Understanding of ballooning mode stability boundaries may lead to performance improvement of toroidal devices through control of disruptions. Toroidally localized ballooning modes have been found as precursors to high beta disruptions on TFTR 1 arising in conditions of n= 1 kink mode asymmetry. Recent optimization has shown that magnetohydrodynamic stability as well as good particle confinement are likely to be achievable in the National Compact Stellarator Experiment (NCSX), a compact, quasiaxially symmetric stellarator (QAS) for values of the plasma near beta = 4%(2). The configuration, with a major radius of 1.42 m, an aspect ratio of 4.4, a toroidal magnetic field 1.2-1.7 T and 6MW of neutral beam heating, is stable to MHD instabilities, and is expected to be limited by high-n kink and ballooning modes. This paper describes the ballooning eigenvalue isosurfaces for NCSX, the first step in an examination of the kinetic stabilization of the ballooning beta limit using a hybrid WKB approach.

Additional information

Authors: REDI M.H, Princeton Plasma Physics Laboratory, New Jersey (US);FREDRICKSON E.D, Princeton Plasma Physics Laboratory, New Jersey (US);JOHNSON S, Princeton Plasma Physics Laboratory, New Jersey (US);CANIK J, Department of Electrical and Computer Engineering, University of Wisconsin, (US);DEWAR R.L, Department of Theoretical Physics, The Australian National University, Canberra (AU);COOPER W.A, Centre de Recherches en Physique des Plasmas, EURATOM Association-Confederation Suisse, Ecole Polytechnique Federale de Lausanne (CH)
Bibliographic Reference: An oral report given at: The 28th EPS Conference of Controlled Fusion and Plasma Physics. Held in: Madeira (PT) June 2001
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