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Abstract

Stability limits for the internal kink mode in tokamaks are calculated for different current profiles and plasma cross sections using ideal magnetohydrodynamics (MHD). The maximum stable poloidal beta at the q = 1 surface (beta(p)) is sensitive to the current profile but, for circular cross sections, it is typically between 0.1 and 0.2. Large aspect ratio theory gives similar predictions when the appropriate boundary conditions are applied at the plasma-vacuum surface. The pressure driven internal kink is significantly destabilised by ellipticity. For JET geometry, the beta(p)-limit is typically between 0.05 and 0.1, but arbitrarily low limits can result if the shear is reduced at the q = 1 surface. A large aspect ratio expansion of the Mercier criterion retaining the effects of ellipticity and triangularity is given, to illustrate the destabilising influence of ellipticity.

Additional information

Authors: LÜTJENS H, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, Lausanne (CH);BONDESON A, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, Lausanne (CH);VLAD G, ENEA, Centro Ricerche Energia Frascati, Roma (IT);LUTJENS H, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Federale de Lausanne, Lausanne (CH)
Bibliographic Reference: Report: LRP 446/91 EN (1992)
Availability: Available from Confédération Suisse, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, 21 avenue des Bains, 1007 Lausanne (CH)
Record Number: 199210876 / Last updated on: 1994-12-02
Category: PUBLICATION
Original language: en
Available languages: en