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Abstract

The linear resistive magnetohydrodynamical (MHD) stability of the internal kink mode in tokamaks is studied by toroidal computations. The stabilising influence of small aspect ratio is confirmed, but it is found that shaping of the cross-section influences the internal kink stability significantly. For finite pressure and small resistivity, curvature effects at the q = 1 surface give rise to a sensitive dependence on shape, and ellipticity (including JET shape) is destabilising. Only a very restricted set of finite pressure equilibria is completely stable for q(0) less than 1. A typical result is that the resistive kink mode is slowed down by toroidal effects to a weak tearing/resistive interchange mode. It is suggested that weak resistive instabilities are stabilised during the ramp phase of the sawteeth by effects not included in the linear resistive MHD model. Possible mechanisms for triggering a sawtooth crash are discussed.

Additional information

Authors: VLAD V, ENEA, Centro Ricerche Energia Frascati, Roma (IT);BODENSON A, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne (CH);LÜTJENS H, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne (CH);LUTJENS H, Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Federale de Lausanne (CH)
Bibliographic Reference: Report: RT/NUCL/92/17 EN (1992) 34 pp.
Availability: Available from Servizio Studi e Documentazione, ENEA, Centro Ricerche Energia Frascati, C.P. 65-00044 Frascati, Roma (IT)
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