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The effect of the electrostatic potential [theta] on the bootstrap current has been calculated and its impact on the global ideal MHD stability of a LHD configuration has been investigated. The bootstrap current can destabilise a m/n=2/3 external kink when it causes the edge rotational transform to approach 1.5. At [theta]=0, the unstable m/n=2/3 structure is strongly coupled with a m/n=9/13 term. Negative [theta] reduces the edge transform below 1.4 and the m/n=2/3 mode couples with a m/n=5/7 component instead. Positive [theta] displaces the edge transfer closer to the critical value 1.5 weakening the contribution of toroidal sidebands like m/n=9/13, but deteriorating the stability conditions slightly further. Global n=1, n=2 and n=4 modes are basically internal and have smaller growth rates than the n=3 external kink. These structures evolve from interchange-like for n=1 to ballooning-like for n=4.

This paper was originally presented at the 11th International Toki Conference on Potential and Structure in Plasmas, December 5-8 2000, Ceratopia Toki, National Institute for Fusion Science, Toki, Gifu, Japan.

Additional information

Authors: COOPER W A, Centre de Recherches en Physique des Plasmas, Association Euratom - Confédération Suisse, École Polytechnique Fédérale de Lausanne (CH);YAMAZAKI K ET AL, National Institute for Fusion Science, Toki (JP)
Bibliographic Reference: An article published in: Journal of Plasma and Fusion Research Series, Volume 4, (2001), pp.418-421
Record Number: 200215024 / Last updated on: 2002-07-26
Original language: en
Available languages: en