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Serious MHD instabilities leading to the degradation of the energy confinement time and the termination of the discharge have not been observed in experiments on the Large Helical Device (LHD). The stability of low-n modes is calculated with the three-dimensional MHD stability analysis code of TERPSICHORE. The results show that the high beta plasma becomes MHD unstable with an external mode (n/m=1/1). In case the rotational transform at the edge decreases below l(edge)/2Pi=1.0, the external mode is also destabilised. By using the limiter, l(edge)/2Pi can be controlled and it is possible to imitate the high beta plasma from the viewpoint of the iota profile. The characteristics of the MHD instabilities in the high beta plasma need to be examined both theoretically and experimentally. We propose, therefore, a reasonable limiter experiment to check the characteristics of the MHD instabilities with external modes.

Additional information

Authors: NARUSHIMA Y ET AL, National Institute for Fusion Science, Toki (JP);COOPER W A, Centre de Recherches en Physique des Plasmas, Association EURATOM-Confederation Suisse, Ecole Polytechnique Federale de Lausanne (CH)
Bibliographic Reference: An article published in: Journal of Plasma Fusion Research, Vol. 5 (2002), pages 514-518.
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