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(THP1/04) Internal Disruptions in Stellarators

(This paper was rapporteured in lecture TH2/2)

B. A. Carreras, V. E. Lynch, H. Zushi¹, K. Ichiguchi², M. Wakatani³

Oak Ridge National Laboratory Oak Ridge, Tennessee 37831, U.S.A.
¹ Research Institute for Applied Mechanics, Kyushu University, Kasuga 816, Japan
² National Institute for Fusion Science, Toki 509-5292, Japan
³ Graduate School of Energy Science, Kyoto University, Kyoto, Japan

Abstract.  Internal disruptions have been observed in different modes of stellarator operation. In Heliotron E shifted-in vacuum magnetic field configuration, the ideal modes of the m/n = 2/1 helicity can be unstable. Their nonlinear evolution leads to a sudden crash of the pressure within the r/a = 0.3 radius (sawtooth oscillation). When beta is increased further, the q = 2 surface moves out of the plasma, and the ideal modes of the m/n = 2/1 helicity are effectively stabilized when q(0) < 1.85. As a result, the sawtooth oscillations are suppressed.

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