Abstract
Nonlinear behaviour of the m=1 internal mode is studied in a straight Heliotron E configuration with net plasma current for both a peaked and a broad current profile case. In the former case the (m, n)=(1, 1) internal kink mode is destabilized in the neighbourhood of the inner l=1 surface for low beta plasmas, although two l=1 surfaces exist in the plasma column, where l is a total rotational transform. When the beta value is increased, the internal kink mode is combined with the interchange mode and the linear mode structure covers the two l=1 resonant surfaces, since Heliotron E has a large magnetic hill. Nonlinear evolution shows two stages: the first one is similar to the nonlinear internal kink mode and the second one to the nonlinear interchange mode. For the broad current profile case only the m=1 interchange mode is destabilized even in the current-carrying plasma and beta limit appears. Nonlinear behaviour is the same as that in currentless plasmas.
Published Version
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