Transport code studies of m=2 mode control by local electron cyclotron heating in TFR

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Abstract
Transport code simulations of m=2, n=1 mode control experiments by local electron cyclotron heating (ECH) in TFR are presented. The mode activity is calculated by means of the quasi-linear theory for tearing modes. Starting from an ohmic target plasma which is unstable to the m=2, n=1 tearing mode, the evolution of the m=2, n=1 magnetic island during a 100 ms ECH pulse is calculated for various positions of the electron cyclotron resonance and levels of injected power. The best results, i.e. a complete suppression of the island, are obtained for heating almost exactly on the q=2 surface. In contrast to experimental results, the suppression of the island is found to be only temporary. It is concluded that the suppression of the MHD activity obtained in the experiment cannot be explained by profile tailoring alone.