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Simulation of the stabilization of magnetic islands by ecrh and eccd

Ayten, Bircan
An almost universal instability in high pressure plasmas is the Neoclassical Tearing Mode (NTM). NTMs are driven by local perturbations in the current density and result in magnetic island like deformations of the magnetic topology. They can be stabilized by compensating the current perturbations with local electron cyclotron resonance heating (ECRH) or with non-inductive current drive (ECCD). The modified Rutherford equation describes the nonlinear evolution of tearing modes as determined by various contributions to the local current density pertubation. An extensive investigation of the two terms representing the stabilizing effects from ECRH and ECCD have been made resulting in accurate description of both terms. The results of this model can now be compared to the experimental observations. For this purpose, an extensive data set exists from the past experiments on tearing mode stabilization by ECRH and ECCD on TEXTOR. The properly benchmarked model can then be used to predict the effectiveness of ECRH and ECCD for NTM stabilization on International Thermonuclear Experimental Reactor (ITER). In addition, a number of predictions on the effects of ECRH and ECCD on the growth of the NTM have been made on the basis of crude approximations to the ECRH and ECCD tems in the modified Rutherford equation. These predictions can now be checked against the more accurate expressions obtained.