Suppression of the m/n=2/1 tearing mode by ECH/ECCD on JFT-2M Tokamak

A nonlinearly saturated large amplitude tearing mode (m/n=2/1) can be stabilized by heating of the center of the magnetic island by ECH in the JFT-2M tokamak. The effectiveness of the island O-point heating was shown by the feedback injection of the pulsed ECH pulse. The tearing mode causes the mode locking and plasma distuption occurs. It is observed that the mode locking is avoided by the ECH. The main mechanism of the present suppression seems to be the resistivity reduction due to the heating by ECH and not by the driven current by ECCD. The result was obtained from the counter ECCD experiment using a variable angle mirror antenna.