Suppression of the m/n = 2/1 tearing mode by electron cyclotron resonance heating on J-TEXT

Stabilization of tearing modes and neoclassical tearing modes is of great importance for the tokamak operation. Electron cyclotron wave (ECW) has been extensively used to stabilize the tearing modes with the virtue of the highly localized power deposition. Complete suppression of the m/n = 2/1 tearing mode (TM) by electron cyclotron resonance heating (ECRH) has been achieved successfully on the J-TEXT tokamak. The effect of ECW deposition location and power amplitude on the 2/1 TM suppression have been investigated. It is found that the suppression is more effective when the ECW power is deposited closer to the rational surface. Partial suppression of the 2/1 TM by ECRH has been observed and the island width is reduced by 65% of the initial island width. The island rotation frequency is increased when the island width is reduced. The experimental results show that the temperature perturbations increase inside the magnetic island produced by the local heating plays a dominant role on tearing modes suppression. As the ECW power increased, the 2/1 island is suppressed to smaller islands width and the flow shear also plays a stabilizing effect on small magnetic islands. With the stabilizing contribution of heating and the flow shear, the 2/1 TM can be completely suppressed.