Effect of the toroidal flow shear on the m/n=2/1 tearing mode by using the rotating resonant magnetic perturbations in the J-TEXT Tokamak

It has been found that a higher-frequency rotating resonant magnetic perturbation (RRMP) can suppress a large tearing mode (TM) and avoid subsequent disruption (Li et al 2020 Nucl. Fusion 60 056022). To clarify the mechanism of the stabilizing effect of the higher-frequency RRMP, experiments on the effects of RRMPs with different frequencies on the TM amplitude are presented in this paper. After eliminating the destabilizing effect of RRMP, the statistical analysis reveals a notable negative correlation between changes in the amplitude of the TM and changes in the mode frequency. Further investigation indicates an absence of a suppressive effect of the toroidal flow on the TM. Instead, the data shows a clear linear relationship between changes in the TM amplitude and the flow shear in proximity to the resonant surface, with a high coefficient of determination (r (2)). Those experimental results suggest that the flow shear plays a significant role in the suppression of TMs and offer a plausible method to prevent disruptions in future devices.