Control of neo-classical double tearing modes by differential poloidal rotation in reversed magnetic shear tokamak plasmas

Abstract

The control of neo-classical tearing modes (NTMs) by the differential rotation in the reversed magnetic shear (RMS) configuration with different separations between two rational surfaces is numerically studied by means of reduced magnetohydrodynamic (MHD) simulations. It is found that the differential rotation with a strong shear at the outer resonant surface can effectively suppress the explosive burst of double tearing modes (DTMs)/NTMs. Critical values of the strength of rotation to suppress the burst are also presented for different bootstrap current fractions . Furthermore, a couple of measurable parameters , corresponding respectively to the triangularity and elongation of the magnetic islands at the outer resonant surface, are introduced to characterize the deformation of islands in the nonlinear phase. It is found that the triangularity is more likely to precisely predict the onset of burst than the island width and elongation . For a given , the critical value of triangularity is obtained by scanning different plasma parameters. Establishing such a database of is helpful to effectively control the development of NTMs in the RMS experimental discharges.