Neoclassical tearing mode stabilization by electron cyclotron current drive for HL-2M tokamak

Investigation of neoclassical tearing mode and its suppression by electron cyclotron current drive (ECCD) has been carried out in HL-2M tokamak. The current driving capability of the electron cyclotron wave is evaluated. It is found that the deposition location can be effectively controlled by changing the poloidal angle. The validation of electron cyclotron wave heating and current driving has been demonstrated for the upper launcher port. We show that 3.0 MW and 2.5 MW modulated ECCD can completely stabilize (2,1) and (3,2) NTMs, respectively. The non-modulated ECCD, radial misalignment as well as current profile broadening have deleterious effect on the NTM stabilization. The time required for suppression of (3,2) mode is shorter than that required for the suppression of (2,1) mode. Moreover, the time needed for complete stabilization at different initial island width has been quantitatively presented and analyzed.