Toroidal modeling of plasma response to high-field side RMP in HL-2A

Application of resonant magnetic perturbation (RMP) is a reasonably mature technique for controlling edge-localized mode (ELM) in high confinement-mode tokamak plasmas. The high-field side (HFS) RMP coils were recently added in the HL-2A tokamak. This study systematically models the plasma response to the n=1 (n is toroidal mode number) HFS RMP, utilizing the single-fluid magnetohydrodynamic (MHD) code MARS-F and the MHD-kinetic hybrid code MARS-K. The results show that the HFS coil is capable of triggering the edge peeling response which facilitates ELM control. The 60-degree phase shift for the n=1 coil current between the upper and lower rows of the RMP coils presents the optimal coil phase. On the other hand, the HFS response field is found to be relatively weak compared to the low-field side (LFS) counterpart, assuming the same coil current level. This implies that the HFS coils are less effective for ELM control than the conventional LFS coil-design. On the positive side, the HFS RMP is found to produce smaller toroidal torques, including the Maxwell and Reynolds stress torques as well as the neoclassical toroidal viscosity (NTV) torque, resulting in less side effects on the plasma as compared to the LFS counterpart. The q95-window for accessing ELM control by the HFS RMP is found to be approximately consistent with that by the LFS RMP.