Plasma response to helical resonant magnetic perturbation coil current is numerically computed for tokamak plasmas, with optimization results compared with that for conventional window-frame coils. The key aspect of study is the robustness of the proposed new concept against variation of plasma equilibrium parameters including (i) the plasma resistivity, (ii) the toroidal rotation and (iii) the plasma shaping (both elongation and triangularity). Toroidal modeling results yield several important conclusions. First, assuming the same coil current, the optimal helical coils robustly outperform the optimal window-frame coils against variation of the aforementioned plasma equilibrium parameters. Secondly, for a chosen toroidal spectrum, the optimal helical coil geometry including the poloidal location, poloidal coverage and the overall shape, is robust against variation of plasma parameters except the safety factor. Finally, in all cases, optimization based on the plasma response naturally yields a single row of helical coils located near the outboard mid-plane of the torus, ensuring a relatively simple design of the coil geometry.
This paper numerically investigates the use of helical resonant magnetic perturbation coils for controlling edge localized modes (ELMs) in tokamak plasmas. The key focus is on the robustness of this new coil concept against variations in plasma parameters like resistivity, rotation, and shaping. The study finds that helical coils outperform conventional window-frame coils and that the optimal helical coil geometry is also robust to most plasma parameter changes.