ELM control based on modeling of plasma response to n = 2 and n = 3 resonant magnetic perturbation fields in DIII-D

Abstract

Toroidal modeling of plasma response to the resonant magnetic perturbation (RMP) fields, with the n = 2 and 3 configurations (n is the toroidal mode number), is carried out for DIII-D discharge utilizing the MARS-F code. In particular, the relative toroidal phase (coil phase) between the lower and upper rows of the I-coil currents is scanned from −180° to 180°, while computing the plasma response. Both the resistive rotating and ideal static plasma response models have been employed to predict the optimum coil phase with typical safety factor (q95) values that are within the windows for suppressing the edge localized modes (ELMs). Six certain criteria, which are constructed from the MARS-F modeling, are proposed and tested to determine the optimum coil phase. For both plasma response models, it is found that the three criteria, namely, the resonant harmonic field including plasma response at the last rational surface, the maximum amplitude of the plasma displacement due to the peeling mode response, and the normal plasma surface displacement amplitude near the X point, can serve as appropriate indicators for determining the optimum coil phase. It is demonstrated that the even parity RMP coil configuration can better control the ELMs within the typical ELM suppression window in DIII-D tokamak.