Heuristic predictions of RMP configurations for ELM suppression in KSTAR and ITER, and their implications for divertor parameters

The three row setup of the in-vessel control coils (IVCC) in KSTAR offers many degrees of freedom for tailoring resonant magnetic perturbations (RMPs) for suppression of edge localized modes (ELMs), and ideal MHD based predictions of RMP configurations for ELM suppression based on empirical thresholds have been validated experimentally [J.-K. Park et al., Nature Physics 14, 1223 (2018)]. It is found that the heuristic ELM suppression window of these predictions can be reproduced based on kink amplitudes from drift-kinetic MHD plasma response (GPEC) calculations. For ITER, the ELM suppression threshold is taken from recent non-linear MHD (JOREK) simulations [M. Becoulet et al., Nucl. Fusion 62 (2022) 066022], and it is shown that edge stability proxies based on the kink amplitude and on the X-point displacement from linear resistive MHD plasma response (MARS-F) yield similar windows in RMP configuration space.

Resulting divertor heat load striations from RMP application are expected to be prominent in ITER and much weaker in KSTAR. This is because the lobe size L_m with perturbed field lines connecting from the plasma to the divertor target is comparable to the traditional heat flux width λ_q at the outboard midplane in KSTAR and one order of magnitude larger in ITER.