Modeling q95 window of resonant magnetic perturbations in HL-2A tokamak

The plasma response with resonant magnetic perturbations during edge localized mode mitigation in the HL-2A tokamak is numerically investigated by the three-dimensional, toroidal-geometry, nonlinear, and resistive code CLT. The maximum depth of the escaped field lines to the divertors, owing to the overlap of two or multiple islands near the last close surface, is used as the figure of merit for ELM mitigation. Since ELM mitigation requires significant enhancement of electron transport on the pedestal top, the maximum depth of the escaped field lines should be larger than a critical value and the connection lengths should be smaller than the mean free path of electrons on the pedestal top. With these two requirements, we find that there exists a q95 window for RMP ELM mitigation in our simulations, which is qualitatively the same as the experimental observations in HL-2A.