A semi-epirical criterion on coil current requirement to control edge localized modes in tokamak plasmas

Recent encouraging results, showing the correlation between the toroidally computed plasma displacement near the X-point on one hand, and the experimentally achieved mitigation or suppression of the type-I edge localized modes (ELMs) by the applied resonant magnetic perturbation (RMP) fields on the other hand, motivates the development of an X-point displacement based criterion, to guide the choice of the magnitude of the ELM control coil current. Full toroidal simulations of the ELM control discharges in four existing devices (MAST,ASDEX Upgrade, has to trigger a minimal level of the has DIII-D and JET), based on the single fluid, resistive magnetiohydrodynamic model with plasma flow, reveal that the applied RMP field has to trigger a minimal level of the X-point displacement, of 1-3 mm, in order for the ELM to be mitigated or suppressed. This plasma response based criterion can be useful for predicting the coil current requirements in future such as ITER.