Dynamic control of divertor heat flux during n = 4 RMP ELM suppression by small variation of q95 in EAST

The experiment in EAST demonstrates effective modulation of the stationary heat flux to the secondary lobes of the magnetic footprint induced by the resonant magnetic perturbations (RMPs) by slightly varying the equilibrium q95, consistent with prior numerical modeling. During the small q95 variation, the edge localized mode (ELM) control is well maintained, and the position of the secondary heat flux peak is effectively shifted, thus avoiding a specific location heat flux accumulation. As the divertor heat load is one of the significant concerns in tokamak, these results provide a promising choice, varying magnetic equilibrium periodically to shift stationary heat load deposition position during static n = 4 ( n is the toroidal mode number) RMP condition, for further fusion devices. In this respect the use of this technique for n =4 RMPs is advantageous because the q95 range that needs to be covered to spread the divertor heat load is reduced because of the smaller toroidal extent of off-separatrix heat deposition zones compared to lower n’s.