Dynamic control of divertor heat flux during n = 4 resonant magnetic perturbation edge localized mode suppression by small variation of q 95 in EAST

Abstract

Experiments at EAST demonstrate 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 q 95, consistent with prior numerical modeling. During the small q 95 variation, the edge localized mode 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 tokamaks, 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 q 95 range that needs to be covered to spread the divertor heat load is reduced due to the smaller toroidal extent of the off-separatrix heat deposition zones compared to lower n’s.