The spectrum analysis of RMP coils with multiple connection modes and the design of high field side coils on J-TEXT

The phase difference △ξ between locked islands(2/1 and 3/1)has been found to influence the heat transport on the thermal quench during disruptions by numerical modeling[Hu Q et al 2019 Nucl.Fusion 59,016005].To verify this experimentally,a set of resonant magnetic perturbation(RMP)coils is required to excite coupled magnetic islands with different △ξ.The spectrum analysis shows that the current RMP coils on J-TEXT can only produce sufficient 2/1 and 3/1 RMP fields with a limited phase difference of △ξ∈[-75°,75°].In order to broaden the adjustable range of △ξ,a set of coils on the high field side(HFS)is proposed to generate 2/1 and 3/1 RMP fields with △ξ=180°.As a result,RMPs with adjustable △ξ∈[-180°,180°]and sufficient amplitudes could be achieved by applying the HFS coils and the low field side(LFS)coils.This work provides a feasible solution for flexible adjustment of the phase difference between m and m+1 RMP,which might facilitate the study of major disruptions and their control.