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

The phase difference Δξ 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 Δξ. 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 Δξ∈[−75°, 75°]. In order to broaden the adjustable range of Δξ, a set of coils on the high field side (HFS) is proposed to generate 2/1 and 3/1 RMP fields with Δξ = 180°. As a result, RMPs with adjustable Δξ∈[−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.