Accelerating the magnetic island by the modulated resonant magnetic perturbation for the disruption avoidance on J-TEXT

The acceleration of the magnetic island rotation by the modulated resonant magnetic perturbation (MRMP) has been studied in J-TEXT tokamak experiments. After applying the MRMP, the phase difference between the tearing mode (TM) and MRMP, Δξ, oscillated near the effective phase difference, Δξ _eff, which was defined as the time averaged value of Δξ. When the Δξ _eff was closed to the—π/2, the MRMP only contributed an accelerating torque on the TM. As the result, the TM rotation frequency was increased by a few kilohertz for the optimized relative phase by small RMPs of the order of 10⁻⁵ of the toroidal field and the locked mode induced disruption was avoided. It is found that the TM rotation could be increased to a higher frequency by applying a stronger MRMP.