Resistive Interchange Instability Response to External RMP, and its Parameter Dependence to Suppress the Instability

We derive an empirical scaling law for the external RMP (Resonant Magnetic Perturbation) amplitude required to completely suppress the resistive interchange MHD instabilities of m/n = 1/1 (m and n are the poloidal and toroidal mode numbers, respectively), which are typically observed in the Large Helical Device (LHD). We also derive the scaling law for the penetration threshold of the external RMP. Both scaling laws are found to have a strong dependence on the beta value and the normalized Larmor radius at the resonant rational surface. On the dependence on the collision parameters, the scaling laws for the external RMP amplitude to suppress the instability and the RMP penetration threshold show an inverse dependence. The above scaling laws suggest that it is easier to completely suppress the resistive interchange instability of the m/n = 1/1 mode in the LHD without degrading the plasma confinement performance due to the RMP penetration with a lower collision frequency, even with the same beta discharges.