Tearing mode stabilization by slowly rotating 3D field in the partially penetrated regime in the presence of an error field

Recent reduced resistive MHD simulations [1-2] have proposed the advantage of partiallypenetrated regime for avoiding TM locking in the presence of static error field. An external 3D field rotating as low as 50-100 Hz with a few times the amplitude of the static EF can stabilize the growth of the island width in present-day tokamak parameters. The response structure is a combination of the kink-like response and the TM-like response, forming a single helicity state. We reported here two examples of the application of slowly-rotating 3D fields; one is applying the 3D field to a marginally locked mode and the other is reducing the torque input towards the locking threshold. In both cases, the observed time evolution of plasma response to 3D field and the formation of single (double) helicity states are qualitatively consistent with the model penetration by taking into account of toroidicity and non-circular configuration. The upgrade of the AEOLUS-IT to multi-helicity version is in the progress. It is expected that the physics of shielding-out external 3D field will be discussed in a quantitative manner with multi-mode coupling formulation. The successful H-mode recovery was demonstrated after a sizable internal collapse was initiated around q~2 domain. The existence of sharp edge density gradient suggests that the application of slowly-rotating 3D field presence has another advantage affecting the edge transport.