Avoidance of m=2, n=1 tearing mode wall-locking by torque-balance control with magnetic feedback in DIII-D and RFX-mod

Recent experiments performed in DIII-D and RFX-mod operated as a tokamak demonstrate that magnetic feedback realized by active saddle coils is able to prevent wall-locking of tearing modes. Disruptions caused by wall-locking of the m=2, n=1 tearing mode (TM) are considered one of the most critical roadblocks to achieve reliable operations in tokamak devices, and these experiments demonstrate a possible new tool for avoiding such disruptions. The result is remarkable, given the many differences of the two experiments both in terms of layout and plasma condition. In DIII-D we performed divertor, D-shaped, high-? plasmas, controlled by coils placed inside the vacuum vessel. Instead, in the RFX-mod experiments circular crosssection, limiter, ohmic discharges are realized with low edge safety factor 2