Synergetic effects of magnetic feedback and plasma flow on resistive wall mode stability in tokamaks

The synergetic effects of feedback and toroidal plasma rotation on the stability of the resistive wall mode are systematically investigated by a full toroidal magnetohydrodynamic stability code MARS-F (Liu Y Q et al 2000 Phys. Plasmas 7 3681). This synergy is studied for both resistive and ideal plasma models. It is found that a magnetic feedback scheme, combined with the passive stabilization from the plasma flow, can open two stability windows as the resistive wall moves away from the plasma, as opposed to the single stability window opened by the plasma flow alone. The width of the new stability window increases with the feedback gain. The plasma rotation frequency affects both stability windows. The synergy is achieved when the feedback pushes the mode rotating in the same direction as the plasma flow. The plasma resistivity significantly enlarges the stable domain in this synergetic scheme, compared to that predicted by the ideal plasma model. (paper)