Optimization of sensor signals for resistive wall mode control in ITER

Active control of the resistive wall mode has been considered as an alternative way, besides passive control by plasma rotation, to stabilize the mode in advanced scenarios in ITER. We show that a significant improvement of the feedback system is achievable by optimizing the detection system, without changing the active coil system in the design. Both analytical theory in cylindrical geometry, and toroidal calculations for ITER equilibria, show that the resistive wall mode can be stabilized for plasma pressures close to the ideal-wall beta limit, using the new technique with even radial sensors. This high plasma pressure is stabilized with the feedback coils outside the vacuum vessel, as in the nominal ITER design.