Feedback control of vertical plasma position in non-circular tokamak TNT-A

An experimental investigation of feedback control of the vertical plasma position in the non-circular tokamak TNT-A is described. When the loop gain of the feedback control system is high, the plasma displacement is small, but the saturation of the servo-amplifier limits the maximum loop gain. It is observed that the stable region in the diagram of the loop gain and the n-index (g-n diagram) shrinks as the n-index approaches a critical value. The experimental results are consistent with the theoretical model in which the effect of the toroidal gaps in the resistive shell and the vacuum vessel is considered.