On the control of plasmas in Tokamak discharges

This paper considers the problem of controlling the drift-tearing modes in a Tokamak plasma which are relevant to disruptions and large anomalous transport. Because of the fact that a plasma is an open dissipative system having a strong self-organizing property, the usual modal stabilizing feedback controls are not suitable. Here, a global approach to the control of these modes is proposed. The basic idea is to program the global plasma parameters such as the plasma density and current to prevent plasma structural modification on a short (linear magnetic instability) time scale so that feedback controls on a slow (diffusive) time scale may be used to control the drift-tearing modes, thereby improving the performance of the machine. The overall structure of the proposed control system is presented and the expected results are discussed.