Analytical study of RWM feedback stabilisation with application to ITER

An analytical model for studying the feedback control of Resistive Wall Modes (RWMs) in a tokamak with single or double conducting wall is presented. The model is based on a cylindrical approximation. It is shown that the outer conducting shell, in the case of ITER-like double wall vacuum vessel, does not significantly reduces the RWM instability growth rate but deteriorates the feedback stabilisation. It is also shown that six side saddle coils with the nominal voltage 40 V per turn is capable of stabilizing the RWM for the expected range of normalized beta. (author)