Magnetic control of a tokamak plasma

he plasma in a tokamak is magnetically confined through electromagnetic fields generated by a set of poloidal field coils, with feedforward nominal voltages or currents based on an approximate plasma model. Therefore, feedback control is necessary. A good magnetic control is essential for achieving good performance in present devices and expected to be of paramount importance in future tokamaks with a burning plasma due to the more stringent requirements in terms of plasma-wall clearance, stability margins, limited number of tolerable disruptions and so on. Magnetic fields are able to control plasma current, position and shape as well as three dimensional instabilities on the resistive time scales (resistive wall modes). They also have an influence on the control of the plasma current density profile. This paper focuses on the axisymmetric control of plasma current, position and shape, illustrating modelling assumptions and techniques, controller design procedures, assessment of controller performance and magnetic diagnostic requirements. © 2008 American Institute of Physics