Control of plasma vertical position in tokamak reactors

The methods to estimate the effects of the eddy currents in the conductive components, such as the first wall, blanket, shield and coil vacuum chamber, on the vertical position control in tokamak reactors are presented. The classical PID feedback control is investigated and the control properties of the Fusion Experimental Reactor (FER) design of JAERI are discussed. The shell structures in the breeding blanket modules, shield structures and belljar type of coil vacuum chamber have important effects on the plasma vertical position controllability. In this FER design, the feedback control power with the coil inside the shield and inner belljar is smaller by a factor of − 10 than the control by the outside coil. The derivative action of the PID controller is essential to control the plasma vertical position stably.