An application of the singular perturbation decomposition to plasma position and shape control

This paper deals with the problem of designing a plasma current, position, and shape controller for the ITER-FEAT tokamak. Exploiting the features of the plant, we show that it is possible to design separately two control loops: a first loop which stabilizes the vertical position by means of a simple derivative action, and a second loop which drives the plasma current and the plasma geometrical shape descriptors as close as possible to the reference values. The reduced-order model for the design of the external loop has been obtained via a singular perturbation decomposition.