Plasma position and shape control in ITER using in-vessel coils

The International Thermonuclear Experimental Reactor (ITER) is the next step toward the realization of electricity-producing fusion power plants. ITER has been designed so as to reach the plasma burning condition, and to operate with high elongated unstable plasmas. However, due to the constraints which affect the machine realization, these open-loop unstable high performance plasmas can be hardly stabilized using the Poloidal Field (PF) coils placed outside the tokamak vessel. For this reason, during the ITER design review phase, it has been proposed to investigate the possibility of using in-vessel coils, in order to improve the best achievable performance of the vertical stabilization system. Because of some technological differences between the in-vessel coils and the PF coils (the former cannot be superconductive), the controller design procedure previously adopted in [1] cannot longer be used. This paper proposes a new approach for the plasma current, position, and shape control design in the presence of in-vessel coils. In particular two control loops are designed: a first loop which guarantees the vertical stabilization by means of a MISO controller which drives the voltage applied to in-vessel coils; a second MIMO loop controls the plasma current and up to 32 geometrical shape descriptors as close as possible to the reference values. © 2008 IEEE