Vertical stability of ITER plasmas with 3D passive structures and a double-loop control system

In this study we derive linear models describing the dynamics of the n = 0 plasma displacements around the main ITER equilibrium configurations. The models derived are consistent with the MHD equilibrium constraint as well as with the 3D geometry of the vacuum vessel and blanket outer triangular support where the main eddy currents flow takes place. Particular emphasis is placed on the analysis of the stability margin, growth time and minimum stabilization voltage. The performances of the present ITER control system (single loop) are compared to those of an upgraded system (double-loop) that is here proposed to improve the stability domain of the ITER plasmas forecast.