A key parameter for the vertical stabilisation system of future fusion devices like ITER is the maximum allowable vertical displacement which can be recovered by the magnetic control system (Gribov 2015 Nucl. Fusion55 073021). The computation of this figure of merit is based on MHD evolutionary equilibrium models: the perturbation of the vertical position implicitly considers a perturbation of the external passive currents which guarantees MHD equilibrium. In this paper, we quantify the consequences of considering non-equilibrium perturbations of the vertical position. In this case, one has to specify separately the initial perturbation of the vertical position and of the external currents. We show in particular under which circumstances the evolution of the vertical position, as predicted by the evolutionary equilibrium models, coincides with that obtained considering also plasma inertia.
Non-axisymmetric magneto- hydrodynamic equilibrium in the presence of internal magnetic islands and external magnetic perturbation coils