Calculation of 3D magnetic fields produced by MHD active control systems in fusion devices

An accurate control of the magnetic boundary of a thermonuclear plasma is an important issue in magnetic confinement research. The development of methods for the active control of magnetohydrodynamic instabilities and correction of error fields is mandatory in view of fusion reactors or experimental test reactors under design. Recently, a very effective control scheme, named clean mode control (CMC), has been proposed in a reversed field pinch experiment (RFX-mod). The CMC is based on the real-time correction (cleaning), under simplifying hypothesis, of the sideband harmonics in the magnetic field produced by the discrete local active coils. In this paper, we focus on the problem of carefully computing the penetration of sidebands through a realistic load assembly, but still with a simplified cylindrical geometry, to allow for a detailed comparison with the crude CMC algorithm without the additional complication of the coupling between the poloidal harmonics due to the toroidal geometry.