Evaluations of CFETR ripple and optimization analyses of ferromagnetic inserts

Toroidal field ripple (TFR) amplitude of CFETR (China Fusion Engineering Test Reactor) was evaluated by ANSYS, and its profile at the plasma region was presented in MATLAB environment. The amplitude of the TFR is about 0.3% at the edge of plasma region, while it will reach 0.5% if the plasma radius is supposed to be larger. In order to investigate the effect of ferromagnetic materials on ripple reduction, ferromagnetic inserts with applicable material, various quantity and different toroidal angle in the shadow of each toroidal field coil were installed between the vacuum vessel shells by simulation and the results indicate ripple reduction is obtained when the angle was proper. By contrast, the ferromagnetic inserts were also installed on the inside of the inner shell and the outside of the outer shell. It shows that the effect on ripple reduction is better as the inserts are closer to plasma. Through the study we can conclude that it is feasible to install ferromagnetic inserts to reduce the TFR amplitude, but not necessary for CFETR at present parameters, while the method of installing ferromagnetic inserts could be developed if experiments with larger radius of plasma were to be done in the future.