Design of fully covering ferritic inside wall to reduce toroidal ripple in JFT-2M

A ripple reduction is made by fully covering ferritic inside wall (FIW) as simulation of the blanket wall. We pay attention on the avoidance of generation of higher harmonic ripple. The n-th higher harmonic mode becomes almost zero in the case that the toroidal width of ferritic steel corresponds to 2/spl pi//(n times number of toroidal field coils). Effective method to reduce toroidal field ripple with FIW is developed. The ripple reduction is confirmed by the magnetic field measurement and the reduction of ripple losses by FIW was successfully demonstrated.