Investigation on ripple loss reduction by ferritic steel plate insertion in JFT-2M: comparison between experimental and computational data

Ripple loss reduction resulting in reduced losses of fast ions was demonstrated successfully at the JFT-2M tokamak by installing ferritic plates between the vacuum vessel and toroidal field coils. This paper describes the comparison between the experimental results and computation based on the orbit following a Monte Carlo code. They are in qualitatively good agreement in the cases where the toroidal distribution of the toroidal field ripple is almost periodic (e.g. ferritic plate installed resulting in a complex periodic structure of the magnetic ripple), but differ in the case of toroidally small average ripple exhibiting non-periodic large local ones (e.g. ferritic plate installed resulting in a more complex non-periodic structure of the magnetic ripple).