(EX/P2-14) Effects of Complex Magnetic Ripple on Fast Ions in JFT-2M Ferritic Insert Experiments

**Abstract.** In JFT-2M, we have obtained new results on the fast ion ripple
losses under the condition of the complex ripple produced by the ferritic
steel plates (FPs), such as non-periodic ripple structure in the toroidal
direction and high harmonic ripple. In the case where large ripple wells
exist in some toroidal sections, the local ripple-trapped ion losses are
small if the toroidal ripple amplitude averaged over the toroidal direction
is small. The result is consistent with ripple-enhanced banana diffusion as
the source of the lost ions because, in this mechanism, the rate is
determined by the averaged ripple amplitude. On the other hand, the location
of the loss at the wall is found to be determined by the local ripple
amplitude itself. We have also observed a heat load to the mid-plane due to
the N=32 (second harmonic) ripple when both the N=16 (fundamental) and N=32
ripple modes co-exist. These findings are important for the practical
application of ferromagnetic inserts for ripple reduction in ITER.

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*IAEA 2003*