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

K. Shinohara¹⁾, H. Kawashima¹⁾, K. Tsuzuki¹⁾, K. Urata¹⁾, M. Sato¹⁾, H. Ogawa¹⁾, K. Kamiya¹⁾, H. Sasao¹⁾, H. Kimura¹⁾, S. Kasai¹⁾, Y. Kusama¹⁾, Y. Miura¹⁾, K. Tobita¹⁾, D.S. Darrow²⁾, JFT-2M Group^1)
 
1) Japan Atomic Energy Research Institute, Tokai-mura, Japan
²⁾ Princeton Plasma Physics Laboratory, Princeton, USA

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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