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Report No.

Effects of ELM mitigation coils on energetic particle confinement in ITER steady-state operation

Tani, Keiji*; Shinohara, Koji; Oikawa, Toshihiro*; Tsutsui, Hiroaki*; Miyamoto, Seiji; Kusama, Yoshinori; Sugie, Tatsuo

The effects of the ELM mitigation coils (ELM coils) on the loss of NB-produced fast ions and fusion-produced alpha particles were investigated using an orbit following Monte-Carlo code. The ELM Mitigation Coil field (EMC field) may cause a significant loss of fast ions produced by NBI on the order of 4-5% for a 9MA steady-state ITER scenario. The loss strongly depends upon the toroidal mode number $$n$$ of the EMC field. A significant loss occurs only in the case of $$n=4$$. The resonance of fast-ion trajectories with the EMC field is important to the loss of fast ions. When the number of ELM coils in each toroidal row is 9, the main toroidal mode $$n=4$$ is accompanied by a complementary mode $$n_c=5$$. Concerning the resonance of fast-ion trajectories, the anti-resonant surfaces of $$n=4$$ are very close to the resonant surfaces of $$n_c=5$$ and vice versa. Since the resonance effect is dominant compared to the anti-resonance, the collaboration of the main and complementary modes effectively enlarges the resonant regions. The peak heat load due to the loss of NB-produced fast ions near the upper ELM coils is in a range that requires attention. Most loss particles hit the inner side of the torus of the dome in the ITER divertor. The loss of alpha particles is acceptably low at less than 0.5%.



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Category:Physics, Fluids & Plasmas



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