K. Nagasaki, G. Motojima, S. Kobayashi, S. Yamamoto, T. Mizuuchi, H. Okada, K. Hanatani, S. Konoshima, K. Masuda, K. Kondo, Y. Nakamura, S.Watanabe, K. Mukai, K. Hosaka, K. Kowada, S. Mihara, Y. Yoshimura, Y. Suzuki, A. Fernandez, A. Cappa, F. Sano
Effect of Magnetic Field Ripple on ECCD in Heliotron J
Date of publication:
21 IAEA Fusion Energy Conference, EX/P6-15
Electron cyclotron current drive (ECCD) experiment has been made in the helical-heliotron device, Heliotron J. A wide configuration scan shows that the EC driven current is strongly dependent on the magnetic ripple structure where the EC power is deposited. As the EC power is deposited on the deeper ripple bottom, the EC driven current flowing in the Fisch-Boozer direction decreases, and the reversal of directly measured EC driven current is observed. High energy electrons are suppressed for ripple bottom heating, indicating that generation and confinement of trapped electrons have an important role on ECCD. For ripple top heating, the typical ECCD efficiency is estimated gamma=n_eI_EC R/P_EC=0,8x10^17 A/Wm^2 and zeta=e^3n_eI_EC R/epsilon_0^2P_ECT_e,=0,05. The normalized ECCD efficiency is found to be independent on the absorbed EC power for both ripple top and bottom heating cases.