K. Nagasaki, S. Yamamoto, H. Yoshino, K. Sakamoto, N. B. Marushchenko, Y. Turkin, T. Mizuuchi, H. Okada, K. Hanatani, T. Minami, K. Masuda, S. Kobayashi, S. Konoshima, M. Takeuchi, Y. Nakamura, S. Ohshima, K. Mukai, H. Y. Lee, K. Mizuno, Y. Yoshimura, G. Motojima, A. Cappa, B. Blackwell, F. Sano
Experimental Study of Second Harmonic ECCD in Heliotron J
Date of publication:
22 IAEA Fusion Energy Conference, EXW/P7-19
Second harmonic electron cyclotron current drive (ECCD) experiments have been made in Heliotron J. A focused Gaussian beam is injected with the parallel refractive index, N_//, ranging from -0.05 to 0.6. The EC driven current is estimated by excluding the bootstrap current from total current. The experimental results show that the EC driven current is determined by local magnetic field structure where the EC power is deposited, and the maximum EC driven current is attained around N_//=0.4 when the EC power is deposited nearly at the top of magnetic ripple. A large increase in ECE signals has been observed when the EC current was driven, indicating the important role of high-energy electrons on the ECCD. The experimental results on the N_// and B dependence agree with a ray tracing simulation using momentum conservation model in which trapped particle effect is included.