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Noninductive Current Drive and Steady-State Operation in JT-60U

K. Ushigusa, S. Ide, T. Oikawa, T. Suzuki, Y. Kamada, T. Fujita, Y. Ikeda, O. Naito, M. Matsuoka, T. Kondoh, A. Isayama, M. Seki, T. Imai, K. Sakamoto, N. Umeda, K. Hamamatsu, T. Fujii, K. Uehara, T. Yamamoto, Y. Miura, M. Kikuchi, M. Kuriyama, H. Ninomiya

Fusion Science and Technology / Volume 42 / Number 2,3 / September-November 2002 / Pages 255-277

Technical Paper /

Studies on noninductive current drive (CD) and development of an integrated steady-state high performance operation in JT-60 are reviewed. Experiments on lower hybrid current drive (LHCD) in JT-60 have shown a large noninductive current up to 3.6 MA, high current drive efficiency of 3.5 × 1019 m-2A/W, and a flexible current profile control. Basic studies on LH waves, such as an effect of accessibility condition, fast electron behaviors, and so on, in JT-60 have contributed to understanding LHCD physics. Significant progress in neutral beam current drive (NBCD) has been made in JT-60 by testing the performance of negative ion-based (N) neutral beam injection (NBI) (N-NBI). The CD efficiency of ~1.5 × 1019 m-2A/W and negative ion-based neutral beam (N-NB) driven current of ~1 MA have been demonstrated in N-NBCD. Strongly localized noninductive driven current by electron cyclotron current drive (ECCD) was identified with a fundamental O-mode scheme from a low field side injection. ECCD in JT-60 has shown CD efficiency of 0.5 × 1019 m-2A/W and EC-driven current of 0.2 MA. Modification of local current profile was demonstrated and was used for suppression of neoclassical tearing mode. Based on these developments, two integrated steady-state operation scenarios were developed in JT-60, which are reversed magnetic shear (R/S) plasmas and high p ELMy H-mode. In these operation regimes, discharges have been sustained near the steady-state current profile under full noninductive current drive (High p; HHy2 ~ 1.4 and N ~ 2.5 with N-NB, R/S; HHy2 ~ 2.2 and N ~ 2 with fBS ~ 80%). High performance plasmas with a high nDoETio and at high normalized density were also produced under fully noninductive condition in high p ELMy H-mode and R/S mode.

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