Stationary high confinement plasmas with large bootstrap current fraction in JT-60U

Sakamoto, Yoshiteru; Fujita, Takaaki; Ide, Shunsuke; Isayama, Akihiko; Takechi, Manabu; Suzuki, Takahiro; Takenaga, Hidenobu; Oyama, Naoyuki; Kamada, Yutaka; JT-60 Team

This paper reports results on the progress in stationary discharges with a large bootstrap current fraction in JT-60U towards steady-state tokamak operation. In weak shear plasma regime, high-_p ELMy H-mode discharges have been optimized under nearly full non-inductive current drive by the large bootstrap current fraction (fBS50%) and the beam driven current fraction (fBD40%), which was sustained for 2.3s with stationary condition. The high confinement enhancement factor H892.3 (HH98y21.0) was also sustained under the condition of TeTi. In reversed shear plasma regime, the large bootstrap current fraction (fBS75%) has been sustained for 7.4 s under nearly full non-inductive current drive condition. The high confinement enhancement factor H893.0 (HH98y21.7) was also sustained, and the profiles of current and pressure approached the stationary condition. The large bootstrap current and the off-axis beam driven current sustained this reversed q-profile. This duration was limited only by the duration of the neutral beam injection.