Achievement of a high fusion triple product and steady state sustainment in high βp ELMy H-mode discharges in JT-60U

This paper reports results on the progress in steady-state high-βp ELMy H-mode discharges in JT- 60U. A fusion triple product nD(0)τETi(0) of 3.1x1020m-3.s.keV under full non-inductive current drive has been achieved at Ip=1.8 MA, which renews the record value of the fusion triple product under full non-inductive current drive by 50%. A high-beta plasma with βN∼2.7 has been sustained for 7.4 s (∼60τE), where the duration is determined only by the facility limit such as the capability of the poloidal field coils and the upper limit of the injection duration of neutral beams. Destabilization of neoclassical tearing modes (NTMs) has been avoided with good reproducibility by tailoring the current and pressure profiles. On the other hand, the real-time NTM stabilization system has been developed, where the detection of the center of magnetic island and the optimization of injection angle of electron cyclotron (EC) wave are done in real-time. By the application of this system, a 3/2 NTM has been completely stabilized in high beta region (βp∼1.2, βN∼1.5), and beta value and confinement enhancement factor have been improved by the stabilization. (author)