Achievement of high fusion triple product, steady-state sustainment and real-time NTM stabilization in high- pELMy H-mode discharges in JT-60U

Abstract

This paper reports results on the progress in steady-state high-β_p ELMy H-mode discharges in JT-60U. A fusion triple product, n_D(0)τ_ET_i(0), of 3.1 × 10²⁰ m⁻³ s keV under full non-inductive current drive has been achieved at I_p = 1.8 MA, which extends the record value of the fusion triple product under full non-inductive current drive by 50%. A high-beta plasma with β_N ~ 2.7 has been sustained for 7.4 s (~60τ_E), with the duration determined only by the facility limits, such as the capability of the poloidal field coils and the upper limit on the duration of injection 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, a real-time NTM stabilization system has been developed where detection of the centre of the magnetic island and optimization of the injection angle of the electron cyclotron wave are done in real time. By applying this system, a 3/2 NTM has been completely stabilized in a high-beta region (β_p ~ 1.2, β_N ~ 1.5), and the beta value and confinement enhancement factor have been improved by the stabilization.