Recent progress in the JT-60U tokamak

Recent progress in the JT-60U experiments from 1998 is summarized in this paper. In May 1997, the open divertor was modified to the W-shaped pumped divertor in order to improve plasma performance towards steady-state operation combining with the negative-ion-based, 500 keV neutral beam injector (N-NBI). The equivalent fusion multiplication factor of Q_DT^eq=1.25 was achieved in a transient state and Q_DT^eq~0.5 was sustained for ~0.8 s in reversed shear discharges. Full non-inductive current drive was sustained for 2 s with the bootstrap current and NB driving current. The ECRF system was introduced and the injection power into the plasma achieved was 0.75 MW for 2 s. With negative-ion based neutral beam injection, the current drive efficiency increased to ~1.3 ×10¹⁹ A/W/m². The W-shaped divertor with pumping was effective to reduce the H-mode threshold power. In N-NB injection, the toroidicity-induced Alfven eigenmode (TAE) was observed for a volume-averaged fast ion beta as low as ~0.1%. Preliminary the D- ³He experiment was carried out using N-NBI, where ~110 kW of D-³He fusion power production was identified