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/sub DT//sup eq/=1.25 was achieved in a transient state and Q/sub DT//sup eq//spl sim/0.5 was sustained for /spl sim/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 /spl sim/1.3 /spl times/10/sup 19/ A/W/m/sup 2/. 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 /spl sim/0.1%. Preliminary the D-/sup 3/He experiment was carried out using N-NBI, where /spl sim/110 kW of D-/sup 3/He fusion power production was identified.