Technological development and progress of plasma performance on the JT-60U

The plasma performance exploration of JT-60U in advanced tokamak regimes based on high βp and reversed shear mode operation has been conducted intensively, by using 500 keV negative-ion based neutral beam injection (N-NBI) and 110 GHz electron cyclotron (EC) systems for plasma heating and current drive, and a repetitive centrifugal pellet injector for efficient core particle fueling. High power injection of 6.2 MW at 381 keV for 1.7 s and a long pulse injection of 10 s at 2.6 MW and 355 keV were achieved. In the EC system capable of generating 4 MW of rf power for 5 s, the maximum injected EC power reached 3.0 MW for 2.7 s so far. Pellet injection at a velocity of 100 m/s from the mid-plane in the HFS has also performed well. With application of N-NBI power of 5.7 MW at 402 keV, a high fusion triple product was increased to ni (0)τETi(0), of 3×1020 keV s/m3 under a full non-inductive current drive condition. By using steerable antennas of the EC system and a tracking technique of the MHD island, suppression of the neoclassical tearing mode in real time has been demonstrated successfully. High-magnetic-field-side pellet injection extended the plasma density up to 0.7 nGW with H89p kept at ∼2.