Progress in Steady-state High Performance Plasmas and Related Technologies in the JT-60U Tokamak
Kenkichi Ushigusa and JT-60 Team
Japan Atomic Energy Research Institute Naka Fusion Research Establishment 801-1, Mukoyama, Naka-machi, Naka-gun, Ibaraki-ken, 311-0193 JAPAN
Abstract.
JT-60U has been optimizing the tokamak operation scenario for simultaneous sustainment of high confinement, high bN, high bootstrap current fraction, full non-inductive current drive and efficient heat and particle exhaust to provide physics bases for ITER and steady-state tokamak reactor. This paper reports latest results on JT-60 experiments and describes progress on key fusion technologies for these results. Various heating and current drive systems, which consist of the positive ion source Nbs, the negative ion source NB (NNB), the LHRF, the ICRF and the ECRF systems, played key role to extend operation region of H-mode, reversed shear mode, high bp ELMy H mode and high performance plasmas with enhanced radiation. Progress on NNB technology enables to demonstrate the N-NB driven current of 0.6MA with the efficiency of 1.3x1019m-2A/W. The new 110GHz ECH system has achieved torus input power of 1.5MW with around 2.7s duration and dmonstrated efficient central electron heating (Te(0)>10keV) and a real time deposition control. The pumping efficiency of the W-shaped divertor was improved by a factor two with increasing the number of particle pumping slot, and reduction of Zeff and improvement of He exhaust efficiency were realized in ELMy H-mode. Pellet injection was also started to extend the density region with the new multiple pellet injector (2mm cubic, 10Hz, 320m/s for high-field-side injection, 1km/s for low-field-side injection). Role of these key technologies to produce and sustain the steady-state high performance discharges will be emphasized.