Performance and development of heating and current drive systems in JT-60U

RF systems of ECH, LH, ICH, and positive and negative ion based NBI systems are equipped in JT-60U to realize highly integrated performance plasma. Their performance and development are presented. The ECH system with the total output of 4 MW at 110 GHz has been developed using four 1 MW gyrotrons. The gyrotron has achieved 1 MW, 5 sec output of the designed value by suppressing the parasitic oscillation with SiC RF absorber built-in. Moreover, 13 MW, 1.5 s output has been attained up to now. A real time system has been developed to stabilize neoclassical tearing mode (NTM) by controlling EC beams, which consists of the ECE measurement system, JT-60 real time processor and ECH system with steerable mirror antennas. This system successfully works to suppress NTMs. The LH launcher mouth was improved for longer pulse operation 30-60 s. The grill mouth made of carbon materials was joined onto the original mouth. Injection performance of the negative-ion based NBI system has been improved by correcting beamlet deflection due to beamlet-beamlet repulsion by space charge effect. This was compensated by a focusing electric field that was made by modification of extractor segment edges. Then, injection of 2.6 MW, 10 s has been achieved reducing temperature rise of the beam limiter by ∼70%.