Completion of JT-60SA construction and contribution to ITER

Construction of JT-60SA tokamak was completed on schedule in March 2020. Manufacture and assembly of all the main tokamak components satisfied technical requirements including dimensional accuracy and functional performances. Development of plasma heating systems and diagnostics have been also progressed, including demonstration of favourable ECRF transmission at multiple frequencies and achievement of long sustainment of high energy intense negative ion beam. Development of all the tokamak operation control systems has been completed together with improved plasma equilibrium control scheme suitable for superconducting tokamaks including ITER. For preparation of tokamak operation, plasma discharge scenarios have been established using this advanced equilibrium controller. Individual commissioning of the cryogenic system and the power supply system confirmed that these systems satisfy design requirements including operational schemes contributing directly to ITER such as active control of heat load fluctuation of the cryoplant essentialy important for dynamic operation in superconducting tokamaks. The Integrated Commissioning has started by vacuum pumping of the Vaccum Vessel and Cryostat, and then moved to cool-down of the tokamak and coil excitation tests. Transition to the super-conducting state was confirmed for all the TF, EF and CS coils. the TF coil current successfully reached 25.7kA, which is the nominal operating current of the TF coil. For this nominal toroidal field of 2.25T, ECRF was applied and an ECRF plasma was created. The integrated commissioning was, however, suspended by an incident of over current of one of the superconducting equilibrium field coil and He leakage caused by insufficient voltage holding capability at a terminal joint of the coil. Unique importance of JT-60SA for H-mode and high- steady-state plasma research has been confirmed using advanced integrated modellings. These experiences of assembly, integrated commissioning and plasma operation of JT-60SA contribute to ITER risk mitigation and efficient implementation of ITER operation.