Achievement of first plasma and successful integrated commissioning in JT-60SA

Abstract

Integrated Commissioning of JT-60SA, which will be the world’s largest tokamak until ITER operates, was completed in 2023. The device is designed to operate under good vacuum condition, which is by nature high insulation, and all superconducting magnets could withstand the operation voltage even if they were not Paschen proof. Applying the fast interlock system detecting vacuum deterioration inside the cryostat and the consideration of limited operation voltage (<2kV) of PF magnets, the integrated commissioning of JT-60SA was restarted in May 2023. The pump-down of the cryostat and vacuum vessel and the cool-down of the magnets were subsequently carried out. Taking advantage of the experience of the first cool-down, its speed was enhanced by increasing helium flow. In addition, the vacuum vessel was baked at 200 °C for wall cleaning during cool-down to save time. Furthermore, glow discharge operation was also executed as another process of wall clearing. After the high voltage (HV) test of all magnets at the operation condition, which were high vacuum (∼10^-6 Pa) and cryogenic temperature (∼4K), the magnet energization was successfully carried out and followed by plasma operation. The first plasma with limiter configuration and plasma current of 130kA was obtained applying Trapped Particle Configuration (TPC) on Oct. 23, 2023. Electron Cyclotron Heating (ECH) assisted plasma breakdown was performed with a low toroidal electric field (∼0.15 V/m).