Performances of the JT-60SA cryogenic system in the integrated commissioning test

A tokamak-type fusion experimental machine, JT-60SA, has been constructed through an international collaboration between Japan and the European Union. The JT-60SA utilizes a superconducting magnet system and a helium refrigerator with an equivalent refrigeration power of 9.5 kW at 4.5 K, providing cold helium gas to cool the magnet system. The second integrated commissioning test for JT-60SA operations began in May 2023, and the magnet system cooled down to operation temperature (<5 K). For plasma experiments, the cryogenic system provided approximately 2 kg/s of supercritical helium to the magnet system, removing static heat loads such as radiation and conduction heat and dynamic heat loads due to AC losses in the conductors, eddy currents in the magnet structures, and joule heating of the joints. The cryogenic system was successfully operated, and the first plasma was achieved on 23 October 2023.