Integrated commissioning test of JT-60SA magnet and cryogenic systems. Cryogenic system operation results

JT-60SA cryogenic system comprises a main refrigerator cold box, auxiliary cold box, warm helium compressor, control system, and utility system (cooling water and instrumentation air). The total equivalent refrigerator power is 9.5 kW at 4.5 K. The cryogenic system supplied 4.4 K supercritical helium to the magnet system, 50 K pressurized helium gas to high-temperature superconducting current lead, and 80 K pressurized helium gas to the thermal shield. Before cooldown, cryostat helium leak testing and helium gas purification were performed. It took approximately 41 days to cool the magnet system from room temperature to superconducting transition temperature. During operation, the refrigerator was stopped three times because of electrical grounding problems and incorrect control parameter values in the cold rotation machine control system. Except for problems, the cryogenic system was steadily operated. This paper describes the cryogenic system operation results during cooldown and magnet operation. (author)