Superconducting magnet control system of JT-60SA

The JT-60U is being upgraded to a full-superconducting tokamak referred as the JT-60 Super Advanced (JT-60SA) as one of the JA-EU broader approach projects [1]. The JT-60SA project will use superconducting magnets to confine the plasma and achieve a plasma current with a typical flat top duration of 100 second in purely inductive mode. The JT-60SA refrigerator will provides 4.4 K for the superconducting magnets (the Toroidal Field (TF) coil and the Poroidal Field (PF) coil), 50 K for High Temperature Superconducting Current Lead (HTS/CL), 80 K for Thermal Shields(TS), and 3.7 K for the divertor cryopumps. In order to harmonize all temperature controls, the JT-60SA will utilize a control system so called "a magnet controller" to supervise the superconducting magnets for cooling the magnets coping with the refrigerator, activation against the interlock signals to trigger the fast discharge by quench or equivalent events, and communication with the central control system (SCSDAS). In particular, cooling sequence needs to be done in close cooperation with the refrigerator because some of the flow for the TF must be bypassed by controlling the flow in the bypass line due to large pressure loss at ambient temperature.The magnet controller also trigger the fast discharge of the TF and the PF coils when it receives the interlock signal from the quench detectors, and other instruments. To move from one refrigerator subsequence such as the short-standby mode(STS), the baking mode(BAK), and the magnet nominal mode to the other, the refrigerator always needs permission from the magnet controller. In the paper, current status of the magnet controller will be presented