Monitoring and control of the magnet system of JT-60SA

Abstract The construction of the full-superconducting tokamak JT-60 Super Advanced (JT-60SA) is in progress under the JA-EU broader approach agreement. The Cryogenic System of JT-60SA has five circuits to cool the Poloidal field coils, Toroidal field coils, thermal shields, high temperature superconducting current leads (HTS-CLs) and feeders, and divertor cryopumps. The physical conditions such as pressures, temperatures and mass flows of the magnet cooling loops are monitored by a Magnet Controller The magnet controller also performs local control of the helium flows. A particular abnormal situation is a quench or a fast discharge of a magnet which would require many hours for recovery to normal operation. In order to avoid fast discharges as far as possible, the MC uses “safety interlocks” to supervise the magnet coils and the HTS CL. This safety interlocks are called slow discharge. In this paper, the slow discharge thresholds of the HTS-CLs are derived from simulations of the cryogenic loops using the thermal analysis programs FLOWER, HEATER, and SUPERMAGNET.