Speaker
Description
The construction of the full-superconducting tokamak JT-60 Super Advanced (JT-60SA) is in progress under the JA-EU broader approach agreement. During cool down, nominal operation and warm-up the thermal shields, the superconducting magnets and their structures, the high temperature superconductor current leads (HTS CL) and the divertor cryo pumps have to be supplied with helium at specific flow rates, pressures and temperatures. The monitoring of temperatures, mass flows, and pressures and the control of the helium flows is performed by a Magnet Controller (MC).
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. These interlocks react on deviations of temperatures, pressures or mass flow rates from their nominal values and initiate appropriate counteractions. If a state reaches a critical threshold, a normal stop (NS) of a magnet is initiated through the “Supervisory Control System and Data Acquisition System” (SCSDAS) by ramping-down the current in the coils. In case of a fast discharge the MC acts directly on the power supplies with parallel information to the SCSDAS.
The thresholds are derived from simulations of the cryogenic loops using the thermal analysis programs FLOWER, HEATER, and SUPERMAGNET.
The presentation will describe the philosophy and logic of the Magnet Controller and explain the calculation of some thresholds.
