Progress of Quench Detection for CFETR TF Prototype Coil

To establish the method and standard for manufacture the key components for CFETR, the Comprehensive Research Facility for Fusion Technology (CRAFT) project started in September 2019. The TF prototype coil is one sub-task of the CRAFT project, which can meet the physical and engineering requirements of CFETR. Although the safety margin has been fully considered in the design, the TF prototype coil could experience a quench during the electrical testing. Due to the large stored magnetic energy of CFETR TF prototype coil, the severe requirements for quench detection have been put to accurately and quickly trigger the current discharge. According to the quench analysis results of the TF prototype coil, the voltage detection with threshold less than 0.2 V and 2 s delay is satisfied to the design criteria of quench detection (hot-spot temperature <150 K). The envisaged voltage detection system is proposed and discussed based on the co-wound tape (CWT) and co-wound wire (CWW), to ensure the inductive voltage compensation. A numerical model is developed for very precise inductance calculations. Based on the analytic results, the installation schemes of CWT and CWW are optimized to achieve the best noise reduction rating (NRR). The sensitivity of the primary quench detection based on voltage measurements is enough for the required voltage detection level (0.2 V).