High-Temperature Superconducting Magnet Quench Detection via Coolant Gas Temperature Measurement
The high-temperature superconductors are being increasingly employed to construct electromagnets to generate strong magnetic field for a broad range of applications: from medical devices, electric motors, to future fusion reactors. These superconductors can experience a quench phenomenon which manifests itself as a fast increase of temperature in superconducting cables leading to disruption and termination of the magnet operation and even serious damages. In-time, fast quench detection, to prevent operation disruption, is currently one of the active developing areas. In this paper a technique based on frequency and time domain reflectometry using electromagnetic microwave signal propagating inside coolant gas channels is suggested and discussed. We demonstrate that the variation of gas permittivity during the heat release can be measured using the reflectometry allowing fast evaluation of the gas temperature. The methods to monitor the heat release and analysis required to recover the information about the gas temperature and heat release location are described. The numerical and experimental studies to demonstrate the application of frequency and time domain reflectometry to monitor the coolant gas temperature were carried out and the results, as well as the future plans are presented and discussed.