Demonstration of temperature-based quench detection on high-current insulated ReBCO coils made of LASSO cables

Fast and reliable quench detection remains a major challenge in the development of high-temperature superconducting (HTS) magnets with large stored energies in the megajoule range and above. Several temperature-based detection methods are investigated at EPFL Swiss Plasma Center, including twisted-pair superconducting wires (SQD), shielded thermocouple chains (TCC) and fiber-optics sensing (FOS). All three methods require strong thermal coupling to the main winding while remaining electrically insulated, thereby eliminating the need for high-voltage penetrations typically associated with voltage taps in fusion magnets. Their integration into the winding pack and their performance during quench events are studied on multiple samples of increasing size and stored energy, made of laminated stacked-tape soldered (LASSO) ReBCO conductors. These include a single racetrack coil tested in SULTAN using a 20 m-long 12-tape LASSO conductor and a double pancake coil tested in JORDI using a 50 m-long 15-tape LASSO conductor. Potential applications of the LASSO conductor and its industrial availability are also discussed.