Speaker
Description
High temperature superconductors are vulnerable to sudden thermal runaway events, or quenches. The loss of superconductivity and resulting dissipation of energy from the transport current leads to temporary failure of the magnet or power cable, irreversible damage, and possible catastrophic failure of the superconducting component. Voltage based detection of a pre-quench condition is challenging in many application environments, where the milli-Volt scale signals are swamped by noise. Fiber-optic sensing is a promising alternative quench protection system, as it is unaffected by electro-magnetic fields, can operate at cryogenic temperatures, and can be integrated as a distributed sensing system. In this work, we demonstrate the integration of fiber-Bragg grating based optical sensing onto spiral-wound monofilament superconducting wires. The response of the fiber-optic sensors is compared with voltage and temperature measurements during both heater and current-sharing induced pre-quench thermal events. We show that the fiber-optic system can detect ~1 K temperature changes at 78 K, and shows clear responses to thermal runaway. The optical signal typically follows the voltage response for the current-sharing induced quench, but by no more than about half a second. These results support the use of fiber-optic sensing and thermometry for monitoring and protecting superconducting magnets or power cables.
