Unraveling quench dynamics and real-time continuous detection in HTS tapes through distributed fiber optic sensing

Abstract High-temperature superconducting (HTS) tapes, coils, and magnets often experiences intricate quench instabilities and failures during high current-carrying operations, posing challenges to their practical applications. This study addresses the need for a measurement approach capable of monitoring multi-field signals in superconducting structures within cryogenic and extreme electromagnetic environments. We explore the application of distributed fiber optic sensing (DFOS) technology, specifically employing the optical frequency domain reflectometry scheme, which offers distinct advantages over traditional point-type electrical testing methods, particularly for superconducting materials and magnets. In this experimental study, we continuously track the quench evolution process in superconducting tapes using both bonded and stress-free fibers for real-time monitoring. A comprehensive analysis of the acquired temperature and thermoelastic strain profiles provides essential insights into the dynamic behavior of quench events. The findings demonstrate the effectiveness of DFOS in identifying and characterizing the onset and propagation of quenches. By arranging bonded and stress-free fibers in parallel on the HTS tape’s surface, we successfully decouple the effects of strain-temperature cross-sensitivity, enabling the extraction of temperature and train profiles. The bonded fiber optic sensor demonstrates rapid sensitivity to the thermally quenched events. Temporal derivatives of voltage and thermal strain exhibit characteristic plateaus and slope changes during quenches, respectively. The voltage rate displays two plateaus corresponding to superconducting-to-normal transitions, while strain rates exhibit potential as criteria for identifying quench events in HTS materials. Moreover, DFOS outperforms traditional terminal average voltage measurement, capturing quench evolution tails from the initial point of quench until the complete transition of the segment into the normal state. This experiment provides a solid foundation for further exploration of the underlying quench mechanism.