Speaker
Description
A robust detection of spontaneous quenching is essential for protecting superconducting magnets and machinery from thermal damage. In coils of high-temperature superconductors (HTS) slow propagation of the normal zone makes common voltage-based quench detection schemes unreliable. Here, we propose and validate an alternative quench detection technique for HTS conductors based on monitoring their internal temperature with acoustic waves. Periodic pulsed excitation is applied using a piezo-transducer to a conductor or coil under test, and the transient mechanical response is recorded, providing a unique acoustic "fingerprint" of the system. Temperature-induced variations of the Young's modulus of <0.01% can then be readily detected by comparing the transient waveform to its undisturbed reference. We demonstrate by simulations and experiments a capability to resolve a temperature rise of < 1 K in the conductor quenching inside a stack at 77 K, on par with voltage detection at 1 microvolt/cm. Acoustic quench detection in a single 120 cm-long HTS conductor at an equivalent voltage sensitivity of 10 microvolt/cm is also demonstrated. The technique is simple, non-invasive, and applicable to a wide range of superconductor devices and beyond where thermal monitoring of interior of a solid object is required.