Acoustic thermometry for detecting quenches in superconducting coils and conductor stacks

Abstract

Quench detection capability is essential for reliable operation and protection of superconducting magnets, coils, cables, and machinery. We propose a quench detection technique based on sensing local temperature variations in the bulk of a superconducting winding by monitoring its transient acoustic response. Our approach is primarily aimed at coils and devices built with high-temperature superconductor materials where quench detection using standard voltage-based techniques may be inefficient due to the slow velocity of quench propagation. The acoustic sensing technique is non-invasive, fast, and capable of detecting temperature variations of less than 1 K in the interior of the superconductor cable stack in a 77 K cryogenic environment. We show results of finite element modeling and experiments conducted on a model superconductor stack demonstrating viability of the technique for practical quench detection, discuss sensitivity limits of the technique, and its various applications.

Dipole Magnets above 20 Tesla: Research Needs for a Path via High-Temperature Superconducting REBCO Conductors

“…Second, reduce the time span when the hot-spot temperature increases with a sensitive quench detection, a significant challenge for instrument and measurement. New quench detection techniques measuring the temperature rise in the normal zone are under investigation [161][162][163][164][165][166][167]. Compared to the voltage-based detection technique, these new optic and acoustic techniques are more immune to electromagnetic interference, attractive for fusion applications.…”

“…As part of the USMDP's effort to develop underpinning technology to advance the magnet science, LBNL and collaborators are developing advanced quench detection and diagnostic techniques for HTS magnets. One example is to use the acoustic thermometry to detect quenches that have been successfully demonstrated in REBCO tapes and small coils [166,220]. A promising concept based on the stray capacitance between the coil and its structural elements has also been successfully tested in Bi-2212 racetrack coils in collaboration with CERN [221,222].…”

Quench Detection for High-Temperature Superconductor Conductors Using Acoustic Thermometry

“…Our approach is similar to the "coda wave interferometry" technique developed primarily for geophysics applications [26], [27]. Details of instrumentation, data processing, and demonstration of EFT-based quench detection for a 10-cm long HTS tape stack were given in [28]. Here, we modify and scale up this technique towards detecting quenches on a ~ 1 m length scale of a typical high-field coil, and extend its applicability to subscale coils wound with HTS CORC ® cable.…”

“…Measuring the latter, differential time shift allows for an efficient suppression of various common mode noise sources, and eliminates spurious signals due to thermal fluctuations of the entire tape, as evident comparing the difference and sum signals. Sensitivity to local hot spots in differential mode is thus significantly improved compared to the original one sender / one receiver detection scheme used in [28]. As heating should increase t for the corresponding tape segment, sign of the differential signal is indicative of whether sensor "1" or sensor "2" adjacent tape side is quenching.…”

A Novel Fault Diagnosis Method for High-Temperature Superconducting Field Coil of Superconducting Rotating Machine

“…Therefore, thermal runaway can occur in a hot spot and damage the HTS coil due to stored magnetic energy before the resistance generated in the normal zone can be measured. For these reasons, various quench detection methods that do not use a traditional voltage tap have been studied [1][2][3][4][5]. Ravaioli et al proposed a quench detection method based on the change in stray capacitance between magnet elements when quenching occurred [1].…”