Abstract
High-temperature superconductors (HTS) are being increasingly used for magnet applications. One of the known challenges of practical conductors made with high-temperature superconductor materials is a slow normal zone propagation velocity resulting from a large superconducting temperature margin in combination with a higher heat capacity compared to conventional low-temperature superconductors (LTS). As a result, traditional voltage-based quench detection schemes may be ineffective for detecting normal zone formation in superconducting accelerator magnet windings. A developing hot spot may reach high temperatures and destroy the conductor before a practically measurable resistive voltage is detected. The present paper discusses various approaches to mitigating this problem, specifically focusing on recently developed non-voltage techniques for quench detection.
Highlights
Since their initial discovery in 1986, high-temperature superconductors [1] have made a long way toward practical use in applications, such as record-field solenoids [2,3,4], energy storage [5], fault current limiters [6,7,8] and transmission lines [9,10]
As the stored energy of modern particle accelerator magnets can reach into the MJ level, various systems for quench detection, protection and energy extraction are normally put in place to prevent the quenching conductor from experiencing thermal damage
We will review some of these latest developments and discuss the prospective of using new and existing quench detection techniques in order to provide an adequate level of protection for future High-temperature superconductors (HTS)-based magnets for particle accelerators
Summary
Since their initial discovery in 1986, high-temperature superconductors [1] have made a long way toward practical use in applications, such as record-field solenoids [2,3,4], energy storage [5], fault current limiters [6,7,8] and transmission lines [9,10]. In magnets built using conventional low-temperature superconductor conductors, such as NbTi or Nb3Sn, quenching would typically result in a redistribution of the current towards the normal metal (copper) stabilizer, with a simultaneous formation of the normal zone, which quickly expands and propagates along the length of the conductor and across coil turns This behavior is driven by a very low enthalpy margin (~10–100 mJ) of a typical LTS cable conductor: a small local mechanical or thermal perturbation can drive the entire cable cross-section into a normal state over a sub-millisecond timescale. We will review some of these latest developments and discuss the prospective of using new and existing quench detection techniques in order to provide an adequate level of protection for future HTS-based magnets for particle accelerators
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