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To achieve magnetic fields above 20 T in modern magnets for fusion devices and high-energy physics accelerators, the use of high-temperature superconductors (HTS) at low temperatures below 20 K is proposed. In recent years, there has been active development of increasingly larger HTS coil systems. However, as the size of the magnets increases, the issues of stability and protection for these systems become more pronounced. One of the key challenges is the slow propagation speed of the normal zone in HTS coils. This leads to difficulties in detecting the normal zone/quench start and timely activating protection systems for the coils. As a result, there is a risk of damage to the magnets, which can lead to significant costs and delays in research projects.
In this work, we analyze the stability issues and quench development in large HTS magnets at temperatures close to liquid hydrogen/helium temperatures, compared to coils based on low-temperature superconductors (LTS). Qualitative approaches to analyzing transition development, previously developed for LTS, are employed [1]. We also consider the applicability of methods that were previously developed for liquid nitrogen temperatures to the analysis of stability and quench development at near-helium temperatures [2]. Thus, this study aims to identify key problems and seek effective solutions to enhance the reliability and safety of HTS coils under magnetic fields exceeding 20 T and temperatures close to liquid hydrogen/helium levels. The results of this work may be beneficial for further research and practical applications in the fields of thermonuclear fusion and high-energy physics.
1. Rusinov A.I. et al, IEEE Trans. Mag., v.25. N2, 1989, 1541-1542
2. . A.L. Rakhmanov, et al, Cryogenics, 2000, v.40, N1, pp.19-27
