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Description
The no-insulation technique in high-temperature superconducting (HTS) coils has significantly advanced HTS magnet technology by introducing an innovative approach to protection. This technique allows current redistribution between adjacent turns, enabling self-protection of the coils. However, it also introduces charging delays. To reduce the charging delay while maintaining self-protection capability, partial insulation and metal-insulation methods have been proposed. These approaches involve adding materials between coil windings to optimize the turn-to-turn electrical resistivity and the overall thermal conductivity.
In this contribution, we demonstrate that integrating pyrolytic graphite between coil windings is a promising approach to achieving turn-to-turn electrical resistivity values comparable to those obtained by competing technologies, such as the metal insulation technique. Furthermore, we show that pyrolytic graphite exhibits exceptional thermal conductivity, surpassing that of copper at temperatures higher than 30 K and exceeds it by nearly an order of magnitude above 80 K. Finally, we present results on the charging times of coils fabricated using HTS tapes co-wound with pyrolytic graphite layers of thicknesses ranging from 70 to 200 micrometers, along with measurements of their overall thermal stability.
