Analysis of Temperature Uniformity During Heat Treatment of Nb₃Sn Coils for DC Magnet in Super-X Test Facility

The Comprehensive Research Facility for Fusion Technology (CRAFT) serves as a pivotal pilot research project of the China Fusion Engineering Test Reactor (CFETR). The superconducting conductor experiment testing platform (Super-X) is a part of CRAFT to assess the performance of future superconducting components. The Direct Current (DC) magnet generates the background field in the Super-X facility. A “wind and react” process is employed in the fabrication of Nb3Sn coils for DC magnet. We designed and constructed a circulating atmosphere heat treatment system for the completion of Nb3Sn coil heat treatment. Given the significant influence of heat treatment temperature, particularly in terms of temperature uniformity, on the critical properties of Nb3Sn, it is imperative to analyze the temporal evolution of temperatures within Nb3Sn coils during the heat treatment process. In this study, the coil temperature field distribution during heat treatment process has been analyzed using finite element method. Additionally, thermocouples are placed on coil's surface to monitor temperature changes during heat treatment. Both simulation results and experimental data demonstrate that the uniformity of heat treatment temperature satisfies technical requirements.