21.7-T Large-Scale High-Temperature Superconducting Toroidal Magnet for Tokamak Fusion Application

With the rapid advancement of magnetic confinement fusion technology, High- Temperature Superconductors (HTS) have emerged as a cornerstone for compact and efficient tokamak systems due to their exceptional current-carrying capacity under high magnetic fields. Against this backdrop, Energy Singularity Fusion Power Technology (ES Company) initiated the JingTian (JT) magnet project in December 2024 to validate the Toroidal Field (TF) magnet design for its next-generation all-HTS tokamak facility, HH170. Prior to the HH170 project, ES Company developed and constructed the world's first all-HTS tokamak. This facility successfully achieved its first plasma operation in June 2024, marking a significant milestone in fusion technology [1, 2]. This paper details the design, fabrication, and performance testing of the JT magnet, a large-scale D-shaped winding pack comprising 32 modular Rare-earth Barium Copper Oxide (ReBCO)-based pancake coils. Operating at 5 K with supercritical helium cooling, the JT magnet achieved a record-breaking peak magnetic field of 21.7 T, the highest reported for an all-HTS tokamak magnet. Steady-state operation at 24.3 kA confirmed its structural integrity, cryogenic cooling efficiency, and alignment with magnetic field modeling predictions. The success of the JT magnet not only provides critical data for the HH170 design but also establishes a foundational milestone for the engineering application of high-field compact tokamaks, demonstrating significant potential to reduce fusion reactor size and cost.