JT-60SA is the fully superconducting 📝Tokamak built jointly by Japan and Europe at the National Institutes for Quantum Science and Technology site in Naka, Japan, which achieved first 📝plasma on 23 October 2023.
The name carries its lineage and its purpose: JT-60 was Japan's flagship copper-coil tokamak from 1985, and "SA" stands for Super Advanced — the rebuild replaced the magnets with 📝superconductors and reshaped the plasma for long-pulse, high-📝beta operation. Published design values are a major radius of 2.96 metres, a minor radius of 1.18, a 📝toroidal field of 2.25 📝tesla and a 📝plasma current of 5.5 megaamperes, produced by eighteen toroidal field coils, four 📝central solenoid modules and six equilibrium field coils. The first operating phase reached plasma volumes of 160 cubic metres and diverted plasmas above 1 megaamp.
It is the largest operating tokamak in the world, and it was built as 📝ITER's satellite under the Broader Approach agreement between Japan and Euratom — a deliberately complementary role rather than a competing one. Its assignments are to retire ITER's technical risks ahead of ITER, and to explore the steady-state, high-performance regimes a 📝DEMO-class plant would need but ITER is not configured to reach. Note the conductor choice: JT-60SA's magnets are 📝low-temperature superconductors, niobium-titanium and niobium-tin, the mature technology whose reactor-scale manufacturing experience the field accumulated before 📝REBCO tape offered an alternative route.