The world’s largest superconducting tokamak prior to ITER, built as a joint Japanese–European satellite facility. It achieved first plasma in October 2023.
JT-60SA (Super Advanced) is a large superconducting tokamak located at the QST (National Institutes for Quantum Science and Technology) Naka Fusion Institute in Naka, Ibaraki Prefecture, Japan. It is a joint project between Japan and the European Union, implemented under the Broader Approach Agreement that complements the ITER project. JT-60SA achieved first plasma on 23 October 2023, becoming the world’s largest operating superconducting tokamak—a milestone that was widely reported and confirmed by both QST and EUROfusion.[1]
JT-60SA was built on the site of its predecessor JT-60U, which operated from 1985 to 2008 and achieved the highest equivalent fusion triple product of any tokamak at the time using deuterium-only plasmas. The new machine reuses the site infrastructure but is an entirely new device, designed with 18 Nb3Sn superconducting toroidal-field coils and a set of NbTi poloidal-field and equilibrium-field coils. Its plasma volume of approximately 132 m3 is roughly half that of ITER but several times larger than any other currently operating superconducting tokamak.[2]
Europe contributed approximately half of the machine’s components, including the toroidal-field magnet conductor, the cryoplant, power supplies, and several heating and diagnostic systems. Japan provided the vacuum vessel, the poloidal-field coils, and the neutral beam injection systems. Assembly took place at the Naka site between 2013 and 2020.[1]
JT-60SA is designed as a “satellite” facility for ITER, intended to explore plasma regimes and operational scenarios that complement ITER’s burning-plasma mission. Its key research objectives include: demonstrating high-beta, steady-state advanced tokamak scenarios; investigating the physics of energetic particles, ELMs, and disruptions at reactor-relevant scale; and providing an integrated test of superconducting tokamak operation at high plasma current.[3]
With up to 41 MW of auxiliary heating (34 MW of negative-ion-based neutral beams and 7 MW of ECRH), JT-60SA can access high normalized-beta regimes (βN > 3) relevant to DEMO-class reactor design.
First plasma was successfully achieved on 23 October 2023 with an inductively driven hydrogen discharge. Following this milestone, the facility entered an initial research phase. Commissioning of the full heating systems and progression toward high-current, high-performance plasmas is planned over the subsequent experimental campaigns. The machine is expected to operate for at least two decades, providing data crucial for both ITER operation and the design of future demonstration reactors.[1]