Speaker
Description
JT-60SA is the world’s biggest operating tokamak (R=3, a=1.2) having achieved a plasma volume of 160m$^3$ in 2023. As the first of a new generation of large fusion experimental machines, its commissioning represents a unique opportunity to gain invaluable operational experience.
The magnets form the backbone of any tokamak, and the superconducting magnet systems of JT-60SA play a critical role in allowing long pulse operation, essential for studying plasma behaviour in conditions relevant to reactor operation.
The novel design of the NbTi Toroidal Field (TF) magnet, providing the main confinement field for the plasma, allows its 18 coils (each 7.5m high) to expand radially when energized within their Outer Intercoil Structures, which in turn provide lateral support. The 100-tonne Nb$_3$Sn Central Solenoid is key to driving current in the plasma while the six NbTi Equilibrium Field coils, up to 12m in diameter, shape and control it.
The TF magnet was successfully operated at its full 2.25 T on-axis field in 2021, and in October 2023 all the magnets could be operated together to produce the first tokamak plasma.
While individual components - such as a coils, power supplies or cryoplants - can be thoroughly tested in isolation, many critical aspects of their interaction can only be assessed during integrated commissioning, where all systems are operated together.
This presentation provides an overview of the magnet system integrated commissioning process and highlights key lessons learned, particularly regarding insulation integrity, Paschen testing, applied voltages, power circuit design, and quench detection.
