02.03.2021 – JT-60SA successfully reaches its full design toroidal field

JT-60SA TF Magnet after its assembly
Animated toroidal field coils displacement during energization

Today the toroidal field magnet was successfully energized with a current of 25.7kA therefore reaching its full design magnetic field.

The toroidal field magnet comprises 18 D-shaped coils arranged in a ring, with the straight sections of their D-shapes pressed together as shown below. The JT-60SA plasma will be created inside the toroidal (i.e. shaped like a ring doughnut) vacuum vessel inside them (passing through the middle of each D). Each of the 18 coils is 7.5m high and 4.5m wide and together they weigh 370 tonnes. They produce a magnetic field running around the torus which has strength of 2.25T at the centre of its cross section. This field is fundamental to confining the superheated plasma of the tokamak.

During energization the coils move as illustrated in the animation (the actual movement is magnified 100 times), with their curved outer legs sliding within their support structures.

The successful generation of the toroidal field demonstrates the simultaneous operation of numerous tokamak systems, in particular the cryoplant, cryodistribution, cryostat and thermal shields maintaining the magnet at 4.2K, the power supply energizing it, the instrumentation ensuring its safe operation and the central control system supervising them.