With a weight equivalent to 200 Fiat 500 cars, JT-60SA‘s single heaviest component, the central solenoid, has been inserted into the heart of the machine today.
The central solenoid is part of JT-60SA’s superconducting coil system which otherwise consists of 18 toroidal field (TF) coils, six equilibrium field (EF) coils and components such as coil feeders and current leads. The insertion of the central solenoid marks the last of the superconducting coils to be installed and is a major milestone for Broader Approach partners Europe and Japan.
In a tokamak, the electrical current flowing in the plasma makes a critical contribution to heating it and to confining that heat so that the fusion reaction can take place. JT-60SA’s central solenoid has 2000 turns of superconducting cable wound around its tokamak axis. When the electrical current in the solenoid changes, a current will also be driven in the plasma and this will help stabilise and heat it. In JT-60SA, the central solenoid is made up of four modules, each carrying 20kA, which can be independently controlled in order to use them to help shape the plasma.
The central solenoid uses niobium tin cable-in-conduit conductors similar to that which will be used for ITER and which have been manufactured by Mitsubishi Electric Co.under contract to QST. The superconducting strand in JT-60SA’s conductors is identical to that used for ITER’s TF conductors, thus illustrating JT-60SA’s relevance and contribution to ITER.
Lifting of the 12m tall central solenoid was carried out by primary assembly contractor Toshiba using the torus hall crane. Because of limited vertical space, during the lift the clearance (the space between the central solenoid and JT-60SA assembly frame) was only 80mm. The central solenoid’s position will now be carefully adjusted before it is secured to its supports on the TF coils which have previously been supplied by Europe. To view the spectacular lifting and insertion operations of the JT-60SA solenoid click here.
The first plasma in JT-60SA is expected to happen in 2020.