Engineers from SIMIC S.p.a., a contractor based in Italy, have wrapped up the first round of cold testing the toroidal field coils manufactured for ITER, a process that involved submitting the coil winding pack to a thermal cycle between room temperature and 80 K. Such testing is the next to the last step in the fabrication process, according to the company, occurring before engineers can insert the magnet’s inner core into a structural case.
The team first performed a series of dimensional and electrical inspection tests and then lifted the component into a specially constructed cryostat, where the winding pack was cooled to 80 K for nearly 20 days using a combined cycle of nitrogen and helium. Electrical connections placed at the exits of the chamber were tested with a current of 1,000 amps.
Cold testing allowed the magnet team to ensure that the coil insulation was robust and that the component could be cooled to superconducting temperatures without cracks forming. The team will now inspect the winding pack through dimensional and electrical tests before transferring it to the assembly rig for insertion.
The final industrial operation for ITER’s toroidal field coils is the insertion of the winding pack into a structural steel coil case. Engineers will fit the case over the winding pack with millimetric precision before welding the vessel shut. Each weld will be 12 centimeters thick and verified through ultrasonic testing. The gap between the inner core and the case will be filled with reinforced resin to ensure the mechanical continuity of the coil.
The cooling chamber, specialized tooling and the laser measuring equipment took almost one year to assemble at SIMIC. The company is collaborating with subcontractor Babcock Noell GmbH for some of the tooling and technologies. Japan is procuring all coil cases, as well as nine of the toroidal field winding packs, while Europe is procuring the other nine toroidal field winding packs plus a single spare.