The workforces at ASG Superconductors, where Europe's ten Toroidal Field (TF) coils are manufactured, perform the final checks on the last of the 70 "Double Pancakes" (DPs). Do not mistake the term for thin, fluffy cakes covered with maple syrup and powdered sugar. When it comes to ITER magnets, DPs are complex and heavy metallic structures that contain lengths of conductor which will generate a massive magnetic cage to confine the hot plasma of the biggest fusion device.
There are seven DPs in each TF coil – in two of them the cable-in-conduit conductor measures 450 m in length, while in the remaining five it measures approximately 750 m. The conductor is composed of about 1 000 superconducting and copper wires cabled inside a 2 mm-thick round stainless steel jacket which is 43.7 mm in diameter. The conductor needs to be wound with an accuracy of 0.05 mm/m and heat-treated at 650 °C in inert atmosphere. The winding of the conductor is extremely challenging because it needs to fit perfectly in the radial plate, a stainless steel D-shaped structure with grooves on both sides. Subsequently, the conductor is insulated and closed inside the heavy radial plates which are laser welded, and wrapped with insulating material.
The completion of the 70 DPs is another important milestone for F4E and its suppliers –
Iberdrola Ingeniería y Construcción,
ICAS – involved in this component. "I believe we have come a long way from the production of the first-ever Double Pancake. The moment we started this adventure, several experts wondered whether it would be feasible to produce even one. Today, we have successfully produced all of the 70 Double Pancakes required for the ITER TF coils that Europe is responsible to deliver. Our determination to defy the odds, the good project management and the team spirit between F4E, our suppliers, ITER IO and the other ITER Domestic Agencies have contributed to this achievement," explains Alessandro Bonito-Oliva, heading the F4E Magnets team.
here to see the manufacturing of a TF coil.