Poloidal field coils are made of spiralled coils of conductor called double pancakes, stacked together and hardened into a rigid assembly by way of resin impregnation. PF6 will be made from nine such double pancakes, while PF5 will be formed from a stack of eight. In order to realize full, two-layer dummy mockups, two 718-metre unit lengths were used for PF6 and two 737-metre unit lengths for PF5.
As part of the qualification of the winding tooling and processes, these mockup pancake windings were validated by manufacturing readiness reviews earlier this year, giving the green light for the start of real double pancake winding for both poloidal field coils.
In a similar manner, the next stage—vacuum impregnation—will be reviewed once the impregnation operations have been completed on the mockups and verified, opening the way for this step to be carried out on the production double pancake windings.