"Dummy" winding takes shape
28 Nov 2016
As orange lights flash and machines softly hum, layer one of a "dummy" pancake winding (the building block of a poloidal field coil) is taking shape on the winding table of the Poloidal Field Coils facility.
The first complete layer, made from "dummy" conductor, reflects the dimensions of ITER's fifth poloidal field coil.
A "dummy" is similar to an actual pancake winding in every aspect except one: the conductor is made of plain copper instead of niobium-titanium superconducting alloy. Winding with dummy conductor serves to qualify tooling and processes before the start of actual production.
In the on-site facility where four of ITER's giant ring-shaped poloidal field coils will be produced by Europe, layer one of the two-layer dummy winding has been realized by a team of ten people. It corresponds to the dimensions of poloidal field coil #5 (17 metres).
As if in slow motion, the steel-jacketed conductor is unspooled, straightened, cleaned in an ultrasound bath, bent to the correct shape, and then sandblasted, washed and dried. Five layers of insulating glass/polyimide tape turn the originally grey conductor to white.
Technicians check the insulation of the dummy conductor winding. Winding is a multi-stage process that begins with de-spooling, straightening, cleaning and sandblasting ... before the conductor is wound into the correct dimensions and insulated with layers of glass/polymide tape.
Winding layer one is now complete, soon to be joined by a second layer placed in a controlled manner on top of the first and separated by joggles. After the creation of helium inlets (ITER's magnets will be cooled by supercritical helium), the dummy pancake will continue on to the impregnation step. The final rigid assembly will be sliced into eight parts and stacked to reproduce a mockup section of poloidal field coil #5, with its eight stacked double pancakes.
More information on the European Domestic Agency website.