Image of the week
Keeping an eye on the hot (double) pancake
25 Jan 2021
An ITER ring-shaped coil begins its existence as cable-in-conduit conductor, wound into "double pancakes" that are eventually stacked one upon the other to form the winding pack at the core of the finalized coil. At one point in the fabrication process, each individual double pancake must be resin-impregnated in order to ensure its electrical insulation.
Data fed by approximately one hundred sensors is displayed on large screens and closely examined by the Fusion for Energy team responsible for the impregnation of the first of the eight double pancakes required for poloidal field coil #4.
The impregnation process is a long and delicate operation: tightly wrapped in insulating fiberglass tape, the double pancake is placed into a leak-tight mould. Several hundred litres of epoxy resin is injected at a temperature of 55-60 °C. As temperature is ramped up and extra pressure applied, the micro spaces inside the winding are filled and the double pancake eventually turns into a massive, rock solid block the colour of burned caramel.
Temperature, the quality of the vacuum inside the mould, and the intensity of the injection pressure must be closely monitored at all times.
In this image, data fed by approximately one hundred sensors is displayed on large screens and closely examined by the European Domestic Agency (Fusion for Energy) team responsible for the impregnation of the first of eight double pancakes required for poloidal field coil #4 (which will be 24 metres in diameter and weigh 350 tonnes).
Three other double pancakes are in various stages of fabrication in the on-site Poloidal Field Coil Winding Facility: one is ready to be impregnated; another is being finalized, and a third is taking shape on the winding table.