The core piece of the device is a wreath of 50 superconducting niobium-titanium magnet coils about 3.5 metres high. Cooled with liquid helium to superconduction temperature close to absolute zero, they need hardly any energy after being switched on. Their bizarre shapes are the result of the optimisation calculations: They are to produce a particularly stable, thermally insulating magnetic cage for the plasma.
To allow the magnetic field to be varied a second set of 20 planar, likewise superconducting coils is superposed on the stellarator coils. A massive ring-shaped support structure keeps the coils in the exact position despite the high magnetic forces.
The entire coil wreath is surrounded by a thermally insulating outer shell 16 metres in diameter, viz. the cryostat. A refrigeration plant later provides 5000 watts of helium cold in order to cool the magnets and their support structure, i.e. a total of 425 tons of material, to superconduction temperature.
Inside the coil wreath is the steel plasma vessel composed of 20 sections, whose peculiar shape is matched to the twisted plasma ring. Through over 250 apertures the plasma will later be observed and heated. An equal number of ports with good thermal insulation are passed through between the cold coils, connecting these apertures with the outer wall of the cryostat.