Types of Fusion Devices
Most of the devices in the world today are of the tokamak type, which is best investigated and comes closest to the ignition conditions.
Both types feature ring-shaped magnetic fields. Tokamaks produce part of these fields by means of an electric current flowing in the plasma. Stellarators, on the other hand, form the magnetic field cage solely by means of external coils. Stellarators are thus suitable for continuous operation, whereas tokamaks without auxiliary facilities can only work in pulsed mode.
Max-Planck-Institut für Plasmaphysik is the only fusion centre in the world investigating both types of experiment. This allows direct comparison.