W7-X, presently under construction in Greifswald, Germany, is the largest, most advanced stellarator ever constructed and was designed to demonstrate steady-state reactor-relevant operation. The confining magnetic field is provided by a set of 50 computer-designed non-planar superconducting coils and does not require a plasma current.
The tokamak is the most common fusion research device. The confining magnetic field is generated by currents flowing in the toroidal field coils and, superimposed on this, a smaller field due to a transformer-induced current flowing in the plasma itself. At fusion temperatures, the plasma conducts current as freely as copper.
Since 1983, JET has been the largest operating tokamak in the world -
the human figure on the lower left of the image above gives a sense of
the scale of the device! It holds many world records for the best
fusion parameters achieved, including that for the most fusion power
created in a plasma.
