Tokamak nuclear fusion reactor, cutaway illustration. This plasma devices uses a series of magnet coils (rings) to confine a plasma (pink) in the shape of a torus, with the aim of containing and controlling a nuclear fusion reaction. Nuclear fusion is what powers the Sun and other stars. Tokamaks were developed in the 1950s. This illustration shows the outer and inner poloidal magnetic field coils, the toroidal magnetic field coils, the containment vessel, the coil current (inner red arrow) and the plasma current (outer red arrow). For this illustration with labels, see image C048/2884.