The ultimate source of energy in the universe is nuclear fusion. It powers the sun and the stars. To work, extremely high temperature and high-pressure gases – plasmas – are required. The stars hold their plasmas by gravity. On Earth, in an attempt to harness fusion for electric power production, magnetic fields are required to hold fusion plasmas. This is an extremely difficult task.
Decades ago, a Russian magnetic field configuration – the tokamak – appeared promising. Countries built ever-larger tokamak experiments to develop this “magnetic bottle.”