An acronym for Joint European Torus the main European fusion experiment. It aims to try to reach the conditions at which the energy produced by deuterium-tritium fusion is greater than the energy required to maintain the extreme temperatures and pressures required for fusion. It is built around the tokamak design that has become the standard for fusion experiments: the plasma is held and compressed in a torus shape by strong magnetic fields. To date it has reached 65% of the theoretical efficiency required to break even, making it the most sucessful experiment so far. It will eventually be superceded by ITER, when the funding for it is secured.