Researchers at the Joint European Torus (JET), the European fusion test reactor in Abingdon, United Kingdom, announced today that they have come closer than ever before to achieving self-sustaining fusion, the point at which a fusion reactor produces as much energy as it consumes. Burning the same mixture of hydrogen isotopes that would be used in an actual fusion power station, JET produced 50% of the energy supplied to the reactor--close to twice the previous record.
In a fusion reactor, deuterium or tritium nuclei (hydrogen atoms with one and two extra neutrons in the nucleus) fuse and form helium nuclei and neutrons. A small amount of mass is lost in the reaction and is converted into energy. However, the deuterium and tritium nuclei must be confined in powerful magnetic fields and heated to temperatures reaching 100 million degrees Celsius before they collide violently enough to fuse. Heating the gas to such temperatures with electric currents and radio waves takes an enormous amount of energy.
Until recently, experimental fusion reactors all used a fuel consisting mainly of deuterium, which yields less energy. Last year, however, the now-defunct Tokamak Fusion Test Reactor in Princeton, New Jersey, burned a deuterium/tritium mixture to produce 28% of the energy needed to heat its plasma. Now JET, using an equal mix of deuterium and tritium for fuel, has moved another step closer to self-sustaining fusion, generating more than 12 megawatts of fusion power. "We hope to improve this [value] somewhat over the next weeks," says JET director Martin Keilhacker. He adds that the experiments will help in the planning of the proposed $10 billion International Thermonuclear Experimental Reactor (ITER), which, if built, would use the same fuel mixture.
Fusion experts are excited by the news. "It is wonderful that they have achieved high performance, and I hope they continue their experiments," says William Dorland, a researcher at the Institute of Fusion Studies of the University of Texas, Austin. "It is too soon to know what it means for ITER, but it could be good."