Nuclear fusion should be the future of any sane government energy policy. It is the most energy dense method of power generation that we are aware of. It's clean, and it doesn't emit any of those harmful, poisonous, carbon dioxide fumes we hear about from time to time.
Whereas nuclear fission - the type of nuclear power generation in use today - occurs when energy is released as the result of splitting an atom apart, fusion occurs when atomic nucleii fuse together to form a heavier nucleus. This is the process going on inside the Sun.
Reproducing the processes going on inside the sun is technically very complex, and therefore difficult. The gas which is used to produce the reactions is heated to several million degrees, at which point it becomes plasma. Sometimes in the plasma, an instability will appear and grow large enough to unsettle the plasma, making it vibrate despite the presence of the magnetic field which contains it. As the vibrations build, it is possible that plasma touches the walls of the reactor. When that happens, it cools rapidly, killing fusion and potentially damaging the reactor.
The challenge is to reduce the instabilities deep within in the interior of the plasma so that they don’t amplify, while at the same time allowing the reactor to continue to function normally, and it is in this area that the breakthrough has been achieved.
Jonathan Graves and his colleagues at the Ecole Polytechnique Federale de Lausanne in Switzerland, were able to quench the instabilities in the gas plasma as soon as they appeared, by adjusting an antenna which emitted strong electromagnetic radiation. Their approach doesn't add any physical complexity to the reactor because the antennae used to quench the instabilities are the same antennae used to heat the plasma in the first place.
The team tested their solution on the Joint European Torus, the largest reactor currently in use. The next step will be to add a detector system which will allow them to control the instibilities in real time automatically. If successful, these improvements will be added to the ITER reactor, currently under development in Souther France.