After 19 years, 1.1 million work hours, and over 1 billion euro, scientists at the Max Planck Institute in Germany have just completed work on a fusion reactor unlike anything built before—and it may turn the world of nuclear power on its head.
The Wendelstein 7-X reactor (designed by a supercomputer) is a device known as a stellarator, and is the largest of its kind ever built. Similar to the tokamak, the nuclear fusion device that scientists normally use, stellarators trap superheated gasses inside a ring of magnetic fields. But the doughnut (torus) shape of the magnetic field cage poses a problem: the rings that create the magnetic field are closer together on the inside of the torus, so the magnetic field is stronger there and weaker along the outer rim.
Stellarators and tokamaks differ in how they solve this problem. Tokamaks use an electrical current to twist the electrons and ions in the plasma so that they loop vertically as well as horizontally (imagine a cruller instead of just a doughnut). Stellarators impose this cruller shape by their construction, by wrapping more coils of wire around the torus. According to Science, this makes them much harder to build than tokamaks, but eliminates the need for the electric current. (This is significant because if the current falters in a tokamak, it can cause a disruption of the magnetic field and potentially damage the reactor.)
Despite this, tokamaks are generally regarded as being better at containing the plasma, and so nuclear power has been focused primarily on those devices for decades. Now, scientists are holding their breath to see how well this new stellarator performs.The Wendelstein 7-X is awaiting approval to switch on from Germany's nuclear regulators, which it expects to be granted at the end of October.