Sparking up the stellarator

By the time you’re reading this, the world could be one step closer to clean, limitless energy. Some time in early December 2015, the Wendelstein 7-X fusion stellarator will be powered up, super-heating plasma to millions of degrees for the very first time. Known as W7-X, it is the largest stellarator ever built, a two-decade labour of love undertaken by the Max Planck Institute for Plasma Physics (IPP) at its Greifswald branch in north-east Germany.

For decades, nuclear fusion has been hyped as a potential solution to humanity’s energy needs. Replicating the same process that fuels the sun, the reactors aim to fuse hydrogen isotopes (deuterium and tritium) together to form helium, releasing huge amounts of neutron energy. Fusion in the sun takes place at extreme pressures, with temperatures of around 10 million degrees Kelvin (K). On Earth, where those pressures can’t be replicated, the temperatures required are about 100 million K. Naturally, that means a massive energy input, and current fusion reactors suck up more energy than they create. It’s a hugely promising technology, but one that remains commercially unviable, the old line being that it is always 20 years away, forever out of reach.