After 19 years of construction, the world’s largest fusion reactor goes online this month

In Germany, a team of researchers are preparing to switch on the largest nuclear fusion plant in the world. Hosted at the Max Planck Institute, the stellarator, also known as Wendelstein 7-X (W7-X), is awaiting regulatory approval for a launch later this month, reports Science.  When it goes online, W7-X will best the Large Helical Device (LHD) in Toki, Japan, which began operating in 1998 and is currently the largest working stellarator.

The project to build the W7-X was started in 1993, after the German government approved the project and established the Greifswald Institute to help build the machine. The project has had its share of ups and downs, with faulty magnets and unexpected technical issues leading to delays. Construction of the W7-X almost came to a standstill when a magnet supplier went bankrupt and technical issues forced the team to send back multiple parts for redesign.

In May of 2014, after more than 1.1 million construction hours over a 19-year period, the €1 billion stellarator was finally finished. Over the past year, the machine underwent vigorous testing to ensure it performs as expected and operates within safe limits. Now scientists are waiting for the green light to bring plasma into the facility and test the nuclear fusion reaction.

Unlike conventional nuclear reactors that rely on the breakdown of atoms, a process called fission, nuclear fusion generates energy by fusing parts of atoms together. The nuclear fusion reactor uses high temperatures, as high as 100 million degrees Fahrenheit, to heat plasma, while powerful magnetic fields — up to 50 six-ton magnetic coils in the case of the W7-X — are used to contain and control it.

Scientists must now wait until the end of the month for government approval before they can bring in plasma and begin their first real test of the W7-X. Because of the stellarator’s design, experts expect the reactor to confine the plasma and generate energy for at least thirty minutes at a time, which is significantly longer than the six and a half minutes of competing fusion reactors that use a tokamak-based design.

“The world is waiting to see if we get the confinement time and then hold it for a long pulse,” said David Gates, the head of stellarator physics at Princeton’s Plasma Physics Laboratory.