Researchers in the Max Planck Institute for Plasma Physics, in Greifswald, Germany said on Dec. 10 that the world's largest stellarator fusion reactor (dubbed Wendelstein 7-X, or W7-X) has started to produce helium plasma.

“Stellarator” is a term coined in the 1950s by the Princeton astrophysicist Lyman Spitzer, who designed the first such machine for exploring fusion reactions in stars. Fusion reactors, such as the W7-X, work by using two kinds of hydrogen atoms — deuterium and tritium — and injecting that gas into a containment vessel. Scientists then add energy that removes the electrons from their host atoms, forming what is described as an ion plasma, which releases huge amounts of energy.

On Dec. 10, researchers injected one milligram of helium into the containment vessel of W7-X and turned on the microwave heating apparatus. Although the helium plasma that was generated only existed for a tenth of a second, researchers were still satisfied with the results and promised that "everything is going according to plan."

After more than 1.1 million construction hours over a 19-year period, the €1 billion stellarator was finally finished in 2014 at the Max Planck Institute for Plasma Physics in Greifswald, Germany. Over the past year, the machine underwent vigorous testing to ensure it performs as expected and operates within safe limits.

Because of the stellarator’s design, experts expect the reactor to confine the plasma and generate energy for at least 30 minutes at a time, which is significantly longer than the 6.5 minutes of competing fusion reactors that use a tokamak-based design.

Nuclear fusion is one of the main possibilities for solving the global energy problem. Tritium and deuterium, both of which are needed for fusion reactions, are found abundantly in nature. The energy produced by one kilogram of material using nuclear fusion is equivalent to the energy produced by 11,000 tons of coal. At the same time, the waste produced by nuclear fusion is less than that currently generated by nuclear fission reactors in nuclear power plants. The radioactivity will disappear in the short term as well. The W7-X stellarator represents the future direction of the development of nuclear reactors.