In a major step towards the possibility of a nuclear fusion reactor, a team of German scientists has confirmed its experimental stellarator has passed tests with “unprecedented accuracy”.

Despite once being thought of as an impossible dream, a working nuclear fusion reactor capable of producing near-limitless, cheap and clean energy is gradually becoming more science than science fiction.

While a number of different reactor designs are currently being tested, one of the most promising examples is found in Germany, where researchers at the Max Planck Institute – in conjunction with the Princeton Plasma Physics Laboratory – are working on the Wendelstein 7-X (W7-X) fusion energy device.

Often referred to as the Greifswald device, it is the world’s most sophisticated stellarator that aims to provide an alternative to the much more common tokamak research model.

The W7-X confines plasma – that fuels fusion reactions – in 3D magnetic fields with little risk of disruption. This differs from the tokamak, which can abruptly halt in 2D fields, resulting in the reactors shutting down.

In a paper published in Nature Communications, the team found during rigorous testing that it only deviated from its designed configuration in less than one part in 100,000, making this a key step towards verifying the feasibility of stellarators as models for future fusion reactors.

‘Unprecedented accuracy’

“To our knowledge,” the authors of the research paper wrote, “this is an unprecedented accuracy, both in terms of the as-built engineering of a fusion device, as well as in the measurement of magnetic topology.”

To actually make these unprecedented measurements, the research team launched an electron beam along the magnetic field lines.

Afterwards, the team obtained a cross-section of the entire magnetic surface by using a fluorescent rod to intersect and sweep through the lines, thereby inducing fluorescent light in the shape of the surface.

This latest breakthrough, the team theorises, could help provide an answer to the question of whether stellarators are the right concept for fusion energy – but admitted that “that task has just started”.