Twisting design of fusion reactor is thanks to supercomputers

The design of the Wendelstein 7-X reactor allows for a magnetic field to hold the high-temperature ionised plasma in place, thus allowing for a stable fusion reaction. Image courtesy of the Max-Planck-Institute for Particle Physics

With hundreds of viewports of different lengths jutting from its outer wall, the Wendelstein 7-X looks otherworldly—more like science fiction than an experimental fusion reactor dreamt up by human beings. That's because the humans had help.

The breakthrough design of the fusion reactor, located in Greifswald, Germany, was only possible using extremely powerful computers known as supercomputers.

'It looks a little bit like an alien ship. But that's just the outcome of a very systemic physics and engineering process that is behind it,' explained project leader Professor Thomas Klinger of the Max-Planck-Institute for Plasma Physics in Germany.

The strange-looking layout of the Wendelstein 7-X, created with the help of EU research funds, is a result of the unique needs of its stellarator design, so-named because it mimics the conditions taking place inside stars, where huge amounts of energy are released by fusing hydrogen into helium.

Nuclear fusion could provide cheap, clean energy if attempts to build a fully operational reactor are successful. However, it is only possible at incredibly high temperatures, around 100 million degrees Celsius, where electrons are stripped from hydrogen atoms to create ionised plasma. Such plasma must be kept hot enough for fusion to occur and material walls would cool it down, which is why scientists must trap the plasma using powerful magnets.

'The magnetic field coils have to have just the shape to create the right magnetic field,' Prof. Klinger said. 'We have been doing a long research phase of 20 years in which it was found out what the actual field is we need, or the plasma needs, for being well-confined.'

Those requirements led to the Wendelstein device, where scientists, with the help of the supercomputers, created a uniquely shaped superconducting magnet system to hold the plasma. That is then surrounded by an outer vessel to keep the coils cool in a vacuum at -270 degrees Celsius with liquid helium.

Keeping the plasma confined is the number one challenge faced by scientists. In February, the project began testing the system with hydrogen plasma for the first time.

'The first hydrogen plasma had a duration of 40 milliseconds, so pretty short. Since then, we have made a lot of progress, and we were able to create hydrogen plasma more recently for 8 seconds. So that's an increase by a factor of 200,' Prof. Klinger said.

By the summer of next year, the team hopes to be running the stellarator at full power for ten seconds, after installing more graphite elements for the wall. After that, they plan to introduce active water cooling, which they hope will enable them to run the device for 30 minutes.

(Read on on Horizon Magazine)

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