German Nuclear Reactor Breaks New Fusion Record

Wendelstein 7-X (W7-X) is tipped to be one of the game-changing designs that could make commercial nuclear fusion reactors a reality. The test so far has been extremely positive and during the latest round of experimentation, it broke several records.

W7-X's latest run started after some important adjustments. Since last September, the reactor has been fitted with new and snazzy interior cladding made of graphite. This allowed W7-X to contain a hotter and denser plasma. Details are published in Nature Physics.

W7-X is a stellarator, one of the two main approaches used to construct a functional nuclear reactor. It is shaped like a twisted doughnut. Magnets are wrapped around the stellarator to keep the plasma confined. The machine was able to take the plasma to a temperature of 40 million degrees Celsius (72 million degrees Fahrenheit). The plasma was kept fusing for up to 26 seconds, a significant increase from the six seconds of the first run. By keeping the plasma in the chamber for longer it got the world record for fusion production using a stellarator.

“This is an excellent value for a device of this size, achieved, moreover, under realistic conditions, i.e. at a high temperature of the plasma ions,” co-author Professor Thomas Sunn Pedersen said in a statement. “First experience with the new wall elements are highly positive. This makes us optimistic for our further work.”

The goal of the project is to make stellarators commercially viable. To do so, it is necessary to create a plasma that exceeds 100 million degrees Celsius (180 million degrees Fahrenheit). At that temperature, the hydrogen from the plasma will convert into helium releasing more energy than is required to heat up the plasma.

Keeping the temperature up is crucial and that’s why the plasma needs to be kept away from the cold walls. The strong magnetic fields and shape of the machine are optimized to minimize interactions. W7-X is made of 50 superconducting magnets, each around 3.5 meters high. Despite its size, W7-X will never produce more energy than it consumes. It is just a proof-of-concept for a much bigger commercial version.

The other design for fusion reactors is called a tokamak. A prototype for a commercial version of this kind is currently being built in France.

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