And it worked!
Physicists in Germany announced that they’ve just fired up one of the world’s largest nuclear fusion machines for the first time – and it was successfully able to contain super-hot blobs of helium gas, otherwise known as plasma.
They call this 16-metre (52-foot) wide machine the W7-X which is a Stellarator type of reactor. Following more than a year of tests, engineers fired up the US$1.1 billion machine for the first time. Known in the plasma physics community as the ‘black horse’ of nuclear fusion reactors, stellarators are notoriously difficult to build.
On 10 December, the Max Planck Institute for Plasma Physics tweeted out this image of its new machine’s first plasma:
This video below demonstrates the construction of W7-X, which took 19 years to complete:
Only a handful of stellarators have ever been attempted, and even fewer have been completed. By comparison, the more popular cousin to the stellarator, called a tokamak, is in wider use. There are over three dozen operational tokamaks across the globe, and more than 200 built throughout history. These machines are easier to construct and, in the past, have proven to do the job of a nuclear reactor better than the stellarator.
But tokamaks have a major flaw that W7-X is reportedly immune to, suggesting that Germany’s latest monster machine could be a game-changer. The W7-X was never built to produce energy. This device is simply a proof-of-concept to show that the stellarator concept actually works. If all goes to plan, the things we learned from W7-X will help us build the next-generation of stellarators
How a nuclear reactor works
The key to a successful nuclear reactor of any kind is to generate, confine, and control a blob of super-heated matter, called a plasma — a gas that has reached temperatures of more than 100 million degrees Celsius (180 million degrees Fahrenheit).
At these blazing temperatures, the electrons are ripped from their atoms, forming what are called ions. Under these extreme conditions, the repulsive forces, which normally make ions bounce off each other like bumper cars, are overcome.
Consequently when the ions collide, they fuse together, generating energy in the process, and you have what is called nuclear fusion. This is the process that has been fuelling our sun for about 4.5 billion years and will continue to do so for another estimated 4 billion years. Once engineers have heated the gas in the reactor to the right temperature, they use super-chilled magnetic coils to generate powerful magnetic fields that contain and control the plasma.
The difference between tokamaks and stellarators
For years, tokamaks have been considered the most promising machine for harnessing the power of the sun because the configuration of their magnetic coils contains a plasma that is better than that of currently operational stellarators. But there’s a problem: Tokamaks can only control the plasma in short bursts that last for no more than 7 minutes. And the energy necessary to generate that plasma is more than the energy engineers get from these periodic bursts.
Tokamaks thus consume more energy than they produce, which is not what you want from nuclear fusion reactors, which have been touted as the “most important energy source over the next millennium.” Because of the stellarators’ design, experts suspect it could sustain a plasma for at least 30 minutes at a time, which is significantly longer than any tokamak. The French tokamak “Tore Supra” holds the record: 6 minutes and 30 seconds.
The W7-X could completely turn the nuclear fusion community on its head and launch stellarators into the lime light.