Scientists are getting ready to switch on the world’s largest ‘Stellarator’ fusion reactor.
Dubbed Wendelstein 7-X (W7-X), the reactor can continuously contain super-hot plasma for more than 30 minutes at a time.
Researchers claim the unusual design, which is housed in a huge lab in Greifswald, Germany, could finally help make fusion power a reality.
Containing super-hot plasma for long periods has been the Holy Grail for reactor designs, and could help scientists provide an inexhaustible source of power.
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.
Scientist 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.
Strong magnetic fields are used to keep the plasma away from the walls; these are produced by superconducting coils surrounding the vessel, and by an electrical current driven through the plasma.
The most common design for a reactor is something known as a Tokamak, which is a hollow metal chamber in the shape of a donut.
The fuel is heated to temperatures in excess of 150 million°C, forming a hot plasma.
While the Tokamak design is ideal for containing this plasma, it poses some safety risks, for instance, if the current fails or there’s a magnetic disruption.
These disruptions can unleash magnetic forces powerful enough to damage the reactor.
Scientists at the Max Planck Institute say the W7-X is a more practical option and can overcome the safety problems of a Tokamak reactor, according to an in-depth report in Science.
‘Tokamak people are waiting to see what happens. There’s an excitement around the world about W7-X,’ engineer David Anderson of the University of Wisconsin, Madison told Science.
In tokamaks, two sets of magnets are used to contain the plasma; an external set surrounding the vacuum chamber and an internal transformer that drives current in the plasma.
This causes the magnetic field to be stronger in the centre than it is on the outer side.
As a result, plasma contained in a tokamak can moves to the outer walls where it then collapses.
In stellarators, plasma is contained by external magnetic coils which create twisted field lines around the inside of the vacuum chamber, according to Science.
As such, it overcomes can continuously hold the plasma away from the walls of the device.
Its key component is a ring 50 superconducting magnetic coils approximately 3.5 metres in height. In total the device is 16-meters-wide.
The stellarator design was first thought up in 1951 by Lyman Spitzer working at Princeton University.
But at the time, it was thought to be too complex for the constraints of materials available in the middle of the 20th Century.
Now using supercomputers and new materials, researchers believe they can finally make Spitzer’s vision a reality.
‘We all know the trend of global development, the hunger for energy of emerging economies and emerging countries,’ said Professor Johanna Wanka, Federal Minister for Education and Research.
‘So when we talk about energy, we need research that keeps all options open. And one of these options is nuclear fusion.
‘Wendelstein 7-X is an important step forward allowing us to better evaluate the ‘fusion option.’
The machine took 1.1 million hours to assemble, using what has been described as one of the world’s most complex engineering models.
Testing of the magnetic field in the Wendelstein 7-X fusion device was completed in June – much sooner than expected.
The test revealed that the magnetic cage for the fusion plasma, which has a temperature of many million degrees, was working as scientists predicted.
The device is currently awaiting regulatory approval for a startup in November.
If the machine works, scientists believe it could herald a change in the direction for fusion power.