German Nuclear Fusion Reactor Moves Closer to Sustainable Fusion Power

Closer and closer
The Wendelstein 7-X stellarator fusion reactor
(Photo: Max Planck Institute for Plasma Physics )

Germany claims it's moved one step closer to generating clean fusion power after another series of successful tests using a different kind of fusion reactor called a "stellarator." 

Located at the Max Planck Institute for Plasma Physics in Germany, the Wendelstein 7-X reactor is the largest stellarator reactor in the world. A stellarator is a device used to confine hot plasma with magnetic fields to sustain a controlled nuclear fusion reaction.

 A stellarator arranges the magnetic fields it generates so that particles circulating around the long axis of the machine follow twisting paths. This circuitous route cancels out instabilities seen in purely toroidal machines such as the doughnut-shaped tokamak.

A tokamak is one of several types of magnetic confinement devices being developed that produce controlled thermonuclear fusion power. It is the favored contender for a practical fusion reactor. On the other hand, a stellarator is one of the earliest fusion power devices, having been invented in 1951, but continues to be used to this day.

The Germans report their Wendelstein 7-X stellarator reactor has broken records for the highest plasma and energy density from fusion. This breakthrough follows the second round of tests lasting from July to November using the Wendelstein 7-X.

The Germans claim their Wendelstein 7-X has now broken records for producing the highest density of plasma (2 x 10^20 particles per cubic meter) and the highest energy density (more than one Megajoule). These steps bring Wendelstein 7-X one step closer to being suitable for clean fusion power.

They also say they've achieved long-lasting plasma reactions of 100 seconds for the first time - another record for a stellarator device.

Nuclear fusion reactors mimic the mechanism our Sun and the stars use to produce a near-infinite amount of heat and light in a process called nuclear fusion. The Sun generates heat and light by fusing together two atoms of hydrogen and this reaction releases enormous amounts of energy. This process of called nuclear fusion has long been bandied about as the future of clean and near-limitless energy on Earth.

The Germans noted that reactors and nuclear energy projects around the world, particularly in the United States and China, have managed to sustain these fusion reactions for several minutes at a time.  For nuclear fusion reactions to be sustainable, however, the plasma (which are charged atoms of a gas at very high temperatures) needs to be suspended by a magnetic field at extremely hot temperatures so the atoms can fuse.

Researchers remain unsure as to what this temperature needs to be. But they do agree the reaction will need at least six times the Sun's core temperature, which 15 million degrees Celsius.

The device used by most reactors in the world to attempt these fusion reactions is the tokamak. But the Wendelstein 7-X stellarator reactor in Germany uses a huge number of twists and turns in which the plasma is contained using a magnetic field.

A stellarator uses a complex 3-dimensional arrangement of coils and loops to control the flow of super-hot plasma through the device's loops, keeping it stable.

Wendelstein 7-X will provide evidence that stellarators are a good design for sustainable nuclear fusion plants, but only if they're successful.

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