German physicists have broken ground with a new record for nuclear fusion reactors, bringing the world one more step closer to the holy grail of nuclear energy.

In their most recent experiment done on Wendelstein 7-X stellarator, scientists at the Max-Planck Institute for Plasma Physics in Greifswald say the magnetic confinement fusion reactor reached a temperature of 40 million Kelvin. This is nearly three times hotter than the core of the sun, which registers at 15 million Kelvin.

What Is Nuclear Fusion?

Nuclear fusion is essentially the same process that gives birth to stars. It involves hydrogen atoms moving at high temperatures and high pressures crashing into each other to form helium.

The collision generates enormous amounts of energy, which can theoretically be used as a clean source of unlimited electricity. A single spoonful of hydrogen atoms can produce as much energy as 28 tons of coal without the nasty side effects made by nuclear fission as can be seen in Chernobyl and Fukushima.

There are, of course, a few requirements for nuclear fusion. For one thing, it requires special types of hydrogen isotopes called tritium and deuterium. For another, fusion reactors need to be as hot as 100 million degrees Kelvin, around the same temperature found at the core of the hottest stars in the universe.

How A Stellarator Works

A stellarator is a type of fusion reactor that uses superconducting magnets to create a soup of highly charged particles called plasma. This is then heated up to fuse the hydrogen atoms that release energy.

Stellarators have mostly gone out of fashion in the 1960s when Soviet scientists unveiled the donut-shaped tokamak, examples of which are MIT's Alcator C-Mod and Tokamak Energy's ST40.

Both fusion reactors use magnets to generate plasma, but stellarators use a bank of magnetic coils to keep the plasma in a twisting, spherical shape. The design's objective is to remove the instabilities that can plague tokamak reactors, suggesting that stellarators may not be so outdated after all.

The Wendelstein 7-X has 50 magnetic coils with a height of 3.5 meters. These keep the twisting plasma in place, allowing it to maintain its temperatures for a longer period of time.

Smashing Records

The Wendelstein 7-X, which was first turned on in 2015, has gone on to break its own records. Previous experiments have registered a temperature of 1 million degrees for 6 seconds. However, the latest test shows the stellarator has created a new record in terms of temperature, plasma density, and time of confinement.

The stellarator has reached a temperature of 40 million Kelvin at a plasma density of 0.8 x 1020 particles per cubic meter. This was maintained for a total of 26 seconds. Operators were also able to feed it as much as 18 times more energy, reaching up to 75 megajoules of energy that was fed into the plasma.

"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," says Thomas Sunn Pedersun, director of institute's Stellerator Edge and Divertor Physics Division. "This makes us optimistic for our further work."

The record-breaking fusion product was made possible by upgrading the interior components of the Wendelstein 7-X. A new lining of graphite tiles for the chamber allowed the plasma to reach higher temperatures. The lining, called a divertor, keeps the plasma in its twisting sphere while protecting it from stray particles that may make it unstable.

Scientists at the institute hope to replace the divertor with water-cooled carbon-reinforced carbon. This will allow the stellarator to reach even higher temperatures at plasma pulses that can last up to 30 seconds.

The details of the new experiment are published in the journal Nature.

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