October 2, 2022


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A big step forward in the field of nuclear fusion.  Stars can appear from the shadow of the tokamak

A big step forward in the field of nuclear fusion. Stars can appear from the shadow of the tokamak

| Astronomy / Physics

Stellarators, complex devices for generating plasma and carrying out a controlled thermonuclear reaction, have always remained in the shadow of the tokamak. In the stellar apparatus, the plasma is obtained in a chamber of complex shape, resembling a Mobius ribbon twisted several times, and the coils needed for operation must have different shapes adapted to the shape of the chamber. This makes stellar instruments very complex, but their big advantage – unlike tokamex – Plasma stabilizes.

Max Planck Institute Scott Maceda, PPPL

The difficulties in fabricating the appropriate magnetic coils and the temperature loss due to the complex shape of the stellar chamber meant that we heard and wrote more about the tokamak. However, that may change.

Scientists from the German Institute for Plasma Physics (IPP) in collaboration with scientists from the US Princeton Plasma Physics Laboratory (PPPL) have shown that the world’s largest and newest star, Wendelstein 7-X (W7-X) in Greifswald, Germany, has achieved a temperature of twice that As high as the temperature of the sun’s core.

This was made possible thanks to the XICS Diagnostic Tool, a joint work of Novimir Pablant of PPPL and Andreas Langenberg of IPP. This instrument showed that it is possible to significantly reduce heat loss in the star. So far, the classic stars have lost a lot more of it than the tokamak.

The weak point of star devices is the entry of particles into the neoclassical mode of transport, which is manifested, among other things, by the push of pollutants into the center of the plasma and its rapid cooling […]. In stars, neoclassical particle entrapment is much greater than in tokamak. […] The advantages of the tokamak include its simple structure (geometry) and neoclassical transmission much lower than in the stellarator, states Natalia Wendler in her doctoral thesis titled Plasma studies using the PHA diagnostic system on a Wendelstein 7-X stellarator.

In the most recent report published in temper nature Experts reported that they were able to reduce the neoclassical transmission by using a properly shaped magnet. This is a huge success that gives hope that nuclear fusion will finally be brought under control.

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Thermonuclear reaction (nuclear fusion) is a phenomenon where lighter nuclei fuse into one heavier nucleus. As a result, a large amount of energy is generated. If it could be mastered, we would have at our disposal an almost inexhaustible source of cheap and safe energy. So fusion has many advantages over nuclear fission of heavy atoms into lighter atoms, which we use in nuclear power plants. The problem is that we still can’t control the fusion reaction and extract excess energy from it, ready for commercial use

The interstellar star is one of the first fusion devices. It was invented in the 1950s by physicist Lyman Spitzer, later founder of the Princeton Plasma Physics Laboratory. By the way, Spitzer was also the founder of the construction of space telescopes.

As already mentioned, stellar stars lose heat more than tokamaks, but they also have many advantages. Its advantage depends on the continuous operation capability, the approximation of the instability of the MHD type, and the abrupt fading of the reaction associated with exceeding the Greenwald limit, which was not observed in this design. All this makes stellar devices more attractive for a future fusion power plant, if only the retention of neoclassical charged particles can be improved. However, over the past 60 years, more emphasis has been placed on the study of tokamak, which has led to significant advances in the field.We read in the works of Natalia Wendler.

Now, in the W7-X stellarator launched a few years ago, it’s been proven that these devices don’t have to lose much heat. The research conducted with the XICS instrument showed that the temperature of the ions was too high to have been possible without a significant reduction in neoclassical transport. The measurements were confirmed with the less accurate CXRS instrument.

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The results of these studies indicate that star devices with a W7-X architecture could be the main reactors through which nuclear fusion can be managed. However, the limitation of neoclassical transmission is not the only problem we have to face. There are still a number of issues involved, including dealing with continuous operation and reducing turbulent transportationBablant says. The turbulent transport causes eddies and waves to travel through the plasma, which is the second most important cause of heat loss.

Next year, the W7-X will be in full swing again. In the past three years, a new cooling system has been installed in the Stellarator, which will enable it to operate for much longer.

stellarator tokamak neoclassical transport plasma nuclear fusion