pushed a reactor at 100 million degrees for 30 seconds

The exploits of this South Korean tokamak will directly benefit ITER, the leading nuclear fusion project in France.

Korean physicists have just taken an important step in the future of nuclear fusion work with their experimental reactor Korea Superconducting Tokamak Advanced Research Center (KSTAR); for 30 seconds it managed to maintain a temperature of 100 million degrees Celsius. Excellent news for ITER, the great international project in France.

The KSTAR is not on the first attempt; since 2008, this reactor has served as an experimental platform to study the concepts that will one day be used to make ITER work. And this combination of truly impressive numbers represents great progress.

This temperature, although close to 7 times larger than that of the solar core, does not in itself constitute a record. The same goes for the 30 second operation. But the fact that it worked? achieving at the same time is a very good first, and a new step towards commercial nuclear fusion.

Don’t touch the wall

Very vulgarly, the purpose of a tokamak, such as EAST, KSTAR, or ITER, is to force carefully prepared atoms to collide at monstrous speed. To achieve this enormous nanometric revolution it is necessary to maintain an absolutely infernal temperature of several tens of millions of degrees.

However, generating such a temperature is not easy, far from it; engineers are constantly trying to push the boundaries of different prototypes to reach the famous 150 million degrees Celsius mark. It is from this temperature (which varies according to the machines) that the conditions become ideal at the threshold of the enclave, and thus the fusion reaction in the plasma can begin.

this furnace, no material in the world can support it. To trap this superheated plasma, the tokamaks are equipped with giant electromagnets; they generate a magnetic field that keeps the ionized material at a good distance from the reactor walls.

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It is very important for the stability of the reaction and it is not just about productivity. Of course, in this context, there is no risk of a Chernobyl-type disaster; but if the plasma comes into contact with the inner walls of the reactor, it can still cause catastrophic damage to this extremely expensive and very difficult to maintain device.

And at this level, researchers have no room for error. The smallest point of contact between the superheated plasma and the inner walls near absolute zero, secretly how-immediately stops the system; this then causes a snowball effect which causes the reaction to fall like a soufflé.

A new form of magnetic field

To avoid this scenario, researchers are experimenting with different forms of magnetic fields. The goal is to collect the plasma as efficiently as possible. It is a very important subject of study in this discipline; for example, we remember the work of DeepMind. The company specializing in artificial intelligence has even gone so far as to develop an algorithm to optimize the shape of the magnetic field.

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To achieve this impressive combination of stability and temperature, KSTAR physicists relied on a modified version of a form of magnetic field called an internal transport barrier. The peculiarity of this model is that it tends to make the plasma in the center of the reactor denser. Instead, it is scarcer on the outskirts, near the walls.

They have a slightly lower density than expected. This is usually not good news. The energy produced by a reactor directly depends on the temperature, density and confinement time of the plasma.

But in this case, the researchers explain that that modest density wasn’t a problem. Eventually it was compensated for by the temperature and the presence of highly energetic ions in the center of the plasma. These play an important role in the stability of the reaction.

The road is still long

Of course, these numbers are very impressive; but in absolute terms, the KSTAR and the other tokamaks are far from being able to maintain the conditions necessary to sustain a fusion reaction for a long period of time. The challenge from now on is to learn how to push these tokamaks further. Even higher temperatures and, above all, longer confinement times are achieved without damaging the reactor.

And this is just the tip of the iceberg of nuclear fusion. There are many other problems waiting for engineers around the corner. At present, for example, there is no indication that the information from these experimental tokamaks will be valid even for larger reactors.

And sooner or later the issue of energy efficiency will also have to be addressed. Because as it is, it’s not even about recovering the energy produced by the reaction. This means that, in addition to the energy used to heat the plasma and cool the enclave, all the energy produced by the reaction is also sacrificed on the altar of experimentation.

Suffice it to say that while this progress is impressive, we will have to be patient. Sure, the underlying physics are starting to take hold. But enormous technical challenges now await the turn of the specialists.

Target temperatures and confinement times are unlikely to be achieved until these experimental tokamaks are repeated for several years. JET, KSTAR and their spouses will therefore remain key players in nuclear fusion research for many years to come.

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