Mirko Salewski at the ITER building site in the South of France. Photo Don Spong

One step closer to realization of fusion energy

Friday 17 Jan 20


Mirko Salewski
Associate Professor
DTU Physics
+45 23 66 84 44
10 years’ research in fast particles in fusion plasma has given increased knowledge of one of the most important fusion energy processes.

Mirko Salewski is Associate Professor at DTU Physics and one of the world’s leading experts in that part of fusion energy which deals with fast plasma particles. He has now gathered his research in a doctoral dissertation that provides an introduction to and overview of this whole area.

Fast particles are formed in connection with the fusion process. They move at high speed and heat the other particles by collision. This generates a high plasma temperature which keeps the fusion process going. The energy is harvested and converted into electricity.

Fusion energy is thus produced by a combination—fusion—of nuclei as opposed to the nuclear fission that occurs in nuclear power plants. Although the fast particles play a crucial role in this process, the current knowledge of these particles is limited. But Mirko Salewski has—through his research—brought us a step closer to characterizing and predicting their movements. We have thus also come closer to being able to control how we can use the particles optimally to generate the desired energy.

“I actually started my research in a completely different field, namely with numerical simulation of fluid dynamics and combustion processes in gas turbines. But already then—at the end of the 1990s—we could see that CO2emissions from the turbines were problematic in terms of global warming. I therefore became interested in fusion energy, which can replace fossil fuels without the risk of radioactivity or meltdown that is connected with nuclear power,” says Mirko Salewski.

Application of well-known method in new area

Part of Mirko Salewski’s work concerns his introduction of tomography as an essential method in the work to understand fast particles. Tomography is a well-known mathematical tool, which has, however, not previously been applied in this area.

“With the tomography method, we’ve been able to demonstrate that fast particles with different speeds behave more or less desirable in terms of heating plasma. Based on this knowledge, we also have a basis for influencing the process in future, so that as much heat as possible is generated in the centre of the plasma, thus producing as much energy as possible,” says Mirko Salewski.

One of the major challenges of fusion energy is that it currently takes more energy to maintain the fusion process than what can be extracted.

Easy to read for non-specialists

There is no doubt that precisely the application of the tomography method has significantly improved the whole research area. Tomography makes it possible to transform the many complicated data measurements of the speeds of fast particles into two-dimensional images. Precisely as we know it from a hospital scanner.

“The images are easy to read, also for non-specialists. For example, our plasma physics students are able to do so after just 3-4 lectures, which obviously increases the scope for greater research initiatives in this area. Initiatives that are necessary to make fusion energy ripe to replace fossil fuels in future,” says Mirko Salewski.

Already before his doctorate, Mirko Salewski—as the leading expert in this area—has been appointed chairman of the group that is to advise the management of ITER on this and related areas. ITER is the world’s largest fusion reactor, which is being constructed in the South of France. Denmark is among the 35 countries behind the plant.

In ITER, the plan is to succeed in extracting ten times more energy than required to drive the fusion process.

The next step for Mirko Salewski’s research is to ensure faster results of the tomography measurements. Today, the large data volumes require a couple of days of calculations before the two-dimensional images are ready. Mirko Salewski would like to reduce this to a few minutes.

“At the same time, I would like to expand the results of the measurements to include 3D images, which can give us new knowledge. In addition, my vision is to include artificial intelligence to help achieve both better and quicker results,” he says.

Fusion energy
Fusion energy is produced by fusing nuclei together—as opposed to the nuclear fission that occurs in nuclear power plants. The process takes place in plasma, which can reach a temperature of well over 100 million degrees Celsius. The temperature at the Sun’s core is approximately 15 million degrees Celsius.

Plasma is formed through the extreme heating of gas, and—in fusion plasmas—helium is produced from hydrogen isotopes in a fusion process. It is the same process that takes place in the sun.

ITER is the world’s largest fusion reactor. It is being constructed in the South of France, between Nice and Marseille.

35 countries are behind ITER. In addition to the 28 EU Member States, the countries involved are Switzerland, China, India, the United States, Russia, and South Korea. Australia and Kazakhstan are affiliated as technical and scientific partners, but are not members of the ITER organization.

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