Photo: Joachim Rode

DTU’s own tokamak for fusion energy research

Monday 05 Aug 19


Stefan Kragh Nielsen
Senior Scientist
DTU Physics
+45 46 77 45 34

North Tokamak

DTU’s tokamak—known as the North Tokamak—will be officially inaugurated on 23 August.

The word tokamak comes from Russian—‘toroidalʹnaya kamera s magnitnym polem’ (toroidal chamber with magnetic field).

As the only university in Northern Europe, DTU can now perform fusion energy experiments using its own tokamak.

In one of DTU’s basements stands a so-called tokamak—a unique device that can well play a pivotal role in the University’s research in microwave physics and fusion energy. The tokamak consists of a reactor and a number of associated measuring instruments—the latter built by DTU itself via, among other things, several student projects.

Getting the tokamak to Denmark has required two years’ intense effort by Professor and Head of Section Volker Naulin. The equipment, which costs in the region of EUR 1,4 million (DKK 10 million), was built by UK start-up Tokamak Energy and is on permanent loan to DTU.

“The tokamak arrived at DTU at the end of 2018, and in the early spring, we succeeded in producing the first plasma. This shows that the tokamak is fit for purpose and can be used in our research as soon as we have finished developing all the necessary measuring equipment,” says Senior Researcher Stefan Kragh Nielsen, DTU Physics.

Currently, work is underway to fully automate the tokamak so it can be used by simply pressing a button, thus enabling students interested in fusion energy to work with it.

“The tokamak will give our students the opportunity to see how experiments take place in this type of reactor before having to perform similar experiments at the major international research facilities—e.g. JET in the UK, the Max Planck Institute in Germany, and the upcoming ITER in France,” says Stefan Kragh Nielsen.

“In addition, in future some of our own experiments will be carried out in the tokamak, so we avoid having to wait to book time with the large research infrastructures—just as it gives us the freedom to try out different and perhaps untraditional ideas,” says Stefan Kragh Nielsen.

Student instruments
A number of DTU students have helped to build the instruments which in future will be used to perform measurements in the plasma when the tokamak is used—e.g. to measure density, temperature, and microwave levels. Stefan Kei Akazawa has developed one of the measuring instruments in connection with his bachelor project.

"The tokamak will give our students the opportunity to see how experiments take place in this type of reactor before having to perform similar experiments at the major international research facilities."
Stefan Kragh Nielsen, DTU Physics

“I’ve developed an instrument that can measure the density of electrons in the plasma. It has been an incredibly exciting and challenging task. If we want to obtain good experimental data from the tokamak, my instrument must perform well,” says student Stefan Kei Akazawa, who is delighted to have the opportunity to work with the tokamak.

Three second year students have also worked with the tokamak in connection with a project where they measured magnetic fields.

“It was incredibly exciting to have access to such an expensive measuring instrument—even though we’d just begun our studies,” says Mathias Timmer Sutherland.

“At the same time, it was a huge responsibility to deliver results that are necessary in order for researchers to assess how plasma is created in the tokamak. We also ended up spending many more hours than normal on this kind of projects because it was so exciting,” says Asbjørn Clod Pedersen.

All three students agree that they are attracted by the idea of continuing to work with fusion energy as a possible future green energy source. Stefan Kragh Nielsen is quick to emphasize that there are a large number of other student projects just waiting to be solved.

Facts about fusion energy

Fusion energy is produced by fusing nuclei together—in contrast to nuclear power plants which split atoms.

A tokamak contains 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 as the Sun’s energy source and the one that releases energy.