Future fusion power plants may experience fewer energy losses in their burning plasma than anticipated. The authors of the study - researchers from the EUROfusion consortium, including Dr. Michał Poradziński from the Institute of Plasma Physics and Laser Microfusion (IPPLM) - published this surprising result in the prestigious journal Nature Communications. Their findings, based on experiments conducted in 2021 in the Joint European Torus machine (JET), reveal that a fuel mix containing tritium stabilizes the plasma, significantly enhancing reactor performance. This stabilization reduces turbulence and energy losses, paving the way for smaller, more efficient fusion power plants.
Experiments with deuterium fuel are the most common ones performed nowadays in tokamak (toroidal magnetic trap) experiments all over the world. Many aspects of controlling such plasmas have been investigated so far and are known. Much less common however are experiments with tritium which is a heavier (contains one proton and two neutrons) and unstable isotope of hydrogen. Deuterium is a lighter isotope which contains one proton and one neutron. By adding tritium, we create a D-T mixture which is the actual fuel mix to be used in a power plant.
The fusion of deuterium and tritium will produce a highly energetic neutron and a heavier but still very fast helium ion. That is why D-T plasmas are called "burning plasmas". The JET (Joint European Torus) experiment carried out in Culham (UK) in 2021 was the third in the history after TFTR (1993) and JET (1997) to include tritium in a fuel mixture. It was a huge unknown how tritium, being heavier than deuterium, would affect the confinement of the plasma which is the ability to trap ions by the magnetic field. Another unknown was to what extent the fast helium ions would affect the plasma stability. A recent article published in Nature Communications shows that in conditions close to the ones expected in a future fusion reactor, fast helium ions have a positive effect on plasma stability and tritium has a beneficial effect on plasma confinement. This discovery puts us one step closer to the working fusion power plant.
Dr. Michał Poradziński from the IPPLM, a co-author of the article, does not hide his enthusiasm: "Thanks to the deuterium-tritium experiments we have been able to explore areas of fusion research that have been available to us only using extrapolation from deuterium and hydrogen experiments and by applying known theoretical models. However, due to the complexity of the processes occurring in tokamak plasmas, the theoretical uncertainty of the physical models was large and required verification in the experiment. This research shows that we are never completely sure what is behind the corner. In this case, it turned out that fast helium ions work in our favour by reducing the instabilities. Moreover, the turbulence usually taking place in the outer regions of the plasma core has been reduced which is an unexpected result. This is very good news. It's a very important step towards fusion reactors."
Source: Nature Communications, EUROfusion