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Title of the thesis: Impact of charge exchange on energetic ions in fusion plasmas

Thesis defender: Patrik Ollus
Opponent: Professor Alessandro Biancalani, Ecole Supérieure d'Ingénieurs Léonard de Vinci, France
Custos: Professor Mathias Groth, Aalto University School of Science

Harnessing fusion, the nuclear reaction that powers the Sun, is a plentiful, sustainable and safe potential future energy production method being developed on Earth. Inside a device called a tokamak, the fusion reactions take place in a doughnut-shaped ionised gas, i.e. plasma, which is confined by a magnetic field and heated to ten times the temperature of the core of the Sun using highly energetic particles called fast ions. At the edge of the plasma, the electrically charged fast ions are neutralised by charge-exchange reactions with electrically neutral particles of low energy, which allows the fast particles to escape the magnetic confinement, thus decreasing the efficiency of the crucial plasma heating.

For this doctoral thesis, a computational model was developed for simulating fast-ion charge exchange to enable detailed study of this process, which has received little attention until now. The model was extensively tested and applied to experiments to improve general understanding of the process and to investigate its concrete impact on fusion plasmas.

It was shown that charge exchange causes significant losses of heating power in present-day tokamaks. However, the losses depend on how the tokamak is configured, and the process can also have beneficial effects, such as locally increasing current drive in the plasma. The ability to predict the impact of charge exchange on fast ions helps in designing successful experiments and enables improved understanding of fast ions in present-day and future fusion devices.

Keywords: fusion, plasma, tokamak, fast ions, charge exchange

Contact information: patrik.ollus@aalto.fi 

Thesis available for public display 10 days prior to the defence at .