Defence of doctoral thesis in the field of engineering physics, M.Sc. Jari Varje

Nuclear fusion is a promising future energy source with few carbon dioxide emissions and nearly limitless source of fuel in heavy isotopes of hydrogen. Energetic particles, such as fusion-born alpha particles play a vital role in reactor-relevant fusion plasmas, as they are responsible for heating the plasma, but can simultaneously cause localized heat loads and risk of damage on the plasma facing components. This work involved development and application of new tools for modelling the behaviour of fast ions in present-day experiments and predict fast ion confinement and losses in next-generation fusion reactors ITER and DEMO.

Over the course of this work, a highly parallelized version of the ASCOT code, called ASCOT5, was developed. The new version substantially increased the performance on modern supercomputer hardware as well as improving its maintainability and extensibility. The code was validated against experimental results from the present-day JET tokamak reactor.

For predictions in the ITER reactor, simulations showed that including magnetic perturbations and the response of the plasma to them is vital, as the response not only affected the magnitude but also the distribution of losses and wall loads. For DEMO plasmas, the sensitivity of fast ion losses due to various magnetic perturbations was studied, and the design was found to be robust with respect to fast ion confinement and losses.

Opponent is Professor Ambrogio Fasoli, EPFL SB – Swiss Plasma Center, Switzerland

Custos is Professor Mathias Groth, Aalto University School of Science, Department of Applied Physics

Contact details of the doctoral student: [email protected]

The public defence will be organised in Otaniemi and via Zoom. Zoom link

The dissertation is publicly displayed 10 days before the defence in the publication archive Aaltodoc of Aalto University

Electronic thesis