From February to August 2025, I had the opportunity to carry out my final-year internship at the Swiss Plasma Center (EPFL), supported by FuseNet. My work took place on TCV (Tokamak à Configuration Variable), a uniquely flexible fusion experiment in Lausanne, where I joined the “fast-ion” group to study the behaviour of energetic particles in magnetically confined plasmas.
Fast ions - produced by neutral beam injection (NBI) or fusion reactions - play a key role in heating the plasma and influencing its stability. However, they are not directly visible, and their distribution must be inferred through indirect diagnostics. I focused on Fast-Ion Deuterium-Alpha (FIDA) spectroscopy, a technique that detects visible light emitted when fast deuterium ions exchange charge with injected neutrals.
Experimentally, I contributed to the commissioning of the FIDA diagnostic, in preparation of future research campaigns, performing dedicated plasma shots with varied beam power, plasma position, and heating conditions. The response to several scenarios has been studied, showing how the distribution of fast ions can be shaped and laying the ground for more advanced studies.
My main task was to set up and validate a forward-modelling workflow integrating simulation codes with magnetic equilibria and plasma kinetic profiles reconstructed from TCV diagnostics. Starting from a theoretical fast-ion distribution predicted by ASCOT (a Monte-Carlo orbit-following code), I simulated the expected FIDA spectra with FIDASIM (a synthetic diagnostic code) and compared them with measurements from the systems installed on TCV. While guiding future improvements in both modelling and hardware diagnostic, this work helped assess the diagnostic’s sensitivity and validate experimental interpretations regarding fast-ion confinement and interplay with magnetohydrodynamic instabilities.
This internship gave me valuable experience at the interface between plasma diagnostics and numerical modelling, and deepened my understanding of how theory and experiment are combined in fusion research. Beyond technical skills in data analysis and programming, I also enjoyed the collaborative atmosphere of the SPC - from explanations and thinking with the scientists to try to understand what is happening inside the plasma to routine meetings with the many research teams.
Working at the Swiss Plasma Center has been both challenging and inspiring, reinforcing my motivation to contribute to the development of fusion energy.