Göttingen 2025 – scientific programme

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P: Fachverband Plasmaphysik

P 17: Poster Session II

P 17.10: Poster

Wednesday, April 2, 2025, 16:15–18:15, ZHG Foyer 1. OG

Gyrokinetic studies of dominant instabilities in different particle transport regimes in Wendelstein 7-X — •Nico J. Guth, Josefine H. E. Proll, Sebastian Bannmann, Oliver P. Ford, and Gabriel G. Plunk — Max Planck Institute for Plasma Physics, Greifswald, Germany

One of the key aspects for ensuring efficient and stable fusion energy production in a future stellarator is to accurately predict the plasma density profiles and their time evolution. In a stellarator, ions and electrons stream freely along magnetic field lines, leading to nested toroidal surfaces of nearly constant density (and temperature). Thus, the main interest of the study of particle transport lies in the perpendicular (radial) direction, with a goal of understanding which plasma conditions lead to favourable density peaking near the magnetic axis and which conditions degrade particle confinement. Optimized stellarators, like Wendelstein 7-X (W7-X), are specifically tailored to reduce the average outward drifts of trapped particle orbits, leading to reduced neoclassical transport. Experiments have however shown that transport is larger than predicted, which can be attributed to turbulent processes in the plasma on the gyroradius scale. Recent experimental work (Bannmann et al 2024) indicates a change in turbulent particle diffusivity (and convectivity) above a critical density gradient. Using gyrokinetic simulations, this qualitative change is investigated with a focus on changes in dominant instabilities as well as simple quasi- linear estimates of the corresponding fluxes.

Keywords: stellarator; fusion; turbulence; simulation; gyrokinetics