Greifswald 2024 – scientific programme

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P: Fachverband Plasmaphysik

P 15: HEPP V

P 15.1: Invited Talk

Wednesday, February 28, 2024, 14:00–14:30, ELP 6: HS 3

Particle fueling, profiles and transport in neutral beam heated plasmas at Wendelstein 7-X — •Sebastian Bannmann, Oliver Ford, Peter Poloskei, Jakob Svensson, Samuel Lazerson, Hakan Smith, and Robert Wolf — Max-Planck-Institut für Plasmaphysik, Greifswald, DE

A spontaneous reduction in anomalous particle transport in the plasma core is seen experimentally in reproducible, purely neutral beam (NBI) heated plasma phases at Wendelstein 7-X (W7-X). A significant acceleration of the density peaking occurs after a certain onset time and is examined with a detailed particle transport analysis in several discharges. By invoking the particle continuity equation, the total experimental radial electron flux is deduced from the time evolution of the electron density profile and the radially resolved particle sources. To calculate the neutral beam particle deposition a full collisional-radiative (CR) neutral beam injection model based on Gaussian pencil (Gausscil) beams and a diffusive CR neutral halo model is implemented and verified. All important parameters defining the neutral beams are inferred from Balmer-alpha (Halpha) emission data and compared to available reference values. By employing Bayesian inference techniques provided by the Minerva framework, the full electron density profile from the plasma core to the edge is inferred solely from neutral hydrogen beam and halo Halpha emission data. Exploiting the evolving plasma conditions, anomalous diffusion and convection coefficients are successfully computed from the flux variation with density and density gradients.