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P: Fachverband Plasmaphysik

P 9: HEPP III

P 9.5: Talk

Tuesday, February 27, 2024, 15:40–16:05, ELP 6: HS 3

Spectroscopy based inference of impurity transport at the plasma edge in different tokamak confinement regimes — •Tabea Gleiter^{1, 2}, Ralph Dux¹, Francesco Sciortino³, Tomáš Odstrčil⁴, Thomas Hayward-Schneider¹, Daniel Fajardo¹, Ulrich Stroth^{1, 2}, and the ASDEX Upgrade Team⁵ — ¹Max-Planck-Institut für Plasmaphysik, Garching, Germany — ²Physik-Department E28, Technische Universität München, Garching, Germany — ³Proxima Fusion GmbH — ⁴General Atomics, San Diego, USA — ⁵Authors of U. Stroth et al. 2022 Nucl. Fusion 62 042006

We present the inference of radial impurity diffusion and convection profiles in steady state discharges. The experimental basis are customized charge exchange recombination spectroscopy (CXRS) measurements, yielding line radiances from multiple impurity charge states. A forward model based on the impurity transport solver Aurora is able to generate synthetic CXRS-data for given transport coefficients. It requires additional inputs, such as neutral beam and thermal deuterium densities, kinetic profiles and atomic rate data. This model is used for a Bayesian inverse inference of transport coefficent probabilities. Due to the complexity, the selection of suitable free parameter sets, prior distributions and data likelihoods is important.

The framework is mostly suitable for the plasma edge, i.e. where impurities are not fully ionized. Since the pedestal impurity transport in tokamaks is crucial for energy confinement and radiative power exhaust, we compare various confinement regimes at ASDEX Upgrade, including promising reactor scenarios without large ELMs.

Keywords: tokamak; impurity transport; spectroscopy; Bayesian inference; plasma edge