Göttingen 2025 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 10: Poster Session I

P 10.41: Poster

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

Density and Temperature Profiles from Upper Divertor Spectroscopy — •Hannah Lindl¹, Ralph Dux¹, and The ASDEX Upgrade Team² — ¹Max Planck Institute for Plasma Physics, Garching, Germany — ²See author list of H. Zohm et al, 2024 Nucl. Fusion

Reducing the power load on material surfaces is essential for prolonging the lifetime of plasma facing components. The final goal is to reach plasma detachment, resulting in reduced heat and ion fluxes onto the divertor target. We can accomplish this by significantly reducing the electron temperatures T_e near the target plates compared to the upstream values, resulting in effective ion recombination before they make contact with the first wall.

A new measurement technique based on divertor spectroscopy is proposed to determine T_e profiles in the upper divertor region of ASDEX Upgrade (AUG), where we can observe the plasma with high fidelity. This enables us to obtain local data for all spectroscopic accessible quantities by a fit similar to an Abel transform. We aim to calculate T_e(r) in diverted plasmas by measuring local electron densities n_e through Stark broadening of the high-n deuterium Balmer lines D_δ and D_є. Furthermore, we calculate line emissivity profiles є_L(r) via a deconvolution of the spectral radiance L. Assuming Saha equilibrium is established between high-n and continuum states of deuterium, we estimate T_e(r) by combining n_e(r) with є_L(r).

In this contribution, the technique is applied to first measurements of the upper divertor spectroscopy in upper single null discharges at AUG and first n_e and T_e profiles in this region are shown.

Keywords: Spectroscopy; Divertor physics; Temperature Measurements; Detachment