München 2019 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 18: Postersitzung

P 18.54: Poster

Donnerstag, 21. März 2019, 16:30–18:30, Foyer Audimax

Influence of the optical thickness on the evaluation of the He beam diagnostics at ASDEX Upgrade — •Daniel Wendler1,2, Michael Griener1, Ralph Dux1, Elisabeth Wolfrum1, Ulrich Stroth1,2, and the ASDEX Upgrade Team11Max-Planck-Institut für Plasmaphysik, Garching, Germany — 2Physik Department E28, TUM, Garching, Germany

For magnetically confined fusion plasmas, the behaviour of the plasma edge layer is crucial to achieve a sufficient confinement. To measure the electron density and temperature at the plasma edge of ASDEX Upgrade, helium is injected by a fast valve. The helium cloud is observed on 20 radial positions with a temporal resolution of 1µs. The injected helium is excited mainly by electron collisions. Four transitions in the visible light range are evaluated. The ratio between a singlet and triplet transition is sensitive to the temperature, whereas a ratio of transitions from different angular momentum states is sensitive to the density. These ratios are then compared with results from a collisional radiative model, which relates the state changing processes in the plasma to the measured emission in order to calculate the underlying electron temperature and density.
First results from this diagnostic show implausible temperatures near the injection valve. This is assumed to be caused by the absorption of ultraviolet resonance lines which causes a change of the population density, leading to a modification of the observed line ratios. The progress in the numerical work to simulate the opacity effects on the evaluation of temperature and density measurements is presented.

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