Bochum 2015 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 15: Poster Session - Magnetic Confinement
P 15.2: Poster
Dienstag, 3. März 2015, 16:30–18:30, Foyer Audimax
Effects of increased microwave heating power in the stellarator TJ-K — •Alejandro Muñoz, Alf Köhn, Ahmed Ali, and Mirko Ramisch — Institute of Interfacial Process Engineering and Plasma Technology, University of Stuttgart, Stuttgart, Germany
One of the microwave heating systems at the stellarator TJ-K has been recently upgraded: a third klystron has been installed, increasing the heating power from 4 kW to 6 kW operating at 14 GHz. A phased-array antenna is used which allows to vary the injection angle by sweeping the microwave frequency in order control the coupling mechanism of the microwave to the plasma. With the two klystrons already installed, ionization degrees of α ≃ 1 have been reached. We expect that an increased heating power, by means of the third klystron put into operation, leads to an increase in the electron temperature Te only, rather than in electron density ne, and thus a decrease in the collision frequency νei ∝ ne Te-3/2 which has an impact on heating flow damping and neoclassical properties.
Parameter scans have been performed in order to characterize the new heating scenario. A radial movable Langmuir probe has been used to obtain radial profiles of the electron density and temperature. An arrangement of bolometers and an optical diode have been used to obtain the power losses by radiation. A particle and power balance model is used to obtain estimated densities and temperatures in order to compare with the experimental results.