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Experimental characterization of helium plasma jets

Abstract : This thesis studies an atmospheric pressure helium plasma jet that is powered by positive, unipolar pulses at a kHz frequency. Experiments are performed that focus on the propagation dynamics, flow structure and temperature in a freely expanding jet, as well as the influence of a metallic target on the plasma.Stark polarization spectroscopy yields an axial electric field of around 10 kV/cm in the capillary of the jet and an increase up to 20 kV/cm in the plume, which is constant for different amplitudes and durations of the applied voltage pulse. Thomson and rotational Raman scattering are used to determine the electron density and electron temperature, at different axial and radial positions, as well as the gas temperature and the density of N2 and O2 that are mixed into the helium from the surrounding air.Quantitative comparison of these experimental results with results from a 2D fluid model show a good agreement and allow for a better understanding of the obtained results, namely that the electric field in the ionization front depends linearly on the flow composition at that location. Schlieren imaging shows the onset of turbulent structures at high applied flow rates and at the application of the voltage pulses. The gas temperature, as measured by a temperature probe, is found to increase by around 12 C when the plasma is ignited and by around 25 C when a metallic target is placed in front of the jet.
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Submitted on : Thursday, December 17, 2020 - 5:13:07 PM
Last modification on : Tuesday, January 26, 2021 - 3:00:30 AM


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  • HAL Id : tel-03080479, version 1


Marlous Hofmans. Experimental characterization of helium plasma jets. Plasma Physics [physics.plasm-ph]. Institut Polytechnique de Paris; Technische hogeschool (Eindhoven, Pays-Bas), 2020. English. ⟨NNT : 2020IPPAX062⟩. ⟨tel-03080479⟩



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