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P: Fachverband Plasmaphysik

P 9: Atmospheric Pressure Plasmas II - Helmholtz Graduate School III

P 9.2: Vortrag

Dienstag, 19. März 2019, 11:30–11:45, HS 21

Channel Reillumination in Pulsed Corona-like Discharges in Water — •Raphael Rataj, Hans Höft, and Juergen F. Kolb — INP Greifswald, Felix-Hausdorff-Straße 2, 17489 Greifswald

Investigations of corona-like discharges in water have shown the importance of the fall time of sub-microsecond high-voltage pulses regarding a reignition of discharge channels. So far it was reported that, despite similar pulse durations and amplitudes, a reillumination starts either during the high-voltage plateau, the falling edge of the pulses or not at all. Furthermore, a reillumination of a single filament or all previously formed channels were reported. For a detailed study, single, reproducible voltage pulses with adjustable fall times between 20 and 45 ns, amplitudes of 50 kV and 100 ns duration were applied to a point-to-plane geometry in deionized water. Time-resolved measurements of voltage, current and emitted visible light intensity were obtained for individual discharges, and plasma current, discharge energy and channel length could be calculated accordingly. In addition, subsequent images of single discharge events were taken with a framing camera and compared to the electrical measurements. While no change in discharge development was found for the initial phase during the high-voltage plateau, a reillumination was observed only during the falling slope for all applied pulses. A transition from a reignition of single filaments to a reillumination of every channel with decreasing fall time was visible both in the framing camera images and the plasma current. The detailed investigation for each fall time will be presented and a possible explanation for the observed transition will be given.