Hannover 2020 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 2: Atmospheric-pressure plasma and applications 1
P 2.3: Vortrag
Montag, 9. März 2020, 11:45–12:00, b305
Breakdown and development of sub-ns pulsed spark discharges in short gaps under overvoltage conditions — •Hans Höft1 and Tom Huiskamp2 — 1Leibniz-Institut für Plasmaforschung und Technologie e.V. (INP Greifswald), Felix-Hausdorff-Straße 2, 17489 Greifswald, Germany — 2Eindhoven University of Technology, Dept. of Electr. Engineering, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
Spark discharges were ignited by unipolar positive and negative rectangular HV pulses with 200 ps rise time and (15 ±2) kV amplitude with 3 ns duration (FWHM) in N2 and synthetic air in a 1.2 mm pin-to-pin gap (tungsten electrodes) at atmospheric pressure. The breakdown and development of the discharges were tracked by synchronised iCCD and streak camera recordings (temporal resolution up to 5 ps, spatial resolution 2 µm) in single shot operation. A two-stage breakdown regime was found, which—to the best of our knowledge—was documented for the first time. The discharge starts with a fast initial breakdown over the complete gap (∼ 107 m/s) followed by a much slower (∼ 105 m/s) propagation from both electrodes towards gap centre. There is a significant difference between positive and negative HV pulses during the initial breakdown phase, while the general discharge structure stays more or less the same, and is only slightly affected by the gas mixture. A possible explanation of the initial rapid breakdown could be field emission caused by the extremely fast rising electric field due to the steep HV slope rising with > 50 kV/ns.