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P: Fachverband Plasmaphysik

P 17: Atmospheric Pressure Plasmas - Poster

P 17.1: Poster

Mittwoch, 7. März 2018, 16:15–18:15, Zelt Ost

Analysis and direct comparison of spark discharges in air and water in a sub-mm gap — •Hans Höft¹ and Tom Huiskamp² — ¹INP Greifswald, Felix-Hausdorff-Straße 2, 17489 Greifswald, Germany — ²TU Eindhoven, Dept. of Electrical Engineering, Eindhoven 5600 MB, The Netherlands

In this study, a direct comparison was made between pulsed spark discharges in air and water. Such discharges are often used as spark-gap switches in pulsed power systems. The discharges were ignited at atmospheric pressure in the same discharge arrangement for air and water, using a solid-state microsecond pulse source with ≈ 1 µs voltage rise time (V_max up to 37 kV). Fast voltage and current measurements were combined with iCCD imaging with high spatial resolution (better than 10 µm) on symmetrical half-sphere tungsten electrodes for electrode gaps of 0.1 to 0.7 mm for air (for water d_gap = 0.1 ... 0.3 mm). Breakdown voltages and electrical field strengths, maximal currents, transferred charges, consumed electrical energies and the discharge emission structures (e.g. discharge channel diameters) were obtained for all cases. Using the synchronisation of the electrical data and the iCCD imaging, current and energy densities were estimated for the sparks in air and water. It was found that the breakdown voltage, the discharge current, the transferred charge, and the consumed electrical energy increase with the gap distance and that this dependence on d_gap is much stronger for discharges in water (compared to air). Due to the use of the same discharge arrangement and the same applied voltage, the difference in the electrical characteristics was directly quantified.