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P: Fachverband Plasmaphysik

P 9: Poster I

P 9.44: Poster

Tuesday, March 29, 2022, 16:00–17:30, P

Ignition and propagation of nanosecond pulsed plasmas in water with different polarities — Katharina Grosse¹, Marina Falke², and •Achim von Keudell¹ — ¹Experimentalphysik 2, Ruhr-Universität Bochum — ²CLICCS, Universität Hamburg

Discharges in liquid enable a variety of applications ranging from wastewater treatment to nanoparticle formation. Pulsed plasmas in liquids ignited by voltage pulses with fast rise times and nanosecond pulse lengths yield a high degree of dissociation of the liquid, a high mass transport and efficient reaction rates with surfaces adjacent to the plasma. However, understanding of the ignition and propagation of these plasmas inside the liquid on these short timescales is still a matter of debate. An indirect method to analyze these processes is the comparison of different voltage polarities applied to the electrode. Different possible processes such as gas bubble or nanopore formation, field effects and the presence of a super critical fluid are evaluated and compared with optical emission spectra and ICCD imaging. A 10 ns long voltage pulse with amplitudes of ±20 kV is applied to a 50 µm thin tungsten wire inside distilled water. The emission intensity, electron density and number of H emitters are similar for both polarities except in the first few ns. This indicates different electron generation mechanisms for different polarities at discharge breakdown. Based on these data, we postulate the ignition and propagation processes to result from electron generation from field effects inside a super critical fluid surrounding the electrode tip.