Hannover 2016 – scientific programme

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P: Fachverband Plasmaphysik

P 2: Plasma Diagnostics I

P 2.4: Talk

Monday, February 29, 2016, 12:10–12:25, b305

Laser four-wave mixing electric field strength measurements of filamentary DBDs — •Patrick Böhm¹, Manfred Kettlitz², Ronny Brandenburg², Hans Höft², and Uwe Czarnetzki¹ — ¹Institute for Plasma and Atomic Physics, Ruhr-University Bochum, 44801 Bochum, Deutschland — ²INP Greifswald, 17489 Greifswald, Germany

In this contribution a four wave mixing technique based on Coherent anti-Stokes Raman spectroscopy (CARS) is used to measure electric field strengths in filamentary DBD discharges. The discharges are operated with a pulsed DC voltage in nitrogen at atmospheric pressure. For the investigation of the electric field an admixture of 5% - 10% of hydrogen is added as a tracer gas to ensure measurable signal intensities. The obtained measurement threshold is below the ignition field strength. Calibrating the system results in the determination of the absolute electric field strength in the measurements and also gives the breakdown voltage of the setup simultaneously. Current and voltage measurements ensure that the technique does not influence the discharges, i.e. that it is non-invasive. Alteration of the electric field has been observed during the internal polarity reversal and the breakdown process. In this case the major advantage over emission based methods is that this technique can be used independently from emission, e.g. in the pre-phase and in between two consecutive, opposite discharge pulses where no emission occurs at all. Therefore the CARS-based method could contribute to a better understanding of surface charge build-up, compensation and relaxation phenomena.