Dielectric barrier discharges (DBD) are frequently used for a variety of applications ranging from plasma assisted combustion to gas cleaning and plasma medicine. An efficient optimization of these applications requires concepts to selectively control the creation of reactive particle species, e.g. oxygen or nitrogen species, in the plasma. For a given gas mixture their generation is determined by the space and time dependent electron energy distribution function (EEDF) in the discharge. In this project, the effects of modifying the shape of the external driving voltage waveform on the plasma generation, the EEDF, and the creation of process relevant reactive particles will be studied systematically in a surface dielectric barrier discharge (SDBD). Nano-, micro-, and milli-second high voltage pulses with different amplitudes, polarities, widths, and pulse repetition frequencies
ranging from several Hz to MHz including damped microsecond sinusoidal waveforms will be used. The effects of using these different waveforms on the plasma breakdown, the electron dynamics, the generation of reactive species, streamer development, and the homogeneity of the discharge will be studied by a variety of state-of-the-art diagnostics and a global model (developed in A9) to understand the plasma chemistry. In different mixtures of Ar/O2 as well as N2/O2 and as a function of the driving voltage waveform, current, voltage, and power will be measured by current/voltage probes. The EEDF, the electron density, and the reduced electric field as well as the spatio-temporal dynamics of energetic electrons will be studied by time averaged Optical Emission Spectroscopy (OES) and Phase Resolved Optical Emission Spectroscopy (PROES), respectively. Densities of NO, O3 (Absorption Spectroscopy), O (Two Photon Laser Induced Fluorescence (TALIF)), and
other reactive species (mass spectrometry) will be measured, too. The effects of using catalytic coatings of the SDBD on the plasma will be studied. The goal is a detailed fundamental understanding of the influence of the voltage characteristics on the plasma as a basis for process optimization based on scientific understanding. In close collaboration with A7 these insights will be used to improve the conversion of volatile organic compounds (VOC) in the same type of SDBD. The performance of SDBDs will be compared to other plasma sources in collaboration with A4 (m-APPJ) and A6 (micro-structured plasma arrays).
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