Dielectric barrier discharges with steep voltage rise: laser absorption spectroscopy of NO concentrations and temperatures

Laser absorption spectroscopy was applied to determine in situ particle concentrations and temperatures in an atmospheric pressure dielectric barrier discharge. The measurements were performed with a small model reactor. The electrical excitation was by fast voltage pulses rising to 20 kV in about 300 ns (in some later measurements in approximately 90 ns); the repetition rate was 50 kHz maximum. Effects of filament distribution and discharge homogeneity were investigated. The fast rising voltage has the consequence that all filaments are generated within a 50 ns interval for each half-cycle. Observation of the NO (0,0)-band allows the determination of NO concentrations, spatially resolved as a function of the distance from a single filament; gas temperatures can be inferred from a comparison of calculated and measured line absorptions in characteristic narrow spectral intervals.