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Investigation of the transition between glow and streamer discharges in atmospheric air

Generally, the parameter p · d (pressure × gap distance) in dielectric barrier discharge (DBD) controls the electrical breakdown and also the plasma characteristics. We investigated the optimum plasma transition p · d by controlling the pressure. To find the transition p · d (p · dtr) condition, optical emission spectroscopy (OES) was used to measure emission spectra from the DBD. All p · d data were normalized by the second positive system of nitrogen molecules, the wavelength of which was 337.1 nm. Then we compared the relative intensities of species generated during the discharge by OES analysis. Species selected for comparison were the first negative system (FNS) of nitrogen molecules (391.4 nm) and atomic oxygen spectra (777.1 nm). Experimental results showed that relative intensities were almost constant as p · d decreased, but at specific p · d data, the intensity started to increase. The increase in FNS of nitrogen molecules means not only an increase in electron energy but also a change in the plasma mode, streamer to glow transition. In the case of DBD using alumina with 1 mm thickness applied ac power, the plasma transition occurred at the 1 Torr cm condition.