Time-Resolved Diagnosis on Plasma Parameters of a Uniform Dielectric Barrier Discharge in Atmospheric Pressure Helium

Time-resolved optical emission spectroscopy is implemented for a 5.0 mm gap atmospheric pressure helium dielectric barrier discharge (DBD) excited by a 36.0 kHz sinusoidal voltage. The emission spectra are mainly composed of atomic lines from helium and hydrogen and emission bands from nitrogen molecules and nitrogen molecular ions. The time-resolved optical emission spectra reveal that penning ionization plays an important role in the formation of the uniform DBD. From the emission spectra, time-resolved vibrational temperature, rotational temperature, and electron density are investigated, all of which first increase and then decrease during one discharge pulse. However, the maxima of the vibrational temperature and the rotational temperature lag behind the current peak, which coincides with the maximal electron density. In addition, the main physicochemical processes involved are discussed.