Discharge comparison of nonequilibrium atmospheric pressure Ar/O2 and He/O2 plasma jets

A plasma jet has been developed that operates using rf power and produces a stable homogeneous discharge at atmospheric pressure. Discharge characteristics for the gas mixture of He/O2 and Ar/O2 were studied. The temperature distribution at the exit of the nozzle of Ar/O2 discharge is about 100 K higher than that for the He/O2 discharge—identified by an increased temperature—extends much farther downstream for Ar/O2 discharge in contrast to the He/O2 discharge—250 mm as compared to 75 mm. Optical emission spectra for both discharges in the jet effluent shows only fractions of the peak intensities of Ar, He, and O atomic lines compared with spectra taken looking obliquely inside the jet volume. The spatial profile of excited atomic oxygen at λ=777 nm (4S0 3p–3s) taken side on to the flow direction outside the nozzle shows good correlation to the temperature distribution for both discharges. These results indicate that the Ar/O2 discharge has better energy transfer efficiency than the He/O2 discharge. Study of the electrical properties of the two discharges shows that the two discharges exhibit a different capacitive nature and the voltage wave form for He/O2 advances that of the Ar/O2 discharge by 16°, which means there is more ohmic component in the Ar/O2 discharge.