Electrical and Spectral Characteristics of a Low-Temperature Argon–Oxygen Plasma Jet With Syringe Needle-Ring Electrodes

Low-temperature atmospheric-pressure argon-oxygen plasma jet is generated with syringe needle-ring electrodes, which is powered by a sinusoidal excitation voltage at 8 kHz. The volume percentage of the oxygen content in the argon gas is as high as 12.5%. It is found that the rotational temperature of nitrogen is in the range of 297-320 K, and the vibrational temperature is almost unchanged to be about 2475 K, which is obtained by comparing the simulated spectrum with the measured spectrum at the C³ Πu → B³Πg (Δv = -2) band transition. The electronic excitation temperature is in the range of 8587-8994 K as obtained by the Boltzmann´s plot method, the electron temperature at the tip of syringe needle is about 7.3 eV as estimated by the Einstein´s equation, and the densities of atomic oxygen and molecular nitrogen are, respectively, on the order of magnitude of 10¹⁶cm^-3 as determined by actinometry method, respectively. Moreover, the 2-D and 1-D distributions of the electric field magnitude are estimated by the 2-D finite-element software. At a time of 45.7 μs and an instantaneous applied voltage of 8 kV, the electric field magnitude at the edge of the ring ground electrode is the largest, and it is 15.9 kV/cm at the tip of the syringe needle.