Optical properties of direct current glow discharge plasmas at high pressures

Abstract

In this work, the parallel bright and dark plasma striations are observed in direct correct glow discharge plasmas at high pressures (>100 Torr, 1 Torr=1.33322×102 Pa), and the effect of working gas on the plasma optical property is studied by combining the measurements of optical emission spectra. With the increase of the methane concentration, the length of striations decreases and the corresponding electron excitation temperature reduces. As the concentration of methane increases, the species with the low ionization energy increases, and the average ionization energy of the species decreases. In this case, the electron accelerated in a smaller distance can obtain enough energy to excite the gas species and produce visible light emission, and thus the length of plasma striations becomes shorter. With the introduction of argon, the plasma striations appear clearly. The length of striations increases with the increase of argon content, which is also correlated with the higher ionization energy of argon, while the corresponding electron excitation temperature rises. The length of plasma striations shows a response to the electron temperature as working gas changes.