Formation and destruction of striation plasmas in helium glow discharge at medium pressures

The striation plasmas are usually generated within a positive column of glow discharge, where rich and complex physical interactions are involved, especially, in the medium or high pressures. Along these lines, our work aims to thoroughly investigate the formation and destruction of helium striation plasmas at kPa level pressures. The characteristics of the helium striation plasmas, and especially the optical emission properties are explored. The emission lines of 706.52 nm and 391.44 nm related to the energetic electrons and the high-energy metastable helium atoms respectively, were focused on in this work. The formation of striation plasmas in a helium glow discharge, is mainly associated with the instability originating from the stepwise ionization of high-energy metastable state atoms, Maxwellization of the electron distribution functions and gas heating. Additionally, the destruction effect of helium striation plasmas is of great significance when a small amount of nitrogen or oxygen is mixed into the discharge plasmas. The reduction of the mean electron energy and the consumption of the high-energy metastable helium atoms are considered as the underlying reasons for the destruction of striation plasmas.