Effects of H2 on Ar plasma jet: From filamentary to diffuse discharge mode

Abstract

Atmospheric-pressure plasma jets have recently attracted significant interest for its widespread applications in many fields from medicine to nanotechnology, yet the issue of the controlling the stability of Ar plasma jets remains a major challenge. In this paper, when 3% or more H2 is added to working gas Ar, it is found that the Ar plasma transits from filamentary mode to diffuse mode. In addition, the electric characteristics and the dynamics of the plasmas are studied. It is found that the peak current flowing through the ground electrode for the filament mode is about 0.5 A, which is much higher than 0.05 A for the diffuse mode. Furthermore, similar with those reported, 100 shots integrated photographs on dynamic of the diffuse discharge are taken, the photographs reveal that the plasma plume propagation appears like a “plasma bullet.” On the other hand, a single shot photographs of the plasma in the diffuse mode show the “plasma bullet” is actually composed of several interacting streamers. Detailed analysis shows that the slow ionization is responsible for the generation of the filamentary-to-diffuse mode transition.