Generation and Characterization of a Large‐Diameter Diffuse Plume in an Atmospheric Pressure Argon Plasma Jet

ABSTRACT In this paper, a large‐diameter diffuse argon plume is generated through being excited by a negatively‐biased sinusoidal voltage. The diffuse plume increases in length with increasing peak voltage and argon flow rate, which transitions to a nonuniform plume when voltage amplitude exceeds a threshold. The diffuse plume initiates at the rising voltage edge, while the nonuniform plume initiates at the rising and falling edges. From fast photography, the diffuse plume originating from the discharges at the rising voltage edge is speculated to operate in a Townsend discharge regime, while the discharge at the falling voltage edge is filamentary in the nonuniform plume. By optical emission spectroscopy, plasma parameters including electron temperature, electron density, and atomic oxygen concentration have been investigated.