Electrical and optical characterization of plasma jet driven by kilohertz frequency ac voltage at atmospheric pressure

At atmospheric pressure, plasma jet source driven by low frequency continuous wave of several tens kHz ac voltage was characterized. The plasma jet source consists of stainless-steel tube (inner electrode) through which helium flow in the middle of glass tube and a ground electrode (outer electrode) roundly surrounds in the vicinity of glass tube end. The electrical and optical properties of the plasma jet source, such as lissajous of current-voltage, optical emission spectrum, and rotational temperature were investigated. With various applied voltage, gas flow rate (1 $\sim $ 5 liter per min), and driven frequency (60 $\sim $ 90 kHz) parameters changed, plasma jet showed different discharge characteristics. Through an analysis of lissajous of voltage-current, plasma jet source has various glow discharge modes. The plume of plasma jet is up to 4 cm and rotational temperature of plasma jet is within 450 $\sim $ 800 K.