Glow-to-arc discharge transitions in a radio frequency atmospheric pressure plasma jet

This study investigates the mechanism of discharge transitions in a radio frequency atmospheric pressure plasma jet (RF APPJ), with the aim of unraveling the underlying mechanisms behind the unexpected arcing-like filament formation on power electrode observed at lower power levels and the subsequent glow-to-arc transition (GAT) at higher powers. Through meticulous analysis of plasma parameter variations under varying power increment rates, this research offers crucial insights into the complex dynamics of plasma behavior. Detailed analysis of discharge current under different power increment rates exhibited distinct discharge phases as power increased, i.e., the normal glow phase, the abnormal glow phase, and the glow-to-arc transition. Notably, the arcing-like filament formation observed on the power electrode during the abnormal glow phase is indicative of complex plasma dynamics driven by the combined effect of thermal instability and the resulting thermo-field emission. Particularly noteworthy is the dynamic relationship between power increment rates and the duration of the abnormal glow discharge phase, shedding light on the multifaceted nature of thermal instability phenomena. Moreover, the ponderomotive force plays a crucial role in restricting thermo-field emission, thereby preventing the transition from glow to arc at low power levels. Additionally, the observed rise in electron density, electron temperature, and the emission intensity of reactive oxygen and nitrogen species during the abnormal glow discharge phase presents exciting possibilities for novel operational regimes characterized by lower gas temperatures. This study paves the way for enhanced understanding and control of atmospheric pressure plasma processes by highlighting the intricate interplay between power increment rates and discharge behavior, offering promising avenues for developing more efficient and stable plasma-based technologies.