Electrical and Optical Characterization of an Argon-based Atmospheric Pressure Plasma Jet Under Non-LTE Conditions

Abstract

This study investigates the generation and detailed characterization of an Argon-based Atmospheric Pressure Plasma Jet (AAPPJ) through systematic electrical and optical diagnostics. Electrical measurements yielded an RMS voltage of 0.79 kV and an RMS current of 5.91 mA, corresponding to a power output of 4.64 W. Analysis of the voltage–current waveforms revealed non-linear discharge behavior indicative of complex plasma dynamics. Optical Emission Spectroscopy (OES) identified emission lines from neutral (Ar I) and singly ionized (Ar II) argon species. Using the Boltzmann plot method, electron excitation temperatures were estimated to be 0.274 eV (Ar I) and 0.302 eV (Ar II). The corresponding electron densities were calculated as 1.043 × 1012 cm−3 and 1.001 × 1013 cm−3 , respectively. These findings reveal electron densities in the order of 1012 cm−3–1013 cm−3 , consistent with typical atmospheric pressure plasma jets. The close agreement between the excitation temperatures suggests a relatively stable plasma operating under weak non-local thermodynamic equilibrium (non-LTE) conditions. Overall, the study highlights the importance of precise electrical and optical diagnostics in understanding the characteristics of plasma discharge.