Impurity intrusion in radio-frequency micro-plasma jets operated in ambient air

TL;DR

This study investigates how impurities from ambient air and the gas supply affect helium metastable atoms in a micro-plasma jet, using laser absorption spectroscopy and emission analysis to quantify impurity intrusion.

Contribution

It provides detailed spatial and temporal measurements of impurity effects in micro-plasma jets operated in ambient air, highlighting the influence of air ingress and supply system impurities.

Findings

Impurities significantly quench helium metastables.

Impurity concentrations vary along the jet axis.

Air ingress impacts plasma stability and composition.

Abstract

Space and time resolved concentrations of helium metastable atoms in an atmospheric pressure radio-frequency micro-plasma jet were measured using tunable diode laser absorption spectroscopy. Spatial profiles as well as lifetime measurements show significant influences of air entering the discharge from the front nozzle and of impurities originating from the gas supply system. Quenching of metastables was used to deduce quantitative concentrations of intruding impurities. The impurity profile along the jet axis was determined from optical emission spectroscopy as well as their dependance on the feed gas flow through the jet.