Argon metastable dynamics in a filamentary jet micro-discharge at atmospheric pressure

TL;DR

This study investigates the behavior of argon metastable atoms in a filamentary micro-discharge jet at atmospheric pressure, revealing how electric field distribution and pulsed operation influence filament dynamics and metastable distribution.

Contribution

It provides detailed spatial and temporal analysis of argon metastables and filament behavior in an atmospheric pressure micro-plasma jet, including effects of target potential and pulsed operation.

Findings

Metastable atom distribution is significantly affected by target potential.

Filamentary structure dynamics are linked to electric field distribution.

Ignition phase and pulsed operation influence excitation mechanisms.

Abstract

Space and time resolved concentrations of Ar ($^{3}P_2$) metastable atoms at the exit of an atmospheric pressure radio-frequency micro-plasma jet were measured using tunable diode laser absorption spectroscopy. The discharge features a coaxial geometry with a hollow capillary as an inner electrode and a ceramic tube with metal ring as outer electrode. Absorption profiles of metastable atoms as well as optical emission measurements reveal the dynamics and the filamentary structure of the discharge. The average spatial distribution of Ar metastables is characterized with and without a target in front of the jet, showing that the target potential and therewith the electric field distribution substantially changes the filaments' expansion. Together with the detailed analysis of the ignition phase and the discharge's behavior under pulsed operation, the results give an insight into the excitation and de-excitation mechanisms.