Axial light emission and Ar metastable densities in a parallel plate dc micro discharge in steady state and transient regimes

TL;DR

This study investigates axial light emission, metastable argon densities, and temperature profiles in a 1mm parallel plate dc micro discharge, revealing transient behaviors and correlations with oscillating discharge currents.

Contribution

It provides detailed time-resolved imaging and spectroscopy data on micro discharges, highlighting transient emission profiles and metastable dynamics not previously characterized.

Findings

Axial emission profiles are similar to larger discharges in steady state.

Relaxation oscillations cause transient emission profile shifts from anode to cathode.

Argon metastable densities correlate with oscillating discharge current.

Abstract

Axial emission profiles in a parallel plate dc micro discharge (feedgas: argon; discharge gap d=1mm; pressure p=10Torr) were studied by means of time resolved imaging with a fast ICCD camera. Additionally, volt-ampere (V-A) characteristics were recorded and Ar* metastable densities were measured by tunable diode laser absorption spectroscopy (TDLAS). Axial emission profiles in the steady state regime are similar to corresponding profiles in standard size discharges (d=1cm, p=1Torr). For some discharge conditions relaxation oscillations are present when the micro discharge switches periodically between low current Townsend-like mode and normal glow. At the same time the axial emission profile shows transient behavior, starting with peak distribution at the anode, which gradually moves towards the cathode during the normal glow. The development of argon metastable densities highly correlates with the oscillating discharge current. Gas temperatures in the low current Townsend-like mode (T= 320-400K) and the high current glow mode (T=469-526K) were determined by the broadening of the recorded spectral profiles as a function of the discharge current.