Gas temperature and electron temperature measurements by emission spectroscopy for an atmospheric microplasma

Abstract

A microplasma suitable for material processing at atmospheric pressure in argon and argon-oxygen mixtures is being studied here. The microplasma is ignited by a high voltage dc pulse and sustained by low power ͑1-5 W͒ at 450 MHz. the mechanisms responsible for sustaining the microplasma require a more detailed analysis, which will be the subject of further study. Here it is shown that the microplasma is in nonequilibrium and appears to be in glow mode. The effect of power and oxygen content is also analyzed in terms of gas temperature and electron temperature. Both the gas temperature and the electron temperature have been determined by spectral emission and for the latter a very simple method has been used based on a collisional-radiative model. It is observed that power coupling is affected by a combination of factors and that prediction and control of the energy flow are not always straightforward even for simple argon plasmas. Varying gas content concentration has shown that oxygen creates a preferential energy channel towards increasing the gas temperature. Overall the results have shown that combined multiple diagnostics are necessary to understand plasma characteristics and that spectral emission can represent a valuable tool for tailoring microplasma to specific processing requirements.

Rapid surface treatment of polyamide 12 by microwave plasma jet

“…This chemical species has often been applied as a 'thermometer tool' in high pressure systems [7,37,[43][44][45][46][47] (the relaxation of rotational states is much faster than the electronic transitions). The Boltzmann plot technique is for OH quite straightforward, as continuum background is rather small and no spectral calibration of the optical system is needed as lines are close in wavelengths.…”

Nonequilibrium and effect of gas mixtures in an atmospheric microplasma

“…This technique has been already applied to micro- plasmas and provides the value for an effective electron temperature. 12 By reducing the distance between the capillary exit and the substrate, the microplasma was reduced in size and, by increasing the distance, the overall microplasma volume was enlarged. For this experiment, a Ni capillary ͑1 mm external diameter and 0.8 mm internal diameter͒ was used.…”

Ultraviolet Rayleigh Scatter Imaging for Spatial Temperature Profiles in Atmospheric Microdischarges

“…Values of , , and were measured for ranging electrode separation and discharge power ranging from 0.5 to 2 Watts. Gas temperatures averaged approximately 600 K, electron densities were on the order of 10 14 cm −3 , while electron temperatures ranged from approximately 1.2 to 1.6 eV [35].…”