Space-resolved characterization of high frequency atmospheric-pressure plasma in nitrogen applying optical emission spectroscopy and numerical simulation

TL;DR

This study combines optical emission spectroscopy, microphotography, and numerical simulation to analyze the spatial distribution of plasma parameters in high-frequency nitrogen plasma at atmospheric pressure.

Contribution

It introduces a method to determine space-resolved plasma parameters using combined experimental and numerical approaches, including inverse Abel transformation.

Findings

Spatial distribution of nitrogen emissions was successfully imaged.

Agreement found between space-resolved and averaged plasma parameters.

Calibration of CCD images enabled accurate parameter extraction.

Abstract

Averaged plasma parameters such as electron distribution function and electron density are determined by characterization of high frequency (2.4 GHz) nitrogen-plasma using both experimental methods, namely optical emission spectroscopy (OES) and microphotography, and numerical simulation. Both direct and stepwise electron-impact excitation of nitrogen emissions are considered. The determination of space-resolved electron distribution function, electron density, rate constant for electron-impact dissociation of nitrogen molecule and the production of nitrogen atoms, applying the same methods, is discussed. Spatial distribution of intensities of neutral nitrogen molecule and nitrogen molecular ion from the microplasma is imaged by a CCD camera. The CCD images are calibrated using the corresponding emissions measured by absolutely-calibrated OES, and are then subjected to inverse Abel transformation to determine space-resolved intensities and other parameters. The space-resolved parameters are compared, respectively, with the averaged parameters, and an agreement between them is established.