Density of hybrid plasma generated by microwave and laser radiation in the Ar:H2:CH4 mixture

TL;DR

This study investigates the electron density and spectral characteristics of hybrid plasma generated by microwave and laser radiation in an Ar:H2:CH4 mixture at atmospheric pressure, revealing inhomogeneity and density variations.

Contribution

It provides the first detailed analysis of the spectral line profiles and electron densities in hybrid microwave-laser plasmas in this specific gas mixture.

Findings

Electron density ranges from 4×10^15 to 2×10^17 cm^-3.

Hα line profile exhibits broad wings indicating inhomogeneity.

Hybrid plasma shows higher electron density than microwave plasma alone.

Abstract

The atmospheric-pressure hybrid plasma in the Ar:H2:CH4 mixture, maintained by microwave radiation (2.47 GHz) and CO2 laser radiation (10.6 {\mu}m) in the chamber of an experimental plasma-chemical reactor designed to study the synthesis of diamond-like coatings was studied. The electron number density was determined from the Stark broadening of the H{\alpha} line shape of atomic hydrogen. It was shown that when laser radiation is focused in the region of a microwave plasma bunch, the H{\alpha} line shape in the hybrid plasma spectra has broad wings and is described by a Lorentz function with a two-contour approximation. The complex structure of the H{\alpha} line profile of the hybrid plasma indicates its spatiotemporal inhomogeneity. The electron number density corresponding to the contour with a smaller half-width exceeds the electron number density in microwave plasma and lies in the range of (4-8)E15 cm-3, and the electron number density measured by the contour with a larger half-width is (1.5-2)E17 cm-3.