Density of hybrid plasma supported by microwave radiation and CO2 laser

The paper is devoted to the study of the electron number density of an atmospheric pressure hybrid plasma supported by microwave radiation (2.47 GHz) and a CO2 laser (10.6 μm) in the chamber of an experimental plasma-chemical reactor developed to study the synthesis of diamond-like and other coatings. The reactor is based on a microwave resonator on the TM012 mode of a quasi-cylindrical shape, into which focused radiation of a CO2 laser is introduced simultaneously with microwave radiation. The shapes of the atomic hydrogen Hα line emitted by microwave and hybrid plasma in H2:Ar:CH4 mixtures are studied. The shapes of the Hα line in the hybrid plasma spectra, in contrast to the shapes of this line emitted by microwave plasma, approximated by the Lorentz function, have wide wings and are described by the Lorentz function with a two-contour approximation, which indicates a significant spatio-temporal inhomogeneity of the hybrid plasma. The density of electrons in the atmospheric pressure microwave plasma measured by the Stark broadening of the Hα lines are in the range of 5×1014-1016 cm-3. In the hybrid plasma, the density of electrons corresponding to the contour with a smaller half-width slightly exceeds the density of electrons in the microwave plasma and is in the range of 1015-5×1016 cm-3. In the case of focusing laser radiation in the region of a microwave plasma bunch, the density of electrons measured by the contour with a larger half-width is ~1017 cm-3.