Electron density in amplitude modulated microwave atmospheric plasma jet as determined from microwave interferometry and emission spectroscopy

Abstract

Time resolved electron density in an atmospheric pressure amplitude modulated microwave plasma jet is determined using the microwave interferometry method, refined by numerical modelling of the propagation of non-planar electromagnetic waves in the vicinity of a small diameter, dense collisional plasma filament. The results are compared to those from the Stark broadening of the β H emission line. Both techniques show, both qualitatively and quantitatively, a similar temporal evolution of electron density during one modulation period.

Batch processing of overlapping molecular spectra as a tool for spatio-temporal diagnostics of power modulated microwave plasma jet

“…This can be explained as follows. The concentration of free electrons in this discharge was measured to be as high as 10 20 m −3 during the whole modulation period [46]. The abundant electrons due to their low mass are much more efficient in exciting electronic and vibrational states of molecules (due to the Franck-Condon principle) compared to changing their rotational states.…”

“…Thus a more advanced method is used to modulate the microwaves by an amplitude envelope. There were a number of surfatron discharges recently investigated in the power modulated regime using the sine wave envelope; these include pure argon [43][44][45], and mixtures of Ar+N 2 [44], Ar+H 2 [46], argon and tetrakis(trimethylsilyloxy)silane (TTMS) [47].…”

Systematic diagnostics of the electrical, optical, and physicochemical characteristics of low-temperature atmospheric-pressure helium plasma sources

“…Stark broadening is induced by the electric field generated by charged particles in the plasma, and so this method is typically limited to systems in which the electron density is greater than approximately 10 14 cm −3 [52]. There have been several studies regarding the measurement of the electron density in an APPJ using Stark broadening [53][54][55][56][57][58].…”

How dielectric, metallic and liquid targets influence the evolution of electron properties in a pulsed He jet measured by Thomson and Raman scattering

“…Electron properties are important in discharge development and in the process of sustaining a plasma. While the determination of the chemical composition and pathways in the complex oxygen-and nitrogen-based chemistry of atmospheric pressure discharges is frequently researched, there are only a handful of measurements of the electron properties in freely expanding atmospheric pressure plasma jets [19][20][21][22][23][24]. The experimental data on electron properties when a plasma jet interacts with a target is scarce [25].…”