Characterization of a microwave argon plasma column at atmospheric pressure by optical emission and absorption spectroscopy coupled with collisional-radiative modelling

Abstract

Optical emission and absorption spectroscopy of argon 2p-1s transitions (Paschen notation) combined with collisional-radiative (CR) modeling of argon 2p states are developed and used to determine the neutral gas temperature, the Ar 1s number density, and the electron temperature along a microwave argon plasma column at atmospheric pressure. The CR model, designed specifically for atmospheric-pressure and optically thick plasma conditions, is fully detailed and validated by comparing the relative line emission intensities of argon 2p-to-1s transitions measured experimentally with the ones predicted by the CR model using the electron temperature as the only adjustable parameter. Subsequently, the neutral gas temperature (∼1300–1600 K; obtained from the broadening of argon 2p2-1s2 and 2p3-1s2 emission lines), the Ar 1s5 number density (1–2 × 1018 m−3; obtained from absorption spectroscopy of the argon 2p9-1s5 transition using a tunable laser diode), and the electron temperature (∼1.4 eV; obtained from the comparison between the measured and simulated 2p-to-1s emission line intensities) are reported as a function of the axial distance along the microwave plasma column. The values and behaviors reveal a good agreement with those reported in previous experimental and modeling studies.

Spatially-Resolved Spectroscopic Diagnostics of a Miniature RF Atmospheric Pressure Plasma Jet in Argon Open to Ambient Air

“…As such, our approach to find T e was based on fitting the experimental spectra with theoretical ones instead of solely relying on an auto-coherent CR model. The details of this method can be found elsewhere [31]; only an overview is presented in the following lines.…”

“…Figure 6 summarizes the different mechanisms that were considered in the particle balance equations. Excitation mechanisms included electron impact from either ground or 1s metastable and resonant states, population mixing between two 2p levels induced by a collision with the ground state Ar atoms [33], as well as radiation trapping [31]. As represented by the box on top of Figure 6, apparent (cascading) cross-sections for electron collisions were used to calculate the corresponding reaction rates, thus ensuring that cascading effects were adequately described without going through the complexity of solving the population of energy levels higher than the 2p.…”

Bread‐making performance of wheat flours enriched with vital gluten treated with non‐thermal plasma

“…Argon plasma acts via electron bombardment (Durocher‐Jean et al ., 2019) and may induce oxidation (Ekezie et al ., 2019) and depolymerisation (Chaple et al ., 2020), thus altering the treated matrix. The energy of these species determines their activity when they come into contact with the surface of VG.…”

Diagnostics of Ne–Ar mixture plasma using a fine‐structure resolved collisional radiative model

“…electron temperature (T e ), electron density (n e ), atomic state population distribution, etc., under various mixture conditions are highly required. [6] Among various available diagnostic approaches, a non-invasive optical diagnostic technique based on OES [7,8] measurements is very effective and often used. The rare gas mixture LTPs mostly exhibit a non-equilibrium nature.…”

“…[10] The modelling of inert gas mixture plasma is much less explored as compared to pure inert gas plasma. [7,[10][11][12][13][14][15] Recently, Khattak et al [16] have studied the electron and excitation temperatures in the Ne-Ar inductively coupled mixture plasma and showed comparison in the values obtained through Langmuir probe measurements and Boltzmann plot methods where they find the Boltzmann temperatures are less than the Langmuir probe measurement. Boffard et al have studied plasma series resonance heating in Ne and Ne-Ar inductively coupled plasma (ICP).…”