Microwave absorption and optical emission spectrometry analyses of ambient air plasmas induced by pulsed electron beams

Abstract

This work is devoted to the characterization of plasmas produced by an intense pulsed relativistic electron beam propagating in air at atmospheric pressure. A large range of a time integrated dose is investigated [0.75 to 7.4] kGy(air) inducing electron densities from 2 × 1012 up to 1.6 × 1014 cm−3. The air plasmas are analyzed by two complementary diagnostics: microwave absorption and optical emission spectroscopy, to deduce plasma parameters during the creation and relaxation phases, respectively. A reduced air kinetics model is used to calculate transmission measurements during the electron beam pulse and to infer electric conductivities, which are compared to the results of three-dimensional Maxwell calculations. Optical emission spectra are measured and compared to calculated ones, giving rotational and vibrational temperatures during the relaxation phase of the plasma. These plasma characterizations may be used to model non-equilibrium atmospheric air plasma chemistry in the framework of, for instance, streamer dynamics as well as corona or dielectric barrier discharges.

Spectral analysis and kinetic modeling of radioluminescence in air and nitrogen

“…15 While effective, both models predicted fluorescence as Dirac functions limiting the ability to accurately predict spectral shapes to estimate the response of deployed imaging equipment. However, while spectral modeling tools have been used to fit spectral emission for vibrational and rotational temperatures in electron beams 16 and air plasmas, 17,18 no spectral analysis has been performed for radioluminescence generated by alpha particles.…”

Third-order transport coefficients for electrons in N2 and CF4: effects of non-conservative collisions, concurrence with diffusion coefficients and contribution to the spatial profile of the swarm

“…However, this can be quite challenging due to a wide variety of effects that determine the nature of non-equilibrium plasma. These effects include collisions of electrons and ions with neutral particles of the background fluid [18][19][20], kinetics of excited species [21][22][23], generation of fast neutrals [24], space charge effects [25,26], and plasma-surface interaction [27,28]. Despite their simplicity, charged-particle swarms are at the heart of non-equilibrium plasma modelling [2,18,29,30].…”

Influence of plasma density on the cross sections of radiative recombination to configuration-averaged excited nitrogen and oxygen atoms and ions

“…During this process, the main physical mechanisms are excitation and ionization induced by electrons and photons, as well as the reverse processes. Consequently, the plasma emits radiations, so the most widespread diagnostic used to analyze the plasma is emission spectrometry [17,18] due to its versatile and non-intrusive character [19]. Depending on the calibration procedure, many quantitative informations may be inferred from the measured spectra: electron density [20], density of the excited states involved in the observed transitions [21,22] and temperature [23,24].…”