Comparison between 1D radial and 0D global models for low-pressure oxygen DC glow discharges

Abstract

This work focuses on the comparison between a zero-dimensional (0D) global model (LoKI) and a one-dimensional (1D) radial fluid model for the positive column of oxygen DC glow discharges in a tube of 1 cm inner radius at pressures between 0.5 Torr and 10 Torr. The data used in the two models are the same, so that the difference between the models is reduced to dimensionality. A good agreement is found between the two models on the main discharge parameters (gas temperature, electron density, reduced electric field and dissociation fraction), with relative differences below 5%. The agreement on other species average number densities, charged and neutral, is slightly worse, with relative differences increasing with pressure from 11% at 0.5 Torr to 57% at 10 Torr. The success of the 0D global model in describing these plasmas through volume averaged quantities decreases with pressure, due to pressure-driven narrowing of radial profiles. Hence, in the studied conditions, we recommend the use of volume-averaged models only in the pressure range up to 10 Torr.

A reaction mechanism for oxygen plasmas

“…A more correct, complex and time-consuming formulation describes the spatial variation of the electron kinetics by solving the space-dependent electron Boltzmann equation [60][61][62][63][64][65][66]. Here, we use the simpler 0D approach, which was verified to provide a good description of the system under study for most species (O 3 being an exception) by comparison with 1D calculations [67], and is further confirmed in section 3.1.…”

“…On the other hand, model equations comprise various approximations. For example, in 0D models, the assumption of certain density profiles to describe the transport of neutral and charged species allows to obtain the correct trends and identify the main elementary processes ruling the discharge, but sometimes the absolute values are somewhat inaccurate [67]. For these reasons, it is more relevant to ensure that the kinetic scheme is physically consistent and describes the observed tendencies of several quantities in a wide range of conditions.…”

Surface recombination in Pyrex in oxygen DC glow discharges: mesoscopic modelling and comparison with experiments

“…where v th are the thermal velocities calculated as in equation ( 3). As noticed in the work by Viegas et al (2023), near the wall it may be more accurate to assume…”

“…The discharge conditions studied experimentally and numerically by Booth et al (2019Booth et al ( , 2020Booth et al ( , 2022Booth et al ( , 2023, Western et al (2020), Viegas et al (2023)and Dias et al (2023) are assessed in this work. The experimental set-up is described in detail by Booth et al (2019Booth et al ( , 2020Booth et al ( , 2022Booth et al ( , 2023and a simplified scheme is presented in figure 1, adapted from the work by Booth et al (2019).…”

Spatio-temporal analysis of power deposition and vibrational excitation in pulsed N2 microwave discharges from 1D fluid modelling and experiments

“…Similarly, a parabolic profile is assumed for gas temperature to determine losses of heat due to conduction to the reactor walls [19]. These assumptions were recently checked by Viegas et al [20] for O 2 DC glow discharges up to 13 mbar, revealing their validity in that pressure range. Modelling of CW CO 2 discharges at higher pressures (above 100 mbar) with a 1D radial fluid model has shown non-parabolic T g profiles [16] and non-Bessel electron density profiles [13].…”