Simulation of positive streamers in CO${}_2$ and in air: the role of photoionization or other electron sources

Abstract

Positive streamer discharges have been studied and modelled extensively in air. Here we study positive streamers in CO${}_2$ with and without oxygen admixtures; they are relevant for current high voltage technology as well as for discharges in the atmosphere of Venus. We discuss that no efficient photoionization mechanism is known for gases with a large CO${}_2$ fraction, as photons in the relevant energy range are rapidly absorbed. Hence positive streamers can propagate only due to some other source of free electrons ahead of the ionization front. Therefore we study positive streamer propagation in CO${}_2$ with different levels of background ionization to provide these free electrons. The effect of replacing photoionization by background ionization is studied with simulations in air. Simulating streamers in background fields of 16 to 20~kV/cm at standard temperature and pressure within a gap of 6.4~cm, we find that streamer propagation is rather insensitive to the level of photoionization or background ionization. We also discuss that the results depend not only on the value of breakdown field and applied electric field, and on preionization or photoionization, but also on the electron mobility $\mu (E)$ and the effective ionization coefficient ${\alpha }_{\mathrm{eff}}(E)$, that are gas-dependent functions of the electron energy or the electric field.

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Cited by in corpus (9)

• Comparing simulations and experiments of positive streamers in air: steps toward model validation
• A computational study of accelerating, steady and fading negative streamers in ambient air
• Simulations of positive streamers in air in different electric fields: steady motion of solitary streamer heads and the stability field
• A computational study on the energy efficiency of species production by single-pulse streamers in air
• Investigation of positive streamers in CO${}_2$: experiments and 3D particle-in-cell simulations
• Full cycle, self-consistent, two-dimensional analysis of a packed bed DBD reactor for plasma-assisted $\mathrm{C}{\mathrm{O}}_2$ splitting: spatiotemporal inhomogeneous, glow to streamer to surface discharge transitions
• Investigating CO${}_2$ streamer inception in repetitive pulsed discharges
• On propagation of positive and negative streamers in air in uniform electric fields
• 3D particle simulations of positive air-methane streamers for combustion