A model study of propagation of the first ionization wave during breakdown in a straight tube containing argon

Abstract

The mechanisms responsible for the propagation of the first anode directed ionization wave that occurs in a straight discharge tube during breakdown are studied by means of a fluid model. The discharge tube contains argon at a pressure of a few Torr and is operated at a dc voltage with the cathode heated to thermal electron emission temperatures. The two-dimensional model incorporates continuity and momentum equations for the electrons, for several effective excited states and for the ions, a balance equation for the electron energy and the Poisson equation. The model is capable of describing the first ionization front in a way that is qualitatively consistent with observations made in experiments. The mechanisms behind the breakdown evolution are investigated by considering the temporal and spatial evolution of the quantities described by the model. Previously, researchers have described this breakdown evolution in terms of an RC-line circuit. The validity of this picture is surveyed by considering the distribution of charges within the lamp. The effect of control parameters on the breakdown process and the assumptions that affect the validity of the model for later stages in breakdown are considered.

Optical and electrostatic potential investigations of electrical breakdown phenomena in a low-pressure gas discharge lamp

“…A normal Fickian diffusion in a cylindricallysymmetric ionized medium is therefore considered [49] and β is thus expressed as: (25) where D e is the electron radial diffusion coefficient, R L the radius of the discharge tube and R Jo the relative radius at the first zero point of the zeroth-order Bessel function (R Jo = 2.405), a dimensionless parameter in the equation. The net rate of electron flux growth dΓ e /dx at a position x can be expressed from relations (22) and (23):…”

“…The lamp was ignited with unipolar voltage pulses of positive and negative polarity whose amplitude ranges from 100 to 800 V. The experimental parameters were chosen so as to provide the simplest case of study enabling the investigation of the fundamental processes occurring during breakdown. Such ideal situation was modeled by Brok et al [22,23] and provides with some critical insights on the microscopic processes occurring inside the lamp. However, the many simplifications made lead to discrepancies with experiments; the nature of the model does not enable the study of positive ignitions and one cannot derive scaling laws for understanding the relative importance of lamp parameters.…”

Modeling of a dielectric barrier discharge used as a flowing chemical reactor

“…It was originally developed by Hagelaar for a DBD used in plasma display panels [3] and later transformed and extended by Brok and van Dijk, and integrated into the Plasimo code [4,5].…”

Investigation of the gas flow effect on an atmospheric pressure RF plasma torch

“…Although there exists advanced experimental and modelling studies a complete picture of the physical and chemical processes determining the performance of this discharge is not obtained, yet. Most of the studies are on the gas breakdown [7][8][9], the transitions of the discharge from  to  mode [10,11] and the concentration of radicals in the afterglow [12,13].…”