Simulation of the discharge propagation in a capillary tube in air at atmospheric pressure

Abstract

Abstract. This paper presents simulations of an air plasma discharge at atmospheric pressure initiated by a needle anode set inside a dielectric capillary tube. We have studied the influence of the tube inner radius and its relative permittivity ε r on the discharge structure and dynamics. As a reference, we have used a relative permittivity ε r = 1 to study only the influence of the cylindrical constraint of the tube on the discharge. For a tube radius of 100 µm and ε r = 1, we have shown that the discharge fills the tube during its propagation and is rather homogeneous behind the discharge front. When the radius of the tube is in the range 300 to 600 µm, the discharge structure is tubular with peak values of electric field and electron density close to the dielectric surface. When the radius of the tube is larger than 700 µm, the tube has no influence on the discharge which propagates axially. For a tube radius of 100 µm, when ε r increases from 1 to 10, the discharge structure becomes tubular. We have noted that the velocity of propagation of the discharge in the tube increases when the front is more homogeneous and then, the discharge velocity increases with the decrease of the tube radius and ε r . Then, we have compared the relative influence of the value of tube radius and ε r on the discharge characteristics. Our simulations indicate that the geometrical constraint of the cylindrical tube has more influence than the value of ε r on the discharge structure and dynamics. Finally, we have studied the influence of photoemission processes on the discharge structure by varying the photoemission coefficient. As expected, we have shown that photoemission, as it increases the number of secondary electrons close to the dielectric surface, promotes the tubular structure of the discharge.

Surface charge deposition inside a capillary glass tube by an atmospheric pressure discharge in air

“…The studied configuration is identical to that described in [14] and is only briefly summarized here. A metallic point anode on a metallic plane holder is set at 0.5 cm from a metallic cathode plane.…”

“…In the experiments, the applied voltage is a single positive high voltage square pulse of 6 -18 kV applied at the tip. In [14], constant voltages applied at the beginning of the discharge simulation have been studied for voltages in the range 6 -9 kV.…”

“…As in [14], a classical fluid model based on the drift-diffusion equations for electrons and ions coupled with Poisson's equation is used to simulate the discharge propagation.…”

“…Recently, we have studied the influence of a radial geometrical constraint on the discharge dynamics in air at atmospheric pressure for an constant applied voltage in the range 6 − 9 kV for a dielectric tube of permittivity ε r in the range 1 − 10 and tube inner radius in the range 100 − 600 µm [14]. The objective of this work is to study the discharge dynamics in conditions closer to experiments carried out in LPGP, Orsay [15] in considering an higher applied voltage in the range 12 -15 kV with a pulsed voltage.…”

“…The objective of this work is to study the discharge dynamics in conditions closer to experiments carried out in LPGP, Orsay [15] in considering an higher applied voltage in the range 12 -15 kV with a pulsed voltage. In [14], we have studied mainly the influence of the tube radius and permittivity on the discharge structure and its propagation velocity. In this work, we propose to focus on the interaction of the discharge with the surface of the capillary tube surface and the influence of the charging of the tube on the discharge propagation.…”