A kinetic Monte Carlo study of positive streamer interaction with complex dielectric surfaces

Abstract

We present a computational study of positive streamers in air propagating over
dielectric plates with square channels running orthogonal to the propagation direction. The
study uses a newly developed non-kinetic Particle-In-Cell model based on Îto diffusion and
Kinetic Monte Carlo, which does not introduce artificial smoothing of the plasma density or
photo-electron distributions. These capabilities permit the computational study to use high-
resolution grids with large time steps, and also incorporates geometric shielding for particle
and photon transport processes. We perform Cartesian 2D simulations for channel dimensions
ranging from 250 μm to 2 mm, and track streamers over a distance of 4 cm and times ranging
up to 300 ns, for various voltages ranging from 15 kV to 30 kV. These baseline simulations
are supplemented by additional studies on the effects of transparency to ionizing radiation,
streamer reignition, dielectric permittivity, and 3D effects. The computer simulations show: 1)
Larger channels restrict streamer propagation more efficiently than narrow channels, and can
lead to arrested surface streamers. 2) Geometric shielding of ionizing radiation substantially
reduces the number of starting electrons in neighboring channels, and thus also reduces the
onset point of streamer reignition. 3) Decreasing the streamer channel separation leads to
slower streamers. 4) Increasing the dielectric permittivity increases the discharge velocity.
The results are of generic value to fields of research involving streamer-dielectric interactions,
and in particular for high-voltage technology where streamer termination is desirable.

Spatio-temporal electric field distributions in an atmospheric plasma jet impinging on a microchannel array surface

“…This is most likely caused by the electric field enhancement near the water surface due to its significantly high dielectric constant, compared to Macor ceramic (ε w ≈ 80 vs. ε c ≈ 6). This result is also consistent with the recent modeling predictions [8], where increasing the dielectric constant of the surface resulted in higher velocity of the surface streamer propagation. Odd-numbered locations and red data points correspond to the measurements over the water-filled channels, even numbers and blue points are the measurements over the ridges between the channels.…”

“…The hopping occurs only outside of the incident plasma jet, while the optical emission fills the channels within the jet. Qualitatively, this is consistent with the behavior predicted in the recent simulations of SIW propagation in air [8], where it was attributed to the shielding of ionization radiation of O 2 by the opaque channel walls. When the channels are filled with water, the plasma tends to 'hug' the surface, that is propagates much closer to it, although smaller gaps between the surface and the plasma emission are still evident.…”

“…Microchannel array surfaces with the channels filled with water or aqueous solutions provide an additional perspective, since they can be used for the efficient and controlled plasma-assisted activation of water. Characterization of plasmas propagating over the microchannel surfaces will also provide the data for the validation of the kinetic models [7,8], which may then be exercised to predict the plasma parameters for more complex surfaces, not readily accessible for the experimental diagnostic study.…”

Genesis of column sprites: formation mechanisms and optical structures

“…All calculations in this paper were done using the chombodischarge code [27], which we have used for numerous discharge simulations in the past [22,[27][28][29][30][31][32]. We solve the equations of motion over a 400 km × 400 km × 200 km region, using an adaptive Cartesian mesh.…”

“…see [34]) in order to eliminate the dielectric relaxation time step constraint. Complete details regarding the discretization method are given in the chombo-discharge documentation [27]. The simulations in this paper used up to 25 600 CPU cores with mesh sizes up to 3 × 10 −9 grid cells, and completed in about a day.…”