V. N. Khudik

Three-dimensional Monte Carlo/particle-in-cell Simulations of the discharge pulse in an AC-PDP cell

The dynamics of the discharge pulse between coplanar electrodes in an alternating current plasma display panel (ac-PDP) cell is studied by the three-dimensional (3-D) Monte Carlo/particle-in-cell (PIC) simulations. The images obtained from the simulations capture all essential features of the discharge (such as a spatial structure of striations above the anode, and an arch-shaped front of the discharge spreading along the cathode) and show a remarkable resemblance to the experimental data.

Dynamics of a barrier discharge at high overvoltage

The dynamics of a strong barrier discharge is investigated analytically in the simplest model that still keeps the essential discharge features. It is shown that at high overvoltage, the discharge develops into the ionizing wave moving from the anode toward the cathode. The velocity of this wave is found to be controlled mainly by the charge production rate in the cathode fall region and can considerably exceed the characteristic ion velocity. The influence of the capacitor formed by the dielectric layers on the discharge dynamics is analyzed. It is shown that, depending on the magnitude of the capacitance, two qualitatively different charging regimes exist.

Electron avalanche sliding along a dielectric surface

We consider the dynamics of an electron avalanche propagating along a dielectric surface in a channel wherein the Townsend breakdown condition does not hold. We show that when the angle θ between the electric field and the channel wall is less than some critical value θcr, the electron avalanche grows. The function θcr = θcr(E) is found by kinetic Monte-Carlo simulations for a mixture of Xe and Ne gasses.

Striations in dielectric barrier discharge systems with a hollow anode

The dynamics of the charging of an elongated hollow anode covered with a dielectric layer by an electron current is studied via three-dimensional particle-in-cell/Monte Carlo kinetic simulations. It is shown that this process is accompanied by the successive formation of striations in the plasma created by the electron impact ionization of the background gas. A number of specially designed numerical experiments are performed to further explore the nature of this phenomenon. An experimental setup where this type of striations should be observed is suggested.

Spreading of discharge plasma above cathode covered with dielectric layer

The dynamics of discharges where the plasma spreads over a plane cathode covered with a dielectric layer is studied via particle-in-cell/Monte-Carlo kinetic simulations. There is a region of strong electric field (between the plasma and the still uncharged areas of the dielectric surface) where most of ionization takes place—this region can be naturally called a dynamic cathode fall. The role of the electron and ion diffusion in maintaining the particle balance in the dynamic cathode fall is established. The dependence of the velocity of plasma spreading on the potential difference between the plasma and the cathode, the dielectric layer thickness, and the secondary electron emission coefficient is found for neon gas.

Dynamic positive column in long-gap barrier discharges

A simple analytical model of the barrier discharge in a long gap between opposing plane electrodes is developed. It is shown that the plasma density becomes uniform over a large part of the gap in the course of the discharge development, virtually forming a dynamic positive column. The column completely controls the dynamics of the barrier discharge and determines such characteristics as the discharge current, discharge duration, light output, etc. Using the proposed model, one can easily evaluate many important discharge parameters.

Three-dimensional Monte Carlo/particle-in-cell studies of anode striations and cathode ionization wave in barrier-discharges in AC-PDP cell

The dynamics of the sustain discharge pulse in an ac-PDP cell is studied via the three-dimensional Monte Carlo/Particle-in-Cell simulations. Key phases in the discharge development are identified and thoroughly illustrated with an extensive set of plots. The main effort is focused on the study of the striations above the dielectric surface of the anode and on understanding the mechanisms responsible for the propagation of the cathode ionization wave. Both of these phenomena are representative examples of dielectric-surface charging processes in strongly collisional plasmas of barrier discharges

Backscattering of secondary electrons to the cathode in the oblique electric field in dielectric barrier discharge systems

In dielectric barrier discharge systems, where the cathode is covered with the dielectric layer, electric field lines may cross the cathode surface at an oblique angle θ. The secondary electrons emitted from this surface either return to the cathode due to collisions with atoms of the background gas or escape from the cathode vicinity. Using the two-term approximation to the Boltzmann equation for electrons, we have found that, for Ramsauer gases, the electron escape factor fes as a function of the angle θ unexpectedly exhibits non-monotonic behaviour. Monte Carlo simulations of backscattering of electrons performed for xenon and argon have confirmed the theoretical results and shown similar trends for non-Ramsauer gases.

Fluctuation dominated dynamics of a Townsend barrier microdischarge

The statistical fluctuations can dramatically change the dynamics of low current barrier microdischarges when the number of charged particles in the discharge gap is small. The systematic approach is developed to incorporate into the equations of the commonly used fluid model the main stochastic processes in Townsend barrier discharges. It is shown that when natural discharge oscillations are undamped, the fluctuations in the number of ions in the gap eventually lead to disruption of the discharge (i.e. to the state when all charged particles are swept out of the gap). For damped oscillations, the level of fluctuations is limited. It is also shown that fluctuations of the shape of the ion distribution over the gap are negligible.

Statistical Fluctuations in Low-Current Barrier Microdischarges

The number of charged particles in barrier microdischarges that operate in Townsend regime (like ldquoramp dischargesrdquo that are widely used in plasma display panels) is relatively small, and the statistical fluctuations should be taken into account when considering the discharge development. The main processes that cause the fluctuations are studied, and a simple analytical model for their description is developed. The model clarifies the mechanism of the statistical instability of the barrier Townsend discharge. Analogy to a nonlinear oscillator driven by a random force is revealed. Results obtained from the model are checked against those from Monte Carlo simulations.