A Monte Carlo modelling study of the electrons in the microdischarges in plasma addressed liquid crystal displays

Fluid models for gas discharges are based on restrictive assumptions for the electron-energy distribution function (EEDF). In this work we investigate the validity and consequences of these assumptions for discharges occurring in plasma addressed liquid crystal (PALC) displays. For this purpose we have developed a Monte Carlo model for electrons, which we compare to a fluid model. A direct current (DC) discharge and afterglow in the PALC geometry are considered, with helium as a discharge gas. In the discharge, the EEDF calculated with the Monte Carlo model displays several non-equilibrium phenomena, such as peaks of fast electrons that have undergone none or only a few collisions, and the absence of a high-energy tail. Although these features are not incorporated in the fluid model, both models lead to virtually the same electron density profile. However, the ionization rate obtained with the Monte Carlo model is spread out over a larger region than the ionization rate in the fluid model. The Monte Carlo calculations reveal that the electrons in the afterglow have a highly non-equilibrium nature, and require a special treatment in the fluid model

Energy loss mechanisms in the microdischarges in plasma display panels

Low luminous efficacy is one of the major drawbacks of plasma display panels (PDPs), where the main limiting factor is the efficiency of the microdischarges in generating UV radiation. In this work we use a two-dimensional self-consistent fluid model to analyze the energy loss mechanisms in neon–xenon discharges in coplanar-electrode color PDPs and interpret experimental data on the luminous efficacy of these PDPs. The modeling results are in good agreement with the measured UV emission spectrum and measured trends in the efficacy. Most of the electrical input energy is transferred to ions and subsequently to the gas and the surface. The electrical energy transferred to electrons is mostly used for ionization and excitation, where the part used for xenon excitation largely ends up in UV radiation. The amplitude, frequency, and rise time of the driving voltage mainly affect the energy losses due to ion heating. The xenon content also affects the conversion of electron energy into UV energy. ©2001 American Institute of Physics

Resonance radiation transport in plasma display panels

In fluid models of the gas discharges in plasma display panels, the trapping of resonance radiation is usually accounted for by a trapping factor. In this work, we present a Monte Carlo model for resonance photons, which gives a much more accurate description. First, we compare the results of this Monte Carlo model with the results of the fluid model trapping factor approach. Although the trapping factor approach does not yield the same spatial distribution for the density of the resonant state atoms, the spatially integrated density is in good agreement with the results of the Monte Carlo model. Next, we compare the results of the Monte Carlo model with measured spectra of emitted resonance radiation. The agreement is very good. Thus we provide, via the Monte Carlo model, experimental support for the widely used trapping factor approach. ©2000 American Institute of Physic

Evaluation of angular scattering models for electron-neutral collisions in Monte Carlo simulations

In Monte Carlo simulations of electron transport through a neutral background gas, simplifying assumptions related to the shape of the angular distribution of electron-neutral scattering cross sections are usually made. This is mainly because full sets of differential scattering cross sections are rarely available. In this work simple models for angular scattering are compared to results from the recent quantum calculations of Zatsarinny and Bartschat for differential scattering cross sections (DCS's) from zero to 200 eV in argon. These simple models represent in various ways an approach to forward scattering with increasing electron energy. The simple models are then used in Monte Carlo simulations of range, straggling, and backscatter of electrons emitted from a surface into a volume filled with a neutral gas. It is shown that the assumptions of isotropic elastic scattering and of forward scattering for the inelastic collision process yield results within a few percent of those calculated using the DCS's of Zatsarinny and Bartschat. The quantities which were held constant in these comparisons are the elastic momentum transfer and total inelastic cross sections

LXCat : an open-access, web-based platform for data needed for modeling low temperature plasmas

\u3cp\u3eLXCat is an open-access platform (www.lxcat.net) for curating data needed for modeling the electron and ion components of technological plasmas. The data types presently supported on LXCat are scattering cross sections and swarm/transport parameters, ion-neutral interaction potentials, and optical oscillator strengths. Twenty-four databases contributed by different groups around the world can be accessed on LXCat. New contributors are welcome; the database contributors retain ownership and are responsible for the contents and maintenance of the individual databases. This article summarizes the present status of the project.\u3c/p\u3