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ABSTRACT: The non-equilibrium atmospheric-pressure parallel-plate helium dielectric barrier discharge (DBD) driven by a realistic 20kHz
distorted-sinusoidal voltage waveform has been investigated by means of simulations and experiments. A self-consistent one-dimensional
fluid modeling code considering the non-local electron energy balance was applied to simulate the helium DBD. The effect of
selecting plasma chemistry was investigated by comparing simulations with experiments. The results show that the simulations,
which include more excited helium, metastable helium and electron–ion-related reaction channels, can faithfully reproduce
the measured discharged temporal current quantitatively. Based on the simulated discharge properties, we have found that there
is complicated mode transition of discharges from the long Townsend-like to the “dark current”-like, then to the short primary
Townsend-like and the short secondary Townsend-like for the helium DBD that is driven by a realistic distorted-sinusoidal
voltage power source. Discharge properties in different periods of discharge are discussed in detail in the paper.
KeywordsTownsend-like discharge–Atmospheric pressure plasmas–Helium–Fluid modelling–Dielectric barrier discharge
Plasma Chemistry and Plasma Processing 05/2012; 31(1):1-21. · 1.60 Impact Factor
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ABSTRACT: Simulation of excimer ultraviolet (EUV) emission from a coaxial xenon excimer ultraviolet lamp driven by distorted bipolar
square voltages is presented in this study. A self-consistent radial one-dimensional fluid model, considering local mean energy
approximation (LMEA), along with a set of simplified xenon plasma chemistry was employed to simulate the discharge physics
and chemistry. Emitted powers of EUV light and deposited powers to the charged species were simulated by varying the values
of four key parameters, which include the driving frequency, gas pressure, gap distance and number of dielectric layers. Results
show that there are three distinct periods that include pre-discharge, discharge and post-discharge ones. It is found that
intensive EUV (172nm) emission occurs during the early part of the discharge period, which correlates very well in time with
the power deposition through electrons. In addition, power deposition through
\textXe + {\text{Xe}}^{ + } and
\textXe2 + {\text{Xe}}_{2}^{ + } occurs mainly in the discharge period and later part of discharge period, respectively. Surprisingly, the emission efficiency
of 172nm increases slightly with increasing driving frequency of power source, while it increases dramatically with increasing
gap distance. In addition, the maximal emission efficiency is found to take place at gas pressure of 600torr. The emission
efficiency of one-dielectric case is found to be better than that of two-dielectric one. The underlying mechanisms in the
above observations are discussed in detail in the paper.
KeywordsCoaxial xenon excimer lamp-Excimer ultraviolet-Fluid modeling-Local mean energy approximation
Plasma Chemistry and Plasma Processing 04/2012; 30(6):907-931. · 1.60 Impact Factor
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ABSTRACT: Summary form only given. Progress in developing a parallelized 2D/2D-axisymmetric fluid and neutral flow modeling code (PFNF) for non-thermal plasma simulations is reported in this paper. Major modules of this PFNF include: 1) a fluid modeling code for gas discharge with power ranging from 10 kH-100 MHz, 2) a Navier- Stokes equation solver for neutral flow, and 3) a coupled external circuit analysis code. The fluid modeling code solves charged species continuity equations using drift-diffusion approximation for the particle flux term, electron energy density equation, Poisson's equation, and Maxwell equation. The Navier-Stokes equation solver solves the continuity equation, momentum equations and energy equation for the mass-averaged neutral flow, which is capable of modeling conjugate heat transfer for solid and gas. The external circuit analysis code applies Kirchoff's current law by considering the external RLC and plasma together at the same time. All model equations are nondimensionalized and discretized using fully implicit finite-difference method with Scharfetter- Gummel scheme for the fluxes in the fluid modeling equations and exponential scheme for the fluxes in the Navier-Stokes equations. Both backward Euler and higher-order temporal schemes are included. All transport coefficients of charged species and rate constants of chemical reactions can be expressed as the nonlinear function of electron temperature or gas temperature. The resulting discretized nonlinear coupled equations are then solved by the parallel Newton-Krylov-Schwarz (NKS) algortihm, in which the overlapping additive Schwarz method (ASM) and bi-CGSTAB scheme is used as the preconditioner and linear matrix equation solver, respectively. Parallel performance is tested on a PC cluster system (IBM-13 50 at NCHC of Taiwan) up to 128 processors. Several test cases, including quasi-1D, quasi-1D-radial, and 2D-axisymmetric parallel plate under various operating conditions will be presented in th- - e presentation.
Plasma Science, 2008. ICOPS 2008. IEEE 35th International Conference on; 07/2008
