Bulletin of the American Physical Society
63rd Annual Gaseous Electronics Conference and 7th International Conference on Reactive Plasmas
Volume 55, Number 7
Monday–Friday, October 4–8, 2010; Paris, France
Session UF4: Modeling and Simulation III |
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Chair: Zoltan Donko, Research Institute for Solid State Physics and Optics Room: 151 |
Friday, October 8, 2010 2:00PM - 2:15PM |
UF4.00001: Boltzmann equation analysis and Monte Carlo simulation of electron transport in N$_{2}$-O$_{2}$ streamer discharge Sasa Dujko, Ute Ebert, Ronald White, Zoran Petrovic A comprehensive investigation of electron transport in N$_{2}$-O$_{2}$ mixtures has been carried out using a multi term theory for solving the Boltzmann equation and Monte Carlo simulation technique instead of conventional two-term theory often employed in plasma modeling community. We focus on the way in which the transport coefficients and spatially resolved transport data are influenced by the amount of O$_{2}$ in the mixture. Emphasis is placed upon the explicit and implicit effects of non-conservative collisions, ionization and attachment on various transport coefficients. In particular, the effects of three-body attachment for electrons on various transport data are considered. It is found that the difference between two sets of transport coefficients, bulk and flux, resulting from the explicit influence of non-conservative collisions depends on the variation of the amount of O$_{2}$ in mixture. The critical values of $E/N$ for which the ionization exactly balances the electron attachment are determined. [Preview Abstract] |
Friday, October 8, 2010 2:15PM - 2:30PM |
UF4.00002: ABSTRACT WITHDRAWN |
Friday, October 8, 2010 2:30PM - 2:45PM |
UF4.00003: Dynamics of Ar metastables in RF CCP discharge: PIC/MCC/DSMC simulation Lu-Jing Hou, Mikhail Pustylnik, Alexei Ivlev, H.M. Thomas, G.E. Morfill Metastables have long been expected to play an important role in determining properties of an argon (Ar) RF plasma discharge. In the past two decades, extensive experimental, theoretical and numerical research had been conducted to reveal their importance in RF discharge. However, obvious contradictions, which cannot be easily accommodated for different discharge conditions, are found between experiments and theories/simulations and between simulations using different models as well. This clearly indicates an insufficient understanding of physical processes involving metastables in RF discharge. To shed new light on the role of metastables on RF discharge, the present work employs combined PIC/MCC and Direct Simulation Monte Carlo (DSMC) methods to study the dynamics of metastables in RF discharge. Both plasmas (ions and electrons) and metastables are treated as particles in the simulation and are coupled though various collision processes, such as metastable excitation, pooling, electron quenching, step ionization, metastable-wall secondary electron emission, neutral-metastable elastic collisions, in addition to those included in typical PIC/MCC simulation, such as direct ionization and excitation. [Preview Abstract] |
Friday, October 8, 2010 2:45PM - 3:00PM |
UF4.00004: Collisionless to space charge dominated transition of a DC low pressure wire discharge Renaud Gueroult, Paul-Quentin Elias, Denis Packan Depending on operating conditions, the low pressure ($10^{-4}-10^{-2}$mbar) DC wire plasma source (WIPS) exhibits two distinct modes of discharge. Experimental measurements show that each mode presents a specific spatial extension in terms of discharge glow. Transition from one mode to the other is sudden and triggers a discharge voltage jump. Using two-dimensional particle in cell modeling, discharge modes of the low pressure low current ($\approx 1$ mA) wire source in Helium are accurately reproduced. The discharge behavior in the transition regime is explained in light of PIC simulations results, which justifies the mode transition as a transition from a collisionless to a space charge dominated regime. Modeling the discharge as an ion flow with both inertial and friction term confirm this analysis, the transition occurring when the pressure reaches a threshold value - function of the discharge voltage and current - permitting the formation of a positive space charge. Confrontation with simulations confirms the efficiency of this simple model for prediction of both the pressure of mode transition and the voltage jump across the transition. [Preview Abstract] |
Friday, October 8, 2010 3:00PM - 3:15PM |
UF4.00005: Simulation of Atmospheric Pressure DC Glow Discharge along a Helium Miniature Gas flow in Air Fumiyoshi Tochikubo, Naoki Shirai, Satoshi Uchida Recently, atmospheric pressure nonthermal plasmas are widely studied for material processing, pollution control technology, and so on. When we use a noble gas flow in air, atmospheric pressure nonthermal plasma is easily obtained along the gas flow line. In these plasmas, the spatial distribution of the gas composition is important factor to determine the plasma property. In this work, we carried out the numerical simulation of atmospheric pressure dc glow discharge with helium gas flow in nitrogen by two-dimensional fluid model. The discharge is generated along helium gas flow between parallel electrodes. The calculated discharge profile is very similar to that observed in the experiment. The discharge clearly has cathode sheath and positive column. The sheath thickness was about 60 $\mu$m, and the plasma density was on the order of 10$^{12}$ cm$^{-3}$. The contribution of Penning ionization was comparable to electron impact ionization. The discharge volume is confined by the increase of nitrogen ratio. The plasma profile reflects the helium distribution because mixture of nitrogen drastically decreases the electron energy. [Preview Abstract] |
Friday, October 8, 2010 3:15PM - 3:30PM |
UF4.00006: Numerical simulations of the influence of an ion beam on the plasma analyzer performance in Njord helicon device Wojciech Miloch, Lekha Mishra, Njal Gulbrandsen, Ashild Fredriksen Recent experiments in Njord helicon plasma device confirmed the presence of an ion beam in a weakly magnetized plasma downstream from the double layer region [1]. The measurements were carried out with the retarding-field energy analyzer (RFEA). Since the housing of RFEA is biased with respect to the plasma, the plasma current to the orifice can depend on the sheath structure in its vicinity, and on its orientation with respect to the flow. Throughout understanding of the problem is needed for the analysis of data from such measurements. Numerical simulations allow to address this problem self-consistently. We simulate weakly magnetized plasmas with an additional ion beam for parameters relevant to experiments in Njord, and study the effect of a biased object, such as RFEA, on the surrounding plasma. The emphasis is given to the plasma flux to the surface, and the plasma energy distribution in the vicinity of the object. Our three-dimensional simulations are carried out with the upgraded DiP3D particle-in-cell numerical code [2], which accounts for collisions and external magnetic field. [1] A. Fredriksen et.al. Plasma Sources Sci. Techn. 19, 034009 (2010). [2] W.J. Miloch et.al. New J.Phys. 11, 043005 (2009). [Preview Abstract] |
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