Bulletin of the American Physical Society
66th Annual Gaseous Electronics Conference
Volume 58, Number 8
Monday–Friday, September 30–October 4 2013; Princeton, New Jersey
Session LW2: Plasma Modelling I |
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Chair: Vladimir Kolobov, University of Alabama Room: Ballroom II |
Wednesday, October 2, 2013 3:30PM - 4:00PM |
LW2.00001: Particle based discharge simulations: electron heating and electromagnetic effects Invited Speaker: Thomas Mussenbrock It is widely acknowledged that kinetic effects play a significant role in almost all kinds of technological plasmas. These plasmas often exhibit several groups of electrons with significantly different energies. The intrinsically non-Maxwellian behavior of the electron energy distribution function in this case invalidates fluid-based simulation approaches, so that a self-consistent kinetic treatment is needed to capture all important physics features. This holds in particular for the heating of electrons. The situation becomes even more complicated if in addition to the kinetic treatment electromagnetic effects have to be considered. This is for example the case when the electrode size and driving frequency of capacitive discharges increase. In this contribution we discuss how electromagnetic models based on the Darwin approximation of Maxwell's equations can be incorporated into kinetic simulations of technological plasmas to meet the goals of scientific accuracy and computational efficiency. [Preview Abstract] |
Wednesday, October 2, 2013 4:00PM - 4:15PM |
LW2.00002: Fluid modeling of low-temperature plasma transport across a magnetic field R. Futtersack, G.J.M. Hagelaar, P. Tamain, A. Simonin While various low-temperature plasma sources operating with a steady magnetic field are widely used in industrial and research applications, the knowledge of magnetized transport in these plasmas is still incomplete. As the transport of charges and currents in such plasma sources may show a complex and ill-understood behavior, we investigate the issue of magnetized transport as such. A new 2D fluid model has been developed, combining the usual methods of low-temperature plasma modeling with techniques drawn from fusion plasmas research, and therefore allowing to explore a large range of magnetic field strengths and topologies. We then analyze simulations related to representative experiments with various magnetic field configurations in order to characterize the transport in these low-temperature plasmas, and compare the results with experimental data and application-oriented models. For two different negative ion sources, the main behavior of the plasma is recovered, with the emergence of asymmetries due to the drifts induced by the magnetic field. The model is also able to capture the transient dynamics of the plasma such as certain types of instabilities. [Preview Abstract] |
Wednesday, October 2, 2013 4:15PM - 4:30PM |
LW2.00003: An External Circuit Model for 3D Electromagnetic Particle-In-Cell Simulations Ming-Chieh Lin, Chuandong Zhou, David N. Smithe In this work, an algorithm for coupling external circuit elements to electromagnetic (EM) particle-in-cell (PIC) simulations is developed. The circuit equation including an external voltage or current source, resistance, inductance, capacitance, and a dynamic load is solved simultaneously with the EM PIC updaters through an instant measured voltage across the system to obtain the supplied current for feeding into the system. This external circuit model has been demonstrated and implemented in a 3D conformal finite-difference time-domain PIC code, Vorpal. [Preview Abstract] |
Wednesday, October 2, 2013 4:30PM - 4:45PM |
LW2.00004: PumpKin: A tool to find principal pathways in plasma chemical models Aram H. Markosyan, Alejandro Luque, Francisco J. Gordillo V\'azquez, Ute Ebert Recent kinetic models of atmospheric chemistry or of many industrial processes contain thousands of chemical reactions and species. The reactions depend on timescales, electric fields, temperature, pressure etc. We have developed a software tool called PumpKin (\underline {\textbf{p}}athway red\underline {\textbf{u}}ction \underline {\textbf{m}}ethod for \underline {\textbf{p}}lasma \underline {\textbf{kin}}etic models) to find all principal pathways in such complex plasma chemistry models, i.e. the dominant reaction sequences. PumpKin is a universal tool, inspired by [Lehmann, \textit{J Atmos Chem} \textbf{41}, 297 (2002)]. It requires to define and to run once a complete plasma kinetics solver, e.g. ZDPlasKin [http://www.zdplaskin.laplace.univ-tlse.fr], up to the time of interest. The stoichiometric matrix of the system, the reaction rates and the temporal profile of the species densities are the input for PumpKin to systematically identify the principal pathways. [Preview Abstract] |
Wednesday, October 2, 2013 4:45PM - 5:00PM |
LW2.00005: Arbitrarily high-order semi-Lagrangian methods for the kinetic description of plasmas Yaman G\"{u}\c{c}l\"{u}, Andrew J. Christlieb, William N.G. Hitchon In the kinetic description of low-temperature plasmas, deterministic mesh-based solvers excel for their capacity to resolve small electric fields in quasi-neutral regions, and to compute accurate ionization rates involving a small population of high energy electrons. Among these, semi-Lagrangian methods like the Convected Scheme (CS) are preferred, because of their ability to take large time-steps (no CFL limit) and their low numerical diffusion. The CS is mass conservative and positivity preserving, and was recently extended to arbitrarily high order of accuracy in phase-space [1,2]: the new scheme was applied to the Vlasov-Poisson system on periodic domains, and validated against classical 1D-1V test-cases. Here we introduce the effect of scattering collisions and wall recombination, include kinetic ions, and extend the model to 1D-2V. We investigate the formation of a planar presheath, and compare the new results to low-order simulations.\\[4pt] [1] Y. G\"u\c{c}l\"u, A.J. Christlieb and W.N.G. Hitchon, ``High order semi-Lagrangian schemes and operator splitting for the Boltzmann equation.'' ICERM, June 3-7 2013. https://icerm.brown.edu/tw13-1-isbeaa.\\[0pt] [2] ---, ``Arbitrarily high-order Convected Scheme solution of the Vlasov-Poisson system.'' Submitted to J. Comput. Phys., July 2013. [Preview Abstract] |
Wednesday, October 2, 2013 5:00PM - 5:15PM |
LW2.00006: A hybrid model to estimate particle fluxes in a fluid mode using a particle-in-cell Monte Carlo collision method Seok Won Hwang, Ho-Jun Lee, Hae June Lee Fluid models have been widely used in plasma simulations and conducted successfully under near-atmospheric pressure conditions such as plasma display panels and atmosphere pressure plasma devices. However, fluid models have drawbacks in low pressure conditions because they cannot describe exact energy distribution of species in spatial and temporal domains. As a result, fluid models are not able to calculate the transport and the reaction coefficients, nor represent non-local effects at low pressure. In order to minimize these, the Monte Carlo collision (MCC) methods have been additionally used to obtain the energy distribution function of each species, especially for electrons in conventional hybrid models. Another problem in conventional fluid models is to utilize a drift-diffusion approximation (DDA) for transport fluxes for electrons and ions instead of the momentum conservation equation. However, if DDA is used at low pressure, the flux is overestimated because the approximation assumes the instant local balanced steady state from collisions. In this work, a new hybrid method is introduced to provide the correct flux using particle-in-cell (PIC) coupled with MCC instead of DDA. The results of the modified hybrid simulation show better agreement with a full PIC simulation. In addition, the effect of boundary conditions on the potential and density distribution is investigated. [Preview Abstract] |
Wednesday, October 2, 2013 5:15PM - 5:30PM |
LW2.00007: Automatic Coarsening of the Particle Interaction Mesh in a Hybrid PIC-DSMC Simulation Stan Moore, Paul Crozier, Chris Moore, Matthew Bettencourt, Matthew Hopkins Hybrid particle-in-cell (PIC) and direct simulation Monte Carlo (DSMC) methods are frequently used to simulate low density interacting plasmas, and a single mesh is often used for both DSMC and PIC calculations. Typically however, the mesh size for the PIC method is limited by the Debye length, while the particle interaction mesh in DSMC is limited by the mean free path, which is often much larger than the Debye length. Insufficient computational particles in a DSMC collision cell can also lead to spurious results when using the no-time-counter scheme. Therefore, the optimal PIC mesh may be suboptimal for calculating DSMC collisions. We have developed a method where a finer unstructured tetrahedral mesh is used for PIC calculations, and a coarser conglomeration of PIC mesh elements is used by the DSMC algorithm to calculate particle interactions (i.e. elastic collisions, ionizations, etc.). This automatic coarsening of the PIC elements into DSMC interaction cells is accomplished using an oct-tree algorithm, based on the mean free path calculated using the previously simulated local collision rate. Using two different sized meshes for PIC vs. DSMC gives greater flexibility to the simulation and allows one to reduce the computational cost by using fewer computational particles while still accurately simulating the DSMC collisions. The new method is demonstrated and results and computational speed are compared to the traditional hybrid PIC-DSMC simulation method. [Preview Abstract] |
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