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 TF2: Low Pressure Plasma Modeling II |
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Chair: Mirko Vukovic, Tokyo Electron Room: Ballroom II |
Friday, October 4, 2013 10:30AM - 11:00AM |
TF2.00001: Verification and Validation in Low Temperature Plasma Physics Invited Speaker: Miles Turner Plasma simulation is a widely used tool, for reasons ranging from clarification of basic scientific questions to engineering design studies. Clearly, activities such as these are valuable only if the simulations are correct, in some relevant sense. Indeed, it is not enough for the simulations to be correct. Evidence that the simulations are correct needs to be available to the community interested in the simulation results. In recent years, these issues have come to seem problematic, in part because of evidence that common practice is ineffective in detecting faulty simulations. Broadly speaking, two kinds of faults in simulations can be distinguished: (1) Incorrect or inappropriate physical models, including inaccurate choices of parameters, and (2) incorrect implementation of the physical model in software. Two kinds of tests are therefore needed to establish that a simulation is fit for purpose: Tests of software correctness, known as verification, and tests of model correctness, known as validation. Verification is a formal activity; Validation involves reference to experiments. This paper will discuss recent progress on application of these concepts in low-temperature plasma physics, with more emphasis on verification than on validation. [Preview Abstract] |
Friday, October 4, 2013 11:00AM - 11:30AM |
TF2.00002: Towards adaptive kinetic-fluid simulations of low-temperature plasmas Invited Speaker: Vladimir Kolobov The emergence of new types of gaseous electronics in multi-phase systems calls for computational tools with adaptive kinetic-fluid simulation capabilities. We will present an Adaptive Mesh and Algorithm Refinement (AMAR) methodology for multi-scale simulations of gas flows and discuss current efforts towards extending this methodology for weakly ionized plasmas. The AMAR method combines Adaptive Mesh Refinement (AMR) with automatic selection of kinetic or fluid solvers in different parts of computational domains. This AMAR methodology was implemented in our Unified Flow Solver (UFS) for mixed rarefied and continuum flows. UFS uses discrete velocity method for solving Boltzmann kinetic equation under rarefied flow conditions coupled to fluid (Navier-Stokes) solvers for continuum flow regimes. The main challenge of extending AMAR to plasmas comes from the distinction of electron and atom mass. We will present multi-fluid, two-temperature plasma models with AMR capabilities for simulations of glow, corona, and streamer discharges. We will briefly discuss specifics of electron kinetics in collisional plasmas, and deterministic methods of solving kinetic equations for different electron groups. Kinetic solvers with Adaptive Mesh in Phase Space (AMPS) will be introduced to solve Boltzmann equation for electrons in the presence of electric fields, elastic and inelastic collisions with atoms. These kinetic and fluid models are currently being incorporated into AMAR methodology for multi-scale simulations of low-temperature plasmas in multi-phase systems. [Preview Abstract] |
Friday, October 4, 2013 11:30AM - 11:45AM |
TF2.00003: Two-dimensional extended fluid model for a dc glow discharge with nonlocal ionization source term Ismail Rafatov, Eugeny Bogdanov, Anatoliy Kudryavtsev Numerical techniques applied to the gas discharge plasma modelling are generally grouped into fluid and kinetic (particle) methods, and their combinations which lead to the hybrid models. Hybrid models usually employ Monte Carlo method to simulate fast electron dynamics, while slow plasma species are described as fluids. However, since fast electrons contribution to these models is limited to deriving the ionization rate distribution, their effect can be expressed by the analytical approximation of the ionization source function, and then integrating it into the fluid model. In the context of this approach, we incorporated effect of fast electrons into the ``extended fluid model'' of glow discharge, using two spatial dimensions. Slow electrons, ions and excited neutral species are described by the fluid plasma equations. Slow electron transport (diffusion and mobility) coefficients as well as electron induced reaction rates are determined from the solutions of the electron Boltzmann equation. The self-consistent electric field is calculated using the Poisson equation. We carried out test calculations for the discharge in argon gas. Comparison with the experimental data as well as with the hybrid model results exhibits good applicability of the proposed model. [Preview Abstract] |
Friday, October 4, 2013 11:45AM - 12:00PM |
TF2.00004: Self-Consistent Simulations of the Radial Line Slot Antenna Plasma Source Peter Ventzek, Rochan Upadhyay, Michitaka Aita, Jun Yoshikawa, Toshihiko Iwao, Kiyotaka Ishibashi, Laxminarayan Raja The radial line slot antenna plasma source couples microwave power through a slot antenna structure and window to a plasma characterized by a generation zone adjacent to the window and a diffusion zone that contacts a substrate. The diffusion zone is characterized by a very low electron temperature. This property renders the source useful for soft etch applications and thin film processing for which low ion energy is desirable. The transport of electrons from the point of generation through the diffusion is characterized by a relaxing electron energy distribution function. The transport is difficult to describe using a quasi-neutral model and a zero dimensional solution of Boltzmann's Equation. A hybrid approach in which test particle electrons are used to describe the electron kinetics is demonstrated. The impact of driving frequency, metastable pooling on the spatial distribution of the electron energy distribution function will be described for argon plasmas. [Preview Abstract] |
Friday, October 4, 2013 12:00PM - 12:15PM |
TF2.00005: Numerical Approaches for the Optimization of Plasma Sources for Space Thrusters Davide Melazzi, Vito Lancellotti, Alessandro Cardinali, Marco Manente, Daniele Pavarin The optimization of radiofrequency magnetized plasma sources for space thrusters has focused on power deposition in nonuniform plasmas. However, many researchers assumed rather than computed the induced current density on the antenna, and considered a uniform and constant magneto-static field aligned with the source axis. To overcome these limitations, we propose two methods: (i) a full-wave approach to compute the current distribution on the antenna and (ii) a ray-tracing approach to investigate the influence of actual magneto-static fields on the wave propagation and power deposition. Plasma density profiles are included in both approaches. In the full-wave method, we derive a surface integral equation for the antenna and a volume integral equation for the plasma by applying the electromagnetic equivalence principles. A comparative study of different antennas will be presented. In the second method, the propagation and absorption of electromagnetic waves are investigated by solving the 3D Maxwell-Vlasov model equations by a WKB asymptotic expansion. Unconventional mode conversions and power deposition profiles are found when realistic confinement magnetic field are considered. [Preview Abstract] |
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