Bulletin of the American Physical Society
68th Annual Gaseous Electronics Conference/9th International Conference on Reactive Plasmas/33rd Symposium on Plasma Processing
Volume 60, Number 9
Monday–Friday, October 12–16, 2015; Honolulu, Hawaii
Session IW3: Modeling and Simulation I |
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Chair: Ute Ebert, Eindhoven University of Technology Room: 305 AB |
Wednesday, October 14, 2015 8:00AM - 8:30AM |
IW3.00001: Numerical Uncertainty Estimation for Stochastic Particle-in-Cell Simulations Applied to Verification and Validation Invited Speaker: Keith Cartwright Numerical error estimation is a key component in verification, validation, and uncertainty quantification. For ParticleIn-Cell (PIC) plasma simulations, error estimation is complicated due to the presence of stochastic noise and multiple convergence parameters (grid size, time step, macro particle weight). In this talk, we will discuss recent developments for the Stochastic Richardson Extrapolation Based Error Quantification method (StREEQ). This method at its core is a multi-regression technique, where nine regression models and multiple bootstrap samples propagate uncertainties due to the fit and the stochasticity of the underlying data for an appropriate error model with unknown convergence rates. Recently, automation of the convergence parameter domain selection has been implemented; this enables efficient error estimation for large data sets, including analysis of multiple quantities of interest and time dependent data. This method is demonstrated for verification of both steady and time-periodic electron diodes, as well as validation of radiation generated plasma in an end-radiated cylinder.\\[4pt] In collaboration with Gregg Radtke, Sandia National Laboratories. [Preview Abstract] |
Wednesday, October 14, 2015 8:30AM - 9:00AM |
IW3.00002: Understanding Plasmas with a High Degree of Correlation Through Modeling: From Rydberg and Fermionic Plasmas to Penning Plasmas Invited Speaker: Andrew Christlieb Ultra cold neutral plasmas have gained attention over the past 15 years as being a unique environment for studying moderately to strongly coupled neutral systems. The first ultra cold neutral plasmas were generated by ionizing a Bose Einstein condensate, generating a plasma with .1K ions and 2-4K electrons. These neutral plasmas have the unique property that the ratio of their potential energy to their kinetic energy, ($\Gamma=PE/KE$), can greatly exceed 1, leading to a strongly correlated system. The high degree of correlation means that everything from wave propagation through collision dynamics behaves quite differently from their counterpart in traditional neutral plasmas. Currently, a range of gases and different methods for cooling have been used to generate these plasmas from supersonic expansion, through penning trap configurations (reference Tom, Jake and Ed). These systems have time scales form picoseconds to milliseconds have a particle numbers from $10^5$ to $10^9$. These systems present a unique environment for studying the physics of correlation due to their low particle number and small size. We start by reviewing ultra cold plasmas and the current sate of the art in generating these correlated systems. Then we introduce the methods we will use for exploring these systems through direct simulation of Molecular Dynamics models; Momentum Dependent Potentials, Treecodes and Particle-Particle Particle-Mesh methods. We use these tools to look at two key areas of ultra cold plasmas; development of methods to generate a plasma with a $\Gamma\gg 1$ and the impact of correlation of collisional relaxation. Our eventual goal is to use what we learn to develop models that can simulate correlation in large plasma systems that are outside of the scope of Molecular Dynamics models.\\[4pt] In collaboration with Gautham Dharmuman, Mayur Jain, Michael Murillo and John Verboncoeur. [Preview Abstract] |
Wednesday, October 14, 2015 9:00AM - 9:15AM |
IW3.00003: Bridging the Gap between Global Models and Full Fluid Models in Electronegative Plasmas Andrew Hurlbatt, Timo Gans, Deborah O'Connell The value of analytical and numerical models has been proven many times over. They allow investigation of complicated discharge phenomena and the interplay that makes plasmas such a complex environment. Global Models are quick to implement and can have almost negligible computation cost, however only approximate bulk values. Fluid Models take longer to develop, and can take days to solve, but provide spatial profiles. The work presented here details a different type of model, analytically similar to Fluid Models, but computationally closer to a Global Model, and extended to give solutions for the challenging environment of electronegative plasmas. Also included are non-isothermal electrons, gas heating, and coupled neutral dynamics. Solutions are reached in minutes, and spatial profiles are given for densities, fluxes, and temperatures. This allows broad parameter sweeps that are not practical with more costly models, as well as exposing non-trivial trends that Global Models do not capture. Examples are given for a low pressure oxygen CCP. Excellent agreement is shown with a Fluid Model, and the limitations of the corresponding Global Model are demonstrated. Applicability to other systems is discussed, particularly Narrow Gap discharges, where spatial non-uniformity is high. [Preview Abstract] |
Wednesday, October 14, 2015 9:15AM - 9:30AM |
IW3.00004: Application of ILDM for Simplifying Complex Plasma Chemistry Tafizur Rehman, Kim Peerenboom, Efe Kemaneci, Wouter Graef, Jan van Dijk Numerical simulation of plasma models involving large numbers of species and reactions is computationally very expensive. One of the solutions to overcome the problem due to complex chemistry is to employ Chemical Reduction Techniques(CRT) used in combustion research. The CRT we apply here is ILDM (Intrinsic Low Dimensional Manifold). ILDM simply uses the fact that, due to wildly varying time scales, the reaction system is not evenly sensitive to all the reactions but some reactions are very fast and attain steady state in a very short interval of time. Based on this information ILDM method finds the lower dimensional space (manifold) inside a complete state-space such that after a short interval of time the fast time scales of the system will quickly move onto this low dimensional manifold and the full system description can be given by this lower dimensional manifold. By constructing the low dimensional manifold the reaction space is described in terms of only a few parameters and it becomes possible to tabulate the results in terms of those few parameters. By generating the look-up table, for given values of controlling parameters the remaining parameters are found explicitly. In this work we apply the ILDM method for the reduced simulation of an argon plasma. [Preview Abstract] |
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