Bulletin of the American Physical Society
70th Annual Gaseous Electronics Conference
Volume 62, Number 10
Monday–Friday, November 6–10, 2017; Pittsburgh, Pennsylvania
Session SR1: Modeling and Simulation II |
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Chair: Francesco Taccogna, CNR Nanotec Room: Salon D |
Thursday, November 9, 2017 1:30PM - 2:00PM |
SR1.00001: An advanced particle-in-cell simulation parallelized with GPUs for a capacitively coupled plasma reactor Invited Speaker: Hae June Lee Many key aspects of low-temperature plasmas include nonlinear transient and kinetic effects related to the spatiotemporal variation of electron energy distribution function (EEDF) which cannot be treated in a fluid simulation model. The particle-in-cell (PIC) simulation calculates kinetic effects through the statistical representation of the EEDF using many particles and thus gives accurate results. However, the computational cost is very expensive to resolve all aspects in a plasma discharge with millions of particles as well as hundreds of thousand of grids during millions of time steps. Additionally, the simulation of discharge plasmas should handle the collision processes and the rapid increase of the total number of simulation particles. In this presentation, details of a two-dimensional PIC simulation parallelized with graphics processing units (GPUs) are explained for the improvement of computation speed. For the simulation of a capacitively coupled plasma reactor with a gas pressure from 10 mTorr to 3 Torr, various kinetic effects are analyzed with the GPU-PIC code by investigating the spatiotemporal variation of EEDFs and electron heating. Finally, the changes of ion energy and angle distribution functions on the substrate are presented with the increase in gas pressure. [Preview Abstract] |
Thursday, November 9, 2017 2:00PM - 2:15PM |
SR1.00002: Particle in Cell Algorithms and Codes Toward the Next Generation Architectures Aram Markosyan, Christopher Moore, Matthew Bettencourt, Janine Bennett, Jonathan Lifflander, David Hollman, Jeremiah Wilke, Hemanth Kolla Massively parallel and heterogeneous next-generation platforms present unprecedented challenges for maximizing efficiency of plasma simulation kernels. Asynchronous many-task (AMT) frameworks use deferred execution and asynchronous tasking to enable runtime capabilities ranging from load balance to data reuse to communication overlap. Many AMT systems are large full stack frameworks with certain programmability or stability concerns, limiting their use in Sandia production codes. We have developed DARMA (Distributed Asynchronous Resilient Models for Application), which instead provides a light-weight translation layer for embedding tasking and deferred execution in C$++$ codes that encourages, rather than restricts, flexible and diverse AMT software stacks. In this work, we focus on leveraging DARMA to better express asynchrony and load imbalance present in particle in cell kernels. In particular, we present empirical performance and productivity results, where DARMA implementation of these kernels is compared to more traditional implementations. [Preview Abstract] |
Thursday, November 9, 2017 2:15PM - 2:30PM |
SR1.00003: Particle-in-Cell modeling of the magnetized direct current microdischarge Dmitry Levko, Laxminarayan Raja Following the Paschen's law, electrical breakdown of gaps with small \textit{pd}, where $p$ is the gas pressure and $d$ is the interelectrode gap, requires extremely high voltages. This means that the breakdown voltage for low-pressure microdischarges is of the order of a few kilovolts. This makes impractical the generation of low-pressure dc microdischarges. The application of dc magnetic field confines electrons in the cathode-anode gap. This leads to the significant decrease of the breakdown voltage because each electron experiences many collisions during its diffusion toward the anode. However, as was obtained experimentally, magnetized low-pressure microdischarges experience numerous instabilities whose nature is still not completely understood. In the present paper, we study the influence of magnetic field on the low-pressure microdischarges. We use self-consistent one-dimensional Particle-in-Cell Monte Carlo collisions model which takes into account the electron magnetization while ions remain unmagnetized. We obtain striations in the discharge. We show that these striations appear in both homogeneous and non-homogeneous magnetic field. We find simple expression for the instability growth rate which shows that the instability results from ionization processes. [Preview Abstract] |
(Author Not Attending)
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SR1.00004: PIC/MCC simulation of magnetized capacitively coupled plasmas Shali Yang, Ya Zhang, Hongyu Wang, Wei Jiang Magnetized capacitively coupled plasma (MCCP) has been widely used in microelectronic industry. External magnetic field is applied to increase the efficiency of power transfer to the plasma and enhance plasma confinement. We used our one-dimensional implicit Particle-in-cell/Monte Carlo collision (PIC/MCC) model to study the symmetric and asymmetric magnetic field on CCP. The PIC/MCC model is one-dimensional in space and three-dimensional in velocity, thus the E¨wB drift is correctly simulated. For the symmetric magnetic field, we studied the electrical asymmetry effects in MCCP. It is found that, with a weaker magnetic field at 10 G, the plasma density is nearly doubled and the self-bias is almost unaffected. And with a stronger magnetic field at 100 G, the plasma density is significantly increased and nearly independent of the phase angle, but at the cost of decreasing the self-bias, which results in a smaller adjustable range of ion bombardment energy. For the asymmetric magnetic field, we studied magnetical asymmetric effect (MAE) in a geometrically and electrically symmetric CCP. It has demonstrated that MAE will generate a DC self-bias and asymmetric plasma response. It can be an effective means to control the plasma properties as an augmentation to conventional measures. [Preview Abstract] |
Thursday, November 9, 2017 2:45PM - 3:00PM |
SR1.00005: Large Scale Simulations of the Plasma-Material Interaction using Electrostatic Particle-in-Cell Code hPIC Rinat Khaziev, Steven Marcinko, Cameron Dart, Alyssa Hayes, Davide Curreli Advancements have been made in the development of the kinetic-kinetic electrostatic Particle-in-Cell code hPIC, designed for large-scale simulations of the Plasma-Material Interface. The Algebraic Multigrid Solver BoomerAMG from the PETSc library was utilized to achieve a weak scaling efficiency of 87\% on more than 64,000 cores of the BlueWaters supercomputer at the University of Illinois at Urbana-Champaign. The code has been validated in two-stream instability simulations and can simulate a volume of plasma over several square centimeters of surface extending out to the pre-sheath of plasma in kinetic-kinetic mode. Results from a parametric study of the plasma sheath in fusion relevant conditions will be presented, as well as a detailed analysis of the plasma sheath structure at grazing magnetic angles. The distribution function and its moments will be reported for plasma species in the simulation domain and at the material surface for plasma sheath simulations. [Preview Abstract] |
Thursday, November 9, 2017 3:00PM - 3:30PM |
SR1.00006: Modeling streamer discharges in strong magnetic fields: from particle to fluid Invited Speaker: Jannis Teunissen In atmospheric air, streamer discharges become magnetized in a magnetic field of a few tens of Tesla. Such strong magnetic fields are experimentally hard to realize, but they can easily be incorporated in a particle model. However, particle-in-cell simulations are computationally expensive, in particular when they need to be performed in 3D. Therefore, I have developed a plasma fluid model for discharges in external magnetic fields. This open-source model uses multi-dimensional electron transport data tables, generated by a Monte Carlo Boltzmann solver. It furthermore includes adaptive mesh refinement and a parallel Poisson solver, making use of the Afivo framework. Two- and three-dimensional numerical simulations show that positive streamers preferably grow parallel to the magnetic field. If the background electric and magnetic field are parallel, the magnetic field accelerates streamers while reducing their radius. For a perpendicular field configuration, deterministic streamer branching parallel to the magnetic field is observed. Surprisingly, the $\vec{E} \times \vec{B}$ drift plays no major role for positive streamers, whereas it does affect negative streamers. One application of the results is the understanding of sprite discharges on Jupiter, which could well be magnetized due to the stronger planetary magnetic field. [Preview Abstract] |
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