Improving PIC-DSMC Simulations of RF Plasmas via Event Splitting
Creators: name:  G. OBLAPENKO 
name:   P. VARGHESE 
name:   D. GOLDSTEIN 
name:   C. MOORE 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: PROPULSION PHYSICS
ELECTRICAL PROPULSION
ADVANCED PROPULSION

description: Electric propulsion (EP) is a widely used technology in satellites, owing to the high specific impulse that can be achieved [1]. Numerous electric thruster designs have been developed over the years, however, both experimental and numerical studies of electric propulsion systems remain challenging [1,2]. Current topics of significant interest include study of thruster erosion [2], search for cheaper and more abundant propellants [3], potential contamination of satellite surfaces instrumentation due to backflow [4]. Numerical studies of EP systems are complicated by the limited applicability of simplified fluid-like models [2,4], and full scale PIC-DSMC (Particle-in-Cell Direct Simulation Monte Carlo) simulations remain the most accurate tool for modeling of EP systems. However, PIC-DSMC is subject to stochastic noise, the level of which is inversely proportional to the square root of the number of simulation particles. Hence, large numbers of simulation particle must be used to obtain reliable results and the calculations become expensive. In the present work, we apply a new algorithm for improved simulation of low-probability processes in DSMC to simulations of 1-D RF (radio frequency) plasmas in xenon. The approach, dubbed event splitting [5,6], has previously been shown to significantly improve the modeling of low-probability processes, such as ionization, in 0-D and 1-D DC (direct current) discharges. The aim of the work is to compare the approach with standard DSMC collision algorithms in terms of computational cost and level of stochastic noise. Demonstration of the accuracy and cost savings of the event splitting algorithm for RF plasma simulation in which rare events drive the dynamics would be a first step in improving the modeling capability for EP systems. Acknowledgments This work was supported by Sandia National Laboratories. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy\'s National Nuclear Security Administration under contract DE-NA0003525. SAND2022-0198 A Georgii Oblapenko acknowledges the funding provided by the Alexander von Humboldt foundation for his stay as a guest researcher at the German Aerospace Agency (DLR). References [1]. D.M. Goebel, I. Katz. Fundamentals of electric propulsion: ion and Hall thrusters (Vol. 1). John Wiley Sons. (2008) [2]. K. Holste, P. Dietz, et al., Ion thrusters for electric propulsion: Scientific issues developing a niche technology into a game changer, Rev. Sci. Instr., 91(6), 061101 (2020) [3]. D. Rafalskyi, J.M. Martinez, et al., In-orbit demonstration of an iodine electric propulsion system, Nature, 599, 411415 (2021) [4]. N.N. Jambunathan, D.A. Levin, Kinetic Modeling of Spacecraft Surfaces in a Plume Backflow Region, IEEE Trans. Plasma Sci., 48(12), 4305-4325 (2020) [5]. G. Oblapenko, D. Goldstein, et al., Hedging Direct Simulation Monte Carlo Bets via Event Splitting, submitted to J. Comp. Phys. [6]. G. Oblapenko, D. Goldstein, et al., Improving PIC-DSMC Simulations of Electrical Breakdown via Event Splitting, AIAA paper 2022-2152, AIAA Scitech 2022 Forum and Exposition, 3-7 January 2022, San Diego, CA