Bulletin of the American Physical Society
74th Annual Gaseous Electronics Conference
Volume 66, Number 7
Monday–Friday, October 4–8, 2021;
Virtual: GEC Platform
Time Zone: Central Daylight Time, USA
Session ET44: Plasma Modeling of Diverse Systems |
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Chair: Amanda Lietz, Sandia National Laboatory Room: Virtual GEC platform |
Tuesday, October 5, 2021 2:00PM - 2:15PM |
ET44.00001: Excitation of solitons and surface waves in three dimensional beam neutralization Nakul Nuwal, Deborah A Levin, Igor Kaganovich Ion beams are used in various engineering applications such as particle accelerators, ion-thrusters, and ion-implantations. The rate of neutralization of beams is affected by the energy and the location of the electron source relative to the ion beam. In recent numerical works by Lan and Kaganovich, electrostatic-solitary-waves (ESWs) were observed when the electrons were injected in a 2D planar ion beam. We will present the beam neutralization in 3D and show the formation of solitons and their movement along the beam axis using the Particle-in-Cell (PIC) method. Prediction of electron solitons is important as they may cause the heating of electrons and slow down the process of neutralization in the beam. A hybrid MPI-GPU code, CHAOS, is used for this work, in which an argon beam is neutralized by the electrons emitted from a circular source along the beam axis. We will present our findings on the formation of solitons and long wavelength surface waves in cylindrical and planar beams for different beam widths. Prediction of the surface waves and their frequencies is important in experimental diagnostics and passive measurements in plasma beams. By comparing our results with the theory of planar surface waves, we will show how the long-wavelength surface waves get excited differently in a 2D planar and 3D cylindrical beam. |
Tuesday, October 5, 2021 2:15PM - 2:30PM |
ET44.00002: Real-time Estimation of Plasma Parameters using an Iterated Extended Kalman Filter Christine Greve, Kentaro Hara The multiscale nature of plasma discharges proves challenging to model due to the need to resolve high-frequency, small-scale turbulent features using low-frequency, device-scale phenomena. High-fidelity physics-based models are used for such research, but the complexities and computational cost of state-of-the-art models leave room for data-driven modeling approaches that use experimental data concurrently with lower-cost algorithms to analyze underlying phenomena. Data-driven modeling techniques are promising to investigate unknown phenomena in plasma processes, including reaction rates and transport coefficients (cf. turbulent transport), which are challenging to measure experimentally or obtain from high-fidelity physics-based models. This work uses an iterated extended Kalman filter coupled with a global argon-oxygen model to estimate the time histories of reaction rate coefficients. The filter uses a predictor-corrector scheme to update the computational estimate as measurement data are acquired in time to better inform the physics-based model as the system evolves. Mathematical constraints are applied to ensure statistically consistent solutions, ensuring robust, physics-satisfying performance of the filter for a variety of experimental measurement data cases. |
Tuesday, October 5, 2021 2:30PM - 2:45PM |
ET44.00003: Simulations of ion heating in the presheath due to ion-acoustic instabilities Lucas P Beving, Matthew Hopkins, Scott D Baalrud We find that ion-acoustic instabilities result in significant ion heating near the sheath edge. The heating extends into the presheath since some of the wave power reflects from the sheath. Particle-in-cell simulations were designed to test whether the instability was the source of heating by varying the source electron temperature across the threshold for exciting the ion-acoustic instability. The simulations confirm the instabilities cause heating and demonstrate that the electron-to-ion temperature ratio is locked to the threshold for instability in the unstable region near the sheath edge. The instability heating effect is significant at low pressures, but is eliminated at higher pressures where the instability is damped by ion-neutral collisions. This effect is distinct from the well understood ion heating caused by inelastic collisions with neutrals. Low temperature plasma systems that utilize a presheath for ion acceleration, such as etching and ion beam sources, could experience unwanted and significant ion heating due to this effect. |
Tuesday, October 5, 2021 2:45PM - 3:00PM |
ET44.00004: Development of a multicomponent diffusion fluid solver for two-temperature plasma sheath Giuseppe Matteo Gangemi, Alejandro Alvarez Laguna, Koen Hillewaert, Thierry Magin Studying the plasma sheath is fundamental to a number of applications, ranging from arcing in high vacuum electronics to charging of space platforms due to plume contamination of electric thrusters: these fields differ for the variety of the species involved in the simulation of the fluid and for the different nature of the wall confining it. In this work we investigate two different approaches to plasma fluid simulations: the multifluid, commonly used in the plasma physics community, and the multicomponent approach, commonly used in the combustion and re-entry flows community; solving the electrostatic Poisson equation ensures charge conservation in the domain and allows for a continuous description of the quasineutral bulk and of the sheath. The proposed multicomponent approach offers advantages when simulating a large number of species as the number of equations (and the model complexity) is lower, with a reduction in computational cost. We compare the results of the two methods by simulating a one-dimensional discharge with an isothermal mixture of argon plasma: we adapt the boundary conditions from the classic multifluid approach and implement a semi-implicit treatment of the electric potential in order to improve the stability of the time integration scheme. |
Tuesday, October 5, 2021 3:00PM - 3:15PM |
ET44.00005: PIC-MCC Characterization of Expanding Plasma Plumes for a Low-Density Hypersonic Aerodynamics Facility Pietro Parodi, Stefano Boccelli, Federico Bariselli, Damien Le Quang, Giovanni Lapenta, Thierry Magin Ground testing of satellite aerodynamics in Very Low Earth Orbit requires facilities able to produce a rarefied flow of particles at hypersonic speeds up to 8 km/s. This is not possible with conventional gas dynamic nozzles. A plasma source, instead, can reach the required velocity by electrostatic acceleration of ions. In this work, we investigate the applicability of such approach to a low-density hypersonic aerodynamics facility currently being designed at the von Karman Institute. First, we present the development and verification of the PIC‑DSMC code PANTERA. Then, we employ it to perform 2D3V axisymmetric simulations of the expansion of an argon plasma plume in the vacuum chamber of the facility. We analyze the behavior of electron and ion currents in the collisionless plume. We notice that the expansion of electrons and ions is not isothermal as often assumed. We study the effect of plume density, showing that the divergence of the plume increases at higher injection densities. We investigate the result of collisions between the plume ions and a background gas, showing that charge exchange collisions can neutralize up to 10% of the ion beam. Finally, the consequences of our findings on the application to aerodynamic testing are addressed, and possible solutions proposed. |
Tuesday, October 5, 2021 3:15PM - 3:30PM |
ET44.00006: Force balance in Hall Effect Thrusters: insights from 2d3v (drift-plane) kinetic simulation Timofey Chernyshev The acceleration mechanism in Hall Effect Thrusters (HETs) is commonly described in terms of force balance. Namely, the reactive force produced by accelerated ions has the same value as Ampère's force acting on a drift current loop. This balance written in integral form provides the basis for quantitative estimations of HETs' parameters and scaling models. However, the balance details are not trivial, and some publications lack a clear understanding of this process. |
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