Bulletin of the American Physical Society
62nd Annual Meeting of the APS Division of Plasma Physics
Volume 65, Number 11
Monday–Friday, November 9–13, 2020; Remote; Time Zone: Central Standard Time, USA
Session PO05: Low Temperature Plasmas: Thrusters, Sheaths, and ModelingLive
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Chair: Benjamin Jorns, University of Michigan |
Wednesday, November 11, 2020 2:00PM - 2:12PM Live |
PO05.00001: Princeton Collaborative Low Temperature Plasma Research Facility: first results and new solicitation of proposals. Yevgeny Raitses, Igor Kaganovich, Mikhail Shneider, Shurik Yatom, Sophia Gershman, Arthur Dogariu Low-temperature plasmas have multiple applications in areas ranging from the manufacture of microelectronics, to the synthesis of novel industrial materials, spacecraft propulsion to medicine, catalysis and waste remediation. The US DOE supports the Princeton Collaborative Low Temperature Plasma Research Facility (PCRF), which provides access to state-of-the-art research capabilities, including specialized diagnostic tools, plasma sources and computational resources, and expertise for the nation's plasma research community. This presentation will provide overviews of the research resources, results from the last year solicitation, and present a solicitation of collaborative proposals for the next fiscal year. [Preview Abstract] |
Wednesday, November 11, 2020 2:12PM - 2:24PM Live |
PO05.00002: Studies of voltage-modulated Hall thrusters Jacob Simmonds, Yevgeny Raitses, Vernon Chaplin, Andrei Smolyakov, Oleksandr Chapurin Externally driven modulations of the anode voltage in resonance with the breathing oscillations have been predicted to improve performance in Hall thrusters [1]. These improvements are due to a combination of increased propellant utilization and higher average ion energy in the thruster plume. This work presents simulations conducted for two low-power Hall thrusters of different ExB configurations operated in voltage modulated regimes: the cylindrical Hall thruster (CHT) [2] and the magnetically shielded miniature (MaSMi) Hall thruster [3]. Simulations were performed using one-dimensional fluid/hybrid code [4]. The predicted effects of externally driven oscillations are similar for both thruster types. These results are compared with experimental measurements. [1] I. Romadanov et al., Plasma Sources Sci. Technol. 25, 011604 (2018); [2] A. Smirnov, Y. Raitses, N. Fisch, J Appl. Phys. 92, 5673 (2002); [3] R. Conversano et al., Plasma Sources Sci. Technol. 28, 105011 (2019); [4] G. Hagelaar, J. Bareilles, L. Garrigues, J.P. Boeuf, Contributions to Plasma Physics, 44 (2004) 529-535 [Preview Abstract] |
Wednesday, November 11, 2020 2:24PM - 2:36PM Live |
PO05.00003: Simulation of a capacitively coupled plasma micro-thruster using the particle-in-cell method. Michael May, Andrew Powis, Igor Kaganovich A radio-frequency (13.56MHz) capacitively coupled plasma (CCP) micro-thruster was simulated in two dimensions by an electrostatic particle-in-cell (PIC) method, using a PPPL-modified version of the commercial LSP code [1]. At the gas valve, the gas pressure is high, up to 5 Torr, and the discharge can operate at high voltages, up to 400 V in argon. Results were benchmarked against the previous 2D fluid simulations of ref. [2] and validated by comparison with the experimental data of ref. [3]. Results show plasma properties depend strongly on the secondary electron emission from walls and dielectric thickness separating electrodes from the plasma. [1] A.T. Powis, J.A. Carlsson, I.D. Kaganovich, Y. Raitses, and A. Smolyakov, \textit{Physics of Plasmas}~\textbf{25}, 072110 (2018). [2] A. Greig, C. Charles, and R. W. Boswell, \textit{Frontiers in Physics}~\textbf{2}, 80 (2015). [3] C. Charles and R. W. Boswell,~\textit{Plasma Sources Sci. Technol~}\textbf{21,~}022002 (2012). [Preview Abstract] |
Wednesday, November 11, 2020 2:36PM - 2:48PM Live |
PO05.00004: Direct continuum Boltzmann solver using spherical harmonic expansion Stephen Swanekamp, David Kessler, Andrew (Steve) Richardson, Tzvetlina Petrova Low temperature, highly collisional plasma have many important applications including the interaction of the solar wind and coronal mass ejections with the atmosphere, biological applications, and the propagation of intense electron beams in rarefied gas. Modeling these plasmas involves the coupling of a model for the plasma dynamics with Maxwell's equations for determining the self-consistent electromagnetic fields. When the collisional mean-free path is small compared to gradient scale lengths, a fluid model can be used to treat the plasma dynamics. In the opposite limit, a kinetic model is required. A particle-in-cell (PIC) solver coupled with a Monte-Carlo collision algorithm is a common approach when a kinetic model is required. However, scattering collisions keep the velocity-space distribution nearly spherical, which can require thousands of particles per cell to adequately represent the distribution function. Alternatively, the Boltzmann equation can be solved directly on a six-dimensional grid. However, for highly collisional plasma with a nearly spherical velocity distribution, spectral methods based on spherical harmonics are attractive. [Preview Abstract] |
Wednesday, November 11, 2020 2:48PM - 3:00PM Live |
PO05.00005: A novel high-fidelity multi-fluid solver for plasma simulations. Xiaowen Wang A particular challenge for plasma research is the diversity of parameter space and conditions. Fortunately, a continuum model used in fluid mechanics can explain as much as 80{\%} of plasma phenomena observed in real experiments (Francis F. Chen, Introduction to Plasma Physics and Controlled Fusion, 2018). The main goal of this abstract is to develop a novel high-fidelity multi-fluid solver for plasma simulations based on self-consistent continuum models. The new solver is capable of simulating electrons, ions, and neutrals with complete transport phenomena and thermochemical non-equilibrium. It is a natural extension from a high-fidelity shock-fitting solver for hypersonic flow simulations where ionization is considered under the assumption of no charge separation. Code implementation is ongoing by coupling purely hyperbolic Maxwell's equations for electromagnetic field and adding the body force from electromagnetic field to the Navier-Stokes equation. [Preview Abstract] |
Wednesday, November 11, 2020 3:00PM - 3:12PM Live |
PO05.00006: Simulation of ion-acoustic wave excitation, reflection and wave-particle scattering in the presheath Lucas Beving, Matthew Hopkins, Scott Baalrud It has been predicted that the ion flow in an ion presheath can excite ion-acoustic waves and that subsequent wave-particle interactions significantly enhance the effective Coulomb collision rate within the presheath. Increased collisionality could explain why ion and electron velocity distribution functions are measured with varying degrees of thermalization at different locations in the presheath. Recent LIF measurements have directly confirmed that the waves are present throughout the presheath, even in regions where linear theory predicts stability. This suggests that the waves are being reflected from the ion sheath, but wave reflection could not be directly diagnosed by the experiment. Here, we use PIC simulations to corroborate the existence of the waves by comparing the power spectrum of density fluctuations to the linear ion-acoustic dispersion relation. The simulations are used to quantify both wave reflection and wave-particle scattering rates that have not been measured experimentally. Wave-particle scattering rates were quantified by calculating time correlations between the distribution fluctuations and the electric-field fluctuations \textless f E\textgreater , while the reflected power was calculated from power spectra. [Preview Abstract] |
Wednesday, November 11, 2020 3:12PM - 3:24PM Live |
PO05.00007: Plasma Sheath Around Long Conductors with Elliptic Cross-sections Luca Chiab\'o, Gonzalo S\'anchez-Arriaga The plasma sheath around an emissive surface immersed in a plasma is a topic of interest for a wide range of applications like emissive probes, electrodynamic tethers, and dusty plasma. This work presents a Vlasov-Poisson solver to study the plasma structure around a long body with an elliptic cross-section. Since angular momentum is not conserved by particle trajectories, the code allows to extend the orbital motion theory to non-integrable configurations. Some subtle physical and numerical features are highlighted, including the filamentation of the distribution function and its fractal structure in velocity space. A parametric analysis varying the probe eccentricity and the emission level is presented. Relevant features and macroscopic magnitudes, like density and potential profiles, and collected and emitted current are shown. Orbital-motion-limited and space-charge-limited regime transitions are both investigated. The stationary nature of the model and its implications in the development of reliable stationary Vlasov-Poisson solvers are discussed. [Preview Abstract] |
Wednesday, November 11, 2020 3:24PM - 3:36PM Live |
PO05.00008: An Efficient Vlasov-Poisson Solver and Deep Parametric Analysis of Cylindrical Emissive Probes Sadaf Shahsavani, Gonzalo Sánchez-Arriaga, Xin Chen The Orbital Motion Theory (OMT) for cylindrical emissive probes immersed in collisionless plasmas, which uses conservation laws to write the Vlasov-Poisson system as a single integro-differential equation, has been developed recently and solved numerically for specific parameter values. This work presents an improvement in the code that reduces the computational cost by a factor of approximately 80, thus opening the opportunity to carry out deep parametric analysis. By varying the probe radius-to-Debye length ratio and the emission level (controlled by the probe temperature), a database of current-voltage characteristics has been computed. The transition boundaries in parameter space from Orbital-Motion-Limited (OML) to non-OML regimes and from space-charge-limited (SCL) to non-SCL regimes have been found. The analysis shows that, depending on the emission level, the probe can float at positive and negative biases, with the floating potential not~ saturated at high emission levels.~~ [Preview Abstract] |
Wednesday, November 11, 2020 3:36PM - 3:48PM Live |
PO05.00009: A Parametric Study using Fluid and Particle-in-Cell Modeling of the Ion Distributions in RF sheaths at ICRH antennas Moutaz Elias, Davide Curreli, James Myra RF sheaths have been a major concern accompanying the use of ICRH systems.~The presence of RF sheaths has been linked to the enhancement of the impurity flux sputtered from the Plasma Facing Components. It is a pivotal task to minimize the impurity emission from the PFC of the ICRH system. Previous attempts to model RF sheaths and PMI are limited to fluid description of the plasma. In this work, we used multi-model approach, using (1) a fluid model of the RF sheath, and (2) a hybrid PIC model (hPIC) to analyze the dependence of the kinetic IEAD impacting the RF antenna on the various RF sheath parameters. We highlighted the dependence of the IEAD on the RF frequency and the magnetic field angle. We also compared the IEAD from the field aligned and poloidal aligned RF antenna configurations. Furthermore, a simulation case representing the latest JET campaign was analyzed. We found that the IEAD for JET campaign case contains a cusp resulting from the kinetic motion of the ions. [Preview Abstract] |
Wednesday, November 11, 2020 3:48PM - 4:00PM Not Participating |
PO05.00010: Overview of Recent Progress on Optical Diagnostics for Hall Thrusters at NASA JPL Vernon Chaplin, Robert Lobbia, Parker Roberts, Timothy Simka, Alejandro Lopez Ortega, Ioannis Mikellides, Richard Hofer, James Polk Non-invasive optical measurements of plasma properties in Hall thrusters are the preferred method for validating hydrodynamic and hybrid particle-in-cell (PIC) modeling codes used to understand life-limiting surface erosion processes. We present an overview of recent work at NASA Jet Propulsion Laboratory (JPL) advancing laser-induced fluorescence (LIF) and passive optical emission spectroscopy (OES) diagnostics. Time-resolved LIF measurements of ion dynamics during both periodic and aperiodic global discharge oscillations were achieved by using transfer function averaging in Fourier space to obtain useable signal-to-noise ratios and synchronize data taken at multiple ion velocities and positions in the plasma. At operating conditions without large-amplitude oscillations, spatial integration of the steady state kinetic equation for ions, starting from the upstream velocity distribution measured by LIF, has revealed evidence of non-classical heating in the acceleration region. To support electron diagnostics using OES, collisional radiative models of neutral and singly-ionized xenon were developed, yielding new predictions of density dependence in neutral line intensity ratios and fundamental bandwidth limitations for time-resolved electron temperature measurements using OES. [Preview Abstract] |
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