Bulletin of the American Physical Society
64th Annual Meeting of the APS Division of Plasma Physics
Volume 67, Number 15
Monday–Friday, October 17–21, 2022; Spokane, Washington
Session CO08: Plasma Propulsion and Plasma SourcesLive Streamed
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Chair: Benjamin Jorns, Univ. Michigan Room: 402 ABC |
Monday, October 17, 2022 2:00PM - 2:12PM |
CO08.00001: Experimental study of electromagnetic wave scattering from a gyrotropic gaseous plasma column Luc S Houriez, Hossein Mehrpour Bernety, Jesse A Rodriguez, Benjamin Wang, Mark A Cappelli We experimentally demonstrate the controlled scattering of incident transverse-electric electromagnetic waves from a gyrotropic magnetized plasma cylindrical discharge. Scattered electromagnetic waves can bend left and right by changing the external magnetic field of a plasma rod. Measured scattered wavefronts are in good agreement with electromagnetic simulations. A gyrotropic response is observed for incident wave frequencies ranging from 3.5 to 5.6 GHz for conditions corresponding to a ratio of cyclotron frequency to plasma frequency around 0.16. The observation of a gyrotropic response from cylindrical plasma discharges paves the way for their use as building blocks for future devices such as magnetized plasma photonic crystals, topological insulators, plasma metamaterials, non-reciprocal waveguide structures, and other devices, which require a tunable gyrotropic response from centimeter to meter-scale materials with application-specific geometry. |
Monday, October 17, 2022 2:12PM - 2:24PM |
CO08.00002: The effect of segmented electrodes on the plasma plume and breathing oscillations in a wall-less Hall thruster Yevgeny Raitses, Jacob Simmonds In the absence of channel walls bounding the plasma, a wall-less Hall thruster [1] is a promising configuration with both a potentially longer lifetime and easier scalability than conventional Hall thrusters. Because the ion acceleration takes place in the fringing magnetic field with a strong axial component, the operation of a typical wall-less thruster is characterized by a large beam divergence of the plasma flow, which reduces the thrust. In this work, the addition of biased segmented electrodes to the wall-less thruster is shown to control the plume divergence and large amplitude breathing oscillations of the discharge current commonly associated with ionization instability. For example, the segmented electrode placed outside the anode narrows the plasma plume and suppress the oscillations [2], while the central segmented electrode broadens the plasma plume, while reducing the ion energy spread [3]. In this work, we will discuss possible physical mechanisms responsible for these effects. |
Monday, October 17, 2022 2:24PM - 2:36PM |
CO08.00003: Design, Construction and Characterization of a Coaxial Plasma Gun for Torsional Magnetic Reconnection Propulsion Neil P Laya, Gabe Xu One of the most promising emerging technologies for high specific impulse space propulsion is the torsional magnetic reconnection (TSR) thruster. Such a system includes three main features: a spine-fan linear null magnetic topology, an azimuthal field, and a plasma source. This presentation covers the design, construction, and characterization of a coaxial plasma gun (CPG) operating in both snowplow and deflagration modes to serve as the azimuthal field and plasma source in a TSR thruster. A 1600 J capable DC pulse power system and a timed gas puff valve mass insertion system are constructed to operate the CPG. Current analysis and voltage values will be measured with the use of Pearson coils and high-voltage oscilloscope probes throughout the circuit to further elucidate the RLC type behavior of the CPG and pulsed circuitry. ICCD imagery will be taken of the plasma discharge in both pre-fed and gas puff operation. These will be compared with electron temperature and density measurements found with stark broadening optical emission spectroscopy. The measurements taken herein will contribute to a greater understanding of CPG operation necessary to maximize the azimuthal magnetic field. All experiments are conducted in a vacuum chamber operating at both low and high vacuum. The data gained herein will be of crucial importance when attempting to integrate the CPG into the larger null field structure to initiate torsional magnetic reconnection. |
Monday, October 17, 2022 2:36PM - 2:48PM |
CO08.00004: Two-dimensional Grid-based Vlasov Simulations of Electric Propulsion Plume Chen Cui, Joseph Wang In this work, a parallel, multi-dimensional grid-based Vlasov solver (Vlasolver) developed at USC is used to study the electric propulsion plume expansion. A comparison of the results from the Vlasov and PIC simulations shows that, while both models agree well in overall plume density and electric potential, the Vlasov model is able to resolve local electron density, temperature, heat flux, and electron velocity distribution without the effects of statistical noise. A core region and a fan region can be found in the electron heat flux. The core region remains a quasi-constant magnitude and shape, the fan region shape grows with time. Near-Maxwellian features are found in the v_x direction while top-hat shape features are found in the v_y direction for electron velocity distribution function (eVDF). The eVDF in the v_y direction at different locations can be mapped to the semi-analytical relations in the 1D finite-size plasma expansion by Mora et. al. This work also extends our recent study to investigate the excitation and propagation of electron-scale perturbations in the plume expansion. The grid-based Vlasov approach, though computationally more expensive than PIC, can be advantageous in applications requiring accurate eVDF and accurate small-scale physical properties. |
Monday, October 17, 2022 2:48PM - 3:00PM |
CO08.00005: Numerical study of rotating spokes in RF magnetron discharges Liang Xu, Denis Eremin, Dmitro Sydorenko, Ralf Peter Brinkmann, Alexander V Khrabrov, Igor D Kaganovich, Tasman Powis, Sathya S Ganta, Kallol Bera, Shahid Rauf DC and RF magnetron discharges are used in a variety of important applications, especially in thin film deposition processes. Notwithstanding wide-spread applications of these devices, a lot of relevant physics is not well understood. Magnetron plasmas are subject to various instabilities resulting in oscillations of plasma parameters with frequencies ranging from kHz to MHz for all magnetron types: DC, pulse, or RF-driven magnetrons. Rotating spokes are prominent low-frequency (on the order of kHz) oscillations in these discharges. In this work, we study the dynamics of rotating spokes in the RF magnetrons using the two-dimensional axial-azimuthal fully kinetic particle-in-cell/Monte Carlo collision code 2D-EDIPIC. Our simulations show that the spokes are excited above the powered electrode and rotate in the azimuthal (+ExB) direction with the propagation speed that is in good agreement with the recent experimental observation in RF magnetrons [M. Panjan, J. Appl. Phys. 125, 203303 (2019)]. We find that the spoke is driven by the density-gradient-drift instability. The high frequency (on the order of MHz) oscillations - electron cyclotron drift instabilities (ECDI) are also found to be excited. The synergistic effects of the ECDI and spokes on electron heating and anomalous transport are carefully analyzed and interpreted. |
Monday, October 17, 2022 3:00PM - 3:12PM |
CO08.00006: 1D and PIC Modeling of Air - Breathing Plasma Engines Salman Sarwar, Alexander V Khrabrov, Dmytro Sydorenko, Igor D Kaganovich Over the past half century, Earth-orbiting artificial satellites have addressed a wide variety of problems in science and technology, from remote sensing and geodesy to defense and navigation. Satellites in low Earth orbit (LEO), in particular, allow for lowered launch costs and communication latencies at the expense of significant atmospheric drag. With renewed interest in LEO satellite networks for telecommunication and deep space mission support, novel propulsion systems are necessary for efficient orbit keeping over the mission lifespan. Unlike traditional electric and thermodynamic systems, air breathing plasma engines (ABPE) do not require on-board propellant, eliminating associated weight, cost, and complexity while increasing service life. In this work, we study the plasma chemistry and physics of an electron beam driven ABPE. |
Monday, October 17, 2022 3:12PM - 3:24PM |
CO08.00007: 2D axisymmetric Particle-In-Cell study of a hollow cathode and its near plume region Svetlana Selezneva, Willca Villafana, David Smith, Alexander V Khrabrov, Igor D Kaganovich, Dmytro Sydorenko Hollow cathodes are efficient plasma sources and have been used in a wide variety of applications including electric propulsion, surface processing and plasma-material interaction studies. |
Monday, October 17, 2022 3:24PM - 3:36PM |
CO08.00008: Dual pulse laser generated plasma for controllable energy deposition Sagar Pokharel, Hunter Hadden, Kenneth Hergenrader, Richard B Miles We study temporal dynamics of plasma generated by a combination of the low energy 800 nm femtosecond laser pulse and high energy nanosecond pulse of 1064 nm. A three-dimensional model is developed which includes multiphoton and tunneling ionization by the first pulse and three-temperature model for the second pulse, combined with the refractive index calculations and Navier-Stokes equations. A numerical study was conducted to examine different patterns formed by the laser pulses, energy exchange mechanisms and optimal pairing depending on spatial beam shaping. It was shown, that electron dynamics is controlled by the first seeded pulse and depends on the initial laser intensity profile. Analysis includes Gaussian and flat top laser intensity profiles. |
Monday, October 17, 2022 3:36PM - 3:48PM |
CO08.00009: Mass separation by a wave ponderomotive force in a plasma Amnon Fruchtman, Gennady Makrinich Mass separation, separation of particles of different mass, is a crucial process in a variety of societal applications [1]. In a significant number of techniques electromagnetic forces are exerted on charged particles or plasmas. Waves at the cyclotron frequency resonance are attempted for mass separation by specificall heating one species. Another way [2, 3] to use waves is by the ponderomotive force by standing shear Alfven waves also near the ion cyclotron resonance [4]. Standing waves can push ions of a small mass difference into opposite directions, if their cyclotron frequency is at opposite sides of the wave frequency. Electrostatic self-fields by the plasma are expected to compete in an unfavourable way with the ponderomotive force and may destroy the mass separation process. We examine theoretically the combined effect of the ponderomotive force and the electrostatic self-fields. We show that parameters can be chosen so that the electrostatic self-fields do not impede but rather support the separation process. |
Monday, October 17, 2022 3:48PM - 4:00PM |
CO08.00010: Empirically extending 1D Child-Langmuir theory to a warm electron beam Jesse M Snelling, Gregory R Werner, John R Cary We use particle-in-cell (PIC) simulation to generalize the space charge limit for 1D diodes to the case of electron beams with finite temperature. As shown in our previous work, a certain class of nanoscale vacuum channel transistor (NVCT) devices can be practically considered a one dimensional diode within the gate-anode gap. 1D Child-Langmuir theory for a cold beam is a common estimate for the space charge limit, despite neglecting the finite temperature inherent in real world devices. Using a 1D approximation and collapsing the five dimensional input space (injected current density, voltage, gap distance, average beam velocity, and temperature) to just three reduced dimensions makes a systematic simulation sweep of the input space feasible. We find that the simulation data can be well approximated by a simple empirical formula with a handful of fitting parameters. The resultant function generally characterizes the current transmitted across the diode for a specific thermal electron emission profile. This empirical model can be easily applied to many diode-like devices, including the previously mentioned class of NVCT devices when coupled with an appropriate field emission model. |
Monday, October 17, 2022 4:00PM - 4:12PM |
CO08.00011: Transient physics of multipactor induced plasmabreakdown near a dielectric surface De-Qi Wen, Peng Zhang, Janez Krek, Yangyang Fu, John P. Verboncoeur Multipactor and plasma ionization breakdown near a dielectric microwave window are limiting factors for high power microwave sources with applications in space-based satellite communications. In this work, we will present the physics of higher harmonic (HH) generation of the normal electric field in multipactor-induced plasma breakdown using kinetic particle-in-cell simulations and a theoretical model. The observed harmonic frequency in simulations is around ten times the fundamental rf driving frequency (1GHz). The theoretical model reveals that the interaction of beam-like secondary electrons injected into the plasma[JV1] is the fundamental mechanism behind the HH generation [Wen et al. Physical Review Letters, (2022)]. With pressure increasing from 0.2Torr to 1Torr, the HH phenomenon disappears. Additionally, a propagating multilayer-like structure is observed for helium discharges. The physical mechanism is attributed to the response of light ions to two neighboring reversed normal electric fields and localized space charge [Wen et al, Applied Physics Letter, 119, 264102 (2021)]. |
Monday, October 17, 2022 4:12PM - 4:24PM |
CO08.00012: Inference of Plasma Wave Dispersion Relation from Transfer-Function Laser-Induced Fluorescence Parker J Roberts, Benjamin A Jorns Hall thrusters are annular ExB plasma devices which are widely used to accelerate ions to high speeds and provide efficient in-space propulsion. These devices are rich with so-called "non-classical" particle transport which presents a difficulty to predictive modeling and improved design. In many cases, this anomalous motion of particles, especially electrons, has been attributed to various plasma wave structures, which can exchange energy and momentum with both electrons and ions. In order to better understand and model the operation of Hall thrusters, it is necessary to experimentally characterize this plasma wave environment throughout the discharge. |
Monday, October 17, 2022 4:24PM - 4:36PM Author not Attending |
CO08.00013: Two dimensional Particle-in-Cell Modeling of Electron-Beam Generated Low Electron Temperature Plasma Willca Villafana, Shahid Rauf, Sierra Jubin, Dmytro Sydorenko, Igor D Kaganovich, Alexander V Khrabrov, S. Ethier Plasmas generated using energetic electron beams can be important for plasma processing applications requiring atomic precision due to their low electron temperature. Electron beam plasmas are typically confined using a static magnetic field and operated at low gas pressures. In previous experimental studies at the Naval Research Lab, Langmuir probes measurements suggested that the plasma transport across the magnetic field lines is non-classical in this operating regime. Consequently, fluid or hybrid modeling must adjust their implemented transport coefficients to empirically fit experimental data. For more predictive results, we propose in this paper a self-consistent fully kinetic 2D axisymmetric Particle-In-Cell study using the open-source code EDIPIC-2D. The model examines the creation and evolution of plasma in low pressure (10 – 40 mTorr) Ar gas on injection of an energetic electron beam (2 keV). A steady-state is reached after a few hundreds of microseconds and the plasma is mostly confined by the imposed magnetic field, near the symmetry axis. Charged particles are able to travel across the magnetic field lines in the x direction and the subsequent transport is being compared with analytical theory. To study the scaling of the electron transport, we also performed a large parametric study with different values of the neutral gas density, beam current, and magnetic field strength. The impact of these parameters on electron density, plasma potential, and electron temperature are found consistent with probe-based experimental measurements. |
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