Bulletin of the American Physical Society
71st Annual Gaseous Electronics Conference
Volume 63, Number 10
Monday–Friday, November 5–9, 2018; Portland, Oregon
Session QR2: DPP/GEC Joint Session: Low Temperature Plasmas II |
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Chair: Pascal Chabert, LPP, Ecole Polytechnique Room: Oregon Convention Center A105 |
Thursday, November 8, 2018 2:00PM - 2:12PM |
QR2.00001: Ionization waves in the PK-4 direct current neon discharge Peter Hartmann, Marlene Rosenberg, Lorin Matthews, Dustin Sanford, Jorge Reyes, Truell Hyde The PK-4 system is a microgravity dusty plasma experiments currently in operation onboard the International Space Station. The experiment utilizes a long DC discharge in neon or argon gases. We apply our 2D particle-in-cell with Monte Carlo collisions (PIC/MCC) discharge simulation to compute local plasma parameters that serve as input data for future dust dynamics models. The simulation includes electrons, Ne$^+$ ions, and Ne metastable atoms in neon gas and their collisions at solid surfaces including secondary electron emission and glass wall charging. On the time-scale of the onboard optical imaging, the positive column appears stable and homogeneous. On the other hand, our simulations show that on microsecond time-scales the positive column is highly inhomogeneous, ionization waves with phase velocities in the range between 500 m/s and 1200 m/s dominate the structure. In these waves, the electric field and charged particle densities can reach amplitudes up to 10 times of their average value. Our experiments on a ground-based PK-4 replica system fully support the numerical findings. In the experiment, the direction of the DC current can be alternated. We show, that during the polarity switching an ionization tsunami swipes along the whole discharge towards the new cathode. [Preview Abstract] |
Thursday, November 8, 2018 2:12PM - 2:24PM |
QR2.00002: 1-D Electric Field Measurements Using Field Induced Second Harmonic Generation Benjamin Goldberg, Stephan Reuter, Aruther Dogariu, Richard B. Miles Electric field measurements are carried out in an atmospheric pressure argon plasma jet using femtosecond laser electric field induced second harmonic generation. The discharge is sustained using an ns pulse generator with peak voltage of 6 kV and FWHM 25 ns. Time resolution is 200 ps and spatial resolution is less than 1 mm along the beam propagation. Calibration of the diagnostic is done using a DC voltage applied between two electrodes in the same argon jet flow. The fs laser is focused using a cylindrical lens, and the measured signal beam is monitored on an ICCD allowing for 1-D spatial resolution. Calibration is carried out for every pixel. Electric field sensitivity is 300 V/cm at the center of the Gaussian laser sheet. Time gated ICCD imaging is also completed allowing for absolute temporal resolution based upon plasma emission. Both ICCD imaging and field measurements indicate the presence of an ionization wave. The results show that femtosecond lasers can be used for 1-D spatially resolved measurements with a high degree of temporal resolution possible. [Preview Abstract] |
Thursday, November 8, 2018 2:24PM - 2:36PM |
QR2.00003: Modeling Gas Breakdown in High Quality-Factor Resonators at GHz to THz Frequencies Dylan Pederson, Laxminarayan L. Raja Recently, there has been an effort to explore and incorporate plasmas into electromagnetically resonating components, for applications in plasma generation, wave control, and sensing, among other things. High quality factor (High-Q) resonators are desirable for gas breakdown because they operator with relatively low input power. Gas breakdown in a resonator is highly dependent upon the operating frequency and the geometry of the resonator. An important characterization of high-Q resonators is the frequency response generated by numerical simulation. However, in order to resolve a high-Q resonance, the number of simulated wave periods must be greater than Q. As the Q-factor is not known a priori, this can lead to very long simulation times of greater than 10$^{6}$ wave periods. Considering that the computation mesh must also resolve small geometrical features, the problem can become unwieldy quickly. We present a method of numerical simulation based on the Finite-Difference Time-Domain (FDTD) method that reduces the computational cost of simulating gas breakdown. We demonstrate the technique of using a time-step operator representation of the electromagnetic simulation to obtain the steady-state plasma response under a diffusive flux assumption. [Preview Abstract] |
Thursday, November 8, 2018 2:36PM - 2:48PM |
QR2.00004: Quantum-mechanical simulations of the synthesis of boron-nitride nano-structures in a hot, high-pressure plasma Predrag Krstic, Longtao Han The clusterization and anglomeration of boron-nitride nano-structures in a hot, high-pressure plasma was simulated on nanosecond time scale using quantum-classical molecular dynamics (QCMD). Eleven different atomic and molecular precursor systems of boron, nitrogen and hydrogen were used, with more than 1500 atoms at temperatures in range 1500 to 6000 K. Several various mechanisms for the nanotube growth, as well as the optimal temperatures (around 2000K) and optimal choice of precursors (containing BN diatomics within the precursor molecular structure ) for growth of nanocages, nanoflakes and diamond-like structures were identified1. The quantum-mechanical component of the QCMD was based on the density-functional tight-binding (DFTB) quantum mechanics in conjunction with a divide-and-conquer (DC) linear scaling algorithm, as implemented in the DC-DFTB-K code2. 1Predrag Krstic, Longtao Han, Stephen Irle and Hiromi Nakai, Chemical Science 9, 3803 (2018). 2 Y.Nishizawa, Y. Nishimura, M. Kobayashi, S. Irle and H. Nakai, J. Comput. Chem. 37, 1983 (2016). [Preview Abstract] |
Thursday, November 8, 2018 2:48PM - 3:00PM |
QR2.00005: An Investigation of the Effect of Packed Bed Plasma Treatment of Soybeans On Seed Surface Contact Angle And Water Absorption Kenneth Engeling, Victoria Fritz, John Foster Recent studies have shown that plasma treatment of seeds give rise to beneficial effects such as improved germination probability or increased growth rate. These mechanisms underlying the observed improvements are not well understood. In this work, we investigate the relationship between contact angle and water absorption capacity. A packed bed array of seed aggregate was exposed to plasma generated through the application of nanosecond, high voltage pulses. The seeds were also treated with plasma activated water (PAW), which allows for the determination of the relative efficacy of both treatment approaches. [Preview Abstract] |
Thursday, November 8, 2018 3:00PM - 3:12PM |
QR2.00006: Modelling biological systems perturbed by plasmas Tomoyuki Murakami Plasma medicine is an interdisciplinary research spreading over physics, chemistry, biology and medical sciences. Instead of the great progress, many aspects still remain to be explored. Computational biology should be a powerful tool in this field. The present modelling work simulates one of the most important inner-cellular systems, mitochondrial function in cellular energetic metabolism. The essential parts of this system are the tricarboxylic acid cycle (TCA cycle), the respiratory chain (electron transport chain) and the adenosine triphosphate (ATP) synthesis machinery. The behavior of the biological system perturbed by low-temperature plasmas is numerically revealed. The key issues to link the plasma-physics and chemistry with biological systems will be presented and discussed in the talk. [Preview Abstract] |
Thursday, November 8, 2018 3:12PM - 3:24PM |
QR2.00007: Pulsed Helium Discharge In Synchronized Bubble Generated In Water Yuchen Luo, Peter Bruggeman Plasma generation in bubbles is intensively studied in the context of developing a plasma-based advanced oxidation technology for water treatment. We report a study of discharges in helium bubbles generated at 5 Hz in a sodium solution with an electrical conductivity approximately 40 $\mu $s/cm using a solenoid valve system through quartz capillary. A voltage pulse synchronized with the bubble generation with an amplitude of 5 kV is used to generate a time-synchronized discharge. The morphology of the discharge is systematically studied by time-resolved imaging during the evolution of the bubble dynamics and the discharge from the first to the tenth pulse. The discharge is diffuse in the voltage rising edge and transits to a more filamentary discharge for voltage pulses in excess of 1 $\mu $s. This transition is more pronounced in the first discharge in a newly formed bubble compared to subsequent discharges in the same bubble. In addition, the power deposition in the first discharge is higher compared to the ones in subsequent discharges when the pulse repetition rate is more than 800 Hz in the positive polarity and 2000 Hz in the negative polarity. The reason for this remarkable effect relates to the presence of the capillary used for bubble generation and will be discussed in detail. [Preview Abstract] |
Thursday, November 8, 2018 3:24PM - 3:36PM |
QR2.00008: Dynamics of bubble generated by spark discharge in water as a diagnostic tool Karel Kolacek, Vitaliy Stelmashuk, Petr Hoffer, Jiri Schmidt, Oleksandr Frolov, Jaroslav Straus, Petr Lukes Electrical discharges in liquids have numerous applications. One of them is in water generated shock wave that can be focused and used e.g. for extracorporeal shock wave lithotripsy. Particularly, an application of high-voltage pulse with a fast rise-time to electrodes submerged in water leads to generation of spark discharge with rapidly expanding plasma channel. As a result of this expansion a shock wave is generated and a cavitation bubble is formed. Several theoretical models have been proposed (and summarized by Naugolnych and Roi in ``Spark discharges in water'') for a simulation of hydrodynamic process initiated by underwater electrical discharge. This contribution will analyse both approaches -- based on either incompressible, or compressible liquid assumption. Comparison of simulation results obtained in both approximations with experimental data obtained by a fast frame camera for a set of parameters of the driving electrical circuit helps to determine not only the pressure development in the bubble and its close vicinity, but also the efficiency of transformation of the electrical energy to the mechanical one. [Preview Abstract] |
Thursday, November 8, 2018 3:36PM - 3:48PM |
QR2.00009: Plasma thruster with oscillating electromagnetic fields Amnon Fruchtman, Gennady Makrinich There is a growing interest in developing electrode-less plasma thrusters to reduce erosion and extend life-time. In the Helicon Plasma Thruster (HPT) [1], a thrust is generated as the plasma heated by radio-frequency waves is ejected away, being accelerated through a magnetic nozzle. The excitation of a double layer at the exit of the HPT was also suggested as a way to impart momentum to the plasma [2]. Another method is imposing a travelling magnetic field [3]. Yet another method is introducing a rotating magnetic field at the exit of a helicon source [4]. Acceleration by rotating electric and magnetic fields, equivalent to the stationary fields Magneto - Plasma Dynamics (MPD) thruster, will be analysed in the talk. In the MPD, either stationary or oscillatory, about half the energy is deposited in the perpendicular electron kinetic energy [5]. The implications of this energy partitioning will be discussed.[1] C. Charles, J. Phys. D: Appl. Phys. 42, 163001 (2009). [2] C. Charles and R. W. Boswell, Appl. Phys. Lett. 82, 1356 (2003). [3] A. L. Fabris and M. A. Cappelli, IEPC-2013-86. [4] S. Shinohara et. al., IEEE Trans. on Plasma Sci. 42, 1245 (2014). [5] A. Fruchtman, Phys. Plasmas 10, 2100 (2003). [Preview Abstract] |
Thursday, November 8, 2018 3:48PM - 4:00PM |
QR2.00010: Unified Hall Thruster Model for Studying Ground Facility Effects Lubos Brieda, Samuel J. Araki, Justin Koo Hall thrusters are spacecraft propulsion devices that utilize a crossed electric and magnetic field configuration to ionize and accelerate propellant gas. The discharge chamber is open to the ambient environment, leading to the possibility that thruster behavior becomes affected by the downstream conditions. While this ground facility effect has been demonstrated repeatedly in the lab[1], numerical models of this influence are still lacking. The primary challenge is that Hall thrusters are generally modeled using a dual approach, in which one set of equations is used for the "device" region, while another set is used for the "plume". The coupling between the models is one directional, with the the device code feeding ions to the plume simulation. In this talk, we report on a recent effort to develop a unified Hall thruster model that captures both the device and the plume region. The model is based on an axisymmetric hybrid-PIC formulation, with particles used for the heavy neutrals and ions, and the fluid equations solved for the electrons[2]. The approach is demonstrated by simulating a generalized Hall thruster operating in a vacuum chamber. [1] Walker, M. Ph.D. Dissertation, U. Mich. 2005 [2] Geng, J., et. al, J. Ap. Phys, 114, 10, 2013 [Preview Abstract] |
Thursday, November 8, 2018 4:00PM - 4:12PM |
QR2.00011: Physics and modeling of ID-HALL, a new concept of double stage HALL thruster Jean-Pierre Boeuf, Loic Dubois, Alexandre Guglielmi, Freddy Gaboriau, Laurent Liard HALL thrusters are EXB plasma devices where a large electric field can be generated in a quasineutral plasma by applying a DC voltage across a magnetic barrier. This electric field allows electron impact ionization of a flux of atoms injected at the anode, and accelerates ions out of the plasma, generating the thrust. In a double stage HALL thruster (DSHT), the plasma is generated in a plasma source independently of the applied voltage, allowing separate control of thrust and ion velocity. A new DSHT design, ID-HALL (Inductive Double-stage HALL thruster), is described. An RF inductive coil is placed inside the inner cylinder of ID-HALL. Thanks to a magnetic field distribution that efficiently connects the cusps of the plasma source to the magnetic barrier, a high density magnetically confined toroidal plasma is formed around the inner cylinder, close to the accelerating field of the magnetic barrier. After a brief discussion of the DSHT concept, we present 2D simulations of ID-HALL performed with the HALLIS hybrid model (\underline {https://www.hallis-model.com}). Plasma density, electron temperature and properties of the extracted ion beam as well as the performance of the thruster are studied as a function of DC voltage, RF power and gas mass flow rate. [Preview Abstract] |
Thursday, November 8, 2018 4:12PM - 4:24PM |
QR2.00012: Investigation of High Frequency Instabilities in the Plume of the VX-200 Magnetic Nozzle Matthew Giambusso, Edgar A. Bering, Mark D. Carter, Jared P. Squire During testing of the Variable Specific Impulse Magnetoplasma Rocket (VASIMR$^{\textregistered}$) VX-200 device, high frequency (HF) harmonics of the ion cyclotron heating (ICH) stage were measured in the radial component of the electric field along the upstream edge of the plasma exhaust. The perpendicular electron density gradient in this portion of the plume could allow growth of the lower hybrid drift instability (LHDI) or the modified two-stream instability (MTSI), but the perpendicular DC electric field is generally not strong enough to support these drift waves. It is theorized that the ICH power excites the unstable drift waves; the amplified ICH harmonics are the ones whose frequencies are close to the theoretical frequency of the instability. In a separate but related study, the stability of the exhaust jet is examined under the assumption of cold, homogenous, and uniformly magnetized plasma. A Clemmow Mullaly Allis (CMA) diagram for singly ionized Argon is drawn and annotated with scans through the plasma plume. Finally, a two-dimensional particle-in-cell model of the exhaust plume is developed, simulating a trans-Alfvénic plasma jet, the ion kinetic Beta transitioning from less than one to greater than one. [Preview Abstract] |
Thursday, November 8, 2018 4:24PM - 4:36PM |
QR2.00013: Spatiotemporally Resolved Ion Velocity Distribution Measurements in the 12.5 kW HERMeS Hall Thruster Vernon H. Chaplin, Robert B. Lobbia, Alejandro Lopez Ortega, Ioannis G. Mikellides, Richard R. Hofer Non-invasive measurements of the ion velocity distribution function (IVDF) obtained using laser-induced fluorescence (LIF) are playing a critical role in the life qualification of NASA’s 12.5 kW Hall Effect Rocket with Magnetic Shielding (HERMeS), which will be accomplished through a combination of limited duration wear testing and computational modeling validated by experiments. Previous LIF measurements on HERMeS have revealed bimodal time-averaged IVDFs in the acceleration region of the thruster, suggestive of oscillations in the acceleration region’s position, as well as time-averaged velocity vectors that are difficult to reproduce in simulations. In order to understand these phenomena in more detail, we are making time-resolved LIF measurements using the transfer function averaging technique, which employs phase-sensitive detection and averaging in Fourier space to enable measurements resolving both periodic and aperiodic oscillations at typically Hall thruster breathing mode frequencies (10-60 kHz). The first time-resolved IVDFs measured in HERMeS will be presented, along with time-averaged 2D velocity vector maps spanning a finer spatial mesh than in previous studies. Implications for performance and life modeling of HERMeS using the Hall2De code will be discussed. [Preview Abstract] |
Thursday, November 8, 2018 4:36PM - 4:48PM |
QR2.00014: Instability-Induced Cross Field Transport in a Low Temperature Magnetic Nozzle Shadrach T. Hepner, Benjamin Jorns Magnetic nozzles consist of a converging-diverging magnetic field that supersonically accelerates a plasma to generate thrust. A central question pertaining to these devices is that of particle detachment from magnetic field lines. As charged particles tend to follow a field line, the plasma may follow the lines as they curve back towards the thruster. In low-power systems, ions tend to be unmagnetized throughout the plume. However, electrons may remain attached and follow the field lines back to the thruster, inciting electric fields that cause ions to diverge or return to the thruster as well. This effect decreases thrust production. To produce thrust, electrons must be able to separate from magnetic field lines. \\ This work focuses on the presence of instabilities in a magnetic nozzle and their influence on electron detachment. We measure wave propagation in three dimensions of both high and low frequencies. We further describe them theoretically and determine the anomalous collision frequency throughout the plume. We measure background plasma potential, number density, and electron temperature and discuss the influence that these waves have on electron detachment. [Preview Abstract] |
Thursday, November 8, 2018 4:48PM - 5:00PM |
QR2.00015: A hybrid immersed boundary-lattice Boltzmann/finite difference method for coupled dynamics of fluid flow, advection, diffusion and adsorption in fractured and porous media Xu Yu, Klaus Regenauer-Lieb, Fang-Bao Tian Gas transport coupled with solid-fluid mass transfer is an important mechanism in porous media. Gas adsorption on the solid surface of the pores occurs in many fields of science and engineering. Geoscience applications include CO2 sequestration, energy storage, and especially coal bed methane (CBM) recovery. There exists to date no suitable method for modelling gas adsorption at pore scale level for cases where adsorption/desorption is the dominant mechanism for gas transfer. One important factor for the lack of a suitable computational tool to investigate the kinetics is that the gas adsorption is a multiscale process covering the micro-, meso-, and macroscale. Lattice Boltzmann Method (LBM) as a mesoscopic method has the advantage of offering a bridge between the physics of microscopic and macroscopic scales. This advantage led us to select LBM as a suitable method for the numerical discretization of macroscopic equations. In this paper, a hybrid immersed boundary-lattice Boltzmann/finite difference method is extended to simulate the coupled dynamics of fluid flow, advection, diffusion and adsorption in fractured and porous media. The numerical method includes three important components: fluid solver, advection-diffusion solver, and immersed boundary method for fluid-solid interaction with coupled mass exchange. In the fluid solver, the single-relaxation time lattice [Preview Abstract] |
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