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 NO03: Fundamental Plasmas: Dusty and Multiphase PlasmasLive
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Chair: Evdokiya Kostadinova, Baylor University |
Wednesday, November 11, 2020 9:30AM - 9:54AM Live |
NO03.00001: Developing Plasma Spectroscopy and Imaging Diagnostics to Understand Astrophysically-Relevant Plasma Experiments (PhD Oral-24) Ryan S. Marshall, Paul M. Bellan One of the main attractions of using laboratory experiments as a proxy to study solar and astrophysical plasmas is the ability to deploy diagnostics. Spectroscopy and imaging tools are especially useful because they do not perturb the subject plasma. This talk will showcase three surprising results obtained using novel diagnostics. First, an X-ray scintillator detector and a CMOS camera acting as an X-ray spectrometer detect a $\sim1$ $\mu$s burst of $\sim6$ keV hard X-rays on the $T = 2$ eV MHD-driven jet at Caltech. This observation leads to a new statistical theory of particle acceleration and the hypothesis that solar prominence microstructure resembles Litz-wire, i.e. small, braided filaments each on the order of a few times the ion skin depth. Second, analysis of a 4,000 frame per second movie of micron-size ice grains growing in the Caltech dusty plasma experiment leads to the conclusion that the grains grow by accretion. The majority of the talk will focus on the third diagnostic: A motorized laser-induced fluorescence (LIF) diagnostic developed for the Caltech dusty plasma. Despite the lack of absolute calibration in diode lasers and wavelength drift due to slight changes in ambient room conditions, 1-2 m/s bulk neutral flow speeds are measured with 0.6 m/s resolution. [Preview Abstract] |
Wednesday, November 11, 2020 9:54AM - 10:06AM Live |
NO03.00002: Dust Acoustic Waves As a Possible Trigger Mechanism For The Rayleigh-Taylor Instability In a Dusty Plasma Katherine Pacha, Robert Merlino Further analysis of the video images as well as new theory concerning the interpretation of a previous experiment on the observation of the Taylor instability in a dusty plasma [K. A. Pacha, \textit{et. al}., Phys. Plasmas \textbf{19}, 014501 (2012)] are presented. The re-examination of the data indicates that the Rayleigh-Taylor instability (RTI) may be triggered by the sudden intensification of high amplitude dust acoustic waves at the boundary between high and low dust density regions. Also, as pointed out and analyzed theoretically by Avinash and Sen [\textit{Phys. Plasmas }\textbf{\textit{22}}\textit{, 083707 (2015)], the curvature of the boundary allows for a perpendicular component of the gravitational acceleration at the boundary between the low and high dust density regions which can drive a RTI. } [Preview Abstract] |
Wednesday, November 11, 2020 10:06AM - 10:18AM Live |
NO03.00003: Dust experiments under strong magnetic fields Andre Melzer, Harald Krueger, Stefan Schuett, Michael Himpel Experiments on dusty plasmas under various magnetic fields strengths have been performed. First, the dynamics of a cluster of micron-sized particles is studied over a wide range of magnetic field strengths. From the cluster dynamics the dust charge and the plasma screening length are derived. Second, the behavior of dust-density waves in dust clouds of micron-sized particles is invesitgated. From the comparison of the measured wave properties and a model dispersion relation, the ion density and the dust charge are extracted. It is seen that the dust and plasma quantities show only little variation with magnetic field strength. [Preview Abstract] |
Wednesday, November 11, 2020 10:18AM - 10:30AM Live |
NO03.00004: New Charge Analysis technique for Magnetized Dusty Plasma Flows Dylan Funk, Uwe Konopka, Edward Thomas Dusty plasmas consist of the standard plasma components (electrons, ions and neutrals) as well as micrometer sized particles. The dust particles are highly charged as a result of their interaction with the other plasma components. The charge of these dust particles is a difficult quantity to estimate precisely, especially when under the influence of a magnetic field. Because of this difficulty, a method for the experimental determination of the dust particle charge under the influence of a magnetic field is required. Our method utilizes the Lorentz force acting on the moving particles due to the static magnetic field. A dust particle density gradient will build up due to the Lorentz force. Utilizing a molecular dynamic simulation we plan on showing how the dust charge value can be determined non-invasively to a higher degree of precision. [Preview Abstract] |
Wednesday, November 11, 2020 10:30AM - 10:42AM Live |
NO03.00005: Laser manipulation of binary mixtures Dietmar Block, Frank Wieben With the possibility to create binary mixtures in dusty plasma an immediate urge to manipulate these systems arose. This contribution summarizes our recent results on how laser manipulation in a binary system works, how this can be utilized to achieve a quantitative understanding of laser manipulation in general and how to realize basic thermodynamic experiments. [Preview Abstract] |
Wednesday, November 11, 2020 10:42AM - 10:54AM Live |
NO03.00006: Impedance Probe Measurements for Plasmas with and without Dust Brandon Doyle, Uwe Konopka, Edward Thomas, Jr. Impedance probe measurements are a class of RF plasma spectroscopy which utilizes plasma resonances near the electron plasma frequency, $\omega _{\mathrm{pe}}$. Impedance probe measurements can be desirable for diagnosis of dusty plasma parameters because the measurements can potentially be performed with only mild or marginal perturbation to the plasma and dust component, in contrast to the significant influence a traditional Langmuir probe would cause. In this presentation, we describe experiments performed using a double-tipped, transmission-type (S$_{\mathrm{21}})$ impedance probe in two different plasma chambers at Auburn University: in the Magnetized Dusty Plasma Experiment (MDPX), and in a dodecahedral plasma chamber prototype which was originally designed for microgravity experiments. The electron density is determined from the transmission spectra of this probe by assuming a lumped-element circuit model for the probe-plasma system and a fluid model for the plasma itself. This probe design is compared to a single-tipped, reflection-type (S$_{\mathrm{11}})$ impedance probe, and advantages and disadvantages of each design are discussed. [Preview Abstract] |
Wednesday, November 11, 2020 10:54AM - 11:06AM Live |
NO03.00007: Time-dependent electron energy distribution functions in radio frequency plasmas containing nanometer-sized dust particles. Uwe Kortshagen Nano-dusty plasmas, plasmas containing nanometer-sized particles generated through plasma chemical reactions, have attracted significant interest for the synthesis of nanomaterials with new properties. In these plasmas, the plasma properties are strongly affected by the presence of the dust particles because a majority of plasma electrons can become attached to the particles. In this presentation, the author investigates the influence of the presence of dust particles on the electron energy distribution function. Nano-dusty plasmas are typically operated at pressures of a few 100 Pa and excited using radio-frequency (RF) power. Under these conditions, even a pristine plasma will exhibit an electron energy distribution function that is time-dependent because the energy relaxation frequency of energetic electrons capable of performing inelastic collisions exceeds the RF angular frequency. The presence of dust particles introduces new phenomena that affect the electron energy distribution function. [Preview Abstract] |
Wednesday, November 11, 2020 11:06AM - 11:18AM Live |
NO03.00008: Dynamics of charged micro-particle clusters in a plasma medium. Srimanta Maity, Amita Das The study of charged particle system trapped in an external potential well is of fundamental interest over the decades concerning its metastable configurations, particle ordering, cluster formations, phase transitions, and a rich variety of structures and dynamical properties. Dusty plasma medium is demonstrated to be an ideal model system to study the structures and dynamics of finite charge particle systems where the background plasma is itself responsible for the confinement of particles. In the present study, we have investigated the possible relaxation states of charged micro-particles in a plasma environment using Molecular Dynamics (MD) simulations. The charged micro-particles interacting via screened Coulomb pair potential. An external two-dimensional (2-D) parabolic potential has been applied to confine the particles in a 2-D plane. The equilibrium configuration of this trapped charge particle system has been explored over a wide range of system parameters i.e., the total number of particles, Np, relative confinement strength. It has been shown that for a low Np, particles are arranged in multiple shell/ring structures where for some specific configurations such an arrangement is stationary. However, it has been shown that, for several cases, particles relax to a state where they display inter-shell rotation along with a radial oscillation in the individual rings. For a larger cluster configuration (higher Np), a novel equilibrium state with coherent rigid angular oscillation of particles around the center of mass of the configuration has been observed and characterized. [Preview Abstract] |
Wednesday, November 11, 2020 11:18AM - 11:30AM Live |
NO03.00009: Theoretical analysis of the transition from field emission to space-charge limited emission in liquids Sarah Lang, Adam Darr, Allen Garner Discharge formation and breakdown in water have critical implications for water sterilization and biomedical applications [1]. Several studies in liquids have demonstrated that current transitions from Fowler-Nordheim (FN) for field emission to Mott-Gurney (MG) for space charge limited emission (SCLE) with increasing voltage [2]. A recent theory unified FN, MG, and Child-Langmuir law (CL) for vacuum SCLE in gases as a function of mobility, pressure, and gap distance [3], yielding a third order nexus when the asymptotic solutions for FN, CL, and MG match. Since the relevant physics is independent of the phase of matter, this study assesses the feasibility of applying this theory to liquids. By treating the emission area and Fowler-Nordheim constants as fitting parameters, we fit the theory to liquid data and observe the transition from FN toward MG. The implications of these results on electron emission in liquids and as the phase transitions to vapors and gases will be discussed. [1] J.E. Foster, Phys. Plasmas \textbf{24}, 055501 (2017). [2] K. Dotoku, H. Yamada, S. Sakamoto, S. Noda, and H. Yoshida, J. Chem. Phys. \textbf{69}, 1121 (1978). [3] A.M. Darr, A.M. Loveless, and A.L. Garner, Appl. Phys. Lett. \textbf{114}, 014103 (2019). [Preview Abstract] |
Wednesday, November 11, 2020 11:30AM - 11:42AM Live |
NO03.00010: A Universal Theory for Microscale Gas Breakdown for a Pin to Plate Geometry Amanda Loveless, Lorin Breen, Russell Brayfield, Allen Garner Decreasing electronics size necessitates better characterization of electron emission at micro- and nanoscales for applications including microplasmas, micro- and nanoelectromechanical systems, and directed energy. While Paschen's Law has historically predicted breakdown voltage based on the Townsend avalanche criterion, field emission, must be incorporated for gap sizes below 15 micrometers. Extensive work has modified Paschen's law to include additional emission and breakdown phenomena for planar geometries [1]; however, practical experiments use pin-to-plate geometries (PPG). This work modifies a previously derived theory coupling Paschen's law and field emission to account for PPG by replacing the field enhancement, which has been used primarily as a fitting parameter, with the vacuum electric field for the PPG. The theory is applied to experimental data, and limiting cases relating gap distance to tip radius will be presented with applications to other geometries discussed. [1] A. L. Garner, A. M. Loveless, J. N. Dahal, and A. Venkattraman, IEEE Trans. Plasma Sci. 48, 808-824 (2020). [Preview Abstract] |
Wednesday, November 11, 2020 11:42AM - 11:54AM Live |
NO03.00011: Experimental and Numerical Modeling of Spark Discharges in Dusty Supersonic Flow. Christopher Kueny, Jens von der Linden, Jason Sears, Allen Kuhl, Dave Grote, Mark Converse, Clare Kimblin, Ian McKenna, Ryan Houim, Skyler Bagley Supersonic particle-laden gas emerging from a nozzle produces radio frequency (RF) emanations, a scenario found at the exhaust of shock tubes and in other applications. A likely source of the RF is streamer or coronae discharge between triboelectrically charged dust particles. The phenomenon has been investigated using burst disks to rapidly expel argon gas entraining various particle compositions. Measured electrical discharges appear to be associated with a standing shock wave known as the Mach disk, characterized by a high density gradient that could provide favorable conditions for spark generation. Hydrodynamic modeling with the HyBurn code shows excellent agreement with experimental measurements. Calculation of ionization rates with the Bolsig$+$ Boltzmann solver and application of the Raether-Meek breakdown criterion allows us to place bounds on the particle charging necessary to support the observed discharges. This combination of multiphysics experiment and modeling is helping to validate theoretical models of particle electrification and discharge in supersonic flows. [Preview Abstract] |
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