Bulletin of the American Physical Society
72nd Annual Gaseous Electronics Conference
Volume 64, Number 10
Monday–Friday, October 28–November 1 2019; College Station, Texas
Session UF2: Basic Plasma Physics Phenomena in Low-Temperature Plasma |
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Chair: Greg Severn, University of San Diego Room: Century II |
Friday, November 1, 2019 10:00AM - 10:15AM |
UF2.00001: The influence of conical and cylindrical hollow cathode geometries on the characteristics of a magnetized plasma column. Montu Bhuva, Shantanu Karkari, Sunil Kumar The characteristics of a magnetized plasma column produced by direct-current (DC) operated hollow cathode plasma source is presented. It is found that by incorporating a conical hollow cathode geometry in the source, the downstream plasma column exhibits a centrally peaked density profile; as opposed to an off-centered density peak observed in case of a cylindrical cathode system. It is also found that owing to the improvement in secondary electron emission yield, the discharge in the case of a conical cathode can be sustained at twice the higher magnetic field than in the cylindrical case. A phenomenological model has been formulated to explain the discharge behavior for each plasma source. The plasma properties obtained from the experimental measurements and from the model has been qualitatively discussed and correlated with the source geometry. [Preview Abstract] |
Friday, November 1, 2019 10:15AM - 10:30AM |
UF2.00002: Investigation on plasma properties of Magnetic X-point simulator system, MAXIMUS, with perturbing magnetic fields Yegeon Lim, Bin Ahn, Yong Sung You, Young-Chul Ghim We present basic properties of low temperature DC plasmas generated in a recently built MAgnetic X-point sIMUlator System, MAXIMUS, a cylindrical multidipole chamber capable of generating tokamak-like poloidal magnetic fields. Steady-state low temperature DC plasmas with typical plasma parameters of T$_{\mathrm{e}}$\textasciitilde 1eV, n$_{\mathrm{e}}$\textasciitilde 10$^{\mathrm{9}}$cm$^{\mathrm{-3}}$, and \textunderscore \textunderscore $_{\mathrm{p}}$\textasciitilde 2V are generated by energetic ionizing electrons emitted from hot ThW filaments and/or an LaB$_{\mathrm{6}}$ cathode plate. Plasma characteristics are measured with Langmuir probes, ion acoustic wave and optical emission spectroscopy with helium CR model, and magnetic field measurements using a Hall-effect sensor. Radial profiles of plasma parameters are mainly determined by the multidipole geometry, and axial profiles can be controlled by varying gas pressure, discharge voltage and current, and poloidal magnetic fields. With a magnetic X-point configuration, clear patterns on the plasma parameters are observed along magnetic field lines, especially on the separatrix region. We also present preliminary results on how the plasmas respond to additional perturbing magnetic fields. [Preview Abstract] |
Friday, November 1, 2019 10:30AM - 10:45AM |
UF2.00003: Structure within the PK-4 Environment Truell Hyde, Lorin Matthews, Peter Hartmann, Marlene Rosenberg, Oleg Petrov, Vladimir Nosenko Complex plasmas have long proven a versatile analog for the study of soft matter systems. On Earth, interparticle interactions can result in particle alignment as well as the formation of various structural states. Unfortunately, the forces behind these interactions are often partially masked by gravity in terrestrial experiments, obscuring the underlying physics. One way of avoiding this issue is through use of the Plasma Kristall-4 (PK-4) device currently in operation on the International Space Station (ISS) [1]. This talk will discuss structural formation observed within the PK-4 on the International Space Station and compare it to that observed using the PK-4 analogue at Baylor University. Results are interpreted using data from numerical simulations of the plasma discharge, dust charging, and plasma-dust interactions. [1] M. Y. Pustylnik, et. al. \textit{Review of Scientific Instruments }87 (2016) 093505. [Preview Abstract] |
Friday, November 1, 2019 10:45AM - 11:00AM |
UF2.00004: Dynamic contraction of the positive column of a self-sustained glow discharge in a reacting flow Hongtao Zhong, Mikhail Shneider, Mikhail Mokrov, Yiguang Ju Contraction occurs when current contracts from a uniform volumetric weakly ionized plasma into a localized channel. This dynamic transition provides a promising technique for reliable ignition of ultra-lean combustion mixtures. In this work we study the dynamic contraction of the positive column of a self-sustained glow discharge in a reacting H2-O2-N2 flow. We developed a one-dimensional numerical model of the plasma contraction in a cylindrical frame. The contraction process is described by a set of time-dependent equations. We analyzed the critical conditions for transitions from the uniform to contracted state. The plasma instability in reacting flows is not only governed by the ionization-thermal mechanism, but also heat release/absorption in chemical reactions. Specifically, electron-impact fuel ionization, combustion heat release and the electron attachment to combustion-related species would shift the critical current for triggering the plasma instability. The study of the plasma instability in a combustion mixture will advance the understanding of the kinetic and thermal interaction between non-equilibrium plasma and combustion and lay foundations for the development of plasma assisted ignition. [Preview Abstract] |
Friday, November 1, 2019 11:00AM - 11:15AM |
UF2.00005: Amplitude modulation of ion acoustic waves in a magnetized spin quantum plasma Nareshpal Singh Saini, Kuldeep Singh Degenerate plasmas are found to play an important role in dense astrophysical objects like white dwarfs and neutron stars. In such a plasma, the density is very high and the temperature is very low. The presence of a strong ambient magnetic field qualitatively changes the properties of atoms, molecules and condensed matter. Ion- acoustic waves are among the most well studied electrostatic modes in both linear and nonlinear regimes in dense astrophysical plasmas. In the present investigation, the modulational instability of ion acoustic waves and evolution of rogue waves have been investigated in a dense magnetized plasma by employing the spin-evolution quantum hydrodynamic model. We have considered degenerate electrons having spin-up and spin-down relative density effects and non-degenerate cold ions. The nonlinear Schr\"{o}dinger equation is derived using the multiple scale perturbation technique and solved numerically to study the effect of various plasma parameters on the modulational instability.The parametric role of the spin density polarization ratio on the amplitude and width of solitary structures is also investigated. The spin-up and spin-down polarization of degenerate electrons are considered via polarization index. The quantum tunneling effects are also taken into account by considering the Bohm potential term in the corresponding momentum equations of degenerate electrons. The findings may also be applicable to astrophysical plasmas (e.g., neutron stars/pulsars) where the spinning effect of fermions is included to describe the dense astrophysical plasma system. [Preview Abstract] |
Friday, November 1, 2019 11:15AM - 11:30AM |
UF2.00006: Understanding discharge inception in air using high-voltage experiments and particle-in-cell simulations Andy Martinez, Shahriar Mirpour, Jannis Teunissen, Sander Nijdam, Ute Ebert Understanding discharge inception is important for fields like lightning research, lightning protection, and high-voltage technology. In this study, the inception times and probabilities of discharges are measured in a vessel filled with dry and humid air between 100 and 1000 mbar. A pin-to-plate electrode geometry is considered, in which tens of kV are applied over a cm-scale gap. The inception time is defined as the moment a photomultiplier tube measures a signal above the background noise. The inception probabilities and spread of inception times are compared to Monte-Carlo particle simulations with different initial charge densities (e-, and O2-) to find conditions that reproduce the statistics from the experiments.\\ \\ Preliminary results show two distinct inception timescales: tens of ns, and hundreds of ns. In the first case the electrons have a high probability of reaching the electrode without getting attached while in the second case negative ions 'transport' the electrons to the high field region. From the high-voltage experiments and simulations, we can estimate the initial charge densities and species in the vessel. [Preview Abstract] |
Friday, November 1, 2019 11:30AM - 11:45AM |
UF2.00007: Parametric study of pressure and frequency modes in a low temperature plasma bounded by a dielectric surface Jose Millan, Venkattraman Ayyaswamy Low-temperature plasmas operating in the presence of a dielectric surface are encountered in several applications involving plasma-surface interactions. Therefore, it is crucial to obtain a better understanding of the interactions between non-thermal plasmas and dielectric surfaces. The primary goal of the current work is to obtain a better understanding of the frequency and pressure response of the operating modes of argon microplasmas ignited in a dielectric barrier discharge configuration. Specifically, one-dimensional simulations based on a continuum approach will be utilized to study microplasmas operating in high radio frequency/microwaves regimes and pressure ranging from 76 torr to 760 torr. The continuum simulations are performed by solving the full-momentum equations for ions and electrons using the plasmaFoam code developed in-house. Results will be presented for the influence of the dielectric properties on plasma properties. The one-dimensional results will be compared to representative two-dimensional simulations in order to highlight the effect of dimensionality. The results are of importance of the design of microwave plasma sources that interact with non-conducting surfaces. [Preview Abstract] |
Friday, November 1, 2019 11:45AM - 12:00PM |
UF2.00008: Plasma temperatures inside cavitation induced by a shrimp-inspired mechanical device Xin Tang, Matthew Burnette, Kunpeng Wang, Christopher Campbell, David Staack In nature, marine animals like snapping shrimp use the cavitation mechanism for hunting, defense, communication, and tunneling activities. In previous research, a manually triggered shrimp-inspired mechanical device was developed and plasma formation was observed in the collapsing cavitation created by this shrimp-like device. The temperature inside the collapsing cavitation is an important plasma parameter for physical and chemical processes. An upgraded automatic snapping version of the shrimp-inspired device with a higher snapping frequency around 0.83 Hz was invented to explore the shrimp cavitation mechanism in a broad range of applications. Since the light emission is so weak, it can be hardly observed by unaided eyes. The light emission was increased by this automatic snapping as well as noble gas doping, making it possible for further spectrum analysis. The emission lines in the cavitation spectrum can be utilized for temperature estimation. Cavitation compression is an effective energy focusing process for plasma generation in liquids. With the measurement of the plasma temperatures, the actual plasma generation efficiency can be estimated. [Preview Abstract] |
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