Bulletin of the American Physical Society
70th Annual Gaseous Electronics Conference
Volume 62, Number 10
Monday–Friday, November 6–10, 2017; Pittsburgh, Pennsylvania
Session MW1: Microdischarges II |
Hide Abstracts |
Chair: Naoki Shirai, Hokkaido University Room: Salon D |
Wednesday, November 8, 2017 1:30PM - 2:00PM |
MW1.00001: Field Emission and its Effect on Microdischarge Formation Invited Speaker: David B. Go The formation of plasmas and discharges at dimensions approaching 1 micrometer have held the plasma community’s interest for nearly two decades as the potential for massive arrays and high electron densities hold significant promise for a wide variety of applications. It is now apparent that at these extreme dimensions, field emission can occur, and as an additional electron source, significantly alter the discharge dynamics. Much of the attention has focused on how field emission can reduce the breakdown voltage for plasma initiation and modify Paschen’s curve [1], but less attention has focused on how it affects other plasma conditions. In recent work, we have sought to measure the canonical direct current (DC) current-voltage (i-V) curve from pre-breakdown conditions through breakdown and the onset of a glow discharge. Measurements with both different cathode materials and in different atmospheric-pressure environments reveal that when field emission is active, it can dramatically alter the i-V curve, showing very little voltage drop from breakdown to glow discharge conditions and a smooth transition through the partial glow regime [2]. Further, while it is typical for i-V curves to exhibit hysteresis, field emission appears to soften this effect and allow for both forward and backward ramping from pre-breakdown to glow and vice versa. This effect, which has also been observed under vacuum conditions, reflects the unique impact field emission has on plasma operation at the microscale, and opens the door for new and novel approaches to microdischarge devices.\\ \\$[1]$ D. B. Go, A. Venkattraman, “Microscale gas breakdown: ion-enhanced field emission and the modified Paschen’s curve,” Journal of Physics D: Applied Physics, vol. 47, art. no 503001, 2014.\newline \\ $[2]$ M. A. Bilici, J. R. Haase, C. Boyle, D. B. Go, R. M. Sankaran, “Experimental evidence for the transition from a field emission-driven Townsend discharge to a self-sustained microplasma,” Journal of Applied Physics, vol. 119, art. no. 223301, 2016. [Preview Abstract] |
Wednesday, November 8, 2017 2:00PM - 2:15PM |
MW1.00002: Power absorption of atmospheric-pressure microwave-line-plasma Hirotaka Toyoda, Haruka Suzuki, Yuto Tamura, Yosuke Koike, Yoshiki Baba Large-scale atmospheric pressure (AP) plasmas have been given much attention because of its high cost benefit and a variety of possibilities for industrial applications. Microwave discharge plasma using slot is attractive due to its ability of high-density and stable plasma production, and we have developed a long-scale AP microwave plasma (AP microwave line plasma: AP-MLP) source up to \textasciitilde 1 m in length using loop-structured waveguide and travelling wave. However, mechanism of uniform plasma production along the slot and power absorption behavior of this plasma source is still unclear. In this study, we discuss power absorption process using an electromagnetic simulation software. In the simulation, a long waveguide with a long slot along the waveguide is supposed. Plasma is assumed inside the slot as a resistive material (conductivity: \textless 10 S/m) based on measured electron density and assumed collision frequency. Electromagnetic wave propagation along the waveguide and through the slot is simulated varying the resistivity of the plasma. The simulation showed that the power absorption decreases with increasing the electron density. Considering the power balance of the slot plasma, this result suggests that the fluctuation of the electron density at a certain position is stabilized by the power absorption property of the plasma, resulting in better uniformity of the plasma along the slot. [Preview Abstract] |
Wednesday, November 8, 2017 2:15PM - 2:30PM |
MW1.00003: Tuning of AC Sheath Thickness by Varying Plasma Excitation Frequency Abbas Semnani, Sergey Macheret, Dimitrios Peroulis It is known that increasing the magnitude of discharge current, either DC or RF, in abnormal glow discharge regime results in shrinking of sheath layer. Since plasma sheath behaves mainly as a capacitor due to its low electron density, this property was successfully employed to make a current-controlled tunable RF capacitor\footnote{A. Semnani et al. IEEE Trans. Plasma Sci., 44, 1396-1404 (2016).}. On the other hand, RF sheath thickness also depends on the frequency of plasma excitation field. In this work and to prove this concept, an $ LC $ resonator with resonant frequency in the range of 100s of MHz was fabricated and measured. In this resonator, a gas discharge tube (GDT) ignited by a kHz-range electric field performs as a variable capacitor. By changing the frequency of the plasma excitation signal in the range of 1-1200 kHz, the measured resonant frequency of the $ LC $ resonator tuned in the range of 410 MHz to 300 MHz. This measurement clearly shows the possibility of achieving frequency-controlled sheath thickness in AC abnormal glow discharge regime. [Preview Abstract] |
Wednesday, November 8, 2017 2:30PM - 2:45PM |
MW1.00004: Contraction phenomena in surface wave driven plasmas in Ar: what are the real causes of contraction? Marco Antonio Ridenti, Jayr de Amorim, Vasco Guerra, George Petrov, Arnaldo Dal Pino In this work we designed a model to describe a surface wave driven plasma in argon at atmospheric pressure. We included the detailed chemical kinetics dynamics of Ar and solved the mass conservation equations of the relevant neutral excited and charged species. The gas temperature radial profile was calculated by means of the thermal diffusion equation. The ground state density was estimated assuming the ideal gas law. The electric field radial profile was calculated directly from the numerical solution of the Maxwell's equations assuming the surface wave to be propagating in the TM$_{00}$ mode. The problem was considered to be radially symmetrical, the axial variations were neglected and the equations were solved in an auto consistent fashion. We probed the model results considering three scenarios: (i) the electron energy distribution function (EEDF) was calculated by means of the Boltzmann equation; (ii) the EEDF was considered to be Maxwellian; (iii) the dissociative recombination was excluded from the chemical kinetics dynamics, but the non-equilibrium EEDF was preserved. From this analysis, we established that dissociative recombination is the leading mechanism in the constriction of surface wave plasmas. [Preview Abstract] |
Wednesday, November 8, 2017 2:45PM - 3:00PM |
MW1.00005: Continuum Simulation of Microplasmas with Prolate Spheroid Field Emitters Abhishek Kumar Verma, Ayyaswamy Venkattraman In past three decades, microscale gas discharges using field emission cathodes have been very active research topics. Since the experimental observations of remarkable field emission with low applied voltage in field emission assisted (FEA) microplasmas, significant efforts have been devoted to fundamental understanding of such systems by means of kinetic and fluid simulations, though limited to one dimension model. This work aims to expand our understanding of FEA microdischarge dynamics over pre-and post-breakdown regime in complex geometries such as prolate spheroid. We performed 2D and 2D-axisymmetric simulation of direct current argon microplasma confined between a prolate spheroid tip and a planar electrode on unstructured grids. We employed fluid model with full momentum equation and simple argon chemistry for plasma simulation along with Fowler-Nordheim equation to model field emission surface. Our results show various plasma parameters with local field enhancement and their dependency on surface location and emitter height to radius aspect ratio, to provide a basis for device characterization, tip current, effective emission area etc. The simulation results are compared with existing experimental literature on Townsend and glow discharge regimes. [Preview Abstract] |
Wednesday, November 8, 2017 3:00PM - 3:15PM |
MW1.00006: Kinetic Simulations of Argon Microwave Microplasmas Arghavan Alamatsaz, Abhishek Kumar Verma, Ayyaswamy Venkattraman Microwave microplasmas have been an active research area in the last decade with applications in various fields such as metamaterials and material processing. Low-frequency microwave microplasmas have been studied experimentally and numerically. Most of these numerical studies utilize continuum modeling while kinetic methods such as Particle-in-cell with Monte Carlo collisions (PIC-MCC) can most accurately capture the nonlinearities in microplasma behavior in this regime. On the other hand, microwave microplasmas with higher frequencies have been less explored. In this regard, in the current study, we perform 1-D PIC-MCC simulations for argon microplasmas in microwave regime for a range of frequencies to explore the effect of frequency on plasma characteristics such as number density and required power to reach a specific number density. In a recent work, we used PIC-MCC for microwave microplasma with a 0.5GHz frequency which showed good agreement with the existing literature. In another study, a comparison between PIC-MCC and an in-house fluid model illustrated reasonable agreement. Another objective of this work would be comparing PIC-MCC and fluid model for higher frequencies in order to assess the validity of the fluid model in predicting microplasma behavior. [Preview Abstract] |
Wednesday, November 8, 2017 3:15PM - 3:30PM |
MW1.00007: Fluid Modeling of Low Temperature Microwave Microplasmas Ayyaswamy Venkattraman, Abhishek Kumar Verma Microwave excited microplasmas are of great interest not only to scientific research but also for developing applications in metamaterials, plasma medicine and industrial scale material processing methods. Recently computational modeling and simulation is found to be of immense importance for the advancement in fabrication, designing and developing applications based on microwave microplasma. This work demonstrates our recent developments on suitable computational model and tools for simulation and insights on physical mechanism of microwave microplasma. We performed 1D and 2D continuum simulation of microwave ignited argon microplasma in simple geometries of split ring resonators and microstrip linear resonators. We employed a widely applicable fluid model including full momentum equation and reasonable rate coefficients and transport parameters for high fidelity simulation in our finite volume parallel computational framework. The simulations intend to show the advantages of using microwave sources over DC and RF sources for transferring energy to electrons and dependence of characteristics of generated plasma on various parameters such as frequency and pressure. Comparison between some simulation cases and available experimental results in literature are also presented. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700