Bulletin of the American Physical Society
67th Annual Gaseous Electronics Conference
Volume 59, Number 16
Sunday–Friday, November 2–7, 2014; Raleigh, North Carolina
Session PR1: Microdischarge Devices |
Hide Abstracts |
Chair: Osamu Sakai, Kyoto University Room: State EF |
Thursday, November 6, 2014 1:30PM - 1:45PM |
PR1.00001: Ignition Dynamics of a Self-pulsing y-mode discharge in a wedge-shaped micro-scaled atmospheric pressure plasma jet ($\mu$-APPJ) Daniel Schr\"oder, Sebastian Burhenn, Volker Schulz-von der Gathen Microplasma jets, operated at atmospheric pressure, are susceptible to instabilities. A prominent one is the ``$\alpha $-$\gamma $ transition'' instability, often resulting in a constricted discharge at high gas temperatures destroying the device. Thus a safe and stable application of these devices for treating heat-sensitive biological materials is limited. In order to analyze the responsible mechanisms for this mode transition, the capacitative coupled, rf-excited (f$=$13.56 MHz) micro-scaled plasma jet ($\mu$-APPJ) has been modified. A wedge-shaped electrode configuration has been developed, forming a 30 mm long discharge gap increasing linearly from 1 mm at the gas inlet to 3 mm at the nozzle. A self-pulsing behavior is observed characterized by a periodical ignition of a constricted y-mode discharge feature at the gas inlet, propagating with the gas flow through the device towards the nozzle. Spectral- and phase-resolved optical emission spectroscopy (PROES) is applied to investigate discharge ignition dynamics and cross-checked with synchronized current /voltage measurements. [Preview Abstract] |
Thursday, November 6, 2014 1:45PM - 2:00PM |
PR1.00002: The formation of a turbulent front in a time modulated argon APPJ Shiqiang Zhang, Eddie van Veldhuizen, Peter Bruggeman, Ana Sobota Cold atmospheric pressure plasma jets (APPJ) are promising tools for biomedical applications such as wound healing, disinfection, decontamination, and material processing. The jet effluent is blown in an open air environment which leads to air diffusion and argon-air mixtures in the effluent flow. Since the reactive species carried by the flow are important in such kinds of applications, knowledge of the characteristics of the flow are crucial for understanding the distribution, evolution, transport, and chemical reactions of these reactive species. The flow dynamics of an non equilibrium argon-based atmospheric pressure plasma jet (APPJ) is investigated in this work. Shadowgraphy results show that turbulent front appears when the plasma is switched on and off and the laminar length of the flow during the plasma on phase is shorter than that during the plasma off phase. Time resolved gas temperature profiles obtained by Rayleigh scattering are used to explain the formation of the turbulent front when the plasma is switched on and off and the reduction of the length of the laminar flow. [Preview Abstract] |
Thursday, November 6, 2014 2:00PM - 2:15PM |
PR1.00003: Dynamics of a Microwave Excited Microplasma Flowing into Very Low Pressures Peng Tian, Mark Denning, Randall Urdahl, Mark J. Kushner Capacitively coupled microplasmas in dielectric cavities have a range of applications from VUV sources for surface treatment to radical production. Due to the small size of these devices, pd (pressure $\times$ size) scaling requires that they operate at high pressure. When the output of the microplasma is needed at low pressure, a plume of radicals and ions flows from the higher pressure microdischarge cavity into the lower pressure workspace. These conditions affect both the delivery of the radicals, ions and photons in the plume, and the dynamics of the microdischarge. In this paper, we discuss results from a computational investigation of a microwave excited microplasma operating at a pressure of several Torr of a rare gas with powers of 2-10s of Watts at 2.5 GHz. The plume from the microdischarge cavity flows into pressures as low as a few mTorr. A 2-d plasma hydrodynamics model with radiation and electron energy transport addressed using Monte Carlo techniques has been modified to enable the plume to flow into near vacuum. Plasma dynamics and reactive fluxes from the cavity will be discussed for different flow boundary conditions, as a function of power, pressure and gas mixtures. [Preview Abstract] |
Thursday, November 6, 2014 2:15PM - 2:30PM |
PR1.00004: Interaction of High-Frequency Electromagnetic Waves with Pre-Breakdown Atmospheric Pressure Micro-Discharge Region Abbas Semnani, Dimitrios Peroulis The properties of a micro-scale gap at atmospheric pressure are completely different in pre- and post-breakdown conditions.\footnote{A. Semnani et al. Appl. Phys. Lett., \textbf{102}, 174102 (2013)} Unlike the quasi-neutral region formed after breakdown, the ion number density is orders of magnitude higher than the electron density in pre-breakdown conditions.\footnote{A. Venkattraman et al. Phys. of Plas., \textbf{19}, 123515 (2012)} Consequently, ions may also contribute on the discharge conductivity even though they are much heavier than electrons. In this work, we study the interaction of high frequency electromagnetic waves with the discharge region before and after breakdown. The study is done at room temperature and atmospheric pressure conditions with gaps in the order of hundreds of nanometers up to a few micrometers. Gas discharge simulations are performed by using the PIC/MCC technique while the finite difference time domain (FDTD) method is used for electromagnetic simulations. The species are imported into EM simulations by a conduction current term in Ampere's law. The validity of conventional wisdom of ignoring the ions' contribution is examined for different cases. [Preview Abstract] |
Thursday, November 6, 2014 2:30PM - 2:45PM |
PR1.00005: Fluid modeling of operating modes in a field emission driven alternating current (FEDAC) microdischarge Ayyaswamy Venkattraman, Arghavan Alamatsaz, Therazhundur Ramesh Shivaprasad The recent interest in electrostatic microscale devices has lead to a great emphasis on electrical breakdown of gases in microgaps. The breakdown process has been shown to be significantly different from its counterpart in macrogaps with field emission of electrons from the cathode playing a major role. This work aims to build on prior work dealing with pre-breakdown and post-breakdown operating modes in direct current field emission driven (FED) microdischarges. Specifically, charged particle dynamics in microscale gaps that are driven by time-varying fields are studied using an in-house two-fluid code with appropriate cathode boundary conditions including field emission. The model includes continuity and energy equations for both electrons and ions to account for the significant non-equilibrium and is augmented by the Poisson's equation for electrostatic potential. The frequency dependence of breakdown behavior as well as pre-breakdown and post-breakdown current-voltage characteristics is determined for a wide range of frequencies from low radio frequency (RF) to microwave and contrasted with existing results for direct current FED microdischarges. The results are also used to explain trends recently observed in an evanescent-mode cavity resonator operating in the microwave regime. [Preview Abstract] |
Thursday, November 6, 2014 2:45PM - 3:00PM |
PR1.00006: Quantum Simulation of Field Emission in Microscale Gas Discharges Yingjie Li, David Go Field emission can be a critical cathode process in microscale gas discharges, especially for electrode gaps less than 10 $\mu $m. In this work, ion-enhanced field emission is determined by solving the one-dimensional Schrodinger's equation. In most prior work, a linear approximation for the ion potential has been coupled with the Fowler-Nordheim equation, but this does not realistically account for the form of potential barrier, and underestimates the impact of the ion's potential well. Here, the tunneling behavior is more accurately represented by determining the wave function of the electrons inside and outside of the cathode in order to predict the emission current. Using this approach, microscale breakdown theory is revisited, in order to understand the deviation from classic breakdown theory at microscale dimensions. [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