Bulletin of the American Physical Society
65th Annual Gaseous Electronics Conference
Volume 57, Number 8
Monday–Friday, October 22–26, 2012; Austin, Texas
Session QR4: Microdischarges II |
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Chair: Julian Schulze, Ruhr-Universit\"at Bochum Room: Classroom 105 |
Thursday, October 25, 2012 10:30AM - 11:00AM |
QR4.00001: Modelling of capacitive microdischarges at atmospheric pressure Invited Speaker: Pascal Chabert A one-dimensional hybrid analytical-numerical global model of atmospheric pressure, radio-frequency (rf) driven capacitive discharges is developed. The feed gas is assumed to be helium with small admixtures of oxygen or nitrogen. The electrical characteristics are modeled analytically as a current-driven homogeneous discharge. The electron power balance is solved analytically to determine a time-varying Maxwellian electron temperature, which oscillates on the rf timescale. Averaging over the rf period yields effective rate coefficients for gas phase activated processes. The particle balance relations for all species are then integrated numerically to determine the equilibrium discharge parameters. The coupling of analytical solutions of the time-varying discharge and electron temperature dynamics, and numerical solutions of the discharge chemistry, allows for a fast solution of the discharge equilibrium. Variations of discharge parameters with discharge composition and rf power are determined. Comparisons are made to more accurate but numerically costly fluid models, with space and time variations, but with the range of parameters limited by computational time. [Preview Abstract] |
Thursday, October 25, 2012 11:00AM - 11:15AM |
QR4.00002: A novel global model for radio-frequency driven plasmas at atmospheric pressure Torben Hemke, Thomas Mussenbrock, Ralf Peter Brinkmann Over the last years microplasma research gained a lot of attention both from an experimental and theoretical perspective. One particular type of microplasma sources that shows a variety of interesting physics and applications are the so called plasma jets. Besides the more elaborated fluid or hybrid approaches the so called global models offer the ability to explore averaged species densities and energies while remaining computationally efficient. This contribution investigates a coplanar radio-frequency driven plasma jet by means of a novel global model. The model takes into account the strong modulation of the electric field in time and space both in the sheath and bulk region. By means of a consistent scale analysis we find an analytical expression for the electric field. We compare our obtained electric field to results from PIC simulations and present the general concept for this novel global model of the microplasma jet. [Preview Abstract] |
Thursday, October 25, 2012 11:15AM - 11:30AM |
QR4.00003: Dynamics and structure of helium discharge in thin dielectric tubes at atmospheric pressure Jaroslav Jansky, Anne Bourdon Since a few years, atmospheric pressure plasma micro-jets formed by pulsed helium discharges ignited in thin dielectric tubes have received considerable interest due to their potential for biomedical applications. So far, most experimental and simulation works have been dedicated to the study of the plasma plume. Recently, to better understand the ignition and dynamics of plasma jets, different experiments have been done to study the discharge inside tubes and close to the tube exit. In this work, we propose to simulate in 2D the discharge ignition and dynamics inside the tube. In particular we propose to discuss the influence of the electrode geometry and of nitrogen admixtures and to compare simulation results with recent experiments done by different research groups. In this work, the dynamics of surface charge deposition during the discharge propagation in the tube is studied. For repetitive voltage pulses, we propose to discuss the influence of some remaining surface charges from previous discharges on the subsequent discharge ignition. Finally, we propose to simulate the interaction of two discharges propagating towards each other in tubes and to compare results with experiments. [Preview Abstract] |
Thursday, October 25, 2012 11:30AM - 11:45AM |
QR4.00004: Line profile and translational temperature of Pb and metastable He atoms at middle pressures in micro hollow cathode discharge Mari Inoue, Takayuki Ohta, Masafumi Ito, Masaru Hori Hollow cathode discharges have been studied as light sources. Conventional hollow cathode discharges have been operated at low pressure, while micro hollow cathode discharges at near atmospheric pressure. At the middle pressures below 40 kPa, the emission of metallic atoms is observed due to sputtering. Moreover, the line profile of atom shits from a Gaussian to Voigt profile as increasing pressure. In this study, the behaviors of Pb and metastable He atoms in the micro hollow cathode discharge at pressures of the order of kPa have been investigated by diode laser absorption spectroscopy. The pressure broadening effect for absorption line-profile was overlapped to Doppler profile and was estimated to be 0.26 MHz/Pa for metastable He atoms in the range from 5 to 10 kPa. The translational temperature decreased from 830 to 410 K with increasing the pressure. For Pb atoms, the temperature decreased from 820 to 610 K with increasing He pressure from 4.9 to 7.4 kPa. The pressure broadening effect for Pb atom has been estimated to be 0.22 MHz/Pa. [Preview Abstract] |
Thursday, October 25, 2012 11:45AM - 12:00PM |
QR4.00005: Characterization and Application of Microplasma Devices for Ambient Mass Spectrometry and Surface Analysis Joshua Symonds, Reuben Gann, Facundo Fern\'andez, Thomas Orlando In ambient mass spectrometry, ionization sources with broad chemical compatibility, low fragmentation, and high reliability are one of the keys necessary to enable effective and rapid analysis of unknown samples. One such approach, employing a variety of ambient-pressure microplasma discharges, has demonstrated itself to be a promising technique with a variety of successful applications and results. This class of devices holds a competitive edge over alternative ambient ionization methods when cost and portability are a concern: microplasmas typically require only modest electrical power and minimal gas flows to operate. We have developed our own such devices and methods, and look more closely into the physical nature of what makes particular designs successful. We focus on the development of these devices to perform mass spectrometry imaging in tandem with optical microscope imaging of samples at ambient pressure. Additionally, we investigate the use of microplasma devices for production of VUV photons, another highly effective ionization source. [Preview Abstract] |
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