Bulletin of the American Physical Society
61st Annual Gaseous Electronics Conference
Volume 53, Number 10
Monday–Friday, October 13–17, 2008; Dallas, Texas
Session QR3: High Pressure Glow Discharges |
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Chair: Masaru Hori, Nagoya University, Japan Room: Addison Room |
Thursday, October 16, 2008 10:00AM - 10:15AM |
QR3.00001: Time resolved studies of an industrial scale APGD system processing polymer film William Graham, Damian Della Croce, Lucas Schaper, Alan Hynes, Liam O'Neill Time-resolved electrical, light emission and imaging characterisation of an industrial scale (1800cm$^{2})$ atmospheric pressure plasma system operated under conditions which optimise polymer film processing is reported. The electrical and emission behaviour generally associated with uniform discharges i.e. a single discharge event per applied voltage half cycle, is observed at low input ($<$500W) powers. As the power and hence applied voltage is increased more, but similar duration, individual discharge events are observed per half cycle until, at $>$ 900W, only about 25{\%} of the applied voltage cycle is free of discharge production. Imaging of the inter-electrode gap shows that, at the peak of each discharge event, crossing the gap there is a uniform layer of emission close to the cathode then evidence of a dark layer and then further emission but at much reduced intensity. This is the spatial structure associated with glow discharge behaviour. Results with static or moving polymer film in the gap, which are similar, will also be reported. The assistance of B. Twomey and D. Dowling (UC Dublin) is gratefully acknowledged. [Preview Abstract] |
Thursday, October 16, 2008 10:15AM - 10:30AM |
QR3.00002: Imminent Glow Discharges in Air at Atmospheric Pressure Using Nanosecond Repetitively Pulsed Discharges David Pai, Deanna Lacoste, Christophe Laux Many applications for atmospheric pressure air plasmas require non-thermal large-volume low-power plasmas with high chemical reactivity at low gas temperature. The Nanosecond Repetitively Pulsed (NRP) method can generate such plasmas for power budgets much lower than those of traditional generation methods. A diffuse non-thermal plasma regime in air at atmospheric pressure from 300-1000 K has been generated using the NRP method. The discharge develops through an initial streamer, followed by a return wave of potential redistribution. In addition, it is an ``imminent'' glow discharge, because the field is switched off before ion-electron emission occurs. Thus, the cathode fall of a glow discharge is not formed. Furthermore, at a given gas temperature, there is a minimum gap distance required for the existence of the diffuse regime. This is a result of the non-uniform electric field generated by the pin-pin geometry, creating strongly ionizing regions near the electrodes and a weakly ionizing region between the electrodes, which can inhibit the diffuse-to-filamentary regime transition. As the gas temperature is decreased, the field in the strongly ionizing regions must be increased to maintain sufficient ionization, and the gap distance must be increased for the weakly ionizing region to remain a buffer against the transition. [Preview Abstract] |
Thursday, October 16, 2008 10:30AM - 10:45AM |
QR3.00003: ABSTRACT WITHDRAWN |
Thursday, October 16, 2008 10:45AM - 11:00AM |
QR3.00004: Microwave Discharge in a Supersonic Flow of Simulated Martian Atmospheric Gas D.J. Drake, S. Popovic, L. Vuskovic Martian entry plasma can be considered a high-volume plasma reactor that is sustained by the dissipation of the spacecraft's kinetic energy. It was estimated that several kg of O$_{2}$ could be ``harvested'' during entry. However, the entry plasma parameters vary considerably depending on the spacecraft's trajectory. Probable range of plasma parameters was evaluated using the existing Martian atmospheric data and all recorded probe trajectories. Comparison to the existing simulation facilities is discussed. An alternative desk-top supersonic flow apparatus is devised for the study of aerothermodynamic and chemical properties of a simulated Martian atmospheric gas (SMAG). We performed detailed laboratory measurements of the excited-species populations in the supersonic flow of weakly ionized SMAG. A cylindrical cavity was used to sustain a discharge in SMAG in the pressure range of 100-600 Pa and a stationary acoustic shock wave was generated by an oblique solid body. Excited state populations of Ar and atomic oxygen were measured using absolute emission and absorption spectroscopy. Comparison was made in a model free flow and across the shock front. The gas and electron temperature were determined from the CO rotational spectra and Ar spectra, respectively. [Preview Abstract] |
Thursday, October 16, 2008 11:00AM - 11:30AM |
QR3.00005: Micro-Discharge Scaling and Development from Centimetres to Microns: DC and RF Breakdown and Discharge Characterization around the Paschen Minimum Invited Speaker: Joint talk with Z. Lj. Petrovic (Institute of Physics, Belgrade) Two aspects of micro discharges are addressed: The scaling of electrical characteristics and the properties of a recently developed RF micro discharge. We review attempts to measure voltage and current waveforms, Paschen curves and oscillation characteristics of dc and rf discharges from the macroscopic (cm) scale to micro discharges, considering pd values below, at and above the Paschen minimum. Conventional scaling (pd, E/N and jd\^{}2) are found to be valid for dimensions down to 100 microns, however anomalous Paschen curves are observed below this value and field emission and or long path breakdown are considered as possible explanations. We also present radial profiles estimates for sub mm discharges in an attempt to determine realistic local current densities. In order to explore fundamental discharge mechanisms at reduced scales, we have developed the first radio frequency micro-hollow cathode (RF-MHC) device. This operates stably, for many hours, in neon and in argon. We present measurements performed with a 50 micro metre diameter RF MHC neon discharge. Electron heating modes and information on the electron energy distribution were investigated through electrical and spectroscopic techniques. A number of discharge modes are observed and analysis points to the possibility of pendular electron heating at low voltages. Collaborators: D. Maric, N. Skoro, G. Malovic {\&}~ M. Radmilovic --Radjenovic (Institute of Physics, Belgrade), C.M.O. Mahony (University of Ulster), WG Graham {\&} T. Gans, (Queen's University Belfast). [Preview Abstract] |
Thursday, October 16, 2008 11:30AM - 11:45AM |
QR3.00006: Production of atomic oxygen in an atmospheric pressure arc in air and its implications for NO$_{2}$ generation Matthew R. King, Christopher J. Oldham, Jenna R. Puckett, Jerome J. Cuomo Given the complexities associated with air plasma chemistry, it is important to understand the formation mechanisms of common reaction products such as NO$_{2}$. Ground state atomic oxygen (OI) is found to be an indicator of NO$_{2}$ formation, as it has been observed that the availability of OI, determined from line emission at 777 nm, has a direct correlation to NO$_{2}$ production. In particular, we find a post-discharge reaction involves the consumption of OI for a two-fold increase in NO$_{2}$. This work investigates the parameters affecting OI generation in an atmospheric pressure arc in air. In order to fully understand the dynamics of this relationship, we have studied the effect of applied power, frequency, nitrogen to oxygen mixing ratio, and gas temperature on OI emission. The data is also compared to a theoretical kinetic model available in the literature that includes various ionic, neutral, and excited metastable species. This work has implications for all air-based plasma applications, given NO$_{2}$ is a ubiquitous, and toxic, byproduct of these discharges. [Preview Abstract] |
Thursday, October 16, 2008 11:45AM - 12:00PM |
QR3.00007: Multivariate analysis of an Industrial atmospheric pressure glow discharge Victor Law, Barry Twomey, John Tynan, Niall O'Connor, Denis Dowling, Stephen Daniels This paper explores the Multivariate Analysis (MVA) of the APGD electrical outputs (non-sinusoidal periodic voltage current waveforms and drive frequency). A Principle Component analysis (PCA) model is used to compress the electrical data for the generation a real-time loading plot. A Lissajous figure projection of the current and voltage waveforms is also used to identify system instabilities and micro-scale events. The purpose the PC-space and phase-space is to provide new coordinate systems where the surface treatment outcomes may be mapped directly. Visual information on the discharge uniformity is also overlaid to aid process interpretation. The complete data acquisition, data compression, and displays are performed in real-time using National Instruments LabVIEW 8.2 software. The results of the MVA demonstrates that a helium discharge, a helium discharges containing 1{\%} oxygen and a helium discharge with hexamethyldisiloxane yields different loading plot scores which allow data-set separation and unique process identification. [Preview Abstract] |
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