Bulletin of the American Physical Society
2006 59th Annual Gaseous Electronics Conference
Tuesday–Friday, October 10–13, 2006; Columbus, Ohio
Session RR2: Lighting Plasmas |
Hide Abstracts |
Chair: James Lawler, University of Wisconsin Room: Holiday Inn Salon B |
Thursday, October 12, 2006 1:30PM - 1:45PM |
RR2.00001: Low-pressure positive column discharges in zinc and zinc halides David Smith Zn-containing discharges were investigated by means of spectroscopic measurements of a capacitively-coupled discharge. Under optimum conditions (2 Torr Ar, 10-40 mW cm$^{-3})$, the Zn positive column converts electrical power into zinc atomic radiation with an efficiency of $>$50{\%}. This value is comparable to the efficiency of a Hg positive column discharge, and does not strongly depend on whether the Zn was introduced as pure metal, or as zinc iodine or zinc bromide, a somewhat surprising result given the additional non-radiative power deposition mechanisms that are available in a plasma that contains molecules. A novel diagnostic based on analysis of selected emission line ratios was used to estimate densities of the ground state and excited states of Zn as a function of lamp wall temperature, and to better understand the important processes in these molecular plasmas. [Preview Abstract] |
Thursday, October 12, 2006 1:45PM - 2:00PM |
RR2.00002: Influence of the cathode composition on the performance of high pressure short arc xenon lamps Olga B. Minayeva, Douglas A. Doughty Thoriated tungsten has been widely used as a cathode material in arc lamps. The addition of thorium reduces the work function of tungsten and allows the cathode to operate at a lower temperature. However, most of the studies on thoriated cathodes were done either for welding arcs or for metal halide lamps, where reactions with the ambient gas could contribute to the cathode erosion. In the case of completely inert, high-purity xenon gas and highly collisional arc plasma, the differences in performance of thoriated and non-thoriated cathodes are mainly material-based. In this talk we will discuss how 2{\%} ThO$_{2}$ addition to tungsten cathodes changes the lifetime, ignition performance, and stability of xenon lamps. [Preview Abstract] |
Thursday, October 12, 2006 2:00PM - 2:15PM |
RR2.00003: Infrared Continuum Radiation from Metal Halide HID Lamps T.M. Herd, J.E. Lawler Lighting consumes 25{\%} of all electrical power. Improving the efficiency of the widely used MH-HID lamps would have a significant impact on power consumption. We are studying the near IR continuum from MH-HID lamps. Near IR radiation from typical MH-HID lamps includes a continuum ($>$50{\%}), atomic lines ($<$50{\%}), and very weak molecular features. Analysis of the near IR is complicated due to the de-mixing of additives. Additive densities are determined by a balance between de-mixing from radial and axial cataphoresis and mixing from free convection and diffusion. The Hg produces most of the arc density and pressure while the additives contribute most of the free electron (e$^{-}$) density and much of the radiation. The line width of the resonance broadened Hg 1014 nm transition is used to find the arc core Hg density. Absolute radiance measurements on optically thin, near IR Hg lines are Abel inverted to find the temperature as a function of radius. The electron density is determined from Dy I and Dy II lines using a Saha analysis. Our absolute near IR continuum measurements are compared to radiation transport simulations using the measured Hg density, temperature data, and e$^{-}$ density as inputs. Results to date indicate that the near IR of MH-HID lamps is primarily e$^{-}$ + Hg atom Bremsstrahlung. [Preview Abstract] |
Thursday, October 12, 2006 2:15PM - 2:30PM |
RR2.00004: Color separation in metal halide lamps W.W. Stoffels, T. Nimalasuriya, A.J. Flikweert, W.J.M. Brok, J.J.A.M. Mullen, G.M.W. Kroesen, M. Haverlag Metal halide discharge lamps are efficient lighting sources. However their widespread application is hindered by several problems. One problem is color separation. This is caused by a non-homogeneous distribution of radiating species within the lamp. It is believed to be the result of a complex interplay between diffusion and convection processes. In this contribution convection in the lamp is varied by placing the lamp in a rotating centrifuge. The resulting centrifugal force of up to ten times the normal gravitational force enhances the convection within the lamp and allows studying its effect on the color separation. [Preview Abstract] |
Thursday, October 12, 2006 2:30PM - 3:00PM |
RR2.00005: Efficient Low-Pressure Metal-Halide Discharge Plasma Radiation Sources Invited Speaker: Several efficient low-pressure metal-halide discharge chemistries have been reported in the patent literature since the year 2000.\footnote{US6972521, US6731070, US6603267, WO2005117064, US20050242737, WO2005031794, US20060071602.} Examples are halides of indium, tin, zinc, and gallium; typical gas mixtures are 200~Pa of a rare-gas and 1~Pa of the metal-halide species. The power density is near 50~mW/cm$^{3}$. The conversion efficiency from electric power to radiation in the positive column exceeds 50 percent in some cases, a value that approaches the efficiency of positive column discharges in mercury and sodium metal vapors. It is not obvious how low-pressure metal-halide plasmas can be so efficient, since the plasma contains not only rare-gas atoms and metal atoms, but also molecules and radicals, where there are many nonradiative loss channels such as attachment, vibration, and dissociation. This talk will focus on work to maximize the fraction of input power that appears as radiation, and at such conditions, identify and understand the important nonradiative power channels. [Preview Abstract] |
Thursday, October 12, 2006 3:00PM - 3:30PM |
RR2.00006: Plasma Breakdown at Low Pressure Invited Speaker: Plasma ignition, the process by which an insulating gaseous medium turns into a conducting plasma, is considered to be well-understood in simple circumstances, involving processes such as electron multiplication, secondary electron emission and ionisation waves. In many practical cases, however, complicated geometry, different material surfaces, different gas mixtures, complex voltage waveforms and varying initial conditions lead to ignition processes that are much less easily described. The aim of this research is to study plasma ignition in simple electrode geometries, in order to identify the main breakdown mechanisms. We use a combination of space- and time-resolved measurements of plasma properties and modelling and simulation tools to study the breakdown behaviour. Phenomena occurring during the pre-ignition and ignition phases will be described. [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