Bulletin of the American Physical Society
62nd Annual Gaseous Electronics Conference
Volume 54, Number 12
Tuesday–Friday, October 20–23, 2009; Saratoga Springs, New York
Session LW3: Lamps |
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Chair: Tim Sommerer, GE Corporate Research Center Room: Saratoga Hilton Ballroom 3 |
Wednesday, October 21, 2009 8:00AM - 8:15AM |
LW3.00001: Plasma Efficiency and Losses for pulsed Xe Excimer DBDs at high Power Densities Mark Paravia, Michael Meisser, Wolfgang Heering The UV water disinfection for example needs efficient lamps with high power densities. Xe$_{2}^{\ast }$ dielectric barrier discharges (DBDs) with phosphor coating can be used due to plasma efficiencies up to 60~{\%} at pulsed electrical power densities of 0.04~W/cm$^{2}$ [1]. The power density can be increased by pressure or (operation) frequency. However, the plasma efficiency declines with frequency. We present measurements of the radiant flux for pulsed DBDs made of fused silica as function of pressure and frequency. By calculation of optical losses the plasma efficiency is estimated to be 52~{\%} at 0.07 W/cm$^{2}$ but decreases to 34 {\%} at 0.8~W/cm$^{2}$. The maximum frequency is pressure dependent and limited due to change-over from homogeneous into filamented mode. In comparison we measured the gas gap voltage and internal plasma current of a pulsed planar DBD for general lighting [2]. This comparison makes it possible to explain the frequency dependence of plasma efficiency and radiant flux. Due to the high frequency the remaining charge density is increased and the discharge becomes a glow discharge. For that reason the typical peak current during ignition drops and explains the declined efficiency by glow phase losses. \\[4pt] [1] Beleznai, S., et al., JPhysD, 41 (2008) \\[0pt] [2] Paravia, M., et al., GEC, Dallas, 2008 [Preview Abstract] |
Wednesday, October 21, 2009 8:15AM - 8:30AM |
LW3.00002: Optical absorption spectroscopy with an UHP-lightsource -- an effective diagnostic method for Dy- and Ce-emitters in high intensity discharge lamps Michael Westermeier, Cornelia Ruhrmann, Jens Reinelt, Peter Awakowicz, Juergen Mentel The so called ``emitter effect'' of elements like dysprosium and cerium is used to lower the work function and thereby the temperature of tungsten electrodes in HID lamps. A special setup for absorption spectroscopy was developed to measure the density of particles within the lamp plasma consisting mainly of a backlight realized by a powerful ultra high pressure (UHP) lamp and a 1D-imaging spectrograph. It allows a direct measurement of the absorption profiles of Dy (\textit{$\lambda $}= 625.91 nm) and Ce (\textit{$\lambda $}= 577.36 nm) resonance lines within the lamp plasma. From these the ground-state atom density of Dy or Ce can be determined independently of the plasma temperature. Phase resolved measurements of the Dy-density and corresponding electrode temperatures in a ceramic HID lamp will be presented for low and high frequency operation. The results will be compared with measurements at lamps doped with Ce given in an accompanying poster and interpreted by the emitter effect. [Preview Abstract] |
Wednesday, October 21, 2009 8:30AM - 8:45AM |
LW3.00003: First principle based calculation of emission properties of positive column of Ar-SnI$_{2}$ glow discharge Maxim Deminsky, Maria Tudorovskaia, Irina Chernysheva, Boris Potapkin, Darryl Michael, David Smith, Timothy Sommerer Possibility of replacement of mercury, an environmental hazard, by non-toxic elements in gas discharge lamps is intensively investigated now. Gases of metal halides are regarded as candidates of non-equilibrium source of emitters (metals) in glow discharge plasma. The model of glowing discharge in Ar/SnI$_{2}$ plasma is built using multilevel approach [1] for calculation of the cross sections and rate constant of electron collision with the metal halides. Sensitivity analysis shows, that dissociative attachment is one of the most important processes in that elecronegative medium and directly influences on steady state parameters of glow discharge plasma. Optimization of the discharge parameters and conclusion about maximal light emission efficiency is performed. \\[4pt] [1] \textit{Adamson S. et al}. J. Phys. D: Appl. Phys. 2007. V.40. P.3857 [Preview Abstract] |
Wednesday, October 21, 2009 8:45AM - 9:00AM |
LW3.00004: Application of coronal model for the emission properties calculations: Ti, Sc and Hg Maxim Deminsky, Irina Chernysheva, Alexaner Eletskii, Valerii Astapenko, Boris Potapkin The purpose of present paper is the theoretical study of titanium atoms emission properties in Ar : Ti and Sc gas mixture under glow discharge conditions. The electronic structure of neutral Ti is extremely rich containing a large number of energy levels. For this reason it is practically impossible to develop state-to-state kinetic model, which is usually used for such kind of studies. To overcome this difficulty the model was applied, which is usually known as ``coronal'' model. The populations of radiative states and emission power are computed using known cross sections for the excitation of these states and transition probabilities. Electron concentration and electric field strength are determined in self--consistent manner from electron energy balance equation and given value of discharge current. In fact, the applicability and reliability of ``coronal'' model is not rather obvious. To clarify the situation test studies were performed for Hg atom, which has relatively simple electronic structure. The calculations were made for Ar : Hg gas mixture under glow discharge conditions using two different approaches: ``coronal'' model and state-to-state kinetic model. The comparison of obtained results shows that ``coronal'' model may be used for the quantitative estimations of the emission properties. [Preview Abstract] |
Wednesday, October 21, 2009 9:00AM - 9:15AM |
LW3.00005: Progress on Radiative Transition Probabilities in Neutral Cerium J.J. Curry Cerium is a rare-earth atom that is currently used in energy-efficient metal-halide lamps because of its rich visible emission spectrum. More than 20,000 lines have been observed and classified for neutral cerium in the wavelength range of 340 nm to 1 $\mu$m (Bill Martin, unpublished). We recently derived more than 500 absolute transition probabilities from existing experimental data (J. Phys. D: Appl. Phys. 2009). Lawler and Den Hartog at the University of Wisconsin have made measurements that are expected to produce a few thousand transition probabilities. These advances, however, leave the data situation far short of what is needed to simulate an accurate global emission spectrum in numerical models of metal-halide lamps containing cerium. One possibility for closing this gap is through atomic structure calculations. Although it may be difficult for calculations to match the accuracy of measurements for any given transition, the global spectral distribution produced with calculated transition probabilities may still be satisfactory. For such a large number of lines, calculations may be the only realistic way to produce a reasonably complete set of data. We will discuss our recent atomic structure calculations of neutral cerium with the Cowan code based on a parametric fit of calculated energy level values to experimental values. [Preview Abstract] |
Wednesday, October 21, 2009 9:15AM - 9:30AM |
LW3.00006: Breakdown characteristics of xenon HID Lamps Natalia Babaeva, Ayumu Sato, Nanu Brates, Koji Noro, Mark Kushner The breakdown characteristics of mercury free xenon high intensity discharge (HID) lamps exhibit a large statistical time lag often having a large scatter in breakdown voltages. In this paper, we report on results from a computational investigation of the processes which determine the ignition voltages for positive and negative pulses in commercial HID lamps having fill pressures of up to 20 atm. Steep voltage rise results in higher avalanche electron densities and earlier breakdown times. Circuit characteristics also play a role. Large ballast resistors may limit current to the degree that breakdown is quenched. The breakdown voltage critically depends on cathode charge injection by electric field emission (or other mechanisms) which in large part controls the statistical time lag for breakdown. For symmetric lamps, ionization waves (IWs) simultaneously develop from the bottom and top electrodes. Breakdown typically occurs when the top and bottom IWs converge. Condensed salt layers having small conductivities on the inner walls of HID lamps and on the electrodes can influence the ignition behavior. With these layers, IWs tend to propagate along the inner wall and exhibit a different structure depending on the polarity. [Preview Abstract] |
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