Bulletin of the American Physical Society
2006 59th Annual Gaseous Electronics Conference
Tuesday–Friday, October 10–13, 2006; Columbus, Ohio
Session QR1: High Pressure Discharges II |
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Chair: Skip Williams, AFRL/WPAFB Room: Holiday Inn Salon CD |
Thursday, October 12, 2006 10:00AM - 10:30AM |
QR1.00001: Micro Discharge Under Supercritical Conditions -- Physics and Application to Materials Processing Invited Speaker: Recently, micro discharge or discharge microplasma have attracted much attention. Miniaturization of discharge or plasma allows us easy generation of discharge or discharge plasma under a high-pressure condition even up to supercritical fluid (SCF). Applying plasma to SCF processing may yield a high efficiency due to a combination of advantages of plasma and SCF. In addition, plasma generated in SCF is anticipated to contain radical and ion clusters, which may lead to novel physical/chemical phenomena and reactions, comparing to typical gas plasma. In our previous works, we succeeded in generating discharge or discharge plasma in high-pressure CO$_{2}$, H$_{2}$O, Xe up to supercritical conditions, and discovered novel phenomena, such as the drastic decrease in the breakdown voltages of 1 micrometer-gap electrodes near the critical point. Furthermore, we have applied SCF plasma to materials synthesis processings, and succeeded in fabricating carbon materials including carbon nanotubes (CNTs), under milder condition (31.1-70$^{\circ}$C, 7.38-12 MPa) of scCO$_{2}$, as a processing media and starting raw material, with no catalyst [3], comparing to conventional thermal equilibrium processing. In this study, we generate stable low-temperature plasma using DBD (dielectric barrier discharge) in supercritical CO$_{2}$ and Xe conditions. In addition to its diagnosis by optical emission spectroscopy and Raman spectroscopy, application of it to film depositions of carbon nanomaterials and Cu will be discussed. [Preview Abstract] |
Thursday, October 12, 2006 10:30AM - 10:45AM |
QR1.00002: Time resolved laser absorption spectroscopy in a self-pulsed microplasma. X. Aubert, A. Rousseau, J.F. Lagrange, N. Sadeghi It was recently shown that microplasmas of the microhollow cathode type geometry may operate in a self-pulsing regime for intermediate current (0.1-1 mA) [1]. At lower current ($<$ 0.1 mA) the plasma is stable and located inside the hole; at higher current ($>$ 1 mA) , the plasma is also stable but expands outside the hole on the cathode backside region. The self pulsing was attributed to the breakdown of the gas, outside the micro-hole, on the cathode backside. However, the mechanisms of the plasma ignition on the cathode backside are not understood and metastable atoms may play a major role. In the present work, time resolved diode laser absorption measurements have been performed through the micro-hole in the self-pulsing regime; the plasma hole ranges is in the range of 100 $\mu$m and the gas pressure ranges from 50 to 300 Torr; the feed gas is argon and the transition studied is 772.376 nm (Paschen notation 1s5-2p7). The objective is i) to measure the time evolution of the 1s5 metastable density, ii) deduce the gas temperature and plasma density from the absorption line profile. Similar results are performed in 3 electrodes configuration \newline [1] A. Rousseau and X. Aubert J. Phys.D~: Appl. Phys. \textbf{39 }(2006) 1619--1622. [Preview Abstract] |
Thursday, October 12, 2006 10:45AM - 11:00AM |
QR1.00003: Absolute Atomic Oxygen Density Measurements by Two-Photon Laser-induced Fluorescence (TALIF) in the Effluent of an Atmospheric Pressure Plasma Jet St. Reuter, K. Niemi, V. Schulz-von der Gathen, H.F. Doebele A 13.56 MHz RF-excited plasma jet$^{1}$ is diagnosed in this work. The jet operates at ambient conditions. It generates a homogeneous plasma in helium or argon$^{2}$ with admixtures ( $\sim $ 1 {\%}) of molecular gases, here oxygen. The temperature of the effluent is well below 100\r{ }C. The jet has been set up in a planar and a concentric version; both were compared by means of TALIF-measurements. Absolute atomic oxygen density profiles have been measured in the effluent of the plasma jet. The atomic oxygen density close to the nozzle amounts to 10$^{16}$ cm$^{-3}$. Even at several centimeters from the nozzle there still is 1{\%} of the initial oxygen density. Emission spectroscopy down to 110 nm has been carried out as a function of distance from the exit nozzle with the effluent hitting an MgF$_{2}$ window in front of the slit of a vacuum UV monochromator. These spectra exhibit strong emission lines e.g. of oxygen at 130 nm, even at a distance of several centimeters from the nozzle. This work was supported by the ``Ministerium f\"{u}r Wissenschaft und Forschung NRW'' \newline $^{1}$J. Y. Jeong, S. E. Babayan, V. J. Tu, J. Park, R. F. Hicks, and G. S. Selwyn, PSST \textbf{7}, 282 (1998). \newline $^{2}$S. Wang, V. Schulz-von der Gathen, H.F. D\"{o}bele, Appl. Phys. Lett. \textbf{83}, 3272 (2003) [Preview Abstract] |
Thursday, October 12, 2006 11:00AM - 11:15AM |
QR1.00004: Electrical and emission studies of a dielectric barrier APGD operating with flowing helium and a moving substrate William Graham, Damian Della Croce, Alan Hynes The electrical and emission characteristics of the APGD created in a Dow Corning Plasma Solutions LabLine{\texttrademark} system have been measured to study the behaviour of a relatively large scale APGD system with flowing gas and a moving film. The LabLine{\texttrademark} system creates a 340mm x 300mm electrode structure with an inter-electrode gap of 5mm. To create a discharge a sinsuoidally-varying voltage of up to 16 kV p to p was applied to brine/glass electrodes at frequencies of around 20kHz. A PET film was suspended, parallel to the glass dielectrics. A Pearson probe measured the time dependence of the discharge current. The time resolved plasma emission was recorded using a gated ICCD. At operating powers of 900 W and with a helium flow rate of 20 l/min, a peak in the discharge current was observed twice per applied voltage period, typical of behaviour reported in other APGD systems. Imaging of emission both through the outer face of one glass/brine electrode and the inter-electrode gap indicated that during these current peaks a spatially uniform discharge is created between the film and electrode surface both when the film is static or moving at up to 1 m/min. The authors gratefully acknowledge the assistance of B Twomey, J Tynan and D Dowling (UC Dublin). [Preview Abstract] |
Thursday, October 12, 2006 11:15AM - 11:30AM |
QR1.00005: Fitting of asymmetric spectral lines as diagnostics for HID-lamps Martin Wendt, Silke Peters, Hartmut Schneidenbach, Manfred Kettlitz Fitting of optically thick side-on spectra is a valuable alternative to the Bartels' method and the Abel inversion for the determination of partial pressures and radial temperature profiles in HID lamps. We investigate a standard 150 W type HID lamp filled with Hg and NaI during dimming from 150 to 60 W. The model includes LTE plasma chemistry, asymmetric line profiles according to Al-Saqabi and Peach [1]. Van der Waals and Stark broadening constants are determined from spectra of a pure Hg lamp. Broadening constants for the Na D lines are taken from literature. We use the spectra at several side-on positions in order to derive pressures and temperature profiles in the Hg/NaI lamp. The results from fitting show with decreasing electrical power a constriction of the radial temperature profile, a linear decrease of the total pressure and a rapid decrease of the sodium content. Temperatures and total pressures are in good agreement with the experiment. \newline [1] Al-Saqabi B N I, Peach G (1984) J. Phys.\ B: At.\ Mol. Phys. {\bf 20} 1175--1191. [Preview Abstract] |
Thursday, October 12, 2006 11:30AM - 11:45AM |
QR1.00006: Dynamic of the plasma current amplitude in a barrier discharge: influence of a photocatalytic material O. Guaitella, S. Celestin, A. Rousseau, A. Bourdon For a better understanding of the plasma/photocatalytic material interaction under plasma exposure, a study of the electrical properties of a cylindrical sinusoidal dielectric barrier discharge (DBD) is performed with and without porous material containing TiO2. The metallic inner electrode is in contact with the gas gap. The presence of porous material made of silica fibres coated with nanoparticles of TiO2 leads to a strong increase of the injected energy for the same applied voltage. For the same injected energy the time evolution of the current amplitude distribution function (CADF) shows two different peak populations on the positive half period (when the metallic inner electrode is positive) [1]. Apart from numerous low intensity plasma filaments (around 1 mA amplitude), much larger ones exist (around 1 A). These large current amplitude peaks are responsible for 50 to 70\% of the injected energy depending on the presence of the photocatalytic material.They are attributed to desorption of charges triggered by light emitted by a first filament. The influence of 900 ppm of C2H2 as well as external ultraviolet irradiation on the CADF is also reported. \newline [1] O. Guaitella, F. Thevenet, C. Guillard, A. Rousseau J. Phys. D~: appl. Phys (2006) accepted. [Preview Abstract] |
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