Bulletin of the American Physical Society
70th Annual Gaseous Electronics Conference
Volume 62, Number 10
Monday–Friday, November 6–10, 2017; Pittsburgh, Pennsylvania
Session RR2: High Pressure Discharges |
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Chair: Svetlana Starikovskaya, Laboratoire de Physique des Plasmas (LPP) UMR CNRS Room: Duquesne |
Thursday, November 9, 2017 10:00AM - 10:15AM |
RR2.00001: Development of ice dielectric barrier discharge for the development of novel reaction field in cryogenic environments Noritaka Sakakibara, Tsuyohito Ito, Kazuo Terashima Multi-phase plasmas, including plasma-liquid interactions, are now receiving increasing attention aiming for the wide range of applications. As a new type of multi-phase plasma, ice dielectric barrier discharge (DBD), whose dielectric barrier is made of ice, was generated at a wide range of cryogenic temperature from room temperature down to 6.5~K. We are expecting plasma-ice interaction system as a novel cryogenic reaction filed, taking advantage of selective chemical reactions on the ice surface. In this research, gas temperature was treated as a control parameter, and variations of optical emission spectra and discharge modes were observed. In particular, we revealed drastic change in power consumption of ice DBD in the vicinity of the melting point of water (273~K). This clearly indicates the importance of gas temperature as a control parameter in the research area of multi-phase plasmas. Moreover, in the presentation, we will present results of material synthesis with using the ice DBD, which is in progress. [Preview Abstract] |
Thursday, November 9, 2017 10:15AM - 10:30AM |
RR2.00002: ABSTRACT WITHDRAWN |
Thursday, November 9, 2017 10:30AM - 10:45AM |
RR2.00003: Spectroscopic measurement of the electric field in a helium plasma jet Marlous Hofmans, Ana Sobota The electric field in a plasma jet is measured spectroscopically utilizing the Stark-effect. A cold atmospheric pressure helium plasma jet is used, which operates at a $\mu$s-pulsed applied voltage of 6 kV, a frequency of 5 kHz and with a helium flow of 1.5 slm. Due to the electric field in the jet, the forbidden and allowed bands of the emission spectrum shift. This is called the Stark-effect. The spectrum of both the He I 492.2 nm line and the He I 447.1 nm line are obtained with an iCCD-camera coupled to a monochromator. From the peak-to-peak wavelength difference between the allowed and forbidden band, the electric field in the jet is calculated. The electric field is determined both inside and outside the capillary of the jet, up to 2 cm in the effluent of the jet. Furthermore, the electric field in the jet is determined, while a target is placed close to the end of the capillary. Grounded and non-grounded, conducting and insulating targets are used and placed at different distances. [Preview Abstract] |
Thursday, November 9, 2017 10:45AM - 11:00AM |
RR2.00004: Student Excellence Award Finalist: Atmospheric Pressure Plasma Multi-jets: Fundamental Properties Amanda M. Lietz, Xavier Damany, Jean-Michel Pouvesle, Eric Robert, Mark J. Kushner A multi-jet plasma source is being developed for large area treatment of surfaces with atmospheric pressure plasma. The multi-jet source is a dielectric tube, capped at the end, with a row of holes aligned on one side. Helium flows through the tube and out the holes, where plumes of the He mix with ambient humid air. An ionization wave (IW) begins at a powered electrode upstream of the holes, propagates along the tube and, passing each hole, launches a separate, secondary ionization wave (SIW) through the hole which extends toward a grounded pump below. The parameters which effect this system have been investigated using \textit{nonPDPSIM}, a 2-D plasma hydrodynamics model. The hole diameter determines the velocity of the SIW as it passes through the holes by controlling the angle of the electric field within the holes. A higher helium flow rate results in a larger region of purer helium outside of the tube, extending the distance the SIW can propagate outside of the hole before encountering air. Positive voltage polarity produces a plasma within the tube which does not hug the wall as tightly, and increases the intensity of the SIW outside of the tube. Comparisons will be made to experimental ICCD imaging of the primary IW and SIW, for which there is good agreement. [Preview Abstract] |
Thursday, November 9, 2017 11:00AM - 11:15AM |
RR2.00005: Experimental and modeling results on the axial and radial breakdown dynamics in dielectric barrier discharges Hans H\"oft, Markus M. Becker, Detlef Loffhagen, Manfred Kettlitz The breakdown of dielectric barrier discharges (DBDs) was investigated with respect to its axial and radial development. For this purpose, a pulsed-driven, single-filament DBD at atmospheric pressure (0.1 vol\% O$_2$ in N$_2$) with 1 mm gap was used. The experimental diagnostics consisted of an iCCD and a streak camera system (50 ps temporal and 10 $\mu$s spatial resolution) combined with fast electrical probes. Additionally, time-dependent, spatially 2D fluid model calculations were performed. A correlation of the axial (cathode-directed) streamer propagation and the streamer diameter was found, i.e. this diameter increases with the axial propagation velocities. Furthermore, the radial expansion velocities ($\sim\,$10$^5$ m/s) during the streamer breakdown phase also increase with the axial propagation velocities ($\sim\,$10$^6$ m/s). The analysis of the radial dynamics allows the separation of the streamer propagation and the transient glow phase during the channel formation, i.e. the discharge channel widens, when the cathode-directed streamer hits the cathode surface. By means of synchronized measurements of the electrical current and the emission intensity, the temporally resolved current density could be determined in reasonable agreement with the modelling results. [Preview Abstract] |
Thursday, November 9, 2017 11:15AM - 11:30AM |
RR2.00006: Spatially-resolved electron temperature in a helium cold RF discharge up to atmospheric pressure Jean-Sebastien Boisvert, Nathan Mauger, Luc Stafford, Francois Vidal, Joelle Margot A cold plasma is generated inside a dielectric tube (inner diameter of 2 mm) using two long linear electrodes painted on diametrically opposed sides of the tube. The plasma can be sustained in helium from 10 to 760 Torr without any gas flow. In order to evaluate the electron temperature, a collisional-radiative model is coupled with optical emission spectroscopy of He ($n=3$) lines. At atmospheric pressure, the spatially averaged T$_e$ increases from 0.2 to 2 eV when the power density is increased from 2 to 12 W cm$^{-3}$ (associated to the transition from the $\Omega$ to $\gamma$ mode). With the help of a camera equipped with different bandpass filters (around 667 and 728 nm), the same collisional-radiative model is used to obtain the spatially-resolved electron temperature in the $\gamma$ mode. It is about 0.5 eV in the bulk but 4 eV in the sheath region, this is in agreement with modelling of plane-parallel CCRF discharges in the literature. When the pressure is decreased below atmospheric pressure, the sheaths broaden and the region of high electron temperature ($>2$ eV) fills the whole tube diameter. In addition, below 100 Torr, a plasma column is generated outside the electrode area, T$_e$ in this region being much lower than between the electrodes. [Preview Abstract] |
Thursday, November 9, 2017 11:30AM - 11:45AM |
RR2.00007: An Investigation of the Effect of Pressure Variations on Micro-Discharge Formation and Propagation in a 2-D Packed Bed Reactor Kenneth Engeling, Juliusz Kruszelnicki, John Foster, Mark Kushner Packed bed dielectric barrier discharge reactors (PBRs) are one of the technologies at the forefront of advanced plasma applications such as plasma-aided combustion, dry reforming of methane, and plasma catalysis. Plasma formation and propagation occurs through the porous media of the PBR in the form of microdischarges and are a function of several parameters. To investigate the kinetic mechanisms of the micro-plasma formation, a 2-dimensional packed bed reactor was designed for optical analysis. The 2-d array of dielectric aggregate with varying dielectric constants is used to simulate and visualize plasma formation as a function of voltage, pressure, gas type, and spacing to gain insight into actual packed bed discharge operation. In this work, we focus particularly on discharge evolution as a function of pressure from sub-atmospheric pressure to 1 Atm. The 2-d geometry is directly observed using fast camera imaging and emission spectroscopy. Microdischarges in the 2-D array are studied with both ns-pulsed discharge excitation as well as low frequency AC excitation. [Preview Abstract] |
Thursday, November 9, 2017 11:45AM - 12:00PM |
RR2.00008: Hydrodynamic effects induced by nanosecond sparks in ambient air. Sergey Stepanyan, Nicolas Minesi, Gabi-Daniel Stancu, Christophe Laux This work presents the results on hydrodynamic effects induced by nanosecond repetitive sparks in ambient air. ~In order to monitor the hydrodynamic effects, four optical diagnostics were combined: emission spectroscopy, Planar Laser Induced Fluorescence, Schlieren and fast imaging. The mentioned diagnostics were synchronized with electrical energy measurements to (i) observe the spatial distribution of gas temperature and active species produced in the discharge afterglow, (ii) investigate hydrodynamic coupling between the discharges at high frequencies of applied pulses. One of the major experimental findings was the synergy between the discharges at higher frequencies (\textgreater 1 kHz). The volume occupied by hot gas and active species after a burst of N sparks is larger than N times the volume occupied after a single discharge. It has been demonstrated that the energy density in the case of high-frequency discharge redistributes spatially during a period shorter than the typical ignition delay time. ~It has also been shown that the value of the energy density is sufficient for ignition of lean mixtures. Therefore we believe that this effect can be used as an efficient tool for volumetric ignition that can improve the combustion of lean mixtures. . [Preview Abstract] |
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