Bulletin of the American Physical Society
51st Annual Meeting of the APS Division of Plasma Physics
Volume 54, Number 15
Monday–Friday, November 2–6, 2009; Atlanta, Georgia
Session CO7: Low Temperature Plasmas I |
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Chair: Michael Keidar, George Washington University Room: Regency VII |
Monday, November 2, 2009 2:00PM - 2:12PM |
CO7.00001: The Electrodeless Lorentz Force Thruster Thomas Weber, Brian Nelson, Richard Milroy, David Kirtley, John Slough The Electrodeless Lorentz Force (ELF) thruster is a novel plasma thruster under development at MSNW and the University of Washington which utilizes Rotating Magnetic Field (RMF) current drive technology to ionize a neutral gas and drive an azimuthal current to form a Field Reversed Configuration (FRC) plasmoid in a diverging magnetic field. The magnetic gradient imparts a net force to the FRC which is ejected from the thruster at high velocity. ELF has been shown to operate from 10 - 100 kW, with an exhaust velocity of 15 - 40 km/s. The ELF thruster is expected to have an extremely large range of efficient power levels, high thrust density, high specific power, long lifetime, and the ability to utilize virtually any type of propellant. Thruster design and operation, novel diagnostics, and a discussion of experimental results detailing the key physical phenomena within the thruster and exhaust plume will be presented. [Preview Abstract] |
Monday, November 2, 2009 2:12PM - 2:24PM |
CO7.00002: Self consistent kinetic simulations of SPT and HEMP thrusters including the near-field plume region Ralf Schneider, Konstantin Matyash, Andreas Mutzke, Oleksandr Kalentev, Francesco Taccogna, Norbert Koch, Martin Schirra SPT (Stationary Plasma Thruster) and HEMP (High Efficiency Multistage Plasma) thrusters are both relying on the creation of propulsive ion beams by ionization of propellant atoms. The specific shape of the magnetic fields in both concepts is used to optimize efficiency and ion acceleration. 2d3v-PIC-MCC calculations are used to compare the two different thruster concepts. They result in quite different plasma-wall interaction characteristics. The SPT thruster relies on the strong secondary electron emission from the dielectric walls of the thruster channel, which causes a large ion flux over the whole channel surface and consequently high erosion rate. In contrast, in the HEMP thruster the plasma contact to the wall is limited only to very small areas of the magnetic field cusps, which results in much smaller ion flux to the thruster channel surface as compared to SPT. Consequently, experimental studies of HEMP gave no evidence of erosion. In order to study the wall erosion for both thrusters, the binary collision approximation (BCA) based Monte-Carlo code SDTrimSP is applied. [Preview Abstract] |
Monday, November 2, 2009 2:24PM - 2:36PM |
CO7.00003: Initial Results of Time-Resolved VUV Spectroscopy of Pulsed Dielectric Surface Flashover in Atmosphere George Laity, Klaus Frank, Garrett Rogers, Andreas Neuber, James Dickens, James Moss This paper describes some initial results from an experimental setup designed for studying the optical emission during pulsed surface flashover for the wavelength range from 115 nm to 180 nm at atmospheric pressures. A VM 505 from Acton Research Corporation was used as the spectrograph, with an Andor DH740 series ICCD camera mounted at the exit flange. Spectra were measured in nitrogen and air at atmospheric pressure with a flashover spark length of 8 mm under pulsed 35 kV excitation. Emission intensities were measured during gated 50 ns intervals, and it was concluded that most VUV emission occurs during the first stage of the flashover event. This is important because it is believed only radiation below 180 nm is energetic enough to cause photoionization leading to streamer discharge, and very little is known about VUV emission during this initial stage. Utilizing the NIST Atomic Spectra Database, a library of temperature dependent emission spectra was generated with SpectraPlot, a spectral software suite developed at TTU. The measured spectra will be discussed in relation to the physics of surface flashover at atmospheric pressure. [Preview Abstract] |
Monday, November 2, 2009 2:36PM - 2:48PM |
CO7.00004: Determination of OH radicals in the far downstream of an atmospheric pressure microwave helium plasma jet Nimisha Srivastava, Chuji Wang A recent study has reported observation of OH radicals in the far downstream of an atmospheric argon microwave plasma jet. The far downstream is referred to as the location where the ratio of the distance from the jet orifice to the length of the jet column is $>$ 3. In this work we report that this phenomenon also exists in a similar plasma jet of 2.5 mm long, operating by helium gas. A detailed characterization of the helium microwave plasma jet was carried out by using UV pulsed cavity ringdown spectroscopy and optical emission spectroscopy. The nonthermal plasma temperatures were determined from stimulations of the emission spectra of several vibronic bands of the 2$^{nd}$ positive system of N$_{2}$, the 1$^{st}$ negative system of N$_{2}^{+}$, the (0,1,2,3-0) bands of NO (A-X), and the (0-0) band of OH (A-X). Absolute number densities of OH were measured along the plasma jet column. Dependence of OH concentration on plasma power and gas flow rate at different locations along the jet axis was characterized. The electron densities were also measured by recording Stark broadening of the hydrogen Balmer beta line (H$_{\beta })$ at 486.1 nm. [Preview Abstract] |
Monday, November 2, 2009 2:48PM - 3:00PM |
CO7.00005: Studies of the vacuum breakdown behavior using refractory-metal thin film coated electrodes Randolph Flauta, John Kionka, Martin John Neumann, David Ruzic, John Caughman A reliable operation of ICRF antennas in fusion devices is often limited by its breakdown threshold. Surface conditions of electrodes during high voltage operations have played a key role in affecting breakdowns. In this work, the effects of coating electrodes with refractory-metal thin films to improve on the reliability and power delivered by ICRF antennas have been investigated. Using the Surface Plasma Arcs by Radiofrequency - Control Study (SPARCS) facility at the Center for Plasma-Material Interactions which is designed as a DC system, the current and voltage breakdown patterns and the measured energy in the arc at an electric field of up to 150 MW/m were studied. Experiments with electrodes coated with W, Mo and Ta operated at high temperature of 600 $^{o}$C and above were explored. Surface studies were also conducted on the electrodes to determine the electrode conditions and other surface reactions after the breakdown. [Preview Abstract] |
Monday, November 2, 2009 3:00PM - 3:12PM |
CO7.00006: Design of experiments on a DC Steady State Atmospheric Pressure Plasma Sterilizer Igor Alexeff, Arun Balasundaram, Rapinder Sawheny Our Resistive Barrier Discharge has been demonstrated to be successful on E. coli, Pseudomonas fluorescens (5RL), spores and bacteriophages. It has been tested successfully in sterilizing pagers at the St. Jude Research Hospital in Memphis, TN. In this recent work, we evaluate three primary factors in the atmospheric pressure resistive barrier discharge, hydrogen peroxide, charged ions and air (oxygen). The experiment used was Analysis of Variance (ANOVA) and regression analysis. The tests used 144 Petri Dishes and the bacteria used were E. coli. The hydrogen peroxide was used as a replacement for the water conductor on the resistive barrier discharge electrode. The charged ions were removed by a double charged wire mesh between the discharge and the Petri Dish. The air was displaced by a slow flow of nitrogen into the experimental area. The basic conclusions are that air, and charged ions are both extremely effective in killing bacteria. In addition, air and charged ions together strongly enhance each other. Hydrogen peroxide in our experiments did not enhance the kill rate. [Preview Abstract] |
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