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Operational characteristics and analysis of the immersed-Bz diode on RITS-3.

Description: The immersed-B{sub z} diode is being developed as a high-brightness, flash x-ray radiography source. This diode is a foil-less electron-beam diode with a long, thin, needle-like cathode inserted into the bore of a solenoid. The solenoidal magnetic field guides the electron beam emitted from the cathode to the anode while maintaining a small beam radius. The electron beam strikes a thin, high-atomic-number anode and produces bremsstrahlung. We report on an extensive series of experiments where an immersed-B{sub z} diode was fielded on the RITS-3 pulsed power accelerator, a 3-cell inductive voltage generator that produced peak voltages between 4 and 5 MV, {approx}140 kA of total current, and power pulse widths of {approx}50 ns. The diode is a high impedance device that, for these parameters, nominally conducts {approx}30 kA of electron beam current. Diode operating characteristics are presented and two broadly characterized operating regimes are identified: a nominal operating regime where the total diode current is characterized as classically bipolar and an anomalous impedance collapse regime where the total diode current is in excess of the bipolar limit and up to the full accelerator current. The operating regimes are approximately separated by cathode diameters greater than {approx}3 mm for the nominal regime and less than {approx} 3 mm for the anomalous impedance collapse regime. This report represents a compilation of data taken on RITS-3. Results from key parameter variations are presented in the main body of the report and include cathode diameter, anode-cathode gap, and anode material. Results from supporting parameter variations are presented in the appendices and include magnetic field strength, prepulse, pressure and accelerator variations.
Date: February 1, 2006
Creator: Bruner, Nichelle "Nicki"; Oliver, Bryan Velten; Portillo, Salvador; Puetz, Elizabeth A.; Johnston, Mark D.; Welch, Dale Robert et al.
Partner: UNT Libraries Government Documents Department
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Final Report: Wetted Cathodes for Low-Temperature Aluminum Smelting

Description: A low-temperature aluminum smelting process being developed differs from the Hall-Heroult process in several significant ways. The low-temperature process employs a more acidic electrolyte than cryolite, an alumina slurry, oxygen-generating metal anodes, and vertically suspended electrodes. Wetted and drained vertical cathodes are crucial to the new process. Such cathodes represent a significant portion of the capital costs projected for the new technology. Athough studies exist of wetted cathode technology with Hall-Heoult cells, the differences make such a study desirable with the new process. This project is such a study. In Phase 1, titanium diboride, zirconium diboride and composites of these with other materials were tested using a statistically useful test matrix. The materials were consolidated both by hot pressing and by a new method, plasma pressure compaction (P2C�). The materials were subject to controlled electrolysis tests under conditions of the low-temperature smelting process. Post-electrolysis characterizations included quantitative atomic analyses and electron microscopic examinations. These methods allowed evaluating the relative merits of the materials, and the mechanisms of their corrosion. Also, a few tests were performed to determine whether oxygen and carbon dioxide bathing vertically suspended cathodes exhibited different current efficiencies. In Phase 2, additional composite materials were fabricated with P2C�, electrolysis tested, and subsequently characterized. The statistical test matrix was not used in this Phase. However, the materials were tested with electrolysis lasting both five and twenty hours. The project demonstrated that good current efficiencies are obtained with the new process at this scale. All of the materials tested except for aluminum infiltrated aluminum nitride wetted well and gave comparable electrolysis voltages. Both hot pressing and P2C� produce grain structures in the consolidated materials. Grain loss to the product metal is the dominant corrosion mechanism of these materials as cathodes. Grain loss is more of a problem with the composites …
Date: September 30, 2002
Creator: Brown, Craig W.
Partner: UNT Libraries Government Documents Department
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A novel electron gun with an independently addressable cathode array.

Description: The design of a novel electron gun with an array of independently addressable cathode elements is presented. Issues relating to operation in a 6.5 Tesla axial magnetic field are discussed. Simulations with the TriComp [1] electromagnetic field code that were used to determine the space charge limited tube characteristic and to model focusing of the electron beam in the magnetic field are reviewed. Foil heating and stress calculations are discussed. The results of CYLTRAN [2] simulations yielding the energy spectrum of the electron beam and the current transmitted through the foil window are presented.
Date: August 1, 2006
Creator: Rudys, Joseph Matthew; Reed, Kim Warren; Peña, Gary Edward & Schneider, Larry X.
Partner: UNT Libraries Government Documents Department
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Batteries: Overview of Battery Cathodes

Description: The very high theoretical capacity of lithium (3829 mAh/g) provided a compelling rationale from the 1970's onward for development of rechargeable batteries employing the elemental metal as an anode. The realization that some transition metal compounds undergo reductive lithium intercalation reactions reversibly allowed use of these materials as cathodes in these devices, most notably, TiS{sub 2}. Another intercalation compound, LiCoO{sub 2}, was described shortly thereafter but, because it was produced in the discharged state, was not considered to be of interest by battery companies at the time. Due to difficulties with the rechargeability of lithium and related safety concerns, however, alternative anodes were sought. The graphite intercalation compound (GIC) LiC{sub 6} was considered an attractive candidate but the high reactivity with commonly used electrolytic solutions containing organic solvents was recognized as a significant impediment to its use. The development of electrolytes that allowed the formation of a solid electrolyte interface (SEI) on surfaces of the carbon particles was a breakthrough that enabled commercialization of Li-ion batteries. In 1990, Sony announced the first commercial batteries based on a dual Li ion intercalation system. These devices are assembled in the discharged state, so that it is convenient to employ a prelithiated cathode such as LiCoO{sub 2} with the commonly used graphite anode. After charging, the batteries are ready to power devices. The practical realization of high energy density Li-ion batteries revolutionized the portable electronics industry, as evidenced by the widespread market penetration of mobile phones, laptop computers, digital music players, and other lightweight devices since the early 1990s. In 2009, worldwide sales of Li-ion batteries for these applications alone were US$ 7 billion. Furthermore, their performance characteristics (Figure 1) make them attractive for traction applications such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and electric vehicles (EVs); a market …
Date: July 12, 2010
Creator: Doeff, Marca M
Partner: UNT Libraries Government Documents Department
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Active Cathodes for Super-High Power Density Solid Oxide Fuel Cells Through Space Charge Effects, 2006, April 10

Description: This report briefly summarizes the work done over the duration of the project, beginning October 1, 2003 and ending September 30, 2005. This project was on understanding cathode mechanisms in intermediate temperature solid oxide fuel cells (SOFC) and developing superior cathodes.
Date: September 30, 2005
Creator: Virkar, Anil V.
Partner: UNT Libraries Government Documents Department
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Approaches to rid cathodic arc plasmas of macro- andnanoparticles: A review

Description: A major obstacle for the broad application of cathodic arc plasma deposition is the presence of micro- and nanoparticles in the plasma, also often referred to as 'macroparticles'. This paper reviews the formation of macroparticles at cathode spots, their interaction with the arc plasma and substrate, and macroparticle separation and removal from the plasma by various filtering methods. Nineteen variants of filters are discussed, including Aksenov's classic 90{sup o}-duct filter, filters of open architecture, and the concept of stroboscopic filtering.
Date: June 1, 1999
Creator: Anders, Andre
Partner: UNT Libraries Government Documents Department
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Conditioning effects on La1-xSrxMnO3-Yttria stabilized Zirconia electrodes for thin-film solid oxide fuel cells

Description: Composite cathodes of 50/50 vol percent LSM-YSZ (La1-xSrxMnO3-yttria stabilized zirconia) were deposited onto dense YSZ electrolytes by a colloidal deposition technique. The cathode characteristics were then examined by scanning electron microscopy (SEM) and studied by an impedance spectroscopy (IS). Conditioning effects of the LSM-YSZ cathodes were seen, and remedies for these effects were proposed for improving the performance of a solid oxide fuel cell (SOFC). LSM surface contamination and modification, cathode bonding to the YSZ electrolyte, changing Pt electrode and bonding paste, and curvature of sintered YSZ electrolytes led to some changes in microstructure and variability in cell performances.
Date: December 6, 2002
Creator: Lee, You-Kee; Kim, Jung-Yeul; Lee, Young-Ki; Kim, Insoo; Moon, Hee-Soo; Park, Jong-Wan et al.
Partner: UNT Libraries Government Documents Department
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Controlling the Plasma Flow in the Miniaturized Cylindrical Hall Thruster

Description: A substantial narrowmg of the plume of the cylindrical RaIl thruster (CRT) was observed upon the enhancement of the electron emission from the hollow cathode discharge, which implies the possibility for the thruster efficiency increase due to the ion beam focusing. It is demonstrated that the miniaturized CRT can be operated in the non-self-sustained regime, with the discharge current limited by the cathode electron emission. The thruster operation in this mode greatly expands the range of the plasma and discharge parameters normally accessible for the CRT.
Date: March 4, 2008
Creator: Smirnov, A.
Partner: UNT Libraries Government Documents Department
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Characterization of SEI layers on LiMn2O4 cathodes with in-situ spectroscopic ellipsometry

Description: In situ spectroscopic ellipsometry was employed to study the initial stage of SEI layer formation on thin-film LiMn{sub 2}O{sub 4} electrodes. It was found that the SEI layer formed immediately upon exposure of the electrode to EC/DMC (1:1 by vol) 1.0 M LiPF{sub 6} electrolyte. The SEI layer thickness then increased in proportion to a logarithmic function of elapsed time. In comparison, the SEI layer thickness on a cycled electrode increased in proportion to a linear function of the number of cycles.
Date: August 30, 2004
Creator: Lei, Jinglei; Li, Lingjie; Kostecki, Robert; Muller, Rolf & McLarnon, Frank
Partner: UNT Libraries Government Documents Department
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Simulating Nonuniform Properties in Polymer-Electrolyte FuelCells

Description: In this transaction, results from mathematical, pseudo 2-D simulations are shown for four different thickness distributions of both the membrane and cathode catalyst layer. The results and subsequent analysis clearly demonstrate that the position along the gas channel is more important than the local thickness variations, especially for the membrane.
Date: July 1, 2006
Creator: Weber, A.Z. & Newman, J.
Partner: UNT Libraries Government Documents Department
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Particle-In-Cell/Monte Carlo Simulation of Ion Back Bombardment in Photoinjectors

Description: In this paper, we report on studies of ion back bombardment in high average current dc and rf photoinjectors using a particle-in-cell/Monte Carlo method. Using H{sub 2} ion as an example, we observed that the ion density and energy deposition on the photocathode in rf guns are order of magnitude lower than that in a dc gun. A higher rf frequency helps mitigate the ion back bombardment of the cathode in rf guns.
Date: March 2, 2009
Creator: Qiang, Ji; Corlett, John & Staples, John
Partner: UNT Libraries Government Documents Department
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A study of surface film formation on LiNi0.8Co0.15Al0.05O2 cathodes u sing attenuated total reflection infrared spectroscopy

Description: The surface films formed on commercial LiNi0.8Co0.15Al0.05O2 cathodes (ATD Gen2) charged from 3.75V to 4.2V vs. Li/Li+ in EC:DEC - 1M LiPF6 were analyzed using ex-situ Fourier transform infrared spectroscopy (FTIR) with the attenuated total reflection (ATR) technique. A surface layer of Li2CO3 is present on the virgin cathode, probably from reaction of the active material with air during the cathode preparation procedure. The Li2CO3 layer disappeared even after soaking in the electrolyte, indicating that the layer dissolved into the electrolyte possibly even before potential cycling of the electrode. IR features only from the binder (PVdF) and a trace of polyamide from the Al current collector were observed on the surfaces of cathodes charged to below 4.2 V, i.e., no surface species from electrolyte oxidation. Some new IR features were, however, found on the cathode charged to 4.2 V and higher. An electrolyte oxidation product was observed that appeared to contain dicarbonyl anhydride and (poly)ester functionalities. The reaction appears to be an indirect electrochemical oxidation with overcharging (removal of > 0.6 Li ions) destabilizing oxygen in the oxide lattice resulting in oxygen transfer to the solvent molecules.
Date: January 19, 2004
Creator: Song, S.-W.; Zhuang, G.V. & Ross Jr., P.N.
Partner: UNT Libraries Government Documents Department
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Electrolytic Reduction of Uranyl Ion

Description: From introduction: "Due to the hydrogen overvoltage at the surface of a mercury cathode, uranium solutions is hydrochloric acid may be reduced not only to the tetravalent state, but until considerable trivalent uranium is formed. Other metallic ions act as oxidation-reduction catalysts as well as being reduced themselves. The following paper is a study of the various reactions taking place in solution and at the surface of the cathode."
Date: May 27, 1946
Creator: Nichols, Ambrose R., Jr.
Partner: UNT Libraries Government Documents Department
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Effects of Membrane- and Catalyst-layer-thickness Nonuniformitiesin Polymer-electrolyte Fuel Cells

Description: In this paper, results from mathematical, pseudo 2-D simulations are shown for four different along-the-channel thickness distributions of both the membrane and cathode catalyst layer. The results and subsequent analysis clearly demonstrate that for the membrane thickness distributions, cell performance is affected a few percent under low relative-humidity conditions and that the position along the gas channel is more important than the local thickness variations. However, for the catalyst-layer thickness distributions, global performance is not impacted, although for saturated conditions there is a large variability in the local temperature and performance depending on the thickness.
Date: September 1, 2006
Creator: Weber, Adam Z. & Newman, John
Partner: UNT Libraries Government Documents Department
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USE OF COUPLED MULTI-ELECTRODE ARRAYS TO ADVANCE THE UNDERSTANDING OF SELECTED CORROSION PHENOMENA

Description: The use of multi-coupled electrode arrays in various corrosion applications is discussed with the main goal of advancing the understanding of various corrosion phenomena. Both close packed and far spaced electrode configurations are discussed. Far spaced electrode arrays are optimized for high throughput experiments capable of elucidating the effects of various variables on corrosion properties. For instance the effects of a statistical distribution of flaws on corrosion properties can be examined. Close packed arrays enable unprecedented spatial and temporal information on the behavior of local anodes and cathodes. Interactions between corrosion sites can trigger or inhibit corrosion phenomena and affect corrosion damage evolution.
Date: February 23, 2006
Creator: Budiansky, N.D.; Bocher, F.; Cong, H.; Hurley, M.F. & Scully, J.R.
Partner: UNT Libraries Government Documents Department
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Synopsis of Cathode #4 Activation

Description: The purpose of this report is to describe the activation of the fourth cathode installed in the DARHT-II Injector. Appendices have been used so that an extensive amount of data could be included without danger of obscuring important information contained in the body of the report. The cathode was a 612 M type cathode purchased from Spectra-Mat. Section II describes the handling and installation of the cathode. Section III is a narrative of the activation based on information located in the Control Room Log Book supplemented with time plots of pertinent operating parameters. Activation of the cathode was performed in accordance with the procedure listed in Appendix A. The following sections provide more details on the total pressure and constituent partial pressures in the vacuum vessel, cathode heater power/filament current, and cathode temperature.
Date: May 26, 2006
Creator: Kwan, Joe; Ekdahl, C.; Harrison, J.; Kwan, J.; Leitner, M.; McCruistian, T. et al.
Partner: UNT Libraries Government Documents Department
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Flash X-Ray Injector Study

Description: The study described in this report1 models the FXR injector from the cathode to the exit of the injector. The calculations are compared to actual experimental measurements, table 1. In these measurements the anode voltage was varied by changing the Marks-Bank charging voltage. The anode-cathode spacing was varied by adjusting the location of the cathode in hopes of finding an island of minimum emittance (none found). The bucking coil current was set for zero field on the cathode. In these measurements, a pepper-pot mask was inserted into FXR at beam bug 135 and viewed downstream via a wiggle probe diagnostic at cell gap J21, figure 1. The observed expansion of the beamlets passing through the mask of known geometric layout and hole size allow a calculation of the phase space beam properties.
Date: March 26, 2004
Creator: Paul, A C
Partner: UNT Libraries Government Documents Department
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High efficiency ionizer using a hollow cathode discharge plasma

Description: A proposal for an ionizer using a hollow cathode discharge plasma is described. Ionization is via the very high current density electron beam component in the plasma, as well as from charge exchange with plasma ions. Extraction of a He/sup +/ current corresponding to approximately 50% of the incoming atomic beam flux should be possible.
Date: January 1, 1984
Creator: Alessi, J.G. & Prelec, K.
Partner: UNT Libraries Government Documents Department
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