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  • 1
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    Global and local current sheet thickness estimates during the late growth phase (1992)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The thinning and intensification of the cross tail current sheet during the substorm growth phase are analyzed during the CDAW 6 substorm (22 Mar. 1979) using two complementary methods. The magnetic field and current sheet development are determined using data from two spacecraft and a global magnetic field model with several free parameters. These results are compared with the local calculation of the current sheet location and structure previously done by McPherron et al. Both methods lead to the conclusion that an extremely thin current sheet existed prior to the substorm onset, and the thicknesses estimated by the two methods at substorm onset agree relatively well. The plasma data from the ISEE 1 spacecraft at 13 R(sub E) show an anisotropy in the low energy electrons during the growth phase which disappears just before the substorm onset. The global magnetic model results suggest that the field is sufficiently stretched to scatter such low energy electrons. The strong stretching may improve the conditions for the growth of the ion tearing instability in the near Earth tail at substorm onset.
    Keywords: GEOPHYSICS
    Type: ESA, Substorms 1; p 131-135
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  • 2
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    Improved Li/TiS2 cell cycling in ether-based electrolytes with synergistic additives (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Based on an extensive series of normalized full cell Li/TiS2 cycling studies, open-circuit storage tests, microcalorimetry and AC impedance studies, and chemical precedent, we propose an integrated chemical model consistent with experimental observations concerning the behavior of numerous LiAsF6/cyclic ether electrolytes. The particularly striking potency of certain additives such as 2-methylfuran and the hydroxide action resides in their ability to intercept several different adverse catalytic processes concurrently in the bulk electrolyte as well as the Li anode and TiS2 cathode.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: In: Primary and secondary lithium batteries (A93-37355 14-25); p. 293-301.
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  • 3
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    Effect of cycling on the lithium/electrolyte interface in organic electrolytes (1993)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Nondestructive methods such as ac impedance spectroscopy and microcalorimetry are used to study the effect of cell cycling on the lithium/electrolyte interface. The reactivity of both uncycled and cycled lithium towards various electrolytes is examined by measuring the heat evolved from the cells under open-circuit conditions at 25 C by microcalorimetry. Cycled cells at the end of charge/discharge exhibited considerably higher heat output compared with the uncycled cells. After 30 d of storage, the heat output of the cycled cells is similar to that of the uncycled cells. The cell internal resistance increases with cycling, and this is attributed to the degradation of the electrolyte with cycling.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Journal of Power Sources (ISSN 0378-7753); 43; 1-3; p. 21-26.
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  • 4
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    Improved Li-TiS2 cell cycling in ether-based electrolytes with synergistic additives (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Results of the application of 2-MeF and KOH additives to improve the lithium stability in THF, dioxolane, and THF/2-MeTHF solvent-based electrolytes are presented. The stability of these electrolytes with and without additives is evaluated by microcalorimetry and AC impedance spectroscopy. A novel method, cathode turnover number, is proposed to represent the electrolyte performance in a given system. The lithium cycling efficiency and cathode turnover number of the electrolytes are calculated from the cycle life data in experimental Li-TiS2 cells. Overall, THF/2-MeTHF electrolyte containing 2-MeF and/or KOH exhibited higher stability, lithium cycling efficiency, and cathode turnover number compared to THF and dioxolane electrolytes with and without additives.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: In: Primary and secondary lithium batteries (A93-37355 14-25); p. 280-292.
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  • 5
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    Evaluation of lithium alloy anode materials for Li-TiS2 cells (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A study was performed to select candidate lithium alloy anode materials and establish selection criteria. Some of the selected alloy materials were evaluated for their electrochemical properties and performance. This paper describes the criteria for the selection of alloys and the findings of the studies. Li-Si and Li-Cd alloys have been found to be unstable in the EC+2-MeTHF-based electrolyte. The Li-Al alloy system was found to be promising among the alloy systems studied in view of its stability and reversibility. Unfortunately, the large volume changes of LiAl alloys during charge/discharge cycling cause considerable 'exfoliation' of its active mass. This paper also describes ways how to address this problem. The rate of disintegration of this anode would probably be surpressed by the presence of an inert solid solution or a uniform distribution of precipitates within the grains of the active mass. It was discovered that the addition of a small quantity of Mn may improve the mechanical properties of LiAl. In an attempt to reduce the Li-Al alloy vs. Li voltage, it was observed that LiAlPb(0.1)Cd(0.3) material can be cycled at 1.5 mA/sq cm without exfoliation of the active mass.
    Keywords: ENERGY PRODUCTION AND CONVERSION
    Type: In: Primary and secondary lithium batteries (A93-37355 14-25); p. 395-406.
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  • 6
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    Low-energy particle layer outside of the plasma sheet boundary (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The ISEE spacecraft in the geomagnetic tail frequently crossed the high-latitude boundary of the plasma sheet. On a number of these crossings on the morningside (between 15 RE and 22 RE) the ISEE instruments detected an enhanced population of low-energy electrons and ions immediately adjacent to the plasma sheet boundary layer (PSBL). The electrons in this low-energy layer (LEL) have energies less than a few hundred eV, and they are aligned along the magnetic field direction propagating in the tailward direction. The ions have energies less than 100 eV and are also streaming along the magnetic field direction but in the earthward direction. These particles are clearly distinguished from the bulk of the particles in the plasma sheet and the PSBL. These observations may help clarify where the various particle features in the geomagnetic tail map to in the ionosphere. It is suggested that the LEL maps to the soft (less than 1 keV) electron precipitation region poleward of the plasma sheet boundary.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 97; A3, M; 2943-295
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  • 7
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    Reactivity of nonaqueous organic electrolytes towards lithium (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The successful operation of an ambient temperature secondary lithium cell is primarily dependent on the stability of the electrolyte towards lithium. The lithium electrode on open circuit must be inert towards the electrolyte to achieve a long shelf life. The reactivity of tetrahydrofuran and 2-methyltetrahydrofuran based electrolytes with additives such as 2-methylfuran, ethylene carbonate, propylene carbonate, and 3-methylsulfolane was investigated by microcalorimetry and ac impedance spectroscopy techniques. Also the stability of electrolytes by open circuit stand tests was studied. Addition of ethylene carbonate and 2-methylfuran additives was found to improve the stability of tetrahydrofuran and 2-methyltetrahydrofuran based electrolytes. Long term microcalorimetry and ac impedance data clearly confirmed the higher stability of ethylene carbonate/2-methyltetrahydrofuran electrolyte compared to the 2-methyltetrahydrofuran and propylene carbonate/2-methyltetrahydrofuran electrolytes.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
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  • 8
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    Advanced CCD imager technology for use from 1 to 10,000 A (1990)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A low-noise, high-sensitivity charge-coupled-device (CCD) technology for imaging applications extending from the soft X-ray (1 A) to the near-infrared (10,000 A) regimes was developed together with a fabrication technology for making back-illuminated versions of these devices with quantum efficiencies as high as 90 percent from 5000 to 7000 A. The efforts have focused on two devices, a 64 x 64 pixel back-illuminated imager with two output ports that operates at 2000 frames per second with 23 electrons read noise, and a larger device, with 420 x 420 pixel format, designed for lower frame rates with noise as low as 1.5 electrons and used at visible, UV, and X-ray wavelengths. Applications to plasma diagnostics include Thomson scattering and high-frame-rate imaging in the visible, as well as X-ray imaging and bolometry.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments (ISSN 0034-6748); 61; 2744-274
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  • 9
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    Thin current sheets in the magnetotail during substorms: CDAW 6 revisited (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The global magnetic field configuration during the growth phase of the Coordinated Data Analysis Workshop (CDAW) 6 substorm (March 22, 1979, 1054 UT) is modeled using data from two suitably located spacecraft and temporally evolving variations of the Tsyganenko magnetic field model. These results are compared with a local calculation of the current sheet location and thickness carried out by McPherron et al. (1987) and Sanny et al. (this issue). Both models suggest that during the growth phase the current sheet rotated away from its nominal location, and simultaneously thinned strongly. The locations and thickness obtained from the two models are in good agreement. The global model suggests that the peak current density is approximately 120 nA/sq m and that the cross-tail current almost doubled its intensity during this very strong growth phase. The global model predicts a field configuration that is sufficiently stretched to scatter thermal electrons, which may be conducive to the onset of ion tearing in the tail. The electron plasma data further support this scenario, as the anisotropy present in the low-energy electrons disappears close to the substorm onset. The electron contribution to the intensifying current in this case is of the order of 10% before the isotropization of the distribution.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A4; p. 5793-5803
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  • 10
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    Oxygen stabilization induced enhancement in J(sub c) and T(sub c) of superconducting oxides (1990)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: In an attempt to enhance the electrical and mechanical properties of the high temperature superconducting oxides, high T(sub c) composites were prepared composed of the 123 compounds and AgO. The presence of extra oxygen due to the decomposition of AgO at high temperature is found to stabilize the superconducting 123 phase. Ag is found to serve as clean flux for grain growth and precipitates as pinning center. Consequently, almost two orders of magnitude enhancement in critical current densities were also observed in these composites. In addition, these composites also show much improvement in workability and shape formation. On the other hand, proper oxygen treatment of Y5Ba6Cu11Oy was found to possibly stabilize superconducting phase with T(sub c) near 250 K. I-V, ac susceptibility, and electrical resistivity measurements indicate the existence of this ultra high T(sub c) phase in this compound. Detailed structure, microstructure, electrical, magnetic and thermal studies of the superconducting composites and the ultra high T(sub c) compound are presented and discussed.
    Keywords: SOLID-STATE PHYSICS
    Type: NASA, Goddard Space Flight Center, AMSAHTS 1990: Advances in Materials Science and Applications of High Temperature Superconductors; p 8
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