20 Matching Results

Search Results

Advanced search parameters have been applied.

Design of a high-current downlink using Bi-based superconductors

Description: Recent processing developments in Bi{sub 1.8}Pb{sub 0.4}Sr{sub 2}Ca{sub 2}Cu{sub 3}0{sub x} (BSCCO-2223) bars have produced bulk BSCCO-2223 bars with properties advantageous for power applications. Cold isostatically pressed (CIP) and sinter-forged BSCCO-2223 both have low AC loss, which make them desirable for use in power devices. Thermal conductivity of the CIP bars is lower than that of the previously used sinter-forged samples by a factor of 2. CIP bars with cross-sectional areas of =0.75 cm{sup 2} and carrying 250 A RMS transport current have AC loss values of 30 pJ/cycle-cm at 50 Hz and 77 K. A pair of prototype downlinks were designed and built with sinter forged bars to deliver a continuous AC current of 1500 A over a temperature gradient of 77 to 4.2 K while delivering about -200 MW of heat to the liquid-helium-cooled end. This paper will discuss the design considerations and modeling of downlinks, which supply high AC currents over the 77 to 4.2 K temperature gradient with low thermal losses.
Date: August 1996
Creator: Fisher, B. L.; Lanagan, M. T.; Balachandran, U.; Honjo, S. & Hara, T.
Partner: UNT Libraries Government Documents Department

Structural and electrical properties of biaxially textured YBa{sub 2}Cu{sub 3}O{sub 7-x} thin films on buffered Ni-based alloy substrates.

Description: Oxide high-T{sub c} superconducting wires and tapes with high critical current density (J{sub c}) are essential in future electrical power applications. Recently, YBa{sub 2}Cu{sub 3}O{sub 7{minus}x} (YBCO) thin films grown on Ni-based alloy tapes have attracted intense interest because of their promise for these applications. In order to achieve high J{sub c}, buffer layers are necessary for fabricating biaxially aligned YBCO thin films. In our studies, yttria-stabilized zirconia (YSZ) layers were deposited on Ni-based alloy substrate by ion-beam assisted deposition, and CeO{sub 2} buffer layers were subsequently deposited on the YSZ layer by pulsed laser deposition (PLD) or electron beam evaporation. In addition, MgO layers were deposited on Ni-based alloy substrates by inclined substrate deposition. Finally, biaxially textured YBCO thin films were deposited on these buffered metallic substrates by PLD under optimized conditions. The orientation and in-plane textures of YBCO and the buffer layers were characterized by X-ray diffraction {Theta}/2{Theta} scan, {phi}-scan, and pole figure analysis. The superconductive transition features were examined by measuring inductive T{sub c} and transport J{sub c}.
Date: December 7, 2000
Creator: Li, M.; Ma, B.; Jee, Y. A.; Fisher, B. L. & Balachandran, U.
Partner: UNT Libraries Government Documents Department

Texture formation and superconducting properties of YBa{sub 2}Cu{sub 3}O{sub x} thin films prepared by solution process on LaAlO{sub 3} single crystals.

Description: YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) thin films were fabricated by the trifluoroacetate (TFA) process on LaAlO{sub 3} (LAO) single crystal in an argon atmosphere. They focused on lowering the heat treatment temperature by decreasing the oxygen partial pressure to adopt the TFA process to metallic substrates. YBCO phase formation was checked by measuring T{sub c} with the inductive method. In-plane and out-of-plane film textures were evaluated by phi-scan and omega scan, respectively. Raman spectroscopy was used to estimate grain connectivity, in-plane texture, and second-phase formation of the films. Although Raman spectroscopy revealed some evidence of cation disorder, the film prepared at 750 C shows a sharp superconducting transition at 91 K and critical current density of 1.3 MA/cm{sup 2} at 77 K. Optimal heat treatment temperature was 750 C in the argon atmosphere, which is consistent with the thermodynamic estimate that heat treatment temperature decreases as oxygen partial pressure decreases.
Date: January 9, 2001
Creator: Jee, Y.-A.; Ma, B.; Fisher, B. L. & Balachandran, U.
Partner: UNT Libraries Government Documents Department

Texture development of MgO buffer layers grown by inclined substrate deposition.

Description: Biaxially textured magnesium oxide (MgO) films used as template layers for YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO)-coated conductors have been grown efficiently and consistently by inclined substrate deposition (ISD). Further improvement in texture and a decrease in surface roughness were obtained by depositing a homoepitaxial MgO layer on the ISD MgO layer at an elevated temperature and flat angle. The texture of the ISD layer was studied as a function of thickness by X-ray diffraction and scanning and transmission electron microscopy. Surface roughness of the ISD and homoepitaxial layers was investigated by atomic force microscopy. Based on the results, the optimal thickness of the ISD layer was determined.
Date: August 16, 2002
Creator: Koritala, R. E.; Ma, B.; Miller, D. J.; Li, M.; Fisher, B. L. & Balachandran, U.
Partner: UNT Libraries Government Documents Department

Critical current densities in Bi-2223 sinter forgings.

Description: (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Bi-2223) bars, prepared by sinter forging, exhibited good phase purity and strong textures with the c axes of the Bi-2223 grains parallel to the forging direction. The initial zero-field critical current density (J{sub c}) of the bars was 10{sup 3} A/cm{sup 2}, but because the forged bars were uncoated, this value decreased with repeated thermal cycling. J{sub c} as a function of applied magnetic field magnitude and direction roughly followed the dependencies exhibited by Ag-sheathed Bi-2223 tapes, but the forged bars were more strongly dependent on field strength and less strongly dependent on field angle.
Date: July 23, 1999
Creator: Balachandran, U.; Fisher, B. L.; Goretta, K. C.; Harris, N. C. & Murayama, N.
Partner: UNT Libraries Government Documents Department

Biaxially aligned template films fabricated by inclined-substrate deposition for YBCO-coated conductor applications.

Description: Inclined substrate deposition (ISD) has the potential for rapid production of high-quality biaxially textured buffer layers, which are important for YBCO-coated conductor applications. We have grown biaxially textured MgO films by ISD at deposition rates of 20-100 {angstrom}/sec. Columnar grains with a roof-tile surface structure were observed in the ISD-MgO films. X-ray pole figure analysis revealed that the (002) planes of the ISD-MgO films are tilted at an angle from the substrate normal. A small {phi}-scan full-width at half maximum (FWHM) of {approx}9{sup o} was observed on MgO films deposited at an inclination angle of 55{sup o}. In-plane texture in the ISD MgO films developed in the first 0.5 {micro}m from the interface, then stabilized with further increases in film thickness. YBCO films deposited by pulsed laser deposition on ISD-MgO buffered Hastelloy C276 substrates were biaxially aligned with the c-axis parallel to the substrate normal. T{sub c} of 91 K with a sharp transition and transport J{sub c} of 5.5 x 10{sup 5} A/cm{sup 2} at 77 K in self-field were measured on a YBCO film that was 0.46-{micro}m thick, 4-mm wide, 10-mm long.
Date: August 12, 2002
Creator: Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Erck, R. A.; Dorris, S. E. et al.
Partner: UNT Libraries Government Documents Department

Characterization of high-current, high-temperature superconductor current lead elements

Description: The refrigeration loads of current leads for superconducting magnets can be significantly reduced by using high-temperature superconductor (HTS) leads. An HTS conductor type that is well suited for this application is a laminated sintered stack of HTS powder-in-tube (PIT) tapes. The superconducting elements are normally characterized by their manufacturer by measuring critical currents at 77 K in self field. Additional characterization, which correlates electrical performance at 77 K and at lower temperatures with applied magnetic fields, provides the current lead designer and conductor element manufacturer with critical information. For HTS conductor elements comprising a laminated and sintered stack of Bi-2223 PIT tapes having an alloyed Ag sheath, this characterization uses variable applied fields and operating temperatures.
Date: August 1, 1996
Creator: Niemann, R.C.; Evans, D.J.; Fisher, B.L.; Brockenborough, W.E.; Roberts, P.R. & Rodenbush, A.J.
Partner: UNT Libraries Government Documents Department

Fabrication and characterization of (Bi,Pb)-Sr-Ca-Cu-O (2223) bars

Description: Bulk bars for current lead applications were fabricated from (Bi,Pb)- Sr-Ca-Cu-O (Bi-2223) for low thermal conductivity and high critical current. Bars measuring 17.8 cm in length were made by uniaxially pressing Bi-2223 powder of controlled (1.7/0.34)223 and (1.8/0.4)223 phase composition. The bulk bars were densified by subjecting them to a schedule of alternate liquid-phase sintering and cold isostatic pressing. Liquid phase sintering temperatures were optimized from differential thermal analysis and microstructure morphology. Phase purity and microstructure were evaluated by x-ray diffraction and scanning electron microscopy. Low-resistance silver contacts were applied to the bars by hot-pressing at 820{degrees}C and 3 MPa. Critical current densities {approx} 1000 A/cm{sup 3} (critical currents of 750 A at 77 K in self-field conditions) were achieved.
Date: August 1996
Creator: Chudzik, M. P.; Polzin, B. J.; Thayer, R.; Picciolo, J. J.; Fisher, B. L. & Lanagan, M. T.
Partner: UNT Libraries Government Documents Department

Fabrication and texture characterization of bulk (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} superconductors

Description: Bulk (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (Bi-2223) and Bi{sub 2}Sr{sub 2}CaCU{sub 2}0{sub x} (Bi-2212) superconductors were fabricated by sinter forging. Bi-2223 ({approx}90% Bi-2223, 10% (Bi,Pb){sub 2}Sr{sub 2}CaCU{sub 2}0. + other phases) and Bi-2212 (nearly phase pure) powders were first synthesized and then cold pressed into bars that were -50% dense. These bars were surrounded by Ag foil, heated in air to {approx}845{degrees}C, and compressed for 3--6 h. The resultant bars were dense and highly textured. At 77 K, the Bi-2223 exhibited transport critical current density (J{sub c}) values of 2000--8000 A/cm{sup 2}; the Bi-2212 exhibited very low J{sub c}. Extent of texture was evaluated by three X-ray diffraction methods: 2{theta} scans, rocking curves, and orientation distribution functions. It was found that J{sub c} correlated best with the orientation distribution functions.
Date: May 1, 1995
Creator: Goretta, K.C.; Chen, Nan; Biondo, A.C.; Fisher, B.L.; Lanagan, M.T. & Kallend, J.S.
Partner: UNT Libraries Government Documents Department

Fabrication of biaxially textured templates for coated conductors by inclined substrate deposition.

Description: YBCO-coated conductors will enable the development of smaller, lighter, more-efficient electric power devices that can be operated at temperatures approaching that of liquid nitrogen. The critical current density (J{sub c}) of YBCO films on flexible metallic substrates has been significantly improved by epitaxially growing the YBCO on biaxially textured template films. Inclined substrate deposition (ISD) offers the potential for rapidly producing high-quality biaxially textured buffer layers that are suitable for YBCO-coated conductors. Using the ISD method, we have grown biaxially textured MgO films at deposition rates of 20-100 {angstrom}/sec. Electron microscopy of the ISD-MgO films revealed columnar grains topped off by MgO (002) planes, and X-ray pole figure analysis showed that the (002) planes are tilted with respect to the substrate normal, giving ISD-MgO films a roof-tile surface morphology. A small phi-scan full-width at half maximum of {approx}10{sup o} was observed on ISD-MgO films deposited with a substrate inclination of 55{sup o}. YBCO films were grown on ISD-MgO buffered Hastelloy substrates by pulsed laser deposition. A sample that was 0.42 {micro}m x 0.45 mm x 1 cm gave a transport J{sub c} of {approx}0.34 MA/cm{sup 2} at 77 K in self-field. Details of ISD-MgO film fabrication and characterization, as well as the results of YBCO deposited on the ISD-MgO architecture, are presented.
Date: August 21, 2002
Creator: Dorris, S. E.; Ma, B.; Li, M.; Fisher, B. L.; Koritala, R. E.; Erck, R. et al.
Partner: UNT Libraries Government Documents Department

Inclined substrate deposition of magnesium oxide for YBCO-coated conductors.

Description: Thin films of YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) were grown on MgO buffered metallic substrates by pulsed laser deposition (PLD). The MgO buffer films, which provide the initial biaxial texture, had been grown on polished Hastelloy C276 (HC) tapes using inclined substrate deposition (ISD). The ISD process is promising for the fabrication of coated superconductor wires because it produces biaxially textured template films on nontextured substrate at high deposition rates. Biaxially aligned MgO films were deposited at deposition rates of 20 to 100 {angstrom}/sec. The buffer films were deposited on these template films before ablation of the YBCO films by PLD. The microstructure was studied by scanning electron microscopy and atomic force microscopy. X-ray pole figure analysis and {phi}- and {omega}-scans were used for texture characterization. Good in- and out-of-plane textures were observed on the ISD MgO films ({approx}1.5 {micro}m thick). The full width at half maximums were 9.2{sup o} for the MgO (002) {phi}-scan and 5.4{sup o} for the {omega}-scan. Cube-on-cube epitaxial growth of yttria-stabilized zirconia (YSZ) and ceria (CeO{sub 2}) films on the ISD MgO films was also achieved by PLD. A superconducting critical temperature of 90 K, with a sharp transition, and transport critical current density of >2.5 x 10{sup 5} A/cm{sup 2} were obtained on a 0.5-{micro}m-thick, 0.5-cm-wide, and 1-cm-long YBCO film with MgO buffer layer at 77 K in self-field.
Date: April 26, 2002
Creator: Ma, B.; Li, M.; Fisher, B. L.; Koritala, R. E.; Dorris, S. E.; Maroni, V. A. et al.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications - annual report for FY 2000.

Description: Most large-scale high-critical-temperature superconductor applications require wires or tapes that an carry high currents in applied magnetic fields. This report describes technical progress of research and development efforts aimed at producing superconducting components and devices in the Y-Ba-Cu-O and Bi-(Pb)-Sr-Ca-Cu-O systems. Topics discussed are formation of first- and second-generation composite conductors, characterization of structures and superconducting and mechanical properties, modeling of grain-boundary current transport, and fabrication and analysis of prototype components.
Date: January 25, 2001
Creator: Balachandran, U.; Cha, Y.S.; Dorris, S.E.; Dusek, J.T.; Emerson, J.E.; Fisher, B.L. et al.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications : annual report for FY 2001.

Description: Most large-scale applications of high-critical-temperature superconductors will require wires or tapes that can carry large current in applied magnetic fields. This report describes research and development efforts at Argonne National Laboratory (ANL) aimed at producing practical superconducting components and devices using the Y-Ba-Cu-O and Bi-(Pb)-Sr-Ca-Cu-O systems. Topics discussed include various methods of forming second- and first-generation composite conductors, characterization of their structures and superconducting and mechanical properties, modeling of grain-boundary current transport, and the testing and modeling of a superconducting fault current limiter.
Date: May 2, 2002
Creator: Cha, Y. S.; Dorris, S. E.; Dusek, J. T.; Emerson, J. E.; Erck, R. A.; Fisher, B. L. et al.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications annual report for FY 1998.

Description: Development of useful high-T{sub c} superconductors requires synthesis of superconducting compounds; fabrication of wires, tapes, and films from these compounds; production of composite structures that incorporate stabilizers or insulators; and design and testing of efficient components. This report describes FY 1998 technical progress of research and development efforts aimed at producing superconducting components in the Bi-(Pb)-Sr-Ca-Cu and Y-Ba-Cu oxide systems. Topics discussed are synthesis and heat treatment of high-T{sub c} superconductors, formation of monolithic and composite conductors, characterization of structures and superconducting and mechanical properties, and fabrication and testing of prototype components. Collaborations with industry and academia are documented.
Date: January 27, 1999
Creator: Askew, T.R.; Balachandran, U.; Cha, Y.S.; Dorris, S.E.; Dusek, J.T.; Emerson, J.E. et al.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications - annual report for FY 2003.

Description: Most large-scale applications of high-critical-temperature superconductors will require conductors that can carry large currents in the presence of applied magnetic fields. This report describes progress at Argonne National Laboratory (ANL) in the research and development of practical superconducting components and devices. These efforts primarily focus on the use of Y-Ba-Cu-O system in second-generation conductors, but they also include investigations of Bi-Pb-Sr-Ca-Cu-O systems for use in first-generation conductors. Results are presented in the areas of processing first-generation superconductors and second-generation (2G) superconductors with several different architectures, applying Raman microscopy to the characterization of 2G conductors, studying the role of oxygen doping in the grain boundary transport of 2G conductors, and evaluating the mechanical properties of 2G conductors.
Date: October 18, 2004
Creator: Balachandran, U.; Baurceanu, R.; Clauss, H.; Dorris, S. E.; Emerson, J. E.; Erck, R. A et al.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications: annual report for FY 2002.

Description: Most large-scale applications of high-critical-temperature superconductors will require conductors that can carry large currents in the presence of applied magnetic fields. This report describes progress at Argonne National Laboratory (ANL) in the research and development of practical superconducting components and devices using the Y-Ba-Cu-O and Bi-Pb-Sr-Ca-Cu-O systems. Results are presented in the areas of fabrication of second- and first-generation composite conductors, characterization of their structures and superconducting properties, investigation of grain-boundary current transport and factors that influence it, testing and modeling of the components of a superconducting fault current limiter, and the measurement and modeling of a superconductor's response to a transient such as that in a fault current limiter after a fault.
Date: April 9, 2003
Creator: Baurceanu, R.; Cha, Y. S.; Dorris, S. E.; Emerson, J. E.; Erck, R. A.; Fisher, B. L. et al.
Partner: UNT Libraries Government Documents Department