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Simple model of the anisotropic penetration depth in high T{sub c} superconductors

Description: We present a simple model of some high {Tc} cuprates based upon superconducting (S) and normal (N) layers, which quantitatively fits the data of Bonn et al. for the low-temperature T dependence of the penetration depths {lambda}{sub a,b,c} in untwinned YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}, assuming s-wave intralyer pairing. This SN model also leads to anisotropic surface states, which complicate analysis of photoemission and tunneling measurements.
Date: April 1, 1996
Creator: Klemm, R.A. & Liu, S.H.
Partner: UNT Libraries Government Documents Department

Fabrication of high critical current density superconducting tapes by epitaxial deposition of YBCO thick films on biaxially textured metal substrates

Description: High critical current density YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (YBCO) tapes were fabricated by epitaxial deposition on rolling- assisted-biaxially-textured-substrates (RABiTS). The RABiTS technique uses well established, industrially scaleable, thermomechanical processes to impart a strong biaxial texture to a base metal. This is followed by vapor deposition of epitaxial buffer layers to yield chemically and structurally compatible surfaces. Epitaxial YBCO films grown on such substrates have critical current densities approaching 10{sup 6} A/cm{sup 2} at 77K in zero field and have field dependences similar to epitaxial films on single crystal ceramic substrates. Deposited conductors made using this technique offer a potential route for fabricating long lengths of high J{sub c} wire capable of carrying high currents in high magnetic fields and at elevated temperatures.
Date: December 31, 1996
Creator: Goyal, A.; Norton, D.P. & Paranthaman, M.
Partner: UNT Libraries Government Documents Department

Development of biaxially textured buffer layers on rolled-Ni substrates for high current YBa{sub 2}Cu{sub 3}O{sub 7{minus}y} coated conductors

Description: This paper describes the development of 3 buffer layer architectures with good biaxial textures on rolled-Ni substrates using vacuum processing techniques. The techniques include pulsed laser ablation, e-beam evaporation, dc and rf magnetron sputtering. The first buffer layer architecture consists of an epitaxial laminate of Ag/Pd(Pt)/Ni. The second buffer layer consists of an epitaxial laminate of CeO{sub 2}/Pd/Ni. The third alternative buffer layer architecture consists of an epitaxial laminate of YSZ/CeO{sub 2}/Ni. The cube (100) texture in the Ni was produced by cold rolling followed by recrystallization. Crystallographic orientations of the Pd, Ag, CeO{sub 2}, and YSZ films grown were all (100). We recently demonstrated a critical- current density of 0.73x10{sup 6} A/cm{sup 2} at 77 K and zero field on 1.4 {mu}m thick YBa{sub 2}Cu{sub 3}O{sub 7-y} (YBCO) film. This film was deposited by pulsed laser ablation on a YBCO/YSZ/CeO{sub 2}/Ni substrate.
Date: December 31, 1996
Creator: Paranthaman, M.; Goyal, A. & Norton, D.P.
Partner: UNT Libraries Government Documents Department

Development of a high gradient magnetic separator using high temperature superconductors

Description: This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). High-gradient magnetic separation (HGMS) is an application of superconducting magnet technology to the process of magnetic separation of solids from other solids, liquids, or gases. The production of both high magnetic fields and large field gradients using superconducting magnet technology has made it possible to separate a previously unreachable but large family of paramagnetic materials. It is possible to separate more than half of the elements in the periodic table using this method. Because HGMS is a physical separation process, no additional or mixed waste is generated. This project sought to develop a high-gradient magnetic separator using a high-temperature superconducting magnet.
Date: September 1, 1996
Creator: Prenger, F.C.; Daney, D.; Daugherty, M. & Hill, D.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications - Argonne National Laboratory - quarterly report for the period ending June 30, 2001.

Description: This is a multiyear experimental research program focused on improving relevant material properties of high-T{sub c} superconductors (HTSs) and on development of fabrication methods that can be transferred to industry for production of commercial conductors. The development of teaming relationships through agreements with industrial partners is a key element of the Argonne (ANL) program.
Date: August 21, 2001
Creator: Dorris, S. E.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications - quarterly report for the period ending June 30, 2004.

Description: This is a multiyear experimental research program that focuses on improving relevant material properties of high-critical-temperature (Tc) superconductors and developing fabrication methods that can be transferred to industry for production of commercial conductors. The development of teaming relationships through agreements with industrial partners is a key element of the Argonne National Laboratory (ANL) program.
Date: September 9, 2004
Creator: Dorris, S. E.
Partner: UNT Libraries Government Documents Department

Practical superconductor development for electrical power applications - quarterly report for the period ending March 31, 2004.

Description: This is a multiyear experimental research program that focuses on improving relevant material properties of high-critical-temperature (Tc) superconductors and developing fabrication methods that can be transferred to industry for production of commercial conductors. The development of teaming relationships through agreements with industrial partners is a key element of the Argonne National Laboratory (ANL) program.
Date: July 21, 2004
Creator: Dorris, S. E.
Partner: UNT Libraries Government Documents Department

Structural study of Sr{sub 2}CuO{sub 3+delta} by neutron powder diffraction

Description: Average crystal structures of superconducting Sr{sub 2}CuO{sub 3+{delta}} synthesized at ambient pressure from a hydroxometallate precursor were refined from neutron powder diffraction data. A simplified model was used to fit the modulated superstructures. Both compounds have an oxygen deficient La{sub 2}CuO{sub 4}-type tetragonal T structure with O vacancies located in the CuO{sub 2} planes, not in the Sr{sub 2}O{sub 2} layers. This raises important questions about the superconductivity in Sr{sub 2}CuO{sub 3+{delta}} reported to be a 70 K superconductor.
Date: November 1, 1996
Creator: Shimakawa, Y.; Jorgensen, J.D.; Mitchell, J.F.; Hunter, B.A.; Shaked, S.; Hinks, D.G. et al.
Partner: UNT Libraries Government Documents Department

Effect of Ag on the peritectic decomposition of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}

Description: During the melt processing of superconducting wires and tapes a number of partial liquid phase regions are entered, and the type and amount of second phases that exist in the melt before cooling are critical in determining the microstructure of the final material. Decomposition pathway of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x}(Bi2212) with 0, 2, and 10 wt% Ag added was examined at 1 bar PO{sub 2} by performing SAME/EDS analysis on oil quenched samples. A variety of quaternary phase diagrams were constructed to describe the evolution of the phase assemblage with temperature. At all Ag contents, Bi2212 first undergoes a peritectic reaction producing (Sr{sub 1-x}Ca{sub x}){sub 14}Cu{sub 24}O{sub 41}(14,24), Bi{sub 2}(Sr{sub 1-x}Ca{sub x}){sub 4}O{sub x}(24x), and liquid.
Date: December 31, 1995
Creator: Margulies, L.; Dennis, K.W.; Kramer, M.J. & McCallum, R.W.
Partner: UNT Libraries Government Documents Department

Investigating the Atomic Scale Superconducting Properties of Grain Boundaries in High-T(Sub c) Superconductors

Description: Presented at Fourteenth International Congress on Electron Microscopy Cancun, Mexico, August 31-September 4, 1998, and published in Proceedings Over ten years after the discovery of high-TC superconductors, their widespread application into viable device structures is still limited by the deleterious effect of grain boundaries. One of the main difficulties associated with understanding this effect is that transport measurements are usually performed on the micron scale. However, the critical parameter for superconductivity, the coherence length, is only ~lnm. To understand grain boundaries on a fundamental level it is therefore necessary to investigate the properties on this atomic scale; a scale attainable only by electron microscopy [12]. As an example of the observed properties of grain boundaries in YB~C~07d (YBCO), the V(I) curves recorded across a 24o boundary for several magnetic fields are shown m figure 1, To explain these properties, a model where the grain boundary is composed of equally sized and spaced dislocation cores separated by a very small fraction of much stronger links has been developed (figure 1). These strong links may carry either the depairing current, the JC of the grains or another Josephson current (a depairing current seems unlikely in view of the field dependence of the experimental data). The simulated behavior obtained for this model, where the fraction of strong links is x=O.005 and JC is the observed J=(B) of the grains, exhibits qualitatively similar behavior to the experimental data (figure 1). However, the fit is not perfect, suggesting that the strong links are more likely to be regions of grain boundary with a higher Josephson current, rather than links with the JC(B) of the grains. Using electron microscopy we can look for the origin of these stronger coupled regions at the grain boundary. Figure 2 shows a Z-contrast image of a similar high-angle [001] tilt ...
Date: August 31, 1998
Creator: Browning, N.D.; Buban, J.P.; Christen, D.K.; Nellist, P.D.; Norton, D.P.; Pennycook, S.J. et al.
Partner: UNT Libraries Government Documents Department

Fluctuation phenomena in layered superconductors

Description: Gaussian fluctuations in layered superconductors have been the subject of study for many years. Although the FD was studied in detail long ago, the FC (fluctuation conductivity) was studied only recently, since the MT and DOS diagrams were previously neglected. Recent comparisons with experiment on YBCO have shown that the DOS diagrams are important and can lead to qualitatively different behaviors for the FC parallel and perpendicular to the layers. In both cases, Gaussian fluctuations fit the data above {Tc} very well, even for YBCO. To date, nearly all calculations of fluctuation quantities were for B{parallel}{cflx c}. Nevertheless, it should be possible to treat an arbitrary B, but the evaluation of the required matrix elements for the fluctuation quantities will be more complicated.
Date: October 1, 1996
Creator: Klemm, R.A.
Partner: UNT Libraries Government Documents Department

Processing and properties of Ag-clad BSCCO superconductors

Description: Long lengths of mono- and multifilament Ag-clad BSCCO (Bi-Sr-Ca-Cu-O) conductors with critical current densities of >10{sup 4} A/cm{sup 2} at 77 K were fabricated by the powder-in-tube method. {Tc} magnets were assembled by stacking pancake coils fabricated from long tapes and then tested vs applied magnetic field at various temperatures. A magnet that contained {approx}2400 m of {Tc} conductor generated a field of 3.2 T at 4.2 K. In-situ tensile and bending properties of the Ag-clad conductors were studied. Multilayer Ag/superconductor composites were fabricated by chemical etching. Preliminary results with multilayer tapes show that continuous Ag reinforcement of the BSCCO core improves strain tolerance of the tapes so they can carry 90% of their initial I{sub c} at 1% bend strain desite a higher superconductor/Ag ratio than that of unreinforced tapes.
Date: March 1, 1996
Creator: Jammy, R.; Iyer, A.N.; Chudzik, M.; Balachandran, U. & Haldar, P.
Partner: UNT Libraries Government Documents Department

Method and apparatus for dissipating remanent fields and preserving diamagnetism of ceramic superconductors

Description: A method for dissipating a remanent field, created when a magnetic field is brought into contact with a superconductor, while preserving the diamagnetism of a superconductor comprises the steps of (1) providing a ceramic superconductor; (2) continuously or intermittently generating an AC current to the ceramic superconductor; and (3) gradually decreasing the AC current until the undesired remanent field is dissipated.
Date: December 1993
Creator: Youngdahl, C. A.
Partner: UNT Libraries Government Documents Department

The Effect of Magnetic Field on HTS Leads What Happens when thePower Fails at RAL?

Description: The key to being able to operate the MICE superconducting solenoids on small coolers is the use of high temperature superconducting (HTS) leads between the first stage of the cooler and the magnet, which operates at around 4.2 K. Because MICE magnets are not shielded, all of the MICE magnets have a stray magnetic field in the region where the coolers and the HTS leads are located. The behavior of the HTS leads in a magnetic field depends strongly on the HTS material used for the leads and the temperature of the cooler first stage temperature. The HTS leads can be specified to operate at the maximum current for the magnet. This report shows how the HTS leads can be specified for use the MICE magnets. MICE magnets take from 1.3 hours (the tracker solenoids) to 3.7 hours (the coupling magnet) to charge to the highest projected operating currents. If the power fails, the cooler and the upper ends of the HTS leads warm up. The question is how one can discharge the magnet to protect the HTS leads without quenching the MICE magnets. This report describes a method that one can use to protect the HTS leads in the event of a power failure at the Rutherford Appleton Laboratory (RAL).
Date: February 14, 2007
Creator: Green, Michael A.
Partner: UNT Libraries Government Documents Department

Magnetic Properties of Dy in Pb

Description: Superconductivity can be induced at high temperatures in Pb{sub 2}Sr{sub 2}RCu{sub 3}O{sub 8} (R - rare earth) by partially doping Ca{sup 2+} for R{sup 3+}. In order to understand the interplay between magnetism and superconductivity, the magnetic properties of the parent compounds, Pb{sub 2}Sr{sub 2}RCu{sub 3}O{sub 8}, have been studied. The work presented here includes magnetic susceptibility and specific heat measurements on R=Dy and extends the previous studies on R=Ce, Pr, Tb, Ho and Er. Specific heat experiments suggest that the Dy ions order antiferromagnetically with an ordering temperature of 1.3K. The magnetic susceptibility data are in good agreement with the susceptibility calculated using crystal field parameters that are extrapolated from previous modeling of the R=Er and Ho analogs of this series.
Date: July 10, 1999
Creator: Skanthakumar, S.; Soderholm, L. & Movshovich, R.
Partner: UNT Libraries Government Documents Department

Melt-processing high-T{sub c} superconductors under an elevated magnetic field [Final report no. 2]

Description: This report presents models for crystallographic texture development for high temperature superconducting oxides processed in the absence of a magnetic field and in the presence of a high magnetic field. The results of the models are confirmed through critical experiments. Processing thick films and tapes of high temperature superconducting oxides under a high magnetic field (5-10T) improves the critical current density exhibited.
Date: September 5, 2001
Creator: Sande, John B. Vander
Partner: UNT Libraries Government Documents Department

Fabrication of large domain YBa{sub 2}Cu{sub 3}O{sub x} for magnetic suspension applications

Description: Large domain YBa{sub 2}Cu{sub 3}O{sub x} levitators have been fabricated using a seeded melt processing technique. Depending upon the seed, either a single or five domained sample can be obtained. The grain boundaries separating each domains in the five domain levitator are found to be 90 degrees. Similar levitation forces can be observed for single and five domained samples. After thermal cycling, however, a small decrease in the levitation force of the five domain levitator was observed as a function of thermal cycles while nearly no change in force was observed in the single domain levitator. Finally it is shown that both, single and five domain YBCO, behave similarly as a function of sample thickness.
Date: December 31, 1995
Creator: Todt, V.R.; Zhang, X.; Miller, D.J.; Sengupta, S.; Corpus, J. & Gains, J.R. Jr.
Partner: UNT Libraries Government Documents Department

Parallel solution of the three-dimensional time-dependent Ginzburg- Landau equation

Description: The recent discovery of superconductivity in a class of copper-oxide compounds (the cuprate superconductors) at liquid nitrogen temperatures has generated a renewed interest in the magnetic properties of type-II superconductors. In our work, we are investigating these properties using the phenomenological time- dependent Ginzburg-Landau equation. This paper describes the parallelization of this equation.
Date: August 1, 1996
Creator: Galbreath, N.; Gropp, W.; Gunter, D.; Leaf, G. & Levine, D.
Partner: UNT Libraries Government Documents Department

Liquid helium boil-off measurements of heat leakage from sinter-forged BSCCO current leads under DC and AC conditions

Description: Liquid helium boil-off experiments are conducted to determine the heat leakage rate of a pair of BSCCO 2223 high-temperature superconductor current leads made by sinter forging. The experiments are carried out in both DC and AC conditions and with and without an intermediate heat intercept. Current ranges are from 0-500 A for DC tests and 0-1,000 A{sub rms} for AC tests. The leads are self-cooled. Results show that magnetic hysteresis (AC) losses for both the BSCCO leads and the low-temperature superconductor current jumper are small for the current range. It is shown that significant reduction in heat leakage rate (liquid helium boil-off rate) is realized by using the BSCCO superconductor leads. At 100 A, the heat leakage rate of the BSCCO/copper binary lead is approximately 29% of that of the conventional copper lead. Further reduction in liquid helium boil-off rate can be achieved by using an intermediate heat intercept. For example, at 500 K, the heat leakage rate of the BSCCO/copper binary lead is only 7% of that of the conventional copper lead when an intermediate heat intercept is used.
Date: June 1, 1995
Creator: Cha, Y.S.; Niemann, R.C.; Hull, J.R.; Youngdahl, C.A.; Lanagan, M.T.; Nakade, M. et al.
Partner: UNT Libraries Government Documents Department

Ac loss calorimeter for three-phase cable

Description: A calorimeter for measuring ac losses in meter-long lengths of HTS superconducting power transmission line cables is described. The calorimeter, which is based on a temperature difference technique, has a precision of 1 mW and measures single, two-phase (coupling), and three-phase losses. The measurements show significant coupling losses between phases.
Date: October 1, 1996
Creator: Daney, D.E.; Boenig, H.J.; Maley, M.P.; McMurry, D.E. & DeBlanc, B.G.
Partner: UNT Libraries Government Documents Department

Relationships between processing temperature and microstructure in isothermal melt processed Bi-2212 thick films

Description: The microstructure and phase assemblage of isothermal melt processed (IMP) Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212) thick films have been evaluated. Results from compositional analysis and phase identification indicate that the characteristics of the partial melt greatly influence the microstructural and chemical development of the thick films. The highest critical current densities were obtained in films processed below 800{degrees}C where the partial melt uniformly coats the substrate without excessive phase segregation.
Date: May 1, 1995
Creator: Holesinger, T.G.; Phillips, D.S.; Willis, J.O. & Peterson, D.E.
Partner: UNT Libraries Government Documents Department

Strongly correlated electronic materials

Description: This is the final report of a 3-year project. Novel electronic materials characterized by strong electronic correlations display a number of unexpected, often extraordinary, properties. These are likely to play a major role in purpose-specific high-technology electronic materials of the future developed for electronic, magnetic, and optical applications. This project sought to develop predictive control of the novel properties by formulating, solving and applying many-body models for the underlying microscopic physics. This predictive control required the development of new analytical and numerical many-body techniques and strategies for materials of varying strengths of interactions, dimensionality and geometry. Results are compared with experiment on classes of novel materials, and the robust techniques are used to predict additional properties and motivate key additional experiments.
Date: April 1, 1996
Creator: Bedell, K.; Albers, R.; Balatsky, A.; Bishop, A.; Bonca, J.; Gubernatis, J. et al.
Partner: UNT Libraries Government Documents Department