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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

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

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

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

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

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 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

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

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

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

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

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 - 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

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

Vortices wiggled and dragged

Description: When a sufficiently strong magnetic field is applied to a superconductor, some of the field can pierce it through the generation of magnetic vortices, each of which contains a quantized amount of magnetic flux. Although the superconducting state of the material outside each vortex is maintained (and destroyed within each vortex), the interaction of vortices with a current passing through the material can cause them to move, dissipating energy and thereby generating a source of electrical resistance. The ability to manipulate an individual superconducting vortex represents a powerful tool for studying the dynamics of vortices and the superconductors that support them. It could also lead to the development of a new class of fluxon-based electronics.
Date: January 1, 2008
Creator: Reichhardt, Charles
Partner: UNT Libraries Government Documents Department

Surface state and normal layer effects in high T{sub c} superconductors

Description: In addition to the conducting CuO{sub 2} (S) layers, most high-{Tc}, superconductors also contain other conducting (N) layers, which are only superconducting due to the proximity effect. The combination of S and N layers can give rise to complicated electronic densities of states, leading to quasilinear penetration depth and NMR relaxation rate behavior at low temperatures. Surface states can also complicate the analysis of tunneling and photoemission measurements. Moreover, geometrical considerations and inhomogeneously trapped flux are possible explanations of the paramagnetic Meissner effect and of corner and ring SQUID experiments. Hence, all of the above experiments could be consistent with isotropic s-wave superconductive within the S layers.
Date: January 1, 1996
Creator: Klemm, R.A.; Ledvij, M. & Liu, Samuel H.
Partner: UNT Libraries Government Documents Department

New technologies for a future superconducting proton collider

Description: New more economic approaches are required to continue the dramatic exponential rise in particle accelerator energies as represented by the well- known Livingston plot. The old idea of low-cost, low-field iron dominated magnets in a small diameter pipe may become feasible in the next decade with dramatic recent advances in technology: (1) high T{sub c} superconductors operating at liquid N{sub 2} or H{sub 2} temperatures, (2) advanced tunneling technologies for small diameter, non human accessible tunnels, (3) accurate remote guidance systems for boring machine steering, (4) industrial applications of remote manipulation and robotics, and (5) digitally multiplexed electronics to minimize cables There is an opportunity for mutually beneficial partnerships between the High Energy Physics community and the commercial sector to develop the necessary technology. This will gain public support, a necessary part of the challenge of building a new, very high energy collider.
Date: June 1, 1996
Creator: Malamud, E. & Foster, G.W.
Partner: UNT Libraries Government Documents Department

Analyses, algorithms, and computations for models of high-temperature superconductivity. Final report

Description: Under the sponsorship of the Department of Energy, the authors have achieved significant progress in the modeling, analysis, and computation of superconducting phenomena. The work so far has focused on mezoscale models as typified by the celebrated Ginzburg-Landau equations; these models are intermediate between the microscopic models (that can be used to understand the basic structure of superconductors and of the atomic and sub-atomic behavior of these materials) and the macroscale, or homogenized, models (that can be of use for the design of devices). The models they have considered include a time dependent Ginzburg-Landau model, a variable thickness thin film model, models for high values of the Ginzburg-landau parameter, models that account for normal inclusions and fluctuations and Josephson effects, and the anisotropic ginzburg-Landau and Lawrence-Doniach models for layered superconductors, including those with high critical temperatures. In each case, they have developed or refined the models, derived rigorous mathematical results that enhance the state of understanding of the models and their solutions, and developed, analyzed, and implemented finite element algorithms for the approximate solution of the model equations.
Date: June 1, 1997
Creator: Du, Q.
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

Joining of melt-textured YBCO : a direct contact method.

Description: We report a method for making weld joints, capable of transmitting high supercurrent densities, in bulk samples of melt textured YBCO. The joining procedure is carried out in a flowing atmosphere of O{sub 2} to eliminate problems associated with nitrogen gas, which can become trapped in the joint. No filler or fluxing material is used. The method can be used to join large areas (several cm{sup 2}) that are capable of transmitting supercurrent densities exceeding 10{sup 4} A/cm{sup 2}.
Date: December 19, 2001
Creator: Chen, L.; Claus, H.; Paulikas, A. P.; Zheng, H. & Veal, B. W.
Partner: UNT Libraries Government Documents Department