WorldWideScience

Sample records for cuprate hts oxides

  1. Magnetron sputtering of Fe-oxides on the top of HTS YBCO films

    Energy Technology Data Exchange (ETDEWEB)

    Nurgaliev, T. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse, 1784 Sofia (Bulgaria); Blagoev, B. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse, 1784 Sofia (Bulgaria); Laboratory of High Magnetic Fields and Low Temperatures, 95 Gajowicka Str., 53-421 Wroclaw (Poland); Buchkov, K. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse, 1784 Sofia (Bulgaria); Mateev, E. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse, 1784 Sofia (Bulgaria); Gajda, G. [Laboratory of High Magnetic Fields and Low Temperatures, 95 Gajowicka Str., 53-421 Wroclaw (Poland); Nedkov, I. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse, 1784 Sofia (Bulgaria); Kovacheva, D. [Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Street, bl. 10, 1113 Sofia (Bulgaria); Slavov, L. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse, 1784 Sofia (Bulgaria); Laboratory of High Magnetic Fields and Low Temperatures, 95 Gajowicka Str., 53-421 Wroclaw (Poland); Starbova, I.; Starbov, N. [Institute of Solid State Physics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse, 1784 Sofia (Bulgaria); Nankovski, M. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse, 1784 Sofia (Bulgaria); Sofia university “St. Kliment Ohridski”, Faculty of Physics, 5 James Bourchier Blvd., 1164 Sofia (Bulgaria)

    2017-05-01

    The possibilities for preparation of bilayers containing magnetic Fe-oxide (Fe-O) and high temperature superconducting (HTS) YBa{sub 2}Cu{sub 3}O{sub 7−x} (YBCO) thin films were investigated. For this purpose, Fe-O films were deposited using reactive magnetron sputtering at comparatively low temperatures T≤250 °C onto dielectric (for example, LaAlO{sub 3} (LAO)) substrates, covered with a HTS YBCO film. The sputtering of the Fe-O layer at such conditions did not lead to a crucial damage of the critical temperature T{sub C} of the YBCO film, but could affect the width of the superconducting transition. A decrease of the critical temperature of the (Fe-O)/YBCO/LAO bilayer kept at ambient conditions was observed, possibly due to the negative effects of the water vapour on the sample characteristics. The double peak structure of the imaginary component of the response signal to the AC harmonic magnetic field, observed in such a (Fe-O)/YBCO/LAO sample, was ascribed from two possible views: as a consequence of morphology determined inter- and intra-granular contributions and/or as transitions from dominant irreversible processes as Bean-Livingston barrier to vortex state chains formation. - Highlights: • Iron-oxide (Fe-O) film sputtered on the top of superconducting HTS YBCO film at not very high temperatures. • No crucially damaged superconducting properties of YBCO film during Fe-O sputtering process. • A negative effect of the ambient conditions on the critical temperature of the obtained samples. • A double peak structure of the response signal to the AC harmonic magnetic field in a (Fe-O)/YBCO/LAO is observed.

  2. Renormalized modes in cuprate superconductors

    Science.gov (United States)

    Gupta, Anushri; Kumari, Anita; Verma, Sanjeev K.; Indu, B. D.

    2018-04-01

    The renormalized mode frequencies are obtained with the help of quantum dynamical approach of many body phonon Green's function technique via a general Hamiltonian (excluding BCS Hamiltonian) including the effects of phonons and electrons, anharmonicities and electron-phonon interactions. The numerical estimates have been carried out to study the renormalized mode frequency of high temperature cuprate superconductor (HTS) YBa2Cu3O7-δ using modified Born-Mayer-Huggins interaction potential (MBMHP) best applicable to study the dynamical properties of all HTS.

  3. Growth of cuprate high temperature superconductor thin films

    Directory of Open Access Journals (Sweden)

    H-U Habermeier

    2006-09-01

    Full Text Available   This paper reviews briefly the development of physical vapour deposition based HTS thin film preparation technologies to today’s state-of-the-art methods. It covers the main trends of in-situ process and growth control. The current activities to fabricate tapes for power applications as well as to tailor interfaces in cuprate are described. Some future trends in HTS thin film research, both for science as well as application driven activities are outlined.

  4. P-Tether-Mediated, Iterative SN2'-Cuprate Alkylation Strategy to Skipped Polyol Stereotetrads: Utility of an Oxidative "Function Switch" with Phosphite-Borane Tethers.

    Science.gov (United States)

    Markley, Jana L; Hanson, Paul R

    2017-05-19

    The development of a P-tether-mediated, iterative S N 2'-cuprate alkylation protocol for the formation of 1,3-skipped polyol stereotetrads is reported. This two-directional synthetic strategy builds molecular complexity from simple, readily prepared C 2 -symmetric dienediols and unites the chemistry of both temporary phosphite-borane tethers and temporary phosphate tethers-through an oxidative "function switch" of the P-tether itself-to generate intermediates that were previously inaccessible via either method alone.

  5. Manipulating oxygen sublattice in ultrathin cuprates: a new direction to engineer oxides

    NARCIS (Netherlands)

    Samal, D.; Koster, Gertjan

    2015-01-01

    Atomic engineering of complex oxide thin films is now reaching a new paradigm: the possibility to control the cation coordination by oxygen anions. Here, we show two examples of stabilization of novel structural phases by manipulating the oxygen sublattices in complex Cu-based oxide thin films grown

  6. Epitaxial thin film growth and properties of unconventional oxide superconductors. Cuprates and cobaltates

    International Nuclear Information System (INIS)

    Krockenberger, Y.

    2006-01-01

    The discovery of high-temperature superconductors has strongly driven the development of suited thin film fabrication methods of complex oxides. One way is the adaptation of molecular beam epitaxy (MBE) for the growth of oxide materials. Another approach is the use of pulsed laser deposition (PLD) which has the advantage of good stoichiometry transfer from target to the substrate. Both techniques are used within this thesis. Epitaxial thin films of new materials are of course needed for future applications. In addition, the controlled synthesis of thin film matter which can be formed far away from thermal equilibrium allows for the investigation of fundamental physical materials properties. (orig.)

  7. Epitaxial thin film growth and properties of unconventional oxide superconductors. Cuprates and cobaltates

    Energy Technology Data Exchange (ETDEWEB)

    Krockenberger, Y.

    2006-07-01

    The discovery of high-temperature superconductors has strongly driven the development of suited thin film fabrication methods of complex oxides. One way is the adaptation of molecular beam epitaxy (MBE) for the growth of oxide materials. Another approach is the use of pulsed laser deposition (PLD) which has the advantage of good stoichiometry transfer from target to the substrate. Both techniques are used within this thesis. Epitaxial thin films of new materials are of course needed for future applications. In addition, the controlled synthesis of thin film matter which can be formed far away from thermal equilibrium allows for the investigation of fundamental physical materials properties. (orig.)

  8. High-Tc superconducting thin films with composition control on a sub-unit cell level; the effect of the polar nature of the cuprates

    NARCIS (Netherlands)

    Koster, Gertjan; Brinkman, Alexander; Hilgenkamp, Johannes W.M.; Rijnders, Augustinus J.H.M.; Blank, David H.A.

    2008-01-01

    Inspired by the work of Ohtomo and Hwang in 2004, we shed new light on thin films of layered cuprate high-Tc superconductors (HTS). In principle all HTS materials consist of charged perovskite-like layers which in thin films can lead to polar discontinuities at the interfaces of different materials.

  9. Prospects for the use of HTS in high field magnets for future accelerator facilities

    CERN Document Server

    Ballarino, A

    2014-01-01

    The enthusiasm that followed discovery of High Temperature Superconductors (HTS) and the initial genuine hope of a replacement technology that could have taken over from conventional Low Temperature Superconductors (LTS) was damped during the years by difficulties in reaching performance levels of competing materials: insufficient current-carrying performance, short piece lengths, and fragility of the brittle oxide superconductors made development of applications slow and limited to demonstrators or devices less demanding from the point of view of conductor performance. However, thanks to a continuous R&D effort, significant progress was made in the past years on the development of cuprate superconductors. Today long lengths of BSCCO 2223 (km range) and REBCO (a more general acronym for YBCO, where RE = Rare Earth) tape (hundreds of meters range) conductor with controlled and homogeneous characteristics are commercially available, and tremendous progress has been made in the development of BSSCO 2212 roun...

  10. HTS machine laboratory prototype

    DEFF Research Database (Denmark)

    High Temperature Superconducting (HTS) electrical machines have the potential to offer outstanding technical performance with regards to efficiency and power density. However, the industry needs to address a large number of challenges in the attempt to harvest the full potential of HTS machines....... Among others a few stand out, e.g. reliability and efficiency of thermal insulation and cooling systems; optimized torque transfer elements and current leads; commercial availability and competitiveness of HTS material etc. Also, HTS conductors lack standardization due to their rapid development where...... many of HTS properties are not known and need to be tested with a specific purpose in mind not just for different types of HTS conductors but also for the same type of HTS conductors made by different manufactures. To address some of these challenges, we have constructed a laboratory prototype HTS...

  11. Thermodynamic properties of yttrium cuprate

    OpenAIRE

    Matskevich, N. I.; Minenkov, Yu. F.; Berezovskii, G. A.

    2014-01-01

    The standard formation enthalpy and enthalpy from binary oxide of yttrium cuprate have been determined by solution calorimetry combining the solution enthalpies of Y2Cu2O5 and Y2O3 + 2CuO mixture in 6 M HCl at 323.15 K and literature data. The heat capacity of Y2Cu2O5 has been measured by adiabatic calorimetry from 8 up to 303 K. Smoothed values of heat capacities, entropies and enthalpies were calculated on the basis of experimental data. The thermodynamic functions (heat capacity, entropy a...

  12. Efficient growth of HTS films with volatile elements

    Energy Technology Data Exchange (ETDEWEB)

    Siegal, M.P.; Overmyer, D.L.; Dominguez, F.

    1998-12-22

    A system is disclosed for applying a volatile element-HTS layer, such as Tl-HTS, to a substrate in a multiple zone furnace, said method includes heating at higher temperature, in one zone of the furnace, a substrate and adjacent first source of Tl-HTS material, to sublimate Tl-oxide from the source to the substrate; and heating at lower temperature, in a separate zone of the furnace, a second source of Tl-oxide to replenish the first source of Tl-oxide from the second source. 3 figs.

  13. Advances in HTS materials

    CERN Document Server

    Tixador, P

    2009-01-01

    HTS (High Temperature Superconductor) offer great opportunities to reach higher magnetic flux densities when compared with LTS (Low Temperature Superconductor). The upper generally accepted limit of 23 T using Nb3Sn can be overstep with HTS. HTS Bi-2212 round wires have shown critical current densities as higher than 1000 MA/m2 under 45 T at 4.2 K. The road for very high fields is open. The round shape suits rather well for magnets, especially with high current specifications since the “classical” high current cables (Rutherford, CIC) require elementary round conductor. The absence of current anisotropy in round conductor is another advantage. The YBaCuO coated conductors (HTS second generation conductors) show large opportunities for high fields. Their higher mechanical performances (IBAD process) compared to Bi conductor bring advantages for high field magnets. The protection of HTS magnet is an identified issue since degradations have been observed in several magnets after a quench. A state of the art ...

  14. Coil Optimization for HTS Machines

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Jensen, Bogi Bech; Abrahamsen, Asger Bech

    An optimization approach of HTS coils in HTS synchronous machines (SM) is presented. The optimization is aimed at high power SM suitable for direct driven wind turbines applications. The optimization process was applied to a general radial flux machine with a peak air gap flux density of ~3T...... is suitable for which coil segment is presented. Thus, the performed study gives valuable input for the coil design of HTS machines ensuring optimal usage of HTS tapes....

  15. Modulated spin and charge densities in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Tranquada, J.M.

    1997-08-01

    Neutron scattering experiments have played a crucial role in characterizing the spin and charge correlations in copper-oxide superconductors. While the data are often interpreted with respect to specific theories of the cuprates, an attempt is made here to distinguish those facts that can be extracted empirically, and the connections that can be made with minimal assumptions.

  16. Armature reaction effects on HTS field winding in HTS machine

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Jensen, Bogi Bech

    2013-01-01

    sensitivity to both armature reaction intensity and angular position with respect to the HTS coils. Furthermore, the characterization of the HTS feld winding has been correlated to the electromagnetic torque of the machine where the maximal Ic reduction of 21% has been observed for the maximum torque....

  17. Ultrasonic attenuation in cuprate superconductors

    Indian Academy of Sciences (India)

    Ultrasonic attenuation in cuprate superconductors. T GUPTA1,∗ and D M GAITONDE1,2. 1Harish-Chandra Research Institute, Allahabad 211 019, India. 2High Pressure Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India. ∗. Email: gupta@mri.ernet.in. Abstract. We calculate the longitudinal ...

  18. Superconducting thallium cuprates obtained by substitution of copper for thallium in the double-thallium layer cuprate (Tl2212)

    International Nuclear Information System (INIS)

    Gopalakrishnan, J.; Shivakumara, C.; Manivannan, V.

    1994-01-01

    A new series of superconducting thallium cuprates of nominal composition, (Tl 2-x Cu x )Ba 2 CaCu 2 O 8 (0 c s in the range 110--99K. The phases are metastable, decomposing at higher temperatures (∼1,150K) to a mixture of thallium cuprates, CuO and BaCuO 2 . Significantly, x=1 member decomposes at 1,150K to mixture of Tl2223, CuO and BaCuO 2 . Chemical titrations involving oxidation of bromide ions reveals that the copper substituting for thallium in (Tl 2-x Cu x )Ba 2 CaCu 2 O 8 most likely occurs in the III oxidation state for x≤0.25 and in a mixed state (II,III) state for x>0.25

  19. An HTS machine laboratory prototype

    DEFF Research Database (Denmark)

    Mijatovic, Nenad; Jensen, Bogi Bech; Træholt, Chresten

    2012-01-01

    This paper describes Superwind HTS machine laboratory setup which is a small scale HTS machine designed and build as a part of the efforts to identify and tackle some of the challenges the HTS machine design may face. One of the challenges of HTS machines is a Torque Transfer Element (TTE) which...... is in this design integral part of the cryostat. The discussion of the requirements for the TTE supported with a simple case study comparing a shaft and a cylinder as candidates for TTE are presented. The discussion resulted with a cylinder as a TTE design rated for a 250Nm and with more then 10 times lower heat...... conduction compared to a shaft. The HTS machine was successfully cooled to 77K and tests have been performed. The IV curves of the HTS field winding employing 6 HTS coils indicate that two of the coils had been damaged. The maximal value of the torque during experiments of 78Nm was recorded. Loaded with 33...

  20. Terahertz oscillations in mercury cuprate superconductors

    Indian Academy of Sciences (India)

    Abstract. It has been recently reported that the three-dimensional Bose–Einstein con- densation of the quasi-particles is valid for the mercury cuprates at liquid helium tem- perature. In this study, the validity of the interlayer theory in three dimensions has been investigated for optimally oxygen-doped mercury cuprates at the ...

  1. Terahertz oscillations in mercury cuprate superconductors

    Indian Academy of Sciences (India)

    It has been recently reported that the three-dimensional Bose–Einstein condensation of the quasi-particles is valid for the mercury cuprates at liquid helium temperature. In this study, the validity of the interlayer theory in three dimensions has been investigated for optimally oxygen-doped mercury cuprates at the temperature ...

  2. Oxygen diffusion in cuprate superconductors

    International Nuclear Information System (INIS)

    Routbort, J.L.; Rothman, S.J.

    1995-01-01

    Superconducting properties of the cuprate superconductors depend on the oxygen content of the material; the diffusion of oxygen is thus an important process in the fabrication and application of these materials. This article reviews studies of the diffusion of oxygen in La 2-x Sr x CuO 4 , YBa 2 Cu 3 O 7- δ, YBa 2 Cu 4 O 8 , and the Bi 2 Sr 2 Ca n-1 Cu n O 2+4 (n = 1, and 2) superconductors, and attempt to elucidate the atomic mechanisms responsible

  3. Archives: HTS Teologiese Studies / Theological Studies

    African Journals Online (AJOL)

    Items 1 - 50 of 120 ... Archives: HTS Teologiese Studies / Theological Studies. Journal Home > Archives: HTS Teologiese Studies / Theological Studies. Log in or Register to get access to full text downloads.

  4. Flywheel Challenge: HTS Magnetic Bearing

    International Nuclear Information System (INIS)

    Werfel, F N; Floegel-Delor, U; Riedel, T; Rothfeld, R; Wippich, D; Goebel, B

    2006-01-01

    A 200 mm cylindrical engineering prototype high temperature superconducting (HTS) was designed and fabricated. Measurements show that the 17 kg PM rotor can suspend safely 1000 kg in axial direction and 470 kg radially. The rationale for the bearing performance is to stabilize a 400 kg rotor of a new compact 5 kWh/280 kW flywheel energy storage system (COM - FESS). Measurements of the magnetic bearing force, stiffness and drag-torque are presented indicated the successful targeting a milestone in the HTS bearing technology. The influence of the PM configuration and the YBCO temperature on the bearing performance was experimentally studied, providing high-force or high-stiffness behaviour. The axial stiffness 5 kN/mm at 0.5 mm displacement is the highest value of a HTS bearing we know

  5. In situ XANES cell used for the study of lanthanum strontium cuprate deNOx catalysts

    DEFF Research Database (Denmark)

    Hagen, Anke

    2011-01-01

    The potential NOx-reduction electro catalyst lanthanum strontium cuprate has been characterized with an in situ X-ray spectrochemical gas reaction cell. In a series of samples with increasing substitution of trivalent lanthanum by divalent strontium ions, the oxidation state of copper increased......, maintaining charge neutrality, with the concentration of oxygen vacancies likely increasing at substitution ratios larger than Sr/La>0.08. During heating in air, the valence of copper ions in the structure increased. Upon exposure to NO at 500 °C the valence of copper ions in a lanthanum strontium cuprate...

  6. HTS Teologiese Studies / Theological Studies

    African Journals Online (AJOL)

    HTS Teologiese Studies/Theological Studies is an acclaimed Open Access journal with broad coverage that promotes multidisciplinary, religious, and biblical aspects of studies in the international theological arena. The journal's publication criteria are based on high ethical standards and the rigor of the methodology and ...

  7. HTS Insert Magnet Design Study

    CERN Document Server

    Devaux, M; Fleiter, J; Fazilleau, P; Lécrevisse, T; Pes, C; Rey, J-M; Rifflet, J-M; Sorbi, M; Stenvall, A; Tixador, P; Volpini, G

    2011-01-01

    Future accelerator magnets will need to reach higher field in the range of 20 T. This field level is very difficult to reach using only Low Temperature Superconductor materials whereas High Temperature Superconductors (HTS) provide interesting opportunities. High current densities and stress levels are needed to design such magnets. YBCO superconductor indeed carries large current densities under high magnetic field and provides good mechanical properties especially when produced using the IBAD approach. The HFM EUCARD program studies the design and the realization of an HTS insert of 6 T inside a Nb3Sn dipole of 13T at 4.2 K. In the2HTS insert, engineering current densities higher than 250 MA/m under 19 T are required to fulfill the specifications. The stress level is also very severe. YBCO IBAD tapes theoretically meet these challenges from presented measurements. The insert protection is also a critical because HTS materials show low quench propagation velocities and the coupling with the Nb3Sn magnet make...

  8. The color of polarization in cuprate superconductors

    International Nuclear Information System (INIS)

    Hoff, H.A.; Osofsky, M.S.; Lechter, W.L.; Pande, C.S.

    1991-01-01

    A technique for the identification of individual anisotropic grains in a heterogeneous and opaque material involves the observation of grain color in reflected light through crossed polarizers (color of polarization). Such colors are generally characteristic of particular phases. When grains of many members of the class of hole carrier cuprate superconductors are so viewed at room temperature with a 'daylight' source, a characteristic color of polarization is observed. This color was studied in many of these cuprate superconductors and a strong correlation was found between color and the existence of superconductivity. Two members were also examined of the electron cuprate superconductors and it was found that they possess the same color of polarization as the hole carrier cuprate superconductors so far examined. The commonality of the characteristic color regardless of charge carrier indicates that the presence of this color is independent of carrier type. The correlation of this color with the existence of superconductivity in the cuprate superconductors suggests that the origin of the color relates to the origin of superconductivity. Photometric techniques are also discussed

  9. Manganite/Cuprate Superlattice as Artificial Reentrant Spin Glass

    KAUST Repository

    Ding, Junfeng

    2016-05-04

    Emerging physical phenomena at the unit-cell-controlled interfaces of transition-metal oxides have attracted lots of interest because of the rich physics and application opportunities. This work reports a reentrant spin glass behavior with strong magnetic memory effect discovered in oxide heterostructures composed of ultrathin manganite La0.7Sr0.3MnO3 (LSMO) and cuprate La2CuO4 (LCO) layers. These heterostructures are featured with enhanced ferromagnetism before entering the spin glass state: a Curie temperature of 246 K is observed in the superlattice with six-unit-cell LSMO layers, while the reference LSMO film with the same thickness shows much weaker magnetism. Furthermore, an insulator-metal transition emerges at the Curie temperature, and below the freezing temperature the superlattices can be considered as a glassy ferromagnetic insulator. These experimental results are closely related to the interfacial spin reconstruction revealed by the first-principles calculations, and the dependence of the reentrant spin glass behavior on the LSMO layer thickness is in line with the general phase diagram of a spin system derived from the infinite-range SK model. The results of this work underscore the manganite/cuprate superlattices as a versatile platform of creating artificial materials with tailored interfacial spin coupling and physical properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Second-generation HTS conductors

    CERN Document Server

    2010-01-01

    The discovery of high temperature superconductors (HTS) in 1986 by two IBM scientists led to an unprecedented explosion of research and development efforts world-wide because of the significant potential for practical applications offered by these materials. However, the early euphoria created by the exciting prospects was dampened by the daunting task of fabricating these materials into useful forms with acceptable superconducting properties. Progress towards this goal has been hindered by many intrinsic materials problems, such as weak-links, flux-creep, and poor mechanical properties. The above problems led to the development of the Second-Generation of HTS wires. Three methods were invented to produce flexible metallic substrates, which were also crystallographically biaxially textured, and resembled a long, mosaic single crystal. The first method invented is the Ion-Beam-Assisted-Deposition (IBAD). The second method developed was the Inclined-Substrate-Deposition (ISD). The third method invented is calle...

  11. Effect of disorder in cuprates and manganites

    Science.gov (United States)

    Yun, Sung Hee

    2008-07-01

    This dissertation is an inquiry into the characteristics of two representative transition metal oxides, cuprates and manganites. The pairing mechanism of cuprates is not yet fully understood. The origin of the normal state gap (a unique feature of high Tc superconductors) needs to be ruminated in various ways to understand its relation to the superconducting gap. We have performed point contact spectroscopy experiments using junctions between a normal metal (Pt-Rh) and electron-doped Pr2-xCexCuO4 (PCCO) films and single crystals. To probe the normal state at low temperatures (T =1.5 K), the superconductivity was suppressed by applying high magnetic fields (up to 31 T). From this experiment, we could infer that the normal state gap may not be the "pseudogap," instead it originates from the presence of disorder in the complex transition metal oxide. Due to the comparable energies of co-existing phases, manganites exhibit unique dependencies on a variety of external parameters such as light, x-rays, mechanical strain, magnetic field and electric field. These properties not only demonstrate its importance in physics as a strongly correlated system but also mark the potential of this material for practical applications. We studied properties of phase separated hole-doped manganite thin films of (La 1-yPry)0.67Ca0.33MnO3 grown on (110) NdGaO3 substrates using pulsed laser deposition (PLD). First, we found a giant positive magnetoresistance of about 30% at magnetic fields less than 1 T in ultra-thin films (7.5 nm) of (La0.5Pr 0.5)0.67Ca0.33MnO3. Second, we were able to control the magnetic phase with an electric field in the out-of-plane direction using a specially designed nano-fabricated double layered structure with two different compositions of manganite, (La0.4Pr0.6 )0.67Ca0.33MnO3 and La0.67Ca 0.33MnO3. Last, we have studied the effect of strain and disorder on the phase-separated state in thin films of (La1-yPr y)0.67Ca0.33MnO3 (LPCMO, y = 0.4, 0.5, 0.6). Our

  12. Identification and characterization of the heme-binding proteins SeShp and SeHtsA of Streptococcus equi subspecies equi

    Science.gov (United States)

    Nygaard, Tyler K; Liu, Mengyao; McClure, Michael J; Lei, Benfang

    2006-01-01

    Background Heme is a preferred iron source of bacterial pathogens. Streptococcus equi subspecies equi is a bacterial pathogen that causes strangles in horses. Whether S. equi has a heme acquisition transporter is unknown. Results An S. equi genome database was blasted with the heme binding proteins Shp and HtsA of Streptococcus pyogenes, and found that S. equi has the homologue of Shp (designated SeShp) and HtsA (designated SeHtsA). Tag-free recombinant SeShp and SeHtsA and 6xHis-tagged SeHtsA (SeHtsAHis) were prepared and characterized. Purified holoSeShp and holoSeHtsA bind Fe(II)-protoporphyrin IX (heme) and Fe(III)-protoporphyrin IX (hemin) in a 1:1 stoichiometry, respectively, and are designated hemoSeShp and hemiSeHtsA. HemiSeShp and hemiSeHtsAHis can be reconstituted from apoSeShp and apoSeHtsAHis and hemin. HemoSeShp is stable in air and can be oxidized to hemiSeShp by ferricyanide. HemiSeHtsA can be reduced into hemoSeHtsA, which autoxidizes readily. HemoSeShp rapidly transfers its heme to apoSeHtsAHis. In addition, hemoSeShp can also transfer its heme to apoHtsA, and hemoShp is able to donate heme to apoSeHtsAHis. Conclusion The primary structures, optical properties, oxidative stability, and in vitro heme transfer reaction of SeShp and SeHtsA are very similar to those of S. pyogenes Shp and HtsA. The data suggest that the putative cell surface protein SeShp and lipoprotein SeHtsA are part of the machinery to acquire heme in S. equi. The results also imply that the structure, function, and functional mechanism of the heme acquisition machinery are conserved in S. equi and S. pyogenes. PMID:17007644

  13. Identification and characterization of the heme-binding proteins SeShp and SeHtsA of Streptococcus equi subspecies equi

    Directory of Open Access Journals (Sweden)

    McClure Michael J

    2006-09-01

    Full Text Available Abstract Background Heme is a preferred iron source of bacterial pathogens. Streptococcus equi subspecies equi is a bacterial pathogen that causes strangles in horses. Whether S. equi has a heme acquisition transporter is unknown. Results An S. equi genome database was blasted with the heme binding proteins Shp and HtsA of Streptococcus pyogenes, and found that S. equi has the homologue of Shp (designated SeShp and HtsA (designated SeHtsA. Tag-free recombinant SeShp and SeHtsA and 6xHis-tagged SeHtsA (SeHtsAHis were prepared and characterized. Purified holoSeShp and holoSeHtsA bind Fe(II-protoporphyrin IX (heme and Fe(III-protoporphyrin IX (hemin in a 1:1 stoichiometry, respectively, and are designated hemoSeShp and hemiSeHtsA. HemiSeShp and hemiSeHtsAHis can be reconstituted from apoSeShp and apoSeHtsAHis and hemin. HemoSeShp is stable in air and can be oxidized to hemiSeShp by ferricyanide. HemiSeHtsA can be reduced into hemoSeHtsA, which autoxidizes readily. HemoSeShp rapidly transfers its heme to apoSeHtsAHis. In addition, hemoSeShp can also transfer its heme to apoHtsA, and hemoShp is able to donate heme to apoSeHtsAHis. Conclusion The primary structures, optical properties, oxidative stability, and in vitro heme transfer reaction of SeShp and SeHtsA are very similar to those of S. pyogenes Shp and HtsA. The data suggest that the putative cell surface protein SeShp and lipoprotein SeHtsA are part of the machinery to acquire heme in S. equi. The results also imply that the structure, function, and functional mechanism of the heme acquisition machinery are conserved in S. equi and S. pyogenes.

  14. Thermal transport in cuprates, cobaltates, and manganites

    Energy Technology Data Exchange (ETDEWEB)

    Berggold, K.

    2006-09-15

    The subject of this thesis is the investigation of the thermal transport properties of three classes of transition-metal oxides: Cuprates, cobaltates, and manganites. The layered cuprates R{sub 2}CuO{sub 4} with R=La, Pr, Nd, Sm, Eu, and Gd show an anomalous thermal conductivity {kappa}. Two maxima of {kappa} are observed as a function of temperature for a heat current within the CuO{sub 2} planes, whereas for a heat current perpendicular to the CuO{sub 2} planes only a conventional phononic low-temperature maximum of {kappa} is present. Evidence is provided that the high-temperature maximum is caused by heat-carrying excitations on the CuO{sub 2} square lattice. Moreover, it is shown that the complex low-temperature and magnetic-field behavior of {kappa} in Nd{sub 2}CuO{sub 4} is most likely caused by additional phonon scattering rather than by heat-carrying Nd magnons, as it was proposed in the literature. In the cobaltates RCoO{sub 3} with R=La, Pr, Nd, and Eu, a temperature-induced spin-state transition of the Co{sup 3+} ions occurs. It is shown that the additional lattice disorder caused by the random distribution of populated higher spin states causes a large suppression of the thermal conductivity of LaCoO{sub 3} for T>25 K. The effect is much weaker in PrCoO{sub 3} and NdCoO{sub 3} due to the increased spin gap. A quantitative analysis of the responsible mechanisms based on EuCoO{sub 3} as a reference compound is provided. A main result is that the static disorder is sufficient to explain the suppression of {kappa}. No dynamical Jahn-Teller distortion, as proposed in the literature, is necessary to enhance the scattering strength. Below 25 K, k is mainly determined by resonant phonon scattering on paramagnetic impurity levels, e.g. caused by oxygen non-stoichiometry. Such a suppression of the thermal conductivity by resonant scattering processes is e.g. known from Holmium ethylsulfate. This effect is most pronounced in LaCoO{sub 3}, presumably due to

  15. Thermal transport in cuprates, cobaltates, and manganites

    International Nuclear Information System (INIS)

    Berggold, K.

    2006-09-01

    The subject of this thesis is the investigation of the thermal transport properties of three classes of transition-metal oxides: Cuprates, cobaltates, and manganites. The layered cuprates R 2 CuO 4 with R=La, Pr, Nd, Sm, Eu, and Gd show an anomalous thermal conductivity κ. Two maxima of κ are observed as a function of temperature for a heat current within the CuO 2 planes, whereas for a heat current perpendicular to the CuO 2 planes only a conventional phononic low-temperature maximum of κ is present. Evidence is provided that the high-temperature maximum is caused by heat-carrying excitations on the CuO 2 square lattice. Moreover, it is shown that the complex low-temperature and magnetic-field behavior of κ in Nd 2 CuO 4 is most likely caused by additional phonon scattering rather than by heat-carrying Nd magnons, as it was proposed in the literature. In the cobaltates RCoO 3 with R=La, Pr, Nd, and Eu, a temperature-induced spin-state transition of the Co 3+ ions occurs. It is shown that the additional lattice disorder caused by the random distribution of populated higher spin states causes a large suppression of the thermal conductivity of LaCoO 3 for T>25 K. The effect is much weaker in PrCoO 3 and NdCoO 3 due to the increased spin gap. A quantitative analysis of the responsible mechanisms based on EuCoO 3 as a reference compound is provided. A main result is that the static disorder is sufficient to explain the suppression of κ. No dynamical Jahn-Teller distortion, as proposed in the literature, is necessary to enhance the scattering strength. Below 25 K, k is mainly determined by resonant phonon scattering on paramagnetic impurity levels, e.g. caused by oxygen non-stoichiometry. Such a suppression of the thermal conductivity by resonant scattering processes is e.g. known from Holmium ethylsulfate. This effect is most pronounced in LaCoO 3 , presumably due to magnetic polaron formation. In the doped compounds La 1-x Sr x CoO 3 with 0≤x≤0.25, a large

  16. Second-generation HTS conductors

    CERN Document Server

    Goyal, Amit

    2006-01-01

    The discovery of high temperature superconductors (HTS) in 1986 by two IBM scientists led to an unprecedented explosion of research and development efforts world-wide because of the significant potential for practical applications offered by these materials. However, the early euphoria created by the exciting prospects was dampened by the daunting task of fabricating these materials into useful forms with acceptable superconducting properties. Progress towards this goal has been hindered by many intrinsic materials problems, such as weak-links, flux-creep, and poor mechanical properties.

  17. Condensation energy of the superconducting bilayer cuprates

    Indian Academy of Sciences (India)

    In the present work, we report the interplay of single particle and Cooper pair tunnelings on the superconducting state of layered high-c cuprate superconductors. For this we have considered a model Hamiltonian incorporating the intra-planar interactions and the contributions arising due to the coupling between the ...

  18. Condensation energy of the superconducting bilayer cuprates

    Indian Academy of Sciences (India)

    May & June 2002 physics pp. 861–866. Condensation energy of the superconducting bilayer cuprates. GOVIND1, AJAY2 and S K JOSHI1,3,∗. 1Theory Group, National Physical Laboratory, Dr. K.S. ... 2Department of Physics, G.B. Pant University of Agriculture and Technology, ..... [1] B Batlogg, Physics Today 44, 45 (1991).

  19. Terahertz oscillations in mercury cuprate superconductors

    Indian Academy of Sciences (India)

    0–15 K. Furthermore, some thermodynamic and electrodynamics parameters of mercury cuprates have been ... to ILT, electron pairing in the superconducting state makes the transport process along the c-axis to be ... in order to provide the coherent transport mechanism along the c-axis, the Josephson coupling energy,.

  20. Condensation energy of the superconducting bilayer cuprates

    Indian Academy of Sciences (India)

    cuprates also depends on the number of CuO2 layers per unit cell and the extent of doping. In a bilayer or ... unit cell is smaller than the adjacent layers in a single layer system; therefore it is natural to include interlayer .... energy conservation principle, the change in the kinetic energy of the electrons in the out- of-plane ...

  1. Spin dynamics in high-Tc cuprates

    International Nuclear Information System (INIS)

    Fukuyama, H.; Kohno, H.; Normand, B.; Tanamoto, T.

    1995-01-01

    Characteristic features of the spin excitations in high-T c cuprates revealed by neutron scattering and nuclear magnetic resonance experiments are summarised, and analysed on the basis of the slave-boson mean-field theory for the extended t-J model, placing special emphasis on the spin-gap phenomenon. (orig.)

  2. Kinetic energy driven pairing in cuprate superconductors

    NARCIS (Netherlands)

    Maier, TA; Jarrell, M; Macridin, A; Slezak, C

    2004-01-01

    Pairing occurs in conventional superconductors through a reduction of the electronic potential energy accompanied by an increase in kinetic energy. In the underdoped cuprates, optical experiments show that pairing is driven by a reduction of the electronic kinetic energy. Using the dynamical cluster

  3. HTS Teologiese Studies / Theological Studies: Contact

    African Journals Online (AJOL)

    Principal Contact. Andries G. van Aarde Professor Phone: +27 21 975 2602. Fax: +27 86 685 1577. Email: editor@hts.org.za. Support Contact. HTS administrator. Email: Publishing@aosis.co.za. ISSN: 2072-8050. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians · for Authors · FAQ's ...

  4. Analysis and experimental validation of an HTS linear synchronous propulsion prototype with HTS magnetic suspension

    International Nuclear Information System (INIS)

    Jin Jianxun; Zheng Luhai; Guo Youguang; Xu Wei; Zhu Jianguo

    2011-01-01

    An HTS linear synchronous propulsion prototype with an HTSLSM drive is developed. The feasibility of combining an HTSLSM with an HTS magnetic suspension system has been verified. Three different PMGs are studied by ECS method and experiment verification to obtain an optimal one. The prototype has been tested to obtain the performance and thrust characteristics of the HTSLSM. The measurement results benefit the optimal design and control scheme development for an HTSLSM. A high temperature superconducting (HTS) linear propulsion system composed of a single-sided HTS linear synchronous motor (HTSLSM) in its middle and HTS magnetic suspension sub-systems on both sides has been developed. The HTSLSM uses an HTS bulk magnet array on the moving secondary, and the field-trapped characteristics of the HTS bulk using different magnetized methods have been measured and compared to identify their magnetization capability. In order to generate a large levitation force for the system, three different types of permanent magnet guideways (PMGs) have been numerically analyzed and experimentally verified to obtain an optimal PMG. Based on comprehensive experimental prototype tests, the results show that the HTS linear propulsion system can run with stable magnetic suspension having a constant air-gap length, and the thrust characteristics versus the exciting current, working frequency and the air-gap length have also been obtained. This work forms the basis for developing a practical HTS linear propulsion system by using HTS bulks both for propulsion and suspension.

  5. Optimal T$_c$ of cuprates: role of screening and reservoir layers

    OpenAIRE

    Raghu, S.; Thomale, R.; Geballe, T. H.

    2012-01-01

    We explore the role of charge reservoir layers (CRLs) on the superconducting transition temperature of cuprate superconductors. Specifically, we study the effect of CRLs with efficient short distance dielectric screening coupled capacitively to copper oxide metallic layers. We argue that dielectric screening at short distances and at frequencies of the order of the superconducting gap, but small compared to the Fermi energy can significantly enhance T$_c$, the transition temperature of an unc...

  6. Toward (-)-Enterocin: An Improved Cuprate Barbier Protocol To Overcome Strain and Sterical Hindrance.

    Science.gov (United States)

    Rizzo, Antonio; Trauner, Dirk

    2018-03-19

    An approach toward (-)-enterocin, an antibiotic isolated from Streptomyces hygroscopicus, is described. Its compact, heavily oxidized protoadamantane core represents a daunting challenge for an efficient synthesis. Convergent assembly of its 2-oxabicyclo[3.3.1]nonane core with a cuprate-mediated Barbier reaction is disclosed. Its functionalization to a suitable substrate for a biomimetic aldol to close the final ring of the natural product is evaluated.

  7. An Overview of Flux Pumps for HTS Coils

    OpenAIRE

    Coombs, Timothy Arthur; Geng, Jianzhao; Fu, L; Matsuda, K

    2016-01-01

    High-Tc superconducting (HTS) flux pumps are capable of injecting flux into closed HTS magnets without electrical contact. It is becoming a promising alternative of current source in powering HTS coils. This paper reviews the recent progress in flux pumps for HTS coil magnets. Different types of HTS flux pumps are introduced. The physics of these flux pumps are explained and comparisons are made. J. Geng would like to acknowledge Cambridge Trust for offering Cambridge International Scholar...

  8. Excess Oxygen Defects in Layered Cuprates

    Science.gov (United States)

    Lightfoot, P.; Pei, S. Y.; Jorgensen, J. D.; Manthiram, A.; Tang, X. X.; Goodenough, J. B.

    1990-09-01

    Neutron powder diffraction has been used to study the oxygen defect chemistry of two non-superconducting layered cuprates, La{sub 1. 25}Dy{sub 0.75}Cu{sub 3.75}F{sub 0.5}, having a T{sup {asterisk}}- related structure, and La{sub 1.85}Sr{sub 1.15}Cu{sub 2}O{sub 6.25}, having a structure related to that of the newly discovered double-layer superconductor La{sub 2-x}Sr{sub x}CaCu{sub 2}O{sub 6}. The role played by oxygen defects in determining the superconducting properties of layered cuprates is discussed.

  9. Tl Cuprate Superconductors Studied by XPS

    Energy Technology Data Exchange (ETDEWEB)

    Vasquez, R. P. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099 (United States); Siegal, M. P. [Sandia National Laboratories, Albuquerque, NM 87185-1421 (United States); Overmyer, D. L. [Sandia National Laboratories, Albuquerque, NM 87185-1421 (United States); Ren, Z. F. [Department of Chemistry, State University of New York, Buffalo, NY 14260-3000 (United States); Lao, J. Y. [Department of Chemistry, State University of New York, Buffalo, NY 14260-3000 (United States); Wang, J. H. [Department of Chemistry, State University of New York, Buffalo, NY 14260-3000 (United States)

    1999-07-01

    XPS measurements on epitaxial thin films of the Tl cuprate superconductors Tl2Ba2CaCu2O8, Tl2Ba2Ca2Cu3O10, and Tl0.78Bi0.22Ba0.4Sr1.6Ca2Cu3O9-{delta} are presented. These data, together with previous measurements in this lab on Tl2Ba2CuO6-{delta} and TlBa2CaCu2O7-{delta}, comprise a comprehensive data set for comparison of Tl cuprates in which the number of Tl-O and Cu-O layers, and hence the chemical and electronic properties, vary. (c) 2000 American Vacuum Society.

  10. Tl Cuprate Superconductors Studied by XPS

    International Nuclear Information System (INIS)

    Vasquez, R. P.; Siegal, M. P.; Overmyer, D. L.; Ren, Z. F.; Lao, J. Y.; Wang, J. H.

    1999-01-01

    XPS measurements on epitaxial thin films of the Tl cuprate superconductors Tl2Ba2CaCu2O8, Tl2Ba2Ca2Cu3O10, and Tl0.78Bi0.22Ba0.4Sr1.6Ca2Cu3O9-δ are presented. These data, together with previous measurements in this lab on Tl2Ba2CuO6-δ and TlBa2CaCu2O7-δ, comprise a comprehensive data set for comparison of Tl cuprates in which the number of Tl-O and Cu-O layers, and hence the chemical and electronic properties, vary. (c) 2000 American Vacuum Society

  11. Quench-Protection Strategies for HTS Superconductors

    National Research Council Canada - National Science Library

    Lawless, William N

    2005-01-01

    Assessments are made of four distinct strategies for the quench protection of HTS coils near 77 K - diamond-film insulation, cryovaristor current shunt, loaded Formvar insulation, and a sputtered ceramic insulation...

  12. Development of HTS Magnet for Rotating Gantry

    Science.gov (United States)

    Tasaki, Kenji; Koyanagi, Kei; Takayama, S. Shigeki; Ishii, Yusuke; Kurusu, Tsutomu; Amemiya, Naoyuki; Ogitsu, Toru; iwata, Yoshiyuki; Noda, Koji

    The effectiveness of heavy-ion radiotherapy for cancer treatment has been recognized by medical experts and the public. However, due to the large size of the equipment, this therapy has not been widely adopted. In particular, the rotating gantries used to irradiate patients with the heavy-ion beams from any direction may be as heavy as 600 tons in our estimation. By employing high-temperature superconducting (HTS) wires in these rotating gantries and increasing the magnetic field generated by the deflecting coils, the total weight of the rotating gantry can be reduced to around the weight of those used for proton radiotherapy. A project for developing an HTS deflecting magnet for heavy-ion radiotherapy has been underway since 2013, supported by the Japanese Ministry of Economy, Trade and Industry (METI) and the Japan Agency for Medical Research and Development (AMED). The aim of this project is to develop fundamental technologies for designing and fabricating HTS deflecting magnets, such as irregular magnetic field estimating techniques, design technology for HTS magnets, high-precision HTS coil winding technology, AC loss estimating techniques, and thermal runaway estimating techniques and to fabricate a small model of an HTS deflecting magnet and evaluate its performance. In this paper, the project's progress will be described.

  13. Theoretical study of magnetoelectric effects in noncentrosymmetric and cuprate superconductors

    Science.gov (United States)

    Kashyap, Manoj K.

    analytical and numerical solutions of the Ginzburg-Landau equations that reveal the spatial structure of this current as well as the associated component of the magnetic field for both a single vortex and in the vortex lattice phase near the upper critical field. The discovery of superconductivity in lanthanum barium copper oxide (LBCO) in 1986, was followed by yttrium barium copper oxide (YBCO) in 1987, commencing the era of high temperature superconductivity. The astonishingly rich phase diagram of cuprates includes the pseudogap phase which was earlier thought to be a precursor to superconductivity. Now signatures of broken symmetries have been seen, indicating a true phase transition. Pair density wave (PDW) order has earlier been proposed to account for superconducting correlations and charge density wave (CDW) order in pseudogap phase. There is evidence that the pseudogap phase in the cuprates also breaks time-reversal symmetry. Here we show that pair density wave (PDW) states give rise to a translational invariant nonsuperconducting order parameter that breaks time-reversal and parity symmetries, but preserves their product. This secondary order parameter has a different origin, but shares the same symmetry properties as a magnetoelectric loop current order that has been proposed earlier in the context of the cuprates to explain the appearance of intracell magnetic order. We further show that, due to fluctuations, this secondary loop current order, which breaks only discrete symmetries, can preempt PDW order, which breaks both continuous and discrete symmetries. In such a phase, the emergent loop current order coexists with spatial short-range superconducting order and possibly short-range charge density wave (CDW) order. Finally, we propose a PDW phase that accounts for intracell magnetic order and the polar Kerr effect, has CDW order consistent with x-ray scattering and nuclear magnetic resonance observations, and quasiparticle (QP) properties consistent with angle

  14. HTS Wire Development Workshop: Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    1994-07-01

    The 1994 High-Temperature Superconducting Wire Development Workshop was held on February 16--17 at the St. Petersburg Hilton and Towers in St. Petersburg, Florida. The meeting was hosted by Florida Power Corporation and sponsored by the US Department of Energy`s Superconductivity Program for Electric Power Systems. The meeting focused on recent high-temperature superconducting wire development activities in the Department of Energy`s Superconductivity Systems program. The meeting opened with a general discussion on the needs and benefits of superconductivity from a utility perspective, the US global competitiveness position, and an outlook on the overall prospects of wire development. The meeting then focused on four important technology areas: Wire characterization: issues and needs; technology for overcoming barriers: weak links and flux pinning; manufacturing issues for long wire lengths; and physical properties of HTS coils. Following in-depth presentations, working groups were formed in each technology area to discuss the most important current research and development issues. The working groups identified research areas that have the potential for greatly enhancing the wire development effort. These areas are discussed in the summary reports from each of the working groups. This document is a compilation of the workshop proceedings including all general session presentations and summary reports from the working groups.

  15. Chasing the cuprates with dilatonic dyons

    Energy Technology Data Exchange (ETDEWEB)

    Amoretti, Andrea [Department of Applied Mathematics and Theoretical Physics, University of Cambridge,Cambridge, CB3 OWA (United Kingdom); Baggioli, Matteo [Institut de Física d’Altes Energies (IFAE), Universitat Autònoma de Barcelona,The Barcelona Institute of Science and Technology,Campus UAB, 08193 Bellaterra (Barcelona) (Spain); Magnoli, Nicodemo [Dipartimento di Fisica, Università di Genova, and I.N.F.N. - Sezione di Genova,via Dodecaneso 33, I-16146, Genova (Italy); Musso, Daniele [Abdus Salam International Centre for Theoretical Physics (ICTP),Strada Costiera 11, I-34151 Trieste (Italy)

    2016-06-20

    Magnetic field and momentum dissipation are key ingredients in describing condensed matter systems. We include them in gauge/gravity and systematically explore the bottom-up panorama of holographic IR effective field theories based on bulk Einstein-Maxwell Lagrangians plus scalars. The class of solutions here examined appears insufficient to capture the phenomenology of charge transport in the cuprates. We analyze in particular the temperature scaling of the resistivity and of the Hall angle. Keeping an open attitude, we illustrate weak and strong points of the approach.

  16. Probing optically silent superfluid stripes in cuprates

    Science.gov (United States)

    Rajasekaran, S.; Okamoto, J.; Mathey, L.; Fechner, M.; Thampy, V.; Gu, G. D.; Cavalleri, A.

    2018-02-01

    In many theoretical models of high-temperature superconductors, remnants of superconductivity persist to temperatures higher than the transition temperature, TC. Rajasekaran et al. used nonlinear terahertz spectroscopy to probe this region of the phase diagram of a cuprate superconductor that is well known for a stripe phase that appears for certain doping levels (see the Perspective by Ergeçen and Gedik). For a sample deep in the stripe phase, a large nonlinear signal persisted from the superconducting region up to temperatures much higher than TC. The findings suggest the formation of a peculiar spatially modulated superconducting state called the pair-density wave.

  17. Pairing correlations in electron-doped cuprates

    Science.gov (United States)

    Aligia, A. A.; Arrachea, Liliana

    2001-12-01

    We calculate on-site s, extended s and dx2-y2 pairing correlation functions in a generalized Hubbard model for the cuprates, for parameters appropriate for electron-doped systems, using numerical diagonalization of a 4×4 cluster. We find indications of d-wave superconductivity for small doping (~0.1 electrons per unit cell) and s-wave superconductivity for overdoped systems (~0.5 electrons per unit cell) or small U. The magnitude of the pairing correlation functions and the vertex contributions to them are in general much smaller than in the hole-doped case. We also present results for the spin-structure factor.

  18. Inverse correlation between quasiparticle mass and T c in a cuprate high-T c superconductor.

    Science.gov (United States)

    Putzke, Carsten; Malone, Liam; Badoux, Sven; Vignolle, Baptiste; Vignolles, David; Tabis, Wojciech; Walmsley, Philip; Bird, Matthew; Hussey, Nigel E; Proust, Cyril; Carrington, Antony

    2016-03-01

    Close to a zero-temperature transition between ordered and disordered electronic phases, quantum fluctuations can lead to a strong enhancement of electron mass and to the emergence of competing phases such as superconductivity. A correlation between the existence of such a quantum phase transition and superconductivity is quite well established in some heavy fermion and iron-based superconductors, and there have been suggestions that high-temperature superconductivity in copper-oxide materials (cuprates) may also be driven by the same mechanism. Close to optimal doping, where the superconducting transition temperature T c is maximal in cuprates, two different phases are known to compete with superconductivity: a poorly understood pseudogap phase and a charge-ordered phase. Recent experiments have shown a strong increase in quasiparticle mass m* in the cuprate YBa2Cu3O7-δ as optimal doping is approached, suggesting that quantum fluctuations of the charge-ordered phase may be responsible for the high-T c superconductivity. We have tested the robustness of this correlation between m* and T c by performing quantum oscillation studies on the stoichiometric compound YBa2Cu4O8 under hydrostatic pressure. In contrast to the results for YBa2Cu3O7-δ, we find that in YBa2Cu4O8, the mass decreases as T c increases under pressure. This inverse correlation between m* and T c suggests that quantum fluctuations of the charge order enhance m* but do not enhance T c.

  19. Microwave properties of HTS films

    International Nuclear Information System (INIS)

    Cooke, D.W.; Arendt, P.M.; Grey, E.R.; Muenchausen, R.E.; Bennett, B.L.; Foltyn, S.R.; Estler, R.C.; Wu, X.D.; Reeves, G.A.; Elliott, N.E.; Brown, D.R.; Portis, A.M.; Taber, R.C.; Mogrocampero, A.

    1990-01-01

    High-frequency applications of high- temperature superconductors generally fall into two categories: 1) devices that require low values (relative to Cu) of surface resistance R S in ambient surface magnetic fields H rf ; and 2) devices that require low R S in modest fields (H rf ∼ 250 Oe). Moreover, many applications can be realized with small- surface-area films (∼ 1 cm 2 ) whereas others require larger areas - radiofrequency (rf) cavities, for example. Regardless of the application, the potential of HTS films is predicted on satisfying one or both of the above-stated requirements. The authors have measured the surface resistance of small-area (1 cm 2 ) and large-area (6.5 cm 2 ) YBa 2 Cu 3 O 7 (YBCO) films that have been laser ablated onto LaA ell O 3 substrates, large-area (5.1 cm 2 YBCO films that have been e-beam deposited onto LaA ell O 3 , and large-area (11.4 cm 2 ) T ell-based films that have been magnetron sputtered onto metallic substrates. The best R S values are obtained from the 1-cm 2 laser-ablated films; they are 40 μΩ and 340 μΩ at 4 K And 77 K, respectively (ω/2π = 10 GHz). Comparable values for Cu are 6 and 13 mΩ, respectively. Large-area T ell-based films yield typical R S values of 4 mΩ and 14 mΩ at 4 K and 77 K, respectively (ω/2π = 18 GHz). The dependence of R S on H rf for these films indicates that surface fields as large as 55 Oe can be achieved with R S increasing only by a factor of 10. This field dependence is associated with c-axis texturing

  20. US effort on HTS power transformers

    Science.gov (United States)

    Mehta, S.

    2011-11-01

    Waukesha Electric Systems has been working in HTS power transformers development program under the auspices of US Government Department of Energy since 1994. This presentation will describe various milestones for this program and program history along with the lessons learned along the way. Our motivations for working on this development program based on man benefits offered by HTS power transformers to power delivery systems will be discussed. Based on various issues encountered during execution of many HTS projects, DOE has set up an independent program review process that is lead by team of experts. This team reviews are integral part of all DOE HTS projects. Success of all projects would be greatly enhanced by identifying critical issues early in the program. Requiring appropriate actions to mitigate the issues before processing further will lead to proactive interrogation and incorporation of expert's ideas in the project plans. Working of this review process will be also described in this presentation. Waukesha Electric Systems team including: Superpower-Inc, Oak Ridge National Laboratory, University of Houston Center for Superconductivity and Southern California Edison company was awarded a cost share grant by US Government in 2010 for development of a fault current limiting HTS power transformer. This multi year's program will require design, manufacture, installation, and monitoring of a 28 MVA tree phase transformer installed at Irvine CA. Smart Grid demonstration site. Transformer specifications along with requirements for fault current limiting and site requirement will be discussed. Design and development of various sub systems in support of this program including: HTS conductor performance specification, Dielectric system design approach, Dewar development for containing phase assemblies, cryo-cooling system design approach, etc. will be described. Finally; overall program schedule, critical milestone events, test plans and progress to date will be

  1. Crucial role of internal collective modes in underdoped cuprates

    Science.gov (United States)

    Mallik, A. V.; Yadav, U. K.; Medhi, A.; Krishnamurthy, H. R.; Shenoy, V. B.

    2017-07-01

    The enigmatic cuprate superconductors have attracted resurgent interest with several recent reports and discussions of competing orders in the underdoped side. Motivated by this, here we address the natural question of fragility of the d-wave superconducting state in underdoped cuprates. Using a combination of theoretical approaches we study t\\text-J –like models, and discover an —as yet unexplored— instability that is brought about by an “internal” (anti-symmetric mode) fluctuation of the d-wave state. This new theoretical result is in good agreement with recent STM and ARPES studies of cuprates. We also suggest experimental directions to uncover this physics.

  2. Isotropic round-wire multifilament cuprate superconductor for generation of magnetic fields above 30 T

    CERN Document Server

    Larbalestier, D C; Trociewitz, U P; Kametani, F; Scheuerlein, C; Dalban-Canassy, M; Matras, M; Chen, P; Craig, N C; Lee, P J; Hellstrom, E E

    2014-01-01

    Magnets are the principal market for superconductors, but making attractive conductors out of the high-temperature cuprate superconductors (HTSs) has proved difficult because of the presence of high-angle grain boundaries that are generally believed to lower the critical current density, J$_c$. To minimize such grain boundary obstacles, HTS conductors such as REBa$_2$Cu$_3$O$_{7−x}$ and (Bi, Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10−x}$ are both made as tapes with a high aspect ratio and a large superconducting anisotropy. Here we report that Bi$_2$2Sr$_2$CaCu$_2$O$_{8−x}$ (Bi-2212) can be made in the much more desirable isotropic, round-wire, multifilament form that can be wound or cabled into arbitrary geometries and will be especially valuable for high-field NMR magnets beyond the present 1 GHz proton resonance limit of Nb$_3$Sn technology. An appealing attribute of this Bi-2212 conductor is that, being without macroscopic texture, it contains many high-angle grain boundaries but nevertheless attains a very hi...

  3. Preparation of Bismuth- and Thallium-Based Cuprate Superconductors

    Science.gov (United States)

    1991-10-01

    erage work period (29); early symptoms of thallium - poisoning include hair loss. Safety considerations in handling thallium compounds should include... Thallium -Based Cuprate Superconductors by S. A. Sunshine and T. A. Vanderah Chemistry Division, Research Department Naval Weapons Center, China Lake, CA...Technical Report #2 10/90-9/91 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS Preparation of Bismuth- and Thallium -Based Cuprate Suoerconductors NOOO14-91 WX

  4. Evidence of magnetic mechanism for cuprate superconductivity

    Science.gov (United States)

    Keren, Amit

    2009-06-01

    A proper understanding of the mechanism for cuprate superconductivity can emerge only by comparing materials in which physical parameters vary one at a time. Here, we present a variety of bulk, resonance and scattering measurements on the (CaxLa1-x) (Ba1.75-xLa0.25+x) Cu3Oy high temperature superconductors, in which this can be done. We determine the superconducting, Néel, glass and pseudopage critical temperatures. In addition, we clarify which physical parameter varies, and, equally important, which does not, with each chemical modification. This allows us to demonstrate that a single energy scale, set by the superexchange interaction J, controls all the critical temperatures of the system. J, in turn, is determined by the in plane Cu-O-Cu buckling angle.

  5. Structural modeling of HTS tapes and cables

    Science.gov (United States)

    Allen, N. C.; Chiesa, L.; Takayasu, M.

    2016-12-01

    Structural finite element analysis (FEA) has been used as an insightful tool to investigate the electromechanical behavior of HTS REBCO tapes and twisted stacked-tape cables under tension, torsion, bending and combined loads. A novel technique was developed for modeling the layered composite structure of the 2G tapes with structural solid-shell elements in ANSYS®. The FEA models produced detailed strain information for the REBCO superconducting layer which was then paired with an analytical model to predict the critical current performance of the 2G HTS tapes under various loads. Two commercially available HTS tapes (SuperPower and SuNAM) under tension, torsion and combined tension-torsion were first analyzed with FEA and compared with available experimental results at 77 K. A sharp critical current degradation was experienced at the yield strength of the tapes under tension and below a 100 mm twist-pitch under torsion. Combined tension-torsion loads had a more gradual degradation of critical current for twist-pitches of 115 mm or shorter but had a negligible difference compared to pure tension for longer twist-pitches. Using the structural solid-shell technique for modeling 2G tapes in ANSYS®, an FEA methodology for simulating full scale three-dimensional HTS stacked-tape cables under pure bending was created. A model of a Twisted-Stacked Tape Cable (TSTC), a configuration first proposed at MIT, was initially developed and then adapted to the slotted-core HTS Cable-In-Conduit Conductor produced by the ENEA laboratory in Italy. The numerical axial strain of the HTS REBCO tapes within the cables as calculated by FEA were found to agree with an analytical model for two cases: perfect-slip (frictionless) and no-slip (bonded). The ENEA CICC model was also compared with recent experimental critical current data at 77 K and was found to match best using a low friction coefficient of 0.02 indicating that the tapes within the cable freely slide with respect to each other

  6. Metal–insulator crossover in high Tc cuprates: A gauge field approach

    Indian Academy of Sciences (India)

    plane resistivity of underdoped cuprates and a range of superconducting cuprates in the presence of a strong magnetic field suppressing superconductivity. We propose an explanation for this phenomenon based on a gauge field theory approach ...

  7. Progress in development of high capacity magnetic HTS bearings

    International Nuclear Information System (INIS)

    Kummeth, P.; Nick, W.; Neumueller, H.-W.

    2005-01-01

    HTS magnetic bearings are inherently stable without an active feedback system. They provide low frictional losses, no wear and allow operation at high rotational speed without lubrication. So they are very promising for use in motors, generators and turbines. We designed and constructed an HTS radial bearing for use with a 400 kW HTS motor. It consists of alternating axially magnetized permanent magnet rings on the rotor and a segmented YBCO stator. Stator cooling is performed by liquid nitrogen, the temperature of the stator can be adjusted by varying the pressure in the cryogenic vessel. At 68 K maximum radial forces of more than 3.7 kN were found. These results range within the highest radial bearing capacities reported worldwide. The encouraging results lead us to develop a large heavy load HTS radial bearing. Currently a high magnetic gradient HTS bearing for a 4 MVA synchronous HTS generator is under construction

  8. Fully filamentized HTS coated conductor via striation and selective electroplating

    Energy Technology Data Exchange (ETDEWEB)

    Kesgin, Ibrahim; Majkic, Goran [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204 (United States); Selvamanickam, Venkat, E-mail: selva@uh.edu [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204 (United States)

    2013-03-15

    Highlights: ► Fully-filamentized coated conductor with 13-fold reduction in ac losses. ► Selective electroplating for filamentization of thick copper stabilizer. ► A twofold decrease in ac loss by filamentization of copper stabilizer. ► Absence of appreciable coupling loss contribution from electroplating. -- Abstract: A simple, cost-effective method involving top-down mechanical scribing, oxidation and bottom-up electroplating has been successfully developed to fabricate fully filamentized HTS coated conductors. The copper stabilizer layer is selectively electroplated on the superconducting filaments while the striations remain copper-free due to the formation of a resistive oxide layer in between filaments by oxidation of the striated grooves at elevated temperature in oxygen atmosphere. Magnetization AC loss measurements, performed in a frequency range of 45–500 Hz at 77 K, confirmed the expected N-fold reduction in AC loss of the filamentized tapes with no significant degradation in critical current beyond that due to the material removal from the striations (N – number of filaments). A considerable reduction in coupling AC loss was observed after high temperature annealing/oxidation of the striated tapes. Furthermore, a significant reduction in eddy current loss was achieved with selective copper electroplating, as evidenced by analyzing the field and frequency dependence of magnetization AC loss, as well as by comparing the AC loss performance of striated samples to that of non-striated samples after electroplating of copper stabilizer.

  9. Fully filamentized HTS coated conductor via striation and selective electroplating

    International Nuclear Information System (INIS)

    Kesgin, Ibrahim; Majkic, Goran; Selvamanickam, Venkat

    2013-01-01

    Highlights: ► Fully-filamentized coated conductor with 13-fold reduction in ac losses. ► Selective electroplating for filamentization of thick copper stabilizer. ► A twofold decrease in ac loss by filamentization of copper stabilizer. ► Absence of appreciable coupling loss contribution from electroplating. -- Abstract: A simple, cost-effective method involving top-down mechanical scribing, oxidation and bottom-up electroplating has been successfully developed to fabricate fully filamentized HTS coated conductors. The copper stabilizer layer is selectively electroplated on the superconducting filaments while the striations remain copper-free due to the formation of a resistive oxide layer in between filaments by oxidation of the striated grooves at elevated temperature in oxygen atmosphere. Magnetization AC loss measurements, performed in a frequency range of 45–500 Hz at 77 K, confirmed the expected N-fold reduction in AC loss of the filamentized tapes with no significant degradation in critical current beyond that due to the material removal from the striations (N – number of filaments). A considerable reduction in coupling AC loss was observed after high temperature annealing/oxidation of the striated tapes. Furthermore, a significant reduction in eddy current loss was achieved with selective copper electroplating, as evidenced by analyzing the field and frequency dependence of magnetization AC loss, as well as by comparing the AC loss performance of striated samples to that of non-striated samples after electroplating of copper stabilizer

  10. HTS axial flux induction motor with analytic and FEA modeling

    International Nuclear Information System (INIS)

    Li, S.; Fan, Y.; Fang, J.; Qin, W.; Lv, G.; Li, J.H.

    2013-01-01

    Highlights: •A high temperature superconductor axial flux induction motor and a novel maglev scheme are presented. •Analytic method and finite element method have been adopted to model the motor and to calculate the force. •Magnetic field distribution in HTS coil is calculated by analytic method. •An effective method to improve the critical current of HTS coil is presented. •AC losses of HTS coils in the HTS axial flux induction motor are estimated and tested. -- Abstract: This paper presents a high-temperature superconductor (HTS) axial-flux induction motor, which can output levitation force and torque simultaneously. In order to analyze the character of the force, analytic method and finite element method are adopted to model the motor. To make sure the HTS can carry sufficiently large current and work well, the magnetic field distribution in HTS coil is calculated. An effective method to improve the critical current of HTS coil is presented. Then, AC losses in HTS windings in the motor are estimated and tested

  11. Chemical bonding in Tl cuprates studied by x-ray photoemission

    International Nuclear Information System (INIS)

    Vasquez, R.P.; Siegal, M.P.; Overmyer, D.L.; Ren, Z.F.; Lao, J.Y.; Wang, J.H.

    1999-01-01

    Epitaxial thin films of the Tl cuprate superconductors Tl 2 Ba 2 CaCu 2 O 8 , Tl 2 Ba 2 Ca 2 Cu 3 O 10 , and Tl 0.78 Bi 0.22 Ba 0.4 Sr 1.6 Ca 2 Cu 3 O 9-δ are studied with x-ray photoemission spectroscopy. These data, together with previous measurements in this lab of Tl 2 Ba 2 CuO 6+δ and TlBa 2 CaCu 2 O 7-δ , comprise a comprehensive data set for a comparative study of Tl cuprates with a range of chemical and electronic properties. In the Cu 2p spectra, a larger energy separation between the satellite and main peaks (E s -E m ) and a lower intensity ratio (I s /I m ) are found to correlate with higher values of T c . Analysis of these spectra within a simple configuration interaction model suggests that higher values of T c are related to low values of the O 2p→Cu 3d charge transfer energy. In the O 1s region, a smaller bond length between Ba and Cu-O planar oxygen is found to correlate with a lower binding energy for the signal associated with Cu-O bonding, most likely resulting from the increased polarization screening by Ba 2+ ions. For samples near optimum doping, maximum T c is observed to occur when the Tl 4f 7/2 binding energy is near 117.9 eV, which is near the middle of the range of values observed for Tl cuprates. Higher Tl 4f 7/2 binding energies, corresponding to formal oxidation states nearer Tl 1+ , are also found to correlate with longer bond lengths between Ba and Tl-O planar oxygen, and with higher binding energies of the O 1s signal associated with Tl-O bonding. copyright 1999 The American Physical Society

  12. What is strange about high-temperature superconductivity in cuprates?

    Science.gov (United States)

    Božović, I.; He, X.; Wu, J.; Bollinger, A. T.

    2017-10-01

    Cuprate superconductors exhibit many features, but the ultimate question is why the critical temperature (Tc) is so high. The fundamental dichotomy is between the weak-pairing, Bardeen-Cooper-Schrieffer (BCS) scenario, and Bose-Einstein condensation (BEC) of strongly-bound pairs. While for underdoped cuprates it is hotly debated which of these pictures is appropriate, it is commonly believed that on the overdoped side strongly-correlated fermion physics evolves smoothly into the conventional BCS behavior. Here, we test this dogma by studying the dependence of key superconducting parameters on doping, temperature, and external fields, in thousands of cuprate samples. The findings do not conform to BCS predictions anywhere in the phase diagram.

  13. Study on Thrust Improvement and Ripple Suppression of HTS Linear Switched Reluctance Motor with Coreless HTS Excitation Windings

    Science.gov (United States)

    Oto, Satoshi; Hirayama, Tadashi; Kawabata, Shuma

    This paper describes a linear switched reluctance motor (LSRM) in which HTS tapes are used for coreless excitation windings in order to reduce the thrust ripple and normal force. This LSRM consists of a mover with saliency structure, coreless HTS coils and a stator back yoke. In this paper, we first describe the operating principle of the HTS-LSRM. Next, we calculate performances of the HTS-LSRM using 3-D FEM analysis. The effects of the motor structure on the thrust characteristic and normal force characteristics are clarified from the numerical results. Furthermore, we investigate the motor structure for thrust improvement, thrust ripple and normal force reduction.

  14. Spin dynamics in high-TC superconducting cuprates

    International Nuclear Information System (INIS)

    Bourges, Ph.

    2003-07-01

    This work is dedicated to the detailed investigations of the magnetic resonance peak in the superconducting state of cuprates. The existence of such a peak could be the signature of a mechanism linked to magnetism that could explain high critical temperature superconductivity. Inelastic neutron scattering is an adequate tool for the understanding of cuprate properties because it reveals magnetic fluctuations whose behaviour and variety depend strongly on temperature and on the level of doping. The last part of this work is dedicated to the study of spin dynamics in YBa 2 Cu 3 O 6+x system

  15. A compact 3 T all HTS cryogen-free MRI system

    Science.gov (United States)

    Parkinson, B. J.; Bouloukakis, K.; Slade, R. A.

    2017-12-01

    We have designed and built a passively shielded, cryogen-free 3 T 160 mm bore bismuth strontium calcium copper oxide HTS magnet with shielded gradient coils suitable for use in small animal imaging applications. The magnet is cooled to approximately 16 K using a two-stage cryocooler and is operated at 200 A. The magnet has been passively shimmed so as to achieve ±10 parts per million (ppm) homogeneity over a 60 mm diameter imaging volume. We have demonstrated that B 0 temporal stability is fit-for-purpose despite the magnet operating in the driven mode. The system has produced good quality spin-echo and gradient echo images. This compact HTS-MRI system is emerging as a true alternative to conventional low temperature superconductor based cryogen-free MRI systems, with much more efficient cryogenics since it operates entirely from a single phase alternating current electrical supply.

  16. Low Friction Cryostat for HTS Power Cable of Dutch Project

    NARCIS (Netherlands)

    Chevtchenko, O.; Zuijderduin, R.; Smit, J.; Willen, D.; Lentge, H.; Thidemann, C.; Traeholt, C.

    2012-01-01

    Particulars of 6 km long HTS AC power cable for Amsterdam project are: a cable has to fit in an annulus of 160 mm, with only two cooling stations at the cable ends [1]. Application of existing solutions for HTS cables would result in excessively high coolant pressure drop in the cable, possibly

  17. Low Friction Cryostat for HTS Power Cable of Dutch Project

    DEFF Research Database (Denmark)

    Chevtchenko, Oleg; Zuijderduin, Roy; Smit, Johan

    2012-01-01

    Particulars of 6km long HTS AC power cable for Amsterdam project are: a cable has to fit in an annulus of 160mm, with only two cooling stations at the cable ends [1]. Application of existing solutions for HTS cables would result in excessively high coolant pressure drop in the cable, possibly aff...

  18. Bulk superconductivity at 84 K in the strongly overdoped regime of cuprates

    Science.gov (United States)

    Gauzzi, A.; Klein, Y.; Nisula, M.; Karppinen, M.; Biswas, P. K.; Saadaoui, H.; Morenzoni, E.; Manuel, P.; Khalyavin, D.; Marezio, M.; Geballe, T. H.

    2016-11-01

    By means of magnetization, specific heat, and muon-spin relaxation measurements, we investigate newly synthesized high-pressure oxidized Cu0.75Mo0.25Sr2YCu2O7.54 , in which overdoping is achieved up to p ˜0.46 hole/Cu, well beyond the Tc-p superconducting dome of cuprates, where Fermi-liquid behavior is expected. Surprisingly, we find bulk superconductivity with Tc=84 K and superfluid density similar to those of optimally doped YBa2Cu3O7 -δ . On the other hand, specific heat data display a large electronic contribution at low temperature, comparable to that of nonsuperconducting overdoped La2 -xSrxCuO4 . These results point at an unusual high-Tc phase with a large fraction of unpaired holes. Further experiments may assess the Fermi-liquid properties of the present phase, which would put into question the paradigm that the high Tc of cuprates originates from a non-Fermi-liquid ground state.

  19. Development of a highly sensitive current and position monitor with HTS squids and an HTS magnetic shield

    International Nuclear Information System (INIS)

    Watanabe, T.; Ikeda, T.; Kase, M.; Yano, Y.; Watanabe, S.; Sasaki, Y.; Kawaguchi, T.

    2005-01-01

    A highly sensitive current and position monitor with HTS (High-Temperature Superconducting) SQUIDs (Superconducting QUantum Interference Device) and an HTS magnetic shield for the measurement of the intensity of faint beams, such as a radioisotope beam, has been developed for the RIKEN RI beam factory project. The HTS magnetic shield and the HTS current sensor including the HTS SQUID are cooled by a low-vibration pulse-tube refrigerator. Both the HTS magnetic shield and the HTS current sensor were fabricated by dip-coating a thin Bi 2 -Sr 2 -Ca 2 -Cu 3 -O x (Bi-2223) layer on 99.9% MgO ceramic substrates. The HTS technology enables us to develop a system equipped with a downsized and highly sensitive current monitor. Recently, a prototype system was completed and installed in the beam transport line of the RIKEN Ring Cyclotron to measure the DC-current of high-energy heavy-ion beams. As a result, we succeeded in measuring the intensity of the 600 nA 40 Ar 17+ beam (95 MeV/u). We describe the present status of the monitor system and the results of the beam measurements. (author)

  20. Levitation characteristics of HTS tape stacks

    Energy Technology Data Exchange (ETDEWEB)

    Pokrovskiy, S. V.; Ermolaev, Y. S.; Rudnev, I. A. [National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow (Russian Federation)

    2015-03-15

    Due to the considerable development of the technology of second generation high-temperature superconductors and a significant improvement in their mechanical and transport properties in the last few years it is possible to use HTS tapes in the magnetic levitation systems. The advantages of tapes on a metal substrate as compared with bulk YBCO material primarily in the strength, and the possibility of optimizing the convenience of manufacturing elements of levitation systems. In the present report presents the results of the magnetic levitation force measurements between the stack of HTS tapes containing of tapes and NdFeB permanent magnet in the FC and ZFC regimes. It was found a non- linear dependence of the levitation force from the height of the array of stack in both modes: linear growth at small thickness gives way to flattening and constant at large number of tapes in the stack. Established that the levitation force of stacks comparable to that of bulk samples. The numerical calculations using finite element method showed that without the screening of the applied field the levitation force of the bulk superconductor and the layered superconductor stack with a critical current of tapes increased by the filling factor is exactly the same, and taking into account the screening force slightly different.

  1. EXACT DIAGONALIZATION RESULTS FOR MULTIMAGNON IR ABSORPTION IN THE CUPRATES

    NARCIS (Netherlands)

    Lorenzana, J.; Eder, R; Meinders, M.B J; Sawatzky, G.A

    1995-01-01

    Recent measured bands in the mid IR of parent insulating compounds of cuprate superconductors [Perkins et al. Phys. Rev. Lett. 71 1621 (1993)] are interpreted as multimagnon infrared (IR) absorption assisted by phonons. We present results for the coupling constant of light with this excitations and

  2. Modeling of Hts Applications Using Emtp with Flux-Pinning Scaling Models for Practical Hts Superconductors

    Science.gov (United States)

    Cave, J. R.; Sood, V. K.

    2008-03-01

    The EMTP software (Electromagnetic Transient Program) for modeling the behavior of electric power systems is commonly used to obtain the transient response of system disturbances, for example caused by fault currents. We have developed specific modules describing practical HTS materials that can be used to describe new architectures involving superconducting power devices, for example fault current limiters. These modules include flux-pinning scaling models that vary smoothly in their parameterization of the J-T-B-E (current density, temperature, magnetic field and electric field) surfaces. In addition, the non-linear low temperature materials properties, such as specific heat, are included for a more accurate description of device behavior. The advantage of this approach is that the complex and non-linear flux-pinning and thermal characteristics of HTS devices can be integrated into power network models. The modeling is presented, with an emphasis on fault current limiters where three domains of operating characteristics are identified.

  3. Experimental Manufacture and Performance Evaluation of Linear Switched Reluctance Motor with HTS Excitation Windings

    Science.gov (United States)

    Hirayama, Tadashi; Oto, Satoshi; Higashijima, Atsushi; Kawabata, Shuma

    This paper presents an experimental manufacture and performance evaluation of prototype linear switched reluctance motor with HTS excitation windings (HTS-LSRM). The Ag-alloy sheathed Bi-2223 tapes are used for HTS coils. We first present a structure of the prototype HTS-LSRM. Next, current-carrying properties of the HTS coils are measured. Furthermore, current and voltage waveforms are measured and we evaluation a control performance of the current and voltage.

  4. A novel ferrimagnetic irido-cuprate: IrSr2GdCu2O8

    International Nuclear Information System (INIS)

    Dos Santos-Garcia, A.J.; Aguirre, Myriam H.; Moran, E.; Saez Puche, R.; Alario-Franco, M.A.

    2006-01-01

    We have performed an investigation of the structural, microstructural and magnetic properties of the new compound IrSr 2 GdCu 2 O 8 . The sample was prepared under high temperature (∼1393K) and high-pressure conditions (∼60Kbars) in a Belt type apparatus. X-ray diffraction (XRD) analysis shows that this irido-cuprate is isostructural with the corresponding Ru-1212 phase. Structurally, this material shows an interesting hierarchy of ordering phenomena, whose observation actually depends on the technique used to analyze the material: from a 'simple' cell a p xa p x3a p which is supported by XRD, through a 'diagonal' one, ∼2a p x2a p x3a p as seen by SAED, to a microdomain texture of this last one cell supported by HREM. A ferrimagnetic Ir IV -Gd III spin ordering is observed below 15K. The iridium oxidation state seems to be +4

  5. Superconductivity-Insensitive Order at q ˜1 /4 in Electron-Doped Cuprates

    Science.gov (United States)

    Jang, H.; Asano, S.; Fujita, M.; Hashimoto, M.; Lu, D. H.; Burns, C. A.; Kao, C.-C.; Lee, J.-S.

    2017-10-01

    One of the central questions in the cuprate research is the nature of the normal state that develops into high-temperature superconductivity (HTSC). In the normal state of hole-doped cuprates, the existence of a charge density wave (CDW) is expected to shed light on the mechanism of HTSC. With evidence emerging for CDW order in the electron-doped cuprates, the CDW is thought to be a universal phenomenon in high-Tc cuprates. However, the CDW phenomena in electron-doped cuprates are quite different than those in hole-doped cuprates. Here, we study the nature of the putative CDW in an electron-doped cuprate through direct comparisons between as-grown and postannealed Nd1.86Ce0.14CuO4 (NCCO) single crystals using Cu L3 -edge resonant soft x-ray scattering (RSXS) and angle-resolved photoemission spectroscopy (ARPES). The RSXS result reveals that the nonsuperconducting NCCO shows the same reflections at the wave vector (˜1 /4 , 0, l ) as the reported superconducting NCCO. This superconductivity-insensitive signal is quite different from the CDW reflection in hole-doped cuprates. Moreover, the ARPES result suggests that the fermiology cannot account for such wave vectors. These results call into question the universality of the CDW phenomenon in the cuprates.

  6. Superconductivity-Insensitive Order at q∼1/4 in Electron-Doped Cuprates

    Directory of Open Access Journals (Sweden)

    H. Jang

    2017-12-01

    Full Text Available One of the central questions in the cuprate research is the nature of the normal state that develops into high-temperature superconductivity (HTSC. In the normal state of hole-doped cuprates, the existence of a charge density wave (CDW is expected to shed light on the mechanism of HTSC. With evidence emerging for CDW order in the electron-doped cuprates, the CDW is thought to be a universal phenomenon in high-T_{c} cuprates. However, the CDW phenomena in electron-doped cuprates are quite different than those in hole-doped cuprates. Here, we study the nature of the putative CDW in an electron-doped cuprate through direct comparisons between as-grown and postannealed Nd_{1.86}Ce_{0.14}CuO_{4} (NCCO single crystals using Cu L_{3}-edge resonant soft x-ray scattering (RSXS and angle-resolved photoemission spectroscopy (ARPES. The RSXS result reveals that the nonsuperconducting NCCO shows the same reflections at the wave vector (∼1/4, 0, l as the reported superconducting NCCO. This superconductivity-insensitive signal is quite different from the CDW reflection in hole-doped cuprates. Moreover, the ARPES result suggests that the fermiology cannot account for such wave vectors. These results call into question the universality of the CDW phenomenon in the cuprates.

  7. Fermion local charged boson model and cuprate superconductors

    International Nuclear Information System (INIS)

    Sinha, K.P.; Kakani, S.L.

    2002-01-01

    One of the most exciting developments in Science in past few years is the discovery of high temperature superconductivity (HTSC) in cuprates. It has been observed that the superconducting state in these cuprates is rather normal compared to the anomalous normal state. This discovery has led to deluge of experimental and theoretical researches all along the world. These cuprates are close to metal-insulator transition and the stability of the insulating and metallic phase depends on the degree of doping. Measurements of physical properties of these systems have revealed many anomalous results both in the superconducting and normal states, e.g. d-wave superconducting gap, the presence of pseudo gap in the normal state, static or dynamic striped structure of CuO 2 planes etc. These have posed serious theoretical challenges towards formulating the mechanisms of pairing and explanation of anomalous behaviour. Several theoretical proposals have been advanced and only a few are likely to survive in the teeth of some reliable experimental data. A combined mechanism mediated by phonons and lochons (local charged bosons, local pairs or bipolarons) for the pairing of fermions (holes or electrons) belonging to a wide band provides a microscopic explanation of anomalous normal state properties of HTSC cuprates and vindicates features of the phenomenological marginal Fermi liquid formulation. In the present review article detailed features of combined lochon and phonon mediated pairing mechanism are presented and a contact with the normal and superconducting state properties of HTSC in YBa 2 Cu 3 O x does indicate pair hopping between planes via such resonant centres lying in between the CuO 2 planes. (author)

  8. From cuprates to manganites spin and orbital liquids

    CERN Document Server

    Kilian, R

    1999-01-01

    First we analyze the peculiar magnetic response of metallic cuprates upon impurity doping. We argue that the magnetic behavior can be well understood if one assumes the spins of the CuO sub 2 planes to form a spin liquid. The subsequent Chapters are devoted to the metallic state of manganites. Elaborating on the notion of an orbital liquid, we study the interplay of electron correlations, orbital degeneracy, and double exchange.

  9. Chemical Bonding in Tl Cuprates Studied by X-Ray Photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Lao, J.Y.; Overmyer, D.L.; Ren, Z.F.; Siegal, M.P.; Vasquez, R.P.; Wang, J.H.

    1999-04-05

    Epitaxial thin films of the Tl cuprate superconductors Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}, Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}, and TL{sub 0.78}Bi{sub 0.22}Ba{sub 0.4}Sr{sub 1.6}Ca{sub 2}Cu{sub 3}O{sub 9{minus}{delta}} are studied with x-ray photoemission spectroscopy. These data, together with previous measurements in this lab of Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7{minus}{delta}}, comprise a comprehensive data set for a comparative study of Tl cuprates with a range of chemical and electronic properties. In the Cu 2p spectra, a larger energy separation between the satellite and main peaks (E{sub s}-E{sub m}) and a lower intensity ratio (I{sub s}/I{sub m}) are found to correlate with higher values of T{sub c}. Analysis of these spectra within a simple configuration interaction model suggests that higher values of T{sub c} are related to low values of the O 2p {r_arrow} Cu 3d charge transfer energy. In the O 1s region, a smaller bond length between Ba and Cu-O planar oxygen is found to correlate with a lower binding energy for the signal associated with Cu-O bonding, most likely resulting from the increased polarization screening by Ba{sup 2+} ions. For samples near optimum doping, maximum T{sub c} is observed to occur when the Tl 4f{sub 7/2} binding energy is near 117.9 eV, which is near the middle of the range of values observed for Tl cuprates. Higher Tl 4f{sub 7/2} binding energies, corresponding to formal oxidation states nearer Tl{sup 1+}, are also found to correlate with longer bond lengths between Ba and Tl-O planar oxygen, and with higher binding energies of the O 1s signal associated with Tl-O bonding.

  10. Chemical bonding in Tl cuprates studied by x-ray photoemission

    Energy Technology Data Exchange (ETDEWEB)

    Vasquez, R.P. [Center for Space Microelectronics Technology, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109-8099 (United States); Siegal, M.P.; Overmyer, D.L. [Sandia National Laboratories, Albuquerque, New Mexico 87185-1421 (United States); Ren, Z.F.; Lao, J.Y.; Wang, J.H. [Materials Synthesis Laboratory, Department of Chemistry, State University of New York, Buffalo, New York 14260-3000 (United States)

    1999-08-01

    Epitaxial thin films of the Tl cuprate superconductors Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8}, Tl{sub 2}Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10}, and Tl{sub 0.78}Bi{sub 0.22}Ba{sub 0.4}Sr{sub 1.6}Ca{sub 2}Cu{sub 3}O{sub 9{minus}{delta}} are studied with x-ray photoemission spectroscopy. These data, together with previous measurements in this lab of Tl{sub 2}Ba{sub 2}CuO{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7{minus}{delta}}, comprise a comprehensive data set for a comparative study of Tl cuprates with a range of chemical and electronic properties. In the Cu 2p spectra, a larger energy separation between the satellite and main peaks (E{sub s}{minus}E{sub m}) and a lower intensity ratio (I{sub s}/I{sub m}) are found to correlate with higher values of T{sub c}. Analysis of these spectra within a simple configuration interaction model suggests that higher values of T{sub c} are related to low values of the O&hthinsp;2p{r_arrow}Cu&hthinsp;3d charge transfer energy. In the O&hthinsp;1s region, a smaller bond length between Ba and Cu-O planar oxygen is found to correlate with a lower binding energy for the signal associated with Cu-O bonding, most likely resulting from the increased polarization screening by Ba{sup 2+} ions. For samples near optimum doping, maximum T{sub c} is observed to occur when the Tl 4f{sub 7/2} binding energy is near 117.9 eV, which is near the middle of the range of values observed for Tl cuprates. Higher Tl&hthinsp;4f{sub 7/2} binding energies, corresponding to formal oxidation states nearer Tl{sup 1+}, are also found to correlate with longer bond lengths between Ba and Tl-O planar oxygen, and with higher binding energies of the O&hthinsp;1s signal associated with Tl-O bonding. {copyright} {ital 1999} {ital The American Physical Society}

  11. Novel processing of HTS based conductors

    International Nuclear Information System (INIS)

    Ginley, D.S.; Venturini, E.L.; Kwak, J.F.; Baughman, R.J.; Bourcier, R.J.; Mitchell, M.A.; Morosin, B.; Halloran, J.W.; Neal, M.J.; Capone, D.W.

    1990-01-01

    Conductor development is one of the major long term goals in high temperature superconductor research. In this paper the authors report on two promising processing technologies that have been utilized to produce superconducting HTS conductors. First, melt spun YBa 2 Cu 3 O 7 fibers rapid thermal processed for 1-8 sec at 950 to 1075 degrees C have T c 's to 92 K, J c to 1100 A/cm 2 and the orthorhombic twinned morphology typical for high quality YBa 2 Cu 3 O 7 . A processing matrix of time, temperature and composition for these fibers shows that slightly CuO-rich starting composition give the best results. Second, silver tube encapsulated wires of Bi 1.7 Pb 0.3 Sr 2 Ca 2 Cu 3 O 10 have been made by extrusion, wire drawing and cold rolling. The resulting tapes show orientation of the crystallites, zero resistance up to 100K and improved magnetic hysteria above 50 K. The combination of mechanical reprocessing and extended thermal anneal near 850 degrees C appears to significantly improve these materials

  12. Large-scale HTS bulks for magnetic application

    Energy Technology Data Exchange (ETDEWEB)

    Werfel, Frank N., E-mail: werfel@t-online.de [Adelwitz Technologiezentrum GmbH (ATZ), Rittergut Adelwitz 16, 04886 Arzberg-Adelwitz (Germany); Floegel-Delor, Uta; Riedel, Thomas; Goebel, Bernd; Rothfeld, Rolf; Schirrmeister, Peter; Wippich, Dieter [Adelwitz Technologiezentrum GmbH (ATZ), Rittergut Adelwitz 16, 04886 Arzberg-Adelwitz (Germany)

    2013-01-15

    Highlights: ► ATZ Company has constructed about 130 HTS magnet systems. ► Multi-seeded YBCO bulks joint the way for large-scale application. ► Levitation platforms demonstrate “superconductivity” to a great public audience (100 years anniversary). ► HTS magnetic bearings show forces up to 1 t. ► Modular HTS maglev vacuum cryostats are tested for train demonstrators in Brazil, China and Germany. -- Abstract: ATZ Company has constructed about 130 HTS magnet systems using high-Tc bulk magnets. A key feature in scaling-up is the fabrication of YBCO melts textured multi-seeded large bulks with three to eight seeds. Except of levitation, magnetization, trapped field and hysteresis, we review system engineering parameters of HTS magnetic linear and rotational bearings like compactness, cryogenics, power density, efficiency and robust construction. We examine mobile compact YBCO bulk magnet platforms cooled with LN{sub 2} and Stirling cryo-cooler for demonstrator use. Compact cryostats for Maglev train operation contain 24 pieces of 3-seed bulks and can levitate 2500–3000 N at 10 mm above a permanent magnet (PM) track. The effective magnetic distance of the thermally insulated bulks is 2 mm only; the stored 2.5 l LN{sub 2} allows more than 24 h operation without refilling. 34 HTS Maglev vacuum cryostats are manufactured tested and operate in Germany, China and Brazil. The magnetic levitation load to weight ratio is more than 15, and by group assembling the HTS cryostats under vehicles up to 5 t total loads levitated above a magnetic track is achieved.

  13. Metal–insulator crossover in high c cuprates: A gauge field ...

    Indian Academy of Sciences (India)

    A metal–insulator crossover appears in the experimental data for in-plane resistivity of underdoped cuprates and a range of superconducting cuprates in the presence of a strong magnetic field suppressing superconductivity. We propose an explanation for this phenomenon based on a gauge field theory approach to the t-J ...

  14. d-Wave superconductivity in the effective extended Hubbard model for cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Arrachea, L.; Aligia, A.A

    2004-08-01

    We consider the effective extended Hubbard Hamiltonian for the cuprates, with nearest-neighbor hopping which depends on the occupation. Using exact diagonalization in a 4 x 4 cluster, we obtain a large enhancement of d-wave pairing correlation functions for optimum doping. The physical picture is consistent with magnetic measurements, the pseudogap and the kinetic energy gain in the cuprates.

  15. d-Wave superconductivity in the effective extended Hubbard model for cuprates

    Science.gov (United States)

    Arrachea, L.; Aligia, A. A.

    2004-08-01

    We consider the effective extended Hubbard Hamiltonian for the cuprates, with nearest-neighbor hopping which depends on the occupation. Using exact diagonalization in a 4 × 4 cluster, we obtain a large enhancement of d-wave pairing correlation functions for optimum doping. The physical picture is consistent with magnetic measurements, the pseudogap and the kinetic energy gain in the cuprates.

  16. Development and characterization of magnetic HTS bearings for a 400 kW synchronous HTS motor

    International Nuclear Information System (INIS)

    Kummeth, P; Ries, G; Nick, W; Neumueller, H-W

    2004-01-01

    Promising results of static and dynamic investigations on various journal type test bearings encouraged us to develop a scaled-up HTS bearing, able to carry the HTS rotor of a 400 kW superconducting motor. The stator, a YBCO hollow cylinder of 203 mm inner diameter and 250 mm length, is cooled by liquid nitrogen. Permanent magnet rings with a diameter of 200 mm were mounted on a shaft with alternating polarity. Characterization of the bearing capacity was performed with three different YBCO stators at temperatures between 66 and 86 K in a test set-up. A significant influence of the temperature was found. At a stator temperature of 72 K and a rotation frequency of 25 Hz (corresponding to nominal motor speed) a radial bearing force of 2700 N was measured for the shaft at centre position. Under rotation of the shaft the bearing capacity is reduced. At present our results range within the highest radial bearing capacities reported world-wide

  17. Lightweight Design of an HTS Coil for the VASIMR Experiment Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Tai-Yang Research of Delaware proposes to design and fabricate an HTS double-pancake coil in support of the VASIMR experiment. The proposed HTS coil will implement...

  18. Proposed parametric cooling of bilayer cuprate superconductors by terahertz excitation.

    Science.gov (United States)

    Denny, S J; Clark, S R; Laplace, Y; Cavalleri, A; Jaksch, D

    2015-04-03

    We propose and analyze a scheme for parametrically cooling bilayer cuprates based on the selective driving of a c-axis vibrational mode. The scheme exploits the vibration as a transducer making the Josephson plasma frequencies time dependent. We show how modulation at the difference frequency between the intrabilayer and interbilayer plasmon substantially suppresses interbilayer phase fluctuations, responsible for switching c-axis transport from a superconducting to a resistive state. Our calculations indicate that this may provide a viable mechanism for stabilizing nonequilibrium superconductivity even above Tc, provided a finite pair density survives between the bilayers out of equilibrium.

  19. Angle-resolved photoemission spectroscopy (ARPES) studies of cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Palczewski, Ari Deibert [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    This dissertation is comprised of three different angle-resolved photoemission spectroscopy (ARPES) studies on cuprate superconductors. The first study compares the band structure from two different single layer cuprates Tl2Ba2CuO6+δ (Tl2201) Tc,max ~95 K and (Bi1.35Pb0.85)(Sr1.47La0.38)CuO6+δ (Bi2201) Tc,max 35 K. The aim of the study was to provide some insight into the reasons why single layer cuprate's maximum transition temperatures are so different. The study found two major di erences in the band structure. First, the Fermi surface segments close to ( π,0) are more parallel in Tl2201 than in Bi2201. Second, the shadow band usually related to crystal structure is only present in Bi2201, but absent in higher Tc Tl2201. The second study looks at the different ways of doping Bi2Sr2CaCu2O8+δ (Bi2212) in-situ by only changing the post bake-out vacuum conditions and temperature. The aim of the study is to systematically look into the generally overlooked experimental conditions that change the doping of a cleaved sample in ultra high vacuum (UHV) experiments. The study found two major experimental facts. First, in inadequate UHV conditions the carrier concentration of Bi2212 increases with time, due to the absorption of oxygen from CO2/CO molecules, prime contaminants present in UHV systems. Second, in a very clean UHV system at elevated temperatures (above about 200 K), the carrier concentration decreases due to the loss of oxygen atoms from the Bi-O layer. The final study probed the particle-hole symmetry of the pseudogap phase in high temperature superconducting cuprates by looking at the thermally excited bands above the Fermi level. The data showed a particle-hole symmetric pseudogap which symmetrically closes away from the nested FS before the node. The data is consistent with

  20. Angle-resolved photoemission spectroscopy (ARPES) studies of cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Palczewski, Ari Deibert [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    This dissertation is comprised of three different angle-resolved photoemission spectroscopy (ARPES) studies on cuprate superconductors. The first study compares the band structure from two different single layer cuprates Tl2Ba2CuO6+δ (Tl2201) Tc, max ≈ 95 K and (Bi 1.35Pb0.85)(Sr1.47La0.38)CuO6+δ (Bi2201) Tc, max ≈ 35 K. The aim of the study was to provide some insight into the reasons why single layer cuprate's maximum transition temperatures are so different. The study found two major differences in the band structure. First, the Fermi surface segments close to (π,0) are more parallel in Tl2201 than in Bi2201. Second, the shadow band usually related to crystal structure is only present in Bi2201, but absent in higher Tc Tl2201. The second study looks at the different ways of doping Bi2Sr2CaCu2O8+δ (Bi2212) in-situ by only changing the post bake-out vacuum conditions and temperature. The aim of the study is to systematically look into the generally overlooked experimental conditions that change the doping of a cleaved sample in ultra high vacuum (UHV) experiments. The study found two major experimental facts. First, in inadequate UHV conditions the carrier concentration of Bi2212 increases with time, due to the absorption of oxygen from CO2/CO molecules, prime contaminants present in UHV systems. Second, in a very clean UHV system at elevated temperatures (above about 200 K), the carrier concentration decreases due to the loss of oxygen atoms from the Bi-O layer. The final study probed the particle-hole symmetry of the pseudogap phase in high temperature superconducting cuprates by looking at the thermally excited bands above the Fermi level. The data showed a particle-hole symmetric pseudogap which symmetrically closes away from the nested FS before the node. The data is

  1. Pairing correlations in a generalized Hubbard model for the cuprates

    Science.gov (United States)

    Arrachea, Liliana; Aligia, A. A.

    2000-04-01

    Using numerical diagonalization of a 4×4 cluster, we calculate on-site s, extended-s, and dx2-y2 pairing correlation functions (PCF's) in an effective generalized Hubbard model for the cuprates, with nearest-neighbor correlated hopping and next-nearest-neighbor hopping t'. The vertex contributions to the PCF's are significantly enhanced, relative to the t-t'-U model. The behavior of the PCF's and their vertex contributions, and signatures of anomalous flux quantization, indicate superconductivity in the d-wave channel for moderate doping and in the s-wave channel for high doping and small U.

  2. Pairing Correlations in a Generalized Hubbard Model for the Cuprates

    OpenAIRE

    Arrachea, L.; Aligia, A.

    1999-01-01

    Using numerical diagonalization of a 4x4 cluster, we calculate on-site s, extended s and d pairing correlation functions (PCF) in an effective generalized Hubbard model for the cuprates, with nearest-neighbor correlated hopping and next nearest-neighbor hopping t'. The vertex contributions (VC) to the PCF are significantly enhanced, relative to the t-t'-U model. The behavior of the PCF and their VC, and signatures of anomalous flux quantization, indicate superconductivity in the d-wave channe...

  3. AC Application of HTS Conductors in Highly Dynamic Electric Motors

    International Nuclear Information System (INIS)

    Oswald, B; Best, K-J; Setzer, M; Duffner, E; Soell, M; Gawalek, W; Kovalev, L K

    2006-01-01

    Based on recent investigations we design highly dynamic electric motors up to 400 kW and linear motors up to 120 kN linear force using HTS bulk material and HTS tapes. The introduction of HTS tapes into AC applications in electric motors needs fundamental studies on double pancake coils under transversal magnetic fields. First theoretical and experimental results on AC field distributions in double-pancake-coils and corresponding AC losses will be presented. Based on these results the simulation of the motor performance confirms extremely high power density and efficiency of both types of electric motors. Improved characteristics of rare earth permanent magnets used in our motors at low temperatures give an additional technological benefit

  4. AC loss analysis of a HTS coil with parallel superconducting tapes of unbalanced current distribution

    International Nuclear Information System (INIS)

    Lee, S.; Byun, S.; Kim, W.; Choi, K.; Lee, H.

    2007-01-01

    Considering the current capacities of the HTS tapes recently being developed, it is inevitable to use these HTS tapes in parallel in order to apply them to power transformers. But non-uniform distributions of current and large AC losses are major problems in a HTS coil with parallel superconducting tapes. Many parallel HTS tapes have been fabricated and tested so far. The results showed that we had to transpose each tape in order to reduce AC losses and have uniform distributions of current. But the measurement of the current distribution process has been quite difficult not only in the case of the parallel HTS tapes but also in the case of the coil with parallel HTS tapes. In our study, we investigated the effect of current distribution on the AC losses in parallel HTS tapes and coils with parallel superconducting tapes. The current distribution in parallel HTS tapes could be measured with small Hall sensors, the dependence of AC losses and critical current on the current distribution was analyzed. We fabricated a parallel HTS tape and HTS coil with the transposed parallel HTS tapes for an application of a power transformer. The performance of non-uniform current distribution in the parallel HTS wires is worse than that of a uniform one

  5. Study of HTS Wires at High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    Turrioni, D.; Barzi, E.; Lamm, M.J.; Yamada, R.; Zlobin, A.V.; Kikuchi, A.; /Fermilab

    2009-01-01

    Fermilab is working on the development of high field magnet systems for ionization cooling of muon beams. The use of high temperature superconducting (HTS) materials is being considered for these magnets using Helium refrigeration. Critical current (I{sub c}) measurements of HTS conductors were performed at FNAL and at NIMS up to 28 T under magnetic fields at zero to 90 degree with respect to the sample face. A description of the test setups and results on a BSCCO-2223 tape and second generation (2G) coated conductors are presented.

  6. Investigation of renormalization effects in high temperature cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zabolotnyy, Volodymyr B.

    2008-04-16

    It has been found that the self-energy of high-T{sub C} cuprates indeed exhibits a well pronounced structure, which is currently attributed to coupling of the electrons either to lattice vibrations or to collective magnetic excitations in the system. To clarify this issue, the renormalization effects and the electronic structure of two cuprate families Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} and YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} were chosen as the main subject for this thesis. With a simple example of an electronic system coupled to a collective mode unusual renormalization features observed in the photoemission spectra are introduced. It is shown that impurity substitution in general leads to suppression of the unusual renormalization. Finally an alternative possibility to obtain a purely superconducting surface of Y-123 via partial substitution of Y atoms with Ca is introduced. It is shown that renormalization in the superconducting Y-123 has similar strong momentum dependence as in the Bi-2212 family. It is also shown that in analogy to Bi-2212 the renormalization appears to have strong dependence on the doping level (no kinks for the overdoped component) and practically vanishes above T{sub C} suggesting that coupling to magnetic excitations fits much better than competing scenarios, according to which the unusual renormalization in ARPES spectra is caused by the coupling to single or multiple phononic modes. (orig.)

  7. Phenomenological view at the two-component physics of cuprates

    Science.gov (United States)

    Teitel'baum, G. B.

    2017-08-01

    In the search for mechanisms of high- T c superconductivity it is critical to know the electronic spectrum in the pseudogap phase from which superconductivity evolves. The lack of ARPES data for every cuprate family precludes an agreement as to its structure, doping and temperature dependence and the role of charge ordering. No approach has been developed yet to address the issue theoretically, and we limit ourselves by the phenomenological analysis of the experimental data. We argue that, in the Fermi-liquid-like regime ubiquitous in underdoped cuprates, the spectrum consists of holes on the Fermi arcs and an electronic pocket in contrast to the idea of the Fermi surface reconstruction via charge ordering. At high temperatures, the electrons are dragged by holes while at lower temperatures they get decoupled. The longstanding issue of the origin of the negative Hall coefficient in YBCO and Hg1201 at low temperature is resolved: the electronic contribution prevails, as its mobility becomes temperature independent, while the mobility of holes, scattered by the shortwavelength charge density waves, decreases.

  8. Numerical assessment of efficiency and control stability of an HTS synchronous motor

    International Nuclear Information System (INIS)

    Xian Wei; Yuan Weijia; Coombs, T A

    2010-01-01

    A high temperature superconducting (HTS) permanent magnet synchronous motor (PMSM) is designed and developed in Cambridge University. It is expected to become cost competitive with the conventional PMSM owing to its high efficiency, high power density, high torque density, etc. The structure and parameters of HTS PMSM are detailed. Both AC losses by transport current and applied filed in stator armature winding of HTS PMSM are also analyzed. Computed and simulated results of the characteristics of the HTS PMSM and conventional PMSM are compared. The improvement on stability of direct torque control (DTC) on the HTS PMSM is estimated, and proved by simulation on Matlab/Simulink.

  9. HTS Teologiese Studies / Theological Studies - Vol 72, No 3 (2016)

    African Journals Online (AJOL)

    Continuous formation of liturgy through social cognition · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Ferdi Kruger, Ben de Klerk. http://dx.doi.org/10.4102/hts.v72i3.3170 ...

  10. Academic Training Lecture Regular Programme: Superconducting Magnets with HTS

    CERN Multimedia

    2012-01-01

    Superconducting Magnets with HTS (1/5), by Justin Schwartz (North Carolina State University).   Monday, June 25, 2012 from 11:00 to 12:00 (Europe/Zurich) at CERN ( 30-7-018 - Kjell Johnsen Auditorium ).   More information here.

  11. Phonons and charge-transfer excitations in HTS superconductors

    International Nuclear Information System (INIS)

    Bishop, A.R.

    1989-01-01

    Some of the experimental and theoretical evidence implicating phonons and charge-transfer excitations in HTS superconductors is reviewed. It is suggested that superconductivity may be driven by a synergistic interplay of (anharmonic) phonons and electronic degrees of freedom (e.g., charge fluctuations, excitons). 47 refs., 5 figs

  12. HTS Teologiese Studies / Theological Studies - Vol 69, No 2 (2013)

    African Journals Online (AJOL)

    A possible solution for corruption in South Africa with the church as initiator: A practical theological approach · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. AL du Plessis, G Breed. http://dx.doi.org/10.4102/hts.v69i2.1298 ...

  13. HTS Teologiese Studies / Theological Studies - Vol 49, No 4 (1993)

    African Journals Online (AJOL)

    Redaksioneel Die Etiek Agter Mede-outeurskap · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Prof Andries van Aarde, 688-689. http://dx.doi.org/10.4102/hts.v49i4.2515 ...

  14. HTS Teologiese Studies / Theological Studies - Vol 72, No 4 (2016)

    African Journals Online (AJOL)

    The text-critical and exegetical value of the Dead Sea Scrolls · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Johann Cook, 1-6. http://dx.doi.org/10.4102/hts.v72i4.3280 ...

  15. The first disciples of Jesus in Galilee | Guijarro | HTS Teologiese ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 63, No 3 (2007) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  16. HTS Teologiese Studies / Theological Studies - Vol 67, No 1 (2011)

    African Journals Online (AJOL)

    Andries van Aarde – A sideways glance: His theological and hermeneutical contribution to the South African scene · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. G de Villiers. http://dx.doi.org/10.4102/hts.v67i1.1033 ...

  17. HTS Teologiese Studies / Theological Studies - Vol 73, No 3 (2017)

    African Journals Online (AJOL)

    Lewensbeskoulike aspekte in die openbare standpunte van twee presidente · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Piet Strauss. http://dx.doi.org/10.4102/hts.v73i3.3580 ...

  18. Modelling, Construction, and Testing of a Simple HTS Machine Demonstrator

    DEFF Research Database (Denmark)

    Jensen, Bogi Bech; Abrahamsen, Asger Bech

    2011-01-01

    This paper describes the construction, modeling and experimental testing of a high temperature superconducting (HTS) machine prototype employing second generation (2G) coated conductors in the field winding. The prototype is constructed in a simple way, with the purpose of having an inexpensive way...

  19. Ancestor worship – is it Biblical? | Sup Bae | HTS Teologiese ...

    African Journals Online (AJOL)

    The article looks at these issues from a Biblical perspective, offers Biblical guidelines in assessing ancestor worship and its cosmology and interprets ancestor worship theologically. The conclusion is that ancestor worship is incompatible with Christian faith. HTS Theological Studies/Teologiese Studies Vol. 64 (3) 2008: pp.

  20. The kingdom of God: Utopian or existential? | Malan | HTS ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 70, No 3 (2014) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  1. Theology of religions in Martin Luther | Shaw | HTS Teologiese ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 73, No 6 (2017) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. Theology of religions in Martin Luther.

  2. HTS Teologiese Studies / Theological Studies - Vol 73, No 6 (2017)

    African Journals Online (AJOL)

    Theology of religions in Martin Luther · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Wilhelmina Magdalena (Elmien) Shaw. http://dx.doi.org/10.4102/hts.v73i6.4882 ...

  3. HTS Teologiese Studies / Theological Studies - Vol 67, No 2 (2011)

    African Journals Online (AJOL)

    Revisiting the role of woman pastors in the church in Tshwane · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. EC Wagner-Ferreira. http://dx.doi.org/10.4102/hts.v67i2.932 ...

  4. HTS Teologiese Studies / Theological Studies - Vol 64, No 3 (2008)

    African Journals Online (AJOL)

    Een teks – meerdere betekenisse: Hoe lees ons die Bybel? EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. E van Eck, 1155-1185. http://dx.doi.org/10.4102/hts.v64i3.82 ...

  5. HTS Teologiese Studies / Theological Studies - Vol 65, No 1 (2009)

    African Journals Online (AJOL)

    Responsibility, God and society: The cry of the other in the sacred texts as a challenge towards responsible global citizenship · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. J-A Meylahn. http://dx.doi.org/10.4102/hts.v65i1.131 ...

  6. The status of commercial and developmental HTS wires

    Energy Technology Data Exchange (ETDEWEB)

    Masur, L.J.; Buczek, D.; Harley, E.; Kodenkandath, T.; Li, X.; Lynch, J.; Nguyen, N.; Rupich, M.; Schoop, U.; Scudiere, J.; Siegal, E.; Thieme, C.; Verebelyi, D.; Zhang, W.; Kellers, J

    2003-10-15

    This paper provides an update on the development, performance and application of first and second generation high temperature superconductor (HTS) wires fabricated at American Superconductor (AMSC). First generation, multifilamentary composite wire is available commercially today in different viable product forms. This conductor carries 140 x the current of copper of the same cross-section, and is robust enough to stand tough industrial requirements. Second generation HTS wires, having a coated conductor composite architecture, are under development today and achieved substantial progress recently. AMSC's first generation wire will continue as the workhorse of the industry for the next 3-4 years while AMSC's second generation coated conductor wire is on track to be reproducible, uniform, scalable, and low cost. This paper provides a product differentiation with a view on the application of HTS wire in the electric power sector. Basic engineering data is reviewed that shall aid the engineer in the selection of the HTS wire product.

  7. HTS Teologiese Studies / Theological Studies - Vol 1, No 4 (1944)

    African Journals Online (AJOL)

    Die heidelbergse kategismus as kerklike simbool · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. SP Engelbrecht, 160-173. http://dx.doi.org/10.4102/hts.v1i4.3327 ...

  8. Large-scale HTS bulks for magnetic application

    Science.gov (United States)

    Werfel, Frank N.; Floegel-Delor, Uta; Riedel, Thomas; Goebel, Bernd; Rothfeld, Rolf; Schirrmeister, Peter; Wippich, Dieter

    2013-01-01

    ATZ Company has constructed about 130 HTS magnet systems using high-Tc bulk magnets. A key feature in scaling-up is the fabrication of YBCO melts textured multi-seeded large bulks with three to eight seeds. Except of levitation, magnetization, trapped field and hysteresis, we review system engineering parameters of HTS magnetic linear and rotational bearings like compactness, cryogenics, power density, efficiency and robust construction. We examine mobile compact YBCO bulk magnet platforms cooled with LN2 and Stirling cryo-cooler for demonstrator use. Compact cryostats for Maglev train operation contain 24 pieces of 3-seed bulks and can levitate 2500-3000 N at 10 mm above a permanent magnet (PM) track. The effective magnetic distance of the thermally insulated bulks is 2 mm only; the stored 2.5 l LN2 allows more than 24 h operation without refilling. 34 HTS Maglev vacuum cryostats are manufactured tested and operate in Germany, China and Brazil. The magnetic levitation load to weight ratio is more than 15, and by group assembling the HTS cryostats under vehicles up to 5 t total loads levitated above a magnetic track is achieved.

  9. HTS Teologiese Studies / Theological Studies - Vol 46, No 3 (1990)

    African Journals Online (AJOL)

    Paradigma-verandering, relativisme en rasionaliteit · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. A.J. Antonites, 312-322. http://dx.doi.org/10.4102/hts.v46i3.2320 ...

  10. HTS Teologiese Studies / Theological Studies - Vol 64, No 2 (2008)

    African Journals Online (AJOL)

    Die hermeneutiek van kerkgeskiedenis en “teologiegeskiedenis”: 'n “Nuwe paradigma” vir kerkgeskiedenis · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. JP Labuschagne, 861-883. http://dx.doi.org/10.4102/hts.v64i2.48 ...

  11. Karl Barth's epistemology: A critical appraisal | Veldsman | HTS ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 63, No 4 (2007) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  12. Logos en ideologia: woord en skynwoord | Geyser | HTS Teologiese ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 16, No 4 (1961) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  13. HTS Teologiese Studies / Theological Studies - Vol 63, No 2 (2007)

    African Journals Online (AJOL)

    Marriage in the theology of Martin Luther – worldly yet sacred: An option between secularism and clericalism · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Johan Buitendag, 445-461. http://dx.doi.org/10.4102/hts.v63i2.228 ...

  14. HTS Teologiese Studies / Theological Studies - Vol 64, No 1 (2008)

    African Journals Online (AJOL)

    Sexuality and partnership: Aspects of theological ethics in the field of marriage, unmarried and homosexual couples · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. UHJ Körtner, 209-225. http://dx.doi.org/10.4102/hts.v64i1.18 ...

  15. HTS Teologiese Studies / Theological Studies - Vol 62, No 4 (2006)

    African Journals Online (AJOL)

    Postmoderne kerk-wees in die lig van publieke teologie – eenheid en verskeidenheid · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. Yolanda Dreyer, 1311-1335. http://dx.doi.org/10.4102/hts.v62i4.417 ...

  16. Defining poverty as distinctively human | Lötter | HTS Teologiese ...

    African Journals Online (AJOL)

    of a claim that poverty is a concept uniquely applicable to humans. It then present a critical discussion of the distinction between absolute and relative poverty and it is then argued that a revision of this distinction can provide general standards applicable to humans everywhere. HTS Theological Studies Vol. 63 (3) 2007: pp.

  17. Leadership for the church: The shepherd model | Resane | HTS ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 70, No 1 (2014) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  18. Communicating hope with one breath | Edwards | HTS Teologiese ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 67, No 2 (2011) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  19. Calculation of AC losses in large HTS stacks and coils

    DEFF Research Database (Denmark)

    Zermeno, Victor; Abrahamsen, Asger Bech; Mijatovic, Nenad

    2012-01-01

    In this work, we present a homogenization method to model a stack of HTS tapes under AC applied transport current or magnetic field. The idea is to find an anisotropic bulk equivalent for the stack of tapes, where the internal alternating structures of insulating, metallic, superconducting and su...

  20. Wyle Prof H G Viljoen | Geyser | HTS Teologiese Studies ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 9, No 2 (1953) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  1. Wyle Prof H G Viljoen | Geyser | HTS Teologiese Studies ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 9, No 2 (1953) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. Wyle Prof H G Viljoen. A S Geyser. Abstract. No Abstract ...

  2. HTS Teologiese Studies / Theological Studies - Vol 49, No 3 (1993)

    African Journals Online (AJOL)

    The production of the Gospel of Mark: An essay on intertextuality · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. W.S. Vorster, 385-396. http://dx.doi.org/10.4102/hts.v49i3.2499 ...

  3. Materials processing and machine applications of bulk HTS

    Science.gov (United States)

    Miki, M.; Felder, B.; Tsuzuki, K.; Xu, Y.; Deng, Z.; Izumi, M.; Hayakawa, H.; Morita, M.; Teshima, H.

    2010-12-01

    We report a refrigeration system for rotating machines associated with the enhancement of the trapped magnetic flux of bulk high-temperature superconductor (HTS) field poles. A novel cryogenic system was designed and fabricated. It is composed of a low-loss rotary joint connecting the rotor and a closed-cycle thermosiphon under a GM cryocooler using a refrigerant. Condensed neon gas was adopted as a suitable cryogen for the operation of HTS rotating machines with field poles composed of RE-Ba-Cu-O family materials, where RE is a rare-earth metal. Regarding the materials processing of the bulks HTS, thanks to the addition of magnetic particles to GdBa2Cu3O7 - d (Gd123) bulk superconductors an increase of more than 20% in the trapped magnetic flux density was achieved at liquid nitrogen temperature. Field-pole Gd123 bulks up to 46 mm in diameter were synthesized with the addition of Fe-B alloy magnetic particles and assembled into the synchronous machine rotor to be tested. Successful cooling of the magnetized rotor field poles down to 35 K and low-output-power rotating operation was achieved up to 720 rpm in the test machine with eight field-pole bulks. The present results show a substantial basis for making a prototype system of rotating machinery of applied HTS bulks.

  4. Materials processing and machine applications of bulk HTS

    Energy Technology Data Exchange (ETDEWEB)

    Miki, M; Felder, B; Tsuzuki, K; Xu, Y; Deng, Z; Izumi, M [Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan); Hayakawa, H [Kitano Seiki Co. Ltd, 7-17-3, Chuo, Ohta-ku, Tokyo 143-0024 (Japan); Morita, M; Teshima, H, E-mail: d082025@kaiyodai.ac.j [Nippon Steel Co. Ltd, 20-1, Shintomi, Huttsu-shi, Chiba 293-8511 (Japan)

    2010-12-15

    We report a refrigeration system for rotating machines associated with the enhancement of the trapped magnetic flux of bulk high-temperature superconductor (HTS) field poles. A novel cryogenic system was designed and fabricated. It is composed of a low-loss rotary joint connecting the rotor and a closed-cycle thermosiphon under a GM cryocooler using a refrigerant. Condensed neon gas was adopted as a suitable cryogen for the operation of HTS rotating machines with field poles composed of RE-Ba-Cu-O family materials, where RE is a rare-earth metal. Regarding the materials processing of the bulks HTS, thanks to the addition of magnetic particles to GdBa{sub 2}Cu{sub 3}O{sub 7-d} (Gd123) bulk superconductors an increase of more than 20% in the trapped magnetic flux density was achieved at liquid nitrogen temperature. Field-pole Gd123 bulks up to 46 mm in diameter were synthesized with the addition of Fe-B alloy magnetic particles and assembled into the synchronous machine rotor to be tested. Successful cooling of the magnetized rotor field poles down to 35 K and low-output-power rotating operation was achieved up to 720 rpm in the test machine with eight field-pole bulks. The present results show a substantial basis for making a prototype system of rotating machinery of applied HTS bulks.

  5. hts 63_4_ vanwyk natie karl barth 2007 _outeur

    African Journals Online (AJOL)

    p1243322

    HTS 63(4) 2007. 1595. – are, according to Barth, structurally identical because they integrate elements of Christian religion into autonomous cultural values and present the new system as a new religion that could offer “salvation”. Faith in the nation. (Fascism) and the belief in the individual (Americanism) produce the same.

  6. Electromagnetic Performance Calculation of HTS Linear Induction Motor for Rail Systems

    Science.gov (United States)

    Liu, Bin; Fang, Jin; Cao, Junci; Chen, Jie; Shu, Hang; Sheng, Long

    2017-07-01

    According to a high temperature superconducting (HTS) linear induction motor (LIM) designed for rail systems, the influence of electromagnetic parameters and mechanical structure parameters on the electromagnetic horizontal thrust, vertical force of HTS LIM and the maximum vertical magnetic field of HTS windings are analyzed. Through the research on the vertical field of HTS windings, the development regularity of the HTS LIM maximum input current with different stator frequency and different thickness value of the secondary conductive plate is obtained. The theoretical results are of great significance to analyze the stability of HTS LIM. Finally, based on theory analysis, HTS LIM test platform was built and the experiment was carried out with load. The experimental results show that the theoretical analysis is correct and reasonable.

  7. Design of an Air-Core HTS quadruple triplet for a heavy ion accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhan; Wei, Shaoqing; Lee, Sang Jin [Uiduk University, Gyeongju (Korea, Republic of)

    2016-12-15

    In recent years, high-temperature superconductor (HTS) Quadruple Triplets are being developed for heavy ion accelerators, because the HTS magnets are suitable to withstand radiation and high heat loads in the hot cell of accelerators. Generally, an iron yoke, which costs a mass of material, was employed to enhance the magnetic field when a quadrupole magnet was designed. The type of the magnet is called iron-dominated magnet, because the total magnetic field was mainly induced by the iron. However, in the HTS superconductor iron-dominated magnets, the coil-induced field also can have a certain proportion. Therefore, the air-core HTS quadrupole magnets can be considered instead of the iron-core HTS quadrupole magnet to be employed to save the iron material. This study presents the design of an air-core HTS quadruple triplet which consists three by air-core HTS quadruple magnet and compare the design result with that of an iron-core HTS quadruple triplet. First, the characteristics of an air-core HTS quadrupole magnet were analyzed to select the magnet system for the magnetic field uniformity impairment. Then, the field uniformity was improved(< 0.1%) exactly using evolution strategy (ES) method for each iron-core HTS quadrupole magnet and the air-core HTS quadruple triplet was established. Finally, the designed air-core triplet was compared with the iron-core HTS quadruple triplet, and the results of beam trajectories were presented with both the HTS quadruple triplet systems to show that the air-core triplet can be employed instead of the iron-core HTS triplet. The design of the air-core quadruple triplet was suggested for a heavy ion accelerator.

  8. Pseudogap temperature T* of cuprate superconductors from the Nernst effect

    Science.gov (United States)

    Cyr-Choinière, O.; Daou, R.; Laliberté, F.; Collignon, C.; Badoux, S.; LeBoeuf, D.; Chang, J.; Ramshaw, B. J.; Bonn, D. A.; Hardy, W. N.; Liang, R.; Yan, J.-Q.; Cheng, J.-G.; Zhou, J.-S.; Goodenough, J. B.; Pyon, S.; Takayama, T.; Takagi, H.; Doiron-Leyraud, N.; Taillefer, Louis

    2018-02-01

    We use the Nernst effect to delineate the boundary of the pseudogap phase in the temperature-doping phase diagram of hole-doped cuprate superconductors. New data for the Nernst coefficient ν (T ) of YBa2Cu3Oy (YBCO), La1.8 -xEu0.2SrxCuO4 (Eu-LSCO), and La1.6 -xNd0.4SrxCuO4 (Nd-LSCO) are presented and compared with previously published data on YBCO, Eu-LSCO, Nd-LSCO, and La2 -xSrxCuO4 (LSCO). The temperature Tν at which ν /T deviates from its high-temperature linear behavior is found to coincide with the temperature at which the resistivity ρ (T ) deviates from its linear-T dependence, which we take as the definition of the pseudogap temperature T★—in agreement with the temperature at which the antinodal spectral gap detected in angle-resolved photoemission spectroscopy (ARPES) opens. We track T★ as a function of doping and find that it decreases linearly vs p in all four materials, having the same value in the three LSCO-based cuprates, irrespective of their different crystal structures. At low p ,T★ is higher than the onset temperature of the various orders observed in underdoped cuprates, suggesting that these orders are secondary instabilities of the pseudogap phase. A linear extrapolation of T★(p ) to p =0 yields T★(p →0 ) ≃TN (0), the Néel temperature for the onset of antiferromagnetic order at p =0 , suggesting that there is a link between pseudogap and antiferromagnetism. With increasing p ,T★(p ) extrapolates linearly to zero at p ≃pc 2 , the critical doping below which superconductivity emerges at high doping, suggesting that the conditions which favor pseudogap formation also favor pairing. We also use the Nernst effect to investigate how far superconducting fluctuations extend above the critical temperature Tc, as a function of doping, and find that a narrow fluctuation regime tracks Tc, and not T★. This confirms that the pseudogap phase is not a form of precursor superconductivity, and fluctuations in the phase of the

  9. Nonlinear optical control of Josephson coupling in cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Casandruc, Eliza

    2017-03-15

    In High-T{sub C} cuprates superconducting Cu-O planes alternate with insulating layers along the crystallographic c-axis, making the materials equivalent to Josephson junctions connected in series. The most intriguing consequence is that the out-of-plane superconducting transport occurs via Cooper pairs tunneling across the insulating layers and can be predicted by the Josephson tunneling equations. Nonlinear interaction between light fields and the superconducting carriers serves as a powerful dynamical probe of cuprates, while offering opportunities for controlling them in an analogous fashion to other stimuli such as pressure and magnetic fields. The main goal of this thesis work is to use intense transient light fields to control the interlayer superconducting transport on ultrafast time scales. This was achieved by tuning the wavelength of such light pulses to completely different ranges, in order to either directly excite Josephson Plasma Waves in the nonlinear regime, or efficiently melt the competing charge and spin order phase, which in certain cuprates quenches the Josephson tunneling at equilibrium. In a first study, I have utilized strong field terahertz transients with frequencies tuned to the Josephson plasma resonance (JPR) to coherently control the c-axis superconducting transport. The Josephson relations have a cubic nonlinearity which is exploited to achieve two related, albeit slightly different, phenomena. Depending on the driving pulse, solitonic breathers were excited with narrow-band multi-cycle pulses in La{sub 1.84}Sr{sub 0.16}CuO{sub 4} while broad-band half-cycle pulses were employed to achieve a parametric amplification of Josephson Plasma Waves in La{sub 1.905}Ba{sub 0.095}CuO{sub 4}. These experiments are supported by extensive modeling, showing exceptional agreement. A comprehensive study illustrates the strong enhancement of the nonlinear effects near the JPR frequency. Then, I turned to investigate the competition between

  10. Lindhard and RPA susceptibility computations in extended momentum space in electron-doped cuprates

    OpenAIRE

    Wang, Y.J.; Barbiellini, B.; Lin, H.; Das, T.; Basak, S.; Mijnarends, P.E.; Kaprzyk, S.; Markiewicz, R.S.; Bansil, A.

    2012-01-01

    We present an approximation for efficient calculation of the Lindhard susceptibility $\\chi^{L}(q,\\omega)$ in a periodic system through the use of simple products of real space functions and the fast Fourier transform (FFT). The method is illustrated by providing $\\chi^{L}(q,\\omega)$ results for the electron doped cuprate Nd$_{2-x}$Ce$_{x}$CuO$_{4}$ extended over several Brillouin zones. These results are relevant for interpreting inelastic X-ray scattering spectra from cuprates.

  11. Helimagnetism and weak ferromagnetism in edge-shared chain cuprates

    International Nuclear Information System (INIS)

    Drechsler, S.-L.; Richter, J.; Kuzian, R.; Malek, J.; Tristan, N.; Buechner, B.; Moskvin, A.S.; Gippius, A.A.; Vasiliev, A.; Volkova, O.; Prokofiev, A.; Rakoto, H.; Broto, J.-M.; Schnelle, W.; Schmitt, M.; Ormeci, A.; Loison, C.; Rosner, H.

    2007-01-01

    The present understanding of a novel growing class of chain cuprates with intriguing magnetic properties is reviewed. Among them, several undoped edge-shared CuO 2 chain compounds show at low temperature a clear tendency to helicoidal magnetical ordering with acute pitch angles and sometimes also to weak ferromagnetism. Our analysis is based on the isotropic 1D frustrated J 1 -J 2 Heisenberg model with ferromagnetic (FM) 1st neighbor and antiferromagnetic 2nd neighbor exchange. The achieved assignment is supported by microscopic calculations of the electronic and magnetic structure. We consider Na(Li)Cu 2 O 2 , LiVCuO 4 as the best studied helimagnets, Li 2 ZrCuO 4 and other systems close to a FM quantum critical point, as well as Li 2 CuO 2 with FM inchain ordering. The interplay of frustrated inchain couplings, anisotropy and interchain exchange is discussed

  12. Overdoped cuprates with high-temperature superconducting transitions

    Directory of Open Access Journals (Sweden)

    M. Marezio

    2013-08-01

    Full Text Available Evidence for high-Tc cuprate superconductivity is found in a region of the phase diagram where non-superconducting Fermi liquid metals are expected. Cu valences estimated independently from both x-ray absorption near-edge spectroscopy and bond valence sum measurements are >2.3, and are in close agreement with each other for structures in the homologous series (Cu0.75Mo0.25Sr2(Y,CesCu2O5+2s+δ with s = 1, 2, 3, and 4. The record short apical oxygen distance, at odds with current theory, suggests the possibility of a new pairing mechanism. The possibility that the charge reservoir layers are able to screen long range coulomb interactions and thus enhance Tc is discussed.

  13. Optical excitation of Josephson plasma solitons in a cuprate superconductor.

    Science.gov (United States)

    Dienst, A; Casandruc, E; Fausti, D; Zhang, L; Eckstein, M; Hoffmann, M; Khanna, V; Dean, N; Gensch, M; Winnerl, S; Seidel, W; Pyon, S; Takayama, T; Takagi, H; Cavalleri, A

    2013-06-01

    Josephson plasma waves are linear electromagnetic modes that propagate along the planes of cuprate superconductors, sustained by interlayer tunnelling supercurrents. For strong electromagnetic fields, as the supercurrents approach the critical value, the electrodynamics become highly nonlinear. Josephson plasma solitons (JPSs) are breather excitations predicted in this regime, bound vortex-antivortex pairs that propagate coherently without dispersion. We experimentally demonstrate the excitation of a JPS in La1.84Sr0.16CuO4, using intense narrowband radiation from an infrared free-electron laser tuned to the 2-THz Josephson plasma resonance. The JPS becomes observable as it causes a transparency window in the opaque spectral region immediately below the plasma resonance. Optical control of magnetic-flux-carrying solitons may lead to new applications in terahertz-frequency plasmonics, in information storage and transport and in the manipulation of high-Tc superconductivity.

  14. Fermi surface of underdoped high-Tc superconducting cuprates

    International Nuclear Information System (INIS)

    Dai, X.; Su, Z.; Yu, L.

    1997-01-01

    The coexistence of a π-flux state and a d-wave resonant-valance-bond (RVB) state is considered in this paper within the slave-boson approach. A critical value of doping concentration δ c is found, below which the coexisting π-flux and d-wave RVB state is favored in energy. The pseudo-Fermi surface of spinons and the physical electron spectral function are calculated. A clear Fermi-level crossing is found along the (0,0) to (π, π) direction, but no such crossing is detected along the (π, 0) to (π, π) direction. Also, an energy gap of d-wave symmetry appears at the Fermi level in our calculation. The above results are in agreement with the angle-resolved photoemission experiments which indicate at a d-wave pseudogap and a half-pocket-like Fermi surface in underdoped cuprates. copyright 1997 The American Physical Society

  15. Strong-coupling approach to nematicity in the cuprates

    Science.gov (United States)

    Orth, Peter Philipp; Jeevanesan, Bhilahari; Schmalian, Joerg; Fernandes, Rafael

    The underdoped cuprate superconductor YBa2Cu3O7-δ is known to exhibit an electronic nematic phase in proximity to antiferromagnetism. While nematicity sets in at large temperatures of T ~ 150 K, static spin density wave order only emerges at much lower temperatures. The magnetic response shows a strong in-plane anisotropy, displaying incommensurate Bragg peaks along one of the crystalline directions and a commensurate peak along the other one. Such an anisotropy persists even in the absence of long-range magnetic order at higher temperatures, marking the onset of nematic order. Here we theoretically investigate this situation using a strong-coupling method that takes into account both the localized Cu spins and the holes doped into the oxygen orbitals. We derive an effective spin Hamiltonian and show that charge fluctuations promote an enhancement of the nematic susceptibility near the antiferromagnetic transition temperature.

  16. Issues in the processing of cuprate ceramic superconductors

    International Nuclear Information System (INIS)

    Clarke, D.R.; Shaw, T.M.; Dimos, D.

    1989-01-01

    A number of the important issues in the processing of dense, superconducting ceramics are addressed and illustrated with examples drawn from our studies of the processing of yttrium barium cuprate. Among the phenomena affecting the attainment of dense, fully superconducting materials are those common to the processing of other ceramics, namely, control of composition, prevention of microcracking, adequate time for the decomposition, and escape of intermediaries prior to surface densification (the so-called binder burn-off problem). On the basis of the processing issues described, it is concluded that the optimum microstructure is one having fine-scale, interconnected porosity (to ensure escape of carbonate-like species and subsequent, rapid oxygenation) with a fine grain size to avoid microcracking

  17. Bec Model of HIGH-Tc Superconductivity in Layered Cuprates

    Science.gov (United States)

    Lomnitz, M.; Villarreal, C.; de Llano, M.

    2013-11-01

    High-Tc superconductivity in layered cuprates is described in a BCS-BEC formalism with linearly-dispersive s- and d-wave Cooper pairs moving in quasi-2D finite-width layers around the CuO2 planes. This yields a closed formula for Tc involving the layer width, the Debye frequency, the pairing energy and the in-plane penetration depth. The new formula has no free parameters and reasonably reproduces empirical values of superconducting Tcs for 11 different layered superconductors over a wide doping regime including YBCO itself as well as other compounds like LSCO, BSCCO and TBCCO. In agreement with the London formalism, the formula also yields a fair description of the Tc dependence of the lower critical magnetic field in highly underdoped YBCO.

  18. Vison Condensation and Bond Density Wave Order in the Cuprates

    Science.gov (United States)

    Patel, Aavishkar; Allais, Andrea; Chowdhury, Debanjan; Sachdev, Subir

    We consider Z2 spin liquids on the square lattice. These can undergo a confinement transition to a valence bond solid (VBS) phase via the condensation of vortex excitations carrying Z2 magnetic flux (visons). The resulting condensed phase is described by a fully frustrated Ising model (FFIM) on the dual square lattice, with additional couplings allowed by symmetries. We argue that such a model can also apply to confinement transitions out of the fractionalized Fermi liquid (FL*) states of doped antiferromagnets. We study the low energy states of such a model and discuss their implications for the incommensurate d-form factor bond density wave order observed in several recent experiments on the cuprate superconductors.

  19. The Origin of Tc Enhancement in Heterostructure Cuprate Superconductors

    Directory of Open Access Journals (Sweden)

    Doron L. Bergman

    2011-10-01

    Full Text Available Recent experiments on heterostructures composed of two or more films of cuprate superconductors of different oxygen doping levels have shown a remarkable Tc enhancement (up to 50% relative to single compound films. We provide a simple explanation of the enhancement which arises naturally from a collection of experimental works. We show that the enhancement could be caused by a structural change in the lattice, namely an increase in the distance of the apical oxygen from the copper-oxygen plane. This increase modifies the effective off-site interaction in the plane which in turn enhances the d-wave superconductivity order parameter. To illustrate this point we study the extended Hubbard model using the fluctuation exchange approximation.

  20. Variational Monte Carlo study of spin dynamics in underdoped cuprates

    Science.gov (United States)

    Yu, Zuo-Dong; Zhou, Yuan; Gong, Chang-De

    2017-11-01

    The hour-glass-like dispersion of spin excitations is a common feature of underdoped cuprates. It was qualitatively explained by the random-phase approximation based on various ordered states with some phenomenological parameters; however, its origin remains elusive. Here, we present a numerical study of spin dynamics in the t -J model using the variational Monte Carlo method. This parameter-free method satisfies the no double-occupancy constraint of the model and thus provides a better evaluation on the spin dynamics with respect to various mean-field trial states. We conclude that the lower branch of the hour-glass dispersion is a collective mode and the upper branch more than the other candidates is likely the consequence of the stripe state.

  1. Development of a REBCO HTS magnet for Maglev - repeated bending tests of HTS pancake coils -

    Science.gov (United States)

    Sugino, Motohikoa; Mizuno, Katsutoshi; Tanaka, Minoru; Ogata, Masafumi

    2018-01-01

    In the past study, two manufacturing methods were developed that can manufacture pancake coils by using REBCO coated conductors. It was confirmed that the conductors have no electric degradation that caused by the manufacturing method. The durability evaluation tests of the pancake coils were conducted as the final evaluation of the coil manufacturing method in this study. The repeated bending deformation was applied to manufactured pancake coils in the tests. As the results of these tests, it was confirmed that the pancake coils that were manufactured by two methods had the durability for the repeated bending deformation and the coils maintained the appropriate mechanical performance and electric performance. We adopted the fusion bonding method as the coil manufacturing method of the HTS magnet Furthermore, using the prototype pancake coil that was manufactured by the fusion bonding method as a test sample, the repeated bending test under the exited condition was conducted. Thus it was confirmed that the coil manufactured by the fusion bonding method has no degradation of the electricity performance and the mechanical properties even if the repeated bending deformation was applied under the exited condition.

  2. Incommensurate Phonon Anomaly and the Nature of Charge Density Waves in Cuprates

    Science.gov (United States)

    Miao, H.; Ishikawa, D.; Heid, R.; Le Tacon, M.; Fabbris, G.; Meyers, D.; Gu, G. D.; Baron, A. Q. R.; Dean, M. P. M.

    2018-01-01

    While charge density wave (CDW) instabilities are ubiquitous to superconducting cuprates, the different ordering wave vectors in various cuprate families have hampered a unified description of the CDW formation mechanism. Here, we investigate the temperature dependence of the low-energy phonons in the canonical CDW-ordered cuprate La1.875 Ba0.125 CuO4 . We discover that the phonon softening wave vector associated with CDW correlations becomes temperature dependent in the high-temperature precursor phase and changes from a wave vector of 0.238 reciprocal lattice units (r.l.u.) below the ordering transition temperature to 0.3 r.l.u. at 300 K. This high-temperature behavior shows that "214"-type cuprates can host CDW correlations at a similar wave vector to previously reported CDW correlations in non-214-type cuprates such as YBa2 Cu3 O6 +δ . This indicates that cuprate CDWs may arise from the same underlying instability despite their apparently different low-temperature ordering wave vectors.

  3. Critical current densities in thick yttrium-barium cuprate (1-2-3) films

    International Nuclear Information System (INIS)

    Ryvkina, G.G.; Gorlanov, S.F.; Vedernikov, G.E.; Telegin, A.B.; Ryabin, V.A.; Khodos, M.Ya.

    1993-01-01

    The study of critical current densities j c of oxide superconductors and their thick films is a very important practical task because the value of j c is one of the main criteria for their utilization in modern cryoelectronics. For most devices based on the Josephson effect, the value of j c ∼ 10 2 - 10 3 A/cm 2 is acceptable, which is easily attainable for polycrystalline thick films obtained by stenciling. The study of the current-transport phenomenon involves a number of difficulties, especially for direct current, because both the sample itself and the lead-in contacts are resistance-heated during the measurements, which, in turn, results in lower values of the j c . Measurements with pulsed currents allow one to lower the power that is applied to the sample; the heat that is released in the sample is reduced, in comparison to measurements with direct current, by a factor of the pulsed-current duty cycle. In addition, measurements with direct current detects only the appearance of resistance; it provides no information on the rest of the transition from the normal to the superconductive state, i.e., on the so-called 'tail' of the transition. In this work, the authors studied critical current densities of thick HTSC yttrium-barium cuprate films of the 1-2-3 composition using pulsed current

  4. Giant superconductivity-induced modulation of the ferromagnetic magnetization in a cuprate-manganite superlattice.

    Science.gov (United States)

    Hoppler, J; Stahn, J; Niedermayer, Ch; Malik, V K; Bouyanfif, H; Drew, A J; Rössle, M; Buzdin, A; Cristiani, G; Habermeier, H-U; Keimer, B; Bernhard, C

    2009-04-01

    Artificial multilayers offer unique opportunities for combining materials with antagonistic orders such as superconductivity and ferromagnetism and thus to realize novel quantum states. In particular, oxide multilayers enable the utilization of the high superconducting transition temperature of the cuprates and the versatile magnetic properties of the colossal-magnetoresistance manganites. However, apart from exploratory work, the in-depth investigation of their unusual properties has only just begun. Here we present neutron reflectometry measurements of a [Y(0.6)Pr(0.4)Ba(2)Cu(3)O(7) (10 nm)/La(2/3)Ca(1/3)MnO(3) (10 nm)](10) superlattice, which reveal a surprisingly large superconductivity-induced modulation of the vertical ferromagnetic magnetization profile. Most surprisingly, this modulation seems to involve the density rather than the orientation of the magnetization and is highly susceptible to the strain, which is transmitted from the SrTiO(3) substrate. We outline a possible explanation of this unusual superconductivity-induced phenomenon in terms of a phase separation between ferromagnetic and non-ferromagnetic nanodomains in the La(2/3)Ca(1/3)MnO(3) layers.

  5. Epitaxial oxide thin films by pulsed laser deposition: Retrospect and ...

    Indian Academy of Sciences (India)

    Epitaxial thin films of high c cuprates, metallic, ferroelectric, ferromagnetic, dielectric oxides, super conduc tor-metal-superconductor Josephson junctions and oxide superlattices have been made by PLD. In this article, an overview of preparation, characterization and properties of epitaxial oxide films and their applications ...

  6. Simulation of magnetization and levitation characteristics of HTS tape stacks

    Science.gov (United States)

    Anischenko, I. V.; Pokrovskii, S. V.; Mineev, N. A.

    2017-12-01

    In this work it is presented a computational model of a magnetic levitation system based on stacks of high-temperature second generation superconducting tapes (HTS) GdBa2Cu3O7-x. Calculated magnetic field and the current distributions in the system for different stacks geometries in the zero-field cooling mode are also presented. The magnetization curves of the stacks in the external field of a permanent NdFeB magnet and the levitation force dependence on the gap between the magnet and the HTS tapes stack were obtained. A model of the magnetic system, oriented to levitation application, is given. Results of modeling were compared with the experimental data.

  7. Development of Prototype HTS Components for Magnetic Suspension Applications

    Science.gov (United States)

    Haldar, P.; Hoehn, J., Jr.; Selvamanickam, V.; Farrell, R. A.; Balachandran, U.; Iyer, A. N.; Peterson, E.; Salazar, K.

    1996-01-01

    We have concentrated on developing prototype lengths of bismuth and thallium based silver sheathed superconductors by the powder-in-tube approach to fabricate high temperature superconducting (HTS) components for magnetic suspension applications. Long lengths of mono and multi filament tapes are presently being fabricated with critical current densities useful for maglev and many other applications. We have recently demonstrated the prototype manufacture of lengths exceeding 1 km of Bi-2223 multi filament conductor. Long lengths of thallium based multi-filament conductor have also been fabricated with practical levels of critical current density and improved field dependence behavior. Test coils and magnets have been built from these lengths and characterized over a range of temperatures and background fields to determine their performance. Work is in progress to develop, fabricate and test HTS windings that will be suitable for magnetic suspension, levitation and other electric power related applications.

  8. Magnetic evaluation of a solar panel using HTS-SQUID

    International Nuclear Information System (INIS)

    Kiwa, Toshihiko; Fukudome, Yohei; Miyazaki, Shingo; Saari, Mohd Mawardi; Sakai, Kenji; Tsukada, Keiji

    2013-01-01

    Highlights: •The magnetic evaluation system of a solar panel using HTS-SQUID has been developed. •The electric circuits made by the discrete devices on the circuit board were visualized. •The electric properties of the commercial solar panels were demonstrated. -- Abstract: The magnetic evaluation system of a solar panel using HTS-SQUID has been proposed and developed. A normal pick-up coil was applied to detect the tangential magnetic field to the panel surface. Since the detected field could be related to the currents of the solar panels, the electric properties of the solar panels could be evaluated. In this work, the evaluation of the electric properties of the commercial solar panels as well as the electric circuits made by the discrete devices on the circuit board was visualized

  9. Extending the Application of HTS in Particle Accelerators

    CERN Document Server

    Ballarino, A; Taylor, T

    2008-01-01

    The year-to-year improvements in the characteristics of high temperature superconductor (HTS) materials encourage periodic reappraisal of their applicability for use in accelerators. With the successful large-scale application of HTS technology for the current leads of the Large Hadron Collider at CERN, this tendency is accentuated, and the new materials are now starting to receive more serious attention as candidates for other accelerator-related applications. The medium- to long-term goal will be to use the materials for magnets, but their characteristics are totally different from those of classical multi-filamentary Nb-Ti material and the transition will be difficult. In particular it seems likely to be inappropriate to carry over the presently conventional coil geometries and conductor excitation levels. A roadmap is proposed for R&D that will lead progressively to achieving the ultimate goal through consolidation of the necessary technology via intermediate steps, and progressive accumulatio...

  10. Quench Detection and Protection of an HTS Coil

    Science.gov (United States)

    Sheehan, Evan; Pfotenhauer, John; Miller, Franklin; Christianson, Owen

    2017-12-01

    A pulsed, modular HTS magnet for energy storage applications was constructed and tested. Charge and discharge pulses were accomplished in about 1 second. A recuperative cryogenic cooling system supplies 42 to 80 Kelvin helium gas to the magnet. A practical solution to overvoltage and overcurrent protection has been implemented digitally using LabVIEW. Voltages as little as 46 μV greater than the expected value trigger the protection system, which stops the pulse profile and begins an immediate current ramp down to zero over 1 second. The protection system has displayed its effectiveness in HTS transition detection and damage prevention. Experimentation has demonstrated that current pulses on the order of seconds with amplitudes of up to 110 Amps can be achieved for extended periods. Higher currents produce joint heating in excess of the available cooling from the existing cryogenic system.

  11. Application of HTS technology to cardiac dysrhythmia detection

    Energy Technology Data Exchange (ETDEWEB)

    Sobel, A.L. [Sandia National Labs., Albuquerque, NM (United States); Avrin, W.F. [Quantum Magnetics, Inc., San Diego, CA (United States)

    1994-12-01

    This paper discusses the conceptual design considerations and challenges for development of a contactless, mobile, single channel biomagnetic sensor system based on High-Temperature Superconductor (HTS) Superconducting Quantum Interference Devices (SQUIDs) and employing the Three-SQUID Gradiometer (TSG) concept. Operating in magnetically unshielded environments, as are encountered in many medical scenarios, this instrument class would monitor cardiac electrical activity with minimal patient preparation and intrusiveness, and would notionally be coupled with a clinically adaptive human-system interface (HSI).

  12. Harmonic analysis and field quality improvement of an HTS quadrupole magnet for a heavy ion accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Zhan; Wei, Shaoqing; Lee, Sang Jin [Uiduk University, Gyeongju (Korea, Republic of); Jo, Hyun Chul; Kim, Do Gyun; Kim, Jong Won [Rare Isotope Science Project, Institute for Basic Science, Daejeon (Korea, Republic of)

    2016-06-15

    In recent years, the iron-dominated high-temperature superconductor (HTS) quadrupole magnets are being developed for heavy ion accelerators. Field analyses for iron-dominated quadrupole magnets were based on the normal-conducting (NC) quadrupole magnet early in the development for accelerators. Some conclusions are still in use today. However, the magnetic field of iron-dominated HTS quadrupole magnets cannot fully follow these conclusions. This study established an HTS quadrupole magnet model and an NC quadrupole magnet model, respectively. The harmonic characteristics of two magnets were analyzed and compared. According to the comparison, the conventional iron-dominated quadrupole magnets can be designed for maximum field gradient; the HTS quadrupole magnet, however, should be considered with varying field gradient. Finally, the HTS quadrupole magnet was designed for the changing field gradient. The field quality of the design was improved comparing with the result of the previous study. The new design for the HTS quadrupole magnet has been suggested.

  13. Topics in electronic structure and spectroscopy of cuprates

    Science.gov (United States)

    Lin, Hsin

    I have applied first-principles calculations to investigate several interrelated problems concerned with the electronic structure and spectroscopy of cuprates. The specific topics addressed in this thesis are as follows. 1. By properly including doping effects beyond rigid band filling, a longstanding problem of the missing Bi-O pocket in the electronic structure of Bi2Sr2CaCu2O8 (Bi2212) is solved. The doping effect is explained in terms of Coulombic effect between layers and is a generic property of all cuprates. 2. A systematic study for Pb/O and rare-earth doping in Bi2212 is carried out to explain the experimental phase diagrams, and a possible new electron doped Bi2212 is predicted. 3. To investigate how the Mott insulators evolve into superconductors with the addition of holes, an analysis of angle-resolved photoemission (ARPES) data of La2-xSr xCuO4 is carried out over a wide doping range of x = 0.03 - 0.30. The spectrum displays the presence of the van Hove singularity (VHS) whose location in energy and three-dimensionality are in accord with the band theory predictions. A nascent metallic state is found in the lightly doped Mott insulator and develops spectral weight as doping increases. This metallic spectrum is 'universal' in the sense that its dispersion depends weakly on doping, in sharp contrast to the common expectation that dispersion is renormalized to zero at half-filling. This finding challenges existing theoretical scenarios for cuprates. 4. Self-consistent mean-field three- and four-band Hubbard models are used to study the Mott gap in electron-doped cuprates. The Hubbard terms are decomposed into a Mott-like term which describes the lifting of Cu bands due to energy cost U and a Slater-like term which describes an additional splitting of Cu bands due to antiferromagnetic (AFM) order. While no set of doping-independent parameters can explain the observed gaps for the entire doping range, the experimental results are consistent with a weakly

  14. Atomic Layer Epitaxy of Superconducting Oxides and Heterostructures

    National Research Council Canada - National Science Library

    Chang, R

    1998-01-01

    ...) materials and insulating metal oxides. Improving the nature of such interfaces is a crucial barrier which must be surmounted before HTS materials can be successfully incorporated on a large scale into a myriad of advanced active...

  15. Study on AC loss measurements of HTS power cable for standardizing

    Science.gov (United States)

    Mukoyama, Shinichi; Amemiya, Naoyuki; Watanabe, Kazuo; Iijima, Yasuhiro; Mido, Nobuhiro; Masuda, Takao; Morimura, Toshiya; Oya, Masayoshi; Nakano, Tetsutaro; Yamamoto, Kiyoshi

    2017-09-01

    High-temperature superconducting power cables (HTS cables) have been developed for more than 20 years. In addition of the cable developments, the test methods of the HTS cables have been discussed and proposed in many laboratories and companies. Recently the test methods of the HTS cables is required to standardize and to common in the world. CIGRE made the working group (B1-31) for the discussion of the test methods of the HTS cables as a power cable, and published the recommendation of the test method. Additionally, IEC TC20 submitted the New Work Item Proposal (NP) based on the recommendation of CIGRE this year, IEC TC20 and IEC TC90 started the standardization work on Testing of HTS AC cables. However, the individual test method that used to measure a performance of HTS cables hasn’t been established as world’s common methods. The AC loss is one of the most important properties to disseminate low loss and economical efficient HTS cables in the world. We regard to establish the method of the AC loss measurements in rational and in high accuracy. Japan is at a leading position in the AC loss study, because Japanese researchers have studied on the AC loss technically and scientifically, and also developed the effective technologies for the AC loss reduction. The JP domestic commission of TC90 made a working team to discussion the methods of the AC loss measurements for aiming an international standard finally. This paper reports about the AC loss measurement of two type of the HTS conductors, such as a HTS conductor without a HTS shield and a HTS conductor with a HTS shield. The AC loss measurement method is suggested by the electrical method..

  16. Hysteresis and reluctance electric machines with bulk HTS elements. Recent results and future development

    International Nuclear Information System (INIS)

    Kovalev, L.K.; Ilushin, K.V.; Penkin, V.T.; Kovalev, K.L.; Koneev, S.M.-A.; Poltavets, V.N.; Larionoff, A.E.; Modestov, K.A.; Larionoff, S.A.; Gawalek, W.; Habisreuther, T.; Oswald, B.; Best, K.-J.; Strasser, T.

    2000-01-01

    Two new types of HTS electric machine are considered. The first type is hysteresis motors and generators with cylindrical and disc rotors containing bulk HTS elements. The second type is reluctance motors with compound HTS-ferromagnetic rotors. The compound HTS-ferromagnetic rotors, consisting of joined alternating bulk HTS (YBCO) and ferromagnetic (iron) plates, provide a new active material for electromechanical purposes. Such rotors have anisotropic properties (ferromagnetic in one direction and diamagnetic in the perpendicular one). Theoretical and experimental results for HTS hysteresis and reluctance motors are presented. A series of hysteresis HTS motors with output power rating from 1 kW (at 50 Hz) up to 4 kW (at 400 Hz) and a series of reluctance HTS motors with output power 2-18.5 kW (at 50 Hz) were constructed and successfully tested. It was shown that HTS reluctance motors could reach two to five times better overall dimensions and specific power than conventional asynchronous motors of the same size and will have higher values of power factor (cos φ≥0.7 to 0.8). (author)

  17. Comprehensive Study of the Model Mercury-Based Cuprate Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Greven, Martin [Univ. of Minnesota, Minneapolis, MN (United States)

    2017-11-13

    This is the Final Report on DE-SC0006858, which opened 15 August 2011 and closed 14 August 2017. The Principal Investigator is Martin Greven, School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 555455 (email: greven@umn.edu). The Administrative Point of Contact is Patricia Jondahl, phone: 612-624-5599, email: awards@umn.edu. The DOE Program is the Office of Basic Energy Sciences, Program manager is Dr. P. Thiyagarajan, Neutron Scattering SC-22.2/ Germantown Bldg. (email: Thiyagarajan@science.doe.gov). The chief activity was the crystal growth, characterization, neutron and X-ray scattering study of the mercury-based cuprates, arguably the most desirable high-Tc superconductors for experimental study due to their record values of Tc and their relatively simple crystal structures. It is thought that the unusual magnetic and charge degrees of freedom of the copper-oxygen sheets that form the fundamental building block of all cuprate superconductors give rise to the high Tc and to many other unusual properties exhibited by the class of quantum materials. Neutron scattering experiments were performed to reveal the nature of the magnetic degrees of freedom of the copper-oxygen sheets, whereas X-ray scattering experiments and complementary charge-transport experiments were performed to reveal the nature of the charge degrees of freedom. In addition, collaborations were initiated with experts in the use of complementary experimental techniques. The primary products are (i) scientific articles published in peer-reviewed scientific journals, (ii) scientific presentations at national and international conferences, and (iii) education of postdoctoral researchers, PhD graduate students and undergraduate researchers by providing a research experience in crystal growth, characterization and scattering. Twenty scientific papers were published in peer-reviewed journals, thirty-one invited talks were presented at national or international conferences, or as

  18. Infrared absorption spectra of various doping states in cuprate superconductors

    International Nuclear Information System (INIS)

    Yonemitsu, K.; Bishop, A.R.; Lorenzana, J.

    1992-01-01

    Doping states in a two-dimensional three-band extended Peierls-Hubbard model was investigated within inhomogeneous Hartree-Fock and random phase approximation. They are very sensitive to small changes of interaction parameters and their distinct vibrational and optical absorption spectra can be used to identify different doping states. For electronic parameters relevant to cuprate superconductors, as intersite electron-phonon interaction strength increases, the doping state changes from a Zhang-Rice state to a covalent molecular singlet state accompanied by local quenching of the Cu magnetic moment and large local lattice distortion in an otherwise undistorted antiferromagnetic background. In a region where both intersite electron-phonon interaction and on-site electron-electron repulsion are large, we obtain new stable global phases including a bond-order-wave state and a mixed state of spin-Peierls bonds and antiferromagnetic Cu spins, as well as many metastable states. Doping in the bond-order-wave region induces separation of spin and charge. 9 refs

  19. Magnetic excitations and amplitude fluctuations in insulating cuprates

    Science.gov (United States)

    Chelwani, N.; Baum, A.; Böhm, T.; Opel, M.; Venturini, F.; Tassini, L.; Erb, A.; Berger, H.; Forró, L.; Hackl, R.

    2018-01-01

    We present results from light scattering experiments on three insulating antiferromagnetic cuprates, YBa2Cu3O6.05 , Bi2Sr2YCu2O8 +δ , and La2CuO4 as a function of polarization and excitation energy using samples of the latest generation. From the raw data we derive symmetry-resolved spectra. The spectral shape in B1 g symmetry is found to be nearly universal and independent of excitation energy. The spectra agree quantitatively with predictions by field theory [Eur. Phys. J. B 88, 237 (2015), 10.1140/epjb/e2015-60438-1] facilitating the precise extraction of the Heisenberg coupling J . In addition, the asymmetric lineshape on the high-energy side is found to be related to amplitude fluctuations of the magnetization. In La2CuO4 alone, minor contributions from resonance effects may be identified. The spectra in the other symmetries are not universal. The variations may be traced back to weak resonance effects and extrinsic contributions. For all three compounds we find support for the existence of chiral excitations appearing as a continuum in A2 g symmetry having an onset slightly below 3 J . In La2CuO4 an additional isolated excitation appears on top of the A2 g continuum.

  20. The anomalous optical conductivity in hole-doped cuprate superconductors

    Science.gov (United States)

    Gao, He; Yuan, Feng; Chen, Shaou; Zhao, Huaisong

    2018-02-01

    Based on the renormalized t- J model and self-consistent mean field theory, the doping and energy dependence of optical conductivity and effective electron number in cuprate superconductors are discussed. As the result of the presence of the pseudogap in normal state, the optical conductivity exhibits two main components from underdoping to overdoping, a narrow band peaked around zero energy and a broadband centered in the mid-infrared region which deviates the Drude formula. With increasing the doping concentration, the spectral weight of the optical conductivity suppressed strongly in underdoped region increases quickly, and the peak position of the mid-infrared band moves towards to the lower energy region, then incorporates into the narrow band centered in zero energy in the heavily overdoped region. By virtue of the integral, the effective electron number is obtained, and it increases monotonically from zero energy to mid-infrared characteristic energy with increasing energy, then shows a plateau feature when the energy is larger. In particular, the mid-infrared characteristic energy scales with the pseudogap, reflecting the presence of the mid-infrared band is the result of the pseudogap effect.

  1. Oxygen hole symmetry and banding in cuprate superconductors

    International Nuclear Information System (INIS)

    Mattheiss, L.F.; Hamann, D.R.

    1989-01-01

    A simple procedure is proposed for modeling the O 2p bands of cuprate compounds in the limit where the Cu 3d electrons are localized by correlation effects such as the on-site Coulomb energy U d . This scheme, which involves orthogonalization of the linear augmented-plane-wave (LAPW) basis to the Cu 3d states, has been applied to Ca 0.86 Sr 0.14 CuO 2 , the parent compound of the Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O high-T c superconductors. Tight-binding fits to the LAPW results for Ca 0.86 Sr 0.14 CuO 2 with localized and itinerant Cu 3d electrons yield O p-p interaction parameters which describe both limits equally well. According to this model, the doping-induced holes in the O 2p manifold depopulate initially bands containing σ-antibonding p(x,y) orbitals that are pointed along the O-Cu bond directions, with π-antibonding p(x,y) and p(z) subbands entering only at larger hole concentrations

  2. Holographic model for the anomalous scalings of the cuprates

    Science.gov (United States)

    Blauvelt, Erin; Cremonini, Sera; Hoover, Anthony; Li, Li; Waskie, Steven

    2018-03-01

    We examine transport in a holographic model in which the dynamics of the charged degrees of freedom is described by the nonlinear Dirac-Born-Infeld (DBI) action. Axionic scalar fields are included to break translational invariance and generate momentum dissipation in the system. Scaling exponents are introduced by using geometries which are nonrelativistic and hyperscaling-violating in the infrared. In the probe DBI limit the theory reproduces the anomalous temperature dependence of the resistivity and Hall angle of the cuprate strange metals, ρ ˜T and cotΘH˜T2. These scaling laws would not be present without the nonlinear dynamics encoded by the DBI interactions. We further show that because of its richness the DBI theory supports a wide spectrum of temperature scalings. This model provides explicit examples in which transport is controlled by different relaxation times. On the other hand, when only one quantity sets the temperature scale of the system, the Hall angle and conductivity typically exhibit the same temperature behavior. We illustrate this point using new fully backreacted analytical dyonic black brane solutions.

  3. Phonon anomalies in trilayer high-Tc cuprate superconductors

    International Nuclear Information System (INIS)

    Dubroka, Adam; Munzar, Dominik

    2004-01-01

    We present an extension of the model proposed recently to account for dramatic chAes below T c (anomalies) of some c-axis polarized infrared-active phonons in bilayer cuprate superconductors, that applies to trilayer high-T c compounds. We discuss several types of phonon anomalies that can occur in these systems and demonstrate that our model is capable of explaining the spectral chAes occurring upon entering the superconducting state in the trilayer compound Tl 2 Ba 2 Ca 2 Cu 3 O 10 . The low-temperature spectra of this compound obtained by Zetterer and coworkers display an additional broad absorption band, similar to the one observed in underdoped YBa 2 Cu 3 O 7-δ and Bi 2 Sr 2 CaCu 2 O 8 . In addition, three phonon modes are strongly anomalous. We attribute the absorption band to the transverse Josephson plasma resonance, similar to that of the bilayer compounds. The phonon anomalies are shown to result from a modification of the local fields induced by the formation of the resonance. The spectral chAes in Tl 2 Ba 2 Ca 2 Cu 3 O 10 are compared with those occurring in Bi 2 Sr 2 Ca 2 Cu 3 O 10 , reported recently by Boris and coworkers

  4. Superconducting fluctuations and pseudogap in high-Tc cuprates

    Directory of Open Access Journals (Sweden)

    Alloul H.

    2012-03-01

    Full Text Available Large pulsed magnetic fields up to 60 Tesla are used to suppress the contribution of superconducting fluctuations (SCF to the ab-plane conductivity above Tc in a series of YBa2Cu3O6+x. These experiments allow us to determine the field Hc’(T and the temperature Tc’ above which the SCFs are fully suppressed. A careful investigation near optimal doping shows that Tc’ is higher than the pseudogap temperature T*, which is an unambiguous evidence that the pseudogap cannot be assigned to preformed pairs. Accurate determinations of the SCF contribution to the conductivity versus temperature and magnetic field have been achieved. They can be accounted for by thermal fluctuations following the Ginzburg-Landau scheme for nearly optimally doped samples. A phase fluctuation contribution might be invoked for the most underdoped samples in a T range which increases when controlled disorder is introduced by electron irradiation. Quantitative analysis of the fluctuating magnetoconductance allows us to determine the critical field Hc2(0 which is found to be be quite similar to Hc’ (0 and to increase with hole doping. Studies of the incidence of disorder on both Tc’ and T* allow us to to propose a three dimensional phase diagram including a disorder axis, which allows to explain most observations done in other cuprate families.

  5. Progress in American Superconductor’s HTS wire and optimization for fault current limiting systems

    Energy Technology Data Exchange (ETDEWEB)

    Malozemoff, Alexis P., E-mail: amalozemoff@amsc.com

    2016-11-15

    Highlights: • AMSC HTS wire critical current needed for rotating machinery is doubled by 16 MeV Au irradiation. • Nonuniformity of HTS wires in power devices causes hot spot formation during power system faults. • Lower normal-state resistivity and critical current lower HTS wire hot spot heating during faults. • HTS wire hot spot heating in HTS cables during faults must stay below lN{sub 2} bubble nucleation point. • HTS wire can be designed to meet hot spot heating limits in fault current limiting cables. - Abstract: American Superconductor has developed composite coated conductor tape-shaped wires using high temperature superconductor (HTS) on a flexible substrate with laminated metal stabilizer. Such wires enable many applications, each requiring specific optimization. For example, coils for HTS rotating machinery require increased current density J at 25–50 K. A collaboration with Argonne, Brookhaven and Los Alamos National Laboratories and several universities has increased J using an optimized combination of precipitates and ion irradiation defects in the HTS. Major commercial opportunities also exist to enhance electric power grid resiliency by linking substations with distribution-voltage HTS power cables [10]. Such links provide alternative power sources if one substation's transmission-voltage power is compromised. But they must also limit fault currents which would otherwise be increased by such distribution-level links. This can be done in an HTS cable, exploiting the superconductor-to-resistive transition when current exceeds the wires’ critical J. A key insight is that such transitions are usually nonuniform; so the wire must be designed to prevent localized hot spots from damaging the wire or even generating gas bubbles in the cable causing dielectric breakdown. Analysis shows that local heating can be minimized by increasing the composite tape's total thickness, decreasing its total resistance in the normal state and

  6. A Possible Path from BCS through HTS to VHTS

    Science.gov (United States)

    Chu, C. W.

    2010-03-01

    Three years after celebrating the 50th anniversary of the BCS theory and the 20th anniversary of the discovery of high temperature superconductivity (HTS), it appears to be most fitting for us to contemplate the possibility of very high temperature superconductivity (VHTS). VHTS, preferably at room temperature, if achieved, could change the world both scientifically and technologically. Unfortunately, it has long been considered by some to belong to the domain of science fiction and to occur only ``at an astronomical distance and under an astronomical pressure.'' With the advent of liquid nitrogen superconductivity in 1987, the outlook has become much brighter. Currently, there appears to be no reason, either theoretical or experimental, why VHTS would be impossible, in spite of the 2006 prediction of the death of HTS by 2010-2015 through the so-called scientometric analysis of the publication record of the previous 20 years. The recent discovery of the new class of Fe-pnictide HTSs fuels more cautious optimism. Since its inception, BCS theory has provided the basic framework for the occurrence and understanding of superconductivity, but it has failed to show where and how to find superconductivity at a higher temperature. This may be attributed to the small energy scale of superconductivity in comparison with those of other excitations in the solids. After examining existing data, we believe that a holistic multidisciplinary enlightened empirical approach appears to be the most effective way to discover novel superconductors with higher transition temperatures. In this talk, I shall present several possible approaches toward VHTS that we are currently pursuing, after briefly summarizing what has happened in the long search for HTS and VHTS.

  7. Semiempirical search for oxide superconductors based on bond valence sums

    International Nuclear Information System (INIS)

    Tanaka, S.; Fukushima, N.; Niu, H.; Ando, K.

    1992-01-01

    Relationships between crystal structures and electronic states of layered transition-metal oxides are analyzed in the light of bond valence sums. Correlations between the superconducting transition temperature T c and the bond-valence-sum parameters are investigated for the high-T c cuprate compounds. Possibility of making nonsuperconducting oxides superconducting is discussed. (orig.)

  8. Issues relating to airborne applications of HTS SQUIDs

    International Nuclear Information System (INIS)

    Foley, C P; Leslie, K E; Binks, R A; Lam, S H K; Du, J; Tilbrook, D L; Mitchell, E E; Macfarlane, J C; Lee, J B; Turner, R; Downey, M; Maddever, A

    2002-01-01

    Airborne application of HTS SQUIDs is the most difficult environment for their successful deployment. In order to operate with the sensitivity required for a particular application, there are many issues to be addressed such as the need for very wide dynamic range electronics, motion noise elimination, immunity to large changing magnetic fields and cultural noise sources. This paper reviews what is necessary to achieve an airborne system giving examples in geophysical mineral exploration. It will consider issues relating to device design and fabrication, electronics, dewar design, suspension system requirements and noise elimination methods

  9. Development of robust HTS-SQUID for non-destructive inspection system in unshielded environment

    International Nuclear Information System (INIS)

    Yoshida, K; Kage, T; Suzuki, T; Hatsukade, Y; Tanaka, S

    2014-01-01

    Cross-shaped YBa 2 Cu 3 O 7−x (YBCO) film was overlapped on directly-coupled multi-pickup-coil HTS-dc-SQUID magnetometer in flip-chip configuration as a superconducting shield, and the characterestics of the SQUID were examined in DC and AC magnetic fields. We created slots in the YBCO film and pickup-coil of HTS-SQUID magnetometer for suppression of flux trapping. In low magnetic field environment, we measured the characteristics of the SQUID without and with HTS film. The most of the parameters were same with and without the HTS films, while S 1/2 φ with the HTS film was a bit smaller than that of the bare SQUID. In the DC field, I c of the HTS-SQUID covered with the HTS film did not change until a DC field over 140 μT was applied to the SQUID, while the bare SQUID's I c decreased with the increase of the applied DC field. In the AC fields at 10 MHz, the SQUID with the HTS film showed degradation of the parameters such as V pp and S 12 φ at lower field amplitude than the bare SQUID.

  10. Design, construction and performance of an EMS-based HTS maglev vehicle

    International Nuclear Information System (INIS)

    Gu Chen; Liu Menglin; Xing Huawei; Zhou, Tong; Yin Wensheng; Zong Jun; Han Zhenghe

    2005-01-01

    A laboratory-scale EMS-based HTS maglev vehicle operating over a 1.5 m guideway has been successfully constructed. The fully integrated system consists of a vehicle chassis, four dependent magnetic circuits, four distance sensors, and control and power amplification circuits. As key component of the system, each magnetic circuit includes a U-shape iron core with one HTS coil forming each pole. Eight HTS coils made of Bi-2223 multi-filamentary tape were used to provide the magnetic motive force. Several questions relating to the unique characteristics of the HTS material in a controlled magnetic circuit are discussed. The most important consideration for such applications is that the anisotropic critical current of the Bi-2223/Ag tape depends strongly on the magnetic field. The commercially available FEA software ANSYS was used to simulate the field distribution along the magnetic circuit and HTS coil winding, and thereby identify how the magnetic circuit alters the field distribution in the coil winding and therefore also the critical current. A general optimization process is described for finding the best position in the U-shape iron core to hold the HTS coils. In this process the critical current of the HTS tape and the force-current characteristic of the magnetic circuit are considered synthetically. The results demonstrate the feasibility and stability of HTS material in a typical maglev system and other similar controllability applications

  11. Design and Development of a 100 MVA HTS Generator for Commercial Entry

    Energy Technology Data Exchange (ETDEWEB)

    None

    2007-06-07

    In 2002, General Electric and the US Department of Energy (DOE) entered into a cooperative agreement for the development of a commercialized 100 MVA generator using high temperature superconductors (HTS) in the field winding. The intent of the program was to: (1) identify and develop technologies that would be needed for such a generator; (2) develop conceptual designs for generators with ratings of 100 MVA and higher using HTS technology; (3) perform proof of concept tests at the 1.5 MW level for GE's proprietary warm iron rotor HTS generator concept; and (4) design, build, and test a prototype of a commercially viable 100 MVA generator that could be placed on the power grid. This report summarizes work performed during the program and is provided as one of the final program deliverables. The design for the HTS generator was based on GE's warm iron rotor concept in which a cold HTS coil is wound around a warm magnetic iron pole. This approach for rotating HTS electrical machinery provides the efficiency benefits of the HTS technology while addressing the two most important considerations for power generators in utility applications: cost and reliability. The warm iron rotor concept uses the least amount of expensive HTS wire compared to competing concepts and builds on the very high reliability of conventional iron core stators and armature windings.

  12. Reduction of Thermal Loss in HTS Windings by Using Magnetic Flux Deflection

    Science.gov (United States)

    Tsuzuki, K.; Miki, M.; Felder, B.; Koshiba, Y.; Izumi, M.; Umemoto, K.; Aizawa, K.; Yanamoto, T.

    Efforts on the generation of intensified magnetic flux have been made for the optimized shape of HTS winding applications. This contributes to the high efficiency of the rotating machines using HTS windings. Heat generation from the HTS windings requires to be suppressed as much as possible, when those coils are under operation with either direct or alternative currents. Presently, the reduction of such thermal loss generated by the applied currents on the HTS coils is reported with a magnetic flux deflection system. The HTS coils are fixed together with flattened magnetic materials to realize a kind of redirection of the flux pathway. Eventually, the magnetic flux density perpendicular to the tape surface (equivalent to the a-b plane) of the HTS tape materials is reduced to the proximity of the HTS coil. To verify the new geometry of the surroundings of the HTS coils with magnetic materials, a comparative study of the DC coil voltage was done for different applied currents in prototype field-pole coils of a ship propulsion motor.

  13. Tests of operating conditions for metrological application of HTS Josephson arrays

    International Nuclear Information System (INIS)

    Sosso, A; Lacquaniti, V; Andreone, D; Cerri, R; Klushin, A M

    2006-01-01

    We report on an experimental study of metrological properties of High Temperature Superconductor arrays, made of shunted bicrystal YBCO Josephson junctions, to assess their accuracy. A detailed analysis of measurement errors is presented, mainly based on a direct comparison of an HTS array against a low temperature array. Owing to the high sensitivity of the comparison, we were able to measure the changes in the HTS array voltage on a step at nanovolt level. A precise estimate of the dependence of the HTS array step width on operating conditions was obtained. Differences were observed with respect to the results provided by the usual, low sensitivity, techniques, confirming that the method we adopted is necessary in the study of HTS arrays for metrology. The high sensitivity analysis was applied in the derivation of the temperature dependence of the critical current as well, providing some insights on the behaviour of the HTS array

  14. Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors

    Science.gov (United States)

    Lee, Patrick A.

    2014-07-01

    The enigmatic pseudogap phase in underdoped cuprate high-Tc superconductors has long been recognized as a central puzzle of the Tc problem. Recent data show that the pseudogap is likely a distinct phase, characterized by a medium range and quasistatic charge ordering. However, the origin of the ordering wave vector and the mechanism of the charge order is unknown. At the same time, earlier data show that precursive superconducting fluctuations are also associated with this phase. We propose that the pseudogap phase is a novel pairing state where electrons on the same side of the Fermi surface are paired, in strong contrast with conventional Bardeen-Cooper-Schrieffer theory which pairs electrons on opposite sides of the Fermi surface. In this state the Cooper pair carries a net momentum and belongs to a general class called pair density wave. The microscopic pairing mechanism comes from a gauge theory formulation of the resonating valence bond (RVB) picture, where spinons traveling in the same direction feel an attractive force in analogy with Ampere's effects in electromagnetism. We call this Amperean pairing. Charge order automatically appears as a subsidiary order parameter even when long-range pair order is destroyed by phase fluctuations. Our theory gives a prediction of the ordering wave vector which is in good agreement with experiment. Furthermore, the quasiparticle spectrum from our model explains many of the unusual features reported in photoemission experiments. The Fermi arc, the unusual way the tip of the arc terminates, and the relation of the spanning vector of the arc tips to the charge ordering wave vector also come out naturally. Finally, we propose an experiment that can directly test the notion of Amperean pairing.

  15. Quasiparticle dynamics and competing order in cuprate superconductors

    Science.gov (United States)

    Orenstein, Joseph

    2014-03-01

    We report time-resolved optical measurements that reveal quasiparticle and collective mode dynamics in the presence of competing order in cuprate superconductors. In these measurements, we use low-intensity short pulses of light to perturb the equilibrium state and time-resolve the ensuing change in optical reflectivity at a photon energy of 1.5 eV. The perturbing pulse generates a nonequilibrium population of quasiparticles near the Fermi energy by allowed dipole transitions as well as collective excitations through a Raman process. Tracking the relaxation of the single particle and collective modes through the phase space of temperature, carrier concentration, and magnetic field allows us to observe the interaction between the competing phases. In this talk I will describe measurements in (i) YBCO ortho III and VIII in which photoexcitation is observed to generated collective oscillations of CDW order whose phase begins to rotate by 180 at the superconducting transition temperature (Tc) . (ii) Nd 2-xCexCuO4+δ that indicate excitation of a collective mode that displays quantum critical dynamics above Tc and competition with superconductivity below. (iii) HgBa2CuO4+δ that indicate a cusp in the quasiparticle recombination lifetime at Tc that we associate with quasiparticle coherence effects. The size of the cusp is maximal at 8% hole concentration, possibly coinciding with the peak of a competing CDW phase, and decreases rapidly with applied magnetic field. Lastly, we observe a complex, non-monotonic temperature dependence in the dynamics near hole concentration of 18%, providing evidence for competing phases within the superconducting dome. This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division, under Contract No. DE-AC02-05CH11231.

  16. AC loss characteristics of Bi-2223 HTS tapes under bending

    International Nuclear Information System (INIS)

    Kim, Hae-Joon; Kim, J.H.; Cho, J.W.; Sim, K.D.; Kim, S.; Oh, S.S.; Kwag, D.S.; Kim, H.J.; Bae, J.H.; Seong, K.C.

    2006-01-01

    Superconductor is developed for applications in high-power devices such as power-transmission cables, transformers, motors and generators. In such applications, HTS tapes are subjected to various kinds of stress or strain. AC loss is also important consideration for many large-scale superconducting devices. In the fabrication of the devices, the critical current (I c ) of the high temperature superconductor degrades due to many reasons including the tension applied by bending and thermal contraction. These mechanical loads reduce the I c of superconducting wire and the I c degradation affects the AC loss of the wire. The I c degradation and AC loss of Bi-2223 HTS tape were measured under tension and bending conditions at 77 K and self-field. Moreover, the frequency characteristics of AC loss was measured at the 30-480 Hz. As a result, self-field penetrates the deeper into the conductor at the lower frequency, which means higher self-field losses per cycle

  17. Large Scale Assembly and Characterization of BI-2223 HTS Conductors

    CERN Document Server

    Ballarino, Amalia; Mathot, Serge; Taylor, T; Brambilla, R

    2007-01-01

    The powering of the LHC machine requires more than 1000 High Temperature Superconducting (HTS) current leads. These leads contain, at their cold end, HTS conductors made of stacks of Bi-2223 tape with gold-doped silver matrix. CERN specified and purchased 31 km of this material, which was delivered on spools in unit lengths of 100 to 300 m. On reception the tape was inspected, cut into short length and vacuum soldered into stacks. All stacks were characterized in liquid nitrogen using a measuring procedure and set-up specifically developed for this purpose. Contact resistance values and critical currents at different electric field criteria were measured, from which the n-values have been extrapolated from the experimental V-I characteristics. This paper reports on the assembly and electrical characterization (up to 800 A) of more than ten thousand Bi-2223 stacks. Three types of stack were made from tape from two manufacturers. The assembly and soldering procedures and the set-up for the series electrical cha...

  18. HTS cables open the window for large-scale renewables

    International Nuclear Information System (INIS)

    Geschiere, A; Willen, D; Piga, E; Barendregt, P

    2008-01-01

    In a realistic approach to future energy consumption, the effects of sustainable power sources and the effects of growing welfare with increased use of electricity need to be considered. These factors lead to an increased transfer of electric energy over the networks. A dominant part of the energy need will come from expanded large-scale renewable sources. To use them efficiently over Europe, large energy transits between different countries are required. Bottlenecks in the existing infrastructure will be avoided by strengthening the network. For environmental reasons more infrastructure will be built underground. Nuon is studying the HTS technology as a component to solve these challenges. This technology offers a tremendously large power transport capacity as well as the possibility to reduce short circuit currents, making integration of renewables easier. Furthermore, power transport will be possible at lower voltage levels, giving the opportunity to upgrade the existing network while re-using it. This will result in large cost savings while reaching the future energy challenges. In a 6 km backbone structure in Amsterdam Nuon wants to install a 50 kV HTS Triax cable for a significant increase of the transport capacity, while developing its capabilities. Nevertheless several barriers have to be overcome

  19. Current distribution evaluation of dye-sensitized solar cell using HTS-SQUID-based magnetic measurement system

    Energy Technology Data Exchange (ETDEWEB)

    Sakai, Kenji, E-mail: Sakai-k@okayama-u.ac.jp; Tanaka, Kohei; Kiwa, Toshihiko; Tsukada, Keiji

    2016-11-15

    Highlights: • Current distribution and direction of dye-sensitized solar cell (DSSC) was measured. • Electrical current flowing in the indium tin oxide (ITO) glass substrate was uniform. • The distribution of electrical current depended on I–V characteristic. • Current direction changed when the performance of DSSC is low. - Abstract: The current flowing inside a dye-sensitized solar cell (DSSC) was measured using a high-temperature superconductor superconducting quantum interference device (HTS-SQUID)-based magnetic measurement system. Further, a new evaluation method of the DSSC, which is difficult to measure using the conventional method, was investigated to improve the characteristics of the DSSC. The tangential components of the magnetic field generated from the DSSC were measured using two HTS-SQUIDs, and the intensity and direction related to the electrical current were obtained by the measured magnetic field. The DSSCs prepared with different dyes and catalytic substances showed different current-intensity mapping. The current direction was different for the DSSC with low performance. In addition, the current flowing in the ITO layer of the ITO glass substrate was also measured and the results confirmed that it had uniform distribution. These results show that the current mapping and the direction of the electrical current depend on the internal factors of the DSSC, and the detection of the magnetic field distribution generated from it is expected to lead to its new evaluation method.

  20. Local density of states of a disordered superconductor applied to cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Kasal, R.B., E-mail: kasal@if.uff.b [Instituto de Fi' sica, Universidade Federal Fluminense, Niteroi, RJ 24210-340 (Brazil); Mello, E.V.L. de [Instituto de Fi' sica, Universidade Federal Fluminense, Niteroi, RJ 24210-340 (Brazil)

    2010-12-15

    We describe the physics of cuprate superconductors by an electronic phase separation (EPS) transition that segregates the holes into high and low density domains. This approach explains the pseudogap and superconducting phases and it also reproduces some recent scanning tunneling microscopy (STM) data.

  1. Quantum critical scaling at the edge of Fermi liquid stability in a cuprate superconductor.

    Science.gov (United States)

    Butch, Nicholas P; Jin, Kui; Kirshenbaum, Kevin; Greene, Richard L; Paglione, Johnpierre

    2012-05-29

    In the high-temperature cuprate superconductors, the pervasiveness of anomalous electronic transport properties suggests that violation of conventional Fermi liquid behavior is closely tied to superconductivity. In other classes of unconventional superconductors, atypical transport is well correlated with proximity to a quantum critical point, but the relative importance of quantum criticality in the cuprates remains uncertain. Here, we identify quantum critical scaling in the electron-doped cuprate material La(2-x)Ce(x)CuO(4) with a line of quantum critical points that surrounds the superconducting phase as a function of magnetic field and charge doping. This zero-temperature phase boundary, which delineates a metallic Fermi liquid regime from an extended non-Fermi liquid ground state, closely follows the upper critical field of the overdoped superconducting phase and gives rise to an expanse of distinct non-Fermi liquid behavior at finite temperatures. Together with signatures of two distinct flavors of quantum fluctuations, these facts suggest that quantum criticality plays a significant role in shaping the anomalous properties of the cuprate phase diagram.

  2. Spectral properties of doped bilayer cuprates at finite temperatures

    Indian Academy of Sciences (India)

    A self-consistent perturbation approach is used to calculate the electronic spectral function for different values of hole density, hole momentum and temperature. We find that the imaginary part of the self energy is strongly momentum dependent which contradicts the suggestion that the Fermi surface of cuprates may be ...

  3. Spiral vs. ferroemagnetic in-chain oredr in edge-shared cuprates

    Czech Academy of Sciences Publication Activity Database

    Drechsler, S.-L.; Richter, J.; Málek, Jiří; Moskvin, A.S.; Klingeler, R.; Rosner, H.

    290-291, - (2005), s. 345-348 ISSN 0304-8853 Institutional research plan: CEZ:AV0Z10100520 Keywords : edge-shared cuprate chain * quantum helix Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.985, year: 2005

  4. Helimagnetism and weak ferromagnetism in the edge-shared chain cuprates

    Czech Academy of Sciences Publication Activity Database

    Drechsler, S.-L.; Richter, J.; Kuzian, R.; Málek, Jiří; Tristan, N.; Büchner, B.; Moskvin, A.S.; Gippius, A.A.; Vasiliev, A.; Volkova, O.; Prokofiev, A.; Rakoto, H.; Broto, J.-M.; Schnelle, W.; Schmitt, M.; Ormeci, A.; Loison, C.; Rosner, H.

    2007-01-01

    Roč. 316, - (2007), s. 306-312 ISSN 0304-8853 Institutional research plan: CEZ:AV0Z10100520 Keywords : edge-shared cuprate chain * weak ferromagnetism * quantum helix * high-field magnetism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.704, year: 2007

  5. Through a Lattice Darkly: Shedding Light on Electron-Phonon Coupling in the High Tc Cuprates

    Directory of Open Access Journals (Sweden)

    D. R. Garcia

    2010-01-01

    Full Text Available With its central role in conventional BCS superconductivity, electron-phonon coupling appears to play a more subtle role in the phase diagram of the high-temperature superconducting cuprates. Their added complexity due to potentially numerous competing phases, including charge, spin, orbital, and lattice ordering, makes teasing out any unique phenomena challenging. In this review, we present our work using angle-resolved photoemission spectroscopy (ARPES exploring the role of the lattice on the valence band electronic structure of the cuprates. We introduce the ARPES technique and its unique ability to the probe the effect of bosonic renormalization (or “kink” on near-EF band structure. Our survey begins with the establishment of the ubiquitous nodal cuprate kink leading to how isotope substitution has shed a critical new perspective on the role and strength of electron-phonon coupling. We continue with recently published work connecting the phonon dispersion seen with inelastic X-ray scattering (IXS to the location of the kink observed by ARPES near the nodal point. Finally, we present very recent and ongoing ARPES work examining how induced strain through chemical pressure provides a potentially promising avenue for understanding the broader role of the lattice to the superconducting phase and larger cuprate phase diagram.

  6. Flop transitions in cuprate and color superconductors: From SO(5) to SO(10) unification?

    Energy Technology Data Exchange (ETDEWEB)

    Chandrasekharan, S.; Chudnovsky, V.; Schlittgen, B.; Wiese, U.-J

    2001-03-01

    The phase diagrams of cuprate superconductors and of QCD at non-zero baryon chemical potential are qualitatively similar. The Neel phase of the cuprates corresponds to the chirally broken phase of QCD, and the high-temperature superconducting phase corresponds to the color superconducting phase. In the SO(5) theory for the cuprates the SO(3){sub s} spin rotational symmetry and the U(1){sub em} gauge symmetry of electromagnetism are dynamically unified. This suggests that the SU(2){sub L} x SU(2){sub R} x U(1){sub B} chiral symmetry of QCD and the SU(3){sub c} color gauge symmetry may get unified to SO(10). Dynamical enhancement of symmetry from SO(2){sub s} x Z(2) to SO(3){sub s} is known to occur in anisotropic antiferromagnets. In these systems the staggered magnetization flops from an easy 3-axis into the 12-plane at a critical value of the external magnetic field. Similarly, the phase transitions in the SO(5) and SO(10) models are flop transitions of a 'superspin'. Despite this fact, a renormalization group flow analysis in 4 -- {epsilon} dimensions indicates that a point with full SO(5) or SO(10) symmetry exists neither in the cuprates nor in QCD.

  7. Flop transitions in cuprate and color superconductors: From SO(5) to SO(10) unification?

    International Nuclear Information System (INIS)

    Chandrasekharan, S.; Chudnovsky, V.; Schlittgen, B.; Wiese, U.-J.

    2001-01-01

    The phase diagrams of cuprate superconductors and of QCD at non-zero baryon chemical potential are qualitatively similar. The Neel phase of the cuprates corresponds to the chirally broken phase of QCD, and the high-temperature superconducting phase corresponds to the color superconducting phase. In the SO(5) theory for the cuprates the SO(3) s spin rotational symmetry and the U(1) em gauge symmetry of electromagnetism are dynamically unified. This suggests that the SU(2) L x SU(2) R x U(1) B chiral symmetry of QCD and the SU(3) c color gauge symmetry may get unified to SO(10). Dynamical enhancement of symmetry from SO(2) s x Z(2) to SO(3) s is known to occur in anisotropic antiferromagnets. In these systems the staggered magnetization flops from an easy 3-axis into the 12-plane at a critical value of the external magnetic field. Similarly, the phase transitions in the SO(5) and SO(10) models are flop transitions of a 'superspin'. Despite this fact, a renormalization group flow analysis in 4 -- ε dimensions indicates that a point with full SO(5) or SO(10) symmetry exists neither in the cuprates nor in QCD

  8. Challenges to high-Tc superconductivity in cuprates by exploring condensate properties

    Science.gov (United States)

    Maeda, A.

    2008-03-01

    In this paper, I introduce recent our results on superconductivity fluctuation measurement of high-Tc cuprate both for the hole-doped La2-xSrxCuO4 (LSCO) and the electron-doped La2-xCexCuO4 (LCCO). In hole doped LSCO, the universality class was found to change twice as a function of doping, starting from the 2D-XY, changing to the 3D XY and another 2D 'unknown' behavior. The results favors theoretical interpretations of the phase diagram of high-Tc cuprate which assume the existence of an additional hidden quantum critical point around at the optimum doping. In electron doped cuprate, the superconductivity fluctuation is 3D XY for all samples with different hole doping, which is in sharp contrast to the hole doped cuprate. Thus, the asymmetry of the phase diagram between the hole doped and the electron doped materials is another important key factor to judge the applicability of various theories on high-Tc superconductivity. Under finite magnetic fields, the scaling relation was valid only for weak fields, and for higher fields, aspects as vortices appeared. However, even at low temperatures, just above the first order phase transition, vortex picture alone cannot describe the data satisfactory. Thus, we need a unified theory for the description of a large superconductivity fluctuation under finite magnetic fields for high-Tc cuprates. Finally, I showed that our novel technique of fabricating high-Tc Josephson bridge junction using a small island of Fe was turned out to be very promising.

  9. The electromagnet design for 3-D superconducting actuator using HTS bulk

    International Nuclear Information System (INIS)

    Kim, S.B.; Inoue, T.; Shimizu, A.; Murase, S.

    2006-01-01

    We have been developing a three-dimensional (3-D) superconducting actuator consists of a field-cooled HTS bulk for mover and two-dimensional arranged multiple electromagnets as a stator. The HTS bulk is magnetically connected with electromagnets and it can be moved in 3-D directions and rotates without upper side electromagnets and spatial restrictions. The current and the polarity of each electromagnet were individually controlled by the switching power supply. In this paper, we experimentally investigated the effects of the shapes of HTS bulks (disk shape with/without inner hole) and electromagnets (4 and 8 polarities) in points of stabilities and forces of levitation

  10. Development of magnetic drug delivery system using HTS bulk magnet

    International Nuclear Information System (INIS)

    Terada, T.; Fukui, S.; Mishima, F.; Akiyama, Y.; Izumi, Y.; Nishijima, S.

    2008-01-01

    Magnetic drug delivery system (MDDS) is the method which the magnetic seeded drug is injected into a blood vessel and then controlled and accumulated by a magnet located outside of the human body. A high accumulation efficiency of the drug to a local diseased part and reduction in side-effects to normal organs are expected by using MDDS. The most important element in MDDS is a magnetic field generator. The high temperature superconducting (HTS) bulk magnet which can generate high magnetic field and magnetic field gradient extending to a point distant from the magnet in several ten millimeters is necessary to achieve the MDDS. In this study, the computer simulation and model experiment were conducted in order to confirm the applicability of MDDS to ovary of the cow body

  11. Multi-Pole HTS Generators for Direct Drive Wind Turbines

    DEFF Research Database (Denmark)

    Jensen, Bogi Bech; Abrahamsen, Asger Bech; Seiler, Eugen

    In this presentation the feasibility of installing a 5MW direct drive superconducting generator for an offshore wind turbine is presented. The reference turbine is a geared 5MW wind turbine that has been installed offshore and has been documented extensively by the National Renewable Energy...... on two different types of coated conductor. In the specific design the allowable current density was 300A/mm^2 for tape 1 and 70A/mm^2 for tape 2. The design is analytical, based on magnetic circuit analysis, which is validated by finite element modelling. The conclusion is that the either price...... or the performance of the coated conductor has to improve significantly (by a factor of 10 or more) in order for HTS generators to become feasible in direct drive offshore wind turbines. This price/performance improvement is not unrealistic in the coming decade. Additionally the reliability of such machines...

  12. LTS and HTS high current conductor development for DEMO

    International Nuclear Information System (INIS)

    Bruzzone, Pierluigi; Sedlak, Kamil; Uglietti, Davide; Bykovsky, Nikolay; Muzzi, Luigi; De Marzi, Gainluca; Celentano, Giuseppe; Della Corte, Antonio; Turtù, Simonetta; Seri, Massimo

    2015-01-01

    Highlights: • Design and R&D for DEMO TF conductors. • Wind&react vs. react&wind options for Nb 3 Sn high grade TF conductors. • Progress in the manufacture of short length Nb 3 Sn proptotypes. • Design and prototype manufacture for high current HTS cabled conductors. - Abstract: The large size of the magnets for DEMO calls for very large operating current in the forced flow conductor. A plain extrapolation from the superconductors in use for ITER is not adequate to fulfill the technical and cost requirements. The proposed DEMO TF magnets is a graded winding using both Nb 3 Sn and NbTi conductors, with operating current of 82 kA @ 13.6 T peak field. Two Nb 3 Sn prototypes are being built in 2014 reflecting the two approaches suggested by CRPP (react&wind method) and ENEA (wind&react method). The Nb 3 Sn strand (overall 200 kg) has been procured at technical specification similar to ITER. Both the Nb 3 Sn strand and the high RRR, Cr plated copper wire (400 kg) have been delivered. The cabling trials are carried out at TRATOS Cavi using equipment relevant for long length production. The completion of the manufacture of the two 20 m long prototypes is expected in the end of 2014 and their test is planned in 2015 at CRPP. In the scope of a long term technology development, high current HTS conductors are built at CRPP and ENEA. A DEMO-class prototype conductor is developed and assembled at CRPP: it is a flat cable composed of 20 twisted stacks of coated conductor tape soldered into copper shells. The 10 kA conductor developed at ENEA consists of stacks of coated conductor tape inserted into a slotted and twisted Al core, with a central cooling channel. Samples have been manufactured in industrial environment and the scalability of the process to long production lengths has been proven.

  13. Test Results of HTS Coil and Magnet R&D for RIA

    CERN Document Server

    Gupta, Ramesh C; Harrison, Michael; Sampson, William; Schmalzle, Jesse D; Zeller, Al

    2005-01-01

    Brookhaven National Laboratory is developing quadrupole magnets for the proposed Rare Isotope Accelerator (RIA) based on commercially available High Temperature Superconductors (HTS). These quadrupoles will be used in the Fragment Separator region and are one of the more challenging elements in the RIA proposal. They will be subjected to several orders of magnitude more energy and radiation deposition than typical beam line and accelerator magnets receive during their entire lifetime. The proposed quadrupoles will operate in the 20-40 K temperature range for efficient heat removal. HTS coils that have been tested so far indicate that the coils meet the magnetic field requirements of the design. We will report the test results of about 10 HTS coils and of a magnetic mirror configuration that simulates the magnetic field and Lorentz force in the proposed quadrupole. In addition, the preliminary design of an HTS dipole magnet for the Fragment Separator region will also be presented.

  14. Study and operating conditions of HTS Josephson arrays for metrological application

    International Nuclear Information System (INIS)

    Sosso, A.; Lacquaniti, V.; Andreone, D.; Cerri, R.; Klushin, A.M.

    2006-01-01

    We report an experimental study of metrological properties of high-temperature superconductor arrays, made of shunted bicrystal YBCO Josephson junctions. The work is mainly based on a direct comparison against a low temperature array. Owing to the high sensitivity of the measurements, we observed at nanovolt level the changes in the HTS array voltage on a step. A precise estimate of the dependence of the HTS array step width on operating conditions was obtained. Differences were observed with respect to the results of low sensitivity techniques, confirming that our method is necessary in the study of HTS arrays for metrology. The high sensitivity analysis was also applied in the derivation of the temperature dependence of the critical current, providing insights on the behavior of the HTS array

  15. High-temperature superconductivity (HTS): summary of case study results; Vorteile der Hochtemperatursupraleitung. Resultate von Fallstudie

    Energy Technology Data Exchange (ETDEWEB)

    Schnyder, G.; Zueger, H. [ABB Secheron, Geneva, (Switzerland); Rhyner, J.; Wiesmann, H.J. [ABB Corporate Research, Baden-Daettwil (Switzerland); Politano, D. [ETH Zuerich, High Voltage Laboratory, Zuerich (Switzerland); Sjoestroem, M.; Dutoit, B. [Swiss Federal Institute of Technology (EPFL), Chaire des circuits et systemes, Lausanne (Switzerland)

    2000-07-01

    The system study 'High Temperature Superconductivity (HTS) in power systems' lists the technical and economical advantages for power generation, transmission and distribution systems using components made of HTS material as seen in the light of current knowledge in the superconductivity area. This report lists the advantages of using high-temperature superconductivity in the power industry area and summarises the results obtained in various case studies on the subject.

  16. prototype Roebel cable to be used to wind a HTS accelerator demonstration dipole

    CERN Multimedia

    Barnard, Henry

    2014-01-01

    This is a prototype Roebel cable to be used to wind a HTS accelerator demonstration dipole, a first of its kind, within the scope of EuCARD2 WP10 (Future Magnets). The strips are stainless steel and copper, but the final one will be an HTS tape (YBCO) and copper. This prototype cable was manufactured by KIT within the scope of EuCARD2.

  17. Principle and analysis of a linear motor driving system for HTS levitation applications

    International Nuclear Information System (INIS)

    Jin, Jian X.; Guo, You G.; Zhu, Jian G.

    2007-01-01

    High temperature superconductor (HTS) high levitation force density with passive and self-stabilizing features allows a number of special applications to be developed. Linear motor driving systems are commonly required for those applications such as levitated transport systems. In this paper a prototype linear motor driving system with HTS is analyzed with calculation details including its magnetic fields and driving forces presented in the paper

  18. A phenomenological model for the structure-composition relationship of the high Tc cuprates based on simple chemical principles

    International Nuclear Information System (INIS)

    Alarco, J.A.; Talbot, P.C.

    2012-01-01

    A simple phenomenological model for the relationship between structure and composition of the high Tc cuprates is presented. The model is based on two simple crystal chemistry principles: unit cell doping and charge balance within unit cells. These principles are inspired by key experimental observations of how the materials accommodate large deviations from stoichiometry. Consistent explanations for significant HTSC properties can be explained without any additional assumptions while retaining valuable insight for geometric interpretation. Combining these two chemical principles with a review of Crystal Field Theory (CFT) or Ligand Field Theory (LFT), it becomes clear that the two oxidation states in the conduction planes (typically d 8 and d 9 ) belong to the most strongly divergent d-levels as a function of deformation from regular octahedral coordination. This observation offers a link to a range of coupling effects relating vibrations and spin waves through application of Hund’s rules. An indication of this model’s capacity to predict physical properties for HTSC is provided and will be elaborated in subsequent publications. Simple criteria for the relationship between structure and composition in HTSC systems may guide chemical syntheses within new material systems.

  19. Electronic bound states in parity-preserving QED{sub 3} applied to high-T{sub c} cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Christiansen, H.R. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil). Coordenacao de Teoria de Campos e Particulas]. E-mail: hugo@cbpf.br; Cima, O.M. Del [Universidade Catolica de Petropolis, RJ (Brazil). Grupo de Fisica Teorica]. E-mail: delcima@gft.ucp.br; Ferreira Junior, M.M. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil). Coordenacao de Teoria de Campos e Particulas]|[Maranhao Univ., Sao Luis, MA (Brazil). Dept. de Fisica]. E-mail: manojr@cbpf.br; Helayel-Neto, J.A. [Universidade Catolica de Petropolis, RJ (Brazil). Grupo de Fisica Teorica]|[Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil). Coordenacao de Teoria de Campos e Particulas]. E-mail: helayel@gft.ucp.br

    2001-08-01

    We consider a parity-preserving QED{sub 3} model with spontaneous breaking of the gauge symmetry as a framework for the evaluation of the electron-electron interaction potential underlying high-T{sub e} superconductivity. The fact that resulting potential, - C{sub s} K{sub o} (Mr), is non-confining and weak (in the sense of Kato) strongly suggests the mechanism of pair-condensation. This potential, compatible with an s-wave order parameters, is then applied to the Schrodinger equation for the sake of numerical calculations, thereby enforcing the existence of bound states. The results worked out by means of our theoretical framework are checked by considering a number of phenomenological data extracted from different copper oxide superconductors. The agreement may motivate a deeper analysis of our model viewing an application to quasi-planar cuprate superconductors. The data analyzed here suggest an energy scale of 1-10 meV for the breaking of the U(1)-symmetry. (author)

  20. Electronic bound states in parity-preserving QED sub 3 applied to high-T sub c cuprate superconductors

    CERN Document Server

    Christiansen, H R; Helayel-Neto, J A; Monteiro del Cima, O

    2001-01-01

    We consider a parity-preserving QED sub 3 model with spontaneous breaking of the gauge symmetry as a framework for the evaluation of the electron-electron interaction potential underlying high-T sub e superconductivity. The fact that resulting potential, - C sub s K sub o (Mr), is non-confining and weak (in the sense of Kato) strongly suggests the mechanism of pair-condensation. This potential, compatible with an s-wave order parameters, is then applied to the Schrodinger equation for the sake of numerical calculations, thereby enforcing the existence of bound states. The results worked out by means of our theoretical framework are checked by considering a number of phenomenological data extracted from different copper oxide superconductors. The agreement may motivate a deeper analysis of our model viewing an application to quasi-planar cuprate superconductors. The data analyzed here suggest an energy scale of 1-10 meV for the breaking of the U(1)-symmetry.

  1. Development and construction of an HTS rotor for ship propulsion application

    International Nuclear Information System (INIS)

    Nick, W; Frank, M; Kummeth, P; Rabbers, J J; Wilke, M; Schleicher, K

    2010-01-01

    A low-speed high-torque HTS machine is being developed at Siemens on the basis of previous steps (400kW demonstrator, 4MVA generator). The goal of the programme is to utilize the characteristic advantages offered by electrical machines with HTS-excited rotor, such as efficiency, compact size, and dynamic performance. To be able to address future markets, requirements from ship classification as well as potential customers have to be met. Electromagnetic design cannot be focused on nominal operation only, but has to deal with failure modes like short circuit too. Utilization of superconductor requires to consider margins taking into account that the windings have to operate reliably not only in 'clean' laboratory conditions, but in rough environment with the stator connected to a power converter. Extensive quality control is needed to ensure homogenous performance (current capacity, electrical insulation, dimensions) for the large quantity of HTS (45 km). The next step was to set up and operate a small-scale 'industrial' manufacturing process to produce HTS windings in a reproducible way, including tests at operating conditions. A HTS rotor includes many more components compared to a conventional one, so tough geometric tolerances must be met to ensure robust performance of the system. All this gives a challenging task, which will be concluded by cold testing of the rotor in a test facility. Then the rotor will be delivered for assembly to the stator. In following machine tests the performance of the innovative HTS drive system will be demonstrated.

  2. Thermal conductivity measurement of HTS tapes and stacks for current lead applications

    International Nuclear Information System (INIS)

    Schwarz, Michael; Weiss, Klaus-Peter; Heller, Reinhard; Fietz, Walter H.

    2009-01-01

    The use of high-temperature-superconductors (HTS) within current leads offers a high potential to save cooling-power. The principle of HTS current leads is well established, e.g. for particle accelerators (LHC-CERN) but also on the commercial sector, which offer HTS current leads ready for use in small scale magnets and magnets systems. Future fusion machines currently under construction like ITER, W7-X or JT-60SA also will use HTS current leads. At the moment the standard material for HTS current leads is a Bi 2 Sr 2 Ca 2 Cu 3 O x (BSCCO)-AgAu composite tape. The common way to receive high current capacity current leads is to form stacks by sintering or soldering these tapes together. The solder changes the thermal conductivity of the stacks compared to the single tape in the temperature range from 4 K to 60 K. To estimate the heat flux from the warm environment to the cold application the measurement of the thermal conductivity of the soldered stack is mandatory. Therefore the thermal conductivity of stacks with different number of tapes is investigated. To measure the thermal conduction in the current flow direction, the axial heat flow method is used. Combining these results with FEM simulations gives the possibility to estimate the thermal conductivity normal to the flat tape plane. The resulting anisotropic thermal conductivity can be used to model the behaviour of the HTS tape under thermal disturbances more accurately.

  3. Numerical and experimental comparison of electromechanical properties and efficiency of HTS and ferromagnetic hysteresis motors

    International Nuclear Information System (INIS)

    Inacio, D; Inacio, S; Pina, J; Goncalves, A; Neves, M Ventim; Rodrigues, A Leao

    2008-01-01

    Hysteresis motors are very attractive in a wide range of fractional power applications, due to its torque-speed characteristics and simplicity of construction. This motor's performance is expected to improve when HTS rotors are used, and in fact, hysteresis motors have shown to be probably the most viable electrical machines using HTS materials. While these motors, either conventional or HTS, are both hysteresis motors, they base their operation on different physical phenomena: hysteretic behaviour in conventional ferromagnetic materials is due to the material's non-linear magnetic properties, while in HTS materials the hysteresis has an ohmic nature and is related with vortices' dynamics. In this paper, theoretical aspects of both conventional and HTS hysteresis motors are discussed, its operation principles are highlighted, and the characteristics of both motors are presented. The characteristics, obtained both by experimental tests and numerical simulation (made with commercial software), are compared, in order to evaluate not only the motor's electromechanical performances but also the overall systems efficiency, including cryogenics for the HTS device

  4. Degradation characteristics of 2G HTS tapes with respect to an electrical breakdown

    International Nuclear Information System (INIS)

    Kang, Jong O; Lee, On You; Mo, Young Kyu; Kim, Jun Il; Bang, Seung Min; Lee, Hong Seok; Kang, Hyoung Ku; Lee, Jae Hun; Jang, Cheol Yeong

    2015-01-01

    The electrical insulation design for a superconducting coil system is important for developing high voltage superconducting apparatuses. Also, the degraded characteristics of superconducting tapes due to an electrical breakdown should be considered for superconducting coils design. In this study, the degradation characteristics of 2G high temperature superconducting (HTS) tapes were studied with respect to electrical breakdown tests. The degradation tests of 2G HTS tapes were performed with various stabilizer materials. The degradation characteristics of 2G HTS tapes such as critical current(Ic) and index number were observed by performing electrical breakdown tests. It was found that the characteristics such as Ic and index number can be degraded by an electrical breakdown. Moreover, it was concluded that the degradation characteristics of 2G HTS tapes were affected by a stabilizer material and applied breakdown voltage. The cross sectional view of 2G HTS tapes was observed by using a scanning electron microscope (SEM). As results, it is found that the degradation characteristics of 2G HTS tapes are concerned with hardness and electrical resistivity of stabilizer layers

  5. Numerical study on AC loss reduction of stacked HTS tapes by optimal design of flux diverter

    Science.gov (United States)

    Liu, Guole; Zhang, Guomin; Jing, Liwei; Yu, Hui

    2017-12-01

    High temperature superconducting (HTS) coils are key parts of many AC applications, such as generators, superconducting magnetic energy storage and transformers. AC loss reduction in HTS coils is essential for the commercialization of these HTS devices. Magnetic material is generally used as the flux diverter in an effort to reduce the AC loss in HTS coils. To achieve the greatest reduction in the AC loss of the coils, the flux diverter should be made of a material with low loss and high saturated magnetic density, and the optimization of the geometric size and location of the flux diverter is required. In this paper, we chose Ni-alloy as the flux diverter, which can be processed into a specific shape and size. The influence of the shape and location of the flux diverter on the AC loss characteristics of stacked (RE)BCO tapes is investigated by use of a finite element method. Taking both the AC loss of the (RE)BCO coils and the ferromagnetic loss of the flux diverter into account, the optimal geometry of the flux diverter is obtained. It is found that when the applied current is at half the value of the critical current, the total loss of the HTS stack with the optimal flux diverter is only 18% of the original loss of the HTS stack without the flux diverter. Besides, the effect of the flux diverter on the critical current of the (RE)BCO stack is investigated.

  6. Angle-Resolved Photoemission Spectroscopy on Electronic Structure and Electron-Phonon Coupling in Cuprate Superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, X.J.

    2010-04-30

    In addition to the record high superconducting transition temperature (T{sub c}), high temperature cuprate superconductors are characterized by their unusual superconducting properties below T{sub c}, and anomalous normal state properties above T{sub c}. In the superconducting state, although it has long been realized that superconductivity still involves Cooper pairs, as in the traditional BCS theory, the experimentally determined d-wave pairing is different from the usual s-wave pairing found in conventional superconductors. The identification of the pairing mechanism in cuprate superconductors remains an outstanding issue. The normal state properties, particularly in the underdoped region, have been found to be at odd with conventional metals which is usually described by Fermi liquid theory; instead, the normal state at optimal doping fits better with the marginal Fermi liquid phenomenology. Most notable is the observation of the pseudogap state in the underdoped region above T{sub c}. As in other strongly correlated electrons systems, these unusual properties stem from the interplay between electronic, magnetic, lattice and orbital degrees of freedom. Understanding the microscopic process involved in these materials and the interaction of electrons with other entities is essential to understand the mechanism of high temperature superconductivity. Since the discovery of high-T{sub c} superconductivity in cuprates, angle-resolved photoemission spectroscopy (ARPES) has provided key experimental insights in revealing the electronic structure of high temperature superconductors. These include, among others, the earliest identification of dispersion and a large Fermi surface, an anisotropic superconducting gap suggestive of a d-wave order parameter, and an observation of the pseudogap in underdoped samples. In the mean time, this technique itself has experienced a dramatic improvement in its energy and momentum resolutions, leading to a series of new discoveries not

  7. HTS Nested magnet wound with 12 mm GdBCO tape and 4.4 mm YBCO tape

    International Nuclear Information System (INIS)

    Kang, Myung Hun; Ku, Myung Hwan; Cha, Guee Soo; Lim, Hyoung Woo

    2015-01-01

    The properties of High Temperature Superconducting (HTS) tapes are progressing, as HTS tapes evolve from 1st generation to 2nd generation. This paper presents design and construction of a 2nd generation HTS magnet consisting of two nested GdBCO and YBCO pancake coils. Two HTS tapes of different widths were used to wind the HTS nested magnet. Considering that a higher magnetic field is applied to the inner magnet than to the outer magnet, 12 mm GdBCO tape was used for winding the inner magnet, which consisted of four single pancake windings. Eight double pancake windings wound with 4.4 mm YBCO tapes were used for the outer magnet. The test results show that the central magnetic field of the HTS nested magnet was 920 mT. The measured critical currents of the inner and outer magnet at 77K were 80.8 A and 32.6 A, respectively

  8. Half-integer flux quantum effect in cuprate superconductors - a probe of pairing symmetry

    International Nuclear Information System (INIS)

    Tsuei, C.C.; Kirtley, J.R.; Gupta, A.; Sun, J.Z.; Moler, K.A.; Wang, J.H.

    1996-01-01

    Based on macroscopic quantum coherence effects arising from pair tunneling and flux quantization, a series of tricrystal experiments have been designed and carried out to test the order parameter symmetry in high-T c cuprate superconductors. By using a scanning SQUID microscope, we have directly and non-invasively observed the spontaneously generated half-integer flux quantum effect in controlled-orientation tricrystal cuprate superconducting systems. The presence or absence of the half-integer flux quantum effect as a function of the tricrystal geometry allows us to prove that the order parameter symmetry in the YBCO and Tl2201 systems is consistent with that of the d x 2 -y 2 pair state. (orig.)

  9. Pseudogap regime in high- Tc cuprates as a manifestation of a frustrated phase separation (NMR view)

    Science.gov (United States)

    Gor'kov, Lev P.; Teitel'baum, Gregory B.

    2005-04-01

    We show that the pseudogap behavior of the nuclear spin relaxation for cuprates may be considered as the dynamical phase separation to the “metallic” and “antiferromagnetic (AF)” regions. It stems from the 1st order phase transition that starts at T*(x) well above T but becomes frustrated because of broken electroneutrality in the CuO 2 plane. In this temperature range for a broad class of cuprates 1/ 63T1 is due to two independent mechanisms: relaxation on the “stripe”-like excitations and that driven by the moving AF regions. For LSCO, our estimations are in quantitative agreement with the neutron scattering data.

  10. Breakdown of the Fermi arcs in underdoped cuprates by incommensurate charge density waves

    Science.gov (United States)

    Gor'kov, L. P.

    2014-11-01

    Interactions between the coherent excitations on disconnected arcs along a "bare" Fermi surface (the socalled Fermi arcs FAs) seen by angle-resolved photo emission spectroscopy (ARPES) in several underdoped (UD) cuprates and incommensurate charge density wave (IC CDW) ordering at lowering of the temperature have been studied. The carriers on FAs scatter strongly on the short-wavelength potential of CDW. The large momentum transfer relates FAs with the electronic states lying deeply under the chemical potential thus involving into consideration the Fermi liquid interactions. At low temperatures IC CDW may fully destroy low lying excitations on the Fermi arcs, leaving electrons on the pocket at the Γ point as the only charged elementary excitations in the CDW phase in UD cuprates. The results infer competition between superconducting and CDW order parameters.

  11. Evolution of Hall resistivity and spectral function with doping in the SU(2) theory of cuprates

    Science.gov (United States)

    Morice, C.; Montiel, X.; Pépin, C.

    2017-10-01

    Recent transport experiments in the cuprate superconductors linked the opening of the pseudogap to a change in electronic dispersion [S. Badoux et al., Nature (London) 531, 210 (2015), 10.1038/nature16983]. Transport measurements showed that the carrier density sharply changes from x to 1 +x at the pseudogap critical doping, in accordance with the change from Fermi arcs at low doping to a large hole Fermi surface at high doping. The SU(2) theory of cuprates shows that short-range antiferromagnetic correlations cause the arising of both charge and superconducting orders, which are related by an SU(2) symmetry. The fluctuations associated with this symmetry form a pseudogap phase. Here we derive the renormalized electronic propagator under the SU(2) dome, and calculate the spectral functions and transport quantities of the renormalized bands. We show that their evolution with doping matches both spectral and transport measurements.

  12. Metal-insulator crossover in superconducting cuprates in strong magnetic fields

    International Nuclear Information System (INIS)

    Marchetti, P.A.; Su Zhaobin; Yu Lu

    2001-02-01

    The metal-insulator crossover of the in-plane resistivity upon temperature decrease, recently observed in several classes of cuprate superconductors, when a strong magnetic field suppresses the superconductivity, is explained using the U(1)xSU(2) Chern-Simons gauge field theory. The origin of this crossover is the same as that for a similar phenomenon observed in heavily underdoped cuprates without magnetic field. It is due to the interplay between the diffusive motion of the charge carriers and the 'peculiar' localization effect due to short-range antiferromagnetic order. We also calculate the in-plane transverse magnetoresistance which is in a fairly good agreement with available experimental data. (author)

  13. Evolution with hole doping of the electronic excitation spectrum in the cuprate superconductors

    International Nuclear Information System (INIS)

    Wilson, John A

    2008-01-01

    The recent scanning tunnelling results of Alldredge and co-workers on Bi-2212 and of Hanaguri and co-workers on Na-CCOC (Ca 2-x Na x CuO 2 Cl 2 ) are examined from the perspective of the Bardeen-Cooper-Schrieffer (BCS)/Bose-Einstein condensation boson-fermion resonant crossover model for the mixed-valence high temperature superconductor (HTSC) cuprates. The model specifies the two energy scales controlling the development of HTSC behaviour and the dichotomy often now alluded to between nodal and antinodal phenomena in the HTSC cuprates. An indication is extracted from the data as to how the choice of the particular HTSC system sees these two basic energy scales (U, the local pair binding energy, and Δ sc , the nodal BCS-like gap parameter) evolve with doping and change in the degree of metallization of the structurally and electronically perturbed mixed-valent environment

  14. Multichannel Kondo approach to the cuprate and recent laser ARPES data

    Directory of Open Access Journals (Sweden)

    M A Mojumder

    2014-12-01

    Full Text Available The existing theoretical approaches have been unable to confront the large corpus of outstanding data on the cuprate superconductor in a persuasive and unified manner. There is a general opinion now growing that these theories miss some essential points. We propose one based on multichannel Kondo effect that is physically justifiable and confronts the data adequately. In addition to earlier data, the definitive proof of involvement of this effect has been now provided by the numerical agreement of the characteristic Kondo temperatures with the fluctuation frequencies at which Eliashberg function peaks. It is, therefore, suggested that the theory of multichannel Kondo effect be accepted as the correct theory of underdoped cuprate.

  15. The Inward Dispersion of the Neutron Scattering Experiments in HTSC Cuprates

    OpenAIRE

    Dayan, Moshe

    2016-01-01

    The theory of the high temperature superconducting cuprates, which is based on the condensation of holes into strings in checker-board geometry, was successful to explain the elastically scattered Neutrons by spin waves. Here it is extended to analyze the inward dispersion curve of its inelastic counterpart, up to the resonance energy- . This extension is done by applying the perturbation theory of the linear response to the condensed strings. The approximated susceptibility is derived by mea...

  16. Topological superconductivity and Majorana fermions in hybrid structures involving cuprate high-T_c superconductors

    OpenAIRE

    Takei, So; Fregoso, Benjamin M.; Galitski, Victor; Sarma, S. Das

    2012-01-01

    The possibility of inducing topological superconductivity with cuprate high-temperature superconductors (HTSC) is studied for various heterostructures. We first consider a ballistic planar junction between a HTSC and a metallic ferromagnet. We assume that inversion symmetry breaking at the tunnel barrier gives rise to Rashba spin-orbit coupling in the barrier and allows equal-spin triplet superconductivity to exist in the ferromagnet. Bogoliubov-de Gennes equations are obtained by explicitly ...

  17. Metal–insulator crossover in high Tc cuprates: A gauge field approach

    Indian Academy of Sciences (India)

    P A Marchetti, Z B Su and L Yu. 2. They can be qualitatively explained within the t-J model for cuprates using: a) A formal spin-charge separation of the electron field into a spinon and a holon field coupled by gauge fluctuations. b) Ioffe–Larkin rule: the physical resistivity is the sum of the resistivity due to spinons and the ...

  18. Systematics of c-axis phonons in the thallium- and bismuth-based cuprate superconductors

    NARCIS (Netherlands)

    Tsvetkov, A.A.; Dulic, Diana; Marel, D. van der; Damascelli, A.; Kaljushnaia, G.A.; Gorina, J.I.; Senturina, N.N.; Kolesnikov, N.N.; Ren, Z.F.; Wang, J.H.; Menovsky, A.A.; Palstra, T.T.M.

    1999-01-01

    We present grazing incidence reflectivity measurements in the far-infrared region at temperatures above and below Tc for a series of thallium- (Tl2Ba2CuO6, Tl2Ba2CaCu2O8) and bismuth- (Bi2Sr2CuO6, Bi2Sr2CaCu2O8, and Bi2-xPbxSr2CaCu2O8) based cuprate superconductors. From the spectra, which are

  19. Proceedings of the IS-HTS-TP'94: 2nd international symposium on high temperature superconductivity and tunneling phenomena

    International Nuclear Information System (INIS)

    Svistunov, V.M.

    1995-01-01

    The main purpose of this symposium is to discuss a problem of the current transfer in HTS: direct and tunneling mechanisms. It was proposed to consider a series of questions concerning spectral function of the electron-phonon interactions in HTS, the linear background conductance, the critical current in magnetic fields in bulk materials, studying in details the role of the weak superconducting links and the different natural contributions in current transfer of HTS

  20. Magnetic excitations of layered cuprates studied by RIXS at Cu L{sub 3} edge

    Energy Technology Data Exchange (ETDEWEB)

    Ghiringhelli, G., E-mail: giacomo.ghiringhelli@fisi.polimi.it [CNR/SPIN, CNISM and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano (Italy); Braicovich, L. [CNR/SPIN, CNISM and Dipartimento di Fisica, Politecnico di Milano, piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2013-06-15

    Highlights: ► We have developed very high resolution RIXS instrumentation. ► Cu L{sub 3} RIXS is ideal for studying magnetic excitations in layered cuprates. ► RIXS has been used to map magnon and paramagnon dispersion in HTcS. ► We have developed the first partial polarization analyzer for RIXS in the soft X-rays. -- Abstract: The inelastic scattering of X-rays is becoming a powerful alternative to better established techniques, based on neutrons or low energy photons, for the study of low- and medium-energy excitations in solids. When performed in the soft range the resonant inelastic X-ray scattering (RIXS) is ideal for strongly correlated electron systems based on 3d transition metals. The remarkable evolution of Cu L{sub 3} RIXS has been boosted by the steady improvement of experimental energy resolution, and by the fortunate fact that cuprates give intense and richly featured spectra. Over the last 8 years several key results were obtained using the AXES (ESRF) and the SAXES (SLS) spectrometers. This initial success is now supporting several new projects for soft X-ray RIXS worldwide. We briefly present here the case of spin excitation dispersion in insulating and superconducting cuprates and the first RIXS spectra with partial polarization analysis of the scattered photons.

  1. Kinetics of excitations on the Fermi arcs in underdoped cuprates at low temperatures

    Science.gov (United States)

    Gor'kov, Lev P.

    2013-07-01

    The Fermi-liquid-like (FL) resistivity recently observed in clean Hg1201 below the pseudogap temperature was related to carriers at the nodal points on the Fermi surface (FS) (N. Barišić , arXiv:1207.1504, doi:10.1073/pnas.13019891109). We show that this has important implications for the electronic spectrum of underdoped (UD) cuprates as a whole. Photoemission experiments (angle-resolved photoemission spectroscopy) in other cuprates picture the spectrum as “metallic arcs” separated from each other by regions with large energy gaps. We rigorously solve the kinetic equation in such a model. The Fermi arcs' carriers contribute to the FL resistivity, if scattering between the opposite nodal points admits the umklapp processes. The Hall coefficient defines the effective number of carriers on the arcs and at weak magnetic fields it has a positive sign. All parameters that determine the arcs' widths are measurable experimentally. We conclude that the T2 resistivity gives support to the Fermi arcs' concept and argue that the idea of a reconstructed FS in UD cuprates is not consistent with the latter.

  2. Cuprate diamagnetism in the presence of a pseudogap: Beyond the standard fluctuation formalism

    Science.gov (United States)

    Boyack, Rufus; Chen, Qijin; Varlamov, A. A.; Levin, K.

    2018-02-01

    It is often claimed that among the strongest evidence for preformed-pair physics in the cuprates are the experimentally observed large values for the diamagnetic susceptibility and Nernst coefficient. These findings are most apparent in the underdoped regime, where a pseudogap is also evident. While the conventional (Gaussian) fluctuation picture has been applied to address these results, this preformed-pair approach omits the crucial effects of a pseudogap. In this paper we remedy this omission by computing the diamagnetic susceptibility and Nernst coefficient in the presence of a normal state gap. We find a large diamagnetic response for a range of temperatures much higher than the transition temperature. In particular, we report semiquantitative agreement with the measured diamagnetic susceptibility onset temperatures, over the entire range of hole dopings. Notable is the fact that at the lower critical doping of the superconducting dome, where the transition temperature vanishes and the pseudogap onset temperature remains large, the onset temperature for both diamagnetic and transverse thermoelectric transport coefficients tends to zero. Due to the importance attributed to the cuprate diamagnetic susceptibility and Nernst coefficient, this work helps to clarify the extent to which pairing fluctuations are a component of the cuprate pseudogap.

  3. 2011 Aspen Winter Conference on Contrasting Superconductivity of Pnictides and Cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, P. [Aspen Center for Physics, CO (United States); Schmalian, J. [Aspen Center for Physics, CO (United States); Canfield, P. [Aspen Center for Physics, CO (United States); Chakravarty, S. [Aspen Center for Physics, CO (United States)

    2011-05-02

    Our quest for materials with better properties is closely integral to the fabric of our society. Currently the development of materials that will allow for improved generation, transport, and storage of energy is at the forefront of our research in condensed matter physics and materials science. Among these materials, compounds that exhibit correlated electron states and emergent phenomena such as superconductivity have great promise, but also difficulties that need to be overcome: problems associated with our need to reliably find, understand, improve and control these promising materials. At the same time, the field of correlated electrons represents the frontier of our understanding of the electronic properties of solids. It contains deep open scientific issues within the broad area of quantum phenomena in matter. The aim of this workshop is to explore and understand the physics of recently discovered Fe-based high-temperature superconductors and contrast and compare them with the cuprates. The superconductivity in iron pnictides, with transition temperatures in excess of 55 K, was discovered in early 2008. The impact of this discovery is comparable to cuprates discovered in 1986. At the same time a number of recent experimental developments in cuprates may lead to a shift in our thinking with regards to these materials. There is therefore much to be learned by devoting a conference in which both classes of superconductors are discussed, especially at this nascent stage of the pnictides.

  4. A tale of two metals: contrasting criticalities in the pnictides and hole-doped cuprates

    Science.gov (United States)

    Hussey, N. E.; Buhot, J.; Licciardello, S.

    2018-05-01

    The iron-based high temperature superconductors share a number of similarities with their copper-based counterparts, such as reduced dimensionality, proximity to states of competing order, and a critical role for 3d electron orbitals. Their respective temperature-doping phase diagrams also contain certain commonalities that have led to claims that the metallic and superconducting (SC) properties of both families are governed by their proximity to a quantum critical point (QCP) located inside the SC dome. In this review, we critically examine these claims and highlight significant differences in the bulk physical properties of both systems. While there is now a large body of evidence supporting the presence of a (magnetic) QCP in the iron pnictides, the situation in the cuprates is much less apparent, at least for the end point of the pseudogap phase. We argue that the opening of the normal state pseudogap in cuprates, so often tied to a putative QCP, arises from a momentum-dependent breakdown of quasiparticle coherence that sets in at much higher doping levels but which is driven by the proximity to the Mott insulating state at half filling. Finally, we present a new scenario for the cuprates in which this loss of quasiparticle integrity and its evolution with momentum, temperature and doping plays a key role in shaping the resultant phase diagram. This key issues review is dedicated to the memory of Dr John Loram whose pioneering measurements, analysis and ideas inspired much of its content.

  5. Structure for hts composite conductors and the manufacture of same

    Science.gov (United States)

    Cotton, James D.; Riley, Jr., Gilbert Neal

    1999-01-01

    A superconducting oxide composite structure including a superconducting oxide member, a metal layer surrounding the superconducting oxide member, and an insulating layer of a complex oxide formed in situ adjacent to the superconducting oxide member and the metal layer is provided together with a method of forming such a superconducting oxide composite structure including encapsulating a superconducting oxide member or precursor within a metal matrix layer from the group of: (i) a reactive metal sheath adjacent to the superconducting oxide member or precursor, the reactive metal sheath surrounded by a second metal layer or (ii) an alloy containing a reactive metal; to form an intermediate product, and, heating the intermediate product at temperatures and for time sufficient to form an insulating layer of a complex oxide in situ, the insulating layer to the superconducting oxide member or precursor and the metal matrix layer.

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

    Energy Technology Data Exchange (ETDEWEB)

    Green, Michael A.

    2007-02-14

    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).

  7. Quench detection method for 2G HTS wire

    International Nuclear Information System (INIS)

    Marchevsky, M; Xie, Y-Y; Selvamanickam, V

    2010-01-01

    2G HTS conductors are increasingly used in various commercial applications and their thermal and electrical stability is an important reliability factor. Detection and prevention of quenches in 2G wire-based cables and solenoids has proven to be a difficult engineering task. This is largely due to a very slow normal zone propagation in coated conductors that leads to formation of localized hotspots while the rest of the conductor remains in the superconducting state. We propose an original method of quench and hotspot detection for 2G wires and coils that is based upon local magnetic sensing and takes advantage of 2G wire planar geometry. We demonstrate our technique experimentally and show that its sensitivity is superior to the known voltage detection scheme. A unique feature of the method is its capability to remotely detect instant degradation of the wire critical current even before a normal zone is developed within the conductor. Various modifications of the method applicable to practical device configurations are discussed.

  8. Quench detection method for 2G HTS wire

    Energy Technology Data Exchange (ETDEWEB)

    Marchevsky, M; Xie, Y-Y; Selvamanickam, V, E-mail: maxmarche@gmail.co, E-mail: yxie@superpower-inc.co [SuperPower, Inc., 450 Duane Avenue, Schenectady, NY 12304 (United States)

    2010-03-15

    2G HTS conductors are increasingly used in various commercial applications and their thermal and electrical stability is an important reliability factor. Detection and prevention of quenches in 2G wire-based cables and solenoids has proven to be a difficult engineering task. This is largely due to a very slow normal zone propagation in coated conductors that leads to formation of localized hotspots while the rest of the conductor remains in the superconducting state. We propose an original method of quench and hotspot detection for 2G wires and coils that is based upon local magnetic sensing and takes advantage of 2G wire planar geometry. We demonstrate our technique experimentally and show that its sensitivity is superior to the known voltage detection scheme. A unique feature of the method is its capability to remotely detect instant degradation of the wire critical current even before a normal zone is developed within the conductor. Various modifications of the method applicable to practical device configurations are discussed.

  9. Consensus approach for modeling HTS assays using in silico descriptors

    Directory of Open Access Journals (Sweden)

    Ahmed eAbdelaziz Sayed

    2016-02-01

    Full Text Available The need for filling information gaps while reducing toxicity testing in animals is becoming more predominant in risk assessment. Recent legislations are accepting in silico approaches for predicting toxicological outcomes. This article describes the results of Quantitative Structure Activity Relationship (QSAR modeling efforts within Tox21 Data Challenge 2014, which calculated the best balanced accuracy across all molecular pathway endpoints as well as the highest scores for ATAD5 and mitochondrial membrane potential disruption. Automated QSPR workflow systems, OCHEM (http://ochem.eu, the analytics platform, KNIME and the statistics software, CRAN R, were used to conduct the analysis and develop consensus models using ten different descriptor sets. A detailed analysis of QSAR models for all 12 molecular pathways and the effect of underlying models’ accuracy on the quality of the consensus model are provided. The resulting consensus models yielded a balanced accuracy as high as 88.1%±0.6 for mitochondrial membrane disruptors. Such high balanced accuracy and use of the applicability domain show a promising potential for in silico modeling to complement design HTS screening experiments. The summary statistics of all models are publicly available online at https://github.com/amaziz/Tox21-Challenge-Publication while the developed consensus models can be accessed at http://ochem.eu/article/98009.

  10. Cuprate-titanate superconductor and method for making

    Science.gov (United States)

    Toreki, Robert; Poeppelmeier, Kenneth; Dabrowski, Bogdan

    1995-01-01

    A new copper oxide superconductor of the formula Ln.sub.1-x M.sub.x Sr.sub.2 Cu.sub.3-y Ti.sub.y O.sub.7+.delta. is disclosed, and exhibits a Tc of 60.degree. K. with deviations from linear metallic behavior as high as 130.degree. K.

  11. Use of in Vitro HTS-Derived Concentration-Response Data as ...

    Science.gov (United States)

    Background: Quantitative high-throughput screening (qHTS) assays are increasingly being employed to inform chemical hazard identification. Hundreds of chemicals have been tested in dozens of cell lines across extensive concentration ranges by the National Toxicology Program in collaboration with the NIH Chemical Genomics Center. Objectives: To test a hypothesis that dose-response data points of the qHTS assays can serve as biological descriptors of assayed chemicals and, when combined with conventional chemical descriptors, may improve the accuracy of Quantitative Structure-Activity Relationship (QSAR) models applied to prediction of in vivo toxicity endpoints. Methods and Results: The cell viability qHTS concentration-response data for 1,408 substances assayed in 13 cell lines were obtained from PubChem; for a subset of these compounds rodent acute toxicity LD50 data were also available. The classification k Nearest Neighbor and Random Forest QSAR methods were employed for modeling LD50 data using either chemical descriptors alone (conventional models) or in combination with biological descriptors derived from the concentration-response qHTS data (hybrid models). Critical to our approach was the use of a novel noise-filtering algorithm to treat qHTS data. We show that both the external classification accuracy and coverage (i.e., fraction of compounds in the external set that fall within the applicability domain) of the hybrid QSAR models was superior to convent

  12. Electrical performance analysis of HTS synchronous motor based on 3D FEM

    International Nuclear Information System (INIS)

    Baik, S.K.; Kwon, Y.K.; Kim, H.M.; Lee, J.D.; Kim, Y.C.; Park, G.S.

    2010-01-01

    A 1-MW class superconducting motor with High-Temperature Superconducting (HTS) field coil is analyzed and tested. This machine is a prototype to make sure applicability aimed at generator and industrial motor applications such as blowers, pumps and compressors installed in large plants. This machine has the HTS field coil made of Bi-2223 HTS wire and the conventional copper armature (stator) coils cooled by water. The 1-MW class HTS motor is analyzed by 3D electromagnetic Finite Element Method (FEM) to get magnetic field distribution, self and mutual inductance, and so forth. Especially excitation voltage (Back EMF) is estimated by using the mutual inductance between armature and field coils and compared with experimental result. Open and short circuit tests were conducted in generator mode while a 1.1-MW rated induction machine was rotating the HTS machine. Electrical parameters such as mutual inductance and synchronous inductance are deduced from these tests and also compared with the analysis results from FEM.

  13. Characterization of pinning stability of HTS Gd123 bulks by using a pulsed-field magnetization

    International Nuclear Information System (INIS)

    Taguchi, R; Miki, M; Tsuzuki, K; Izumi, M; Yamaguchi, K; Kimura, Y; Ida, T

    2010-01-01

    High-temperature superconductor (HTS) Gd-bulks are used for field-pole magnets of rotating machines. We have conducted a study of pulsed-field magnetization (PFM) for the bulks to be magnetized alternatively on the rotor. Performances of HTS bulks have been qualified on the basis of the field-cooling magnetization (FCM). HTS bulks are a kind of crystals containing lots of tiny crystals boundaries. It is difficult to find comparable data between PFM and FCM results, mainly because of the different pinning stability through both processes. We need to assess an effective method of characterization for the flux pinning stability under PFM. We compared two HTS bulks: one shows a flux flow and relatively small trapped flux while the other is magnetized with a little flux instability and a large integrated trapped flux. These Gd123 bulks are 100 mm in diameter and 20 mm in thickness. After applying PFM at the liquid nitrogen temperature, we measured the trapped field density distribution and introduced a new parameter representing the trapped flux instability at each position on the surface of the bulk. We propose a way of visualization of the flux pinning instability of the HTS bulks.

  14. Design of conduction cooling system for a high current HTS DC reactor

    Science.gov (United States)

    Dao, Van Quan; Kim, Taekue; Le Tat, Thang; Sung, Haejin; Choi, Jongho; Kim, Kwangmin; Hwang, Chul-Sang; Park, Minwon; Yu, In-Keun

    2017-07-01

    A DC reactor using a high temperature superconducting (HTS) magnet reduces the reactor’s size, weight, flux leakage, and electrical losses. An HTS magnet needs cryogenic cooling to achieve and maintain its superconducting state. There are two methods for doing this: one is pool boiling and the other is conduction cooling. The conduction cooling method is more effective than the pool boiling method in terms of smaller size and lighter weight. This paper discusses a design of conduction cooling system for a high current, high temperature superconducting DC reactor. Dimensions of the conduction cooling system parts including HTS magnets, bobbin structures, current leads, support bars, and thermal exchangers were calculated and drawn using a 3D CAD program. A finite element method model was built for determining the optimal design parameters and analyzing the thermo-mechanical characteristics. The operating current and inductance of the reactor magnet were 1,500 A, 400 mH, respectively. The thermal load of the HTS DC reactor was analyzed for determining the cooling capacity of the cryo-cooler. The study results can be effectively utilized for the design and fabrication of a commercial HTS DC reactor.

  15. Progress in second-generation HTS wire development and manufacturing

    International Nuclear Information System (INIS)

    Selvamanickam, V.; Chen, Y.; Xiong, X.; Xie, Y.; Zhang, X.; Rar, A.; Martchevskii, M.; Schmidt, R.; Lenseth, K.; Herrin, J.

    2008-01-01

    2007 has marked yet another year of continued rapid progress in developing and manufacturing high-performance, long-length second-generation (2G) HTS wires at high speeds. Using ion beam assisted deposition (IBAD) MgO and associated buffer sputtering processes, SuperPower has now exceeded piece lengths of 1000 m of fully buffered tape reproducibly with excellent in-plane texture of 6-7 degrees and uniformity of about 2%. These kilometer lengths are produced at high speeds of about 350 m/h of 4 mm wide tape. In combination with metal organic chemical vapor deposition (MOCVD), 2G wires up to single piece lengths to 790 m with a minimum critical current value of 190 A/cm corresponding to a Critical current x Length performance of 150,100 Am have been achieved. Tape speeds up to 180 m/h have been reached MOCVD while maintaining critical currents above 200 A/cm in 100+ m lengths. Thick film MOCVD technology has been transitioned to Pilot manufacturing system where a minimum critical current of 320 A/cm has been demonstrated over a length of 155 m processed at a speed of 70 m/h in 4 mm width. Finally, nearly 10,000 m of 2G wire has been produced, exhaustively tested, and delivered to the Albany Cable project. The average minimum critical current of the wire delivered in 225 segments of 43-44 m is 70 A in 4 mm widths. A 30 m cable has been fabricated with this wire by Sumitomo Electric and has been installed in the power grid of National Grid in downtown Albany and is the world's first 2G device installed in the grid

  16. Progress in second-generation HTS wire development and manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V. [SuperPower, Inc., 450 Duane Avenue, Schenectady, NY 12304 (United States)], E-mail: vselva@superpower-inc.com; Chen, Y.; Xiong, X.; Xie, Y.; Zhang, X.; Rar, A.; Martchevskii, M.; Schmidt, R.; Lenseth, K.; Herrin, J. [SuperPower, Inc., 450 Duane Avenue, Schenectady, NY 12304 (United States)

    2008-09-15

    2007 has marked yet another year of continued rapid progress in developing and manufacturing high-performance, long-length second-generation (2G) HTS wires at high speeds. Using ion beam assisted deposition (IBAD) MgO and associated buffer sputtering processes, SuperPower has now exceeded piece lengths of 1000 m of fully buffered tape reproducibly with excellent in-plane texture of 6-7 degrees and uniformity of about 2%. These kilometer lengths are produced at high speeds of about 350 m/h of 4 mm wide tape. In combination with metal organic chemical vapor deposition (MOCVD), 2G wires up to single piece lengths to 790 m with a minimum critical current value of 190 A/cm corresponding to a Critical current x Length performance of 150,100 Am have been achieved. Tape speeds up to 180 m/h have been reached MOCVD while maintaining critical currents above 200 A/cm in 100+ m lengths. Thick film MOCVD technology has been transitioned to Pilot manufacturing system where a minimum critical current of 320 A/cm has been demonstrated over a length of 155 m processed at a speed of 70 m/h in 4 mm width. Finally, nearly 10,000 m of 2G wire has been produced, exhaustively tested, and delivered to the Albany Cable project. The average minimum critical current of the wire delivered in 225 segments of 43-44 m is 70 A in 4 mm widths. A 30 m cable has been fabricated with this wire by Sumitomo Electric and has been installed in the power grid of National Grid in downtown Albany and is the world's first 2G device installed in the grid.

  17. Frequency dependence of magnetic shielding performance of HTS plates in mixed states

    Energy Technology Data Exchange (ETDEWEB)

    Kamitani, Atsushi; Yokono, Takafumi [Yamagata Univ., Yonezawa (Japan). Faculty of Engineering; Yokono, Takafumi [Tsukuba Univ., Ibaraki (Japan). Inst. of Information Sciences and Electronics

    2000-06-01

    The magnetic shielding performance of the high-Tc superconducting (HTS) plate is investigated numerically. The behavior of the shielding current density in the HTS plate is expressed as the integral-differential equation with a normal component of the current vector potential as a dependent variable. The numerical code for solving the equation has been developed by using the combination of the Newton-Raphson method and the successive substitution method and, by use of the code, damping coefficients and shielding factors are evaluated for the various values of the frequency {omega}. The results of computations show that the HTS plate has a possibility of shielding the high-frequency magnetic field with {omega} > or approx. 1 kHz. (author)

  18. Numerical studies on the force characteristic of superconducting linear synchronous motor with HTS bulk magnet

    Science.gov (United States)

    Tang, Junjie; Li, Jing; Li, Xiang; Han, Le

    2018-03-01

    High temperature superconductor (HTS) bulks have significant potential use in linear motor application act as quasi-permanent magnet to replace traditional magnets. Force characteristic between HTS bulk magnet and traveling magnetic field was investigated with numerical simulation and experimental measurement in this paper. Influences of bulk height and number on the force characteristic were studied by the finite element model considering the nonlinear E-J relationship. Study was also made on addition of a back iron plate to the bulk magnet. Besides, force characteristic of bulk was compared with the permanent magnet results. The small initial decrease of the thrust could be explained by inside superconducting current redistribution. It was found that efficiency of linear motor did not increase by adding more bulk magnets. The bulk magnet will be remagnetized instead of erasing trapped field with the increase of the traveling magnetic field strength. The conclusions are helpful in prediction and design the linear motor with HTS bulk magnet.

  19. Modelling and construction of a compact 500 kg HTS magnetic bearing

    International Nuclear Information System (INIS)

    Werfel, F N; Floegel-Delor, U; Rothfeld, R; Goebel, B; Wippich, D; Riedel, T

    2005-01-01

    The progress of heavy-load HTS bearings depends on improvements in design, material quality and reliable cooling. We have constructed, manufactured and tested a 200 mm HTS journal bearing with a thermally encapsulated YBCO ring. For maximum force the larger gap due to the bearing cryostat (>4 mm) requires adjustment of the magnetic excitation pole distance and the Fe collector shim thickness. HTS material progress is obtained by top-seeded single- or multiple-grain growth which increases the averaged trapped magnetic flux density. Successful YBCO ring growth with radial c axis distribution by seeding the inner ring surface has been performed. The encapsulation ensures a substantially reduced cryogenic effort and stabilizes bearing operation at 78-79 K

  20. Test results of the 18 kA EDIPO HTS current leads

    Energy Technology Data Exchange (ETDEWEB)

    Wesche, Rainer, E-mail: rainer.wesche@psi.ch [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas (CRPP), Association Euratom - Confederation Suisse, 5232 Villigen PSI (Switzerland); Bagnasco, Maurizio; Bruzzone, Pierluigi; Felder, Roland; Guetg, Marc; Holenstein, Manuel; Jenni, Markus; March, Stephen; Roth, Felix; Vogel, Martin [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas (CRPP), Association Euratom - Confederation Suisse, 5232 Villigen PSI (Switzerland)

    2011-10-15

    For the new test facility EDIPO (European DIPOle), to be hosted by CRPP, two 18 kA HTS current leads were manufactured and successfully tested. The HTS module, made of AgMgAu/Bi-2223 tapes, is cooled only by heat conduction to the cold end, while the copper part is cooled by forced flow helium gas. The current leads were tested at low voltage up to the maximum current of 18 kA. The helium mass flow rates required for stable operation at various currents were determined. In addition to the steady state operation, the transient behavior in the case of a loss of flow was studied experimentally. The test results provide an estimate of the operational limits of the EDIPO HTS current leads.

  1. Frequency dependence of magnetic shielding performance of HTS plates in mixed states

    International Nuclear Information System (INIS)

    Kamitani, Atsushi; Yokono, Takafumi; Yokono, Takafumi

    2000-01-01

    The magnetic shielding performance of the high-Tc superconducting (HTS) plate is investigated numerically. The behavior of the shielding current density in the HTS plate is expressed as the integral-differential equation with a normal component of the current vector potential as a dependent variable. The numerical code for solving the equation has been developed by using the combination of the Newton-Raphson method and the successive substitution method and, by use of the code, damping coefficients and shielding factors are evaluated for the various values of the frequency ω. The results of computations show that the HTS plate has a possibility of shielding the high-frequency magnetic field with ω > or approx. 1 kHz. (author)

  2. Fabrication and Test of a 60-kA HTS Current Lead for Fusion Magnet System

    Science.gov (United States)

    Ando, T.; Isono, T.; Kawano, K.; Hamada, K.; Matsui, K.; Nunoya, Y.; Hara, E.; Kato, T.; Okuno, K.; Bono, T.; Tomioka, A.; Sanuki, Y.; Ito, I.; Sakaki, K.; Konno, M.; Uede, T.

    2004-06-01

    A 60-kA HTS current lead was fabricated and tested in the frame of the R&D work for large fusion magnets such as the ITER magnet. The design of the current lead was characterized by its safe thermal protection for the current decay of about ten seconds after quench as well as lower electrical power consumption for its cryogenic equipment. The 60-kA current lead is composed of a lower temperature HTS part using HTS and a high temperature copper part using a conventional copper cable. The HTS part consists of 48 HTS units installed in the cylindrical array into the grooves provided on the outer surface of a stainless steel cylinder with a diameter of 146 mm. The unit was composed of six Bi2223/Ag-10at%Au tapes and its cross-sectional dimension is 6.5 mm × 2.7 mm. The stainless steel cylinder and Ag alloy sheath have a share in thermal protection for quench. The current lead was tested under the cooling condition that the bottom of the HTS part was immersed into 4.2 K liquid helium, and the bottom of the copper part was forced cooled with a helium gas of 3.2 g/s at 20 K. The lead was successfully operated at 60 kA without quench. Heat load to liquid helium was 4.8 W. The total electrical power consumption for the cryogenic equipment was estimated as 37 % of that of conventional copper current lead.

  3. Field Test of 3 phase, 22.9kV, 100m HTS Cable System in KEPCO

    Energy Technology Data Exchange (ETDEWEB)

    Sohn, S H [Superconductivity and Application Group, Korea Electric Power Research Institute (Korea, Republic of); Choi, H S [Superconductivity and Application Group, Korea Electric Power Research Institute (Korea, Republic of); Kim, H R [Superconductivity and Application Group, Korea Electric Power Research Institute (Korea, Republic of); Hyun, O B [Superconductivity and Application Group, Korea Electric Power Research Institute (Korea, Republic of); Yim, S W [Department of superconductivity, University of Tokyo (Japan); Masuda, T [HTS R and D Department, Sumitomo Electric Industries Ltd (Japan); Yatsuka, K [HTS R and D Department, Sumitomo Electric Industries Ltd (Japan); Watanabe, M [HTS R and D Department, Sumitomo Electric Industries Ltd (Japan); Ryoo, H S [Underground System Group, Korea Electrotechnology Research Institute (Korea, Republic of); Yang, H S [High Magnetic Field R and D Team, Korea Basic Science Institute (Korea, Republic of); Kim, D L [High Magnetic Field R and D Team, Korea Basic Science Institute (Korea, Republic of); Hwang, S D [Superconductivity and Application Group, Korea Electric Power Research Institute (Korea, Republic of)

    2006-06-01

    Starting from investigation of feasibility and basic studies, KEPCO/KEPRI has carried an enterprising project for HTS cable system since 2002. The objectives of this project are to demonstrate HTS cable system and evaluate the feasibility in electricity utility's view. The installation of 100m/3phase/22.9kV/50MVA HTS cable system is undergoing in KEPCO's test yard, located in Gochang, Korea. The HTS cable system consists of 100m long cable, two terminations and a cooling system. To simulate the actual cable installation, the 55m section of the 100m long cable was installed into an underground tunnel. Commissioning test is scheduled at the end of September, 2005 and followed by long term operation test. In this paper, the installation of HTS cable system and initial results of system operation will be summarized.

  4. Progress in AMSC scale-up of second generation HTS wire

    International Nuclear Information System (INIS)

    Zhang, W.; Rupich, M.W.; Schoop, U.; Verebelyi, D.T.; Thieme, C.L.H.; Li, X.; Kodenkandath, T.; Huang, Y.; Siegal, E.; Buczek, D.; Carter, W.; Nguyen, N.; Schreiber, J.; Prasova, M.; Lynch, J.; Tucker, D.; Fleshler, S.

    2007-01-01

    American Superconductor has successfully scaled up its low-cost, high volume second generation (2G) HTS wire process into pre-pilot scale production, with performance approaching first generation (1G) HTS wire. AMSC's manufacturing approach is based on RABiTS TM /MOD wide strip technology, with metal organic deposition (MOD) process for the YBCO layer and the Rolling Assisted Biaxially Textured Substrate (RABiTS) process for the template. In this paper, we review the status of the 2G manufacturing scale up at AMSC and describe the properties and architecture of the 2G wire being manufactured and developed for various applications

  5. Progress in AMSC scale-up of second generation HTS wire

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, W. [American Superconductor Corporation, 2 Technology Drive, Westborough, MA 01545 (United States)], E-mail: wzhang@amsuper.com; Rupich, M.W.; Schoop, U.; Verebelyi, D.T.; Thieme, C.L.H.; Li, X.; Kodenkandath, T.; Huang, Y.; Siegal, E.; Buczek, D.; Carter, W.; Nguyen, N.; Schreiber, J.; Prasova, M.; Lynch, J.; Tucker, D.; Fleshler, S. [American Superconductor Corporation, 2 Technology Drive, Westborough, MA 01545 (United States)

    2007-10-01

    American Superconductor has successfully scaled up its low-cost, high volume second generation (2G) HTS wire process into pre-pilot scale production, with performance approaching first generation (1G) HTS wire. AMSC's manufacturing approach is based on RABiTS{sup TM}/MOD wide strip technology, with metal organic deposition (MOD) process for the YBCO layer and the Rolling Assisted Biaxially Textured Substrate (RABiTS) process for the template. In this paper, we review the status of the 2G manufacturing scale up at AMSC and describe the properties and architecture of the 2G wire being manufactured and developed for various applications.

  6. Dielectric properties of glasses prepared by quenching melts of superconducting Bi-Ca-Sr-Cu-O cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Varma, K. B. R.; Subbanna, G. N.; Ramakrishnan, T. V.; Rao, C. N. R.

    1989-07-03

    Glasses obtained from quenching melts of superconducting bismuth cuprates of the formula Bi/sub 2/(Ca,Sr)/sub /ital n/+1/Cu/sub /ital n//O/sub 2/ital n/+4/ with /ital n/=1 and 3 exhibit novel dielectric properties. They possess relatively high dielectric constants as well as high electrical conductivity. The novel dielectric properties of these cuprate glasses are likely to be of electronic origin. They exhibit a weak microwave absorption due to the presence of microcrystallites.

  7. Theory of high-Tc superconducting cuprates based on experimental evidence

    International Nuclear Information System (INIS)

    Abrikosov, A. A.

    1999-01-01

    A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated interaction between electrons plus a small short-range repulsion of Hund's, or spin-fluctuation, origin. This permits to explain the large values of Tc, features of the isotope effect on oxygen and copper, the existence of two types of the order parameter, the peak in the inelastic neutron scattering, the positive curvature of the upper critical field, as function of temperature etc

  8. Model Evidence of a Superconducting State with a Full Energy Gap in Small Cuprate Islands

    Science.gov (United States)

    Black-Schaffer, Annica M.; Golubev, Dmitri S.; Bauch, Thilo; Lombardi, Floriana; Fogelström, Mikael

    2013-05-01

    We investigate subdominant order parameters stabilizing at low temperatures in nanoscale high-Tc cuprate islands, motivated by the recent observation of a fully gapped state in nanosized YBa2Cu3O7-δ [D. Gustafsson et al., Nature Nanotech. 8, 25 (2013)]. Using complementary quasiclassical and tight-binding Bogoliubov-de Gennes methods, we show on distinctly different properties dependent on the symmetry being dx2-y2+is or dx2-y2+idxy. We find that a surface-induced dx2-y2+is phase creates a global spectroscopic gap which increases with an applied magnetic field, consistent with experimental observation.

  9. Theory of High-T{sub c} Superconducting Cuprates Based on Experimental Evidence

    Science.gov (United States)

    Abrikosov, A. A.

    1999-12-10

    A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated interaction between electrons plus a small short-range repulsion of Hund's, or spin-fluctuation, origin. This permits to explain the large values of T{sub c}, features of the isotope effect on oxygen and copper, the existence of two types of the order parameter, the peak in the inelastic neutron scattering, the positive curvature of the upper critical field, as function of temperature etc.

  10. Development of the cryo-rotary joint for a HTS synchronous motor with Gd-bulk HTS field-pole magnets

    Energy Technology Data Exchange (ETDEWEB)

    Miki, M; Felder, B; Tsuzuki, K; Izumi, M [Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, 2-1-6, Etchu-jima, Koto-ku, Tokyo 135-8533 (Japan); Hayakawa, H, E-mail: d082025@kaiyodai.ac.j [Kitano Seiki Co. Ltd., 7-17-3, Chuo, Ohta-ku, Tokyo 143-0024 (Japan)

    2010-06-01

    We have studied a prototype of an axial-gap type synchronous motor with Gd-bulk HTS field-pole magnets since 2001. At the liquid nitrogen temperature, these bulks have trapped over 1 T inside the motor after being applied the pulsed field magnetization method. Increasing the flux of the field poles is the most straightforward way of improving the output power of the motor. Cooling down the bulk HTS magnets below the liquid nitrogen temperature provides an effective alternative to increase the magnetic flux trapping. In 2007, we exchanged the cryogen from liquid nitrogen to condensed neon. The key technology of this challenge is a rotary joint, introducing a fluid cryogen into the rotating body in the motor from the static reservoir. We have successfully developed a compact rotary joint which is smaller and lighter than the existent one (1/10 volume, 1/3 length and 1/12 weight). The present joint was manufactured and evaluated with liquid nitrogen and condensed neon. We presume a total heat loss of this rotary joint of less than 10 watts. Successful cooling and rotating tests of the bulk-HTS motor with this novel rotary joint are conducted.

  11. Magnetization studies of oxides related to the high temperature cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Zhaorong [Iowa State Univ., Ames, IA (United States)

    1995-06-19

    The magnetic properties related to the following high temperature superconductors were measured utilizing a Faraday magnetometer: BaCuO2+x , La2 CuO4 , Sr2 RhO4 , Sr2 VO4, and Sr2 CuO3. Neutron diffraction, magnetic susceptibility, and heat capacity measurements are discussed.

  12. In memory Prof. Dr. L.H.K Bleeker | Gemser | HTS Teologiese ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 1, No 3 (1944) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. In memory Prof. Dr. L.H.K Bleeker. B Gemser ...

  13. Sensitivity of surface resistance measurement of HTS thin films by ...

    Indian Academy of Sciences (India)

    Sensitivity of surface resistance measurement of HTS thin films by cavity resonator, dielectric resonator and microstrip line resonator ... 012, India; Research Center for Superconductor Photonics, Osaka University, Osaka 565 0871, Japan; Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India ...

  14. A Simplified Model to Calculate AC Losses in Large 2G HTS Coils

    DEFF Research Database (Denmark)

    Song, Xiaowei (Andy); Mijatovic, Nenad; Jensen, Bogi Bech

    2015-01-01

    . The model presented uses H formulation which directly solves magnetic fields, and the general partial differential equations (PDEs) module in Comsol Multiphysics is used to implement the model. Afterwards, the model is used to simulate the excitation stage of a racetrack HTS coil with 350 tapes. The AC...

  15. Daniël 2 as satire | Nel | HTS Teologiese Studies / Theological Studies

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 68, No 1 (2012) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  16. HTS Teologiese Studies / Theological Studies - Vol 15, No 2-4 (1959)

    African Journals Online (AJOL)

    Die ontwerp van 'n sendingbeleid in die huidige situasie · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. P.S. Dreyer, 56-66. http://dx.doi.org/10.4102/hts.v15i2/3/4.3781 ...

  17. Elders as leaders in 1 Peter and the early Church | Elliot | HTS ...

    African Journals Online (AJOL)

    As one of the earliest witnesses to this constellation and its symbolization of community leaders as elders-pastors-overseers, the text of 1 Peter 5:1-5a deserves more attention than it has hitherto been accorded in the study of early Christian ministry and church order. HTS Theological Studies Vol. 64 (2) 2008: pp. 681-695 ...

  18. HTS 63_4_ KRITZINGER.TambacH _REVISED.AUTHOR

    African Journals Online (AJOL)

    p1243322

    This article analyses Karl Barth's 1919 Tambach lecture on “The. Christian in society” in the context of post ... “The Christian in society”:Reading Barth's Tambach lecture. 1664. HTS 63(4) 2007. Tambach lecture ..... Lord of the universe, a critical No and a creative Yes in regard to all the content of our thought, a facing away ...

  19. What kind of “Judean” was Jesus? | Cromhout | HTS Teologiese ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 63, No 2 (2007) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  20. Editorial: P.G.R. de Villiers Dedication – A tribute | van Eck | HTS ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 71, No 1 (2015) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. Editorial: P.G.R. de Villiers Dedication – A tribute. Ernest van ...

  1. Low AC Loss in a 3 kA HTS Cable of the Dutch Project

    NARCIS (Netherlands)

    Chevtchenko, O.; Zuijderduin, R.; Smit, J.; Willen, D.; Lentge, H.; Thidemann, C.; Traeholt, C.; Melnik, I.; Geschiere, A.

    2012-01-01

    are: a cable has to fit in an annulus of 160 mm, with two cooling stations at the cable ends only. Existing solutions for HTS cables would lead to excessively high coolant pressure drop in the cable, potentially affecting public acceptance of the project. A way out would be to substantially reduce

  2. Low AC Loss in a 3 kA HTS Cable of the Dutch Project

    DEFF Research Database (Denmark)

    Chevtchenko, Oleg; Zuijderduin, Roy; Smit, Johan

    2012-01-01

    in the cable, potentially affecting public acceptance of the project. A way out would be to substantially reduce AC losses from 1 down to about 0.1W/m per phase at rated current of 3 kArms, frequency of 50Hz and temperature of 77K. In this paper we discuss a strategy towards this ambitious goal, a concept...... pitch angles for two-layer cable conductor of relatively large diameter, by minimizing the gaps between the HTS tapes, and by using narrow HTS tapes that conform well to the roundness of the underlying former. AC loss of 0.12W/m at 3 kArms was measured at a frequency of 60Hz and at a temperature of 77K.......Requirements for a 6km long high temperature superconducting (HTS) AC power cable of the Amsterdam project are: a cable has to fit in an annulus of 160mm, with two cooling stations at the cable ends only. Existing solutions for HTS cables would lead to excessively high coolant pressure drop...

  3. Die paradigmas van 'Kerk en wêreld 2000' | Buitendag | HTS ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT · Advanced Search · Current Issue · Archives · Journal Home > Vol 46, No 4 (1990) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you selected should ...

  4. By die uittrede van Prof. H.P. Wolmarans | Oosthuizen | HTS ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 15, No 2-4 (1959) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register. By die uittrede van Prof. H.P. Wolmarans.

  5. By die uittrede van Prof. H.P. Wolmarans | Oosthuizen | HTS ...

    African Journals Online (AJOL)

    HTS Teologiese Studies / Theological Studies. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 15, No 2-4 (1959) >. Log in or Register to get access to full text downloads. Username, Password, Remember me, or Register · Download this PDF file. The PDF file you ...

  6. Trapped magnetic field measurements on HTS bulk by peak controlled pulsed field magnetization

    International Nuclear Information System (INIS)

    Ida, Tetsuya; Watasaki, Masahiro; Kimura, Yosuke; Miki, Motohiro; Izumi, Mitsuru

    2010-01-01

    For the past several years, we have studied the high-temperature superconducting (HTS) synchronous motor assembled with melt-textured Gd-Ba-Cu-O bulk magnets. If the single pulse field magnetizes a bulk effectively, size of electrical motor will become small for the strong magnetic field of the HTS magnets without reducing output power of motor. In the previous study, we showed that the HTS bulk was magnetized to excellent cone-shape magnetic field distribution by using the waveform control pulse magnetization (WCPM) method. The WCPM technique made possible the active control of the waveform on which magnetic flux motion depended. We generated the pulse waveform with controlled risetime for HTS bulk magnetization to suppress the magnetic flux motion which decreases magnetization efficiency. The pulsed maximum magnetic flux density with slow risetime is not beyond the maximum magnetic flux density which is trapped by the static field magnetization. But, as for applying the pulse which has fast risetime, the magnetic flux which exceed greatly the threshold penetrates the bulk and causes the disorder of the trapped magnetic distribution. This fact suggests the possibility that the threshold at pulsed magnetization influences the dynamic magnetic flux motion. In this study, Gd-Ba-Cu-O bulk is magnetized by the controlled arbitrary trapezoidal shape pulse, of which the maximum magnetic flux density is controlled not to exceed the threshold. We will present the trapped magnetic characteristics and the technique to generate the controlled pulsed field.

  7. Investigation of electrical characteristics of no-insulation coil wound with surface-processed HTS tape

    Science.gov (United States)

    Jeon, Haeryong; Lee, Woo Seung; Kim, Jinsub; Baek, Geonwoo; Jeon, Sangsu; Yoon, Yong Soo; Ko, Tae Kuk

    2017-08-01

    This paper deals with the electrical characteristics of no-insulation coil wound with surface-processed HTS tape. The bypassing current path through turn-to-turn contacts within a coil is formed in the no-insulation coil, and this bypassing current path determines two characteristics: 1) self-protection and 2) charge-discharge delay. The amplitude of bypassing current is determined by contact resistance between the turn-to-turn contacts of the no-insulation coil. The surface roughness of the HTS tape is one of the parameters to change the contact resistance. The HTS tapes were processed to roughen by bead blast and abrasive paper, and the no-insulation coil is fabricated using processed HTS tape. We have studied the charge-discharge delay and self-protecting characteristic of each no-insulation coil by 1) sudden discharge tests and 2) overcurrent tests. The FEM simulations of contact resistance of no-insulation coil were carried out. The contact surface resistance of a case processed by abrasive paper has almost three times larger than that of reference no-insulation coil, and a case processed by bead blast presents almost same contact surface resistance with reference no-insulation coil.

  8. Effect of ferromagnetism on superconductivity in manganite/cuprate heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Pang, B.S.H. [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, New Museum Site, Pembroke St., Cambridge CB2 3QZ (United Kingdom)]. E-mail: bshp2@cam.ac.uk; Tomov, R.I. [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, New Museum Site, Pembroke St., Cambridge CB2 3QZ (United Kingdom); Bell, C. [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, New Museum Site, Pembroke St., Cambridge CB2 3QZ (United Kingdom); Blamire, M.G. [Device Materials Group, Department of Materials Science and Metallurgy, University of Cambridge, New Museum Site, Pembroke St., Cambridge CB2 3QZ (United Kingdom)

    2004-10-15

    In this investigation, we deposited multilayers of [(La{sub 0.67}Sr{sub 0.33}MnO{sub 3}){sub d}/(YBa{sub 2}Cu{sub 3}O{sub y}){sub x}], [(La{sub 0.7}Ca{sub 0.3}MnO{sub 3}){sub 4}/(YBa{sub 2}Cu{sub 3}O{sub 7}){sub x}]{sub 180nm} and [(La{sub 0.45}Ca{sub 0.55}MnO{sub 3} ){sub 4}/(YBa{sub 2}Cu{sub 3}O{sub 7}){sub x}]{sub 180nm} of varying individual layer thicknesses using the 'eclipse' pulsed laser deposition technique. Transport measurements were performed to obtain the films' critical temperatures (T{sub c}). We study the interaction between superconductivity and magnetism within these heterostructures, paying attention to the superconducting and ferromagnetic coherence lengths, {xi}{sub F} and {xi}{sub S} respectively, of the materials in the system, and analyzing how these parameters affect the suppression of T{sub c}, eliminating stray field as a possible cause of T{sub c} suppression. We compared our data to previous work to achieve a more comprehensive study of oxide F/S multilayers. We observe that the magnetic nature of the manganite layers do not have much influence on T{sub c} suppression in the multilayers. We show that within certain limits, the thicknesses of both the superconducting and ferromagnetic layers individually affect the T{sub c} of the multilayers. The critical thickness of YBCO in our multilayers was estimated to be {approx}20 nm.

  9. Open metal-organic framework containing cuprate chains.

    Science.gov (United States)

    Tran, Dat T; Fan, Xiaojuan; Brennan, Daniel P; Zavalij, Peter Y; Oliver, Scott R J

    2005-09-05

    A three-dimensional Cu(II) metal-organic framework, copper hydroxide p-pyridinecarboxylate hydrate, [Cu(OH)(C5H4NCO2).H2O], was synthesized by hydrothermally reacting copper nitrate with p-pyridinecarboxylic acid. The crystals were suitable for single-crystal X-ray diffraction analysis, which showed that the Cu(II) centers adopt a slightly distorted square pyramidal geometry. They coordinate to both the pyridyl and carboxylate functionalities of the pyridinecarboxylate bridging ligands. Infinite copper oxide chains run through the structure and are connected by p-pyridinecarboxylate (p-PyC) ligands. Crystal data: monoclinic, space group P2(1)/n, a = 3.5521(2) A, b = 15.8665(11) A, c = 12.9977(9) A, beta = 95.285(2) degrees , and Z = 4. Thermogravimetric analysis (TGA) revealed that the guest H2O molecules in the channels may be removed, and the material is stable to ca. 245 degrees C. Magnetic measurements indicated the material has one-dimensional (1D) antiferromagnetic ordering within the Cu2+ chains with a Néel temperature of ca. 51 K. Data fitting to the Bonner-Fisher model yielded a coupling constant, J, of -7.3 cm(-1) and g factor of 2.15. The Curie tail below 20 K is due to a small amount of paramagnetic impurities, calculated to be approximately 0.2% in concentration. Further characterization of crystallinity and morphology are discussed, including powder X-ray diffraction (PXRD), elemental analysis, and optical microscopy.

  10. Universal spectral signatures in pnictides and cuprates: the role of quasiparticle-pair coupling

    Science.gov (United States)

    Sacks, William; Mauger, Alain; Noat, Yves

    2017-11-01

    Understanding the physical properties of a large variety of high-T c superconductors (SC), the cuprate family as well as the more recent iron-based superconductors, is still a major challenge. In particular, these materials exhibit the ‘peak-dip-hump’ structure in the quasiparticle density of states (DOS). The origin of this structure is explained within our pair-pair interaction (PPI) model: The non-superconducting state consists of incoherent pairs, a ‘Cooper-pair glass’ which, due to the PPI, undergoes a Bose-like condensation below T c to the coherent SC state. We derive the equations of motion for the quasiparticle operators showing that the DOS ‘peak-dip-hump’ is caused by the coupling between quasiparticles and excited pair states, or ‘super-quasiparticles’. The renormalized SC gap function becomes energy-dependent and non retarded, reproducing accurately the experimental spectra of both pnictides and cuprates, despite the large difference in gap value.

  11. Hypertonic saline (HTS versus standard (isotonic fluid therapy for traumatic brain injuries: a systematic review

    Directory of Open Access Journals (Sweden)

    Andrit Lourens

    2014-12-01

    Full Text Available Traumatic Brain Injury (TBI is one of the foremost causes of mortality secondary to trauma. Poorer outcomes are associated with secondary insults, after the initial brain injury occurred. The management goal of TBI is to prevent or minimise the effects of secondary brain injuries. The primary objective of this systematic review/meta-analysis was to assess the effects of Hypertonic Saline (HTS compared to Standard Fluid Therapy (SFT in the treatment and resuscitation of TBI patients. We searched CENTRAL, MEDLINE (from 1966, EBSCOhost, Scopus, ScienceDirect, Proquest Medical Library and EMBASE (from 1980 in May 2010 and updated searches in February 2011. Data were assessed and extracted by two independent authors. Risk ratios (RR with a 95% confidence interval (CI were used as the effect measure. The review included three RCTs (1184 participants of which two were of high to moderate quality (1005 participants. HTS was not found to be associated with a reduction in mortality (3 RCTs, 1184 participants, RR 0.91, 95%CI 0.76 to 1.09 and morbidity in TBI patients. No significant improvement in haemodynamical stability was found whereas insufficient data were available to indicate a reduction in the intracranial pressure (ICP. In the HTS group, cerebral perfusion pressure (CPP (MD 3.83 mmHg, 95%CI 1.08 to 6.57 and serum sodium level (MD 8 mEq/L, 95%CI 7.47 to 8.53 were higher. Existing studies show no indication that HTS, in comparison to SFT, reduces mortality or morbidity after the occurrence of TBI. Against this backdrop, some uncertainties still exist in terms of the use of different concentrations and volumes of HTS, the timing of administration as well as the benefit in specific injury profiles. As a result, formulating conclusive recommendations is complex.

  12. Low-energy charge excitations in an undoped cuprate:Description beyond the standard pdĺ-model?

    Czech Academy of Sciences Publication Activity Database

    Drechsler, S.L.; Málek, Jiří; Hayn, R.; Knupfer, M.; Moskvin, A. S.; Fink, J.

    2003-01-01

    Roč. 17, 18, 19 & 20 (2003), s. 3324-3328 ISSN 0217-9792 Institutional research plan: CEZ:AV0Z1010914 Keywords : cuprates * EELS * loss function exact diagonalization Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.473, year: 2003

  13. Relaxation of strongly coupled electron and phonon fields after photoemission and high-energy part of ARPES spectra of cuprates

    Science.gov (United States)

    Myasnikova, A. E.; Zhileeva, E. A.; Moseykin, D. V.

    2018-03-01

    An approach to considering systems with a high concentration of correlated carriers and strong long-range electron–phonon interaction and to calculating the high-energy part of the angle-resolved photoemission spectroscopy (ARPES) spectra of such systems is suggested. Joint relaxation of strongly coupled fields—a field of correlated electrons and phonon field—after photoemission is studied to clarify the nature of characteristic features observed in the high-energy part of the ARPES spectra of cuprate superconductors. Such relaxation occurs in systems with strong predominantly long-range electron–phonon interaction at sufficiently high carrier concentration due to the coexistence of autolocalized and delocalized carriers. A simple method to calculate analytically a high-energy part of the ARPES spectrum arising is proposed. It takes advantage of using the coherent states basis for the phonon field in the polaron and bipolaron states. The approach suggested yields all the high-energy spectral features like broad Gaussian band and regions of ‘vertical dispersion’ being in good quantitative agreement with the experiments on cuprates at any doping with both types of carriers. Demonstrated coexistence of autolocalized and delocalized carriers in superconducting cuprates changes the idea about their ground state above the superconducting transition temperature that is important for understanding transport and magnetic properties. High density of large-radius autolocalized carriers revealed may be a key to the explanation of charge ordering in doped cuprates.

  14. A simple model for normal state in- and out-of-plane resistivities of hole doped cuprates

    Science.gov (United States)

    Naqib, S. H.; Azam, M. Afsana; Uddin, M. Borhan; Cole, J. R.

    2016-05-01

    The highly anisotropic and qualitatively different nature of the normal state in- and out-of-plane charge dynamics in high-Tc cuprates cannot be accommodated within the conventional Boltzmann transport theory. The variation of in-plane and out-of-plane resistivities with temperature and hole content are anomalous and cannot be explained by Fermi-liquid theory. In this study, we have proposed a simple phenomenological model for the dc resistivity of cuprates by incorporating two firmly established generic features of all hole doped cuprate superconductors-(i) the pseudogap in the quasiparticle energy spectrum and (ii) the T-linear resistivity at high temperatures. This T-linear behavior over an extended temperature range can be attributed to a quantum criticality, affecting the electronic phase diagram of cuprates. Experimental in-plane and out-of-plane resistivities (ρp(T) and ρc(T), respectively) of double-layer Y(Ca)123 have been analyzed using the proposed model. This phenomenological model describes the temperature and the hole content dependent resistivity over a wide range of temperature and hole content, p. The characteristic PG energy scale, εg(p), extracted from the analysis of the resistivity data, agrees quite well with those found in variety of other experiments. Various other extracted parameters from the analysis of ρp(T) and ρc(T) data showed systematic trends with changing hole concentration. We have discussed important features found from the analysis in detail in this paper.

  15. Superconductivity and antiferromagnetism in cuprates and pnictides: Evidence of the role of Coulomb correlation

    International Nuclear Information System (INIS)

    Fan, J.D.; Malozovsky, Y.M.

    2013-01-01

    Highlights: • In a layered 2D cuprates the long-range order antiferromagnetism is driven mainly by the Van Hove singularity. • The long-range antiferromagnetism quickly disappear with doping away from the Van Hove singularity. • For pnictides the antiferromagnetism exists as a result of the nesting condition. • Since the doping steadily changes the nesting conditions, the antiferromagnetism and superconductivity may coexist. -- Abstract: We consider the Hubbard model in terms of the perturbative diagrammatic approach (UN F ⩽1) where the interaction between two electrons with antiparallel spins in the lowest order of perturbation is described by the short-range repulsive contact (on-site) interaction (U>0). We argue that in layered 2D cuprates the long-range order antiferromagnetism is driven mainly by the Van Hove singularity, whereas in the case of pnictides the antiferromagnetism exists as a result of the nesting condition. We show that when the interaction is quite strong (UN F ≈1) in the case of the Van Hove singularity the electron system undergoes the antiferromagnetic phase transition with the log-range order parameter and large insulating gap. The long-range antiferromagnetism quickly disappear, as shown, with the doping away from the Van Hove singularity, but the antiferromagnetic short-range correlation persists (UN F < 1) due to Coulomb repulsive interaction which is the mechanism for superconductivity in cuprates. We argue that in the case of pnictides the antiferromagnetism appears when the nesting conditions for the Fermi surface are met. Since the doping steadily changes the nesting conditions, the antiferromagnetism and superconductivity may coexist as has been observed in pnictides. We show that the proximity of the antiferromagnetism and superconductivity implies the repulsive interaction between electrons, which turns into attractive between quasiparticles as shown by the authors in the article published on the same issue as this one

  16. Effect of a silver contact layer on the annealing and quench behaviour of HTS tapes; Einfluss einer Silberkontaktschicht auf das Belade- und Quenchverhalten von HTS-Bandleitern

    Energy Technology Data Exchange (ETDEWEB)

    Handke, Joerg

    2009-10-14

    The present thesis deals with the optimization of HTS band conductors of the 2nd generation. Thereby on the one hand the charging behaviour of the superconducting layers should be improved in a continuous process. On the other hand the electrical stabilization of coated conductors for the application in superconducting current limiters was studied. It was shown that for both question formulations the configuration of the band concerning the epitactical metal layer plays a deciding role, so that the two first independent seeming problems can be viewed in a common context.

  17. Dichotomy and pseudogap signature in the Raman response of high- Tc cuprates

    Science.gov (United States)

    Azzouz, M.; Hewitt, K. C.; Saadaoui, H.

    2010-05-01

    The signature of the pseudogap in the normal-state Raman response of high- Tc cuprates is examined within the rotating antiferromagnetism theory. The results for the B1g and B2g response functions, including spectral weight transfer and quasiparticle’s dichotomy, compare well with experiment. A pseudogap-induced peak in the B1g response is found to behave like the superconducting peak; the low-frequency B1g response behaves as ωa with ã3 in the clean limit, and a=1 in the dirty limit. Also, we find that the zero-frequency slopes for both B1g and B2g scale as the inverse (inverse squared) of the zero-frequency scattering rate in the clean limit (dirty limit).

  18. Mirror nesting of the Fermi contour and enhanced diamagnetism of the pseudogap state in cuprates

    International Nuclear Information System (INIS)

    Kapaev, V.V.; Belyavsky, V.I.; Kopaev, Yu.V.; Smirnov, M.Yu.

    2007-01-01

    Since the insulating gap in parent spin antiferromagnet survives under a hole underdoping, it might result in a rise of a metal state with a pocket-like Fermi contour with both conventional and mirror nesting corresponding to the same momentum K = (π, π). The nesting leads to a possibility of singlet orbital antiferromagnetic order whereas the mirror nesting promotes the superconducting pairing with the momentum K. We assume screened Coulomb repulsion to be the dominating pairing interaction in the cuprates resulting in the two-component superconducting order parameter. The relative phase of the parameter can be related to orbital current circulations as it follows from the Ginzburg-Landau phenomenology. The orbital antiferromagnetic state with the insulating gap on the Fermi contour is related to the pseudogap state with enhanced diamagnetic response

  19. Role of Lattice Coupling in Establishing Electronic and Magnetic Properties in Quasi-One-Dimensional Cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Lee, W. S.; Johnston, S.; Moritz, B.; Lee, J.; Yi, M.; Zhou, K. J.; Schmitt, T.; Patthey, L.; Strocov, V.; Kudo, K.; Koike, Y.; van den Brink, J.; Devereaux, T. P.; Shen, Z. X.

    2013-06-25

    High resolution resonant inelastic x-ray scattering has been performed to reveal the role of lattice coupling in a family of quasi-1D insulating cuprates, Ca2+5xY2-5xCu5O10. Site-dependent low-energy excitations arising from progressive emissions of a 70 meV lattice vibrational mode are resolved for the first time, providing a direct measurement of electron-lattice coupling strength. We show that such electron-lattice coupling causes doping-dependent distortions of the Cu-O-Cu bond angle, which sets the intrachain spin exchange interactions. Our results indicate that the lattice degrees of freedom are fully integrated into the electronic behavior in low-dimensional systems.

  20. A structural-based microscopic theory on high-temperature cuprate superconductors

    International Nuclear Information System (INIS)

    Wong, K.W.; Ching, W.Y.

    2004-01-01

    Based entirely on the cuprate structure, a microscopic theory for high-temperature superconductivity is proposed. This theory produces quantitative fits to the normal phase properties such as Hall effect, resistivity, thermoelectric power, etc. It also reveals the existence of a pseudo-gap structure that has nodes along the diagonals of the basal plane. In the superconducting phase, an inverse parabolic dependences of T c on hole density is a natural consequence. The optimum T c value derived from the corresponding intrinsic hole density obtained from electronic structure agrees with the value obtained experimentally. This theory can also explain the observation of a strong spin fluctuation near T c in the YBa 2 Cu 3 O 7 (YBCO) and the absence of such in the Bi 2 Sr 2 CaCu 2 O 8 (BiSCCO) system

  1. The two-component physics in cuprates in the real space and in the momentum representation

    Science.gov (United States)

    Gor'kov, L. P.; Teitel'Baum, G. B.

    2008-03-01

    Gradual evolution of two phase coexistence between dynamical and static regimes in cuprates is first investigated in the real space by making use of available neutron scattering, NMR and μSR data. Analyses of the Hall effect and the ARPES spectra reveals the presence of two groups of charge carriers in LSCO. The T-dependent component is due to the thermal activation of bound electron-hole structures seen near antinodal points in the Brillouin zone, thus introducing the two component physics also for the momentum representation. Interpretation of so-called 'van Hove bands' undergoes drastic changes. Importance of the findings for pseudo-gap physics is stressed. Relation to some recent STM and STS results is discussed.

  2. On electron hole symmetry and phase separation in someelectron doped cuprates

    Science.gov (United States)

    Gor'kov, Lev P.; Teitel'baum, Gregory B.

    2005-12-01

    We conclude from the analysis of the experimental NMR data for electron-doped cuprates that the Coulomb effects caused by doping lead to dynamical spatial phase separation that contributes to the nuclear spin relaxation. Remarkable, the 'infinite-layer' Sr 0.9La 0.1CuO 2 reveals unexpected electron-hole symmetry. Its 63Cu nuclear spin relaxation rate is the sum of a constant and the temperature dependent dissipation components, moreover, the latter turns out to be identical to the 1/ 63T1( T)-behavior in the stoichiometric hole-type compound YBa 2Cu 4O 8. Connection to fluctuations of a magnetic sub-phase is discussed.

  3. The two-component physics in cuprates in the real space and in the momentum representation

    Energy Technology Data Exchange (ETDEWEB)

    Gor' kov, L P [NHMFL, Florida State University, 1800 E P. Dirac Dr., Tallahassee FL 32310 (United States); Teitel' baum, G B [E.K.Zavoiskii Institute for Technical Physics of the RAS, Sibirskii Trakt 10/7, Kazan 420029 (Russian Federation)], E-mail: gorkov@magnet.fsu.edu, E-mail: grteit@yahoo.com

    2008-03-15

    Gradual evolution of two phase coexistence between dynamical and static regimes in cuprates is first investigated in the real space by making use of available neutron scattering, NMR and {mu}SR data. Analyses of the Hall effect and the ARPES spectra reveals the presence of two groups of charge carriers in LSCO. The T-dependent component is due to the thermal activation of bound electron-hole structures seen near antinodal points in the Brillouin zone, thus introducing the two component physics also for the momentum representation. Interpretation of so-called 'van Hove bands' undergoes drastic changes. Importance of the findings for pseudo-gap physics is stressed. Relation to some recent STM and STS results is discussed.

  4. Comparison of electromechanical properties and lattice distortions of different cuprate high temperature superconductors

    CERN Document Server

    Scheuerlein, C.; Grether, A; Rikel, M O; Hudspeth, J; Sugano, M; Ballarino, A; Bottura, L

    2016-01-01

    The electromechanical properties of different cuprate high-temperature superconductors, notably two ReBCO tapes, a reinforced and a nonreinforced Bi-2223 tape, and a Bi-2212 wire, have been studied. The axial tensile stress and strain, as well as the transverse compressive stress limits at which an irreversible critical current degradation occurs, are compared. The experimental setup has been integrated in a high-energy synchrotron beamline, and the self-field critical current and lattice parameter changes as a function of tensile stress and strain of a reinforced Bi-2223 tape have been measured simultaneously. Initially, the Bi-2223 filaments exhibit nearly linear elastic behavior up to the strain at which an irreversible degradation is observed. At 77 K, an axial Bi-2223 filament precompression of 0.09% in the composite tape and a Bi-2223 Poisson ratio ν = 0.21 have been determined.

  5. Electronic properites of electron-doped cuprate superconductors probed by high-field magnetotransport

    Energy Technology Data Exchange (ETDEWEB)

    Helm, Toni

    2013-09-18

    In the present work the normal-state properties of the electron-doped cuprate superconductor Nd{sub 2-x}Ce{sub x}CuO{sub 4} (NCCO) are investigated for a broad doping range, covering almost the whole phase diagram of this material. Magnetotransport measurements in the world's highest non-destructive magnetic fields were used as a spectroscopic tool for probing the electronic structure of single-crystalline NCCO as a function of the carrier concentration x. Quantum and semiclassical oscillations in the magnetoresistance provided new insights into various properties of the Fermi surface and the nature of the ground state in the system. The detailed investigations of the field- and temperature-dependent transport and its dependence on the field orientation have revealed a close correlation between symmetry-breaking ordering instabilities and the superconducting state.

  6. Inequivalence of single-particle and population lifetimes in a cuprate superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Shuolong [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Sobota, J. A. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Leuenberger, D. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); He, Y. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States); Hashimoto, M. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Lu, D. H. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Eisaki, H. [National Institute of Advanced Industrial Science and Technology, Ibaraki (Japan); Kirchmann, P. S. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Shen, Z. -X. [SLAC National Accelerator Lab., Menlo Park, CA (United States); Stanford Univ., Stanford, CA (United States)

    2015-06-15

    We study optimally doped Bi-2212 (Tc=96 K) using femtosecond time- and angle-resolved photoelectron spectroscopy. Energy-resolved population lifetimes are extracted and compared with single-particle lifetimes measured by equilibrium photoemission. The population lifetimes deviate from the single-particle lifetimes in the low excitation limit by 1–2 orders of magnitude. Fundamental considerations of electron scattering unveil that these two lifetimes are in general distinct, yet for systems with only electron-phonon scattering they should converge in the low-temperature, low-fluence limit. As a result, the qualitative disparity in our data, even in this limit, suggests that scattering channels beyond electron-phonon interactions play a significant role in the electron dynamics of cuprate superconductors.

  7. Electronic properites of electron-doped cuprate superconductors probed by high-field magnetotransport

    International Nuclear Information System (INIS)

    Helm, Toni

    2013-01-01

    In the present work the normal-state properties of the electron-doped cuprate superconductor Nd 2-x Ce x CuO 4 (NCCO) are investigated for a broad doping range, covering almost the whole phase diagram of this material. Magnetotransport measurements in the world's highest non-destructive magnetic fields were used as a spectroscopic tool for probing the electronic structure of single-crystalline NCCO as a function of the carrier concentration x. Quantum and semiclassical oscillations in the magnetoresistance provided new insights into various properties of the Fermi surface and the nature of the ground state in the system. The detailed investigations of the field- and temperature-dependent transport and its dependence on the field orientation have revealed a close correlation between symmetry-breaking ordering instabilities and the superconducting state.

  8. Complementary Response of Static Spin-Stripe Order and Superconductivity to Nonmagnetic Impurities in Cuprates

    Science.gov (United States)

    Guguchia, Z.; Roessli, B.; Khasanov, R.; Amato, A.; Pomjakushina, E.; Conder, K.; Uemura, Y. J.; Tranquada, J. M.; Keller, H.; Shengelaya, A.

    2017-08-01

    We report muon-spin rotation and neutron-scattering experiments on nonmagnetic Zn impurity effects on the static spin-stripe order and superconductivity of the La214 cuprates. Remarkably, it was found that, for samples with hole doping x ≈1 /8 , the spin-stripe ordering temperature Tso decreases linearly with Zn doping y and disappears at y ≈4 %, demonstrating a high sensitivity of static spin-stripe order to impurities within a CuO2 plane. Moreover, Tso is suppressed by Zn in the same manner as the superconducting transition temperature Tc for samples near optimal hole doping. This surprisingly similar sensitivity suggests that the spin-stripe order is dependent on intertwining with superconducting correlations.

  9. Kinetics-Driven Superconducting Gap in Underdoped Cuprate Superconductors Within the Strong-Coupling Limit

    Directory of Open Access Journals (Sweden)

    Yucel Yildirim

    2011-09-01

    Full Text Available A generic theory of the quasiparticle superconducting gap in underdoped cuprates is derived in the strong-coupling limit, and found to describe the experimental “second gap” in absolute scale. In drastic contrast to the standard pairing gap associated with Bogoliubov quasiparticle excitations, the quasiparticle gap is shown to originate from anomalous kinetic (scattering processes, with a size unrelated to the pairing strength. Consequently, the k dependence of the gap deviates significantly from the pure d_{x^{2}-y^{2}} wave of the order parameter. Our study reveals a new paradigm for the nature of the superconducting gap, and is expected to reconcile numerous apparent contradictions among existing experiments and point toward a more coherent understanding of high-temperature superconductivity.

  10. Extremely correlated Fermi-liquid description of normal-state ARPES in cuprates.

    Science.gov (United States)

    Gweon, G-H; Shastry, B S; Gu, G D

    2011-07-29

    The normal-state single particle spectral function of the high temperature superconducting cuprates, measured by the angle-resolved photoelectron spectroscopy (ARPES), has been considered both anomalous and crucial to understand. Here, we report an unprecedented success of the new extremely correlated Fermi liquid theory by one of us [B. S. Shastry, Phys. Rev. Lett. 107, 056403 (2011)] to describe both laser and conventional synchrotron ARPES data (nodal cut at optimal doping) on Bi(2)Sr(2)CaCu(2)O(8+δ) and synchrotron data on La(1.85)Sr(0.15)CuO(4). It fits all data sets with the same physical parameter values, satisfies the particle sum rule and successfully addresses two widely discussed kink anomalies in the dispersion. © 2011 American Physical Society

  11. A structural-based microscopic theory on high-temperature cuprate superconductors

    Science.gov (United States)

    Wong, K. W.; Ching, W. Y.

    2004-11-01

    Based entirely on the cuprate structure, a microscopic theory for high-temperature superconductivity is proposed. This theory produces quantitative fits to the normal phase properties such as Hall effect, resistivity, thermoelectric power, etc. It also reveals the existence of a pseudo-gap structure that has nodes along the diagonals of the basal plane. In the superconducting phase, an inverse parabolic dependences of Tc on hole density is a natural consequence. The optimum Tc value derived from the corresponding intrinsic hole density obtained from electronic structure agrees with the value obtained experimentally. This theory can also explain the observation of a strong spin fluctuation near Tc in the YBa 2Cu 3O 7 (YBCO) and the absence of such in the Bi 2Sr 2CaCu 2O 8 (BiSCCO) system.

  12. Monte Carlo studies of diamagnetism and charge density wave order in the cuprate pseudogap regime

    Science.gov (United States)

    Hayward Sierens, Lauren; Achkar, Andrew; Hawthorn, David; Melko, Roger; Sachdev, Subir

    2015-03-01

    The pseudogap regime of the hole-doped cuprate superconductors is often characterized experimentally in terms of a substantial diamagnetic response and, from another point of view, in terms of strong charge density wave (CDW) order. We introduce a dimensionless ratio, R, that incorporates both diamagnetic susceptibility and the correlation length of CDW order, and therefore reconciles these two fundamental characteristics of the pseudogap. We perform Monte Carlo simulations on a classical model that considers angular fluctuations of a six-dimensional order parameter, and compare our Monte Carlo results for R with existing data from torque magnetometry and x-ray scattering experiments on YBa2Cu3O6+x. We achieve qualitative agreement, and also propose future experiments to further investigate the behaviour of this dimensionless ratio.

  13. A compactly integrated cooling system of a combination dual 1.5-MW HTS motors for electric propulsion

    Energy Technology Data Exchange (ETDEWEB)

    Le, T. D.; Kim, J. H.; Hyeon, C. J.; Kim, H. M.; Kim, D. K. [Jeju National University, Jeju (Korea, Republic of); Kim, Y. S. [Shin Ansan University, Ansan (Korea, Republic of); Lee, J.; Park, Y. G.; Jeon, H. [Yonsei University, Seoul (Korea, Republic of); Quach, H. L. [Electronic and Telecommunication Engineering, Can Tho University of Technology, Can Tho (Viet Nam)

    2016-12-15

    The high temperature superconducting (HTS) contra-rotating propulsion (CRP) systems comprise two coaxial propellers sited on behind the other and rotate in opposite directions. They have the hydrodynamic advantage of recovering the slipstream rotational energy which would otherwise be lost to a conventional single-screw system. However, the cooling systems used for HTS CRP system need a high cooling power enough to maintain a low temperature of 2G HTS material operating at liquid neon (LNe) temperature (24.5 - 27 K). In this paper, a single thermo-syphon cooling approach using a Gifford-McMahon (G-M) cryo-cooler is presented. First, an optimal thermal design of a 1.5 MW HTS motor was conducted varying to different types of commercial 2G HTS tapes. Then, a mono-cryogenic cooling system for an integration of two 1.5 MW HTS motors will be designed and analyzed. Finally, the 3D finite element analysis (FEA) simulation of thermal characteristics was also performed.

  14. Impurity scattering effect on charge transport in high-Tc cuprate junctions

    International Nuclear Information System (INIS)

    Tanaka, Y.; Asano, Y.; Kashiwaya, S.

    2004-01-01

    It is known that the zero-bias conductance peak (ZBCP) is expected in tunneling spectra of normal-metal/high-Tc cuprate junctions because of the formation of the midgap Andreev resonant states (MARS) at junction interfaces. In the present review, we report the recent theoretical study of impurity scattering effects on the tunneling spectroscopy. In the former part of the present paper, we discuss impurity effects in normal metal. We calculate tunneling conductance for diffusive normal metal (DN)/high Tc cuprate junctions based on the Keldysh Green's function technique. Besides the ZBCP due to the MARS, we can expect ZBCP caused by the different origin, i.e., the coherent Andreev reflection (CAR) assisted by the proximity effect in DN. Their relative importance depends on the angle a between the interface normal and the crystal axis of high-Tc superconductors. At α = 0, we find the ZBCP by the CAR for low transparent junctions with small Thouless energies in DN; this is similar to the case of diffusive normal metal/insulator/s-wave superconductor junctions. Under increase of α from zero to π/4, the contribution of MARS to ZBCP becomes more prominent and the effect of the CAR is gradually suppressed. Such complex spectral features would be observable in conductance spectra of high-Tc junctions at very low temperatures. In the latter part of our paper, we study impurity effects in superconductors. We consider impurities near the junction interface on the superconductor side. The conductance is calculated from the Andreev and the normal reflection coefficients which are estimated by using the single-site approximation in an analytic calculation and by the recursive Green function method in a numerical simulation. We find splitting of the ZBCP in the presence of the time reversal symmetry. Thus the zero-field splitting of ZBCP in the experiment does not perfectly prove an existence of broken time reversal symmetry state

  15. Concepts for using trapped-flux HTS in motors and generators

    Energy Technology Data Exchange (ETDEWEB)

    Hull, John R., E-mail: john.r.hull2@boeing.com [Boeing Research and Technology, PO Box 3707, Seattle, WA 98124 (United States); Strasik, Michael [Boeing Research and Technology, PO Box 3707, Seattle, WA 98124 (United States)

    2013-01-15

    Highlights: ► Use of Dy for core material increases t in situ magnetization of trapped-flux HTS. ► Hysteresis loss in Dy needs to be reduced. ► Bootstrap in situ magnetization can be done with two pulsed-power generators. -- Abstract: We examine the expected performance of a brushless motor/generator that uses trapped-flux (TF) bulk high-temperature superconductors (HTSs) to provide magnetomotive force, where the stator windings are used to create the TF. A key feature is the use of dysprosium (Dy) for the stator and rotor cores. We also examine methods to energize TF in HTS for generators used in pulsed-power applications.

  16. Magnet design with 100-kA HTS STARS conductors for the helical fusion reactor

    Science.gov (United States)

    Yanagi, N.; Terazaki, Y.; Ito, S.; Tamura, H.; Hamaguchi, S.; Mito, T.; Hashizume, H.; Sagara, A.

    2016-12-01

    The high-temperature superconducting (HTS) option is employed for the conceptual design of the LHD-type helical fusion reactor FFHR-d1. The 100-kA-class STARS (Stacked Tapes Assembled in Rigid Structure) conductor is used for the magnet system including the continuously wound helical coils. Protection of the magnet system in case of a quench is a crucial issue and the hot-spot temperature during an emergency discharge is estimated based on the zero-dimensional and one-dimensional analyses. The number of division of the coil winding package is examined to limit the voltage generation. For cooling the HTS magnet, helium gas flow is considered and its feasibility is examined by simple analysis as a first step.

  17. Transport Jc Measurements of HTS Conductors under High Magnetic Field at LNCMI

    Science.gov (United States)

    Chaud, Xavier; Debray, François; Mossang, Eric; Tixador, Pascal; Rey, Jean-Michel; Lecrevisse, Thibault; Bruzek, Christian-Eric

    The LNCMI, the national French high magnetic field facility, provides high fields generated mainly by resistive magnets. Because of the forecast increasing price of electricity, LNCMI has a strong incentive to participate to the development and characterizations of HTS conductors in view of their use for the generation of strong field. Latest YBCO coated conductors have improved properties showing a great potential with that respect, without excluding Bi2212 and MgB2 for particular cases. We present the existing set-up to measure short straight or VAMAS type coil samples at variable temperature and high field up to 30 T, and some measurements obtained on different HTS conductors, Bi2212 round wires and YBCO coated conductors. We also report on the first results obtained at 18 T with a pancake coil made of commercial YBCO coated conductor tapes on a newly developed solenoid test bench.

  18. Design of HTS tri-axial cable in steady-state operation

    Energy Technology Data Exchange (ETDEWEB)

    Hu, N., E-mail: hunannan@ecei.tohoku.ac.j [Electrical Engineering Department, Graduate School, Tohoku University, 6-6-05 Aoba Aramaki, Aoba-ku, Sendai 980-8579 (Japan); Toda, M.; Ozcivan, A.N.; Yagai, T.; Tsuda, M.; Hamajima, T. [Electrical Engineering Department, Graduate School, Tohoku University, 6-6-05 Aoba Aramaki, Aoba-ku, Sendai 980-8579 (Japan)

    2010-11-01

    By the advantage of more compact structure, small leakage field, and low heat loss, tri-axial cable become to be mainstream design in recently HTS practical project. However, the imbalance current problem was also reported by some practice experiments. Since the HTS tri-axial cable is composed of three concentric phases, an unsymmetrical inductance and capacitance distribution which is determined by twist pitches and radii, gives an inherent imbalance in three-phase currents distribution. In our previous research, we proposed a two sections structure design to overcome this limitation. Inductance has been balanced by twist pitch adjusting. In that case, the imbalance ratio of current only can be caused by capacitance distribution which is depending on voltage and line length. In this paper, we evaluate the thickness of insulation, the unsymmetrical capacitance distribution and cable fabrication error. Then we investigate the imbalance ratio due to the capacitance as functions of voltage and length by using Electromagnetic Transients Program (EMTP).

  19. A method to enhance the curve negotiation performance of HTS Maglev

    Science.gov (United States)

    Che, T.; Gou, Y. F.; Deng, Z. G.; Zheng, J.; Zheng, B. T.; Chen, P.

    2015-09-01

    High temperature superconducting (HTS) Maglev has attracted more and more attention due to its special self-stable characteristic, and much work has been done to achieve its actual application, but the research about the curve negotiation is not systematic and comprehensive. In this paper, we focused on the change of the lateral displacements of the Maglev vehicle when going through curves under different velocities, and studied the change of the electromagnetic forces through experimental methods. Experimental results show that setting an appropriate initial eccentric distance (ED), which is the distance between the center of the bulk unit and the center of the permanent magnet guideway (PMG), when cooling the bulks is favorable for the Maglev system’s curve negotiation. This work will provide some available suggestions for improving the curve negotiation performance of the HTS Maglev system.

  20. Flux pumping for non-insulated and metal-insulated HTS coils

    Science.gov (United States)

    Ma, Jun; Geng, Jianzhao; Coombs, T. A.

    2018-01-01

    High-temperature superconducting (HTS) coils wound from coated conductors without turn-to-turn insulation (non-insulated (NI) coils) have been proven with excellent electrical and thermal performances. However, the slow charging of NI coils has been a long-lasting problem. In this work, we explore using a transformer-rectifier HTS flux pump to charge an NI coil and a metal-insulated coil. The charging performance comparison is made between different coils. Comprehensive study is done to thoroughly understand the electrical-magnetic transience in charging these coils. We will show that the low-voltage high-current flux pump is especially suitable for charging NI coils with very low characteristic resistance.

  1. Epitaxial effects in thin films of high-Tc cuprates with the K2NiF4 structure

    Science.gov (United States)

    Naito, Michio; Sato, Hisashi; Tsukada, Akio; Yamamoto, Hideki

    2018-03-01

    La2-xSrxCuO4 (LSCO) and La2-xBaxCuO4 (LBCO) have been recognized as the archetype materials of "hole-doped" high-Tc superconductors. Their crystal structures are relatively simple with a small number of constituent cation elements. In addition, the doping level can be varied by the chemical substitution over a wide range enough to obtain the full spectrum of doping-dependent electronic and magnetic properties. These attractive features have dedicated many researchers to thin-film growth of LSCO and LBCO. The critical temperature (Tc) of LSCO and LBCO is sensitive to strain as manifested by a positive pressure coefficient of Tc in bulk samples. In general, films are strained if they are grown on lattice-mismatched substrates (epitaxial strain). Early attempts (before 1997) at the growth of LSCO and LBCO films resulted in depressed Tc below 30 K as they were grown on a commonly used SrTiO3 substrate (in-plane lattice parameter asub = 3.905 Å): the in-plane lattice parameters of LSCO and LBCO are ≤3.80 Å, and hence tensile epitaxial strain is introduced. The situation was changed by the use of LaSrAlO4 substrates with a slightly shorter in-plane lattice constant (asub = 3.756 Å). On LaSrAlO4 substrates, the Tc reaches 45 K in La1.85Sr0.15CuO4, 47 K in La1.85Ba0.15CuO4, and 56 K in ozone-oxidized La2CuO4+δ films, substantially higher than the Tc's of the bulk compounds. The Tc increase in La1.85Sr0.15CuO4 films on LaSrAlO4 and decrease on SrTiO3 are semi-quantitatively in accord with the phenomenological estimations based on the anisotropic strain coefficients of Tc (dTc/dεi). In this review article, we describe the growth and properties of films of cuprates having the K2NiF4 structure, mainly focusing on the increase/decrease of Tc by epitaxial strain and quasi-stable phase formation by epitaxial stabilization. We further extract the structural and/or physical parameters controlling Tc toward microscopic understanding of the variation of Tc by epitaxial strain.

  2. Optimization of a condensed-neon cooling system for a HTS synchronous motor with Gd-bulk HTS field-pole magnets

    Energy Technology Data Exchange (ETDEWEB)

    Felder, B; Miki, M; Tsuzuki, K; Izumi, M [Department of Marine Electronics and Mechanical Engineering, Tokyo University of Marine Science and Technology, 2-1-6, Etchujima, Koto-ku, Tokyo 135-8533 (Japan); Hayakawa, H, E-mail: d082028@kaiyodai.ac.j [Kitano Seiki Co. Ltd., 7-17-3, Chuo, Ota-ku, Tokyo 143-0024 (Japan)

    2010-06-01

    The axial-gap synchronous machine developed in our laboratory is based on Gd-bulk HTS field-pole magnets, able to trap a part of the magnetic flux they are submitted to when cooled down below T{sub c}. At the liquid nitrogen temperature, by the Pulsed-Field Magnetization (PFM), 1.04 T was trapped in 60 mm-diameter and 20 mm-thickness magnets, leading to an output power of the motor of 10 kW at 720 rpm. To enhance this performance, we have to increase the total amount of trapped flux in the bulk, the shortest way being to decrease the temperature of the bulk HTS. Thus, we focused on the improvement of the condensed-neon cooling system, a closed-cycle thermosyphon, so that it provided enough cooling power to lead the rotor plate enclosing the magnets to a low temperature. The present study implied coming out with a new fin-oriented design of the condensation chamber; hence, the numeric calculations and FEM software (ANSYS) heat transfer simulations were conducted for various shapes and positions of the fins. The trapezoidal design offering the best efficiency was then manufactured for testing in a heat-load test configuration, leading to cooling times divided by three and a maximum heat load endured of 55 W.

  3. Optimization of a condensed-neon cooling system for a HTS synchronous motor with Gd-bulk HTS field-pole magnets

    Science.gov (United States)

    Felder, B.; Miki, M.; Tsuzuki, K.; Izumi, M.; Hayakawa, H.

    2010-06-01

    The axial-gap synchronous machine developed in our laboratory is based on Gd-bulk HTS field-pole magnets, able to trap a part of the magnetic flux they are submitted to when cooled down below Tc. At the liquid nitrogen temperature, by the Pulsed-Field Magnetization (PFM), 1.04 T was trapped in 60 mm-diameter and 20 mm-thickness magnets, leading to an output power of the motor of 10 kW at 720 rpm. To enhance this performance, we have to increase the total amount of trapped flux in the bulk, the shortest way being to decrease the temperature of the bulk HTS. Thus, we focused on the improvement of the condensed-neon cooling system, a closed-cycle thermosyphon, so that it provided enough cooling power to lead the rotor plate enclosing the magnets to a low temperature. The present study implied coming out with a new fin-oriented design of the condensation chamber; hence, the numeric calculations and FEM software (ANSYS) heat transfer simulations were conducted for various shapes and positions of the fins. The trapezoidal design offering the best efficiency was then manufactured for testing in a heat-load test configuration, leading to cooling times divided by three and a maximum heat load endured of 55 W.

  4. Inhomogeneity effects in HTS coated conductors used as resistive FCLs in medium voltage grids

    Science.gov (United States)

    Colangelo, Daniele; Dutoit, Bertrand

    2012-09-01

    For resistive fault current limiters (RFCLs) based on high temperature superconducting coated conductors (HTS-CCs), inhomogeneity, in terms of critical current and geometrical imperfections such as stabilizer and substrate thicknesses, plays a very important role and it may limit the penetration of such devices into the electrical market. This paper presents an electrothermal model, developed in SimPowerSystem™, able to describe the transient response of HTS-CC candidates with different degrees of inhomogeneity, both in terms of critical current and of stabilizer thickness. Critical current inhomogeneity has been modeled with Gaussian distributions. The layer thicknesses used in the simulations have been chosen by fitting the temperature dependence of real tape resistances. Our approach considers relative inhomogeneity positions as well as thermal conduction along the HTS-CC length. The model is tuned using experimental measurements made on ReBaCuO coated conductors. A new dynamical thermal calibration of the model is proposed using finite element method calculations. Inhomegeneity effects with different possible faults (e.g. three phase and single phase short-circuit) are presented.

  5. Numerical models of delamination behavior in 2G HTS tapes under transverse tension and peel

    Science.gov (United States)

    Duan, Yujie; Ta, Wurui; Gao, Yuanwen

    2018-02-01

    In extreme operating environments, delamination in 2G HTS tapes occurs within and/or near the superconductor layer from high transverse tensile stresses caused by fabrication, Lorentz forces and thermal mismatch, etc. Generally, transverse opening and peeling off are the main delamination modes, and are always studied in anvil and peel tests, respectively. Numerical models of these modes for 2G HTS tape are presented wherein the mixed-mode traction-separation law at the interface of the silver and superconductor layers is considered. Plastic deformations of copper, silver, and Hastelloy® in the HTS tape are taken into account. The results obtained from the transverse opening model show that the maximum average tensile stress is smaller than the delamination tensile strength because delamination is asynchronous in the tape. When a crack appears in the tape, only a small stress ( ≤ 1 MPa) is required to expand the crack to other stress free areas through peeling. Using the peeling model, the dependency of the peel strength on peeling angle is investigated under constant fracture toughness. Peel strength decreases with the peeling angle until the minimum value is reached at 150°, and thereafter increases slightly. Other results indicate that peel strength depends strongly on delamination strength, fracture toughness, and thickness of copper layer. The fracture toughness of the delamination interface, which is difficult to obtain by experiment, can be extracted using the present model.

  6. Development of a field pole of 1 MW-class HTS motor

    International Nuclear Information System (INIS)

    Yuan, S; Kimura, Y; Miki, M; Felder, B; Tsuzuki, K; Izumi, M; Ida, T; Umemoto, K; Aizawa, K; Yokoyama, M

    2010-01-01

    We report a field-pole high-temperature superconductor (HTS) magnet designed for 1 MW-class motor for propulsion. The field pole is assembled to the rotor of the radial-type motor. Each field pole is composed of HTS-Bi2223 tape wound into coils which have been piled up as a double pancake coils. In the design concept of the motor, we employ field poles without iron core. We prepared the test field-pole coil, whose dimension is smaller than the designed one for 1 MW, and tested its performances after cooling under self-field and external magnetic field. We verified the operation with the minimum bend radius of the coils required in the motor design, while keeping an optimal current which is lower than the critical current of the field-pole coil. The test HTS field poles were successfully cooled down and operated under a magnetic field ranging up to 5 T. We report the results of the test field-pole coil and the manufacture of a practical racetrack coil with Bi2223 and discuss the adaptability to 1 MW-class motors.

  7. Development of an HTS hydroelectric power generator for the hirschaid power station

    Energy Technology Data Exchange (ETDEWEB)

    Fair, Ruben; Lewis, Clive; Eugene, Joseph; Ingles, Martin, E-mail: ruben.fair@converteam.co [Advanced Technology Group, Converteam, Rugby, CV21 1BD (United Kingdom)

    2010-06-01

    This paper describes the development and manufacture of a 1.7MW, 5.25kV, 28pole, 214rpm hydroelectric power generator consisting of superconducting HTS field coils and a conventional stator. The generator is to be installed at a hydro power station in Hirschaid, Germany and is intended to be a technology demonstrator for the practical application of superconducting technology for sustainable and renewable power generation. The generator is intended to replace and uprate an existing conventional generator and will be connected directly to the German grid. The HTS field winding uses Bi-2223 tape conductor cooled to about 30K using high pressure helium gas which is transferred from static cryocoolers to the rotor via a bespoke rotating coupling. The coils are insulated with multi-layer insulation and positioned over laminated iron rotor poles which are at room temperature. The rotor is enclosed within a vacuum chamber and the complete assembly rotates at 214rpm. The challenges have been significant but have allowed Converteam to develop key technology building blocks which can be applied to future HTS related projects. The design challenges, electromagnetic, mechanical and thermal tests and results are presented and discussed together with applied solutions.

  8. Evaluation of the invasion heat for the HTS current lead using YBCO

    Energy Technology Data Exchange (ETDEWEB)

    Endoh, R.; Kato, H.; Izumi, T.; Shiohara, Y

    2003-10-15

    Current leads using high-T{sub C} superconductors (HTS current leads) are one of cryogenic key devices to assemble compact superconducting magnets such as applied for maglev trains etc. It is essential to evaluate effective thermal conductance through a HTS current lead package together with evaluating Joule heat and critical current for efficient design that has high current capacity and low heat invasion. We have designed the 500 A class HTS current lead package using a YBCO rod whose size is diameter 3 x 30 mm, and developed an apparatus to measure its heat invasion. Temperature drop as a function of heat flow between the two ends of the package was measured by a conventional steady heat flow method. The quantity of heat invasion of the package under typical practical conditions, from 80 K hot end to 20 K cold end, was 163 mW. This value was simulated to the total value of 158 mW by counting contributions of all the component materials.

  9. A study on electromagnetic and mechanical characteristics of the field coil in HTS motor

    International Nuclear Information System (INIS)

    Kim, S.B.; Kadota, T.; Joo, J.H.; Sano, H.; Murase, S.; Lee, S.H.; Hong, J.P.; Kim, H.M.; Kwon, Y.K.; Jo, Y.S.

    2010-01-01

    High temperature superconducting (HTS) motors electromagnetically consist of a rotator wound with HTS wires and an armature with conventional copper wires like Litz wire. The HTS rotor windings, as field coils, consist of a straight part and an end-ring part. Because a major rotation torque is induced by an interaction between magnetic fields and current-carrying conductors in the straight part, most of mechanical stresses in the motor occur at the straight part. An end-ring is placed in the edge of the straight part and used to connect to each adjacent straight-part coils. The magnetic fields by coil currents concentrate on the end-ring part, therefore, it is expected that the critical current of the entire coil, straight and end-ring, can be determined by the magnitude of the field in the end-ring. This paper deals with the overall J c degradation in the end-ring part by self-field generated from the coil. In addition to electromagnetic analyses, we have performed a numerical analysis in order to evaluate mechanical stresses in the straight part of field coil by armature reaction on steady-state operation. The analytical results will be presented in this paper.

  10. [Treating anisometric amblyopia with HTS Amblyopia iNet Software--preliminary results].

    Science.gov (United States)

    Avram, Elena; Stănilă, Adriana

    2013-01-01

    Amblyopia or "lazy eye" represents a disorder of the visual system characterized by poor vision in an eye that is otherwise physically normal. Anisometropia, the condition in which the two eyes have an unequal refractive error, is considered the second most common cause of amblyopia. The purpose of this study is to determine the efficiency of HTS Amblyopia iNet Software by studying the progress of visual acuity, contrast sensitivity and stereopsis vision in anisometropic amblyopic children. 5 patients (age: 5-13 years), treated with HTS Amblyopia iNet Software at OftaTotal Clinic from Sibiu, between 2010-2013, participated in this clinical trial. Initially, visual acuity ranged from 0.25 to 0.8, contrast sensitivity from 1.35 to 1.65 Log. Unit. and 1 patient presented stereoscopic vision. After treatment, visual acuity ranged from 0.8 to 1, contrast sensitivity from 1.35 to 1.95 Log. Unit., also all patients presented stereoscopic vision. HTS Amblyopia iNet Software represents an effective modern approach in the treatment of anisometropic amblyopia.

  11. A compact HTS bandpass microstrip filter with novel coupling structure for on-chip integration

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ting, E-mail: ting.zhang@csiro.au [CSIRO ICT Centre, Epping, NSW 1710 (Australia); Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai 200050 (China); Du, Jia [CSIRO Materials Science and Engineering, PO Box 218, Lindfield, NSW 2070 (Australia); Guo, Yingjie Jay [CSIRO ICT Centre, Epping, NSW 1710 (Australia); Sun, Xiaowei [Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Science, Shanghai 200050 (China)

    2013-12-15

    Highlights: •A novel coupling scheme is used to introduce two transmission zeros using only three resonators. •The filter has a low insertion loss at 40 K, and a wide stopband with good rejection. •The filter has compactness and high-selectivity. •The filter is a suitable candidate for on-chip integration of HTS receiver front-ends. -- Abstract: A compact low-complexity high-selectivity high-temperature superconducting (HTS) microstrip bandpass filter is presented in this paper, which consists of only three half-wavelength resonators. A novel coupling scheme is used to provide a pair of transmission zeros outside the passband, so that the selectivity of the filter is improved. The filter is fabricated on an MgO substrate with YBa{sub 2}Cu{sub 3}O{sub 7−x} (YBCO) coating. Measurement result shows an in-band insertion loss at 0.5 dB, a sharp slope, and a stopband rejection better than 20 dB. The compactness and high-selectivity features make the filter suitable for on-chip integration of HTS receiver front-ends.

  12. Design study of superconducting sextupole magnet using HTS coated conductor for neutron-focusing device

    International Nuclear Information System (INIS)

    Tosaka, T.; Koyanagi, K.; Ono, M.; Kuriyama, T.; Watanabe, I.; Tsuchiya, K.; Suzuki, J.; Adachi, T.; Shimizu, H.M.

    2006-01-01

    We performed a design study of sextupole magnet using high temperature superconducting (HTS) wires. The sextupole magnet is used as a focusing lens for neutron-focusing devices. A neutron-focusing device is desired to have a large aperture and a high magnetic field gradient of G, where G = 2B/r 2 , B is the magnetic field and r is a distance from the sextupole magnet axis. Superconducting magnets offer promising prospects to meet the demands of a neutron-focusing device. Recently NbTi coils of low temperature superconducting (LTS) have been developed for a sextupole magnet with a 46.8 mm aperture. The maximum magnetic field gradient G of this magnet is 9480 T/m 2 at 4.2 K and 12,800 T/m 2 at 1.8 K. On the other hand, rapid progress on second generation HTS wire has been made in increasing the performance of critical current and in demonstrating a long length. The second generation HTS wire is referred to as coated conductor. It consists of tape-shaped base upon which a thin coating of superconductor, usually YBCO, is deposited or grown. This paper describes a design study of sextupole magnet using coated conductors

  13. Evaluation of the invasion heat for the HTS current lead using YBCO

    Science.gov (United States)

    Endoh, R.; Kato, H.; Izumi, T.; Shiohara, Y.

    2003-10-01

    Current leads using high- TC superconductors (HTS current leads) are one of cryogenic key devices to assemble compact superconducting magnets such as applied for maglev trains etc. It is essential to evaluate effective thermal conductance through a HTS current lead package together with evaluating Joule heat and critical current for efficient design that has high current capacity and low heat invasion. We have designed the 500 A class HTS current lead package using a YBCO rod whose size is ∅ 3 × 30 mm, and developed an apparatus to measure its heat invasion. Temperature drop as a function of heat flow between the two ends of the package was measured by a conventional steady heat flow method. The quantity of heat invasion of the package under typical practical conditions, from 80 K hot end to 20 K cold end, was 163 mW. This value was simulated to the total value of 158 mW by counting contributions of all the component materials.

  14. HTS-SQUID NDE Technique for Pipes based on Ultrasonic Guided Wave

    International Nuclear Information System (INIS)

    Hatsukade, Y; Masutani, N; Teranishi, S; Masamoto, K; Kanenaga, S; Adachi, S; Tanabe, K

    2017-01-01

    This article describes research on the novel high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) non-destructive evaluation (NDE) technique for metallic pipes based on ultrasonic guided waves. We constructed HTS-SQUID NDE system for pipes based on ultrasonic guided waves, which were generated and received by means of the magnetostrictive effects. Using the system, we measured magnetic signals due to T (0, 1) mode ultrasonic guided waves that transmitted on aluminium pipe, and investigated influences of measurement parameters to the magnetic signals, such as direction of a HTS-SQUID gradiometer, lift-off distance, and intensity and frequency of input current fed to a magnetostrictive transmitter. With the gradiometer oriented parallel to the pipe axis, more than 10 times larger signals were measured compared with that oriented perpendicular to the pipe axis. Magnetic signals measured by the gradiometer were inverse proportional to the power of the list- off distance, and proportional to the intensity of the input current up to 1 A pp . Relation between the frequency of the input current and the measured signal was shown and discussed. (paper)

  15. Conceptual design of cooling anchor for current lead on HTS field coils

    Energy Technology Data Exchange (ETDEWEB)

    Hyeon, C. J.; Kim, J. H.; Quach, H. L. [Dept. of Electrical Engineering, Jeju National University, Jeju (Korea, Republic of); and others

    2017-06-15

    The role of current lead in high-temperature superconducting synchronous machine (HTSSM) is to function as a power supply by connecting the power supply unit at room temperature with the HTS field coils at cryogenic temperature. Such physical and electrical connection causes conduction and Joule-heating losses, which are major thermal losses of HTSSM rotors. To ensure definite stability and economic feasibility of HTS field coils, quickly and smoothly cooling down the current lead is a key design technology. Therefore, in this paper, we introduce a novel concept of a cooling anchor to enhance the cooling performance of a metal current lead. The technical concept of this technology is the simultaneously chilling and supporting the current lead. First, the structure of the current lead and cooling anchor were conceptually designed for field coils for a 1.5 MW-class HTSSM. Then, the effect of this installation on the thermal characteristics of HTS coils was investigated by 3D finite element analysis.

  16. HTS-SQUID NDE Technique for Pipes based on Ultrasonic Guided Wave

    Science.gov (United States)

    Hatsukade, Y.; Masutani, N.; Teranishi, S.; Masamoto, K.; Kanenaga, S.; Adachi, S.; Tanabe, K.

    2017-07-01

    This article describes research on the novel high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) non-destructive evaluation (NDE) technique for metallic pipes based on ultrasonic guided waves. We constructed HTS-SQUID NDE system for pipes based on ultrasonic guided waves, which were generated and received by means of the magnetostrictive effects. Using the system, we measured magnetic signals due to T (0, 1) mode ultrasonic guided waves that transmitted on aluminium pipe, and investigated influences of measurement parameters to the magnetic signals, such as direction of a HTS-SQUID gradiometer, lift-off distance, and intensity and frequency of input current fed to a magnetostrictive transmitter. With the gradiometer oriented parallel to the pipe axis, more than 10 times larger signals were measured compared with that oriented perpendicular to the pipe axis. Magnetic signals measured by the gradiometer were inverse proportional to the power of the list- off distance, and proportional to the intensity of the input current up to 1 App. Relation between the frequency of the input current and the measured signal was shown and discussed.

  17. Development of a field pole of 1 MW-class HTS motor

    Science.gov (United States)

    Yuan, S.; Kimura, Y.; Miki, M.; Felder, B.; Tsuzuki, K.; Ida, T.; Izumi, M.; Umemoto, K.; Aizawa, K.; Yokoyama, M.

    2010-06-01

    We report a field-pole high-temperature superconductor (HTS) magnet designed for 1 MW-class motor for propulsion. The field pole is assembled to the rotor of the radial-type motor. Each field pole is composed of HTS-Bi2223 tape wound into coils which have been piled up as a double pancake coils. In the design concept of the motor, we employ field poles without iron core. We prepared the test field-pole coil, whose dimension is smaller than the designed one for 1 MW, and tested its performances after cooling under self-field and external magnetic field. We verified the operation with the minimum bend radius of the coils required in the motor design, while keeping an optimal current which is lower than the critical current of the field-pole coil. The test HTS field poles were successfully cooled down and operated under a magnetic field ranging up to 5 T. We report the results of the test field-pole coil and the manufacture of a practical racetrack coil with Bi2223 and discuss the adaptability to 1 MW-class motors.

  18. Pseudogap regime in high-T{sub c} cuprates as a manifestation of a frustrated phase separation (NMR view)

    Energy Technology Data Exchange (ETDEWEB)

    Gor' kov, Lev P. [NNHMFL, Florida State University, 1800 E P.Dirac Dr., Tallahassee FL 32310 (United States); Teitel' baum, Gregory B. [E.K.Zavoiskii Institute for Technical Physics of the RAS, Sibirskii Trakt 10/7, Kazan 420029 (Russian Federation)]. E-mail: grteit@kfti.knc.ru

    2005-04-30

    We show that the pseudogap behavior of the nuclear spin relaxation for cuprates may be considered as the dynamical phase separation to the 'metallic' and 'antiferromagnetic (AF)' regions. It stems from the 1st order phase transition that starts at T*(x) well above T{sub c} but becomes frustrated because of broken electroneutrality in the CuO{sub 2} plane. In this temperature range for a broad class of cuprates 1/{sup 63}T{sub 1} is due to two independent mechanisms: relaxation on the 'stripe'-like excitations and that driven by the moving AF regions. For LSCO, our estimations are in quantitative agreement with the neutron scattering data.

  19. Improved magnetic-field homogeneity of NMR HTS bulk magnet using a new stacking structure and insertion of an HTS film cylinder into a bulk bore

    International Nuclear Information System (INIS)

    Itoh, Yoshitaka; Yanagi, Yousuke; Nakamura, Takashi

    2017-01-01

    A new type of superconducting bulk magnet for compact nuclear magnetic resonance (NMR) devices with high magnetic-field homogeneity has been developed by inserting an HTS film cylinder into a bulk superconductor bore. Annular 60 mmϕ Eu-Ba-Cu-O bulk superconductors with a larger inner diameter (ID) of 36 mm were sandwiched between bulk superconductors with a smaller ID of 28 mm, and the total height of the bulk superconductor set was made to be 120 mm. The inner height of central wide bore space was optimized by magnetic-field simulation so that the influence of the bulk superconductor's paramagnetic moment on applied field homogeneity was minimized during the magnetization process. An HTS film cylinder, in which Gd-Ba-Cu-O tapes were wound helically in three layers around a copper cylinder, was inserted into the bulk bore in order to compensate for the inhomogeneous field trapped by the bulk superconductor. The superconducting bulk magnet composed of the above bulk superconductor set and the film cylinder were cooled by a GM pulse tube refrigerator and magnetized at 4.747 T using the field cooling (FC) method and a conventional superconducting coil magnet adjusted to below 0.5 ppm in magnetic-field homogeneity. The NMR measurement was conducted for an H 2 O sample with a diameter of 6.9 mm and a length of 10 mm by setting the sample in the center of the 20 mm ID room-temperature bore of the bulk magnet. The magnetic-field homogeneity derived from the full width at half maximum (FWHM) of the 1 H spectrum of H 2 O was 0.45 ppm. We confirmed that the HTS film inner cylinder was effective in maintaining the homogeneity of the magnetic field applied in the magnetization process, and as a result, a magnetic field with a homogeneity of less than 1 ppm can be generated in the bore of the bulk magnet without using shim coils. (author)

  20. Simulation of YBCO Tape and Coils in HTS Maglev System

    Directory of Open Access Journals (Sweden)

    Song Mengxiao

    2017-01-01

    Full Text Available In the process of running high temperature superconducting maglev train, the AC(Alternating Current loss of superconducting coil is directly related to its safe operation and operating cost. In this paper, the simulation model was built based on the finite element software COMSOL Multiphysics, and mainly simulated and calculated the AC losses of YBCO(Yttrium Barium Copper Oxide tape and coils. In this model, as the solving object, the singular and infinite long YBCO tape and coils model was solved with H-formulation and the nonlinear characteristic (E-J constitutive law and anisotrophy (B-J characteristic were taken into consideration as the theoretical foundation. Then on the basis of the model under maglev suspension system, AC losses under different amplitude and frequence AC currents were calculated. The results shows that under different frequencies and dynamic components, the local maximum AC loss of YBCO tape and coils occurs when the steady-state DC(Direct Current current is 30A. Then comparing with old maglev suspension system, the new system can greatly reduce the energy consumption and the material cost.

  1. Effects of extra oxygen on the structure and superconductivity of La2-xCaxCuO4+y prepared by chemical oxidation

    DEFF Research Database (Denmark)

    Rial, C.; Moran, E.; Alario Franco, M.A.

    1998-01-01

    The insertion of an excess of oxygen within the structure of La2-xCaxCuO4 (x less than or equal to 0.12) by means of room temperature chemical oxidation modifies the physical properties and the crystal structure of these cuprates. The superconducting features of the starting La2-xCaxCuO4 samples...

  2. U(1) x SU(2) Chern-Simons gauge theory of underdoped cuprate superconductors

    International Nuclear Information System (INIS)

    Marchetti, P.A.; Su Zhao-Bin; Yu Lu

    1998-05-01

    The Chern-Simons bosonization with U(1)xSU(2) gauge field is applied to the 2-D t-J model in the limit t>>J, to study the normal state properties of underdoped cuprate superconductors. We prove the existence of an upper bound on the partition function for holons in a spinon background, and we find the optimal spinon configuration saturating the upper bound on average - a coexisting flux phase and s+id-like RVB state. After neglecting the feedback of holon fluctuations on the U(1) field B and spinon fluctuations on the SU(2) field V, the holon field is a fermion and the spinon field is a hard-core boson. Within this approximation we show that the B field produces a π flux phase for the holons, converting them into Dirac-like fermions, while the V field, taking into account the feedback of holons produces a gap for the spinons vanishing in the zero doping limit. The nonlinear σ-model with a mass term describes the crossover from the short-ranged antiferromagnetic (AF) state in doped samples to long range AF order in reference compounds. Moreover, we derive a low-energy effective action in terms of spinons holons and a self-generated U(1) gauge field. Neglecting the gauge fluctuations, the holons are described by the Fermi liquid theory with a Fermi surface consisting of 4 ''half-pockets'' centered at (+-π/2,+-π/2) and one reproduces the results for the electron spectral function obtained in the mean field approximation, in agreement with the photoemission data on underdoped cuprates. The gauge fluctuations are not confining due to coupling to holons, but nevertheless yield an attractive interaction between spinons and holons leading to a bound state with electron quantum numbers. The renormalisation effects due to gauge fluctuations give rise to non-Fermi liquid behaviour for the composite electron, in certain temperature range showing the linear in T resistivity. This formalism provides a new interpretation of the spin gap in the underdoped superconductors

  3. Study on the Persistent Current Switch in HTS Coils Wound with 2G Wire for Compact NMR Magnets

    Science.gov (United States)

    Sugo, K.; Kim, S. B.; Nomura, R.; Ueda, H.

    2017-07-01

    High temperature superconducting (HTS) magnets wound with REBCO wires are used in many applications, and the superconducting magnet which is operated in persistent current mode has many advantages. Therefore, we have been developing compact NMR relaxometry devices using HTS coils operated at liquid nitrogen temperature. The required strength and homogeneity of magnetic field of proposed NMR relaxometry devices are 1.5 T and 150 ppm/cm3 respectively. The proposed HTS magnet for NMR relaxometry device consists with stacked HTS double pancake coils wound with REBCO wires and operated by persistent current mode (PCM) using superconducting joint between REBCO wires. In PCM operation, the ability of persistent current switch (PCS) is very important, so, in this study, the thermal properties of YBCO wire against the various thermal inputs by heater were investigated experimentally to design the PCS for PCM HTS magnets. The thermal behaviors of the YBCO wires were measured as functions of amount of heat input using two types of epoxy resin. The current bypassing properties on the YBCO loop coil with developed PCS were studied experimentally.

  4. Status of series production and test of the HTS current leads for Wendelstein 7-X

    Energy Technology Data Exchange (ETDEWEB)

    Heller, Reinhard, E-mail: reinhard.heller@kit.edu [Karlsruhe Institute of Technology, Karlsruhe (Germany); Buscher, Klaus-Peter [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Greifswald (Germany); Drotziger, Sandra; Fietz, Walter H.; Kienzler, Andreas; Lietzow, Ralph [Karlsruhe Institute of Technology, Karlsruhe (Germany); Mönnich, Thomas [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Greifswald (Germany); Richter, Thomas [Karlsruhe Institute of Technology, Karlsruhe (Germany); Rummel, Thomas [Max-Planck-Institut für Plasmaphysik, Teilinstitut Greifswald, Greifswald (Germany); Urbach, Elisabeth [Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2013-10-15

    Highlights: ► KIT is responsible for design, production and test of the HTS current leads for W7-X. In total 14 current leads with a max. current of 18.2 kA are required. ► Final acceptance test of the current leads performed at KIT using a test cryostat connected to the main vacuum vessel of the TOSKA facility. ► In general the performance of the leads is excellent and reproducible. ► Problems during series production and test related to electrical insulation, leak tightness, contact resistance between current lead and bus bar joint box. -- Abstract: The Karlsruhe Institute of Technology (KIT) is responsible for design, production and test of the High Temperature Superconductor (HTS) current leads for the stellarator Wendelstein 7-X (W7-X). In total 14 current leads with a maximum current of 18.2 kA are required. Special feature is the upside-down orientation of the current leads because of the location of the power supplies in the basement of the experimental area of W7-X. One further important requirement is the Paschen tight electrical insulation of current leads and the connection to the bus bar system. Due to some very specific manufacturing steps, budget and time restrictions, it has been mutually decided between the project partners to manufacture most of the components in house, except the HTS stacks which have been produced and delivered by industry. As the semi-finished parts were manufactured in the central workshop of KIT, the assembly of the current leads was performed in the ITEP (Institute for Technical Physics). The final acceptance test of the current leads is performed at KIT, using a dedicated test cryostat assembled beside and connected to the main vacuum vessel of the TOSKA facility. The paper describes the status of the manufacturing of the current leads. In addition attention is given to specific problems that occurred during the manufacturing and testing.

  5. Recovery time analysis in a tri-axial HTS cable after an over-current fault

    International Nuclear Information System (INIS)

    Hu, N.; Toda, M.; Watanabe, T.; Tsuda, M.; Hamajima, T.

    2011-01-01

    We make a CFD code to simulate the tri-axial HTS cable transient thermal behavior. There is a temperature gradient along the forced LN 2 flow cooling cable pipe. Long recovery time is required due to a low thermal conductivity of insulation layer. The temperature of liquid nitrogen gradually rises even after the fault stopped. A tri-axial HTS cable with the advantage of compact structure, low heat loss, and low cost is a perfect solution for future distribution power network demand. In our previous research, a typical single line to ground (SLG) fault simulation was carried out in an adiabatic condition. A stabilizer layer thickness design of the tri-axial HTS cable based on a calculation of maximum temperature rise in the worst condition was proposed. However, in practical application, after the quenched cable is removed from the network by a breaker, a recovery time is also a very important parameter to decide if the cable is allowed to reconnect to the power network. In this paper, a one-dimensional computational fluid dynamics (CFD) analysis is carried out to simulate the transient thermal behavior of the cable. The result shows that it takes time to recover the cable temperature to the steady-state operation level due to a low thermal conductivity of the insulation layer. Since the cable is cooled by forced liquid nitrogen (LN 2 ) flow, there is a temperature gradient along the cable. The temperature of LN 2 gradually rises after the fault until the warmed coolant runs out of the cable.

  6. 3D modeling and simulation of 2G HTS stacks and coils

    International Nuclear Information System (INIS)

    Zermeño, Víctor M R; Grilli, Francesco

    2014-01-01

    Use of 2G HTS coated conductors in several power applications has become popular in recent years. Their large current density under high magnetic fields makes them suitable candidates for high power capacity applications such as stacks of tapes, coils, magnets, cables and current leads. For this reason, modeling and simulation of their electromagnetic properties is very desirable in the design and optimization processes. For many applications, when symmetries allow it, simple models consisting of 1D or 2D representations are well suited for providing a satisfying description of the problem at hand. However, certain designs such as racetrack coils and finite-length or non-straight stacks, do pose a 3D problem that cannot be easily reduced to a 2D configuration. Full 3D models have been developed, but their use for simulating superconducting devices is a very challenging task involving a large-scale computational problem. In this work, we present a new method to simulate the electromagnetic transient behavior of 2G HTS stacks and coils. The method, originally used to model stacks of straight superconducting tapes or circular coils in 2D, is now extended to 3D. The main idea is to construct an anisotropic bulk-like equivalent for the stack or coil, such that the geometrical layout of the internal alternating structures of insulating, metallic, superconducting and substrate layers is reduced while keeping the overall electromagnetic behavior of the original device. Besides the aforementioned interest in modeling and simulating 2G HTS coated conductors, this work provides a further step towards efficient 3D modeling and simulation of superconducting devices for large-scale applications. (paper)

  7. A novel flow cytometric HTS assay reveals functional modulators of ATP binding cassette transporter ABCB6.

    Directory of Open Access Journals (Sweden)

    Kishore Polireddy

    Full Text Available ABCB6 is a member of the adenosine triphosphate (ATP-binding cassette family of transporter proteins that is increasingly recognized as a relevant physiological and therapeutic target. Evaluation of modulators of ABCB6 activity would pave the way toward a more complete understanding of the significance of this transport process in tumor cell growth, proliferation and therapy-related drug resistance. In addition, this effort would improve our understanding of the function of ABCB6 in normal physiology with respect to heme biosynthesis, and cellular adaptation to metabolic demand and stress responses. To search for modulators of ABCB6, we developed a novel cell-based approach that, in combination with flow cytometric high-throughput screening (HTS, can be used to identify functional modulators of ABCB6. Accumulation of protoporphyrin, a fluorescent molecule, in wild-type ABCB6 expressing K562 cells, forms the basis of the HTS assay. Screening the Prestwick Chemical Library employing the HTS assay identified four compounds, benzethonium chloride, verteporfin, tomatine hydrochloride and piperlongumine, that reduced ABCB6 mediated cellular porphyrin levels. Validation of the identified compounds employing the hemin-agarose affinity chromatography and mitochondrial transport assays demonstrated that three out of the four compounds were capable of inhibiting ABCB6 mediated hemin transport into isolated mitochondria. However, only verteporfin and tomatine hydrochloride inhibited ABCB6's ability to compete with hemin as an ABCB6 substrate. This assay is therefore sensitive, robust, and suitable for automation in a high-throughput environment as demonstrated by our identification of selective functional modulators of ABCB6. Application of this assay to other libraries of synthetic compounds and natural products is expected to identify novel modulators of ABCB6 activity.

  8. Antiferromagnetic and superconducting gaps and their interrelation in high-T sub c cuprates

    CERN Document Server

    Arrigoni, E; Eckl, T; Hanke, W

    2003-01-01

    We propose a phenomenological model, comprising a microscopic SO(5) model plus the on-site Hubbard interaction U (projected SO(5) model) to understand the interrelation between the d-wave-gap modulation observed by recent angle-resolved photoemission experiments in the insulating antiferromagnet Ca sub 2 CuO sub 2 Cl sub 2 and the d-wave gap of high-T sub c superconducting materials. The on-site interaction U is important in order to produce a Mott gap of the correct order of magnitude, which would be absent in an exact SO(5) theory. The projected SO(5)-model explains the gap characteristics, namely both the symmetry and the different order of magnitude of the gap modulations between the AF and the SCc phases. Furthermore, it is shown that the projected SO(5) theory can provide an explanation for a recent observation [E. Pavarini et al., Phys. Rev. Lett. 87, 47003 (2001)], i. e. that the maximum T sub c observed in a large variety of high-T sub c cuprates scales with the next-nearest-neighbor hopping matrix e...

  9. Two regimes in conductivity and the Hall coefficient of underdoped cuprates in strong magnetic fields.

    Science.gov (United States)

    Gor'kov, L P; Teitel'baum, G B

    2014-01-29

    We address recent experiments shedding light on the energy spectrum of under and optimally doped cuprates at temperatures above the superconducting transition. Angle resolved photoemission reveals coherent excitation only near nodal points on parts of the 'bare' Fermi surface known as the Fermi arcs. The question debated in the literature is whether the small normal pocket, seen via quantum oscillations, exists at higher temperatures or forms below a charge order transition in strong magnetic fields. Assuming the former case as a possibility, expressions are derived for the resistivity and the Hall coefficient (in weak and strong magnetic fields) with both types of carriers participating in the transport. There are two regimes. At higher temperatures (at a fixed field) electrons are dragged by the Fermi arcs' holes. The pocket being small, its contribution to conductivity and the Hall coefficient is negligible. At lower temperatures electrons decouple from holes behaving as a Fermi gas in the magnetic field. As the mobility of holes on the arcs decreases in strong fields with a decrease of temperature, below a crossover point the pocket electrons prevail, changing the sign of the Hall coefficient in the low temperature limit. Such behavior finds its confirmation in recent high-field experiments.

  10. Raman scattering in cuprate superconductors : an analysis in the spin bag model

    International Nuclear Information System (INIS)

    Behera, S.N.; Gaitonde, D.M.

    1992-01-01

    The spin bag model for the high temperature superconductivity (SC) in the cuprates is reformulated, so that the spin density wave (SDW) collective mode mediated pairing interaction between the doped charge carriers, has a formal similarity to the usual phonon mediated BCS mechanism. The collective modes of the spin bag superconductor are calculated and the spectral density function for the amplitude mode is plotted. The self energy and the spectral density function of an optic phonon are calculated in the spin bag superconducting state. The spectral density function does not couple to the SDW-amplitude mode. A low frequency is shown to harden while the high frequency (greater than the SC-gap) one softens; which are features in qualitative agreement with the behaviour seen in the Raman data. When the phonon frequency is larger than the SC-gap, its spectral function shows a low frequency weak peak, attributed to the SC-gap excitation which is not observed experimentally. (author). 21 refs., 3 figs

  11. Two methods for a first order hardware gradiometer using two HTS SQUIDs

    Energy Technology Data Exchange (ETDEWEB)

    Espy, M.A.; Flynn, E.R.; Kraus, R.H. Jr.; Matlachov, A.

    1998-12-31

    Two different systems for noise cancellation (first order gradiometers) have been developed using two similar high temperature superconducting (HTS) SQUIDs. Analog gradiometry is accomplished in hardware by either (1) subtracting the signals from the sensor and background SQUIDs at a summing amplifier (parallel technique) or (2) converting the inverted background SQUID signal to a magnetic field at the sensor SQUID (series technique). Balance levels achieved are 2000 and 1000 at 20 Hz for the parallel and series methods respectively. The balance level as a function of frequency is also presented. The effect which time delays in the two sets of SQUID electronics have on this balance level is presented and discussed.

  12. Calculation of AC losses in HTS stacks and coils for large scale applications

    DEFF Research Database (Denmark)

    Rodriguez Zermeno, Victor Manuel; Abrahamsen, Asger Bech; Mijatovic, Nenad

    2012-01-01

    operation. Calculating these losses is fundamental for performance evaluation and design. In many cases, this boils down to computing AC losses in stacks of tapes that are subjected to transport current and/or applied magnetic field. In this work, we present a homogenization method to model a stack of HTS...... and Sokolovsky. We disregard assumptions upon the shape of the critical region and use a power law E-J relationship allowing for overcritical current densities to be considered. This plays an important role when considering transient response of devices or non-harmonic oscillations. The method presented here...

  13. Influence of AC external magnetic field on guidance force relaxation between HTS bulk and NdFeB guideway

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Longcai [Applied Superconductivity Laboratory, P.O. Box 152, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)], E-mail: zhlcai2000@163.com; Wang Suyu; Wang Jiasu; Zheng Jun [Applied Superconductivity Laboratory, P.O. Box 152, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)

    2007-12-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to time-varying external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. So it is required to study whether the guidance force of the bulks is influenced by the inhomogeneity. In this paper, we studied the characteristics of the guidance force relaxation between the HTS bulk and the NdFeB guideway by an experiment in which AC external magnetic field generated by an electromagnet was used to simulate the time-varying external magnetic field caused by the inhomogeneity of the guideway. From the experiment results, it was found that the guidance force was decreased with the application of the AC external magnetic field, and the decay increased with the amplitude and was almost independent of the frequency.

  14. Numerical calculation of primary slot leakage inductance of a Single-sided HTS linear induction motor used for linear metro

    Science.gov (United States)

    Li, Dong; Wen, Yinghong; Li, Weili; Fang, Jin; Cao, Junci; Zhang, Xiaochen; Lv, Gang

    2017-03-01

    In the paper, the numerical method calculating asymmetric primary slot leakage inductances of Single-sided High-Temperature Superconducting (HTS) Linear Induction Motor (HTS LIM) is presented. The mathematical and geometric models of three-dimensional nonlinear transient electromagnetic field are established and the boundary conditions are also given. The established model is solved by time-stepping Finite Element Method (FEM). Then, the three-phase asymmetric primary slot leakage inductances under different operation conditions are calculated by using the obtained electromagnetic field distribution. The influences of the special effects such as longitudinal end effects, transversal edge effects, etc. on the primary slot leakage inductance are investigated. The presented numerical method is validated by experiments carried out on a 3.5 kW prototype with copper wires which has the same structures with the HTS LIM.

  15. Accelerator Quality HTS Dipole Magnet Demonstrator designs for the EuCARD-2, 5 Tesla 40 mm Clear Aperture Magnet

    CERN Document Server

    Kirby, G; Ballarino, A; Bottura, L; Chouika, N; Clement, S; Datskov, V; Fajardo, L; Fleiter, J; Gauthier, R; Lambert, L; Lopes, M; Perez, J; DeRijk, G; Rijllart, A; Rossi, L; Ten Kate, H; Durante, M; Fazilleau, P; Lorin, C; Haro, E; Stenvall, A; Caspi, S; Marchevsky, M; Goldacker, W; Kario, A

    2014-01-01

    Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 work-package-10 is a collaborative push to take HTS materials into an accelerator quality demonstrator magnet. The demonstrator will produce 5 T standalone and between 17 T and 20 T, when inserted into the 100 mm aperture of Fresca-2 high field out-sert magnet. The HTS magnet will demonstrate the field strength and field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using multi strand Roebel cable that develops a stand-alone field of 5 T in a 40 mm clear aperture and discusses the challenges associated with good field quality using this type of material. A selection of magnet designs is presented as result of a first phase of development.

  16. Accelerator Quality HTS Dipole Magnet Demonstrator Designs for the EuCARD-2, 5 Tesla 40 mm Clear Aperture Magnet

    CERN Document Server

    Kirby, G A; Ballarino, A; Bottura, L; Chouika, N; Clement, S; Datskov, V; Fajardo, L; Fleiter, J; Gauthier, R; Gentini, L; Lambert, L; Lopes, M; Perez, J C; de Rijk, G; Rijllart, A; Rossi, L; ten Kate, H; Durante, M; Fazilleau, P; Lorin, C; Härö, E; Stenvall, A; Caspi, S; Marchevsky, M; Goldacker, W; Kario, A

    2015-01-01

    Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 work-package-10 is a collaborative push to take HTS materials into an accelerator quality demonstrator magnet. The demonstrator will produce 5 T standalone and between 17 T and 20 T, when inserted into the 100 mm aperture of Fresca-2 high field out-sert magnet. The HTS magnet will demonstrate the field strength and field quality that can be achieved. An effective quench detection and protection system will have to be developed to operate with the HTS superconducting materials. This paper presents a ReBCO magnet design using multi strand Roebel cable that develops a stand-alone field of 5 T in a 40 mm clear aperture and discusses the challenges associated with good field quality using this type of material. A selection of magnet designs is presented as result of a first phase of development.

  17. Long-term test of the 22.9kV HTS power cable system in LS Cable Ltd

    International Nuclear Information System (INIS)

    Jang, Hyun Man; Lee, Chang Young; Kim, Choon Dong; Kim, Do Hyung; Park, In Son; Ji, Bong Ki; Kim, Dong Wook; Cho, Jeonwook

    2006-01-01

    Since 2001, LS cable Ltd. has been developing the design, manufacturing and evaluation technologies for high temperature superconducting (HTS) power cable system as a member of DAPAS (Dream for Advanced Power system by Applied Superconductivity technology) program in Korea. The 30 m HTS cable system that is rated at 22.9 kV and 1.2 kA giving a rated capacity of 50 MVA had been developed and tested. The cable was designed as a cold dielectric type employing Bi-2223 HTS tapes and polypropylene (PP) laminated paper as the conductor and electrical insulation, respectively. The cable is cooled with sub-cooled liquid nitrogen at temperature from 75 to 77 K. The manufacturing and the installation of the cable system were completed in 2004. Long-term performance test of the cable system has been conducted for six months to verify its electric and mechanical properties in 2005

  18. Probe molecules (PrM) approach in adverse outcome pathway (AOP) based high throughput screening (HTS): in vivo discovery for developing in vitro target methods

    Science.gov (United States)

    Efficient and accurate adverse outcome pathway (AOP) based high-throughput screening (HTS) methods use a systems biology based approach to computationally model in vitro cellular and molecular data for rapid chemical prioritization; however, not all HTS assays are grounded by rel...

  19. The fundamental study to control the magnetic field for MDDS using shielding currents of HTS tapes and bulks

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.B., E-mail: kim@ec.okayama-u.ac.jp; Eritate, I.; Abe, T.; Shima, S.; Takahashi, M.

    2014-11-15

    Highlights: • MDDS is a key technology to reduce the side effects. • The field control method for MDDS was studied using HTS tapes and bulks. • The shielding current due to Meissner effect was used to generate the field gradient. • HTS bulks and films were combined with iron blocks, and they are very effective. • The magnetic field gradient which is higher than the external field was obtained. - Abstract: The magnetic drug delivery system (MDDS) is a key technology to reduce the side effects in the medical applications, and the magnetic force control is a very important issue in MDDS. In general, the high magnetic field along the axial direction and high magnetic field gradient along the longitudinal direction are very useful for MDDS. So, we proposed the new magnetic force control system that consists of superconducting magnet, high temperature superconductors (HTS) bulks or tapes and ferromagnetic substances. In this new system, the shielding currents in HTS bulks and tapes due to diamagnetism of the superconductor generate the magnetic field with same direction of external magnetic field, and we can control the magnetic field gradient along the longitudinal direction by the arrangement of the HTS bulks, tapes and ferromagnetic substances. In this study, the stacked GdBCO tapes without stabilizer were used in experiments and electromagnetic analysis based on finite element method (FEM) was carried out to optimize the arrangement of the superconductors and the irons. It was confirmed that the control of magnetic field gradient along the longitudinal direction was possible by arranging the HTS bulks, tapes and irons on the superconducting magnet and then it was possible to obtain a magnetic field higher than the external field.

  20. Study on the Rotation Properties and the Design Issue of Non-Contact Rotating System Using HTS Bulks and Permanent Magnets

    Science.gov (United States)

    Okamura, R.; Kim, S. B.; Ozaki, Y.; Ueda, H.

    2017-07-01

    In previous study, non-contact rotating system consisting of the ring-shaped high temperature superconducting (HTS) bulks, ring-shaped permanent magnets (PMs) and stator coil was proposed. In this system, HTS bulks were magnetized by PMs and PMs were levitated with strong restoring force. In our previous study, we have constructed the rotating system with the ring-shaped HTS bulks with ID 20 mm, OD 60 mm, and 15-mm thickness. However, since these bulks costs too much, we switched to use HTS bulks with ID 20 mm, OD 60 mm, and 5-mm-thickness to miniaturize the system. However, this system have potential to fail the radial stability of rotating shaft. Therefore, we focused on the rotating and the radial restoring force in terms of the stability of the rotating shaft in the rotating system with 5-mm thickness HTS bulks.

  1. Hypertonic saline solution reduces the oxidative stress responses in traumatic brain injury patients

    Directory of Open Access Journals (Sweden)

    Mojtaba Mojtahedzadeh

    2014-01-01

    Full Text Available Background: Oxidative stress processes play an important role in the pathogenesis of secondary brain injury after traumatic brain injury (TBI. Hypertonic saline (HTS has advantages as being preferred osmotic agent, but few studies investigated oxidant and antioxidant effects of HTS in TBI. This study was designed to compare two different regimens of HTS 5% with mannitol on TBI-induced oxidative stress. Materials and Methods: Thirty-three adult patients with TBI were recruited and have randomly received one of the three protocols: 125 cc of HTS 5% every 6 h as bolus, 500 cc of HTS 5%as infusion for 24 h or 1 g/kg mannitol of 20% as a bolus, repeated with a dose of 0.25-0.5 g/kg every 6 h based on patient′s response for 3 days. Serum total antioxidant power (TAP, reactive oxygen species (ROS and nitric oxide (NO were measured at baseline and daily for 3 days. Results: Initial serum ROS and NO levels in patients were higher than control(6.86± [3.2] vs. 1.57± [0.5] picoM, P = 0.001, 14.6± [1.6] vs. 7.8± [3.9] mM, P = 0.001, respectively. Levels of ROS have decreased for all patients, but reduction was significantly after HTS infusion and mannitol (3. 08 [±3.1] to 1.07 [±1.6], P = 0.001, 5.6 [±3.4] to 2.5 [±1.8], P = 0.003 respectively. During study, NO levels significantly decreased in HTS infusion but significantly increased in mannitol. TAP Levels had decreased in all patients during study especially in mannitol (P = 0.004. Conclusion: Hypertonic saline 5% has significant effects on the oxidant responses compared to mannitol following TBI that makes HTS as a perfect therapeutic intervention for reducing unfavorable outcomes in TBI patients.

  2. Magnetic correlations in doped transition metal oxides

    International Nuclear Information System (INIS)

    The authors review recent reactor- and spallation-source-based neutron scattering experiments on the magnetic fluctuations and order in a variety of doped transition metal oxides. In particular, data are shown for the NiO chain compound, Y 2-x Ca x BaNiO 5 , the two-dimensional cuprate superconductors La 2-x Sr x CuO 4 and YBa 2 Cu 3 O 6+x , and the classical three-dimensional ''Mott-Hubbard'' system V 2-y O 3

  3. Nondestructive evaluation of braided carbon fiber composites with artificial defect using HTS-SQUID gradiometer

    International Nuclear Information System (INIS)

    Shinyama, Y.; Yamaji, T.; Hatsukade, Y.; Takai, Y.; Aly-Hassan, M.S.; Nakai, A.; Hamada, H.; Tanaka, S.

    2011-01-01

    We applied a current-injection-based NDE method using a HTS-SQUID gradiometer to a braided CFRP with artificial cracks. Current distributions in the braided CFRP were estimated from measured field gradient distributions. A small crack, in which a few carbon-fiber bundles were cut, was well detected from the current distributions. A cross-section of the CFRP showed that a density of the bundles at edges is higher than the other part. The experimental results demonstrated the capability of the method to detect sub-mm cracks. Braided carbon fiber reinforced plastics (CFRPs) are one of multifunctional materials with superior properties such as mechanical strength to normal CFRPs since the braided CFRPs have continuous fiber bundles. In this paper, we applied the current-injection-based nondestructive evaluation (NDE) method using a HTS-SQUID gradiometer to the braided CFRP for the detection of the breakage of the bundles. We prepared planar braided CFRP samples with and without artificial cracks of 1 and 2 mm lengths, and measured the current density distribution above the samples using the NDE method. In the measurement results, not only a few completely-cut bundles but also the additional partially-cut bundles were detected from decrease in the measured current density along the cut bundle around the cracks. From these results, we showed that it is possible to inspect a few partially-cut bundles in the braided CFRPs by the NDE method.

  4. Progress in scale-up of second-generation HTS conductor

    International Nuclear Information System (INIS)

    Selvamanickam, V.; Chen, Y.; Xiong, X.; Xie, Y.; Zhang, X.; Qiao, Y.; Reeves, J.; Rar, A.; Schmidt, R.; Lenseth, K.

    2007-01-01

    Tremendous progress has been recently made in the achievement of high-performance, high-speed, long-length second-generation (2G) HTS conductors. Using ion beam assisted deposition (IBAD) MgO and metal organic chemical vapor deposition (MOCVD), SuperPower has scaled up tape lengths to 427 m with a minimum critical current value of 191 A/cm corresponding to a critical current x length performance of 81,550 m. Tape speeds up to 120 m/h have been reached with IBAD MgO, up to 80 m/h with buffer deposition and up to 45 m/h with MOCVD, all in single pass processing of 12 mm wide tape. Critical current value of 227 A/cm has been achieved in a 203 m long tape produced in an all-high-speed fabrication process. Critical current values have been raised to 721 A/cm, 592 A/cm and 486 A/cm in short, reel-to-reel processed tape, over 1 m length and over 11.1 m, respectively, using thicker MOCVD HTS films. Finally, over 10,000 m of copper-stabilized, 4 mm wide conductor has been produced and tested for delivery to the Albany Cable project. The average critical current of the 10,000 m lot was 81 A

  5. Progress in scale-up of second-generation HTS conductor

    Energy Technology Data Exchange (ETDEWEB)

    Selvamanickam, V. [SuperPower Inc., 450 Duane Avenue, Schenectady, NY 12304 (United States)], E-mail: vselva@igc.com; Chen, Y.; Xiong, X.; Xie, Y.; Zhang, X.; Qiao, Y.; Reeves, J.; Rar, A.; Schmidt, R.; Lenseth, K. [SuperPower Inc., 450 Duane Avenue, Schenectady, NY 12304 (United States)

    2007-10-01

    Tremendous progress has been recently made in the achievement of high-performance, high-speed, long-length second-generation (2G) HTS conductors. Using ion beam assisted deposition (IBAD) MgO and metal organic chemical vapor deposition (MOCVD), SuperPower has scaled up tape lengths to 427 m with a minimum critical current value of 191 A/cm corresponding to a critical current x length performance of 81,550 m. Tape speeds up to 120 m/h have been reached with IBAD MgO, up to 80 m/h with buffer deposition and up to 45 m/h with MOCVD, all in single pass processing of 12 mm wide tape. Critical current value of 227 A/cm has been achieved in a 203 m long tape produced in an all-high-speed fabrication process. Critical current values have been raised to 721 A/cm, 592 A/cm and 486 A/cm in short, reel-to-reel processed tape, over 1 m length and over 11.1 m, respectively, using thicker MOCVD HTS films. Finally, over 10,000 m of copper-stabilized, 4 mm wide conductor has been produced and tested for delivery to the Albany Cable project. The average critical current of the 10,000 m lot was 81 A.

  6. AC surface flashover strength and barrier effect of LN 2 for HTS transformer with simulated electrode

    Science.gov (United States)

    Joung, Jong-Man; Baek, Seung-Myeong; Kim, Hae-Jong; Kim, Sang-Hyun

    2003-10-01

    In the response to an increasing demand for electrical energy, much effort aimed to develop and commercialise HTS power equipments is going on around the world. For the development, it is necessary to establish the dielectric technology in LN 2. Hence many types of dielectric tests should be carried out to understand the dielectric phenomena at cryogenic temperature and to gather various dielectric data. Among the many types dielectric tests, the characteristic of surface flashover and the barrier effect were conducted with the simulated electrode after analysing the insulating configuration of the pancake-coil-type HTS transformer. The influence of a barrier on the dielectric strength was measured according to the size of the barrier, the position of the barrier and the effect of the back-electrode. It was shown that the effectiveness, namely the ratio of the breakdown voltage in presence of barrier to the voltage without barrier, is highest when the barrier is placed at the needle electrode side. The effect increased up to 1.8 times when collar length is 10 mm. The flashover characteristic with back-electrode was remarkably lower than the characteristic without one in the case the electrodes located at the same surface of dielectric plate. On the contrary, in the case the barrier was placed between the electrodes, the characteristic was even improved slightly.

  7. Calculated E-I characteristics of HTS pancakes and coils exposed to inhomogeneous magnetic fields

    Science.gov (United States)

    Adanny, Y.; Wolfus, Y.; Friedman, A.; Kopansky, F.; Yeshurun, Y.; Bar-Haim, Z.; Ron, Z.; Pundak, N.

    2006-06-01

    The upper limit of the operating current of LTS solenoids can be estimated as the coordinate of the crossing point of its load line with IC (B) line of the superconductor. For HTS coils this approach seems to underestimate the allowable operating current of the coil. A better approach is to obtain a full electric field distribution over the coil and to use it as the base for a more sophisticated coil design criteria. We developed an algorithm and a Matlab program for calculating distributions of the current density, magnetic field and electric field in HTS solenoids made of pancakes, considering the inhomogeneous current density distribution inside the anisotropic tape. I-V curves of several Bi-2223 coils are calculated and good agreeement of the calculated and measured critical currents, IC, and indexes, n, are attained. One can utilize the program in the coil design choosing his own criteria of coil's critical current, e.g., 1) The average electric field 10-4 V/m over the coil, 2) The electric field 10-4 V/m at the weak point of the coil, 3) The energy dissipation in the entire coil, 4) Distribution of local energy dissipation.

  8. Mechanical and electric characteristics of vacuum impregnated no-insulation HTS coil

    International Nuclear Information System (INIS)

    Park, Heecheol; Kim, A-rong; Kim, Seokho; Park, Minwon; Kim, Kwangmin; Park, Taejun

    2014-01-01

    Highlights: • A single pancake no-insulation coil was fabricated with a brass lamination conductor. • Charging/discharging test was performed using liquid nitrogen and conduction-cooling. • Consistent contact resistance was verified after epoxy impregnation. • Equivalent circuit was used to estimate the heat generation during charging operation. • The HTS coil did not showed delamination problem for the conduction cooling. - Abstract: For the conduction cooling application, epoxy impregnation is inevitable to enhance the thermal conduction. However, there have been several research results on the delamination problem with coated conductor and the main cause of the delamination is related with the different thermal contraction between epoxy, the insulation layer and the weak conductor. To avoid this problem, the amount of epoxy and insulation layer between conductors should be minimized or removed. Therefore, no insulation (NI) winding method and impregnation after dry winding can be considered to solve the problem. The NI coil winding method is very attractive due to high mechanical/thermal stability for the special purpose of DC magnets by removing the insulation layer. In this paper, the NI coil winding method and vacuum impregnation are applied to a HTS coil to avoid the delamination problem and enhance the mechanical/thermal stability for the conduction cooling application. Through the charging/discharging operation, electric/thermal characteristics are investigated at 77 K and 30 K

  9. Investigation and comparison of AC losses on stabilizer-free and copper stabilizer HTS tapes

    Science.gov (United States)

    Shen, Boyang; Li, Jing; Geng, Jianzhao; Fu, Lin; Zhang, Xiuchang; Li, Chao; Zhang, Heng; Dong, Qihuan; Ma, Jun; Coombs, T. A.

    2017-10-01

    This paper presents the measurement and simulation of Alternating Current (AC) losses on the Stabilizer-free and Copper Stabilizer High Temperature Superconducting (HTS) Tapes: SuperPower SF12100 and SCS12050. The AC loss measurement utilised electrical method to obtain overall losses with AC transport currents. The 2D H-formulation by COMSOL Multiphysics has been used to simulate the real geometry and multi-layer HTS tapes. Ferromagnetic AC losses of substrate have been assumed to be ignored as the substrates of SF12100 and SCS12050 are non-magnetic. Hysteresis AC losses in the superconducting layer, and eddy-current AC losses in copper stabilizer, silver overlayer and substrate were concerned in this investigation. The measured AC losses were compared to the AC losses from simulation, with 3 cases of different AC frequency 10, 100, and 1000 Hz. The eddy-current AC losses of copper stabilizer at frequency 1000 Hz were determined from both experiment and simulation. The estimation of AC losses with frequency at 10,000 Hz was also carried out using simulation method. Finally, the frequency dependence of AC losses from Stabilizer-free Tape and Copper Stabilizer Tape were compared and analysed.

  10. Design, manufacture and performance evaluation of HTS electromagnets for the hybrid magnetic levitation system

    Energy Technology Data Exchange (ETDEWEB)

    Chu, S.Y.; Hwang, Y.J.; Choi, S.; Na, J.B.; Kim, Y.J.; Chang, K.S. [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of); Bae, D.K. [Chungju National University, Chungju 380-702 (Korea, Republic of); Lee, C.Y. [Ultra High-Speed Train Research Department, Korea Railroad Research Institute, Uiwang-Si 437-757 (Korea, Republic of); Ko, T.K., E-mail: tkko@yonsei.ac.kr [School of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2011-11-15

    A high speed electromagnetic suspension (EMS) maglev has emerged as the solution to speed limit problem that conventional high-speed railroad has. In the EMS maglev, small levitation gap needs uniform guide-way which leads to increase the construction cost. The large levitation gap can reduce the construction cost. However it is hard for normal conducting electromagnet to produce larger magneto-motive force (MMF) for generating levitation force as increased levitation gap. This is because normal conductors have limited rating current to their specific volume. Therefore, the superconducting electromagnet can be one of the solutions for producing both large levitation gap and sufficient MMF. The superconducting electromagnets have incomparably high allowable current density than what normal conductors have. In this paper, the prototype of high temperature superconducting (HTS) electromagnets were designed and manufactured applicable to hybrid electromagnetic suspension system (H-EMS). The H-EMS consists of control coils for levitation control and superconducting coils for producing MMF for levitation. The required MMF for generating given levitation force was calculated by both equations of ideal U-core magnet and magnetic field analysis using the finite element method (FEM). The HTS electromagnets were designed as double pancakes with Bi-2223/Ag tapes. Experiments to confirm its operating performance were performed in liquid nitrogen (LN{sub 2}).

  11. HTS Transmission Cable System for installation in the Long Island Power Grid

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Frank [American Superconductor Corporation, Devens, MA (United States); Durand, Fabien [American Superconductor Corporation, Devens, MA (United States); Maguire, James [American Superconductor Corporation, Devens, MA (United States)

    2015-10-05

    Department of Energy (DOE) Award DE-FC26-07NT43240 was issued on October 1, 2007. Referred to as LIPA2, the principal objectives of the project were to develop key components required to deploy and demonstrate second-generation (2G) high temperature superconductor (HTS) cables in a 600 meter (2000 feet) underground segment of a 138kV three-phase transmission circuit of the Long Island Power Authority (LIPA) power grid. A previous effort under DOE Award DE-FC36-03GO13032 (referred to as LIPA1) resulted in installation (and subsequent successful operation) of first-generation (1G) HTS cables at the LIPA site. As with LIPA1, American Superconductor (AMSC) led the effort for LIPA2 and was responsible for overall management of the project and producing sufficient 2G wire to fabricate the required cable. Nexans' tasks included design/manufacture/installation of the cable, joint (splice), cable terminations and field repairable cryostat; while work by Air Liquide involved engineering and installation support for the refrigeration system modifications.

  12. Thermal and mechanical properties of advanced impregnation materials for HTS cables and coils

    International Nuclear Information System (INIS)

    Bagrets, N; Otten, S; Weiss, K-P; Kario, A; Goldacker, W

    2015-01-01

    In the growing field of high-temperature superconducting (HTS) applications, finding an appropriate impregnation material for cables and coils remains a challenging task. In HTS cables and coils, tapes have to be able to withstand mechanical loads during operation. Impregnation is playing a role as mechanical stabilization. However, material properties usually change significantly when going to low temperatures which can decrease performance of superconducting devices. For example, a large mismatch in thermal expansion between a conductor and impregnation material at low temperatures can lead to delamination and to degradation of the critical current. Impregnation materials can insulate tapes thermally which can lead to damage of the superconducting device in case of quench. Thus, thermal conductivity is an important property which is responsible for the temperature distribution in a superconducting cable or in a coil. Due to Lorentz forces acting on structural materials in a superconducting device, the mechanical properties of these materials should be investigated at operating temperatures of this device. Therefore, it is important to identify an advanced impregnation material meeting all specific requirements. In this paper, thermal and mechanical properties of impregnation material candidates with added fillers are presented in a temperature range from 300 K to 4 K. (paper)

  13. Statistical Evaluation of HTS Assays for Enzymatic Hydrolysis of β-Keto Esters.

    Directory of Open Access Journals (Sweden)

    O Buß

    Full Text Available β-keto esters are used as precursors for the synthesis of β-amino acids, which are building blocks for some classes of pharmaceuticals. Here we describe the comparison of screening procedures for hydrolases to be used for the hydrolysis of β-keto esters, the first step in the preparation of β-amino acids. Two of the tested high throughput screening (HTS assays depend on coupled enzymatic reactions which detect the alcohol released during ester hydrolysis by luminescence or absorption. The third assay detects the pH shift due to acid formation using an indicator dye. To choose the most efficient approach for screening, we assessed these assays with different statistical methods-namely, the classical Z'-factor, standardized mean difference (SSMD, the Kolmogorov-Smirnov-test, and t-statistics. This revealed that all three assays are suitable for HTS, the pH assay performing best. Based on our data we discuss the explanatory power of different statistical measures. Finally, we successfully employed the pH assay to identify a very fast hydrolase in an enzyme-substrate screening.

  14. Waste water purification by magnetic separation technique using HTS bulk magnet system

    International Nuclear Information System (INIS)

    Oka, T.; Kanayama, H.; Tanaka, K.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Terasawa, T.; Itoh, Y.; Yabuno, R.

    2009-01-01

    We have investigated the feasibility of strong magnetic field generators composed of the high temperature superconducting (HTS) bulk magnet systems to the magnetic separation techniques for the waste water including thin emulsion bearing the cutting oil. Two types of the strong field generators were prepared by the face-to-face HTS bulk magnet systems, which emit the magnetic field density of 1 and 2 T in the open spaces between the magnetic poles activated by the pulsed field magnetization and the field cooling methods, respectively. A couple of water channels containing iron balls were settled in the strong field to trap the magnetized flocks in the waste water. The separation ratios of flocks containing 200 ppm magnetite powder were evaluated with respect to the flow rates of the waste water. The performances of bulk magnet system have kept showing values of around 100% until the flowing rate reached up to 18 l/min. This suggests that the magnetic separation by using bulk magnets is effective for the practical water purification systems.

  15. Manufacturing and test of 2G-HTS coils for rotating machines: Challenges, conductor requirements, realization

    International Nuclear Information System (INIS)

    Oomen, Marijn; Herkert, Werner; Bayer, Dietmar; Kummeth, Peter; Nick, Wolfgang; Arndt, Tabea

    2012-01-01

    We investigate the use of 2nd-generation High-Temperature Superconductors (2G-HTSs) in the rotors of electrical motors and generators. For these devices the conductor must be wound into robust impregnated coils, which are operated in vacuum at temperatures around 30 K, in strong magnetic fields of about 2T. Differences in thermal contraction between the coil former, conductor constituents, impregnation resin, bandage and heat-sink materials (assembled at room temperature) cause mechanical stresses at operating temperature. Rotating-machine operation adds Lorentz forces and challenging centripetal accelerations up to thousands of g. Second generation-HTS conductors withstand large tensile stresses in axial direction and compression in normal direction. However, shear stresses, axial compression, and tension normal to the conductor can cause degradation in superconducting properties. Such stresses can be mitigated by correct choice of materials, coil lay-out and manufacturing process. A certain stress level will remain, which the conductor must withstand. We have manufactured many impregnated round and race-track coils, using different 2G-HTS conductors, and tested them at temperatures from 25 K to 77 K. Degradation of the superconductor in early coils was traced to the mentioned differences in thermal contraction, and was completely avoided in coils produced later. We will discuss appropriate coil-winding techniques to assure robust and reliable superconductor performance.

  16. A 100-W grade closed-cycle thermosyphon cooling system used in HTS rotating machines

    Science.gov (United States)

    Felder, Brice; Miki, Motohiro; Tsuzuki, Keita; Shinohara, Nobuyuki; Hayakawa, Hironao; Izumi, Mitsuru

    2012-06-01

    The cooling systems used for rotating High-Temperature Superconducting (HTS) machines need a cooling power high enough to ensure a low temperature during various utilization states. Radiation, torque tube or current leads represent hundreds of watts of invasive heat. The architecture also has to allow the rotation of the refrigerant. In this paper, a free-convection thermosyphon using two Gifford-McMahon (GM) cryocoolers is presented. The cryogen is mainly neon but helium can be added for an increase of the heat transfer coefficient. The design of the heat exchangers was first optimized with FEM thermal analysis. After manufacture, they were assembled for preliminary experiments and the necessity of annealing was studied for the copper parts. A single evaporator was installed to evaluate the thermal properties of such a heat syphon. The maximum bearable static heat load was also investigated, but was not reached even at 150 W of load. Finally, this cooling system was tested in the cooling down of a 100-kW range HTS rotating machine containing 12 Bi-2223 double-pancake coils (DPC).

  17. Applied Hts Bulks and Wires to Rotating Machines for Marine Propulsion

    Science.gov (United States)

    Miki, M.; Felder, B.; Kimura, Y.; Tsuzuki, K.; Taguchi, R.; Shiliang, Y.; Xu, Y.; Ida, T.; Izumi, M.

    2010-04-01

    High-temperature superconductors allow a compact and efficient way to provide high-torque density to rotating machines with excellent operation. A field pole, providing flux density of more than 1.5 T around the armature, was initially designed for an axial-gap type with the flux parallel to the rotor axis. Melt-growth Gd-123 bulks as well as Bi-2223 wire windings have been successfully assembled on the rotor disk. No iron core was used, though being an auxiliary flux control found in most HTS motors. Both bulk and wire types have realized a practical motor operation within a limited output range. For bulks, a 15 kW, 720 rpm, synchronous motor was designed and tested in the group of TUMSAT, Kitano Seiki and University of Fukui. A bulk field pole was cooled down by liquid nitrogen and was magnetized in the motor. To enhance the output power to more than 30 kW, we developed a thermosyphon system using condensed neon. Another field pole with HTS wire for large-scale marine propulsion is also discussed on a 100 kW, 230 rpm tested machine. A closed-cycle condensed neon associated with thermal insulation is also reported.

  18. Ionothermal Design of Crystalline Halogeno(cyano)cuprate Family: Structure Diversity, Solid-State Luminescence, and Photocatalytic Performance.

    Science.gov (United States)

    Zhang, Ya-Li; Ding, Rui; Li, Shu-Ni; Jiang, Yu-Cheng; Hu, Man-Cheng; Zhai, Quan-Guo

    2017-06-19

    A general preparative method for multifunctional halogeno(cyano)cuprate materials in ionic liquids is developed in this work. Under ionothermal conditions, alkylimidazolium-based ionic liquids serving as solvent, charge-compensating, and structure-directing agent, as well as reactant lead to 12 members of the novel hybrid halogeno(cyano)cuprate family with a general formula of [R 1 R 2 R 3 IM] b+c-a [Cu a X b (CN) c ] (R 1 R 2 R 3 IM = alkylimidazolium cations, X = halide anions). X-ray single-crystal diffractions show that diverse inorganic halogeno(cyano)cuprate components vary from discrete complexes (1 and 2), one-dimensional (1D) chains (3-7), two-dimensional (2D) layer (8), to three-dimensional (3D) open frameworks (9-12). 1 and 2 are of zero-dimensional discrete structures containing triangular [CuX 3 ] 2- anions. In complexes 3-7, pentagonal bipyramidal [Cu 2 X 3 ] units are bridged by CN groups to give 1D [Cu 2 X 3 (CN)] 2- inorganic chains, which are charge-balanced by the surrounded alkylimidazolium cations. 2D inorganic [Cu 5 ClI 2 (CN) 4 ] 2- layer in complex 8 is alternately packed with [VMIM] + organic cations. In complex 9, left- and right-handed Cu-CN helical chains connect each other to give a 3D open framework, which are further entrapped by 1D zigzag Cu-CN chains and [PMIM] + cations. Diverse unique Cu(I) atoms and cyanide or halide bridging groups in 10, 11, and 12 are extended into 3D anionic open frameworks with 1D channels, which are occupied by alkylimidazolium cations. For all hybrid halogeno(cyano)cuprate complexes, the extensively existing C-H···X or C-H···π hydrogen bonds help to stabilize the ultimate supramolecular packing structures. Notably, the distances between adjacent Cu(I) centers range from 2.420(2) to 2.989(2) Å in all polymeric frameworks, which indicate strong Cu···Cu interactions. Thanks to the cooperation of conjugate π electron cyanide systems with halide ions and/or Cu···Cu interactions, compounds 1

  19. Spin dynamics in high-T{sub C} superconducting cuprates; Dynamique de spins dans les oxydes de cuivre supraconducteurs a haute temperature critique

    Energy Technology Data Exchange (ETDEWEB)

    Bourges, Ph

    2003-07-01

    This work is dedicated to the detailed investigations of the magnetic resonance peak in the superconducting state of cuprates. The existence of such a peak could be the signature of a mechanism linked to magnetism that could explain high critical temperature superconductivity. Inelastic neutron scattering is an adequate tool for the understanding of cuprate properties because it reveals magnetic fluctuations whose behaviour and variety depend strongly on temperature and on the level of doping. The last part of this work is dedicated to the study of spin dynamics in YBa{sub 2}Cu{sub 3}O{sub 6+x} system.

  20. Characteristics of the Mott transition and electronic states of high-temperature cuprate superconductors from the perspective of the Hubbard model

    Science.gov (United States)

    Kohno, Masanori

    2018-04-01

    A fundamental issue of the Mott transition is how electrons behaving as single particles carrying spin and charge in a metal change into those exhibiting separated spin and charge excitations (low-energy spin excitation and high-energy charge excitation) in a Mott insulator. This issue has attracted considerable attention particularly in relation to high-temperature cuprate superconductors, which exhibit electronic states near the Mott transition that are difficult to explain in conventional pictures. Here, from a new viewpoint of the Mott transition based on analyses of the Hubbard model, we review anomalous features observed in high-temperature cuprate superconductors near the Mott transition.

  1. Cu-O network dependent core-hole screening in low-dimensional cuprates: A theoretical analysis

    OpenAIRE

    Waidacher, C.; Richter, J.; Becker, K. W.

    2000-01-01

    We analyze the influence of the dimensionality on the Cu 2p_3/2 core level X-ray photoemission spectra of undoped cuprates. Both exchange splitting and delocalization properties are described within one framework using a multi-band Hubbard model. The spectral intensity is calculated by means of the Mori-Zwanzig projection technique for a CuO_4 plaquette ('zero'-dimensional), an infinite CuO_3 chain (one-dimensional), and an infinite CuO_2 plane (two-dimensional). The results are compared to t...

  2. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    International Nuclear Information System (INIS)

    Yung Moo Huh

    2001-01-01

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La 2-x Sr x CuO 4-δ , La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H(parallel)c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T c , magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T c0 vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La 2-x Sr x CuO 4 (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to T c . The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance ζ c becomes comparable to the spacing between adjacent CuO 2 layers s at sufficiently high magnetic fields near H c2

  3. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    International Nuclear Information System (INIS)

    Finnemore, Douglas K.

    2001-01-01

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La 2-x Sr x CuO 4-δ , La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H (parallel) c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below T c , magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the T c0 vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La 2-x Sr x CuO 4 (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to T c . The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance ξ c becomes comparable to the spacing between adjacent CuO 2 layers s at sufficiently high magnetic field near H c2

  4. Thermodynamic Critical Field and Superconducting Fluctuation of Vortices for High Temperature Cuprate Superconductor: La-214

    Energy Technology Data Exchange (ETDEWEB)

    Finnemore, Douglas K. [Iowa State Univ., Ames, IA (United States)

    2001-01-01

    Thermodynamics has been studied systematically for the high temperature cuprate superconductor La2-xSrxCuO4-δ, La-214, in the entire superconductive region from strongly underdoped to strongly overdoped regimes. Magnetization studies with H $\\parallel$ c have been made in order to investigate the changes in free energy of the system as the number of carriers is reduced. Above the superconducting transition temperature, the normal-state magnetization exhibits a two-dimensional Heisenberg antiferromagnetic behavior. Below Tc, magnetization data are thermodynamically reversible over large portions of the H-T plane, so the free energy is well defined in these regions. As the Sr concentration is varied over the wide range from 0.060 (strongly underdoped) to 0.234 (strongly overdoped), the free energy change goes through a maximum at the optimum doped in a manner similar to the Tc0 vs. x curve. The density of states, N(0), remains nearly constant in the overdoped and optimum doped regimes, taking a broad maximum around x = 0.188, and then drops abruptly towards zero in the underdoped regime. The La2-xSrxCuO4 (La-214) system displays the fluctuating vortex behavior with the characteristic of either 2D or 3D fluctuations as indicated by clearly identifiable crossing points T* close to Tc. The dimensional character of the fluctuations depends on both applied magnetic fields and the density of charge carriers. The dimensional crossover from 2D to 3D occurs in the strongly underdoped regime when the c-axis coherence distance ξc becomes comparable to the spacing between adjacent CuO2 layers s at sufficiently high magnetic field near Hc2.

  5. Optical, magnetic, and single-particle excitations in the multiband Hubbard model for cuprate superconductors

    Science.gov (United States)

    Wagner, J.; Hanke, W.; Scalapino, D. J.

    1991-05-01

    On the basis of exact diagonalizations, a comparative study of two-particle optical and magnetic, as well as single-particle, excitations is presented for a two-dimensional (2D) multiorbital Hubbard model. For reasonable parameter sets appropriate for the cuprate superconductors, the single-particle excitations display strongly correlated states related to the Zhang-Rice Cu-O singlet construction. These states define the gap (to the upper Hubbard band) at half-filling and become partially occupied by doping holes in our 2×2 unit-cell system. The optical results, which are the first quantitative calculations performed for realistic parameters of the three-band Hubbard model, clearly show three allowed optical transitions: (i) itinerant motion of the Cu-O singlets, having (for doping concentrations x≠0) a spectral Drude distribution around ω=0 with spectral weight proportional to x; (ii) unbinding of the O hole from the Cu spin in the singlet. This gives, in particular, a strong absorption peak due to singlet-->nonbonding oxygen transitions, again with relative weight ~x. It is roughly centered at ω~JKondoUpd. They show a pronounced excitonic effect due to the p-d interaction Upd and have a reduced spectral weight shifted to higher energies for increased dopings. Findings (i)-(iii) are in general accordance with recent experimental data. Our study of the low-energy absorption is complemented with a numerical scaling analysis of the Drude weight in 1D, where, in particular, we find an interesting violation of Lenz's law for 4n-site Hubbard rings. Finally, the magnetic structure factor is calculated for the 2D case. For finite doping it contains a peak at 2JKondo, which should be detectable in experiment.

  6. Understanding the superconductivity in copper oxides

    CERN Document Server

    2019-01-01

    The aim of this book is to clarify the situation by adopting a very different approach from the above electronic/magnetic models, where explicitly local dynamical distortions are considered. These are distinctly different from conventional phonons which are a property of the infinite translational invariant symmetric lattice. The local dynamical distortions are shown to account for bulk properties and provide consistent and quantitative agreement with experimental data together with explicit predictions. Selected published experimental and theoretical papers are presented which support the above arguments, but have been ignored on purpose by the originators of the RVB/t-J bubble. To summarize the scope of this book, comprising nine chapters, it is shown, that the phenomenon of HTS in copper oxides is much better understood than publically claimed by RVB/t-J followers. Using the words of B. Laughlin, the presence of the antiferromagnetism in HTS masks the underlying physics where vibronic bipolarons with spin...

  7. 'Leak Current' correction for critical current measurement of no-insulation HTS coil

    Energy Technology Data Exchange (ETDEWEB)

    Song, Jung Bin [Laboratoire National des Champs Magnétiques Intenses, CNRS, Grenoble (France); Hahn, Seung Yong [Dept. of Electrical and Computer Engineering, Seoul National University, Seoul (Korea, Republic of)

    2017-06-15

    Discrepancy between a power supply current and an actual “spiral” coil current makes the conventional 4-probe measurement of a critical current (I{sub c}) of a no-insulation (NI) high temperature superconductor (HTS) coil inaccurate and time-consuming. This paper presents a fast and accurate approach for I{sub c} measurement of NI HTS coils. With an NI HTS coil energized at a constant ramping rate, a complete analytic expression for the spiral coil current was obtained from a first-order partial differential equation that derived from an equivalent circuit model of the NI coil. From the analytic solution, both spiral coil current and radial leak current can be obtained simultaneously, which enables fast and accurate measurement of the NI coil I{sub c}. To verify the proposed approach, an NI double-pancake (DP) coil, wound with GdBCO tapes of 6 mm × 0.1 mm, was constructed and its Ic was repeatedly measured with various ramping rates in a bath of liquid nitrogen at 77 K. The measured results agreed well with the calculated ones, which validates the proposed approach to measure I{sub c} of an NI HTS coil.

  8. Development of 66 kV/6.9 kV 2 MV A prototype HTS power transformer

    International Nuclear Information System (INIS)

    Bohno, T.; Tomioka, A.; Imaizumi, M.; Sanuki, Y.; Yamamoto, T.; Yasukawa, Y.; Ono, H.; Yagi, Y.; Iwadate, K.

    2005-01-01

    We have developed the technology of the producing a HTS magnet for the power transformer. Three subjects have been mainly studied, high voltage technologies, large current and low AC loss technologies and sub-cooling system technologies to establish the technology of 66 kV/6.9 kV 10 MV A class HTS power transformer. In order to verify the validity of elemental technologies, such as high voltage technologies, large current and low AC loss technologies and sub-cooling system technologies, single-phase 2 MV A class 66 kV/6.9 kV prototype HTS transformer was manufactured and tested. In the load loss (AC loss) measurement, it was obtained that the measured value of 633 W was almost corresponding to the calculated value of 576 W at the rated operation of 2 MV A. Moreover, the breakdown was not found all voltage withstand test. These test results indicate that elemental technologies were established for the development of 66 kV/6.9 kV 10 MV A class HTS power transformer

  9. Development and test of an axial flux type PM synchronous motor with liquid nitrogen cooled HTS armature windings

    International Nuclear Information System (INIS)

    Sugimoto, H; Morishita, T; Tsuda, T; Takeda, T; Togawa, H; Oota, T; Ohmatsu, K; Yoshida, S

    2008-01-01

    We developed an axial gap permanent magnet type superconducting synchronous motor cooled by liquid nitrogen (LN 2 ). The motor includes 8 poles and 6 armature windings. The armature windings are made from BSCCO wire operated at the temperature level between 66K∼70K. The design of the rated output is 400kW at 250rpm. Because HTS wires produce AC loss, there are few motors developed with a superconducting armature winding. In a large capacity motor, HTS windings need to be connected in parallel way. However, the parallel connection causes different current flowing to each HTS winding. To solve this problem, we connected a current distributor to the motor. As a result, not only the current difference can be suppressed, but also the current of each winding can be adjusted freely. The low frequency and less flux penetrating HTS wire because of current distributor contribute to low AC loss. This motor is an axial gap rotating-field one, the cooling parts are fixed. This directly leads to simple cooling system. The motor is also brushless. This paper presents the structure, the analysis of the motor and the tests

  10. Development of a single-phase 330kVA HTS transformer using GdBCO tapes

    Science.gov (United States)

    Hu, Daoyu; Li, Zhuyong; Hong, Zhiyong; Jin, Zhijian

    2017-08-01

    With the mature of manufacture process and technology of high temperature superconductors, the critical current and stability are gradually increased. High temperature superconductors could be used in transformer, current limiter, generator, magnet and etc. This paper focuses on development and characteristic tests of a single-phase high temperature superconducting (HTS) power transformer with capacity of 330 kVA by using GdBCO tapes, which is 1/3 model of a 1 MVA / 10 kV / 0.4 kV HTS transformer. The specifications of iron core, HTS windings and cryostat are described in detail. The iron core is made of silicon steel plate. The arrangement of HTS windings are based on experimental and simulated results. The cryostat with a room temperature bore is manufactured using nonmetallic materials. Several characteristic tests and insulation tests are performed in liquid nitrogen of 77 K. The efficiency and AC loss at rated load is 99.90% and 243.7 W, respectively. In addition, an overload test was also performed.

  11. Design of 154 kV class 100 MVA 3 phase HTS transformer on a common magnetic core

    Science.gov (United States)

    Choi, J.; Lee, S.; Park, M.; Kim, W.; Kim, S.; Han, J.; Lee, H.; Choi, K.

    2007-10-01

    We have proposed a high temperature superconducting (HTS) transformer which can substitute for a conventional oil transformer for power distribution in Korea. The conventional transformer is composed of three identical single phase transformers because of the limitations on volume and weight. Now the Korean power company has started to consider the possibility of a transformer on a common magnetic core because it can be a solution for the increment of capacity without new construction of substations. In this paper, we proposed an HTS transformer on a common core. Its capacity is the same as the previous HTS transformer, which was 100 MVA, 154 kV/22.9 kV. The former is smaller and lighter than the latter. We assumed a transformer tank which covers the common core and windings. The tank also acts as a vacuum seal for a cooling system and so the cryostats for the windings do not need to have vacuum layers. The design parameters are compared with those of both a conventional one and an HTS transformer with separate cores.

  12. Development of a Fault Analysis Algorithm for HTS Power Cable Using RTDS Considering Both Conducting and Shield Layers

    Science.gov (United States)

    Kim, J. H.; Park, C. H.; Park, M.; Yu, I. K.

    High Temperature Superconducting (HTS) power cable consists of a conducting layer and a shield layer for carrying the required current. Geometrically, the conducting and shield layers each have self inductance; and the mutual inductance exists between the conducting and shield layers. Therefore, the direction of the current of shield the layer is opposite that of the conducting layer current. The value of the shield layer current is over 95% of the conducting layer current at the steady state. However, if a fault current passes through an HTS power cable, the quench occurs in both the conducting and shield layers. After the quench, resistance appears, and the even self inductance values are not changed a great deal, but the mutual inductance value is directly affected. According to the above mentioned processes, the current distribution of the conducting and shield layers changes due to the fault current. In this paper, the authors describe the transient state analysis of a real manufactured HTS power model cable, considering both the conducting and the shield layers. The manufactured system is coupled with RTDS, in which a utility grid is composed and simulated. These results provide important data for the design of an HTS power cable.

  13. Performance and analysis of wireless power charging system from room temperature to HTS magnet via strong resonance coupling method

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Y. D.; Lee, S. Y.; Lee, T. W.; Kim, J. S. [Suwon Science College, Suwon (Korea, Republic of); Lee, C. Y. [Korea Railroad Institute, Uiwang (Korea, Republic of)

    2016-03-15

    The technology of supplying the electric power by wireless power transfer (WPT) is expected for the next generation power feeding system since it can supply the power to portable devices without any connectors through large air gap. As such a technology based on strongly coupled electromagnetic resonators is possible to deliver the large power and recharge them seamlessly; it has been considered as a noble option to wireless power charging system in the various power applications. Recently, various HTS wires have now been manufactured for demonstrations of transmission cables, motors, MAGLEV, and other electrical power components. However, since the HTS magnets have a lower index n value intrinsically, they are required to be charged from external power system through leads or internal power system. The portable area is limited as well as the cryogen system is bulkier. Thus, we proposed a novel design of wireless power charging system for superconducting HTS magnet (WPC4SM) based on resonance coupling method. As the novel system makes possible a wireless power charging using copper resonance coupled coils, it enables to portable charging conveniently in the superconducting applications. This paper presented the conceptual design and operating characteristics of WPC4SM using different shapes' copper resonance coil. The proposed system consists of four components; RF generator of 370 kHz, copper resonance coupling coils, impedance matching (IM) subsystem and HTS magnet including rectifier system.

  14. First operation experiences from a 30 kV 104 MVA HTS power cable installed in a utility substation

    DEFF Research Database (Denmark)

    Willen, D.; Hansen, F.; Daumling, M.

    2002-01-01

    realistic conditions in the substation of Amager (AMK). Approximately 50 000 private and business customers are supplied from this cable. The load can be adjusted from 20% to 100% of the power supplied and the number of branches connected can be altered. This and other early HTS power installations...

  15. Evaluation of High-resolution Geomagnetic Field Observation System Using HTS-SQUID Magnetometer and its Application.

    Science.gov (United States)

    Katori, Y.; Okubo, K.; Hato, T.; Tsukamoto, A.; Tanabe, K.; Onishi, N.; Furukawa; Isogami, S.; Takeuchi, N.

    2014-12-01

    Magnetic field changes associated with earthquakes have been investigated previously (1964 Stacey, 1994 Johnston et al.). Our research group also reported successful observation of "co-faulting" Earth's magnetic field changes due to piezomagnetic effects caused by earthquake rupturing in 2008 Iwate-Miyagi Nairiku earthquake of M7.2 (2011 Okubo et al.) using optoelectronic observation system with flux-gate magnetometers. This is an important finding; the electromagnetic fields originating from such sources satisfy the Maxwell equations and hence they propagate from the sources to the observation site at a speed of light in the crustal materials. Further efforts could lead us to a new system for super-early warning of destructive earthquakes with the magnetic measurements. On the other hand, the observed result in 2008 Iwate-Miyagi Nairiku earthquake was suggested that the geomagnetic variation signal accompanying fault movement, whose sources are the piezomagnetic effects, is very small; therefore development of a high-sensitive magnetometer system is very important. To solve this problem, we introduce long-term precise geomagnetic observations using high-temperature-superconductor based superconducting-quantum-interference-device (HTS-SQUID) magnetometer system. That is, our research group developed the HTS-SQUID magnetometer system for high-resolution observation of Earth's magnetic field. Since March 2012, we have observed the geomagnetic field using a HTS-SQUID magnetometer at Iwaki observation site (IWK) in Fukushima, Japan. The sampling interval of the magnetometer is 0.04 sec. The observation clock has been synchronized by use of GPS signals. An accelerometer is also installed at observation point. Additionally, in the next stage, we develop the HTS- SQUID magnetometer system Unit No.2 (mark II). In the present study, we show the results observed by our HTS-SQUID magnetometer system and make an evaluation of our geomagnetic field observation system.

  16. Two-particle self-consistent analysis for the electron-hole asymmetry of superconductivity in cuprate superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, Daisuke; Kuroki, Kazuhiko [Department of Physics, Graduate School of Science, Osaka University, Toyonaka (Japan)

    2017-06-15

    In the hole-doped type cuprate superconductors, it is well-known that the superconducting transition temperature T{sub c} exhibits a dome-like structure against doping. On the other hand, recent experiments unveil that T{sub c} in the electron-doped compounds shows a monotonic increase with decreasing the doping, at least down to a very small doping rate. Our recent study for the three-band d-p model has unveiled that this asymmetric behavior can be explained as a combined effect of the intrinsic electron-hole asymmetry in systems comprising Cu3 d and O2 p orbitals and the band-filling-dependent vertex correction. In the present study, we study another compound Tl{sub 2} Ba{sub 2} CuO{sub 6} to show that this explanation can be applied to other cuprate superconductors with the small d{sub z{sup 2}} orbital mixture. By varying the d-p offset, we also study how the strength of the d-p hybridization controls the spin fluctuation and hence the pairing interaction. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Two-component energy spectrum of cuprates in the pseudogap phase and its evolution with temperature and at charge ordering

    Science.gov (United States)

    Gor'kov, Lev P.; Teitel'Baum, Gregory B.

    2015-02-01

    In the search for mechanisms of high-temperature superconductivity it is critical to know the electronic spectrum in the pseudogap phase from which superconductivity evolves. The lack of angle-resolved photoemission data for every cuprate family precludes an agreement as to its structure, doping and temperature dependence and the role of charge ordering. Here we show that, in the entire Fermi-liquid-like regime that is ubiquitous in underdoped cuprates, the spectrum consists of holes on the Fermi arcs and an electronic pocket. We argue that experiments on the Hall coefficient identify the latter as a permanent feature at doped hole concentration x > 0.08-0.10, in contrast to the idea of the Fermi surface reconstruction via charge ordering. The longstanding issue of the origin of the negative Hall coefficient in YBCO and Hg1201 at low temperature is resolved: the electronic contribution prevails as mobility of the latter (evaluated by the Dingle temperature) becomes temperature independent, while the mobility of holes scattered by the short-wavelength charge density waves decreases.

  18. Adhesion strength study of IBAD-MOCVD-based 2G HTS wire using a peel test

    International Nuclear Information System (INIS)

    Zhang, Y.; Hazelton, D.W.; Knoll, A.R.; Duval, J.M.; Brownsey, P.; Repnoy, S.; Soloveichik, S.; Sundaram, A.; McClure, R.B.; Majkic, G.; Selvamanickam, V.

    2012-01-01

    A peel test was used to study the adhesion strength of a commercial grade 2G HTS wire which features a characteristic multilayer structure with the rare earth-based MOCVD superconducting film deposited on an IBAD-MgO template. The peel test could be carried out at various peeling angles (from 90° to 180°) and the peel strength of a wire was defined as the steady-state peeling load determined from a load-displacement curve. The test results had good reproducibility and accuracy, making the test a reliable and useful method for studying the adhesion strength of the wire. By characterizing the peeled surfaces the weakest interface in a wire could be identified. The peel strength data of the wire was analyzed together with the performance of the experimental magnet coils fabricated using the wire. The effect of the silver contact layer annealing on the peel strength is discussed.

  19. Adhesion strength study of IBAD-MOCVD-based 2G HTS wire using a peel test

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y., E-mail: yzhang@superpower-inc.com [SuperPower Inc., 450 Duane Avenue, Schenectady, NY 12304 (United States); Hazelton, D.W.; Knoll, A.R.; Duval, J.M.; Brownsey, P.; Repnoy, S.; Soloveichik, S.; Sundaram, A.; McClure, R.B. [SuperPower Inc., 450 Duane Avenue, Schenectady, NY 12304 (United States); Majkic, G.; Selvamanickam, V. [University of Houston, 4800 Calhoun Road, Houston, TX 77204 (United States)

    2012-02-15

    A peel test was used to study the adhesion strength of a commercial grade 2G HTS wire which features a characteristic multilayer structure with the rare earth-based MOCVD superconducting film deposited on an IBAD-MgO template. The peel test could be carried out at various peeling angles (from 90 Degree-Sign to 180 Degree-Sign) and the peel strength of a wire was defined as the steady-state peeling load determined from a load-displacement curve. The test results had good reproducibility and accuracy, making the test a reliable and useful method for studying the adhesion strength of the wire. By characterizing the peeled surfaces the weakest interface in a wire could be identified. The peel strength data of the wire was analyzed together with the performance of the experimental magnet coils fabricated using the wire. The effect of the silver contact layer annealing on the peel strength is discussed.

  20. Effect of Fast Neutron Irradiation on Current Transport Properties of HTS Materials

    CERN Document Server

    Ballarino, A; Kruglov, V S; Latushkin, S T; Lubimov, A N; Ryazanov, A I; Shavkin, S V; Taylor, T M; Volkov, P V

    2004-01-01

    The effect of fast neutron irradiation with energy up to 35 MeV and integrated fluence of up to 5 x 10**15 cm-2 on the current transport properties of HTS materials Bi-2212 and Bi-2223 has been studied, both at liquid nitrogen and at room temperatures. The samples irradiated were selected after verification of the stability of their superconducting properties after temperature cycling in the range of 77 K - 293 K. It has been found that the irradiation by fast neutrons up to the above dose does not produce a significant degradation of critical current. The effect of room temperature annealing on the recovery of transport properties of the irradiated samples is also reported, as is a preliminary microstructure investigation of the effect of irradiation on the soldered contacts.

  1. Thermomechanical Properties of 30M HTS Power Cable in DAPAS Project

    Science.gov (United States)

    Kim, D. H.; Kim, C. D.; Kim, I. S.; Park, I. S.; Jang, H. M.; Lee, C. Y.; Kim, D. W.

    2006-04-01

    The 22.9 kV 3 phase 30 m HTS (High Temperature Superconducting) power cable system that contributes to the research for commercial applications was developed as a part of "DAPAS (Dream for Advanced Power system by Applied Superconductivity technologies) Project" in Korea. LS Cable Ltd. has been playing a significant role in design, manufacture, installation, and test of the 30m power cable system. The manufacture and the installation of the cable system were completed in 2004. We performed the initial cool down and the basic operation test of the cable system. We have performed a long period of operation test of the cable system since February 2005. This paper reports the thermo-mechanical properties of the cable system measured during test.

  2. AC magnetization loss characteristics of HTS coated-conductors with magnetic substrates

    International Nuclear Information System (INIS)

    Tsukamoto, O.; Liu, M.; Odaka, S.; Miyagi, D.; Ohmatsu, K.

    2007-01-01

    AC magnetization loss characteristics of an HTS coated tape conductor with magnetic substrate subjected to an external AC magnetic field were investigated. The external magnetic field was perpendicular or parallel to the wide face of the tape conductor. Magnetization losses in the conductor and in the magnetic substrate itself without the superconductor layer, were measured by electric and calorimetric methods. The influence of the magnetic property of the substrate was strongly dependent on the direction of the external magnetic field. When the external magnetic field was perpendicular, magnetic property of the substrate did not affect the magnetization loss characteristics. This result suggests that the magnetization losses can be reduced by subdivisions of the superconducting layers even in the case of magnetic substrate conductors. When the external magnetic field was parallel, the magnetization losses were dominated by the losses in the magnetic substrate. Therefore, to reduce the magnetization losses in this case, reduction of magnetization losses in the substrate is necessary

  3. DC current distribution mapping system of the solar panels using a HTS-SQUID gradiometer

    International Nuclear Information System (INIS)

    Miyazaki, Shingo; Kasuya, Syohei; Saari, Mohd Mawardi; Sakai, Kenji; Kiwa, Toshihiko; Tsukada, Keiji; Tsukamoto, Akira; Adachi, Seiji; Tanabe, Keiichi

    2014-01-01

    Solar panels are expected to play a major role as a source of sustainable energy. In order to evaluate solar panels, non-destructive tests, such as defect inspections and response property evaluations, are necessary. We developed a DC current distribution mapping system of the solar panels using a High Critical Temperature Superconductor Superconducting Quantum Interference Device (HTS-SQUID) gradiometer with ramp edge type Josephson junctions. Two independent components of the magnetic fields perpendicular to the panel surface (∂Bz/∂x, ∂Bz/∂y) were detected. The direct current of the solar panel is visualized by calculating the composition of the two signal components, the phase angle, and mapping the DC current vector. The developed system can evaluate the uniformity of DC current distributions precisely and may be applicable for defect detection of solar panels.

  4. Investigation of a magnetic flux-guide for a HTS scanning superconducting quantum interference device microscope

    International Nuclear Information System (INIS)

    Baek, B; Moon, S H; Lee, Su-Young; Lee, S M; Kye, J I; Lee, H J; Khim, Z G

    2004-01-01

    A magnetic flux-guide in the form of a sharp needle is known to enhance the spatial resolution of the scanning SQUID microscope. We investigated the properties of a soft ferromagnetic tip as a flux-guide by measuring the local field of the tip end. The effects of the flux-guide, such as the transmission of a magnetic signal, length dependence, and nonlinear distortion, were observed. We also present the design and construction of a HTS scanning SQUID microscope with a flux-guide and a planar gradiometer. The gradiometer with a flux-guide is an appropriate solution for improving the performance of the scanning SQUID microscope with a flux-guide as regards the prevention of external field noise without magnetic shields

  5. Electron-lattice interactions strongly renormalize the charge-transfer energy in the spin-chain cuprate Li.sub.2./sub.CuO.sub.2./sub.

    Czech Academy of Sciences Publication Activity Database

    Johnston, S.; Monney, C.; Bisogni, V.; Zhou, K.J.; Kraus, R.; Behr, G.; Strocov, V.N.; Málek, Jiří; Drechsler, S.L.; Geck, J.; Schmitt, T.; van den Brink, J.

    2016-01-01

    Roč. 7, Feb (2016), 1-7, č. článku 10653. ISSN 2041-1723 Institutional support: RVO:68378271 Keywords : X-ray scattering * electron-lattice interactions * spin-chain cuprates * renormalization of charge- transfer energy Subject RIV: BE - Theoretical Physics Impact factor: 12.124, year: 2016

  6. Helimagnetism and weak ferromagnetism in NaCu.sub.2./sub.O.sub.2./sub. and related frustrated chain cuprates

    Czech Academy of Sciences Publication Activity Database

    Drechsler, S.-L.; Tristan, N.; Klingeler, R.; Büchner, B.; Richter, J.; Málek, Jiří; Volkova, O.; Vasiliev, A.; Schmitt, M.; Ormeci, A.; Loison, C.; Schnelle, W.; Rosner, H.

    2007-01-01

    Roč. 19, č. 14 (2007), 145230/1-145230/7 ISSN 0953-8984 Institutional research plan: CEZ:AV0Z10100520 Keywords : chain cuprates * helicoidal magnetic ordering * weak ferromagnetism Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.886, year: 2007

  7. The effect of gap fluctuations on interacting and non-interacting polarization for nano-superconducting grains in electron- and hole-doped cuprates

    Science.gov (United States)

    Afzali, R.; Alizadeh, A.

    2017-12-01

    The behavior of non-interacting and interacting polarization under influence of fluctuations of the superconducting gap with D-wave symmetry and under consideration of the gap dependence on nano- grain size is obtained in terms of the frequency, temperature and the size at zero and finite temperatures for rectangular cuprate nano-superconducting grains. By using Eliashberg equations and applying the relations of the fermionic dispersion for the hole-doped and electron-doped cuprates, we numerically compute the real part of size-dependent polarization for both types of cuprates. We show that the peak of real part of polarization moves to higher frequency by including the additional fluctuating part of gap (or the nano-size effect). Also, we obtain the temperatures for different frequencies, in which the effect of gap fluctuations fades. In the case of size-dependent gap, there is a critical frequency; for frequencies lower (higher) than the critical frequency, the nano-effect weakens (improves) the superconducting state. Moreover, it is concluded that the real part of polarization for hole- doped cuprates in terms of the grain size has more significant amount in comparison with electron-doped ones.

  8. Topological superconductivity and Majorana fermions in hybrid structures involving cuprate high-Tc superconductors

    Science.gov (United States)

    Takei, So; Fregoso, Benjamin M.; Galitski, Victor; Das Sarma, S.

    2013-01-01

    The possibility of inducing topological superconductivity with cuprate high-temperature superconductors (HTSC) is studied for various heterostructures. We first consider a ballistic planar junction between a HTSC and a metallic ferromagnet. We assume that inversion symmetry breaking at the tunnel barrier gives rise to Rashba spin-orbit coupling in the barrier and allows equal-spin triplet superconductivity to exist in the ferromagnet. Bogoliubov-de Gennes equations are obtained by explicitly modeling the barrier and taking account of the transport anisotropy in the HTSC. By making use of the self-consistent boundary conditions and solutions for the barrier and HTSC regions, an effective equation of motion for the ferromagnet is obtained where Andreev scattering at the barrier is incorporated as a boundary condition for the ferromagnetic region. For a ferromagnet layer deposited on a (100) facet of the HTSC, triplet p-wave superconductivity is induced. For the layer deposited on a (110) facet, the induced gap does not have the p-wave orbital character, but has an even orbital symmetry and an odd dependence on energy. For the layer on the (001) facet, an exotic f-wave superconductivity is induced. We also consider the induced triplet gap in a one-dimensional half-metallic nanowire deposited on a (001) facet of a HTSC. Due to the breaking of translational symmetry in the direction perpendicular to the wire axis, the expression for the gap receives contributions from different perpendicular momentum eigenstates in the superconductor. We find that for a wire axis along the a axis, these different contributions constructively interfere and give rise to a robust triplet p-wave gap. For a wire oriented 45∘ away from the a axis, the different contributions destructively interfere and the induced triplet p-wave gap vanishes. For the appropriately oriented wire, the induced p-wave gap may give rise to Majorana fermions at the ends of the half-metallic wire. In light of the

  9. Neutron diffraction and oxide research

    International Nuclear Information System (INIS)

    Hunter, B.; Howard, C.J.; Kennedy, B.J.

    1999-01-01

    Oxide compounds form a large class of interesting materials that have a diverse range of mechanical and electronic properties. This diversity and its commercial implications has had a significant impact on physics research. This is particularly evident in the fields of superconductivity magnetoresistivity and ferroelectricity, where discoveries in the last 15 years have given rise to significant shifts in research activities. Historically, oxides have been studied for many years, but it is only recently that significant effort has been diverted to the study of oxide materials for their application to mechanical and electronic devices. An important property of such materials is the atomic structure, for the determination of which diffraction techniques are ideally suited. Recent examples of structure determinations using neutron diffraction in oxide based systems are high temperature superconductors, where oxygen defects are a key factor. Here, neutron diffraction played a major role in determining the effect of oxygen on the superconducting properties. Similarly, neutron diffraction has enjoyed much success in the determination of the structures of the manganate based colossal magnetoresistive (CMR) materials. In both these cases the structure plays a pivotal role in determining theoretical models of the electronic properties. The neutron scattering group at ANSTO has investigated several oxide systems using neutron powder diffraction. Two such systems are presented in this paper; the zirconia-based materials that are used as engineering materials, and the perovskite-based oxides that include the well known cuprate superconductors and the manganate CMR materials

  10. Novel attempt to create uniform magnetic-field space generated by face-to-face settled HTS bulk magnets

    International Nuclear Information System (INIS)

    Oka, Tetsuo; Ichiju, Kana; Higa, Kazuya; Fukui, Satoshi; Ogawa, Jun; Sato, Takao; Yokoyama, Kazuya; Nakamura, Takashi

    2017-01-01

    Various experimental attempts have been made to obtain a uniform magnetic field in the space between face-to-face HTS bulk magnets that could possibly be utilized as NMR magnets. In general, the magnetic fields emitted from the magnetic pole surfaces containing HTS bulk magnets are characterized as non-uniform field distributions. Since the NMR magnets require highly uniform magnetic-field spaces, it has been assumed to be difficult to form uniform magnetic-field spaces between magnetic poles placed face-to-face. The authors modified the shapes of the magnetic-field distribution from convex to concave by attaching ferromagnetic iron plates to the pole surfaces. The magnets were then set face-to-face with various gaps of 30-70 mm, and the experimental data on magnetic-field uniformity was precisely measured in the space. In order to detect the NMR signals, the target performance for uniformity was set as 1,500 ppm throughout the 4-mm span on the x-axis, which is equivalent to performance in the past when the world's first detection of NMR signals was observed in the bore of hollow-type HTS bulk magnets. When we combined the concave and convex field distributions to compensate the uneven field distributions, the data of the best uniformity reached 358 ppm and 493 ppm in the 30 mm and 50 mm gaps, respectively, which exceeded the target value for the purpose of detecting the NMR signals within the space. Furthermore, it was shown that the field distributions change from concave to convex shape without any change at 1.1 T in the range from 7 to 11 mm in the 30-mm gap, indicating that the distributions are uniform. This suggests the possibility that the uniform magnetic-field space between the HTS bulk magnets set face-to-face expands. (author)

  11. Effects of magnetic field on the cuprate high-Tc superconductor La2-xSrxCuO4

    DEFF Research Database (Denmark)

    Lake, B.; Aeppli, G.; Christensen, N.B.

    2004-01-01

    This article discusses neutron scattering measurements on the cuprate, high transition temperature superconductor La2-xSrxCuO4 (LSCO) in an applied magnetic field. LSCO is a type-II superconductor and magnetic flux can penetrate the material via the formation of vorticies. Phase coherent...... = 7.5 T show that inelastic sub-gap spin fluctuations first disappear with the loss of finite resistivity at T-irr, but then reappear at a lower temperature with increased lifetime and correlation length compared to the normal state. In the underdoped system elastic antiferromagnetism develops below T......-c in zero field, and is significantly enhanced by application of a magnetic field; phase coherent superconductivity is then established within the anti- ferromagnetic phase at T-irr. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim....

  12. Angle-resolved photoemission studies of lattice polaron formation in the cuprate Ca2CuO2Cl2

    Energy Technology Data Exchange (ETDEWEB)

    Shen, K.M.

    2010-05-03

    To elucidate the nature of the single-particle excitations in the undoped parent cuprates, we have performed a detailed study of Ca{sub 2}CuO{sub 2}Cl{sub 2} using photoemission spectroscopy. The photoemission lineshapes of the lower Hubbard band are found to be well-described by a polaron model. By comparing the lineshape and temperature dependence of the lower Hubbard band with additional O 2p and Ca 3p states, we conclude that the dominant broadening mechanism arises from the interaction between the photohole and the lattice. The strength of this interaction was observed to be strongly anisotropic and may have important implications for the momentum dependence of the first doped hole states.

  13. Application of the new LDA+GTB method for the band structure calculation of n-type cuprates

    International Nuclear Information System (INIS)

    Korshunov, M.M.; Ovchinnikov, S.G.; Gavrichkov, V.A.; Nekrasov, I.A.; Pchelkina, Z.V.; Anisimov, V.I.

    2006-01-01

    A novel hybrid scheme is proposed and applied for band structure calculations of undoped n-type cuprate Nd 2 CuO 4 . The ab initio LDA calculation is used to obtain single electron and Coulomb parameters of the multiband Hubbard-type model. In strong correlation regime the electronic structure within this model is calculated by the generalized tight-binding (GTB) method, that combines the exact diagonalization of the model Hamiltonian for a small cluster with perturbation treatment of the intercluster hopping and interactions. For Nd 2 CuO 4 , this scheme results in charge transfer insulator with value of the gap and band dispersion in agreement to the experimental data

  14. The intrinsic crossing point of the magnetization vs. temperature curves in superconducting cuprates in the high-magnetic-field limit

    International Nuclear Information System (INIS)

    Mosqueira, J.; Torron, C.; Veira, J.A.; Vidal, F.

    1998-01-01

    The crossing point of the magnetization vs. temperature curves that appears below T c in highly anisotropic superconducting cuprates was measured in different compounds, with a different number, N, of superconducting CuO 2 layers per periodicity length, s, and also with different values of s. By correcting the measurements from different extrinsic inhomogeneity effects through the Meissner fraction, it is demonstrated experimentally for the first time that in the high-magnetic-field limit the intrinsic crossing point may be explained at a quantitative level in terms of the Tesanovic and coworkers approach based on thermal fluctuations of quasi-2D vortices (pancakes), with an effective periodicity length equal to s, independently of N. (orig.)

  15. Transformation of the superconducting gap to an insulating pseudogap at a critical hole density in the cuprates

    Science.gov (United States)

    Liu, Ye-Hua; Wang, Wan-Sheng; Wang, Qiang-Hua; Zhang, Fu-Chun; Rice, T. M.

    2017-07-01

    We apply the recent wave-packet formalism developed by Ossadnik to describe the origin of the short-range ordered pseudogap state as the hole doping is lowered through a critical density in cuprates. We argue that the energy gain that drives this precursor state to Mott localization, follows from maximizing umklapp scattering near the Fermi energy. To this end, we show how energy gaps driven by umklapp scattering can open on an appropriately chosen surface, as proposed earlier by Yang, Rice, and Zhang. The key feature is that the pairing instability includes umklapp scattering, leading to an energy gap not only in the single-particle spectrum but also in the pair spectrum. As a result the superconducting gap at overdoping is turned into an insulating pseudogap in the antinodal parts of the Fermi surface.

  16. IrSr2TbCu2O8, a high-pressure metamagnetic cuprate: Structure, microstructure and properties

    International Nuclear Information System (INIS)

    Dos Santos-Garcia, A.J.; Duijn, J. van; Saez-Puche, R.; Heymann, G.; Huppertz, H.; Alario-Franco, M.A.

    2008-01-01

    The synthesis, structure and microstructure of the IrSr 2 TbCu 2 O 8 cuprate showing metamagnetic properties are described. The sample was prepared at high temperatures and pressures up to 9.2 GPa. The structure is tetragonal, showing a 1212 type structure, that derives from the classical YBaCuO superconductor structure, replacing the tetracoordinated square planar copper [Cu-O 4 ] in the 'chains' by octahedral [Ir-O 6 ] groups that form a perovskite-like layer in the basal plane of the unit cell. A 'simple' cell, ∼a p xa p x3a p , where a p is the basic perovskite unit cell parameter (a p ∼3.8 A), is supported by X-ray powder diffraction (XRD) and a so-called 'diagonal' one, ∼√2a p x√2a p x3a p , by SAED; a microdomain texture of latter cell and a series of very interesting extended defects have been observed by HREM. Magnetic susceptibility measurements show a magnetic transition, T N ∼6 K, with negative Weiss temperature, that indicates antiferromagnetic interactions among the Tb moments. The magnetic structure has been determined by neutron diffraction. A detailed magnetic study has revealed a metamagnetic behavior, something not previously observed in this type of cuprates. Specific heat and resistivity measurements have also been performed to characterize the transition. - Graphical abstract: Reconstructed image from the SAED of the long c tetragonal axis (3a p ) of a IrSr 2 TbCu 2 O 8 crystal. A unit cell picture is included for comparison. Display Omitted

  17. Pairing symmetries of several iron-based superconductor families and some similarities with cuprates and heavy-fermions

    Directory of Open Access Journals (Sweden)

    Das Tanmoy

    2012-03-01

    Full Text Available We show that, by using the unit-cell transformation between 1 Fe per unit cell to 2 Fe per unit cell, one can qualitatively understand the pairing symmetry of several families of iron-based superconductors. In iron-pnictides and iron-chalcogenides, the nodeless s±-pairing and the resulting magnetic resonance mode transform nicely between the two unit cells, while retaining all physical properties unchanged. However, when the electron-pocket disappears from the Fermi surface with complete doping in KFe2As2, we find that the unit-cell invariant requirement prohibits the occurrence of s±-pairing symmetry (caused by inter-hole-pocket nesting. However, the intra-pocket nesting is compatible here, which leads to a nodal d-wave pairing. The corresponding Fermi surface topology and the pairing symmetry are similar to Ce-based heavy-fermion superconductors. Furthermore, when the Fermi surface hosts only electron-pockets in KyFe2-xSe2, the inter-electron-pocket nesting induces a nodeless and isotropic d-wave pairing. This situation is analogous to the electron-doped cuprates, where the strong antiferromagnetic order creates similar disconnected electron-pocket Fermi surface, and hence nodeless d-wave pairing appears. The unit-cell transformation in KyFe2-xSe2 exhibits that the d-wave pairing breaks the translational symmetry of the 2 Fe unit cell, and thus cannot be realized unless a vacancy ordering forms to compensate for it. These results are consistent with the coexistence picture of a competing order and nodeless d-wave superconductivity in both cuprates and KyFe1.6Se2.

  18. Modelling of the fin type heat exchanger for the HTS current leads of W7-X and JT-60SA

    Science.gov (United States)

    Heller, R.; Class, A.; Batta, A.; Lietzow, R.; Neumann, H.; Tischmacher, M.

    2010-03-01

    The Forschungszentrum Karlsruhe has taken over the responsibility for the design, construction and testing of the high temperature superconductor (HTS) current leads for two fusion experiments, i.e. the stellarator Wendelstein 7-X (W7-X) and the satellite tokamak JT-60SA. One important task for the design of the HTS current lead is the heat exchanger (HEX). In the current leads for W7-X and JT-60SA the HEX consists of the central conductor with meander flow fins to achieve a cross flow HEX. A design optimisation requires the knowledge of the heat transfer characteristics of the HEX. Therefore, 3D CFD simulations were performed to compute local Nusselt and Reynolds numbers. From the CFD results a 1D system code description and heat transfer correlations have been deduced. This paper describes the 3D-CFD and 1D system code as well as the results of the numerical calculations. The results were validated using experimental results of HEX mock-ups. The model was extended to the HEX covering the temperature range between 60 K and room temperature leading to a single Nusselt-Reynolds number correlation. Finally the parameters for optimised HTS current leads for W7-X and JT-60SA are presented.

  19. Magnetic separation technique for groundwater by five HTS melt-processed bulk magnets arranged in a line

    International Nuclear Information System (INIS)

    Oka, T.; Seki, H.; Kimura, T.; Mimura, D.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Fujishiro, H.; Hayashi, H.; Yokoyama, K.; Stiehler, C.

    2011-01-01

    A magnetic separation was practically conducted by 10-pole HTS bulk magnets. The HTS bulk magnets were activated to 2.5 T by feeding pulsed fields of 6 T. The separation ratio of actual groundwater exceeded 70% at less than 4.8 l/min. The flocks without magnetite powder were obviously attracted to the magnetic poles. A magnetic separation study for groundwater purification has been practically conducted by using the multi-pole magnet system. The magnetic pole was composed of 10 open magnetic spaces by arranging five HTS melt-processed bulk magnets in a line in a vacuum sheath. The individual bulk magnets were activated by feeding intense pulsed magnetic fields up to 6 T. The magnetic field distribution was estimated with respect to various pole arrangements. The actual groundwater samples of Sanjo City were processed so as to form large precipitates by adding the coagulant and pH controlling. The maximum separation ratio of the iron-bearing precipitates has exceeded over 70% when slurry water was exposed to 10 magnetic poles of up to 2.5 T at a flowing rate of less than 4.8 l/min. An obvious attraction of flocks to the magnetic poles was observed even when the water contains no magnetite powder at the flow rate of 1.01 l/min. This implies the validity of the multi-pole magnet system with respect to the actual application to water purification.

  20. Evaluation of mechanical and thermal properties of insulation materials for HTS power devices at liquid nitrogen temperature

    Energy Technology Data Exchange (ETDEWEB)

    Shin, Hyung Seop; Diaz, Mark Angelo [Dept. of Mechanical Design Engineering, Andong National University, Andong (Korea, Republic of)

    2017-06-15

    In superconducting power devices including power cables in which high temperature superconducting (HTS) tapes are utilized, a reliable electrical insulation should be achieved for its maximum performance. For an efficient design of HTS superconducting devices, a comparative evaluation of the mechanical and thermal propperties for various insulation materials at cryogenic temperatures is required. Especially, in the process of the property evaluation of the sheet-shaped insulation materials, anisotropy according to the machining direction should be considered because the mechanical and thermal properties are significantly influenced by the sample orientation. In this study, the cryogenic thermal and mechanical properties of various insulation material sheets such as PPLP, Cryoflex, Teflon, and Kapton were determined considering sample orientation. All samples tested at cryogenic temperature showed significantly higher tensile strength as compared with that of room temperature. The ultimate tensile strength at both temperature conditions significantly depended upon the sample orientation. The thermal properties of the insulation materials exhibited a slight difference among samples depending on the orientation: for the PPLP and Cryoflex, the CD orientation showed larger thermal contraction up to 77 K as compared to the MD one. MD samples in PPLP and Cryoflex showed a lower CTE and thermal contraction which made it more promising as an insulation material due to its comparable CTE with HTS CC tapes.

  1. Study of the electric Held in HTS tape caused by perpendicular AC magnetic field

    International Nuclear Information System (INIS)

    Roiberg, V; Kopansky, F.

    2004-01-01

    Full Text: In a previous work we studied the influence of AC magnetic fields on voltage-currents (V-I) characteristics of high temperature superconducting (HTS) multi filament BSCC0-2223 tapes. It was found that AC magnetic fields perpendicular to the ab plane (the wide surface of the tape) cause a linear decrease of the critical current (IC) with amplitude of the AC magnetic field. The degradation of IC in .AC field was explained by the geometrical model according to which the transport current floe: is confined to the central zone of the tape where .AC field does not penetrate. For deeper understanding of the observed phenomena we carried out a study of the time dependence of the electric field during the cycle of AC field. At the same time we expanded the frequency range to low frequencies down to 1 Hz. The main results of the work are as following. 1. The time modulation of the electric field E in the HTS tape carrying transport DC current has the double frequency relating to AC magnetic field. 2. In field amplitudes less than 70 G the electric field modulation decreases with increasing frequency in opposite to its well-pronounced increase in higher AC field amplitudes. Alcove 70 G, the electric field increases with increasing the frequency of the external magnetic field. The wave forms of the electric field are different in both amplitudes ranges. 3. E-I curves of the tape in low amplitudes are frequency independent and coincide with E-l curves in AC field with intensity equal to the AC field amplitude. 4. In high AC field amplitudes, a strong dependence of the E-I curves on frequency is observed in the frequency range of 1-40 Hz and no dependence is observed in higher frequencies. Our results suggest that a combination of the geometrical model with flux creep concepts is necessary for a better understanding of the electric field behavior in our measurement conditions

  2. Foetal magnetocardiography with a multi-channel HTS rf SQUID gradiometer

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Y [Institute of Thin Films and Interfaces, Forschungszentrum Juelich, 52425 Juelich (Germany); Wolters, N [Institute of Thin Films and Interfaces, Forschungszentrum Juelich, 52425 Juelich (Germany); Lomparski, D [Institute of Thin Films and Interfaces, Forschungszentrum Juelich, 52425 Juelich (Germany); Zander, W [Institute of Thin Films and Interfaces, Forschungszentrum Juelich, 52425 Juelich (Germany); Banzet, M [Institute of Thin Films and Interfaces, Forschungszentrum Juelich, 52425 Juelich (Germany); Schubert, J [Institute of Thin Films and Interfaces, Forschungszentrum Juelich, 52425 Juelich (Germany); Krause, H-J [Institute of Thin Films and Interfaces, Forschungszentrum Juelich, 52425 Juelich (Germany); Geue, D [Groenemeyer Institute for Microtherapy, University of Witten/Herdecke, Universitaetsstrasse 142, D-44799 Bochum (Germany); Leeuwen, P van [Groenemeyer Institute for Microtherapy, University of Witten/Herdecke, Universitaetsstrasse 142, D-44799 Bochum (Germany)

    2006-05-15

    Foetal magnetocardiography (fMCG) is a promising technique for prenatal cardiac diagnosis. In this paper, we discuss the special requirements of a system for fMCG measurements. A SQUID system incorporating five HTS rf SQUID magnetometers has been developed and constructed. Four magnetometers are arranged at the bottom of the cryostat in a 4 cm x 4 cm square configuration. One reference magnetometer is located 20 cm above the plane to form four first-order axial gradiometers with the four bottom magnetometers. The magnetometer with a 18 mm diameter flux focuser, which reaches a field sensitivity of 20-30 fT Hz{sup -1/2}, proved sufficient for recording foetal magnetocardiograms in a magnetically shielded room. The cardiac activities of two foetuses (31st and 33rd weeks of gestation) were recorded in 90 Hz bandwidth. The foetal QRS peak signals ranged from 4 to 7 pT and could easily be identified in the real-time gradiometer outputs with a signal-to-noise ratio of up to five. Furthermore, the averaged fMCG data enabled the determination of de- and repolarization time intervals. Overall, the fMCG signals proved of sufficient quality to perform foetal heart diagnostics.

  3. Reaction wheel with HTS bearings for mini-satellite attitude control

    Science.gov (United States)

    Zhang, Yong; Postrekhin, Yevgeniy; Bui Ma, Ki; Chu, Wei-Kan

    2002-05-01

    We have developed a small reaction wheel, designed to be lightweight, compact and energy efficient. The main innovation is the use of the HTS magnet's bearings that promise low friction so that high momentum storage can be achieved with high spin speed. The bearings consist of seeded growth superconducting discs arranged in rings located above and below the rotating levitated wheel containing ring-magnets embedded at the top and bottom. The reaction wheel is in the shape of a hollow stainless steel cylinder. A brushless dc motor is installed inside the hollow cylinder to provide the necessary torque to the reaction wheel. The maximum design spin speed is 15 000 RPM to store 3.5 J s-1 of angular momentum. Spin-down test of the reaction wheel was performed in air. We have also measured the input power required to sustain rotational speed of the reaction wheel in air. Results from both of these measurements, when extrapolated to full speed in vacuum, indicate that power consumption, even accounting for the needs of the cooling system, is significantly smaller than that for state of the art commercial reaction wheels using mechanical ball bearings.

  4. Pareto-Optimization of HTS CICC for High-Current Applications in Self-Field

    Directory of Open Access Journals (Sweden)

    Giordano Tomassetti

    2018-01-01

    Full Text Available The ENEA superconductivity laboratory developed a novel design for Cable-in-Conduit Conductors (CICCs comprised of stacks of 2nd-generation REBCO coated conductors. In its original version, the cable was made up of 150 HTS tapes distributed in five slots, twisted along an aluminum core. In this work, taking advantage of a 2D finite element model, able to estimate the cable’s current distribution in the cross-section, a multiobjective optimization procedure was implemented. The aim of optimization was to simultaneously maximize both engineering current density and total current flowing inside the tapes when operating in self-field, by varying the cross-section layout. Since the optimization process involved both integer and real geometrical variables, the choice of an evolutionary search algorithm was strictly necessary. The use of an evolutionary algorithm in the frame of a multiple objective optimization made it an obliged choice to numerically approach the problem using a nonstandard fast-converging optimization algorithm. By means of this algorithm, the Pareto frontiers for the different configurations were calculated, providing a powerful tool for the designer to achieve the desired preliminary operating conditions in terms of engineering current density and/or total current, depending on the specific application field, that is, power transmission cable and bus bar systems.

  5. The influence of oxygen content on the Tc of HTS Hg-1245

    International Nuclear Information System (INIS)

    Itskevich, E.S.

    1999-01-01

    We have observed an extraordinary behavior oh the Hg Ba 2 Ca 4 Cu 5 O 12+δ layered HTS (phase 1245) in the over doped state. Earlier we have synthesized the phase Hg-1245 with different oxygen content and consequently different values of the lattice parameter a. We have observed a coincidence of a values when the T c (a) cupolas reach their maxima for phases Hg-1223, 1234, 1245 and a merging of their over doped parts together with abrupt falling off of the T c values. The Hg-1245 phase has shown the most unusual behavior. Contrary to other phases, this one contains three types of Cu O 2 layers in a unit cell. We supposed that, in the case of the Hg-1245 phase, the holes coming from the reservoir, which is the Hg-O plane, cannot reach the 'far' Cu O 2 layer which is notable for this phase. We have calculated the hole concentration for each layer for 1223, 1234 and 1245 phases. The hole concentration appears negligibly small for the over doped 1245 phase. We can consider the 'fifth' Cu O 2 layer as not taking part in superconductivity. The analysis of the behavior of the T c (a) cupolas for the phases with different number of Cu O 2 layers and of hole density distribution between the layers has been carried out

  6. Project Overview of HTS Magnet for Ultra-high-field MRI System

    Science.gov (United States)

    Tosaka, Taizo; Miyazaki, Hiroshi; Iwai, Sadanori; Otani, Yasumi; Takahashi, Masahiko; Tasaki, Kenji; Nomura, Shunji; Kurusu, Tsutomu; Ueda, Hiroshi; Noguchi, So; Ishiyama, Atsushi; Urayama, Shinichi; Fukuyama, Hidenao

    A project to develop an ultra-high-field magnetic resonance imaging (MRI) system based on HTS magnets using (RE)Ba2Cu3O7 (REBCO; RE=rear earth) coils is underway. The project is supported by the Japanese Ministry of Economy, Trade and Industry and aims to establish magnet technologies for a whole-body 9.4 T MRI system. REBCO wires have high critical current density in high magnetic fields and high strength against hoop stresses, and therefore, MRI magnets using REBCO coils are expected to have cryogenic systems that are smaller, lighter, and simpler than the conventional ones. A major problem in using REBCO coils for MRI magnets is the huge irregular magnetic field generated by the screening current in REBCO tapes. Thus, the main purpose of this project is to make the influence of this screening current predictable and controllable. Fundamental technologies, including treatment of the screening currents, were studied via experiments and numerical simulations using small coils. Two types of model magnets are planned to be manufactured, and the knowledge gained in the development of the model magnets will be reflected in the magnet design of a whole-body 9.4 T MRI system.

  7. Effects of High Temperature Heat Treatment on the Microstructure and Superconducting Property of HTS Coated Conductor

    International Nuclear Information System (INIS)

    Doh, Min Ho; Hong, Gye Won; Lee, Hee Gyoun

    2009-01-01

    HTS coated conductor was heat treated at high temperatures below the melting points of silver and YBCO at different oxygen partial pressures. Current carrying capacity and microstructure were varied depending on the presence of silver protection layer. Critical current of coated conductor without silver protection layer was not changed when heat treatment was performed at 850 degree C for 2 hr in an oxygen atmosphere. However, coated conductor with silver protection layer revealed abrupt drop of Ic from 140 A to 8 A when heat treatment was performed at 800 degree C for 2 hr in an oxygen atmosphere. Coated conductor with silver protection layer retained 70-80 percent of its original I c when heat treatment was performed at 800 degree C for 2 hr in an argon atmosphere containing 1000 ppm oxygen. SEM and XRD observations showed the presence of interaction between YBCO and silver depending on the atmosphere of heat treatment. The reaction between YBCO superconductor and silver was accelerated at high oxygen partial pressure and resulted in the change in microstructure and decrease of critical current density even by the heat treatment performed at temperature much lower than the melting points of silver and YBCO.

  8. R&D Progress of HTS Magnet Project for Ultrahigh-field MRI

    Science.gov (United States)

    Tosaka, Taizo; Miyazaki, Hiroshi; Iwai, Sadanori; Otani, Yasumi; Takahashi, Masahiko; Tasaki, Kenji; Nomura, Shunji; Kurusu, Tsutomu; Ueda, Hiroshi; Noguchi, So; Ishiyama, Atsushi; Urayama, Shinichi; Fukuyama, Hidenao

    An R&D project on high-temperature superconducting (HTS) magnets using rare-earth Ba2Cu3O7 (REBCO) wires was started in 2013. The project objective is to investigate the feasibility of adapting REBCO magnets to ultrahigh field (UHF) magnetic resonance imaging (MRI) systems. REBCO wires are promising components for UHF-MRI magnets because of their superior superconducting and mechanical properties, which make them smaller and lighter than conventional ones. Moreover, REBCO magnets can be cooled by the conduction-cooling method, making liquid helium unnecessary. In the past two years, some test coils and model magnets have been fabricated and tested. This year is the final year of the project. The goals of the project are: (1) to generate a 9.4 T magnetic field with a small test coil, (2) to generate a homogeneous magnetic field in a 200 mm diameter spherical volume with a 1.5 T model magnet, and (3) to perform imaging with the 1.5 T model magnet. In this paper, the progress of this R&D is described. The knowledge gained through these R&D results will be reflected in the design of 9.4 T MRI magnets for brain and whole body imaging.

  9. Recent development status of stirling type pulse tube cryocooler for HTS

    International Nuclear Information System (INIS)

    Hiratsuka, Y; Nakano, K; Kato, T

    2014-01-01

    Sumitomo Heavy Industries, Ltd. (SHI) has been developing a high power stirling type pulse tube cryocooler. For the purpose of cooling high-temperature superconductor (HTS) devices, such as superconductor motor, SMES and current fault limiter, requested specifications from the devices to a cryocooler are compact size, light weight, high efficiency and high reliability. Especially, the cryocooler must be demanded COP > 0.1 in the efficiency. The experimental results of prototype pulse tube cryocooler were reported in June 2012 [1]. For an In-line type expander, the cooling capacity was 210 W at 77 K and the minimum temperature was 37 K when the compressor input power was 3.8 kW and the operating frequency was 49 Hz. Accordingly, COP was about 0.055. Moreover, for miniaturization a U type expander was tested and the performance is about 10 % less than that of an In-line type expander. After that, we have estimated that the cooling performance is influenced by the environment such as the effect of the pulse-tube inclination, the temperature and the flowing quantity of cooling water. The detailed results are reported in this paper.

  10. Study of reverse Brayton cryocooler with Helium-Neon mixture for HTS cable

    Science.gov (United States)

    Dhillon, A. K.; Ghosh, P.

    2017-12-01

    As observed in the earlier studies, helium is more efficient than neon as a refrigerant in a reverse Brayton cryocooler (RBC) from the thermodynamic point of view. However, the lower molecular weight of helium leads to higher refrigerant inventory as compared to neon. Thus, helium is suitable to realize the high thermodynamic efficiency of RBC whereas neon is appropriate for the compactness of the RBC. A binary mixture of helium and neon can be used to achieve high thermodynamic efficiency in the compact reverse Brayton cycle (RBC) based cryocooler. In this paper, an attempt has been made to analyze the thermodynamic performance of the RBC with a binary mixture of helium and neon as the working fluid to provide 1 kW cooling load for high temperature superconductor (HTS) power cables working with a temperature range of 50 K to 70 K. The basic RBC is simulated using Aspen HYSYS V8.6®, a commercial process simulator. Sizing of each component based on the optimized process parameters for each refrigerant is performed based on a computer code developed using Engineering Equation Solver (EES-V9.1). The recommendation is provided for the optimum mixture composition of the refrigerant based on the trade-off factors like thermodynamic efficiency such as the exergy efficiency and equipment considerations. The outcome of this study may be useful for recommending a suitable refrigerant for the RBC operating at a temperature level of 50 K to 70 K.

  11. ARPES study of T*-phase cuprate superconductor SmLa0.85Sr0.15CuO4-δ

    International Nuclear Information System (INIS)

    Ino, A.; Higashiguchi, M.; Yamazaki, K.; Yamasaki, T.; Narimura, T.; Kobayashi, K.; Shimada, K.; Namatame, H.; Taniguchi, M.; Yoshida, T.; Fujimori, A.; Shen, Z.-X.; Kakeshita, T.; Uchida, S.; Adachi, S.; Tajima, S.

    2004-01-01

    The electronic structure of the T*-phase cuprate superconductor SmLa0.85Sr0.15CuO4-δ has been studied by angle-resolved photoemission spectroscopy (ARPES). While a clear Fermi surface has been observed near (π/2,π/2), the electronic band is lowered to ∼-180meV around (π,0) due to the pseudogap formation. These features are quite similar to the ARPES result of Ca 1.9 Na 0.1 CuO 2 Cl 2 rather than La 2-x Sr x CuO 4 . We have also observed a distinct 'kink' in the nodal band dispersion as in all the other hole-doped cuprates

  12. Spin-fluctuation mediated superconductivity and magnetic order in the cuprate La1.88Sr0.12CuO4

    DEFF Research Database (Denmark)

    Rømer, Astrid Tranum

    High-temperature superconductivity in cuprates emerges as one out of many electronic phases when doping the antiferromagnetic Mott insulator La2CuO4 away from half _lling. The description of the superconducting phase is therefore complicated by intertwined electronic orders that compete...... with superconductivity. However, it is possible that the tendency towards additional ordering phenomena is a necessary condition for unconventional superconductivity to develop. Indeed most superconductors discovered throughout the last 29 years, including also the recently discovered class of iron-based superconductors......, show a very rich electronic phase diagram. A common feature that characterizes both cuprates, heavy fermions, and iron pnictides is the proximity to magnetic order. Therefore, the idea of spin-uctuation mediated pairing is a popular paradigm proposed for unconventional superconductivity. A _ngerprint...

  13. STM sub-gap structure in cuprates is a consequence of density waves, according to Mean-Field Theory and CDMFT

    Science.gov (United States)

    Verret, Simon; Roy, Jyotirmoy; Sénéchal, David; Tremblay, A.-M. S.

    Much work has been done to find how the pseudogap is related to charge density waves in cuprates. In scanning tunneling microscopy (STM) measurements, the superconducting gap and pseudogap of cuprates are sometimes accompanied by a small sub-gap structure at very low energy. This was documented early in vortex cores studies, and has now been reported at zero field for YBCO.(1) Here, we show that this can be caused by density waves, first through a standard mean-field approach, and then with Cellular Dynamical Mean-Field Theory for the Hubbard model using an exact diagonalization solver. We comment on the implication of these results for the relation between pseudogap and charge order. (1) Jens Bruér et al. arXiv:1507.06775 Supported by NSERC, CIFAR and the Tier I Canada Research Chair Program.

  14. Magnetic properties of high quality single crystals of the electron underdoped cuprate superconductor Nd{sub 2-x}Ce{sub x}CuO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Dorantes, Alma; Qi, Cai; Kartsovnik, Mark; Erb, Andreas [Walther-Meissner Institut, Garching (Germany)

    2015-07-01

    We present investigations of the magnetic properties of the electron-doped cuprate superconductor Nd{sub 2-x}Ce{sub x}CuO{sub 4} (NCCO) with particular attention to the underdoped regime of the phase diagram. Special attention is given to the region between the antiferromagnetic (AF) and superconducting (SC) state of the electron-doped cuprate superconductors. We tried to investigate whether the AF and SC regions are separated by an intrinsic phase separation or if a microscopic coexistence exists between these two states. Experiments on high quality single crystals were performed to probe the relation between the transition temperature (T{sub c}) and dopant concentration x, and to estimate the superconducting volume fraction. The results indicated that a SC transition can be observed after an appropriate annealing process, even for highly underdoped samples and that bulk superconductivity is present. In addition we find indications of a deviation in the monotonic doping dependence of the transition temperature T{sub c} between samples with 12% and 13% Ce doping, which could signify a first evidence of the so-called 1/8 anomaly in the electron-doped cuprate superconductors.

  15. Angle-resolved photoelectron spectroscopy studies of the many-body effects in the electronic structure of high-T{sub c} cuprates

    Energy Technology Data Exchange (ETDEWEB)

    Inosov, Dmytro S.

    2008-06-18

    In the present work some steps are done towards understanding the anomalous effects observed in the single-particle excitation spectra of cuprates. First, the electronic properties of BSCCO are considered. The main result of this part of the work is a model of the Green's function that is later used for calculating the two-particle excitation spectrum. Then, the matrix element effects in the photoemission spectra of cuprates are discussed. After a general introduction to the problem, the thesis focuses on the recently discovered anomalous behavior of the ARPES spectra that partially originates from the momentum-dependent photoemission matrix element. The momentum- and excitation energy dependence of the anomalous high-energy dispersion, termed ''waterfalls'', is covered in full detail. Understanding the role of the matrix element effects in this phenomenon proves crucial, as they obstruct the view of the underlying excitation spectrum that is of indisputable interest. For the optimally doped bilayer Bi-based cuprate, the renormalized two-particle correlation function in the superconducting state is calculated from ARPES data within an itinerant model based on the random phase approximation (RPA). (orig.)

  16. Thermodynamic properties of underdoped YBa2Cu3O6+x cuprates for doping values x ∈ (0 . 5 , 0 . 9)

    Science.gov (United States)

    Salas, P.; Solis, M. A.; Fortes, M.

    We extend the Boson-Fermion superconductivity model to include layered systems, such as underdoped cuprate superconductors YBa2Cu3O6+x, with x ∈ (0 . 5 , 0 . 9) ranging from underdoped to optimally doped. We model cuprates as a boson-fermion quantum gas mixture immersed in a layered structure, generated via a Dirac comb potential applied in one direction while the particles move freely in the other two directions. The optimum parameters of the system, which are the impenetrability of the planes and the paired fermion fraction, are obtained by minimizing the Helmholtz free energy and setting the experimental critical temperature Tc. Using this optimized scheme, we are able to predict the following thermodynamic properties of cuprates as a function of temperature: the entropy; the Helmholtz free energy; the electronic specific heat and the total specific heat for different doping values. Furthermore, we determinate the behavior of the jump height in the electronic specific heat, the normal electronic specific heat coefficient γ (Tc) , the quadratic α and cubic β terms of the specific heat for low temperatures, the ground state energy and the mass anisotropy as a function of doping. Comparison to experimental values reported is analyzed. We aknowledge the support from Grants UNAM-DGAPA-PAPIIT IN-111613 and CONACYT 221030, Mexico.

  17. Oxide superconductors

    International Nuclear Information System (INIS)

    Cava, R.J.

    2000-01-01

    This article briefly reviews ceramic superconductors from historical and materials perspectives. It describes the factors that distinguish high-temperature cuprate superconductors from most electronic ceramics and places them in the context of other families of superconducting materials. Finally, it describes some of the scientific issues presently being actively pursued in the search for the mechanism for high-temperature superconductivity and the directions of research into new superconducting ceramics in recent years

  18. Numerical evaluation of guidance force decay of HTS bulk exposed to AC magnetic field over a NdFeB guideway

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Longcai [P.O. Box 152, Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)], E-mail: zhlcai2000@163.com; Wang Jiasu; Wang Suyu; Zheng Jun; He Qingyong [P.O. Box 152, Applied Superconductivity Laboratory, Southwest Jiaotong University, Chengdu, Sichuan 610031 (China)

    2007-12-01

    The guidance force of the YBCO bulk over a NdFeB guideway used in the high-temperature superconducting maglev vehicle system was decayed by the application of the AC external magnetic field. In our previous work, we explained that the decay was due to the temperature rise of the HTS bulk caused by AC losses. In this paper, we adopted an analytic model to evaluate the decay of the critical current density of the bulk. And based on the analytic results and the Bean critical-state model, we calculated the guidance force as a function of times. Compared with the experimental results, the calculation results have almost the same trend and can qualitatively reveal the characteristics of guidance force of HTS bulk in this situation. Therefore, the guidance force decay of HTS bulk in the maglev vehicle system can be evaluated simply by this numerical method.

  19. Pulsed laser deposition of {CeO_2} and {Ce_{1-x}M_xO_2} (M = La, Zr): Application to insulating barrier in cuprate heterostructures

    Science.gov (United States)

    Berger, S.; Contour, J.-P.; Drouet, M.; Durand, O.; Khodan, A.; Michel, D.; Régi, F.-X.

    1998-03-01

    SrTiO_3 had been often tentatively used as an insulating barrier for HT superconductor/insulator heterostructures. Unfortunately, the deposition of SrTiO_3 on the YBa_2Cu_3O_7 inverse interface results in a poor epitaxial regrowth producing a high roughness dislocated titanate layer. Taking into account the good matching with YBa_2Cu_3O_7 and LaAlO_3, CeO_2 and Ce_{1-x}M_xO_2 (M = La, Zr), epitaxial layers were grown by pulsed laser deposition on LaAlO_3 substrates and introduced into YBa_2Cu_3O_7 based heterostructures as insulating barrier. After adjusting the growth parameters from RHEED oscillations, epitaxial growth is achieved, the oxide crystal axes being rotated by 45^circ from those of the substrate. The surface roughness of 250 nm thick films is very low with a rms value lower than 0.5 nm over 1;μ m^2. The YBa_2Cu_3O_7 layers of a YBa_2Cu_3O_7/CeO_2 /YBa_2Cu_3O_7 heterostructures grown using these optimized parameters show an independent resistive transition, when the thickness is larger than 25 nm, respectively at T_c_1 = 89.6;K and T_c_2 = 91.4;{K}. SrTiO3 est souvent utilisé comme barrière isolante dans des hétérostructures SIS de cuprates supraconducteurs, cependant les défauts générés lors de la croissance de ce titanate sur l'interface inverse de YBa2Cu3O7 conduisent à un matériau dont la qualité cristalline et les propriétés physiques sont médiocres. L'oxyde de cérium CeO2 est également une barrière isolante potentielle intéressante pour ces structures SIS basées sur YBa2Cu3O7 car cet oxyde cubique (a = 0,5411 nm, asqrt{2}/2 = 0,3825 nm) qui est peu désaccordé par rapport au plan ab du cuprate (Δ a/a = - 0,18 %, Δ b/a = 1,6 %) présente de plus un coefficient de dilatation thermique (10,6 × 10^{-6 circ}C^{-1}) très voisin de celui de YBa2Cu3O7 (13 × 10^{-6 circ}C^{-1}). Nous avons donc étudié l'épitaxie de CeO2 et des oxydes de type Ce{1-x}MxO2 (M = La, Zr) en ablation laser pulsée afin de définir des conditions de

  20. Nernst effect in the electron-doped cuprate superconductor L a2 -xC exCu O4

    Science.gov (United States)

    Mandal, P. R.; Sarkar, Tarapada; Higgins, J. S.; Greene, Richard L.

    2018-01-01

    We report a systematic study of the Nernst effect in films of the electron-doped cuprate superconductor L a2 -xC exCu O4 as a function of temperature and magnetic field (up to 14 T) over a range of doping from underdoped (x =0.08 ) to overdoped (x =0.16 ). We have determined the characteristic field scale HC2 * of superconducting fluctuation which is found to track the domelike dependence of superconductivity (TC). The fall of HC2 * and TC with underdoping is most likely due to the onset of long-range antiferromagnetic order. We also report the temperature onset, Tonset, of superconducting fluctuations above TC. For optimally doped x =0.11 Tonset (≅39 K ) is high compared to TC (26 K). For higher doping Tonset decreases and tends to zero along with the critical temperature at the end of the superconducting dome. The superconducting gap closely tracks HC2 * measured from the temperature- and field-dependent Nernst signal.

  1. Radiation of terahertz electromagnetic waves from build-in nano Josephson junctions of cuprate high-T(c) superconductors.

    Science.gov (United States)

    Lin, Shi-Zeng; Hu, Xiao

    2011-04-01

    The nano-scale intrinsic Josephson junctions in highly anisotropic cuprate superconductors have potential for generation of terahertz electromagnetic waves. When the thickness of a superconductor sample is much smaller than the wavelength of electromagnetic waves in vacuum, the superconductor renders itself as a cavity. Unlike conventional lasers, the presence of the cavity does not guarantee a coherent emission because of the internal degree of freedom of the superconductivity phase in long junctions. We study the excitation of terahertz wave by solitons in a stack of intrinsic Josephson junctions, especially for relatively short junctions. Coherent emission requires a rectangular configuration of solitons. However such a configuration is unstable against weak fluctuations, contrarily solitons favor a triangular lattice corresponding to an out-phase oscillation of electromagnetic waves. To utilize the cavity, we propose to use an array of stacks of short intrinsic Josephson junctions to generate powerful terahertz electromagnetic waves. The cavity synchronizes the plasma oscillation in different stacks and the emission intensity is predicted to be proportional to the number of stacks squared.

  2. Screening of point charge impurities in highly anisotropic metals: application to mu+-spin relaxation in underdoped cuprate superconductors.

    Science.gov (United States)

    Shekhter, Arkady; Shu, Lei; Aji, Vivek; MacLaughlin, D E; Varma, C M

    2008-11-28

    We calculate the screening charge density distribution due to a point charge, such as that of a positive muon (mu+), placed between the planes of a highly anisotropic layered metal. In underdoped hole cuprates the screening charge converts the charge density in the metallic-plane unit cells in the vicinity of the mu+ to nearly its value in the insulating state. The current-loop-ordered state observed by polarized neutron diffraction then vanishes in such cells, and also in nearby cells over a distance of order the intrinsic correlation length of the loop-ordered state. This strongly suppresses the magnetic field at the mu+ site. We estimate this suppressed field in underdoped YBa2Cu3O6+x and La2-xSrxCuO4, and find consistency with the observed approximately 0.2 G field in the former case and the observed upper bound of approximately 0.2 G in the latter case. This resolves the controversy between the neutron diffraction and mu-spin relaxation experiments.

  3. Sharp low-energy feature in single-particle spectra due to forward scattering in d-wave cuprate superconductors.

    Science.gov (United States)

    Hong, Seung Hwan; Bok, Jin Mo; Zhang, Wentao; He, Junfeng; Zhou, X J; Varma, C M; Choi, Han-Yong

    2014-08-01

    There is an enormous interest in the renormalization of the quasiparticle (qp) dispersion relation of cuprate superconductors both below and above the critical temperature T_{c} because it enables the determination of the fluctuation spectrum to which the qp's are coupled. A remarkable discovery by angle-resolved photoemission spectroscopy (ARPES) is a sharp low-energy feature (LEF) in qp spectra well below the superconducting energy gap but with its energy increasing in proportion to T_{c} and its intensity increasing sharply below T_{c}. This unexpected feature needs to be reconciled with d-wave superconductivity. Here, we present a quantitative analysis of ARPES data from Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} (Bi2212) using Eliashberg equations to show that the qp scattering rate due to the forward scattering impurities far from the Cu-O planes is modified by the energy gap below T_{c} and shows up as the LEF. This is also a necessary step to analyze ARPES data to reveal the spectrum of fluctuations promoting superconductivity.

  4. Mechanical Effects of the Non-Uniform Current Distribution on HTS Coils for Accelerators Wound with REBCO Roebel Cable

    CERN Document Server

    Murtomaeki, Jaako; Kirby, Glen; Rossi, Lucio; Ruuskanen, Janne; Stenvall, Antti; Murtomaeki, Jaako

    2017-01-01

    Future high-energy accelerators will need very high magnetic fields in the range of 20 T. The EuCARD-2 WP10 Future Magnets collaboration is aiming at testing HTS-based Roebel cables in an accelerator magnet. The demonstrator should produce around 17 T, when inserted into the 100 mm aperture of Feather-M2 13 T outsert magnet. HTS Roebel cables are assembled from meander shaped REBCO coated conductor tapes. In comparison with fair level of uniformity of current distribution in cables made out of round Nb-Ti or Nb$_{3}$Sn strands, current distribution within the coils wound from Roebel cables is highly non-homogeneous. It results in nonuniform electromagnetic force distribution over the cable that could damage the very thin REBCO superconducting layer. This paper focuses on the numerical models to describe the effect of the non-homogenous current distribution on stress distribution in the demonstrator magnet designed for the EuCARD-2 project. Preliminary results indicate that the impregnation bonding betweenthe...

  5. 380 kW synchronous machine with HTS rotor windings--development at Siemens and first test results

    Science.gov (United States)

    Nick, W.; Nerowski, G.; Neumüller, H.-W.; Frank, M.; van Hasselt, P.; Frauenhofer, J.; Steinmeyer, F.

    2002-08-01

    Applying HTS conductors in the rotor of synchronous machines allows the design of future motors or generators that are lighter, more compact and feature an improved coefficient of performance. To address these goals a project collaboration was installed within Siemens, including Automation & Drives, Large Drives as a leading supplier of electrical machines, Corporate Technology as a competence center for superconducting technology, and other partners. The main task of the project was to demonstrate the feasibility of basic concepts. The rotor was built from racetrack coils of Bi-2223 HTS tape conductor, these were assembled on a core and fixed by a bandage of glass-fibre composite. Rotor coil cooling is performed by thermal conduction, one end of the motor shaft is hollow to give access for the cooling system. Two cooling systems were designed and operated successfully: firstly an open circuit using cold gaseous helium from a storage vessel, but also a closed circuit system based on a cryogenerator. To take advantage of the increased rotor induction levels the stator winding was designed as an air gap winding. This was manufactured and fitted in a standard motor housing. After assembling of the whole system in a test facility with a DC machine load experiments have been started to prove the validity of our design, including operation with both cooling systems and driving the stator from the grid as well as by a power inverter.

  6. HTS dual-band bandpass filters using stub-loaded hair-pin resonators for mobile communication systems

    Energy Technology Data Exchange (ETDEWEB)

    Sekiya, N., E-mail: nsekiya@yamanashi.ac.jp; Sugiyama, S.

    2014-09-15

    Highlights: • We have developed a HTS five-pole dual-band bandpass filter using stub-loaded hair-pin resonators. • The proposed dual-band BPF can independently control of the center frequency. • Flexibly adjustment of the bandwidth can be achieved by the H-shaped waveguide. • The proposed BPF is evaluated by simulation and measurement with good agreement. - Abstract: A HTS dual-band bandpass filter is developed to obtain sharp-cut off characteristics for mobile communication systems. The filter is composed of five stub-loaded hair-pin resonators with H-shaped waveguides between them. The main advantage of the proposed filter is to allow independent control of the center frequency of the first and second bands. The bandwidths can be flexibly adjusted using the H-shaped waveguide. An electromagnetic simulator was used to design and analyze the filter, which have a 3.5-GHz center frequency and a 70-MHz (2%) bandwidth for the first band and a 5.0-GHz center frequency and a 100-MHz (2%) bandwidth for the second band. The filter was fabricated using YBa{sub 2}Cu{sub 3}O{sub y} thin film on an Al{sub 2}O{sub 3} substrate. Ground plane was fabricated using Au thin film. The measured frequency responses of the filter tally well with the simulated ones.

  7. Inhomogeneity of surface magnetic field over a NdFeB guideway and its influence on levitation force of the HTS bulk maglev system

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Longcai [Applied Superconductivity Laboratory, Southwest Jiaotong University, P.O. Box 152, Chengdu 610031 (China)]. E-mail: zhlcai2000@163.com; Wang Jiasu [Applied Superconductivity Laboratory, Southwest Jiaotong University, P.O. Box 152, Chengdu 610031 (China); He Qingyong [Applied Superconductivity Laboratory, Southwest Jiaotong University, P.O. Box 152, Chengdu 610031 (China); Zhang Jianghua [Applied Superconductivity Laboratory, Southwest Jiaotong University, P.O. Box 152, Chengdu 610031 (China); Wang Suyu [Applied Superconductivity Laboratory, Southwest Jiaotong University, P.O. Box 152, Chengdu 610031 (China)

    2007-08-01

    Superconducting maglev vehicle system was one of the most promising applications of HTS bulks. The NdFeB guideway in this system was composed of many NdFeB permanent magnets and screws, so the air gaps (airgaps) between two permanent magnets and the screws would result in the inhomogeneity of the surface magnetic field. In this paper, we studied the magnetic inhomogeneity over the permanent magnet guideway (PMG) used in high-temperature superconducting (HTS) maglev vehicle system and its influence on the levitation force of the HTS bulk. Firstly, we measured the transverse magnetic field above the airgap, the screw and the place under where there was no airgap and screw. It was found that the magnetic field 10 mm above the guideway was roughly uniform. Secondly, we investigated the influence of the magnetic inhomogeneity of the PMG on levitation force of the bulk superconductor. From the experiment results, we found that the influence was very small, and would be ignored. Therefore, we could conclude that the PMG made by this method satisfied the requirements of the HTS maglev vehicle system in a quasi-static state.

  8. A comparison on the heat load of HTS current leads with respect to uniform and non-uniform cross-sectional areas

    Energy Technology Data Exchange (ETDEWEB)

    Han, Seung Hak; Nam, Seok Ho; Lee, Je Yull; Song, Seung Hyun; Jeon, Hae Ryong; Baek, Geon Woo; Ko, Tae Kuk [Yonsei University, Seoul (Korea, Republic of); Kang, Hyoung Ku [Korea National University of Transportation, Chungju (Korea, Republic of)

    2017-09-15

    Current lead is a device that connects the power supply and superconducting magnets. High temperature superconductor (HTS) has lower thermal conductivity and higher current density than normal metal. For these reasons, the heat load can be reduced by replacing the normal metal of the current lead with the HTS. Conventional HTS current lead has same cross-sectional area in the axial direction. However, this is over-designed at the cold-end (4.2 K) in terms of current. The heat load can be reduced by reducing this part because the heat load is proportional to the cross-sectional area. Therefore, in this paper, heat load was calculated from the heat diffusion equation of HTS current leads with uniform and non-uniform cross-sectional areas. The cross-sectional area of the warm-end (65K) is designed considering burnout time when cooling system failure occurs. In cold-end, Joule heat and heat load due to current conduction occurs at the same time, so the cross-sectional area where the sum of the two heat is minimum is obtained. As a result of simulation, current leads for KSTAR TF coils with uniform and non-uniform cross-sectional areas were designed, and it was confirmed that the non-uniform cross-sectional areas could further reduce the heat load.

  9. Nodeless superconductivity in the infinite-layer electron-doped Sr_0.9La_0.1CuO_2 cuprate superconductor

    OpenAIRE

    Khasanov, R.; Shengelaya, A.; Maisuradze, A.; Di Castro, D.; Savić, I. M.; Weyeneth, S.; Park, M. S.; Jang, D. J.; Lee, S. -I.; Keller, H.

    2008-01-01

    We report on measurements of the in-plane magnetic penetration depth \\lambda_{ab} in the infinite-layer electron-doped high-temperature cuprate superconductor Sr_0.9La_0.1CuO_2 by means of muon-spin rotation. The observed temperature and magnetic field dependences of \\lambda_{ab} are consistent with the presence of a substantial s-wave component in the superconducting order parameter in good agreement with the results of tunneling, specific heat, and small-angle neutron scattering experiments.

  10. Characteristics of an HTS-SQUID gradiometer with ramp-edge Josephson junctions and its application on robot-based 3D-mobile compact SQUID NDE system

    Energy Technology Data Exchange (ETDEWEB)

    Hatsukade, Y., E-mail: hatukade@ens.tut.ac.jp [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Hayashi, K.; Shinyama, Y.; Kobayashi, Y. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Adachi, S.; Tanabe, K. [International Superconductivity Technology Center/Superconductivity Research Laboratory, 10-13, Shinonome 1-chome, Koto-ku, Tokyo 135-0062 (Japan); Tanaka, S. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan)

    2011-11-15

    We investigated behavior of HTS-dc-SQUID gradiometers with ramp-edge Josephson junctions (JJs) in ac and dc magnetic fields. In the both fields, the gradiometers show higher durability against entry of flux vortices than SQUIDs with bicrystal JJs. A robot-based SQUID NDE system utilizing the gradiometer was developed in an unshielded environment. Detectability of the system to detect non-through cracks in double-layer structures was demonstrated. A new excitation coil was applied to detect cracks that oriented vertical and parallel to the baseline of the gradiometer. In this paper, we investigated detailed behavior of novel HTS-dc-SQUID gradiometers with ramp-edge Josephson junctions (JJs) in both an ac magnetic field and a dc magnetic field. In the both fields, the novel gradiometers shows the superior performance to the conventional YBa{sub 2}Cu{sub 3}O{sub 7-x} (YBCO) HTS-dc-SQUID gradiometer and a bare HTS-dc-SQUID ring with bicrystal JJs concerning durability against entry and hopping of flux vortices, probably due to their differential pickup coils without a grain boundary and multilayer structure of the ramp-edge JJs. A robot-based compact HTS-SQUID NDE system utilizing the novel gradiometer was reviewed, and detectability of the system to detect non-through cracks in a carbon fiber reinforced plastic (CFRP)/Al double-layer structure was demonstrated. A new excitation coil in which the supplied currents flowed in the orthogonal directions was applied to detect cracks that oriented vertical and parallel to the baseline of the gradiometer.

  11. A universal order underlying the pseudogap regime of the underdoped high Tc cuprates

    Science.gov (United States)

    Harrison, Neil

    2014-03-01

    A major achievement in condensed matter physics in the last quarter century has been a step towards the understanding of the unconventional d-wave superconducting state in the copper-oxide materials. Surprisingly, the normal state out of which the superconducting state emerges remains a mystery at low charge carrier densities, i.e., in the underdoped regime. This regime is of particular interest because it is characterised by an unusual momentum dependent energy pseudogap in the excitation spectrum that has defied explanation and is key to a full understanding of the unconventional d-wave superconducting state. I will present new quantum oscillation experimental results within the pseudogap regime of the high Tc superconductors YBa2Cu3O6+x and YBa2Cu4O8 which now extend up to the optimally-doped regime. These data reveal the evolution of the Fermi surface approaching the putative quantum critical point under the superconducting dome. A comprehensive angle-resolved study of the Fermi surface enables us to unambiguously identify a specific form of order that accounts for the observed quantum oscillations as well as other spectroscopic, transport and thermodynamic probes within the pseudogap regime. The author would like to thank B. Ramshaw, S. Sebastian, F. Balakirev, C. Mielke, M. Altarawneh, P. Goddard, S. Sabok, B. Babrowski, D. Bonn, W. Hardy, R. Liang and G. Lonzarich. This work was supported by the DOE BES ``Science of 100 tesla'' project and by the NSF and Florida State.

  12. Dynamical magnetic susceptibility in the spin-fermion model for cuprate superconductors

    Science.gov (United States)

    Val'kov, V. V.; Dzebisashvili, D. M.

    2017-12-01

    Using the method of diagram techniques for the spin and Fermi operators in the framework of the SU(2)- invariant spin-fermion model of the electron structure of the CuO 2 plane of copper oxides, we obtain an exact representation of the Matsubara Green's function D ⊥( k, iω m ) of the subsystem of localized spins. This representation includes the Larkin mass operator ΣL( k, iω m ) and the strength and polarization operators P( k, iω m ) and Π( k, iω m ). The calculation in the one-loop approximation of the mass and strength operators for the Heisenberg spin system in the quantum spin-liquid state allows writing the Green's function D ⊥( k, iω m ) explicitly and establishing a relation to the result of Shimahara and Takada. An essential point in the developed approach is taking the spin-polaron nature of the Fermi quasiparticles in the spin-fermion model into account in finding the contribution of oxygen holes to the spin response in terms of the polarization operator Π( k, iω m ).

  13. ∊-constraint heat transfer search (∊-HTS algorithm for solving multi-objective engineering design problems

    Directory of Open Access Journals (Sweden)

    Mohamed A. Tawhid

    2018-01-01

    Full Text Available In this paper, an effective ∊-constraint heat transfer search (∊-HTS algorithm for the multi-objective engineering design problems is presented. This algorithm is developed to solve multi-objective optimization problems by evaluating a set of single objective sub-problems. The effectiveness of the proposed algorithm is checked by implementing it on multi-objective benchmark problems that have various characteristics of Pareto front such as discrete, convex, and non-convex. This algorithm is also tested for several distinctive multi-objective engineering design problems, such as four bar truss problem, gear train problem, multi-plate disc brake design, speed reducer problem, welded beam design, and spring design problem. Moreover, the numerical experimentation shows that the proposed algorithm generates the solution to represent true Pareto front.

  14. Multi-scale model of resistive-type superconducting fault current limiters based on 2G HTS coated conductors

    Science.gov (United States)

    Bonnard, Charles-Henri; Sirois, Frédéric; Lacroix, Christian; Didier, Gaëtan

    2017-01-01

    In order to plan the integration of superconducting fault current limiters (SFCLs) in power systems, accurate models of SFCLs must be made available in commercial power system transient simulators. In this context, we developed such a model for the EMTP-RV software package, a power system transient simulator widely used by power utilities. The model can be used with any resistive-type SFCL (rSFCL) made of high temperature superconductor (HTS) tapes, which are discretized in ‘electro-thermal elements’. Those elements consist solely of electric circuit components, and are used to represent portions of tape of various sizes and dimensions (a ‘multi-scale’ approach). Both the electrical and thermal behaviors of the tape are modeled, including interfacial effects, nonlinear properties of materials and heat transfer to the surrounding environment. Such a multi-scale model can simulate accurately both the local quench dynamics of HTS tapes (microscopic scale) and the global impact of the rSFCL on the power system (macroscopic/system scale). In this paper, the model is used to compute phenomena such as propagation velocity of a hot spot and heat diffusion through the thickness of the tape. Results were verified by comparing EMTP-RV results with finite element simulations. In addition to the development of the multi-scale model itself, which is the major contribution of this paper, the use of the model allowed us to determine the conditions of validity of the commonly used ‘homogenization’ of the thermal properties across the tape thickness. Indeed, when the current flowing into the rSFCL is slightly above its critical current I c (and up to 2{I}{{c}}), very important errors in the power waveforms arise, leading to potentially wrong decisions of protection systems. Homogenized thermal models should thus be used with great care in practice.

  15. Fermi-surface transformation across the pseudogap critical point of the cuprate superconductor La1.6 -xNd0.4SrxCuO4

    Science.gov (United States)

    Collignon, C.; Badoux, S.; Afshar, S. A. A.; Michon, B.; Laliberté, F.; Cyr-Choinière, O.; Zhou, J.-S.; Licciardello, S.; Wiedmann, S.; Doiron-Leyraud, N.; Taillefer, Louis

    2017-06-01

    The electrical resistivity ρ and Hall coefficient RH of the tetragonal single-layer cuprate La1.6 -xNd0.4SrxCuO4 were measured in magnetic fields up to H =37.5 T, large enough to access the normal state at T →0 , for closely spaced dopings p across the pseudogap critical point at p=0.23 . Below p, both coefficients exhibit an upturn at low temperature, which gets more pronounced with decreasing p . Taken together, these upturns show that the normal-state carrier density n at T =0 drops upon entering the pseudogap phase. Quantitatively, it goes from n =1 +p at p =0.24 to n =p at p =0.20 . By contrast, the mobility does not change appreciably, as revealed by the magnetoresistance. Our data are in excellent agreement with recent high-field data on YBa2Cu3Oy and La2 -xSrxCuO4 . The quantitative consistency across three different cuprates shows that a drop in carrier density from 1 +p to p is a universal signature of the pseudogap transition at T =0 . We discuss the implication of these findings for the nature of the pseudogap phase.

  16. Ordered state of magnetic charge in the pseudo-gap phase of a cuprate superconductor (HgBa2CuO4+δ )

    Science.gov (United States)

    Lovesey, S. W.; Khalyavin, D. D.

    2015-12-01

    A symmetry-based interpretation of published experimental results demonstrates that the pseudo-gap phase of underdoped HgBa2CuO4+δ (Hg1201) possesses an ordered state of magnetic charge epitomized by Cu magnetic monopoles. Magnetic properties of one-layer Hg1201 and two-layer YBa2Cu3O6+x (YBCO) cuprates have much in common, because their pseudo-gap phases possess the same magnetic space-group, e.g. both underdoped cuprates allow the magneto-electric (Kerr) effect. Differences in their properties stem from different Cu site symmetries, leaving Cu magnetic monopoles forbidden in YBCO. Resonant x-ray Bragg diffraction experiments can complement the wealth of information available from neutron diffraction experiments on five Hg1201 samples on which our findings are based. In the case of Hg1201 emergence of the pseudo-gap phase, with time-reversal violation, is accompanied by a reduction of Cu site symmetry that includes loss of a centre of inversion symmetry. In consequence, parity-odd x-ray absorption events herald the onset of the enigmatic phase, and we predict dependence of corresponding Bragg spots on magneto-electric multipoles, including the monopole, and the azimuthal angle (crystal rotation about the Bragg wavevector).

  17. Ferro-type order of magneto-electric quadrupoles as an order-parameter for the pseudo-gap phase of a cuprate superconductor

    Science.gov (United States)

    Lovesey, S. W.; Khalyavin, D. D.; Staub, U.

    2015-07-01

    There is general agreement within the community of researchers that investigate high-Tc materials that it is most important to understand the pseudo-gap phase. To this end, many experiments on various cuprates have been reported. Two prominent investigations—Kerr effect and neutron Bragg diffraction—imply that underdoped YBCO samples possess long-range magnetic order of an unusual kind. However, other measurements do not support the existence of magnetic order. Here we show that the Kerr effect and magnetic Bragg diffraction data are individual manifestations of ordered magneto-electric quadrupoles at Cu sites. While the use of magneto-electric multipoles is new in studies of the electronic properties of cuprates, they are not unknown in other materials, including an investigation with x-rays of the parent compound CuO. We exploit the recent prediction that neutrons are deflected by magneto-electric multipoles. The outcome of our study is a theory for the order-parameter of the pseudo-gap phase without the aforementioned conflict with other measurements, and the first experimental evidence that neutrons interact with multipoles belonging to a state of magnetic charge.

  18. Asymptotic Slavery in the Copper Oxide High Temperature Superconductors

    Science.gov (United States)

    Phillips, Philip

    2004-05-01

    Vast progress in theoretical solid state physics has been made by constructing models which mimic the low-energy properties of solids. Essential to the success of this program is the separability of the high and low energy degrees of freedom. While it is hoped that a high energy reduction can be made to solve the problem of high temperature superconductivity in the copper oxide materials, I will show that no consistent theory is possible if the high energy scale is removed. At the heart of the problem is the mixing of all energy scales (that is, UV-IR mixing) in the copper-oxide materials. Optical experiments demonstrate that the number of low-energy degrees of freedom is derived from a high energy scale. The implications of the inseparability of the high and low energy degrees of freedom on the phase diagram of the cuprates is discussed.

  19. Structural phase transitions and superconductivity in lanthanum copper oxides

    International Nuclear Information System (INIS)

    Crawford, M.K.; Harlow, R.L.; McCarron, E.M.

    1996-01-01

    Despite the enormous effort expended over the past ten years to determine the mechanism underlying high temperature superconductivity in cuprates there is still no consensus on the physical origin of this fascinating phenomenon. This is a consequence of a number of factors, among which are the intrinsic difficulties in understanding the strong electron correlations in the copper oxides, determining the roles played by antiferromagnetic interactions and low dimensionality, analyzing the complex phonon dispersion relationships, and characterizing the phase diagrams which are functions of the physical parameters of temperature and pressure, as well as the chemical parameters of stoichiometry and hole concentration. In addition to all of these intrinsic difficulties, extrinsic materials issues such as sample quality and homogeneity present additional complications. Within the field of high temperature superconductivity there exists a subfield centered around the material originally reported to exhibit high temperature superconductivity by Bednorz and Mueller, Ba doped La 2 CuO 4 . This is structurally the simplest cuprate superconductor. The authors report on studies of phase differences observed between such base superconductors doped with Ba or Sr. What these studies have revealed is a fascinating interplay of structural, magnetic and superconducting properties which is unique in the field of high temperature superconductivity and is summarized in this paper

  20. Doping and temperature dependence of the superconducting energy gap in the electron-doped cuprate Pr{sub 2-x}Ce{sub x}CuO{sub 4-{delta}}

    Energy Technology Data Exchange (ETDEWEB)

    Diamant, I., E-mail: diamanti@post.tau.ac.i [Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, 69978 Tel-Aviv (Israel); Greene, R.L. [Center for Nanophysics and Advanced Materials, Physics Department, University of Maryland, College Park, MD 20743 (United States); Dagan, Y. [Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, 69978 Tel-Aviv (Israel)

    2010-12-15

    In hole-doped cuprate superconductors at low carrier concentrations two energy scales are identified: the superconducting energy gap and the pseudogap. The relation between these energy scales is still a puzzle. In these compounds a measurement of the energy gap is not necessarily a probe of the order parameter. In the electron-doped cuprates the pseudogap does not obscure the superconducting state. Consequently, the superconducting gap can be studied directly in a tunneling experiment. Here we show that by studying superconductor/insulator/superconductor planar tunnel junctions we are able to map the behavior of the gap amplitude for the entire (doping-temperature) phase diagram of the electron-doped cuprate superconductor Pr{sub 2-x}Ce{sub x}CuO{sub 4-{delta}}. The superconducting gap, {Delta}, shows a BCS-like temperature dependence even for extremely low carrier concentrations. Moreover, {Delta} follows the doping dependence of T{sub c}. We can therefore conclude that there is a single superconducting energy scale in the electron-doped cuprates.

  1. Proposal to negotiate three collaboration agreements in the context of the Future Circular Collider Study (FCC) concerning the development of HTS coated tapes integrated into the beam screen for impedance mitigation

    CERN Document Server

    2016-01-01

    Proposal to negotiate three collaboration agreements in the context of the Future Circular Collider Study (FCC) concerning the development of HTS coated tapes integrated into the beam screen for impedance mitigation

  2. Influence of B4C-doping and high-energy ball milling on phase formation and critical current density of (Bi,Pb)-2223 HTS

    Science.gov (United States)

    Margiani, N. G.; Mumladze, G. A.; Adamia, Z. A.; Kuzanyan, A. S.; Zhghamadze, V. V.

    2018-05-01

    In this paper, the combined effects of B4C-doping and planetary ball milling on the phase evolution, microstructure and transport properties of Bi1.7Pb0.3Sr2Ca2Cu3Oy(B4C)x HTS with x = 0 ÷ 0.125 were studied through X-ray diffraction (XRD), scanning electron microscopy (SEM), resistivity and critical current density measurements. Obtained results have shown that B4C additive leads to the strong acceleration of high-Tc phase formation and substantial enhancement in Jc. High-energy ball milling seems to produce a more homogeneous distribution of refined doped particles in the (Bi,Pb)-2223 HTS which results in an improved intergranular flux pinning and better self-field Jc performance.

  3. HTS flywheel energy storage system with rotor shaft stabilized by feed-back control of armature currents of motor-generator

    International Nuclear Information System (INIS)

    Tsukamoto, O.; Utsunomiya, A.

    2007-01-01

    We propose an HTS bulk bearing flywheel energy system (FWES) with rotor shaft stabilization system using feed-back control of the armature currents of the motor-generator. In the proposed system the rotor shift has a pivot bearing at one end of the shaft and an HTS bulk bearing (SMB) at the other end. The fluctuation of the rotor shaft with SMB is damped by feed-back control of the armature currents of the motor-generator sensing the position of the rotor shaft. The method has merits that the fluctuations are damped without active control magnet bearings and extra devices which may deteriorate the energy storage efficiency and need additional costs. The principle of the method was demonstrated by an experiment using a model permanent magnet motor

  4. Influence of shape and thickness on the levitation force of YBaCuO bulk HTS over a NdFeB guideway

    International Nuclear Information System (INIS)

    Ren Zhongyou; Wang Jiasu; Wang Suyu; Jiang He; Zhu Min; Wang Xiaorong; Song Honghai

    2003-01-01

    Levitation forces of YBaCuO bulk high temperature superconductors (HTS) with different shape and size over a NdFeB guideway were studied. Here, the concentrating magnetic field of the NdFeB guideway was 1.2 T, and the YBaCuO bulk HTSs include three cylindrical samples with different diameter and thickness and one hexagonal sample. The maximum levitation force is as high as 85.3 N at a gap of 5 mm between the bottom surface of YBaCuO bulk HTS and the top surface of the NdFeB guideway, where the applied magnetic field is about 0.8 T. The results show that the shape and the size have large influences on the levitation force of YBaCuO bulk HTSs

  5. Theoretical estimation of quench occurrence and propagation based on generalized thermoelasticity for LTS/HTS tapes triggered by a spot heater

    Science.gov (United States)

    Tong, Yujin; Guan, Mingzhi; Wang, Xingzhe

    2017-04-01

    The present study deals with the thermal characteristics and mechanical behaviors of low/high temperature superconducting (LTS/HTS) composite tapes during quench processes triggered by a spot heater. Based on the generalized thermoelastic theory, a dynamic thermoelastic model with a relaxation time is developed which takes into account the temperature dependence and finite speed of heat propagation for the superconducting tapes under cryogenic condition. The analyses were performed using the finite element method to solve the coupled differential equations of dynamic heat conduction and elastic equilibrium. The results show that the thermoelastic behaviors exhibit a strong relevance to quench characteristics of the superconductors. As a quench occurs, the thermoelastic strain-rate has an obvious jumping variation with the instant of time of its peak being fortunately coincident with the time at which the critical temperature is reached. Such a jumping change of strain-rate could be a way of estimation and detection of quench occurrence, and the theoretical predictions coincide with the existing experimental observations on thermoelastic strain-rate in LTS magnets. For a HTS tape, the thermoelastic strain-rate or temperature-rate variation and a small jump also are illustrated as the quench occurrence is determined. Additionally, the normal zone propagation velocities for the LTS/HTS tapes are predicted by the critical temperature and thermoelastic strain-rate to show quite good agreements with the results evaluated by Wilson’s formula for a LTS tape or the experimental measurements for a HTS tape. The influences of the relaxation time of heat conduction and thermoelastic coupling on the thermal distribution and strain profile are also discussed in details.

  6. Influence of AC external magnetic field perturbation on the guidance force of HTS bulk over a NdFeB guideway

    International Nuclear Information System (INIS)

    Zhang Longcai; Wang Jiasu; Wang Suyu; He Qingyong

    2007-01-01

    Superconducting maglev vehicle system requires that the surface magnetic field of the guideway is uniform along the forward direction. But in practice the surface magnetic field of the NdFeB permanent magnet guideway is not always immutable. So the HTS bulks in this case are exposed to AC external magnetic field, which may induce the energy loss in the bulk and influence the guidance force between the HTS bulks and the NdFeB guideway. In this paper, we experimentally studied the influence of the AC external magnetic field perturbation on the guidance force of a HTS bulk over the NdFeB guideway. The experimental results showed that the guidance force was influenced by the application of the AC external magnetic. The guidance fore hysteresis became more evident with the amplitude of the AC field and was independent of the frequency in the range 90-400 Hz. We attributed the reason to magnetic hysteresis loss in the superconductor

  7. Influence of AC external magnetic field perturbation on the guidance force of HTS bulk over a NdFeB guideway

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Longcai [Applied Superconductivity Laboratory, Southwest Jiaotong University, P.O. Box 152, Chengdu, Sichuan 610031 (China)]. E-mail: zhlcai2000@163.com; Wang Jiasu [Applied Superconductivity Laboratory, Southwest Jiaotong University, P.O. Box 152, Chengdu, Sichuan 610031 (China); Wang Suyu [Applied Superconductivity Laboratory, Southwest Jiaotong University, P.O. Box 152, Chengdu, Sichuan 610031 (China); He Qingyong [Applied Superconductivity Laboratory, Southwest Jiaotong University, P.O. Box 152, Chengdu, Sichuan 610031 (China)

    2007-08-01

    Superconducting maglev vehicle system requires that the surface magnetic field of the guideway is uniform along the forward direction. But in practice the surface magnetic field of the NdFeB permanent magnet guideway is not always immutable. So the HTS bulks in this case are exposed to AC external magnetic field, which may induce the energy loss in the bulk and influence the guidance force between the HTS bulks and the NdFeB guideway. In this paper, we experimentally studied the influence of the AC external magnetic field perturbation on the guidance force of a HTS bulk over the NdFeB guideway. The experimental results showed that the guidance force was influenced by the application of the AC external magnetic. The guidance fore hysteresis became more evident with the amplitude of the AC field and was independent of the frequency in the range 90-400 Hz. We attributed the reason to magnetic hysteresis loss in the superconductor.

  8. New magnetic rails with double-layer Halbach structure by employing NdFeB and ferrite magnets for HTS maglev

    Science.gov (United States)

    Sun, Ruixue; Zheng, Jun; Zheng, Botian; Qian, Nan; Li, Jipeng; Deng, Zigang

    2018-01-01

    In the high temperature superconducting (HTS) maglev system, the magnetic rail as an essential infrastructure is needed all along the route to carry passengers and goods to the destinations. Thus, large amount of rare earth magnetic materials are required in the magnetic rail construction. In order to decrease the dependence of magnetic rails on rare earth elements, the ferrite magnet is employed to replace part of the NdFeB magnets containing rare earth elements. Consequently, a new type rail with double-layer Halbach structure is presented, which is consisted of NdFeB and ferrite magnets. In this paper, we designed and fabricated the proposed rail, and further measured its magnetic flux density distribution and electromagnetic force interacting with HTS bulks. Experimental results indicate that, this new type rail, in double-layer Halbach structure, can achieve an equivalent distribution of magnetic flux density and levitation performance as the pure NdFeB Halbach rail, while a 10% reduction in NdFeB magnet consumption can be realized at the same time. In addition this work explores another magnetic material selection for HTS maglev applications. The dependence on rare earth element and the cost of magnetic rails can be further reduced, as the coercive force of ferrite magnets improved.

  9. The effect of condensation area and operating temperature on heat transfer capacity of a closed loop thermosyphon cooling system for HTS machinery

    Science.gov (United States)

    Yamaguchi, K.; Miki, M.; Izumi, M.; Murase, Y.; Oryu, T.; Yanamoto, T.

    2017-12-01

    A sophisticated cooling system is necessary for applications of high-temperature superconductor (HTS) for electric devices. Among them, status of rotating machine requests to maintain the temperature of HTS field poles under 40 K. We have employed a thermosyphon (TS) as cooling system for HTS rotating machines. The TS cooling is based on natural convection of coolant and does not require a forced circulation. Advantages of the TS cooling system are simple, light weight mechanical composition and high heat transfer coefficient with latent heat. The operating temperature of the TS cooling system depends on the saturation temperature and the pressure of coolant. Thus, the saturation pressure of the TS affects the performance of the TS cooling system. In this paper, we investigate the relationship between the saturation pressure and the condenser heat transfer area. We studied a heat transfer capacity under the heat load with different neon quantities using the TS cooling system. The saturation pressure increases with the heat load and/or condenser temperature increment. Reducing the number of condensers i.e. decrease of condensation area, the saturation pressure increases and the heat transfer capacity decreases. This result shows that the saturation pressure is proportional to the temperature difference between condenser temperature and the saturation temperature calculated by saturation pressure.

  10. Generic superconducting phase behavior in high-Tc cuprates: Tc variation with hole concentration in YBa2Cu3O7-δ

    International Nuclear Information System (INIS)

    Tallon, J.L.; Bernhard, C.; Shaked, H.; Hitterman, R.L.; Jorgensen, J.D.

    1995-01-01

    A direct determination of the relationship between T c and hole concentration p for Y 1-x Ca x Ba 2 Cu 3 O 7-δ is obtained by investigating the properties of the fully oxygen-deficient (δ∼1.0) compound for which p=x/2. Measurements of T c , the thermoelectric power S, and bond-valence sums calculated from neutron-diffraction refinements for various values of x and δ allow the full determination of the relations p=p(δ), T c =T c (p), and S=S(T,p) confirming that YBa 2 Cu 3 O 7-δ satisfies the same universal relations in these quantities as the other high-T c superconducting cuprates

  11. Multilayered cuprate superconductor Ba2Ca5Cu6O12(O1-x,Fx) 2 studied by temperature-dependent scanning tunneling microscopy and spectroscopy

    Science.gov (United States)

    Sugimoto, Akira; Ekino, Toshikazu; Gabovich, Alexander M.; Sekine, Ryotaro; Tanabe, Kenji; Tokiwa, Kazuyasu

    2017-05-01

    Scanning tunneling microscopy/spectroscopy (STM/STS) measurements were carried out on a multilayered cuprate superconductor Ba2Ca5Cu6O12 (O1 -x,Fx )2. STM topography revealed random spot structures with the characteristic length ≤0.5 nm. The conductance spectra d I /d V (V ) show the coexistence of smaller gaps ΔS and large gaps (pseudogaps) ΔL. The pseudogap-related features in the superconducting state were traced with the spatial resolution of ˜0.07 nm. Here, I and V are the tunnel current and bias voltage, respectively. The temperature, T , dependence of ΔS follows the reduced Bardeen-Cooper-Schrieffer (BCS) dependence. The hallmark ratio 2 ΔS(T =0 ) /kBTc equals to 4.9, which is smaller than those of other cuprate superconductors. Here, Tc is the superconducting critical temperature and kB is the Boltzmann constant. The larger gap ΔL survives in the normal state and even increases with T above Tc. The T dependencies of the spatial distributions for both relevant gaps (Δ map), as well as for each gap separately (ΔS and ΔL), were obtained. From the histogram of Δ map, the averaged gap values were found to be Δ¯S=˜24 meV and Δ¯L=˜79 meV. The smaller gap ΔS shows a spatially homogeneous distribution while the larger gap ΔL is quite inhomogeneous, indicating that rather homogeneous superconductivity coexists with the patchy distributed pseudogap. The spatial variation length ξΔ L of ΔL correlates with the scale of the topography spot structures, being approximately 0.4 nm. This value is considerably smaller than the coherence length of this class of superconductors, suggesting that ΔL is strongly affected by the disorder of the apical O/F.

  12. Status and Progress of a Fault Current Limiting Hts Cable to BE Installed in the con EDISON Grid

    Science.gov (United States)

    Maguire, J.; Folts, D.; Yuan, J.; Henderson, N.; Lindsay, D.; Knoll, D.; Rey, C.; Duckworth, R.; Gouge, M.; Wolff, Z.; Kurtz, S.

    2010-04-01

    In the last decade, significant advances in the performance of second generation (2G) high temperature superconducting wire have made it suitable for commercially viable applications such as electric power cables and fault current limiters. Currently, the U.S. Department of Homeland Security is co-funding the design, development and demonstration of an inherently fault current limiting HTS cable under the Hydra project with American Superconductor and Consolidated Edison. The cable will be approximately 300 m long and is being designed to carry 96 MVA at a distribution level voltage of 13.8 kV. The underground cable will be installed and energized in New York City. The project is led by American Superconductor teamed with Con Edison, Ultera (Southwire and nkt cables joint venture), and Air Liquide. This paper describes the general goals, design criteria, status and progress of the project. Fault current limiting has already been demonstrated in 3 m prototype cables, and test results on a 25 m three-phase cable will be presented. An overview of the concept of a fault current limiting cable and the system advantages of this unique type of cable will be described.

  13. Covalency, Excitons, Double Counting and the Metal-Insulator Transition in Transition Metal Oxides

    Science.gov (United States)

    Wang, Xin

    2012-02-01

    We present single-site dynamical mean-field studies of realistic models of transition metal oxides, including the cuprate superconductors and rare earth nickelates (in bulk and superlattice form). We include orbital multiplet effects and hybridization to ligands. We explicitly calculate the d-d exciton spectra for cuprates, finding sharp exciton lines in both metallic and insulating phases, which should be visible in experiments. We also find that the additional d3z^2-r^2 orbital does not contribute to an additional Fermi surface at any reasonable doping, in contradiction to previous slave-boson studies. The hybridization to ligands is shown to have crucial effects, for example suppressing the ferro-orbital order previously found in Hubbard model studies of nickelates. Hybridization to ligands is shown to be most naturally parametrized by the d-orbital occupancy. For cuprates and nickelates, insulating behavior is found to be present only for a very narrow range of d-occupancy, irrespective of the Coulomb repulsion. The d-occupancy predicted by standard band calculations is found to be very far from the values required to obtain an insulating phase, calling into question the interpretation of these materials as charge transfer insulators. [4pt] This work is done in collaboration with A.J. Millis, M.J. Han, C.A. Marianetti, L. de' Medici, and H.T. Dang, and is supported by NSF-DMR-1006282, the Army Office of Scientific Research, and the Condensed Matter Theory Center and CNAM at University of Maryland. [4pt] [1] X. Wang, H. T. Dang, and A. J. Millis, Phys. Rev. B 84, 014530 (2011).[0pt] [2] X. Wang, M. J. Han, L. de' Medici, C. A. Marianetti, and A. J. Millis, arXiv:1110.2782.[0pt] [3] M. J. Han, X. Wang, C. A. Marianetti, and A. J. Millis, Phys. Rev. Lett. 107, 206804 (2011).

  14. Characterization of Bacterial and Fungal Community Dynamics by High-Throughput Sequencing (HTS) Metabarcoding during Flax Dew-Retting.

    Science.gov (United States)

    Djemiel, Christophe; Grec, Sébastien; Hawkins, Simon

    2017-01-01

    Flax dew-retting is a key step in the industrial extraction of fibers from flax stems and is dependent upon the production of a battery of hydrolytic enzymes produced by micro-organisms during this process. To explore the diversity and dynamics of bacterial and fungal communities involved in this process we applied a high-throughput sequencing (HTS) DNA metabarcoding approach (16S rRNA/ITS region, Illumina Miseq) on plant and soil samples obtained over a period of 7 weeks in July and August 2014. Twenty-three bacterial and six fungal phyla were identified in soil samples and 11 bacterial and four fungal phyla in plant samples. Dominant phyla were Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes (bacteria) and Ascomycota, Basidiomycota, and Zygomycota (fungi) all of which have been previously associated with flax dew-retting except for Bacteroidetes and Basidiomycota that were identified for the first time. Rare phyla also identified for the first time in this process included Acidobacteria, CKC4, Chlorobi, Fibrobacteres, Gemmatimonadetes, Nitrospirae and TM6 (bacteria), and Chytridiomycota (fungi). No differences in microbial communities and colonization dynamics were observed between early and standard flax harvests. In contrast, the common agricultural practice of swath turning affects both bacterial and fungal community membership and structure in straw samples and may contribute to a more uniform retting. Prediction of community function using PICRUSt indicated the presence of a large collection of potential bacterial enzymes capable of hydrolyzing backbones and side-chains of cell wall polysaccharides. Assignment of functional guild (functional group) using FUNGuild software highlighted a change from parasitic to saprophytic trophic modes in fungi during retting. This work provides the first exhaustive description of the microbial communities involved in flax dew-retting and will provide a valuable benchmark in future studies aiming to evaluate

  15. Characterization of Bacterial and Fungal Community Dynamics by High-Throughput Sequencing (HTS Metabarcoding during Flax Dew-Retting

    Directory of Open Access Journals (Sweden)

    Christophe Djemiel

    2017-10-01

    Full Text Available Flax dew-retting is a key step in the industrial extraction of fibers from flax stems and is dependent upon the production of a battery of hydrolytic enzymes produced by micro-organisms during this process. To explore the diversity and dynamics of bacterial and fungal communities involved in this process we applied a high-throughput sequencing (HTS DNA metabarcoding approach (16S rRNA/ITS region, Illumina Miseq on plant and soil samples obtained over a period of 7 weeks in July and August 2014. Twenty-three bacterial and six fungal phyla were identified in soil samples and 11 bacterial and four fungal phyla in plant samples. Dominant phyla were Proteobacteria, Bacteroidetes, Actinobacteria, and Firmicutes (bacteria and Ascomycota, Basidiomycota, and Zygomycota (fungi all of which have been previously associated with flax dew-retting except for Bacteroidetes and Basidiomycota that were identified for the first time. Rare phyla also identified for the first time in this process included Acidobacteria, CKC4, Chlorobi, Fibrobacteres, Gemmatimonadetes, Nitrospirae and TM6 (bacteria, and Chytridiomycota (fungi. No differences in microbial communities and colonization dynamics were observed between early and standard flax harvests. In contrast, the common agricultural practice of swath turning affects both bacterial and fungal community membership and structure in straw samples and may contribute to a more uniform retting. Prediction of community function using PICRUSt indicated the presence of a large collection of potential bacterial enzymes capable of hydrolyzing backbones and side-chains of cell wall polysaccharides. Assignment of functional guild (functional group using FUNGuild software highlighted a change from parasitic to saprophytic trophic modes in fungi during retting. This work provides the first exhaustive description of the microbial communities involved in flax dew-retting and will provide a valuable benchmark in future studies aiming

  16. HTS current lead units prepared by the TFA-MOD processed YBCO coated conductors

    International Nuclear Information System (INIS)

    Shiohara, K.; Sakai, S.; Ishii, Y.; Yamada, Y.; Tachikawa, K.; Koizumi, T.; Aoki, Y.; Hasegawa, T.; Tamura, H.; Mito, T.

    2010-01-01

    Two superconducting current lead units have been prepared using ten coated conductors of the Tri-Fluoro-Acetate - Metal Organic Deposition (TFA-MOD) processed Y 1 Ba 2 Cu 3 O 7-δ (YBCO) coated conductors with critical current (I c ) of about 170 A at 77 K in self-field. The coated conductors are 5 mm in width, 190 mm in length and about 120 μm in overall thickness. The 1.5 μm thick superconducting YBCO layer was synthesized through the TFA-MOD process on Hastelloy TM C-276 substrate tape with two buffer oxide layers of Gd 2 Zr 2 O 7 and CeO 2 . The five YBCO coated conductors are attached on a 1 mm thick Glass Fiber Reinforced Plastics (GFRP) board and soldered to Cu caps at the both ends. We prepared two 500 A-class current lead units. The DC transport current of 800 A was stably applied at 77 K without any voltage generation in all coated conductors. The voltage between both Cu caps linearly increased with increasing the applied current, and was about 350 μV at 500 A in both current lead units. According to the estimated values of the heat leakage from 77 K to 4.2 K, the heat leakage for the current lead unit was 46.5 mW. We successfully attained reduction of the heat leakage because of improvement of the transport current performance (I c ), a thinner Ag layer of YBCO coated conductor and usage of the GFRP board for reinforcement instead of a stainless steel board used in the previous study. The DC transport current of 1400 A was stably applied when the two current lead units were joined in parallel. The sum of the heat leakages from 77 K to 4.2 K for the combined the current lead units was 93 mW. In comparison with the conventional Cu current leads by gas-cooling, it could be noted that the heat leakage of the current lead is about one order of magnitude smaller than that of the Cu current lead.

  17. Unconventional superconductivity in cuprates, cobaltates and graphene. What is universal and what is material-dependent in strongly versus weakly correlated materials?

    International Nuclear Information System (INIS)

    Kiesel, Maximilian Ludwig

    2013-01-01

    A general theory for all classes of unconventional superconductors is still one of the unsolved key issues in condensed-matter physics. Actually, it is not yet fully settled if there is a common underlying pairing mechanism. Instead, it might be possible that several distinct sources for unconventional (not phonon-mediated) superconductivity have to be considered, or an electron-phonon interaction is not negligible. The focus of this thesis is on the most probable mechanism for the formation of Cooper pairs in unconventional superconductors, namely a strictly electronic one where spin fluctuations are the mediators. Studying different superconductors in this thesis, the emphasis is put on material-independent features of the pairing mechanism. In addition, the investigation of the phase diagrams enables a view on the vicinity of superconductivity. Thus, it is possible to clarify which competing quantum fluctuations enhance or weaken the propensity for a superconducting state. The broad range of superconducting materials requires the use of more than one numerical technique to study an appropriate microscopic description. This is not a problem but a big advantage because this facilitates the approach-independent description of common underlying physics. For this evaluation, the strongly correlated cuprates are simulated with the variational cluster approach. Especially the question of a pairing glue is taken into consideration. Furthermore, it is possible to distinguish between retarded and non-retarded contributions to the gap function. The cuprates are confronted with the cobaltate Na x CoO 2 and graphene. These weakly correlated materials are investigated with the functional renormalization group (fRG) and reveal a comprehensive phase diagram, including a d+id-wave superconductivity, which breaks time-reversal symmetry. The corresponding gap function is nodeless, but for NaCoO, it features a doping-dependent anisotropy. In addition, some general considerations on

  18. Unconventional superconductivity in cuprates, cobaltates and graphene. What is universal and what is material-dependent in strongly versus weakly correlated materials?

    Energy Technology Data Exchange (ETDEWEB)

    Kiesel, Maximilian Ludwig

    2013-02-08

    A general theory for all classes of unconventional superconductors is still one of the unsolved key issues in condensed-matter physics. Actually, it is not yet fully settled if there is a common underlying pairing mechanism. Instead, it might be possible that several distinct sources for unconventional (not phonon-mediated) superconductivity have to be considered, or an electron-phonon interaction is not negligible. The focus of this thesis is on the most probable mechanism for the formation of Cooper pairs in unconventional superconductors, namely a strictly electronic one where spin fluctuations are the mediators. Studying different superconductors in this thesis, the emphasis is put on material-independent features of the pairing mechanism. In addition, the investigation of the phase diagrams enables a view on the vicinity of superconductivity. Thus, it is possible to clarify which competing quantum fluctuations enhance or weaken the propensity for a superconducting state. The broad range of superconducting materials requires the use of more than one numerical technique to study an appropriate microscopic description. This is not a problem but a big advantage because this facilitates the approach-independent description of common underlying physics. For this evaluation, the strongly correlated cuprates are simulated with the variational cluster approach. Especially the question of a pairing glue is taken into consideration. Furthermore, it is possible to distinguish between retarded and non-retarded contributions to the gap function. The cuprates are confronted with the cobaltate Na{sub x}CoO{sub 2} and graphene. These weakly correlated materials are investigated with the functional renormalization group (fRG) and reveal a comprehensive phase diagram, including a d+id-wave superconductivity, which breaks time-reversal symmetry. The corresponding gap function is nodeless, but for NaCoO, it features a doping-dependent anisotropy. In addition, some general

  19. Inductive crystal field control in layered metal oxides with correlated electrons

    Energy Technology Data Exchange (ETDEWEB)

    Balachandran, P. V.; Cammarata, A.; Rondinelli, J. M., E-mail: jrondinelli@nortwestern.edu [Department of Materials Science and Engineering, Drexel University, Philadelphia, Pennsylvania 19104 (United States); Nelson-Cheeseman, B. B. [School of Engineering, University of St. Thomas, St. Paul, Minnesota 55105 (United States); Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Bhattacharya, A. [Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Center for Nanoscale Materials, Argonne National Laboratory, Argonne, Illinois 60439 (United States)

    2014-07-01

    We show that the NiO{sub 6} crystal field energies can be tailored indirectly via heterovalent A cation ordering in layered (La,A)NiO{sub 4} Ruddlesden–Popper (RP) oxides, where A = Sr, Ca, or Ba, using density functional calculations. We leverage as a driving force the electrostatic interactions between charged [LaO]{sup 1+} and neutral [AO]{sup 0} planes to inductively tune the Ni–O bond distortions, without intentional doping or epitaxial strain, altering the correlated d-orbital energies. We use this strategy to design cation ordered LaCaNiO{sub 4} and LaBaNiO{sub 4} with distortions favoring enhanced Ni e{sub g} orbital polarization, and find local electronic structure signatures analogous to those in RP La-cuprates, i.e., parent phases of the high-temperature superconducting oxides.

  20. Fracton pairing mechanism for unconventional superconductors: Self-assembling organic polymers and copper-oxide compounds

    DEFF Research Database (Denmark)

    Milovanov, A.V.; Juul Rasmussen, J.

    2002-01-01

    Self-assembling organic polymers and copper-oxide compounds are two classes of unconventional superconductors, whose challenging behavior does not comply with the traditional picture of Bardeen-Cooper-Schrieffer (BCS) superconductivity in regular crystals. In this paper, we propose a theoretical...... or holes) exchange fracton excitations, quantum oscillations of fractal lattices that mimic the complex microscopic organization of the unconventional superconductors. For the copper oxides, the superconducting transition temperature T-c as predicted by the fracton mechanism is of the order of similar to......150 K. We suggest that the marginal ingredient of the high-temperature superconducting phase is provided by fracton coupled holes that condensate in the conducting copper-oxygen planes owing to the intrinsic field-effect-transistor configuration of the cuprate compounds. For the gate...

  1. Investigation of a CDDW Hamiltonian to Explore Possibility of Magneto-Quantum Oscillations in Electronic Specific Heat of Hole-Doped Cuprates

    International Nuclear Information System (INIS)

    Goswami, P.; Rani, M.; Rani, M.

    2010-01-01

    We investigate a chiral d-density wave (CDDW) mean field model Hamiltonian in the momentum space suitable for the hole-doped cuprates, such as YBCO, in the pseudo gap phase to obtain the Fermi surface (FS) topologies, including the anisotropy parameter(ε) and the elastic scattering by disorder potential (|v0|). For ε=0, with the chemical potential μ=-0.27 eV for 10% doping level and |v0|=|t| (where |t|=0.25 eV is the first neighbor hopping), at zero/non-zero magnetic field (B), the FS on the first Brillouin zone is found to correspond to electron pockets around antinodal regions and barely visible patches around nodal regions. For ε0, we find Pomeranchuk distortion of FS. We next relate our findings regarding FS to the magneto-quantum oscillations in the electronic specific heat. Since the nodal quasiparticle energy values for B=0 are found to be greater than μ for |v0|=|t|, the origin of the oscillations for nonzero B corresponds to the Fermi pockets around antinodal regions. The oscillations are shown to take place in the weak disorder regime (|v0|=0.25eV) only.

  2. Investigation of a CDDW Hamiltonian to Explore Possibility of Magneto-Quantum Oscillations in Electronic Specific Heat of Hole-Doped Cuprates

    Directory of Open Access Journals (Sweden)

    Partha Goswami

    2010-01-01

    Full Text Available We investigate a chiral d-density wave (CDDW mean field model Hamiltonian in the momentum space suitable for the hole-doped cuprates, such as YBCO, in the pseudogap phase to obtain the Fermi surface (FS topologies, including the anisotropy parameter(́ and the elastic scattering by disorder potential (|0|. For ́=0, with the chemical potential =−0.27 eV for 10% doping level and |0|≥|| (where ||=0.25 eV is the first neighbor hopping, at zero/non-zero magnetic field (, the FS on the first Brillouin zone is found to correspond to electron pockets around antinodal regions and barely visible patches around nodal regions. For ́≠0, we find Pomeranchuk distortion of FS. We next relate our findings regarding FS to the magneto-quantum oscillations in the electronic specific heat. Since the nodal quasiparticle energy values for =0 are found to be greater than for |0|≥||, the origin of the oscillations for nonzero corresponds to the Fermi pockets around antinodal regions. The oscillations are shown to take place in the weak disorder regime (|0|=0.25eV only.

  3. Anisotropy of the Seebeck Coefficient in the Cuprate Superconductor YBa_{2}Cu_{3}O_{y}: Fermi-Surface Reconstruction by Bidirectional Charge Order

    Directory of Open Access Journals (Sweden)

    O. Cyr-Choinière

    2017-09-01

    Full Text Available The Seebeck coefficient S of the cuprate YBa_{2}Cu_{3}O_{y} is measured in magnetic fields large enough to suppress superconductivity, at hole dopings p=0.11 and p=0.12, for heat currents along the a and b directions of the orthorhombic crystal structure. For both directions, S/T decreases and becomes negative at low temperature, a signature that the Fermi surface undergoes a reconstruction due to broken translational symmetry. Above a clear threshold field, a strong new feature appears in S_{b}, for conduction along the b axis only. We attribute this feature to the onset of 3D-coherent unidirectional charge-density-wave modulations seen by x-ray diffraction, also along the b axis only. Because these modulations have a sharp onset temperature well below the temperature where S/T starts to drop towards negative values, we infer that they are not the cause of Fermi-surface reconstruction. Instead, the reconstruction must be caused by the quasi-2D bidirectional modulations that develop at significantly higher temperature. The unidirectional order only confers an additional anisotropy to the already reconstructed Fermi surface, also manifest as an in-plane anisotropy of the resistivity.

  4. The two-component spin-fermion model for high-Tc cuprates: its applications in neutron scattering and ARPES experiments

    International Nuclear Information System (INIS)

    Bang, Yunkyu

    2012-01-01

    Motivated by neutron scattering experiments in high-T c cuprates, we propose the two-component spin-fermion model as a minimal phenomenological model, which has both local spins and itinerant fermions as independent degrees of freedom (d.o.f.). Our calculations of the dynamic spin correlation function provide a successful description of the puzzling neutron experiment data and show that: (i) the upward dispersion branch of magnetic excitations is mostly due to local spin excitations; (ii) the downward dispersion branch is from collective particle-hole excitations of fermions; and (iii) the resonance mode is a mixture of both d.o.f. Using the same model with the same set of parameters, we calculated the renormalized quasiparticle (q.p.) dispersion and successfully reproduced one of the key features of the angle-resolved photoemission spectroscopy (ARPES) experiments, namely the high-energy kink structure in the fermion q.p. dispersion, thus supporting the two-component spin-fermion phenomenology. (paper)

  5. Pseudogap in cuprates driven by D-wave flux-phase order proximity effects: a theoretical analysis from Raman and ARPES experiments.

    Science.gov (United States)

    Greco, Andrés; Bejas, Matías

    2014-12-03

    One of the puzzling characteristics of the pseudogap phase of high-Tc cuprates is the nodal-antinodal dichotomy. While the nodal quasiparticles have a Fermi liquid behaviour, the antinodal ones show non-Fermi liquid features and an associated pseudogap. Angle-resolved photoemission spectroscopy and electronic Raman scattering are two valuable tools which have shown universal features which are rather material-independent, and presumably intrinsic to the pseudogap phase. The doping and temperature dependence of the Fermi arcs and the pseudogap observed by photoemission near the antinode correlates with the non-Fermi liquid behaviour observed by Raman for the B(1g) mode. In contrast, and similar to the nodal quasiparticles detected by photoemission, the Raman B(2g) mode shows Fermi liquid features. We show that these two experiments can be analysed, in the context of the t-J model, by self-energy effects in the proximity to a D-wave flux-phase order instability. This approach supports a crossover origin for the pseudogap, and a scenario of two competing phases. The B(2g) mode shows, in an underdoped case, a depletion at intermediate energy which has attracted renewed interest. We study this depletion and discuss its origin and relation with the pseudogap.

  6. Evaluation of GeneMarker® HTS for improved alignment of mtDNA MPS data, haplotype determination, and heteroplasmy assessment.

    Science.gov (United States)

    Holland, Mitchell M; Pack, Erica D; McElhoe, Jennifer A

    2017-05-01

    Existing software has not allowed for effective alignment of mitochondrial (mt) DNA sequence data generated using a massively parallel sequencing (MPS) approach, combined with the ability to perform a detailed assessment of the data. The regions of sequence that are typically difficult to align are homopolymeric stretches, isolated patterns of SNPs (single nucleotide polymorphisms), and INDELs (insertions/deletions). A custom software solution, GeneMarker ® HTS, was developed and evaluated to address these limitations, and to provide a user-friendly interface for forensic practitioners and others interested in mtDNA analysis of MPS data. GeneMarker ® HTS generates an exportable consensus mtDNA sequence that produces phylogenetically correct SNP and INDEL calls using a customizable motif-based alignment algorithm. Sequence data from 500 individuals, with various alignment asymmetries and levels of heteroplasmy, were used to assess the software. Accuracy in producing mtDNA haplotypes, the ability to correctly identify low-level heteroplasmic sequence variants, and the user-based features of the software were evaluated. Analyzed sequences yielded correct mtDNA haplotypes, and heteroplasmic variants were properly identified with minimal manual interpretation. The software offers numerous user-defined parameters for filtering the data that address the interests of researchers and practitioners, and provides multiple options for viewing and navigating through the data. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. The attenuation of the levitation force of HTS bulk exposed to AC magnetic field on the above NdFeB guideway

    Energy Technology Data Exchange (ETDEWEB)

    Liu Minxian, E-mail: liukey_sjtu@263.net [School of Computer Science and Technology, Southwest University of Science and Technology, Mianyang, Sichuan 621010 (China); Wang Yan [Luoyang Institute of Science and Technology, Luoyang, Henan 471023 (China)

    2012-01-15

    The characteristic of the levitation force relaxation was studied by experiment. The levitation force is attenuated with the application of the AC external magnetic field. The decay increases with the amplitude of the A external magnetic field. The decay is almost independent of the frequency of AC field. In the present High Temperature Superconducting (HTS) maglev vehicle system, the air gaps between the adjacent permanent magnets make the magnetic fields above the NdFeB guideway non-uniform. So it is required to study the characteristics of levitation force of the HTS bulk affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we have studied the characteristics of the levitation force relaxation by an experiment in which AC magnetic field generated by an electromagnet is used to simulate the time-varying magnetic field caused by the inhomogeneity of the NdFeB guideway. From the experiment results, it is found that the levitation force is attenuated with the application of the AC field, and the attenuation is increased with the amplitude of the AC field, but the attenuation is almost independent of the frequency the AC magnetic field.

  8. The attenuation of the levitation force of HTS bulk exposed to AC magnetic field on the above NdFeB guideway

    International Nuclear Information System (INIS)

    Liu Minxian; Wang Yan

    2012-01-01

    The characteristic of the levitation force relaxation was studied by experiment. The levitation force is attenuated with the application of the AC external magnetic field. The decay increases with the amplitude of the A external magnetic field. The decay is almost independent of the frequency of AC field. In the present High Temperature Superconducting (HTS) maglev vehicle system, the air gaps between the adjacent permanent magnets make the magnetic fields above the NdFeB guideway non-uniform. So it is required to study the characteristics of levitation force of the HTS bulk affected by the non-uniform applied magnetic fields along the moving direction. In this paper, we have studied the characteristics of the levitation force relaxation by an experiment in which AC magnetic field generated by an electromagnet is used to simulate the time-varying magnetic field caused by the inhomogeneity of the NdFeB guideway. From the experiment results, it is found that the levitation force is attenuated with the application of the AC field, and the attenuation is increased with the amplitude of the AC field, but the attenuation is almost independent of the frequency the AC magnetic field.

  9. Tunable HTS Filters

    National Research Council Canada - National Science Library

    Mancusi, Joseph

    2002-01-01

    ... capacitor and the continuously variable inductor. The target application is for this technology is SIGINT applications in the 400 MHz to 3000 MHz frequency band, with potential applications in areas from 20 MHz to 20 GHz...

  10. HTS Teologiese Studies

    African Journals Online (AJOL)

    2009-12-10

    Dec 10, 2009 ... ethics questions of analytic ethics, or metaethics, tend to be bracketed (Barton 2003:45). ... 23; Audi & Wainwright 1986; Copan 2003:295–304, Hare 1997, 2008; Kant 1993, Kierkegaard 1985; ... To say that ethical obligation is obedience to the will of the national God is to say that it is not the observation.

  11. Anomalous Enhancement of the Superconducting Transition Temperature of Electron-doped La2-xCexCuO4 and Pr2-xCexCuO4 Cuprate Heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    K Jin; P Vach; X Zhang; U Grupel; E Zohar; I Diamant; Y Dagan; S Smadici; P Abbamonte; R Greene

    2011-12-31

    The superconducting transition temperature T{sub c} of multilayers of electron-doped cuprates, composed of underdoped (or undoped) and overdoped La{sub 2-x}Ce{sub x}CuO{sub 4} (LCCO) and Pr{sub 2-x}Ce{sub x}CuO{sub 4} (PCCO) thin films, is found to increase significantly with respect to the T{sub c} of the corresponding single-phase films. By investigating the critical current density of superlattices with different doping levels and layer thicknesses, we find that the T{sub c} enhancement is caused by a redistribution of charge over an anomalously large distance.

  12. HTS Theological Studies and Verbum et Ecclesia – the journals of the Faculty of Theology at the University of Pretoria: Historical overview and strategic planning

    Directory of Open Access Journals (Sweden)

    Dirk Human

    2008-01-01

    Full Text Available This article celebrates the centenary of the University of Pretoria (UP in 2008. The editors of Verbum et Ecclesia and HTS Theological Studies, the two theological journals associated with the Faculty of Theology at UP, reflect on the journals’ historical roots, editorial focuses, distinctive features, subscription and language statistics and on their’ contribution to support the academic study of theology and related disciplines. The Faculty of Theology was founded in 1917 and celebrated its ninetieth birthday in 2007. The origin of its journals dates back to 1943. This article discusses the challenges that academic journals face in South Africa and undertakes strategic planning for the future. A concluding addendum, consisting of statistical diagrams with regard to the journals’ profile during the last five years, illustrates the argument.

  13. Critical Doping for the Onset of Fermi-Surface Reconstruction by Charge-Density-Wave Order in the Cuprate Superconductor La_{2-x}Sr_{x}CuO_{4}

    Directory of Open Access Journals (Sweden)

    S. Badoux

    2016-04-01

    Full Text Available The Seebeck coefficient S of the cuprate superconductor La_{2-x}Sr_{x}CuO_{4} (LSCO was measured in magnetic fields large enough to access the normal state at low temperatures, for a range of Sr concentrations from x=0.07 to x=0.15. For x=0.11, 0.12, 0.125, and 0.13, S/T decreases upon cooling to become negative at low temperatures. The same behavior is observed in the Hall coefficient R_{H}(T. In analogy with other hole-doped cuprates at similar hole concentrations p, the negative S and R_{H} show that the Fermi surface of LSCO undergoes a reconstruction caused by the onset of charge-density-wave modulations. Such modulations have indeed been detected in LSCO by x-ray diffraction in precisely the same doping range. Our data show that in LSCO this Fermi-surface reconstruction is confined to 0.085

  14. Optical Study of Electron-Doped Cuprate Pr1.3-xLa0.7CexCuO4+δ in Under-Doped Regime: Revisit the Phase Diagram

    Science.gov (United States)

    Ohnishi, Ryota; Nakajima, Masamichi; Miyasaka, Shigeki; Tajima, Setsuko; Adachi, Tadashi; Ohgi, Taro; Takahashi, Akira; Koike, Yoji

    2018-04-01

    A recent progress of reduction process for electron-doped cuprates enabled us to get superconducting samples at very low doping levels. In order to clarify the electronic state of strongly reduced Pr1.3-xLa0.7CexCuO4+δ (x = 0.05, 0.10) which exhibit high Tc (˜27 K) superconductivity, we have measured their optical spectra. The reflectivity of these samples was found much higher than the published data for the moderately reduced and non-superconducting samples with the same Ce concentrations. Moreover, the estimated effective electron numbers Neff for x = 0.05 and 0.10 were close to that of the optimally doped and superconducting sample with x = 0.15. Given that the parent compound is a Mott insulator, these results indicate that in the electron-doped cuprates only a small amount of carrier doping changes the system to a high Tc superconductor with a large Fermi surface. At low temperatures, a broad mid-infrared peak appeared even in the superconducting samples.

  15. Modifying zirconia solid electrolyte surface property to enhance oxide transport

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, B.Y.; Song, S.Y. [Univ. of Hawaii, Honolulu, HI (United States)

    1996-12-31

    Bismuth-strontium-calcium-copper oxide (Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}, BSCCO) is known for its high T{sub c} superconducting behavior and mixed conducting property. The applicability of similar high T{sub c} cuprates for intermediate-temperature solid oxide fuel cell (SOFC) application has been studied recently. We investigated the electrochemical behavior of several Ag{vert_bar}BSCCO{vert_bar}10 mol% yttria-stabilized zirconia (YSZ){vert_bar}Ag and Ag{vert_bar}YSZ{vert_bar}Ag cells using complex impedance spectroscopy. A highly uniform and porous microstructure was observed at the interface of the YSZ and BSCCO. The ionic conductivity determined from the Nyquest plots in the temperature range of 200-700{degrees}C agrees with the values reported in the literature. The specific resistance of the BSCCO{vert_bar}YSZ interface was also determined to be lower than those of the conventional manganite electrode, suggesting that BSCCO seems attractive for cathode applications in SOFC.

  16. Preparation and characteristics of superconducting cuprate thin films: Nd(2-x)Ce(x)CuO4 and substituted Bi-system

    Science.gov (United States)

    Adachi, H.; Hayashi, S.; Setsune, K.; Kohiki, S.; Ichikawa, Y.; Wasa, K.

    1990-01-01

    Characteristics of the electron-doped-type Nd(2-x)Ce(x)CuO4 systems and substituted Bi2(Sr,Ln)3Cu2Oy system were systematically studied using the high quality thin-film samples. The Nd(2-x)Ce(x)CuO4 thin films with various Ce concentrations, x, were prepared by RF magnetron sputtering on SrTiO3 heated at around 500 C. After subsequent annealing at 1100 C in air, the films showed the c-axis orientation normal to the substrates. By means of the reducing treatment (annealing in a vacuum), superconductivity was induced for the films with 0.14 is less than or equal to x is less than or equal to 0.18. The superconductivity and transport properties of the films were strongly affected by the reducing treatment. The x = 0.15 film exhibited a sharp superconducting transition with zero resistivity at 22 K, in consistent with the diamagnetic properties. The resistivity of the films was fairly low with metallic characteristics, and the sight of the Hall coefficient was negative in the normal state. On the other hand, the normal-state optical measurements showed that the undoped Nd2CuO4 is a semiconductor with a charge transfer gap of 1.3 eV, and that, when Ce ions were doped, a plasma reflection due to the free-carriers came to be seen with the plasma frequency of 1.07 eV for 0.14 is less than or equal to x is less than or equal to 0.18. Moreover, x ray photoemission study revealed that the Cu valence of the film decreased for 2(+) for x = 0 to 1(+) for x = 0.15. These physical properties are in contrast with those of hole-doped-type cuprate superconductors. Bi2(Sr,Ln)3Cu2Oy thin films were also prepared on MgO substrates heated at 600 to 700 C by similar methods. It was found that the growth conditions for Bi-systems with two CuO2 planes were different for each composition and species of lanthanoid in the films. Moreover, preparation of Bi-system with three CuO2 planes was very difficult when lanthanoid atoms were doped in the system. Their electric transport properties and x

  17. Ethylene Oxide

    Science.gov (United States)

    Learn about ethylene oxide, which can raise your risk of lymphoma and leukemia. Exposure may occur through industrial emissions, tobacco smoke, and the use of products sterilized with ethylene oxide, such as certain medical products or cosmetics.

  18. Effects on Jc of pinning center morphology for multiple-in-line-damage in coated conductor and bulk, melt-textured HTS

    International Nuclear Information System (INIS)

    Weinstein, R.; Parks, D.; Sawh, R.-P.; Mayes, B.; Gandini, A.; Goyal, A.; Chen, Y.; Selvamanickam, V.

    2009-01-01

    The properties of discontinuous aligned pinning centers (PCs) created by high-energy heavy-ions are compared for bulk melt-textured and coated conductor HTS. Properties of PCs, which increase J c (pinning potential and entanglement), and negative properties which decrease J c (e.g., decreased T c and percolation paths) are evaluated. Mechanisms are proposed to explain the very large increases in J c resulting from multiple-in-line-damage (MILD) compared to continuous columnar pinning centers (CCPC). In particular, a mechanism which results in fluxoid entanglement, even for parallel (unsplayed) PCs, is discussed. The same mechanism is found to also account for restoration of much of the pinning potential expected to be lost due to the gaps in MILD PCs. It also accounts for the fact that at high fluence, J c increases as fluence is increased, instead of decreasing as expected. The very low self-field in coated conductor permits separation of the negative and positive effects of PCs. It is found that parameters developed to quantify the negative effects in bulk melt-textured YBCO, by 63 GeV U 238 ions, successfully describe damage to 2.1 μm thick coated conductor by 1 GeV Ru 44 ions. Coated conductor at 77 K and self-field is generally known to have J c about 100 times that of melt-textured YBCO. However, at 77 K and applied field of 1 T, when both forms of HTS are processed with comparable numbers of near-optimum MILD PCs, the difference in J c is reduced to a factor of 1.3-2. Whereas J c for melt-textured YBCO increased sharply, by a factor of up to 16.8 for high-fluence MILD PCs, J c in coated conductor increased by a smaller factor of 2.5-3.0. Nevertheless, 2.1 μm thick coated conductor, with near-optimum MILD PCs, exhibits J c = 543 kA/cm 2 at 77 K and applied field of 1.0 T, and I c = 114 A/cm-width of conductor. This is the highest value we find in the literature. The phenomenology developed indicates that for optimum MILD PCs in coated conductor, J c ∼ 700

  19. Effects on Jc of Pinning Center Morphology for Multiple-in-Line-Damage in Coated Conductor and Bulk, Melt-Textured HTS

    Energy Technology Data Exchange (ETDEWEB)

    Weinstein, R. [University of Houston, Houston; Parks, D. [University of Houston, Houston; Sawh, R.-P. [University of Houston, Houston; Mayes, B. [University of Houston, Houston; Gandini, A. [University of Houston, Houston; Goyal, Amit [ORNL; Chen, Y. [SuperPower Incorporated, Schenectady, New York; Selvamanickam, V. [SuperPower Incorporated, Schenectady, New York

    2009-01-01

    The properties of discontinuous aligned pinning centers (PCs) created by high-energy heavy-ions are compared for bulk melt-textured and coated conductor HTS. Properties of PCs, which increase J{sub c} (pinning potential and entanglement), and negative properties which decrease J{sub c} (e.g., decreased T{sub c} and percolation paths) are evaluated. Mechanisms are proposed to explain the very large increases in J{sub c} resulting from multiple-in-line-damage (MILD) compared to continuous columnar pinning centers (CCPC). In particular, a mechanism which results in fluxoid entanglement, even for parallel (unsplayed) PCs, is discussed. The same mechanism is found to also account for restoration of much of the pinning potential expected to be lost due to the gaps in MILD PCs. It also accounts for the fact that at high fluence, J{sub c} increases as fluence is increased, instead of decreasing as expected. The very low self-field in coated conductor permits separation of the negative and positive effects of PCs. It is found that parameters developed to quantify the negative effects in bulk melt-textured YBCO, by 63 GeV U{sup 238} ions, successfully describe damage to 2.1 {micro}m thick coated conductor by 1 GeV Ru{sup 44} ions. Coated conductor at 77 K and self-field is generally known to have J{sub c} about 100 times that of melt-textured YBCO. However, at 77 K and applied field of 1 T, when both forms of HTS are processed with comparable numbers of near-optimum MILD PCs, the difference in J{sub c} is reduced to a factor of 1.3-2. Whereas J{sub c} for melt-textured YBCO increased sharply, by a factor of up to 16.8 for high-fluence MILD PCs, J{sub c} in coated conductor increased by a smaller factor of 2.5-3.0. Nevertheless, 2.1 {micro}m thick coated conductor, with near-optimum MILD PCs, exhibits J{sub c} = 543 kA/cm{sup 2} at 77 K and applied field of 1.0 T, and I{sub c} = 114 A/cm-width of conductor. This is the highest value we find in the literature. The

  20. Investigations of the electronic, magnetic and crystalline structure of perovskite oxides and an oxide-oxide interface

    International Nuclear Information System (INIS)

    Raisch, Christoph Werner

    2013-01-01

    The mineral perovskite CaTiO 3 lends its name to the class of compounds with composition ABX 3 , which have the same type of crystal structure known as the perovskite structure. Here, A and B are cations while X is typically a halogen or oxygen anion. The bigger cation A and the X anions form a cubic close packing AX 3 with the smaller B cation occupying one quarter of the octahedral sites. The underlying work deals with three classes of perovskite oxides, the ''titanates'', the ''cuprates'' and the ''manganites'', where the central B cations are Ti, Cu and Mn respectively, each class with very characteristic properties. Strontium titanate, STO, like so many oxides is an insulator, yet paraelectric and diamagnetic. It gained special interest as a commercially available, high quality substrate for the growth of hightemperature superconductors and other oxide thin films. The huge class of perovskite cuprates is most famous for members like YBCO, the well-known high-temperature superconductor. Finally, the doped, mixed-valent perovskite manganites LXMO (here X = Sr, Ca, Ce) have to be mentioned. They appeared on the screen of experimental and theoretical physicists in the 1950s when ferromagnetism and magnetoresistance were discovered in these compounds, leading to the theory of double exchange. In the mid-1990s they further increased their importance, following the description of the Jahn-Teller polaron and the discovery of the colossal magnetoresistance phenomenom. They may be derived from an insulator, LaMnO 3 , but the doping allows the control of electric and magnetic properties over a wide range, i.e. from insulating behavior to metallic conductivity or from diamagnet to ferromagnet. Further notable effects are found when electric or magnetic fields are applied, including spin polarization and the related effect of colossal magnetoresistance. These substances may be approximated as consisting of