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Applied Superconductivity, IEEE Transactions on

Issue 2 • Date April 2013

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Displaying Results 1 - 16 of 16
  • Front cover

    Publication Year: 2013 , Article#: 0000801
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  • IEEE Transactions on Applied Superconductivity publication information

    Publication Year: 2013 , Article#: 0000901
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  • Table of contents

    Publication Year: 2013 , Article#: 0001002
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  • YBCO Josephson Junctions and Striplines for RSFQ Circuits Made by Ion Irradiation

    Publication Year: 2013 , Article#: 1101205
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    We have investigated the electrodynamic properties of high-Tc Josephson junctions (JJs) and striplines made by ion irradiation in order to evaluate the potential of such a technology for low-power rapid single flux quantum superconductor digital electronics. The process is briefly presented, together with the JJ characteristics in the context of high-speed electronics. Line inductances of different geometries and at different temperatures have been measured through superconducting quantum interference device (SQUID) modulation. A detailed comparison with 3-D numerical calculations has been made, and a quantitative agreement that shows typical values of 4-8 pH per square without a ground plane, depending on linewidth and the gap to the ground line, has been obtained. View full abstract»

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  • Nonlinear Circuit Model for Discontinuity of Step in Width in Superconducting Microstrip Structures and Its Impact on Nonlinear Effects

    Publication Year: 2013 , Article#: 1301208
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    Superconducting materials are known to exhibit nonlinear effects and to produce harmonic generation and intermodulation distortion in superconductive circuits. In planar structures, these nonlinearities depend on the current distribution on the strip which is mainly determined by the structure of the device. This paper investigates the current distribution at the step-in-width discontinuity in superconducting microstrip transmission lines, which is computed by a numerical approach based on a 3-D finite-element method. This current distribution is used to obtain the parameters of the nonlinear circuit model for the superconducting microstrip step-in-width discontinuity. The proposed equivalent nonlinear circuit can be solved using the harmonic balance method. Examples of two superconducting structures which contain the steps in width are given and validated by comparison with electromagnetic full-wave results. The proposed model can be used for effective optimization of the superconducting microwave filter resonators in order to minimize their nonlinear distortions. View full abstract»

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  • Complex Conductivity of YBCO Films in Normal and Superconducting States Probed by Microwave Measurements

    Publication Year: 2013 , Article#: 1501011
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    We report on microwave frequency characterization of yttrium barium copper oxide (YBCO) thin films in both normal and superconducting states. A microwave single-post dielectric resonator technique using two different resonators was used for the complex conductivity determination of YBCO samples deposited on dielectric substrates. The intrinsic complex conductivity of YBCO films was determined from the measured resonator quality factor Q and resonant frequency values employing rigorous electromagnetic modeling of the resonant structures with the mode-matching and Rayleigh-Ritz techniques. Such approach allowed us to determine the intrinsic properties of the films (conductivity, permittivity, and penetration depth) without any simplifications and errors associated with approximate modeling employing perturbation theory. We describe the superconducting material only through its intrinsic material properties, such as the complex conductivity, which does not depend on the thickness of the sample and other parameters. From both simulations and experimental results, we show that the proposed method of intrinsic complex conductivity determination is particularly useful for the characterization of very thin YBCO layers. To support the novelty of our approach, it is shown that significant differences appear between the rigorous and perturbation computations for thin superconducting films (below 50 nm). View full abstract»

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  • Increasing the Flux Measurement Range of an RF-SQUID Resonant Detection Circuit Using the Robust Symmetrical Number System

    Publication Year: 2013 , Article#: 1602910
    Cited by:  Papers (1)
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    The design and simulation of a new low temperature Niobium radio frequency superconducting quantum interference devices (RF-SQUID) flux measurement architecture concept that uses N = 3 RF-SQUID rings (or channels) to significantly extend the range of the flux measurement capability beyond ±Φ0/4 is presented. A resonant detection method based on a robust symmetrical number system (RSNS) preprocessing technique is shown to provide a large increase in the flux measurement range while producing a high-resolution representation of the input magnetic field. The RSNS preprocessing is a modular scheme in which a modulus number of comparators is used at the output of each RF SQUID. The number of comparators with logic 1 in each channel represents the integer values within each RSNS modulus sequence. When considered together, the integers within each sequence change one at a time at the next code position, resulting in an integer Gray code property. We show that the RSNS preprocessing has the feature that the maximum nonlinearity is less than a least significant bit. View full abstract»

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  • Design and Analysis of the Thermal Shield of the Prototype Superconducting Dipole Magnet for GSI

    Publication Year: 2013 , Article#: 4001108
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    For the prototype superconducting dipole magnet of the collector ring for Gesellschaft für Schwerionenforschung, Germany, the thermal radiation from outside would be shielded by the thermal shield (TS). Considering thermal and mechanical properties, the detailed structure of the TS is discussed. For example, the overview and the design concept of the TS scheme are presented. The layout of the cooling pipe system on the outer and inner surfaces has been considered in terms of the forced-flow liquid nitrogen. Moreover, the multilayer insulation made of aluminized Mylar with woven Dacron netting between the layers is applied to the TS's surface for shielding the thermal radiation. In addition, the eddy-current and mechanical analyses are performed. The cryogenic performance testing indicated that the TS can meet the requirements. View full abstract»

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  • The Sintering Process and Superconductivity of Polycrystalline Milled Fe–Se

    Publication Year: 2013 , Article#: 7000405
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    The structural evolution of premilled FeSe powder mixture was investigated by using differential thermal analysis (DTA) and X-ray diffraction (XRD) to elucidate the sintering process. The DTA results showed that the reaction process between Fe and Se powders underwent two different stages: formation of FeSe2 at the solid-solid reaction stage and formation of Fe7Se8 at the solid-liquid reaction stage. However, the XRD data showed that more reactions occurred during the sintering process; hence, DTA may not show peaks for transformation of Fe7 Se8 → β-FeSe and β-FeSe → δ-FeSe due to only a small amount of heat given off in the reactions. In addition, polycrystalline β-FeSe bulk samples were synthesized at a series of different temperatures, and the content of β-FeSe increased with the sintered temperature increasing. Combined with microstructure observation, it was observed that iron selenides exhibited different morphology during the successive phase formation process. The superconductivity of sintered samples was also measured, and the results indicated that the value of Tconset for the sample sintered at 750°C had the highest value. View full abstract»

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  • Thickness Dependence of Structural and Superconducting Properties of Single-Crystal-Like GdBCO Films Prepared by Photo-Assisted MOCVD

    Publication Year: 2013 , Article#: 7200606
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    High-quality GdBa2Cu3O7-δ (GdBCO) films with thicknesses of 0.14-1.62 μm were deposited on (100)-oriented LaAlO3 substrates by photo-assisted metal-organic chemical vapor deposition technique. Evaluation of film microstructure and strain-relaxation phenomenon in the growing films and their effects on the crystallographic and superconducting properties of the GdBCO films have been investigated. A single-crystal-like cross-sectional morphology with dense and crack-free surface and no grain boundary visible was observed. The c-axis lattice parameters of the GdBCO films grown with different thicknesses were used to determine the out-of-plane strain. The result shows that the strain could be gradually relieved as film thickness increases. Highly biaxially textured GdBCO films have been obtained. For a 0.31-μm GdBCO film sample, the full-widths at half-maximum were 0.08° and 0.47° for out-of-plane and in-plane orientations, respectively. Such low values were similar to that of single-crystal GdBCO. The highest critical current density (Jc) value is ~ 2.5MA/cm2 (77 K and 0 T). As films were getting thicker, their Jc values decrease gradually. This is mainly attributed to a lack of pinning centers in the thicker films. View full abstract»

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  • Analytical Methods and Formulas for Modeling High Temperature Superconductors

    Publication Year: 2013 , Article#: 8001920
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    The electrodynamics of type-II superconductors is considered in the quasi-static limit when the concept of the so-called critical state is well applicable to the superconductors. We review analytical techniques and formulas used to describe the critical states in the superconductors of the various shapes characteristic of high-temperature superconducting materials. In particular, it is explained how 3-D critical-state problems for thin planar superconductors can be reduced to more simple 2-D problems. Within this approach, the critical states in a thin infinitely long superconducting strip are analytically described not only in the simplest case of a constant critical current density jc but also in the case of anisotropic flux-line pinning and for simple model dependence of jc on the magnetic-field magnitude. We also present the analytical solutions of the critical-state problem for superconducting strips with ferromagnetic substrates and for various arrays of superconducting strips with a transport current or in an external magnetic field. In particular, one of the discussed configurations of the strips can model superconducting power transmission cables. We also describe some analytical solutions of the electrodynamic equations for type-II superconductors with power-law voltage-current characteristics. View full abstract»

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  • AC Losses in HTS Tapes and Devices With Transport Current Solved Through the Resistivity-Adaption Algorithm

    Publication Year: 2013 , Article#: 8201708
    Cited by:  Papers (2)
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    Alternating current (ac) losses in high-temperature superconductor tapes and devices with transport current are solved by using the resistivity-adaption algorithm (RAA). The most advanced feature of the RAA is that it enables the simulation of any model derived from the flux motion theory on finite-element analysis (FEA) packages that have an eddy current solver. The principle of the RAA, as well as its realization on the ANSYS FEA package, is introduced. The simulation begins with the calculation of the ac loss of an ellipse and of strips with aspect ratios ranging from 50 to 2000. The accuracy and efficiency of the calculation are verified through comparisons with the Norris theoretical curves. The possible errors and the method to overcome such errors are discussed. The most significant improvement in the proposed RAA from that discussed in a previous study is that the RAA was proven to be valid for calculating the field-dependent critical state model by using the descendant process from +Im to -Im. We then extend this method to calculate the transport ac loss of a stack of ellipses with Jc(B) characteristic from a typical Bi2223/Ag tape and the transport ac loss of a stack of strips with Jc(B) characteristic from a typical YBCO-coated conductor. View full abstract»

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  • Study of Dielectric Properties of Oxygen-Postannealed \hbox {Cu}_{0.5} \hbox {Tl}_{0.5}\hbox {Ba}_{2}\hbox {Ca}_{2}(\hbox {Cu}_{3 \hbox {-} {y}}\hbox {M}_{y})\hbox {O}_{10\hbox {-}\delta } Superconductor

    Publication Year: 2013 , Article#: 8800108
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    The superconducting properties [onset temperature (Tconset) and zero-resistivity critical temperature Tc (R = 0) ] and the dielectric properties [dielectric constants (εr/, εr//), absolute dielectric loss | tan δ|, and ac conductivity (σac)] of oxygen-postannealed Cu0.5Tl0.5Ba2Ca2(Cu3-yMy)O10-δ(M = Si, Ge, Sn; y = 0, 1) superconductor have been studied. The superconducting properties have been increased in all undoped and Si-, Ge-, and Sn-doped samples after oxygen postannealing. The negative capacitance (NC) has been also observed in all postannealed Cu0.5Tl0.5Ba2Ca2(Cu3-yMy)O10-δ samples. Capacitance C and conductance G of Ge-doped Cu0.5Tl0.5Ba2 Ca2(Cu2Ge1)O10 - δ and Sn-doped Cu0.5Tl0.5Ba2Ca2(Cu2 Sn1) O10-δ samples have been increased after oxygen postannealing. In contrary, the values of C and G have been decreased in both the undoped Cu0.5Tl0.5Ba2Ca2Cu3 O10-δ and Si-doped Cu0.5 Tl0.5Ba2Ca2(Cu2Si1)O10-δ samples after oxygen postannealing. The variation of C and G depends upon the degree of polarizibility, which is associated with carrier's density. The carrier's density depends upon the oxygen content, which can be controlled by oxygen postannealing. The appreciable change in the dielectric properties of Cu0.5Tl0.5Ba2Ca2(Cu3-yMy)O10-;- ; samples is the indication of oxygen variation after oxygen postannealing. These studies also show that the dielectric response of Cu0.5Tl0.5 Ba2Ca2(Cu3-yMy)O10-δ samples is strongly temperature and frequency dependent. View full abstract»

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  • Considerations for Designing a Conduction-Cooled Sample Holder

    Publication Year: 2013 , Article#: 9500309
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    Usually, superconductive strands are characterized and quality controlled by performing short sample tests. These tests are often carried out using liquid cryogen or cold gas flow as coolant. However, in some measurements, the use of a more adiabatic approach is beneficial. This can be achieved with a conduction-cooled system. The advantages and the disadvantages of using a conduction-cooled measurement are presented. The thermal and electrical aspects of a typical conduction-cooled sample holder are discussed by studying the steady-state and transient operation of such a setup with a 3-D finite-element method model. Also, improving the electrical contact resistance of a clamped current/cooling contact facilitating fast sample changeover was experimentally analyzed. The obtained results indicated that an inadequate sample holder can cause excessive heat generation, can slow down quench recovery, and can complicate burnout protection. Finally, the electrical and thermal properties of typical MgB2 samples under test were modeled to have a significant effect on the operation of a conduction-cooled measurement system. An order of magnitude increase was observed in both ohmic losses and quench recovery time, when the outer sheath material of the simulated superconductor was changed from copper to Monel. View full abstract»

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  • IEEE Transactions on Applied Superconductivity subject categories for article numbering

    Publication Year: 2013 , Article#: 0001101
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  • IEEE Transactions on Applied Superconductivity information for authors

    Publication Year: 2013 , Article#: 0001201
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Aims & Scope

IEEE Transactions on Applied Superconductivity contains articles on the applications of superconductivity and other relevant technology.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Britton L. T. Plourde
Syracuse University
bplourde@syr.edu
http://www.phy.syr.edu/~bplourde