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Applied Superconductivity, IEEE Transactions on

Issue 4 • Date Aug. 2012

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Displaying Results 1 - 21 of 21
  • [Front cover]

    Publication Year: 2012 , Article#: 0002701
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  • IEEE Transactions on Applied Superconductivity publication information

    Publication Year: 2012 , Article#: 0002801
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  • Table of contents

    Publication Year: 2012 , Article#: 0000602
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  • A Wideband HTS Planar Microwave Balun

    Publication Year: 2012 , Article#: 1500304
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (133 KB) |  | HTML iconHTML  

    This paper presents a high-temperature superconducting (HTS) planar balun. The balun exhibits an excellent amplitude and phase balance performance. The balun was fabricated using double-sided HTS YBCO films on a 0.5-mm-thick 3-in LaAlO3 substrate. The balun demonstrates a wideband operation and a low insertion loss. The center frequency of the balun is 1.25 GHz. The return loss bandwidth of 18 dB is 1.02 GHz (the fractional bandwidth is 82%). The phase imbalance is less than 7. The amplitude imbalance is less than 0.7 dB, and the insertion loss is less than 0.31 dB over 0.69-1.77 GHz. View full abstract»

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  • Terahertz Radiation Power Characterization and Optimization of Stack of Intrinsic Josephson Junctions

    Publication Year: 2012 , Article#: 1500407
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    Terahertz radiation of the stack of intrinsic Josephson junctions in the mesa structure of the layered high- superconductors is analyzed and presented in this paper. The dependence of the radiated power to the geometrical parameters, cavity-waveguide boundaries, and magnetic and electric biases has been investigated. This has been done by numerical calculation of the previously proposed coupled sine-Gordon equations, which characterize the electromagnetic dynamics of the stack of the intrinsic Josephson junctions. Using the obtained numerical results from these coupled equations, the effect of the design parameters, such as dimensions of the mesa structure, the magnitude of the applied magnetic field, and the direct current on the enhancement of the radiated power, is studied. Thus, the radiated power is optimized with respect to these considered parameters. By variation of the number of layers, we also investigate the effect of the number of intrinsic Josephson junctions on the total radiated power. The results from this part are also compared with the previous analytical models. View full abstract»

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  • A Multiloop SQUID and a SQUID Array With 1- \mu \hbox {m} and Submicrometer Input Coils

    Publication Year: 2012 , Article#: 1600105
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (630 KB) |  | HTML iconHTML  

    We have constructed a niobium multiloop SQUID current sensor and a 60-SQUID series array as a mix-and-match fabrication experiment utilizing our in-house projection stepper. The multiloop SQUID includes an input coil with a linewidth of 0.8 μm and a pitch of 1.6 μm, resulting in the mutual inductance M-1 = 1.8 μA/Φ0. The SQUID array is built on the same chip as the second-stage amplifier. The array and the multiloop showed white flux noise of 0.2 and 0.8 μΦ0 Hz-1/2 at 4.2 K, respectively. Owing to the well-balanced gradiometric narrow-line construction, the two-SQUID system can be cooled down in the Earth's magnetic field and can be operated without superconducting or mu-metal shields. Excess low frequency noise was observed, whose possible origin in Josephson dynamics has been briefly studied with numerical simulation. View full abstract»

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  • Crosstalk Suppression and High-Fidelity Measurement in 2-D Tunneling of Coupled Josephson Junctions

    Publication Year: 2012 , Article#: 1700110
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    We present a new configuration concept in which two similar Josephson junctions are coupled through a capacitor placed in parallel to a dc-superconducting quantum interference device (SQUID) to improve the characteristics of phase qubits. In real coupled quantum systems, because of mutual effects such as crosstalk, entangled quantum states cannot be independently measured. The proposed two-qubit system is demonstrated to have a negligible crosstalk, obtained from the application of a single measurement pulse and an appropriate external flux to one of the junctions and the dc-SQUID, respectively. Surprisingly, the theoretically predicted fidelity for a single-qubit design increases to 99.99% for typical Josephson junction parameters. The high-fidelity measurement is reached even with pulse times less than 1 ns, while the highest fidelities reported so far are obtained by wide temporal pulses through single-shot current pulse measurements. This is accomplished by proper coupling capacitance, which determines the coupling time, the measurement time, and their proportion. Furthermore, the ratio of decoherence time for this structure with respect to the one belonging to a typical qubit is found to be more than 1.42. View full abstract»

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  • Device Modeling of Superconductor Transition-Edge Sensors Based on the Two-Fluid Theory

    Publication Year: 2012 , Article#: 2100212
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    In order to support the design and research of sophisticated large-scale transition-edge sensor (TES) circuits, we use basic SPICE elements to develop device models for TESs based on the superfluid-normal fluid theory. In contrast to previous studies, our device model is not limited to small-signal simulation, and it relies only on device parameters that have clear physical meaning and can be easily measured. We integrate the device models in design kits based on powerful electronic design automation tools such as CADENCE and OrCAD and use them for versatile simulations of TES circuits. Comparing our simulation results with published experimental data, we find good agreement which suggests that device models based on the two-fluid theory can be used to predict the behavior of TES circuits reliably. Hence, they are valuable for assisting the design of sophisticated TES circuits. View full abstract»

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  • Optimization of High-Temperature Superconducting Coil Employing Edge Vacancies and Central Separation

    Publication Year: 2012 , Article#: 3900606
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (639 KB) |  | HTML iconHTML  

    In this paper, we propose a new high-temperature superconducting (HTS) coil with shorter HTS tape length. In general, the critical current and n-value of an HTS tape depend on the applied magnetic field magnitudes and angles. Therefore, we derived fitting equations for the critical current and n-value in terms of these parameters obtained from the measurements of a Bi-2223/Ag tape at 77 K. Relatively large electric fields were generated at the coil edges because of the large magnetic fields and angles. This phenomenon prevents improvement of transport-current performance of an HTS coil. To solve this problem, we created a new HTS coil with edge vacancies and central separation. Analysis results revealed that the coil critical current increased significantly. Furthermore, we found an optimum coil shape that results in the improvement of the central magnetic field and stored energy by 33% and 99.5%, respectively, compared with those of the normal coil, irrespective of the reduction in the total HTS tape length owing to edge vacancies. View full abstract»

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  • Generalized Electrical Image Method for Field Reconstruction

    Publication Year: 2012 , Article#: 4004507
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1142 KB) |  | HTML iconHTML  

    A technique for magnetic field reconstruction is proposed with the use of a generalized electrical image method (GEIM). The basic idea behind the GEIM is that by understanding fundamental properties of the strategic dual image (SDI) method and applying the equivalence principle on the SDI boundary, a simple form of the interior/exterior magnetic field can be determined. As an example of this technique, a field reconstruction of a quadruple magnet is demonstrated. View full abstract»

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  • Self-Inductance of a Racetrack Coil

    Publication Year: 2012 , Article#: 4905509
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (169 KB) |  | HTML iconHTML  

    Superconducting racetrack coils are used for magnetic levitation, magnetic resonance imaging, etc. When using racetrack coils, it is important to determine the coil characteristics (the resistance, self-inductance, mutual inductance, and distributed capacity of the coil). It is difficult to analyze the racetrack coil that has straight and semicircle parts. Therefore, the analytical solution of this coil has not been obtained yet. In this paper, we derive the analytical solution of the magnetic field of a single-layer racetrack coil based on the magnetic field of the one-turn racetrack coil. In addition, the analytical solution of the self-inductance is derived on the basis of this theory. The validity of this theory is confirmed by comparing measured self-inductance values with the calculated values. View full abstract»

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  • Application of SMES to Enhance the Dynamic Performance of DFIG During Voltage Sag and Swell

    Publication Year: 2012 , Article#: 5702009
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (852 KB) |  | HTML iconHTML  

    The integration of wind turbines into modern power grids has significantly increased during the last decade. Wind turbines equipped with doubly fed induction generators (DFIGs) have been dominating wind power installation worldwide since 2002. In this paper, a superconducting magnetic energy storage (SMES) unit is proposed to improve the dynamic performance of a wind energy conversion system equipped with DFIG during voltage sag and voltage swell events. The converter and the chopper of the SMES unit are controlled using a hysteresis current controller and a fuzzy logic controller, respectively. Detailed simulation is carried out using MATLAB/SIMULINK software to highlight the impact of the SMES unit in improving the overall system performance under voltage sag and voltage swell conditions. View full abstract»

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  • A Novel Process to Produce Amorphous Nanosized Boron Useful for \hbox {MgB}_{2} Synthesis

    Publication Year: 2012 , Article#: 6200606
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (553 KB) |  | HTML iconHTML  

    In this paper, we report a new synthesis route to produce boron powders characterized as being amorphous and having very fine particle size. This route has been developed to improve the performances of superconducting MgB2 powders, which can be directly synthesized from this nanostructured boron precursor by following the ex-situ or the in-situ PIT method during manufacturing of tapes, wires, and cables. All the procedure steps are explained, and the chemical-physical characterization of the boron powder, using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy techniques, is reported. Furthermore, a comparison with commercial boron is given. Preliminary results of the magnetic and electrical characterization, such as critical temperature TC and transport critical current density JC t, for the MgB2 tape are reported and compared with those for the tape prepared with commercial boron. View full abstract»

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  • Effects of Ball Milling on the Sintering Process and Superconducting Properties of (\hbox {MgB}_{2})_{0.96}\hbox {Ni}_{0.04} Bulks

    Publication Year: 2012 , Article#: 6800405
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (499 KB) |  | HTML iconHTML  

    Samples of (MgB2)0.96Ni0.04 prepared by mechanical alloying were sintered at 750°C for 30 min. The reactive process and generating temperature of the second phase were investigated by employing differential thermal analysis, X-ray diffraction, and scanning electronic microscopy. Corresponding microstructures and superconducting properties have also been analyzed. It is found that two-step milling is effective in refining the structure and in eliminating flux jumps, although the corresponding Jc is slightly lowered due to the existence of excessive MgO. This observation indicates that the bulk samples prepared by two-step milling possess stable properties of magnetism and heat compared with the sample prepared by manual milling. View full abstract»

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  • Estimation of the Instantaneously Dissipated Hysteresis Losses in Superconductors

    Publication Year: 2012 , Article#: 8200209
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (642 KB) |  | HTML iconHTML  

    Cables in superconducting magnets are subjected to field-dependent losses, i.e., induced interstrand and interfilament coupling losses, and superconductor hysteresis losses. For the two kinds of induced eddy currents, analytical and numerical models are available, allowing calculating the dissipated power under various operating conditions. For the losses stemming from the superconductor magnetization, the literature only gives formulas for the dissipated energy over closed excitation cycles. We derive an expression for the instantaneously dissipated hysteresis losses during an arbitrary ramp profile using a simplified geometry and hysteresis model. This allows estimating the losses dissipated in nonclosed excitation loops. View full abstract»

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  • Integral Equations for Computing AC Losses of Radially and Polygonally Arranged HTS Thin Tapes

    Publication Year: 2012 , Article#: 8401006
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (605 KB) |  | HTML iconHTML  

    In this paper, we derive integral equations for radially and polygonally arranged high-temperature superconductor thin tapes, and we solve them by finite-element method. The superconductor is modeled with a nonlinear power law, which allows the possibility of considering the dependence of the parameters on the magnetic field or the position. The ac losses are computed for a variety of geometrical configurations and for various values of the transport current. Differences with respect to existing analytical models, which are developed in the framework of the critical state model and only for certain values of the transport current, are pointed out. View full abstract»

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  • Serial Biasing of 16 Modular Circuits at 50 Gb/s

    Publication Year: 2012 , Article#: 1300103
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (303 KB) |  | HTML iconHTML  

    Rapid single-flux quantum circuits are generally biased in parallel with a common ground. As the integration scale increases, the total dc bias current can become too large to be practical. Applications such as large-scale Josephson-junction circuits for petaflops computers must avoid prohibitive dc bias requirements. Serial dc bias of multiple-circuit modules enables more efficient and effective operation of large circuits. This paper describes a circuit containing 1488 junctions in which the bias current was reused 16 times to reduce the required bias from ~100 mA to roughly 12 times less. We report initial results in which this circuit was operated up to 50 Gb/s with a negligible error rate. View full abstract»

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  • Hydrostatic Pressure Effects on the Critical Current of YBCO Coated Conductor Wire

    Publication Year: 2012 , Article#: 8401103
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (192 KB) |  | HTML iconHTML  

    The critical current density of optimally doped bulk YBCO superconductor has been found to increase with the application of external hydrostatic pressure. This paper reports the transport measurements of the critical current (Ic) of YBCO in the form of a coated conductor (CC) wire under hydrostatic pressure up to 0.24 GPa at 77 K. No noticeable change was observed in both the Ic and n-value of the CC sample in the studied pressure range. Two possible scenarios are discussed to explain the observed effect. View full abstract»

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    Publication Year: 2012 , Article#: 9800801
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  • IEEE Transactions on Applied Superconductivity subject categories for article numbering

    Publication Year: 2012 , Article#: 0002901
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    Publication Year: 2012 , Article#: 0003001
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Aims & Scope

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

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Meet Our Editors

Editor-in-Chief
Britton L. T. Plourde
Syracuse University
bplourde@syr.edu
http://asfaculty.syr.edu/pages/phy/plourde-britton.html