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Applied Superconductivity, IEEE Transactions on

Issue 4 • Date Dec. 2008

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Displaying Results 1 - 15 of 15
  • [Front cover]

    Page(s): C1
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  • IEEE Transactions on Applied Superconductivity publication information

    Page(s): C2
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  • Table of contents

    Page(s): 1753
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  • Phase Transformations During the Reaction Heat Treatment of Internal Tin Nb _{3} Sn Strands With High Sn Content

    Page(s): 1754 - 1760
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1957 KB) |  | HTML iconHTML  

    The phase transformations that occur during the reaction heat treatment (HT) of Nb3Sn superconductors depend on the overall elemental composition of the strand subelements. In the case of modern high Jc strands with a relatively low Cu content, liquid phases are present during large temperature intervals and phases that can be detrimental for the microstructural and microchemical homogeneity of the fully reacted strand are formed. We report synchrotron X-ray diffraction measurements during in-situ reaction HT of a state-of-the-art high Jc Nb3 Sn internal tin strand. In this strand, Cu3Sn is formed upon Cu 6Sn 5 decomposition at 415degC, a Sn-rich ternary Cu-Nb-Sn phase is detected in the approximate temperature interval 345degC-575degC, and NbSn2 is present in the temperature interval 545degC-630degC. The formation of voids in the strand subelements has been monitored by synchrotron microtomography during in-situ reaction HT. View full abstract»

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  • Theory of Superconductive Traveling-Wave Photodetectors

    Page(s): 1761 - 1768
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (381 KB) |  | HTML iconHTML  

    This paper studies the theory of traveling-wave photodetection in superconductive multilayer optical waveguides, as a general platform for ultrafast, ultrasensitive, and ultralow-noise optoelectronics. The kinetic inductance theory of superconductive thin films and the modified transmission line theory are employed to investigate the distributed photodetection and signal generation mechanisms in superconductive traveling-wave devices. A general model for calculation of the optical responsivity of superconductive traveling-wave photodetectors is developed and operation regimes of interest are highlighted. Moreover, the inclusion of a photoconductive layer in the device structure and some important loading schemes are discussed and their effects on the device performance, such as quantum efficiency and electrical bandwidth, are addressed. View full abstract»

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  • Vortex Interaction in Arrays of Fully Coupled Josephson Junctions

    Page(s): 1769 - 1773
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (142 KB) |  | HTML iconHTML  

    The vortex-vortex interaction energy is analyzed in two-dimensional arrays of Josephson junctions in which the effects of self-induced fields are important. We find that only if all the junctions are coupled by the magnetic inductive fields, the interactions between vortices are similar to the interactions between vortices in thin superconducting films and that approximate inductance models can lead to results physically unexpected. View full abstract»

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  • Analytic Estimates of Magnetic Energy in Superconducting Quadrupoles

    Page(s): 1774 - 1780
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (383 KB) |  | HTML iconHTML  

    In this paper, we propose analytical formulae to determine the magnetic energy stored in superconducting quadrupoles made of sector coils. The study is based on the Fourier transformation of the current density flowing within the coils. The case of real magnets (i.e., magnets which are not made of pure sector coils) is treated and a heuristic corrective coefficient allowing taking into account the energy enhancement due to current grading is derived from a numerical study. We also introduce the effect of an unsaturated iron yoke on the stored energy and we discuss the issue of the yoke saturation. View full abstract»

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  • A Low-Noise Broadband Cryogenic Preamplifier Operated in a High-Field Superconducting Magnet

    Page(s): 1781 - 1789
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (529 KB) |  | HTML iconHTML  

    The recently developed cryogenic Fourier-transform ion cyclotron resonance mass spectrometer (FTICRMS) has provided an opportunity for improvement in the limit of detection of FTICRMS by cooling the detection preamplifier to 4 K, thus reducing the thermal noise in the preamplifier. In this manuscript, we describe the development of a low-noise cryogenic preamplifier for FTICRMS and its performance in a high-field superconducting electromagnet. The preamplifier has a voltage gain of 250 with - 3-dB roll off at 850 kHz. The cryogenic preamplifier circuit has shown about 20 times improvement in signal-to-noise ratio, over the room temperature version. View full abstract»

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  • Large-Scale SFQ Switches Using Miniaturized 2 ,\times, 2 Switch Cell

    Page(s): 1790 - 1796
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3451 KB) |  | HTML iconHTML  

    We have developed a miniaturized 2times2 switch cell, a key component of single-flux-quantum switches. The cell was optimized using a full-custom design approach instead of our conventional cell-based design approach. The cell contains 74 Josephson junctions, and its power consumption is 16.8 muW. Its area is significantly reduced to 160 mum times 200 mum, which is 69% smaller than our conventional cell-based switch. We fabricated test chips using our 2.5-kA/cm2 Nb standard process and confirmed a 40-GHz operation with a bias margin of plusmn8.5% by an on-chip test. We also designed 4times4 and 8times8 cross-bar switches using the 2times2 switch cells. The 40-GHz operation of the 4times4 switch was confirmed with a bias margin of plusmn4% by an on-chip test. The full function of the 8times8 switch was also confirmed with a bias margin of plusmn5% at a low-frequency (10 kHz). The area of these switches was reduced to about half of that of our conventional switches. We discussed large-scale switches using our advanced high- Jc multilayer process. We estimated that area of a 32 times 32 switch designed for the advanced process are reduced by 83% compared to a switch designed for the standard process. View full abstract»

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  • High-Speed Nb/Nb–Si/Nb Josephson Junctions for Superconductive Digital Electronics

    Page(s): 1797 - 1800
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    Josephson junctions with cosputtered amorphous Nb-Si barriers are being developed at NIST for use in voltage standard circuits. These junctions have the potential for a wide range of applications beyond voltage standards because their electrical properties can be tuned by controlling both the composition and the thickness of the barrier. If the composition of the barrier is tuned so that the resistivity is close to the metal-insulator transition, the high resistivity allows junctions with a large characteristic voltage and reproducible critical-current densities, which should be ideal for high-speed digital superconductive device applications. Because these junctions are intrinsically shunted, there is no need for external shunt resistors, which could start to become a limitation as the development of devices leads to higher critical-current densities and greater circuit densities. Presently, the AlOx-barrier junctions used in digital superconducting electronics suffer from poor reproducibility, particularly for the high critical-current densities needed for high-speed applications. In this paper, amorphous Nb-Si barrier junctions with characteristic voltages on the order of 1 mV and characteristic frequencies on the order of hundreds of gigahertz are demonstrated. This junction technology looks promising for applications in high-speed digital electronics. View full abstract»

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  • Corrections to “Growth of Lanthanum Manganate Buffer Layers for Coated Conductors via a Metal–Organic Decomposition Process”

    Page(s): 1801 - 1803
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    In our prior paper, we reported forming (110)-oriented LaMnO3 on a biaxially textured Ni-3at%W substrate. Chemical analysis of these films subsequent to publishing the paper showed only La and O-there was no Mn present in the film. The film was actually (400)-oriented La2O3 with the cubic bixbyite structure. Subsequent studies also showed that MnO film is not stable on Ni and Ni-W substrate surfaces at 1100 degC and PO2 = 10-16 atm where bulk MnO is stable. View full abstract»

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  • Why we joined ... [advertisement]

    Page(s): 1804
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  • 2008 Index IEEE Transactions on Applied Superconductivity Vol. 18

    Page(s): 1805 - 1868
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  • IEEE Transactions on Applied Superconductivity upcoming special conference issues

    Page(s): C3
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  • IEEE Transactions on Applied Superconductivity information for authors

    Page(s): C4
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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://www.phy.syr.edu/~bplourde