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Applied Superconductivity, IEEE Transactions on

Issue 2 • Date April 2011

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  • [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): 41
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  • Eddy-Current Analysis of Cold Mass and Thermal Shield for Series-Connected Hybrid Magnet

    Page(s): 42 - 47
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (785 KB) |  | HTML iconHTML  

    The National High Magnetic Field Laboratory currently has three series-connected hybrid (SCH) magnet projects, where resistive coils are connected in series with superconducting coils using cable-in-conduit-conductor (CICC) underway: first for the magnet laboratory in Tallahassee, FL; second for the Helmholtz Zentrum Berlin for Materials and Energy (HZB), Germany; and the third for the Spallation Neutron Source at the Oak Ridge National Laboratory, TN. The one for HZB has a horizontal conical bore with a 30^ opening angle for neutron scattering experiments. During power supply trip, superconducting magnet quench, resistive insert short, and insert fault, transient electromagnetic effects as a result of fast decay of the coil current introduce a significant amount of eddy current and Lorentz force on the conductive components of the cryostat such as the metallic cold-mass magnet frame and the 50-K thermal radiation shield. Although the eddy-current heating is not a concern during quench and fault operations, the eddy-current-induced Lorentz forces need to be taken into account in the structural design of the SCH cryostat. In this paper, a detailed eddy-current analysis for the HZB magnet during abnormal operations has been performed for its cryostat based on the dry magnet design concept. The nonuniform eddy-current distribution from the finite-element analysis implies that local hot spots may develop under abnormal operations. The eddy-current-induced Lorentz forces are quantified to ensure the strength and stability of the cryostat structure and, most importantly, safety of the SCH magnet during abnormal conditions. View full abstract»

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  • A Simple Wide-Range Noise Thermometer With DC SQUID Readout for Operation Down to 10 mK

    Page(s): 48 - 51
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (297 KB) |  | HTML iconHTML  

    The design and performance of a compact and easy-to-build thermometer for the temperature range of 10 mK-4.2 K, which is wide enough to cover the entire temperature range of a typical dilution refrigerator, are described here. A commercial low-Tc dc superconducting quantum interference device (SQUID) is used to measure the thermal current noise of a resistor, i.e., an insulated copper wire, that scales linearly with the temperature, as expected from the Nyquist formula. Although, in principle, this thermometer is a primary thermometer, its performance was evaluated as a secondary thermometer. The relative precision of the temperature, which is independent of the temperature, was estimated at 0.4% in a measuring time of 130 s, in good agreement with the expectations. The accuracy evaluated from the comparison with other calibrated thermometers (i.e., superconducting reference point (SRP), cerium magnesium nitrate, and germanium) on different temperature ranges is better than 2% between 10 mK and 4.2 K. If only the SRP thermometer is considered for the comparison in the temperature range of 20-207 mK, the accuracy improves to 1%. The calibrations performed with a single fixed point have a typical accuracy value of about 1%. View full abstract»

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  • Mechanical Properties of \hbox {REBa}_{2}\hbox {Cu}_{3} \hbox {O}_{7 - \delta } Superconductor With RE Obtained From Xenotime Mineral

    Page(s): 52 - 59
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (553 KB) |  | HTML iconHTML  

    The mechanical properties of REBa2Cu3O7-δ super conductor samples produced by different processing routes are compared, where RE corresponds to a natural mixture of rare-earth (RE) elements extracted from xenotime mineral. Xeno time can be used as a precursor for RE oxides that are used to produce electrotechnical devices that do not demand high-purity yttrium or other pure lanthanide element on Y site. The different processing routes lead to the production of polycrystalline, melt textured, and single-crystal samples. Hardness, elastic modulus, and indentation fracture toughness were measured by instrumented indentation and conventional Vickers microindentation. The highest hardness and elastic modulus are of the melt-textured samples because of their microstructure of 211 inclusions and pores embedded in the 123 matrix. The lowest hardness is observed for the polycrystalline sample due to its high porosity. The lowest elastic modulus is of the single crystal. Indentation fracture toughness for melt-textured and single-crystal samples are in the range of literature values (~1 MPa.m1/2). Our results indicate that melt-textured REBa2Cu3O7-δ samples have the most favor able mechanical properties for technological applications. View full abstract»

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  • A Hybrid Field-Harmonics Approach for Passive Shimming Design in MRI

    Page(s): 60 - 67
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (846 KB) |  | HTML iconHTML  

    This paper presents a new passive shimming (PS) design scheme for the correction of static magnetic-field inhomogeneities in magnetic resonance imaging (MRI) systems. In MRI, the PS procedure usually employs magnetic-field-based or harmonic-based methods to find an optimal iron-piece configuration to improve the uniformity of the static magnetic field in the imaging region. For the field-based PS technique, the peak-to-peak field inhomogeneity is minimized, and the harmonic components are inherently unconstrained; in the harmonic-based scheme, selected unwanted harmonics are minimized, and the overall field uniformity is consequently reduced. The field approach usually provides good field homogeneity but lacks flexibility in managing all terms of spherical harmonic field expansion; the harmonic approach is capable of controlling targeted low-order harmonic terms but can have difficulty in producing optimal overall field homogeneity and in controlling high-order harmonics. The new algorithm proposed herein attempts to combine the strengths of these two methods for a better PS solution. During the PS implementation, an explicit expression of the system matrix with both the field and harmonic sensitivities is generated, and then, an optimization procedure is performed for the determination of shim-piece thicknesses and locations. A case study presented shows that the hybrid method provides good quality, flexible solutions for controlling individual harmonic impurities, and also overall field uniformity. This method is not only applicable to conventional MRI magnets, but also, its flexibility means that it can be easily used to shim unconventional electromagnets. View full abstract»

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  • A High-Temperature Superconducting Notch Filter to Suppress Cellular-Band Interference in Radiotelescopes

    Page(s): 68 - 70
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    An experimental high-temperature superconducting four-pole filter for mitigation of the IMT 2000 cellular band in radiotelescopes is presented. The filter uses a novel capacitive cross-coupling to achieve a quasi-elliptic response. Composite right/left-handed (CRLH) zeroth-order resonators are used to avoid harmonic generation throughout the UHF and L-bands. View full abstract»

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    Page(s): 71
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    Page(s): 72
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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

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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