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Applied Superconductivity, IEEE Transactions on

Issue 1 • Date March 1998

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Displaying Results 1 - 7 of 7
  • Correction factor for determining the London penetration depth from strip resonators

    Page(s): 3 - 6
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB)  

    The strip resonator technique is a popular way to measure the temperature (T)-dependent London penetration depth /spl lambda//sub L/(T) in superconducting thin films. The temperature dependence can provide fundamental information about the superconducting energy gap and hence insight into the pairing mechanism. Since /spl lambda//sub L/(T) characterizes the film's response to a magnetic field near the surface, it qualifies the suitability of the superconducting film for microwave device applications. There has been much controversy regarding the actual form of the temperature dependency, with some researchers reporting a weak-coupled Bardeen-Cooper-Schriefer (BCS)-like behavior and others favoring a Gorter-Casimir type fit. This paper shows that the disagreement can be at least partially attributed to a temperature sensitive term traceable to stray susceptance coupled into the resonator. The effect is inherent to the technique, but a simple procedure to compensate for it can be used and is presented here as a correction factor (1+/spl xi/). View full abstract»

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  • Theoretical studies and experimental results of a SMES used in a pulsed current supply

    Page(s): 7 - 13
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (215 KB)  

    A superconducting magnet energy storage (SMES) can be used as a pulsed power supply. A superconducting coil stores energy without electrical losses and this energy can be recovered through a second wire on which the charge (electromagnetic launcher, for example) is linked. The design of such an apparatus needs to solve simultaneously thermal, magnetic, and electric equations. We proposed a three-dimensional finite difference method to solve these coupled problems. This tool enables us to describe resistive zones of expansion in thick coils during a quench and to predict the duration and the efficiency of the discharge. Moreover, it indicates if the coil is prevented from an excessive temperature increase. Then, a probative device is described and experimental results are compared with theoretical ones. View full abstract»

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  • All-digital 1-bit RSFQ autocorrelator for radioastronomy applications: design and experimental results

    Page(s): 14 - 19
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (118 KB)  

    We present the design of a rapid single-flux-quantum all-digital 1-bit autocorrelator for submillimeter spectrometry applications, featuring 4-GHz input signal bandwidth, double oversampling quantizer, and 16-Mb/s-per-channel output rate. The correlator consists of a digital delay line with multiplication and an array of accumulators with parallel readout. We report experimental results for a three-stage delay line (294 Josephson junctions) and a 4/spl times/4 array of accumulators (288 Josephson junctions) fabricated in HYPRES' standard 3.5-/spl mu/m 1000-A/cm/sup 2/ Nb-trilayer process. View full abstract»

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  • Analysis of a passive superconducting fault current limiter

    Page(s): 20 - 25
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (183 KB)  

    An analysis was carried out to predict the forced response of the equivalent circuit of an innovative superconducting fault current limiter (FCL). The FCL employs two superconducting coils with differing critical currents wound noninductively. The analysis shows that to reduce the voltage drop under normal operating conditions, the coupling coefficient should be kept fairly high (k>0.90). For a given coil configuration (/spl omega/L=constant), the limiting capability of the device increases with the resistance R of the trigger coil up to a certain value of R, then further increase in R changes very little the limiting capability of the FCL. However, further increase in R can reduce the heat generation rate in the device which will help alleviate the problem of relatively long recovery time. The fault current predicted from estimated values of R compares fairly well with results of an experiment reported in the literature. The discrepancy between the predicted and measured current is due mainly to the uncertainty in the estimated resistance R, because both the purity of Cu and the percentage of Cu in CuNi are not known. By varying the ratio of NbTi-Cu-CuNi in the matrix, the purity of Cu, and the percentage of Cu in CuNi various values of R, can be achieved, which should help to alleviate the problem of excessive Joule heating and recovery time. View full abstract»

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  • Inductance measurements in YBa/sub 2/Cu/sub 3/O/sub 7/ DC SQUID's with a submicrometer line width

    Page(s): 26 - 29
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (135 KB)  

    We measured the inductances of submicrometerwide strip lines by using DC superconducting quantum interference devices (SQUID's) fabricated from a single layer of YBa/sub 2/Cu/sub 3/O/sub 7/ thin film, The measured inductances coincided well with some numerically calculated inductances consisting of a magnetic and kinetic component. The proportion of the magnetic component in the total inductance for the line width of 2 /spl mu/m was estimated from calculation to be 56%, The kinetic component increased with the decrease of the line width and was dominant for line widths less than 1 /spl mu/m. The inductance per square at 4.2 K was measured to be 1.3 pH//spl square/ for line widths from 0.5 to 2 /spl mu/m. View full abstract»

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  • Ion beam switching magnet employing HTS coils

    Page(s): 30 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (83 KB)  

    This paper describes the design, construction, and testing of an ion beam switching high-temperature superconducting (HTS) magnet installed at Institute of Geological and Nuclear Science (IGNS) in New Zealand. It was designed by a consortium comprising American Superconductor Corporation (ASC), ISYS, Applied Engineering Technologies (AET), the New Zealand Institute for Industrial Research and Development (IRL), and Alphatech. The work was also supported in part by New Zealand Foundation for Research and Technology-Technology for Business Growth Programme. The magnet generates 0.72 T in the airgap between two 410/spl times/700 mm warm iron poles. The Bi-2223 HTS coils are conduction-cooled with a single stage Gifford-McMahon (G-M) type cryocooler for steady-state operation. The magnet was fully tested at ASC during the fall of 1996. This represents the first large-scale fully operational HTS physics magnet announced so far. The successful operation of this magnet has verified maturation of HTS magnet technology employing conduction cooling techniques with G-M type cryocoolers. Long term operation of this magnet in continuous use will prove the reliability of HTS magnet systems in critical applications and is expected to open future opportunities for HTS in other related areas. View full abstract»

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  • Anisotropic Jc-/spl thetav/ measurements at low fields on a-MoSi thin films: evidence of a two-dimensional regime

    Page(s): 34 - 37
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (125 KB)  

    Transport critical current versus applied field inclination (Jc-/spl thetav/ plots) have been made on a-MoSi thin films in low fields of order 0.04 T. The applied field was rotated (at fixed magnitude) in a plane both parallel (/spl phi/=0/spl deg/) and perpendicular (/spl phi/=90/spl deg/) to the film's longitudinal axis. The results indicate a Jc governed by the perpendicular component of the applied field as is sometimes observed in the layered high-temperature superconducting (HTS) thin films. These results also suggest that the peaks in the Jc-/spl thetav/ occur when the vortex density coming from external sources becomes comparable to that induced internally from the self field of the transport current. A broad peak in the Jc when the field is incident perpendicular to the film surface is observed on the silicon substrate film but not on the sapphire substrate film. Possible reasons for this broad peak are discussed. View full abstract»

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

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