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Applied Superconductivity, IEEE Transactions on

Issue 3 • Date Sept. 1993

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Displaying Results 1 - 6 of 6
  • Testing of an inductive current-limiting device based on high-T/sub c/ superconductors

    Publication Year: 1993 , Page(s): 3033 - 3036
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB)  

    An inductive current-limiting device (CLD) based on transition of a superconductor to the normal state is investigated. The device has low impedance under normal conditions of the circuit to be protected, and a high impedance developed rapidly in a self-switching mode under fault conditions. A model of the device consisting of a copper coil and a high-temperature superconducting ring, coupled magnetically, was tested. It is shown that the transition of the ring to the normal state and its return to the superconducting state take place in a relatively smooth manner, and do not lead to overvoltages across circuit elements. On the other hand, the rate of impedance rise is sufficient to limit both the steady-state and transient components of fault current. The influence of thermal processes in the ring on transient responses in the circuit with the CLD is discussed. Some considerations for a full a size design are also presented.<> View full abstract»

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  • High-temperature superconducting delay lines and filters on sapphire and thinned LaAlO/sub 3/ substrates

    Publication Year: 1993 , Page(s): 3037 - 3042
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (574 KB)  

    The very low microwave surface resistance of high-temperature-superconductor (HTS) thin films allows the realization of microwave devices with performance superior to those made by conventional technology. Superconducting delay lines, for example, have very low propagation loss and dispersion. Long, low-loss, superconducting delay lines on both thinned LaAlO/sub 3/ and sapphire substrates are presented. Delay lines with 27- and 44-ns delay have been made, for the first time, on 5-cm-diameter 254- and 127- mu m-thick LaAlO/sub 3/ substrates, respectively. The insertion losses at 77 K and 6 GHz are 6 and 16 dB, respectively. Delay lines with 9-ns delay have, for the first time, been produced on M-plane sapphire substrates and demonstrate, at 77 K, an insertion loss of 1.0 dB at 6 GHz. A 2.5%-bandwidth 10 GHz four pole edge-coupled bandpass filter on M-plane sapphire substrates is also reported. The filter has minimum insertion loss of less than 0.5 dB at 9.75 GHz and 71 K.<> View full abstract»

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  • Surface resistance measurements of HTS films by means of sapphire dielectric resonators

    Publication Year: 1993 , Page(s): 3043 - 3048
    Cited by:  Papers (44)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (590 KB)  

    A sapphire dielectric resonator with a copper cylindrical shield and two endplates replaced by high-temperature superconducting (HTS) layers was used for very accurate surface resistance measurements on laser-ablated YBCO films. A system using the TE/sub 011/ mode has a resonant frequency of about 18.1 GHz and parasitic-loss Q factor of about 120000. It allows 10 mm*10 mm samples to be measured with sensitivity of +or-30 mu Omega . Individual samples can be measured with somewhat lower accuracy. Using larger HTS samples, one can reduce parasitic losses of the system to an unsignificant level. The exact formulas presented for the resonant system allow for avoiding calibration procedures during the evaluation of the surface resistance.<> View full abstract»

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  • High-resistivity Zr resistors with Ti barrier layer for Nb Josephson circuits

    Publication Year: 1993 , Page(s): 3049 - 3053
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (497 KB)  

    Zr resistors are applied to Josephson integrated circuits in place of Mo because a Zr thin film has about five times the resistivity of Mo. Zr resistors do not need to be protected during etching, unlike conventional Mo resistors, because Zr has much smaller etching rate than Nb. Zr resistors occupy only 25% of a unit cell area. Using Zr resistors reduces the area of the Josephson gate and allows increased circuit integration. Increased contact resistance between Zr and Nb films after annealing at about 350 degrees C was found but suppressed with a Ti barrier. Resistors with a resistance variation throughout a wafer of within +or-2.8% were fabricated.<> View full abstract»

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  • Impact of noise of linearity of SQUID feedback loops at high slew rate

    Publication Year: 1993 , Page(s): 3054 - 3058
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (434 KB)  

    A simplified digital DC SQUID (superconducting quantum interference device) system has been simulated to determine the degree of linearity in a digital flux-locked-loop (FLL), with 12-b D/A converter. The influence of comparator noise and quantization noise on the feedback loops corresponding to single- and two-pole integrators is investigated as a function of the normalized slew rate s/sub N/=s/s/sub max/. A simple approximation describing the attainable linearity up to a specific slew rate range is suggested. Measurements with and without a DC SQUID magnetometer in a digital FLL system yielded a satisfying agreement with simulations in the range 0.3> View full abstract»

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  • Thin-film superconducting inductors for power electronics

    Publication Year: 1993 , Page(s): 3059 - 3060
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (233 KB)  

    Superconducting thin-film inductors promise to be key elements in high-frequency, high-power density, high-efficiency power supplies. A thin-film (0.6 mu m-thick) YB/sub 2/Cu/sub 3/O/sub 7/ inductor capable of handling currents up to 12 A DC was found to have a Q value of 1300 at 260 MHz and 77 K, a factor of 20 higher than an identical inductor made of 15 mu m thick Cu; this improvement factor is shown to be >64 at lower frequencies (a few MHz).<> 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