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Applied Superconductivity, IEEE Transactions on

Issue 2 • Date June 1994

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Displaying Results 1 - 9 of 9
  • Modular based design for a small to medium scale toroidal type SMES

    Publication Year: 1994 , Page(s): 51 - 55
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    A small to medium scale SMES (superconducting magnetic energy storage) is one of the most attractive devices as a controller in electric power systems. This paper proposes one design strategy for a small to medium scale toroidal type SMES based on the idea of a modular structure of a superconducting toroidal coil and a power conditioning system. The idea of the modular structure, an example of design of SMES using the proposed idea, and characteristics of the designed system are presented. The power conditioning system using a voltage-source type ac/dc converter circuit and a chopper circuit is presented for this structure.<> View full abstract»

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  • Analysis on influence of temporal and spatial profiles of disturbance on stability of pool-cooled superconductor [in LHD]

    Publication Year: 1994 , Page(s): 56 - 60
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (502 KB)  

    An influence of temporal and spatial profiles of thermal disturbance on the transient stability of superconductors is analyzed. We consider two types of pool-cooled superconductors: one conductor has the cross-sectional pattern where the stabilizer is located outside the superconducting cable; the other conductor has the stabilizer inside the superconducting cable. The computational result shows the former type of conductor is more affected by variations of the transport current and the temporal and spatial profiles of the disturbance than the latter. As a result, we recommend that the superconducting cable be located near the coolant in high current monolithic superconductor.<> View full abstract»

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  • High current pressure contacts to Ag pads on thin film superconductors

    Publication Year: 1994 , Page(s): 61 - 64
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    High current, low resistance, nonmagnetic, and nondestructive pressure contacts to Ag pads on YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thin film superconductors were developed in this study. The contact resistance reported here includes the resistance of the current lead/Ag pad interface, the Ag pad/YBCO interface, and the bulk resistance of the contact material. This total contact resistance is the relevant parameter which determines power dissipation during critical-current measurements. It was found that regardless of the optimization of the Ag pad/YBCO interface through annealing, a pressure contact can yield a lower total resistance than a soldered contact. The lowest resistance obtained with pressure contacts was 3 /spl mu//spl Omega/ (for a 2/spl times/4 mm/sup 2/ contact). These contacts may be useful for many different high temperature superconductor (HTS) studies where high-current contacts with low heating are needed.<> View full abstract»

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  • Field response of ultra-thin type II superconducting transmission lines

    Publication Year: 1994 , Page(s): 65 - 75
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1150 KB)  

    This work describes the effect of a tangential magnetic field on the superconducting penetration depth, /spl lambda/, as modeled by the theory of Ginzburg and Landau. In particular, an increasing magnetic field decreases the magnitude of the order parameter /spl Psi/. Consequently, the London equations have been modified to include field dependent values of the penetration depth, /spl lambda/(T,H) and complex conductivity, /spl sigma/(T,H). The analysis assumes that the superconducting films are free of vortices. For Type II films, this criteria can only be met when the thickness of the conductors is less than 1.8/spl xi//sub GL/. The G-L theory is used to find closed form solutions that describe the electromagnetic characteristics of a kinetic inductance transmission line including phase velocity, impedance, and energy loss, as functions of power, temperature and magnetic fields. Limitations of power are also discussed. To validate these concepts, experiments verifying the effects of temperature and bias field were implemented using niobium superconductors 500 /spl Aring/ thick separated by 1000 /spl Aring/ of Al/sub 2/O/sub 3/. Potential device applications include variable phase-shifters, tunable filters, and extremely sensitive bolometers.<> View full abstract»

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  • Increasing the current density of dielectric-base transistors with an MgO emitter-base barrier

    Publication Year: 1994 , Page(s): 76 - 80
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (557 KB)  

    We measured the current-voltage characteristics of YBa/sub 2/Cu/sub 3/O/sub 7-x//oxide/n-SrTiO/sub 3/ diodes using NdGaO/sub 3/, LaAlO/sub 3/, CeO/sub 2/, and MgO as the oxide. MgO films had the highest current density. We then fabricated dielectric-base transistors with a YBa/sub 2/Cu/sub 3/O/sub 7-x/(YBCO) emitter/collector on a SrTiO/sub 3/ dielectric base with an MgO barrier. The transistors had both voltage and current gains exceeding unity at 4.2 K. The emitter current density was about 4/spl times/10/sup 3/ A/cm/sup 2/ at a collector-emitter voltage of 10 V and base-emitter voltage 10 V; this is 2 to 3 orders of magnitude larger than that of transistors with NdGaO/sub 3/ emitter-base barrier. We obtained a transconductance of around 0.4 mS at a collector-emitter voltage of 10 V for a device with a 6-/spl mu/m-diameter emitter.<> View full abstract»

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  • Deep nondestructive testing using a bulk high T/sub c/ RF-SQUID

    Publication Year: 1994 , Page(s): 81 - 86
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (625 KB)  

    We report the utilization of a high T/sub c/ symmetric two-hole RF-SQUID (superconducting quantum interference device) operating at liquid nitrogen temperature as a gradiometer in nondestructive testing (NDT). This technology offers a possibility of solving simultaneously four requirements: sensitivity, penetration depth, resolution, and portability of the device. We used the simple dipole model, and showed that the signal attenuation in the near zone agreed with our experimental results and is less than that of a plane wave. In our experiment we used a low frequency current of 30 Hz and demonstrated that the amplitude of the signal was reduced only by 20% after the insertion of 1" (2.54 cm) of aluminum alloy plates between the mock crack and the SQUID in agreement with the theoretical calculations.<> View full abstract»

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  • A wide dynamic range single-chip SQUID magnetometer

    Publication Year: 1994 , Page(s): 87 - 91
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (437 KB)  

    A single-chip SQUID magnetometer is described and demonstrated that integrates a SQUID sensor with feedback circuitry on the same chip. This chip has a very large dynamic range, determined by the sensitivity of the input SQUID and by the current-carrying capacity of the input superconducting lines. This chip can eliminate the need for the sophisticated room temperature circuitry currently used with conventional analog SQUID magnetometers and replace these electronics with a simple bi-directional counter. Furthermore, on-chip multiplexing can be easily implemented for use in multi-channel systems where arrays of more than 100 sensors are required for magnetic imaging. In addition, due to its extremely wide dynamic range and high slew rate, a system based on this chip can be operated in a relatively high magnetic field environment without extensive magnetic shielding.<> View full abstract»

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  • A niobium nitride-based analog to digital converter using rapid single flux quantum logic operating at 9.5 K

    Publication Year: 1994 , Page(s): 92 - 96
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (415 KB)  

    An analog to digital converter (ADC) using the rapid single flux quantum (RSFQ) logic family implemented in niobium nitride (NbN) technology is described. The circuit was originally developed and demonstrated in niobium technology. An identical circuit was then laid out, fabricated and demonstrated in NbN technology. The chips were fabricated using an eight-layer NbN-based process with Josephson junction critical current density of 500 A/cm/sup 2/. In this paper, we report on the measurement results for a 6-bit flux quantizing ADC which exhibited proper operation and good DC bias margins. We also demonstrate results from an ADC chip operating up to 9.5 K.<> View full abstract»

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  • The design for a Josephson micro-pipelined processor

    Publication Year: 1994 , Page(s): 97 - 106
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (962 KB)  

    A novel processor with micro-pipelined architecture is proposed for latch-type Josephson logic devices. The processor is segmented into several operating stages activated by a multi-phase power system. Independent register groups are allocated to each stage in order to support pipeline processing of several instruction streams. This architecture allows building of a fine pipeline pitch processor which is capable of MIMD processing. A 12-bit micro-pipelined Josephson processor, containing an ALU, a multiplier and 16 registers, is described. Driven by a 3-phase AC power system, it is able to process 4 instruction streams simultaneously. A pipeline pitch of 3.3 GHz is expected using conventional Josephson device technology. A 4-bit processor design for 12-bit data length is also 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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Meet Our Editors

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