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Applied Superconductivity, IEEE Transactions on

Issue 4 • Date Dec. 1999

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Displaying Results 1 - 16 of 16
  • Superconducting magnet system of the CMD-2 detector

    Publication Year: 1999 , Page(s): 4644 - 4647
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (71 KB)  

    This paper describes the superconducting magnet system of the CMD-2 detector. The magnetic field is provided by the main and two compensating superconducting solenoids. The unique features of this system are the solenoids protection method utilizing a distributed resistance along the coil and the power supply being a fluxpump type. The main solenoid produces a field up to 1.2 T in a volume of /spl phi/ 0.71 m/spl times/0.9 m. Its radiation thickness and E/M ratio are 0.38 X/sub 0/ and 5 kJ/kg, respectively. NbTi/Cu superconducting cables without any insulation and an aluminum stabilizer were used for the design of solenoid coils. The superconducting cable was wound in a stainless-steel bobbin and soldered by a PbSn alloy. The cooling bath provides a temperature of 4.2 K in the system. The superconducting magnet system of the CMD-2 detector was manufactured and tested in 1989. View full abstract»

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  • Acoustic emission occurrence induced from a NbTi superconducting coil under alternating current operation

    Publication Year: 1999 , Page(s): 4648 - 4653
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (161 KB)  

    Acoustic emission (AE) induced from an alternating current (ac) superconducting coil was studied during operation in liquid helium. The operating current of the coil was increased from zero with a constant ramp rate at a commercial frequency of 50 Hz until quenching in the coil. The AE signals induced from the coil around the time of the quenching initiation were compared with the operating current, the coil voltage, and the phase difference between the current and the voltage in order to estimate the changes in those signals which resulted from the quenching process. The AE signals continued almost at very low levels before the quenching, At the moment of the quenching initiation, the AE signals clearly and drastically rose approximately 10-15 ms earlier than the decrease in the operating current or the phase difference. The AE signals induced by the wire motion during 50-Hz ac operation were also compared with the operating current. View full abstract»

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  • Electrically small resonator using thick-film high-T/sub c/ superconducting wire helix

    Publication Year: 1999 , Page(s): 4654 - 4660
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (150 KB)  

    A method for optimizing the geometry of half wave shielded helical resonators is presented, Copper and superconducting helical resonators, the latter made of YBCO thick film coated on zirconia wire, were designed and fabricated for tests. The resonant frequency could be predicted in relation to the helix and shield parameters. The surface resistance of YBCO was found at different frequencies and temperatures by the two-fluid model approximations and used to calculate the total loss resistance of the helix. The key parameters of the resonators were predicted, measured and compared. Good agreement was found for copper, but the unloaded Q of the superconducting resonator was lower than predicted, although this was expected, due to the polycrystalline nature of the superconductor. View full abstract»

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  • Penetration of magnetic field into high-temperature superconductors

    Publication Year: 1999 , Page(s): 4661 - 4665
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    The penetration of a monotonically time-increasing magnetic field in high-temperature superconductors (HTSC) slabs with the power law dependencies of the critical current density and resistivity on the magnetic field is investigated theoretically. It is shown that the asymptotic solutions of the extended critical state model correspond to the cases of the classical critical state model and the model of viscous flux flow without pinning. The ranges of the applicability of these models and the conditions for the transition from one model to the other are determined. These theoretical conclusions explain experimental data presented in scientific literature. View full abstract»

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  • Performance of an inductive fault current limiter employing BSCCO superconducting cylinders

    Publication Year: 1999 , Page(s): 4666 - 4676
    Cited by:  Papers (24)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (146 KB)  

    Inductive fault current limiters operating at high levels of short-circuit currents are plagued by appearance of overheated thermal domains in active superconducting elements. Excessive growth of thermal domains may lead to a fatal mechanical destruction of the superconducting element during a fault event. It has been determined that employment of superconductors with gradual dissipation onset controlled by flux relaxation processes can efficiently prevent local overheating. Operation of such elements, fabricated by melt cast technique, has been investigated experimentally in a small-scale open-core model of an inductive fault current limiter. The results of the experiments demonstrate the feasibility of application of superconducting cylinders having properties dominated by flux relaxation processes in inductive current limiters. The most important parameter of a superconducting element designated to operate in such devices is the rate of flux relaxation and its dependence on ac current amplitude. It has been found that ac losses associated with flux relaxation in the investigated cylinders allow for a reliable limiter operation at the nominal current level. Projection of the parameters of the investigated small-scale model to the full-scale device has been performed using the concept of physical modeling. The obtained results indicate that it is possible to build a full-scale device based on flux creep dissipation mechanisms for distribution networks. View full abstract»

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  • Magnetically enhanced terahertz response of Josephson junctions

    Publication Year: 1999 , Page(s): 4677 - 4681
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (146 KB)  

    We investigate the magnetic field effects on the terahertz (THz) response of grain boundary Josephson junctions. First, we show some experimental results of the THz response enhanced by a dc magnetic field. The experimental results and device configuration indicate that the THz RF magnetic field plays a role in enhancing the response. Second, we numerically simulate the current-voltage characteristics and obtain the power dependence of Shapiro steps. Since the junctions are wide compared to the inferred Josephson penetration depth, multiple current paths within a junction are possible and superconducting quantum interference device (SQUID) models should be used. Two kinds of SQUID models are used: an RF-current drive model and an RF-field activation model. Shapiro step enhancement by a dc magnetic field can be reproduced with the use of the RF-field activation model. Finally, we discuss step-height dependence on SQUID parameters as well as give a qualitative explanation for the different predictions of two SQUID models. View full abstract»

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  • RSFQ circuitry realized in a SINIS technology process

    Publication Year: 1999 , Page(s): 4682 - 4687
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (181 KB)  

    We have developed integrated circuits in rapid single flux quantum (RSFQ) impulse logic based on intrinsically shunted tunnel junctions as the active circuit elements. The circuits have been fabricated using superconductor-insulator-normalconductor-insulator-superconductor (SINIS) multilayer technology. The paper presents experimental results of the operation of various RSFQ circuits realized in different designs and layouts. The circuits comprise dc/SFQ and SFQ/dc converters, Josephson transmission lines (JTLs), T-flipflops, and analog key components. Functionality has been proved; the circuits have been found to operate correctly in switching. The circuits investigated have a critical current density of j/sub C/=400 A/cm/sup 2/ and a characteristic voltage of V/sub C/=165 /spl mu/V, the area of the smallest junction is A=24 /spl mu/m/sup 2/. The junctions exhibit nearly hysteresis-free current-voltage characteristics (hysteresis: less than 7%), the intra-wafer parameter spread for j/sub C/ is below /spl plusmn/8%. The margins of the bias current I/sub b/ of the circuits have been experimentally determined and found to be larger than /spl plusmn/24%. At preset, constant values of I/sub b/, the range of a separate bias current I/sub bsw/ fed to a switching stage integrated between two segments of JTL's is fully covered by the operation margins which are larger than /spl plusmn/56%. View full abstract»

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  • Pulse motor with high-temperature superconducting levitation

    Publication Year: 1999 , Page(s): 4688 - 4694
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    A simple but stable noncontact high T/sub c/ superconducting levitation system with a vertical shaft has been presented. The system consists of a superconductor and permanent magnets. In the system, only a high T/sub c/ superconductor supports the lower end of the shaft, and the other end is supported by two ordinary permanent magnets. Since the restoring force is small with respect to the radial direction, the system becomes unstable when the force acts in the radial direction, so it is difficult to drive the shaft by electromagnetic forces when using motors. A driving system using electromagnets has been presented, in which the balanced forces act on two opposite sides of the disc-type rotor in the axial direction. Since the system has no unbalanced force from an analytical point of view, the rotor will be able to rotate without control. In the system, however, since there is eccentricity between the center of rotation and the magnetic center, vibrations are generated. This study also presents an optimal control method for the vibrations. To validate the proposed system and the control method experimental tests have been carried out. View full abstract»

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  • Comparison of radio-frequency and microwave superconducting properties of YBaCuO dedicated to magnetic resonance imaging

    Publication Year: 1999 , Page(s): 4695 - 4701
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (187 KB)  

    Properties of YBaCuO thin films are evaluated in two distinct frequency ranges using different patterns made during the same process on LaAlO/sub 3/ substrate. Microwave superconducting properties in the range 1-45 GHz are determined by S-parameters measurement of a superconducting coplanar waveguide in the range 53-95 K. We obtain a surface resistance of 0.4 m/spl Omega/ at 10.8 GHz and 77 K. Radio-frequency properties are obtained by measuring the Q-factor of a superconducting resonator (YBCO multiturn transmission lines separated by a sapphire sheet) dedicated to surface magnetic resonance imaging. At 52 MHz and 77 K we measure a Q-factor of 33180. The extraction of the radio-frequency surface resistance from Q-factor measurements in the 64-95 K range takes into account external loss mechanisms and nonuniform normal current distribution and leads to a 0.0093-/spl mu//spl Omega/ surface resistance at 52 MHz and 77 K, in good agreement with the value extrapolated from microwave measurements assuming an /spl omega//sup 2/ frequency dependence. The evaluation of /spl lambda//sub 0/ is carried out by using several models for X/sub L/(t). Least squares fits to data in the microwave and radio-frequency domain are performed using the Gorter-Casimir expression for X/sub L/(t) and give the same /spl lambda//sub 0/ value for both devices. View full abstract»

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  • Finite-element calculation of Meissner currents in multiply connected superconductors

    Publication Year: 1999 , Page(s): 4702 - 4707
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB)  

    A three-dimensional (3D) finite-element formulation for calculating Meissner currents in multiply connected superconductors is presented. The fluxoid quantization condition is ensured as simply as possible. The problem is formulated so that we have to solve two systems of equations by the use of a conjugate gradient algorithm without preconditioning. Meissner currents and magnetic-flux density are numerically evaluated in a superconducting tube and around a vortex. These results are compared with analytical solutions. View full abstract»

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  • Analysis of the operational characteristics of a heater-trigger type high-T/sub c/ superconducting power supply

    Publication Year: 1999 , Page(s): 4708 - 4714
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (210 KB)  

    This paper deals with the design and fabrication of a heater-trigger type high-T/sub c/ superconducting (HTSC) power supply, and its characteristics has been analyzed through experiments. A heater-trigger HTSC power supply consists of two heaters, an electromagnet, and a YBCO superconducting bulk. In this experiment, a 0.6-T magnet and a 2.3-A dc heater current were used and 190 s and 380 s were used for the pumping period. In order to measure the pumping current with respect to the magnet flux changes, hall sensors were installed at the surface of the YBCO bulk and inside of an iron core. The experimental observations have been compared with the theoretical predictions. In this experiment, the pumping current has reached about 12 A. In computer simulation, the maximum pumping current of the system has been predicted to be about 13 A. View full abstract»

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  • Transient modeling and simulation of a SMES coil and the power electronics interface

    Publication Year: 1999 , Page(s): 4715 - 4724
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (249 KB)  

    This paper presents the modeling and simulation results of a superconducting magnetic energy storage (SMES) system for power transmission applications. This is the largest SMES coil ever built for power utility applications and has the following unique design characteristics: 50 MW (96 MW peak), 100 MJ, 24 kV dc interface. As a consequence of the high-power and high-voltage interface, special care needs to be taken with overvoltages that can stress the insulation of the SMES coil, especially in its cryogenic operating environment. The transient overvoltages impressed on the SMES coil are the focus of this investigation. Suppression methods were also studied to minimize transients. The simulation is based on detailed coil and multiphase gate turn-off (GTO)-based chopper models. The study was performed to assist in the design of the SMES coil insulation, transient protection, and the power electronics specification and interface requirements. View full abstract»

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  • Circularly polarized 20-GHz high-temperature superconducting microstrip antenna array

    Publication Year: 1999 , Page(s): 4725 - 4732
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (201 KB)  

    A four-element array of circularly polarized 20-GHz YBa/sub 2/Cu/sub 3/O/sub x/ microstrip antennas has been fabricated on LaAlO/sub 3/ and characterized. The array produced good circular polarization, and the gain of the array at 77 K, relative to a copper array of the same design at 77 K, was approximately 0.75 and 1.3 dB for the two gain measurement methods presented. The relative gain increased to approximately 2.2 dB at 30 K. The results demonstrate that high-temperature superconductors, when used in microstrip antenna arrays, improve the efficiency of the array, and that circularly polarized microstrip arrays can be fabricated on LaAlO/sub 3/. View full abstract»

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  • Call for papers

    Publication Year: 1999 , Page(s): 4733
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    Freely Available from IEEE
  • Author index

    Publication Year: 1999 , Page(s): 1 - 53
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    Freely Available from IEEE
  • Subject index

    Publication Year: 1999
    Save to Project icon | Request Permissions | PDF file iconPDF (970 KB)  
    Freely Available from IEEE

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