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Applied Superconductivity, IEEE Transactions on

Issue 1 • Date March 2004

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  • Table of contents

    Publication Year: 2004 , Page(s): c1
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  • IEEE Transactions on Applied Superconductivity publication information

    Publication Year: 2004 , Page(s): c2
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  • Two-pole tunable bandpass filter based on YBCO plated single crystal KTO disk resonators

    Publication Year: 2004 , Page(s): 1 - 6
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (416 KB)  

    This paper addresses design and experimental characterization of a two-pole 1.5% bandpass tunable filter operating at 0.9 GHz and 77 K. The filter is based on two YBCO plated KTaO3 disc resonators (0.5-mm-thick, 10 mm in diameter) and utilizes the TM020 mode. The tunability is achieved through the nonlinear DC electric field dependence of the relative dielectric constant of KTaO3. About 5% tuning range is achieved at 500 V driving voltage. Although the insertion losses are relatively high (about -5 dB at 500 V) the shape of the passband is essentially stable. A rather good agreement between simulated and experimental performances is found. View full abstract»

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  • The inductance model of coupled high-Tc superconducting microstrip lines

    Publication Year: 2004 , Page(s): 7 - 12
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    A simple analytical model of odd and even mode external inductance and kinetic inductance for coupled high-temperature superconducting (HTS) microstrip lines is developed. The kinetic inductance model is derived with the extended incremental inductance rule which is applied in a different way for different conductor thickness. The odd and even mode inductance, self- and mutual inductance, characteristic impedance, and attenuation constant are computed with the presented model expressions and the results agree well with that in published literature. View full abstract»

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  • Optimization of the double-barrier Josephson junction switching dynamics

    Publication Year: 2004 , Page(s): 13 - 21
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB) |  | HTML iconHTML  

    The switching dynamics of a double-barrier Josephson junction is analyzed as a function of the microscopic properties of its electrodes. In particular, it is found that the nonstationary behavior of the Josephson phase difference is very sensitive to dissipation mechanisms acting inside the intrinsic shunt. The leading factor that determines the dissipation is the local electron density of states N(E) inside the electrodes. The roles of junction geometry, electrode purity, and interface quality are discussed and how they affect the details of N(E), hence the resulting phase dynamics. The microscopic analyses allow optimization of the performance of double-barrier Josephson junction-based rapid-single-flux-quantum circuits in two ways: 1) decreasing the switching time of Josephson elements and 2) reducing the excess wiring. Such an analysis is facilitated with the aid of a lumped circuit representation which generalizes the nonlinear resistive-shunted-junction model. View full abstract»

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  • AC losses in HTS tapes in applied longitudinal magnetic fields at variable temperatures

    Publication Year: 2004 , Page(s): 22 - 27
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    In most power devices, the conductor is carrying an ac transport current while it is exposed to an ac magnetic field transverse to the current path. In certain applications, such as power cables or a control winding in a controllable reactor, the conductors are exposed to a magnetic field component longitudinal to the tape axis that is parallel to the current path. To create an improved base for the design of such power devices it is of interest to study the losses in high-temperature superconductor tapes due to longitudinal field in detail. We have investigated the losses at several temperatures of a nontwisted multifilamentary Bi-2223 tape when it was exposed to a longitudinal magnetic field. The losses were measured with a calorimetric method and the results were compared with the critical state hysteresis loss model. The hysteresis losses are dominating at power frequencies (50, 60 Hz) in the investigated field range 2-200 mT and are accurately described by the critical state hysteresis model. View full abstract»

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  • HTS coplanar meander-line resonator filters with a suppressed slot-line mode

    Publication Year: 2004 , Page(s): 28 - 32
    Cited by:  Papers (9)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    The design and experimental results of a four-pole coplanar waveguide (CPW) quasi-elliptic filter using high-temperature superconductor (HTS) films are presented. Quarter-wavelength meander-line resonators are used in the filter topology. Although the resonators are aligned in two lines, no bond-wire bridges are required to balance the ground planes in the design and measurement. The slot-line mode of the filter was shifted to be higher than its third harmonic. The filter is highly miniaturized and the performance is significantly improved by the use of superconductors. The main circuit of the filter only has an area of about 6.6 mm × 2.4 mm on a magnesium oxide substrate, coated with 600-nm-thick YBCO HTS thin film on single side of the substrate. The 3-dB bandwidth is about 1.6% centered at 2.95 GHz. The performance measured at 30 K, without any tuning, gives an insertion loss of better than 0.4 dB and a return loss of about 12 dB in the passband. The first spurious mode is about triple the center frequency. View full abstract»

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  • Uranium doping and thermal neutron irradiation flux pinning effects in MgB2

    Publication Year: 2004 , Page(s): 33 - 39
    Cited by:  Papers (1)
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    The U/n method is a well-established means of improving flux pinning and critical current performance in cuprate superconductors. The method involves the doping of the superconductor with 235U followed by irradiation with thermal neutrons to promote fission. The resultant columnar damage tracks produced by the energetic fission products pin flux vortices and improve critical current performance in magnetic fields. No such improvement could be observed when the U/n method was applied to the MgB2 superconductor. No fission tracks could be observed in TEM, even for samples that were irradiated at the highest fluence. Gamma-ray spectroscopy indicated that fission had occurred in the expected way. The likely resistance of MgB2 to the formation of fission tracks is highly relevant to attempts to improve flux pinning and superconducting performance in this material through the introduction of columnar defects. View full abstract»

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  • Design of front-end circuit for Superconductive A/D converter and demonstration of operation up to 43 GHz

    Publication Year: 2004 , Page(s): 40 - 45
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    We designed a front-end circuit for an analog-to-digital (A/D) converter based on single flux quantum circuitry and tested its functionality at a frequency of up to 43 GHz. The front-end circuit consisted of a pulse generator, a sigma-delta modulator, a 1-to-8 demultiplexer (DEMUX), and superconducting quantum interference device (SQUID) amplifiers. There were 2518 Josephson junctions in the front-end circuit. To operate the circuit at high speed, we designed robust timing against variations in circuit parameters. By using circuit simulations based on the Monte Carlo method, we estimated spread in time lag between clock and data pulses. From this estimate, the timing was optimized to operate the circuit at 40 GHz. The demonstration of the front-end circuit was carried out using the on-chip testing method. Output data were acquired from the modulator through DEMUX. We confirmed proper sigma-delta modulation by analyzing the dependence of the density "1" in the output data on input current level. The proper operation was confirmed in a range of 37-43 GHz. Furthermore, the amplification by the SQUID amplifier was also confirmed at low speed. These results indicate the complete operation of the front-end circuit for superconductive A/D converter. View full abstract»

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  • Underground wireless communications using high-temperature superconducting receivers

    Publication Year: 2004 , Page(s): 46 - 53
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB) |  | HTML iconHTML  

    The authors have developed a method for communicating in underground areas with voice. This system utilizes low-frequency electromagnetic radiation and high-temperature superconducting quantum interference devices (SQUIDs) as receivers. The system is primarily used to communicate in underground areas using through-the-earth electromagnetic waves. The underground areas are typically mines, but the application is not restricted to that purpose. The communication channel is being used to send voice that has been digitally compressed. Typical rock masses do not allow conventional radio frequency electromagnetic waves to penetrate significant distances. Here, the authors use carrier frequencies of a few kilohertz that penetrate hundreds of meters into rock masses. They are using low-noise broadband superconducting receivers and have established that the signals propagate several hundred meters with modest power levels. Audio has been successfully received at distances in excess of 100 m through solid rock. View full abstract»

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  • Design of a linear bulk superconductor magnet synchronous motor for electromagnetic aircraft launch systems

    Publication Year: 2004 , Page(s): 54 - 62
    Cited by:  Papers (40)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (936 KB) |  | HTML iconHTML  

    High-temperature superconducting (HTS) material in bulk form is used to design a linear synchronous motor for an electromagnetic aircraft launch system. The motor is designed without an iron core. Stator coils are placed in the air while the permanent magnets used in conventional design of linear permanent magnet synchronous motors are replaced by the HTS bulk magnets. The physical, operational, and equivalent circuit parameters of the linear motor with HTS bulk magnets are compared with those of a linear permanent magnet synchronous motor and linear induction motor designed for the same application. Results show that utilizing superconducting magnets is only superior at temperatures below 40 K. View full abstract»

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  • High-speed operation of HTS SQUID-array interface circuits with a cryocooler

    Publication Year: 2004 , Page(s): 63 - 68
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    The authors evaluated the operation of high-temperature superconducting quantum interference device (SQUID)-array interface circuits (IFCs) with normal-metal control lines. Transimpedance amplification was obtained at an operating speed of 1 Gb/s using a cryocooler. The effect of the number of SQUIDs connected in series and the number of arrays connected in parallel on the level of output from the SQUID-array IFCs was examined by Josephson circuit simulation, and then the effect of statistical spreads of junction characteristics was evaluated by Monte Carlo simulation. It was found that the configuration of two parallel SQUID arrays with 64 SQUIDs gives the highest output when the junction characteristics in the arrays have a certain spread. The authors fabricated the IFCs by using the conventional interface-engineered junction process. The process reproducibility was 100 μA ±25% for junction Ic, and 3.02 pH ±5% and 2.57 pH ±17% for the sheet inductance of the upper and lower electrodes, respectively. The transimpedance at low frequencies reached 20 and 4 V/A for input levels of 20 and 100 μA, respectively. Output voltages as high as 4.4 mV at 4.2 K and 2.3 mV at 40 K were obtained. Furthermore, an output voltage of 600 μV was obtained for a 1-Gb/s 215-1 pseudo-random binary signal input at 40 K. View full abstract»

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  • AC losses in type-II superconductors induced by nonuniform fluctuations of external magnetic field

    Publication Year: 2004 , Page(s): 69 - 81
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (600 KB) |  | HTML iconHTML  

    Magnetic field fluctuations are inevitable in practical applications of superconductors and it is often necessary to estimate the ac losses these fluctuations induce. If the fluctuation wavelength is greater than the size of a superconductor, known estimates for an alternating uniform external magnetic field can be employed. The authors consider the opposite case and analyze, using a model critical-state problem, penetration of spatially nonuniform fluctuations into type-II superconductors. Numerical simulation is based on a variational formulation of the Bean model. The analytical solutions, found in a weak penetration limit, are used to evaluate ac losses for two types of fluctuations: the running and standing waves. It is shown that for spatially nonuniform fluctuations the losses are better characterized by the fluctuation penetration depth than by the fluctuation amplitude. The results can be used to estimate the ac losses in flywheels, electric motors, magnetic shields, etc. View full abstract»

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  • Operational characteristics of a flux-lock-type high-Tc superconducting fault current limiter with a tap changer

    Publication Year: 2004 , Page(s): 82 - 86
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (248 KB) |  | HTML iconHTML  

    The authors investigate the operational characteristics of a flux-lock-type high-Tc superconducting (HTSC) fault current limiter (SFCL) with a tap changer which could adjust the number of turns of the third winding. In the case of conventional flux-lock-type SFCL, the phase adjusting capacitor is connected in series with magnetic field coil to adjust the magnetic field applied to the HTSC element in phase with the current flowing through the HTSC element during a fault time. However, the current flowing at the third winding, which is connected with magnetic field coil, affects the fault current limiting characteristics. To analyze the influence of current flowing at the third winding on the fault current limiting characteristics, the fault current limiting characteristics of the flux-lock type SFCL, whose inductance of coil 3 could be adjustable through a tap changer, are investigated through the experiments and the computer-aided simulations. The relation of line currents flowing into the flux-lock-type SFCL during a fault time and numbers of turns of a tap changer is drawn. View full abstract»

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  • Josephson fluxonic bipolar junction transistor

    Publication Year: 2004 , Page(s): 87 - 93
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (440 KB) |  | HTML iconHTML  

    Josephson fluxonic bipolar junction transistor (JFBJT) has been proposed as a superconducting amplifying element. The results on a simple realization of this device are provided to demonstrate its working principle. These experiments demonstrate that JFBJT provides current gain without suffering from the problems associated with the regular long junction vortex flow transistors. In particular, no resonance structure is present in its I-V characteristics and its impedance can be matched to any load without degradation of its characteristics. Suggestion is made on how a practical device can be fabricated. View full abstract»

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  • Numerical analysis of the effects of the magnetic self-field on the transport properties of a multilayer HTS cable

    Publication Year: 2004 , Page(s): 94 - 102
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (448 KB) |  | HTML iconHTML  

    In this paper, the effects of the magnetic self-field on the transport properties of a multilayer high-Tc superconducting (HTS) cable are investigated by means of two-dimensional finite-element method (FEM) simulations. Analyzed is a three-layer HTS cable, but the developed methods can be used for a different number of layers. The superconductor is described by the nonlinear power-law relation E=Ec(J/Jc)n, where the parameters Jc and n depend on the magnetic field experienced by the material. This dependence decreases the global transport capacity of the superconductor, enhancing its AC losses. It is shown that, especially at high transport currents, the AC losses are considerably higher than in the case where the dependence on the magnetic field is neglected. A simple electrical model, considering the cable from macroscopic point of view, has been proposed for finding the optimal winding pitches, leading to a uniform current repartition. The use of this electrical model allows to overcome the difficulties of direct three-dimensional FEM computations. In addition, the rapidity of solutions by the electric model gives the possibility of testing quickly many geometrical configurations in order to find the ones leading to an even current repartition. This optimization process would not be possible with detailed FEM simulations. View full abstract»

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  • Study of CeO2+SnO2+Ag doped YBCO as a candidate for welding composition

    Publication Year: 2004 , Page(s): 103 - 106
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    The doping mixture CeO2+SnO2+Ag has been added to YBa2Cu3O7-δ(Y123). The basic idea was to combine the greatly enhanced superconducting properties of CeO2+SnO2 doped Y123 and the silver faculty to decrease the melting peritectic decomposition temperature of Y123, in order to use this material as a welding material for CeO2+SnO2 doped Y123 textured blocks. Consequently, different physico-chemical properties of this composition have been studied. It is shown that silver decreases the decomposition temperature of CeO2+SnO2 doped Y123 from at least 30°C and that, for an addition of 5 wt%Ag, the critical current densities under all magnetic fields are totally similar to the CeO2+SnO2 doped Y123 ones. Hence, this composition appears really promising as a candidate for realizing high quality welds of CeO2+SnO2 doped Y123 blocks. View full abstract»

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  • Miniaturized 3 GHz cross-coupled planar microwave filters

    Publication Year: 2004 , Page(s): 107 - 111
    Cited by:  Papers (4)
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    Cross-coupled planar microwave filters were fabricated using YBa2Cu3O7-δ superconducting thin films deposited on both sides of a LaAlO3 single crystal substrate by pulsed laser deposition. The hairpin resonator geometry allows one to miniaturize the 3-GHz filters by compacting the entire filter onto a substrate with dimensions 0.5 cm × 1 cm. By adjusting the relative spacing among the resonators to establish adequate couplings, filters with very sharp rejection skirt and extremely small insertion loss in passband were obtained. View full abstract»

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  • EMP effects on high-Tc superconducting devices

    Publication Year: 2004 , Page(s): 112 - 118
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (296 KB) |  | HTML iconHTML  

    The results of a study of irreversible damage induced in microstrips made from high-Tc thin films by high-power electromagnetic pulses is presented. It was demonstrated that at high supercritical currents, the magnetic flux flow process induces fast thermomagnetic instability. The result of this instability is local magnetic flux propagation, and subsequent irreversible damage of the high-Tc film. The parameter D=(Id-Ic)/Ic, where Id and Ic are the critical damaging and superconducting-to-dissipative state transition currents, respectively, which represents the capability of the high-Tc microstrip to withstand supercritical current, depends on the quality and critical current density of the film. View full abstract»

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  • IEEE copyright form

    Publication Year: 2004 , Page(s): 119 - 120
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  • Blank page [back cover]

    Publication Year: 2004 , Page(s): c3
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  • IEEE Transactions on Applied Superconductivity Information for authors

    Publication Year: 2004 , Page(s): c4
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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