By Topic

Applied Superconductivity, IEEE Transactions on

Issue 6 • Date Dec. 2011

Filter Results

Displaying Results 1 - 20 of 20
  • [Front cover]

    Publication Year: 2011 , Page(s): C1
    Save to Project icon | Request Permissions | PDF file iconPDF (301 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Applied Superconductivity publication information

    Publication Year: 2011 , Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (131 KB)  
    Freely Available from IEEE
  • Table of contents

    Publication Year: 2011 , Page(s): 3573
    Save to Project icon | Request Permissions | PDF file iconPDF (42 KB)  
    Freely Available from IEEE
  • A 40-mm High-Temperature Superconducting Surface Resonator in a 3-T MRI System: Simulations and Measurements

    Publication Year: 2011 , Page(s): 3574 - 3580
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (374 KB) |  | HTML iconHTML  

    In this paper, the Ansoft high-frequency structure simulation (HFSS) was adapted to investigate the unloaded quality-factor value of the radio-frequency (RF) receiving resonator. This paper focused on the materials aspects, and a comparison between electromagnetic stimulations and measurement was conducted. A 40 mm in diameter Bi2Sr2Ca2Cu3Ox (Bi-2223) tape high-Tc superconducting RF resonator in 3 T was stimulated and built. The simulation models were established according to the experimental dimension of the Bi-2223 surface resonator. Measurements show that the Bi-2223 surface resonator at 77 K provides a gain of 3.84-fold signal-to-noise ratio on phantom images over that of the homemade copper resonator at 300 K. Measuring results were in accordance with predicted ones, and the difference between the predicted SNR gains and measured SNR gains is 1%. This paper suggests that using a Bi-2223 surface resonator at 77 K could be more useful for magnetic resonance imaging coils than a copper surface resonator at 300 K. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A Finite Element Model of Magnetization of Superconducting Bulks Using a Solid-State Flux Pump

    Publication Year: 2011 , Page(s): 3581 - 3586
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (840 KB) |  | HTML iconHTML  

    Superconductors have a bright future; they are able to carry very high current densities, switch rapidly in electronic circuits, detect extremely small perturbations in magnetic fields, and sustain very high magnetic fields. Of most interest to large-scale electrical engineering applications are the ability to carry large currents and to provide large magnetic fields. There are many projects that use the first property, and these have concentrated on power generation, transmission, and utilization; however, there are relatively few, which are currently exploiting the ability to sustain high magnetic fields. The main reason for this is that high field wound magnets can and have been made from both BSCCO and YBCO, but currently, their cost is much higher than the alternative provided by low-Tc materials such as Nb3Sn and NbTi. An alternative form of the material is the bulk form, which can be magnetized to high fields. This paper explains the mechanism, which allows superconductors to be magnetized without the need for high field magnets to perform magnetization. A finite-element model is presented, which is based on the E-J current law. Results from this model show how magnetization of the superconductor builds up cycle upon cycle when a traveling magnetic wave is induced above the superconductor. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characterization of a Transition-Edge Bolometer Made of YBCO Thin Films Prepared by Nonfluorine Metal–Organic Deposition

    Publication Year: 2011 , Page(s): 3587 - 3591
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (549 KB) |  | HTML iconHTML  

    We present the results of a bolometric transition-edge sensor made of a high-Tc superconductor YBCO thin film prepared by fluorine-free metal-organic deposition. The structure of the films was characterized by X-ray diffraction and scanning electron microscopy, and the superconducting properties were determined by R-T measurements. The applicability of the resulting film as an infrared sensor is reported here. The optical response in the range of near infrared and the noise characteristics of the patterned bolometer are measured and analyzed. The dependence of device sensitivity on the bias current and modulation frequency is also investigated. As it is presented in this paper, the results of the fabricated device are comparable to the devices made of high-quality pulsed laser deposition YBCO thin films. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Simulation of Gradient-Coil-Induced Eddy Currents and Their Effects on a Head-Only HTS MRI Magnet

    Publication Year: 2011 , Page(s): 3592 - 3598
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (591 KB) |  | HTML iconHTML  

    In this paper, we simulate the effects of eddy currents induced by switched gradient coils in the cylindrical cryostat structures of a high-temperature superconducting (HTS) magnetic resonance imaging magnet. A novel network method was used with spectral decomposition of the current density in the φ- and z-directions to simulate the effects of X-gradient coils. Two types of active magnetic shielding were simulated, and it was found that one type is able to reduce the power of the eddy currents in the cryostat to a greater extent than the other. These results will inform the design of gradient coils that protect the HTS magnet from eddy-current-induced heating and vibrations. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • AC Losses in \hbox {Bi}_{2}\hbox {Sr}_{2}\hbox {Ca}_{2} \hbox {Cu}_{3}\hbox {O}_{10 + x} Tapes and a 3.15-m-Long Single-Phase Cable

    Publication Year: 2011 , Page(s): 3599 - 3603
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (198 KB) |  | HTML iconHTML  

    The alternating-current losses in superconducting multifilament BiSCCO-2223 tapes and a 3.15-m single-phase test cable were measured at 77 K using an electrical transport method. The cable had an inner diameter of 42 mm; it was composed of a single layer of 31 multifilament tapes and had a critical current of Ic = 4.1 kA. The measured losses of the tapes were found to be in good agreement with the Norris ellipse (NE) model. The losses of the cable were, for high currents, found to be bounded by the monoblock and independent NE models. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Design and Operation of 64-Fold Variable Single-Flux-Quantum Pulse-Number Multiplier

    Publication Year: 2011 , Page(s): 3604 - 3607
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (413 KB) |  | HTML iconHTML  

    One of the unique applications of the single-flux-quantum (SFQ) circuitry is a digital-to-analog converter (DAC) with fundamental accuracy based on the Josephson effect. Recently, we have proposed a DAC based on frequency modulation of the output SFQ pulse train. A variable SFQ pulse-number multiplier (PNM) is a key component for the frequency-modulation DAC. In this paper, we report our design and test of a variable PNM in which the multiplication factor is determined by the sum of selected SFQ trains coming from a series array of toggle flip-flops. A 64-fold variable PNM is designed and tested using chips based on Nb. The low-speed test shows its correct functions of variable multiplication of one- to 64-fold. The high-speed test demonstrates the operation of output SFQ repetition frequency up to 0.82 GHz for 64-fold multiplication. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermal Performance Simulation of a Model Coil for a 40-T Hybrid Magnet

    Publication Year: 2011 , Page(s): 3608 - 3611
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB) |  | HTML iconHTML  

    A model coil for the 40-T hybrid magnet is under construction at the High Magnetic Field Laboratory, Chinese Academy of Sciences. The model coil is layer wound with a rectangular Nb3Sn cable-in-conduit conductor and adopts "wind-and-react" manufacturing technology. The model coil will simulate same electromagnetic loads of B × I as the superconducting outsert of the 40-T hybrid magnet in the performance tests. The thermohydraulic behavior of the model coil during various operating scenarios was simulated by the numerical model Gandalf. The charging process and the cyclic operation of the model coil are analyzed in this study. The temperature rise and margin of the conductor due to the ac losses are computed and presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Extensive Nanotwinning: Origin of High Current Density to High Fields in Preform-Optimized Infiltration-Growth-Processed \hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7 - \delta } Superconductor

    Publication Year: 2011 , Page(s): 3612 - 3620
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1175 KB) |  | HTML iconHTML  

    The origin of high current densities to very high magnetic fields (better than 103 A · cm-2 to 6.5 T at 77 K) in YBa2Cu3O7-δ superconductor fabricated by the preform-optimized infiltration-growth process (POIGP) is investigated. The main techniques used in the paper are field-emission scanning electron microscopy and transmission electron microscopy (TEM). An electron-backscattered-diffraction study of the samples is also carried out. A comparison between the microstructures of the optimized sample with the nonoptimized ones show that extensive twinning on a nanometer scale with crossing twins occurring near the optimally separated Y2BaCuO5 precipitates can be the origin of the observed high Jc (H) in the POIGP sample. The TEM study reveals the presence of very fine defects starting from the twin boundaries. The observed defect spacing and densities account for the uniformly high current densities observed to high fields. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Development and Testing of a 10-kA Hybrid Mechanical–Static DC Circuit Breaker

    Publication Year: 2011 , Page(s): 3621 - 3627
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (839 KB) |  | HTML iconHTML  

    This paper presents the development and testing of the prototype of a hybrid mechanical-static dc circuit breaker (CB) for quench protection of superconducting magnets based on a mechanical switch paralleled to a static CB. In normal operation, the mechanical switch is closed and it handles the continuous flow of dc current, minimizing the on-state losses. In case of intervention, the mechanical switch opens, commutating the current into the static CB that quickly interrupts and transfers the current into a discharge resistor, withstanding the reapplied voltage. This paper was carried out to face and solve some issues of this design solution being not available in the literature examples of similar applications rated for significant power levels. The operation of the hybrid CB has been successfully tested up to a current of 10 kA with a recovery voltage of about 1 kV. Special tests have been dedicated to characterize the reliability and the repeatability of the current commutation from the mechanical switch to the static CB and to characterize the arc voltage under different conditions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Three-Dimensional Micrometer-Scale Modeling of Quenching in High-Aspect-Ratio \hbox {YBa}_{2}\hbox {Cu}_{3}\hbox {O}_{7-\delta } Coated Conductor Tapes—Part II: Influence of Geometric and Material Properties and Implications for Conductor Engineering and Magnet Design

    Publication Year: 2011 , Page(s): 3628 - 3634
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (396 KB) |  | HTML iconHTML  

    YBa2Cu3O7-δ (YBCO) coated conductors (CCs) show great promise for applications, but due to a very slow normal-zone propagation velocity (NZPV), quench detection and protection in YBCO magnets may be difficult. Present YBCO CCs have been developed with a primary focus on maximizing the critical current density for elevated-temperature low-field or low-temperature high-field applications. As the market for magnet applications progresses, it becomes important to consider design parameters such as the thicknesses and properties of all YBCO CC components, with the intent of considering quench-related behaviors as an integral part of the conductor and magnet design processes. Thus, it is important to know the impacts of conductor parameters on quench behavior. Considering that the YBCO layer itself is on the order of a micrometer in thickness, quench behavior must also be considered at this scale length. Here, the highly accurate experimentally validated micrometer-scale 3-D tape model reported in Part I is used to study how variations in CC geometry and material properties affect quench behavior, including the NZPV, hot-spot temperature, and minimum quench energy. The parametric variations focus on quantities that can be most readily modified by CC manufacturers. Based on simulation results, the relative sensitivities of the quench quantities to the parametric variations are calculated to identify which CC design parameters are most impactful on quench behavior. The implications of these results for quench detection and protection are discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical Response of a Cold-Electron Bolometer Array Integrated in a 345-GHz Cross-Slot Antenna

    Publication Year: 2011 , Page(s): 3635 - 3639
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (223 KB) |  | HTML iconHTML  

    Two series/parallel arrays of ten cold-electron bolometers with superconductor-insulator-normal tunnel junctions were integrated in orthogonal ports of a cross-slot antenna. To increase the dynamic range of the receiver, all single bolometers in an array are connected in parallel for the microwave signal by capacitive coupling. To increase the output response, bolometers are connected in series for dc bias. With the measured voltage-to-temperature response of 8.8 μV/mK, absorber volume of 0.08 μm3, and output noise of about 10 nV/Hz1/2, we estimated the dark electrical noise equivalent power (NEP) as NEP = 6 * 10-18 W/Hz1/2. The optical response down to NEP = 2 * 10-17 W/Hz1/2 was measured using a hot/cold load as a radiation source and a sample temperature down to 100 mK. The fluctuation sensitivity to the radiation source temperature is 1.3 * 10-4 K/Hz1/2. A dynamic range over 43 dB was measured using a backward-wave oscillator, a variable polarization grid attenuator, and cold filters/attenuators. View full abstract»

    Open Access
  • Theoretical Model of a Cold Mass Strap Suspension System for Superconducting Magnets

    Publication Year: 2011 , Page(s): 3640 - 3645
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (149 KB) |  | HTML iconHTML  

    Strap suspension structures are widely used in superconducting magnet systems for high strength and low heat leak. A theoretical model is developed to design and analyze strap suspension structures. The supported cold mass, the tensile stress due to a cooldown, and a quasi-static acceleration load are considered in the model. In addition, the load conditions during transportation and operating the superconducting magnet system are analyzed. Design rules composed of mechanical strength, minimum resonant frequency, and heat load are presented. A suspension structure consisting of eight strap assemblies for a superconducting magnet is analyzed based on the model. The maximum pretension force is calculated, and the allowable accelerations for the maximum pretension are given. The vertical dynamic performance is better than the horizontal directions for the given strap configuration. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Surface Plasmon-Enhanced Coupling of Optical Guided Waves to High-Temperature Superconducting Optoelectronic Structures

    Publication Year: 2011 , Page(s): 3646 - 3651
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (507 KB) |  | HTML iconHTML  

    A novel technique is proposed for coupling near-infrared and visible optical power to high-temperature superconducting (HTS) optoelectronic structures, fabricated on a high-index substrate, by means of the excitation of surface plasmon polariton (SPP) waves at the interface of the HTS layer and a metal cladding. The modal characteristics of these guided waves differ from those of the SPP modes of a metal slab bounded by symmetric or asymmetric dielectric layers because of the presence of a high-index semi-infinite substrate at close proximity. The modal dispersion of the guided mode exhibits a cutoff with increasing HTS thicknesses. Inasmuch as the HTS layer possesses a large extinction factor, it absorbs most of the optical power, whereas in a conventional dielectric-metal structure, the power is virtually absorbed by the metal. Furthermore, the variation of the coupling efficiency as a function of the HTS thickness is examined, and it will be demonstrated that the surface plasmon-assisted coupling technique outperforms unguided illumination schemes. The proposed technique and structure are particularly useful for guided-wave superconducting optoelectronic devices, including superconducting photodetectors and photomixers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nondissipative Addressing for Time-Division SQUID Multiplexing

    Publication Year: 2011 , Page(s): 3652 - 3654
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (490 KB) |  | HTML iconHTML  

    Recent and future astronomical instruments are based on a focal plane mapped by a large array of superconducting bolometers. Cryogenic analog multiplexing readout techniques, based on superconducting quantum interference devices (SQUIDs), are currently developed to achieve the readout of large arrays of this kind of low noise background-limited detectors. To effectively reduce the number of cryogenic wires (particularly, SQUID biasing), line/column addressing is currently used in time-division multiplexing, i.e., same biasing is applied to a few SQUIDs (on a line) of different columns. This technique should dramatically increase power consumption if parallel biasing is applied via resistors to isolate each column; the power budget is particularly limited on this kind of front-end cryogenic readout. A design with one transformer per SQUID is also used to read out SQUID biased in series with no excess of consumption and crosstalk. We propose here a new biasing technique using simple surface-mounted capacitors, which is easier to implement. These capacitors are used to parallel bias SQUIDs without additional Joule effect while minimizing crosstalk. However, capacitors do not allow dc biasing and need a current mean value equal to zero to avoid biasing source saturation. We have then tested square current biasing through capacitors on a commercial SQUID. This measurement shows that capacitors are able to proper bias SQUID and then to perform a nondissipative addressing for time-division SQUID multiplexing. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 2011 Index IEEE Transactions on Applied Superconductivity Vol. 21

    Publication Year: 2011 , Page(s): 3655 - 3792
    Save to Project icon | Request Permissions | PDF file iconPDF (1977 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Applied Superconductivity upcoming special conference issues

    Publication Year: 2011 , Page(s): C3
    Save to Project icon | Request Permissions | PDF file iconPDF (84 KB)  
    Freely Available from IEEE
  • IEEE Transactions on Applied Superconductivity information for authors

    Publication Year: 2011 , Page(s): C4
    Save to Project icon | Request Permissions | PDF file iconPDF (29 KB)  
    Freely Available from IEEE

Aims & Scope

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

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Britton L. T. Plourde
Syracuse University
bplourde@syr.edu
http://asfaculty.syr.edu/pages/phy/plourde-britton.html