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Applied Superconductivity, IEEE Transactions on

Issue 4 • Date Dec. 2006

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Displaying Results 1 - 14 of 14
  • Table of contents

    Page(s): C1
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  • IEEE Transactions on Applied Superconductivity publication information

    Page(s): C2
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  • Substrate and Device Pattern Dependence of the Thermal Crosstalk in Y Ba _2 Cu _3 O _{7-\delta } Transition Edge Bolometer Arrays

    Page(s): 1953 - 1958
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    Using YBa2Cu3O7-delta (YBCO) thin films, pulsed laser deposited on 1-mm-thick LaAlO3 or SrTiO3 substrates, we made 4times1 pixel arrays of transition edge bolometers with separations between neighboring pixels ranging from 40 mum to 170 mum for testing purposes. We investigated the effects of the YBCO film thickness (200 and 400 nm), substrate material, and back-etching of the substrate, on the crosstalk between the pixels of the arrays. The investigation was based on the analysis of the voltage response of the dc current biased bolometers versus the modulation frequency of a near-infrared laser source. We observed that the bolometer arrays made of 400-nm-thick films had less interpixel thermal crosstalk than the 200-nm-thick films. The effect of substrate thickness on the response of the pixels was investigated by up to 500 mum back-etching of the substrates. The bolometers made on back-etched LaAlO3 substrates had anomalous crosstalk response behavior, which was effective at higher modulation frequencies. In addition, we present an analytical thermal model for explaining the observed effects of the thermal crosstalk on the response characteristics of the pixels of the arrays. We report the measured response and the anticipated thermal crosstalk of the characterized bolometers'. We describe the responses based on the thermal models and discrepancies from the model's predictions View full abstract»

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  • Effect of Thermal Noise and Trigger Jitter on the Operation of HTS Sampler

    Page(s): 1959 - 1965
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (582 KB) |  | HTML iconHTML  

    We have studied the effect of thermal noise and trigger jitter on the bandwidth of a high-Tc superconducting sampler by computer simulation and analytical calculation. Simulation results showed that the minimum IcRn product of the junctions required to obtain 100-GHz bandwidth is raised from 0.63 to 0.75 mV under the influence of the thermal noise at 40K. On the other hand, the maximum trigger jitter for 100-GHz bandwidth is 1.87 ps when only an averaging effect is assumed. Considering both the effects of thermal noise and trigger jitter, we found, for example, that trigger jitter must be reduced down to 1 ps to realize the bandwidth above 100 GHz with an IcRn product of 1 mV at an operating temperature of 40 K View full abstract»

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  • Co-Sputtered Amorphous Nb _{ x} Si _{1 - { x}} Barriers for Josephson-Junction Circuits

    Page(s): 1966 - 1970
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    Co-sputtered amorphous NbxSi1-x has been developed as a barrier material for Josephson-junction array circuits. This material is quite promising as a normal-metal barrier for state-of-the-art Josephson voltage standards. In addition, the capability of tuning the barrier resistivity over a wide range that includes the metal-insulator transition could lead to applications in high-speed superconductive electronics. The electrical characteristics and uniformity of amorphous NbxSi1-x-barrier junctions are similar to those of other normal-metal barriers, but the superior etching properties makes this barrier material especially promising for tall, stacked junctions that are required for high-junction-density applications. Under appropriate deposition conditions, the reproducibility of devices with co-sputtered amorphous NbxSi1-x is sufficient to produce high-quality stacked-junction superconductive devices View full abstract»

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  • Performance of an HTS Generator Field Coil Under System Fault Conditions

    Page(s): 1971 - 1975
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    High-temperature superconducting (HTS) coils are generally stable against transient thermal disturbances. Protection against spontaneous quenches is not a main design issue for an HTS coil. However, HTS coils used in many electric devices such as motors, generators, transformers, and current limiters will operate under over-current fault conditions, which may result in a coil quench and thermal runaway. Those electric devices should be able to ride through some grid fault conditions and remain functional. This requires a certain over-current capability of the HTS coils. This paper discusses the over-current requirements from grid faults and the thermal transient responses of a BSCCO coil. It presents the analysis results of the coil subjected to over-current pulses at different operating conditions. The study also investigates the thermal runaway current and its relationship with the over-current pulse View full abstract»

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  • Observation of Bifurcations and Hysteresis in Nonlinear NbN Superconducting Microwave Resonators

    Page(s): 1976 - 1987
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    In this paper, we report some extraordinary nonlinear dynamics measured in the resonance curve of NbN superconducting stripline microwave resonators. Among the nonlinearities observed: abrupt bifurcations in the resonance response at relatively low input powers, asymmetric resonances, multiple jumps within the resonance band, resonance frequency drift, frequency hysteresis, hysteresis loops changing direction and critical coupling phenomenon. Weak links in the NbN grain structure are hypothesized as the source of the nonlinearities View full abstract»

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  • Controlling Chaos in Josephson-Junction Using Nonlinear Backstepping Controller

    Page(s): 1988 - 1998
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    In this paper, a nonlinear backstepping controller has been designed to control bifurcation as well as incipient chaos that has been experienced in the RCLSJ (shunted nonlinear resistive-capacitive-inductance) Josephson-Junction. The results show that the system, without controller, has a dangerous Hopf bifurcation point that lead to chaotic behavior. For certain values of the external direct current (I0), the system becomes chaotic. On the other hand, the nonlinear backstepping controller converts the chaotic region into a stable periodic solution region View full abstract»

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  • Study of Superconducting Fault Current Limiter Using Vacuum Interrupter Driven by Electromagnetic Repulsion Force for Commutating Switch

    Page(s): 1999 - 2004
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    Using a high-temperature superconductor, we constructed and tested a model superconducting fault current limiter (SFCL). The superconductor and the vacuum interrupter as the commutation switch were connected in parallel using a bypass coil. When the fault current flows in this equipment, the superconductor is quenched and the current is transferred to the parallel coil because of the voltage drop in the superconductor. This large current in the parallel coil actuates the magnetic repulsion mechanism of the vacuum interrupter. Due to the opening of the vacuum interrupter, the current in the superconductor is broken. By using this equipment, the current flow time in the superconductor can be easily minimized. On the other hand, the fault current is also easily limited by large reactance of the parallel coil View full abstract»

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  • Lumped 50- \Omega Arrays of SNS Josephson Junctions

    Page(s): 2005 - 2010
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    For the first time, lumped series arrays of Josephson junctions have been fabricated with a transmission line-matched 50-Omega resistance. These arrays also have the thousands of junctions necessary to produce a metrologically significant voltage. This approach is expected to increase the output voltage per array and to optimize their performance for Josephson voltage standards. Traditional Josephson arrays for voltage standards have used distributed microwave structures, where array lengths are several multiples of the driving wavelength. The lumped arrays in this work have physical lengths shorter than a quarter of the microwave drive wavelength and total normal-state resistances nearly equal to the transmission line impedance. Fabrication of these arrays was made possible by use of a newly developed Nb-(MoSi2-Nb)n stacked junction technology. We present measurements of the microwave response of lumped arrays with total normal resistances up to 54 Omega and with various termination resistances. A simple numerical model is presented that accounts for the spatial distribution of the microwave current and for the nonuniformity of the junction critical currents. The resulting simulations agree well with experimental results View full abstract»

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  • Operation of HTS Toggle-Flip-Flop Circuit With Improved Layout Design

    Page(s): 2011 - 2017
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    Toggle-flip-flop (T-FF) is one of the most important high-Tc superconducting single-flux quantum (HTS SFQ) circuit components and has been designed and fabricated by using YBa2Cu3 O7-delta ramp-edge junction technology. The circuit layout of the T-FF was improved to suppress the junction critical current (Ic) spread in the circuit. Test circuits, which include a T-FF with a single output for evaluating the logic operation and measuring the operating frequency, were fabricated and their operation characteristics were investigated. The T-FF circuit with a single output was successfully operated and finite direct current (dc) supply current margins were obtained at temperatures from 27 to 34 K. Moreover, the maximum operating frequency of the T-FF was estimated to be 360 GHz at 4.2 K and 114 GHz at 41 K. In addition, reduction of dc supply current margins due to thermal noise was also investigated. According to the numerical simulation in which parasitic inductances were taken into account, the narrowest margin in the T-FF circuit wider than plusmn10% was maintained with a bit-error rate (BER) of 10-6 up to 40 K View full abstract»

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  • 2006 Index

    Page(s): 2018 - 2088
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  • IEEE Transactions on Applied Superconductivity upcoming special conference issues

    Page(s): C3
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  • IEEE Transactions on Applied Superconductivity Information for authors

    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