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Applied Superconductivity, IEEE Transactions on

Issue 4 • Date Aug. 2009

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Displaying Results 1 - 18 of 18
  • [Front cover]

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

    Page(s): C2
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  • Table of contents

    Page(s): 3629
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  • Viable Superconductor-Based Current Control Circuit for High Current Injection System

    Page(s): 3630 - 3636
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (526 KB) |  | HTML iconHTML  

    This paper explains novel methods of the excessive current protection for a single unit 25-kA current injection system (CIS) with no test interruption. The principle object of this paper is to provide a fast detection of excessive current in the system by means of an unbalanced magnetic flux current limiting device (CLD) for the predetermined current tests. The proposed techniques will be used to investigate the performances of different CLD core structures. The paper will also push the state of the art by applying magnetic fields to the high-temperature superconductor element through an external source, to get higher resistance in the current-limiting phase. A further object of this investigation is to provide the use of open-core in two different mechanisms for limitation and protection purposes of the CIS. This can be considered as a viable alternative CLD for applications in the power industry. This will result in a more thorough knowledge of ldquoscaling factorsrdquo and the excessive current limitation mechanism which will enable the most efficient limitation in terms of compactness and cost to be specified. Completion of this development will mark an important milestone in superconductor technology, and significant efficiency improvement will be realized. View full abstract»

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  • Temperature Dependence of Total AC Loss in High-Temperature Superconducting Tapes

    Page(s): 3637 - 3644
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1163 KB) |  | HTML iconHTML  

    A versatile experimental facility was designed and set up to measure transport ac losses, magnetization ac losses, and total ac losses in high-temperature superconductors at variable temperatures. Several sets of measurements were carried out in the temperature range of 35 K to 100 K. Sample temperature during the measurements could be controlled within plusmn0.5 K of set temperature. Temperature dependence of transport losses reflects variation of critical current density of the tapes with temperature. Temperature dependence of magnetization losses exhibits an interesting behavior with a peak, whose position shifts to lower temperatures as the magnetic field is increased. Experimental data of ac losses at various temperatures are compared with those calculated using numerical methods. Generally, the simulated results reproduce well the experimental data. View full abstract»

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  • Minimum Stored Energy High-Field MRI Superconducting Magnets

    Page(s): 3645 - 3652
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (841 KB) |  | HTML iconHTML  

    A globally optimum minimum stored energy optimization strategy is implemented to design actively shielded superconducting magnet configurations used in high-field applications. The current density map is first obtained and used as a foundation for the magnet configurations by placing coils at current density local extremities. Optimized current density maps based on the stored energy formulation along with final magnet arrangements are provided to illustrate the findings. In this work, the focus was on compact superconducting magnets as measured by physical size and system footprint for given magnetic field properties inside the imaging region. The process of obtaining the current density maps proposed here over the given magnet domain, where superconducting coils are laid out, suggests that peak current densities occur around the perimeter of the domain, where in the most compact designs, with the domain length less than 1 m, the current direction alternates amongst adjacent coils. To reduce the peak magnetic field to acceptable levels on the superconductors in high-field designs, the size of the magnet domain is made larger, to the extent that the current densities no longer alternate between coils. View full abstract»

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  • A Superconductor THz Modulator Based on Vortex Flux Flow

    Page(s): 3653 - 3657
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (400 KB) |  | HTML iconHTML  

    A terahertz modulator based on the Type-II superconductor flux flow oscillator has been proposed. Analytical calculations are presented and the effects of intrinsic and extrinsic parameters such as disorder strength of crystal, penetration depth, frequency, and amplitude of the modulated current on the radiation power spectrum have been studied. The proposed structure also exhibits a mixer-like behavior, in the sense that its output harmonics range from the washboard frequency up to the superconductor gap frequency, so the input signal is practically mixed with the washboard frequency and its harmonics. The modulation index for each harmonic of this modulator has also been investigated. This well-featured modulator has a potential to be used in next-generation terahertz integrated transceivers. View full abstract»

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  • Applications of DC Breakers and Concepts for Superconducting Fault-Current Limiter for a DC Distribution Network

    Page(s): 3658 - 3664
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1156 KB) |  | HTML iconHTML  

    Many alternative energy power generation systems create DC electricity. Also, many devices consume DC converted from AC. Therefore, it may be possible to reduce conversion losses and CO2 emissions by adopting DC distribution. We assume that superconducting cables will be used for dc distribution because their electrical resistance is almost zero. However, if a superconducting cable is adopted, it is of great concern that if an excessive current flows because of, for instance, a short circuit, then there is a possibility that this current cannot be interrupted by a circuit breaker alone. We propose that the fault current be limited by a superconducting fault-current limiter (SFCL) and that this limited current is then interrupted by a DC circuit breaker. In this paper, we have separately investigated the SFCL and DC breaker and their use in combination. View full abstract»

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  • Performance of \hbox {YBa}_{2}\hbox {Cu}_{3} \hbox {O}_{x} Tapes With Different Structures Under AC Overcurrent Conditions

    Page(s): 3665 - 3669
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (363 KB) |  | HTML iconHTML  

    The voltage and temperature of YBa2Cu3Ox (YBCO) tapes with different structures were measured at alternating-current overcurrent conditions in liquid nitrogen. A safety temperature limit of the tapes with different structure was obtained based on the measured critical-current degradation data of the YBCO tapes. According to heat conduction model, the electrical and thermal performances of YBCO tapes were analyzed for tapes with different stabilizers. The comparison was presented for simulation and test data. The results are helpful for the design of superconducting electrical equipment. View full abstract»

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  • Study of the Superconducting and Thermal Properties of ex situ GlidCop-Sheathed Practical \hbox {MgB}_{2} Conductors

    Page(s): 3670 - 3674
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (187 KB) |  | HTML iconHTML  

    In dc and ac practical applications of MgB2 superconducting wires, an important role is represented by the material sheath that has to provide, among other things, a suitable electrical and thermal stabilization. One way to obtain a large-enough amount of low-resistivity material into the conductor architecture is to use it as the external sheath. In this paper, we study ex situ multifilamentary MgB2 wires fabricated with oxide-dispersion-strengthened copper (GlidCop) as the external sheath in order to reach a good compromise between critical current density and thermal properties. We prepared three GlidCop samples with different contents of dispersed submicroscopic Al2O3 particles. We characterized the superconducting and thermal properties, and we showed that the good thermal conductivity, together with the good mechanical properties and a reasonable critical current density, makes the GlidCop composite wire a useful conductor for applications where high thermal conductivity is required at temperatures above 30 K, such as superconducting fault-current limiters. View full abstract»

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  • Multiobjective Optimization for HTS Fault-Current Limiters Based on Normalized Simulated Annealing

    Page(s): 3675 - 3682
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (960 KB) |  | HTML iconHTML  

    This paper presents an improved simulated annealing (SA) algorithm for multiobjective optimization, which is a positive approach in the design of high-temperature superconducting (HTS) fault-current limiters (SFCLs).The main goal of this paper is to achieve an effective and feasible approach in the structural design of HTS FCLs by means of multiobjective decision-making techniques, based on normalized SA. The combination of electrical and thermal models of a purpose-designed resistive-type HTS FCL is defined as a component in PSCAD/EMTDC simulations from which the proposed method will be used to optimize the selective parameters of the SFCL. The above requires the need of advanced numerical techniques for simulation studies by PSCAD on a sample distribution system for determining a global optimum HTS FCL, by considering individual parameters and accounting for the constraints, which is the main motivation for initiating this paper. View full abstract»

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  • Center Frequency Tuning for a Narrowband Superconducting Filter in the Time Domain

    Page(s): 3683 - 3687
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (198 KB) |  | HTML iconHTML  

    This paper presents a mechanical tuning method for tuning the center frequency of a narrowband high-temperature superconducting filter. The filter is designed with 0.5-MHz bandwidth at 166.9 MHz and is fabricated. Tuning is carried out based on the time-domain response of filter return loss. The filter can be precisely tuned to a desired center frequency while maintaining a high-frequency performance. The center frequency is tuned from 167.2 to 166.5 MHz. The tuning range is 0.7 MHz and is sufficient to compensate the frequency offset caused by 0.72% variation in the substrate effective dielectric constant or 4% that of the substrate thickness. View full abstract»

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  • Investigation of Bias Current and Modulation Frequency Dependences of Detectivity of YBCO TES and the Effects of Coating of Cu–C Composite Absorber Layer

    Page(s): 3688 - 3693
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (415 KB) |  | HTML iconHTML  

    Bolometric response and noise characteristics of YBCO superconductor transition edge IR detectors with relatively sharp transition and its resulting detectivity are investigated both theoretically and experimentally. The magnitude of response of a fabricated device was obtained for different bias currents and modulation frequencies. Using the measured and calculated bolometric response and noise characteristics, we found and analyzed the device detectivity versus frequency for different bias currents. The detectivity versus chopping frequency of the device did not decrease following the response strongly, due to the decrease of the noise at higher frequencies up to 1 kHz, resulting in maximum detectivity around the modulation frequency of 100 Hz. We also improved the responsivity of the device through the increase of the surface absorption by using a novel infrared absorber, which is made of a copper-carbon composite, coated in a low-temperature process. Within the modulation frequency range studied in this paper, comparison of device detectivity before and after coating is also presented. View full abstract»

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    Page(s): 3694
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    Page(s): 3695
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    Page(s): 3696
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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.

Full Aims & Scope

Meet Our Editors

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