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  Subjects -> ELECTRONICS (Total: 207 journals)
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Superconductor Science and Technology
Journal Prestige (SJR): 1.036
Citation Impact (citeScore): 3
Number of Followers: 3  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0953-2048 - ISSN (Online) 1361-6668
Published by IOP Homepage  [7 journals]
  • Reducing cross-field demagnetization of superconducting stacks by
           soldering in pairs

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      Authors: Anang Dadhich; Shuo Li, Mykola Solovyov, Ján Šouc, Marek Mošat’ Enric Pardo
      First page: 115001
      Abstract: Superconducting stacks can be used as strong permanent magnets in several applications. One of their uses is to build light and compact superconducting motors for aviation, where these magnets can be used in the rotor, but they can demagnetize quickly in the presence of cross fields. In this article, we propose a new configuration of soldered stacks face-to-face, which can be constructed by relatively simple joining techniques. Based on numerical modeling of the cross-field demagnetization of stacks of two and 16 tapes, we show that such a sample can withstand around twice as high ripple field amplitudes than isolated stacks. This is due to the increase in the parallel penetration field by around a factor 2. For cross-field amplitudes below this value, a soldered stack can retain higher permanent magnetization than isolated stacks. This method of reducing cross-field demagnetization does not decrease the power or torque rating of a motor, compared to other strategies like the increase in the gap between rotor and stator.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-19T23:00:00Z
      DOI: 10.1088/1361-6668/ac908f
      Issue No: Vol. 35, No. 11 (2022)
       
  • Formation and propagation of cracks in RRP Nb3Sn wires studied by deep
           learning applied to x-ray tomography

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      Authors: Tommaso Bagni; Diego Mauro, Marta Majkut, Alexander Rack Carmine Senatore
      First page: 104003
      Abstract: This paper reports a novel non-destructive and non-invasive method to investigate crack formation and propagation in high-performance Nb3Sn wires by combining x-ray tomography and deep learning networks. The next generation of high field magnet applications relies on the development of new Nb3Sn wires capable to withstand the large stresses generated by Lorentz forces during magnets operation. These stresses can cause a permanent reduction of the transport properties generated by residual deformation of the Nb3Sn crystal lattice as well as the formation of cracks in the brittle Nb3Sn filaments. Studies for the development of the high luminosity LHC (HL-LHC) upgrade showed that nominal transverse compressive stresses above 150 MPa may be sufficient to generate cracks in the wires. In the case of fusion magnets, wires experience periodic bending due to the electro-magnetic cycles of the reactor which over time may induce wire deformation and filament cracks. Therefore, it has become essential to develop a quantitative method for the characterization of crack formation and propagation under compressive loads. The x-ray tomographic data of a series of restacked-rod-process (RRP) Nb3Sn wires was acquired at the micro-tomography beamline ID19 of the European Synchrotron Radiation Facility (ESRF), after intentionally inducing a broad spectrum of cracks in the Nb3Sn sub-elements. The samples were submitted to transvers compressive stresses, with and without epoxy impregnation, at different pressures, up to 238 MPa. The resulting tomographic images were analysed by means of deep learning semantic segmentation networks, using U-net, a convolutional neural network (CNN), to identify and segment cracks inside the wires. The trained CNN was able to analyse large volumes of tomographic data, thus enabling a systematic approach for investigating the mechanical damages in Nb3Sn wires. We will show the complete three-dimensional reconstruction of various cracks and discuss their impact on the electro-mechanical performance of the analysed wires.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-05T23:00:00Z
      DOI: 10.1088/1361-6668/ac86ac
      Issue No: Vol. 35, No. 10 (2022)
       
  • Influence of growth temperature on the pinning landscape of YBa2Cu3O7−
           δ films grown from Ba-deficient solutions

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      Authors: Jordi Alcalà; Pau Ternero, Cornelia Pop, Laura Piperno, Susagna Ricart, Narcís Mestres, Teresa Puig, Xavier Obradors, Alexander Meledin, Giuseppe Celentano Anna Palau
      First page: 104004
      Abstract: Cuprate coated conductors are promising materials for the development of large-scale applications, having superior performance over other superconductors. Tailoring their vortex pinning landscape through nanostructure engineering is one of the major challenges to fulfill the specific application requirements. In this work, we have studied the influence of the growth temperature on the generation of intrinsic pinning defects in YBa2Cu3O7−δ films grown by chemical solution deposition using low Ba precursor solutions. We have analysed the critical current density as a function of the temperature, applied magnetic field magnitude and orientation, Jc(T,H,θ), to elucidate the nature and strength of pinning sites and correlate the microstructure of the films with their superconducting performance. An efficient pinning landscape consisting of stacking faults and associated nanostrain is naturally induced by simply tuning the growth temperature without the need to add artificial pinning sites. Samples grown at an optimized temperature of 750 °C show very high self-field Jc values correlated with an overdoped state and improved Jc(T,H,θ) performances.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-05T23:00:00Z
      DOI: 10.1088/1361-6668/ac8580
      Issue No: Vol. 35, No. 10 (2022)
       
  • A low-cost approach for recycling large GdBCO bulk superconductors using
           an infiltration technique with different liquid sources

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      Authors: M Wang; Y N Wang W M Yang
      First page: 104005
      Abstract: The high-temperature superconductor has become a research hotspot, because of its high critical temperature, strong trapped flux density, stable suspension characteristics and large magnet levitation force. Single-domain REBa2Cu3O7−δ (REBCO) superconductors, where RE is a rare-earth element such as Y, Gd, Sm or Nd, have wide and potential applications in high-tech fields, such as micro-magnet superconducting maglev trains, superconducting motors and superconducting magnetic separation systems. However, a large number of multi-domain samples are easily produced in the preparation process, resulting in a significantly lower success rate and a significant increase in cost, which restricts their practical applications. Thus, we successfully recycle a series of GdBCO samples by re-supplementing the liquid phase lost in the primary growth process and pre-treating the failed sample as solid-phase source billets, which was proposed by Shi. The growth morphology and superconducting properties of the recycled GdBCO bulk superconductors are investigated in detail in this study. The results show that the key superconductivity properties have been significantly improved, which provides the scientific basis and new ideas for the development of low-cost and highly efficient fabrication yields of REBCO bulk superconductors.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-14T23:00:00Z
      DOI: 10.1088/1361-6668/ac8774
      Issue No: Vol. 35, No. 10 (2022)
       
  • Nonvolatile memory cell using a superconducting-ferromagnetic π
           Josephson junction

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      Authors: Junwen Zeng; Lei Chen, Xianghai Zhong, Yue Wang, Yinping Pan, Denghui Zhang, Shujie Yu, Ling Wu, Lu Zhang, Wei Peng Zhen Wang
      First page: 105009
      Abstract: Storage of a single magnetic flux quantum in a superconducting loop containing a Josephson junction represents a promising unit cell configuration for construction of a cryogenic memory of superconducting digital circuits. However, application of a DC bias current is required for operation of such a memory cell to maintain trapping of the flux quantum in the storage loop. In this work, we present a superconducting memory cell that uses a superconducting-magnetic π junction. The cell characteristics show flux quantum hysteresis centering at the zero-bias current. We develop a fabrication process that combines superconductor–ferromagnet–superconductor (SFS) junctions with superconductor–normal metal–superconductor (SNS) junctions. The critical current density of the SFS junctions shows a 0–π oscillation as a function of the ferromagnetic layer thickness. The formation of the π junction is confirmed further by the flux modulation curves of a superconducting quantum interference device made from SNS junctions with an additional SFS junction.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-04T23:00:00Z
      DOI: 10.1088/1361-6668/ac80d9
      Issue No: Vol. 35, No. 10 (2022)
       
  • Synchronous chip-to-chip communication with a multi-chip resonator clock
           distribution network *

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      Authors: Jonathan Egan; Max Nielsen, Joshua Strong, Vladimir Talanov, Ed Rudman, Brainton Song, Quentin Herr Anna Herr
      First page: 105010
      Abstract: Superconducting digital circuits are a promising approach to build integrated systems with high energy-efficiency and computational density of the packaged chips. In such systems, performance of the data link between chips mounted on a multi-chip-module (MCM) is a critical driver of performance. In this work we report a synchronous data link using reciprocal quantum logic enabled by resonant clock distribution on-chip and on the MCM carrier. The simple physical link has only four Josephson junctions and 3 fJ/bit dissipation, including a 300 W/W cooling overhead. The driver produces a signal with 35 GHz analog bandwidth and connects to a single-ended receiver via 20 Ω Nb passive transmission line. To validate this link, we have designed, fabricated, and tested two 32 × 32 mm2 MCMs with eight 5 × 5 mm2 chips connected serially and powered by a traveling-wave clock, and with four 10 × 10 mm2 chips powered with a 2 GHz resonant clock. The traveling-wave clock MCM validates performance of the data link components and achieves a 5.4 dB AC bias margin with no degradation relative to individual chip tests. The resonator MCM validates synchronization between chips, with a measured AC bias margin up to 4.8 dB between two chips. The resonator MCM is capable of powering circuits of 4 million Josephson junctions across the four chips with a projected 10 Gbps serial data rate.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-07T23:00:00Z
      DOI: 10.1088/1361-6668/ac8e38
      Issue No: Vol. 35, No. 10 (2022)
       
  • Differential geometry method for minimum hard-way bending 3D design of
           coils with ReBCO tape conductor

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      Authors: T H Nes; G de Rijk, A Kario H H J ten Kate
      First page: 105011
      Abstract: The use of tape conductor poses design challenges for superconducting magnets. Due to its very high aspect ratio, it is hardly possible to bend the conductor over its thin edges (hard-way bending) rather than over its wide side (easy-way bending). Overstraining the conductor causes critical current degradation. In this paper, we propose a new design approach to three-dimensional coil layouts and coil end geometries with tape conductor, which considers the tape’s geometrical limitations. To geometrically describe the conductor surface, we use the thin strip model, also referred to as constant perimeter geometry. To prevent conductor degradation, new optimization criteria valid for three-dimensional geometries are presented, which are prevention of conductor creasing, minimization of overall bending energy, and prevention of over-straining the conductor. We will apply this to two 3D coil designs called helix and canted cosine theta. For the design of the coil ends, we propose a new design method using Bézier splines, which allows for much greater design flexibility than previous methods. Two examples of coil end geometries generated with Bézier splines are presented: the so-called cloverleaf and cosine-theta.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-08T23:00:00Z
      DOI: 10.1088/1361-6668/ac8e39
      Issue No: Vol. 35, No. 10 (2022)
       
  • Prediction of strain, inter-layer interaction and critical current in
           CORC® wires under axial strain by T-A modeling

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      Authors: K Wang; Y W Gao, V A Anvar, K Radcliff, J D Weiss, D C van der Laan, Y H Zhou A Nijhuis
      First page: 105012
      Abstract: Superconducting conductors on round core (CORC®) cables and wires can meet the needs of large high-field magnets, such as particle accelerators and compact nuclear fusion machines, due to their simple cabling process, high current-carrying capacity and reliable operation under high mechanical stresses. Many high-field magnets require CORC® cables to carry a current of thousands of amperes in a background magnetic field exceeding 20 T. As a result, the large electromagnetic forces will deform the cable in the axial direction due to hoop stress and in the transverse direction by compressive stress. Therefore, it is essential to determine the irreversible deformation limit of the CORC® cable under axial tensile load and optimize the cabling parameters to potentially extend this limit. Analytical and numerical methods are developed to assess the performance degradation of CORC® wires under axial tensile load. The strain level, interlayer contact pressure and friction and their impact on the critical current are calculated by combining the mechanical response and the T-A method. Analyzing the results shows that the winding angle of the tape and the Poisson’s ratio of the inner core are key factors affecting the irreversible tensile strain limit of CORC® wires. The smaller the winding angle and the higher the Poisson’s ratio of the inner core, the higher the irreversible tensile strain limit. For multi-layer CORC® wires, the initial contact pressure caused by the cabling process must also be considered. The inter-layer interaction is coupled with the tape strain of each layer. The results of this research can serve as a basis for optimizing and designing CORC® wires with extended irreversible strain limits.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-08T23:00:00Z
      DOI: 10.1088/1361-6668/ac8a23
      Issue No: Vol. 35, No. 10 (2022)
       
  • Materials for a broadband microwave superconducting single photon detector

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      Authors: Viktor Lubsanov; Vladimir Gurtovoi, Alexander Semenov, Evgenii Glushkov, Vladimir Antonov Oleg Astafiev
      First page: 105013
      Abstract: In this work, we develop and study superconducting materials for a broadband microwave single-photon detector for wide-range applications in superconducting quantum devices. Ideal materials of this type should have a superconducting gap of the order of 10 GHz (0.2 K), and possess a normal sheet resistance of the order of 50 . We find that Ti/Pt bilayers are good candidates: it enables to vary the superconducting transition temperature in a wide range, from 0.1 to 0.4 K, and the sheet resistance in the range from 10 to 50 . We present a proof-of-principle demonstration of a low-level microwave power detector based on a nanobridge made of a designed Ti/Pt bilayer. The response to the absorbed microwave power is consistent with the picture of the kinetic inductance detection in superconductors. The extracted response time corresponds to the recombination of quasiparticles with the emission of a photon to the microwave line.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-12T23:00:00Z
      DOI: 10.1088/1361-6668/ac8a24
      Issue No: Vol. 35, No. 10 (2022)
       
  • Design, fabrication and experimental demonstration of a highly sensitive
           SQUID-based accelerometer

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      Authors: Gracia Kim; In Mook Choi
      First page: 105014
      Abstract: In this paper, a newly designed accelerometer based on a SQUID detection technology and the experimental results are presented. The levitated proof mass was manufactured in the shape that combines a disk and a cylinder on the basis of an earlier patent by the authors. The advantage of this shape is, given that the bottom part is cylindrical, even if the proof mass is mounted mechanically tilted, it can be moved to the center depending on the magnetic flux. The inside of the accelerometer is unobservable after the sealing of the superconducting housing; therefore, the initial set current values on both the solenoid and flat spiral coil are crucial. It was easily able to determine the levitation status at equilibrium position of the proof mass by investigating the inductance change according the persistent current for sensing and solenoid coils. At the levitation status, the movement of the proof mass caused by an external acceleration could be detected with a SQUID optimization. Accordingly, levitation experimental results and the flux noise spectra of the levitated proof mass are described.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-18T23:00:00Z
      DOI: 10.1088/1361-6668/ac8fc0
      Issue No: Vol. 35, No. 10 (2022)
       
 
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