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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]
  • Maximum DC operating current degradation and magnetization loss of
           no-insulation (RE)Ba2Cu3O x coil under AC axial background magnetic fields
           

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      Authors: Wenbo Xue; Yutong Fu, Zhen Lu, Qingqing Yang, Ke Li, Yue Zhao Yawei Wang
      First page: 114001
      Abstract: No-insulation (NI) high-temperature superconductor (HTS) coils show a great advantage on enhanced thermal stability during quenches. It is inevitably exposed to ripple AC magnetic fields in some applications, such as synchronous machines, tokamak magnets and maglev trains. The AC applied fields can induce an eddy current in NI coils due to the absence of turn-to-turn insulation. This eddy current may cause considerable maximum DC operating current degradation and additional magnetization loss in NI coils, which are still unclear. In this paper we study this issue using both experiments and simulations. An experimental platform is built to measure the maximum operating current of HTS coils exposed to AC axial applied fields, and the results show that the axial AC applied fields can lead to a significant maximum operating current degradation (22.9% in this study) on the NI HTS coil due to the eddy current induced even though the field is parallel to tape’s ab-plane and has a very low amplitude and frequency (26.88 mT/50 Hz). Meanwhile, this low applied field has little effect on the critical current of insulated HTS coils. A numerical model is applied to elucidate the underlying physical mechanism of this phenomenon, and the magnetization loss induced by an additional transport current is analyzed using this model. The influence of graded turn-to-turn resistivity technique is also investigated, and the results show that this technique can effectively prevent the maximum operating current degradation and reduce the magnetization loss of NI HTS coils exposed to AC axial applied fields.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-21T23:00:00Z
      DOI: 10.1088/1361-6668/ac90f3
      Issue No: Vol. 35, No. 11 (2022)
       
  • Non-trivial band topology in the superconductor AuSn4: a first principle
           study

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      Authors: N K Karn; M M Sharma V P S Awana
      First page: 114002
      Abstract: Topological semimetals such as Weyl or Dirac semimetal with superconductivity have emerged as a new class of topological materials to realize and study Majorana Fermion. This article reports the density functional theory calculated bulk electronic band structure of recently discovered topological superconductor candidate AuSn4. The study has been performed on AuSn4 considering two space groups symmetries viz. Aea2 and Ccce as reported earlier. This study is further extended to the calculation of Z2 invariants. The Fermi surfaces corresponding to the bands, which are responsible for non-trivial band topology along with the surface states are also mapped. The complete study suggests that AuSn4 is a topological semimetal. On AuSn4, it is the first report in the literature showing the non-trivial band topology based on first-principle calculations.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-25T23:00:00Z
      DOI: 10.1088/1361-6668/ac9160
      Issue No: Vol. 35, No. 11 (2022)
       
  • 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)
       
  • Electron correlations in the Hc2 of Fe y Se 1−x S x (0.10 ⩽x⩽
           0.24, y⩾ 0.9)

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      Authors: Aifeng Wang; C Petrovic
      First page: 115002
      Abstract: We report on the evolution of the electronic correlation strength across the nematic critical point in FeySeSx (), inferred from the measurements of the slope of the upper critical field . Superconducting transition Tc and quasiparticle mass exhibit similar reduction with sulfur content x. Our results indicate that electronic correlations from all Fermi surface pockets show strong interconnection with pairing strength and are not governed by the change of nematic fluctuations. The upper critical field anisotropy γH = / exhibits a minimum in the critical region and stronger temperature dependence away from it.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-21T23:00:00Z
      DOI: 10.1088/1361-6668/ac9161
      Issue No: Vol. 35, No. 11 (2022)
       
  • High-current-density Rutherford MgB2 cable sheathed by CuNi30 alloy

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      Authors: P Kováč; L Kopera, D Berek, M Hain, T Melišek, I Hušek, J Kováč M Búran
      First page: 115003
      Abstract: A Rutherford-type MgB2 cable has been fabricated from 12 six-core strands prepared by an internal magnesium diffusion (IMD) process with a resistive CuNi30 outer sheath. The uniformity of individual strands of diameter 0.448 mm prior to and after additional densification by rolling was studied by x-ray micro-tomography. The engineering current densities of the cable samples were measured at 4.2 K and external magnetic fields between 4.0 T and 8.0 T and compared with available published data. The presented Rutherford cable has the highest engineering current density with Je = 104 A cm2 measured in an external magnetic field of 5.73 T. The bending tolerance of the cable shows a critical diameter of 60 mm and less gradual critical current degradation in comparison to similar cables fabricated from single-core strands. The AC loss measurements of the present cable show lower coupling losses in comparison to monolithic multicore IMD conductors. The obtained results are promising for high-current-density and low-AC-loss MgB2 superconducting cables that are suitable especially for motors and generators.
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-21T23:00:00Z
      DOI: 10.1088/1361-6668/ac8ad5
      Issue No: Vol. 35, No. 11 (2022)
       
  • Synthesis and design of asymmetric cul-de-sac structure HTS filter with
           transmission zero introduced in Pairs

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      Authors: Liguo Zhou; Wen Zhang, Ping Kwan Johnny Wong, Xudong Bai, Zhihe Long Tianliang Zhang
      First page: 115004
      Abstract: An asymmetric prototype of a cul-de-sac topology filter to introduce finite frequency transmission zeros (FTZs) in pairs with the least cross-coupling is synthesized and designed in this paper, which is suitable for the design of the high temperature superconducting (HTS) narrowband filter with high selectivity sideband suppression and symmetrical frequency response about the central frequency, especially. The resonator in the cul-de-sac structure filter can adopt the same frequency resonator without self-coupling so that the cul-de-sac structure filter can have fewer coupling coefficients and fewer resonator types. These characteristics of cul-de-sac structure filters are convenient for the design of high-order HTS filters with temperature shifts. A typical 7-order HTS filter with a central frequency of 4000 MHz, 5% relative bandwidth, five coupling coefficients, one cross-coupling, and one pair of FTZs is designed and fabricated on a 0.5 mm-thick MgO wafer with double-sided YBa2Cu3O7 (YBCO) thin films employing this cul-de-sac filter theory. The analyzed frequency response characteristic obtained with full-wave tools of this filter agrees well with the synthesis results and measured results at 77 K (Kelvin temperature).
      Citation: Superconductor Science and Technology
      PubDate: 2022-09-21T23:00:00Z
      DOI: 10.1088/1361-6668/ac925b
      Issue No: Vol. 35, No. 11 (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)
       
  • 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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