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ISSN: 2772-8307
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cited:95
Interface properties and failures of REBCO coated conductor tapes: Research progress and challenges
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Article Number:Article 100068
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Abstract
Corresponding email:xzwang@lzu.edu.cn
RE-Ba-Cu-O (REBCO, where RE = Y, Gd, Sm, and other rare earth elements) coated conductor (CC) tapes are promising for applications in high-energy physics and high-field science owing to their significant advantages such as high critical magnetic field, high current density, and the ability to achieve superconductivity at liquid nitrogen temperatures. Nevertheless, the mechanical and superconducting performances of these CC tapes are significantly affected by interface failures, such as interfacial delamination and coating fractures, which arise from the complex interplay of mechanical stress induced by magnet processing, thermal mismatch stress during cooling, electromagnetic stress under high magnetic fields, and thermal stress during quenching. This study comprehensively reviews the interface properties and failure behavior of REBCO CC tapes. First, the research progress in characterizing the intricate interface properties of REBCO CC is systematically reviewed. Furthermore, the interface failure behavior in extreme multifield environments was analyzed and summarized. Subsequently, this study outlines optimization strategies to mitigate interface failure risks in REBCO superconducting magnet structures. Finally, we address the current challenges and future perspectives on interface issues in REBCO CC tapes. By addressing these challenges, this study offers valuable insights for advancing the development and practical implementation of superconducting technologies in diverse applications.
cited:18
Experimental investigation of axial tensile and fatigue behaviors of HTS round strands
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Article Number:Article 100069
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Corresponding email:laixq@swip.ac.cn
For the development of high-temperature superconducting (HTS) magnet systems of future fusion devices, a novel HTS round strand based on a stacking structure was designed and manufactured using second generation (2G) HTS tapes. Different mechanical loads during operation can result in irreversible degradation of the strand. The axial tension and fatigue loads need particular attention. Therefore, it is important to investigate the electromechanical behavior of the round strand under various axial tension and cyclic loads. In this paper, the axial tensile and fatigue tests were conducted at 77 K, self-field. Taking 95% critical current (Ic) retention as the criterion, the results of the tensile tests revealed that the average tensile stress and strain were as high as 344 MPa and 0.47%, respectively. Fatigue characteristics were also investigated as a function of axial tensile stress. No significant performance degradation was observed up to 100,000 loading cycles with stress amplitudes ranging from 20 MPa to 200 MPa. Ic degradation occurs after 16,000 loading cycles with 380 MPa as the maximum stress. Furthermore, the microscopic defects of the round strand samples due to fabrication imperfections and mechanical loading were investigated using metallographic microscope and scanning electron microscope. These results presented in this paper are useful for comprehending and improving the mechanical behaviors of the strand in high-field and large-scale fusion magnet systems.
cited:4
Superfluid density dominated junction resistance of bulk polycrystalline YBa2Cu3O7−δ and DyBa2Cu3O7−δ superconductors at low temperature
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Article Number:Article 100070
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Corresponding email:ajayk.ghosh@jadavpuruniversity.in
Resistances of grain junctions of bulk polycrystalline YBa2Cu3O7−δ (YBCO) and DyBa2Cu3O7−δ (DyBCO) superconductors have been extracted following (i) Ambegaokar- Baratoff (AB) and (ii) de Gennes (dG) equations. Current–voltage (IV) below the critical temperature () has been used to extract transport critical current density (). The variations of the junction resistances, () with temperature (T) exhibit that below a critical value of the normalised superfluid density (NSD), junctions become very low resistive and exhibit metallicity. Dependence of this feature of on the energy gaps has also been explored. Weak scattering limit is found to be compatible with the maximum of (T) as is observed from the corresponding NSD.
cited:12
Ic measurement of twisted multifilamentary MgB2 wires with non-magnetic sheath over a wide range of temperatures and fields
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Article Number:Article 100072
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Corresponding email:nick.strickland@vuw.ac.nz
All-superconducting rotating machines have the potential for meeting the high power density and high efficiency required for electrical aircraft applications. However, very high AC loss encountered in superconducting armature windings could hinder their development. Multifilamentary MgB2 wires are one of the promising candidates for the stator windings, due to their potentially low AC loss properties with small filament size and twist pitches. As the first step, the dependence of critical current and n-value on magnetic fields and temperatures Ic(B, T) and n(B,T), which are basic input parameters for AC loss simulation, needs to be measured. In this work, we present transport Ic measurements in three non-magnetic multifilamentary MgB2 wires (MgB2/Nb/CuNi/CuZn): one large wire with a 0.70 mm diameter and 25 mm twist pitch, and two small wires with a 0.48 mm diameter each and a 10 mm and 30 mm twist pitch respectively. A four-probe direct current method is used to measure Ic of the MgB2 wires with variations in temperature (15 – 35 K) and magnetic field (0 – 5.5 T). Full Ic data for the small wire with 10 mm twist pitch was obtained, and the n-values were mostly less than 20. While the Ic data for the large wire at low fields was more limited due to heating, the n-values were higher and could be up to around 100. The difference is attributed to the different filament sizes. Experiments also found that there is no significant hysteresis in the transport critical current measured by decreasing or increasing magnetic fields due to the non-magnetic sheaths. This non-hysteretic characteristic is critical for lowering AC loss because the additional losses from magnetic sheaths can be eliminated. From the magnetic-field dependence of critical current density, an empirical expression has been developed that provides suitable extrapolations to lower fields for the large wire.
cited:7
Characterizations of the electrothermal parameters of a transition edge sensor microcalorimeter and its energy resolution
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Article Number:Article 100051
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Corresponding email:bo_f_gao@mail.sim.ac.cn
We developed a transition-edge sensor microcalorimeter (μ-calorimeter) using Mo/Au/Au thin films. We report the detector fabrication, the measurements of the electrothermal parameters and the noise characterizations of the transition-edge sensor μ-calorimeters. We estimated the energy resolution of the μ-calorimeter using the measured noise spectrum and the calculated power-to-current responsivity. Using a 55Fe radioactive X-ray source, we characterized the detector responses to incident photons at various working points. The best instrumental energy resolution achieved was 4.13 eV @ 5.9 keV, which agrees qualitatively with the resolution of 4.01 eV estimated from the noise spectrum.
cited:6
Field and current driven versions of Brandt method for calculating transport ac loss of superconducting cylinder and strip
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Article Number:Article 100052
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Corresponding email:xf_li@sjtu.edu.cn
As an elegant and fast numerical tool for solving time-dependent electromagnetic field problems in hard superconductors, Brandt’s method has played an important role in understading the magnetic behavior of superconducting strips, discs, bars and cylinders in various aspect ratios. However, the application of this convenient method was mainly in magnetization processes. Traditionally, the solution of current transport problem needs to introduce a driving electric field , which requires a low efficiency iterative process and itself was not clearly explained. In this work, three integral algorithms based on the Brandt’s method are developed to deal with current transport problems, which directly adopt the applied current as a boundary condition. Namely the current (I)-driven version and two current-field-driven versions A and B. Moreover, the arbitrary applied magnetic field can also be included in the I-driven version. The derivation with all necessary formulas for the methods are given in this work. As an example, the new methods, as well as the traditional method are used for calculating transport ac loss Q of a superconducting cylinder or strip obeying a power-law relation of as a function of a given . Derived from the Ampère law and the differential rather than the integral expression of the Faraday law, the current-driven version can be used for more accurate and much quicker computation. Being an intermediate quantity, in the two current-field-driven versions is accurately calculated under the given , but version B is much quicker than A. Problems relating to and Q stabilization process are discussed.
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