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ISSN: 2772-8307
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Abstract
Corresponding email:rries@fsu.edu
REBCO coated conductors (CCs) exhibit strong critical current anisotropy with respect to the magnetic field orientation relative to the tape plane, Ic(θ, φ), which is crucial for high-field applications such as fusion magnets operating in complex field geometries. Quantitative characterization of this anisotropy using transport measurements becomes increasingly challenging at low temperatures, high magnetic fields, and high critical currents. In this work, we introduce a torque-magnetometry-based method that extends the capability of the standard two-dimensional (2D) torque measurements Ic(θ) limited by fixed φ = 0° to full three-dimensional (3D) characterization Ic(θ, φ) with variable angle φ, as well as improves the accuracy of the evaluated critical currents. The study combines an analytical framework with redesigned torque probe components and is demonstrated experimentally up to 45 T. The effects of sample geometry, current redistribution, and intrinsic longitudinal–transverse anisotropy are quantified and incorporated into the analysis. The experimental part focuses on principal field anisotropies, i.e. Ic(θ, 0°) and Ic(θ, 90°), corresponding to maximum (MLF) and variable Lorentz force (VLF) configurations, respectively. It was observed that their ratio follows higher-order angular dependence and increases with the applied magnetic field. The presented method enables rapid, non-destructive 3D anisotropy characterisation Ic(θ,φ,B,T) of the REBCO CCs in the temperature range 4.2 - 50 K and fields up to 45 T, extending anisotropy measurements into regimes difficult to access using conventional transport methods.
Abstract
Corresponding email:gaopf@lzu.edu.cn
High-temperature superconducting (HTS) rare-earth barium copper oxide (REBCO)-coated conductors (CCs) are widely used in large-scale applications owing to their high critical performance and excellent mechanical stability. However, defects can significantly degrade their performance by distorting current distributions. Conventional nondestructive evaluation techniques typically involve stepwise inversion from magnetic field measurements to current distributions, and then to defect morphology. However, these approaches suffer from intrinsic ill-posedness and limited ability to identify complex or multiple defects. To address these challenges, we propose an integrated inverse-forward framework that combines deep learning with physical modeling to directly map surface magnetic field measurements to internal defect morphology and current density distributions. The core of this method is a specially designed conditional generative adversarial network (cGAN) as the primary learner. It undergoes adversarial training on a dataset containing complex multi-defect configurations and their corresponding magnetic field distributions, enabling robust inverse prediction of defect morphology. The reconstructed defect geometry is then incorporated as a boundary constraint into the forward solution of Maxwell's equations coupled with superconducting nonlinear constitutive relations, enabling high-fidelity reconstruction of the current density distribution. Validation was performed using finite element simulations of REBCO-CCs with various defect types under current-carrying conditions. The adversarial training was performed using the generated finite element dataset. The trained model accurately identified multiple complex defect morphologies across different operating conditions and demonstrated strong generalization capability. Furthermore, the reconstructed current density accurately reproduced the original magnetic field distribution, confirming the reliability of the proposed method. This work integrates data-driven inference with physics-based modeling to establish a unified “magnetic field–defect morphology–current density” inversion paradigm, providing an efficient and reliable approach for nondestructive evaluation and performance assessment of REBCO-CCs.
cited:0
A novel Pre-HIP two-step annealing process for enhancing the critical current of Ba1-xKxFe2As2 superconducting tapes
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Article Number:Article 100221
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Abstract
Corresponding email:liuhj@ipp.ac.cn; fangliu@ipp.ac.cn
Iron-based superconductors (IBSs) are compelling candidates for high-field magnet applications due to their excellent intrinsic properties. The hot isostatic pressing (HIP) effectively enhances their critical current density by increasing core density. However, IBS tapes are highly stress-sensitive after heat treatment. This necessitates fabricating magnets prior to the HIP process. Consequently, the requirement for large-volume HIP furnaces for full-scale magnets presents significant technological and cost barriers. To circumvent this manufacturing bottleneck, this paper introduces a novel “pre-HIP” two-step annealing process. The principle involves an initial, low-temperature HIP (pre-HIP) heat treatment on IBS tapes to achieve densification. Subsequently, the tapes are wound into the desired magnet or conductor geometry, followed by a final heat treatment at atmospheric pressure (AP). This strategy allows large-scale magnets to be treated in conventional, cost-effective furnaces. We systematically evaluated the effect of the pre-HIP temperature (370-450 °C at 50 MPa) on the transport properties and bend performance of 7-filamentary Ba1-xKxFe2As2 (Ba-122) tapes. Results show that pre-HIP significantly enhances the critical current. However, a critical trade-off was identified: higher pre-HIP temperatures yield superior critical performance but induce local grain growth, causing severe degradation during bending. Samples pre-HIP at 370 °C retained 78 % of their initial performance after bending to 10 mm diameter, whereas the 450 °C samples degraded significantly. This study confirms that pre-HIP is a cost-effective method to improve IBS magnet performance when the optimal temperature is selected.
cited:0
Fracture behavior of high-temperature superconducting filmswith an edge slit produced by flux avalanches
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Article Number:Article 100222
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Abstract
Corresponding email:lujiang@upc.edu.cn；liujianlin@upc.edu.cn
In type-II superconducting films, the metastable state can be disrupted by flux avalanches, leading to severe degradation of the electromagnetic properties and irreversible damage to the material in even relatively lower fields. In this study, an electrical-magnetic-thermal-mechanical coupling model is developed to investigate the electromagnetic and mechanical responses of YBa2Cu3O (YBCO) superconducting films with an edge slit during the flux avalanche, taking into account the effects of the edge slit on the triggering of the first flux avalanche. The distribution of magnetic field, temperature, and stress within the superconducting film, as well as the initiation and propagation of crack is numerically simulated by combining the Fast Fourier Transform (FFT) method and the Extended Finite Element Method (XFEM), allowing for an in-depth analysis of the fracture mechanism. The results indicate that thermal stress induced by magnetic flux avalanches is the dominant driving force behind the initiation and propagation of cracks, which has also previously been observed at the trunk of the dendritic flux avalanche in the YBCO superconducting film. Detailed analyzes are performed to discuss the influence of the working temperature, magnetic field ramp rate, and edge slit geometry on crack behavior. It is found that higher working temperatures lead to larger-scale avalanches and more pronounced non-uniform temperature rises, thereby significantly increasing fracture risk. Moreover, the applied magnetic field with lower ramp rates is more likely to induce fracture during the first flux avalanche. As for edge slit geometry, smaller edge slit widths or lengths intensify local heating and thermal stress concentration, further promoting crack propagation.
cited:5
Opportunities and challenges of offshore direct drive high-temperature superconducting wind turbine generators
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Article Number:Article 100230
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Abstract
Corresponding email:zhen.huang@sjtu.edu.cn
Offshore direct drive high-temperature superconducting (HTS) wind turbine generators, a key application of superconductors in the energy sector, are entering a phase of commercial opportunity. In the wind power industry, one clear trend is the increasing power rating of units: current models exceed 15 MW, with over 20 MW generators emerging. For such high-power units, the high power density of superconducting generators minimizes mass and material usage, thereby achieving a higher power-to-weight ratio. Beyond power scaling, another trend is the deployment of wind turbines in deep waters to tap into more abundant wind resources and reduce the need for onshore land; however, operating expenditure (OpEx) in deep waters drives increased demand for reliability. HTS generators operate without a gearbox, offering a reliability advantage—especially critical in deep waters subject to multiple excitations and strong dynamic loads. As a result, modular direct drive HTS generators are increasingly becoming the preferred choice for this scenario. Modularization—dividing the generator's rotor and stator into symmetrical sectors and assembling them at the end of the production chain—facilitates manufacturing, transportation, installation, and replacement. Notably, the price of HTS tape has been declining lately, a trend driven by the surge in compact magnetic confinement fusion reactors. This reduction lowers the capital expenditure (CapEx) of superconducting generators, enhances market competitiveness, and underpins research into high-magnetomotive force (MMF) machine designs. Nevertheless, HTS generator design and manufacturing are system-level endeavors, involving trade-offs across electromagnetic, thermal, and mechanical aspects that demand targeted optimization and rigorous reliability testing.
cited:2
Design and tests of a superconducting magnet system for demonstration operation in orbit
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Article Number:Article 100231
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Abstract
Corresponding email:nick.strickland@vuw.ac.nz
Applied-field magnetoplasmadynamic (AF-MPD) thrusters have been proposed as highly propellant-efficient thrusters for satellites and spacecraft. The electromagnets for these devices have only been reducible to practical dimensions with the maturation of high-temperature superconductors. We report the development and ground testing of such a magnet which has been designed and constructed with the intention of deploying to the International Space Station and testing in orbit. The magnet is of dimensions suitable for accommodating a small thruster, will be cooled by a miniature space-compatible cryocooler and energized by a flux pump. It can generate a magnetic field of up to 760 mT operating at around 77 K in that configuration. A passive magnetic shield has been incorporated in order to comply with stray-field requirements of the ISS when operating at the target operational field of 300 mT.
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