Search

This paper presents a novel two-step procedure for measuring the critical current (I c) properties as a function of tensile stress. The proposed method completely eliminates the possible negative effect of the voltage tap used during the tensile procedure, allowing the actual I c irreversible degradation stress to be clearly determined. Six different commercial REBCO tapes from five manufacturers were tested. The I c value does not degrade until the stress reaches the 'inflection area' in the tensile curve, which corresponds to the most pronounced transformation step from elastic to plastic deformation. This allows easy estimation of the stress corresponding to I c irreversible degradation by a simple and accurate cryogenic tensile curve instead of complicated in-situ I c tensile measurement. A feasible composite-material tensile model is established to explain the phenomenon. In addition, fatigue measurements on a commercial REBCO tape from Shanghai Superconductor technology show that the tape can withstand 10 000 cycles under 580 MPa and over 5000 cycles under 695 MPa, which also is consistent with the proposed composite-materials tensile model and is confirmed by the EBSD experiments on the Hastelloy substrate. This research provides better insight and tools for designing and fabricating extremely high-field magnets. [ABSTRACT FROM AUTHOR]

The high aspect ratio of REBCO tapes has a significant impact on several characteristics in high-temperature superconducting applications, such as critical current and AC loss. Narrow filamentary technology can effectively reduce the impact of magnetic field dependence and enhance the electromagnetic performance of REBCO tapes. However, the existing methods are constrained by the trade-off between the narrow degree of REBCO filaments and high current capacity. Meanwhile, when processing REBCO tapes for large-scale magnets, there is a great possibility that local defects are lurking. A striated narrow-stacked (NS) structure is proposed based on the existing narrowing methods to address these challenges. To verify the validity of this structure, it is imperative to explore the non-uniform critical current and stacking effect on performance for multi-filament REBCO tapes with potential defects. This article introduces a magnetic extended network (MEN) model to analyze the electrical characteristics of striated NS structures with different types of potential defects. Then, by coupling with a 3D finite element method electromagnetic module, the calculation results of the MEN model are visualized and used to analyze the electromagnetic characteristics including current sharing mechanism, magnetic field distribution, and critical current compensation due to stacking effect. It is found that stack structures successfully provide the performance remedy for multi-filament REBCO tapes with potential defects. This study aims to promote the narrowing improvement of REBCO tapes in high-field magnets and high-current applications. [ABSTRACT FROM AUTHOR]

The VEGA-3 laser system at the Centro de Láseres Pulsados delivers laser pulses up to 1 PW at 1 Hz repetition rate, focused to intensities up to 2.5 × 10 20 W cm−2. A versatile and compact solid target suitable for up to 0.05 Hz is presented which can operate in the challenging petawatt laser environment close to the laser-plasma interaction. Strips are spooled in a tape target system to deliver a solid density target to the laser focus for every shot. Results are presented for different tape materials and thicknesses, and a shot-to-shot standard deviation of the cut-off energy of 1.5% was obtained for Kapton reinforced aluminium tapes of 9 µ m thickness. Experimental ion spectra are recorded by a Thomson Parabola Ion Spectrometer coupled with a scintillator screen; and an antenna array is used for the characterization of electromagnetic pulses. The results of both diagnostics show a good shot-to-shot stability of the system. [ABSTRACT FROM AUTHOR]

More than a century after the discovery of superconductors (SCs), numerous studies have been accomplished to take advantage of SCs in physics, power engineering, quantum computing, electronics, communications, aviation, healthcare, and defence-related applications. However, there are still challenges that hinder the full-scale commercialization of SCs, such as the high cost of superconducting wires/tapes, technical issues related to AC losses, the structure of superconducting devices, the complexity and high cost of the cooling systems, the critical temperature, and manufacturing-related issues. In the current century, massive advancements have been achieved in artificial intelligence (AI) techniques by offering disruptive solutions to handle engineering problems. Consequently, AI techniques can be implemented to tackle those challenges facing superconductivity and act as a shortcut towards the full commercialization of SCs and their applications. AI approaches are capable of providing fast, efficient, and accurate solutions for technical, manufacturing, and economic problems with a high level of complexity and nonlinearity in the field of superconductivity. In this paper, the concept of AI and the widely used algorithms are first given. Then a critical topical review is presented for those conducted studies that used AI methods for improvement, design, condition monitoring, fault detection and location of superconducting apparatuses in large-scale power applications, as well as the prediction of critical temperature and the structure of new SCs, and any other related applications. This topical review is presented in three main categories: AI for large-scale superconducting applications, AI for superconducting materials, and AI for the physics of SCs. In addition, the challenges of applying AI techniques to the superconductivity and its applications are given. Finally, future trends on how to integrate AI techniques with superconductivity towards commercialization are discussed. [ABSTRACT FROM AUTHOR]

The repeatability of superconducting DC limiters has not been introduced by other literature. Understanding the performance degradation characteristics of high-temperature superconducting (HTS) tapes under the overcurrent is of great significance for popularizing the application of a resistive-type DC superconducting fault current limiter. In this paper, the threshold experiment and repeated DC overcurrent experiment of HTS tape were carried out. With the critical current decay of the tapes under repeated DC overcurrent recorded, the current threshold under the DC overcurrent was obtained. And the performance degradation characteristics of the tapes under different repeated overcurrents were analysed, the resistance characteristics of the samples during different currents were compared. The results show that the DC overcurrent threshold of the copper-encapsulated second-generation (2G) YBCO tapes samples of Suzhou Advanced Materials Research Institute is 2.3/4 ms/3700 A. Under the repeated overcurrent, the performance degradation of the samples is abrupt, and the critical value is between 2.3/4 ms/3500 A and 2.3/4 ms/3550 A. The overcurrent has a limited influence on the magnitude of the resistance and will not affect the change trend of the resistance. The resistance at the falling edge of the current was greater than that at the rising edge of the current. The simulation was carried out by using COMSOL Multiphysics, and the simulation results matched the experimental results. The life prediction model of the samples was established and it was found that there is a custom equation relationship between the reliability of superconducting tapes and the number of the overcurrent, and the performance decline of this kind of samples is catastrophic. [ABSTRACT FROM AUTHOR]

This work proposes two alternative analytical models to evaluate the ac losses of high-temperature superconducting (HTS) tapes during their hysteretic and resistive modes. These models intend to extend the application range of state-of-the-art analytical models for current values higher than the critical one, i.e. for the resistive state, and to correctly predict the ac losses during the transition between the hysteretic and resistive modes. Two analytical models are proposed, one considering an extension of the Norris model for the HTS tape's resistive mode and the other based on a sigmoid function to characterize the hysteretic losses and their smooth transition to the resistive mode. Analytical models capable of estimating ac losses of superconducting (SC) tapes are an important tool for the design of complex SC systems, such as SC fault current limiters, SC electrical machines and SC cables. The proposed models are validated experimentally, for a 1st generation BSCCO tape and a 2nd generation REBCO tape. Finite element simulation is also carried out to verify the accuracy of the proposed models. Results show that the proposed extended-Norris model presents some deviation at the transition between the hysteretic and resistive modes, while the sigmoid model presents very accurate results for the whole spectrum of applied current. Also, the parameters of the sigmoid models are independent of the tape geometry. [ABSTRACT FROM AUTHOR]

A superconducting joint for multi-filamentary Bi2Sr2Ca2Cu3O10+ δ (Bi2223) tape, which has applications in nuclear magnetic resonance and magnetic resonance imaging, has been developed based on incongruent melting and multi-junction methods. In this study, the critical current limit, optimal oxygen annealing conditions, and reproducibility of this joint are experimentally evaluated. The results indicate that the critical current limit of the joint at 77 K is determined by that of the tape. The critical current limit was estimated to be about 40 A. Additional oxygen annealing after heat treatment below 1143 K. appears to have no effect on the critical current, and that above 1153 K slightly increases the critical current. It is found that the multi-junction method effectively increases the reproducibility of obtaining a high critical current. To obtain a high critical current at 77 K, the highest temperature in the joint creation process should be lowered to near the incongruent melting temperature of Bi2223 (about 1133 K in air). Two Bi2223 coils, each with one joint (four junctions), were prepared and their persistent current at 77 K was tested. A persistent current of above 20 A was measured with a resistance of about 10 pΩ. [ABSTRACT FROM AUTHOR]

Significant development has been made toward guaranteeing the performance of high-temperature superconducting (RE)Ba2Cu3O7âˆ' x coated conductor (CC) tapes in superconducting devices such as high-field magnets and coils. To understand the superconducting behaviors of CC tapes used in such devices under various mechanical- and thermal-induced loads, their mechanical and electromechanical properties should be evaluated in consideration of their application environments. Under static or cyclic fatigue loads, critical current (I c) can degrade as a result of damage to the superconducting layer, even under loads that do not exceed the irreversible stress limits for I c degradation (σ irr). Therefore, prediction of the stress level that can degrade I c under various conditions, such as the endurance limit (stress), is significant for actual coil or magnet applications of CC tapes. A static fatigue tester for CC tapes at 77 K was used in this study to apply a static fatigue load to a 12 mm wide GdBa2Cu3O7âˆ' x CC tape specimen under simultaneous axial tension and bending stresses in a U-shaped configuration. Bending mandrels were used to superimpose various bending strains onto the applied static axial tensile strain, and I c across various voltage tap separations was measured over time, up to 100 h. The electrical static fatigue strength and endurance limit for I c degradation were determined based on the 95% I c retention criterion and 100 h of elapsed time, respectively. Results show that bending strain, dependent on mandrel diameter, can greatly influence I c degradation behaviors and that I c can drop considerably in the bent sections compared to the straight sections over time. Analyses of the combined strains in the bent sections allowed the prediction of diameter-dependent electrical static endurance limits under subcritical crack growth. The CC tape’s electrical static endurance limit was greatly affected at smaller bending diameters. When CC coils with diameters smaller than or equal to 50 mm are made using 12 mm wide CC tapes, the electrical static endurance limit is low, roughly â©˝0.63 σ irr. [ABSTRACT FROM AUTHOR]

A solid oxide electrochemical oxygen pump was developed in tubular geometry with YSZ electrolyte and LSCF/CGO symmetrical air electrodes. The cells were manufactured based on green symmetrical porous YSZ electrode backbones cast on the green YSZ electrolyte tape, rolled into tubular geometry, co-sintered and impregnated with functional materials. The prepared cell had a thin 16 μm-electrolyte and supporting 76 μm-symmetric electrodes. At 700 °C, 2.8 A current (0.8 A cm−2 ) was obtained under 0.5 V in the single tubular cell infiltrated with 30% CGO and 45% LSCF. A four cell bundle produced theoretical 1.82 l hr−1 O2 with a power consumption of 2.18 W at 700 °C. Excellent stability of the cells was achieved during severe current and thermal cycling tests, indicating the successful fabrication of the tubular cells using the tape co-casting method. [ABSTRACT FROM AUTHOR]