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Distribution characteristics of the current, ampere force and magnetic flux density (B [T]) of a novel high temperature superconducting (HTS) cable woven by transposed REBCO tapes under different transposition lengths are proposed, and these characteristics of the cable stacked with 3 REBCO tapes are also carried out in this paper for comparison. The objective is to enhance the current density and the compactness of the HTS tapes combination, and uniform the current, ampere force and magnetic flux density (B [T]) distributions. A three-dimensional (3D) finite element model, based on Maxwell's equations without consideration of the displacement current, is established to describe the state of the system in the liquid nitrogen condition. The distributions characteristics, maximum and minimum values of current, ampere force and magnetic flux density (B [T]) show significant differences in the simulation results between the novel HTS cable woven by 3 transposed REBCO tapes and the cable stacked with 3 REBCO tapes. The simulated results show that the distribution characteristics are improved, with a more uniform distribution characteristic than that of the cable stacked with REBCO tapes. This is due to fully transposed REBCO tapes. In addition, the experimental E–I curve was also reached. The experimental results show that using a shorter transposition length in the cable can improve the critical current. However, a too small transposition length can cause significant damage to the HTS tape, resulting in deformation of the HTS tape and a reduction in the electromagnetic properties of the HTS tape. This affects the critical current of the HTS tape and, ultimately, the critical current of the cable. From the point of view of whether the production process is convenient, meets the requirements of economy and reduces costs, we need to find a suitable transposition length. The measured optimal transposition length is 95 mm for the cable woven by 3 REBCO tapes. [ABSTRACT FROM AUTHOR]

We present a method of creating high-density superconducting flexible wiring on flexible thin silicon substrates. The flexible wiring, called SOI flex, is created by depositing superconducting wiring on a silicon-on-insulator (SOI) wafer, selectively etching away the thicker silicon section handle layer, and bending the thinner silicon device layer. We show measurements of superconducting transition temperature and critical current for Mo, Nb, and Al on SOI flex. We discuss the expected advantages of SOI flex for low-temperature detector applications, as well as the role of stress and strain in bent silicon and niobium. [ABSTRACT FROM AUTHOR]

Step edge Josephson junctions are fabricated with varying step angles ranging from 10° to 35° on the MgO (100) single-crystal substrate. The impact of step angle on the transport characteristics of the step edge junction is studied. It is found that as the step angle increases, the critical current (Ic) of the junction drops while its normal state resistance (Rn) rises. The overall IcRn product is found to be increasing with an increase in the step angle at all temperatures from 68 K to 77 K. For the 35° step angle junction, the IcRn value is obtained to be 0.34 mV at 77 K, which is comparable to the best values of IcRn products at 77 K so far. For lower step angle junctions, the superconductor grain to grain coupling exhibits more superconductor-normal-superconductor (SNS) type behavior, but as the step angle increases, the superconductor-insulator-superconductor (SIS) type behavior becomes apparent. MgO-based step edge junctions perform well in SQUID and terahertz detection applications. [ABSTRACT FROM AUTHOR]

We measured the temporal voltage response of NbTi superconducting filaments with varied nanoscale thicknesses to step current pulses that induce non-equilibrium superconducting states governed by a hot spot mechanism. Such detected voltage emerges after a delay time  t d , which is intimately connected to the gap relaxation and heat escape times. By employing time-dependent Ginzburg–Landau theory to link the delay time to the applied current, we determined that the gap relaxation time depends linearly on film thickness, aligning with the acoustic mismatch theory for phonon transmission at the superconductor–substrate interface. We thereby find a gap relaxation time of 104 ps per nm of thickness for NbTi films on polished sapphire. We further show that interfacial interaction with the substrate significantly impacts the gap relaxation time, with observed values of 9 ns on Si O x , 6.8 ns on fused silica, and 5.2 ns on sapphire for a 50 nm thick NbTi strip at  T = 5.75  K. These insights are valuable for optimizing superconducting sensing technologies, particularly the single-photon detectors that operate in the transient regime of nanothin superconducting bridges and filaments. [ABSTRACT FROM AUTHOR]

Recent advances in high-temperature superconductors (HTS) have made them extremely attractive for low-temperature, high-magnetic-field-power applications such as in fusion technology, where the advantages over traditional low-temperature superconductors (LTS) allow for the design of fusion reactors operating in different and more convenient regimes. However, the performance enhancement exhibited by novel conductors poses several challenges for the measurement of their superconducting properties. The high critical currents coupled with the relatively low thermal stability of the conductors and their mechanical fragility render this task a challenge, as the angular anisotropies complicate the experimental setup. In this work, we describe the development of our novel high-current measurement facility, focusing on the solutions introduced regarding critical aspects such as the superconducting leads and the sample holder design. We show how simple but effectively designed solutions can be adopted to combat the complexity of the measurement. The results reported in this work guide the development of a measurement system able to withstand high critical currents (I > 1500 A) at high magnetic fields (µ0H > 12 T) by evaluating the angular response of 4 mm wide short samples (L ~ 7.5 cm) in a robust and reproducible manner. [ABSTRACT FROM AUTHOR]

The investigation results of magnetization, dynamic magnetic susceptibility and microstructure of samples of second generation high-temperature superconducting wires irradiated by Bi ions at room temperature with energy of 670 MeV and fluences of 1011 and 1012 cm–2 are presented. The dependences of the superconducting transition temperature and critical current density on the fluence have been determined. For the sample irradiated to fluence 1011 cm–2, an increase in the critical current density is observed compared to the control nonirradiated sample. The microstructure analysis of irradiated samples demonstrates the presence of amorphous tracks, which can act as effective pinning centers. [ABSTRACT FROM AUTHOR]

In this contribution, we study the oscillations of the electrical-potential in a mesoscopic superconducting thin film when an external current is applied. We analyze the resistivity and electrical-potential as a function of the applied current for several external applied magnetic field and size of the sample. Also, we have calculated the electrical-potential as a function of the characteristic time. To study this problem, we solve the well know generalized time dependent-Ginzburg-Landau equations using the link-variable method. We found that the critical current decreases when the external magnetic field increases and the size of the sample decreases. Furthermore, the oscillation frequency of the kinematic vortex, evidenced in the oscillations of the electrical potential, is highly dependent on the applied magnetic field. [ABSTRACT FROM AUTHOR]

High-temperature superconducting (HTS) cable, with massive current carrying capability and low electric power loss, is always at the cutting edge of the strong electric fields. The concentric three-phase HTS cable usually subjects to the impact of electromagnetic and mechanical forces. The forces will lead to the shape change of the cable, which may damage the cable and cause the degeneration of the critical current (Ic). In this paper, an analysis model of stress-strain and bending properties of the 10 kV/1 KA cable based on laminated theory is built. Laminated beam theory can simplify REBCO superconducting tape and concentric three-phase HTS cable to analyze stress-strain distribution. A finite element method (FEM) simulation model is established to analyze the critical bending radius of the HTS cable. Meanwhile, the normalized of the critical current of the cable is obtained at different bending radii. The analysis results will provide the theoretical basis for cable pipelaying and line relay protection in grid. [ABSTRACT FROM AUTHOR]

The optimized design of a new high-temperature superconducting rotating pole machine is presented. Its main structural feature is the use of a double stator core which separates the synchronous machine pole shoe from the pole body to rotate separately as the machine rotor, allowing the superconducting coil to operate in a stationary state. The inner stator core, the stationary dewar and the rotor core together form the excitation system of the machine. The excitation coil windings adopt a rectangular cross-section, with flux divertor strategically placed between the high-temperature superconducting coils. This configuration aims to modulate the background magnetic field, specifically reducing the perpendicular magnetic field component. This mitigation minimizes the impact of ambient magnetic fields on the superconducting coil's current carrying capacity, ensuring an optimized magnetic field environment for its operation. Through the integration of these modifications, the technical and economic parameters of the enhanced high-temperature superconducting machine have been significantly improved. The optimization of design, coupled with detailed calculations of the 3D electromagnetic field, was achieved utilizing the commercial software Ansys EM module. [ABSTRACT FROM AUTHOR]

We have modified the fabrication processes of metallic magnetic calorimeters (MMCs) to improve production yield. Key modifications include (i) the stress mitigation of the sputtered Nb film by optimizing the Argon deposition gas pressure, (ii) an optimized SiO x insulator layer fabrication by switching from a lift-off to a wet-etching method and controlling the optimizing the temperature, (iii) the joint electroplating of thick gold structures for persistent current switch leads and a thermalization layer, and (iv) a reduced sputter-deposition time of the Ag:Er sensor material by introducing a new wafer holder. These modifications contribute to increased production yield, reduced fabrication time, and enhanced overall performance. Tests on MMCs fabricated with these modifications demonstrated uniformly improved critical current of the Nb meander coils, enhanced SiO x insulation properties, strengthened persistent current switch systems, and reduced probability of Ag:Er oxidation. These modified MMC detectors also functioned well in tests for alpha spectrometry measurements, demonstrating good performance. [ABSTRACT FROM AUTHOR]

In this study, the prediction of n-value (index-value) surfaces—a key indicator of the field and temperature dependence of critical current density in superconductors—across various high-temperature superconducting materials is addressed using a deep learning modeling approach. As superconductors play a crucial role in advanced technological applications in aerospace and fusion energy sectors, improving their performance model is essential for both practical and academic research purposes. The feed-forward deep learning network technique is employed for the predictive modeling of n-value surfaces, utilizing a comprehensive dataset that includes experimental data on material properties and operational conditions affecting superconductors' behavior. The model demonstrates enhanced accuracy in predicting n-value surfaces when compared to traditional regression methods by a 99.62% goodness of fit to the experimental data for unseen data points. In this paper, we have demonstrated both the interpolation and extrapolation capabilities of our proposed DFFNN technique. This research advances intelligent modeling in the field of superconductivity and provides a foundation for further exploration into deep learning predictive models for different superconducting devices. [ABSTRACT FROM AUTHOR]

We present a novel method combining anodic aluminum oxide template synthesis and nanolithography to selectively deposit vertically patterned magnetic nanowires on a Si substrate. With this approach we fabricated three-dimensional nanowire-based spin valve devices without the need of complex etching processes or additional spacer coating. Through this method, we successfully obtained NiCu/Cu multilayered nanowire arrays with a controlled sequence along the long axis of the nanowires. Both magnetic switching and excitation phenomena driven by spin-polarized currents were clearly demonstrated in our NiCu/Cu multilayered nanowires. Moreover, the critical currents for switching and excitation were observed to be modulated in an oscillatory manner by the magnetic field in the nanowire-based devices. We present a toy model to qualitatively explain these observations.

We report calculations of current‒voltage characteristics (I‒V characteristics) of Josephson junctions using the resistive model. The I‒V characteristics are found to be stable to deviations of the dependence of the superconducting current on the phase difference (φ) of the order parameter at the junction boundaries from the simple sinusoidal one, characteristic of ideal Josephson junctions. It is shown that to analyze the processes occurring in Josephson junctions, it is important to measure the spectral composition of generation from these junctions. [ABSTRACT FROM AUTHOR]

In this article, a novel non-uniform gap optimization method was proposed for high-current stacked HTS conductors. The proposed configuration was easy for fabrication, but also resulted in good electromagnetic performance. The experiment matched the modeling regarding the critical currents of different stacked HTS conductors, and they presented the optimal critical currents was by the non-uniform gap optimization. After proving the reliability of modeling, the zero gap and non-uniform gap stacked conductors with 15 HTS tapes were comprehensively evaluated with respect to the critical current, AC loss, and fault tolerance. Compared with zero gap stacked HTS conductor, the critical current of the stacked HTS conductor by the non-uniform gap optimization increased by 5%, while the AC loss was reduced by 30%, and the temperature rise due to fault was reduced by 50%. Overall, the stacked HTS conductors with novel non-uniform gap optimization can carry reasonably high currents, with less loss and better fault tolerance. [ABSTRACT FROM AUTHOR]

The effect of 132Xe27+ ion (167 MeV) irradiation at angles of 20°, 30°, 60°, and 90° to the tape surface is studied. The critical parameters of the second-generation superconducting tapes are explored. The tapes on the based of the GdBa2Cu3O7 – x compound are produced by SuperOx. The critical current (Ic) at 77 K in self magnetic field and the critical temperature (Tc) are plotted as a functions of ion irradiation fluence at different irradiation angles. A minor (up to ~5%) increase in the critical current of high-temperature superconducting (HTSC) tapes is observed for all studied irradiation angles for fluences in a range from 3.4 × 108 to 5 × 109 ions/cm2. The radiation resistance of the superconductor to ion irradiation is determined as a function of the irradiation angle. The threshold irradiation fluence Φth is measured to determine the radiation resistance of the tape. This is the value at which the critical current approaches zero. The dependence of Φth on the irradiation angle α can be approximated by the formula . [ABSTRACT FROM AUTHOR]

In this contribution, we study the oscillations of the electrical-potential in a mesoscopic superconducting thin film when an external current is applied. We analyze the resistivity and electrical-potential as a function of the applied current for several external applied magnetic field and size of the sample. Also, we have calculated the electrical-potential as a function of the characteristic time. To study this problem, we solve the well know generalized time dependent-Ginzburg-Landau equations using the link-variable method. We found that the critical current decreases when the external magnetic field increases and the size of the sample decreases. Furthermore, the oscillation frequency of the kinematic vortex, evidenced in the oscillations of the electrical potential, is highly dependent on the applied magnetic field.

A hybrid energy transmission pipeline is proposed with the aim of long-distance cooperative transmission of electricity and chemical fuels, which is composed of an inner high-temperature superconducting (HTS) power cable and outer liquefied natural gas (LNG) pipeline. The flowing LNG could maintain the operating temperature of the inner HTS power cable within the range of 85 K-90 K, thus the Bi-2223 superconductors in the HTS power cable produce little Joule loss with the transmission current below the critical current. Owing to the advantages of high power density, low transmission losses and economical manufacturing costs, the hybrid energy transmission pipeline is expected to be widely utilized in the near future. In order to ensure the safety of the HTS power cable and explosive LNG in case of short-circuit faults, this paper tests and analyzes the characteristics of Bi-2223 HTS tapes of the Type HT-CA, Type HT-SS and Type H models under short-circuit current impacts at the LNG cooling temperature (85 K-90 K). An experimental platform is designed and established for the ampacity tests of HTS tapes above LN2 cooling temperature (77 K). The AC over-current impact tests at 85 K-90 K are carried out on each sample of Bi-2223 tapes respectively, and the experimental results are analyzed and compared to evaluate their performances under different operating conditions. The results indicate that the Type HT-CA tape can withstand 50 Hz short-circuit current impact with the amplitude of 1108 A (10 times of critical current $I_{\mathrm{c}}$ ) for 100 ms at 90 K, and its resistance is the smallest of the three tested samples under similar current impacts. Therefore, the Type HT-CA Bi-2223 tape is the optimal superconductor of the HTS power cable in the hybrid energy transmission pipeline.

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For high-temperature superconducting (HTS) cables carrying substantial currents, the current carrying capacity of a single YBCO tape is limited, and multiple tapes need to be connected in parallel. The current sharing design of parallel YBCO tapes has emerged as a central concern in the HTS cable design. However, various tape parameters, including critical current I c , n-value, and joint resistance, can significantly influence the current distribution in the system. In this paper, the influence of YBCO tape parameters on the current distribution characteristics of the cable was studied. The results showed that the current distribution and quench characteristics were regulated by tape I c , tape n-value, and tape joint resistance together, and that meanwhile, the total current also served as an important factor. Significant influence of the joint resistance was also observed in the event of a limited total current, which was no longer obvious for a total current close to the total I c . For the parallel tapes with the same I c , the one with higher resistance quenched later, while in the case of the same resistance, the effect of the tape I c is greater than that of the tape n-value. [ABSTRACT FROM AUTHOR]

Current-voltage characteristics have been calculated for a high-temperature superconductor containing triangular and square periodic arrays of pinning centers with various disorder rates. Non-monotonic dependences of critical current density on the disorder rate have been obtained for the triangular lattice, showing that a perfectly ordered lattice provides smaller critical currents than that with minor distortions, especially at high magnetic fields. For the square lattice, the critical current was mostly declining, with minor peaks at small disorder rates. A thorough analysis of the vortex dynamics has been done, showing the differences in the way vortices move through the disordered lattice and how their paths affect the critical current density. [ABSTRACT FROM AUTHOR]

Emergent inhomogeneous electronic phases in metallic quantum systems are crucial for understanding high‐Tc superconductivity and other novel quantum states. In particular, spin droplets introduced by nonmagnetic dopants in quantum‐critical superconductors (QCSs) can lead to a novel magnetic state in superconducting phases. However, the role of disorders caused by nonmagnetic dopants in quantum‐critical regimes and their precise relation with superconductivity remain unclear. Here, the systematic evolution of a strong correlation between superconductive intertwined electronic phases and antiferromagnetism in Cd‐doped CeCoIn5 is presented by measuring current–voltage characteristics under an external pressure. In the low‐pressure coexisting regime where antiferromagnetic (AFM) and superconducting (SC) orders coexist, the critical current (Ic) is gradually suppressed by the increasing magnetic field, as in conventional type‐II superconductors. At pressures higher than the critical pressure where the AFM order disappears, Ic remarkably shows a sudden spike near the irreversible magnetic field. In addition, at high pressures far from the critical pressure point, the peak effect is not suppressed, but remains robust over the whole superconducting region. These results indicate that magnetic islands are protected around dopant sites despite being suppressed by the increasingly correlated effects under pressure, providing a new perspective on the role of quenched disorders in QCSs. [ABSTRACT FROM AUTHOR]

Emergent inhomogeneous electronic phases in metallic quantum systems are crucial for understanding high‐Tc superconductivity and other novel quantum states. In particular, spin droplets introduced by nonmagnetic dopants in quantum‐critical superconductors (QCSs) can lead to a novel magnetic state in superconducting phases. However, the role of disorders caused by nonmagnetic dopants in quantum‐critical regimes and their precise relation with superconductivity remain unclear. Here, the systematic evolution of a strong correlation between superconductive intertwined electronic phases and antiferromagnetism in Cd‐doped CeCoIn5 is presented by measuring current–voltage characteristics under an external pressure. In the low‐pressure coexisting regime where antiferromagnetic (AFM) and superconducting (SC) orders coexist, the critical current (Ic) is gradually suppressed by the increasing magnetic field, as in conventional type‐II superconductors. At pressures higher than the critical pressure where the AFM order disappears, Ic remarkably shows a sudden spike near the irreversible magnetic field. In addition, at high pressures far from the critical pressure point, the peak effect is not suppressed, but remains robust over the whole superconducting region. These results indicate that magnetic islands are protected around dopant sites despite being suppressed by the increasingly correlated effects under pressure, providing a new perspective on the role of quenched disorders in QCSs. [ABSTRACT FROM AUTHOR]

The paper describes a method for calculating critical parameters of an inhomogeneous superconducting layer surrounded by nonsuperconducting layers. The calculation is performed using Ginzburg‒Landau equations modified for a thickness-inhomogeneous superconducting layer. The effect of adjacent nonsuperconducting layers is specified using general boundary conditions to these equations. Dependences of the critical current of a superconducting layer on the external magnetic field is calculated numerically. It is shown that for a layer of inhomogeneous thickness, in the model of which the effect of adjacent layers is introduced, an estimate of the critical current yields lower values than those for a homogeneous layer without any influence of boundaries. It is found that at a certain value of the external magnetic field, the critical current is independent of the degree of the superconducting layer inhomogeneity. In this case, the influence of adjacent layers on its superconducting state does not lead to a significant change in the value of this field. [ABSTRACT FROM AUTHOR]

We measured the temporal voltage response of NbTi superconducting filaments with varied nanoscale thicknesses to step current pulses that induce non-equilibrium superconducting states governed by a hot spot mechanism. Such detected voltage emerges after a delay time td, which is intimately connected to the gap relaxation and heat escape times. By employing time-dependent Ginzburg–Landau theory to link the delay time to the applied current, we determined that the gap relaxation time depends linearly on film thickness, aligning with the acoustic mismatch theory for phonon transmission at the superconductor–substrate interface. We thereby find a gap relaxation time of 104 ps per nm of thickness for NbTi films on polished sapphire. We further show that interfacial interaction with the substrate significantly impacts the gap relaxation time, with observed values of 9 ns on SiOx, 6.8 ns on fused silica, and 5.2 ns on sapphire for a 50 nm thick NbTi strip at T=5.75 K. These insights are valuable for optimizing superconducting sensing technologies, particularly the single-photon detectors that operate in the transient regime of nanothin superconducting bridges and filaments.

Recent advances in high-temperature superconductors (HTS) have made them extremely attractive for low-temperature, high-magnetic-field-power applications such as in fusion technology, where the advantages over traditional low-temperature superconductors (LTS) allow for the design of fusion reactors operating in different and more convenient regimes. However, the performance enhancement exhibited by novel conductors poses several challenges for the measurement of their superconducting properties. The high critical currents coupled with the relatively low thermal stability of the conductors and their mechanical fragility render this task a challenge, as the angular anisotropies complicate the experimental setup. In this work, we describe the development of our novel high-current measurement facility, focusing on the solutions introduced regarding critical aspects such as the superconducting leads and the sample holder design. We show how simple but effectively designed solutions can be adopted to combat the complexity of the measurement. The results reported in this work guide the development of a measurement system able to withstand high critical currents (I > 1500 A) at high magnetic fields (µ0H > 12 T) by evaluating the angular response of 4 mm wide short samples (L ~ 7.5 cm) in a robust and reproducible manner.

In this study, the prediction of n-value (index-value) surfaces—a key indicator of the field and temperature dependence of critical current density in superconductors—across various high-temperature superconducting materials is addressed using a deep learning modeling approach. As superconductors play a crucial role in advanced technological applications in aerospace and fusion energy sectors, improving their performance model is essential for both practical and academic research purposes. The feed-forward deep learning network technique is employed for the predictive modeling of n-value surfaces, utilizing a comprehensive dataset that includes experimental data on material properties and operational conditions affecting superconductors’ behavior. The model demonstrates enhanced accuracy in predicting n-value surfaces when compared to traditional regression methods by a 99.62% goodness of fit to the experimental data for unseen data points. In this paper, we have demonstrated both the interpolation and extrapolation capabilities of our proposed DFFNN technique. This research advances intelligent modeling in the field of superconductivity and provides a foundation for further exploration into deep learning predictive models for different superconducting devices.

A research facility for neutron irradiation effect on superconducting materials has been installed at Oarai center in Tohoku University in 2012 as part of a post irradiation experiment. It consists of a 15.5 T superconducting magnet, a variable temperature insert and a data acquisition and control system. Since the sample holder is cooled by thermal conduction with G-M refrigeration, there is a small temperature difference between positive and negative electrodes and the sample temperature rises during the critical current test due to joule heating. To evaluate the temperature rise precisely, a new data acquisition system with a sampling rate of 50 Hz has been installed. By measuring the temperatures of both electrodes and the voltage at the center of the sample, the temperature of the sample was estimated and the measured critical current (IC) was converted to the current at 4.2 K with a critical surface equation. The comparison of IC at different conditions including neutron irradiated samples was implemented and the neutron irradiation effect on superconductivity of Nb3Sn wire is discussed based on the 4.2 K superconductivity. This paper will describe the outline of the new data acquisition system and some results of neutron irradiated Nb3Sn wires.

Abstract Emergent inhomogeneous electronic phases in metallic quantum systems are crucial for understanding high‐Tc superconductivity and other novel quantum states. In particular, spin droplets introduced by nonmagnetic dopants in quantum‐critical superconductors (QCSs) can lead to a novel magnetic state in superconducting phases. However, the role of disorders caused by nonmagnetic dopants in quantum‐critical regimes and their precise relation with superconductivity remain unclear. Here, the systematic evolution of a strong correlation between superconductive intertwined electronic phases and antiferromagnetism in Cd‐doped CeCoIn5 is presented by measuring current–voltage characteristics under an external pressure. In the low‐pressure coexisting regime where antiferromagnetic (AFM) and superconducting (SC) orders coexist, the critical current (Ic) is gradually suppressed by the increasing magnetic field, as in conventional type‐II superconductors. At pressures higher than the critical pressure where the AFM order disappears, Ic remarkably shows a sudden spike near the irreversible magnetic field. In addition, at high pressures far from the critical pressure point, the peak effect is not suppressed, but remains robust over the whole superconducting region. These results indicate that magnetic islands are protected around dopant sites despite being suppressed by the increasingly correlated effects under pressure, providing a new perspective on the role of quenched disorders in QCSs.

The paper presents the results of studies of non-equilibrium states in ribbon high-temperature superconductors under pulse current loading. To study transient processes in a superconductor at critical current loads, an experimental stand is developed, which permits visualization of thermal processes in the composite at critical current loads with high temporal resolution. The dynamics of the thermal processes in the HTS tape under current loads is studied and the features of the thermal processes leading to the change of the liquid refrigerant boiling modes are shown. The process of HTS sample fracture under supercritical current load is studied on a millisecond scale. [ABSTRACT FROM AUTHOR]

This article studies the deformation resistance of high-temperature superconducting (HTSC) tapes for various parameters of deformation. The four-contact method has been used to measure the critical current in specimens deformed on indenters with diameters of 5–20 mm by tensile forces up to 200 N. The damage to the superconducting layer and local superconducting properties of mechanically impacted specimens have been investigated using scanning electron microscopy and scanning Hall magnetometry. [ABSTRACT FROM AUTHOR]

The effect of irradiation with Cu+ ions with an energy of E = 6.3 eV on the crystal structure and critical characteristics of high-temperature copper-based superconductors in the regime of radiation defect formation has been studied. The degradation of the superconducting properties and the growth of the lattice parameters and the magnitude of the relative stresses due to disorder along the c axis with increasing fluence up to the complete disappearance of the superconducting properties at the fluence F = 1.5 × 1014 cm–2 are shown. [ABSTRACT FROM AUTHOR]

Effect of wire diameter and annealing on the properties of internal magnesium diffusion (IMD)-processed MgB 2 composite wires is studied by establishing a correlation with the characteristics of the interfacial reaction zones developed at Mg − B and barrier (Nb) – sheath (Al + Al 2 O 3) interfaces. The MgB 2 superconductor phase grows at the Mg − B interface along with the B-rich MgB 4 phase. Formation of MgB 2 prior to MgB 4 is anticipated owing to a relatively lower Gibbs free energy at annealing temperatures studied. An intermetallic NbAl 3 phase has developed at the barrier – sheath interface whose thickness decreases with an increase in the wire diameter. Development of NbAl 3 further provides mechanical reinforcement and aids at yielding a dense superconductor phase. Resistivity – voltage characteristics of wire indicates the formation of MgB 2 through a huge drop in resistivity values across the core of the wire. An annealing temperature of 645 °C near the melting point of pure Mg (650 °C) and annealing time of 120 min results in highest critical current of the MgB 2 wire. Annealing time beyond 120 min has shown an impediment to the flow current due to crack propagation possibly because of accumulation of stresses within the developed superconductor phase due to grain growth. A significantly greater resistance for the wire with the smallest diameter is attributed to the formation of a thicker NbAl 3 phase. However, highest engineering current density has also been attained by the wire with the smallest diameter annealed at 645 °C for 60 min. [ABSTRACT FROM AUTHOR]

The article presents the results of studies aimed at improving GET 13-01 State Primary Voltage Standard that relies on the quantum Josephson effect. GET 13-01 improvement achieved the following results: extended DC voltage reproduction range due to the transition from two reference points having nominal voltages of 1 and 10 V to the range of 1 · 10−3–10 V; increased noise immunity of reproduced voltage due to the introduction of a voltage measure having a hysteresis-free Josephson array chip; provided stability of reproduced voltage; automated transfer of the unit of voltage to both voltage measures and voltage meters; ensured process of setting the specified voltage in the time domain. With a new composition, the improved GET 13-01 was approved as GET 13-2023 State Primary Voltage Standard. GET 13-2023 uses quantum voltage measures on the basis of various Josephson array chips. The metrological characteristics of GET 13-2023 are studied in the process of comparing quantum measures comprising it (with hysteretic and hysteresis-free Josephson array chips). GET 13-2023 realizes the unit of voltage with the standard deviation of the measurement result not exceeding 1–10−9 V and a residual systematic error of 1 · 10−9 V within the voltage range of 1 · 10−3–1 V and reproduces the unit of voltage with the standard deviation of the measurement result not exceeding 10−9 multiplied by the value of reproduced voltage and a residual systematic error of 10−9 multiplied by the value of reproduced voltage within the voltage range of 1–10 V. The obtained results are relevant for ensuring the uniformity of DC voltage measurements and for performing international key comparisons. [ABSTRACT FROM AUTHOR]

Some electrical parameters of the SIS-type hysteretic underdamped Josephson junction (JJ) can be measured by its current-voltage characteristics (IVCs). Currents and voltages at JJ are commensurate with the intrinsic noise level of measuring instruments. This leads to the need for multiple measurements with subsequent statistical processing. In this paper, the digital algorithms are proposed for the automatic measurement of the JJ parameters by IVC. These algorithms make it possible to implement multiple measurements and check these JJ parameters in an automatic mode with the required accuracy. The complete sufficient statistics are used to minimize the root-mean-square error of parameter measurement. A sequence of current pulses with slow rising and falling edges is used to drive JJ, and synchronous current and voltage readings at JJ are used to realize measurement algorithms. The algorithm performance is estimated through computer simulations. The significant advantage of the proposed algorithms is the independence from current source noise and intrinsic noise of current and voltage meters, as well as the simple implementation in automatic digital measuring systems. The proposed algorithms can be used to control JJ parameters during mass production of superconducting integrated circuits, which will improve the production efficiency and product quality.

The escape rate of S→R switching (from superconducting S state to unstable resistive R state) in an ac SQUID with Josephson junction based on single- and multi-band superconductors is investigated by taking the frustration effects in a multi-band superconducting state into account. Using the effective critical current approach, it is shown that the escape rate in thermal activation regime can manifest qualitative features caused by the frustration effects in two- and three-band superconductors. [ABSTRACT FROM AUTHOR]

In this paper, we conducted the calculation of the critical current of DC SQUID based on the Josephson junction on a multi-band superconductor with frustration effect. It is shown that the critical current of DC SQUID on the frustrated multi-band superconductor with a small geometrical inductance of the loop is determined by the supercurrent amplitude in different channels and by the external magnetic field. In the case of a DC SQUID with high inductance, frustration effects can be ignored. [ABSTRACT FROM AUTHOR]

The effects of graphene addition on the phase formation and superconducting properties of (Bi1.6Pb0.4)Sr2Ca2Cu3O10 (Bi-2223) ceramics synthesized using the co-precipitation method were systematically investigated. Series samples of Bi-2223 were added with different weight percentages (x = 0.0, 0.3, 0.5 and 1.0 wt.%) of graphene nanoparticles. The samples' phase formations and crystal structures were characterized via X-ray diffraction (XRD), while the superconducting critical temperatures, Tc, were investigated using alternating current susceptibility (ACS). The XRD showed that a high-Tc phase, Bi-2223, and a small low-Tc phase, Bi-2212, dominated the samples. The volume fraction of the Bi-2223 phase increased for the sample with x = 0.3 wt.% and 0.5 wt.% of graphene and slightly reduced at x = 1.0 wt.%. The ACS showed that the onset critical temperature, Tc-onset, phase lock-in temperature, Tcj, and coupling peak temperature, TP, decreased when graphene was added to the samples. The susceptibility–temperature (χ′-T) and (χ″-T) curves of each sample, where χ′ and χ″ are the real and imaginary parts of the susceptibility, respectively, were obtained. The critical temperature of the pure sample was also measured. [ABSTRACT FROM AUTHOR]

Future collider accelerators will rely on high-temperature superconductors reaching high field up to 20 T and above. Among the existing high-temperature superconducting materials, the Rare-earth Barium Copper Oxide (ReBCO) tapes arranged according to the Conductor-on-Round-Core (CORC®) concept could be a viable solution to wound accelerator magnets such as Cosine Canted Theta (CCT) magnets. Dedicated experimental characterization of the critical current to quantify the degradation due to the winding process and operating conditions should proceed in parallel to the development of numerical models capable to reproduce and, in perspective, predict the cable performance. This paper presents the development of a new multi-physics model for a CORC® wound with ReBCO tapes together with its validation. The $T-A$ formulation has been used leveraging the high aspect ratio of tapes, suitably coupled with a conduction thermal model which for the first time properly accounts for the cable convective cooling. The model developed in this work can accurately simulate the thermal, electric and magnetic behaviors and the current sharing among tapes by using a set of self-consistent boundary conditions adopted for the first time in this kind of simulations. The model is verified and benchmarked against other well-established formulations on a set of test cases. The comparison of the computed $V-I$ characteristic of the straight cable to available experimental data shows that the main physics features of the cable are well captured by the model, including performance degradation due to cable tapering at the terminations.

This paper discusses issues of using superconductors in modern accelerators, such as free-electron laser type, in a radioactive environment. It shows how irradiation damages the subtle structure of superconducting materials, especially 1D and 2D high-temperature superconductors, in which it leads to the creation of nano-sized columnar-type defects. The influence of the radiation-induced structural defects on the current-carrying properties of the superconducting materials is investigated according to a developed energetic description of the capturing process on these defects, acting as pinning centres of magnetic pancake vortices. Various initial positions of the captured vortices are analysed. The influence of the irradiationinduced defects on the current-voltage characteristics is investigated, and the maximum current density is determined as a function of irradiation intensity and such physical parameters as magnetic field, temperature, and nano-defect size. This analysis is therefore of scientific interest and should also be helpful in determining the proper operating conditions of solenoids and other superconducting elements in free-electron laser facilities. [ABSTRACT FROM AUTHOR]

Low activation isotopic boron (11B) based magnesium diboride (Mg11B2) superconductors doped with biomass-derived activated carbon were synthesized using 11B and magnesium powder via solid-state reaction. The effect of carbon doping on the lattice structure and superconducting properties of Mg11B2 bulks were evaluated using X-ray powder diffraction, high resolution transmission electron microscopy, scanning electron microscopy and magnetization measurements. Precise refinement of structural parameters indicates successful substitution of carbon in Mg11B2 bulks. The critical current density (Jc) of carbon doped Mg11B2 synthesized at 650 °C was enhanced more than two times compared with the pure Mg11B2 bulk. Similar improvement was observed for the Mg11B2 bulks heat-treated at 800 °C. This enhancement is due to successful substitution of biomass-derived carbon with high surface area into Mg11B2 lattice. The flux pinning mechanism of pure and doped Mg11B2 bulks were investigated using the Dew-Hughes model. This study provides information regarding enhancement of the Jc of low activation Mg11B2 superconductors suitable for next-generation fusion magnets.

Josephson junctions (JJs) with Josephson energy E J ≲ 1 K are widely employed as non-linear elements in superconducting circuits for quantum computing operating at milli-Kelvin temperatures. In the qubits with small charging energy E C ( E J / E C ≫ 1 ), such as the transmon, the incoherent phase slips (IPS) might become the dominant source of dissipation with decreasing E J . In this work, a systematic study of the IPS in low- E J JJs at milli-Kelvin temperatures is reported. Strong suppression of the critical (switching) current and a very rapid growth of the zero-bias resistance due to the IPS are observed with decreasing E J below 1 K. With further improvement of coherence of superconducting qubits, the observed IPS-induced dissipation might limit the performance of qubits based on low- E J junctions. These results point the way to future improvements of such qubits. [ABSTRACT FROM AUTHOR]

Fluctuations in the critical current along the length of high-temperature superconducting (HTS) tapes manufactured in the form of coated conductors is a common manufacturing phenomenon. These fluctuations originate in the generation of weak points through the length of HTS tapes that may cause quenching later. By means of the propagation of quenches in HTS tapes, the reliability, stability, and the performance of the device and the system that contain HTS tapes could be seriously degraded. In this study, an artificial intelligence technique based on artificial neural networks (ANN) was proposed to estimate the probability of quenches in HTS tapes caused by weak points. For this purpose, six different HTS tapes were considered with different widths, total thicknesses, and thicknesses of sub-layers. Then, for each one of these tapes, different operating conditions were considered, where the operating temperature changed from 40 K to 80 K, in 1 K steps. Under each operating temperature, different operating currents were considered from 50% to 100% of tape critical current. All of these resulted in more than 5000 different data points. Then, for each of these data points, analytical modelling was performed to provide initial inputs and outputs for the ANN model. It should be noted that the performed simulations were conducted based on an analytical method that was experimentally validated in the literature. After that, a sensitivity analysis was conducted to select the hyperparameters and structure of the ANN-based model. The last step was to take advantage of the trained model, as a function in the MATLAB software package to estimate the probability of quenches in different case studies. The significant feature of the proposed model is the capability for estimating the probability of quenches under different operating temperatures and currents for different types of HTS tapes. [ABSTRACT FROM AUTHOR]

A misalignment of anisotropic crystallites causes small values of anisotropy and decreases the critical current density of textured polycrystalline superconductors. To relate the crystallite misalignment and out-plane anisotropy, the magnetic properties of the textured Bi2223 polycrystalline superconductor were investigated. A distribution of orientation angles of crystallites was determined using different data: scanning electron microscopy images and hysteresis magnetization loops when an external magnetic field was applied at different angles with respect to the texturing plane of the sample. It was demonstrated that the standard deviation of the distribution and the magnetic disorder angle of crystallites in textured samples can be determined from the magnetization data in perpendicular directions. These data may be either the irreversible magnetization measured for two different orientations of the sample or the simultaneously measured magnetization projections parallel and perpendicular to the magnetic field. [ABSTRACT FROM AUTHOR]

• We investigated the microscopic morphology of the prepared multi-filamentary tapes. • We compare the short sample current-carrying performance of non-striated tapes with that of 2, 3, 6, 10-filament tapes. • The current-carrying characteristics of multi-filamentary tapes wound on metal cores of different sizes were compared for the first time. The second generation of high temperature superconductivity (HTS) is one of the candidate materials for future superconducting cables (such as CORC), CICC conductors and high field magnets due to its high current carrying performance and excellent mechanical strength. Currently, it has been demonstrated that the utilization of REBCO multi-filamentary tapes in the fabrication of CORC cables can further reduce AC losses. This study involved the preparation of various types of REBCO multi-filamentary tapes through reel-to-reel ultraviolet picosecond laser cutting technology, as well as the manual winding of multiple single-layer CORC cable samples. This work focused on the impact of core diameter on the current-carrying performance of REBCO multi-filamentary tapes under self-field conditions at 77 K. The results indicate that the critical current (I C) of REBCO multi-filamentary tapes decreases as the core diameter decreases. Furthermore, the decrease in I C becomes more significant with an increasing number of cores. When the cable core diameter is 4.6 mm, the critical current of the 3-filament tape is 180.49 A with an n -value of 24.84, which is only a 3.1 % recession compared to the critical current of the commercialized tape. The conclusion of this paper will provide a certain data reference for the subsequent selection of CORC cable core size prepared by REBCO multi-filamentary tapes. [ABSTRACT FROM AUTHOR]

To meet the application requirements of high magnetic field and high current in future fusion magnet systems, a compact twisted stacked tape cable with high current density is proposed. Three stepped grooves are evenly distributed around a circular former, and a 20+10 superconducting tapes configuration is arranged in each single groove. The performance of the cable under self-field is investigated through simulation modeling and experiment on a 1-meter sample. Firstly, the electromagnetic and mechanical properties of cables are studied through simulation. According to the simulation results, the prospective critical current reaches 5090 A under self-field at 77 K while the maximum von Mises stress and volumetric strain obtained from the simulation during the current-carrying process are within acceptable ranges. A sample with a twist pitch of 300 mm is fabricated, consisting of 18 superconducting tapes and 72 copper tapes. The measured and simulated results of the critical current of this sample are 1900 A and 1970 A respectively, with a deviation of 3.5 percent. The feasibility of the proposed cable has been preliminarily demonstrated through these experimental and simulation results. Subsequent research will be conducted on the optimization of cable parameters, including geometric dimensions and tape capacity, to achieve better performance. • A stepped, twisted stacked-tape cable layout with high current density is proposed. • Electromagnetic and mechanical simulations are conducted to demonstrate its feasibility. • A cable sample is fabricated and the experimental result validates simulations. [ABSTRACT FROM AUTHOR]

The stochastic neuron has great importance in neural networks and is one of the most important subjects in machine learning algorithms. Hardware implementation of neural networks has always been of interest to researchers and can significantly increase the performance and applications of neural networks. Hence hardware implementation of the stochastic neuron is also important. In this paper, utilizing stochastic behavior of MTJs in subcritical current regime a hardware model for stochastic neurons is proposed. Using HSpice tool, the proposed model was simulated and simulation results show that the proposed model functionality is similar to the mathematical description of the stochastic neuron and the error of this model is always less than 4.8% compared to the mathematical description of the stochastic neuron. Also using corner simulation, it was shown that this model performs properly even in the presence of process variation and its error rate is less than 15.46% and 17.43% compared to the mathematical model and ideal simulation, respectively.

High-temperature superconducting (HTS) composite tapes of the second generation are promising materials for the development of sources of high magnetic fields, including for accelerators and tokamaks, where superconductors can be exposed to radiation for a long time. Such an impact causes defects in superconductors, the presence of which can both decrease the current-carrying capacity of the HTS due to the degradation of the superconducting layer and increase it due to the formation of additional pinning centers for magnetic field vortices. In this work, we simulated the processes of defect formation in a single tape and a stack of 10 HTS tapes upon irradiation with protons with an energy of E = 6–20 MeV. The results were verified experimentally by irradiating a stack of 10 HTS tapes with protons with an energy of E = 6 MeV and a fluence of up to 5 × 1015 cm–2. For experimental studies, an industrial SuperOx HTS tape with a double-sided copper coating 20 µm thick was used. Upon irradiation with 6-MeV protons, the radiation does not pass through a single tape, which is confirmed by the fact that the critical current of the superconductor drops only in the first layer of a stack of HTS tapes, and the value of the critical temperature for this layer differs by less than 0.5% compared to the nonirradiated tape. We concluded that in real systems, HTS tapes can be easily protected from radiation with an energy of E = 6 MeV, but as the energy increases, a more complex protection design is required. [ABSTRACT FROM AUTHOR]