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Common terminal voltage measurement can be hardly applied to detect quenches in long high temperature superconducting (HTS) conductor on round core (CORC) cable because not only the HTS normal zone propagation velocity (NZPV) is low but also immobilizing a large number of voltage leads is inconvenient. Distributed optical fiber sensing (DOFS) technology is a promising method for quench detection of long superconductors. To sense the thermal changes of CORC cables during quenches more directly and prevent optical fibers from damages by external stress, a fiber-superconducting composite (FSC) CORC cable was fabricated. For this cable, three optical fibers were placed in three grooves of the copper core respectively, then three HTS tapes were spirally wound on the copper core in sequence. Comparing to a traditional CORC cable, obviously, the FSC CORC cable structure has been changed. To promote FSC CORC cable engineering applications, it is necessary to study the fundamental performance of the cable. In this paper, we investigated the electromagnetic, thermal and mechanical properties of the FSC CORC cable by comparing those with a common one. The results demonstrated that, compared to the common one, the magnetic distribution of the FSC CORC cable hardly changed, but the current distribution of the copper core in the FSC CORC cable slightly changed which led to decreases of transport AC loss, in addition, the thermal characteristics of the FSC CORC cable was slightly changed and the bending tolerance ability of the cables reduced within a bending diameter range of 15 cm. What's more, the embedded optical fibers combined with DOFS system are successfully used to detect the temperature changes of the cable surface. Finally, to study the quench behaviors of the cable, we built a quench detection platform, which equips with a voltage acquisition system, a thermocouple temperature acquisition system and the DOFS system. By using the platform to detect the quenches of the FSC CORC cable, minimum quench energy of the cable and NZPV of the tape and cable at different currents was tested. [ABSTRACT FROM AUTHOR]

A novel multistep film growth method is developed to prepare high‐performance BaHfO3(BHO)‐nanocrystal‐added YBa2Cu3O7−δ(YBCO) tapes. Upscaled YBCO tapes with high concentrations of 6.2 nm BHO nanocrystals exhibit better self‐field and in‐field performances when grown by the multistep method compared to those grown by the traditional method. The in‐field critical current (Ic) of the 1.6‐µm‐thick BHO‐added YBCO film at 30 K@3 T is enhanced by 50% in the optimal traditional cases, whereas it is further increased to 180% using a multistep growth strategy. The high‐performance YBCO layer is thickened to 2.3 µm using the multistep method, and the improvement of in‐field Ic at 30 K@3 T is enhanced by 215% to 360 A per 4 mm‐width compared to the pristine. The BHO size evolution during the high‐temperature process reveals that the added nanocrystals coarsened by 4 to 10.5 nm in both the traditional and multistep cases, thereby indicating that the further improvement in performance is attributed to the better film quality grown by the multistep method. This technique can be applied directly to the preparation of scaled REBCO tapes with a length of hundreds of meters. [ABSTRACT FROM AUTHOR]

It took longer time than initially expected for development of cuprate superconducting materials for practical applications. However, there are about 20 companies that manufacture and supply long conductors and bulk materials at present. Although various large‐scale projects have supported the process of material development, material and equipment developments have been progressing under the leadership of manufacturers in recent years. In this paper, current status of development of high‐temperature superconducting materials, including MgB2, which is classified as a high temperature superconductor, and their applications are summarized, along with the history, basic physical features and recent topics. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

The effect of the location with different concentrations of La atoms (x = 0; 0.02; 0.028; 0.11) on some superconducting and electrotransport characteristics of Y1-xLaxBa2Cu3Oy polycrystalline compounds was studied by recording the temperature dependence ρ(T) curves of resistivity in the case of direct current in the range of temperatures (77K - 300K). The temperatures at the onset (Tc on) and offset (Tc 0) of the transition, as well as the width of the transition - ΔTc = Tc on-Tc 0, were considered as the superconducting characteristics. The absolute values of ρ(300K) and ρ(100K) and their ratio a = ρ(300K)/ρ(100K) were considered as electric transport characteristics, as well as the temperature coefficient of resistivity dρ/dT, which was determined by ρ(T) in the range of linear dependence with the slope of the curve. From the comparison of these characteristics, it was concluded that there is a certain correlation between the superconducting and electrotransport properties of the studied compounds depending on the concentration x of the partial location of Y atoms with La. [ABSTRACT FROM AUTHOR]

ReBCO superconducting cables have the potential to enable compact thermonuclear fusion reactors that operate at magnetic fields exceeding 20 T and allow operation at temperatures far exceeding the boiling point of liquid helium, potentially allowing for demountable magnets. Normal zone detection remains a challenge, and while novel quench detection techniques are an active area of research, few are non-invasive, provide real-time quench detection, and have been demonstrated with current ramp rates relevant for fusion reactors. To address this problem, a CORC® cable termination is developed with integrated Hall sensors to monitor current redistribution as a proxy for quench detection. The methodology exploits the current sharing and layered topology in CORC® cables, and allows quench detection using a localized sensor instead of co-wound voltage wires or optical fibers. Experiments are presented where current redistribution is measured from induced quenches, and in a 0.2 meter CORC® sample it is found that the Hall sensors detect normal zone transitions with a similar magnitude and temporal resolution as voltage measurements. To emulate the conditions of dynamic poloidal and central solenoidal fields, experiments are repeated with ramp rates up to 10 kA s-1 that demonstrate the potential to detect normal zone development over a range of experimental parameters.

AbstractFast quench detection is a key requirement for the successful implementation of superconducting magnet technology. In high temperature superconductor (HTS) magnets, this issue is especially challenging due to the low quench propagation velocity, and presently represents one of the main factors limiting their application. A new detection technique based on stray-capacitance monitoring is proposed. The capacitance between electrically-insulated magnet elements, such as magnet structure and end parts, is utilized as an indication of local heat deposition in the conductor. In fact, the relative permittivity of helium drops when it changes from the liquid to the gaseous phase. Thus, when heating occurs, part of the helium impregnating the insulation layers boils off, and the monitored stray-capacitance decreases. The proposed technique is successfully demonstrated on three small-scale Bi-2212 magnets manufactured at the Lawrence Berkeley National Laboratory. Results from the detection of thermal runaways and spot-heater induced quenches are reported and discussed. Advantages and limitations of the stray-capacitance method with respect to conventional quench detection methods are assessed.Export citation and abstract BibTeX RISCC BYAs the Version of Record of this article is going to be/has been published on a gold open access basis under a CC BY 3.0 licence, this Accepted Manuscript is available for reuse under a CC BY 3.0 licence immediately.Although reasonable endeavours have been taken to obtain all necessary permissions from third parties to include their copyrighted content within this article, their full citation and copyright line may not be present in this Accepted Manuscript version. Before using any content from this article, please refer to the Version of Record on IOPscience once published for full citation and copyright details, as permission may be required. All third party content is fully copyright protected, and is not published on a gold open access basis under a CC BY licence, unless that is specifically stated in the figure caption in the Version of Record.

Fast quench detection is a key requirement for the successful implementation of superconducting magnet technology. In high temperature superconductor magnets, this issue is especially challenging due to the low quench propagation velocity, and presently represents one of the main factors limiting their application. A new detection technique based on stray-capacitance monitoring is proposed. The capacitance between electrically-insulated magnet elements, such as magnet structure and end parts, is utilized as an indication of local heat deposition in the conductor. In fact, the relative permittivity of helium drops when it changes from the liquid to the gaseous phase. Thus, when heating occurs, part of the helium impregnating the insulation layers boils off, and the monitored stray-capacitance decreases. The proposed technique is successfully demonstrated on three small-scale Bi-2212 magnets manufactured at the Lawrence Berkeley National Laboratory. Results from the detection of thermal runaways and spot-heater induced quenches are reported and discussed. Advantages and limitations of the stray-capacitance method with respect to conventional quench detection methods are assessed.

High temperature superconductors (HTSs) expand the design space of stellarator power-plants (PPs) toward high magnetic fields B , enabling compact major radii R . The present paper scans the space of B , R and other design parameters, finding solutions that are promising from a physics and engineering standpoint, while minimizing the capital cost of the PP and the levelized cost of fusion electricity. Similarly, it identifies minimum-cost design points for next-step burning plasma stellarator experiments of fusion gain $1 \lt Q \lt 10$ . The study assumes advanced stellarator configurations of reduced aspect ratio, heated by neutral beam injection. Plasma-facing, flowing liquid metal (LM) walls protect it from high heat and neutron fluxes. The study relies on analytical first-principle calculations, and established zero-dimensional (0D) empirical scaling laws. Power flows are illustrated by Sankey diagrams. Plasma operating contours are used to determine the reactor’s start-up path. Sensitivity analyses are conducted to identify the most critical reactor parameters within physics, engineering and costing, quantifying their influence on the economics of the PPs. Such 0D study suggests that the assumed next generation HTS, flowing LM walls, and advances in compact plasma configurations could lead to an ignited stellarator PP of aspect ratio $A \sim 4$ , $R \unicode{x2A7D} 4$ m, B > 9 T, and normalized plasma pressure $\beta \sim 5\%$ which would minimize both the cost of electricity and capital cost while achieving a net electric power of about 1 GW.

The aim of the presented study is to optimize the different classes of high-temperature superconducting (HTS) DC cables for improving their performances in a cryo-electric aircraft considering their weight, peak temperature during faults, and the ratio of current passing through each tape to the critical current of HTS tapes. These terms were interpreted into three objective functions, and a multi-objective optimization algorithm known as non-dominated sorting genetic algorithm II was used to find the optimal solution clusters. The cable optimization was conducted for different former materials by changing the former thickness and radius. Results showed that the DC HTS cables with aluminum former have the lowest weight while cables with copper formers have the best thermal performance against faults. [ABSTRACT FROM AUTHOR]

In this paper, the effect of non-uniform critical current density on bulk superconductors is studied, the case of a long cylindrical superconductor with transport current is chose to discussed. The critical current density is distributed non-uniformly along the radius of the cylinder. Based on the Bean critical state model, the distributions of trapped magnetic flux and shielding current in the cylinder are investigated. Combined with the plane strain approach, the analytical expressions of magnetic flux pinning force and stress are obtained. The magnetostriction of the cylinder is also discussed. Results show that the non-uniform critical current density changes the distribution law of the shielding current and trapped magnetic flux in the cylinder. The increase of non-uniform parameters n leads to an obvious increase in the flux pinning force. Thus, a larger extreme value of the pinning stress is obtained, a bigger structure deformation is produced inside the superconducting cylinder. All those conclusions will provide a helpful guide for engineering application. [ABSTRACT FROM AUTHOR]

The superconducting and electrotransport properties were studied in Y0.89R0.11Ba2Cu3O7-d polycrystals, with the same concentration of rare earth metal elements (R = La, Pr) but with different valence and magnetic moments, by recording the temperature dependence ρ(T) curves of the resistivity in the temperature range (77-300) K. It was considered the influence of La and Pr on the width of the superconducting transition of the samples (ΔC), its critical temperature (determined by the onset of transition - TC on and the offset - Tc 0), the absolute values of the resistivity of the fluctuation and normal regions ρ(300 K) and ρ(100 K)], as well as on their ratio [a = ρ(300 K)/ρ(100 K)]. It has been revealed that there is a certain correlation between the aforementioned characteristics. It is emphasized that Pr is more critical than La in terms of its effect on characteristics. It is believed that the different behavior of the correlations observed between these characteristics for La and Pr is largely due to the differences in their ionic radii, displayed valence, as well as their intrinsic magnetic moments. It is shown that these differences in the case of La and Pr are manifested in the form of the phase separation phenomenon and the "Pranomaly", respectively. [ABSTRACT FROM AUTHOR]

Brain imaging MRI comprises a significant proportion of MRI scans, but the requirement for including the shoulders in the magnet bore means there is not a significant size reduction in the magnet compared to whole-body magnets. Here we present a new design approach for brain imaging MRI magnets targeting ±20 kHz B 0 variation over the imaging volume rather than the more usual ±200 Hz making use of novel high-bandwidth MRI pulse sequences and distortion correction. Using this design approach, we designed and manufactured a 1.5 T class ReBCO cryogen-free magnet. The magnet is dome-like in form, completely excludes the shoulders and is <400 mm long. The magnet was wound using no-insulation style coils with a conductive epoxy encapsulant where the contact resistance of the coils was controlled so the emergency shut-down time of the magnet was less than 30 s. Despite acceptable coil testing results ahead of manufacture, during testing of the magnet, several of the epoxy coils showed signs of damage limiting stable performance to <55 A compared to the designed 160 A. These coils were replaced with insulated paraffin encapsulated coils. Subsequently the magnet was re-ramped and was stable at 81 A, generating 0.71 T as several other coils had sustained damage not visible in the first magnet iteration. The magnet has been passive shimmed to ±20 kHz B 0 variation over the imaging volume and integrated into an MRI scanner. The stability of the magnet has been evaluated and found to be acceptable for MRI., (© 2024 The Author(s). Published by IOP Publishing Ltd.)

The development of superconducting technology has seen continuously increasing interest, especially in the area of clean power systems and electrification of transport with low CO2 emission. Electric machines, as the major producer and consumer of the global electrical energy, have played a critical role in achieving zero carbon emission. The superior current carrying capacity of superconductors with zero DC loss opens the way to the next-generation electric machines characterized by much higher efficiency and power density compared to conventional machines. The persistent current mode is the optimal working condition for a superconducting magnet, and thus the energization of superconducting field windings has become a crucial challenge to be tackled, to which high temperature superconducting (HTS) flux pumps have been proposed as a promising solution. An HTS flux pump enables current injection into a closed superconducting coil wirelessly and provides continuous compensation to offset current decay, avoiding excessive cryogenic losses and sophisticated power electronics facilities. Despite many publications regarding the design and analyses of various types of HTS flux pumps, the practical application of HTS flux pumps in a high-performance superconducting machine has been rarely reported. Therefore, it is of significance to specify the main challenges for building and implementing a reliable HTS flux pump. In addition, the physical mechanisms of distinct HTS flux pumps have caused some confusion, which should be clarified. Above all, a systematic review of the recent development and progress of HTS flux pumps remains lacking. Given the above-mentioned issues, this paper summarized the most up-to-date advances of this emerging technology, clarified the working mechanisms and commonly adopted modeling approaches, presented objective analyses of the applicability of various HTS flux pumps, specified the primary challenges for implementing HTS flux pumps, and proposed useful suggestions to improve this wireless excitation technology. The overall aim of this work is to bring a deep insight into the understanding of HTS flux pumps and provide comprehensive guidance for their future research and applications. [ABSTRACT FROM AUTHOR]

Pb 0.92 La 0.08 (Zr 0.52 Ti 0.48)O 3 /YBa 2 Cu 3 O 7-x (PLZT/YBCO) heterostructures with high c-axis epitaxial properties were prepared by PLD method. Hysteresis loops, photovoltaic effects, and current transfer properties of this structure were investigated. Hysteresis loop test results showed that residual polarization intensity of PLZT gradually decreases with decreasing temperature but coercivity field increases. I–V curve of PLZT/YBCO heterostructure in dark state was tested and found to have significant rectification characteristics, indicating the existence of potential barrier at interface of the heterostructure. UV illumination experiments showed that PLZT/YBCO heterostructure has clear photovoltaic effect, with both photovoltage and photocurrent decreasing as the temperature is decreased. Moreover, photovoltage and photocurrent display jump phenomenon when superconducting transition of YBCO occurs. Further analysis of jump phenomenon revealed that the difference of photovoltage with temperature before and after superconducting transition of YBCO is consistent with superconducting energy bandgap of YBCO. The opening of superconducting energy gap of YBCO lowers PLZT/YBCO interfacial potential barrier and promotes migration of photogenerated carriers, consequently increasing photovoltage and photocurrent. This work describes novel method to measure superconducting energy gap. [ABSTRACT FROM AUTHOR]

AC losses in a high temperature superconducting (HTS) coil are experimentally evaluated. Double-pancake (DP) coils with turn-to-turn electrical insulations are wound using bundle conductors formed with two pieces of rare-earth-based coated conductors located face-to-face without insulation to improve thermal stability. Five DP coils are stacked and subsequently four copper plates are soldered between the adjacent DP coils to form a small-size HTS coil for AC loss measurements. The fabricated HTS coil is immersed in liquid nitrogen. Before measuring the AC losses, the contact resistances between the DP coils are observed in DC operations of the HTS coil at first. After that, the total losses including the Joule losses in the joints between the DP coils are measured by integrating the products of almost resistive components extracted from the terminal voltages in the HTS coil and applied transport currents observed using a pickup coil over a cycle under AC operations. Net AC losses in the two-ply bundle conductor windings are obtained by subtracting the Joule losses from the measured ones. In order to understand the mechanism of AC losses in the two-ply bundle conductor windings, the influences of current amplitudes and frequencies are investigated experimentally and theoretically. [ABSTRACT FROM AUTHOR]

Energy conservation and emission reduction is a critical task for China's aluminum industry. During the last decade, the high temperature superconducting (HTS) technology has been successfully demonstrated to have great potential for energy conservation in this field. Different from the present AC induction heater, this HTS direct current (DC) induction heater is expected to significantly improve the energy efficiency of preheating aluminium billets before extrusion process. This paper thoroughly presents the development of the world's first commercial megawatt HTS DC inducting heater based on 2nd generation HTS tapes. Firstly, the commercial design of this 1MW HTS DC induction heater including design specifications, energy efficiency and commercial potential are analyzed carefully. Subsequently, the manufacture and operation of three core parts including HTS magnet with extra-large diameter, iron core structure and electrical driving system, are introduced. A low cost and practical driving system consisting of motors and gearboxes is developed to solve the problem of peak electromagnetic torque at low rotation. Meanwhile, the heating quality of aluminium billets (i.e., temperature distribution along the radial and axial direction) can be accurately controlled by an adjustable air gap structure. Finally, the present technique challenges and corresponding solutions of this commercial HTS DC induction heaters are summarized and proposed. Compared with an energy efficiency of 45-60% in the MW-class conventional heater, the energy efficiency of this HTS DC induction heater can achieve up to 80.6% based on test results. This work can also provide guidance for the design and optimization of HTS DC induction heaters.

A novel dualband high-temperature superconducting (HTS) bandpass filter is proposed with group delay equalization for 5G emergency communication receivers with N41 and N79 bands in this paper. The dual-folded stub-loaded stepped impedance resonator (DSLSIR) is applied to realize dualband performance. The proposed DSLSIR has miniaturized circuit size and more design freedom to independently adjust the two designed center frequencies, comparing with other reported DSLSIRs. Two cross-coupling transmission lines are added at the top and bottom parts of the cascaded sixth-order filter with DSLSIRs to flatten the group delay of the passband at both bands. A dualband bandpass HTS filter etched on the YBCO superconducting material is fabricated to verify the proposed design method. The measurement is actualized at the temperature of 77 K to make YBCO microstrip lines perform superconducting features. The results show that the first center frequency is 2.595 GHz with 6.2% bandwidth for N41 band and 0.3 dB insertion loss while the second center frequency is 4.85 GHz with 2% bandwidth for N79 band and 0.4 dB insertion loss. Meanwhile, the group delays at the N41 and N79 bands keep 2 ns fluctuations in the 60% passband. The agreement between the measured and simulated results indicates that the proposed dualband bandpass HTS filter with low insertion loss, sharp roll-off skirt and flat group delay is a promising candidate for emergency communication receiver.

Offshore wind turbines are the key enabling technology to increase the green energy penetration in the electricity market. Increasing the power generation per tower and reducing the levelized cost of energy are the two significant problems faced by wind turbine manufacturers. Traditional turbine manufacturers use rare-earth permanent magnets (PMs) to increase the air-gap flux density and maximize the machine outer diameter (OD) to increase the torque output. Since the air-gap flux density achievable with available PM is limited, increasing the power output of a traditional generator invariably leads to a significant increase in the volume and mass on top of the turbine tower and associated manufacturing, transportation, and installation costs. Superconducting (SC) wind turbine generators offer 5 to 10 times the air-gap flux density of a PM generator, and a corresponding increase in specific power and power density. Previous MW scale SC wind turbines designs used heavy back iron in the design, iron saturation limits the achievable air-gap flux density in the designs and resulted in bulky generators and moderate efficiency. In this article, a hybrid design approach is proposed to reach an ultrahigh field (5 to 10 times of PM air-gap flux density) and high efficiency (>98%) SC wind turbine for offshore wind turbine. An additional stray field limitation is introduced for safety concerns and shielding techniques are explored. Electromagnetic, mechanical, and cooling designs are provided to support the feasibility of proposed SC wind turbines. A nacelle integration inside a commercially available 6 MW wind turbine is shown to demonstrate the size comparison of the proposed generator. [ABSTRACT FROM AUTHOR]

The features of the amplitude behavior of the electromagnetic waves (the profile of a standing wave) reflected by antenna arrays have been studied. These arrays are Golomb rulers of different orders made of copper and HTSC structures. The dependences of the amplitude on the array’s arrangement with respect to the excitation source and the receiving device, as well as on the temperature. An analysis of obtained results revealed no dips in the standing wave amplitude profile for the 3rd and 4th order Golomb rulers. It was shown that for the Golomb rulers based on HTSC structures, an observed increase in the amplitude of the received signal on their cooling was associated with the transition to the superconducting state.

Bi2Sr2Ca2Cu3O10+δ (Bi-2223) precursors for the fabrication of high temperature superconducting tapes were prepared by spray pyrolysis technique followed by a calcination process. The influences of precursor powder phase composition on the phase evolution dynamics and final current capacity of Bi-2223 superconducting tapes were systematically studied. It was interesting to notice that slight increase of Cu content in chemical composition could cause obvious variations of both the phase composition and the morphology of CuO particles in precursors. Therefore, the Bi-2223 phase formation process during the sintering process of tapes could be affected, and the current capacity changed accordingly. On the other hand, during the calcination temperature optimization process, the Bi-2223 phase content in precursors changed accordingly, thus the Bi-2223 phase formation dynamics were also studied. More Bi-2223 nuclei were formed due to the pre-existed Bi-2223 grains, which worked as inhomogeneous nuclei centers. Thus, although the final Bi-2223 phase contents were similar in all the tapes, the particle size and texture structure of Bi-2223 varied greatly, which caused a dramatic decrease of critical current in Bi-2223 tapes with the formation of Bi-2223 in precursors. Therefore, it could be concluded that both the morphology of CuO particles and the Bi-2223 phase content in precursors were the factors controlling the phase evolution dynamics during Bi-2223 tape sintering process. [ABSTRACT FROM AUTHOR]

Tokamak device requires a very high current power supply from the local power distribution sources to the targeted magnets such as toroidal field (TF) coils and poloidal field (PF) coils. This paper presents a preliminary design of a 30-m/1-kV/10-kA low voltage direct current (LVDC) superconducting cable for the potential in Tokamak applications. The outer diameter of the DC cable is 122.41 mm, and the pressure drop of liquid nitrogen (LN2) in the inner and outer channels is about 6.59 kPa. The flow velocity of inner and outer LN2 channels are 0.5 m/s and 0.25 m/s, respectively. The temperature rise of the entire cable was designed to be less than 5 K, which enhances the electricity supply safety and reliability. These preliminary design lays some technical bases for achieving high current and low loss power transmission. The designing results show that the LVDC superconducting cable has significant potentials for Tokamak applications compared with conventional copper cables. [ABSTRACT FROM AUTHOR]

In this paper, investigations were carried out on the effects of simultaneous partial substitution of Tl at the Hg site on the physical properties of an Hg1- xTlxBa2Ca2Cu3O8+δ cuprate superconductor with x= 0, 0.1, 0.2, 0.3 and 0.4. Two steps of the solid state reaction method were used to prepare samples in capsule. The results showed that the optimum sintering temperature was equal to 850 ᵒC and the sintering time was equal to 20 h for the prepared samples. The best conditions for constitution and stabilization of the high Tc phase-1223 were obtained by investigating the effects of Tl substitution on Hg site and oxygen content (δ) on the superconducting properties. Structural investigation revealed that all the samples have a tetragonal structure with two phases, namely an Hg-1223 high Tc phase as a main phase and an Hg-1212 low Tc phase. Besides, some impurity phases like CuO and CaHgO2 were found. The increase of Tl content in Hg1-xTlxBa2Ca2Cu3O8+δ compound from 0 to 0.4 caused a change in the lattice parameter, density of the unit cell (ρm), and c/a values. HgBa2Ca2Cu3O8+δ compound exhibited a critical transition temperature that is equal to 115 K. On the other side, the results showed that the highest Tc was 119 K for Hg0.8Tl0.2 Ba2Ca2Cu3O8+δ. The oxygen content (δ= 0.46) was expected to be the optimum hole doping for Hg0.8Tl0.2 Ba2Ca2Cu3O8+δ compound, which means in our opinion that δ plays a remarkable role in the assessment of Tc. [ABSTRACT FROM AUTHOR]

The aim of the presented study is to optimize the different classes of high-temperature superconducting (HTS) DC cables for improving their performances in a cryo-electric aircraft considering their weight, peak temperature during faults, and the ratio of current passing through each tape to the critical current of HTS tapes. These terms were interpreted into three objective functions, and a multi-objective optimization algorithm known as non-dominated sorting genetic algorithm II was used to find the optimal solution clusters. The cable optimization was conducted for different former materials by changing the former thickness and radius. Results showed that the DC HTS cables with aluminum former have the lowest weight while cables with copper formers have the best thermal performance against faults.

Radiofrequency (RF) coils fashioned from high-temperature superconductor (HTS) have the potential to increase the sensitivity of the magnetic resonance imaging (MRI) experiment by more than a dozen times compared to conventional copper coils. Progress, however, has been slow due to a series of technological hurdles. In this article, we present the developments that recently led to new perspectives for HTS coil in MRI, and challenges that still need to be solved. First, we recall the motivations for the implementations of HTS coils in MRI by presenting the limits of cooled copper coil technology, such as the anomalous skin effect limiting the decrease of the electric resistance of normal conductors at low temperature. Then, we address the progress made in the development of MRI compatible cryostats. New commercially available low-noise pulsed-tube cryocoolers and new materials removed the need for liquid nitrogen-based systems, allowing the design of cryogen-free and more user-friendly cryostats. Another recent advance was the understanding of how to mitigate the imaging artifacts induced by HTS diamagnetism through field cooling or temperature control of the HTS coil. Furthermore, artifacts can also originate from the RF field coupling between the transmission coil and the HTS reception coil. Here, we present the results of an experiment implementing a decoupling strategy exploiting nonlinearities in the electric response of HTS materials. Finally, we discuss the potential applications of HTS coils in bio-imaging and its prospects for further improvements. These include making the technology more user-friendly, implementing the HTS coils as coil arrays, and proposing solutions for the ongoing issue of decoupling. HTS coil still faces several challenges ahead, but the significant increase in sensitivity it offers lends it the prospect of being ultimately disruptive.

Superconducting cables have been developed around the world and demonstrated its operation in the grid. One of the important subjects is to study what happens in case of fault events, such as a ground fault, short circuit fault and so on, occurred in the superconducting cable. Therefore, we have conducted experimental and numerical simulations at the fault events. For the short circuit accidents, we conducted experimental simulation with a 66 kV 3-core cable in 40 m length to measure LN2 temperatures and pressures in the cable during and after simulated fault current as 16 kA- 8 sec, which has the same heat generation as the worst fault condition in the Japanese 66 kV network as 31.5 kA for 2 sec. The measured values of temperature and pressure are almost good agreement with calculated values. Using the same calculation code, temperatures and pressures at the fault event are estimated in the superconducting cable with 3 km length for practical use. As the results, in case of 31.5 kA in 2 sec, maximum temperature at superconducting conductor is calculated as 112 K and maximum pressure is as 3 MPa under the base pressure of 1 MPa. In that case, no gasification of LN2 is occurred. So, blowout of cryostat would not be occurred. However, it expects that several hours are necessary to turn back original state. For the ground fault, we conducted experimental simulations using samples with protection sheets and short cable samples. The fault current condition is assumed as 1.5 kA for 2 sec, which is the worst case in the Japanese 66 kV network. In such condition, the cable cryostat can be penetrated by the arc energy of the insulation break down and then LN2 would be blown out to make some damage for surrounding apparatus. So, we conducted LN2 leakage test in the manhole to measure LN2 accommodation level and concrete temperatures. Using experimental results and diffusion equation with thermal conductivity of concrete, inner pressure of manhole was simulated. The calculation results show the pressure rising is not so fast that the manhole lid can be blown off. [ABSTRACT FROM AUTHOR]

Maglev technologies have been extensively studied for modern transport systems; however, their main applications are limited to transportation systems with fixed tracks. On-road vehicles could have a broader outlook if combined with maglev technologies, for which electrodynamic wheels (EDWs) have provided a possible solution. Conventional EDWs are designed based on permanent magnets (PMs), which generate limited thrust and lift forces while having a low power density. In order to enhance the feasibility of EDWs in maglev vehicles, a novel design of EDWs based on high-temperature superconducting (HTS) Halbach array magnets (HAMs) has been proposed in this paper. The suggested design is made of the second generation (2G) superconducting coils, which have been modeled with the A-formulation and T-formulation based finite element methods. Simulation results show that the proposed HTS HAM EDW can generate higher thrust and lift forces, improve the magnetic flux density distribution in the airgap, and greatly reduce the weight of the magnets compared with the conventional design. This paper provides a possibility for future on-road maglev vehicles. [ABSTRACT FROM AUTHOR]

The development of superconducting technology has seen continuously increasing interest, especially in the area of clean power systems and electrification of transport with low CO2 emission. Electric machines, as the major producer and consumer of the global electrical energy, have played a critical role in achieving zero carbon emission. The superior current carrying capacity of superconductors with zero DC loss opens the way to the next-generation electric machines characterized by much higher efficiency and power density compared to conventional machines. The persistent current mode is the optimal working condition for a superconducting magnet, and thus the energization of superconducting field windings has become a crucial challenge to be tackled, to which high temperature superconducting (HTS) flux pumps have been proposed as a promising solution. An HTS flux pump enables current injection into a closed superconducting coil wirelessly and provides continuous compensation to offset current decay, avoiding excessive cryogenic losses and sophisticated power electronics facilities. Despite many publications regarding the design and analyses of various types of HTS flux pumps, the practical application of HTS flux pumps in a high-performance superconducting machine has been rarely reported. Therefore, it is of significance to specify the main challenges for building and implementing a reliable HTS flux pump. In addition, the physical mechanisms of distinct HTS flux pumps have caused some confusion, which should be clarified. Above all, a systematic review of the recent development and progress of HTS flux pumps remains lacking. Given the above-mentioned issues, this paper summarized the most up-to-date advances of this emerging technology, clarified the working mechanisms and commonly adopted modeling approaches, presented objective analyses of the applicability of various HTS flux pumps, specified the primary challenges for implementing HTS flux pumps, and proposed useful suggestions to improve this wireless excitation technology. The overall aim of this work is to bring a deep insight into the understanding of HTS flux pumps and provide comprehensive guidance for their future research and applications.

A high-performance superconducting undulator concept, incorporating stacked YBa2Cu3O7δ (YBCO) tapes operating at 4.2 K, is currently under investigation at LBNL as one of many technology options for future FEL applications. The concept is particularly promising for narrow-gap, short period (

Superconducting Bi _1.68 Pb _0.32 Sr _1.75 Ca _1.85 Cu _2.85 O _10+ _y (Bi-2223) powders were prepared by a conventional solid-state reaction using hand grinding and wet ball milling. The effects of the ball milling and sintering times on the phase evolution were examined by x-ray diffraction and magnetic susceptibility measurements. Single-phase Bi-2223 powders with a superconducting transition temperature of about 108 K were optimally prepared by wet ball milling for 20 h and sintering at 867 °C for 80 h. Finding these optimal preparation conditions were crucial for mass producing high-quality single-phase Bi-2223 precursor powders with a much lower cost of energy. Furthermore, we found that ball milling led to thinner grains than hand grinding.

High temperature superconducting (HTS) generators could enable a lightweight and cost-effective direct drive (DD) wind turbines with large power ratings. The EU-funded EcoSwing project successfully demonstrated the world's first full-scale MW-class HTS generator on a commercial DD wind turbine. This paper focuses on the commissioning of the EcoSwing HTS generator on the wind turbine. The commissioning campaigns, including the rotor cool-down, excitation of the HTS field winding, and the power production of the generator, are presented in the paper. In the testing period, the generator was grid-connected for more than 650 hours and accumulatively produced more than 600 MWh to the grid. The target output power of the 3 MW class was reached. Throughout the real-life testing on the wind turbine, the generator performed well from the electromagnetic, thermal, and mechanical perspectives. Moreover, the generator even sustained three sudden short circuits in the converter system. The work reported has shown that HTS generators are technologically feasible for wind turbine applications, and the technology readiness level of HTS wind turbine generators has been improved to 6 $\sim$ 7 for the first time. [ABSTRACT FROM AUTHOR]

The article presents a full-size pole pair set-up of an MW-class direct drive (DD) high temperature superconducting (HTS) wind turbine generator. The set-up serves as a precursor to the world's first full-scale DD HTS generator developed within the EU-funded EcoSwing project. The set-up built for de-risking employs an HTS field winding in the rotor and a conventional copper armature winding in the stator, representing a minimum independent unit of the corresponding full generator. Such a prototyping approach well reflects the performance of the full generator at a low cost. The article first explains the main design considerations of the full generator, followed by designing and construction details of the set-up. Afterward, a number of tests for determining the key performance of the set-up are reported. The testing results showed that the HTS field winding ran stably at its rated current of 480 A and was well maintained below 30 K. Moreover, the tangential force in the set-up reached 29.8 kN, projecting the 2 MW target output power of the full generator. The set-up developed effectively validated the design ideas and engineering feasibilities of the full generator, leading to successful kick-off of the EcoSwing project. [ABSTRACT FROM AUTHOR]

Copyright of Rare Metal Materials & Engineering is the property of Northwest Institute for Nonferrous Metal Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Rare Metal Materials & Engineering is the property of Northwest Institute for Nonferrous Metal Research and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Electric machines with very high power-to-weight ratios are inevitable for hybrid electric aircraft applications. One potential technology that is very promising to achieve the required power-to-weight ratio for short-range aircraft is using superconductors for high current densities in the stator or high magnetic fields in the rotor. In this work, an in-depth analysis of potential fully and partially superconducting machines is performed, taking into account all relevant physical domains such as electromagnetics, superconducting properties, thermal behavior as well as structural mechanics. For the requirements of the motors in the NASA N3-X concept aircraft, we find that fully superconducting machines could achieve 3.5 times higher power-to-weight ratio than partially superconducting machines. Furthermore, the model can be used to calculate the relevant key performance indicators such as mass, efficiency, and cryogenic cooling requirements for any other machine design. [ABSTRACT FROM AUTHOR]

In this paper, the optical spectra of one-dimensional photonic crystal (PCs) are numerically investigated in UV, Visible and Infrared ranges. PCs consisting of a HTc superconducting material (YaBa 2 Cu 3 O 7) are sandwiched between dielectric layer (SiO 2 or AlN) and semiconductor layer (GaAs), where superconducting layer is considered as defects. Using transfer matrix method, all the numerical results are performed and inferred that photonic band gap shifted to higher wavelengths by increasing the temperature. It is found that when the temperature increases the PBG shifted to a long wavelength. When the defect is used in structure as dielectric or superconductor, the peak appears in PBG and his value increases as the temperature increases. [ABSTRACT FROM AUTHOR]

Our work presents a study of High Temperature Superconductor (HTS) Yttrium Barium Copper Oxide YBaCuO rectangular thin film. It is considered to be etched on lanthanum aluminate (LaAlO3) substrate. Results are exhibited for different values of temperature and patch thickness. Validated and compared to those in literature, these results show direct proportionality between patch thickness and both of resonant frequency and bandwidth for temperatures relatively far from the critical temperature TC. When temperature becomes very close to TC, proportionality between resonant frequency and patch thickness is maintained; but it is inverted between bandwidth and patch thickness. Bandwidth is broadened at low values of thickness, but it decreases considerably when thickness increases. [ABSTRACT FROM AUTHOR]

High temperature superconducting (HTS) technologies are expected to be a key enabler for lightweight and cost-effective direct-drive (DD) trains for large wind turbines. This paper reports the designing and basic experimental validation of the world's first full-scale DD HTS generator demonstrated on a commercial wind turbine. The HTS generator has its rotor with an HTS field winding working below 30 K, which is achieved by using off-the-shelf Gifford-McMahon cryocoolers. The stator of the generator is essentially conventional, except that the armature winding has four segments to limit fault torques in case of sudden short circuits due to converter failures. Compared to an existing DD permanent magnet generator on the turbine, the air gap shearing stress of the HTS generator is doubled, and the weight is reduced by 24%. The overall design requirements from the turbine integration perspective, as well as the topological considerations, are first described in this paper. The electromagnetic and cryogenic designs are then presented, followed by performance testing of HTS coils. The basic experimental validation shows that the cryogenic design is satisfactory and the measured no-load voltage matches the finite element calculation very well. [ABSTRACT FROM AUTHOR]

Our work presents a study of High Temperature Superconductor (HTS) Yttrium Barium Copper Oxide YBaCuO rectangular thin film. It is considered to be etched on lanthanum aluminate (LaAlO3) substrate. Results are exhibited for different values of temperature and patch thickness. Validated and compared to those in literature, these results show direct proportionality between patch thickness and both of resonant frequency and bandwidth for temperatures relatively far from the critical temperature TC. When temperature becomes very close to TC, proportionality between resonant frequency and patch thickness is maintained; but it is inverted between bandwidth and patch thickness. Bandwidth is broadened at low values of thickness, but it decreases considerably when thickness increases. [ABSTRACT FROM AUTHOR]

The mechanism of high-temperature superconductivity remains one of the great challenges of contemporary physics. Here, we review efforts to image the vortex lattice in copper oxide-based high-temperature superconductors and to measure the characteristic electronic structure of the vortex core of a d -wave superconductor using scanning tunneling spectroscopy. [ABSTRACT FROM AUTHOR]