Search

We report a fine tuned doping study of strongly overdoped Bi2Sr2CaCu2O8+δ single crystals using electronic Raman scattering. Combined with theoretical calculations, we show that the doping, at which the normal-state pseudogap closes, coincides with a Lifshitz quantum phase transition where the active holelike Fermi surface becomes electronlike. This conclusion suggests that the microscopic cause of the pseudogap is sensitive to the Fermi surface topology. Furthermore, we find that the superconducting transition temperature is unaffected by this transition, demonstrating that their origins are different on the overdoped side. [ABSTRACT FROM AUTHOR]

Design activities on the helical-type fusion DEMO reactor, FFHR-d1, are progressing at NIFS. A 100 kA current-capacity is required for the helical coil conductors under the maximum magnetic field of \sim13 T. High-temperature superconducting conductor has been proposed as one of the conductor options for the FFHR-d1 magnet. In this study, a 30 kA class HTS conductor sample has been fabricated and tested. The sample had no current feeders and the current was induced by changing the background magnetic field generated by the 9 T split coils in the cryostat. Rogowski coils and Hall probes were used for the measurement of the transport current of the sample. The critical current of the sample was measured at various temperatures and bias magnetic fields. To verify the self-field effect of the sample, a numerical analysis was performed by considering the current and magnetic field distribution among the tapes self-consistently. The analysis result was compared with the experimental observation. [ABSTRACT FROM PUBLISHER]

Multi-wire conductors consisting of YBCO wires with magnetic substrate are usually applied in the high temperature superconductor (HTS) applications. In these applications, ac loss is a critical factor to determine the capacity of a refrigerator. And the ac losses of YBCO-NiW wires will be affected by the magnetic substrate. In this work, the self-field loss of the YBCO wire with the magnetic substrate is firstly measured, and compared with the numerical data. Moreover, the ac losses of a multi-wire YBCO-NiW conductor consisting of three wires are investigated for three transport modes. The main results show that the measured self-field loss of the wire is identical with the numerical ones. Accordingly, the reliability of the experimental and numerical methods is verified. Also, the ac losses of the conductor are in good agreement with the numerically calculated losses. As for the multi-wire conductor's total losses, the change of the direction of current in wires will not have an apparent influence on the total ac losses. [ABSTRACT FROM PUBLISHER]

This paper deals with the latest design of an all High Temperature Superconductor (HTS) insert for our 1.3 GHz NMR program. Due to a loss of our original 600 MHz HTS insert, the entire program was revised, and upon further examination of the options available for the HTS insert, which included not only conductor material properties, but also new winding technologies recently developed here at the FBML, it has finally been decided to build an 800 MHz (H800) insert purely based in SuperPower YBCO conductor. The new H800 will still be comprised of nested stacks of double-pancake coils and will run in the background of a 500 MHz LTS NMR magnet already available at FBML. We present here electromagnetic and mechanical details of the H800 design, winding technique employed, and testing of individual coils. [ABSTRACT FROM PUBLISHER]

Recent experiments on synchronized radiation from intrinsic Josephson junctions in high-temperature superconductors showed that the difference of temperatures of the junctions can influence synchronization. We investigated numerically the mechainsm of this influence on the example of two overdamped Josephson junctions loaded by a shunt consisting of the resistance and the inductance. We showed that strong synchronization of radiation was obtained by means of external separate heating/cooling of junctions. Due to the change of critical currents in the process of heating or cooling, the current-voltage ( I- V) characteristics of the junctions cross each other and junctions are synchronized by the ac current in the load in the vicinity of this crossing. The maximal tolerant spread of critical currents for this mechanism of synchronization is 15-20% that is twice larger than the maximal tolerant spread for this system without the separate heating. I- V characteristics of two separately heated junctions. Phase locking in this system is impossible without heating for such large spreads of critical currents. [ABSTRACT FROM AUTHOR]

Substrate engineering is a key factor in the synthesis of new complex materials. The substrate surface has to be conditioned in order to minimize the energy threshold for the formation of the desired phase or to enhance the catalytic activity of the substrate. The mechanism of the substrate activity, especially of technologically relevant oxide surfaces, is poorly understood. Here we design and synthesize several distinct and stable CeO2 (001) surface reconstructions which are used to grow epitaxial films of the high-temperature superconductor YBa2Cu3O7. The film grown on the substrate having the longest, fourfold period, reconstruction exhibits a twofold increase in performance over surfaces with shorter period reconstructions. This is explained by the crossover between the nucleation site dimensions and the period of the surface reconstruction. This result opens a new avenue for catalysis mediated solid state synthesis. [ABSTRACT FROM AUTHOR]

Highlights: [•] We studied the high-Tc superconductivity (SC) in cuprates by using the d–p model. [•] We transformed the d–p model into a non-local Hubbard model. [•] Applying Kondo’s gap equation to it, we evaluated a SC strength parameter x. [•] It gives the (εp − εd )-dependence of SC (εp − εd : level difference between O and Cu). [•] In the case of εp − εd <0, the result explains two basic systematics of Tc . [Copyright &y& Elsevier]

Abstract: It has long been known that high temperature superconductors (HTS) could have an important role to play in the future of tokamak fusion research. Here we report on first results of the use of HTS in a tokamak magnet and on the progress in design and construction of the first fully-HTS tokamak. [Copyright &y& Elsevier]

Abstract: A single-sided high temperature superconducting (HTS) linear synchronous motor (HTSLSM) with an HTS bulk magnet array as its secondary has been developed. The thrust and normal force characteristics are essential to describe the performance of the HTSLSM. In this paper, a compositive control and experimental testing system has been developed to measure the thrust and normal force of the HTSLSM. The traits of the thrust and normal force have been comprehensively identified experimentally, and the results from the experiments and analysis benefit the electromagnetic design and the control scheme development for the HTSLSM. [Copyright &y& Elsevier]

A characteristic study of the temperature and field dependence magnetization of high temperature superconductors (HTSCs) HgBaCuO and TlBaCaCuO have been carried out in this present work. The field dependence of dM/ dln B has been discussed and compared using few existing models. The findings of variation of magnetization with temperature for different applied fields are found to give correct behavior as observed in experiments. [ABSTRACT FROM AUTHOR]

For YBCO bulk levitating over a permanent magnet guideway (PMG), the magnetic stiffness is connected directly with the pinning properties of the measured sample. An experimental setup has been built to investigate the vertical and lateral magnetic stiffness of five high-temperature superconducting (HTS) bulk arrays over a PMG by two methods: the additive method, i.e., calculating the summation of the measured magnetic stiffness values of each HTS bulk in the array; the direct method, i.e., measuring directly the magnetic stiffness of the HTS bulk array. From the experimental results, it is found that the resultant magnetic stiffness of the HTS bulk array composing of multiple YBCO bulk is related with the magnetic stiffness of each individual single bulk, but the additive method does not predict the magnetic stiffness of the array very well because of the interaction between adjacent HTS bulk. The resultant magnetic stiffness of the HTS bulk array is less than the summation magnetic stiffness of each single HTS bulk. One numerical method is used to calculate the magnetic stiffness for comparing with experimental results. The results may be helpful to the design and optimization of the superconducting magnetic levitation system. [ABSTRACT FROM AUTHOR]

method of calculation of current leads containing high-temperature semiconductors and cooled by cryogenic gas machines (cryocoolers) has been proposed. The method is based on subdivision of current leads into individual portions (sections) differing in the character of traversal of the current and cooling conditions. The results of the change in the required refrigerating capacity of the coolers operating at different temperature levels as a function of the length and arrangement of the sections have been shown. The distinctive features of the variation in the temperature and the heat flux along cryocooler-cooled current leads have been analyzed. [ABSTRACT FROM AUTHOR]

We report on avalanche-like flux features in the response of superconducting films of MgB, prepared by magnetron sputtering and an ex-situ annealing process, when a single high-frequency pulse is used as a perturbative source. The instability is observed as an abrupt jump in the output voltage signal of the SQUID magnetometer where the sample is measured as a function of temperature, magnetic field, and pulse width, at fixed nominal power and frequency values. The interaction between the high-frequency surface currents and the relaxing vortex system is suggested to explain the nucleation of avalanches. Local heating due to the pulse application is also considered as a contributing mechanism. [ABSTRACT FROM AUTHOR]

It is well known that high temperature superconductors (HTS) are promising for a magnet application, but it has been almost impossible so far to apply them to the magnet in persistent current mode because of poor qualities of their superconducting joint at higher current as well as lower index values. In this paper, in order to get rid of the joints from an HTS superconducting magnet, a prototype HTS pancake coil using YBCO coated conductors by the technique of wind-and-flip pancake coil was made and will be tested later. This paper presents a design, fabrication, and thermal analysis of the prototype pancake coil. The coil will be cooled down around 20 K by conduction cooling using a GM cryocooler. The expected current drift rate for an MRI application has not been achieved, probably caused by large flux flow resistance of coated conductor at higher temperature, 77.3 K. A temperature dependency of temporal stability of the persistent current will be measured by monitoring the long-term drift of the magnetic field at different operating temperatures by Hall sensors. [ABSTRACT FROM AUTHOR]

The insulation characteristics of high temperature superconducting (HTS) coil or winding are significant for their power application, which mainly includes partial discharging (PD), withstand voltage, breakdown voltage, flashover, fatigue effect through thermal cycles and lifetime. In this paper, we focused on investigation of the partial discharging of two HTS DP made of commercial multifilamentary Bi2223/Ag tapes and YBCO coated conductors. PD test was performed in order to ascertain the partial discharge inception voltage of DP in different conditions, which included static and quenching conditions. Experimental results revealed that PD density does not change obviously in different conditions. Useful results with combined conditions for PD characteristics were experimentally obtained. [ABSTRACT FROM AUTHOR]

The current distribution and stability of low temperature superconductor (LTS) and high temperature superconductor (HTS) hybrid superconductor, made of NbTi wire and YBCO coated-conductor, are described. The current distribution, quench propagation velocity (QPV) and the minimum quench energy (MQE) are numerically analysed by finite element method (FEM) based on the different power-law models since the n value in LTS is much larger than that in HTS. It is shown that the transport current in LTS is larger than in HTS if both of them have the same critical currents, and the ratio of transport current in LTS to that in HTS decreases with increase of the total transport current near their critical currents. The stability of the hybrid NbTi/YBCO composite conductor is also simulated, which indicates that MQE in the hybrid conductor is much higher than in NbTi wire but smaller than in YBCO conductor. However, the quench propagation velocity is in the range of low-temperature superconductor through the high-temperature superconductor. With advantages of high engineering current density and improvement of stability, the hybrid superconductor is expected to have potential application in large scale magnet and conducting-cooled magnet particularly. [ABSTRACT FROM AUTHOR]

High Temperature Superconductor (HTS) current leads provide the transition of the current transfer system from room temperature to the 4.5 K. For the ITER superconducting magnet system, a total of 60 HTS current leads are required, with a total nominal current capacity of 2.64 MA. By the use of HTS leads significant power savings can be achieved during the operation of the ITER magnet system. Based on the functional specification by the ITER Organization (IO), ASIPP manufactured and tested a first pair of trial HTS current leads for the ITER coils. The cryogenic test of these 68 kA and 52 kA trial HTS leads was performed at ASIPP using the cryo-plant and power supplies of the EAST Tokamak. The following paper presents the results of the tests and concludes with a discussion of the design features of the next generation prototype of the ITER HTS leads based on the results of the trial lead tests. [ABSTRACT FROM AUTHOR]

2nd generation high temperature superconducting (2G-HTS) tape consists of multi-layers such substrate, buffer layer, superconducting layer and reinforced lamination tapes. 2G HTS tape is a candidate of good materials for current lead of superconducting magnet system owing to its low thermal conductivity. However, joint resistance between 2G HTS tapes and terminal block can be a major problem because of high electrical resistivity of substrate, buffer layer and reinforced lamination tapes of 2G HTS. So specially considering joint resistance between 2G tapes and terminal block, 2G HTS current lead for 400 A was designed and fabricated. This current lead was consisting of two terminal blocks, a support bar or tube, protection tube and six 2G HTS tapes. Its total length was 300 mm and body diameter 18.3 mm. At liquid nitrogen temperature (77 K) critical current (Ic) of this HTS current lead was 600 A, about 1.5 times the operating current 400 A. Conductive heat loss of 2G HTS current lead between 60 K and 7 K was 50 mW. [ABSTRACT FROM AUTHOR]

This paper describes the NMR/MRI magnets that are currently being developed at the MIT Francis Bitter Magnet Laboratory: 1) a 1.3 GHz NMR magnet; 2) a compact NMR magnet assembled from YBCO annuli; and 3) a persistent-mode, fully-protected MgB2 0.5-T/800-mm whole-body MRI magnet. [ABSTRACT FROM AUTHOR]

The dynamic responses and levitation forces of a high temperature superconducting (HTS) maglev vehicle system were investigated through the propagation simulation of seismic waves by a horizontal vibration platform. The HTS maglev vehicle system consisted of an array of seven YBaCuO high temperature superconductor (HTSC) bulk samples suspended above a permanent magnet guideway. Excitation frequencies of 0 to 60 Hz and excitation amplitudes of 1 to 3 mm were used to measure the HTS bulks characteristics in the time domain and horizontal displacements under horizontal vibrations. Results show that lateral stability and levitation performance is correlated to the excitation amplitude and the excitation frequency at the resonance frequency 5 Hz. This in turn is helpful towards the application of HTS maglev vehicles in the future. [ABSTRACT FROM AUTHOR]

The heat leakage of the current lead which connects the power supply and superconducting equipment are very important for a stable and economical operation of critical superconducting devices. An improved segment algorithm is used to obtain the optimal length and cross-section of a gas cooled current lead with varying cross-sections. Based on the improved method, we have designed a current lead with varying cross-section for the critical current test of HTS YBCO tapes with less conductive heat loss. Finally the temperature distribution of the current lead are measured experimentally. The experimental results are in agreement with the design, which proves the optimization effect of the current lead. The optimal design method and experimental research contribute to the utility of HTS current leads. [ABSTRACT FROM AUTHOR]

Various types of high-temperature superconducting (HTS) devices have been developed, some of which have completed field testing and are ready for use in commercial applications. In order to facilitate the commercialization of HTS electric equipment for extra high voltage levels, cryogenic dielectric technologies should be established. In this work, in order to develop partial discharge (PD) measurement techniques for HTS transformers, artificial defects were installed both in liquid nitrogen and insulating oil. Experimental investigations were carried out for the diagnosis of the HTS transformer, and various PD patterns, which occurred due to the artificial defects of immersion in both insulating oil and liquid nitrogen, were measured. Throughout this work, the PD patterns that occurred in liquid nitrogen were detected, analyzed, and compared to those in insulating oil through the use of a high frequency current transformer (HFCT) diagnostic method. The partial discharge measuring techniques we developed could be fundamental in establishing HTS transformer diagnosis technologies for power applications. [ABSTRACT FROM AUTHOR]

The superconductor-triggered type fault current limiter (STFCL), which was developed by Korea Electric Power Corporation (KEPCO) and LS Industrial Systems (LSIS), is under operation for the verification test at KEPCO's power testing center. The STFCL is composed of superconductor, fast switch and current limiting resistor. The fault current is suppressed after a half cycle by the method of a line commutation. In this paper, we investigated the empirical modeling of STFCL using principal components and auto-associative support vector regression (PCSVR) for the prediction and fault detection of the STFCL. Signals for the model are currents and voltages acquired from high-temperature superconductor (HTS), driving coil (DC) and current limiting resistor (CLR). After developing the empirical model we analyse the accuracy of the model. The results were compared with that of auto-associative neural networks (AANN). PCSVR showed much better performance in accuracy aspect. Moreover, this model can be used for the prognosis of STFCL system. [ABSTRACT FROM AUTHOR]

A permanent-magnet synchronous motor with high-Tc superconducting (HTS) armature operated at sub-cooled liquid nitrogen temperature has been designed. The prototype model has a ten-pole rotor and twelve sets of armature windings which are fabricated with BSCCO tapes, and its output power is 400 kW at the rated speed of 250 rpm. In order to decrease the AC loss of HTS coils to an appropriate level, the conventional stator iron cores are adopted. The coil design, behaviors of HTS conductors, even cooling system design will be proved in the armature case. And the prediction of AC loss in stacked tape conductor exposed to external magnetic fields with various directions have been carried out using FEA method. Based on the 3D magnetic field finite element analyses, this paper presents an AC loss analysis method for the armature winding and provides upper the limit of operating temperature for the cooling system. [ABSTRACT FROM AUTHOR]

We are developing a cryogen-free high temperature superconducting (HTS) magnet system for a compact 3T MRI system for human brains. In the conceptual design, the magnet system consists of 5 main coils that are layer windings of Bi-2223 tapes. The magnet system will have 500 mm room temperature bore and be operated at 20 K using G-M cryocoolers. The target field is 3 T ± 5 ppm for 250mm(dia,) and 200mm(length) volume. All the coils will be connected in series and operated in driven mode. Controlled overpressure (CT-OP) processed Bi-2223/Ag tapes which are reinforced with Cu-alloy laminations are to be used for these coils. We investigated Ic-B-T performance in detail for short samples of the tape. We fabricated and tested five small layer-wound coils using the tape (38.4 ~ 46.2 m piece for each coil). Each small coil could be energized up to its expected current that was calculated using the short sample performance and the coil parameters. The maximum electromagnetic force (hoop stress) reached 137 MPa, and caused no degradation in the coil performance. These results show that our layer-winding techniques and the conductor performance (Ic-B-T and homogeneity along length) can be applicable and suitable for our 3T MRI magnet. [ABSTRACT FROM AUTHOR]

A Bi-2223 surface RF coil was developed for a 0.3T permanent MRI system to achieve better signal-to-noise ratio (SNR) of images. Based on the finite element method (FEM), the SNR of a copper-made surface coil is analyzed, and the emphasis is put on the coil self-resistance that accounts for much higher percentage of the equivalent noise resistance in low field MRI than that in high field MRI. In order to improve SNR, a surface coil that is made of a Bi-2223 tape is fabricated for a 0.3T permanent MRI system. Phantom images are acquired, and the image SNR by the Bi-2223 coil in liquid nitrogen is improved by up to 35% compared with that by a copper coil at room temperature. [ABSTRACT FROM AUTHOR]

A novel method for microwave surface resistance measurement of high temperature superconductor thin film at multi-frequency by multimode of sapphire rod is introduced. This method has the advantages of high sensitivity and large dynamic range of the measurement. By using this method, the frequency dependent microwave surface resistance of a single piece of high temperature superconductor thin film can be characterized within one temperature cycle. This method is capable of reducing the amount of work in surface resistance measurement and providing supports to the research and the industrialization of high temperature superconductor thin film. [ABSTRACT FROM AUTHOR]

This paper discusses the different possible designs of both cored and coreless superconducting synchronous generators using high-temperature superconducting (HTS) tapes, with particular reference to demonstrators built at the University of Southampton using BiSCCO conductors. An overview of the electromagnetic, thermal, and mechanical issues is provided, the advantages and drawbacks of particular designs are highlighted, the need for compromises is explained, and practical solutions are offered. The scalability of results obtained from small demonstrators is considered. [ABSTRACT FROM AUTHOR]

A multimode sapphire resonator is developed for multiple frequency surface resistance measurement of a single piece of high-temperature superconductor thin film. Simple formulas are used for the calculations of surface resistances. On this sapphire resonator, three modes, TE011+ ε, TE012+ δ and TE021+ξ (0< ε, δ,ξ<1), which had resonances at 11.84, 17.49 and 31.99 GHz were used simultaneously and the measured surface resistances at these frequencies were 0.553, 1.32 and 3.75 mΩ, respectively. The measured result matches the theory very well. [ABSTRACT FROM AUTHOR]

Metallization of pure solid hydrogen is of great interest, not least because it could lead to high-temperature superconductivity, but it continues to be an elusive goal because of great experimental challenges. Hydrogen-rich materials, in particular, (H[sub4], SiH[sub4], and GeH[sub4], provide an opportunity to study related phenomena at experimentally achievable pressures, and they too are expected to be high-temperature superconductors. Recently, the emergence of a metallic phase has been observed in silane for pressures just above 60 GPa. However, some uncertainty exists about the crystal structure of the discovered metallic phase. Here, we show by way of elimination, that a single structure that possesses all of the required characteristics of the experimentally observed metallic phase of silane from a pool of plausible candidates can be identified. Our density functional theory and GW calculations show that a structure with space group P4Inbm is metallic at pressures >60 GPa. Based on phonon calculations, we furthermore demonstrate that the P4Inbm structure is dynamically stable at >43 GPa and becomes the ground state at 97 GPa when zero-point energy contributions are considered. These findings could lead the way for further theoretical analysis of metallic phases of hydrogen-rich materials and stimulate experimental studies. [ABSTRACT FROM AUTHOR]

Abstract: High temperature superconducting (HTS) cables using YBCO tapes are expected to be more economical because AC losses will be much smaller than conventional cables. To reduce AC loss, 10mm wide YBCO tapes were divided into five strips using a YAG laser. Using narrower strips and optimizing the space between the strips were effective in reducing AC loss. A 1m conductor was fabricated, and AC loss was 0.048W/m at 1kA and 50Hz. Based on the successful AC loss reduction in the 1m conductor, we will fabricate a 10m HTS cable with a three-layer HTS conductor, electrical insulation, and a one-layer HTS shield and cupper protection layer for overcurrent. In addition, we have developed a prototype of the HTS cable joint that can withstand an overcurrent condition of 31.5kA for 2s. [Copyright &y& Elsevier]

Abstract: High temperature superconductor (HTS) cables have been studied because they are more compact compared to conventional copper cables. In power applications of HTS cable AC loss is significantly important, as it is related with capacity and efficiency of the power line. Recently, a tri-axial cable composed of three concentric phases has been intensively developed, because of their reduced amount of HTS tapes, small leakage field, low heat loss when compared to three coaxial HTS cable. However, it experiences additional losses and large leakage field due to inherent imbalanced currents. Inside the tri-axial cable, each phase is subject to out-of-phase magnetic fields formed by other phase layer currents. Because tapes are twisted on successive layers, axial field by outer layers and azimuthal field by inner layers are produced in a tri-axial HTS cable. Any slab in the cable experiences parallel component of magnetic field on the wide faces of the tapes; induced by currents of all layers. Since the fields on tapes generate magnetization losses, they should be calculated in consideration of the balanced current distribution of the tri-axial cable. In this paper, AC loss in the tri-axial HTS cable consisting of one layer per phase is described, theoretically, where the balanced phase current distribution is satisfied through treating two different cable segments. The average AC losses in the cable are calculated as functions of the segment lengths and the segment twist pitches. [Copyright &y& Elsevier]

Not withstanding their high stability at liquid nitrogen temperatures, quench propagation due local disturbances remains a crucial issue for high temperature superconductors (HTS) operating at low temperatures as high field insert coils and cryogen-free magnets. In contrast to low temperature superconductors (LTS), normal zone in HTS at low temperatures must develop over a much extended temperature range for current sharing with a highly non-linear dependence on temperature. The present work addresses this issue directly using both computer simulation and experimental studies. Several quench characteristics unique to HTS have identified using a comparative study of the underlying quasilinear parabolic equation represented in an appropriate dimensionless form for proper isolation of the known effects of temperature dependence of thermal properties. Most notable and counter-intuitive finding is that the minimum propagation zone (MPZ) was found to increase with transport current. The correlations of minimum quench energy (MQE) and the quench temperature of MPZ with operating temperature and current have been obtained for comparison with experimental results. [ABSTRACT FROM AUTHOR]

The working features of 2nd generation high temperature superconducting tapes related to applications, such as their stability, are becoming of real interest as long tape lengths become available. In this work, we present results on normal zone propagation velocity obtained on a 40 cm long YBCO coated conductor, called 344 superconductors, manufactured by American Superconductor Corp. Although the tape is wound on a 40 mm diameter cylinder support, its transport features are unaffected compared to the straight tape. The quench is induced by an external heater, and the propagation is observed from the increasing voltages along the tape. In the range 75 ÷ 80 K, we observed a propagation velocity lower than 2 cm/s at current bias slightly below 80% of the critical current. Our investigation covers different bias current values as well as temperatures, and experimental analysis is also compared to an approximate numerical model. [ABSTRACT FROM AUTHOR]

In order to evaluate the stable operation of high temperature superconducting (HTS) power cable, the calculation of AC loss on HTS power cable is important factor. Because AC loss has a big effect on many superconducting equipments, which are fabricated using the HTS tape. In general, AC loss of the HTS tape can be calculated by using voltage variations of the tape with respect to the external magnetic field when AC current applied to the tape. In case of HTS power cable carrying AC current, however, because the magnetic field distribution in the cable is very complicated, it is hard to compute AC loss of the HTS cable directly using above method. In this paper, the stability evaluation of the HTS power cable was performed by the following procedures. Firstly, the voltage variations of the HTS tape carrying AC current in the external magnetic field with different field angle were measured and the magnetic field distribution of HTS power cable with AC current was analyzed. Then, AC loss of the HTS power cable was calculated by using the results of both the measurement and the analysis. The stable operation of the HTS power cable was evaluated on the basis of AC loss of the cable. [ABSTRACT FROM AUTHOR]

According to recent studies, economical feasibility of resistive superconducting fault current limiters (FCL5) in transmission and distribution power line is confirmed. Since the SFCL is operated under alternating current (AC), it causes power loss, so-called AC loss, during normal operation condition even though it is superconductor. Bifilar pancake winding with coated conductor (CC) is expected to reduce AC loss of the SFCL by canceling magnetic fields efficiently as compared with other type SFCLs using CC in the same length. AC loss characteristic of the bifilar pancake type coil for SFCL application was investigated in this paper. Two bifilar pancake coils were wound using CC with facing on high temperature superconductor (HTS) sides each other and substrate (Ni-W) sides each other, respectively. AC losses of the coils were measured at 77 K and theoretical analysis was performed by finite element method (FEM). The experimental results are compared with the Norris equations and numerical values using FEM. [ABSTRACT FROM AUTHOR]

High-temperature superconductors (HTS) are considered to be indispensable to realize NMR magnets that exceed 1 GHz owing to their high critical current densities even in high magnetic fields exceeding 20 T. Feasibility studies of the > 1-GHz NMR magnet with the HTS inner coil have been reported. HTS conductors are brittle, and it is not easy to apply to superconducting coils such as the inner coils of the > 1-GHz NMR magnet. Investigations into the mechanical properties of HTS coils are quite important. The hoop stress is an important factor in magnet design. Bi-2223 conductors are most promising because they are commercially available and can be obtained with lengths of more than 1,000 m. Double pancake coils with an inner diameter of 260 mm wound from Bi-2223/Ag conductors of the Sumitomo DI-BSCCO (high-Ic type and high-strength type) were fabricated to evaluate the hoop stress dependence of the critical current of the coil. The double pancake coils were tested using the 14-T superconducting magnet with a room temperature bore of 400 mm in diameter at the Tsukuba Magnet Laboratory (TML). The critical current of the high-Ic test coil was 164 A, where the hoop stress was estimated at 323 MPa. The critical current decreased to 140 A after energizing the coil above a hoop stress of 300 MPa. The high-strength test coil burst at a hoop stress of approximately 200 MPa. [ABSTRACT FROM AUTHOR]

For the development of high magnetic field application using high temperature superconductor (HTS), Bi-2223/Ag tape is one of the promising materials because of its high current capacity and upper critical field. However, Bi-2223/Ag tape shows very strong anisotropy and significant deterioration of critical current in the magnetic field. To explore the possibility of HTS in high field applications, we evaluated the critical current and index value of Bi-2223/Ag conductor in high magnetic field. The Bi-2223/Ag tape was characterized as a function of increasing and decreasing field. The temperature dependence was also examined lower than 4.2 K. All measurements were carried out with hybrid magnet system up to 30 T and the experimental results are reported. [ABSTRACT FROM AUTHOR]