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Superconducting windings will be necessary in future fusion reactors to generate the strong magnetic fields needed to confine the plasma, and these superconducting materials will inevitably be exposed to neutron damage. It is known that this exposure results in the creation of isolated damage cascades, but the presence of these defects alone is not sufficient to explain the degradation of macroscopic superconducting properties and a quantitative method is needed to assess the subtle lattice damage in between the clusters. We have studied REBCO‐coated conductors irradiated with neutrons to a cumulative dose of 3.3 × 1022 n/m2 that show a degradation of both Tc and Jc values, and use HRTEM analysis to show that this irradiation introduces ∼10 nm amorphous collision cascades. In addition, we introduce a new method for the analysis of these images to quantify the degree of lattice disorder in the apparently perfect matrix between these cascades. This method utilises Fast Fourier and Discrete Cosine Transformations of a statistically relevant number of HRTEM images of pristine, neutron‐irradiated and amorphous samples and extracts the degree of randomness in terms of entropy values. Our results show that these entropy values in both mid‐frequency band FFT and DCT domains correlate with the expected level of lattice damage, with the pristine samples having the lowest and the fully amorphous regions the highest entropy values. Our methodology allows us to quantify 'invisible' lattice damage to and correlate these values to the degradation of superconducting properties, and also has relevance for a wider range of applications in the field of electron microscopy where small changes in lattice perfection need to be measured. [ABSTRACT FROM AUTHOR]

In this contribution, the usage of a pyramid-like buffer stack for optimization of the top-seeded melt growth process of GdBCO (GdBa 2 Cu 3 O 7-δ) single-domain superconductors is demonstrated. The process was optimized by the addition of SmBCO into GdBCO/Ag into the buffer precursor powder, which effectively increased the peritectic temperature of the final mixed powder in the pyramid-like buffer stack. As such, this approach can be also used for other REBCO systems by selecting rare earth with a higher peritectic temperature and adding it to the buffer pellets. The thermal behavior of the powders was studied by STA. This enables fast and effective crystal growth through the buffer stack and the formation of large effective seeds. This approach also allows for reliable and precise tuning of growth angle and together with effective seed size facilitates tuning of a - b to c sector ratio. The phase composition of precursors and prepared bulks were studied by XRD. The microstructure was also studied by SEM and OM in detail. Subsequently, levitation force and trapped field were measured. Results confirmed that the addition of at least a single buffer pellet improved the melt growth process significantly by acting as a large effective seed. Superconducting properties of the samples grown by pyramid-like buffer stack are superior in comparison to reference TSMG samples. [ABSTRACT FROM AUTHOR]

Future all-electric aircraft will employ highly efficient compact and lightweight machines for power generation and propulsion applications. Previous studies have indicated that the most attractive options include synchronous machines employing superconducting excitation and stator windings for achieving high power density and efficiency. The dc excitation winding could be constructed using a variety of superconductors, but the choice for ac stator windings is limited. High conductivity aluminum conductor at cryogenic temperature is a possible option but it is expected to be heavier than a superconducting winding and will require more extensive cooling as the losses within the winding pack will be much larger. A conductor-on-round-core (CORC) cable using REBCO tapes looks like an attractive option as it enables compound bending for constructing saddle coils. Here, we investigate using this cable for the stator winding of a 3 MW, 4500 RPM, 4-pole propulsion motor and compare with an identical motor employing an MgB2 stator winding. The motor configuration assumes saddle-shaped coils for the stator winding. Each saddle coil constitutes a double pancake. A round conductor capable of bending in three-dimensional is preferred for such coils, making the round CORC cable ideal for this application. The cable employs striated REBCO with striation width as small as 1/3 mm. The ac field in the stator winding region is about 0.7 T at 150 Hz and the cable is operated at 50% of its critical current for limiting ac losses and for providing a safety margin. Individual tapes in the CORC cable experience field perpendicular to its broad face resulting in high ac losses. Comparing the performance of motors employing CORC and MgB2 cables for the stator, we find that the ac losses in the CORC stator are much larger than the MgB2 stator. High losses in the CORC stator winding make this option less attractive unless coolant power is freely available, such as in LH2-fueled planes. However, this machine with CORC coils is the most compact and lightweight option. Such compact light mass motors could be attractive for LH2 fueled applications, such as interstate trucks, heavy machinery, locomotive hauling goods trains, ships (especially for podded propellers), etc. [ABSTRACT FROM AUTHOR]

We report on strain and composition effects associated with growth of self-assembled BaZrO3 (BZO) nanorods in REBa2Cu3O7âˆ' δ (REBCO) superconductors (RE = rare earth = Y and Gd), which have a profound effect on flux pinning and in-field critical current performance. The a-b plane mismatch between BZO and REBCO is never fully coherently accommodated. Instead, the nanorods always assume a size at least one unit cell smaller than the corresponding ‘hole’ in the REBCO matrix, thus providing deep minima of in-plane mismatch strain. Next, we show that the nominal BZO nanorods are in fact solid solution Ba2+(Zr4+1âˆ' z RE3+z)O3âˆ' δ perovskite, thus strongly affecting the stoichiometry and relative amounts of REBCO and BZO. We demonstrate that by varying only the Ba content in the nominal composition of 15 mol.% BZO + REBCO, the unit cell density of BZO can be tuned from 5% to 23%, and the linear density of RE2O3 (REO) precipitates from 18 to 1 ÎĽ mâˆ'1. The results explain the wide range of pinning performances observed for the same nominal amount of Zr addition and provide insight into the mechanisms behind the complex phenomenon of growth of nanorods by self-assembly in REBCO superconductors. [ABSTRACT FROM AUTHOR]

Practical superconducting materials and technologies have been enabled with availability for large scale devices and applications. Various large scale and strong magnetic field applications of superconductors have been developed, and a series of those applications are explored with technical details mainly including i) applied superconducting materials and their characteristics; ii) superconducting magnets and their techniques; iii) large and advanced electromagnetic devices and applications. The applied superconductivity, application technology, and availability are especially focused and verified with the trend of large scale applications’ development prospection. [ABSTRACT FROM AUTHOR]

The joint-free superconducting annular disks and their stacks, obtained by cutting REBCO (REBa2Cu3O7–δ, RE: rare earth) wide tapes, are proposed as promising passive magnetic shields in this paper. The shielding properties of the disks have been numerically studied using the finite element method. The shielding factor (SF), defined as the ratio between the applied field and the central field, had a frequency-independent value when the magnetic field is much lower than the full penetration field. It appears to have a linear relationship with the ratio of the outer and inner diameter of the disk. Furthermore, various architectures with stacked disks were studied. High shielding factors (SF > 104) under enhanced full penetration fields of above 100 mT can be obtained in the configuration of more disks and proper disk distance (the distance between the disks on each layer). Two stacked disks were designed. In a 1-mT, 1-Hz applied field, the SF of the 4-mm inner diameter discrete stack is 1.21 × 107 (140 dB), and the SF of the 20-mm inner diameter split stack reaches 3.44 × 104 (90 dB). It implies that the stacked REBCO disks have great potential for the application of high-efficiency magnetic shielding. [ABSTRACT FROM AUTHOR]

Porosity affects the properties of high- T c superconductors and can improve their performance by enhancing oxygenation, cryocooling, etc. Among other factors, the presence of pores plays a significant role in the process of magnetic flux trapping. Relationships with the porosity manifest in the irreversibility field, the full penetration field, and the remnant magnetization of the samples. To account for the effect of porosity on the trapped magnetic flux into type-II superconductors, a simple toy model is suggested. Generally, as the porosity increases, the trapped flux and related parameters tend to diminish. However, in the case of microscopic samples, porosity can enhance magnetic flux trapping. [ABSTRACT FROM AUTHOR]

Due to the nonlinear properties of superconductors, modeling of high-temperature superconducting (HTS) devices is difficult, especially for the ones in large scale. In this paper, we develop the multiscale model from a two-dimensional (2-D) planar geometry to a 2-D axisymmetric geometry to successfully calculate ac loss of large-scale HTS coils. By applying appropriate boundary conditions, the infinite-turn coil is built in the 2-D-axisymmetric model to produce approximated current density for an HTS coil. Besides, the multiscale model is improved in terms of coupling, so that submodels can be connected in one file and the external data processing is not needed. Validation on accuracy and efficiency is demonstrated through a double-pancake coil. Results are compared with a conventional model that considers the superconducting characteristics on each turn of the coil in actual size. This paper shows the development and improvement of multiscale model in the 2-D axisymmetric geometry is feasible. Due to its high accuracy and efficiency, the developed multiscale model can be a useful approach to analyze electromagnetic characteristics and calculate ac losses in large-scale HTS magnets. [ABSTRACT FROM AUTHOR]

• High current superconductors by texturing. • Scale-up of thin film superconductor tapes to manufacturing. • High magnetic field applications of HTS. This article is a lookback at the road traveled in the last 36 years to realize the abundant potential of high temperature superconductors (HTS) that had evoked worldwide excitement on their discovery. Numerous advances have been made in the materials science and manufacturing of HTS to overcome the many obstacles in implementing them in applications. [ABSTRACT FROM AUTHOR]

The problem of Abrikosov vortices depinning from extended linear (columnar) defect in 3D-anisotropic superconductor film under non-uniformly distributed Lorentz force is studied for the case of low temperatures, disregarding thermal activation processes. We treat it as a problem of mechanical behavior of an elastic vortex string settled in a potential well of a linear defect and exerted to Lorentz force action within the screening layer about the London penetration depth near the specimen surface. The stability problem for the vortex pinning state is investigated by means of numerical modeling, and conditions for the instability threshold are obtained as well as the critical current density jc and its dependence on the film thickness and magnetic field orientation. The instability leading to vortex depinning from extended linear defect first emerges near the surface and then propagates inside the superconductor. This scenario of vortex depinning mechanism at low temperatures is strongly supported by some recent experiments on high-Tc superconductors and other novel superconducting materials, containing columnar defects of various nature. [ABSTRACT FROM AUTHOR]

This study investigated the magnetic shielding performance of various configurations of superconducting cylinders based on high temperature superconducting Coated Conductor (CC) tapes. We applied ac magnetic fields with various frequencies and amplitudes to superconducting cylinders with CC tapes. The magnetic shielding performances of the cylinders with a variety of layer number and length of the cylinder were compared. We also performed the numerical simulations, and got the same tendency as the experimental results. We clarified that the shielding factor lineally increaseswith the layer number of the CCtape. More than five layers of the CC tape wound with the same orientation and angle to cover the gaps of an inner layer achieves 98% attenuation of the magnetic field. However, the simulation and experimental results show that shielding factor is not greatly improved by increasing the length of the cylinder due to the magnetic field penetration from the gaps between each winding of the CC tape. This study demonstrates a good possibility and also the limitation to use CC tapes for the magnetic shielding. [ABSTRACT FROM AUTHOR]

VAMAS TWA 16 promoted an international round robin test (RRT) on critical current (Ic ) measurement of RE-Ba-Cu-O (REBCO; RE=rare earth) superconductors to establish the transport Ic measurement method in liquid nitrogen bath without an external magnetic field. Ten laboratories from five countries participated in the RRT and tested commercially available REBCO superconductors. Ic and measurement conditions were reported. In parallel, intrinsic Ic nonuniformity of the superconductors were evaluated by reel-to-reel scanning Hall-probe microscopy for 10-m conductors. Statistical analyses of Ic provided uncertainty of the measurement method. Combined standard uncertainty was analyzed considering the intrinsic nonuniformity of Ic . The analysis indicated that the intrinsic nonuniformity has the largest contribution to the uncertainty of Ic. [ABSTRACT FROM AUTHOR]

The ac loss properties of stacks of nonstriated and striated REBa2Cu3Oy (REBCO, RE = rare earth elements, Y, Gd, Eu) superconducting tapes were investigated over a wide range of temperature and magnetic field amplitude, and compared with each other. The results obtained show that the penetration field (Bp ), in which the magnetic flux front penetrates the center of the tape, increases with increasing number of stacked tapes (N) for the nonstriated tapes. In addition, the ac losses in the nonstriated tapes for a smaller magnetic field amplitude (B) than Bp decreases as N increases. On the contrary, for the striated tapes, Bp marginally depends on N and the ac losses also show slight variations with N. These phenomena seem to be due to the demagnetizing effect. Itwas shown that the ac losses in the striated REBCO and nonstriated tapes are scaled with temperature regardless of the number of stacked tapes. This suggests that the ac losses of REBCO tapes can be easily estimated for temperature measured in this study regardless of striating and stacking, provided that the impact level of temperature on the critical current at self-field and the ac losses at certain temperatures are known. [ABSTRACT FROM AUTHOR]

High temperature superconducting magnetic energy storage systems (HTS SMES) have attracted significant attention for fast response and ensure a reliable power supply. However, the current carrying capacity of single superconducting tape often meets limitation for the large scaleHTS SMES applied in the power grid. Therefore, a high temperature superconducting composite cable with inner helical cooling tunnel and kA class current carrying ability is proposed for SMES magnet by using REBCO tape. The critical current characteristics of this internal cooling composite cable are analyzed considering the influence of anisotropy in magnetic field. A 100 m length, high temperature composite cable is manufactured in China Electric Power Research Institute (CEPRI). The critical current experimental system with a 3 kA DC current power source and a high-precision Digital Data Acquisition system have been set up to investigate the current carrying ability of a straight and a bending demo composite cable in LN2. The results show that critical current of HTS composite cable consisted of 4 REBCO tapes can achieve 780 A at 77 K self-field and the experimental I-V curve of each REBCO tape in the composite cable is not uniform because of the influence of anisotropy. When the HTS composite cable is bent, its critical current is about 90% of the straight HTS composite cable. Therefore, the design method and the proposed experimental system are proved to be effective as well. [ABSTRACT FROM AUTHOR]

• This paper proposes and introduces a new design structure for a 20 kA ReBCO high temperature superconducting current lead. • The main parameters of the new structure, such as heat load and safety performance, were studied through theoretical calculations. • Key performance experiments were conducted on the samples. • The results show that the new design structure is significantly superior to the first generation HTSCL and the simple ReBCO design structure in many performance aspects. This paper proposes and introduces a new design structure for a 20 kA ReBCO high temperature superconducting current lead (HTSCL). The main parameters of the new structure, such as heat load and safety performance, were studied through theoretical calculations. Subsequently, critical performance experiments were conducted on the samples. The results show that the new design structure is significantly superior to the first generation HTSCL and the simple ReBCO design structure in many performance aspects and thus has certain application prospects. This research will accumulate valuable experience for the application of ReBCO high-temperature superconducting materials. [ABSTRACT FROM AUTHOR]

Actual progress of High Temperature Superconductor (HTS) RE BCO tapes show an enormous increase of critical current density especially at highest field. These results offer new possibilities for the application of RE BCO for large fusion magnets with a magnetic field well above 13 T at the conductor and a large temperature margin > 10 K. In parallel promising new proposals for the formation of high current HTS fusion conductors from these RE BCO tapes are emerging, promising the applicability for fusion magnets, e.g. for a TF magnet of an European DEMO. The actual progress of RE BCO tapes and several promising HTS fusion cable proposals will be highlighted which open the path to future high field HTS magnets for fusion. Using such RE BCO tape data, calculations and modeling of a TF coil for an EU-DEMO based on the PROCESS code will be presented, showing that with today's HTS performance an EU-DEMO TF conductor is feasible, which can be operated at 4.5 K with a maximum field at the conductor of approximately 13.3 T (magnetic field at the plasma center approximately 6.8 T) with a temperature margin of approximately 12 K. Special attention will be given to a new stacked HTS conductor fabrication technique proposed by KIT which is optimized for long length production of HTS strands with high engineering current density. Due to the cross shape of the soldered superconductor stacked, this type of strand is called HTS CrossConductor or HTS CroCo. The implementation of the simple, reliable and easily scalable fabrication routine will be outlined. Measurement results of first samples show the expected critical current calculated from the individual tape opening the way to a compact kA-class HTS strands. These HTS strands can be used as a basis to build a fusion cable for a TF-coil for an EU-DEMO. [ABSTRACT FROM AUTHOR]

The use of second-generation high-temperature superconducting-coated conductors enables an enhancement of the performance of undulator magnets. However, preventing the motion of the wire and providing sufficient conduction cooling to the winding stacks have remained challenges. In this study, we have evaluated epoxy impregnation techniques to address these issues. Epoxy resin was prepared with different nanopowders and the effect on the performance of the undulator coil pack was investigated. All epoxy impregnated coils showed smaller n values and some degree of deterioration of the critical current Ic. The Ic degradation was most pronounced for epoxy mixed with high aspect ratio multiwalled carbon nanotubes (MWCNTs). It has been found that the crack formation in the epoxy results in plastic deformation of the copper stabilizer layer, which causes the underlying ceramic REBCO superconducting layer to crack resulting in degradation of the superconducting tape performance. Careful adjustment of epoxy thickness surrounding the superconductor and the powder ratio in the epoxy eliminate the performance degradation. [ABSTRACT FROM PUBLISHER]

REBCO coated tapes have become one of the most practical superconducting materials, which have been considered in the design of high-field magnets for fusion in the future. At present, several manufacturers are able to produce commercial REBCO tapes. During the fabrication and operation of REBCO magnets, REBCO tapes are subjected to tension, compression, bending, and torsion loads, resulting in applied strains. However, the critical current (I c) of REBCO tape is strain dependence. Therefore, the clear I c performance of a single REBCO tape under applied uniaxial strain is required before designing REBCO conductors/magnets in order to help select an appropriate tape specification and manufacturer. In this paper, several measurements of I c and n-value versus applied uniaxial strain were performed on different kinds of REBCO tapes, which were produced by Shanghai Superconductor Technology and Fujikura at 77 K with self-field on the U-spring device. The width of the REBCO tape is from 3 mm to 5 mm, and the thickness of the substrate is from 25 μm to 50 μm. The results show that the I c of most of the tapes are reversible under applied uniaxial compressive strain. The width of the tape and the thickness of the substrate affects the irreversible tensile strain limit. The n-value of the REBCO tape hardly depends on the strain condition. [ABSTRACT FROM AUTHOR]

Two types of mechanical contact joint termination methods for a 2G YBCO cable have been developed. Each YBCO tape of a cable is connected to a BSCCO tape while the other ends of BSCCO tapes are bundled together and soldered inside a copper tube. Another termination method uses only YBCO tapes. It has been confirmed that both joint termination methods are very useful for 2G HTS cables. Mechanical contact joint resistances between YBCO-BSCCO tapes and YBCO-YBCO tapes have been measured under various contact pressures and contact surface conditions at 77 K. Joint resistance distribution among the tapes in the cable have been also evaluated for both termination methods. These contact joint methods can be used for a demountable joint. Joint resistance is greatly reduced with increasing applied pressure especially for YBCO-YBCO joints. However, in the case of a YBCO-BSCCO joint, the BSCCO tapes may degrade at high pressure. The contact pressure should be optimized to obtain low joint resistance. [ABSTRACT FROM PUBLISHER]

Abstract: RE1Ba2Cu3O7-≏(RE: Rare Earth, Y, Gd and so on, REBCO) superconducting tapes have high performance in critical current density, Jc, property even in high magnetic field and at liquid nitrogen temperature. We have proposed the ac loss reduction method of REBCO superconducting tape, which are the combination of a laser–scribing into a multifilamentary structure and a special winding process. Using the ac loss reduction technique, we could realize REBCO superconducting transformers with the advantage of light weight, compactness and high efficiency in comparison to conventional one. Further we aim to add a current limiting function to REBCO superconducting transformers. Recently we manufactured a 10kVA four-winding transformer with REBCO tapes. We carried out a sudden short circuit test and investigated the response against the fault excess current. We developed a numerical analysis program so as to quantitatively simulate the phenomena taking into account of a flux-flow resistance. As a result, it was shown that the whole of the REBCO winding did not shift to normal state even though the current exceeded the critical current all over the length. In this paper, we report the outlines. [Copyright &y& Elsevier]

The design and fabrication of a 32 T, 32 mm cold bore superconducting magnet with high field REBCO inner coils is underway at the NHMFL. In support of the design, conductor characterization measurements have been made including critical current as a function of field, field orientation, temperature, and strain on conductors and joints. Various conductor and turn insulation systems were examined. The selected coil fabrication method for the 32 T magnet is pancake wind, dry wind coils with sol-gel insulation on a stainless steel co-wind. Quench protection of the REBCO coils by distributed heaters is under development. Small REBCO coils have been made and tested in a 20 T background field to demonstrate performance of the technology. The design of the 32 T magnet is described, including coil configuration and conductor lengths, fraction of critical current, selection of conductor copper content for protection, and stress in the windings. [ABSTRACT FROM PUBLISHER]

In this paper we analyse numerically and experimentally the quench behavior of Cu-stabilized second-generation high temperature superconducting (2G HTS) wires at self-field and in adiabatic conditions. The electric field profiles along the superconductor after applying an energy pulse to the conductor have been obtained together with the parameters characterizing the quench: minimum quench energy (MQE) and the normal zone propagation velocity (NZPV). The analysis has been performed at different temperatures, T, between 72 K and 77 K, and at different applied currents, I/Ic(T)<1, Ic being the critical current. Our analysis shows that the numerical results obtained by finite element method (FEM) are closer to the experimental MQE values when the contribution of the thermal mass of the heater is taken into account. [ABSTRACT FROM AUTHOR]

TmBa2Cu3O7-x films which is one of the (Rare earth)Ba2Cu3O7-x high temperature superconductors with small ionic radius of rare earth element, were deposited on STO (100) single crystal substrates and Y2O3/YSZ/CeO2 buffered metal substrates by pulsed laser deposition. The Jc (77 K) and the value of onset TC of TmBCO thin film on STO substrate was 4.5 MA/cm2 and 86 K, respectively. The JC of TmBCO coated conductor on metal substrate was 1 MA/cm2. In-field property measurement was carried out at temperatures between 10 K and 77 K in magnetic filed up to 6 T in PPMS system. This is the first report, to the best of our knowledge, of TmBCO thin films and coated conductors with TmBCO film as the superconducting layer which have critical current densities at 77 K of 4.5 MA/cm2 and 1 MA/cm2, respectively. The superconducting properties of TmBCO films and the possibility of using TmBCO film as the superconducting layer of the HTS coated conductor, were investigated. [ABSTRACT FROM AUTHOR]

Abstract: Nanoparticles should be strong artificial pinning centers in high-temperature superconducting films. We successfully used pulse laser deposition to introduce gold nanoparticles in REBa2Cu3O7−δ (RE=Y, Gd) films. We used small angle X-ray scattering (SAXS) to obtain macroscopic information for the nanoparticles. SAXS showed that the average spacing and radius of the nanoparticles were 110–160nm and 14–18nm, respectively, which were consistent with the results from transmission electron microscopy. SAXS also suggested that the interface between the REBa2Cu3O7−δ matrix and the nanoparticles is sharp. This indicated that gold nanoparticles could work as strong artificial pinning centers. [Copyright &y& Elsevier]

We have studied the microstructures of subgrains in large single-domain RE–Ba–Cu–O (RE=Y, Nd, Sm) bulk superconductors through microscopic observation and microarea X-ray pole figure analyses. The misorientation angle of subgrains increases as the crystal growth proceeds, and thus more crystal defects such as dislocations are seen at the later stage of the growth. Electron backscatter diffraction technique was successfully utilized for characterizing the subgrain boundaries. Electric and magnetic measurements for several samples containing different subgrain geometries have been performed. The results of I–V and resistivity measurements indicated that subgrains act as weak-links especially in a high magnetic field region. [Copyright &y& Elsevier]

We have studied the microstructures of subgrains in large single-domain RE123 (RE=Y, Sm) bulk superconductors through microscopic observation and X-ray pole figure analyses. We have found that misorientation of the subgrains increases along with the crystal growth, and also that the misorientation has positive relation to the size and concentration of the second-phase particles. Such subgrains are considered to affect current carrying capabilities in bulk materials, so that we performed magnetic and electric measurements for several samples having different subgrain structures. The relationships between obtained Jc–B or AC transport characteristics and subgrain geometries are discussed. [ABSTRACT FROM AUTHOR]

Thin films of the superconducting Nd1+xBa2−xCu3O7−δ (NBCO) and Y1(NdxBa2−x)Cu3O7−δ (YNBCO) compounds have been deposited by dc magnetron sputtering and diode high pressure oxygen sputtering. Different techniques, including scanning tunneling microscopy, atomic force microscopy, X-ray diffraction and transmission electron microscopy (TEM) have been used to study the film microstructures and the surface morphology. It is shown that the Nd/Ba exchange promotes a 2D heteroepitaxial growth in the case of the NBCO films deposited on (1 0 0) SrTiO3 substrates, with a suppression of the characteristic 3D spirals structures. On the contrary in YNBCO the Nd/Ba exchange does not provide a driving force for the suppression of screw-dislocations, since spirals or towers originated by screw and half loop dislocations are observed on the surface. TEM reveals that anti-phase boundaries are eliminated during the growth of NBCO films thanks to the Nd/Ba exchange while this mechanism is not operating in the case of YNBCO films. [Copyright &y& Elsevier]

• The critical current degradation of three different YBCO coated conductors under bending and uniaxial tensile strain at 77 K and self-field were investigated. • The bending tensile strain and uniaxial tensile strain dependence of critical current performance have a good agreement. • All the tapes showed better bending tolerance under compressive strain than tensile strain. Bending tolerance is one of the most fundamental mechanical properties of REBCO coated conductors for application to a superconducting coil. In this study, we investigated critical current degradation of REBCO coated conductors under bending and uniaxial tensile strain at 77 K and self-field with three different kinds of production from SuperPower Inc, Suzhou Advanced Materials Research Institute (SAMRI) and Shanghai Superconductor Technology (STT), respectively. All the tapes showed better bending tolerance under compressive strain than tensile strain, particularly for STT tapes, which showed no Ic degradation in compressive bending strain even with bending radius of 4.5 mm, but a 5% Ic degradation in tensile strain with bending radius of 6–6.5 mm. A uniaxial tensile strain test was also carried out to verify the dependence of Ic under tensile bending strain, the test results showed a good agreement between them. The tensile strain tolerance was 0.28–0.29% for STT tapes, 0.4–0.43% for SAMRI tapes, and 0.5–0.55% for SuperPower tapes. [ABSTRACT FROM AUTHOR]

Since the discovery of high-temperature superconductivity, significant progress in the fabrication of REBCO-based (Rare Earth Barium Copper mixed Oxides) thin-films superconductors has been achieved. In our review, we described the approaches and possibilities of the improvement of superconducting properties by the introduction of nanosized pinning centers. We focused on the synthesis and viability of the material for artificial pinning centers and methods used for the introduction of the pinning centers into superconducting REBCO-based thin-films. This article summarizes available materials and procedures regardless of the financial cost of the individual method. According to available literature, the most significant superconducting REBCO tapes can be obtained when a combination of 1D and 0D nanoparticles are used for nanoscale pinning. [ABSTRACT FROM AUTHOR]