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NdBCO seed crystals and high-performance GdBCO bulk superconductors were prepared successfully by a modified top-seeded melt-textured growth (TSMG) process and by Gd + 011 top-seeded infiltration growth (TSIG) process. The modified TSMG process used a new composition powder (NCP, 0.9 Nd2O3 + 2.4 BaCuO2 + CuO) instead of the conventional composition powder (CCP, NdBa2Cu3O7-x + 0.4 Nd2BaCuO5), the GdBCO bulk superconductor seeded by the self-made NdBCO seed crystal. In the whole procedure above, only one precursor powder (BaCuO2) needs to be sintered, three kinds of powder and three pellets are required, so time and energy consumption were greatly reduced. The results of thermal analysis and X-ray diffraction (XRD) patterns revealed the reaction mechanism of the modified TSMG process. Superconductivity properties of the GdBCO sample were measured employing a levitation force measurement system and a vibrating-sample magnetometer (VSM); the maximum value of the levitation force of the GdBCO sample was 44.78 N (77 k, 0.5 T); the onset superconductivity transition temperature (Tc) was approximately 93.7 K; the transition width was 6.2 K, and the maximum value of critical current density (Jc) was 1.5 × 105 A∙cm−2 (0 T, 77 K). These results indicate that, by combing the modified TSMG process and Gd + 011 TSIG process, a practical processing method for preparing the NdBCO seed crystals and the high-performance single-domain GdBCO bulk superconductors was developed. [ABSTRACT FROM AUTHOR]

Single domain YBCO bulk superconductors with different additions of ZnO have been successfully fabricated by RE011 TSIG process with a new solid phase of [(100-)(Y2OBaCuO2)+ZnO] and a new liquid phase of (Y2O3+6CuO+10BaCuO2). The effects of ZnO additions on the growth morphology, microstructure, critical temperature (), the levitation force and trapped field of the YBCO bulks have been investigated. It is found that within the range of ZnO additions =0-1.0 wt.%, all the samples are of the typical characteristic of single-domain YBCO bulk; the of the samples decreases from 92 K to 80 K when the ZnO addition increases from =0 wt.% to =1.0 wt.%; the levitation force and trapped field of the samples firstly increase and then decrease with increase of ZnO additions after going through a maximum, which is closely related with the ZnO addition and the resulting flux pinning force caused by lattice distortion due to the substitution of Zn for Cu site in the YBCO crystal; the largest levitation force 36.8 N (77 K, 0.5 T) and trapped field 0.416 T (77 K, 0.5 T) of the samples are obtained when =0.1 wt.%, respectively. This result is significantly important and helpful for us to improve the properties of YBCO bulk superconductors. [ABSTRACT FROM AUTHOR]

Chinese Fusion Engineering Test Reactor (CFETR) is a new superconducting tokamak device being designed in China, which aims at bridging the gap between ITER and DEMO, where DEMO is a tokamak demonstration fusion reactor. Two diagnostic cases, ITER-like case and towards DEMO case, have been considered for CFETR early and later operating phases, respectively. In this paper, some preliminary consideration of ITER-like case will be presented. Based on ITER diagnostic system, three versions of increased complexity and coverage of the ITER-like case diagnostic system have been developed with different goals and functions. Version A aims only machine protection and basic control. Both of version B and version C are mainly for machine protection, basic and advanced control, but version C has an increased level of redundancy necessary for improved measurements capability. The performance of these versions and needed R&D work are outlined. [ABSTRACT FROM AUTHOR]

Single-domain YBCO superconductors with different additions of nanometer Y Ba CuNbO (YNb2411), based on the solid phase of [(100- x)Y BaCuO (Y211) + x YNb2411] ( x = 3, 5, 7, 10, 12) and liquid phase of (Y211 + 9BaCuO + 6CuO), were successfully fabricated by a modified top seeded infiltration and growth process (TSIG), the growth morphology, microstructure, levitation force and the trapped magnetic field were investigated in details. Results indicate that single-domain YBCO superconductors can be fabricated with x ≤ 7 wt % but random nucleation of YBCO crystal occurs near the edge of the sample and seriously reduced the size of the single domain grown from the NdBCO seed when x ≥ 10 wt %. The YNb2411 particles were successfully introduced into the YBCO matrix, and the size of the YNb2411 particles embedded in the YBCO matrix is about 300 nm. However, agglomeration usually occurs when the addition of YNb2411 ≥ 10 wt %. As a result, the levitation force increases firstly from 32 to 42.5 N and then reduces down to 7 N with the increasing of YNb2411 additions from 3 to 7 wt % and 12 wt %. The results are helpful to improve the properties of YBCO bulk superconductors. [ABSTRACT FROM AUTHOR]

The top-seeded infiltration and growth process (TSIG) is a very effective method for the preparation of YBa 2Cu 3O 7−x (YBCO) bulk superconductors. In this paper, single-domain YBCO bulk superconductors with different ratio of nanoscale Y 2Ba 4CuBiO y (YBi2411) inclusions have been fabricated by TSIG process. The growth morphology, microstructure and levitation force of the YBCO bulks have been investigated. The amount of nanoscale YBi2411 added to Y 2BaCuO 5 (Y211) is in the range from 0.5 wt.% to 5 wt.%. It is found that the optimum proportion is obtained in the sample with 3.0 wt.% YBi2411 addition. The results are very helpful for the fabrication of high-quality single-domain YBCO bulk superconductors. [ABSTRACT FROM AUTHOR]

The top-seeded infiltration and growth process (TSIG) is an important method for the preparation of YBaCuO (YBCO) bulk superconductors. In this paper, single domain YBCO bulk superconductors with different content of nanoscale YBaCuNbO (YNb2411) inclusions have been fabricated by TSIG process. The growth morphology, microstructure and levitation force of the YBCO bulks have been investigated. It is found that the levitation force is increasing from 16.2 N to 20.9 N with the increasing of YNb2411 additions from 0 wt% to 2 wt%, and decreasing from 20.9 N to 14.0 N with the increasing of YNb2411 additions from 2 wt% to 5 wt%. The largest levitation force is obtained in the sample with 2 wt% YNb2411 addition. This is closely related with the addition content of YNb2411 nanoparticles and its distribution in the samples. [ABSTRACT FROM AUTHOR]

Na-doped single domain YBaNaCuO (YBCO, x=0.05, 0.1, 0.15, 0.2, 0.25, 0.3) bulk superconductors were prepared by a modified melt textured process and the effect of Na substitution on the levitation force of YBCO bulks have been investigated. The maximum levitation forces (MLF) are much different for samples with a different Na element content. It is found that the optimum Na element content in YBCO for the strong MLF is around x=0.2. It is also found that the addition of Na could reduce and increase the ATH of the YBCO platelet while x less than 0.1 and larger than 0.1, some of adjacent platelet grains are well intergrown each other in the sample with x=0.2 comparing to the other samples and the influence of the Na addition on the Y211 particle size is not obvious. [ABSTRACT FROM AUTHOR]

We study a hybrid quantum computing system using a nitrogen-vacancy center ensemble (NVE) as quantum memory, a current-biased Josephson junction (CBJJ) superconducting qubit fabricated in a transmission line resonator (TLR) as the quantum computing processor, and the microwave photons in TLR as the quantum data bus. The storage process is seriously treated by considering all kinds of decoherence mechanisms. Such a hybrid quantum device can also be used to create multiqubit W states of NVEs through a common CBJJ. The experimental feasibility is achieved using currently available technology. [ABSTRACT FROM AUTHOR]

We report a successful observation of pressure-induced superconductivity in a topological compound Bi21e3 with Tc of ∼3 K between 3 to 6 GPa. The combined high-pressure structure investigations with synchrotron radiation indicated that the superconductivity occurred at the ambient phase without crystal structure phase transition. The Hall effects measurements indicated the holetype carrier in the pressure-induced superconducting Bi2Te3 single crystal. Consequently, the first-principles calculations based on the structural data obtained by the Rietveld refinement of X-ray diffraction patterns at high pressure showed that the electronic structure under pressure remained topologically nontrivial. The results suggested that topological superconductivity can be realized in Bi2Te3 due to the proximity effect between superconducting bulk states and Dirac-type surface states. We also discuss the possibility that the bulk state could be a topological superconductor [ABSTRACT FROM AUTHOR]

small spacecraft model flying around a levitated globe has been designed based on magnetic force. The globe can be levitated in mid-air by the interaction between the magnets fixed at the North and South poles and the YBCO bulk superconductors installed on the globe frame near each of the poles. The magnetic track for the spacecraft is located at the equatorial circumference. When the small spacecraft with YBCO bulks is being cooled to LN temperature at a certain distance apart from the track, then the spacecraft can be automatically suspended in mid-air near the track and moved along the track without any obvious friction after a push by a hand. The model can be used as a demonstration of magnetic levitation, suspension, side suspending, magnetic bearing, flywheel energy storage, flying spacecraft principle, and can also be used as an educational experiment for the diamagnetic effect and applications of superconducting materials to students. [ABSTRACT FROM AUTHOR]

A characteristic feature of the copper oxide high-temperature superconductors is the dichotomy between the electronic excitations along the nodal (diagonal) and antinodal (parallel to the Cu–O bonds) directions in momentum space, generally assumed to be linked to the ‘d-wave’ symmetry of the superconducting state. Angle-resolved photoemission measurements in the superconducting state have revealed a quasiparticle spectrum with a d-wave gap structure that exhibits a maximum along the antinodal direction and vanishes along the nodal direction. Subsequent measurements have shown that, at low doping levels, this gap structure persists even in the high-temperature metallic state, although the nodal points of the superconducting state spread out in finite ‘Fermi arcs’. This is the so-called pseudogap phase, and it has been assumed that it is closely linked to the superconducting state, either by assigning it to fluctuating superconductivity or by invoking orders which are natural competitors of d-wave superconductors. Here we report experimental evidence that a very similar pseudogap state with a nodal–antinodal dichotomous character exists in a system that is markedly different from a superconductor: the ferromagnetic metallic groundstate of the colossal magnetoresistive bilayer manganite La1.2Sr1.8Mn2O7. Our findings therefore cast doubt on the assumption that the pseudogap state in the copper oxides and the nodal-antinodal dichotomy are hallmarks of the superconductivity state. [ABSTRACT FROM AUTHOR]

We propose a modified two-tone method that could be used for sensitive measurements of the intrinsic microwave surface impedance (Zs) of thin superconductor films and the tanδ of a low-loss dielectric. An open-gap resonator scheme is used to measure the penetration depth (l) of thin superconductor films and extract the intrinsic Zs of the superconductor films from its measured Reseff and l. We use a very small gap of 10 μm between the top plate and the rest parts of the resonator. The tanδ of rutile in the low 10-7 range and the dielectric constant as high as ∼ 110 are observed at temperatures below 10 K at ∼ 15.2 GHz, which enable to measure the Rs of the 10 mm-in-diameter YBCO films as low as ∼ 100 μΩ at the same frequency (f). The discrepancy between the Rseff at ∼ 15.2 GHz and that at ∼ 8.5 GHz scaled to ∼ 15.2 GHz appears less than 2% when the relations of Rs ∝ f² and tanδ ∝ f are used. We describe usefulness of our measurement method for measuring the intrinsic microwave properties of various superconductor samples. [ABSTRACT FROM AUTHOR]

By systematic chemical substitution of Pt and Ni in the newly discovered superconductor Nb2PdS5 (Tc ~ 6 K), we study the evolution of its superconducting properties with doping, focusing on the behavior of the upper critical field Hc2. In contrast to the previous results of Se doping on S sites, superconductivity is found to be rather robust against the Pt and Ni dopants on the one-dimensional Pd chains. Most strikingly, the reduced Hc2, i.e., the ratio of Hc2/Tc, is seen to be significantly enhanced by the heavier Pt doping but suppressed in the Ni-doped counterparts, distinct from the nearly constant value in the Se-doped samples. Our findings therefore suggest that the upper critical field of this system can be modified in a tunable fashion by chemical doping on the Pd chains with elements of varying mass numbers. The spin-orbit coupling on the Pd sites, by inference, should play an important role in the observed superconductivity and on the large upper critical field beyond the Pauli pair-breaking field. [ABSTRACT FROM AUTHOR]

We report a successful observation of pressure-induced superconductivity in a topological compound Bi21e3 with Tc of ∼3 K between 3 to 6 GPa. The combined high-pressure structure investigations with synchrotron radiation indicated that the superconductivity occurred at the ambient phase without crystal structure phase transition. The Hall effects measurements indicated the holetype carrier in the pressure-induced superconducting Bi2Te3 single crystal. Consequently, the first-principles calculations based on the structural data obtained by the Rietveld refinement of X-ray diffraction patterns at high pressure showed that the electronic structure under pressure remained topologically nontrivial. The results suggested that topological superconductivity can be realized in Bi2Te3 due to the proximity effect between superconducting bulk states and Dirac-type surface states. We also discuss the possibility that the bulk state could be a topological superconductor [ABSTRACT FROM AUTHOR]

Abstract: The induced activity, radiation damage, and compositional change of several superconductor materials, such as Nb-based alloys, V-based alloys, and MgB2, for the toroidal field (TF) and central solenoid (CS) magnets of a tokamak-type fusion reactor have been evaluated under the first wall neutron loading of 1MW/m2 with a numerical calculation. The damage rates of both Nb- and V-based alloys calculated are about (1–3)×10−4 dpa/y at the TF coils adjacent to the vacuum vessel and (2–6)×10−7 dpa/y at the surface of CS coil. The damage rate of MgB2 is about 1 order magnitude higher than those of Nb- and V-based superconducting materials. Most of the induced activity of V-based alloys and MgB2 after shutdown of the reactor is controlled by 60Co formed from Cu. Nb-based alloys are predicted to emit gamma rays for tens of thousands years due to 94Nb from Nb. In the case of the CS coils, the formation of 94Nb is minimal, and the gamma ray decay of Nb-based alloys is expected to be faster than that of V-based alloys. [Copyright &y& Elsevier]

A general feature of unconventional superconductors is the existence of a superconducting dome in the phase diagram. Here we report a series of discrete superconducting phases in the simplest iron-based superconductor, FeSe thin flakes, by continuously tuning the carrier concentration through the intercalation of Li and Na ions with a solid ionic gating technique. Such discrete superconducting phases are robust against the substitution of 20% S for Se, but they are vulnerable to the substitution of 2% Cu for Fe, highlighting the importance of the iron site being intact. The superconducting phase diagram for FeSe derivatives is given, which is distinct from that of other unconventional superconductors. [ABSTRACT FROM AUTHOR]