Showing papers in "Physica C-superconductivity and Its Applications in 2002"
TL;DR: The first man-loading high temperature superconducting Maglev test vehicle in the world is reported in this paper, where the onboard superconductors are melt-textured YBaCuO bulks.
Abstract: The first man-loading high temperature superconducting Maglev test vehicle in the world is reported. This vehicle was first tested successfully on December 31, 2000 in the Applied Superconductivity Laboratory, Southwest Jiaotong University, China. Heretofore over 17,000 passengers took the vehicle, and it operates very well from beginning to now. The function of suspension is separated from one of propulsion. The high temperature superconducting Maglev provides inherent stable forces both in the levitation and in the guidance direction. The vehicle is 3.5 m long, 1.2 m wide, and 0.8 m high. When five people stand on vehicle and the total weight is 530 kg, the net levitation gap is more than 20 mm. The whole vehicle system includes three parts, vehicle body, guideway and controlling system. The high temperature superconducting Maglev equipment on board is the most important for the system. The onboard superconductors are melt-textured YBaCuO bulks. The superconductors are fixed on the bottom of liquid nitrogen vessels and cooled by liquid nitrogen. The guideway consists of two parallel permanent magnetic tracks, whose surface concentrating magnetic field is up to 1.2 T. The guideway is 15.5 m long.
434 citations
TL;DR: A new cell-based circuit design for single flux quantum (SFQ) circuit, called CONNECT cell library, which can easily expand designable circuit scale without the time-consuming dynamic simulations of whole circuits.
Abstract: To expand designable circuit scale, we have developed a new cell-based circuit design for single flux quantum (SFQ) circuit. We call it CONNECT cell library. The CONNECT cell library has over 100 cells at present. Each CONNECT cell consists of a Verilog digital behavior model, circuit information, and a physical layout. All circuit parameter values have been optimized for obtaining the widest margins and minimizing interactions between cells. At the layout level, we have defined a minimum standard cell size and made cell height and width a multiple of the size. Using this cell library, we can easily expand circuit scale without the time-consuming dynamic simulations of whole circuits. For estimation of the reliability of the library, we designed and fabricated test circuits using CONNECT cells. We demonstrated experimentally correct operations, which means the CONNECT cell library is sufficiently reliable.
296 citations
TL;DR: In this article, the authors review the superconducting quantum interface device (SQUID) multiplexer schemes that are being developed to instrument large-format arrays of super-conducting transition-edge sensors.
Abstract: We review the superconducting quantum interface device (SQUID) multiplexer schemes that are being developed to instrument large-format arrays of superconducting transition-edge sensors. We discuss the choice of an orthogonal basis set to represent the multiplexed signal (such as time or frequency) and the practical issues of implementation, including bandwidth-limiting filters, SQUID noise, and power dissipation.
132 citations
TL;DR: In this article, the authors present a phase 6.4 MVA superconducting fault current limiter (SCFCL) demonstrator, which is based on a novel conductor design and innovative Bi-2212 ceramic fabrication technology.
Abstract: ABB has recently successfully developed and tested a single phase 6.4 MVA superconducting fault current limiter (SCFCL) demonstrator, which is based on a novel conductor design and innovative Bi-2212 ceramic fabrication technology. At present, it represents the highest rated power reported for HTS based SCFCL. The employed SCFCL component is a composite consisting of layers of bulk Bi-2212 ceramic, resistive metallic electrical bypass and fibre reinforced plastic (FRP). The Bi-2212 conductor is fabricated in sheets with an area of 30×40 cm 2 by using a modified partial melt process and is subsequently structured into long length meanders. The as-processed Bi-2212 is non-textured and exhibits a uniform j c in the range of 3000–5000 A/cm 2 . The employment of a robust bypass facilitates a uniform quench in the SCFCL component during a fault event. Depending on the level of prospective fault current, a fault current is typically reduced to around 10 times nominal current in the first current peak and further to 2–5 times after 50 ms into the fault. Test and simulation results of the 6.4 MVA demonstrator, together with the application prospects of such Bi-2212 based SCFCL are presented and discussed.
126 citations
TL;DR: In this paper, the authors reported the successful replacement of B by C in the series MgB2−xCx for values of x upto 0.3 is reported.
Abstract: Successful replacement of B by C in the series MgB2−xCx for values of x upto 0.3 is reported. Resistivity and ac susceptibility measurements have been carried out in the samples. Solubility of carbon, inferred from the observed change in the lattice parameter with carbon content indicates that carbon substitutes upto x=0.30 into the MgB2 lattice. The superconducting transition temperature, Tc measured both by zero resistivity and the onset of the diamagnetic signal shows a systematic decrease with increase in carbon content upto x=0.30, beyond which the volume fraction decreases drastically. The temperature dependence of resistivity in the normal state fits to the Bloch–Gruneisen formula for all the carbon compositions studied. The Debye temperature, θD, extracted from the fit, is seen to decrease with carbon content from 900 to 525 K, whereas the electron–phonon interaction parameter, λ, obtained from the McMillan equation using the measured Tc and θD, is seen to increase monotonically from 0.8 in MgB2 to 0.9 in the x=0.50 sample. The ratio of the resistivities between 300 and 40 K versus Tc is seen to follow the Testardi correlation for the C substituted samples. The decrease in Tc is argued to mainly arise due to large decrease in θD with C concentration and a decrease in the hole density of states at N(EF).
121 citations
TL;DR: In this paper, applied field measurements were taken on short samples of YBa 2 Cu 3 O 7− δ (YBCO) thin films which were divided into narrow filaments.
Abstract: Magnetization vs. applied field measurements ( M–H loops) were taken on short samples of YBa 2 Cu 3 O 7− δ (YBCO) thin films which were divided into narrow filaments. The YBCO was deposited using pulsed laser deposition onto single-crystal LaAlO 3 substrates, with a range of film thicknesses from 0.25 to 0.33 μm. Using a YAG laser, the thin films were patterned into linear striations by removing strips of the superconductor by laser ablation. The resulting striated filamentary structure serves to reduce the effective width of the YBCO films and hence the hysteresis loss in the superconducting samples. The magnetization measurements were taken over the temperature range of 4.2–77 K in applied fields of 0–17 kOe using a vibrating sample magnetometer. The measured hysteresis losses show a highly linear relationship between superconductor filament width and hysteresis loss as anticipated. However, the laser ablation process did result in the redeposition of YBCO along the edges of individual filaments. Degradation of T c and J c due to the ablation process is discussed.
106 citations
TL;DR: The system Mg x B 2 has been studied to investigate possible nonstoichiometry in MgB 2, a line compound with a possible Mg vacancy content of about 1% as discussed by the authors.
Abstract: The system Mg x B 2 has been studied to investigate possible nonstoichiometry in MgB 2 . When synthesized at 850 °C, MgB 2 is a line compound with a possible Mg vacancy content of about 1%. Small changes in lattice constants as a function of starting composition result from grain-interaction stresses, whose character is different in the Mg-rich, near-stoichiometric, and Mg-deficient regimes. A small linear decrease of the superconducting transition temperature, T c , in the Mg-rich regime results from accidental impurity doping.
98 citations
TL;DR: A detailed overview of NDE methods using SQUID magnetometers is given in this article, along with a brief summaries of recent application highlights and a comparison of different NDE techniques.
Abstract: By presenting brief summaries of recent application highlights, an overview of NDE methods using SQUIDs is given. Bridge inspection with a SQUID array integrated with a yoke magnet excitation was shown by scanning along the pre-stressed steel of bridges and verified by opening the bridge deck. As the construction of the megaliner Airbus aircraft progresses, testing procedures for extremely thick-walled structures are needed. Defects at a depth of up to 40 mm were measured in a bolted three-layer aluminum sample with a total thickness of 62 mm. For the investigation of aircraft wheels, a remote eddy current (EC) excitation scheme yields better depth selectivity. Defects with an inside penetration of only 10% could be detected. SQUID magnetometers are well suited for pulsed EC techniques which cover a broader depth range than standard single frequency EC. An inversion procedure is presented providing a tomographic-like conductivity image of stacked aluminum samples. A recent SQUID application is nondestructive testing of niobium sheets used for superconducting cavities of particle accelerators. The detection of tantalum inclusions and other impurities which lower the cavity performance is based on the measurement of local current inhomogeneities caused by EC excitation or thermal gradients. Alternate techniques using SQUID sensors, such as modulated excitation arrays, rotating field schemes, sensor multiplexing, magnetic moment detection, and microscopy setups, are discussed.
94 citations
TL;DR: Superconductivity with T c above 9 K was found in metal-deficient NbB 2 prepared under 5 GPa, while no clear superconductivity was observed down to 3 K as mentioned in this paper.
Abstract: Superconductivity with T c above 9 K was found in metal-deficient NbB 2 prepared under 5 GPa, while no clear superconductivity was observed down to 3 K in stoichiometric NbB 2 . The superconductivity was observed above x =0.04 in Nb 1− x B 2 , and the lattice parameters also changed abruptly at x =0.04. As x increased, the transition temperature T c slightly rose and fell with the maximum value of 9.2 K at x =0.24 for the samples sintered at 5 GPa and 1200 °C. The T c -value changed in the range from 7 to 9 K, depending on the sintering pressure. A series of Ta 1− x B 2 (0⩽ x ⩽0.24) was also synthesized under high pressure to examine a special effect of high-pressure synthesis.
82 citations
TL;DR: In this article, it was shown that a combination of synthetic gradiometers, adaptive signal processing, and moderately shielded rooms can provide environmental noise attenuation in excess of 10 7.
Abstract: The brain's magnetic signals are much weaker than the magnetic disturbances inside the typical commercial magnetically-shielded room. Magnetic noise arises from far-field environmental sources (power lines, vehicles, etc.) and from near-field biological sources (electrically active tissues, such as muscle, heart, unwanted brain signals, etc.). Some form of inverse solution is generally used to solve for the sources that account for the MEG measurements. However, the inversion problem is non-unique and ill defined. Given the large amounts of noise and the non-uniqueness, how can MEG inversion succeed? One must provide methods for efficient attenuation of environmental noise, combined with MEG localization methods that are robust against the background clutter. Noise cancellation methods will be reviewed, and it will be shown that a combination of synthetic gradiometers, adaptive signal processing, and moderately shielded rooms can provide environmental noise attenuation in excess of 10 7 . Two types of MEG signal analysis techniques will be discussed: those depending solely on prior noise cancellation (e.g., equivalent current dipole fit and minimum norm), and those intrinsically providing additional cancellation of far and near field noise (e.g., beamformers). The principles and behavior of beamformers for variations in signal and noise will be explained. Several beamformer classes will be discussed, and the presentation will conclude with examples of their clinical applications.
82 citations
TL;DR: In this paper, a biaxially textured, strengthened Ni substrate with small alloying additions of W and Fe is reported, which has significantly improved mechanical properties compared to 99.99% Ni and surface characteristics which are similar to that of 99.
Abstract: Fabrication of a biaxially textured, strengthened Ni substrate with small alloying additions of W and Fe is reported. The substrates have significantly improved mechanical properties compared to 99.99% Ni and surface characteristics which are similar to that of 99.99% Ni substrates. High quality oxide buffer layers can be deposited on these substrates without the need for any additional surface modification steps. Grain boundary misorientation distributions obtained from the substrate show a predominant fraction of low-angle grain boundaries. A high critical current density, J c , of 1.9 MA/cm 2 at 77 K, self-field is demonstrated on this substrate using a multilayer configuration of YBCO/CeO 2 /YSZ/Y 2 O 3 / Ni–3at.%W–1.7at.%Fe. This translates to a I c /width of 59 A/cm at 77 K and self-field. J c at 0.5 T is reduced by only 21% indicating strongly-linked grain boundaries in the YBCO film on this substrate.
TL;DR: The intermetallic compounds AAl 2− x Si x, where A=Ca, Sr or Ba, crystallize in the C32 structure, same as the recently discovered MgB 2 with a high superconducting transition temperature of 39 K as mentioned in this paper.
Abstract: The intermetallic compounds AAl 2− x Si x , where A=Ca, Sr or Ba, crystallize in the C32 structure, same as the recently discovered MgB 2 with a high superconducting transition temperature of 39 K. For x =1, superconductivity has been observed in AAlSi with A=Ca and Sr, but not with A=Ba. The transition temperatures are 7.8 and 5.1 K, respectively for CaAlSi and SrAlSi. The CaAl 2− x Si x compound system display a T c -peak at x =1, a possible x -induced electronic transition at x ∼0.75 and a possible miscibility gap near x ∼1.1 which results in a very broad superconducting transition. The Seebeck coefficients of AAlSi indicate that their carriers are predominantly electrons in nature, in contrast to the holes in MgB 2 .
TL;DR: In this article, a low noise heterodyne receiver was developed for the terahertz range using a phonon-cooled hot-electron bolometric mixer based on 3.5 nm thick superconducting NbN film.
Abstract: A low noise heterodyne receiver is being developed for the terahertz range using a phonon-cooled hot-electron bolometric mixer based on 3.5 nm thick superconducting NbN film. In the 1–2 GHz intermediate frequency band the double-sideband receiver noise temperature was 450 K at 0.6 THz, 700 K at 1.6 THz and 1100 K at 2.5 THz. In the 3–8 GHz IF band the lowest receiver noise temperature was 700 K at 0.6 THz, 1500 K at 1.6 THz and 3000 K at 2.5 THz while it increased by a factor of 3 towards 8 GHz.
TL;DR: In this article, a qubit circuit based on the single Cooper-pair transistor (which consists of two ultrasmall Josephson junctions in series) connected in parallel with a large Josephson junction is discussed.
Abstract: We discuss a qubit circuit based on the single Cooper-pair transistor (which consists of two ultrasmall Josephson junctions in series) connected in parallel with a large Josephson junction. The switching of this junction out of its zero-voltage state is used to readout the qubit. We report measurements of the discriminating power of the readout process, and we discuss its back-action on the qubit.
TL;DR: In this article, the authors observed that the dendrites are formed only in areas lacking the thermal conductor and that when dendritic development in the uncovered part they never invade into the covered region.
Abstract: The dendritic patterns of magnetic flux motion formed during field penetration into an MgB2 film were observed using magneto-optic imaging. To investigate the origin of the dendrites, experiments were performed where the sample was partially covered with an thermally conducting foil serving as an efficient heat sink. We observed that the dendrites are formed only in areas lacking the thermal conductor. When dendrites develop in the uncovered part they never invade into the covered region. The results strongly suggest that the dendritic instability is thermal in origin. 2001 Published by Elsevier Science B.V.
TL;DR: In this article, the potential of this metallurgical system for rolling assisted biaxially textured substrate (RABiTS) tapes of high performance was investigated and the effect of the initial grain size on the final texture quality was shown.
Abstract: The investigation of Ni–W alloys in the concentration range of solid solubility of tungsten in nickel proved the potential of this metallurgical system for rolling assisted biaxially textured substrate (RABiTS) tapes of high performance. The cube texture of Ni+5 at.%W was characterized by a maximum of the deviation frequency at about 4°. For this material the beneficial effect of the initial grain size on the final texture quality was shown. The YBCO (YBa 2 Cu 3 O 7− δ ) type coatings on CeO 2 buffer layers carried absolute currents up to I =130 A at 77 K. A critical current density of j c =1.2 MA/cm 2 was achieved at 77 K and zero field on tapes up to 20 cm long.
TL;DR: A series of biaxially textured Ni1−xCrx materials, with compositions x=0, 7, 9, 11, and 13 at.%Cr, have been studied for use as substrate materials in coated conductor applications with high temperature superconductors as discussed by the authors.
Abstract: A series of biaxially textured Ni1−xCrx materials, with compositions x=0, 7, 9, 11, and 13 at.%Cr, have been studied for use as substrate materials in coated conductor applications with high temperature superconductors. The magnetic properties were investigated, including the hysteretic loss in a Ni–7at.%Cr sample that was controllably deformed; for comparison, the loss was also measured in a similarly deformed pure Ni substrate. Complementary X-ray diffraction studies show that thermomechanical processing produces nearly complete {1 0 0}〈1 0 0〉 cube texturing, as desired for applications.
TL;DR: In this paper, the authors investigated the relationship between precompression and irreversible strain limit with a set of tapes made with different filling factors as well as an in situ Inconel 600-reinforced tape.
Abstract: The behaviour of the critical current in longitudinally strained Bi,Pb(2223) tapes shows a strain-insensitive plateau up to an irreversible strain limit e irr . For higher strains, the formation of cracks induces an abrupt decrease of the critical current. We investigate the relationship between precompression and irreversible strain limit with a set of tapes made with different filling factors as well as an in situ Inconel 600-reinforced tape. I c ( e ) curves were measured in a longitudinal strain apparatus at 77 K. The precompression at the measurement temperature is numerically estimated for each sample as well as the evolution of precompression during the cool-down. These calculated values are compared to the fracture susceptibility of extracted filaments, which gives an empirical estimate of the precompression. The main hypothesis of the “Irreversible I c Reduction Model” is confirmed, i.e. the irreversible strain limit essentially depends on precompression. However, we also found that the regime where I c remains constant contains a tensile component: the plateau extends beyond the external tensile strain needed to relieve the thermal precompression and includes a regime where the ceramic is further elongated non-destructively. This non-destructive deformation can be understood as a “connected-grains” behaviour, and extends the strain-insensitive plateau ∼0.1% beyond the precompression strain. This value is confirmed with a three points bending experiment performed on single filaments which gives a similar value for the bending failure strain. A comparable regime was found to exist also under compressive strain. These non-destructive regimes are of great importance for practical applications since up to a certain level the precompression can develop without any I c degradation.
TL;DR: In this paper, a powder-in-tube (P2T) method was used to fabricate MgB2 tapes with high packing density and high anisotropy with respect to the field direction.
Abstract: We fabricated MgB2 tapes using a powder-in-tube method without any heat treatment. Commercial MgB2 powder was put into stainless steel, Cu–Ni and pure Cu tubes, and the powder/tube composites were cold worked into tapes. The packing density of the MgB2 layers and Jc increased with increasing the mechanical hardness of the tube. A very dense and hard MgB2 layer was obtained in the stainless-steel sheathed tape, and a high Jc of ∼4.5×105 A/cm2 at 4.2 K and zero field was obtained by extrapolating the Jc–B curves. Some c-axis grain alignment of the MgB2 layer was obtained for the tape conductors. The degree of this grain alignment increased with increasing the hardness of the sheath material. This grain alignment brought about the anisotropy in Jc with respect to the field direction. A large anisotropy factor of about 10 was obtained in a field of 7 T for the MgB2/(SUS 316) tape.
TL;DR: The main task of the project was to demonstrate the feasibility of basic concepts of HTS conductors in the rotor of synchronous machines, including operation with both cooling systems and driving the stator from the grid as well as by a power inverter.
Abstract: Applying HTS conductors in the rotor of synchronous machines allows the design of future motors or generators that are lighter, more compact and feature an improved coefficient of performance. To address these goals a project collaboration was installed within Siemens, including Automation & Drives, Large Drives as a leading supplier of electrical machines, Corporate Technology as a competence center for superconducting technology, and other partners. The main task of the project was to demonstrate the feasibility of basic concepts. The rotor was built from racetrack coils of Bi-2223 HTS tape conductor, these were assembled on a core and fixed by a bandage of glass-fibre composite. Rotor coil cooling is performed by thermal conduction, one end of the motor shaft is hollow to give access for the cooling system. Two cooling systems were designed and operated successfully: firstly an open circuit using cold gaseous helium from a storage vessel, but also a closed circuit system based on a cryogenerator. To take advantage of the increased rotor induction levels the stator winding was designed as an air gap winding. This was manufactured and fitted in a standard motor housing. After assembling of the whole system in a test facility with a DC machine load experiments have been started to prove the validity of our design, including operation with both cooling systems and driving the stator from the grid as well as by a power inverter.
TL;DR: In this article, hot-electron bolometer frequency downconverters (mixers) based on superconducting films have been found to offer record sensitivity for THz receivers to be used in radio astronomy.
Abstract: Hot-electron bolometer frequency down-converters (mixers) based on superconducting films have been found to offer record sensitivity for THz receivers to be used in radio astronomy. In this paper we focus on mixers using NbN phonon-cooled devices. We show that recent theoretical models predict a performance that agrees well with experiments. Important mixer properties such as conversion efficiency, noise (sensitivity), and their variation with the intermediate frequency are discussed in view of our physical understanding using both experiments and theory. We conclude that despite the excellent results obtained so far, further improvements are to be expected when technology has developed further and unnecessary shortcomings in the measurement set-up have been taken care of.
TL;DR: In this article, the effects of Pr-doping on the critical current density Jc and the critical temperature Tc in YBa2Cu3O7−δ have been investigated.
Abstract: The effects of Pr-doping on the critical current density Jc and the critical temperature Tc in YBa2Cu3O7−δ (YBCO) have been investigated. In spite of the monotonic decrease in Tc with increasing Pr-concentration (x), the increasing of Jc occurs as a field is applied and Jc displays a maximum at a certain x. Moreover, this maximum shifts to lower x by increasing fields. The characteristic behavior of Jc with Pr-doping can be explained in terms of the counterbalance of two different effects simultaneously caused by Pr-doping: the suppression of matrix superconductivity which leads to the decrease in depairing critical current density J0, and the formation of nanometric inhomogeneity which leads to the enhancement of pinning force.
TL;DR: In this article, a superconducting YBa2Cu3O7−δ nanopowder is prepared by the citrate-gel modification of the sol-gel method.
Abstract: Superconducting YBa2Cu3O7−δ nanopowder is prepared by the citrate-gel modification of the sol–gel method. Most important advantages of this method are the homogeneity at atomic level and possibility to reduce the calcination temperature to limit thermal agglomeration of the particles. A preparation temperature ⩽800 °C is used with a deoxydation step in Ar before the final oxidation. The X-ray diffraction data confirm the orthorhombic structure of the nanopowder. Superconducting properties are investigated with a SQUID magnetometer showing that the global Tc=92 K. Single grains of the powder have average diameter of 60–80 nm, depending on the calcination process used. The grains are weakly connected stacks of flat particles having thickness of a few nanometer.
TL;DR: In this paper, both Co and Fe were incorporated into the MgB 2 lattice to some extent and small amounts of Co or Fe decreased the T c(0)-values but did not destroy the superconducting behavior.
Abstract: The addition of Sn to the preparation of MgB 2 led to the formation of Mg 2 Sn. Both Co and Fe were to some extent incorporated into the MgB 2 lattice. Small amounts of Co or Fe decreased the T c(0) -values but did not destroy the superconducting behavior of MgB 2 . Larger amounts of Co produced amorphous material and CoB. Fe 2 B was found at higher Fe contents as a secondary phase.
TL;DR: In this paper, the authors demonstrate a novel method of effectively patterning vortex pinning sites in single crystals of the high temperature superconductors YBa 2 Cu 3 O 7-d and Bi 2 Sr 2 CaCu 2 O x using heavy ion irradiation.
Abstract: Columnar defects induced by high-energy heavy ion irradiation constitute one of the most effective vortex pinning sites in high temperature superconductors. We demonstrate a novel method of effectively patterning vortex pinning sites in single crystals of the high temperature superconductors YBa 2 Cu 3 O 7-d and Bi 2 Sr 2 CaCu 2 O x using heavy ion irradiation. These patterns include linear channels, a lattice of squares, and asymmetric pinning gradient sites where vortices can either flow unimpeded or are trapped in spatially periodic arrangements.
TL;DR: In this paper, a powder X-ray diffraction was performed on different types of silicides and it was shown that they have the AlB 2 -type structure, in which Si and M II atoms are arranged in honeycomb layers and M I atoms are intercalated between them.
Abstract: Ternary silicides M I (M II0.5 ,Si 0.5 ) 2 (M I =Sr and Ba, M II =Al and Ga) were prepared by Ar arc melting. Powder X-ray diffraction indicates that they have the AlB 2 -type structure, in which Si and M II atoms are arranged in honeycomb layers and M I atoms are intercalated between them. Electrical resistivity and dc magnetization measurements revealed that Sr(Al 0.5 ,Si 0.5 ) 2 is superconductive, with a critical temperature for superconductivity ( T C ) of 4.2 K, while Ba(Al 0.5 ,Si 0.5 ) 2 is not at temperatures ranging above 2.0 K. Sr(Ga 0.5 ,Si 0.5 ) 2 and Ba(Ga 0.5 ,Si 0.5 ) 2 are also superconductors, with T C s of 5.1 and 3.3 K, respectively.
TL;DR: In this article, a columnar grain with a roofing-tile-shaped surface was observed in these MgO films, which were epitaxially grown on ISD-MgO-buffered Hastelloy C substrates by pulsed laser deposition.
Abstract: Highly textured MgO films were grown by the inclined-substrate deposition (ISD) technique at a high deposition rate. A columnar grain with a roofing-tile-shaped surface was observed in these MgO films. X-ray pole figure, and /and x-scan were used to characterize in-plane and out-of-plane textures. MgO films deposited when the incline angle a was 55 and 30 exhibited the best in-plane and out-of-plane texture, respectively. High-quality YBCO films were epitaxially grown on ISD-MgO-buffered Hastelloy C substrates by pulsed laser deposition. Tc ¼ 88 K, with sharp transition, and jc values of � 2 � 10 5 A/cm 2 at 77 K in zero field were observed on films 5 mm wide and 1 cm long. This work has demonstrated that biaxially textured ISD MgO buffer layers deposited on metal substrates are excellent candidates for fabrication of high-quality YBCO coated conductors. 2002 Elsevier Science B.V. All rights reserved.
TL;DR: In this article, a mesoscopic superconducting lead nanowires with high aspect ratio and diameter ranging from 40 to 270 nm have been grown by electrodeposition inside nanoporous polycarbonate membranes.
Abstract: Mesoscopic superconducting lead nanowires with high aspect ratio and diameter ranging from 40 to 270 nm have been grown by electrodeposition inside nanoporous polycarbonate membranes. Nanowires with a diameter less than 50 nm were insulators due to a poor crystal structure. The others are shown to be type II superconductors because of their small electronic mean free path, instead of being type I which is usual for the bulk form of lead. An increase in the thermodynamic critical field H-c is observed and is attributed to the small transversal dimension leading to an incomplete Meissner effect. Finally, it is demonstrated that this enhancement agrees with numerical simulations based on the Ginzburg-Landau theory. (C) 2002 Elsevier Science B.V. All rights reserved.
TL;DR: In this article, the use of single substrates as resonators for radio-frequency (RF) superconducting quantum interference devices (SQUID) operation is described, where a standard strontium-titanate substrate with dimensions 10×10×1 mm 3 serves as a tank circuit (resonator), a YBCO thin film SQUID washer structure is patterned on it, and a small rf washer washer with a step-edge junction is positioned in flip-chip geometry, thus forming a magnetometer sensor.
Abstract: We describe the use of single substrates as resonators for radio-frequency (rf) superconducting quantum interference devices (SQUID) operation. A standard strontium-titanate substrate with dimensions 10×10×1 mm 3 serves as a tank circuit (resonator), a YBCO thin film SQUID washer structure is patterned on it. On the resonator substrate, a small rf washer SQUID with a step-edge junction is positioned in flip-chip geometry, thus forming a magnetometer sensor. This resonator is inductively coupled to the readout electronics. At 77 K, the field sensitivity of this SQUID magnetometer achieved 24 fT/ Hz in the white noise range, 38 fT/ Hz at 10 Hz, and 83 fT/ Hz at 1 Hz.
TL;DR: In this paper, the microstructure of 2×12° [1−0−0]-tilt grain boundary Josephson junctions was investigated by atomic force and cross-sectional transmission electron microscopy.
Abstract: The microstructure of 2×12° [1 0 0]-tilt grain boundary Josephson junctions was investigated by atomic force and cross-sectional transmission electron microscopy. The junctions were prepared by depositing about 100 nm thick epitaxial YBa2Cu3O7 films on the vicinal bicrystal substrates of SrTiO3 with high pressure oxygen sputtering and showed a 2×12° tilt of the YBa2Cu3O7 c-axis towards the grain boundary. The film grain boundary was very straight and followed the bicrystal substrate boundary. It showed a low degree of meandering in comparison to the behaviour of conventional [0 0 1]-tilt grain boundaries. Due to step bunching the film surface exhibited a profile of 12° inclined terraces with a valley depth of 5–20 nm and at the grain boundary a straight V-shaped surface suppression of about 40 nm depth was observed. The fact that the IcRn-products of such Josephson junctions showed high values of up to 1.2 mV at 77 K and up to 8 mV at 4.2 K as well as a smaller scattering of the values for Ic and Rn in comparison to [0 0 1]-tilt grain boundaries is attributed to the observed microstructure. The junctions showed clear Shapiro steps as a response to 94 GHz microwave radiation.