Search

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

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

High-temperature superconducting magnetic bearings can be suspended without contact and self-stability. They are widely used in many industries. Before the actual production of magnetic bearings, the structural design and parameter optimization are very important. The design and optimization method of radial high-temperature magnetic bearing are studied in this paper. The force calculation expression was deduced. The bearing capacity of high-temperature magnetic bearings was optimized. The performance of the radial HTSMB was analyzed and verified by FEM. [ABSTRACT FROM AUTHOR]

High-temperature superconductor (HTS) technology has been studied recently for the use with superconducting high-power transmission and distribution, motors, generators, and fault-current-limiting devices such as cables and transformers. HTS technology, which can provide a large electromotive force in a small area owing to its large current density compared to that of a normal conductor, can reduce the weight and loss of a generator when compared to the attributes of a conventional machine. Moreover, once the HTS conductor has stabilized, the challenge of cooling the windings in large-scale generators can be resolved. Therefore, the technology has been studied for application with 10-MW-class superconductor wind-turbine generators. Although an HTS conductor generator offering a higher torque density, lower weight, and higher efficiency than a conventional generator can be designed, the design must satisfy the requirements of the critical magnetic field, critical current, and critical temperature of the superconducting winding. The HTS homopolar superconducting synchronous generators have a simple structure with a fixed HTS conductor and are one of the most suitable types of generator that is able to satisfy these requirements more easily. In this paper, we propose a 10-MW homopolar-type wind-turbine generator. [ABSTRACT FROM PUBLISHER]

This paper presents a study on the coil voltage of the no-insulation (NI) high-temperature superconductor (HTS) pancake coils during fast discharging operations. Fast discharging tests are performed on both a double pancake (DP) and an single pancake (SP) NI coil. The measured coil voltages are compared with that from an equivalent circuit model, which has been widely used in previous studies. A voltage pulse is observed on both the NI coils at the beginning of the fast-discharging operation. It is much higher than that from the modeling. The peak value of the voltage pulse increases linearly with the initial current. Comparison tests show that the coupling iron core has little influence on this coil voltage pulse though the inductance of the coils is enlarged seven times by coupling iron core. This coil voltage pulse shows that, during the fast discharging operation, the NI coil has a much higher turn-to-turn resistivity at the beginning stage than that in following process. Since the coil voltage pulse can be 600 times of the modeling estimation, it may be a potential risk to the coil protection system and measuring instruments. Therefore, special attentions are required on this aspect in the design of NI magnets. [ABSTRACT FROM PUBLISHER]

The basic concept of superconductive magnetic gears (SMGs) is to maximize the benefits and impact of the magnetic gearing technology by highlighting the future perspective of SMGs to produce a more efficient and compact system. This paper deals with a new analytical method (AM) for the calculation of magnetic field distribution in an SMG. A 2-D AM based on Laplace's partial differential equations of magnetic scalar potential in the different subdomains of a magnetic gear is introduced and solved by considering the corresponding boundary conditions. The proposed method shows a significant reduction in the consumed calculation time compared with the finite-element method (FEM) and can be used as a basis for design optimizations. Two-dimensional AM results are compared against those obtained from 2-D FEM simulations, using an accurate, yet efficient, high-temperature superconductor (HTS) modeling, yielded by a detailed localized E-J power law approach combining the different aspects of HTS in a numerical method, so as to find out the benefits and validity of the presented AM. Finally, the effects of PMs and pole pieces' dimensions on torque density are realized. [ABSTRACT FROM AUTHOR]

In this paper, a high-temperature superconducting composite right/left-handed (HTS CRLH) resonator is proposed, which is constructed by microstrip spiral coupled lines and step-like microstrip lines. The dispersion characteristics of the CRLH resonator is obtained and analyzed by an equivalent circuit model and a transmission matrix method. To verify this design methodology, the HTS CRLH resonator is designed and fabricated with a compact size of 11.25 mm $\times$ 16 mm on YBa2Cu3O7 films. The power handling capability of the filter is studied. Finally, the measured and simulated results are in good agreement with each other. [ABSTRACT FROM PUBLISHER]

In this paper, the high temperature superconductor (HTS) winding and multitoothed structure are newly incorporated into the doubly salient (DS) and flux-switching (FS) machines, leading to create two new magnetless machines, namely the HTS-based multitoothed switched reluctance (HTS-MSR) and HTS-based multitoothed flux-switching (HTS-MFS) machines. Consequently, the design equations of the three machines, namely the MSR, HTS-MSR, and HTS-MFS, are formulated. The corresponding performances are analyzed by using the time-stepping finite element method (TS-FEM). By utilizing both torque-producing zones, the two HTS-based machines can achieve better performances than the MSR one. Moreover, the HTS-MFS can offer higher torque density than the HTS-MSR, but associated with larger torque ripple. [ABSTRACT FROM PUBLISHER]

This paper quantitatively compares three types of double-stator flux-modulation permanent-magnet (PM) machines, namely the vernier machine, vernier machine with HTS bulks, and magnetic-geared machine. Due to adopting the double-stator topology, these PM machines achieve the higher energy transmission and power conversion than the single-stator counterparts. Also, the design for the proposed machines are to respectively use the flux-modulation pole, HTS bulk and the flux-modulation ring for modulating the low speed rotating field of the PM rotor and the high speed rotating field of the armature windings, hence obtaining the gear effect for low speed operation. It should be noted that by using the HTS bulks can not only efficiently improve the flux modulation effect of the vernier machine, but also greatly reduce the machine flux leakage. By using the finite-element-method, their performances are compared, hence verifying the validity of the machine design. [ABSTRACT FROM PUBLISHER]

This paper proposes a novel high-temperature superconductor (HTS) brushless doubly-fed doubly-salient (BDFDS) machine, which can effectively improve the performance of this kind of BDFDS machines. In addition, a new criterion of winding arrangement with the outer-rotor topology is adopted for the proposed machine design, which can further benefit the machine characteristics. Moreover, two natural operation modes for the proposed machine are discussed. The corresponding calculation results are given to prove the validity of the proposed machine. [ABSTRACT FROM AUTHOR]

The Karlsruhe Institute of Technology (which is a merger of former Forschungszentrum Karlsruhe and Karlsruhe University) is responsible for the design, construction and testing of the high temperature superconductor (HTS) current leads for the stellarator Wendelstein 7-X (W7-X) which is presently under construction at the Greifswald branch of the Max-Planck-Institute for Plasma Physics. The current leads are of the binary type, the HTS part covering the temperature range between 4.5 K and 60 K while the heat exchanger covers the range between 60 K and room temperature being cooled by 50 K He. In total 2 prototypes and 14 series current leads are required with a nominal current of 14 kA and a maximum current of 18.2 kA. The paper describes the design and first test results of the prototype HTS current leads. [ABSTRACT FROM AUTHOR]

The Korea Electric Power Corporation (KEPCO) HTS power cable has been successfully installed and operated for feasible confirmation since 2006 at Gochang power test center. The 3-phase 100 m long HTS power cable with 22.9 kV/1.25 kA was manufactured and cooled by subcooled liquid nitrogen. At the beginning stage, the cooling system was composed of a liquid nitrogen decompression cooling unit. No major fault has been observed during long term operating test. As a next step, cooling system was modified that a cryocooler was employed, resulting in the total cooling capacity of 4 kW at liquid nitrogen temperature. In this paper, the progress on the performance test of HTS power cable is reported. Temperature as well as pressure in the system is discussed with respect to the supplied current levels. Also, the installation of hybrid cooling system for real power grid application is described. [ABSTRACT FROM AUTHOR]

A copper coil dipole magnet from the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL) has been retrofitted by HTS-110 Ltd with coils made from Bi-2223 wire and a self-contained cryogenic cooling system, while keeping the magnet's original iron yoke. This modified bending dipole, which is the first such known retrofit HTS-based accelerator magnet, provides the benefits of a compact coil design to accommodate space-limited experimental issues and a significant reduction in power costs as compared to the original copper magnet. In order to validate this modified design for use in the synchrotron, a detailed magnetic field map has been measured using a multiple-Hall probe assembly and transporter system. The results are discussed in this paper, along with the performance of the closed circuit cryogenics system in keeping the coils below 45 K. [ABSTRACT FROM AUTHOR]

A method for estimating the current distribution on the HTS strands which is composed of the HTS power cable was developed. A group of hall sensors which are well-arranged around the HTS cable were used in measuring the circumferential magnetic field. The current distribution can be calculated by solving a matrix equation which contains the measured magnetic field values as its elements. The contribution of the magnetic field generated by each strand in each hall sensor should be known to solve the matrix equation. The contribution can be calculated by FEM analysis simulating the HTS cable or can be measured using a duplicated short HTS cable of which current terminals are modified to apply the current to each strand independently. A simple computer simulation was performed to investigate the feasibility of the method and the performance characteristics of the method was examined for the HTS cable which is composed of several HTS strands. In this paper, a simple mathematics for estimating the current distribution and the results of experiment using the designed and manufactured measuring apparatus will be introduced. [ABSTRACT FROM AUTHOR]

In this paper, a novel coaxial magnetic gear (CMG) using bulk high temperature superconductors (HTS) is proposed. By substituting bulk HTS for ferromagnetic material, a novel stationary ring is resulted, which can not only provide the desired field modulation effect but also suppress the end-effects that commonly occurred in the traditionalCMG. The performance of the proposed bulk HTSCMGis assessed and then verified by using finite element analysis. [ABSTRACT FROM AUTHOR]

Forschungszentrum Karlsruhe has taken over the responsibility for the design, construction and testing of the High Temperature Superconductor (HTS) current leads for two fusion experiments, i.e. the stellarator WENDELSTEIN 7-X. (W7-X) and the satellite tokamak JT-60SA. W7-X is presently under construction at the Greifswald branch of the Max-Planck-Institute for Plasma Physics and consists of 50 non-planar and 20 planar coils with a maximum conductor current of 17.6 kA. In total 14 current leads are required with a nominal current of 14 kA that are mounted upside down with the warm end at the bottom. In the frame of the Broader Approach Agreement between Japan and the EU and concomitantly to the ITER project, the satellite tokamak project JT-60SA has been agreed in 2006. The magnet system of JT-60SA consists of 18 toroidal field coils, 4 central solenoid modules and 7 poloidal field coils. In total 26 leads mounted in vertical, normal position are required. For W7-X and JT-60SA a common basic design will be used which will be adapted to the special needs of the machines. All current leads will be of the Cu-HTS binary type. The HTS part covers the range between 4.5 K and 60 K and is cooled by heat conduction from the 4.5 K end, only. The Cu heat exchanger is cooled with 50 K He and covers the range between 60 K and room temperature. The paper describes the status of the HTS current lead development for W7-X and JT-60SA. [ABSTRACT FROM AUTHOR]

After the first man-loading high temperature superconducting (HTS) Maglev demonstration had been tested successfully years ago, its future application attracts more and more researchers and engineers. This paper reviews the recent development of HTS Maglev system in China. In the past seven years, quasi-static forces, dynamic characteristics and running performances have been studied by three self-developed HTS maglev measurement systems and 11-ch vibration measurement apparatus. Some practical problems are considered in details for further engineering application of HTS Maglev train, such as running along the forward direction with inhomogeneous magnetic field, construction cost estimation, propulsion optimization, and so on. On the other hand, a systematic method is introduced to analyze or optimize the force interaction between bulk high temperature superconductor and permanent magnetic guideway. Primary running parameters and data are obtained for the safety design of future HTS Maglev system. Furthermore, a low-mid speed HTS Maglev test line is blue printed with a maximum speed of 100 km/h, which will be the first step of practical HTS Maglev engineering application. [ABSTRACT FROM AUTHOR]

The US Department of Homeland Security is currently funding the design, development and demonstration of an inherently fault current limiting HTS cable, called Secure Super Grids, under the Hydra project with Con Edison. The cable is 300 m long and is being designed to carry 96 MVA at a distribution level voltage of 13.8 kV. The cable will be built using cable system experience gained by AMSC and Ultera (a Southwire and nkt Cables joint venture) on previous projects. The underground cable will be permanently installed and energized in New York City in 2010. The project is led by American Superconductor who is teamed with Ultera and Con Edison. This paper describes the general goals and design criteria of the project. An overview of the concept of Secure Super Grids and advantages of this type of cable are presented in a grid-based network modeling. In addition, the design issues such as tailoring of the HTS wire to provide adequate thermal stability and electrical properties both under normal operation and during a fault are presented. [ABSTRACT FROM AUTHOR]

For the superconducting magnet system of the International Thermonuclear Experimental Reactor, ITER, 60 current leads for a total current of more than 2500 kA are needed. The use of High Temperature Superconductor current leads (HTS-CL) will reduce the resultant large refrigerator load considerably. Within the EU Fusion Technology Programme, the Forschungszentrum Karlsruhe and CRPP have developed and built a 70 kA HTS-CL demonstrator optimized for 50 K Helium operation. In 2004-2005, the CL was successfully tested with 50 K as well as 80 K Helium, and finally with LN2. In the meantime, ITER has decided to use HTS-CLs for the magnet system and China has taken the responsibility to provide the sc feeders for ITER including the current leads. In this paper, the performance of a 70 kA HTS-CL in fault conditions will be analysed using the FZK-CRPP demonstrator as a model. In particular, the quench performance and the safety behavior in case of a loss-of-flow accident (LOFA) will be described and an extrapolation of the leads performance in real ITER conditions will be given. Finally the effect of different shunt materials is discussed. [ABSTRACT FROM AUTHOR]

The superconducting magnet system of the W7-X stellarator presently under construction at the Max-Planck-Institute for Plasmaphysics in Greifswald, Germany, requires 7 pairs of current leads for a maximum current of 18.2 kA. The Forschungszentrum Karlsruhe is responsible for construction, manufacturing and performance testing of the current leads prior to installation in the W7-X machine. To reduce the overall cooling power for the refrigerator as well as the free convection problem due to the upside-down orientation of the leads, it was decided to use HTS material in the temperature range between approx. 5 K and 60 K. The optimization of the HTS part requires to know exactly the electrical, mechanical and thermal parameters of the HTS material. Actually two suppliers, EHTS and Sumitomo offer such Bi-2223/AgAu material. Single tapes as well as stacks were used to measure the critical current as a function of applied magnetic field for various temperatures. The thermal conductivity, the stress-strain dependence and the thermal contraction were also measured. In the paper the electrical, mechanical and thermal performance of different tapes and stacks will be described and discussed. [ABSTRACT FROM AUTHOR]

This paper presents a new synchronous motor whose stator uses 2 High Temperature Superconducting (HTS) pancake-coils wound from 2G HTS tapes and 4 conventional copper coils, while the rotor contains 75 buLk HIS elements. All superconducting materials are cooled by liquid nitrogen (77 K). The HIS and copper armature includes 3 phase circuit and is mounted in the slots of a nonmagnetic and insulating material. Each phase winding, fabricated in the form of a pancake-coil, is distributed in slots of 60-degree intervals. YBCO melt-textured pucks were incorporated into the rotor and the reluctance was tested. In addition, a unique cooling system using a copper conductor is designed, which is similar to that of a superconducting flywheel. Finally, we present and analyse results on measuring DC critical current and self-field AC loss in HIS tape supplied by American Superconductor. The measurement systems are described. The results on the AC loss measurement of YBCO samples are presented and analyzed within the framework of the critical state model. [ABSTRACT FROM AUTHOR]

The metal organic deposition (MOD) of YBCO High Temperature Superconducting films on RABiTS (Rolling Assisted Biaxially Textured Substrates) templates has been developed at American Superconductor as a low-cost, scalable manufacturing process for the commercialization of the Second Generation (2G) HTS wire. The MOD process is based on the deposition of a trifluoroacetate (TFA) based metal organic precursor film which is converted, in an ex-situ process, to the superconducting YBCO film. A major goal of the development has been achieving high critical currents. This paper reports the preparation and characterization of MOD-YBCO films with critical currents exceeding 500 A/cm-w (77 K, self-field) using a scaleable thick film approach on RABiTS templates. The high critical current films were obtained through optimization of the precursor composition, nucleation and growth conditions. The through-thickness dependence of the critical current density of MOD films as a function of film thickness and a correlation of the through-thickness transport properties and microstructure of the thick MOD/RABiTS samples is reported. [ABSTRACT FROM AUTHOR]

An 8 MVAR, 13.8 kV Superconducting Dynamic Synchronous Condenser (SDSC) prototype was tested on the Tennessee Valley Authority (TVA) grid for about a year. It shared a bus with an arc furnace. The SDSC was subjected to transient currents and harmonics created by the arc furnace, which consisted of up to 50 % negative sequence and 20% zero sequence components. The SDSC operated successfully in the presence of such high transient/harmonic currents. It provided cycle by cycle correction of voltage during operation. The benefits of voltage correction were observed both at the local bus and at the generator bus of a power generation station several miles away. Currently two commercial units rated 12 MVAR, 13.8 kV, are on order by TVA and are scheduled for delivery in December 2006 and March 2007. These units will be skid-mounted for easy installation on site. This paper discusses test results of the prototype unit operation on the grid and describes its potential applications for voltage support in wind farms. [ABSTRACT FROM AUTHOR]

When a synchronous generator connected to the power grid experiences a fault, it is required to stay on line, ride through the fault, and be able to carry full rated field current when the fault is cleared. The peak current during these events could be 2 times higher than the normal operating current. This may cause an HTS rotor coil to go into normal state and generate Joule heating. If the fault event is short enough and the heat dumped can be carried away by the cooling system, the coil may recover to the superconducting state at the end of the fault. Otherwise, the coil may thermally run away, or ‘quench’. To investigate the quench behavior of the HTS rotor coil of the 100 MVA generator at GE Global Research Center, a 1.5 MVA prototype coil was developed and tested to quench under different conditions. The experiment design, set up, tests and test results are presented in this paper. [ABSTRACT FROM AUTHOR]

Over the past few years, first generation (1G) high temperature superconductor (HTS) wires have been used to demonstrate large-scale prototype devices, including a 5 MW U. S. Navy motor and an 8 MW synchronous condenser. In addition, the fabrication and testing of larger devices (a 36.5 MW motor and a 12 MW synchronous condenser) are currently underway. Although 1G HTS wire will continue to be a workhorse for demonstrating this technology over the next few years, the lower cost potential of second-generation (2G) HTS wire is driving its rapid development and scale-up. In addition to reporting on key material properties of this wire for coil applications, this paper presents thermal cycling data on 2G racetrack coils, showing excellent robustness under conditions of significant thermal strain. A 2G solenoid coil with a 5 cm inner diameter has achieved 1.5 T at 64 K. These results are a major step in confirming the viability of 2G HTS wire in coil applications. [ABSTRACT FROM AUTHOR]

This paper presents design and test of a single-phase HTS transformer with capacity of 45 kVA operated in liquid nitrogen of 77 K for primary/secondary voltages of 2400/160 V. The windings were wound by stainless steel-enforced multifilamentary Bi2223/Ag tapes. The structures of primary and secondary windings are solenoid and double-pancake respectively. The gas-cooling current leads of secondary windings were chosen in order to reduce heat input. Cryostat is made from electrical insulating materials with room temperature bore for iron core made of the commercial Fe-Si steel. Fundamental characteristics of the transformer are obtained by standard short-circuit and no-load tests. The AC losses were calculated and measured by calorimetric method with a mass flow meter of nitrogen gas at room temperature. The performances of the transformer in accidental cases of sudden short-circuit and lightning impulse were also tested. [ABSTRACT FROM AUTHOR]

For the superconducting magnet system of the International Thermonuclear Experimental Reactor, ITER, 60 current leads for a total current of more than 2500 kA are needed. To reduce the resultant large refrigerator load at 4.5 K, High Temperature Superconductor current leads (HTS-CL) could be used. Therefore, EFDA CSU Garching had launched a development program for a 70 kA HTS-CL demonstrator. The Forschungszentrum Karlsruhe and CRPP developed and built this CL optimized for 50 K Helium operation. In 2004, the CL was successfully tested in the TOSKA facility at the Forschungszentrum Karlsruhe. The very encouraging results lead to testing this CL with 80 K Helium because ITER provides a large 80 K Helium cooling capacity for the thermal shields. At the end of last year, the test could be successfully performed demonstrating that high current capacity current leads can be stably operated at about 80–85 K. Recently, the CL was retested using liquid nitrogen which would be an interesting alternative option. In this paper, the test results for the 80 K He cooling operation as well as for the operation with LN2 are presented and compared to the results obtained before for nominal conditions. [ABSTRACT FROM AUTHOR]

The introduction of new generating facilities by independent power producers and increasing load demand can result in fault-current over-duty on existing transmission system protective equipment. Conventional solutions to fault current over-duty such as major substation upgrades, splitting existing substation busses or multiple circuit breaker upgrades could be very expensive and require undesirable extended outages and result in lower power system reliability. Less expensive solutions such as current limiting reactors may have unwanted side effects, such as increase in system losses, voltage regulation problems or possibly could compromise system stability. This paper discusses the benefits of superconducting Fault Current Limiters (FCLs) which can be economically competitive with expensive conventional solutions. Superconducting FCLs are invisible in normal operation and do not introduce unwanted side effects. The performance of a particular type of limiter, the Matrix Fault Current Limiter (MFCL) is presented and examples are provided on how it could relieve fault current over-duty problems. The use of this device in a particular application in the American Electric Power (AEP) 138 kV transmission grid is also discussed. [ABSTRACT FROM AUTHOR]

SuperPower, Inc. and Nexans SuperConductors GmbH have partnered to develop a superconducting fault current limiter for transmission level applications. The device employs SuperPower's Matrix Fault Current Limiter (MFCL) technology and BSCCO-2212 bulk material manufactured by Nexans' melt cast processing technique. The development program has been underway since June 2002 and is divided into a series of prototype demonstrations of progressive capability, culminating in a Beta prototype that will be installed at a host utility on a 138 kV line. This paper describes the test results of the first major program milestone, a proof-of-concept prototype at distribution level voltage. The test results show the expected current limiting performance of the MFCL technology to provide fast current limiting and dynamic resistance development before the first peak of the fault. The fault current evenly distributes among the elements of the MFCL array, which employs a resistive-inductive approach for limiting the current. The results also show the excellent electric field performance of the BSCCO-2212 material. [ABSTRACT FROM AUTHOR]

In the frame of the European Fusion Technology Programme, the Forschungszentrum Karlsruhe and the CRPP Villigen have designed and built a 70 kA current lead for the ITER TF Coils using High Temperature Superconductors (HTS). At the beginning of 2004 the HTS current lead was installed and tested in the TOSKA facility of the Forschungszentrum Karlsruhe. The scope of the experiment was to characterize the current lead in steady state conditions and to explore the operation limits as well. For this, the temperature profile, the contact resistances, the heat load at 4.5 K, the required 50 K He mass flow rate, and the temperature margin were evaluated. The safety margin in case of a loss of He mass flow was studied, too. The paper describes the experimental results as well as the thermal and electrical models developed. [ABSTRACT FROM AUTHOR]

Technologically, the most advanced conductor utilising high temperature superconductors is the multifilamentary tape produced by the powder in tube method. Previous investigations have indicated that the filaments in these materials are strongly connected by superconducting paths. This connectivity is of particular importance in, amongst other things, governing the dissipation of the conductors when carrying AC currents or exposed to varying magnetic fields. In this paper we report direct measurements of the transverse (in contrast to the more usual longitudinal) current carrying capability. Measurements of electric field versus current ('E-I characteristics') for transverse and longitudinal transport currents as a function of applied magnetic field and temperature are reported. Our data indicates that the filaments are indeed strongly connected by superconducting paths but also that the E-I characteristics for the transverse and longitudinal connections are different. [ABSTRACT FROM PUBLISHER]

This paper reports a study on the fabrication technology of high performance functional devices, where high temperature superconductor and compound semiconductor devices are monolithically integrated on the same substrate. We investigated optimal conditions for epitaxial liftoff process and succeeded in fabricating HTS device and GaAs MESFET on SrTiO/sub 3/ substrate without degrading characteristics of superconductor and semiconductor devices. We also carried out basic integrated circuit fabrication processes such as patterning and etching for quasi-monolithic structure. The results confirmed that fabricating high performance functional devices is feasible. [ABSTRACT FROM PUBLISHER]

The high speed and low power of Single Flux Quantum logic (SFQ) are extremely attractive, and significant capabilities have been demonstrated in Nb technology. However the burden of cooling to 4.2K has been a barrier to its widespread implementation. The advent of High Temperature Superconductors (HTS), raises the prospect of more accessible temperatures. This paper examines some theoretical constraints on the implementation of SFQ in HTS, and derives some ideas about the parameters required of any HTS SFQ technology. [ABSTRACT FROM PUBLISHER]

Three dimensional structures can have high geometric factors and have thus been favoured in applications requiring high Q resonant elements. In this paper the surface resistance of YBCO thick film materials measured in the frequency range 1-10 GHz in a variety of resonant structures is discussed. The power dependence of the materials in the 1 to 2 GHz region is also examined and at these frequencies it is possible to attain Q's of over 150000 using thick film materials. [ABSTRACT FROM PUBLISHER]

The use of melt processed YBCO in permanent magnet applications requires the calculation of magnetic fields in the interior of superconductors. Although the Bean model can be used, analytic solutions are only available for simple shapes and numerical methods are required for most cases. In this paper, the technique of adjusting the boundary between current carrying and current free regions to ensure zero field within the boundary is used, in combination with the Kim model for Jc. The results are applied to discs being magnetised in a uniform field and trapping fields after saturated magnetisation. It was found that a good approximation can be obtained by using a constant Jc of the value at half the applied field instead of the Kim model. This may be of great importance for the practical applications of melt processed YBCO permanent magnets. [ABSTRACT FROM PUBLISHER]