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This paper proposes a way to represent the anisotropic nonlinear superconducting properties using a discrete model for magnetization with the corresponding critical parameters, equivalent to the Power Law model for currents. This simplified model makes it possible to analyze magnetic systems with superconducting elements in a stationary mode, which reduces the calculation time. Using of proposed model is demonstrated by the calculation of force interactions between high-temperature superconducting (HTS) samples and permanent magnet in zero-field-cooling (ZFC) and field-cooling (FC) modes. HTS bulks in the form of a prism and stack made of HTS tape are considered. The calculation of the electromagnetic field was carried out using the method of integral equations for field sources. The data of calculations are compared with the results of experimental studies. [ABSTRACT FROM AUTHOR]

MgB2 in bulk form shows great promise as an inexpensive, lightweight alternative to bulk (RE)-Ba-Cu-O materials to act as trapped field magnets (TFMs), which can replace permanent magnets in applications such as desktop high-field magnet systems and rotating machines. In this paper, we investigate the thickness dependence of the trapped magnetic field in bulk MgB2 superconductors. Two bulk MgB2 samples, 20 mm in diameter and 10 mm in thickness, were fabricated using the powder-in-closed-tube (PICT) technique. The trapped field was then measured after field-cooled magnetisation for thicknesses of approximately 20 mm (both bulks stacked), 10 mm (single bulk), and then 7.5, 5, 4, 3, 2, 1.5 and 1 mm, for which the sample was machined down to the designated thickness using an automated-wet-polishing technique. A 2D axisymmetric finite-element model based on the H-formulation is used to simulate the experimental results and explain the observed thickness dependence of the trapped field. The numerical results assume a Jc(B) dependence based on the measured characteristics of small specimens taken from the bulk before and after machining. The Jc(B) measurements suggested a degradation of Jc occurred as the bulk was machined thinner and thinner: a decrease in Jc(0 T) of ∼35% was observed between the pre- and post-machining specimens. Taking this into account in the models, by assuming a linear reduction in Jc with each machining process, reproduced the experimental results with very good agreement. Consistent trapped field measurements on the top and bottom surfaces suggest this degradation occurred globally, rather than local to the machined surface. [ABSTRACT FROM AUTHOR]

The realization and preliminary tests of a high temperature superconducting axial-field synchronous machine (HTS-AFSM) prototype are presented in this paper. The HTS machine consists of a 3-phase stator with HTS armature winding and a permanent magnet (PM) rotor. The HTS armature winding contains three pancake coils made of BSCCO tape forming a single layer nonoverlapping concentrated stator windings. The rotor is composed of four NdFeB permanent magnets. Several tests have been carried out such as voltage vs. currents curves of the HTS coils, static torque, back-EMF and load tests in generator mode. A 3D semi-analytical model, based on integral equations, has been used to check out the measured electromagnetic quantities. It has been shown that the measured and the calculated quantities are in satisfactory agreement. [ABSTRACT FROM AUTHOR]

With the advantages of high-speed, low-noise and environment-friendly, magnetic levitation (maglev) train has the potential to become a high-speed transportation mode. High-temperature superconducting (HTS) maglev, which can remain stable levitation without any control system, is a competitive type of maglev rail transit. As a kind of high-speed transit, the vibration of the HTS maglev system is inevitable. Hence, studies about its dynamics are necessary and significant. The developments and researches for the HTS maglev vehicle dynamics in Applied Superconductivity Laboratory (ASCLab) are elaborated in detail in this paper. Based on the improved HTS maglev ring test line “Super-Maglev”, a series of research works have been carried out. First, the mathematical model of the pinning force was proposed. Second, motion stability and nonlinear vibration characteristics were studied. Then, the dynamic simulation of vehicle-bridge coupled system of the HTS maglev train was performed. Finally, certain vibration reduction optimizations were added. These dynamics researches give a strong verification for the future application prospect and feasibility of HTS maglev transportation, and the results can provide reference for the engineering application. [ABSTRACT FROM AUTHOR]

In hadron colliders such as the LHC, the energy deposited in the superconductors by the particles lost from the beams or coming from the collision debris may provoke quenches detrimental to the accelerator operation. In previous papers, a Network Model has been used to study the thermodynamic behavior of magnet coils and to calculate the quench levels in the LHC magnets for expected beam loss profiles. This model was subsequently used for thermal analysis and design optimization of \ Nb3{\ {Sn}} quadrupole magnets, which LARP (US LHC Accelerator Research Program) is developing for possible use in the LHC luminosity upgrade. For these new magnets, the heat transport efficiency from the coil to the helium bath needs to be determined and optimized. In this paper the study of helium cooling channels and the heat evacuation scheme are presented and discussed. [ABSTRACT FROM PUBLISHER]

This paper numerically analyzes the influence of second harmonics on the characteristics of Josephson junction quantum bits (qubits). It is shown that the splitting of energy states of phase qubits is sensitive to energy scale and unharmonicity parameters. On the other hand, for charge qubits, the expectation value of the Cooper-pair number is not affected by the inclusion of unharmonicity parameters, whereas the expectation value of the superconducting current is strongly influenced by energy scale and unharmonicity parameters. The numerical results seem to present the importance of second harmonics in the realization of superconducting qubits. [ABSTRACT FROM AUTHOR]

This paper presents numerical analysis of the thermally actuated superconducting flux pump. Visualization of the behavior of the magnetic flux helps our understanding of flux injection mechanism. In addition, in order to confirm validity of the result, we conducted a preliminary flux pump experiment. This result qualitatively agrees well with the experimental one. The flux pump system utilizes a particular behavior that permeability of some materials such as Gadolinium is sensitive to the temperature. In this paper a simple heater is used to control the flux pump system. [ABSTRACT FROM AUTHOR]

High-temperature superconductors have created the opportunity for a step change in the technology of power applications. Racetrack superconducting coils made from YBCO coated conductors have been used in several engineering applications including SMES, rotor or stator windings of electric machines. AC loss is one of the most important factors that determine the design and performance of superconducting devices. In this paper, a numerical model is developed to calculate the AC losses in superconducting racetrack coils in different magnetic conditions. This paper first discusses the AC losses of the coils in self-field or external field only. It then goes to investigate the AC losses of the coils being exposed to AC ripple field and a DC background field. Finally, the AC losses of the coils carrying DC current and being exposed to AC field are calculated. These two scenarios correspond to using superconducting coils as the rotor field winding of an electric machine. [ABSTRACT FROM AUTHOR]

A magnetic levitation technique with high-Tc superconductor (HTS) has received significant interest for a wide range of applications after its discovery due to its unique inherent stability, which gives a fundamental significance to evaluate the HTS magnetic levitation in both experiment and calculation. To numerically investigate the HTS magnetic levitation, a 3-D model describing the electromagnetic property of the HTS, including its anisotropic behavior, was established by incorporating the current vector potential and Helmholtz's theorem. In addition to the commonly considered nonlinear E--J characteristic in the reported calculation, we introduce an elliptical model to formulate the angular dependence of the critical current density Jc resulting from the anisotropic behavior of the HTS. To numerically resolve the governing equations of the 3-D model, Galerkin's finite-element method and the Crank--Nicolson-θ method were employed to discretize the governing equations in space and time domains, respectively. The obtained algebraic equations were firstly linearized by the Newton--Raphson method, and then an extended format of the incomplete Cholesky-conjugate gradient method was applied to solve the linear algebraic equations. The 3-D model was implemented by a self-written numerical program based on a VC++ platform to calculate the magnetic force of a bulk HTS exposed to applied field generated by a permanent magnet guideway (PMG) assembled by the Nd-F-e-B magnets. In this paper, we present the numerical results of the levitation force of a moving bulk HTS above the PMG with different mesh densities and number of time steps. This presents a preliminary validation of the 3-D model proposed in this paper. [ABSTRACT FROM AUTHOR]

It is well known that the critical current density Jc of a superconducting material depends on the magnetic flux density B. There exists an electric method to measure the Jc(B) deduced from the U(I) measurements. The problem with this method is the self field effect because the magnetic flux density is always the sum of the applied magnetic flux density and the self magnetic flux density. This paper presents a special experimental arrangement, compensating fully or partially the self magnetic flux density in an HTS tube. It allows characterizing the true zero magnetic flux density behaviour of the superconducting material. The experimental results of the compensation are discussed. A theoretical analysis based on Bean's model is presented and gives results close to the experimental ones. The proposed compensation is not perfect but the experiments and the theoretical analysis allow validation of the compensation principle. [ABSTRACT FROM AUTHOR]

This article presents an integral modeling approach for computing ac losses in high-temperature superconductors near magnetic materials. The current density and magnetic field distributions are calculated by solving Maxwell's equations in integral form in the active parts. Equivalent surface and interface current densities are considered in the magnetic material to take into account its magnetic field-dependent relative permeability. The proposed approach is applied to compute ac losses in a second-generation high-temperature superconducting tape with a magnetic substrate. The obtained results are compared with the finite element method using H formulation to check the validity and performances of the proposed integral approach. [ABSTRACT FROM AUTHOR]

This paper presents a novel current sensor, which includes a giant magnetoresistance (GMR) chip, a toroidal magnetic core, and a feedback winding on the core. The mathematical model of the sensor was built, which was used to analyze the influence factors of the closed-loop current sensor. The closed-loop configuration with the magnetic core and the feedback winding improved the sensitivity of the sensor, eliminated the offset and drift related to temperature of the chip, and greatly reduced the error caused by magnetic hysteresis phenomenon. The simulation and test results showed that the novel current sensor has very low linear error (less than \pm 0.7%). The designed sensor can measure frequency of currents up to 100 kHz. The current sensor has high linearity with the range from 10 mA to 20 A. [ABSTRACT FROM PUBLISHER]

The design of a cable-in-conduit conductor (CICC) is a very complicated engineering process. In order to simplify the design for CICCs, a simulation design method is presented in this paper with the relationship between the operating current and the critical current, and the extreme case that the Stekly parameter is equal to 1. In addition, a novel optimization model for CICC design is proposed for solving the difference or uncertainty in the subsequent cabling layout of the conductor. This mathematical constraint model, which can maximize the CICC energy (stability) margin, is built to generate a more reasonable conductor structure. For an optimum design of a CICC, although there exists a cabling variety in the fourth stage (level) between the engineering design and the optimization design, the result shows that the optimized conductor structure and the correlated performance conforms reasonably well to the present engineering design that was adopted by the Option II CICC of the International Thermal Nuclear Experimental Reactor experimental fusion reactor project. [ABSTRACT FROM AUTHOR]

An automated level control in cryogenic systems requires a precise and continuous level measurement. If properly characterized, superconducting level sensors are a viable option for the same. The operation of a superconducting level sensor is based on the difference in the heat transfer from the sensor wire to the liquid and the gaseous phases of the cryogen. The higher heat transfer in the liquid phase results in a superconductive status, whereas the lower heat transfer in the gaseous phase results in a normal conductive status with a voltage drop corresponding to the length of the wire in the gaseous phase. Hence, it demands a judicious selection of the sensor and the operational parameters such as the current input, for an accurate level measurement as well as the reduction of the liquid boil off. In this paper, to simulate the operation of a superconducting level sensor, a model has been developed by taking the steady-state heat balance along the sensor wire. It is then used for the investigation of the sensor current, voltage output at various liquid levels, and temperature profile of the sensor wires of NbTi and MgB2/SS level sensors in LHe. Furthermore, design guidelines have been proposed for an MgB2/SS superconducting level sensor for LH2 level measurement. The parameters considered for the analysis are the sensor wire diameter and the active length. In addition, the effect of an external resistor on the sensor operation is also studied. [ABSTRACT FROM AUTHOR]

Superconducting devices are known to indicate nonlinear behaviors such as harmonic generation and intermodulation distortion even at low input powers. In this paper, a nonlinear equivalent circuit model for a superconducting interdigital capacitor (SIDC) is proposed. A numerical approach based on a 3-D finite-element method is used to compute the current distribution in SIDCs. Then, closed-form expressions for kinetic inductance, resistance, and geometrical nonlinear factor of SIDCs are proposed. The proposed model can be analyzed nonlinearly by using a harmonic balance method to predict nonlinear phenomena. To validate accuracy of the proposed nonlinear model, nonlinearity in a superconducting metamaterial structure consisting of two SIDCs is predicted. A good agreement between calculated results and measured ones was found. Thereafter, based on the proposed model, other nonlinear behaviors of the considered structures are predicted, and based on our new method, effects of nonlinearity on main parameters of the superconducting metamaterial structure such as phase constant, attenuation factor, plasma frequency, permittivity, and permeability are analyzed. [ABSTRACT FROM AUTHOR]

Now that ITER is entering construction, many of its systems are in the final stages of design and analysis. Among them the 31 feeders, which will be supplied in-kind by the Chinese ITER partner. The feeders supply the electrical power and cryogens through the warm-cold barrier to the ITER superconducting magnet systems. They are complex systems with their independent cryostats and thermal shields, densely packed with many components, such as the current feeds, the cryogenic valves and High-Voltage (HV) instrumentation hardware. Some of the feeder components are particularly critical and have been designed with great care. Among them the High-Temperature Superconductor (HTS) current leads, designed for unprecedented currents, the 30 kV class, Paschen-hard HV insulation and the bus bar support system, designed to react the multi-ton Lorentz-forces from the bus bars at minimal heat load. This paper discusses the design challenges for these (and other) key components of the ITER magnet feeders. [ABSTRACT FROM PUBLISHER]

Thermal stability and protection in the event of quench are key issues in the design of superconducting magnets. Quench development and propagation strongly depend on the conductor characteristics and the magnet configuration. An adequate quench protection method must maintain both the peak temperature and the peak voltage during the event within acceptable limits. This paper presents quench modeling and evaluation of candidate protection schemes for a superconducting coil based on a magnesium diboride ( \MgB2) wire, designed for use in a new cryogen-free magnetic resonance imaging scanner. The wire properties are different, and the current density is significantly higher from those previously reported. In contrast to previous studies, it is concluded that the coil cannot be considered self-protecting and that protection using external resistance provides a practically acceptable solution. [ABSTRACT FROM AUTHOR]

A model coil developed at the High Magnetic Field Laboratory, Chinese Academy of Sciences, will be wound with a \Nb3\Sn cable-in-conduit conductor (CICC). In this paper, we first introduce the model coil structure and its design requirements and then explicate the important components of the model coil structure, such as the preload structure, joint, cooling circuit, etc. Stress analyses of the preload structure, lead-in and lead-out CICC, joint, transitive CICC, and some supporting structures are performed, and the results are compared with the International Thermonuclear Experimental Reactor metallic and composite structural component design criteria. [ABSTRACT FROM AUTHOR]

Distributed power generation and the ever-growing load demand have caused fault current levels to exceed the nominal rating of the power system devices, and fault current limiters are more needed. Superconducting fault current limiter (SFCL) forms an important category of current limiters. In this paper, a novel flux-based model for the inductive shield-type high-temperature SFCL is developed based on the Bean model. This model is employed to simulate the SFCL performance in a sample circuit. Utilizing the model, the signal characterization of the limited current is determined. A prototype laboratory scale SFCL has been fabricated with superconducting rings. Yttrium barium copper oxide powders have been used for superconducting ring production. The critical current density of fabricated rings has been measured with an innovative method based on application of a magnet device. The fabricated SFCL has been tested in a circuit by applying different types of faults. The related experimental results are recorded and compared with the model results. The results obtained based on the modeling shows full compatibility with the experimental results. [ABSTRACT FROM AUTHOR]

A new structure of superconducting suspension system is proposed based on a method used to calculate the magnetic field in a thin clearance between superconducting blocks. Force characteristic of the passive superconducting suspension system is analysed. Based on the existing structure of superconducting suspension system, an electrostatic suspension system is introduced to obtain high suspension stiffness. Details of the hybrid suspension system are introduced and the corresponding controller is also described. This paper provides a theoretical guidance for the next experiment, and also has reference to designing high stiffness suspension system. [ABSTRACT FROM AUTHOR]

YBaCuO-coated conductors offer great potential in terms of performance and cost-saving for superconducting fault current limiter (SFCL). A resistive SFCL based on coated conductors can be made from several tapes connected in parallel or in series. Ideally, the current and voltage are shared uniformly by the tapes when quench occurs. However, due to the non-uniformity of property of the tapes and the relative positions of the tapes, the currents and the voltages of the tapes are different. In this paper, a numerical model is developed to investigate the current and voltage sharing problem for the resistive SFCL. This model is able to simulate the dynamic response of YBCO tapes in normal and quench conditions. Firstly, four tapes with different Jc's and n values in E\-J power law are connected in parallel to carry the fault current. The model demonstrates how the currents are distributed among the four tapes. These four tapes are then connected in series to withstand the line voltage. In this case, the model investigates the voltage sharing between the tapes. Several factors that would affect the process of quenches are discussed including the field dependency of Jc, the magnetic coupling between the tapes and the relative positions of the tapes. [ABSTRACT FROM AUTHOR]

The superconductor-triggered type fault current limiter (STFCL), which was developed by KEPCO and LS Industrial Systems, is under operation for a verification test at KEPCO's power testing center. The STFCL is composed of a superconductor, a fast switch and a current limiting resistor. In this paper, we investigated the empirical modeling of the STFCL using principal component based and fuzzy support vector regression (PCFSVR) for the prediction and detection of faults in the STFCL. Signals for the model are the currents and voltages acquired from the high-temperature superconductor (HTS), driving coil (DC) and current limiting resistor (CLR). After developing an empirical model, we analyzed the accuracy of the model. The results were compared with those of principal component based support vector regression (PCSVR) as presented in MT21. PCFSVR showed better performance in terms of the average level of accuracy. This model can be used for the condition-based monitoring of STFCL systems to predict any fault symptoms of the system through the advantage of the auto-correction function of the model. [ABSTRACT FROM AUTHOR]

The Facility for Anti-proton and Ion Research (FAIR), under development at GSI, includes the synchrotron SIS300, so called because the magnetic rigidity is 300 Tm. In order to reach the required high intensities of proton and heavy ions beams, the bending dipole magnets have to be pulsed from the injection magnetic field of 1.5 T up to 4.5 T maximum field at the rate of 1 T/s. These 7.8 m long magnets have \cos\theta shaped coils with a 100 mm bore and the particular characteristic to be geometrically curved, with a sagitta of 112.9 mm. These challenging requirements triggered R&D activities, aimed at the development of suitable construction technologies for fast ramped curved coils. The heart of the R&D program is the construction of a 3.9 m long model. The paper discusses the main problems faced during the design and the construction of the cold mass, mainly covering the aspects related to the manufacture. [ABSTRACT FROM AUTHOR]

This paper begins with introducing the winding techniques of two superconducting double-pancake coils wound using 2G coated conductors. These winding techniques are able to guarantee a good performance for the superconducting coils. Then the coil critical currents were measured and compared with a simulation model. The results were consistent. Finally the coil AC losses were measured using an experimental circuit including a compensation coil. The simulation results are close to the experiment results. [ABSTRACT FROM AUTHOR]

A study on protective relay systems is one of the important technical issues concerning power systems that use Superconducting Fault Current Limiters (SFCL). We used a Real Time Digital Simulator (RTDS) in order to study the true interaction of the protection system with the power systems. RTDS modeling of SFCL is necessary to obtain detailed protective relay tests. In this paper, we developed an analysis model using RTDS in order to study the transient behavior of a 22.9 kV hybrid SFCL and performed closed-loop testing on a protective relay in a distribution power system using the developed SFCL model. The model uses an operation mechanism of the real SFCL. The 22.9 kV hybrid SFCL is under development by LSIS (LS Industrial Systems Co., Ltd.) and KEPRI (Korea Electric Power Research Institute) in Korea. The parameters of the model are based on the test data from the real SFCL. Power system planners and operators will be able to solve the problems that are expected in the application of SFCLs to power systems by using these protective relay testing results. [ABSTRACT FROM AUTHOR]

In this paper, we manufactured a vertical axial type Superconductor Flywheel Energy Storage System (SFES) with journal type SMB using HTS for assessing the loss of SFES. The accurate method for measuring energy loss for each part of SFES was presented through the spin down test. Energy losses according to core type, coil thickness and leakage flux of PMSM/G were experimentally assessed. The mathematical model for PMSM core loss was proposed through the experimentally data analysis for the core of PMSM/G and the analytical method using the alternating and rotation magnetic field analysis. Experimental results and the proposed mathematical model of PMSM core loss using alternating and rotating magnetic field had good agreement. Also it was confirmed that the proposed new type PMSM/G core could considerably improve the energy storage efficiency of the SFES. These results will be very useful for the design of a low loss PMSM/G for the SFES. [ABSTRACT FROM AUTHOR]

Superconducting devices operating within a power system are expected to go through transient overload conditions during which the superconducting coil has to carry currents above the rated values. Designing the coil to remain superconducting through any possible fault scenario can be cost prohibitive, necessitating operation beyond the critical current for short periods. In order to set operating limits and design adequate protection systems for superconducting devices connected to a power system, the region of safe operation of these devices has to be described with general capability curves. Existing standards that define limits for these over-current situations are based on copper winding experience that do not apply to devices with superconducting components because of the highly nonlinear interaction between magnetic fields, operating temperature, and current density in the superconductor, and the rapidly varying material properties at cryogenic temperatures. In this paper, the behavior of superconducting coils during over-currents is discussed and a simplified capability curve is described to help standardize device capabilities. These curves are necessary to aid power system designers in appropriately designing the system and associated protection systems. [ABSTRACT FROM AUTHOR]

In this paper, the effects of the magnetic self-field on the transport properties of a multilayer high-T superconducting (HTS) cable are investigated by means of two-dimensional finite-element method (FEM) simulations. Analyzed is a three-layer HTS cable, but the developed methods can be used for a different number of layers. The superconductor is described by the nonlinear power-law relation E = E3(J/Je)n, where the parameters J2 and n depend on the magnetic field experienced by the material. This dependence decreases the global transport capacity of the superconductor, enhancing its AC losses. It is shown that, especially at high transport currents, the AC losses are considerably higher than in the case where the dependence on the magnetic field is neglected. A simple electrical model, considering the cable from macroscopic point of view, has been proposed for finding the optimal winding pitches, leading to a uniform current repartition. The use of this electrical model allows to overcome the difficulties of direct three-dimensional FEM computations. In addition, the rapidity of solutions by the electric model gives the possibility of testing quickly many geometrical configurations in order to find the ones leading to an even current repartition. This optimization process would not be possible with detailed FEM simulations. [ABSTRACT FROM AUTHOR]

In order to solve the problem of DC electric field distortion of superconducting fault current limiter (SFCL) bushing under the huge temperature range of 77 K-300 K, the glass fiber-reinforced epoxy resin (GFRP) insulation with reduced temperature coefficient of conductivity is used to improve the DC electric field distribution. For the DC 160 kV/1 kA SFCL bushing, the electric field distribution of condenser core has been figured out to analyze the effectiveness of reduced temperature coefficient of conductivity. The results show that, compared to traditional insulation, the modified GFRP material can significantly reduce the electric field distortion. [ABSTRACT FROM AUTHOR]

What is the ultimate limit to high fields in superconducting magnets for particle accelerators? In this paper we review the present status of the technology, outlining the main limitations. We first analyse the needed margin for operating a magnet in an accelerator. We then review the relation between current densities, coil widths, and fields in the magnets build so far. The issue of stress and the dependence on the coil lay-out is then discussed: a careful optimization between current density and coil width can be needed to keep the forces and associated strain within acceptable limits. The main issues related to cable lay-out (strand diameter, filament size) are then discussed. We conclude by giving a hint on the requirements on a HTS conductor, and a summary of Nb-Ti and Nb3Sn. [ABSTRACT FROM PUBLISHER]

In high current ac applications, such as CERN and ITER magnets, superconducting cables are used. These cables typically consist of several individual strands and therefore have very complex geometries. Even a single NbTi strand designed for ac applications may consist of tens of thousands of filaments embedded in a normal conducting matrix. It is not practical to numerically model the cable or the strand at the filament level in the ac loss analysis due to extremely long computation times. However, an approximation for the ac losses can be computed if the filament zones or bundles are considered as a homogeneous mixture of superconducting filaments and matrix metal. This means, for example, substantial savings in the computation times of optimization procedures where hundreds of geometries are analysed. In this paper we compare the ac losses computed with both a homogenized bundle model and a detailed model (all or some of the bundles are modeled at the filament level) for different NbTi strand geometries to benchmark the accuracy of the bundle approximation. The results show that the bundle model is a suitable approximation, especially for certain bundle geometries. [ABSTRACT FROM PUBLISHER]

The hardware commissioning of the Large Hadron Collider required the testing and the qualification of the cryogenic and vacuum system, as well as the electrical systems for the powering of more than 10 000 superconducting magnets. Nonconformities had to be resolved within a tight schedule. In this paper, we focus on the role that electromagnetic-field computation has played during hardware commissioning in terms of the analysis of a magnet quench and electromagnetic-force calculations in busbars and splices, as well as field-quality prediction for the optimization of powering cycles. [ABSTRACT FROM AUTHOR]

The applications of high-temperature superconductors (HTS) in electric power components have been widely reported and various studies have been made to define their alternating current (AC) losses-a key design parameter for many practical high power electrical engineering applications. However, very few studies over the range 25 to 45 K have been conducted even though this is one of the favored temperature ranges for cost-effective applications of HTS. Methods and techniques used to characterize and measure these losses have been so far grouped into ‘electrical’ and ‘calorimetric’ approaches with external conditions set to resemble the application conditions. In this paper, we present an approach using the calorimetric method to accurately determine losses in the superimposed AC and DC fields likely to be experienced in practical devices such as Fault Current Limiters. This technique provides great simplification compared to pick-up coil and lock-in amplifier methods and is applied to a lower temperature range. The preliminary loss data at 40 K will be presented in applied AC magnetic fields with DC fields up to 1T. The data of losses obtained on this sample will allow the estimation and minimization of losses in practical high power HTS coils and will be used in the verification of numerical coil models. [ABSTRACT FROM AUTHOR]

Superconducting Fault Current Limiting Transformer (SFCLT) is expected to function as superconducting transformer in steady state and superconducting fault current limiter in fault condition. We have designed, fabricated and tested SFCLT with YBCO coated conductors to be operated in liquid nitrogen (LN2) at 77 K and verified its technological feasibility. In this paper, we developed a simulation model to analyze electrical and thermal behaviors of SFCLT by solving the circuit equation and the heat conduction equation. By the use of this simulation model, we could evaluate the transition of resistance and temperature of the YBCO coated conductors during the fault current limitation as well as after the fault clearance, and verified the recovery criteria of SFCLT. [ABSTRACT FROM AUTHOR]

The recent increase in distributed power generation is highlighting the demand to investigate and implement better and more efficient power distribution grids. High-temperature superconducting (HTS) DC transmission cables have the potential to address the need for more efficient transmission and their usage is expected to increase in the future. Thermal modeling of HTS DC cables is a critical tool to have in order to better understand and characterize the operation of such transmission lines. This paper introduces a general computational model for a HTS DC cable. A physical model, based on fundamental correlations and principles of classical thermodynamics, mass and heat transfer, was developed and the resulting differential equations were discretized in space. Therefore, the combination of the physical model with the finite volume scheme for the discretization of the differential equations is referenced as Volume Element Model, (VEM). The model accounts for heat transfer by conduction, convection and radiation obtaining numerically the temperature distribution of superconductive cables operating under different environmental, operational and design conditions. As a result, the model is expected to be a useful tool for simulation, design, and optimization of HTS DC transmission cables. [ABSTRACT FROM AUTHOR]

This paper deals with effect of an additional mass on nonlinear resonance in a high-Tc superconducting magnetic levitation. The concept of an additional mass can be found in studies of various machines. In this research, using an elastic beam levitated above high-Tc superconductors, occurrence of internal resonance between the beam's two modes was investigated with respect to the mass position theoretically and experimentally. As a result, the beam's natural frequencies can change by the additional mass position. Accordingly, the frequency ratio between the 1st mode and the 3rd mode can be nearly 1 to 2 for a certain mass position. In that condition internal resonance between both the modes can occur by nonlinearity of the electromagnetic force. Its mechanism was explained theoretically, and its features were clarified by numerical analysis and confirmed by experiments. [ABSTRACT FROM AUTHOR]

A superconducting magnet was developed for high magnetic field nuclear magnetic resonance by the Institute of Electrical Engineering, Chinese Academy of Sciences. The superconducting coils are fabricated with various superconducting wires in diameter to improve the performance of the magnet. For adjacent coils mechanically dependent, large difference in diameter of superconducting wires will increase the electromagnetic stress between one coil and the neighbor. In the paper, a detailed finite element model for solenoid magnets was developed using the program ANSYS and employed to solve the stress caused by the diameter change of superconducting wires. The reasonable range of the diameter of superconducting wires of adjacent coils is presented. [ABSTRACT FROM AUTHOR]

Cable-In-Conduit Conductors made with Nb3Sn strands will be used in ITER magnets. The current carrying capability of these Nb3Sn strands is known to be highly dependant on the strain state resulting from mechanical loading. The intricate cabling pattern of CICC, added to the thermal differential shrinkage between conductor jacket and Nb3Sn filaments induce complex strand trajectories and a highly inhomogeneous strain state. This “cable strain map” also evolves with operating loads (Lorentz force/hoop stress). The SAMAN experiment, conducted in the FBI facility at Karlsruhe Institute of Technology, aimed to stretch subsize, ITER-like conductors, in order to observe the evolution of the critical current associated with these loadings. The application of the Multifil finite element code, developed at Ecole Centrale de Paris, has helped quantifying the local strains along every individual strand, and their evolutions during cooldown (from heat treatment), energizing and stretching phenomena. Using Multifil output mechanical data as input in the CEA electrical code CARMEN has allowed computing the critical current in every strand, thus leading to an understanding of the critical current degradation of such subsize conductors. This paper shows, for two SAMAN samples, what is the impact of bending strain concentration on a CICC current transport capability. [ABSTRACT FROM AUTHOR]

Following the development of Nb3Sn and niobium based solution alloys in 1961 the field of High Energy Physics has witnessed a continual development of magnets and devices for the generation, beam handling and analysis of particle beams and their interactions. This paper will examine the technology development of these devices from the earliest bubble chambers through the development of theories of stability and on to the construction of superconductivity based particle accelerators and their associated detectors. The latest advances in superconducting radio frequency accelerating cavities will be considered within this R&D model. This development of technology was accomplished by universities, national laboratories and industry working in a most cooperative way. [ABSTRACT FROM AUTHOR]

The National High Magnetic Field Laboratory (NHMFL) is designing a series-connected hybrid magnet, which has a 40 mm diameter vertical warm bore with a cylindrical profile. The magnet will generate a 36 T field with 13 MW power for a high homogeneity version (1 ppm homogeneity) or >40 T for a high field version. This hybrid shares the design of superconducting coil with another SCH designed for Berlin, Germany. The cryostat design is quite different however. In this paper the design of the NHMFL cryostat is presented. The main features are described at first followed by the discussion of the FEA models and results. [ABSTRACT FROM AUTHOR]

In a magnet with pancake windings, inserting a gap between the pancake windings can increase the central magnetic field. This paper shows the optimized length of each gap is able to maximize the central magnetic field. Inserting a gap also improves field uniformity because the pancake windings are spread across a wider area. A high temperature superconducting (HTS) magnet consisting of BSCCO-2223 pancake windings was chosen for the calculation model to show the effectiveness of the proposed method. The E-J relation was used to determine the critical current, and an evolution strategy was adopted for the optimization of gap length. The results of calculations show that the critical current and the central magnetic field increased by 86.0% and 33.7%, respectively, for a magnet consisting of ten pancake windings. [ABSTRACT FROM AUTHOR]

The FAIR facility, under development at GSI, includes the synchrotron SIS300 (300 Tm rigidity). In order to reach the required high intensities of proton and heavy ions beams, the bending dipole magnets have to be pulsed from the injection magnetic field of 1.5 T up to 4.5 T maximum field at the rate of 1 T/s in a 100 mm diameter bore. The first 3.9 m long model dipole is in advanced construction and a functional test is foreseen at LASA Lab. This test will be performed inside a vertical cryostat in boiling helium at 4.2 K, and it is aimed to verify the operation of the magnet, also in pulsed regime, and to assess the losses. A final full characterization of the magnet will be performed later in a laboratory equipped for operation at the design conditions, i.e. supercritical helium at 4.7 K. This paper illustrates the design and the installation activity of the test station and its capabilities at LASA. [ABSTRACT FROM AUTHOR]

The electrical resistivity of coated conductors is strongly related to the inter-dependent set of parameters (J, H, T), respectively current density, magnetic field and temperature. On the one hand, it is difficult to isolate the contribution of each of these parameters on the resistivity measured experimentally. On the other hand, numerical methods, which may allow this separation, require a good knowledge of the fundamental laws governing the superconducting transition which are, up to now, derived from curve fitting with experimental data. In this paper, we investigate the influence of phenomenological formulas on the outputs of a recently developed finite element model. The outputs are compared against experimental voltage curves, which have been obtained under pulsed transport currents between 80 and 160 A and external magnetic fluxes of 0 to 350 mT. The comparisons indicate that the numerical models may reproduce well the measurements, using the right set of phenomenological laws parameters. Nevertheless, the solution may still be inaccurate at low field values and high current amplitudes, where the curvature of the simulated E–J curves is more pronounced, indicating that further refinement is required in order to obtain models valid over a wider range of parameters. [ABSTRACT FROM AUTHOR]

Superconducting undulators are being constructed to satisfy an increasing need within the synchrotron radiation community for higher and higher energy photon beams. The paper focuses attention on the design of a helical undulator for the ILC photon (hence positron) source. Finite element method (FEM) modeling was performed to extend the design of our existing 14 mm period undulator design to shorter periods with a view towards the final design, construction and testing of a 10 mm undulator. To launch this task we modeled the properties of 10 mm period undulators formed around bore tubes of the 6 mm and 8 mm OD with winding-pack cross-sections of 3 mm \times 6 mm and 3 mm \times 11 mm. These windings do allow a pole width of 2 mm and can take advantage of the corresponding about 0.2 T field increment due to it. In order to reach the target bore field of 1.1 T it is necessary to either reduce the bore size and tighten the associated tolerances, or to use a higher performing strand. In the present work we have chosen to optimize the undulator design basing it on the properties of an advanced tube-type strand keeping the bore tube diameter at 6–8 mm in order to see the needed performance to meet this undulator specification. [ABSTRACT FROM AUTHOR]

It is considered that particle deposition on the photo mask, such as oil dusts which are generated from mechanical bearings of the spin processors, is one of main causes of the deterioration of pattern preciseness. In our R & D, application of magnetic levitation utilizing bulk HTSs to the spin processors for the photo mask production has been proposed. In this study, we try to develop a new model apparatus demonstrating non-contact spinning clean-up processor in photo mask production system. The levitation and rotation test by using this model apparatus showed that this new model apparatus accomplished the remarkable improvement of the levitation and the rotation ability. This paper describes the levitation and rotation test results of the new model spinner comparing with those obtained in our previous study. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a first order planar SQUID gradiometer with a long baseline, with regard its application to biomagnetism, is presented. In particular, we report on the analysis of the device response to the current dipole which is the most fundamental model used in biomagnetism. The planar gradiometer is arranged to measure the field components. The results have been compared with those of an axial SQUID gradiometer having the same baseline, pickup coil's size and the same SQUID design parameters. The performance study involves the computation of the magnetic flux measured by the sensors in the presence of a current dipole and the minimum detectable dipole as function of both off-axis and on-axis distance from the gradiometer. A comparative study as a function of sensor baseline has been also performed. Furthermore, the spatial resolution has been investigated by computing the response of both sensor type to a pair of current dipoles. The results have shown that the dipole current sensitivity of a planar gradiometer, (which measures the tangential magnetic fields), is better than those of the axial gradiometer suggesting that it is possible to employ planar gradiometers in multichannel systems for biomagnetism. [ABSTRACT FROM AUTHOR]

Complex impedance measurements are widely used to characterize superconducting transition edge sensors (TESs) in bolometers and microcalorimeters. Typically, models are fit to impedance data to find parameters which pertain to the performance of these detectors. After the parameters are determined, the models are then used to compute the response and noise of these devices. In this paper, we present general relationships between the measured impedance, the thermal response to power in the TES, and noise. We describe a method for measuring \alphaI and \betaI of the superconducting phase transition, which does not require model fitting. We find bolometer response is determined from the impedance provided that the absorber is strongly coupled to the TES electron system. We also demonstrate how to calculate upper and lower limits on the noise directly from the impedance data without modeling. Additionally, the relations can be used to check the validity of the models and to understand what information can and cannot be obtained from measurements of impedance, response, and noise. [ABSTRACT FROM AUTHOR]

In this paper, the 3-D model proposed in Part I of this study is verified in detail on the basis of a levitation/suspension system composed of a rectangular single-domain Y-Ba-Cu-O and a cylindrical Nd-Fe-B magnet or a permanent magnet guideway (PMG) assembled by the Nd-Fe-B magnets. The magnetic forces along the vertical direction perpendicular or the transverse direction parallel to the surface of the PMG(or magnet) were calculated and compared well with the measured data under vertical and transverse displacements. The computed results of the induced current distribution within the Y-Ba-Cu-O domain, as well as the magnetic field profiles in the Y-Ba-Cu-O and its vicinal region, were also presented and discussed. [ABSTRACT FROM AUTHOR]

This paper presents our study on differential pressure sensors realized with magnetic liquids. We illustrate our work using a "U" tube type magnetic liquid sensor model and the corresponding experimental setup. Three major efforts are: developing the mathematical model describing the dynamic characteristic of the sensor based on the first law of thermodynamics, conducting FE simulation of electromagnetic field with magnetic liquids, and performing experimental implementation and examination using a non-magnetic based differential pressure sensor purchased. Experimental observation indicates a good agreement between the step-response and random response given by the developed magnetic liquids based sensor and the purchased non-magnetic liquids based sensor. [ABSTRACT FROM AUTHOR]

The Superconducting Fault Current Limiter (SFCL) is one of the most attractive devices for the electrical power network. The inductive SFCL consists of two coaxial windings and an optional magnetic core. The primary winding, connected in series to the circuit, is conventionally made of the copper wire, the secondary is made of a superconductor. The 15 kV class SFCL has been designed. It consists of 7 units. The primary copper winding of units has 27 turns/unit and the operating current is 1 kA. The HTS winding of units is wound with 140 turns of YBCO coated conductor SF12050 tape (SuperPower Inc.). The HTS winding has an internal diameter of 0.455 m. The SFCL is cooled in the liquid nitrogen bath. In this paper, we have described the numerical model and the numerically calculated electric parameters of the 15 kV class inductive type SFCL in the stand-by state and during current limitation. [ABSTRACT FROM AUTHOR]