Showing papers in "IEEE Transactions on Applied Superconductivity in 2004"

Design of a linear bulk superconductor magnet synchronous motor for electromagnetic aircraft launch systems

Abstract: High-temperature superconducting (HTS) material in bulk form is used to design a linear synchronous motor for an electromagnetic aircraft launch system. The motor is designed without an iron core. Stator coils are placed in the air while the permanent magnets used in conventional design of linear permanent magnet synchronous motors are replaced by the HTS bulk magnets. The physical, operational, and equivalent circuit parameters of the linear motor with HTS bulk magnets are compared with those of a linear permanent magnet synchronous motor and linear induction motor designed for the same application. Results show that utilizing superconducting magnets is only superior at temperatures below 40 K.

Superconducting FCL: design and application

Abstract: Design, parameters, and application areas of a superconducting fault current limiter (FCL) are analyzed on the basis of the requirements of power systems. The comparison of resistive and inductive designs is carried out. An example of the effective application of FCLs in distribution substations is considered and the gain from the FCL installation is discussed. It is shown that an FCL not only limits a fault current but also increases the dynamic stability of the synchronous operation of electric machines. The calculation procedure of the parameters of an inductive FCL for a specific application case is described.

Modeling and simulation of high temperature resistive superconducting fault current limiters

Abstract: In order to introduce the high temperature superconducting fault-current limiters (SFCL) into electric power systems, we need a way to conveniently predict the limiting characteristic in a given situation. The most important physical property dominating the current limiting behavior of the SFCL is the electric field-current density (E-J) characteristics of high temperature superconductors (HTS) which is dependent on temperatures. So we have developed an EMTP/ATP model of high temperature resistive type SFCL using MODELS language based on E /spl sim/ J characteristics of HTS. Real-time circuit current is as an input signal to the SFCL model, and the output of the model is controlled by a TACS-controlled time-dependent resistance. The operating characteristics and limitation behaviors of SFCL have been investigated in detail.

Superconducting high gradient magnetic separation for purification of wastewater from paper factory

Abstract: High gradient magnetic separation (HGMS) can be one of the promising ways for a new environmental purification technique because of producing no contamination such as flocculants and having possibility of treating large amount of wasted water within a short time. The magnetic separation system for purification of wastewater from the paper factory has been developed. The test plant of 2000 ton/day was set up in the actual paper manufacturing process and a purification test of the wastewater was performed. The magnetic seeding of the organic pulp and dyes were successfully performed and the Chemical Oxygen Demand (COD) value for recycling was reached to less than 40 ppm after magnetic separation. The superconducting magnet for the system is 3 T, 680 mm long and 400 mm bore NbTi solenoid. The system mainly consists of a mixing tank (magnetic seeding tank), a settling tank, and a superconducting magnet. Floating magnetic flocks composed of magnetite particles and organic polymers such as pulp and dye are captured by magnetic force in the superconducting magnet chamber. Some magnetic flocks are precipitated at the settling tank by the gravity, which helps to reduce the amount of magnetic flocks going through the magnet chamber. The system has been successfully operated for several months

Experimental investigation on the effect of transverse electromagnetic force on the V-T curve of the CIC conductor

Abstract: The voltage-temperature characteristic curve (V-T curve) observed in the large-current Nb/sub 3/Sn CIC conductor, which was used in the ITER CS Insert, showed more gradual take-off toward normal state than that of an individual strand composing the conductor. More gradual take-off corresponds to a reduction in so-called "n-value", and measured n-values of the strand and conductor of the CS Insert were 30 and 7, respectively. This reduction cannot be explained by a tensile strain of the conductor caused by a hoop deformation which is uniform along the conductor length. Investigation is therefore required to clarify the strain states of each strand, especially those caused by a transverse electromagnetic force acting on each strand. In a CIC conductor, since strands are twisted to form a cable, each strand is mechanically supported by nearby strands at an interval (typically 5 mm) set by the twist pitch. Between two supporting points, the strand is free to move under the transverse force and a cyclic deformation may occur along the strand length. This deformation will produce nonuniform bending strain along the strand. In order to verify the above consideration and to quantitatively evaluate the effect of this deformation, we prepared an apparatus to simulate this cyclic deformation by artificially applying a transverse load on the strand and its V-T characteristic was measured. When the strand received the transverse force of 10/sup 3/ /spl sim/10/sup 4/ N/m (which is expected value for a strand of the CS Insert operated at 13 T, 46 kA), n-value reduced to less than 15 from the original value of 30, which agreed to the phenomena observed in the CS Insert. This indicates that the transverse force acting on each strand causes the reduction in n-value of the CIC conductor.

Superconducting magnets for the LHC main lattice

Abstract: The main lattice of the Large Hadron Collider (LHC) employs about 1600 main magnets and more than 4000 corrector magnets. All superconducting and working in pressurized superfluid helium bath, these impressive line of magnets fills more than 20 km of the underground tunnel. With almost 70 main dipoles already delivered and 10 main quadrupoles almost completed, we passed the 5% of the production and now all manufacturers have fully entered into series production. In this paper the most critical issues encountered in the ramping up in such a real large scale fabrication is addressed; uniformity of the coil size and of prestress, special welding technique, tolerances on curvature (dipoles) or straightness (quadrupoles) and of the cold mass extremities, harmonic content and, most important, the integrated field uniformity among magnets. The actual limits and the solution for improvements are discussed. Finally a realistic schedule based on actual achievements is presented.

Test results for HD1, a 16 tesla Nb/sub 3/Sn dipole magnet

Abstract: The Superconducting Magnet Group at Lawrence Berkeley National Laboratory has been developing the technology for using brittle superconductor in high-field accelerator magnets. HD1, the latest in a series of magnets, contains two, double-layer Nb/sub 3/Sn flat racetrack coils. This single-bore dipole configuration, using the highest performance conductor available, was designed and assembled for a 16 tesla conductor/structure/pre-stress proof-of-principle. With the combination of brittle conductor and high Lorentz stress, considerable care was taken to predict the magnet's mechanical responses to pre-stress, cool-down, and excitation. Subsequent cold testing satisfied expectations: Training started at 13.6 T, 83% of "short-sample", achieved 90% in 10 quenches, and reached its peak bore field (16 T) after 19 quenches. The average plateau,/spl sim/92% of "short-sample", appeared to be limited by "stick-slip" conductor motions, consistent with the 16.2 T conductor "lift-off" pre-stress that was chosen for this first test. Some lessons learned and some implications for future conductor and magnet technology development are presented and discussed.

Development of wide-bore conduction-cooled superconducting magnet system for material processing applications

Abstract: The application of high magnetic field to material processing, so called electromagnetic processing of material (EPM) has been recognized as cutting edge technology, especially in the field of advanced material processing. It is the most effective methods to control thermal, mass and energy transfer during material solidification. A wide-bore conduction-cooled superconducting magnet with operating current of 116 A was designed, fabricated and tested for the material processing devices. The superconducting magnet has the effective warm hole of 18 cm, the maximum center field of 6 T and homogeneity of 5% in diameter of 5 cm. After the Nb/sub 3/Sn coil insert installed, the magnet can provide the maximum center field of 10 T with effective warm bore of 10 cm. A second-stage GM cryocooler with the second-stage cooling power of 1 W is used to cool the superconducting magnet from room temperature to 4.2 K. In this paper, the design, fabrication, test, stress analysis and quench protection characteristics are presented.

Characteristics analysis of transformer type superconducting fault current limiter

Abstract: The transformer type superconducting fault current limiter, which is made up of a series transformer and a superconducting current limiting device, has many advantages such as the design flexibility of the current limiting device. However, the design strategy for determining the superconducting current limiting device ratings and the transformer ratings is unclear because the relations between the current limiting characteristics and these ratings are not analyzed enough. In this paper, the relations between the current limiting characteristics and these ratings are analyzed theoretically. The experimental results of the transformer type superconducting fault current limiter are also shown.

Development and performance results of 5 MVA SMES for bridging instantaneous voltage dips

Abstract: The superconducting magnetic energy storage system (SMES) of output 5 MVA has been developed to bridge instantaneous voltage dips. The field examination is executed by setting up this system at the new and large liquid crystal factory in Japan. The developed SMES system can store up to 7.34 MJ of magnetic energy in superconducting coils using the NbTi Rutherford conductor. The maximum output of the developed SMES is 5 MVA, and the system can discharge the output for one s. The operating current of the coil is 2.7 kA, and the rated voltage is 2.5 kV. The field examination was started in July 2003. During the field test, we will confirm the performance of bridging instantaneous voltage dips by SMES, the long-term drive reliability and the standby loss characteristic.

Performance of an ITER CS1 model coil conductor under transverse cyclic loading up to 40,000 cycles

Abstract: The large currents in the cable-in-conduit conductors (CICC) destined for the high field magnets in the International Thermonuclear Experimental Reactor (ITER), cause huge transverse forces on the strands compressing the cable against one side of the conduit. This load causes transverse compressive strain in the strands at the crossovers contacts. Moreover, the strands are also subjected to bending and contact surfaces micro-sliding, which results into friction and anomalous contact resistance versus force behavior. Three Nb/sub 3/Sn central solenoid model coil (CSMC) conductors were tested previously in the Twente Cryogenic Cable Press up to 40 cycles with a transverse peak load of 650 kN/m. This press can transmit a variable (cyclic) transverse force directly to a cable section of 400 mm length at a temperature of 4.2 K (or higher). To explore life-time cycling, we tested a CSMC Nb/sub 3/Sn conductor up to 40,000 cycles. The coupling loss and the associated interstrand resistance between various strands and strand bundles are measured at various loads. The force on the cable and the displacement are monitored in order to determine the effective cable Young's modulus and the mechanical heat generation. Some aspects of strand deformation in CICC's are discussed. The test results are discussed in view of previous press results and data extracted from the ITER model coil tests.

Numerical analysis of high-temperature superconductors with the critical-state model

Abstract: A numerical method is proposed to analyze the electromagnetic behavior of systems that include high-temperature superconductors. The algorithm uses the finite-element method and the critical-state model, and it solves two-dimensional and axially symmetric problems that include superconductors and other materials. The main advantages of the algorithm are its speed, its robustness, and its ease of coupling with circuit equations. This method is used to analyze two different systems: 1) Magnet-superconductor levitation system-the levitation forces are calculated. In order to validate the model, experimental results of such a system are obtained and compared with simulation results. 2) Nine-wire superconducting cable. Parallel and series-type configurations of the current driven in the wires are analyzed. Hysteresis ac losses are also calculated and compared for both scenarios.

Effective application of superconducting magnetic energy storage (SMES) to load leveling for high speed transportation system

Abstract: The consecutive pulse power demand of the high speed transportation systems like Shinkansen, gives deteriorative influences to the power supply system and increases its operational costs. To cope with this problem, it has been studied to install the superconducting magnetic energy storage system (SMES) in railway substations. However, the scale of installation becomes too large because of low space factor of SMES, and hampers its realization. Then, it is considered to use SMES only for suppression of the high frequency component of load fluctuation, and to combine with a large capacity battery storage (BEMS), which can not follow fast fluctuation and covers its low frequency component. A novel control scheme of this combined energy storage system is proposed. The fluctuation of power demand caused by high speed train operations in a railway substation is measured separately in the frequency range and used to regulate both SMES and BEMS to suppress fluctuation. With simulation studies based on the load model of high speed train operation at a certain substation, this hybrid approach and its control scheme are verified effective. The system configuration is compact enough to be installed at a substation.

An FDTD model for calculation of gradient-induced eddy currents in MRI system

Abstract: In most magnetic resonance imaging (MRI) systems, pulsed magnetic gradient fields induce eddy currents in the conducting structures of the superconducting magnet. The eddy currents induced in structures within the cryostat are particularly problematic as they are characterized by long time constants by virtue of the low resistivity of the conductors. This paper presents a three-dimensional (3-D) finite-difference time-domain (FDTD) scheme in cylindrical coordinates for eddy-current calculation in conductors. This model is intended to be part of a complete FDTD model of an MRI system including all RF and low-frequency field generating units and electrical models of the patient. The singularity apparent in the governing equations is removed by using a series expansion method and the conductor-air boundary condition is handled using a variant of the surface impedance concept. The numerical difficulty due to the "asymmetry" of Maxwell equations for low-frequency eddy-current problems is circumvented by taking advantage of the known penetration behavior of the eddy-current fields. A perfectly matched layer absorbing boundary condition in 3-D cylindrical coordinates is also incorporated. The numerical method has been verified against analytical solutions for simple cases. Finally, the algorithm is illustrated by modeling a pulsed field gradient coil system within an MRI magnet system. The results demonstrate that the proposed FDTD scheme can be used to calculate large-scale eddy-current problems in materials with high conductivity at low frequencies.

Design of superconducting combined function magnets for the 50 GeV proton beam line for the J-PARC neutrino experiment

Abstract: Superconducting combined function magnets will be utilized for the 50 GeV-750 kW proton beam line for the J-PARC neutrino experiment and an R&D program has been launched at KEK. The magnet is designed to provide a combined function with a dipole field of 2.59 T and a quadrupole field of 18.7 T/m in a coil aperture of 173.4 mm. A single layer coil is proposed to reduce the fabrication cost and the coil arrangement in the 2D cross-section results in left-right asymmetry. This paper reports the design study of the magnet.

An optimal design of interior permanent magnet synchronous motor for the next generation commuter train

Abstract: In this paper, we propose a computational approach to the design of an interior permanent magnet synchronous motor to clarify its optimal design applied for traction systems of the next generation commuter train. In the approach, the finite element method, the multiobjective optimization technique, and the response surface methodology are effectively introduced. This approach enables us to save the CPU-time dramatically without degrading accuracies. Additionally, the proposed approach provides the effective information to design engineers. Finally we validate the proposed approach.

Design and fabrication of a 70 kA current lead using Ag/Au stabilized Bi-2223 tapes as a demonstrator for the ITER TF-coil system

Abstract: In the frame of the European Fusion Technology Programme, the Forschungszentrum Karlsruhe and the Centre de Recherches en Physique des Plasmas, CRPP, Villigen, develop a 70 kA current lead to demonstrate the feasibility of the usage of High Temperature Superconductors (HTS) for the current leads of the ITER TF coils. Design and fabrication of the conventional heat exchanger that covers the temperature range from 65 K to room temperature is done at the Forschungszentrum Karlsruhe. The HTS module connects the current feeder terminal at 4.5 K with the conventional heat exchanger and is cooled only by heat conduction from the cold end. Its design and fabrication has been performed by American Superconductor, AMSC. This module consists of Bi-2223 Ag/Au tapes embedded in stainless steel carriers with copper end caps. It is highly instrumented with voltage taps, temperature sensors and Hall probes. The integration with the heat exchanger and the current feeder terminal is carried out at the Forschungszentrum Karlsruhe. The current lead will be tested in the TOSKA facility in the first months of 2004. The paper describes the design, fabrication and results of pretests carried out at AMSC and Forschungszentrum Karlsruhe.

Prototype of superferric quadrupole magnets for the BigRIPS separator at RIKEN

Abstract: Three superferric quadrupoles with a pole-tip radius of 170 mm and a design field gradient of 14.1 T/m have been constructed and mapped for use as spectrometer elements. All three quadrupoles are assembled into a single cryostat and cooled by liquid-He bath cooling method. A small Gifford-McMahon/Joule-Thomson (GM/JT) cooler, mounted on the cryostat, requiries He gas that evaporates in the He vessel. The high-T/sub c/ superconducting current leads and radiation shield surrounding the He-vessel, cooled by a small GM cooler, reduce the heat load of the He vessel. Both cryocoolers operate using separate water-cooled compressors and allow us a stand-alone operation of the quadrupole magnets without big cryoplant. Results of quench protection tests, measured heat loads and mapped results are presented.

Status of the construction of the CMS magnet

Abstract: CMS (compact muon solenoid) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive features include a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10,000-ton return yoke. The stored magnetic energy is 2.6 GJ. The magnet is being assembled in a surface hall and will be tested at the beginning of 2005 before being transferred to an experimental hall 90 m below ground level. The design and construction of the magnet is a common project of the CMS Collaboration. The task is organized by a CERN based group with strong technical and contractual participation of CEA Saclay, ETH Zurich, Fermilab, INFN Genova, ITEP Moscow, University of Wisconsin and CERN. The return yoke, 21 m long and 14 m in diameter, is equivalent to a thickness of 1.5 m of saturated iron interleaved with four muon stations. Manufacture of the yoke and vacuum tank is completed and the first sub-detectors have been installed. The indirectly-cooled, pure-aluminum-stabilized coil is made up from five modules internally wound with four layers of a 20 kA mechanically-reinforced conductor. The manufacture of the conductor is completed and winding is in progress for a final assembly in 2004. All ancillaries are delivered or under contract. The magnet project is described, with emphasis on the present status of the fabrication.

Optimization of hysteresis parameters for the Jiles-Atherton model using a genetic algorithm

Abstract: A dynamic model with hysteretic nonlinearity for magnetostrictive actuators has been established, combined with the Jiles-Atherton model. The hysteresis parameters for the model have been optimized using the genetic algorithm (GA). Simulation and experimental results demonstrated the effectiveness of the model and parameter identification approach.

Development of MJ-class HTS SMES for bridging instantaneous voltage dips

Abstract: MJ-class HTS SMES has been developed for bridging instantaneous voltage dips using newly-developed Bi-2212 cable. The developed Bi-2212 wire for SMES coils achieves high-performance conductive characteristics that do not deteriorate in high magnetic fields beyond 10 T, which enable compactly arranged SMES coils to be operated in a high magnetic field, and SMES coils of the Bi-2212 wire can be adequately insulated due to a high temperature margin. Therefore it is possible for the SMES coils to enhance dielectric strength and output power. The insulating, cooling and conductive characteristics of 4 unit coils (Outer Diameter: 700 mm, Height: 127 mm, Stored Energy: 90 kJ) were checked under a variety of conditions. Moreover, fundamental performance tests were done on bridging instantaneous voltage dips, using a 125 kW resistance and 50 kW motor as imitation loads. Testing showed that the HTS SMES operated reliably. Up to the present, 11 unit coils (Outer Diameter: 700 mm, Height: 390 mm, Stored Energy: 560 kJ) have been stacked and tested.

Development of low carbon and boron added 22Mn-13Cr-9Ni-1Mo-0.24N steel (JK2LB) for jacket which undergoes Nb/sub 3/Sn heat treatment

Abstract: Japan Atomic Energy Research Institute has developed a low carbon and boron added 0.03C-22Mn-13Cr-9Ni-1Mo-0.24N-0.003B steel (JK2LB) for a conductor jacket of the central solenoid for the International Thermonuclear Experimental Reactor in collaboration with Kobe Steel Ltd. The feature of JK2LB is to have enough ductility and toughness after reaction heat treatment to produce Nb/sub 3/Sn. Tensile properties, fracture toughness, and fatigue crack propagation rate were measured at 4 K by using samples taken from an intermediate billet and the final jacket of JK2LB, which were produced with a mass production line. The average elongation and fracture toughness at 4 K after the heat treatment are 33% and 93 MPa/spl radic/m for the final jacket, and 30% and 121MPa/spl radic/m for the intermediate billet, respectively. The mechanical properties of weld metals were also evaluated and all data satisfied the ITER targets. It was also clarified that improvement of ductility and toughness were caused by reduction of chromium carbide precipitations due to low carbon and boron addition.

12 kA HTS Rutherford cable

Abstract: One of the advantages of Bi-2212 is that a high J/sub c/ value can be obtained in wires with various shapes and filament configurations. Realization of a high J/sub c/ round wire made it possible to fabricate many kinds of cable developed for applications of low temperature superconductors (LTC). We successfully fabricated a 30-strand Rutherford cable using 0.8 mm/sup d/ round wire. Optimization of cabling factor enables to reduce the I/sub c/ degradation at the cable edge. I/sub c/ values were about 650-750 A at 65 K in a noninductive winding condition, which corresponds to 11-13 kA at 4.2 K in self-field.

Stability of bare and copper-laminated YBCO samples: experimental & simulation results

Abstract: In this study of stability of YBCO composite, we investigate quench/recovery behavior of YBCO test samples, bare and copper-laminated, by subjecting each test sample, immersed in a bath of liquid nitrogen boiling at 77.3 K, to a transport current pulse superimposed to a baseline DC current of 90-95% the critical current. The current pulse has an amplitude up to /spl sim/4.5 times the critical current and a duration of 300 ms. This paper presents both experimental and simulation results showing that composite YBCO tape that incorporates a copper lamina stabilizes and to a degree protects the conductor against large over-current pulses.

High gradient magnetic separation combined with electrocoagulation and electrochemical oxidation for the treatment of landfill leachate

Abstract: Landfill leachate was treated in a bench scale plant by high gradient magnetic separation combined with electrocoagulation using iron electrodes and electrochemical oxidation. The electrocoagulation with iron electrodes was used as a magnetic seeding method for phosphorus and organic compounds. Some organic compounds in landfill leachate was coagulated by iron(II) hydrates or hydroxides produced from iron electrodes. Phosphorus in landfill leachate was also suspended as iron phosphate. These magnetized solids were removed by high gradient magnetic separation using a superconducting magnet. The removal rate of total phosphate (T-P) was approximately 90% at a flow rate of 100 L/h. Residuals in the effluent of magnetic filter such as ammonium nitrogen (NH/sub 4/ - N) and chemical oxygen demands (COD) were destroyed by electrochemical oxidation using Ti/PbO/sub 2/ anode. The hypochlorite generated from oxidation of chloride in leachate might play a key oxidant in the effective removal of NH/sub 4/ - N. The experimental result showed that the pretreatment combined process of electrocoagulation using iron electrodes and high gradient magnetic separation might improve the charge efficiency in electrochemical oxidation. Several chemicals that were suspected of having environmental endocrine disrupting effects was also decreased.

HD1: design and fabrication of a 16 Tesla Nb/sub 3/Sn dipole magnet

Abstract: The Lawrence Berkeley National Laboratory (LBNL) Superconducting Magnet Group has completed the design, fabrication and test of HD1, a 16 T block-coil dipole magnet. State of the art Nb/sub 3/Sn conductor was wound in double-layer racetrack coils and supported by an iron yoke and a tensioned aluminum shell. In order to prevent conductor movement under magnetic forces up to the design field, a coil pre-stress of 150 MPa was required. To achieve this level without damaging the brittle conductor, the target stress was generated during cool-down to 4.2 K by exploiting the thermal contraction differentials between yoke and shell. Accurate control of the shell tension during assembly was obtained using pressurized bladders and interference load keys. An integrated 3D CAD model was used to optimize magnetic and mechanical design and analysis.

Multiobjective design optimization of brushless permanent magnet motor using 3D equivalent magnetic circuit network method

Abstract: In this paper, we discuss multiobjective design optimization of brushless permanent magnet motor (BLPMM) solved by genetic algorithm (GA) and 3D equivalent magnetic circuit network (EMCN) method. In the multiobjective optimization (MO) problem, we choose the decrease of cogging torque and the increase of torque as objectives. The airgap length, teeth width and magnetization angle of permanent magnet (PM) are also selected for the design variables respectively. From the results, our approach method enabled us to efficiently obtain diverse Pareto optimal (PO) solutions from the practical point of view. The experimental results are shown to confirm the validity of the optimization results.

Development of a persistent current switch for HTS magnets

Abstract: This paper describes design concept, fabrication, and experimental results of a persistent-current switch (PCS) for high temperature superconducting (HTS) magnets. Recently large-size HTS magnets have been fabricated with Ag-sheathed Bi2223 wires. Even in the case of HTS magnets, persistent-current mode has the advantage of maintaining a steady magnetic field for long periods. A PCS for an HTS magnet is a key component to realize persistent-current mode. A PCS for an HTS magnet must work at the same operating temperature as an HTS coil, and electrical resistivity for a PCS conductor should be sufficiently large to reduce the energy dissipation during charge and to shorten the switching time. To satisfy these requirements, a YBCO thin film is adopted for a PCS conductor. The PCS is used in a vacuum and conductively cooled by a cryocooler at around 20 K when the switch is "on". To change the PCS from "on" to "off", the temperature of the PCS is increased to around 100 K by electrical heaters. A new design concept of a PCS for an HTS magnet is introduced. And the test results of rated current operation, switching operation and persistent-current operation are shown.

Development of a thin-wall superconducting magnet for the positron spectrometer in the MEG experiment

Abstract: A thin-wall superconducting magnet was developed for the positron spectrometer in the MEG experiment. The magnet is specially designed to provide a gradient magnetic field to achieve good features of the spectrometer such as constant projected bending radius for monochromatic positrons and much quicker sweep of positrons than in the conventional uniform solenoidal field, which allows a stable operation of the spectrometer in a high rate muon beam. A high-strength aluminum-stabilized conductor was developed so as to minimize the thickness of the coil between the target and photon detector. A pair of compensation coils is implemented in the magnet to cancel stray field around the photon detector to be placed closely to the magnet. Design of the magnet and results from the excitation tests to measure performance of the magnet will be presented here.

Numerical evaluation of AC loss in high temperature superconducting coil

Abstract: An approximated method to estimate the electro-magnetic AC loss in high temperature superconducting coil was proposed. We applied this method to estimate the AC loss characteristics of the high temperature superconducting coil made by stacking pancake coils which are wound by Bi2223/Ag tape. The analytical AC losses of the HTS coil were compared with the measured AC losses before and after impregnation by epoxy resin obtained in the previous work by National Institute of Advanced Industrial Science and Technology. The analytically estimated electro-magnetic AC losses in the HTS coil were much smaller than the measured AC loss of the coil. The AC loss characteristics could not be explained by the method proposed in this paper. The main reason of this discrepancy was considered that the measured AC losses in the HTS coil contained large amount of the mechanical AC loss due to the AC vibration of the winding even if the HTS coil was impregnated.