Search

The Broader Approach agreement between Europe and Japan includes the construction of a fully superconducting tokamak, the JT-60 Super Advanced (JT-60SA), as a satellite experiment to ITER. In particular, the whole Toroidal Field magnet system, described in this paper, will be provided to Japan by the EU. All the TF coil main constituents, i.e. conductor, winding pack, joints, casing, current leads, are here presented and discussed as well as the design criteria adopted to fulfil the machine requirements. The results of the analyses performed by the EU and JA to define and assess the TF magnet system conceptual design are reported and commented. Future work plan is also discussed. [ABSTRACT FROM AUTHOR]

We analyse the issues of quench propagation in the NbTi Poloidal Field Conductor Insert (PFCI), recently tested at JAEA Naka, Japan. The simulation tools Mithrandir, already validated against data from previous Nb3Sn Insert Coils, and M3, implementing a more detailed thermal-hydraulic description of the CICC cross section, are used. The results of the analysis are reported in the paper and compared with experimental data, with particular attention to NbTi versus Nb3Sn features and to the effects of different model assumptions. [ABSTRACT FROM AUTHOR]

Since 2003, three years of the current 5-year national project for development of coated conductors using Y-system superconductors have passed and remarkable results have been achieved. In this paper, the current status and future prospects are reviewed. The group of Fujikura and SRL has worked on a long tape with high performance in the PLD-YBCO supercon- ducting tapes on the IBAD-GZO buffered substrates. The highest Ic × L value of the tape is over 50 k Am which is 212 m in length and 245 A of critical current (Ic). Additionally, a 500 m long IBAD-buffered tape with a reasonable in-plane texture was produced using a large scale IBAD apparatus by Fujikura. In the other group, long tape processing has been developed focusing on lowering production cost. An extremely high Ic value of 692 A was obtained in a short sample by the advanced TFA-MOD method on a CeO2 (PLD)/GZO(IBAD)/Hastelloy substrate. In the efforts for the long tape processing, a 25 m long tape with the Ic value of 100 A by a continuous reel-to-reel system and a 40 m long tape with 155 A by a batch system were realized. 100 m class long tapes were also obtained with the MOCVD and PLD-HoBCO processes. Both groups are aiming for 500 m long tapes with the high Ic value of 300 A/cm-w with a production rate of 5 m/h. Furthermore, feasibility studies for applications using coated conductors have already began due to the above mentioned success of long tape production. Several kinds of coils using the long coated conductors such as solenoid and pancake types and spiral shaped conductors for the cable were made. Reasonable high performance results were confirmed in the trials. New approaches on the preliminary studies for the applications of cables, transformers, motors and current limiters etc. are planned in this project. [ABSTRACT FROM AUTHOR]

Development of the SMES using high temperature superconducting (HTS) coil has progressed as a Japanese national project since FY 2004. The objective of the project is to obtain around twice the normal energy density via an HTS-LTS ‘hybrid’ coil system compared to an LTS coil system. The HTS coil is composed of sixteen double-pancake coils and the double-pancake coil is wound with a Bi2212 Rutherford-type cable. The HTS coil is operated at 4.2 K in liquid helium bath with the LTS coil, and operated at maximum field of 8.9 T. Before we made a hybrid coil system, we verified the design issues using HTS experimental coils. In this paper mechanical compression tests, DC operation tests and thermal runaway tests using the experimental coils are discussed. [ABSTRACT FROM AUTHOR]

R&D of fundamental technologies for superconducting AC Power equipment (Super-ACE project) started as a national project, for a five-year plan since fiscal 2000 by MIT and NEDO. This project is to research and develop the basic technology of super-conductive cable, fault current limiter and transformer. This paper summarizes the research and development of following 2 types FCL. The R&D of the SN transition resistive type superconducting thin film fault current limiter aims to establish large-current/high-voltage technology by arranging films in multi-parallel/series, and increasing the current-carrying capacity through widening the area of the thin film of the current limiting element. The R&D of the reactor for a rectifier-type fault current limiter using coils of superconducting wire of the Ag sheath Bi2223 tape, aiming to apply it to high-voltage systems. [ABSTRACT FROM AUTHOR]

Studies on superconducting generators have been carried out worldwide. Especially in Japan, it is worthy of attention that Super-GM led the national project concerning the successful development of the 70 MW-class superconducting generators. Low-temperature superconducting wires have been applied to field windings of generators. In Japan, the next-generation coated conductors, namely, high-temperature superconducting wires, have proceeded under the national project supported by NEDO. Provided that the next-generation coated conductors are applied to field windings, the weight and volume of superconducting generators will be reduced. Furthermore, using liquid nitrogen as a coolant instead of liquid helium, the reliability of high-temperature superconducting generators is expected to improve. This paper provides tentative designs of a high-temperature superconducting generator whose field windings are composed of YBa2Cu3O7-x wires. By comparison with the low-temperature superconducting generator developed by Super-GM, the usefulness of the high-temperature superconducting generator is discussed. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(1): 1–7, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10052 [ABSTRACT FROM AUTHOR]

The superconducting tokamak JT-60SA is currently being assembled at the QST laboratories in Naka (Japan). Within the European contribution in the framework of the Broder Approach, Spain is responsible for providing JT-60SA cryostat. It is a stainless steel vacuum vessel which encloses the tokamak providing the vacuum environment. Due to functional purposes, the cryostat was divided into three large assemblies: the Cryostat Base, the Cryostat Vessel Body Cylindrical Section and the Top Lid. The second is an envelope made from SS304 that will be assembled by mechanical connection between the individual sectors. As part of the manufacturing process, dimensional inspections are carried out by laser tracker to check the tolerances of the pieces. Due to the high mechanical flexibility of the sectors, the way to support the pieces resulted very critical for the inspections as it was predicted by FEA carried out. The paper summarizes the measurement procedure for the dimensional inspections as well as the pre-assembly procedure of the whole component. [ABSTRACT FROM AUTHOR]

In commercializing the superconducting Maglev system it is important to reduce the cost, especially that of ground coils constructed along the whole length of the guideway. For this purpose we have examined the combined propulsion, levitation and guidance system (PLG system) which can generate levitation, guidance and propulsion, forces by the same coil. This paper describes the test run of the PLG system, whose ground coils (PLG coil) are constructed in one part of the Miyazaki test track. In designing the PLG coil, we make clear the magnitudes of the force acting both under normal and unusual conditions because the electromagnetic force, which levitates, guides, and propels the vehicle, directly acts on the magnet winding of the PLG coil. In the experiment, we examine both the performance of the vehicle and the force of a PLG coil. The measurement of the force at the PLG coil gives not only propulsion force and levitation force directly, but also guidance stiffness by sifting the measured coil. Good correlation recognized between the calculation and the experiment in the propulsion force, levitation force, and guidance stiffness proves that the required characteristics can be expected from the PLG system even under combination of propulsion, levitation and guidance. [ABSTRACT FROM AUTHOR]

Since the discovery of the new high Tc superconductor, various kinds of film growth techniques have been reported on fabrication of an oxide superconducting film, especially YBCO and BSCCO above liquid nitrogen temperature. All these techniques require the so-called post-growth heat treatment or a heating of the substrate during the deposition to grow an adequate polycrystal which can realize the superconducting state in the oxide. Such a heating process, however, yields some intermediate products at a boundary layer between the starting materials and the substrate, and the products result in degradation of the superconducting property. In this paper, the annealing effect on the growth of YBCO or BSCCO oxide superconducting film and the substrate is investigated by using EDX analysis and SEM examination. To enhance the annealing effect, relatively thin YBCO and BSCCO films are fabricated with the starting materials pasted on substrates, and rather than sputtered thin films used for the analysis. Mg0, A1203, SrTi03, 5 or 8 percent Y stabilized Zr02 (YTZ or YSZ), and so on, are chosen as a substrate. The results show that the heat treatment yields Ba compounds between YBCO and the substrafes and Sr and Bi compounds between BSCCO and the substrates. Since the product boundary layer of the intermediate product is the thinnest, Mg0 substrate can be recommended for YBCO film, and SrTi03 substrate for BSCCO film. [ABSTRACT FROM AUTHOR]

Abstract: The upgrade of JT-60U magnet system to superconducting coils (JT-60SA) is progressing by both parties of Japanese government and European commission in the framework of the Broader Approach agreement. The magnet system for JT-60SA consists of 18 Toroidal Field (TF) coils, a Central Solenoid (CS) with four modules, six Equilibrium Field (EF) coils. The TF coil case encloses the winding pack and is the main structural component of the magnet system. The CS consists of four independent winding pack modules, which is support from the bottom of the TF coils. The six EF coils are attached to the TF coil cases through supports with flexible plates allowing radial displacements. The construction of CS and EF coils was started in 2008 by Japan Atomic Energy Agency (JAEA). The construction of TF coils will be started in 2009 by Fusion for Energy and European voluntary contributors. This paper introduces the design of the JT-60SA superconducting magnet system and activities for development of magnet components in Japan. [ABSTRACT FROM AUTHOR]

Abstract: The mission of the JT-60SA Tokamak, to be built in Japan, is to contribute to the early realization of fusion energy by its exploitation in support of the ITER program. JT-60SA project is an important part of the “broader approach” activity as a satellite program for ITER. The toroidal field (TF) coils are a European “in kind” contribution and they will partly be built by France. JT-60SA TF coil uses the Cable In Conduit Conductor (CICC) with NbTi superconductor strands. TF conductors will have to operate at 5.7T, 5K and at current density of 450A/mm2 with sufficient margins. In the framework of JT-60SA TF coil manufacture, the variable temperature characterization is an important step to select NbTi strand. At an early stage of design, we had to choose the strand with acceptable performances. During the design qualification and validation stage, it is important to qualify strands in conditions close to the operation conditions. The industry has proposed various strands manufactured with different processes. This work and publication examines a strand with an internal CuNi barrier, which is expected to lead to better current distribution between strands, by more precise calibration and control of the inter-strand resistance. The strands were tested at the Grenoble High Magnetic Field Laboratory facility. The domain (B,T,J) explored was in the range of 4.5–11T for the magnetic field intensity, 4.2–6.5K for the temperature and between 40A/mm2 and 1200A/mm2 for the current density. For each strand, “critical current density” and “current sharing temperature” measurements have been carried out, with a temperature precision of few tens of mK. Once the measurements performed, the fitting parameters (of type J C =f(B,T)) of each strand have been found, by performing regression analysis. This work will lead to select the strand with the best characteristics. In this paper, we present the results of this measurement task, the data and regression analysis (fits, T cs, etc.) and the conclusion about the strand choice. [Copyright &y& Elsevier]

Abstract: The current 5-year national project since 2003 for development of coated conductors (CC) using Y-system superconductors has passed for almost a half term and has achieved satisfactory results. In this paper, the current status and the future prospect are reviewed. The group of Fujikura Ltd. and SRL-ISTEC has worked on the long tape with high performance in the PLD-YBCO superconducting tapes on the IBAD-Gd2Zr2O7 buffered substrates. The highest value on the product of I c × L in the world was marked by the result which were 51,940Am (212m×245A) by the SRL group. Fujikura Ltd. also realized the longest tape of 200m with a reasonable high I c value of 100A. The values have been steadily improved and the trend is going to be continued, since the large equipments for both IBAD and PLD have been installed, and ready to work on large tapes with a high production rate. In another group, the long tape processing has been developed focusing on lowering the production cost. The extremely high I c value of 470A was obtained in the film by the TFA-MOD method on CeO2 (PLD)/GZO(IBAD)/hastelloy substrate. In the efforts for the long tape in the process, a 25m long tape with its I c value of 100A was realized by a continuous reel-to-reel system. Additionally, 100m class long tapes were also obtained by the MOCVD and PLD-HoBCO processes. Both groups are aiming to achieve the final goals of 500m long tapes with the high I c value of 300A/cm-w by the production rate of 5m/h. Furthermore, the feasibility study for applications using coated conductors has been already started due to the above-mentioned success of long tape production. Several kinds of coils using long coated conductors such as a solenoid and a pancake coils and the spiral shaped conductors for cable applications were firstly made. Reasonable high performances were confirmed in the trials. For the future plans of coated conductor applications, the following power devices using coated conductors have been proposed; (1) power cable, (2) transformer, (3) motor, (4) fault current limiter, (5) cryocooler, and so on. [Copyright &y& Elsevier]

Japan Atomic Energy Research Institute (JAERI) plans to construct a tokamak fusion device called JT-60SC in which superconducting magnet systems will be used. The purpose in this paper is to qualify type 316LN stainless steel (SS316LN) for use as the conduit material of the Nb3Sn cable-in-conduit conductor for the central solenoid (CS) of JT-60SC. Tensile properties, fracture toughness and fatigue crack growth rates of the as-welded metal and the aged (923 K × 240 h) one of SS316LN were evaluated at 4 K. The tensile properties and fatigue crack growth rates were adequate to ensure the design requirements for JT-60SC. However, fracture toughness of the aged weld metal could not be validated due to unstable crack growth. It was concluded that improvement of fracture toughness after aging was required to ensure the structural integrity of the CS conduit. [Copyright &y& Elsevier]

Railway transportation is of safety, convenience, economy, and environmental friendliness. However, with energy issues becoming increasingly important in this century, it is important to assess the situation in the transportation sector. When the superconducting cable is used as a feeder of the railway electrification system, the voltage drop can be significantly reduced. Therefore, the superconducting feeder has many effects, for example, the reduction transmission losses, the improvement of the regeneration factor, and the reduction of substations. We designed superconducting feeder and introduced to the Izuhakone Railway Sunzu line in Japan. After the system was checked from the aspect of cooling and current properties, the train running test was conducted. From the result of switching notch tests, it was found that the current flows continuously via the superconducting cable according to the notch operation. Furthermore, to inspect the influence of superconducting material, a large pulse current test was performed using the transmission equipment of a railway. It can be confirmed that superconductor can be used as railway feeder because the materials can cope with the current change peculiar to railway required for practical use. [ABSTRACT FROM AUTHOR]

The 12th International Superconductive Electronics Conference (ISEC 09) was held in June 2009 in Fukuoka, Japan. The conference was very successful, with 253 participants from 17 countries. This special issue is a compendium of selected papers based on the technology presented at that meeting. ISEC has established itself as the leading meeting specializing in superconductor-based electronics and has been organized every two years since 1987. This conference provides an opportunity to present the latest developments in superconductive electronics research, and to interact among the world''s experts with maximal interchange between the various topics. The main theme at ISEC 09 was developments in superconductive devices and electronics systems for advanced sensing, medical, communication and information technologies. Technical topics covered at ISEC 09 include: Digital/mixed signal processing RF electronics SQUIDs and their applications Mixers and detectors Thin film materials, junctions and novel devices. Among the 210 presentations, including plenary, oral and poster, only very high quality presentations have been selected for this special issue. Since the success of the conference depends on many invaluable contributions, I must express my appreciation to many individuals and organizations, in no particular order. I would like to thank the Japan Society for the Promotion of Science (JSPS) 146 Committee for co-organization of the conference. I owe a huge debt of gratitude to Akira Fujimaki and the rest of the program committee members for the stimulating conference program. Catherine Foley and Hideo Itozaki both played a prominent part in arranging the special issue as Guest Editors. I would also like to acknowledge the support of JSPS, The Fukuoka Convention and Visitors Bureau, The Murata Science Foundation, Tateisi Science and Technology Foundation, and Kyushu University. Finally, I would like to thank each and every participant at ISEC 09 for making a worthwhile contribution. Your work and your willingness to make this conference a success are indispensable. [ABSTRACT FROM AUTHOR]

The article reports on the discovery of iron-based superconductors by Hideo Hosono of the Tokyo Institute of Technology in Japan. It indicates that superconductivity of the iron-based materials occurs in corrugated layer which is composed of iron and either phosphorus or arsenic. It also mentions that the atoms of iron in an iron-based superconductor are more closer to each other compared with the copper atoms in a cuprate superconductors. INSET: Discovering new superconductors in old materials.

Japan Atomic Energy Agency has developed four types of Nb3Sn strand which can be used in the ITER TF coils. One is a strand made by an internal tin process strand and the others are bronze process strands. The achieved critical current density is more than 790 A/mm2 in the bronze process strands and more than 980 A/mm2 in the internal tin process strand under 4.2 K temperature and 12 T magnetic field and there is hysteresis loss of less than 770 mJ/cc under ± 3 T cycle. Since these strands are utilized with an external strain, it is necessary to evaluate strain dependency to confirm the ITER conductor design. An apparatus to measure the strain dependency was newly developed. It has a horseshoe-shaped ring to produce uniform axial compressive or tensile strain along the strand length, a strand being soldered on the outer surface of the ring. The detailed strand characteristics were investigated subjecting the developed strands to a magnetic field from 10 T to 13 T, a strain from about -0.8% to 0.5%, and a temperature from 4.2 K to the critical temperature. When the critical current is normalized to that under the conditions where strain is intrinsically zero, the bronze process strands exhibit better performance than the internal tin process strand. However, the three bronze process strands do not exhibit the same Ic-strain characteristics. Two types of scaling relations are applied to the data, and good expressions of strand performance were obtained by the least square method within 3 A as RMS. [ABSTRACT FROM AUTHOR]

Power supply for the large-scale accelerator magnets draws a large amount of power from the utility network. For an example, the new proton accelerator complex for high intensity beam (Japan Particle Accelerator Research Complex, J-PARC) is under construction at the Tokai campus of Japan Atomic Energy Agency (JAEA) as a joint project between KEK and JAEA. The J-PARC SO GeV proton synchrotron (50 GeV-PS) magnets power supplies are constructed with IGBT and IEGT, then the power factor is almost 100%. However, the swing of an active power becomes almost 170 MW, although the average power is about 50 MW. Such large pulse power will give un-allowed disturbances to an ac power line. A SMES system will be required for compensating such as pulse electric power and reducing the disturbances. Case study on circuit configuration of the power supply with SMES and present status of the R & D for the SMES system will be discussed. [ABSTRACT FROM AUTHOR]

The toroidal magnetic field of ITER is provided by 18 Nb3 Sn superconducting coils that provide 5.3 Tin the Tokamak magnetic centre thanks to a nominal current of 68 kA. Two major procurement packages will be integrated to accomplish the final assembly of the coils: 1) the winding pack which houses the double pancakes in 7 stacked radial plates (RP) and 2) the TF coil case which houses the winding pack (WP) and is the main structural component of the ITER machine. 19 TF coil cases (18+1 spare) will be entirely procured by Japan, whereas the WP and the TF coil assembly will be shared between Japan (9) and Europe (10). The insertion process of the WP inside the coil case, VPI and final closure welding is presented with an emphasis on the R&D still remaining. An appropriate metrology strategy and correct benchmarking of the WP current center line (CCL) in the coil case external walls is essential to allow the correction of the error fields during operation. The TF coils will be assembled and pre-aligned in pairs together with their corresponding VV sector and craned to the Tokamak hall hanging from 2 independent hooks. The integration of the IF coils in the Tokamak primary datum system will have to bc accomplished within the maximum tolerances defined by the error field analysis. As-built 3D data collected during manufacture will be used to ensure the correct positioning of the CCL against the Tokamak datum system and ease the alignment process. Shimming will be used in the gravity support for vertical alignment and in the upper and lower OIS for toroidal alignment. A subsequent survey of the `as-installed' TF coils will determine the final Tokamak Datum System. [ABSTRACT FROM AUTHOR]

The demonstration and verification tests of a 500 m High-Tc superconducting (HTS) cable were carried out at the CRIEPI laboratory in Yokosuka from March 2004 to March 2005. The HTS cable consisted of a cold dielectric core with nominal capacity of 77 kV and 1 kA that had an HTS shield layer. CRIEPI and Furukawa have conducted tests for investigating the basic properties of the cable and a long-term loading test for confirming 30-year operations. Moreover, we conducted an ‘over-loading test’ and a ‘cooling system fault test’ to investigate the reliability and safety of the cable. After all field tests, the cable was dismantled and taken away from the site to Furukawa's factory for internal inspection. No Ic degradation was found in the HTS conductor, but local degradation was seen in the HTS shield. These degradations might have arisen because protective layer for the shield did not have enough thickness but were within the acceptable range of about 5%. [ABSTRACT FROM AUTHOR]

Recent progress in single flux quantum (SFQ) device technologies in Japan is described, mainly focusing on those developed in the NEDO ‘Superconductors Network Device Project’ which includes developments of both LTS and HTS devices. The advanced Nb process which consists of a planarized structure with nine Nb layers and 10 kA/cm2 Josephson junctions (JJs) has been developed. This enables fabrication of chips including 100,000 JJs and operating frequency up to 80 GHz. We have also developed the CAD tool by which one can generate SFQ circuit layouts including about 400,000 JJs from logic descriptions. For demonstration of a small-scale switch system, a 4 x 4 switch chip, a 117 Gbps multi- chip-module (MCM) technology, and a packaging technology with 32-ch 10 Gbps I/Os to an MCM have been developed. By using the multilayer process with three HTS epitaxial layers and interface- engineered ramp-edge JJs, we demonstrated operation of SFQ circuits with up to 200 JJs. A variety of elementary SFQ circuits such as a T-FF and a 1:2 switch required for an A/D converter front-end circuit have been designed based on a new layout method, and their operation at 30-50 K has been confirmed. A prototype sampler system is being developed for demonstration of bandwidth over 100 GHz for optical input signals. [ABSTRACT FROM AUTHOR]

The plasma confinement device ‘RT-1’ which had a high temperature superconducting (HTS) floating magnet was constructed for advanced high-beta plasma and fusion research at the University of Tokyo. The high temperature superconducting (HTS) floating magnet is magnetically levitated inside the plasma vacuum vessel. Plasma is confined by a magnetic dipole field around the HTS floating magnet. The HTS floating magnet is operated in persistent-current mode and it consists of an HTS coil, an HTS persistent-current switch (PCS), a pair of demountable joints of current leads, detachable joints of a cooling tube, a thermal shield and a vacuum vessel. The HTS coil and the PCS and the thermal shield are cooled below 20 K by a flow of helium gas through the cooling tube. The floating HTS magnet is designed to operate in the temperature range from 20 K to 30 K without being cooled while it is levitated. We fabricated a persistent-current HTS coil that consists of the HTS coil and the PCS. Persistent-current operations and protection tests were conducted with the persistent-current HTS coil before it was mounted in the floating magnet cryostat. The current-decay rate was 0.9% in an 8 hour operation. The coil energy was safely discharged by inducing PCS quench in a protection test. [ABSTRACT FROM AUTHOR]

After a brief review on advanced applications of magnetic fields generated by high-Ta bulk superconductors in Japan, the outline and present status of the CREATE (Collaboration of Regional Entities for the Advancement of Technological Excellence) Iwate Project "Advanced Application of Magnetic Fields-The creation of industries based on magnetic fields application-" will be described. [ABSTRACT FROM AUTHOR]

Second generation superconducting tape made of an REBa[sub 2]Cu[sub 3]O[sub 7-δ] (RE-Ba-Cu-O) is expected to show improved magnetic field dependence and more economical production cost than that shown by the first generation one of Bi-compound tape. It consists of at least three layers: a metal layer, a buffer layer of some oxide, and a superconducting layer of RE-Ba-Cu-O. Therefore, it is called a "coated conductor." There are several choices of materials and processes when making a metal-buffer layer structure and the processing of the RE-Ba-Cu-O layer. The main difficulties in producing a long superconducting tape are that the RE-Ba-Cu-O layer grains must be in-plane aligned and any defects must not exist throughout the whole length of the tape. Several different processes to obtain the biaxially textured buffer layers or metal substrates, as well as nonvacuum process for deposition of superconducting layers and buffer layers, have been developed. At present, we have developed a coated conductor tape, 30 m in length and about 0.1 mm in thickness, by means of ion beam assisted deposition (IBAD) and pulsed laser deposition (PLD), with J[sub c] of 0.79 MA/cm² at 77 K. This presentation will review the current status of R & D on coated conductors in Japan, which includes developments of textured metal substrates including surface-oxidation epitaxy, IBAD and inclined substrate deposition for a buffer layer, and PLD and metal organic deposition for the superconducting layer. [ABSTRACT FROM AUTHOR]

Discusses the activities in High Field Laboratory for Superconducting Materials (HFLSM) at the Tohoku University in Sendai, Japan. High field magnets operated in HFLSM; Principal achievements and research planning; Research on magnetism, optical properties and high field physical properties.

A mirror furnace system for annealing of superconducting thin films, which is adapted for the world's longest dropshaft completed at Kamisunagawa, Japan, is described. The system must be designed for completing both melting and solidification processes during a short 10-s microgravity period, and also for withstanding the deceleration of a drop capsule in which the furnace system is Contained. All moving components must be operated so as not to disturb the microgravity environment. A random vibration test for the entire system was carried out before the microgravity experiment, and structural compatibility was verified. The furnace system worked well, and the accumulated number of free falls was 19. Results of annealing of the superconducting material at one gravity and microgravity were compared using scanning electron microscopy and x-ray microanalysis. [ABSTRACT FROM AUTHOR]

A medium-sized, high magnetic field magnet was designed using data on the mechanical properties of Bi/Ag oxide tape superconductors. Due to the poor mechanical properties of tape superconductors, the size of a superconductive magnet is limited to a narrow region of radius and magnetic field. In order to build a large superconductive magnet, key mechanical properties of the Bi/Ag oxide tape superconductors, such as irreversible strain and matrix yield strength, have to be improved significantly. [ABSTRACT FROM AUTHOR]

Focuses on the results of the design of a two-pole 600-MW superconducting generator to be installed at a power station in Japan. Stability requirements of the power system; Use of superconductors in the field windings of the superconducting generator; Means of reducing the self-inductance of the field winding.

Japan Atomic Energy Agency has successfully developed Nb3Sn strand which fulfills ITER requirements. Because Nb3Sn is very susceptible to external strain which reduces critical current, critical temperature, and critical field, it is necessary to evaluate strain dependency of these Nb3Sn strands to confirm an ITER conductor design. An apparatus to measure the strain dependency was newly developed. It has a horseshoe-shaped ring and a strand is soldered on its outer surface. This shape produces uniform axial compressive or tensile strain along strand length by expanding or closing the opening of the ring. Critical current can be measured by the apparatus under a magnetic field up to 1ST, a temperature range of 4.2K to 15K, and strains. The maximum allowable current is about 300A. The details of the apparatus and results of strand characterization are presented. [ABSTRACT FROM AUTHOR]