Mitsuho Furuse

National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki, Japan

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Publications (72)68.83 Total impact

  • Hirofumi Yamasaki · Naotake Natori · Mitsuho Furuse
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    ABSTRACT: Wind turbines larger than the present 5 MW class have recently been developed because adoption of larger capacity turbines can increase the total capacity of a wind farm. The realization of compact and lightweight superconducting direct-drive generators is desired. From a cost standpoint the salient-pole iron-core rotor design is superior, because it requires much less amount of expensive high-temperature superconducting (HTS) wires than air-core HTS rotors. In this study we have investigated how to compose a salient-pole 10 MW-class HTS rotor and selected a coil-module system with a warm iron core in which only the HTS racetrack coils are cooled. Based on basic consideration of the coil support system and the structure of the vacuum vessel, we fabricated a model coil module in which an approximately half-sized dummy coil made of copper bar is cooled in a doughnut-shaped vacuum vessel. Cooling tests using liquid nitrogen and liquid helium were successfully performed, and the amount of heat inleak was evaluated. We estimate that the heat inleak in a 10 MW rotor can be less than 500 W.
    No preview · Article · Jun 2015 · IEEE Transactions on Applied Superconductivity
  • H Yamasaki · M Furuse · K Kaiho
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    ABSTRACT: We have been developing superconducting thin-film fault current limiter (FCL) elements, in which high-resistivity Au–Ag alloy shunt layers are used to protect YBa2Cu3O7 (YBCO) thin films deposited on CeO2-buffered sapphire substrates. The high resistance of the thin films enables the element to withstand high electric fields of more than 40 Vpeak cm−1 during the current-limiting period after quenching, thus greatly reducing the amount of YBCO thin film needed and, consequently, the cost of an FCL. We have succeeded in fabricating and testing 500 V/200 A FCL modules using two 20 cm long YBCO films connected in parallel. In the present study, we performed extensive switching experiments on FCL elements, in which two YBCO films are connected in parallel to achieve higher rated currents, and confirmed the previously observed phenomenon that the hot-spot problem causing film damage just after quench initiation becomes more severe when the total critical current of the thin films is higher. We have investigated the origin of this phenomenon and found that a rapid current transfer from the first-quenched film with lower critical current to the other film causes higher current in the secondly-quenched film that sometimes leads to hot spots. It is demonstrated that the serious hot-spot problem can be mitigated by the use of inductors when the high-resistance FCL elements are connected in parallel. Based on these findings we propose an appropriate architecture of a high electric-field superconducting thin-film FCL that can be used in a real power grid.
    No preview · Article · Jun 2015 · Superconductor Science and Technology
  • Mitsuho Furuse · Shuichiro Fuchino
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    ABSTRACT: We measured the thermal conductivity of polypropylene laminated paper (PPLP) impregnated with subcooled liquid nitrogen. PPLP is widely used for the electrical insulation of high-Tc superconducting (HTS) power transmission cables. Although the thermal conductivity of PPLP is an important factor in the design of HTS cables, there has been very limited work on its measurement in subcooled liquid nitrogen. We prepared PPLP samples and symmetrically stacked them on both sides of a heater. The stacked samples were immersed in liquid nitrogen in an open cryostat. A cryocooler mounted on the cryostat was used to maintain the subcooled temperature of the liquid nitrogen. The thermal conductivity of the stacked PPLPs was measured by the steady state method at a bath temperature of 65–75 K and was found to be 0.23–0.26 W/mK, which is about five times that measured in a vacuum as presented in available literature. We also discuss possible mechanisms for boosting the thermal conductivity of PPLP by liquid nitrogen impregnation.
    No preview · Article · Sep 2014 · Cryogenics
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    ABSTRACT: Medical proteins such as monoclonal antibodies and immunoglobulins are important substances for the manufacture of medicines for cancer, etc. However, the conventional separation system for these medical proteins has very low separation rate and the cost is extremely high. To address these issues, we have developed a high gradient magnetic separation system for medical proteins using affinity magnetic nanobeads. Our system shows very high separation efficiency and can achieve low cost owing to its large production rate compared with conventional systems. The system consists of a 3T superconducting magnet cooled by a cryocooler, a filter made of fine magnetic metal fibers of about 30 μm in diameter with demagnetization circuit and liquid circulation pump for the solvent containing the medical proteins. Reducing the size of the system entails reduction of the cryocooler size, thereby resulting in reduced cooling capacity. Therefore, the heat load on the cryocooler has been considered carefully in the design of the cryogenic system. The calculated heat load of the 1st and 2nd stages was made to satisfy the cooling capacity of the cryocooler. As a result, a magnet temperature of 4.2 K and a thermal shield temperature of 60 K have been achieved, enabling smooth operation and good performance of the HGMS separation system.
    No preview · Article · Jun 2014 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: We have successfully developed a high-gradient magnetic separation system for medical proteins using affinity magnetic nanobeads. Our system shows very high separation efficiency and can also be expected to realize lower cost due to larger production rate compared to the conventional system. The developed system consists of a 3-T superconducting magnet and a filter made of fine magnetic metal fibers. The superconducting magnet is wound with a NbTi twisted multifilamentary wire, and cooled by a 4-K Gifford-McMahon cryocooler. In order to achieve high recovery ratio of the magnetic nanobeads trapped on the filter located in a room-temperature clear bore of the cryostat, the ac degaussing system for the filter is fabricated using an inductance-capacitance resonance circuit composed of a series connection with the superconducting magnet and an additional capacitor. To perform the inductance-capacitance resonance more than a few cycles between superconducting magnet and capacitor, the superconducting magnet has a slit in the bobbin to prevent an eddy current coupled with an alternating magnetic field. It also has a control system for a high-speed switching circuit. This magnet can successfully generate a magnetic field of 3.0 T in the clear bore of the cryostat with a diameter of 30 mm in a relatively fast sweep time of 150 s due to the slit in the magnet bobbin. Using our degaussing system, a high recovery ratio of the nanobeads in pure water has been performed about 94.1%.
    No preview · Article · Jun 2014 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: Medical proteins such as monoclonal antibodies or immunoglobulin are important as medicine for cancer and other uses. Today, we can easily sort and analyze medical proteins using various types of commercially available affinity magnetic beads. However, separation systems for these medical proteins have a very low separation rate, and the cost of the product is extremely high. We successfully developed a high gradient magnetic separation system using a cryocooler-cooled low-temperature superconducting magnet and conducted experiments on separating affinity magnetic nanobeads. Our system demonstrated very high separation efficiency and can achieve low costs with a large production rate compared to systems now used in this field. The design of a filter to trap and recover the nanobeads is important to this application. In order to achieve a filter with a high trapping ratio of magnetic beads, the parameters need to be optimized because the ratio depends on the dimensions and arrangement of the filter made of fine magnetic metal fibers. In this study, we investigated the performance of filters in the high gradient magnetic separation system. The test results show 97.8% of the magnetic nanobeads in pure water were captured, and 94.1% of the total beads were collected.
    No preview · Article · Jun 2014 · IEEE Transactions on Applied Superconductivity

  • No preview · Article · Jan 2014 · TEION KOGAKU (Journal of the Cryogenic Society of Japan)
  • Hirofumi YAMASAKI · Mitsuho FURUSE
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    ABSTRACT: Nondestructive, AC inductive methods detecting third-harmonic voltages are widely used to measure the distribution of local critical current densities Jc of superconducting films deposited on large-area single-crystal substrates. We have extended this method to determine the electric field E versus current density J relation and the n-value (index of the power-law E-J characteristics) by evaluating the dependence of Jc on measurement frequency. The method to determine Jc with an electric-field criterion has been established as an international standard. This convenient method can also be applied to coated conductors with metallic substrates. Magnetic-field angular dependent Jc measurements are possible, and such measurements are of practical importance in applying coated conductors to superconducting coils. They are also useful in investigating the flux pinning mechanism. In this focused review, we briefly introduce the measuring method that has been based on our long years of research, and describe the precautionary points when recent coated conductors with high critical currents per unit width are measured.
    No preview · Article · Jan 2014 · TEION KOGAKU (Journal of the Cryogenic Society of Japan)
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    ABSTRACT: A high gradient magnetic separation system for medical protein using affinity magnetic nano-beads has been developed. Medical protein such as monoclonal antibody or immunoglobulin is an important substance as a medicine for cancer etc. However; the separation system of these medical protein has very low separation rate and the cost of product is extremely high. The developed system shows very high separation efficiency and can achieve low cost by large production rate compared to the system now using in this field. The system consists of a 3T superconducting magnet cooled by a cryo-cooler, a filter made of fine magnetic metal wires of about 30μm diameter and a demagnetization circuit and a liquid circulation pump for solvent containing medical protein. Affinity magnetic nano-beads is covered with the medical protein after agitation of solvent containing the protein and nano-beads, then the solvent flows through the system and the beads are trapped in the filters by high gradient magnetic field. The beads are released and flow out of the system by the AC demagnetization of the filters using LC resonance circuits after discharge of the magnet. The test results shows 97.8% of the magnetic nano-beads in pure water were captured and 94.1% of total beads were collected.
    No preview · Article · Dec 2013
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    ABSTRACT: In this study, we developed a two-dimensional vector magnet with Y-Ba-Cu-O (YBCO) tape conductors for use in an X-ray magnetic circular dichroism measurement system. The characteristics of this high- Tc superconducting vector magnet are as follows: (a) it is a split magnet comprising four unit coils that enable an X-ray magnetic circular dichroism system to access the center sample space along three axes; (b) it is compact with a high magnetic field, and it exhibits a cone-shaped design to enable the split unit coils to come close together and to achieve a maximum magnetic field up to 1 T at the center; and (c) it is conduction-cooled by a cryocooler and a cryogen-free system. We fabricated four unit coils with YBCO tape conductors (manufactured by SuperPower Inc.). Two pairs of the unit coils were configured at right angles to each other in a cryostat and cooled below 30 K by the cryocooler. We confirmed that the magnetic field orientation can be controlled by adjusting the current of the unit coils. However, we observed hysteresis and drift of the magnetic field owing to the screening current induced in the YBCO tape conductors. Here, we design a high- Tc superconducting vector magnet and present its excitation test results.
    No preview · Article · Jun 2013 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: We are developing a high-Tc superconducting vector magnet for use in solid-state physics apparatus. The vector magnet features are (a) 1 T peak and two-dimensional magnetic field vector controllable (b) comprising four split magnet units enabling free access in three directions to a sample space (c) cryogen-free conduction-cooled magnet. To obtain a vector controllable magnetic field as high as 1 T using a compact magnet, we adopted a tapered design for split magnet units. We fabricated a test magnet unit with YBCO tape conductors and examined its basic performance. The magnet unit generated the rated magnetic field. This paper describes the vector magnet design, fabrication procedures, and the magnet unit test results.
    No preview · Article · Jun 2012 · IEEE Transactions on Applied Superconductivity
  • Yoonseok Lee · Hirofumi Yamasaki · Mitsuho Furuse
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    ABSTRACT: The magnetic-field angle dependence of critical current densities Jc(H,θ) in commercial YBCO tapes grown by MOCVD and MOD was examined at liquid nitrogen temperatures. We first measured Jc(H,θ) in MOCVD-YBCO tapes at 70 and 77.3 K in fields up to 2 T using both transport and inductive (the third harmonic voltage) methods and compared the results. It was observed that, in low magnetic fields, the transport measurements gave higher Jc than the inductive ones; however, in high fields they agreed well, which is well explained by the effects of weak links due to low-angle grain boundaries. We then investigated Jc(H,θ) in MOCVD- and MOD-YBCO tapes at 77.3 K in fields up to 2 T. All the tapes exhibited peaks at H//ab in the shape of Mount Fuji, which shows that small random pinning plays a major role. However, an anisotropic scaling analysis showed that the flux pinning mechanisms in those tapes were different, resulting in distinctive angular behaviors of Jc(H,θ). It is suggested that the difference in the flux pinning mechanisms of the two types of tapes came from the different sizes of point defects originating from the growing processes.
    No preview · Article · Nov 2011 · Cryogenics
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    ABSTRACT: In plant and industrial complex, further energy saving can be realized by DC interconnection between the ends of AC radial distribution system. We fabricated a power system simulator to verify that the DC interconnection is effective for energy saving in the distribution system. An YBCO toroidal coil composed of eight double pancake coils was fabricated and adopted in the simulator as a DC reactor. Harmonic current with DC-offset component were observed in the YBCO toroidal coil and the frequency component ratio of harmonic current depended on the inductance of the toroidal coil. Energy loss in the YBCO toroidal coil during the DC interconnection in the power system simulator decreased with the inductance of the YBCO toroidal coil because the magnitude of harmonic current component decreased with the inductance. To clarify the loss characteristics in the YBCO toroidal coil, we investigated influence of the magnitude of harmonic-frequency component and DC-offset component on the transport current loss in YBCO tape conductor. The transport current lose was independent of the magnitude of DC-offset component. The energy loss characteristics in the YBCO toroidal coil were closely related to the transport current loss in the YBCO tape conductor with harmonic current.
    No preview · Article · Jul 2011 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: We numerically calculated the transient temperature distribution of flowing subcooled liquid nitrogen in a high- T <sub>c</sub> superconducting (HTS) model cable when faults occur. The coolant and cable core temperatures were calculated by numerically solving the heat equation using the finite difference method. In the calculation, we assume that the heat transfer coefficient between the flowing subcooled liquid nitrogen and the cable core surface is described by the Dittus-Boelter correlation. The calculation results reveal that the coolant temperature increases even after the fault has been removed and that it continues increasing until fresh coolant arrives from the inlet. The calculated temperature profile of the coolant agrees well with measured data obtained by conducting over-current tests on a model HTS cable. Using our computational code, we also evaluated the maximum HTS cable lengths that ensure that the coolant remains in the liquid phase for certain fault currents for an HTS model cable.
    No preview · Article · Jul 2011 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: Recently, affinity magnetic beads have been widely used in immunomagnetic cell sorting (IMCS) technology. Today, we can easily sort and analyse DNA and antibodies (immunoglobulin) using various types of affinity magnetic beads available in the market. The diameters of the affinity magnetic beads used in immunomagnetic cell sorting are above approximately 1 ??m because of the low magnetic fields induced by permanent magnets. At present, nanosized affinity magnetic beads are strongly desired to achieve high resolutions. We have been studying and attempting to develop a high-gradient magnetic separation (HGMS) system that employs a superconducting magnet to induce a considerably higher magnetic field than that induced by a permanent magnet. The objective is to trap smaller nanosized affinity magnetic beads using a filter made of fine stainless steel wool. In a previous study, we constructed a prototype of a desktop-type HGMS system using a cryocooler-cooled LTS magnet; we conducted preliminary experiments on trapping nanosized magnetic particles and investigated the magnetic field distribution and magnetic force around a magnetic wire in the filter by means of a numerical simulation. In this study, we succeeded in producing prototype nanobeads covered with the biosurfactant of a high-affinity ligand system for immunoglobulin G and M. Furthermore, we attempted to improve the recovery of nanobeads by adding a resonance circuit to the HGMS system. In practice, the trapped nanobeads attract one another and agglomerate due to their remaining magnetization when the magnetic field is decreased to 0 T. Therefore, the nanobeads and wire are demagnetized in the AC magnetic field by the resonance circuit, making good use of the superconducting magnet of the HGMS system.
    No preview · Article · Jul 2010 · IEEE Transactions on Applied Superconductivity
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    ABSTRACT: These days, voltage stability of power system is very important for example in semiconductor industries. So, development of a device suppressing voltage sags in power system is expected. In this article, the authors propose a new voltage stabilizing device using a LC resonance circuit composed of superconducting coil and capacitor connected in parallel. This power system voltage stabilizer acts automatically against a voltage sag or a steep voltage change, and it suppresses the voltage drop for several cycles by releasing its stored energy. The authors have confirmed this principle experimentally using a small model system using a LC resonance circuit with a superconducting coil and a capacitor. The experimental results and some theoretical analyses are presented.
    No preview · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
  • M. Furuse · K. Agatsuma · S. Fuchino
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    ABSTRACT: We measured the heat flow of current leads used for high-Tc superconducting apparatuses operating at liquid nitrogen temperature by the nitrogen boil-off method. To reduce the heat flow at the cold end of the current leads, the use of commercial Bi2223 silver-sheathed (Bi2223/Ag) tape conductors for current leads above liquid nitrogen temperature was also studied. We derived average Lorenz numbers between room temperature and liquid nitrogen temperature from the measurement results to assess the performance of the current leads. We tested Bi2223/Ag-soldered oxygen-free copper leads and obtained slightly lower heat flows and average Lorenz numbers than those of solid copper leads. The average Lorenz numbers of copper alloys were measured as well.
    No preview · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
  • [Show abstract] [Hide abstract]
    ABSTRACT: Recently, affinity magnetic beads have been widely used in immunomagnetic cell sorting (IMCS) technology. Today, we can easily sort and analyze DNA and antibodies (immunoglobulin) using various types of affinity magnetic beads available in the market. The diameters of these affinity magnetic beads used in immunomagnetic cell sorting are limited to above approximately 1 mum because of the low magnetic fields induced by permanent magnets. Now, nano-sized affinity magnetic beads are strongly desired to achieve high resolutions. We have been studying and attempting to develop a high-gradient magnetic separation (HGMS) system that employs a superconducting magnet to induce a considerably higher magnetic field than that induced by a permanent magnet in order to trap smaller nano-sized affinity magnetic beads by a filter made of fine stainless steel wool. In this study, we constructed a prototype of a desktop-type HGMS system using a cryocooler-cooled LTS magnet and conducted preliminary experiments on trapping the nano-sized magnetic particles. Furthermore, we investigated the magnetic field distribution and magnetic force around a magnetic wire in the filter by means of a numerical simulation.
    No preview · Article · Jul 2009 · IEEE Transactions on Applied Superconductivity
  • Mitsuho Furuse · Koh Agatsuma · Shuichiro Fuchino
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    ABSTRACT: This paper evaluates the losses of current leads made of various metals used in high-Tc superconducting power apparatuses operating at liquid nitrogen temperatures. The heat flow into liquid nitrogen conducting adiabatic current leads was measured by the nitrogen boil-off method. The results were used to derive average Lorenz numbers for metals between room temperature and liquid nitrogen temperatures. The average Lorenz number is a good index of performance of current leads. A theory of loss evaluation of current leads using the average Lorenz number and a method for the optimum current lead design were described as well. In addition, the loss of current leads made of Bi2223/Ag tape conductors was evaluated above the liquid nitrogen temperature, and a higher efficiency was achieved than with pure metal current leads.
    No preview · Article · Jun 2009 · Cryogenics
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    ABSTRACT: We performed fault current limiting tests using YBCO thin films and investigated the reasons for their breakdown during current limiting. There were two patterns of film breakdown. One occurred immediately after current limiting and the other occurred during current limiting. In film breakdown, the quench propagation speed showed almost no change with increasing energy consumption per unit time, but the energy consumption per unit area increased with increasing energy consumption per unit time. Therefore, local areas of the film reached the melting point and arcing occurred. It is therefore concluded that the performance of the films can be improved by decreasing the energy consumption per unit time. Connecting a parallel capacitor to the film in order to limit the energy consumption per unit time is proposed and tested as a measure to improve the current limiting performance of thin films. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(1): 20–27, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20709
    No preview · Article · Jan 2009 · Electrical Engineering in Japan

Publication Stats

366 Citations
68.83 Total Impact Points

Institutions

  • 2002-2014
    • National Institute of Advanced Industrial Science and Technology
      • Advanced Manufacturing Research Institute
      Tsukuba, Ibaraki, Japan
  • 2006
    • Sophia University
      Edo, Tōkyō, Japan
  • 2002-2003
    • Japan Advanced Institute of Science and Technology
      KMQ, Ishikawa, Japan
  • 2000-2003
    • Yokohama National University
      • Department of Physics, Electrical and Computer Engineering
      Yokohama, Kanagawa, Japan