Shuichiro Fuchino

Feasibility study of low-Voltage DC Superconducting distribution system

This paper describes the advantages of using superconducting cables in low-voltage DC distribution systems, focusing on total cost reduction. Demand for DC electric power has been rapidly increasing, requiring reductions in total costs and power supply system losses. The effects of using superconducting cables were investigated by changing parameters such as the current and length of cables, and it is shown that DC superconducting distribution systems are feasible even for small-capacity power systems and savings can be obtained beyond the extra cost of the superconductors and refrigeration systems. In this study, a test model of a DC superconducting distribution system, constructed by modification of an AC superconducting power transmission system, is presented and evaluated.

Study of practical applications of HTS synchronous Machines

A small research and study committee, composed of corporations in the industrial/governmental/academic fields, was established, and a feasibility study of HTS synchronous machines (HTSMs) was carried out. Promising application fields for HTSMs were considered and their applicability was studied. Fundamental designs of these HTSMs were then carried out using a specially developed design program, and their merits and demerits were clarified. As key components, HTS field coils and refrigeration systems were examined closely, and technological problems related to their development were studied.

Characteristics of the magnetic gear using a bulk high-Tc superconductor

A magnetic gear which can transmit force without contact has operational benefits of requiring neither vibration, noise, nor lubrication. Still, its transmission force is considerably smaller than a mechanical gear. Strong magnets are needed to improve magnetic gear transmission force. For this purpose, a magnet formed by the pinning effect in a bulk superconductor might have magnetic flux density several times stronger than rare-earth permanent magnets. We propose a noncontact magnetic gear using a bulk high-Tc superconductor. In this paper, a three-dimensional electromagnetic field analysis program has been developed to analyze characteristics of the proposed gear. Two superconducting magnetic gears with different magnet configuration are manufactured, and their characteristics are measured. The analysis and the experiment explore the possibility of a magnetic gear using the pinning magnet formed in the superconductor.

Design and Test of Filter of High Gradient Magnetic Separation System for Trapping Immunoglobulin in Serum

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.

Stability Analysis of HTS Power Cable With Fault Currents

We numerically calculated the transient temperature distribution of flowing subcooled liquid nitrogen in a high-Tc 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.

Improvement of a High-Gradient Magnetic Separation System for Trapping Immunoglobulin in Serum

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.

Magnetic rail construction for a low loss superconducting magnetic levitation linear guide

A pinning-type superconducting magnetic levitation linear guide which consists of bulk high-T/sub c/superconductors and a magnetic linear rail with permanent magnets and steel plates was investigated for a goods transportation system, an energy storage system, and other uses. This paper describes the loss of this linear guide and a construction of the magnetic linear rail in which no inhomogeneous magnetic field is generated in a comparatively large gap in a long distance configuration. The loss is evaluated analytically by a newly developed electromagnetic analysis program. This proposed magnetic rail construction suppresses inhomogeneous magnetic fields generated by the existence of such spaces as temperature change countermeasures. We performed analyses and experiments on this construction. Results show that calculated and measured values concur well both quantitatively and qualitatively, proving that the proposed magnetic linear rail shows magnetic field distribution that is uniform in the running direction in the required gap.

Investigation of structure of superconducting power transmission cables with LN2 counter-flow cooling

Abstract Establishment of long-distance cooling techniques and design of a compact cross section are required for development of HTC superconducting underground power cables. To save space of return coolant, a counter-flow cooling system appears promising. However, it is difficult to cool down long cables because of heat exchange between counter-flows due to high thermal conductivity of dielectric materials which separate both flows in range of liquid nitrogen temperature. We estimated temperature distributions analytically along model HTS power cables with counter-flow. Results of calculation showed that when liquid-nitrogen-impregnated polypropylene laminated paper was chosen for a dielectric material, great thickness was required to reduce heat exchange between counter-flows. We investigated various cable structures to optimize the counter-flow cooling system and cable size.

Longitudinal temperature distribution in superconducting power cables with counter-flow cooling

This study examines cooling of superconducting power cables with counter-flow of liquid nitrogen with thermal contact through the cable dielectric. We investigate the effect of thermal conductance of the cable dielectric between coolant streams flowing in opposite directions, analyze longitudinal temperature distribution in superconducting power cables using heat balance equations, and give some examples taken from a cooling design study on superconducting power cables.

Properties of

Since MgB2 superconductor was discovered by Akimitsu, many scientists has been studied this new intermediate temperature superconductor material. Recently Dou reported the critical current density and flux pinning of MgB2 is enhanced by doping of SiC nano powder, and Fujii reported MgB2 superconductor made by the powder-in-tube in-situ process using MgH2 as a precursor powder enhanced the critical current density especially under high magnetic field. Also Matsumoto reported the irreversibility field of MgB 2 tape prepared by the in-situ powder in tube process using MgH2 as a precursor powder increased to 23 T by the SiC doping. These results show MgB2 has high potential as a strong candidate for a practical use. We study the effects of doping nano carbon impurity because graphite has the same structure as the hexagonal Boron structure in MgB2. We added carbon impurities of graphite, C60, and open-ended carbon nano tube respectively to MgB2 conductors made by powder in tube ex-situ process