Hitachi, Ltd.

The University of Tokyo

Central Japan Railway Company

Kazuhide Tanaka

Michiya Okada

Toshiya Doi

Shinpei Matsuda

Motomune Kodama

Toyotaka Yuasa

Toshimi Matsumoto

Masaya Takahashi

Keiji Fukushima

Hiroshi Morita

Tomoichi Kamo

Tsuyoshi Wakuda

Takahiko Kato

Hiroshi Satoh

Yasuo Suzuki

Yoshimi Yanai

Yota Ichiki

Akira Okayama

Tadaoki Morimoto

Takeshi Ozawa

Katsuzo Aihara

Hideki Abe

Hiroaki Kumakura

Kimihiko Akahori

Hitoshi Kitaguchi

Hideyuki Yamada

Yoshiteru Chiba

Akiyasu Yamamoto

Junichi Shimoyama

Masazumi Hirakawa

Motoharu Imai

Youta Ichiki

An MgBsuperconducting wire includes a core containing MgBand a metal sheath which surrounds the core. The core includes at least a first MgBcore positioned on the center side, and a second MgBcore positioned outside the first MgBcore, and the density of the second MgBcore is lower than the density of the first MgBcore.

[object Object]

A technical problem is to turn a persistent current switch on and off at high speed with less heat input. The invention relates to a conductive cooling-type persistent current switch, including: a superconductive wirethrough which a current is passed; a cooling stagewhich cools the superconductive wire; and a heaterwhich heats the superconductive wire, wherein the superconductive wire is placed between faces which are each formed by the cooling stage and the heater, a core of the superconductive wire is magnesium diboride, and a base materialplaced around an outer periphery of the core is a material having a resistivity of 10 &#x3bc;&#x3a9;cm or more at 40 K.

Conductive cooling-type persistent current switch, MRI apparatus and NMR apparatus

An MgBsuperconducting wire excellent in critical current density property is supplied by using a crystalline boron powder which is low in costs and easy to obtain. For the wire, a precursor of the MgBsuperconducting wire is used, the precursor having a linear structure including a core region containing a magnesium powder and a boron powder, and a sheath region formed of a metal covering an outer circumferential portion of the core region. The boron powder is crystalline, and has a volume-mean particle size of 2 &#x3bc;m or less.

Precursor of MgB2 superconducting wire, and method for producing the same

Provided is a superconducting apparatus, including a joint of superconducting wires having high electric conduction characteristics and a superconducting magnet or the like. The superconducting joint comprises a plurality of superconducting wires and a sinter which integrates the plurality of superconducting wires. Herein, at least any one of the superconducting wires is a MgBsuperconducting wire, the sinter contains MgB, and the sinter is compressed form the direction different from the direction toward which the superconducting wires protrude. Further, in order to form such a joint, a compression vessel provided with an opening used for introducing raw material powders to construct the sinter and another opening used for inserting the superconducting wires is utilized, and the openings are directed to different directions each other. Accordingly, MgBis filled in the sinter at high density, allowing the joint structure to have a good bonding property among particles.

Joint of superconducting wires and method for joining superconducting wires

An MgBcompound sheath superconducting wire includes a high stable metal having a specific electric resistance 7 &#x3bc;&#x3a9;cm or below at a room temperature and a high strength metal having a Vickers hardness 50 or above at a room temperature, both of which are assembled therewith to realize a high strength and a lengthy superconductor.

An object is to provide a liquid level sensor device for liquefied gas enabling measurement on a liquid level of liquefied gas having a boiling point in the vicinity of 21 K, e.g. liquid hydrogen, accurately and with good reproducibility and enabling simple production with good reproducibility. The present invention is a liquid level sensor device for liquefied gas including compound containing magnesium and boron arranged in succession in the longitudinal direction over the entire or a part of surface of a linear conductor made of metal and a portion of the compound thereof dipped in liquid is in a superconductive state at liquid level measurement.

Liquid level sensor device for liquefied gas

There is disclosed a permanent current switch which has a high temperature margin and which is thermally stable and which securely performs a switching operation between a superconducting state and a normal conducting state. The permanent current switch of the present invention has a coiled superconducting wire and a heater wire which switches the superconducting wire between the superconducting state and the normal conducting state, the superconducting wire is a magnesium diboride superconducting wire having a high-resistance metal on an outer side and a magnesium diboride superconducting portion on an inner side and prepared by forming a superconducting metal on a layer between the high-resistance metal and the magnesium diboride superconducting portion, and the permanent current switch further comprises a superconductive connecting section superconductively connected to a lead wire guided from the superconducting wire and a superconducting wire for a wiring line.

Permanent current switch

In a metal sheath MgBsuperconducting wire, it is intended to achieve a wire having increased current density and a long length at the same time, by densitying superconducting core part. The superconducting wire is manufactured by forming diffusion hardened layer on the inner surface of the sheath such that the hardness of the inner surface becomes higher than that of the outer surface, filling MgBsuperconductor, and further if necessary, a critical current density increasing material such as indium, copper, and tin, in a metal sheath, to subject it to wire drawing. For the metal sheath, a material with toughness such as steel is used. Even if the sheath is made to a long wire, it does not break, thereby, enabling to density superconducting core part.

Metal sheath magnesium diboride superconducting wire and its manufacturing method

A method of producing an electrical connection structure between at least two superconducting lines. The method comprises adding metal powder or alloy powder to a superconducting material comprising magnesium diboride, intervening the superconducting material between at least two superconducting lines, and heating said superconducting lines and said superconducting material to a temperature lower than the melting point of said superconducting material prior to the addition of said metal powder or alloy powder thereto, but higher than the melting point of said metal powder or alloy powder.

Superconductor connection structure

Electrical connection of superconducting lines can be achieved by using a low-melting point metal, by mechanical contact of superconducting lines or by welding. According to these methods, however, critical current and critical magnetic field at the connection point are low, and stable connection in a superconducting state has been difficult. The present invention solves these problems and provides a structure and method for connecting superconducting lines. The present invention provides high-performance, high-stability connection of superconducting lines through magnesium diboride (MgB) powder arranged between superconducting lines.

The cross section of a wire is round and is composed of several units, each consisting of tape-like superconductors laminated in an approximately rhombic shape, which are arranged such that they form a hexagon as a whole. Oxide superconducting tape wires each consisting of a plurality of oxide superconducting filaments are arranged in rotational symmetry to a core. The oxide superconducting filaments have the cross section such that the average thickness is 3 to 20 &mgr;m and the average aspect ratio is larger than 2 and smaller than 10. A step of arranging the oxide superconducting tape-like wires in rotational symmetry is accomplished when the multi-core tape-like wires are packed in a third metal pipe which becomes a metal sheath later. Since the multi-core tape wires having oxide superconducting filaments are arranged in rotational symmetry, the oxide superconductor in the oxide superconducting filaments permits its c axis to orient in various directions. This makes it possible to prevent the critical current from decreasing irrespective of the direction in which the magnetic field is applied and to increase the critical current density (Jc) because the oxide superconducting filament has an optimal size. The oxide superconductor should be a bismuth-based oxide superconductor, preferably be the one which has a composition of Bi Sr Ca Cu O .

Rotationally symmetric oxide superconducting wire and solenoid coil or magnetic field generator incorporating the same

A method for manufacturing an oxide superconducting coil can suppress deterioration of superconducting characteristics caused by a strong electromagnetic force and deformation and a reaction during heat treatment. The oxide superconducting coil is manufactured by a wind-and-react (W&R) method using a metal sheathed oxide superconducting wire material and an insulator, wherein an oxide film formed on a surface of a heat resistant alloy during a heat treatment is used for insulating the coil, and the heat resistant alloy has a sufficient strength to prevent the deformation of the coil generated by the weight of the coil itself during the heat treatment and to endure a strong electromagnetic force. An oxide superconducting coil operable with a coolant, such as liquid nitrogen, liquid helium, and the like, or a refrigerator, can be realized.

Oxide-superconducting coil and a method for manufacturing the same

Structure for joining together metal-coated multi-core oxide superconductor wire material parts in a tape shape. The C axis of a oxide superconductor crystal is substantially oriented along the longitudinal (length) direction that the wire material extends. The end faces of the wire material parts contact each other at the joint part; and the C face of the oxide superconductor crystal is continuously oriented at the joint part.

Oxide superconductor wire material and method for jointing the same

This invention provides an oxide-type superconducting flat wire having a critical current density of at least 1,000 A/cm.sup.2, which comprises a Y--Ba--Cu oxide layer having a superconducting property and a silver layer surrounding the oxide layer and has so flat a cross section vertical to the longitudinal direction of the wire that the upper and lower lines between the oxide layer and the silver layers appearing on the cross section having a zone over they are parallel to each other, the thickness of the oxide layer being cold rolled in the range of 0.35 to 0.75 based on the whole thickness of the wire, the whole thickness being 0.2 mm or less, and the metal layer being deformable to follow the shrink deformation of the oxide layer when heat treated to be sintered, but rigid when used. This flat wire is produced by filling a silver-made tube with a Y--Ba--Cu oxide powder having a superconducting property, drawing the tube into a rod wire having a round cross section, then cold rolling the rod wire in the flat wire so that (t.sub.i -t)/t.sub.i .times.100 is equal to or greater than 90%, wherein t.sub.i is the whole thickness of the cross section of the rod wire before the cold rolling and t is the whole thickness of the cold-rolled flat wire, and then heat treating the flat wire to sinter the superconducting oxide.

Superconducting wire and method of producing the same

An elongate superconductor wiring element having, as seen in section, oxide superconductor material regions in each of which the c-axes of the oxide superconductor crystals are aligned with each other and are transverse to the longitudinal axis of the element. To reduce the dependence of critical current density on angular position of the element relative to a magnetic field, there are a plurality of said regions whose alignment directions of the c-axes are different as between different ones of said regions, so that the wiring element comprises a plurality of said regions having respectively different c-axis alignment directions.

Growing community of inventors

Hitachi, Japan

Kazuhide Tanaka