JP5266852B2 - Superconducting current lead - Google Patents

Description

  The present invention relates to an assembly structure of a superconducting current lead having a large energizing capacity applied to a superconducting device such as a superconducting coil for storing superconducting energy, a current limiting device, a superconducting cable, a superconducting generator, and a superconducting transformer.

  Superconducting magnets are used for physical property research and magnetic resonance devices, and are expected to be applied to magnetic levitation trains and magnetic confinement devices for nuclear fusion in the future. By the way, when a current is supplied to the superconducting magnet placed in the cryostat container of the cryostat through the current lead from the excitation power source placed on the room temperature side, the current lead is used as a heat transfer path from the outside in the cryogenic region. The heat that invades is a big problem. That is, liquid helium is an expensive refrigerant material, and a refrigerator used to re-liquefy liquid helium evaporated by heat penetration also consumes a large amount of power. Therefore, a large amount of heat penetration through the current leads not only increases the cost associated with the purchase of liquid helium, but also increases the size and capacity of the refrigerating machine, resulting in low resistance and high conductivity. The development of current leads with low conduction heat intrusion from the outside is an important development issue.

  Therefore, a high-temperature superconducting current lead has been developed that uses a high-temperature superconducting material at the low-temperature lead part of the current lead to reduce conduction heat intrusion into the cryogenic part, and one example is superconducting equipment in liquid helium. A thermal anchor that cools to the temperature of liquid nitrogen is provided in the middle portion of the current lead that supplies current, and a superconductor (for example, Y-Ba) having a critical temperature equal to or higher than the boiling point (77.3 K) of liquid nitrogen is provided on the low temperature side of the current lead. A superconducting current lead using -Cu-O) is known (for example, see Patent Document 1). In addition, the superconducting current lead is divided into a low temperature part, a medium temperature part, and a high temperature part conductor, and the low temperature part conductor uses a Bi-based oxide superconducting layer provided on an insulating substrate having a low thermal conductivity. There is also known a superconducting current lead having a structure in which a core made of an oxide-based superconductor is covered with a coating material (sheath) such as Ag as a conductor in a middle temperature part and a high temperature part, and is laminated and assembled. (For example, refer to Patent Document 2).

  In addition, the superconducting current lead is divided into a high temperature side lead portion bundled with a copper wire and a low temperature side lead portion composed of a tape-like superconducting wire, where the low temperature side lead portion is, for example, a Bi-based tape-like oxide superconducting wire. A conductor unit in which a plurality of conductors are assembled and arranged on the circumferential surface of a cylindrical support member so that the tape surface of the superconducting wire is parallel to the circumferential direction in the cylindrical coordinate system. A superconducting current lead is known (see, for example, Patent Document 3). Next, a specific structure of the superconducting current lead is shown in FIGS.

  FIG. 5 shows an example of application to a superconducting coil. In the figure, 1 is a cryostat cryogenic container filled with liquid helium, 2 is a superconducting coil, 2a is a connection terminal of the superconducting coil 2, and 3 is a superconducting coil 2 from an external excitation power source. The superconducting current leads 3a and 3b for supplying electric power to the terminals are connection terminals. The superconducting current leads 3 are made of a high-temperature side lead portion 4 made of a highly conductive metal such as copper or copper alloy, and a tape-shaped superconducting wire. And a low-temperature side lead portion 5 configured as described above.

  Here, as shown in FIGS. 6A and 6B, the low temperature side lead portion 5 is superconducting on the peripheral surface of a cylindrical (pipe-shaped) support member 6 made of FRP or stainless steel or the like. A large number of conductor units 7 are arranged and laid in the axial direction of the support member. In addition, the conductor unit 7 includes, for example, a Bi (bismuth) tape-shaped superconducting wire (silver sheath superconducting wire) 8 such that the tape surface of the superconducting wire is parallel to the circumferential direction in the cylindrical coordinate system. It is laid in a concave groove formed on the peripheral surface of the support member 6 by stacking. Further, as shown in FIGS. 7A and 7B, electrodes 9 made of metal such as copper or copper alloy are arranged at both ends of the support member 6, and the electrodes 9 and the respective superconducting wires 8 and The low-temperature-side lead portion 5 is configured by conducting conductive bonding between them with solder or the like.

On the other hand, as a next-generation tape-shaped superconducting wire in recent years, rare earth metal (Re) -based tape-like oxides such as yttrium-based (Y-based), which are expected to be capable of high current density and low cost. Development of superconducting wire is progressing. Specific examples of the tape-shaped oxide superconducting wires that are being developed include yttrium (Y-based), holmium (Ho-based), and gadolinium (Gd-based). Further, for example, as described in Patent Document 4, this tape-shaped oxide superconducting wire includes an intermediate layer (YSZ or the like) deposited by an IBAD method on a plate surface of a tape-shaped metal substrate (Hastelloy or the like), a PLD method. A Y-based or Ho-based oxide superconductor layer is formed through a cap layer (CeO2) deposited in 1), and the oxide superconductor layer is covered with a thin film (protective film) of gold, silver or an alloy thereof. The schematic diagram is shown in FIG.
JP-A 64-76707 JP-A-5-109530 Japanese Patent Laid-Open No. 10-188691 JP 2004-71359 A

  By the way, if the tape-like superconducting wire 8 is replaced with the tape-like oxide superconducting wire as described in Patent Document 2 with respect to the low temperature side lead portion 5 shown in FIGS. There is a problem of the current conduction as described above, and it is difficult to increase the capacity of the superconducting current lead.

  That is, since the current flows in the above-described silver sheath superconducting wire through the entire cross-section of each wire and through the overlapping surface between the wires, the current leads can be obtained by stacking and assembling a plurality of tape-like wires in the thickness direction. The current carrying capacity can be increased. In contrast, the yttrium-based (Y-based) or holmium-based (Ho-based) tape-shaped oxide superconducting wire shown in FIG. 8 has an intermediate layer and a cap layer insulating layer formed in the wire layer. Therefore, even if a plurality of wires are laminated as shown in FIG. 6, the current flowing from the end surface of the wire conductively joined to the electrode 9 (see FIG. 7) is only on the superconducting layer side of each tape-like wire, that is, on one side of the wire. The current cannot flow between the superconducting wires through the laminated surfaces that overlap each other.

  For this purpose, the tape-shaped oxide superconducting wire shown in FIG. 8 is employed in the low-temperature side lead portion of FIG. 7 to support a conductor unit 7 in which a plurality of tape-shaped oxide superconducting wires are stacked and assembled. When both ends of the wire rod are soldered to the electrode 9 after being laid out on the peripheral surface of the member 6, if there are variations in the solder joint state between the end surface of each tape-shaped wire rod 8 and the electrode 9, etc. As a result, current does not flow evenly in each superconducting wire.

  Further, as shown in FIG. 7, with respect to each tape-shaped superconducting wire 8 of the conductor unit 7 laid on the peripheral surface of the cylindrical support member 6, the electrodes 9 arranged at both ends thereof are used as rings having an L-shaped cross section. In the tape-like superconducting wires 8 stacked one above the other, the inner wire that is in contact with the peripheral surface of the support member 6 is conductively bonded so that the wire surfaces at both ends thereof overlap the peripheral surface of the electrode 9. It will be soldered). From this, when each tape-like wire is laminated up and down with the superconducting layer side of the tape-like oxide superconducting wire shown in FIG. 8 facing the lower surface, the current flows only to the specific tape-like wire that contacts the peripheral surface of the electrode 9. Since it flows in a concentrated manner, it becomes difficult to increase the current carrying capacity (critical current) of the current lead in proportion to the number of stacked tape-shaped oxide superconducting wires.

  The present invention has been made in view of the above points, and its purpose is to adopt a next-generation tape-shaped oxide superconducting wire (ta-based oxide superconducting wire such as Y-based or Ho-based), and a superconducting current lead. When constructing the low temperature side lead part, the assembly structure is improved so that the current flows evenly to each of the tape-shaped oxide superconducting wires assembled by laminating multiple sheets, and the current carrying capacity can be easily increased. It is an object of the present invention to provide a superconducting current lead that can be increased.

In order to achieve the above object, according to the present invention, there is provided a superconducting current lead for supplying power to a superconducting device cooled by a cryogenic refrigerant such as liquid helium or liquid nitrogen, or a refrigerator, etc. A metal electrode in which a lead unit is laid and arranged on the circumferential surface of a cylindrical or columnar support member, and the conductor units are formed by laminating a plurality of tape-shaped superconducting wires and assembled to each other. In what is conductively joined between the conductor unit and
The tape-shaped superconducting wire constituting the conductor unit includes a tape-shaped oxide superconducting layer in which an yttrium-based (Y-based), holmium-based (Ho-based) oxide superconducting layer is formed on a metal substrate via an intermediate layer. A wire rod is used, and between the end of the conductor unit and the electrode, a surface of the tape-shaped wire rod is superposed on the oxide superconducting layer side and a conductive spacer made of a highly conductive metal is inserted, and the conductive spacer and The oxide superconducting wire and the electrode are conductively bonded (claim 1), and specifically, can be configured in the following manner.
(1) The conductive spacer is formed of a stepped copper or copper alloy plate formed with a superposed surface corresponding to each tape-shaped superconducting wire constituting the conductor unit, and a stepped portion of the conductive spacer. Are superposed on the end of the superconducting wire, and solder bonding is performed between the conductive spacer, the superconducting wire, the electrodes, and between the conductive spacers.
(2) The conductive spacer is composed of a copper or copper alloy block formed with a concave groove into which the end of each tape-like superconducting wire constituting the conductor unit is individually inserted on the end face, and the superconducting wire is formed in the concave groove. Are inserted, and solder bonding is performed between the conductive spacer, the superconducting wire, and the electrode.
(3) In the above-mentioned superconducting current lead, a low thermal conductive insulating spacer is interposed in the gap between the wires along the longitudinal direction of the tape-shaped superconducting wire, except for the joint with the conductive spacer. 4).

  According to the superconducting current lead (low temperature side lead portion) having the above-described configuration, the tape-shaped oxide superconducting wire assembled by laminating a plurality of sheets is connected to the end of the wire through a conductive spacer surface-bonded. The electric current from the electrodes flows evenly through the wires. In addition, a large bonding area (conductive area) can be ensured between each wire and the conductive spacer, and the conductivity is improved. This eliminates the concentration of current bias on specific wires, which has been a problem with conventional structures, and is a next-generation tape-shaped oxide superconductor in which an oxide superconductor layer is formed on a metal substrate via an insulating intermediate layer. Large capacity of the superconducting current lead can be easily achieved by using the wire.

  In addition, the heat conduction penetration from the high temperature side is increased by placing low thermal conductivity insulating spacers in the gaps between the wires along the longitudinal direction of the tape-shaped superconducting wire, excluding the junction with the conductive spacer. It is possible to safely protect an oxide superconducting layer that is brittle and easily cracked.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on the examples shown in FIGS. 1 is a configuration diagram of the entire superconducting current lead applied to the superconducting coil device, FIGS. 2A and 2B are configuration cross-sectional views of the low-temperature side lead portion corresponding to Example 1, and an enlarged conductor unit thereof. 3 (a) and 3 (b) are cross-sectional views in the axial direction of the low-temperature lead portion along the line YY in FIG. 2 (a), and an enlarged cross-sectional view of the main part. FIG. It is principal part sectional drawing of the low temperature side lead part corresponding to Example 2, and the same code | symbol is attached | subjected to the member corresponding to FIGS. 5-7 in each figure.

  The superconducting current lead 3 of the first embodiment is basically the same as the conventional structure shown in FIGS. 5 to 7, but constitutes a conductor unit 7 laid on the periphery of the support member 6 of the low temperature side lead portion 5. As the tape-shaped superconducting wire, the tape-shaped oxide superconducting wire 10 described in FIG. 8 is adopted, and a plurality of the tape-shaped oxide superconducting wires 10 are laminated and formed on the peripheral surface of the support member 6. It is laid in the groove.

  Here, the tape-shaped oxide superconducting wire 10 is disposed with the superconducting layer of each wire facing upward, and between the electrodes 9 disposed at both ends of the low temperature side lead portion 5 and both ends of each wire 10. As shown in FIGS. 3A and 3B, a stepped conductive spacer 11 in which the lower surface side of the tip portion is cut out by a half thickness is inserted, and the stepped portion 11 a of the conductive spacer 11 is connected to the superconducting wire 10. Then, the conductive spacer 11 / tape-shaped oxide superconducting wire 10, the conductive spacer 11 / electrode 9, and the conductive spacers 11 that overlap each other are soldered.

  Also, between the plurality of oxide superconducting wires 10 arranged vertically, a low thermal conductivity insulation made of FRP or the like in the longitudinal region excluding the joints at both ends so as to fill the gaps between the wires. The spacer 12 is inserted to protect the oxide superconducting layer of the wire that is brittle and easily broken while suppressing conduction heat penetration from the high temperature side.

  According to the assembly structure of the low-temperature-side lead portion 5 described above, each of the tape-shaped oxide superconducting wires 10 laminated in a plurality of layers and laid on the peripheral surface of the support member 6 has both ends in the longitudinal direction. Are connected in parallel to the electrode 9 through a conductive spacer 11 which is conductively bonded by overlapping. Therefore, the current flowing from the electrode 9 to each oxide superconducting wire 10 through the conductive spacer 11 flows evenly to each wire without concentrating on the specific wire. As a result, the next generation tape-shaped oxide superconducting wire 10 (see FIG. 8) in which current flows only on one side is adopted, and a plurality of these wires are stacked and assembled to provide a high-temperature superconducting current lead having a large current carrying capacity. Can be configured easily.

  In addition, although the supporting member 6 in the illustrated example is cylindrical, the low-temperature-side lead portion can be configured using a columnar supporting member.

  Next, FIG. 4 shows the configuration of Embodiment 2 corresponding to claim 3 of the present invention. That is, in the first embodiment, the conductive spacer 11 is formed of a stepped copper plate individually corresponding to each tape-shaped oxide superconducting wire 10, whereas in the second embodiment, the conductive spacer 11 is conductive. The spacer 13 becomes a copper block body. A plurality of tape-shaped oxide superconducting wires 10 and concave grooves 13a corresponding to the respective tape-shaped oxide superconducting wires 10 are cut in advance on the end face of the conductive spacer 13, and the tape-shaped oxide superconducting wires are assembled when the low temperature side lead portion 5 is assembled. 10 end portions are inserted into the concave grooves 13a one by one, and then the conductive spacers 13 are soldered together. Insulating spacers 12 are interposed between the oxide superconducting wires 10 except for the joints along the longitudinal direction of the wires as in the first embodiment.

Configuration diagram of superconducting current lead according to Embodiment 1 of the present invention applied to a superconducting coil device FIG. 2 is a configuration diagram of a low-temperature side lead portion in FIG. 1, (a) is a cross-sectional view taken along the line XX in FIG. 2A and 2B are detailed structural views of a low-temperature lead portion in FIG. 1, wherein FIG. 2A is a longitudinal sectional view taken along the line YY in FIG. 2A, and FIG. Sectional drawing showing the principal part structure of the low temperature side lead part concerning Example 2 of this invention Conventional configuration diagram of superconducting current lead applied to superconducting coil device FIG. 6 is a configuration diagram of the low-temperature-side lead portion in FIG. 5, (a) is a cross-sectional view taken along the line XX in FIG. FIG. 6 is a detailed structural view of the low-temperature-side lead portion in FIG. 5, (a) is a longitudinal sectional view taken along the line YY in FIG. Schematic structure diagram of next-generation tape-shaped oxide superconducting wire

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cryogenic container 2 Superconducting coil 3 Superconducting current lead 4 High temperature side lead part 5 Low temperature side lead part 6 Cylindrical support member 7 Conductor unit 9 Electrode 10 Tape-shaped oxide superconducting wire 11 Stepped conductive spacer 11a Stepped part 12 Insulating spacer 13 Conductive spacer 13a of block body

Claims (4)

A superconducting current lead for supplying power to the superconducting device which is more cooled to cryogenic refrigerant, or refrigerator, the cold side lead section, the conductor unit which is aggregated by stacking a plurality of tape-shaped superconducting wires In the cylindrical or columnar support member arranged and laid on the peripheral surface, and conductively bonded between the metal electrode and the conductor unit disposed on both ends of the support member,
Wherein the tape-shaped superconducting wires constituting the conductor units, the tape-shaped oxide superconducting wire obtained by stratification of oxides superconducting layer via an intermediate layer on a metal substrate is adopted, the end portion and the electrodes of the conductor unit In between, the surface is overlapped with the end portion of each tape-shaped wire on the oxide superconducting layer side, a conductive spacer is inserted, and the conductive spacer is electrically connected to the oxide superconducting wire and the electrode. Superconducting current lead. 2. The superconducting current lead according to claim 1, wherein the conductive spacer is a stepped copper or copper alloy plate in which overlapping surfaces respectively corresponding to the tape-shaped oxide superconducting wires constituting the conductor unit are formed. the stepped portions of the conductive spacer superimposed on an end portion of the oxide superconducting wire, conductive spacers and the oxide superconducting wire, between the electrodes, and the superconducting current between mutual conductive spacers, characterized in that the solder joint Lead. 2. The superconducting current lead according to claim 1, wherein the conductive spacer is a block of copper or copper alloy in which a concave groove for individually inserting a tape-like end of each superconducting wire constituting the conductor unit is formed on the end surface thereof, A superconducting current lead, wherein an end portion of the oxide superconducting wire is inserted into a groove and soldered between the conductive spacer, the oxide superconducting wire and the electrode. A superconducting current lead according to any one of claims 1 to 3, with the exception of the junction between the conductive spacer, the insulation spacer in a gap between the wires mutually in the longitudinal direction of the tape-shaped oxide superconducting wire A superconducting current lead characterized by being disposed.

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