JP5011181B2 - Oxide superconducting current lead - Google Patents

Description

  The present invention relates to a low-temperature device using superconductivity, for example, a current lead using an oxide superconducting wire for supplying current from a power source to a superconducting magnet.

  When operating a superconducting application device, for example, a superconducting magnet, it is necessary to cool the magnet to a cryogenic temperature in order to bring the magnet into a superconducting state, and two methods are known as this cooling method. That is, a method of immersing in a refrigerant such as liquid helium or liquid nitrogen (immersion cooling method) and a method of utilizing heat conduction from a refrigerator or a refrigerant (conduction cooling method). In order to excite the cooled magnet, a current must be passed through the superconducting coil, and a current lead for supplying current from the power source is required. In this case, the current lead needs to be a conductor, but if a metal such as Cu or Al with low electrical resistance and high thermal conductivity is used, in addition to Joule heating of the current lead itself, external heat penetration As a result, the cooling efficiency of the superconducting magnet deteriorates, and there is a problem that the cooling cost becomes enormous in order to maintain the superconducting state. In particular, this tendency is remarkable in the case of a conduction cooling system using a refrigerator, and cooling may be impossible.

  In order to solve this problem, it is necessary to achieve both conductivity and low thermal conductivity as the current lead used in the superconducting magnet. In the superconducting magnet, the current lead part is also cooled below the liquid nitrogen temperature. By using an oxide superconductor having a low thermal conductivity as a current lead, the amount of heat penetration can be suppressed while supplying current.

In this case, as a superconductor used for the superconducting current lead, Bi (2223) -based or Bi (2212) -based Bi-based and Re-based oxide superconductors typified by YBa ₂ Cu ₃ O _y (YBCO) are used. Silver sheath wire with a high critical current density (Jc) of a superconductor portion coated with silver or a silver alloy has been used in which a bulk body is formed into a rod shape or a cylindrical shape, and a superconducting filament is contained in a silver matrix. A tape-shaped current lead in which a large number of wires are arranged is known (for example, see Patent Document 1).

  When the former oxide superconductor bulk body is used for a current lead, the bulk body is brittle and its mechanical strength is low, which causes problems in its manufacture and use. That is, the bulk body itself is not flexible and has a problem that it is damaged when a bending strain of a certain level or more is applied. For this reason, the current lead is attached only in a linear direction, and handling and magnets during attachment work are also included. In order to avoid the application of strain due to vibration during operation, it has been necessary to provide a structure in which strain is not transmitted to the bulk body, such as by providing a flat knitted wire on the electrode portion.

  In addition, the latter silver or silver alloy sheath wire needs to be formed into a tape shape by rolling to increase the crystal orientation, and therefore a silver or silver alloy sheath with a certain thickness is required. Since the sheath material is made of silver or a silver alloy having a very high thermal conductivity, there is a drawback in that the thermal conductivity of the current lead itself is increased.

  On the other hand, as a current lead, the use of a tape-shaped superconductor in which an oxide superconducting layer is provided on a metal substrate has been studied, and a tape-shaped superconducting current lead in which an oxide superconductor and a silver tape are alternately laminated. (For example, refer to Patent Documents 2 and 3). Even in this case, there is a problem that the thermal conductivity of the current lead itself increases.

  Further, there is provided a tape-shaped oxide superconducting wire having an intermediate layer formed on a metal substrate, an oxide superconducting layer formed on the intermediate layer, and a stabilization layer formed on the oxide superconducting layer. This tape-shaped oxide superconducting wire has a high critical current value, and a Ni-based alloy substrate usually used as a metal substrate is silver or a silver alloy. Compared with, the thermal conductivity is as small as about 1/4, and the mechanical strength of this Ni-based alloy substrate is very large and easy to handle, making it very suitable for application to oxide superconducting current leads. It can be said that it is a wire.

  This tape-shaped oxide superconducting wire is a wire that is very suitable for application to current leads, but in order to improve Jc of the oxide superconductor, the c-axis of the crystal grain is used as the film surface (tape surface). For this reason, a thin layer of oxide superconductor is formed on a metal substrate via an intermediate layer, and in order to supply a large current to the superconducting magnet, a tape-like oxidation It is necessary to have a laminated structure of a physical superconducting wire and a reinforcing tape or a structure in which a tape-like oxide superconducting wire is wound around the outer periphery of a reinforcing member such as a former. In this case, in the former case, there is a problem that the manufacturing process is complicated and the thermal conductivity of the current lead itself tends to increase. On the other hand, in the latter case, it is necessary to improve the flexibility of the former. In addition, there is a problem that the superconducting characteristics are likely to be deteriorated due to the strain applied to the tape-shaped oxide superconducting wire wound around the outer periphery of the reinforcing member such as a former.

  In order to solve such problems, the present applicant has previously filed an oxide superconducting current lead that has excellent flexibility and mechanical properties, reduces heat conduction, and has excellent superconducting properties ( (See Japanese Patent Application No. 2007-154372).

  The oxide superconducting current lead according to the present invention is a current lead for connecting a superconducting device and a power supply source, and has low heat composed of an electrically insulating material on both sides of a flexible pipe-shaped support member. An electrode connected via a conductive member, and a tape-shaped oxide superconducting wire wound around an outer periphery of the support member via an insulating material and electrically connected to both electrodes. The spiral pitch of the oxide superconducting wire is made smaller than the axial length of the support member.

JP-A-9-115356 Japanese Patent Laid-Open No. 5-243044 JP-A-6-28930 JP 2004-171841 A

  The above oxide superconducting current lead suppresses a decrease in the critical current value of the superconductor when a bending strain is applied, but uses silver having a very high thermal conductivity as a stabilizing layer. It is necessary to reduce the amount of heat penetration by making the length larger than the bulk of the superconductor. By winding a tape-shaped oxide superconducting wire around the support member, the length problem can be solved, but two current leads are required to supply current to the superconducting device. Therefore, it is necessary to secure a space necessary for arranging the current leads between the power supply source and the superconducting device, and there is a problem that the cooling space must be enlarged. Further, there is a problem that the characteristics of the current lead are deteriorated by the self magnetic field generated in the winding portion of each current lead.

  The present invention has been made to solve the above problems, and is excellent in flexibility and mechanical characteristics, reduces the amount of heat conduction, reduces the length of the current lead, is compact and superconducting. An object of the present invention is to provide an oxide superconducting current lead having excellent characteristics.

  In order to solve the above problem, the oxide superconducting current lead of the present invention is a current lead for supplying power from a power supply source to a superconducting device, and the current lead is interposed through an electrically insulating material. Current lead supports made of support members disposed on both sides of the support member, current terminals made of a conductive material joined to both ends of each support member, and current terminals at both ends of each support member, respectively. And two tape-shaped oxide superconducting wires wound around the outer periphery of the current lead support, and each tape-shaped oxide superconducting wire is non-inductively wound around the outer periphery of the current lead support in the same direction. It is configured as follows.

This current lead is formed from a support member having a semi-cylindrical or semi-cylindrical shape made of a non-magnetic material and electrically insulating and low thermal conductivity disposed on both sides of the current lead. Current lead support, a current terminal made of a conductive material bonded to both ends of each support member, and a current terminal connected to both ends of each support member, respectively, and wound around the outer periphery of the current lead support Two tape-shaped ReBa _x Cu ₃ O _y- based oxide superconducting wires (where Re is any one selected from Y, Gd, Sm, Nd, Ho, Dy, Eu, Tb, Er, and Yb) Each of the tape-shaped oxide superconducting wires has a substrate surface on the outer side, which represents a seed or two or more elements, and represents a range of x ≦ 2, y = 6.2 to 7. In the same direction on the outer periphery of the current lead support It may be configured to be electrically wound.

  The non-inductive winding in the above invention means that the tape-like oxide superconducting wire connected between the current terminals at both ends of the current lead support is energized in the opposite direction in the use state, thereby Indicates that the generated magnetic field is wound around the outer periphery of the current lead support in the same direction so as to cancel each other. In this case, power is supplied from the power supply source to the superconducting device with a single current lead. be able to.

Further, the tape-shaped oxide superconducting wire in the invention described above includes a ReBa _x Cu including a superconducting layer and a stabilizing layer laminated on an Ni-based alloy substrate such as Hastelloy (registered trademark) via an intermediate layer. _{A 3} O _y- based oxide superconducting wire can be used, and it is particularly preferable to use a YBa _x Cu ₃ O _y (YBCO) superconducting wire.

  According to the present invention, the tape-like oxide superconducting wire connected between the current terminals joined to both ends of the current lead support is non-inductively wound around the outer periphery of the current lead support in the same direction. A single current lead can supply power to a superconducting device from a power supply source, thereby providing excellent flexibility and mechanical properties, reducing heat conduction, and being compact and It is possible to suppress a decrease in superconducting characteristics due to a self magnetic field generated in the winding portion of the current lead.

  FIG. 2 shows the current lead support 10 used in the oxide superconducting current lead of the present invention and the current terminals 11a, 11b, 11c and 11d joined to both ends thereof. ) And (c) respectively show a plan view, a front view, and a right side view (the left side view is also symmetric).

  In FIG. 2, the current lead support 10 is composed of support members 13a and 13b arranged on both sides of an electrically insulating material 12 such as GFRP (glass fiber reinforced plastic), and the current terminals 11a and 11b are The current terminals 11c and 11d are joined to both ends of the support member 13b.

  The support members 13a and 13b have a semi-cylindrical shape (or semi-columnar shape) made of a non-magnetic material with low thermal conductivity, while the current terminals 11a, 11b, 11c and 11d are made of oxygen-free copper. Each of the support members 13a and 13b has a shape in which rectangular connection members 14a, 14b, 14c and 14d are formed on one side of a semicircular plate made of a conductive material such as .

  The current terminals 11a, 11c and 11b, 11d are joined through an electrically insulating material such as GFRP, and have the same outer diameter as that of the current lead support 10 by joining the semicircular parts. It is joined to both sides of the current lead support 10 so as to form the same surface as the surface of the lead support 10. As shown in FIG. 2A, the current terminals 11a, 11c, 11b, and 11d joined through the electrically insulating material extend to both ends of the support members 13a and 13b and extend electrically. It can be bonded to both sides of the current lead support 10 via the material 12, or the current terminals 11a, 11c and 11b, 11d can be spaced apart from each other.

  The supporting members 13a and 13b made of a non-magnetic material with low thermal conductivity forming the current lead support 10 are made of any one of stainless steel alloy, Ni-base alloy, and titanium alloy in addition to GFRP. Things can be used. In this case, when the current lead support 10 is a stainless alloy or the like that does not have electrical insulation, the current terminals 11a, 11c and 11b, 11d are electrically connected to GFRP or the like as shown in FIG. It is joined to both sides of the current lead support 10 via intermediate members 15a, 15b, 15c and 15d which are electrically insulating and have low thermal conductivity.

FIG. 1 shows an oxide superconducting current lead 20 in which a tape-shaped superconducting wire is connected between current terminals 11a and 11b, 11c and 11d joined to both ends of the current lead support 10 described above. 2, the same parts as those in FIG. 2 are indicated by the same reference numerals. In FIG. 1, the tape-shaped ReBa _x Cu ₃ O _y- based oxide superconducting wire A (thick solid line) and B (thick dotted line) schematically shown. Is composed of a ReBa _x Cu ₃ O _y oxide superconducting wire having a superconducting layer and a stabilizing layer laminated on a Ni-based alloy substrate such as Hastelloy via an intermediate layer, and Kapton is formed on the outer periphery of the current lead support. Each superconducting wire is wound so as to be non-inductively wound around the outer periphery of the current lead support 10 in the same direction through an electrically insulating tape such as a tape (registered trademark) with the substrate surface facing outward. A and B are insulated, and the superconducting wire A has a superconducting layer solder-connected to the semicircular plate-like portions of the current terminals 11a and 11b. Similarly, the superconducting wire B is a half of the current terminals 11c and 11d. Disc The superconducting layer is soldered to the parts. In this case, when the current lead support 10 is made of an electrically insulating material, it is possible to omit insulation of the electrical insulating tape or the superconducting wires A and B on the outer periphery of the current lead support.

In addition, the ReBa _x Cu ₃ O _y- based oxide superconducting wires A and B usually have a width of 1.0 to 5.0 mm, a superconducting layer thickness of 0.5 to 3.0 μm, and a stabilization layer thickness. In the range of 0.01 to 0.2 mm is used. If the width of the superconducting wire is less than 1.0 mm, it will be difficult to ensure a current carrying capacity as a current lead. On the other hand, if the width exceeds 5.0 mm, a generally used small diameter columnar or cylindrical shape will be used. It becomes difficult to wind around the outer periphery of the current lead support. On the other hand, if the thickness of the superconducting layer is less than 0.5 μm, it is difficult to secure a current carrying capacity as a current lead. On the other hand, if the thickness exceeds 3.0 μm, the density of the superconducting layer is reduced or cracks are generated. The superconducting properties deteriorate due to the occurrence of. Furthermore, if the thickness of the stabilization layer is less than 0.01 mm, the role as the stabilization layer, that is, when the transition from the superconducting state to the normal conducting state due to overcurrent, temperature rise, etc. is made to split into the stabilizing layer. It becomes difficult to prevent the superconducting layer from being burned out. On the other hand, when the thickness exceeds 0.2 mm, the amount of heat penetration increases and the performance of the current lead is deteriorated.

The ReBa _x Cu ₃ O _y- based oxide superconducting wires A and B can be constituted by a laminate in which a plurality of tape-shaped ReBa _x Cu ₃ O _y- based oxide superconducting wires are laminated, or a plurality of them. It can also be configured by arranging the sheets in parallel.

  The superconducting wires A and B can be wound around the outer periphery of the current lead support 10 with the substrate surface facing outward, thereby suppressing degradation of superconducting characteristics when bending strain is applied. That is, when the superconducting wires A and B are wound so that the spiral pitch is smaller than the axial length of the current lead support and can be moved around the current lead support, bending strain is applied to the current lead 20. In this case, the superconducting wires A and B can slide on the insulating tape to offset and absorb the compression and tensile strain within the spiral pitch P, and thus when the bending strain is applied to the current lead 20. It is possible to reduce the amount of strain added to the superconducting layer.

As is apparent from the above, the oxide superconducting current lead according to the present invention can supply power from the power supply source to the oxide superconducting device with a single current lead, and self-generated in the winding portion of the current lead. Since the deterioration of the superconducting characteristics due to the magnetic field can be suppressed, the heat intrusion is compared with the case where two current leads each having a tape-like superconducting wire wound around the current lead body of the conventional comparative example 1 are used. The amount can be significantly reduced.

  The oxide superconducting current lead according to the present invention can be used as a current lead for supplying current from a power supply source to a superconducting device.

It is a front view which shows one Example of the oxide superconducting current | flow lead of this invention. It is the top view (a), front view (b), and right view (c) which show one Example of the current lead support body used for the oxide superconducting current lead of this invention, and the current terminal joined to the both ends. .

10 Current lead support 11a, 11b, 11c, 11d Current terminal 12, 12 'Electrical insulating material 13a, 13b Support member 14a, 14b, 14c, 14d Connection member 15a, 15b, 15c, 15d Intermediate member 20 Oxide superconductivity Current lead A, B ReBa _x Cu ₃ O _y- based oxide superconducting wire

Claims (9)

  A current lead for supplying electric power from a power supply source to a superconducting device, wherein the current lead includes a current lead support body including support members disposed on both sides of the current lead, and each of the current leads. Two tape-shaped current terminals made of a conductive material respectively joined to both ends of the support member, and two tapes connected between the current terminals at both ends of each support member and wound around the outer periphery of the current lead support An oxide superconducting current lead, wherein each of the tape-shaped oxide superconducting wires is non-inductively wound around the outer periphery of the current lead support in the same direction.   2. The oxide superconducting current lead according to claim 1, wherein the pair of current terminals respectively joined to both sides of the current lead support are disposed apart from each other.   2. The oxide superconducting current lead according to claim 1, wherein a pair of current terminals respectively joined to both sides of the current lead support are disposed with an electrically insulating material therebetween. The oxide superconducting current lead according to any one of claims 1 to 3 , wherein the tape-shaped oxide superconducting wire is wound around the outer periphery of the current lead support via an electrically insulating material. . 5. The oxide superconducting current lead according to claim 4 , wherein the tape-shaped oxide superconducting wire comprises a laminate in which a plurality of the oxide superconducting wires are laminated. 5. The oxide superconducting current lead according to claim 4 , wherein a plurality of tape-shaped oxide superconducting wires are arranged in parallel. The tape-shaped oxide superconducting wire is a ReBa _x Cu ₃ O _y- based oxide superconducting wire comprising a superconducting layer and a stabilization layer laminated on a substrate via an intermediate layer (where Re is Y, Gd, Any one or two or more elements selected from Sm, Nd, Ho, Dy, Eu, Tb, Er, and Yb are shown, and a range of x ≦ 2, y = 6.2 to 7 is shown. oxide superconducting current lead according to claim 1 or 4 to 6 any one of claims, characterized in that there. 8. The oxide superconducting current lead according to claim 7, wherein the tape-shaped oxide superconducting wire is wound around the outer periphery of the current lead support with the substrate surface facing outward. A current lead for supplying power from a power supply source to a superconducting device, wherein the current lead is a nonmagnetic GFRP (glass fiber reinforced plastic), stainless steel disposed on both sides of the current lead via an electrically insulating material A current lead support made of a support member having a semi-cylindrical or semi-columnar shape made of any one of an alloy, a Ni-based alloy and a titanium alloy, and a conductive material bonded to both ends of each of the support members And two tape-shaped ReBa _x Cu ₃ O _y oxide superconducting wires connected between current terminals at both ends of each support member and wound around the outer periphery of the current lead support (Here, Re represents one or more elements selected from Y, Gd, Sm, Nd, Ho, Dy, Eu, Tb, Er, and Yb, and x ≦ 2, y = Shows the range of .2～7.) Becomes from the said each tape-shaped oxide superconducting wire, it is unguided wound in the same direction on the outer circumference of the current lead support to the substrate surface to the outside Oxide superconducting current lead characterized by.

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