JP4838199B2 - Oxide superconducting current lead - Google Patents

Description

  The present invention relates to a superconducting current lead for supplying a current from a power source to a low-temperature apparatus to which superconductivity is applied, for example, 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, a Bi body such as Bi (2223) or Bi (2212) system and a bulk body of Re-based oxide superconductor represented by YBa ₂ Cu ₃ O _x are used. Silver sheathed wires coated with silver or a silver alloy with a high critical current density (Jc) in the superconductor part have been used, and many superconducting filaments are used in a silver matrix. An arranged tape-like current lead 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, 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 is known. 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 compared with silver or a silver alloy. Then, its thermal conductivity is as small as about 1/4, and the mechanical strength of this Ni-based alloy substrate is very large, so that it is a wire suitable for application to an oxide superconducting current lead. I can say that.

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

  As described above, the tape-shaped oxide superconducting wire is a wire that is very suitable for application to a current lead. However, in order to improve the Jc of the oxide superconductor, the c-axis of the crystal grain is formed on the film surface ( Therefore, a thin layer of an oxide superconductor is formed on a metal substrate via an intermediate layer, and a reinforcing tape is used to supply a large current to the superconducting magnet. It is necessary to wind around the outer periphery of a reinforcing member such as a laminated structure or 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.

  The present invention has been made to solve the above-described problems, and provides an oxide superconducting current lead that is excellent in flexibility and mechanical properties, reduces the amount of maturation, and is excellent in superconducting properties. That is the purpose.

  In order to solve the above problems, the oxide superconducting current lead of the present invention is a current lead for connecting an oxide superconducting device and a power supply source, and is a flexible pipe-like support member. An electrode connected to both sides via a low thermal conductive member made of an electrically insulating material, and a tape-like shape that is wound around the outer periphery of the support member via an insulating material and electrically connected to both electrodes And the spiral pitch of the tape-shaped oxide superconducting wire is smaller than the axial length of the support member.

  In the above oxide superconducting current lead, when 0.5% bending strain is applied to the current lead, the decrease in critical current value is 5% or less and / or the current carrying current is 1000A. Sometimes, it is preferable that the heat penetration amount is 0.5 W or less.

  Further, in the present invention, the tape-shaped oxide superconducting wire has an outer periphery of a flexible pipe-shaped support member in order to suppress a decrease in the critical current value of the superconductor when bending strain is applied. In this case, a predetermined plurality of tape-shaped oxide superconducting wires are arranged in parallel and wound around the outer periphery of the support member. The rated current can be easily obtained.

The tape-shaped oxide superconducting wire includes a ReBa ₂ Cu ₃ O _7-y- based oxide superconducting wire material (here, ReBa ₂ Cu ₃ O _7-y oxide superconductor layer laminated on an Ni-based alloy substrate such as Hastelloy via an intermediate layer). Represents any one or more elements selected from Y, Gd, Sm, Nd, Ho, Dy, Eu, Tb, Er, and Yb. The same shall apply hereinafter.) ₂ Cu ₃ O _7-y (YBCO) is preferably formed of a superconductor.

  An oxide superconducting current lead as a preferred embodiment of the present invention is a current lead for connecting an oxide superconducting device and a power supply source, on both sides of a flexible pipe-shaped support member, Each of the electrodes connected via a low thermal conductive member made of an electrically insulating material, and a plurality of tapes wound in parallel around the support member so as to be movable via an insulating material, and electrically connected to both electrodes When the spiral pitch of the tape-shaped oxide superconducting wire is made smaller than the axial length of the support member and a 0.5% bending strain is applied to the current lead The amount of heat penetration is 0.5 W or less when the decrease in critical current value is 5% or less and the current flowing through the current lead is 1000 A.

  According to the present invention, the tape-shaped oxide superconducting wire can be moved to the outer periphery of a flexible pipe-shaped support member having low thermal conductivity members disposed at both ends, and the spiral pitch of the support member is a spiral pitch. Since it is wound so as to be smaller than the length in the axial direction, it is possible to obtain a current lead having excellent flexibility and mechanical characteristics, reducing the amount of heat penetration, and having a large current capacity.

  1A and 1B show an oxide superconducting current lead 1 according to the present invention. FIG. 1A is a plan view and FIG. 1B is a front view.

  The current lead 1 includes electrodes 4a and 4b connected to both sides of a flexible pipe-like support member (former) 2 via low thermal conductive members 3a and 3b made of an electrically insulating material such as ceramic, respectively. And a tape-like oxide superconducting wire 5 wound around the outer periphery of the support member 2. In the figure, a state where one tape-shaped oxide superconducting wire 5 is wound around the outer periphery of the support member 2 is shown. In order to obtain the required rated current as described above, A plurality of tape-shaped oxide superconducting wires 5 are wound in parallel.

  Since the pipe-shaped support member 2 is used in an environment of 77K (liquid nitrogen temperature) or less, in order to ensure flexibility and mechanical strength, a corrugated tube having a circular cross section, a spiral tube, or a cylindrical mesh In order to prevent a short circuit, the outer periphery is insulated by an insulating tape (not shown) such as Kapton tape, and the tape-like shape is formed on the insulating tape. The oxide superconducting wire 5 is wound. Both ends of the tape-shaped oxide superconducting wire 5 are electrically connected to the electrodes 4a and 4b, but are movable on the insulating tape, that is, wound in a non-adhesive state (non-fixed state). ing. The support member 2 is fitted to the columnar convex portions 6a and 6b provided on the low heat conductive members 3a and 3b, while the columnar convex portions 7a and 7b provided on the low heat conductive members 3a and 3b. Is fitted with concave portions (not shown) of both electrodes 4a, 4b.

  In this case, by winding the tape-shaped oxide superconducting wire 5 on the outer periphery of the support member 2 with the substrate surface facing outward, a decrease in superconducting characteristics when bending strain is applied can be suppressed.

  As shown in FIG. 1, the tape-shaped oxide superconducting wire 5 is movably wound around the outer periphery of the support member 2 so that the spiral pitch P is smaller than the axial length L of the support member 2. As a result, the amount of strain applied to the superconducting layer when bending strain is applied to the current lead 1 can be reduced. That is, when a bending strain is applied to the support member 2, a compressive strain is applied to the inner side of the bending and a tensile strain is applied to the outer side with the central axis as a neutral axis. Therefore, when the tape-shaped oxide superconducting wire 5 is not movable on the support member 2, the tape-shaped oxide superconducting wire 5 wound around the support member 2 is similarly subjected to compression and tensile strain. As a result, the superconducting characteristics are deteriorated. On the other hand, in the current lead shown in FIG. 1, the tape-shaped oxide superconducting wire 5 is wound so as to be movable on the insulating tape, and when bending strain is applied to the current lead 1, the wire 5 Slips on the insulating tape to absorb and absorb compression and tensile strain within the spiral pitch P. For this purpose, it is necessary to make the spiral pitch P smaller than the axial length L of the support member 2. When L <P, the tape length on the compression and tensile strain side is the same. The compressive and tensile strains cannot be offset and absorbed (except in special cases), and residual strains are generated in the wire 5 to cause deterioration of superconducting characteristics.

  FIG. 2 is an electrical diagram in which a support member 2 having a circular cross section having the same flexibility as in FIG. 1 and an electrode 4c made of a cylindrical body (or a cylindrical body) larger in diameter than the support member 2 have a truncated cone shape. Each of the outer surfaces is connected by a low heat conductive member 3c made of an insulating material. In FIG. 2, the two tape-shaped oxide superconducting wires 5 a and 5 b are illustrated separately for easy understanding. However, by adopting such an end structure, the adjacent wire rods 5 a and 5 b are separated. It is possible to easily perform the soldering work by widening the gap between the ends.

Example 1
A frustoconical spacer having a small diameter equal to the outer diameter of the corrugated pipe and a large diameter of 30.5 mm and a height of 30 mm is attached to both ends of the corrugated pipe having a thickness of 1.2 mm. A Cu electrode having an outer diameter of 30.5 mm was attached. A predetermined number of tape-shaped superconducting wires provided with a superconducting layer on the substrate on the outer periphery of a predetermined length of a former with a Kapton tape attached to the outside of the corrugated tube with the superconducting layer inside. The coil was wound in parallel in a spiral shape at a predetermined pitch, and the superconducting layers at both ends thereof were soldered to the electrodes.

The tape-shaped superconducting wire comprises a Ce-Gd-O-based oxide layer as a first intermediate layer and a Ce-Zr-O-based oxide layer as a second intermediate layer on a Hastelloy substrate by a MOD method. As the intermediate layer, a 0.15 mm thick YBCO superconducting layer formed by the TFA-MOD method was used on the intermediate layer having a three-layer structure in which a CeO ₂ oxide layer was formed by the RF sputtering method. The critical current value of this superconducting wire was 90 A in liquid nitrogen.

  The critical current value (Ic) at the liquid nitrogen temperature of the oxide superconducting current lead produced as described above, Ic when 0.5 and 1.0% bending strain is applied, and its reduction rate, at 1000 A energization Table 1 shows the heat intrusion amount along with the number of superconducting wires, former material, outer diameter and length, spiral pitch, and spacer material.

Example 2
The oxide superconducting current lead was manufactured in the same manner as in Example 1 except that the number of superconducting wires, the outer diameter of the former, and the spiral pitch were changed, and the outer diameter of the spacer and the electrode was the same as the outer diameter of the former. The critical current value (Ic) at the liquid nitrogen temperature, Ic when 0.5 and 1.0% of bending strain were applied, the rate of decrease thereof, and the amount of heat penetration at 1000 A energization were measured. The results are shown in Table 1.
Example 3
Oxide superconductivity in the same manner as in Example 1 except that the number of superconducting wires, former material and outer diameter, spiral pitch and spacer material were changed, and the outer diameter of the spacer and electrode was the same as the outer diameter of the former. A current lead was manufactured, and the critical current value (Ic) at liquid nitrogen temperature, Ic when 0.5 and 1.0% bending strain was applied, its reduction rate, and the amount of heat penetration at 1000 A energization were measured. . The results are shown in Table 1.
Example 4
An oxide superconducting current lead was manufactured in the same manner as in Example 1 except that the width and number of superconducting wires and the length of the former were changed, and the critical current value (Ic) at liquid nitrogen temperature, 0.5 and 1. Ic when 0% bending strain was applied, the rate of decrease thereof, and the amount of heat penetration during 1000 A energization were measured. The results are shown in Table 1.
Comparative Example 1
An oxide superconducting current lead was manufactured in the same manner as in Example 1 except that the spiral pitch was made longer than the length of the former, and the critical current value (Ic) at the liquid nitrogen temperature was bent at 0.5 and 1.0%. Ic and the rate of decrease when strain was applied, and the amount of heat penetration when energizing 1000 A were measured. The results are shown in Table 2.

Comparative Example 2
Oxide superconductivity in the same manner as in Example 1, except that the number of superconducting wires, former material and outer diameter, spiral pitch, and spacer material were changed, and the outer diameter of the spacer and electrode was the same as the outer diameter of the former. A current lead was manufactured, and the critical current value (Ic) at liquid nitrogen temperature, Ic when 0.5 and 1.0% bending strain was applied, its reduction rate, and the amount of heat penetration at 1000 A energization were measured. . The results are shown in Table 2.

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

It is the top view (a) and front view (b) which show one Example of the oxide superconducting current lead of this invention. It is a front view which shows a part of other Example of the oxide superconducting current | flow lead of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Current lead 2 ... Support member 3a, 3b, 3c ... Low heat conduction member 4a, 4b, 4c ... Electrode 5, 5a, 5b ... Oxide superconducting wire 6a, 6b ... Convex part 7a, 7b ... Convex part P ... Spiral pitch L ... Length of supporting member in the axial direction

Claims (10)

  A current lead for connecting an oxide superconducting device and a power supply source, wherein the current lead is provided with a low heat conduction member made of an electrically insulating material on each side of a flexible pipe-like support member. A tape-like oxide superconducting wire that is wound around an outer periphery of the support member via an insulating material and electrically connected to the electrodes. The oxide superconducting current lead is characterized in that the spiral pitch of the oxide superconducting wire is smaller than the axial length of the support member.   A current lead for connecting an oxide superconducting device and a power supply source, wherein the current lead is provided with a low heat conduction member made of an electrically insulating material on each side of a flexible pipe-like support member. A tape-like oxide superconducting wire that is wound around an outer periphery of the support member via an insulating material and electrically connected to the electrodes. When the spiral pitch of the oxide superconducting wire is made smaller than the axial length of the support member and a bending strain of 0.5% is applied to the current lead, the critical current value decreases by 5% or less. An oxide superconducting current lead.   A current lead for connecting an oxide superconducting device and a power supply source, wherein the current lead is provided with a low heat conduction member made of an electrically insulating material on each side of a flexible pipe-like support member. A tape-like oxide superconducting wire that is wound around an outer periphery of the support member via an insulating material and electrically connected to the electrodes. The oxide superconducting wire has a spiral pitch smaller than the axial length of the support member, and the amount of heat penetration is 0.5 W or less when the energizing current of the current lead is 1000 A. Superconducting current lead.   4. A plurality of tape-shaped oxide superconducting wires are wound in parallel around an outer periphery of a flexible pipe-shaped support member via an insulating material. The oxide superconducting current lead according to claim 1. The tape-shaped oxide superconducting wire is a ReBa ₂ Cu ₃ O _7-y- based oxide superconducting wire having a superconducting layer laminated on a substrate via an intermediate layer (where Re is Y, Gd, Sm). 1, Nd, Ho, Dy, Eu, Tb, Er, Yb, or any one or two or more elements, the same shall apply hereinafter). The oxide superconducting current lead according to the item.   6. The tape-shaped oxide superconducting wire is wound around an outer periphery of a flexible pipe-shaped support member with the substrate surface facing outside via an insulating material. Oxide superconducting current lead.   7. The oxide superconductor according to claim 1, wherein the flexible pipe-shaped support member is formed of a corrugated tube, a spiral tube, or a pipe-shaped metal member having a cylindrical network structure. Current lead.   8. The oxide superconducting current lead according to claim 7, wherein the metal member is made of SUS, Cu, Al, or Ag.   The electrode is made of a cylindrical body or cylindrical body having a diameter larger than that of the pipe-shaped support member having flexibility, and the outer peripheral surface of the electrode and the support member is made of an electrically insulating material having a truncated cone shape. 9. The oxide superconducting current lead according to claim 7, wherein the oxide superconducting current lead is connected to the surface of the oxide superconducting current lead.   A current lead for connecting an oxide superconducting device and a power supply source, wherein the current lead is provided with a low heat conduction member made of an electrically insulating material on each side of a flexible pipe-like support member. And a tape-like Re-based oxide superconducting wire wound in parallel on the outer periphery of the support member so as to be movable via an insulating material in parallel and electrically connected to the electrodes. When the spiral pitch of the tape-shaped oxide superconducting wire is made smaller than the axial length of the support member, and a 0.5% bending strain is applied to the current lead, the critical current value decreases The oxide superconducting current lead is characterized in that when the energizing current of the current lead is 1000 A, the heat penetration amount is 0.5 W or less.

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