JP2020074284A - Superconducting wire, superconducting coil and superconducting device - Google Patents

Abstract

To provide a superconducting wire that can suppress a quenching burning accident.SOLUTION: A superconducting wire of an embodiment includes an oxide superconductor layer. The oxide superconductor layer has a continuous Perovskite structure including rare earth elements, barium (Ba), and copper (Cu). The rare earth elements include a first element which is praseodymium (Pr), at least one second element selected from the group consisting of neodymium (Nd), samarium (Sm), europium (Eu), and gadolinium (Gd), at least one third element selected from the group consisting of yttrium (Y), terbium (Tb), dysprosium (Dy), and holmium (Ho), and at least one fourth element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a superconducting wire, a superconducting coil, and a superconducting device.

  Most applications of superconducting equipment, except transmission cables, are used in magnetic fields. In the case of a power transmission cable, if liquid helium is used for cooling at around 4K, the cooling cost becomes enormous. Therefore, the superconductor used for the power transmission cable is limited to the high temperature oxide superconductor.

  The superconductor used for the power transmission cable is a Y (yttrium) -based wire rod. Most of the superconductors used for power transmission cables are Y-based wire rods made by the TFA-MOD (Metal Organic Deposition using TriFluoroAcetates) method.

  When a superconductor is applied to a coil, the superconductor is exposed to a magnetic field except for special cases such as a superconducting fault current limiter that suppresses the influence of magnetic field generation. The characteristics of a superconductor deteriorate under a magnetic field due to Lorentz force or the like. Therefore, it is assumed that the metal-based superconductor is used at a temperature of 4K, the Bi-based superconductor is used at a temperature of 15 to 20K, and the Y-based superconductor is used at a temperature of 30 to 50K.

  When applying superconductivity to a coil, it was mainly used at 4K using a metal-based superconductor. However, when the superconducting coil is immersed in liquid helium for use, the helium required at the initial stage of immersion is about four times the volume of the container. For example, the amount of helium required for immersion in a 400 L (liter) container is 1600 L.

  The price of helium is soaring, and it is expected that the price will rise further in the future. Helium is produced together with natural gas stored in the upper rock. For this reason, it is not produced in the shale gas field located below the bedrock. It is considered that the amount of helium produced together with natural gas has already exceeded the peak, and it is thought that depletion will continue and prices will rise sharply in the future.

  The price of helium is soaring up to about 5000 yen per liter. For example, if 1600 L is required for immersion in a 400 L container, a helium price of 8 million yen is required. Therefore, in recent years, a superconducting system that can be used for cooling a refrigerator is expected. Basically, it is expected to use a superconductor at a temperature of 30K or higher, instead of 4K, which has a large cooling cost.

  The superconducting coil is a technology that requires heat insulation by vacuum. When the degree of vacuum decreases, it becomes difficult to maintain cooling in the refrigerator, and the entire system stops. Therefore, maintaining the degree of vacuum is an important issue for superconducting application systems.

  The seal of many metal welds is essential for maintaining the vacuum level. If the seal becomes weak, vacuum insulation cannot be maintained, and maintenance such as evacuation is required again. In that case, the maintenance cost increases and the reliability of the system decreases.

  As a general theory, a metal welded part deteriorates when vibration is applied at a low temperature, and the leak probability increases. The metal bond is a bond that is maintained by the movement of free electrons, and the mobility of the free electrons is lowered by cooling to an extremely low temperature, and the metal bond is weakened. Especially, it is considered that the damage is great when it is vibrated at 4K. Therefore, it is desirable to use the Bi-based superconductor at 15 to 20K or the Y-based superconductor at 30 to 50K for the superconducting coil.

  Bi-based superconductors and Y-based superconductors, which are high-temperature metal oxide superconductors, are used at a low temperature below the liquid nitrogen temperature in a magnetic field. Of these, Bi-based superconductors have further problems. The Bi-based superconductor has a minimum silver ratio of 60% in the cross section of the wire and is high in cost. Oxygen permeation is required during heat treatment, and a noble metal such as gold is required to improve strength, which further increases the cost. Even so, it is difficult to obtain sufficient strength. For this reason, it is difficult to use the Bi-based superconductor in a large-sized device in which a hoop force of several tens of tons is applied to the coil.

  For the above reason, the withdrawal of Bi-based wire rods is one after another, and the Y-based wire rods account for most of the superconducting wire rods used in the superconducting coil.

  Not only Y-based wires, but generally superconductors of the type 2 can coexist with magnetic flux lines. Artificial pin technology is a technology that partially fixes the magnetic flux lines and exerts superconducting properties even in a magnetic field. The size of the artificial pin depends on the application temperature, but it is considered that a size of about 3 nm is required around 30K.

Regarding the formation of artificial pins in Y-based superconducting wires, the TFA-MOD method, which has dominated the power transmission cable market, has so far not provided good results in magnetic field applications. In this situation, it is impossible to form an effective artificial pin and there is not even a prototype of a coil used in a magnetic field. In this system, an artificial pin such as Dy ₂ O ₃ is formed inside, but its size is very large, 20-30 nm, and it is considered that it does not function as an artificial pin.

  Huge size artificial pins are ineffective in two ways. One is that the pinning effect is reduced due to the reduced number of artificial pins. If the volume occupied by the wire of the artificial pin is constant in order to maintain the current amount, the number of artificial pins of 30 nm is 1/1000 of the number of artificial pins of 3 nm. Therefore, the magnetic flux lines may not be fixed sufficiently.

  The other is that the size of the artificial pin is too large, which reduces the pinning effect. If the size of the artificial pin is large, many magnetic flux lines will enter inside. The force that holds the magnetic flux of the artificial pin works only on the interface between superconducting and non-superconducting. Therefore, if a plurality of magnetic flux lines enter the artificial pin, stress corresponding to the total Lorentz force is applied, and the magnetic flux crosses the interface. Therefore, the magnetic flux lines may not be fixed sufficiently.

Under these circumstances, physical vapor deposition methods such as the Pulsed Laser Deposition (PLD) method and the Metal Organic Chemical Vapor Deposition (MOCVD) method have been previously developed as applications of magnetic fields. In the physical vapor deposition method, artificial pins are easily introduced, and BaZrO ₃ (BZO) artificial pins are often introduced. Many efforts have been made to control the size of artificial pins to 3 nm. In recent years, even artificial pins having a size of about 5 nm have been developed.

  Although it is this BZO artificial pin, it seems that quenching accidents frequently occur in coil applications, and there are no successful cases. Moreover, it is said that the quench burnout accident occurs at a current lower than half of the current value that can be passed. For example, it is said that a quench burn accident will occur at a current of 80A when a maker is capable of supplying a current of up to 100A with a superconducting wire that can carry a current of 200A. In extreme cases, it is reported that the current becomes unstable at about 25% of the maximum current value.

  The cause of this quench burn accident is not always clear. It is expected to realize a superconducting coil that suppresses quench burnout accidents.

  In addition, even if the quench burnout accident does not occur, the uniformity of the generated magnetic field is inferior and the result that the specifications are not satisfied is also reported. The realization of a superconducting coil that can generate a stable magnetic field is also expected.

M. Rupich, et al., Supercond. Sci. Technol. 23 (2010) 014015 (9pp) P. Mele, et al., Physica C, 468, (2008), 1631-1634

  An object of the present invention is to provide a superconducting wire, a superconducting coil, and a superconducting device capable of suppressing quench burnout.

  The superconducting wire according to the embodiment includes an oxide superconducting layer. The oxide superconducting layer has a continuous perovskite structure containing a rare earth element, barium (Ba), and copper (Cu), and the rare earth element is neodymium (Nd), which is a first element that is praseodymium (Pr). , At least one second element of the group of samarium (Sm), europium (Eu) and gadolinium (Gd), at least the group of yttrium (Y), terbium (Tb), dysprosium (Dy) and holmium (Ho). One type of third element and at least one type of fourth element of the group of erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).

The schematic diagram of the superconducting coil of 1st Embodiment. The schematic cross section of the superconducting wire of 1st Embodiment. The transmission electron microscope image of the oxide superconducting layer of 1st Embodiment. The figure which shows the result of the X-ray-diffraction measurement of the oxide superconducting layer of 1st Embodiment. The figure which shows the result of the X-ray-diffraction measurement of the oxide superconducting layer of 1st Embodiment. The flowchart which shows an example of coating solution preparation of 1st Embodiment. The flowchart which shows an example of the method of forming a superconductor into a film from the coating solution of 1st Embodiment. The figure which shows the typical calcination profile of 1st Embodiment. The figure which shows the typical main baking profile of 1st Embodiment. The flowchart which shows an example of the method of manufacturing the superconducting coil of 1st Embodiment. Explanatory drawing of the effect | action and effect of 1st Embodiment. Explanatory drawing of the effect | action and effect of 1st Embodiment. Explanatory drawing of the effect | action and effect of 1st Embodiment. Explanatory drawing of the effect | action and effect of 1st Embodiment. Explanatory drawing of the effect | action and effect of 1st Embodiment. Explanatory drawing of the effect | action and effect of 2nd Embodiment. Explanatory drawing of the effect | action and effect of 2nd Embodiment. The block diagram of the superconducting apparatus of 4th Embodiment. 6 is a graph showing current-voltage characteristics of Comparative Example 1. 6 is a graph showing current-voltage characteristics of Comparative Example 1. 6 is a graph showing current-voltage characteristics of Comparative Example 1. 6 is a graph showing current-voltage characteristics of Comparative Example 1. 6 is a graph showing current-voltage characteristics of Comparative Example 1. 6 is a graph showing current-voltage characteristics of Comparative Example 1. 9 is a graph showing current-voltage characteristics of Comparative Example 2. 9 is a graph showing current-voltage characteristics of Comparative Example 2. 9 is a graph showing current-voltage characteristics of Comparative Example 2. 9 is a graph showing current-voltage characteristics of Comparative Example 2. 3 is a graph showing current-voltage characteristics of Example 1. 3 is a graph showing current-voltage characteristics of Example 1. 3 is a graph showing current-voltage characteristics of Example 1. 3 is a graph showing current-voltage characteristics of Example 1. 3 is a graph showing current-voltage characteristics of Example 1. 3 is a graph showing current-voltage characteristics of Example 1. 9 is a graph showing the current-voltage characteristics of Example 5. 9 is a graph showing the current-voltage characteristics of Example 5. 9 is a graph showing the current-voltage characteristics of Example 5. 9 is a graph showing the current-voltage characteristics of Example 5. 9 is a graph showing the current-voltage characteristics of Example 5. 9 is a graph showing the current-voltage characteristics of Example 5.

  In the present specification, a crystallographically continuous structure is regarded as a “single crystal”. A crystal including a low-angle grain boundary with a difference in the direction of the c-axis of 1.0 degree or less is also regarded as a "single crystal".

  In the present specification, PA (Pinning Atom) is a rare earth element that serves as an artificial pin of an oxide superconducting layer. PA forms a non-superconducting unit cell. PA is praseodymium (Pr) only.

  In the present specification, SA (Supporting Atom) is a rare earth element that promotes clustering of artificial pins. The trivalent ionic radius of SA is smaller than the trivalent ionic radius of PA, and is larger than the trivalent ionic radius of MA described later.

  In the present specification, MA (Matrix Atom) is a rare earth element forming a matrix phase of an oxide superconducting layer.

  In the present specification, CA (Counter Atom) is a rare earth element that forms a cluster with PA or SA. The trivalent ionic radius of CA is smaller than the trivalent ionic radius of MA.

  In the present specification, the first-generation atom-substitution type artificial pin (1st-ARP: 1st-Atom Replaced Pin) means that the non-superconducting unit cell containing PA is the ultimate in the matrix phase of the superconducting unit cell containing MA. It means an artificial pin in a dispersed form. Ultimate dispersion is a form in which a non-superconducting unit cell exists solely in the matrix phase.

  In the present specification, the second-generation clustered atom-substituted artificial pin (2nd-CARP: 2nd generation-Clustered Atom Replaced Pin) is a unit cell containing PA in the matrix phase of a superconducting unit cell containing MA. , Unit cells containing SA and unit cells containing CA are artificial pins in a clustered form. The size of the artificial pin is larger than that of 1st-ARP.

  In the present specification, the third generation clustered atom-substituted artificial pin (3rd-CARP: 3rd generation-Clustered Atom Replaced Pin) is a unit cell containing PA in a matrix phase of a superconducting unit cell containing MA. And CA means an artificial pin having a clustered form of unit cells. It differs from 2nd-CARP in that it does not contain SA.

  In the present specification, “superconducting device” is a general term for devices using a superconductor.

  Hereinafter, the superconducting coil of the embodiment will be described with reference to the drawings.

(First embodiment)
The superconducting coil of this embodiment includes a superconducting wire. The superconducting wire has an oxide superconducting layer. The oxide superconducting layer has a continuous perovskite structure containing a rare earth element, barium (Ba), and copper (Cu). The rare earth element is at least one second element of the group of the first element which is praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu) and gadolinium (Gd), yttrium (Y). ), Terbium (Tb), at least one third element of the group of dysprosium (Dy) and holmium (Ho), and of erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu). Contain at least one fourth element of the group

  FIG. 1 is a schematic view of the superconducting coil of this embodiment. 1A is a sectional view, and FIG. 1B is a perspective view of a pancake coil which is a part of a superconducting coil.

  As shown in FIG. 1 (a), the superconducting coil 100 has four pancake coils 14 a, 14 b, 14 c, 14 d around the axis of the bobbin (reel) 12 as shown in FIG. 1 (b). It is in a stacked state. The pancake coils 14a, 14b, 14c, 14d are formed by spirally winding the superconducting wire 20. The periphery of the pancake coils 14a, 14b, 14c, 14d is covered with an impregnated resin layer 15 such as an epoxy resin.

  The superconducting coil 100 of this embodiment can take various shapes such as a saddle shape. Further, the superconducting coil 100 of the present embodiment can be used for various applications such as a heavy ion beam therapy device, a superconducting magnetic levitation railway vehicle, or a nuclear fusion test coil.

  FIG. 2 is a schematic cross-sectional view of the superconducting wire according to this embodiment. 2A is an overall view, and FIG. 2B is an enlarged schematic cross-sectional view of a superconducting wire.

  As shown in FIG. 2A, the superconducting wire 20 includes a tape-shaped base material 22, an intermediate layer 24, an oxide superconducting layer 30, and a metal layer 40. The base material 22 enhances the mechanical strength of the oxide superconducting layer 30. The intermediate layer 24 is a so-called oriented intermediate layer. The intermediate layer 24 is provided to orient the oxide superconducting layer 30 into a single crystal when the oxide superconducting layer 30 is formed. The metal layer 40 is a so-called stabilizing layer. The metal layer 40 protects the oxide superconducting layer 30. In addition, the metal layer 40 has a function of diverting the current when the superconducting wire 20 is actually used even if the superconducting state becomes partially unstable.

The tape-shaped substrate 22 is, for example, a metal tape such as a nickel-tungsten alloy. The intermediate layer 24 is, for example, yttrium oxide (Y ₂ O ₃ ), yttria-stabilized zirconia (YSZ), or cerium oxide (CeO ₂ ) from the base material 22 side. The layer structure of the base material 22 and the intermediate layer 24 is, for example, nickel tungsten alloy / yttrium oxide / yttria-stabilized zirconia / cerium oxide. In this case, the oxide superconducting layer 30 is formed on the cerium oxide.

  As the base material 22 and the intermediate layer 24, for example, an IBAD (Ion Beam Assisted Deposition) substrate can be used. In the case of an IBAD substrate, the base material 22 is a non-oriented layer. The intermediate layer 24 has, for example, a five-layer structure. For example, the lower two layers are a non-oriented layer, an orientation origin layer produced by the IBAD method, and two oriented layers of a metal oxide are formed thereon. In this case, the uppermost alignment layer is lattice-matched with the oxide superconducting layer 30.

  The oxide superconducting layer 30 has a continuous perovskite structure containing a rare earth element, barium (Ba), and copper (Cu). The rare earth element is at least one second element of the group of the first element which is praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu) and gadolinium (Gd), yttrium (Y). ), Terbium (Tb), dysprosium (Dy) and at least one third element of the group holmium (Ho), and erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu). At least one fourth element of the group.

  Hereinafter, the first element is referred to as PA (Pinning Atom), the second element is referred to as SA (Supporting Atom), the third element is referred to as MA (Matrix Atom), and the fourth element is referred to as CA (Counter Atom).

  The oxide superconducting layer 30 of the present embodiment includes a second generation type clustered atom substitution type artificial pin (2nd-CARP).

  The type of rare earth element contained in the oxide superconducting layer 30 can be identified by using SIMS (Secondary Ion Mass Spectrometry).

The oxide superconducting layer 30 is a single crystal having a continuous perovskite structure. The perovskite structure is described by, for example, REBa ₂ Cu ₃ O _7-y (−0.2 ≦ y ≦ 1) (hereinafter, REBCO). RE is a rare earth site.

  The layer thickness of the oxide superconducting layer 30 is, for example, 0.1 μm or more and 10 μm or less. The oxide superconducting layer 30 is, for example, all single crystal in the layer thickness direction.

  In addition, the single crystal is present in the oxide superconducting layer 30 within a range of 50 nm or more from the base material 22 side of the oxide superconducting layer 30 and 70% or less of the average layer thickness of the oxide superconducting layer 30, for example. To do. The single crystal has a size of, for example, 500 nm × 100 nm or more in the cross section in the layer thickness direction of the oxide superconducting layer 30.

The oxide superconducting layer 30 includes, for example, 2.0 × 10 ¹⁵ atoms / cc or more and 5.0 × 10 ¹⁹ atoms / cc or less of fluorine, and 1.0 × 10 ¹⁷ atoms / cc or more 5.0 × 10 ²⁰ atoms. / Cc or less carbon is included. Fluorine and carbon contained in the oxide superconducting layer 30 are residual elements resulting from the film formation of the oxide superconducting layer 30 by the TFA-MOD method. Fluorine and carbon in the oxide superconducting layer 30 exist, for example, at the grain boundaries of a single crystal.

The concentration of fluorine contained in the oxide superconducting layer 30 is, for example, 2.0 × 10 ¹⁶ atoms / cc or more. The concentration of carbon contained in the oxide superconducting layer 30 is, for example, 1.0 × 10 ¹⁸ atoms / cc or more.

  The concentrations of fluorine and carbon in the oxide superconducting layer 30 can be measured using SIMS, for example.

  The metal layer 40 is, for example, a base metal of silver (Ag) or copper (Cu) and may be an alloy. In addition, a small amount of precious metal such as gold (Au) may be contained.

  FIG. 2B is an enlarged schematic cross-sectional view seen from above the film of the oxide superconducting layer 30, that is, from the c-axis direction. Each square represents a unit cell in a single crystal.

  In FIG. 2B, the case where PA is praseodymium (Pr), SA is samarium (Sm), MA is yttrium (Y), and CA is lutetium (Lu) is illustrated. The oxide superconducting layer 30 is composed of a unit cell of PBCO containing praseodymium (Pr), SmBCO containing samarium (Sm), YBCO containing yttrium (Y), and LuBCO containing lutetium (Lu).

  Pr, Sm, and Lu are described in the quadrangle indicating each unit cell of PrBCO, SmBCO, and LuBCO. Blank squares in the figure are unit cells of YBCO, which is a matrix phase.

  In the oxide superconducting layer 30, PrBCO, SmBCO, and LuBCO unit cells form an aggregate in YBCO that is a matrix phase. This aggregate is called a cluster. In FIG. 2B, a region surrounded by a thick solid line is a cluster.

  PrBCO is a non-superconductor. The cluster containing PrBCO functions as an artificial pin of the oxide superconducting layer 30.

  The relationship of the trivalent ionic radii of praseodymium (Pr), samarium (Sm), yttrium (Y), and lutetium (Lu) is Pr> Sm> Y> Lu. PrBCO and SmBCO containing a rare earth element larger than YBCO, which is a matrix phase, and LuBCO containing a rare earth element smaller than YBCO, are assembled in the cluster. Hereinafter, a unit cell containing a rare earth element larger than the matrix phase is called a large unit cell, and a unit cell containing a rare earth element smaller than the matrix phase is called a small unit cell.

  The unit cell containing MA is in the matrix phase. Among the rare earth elements contained in the oxide superconducting layer 30, the amount of MA is the maximum. For example, when the number of atoms of the rare earth element is N (RE) and the number of atoms of MA that is the third element is N (MA), N (MA) / N (RE) ≧ 0.6. In other words, the molar ratio of MA in the rare earth element contained in the oxide superconducting layer 30 is 0.6 or more.

  The number ratio of the number of atoms or the number of moles of the rare earth element in the oxide superconducting layer 30 can be calculated, for example, based on the result of element concentration measurement by SIMS.

  FIG. 3 is a transmission electron microscope (TEM) image of the oxide superconducting layer 30 of this embodiment. More specifically, it is a HAADF-STEM (High-Angle Annular Dark Field Scanning TEM) image.

  It is an observation image of 4 million times. FIG. 3 is a cross section in the layer thickness direction of the oxide superconducting layer 30, that is, in the direction parallel to the c-axis. When the number of atoms of the rare earth element in the oxide superconducting layer 30 is 100%, the cross section of the sample in which the numbers of praseodymium (Pr), samarium (Sm), and lutetium (Lu) atoms are 4%, 4%, and 8%, respectively. It is a figure.

  From the observation image of FIG. 3, the perovskite structure oriented at the atomic level can be confirmed. It can be seen that there are no different phases in the oxide superconducting layer 30 and unit cells having the same lattice constant are lined up. In other words, the oxide superconducting layer 30 of FIG. 3 is a single crystal having a perovskite structure.

  In FIG. 3, the single crystal has a perovskite structure in the layer thickness direction. The single crystal has a size of 500 nm × 100 nm or more.

  In FIG. 3, the region indicated by the white solid line frame is a cluster. Of the three rows of atoms arranged horizontally in the white solid line frame, the upper and lower two rows are atoms of the barium (Ba) site. One row sandwiched between is the atom of the rare earth site.

  Similarly, in the region indicated by the white broken line frame, among the three rows of atoms arranged horizontally, the upper and lower two rows are atoms of the barium (Ba) site, and the one row sandwiched between them is the atom of the rare earth site. Is. The atoms of the rare earth site in the region indicated by the white solid line frame are brighter than the atoms of the rare earth site in the region indicated by the white broken line frame.

  In the HAADF-STEM image, an element having a large atomic weight shines brighter. The region shown by the white solid line frame is considered to be brighter than the region shown by the white broken line frame because it contains praseodymium (Pr), samarium (Sm), and lutetium (Lu), which have larger atomic weights than yttrium (Y). Be done.

  For example, in the HAADF-STEM image of the oxide superconducting layer 30, when the brightness of barium is I (Ba) and the brightness of the rare earth element sandwiched by barium is I (RE), I (I) in the first region is There is a first region and a second region in which RE) / I (Ba) is 1.3 times or more of I (RE) / I (Ba) of the second region. The first region is the cluster.

  The first region and the second region are, for example, as shown in FIG. 3, 10 atoms of one row of rare earth sites arranged in the horizontal direction and 10 atoms of each of the upper and lower two rows of barium sites sandwiching the rare earth site. And a region having. In FIG. 3, the white solid line frame is the first region, and the white broken line frame is the second region.

  As can be seen from the TEM image of FIG. 3, it is considered that lattice distortion occurs at the barium site and the distortion angle exceeds 1 degree. However, as can be seen from FIG. 3, the intervals between adjacent atoms are clearly equal to each other, and it can be considered that a bond as a crystal exists. Therefore, the structure of FIG. 3 is defined as a single crystal.

  4 and 5 are diagrams showing the results of X-ray diffraction (XRD) measurement of the oxide superconducting layer 30 of this embodiment. The oxide superconducting layer was measured by the 2θ / ω method of XRD measurement.

  FIG. 4 shows the results of measurement of a YBCO sample containing no rare earth element other than yttrium and a sample in which the proportions of praseodymium, samarium, yttrium, and lutetium in the rare earth element are 4%, 4%, 84%, and 8%. is there. In addition, FIG. 5 shows that the ratio of praseodymium, samarium, yttrium, and lutetium in the rare earth elements is 1%, 1%, 96%, and 2%, and the ratio of praseodymium, samarium, yttrium, and lutetium in the rare earth elements is 2%. %, 2%, 92%, and 4% samples.

  In FIG. 4, even in the sample containing praseodymium, samarium, and lutetium, the peak coincides with the peak of YBCO, and no other clear peak is confirmed. In addition, peak separation is not observed in the samples containing praseodymium, samarium, and lutetium. Therefore, it can be seen that the sample containing praseodymium, samarium, and lutetium is also a single crystal having a continuous perovskite structure.

  Also in FIG. 5, no separation of peaks is seen. Therefore, it can be seen that the sample containing praseodymium, samarium, and lutetium is a single crystal having a continuous perovskite structure.

  The peak of LAO used for the substrate also appears in FIGS. 4 and 5.

  Next, a method for manufacturing the superconducting coil 100 of this embodiment will be described. First, the superconducting wire 20 is manufactured. The intermediate layer 24 is formed on the tape-shaped substrate 22, the oxide superconducting layer 30 is formed on the intermediate layer 24, and the metal layer 40 is formed on the oxide superconducting layer 30. The oxide superconducting layer 30 is formed by the TFA-MOD method.

  The oxide superconducting layer 30 is first formed by at least one kind selected from the group consisting of praseodymium (Pr) acetate of the first element, neodymium (Nd), samarium (Sm), europium (Eu) and gadolinium (Gd). The second element acetate, yttrium (Y), terbium (Tb), dysprosium (Dy) and holmium (Ho), at least one third element acetate, erbium (Er), thulium ( Tm), an ytterbium (Yb) and lutetium (Lu) group at least one fourth element acetate, a barium (Ba) acetate, and a copper (Cu) acetate aqueous solution are prepared. .. Next, the aqueous solution is mixed with perfluorocarboxylic acid mainly containing trifluoroacetic acid to prepare a mixed solution, and the mixed solution is reacted and purified to prepare the first gel. Next, alcohol containing methanol is added to the first gel and dissolved to prepare an alcohol solution, and the alcohol solution is reacted and purified to prepare a second gel. Next, an alcohol containing methanol is added to the second gel and dissolved to prepare a coating solution in which the total weight of residual water and residual acetic acid is 2% by weight or less, and the coating solution is applied onto a substrate to form a gel film. To form. Next, the gel film is calcined at 400 ° C. or lower to form a calcined film. Next, the calcined film is subjected to main baking at 725 ° C. or more and 850 ° C. or less and oxygen annealing in a humidified atmosphere to form an oxide superconductor film, that is, the oxide superconducting layer 30.

  The perfluorocarboxylic acid preferably contains 98 mol% or more of trifluoroacetic acid from the viewpoint of not deteriorating the superconducting property.

  FIG. 6 is a flowchart showing an example of preparation of the coating solution of this embodiment. Hereinafter, PA as the first element is praseodymium (Pr), SA as the second element is samarium (Sm), MA as the third element is yttrium (Y), and CA as the fourth element is lutetium. A case of (Lu) will be described as an example.

  As shown in FIG. 6, metal acetates of yttrium, praseodymium, samarium, lutetium, barium, and copper are prepared (a1). In addition, trifluoroacetic acid is prepared (a2). Next, the prepared metal acetate is dissolved in water (b) and mixed with the prepared trifluoroacetic acid (c). The resulting solution is reacted and purified (d) to obtain an impurity-containing first gel (e). Then, the obtained first gel is dissolved in methanol (f) to prepare a solution containing impurities (g). The resulting solution is reacted and purified to remove impurities (h), and a second gel containing a solvent is obtained (i). Further, the obtained second gel is dissolved in methanol (j) to prepare a coating solution (k).

  The metal acetate is mixed with RE site (Y, Pr, Sm, Lu): Ba: Cu = 1: 2: 3. Mix so that the amount of Pr in the RE site is 0.00000001 or more and 0.20 or less. After mixing and reaction, the amount of residual water and acetic acid in the coating solution is reduced to 2 wt% or less by a high-purity solution purification process by the SIG (Stabilized Sovent-Into-Gel) method. The SIG method of the present embodiment is a method of highly purifying a solution for partial stabilization in order to prevent decomposition of PrBCO, and is a PS-SIG (Partially Stabilized Sovent-Into-Gel) method. The amount of Pr / (Y + Pr + Sm + Lu) is mixed so as to be 0.0025, for example.

  FIG. 7 is a flowchart showing an example of a method for forming a superconductor film from the coating solution of this embodiment.

  As shown in FIG. 7, first, the previously prepared coating solution is prepared (a). The coating solution is applied onto the substrate by, for example, a die coating method to form a film (b) and a gel film is obtained (c). Then, the obtained gel film is calcined as a primary heat treatment to decompose organic substances (d) to obtain a calcined film (e). Further, the calcined film is subjected to a secondary heat treatment of main baking (f), and thereafter, for example, pure oxygen annealing is carried out (h) to obtain an oxide superconductor film (h).

  FIG. 8 is a diagram showing a typical calcination profile of this embodiment. In the calcination under normal pressure, the trifluoroacetate is decomposed mainly at 200 ° C or higher and 250 ° C or lower. In order to prevent rushing into that temperature range, the rate of temperature rise is reduced near 200 ° C. When the temperature is gradually raised to 250 ° C., the substance decomposed from trifluoroacetate contains fluorine and oxygen, and fluorine and oxygen are likely to remain in the film due to hydrogen bond. The temperature is raised to 400 ° C. to remove the substance. The final temperature is generally 350 to 450 ° C. In this way, a semitransparent brown calcined film composed of oxides and fluorides is obtained.

  FIG. 9 is a diagram showing a typical main firing profile of the present embodiment. It is a dry mixed gas up to tb1 at 100 ° C., but humidification is performed from there. The humidification start temperature may be 100 ° C. or higher and 400 ° C. or lower. It seems that the formation of the pseudo liquid layer is started from around 550 ° C., and the humidification gas is humidified at a temperature lower than 550 ° C. so that the humidified gas is spread throughout the film to form the pseudo liquid layer uniformly.

FIG. 9 shows a typical temperature profile of 800 ° C. main firing, but the temperature rising profile is gentle from 775 ° C. to 800 ° C. so that there is no temperature overshoot at tb3. Even with this, the overshoot at 800 ° C. may remain at 2 to 3 ° C., but this does not cause any particular problem. The oxygen partial pressure at the highest temperature depends on the matrix phase. In the case of YBCO superconductor firing, it is 1000 ppm at 800 ° C, and the optimum oxygen partial pressure is halved each time the temperature is lowered by 25 ° C. That is, it is 500 ppm at 775 ° C. and 250 ppm at 750 ° C. In this main firing, YBa ₂ Cu ₃ O ₆ is formed in the case of YBCO type. It is not a superconductor at this point.

  In the highest temperature main firing, a drying gas is passed at tb4 before the main firing is completed and the temperature starts to be lowered. Since the humidified gas decomposes the superconductor into oxides at 700 ° C. or lower, oxygen annealing is performed at tb6 to change the number of oxygen in the superconductor from 6.00 to 6.93. This number of oxygen becomes a superconductor. However, only PrBCO has a perovskite structure but is not a superconductor. Further, since the valence of Pr is unknown, the oxygen number of the unit cell is unknown, but it seems that the oxygen number is high. This is because the valence of Pr takes a value between 3 and 4 and the number of oxygen increases in the unit cell accordingly. The start temperature of oxygen annealing is 375 ° C. or higher and 525 ° C. or lower. After the temperature is maintained thereafter, the furnace is cooled from tb8.

  By the above manufacturing method, the superconducting wire 20 including the oxide superconducting layer 30 is manufactured.

  FIG. 10: is a flowchart which shows an example of the method of manufacturing the superconducting coil 100 from the superconducting wire 20 of this embodiment.

  As shown in FIG. 10, first, the superconducting wire 20 manufactured previously is prepared (a). Next, the superconducting wire 20 is wound around the axis of the bobbin 12 to form the pancake coils 14a, 14b, 14c, 14d (b). The pancake coils 14a, 14b, 14c and 14d in this state are non-impregnated coils (c). Then, the pancake coils 14a, 14b, 14c, 14d are impregnated with a resin such as an epoxy resin (d). An impregnated resin layer 15 is formed around the pancake coils 14a, 14b, 14c, 14d to form an impregnated coil (e).

  The impregnated coil has higher mechanical strength than the non-impregnated coil.

  The superconducting coil 100 of this embodiment is manufactured by the above manufacturing method.

  Next, the operation and effect of the superconducting coil 100 of this embodiment will be described.

  The superconducting coil 100 of this embodiment uses the superconducting wire 20 having clustered PrBCO as an artificial pin. Since the superconducting wire 20 has excellent magnetic field characteristics, the characteristics of the superconducting coil 100 used in a magnetic field are improved. Furthermore, by using this superconducting wire 20, it is possible to suppress the quench burn accident of the superconducting coil 100. Furthermore, by using this superconducting wire 20, superconducting coil 100 that generates a stable magnetic field is realized.

  First, the improvement of magnetic field characteristics by the superconducting wire 20 of the present embodiment will be described.

  In the superconducting wire 20 of this embodiment, the oxide superconducting layer 30 contains YBCO in a matrix phase. The non-superconductor PrBCO is clustered in the matrix phase with the superconductors SmBCO and LuBCO. These clusters function as artificial pins at the atomic level, improving the magnetic field characteristics.

  The oxide superconducting layer 30 of the present embodiment is made of PA, SA, MA, CA. SA and CA cause a clustering phenomenon. PA is taken into a cluster as a part of SA, and a clustered atom-substitution type artificial pin (Clustered Atom-Replaced Pin: CARP) is formed. This clustered atom-substitution type artificial pin improves magnetic field characteristics.

  FIG. 11 is an explanatory diagram of the operation and effect of this embodiment. FIG. 11 is a diagram showing the relationship between the magnetic field and the critical current density of the superconducting wire 20 of this embodiment. The measurement results at a temperature of 77K are shown.

Samples of YBCO containing no rare earth elements other than yttrium (cross mark in FIG. 11), which are comparative forms, and 1%, 1%, and 96% of the rare earth elements of praseodymium, samarium, yttrium, and lutetium of the present embodiment. 2% sample (square mark in FIG. 11), praseodymium, samarium, yttrium, and lutetium in the rare earth elements at 2%, 2%, 92%, and 4% ratios (triangle mark in FIG. 11), It is the result of measuring the samples (circles in FIG. 11) in which the proportions of praseodymium, samarium, yttrium, and lutetium in the rare earth elements are 4%, 4%, 84%, and 8%. The horizontal axis is the magnetic field (T) and the vertical axis is the Jc value (MA / cm ² ).

  As is clear from FIG. 11, in the present embodiment, a high critical current density is obtained compared to the comparative form, especially in the region exceeding 3T.

  The ratio of praseodymium in the rare earth element (Pr ratio) is preferably 10 ppb (= 0.00000001) or more. When it is 10 ppb or more, the effect of improving the magnetic field characteristics can be obtained.

  When the number of atoms of the rare earth element is N (RE) and the number of atoms of the first element that is PA, that is, praseodymium is N (PA), the Pr ratio can be described as N (PA) / N (RE). .. Therefore, it is desirable that 0.00000001 ≦ N (PA) / N (RE).

  When the ratio of praseodymium to the total sum of praseodymium and samarium exceeds 50%, the Jc value decreases. If the ratio of praseodymium is less than 5%, the effect of improving the magnetic field characteristics may not be obtained.

  Therefore, when the number of atoms of the first element that is PA is N (PA) and the number of atoms of the second element that is SA is N (SA), 0.05 ≦ N (PA) / (N It is desirable that (PA) + N (SA)) ≦ 0.5.

  When the number of atoms of the rare earth element is N (RE) and the number of atoms of the third element that is MA is N (MA), it is desirable that N (MA) / N (RE) ≧ 0.6. .. If it is less than the above range, the ratio of the superconducting unit cells may be reduced, and sufficient superconducting properties may not be obtained.

  When the number of atoms of the third element that is MA is N (MA) and the number of atoms of yttrium contained in the third element is N (Y), N (Y) / N (MA) ≧ 0. 5 is desirable. Since the material of yttrium (Y) is relatively inexpensive, the cost of the superconducting wire 20 can be reduced.

  When the number of atoms of the rare earth element is N (RE), the number of atoms of the first element that is PA is N (PA), and the number of atoms of the second element that is SA is N (SA), It is desirable that N (PA) + N (SA)) / N (RE) ≦ 0.2. Further, it is more desirable that (N (PA) + N (SA)) / N (RE) ≦ 0.1. If it exceeds the above range, the ratio of the superconducting unit cells decreases, and there is a possibility that sufficient superconducting properties cannot be obtained.

  The number of atoms of the first element that is PA is N (PA), the number of atoms of the second element that is SA is N (SA), and the number of atoms of the fourth element that is CA is N (CA). In this case, it is desirable that 0.8 × N (CA) ≦ N (PA) + N (SA) ≦ 1.2 × N (CA). If the above conditions are not satisfied, the number of PAs, SAs, or CAs that do not form clusters may increase and the superconducting properties may deteriorate.

The oxide superconducting layer 30 includes fluorine of 2.0 × 10 ¹⁵ atoms / cc or more and 5.0 × 10 ¹⁹ atoms / cc or less, and 1.0 × 10 ¹⁷ atoms / cc or more of 5.0 × 10 ²⁰ atoms / cc. It is desirable to include the following carbons.

  Residual fluorine and residual carbon are considered to have an effect of maintaining the magnetic field characteristics in a very high magnetic field exceeding 15 T, for example.

From the above viewpoint, the fluorine contained in the oxide superconducting layer 30 is more preferably 2.0 × 10 ¹⁶ atoms / cc or more. Further, the carbon contained in the oxide superconducting layer 30 is more preferably 1.0 × 10 ¹⁸ atoms / cc or more, for example.

  It is assumed that no PrBCO-containing cluster is formed in the oxide superconducting layer and PrBCO is ultimately dispersed in the YBCO matrix phase. The ultimate dispersion is a state in which PrBCO is dispersed as a single unit cell in the matrix phase of YBCO.

  It is considered that Pr forms a perovskite structure with a valence of 3 and then becomes valence of 4 to make the unit cell non-superconducting. At this time, it is considered that the 1/3 perovskite unit cell containing Pr contracts about 14% and becomes non-superconducting. It is considered that the deformation propagates to the first adjacent unit cell in the a / b plane, and the four unit cells also become non-superconducting. In this way, when clusters are not formed and Pr is finally dispersed, a "5 times degradation phenomenon" (5 times degradation phenomenon) in which Jc degradation of 5 times the Pr amount is observed is confirmed.

  Next, the effect of suppressing the quench burnout accident of the superconducting coil of this embodiment and the effect of stabilizing the generated magnetic field will be described.

  As described above, a quench burn accident is likely to occur in the superconducting wire formed by the physical vapor deposition method. It is considered that the cause is an internal bypass current (IBC). It is conceivable that in the IBC, the current meanders in the superconducting wire, and the energy that does not contribute to the formation of the magnetic field becomes thermal energy, causing a quench burn accident. Further, it is considered that the magnetic field generated by the superconducting coil becomes unstable due to IBC.

IBC is considered to occur due to the difference in local critical temperature (Tc) inside the superconducting wire. When the superconducting wire has a portion having a different Tc, the local Critical Current Density (Jc) value at each location, that is, the local Critical Current (Ic) value is different. IBC is always formed in a superconductor in which Tc is lowered. For example, although Tc = 90.7K in YBa ₂ Cu ₃ O _7-x (YBCO) of good Jc, IBC is formed even in Tc = 89.7K. It

  When a difference in local ease of current flow occurs at 77K, the tendency seems to remain unchanged even when cooled at 30K, for example. Jc-B-T curves show the same tendency in superconductors having the same structure. Therefore, it is easy for the current to flow easily at 77K or 30K. The number of points to reverse is not zero, but it seems that this trend is generally maintained. Therefore, it is considered that IBC occurs even at a low temperature.

  The BZO artificial pin acts as an obstacle by itself, and also reduces ambient oxygen to be non-superconducting and form IBC. Even with a TFA-MOD superconducting wire, Tc is lowered by irradiation with radiation. That is, it is considered that the IBC is formed by the irradiation of the radiation even in the superconducting wire made by the TFA-MOD method.

  IBC steady-state measurements are rather difficult. For example, in the case of a superconducting wire that requires a magnetic field accuracy of 0.01%, the instantaneous fluctuation of the current value is also 0.01%. Since the quench of the superconductor is measured at μV, it is difficult to observe a displacement smaller than this by several orders of magnitude, and it is necessary to expand the influence of IBC for measurement. For that purpose, it seems effective to increase the current value in a short time for measurement.

  When the current value is significantly increased in a short time, the presence of the IBC increases the electromotive force of noise due to the IBC, which facilitates the measurement. From this, it is considered that the presence of IBC can be indirectly measured and the magnitude of the possibility of a quench burnout accident when a coil is formed can be known.

  This is the IBC indirect measurement method. For the current value up to Ic, increase the current in about 4 seconds and measure (current value up to 1.25 times the Ic value in 5 seconds), and measure the voltage fluctuation up to 90% of the Ic value as V (IBC). You can compare by defining.

  In the IBC indirect measurement method, V (IBC), which is a voltage fluctuation, is obtained. By comparing V (IBC) between materials, it is possible to compare the possibility of a quench burnout accident.

The definition of V (IBC) calculation is as follows. The current is increased to the Ic value for a certain period of time (here, 4 seconds), and the maximum voltage Vmax and the minimum voltage Vmin observed in the data up to 90% of the Ic value are used, and the background noise of the measurement system is 0.20 μV. Calculated by subtracting. That is, V (IBC) is expressed by the following equation.
V (IBC) = Vmax-Vmin-0.20

  An extremely large V (IBC) is confirmed by the IBC indirect measurement of the superconducting wire having the BZO artificial pin manufactured by the physical vapor deposition method. V (IBC) = 36.05 μV at 50K · 5T. Although it is a value obtained by increasing the current in a short time, it cannot be directly compared with 1 μV / cm which is a superconducting transition, but it is considered that it is not a mysterious result even if IBC is the cause of quench burning.

There is also a superconducting wire in which IBC hardly occurs. It is a superconducting wire made by the TFA-MOD method and having a Dy ₂ O ₃ artificial pin with a diameter of 20 nm to 30 nm therein. In this superconducting wire, the YBCO perovskite structure is maintained and Tc is 90.7K. At 50K · 5T, V (IBC) = 0.14 μV, which is V (IBC) which is only 1/250 that of the wire rod of the physical vapor deposition method.

The reason for this is that the V (IBC) of the superconducting wire having the Dy ₂ O ₃ artificial pin manufactured by the TFA-MOD method is small, but the current goes straight through most of the internal perovskite structure and the current flows to Dy ₂ O ₃ . It seems that it is for detouring only when it hits. In the BZO artificial pin, the Tc is locally different, and the local Ic and Jc are also different. Therefore, it is considered that the current does not always go straight. The presence / absence of IBC can be rephrased as the presence / absence of this rectilinear current.

However, the effect of the artificial pin can hardly be expected in the superconducting wire having the Dy ₂ O ₃ artificial pin. This is because Dy ₂ O ₃ freely grows in the pseudo liquid phase during the main firing and grows to a size of 20 nm to 30 nm. It is too large to function as an artificial pin.

  As described above, in the Y-based superconducting wire, if a coil is formed from a wire having a large V (IBC), extra energy is lost and heat is generated, which may lead to a quench burn accident. Moreover, it is considered that the generated magnetic field is not stable. On the other hand, since the artificial pinning force cannot be expected in the TFA-MOD normal wire having a small V (IBC), the magnetic field characteristics are not improved.

  Therefore, if a superconducting wire having a small V (IBC) and an effective artificial pin is manufactured, it is expected that quench quenching accident will be suppressed. Also, stability of the forming magnetic field can be expected.

FIG. 12 is an explanatory diagram of the operation and effect of this embodiment. FIG. 12 is a schematic diagram showing the internal structure of a superconducting wire having a Dy ₂ O ₃ artificial pin manufactured by the TFA-MOD method. Dy ₂ O ₃ is formed in the matrix phase of YBCO. Dy ₂ O ₃ has a diameter of 20 nm to 30 nm, for example.

  In the superconducting wire of FIG. 12, the matrix phase of YBCO maintains the perovskite structure, and Tc is 90.7K. It shows a high value in Jc measurement in liquid nitrogen. This indicates that the portion where Tc has decreased is small and the superconducting current flows sufficiently even at the liquid nitrogen temperature.

In the TFA-MOD method, a unit liquid grows by forming a pseudo liquid phase during main firing. Therefore, particles such as Dy ₂ O ₃ that do not form a perovskite structure tend to collect alone and grow large.

When a superconducting current is passed, most of the current flows linearly. However, it detours where it encounters Dy ₂ O ₃ particles. A current detour index Ib is defined to represent the degree of current detour. The current bypass index Ib is an index indicating how much the current has decreased from the amount that should originally flow due to the occurrence of IBC. The current detour index Ib can be calculated geometrically.

  FIG. 13 is an explanatory diagram of the operation and effect of this embodiment. FIG. 13 is an explanatory diagram of how to obtain the current bypass index Ib in a superconducting wire having an artificial pin.

  As shown in FIG. 13A, it is assumed that the artificial pin is a sphere having a radius R, the artificial pin interval is Dp, and the artificial pin introduction volume ratio is Rvp.

The artificial pin introduction volume ratio Rvp can be expressed as follows.
^{Rvp = (4πR 3/3)} / (πR 2 Dp)
= 4R / (3Dp)

Therefore, the artificial pin spacing Dp can be expressed as follows.
Dp = 4R / (3Rvp)

In order for the current at the position r from the center of the artificial pin shown in FIG. 13B to bypass the artificial pin, (R-r) must be moved. Integration is performed to obtain an average value of moving distances (average moving distance Dm) in the entire superconducting wire.

The average movement distance Dm can be expressed as follows.
^{Dm = (πR 3/3)} / πR 2 = R / 3

The average moving distance Dm is the distance that the current moves laterally on average while the current travels between the distances Dp. The average current bypass ratio (Rib) can be calculated as follows.
Rib = Dm / Dp
= (R / 3) / (4R / 3Rvp)
= Rvp / 4

  The average current bypass ratio (Rib) is an index indicating how much the current moves in the direction perpendicular to the drawing direction when the current advances by a unit length in the drawing direction. It can be seen that Rib does not depend on the radius R of the artificial pin, but only on the artificial pin introduction volume ratio Rvp.

The current detour index Ib can be calculated as follows.
Ib = 1-cos θ
tan θ = Rib = Rvp / 4
θ = arctan (Rvp / 4)
Ib = 1-cos {arctan (Rvp / 4)}

  The current bypass index Ib also does not depend on the radius R of the artificial pin, but only on the artificial pin introduction volume ratio Rvp. The current detour index Ib indicates how much the current diminishes from the amount that should originally flow when the actual current travels with the angle θ.

  Taking an extreme case as an example, when the current advances to an angle of 45 degrees, the current amount decreases by about 29% in the current direction, and the loss amount is represented by Ib. That is, Ib = 29%.

  Table 1 shows calculated values of the current bypass index Ib with respect to the artificial pin introduction volume ratio Rvp.

  If the artificial pin maintains Tc, Rbp = 20%, but Ib = 0.12%. Even with the artificial pin introduction volume ratio of 20%, only this amount of bypass current is generated. Therefore, the influence of IBC can be suppressed small.

With a superconducting wire that maintains Tc, the amount of bypass current is small. However, as described above, if the artificial pin size is large like the Dy ₂ O ₃ artificial pin, the effect of improving the magnetic field characteristics cannot be expected.

FIG. 14 is an explanatory diagram of the operation and effect of this embodiment. FIG. 14 is a schematic diagram showing the internal structure of a superconducting wire having BaZrO ₃ (BZO) artificial pins manufactured by physical vapor deposition.

The BZO artificial pin has a perovskite structure, and the size of the artificial pin can be made smaller than that of Dy ₂ O ₃ . However, since the lattice mismatch between BZO and YBCO is about 9%, a void exists between BZO and YBCO. The non-superconductivity of the void portion is high.

  It is also known that when YBCO and BZO are adjacent to each other, BZO extracts oxygen from YBCO, and thus Jc and Tc of YBCO are reduced. Therefore, it is considered that the structure having the internal distribution of Tc as shown in FIG. 14 is formed. In FIG. 14, the hatched portion in the matrix phase of YBCO is a region with a low Tc, and the thin hatched portion is a region with a high Tc.

  The region where Tc is low is often the region where the Jc value is small in the comparison of the same temperature. In the superconducting wire having the same structure, the magnitude of the Jc value inside the wire maintains the same tendency even at low temperature as at high temperature. The presence of the difference in Jc value inside the wire leads to the formation of IBC.

  The IBC has a great influence particularly when a current having a magnitude close to the Jc value is passed. When the current is smaller than the Jc value, the current capacity in each region has a relatively large margin, and therefore the current flows straight. However, when an electric current is caused to flow near the Jc value, there is almost no region where the current capacity has a surplus in the entire wire, and the influence of the current detour inside the wire increases.

  It is presumed that the influence of IBC is greater as the magnetic field is stronger. Although FIG. 14 shows the current flowing from right to left, each current deviates from its vector direction. It is considered that the component flowing in the current direction becomes smaller than 100%, and the surplus becomes thermal energy to further increase the possibility of a quench burnout accident.

In order to make the improvement of the magnetic field characteristics and the suppression of the quench burnout accident compatible, it is conceivable to make the Dy ₂ O ₃ artificial pin of FIG. 12 small or to reduce the influence of the BZO artificial pin of FIG. 14, for example.

However, when a different phase other than the perovskite structure is formed during the main firing of the TFA-MOD method, the growth takes place in the liquid phase at 800 ° C. For this reason, it is difficult to make the Dy ₂ O ₃ artificial pin smaller than ₂₀ nm to 30 nm in which grain growth is fast. Also in the physical vapor deposition method, the pins that do not form the perovskite structure are similarly large.

  On the other hand, an artificial pin having a perovskite structure, such as a BZO artificial pin, has a gap in the lattice or draws out oxygen to make the superconducting property nonuniform. Therefore, it is difficult to reduce the influence on the superconducting property of the BZO artificial pin.

  FIG. 15 is an explanatory diagram of actions and effects of the present embodiment. FIG. 15 is a schematic diagram showing the internal structure of the superconducting wire 20 of the present embodiment.

  FIG. 15 is an enlarged schematic cross-sectional view of the oxide superconducting layer 30 observed such that the lower side is the base material 22 and the upper side is the metal layer 40. Each square represents a unit cell in a single crystal. The c-axis length of the unit cell is about 3 times the a-axis length and the b-axis length. Therefore, when the unit cell is observed, it is observed as shown in FIG.

  In FIG. 15, a square with a blank interior indicates a unit cell having a matrix phase atom (MA: Matrix Atoms) at a rare earth site. For example, the element that enters the rare earth site is Y or the like. A horizontal line indicates an atom (PA: Pinning Atom) that serves as an artificial pin. The rare earth element forming PA is only Pr. The unit cell indicated by a vertical line is an atom (SA: Supporting Atom) of the supporting phase, and for example, Sm or the like is used. There may be cases where there is no SA alone. The unit cell indicated by a check pattern is a counter phase atom (CA: Counter Atom). For example, Yb is used for rare earth sites.

  MA accounts for 60% of the number of elements. The type of MA element is not limited to one type, and Gd, Ho, Dy, etc. may be used in addition to Y. The upper limit values of PA + SA and CA are 20%, respectively. PA and SA are large unit cells when the perovskite structure is formed, and CA is a small unit cell. The large and small unit cells are integrated by a clustering phenomenon that is aggregated due to shape anisotropy. FIG. 15 illustrates a state in which the data is collected at two places.

  In FIG. 15, unit cells adjacent in the a / b axis direction of PA are non-superconducting, and in a cluster in which unit cells are integrated to some extent, the superconducting state is an artificial pin whose average is lowered by 75%. The blank portion is the YBCO superconductor, and Tc is considered to be 90.7K except for the portion adjacent to Pr. Therefore, the superconducting current, except for the clustered artificial pins (CARP), flows straight in the drawing direction of the wire as shown in FIG. Therefore, it is possible to improve the magnetic field characteristics and suppress quench burn accidents.

  In the superconducting coil 100 of the present embodiment, since the artificial pin having a small size is included, the magnetic field characteristic is improved. Further, since the decrease in Tc of the matrix phase can be suppressed, the influence of IBC can be reduced.

  It is considered that the IBC generates an unnecessary voltage when the superconducting current flows, and at the same time, the energy loss leads to the generation of thermal energy, which causes the quench and burn accident.

  CARP of the present embodiment is a system in which YBCO is MA, and IBC hardly occurs even if 4% Pr (PA), 4% Sm (SA), and 8% Lu (CA) are added. As described above, since it is difficult to directly observe IBC, it can be investigated by an IBC indirect measurement method in which the current value is increased to near Jc in a short time and V (IBC) is detected.

  For example, in the above configuration, V (IBC) = 0.11 μV at 50K · 5T, which is a considerably small value.

Note that V (IBC) is disadvantageous when the calculated Ic value is large. V (IBC) is proportional to the current if the inductance component is involved. Since the current increases to the Ic value in about 4 seconds, the current flows in the direction other than the original current component. Even when V (IBC) is generated by the Lorentz force in the magnetic field applied to the current, it is still proportional to the current value. Therefore, it is considered that the degree of influence If (IBC) (Influence of IBC) of the internal bypass current is represented by the quotient of the Ic value as follows.
If (IBC) = V (IBC) / Ic

At this time, it is not always possible to specify what value If (IBC) the coil can operate without causing a quench burnout accident. However, the Dy ₂ O ₃ artificial pin superconducting wire has a track record of 30 times of switching operations with a current limiting device. Further, in the case of a BZO artificial pin superconducting wire, when it is applied to a coil, a quench burnout accident is observed. Therefore, it is considered to be between If (IBC) of each superconducting wire. If (IBC) at 50K / 5T was 0.004 and 0.361, respectively.

  The IBC indirect measurement method is a measurement in which an electric current is increased to an Ic value in 4 seconds and V (IBC) is increased to attempt detection. If the quench burn accident can be avoided if the voltage of 2 μV can be suppressed at 100 A by this measuring method, If (IBC) = 0.020 is the boundary value. In the discussion of this specification, this value is used as a provisional guide. If the relationship between the quench burnout accident and If (IBC) becomes clear in the future, the boundary value will become clear.

  As described above, according to this embodiment, it is possible to realize a superconducting coil capable of suppressing a quench burnout accident. Further, it is possible to realize a superconducting coil having improved magnetic field characteristics and capable of generating a stable magnetic field.

(Second embodiment)
In the superconducting coil of this embodiment, the second element is at least one kind of the group of neodymium (Nd) and samarium (Sm), and the third element is yttrium (Y), dysprosium (Dy) and holmium (Ho). Is the same as the first embodiment, except that the fourth element is limited to at least one kind of the group of erbium (Er) and thulium (Tm). Therefore, the description of the contents overlapping with those of the first embodiment will be omitted.

  In the present embodiment, the nucleation frequency is high because the difference between the ionic radius of MA, which is the third element, and the ionic radius of CA, which is the fourth element, is relatively small. Therefore, the size of the artificial pin is reduced, and in particular, a superconducting coil having excellent magnetic field characteristics in a low temperature region can be realized.

  From the viewpoint of realizing a superconducting coil having excellent magnetic field characteristics in a low temperature region, in particular, the second element is samarium (Sm) and the third element is at least one of the groups of yttrium (Y) and holmium (Ho). It is a kind, and it is desirable that the fourth element is thulium (Tm).

  Hereinafter, the operation and effect of the present embodiment will be described, and also the formation model of CARP will be described.

  FIG. 16 is an explanatory diagram of the operation and effect of this embodiment. FIG. 16 is a diagram showing the relationship between the magnetic field and the critical current density of the superconducting wire 20 of this embodiment. The measurement results at a temperature of 30K are shown.

Samples of YBCO containing no rare earth element other than yttrium (cross mark in FIG. 16) which is a comparative form, and the proportions of praseodymium, samarium, yttrium, and thulium of the present embodiment in the rare earth elements are 1%, 1%, and 96%. 2% samples (black circles in FIG. 16), praseodymium, samarium, yttrium, and thulium in the rare earth elements are 2%, 2%, 92%, and 4% samples (white circles in FIG. 16). It is the result of measurement. The horizontal axis is the magnetic field (T) and the vertical axis is the Jc value (MA / cm ² ).

  As is clear from FIG. 16, in this embodiment, a higher critical current density can be obtained than in the comparative embodiment.

  For example, in the case of application to a power transmission cable or a fault current limiter, it is required that the magnetic field characteristics be improved in the temperature range of 77K to 50K. On the other hand, for example, in the case of application to a superconducting coil used in a heavy ion beam cancer therapy machine, a magnetic levitation train, or the like, it is required to improve the magnetic field characteristics near 30K. Therefore, it is also necessary to improve the magnetic field characteristics in the low temperature region.

  In order to exert the effect as an artificial pin in the low temperature range, it is necessary to reduce the size of the artificial pin. This is because even if the same artificial pin volume is introduced, the smaller the size, the larger the area adjacent to the superconductor, and the potential difference on that surface becomes the microscopic pin force of the artificial pin. Therefore, when CARP is used as the artificial pin, it is necessary to reduce the size of CARP. In order to reduce the CARP size, it is necessary to grasp the size of the CARP currently realized and control the size to be small. However, it is difficult to understand the size of CARP.

Since the BaZrO ₃ artificial pin that has been developed in the past has a different structure from that of YBCO in the matrix phase, the structure is separated and a clear interface exists. Therefore, it was easy to specify the position of BZO. Therefore, it was easy to understand the size.

  However. CARP has a completely different structure from conventional BZO, and a part of the continuous perovskite structure forms an artificial pin. Therefore, it is difficult to determine whether it is CARP or YBCO superconductor even by TEM observation, and it is extremely difficult to directly observe the size of CARP.

  Although it is difficult to directly observe the size of CARP, there is a sample in which a small magnetic field characteristic improving effect is obtained under the conditions of a temperature of 30K and a magnetic field of 1T to 3T by using a pin size control technique. Considering the conventional reports, the size of the artificial pin of this sample is estimated to be about 15 nm to 20 nm. Therefore, it is estimated that the size of CARP is about 15 nm to 20 nm.

  The existence positions of CARP are highly likely to be distributed in a lump form throughout the film, by analogy with fluctuations in the positions of Cu atoms that can be observed by TEM. The massive CARP is distributed almost uniformly in the film, and its diameter is assumed to be 15 nm to 20 nm. Therefore, if the CARP formation model (CARP growth model) can be understood, the size of CARP can be controlled by applying the model.

  The CARP is formed by clustering a phenomenon in which PA, SA, and CA are integrated, and PA makes the adjacent 4 unit cells in the a / b plane non-superconducting. It is speculated that the entire CARP functions as an artificial pin. In order to control the size of CARP, it is necessary to know which unit cell is the origin of CARP formation.

  The origin of CARP formation is likely to be CA. In the YBCO perovskite structure, there is a correlation between the ionic radius of the element that enters the Y site and the optimum oxygen partial pressure during film formation. The optimum oxygen partial pressure is the value at which the Jc value of the obtained superconductor becomes maximum in liquid nitrogen. The oxygen partial pressure is inversely related to the ionic radius.

  For example, in LaBCO, the optimum oxygen partial pressure is 0.2 ppm, in NdBCO it is 5 ppm, and in SmBCO it is 20 ppm. The ionic radius is La> Nd> Sm> Y> Tm> Yb> Lu. It is 1000 ppm for YBCO. Although the exact values of TmBCO, YbBCO, and LuBCO are unknown, it is considered to be around 2000 ppm, 3000 ppm, and 4000 ppm.

  It is considered that the effective difference in ionic radius between elements depends on the logarithmic difference from the optimum oxygen partial pressure of YBCO. The difference between the optimum oxygen partial pressure of YBCO and the optimum oxygen partial pressure of SmBCO forming CARP is 1/50 of that of YBCO, that is, a difference of 50 times. TmBCO is 2 times, YbBCO is 3 times, and LuBCO is 4 times. Although there is no data on PrBCO, it is located between La and Nd and is estimated to be 0.2 ppm to 5 ppm, but it is considered to be about 1 ppm. CA has the smallest difference in effective ion radius from YBCO. The smaller the difference in ionic radius, the higher the frequency of nucleation should be, and it is highly possible that the origin of CARP growth is CA. The nucleation frequency of PA and SA is lower than that of CA.

  An important factor that determines CARP size is the nucleation frequency of MA and CA. When the nucleation frequency of CA is 1 / 1,000,000 that of MA, one CA grows for one million MA, and the surrounding CARP constituent elements are accumulated. They form CARP. Assume that one CA grows to one million MAs when CA is Lu. It is also assumed that one CA grows into 10,000 MAs when CA is Tm.

  CARP containing Lu nucleates with a probability of 1,000,000, and after nucleation, CARP construction proceeds until the concentration of surrounding CARP constituent elements is diluted. Then, it can be easily inferred that a considerably large CARP is completed. If the CARP constituent element is 8%, one CARP consisting of 12,500 unit cells can be produced in 1,000,000 unit cells of MA.

  On the other hand, in the case of Tm, the frequency of nucleation is 1/10000. In this case, it means that 100 nuclei of Tm are produced in the region where Lu-CARP can be formed. That is, 12,500 unit cells are divided into about 100 equal parts, and 100 CARPs consisting of 125 unit cells are formed.

  FIG. 17 is a diagram showing the operation and effect of the second embodiment. FIG. 17 is a diagram schematically showing the difference in CARP growth when CAs having different ionic radii are applied.

  FIG. 17A shows the case where CA is Tm, and FIG. 17B shows the case where CA is Lu. Tm has a smaller ionic radius difference from Y than Lu. For this reason, the difference between the unit cell size of TmBCO and the unit cell size of YBCO is smaller than the difference between the unit cell size of YbBCO and the unit cell size of YBCO, and the frequency of nucleation increases.

  When CA is Lu, nucleation does not occur easily, and when it occurs, the surrounding CARP constituent elements gather to form CARP. Therefore, a large CARP is generated as shown in FIG. On the other hand, when CA is Tm, a large number of nuclei are formed because the nucleation rate is high. The CARP constituent elements migrate to each of a large number of nuclei to form CARP. Since the amount of CARP constituent elements that migrate to each nucleus is small, the size of CARP becomes smaller than that when CA is Lu, as shown in FIG.

  CARP formed with Pr: Sm: Yb = 1: 1: 2 is presumed to form CARP of the same size even when the amount of CARP constituent elements is doubled. It is assumed that a film of Pr: Sm: Yb = 1: 1: 2 (%) is formed as a sample 1, and a film of the same ratio 2: 2: 4 (%) is formed as a sample 2.

  Since the latter Yb nucleation amount is twice that of the former, the CARP number is doubled within the same volume. The area where the CARP constituent elements can be taken in is halved. However, since the concentration of CARP constituent elements is doubled in that region, the same CARP size is eventually obtained. Further generalization gives the same result with n times 1: 1: 2. If the PA: SA: CA ratio is the same and the total amount is different, the number of CARPs having the same size is increased.

  In the above case, for example, in the case of PA: SA: CA = 1: 1: 2, if only CA is increased and PA: SA: CA = 1: 1: 8, the volume of CARP constituent elements is the same (CA The surplus of 6% does not form CARP), and the number of nucleation is four times that before CA increase. That is, four times as many CARPs as the conventional CAs are formed. From this, it has been confirmed that the characteristics of Yb-based CARP are improving at 30K · 1 to 3T. The above is the CARP formation model known at this time.

  A particularly effective way to reduce CARP size is to (1) increase CA only, and (2) use CA with higher nucleation frequency. Also, when the number of nucleation is increased, the final CARP size is determined by the amount of CARP constituent elements. The CARP size in the current CARP growth model can be expressed as follows.

D (CP) = k × M (CP) × V (MA) / V (CA),
In the above formula, the definition of each symbol is as follows.
D (CP): Average diameter of CARP (Diameter of CARP)
M (CP): number of moles of CARP constituent elements per unit volume (Mass of CARP)
V (MA): MA nucleation rate (frequency) (Velocity of MA nucleation)
V (CA): CA nucleation rate (frequency) (Velocity of CA nucleation)
k: constant in CARP growth model (CARP constant).

  In order to reduce D (CP) and exert the effect at 30K, V (MA) should be reduced or V (CA) should be increased when M (CP) is the same. The elements that can be used for MA are limited, and if Gd is used for 100% MA, the solution is likely to precipitate. Therefore, selecting an element of CA or using a mixture of CA is the key to reducing D (CP) and improving the characteristics at 30K.

  When the above (1) is used as a means for reducing the CARP size, the effect is confirmed by using Yb for CA. However, increasing the amount of CA also results in the formation of a region having a small Tc inside, which may lead to an increase in the internal bypass current. However. At present, no significant adverse effects have been confirmed.

  In coil applications where it is desired to avoid voltage formation due to an internal bypass current, it is considered more effective to use the above technique (2) alone to exert the effect at 30K as a means for reducing the CARP size. That is, a technique for increasing V (CA) while maintaining the amount of PA + SA = CA is desired.

  It has been found that in order to realize a large V (CA), the lattice mismatch with MA should be reduced. The nucleation frequency of CA is determined by the lattice mismatch with MA. The velocity is naturally maximized when the lattice mismatch is zero, ie the MA itself nucleates on the MA.

  However, it is said that as the lattice mismatch increases, the nucleation frequency or the nucleation rate decreases, and if the lattice mismatch exceeds 7%, the cube-on-cube will not grow. That is, the speed is zero.

  There are no reports on specific experimental results regarding how much the nucleation rate increases when the lattice mismatch becomes 4%, 3%, 2%, but according to the theory of computational scientists, the 1% lattice mismatch should be small. For example, the nucleation rate may increase about 10 times.

  It is considered difficult to directly measure the exact lattice constant at the time when the perovskite structure is formed by the TFA-MOD method in which HF gas is generated. Conjecturely, the lattice mismatch when Lu, Yb, and Tm come to the Y site seems to be 4%, 3%, and 2%. The nucleation rate from Lu to Yb is about 10 times, and Tm is about 100 times.

  The nucleation rate is mainly adjusted by adding Er or Yb to the base of Tm. If the nucleation rate is high at Tm, Yb is partially mixed, and if the rate is not sufficient, Er is mixed. As a result, a superconductor having excellent characteristics can be obtained at 30K. Moreover, since the area other than the CARP area is made of MA, the voltage disturbance due to the internal bypass current is small. Even if CARP is formed small, the noise of the internal bypass current is small.

  Although it is a voltage disturbance due to an internal bypass current, a huge voltage disturbance has been confirmed in the BZO artificial pin. In CARP made from Yb, that is, Yb-CARP, the voltage noise is only about 1/300. This small voltage noise seems to depend on how far the superconducting current is moved to a position displaced from the traveling direction after moving for a certain distance. It seems to be related to the ratio of the amount of displacement in the direction perpendicular to the direction of current flow.

  As shown in the calculation result in Table 1, only Ib = 0.020% at Rvp = 8%. Moreover, this value does not depend on the radius R when the artificial pin is assumed to be a sphere. In other words, theoretically CARP seems to be an artificial pin that does not increase the internal bypass current even if the pin size becomes smaller and does not increase noise.

  From the above calculation, it is expected that when CA is made to contain at least Tm or Er and MA is Y, clustering will improve the characteristics at 30K. The theoretically large voltage noise does not occur in the superconducting wire containing CARP. If a coil is made using this new superconducting wire containing CARP, a superconducting coil that is hard to quench can be made.

(Third Embodiment)
The superconducting coil of this embodiment includes a superconducting wire. The superconducting wire has an oxide superconducting layer. The oxide superconducting layer has a continuous perovskite structure containing a rare earth element, barium (Ba), and copper (Cu). The rare earth element is at least one second element of the group of the first element which is praseodymium (Pr), gadolinium (Gd), yttrium (Y), terbium (Tb), dysprosium (Dy) and holmium (Ho). The element includes at least one third element of the group of erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).

  The superconducting coil of the present embodiment is different from the first embodiment in that the oxide superconducting layer 30 does not include the SA (Supporting Atom) of the first embodiment. Hereinafter, the description of the same contents as those in the first embodiment will be omitted.

  The oxide superconducting layer 30 of the present embodiment includes a third generation type clustered atom-substitution type artificial pin (3rd-CARP).

  The oxide superconducting layer 30 of this embodiment is made of PA, MA, CA. The first element is PA (Pinning Atom), the second element is MA (Matrix Atom), and the third element is CA (Counter Atom).

  By adjusting the average size of MA and directly bringing the ionic radius averages of PA and CA closer to MA, clusters are formed and become artificial pins.

  Since the oxide superconducting layer 30 of the present embodiment does not have SA, which is a superconducting unit cell, the potential of the artificial pin site is equal to that of a perfect non-superconductor. Therefore, the pin force is theoretically maximum.

  When the number of atoms of the rare earth element is N (RE) and the number of atoms of the second element that is MA is N (MA), N (MA) / N (RE) ≧ 0.6. Is desirable. If it is less than the above range, the ratio of the superconducting unit cells may be reduced, and sufficient superconducting properties may not be obtained.

  Further, when the number of atoms of the second element is N (MA) and the number of atoms of yttrium contained in the second element which is MA is N (Y), N (Y) / N (MA) ≧ It is preferably 0.5. Since the material of yttrium (Y) is relatively inexpensive, it is possible to reduce the cost of the oxide superconductor.

  Further, when the number of atoms of the rare earth element is N (RE) and the number of atoms of the first element that is PA is N (PA), 0.00000001 ≦ N (PA) / N (RE) Is desirable. If it is less than the above range, a sufficient effect of improving the magnetic field characteristics may not be obtained.

  Further, when the number of atoms of the rare earth element is N (RE) and the number of atoms of the first element which is PA is N (PA), N (PA) / N (RE) ≦ 0.2. Is desirable. Further, it is more preferable that N (PA) / N (RE) ≦ 0.1. If it exceeds the above range, the ratio of the superconducting unit cells decreases, and there is a possibility that sufficient superconducting properties cannot be obtained.

  As described above, according to this embodiment, as in the first embodiment, it is possible to realize a superconducting coil capable of suppressing a quench burnout accident. Further, it is possible to realize a superconducting coil having improved magnetic field characteristics and capable of generating a stable magnetic field.

(Fourth Embodiment)
The superconducting device according to the present embodiment is a superconducting device including the superconducting coil according to the first embodiment or the second embodiment. Hereinafter, the description of the first embodiment, the second embodiment, or the contents overlapping the second embodiment will be omitted.

  FIG. 18 is a block diagram of the superconducting device of this embodiment. The superconducting device of this embodiment is a heavy particle beam therapy device 200.

  The heavy particle beam therapy device 200 includes an incident system 50, a synchrotron accelerator 52, a beam transport system 54, an irradiation system 56, and a control system 58.

  The injection system 50 has a function of, for example, generating carbon ions used for treatment and performing pre-acceleration for injection into the synchrotron accelerator 52. The injection system 50 has, for example, an ion generation source and a linear accelerator.

  The synchrotron accelerator 52 has a function of accelerating the carbon ion beam incident from the incident system 50 to an energy suitable for treatment. The superconducting coil 100 according to the first embodiment or the second embodiment is used for the synchrotron accelerator 52.

  The beam transport system 54 has a function of transporting the carbon ion beam incident from the synchrotron accelerator 52 to the irradiation system 56. The beam transport system 54 has, for example, a bending electromagnet.

  The irradiation system 56 has a function of irradiating the patient, which is the irradiation target, with the carbon ion beam incident from the beam transport system 54. The irradiation system 56 has, for example, a rotating gantry that can irradiate the carbon ion beam from any direction. The superconducting coil 100 of the first embodiment or the second embodiment is used for the rotating gantry.

  The control system 58 controls the incident system 50, the synchrotron accelerator 52, the beam transport system 54, and the irradiation system 56. The control system 58 is, for example, a computer.

  In the heavy particle radiotherapy device 200 of this embodiment, the superconducting coil 100 of the first embodiment or the second embodiment is used for the synchrotron accelerator 52 and the rotating gantry. Therefore, quench burnout accident is suppressed and high reliability is realized. In addition, since the superconducting coil 100 can generate a stable magnetic field, it is possible to accurately irradiate the affected part with an ion beam.

  Examples will be described below.

  In the following examples, a large number of metal acetates are mixed to prepare a solution or a superconductor having a perovskite structure. In a Y-based superconductor having a perovskite structure, Y or a lanthanoid group element enters the Y site (rare earth site), and the other elements are Ba and Cu. The ratio is 1: 2: 3. Therefore, paying attention to the metal element used for the Y site, it is described as follows.

  Four types of elements (some of which are three types) are used as the Y-site elements in the following examples. PA that creates artificial pins, SA that supports them. MA in matrix phase. Finally, CA has a small ionic radius and is necessary for forming clusters. There is only Pr in PA. SA can use Nd, Sm, Eu, and Gd. MA can use Tb, Dy, Ho, and Y. Er, Tm, Yb, and Lu can be used for CA. Gd can also be used as a part of MA as 3rd-CARP.

  In most of the examples, PA = SA and PA + SA = CA in moles (atoms). The amount excluding PA + SA + CA from the whole is equal to MA. PA + SA + MA + CA = 100%. For example, it is assumed that there is a mixing ratio of 4% Pr (PA), 4% Sm (SA), 84% Y (MA), 8% Lu (CA). It is described herein as 4% Pr4% Sm-Y-8% Lu. However, in the case of PA + SA = CA in which the numbers of the large element and the small element in the cluster part are the same, the amount of CA is omitted and the description is given as 4% Pr4% Sm-Y-Lu. Further, in the case of PA = SA, and when there is one kind of SA, the amount is also omitted. That is, in the above case, it is described as 4% PrSm-Y-Lu. This description indicates 4% Pr4% Sm-84% Y-8% Lu.

  The elements are listed in order from the smallest lanthanoid group atomic number, in the order of PA, SA, MA, CA. When using Y in MA, write Y last. PA + SA, MA, CA are connected by a bar. That is, it is described as 4% Pr4% Sm-Y-Lu. There are some that do not have SA, but in that case, when PA + SA = CA, the amount of CA can be omitted. For example, in the case of 4% Pr-Y-4% Lu, it is described as 4% Pr-Y-Lu.

(Comparative Example 1)
As Comparative Example 1, a superconducting wire having a Dy ₂ O ₃ artificial pin manufactured by the TFA-MOD method was evaluated. The width of the superconducting wire is 4 mm, and the film thickness is estimated to be about 2 μm. The superconducting wire was cut into 3 cm, and current terminals were attached to both ends. Further, two voltage terminals were attached inside the superconducting wire at intervals of 1 cm. The sample was placed in a refrigerator cooling device, a magnetic field was applied, current-voltage measurement (IV measurement) was performed, and V (IBC) and If (IBC) were determined by the IBC indirect measurement method.

  The measurement was performed at a temperature of 50K and a magnetic field of 1T to 15T, and at a temperature of 30K and under conditions of 5T to 15T.

  Table 2 shows the measurement results of V (IBC) and If (IBC). The background noise (delta VBG) was set to 0.20 μV based on the observation result.

19, FIG. 20, FIG. 21, FIG. 22, FIG. 23, and FIG. 24 are graphs showing the current-voltage characteristics of Comparative Example 1. 19, FIG. 20, FIG. 21, and FIG. 22 are measurements at a temperature of 50K, and FIGS. 23 and 24 are measurements at a temperature of 30K. The black circles are the data points considered to have reached the Ic value.

  As can be seen from the graphs of FIGS. 19, 20, 21, and 22, V (IBC) was low and the results were stable. However, from Table 2, it can be seen that the value of If (IBC) increases as the magnetic field increases, that is, deteriorates.

  At 50K · 5T, If (IBC) = 0.004, which is a stable result extremely close to zero. However, the numerical value increases with the magnetic field strength, and at 12.5T, it becomes 0.031, which exceeds the provisional boundary value of 0.020. Conversely, it can be seen that the value is 0.019 or less up to 10T, which is equal to or less than the boundary value.

  The measurement result of If (IBC) of 30K was almost the same as that of 50K. Although it seems to be improved a little at 15T, other results were almost the same, which was a good result. It was also found that there was no significant improvement at 30K.

  The measurement results of the current-voltage characteristics of FIGS. 23 and 24 seem to change because they are not corrected by the Ic value, but it was found that there is not much change if the value of If (IBC) is taken. .. The effect of IBC was also considered to be more prominent at high temperatures, but no difference was confirmed between 50K and 30K.

(Comparative example 2)
As Comparative Example 2, a superconducting wire having a BZO artificial pin manufactured by a physical vapor deposition method was evaluated in place of the superconducting wire having the Dy ₂ O ₃ artificial pin of Comparative Example 1. The width of the superconducting wire is 4 mm, and the film thickness is estimated to be about 1 μm. The superconducting wire was cut into 3 cm, and current terminals were attached to both ends. Further, two voltage terminals were attached inside the superconducting wire at intervals of 1 cm. The sample was placed in a refrigerator-cooled device, a magnetic field was applied to perform IV measurement, and V (IBC) and If (IBC) were obtained as in Comparative Example 1.

  The measurement was performed at a temperature of 50K and a magnetic field of 1T to 15T.

  Table 2 shows the measurement results of V (IBC) and If (IBC). 25, 26, 27, and 28 are graphs showing current-voltage characteristics of Comparative Example 2. The black circles are the data points considered to have reached the Ic value.

  As is clear from the graphs of FIG. 25, FIG. 26, FIG. 27, and FIG. 28, V (IBC), which is a voltage disturbance, is clearly observed from 2T at 50K. If (IBC) seen in Table 2 is less than 0.020, which is the provisional boundary value, only 0.013 of 1T was observed, and the numerical value was greatly deteriorated at 2T or more. Then, at 50K / 5T, it was 0.361, which was a large value nearly 100 times that of Comparative Example 1 which was close to background noise.

  In the superconducting wire of Comparative Example 2, If (IBC) continues to increase as the magnetic field strength increases, reaching 3.08 at 12.5T. The possibility of quench burnout accident of the coil due to the influence of IBC can be indirectly known from the measurement result.

  Even the superconducting wire of Comparative Example 2 does not seem to have a dramatic improvement in If (IBC) at least at 30K, and it is highly possible that If (IBC) will still greatly exceed 0.020 even at 30K. It is speculated that this may have led to the quench burn accident.

  Considering that the superconducting wire of Comparative Example 1 has succeeded in the current limiting device, if the superconducting wire of If (IBC) ≦ 0.020 is made, the influence of IBC can be suppressed and the product may be successful. There is. In other words, this means the same as forming a superconductor having Tc = 90.7K and forming an artificial pin inside while maintaining the Tc.

  Even if a material that suppresses the influence of IBC is developed, it will take 4 to 5 years until it is made into a long wire and actually made into a coil, and it is possible to actually measure and pass an electric current close to the Ic value. However, if the value of If (IBC) is similar to that of the superconducting wire rod of Comparative Example 1 and also functions as an artificial pin, it is considered that a stable system can be achieved while preventing a quench burnout accident of the coil. ..

(Example 1)
First, two types of coating solutions for superconductors are synthesized and purified according to the flowchart shown in FIG. Is a metal acetate _{Pr (OCOCH 3) 3, Sm} (OCOCH 3) 3, Y (OCOCH 3) 3, Lu (OCOCH 3) 3, Ba (OCOCH 3) 2, Cu (OCOCH 3) 2 hydrate Was dissolved in ion-exchanged water at a metal ion molar ratio of 0.01: 0.01: 0.96: 0.02: 2: 3, mixed with a reaction equimolar amount of CF ₃ COOH, and stirred, The obtained mixed solution was put in an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours under reduced pressure in a rotary evaporator. A semi-transparent blue substance 1Mi-1% PrSm-Y-Lu (the substance described in Example 1, Y-based Material with immunity) was obtained.

Similarly, each of Pr (OCOCH ₃ ) ₃ , Sm (OCOCH ₃ ) ₃ , Y (OCOCH ₃ ) ₃ , Lu (OCOCH ₃ ) ₃ , Ba (OCOCH ₃ ) ₂ , Cu (OCOCH ₃ ) ₂ which are metal acetates. Using a hydrate powder, metal ion molar ratios of 0.02: 0.02: 0.92: 0.04: 2: 3, and 0.04: 0.04: 0.84: 0.08: 2: Prepared by dissolving in ion-exchanged water in ₃ , mixed with an equimolar amount of reaction CF ₃ COOH and stirred, put the obtained mixed solution in an eggplant-shaped flask, and carry out reaction and purification under reduced pressure in a rotary evaporator. Was carried out for 12 hours. A semi-transparent blue substance 1Mi-2% PrSm-Y-Lu and 1Mi-4% PrSm-Y-Lu were obtained.

  The obtained semitransparent blue substance 1Mi-1% PrSm-Y-Lu, 1Mi-2% PrSm-Y-Lu, 1Mi-4% PrSm-Y-Lu was a reaction by-product during solution synthesis. It contains about 7 wt% of certain water and acetic acid.

  The obtained semitransparent blue substance 1Mi-1% PrSm-Y-Lu, 1Mi-2% PrSm-Y-Lu, 1Mi-4% PrSm-Y-Lu, respectively, was methanol equivalent to about 100 times its weight. (F in FIG. 6) was added and completely dissolved, and the solution was subjected to reaction and purification in a rotary evaporator under reduced pressure again for 12 hours, and then a semitransparent blue substance 1M-1% PrSm-Y-Lu (Example) was obtained. 1-M-2% PrSm-Y-Lu and 1M-4% PrSm-Y-Lu, respectively, were obtained as the materials described in 1 above, Y-based Material without purity).

  Semi-transparent blue substance 1M-1% PrSm-Y-Lu, 1M-2% PrSm-Y-Lu, 1M-4% PrSm-Y-Lu was dissolved in methanol (j in FIG. 6) and a volumetric flask was placed. 1.50 mol / l of coating solution 1 Cs-1% PrSm-Y-Lu (Example 1, Coating Solution for Y-based superconductor) and 1 Cs-4% PrSm-Y-Lu. Respectively obtained. The coating solution 1Cs-1% PrSm-Y-Lu, 1Cs-2% PrSm-Y-Lu, and 1Cs-4% PrSm-Y-Lu were used to form a film at a maximum rotation speed of 2000 rpm by a spin coating method.

  Next, calcination was performed in a pure oxygen atmosphere at 400 ° C. or lower with the profile shown in FIG. Next, with the profile shown in FIG. 9, main firing was performed in 800 ppm of 1000 ppm oxygen-mixed argon gas, and annealing was performed in pure oxygen of 525 ° C. or lower. Superconducting films 1FS-1% PrSm-Y-Lu (Example 1, Y-based Film of Superconductor), 1FS-2% PrSm-Y-Lu, and 1FS-4% PrSm-Y-Lu were obtained, respectively.

  The superconducting films 1FS-1% PrSm-Y-Lu and 1FS-4% PrSm-Y-Lu were measured by the 2θ / ω method of XRD measurement, and the results are shown in FIGS. 4 and 5. From FIGS. 4 and 5, it was confirmed that only one peak was obtained at almost the same position as the YBCO (00n) peak. A good peak intensity was also confirmed, which is one of the evidences that the added rare earth element forms a continuous perovskite structure without separation.

  Next, FIG. 3 shows the results of high-power TEM observation of the superconducting film 1FS-2% PrSm-Y-Lu. As can be seen from FIG. 3, a structure in which a continuous perovskite structure is maintained throughout is shown. Since the lattice constant is almost the same as that of YBCO, it is a result that it can be confirmed that Pr, Sm, and Lu are incorporated in the rare earth site to form a continuous perovskite structure.

  FIG. 3 is a HAADF-STEM image, which shines brightly when the atomic weight is large. In the regular horizontal pattern of three rows, the bright two rows are Ba, and the rest are rare earths. In the solid line frame, the central portion is brighter than the bright Ba at both ends, and the broken line frame is dark. This indicates that a cluster in which Pr, Sm, and Lu are aggregated is formed inside the solid line frame.

When superconducting films 1FS-1% PrSm-Y-Lu and 1FS-4% PrSm-Y-Lu were respectively placed in liquid nitrogen and the superconducting properties under a self-magnetic field were measured by the induction method, the Jc values were 6. It was 3, 6.2 MA / cm ² (77K, 0T). This Jc value is relatively good. The 5-fold deterioration phenomenon due to the ultimate dispersion of PrBCO should be confirmed if the Jc value is reduced by 20% in the latter sample, especially 1FS-4% PrSm-Y-Lu, but it is not confirmed. It was It is considered that the result shows that the atom-substitution type artificial pins are clustered, aggregated, and accumulated in places.

  The superconducting film 1FS-1% PrSm-Y-Lu, 1FS-2% PrSm-Y-Lu, 1FS-4% PrSm-Y-Lu was measured at 77K in the magnetic field of 1 to 5T for the Jc value. It shows in FIG. In the figure, the horizontal axis is the magnetic field, the unit is T, and the vertical axis is the Jc value, which is the logarithmic axis.

  It can be seen that in all the samples, the Jc value at 1T is YBCO or less, but the value is almost the same at 3T and improved at 5T. It shows that the magnetic field characteristics were improved by CARP.

  For FS-4% PrSm-Y-Lu, Jc-B-T measurement was performed at 50K for 1 to 15T and at 30K for 5 to 15T in order to investigate the influence of IBC. The results are shown in Table 2 and FIGS. 29, 20, 31, 32, 33 and 34. In FIG. 29, FIG. 30, FIG. 31, FIG. 32, FIG. 33, and FIG. 34, the black circles are the data points considered to have reached the Ic value.

  29, FIG. 30, FIG. 31, and FIG. 32 are the results of examining V (IBC) at 50K. Almost no fluctuation of the voltage is confirmed up to 15T. Since the sample is only 220 nm thick, Table 2 shows the results obtained by examining If (IBC) in order to correct the effect. It can be seen from Table 2 that If (IBC) ≦ 0.020 is achieved up to 10T at 50K. This is almost the same result as the superconducting wire of Comparative Example 1.

  The reason why the result was almost the same as that of the superconducting wire of Comparative Example 1 is considered that the YBCO superconductor of MA maintained Tc = 90.7K and the influence of IBC was small. Moreover, in the Jc-B measurement showing the effect of the artificial pin in the superconductor of Example 1, the result that the magnetic field characteristics are improved is also shown. This experimental result shows that the improvement of the magnetic field characteristics could be realized while avoiding the influence of IBC.

  33 and 34 show the results of examining V (IBC) at 30K. The results of FIGS. 33 and 34 show stable results with little voltage fluctuation. When If (IBC) in which the influence of the current value is corrected is compared, it is found from Table 2 that If (IBC) ≦ 0.020 up to 10T at 30K. The reason why it is as stable as the superconducting wire of Comparative Example 1 is that it has the same structure as Comparative Example 1 and has a Tc value of 90.7K.

CARP has a structure in which the influence of IBC is equal to or smaller than that of the Dy ₂ O ₃ artificial pin. Moreover, although the Dy ₂ O ₃ artificial pin does not have the effect of improving the magnetic field characteristics, CARP has the effect of improving the magnetic field characteristics. If a superconducting wire having CARP is coiled and mounted in a superconducting device, stable operation can be expected, and the possibility of a quench burn accident can be greatly reduced.

  CARP has never been realized with Y-based superconducting wire. This is because the firing conditions for PrBCO and YBCO are too different. The optimum oxygen partial pressures are 1 ppm and 1000 ppm, respectively, which is a condition under which one is surely decomposed in the physical vapor deposition method. Further, it is difficult to realize the CARP structure by sharing the same perovskite structure even in the production of a bulk superconductor. This is because the condition that one film is formed is the condition that the other decomposes.

  Even with the TFA-MOD method, it is not easy to make a CARP structure. This is because if any impurities are present in the solution, the other substance is decomposed when the film is formed under the film forming conditions of the one substance during the main baking. In addition, it is desirable to use the clustering phenomenon to adjust the size of the artificial pin. There is no example in which YBCO is intentionally mixed with PrBCO, LuBCO, or the like, or SmBCO is mixed as a support element. It is considered that CARP having magnetic field characteristics was introduced for the first time in the TFA-MOD method, which has mass productivity and a track record, and a superconductor having a low If (IBC) and a low possibility of a quench burn accident was formed.

(Example 2)

First, two types of coating solutions for superconductors are synthesized and purified according to the flowchart shown in FIG. Is a metal acetate _{Pr (OCOCH 3) 3, Sm} (OCOCH 3) 3, Y (OCOCH 3) 3, Tm (OCOCH 3) 3, Ba (OCOCH 3) 2, Cu (OCOCH 3) 2 hydrate Was dissolved in ion-exchanged water at a metal ion molar ratio of 0.01: 0.01: 0.96: 0.02: 2: 3, mixed with a reaction equimolar amount of CF ₃ COOH, and stirred, The obtained mixed solution was put in an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours under reduced pressure in a rotary evaporator. A semi-transparent blue substance 2Mi-1% PrSm-Y-Tm (the substance described in Example 2, Y-based Material with immunity) was obtained.

Similarly, water of Pr (OCOCH ₃ ) ₃ , Sm (OCOCH ₃ ) ₃ , Y (OCOCH ₃ ) ₃ , Yb (OCOCH ₃ ) ₃ , Ba (OCOCH ₃ ) ₂ , Cu (OCOCH ₃ ) ₂ which are metal acetates. Using a Japanese powder, a metal ion molar ratio of 0.01: 0.01: 0.84: 0.02: 2: 3 dissolved in ion-exchanged water was prepared, and a reaction equimolar amount of CF ₃ COOH was prepared. After mixing and stirring, the obtained mixed solution was put into an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours under reduced pressure in a rotary evaporator. A semi-transparent blue substance 2Mi-1% PrSm-Y-Yb was obtained.

  The obtained semi-transparent blue substance 2Mi-1% PrSm-Y-Tm, 2Mi-1% PrSm-Y-Yb contains about 7 wt% of water and acetic acid, which are reaction by-products during solution synthesis. ..

  The obtained semi-transparent blue substance 2Mi-1% PrSm-Y-Tm and 2Mi-1% PrSm-Y-Yb, respectively, were added with methanol (f in FIG. 6) corresponding to about 100 times the weight of each substance to complete the substance. And the solution was subjected to reaction and purification in a rotary evaporator under reduced pressure again for 12 hours. As a result, a semitransparent blue substance 2M-1% PrSm-Y-Tm (the substance described in Example 2, Y-based Material) was obtained. 2m-1% PrSm-Y-Yb, respectively.

  A semi-transparent blue substance 2M-1% PrSm-Y-Tm, 2M-1% PrSm-Y-Yb was dissolved in methanol (j in Fig. 6), diluted using a volumetric flask, and each was converted to metal ion. Coating solutions 2Cs-1% PrSm-Y-Tm (Coating Solution for Y-based superconductor) of 1.50 mol / l and 2Cs-1% PrSm-Y-Yb were obtained, respectively. The coating solution 2Cs-1% PrSm-Y-Tm and 2Cs-1% PrSm-Y-Yb were used to form a film at a maximum rotation speed of 2000 rpm using a spin coating method.

  Next, calcination was performed in a pure oxygen atmosphere at 400 ° C. or lower with the profile shown in FIG. With the profile shown in FIG. 9, main firing was performed in a 1000 ppm oxygen-mixed argon gas at 800 ° C., and annealing was performed in pure oxygen at 525 ° C. or lower. Superconducting films 2FS-1% PrSm-Y-Tm (Example 2, Y-based Film of Superconductor) and 2FS-1% PrSm-Y-Yb were obtained.

  The superconducting film 2FS-1% PrSm-Y-Tm and 2FS-1% PrSm-Y-Yb were measured by the 2θ / ω method of XRD measurement, and only one peak was obtained at almost the same position as the YBCO (00n) peak. Was confirmed. Also, a good peak intensity has been confirmed, and it is considered that the added rare earth element forms a continuous perovskite structure without separation.

The superconducting films 2FS-1% PrSm-Y-Tm and 2FS-1% PrSm-Y-Yb were respectively placed in liquid nitrogen, and the superconducting characteristics under a self-magnetic field were measured by the induction method. It was 1, 6.0 MA / cm ² (77K, 0T). This Jc value is considered to be a relatively good Jc value. The 5 times deterioration phenomenon due to the ultimate dispersion of PrBCO is difficult to confirm because it corresponds to a 5% decrease in the above sample. However, looking at the magnetic field characteristics described below, it is considered that clustering has occurred.

  The superconducting films 2FS-1% PrSm-Y-Tm and 2FS-1% PrSm-Y-Yb were measured for Jc values in a magnetic field of 1 to 5T at 60K, and improvement of the Jc values was confirmed at 60K. ..

  For the superconducting film 2FS-1% PrSm-Y-Tm, Jc-BT measurement was performed at 50K for 1 to 15T and at 30K for 5 to 15T in order to investigate the effect of IBC. With respect to the superconducting film 2FS-1% PrSm-Y-Tm, a result that If (IBC) ≦ 0.20 was satisfied was obtained at 7T or less for both 50K and 30K. The superconducting film 2FS-1% PrSm-Y-Yb has a result that If (IBC) ≦ 0.20 is satisfied at 8T or less.

  Although the magnetic field intensity range where the effect is produced is slightly different from the case where CA is Lu, the effect of improving the magnetic field characteristics as an artificial pin was confirmed while avoiding the influence of IBC. In particular, it is known from the experimental results that the use of Tm or Yb for Lu increases the frequency of nucleation and has the effect of improving the magnetic field characteristics at lower temperatures.

  Further, since the influence of IBC is small, it is considered that by incorporating these superconducting wires as coils into the system, it is possible to construct a stable superconducting application system in which a quench burn accident does not easily occur. A coil that is less affected by IBC is considered to have excellent magnetic field stability, and is also advantageous for application to a system that requires high magnetic field accuracy.

  It has been found that even if the CA site is changed from Lu to Tm or Yb, the effect of CARP is maintained and a coil that is less likely to cause a quench burn accident is formed.

(Example 3)
First, a coating solution for a superconductor is synthesized and purified according to the flowchart shown in FIG. Is a metal acetate _{Pr (OCOCH 3) 3, Gd} (OCOCH 3) 3, Y (OCOCH 3) 3, Tm (OCOCH 3) 3, Ba (OCOCH 3) 2, Cu (OCOCH 3) 2 hydrate Was dissolved in ion-exchanged water at a metal ion molar ratio of 0.02: 0.48: 0.48: 0.02: 2: 3, mixed with a reaction equimolar amount of CF ₃ COOH, and stirred, The obtained mixed solution was put in an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours under reduced pressure in a rotary evaporator. A semi-transparent blue substance 3Mi-2% Pr-GdY-Tm (the substance described in Example 3, Y-based Material with immunity) was obtained.

  The obtained semi-transparent blue substance 3Mi-2% Pr-GdY-Tm contains about 7 wt% of water and acetic acid, which are reaction by-products during solution synthesis.

  The obtained semitransparent blue substance 3Mi-2% Pr-GdY-Tm was completely dissolved by adding methanol (f in FIG. 6) corresponding to about 100 times its weight, and the solution was placed in a rotary evaporator. Then, when the reaction and purification were performed again under reduced pressure for 12 hours, a semitransparent blue substance 3M-2% Pr-GdY-Tm (the substance described in Example 3, Y-based Material without purity) was obtained.

  Semi-transparent blue substance 3M-2% Pr-GdY-Tm was dissolved in methanol (j in FIG. 6), diluted using a measuring flask, and 1.50 mol / l of coating solution 3Cs-in terms of metal ion, respectively. 2% Pr-GdY-Tm (Example 3, Coating Solution for Y-based superconductor) was obtained. The coating solution 3Cs-2% Pr-GdY-Tm was used to form a film at a maximum rotation speed of 2000 rpm by a spin coating method.

  Next, calcination was performed in a pure oxygen atmosphere at 400 ° C. or lower with the profile shown in FIG. Next, with the profile shown in FIG. 9, main firing was performed in 800 ppm of 1000 ppm oxygen-mixed argon gas, and annealing was performed in pure oxygen of 525 ° C. or lower. Superconducting film 3FS-2% Pr-GdY-Tm (Example 3, Y-based Film of Superconductor) was obtained.

  The superconducting film 3FS-2% Pr-GdY-Tm was measured by the 2θ / ω method of XRD measurement, and it was confirmed that only one peak was obtained on the slightly lower angle side from the YBCO (00n) peak. Also, a good peak intensity has been confirmed, and it is considered that the added rare earth element forms a continuous perovskite structure without separation.

When the superconducting film 3FS-2% Pr-GdY-Tm was placed in liquid nitrogen and the superconducting characteristics under a self-magnetic field were measured by the induction method, the Jc values were 5.7 MA / cm ² (77K, 0T), respectively. there were. This Jc value is a relatively good Jc value. The 5 times deterioration phenomenon due to the ultimate dispersion of PrBCO corresponds to a 10% decrease in the above sample, but the Jc decrease to that extent is not observed. It seems that CARP is formed.

  The Jc value of each of the superconducting films 3FS-2% Pr-GdY-Tm was measured at 77K in a magnetic field of 1, 5T, and the improvement effect that the Jc value becomes 1.3 times at 77K was confirmed.

  For the superconducting film 3FS-2% Pr-GdY-Tm, Jc-BT measurement was performed at 1K to 15T at 50K and 5 to 15T at 30K in order to investigate the effect of IBC. The superconducting film 3FS-2% Pr-GdY-Tm was 6T or less at 50K and 7T or less at 30K, and the result was that If (IBC) ≤0.020 was satisfied.

  Example 3 has a shape in which MA is composed of Gd and Y, and is an artificial pin called 3rd-CARP described in the second embodiment. Since the artificial pinning force is not as high as expected, it is possible that the conditions could be insufficient, but it was possible to form a superconductor that is unlikely to cause a quench burnout accident. It is considered that by incorporating this into a coil, and by incorporating the coil into a superconducting device, it is possible to construct a superconducting applied device system in which quench burn accidents are less likely to occur and magnetic field disturbance is small.

(Example 4)
First, a coating solution for a superconductor is synthesized and purified according to the flowchart shown in FIG. Is a metal acetate _{Pr (OCOCH 3) 3, Sm} (OCOCH 3) 3, Y (OCOCH 3) 3, Yb (OCOCH 3) 3, Ba (OCOCH 3) 2, Cu (OCOCH 3) 2 hydrate Was dissolved in ion-exchanged water at a metal ion molar ratio of 0.10: 0.10: 0.60: 0.20: 2: 3, mixed with a reaction equimolar amount of CF ₃ COOH, and stirred, The obtained mixed solution was put in an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours under reduced pressure in a rotary evaporator. A semi-transparent blue substance 4Mi-10% PrSm-Y-Yb (the substance described in Example 4, Y-based Material with immunity) was obtained.

  The obtained semi-transparent blue substance 4Mi-10% PrSm-Y-Yb contains about 7 wt% of water and acetic acid, which are reaction by-products during solution synthesis.

  Each of the obtained translucent blue substances 4Mi-10% PrSm-Y-Yb was completely dissolved by adding methanol (f in FIG. 6) corresponding to about 100 times its weight, and the solution was placed in a rotary evaporator. When the reaction and purification were carried out again under reduced pressure for 12 hours, a semitransparent blue substance 4M-10% PrSm-Y-Yb (the substance described in Example 4, Y-based Material without purity) was obtained.

  A semi-transparent blue substance 4M-10% PrSm-Y-Yb was dissolved in methanol (j in FIG. 6), diluted using a measuring flask, and 1.50 mol / l of coating solution 4Cs-in terms of metal ion, respectively. 10% PrSm-Y-Yb (Example 4, Coating Solution for Y-based superconductor) was obtained.

  Similarly, a coating solution 4Cs-Y for YBCO was prepared, and the following solution was prepared by diluting and mixing with 4Cs-10% PrSm-Y-Yb. 4Cs-1% PrSm-Y-Yb, 4Cs-1000ppm PrSm-Y-Yb, 4Cs-100ppmPrSm-Y-Yb, 4Cs-10ppmPrSm-Y-Yb, 4Cs-1ppmPrSm-Y-Yb, 4Cs-100ppbPrSm-Y-Yb, 4Cs-10ppbPrSm-Y-Yb and 4Cs-1ppbPrSm-Y-Yb were obtained.

  Coating solution 4Cs-10% PrSm-Y-Yb, 4Cs-1% PrSm-Y-Yb, 4Cs-1000ppm PrSm-Y-Yb, 4Cs-100ppm PrSm-Y-Yb, 4Cs-10ppm PrSm-Y-Yb, 4Cs-1ppmPrSm- Using Y-Yb, 4Cs-100ppbPrSm-Y-Yb, 4Cs-10ppbPrSm-Y-Yb, and 4Cs-1ppbPrSm-Y-Yb, a spin coating method was used to form a film at a maximum rotation speed of 2000 rpm.

  Next, calcination was performed in a pure oxygen atmosphere at 400 ° C. or lower with the profile shown in FIG. Next, with the profile shown in FIG. 9, main firing was performed in 800 ppm of 1000 ppm oxygen-mixed argon gas, and annealing was performed in pure oxygen of 525 ° C. or lower. Superconducting film 4FS-10% PrSm-Y-Yb (Example 4, Y-based Film of Superconductor), 4FS-1% PrSm-Y-Yb, 4FS-1000ppmPrSm-Y-Yb, 4FS-100ppmPrSm-Y-Yb, 4FS-10ppmPrSm-Y-Yb, 4FS-1ppmPrSm-Y-Yb, 4FS-100ppbPrSm-Y-Yb, 4FS-10ppbPrSm-Y-Yb, 4FS-1ppbPrSm-Y-Yb were obtained, respectively.

  Superconducting film 4FS-10% PrSm-Y-Yb, 4FS-1% PrSm-Y-Yb, 4FS-1000ppm PrSm-Y-Yb, 4FS-100ppmPrSm-Y-Yb, 4FS-10ppmPrSm-Y-Yb, 4FS-1ppmPrSm- Y-Yb, 4FS-100ppbPrSm-Y-Yb, 4FS-10ppbPrSm-Y-Yb, and 4FS-1ppbPrSm-Y-Yb were measured by the 2θ / ω method of XRD measurement. It was confirmed that one peak was obtained at almost the same position as the YBCO (00n) peak in all the samples. In addition, a good peak intensity was also confirmed, and it is considered that the added rare earth element forms a continuous perovskite structure without separation.

Superconducting film 4FS-10% PrSm-Y-Yb, 4FS-1% PrSm-Y-Yb, 4FS-1000ppm PrSm-Y-Yb, 4FS-100ppmPrSm-Y-Yb, 4FS-10ppmPrSm-Y-Yb, 4FS-1ppmPrSm- Each of Y-Yb, 4FS-100ppbPrSm-Y-Yb, 4FS-10ppbPrSm-Y-Yb, 4FS-1ppbPrSm-Y-Yb was placed in liquid nitrogen, and the superconducting property under a self-magnetic field was measured by an induction method. Jc values were 5.5, 5.8, 6.0, 6.1, 6.0, 6.2, 6.0, 6.2, 6.1 MA / cm ² (77K, 0T), respectively. .. All Jc values are considered to be relatively good values. The 5-fold deterioration phenomenon due to the ultimate dispersion of PrBCO was not observed, and it is considered that CARP is formed.

  Superconducting film 4FS-10% PrSm-Y-Yb, 4FS-1% PrSm-Y-Yb, 4FS-1000ppm PrSm-Y-Yb, 4FS-100ppmPrSm-Y-Yb, 4FS-10ppmPrSm-Y-Yb, 4FS-1ppmPrSm- The Jc values of Y-Yb, 4FS-100ppbPrSm-Y-Yb, 4FS-10ppbPrSm-Y-Yb, 4FS-1ppbPrSm-Y-Yb were measured at 77K in a magnetic field of 1 and 5T, respectively. It was when the Pr amount was 10 ppb or more that the Jc value improved to 1.3 times at 77K. When the amount of Pr was 1 ppb, the effect was almost 1 time and no effect was observed.

  Superconducting film 4FS-10% PrSm-Y-Yb, 4FS-1% PrSm-Y-Yb, 4FS-1000ppm PrSm-Y-Yb, 4FS-100ppmPrSm-Y-Yb, 4FS-10ppmPrSm-Y-Yb, 4FS-1ppmPrSm- For Y-Yb, 4FS-100ppbPrSm-Y-Yb, 4FS-10ppbPrSm-Y-Yb, Jc-BT measurement was performed at 50K for 1 to 15T and 30K for 5 to 15T in order to examine the effect of IBC. In all samples, If (IBC) ≦ 0.020 could be confirmed at 50 K and 30 K at 10 T or less. When the amount of clusters becomes small, it seems that the result shows that the effect of IBC does not occur.

  Although the artificial pin of Example 4 is 2nd-CARP, it is clustered and the influence of IBC can be reduced. The coil formed using the superconductor of Example 4 is less likely to suffer a quench burnout accident and has excellent magnetic field stability. Therefore, it is considered that quenching accidents are unlikely to occur and the magnetic field is excellent in stability and a superconducting device can be produced.

(Example 5)
The superconducting coating solution is synthesized and purified according to the flow chart shown in FIG. Is a metal acetate _{Pr (OCOCH 3) 3, Sm} (OCOCH 3) 3, Y (OCOCH 3) 3, Tm (OCOCH 3) 3, Ba (OCOCH 3) 2, Cu (OCOCH 3) 2 hydrate Was dissolved in ion-exchanged water at a metal ion molar ratio of 0.02: 0.02: 0.92: 0.04: 2: 3, mixed with a reaction equimolar amount of CF ₃ COOH, and stirred, The obtained mixed solution was put in an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours under reduced pressure in a rotary evaporator. A semi-transparent blue substance 5Mi-2% PrSm-Y-Tm (the substance described in Example 5, Y-based Material with immunity) was obtained.

Similarly, to the metal acetate, each of Pr (OCOCH ₃ ) ₃ , Sm (OCOCH ₃ ) ₃ , Y (OCOCH ₃ ) ₃ , Tm (OCOCH ₃ ) ₃ , Ba (OCOCH ₃ ) ₂ , Cu (OCOCH ₃ ) ₂ water. Using a Japanese powder, a metal ion molar ratio of 0.01: 0.01: 0.96: 0.02: 2: 3 dissolved in ion-exchanged water was prepared, and a reaction equimolar amount of CF ₃ COOH was prepared. After mixing and stirring, the resulting mixed solution was placed in an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours under reduced pressure in a rotary evaporator. A semi-transparent blue material 5Mi-1% PrSm-Y-Tm was obtained.

  The obtained semi-transparent blue substance 5Mi-2% PrSm-Y-Tm, 5Mi-1% PrSm-Y-Tm contains about 7 wt% of water and acetic acid which are reaction by-products during solution synthesis. ..

  The obtained semi-transparent blue substance 5Mi-2% PrSm-Y-Tm and 5Mi-1% PrSm-Y-Tm, respectively, were completely added by adding methanol (f in FIG. 6) corresponding to about 100 times the weight thereof. And the solution was again reacted and reduced in a rotary evaporator under reduced pressure for 12 hours to give a semitransparent blue substance 5M-2% PrSm-Y-Tm (the substance described in Example 5, Y-based Material). each with 5M-1% PrSm-Y-Tm.

  The semitransparent blue substance 5M-2% PrSm-Y-Tm, 5M-1% PrSm-Y-Tm was dissolved in methanol (j in FIG. 6), diluted using a volumetric flask, and each was converted into metal ion. Coating solutions 5Cs-2% PrSm-Y-Tm (Example 5, Coating Solution for Y-based superconductor) of 1.50 mol / l and 5Cs-1% PrSm-Y-Tm were obtained, respectively.

  A coating solution 5Cs-2% PrSm-Y-Tm and 5Cs-1% PrSm-Y-Tm were used to form a film at a maximum rotation speed of 2000 rpm using a spin coating method. Calcination was performed in an oxygen atmosphere, main firing was performed in a 1000 ppm oxygen-mixed argon gas at 800 ° C. in the profile shown in FIG. 9, annealing was performed in pure oxygen at 525 ° C. or lower, and the superconducting film 5FS-2% PrSm-Y was used. -Tm (Example 5, Y-based Film of Superconductor) and 5FS-1% PrSm-Y-Tm were obtained, respectively.

  The superconducting films 5FS-2% PrSm-Y-Tm and 5FS-1% PrSm-Y-Tm were measured by the 2θ / ω method of XRD measurement, and a peak could be obtained at almost the same position as the YBCO (00n) peak. confirmed.

  The superconducting films 5FS-2% PrSm-Y-Tm and 5FS-1% PrSm-Y-Tm were measured by the 2θ / ω method of XRD measurement. Although a small hetero phase of the BaCu-based composite oxide was observed, the same peak as a single YBCO (00n) peak was obtained. Each peak was one without separation. Even from the YBCO (006) peak at 2θ = 46.68 degrees, the peak was not separated and was apparent with one peak.

  The intensity of the peak is sufficiently strong, and it is estimated that all the materials form a perovskite structure. That is, in this system, it is shown that PrBCO, SmBCO, and TmBCO are incorporated in the perovskite structure of YBCO.

  FIG. 16 shows the results of Jc measurement of superconducting films 5FS-2% PrSm-Y-Tm and 5FS-1% PrSm-Y-Tm at 30K and 1-5T. The data (circles) on the upper side of FIG. 16 is the sample. In FIG. 16, the measurement results of YBCO not containing CARP are also shown by cross marks and broken lines.

  The CARP of the superconducting film 5FS-2% PrSm-Y-Tm is 8%. It is expected that the characteristics will deteriorate by that much in the vicinity of 30K / 5T, but as can be seen from the results of FIG. 16, a Jc value much higher than that of YBCO is obtained. Although the detailed data of the lattice mismatch of Yb and Tm with respect to Y at 800 ° C. at the time of main firing are unknown, it is considered to be about 3% and about 2%, respectively. With this lattice mismatch difference, Tm may have a nucleation frequency about 10 times greater than Yb, or the nucleation rate may be faster.

  The CARP formation model shows that if the nucleation rate is about 10 times faster, the CARP number in a unit volume is also about 10 times. Since the CARP size is proportional to the reciprocal of its cube root, the CARP radius seems to be 0.46 times. It is considered that when the effect was apparent in the Yb-excessive CARP, the CARP was suddenly reduced by using Tm, so that the quantum magnetic flux was easily trapped in CARP and the effect was exhibited.

  In order to confirm the effect, the measurement result in the magnetic field of the superconducting film 5FS-1% PrSm-Y-Tm in which the CARP amount is halved is also shown in FIG. The white circles in the figure are the data. CARP in this superconducting film theoretically has the same size and the number is half. The result is that the result is about half. Strictly discussing, it seems that the decrease amount of CARP as an obstacle and the intermediate value of 5FS-2% PrSm-Y-Tm, but the difference is not understood by the experimental error.

  As can be seen from these results, it is theoretically understood that CARP exerts its effect when CA uses Tm or an element closer to MA than CA. This is because the CARP size can be explained by the CARP formation model. Since the CARP size is determined by the nucleation frequency and the amount of substances present therein, the combination of MA and CA having a high nucleation frequency is effective.

  From the experiments so far, the substance that can be used for MA is Y or Gd alone. However, it has been found that when mixed, it becomes a solution. On the other hand, CA has good Er and Tm, and it may be possible to add Yb to adjust the size. Of course, it is also possible to mix and adjust some elements having an atomic number smaller than Er. With this combination, characteristic improvement at 30K, which is considered to be particularly important for practical use, is observed.

  As described above, by applying the CARP formation model, a combination in which an artificial pin whose characteristics are improved at 30 K is particularly easy to form was found. This is a case where a superconductor mainly using Er or Tm for CA and Y or the like for MA. Also, it is considered that the combination will be effective if it is a combination that matches this model, and the above combination seems to be good for the effect display especially at 30K.

  The above-mentioned CARP has another feature, and Tc of the superconductor does not decrease. It is also known from experimental data that almost no internal bypass current is generated.

  34, 35, 36, 37, 38, 39, and 40 are graphs showing the current-voltage characteristics of the fifth embodiment. The result at the time of Jc-BT measurement of the superconducting film 5FS-2% PrSm-Y-Tm is shown. As can be seen from the figure, the noise during IV measurement is extremely low.

  The data of Example 5 is listed below Table 2. In addition, 50K data measured only 1-5T. All 50K data are zero within the experimental error range. Also, 30K is a result close to zero except that the value is slightly larger at 15T. This result is in agreement with the assumption from the model that the voltage due to the internal bypass current of CARP theoretically does not occur. Furthermore, this result is consistent with the theory that the voltage due to the internal bypass current does not depend on the pin size even if the CARP pin size is reduced. The data also support the fact that it is an artificial pin that has never been seen before.

(Example 6)
The superconducting coating solution is synthesized and purified according to the flow chart shown in FIG. Is a metal acetate _{Pr (OCOCH 3) 3, Sm} (OCOCH 3) 3, Y (OCOCH 3) 3, Er (OCOCH 3) 3, Ba (OCOCH 3) 2, Cu (OCOCH 3) 2 hydrate Was dissolved in ion-exchanged water at a metal ion molar ratio of 0.02: 0.02: 0.92: 0.04: 2: 3, mixed with a reaction equimolar amount of CF ₃ COOH, and stirred, The obtained mixed solution was put in an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours under reduced pressure in a rotary evaporator. A semi-transparent blue substance 6Mi-2% PrSm-Y-Er (the substance described in Example 6, Y-based Material with immunity) was obtained.

Similarly, water of Pr (OCOCH ₃ ) ₃ , Sm (OCOCH ₃ ) ₃ , Y (OCOCH ₃ ) ₃ , Tm (OCOCH ₃ ) ₃ , Ba (OCOCH ₃ ) ₂ , Cu (OCOCH ₃ ) ₂ which are metal acetates. Using a Japanese powder, a metal ion molar ratio of 0.02: 0.02: 0.92: 0.04: 2: 3 dissolved in ion-exchanged water was prepared, and a reaction equimolar amount of CF ₃ COOH was prepared. After mixing and stirring, the resulting mixed solution was placed in an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours under reduced pressure in a rotary evaporator. A semitransparent blue material 6Mi-2% PrSm-Y-Tm was obtained.

Further, similarly, metal acetate salts of Pr (OCOCH ₃ ) ₃ , Sm (OCOCH ₃ ) ₃ , Y (OCOCH ₃ ) ₃ , Yb (OCOCH ₃ ) ₃ , Ba (OCOCH ₃ ) ₂ , Cu (OCOCH ₃ ) ₂ A hydrate powder was used, which was dissolved in ion-exchanged water at a metal ion molar ratio of 0.02: 0.02: 0.92: 0.04: 2: 3, and a reaction equimolar amount of CF ₃ COOH was prepared. The resulting mixed solution was placed in an eggplant-shaped flask, and the reaction and purification were carried out for 12 hours in a rotary evaporator under reduced pressure. A semitransparent blue substance 6Mi-2% PrSm-Y-Yb was obtained.

  The obtained semitransparent blue substances 6Mi-2% PrSm-Y-Er, 6Mi-2% PrSm-Y-Tm, and 6Mi-2% PrSm-Y-Yb were reaction by-products during solution synthesis. It contains about 7 wt% of certain water and acetic acid.

  The obtained semi-transparent blue substances 6Mi-2% PrSm-Y-Er, 6Mi-2% PrSm-Y-Tm, and 6Mi-2% PrSm-Y-Yb were each methanol equivalent to about 100 times its weight. (F in FIG. 6) was added and completely dissolved, and the solution was subjected to reaction and purification in a rotary evaporator under reduced pressure again for 12 hours to give a semitransparent blue substance 6M-2% PrSm-Y-Er (Example). 6-M-2% PrSm-Y-Tm and 6M-2% PrSm-Y-Yb were obtained, respectively.

  Semi-transparent blue substances 6M-2% PrSm-Y-Er, 6M-2% PrSm-Y-Tm, 6M-2% PrSm-Y-Yb were dissolved in methanol (j in FIG. 6) and a volumetric flask was placed. 1.50 mol / l of coating solution 6Cs-2% PrSm-Y-Er (Example 6, Coating Solution for Y-based superconductor), 6Cs-2% PrSm-Y-Tm. , 6Cs-2% PrSm-Y-Yb was obtained.

  Coating solution 6Cs-2% PrSm-Y-Er and 6Cs-2% PrSm-Y-Tm were mixed at 1: 9, 2: 8, 3: 7, and coating solution 6Cs-2% PrSm-Y-0. 4% Er3.6% Tm, 6Cs-2% PrSm-Y-0.8% Er3.2% Tm, 6Cs-2% PrSm-Y-1.2% Er2.8% Tm were obtained, respectively.

  Coating solution 6Cs-2% PrSm-Y-Tm and 6Cs-2% PrSm-Y-Yb were mixed at 8: 2, 6: 4, 4: 6, and coating solution 6Cs-2% PrSm-Y-3. 2% Tm0.8% Yb, 6Cs-2% PrSm-Y-2.4% Tm1.6% Yb, 6Cs-2% PrSm-Y-1.6% Tm2.4% Yb were obtained, respectively.

  Coating solution 6Cs-2% PrSm-Y-0.4% Er3.6% Tm, 6Cs-2% PrSm-Y-0.8% Er3.2% Tm, 6Cs-2% PrSm-Y-1.2% Er 2.8% Tm, 6Cs-2% PrSm-Y-3.2% Tm 0.8% Yb, 6Cs-2% PrSm-Y-2.4% Tm 1.6% Yb, 6Cs-2% PrSm-Y- Using 1.6% Tm2.4% Yb, a spin coat method was used to form a film at a maximum rotation speed of 2000 rpm, and calcination was performed in a pure oxygen atmosphere at 400 ° C. or lower according to the profile shown in FIG. According to the profile, main firing was performed in 1000 ppm oxygen mixed argon gas at 800 ° C., annealing was performed in pure oxygen at 525 ° C. or less, and superconducting film 6FS-2% PrSm-Y-0.4% Er3.6% Tm (implemented Example 6, Y-based ilm of Superconductor), 6FS-2% PrSm-Y-0.8% Er3.2% Tm, 6FS-2% PrSm-Y-1.2% Er2.8% Tm, 6FS-2% PrSm-Y-3. 2% Tm0.8% Yb, 6FS-2% PrSm-Y-2.4% Tm1.6% Yb, 6FS-2% PrSm-Y-1.6% Tm2.4% Yb were obtained, respectively.

  Superconducting film 6FS-2% PrSm-Y-0.4% Er3.6% Tm, 6FS-2% PrSm-Y-0.8% Er3.2% Tm, 6FS-2% PrSm-Y-1.2% Er 2.8% Tm, 6FS-2% PrSm-Y-3.2% Tm 0.8% Yb, 6FS-2% PrSm-Y-2.4% Tm 1.6% Yb, 6FS-2% PrSm-Y- 1.6% Tm 2.4% Yb was measured by the 2θ / ω method of XRD measurement, respectively, and it was confirmed that a peak was obtained at almost the same position as the YBCO (00n) peak.

  Superconducting film 6FS-2% PrSm-Y-0.4% Er3.6% Tm, 6FS-2% PrSm-Y-0.8% Er3.2% Tm, 6FS-2% PrSm-Y-1.2% Er 2.8% Tm, 6FS-2% PrSm-Y-3.2% Tm 0.8% Yb, 6FS-2% PrSm-Y-2.4% Tm 1.6% Yb, 6FS-2% PrSm-Y- 1.6% Tm 2.4% Yb was measured by the 2θ / ω method of XRD measurement. Although a small hetero phase of the BaCu-based composite oxide was observed, the same peak as a single YBCO (00n) peak was obtained. Each peak was one without separation. Even from the YBCO (006) peak at 2θ = 46.68 degrees, the peak was not separated and was apparent with one peak.

  The intensity of the peak is sufficiently strong, and it is estimated that all the materials form a perovskite structure. That is, in this system, PrBCO, SmBCO, ErBCO, TmBCO, and YbBCO are incorporated in the YBCO perovskite structure.

Superconducting film 6FS-2% PrSm-Y-0.4% Er3.6% Tm, 6FS-2% PrSm-Y-0.8% Er3.2% Tm, 6FS-2% PrSm-Y-1.2% Er 2.8% Tm, 6FS-2% PrSm-Y-3.2% Tm 0.8% Yb, 6FS-2% PrSm-Y-2.4% Tm 1.6% Yb, 6FS-2% PrSm-Y- The Jc measurement results (MA / cm ² ) of 1.6% Tm 2.4% Yb at 30 K and 5 T are 2.13, 2.39, 2.60, 1.65, 1. It was 44 and 1.21.

  The discussion of the lattice mismatch between Tm and Yb is as described above, and there was a strong tendency that the CARP size increased as the Yb ratio increased and the characteristics of 30K / 5T deteriorated. This result also follows the CARP formation model in which the nucleation rate determines the CARP size.

  On the other hand, the characteristics of the sample in which a small amount of Er was added to Tm were significantly improved. This also shows that the nucleation rate of Er is considerably higher than that of Tm, which suggests that the CARP size is reduced. It seems that the characteristics of 30K / 5T were improved by it.

  Superconducting film 6FS-2% PrSm-Y-0.4% Er3.6% Tm, 6FS-2% PrSm-Y-0.8% Er3.2% Tm, 6FS-2% PrSm-Y-1.2% Er 2.8% Tm, 6FS-2% PrSm-Y-3.2% Tm 0.8% Yb, 6FS-2% PrSm-Y-2.4% Tm 1.6% Yb, 6FS-2% PrSm-Y- The noise at the time of IV measurement at 1.6% Tm2.4% Yb at 30K · 5T was about 1/100 to 1/300 as compared with the superconducting film of the physical vapor deposition method in which the BZO artificial pin was introduced. The result is almost zero.

  Although the CARPs formed inside the superconductors measured in the above examples have different sizes, it is theoretically possible to detour without depending on the CARP radius R from the calculation of the current detour by the superconducting current and CARP. I understand. From the results, the voltage due to all the internal detour currents should be around 1/300, but a voltage of about 1/100 could be confirmed. However, this voltage level is probably not a problem for practical use.

  The BZO artificial pin-containing superconducting film formed by the PLD method has a measured value of 0.1% at 0.01% at the required magnetic field accuracy of 5T in a coil prototype applied to a heavy particle beam cancer therapy machine. The figure is 1%, which is more than 10 times. With this, it is not possible to accurately irradiate the affected area of the patient with the particle beam.

  However, when a coil is made with the newly developed CARP pin-containing wire, the magnetic field accuracy is expected to improve about 100 times, and the accuracy at 5T is likely to be 0.001%. It will take several years for this technology to be used as a long wire to make a coil. Therefore, the accuracy of the magnetic field formed is unknown at this point, but it is possible to improve the noise voltage due to the internal bypass current by about 100 times. It is supposed to be. A 10-fold improvement in accuracy is easy to reach, and there is a high possibility that it will be the first technology to provide a practical level Y-based coil.

  In the embodiment, the heavy particle beam therapy device is described as an example of the superconducting device, but the superconducting device may be applied to a superconducting device such as a superconducting magnetic levitation railway vehicle or a fusion reactor.

  Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. For example, the components of one embodiment may be replaced or changed with the components of other embodiments. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the scope equivalent thereto.

20 superconducting wire 22 base material 24 intermediate layer 30 oxide superconducting layer 40 metal layer 100 superconducting coil 200 heavy particle radiotherapy device

Claims (16)

  It has a continuous perovskite structure containing a rare earth element, barium (Ba), and copper (Cu), and the rare earth element is a first element that is praseodymium (Pr), neodymium (Nd), samarium (Sm), At least one second element of the group europium (Eu) and gadolinium (Gd), at least one third element of the group yttrium (Y), terbium (Tb), dysprosium (Dy) and holmium (Ho). A superconducting wire comprising an oxide superconducting layer containing an element and at least one fourth element of the group of erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu).   The second element is at least one kind of the group of neodymium (Nd) and samarium (Sm), and the third element is at least one kind of the group of yttrium (Y), dysprosium (Dy) and holmium (Ho). 2. The superconducting wire according to claim 1, wherein the fourth element is at least one selected from the group consisting of erbium (Er) and thulium (Tm).   The second element is samarium (Sm), the third element is at least one kind of the group of yttrium (Y) and holmium (Ho), and the fourth element is thulium (Tm). The superconducting wire according to claim 1 or 2. The oxide superconducting layer contains fluorine (F) of 2.0 × 10 ¹⁵ atoms / cc or more and 5.0 × 10 ¹⁹ atoms / cc or less, and 1.0 × 10 ¹⁷ atoms / cc or more 5.0 × 10 ^20. The superconducting wire according to any one of claims 1 to 3, further comprising carbon (C) having an atom / cc or less.   N (MA) / N (RE) ≧ 0.6, where N (RE) is the number of atoms of the rare earth element and N (MA) is the number of atoms of the third element. The superconducting wire according to claim 4.   When the number of atoms of the rare earth element is N (RE) and the number of atoms of the first element is N (PA), 0.00000001 ≦ N (PA) / N (RE) is satisfied. The superconducting wire according to claim 5.   When the number of atoms of the rare earth element is N (RE), the number of atoms of the first element is N (PA), and the number of atoms of the second element is N (SA), (N (PA) ) + N (SA)) / N (RE) ≤ 0.2, The superconducting wire according to any one of claims 1 to 6.   When the number of atoms of the first element is N (PA), the number of atoms of the second element is N (SA), and the number of atoms of the fourth element is N (CA), 0.8 The superconducting wire according to claim 1, wherein N (CA) ≦ N (PA) + N (SA) ≦ 1.2 × N (CA).   It has a continuous perovskite structure containing a rare earth element, barium (Ba), and copper (Cu), and the rare earth element is a first element that is praseodymium (Pr), gadolinium (Gd), yttrium (Y), A terbium (Tb), dysprosium (Dy) and holmium (Ho) group of at least one second element, and an erbium (Er), thulium (Tm), ytterbium (Yb) and lutetium (Lu) group. A superconducting wire comprising an oxide superconducting layer containing at least one kind of a third element. The oxide superconducting layer has a fluorine content of 2.0 × 10 ¹⁵ atoms / cc or more and 5.0 × 10 ¹⁹ atoms / cc or less and 1.0 × 10 ¹⁷ atoms / cc or more and 5.0 × 10 ²⁰ atoms / cc. The superconducting wire according to claim 9, comprising the following carbon.   10. N (MA) / N (RE) ≧ 0.6 when the number of atoms of the rare earth element is N (RE) and the number of atoms of the second element is N (MA). The superconducting wire according to claim 10.   10. When the number of atoms of the rare earth element is N (RE) and the number of atoms of the first element is N (PA), 0.00000001 ≦ N (PA) / N (RE) is satisfied. The superconducting wire according to claim 11.   10. N (PA) / N (RE) ≦ 0.2, where N (RE) is the number of atoms of the rare earth element and N (PA) is the number of atoms of the first element. The superconducting wire according to claim 12. Further comprising a tape-shaped base material and a metal layer,
The superconducting wire according to any one of claims 1 to 13, wherein the oxide superconducting layer is present between the base material and the metal layer.   A superconducting coil comprising the superconducting wire according to any one of claims 1 to 14.   A superconducting device comprising the superconducting coil according to claim 15.