Superconducting magnet and method of manufacturing superconducting magnet

Abstract

To provide a superconducting magnet which can be reduced in size while suppressing a decrease in critical current at a joint.SOLUTION: A superconducting magnet according to the present disclosure includes a coil. The coil has a first superconducting layer, a second superconducting layer, and a first joint portion at which the first superconducting layer and the second superconducting layer are joined to each other in a superconducting manner. The coil forms a closed loop. The orientation of the first junction is determined based on the data of the applied magnetic field angle dependence of the critical current in a junction having the same configuration as the first junction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to superconducting magnets and methods for manufacturing superconducting magnets. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2022-099126 (Patent Document 1) describes a superconducting coil device used in a superconducting magnet. The superconducting coil device includes a superconducting wire having a winding portion and a guide portion. The joints between the wires constituting the superconducting wire are fixed to the guide portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-099126 Summary of the Invention [Problem to be solved by the invention]

[0004] Higher critical current characteristics are required for superconducting coil devices. The superconducting coil device described in Patent Document 1 still has room for improvement in this regard. Furthermore, in the superconducting coil device described in Patent Document 1, if the distance between the coil and the joint is increased to suppress a decrease in critical current, the superconducting coil device will become larger.

[0005] An object of the present disclosure is to provide a superconducting magnet that can be made smaller while suppressing a decrease in critical current at the joint. [Means for solving the problem]

[0006] A superconducting magnet according to the present disclosure includes a coil. The coil includes a first superconducting layer, a second superconducting layer, and a first junction where the first superconducting layer and the second superconducting layer are superconductively joined. The coil forms a closed loop. The orientation of the first junction is determined based on data on the applied magnetic field angle dependence of the critical current in a junction having the same configuration as the first junction. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide a superconducting magnet that can be made smaller while suppressing a decrease in critical current at the joint. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic front view showing the configuration of a superconducting magnet according to this embodiment. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of the coil according to this embodiment. [Figure 3] FIG. 3 is a partial cross-sectional schematic view showing region III in FIG. [Figure 4] FIG. 4 is a cross-sectional view showing a configuration of a first bonding portion according to one example of this embodiment. [Figure 5] FIG. 5 is a cross-sectional view showing a configuration of a second bonding portion according to one example of this embodiment. [Figure 6] FIG. 6 is a schematic perspective view showing the configuration of a first bonding portion according to another example of this embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing a configuration of a first bonding portion according to another example of the present embodiment. [Figure 8] FIG. 8 is a cross-sectional view showing a configuration of a second bonding portion according to another example of this embodiment. [Figure 9] FIG. 9 is a schematic diagram showing how a magnetic field is generated by a current flowing through a coil. [Figure 10] FIG. 10 is a cross-sectional view showing a state in which a magnetic field is applied to the first joint. [Figure 11]FIG. 11 is a schematic diagram illustrating the dependency of the critical current in the first junction on the angle of the applied magnetic field. [Figure 12] FIG. 12 is a cross-sectional view showing a state in which a magnetic field is applied to the second joint. [Figure 13] FIG. 13 is a schematic diagram illustrating a method for measuring the angular dependency of the applied magnetic field. [Figure 14] FIG. 14 is a schematic perspective view showing the configuration of the first protective case. [Figure 15] FIG. 15 is a schematic diagram showing a state in which the first excess length member and the second excess length member are wound around the outer peripheral surface of the first protective case one or more times. [Figure 16] FIG. 16 is a schematic cross-sectional view taken along line XVI-XVI in FIG. [Figure 17] FIG. 17 is a schematic plan view showing the configuration of the base member. [Figure 18] FIG. 18 is a schematic bottom view showing the configuration of the lid member. [Figure 19] FIG. 19 is a flow diagram that schematically shows a method for manufacturing a superconducting magnet according to this embodiment. [Figure 20] FIG. 20 shows the measurement results of the dependence of the critical current on the angle of the applied magnetic field in the junction under test. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A superconducting magnet according to the present disclosure has a coil. The coil has a first superconducting layer, a second superconducting layer, and a first junction at which the first superconducting layer and the second superconducting layer are superconductively joined. The coil forms a closed loop. The orientation of the first junction is determined based on data on the applied magnetic field angle dependence of the critical current at a junction having the same configuration as the first junction. This makes it possible to miniaturize the superconducting magnet while suppressing a decrease in the critical current at the first junction.

[0011] (2) According to the superconducting magnet of (1) above, the coil may have a third superconducting layer, a fourth superconducting layer, and a second junction where the third superconducting layer and the fourth superconducting layer are superconductively joined. The orientation of the second junction may be determined based on data on the applied magnetic field angle dependence of the critical current at a junction having the same configuration as the second junction. This makes it possible to miniaturize the superconducting magnet while suppressing a decrease in critical current at the junction, even when the coil has a first junction and a second junction.

[0012] (3) In the superconducting magnet according to (1) or (2) above, the first junction may be disposed so as to be inclined from the direction in which the critical current is at its maximum value. In this way, even when the first junction is disposed so as to be inclined from the direction in which the critical current is at its maximum value, it is possible to prevent the critical current at the first junction from decreasing excessively. Therefore, it is possible to improve the degree of freedom in the arrangement of the first junction in the superconducting magnet.

[0013] (4) In the superconducting magnet according to (2) above, each of the first and second junctions may be disposed at an angle from the direction in which the critical current is maximized, thereby improving the degree of freedom in the arrangement of each of the first and second junctions in the superconducting magnet.

[0014] (5) In the superconducting magnet according to any one of (1) to (4) above, the first superconducting layer may have a first end. The second superconducting layer may have a second end. The second end may be superconductively joined to the first end at a first joint. When viewed in the thickness direction of the first end, the first end and the second end may overlap.

[0015] (6) In the superconducting magnet according to any one of (1) to (4) above, the first superconducting layer may have a first end. The second superconducting layer may have a second end. The first joint may have a joint material. The joint material may superconductively join the first end and the second end. The joint material may be disposed on each of the first end and the second end in the thickness direction of the first end. The joint material may bridge the first end and the second end.

[0016] (7) In the superconducting magnet according to (6) above, the joining material may have a superconducting joining layer. The superconducting joining layer may be disposed on each of the first end and the second end in the thickness direction of the first end. The sum of the thickness of the first end and the thickness of the superconducting joining layer and the sum of the thickness of the second end and the thickness of the superconducting joining layer may each be 1.5 μm or more and 3.5 μm or less. This makes it possible to suppress a decrease in the critical current at the first joint due to the magnetic field applied to the first joint.

[0017] (8) The superconducting magnet according to any one of (1) to (7) above may further include a protective case that houses the first joint and a support that supports the protective case. The coil may include a winding and a plurality of surplus members that are drawn out from the winding and supported by the support. At the first joint, the ends of two of the plurality of surplus members may be superconductively joined. The support may be made of a non-magnetic material. This can prevent the support and the first joint from vibrating due to a magnetic field generated by a current flowing through the coil.

[0018] (9) A method for manufacturing a superconducting magnet according to the present disclosure includes the following steps: The superconducting magnet includes a coil; The coil includes a first superconducting layer, a second superconducting layer, and a first junction that superconductively joins the first superconducting layer and the second superconducting layer; A closed-loop wire is prepared that includes a superconducting layer to be measured and a junction to be measured, where both ends of the superconducting layer to be measured are superconductively joined; An external magnetic field is applied to the junction to be measured, and the critical current at the junction to be measured is measured while changing the angle between the direction of the external magnetic field and the orientation of the junction to be measured; The arrangement of the first junction in the coil is determined based on the measured critical current; This makes it possible to miniaturize the superconducting magnet while suppressing a decrease in the critical current at the first junction.

[0019] [Details of the embodiments of the present disclosure] Hereinafter, an embodiment of the present disclosure (also referred to as the present embodiment) will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0020] (Configuration of superconducting magnet) First, the configuration of the superconducting magnet 100 according to this embodiment will be described.

[0021] As shown in FIG. 1, the superconducting magnet 100 mainly includes a coil 1, a cryostat 2, a bobbin 3, a support 4, a first protective case 71, and a second protective case 72.

[0022] The coil 1 is disposed inside the cryostat 2. The coil 1 is, for example, a solenoid coil. The coil 1 is formed by winding a superconducting wire around a central axis O in a spiral shape.

[0023] As shown in Fig. 2, the coil 1 forms a closed loop. The coil 1 has a winding portion 50, an excess length portion 60, a first joint portion 31, and a second joint portion 32. The winding portion 50 is wound around a bobbin 3 (see Fig. 1). The excess length portion 60 is a portion that is pulled out from the winding portion 50.

[0024] The winding portion 50 has a first winding member 51 and a second winding member 52. The first winding member 51 and the second winding member 52 are connected in series. The excess length portion 60 has a first excess length member 61, a second excess length member 62, a third excess length member 63, and a fourth excess length member 64. In other words, the coil 1 has a plurality of excess length members.

[0025] The first surplus length member 61 is pulled out from the first winding member 51. The second surplus length member 62 is pulled out from the second winding member 52. The third surplus length member 63 is pulled out from the first winding member 51. Specifically, the third surplus length member 63 is pulled out from the end of the first winding member 51 opposite to the end of the first winding member 51 from which the first surplus length member 61 is pulled out. The fourth surplus length member 64 is pulled out from the second winding member 52. Specifically, the fourth surplus length member 64 is pulled out from the end of the second winding member 52 opposite to the end of the second winding member 52 from which the second surplus length member 62 is pulled out.

[0026] The first excess length member 61 and the second excess length member 62 are joined at a first joining portion 31. The third excess length member 63 and the fourth excess length member 64 are joined at a second joining portion 32. The first joining portion 31 and the second joining portion 32 will be described in detail later.

[0027] As shown in FIG. 1, the reel 3 supports the winding portion 50. The central axis O is the central axis of the winding portion 50. The central axis O may overlap the central axis of the reel 3. The support portion 4 is connected to the reel 3, for example. The support portion 4 supports each of the excess length portion 60, a first protective case 71, and a second protective case 72. The first protective case 71 houses the first joint portion 31 (see FIG. 2). The second protective case 72 houses the second joint portion 32 (see FIG. 2).

[0028] The support part 4 is made of a non-magnetic material. Specifically, the support part 4 is made of, for example, fiber reinforced plastics (FRP) or non-magnetic stainless steel. The support part 4 may have a portion made of a magnetic material, such as a screw for fastening components.

[0029] The support portion 4 has a columnar portion 43, a plurality of first guide portions 41, and a plurality of second guide portions 42. The columnar portion 43 is a portion that is connected to the reel 3. The columnar portion 43 is disposed on the reel 3. The direction from the reel 3 toward the columnar portion 43 is defined as a first direction 101. The first direction 101 is a direction along the central axis O.

[0030] The columnar portion 43 has, for example, a cylindrical shape. The columnar portion 43 extends along the central axis O. The central axis of the columnar portion 43 may overlap the central axis O. The columnar portion 43 guides a portion of the excess length portion 60 along the first direction 101. A portion of the excess length portion 60 is wound around the columnar portion 43. The portion of the excess length portion 60 wound around the columnar portion 43 is wound more sparsely than the winding portion 50.

[0031] Each of the multiple first guide portions 41 is connected to a columnar portion 43. Each of the multiple first guide portions 41 is positioned in a first direction 101 relative to the winding frame 3. The multiple first guide portions 41 extend, for example, along the radial direction. The radial direction is perpendicular to the central axis O and is a direction from the central axis O toward the winding portion 50. When viewed in the first direction 101, the multiple first guide portions 41 extend radially from the central axis O as the center. The first guide portions 41 support a portion of the excess length portion 60. The first guide portions 41 guide a portion of the excess length portion 60 along the radial direction.

[0032] Each of the multiple second guide portions 42 is connected to a corresponding one of the multiple first guide portions 41. Each of the multiple second guide portions 42 extends, for example, along the first direction 101. Note that the direction in which each of the multiple second guide portions 42 extends may be inclined with respect to the first direction 101, for example.

[0033] The multiple second guide parts 42 support a portion of the excess length part 60 and each of the first protective case 71 and the second protective case 72. Each of the multiple second guide parts 42 can fix each of the first protective case 71 and the second protective case 72 at any three-dimensional position and any angle. From another perspective, the position and angle of each of the first protective case 71 and the second protective case 72 can be adjusted three-dimensionally with respect to the multiple second guide parts 42.

[0034] The cryostat 2 maintains the temperature inside the cryostat 2 at a low temperature. The inside of the cryostat 2 is cooled, for example, by a cooling medium (not shown). This cools the coil 1. The cooling medium is, for example, liquid helium, liquid nitrogen, or the like. The inside of the cryostat 2 may be cooled by conduction using a refrigerator (not shown). In this case, the coil 1 is also cooled by conduction.

[0035] Cryostat 2 is configured to maintain an internal temperature of 77 Kelvin (liquid nitrogen temperature) or less. Cryostat 2 may be configured to maintain an internal temperature of 4.2 Kelvin (liquid helium temperature) or less. Cryostat 2 is configured to maintain an internal temperature of 2.0 Kelvin or more.

[0036] As shown in FIG. 3, the first excess length member 61 and the second excess length member 62 are both supported by the same first guide portion 41 and the same second guide portion 42.

[0037] The first protective case 71 has an outer peripheral surface 10. The first excess length member 61 is in contact with the outer peripheral surface 10 of the first protective case 71. The first excess length member 61 and the second excess length member 62 are wound around the outer peripheral surface 10 of the first protective case 71, for example, one or more times. This allows the excess length portion 60 to be disposed of compactly.

[0038] A blind hole 16 is provided in the outer peripheral surface 10. The blind hole 16 of the first protective case 71 accommodates a portion of each of the first excess length member 61 and the second excess length member 62, and the first joint portion 31.

[0039] The configuration of second protective case 72 (see FIG. 1) is substantially the same as the configuration of first protective case 71. Second protective case 72 houses a portion of each of third excess length member 63 and fourth excess length member 64 and second joint portion 32. Details of first protective case 71 and second protective case 72 will be described later.

[0040] <Example of a joint> Next, an example of the joint will be described. Fig. 4 shows a cross section parallel to the direction in which first excess length member 61 extends. As shown in Fig. 4, first excess length member 61 has first base material 11a, first intermediate layer 11b, first superconducting layer 11c, first protective layer 11d, and first stabilizing layer 11e. From another perspective, coil 1 (see Fig. 1) has first superconducting layer 11c.

[0041] The first substrate 11a is formed of a clad material having a tape member made of, for example, stainless steel, a copper (Cu) layer disposed on the tape member, and a nickel (Ni) layer disposed on the copper layer. The crystals of the copper layer are oriented. The crystals of the nickel layer are also oriented along the crystals of the copper layer.

[0042] The material of the first substrate 11a is not limited to the clad material. The first substrate 11a may be made of, for example, Hastelloy (registered trademark). The first substrate 11a may be a tape member made of a biaxially oriented metal material or a tape member made of a non-oriented metal material.

[0043] The first intermediate layer 11b is disposed on the first substrate 11a. When the first substrate 11a is formed of the above-mentioned clad material, the first intermediate layer 11b is disposed on the nickel layer of the first substrate 11a. The first intermediate layer 11b is formed of a material that has extremely low reactivity with the first superconducting layer 11c and does not deteriorate the superconducting properties of the first superconducting layer 11c.

[0044] The first intermediate layer 11b is formed of at least one of yttria-stabilized zirconia (YSZ), magnesium oxide (MgO), cerium oxide (CeO), yttrium oxide (YO), lanthanum manganese oxide (LaMnO), gadolinium zirconate (GdZrO), and strontium titanate (SrTiO). The first intermediate layer 11b is formed by, for example, magnetron sputtering or ion beam assisted deposition (IBAD).

[0045] As described above, since the crystals of the nickel layer of the first base material 11a are oriented, the crystals of each layer of the first intermediate layer 11b are also oriented. The first intermediate layer 11b may have a two-layer structure or a single-layer structure. Note that even if the material constituting the first base material 11a is formed from a non-oriented metal material, it is sufficient that the crystals of the first intermediate layer 11b are oriented.

[0046] The first superconducting layer 11c is disposed on the first intermediate layer 11b. The first superconducting layer 11c is a portion of the first excess length member 61 through which a superconducting current flows. The first superconducting layer 11c is formed of a high-temperature superconductor. A high-temperature superconductor is a material whose superconducting transition temperature is equal to or higher than the liquid nitrogen temperature (77 Kelvin). Specifically, the first superconducting layer 11c is formed of, for example, an oxide superconducting material. More specifically, the first superconducting layer 11c is formed of, for example, REBa2Cu3O x(hereinafter referred to as REBCO). RE is a rare earth element such as gadolinium (Gd), yttrium (Y), or europium (Eu). The material constituting the first superconducting layer 11c is not limited to the above-mentioned materials. The material constituting the first superconducting layer 11c is, for example, Bi2Sr2Ca2Cu3O x It may also be a bismuth-based oxide superconducting material such as (Bi-2223).

[0047] The first superconducting layer 11c has, for example, a uniform crystal orientation. Specifically, the c-axis of the material constituting the first superconducting layer 11c is aligned along the direction from the first intermediate layer 11b toward the first protective layer 11d (the thickness direction of the first superconducting layer 11c). From another perspective, the ab-plane of the material constituting the first superconducting layer 11c is parallel to the longitudinal and width directions of the first excess length member 61. The first superconducting layer 11c is formed by a metal organic decomposition (MOD) method, a pulsed laser deposition (PLD) method, or the like.

[0048] The first protective layer 11d is disposed on the first superconducting layer 11c. The first protective layer 11d is formed of, for example, silver (Ag) or a silver alloy. The first protective layer 11d is formed by, for example, a sputtering method. The first stabilization layer 11e is disposed on the first protective layer 11d. The first stabilization layer 11e is formed of, for example, copper (Cu) or a copper alloy. The first stabilization layer 11e is formed by, for example, a plating method. The first protective layer 11d and the first stabilization layer 11e are layers for bypassing current when a quench (a phenomenon in which the superconducting state transitions to a normal conducting state) occurs in the first superconducting layer 11c.

[0049] The configuration of second excess length member 62 is substantially the same as the configuration of first excess length member 61. Second excess length member 62 has second base material 12a, second intermediate layer 12b, second superconducting layer 12c, second protective layer 12d, and second stabilizing layer 12e. From another perspective, coil 1 (see FIG. 1) has second superconducting layer 12c. Second base material 12a, second intermediate layer 12b, second superconducting layer 12c, second protective layer 12d, and second stabilizing layer 12e correspond to first base material 11a, first intermediate layer 11b, first superconducting layer 11c, first protective layer 11d, and first stabilizing layer 11e, respectively.

[0050] 4, an end of the first surplus length member 61 and an end of the second surplus length member 62 are superconductively joined at the first joint 31. Specifically, a first superconducting layer 11c of the first surplus length member 61 and a second superconducting layer 12c of the second surplus length member 62 are superconductively joined at the first joint 31. Here, the term "superconducting joining" refers to joining two superconducting layers such that, when the joint between the two superconducting layers is cooled to a temperature equal to or lower than the superconducting transition temperature, a current flows between the two superconducting layers in a superconducting state.

[0051] The first superconducting layer 11c has a first end 11f. The first end 11f is an end in the direction in which the first superconducting layer 11c extends. The second superconducting layer 12c has a second end 12f. The second end 12f is an end in the direction in which the second superconducting layer 12c extends.

[0052] The first joint portion 31 has a first superconducting joining layer 91. In the first joint portion 31, the first end portion 11f and the second end portion 12f are superconductively joined to each other via the first superconducting joining layer 91. From another perspective, the first joint portion 31 has the first end portion 11f, the second end portion 12f, and the first superconducting joining layer 91.

[0053] The thickness direction of the first end 11f is defined as a second direction 102. The second direction 102 is a direction from the first substrate 11a toward the first end 11f along the thickness direction of the first end 11f. The second direction 102 may be inclined with respect to the first direction 101 (see FIG. 1), for example, or may be parallel to the first direction 101. When viewed in the second direction 102, for example, the first end 11f and the second end 12f overlap. In the second direction 102, the first end 11f, the first superconducting joining layer 91, and the second end 12f are, for example, overlapped. In the first joining portion 31, the direction in which the first excess length member 61 extends is defined as a third direction 103. The third direction 103 is perpendicular to the second direction 102.

[0054] The first superconducting joining layer 91 is formed of a high-temperature superconductor. The first superconducting joining layer 91 is formed, for example, of the same material as the high-temperature superconductor that forms the first superconducting layer 11c. The first superconducting joining layer 91 is arranged so that the crystal orientation of the first superconducting joining layer 91 is aligned with the crystal orientation of each of the first end 11f and the second end 12f. Specifically, the first superconducting joining layer 91 is arranged so that the c-axis of the first superconducting joining layer 91 is aligned with the c-axis of each of the first end 11f and the second end 12f.

[0055] The first bonding portion 31 is formed, for example, by the following method. An organic compound of elements constituting the high-temperature superconductor that forms the first superconducting bonding layer 91 is applied to at least one of the first end 11f or the second end 12f. The coating of the organic compound is heat-treated, so that the coating becomes a precursor of the high-temperature superconductor that forms the first superconducting bonding layer 91 (hereinafter, a film containing this precursor is also referred to as a calcined film). The precursor contains carbides of elements constituting the high-temperature superconductor that forms the first superconducting bonding layer 91. The heat treatment is performed at a processing temperature that is equal to or higher than the decomposition temperature of the organic compound and lower than the generation temperature of the high-temperature superconductor used in the first superconducting bonding layer 91.

[0056] Next, the calcined film is subjected to a heat treatment, which causes the carbides contained in the calcined film to decompose and become a high-temperature superconductor that forms first superconducting bonding layer 91, and a microcrystalline film. The heat treatment of the calcined film is performed in an atmosphere with an oxygen concentration of 1% or more.

[0057] Next, first end 11f is positioned to face second end 12f across the microcrystalline film. Pressure is applied between first end 11f and second end 12f along a direction parallel to second direction 102. First end 11f, second end 12f, and the microcrystalline film are heated. As a result, fine crystals of the high-temperature superconductor contained in the microcrystalline film grow epitaxially along the crystal orientation of first end 11f and second end 12f, forming first superconducting joining layer 91. After first superconducting joining layer 91 is formed, heat treatment is performed in an oxygen-containing atmosphere, thereby introducing oxygen into first superconducting joining layer 91. As a result, a superconducting joining is achieved between first end 11f and second end 12f. This forms first joining portion 31.

[0058] As shown in Fig. 5, the configuration of second joint 32 (see Fig. 2) is substantially the same as the configuration of first joint 31. Third surplus member 63 has third base material 13a, third intermediate layer 13b, third superconducting layer 13c, third protective layer 13d, and third stabilizing layer 13e. Fourth surplus member 64 has fourth base material 14a, fourth intermediate layer 14b, fourth superconducting layer 14c, fourth protective layer 14d, and fourth stabilizing layer 14e. From another perspective, coil 1 has third superconducting layer 13c and fourth superconducting layer 14c.

[0059] The third substrate 13a, the third intermediate layer 13b, the third superconducting layer 13c, the third protective layer 13d, and the third stabilization layer 13e correspond to the first substrate 11a, the first intermediate layer 11b, the first superconducting layer 11c, the first protective layer 11d, and the first stabilization layer 11e, respectively. The fourth substrate 14a, the fourth intermediate layer 14b, the fourth superconducting layer 14c, the fourth protective layer 14d, and the fourth stabilization layer 14e correspond to the second substrate 12a, the second intermediate layer 12b, the second superconducting layer 12c, the second protective layer 12d, and the second stabilization layer 12e, respectively.

[0060] The third superconducting layer 13c has a third end 13f. The third end 13f is an end in the direction in which the third superconducting layer 13c extends. The fourth superconducting layer 14c has a fourth end 14f. The fourth end 14f is an end in the direction in which the fourth superconducting layer 14c extends. The second joint portion 32 has a second superconducting joining layer 92. In the second joint portion 32, the third end 13f and the fourth end 14f are superconductively joined to each other via the second superconducting joining layer 92. The second joint portion 32 has the third end 13f, the fourth end 14f, and the second superconducting joining layer 92.

[0061] The thickness direction of the third end portion 13f is defined as a fourth direction 104. The fourth direction 104 is a direction from the third base material 13a toward the third end portion 13f along the thickness direction of the third end portion 13f. The fourth direction 104 may be inclined with respect to each of the first direction 101 (see FIG. 1 ) and the second direction 102 (see FIG. 4 ), or may be parallel to at least one of the first direction 101 and the second direction 102. In the second joint portion 32, the direction in which the third excess length member 63 extends is defined as a fifth direction 105. The fifth direction 105 is perpendicular to the fourth direction 104.

[0062] <Another example of a joint> Next, another example of the joint will be described, focusing on the differences from the example of the joint described above (see FIGS. 4 and 5), and the same description will not be repeated.

[0063] 6 and 7, the first joint portion 31 may have a first joining material 81. The first joining material 81 has the above-mentioned first superconducting joining layer 91. In the first joint portion 31, the superconducting layer (first end portion 11f) of the first excess length member 61 and the superconducting layer (second end portion 12f) of the second excess length member 62 are superconductively joined to each other via the first superconducting joining layer 91 of the first joining material 81.

[0064] 6, in the first joint 31, the first excess length member 61 and the second excess length member 62 are arranged so that the first end 11f and the second end 12f are aligned in a direction perpendicular to the second direction 102. From another perspective, the first excess length member 61 and the second excess length member 62 do not face each other in the second direction 102. In the first joint 31, the direction in which the first end 11f and the second end 12f are aligned is defined as the sixth direction 106. The first end 11f and the second end 12f are spaced apart from each other.

[0065] In the second direction 102, the first bonding material 81 is disposed on each of the first end 11f and the second end 12f. The first bonding material 81 bridges the first end 11f and the second end 12f. From another perspective, the first bonding material 81 connects the first end 11f and the second end 12f, which are disposed side by side and spaced apart from each other. The first bonding material 81 extends along the sixth direction 106.

[0066] The first bonding material 81 has a first support member 81a and a first superconducting layer portion 81b. The first support member 81a is made of, for example, silver (Ag) or a silver alloy. The first support member 81a is made of, for example, a texture in which crystal grains are oriented. This texture is obtained by, for example, performing wire drawing, warm rolling, and heat treatment on a raw material made of silver or the like.

[0067] The first superconducting layer portion 81b is formed of a high-temperature superconductor. The first superconducting layer portion 81b is formed of, for example, the same material as the high-temperature superconductor that forms the first superconducting layer 11c. The first superconducting layer portion 81b is disposed on the first support member 81a. The crystal orientation of the first superconducting layer portion 81b reflects the crystal orientation of the outermost surface of the first support member 81a.

[0068] The first superconducting joining layer 91 is disposed on the first superconducting layer portion 81b. The first superconducting joining layer 91 is epitaxially grown (has a crystal orientation) from the first end 11f and the second end 12f. From another perspective, the first superconducting joining layer 91 has the same crystal orientation as the first end 11f and the second end 12f.

[0069] The sum of the thickness of first end 11f in second direction 102 and the thickness of first superconducting junction layer 91 is defined as first thickness H1. First thickness H1 is, for example, 1.5 μm or more and 3.5 μm or less. First thickness H1 may be, for example, 1.8 μm or more, or 2.0 μm or more. First thickness H1 may be, for example, 3.2 μm or less, or 3.0 μm or less.

[0070] The sum of the thickness of second end 12f in second direction 102 and the thickness of first superconducting junction layer 91 is defined as second thickness H2. Second thickness H2 is, for example, 1.5 μm or more and 3.5 μm or less. Second thickness H2 may be, for example, 1.8 μm or more, or 2.0 μm or more. Second thickness H2 may be, for example, 3.2 μm or less, or 3.0 μm or less.

[0071] The superconducting junction between the first end 11f and the second end 12f using the first superconducting junction layer 91 is formed, for example, by the following method: The first superconducting layer portion 81b is formed on the first support member 81a by the PLD method or the like. A microcrystalline film is formed on the first superconducting layer portion 81b by the above-mentioned method for forming a microcrystalline film.

[0072] The first bonding material 81 is arranged so that the microcrystalline film contacts each of the first end 11f and the second end 12f. Pressure is applied between the first end 11f and the microcrystalline film and between the second end 12f and the microcrystalline film along a direction parallel to the second direction 102. The first end 11f, the second end 12f, and the microcrystalline film are heated. As a result, fine crystals of the high-temperature superconductor contained in the microcrystalline film grow epitaxially along the crystal orientation of the first end 11f and the second end 12f, forming a first superconducting bonding layer 91. After the first superconducting bonding layer 91 is formed, heat treatment is performed in an oxygen-containing atmosphere, thereby introducing oxygen into the first superconducting bonding layer 91. As a result, a superconducting bond is formed between the first end 11f and the second end 12f. This forms the first bonding portion 31.

[0073] 8, the second joint portion 32 may have a second joint material 82. The second joint material 82 has the above-mentioned second superconducting joint layer 92. In the second joint portion 32, the superconducting layer (third end portion 13f) of the third excess length member 63 and the superconducting layer (fourth end portion 14f) of the fourth excess length member 64 are superconductively joined to each other via the second superconducting joint layer 92 of the second joint material 82.

[0074] The third excess length member 63 and the fourth excess length member 64 are arranged so that the third end portion 13f and the fourth end portion 14f are aligned in a direction perpendicular to the fourth direction 104. The direction in which the third end portion 13f and the fourth end portion 14f are aligned is defined as a seventh direction 107. The second bonding material 82 extends along the seventh direction 107.

[0075] The configuration of the second bonding material 82 is substantially the same as the configuration of the first bonding material 81. The second bonding material 82 has a second support member 82a and a second superconducting layer portion 82b. The second support member 82a corresponds to the first support member 81a. The second superconducting layer portion 82b corresponds to the first superconducting layer portion 81b. The second superconducting bonding layer 92 is disposed on the second superconducting layer portion 82b.

[0076] The sum of the thickness of third end 13f in fourth direction 104 and the thickness of second superconducting joining layer 92 is defined as a third thickness H3. Third thickness H3 is, for example, 1.5 μm or more and 3.5 μm or less. The sum of the thickness of fourth end 14f in fourth direction 104 and the thickness of second superconducting joining layer 92 is defined as a fourth thickness H4. Fourth thickness H4 is, for example, 1.5 μm or more and 3.5 μm or less.

[0077] (Applied magnetic field angle dependence) In Fig. 9, magnetic field lines are indicated by two-dot chain lines. As shown in Fig. 9, a magnetic field is generated when a current flows through the coil 1. This magnetic field is applied to each of the first joint 31 and the second joint 32. In this specification, this magnetic field is also referred to as an applied magnetic field B1.

[0078] As shown in FIG. 10, the angle formed between the orientation of the first joint 31 and the direction of the applied magnetic field B1 at the first joint 31 is defined as a first applied magnetic field angle θ1. In this specification, the orientation of the first joint 31 refers to the thickness direction (second direction 102) of the first end portion 11f. The orientation of the first joint 31 is the same as the direction of the normal to the joint interface at the first joint 31. Specifically, the direction of the applied magnetic field B1 at the first joint 31 is defined as the direction of the applied magnetic field B1 at the joint interface at the first joint 31. A straight line 111 shown in FIG. 10 is a straight line parallel to the orientation of the first joint 31.

[0079] The bonding interface is an imaginary plane located midway between the first end 11f and the second end 12f in the first bonding part 31 according to one example of this embodiment shown in Fig. 4. The bonding interface is an imaginary plane including the interface between the first end 11f and the first superconducting bonding layer 91 and the interface between the second end 12f and the first superconducting bonding layer 91 in the first bonding part 31 according to another example of this embodiment shown in Figs.

[0080] The orientation of the first junction 31 is determined based on data on the applied magnetic field angle dependency of the critical current in a junction having the same configuration as the first junction 31. The applied magnetic field angle dependency will be described in detail below with reference to FIG. 11. In FIG. 11, the horizontal axis represents the first applied magnetic field angle θ1, and the vertical axis represents the critical current in the first junction 31.

[0081] 11, when the strength of the magnetic field applied to the first junction 31 is constant, the critical current at the first junction 31 changes with the change in the angle θ1 of the first applied magnetic field. In other words, the critical current at the first junction 31 has dependency on the angle of the applied magnetic field.

[0082] The applied magnetic field angle dependence of the critical current in a junction having the same configuration as the first junction 31 can be considered to be the same as the applied magnetic field angle dependence of the critical current in the first junction 31. Therefore, by measuring the applied magnetic field angle dependence of the critical current in a junction having the same configuration as the first junction 31, it is possible to estimate the applied magnetic field angle dependence of the critical current in the first junction 31. The method for measuring the applied magnetic field angle dependence will be described in detail later.

[0083] 11, the first applied magnetic field angle θ1 at which the critical current in the first joint 31 reaches a maximum value I1 is set to a first angle φ1. The first angle φ1 varies depending on the crystal structure of the crystals forming the first superconducting layer 11c. The first angle φ1 is, for example, not less than 80° and not more than 100°.

[0084] The first applied magnetic field angle θ1 when the critical current in the first joint 31 becomes the reference value I2 is set to the second angle φ2 and the third angle φ3. The reference value I2 is a current value that is predetermined when the superconducting magnet 100 is manufactured. The reference value I2 is, for example, a required specification value of the coil 1.

[0085] The first joint 31 is oriented so that the critical current in the first joint 31 is between the maximum value I1 and the reference value I2. From another perspective, the first joint 31 is oriented so that the first applied magnetic field angle θ1 is between the second angle φ2 and the third angle φ3. Specifically, the first protective case 71 (see FIG. 3) is attached to the second guide part 42 (see FIG. 3) so that the first applied magnetic field angle θ1 is between the second angle φ2 and the third angle φ3.

[0086] The first joint 31 may be oriented in such a way that the critical current in the first joint 31 has a maximum value I1, or may be inclined from the direction in which the critical current has a maximum value I1. From another perspective, the first applied magnetic field angle θ1 may be the same as the first angle φ1 or may be different from the first angle φ1.

[0087] As shown in FIG. 12, the angle formed between the orientation of the second joint 32 and the direction of the applied magnetic field B1 at the second joint 32 is defined as a second applied magnetic field angle θ2. The orientation of the second joint 32 refers to the thickness direction (fourth direction 104) of the third end 13f. The orientation of the second joint 32 is the same as the direction of the normal to the joint interface at the second joint 32. Specifically, the direction of the applied magnetic field B1 at the second joint 32 is the direction of the applied magnetic field B1 at the joint interface at the second joint 32. A straight line 112 shown in FIG. 12 is a straight line parallel to the orientation of the second joint 32.

[0088] The orientation of the second junction 32 is determined based on data on the dependency of the critical current on the angle of the applied magnetic field in a junction having the same configuration as the second junction 32. The dependency of the critical current on the angle of the applied magnetic field in the second junction 32 is substantially the same as the dependency of the critical current on the angle of the applied magnetic field in the first junction 31.

[0089] In the superconducting magnet 100 according to this embodiment, the second applied magnetic field angle θ2 may be different from, for example, the first applied magnetic field angle θ1. The second joint 32 is oriented so that the critical current in the second joint 32 is between the maximum value I1 and the reference value I2. From another perspective, the second joint 32 is oriented so that the second applied magnetic field angle θ2 is between the second angle φ2 and the third angle φ3. Specifically, the second protective case 72 (see FIG. 3) is attached to the second guide part 42 (see FIG. 3) so that the second applied magnetic field angle θ2 is between the second angle φ2 and the third angle φ3.

[0090] The second joints 32 may be oriented in such a way that the critical current in the second joints 32 has a maximum value I1, or may be inclined from the direction in which the critical current has a maximum value I1. From another perspective, the second applied magnetic field angle θ2 may be the same as the first angle φ1 or may be different from the first angle φ1. Each of the first joints 31 and the second joints 32 may be inclined from the direction in which the critical current has a maximum value I1.

[0091] (Method for measuring the angular dependence of applied magnetic field) Next, a method for measuring the angular dependency of an applied magnetic field will be described. As shown in Fig. 13, in measuring the angular dependency of an applied magnetic field, a closed-loop wire 210 and a measurement device 200 are prepared. The closed-loop wire 210 is a sample for measurement. The closed-loop wire 210 is formed of a superconducting wire. The configuration of the superconducting wire that forms the closed-loop wire 210 is substantially the same as the configuration of the superconducting wire that forms the coil 1.

[0092] The closed-loop wire 210 has a superconducting layer 211 to be measured and a junction 212 to be measured. The configuration of the superconducting layer 211 to be measured is substantially the same as the configuration of the first superconducting layer 11c. The configuration of the junction 212 to be measured is substantially the same as the configuration of the first junction 31. The closed-loop wire 210 has a winding 215 to be measured. The winding 215 to be measured is a portion around which the superconducting layer 211 to be measured is wound one or more times.

[0093] The measuring device 200 includes a Hall sensor 201, an electromagnet 202, a support plate 203, and a copper coil (not shown). The Hall sensor 201 is attached to a winding portion 215 to be measured. The Hall sensor 201 measures the current flowing through the winding portion 215 to be measured.

[0094] The support plate 203 supports the closed-loop wire 210. The closed-loop wire 210 is disposed on the support plate 203. The support plate 203 is rotatable around a rotation axis C. From another perspective, the closed-loop wire 210 is rotatable around the rotation axis C. The extension direction of the rotation axis C is parallel to the extension direction of the superconducting layer 211 to be measured in the joint 212 to be measured, for example. From another perspective, the extension direction of the rotation axis C corresponds to the third direction 103 (see Figures 4 and 6) in the first joint 31, for example.

[0095] Electromagnet 202 applies a magnetic field B2 to junction 212 under test. The direction of magnetic field B2 is perpendicular to the direction in which axis of rotation C extends. Electromagnet 202 is a split-pair magnet. A copper coil (not shown) is placed at the center of winding 215 under test.

[0096] In measuring the angular dependence of the applied magnetic field, the electromagnet 202 is cooled to 4 Kelvin. The closed-loop wire 210, the Hall sensor 201, and the support plate 203 are each cooled to, for example, 77 Kelvin (liquid nitrogen temperature). A current is passed through the copper coil. A current IL flows in the closed-loop wire 210 due to magnetic induction. The value of the current IL is set to a value close to the critical current of the superconducting layer 211 to be measured. The critical current of the closed-loop wire 210 can be measured by measuring the time change of the current IL using the Hall sensor 201.

[0097] A magnetic field B2 is applied to the test junction 212 using the electromagnet 202. The strength of the magnetic field B2 is set to, for example, 0.5 Tesla. This reduces the critical current in the test junction 212. Therefore, the critical current in the entire closed-loop wire 210 is reduced. With the magnetic field B2 applied to the test junction 212, the critical current measured using the Hall sensor 201 is considered to be the critical current in the test junction 212.

[0098] After the critical current of the junction 212 to be measured is measured, the closed-loop wire 210 rotates around the rotation axis C, thereby changing the orientation of the junction 212 to be measured relative to the direction of the magnetic field B2. The orientation of the junction 212 to be measured corresponds to the orientation of the first junction 31.

[0099] After changing the angle between the direction of the magnetic field B2 and the orientation of the junction 212 to be measured by, for example, 5°, the critical current of the closed-loop wire 210 is measured again. By repeating the same procedure, it is possible to measure the dependency of the critical current of the junction 212 on the angle between the direction of the magnetic field B2 and the orientation of the junction 212 to be measured (dependence on the angle of the applied magnetic field). The dependency of the junction 212 to be measured on the angle of the applied magnetic field is considered to be the dependency of each of the first junction 31 and the second junction 32 to be applied on the angle of the applied magnetic field.

[0100] In the above-described measurement method, measurements are taken when the angle of the applied magnetic field changes in the rotation direction around the rotation axis C. The orientations of the first joint 31 and the second joint 32 may be determined by regarding the applied magnetic field angle dependency when the applied magnetic field angle changes in the rotation direction as the same as the applied magnetic field angle dependency when the applied magnetic field angle changes three-dimensionally.

[0101] In addition to the above-described measurement method, measurements may be made when the angle of the applied magnetic field changes in the direction of rotation about the axis D in Fig. 13. The applied magnetic field angle dependence measured for each of the direction of rotation about the rotation axis C and the direction of rotation about the axis D may be used to determine the applied magnetic field angle dependence when the angle of the applied magnetic field changes three-dimensionally. The direction in which the axis D extends corresponds to the direction (sixth direction 106) perpendicular to each of the second direction 102 and the third direction 103 in the first joint 31.

[0102] (Protective case configuration) The protective cases will be described in detail below. The configuration of the first protective case 71 will be described below, but the configuration of the second protective case 72 is substantially the same as the configuration of the first protective case 71. As shown in FIG. 14 , the first protective case 71 mainly has a main body 8 and a fixing member 9.

[0103] The main body 8 forms an outer peripheral surface 10. The outer peripheral surface 10 is, for example, a side surface of the main body 8. The thickness direction of the main body 8 is the Z direction. When viewed from the Z direction (hereinafter also referred to as a plan view), the main body 8 has, for example, an oval shape, an elliptical shape, or a hamburger shape. The Z direction is a direction perpendicular to both the circumferential direction of the outer peripheral surface 10 and the normal to the outer peripheral surface 10.

[0104] 15 shows a state in which the first excess length member 61 and the second excess length member 62 are wound one or more times around the outer peripheral surface 10 of the first protective case 71. For ease of explanation, the cover member 25 is not shown in FIG. 15. The number of times the first excess length member 61 and the second excess length member 62 are wound around the outer peripheral surface 10 varies depending on the lengths of the first excess length member 61 and the second excess length member 62.

[0105] As shown in FIG. 15 , the outer peripheral surface 10 has a first flat surface 11, a second flat surface 12, a first curved surface 13, and a second curved surface 14. The shorter side of the main body 8 in a plan view is the X direction. The longer side of the main body 8 in a plan view is the Y direction. In the main body 8, the second flat surface 12 is opposite the first flat surface 11. In a plan view, each of the first flat surface 11 and the second flat surface 12 is a portion of the outer peripheral surface 10 of the main body 8 that is located in the X direction with respect to the center 8c of the main body 8. The center 8c of the main body 8 is the intersection of the center line in the X direction and the center line in the Y direction.

[0106] Each of the first curved surface 13 and the second curved surface 14 connects the first flat surface 11 and the second flat surface 12. In a plan view, each of the first curved surface 13 and the second curved surface 14 has a convex shape facing outward from the main body 8. For example, each of the first curved surface 13 and the second curved surface 14 has a semicircular arc shape. The radius of curvature of each of the first curved surface 13 and the second curved surface 14 (first radius of curvature R1) is, for example, 25 mm or more.

[0107] In the main body 8, the second curved surface 14 is opposite to the first curved surface 13. In a plan view, each of the first curved surface 13 and the second curved surface 14 is a portion of the outer peripheral surface 10 of the main body 8 that is located in the Y direction relative to the center 8c of the main body 8. In a plan view, the maximum distance between the first curved surface 13 and the second curved surface 14 is greater than the maximum distance between the first flat surface 11 and the second flat surface 12.

[0108] The blind hole 16 is provided in the first flat surface 11. The blind hole 16 is provided, for example, in a portion of the outer peripheral surface 10 of the main body 8 that is located in the X direction relative to the center 8c of the main body 8. In a plan view, the first flat surface 11 extends along the tangent direction (Y direction) of the blind hole 16 at the connection portion between the blind hole 16 and the outer peripheral surface 10 of the main body 8. This reduces the stress applied to the excess length portion 60, thereby preventing deterioration and breakage of the first excess length member 61.

[0109] As shown in FIG. 15 , the blind hole 16 includes a first hole portion 17 and a second hole portion 18. The first hole portion 17 is connected to the outer peripheral surface 10 of the main body portion 8. The first hole portion 17 is provided on the first flat surface 11. In a plan view, the first hole portion 17 has a curved shape. For example, the first hole portion 17 has the shape of a portion of an arc, such as a quarter circle. This reduces the stress applied to the excess length portion 60 when the excess length portion 60 is inserted into the first hole portion 17.

[0110] The radius of curvature (second radius of curvature R2) of the first hole portion 17 is, for example, 15 mm or more and 100 mm or less. This makes it possible to effectively reduce the stress applied to the excess length portion 60 when the excess length portion 60 is inserted into the first hole portion 17.

[0111] The first curvature radius R1 is larger than the second curvature radius R2. For example, the first curvature radius R1 is 1.2 times or more the second curvature radius R2. This reduces the stress applied to the excess length portion 60 when the excess length portion 60 is wound around the outer peripheral surface 10.

[0112] The second hole portion 18 accommodates the first joint portion 31. The second hole portion 18 may accommodate a portion of each of the first excess length member 61 and the second excess length member 62. The second hole portion 18 is connected to the first hole portion 17. The second hole portion 18 defines the bottom of the blind hole 16. The second hole portion 18 extends, for example, in the X direction. The second hole portion 18 has, for example, a straight shape. The second hole portion 18 is provided, for example, in the Y direction relative to the center 8c of the main body portion 8.

[0113] FIG. 16 shows the cover member 25 attached to the base member 20. Hatching of the first excess length member 61 and the second excess length member 62 is omitted in FIG. 16. As shown in FIG. 16, in a cross section perpendicular to the longitudinal direction of the blind hole 16, a gap G between the side wall of the blind hole 16 and the first excess length member 61 and the second excess length member 62 is, for example, 2 mm or less. This prevents condensation water from entering the blind hole 16. When the gap G is 0 mm, condensation water can be effectively prevented from entering. To facilitate accommodating the first excess length member 61, the second excess length member 62, and the first joint portion 31 in the blind hole 16, the gap G may be 0.01 mm or more, or may be 0.03 mm or more.

[0114] The main body 8 is made of a material that does not react with the cooling refrigerant and that can be used at temperatures below the critical temperature (Tc) of the first superconducting layer 11c and the second superconducting layer 12c (see FIGS. 4 and 7). For example, the main body 8 is made of a metal such as Hastelloy, a resin, or a ceramic. By making the main body 8 from Hastelloy, deterioration of the main body 8 due to heat cycles can be effectively suppressed. Furthermore, the mechanical strength of the main body 8 can be effectively improved.

[0115] 17, the base member 20 includes a first main surface 21 and a first side surface 22 connected to the first main surface 21. A first groove 23 is provided in the first main surface 21 of the base member 20. The first groove 23 forms a part of the blind hole 16.

[0116] 18, the cover member 25 includes a second main surface 26 and a second side surface 27 connected to the second main surface 26. As shown in FIGS. 14, 17, and 18, the cover member 25 is attached to the base member 20 so as to cover the first groove 23. The second main surface 26 of the cover member 25 faces the first main surface 21 of the base member 20, and the cover member 25 covers the first main surface 21 of the base member 20. The cover member 25 does not cover the first side surface 22 of the base member 20.

[0117] A second groove 28 is provided in the second main surface 26 of the cover member 25. The second groove 28 forms a part of the blind hole 16. When the first main surface 21 and the second main surface 26 are arranged facing each other, the base member 20 and the cover member 25 have shapes that are generally symmetrical with respect to the first main surface 21 and the second main surface 26.

[0118] The outer peripheral surface 10 of the main body 8 is formed by the first side surface 22 of the base member 20 and the second side surface 27 of the cover member 25. The blind hole 16 is formed by the first groove 23 and the second groove 28.

[0119] As shown in FIG. 14 , the lid member 25 is fixed to the base member 20 by, for example, a fixing member 9. The fixing member 9 is, for example, a screw. Specifically, as shown in FIG. 17 , a threaded hole 24 is provided in the first main surface 21 of the base member 20. As shown in FIG. 18 , a through hole 29 is provided in the second main surface 26 of the lid member 25. A screw passes through the through hole 29 and is threaded into the threaded hole 24 of the base member 20. Another example of the fixing member 9 is a joining member such as an adhesive. The lid member 25 is joined to the base member 20 via the joining member provided on the first main surface 21 of the base member 20. In this way, since the main body portion 8 is formed by the base member 20 and the lid member 25, it is easy to accommodate the first joining portion 31 and the excess length portion 60.

[0120] As shown in Figures 15 and 16, the first protective case 71 further has a sealing member 7. The sealing member 7 closes at least a portion of the gap between the first excess length member 61 and the second excess length member 62 and the side wall of the blind hole 16. This effectively prevents condensation water from adhering to the first joint portion 31. The sealing member 7 is made of grease such as low-temperature grease (for example, Apiezon N (manufactured by Aram Co., Ltd.)), rubber, clay, or the like.

[0121] The second groove 28 does not necessarily have to be provided in the cover member 25. In this case, the blind hole 16 is formed by the first groove 23 and the second main surface 26 of the cover member 25 that covers the first groove 23. The base member 20 and the cover member 25 may be integrated, and the main body 8 may be formed from a single member.

[0122] (Manufacturing method of superconducting magnets) Next, a method for manufacturing a superconducting magnet according to this embodiment will be described. As shown in Fig. 19, the method for manufacturing a superconducting magnet according to this embodiment mainly includes a step (S10) of preparing a closed-loop wire, a step (S20) of measuring the angular dependency of an applied magnetic field, and a step (S30) of determining the arrangement of a joint.

[0123] First, a step (S10) of preparing a closed-loop wire is performed. Specifically, a wire to be measured (not shown) is prepared. The configuration of the wire to be measured is substantially the same as the configurations of the first excess length member 61, the second excess length member 62, the third excess length member 63, and the fourth excess length member 64. The wire to be measured has a superconducting layer 211 to be measured. Both longitudinal ends of the superconducting layer 211 to be measured are superconductingly joined to form a joint 212 to be measured. Specifically, the joint 212 to be measured is formed so that its configuration is substantially the same as that of the first joint 31. In this manner, a closed-loop wire 210 to be used in the above-described method for measuring the angular dependence of an applied magnetic field is prepared.

[0124] Next, a step (S20) of measuring the angular dependency of the applied magnetic field is performed. Specifically, using the above-described method for measuring the angular dependency of the applied magnetic field, the critical current in the junction 212 is measured while changing the angle between the direction of the magnetic field B2 and the orientation of the junction 212. This allows data on the angular dependency of the critical current in the junction 212 to be measured.

[0125] Next, a step (S30) of determining the arrangement of the junction is performed. The arrangement of the first junction 31 is determined based on data on the applied magnetic field angle dependency of the critical current at the measured junction 212 measured in the step (S20) of measuring the applied magnetic field angle dependency. Specifically, the direction and strength of the applied magnetic field B1 around the coil 1 are determined by simulation. Based on the results of the simulation and the data on the applied magnetic field angle dependency of the first junction 31, the arrangement of the first junction 31 is determined so that the value of the critical current at the first junction 31 is equal to or greater than, for example, a predetermined reference value I2. In this way, the superconducting magnet 100 according to this embodiment is manufactured.

[0126] The first joint 31 is formed by placing a portion of each of the first excess length member 61 and the second excess length member 62 in a heating furnace and heat-treating the portion. If the first joint 31 does not have sufficient performance, the first joint 31 is cut. The heat treatment is then performed again to form the first joint 31 again. Therefore, to form the first joint 31, the first excess length member 61 and the second excess length member 62 are each formed. Similarly, to form the second joint 32, the third excess length member 63 and the fourth excess length member 64 are each formed.

[0127] Next, the effects of the superconducting magnet 100 and the method for manufacturing the superconducting magnet 100 according to this embodiment will be described.

[0128] When the superconducting magnet 100 operates, a magnetic field is generated by the flow of current through the coil 1. When this magnetic field is applied to the joint of the coil 1, the critical current at the joint decreases. Usually, the decrease in critical current can be suppressed by increasing the distance between the joint and the winding part 50 of the coil 1. In this case, the superconducting magnet 100 becomes larger.

[0129] According to the superconducting magnet 100 of this embodiment, the orientation of the first joint 31 is determined based on data on the applied magnetic field angle dependency of the critical current at a joint having the same configuration as the first joint 31. This makes it possible to suppress a decrease in critical current at the first joint 31 without increasing the distance between the first joint 31 and the winding part 50 of the coil 1. Therefore, it is possible to reduce the size of the superconducting magnet 100 while suppressing a decrease in critical current at the first joint 31.

[0130] According to the superconducting magnet 100 of this embodiment, the orientation of the second junction 32 is determined based on data on the applied magnetic field angle dependency of the critical current at a junction having the same configuration as the second junction 32. This makes it possible to suppress a decrease in critical current at the second junction 32 without increasing the distance between the second junction 32 and the winding unit 50. Therefore, even when the coil 1 has the first junction 31 and the second junction 32, it is possible to reduce the size of the superconducting magnet 100 while suppressing a decrease in critical current at the junction.

[0131] According to the superconducting magnet 100 of this embodiment, the first joint 31 may be disposed so as to be inclined from the direction in which the critical current is at its maximum value. In this way, even when the first joint 31 is disposed so as to be inclined from the direction in which the critical current is at its maximum value, it is possible to prevent the critical current at the first joint 31 from decreasing excessively. Therefore, it is possible to improve the degree of freedom in the arrangement of the first joint 31 in the superconducting magnet 100.

[0132] In the superconducting magnet 100 according to this embodiment, the first joint portion 31 may include a first joint material 81. The first joint material 81 includes a first superconducting joint layer 91. In the thickness direction of the first end portion 11f, the sum of the thickness of the first end portion 11f and the thickness of the first superconducting joint layer 91 (first thickness H1) is 1.5 μm or more and 3.5 μm or less. In the thickness direction of the second end portion 12f, the sum of the thickness of the second end portion 12f and the thickness of the first superconducting joint layer 91 (second thickness H2) is 1.5 μm or more and 3.5 μm or less. If each of the first thickness H1 and the second thickness H2 is excessively thick, the critical current will be excessively reduced due to the applied magnetic field. In the superconducting magnet 100 according to this embodiment, the first thickness H1 and the second thickness H2 are each 3.5 μm or less, thereby suppressing the reduction in critical current due to the applied magnetic field.

[0133] The superconducting magnet 100 according to this embodiment has a first protective case 71 and a support portion 4. The support portion 4 supports the multiple excess length members of the coil 1 and the first protective case 71. The first protective case 71 houses the first joint portion 31. The support portion 4 is made of a non-magnetic material. This makes it possible to prevent the support portion 4 from vibrating due to the magnetic field generated by the coil 1, compared to when the support portion 4 is made of a magnetic material. This therefore makes it possible to prevent the applied magnetic field angle (first applied magnetic field angle θ1) at the first joint portion 31 from changing when a current flows through the coil 1.

[0134] In a superconducting coil device, the temperature of the superconducting wires and their joints may be raised from a low temperature such as the temperature of liquid helium or liquid nitrogen to room temperature for maintenance of the superconducting coil device. This temperature rise may cause condensation water to adhere to the joints of the superconducting wires, resulting in deterioration of the joints of the superconducting wires.

[0135] According to the superconducting magnet 100 of this embodiment, the first joint 31 is housed in the first protective case 71. Therefore, even if the first joint 31 is subjected to a heat cycle including a temperature increase from a low temperature such as the temperature of liquid helium or liquid nitrogen to room temperature, it is possible to prevent condensation from adhering to the first joint 31. This makes it possible to prevent deterioration of the first joint 31.

[0136] According to the method for manufacturing the superconducting magnet 100 of this embodiment, the dependency of the critical current on the angle of the applied magnetic field at the joint 212 to be measured is measured. The arrangement of the first joint 31 in the coil 1 is determined based on the measured data on the dependency on the angle of the applied magnetic field. This makes it possible to suppress a decrease in the critical current at the first joint 31 without increasing the distance between the first joint 31 and the winding part 50 of the coil 1. This makes it possible to reduce the size of the superconducting magnet 100 while suppressing a decrease in the critical current at the first joint 31.

[0137] Although the above description has been given of a configuration in which the number of coils 1 is one, the number of coils 1 may be two or more. When the number of coils 1 is two or more, each of the two or more coils 1 is arranged concentrically around the central axis O.

[0138] Furthermore, although the configuration in which the winding section 50 has two winding members has been described, the winding section 50 may have three or more winding members. The number of joints in the coil 1 is the same as the number of winding members in the winding section 50. The number of surplus members in the surplus section 60 of the coil 1 is twice the number of winding members in the winding section 50. [Example]

[0139] (Evaluation method) The applied magnetic field angle dependency of the critical current in the junction was evaluated. First, the above-described closed loop wire 210 was prepared. The configuration of the measured junction 212 of the closed loop wire 210 was the same as that of the first junction 31 (see FIGS. 6 and 7) according to another example of this embodiment. The applied magnetic field angle dependency of the critical current in the measured junction 212 was measured according to the above-described method for measuring the applied magnetic field angle dependency.

[0140] The electromagnet 202 of the measuring device 200 was cooled to 4 Kelvin. The closed-loop wire 210, the Hall sensor 201, and the support plate 203 were each cooled to 77 Kelvin. The strength of the magnetic field B2 was set to 0.5 Tesla. When the applied magnetic field angle was 0°, the c-axis direction of the material constituting the superconducting layer 211 to be measured of the closed-loop wire 210 was parallel to the direction of the magnetic field B2.

[0141] (Evaluation results)

[0142] [Table 1]

[0143] The measurement results shown in Table 1 are plotted in FIG. 20. As shown in FIG. 20 and Table 1, the critical current in the junction 212 under test was maximum when the applied magnetic field angle was 90°. In other words, the critical current was maximum when the orientation of the junction 212 under test was perpendicular to the direction of the magnetic field B2. The critical current decreased as the orientation of the junction 212 under test approached parallel to the direction of the magnetic field B2. This confirmed that the junction described above has an applied magnetic field angle dependency.

[0144] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments, and it is intended to include any modifications within the scope of the claims and meanings equivalent to the claims. [Explanation of symbols]

[0145] REFERENCE SIGNS LIST 1 coil, 2 cryostat, 3 bobbin, 4 support, 7 sealing member, 8 main body, 8c center, 9 fixing member, 10 outer peripheral surface, 11 first flat surface, 11a first substrate, 11b first intermediate layer, 11c first superconducting layer, 11d first protective layer, 11e first stabilizing layer, 11f first end, 12 second flat surface, 12a second substrate, 12b second intermediate layer, 12c second superconducting layer, 12d second protective layer, 12e second stabilizing layer, 12f second end, 13 first curved surface, 13a third substrate, 13b third intermediate layer, 13c third superconducting layer, 13d third protective layer, 13e third stabilizing layer, 13f third end, 14 second curved surface, 14a fourth substrate, 14b fourth intermediate layer, 14c Fourth superconducting layer, 14d Fourth protective layer, 14e Fourth stabilizing layer, 14f Fourth end portion, 16 Blind hole, 17 First hole portion, 18 Second hole portion, 20 Base member, 21 First main surface, 22 First side surface, 23 First groove, 24 Screw hole, 25 Cover member, 26 Second main surface, 27 Second side surface, 28 Second groove, 29 Through hole, 31 First joint portion, 32 Second joint portion, 41 First guide portion, 42 Second guide portion, 43 Columnar portion, 50 Winding portion, 51 First winding member, 52 Second winding member, 60 Excess portion, 61 First excess member, 62 Second excess member, 63 Third excess member, 64 Fourth excess member, 71 First protective case, 72 Second protective case, 81 First joint material, 81a First support member, 81b First superconducting layer portion, 82 second joining material, 82a second support member, 82b second superconducting layer portion, 91 first superconducting joining layer, 92 second superconducting joining layer, 100 superconducting magnet, 101 first direction, 102 second direction, 103 third direction, 104 fourth direction, 105 fifth direction, 106 sixth direction, 107 seventh direction, 111, 112 straight line, 200 measuring device, 201 Hall sensor, 202 electromagnet, 203 support plate, 210 closed loop wire, 211 superconducting layer to be measured, 212 joint to be measured, 215 winding to be measured, B1 applied magnetic field, B2 magnetic field, C rotation axis, D axis, G gap, H1 first thickness, H2 second thickness, H3 third thickness, H4 fourth thickness, I1 maximum value, I2 Reference value, III region, IL current, O central axis, R1 first radius of curvature, R2 second radius of curvature, θ1 first applied magnetic field angle, θ2 second applied magnetic field angle, φ1 first angle, φ2 second angle, φ3 third angle.

Claims

1. a coil including a first superconducting layer, a second superconducting layer, and a first joint portion where the first superconducting layer and the second superconducting layer are superconductively joined; The coil forms a closed loop, A superconducting magnet in which the orientation of the first junction is determined based on data on the dependency of critical current on the angle of an applied magnetic field in a junction having the same configuration as the first junction.

2. the coil includes a third superconducting layer, a fourth superconducting layer, and a second joint portion where the third superconducting layer and the fourth superconducting layer are superconductively joined, 2. The superconducting magnet according to claim 1, wherein the orientation of said second junction is determined based on data on the dependency of critical current on the angle of an applied magnetic field in a junction having the same configuration as said second junction.

3. 3. The superconducting magnet according to claim 1, wherein the first junction is disposed so as to be inclined from a direction in which the critical current is at a maximum value.

4. 3. The superconducting magnet according to claim 2, wherein each of the first junction and the second junction is disposed so as to be inclined from an orientation in which the critical current is at a maximum value.

5. the first superconducting layer has a first end; the second superconducting layer has a second end portion superconductively joined to the first end portion at the first joint portion, 3. The superconducting magnet according to claim 1, wherein the first end and the second end overlap each other when viewed in a thickness direction of the first end.

6. the first superconducting layer has a first end; the second superconducting layer has a second end; the first joint portion has a joint material that superconductively joins the first end portion and the second end portion, 3. The superconducting magnet according to claim 1, wherein the bonding material is disposed on each of the first end and the second end in a thickness direction of the first end and bridges the first end and the second end.

7. the bonding material has a superconducting bonding layer disposed on each of the first end and the second end in a thickness direction of the first end, 7. The superconducting magnet according to claim 6, wherein a total value of the thickness of the first end and the thickness of the superconducting joining layer and a total value of the thickness of the second end and the thickness of the superconducting joining layer are each 1.5 μm or more and 3.5 μm or less.

8. a protective case that houses the first joint portion; a support portion that supports the protective case, the coil has a winding portion and a plurality of excess length members that are drawn out from the winding portion and supported by the support portion, In the first joint, end portions of two of the plurality of excess length members are superconductingly joined, 3. The superconducting magnet according to claim 1, wherein the support portion is made of a non-magnetic material.

9. A method for manufacturing a superconducting magnet including a coil including a first superconducting layer, a second superconducting layer, and a first joint that superconductively joins the first superconducting layer and the second superconducting layer, the method comprising: a step of preparing a closed loop wire having a superconducting layer to be measured and a junction to be measured in which both ends of the superconducting layer to be measured are superconductively joined; measuring the angular dependence of the critical current of the junction under test on the applied magnetic field by measuring the critical current of the junction under test while changing the angle between the direction of the external magnetic field and the orientation of the junction under test; and determining the arrangement of the first junction in the coil based on the measured data on the angle dependency of the applied magnetic field.

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