Superconducting magnet device

Abstract

To provide a superconducting magnet device having an improved support structure for a saddle-type superconducting coil.SOLUTION: A superconducting magnet device 10 comprises a cryostat 12, a pair of saddle-type superconducting coils 20 and a support frame 30. The cryostat 12 comprises an inner circumference wall 12a arranged in radially outside of a bore 18 in such a manner that the inner circumference wall 12a surrounds the bore 18, and an outer circumference wall 12b arranged in radially outside of the inner circumference wall 12a in such a manner that the outer circumference wall 12b surrounds the inner circumference wall 12a, and the cryostat 12 provides vacuum environment to an internal space 14 defined between the inner circumference wall 12a and the outer circumference wall 12b, the pair of saddle-type superconducting coils 20 face each other across the bore 18 and are arranged in the internal space 14 in such a way as to be exposed to the vacuum environment, the support frame 30 is arranged in radially outside of the pair of saddle-type superconducting coils 20 in the internal space 14 and supports the pair of saddle-type superconducting coils 20.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a superconducting magnet device. [Background technology]

[0002] Superconducting magnet devices are used as a magnetic field source for single crystal pulling devices using the MCZ (Magnetic field applied Czochralski) method. Single crystal pulling devices generally include a single crystal pulling furnace and a cryostat that is arranged to surround the furnace and contains multiple superconducting coils. Saddle coils or round coils are typically used for the superconducting coils. The strong magnetic field generated by the superconducting coils can suppress thermal convection in the melt in the pulling furnace. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-28147 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an existing design of a single crystal pulling apparatus using a saddle coil as a superconducting coil, the coil core used for manufacturing the saddle coil is used as a support structure for the saddle coil. The saddle coil is housed in a cryostat together with the core. The saddle coil is wound on the outside of the core, while the single crystal pulling furnace to which the magnetic field should be applied by the superconducting coil is placed inside the cryostat, i.e., inside the core. In other words, the core is placed between the magnetic field application location and the saddle coil. In this configuration, the saddle coil is placed farther away from the magnetic field application location by the amount of space occupied by the core. According to Biot-Savart's law, the magnetic field generated by a coil is proportional to the negative third power of the distance. Therefore, if the coil is moved away from the magnetic field application location, even if the distance is small, the magnetomotive force of the coil required to generate the same magnetic field can be significantly increased. This leads to an increase in the required superconducting wire, which can undesirably increase the manufacturing costs of the superconducting magnet device.

[0005] Furthermore, in single crystal pulling apparatuses, a magnetic shield is often installed around the outer periphery of the cryostat to reduce leakage magnetic fields. When a magnetic field is generated, a correspondingly strong electromagnetic force acts on the superconducting coil in a direction toward the magnetic shield, i.e., radially outward. In a configuration in which a core is used as a support structure for a saddle-shaped superconducting coil as described above, this electromagnetic force acts to pull the superconducting coil away from the core. To avoid this, it may be necessary to add structural members or strengthen the support structure in order to press the superconducting coil against the core. The resulting increase in weight and size may also lead to an increase in the manufacturing cost of the superconducting magnet device.

[0006] It is an exemplary object of an embodiment of the present invention to provide a superconducting magnet apparatus having an improved support structure for a saddle-type superconducting coil. [Means for solving the problem]

[0007] According to one aspect of the present invention, a superconducting magnet device includes an inner wall arranged radially outside the bore so as to surround the bore, and an outer wall arranged radially outside the inner wall so as to surround the inner wall, a cryostat that provides a vacuum environment in an internal space defined between the inner wall and the outer wall, a pair of saddle-type superconducting coils facing each other across the bore, the pair of saddle-type superconducting coils being arranged in the internal space so as to be exposed to the vacuum environment, and a support frame that is arranged radially outside the pair of saddle-type superconducting coils in the internal space and supports the pair of saddle-type superconducting coils. Effect of the Invention

[0008] According to the present invention, it is possible to provide a superconducting magnet apparatus having an improved support structure for a saddle-type superconducting coil. [Brief description of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view illustrating a single crystal pulling apparatus equipped with a superconducting magnet device according to an embodiment of the present invention. [Diagram 2] 1 is a cross-sectional view illustrating a single crystal pulling apparatus equipped with a superconducting magnet device according to an embodiment of the present invention. [Diagram 3] FIG. 1 is a perspective view showing a schematic appearance of a superconducting magnet device according to an embodiment. [Figure 4] FIG. 2 is a perspective view illustrating a schematic arrangement of superconducting coils in a superconducting magnet device according to an embodiment. [Diagram 5] FIG. 1 is a cross-sectional view illustrating a superconducting magnet device according to an embodiment. [Figure 6] FIG. 2 is a schematic diagram showing a part of a developed view of a saddle-shaped superconducting coil and a support frame as viewed from the radially inner side in the embodiment. [Figure 7] FIG. 11 is a front view illustrating the support frame as viewed from the radially outer side in the embodiment. [Figure 8] FIG. 11 is a perspective view illustrating another example of a superconducting coil arrangement in a superconducting magnet device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, the embodiments for carrying out the present invention will be described in detail with reference to the drawings. In the description and drawings, the same or equivalent components, members, and processes are given the same reference numerals, and duplicated descriptions are omitted as appropriate. The scale and shape of each part shown in the drawings are set for convenience in order to facilitate the description, and are not to be interpreted as being limiting unless otherwise specified. The embodiments are merely examples, and do not limit the scope of the present invention in any way. All features and combinations thereof described in the embodiments are not necessarily essential to the invention.

[0011] 1 and 2 are cross-sectional views showing a single crystal pulling apparatus 100 equipped with a superconducting magnet device 10 according to an embodiment. FIG. 3 is a perspective view showing an external appearance of the superconducting magnet device 10 according to an embodiment. FIG. 4 is a perspective view showing a superconducting coil arrangement in the superconducting magnet device 10 according to an embodiment. FIG. 5 is a cross-sectional view showing the superconducting magnet device 10 according to an embodiment. FIG. 1 shows a BB cross section of FIG. 2, and FIG. 2 shows an AA cross section of FIG. 1. Also, FIG. 5 shows a CC cross section of FIG. 3.

[0012] The single crystal pulling apparatus 100 includes a single crystal pulling furnace 102 and a superconducting magnet device 10. The single crystal pulling apparatus 100 is, for example, a silicon single crystal pulling apparatus using the HMCZ (Horizontal-MCZ; transverse magnetic field type MCZ) method.

[0013] As shown in FIG. 1, the single crystal pulling furnace 102 includes a crucible 104, a single crystal pulling mechanism 106, and a heater 108.

[0014] The crucible 104 is a container for storing a molten material (eg, molten silicon) and is made of, for example, quartz.

[0015] The single crystal pulling mechanism 106 is a drive device that pulls the single crystal 110 upward from the molten material in the crucible 104 along the single crystal pulling shaft 112, and includes a pulling drive source that is disposed above and outside the single crystal pulling furnace 102. The single crystal pulling shaft 112 is an axis that extends in the vertical direction (i.e., in a direction perpendicular to a horizontal plane). The single crystal pulling mechanism 106 is configured to pull the single crystal 110 while rotating the single crystal 110 around the single crystal pulling shaft 112.

[0016] The heater 108 is disposed around the crucible 104 in the single crystal pulling furnace 102, and heats the crucible 104. The molten material in the crucible 104 is maintained in a molten state by the heating by the heater 108.

[0017] The superconducting magnet apparatus 10 includes a cryostat 12, a pair of saddle-type superconducting coils 20, a heat shield 24, a magnetic shield 26, and a support frame 30. The superconducting magnet apparatus 10 is used as a magnetic field generation source for a single crystal pulling apparatus 100.

[0018] The cryostat 12 has an internal space 14 isolated from an ambient environment 16 surrounding the cryostat 12, and a saddle-type superconducting coil 20, a heat shield 24, and a support frame 30 are disposed in the internal space 14. The internal space 14 is a cylindrical space. The cryostat 12 is an insulated vacuum vessel, and during operation of the superconducting magnet apparatus 10, an extremely low temperature vacuum environment suitable for bringing the saddle-type superconducting coil 20 into a superconducting state is provided in the internal space 14 of the cryostat 12.

[0019] The cryostat 12 defines a bore 18 therein and has a cylindrical shape extending along a central axis, i.e., a single crystal pulling axis 112, passing through the bore 18. When the superconducting magnet device 10 is mounted on the single crystal pulling apparatus 100, a single crystal pulling furnace 102 is disposed in the bore 18. The bore 18 is part of the surrounding environment 16 surrounding the cryostat 12 (i.e., it is outside the cryostat 12) and is, for example, a cylindrical space surrounded by the cryostat 12.

[0020] The cryostat 12 includes an inner peripheral wall 12a arranged radially outside the bore 18 so as to surround the bore 18, and an outer peripheral wall 12b arranged radially outside the inner peripheral wall 12a so as to surround the inner peripheral wall 12a. The inner peripheral wall 12a and the outer peripheral wall 12b are both cylindrical, and a saddle-shaped superconducting coil 20, a heat shield 24, and a support frame 30 are arranged between them. The inner peripheral wall 12a and the outer peripheral wall 12b are arranged coaxially with the single crystal pulling shaft 112 as the center. The cryostat 12 also includes a top plate 12c and a bottom plate 12d that connect the inner peripheral wall 12a and the outer peripheral wall 12b at the top and bottom, respectively. The top plate 12c and the bottom plate 12d are annular in shape and have generally flat surfaces. An internal space 14 of the cryostat 12 is defined between an inner peripheral wall 12a and an outer peripheral wall 12b in the radial direction, and between a top plate 12c and a bottom plate 12d in the vertical direction (the direction of the single crystal pulling axis 112).

[0021] At least the inner peripheral wall 12a of the cryostat 12 is made of a non-magnetic material (e.g., a non-magnetic metal material such as stainless steel) so as not to prevent the saddle-type superconducting coil 20 from generating a magnetic field in the bore 18. Other parts of the cryostat 12, i.e., the outer peripheral wall 12b, the top plate 12c, and the bottom plate 12d, may also be made of the same material as the inner peripheral wall 12a.

[0022] The pair of saddle-type superconducting coils 20 face each other across the bore 18 and are arranged symmetrically with respect to the single crystal pulling axis 112. Each of the saddle-type superconducting coils 20 is curved concavely toward the bore 18, for example, curved in an arc shape along the cylindrical shape of the cryostat 12. These two saddle-type superconducting coils 20 have the same shape and the same size.

[0023] One of the two saddle-shaped superconducting coils 20 generates a magnetic field radially inward, i.e., toward the single crystal pulling axis 112, and the other saddle-shaped superconducting coil 20 generates a magnetic field radially outward, i.e., away from the single crystal pulling axis 112. By superposing these magnetic fields, the pair of saddle-shaped superconducting coils 20 generates a composite magnetic field 22. The composite magnetic field 22 is on the single crystal pulling axis 112 and is perpendicular to the single crystal pulling axis 112.

[0024] For ease of explanation, an XY coordinate plane perpendicular to the single crystal pulling axis 112 will be considered below as shown in Figures 2 and 3. The origin of this coordinate plane is on the single crystal pulling axis 112, the X axis extends in the direction of the composite magnetic field 22 on the single crystal pulling axis 112, and the Y axis is perpendicular to the single crystal pulling axis 112 and the X axis. The single crystal pulling axis 112 can also be regarded as the Z axis.

[0025] The heat shield 24 is disposed in the internal space 14 of the cryostat 12 so as to surround the saddle-type superconducting coil 20 and the support frame 30. The heat shield 24 is provided to suppress the intrusion of radiant heat from the surrounding environment 16 into the saddle-type superconducting coil 20.

[0026] In order to prevent the magnetic field generated by the saddle-shaped superconducting coil 20 from leaking to the outside, the magnetic shield 26 covers the outer peripheral wall 12b, the top plate 12c, and the bottom plate 12d of the cryostat 12. The magnetic shield 26 is formed of a magnetic material such as iron, and is disposed adjacent to the outer peripheral wall 12b, the top plate 12c, and the bottom plate 12d of the cryostat 12. The magnetic shield 26 does not cover the inner peripheral wall 12a of the cryostat 12 so as not to prevent the saddle-shaped superconducting coil 20 from generating a magnetic field in the bore 18.

[0027] Cryostat 12 includes a pair of cryocoolers 28 that cool a pair of saddle-shaped superconducting coils 20, a thermal shield 24, and a support frame 30. An exemplary arrangement of cryocoolers 28 in cryostat 12 is shown in Figures 2 and 3.

[0028] The cryocooler 28 is, for example, a two-stage Gifford-McMahon (GM) refrigerator, and includes a first cooling stage cooled to a first cooling temperature and a second cooling stage cooled to a second cooling temperature lower than the first cooling temperature. The cryocooler 28 is installed in the cryostat 12 such that the first cooling stage and the second cooling stage are disposed in the internal space 14 of the cryostat 12. The first cooling stage of the cryocooler 28 cools the thermal shield 24 to the first cooling temperature, and the second cooling stage cools the saddle-type superconducting coil 20 and the support frame 30 to the second cooling temperature. The first cooling temperature may be, for example, in the range of 30K to 80K, and the second cooling temperature may be, for example, in the range of 3K to 20K.

[0029] The pair of saddle-type superconducting coils 20, the heat shield 24, and the support frame 30 are disposed in the internal space 14 so as to be exposed to a vacuum environment. These internal components of the cryostat 12 are cooled by a cryogenic refrigerator 28, by so-called conduction cooling. The heat shield 24 is thermally coupled to a first cooling stage of the cryogenic refrigerator 28 via a first heat transfer member, and is directly cooled by the first cooling stage. The saddle-type superconducting coil 20 is thermally coupled to a second cooling stage of the cryogenic refrigerator 28 via a second heat transfer member, and is directly cooled by the second cooling stage.

[0030] Therefore, in this embodiment, the cryostat 12 does not use immersion cooling in which the saddle-type superconducting coil 20 is immersed in a cryogenic liquid refrigerant such as liquid helium for cooling. The cryostat 12 is not provided with a liquid refrigerant tank for accommodating the saddle-type superconducting coil 20 together with a cryogenic liquid refrigerant. The support frame 30 is merely adjacent to the saddle-type superconducting coil 20 in the internal space 14 of the cryostat 12, and does not form a closed compartment surrounding the saddle-type superconducting coil 20.

[0031] One of the pair of cryogenic refrigerators 28 is installed in the cryostat 12 on one side of the bore 18 between the pair of saddle-shaped superconducting coils 20 in the circumferential direction of the cryostat 12. The other cryogenic refrigerator 28 is installed in the cryostat 12 on the opposite side of the bore 18 between the pair of saddle-shaped superconducting coils 20 in the circumferential direction of the cryostat 12. For example, as shown in the figure, the pair of cryogenic refrigerators 28 may be arranged on the Y axis. One of the pair of cryogenic refrigerators 28 may be arranged on the +Y side and the other on the -Y side with the single crystal pulling shaft 112 in between. As an example, the cryogenic refrigerator 28 is installed on the top plate 12c of the cryostat 12. As shown in FIG. 3, a part of the cryogenic refrigerator 28 protrudes upward from the upper plate of the magnetic shield 26 adjacent to the top plate 12c.

[0032] Such a symmetrical arrangement of the cryogenic refrigerators 28 allows the heat transfer distances from each cryogenic refrigerator 28 to the saddle-type superconducting coil 20 to be equal, thereby allowing the pair of saddle-type superconducting coils 20 to be uniformly cooled.

[0033] Furthermore, the strong magnetic field generated by the saddle-type superconducting coil 20 may affect the behavior of the cryogenic refrigerator 28, and in some cases may result in a decrease in the refrigeration capacity. On the XY plane, the magnetic field is strongest on the X axis and weakest on the Y axis. Therefore, the location where the above-mentioned cryogenic refrigerator 28 is installed is selected to be a place with a low magnetic field. This makes it possible to reduce the adverse effects of the magnetic field on the cryogenic refrigerator 28.

[0034] In order to achieve such advantageous effects, it is not essential that the two cryocoolers 28 are disposed strictly on the Y-axis. As shown in Fig. 2, the cryocoolers 28 may be disposed at an angle Δθ away from the circumferential end of the saddle-type superconducting coil 20 in the circumferential direction. The angle Δθ may be, for example, at least 4 degrees. In this manner, by disposing the cryocoolers 28 away from the saddle-type superconducting coil 20 in the circumferential direction, adverse effects of the magnetic field on the cryocoolers 28 can be reduced.

[0035] The support frame 30 is disposed radially outside the pair of saddle-type superconducting coils 20 in the internal space 14 of the cryostat 12, and supports the pair of saddle-type superconducting coils 20. The support frame 30 is formed in a ring shape so as to surround the bore 18. The support frame 30 is a structure that rigidly connects the saddle-type superconducting coils 20 so as to maintain the relative positions of the saddle-type superconducting coils 20 against the electromagnetic force acting on the saddle-type superconducting coils 20 during operation of the superconducting magnet device 10, and may also be called a rigid frame. The support frame 30 is formed of a metal material such as stainless steel or other suitable high-strength material to achieve the required rigidity.

[0036] The support frame 30 includes a pair of coil mounts 32 having a curved shape based on the curvature of the saddle-type superconducting coil 20 , and a pair of linear connecting beams 34 connecting the pair of coil mounts 32 .

[0037] The coil mount 32 is a portion of the support frame 30 on which the saddle-type superconducting coil 20 is installed. The coil mount 32 is curved along the saddle-type superconducting coil 20, adjacent to the radially outer side of the saddle-type superconducting coil 20, and supports the saddle-type superconducting coil 20. By making the coil mount 32 have a curved shape in accordance with the saddle-type superconducting coil 20 in this manner, when an electromagnetic force acts on the saddle-type superconducting coil 20 during operation of the superconducting magnet device 10, the coil mount 32 can effectively support this electromagnetic force and suppress deformation that may occur in the saddle-type superconducting coil 20.

[0038] One connecting beam 34 connects one ends of the coil mounts 32 to each other, and the other connecting beam 34 connects the other ends of the coil mounts 32 to each other. The connecting beam 34 is not a portion where the saddle-type superconducting coil 20 is installed, and therefore does not need to have a curved shape along the saddle-type superconducting coil 20, unlike the coil mount 32. By making the connecting beam 34 flat, it is easier to manufacture than a curved shape. This can lead to a reduction in the manufacturing cost of the support frame 30.

[0039] 3, the pair of linear connecting beams 34 may have a smaller dimension in the vertical direction (i.e., in the direction of the single crystal pulling axis 112) than the pair of coil mounts 32. This allows the connecting beams 34 and, in turn, the support frame 30 to be lighter than when the connecting beams 34 and the coil mounts 32 have the same vertical dimension. In addition, by utilizing the fact that the height of the connecting beams 34 is lower than the coil mounts 32, it is also possible to ensure a space for arranging the cryogenic refrigerator 28 above the connecting beams 34.

[0040] As an alternative example, the connecting beam 34 may be curved in an arc shape along the cylindrical shape of the cryostat 12, similar to the coil mount 32. The support frame 30 may be formed in an annular shape from the coil mount 32 and the connecting beam 34. Also, the coil mount 32 and the connecting beam 34 may be prepared as separate members, and the support frame 30 may be formed by connecting these members. Alternatively, the support frame 30 may be formed as a single structure in which the coil mount 32 and the connecting beam 34 are integrated.

[0041] 3 and 5, the superconducting magnet device 10 is provided with a plurality of horizontal load supports 36 that horizontally support the support frame 30. The horizontal load supports 36 support the radially outward electromagnetic force acting on the saddle-type superconducting coil 20 during operation of the superconducting magnet device 10.

[0042] The horizontal load support 36 has a rod-like shape extending in the radial direction of the cryostat 12, one end of which is supported by the magnetic shield 26, and the other end of which is supported by the coil mount 32 of the support frame 30. The horizontal load support 36 extends from the magnetic shield 26 through the outer peripheral wall 12b and the thermal shield 24 of the cryostat 12 to the coil mount 32. The radially outward electromagnetic force acting on the saddle-type superconducting coil 20 is supported by the horizontal load support 36 with the magnetic shield 26 as a fulcrum.

[0043] At least a part of the horizontal load support 36, for example, the end of the horizontal load support 36, may be made of a metal material such as stainless steel. In order to suppress heat input from the magnetic shield 26 to the saddle-type superconducting coil 20 through the horizontal load support 36, at least a part of the horizontal load support 36, for example, a rod-shaped body connecting both ends of the horizontal load support 36, may be made of a heat insulating material such as fiber-reinforced plastic.

[0044] The support frame 30 has a recess 38 formed radially inward from the outer circumferential surface of the support frame 30. The recess 38 is provided in the coil mount 32 of the support frame 30 to receive the end of the horizontal load support 36 on the support frame 30 side. The support frame 30 is supported by the horizontal load support 36 at the recess 38. The recess 38 is also formed in the coil mount 32 as a protrusion 39 that protrudes radially into the inner space of the saddle-type superconducting coil 20.

[0045] In this way, a part of the horizontal load support 36 is accommodated in the recess 38 of the support frame 30, so that the total radial dimension of the horizontal load support 36 and the support frame 30 can be reduced. This can lead to a reduction in the size of the superconducting magnet device 10. At the same time, the radial length of the horizontal load support 36 can be increased. This makes it possible to ensure a heat insulating distance between the magnetic shield 26 and the support frame 30 by the horizontal load support 36, and to reduce the thermal load on the saddle-type superconducting coil 20.

[0046] Two horizontal load supports 36 are arranged for one saddle-type superconducting coil 20. When an electromagnetic force acts on the saddle-type superconducting coil 20, bending stress is likely to occur in the coil at the corners of the coil (i.e., the ends of the coil in the circumferential direction of the cryostat 12). In order to effectively suppress bending deformation of the coil due to this bending stress, the horizontal load supports 36 may be arranged near the corners of the saddle-type superconducting coil 20. Therefore, recesses 38 for receiving the horizontal load supports 36 may be formed at the circumferential ends of the coil mounts 32 of the support frame 30. If necessary, an additional (i.e., a third) horizontal load support 36 may be arranged for each saddle-type superconducting coil 20.

[0047] 6 is a schematic diagram showing a part of a developed view of the saddle-type superconducting coil 20 and the support frame 30 as viewed from the radially inner side according to the embodiment. As shown in FIG. 5 and FIG. 6, a first support 40 and a second support 42 are attached to the support frame 30 in order to fix the saddle-type superconducting coil 20 to the support frame 30.

[0048] The first support 40 is a plate disposed radially inward of the saddle-type superconducting coil 20, and is attached to the coil mount 32 of the support frame 30 to press the saddle-type superconducting coil 20 radially outward toward the support frame 30. Each saddle-type superconducting coil 20 has a first coil end face 20a facing radially outward and a second coil end face 20b facing radially inward, and the first coil end face 20a contacts the coil mount 32 and the second coil end face 20b contacts the first support 40. The first support 40 is attached to the support frame 30 so as to sandwich the saddle-type superconducting coil 20 between these two coil end faces. The first support 40 may be attached to the support frame 30 via the second support 42, or may be attached directly to the support frame 30.

[0049] In this way, by pressing the saddle-type superconducting coil 20 against the support frame 30 by the first support 40, the displacement of the saddle-type superconducting coil 20 in the radial direction of the cryostat 12 can be suppressed, and the radial position of the saddle-type superconducting coil 20 on the support frame 30 can be maintained.

[0050] Each saddle-type superconducting coil 20 has two coil side faces connecting the first coil end face 20a and the second coil end face 20b, i.e., the first coil side face 20c on the outer periphery of the coil and the second coil side face 20d on the inner periphery of the coil. The second support 42 is attached to the support frame 30 so as to sandwich the saddle-type superconducting coil 20 between these two coil side faces.

[0051] The second support 42 includes a first member 42a and a second member 42b, the first member 42a contacting the first coil side surface 20c and the second member 42b contacting the second coil side surface 20d. The first member 42a is a wall covering a part of the first coil side surface 20c, and the second member 42b is a wall covering a part of the second coil side surface 20d. The first member 42a and the second member 42b are each attached to the support frame 30. In order to sandwich the saddle-type superconducting coil 20 between the first member 42a and the second member 42b, one of the first member 42a and the second member 42b, for example the second member 42b, is provided with a pressing tool such as a leveling block, a screw jack, or a leaf spring.

[0052] In this manner, by sandwiching the saddle-type superconducting coil 20 between the second supports 42, bending of the saddle-type superconducting coil 20 that may occur when an electromagnetic force acts on the saddle-type superconducting coil 20 can be suppressed.

[0053] By providing both the first support 40 and the second support 42, the displacement and deformation of the saddle-type superconducting coil 20 relative to the support frame 30 is effectively suppressed. This helps to suppress the occurrence of quenching in the saddle-type superconducting coil 20.

[0054] 6, these coil supports are provided not only at the top and bottom of the saddle-type superconducting coil 20 but also at the corners. In this way, the first supports 40 and the second supports 42 are provided at multiple points along the saddle-type superconducting coil 20, thereby enabling the saddle-type superconducting coil 20 to be firmly fixed to the support frame 30 over the entire circumference.

[0055] The first support 40 and the second support 42 are provided discretely at a plurality of locations instead of being provided continuously along the entire set of the saddle-type superconducting coil 20. By adopting such a divided structure, the first support 40 and the second support 42 can be easily manufactured.

[0056] FIG. 7 is a front view showing a schematic diagram of the support frame 30 seen from the radially outer side according to the embodiment. The superconducting magnet device 10 is provided with a plurality of vertical load supports 44 that support the support frame 30 in the vertical direction. The vertical load supports 44 can support the weight acting on the internal components of the cryostat 12, such as the saddle-type superconducting coil 20. The plurality of vertical load supports 44 may be arranged at equal angular intervals in the circumferential direction of the cryostat 12. For example, six vertical load supports 44 may be arranged at 60 degree intervals. Note that FIG. 7 shows the cryocooler 28 together with the support frame 30.

[0057] The vertical load support 44 has a rod-like shape extending in the vertical direction, one end of which is supported on the bottom surface of the cryostat 12, and the other end of which is supported by the coil mount 32 of the support frame 30. At least a part of the vertical load support 44, for example, the end of the vertical load support 44, may be made of a metal material such as stainless steel. In order to suppress heat input from the cryostat 12 to the saddle-type superconducting coil 20 through the vertical load support 44, at least a part of the vertical load support 44, for example, a rod-like body connecting both ends of the vertical load support 44, may be made of a heat insulating material such as fiber-reinforced plastic.

[0058] 7, the support frame 30 has ribs 46 formed radially outward from the outer circumferential surface of the support frame 30, and is supported by the vertical load supports 44 at the ribs 46. The ribs 46 extend in the circumferential direction on the outer circumferential surface of the coil mount 32 of the support frame 30. By connecting the vertical load supports 44 to the horizontally extending ribs 46 in this way, the ribs 46 act as a sort of buffer material, and it is possible to reduce the direct load on the vertical load supports 44 due to the impact load on the support frame 30 (for example, the electromagnetic force of the saddle-type superconducting coil 20, impacts that may occur during transportation of the superconducting magnet device 10, etc.).

[0059] Although not shown, the cryostat 12 may be provided with other components, such as a current introduction terminal connected to the saddle-type superconducting coil 20, a vacuum exhaust port for evacuating the cryostat 12, and a measurement port connected to a measuring device in the cryostat 12. At least one of the current introduction terminal, the vacuum exhaust port, and the measurement port may be provided on the upper or lower surface of the cryostat 12.

[0060] As mentioned at the beginning of this book, in the existing designs of single crystal pulling equipment using saddle-type superconducting coils, the support structure of the saddle-type superconducting coil is often attached radially inside the saddle-type superconducting coil. In this case, the saddle-type superconducting coil is placed radially away from the single crystal pulling furnace to which the magnetic field is to be applied by the amount of space occupied by the support structure. Since the magnetic field generated by the coil is proportional to the negative third power of the distance, the magnetomotive force required for the coil can increase significantly as the saddle-type superconducting coil is moved away from the single crystal pulling furnace. In other words, the efficiency of magnetic field generation tends to decrease. This leads to an increase in the amount of superconducting wire required for the coil, which can undesirably increase the manufacturing cost of the superconducting magnet device.

[0061] In contrast, according to the embodiment, the saddle-type superconducting coil 20 is supported by the support frame 30 at its radially outer side, so that the saddle-type superconducting coil 20 can be disposed close to the bore 18. This improves the efficiency of magnetic field generation, reduces the amount of superconducting wire used, and further reduces the manufacturing cost of the superconducting magnet device 10.

[0062] Furthermore, during operation of the superconducting magnet device 10, a correspondingly strong electromagnetic force acts on the saddle-type superconducting coil 20 in a direction toward the magnetic shield 26, i.e., in the radially outward direction, in response to the strong magnetic field generated by the saddle-type superconducting coil 20. The saddle-type superconducting coil 20 is strongly pulled toward the magnetic shield 26.

[0063] In the above-mentioned existing designs, since the support structure of the saddle-type superconducting coil is provided radially inward, the radially outward force acting on the coil tends to pull the coil away from the support structure. In order to prevent the coil from being separated from the support structure, it may be necessary to add structural members or strengthen the support structure. The resulting weight and size increase may lead to an increase in the manufacturing cost of the device, which is undesirable.

[0064] In contrast, according to the embodiment, the radially outward force acting on the saddle-type superconducting coil 20 acts to press the saddle-type superconducting coil 20 against the support frame 30. Therefore, contrary to the existing technology, the support frame 30 can effectively support the saddle-type superconducting coil 20 with a relatively simple structure. As a result, the weight of the superconducting magnet device 10 can be reduced.

[0065] Typically, the cryostat 12 mounted on the single crystal pulling apparatus 100 has an outer diameter that is approximately 1.5 times its inner diameter (i.e., the diameter of the bore 18). In order to accommodate the cryostat 12 having such radial dimensions, the pair of saddle-type superconducting coils 20 may be preferably disposed in the internal space 14 of the cryostat 12 within a range of 1.05 to 1.32 times the diameter of the bore 18. In other words, the lower limit of the inner diameter of the saddle-type superconducting coil 20 may be set to 1.05 times the diameter of the bore 18 of the cryostat 12. Also, the upper limit of the outer diameter of the saddle-type superconducting coil 20 may be set to 1.32 times the diameter of the bore 18 of the cryostat 12.

[0066] A heat shield 24 is disposed radially inside the saddle-type superconducting coil 20 in the internal space 14. In order to cool the saddle-type superconducting coil 20 to a temperature lower than that of the heat shield 24, it is desirable to reliably avoid physical contact between the saddle-type superconducting coil 20 and the heat shield 24. From this viewpoint, the lower limit value of 1.05 times as described above is set.

[0067] A heat shield 24 is also disposed radially outside the support frame 30 in the internal space 14. The support frame 30, together with the saddle-type superconducting coil 20, is cooled to a lower temperature than the heat shield 24. It is desirable to reliably avoid physical contact between the support frame 30 and the heat shield 24. Also, in order to provide the desired rigidity, the support frame 30 needs to have a certain radial size. From this viewpoint, the above-mentioned upper limit value of 1.32 times is set.

[0068] Similarly, the pair of linear connecting beams 34 may be disposed within a range of 1.05 to 1.32 times the diameter of the bore 18 in the internal space 14 of the cryostat 12. In this manner, in consideration of avoiding physical contact between the connecting beams 34 and the thermal shield 24 and ensuring thermal insulation therebetween, the lower limit of the radial inner dimension of the connecting beams 34 may be set to 1.05 times the diameter of the bore 18, and the upper limit of the radial outer dimension of the connecting beams 34 may be set to 1.32 times the diameter of the bore 18.

[0069] The present invention has been described above based on examples. It will be understood by those skilled in the art that the present invention is not limited to the above-described embodiments, that various design changes are possible, that various modifications are possible, and that such modifications are also within the scope of the present invention. Various features described in relation to one embodiment can also be applied to other embodiments. A new embodiment resulting from a combination has the combined effects of each of the combined embodiments.

[0070] FIG. 8 is a perspective view showing a schematic diagram of another example of the arrangement of superconducting coils in the superconducting magnet device 10 according to the embodiment. As shown in the figure, the superconducting magnet device 10 may include an additional superconducting coil 50 in addition to the pair of saddle-type superconducting coils 20 to assist in adjusting the magnetic field distribution in the superconducting magnet device 10. The additional superconducting coil 50 may be a coil smaller than the saddle-type superconducting coil 20 and may be disposed inside the saddle-type superconducting coil 20. The additional superconducting coil 50 may be a circular coil or a saddle-type coil. Both the saddle-type superconducting coil 20 and the additional superconducting coil 50 may be supported by the support frame 30 described above.

[0071] The single crystal pulling apparatus equipped with the superconducting magnet apparatus 10 according to the embodiment may be a single crystal pulling apparatus for producing single crystals of semiconductor materials other than silicon or other materials.

[0072] If applicable, the superconducting magnet device 10 may be mounted on an apparatus other than a single crystal pulling apparatus. The superconducting magnet device 10 is mounted on a high magnetic field device as a magnetic field source for the high magnetic field device, and can generate a high magnetic field required for the device.

[0073] The present invention has been described using specific terms based on the embodiments, but the embodiments merely show one aspect of the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments without departing from the spirit of the present invention as defined in the claims. [Explanation of symbols]

[0074] 10 superconducting magnet device, 12 cryostat, 12a inner wall, 12b outer wall, 14 internal space, 18 bore, 20 saddle-shaped superconducting coil, 20a first coil end face, 20b second coil end face, 28 cryogenic refrigerator, 30 support frame, 32 coil mount, 34 connecting beam, 36 horizontal load support, 38 recess, 40 first support, 42 second support, 44 vertical load support, 46 rib.

Claims

1. a cryostat including an inner peripheral wall disposed radially outside the bore so as to surround the bore, and an outer peripheral wall disposed radially outside the inner peripheral wall so as to surround the inner peripheral wall, the cryostat providing a vacuum environment in an internal space defined between the inner peripheral wall and the outer peripheral wall; a pair of saddle-shaped superconducting coils facing each other across the bore, the pair of saddle-shaped superconducting coils being disposed in the internal space so as to be exposed to the vacuum environment; a support frame disposed radially outside the pair of saddle-shaped superconducting coils in the internal space, the support frame supporting the pair of saddle-shaped superconducting coils.

2. 2. The superconducting magnet apparatus according to claim 1, wherein the pair of saddle-shaped superconducting coils are disposed within a range of 1.05 to 1.32 times the diameter of the bore in the internal space.

3. The pair of saddle-shaped superconducting coils are concavely curved toward the bore, 2. The superconducting magnet apparatus according to claim 1, wherein the support frame comprises a pair of coil mounts having a curved shape based on the curvature of the saddle-shaped superconducting coil, and a pair of linear connecting beams connecting the pair of coil mounts.

4. 4. The superconducting magnet apparatus according to claim 3, wherein the pair of linear connecting beams have a smaller vertical dimension than the pair of coil mounts.

5. 4. The superconducting magnet apparatus according to claim 3, wherein the pair of linear connecting beams are disposed within a range of 1.05 to 1.32 times the diameter of the bore in the internal space.

6. Further, a horizontal load support is provided to support the support frame in a horizontal direction.

6. A superconducting magnet device according to claim 1, wherein the support frame has a recess formed radially inward from an outer circumferential surface of the support frame, and the horizontal load support is supported by the recess.

7. Further comprising a vertical load support that supports the support frame in a vertical direction, 6. A superconducting magnet device according to claim 1, wherein the support frame has ribs formed radially outward from the outer circumferential surface of the support frame, and the support frame is supported by the vertical load support at the ribs.

8. 6. The superconducting magnet apparatus according to claim 1, further comprising a first support attached to the support frame so as to press the saddle-shaped superconducting coil radially outward against the support frame.

9. Each saddle-shaped superconducting coil includes a first coil end surface facing radially outward, a second coil end surface facing radially inward, and two coil side surfaces connecting the first coil end surface and the second coil end surface, 6. The superconducting magnet apparatus according to claim 1, further comprising a second support attached to the support frame so as to sandwich the saddle-shaped superconducting coil on the two coil sides.

10. the cryostat includes a pair of cryogenic refrigerators that cool the pair of saddle-type superconducting coils, one of the pair of cryogenic refrigerators is installed in the cryostat between the pair of saddle-shaped superconducting coils in the circumferential direction of the cryostat and on one side of the bore; 6. The superconducting magnet device according to claim 1, wherein the other of the pair of cryogenic refrigerators is installed in the cryostat between the pair of saddle-shaped superconducting coils in the circumferential direction of the cryostat and on the opposite side to the bore.

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