cryogenic equipment

Abstract

To improve usability of a cryogenic device.SOLUTION: A cryogenic device 10 includes: a cryogenic freezing machine 20; a vacuum vessel 30 having a receiving recessed part 50 at the outer side; and a cover member 52 which is attached to the vacuum vessel 30 so as to cover the receiving recessed part 50. The cryogenic freezing machine 20 is installed in the vacuum vessel 30 so that one part thereof is disposed in the vacuum vessel 30 and the other part is disposed in the receiving recessed part 50 of the vacuum vessel 30, which is covered by the cover member 52. The cryogenic device 10 may further include flexible pipes which are connected to the cryogenic freezing machine 20 and wound around the vacuum vessel 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to cryogenic devices. [Background technology]

[0002] Conventionally, cryogenic devices have been known that include a cryogenic refrigerator and a vacuum vessel. The vacuum vessel contains various objects to be cooled, such as superconducting equipment such as a superconducting coil, other equipment used in a cryogenic environment, and cryogenic refrigerants for cooling these equipment. The cryogenic refrigerator is used to cool the objects. The cryogenic refrigerator has a refrigerant gas expander, also known as a cold head. The cold head is equipped with a low-temperature section for cooling the objects to be cooled and a drive unit for repeatedly generating a refrigeration cycle in the low-temperature section. The low-temperature section is inserted into the vacuum vessel through an opening, and the drive unit is attached to the outside of the vacuum vessel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-132568 Summary of the Invention [Problem to be solved by the invention]

[0004] The inventors have studied the above-mentioned cryogenic device and discovered several problems from the viewpoint of usability. For example, during operation of the cryogenic refrigerator, driving noise caused by the periodic supply and discharge of refrigerant gas to the cold head is constantly generated from the cold head and the refrigerant gas piping, such as the flexible pipe connecting the cold head to the compressor. If quietness is desired in the site where the cryogenic device is used, this driving noise may be unpleasant to the ear.

[0005] Refrigerant gas piping is typically relatively long (for example, 10 to 20 m). This is useful for increasing the flexibility of placement, such as placing the compressor far from the cold head, but if it is placed close to the cold head, the excess piping may get in the way on site. However, because the volume of the piping affects the refrigeration performance of the cryogenic refrigerator, simply changing the length on site is not necessarily permitted in the design of the cryogenic refrigerator.

[0006] The cold head drive mechanism protrudes from the wall of the vacuum vessel, which can be an obstacle when workers work around the cryogenic device. For example, in large cryogenic devices, workers may walk on the top of the vacuum vessel, and there is a risk that the worker may trip over the cold head drive mechanism protruding from the top of the vacuum vessel. It is desirable to further improve safety.

[0007] One exemplary purpose of certain aspects of the present invention is to address at least one of these problems and improve the usability of cryogenic devices. [Means for solving the problem]

[0008] According to one aspect of the present invention, a cryogenic device includes a hollow cylindrical vacuum vessel defining a vacuum region in which multiple superconducting coils are disposed, a drive unit, and a cooling stage for cooling at least one of the multiple superconducting coils, the cold head being installed in the vacuum vessel such that the drive unit is located outside the vacuum vessel and the cooling stage is located in the vacuum region. The multiple superconducting coils include a first superconducting coil and a second superconducting coil disposed circumferentially of the vacuum vessel and spaced apart from the first superconducting coil. The vacuum vessel includes a receiving recess in which the drive unit is disposed, between the first and second superconducting coils in the circumferential direction.

[0009] According to one aspect of the present invention, a cryogenic device includes a cryogenic refrigerator, a vacuum vessel having an external receiving recess, and a cover member attached to the vacuum vessel so as to cover the receiving recess. The cryogenic refrigerator is installed in the vacuum vessel such that a portion of the cryogenic refrigerator is disposed within the vacuum vessel and another portion is disposed within the receiving recess of the vacuum vessel covered by the cover member.

[0010] According to one aspect of the present invention, a cryogenic device includes a cryogenic refrigerator and a vacuum vessel. The cryogenic refrigerator is installed in the vacuum vessel such that a portion of the cryogenic refrigerator is disposed inside the vacuum vessel and another portion is disposed outside the vacuum vessel. The cryogenic device further includes a flexible tube connected to the cryogenic refrigerator and wound around the vacuum vessel. [Effects of the Invention]

[0011] According to the present invention, the usability of a cryogenic device can be improved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram schematically illustrating a cryogenic device according to an embodiment. [Figure 2] 1 is a diagram schematically illustrating a cryogenic device according to an embodiment. [Figure 3] FIG. 10 is a diagram schematically illustrating an example of a cryogenic device according to another embodiment. [Figure 4] FIG. 10 is a diagram schematically illustrating another example of a cryogenic device according to another embodiment. [Figure 5] FIG. 10 is a diagram schematically illustrating a cryogenic device according to yet another embodiment. [Figure 6] FIG. 10 is a diagram schematically illustrating a cryogenic device according to yet another embodiment. [Figure 7] FIG. 10 is a perspective view schematically illustrating a cryogenic device according to a further embodiment. [Figure 8] FIG. 8 is a top view schematically showing the cryogenic device shown in FIG. 7. [Figure 9]8 is a schematic side development view of the cryogenic device shown in FIG. 7 as viewed from the direction of arrow A. FIG. [Figure 10] 10(a) to 10(c) are diagrams showing schematic diagrams of other examples of the arrangement of the driving parts of the cold head. [Figure 11] 11(a) to 11(c) are diagrams showing schematic diagrams of other receiving recesses. [Figure 12] FIG. 10 is a perspective view schematically showing another example of a cryogenic device according to a further embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the description and drawings, identical or equivalent components, parts, and processes are designated by the same reference numerals, and redundant explanations will be omitted as appropriate. The scale and shape of each part shown in the drawings are set for convenience to facilitate explanation, and should not be interpreted as 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.

[0014] 1 and 2 are diagrams schematically showing a cryogenic device 10 according to an embodiment. Fig. 1 schematically shows the internal structure of the cryogenic device 10, and Fig. 2 schematically shows the external appearance of the cryogenic device 10.

[0015] The cryogenic device 10 includes an object 12 to be cooled, a cryogenic refrigerator 20 that cools the object 12 to be cooled, and a vacuum vessel 30 in which the cryogenic refrigerator 20 is installed and which contains the object 12 to be cooled.

[0016] As will be described in detail later, the vacuum vessel 30 has a receiving recess 50 on the outside, and the cryogenic device 10 has a cover member 52 attached to the vacuum vessel 30 so as to cover the receiving recess 50. The cryogenic refrigerator 20 is installed in the vacuum vessel 30 such that a portion of the cryogenic refrigerator 20 is disposed inside the vacuum vessel 30, and another portion of the cryogenic refrigerator 20 is disposed inside the receiving recess 50 of the vacuum vessel 30 covered by the cover member 52.

[0017] In this embodiment, the cryogenic device 10 is a superconducting magnet device, and the object to be cooled 12 is a superconducting coil. The superconducting magnet device is installed in high-magnetic-field-utilizing equipment as a magnetic field source for, for example, a single crystal pulling device, an NMR system, an MRI system, an accelerator such as a cyclotron, a high-energy physics system such as a nuclear fusion system, or other high-magnetic-field-utilizing equipment (not shown), and can generate the high magnetic field required for the equipment. Note that the cryogenic device 10 may be various devices that utilize a cryogenic environment, and the object to be cooled 12 may be various devices such as sensors used in a cryogenic environment, or even a cryogenic refrigerant such as helium that cools such devices.

[0018] The cryogenic refrigerator 20 includes a compressor (not shown) for a refrigerant gas (e.g., helium gas) and an expander, also called a cold head. The compressor and expander form a refrigeration cycle of the cryogenic refrigerator 20, thereby providing cryogenic cooling. The cryogenic refrigerator 20 is, for example, a two-stage Gifford-McMahon (GM) refrigerator. The cryogenic refrigerator 20 includes a first cooling stage 22a and a second cooling stage 22b as low-temperature sections that are cooled to cryogenic temperatures. These cooling stages are disposed within a vacuum vessel 30. The first cooling stage 22a and the second cooling stage 22b are formed of, for example, a metal material such as copper or another material with high thermal conductivity.

[0019] Cryogenic refrigerator 20 also includes a first cylinder 24a, a second cylinder 24b, a drive unit 26, and a mounting flange 28. First cylinder 24a connects mounting flange 28 to first cooling stage 22a, and second cylinder 24b connects first cooling stage 22a to second cooling stage 22b. Drive unit 26 is attached to mounting flange 28 on the side opposite first cylinder 24a.

[0020] As an example, the first cylinder 24a and the second cylinder 24b are cylindrical members, with the second cylinder 24b having a smaller diameter than the first cylinder 24a. The first cylinder 24a and the second cylinder 24b are arranged coaxially, with the lower end of the first cylinder 24a rigidly connected to the upper end of the second cylinder 24b. When the cryogenic refrigerator 20 is a GM refrigerator, the first cylinder 24a and the second cylinder 24b house a first displacer and a second displacer, respectively, that contain a regenerator material. The first displacer and the second displacer are connected to each other and can reciprocate along the first cylinder 24a and the second cylinder 24b, respectively.

[0021] The drive unit 26 includes a motor and a coupling mechanism that couples the motor to the first and second displacers so as to convert the rotational motion output by the motor into reciprocating motion of these displacers. The drive unit 26 also includes pressure switching valves that periodically switch the pressure inside the first cylinder 24a and the second cylinder 24b between high and low pressures, and these pressure switching valves are also driven by the same motor.

[0022] It should be noted that the cryocooler 20 may be a single-stage GM cryocooler, or alternatively, the cryocooler 20 may be a pulse tube cryocooler, a Stirling cryocooler, or any other type of cryocooler.

[0023] The vacuum vessel 30 includes a vacuum vessel body 30a and a support portion 30b that supports the vacuum vessel body 30a on the floor surface 16. The vacuum vessel 30 may be, for example, a cryostat. A vacuum region 32 is defined within the vacuum vessel body 30a, and the vacuum vessel body 30a is configured to separate the vacuum region 32 from the external environment 14. The external environment 14 may be an atmospheric region. The object to be cooled 12 and the low-temperature portion of the cryogenic refrigerator 20 are disposed in the vacuum region 32 and are vacuum-insulated from the external environment 14. To improve the insulating performance, an insulating material may be provided along the surface of or inside the wall member of the vacuum vessel body 30a that separates the vacuum region 32 from the external environment 14.

[0024] As an example, the vacuum vessel body 30a is a cylindrical airtight vessel having flat upper and lower end faces and a cylindrical side surface connecting these two end faces. The support part 30b is a cylindrical base with a smaller diameter than the vacuum vessel body 30a, and connects the lower end face of the vacuum vessel body 30a to the floor surface 16. However, the vacuum vessel body 30a is not limited to this specific shape and may have other shapes, such as a square box. The support part 30b may also have various shapes.

[0025] In this embodiment, the opening of the vacuum vessel body 30a into which the cryogenic refrigerator 20 is inserted is provided on the upper end surface of the vacuum vessel body 30a. A buried pipe 54 extends from this opening toward the interior of the vacuum vessel body 30a. The upper end of the buried pipe 54 is attached to the opening of the vacuum vessel body 30a, and the mounting flange 28 of the cryogenic refrigerator 20 is attached to the lower end of the buried pipe 54. Low-temperature parts of the cryogenic refrigerator 20, such as the first cooling stage 22a and the second cooling stage 22b, are inserted into the vacuum vessel body 30a through the buried pipe 54. The drive unit 26 on the mounting flange 28 is placed in a receiving recess 50 defined within the buried pipe 54. A cover member 52 is attached to the upper end of the buried pipe 54 or to the vacuum vessel body 30a so as to cover the receiving recess 50. The buried pipe 54 is, for example, cylindrical, and the cover member 52 may be a disk shape having approximately the same diameter as the upper end of the buried pipe 54.

[0026] In this way, the cryogenic refrigerator 20 is installed in the vacuum vessel 30 such that the drive unit 26 is placed in the receiving recess 50 outside the vacuum vessel 30 covered with the cover member 52, and the low temperature unit is placed inside the vacuum vessel 30. The cryogenic refrigerator 20 is also installed in the vacuum vessel 30 in a vertical orientation with the drive unit 26 facing upward and the low temperature unit facing downward.

[0027] A first seal 56a that seals the vacuum region 32 from the external environment 14 is provided between the opening of the vacuum vessel body 30a and the upper end of the buried pipe 54 attached to the opening. A second seal 56b that seals the vacuum region 32 from the external environment 14 is provided between the mounting flange 28 of the cryogenic refrigerator 20 and the lower end of the buried pipe 54 attached thereto. The first seal 56a and the second seal 56b may be appropriate sealing members such as O-rings. In this way, the buried pipe 54, together with the vacuum vessel body 30a, defines the vacuum region 32. Therefore, the receiving recess 50 defined inside the buried pipe 54 is in the external environment 14, not the vacuum region 32.

[0028] A radiant heat shield 40 is disposed in the vacuum region 32, along with the low-temperature portion of the cryogenic refrigerator 20 and the object to be cooled 12. The radiant heat shield 40 is thermally coupled to the first cooling stage 22a and cooled to a first cooling temperature. The radiant heat shield 40 is directly attached to the first cooling stage 22a and thermally coupled thereto. Alternatively, the radiant heat shield 40 may be attached to the first cooling stage 22a via a flexible or rigid heat-transfer member. The radiant heat shield 40 is formed of a metal material, such as copper, or another material with high thermal conductivity. The radiant heat shield 40 is disposed to surround the object to be cooled 12, which is cooled to a second cooling temperature, the second cooling stage 22b of the cryogenic refrigerator 20, and other low-temperature portions, and can thermally protect these low-temperature portions from external radiant heat.

[0029] The object 12 to be cooled is thermally coupled to the second cooling stage 22b via the heat transfer member 42 and is cooled to the second cooling temperature. The heat transfer member 42 may be a flexible or rigid heat transfer member, and is made of, for example, a metal material such as copper or other material with high thermal conductivity. The object 12 to be cooled may be directly attached to the second cooling stage 22b.

[0030] During operation of the cryogenic refrigerator 20, the first cooling stage 22a is cooled to a first cooling temperature, for example, 30K to 80K, and the second cooling stage 22b is cooled to a second cooling temperature lower than the first cooling temperature, for example, 3K to 20K. The radiant heat shield 40 is cooled to the first cooling temperature by the first cooling stage 22a. The object 12 to be cooled is cooled to the second cooling temperature by the second cooling stage 22b.

[0031] In many existing cryogenic equipment designs, the drive unit of the cryogenic refrigerator is exposed to the outside of the vacuum vessel, protruding from the wall of the vacuum vessel. Generally, cryogenic refrigerators generate intake and exhaust noise during operation. This noise is primarily caused by the refrigerant gas flow associated with the periodic pressure switching between high and low pressures by the pressure switching valve in the drive unit. The drive noise of such cryogenic refrigerators occurs continuously at the frequency of the pressure switching (e.g., approximately 1 Hz). In environments where quietness is desired, there is concern that this noise may be unpleasant to the ears. Additionally, the protruding portion of the drive unit from the wall of the vacuum vessel can be an obstacle for workers working around the cryogenic equipment.

[0032] In the cryogenic device 10 according to the embodiment, a portion of the cryogenic refrigerator 20, which is a noise source, is covered with the cover member 52. The soundproofing effect of the cover member 52 can reduce the driving noise of the cryogenic refrigerator 20. In particular, because the drive unit 26 of the cryogenic refrigerator 20 is covered with the cover member 52, it is possible to effectively reduce the noise generated by the drive unit 26 being heard in the surrounding area. This can improve the quietness of the cryogenic device 10.

[0033] Furthermore, in the cryogenic device 10 according to the embodiment, a portion of the cryogenic refrigerator 20 is disposed within the receiving recess 50. This allows the portion of the cryogenic refrigerator 20 that protrudes from the vacuum vessel 30 to be reduced or eliminated. This makes it possible to prevent the protruding portion from getting in the way of workers. In a large cryogenic device 10, workers may walk on the top surface of the vacuum vessel 30, but since the protruding portion from the top surface of the vacuum vessel is small, the risk of the worker tripping over it is reduced, thereby improving safety.

[0034] 2, the vacuum vessel 30 has an overall cylindrical shape with the cover member 52 attached. The upper end surface of the vacuum vessel body 30a with the cover member 52 attached is substantially flat, and may have only a slight step of approximately the thickness of the cover member 52. This can be considered to have no protruding parts on the upper end surface of the vacuum vessel body 30a, minimizing the risk of an operator tripping when walking.

[0035] Furthermore, in the cryogenic device 10 according to the embodiment, by burying the cryogenic refrigerator 20 in the vacuum vessel 30, it becomes easier to position the low-temperature part of the cryogenic refrigerator 20 further inside the vacuum vessel 30, i.e., closer to the object to be cooled 12, compared to existing designs that do not do so. This shortens the heat transfer path from the low-temperature part of the cryogenic refrigerator 20 to the object to be cooled 12, which can lead to efficient cooling of the object to be cooled 12.

[0036] The drive unit 26 of the cryogenic refrigerator 20 may generate heat during operation. Covering the drive unit 26 with the cryogenic refrigerator 20 may trap heat within the receiving recess 50. Therefore, as illustrated in Fig. 1 , a heat dissipation measure for the cryogenic refrigerator 20 may be taken within the receiving recess 50. The cryogenic device 10 may include a heat transfer element 60 disposed in the receiving recess 50 so as to thermally couple a portion of the cryogenic refrigerator 20 disposed in the receiving recess 50 to the cover member 52.

[0037] The heat transfer element 60 may be disposed in the receiving recess 50 so as to be sandwiched between the cover member 52 and a portion of the cryogenic refrigerator 20 (e.g., the drive unit 26). Alternatively, the heat transfer element 60 may be disposed in the receiving recess 50 so as to be sandwiched between the buried pipe 54 and a portion of the cryogenic refrigerator 20. By fixing the cover member 52 to the buried pipe 54, the heat transfer element 60 may be pressed against the top surface, side surface, or other surface of the portion of the cryogenic refrigerator 20 disposed in the receiving recess 50.

[0038] The heat transfer element 60 may be an elastic heat transfer member made of a highly thermally conductive material (e.g., a metal material such as copper) so as to act as a spring that is compressed between the cover member 52 and the cryogenic refrigerator 20. Alternatively, the heat transfer element 60 may be a sheet-like heat transfer member that is sandwiched between the cover member 52 and the cryogenic refrigerator 20, and may be made of a highly thermally conductive resin material such as highly thermally conductive rubber or other highly thermally conductive materials.

[0039] To facilitate heat dissipation, heat dissipation fins may be formed on the outer surface of the cover member 52.

[0040] 3 is a schematic diagram showing an example of a cryogenic device 10 according to another embodiment. In this embodiment, the vacuum vessel 30 does not have a receiving recess 50, so the drive unit 26 of the cryogenic refrigerator 20 protrudes from the upper end surface of the vacuum vessel body 30a.

[0041] The drive unit 26 is provided with a high-pressure port 62a that receives high-pressure refrigerant gas and a low-pressure port 62b that delivers low-pressure refrigerant gas. A high-pressure refrigerant gas pipe 64a is connected to the high-pressure port 62a, and a low-pressure refrigerant gas pipe 64b is connected to the low-pressure port 62b. In this embodiment, the high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b are flexible pipes and have flexibility. The high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b are connected to the discharge port and the suction port of the compressor 18, respectively.

[0042] The high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b are relatively long (for example, 10 to 20 m). As mentioned above, this is useful for increasing the flexibility of the placement location, such as placing the compressor 18 far from the cold head, but if they are placed close to each other, the excess piping may become a hindrance on-site. However, because the volume of the refrigerant gas pipe affects the refrigeration performance of the cryogenic refrigerator 20, simply changing the length alone on-site is not necessarily permitted in the design of the cryogenic refrigerator 20. Furthermore, because the refrigerant gas pipe, together with the cryogenic refrigerator 20, constitutes a high-pressure gas container, it is difficult to simply cut the refrigerant gas pipe midway.

[0043] Therefore, the flexible pipes connected to the cryogenic refrigerator 20, i.e., the high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b, are wound around the vacuum vessel 30. As shown in the figure, the high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b are wound like a reel around the outer periphery of the support part 30b of the vacuum vessel 30, taking advantage of its cylindrical shape. Recesses for accommodating these flexible pipes may be provided on the outer periphery of the support part 30b. In this way, excess flexible pipes can be stored.

[0044] Alternatively, the high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b may be wound around the side or end face (e.g., the lower end face) of the vacuum vessel body 30a. A recess 65 for accommodating these flexible pipes may be provided in the surface of the vacuum vessel body 30a.

[0045] A flexible pipe cover 66 may be provided on the vacuum vessel 30 so as to cover the flexible pipe wound around the vacuum vessel 30. In the example shown in Fig. 3, the flexible pipe cover 66 is attached to the support part 30b of the vacuum vessel 30 so as to cover the entire circumference of the flexible pipe wound around the support part 30b. This allows the soundproofing effect of the flexible pipe cover 66 to suppress noise generated from the high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b, thereby improving the quietness of the cryogenic device 10.

[0046] A holding portion 68 may be provided to hold the flexible tube wound around the vacuum container 30. The holding portion 68 may be, for example, a hook attached to the surface of the vacuum container 30. Alternatively, the holding portion 68 may be a flexible gripping tool attached to the surface of the vacuum container 30 and gripping the flexible tube. The holding portion 68 may also be a fastener that is screwed to the surface of the vacuum container 30 to secure the flexible tube. The holding portion 68 may take various forms. Because the flexible tube repeatedly expands and contracts slightly due to pressure fluctuations of the refrigerant gas passing through it, a buffer material may be sandwiched between the holding portion 68 and the flexible tube.

[0047] FIG. 4 is a diagram schematically illustrating another example of a cryogenic device 10 according to another embodiment. As shown in FIG. 4, the cryogenic device 10 may include multiple cryogenic refrigerators 20. The vacuum vessel 30 may include a cylindrical vacuum vessel body 30a and a support portion 30b that supports the vacuum vessel body 30a on the floor surface 16. The multiple cryogenic refrigerators 20 are installed at equal intervals in the circumferential direction on the upper surface of the cylindrical vacuum vessel body 30a. The support portion 30b may be multiple support legs. In this example, four cryogenic refrigerators 20 are provided. In addition, four support legs are provided.

[0048] The winding space for the flexible pipes (high-pressure refrigerant gas pipe 64a, low-pressure refrigerant gas pipe 64b) may be divided for each cryogenic refrigerator 20. For example, as shown in Fig. 4, a different support leg may be used for winding the flexible pipe for each cryogenic refrigerator 20. In this way, when removing one cryogenic refrigerator 20 from the vacuum vessel 30, it is easier to remove only the flexible pipe of that cryogenic refrigerator 20, compared to when the flexible pipes of multiple cryogenic refrigerators 20 are wound in the same winding space.

[0049] Also, separate winding spaces may be provided for the high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b for the same cryogenic refrigerator 20. This can also be applied to the embodiment shown in FIG.

[0050] In the embodiment of Figures 3 and 4, the drive unit 26 of the cryogenic refrigerator 20 protrudes from the vacuum vessel 30 (a receiving recess 50 is not provided in the vacuum vessel 30), but as in the embodiment shown in Figures 1 and 2, the drive unit 26 may be arranged in a receiving recess 50 of the vacuum vessel 30 covered with a cover member 52.

[0051] It is not essential that the receiving recess 50 be formed on one surface of the vacuum vessel 30 as in the embodiment of Figures 1 and 2. As illustrated in Figure 5, the receiving recess 50 may be formed as a notch in a corner formed by two adjacent surfaces of the vacuum vessel 30.

[0052] 5 and 6 are diagrams schematically showing a cryogenic device 10 according to still another embodiment. Fig. 5 schematically shows a part of the internal structure of the cryogenic device 10, and Fig. 6 schematically shows a part of the external appearance of the cryogenic device 10.

[0053] In this embodiment, a receiving recess 50 is formed at the corner formed by the top surface and side surface of the vacuum vessel body 30a. An L-shaped cover member 52 is attached to the vacuum vessel body 30a so as to cover this receiving recess 50. The drive unit 26 of the cryogenic refrigerator 20 is disposed in the receiving recess 50. Unlike the embodiments of FIGS. 1 and 2, in the embodiment of FIG. 5, instead of providing an embedded pipe 54, the receiving recess 50 is formed between the cover member 52 and the surface of the vacuum vessel 30.

[0054] The cover member 52 may be provided with two piping outlets 70 and a wiring outlet 72. These outlets may be openings such as through holes formed in the cover member 52. The high-pressure port 62a and the low-pressure port 62b each extend from the actuator 26 toward the cover member 52 within the receiving recess 50. The high-pressure port 62a is led out of the receiving recess 50 through one of the piping outlets 70, and the low-pressure port 62b is led out of the receiving recess 50 through the other piping outlet 70. Furthermore, electrical wiring connected to the actuator 26 is led out of the receiving recess 50 through the wiring outlet 72. In the illustrated example, the piping outlets 70 and the wiring outlet 72 are provided on a surface of the cover member 52 adjacent to a side surface of the vacuum vessel body 30a. Alternatively, the piping outlets 70 and the wiring outlet 72 may be provided on a surface of the cover member 52 adjacent to the upper end surface of the vacuum vessel body 30a.

[0055] The piping outlet 70 and the wiring outlet 72 may be provided on the cover member 52 shown in FIGS.

[0056] A high-pressure refrigerant gas pipe 64a and a low-pressure refrigerant gas pipe 64b are connected to the high-pressure port 62a and the low-pressure port 62b, respectively. The high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b may be covered with a flexible pipe cover 66. For ease of explanation, the high-pressure refrigerant gas pipe 64a, the low-pressure refrigerant gas pipe 64b, and the flexible pipe cover 66 are omitted from FIG. 6.

[0057] The high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b may be wound around the vacuum vessel 30, similar to the embodiment shown in FIG.

[0058] FIG. 7 is a perspective view that schematically shows a cryogenic device 10 according to a further embodiment. FIG. 8 is a top view that schematically shows the cryogenic device 10 shown in FIG. 7. FIG. 9 is a schematic side development view of the cryogenic device 10 shown in FIG. 7 when viewed from the direction of arrow A. For ease of understanding, FIGS. 8 and 9 show a state in which the cover member 52 shown in FIG. 7 has been removed from the vacuum vessel 30. Also, in FIGS. 8 and 9, some of the components arranged inside the vacuum vessel 30 are shown with dashed lines.

[0059] In this embodiment, the cryogenic device 10 is a superconducting magnet device and includes a plurality of superconducting coils 74, a cryogenic refrigerator cold head 76 that cools the superconducting coils 74, and a vacuum vessel 30 in which the cold head 76 is installed and the superconducting coils 74 are housed. The MCZ (Magnetic Field Applied Czochralski) method is known, in which a magnetic field is applied to a melt in a crucible in a single crystal pulling apparatus in order to control convection of the melt in the crucible, and the cryogenic device 10 can be used as a magnetic field generating source for such a single crystal pulling apparatus. The single crystal pulling apparatus may be, for example, a silicon single crystal pulling apparatus.

[0060] The vacuum vessel 30 has a hollow cylindrical shape and defines a vacuum region within which multiple superconducting coils 74 are disposed. This vacuum region is isolated from the ambient environment surrounding the vacuum vessel 30. The vacuum vessel 30 may be, for example, a cryostat, and during operation of the cryogenic device 10, a cryogenic vacuum environment suitable for turning the superconducting coils 74 into a superconducting state is provided within the interior space of the vacuum vessel 30. The vacuum vessel 30 is formed of a metallic material such as stainless steel or other suitable high-strength material to withstand ambient pressure (e.g., atmospheric pressure). The vacuum vessel 30 is provided with a support portion 30b that supports a vacuum vessel body 30a, which defines the vacuum region within, on the floor surface 16. The support portion 30b may be a plurality of support legs (e.g., four).

[0061] The vacuum vessel 30 defines a central cavity 78 therein. A superconducting coil 74 is disposed outside the central cavity 78 so as to surround the central cavity 78. When the cryogenic device 10 is mounted on a single crystal pulling apparatus, a single crystal pulling furnace including a crucible for containing a melt of single crystal material is disposed in the central cavity 78. The central cavity 78 is part of the environment surrounding the vacuum vessel 30 (i.e., it is outside the vacuum vessel 30) and is, for example, a cylindrical space surrounded by the vacuum vessel 30.

[0062] The multiple superconducting coils 74 include two first superconducting coils 74a and two second superconducting coils 74b. The two first superconducting coils 74a are arranged adjacent to each other in the circumferential direction, and the two second superconducting coils 74b are arranged adjacent to each other in the circumferential direction. The second superconducting coil 74b is arranged spaced apart from the first superconducting coil 74a in the circumferential direction of the vacuum vessel 30. The first superconducting coil 74a and the second superconducting coil 74b are arranged on opposite sides of the central cavity 78. Each superconducting coil 74 has the same shape and size, and in this example, they are circular coils with the same diameter.

[0063] These superconducting coils 74 are each arranged with its central axis oriented in the radial direction of the vacuum vessel 30 (perpendicular to the central axis of the vacuum vessel 30), and generate a magnetic field in the radial direction. The combined magnetic field generated by the superconducting coils 74 may be a magnetic field horizontal to the central cavity 78 (parallel to the floor surface 16). In this case, the cryogenic apparatus 10 can be used as a magnetic field generation source for an HMCZ (Horizontal-MCZ; transverse magnetic field type MCZ) single crystal pulling apparatus, which is known as an example of the MCZ method.

[0064] In this embodiment, the cryogenic device 10 has four superconducting coils 74, but may have a fewer number of superconducting coils 74. For example, the cryogenic device 10 may have one first superconducting coil 74a and one second superconducting coil 74b. In this case, the first superconducting coil 74a and the second superconducting coil 74b may be saddle-shaped coils arranged on opposite sides of the central cavity 78. Alternatively, the cryogenic device 10 may have more superconducting coils 74, such as three (or more) first superconducting coils 74a and three (or more) second superconducting coils 74b.

[0065] The superconducting coils 74 are supported on the vacuum vessel 30 by a support structure disposed within the vacuum vessel 30. The support structure includes, for example, a first support member 80a, a second support member 80b, and a third support member 80c. The first support member 80a is a ring-shaped member that extends around the entire circumference of the vacuum vessel 30 in the circumferential direction of the vacuum vessel 30. The second support member 80b is a coil positioning plate provided for each superconducting coil 74. The second support member 80b is fixed to the end face of the corresponding superconducting coil 74 and is attached to a predetermined location on the first support member 80a. The third support member 80c fixes the second support member 80b to the vacuum vessel 30. For example, the third support member 80c fixes the lower portion of the second support member 80b to the bottom surface of the vacuum vessel 30.

[0066] The cold head 76 includes a drive unit 26 and a cooling stage (e.g., the second cooling stage 22b shown in FIG. 1) that cools at least one of the multiple superconducting coils 74, and is installed in the vacuum vessel 30 such that the drive unit 26 is outside the vacuum vessel 30 and the cooling stage is located in the vacuum region. The cooling stage is thermally coupled to the superconducting coils 74, and the cold head 76 can cool the superconducting coils 74. As in the above-described embodiment, the cold head 76 may be, for example, an expander of a two-stage Gifford-McMahon (GM) refrigerator.

[0067] In this embodiment, two cold heads 76 are installed in the vacuum vessel 30, one cold head 76 cools the first superconducting coil 74a, and the other cold head 76 cools the second superconducting coil 74b. In this manner, one cold head 76 may cool two or more superconducting coils 74. Alternatively, a cold head 76 may be provided for each superconducting coil 74, and one cold head 76 may cool one corresponding superconducting coil 74.

[0068] The vacuum vessel 30 has a receiving recess 50 on the outside, and the cryogenic device 10 includes a cover member 52 attached to the vacuum vessel 30 to cover the receiving recess 50. The cold head 76 is installed on the vacuum vessel 30 such that the drive unit 26 is disposed in the receiving recess 50 on the outside of the vacuum vessel 30 covered by the cover member 52, and the low-temperature unit is disposed inside the vacuum vessel 30. The cold head 76 is installed on the vacuum vessel 30 in a vertical orientation with the drive unit 26 facing upward and the low-temperature unit facing downward. The cover member 52 may be provided with a piping outlet and / or a wiring outlet, similar to the embodiment described with reference to FIGS. 5 and 6.

[0069] The receiving recess 50 is located between the first superconducting coil 74a and the second superconducting coil 74b in the circumferential direction of the vacuum vessel 30. Therefore, in this embodiment, the receiving recess 50 is provided in two locations, and these receiving recesses 50 are located on opposite sides of the central cavity 78. The receiving recess 50 is formed in the upper part of the vacuum vessel 30. By using part of the space between the first superconducting coil 74a and the second superconducting coil 74b as the receiving recess 50, the cryogenic device 10 can be made compact.

[0070] In this way, in the cryogenic device 10 according to the embodiment, the drive unit 26 of the cold head 76 is disposed within the receiving recess 50. This allows the portion of the cold head 76 that protrudes from the vacuum vessel 30 to be reduced or eliminated. This makes it possible to prevent the protruding portion from getting in the way of the worker. In a large cryogenic device 10, workers may walk on the top surface of the vacuum vessel 30, but the small protruding portion from the top surface of the vacuum vessel reduces the risk of the worker tripping over it, thereby improving safety.

[0071] In particular, in this embodiment, the vacuum vessel 30 has an overall cylindrical shape with the cover member 52 attached. The upper end surface of the vacuum vessel body 30a with the cover member 52 attached is almost flat, and may have only a slight step of about the thickness of the cover member 52. This can be considered to have no protruding parts on the upper end surface of the vacuum vessel body 30a, minimizing the risk of an operator tripping when walking.

[0072] In addition to the drive unit 26 of the cold head 76, the receiving recess 50 may also accommodate other devices that would typically protrude from the surface of the vacuum vessel of a cryogenic device. For example, a current introduction terminal 82a for the superconducting coil 74 may be disposed in the receiving recess 50. The receiving recess 50 may also be provided with a port 82b for connecting wiring and piping to internal equipment of the vacuum vessel. This arrangement also reduces or eliminates the portion of the cold head 76 that protrudes from the vacuum vessel 30.

[0073] A magnetic shield 83 may also be provided in the receiving recess 50. The magnetic shield 83 is made of a magnetic material such as iron. The magnetic shield 83 may be disposed in the receiving recess 50 so as to surround at least a portion of the driving unit 26 of the cold head 76. As shown in FIG. 8 , for example, the magnetic shield 83 may be disposed so as to surround the inner circumferential side and both circumferential sides of the driving unit 26. This effectively reduces the magnetic influence of the strong magnetic field generated in the central cavity 78 by the superconducting coil 74 on the operation of the driving unit 26. In addition to or instead of the magnetic shield 83, the cover member 52 may be made of a magnetic material and form a part of the magnetic shield 83.

[0074] A radiation shield (for example, the radiation heat shield 40 shown in FIG. 1) may be provided inside the vacuum vessel 30 so as to surround the superconducting coil 74 and the low-temperature portion of the cold head 76. This radiation shield may have a cylindrical shape that matches the shape of the vacuum vessel 30 and may have a recess at a position that matches the receiving recess 50. In such a recess in the radiation shield, the height of the radiation shield is reduced, thereby making it possible to reduce the temperature difference that may occur above and below the radiation shield.

[0075] In this embodiment, as in the embodiment described with reference to FIG. 1, the cryogenic device 10 may also include a heat transfer element 60 disposed in the receiving recess 50 and thermally coupling the drive portion 26 of the cold head 76 to the cover member 52.

[0076] 10(a) to 10(c) are diagrams showing schematic diagrams of other examples of the arrangement of the drive unit 26 of the cold head 76. As in the embodiment described with reference to FIGS. 7 to 9, the receiving recess 50 is formed in the upper part of the vacuum vessel 30 and is located between the first superconducting coil 74a and the second superconducting coil 74b in the circumferential direction of the vacuum vessel 30 (note that the first superconducting coil 74a and the second superconducting coil 74b are not shown in FIGS. 10(a) to 10(c)).

[0077] 10(a), the cold head 76 may be installed horizontally in the vacuum vessel 30, and in this case, the drive unit 26 of the cold head 76 may also be disposed in the receiving recess 50. Alternatively, as shown in FIG. 10(b), the cold head 76 may be installed diagonally in the vacuum vessel 30. In this way, when the cold head 76 is installed horizontally or diagonally in the vacuum vessel 30, the cooling stage of the cold head 76 can be located closer to the superconducting coil 74 (not shown) than when the cold head 76 is installed vertically, thereby shortening the heat transfer path and enabling more efficient cooling.

[0078] As shown in Figure 10(c), multiple (e.g., two) cold heads 76 may be installed in one receiving recess 50. The two cold heads 76 may be disposed at the circumferential ends of the receiving recess 50. This configuration may be used as an alternative to the embodiment described with reference to Figures 7 to 9 (in which a cold head 76 is disposed in each of the two receiving recesses 50).

[0079] 11(a) to 11(c) are diagrams schematically showing another receiving recess 51. The receiving recess 51 may be formed in the lower part of the vacuum vessel 30. The lower receiving recess 51 is also located between the first superconducting coil 74a and the second superconducting coil 74b in the circumferential direction of the vacuum vessel 30 (note that the first superconducting coil 74a and the second superconducting coil 74b are not shown in FIGS. 11(a) to 11(c)).

[0080] 11(a), the cold head 76 may be installed in the upper receiving recess 50, and the current introduction terminal 82a and the port 82b may be installed in the lower receiving recess 51. Alternatively, conversely, the current introduction terminal 82a and the port 82b may be installed in the upper receiving recess 50, and the cold head 76 may be installed in the lower receiving recess 51.

[0081] As shown in FIG. 11(b), the compressor 18 that supplies working gas to the cold head 76 may be disposed in the lower receiving recess 51. The compressor 18 may be installed on the floor 16, with the upper part of the compressor 18 housed within the receiving recess 51. The compressor 18, together with the cold head 76, constitutes a cryogenic refrigerator. A high-pressure refrigerant gas pipe 64a connects the discharge port of the compressor 18 to the high-pressure port 62a of the drive unit 26, and a low-pressure refrigerant gas pipe 64b connects the suction port of the compressor 18 to the low-pressure port 62b of the drive unit 26. The high-pressure refrigerant gas pipe 64a and the low-pressure refrigerant gas pipe 64b are flexible pipes and have flexibility.

[0082] 11(c), both the cold head 76 and the compressor 18 may be disposed in the lower receiving recess 51. Flexible pipes (e.g., high-pressure refrigerant gas pipe 64a and low-pressure refrigerant gas pipe 64b) connecting the cold head 76 and the compressor 18 may also be housed in the receiving recess 51. The flexible pipes may be wound around the vacuum vessel, for example, in the receiving recess 51. Note that when the receiving recess 51 is provided in the lower part of the vacuum vessel 30, the receiving recess 50 in the upper part of the vacuum vessel 30 may be omitted.

[0083] FIG. 12 is a perspective view schematically illustrating another example of a cryogenic device 10 according to a further embodiment. A fall prevention wall 84 may be provided on the inner periphery of the upper surface of the vacuum vessel 30. The fall prevention wall 84 is provided so as to surround the entire periphery of the central cavity 78 of the vacuum vessel 30. As described above, workers may walk or work on the upper surface of the vacuum vessel 30. The fall prevention wall 84 serves to prevent the worker from dropping a work tool into the central cavity 78 (or the gap between the central cavity 78 and a single crystal pulling furnace arranged in the central cavity 78) or from falling into the central cavity 78. Note that the fall prevention wall 84 may be provided on the outer periphery of the upper surface of the vacuum vessel 30 in addition to or instead of the inner periphery of the upper surface of the vacuum vessel 30.

[0084] Furthermore, to improve safety when workers walk on the top surface of the vacuum vessel 30, the top surface of the vacuum vessel 30 (and / or the cover member 52) may be provided with an anti-slip portion, such as by attaching a checkered steel plate or applying a rubber matte coating. Such an anti-slip portion may be provided on the entire top surface of the vacuum vessel 30, or may be provided only on the outer periphery (or inner periphery) of the top surface of the vacuum vessel 30. To alert workers, the anti-slip portion may be painted in a color different from that of the other portions. Furthermore, the anti-slip portion may be provided so as to cover small irregularities (e.g., bolt heads and countersunk holes) on the top surface of the vacuum vessel 30. This helps prevent dust and the like from accumulating on these irregularities.

[0085] 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, and that various design changes and 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 created by combining embodiments will have the combined effects of the respective combined embodiments.

[0086] The vacuum vessel 30 may include a magnetic shield surrounding at least a portion of the vacuum vessel body 30a. The receiving recess 50 may be formed in the magnetic shield, and the cover member 52 may be attached to the magnetic shield.

[0087] A magnetic shield may be formed to surround the drive unit 26 of the cryogenic refrigerator 20. The cover member 52 may be made of a magnetic material and form part of the magnetic shield. Other members that define the receiving recess 50 (e.g., the buried pipe 54 or the wall surface of the vacuum vessel 30) may be made of a magnetic material and form part of the magnetic shield.

[0088] To improve sound insulation, sound absorbing material may be provided within the receiving recess 50, for example, on the inside of the cover member 52. Similarly, sound absorbing material may be provided on the inside of the flexible tube cover 66.

[0089] Alternatively, instead of a plate that closes the receiving recess 50, the cover member 52 may be a member such as a wire mesh that does not completely close the receiving recess 50. In this case, the soundproofing effect of the cover member 52 decreases, but the refrigerant gas piping and electrical wiring can be easily removed.

[0090] A handle may be provided on the drive portion 26 of the cryogenic refrigerator 20 to facilitate the attachment (i.e., insertion) of the cryogenic refrigerator 20 to the receiving recess 50 of the vacuum vessel 30 and the removal (i.e., pulling out) of the cryogenic refrigerator 20 from the receiving recess 50.

[0091] In the above-described embodiment, the cryogenic refrigerator 20 is installed vertically in the vacuum vessel 30, but the cryogenic refrigerator 20 may be installed in another orientation in the vacuum vessel 30. For example, the cryogenic refrigerator 20 may be installed horizontally in the vacuum vessel 30, in which case the receiving recess 50 may be provided on the side of the vacuum vessel 30. Alternatively, as in the embodiment of FIG. 5, the receiving recess 50 may be provided in a corner of the vacuum vessel 30.

[0092] In the above-described embodiment, the depth of the receiving recess 50 is determined so that the entire height of the drive unit 26 of the cryogenic refrigerator 20 fits into the receiving recess 50. Alternatively, the receiving recess 50 may be shallower, and the depth of the receiving recess 50 may be determined so that a portion (e.g., half) of the height of the drive unit 26 fits into the receiving recess 50. In other words, the cover member 52 may protrude somewhat from the wall of the vacuum vessel 30 surrounding the cover member 52 when attached to the vacuum vessel 30. Even in this case, the protruding portion can be made smaller (lower) than in existing designs in which the entire drive unit 26 protrudes from the vacuum vessel 30.

[0093] The present invention has been described using specific terms based on the embodiments, but the embodiments merely illustrate one aspect of the principles and applications of the present invention, and many modifications and changes in arrangement are permitted to the embodiments as long as they do not deviate from the concept of the present invention as defined in the claims. [Explanation of symbols]

[0094] 10 cryogenic device, 20 cryogenic refrigerator, 22a first cooling stage, 22b second cooling stage, 26 drive unit, 30 vacuum vessel, 50 receiving recess, 52 cover member, 54 buried pipe, 60 heat transfer element, 64a high-pressure refrigerant gas piping, 64b low-pressure refrigerant gas piping, 66 flexible pipe cover.

Claims

1. A plurality of superconducting coils; a hollow cylindrical vacuum vessel defining a vacuum region in which the plurality of superconducting coils are disposed; a cold head including a drive unit and a cooling stage that cools at least one of the plurality of superconducting coils, the cold head being installed in the vacuum vessel such that the drive unit is located outside the vacuum vessel and the cooling stage is located in the vacuum region; the plurality of superconducting coils include a first superconducting coil and a second superconducting coil disposed apart from the first superconducting coil in a circumferential direction of the vacuum vessel, The cryogenic device is characterized in that the vacuum vessel has a receiving recess in which the drive unit is disposed, the receiving recess being located between the first superconducting coil and the second superconducting coil in the circumferential direction.

2. 2. The cryogenic device according to claim 1, wherein the receiving recess is formed in an upper part or a lower part of the vacuum vessel.

3. 3. The cryogenic device according to claim 1, wherein the vacuum vessel further comprises another receiving recess in which a compressor for supplying a working gas to the cold head is disposed.

4. 4. The cryogenic device according to claim 1, further comprising a cover member attached to the vacuum vessel so as to cover the receiving recess.

5. The cryogenic device according to claim 4, further comprising a heat transfer element disposed in the receiving recess and thermally coupling the drive unit to the cover member.

6. 6. The cryogenic device according to claim 1, further comprising a flexible tube connected to the cold head and wound around the vacuum vessel.

7. A cryogenic refrigerator, a vacuum vessel having an exterior receiving recess; a cover member attached to the vacuum vessel so as to cover the receiving recess, the cryogenic refrigerator is installed in the vacuum container such that a portion of the cryogenic refrigerator is disposed within the vacuum container and another portion of the cryogenic refrigerator is disposed within the receiving recess of the vacuum container covered with the cover member; a heat transfer element disposed in the receiving recess and thermally coupling the other portion of the cryogenic refrigerator to the cover member;

8. 8. The cryogenic device according to claim 7, wherein the vacuum vessel has an overall cylindrical shape with the cover member attached.

9. 9. The cryogenic device according to claim 7, further comprising a flexible tube connected to the cryogenic refrigerator and wound around the vacuum vessel.

10. 10. The cryogenic device according to claim 9, further comprising a flexible tube cover attached to the vacuum vessel so as to cover the flexible tube wound around the vacuum vessel.

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