Initial cooling method for cryogenic device and cryogenic device

Abstract

To easily shorten initial cooling time of a cryogenic device.SOLUTION: A cryogenic device 10 includes: a vacuum vessel 30 having a vacuum valve 34; a cryogenic refrigerator 20 including a first cooling stage 22a and a second cooling stage 22b cooled to a temperature lower than that of the first cooling stage 22a, and installed in the vacuum vessel 30 so that the first cooling stage 22a and the second cooling stage 22b are arranged in the vacuum vessel 30; and a second heat transfer terminal 52 arranged in the vacuum vessel 30 so as to be accessible from the vacuum valve 34 via a straight path 36, and thermally connected to the second cooling stage 22b. The cryogenic device 10 may further include a first heat transfer terminal 50 arranged in the vacuum vessel 30 so as to be accessible from the vacuum valve 34 via the straight path 36 and thermally connected to the first cooling stage 22a.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an initial cooling method for a cryogenic device, and to a cryogenic device. [Background technology]

[0002] For example, in a cryogenic device that operates at extremely low temperatures, such as a superconducting magnet device, initial cooling is performed when the device is started up, from an initial temperature, such as room temperature, to a target cooling temperature. The use of the cryogenic device, such as providing a high magnetic field using a superconducting magnet, becomes possible after the initial cooling is completed.

[0003] In cryogenic devices, two-stage cryogenic refrigerators such as Gifford-McMahon (GM) refrigerators are often used for cryogenic cooling. The second stage of the cryogenic refrigerator, which is cooled to a lower temperature, cools the objects to be cooled in the cryogenic device, such as superconducting coils, and the first stage of the cryogenic refrigerator, which is cooled to a higher temperature, cools the objects to be cooled in the first stage, such as a radiation shield to reduce the heat input to the objects to be cooled in the second stage. Since the refrigeration capacity of the first stage is relatively large, the objects to be cooled in the first stage can be initially cooled in a relatively short time. However, since the refrigeration capacity of the second stage is generally much smaller than that of the first stage, the objects to be cooled in the second stage tend to take longer to initially cool than those in the first stage. In particular, the time required for initial cooling may be quite long in cryogenic devices with large superconducting coils, for example. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-312210 Summary of the Invention [Problem to be solved by the invention]

[0005] In order to shorten the initial cooling time, it has been proposed to incorporate various dedicated mechanisms into the cryogenic equipment. However, such dedicated initial cooling mechanisms are usually large-scale, even though they are not used in the normal operation of the cryogenic equipment after the initial cooling is completed, and tend to increase the cost of the cryogenic equipment in which they are incorporated. In addition, if the initial cooling mechanism incorporated in the cryogenic equipment should fail during normal operation of the cryogenic equipment, the normal operation of the cryogenic equipment may have to be interrupted to repair or replace the initial cooling mechanism, which may have a significant impact on the operation of the cryogenic equipment. If the initial cooling mechanism is designed to ensure high reliability in order to avoid this, this may also lead to an increase in the cost of the equipment.

[0006] An exemplary object of an embodiment of the present invention is to simply and easily achieve a reduction in the initial cooling time of a cryogenic device. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a method for initial cooling of a cryogenic device. The cryogenic device includes a vacuum vessel having a vacuum valve, and a first cooling section and a second cooling section disposed in the vacuum vessel. The second cooling section is cooled to a lower temperature than the first cooling section. The method includes attaching a cooling auxiliary tool having a heat transfer body to the vacuum valve, inserting the heat transfer body from the vacuum valve into the vacuum vessel, bringing the heat transfer body into physical contact with the second cooling section, and cooling the second cooling section through the heat transfer body.

[0008] According to an embodiment of the present invention, there is provided a method for initial cooling of a cryogenic device. The cryogenic device includes a vacuum vessel having a vacuum valve, a first cooling section and a second cooling section disposed in the vacuum vessel, and a cryogenic refrigerator having a first cooling stage for cooling the first cooling section and a second cooling stage for cooling the second cooling section. The second cooling section is cooled to a lower temperature than the first cooling section. The method includes attaching a cooling auxiliary tool having a contact tool to the vacuum valve, physically contacting the contact tool with at least one of the first cooling section and the second cooling section through the vacuum valve so as to thermally couple the first cooling section with the second cooling section, and cooling the second cooling section using the first cooling stage as a cooling source.

[0009] According to one embodiment of the present invention, a cryogenic device includes a vacuum vessel having a vacuum valve, a first cooling stage, and a second cooling stage cooled to a lower temperature than the first cooling stage, and a cryogenic refrigerator installed in the vacuum vessel such that the first cooling stage and the second cooling stage are disposed within the vacuum vessel, and a heat transfer terminal disposed within the vacuum vessel so as to be accessible via a linear path from the vacuum valve and thermally coupled to the second cooling stage. Effect of the Invention

[0010] According to the present invention, the initial cooling time of a cryogenic device can be easily shortened. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of a cryogenic device according to an embodiment; [Diagram 2] 1A and 1B are diagrams illustrating a cooling auxiliary device according to an embodiment of the present invention. [Diagram 3] 1A to 1C are diagrams illustrating an initial cooling method for a cryogenic device according to an embodiment. [Figure 4] 4(a) and 4(b) are diagrams illustrating a schematic diagram of another example of the cooling auxiliary device according to the embodiment. [Diagram 5]5(a) and 5(b) are diagrams illustrating another example of the cooling auxiliary device and the heat transfer terminal structure according to the embodiment. [Figure 6] FIG. 11 is a diagram illustrating another example of a cryogenic device according to the embodiment. [Figure 7] 7(a) and 7(b) are diagrams illustrating another example of a cryogenic device and a cooling auxiliary device according to an embodiment. [Figure 8] 11A and 11B are diagrams illustrating another example of a cryogenic device and a cooling auxiliary device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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.

[0013] 1 is a diagram showing a schematic diagram of a cryogenic device 10 according to an embodiment. The cryogenic device 10 includes an object 12 to be cooled, a cryogenic refrigerator 20 that cools the object 12, and a vacuum vessel 30 in which the cryogenic refrigerator 20 is installed and which contains the object 12 to be cooled.

[0014] The cryogenic device 10 may be a superconducting magnet device, and the object to be cooled 12 may be a superconducting coil. The superconducting magnet device is mounted in a high magnetic field device 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 device (not shown), and can generate a high magnetic field required for the device. The cryogenic device 10 may be various devices that use a cryogenic environment, and the object to be cooled 12 may be various devices such as a sensor used in a cryogenic environment, or a cryogenic refrigerant such as helium that cools such devices.

[0015] 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 the 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 parts that are cooled to a cryogenic temperature. The cryogenic refrigerator 20 is installed in the vacuum vessel 30 such that these cooling stages are disposed within the 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 (e.g., pure copper such as oxygen-free copper or tough pitch copper) or other material having high thermal conductivity. 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, for example, 3K to 20K, which is lower than the first cooling temperature.

[0016] Although FIG. 1 shows one cryogenic refrigerator 20 as an example, if necessary, for example when the object to be cooled 12 is large, the cryogenic device 10 may be provided with multiple cryogenic refrigerators 20 each for cooling the same object to be cooled.

[0017] The vacuum vessel 30 is configured to separate the vacuum region 32 from the external environment 14. The vacuum vessel 30 may be, for example, a cryostat. The vacuum region 32 is defined within the vacuum vessel 30, and the external environment 14 may be an atmospheric region. The object to be cooled 12 and the low temperature part of the cryogenic refrigerator 20 are disposed in the vacuum region 32 and are vacuum insulated from the external environment 14. To improve the insulation performance, a heat insulating material may be provided along the surface of or inside the wall member of the vacuum vessel 30 that separates the vacuum region 32 from the external environment 14.

[0018] Typically, the vacuum vessel 30 has a columnar shape or a cylindrical shape having a hollow portion at the center. Thus, the vacuum vessel 30 has a generally flat circular or annular top plate 30a and bottom plate 30b, and a cylindrical side wall (cylindrical outer peripheral wall, or coaxially arranged cylindrical outer peripheral wall and inner peripheral wall) 30c connecting them. In the illustrated example, the cryogenic refrigerator 20 is installed on the top plate 30a of the vacuum vessel 30. Alternatively, the cryogenic refrigerator 20 may be installed in another portion, such as the bottom plate 30b of the vacuum vessel 30. The vacuum vessel 30 is formed of a metal material, such as stainless steel, or other suitable high-strength material, so as to withstand ambient pressure (e.g., atmospheric pressure).

[0019] The vacuum vessel 30 includes a vacuum valve 34. The vacuum valve 34 is configured to maintain the airtightness of the vacuum region 32 in the vacuum vessel 30 when closed, and to connect the vacuum region 32 to the external environment 14 when opened. The vacuum valve 34 is provided, for example, on a side wall 30c of the vacuum vessel 30. Alternatively, the vacuum valve 34 may be provided on another wall of the vacuum vessel 30, such as the top plate 30a or the bottom plate 30b. The vacuum valve 34 may be, for example, a butterfly valve, in which case, as is known, a disk-shaped valve body is opened and closed by rotating around an axis that coincides with or is parallel to its diameter. Alternatively, the vacuum valve 34 may be a gate valve.

[0020] In the vacuum region 32, a radiation shield 40 is disposed together with the low-temperature portion of the cryogenic refrigerator 20 and the object to be cooled 12. The radiation shield 40 is thermally coupled to the first cooling stage 22a and cooled to a first cooling temperature. The radiation shield 40 is directly attached to the first cooling stage 22a and thermally coupled to the first cooling stage 22a. Alternatively, the radiation shield 40 may be attached to the first cooling stage 22a via a flexible or rigid heat transfer member. The radiation shield 40 is formed of a metal material such as copper or other material having high thermal conductivity. The radiation shield 40 is disposed so as to surround the object to be cooled 12 to be 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 radiant heat from the outside.

[0021] The object 12 to be cooled is thermally coupled to the second cooling stage 22b and cooled to a second cooling temperature. The object 12 to be cooled is directly attached to the second cooling stage 22b, or is thermally coupled to the second cooling stage 22b via a flexible or rigid heat transfer member.

[0022] The cryogenic device 10 also includes a first heat transfer terminal 50 and a second heat transfer terminal 52 disposed within the vacuum vessel 30 so as to be accessible from the vacuum valve 34 via a linear path 36. The first heat transfer terminal 50 and the second heat transfer terminal 52 are disposed inside the radiation shield 40.

[0023] The first heat transfer terminal 50 is thermally coupled to a first cooling part, such as the first cooling stage 22a or the radiation shield 40, which is cooled to a first cooling temperature in the vacuum vessel 30, and is cooled to the first cooling temperature by the first cooling stage 22a. The second heat transfer terminal 52 is thermally coupled to a second cooling part, such as the second cooling stage 22b or the object to be cooled 12, which is cooled to a second cooling temperature in the vacuum vessel 30, and is cooled to a second cooling temperature by the second cooling stage 22b. The first heat transfer terminal 50 may be rigidly attached to the first cooling part, and the second heat transfer terminal 52 may be rigidly attached to the second cooling part. The first heat transfer terminal 50 may be fixed to the first cooling stage 22a or the radiation shield 40, and the second heat transfer terminal 52 may be fixed to the second cooling stage 22b or the object to be cooled 12. These heat transfer terminals are formed of a metal material, such as copper, or other material having a high thermal conductivity.

[0024] The first heat transfer terminal 50 and the second heat transfer terminal 52 are separated by the isolation gap 54 so as not to come into physical contact with each other. Thus, the first heat transfer terminal 50 and the second heat transfer terminal 52 are not thermally coupled. However, as described below, by using a cooling auxiliary tool 60, these two heat transfer terminals can be thermally coupled. The width of the isolation gap 54 (i.e., the distance between the first heat transfer terminal 50 and the second heat transfer terminal 52 at the isolation gap 54) may be, for example, 0.1 mm or more, or 1 mm or more, in order to ensure non-contact between the two heat transfer terminals. Moreover, the isolation gap 54 may be, for example, 5 mm or less, or 2 mm or less, in order to facilitate connection between the heat transfer terminals using the cooling auxiliary tool 60.

[0025] The first heat transfer terminal 50, the second heat transfer terminal 52 and the isolating gap 54 are arranged so as to be visible when looking inside the vacuum vessel 30 along the linear path 36 from the vacuum valve 34. Because the radiation shield 40 has a shield opening 42 formed on the linear path 36, the first heat transfer terminal 50, the second heat transfer terminal 52 and the isolating gap 54 can be directly seen from the vacuum valve 34 through the shield opening 42. In other words, a working space 38 for accessing the two heat transfer terminals (and the isolating gap 54) from the external environment 14 through the vacuum valve 34 is secured within the vacuum vessel 30 along the linear path 36 between the vacuum valve 34 and the two heat transfer terminals.

[0026] As in this example, when the vacuum valve 34 is attached to the side wall 30c, the vacuum valve 34 is provided on the side wall 30c at a height position that matches the isolating gap 54. The straight path 36 is parallel to a direction perpendicular to the side wall 30c, typically the horizontal direction, and the first heat transfer terminal 50 and the second heat transfer terminal 52 are separated by the isolating gap 54 in a direction perpendicular to the straight path 36, for example, in the vertical direction.

[0027] As described at the beginning of this document, when the cryogenic device 10 is installed at the site where it will be used and the device is started for the first time, or when the cryogenic device 10 is started again after maintenance, initial cooling is performed to cool the cryogenic device 10 from an initial temperature (for example, an ambient temperature such as room temperature) to a target cryogenic temperature at which the cryogenic device 10 can be operated. In the two-stage cryogenic refrigerator 20 that cools the cryogenic device 10, the refrigeration capacity of the first stage is generally relatively large, and the refrigeration capacity of the second stage is considerably smaller than that of the first stage. For example, the refrigeration capacity of the second stage may be several tens of times smaller than that of the first stage. Therefore, the initial cooling of the second cooling section tends to take a long time. The initial cooling typically takes at least several days, and for example, in the case of a large superconducting coil, it may take a long time of more than a week.

[0028] Therefore, in this embodiment, in the initial cooling, in addition to the cryogenic refrigerator 20, a cooling auxiliary device 60 is used. As described later, the cooling auxiliary device 60 can thermally couple the first heat transfer terminal 50 and the second heat transfer terminal 52. During the initial cooling, the cooling capacity of the first stage of the cryogenic refrigerator 20 can be used to assist in cooling the second cooling section, and the initial cooling time can be shortened.

[0029] 2 is a schematic diagram of a cooling auxiliary device 60 according to an embodiment. The cooling auxiliary device 60 includes a contact tool 62 that can be inserted into the vacuum vessel 30 from the vacuum valve 34. The contact tool 62 includes a heat transfer body 62a and a support column 62b. The heat transfer body 62a is attached to the tip of the support column 62b. The heat transfer body 62a is formed of a metal material having high thermal conductivity, such as copper (e.g., pure copper such as oxygen-free copper or tough pitch copper) or aluminum. The support column 62b is formed of a heat insulating material such as glass fiber reinforced plastic (GFRP) or a low thermal conductive material (e.g., stainless steel) having a lower thermal conductivity than the heat transfer body 62a.

[0030] The cooling auxiliary device 60 is attachable to the vacuum valve 34 and includes a support 64 that supports the contact device 62. The support 64 is extendable so as to linearly advance and retreat the contact device 62 (i.e., the heat transfer body 62a). The support 64 is configured to maintain the airtightness of an internal space 66 of the cooling auxiliary device 60 in which the contact device 62 is housed.

[0031] More specifically, the support 64 includes a mounting flange 64a, a vacuum bellows 64b, and a vacuum flange 64c. The mounting flange 64a can be attached to the vacuum valve 34 so as to maintain the airtightness of the internal space 66. The vacuum bellows 64b is airtightly connected at one end to the mounting flange 64a, and at the other end to the vacuum flange 64c. The end of the vacuum bellows 64b on the vacuum flange 64c side is closed by the vacuum flange 64c. The other end (the end opposite to the heat transfer body 62a) of the support column 62b of the contact tool 62 is attached to the vacuum flange 64c, and the support column 62b extends from the vacuum flange 64c to the opening of the mounting flange 64a along its central axis direction within the vacuum bellows 64b. Therefore, the heat transfer body 62a can be linearly advanced and retreated through the opening of the mounting flange 64a by the expansion and contraction of the vacuum bellows 64b. It should be noted that the vacuum flange 64c and the support column 62b may be separate components connected to each other, or may be an integrated single component.

[0032] FIG. 3 is a diagram showing a schematic diagram of an initial cooling method of the cryogenic device 10 according to the embodiment. In this initial cooling method, first, the cooling auxiliary tool 60 is attached to the vacuum valve 34 (S10). The cooling auxiliary tool 60 is removably attached to the vacuum valve 34. The cooling auxiliary tool 60 may be attached to the vacuum valve 34 by fastening a mounting flange 64a of the cooling auxiliary tool 60 to a flange of the vacuum valve 34 or to a wall surface of the vacuum vessel 30 surrounding the vacuum valve 34 using a fastener such as a bolt. Before or after the cooling auxiliary tool 60 is attached, the vacuum valve 34 is opened. Note that, before the cooling auxiliary tool 60 is attached to the vacuum valve 34, the vacuum vessel 30 may be opened to the atmosphere by opening the vacuum valve 34 or by opening a relief valve (not shown) provided in the vacuum vessel 30 separate from the vacuum valve 34.

[0033] After the cooling auxiliary device 60 is attached to the vacuum valve 34, the vacuum vessel 30 is evacuated using a vacuum pump (not shown). Since the vacuum valve 34 is open, the internal space 66 of the cooling auxiliary device 60 is also evacuated together with the vacuum vessel 30.

[0034] Next, the contact tool 62 of the cooling auxiliary tool 60 is inserted into the vacuum vessel 30 through the vacuum valve 34 (S12). As shown in the figure, the vacuum flange 64c is operated to contract the vacuum bellows 64b, whereby the heat transfer body 62a at the tip of the contact tool 62 advances into the vacuum vessel 30 through the opened vacuum valve 34. The heat transfer body 62a moves through the working space 38 in the vacuum vessel 30 along the linear path 36 described above toward the isolation gap 54.

[0035] The heat transfer body 62a is in physical contact with the second cooling unit (S14). In this embodiment, the heat transfer body 62a is in physical contact with both the first cooling unit and the second cooling unit. As shown in the figure, the heat transfer body 62a is in contact with both the first heat transfer terminal 50 and the second heat transfer terminal 52 so as to bridge the isolation gap 54. As a result, the first cooling stage 22a and the second cooling stage 22b of the cryogenic refrigerator 20 are thermally coupled via the first heat transfer terminal 50, the heat transfer body 62a, and the second heat transfer terminal 52.

[0036] The heat conductor 62a has a size and shape that allows it to contact both the first heat transfer terminal 50 and the second heat transfer terminal 52 so as to bridge the isolation gap 54. The length L (see FIG. 2) of the heat conductor 62a is longer than the width of the isolation gap 54 (i.e., the distance between the first heat transfer terminal 50 and the second heat transfer terminal 52 at the isolation gap 54) so ​​as to be able to bridge the isolation gap 54. The length of the heat conductor 62a may be, for example, 1 mm or more, or 5 mm or more. In order to increase the contact area between the heat conductor 62a and the two heat transfer terminals for good thermal contact between them, it is desirable that the length L of the heat conductor 62a is as long as possible. However, the length L of the heat conductor 62a is restricted by the diameter of the opening of the vacuum valve 34. The opening diameter of the vacuum valve 34 is often, for example, 100 mm or less, and therefore the length of the heat conductor 62a may be less than 100 mm, less than 50 mm, or less than 10 mm so as to be able to pass through the opening of the vacuum valve 34.

[0037] The vacuum flange 64c of the cooling auxiliary device 60 is operated so as to maintain the heat transfer body 62a pressed against the first heat transfer terminal 50 and the second heat transfer terminal 52. For example, the vacuum flange 64c may be fixed to the vacuum container 30 or the vacuum valve 34 by, for example, screwing or the like.

[0038] Then, the second cooling section is cooled through the heat transfer body 62a (S16). The cryogenic refrigerator 20 is operated to perform cooling, and the first cooling stage 22a and the second cooling stage 22b are cooled from an initial temperature (for example, an ambient temperature such as room temperature) to a first cooling temperature and a second cooling temperature, respectively. Until the second cooling stage 22b reaches the first cooling temperature, the first cooling stage 22a can be used as a cooling source to cool the second cooling section, such as the second cooling stage 22b and the object to be cooled 12, through the first heat transfer terminal 50, the heat transfer body 62a, and the second heat transfer terminal 52. The cooling temperatures of the first cooling stage 22a and the second cooling stage 22b may be obtained by temperature sensors (not shown) provided in each cooling stage.

[0039] After cooling, the cooling auxiliary tool 60 is removed from the vacuum valve 34. After the cooling temperature of the second cooling section reaches the first cooling temperature, the cooling auxiliary tool 60 can be removed. The cooling auxiliary tool 60 can be removed in the reverse order to the above-mentioned attachment. That is, the cooling auxiliary tool 60 can be operated so as to separate the heat transfer body 62a from the two heat transfer terminals and pull the heat transfer body 62a out of the vacuum vessel 30 through the vacuum valve 34. The thermal coupling between the first heat transfer terminal 50 and the second heat transfer terminal 52 is released. After the heat transfer body 62a is taken out of the vacuum valve 34, the vacuum valve 34 is closed and the cooling auxiliary tool 60 is removed from the vacuum valve 34.

[0040] Thus, the cryogenic device 10 returns to the state shown in Fig. 1. The first cooling section is maintained at the first cooling temperature by the first cooling stage 22a, while the second cooling section is further cooled by the second cooling stage 22b, and finally cooled to the second cooling temperature. The cryogenic device 10 can then start normal operation.

[0041] Therefore, according to the embodiment, the initial cooling time of the cryogenic device 10 can be shortened by using the cooling auxiliary device 60. That is, during the initial cooling, the first heat transfer terminal 50 and the second heat transfer terminal 52 are thermally coupled by the heat transfer body 62a of the cooling auxiliary device 60, and the cooling capacity of the first stage of the cryogenic refrigerator 20 is utilized to assist in cooling the second cooling section, thereby shortening the initial cooling time.

[0042] In the existing technology, it has been proposed to incorporate various dedicated mechanisms into the cryogenic device in advance in order to shorten the initial cooling time. However, such dedicated initial cooling mechanisms are usually large-scale, even though they are not used in the normal operation of the cryogenic device after the initial cooling is completed, and tend to increase the cost of the cryogenic device in which they are incorporated. In addition, if the initial cooling mechanism incorporated in the cryogenic device should fail during the normal operation of the cryogenic device, the normal operation of the cryogenic device may have to be interrupted to repair or replace the initial cooling mechanism, which may have a significant impact on the operation of the cryogenic device. If the initial cooling mechanism is designed to ensure high reliability in order to avoid this, this may also lead to an increase in the cost of the device.

[0043] In contrast, according to the embodiment, the cooling auxiliary device 60 is only attached to the cryogenic equipment 10 for initial cooling. The cooling auxiliary device 60 is removed from the cryogenic equipment 10 after the initial cooling. The cryogenic equipment 10 does not need to have a dedicated initial cooling mechanism as shown in FIG. 1. The cost of the cryogenic equipment 10 can be reduced. Also, the cryogenic equipment 10 does not suffer from failure of the initial cooling mechanism during normal operation.

[0044] Additionally, after being removed from the cryogenic device 10, the cooling support 60 can be reused for subsequent initial cooling of the cryogenic device 10 or for initial cooling of another cryogenic device.

[0045] 4(a) and 4(b) are diagrams showing another example of the cooling auxiliary tool 60 according to the embodiment. The cooling auxiliary tool 60 may be switchable between a stored state shown in FIG. 4(a) and an expanded state shown in FIG. 4(b). The contact tool 62 of the cooling auxiliary tool 60 includes a heat transfer body 62a and a support column 62b. The heat transfer body 62a is foldably (e.g., rotatably) attached to the tip of the support column 62b. For ease of viewing, other components of the cooling auxiliary tool 60, such as vacuum bellows 64b, are omitted from the illustration.

[0046] 4(a), in the stored state, the heat transfer body 62a is folded along the support pillar 62b so as to be able to pass through the vacuum valve 34. To maintain the stored state, the heat transfer body 62a may be pulled against the support pillar 62b by a spring 62c.

[0047] In the deployed state of the cooling auxiliary device 60, as shown in FIG. 4(b), the heat transfer body 62a is deployed from the support column 62b so as to face a heat transfer terminal (for example, the first heat transfer terminal 50 or the second heat transfer terminal 52). The heat transfer body 62a may be deployed by inserting the contact tool 62 into the vacuum container 30 through the vacuum valve 34 and abutting against the heat transfer terminal. The length L of the heat transfer body 62a may be larger than the opening diameter of the vacuum valve 34, and the heat transfer body 62a cannot pass through the vacuum valve 34 in the deployed state. The deployed heat transfer body 62a contacts both the first heat transfer terminal 50 and the second heat transfer terminal 52 so as to bridge the isolation gap 54. In this way, by making the heat transfer body 62a movable, the contact area between the heat transfer body 62a and the heat transfer terminal can be increased, and the thermal contact between the heat transfer body 62a and the heat transfer terminal during initial cooling can be improved.

[0048] 5(a) and 5(b) are diagrams showing another example of the cooling auxiliary device 60 and the heat transfer terminal structure according to the embodiment. Fig. 5(a) shows a state in which the cooling auxiliary device 60 is attached to the open vacuum valve 34 and the contact device 62 has not yet been inserted. Therefore, in Fig. 5(a), the first heat transfer terminal 50 and the second heat transfer terminal 52 are not in physical contact with each other and are not thermally coupled.

[0049] As shown in Fig. 5(a), the intermediate heat conductor 68 is connected to the first heat transfer terminal 50 by a flexible heat conductor 70 and is arranged so as to be movable toward and away from the second heat transfer terminal 52. The intermediate heat conductor 68 is formed of a metal material such as copper or other material having high thermal conductivity. A spring 72 may be provided to ensure that the intermediate heat conductor 68 does not come into physical contact with the second heat transfer terminal 52 when the cooling auxiliary device 60 is not present. The spring 72 connects the intermediate heat conductor 68 to the first heat transfer terminal 50 so that the intermediate heat conductor 68 is held in a position away from the second heat transfer terminal 52.

[0050] The contact 62 of the cooling support 60 has a support pole 62b. The support pole 62b may be formed of a heat insulating material or a low heat conductive material as described above. As shown in the figure, the contact 62 does not have to include the heat conductor 62a.

[0051] FIG. 5(b) shows a state in which the first heat transfer terminal 50 and the second heat transfer terminal 52 are in physical contact and thermally coupled. The contact tool 62 (i.e., the support column 62b) is inserted into the vacuum vessel 30 through the vacuum valve 34 by contraction of the vacuum bellows 64b, the tip of the support column 62b contacts the intermediate heat transfer body 68, and the intermediate heat transfer body 68 physically contacts the second heat transfer terminal 52. The intermediate heat transfer body 68 is pressed against the second heat transfer terminal 52 by the contact tool 62, the isolation gap 54 is bridged, and the first heat transfer terminal 50 and the second heat transfer terminal 52 are thermally coupled. In this way, the contact tool 62 is brought into physical contact with the first cooling part through the vacuum valve 34, and the first cooling part can be thermally coupled to the second cooling part. Thus, similar to the above-mentioned embodiment, the second cooling part can be cooled using the first cooling stage 22a as a cooling source.

[0052] Contrary to the illustrated example, the intermediate heat transfer body 68 may be connected to the second heat transfer terminal 52 by a flexible heat transfer body 70 and may be arranged so as to be movable toward and away from the first heat transfer terminal 50. The spring 72 may connect the intermediate heat transfer body 68 to the second heat transfer terminal 52 so that the intermediate heat transfer body 68 is held at a position away from the first heat transfer terminal 50. In this case, the tip of the support column 62b contacts the intermediate heat transfer body 68, and the intermediate heat transfer body 68 physically contacts the first heat transfer terminal 50. The intermediate heat transfer body 68 is pressed against the first heat transfer terminal 50 by the contact tool 62, and the first heat transfer terminal 50 and the second heat transfer terminal 52 are thermally coupled. In this way, the contact tool 62 is physically contacted with the second cooling unit through the vacuum valve 34, the first cooling unit is thermally coupled to the second cooling unit, and the second cooling unit can be cooled using the first cooling stage 22a as a cooling source.

[0053] FIG. 6 is a diagram showing a schematic diagram of another example of the cryogenic device 10 according to the embodiment. A movable shutter 44 may be provided in the shield opening 42 of the radiation shield 40. The movable shutter 44 is configured to open and close the shield opening 42 as shown by an arrow 46 in FIG. 6. When the cooling auxiliary tool 60 is attached to the vacuum valve 34 and the first heat transfer terminal 50 and the second heat transfer terminal 52 are thermally coupled by the cooling auxiliary tool 60, the movable shutter 44 is opened. This allows the cooling auxiliary tool 60 to access the first heat transfer terminal 50 and the second heat transfer terminal 52 through the vacuum valve 34 and the shield opening 42. On the other hand, when the cooling auxiliary tool 60 is detached from the vacuum valve 34, the movable shutter 44 is closed. This allows the movable shutter 44 to block the intrusion of heat into the second cooling section (for example, the second cooling stage 22b of the cryogenic refrigerator 20) through the shield opening 42.

[0054] The movable shutter 44 shown in Fig. 6 may be applied to the embodiments of Fig. 1 to Fig. 3, the embodiments of Fig. 4(a) and Fig. 4(b), and the embodiments of Fig. 5(a) and Fig. 5(b). Alternatively, the movable shutter 44 shown in Fig. 6 may be applied to the embodiments of Fig. 7(a) and Fig. 7(b) described below.

[0055] 7(a) and 7(b) are diagrams illustrating another example of the cryogenic device 10 and the cooling auxiliary device 60 according to the embodiment. Fig. 7(a) shows the cryogenic device 10 with the cooling auxiliary device 60 attached, and Fig. 7(b) shows the cooling auxiliary device 60 removed from the cryogenic device 10.

[0056] As shown in FIG. 7(a), the cryogenic device 10 includes an object 12 to be cooled, a cryogenic refrigerator 20 for cooling the object 12, and a vacuum vessel 30 in which the cryogenic refrigerator 20 is installed and in which the object 12 is accommodated. The cryogenic refrigerator 20 includes a first cooling stage 22a that is cooled to a first cooling temperature, and a second cooling stage 22b that is cooled to a second cooling temperature that is lower than the first cooling temperature. A vacuum valve 34 is provided on the wall of the vacuum vessel 30. A radiation shield 40 is disposed in the vacuum vessel 30, which is cooled by the first cooling stage 22a and surrounds the object 12 and the second cooling stage 22b. The object 12 is cooled by the second cooling stage 22b.

[0057] The cryogenic device 10 also includes a heat transfer terminal 74 disposed within the vacuum vessel 30 so as to be accessible from the vacuum valve 34 via the linear path 36. The heat transfer terminal 74 is disposed inside the radiation shield 40. The heat transfer terminal 74 is thermally coupled to a second cooling section that is cooled to a second cooling temperature within the vacuum vessel 30, such as the second cooling stage 22b or the object to be cooled 12, and is cooled to the second cooling temperature by the second cooling stage 22b. The heat transfer terminal 74 is formed of a metal material, such as copper, or another material having high thermal conductivity.

[0058] As shown in FIG. 7(b), the cooling auxiliary device 60 includes a heat transfer body 62a, a cooling source 76 thermally coupled to the heat transfer body, and a cryostat 78 housing the cooling source 76. The heat transfer body 62a is formed of a metallic material such as copper or other material with high thermal conductivity. The cooling source 76 may be, for example, a single-stage cryogenic refrigerator (e.g., a single-stage GM refrigerator). The cooling source 76 may provide cryogenic cooling to a first cooling temperature, similar to the first cooling stage 22a of the cryogenic refrigerator 20. Alternatively, the cooling source 76 may provide cryogenic cooling to a cooling temperature lower than the first cooling temperature (e.g., the above-mentioned second cooling temperature, or a cooling temperature higher than the second cooling temperature).

[0059] The cooling auxiliary device 60 is also provided with a support 64 that can be attached to the vacuum valve 34 and supports the heat transfer body 62a. The support 64 is expandable so as to linearly advance and retreat the heat transfer body 62a, and is configured to maintain airtightness of the internal space 66 of the cooling auxiliary device 60 in which the heat transfer body 62a is housed. The support 64 includes a mounting flange 64a and a vacuum bellows 64b, and constitutes a part of a cryostat 78. The mounting flange 64a can be attached to the vacuum valve 34 so as to maintain airtightness of the internal space 66. The vacuum bellows 64b is airtightly connected at one end to the mounting flange 64a, and at the other end to the cryostat 78. The base end of the heat transfer body 62a is thermally coupled to the cooling source 76 (for example, attached to the cooling stage of a single-stage cryogenic refrigerator), and extends within the vacuum bellows 64b along its central axis toward the opening of the mounting flange 64a. Therefore, the heat transfer body 62a can be moved linearly back and forth through the opening of the mounting flange 64a by expanding and contracting the vacuum bellows 64b.

[0060] In the initial cooling method using the cryogenic device 10 and the cooling auxiliary tool 60 shown in Figures 7(a) and 7(b), first, the cooling auxiliary tool 60 is attached to the vacuum valve 34. The cooling auxiliary tool 60 is removable from the vacuum valve 34. The vacuum valve 34 is opened before or after the cooling auxiliary tool 60 is attached. After the cooling auxiliary tool 60 is attached to the vacuum valve 34, the vacuum vessel 30 is evacuated using a vacuum pump (not shown). Since the vacuum valve 34 is opened, the internal space 66 of the cooling auxiliary tool 60 is also evacuated together with the vacuum vessel 30.

[0061] Next, the heat transfer body 62a of the cooling auxiliary device 60 is inserted into the vacuum vessel 30 through the vacuum valve 34. The cryostat 78 is operated to contract the vacuum bellows 64b, whereby the heat transfer body 62a enters the vacuum vessel 30 through the opened vacuum valve 34. The heat transfer body 62a moves toward the isolation gap 54 along the linear path 36. The heat transfer body 62a then physically contacts the second cooling portion, specifically, the heat transfer terminal 74. As a result, the cooling source 76 is thermally coupled to the second cooling stage 22b of the cryogenic refrigerator 20 via the heat transfer body 62a and the heat transfer terminal 74.

[0062] Next, the second cooling section is cooled through the heat transfer body 62a. Due to the cooling operation of the cooling source 76, the second cooling stage 22b of the cryogenic refrigerator 20 is cooled from an initial temperature (for example, an ambient temperature such as room temperature) to the cooling temperature of the cooling source 76. At this time, the cooling operation of the cryogenic refrigerator 20 is also performed. In this way, the first cooling section and the second cooling section of the cryogenic device 10 are cooled to the first cooling temperature and the second cooling temperature, respectively.

[0063] After cooling, the cooling auxiliary tool 60 is removed from the vacuum valve 34. The cooling auxiliary tool 60 is removed in the reverse order to the above-mentioned installation. That is, the cooling auxiliary tool 60 is operated so as to separate the heat transfer body 62a from the heat transfer terminal 74 and pull the heat transfer body 62a out of the vacuum vessel 30 through the vacuum valve 34. The thermal connection between the heat transfer body 62a and the heat transfer terminal 74 is released. After the heat transfer body 62a is taken out of the vacuum valve 34, the vacuum valve 34 is closed and the cooling auxiliary tool 60 is removed from the vacuum valve 34. In this manner, as in the above-mentioned embodiment, the initial cooling time of the cryogenic device 10 can be easily shortened.

[0064] Alternatively or in addition to a single-stage cryogenic refrigerator, as shown in Fig. 8, the cooling source 76 may include a cryogenic refrigerant, e.g., a cryogenic liquid such as liquid nitrogen. In this case, the cooling source 76 may include a cryogenic refrigerant tank 80 thermally coupled to the heat transfer body 62a and configured to store a cryogenic refrigerant 82. Alternatively, the cooling source 76 may include a cooling pipe thermally coupled to the heat transfer body 62a and configured to allow the cryogenic refrigerant to flow therethrough.

[0065] 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.

[0066] In the above embodiment, the contact tool 62 or the heat transfer body 62a advances and retreats relative to the vacuum valve 34 due to the expansion and contraction of the vacuum bellows 64b, but the present invention is not limited to this. In one embodiment, the cooling auxiliary device 60 may include a contact tool 62 including a heat transfer body 62a and a support column 62b, and a support 64 that can be attached to the vacuum valve 34 and supports the contact tool 62, and the support column 62b may be expandable and contractible so as to advance and retreat the heat transfer body 62a relative to the vacuum valve 34. The support 64 may include a mounting flange 64a and a vacuum flange 64c, and a cylindrical member that connects the mounting flange 64a and the vacuum flange 64c and accommodates the contact tool 62 therein.

[0067] In the above embodiment, the cryocooler 20 is a two-stage GM refrigerator, but the cryocooler 20 may be a single-stage GM refrigerator or another multi-stage GM refrigerator such as a three-stage GM refrigerator. Also, the cryocooler 20 is not limited to a GM refrigerator. The cryocooler 20 may be a pulse tube refrigerator, a Stirling refrigerator, or another type of cryocooler.

[0068] In the above-described embodiment, the cryogenic device 10 is configured as a conduction cooling type in which the object to be cooled 12 is directly cooled by the cryogenic refrigerator 20. However, in some embodiments, the cryogenic device 10 may be configured as an immersion cooling type in which the object to be cooled 12 is immersed in a cryogenic refrigerant such as liquid helium and cooled.

[0069] 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]

[0070] 10 cryogenic device, 20 cryogenic refrigerator, 22a first cooling stage, 22b second cooling stage, 30 vacuum vessel, 34 vacuum valve, 36 linear path, 38 working space, 40 radiation shield, 42 shield opening, 44 movable shutter, 50 first heat transfer terminal, 52 second heat transfer terminal, 54 isolation gap, 60 cooling auxiliary device, 62 contact device, 62a heat transfer body, 64 support device, 64a mounting flange, 64b vacuum bellows, 64c vacuum flange, 68 intermediate heat transfer body, 70 flexible heat transfer body, 74 heat transfer terminal, 76 cooling source.

Claims

1. A method for initial cooling of a cryogenic device, the cryogenic device comprising a vacuum vessel having a vacuum valve, and a first cooling section and a second cooling section disposed within the vacuum vessel, the second cooling section being cooled to a lower temperature than the first cooling section, the method comprising: attaching a cooling aid having a heat transfer body to the vacuum valve; bringing the heat transfer body into physical contact with the second cooling portion through the vacuum valve; and cooling the second cooling portion through the heat transfer body.

2. the cooling aid further comprising a cooling source thermally coupled to the heat transfer body; The method of claim 1 , wherein the cooling step comprises cooling the second cooling portion through the heat transfer body using the cooling source.

3. The method of claim 2 , wherein the cooling source comprises a single stage refrigerator or a cryogenic refrigerant.

4. The cryogenic device further includes a cryogenic refrigerator including a first cooling stage that cools the first cooling unit and a second cooling stage that cools the second cooling unit, the contacting comprises physically contacting the heat transfer body with both the first cooling portion and the second cooling portion; 2. The method of claim 1, wherein the cooling comprises cooling the second cooling portion through the heat transfer body using the first cooling stage as a cooling source.

5. A method for initial cooling of a cryogenic device, the cryogenic device comprising: a vacuum vessel having a vacuum valve; a first cooling section and a second cooling section disposed within the vacuum vessel; and a cryogenic refrigerator comprising a first cooling stage for cooling the first cooling section and a second cooling stage for cooling the second cooling section, the second cooling section being cooled to a lower temperature than the first cooling section, the method comprising: Attaching a cooling aid having a contact to the vacuum valve; bringing the contact tool into physical contact with at least one of the first cooling unit and the second cooling unit through the vacuum valve so as to thermally couple the first cooling unit to the second cooling unit; and cooling the second cooling portion using the first cooling stage as a cooling source.

6. 6. The method of claim 1, further comprising removing the cooling aid from the vacuum valve after the cooling.

7. a vacuum vessel having a vacuum valve; a cryogenic refrigerator including a first cooling stage and a second cooling stage cooled to a lower temperature than the first cooling stage, the cryogenic refrigerator being installed in the vacuum container such that the first cooling stage and the second cooling stage are disposed within the vacuum container; a heat transfer terminal disposed within the vacuum vessel so as to be accessible via a linear path from the vacuum valve, the heat transfer terminal being thermally coupled to the second cooling stage.

8. 8. The cryogenic device of claim 7, further comprising an additional heat transfer terminal disposed within the vacuum vessel so as to be accessible via a linear path from the vacuum valve and thermally coupled to the first cooling stage.

9. The cryogenic device according to claim 8, further comprising an intermediate heat transfer body connected to one of the heat transfer terminal and the additional heat transfer terminal by a flexible heat transfer body and arranged so as to be capable of being brought into contact with and separated from the other of the heat transfer terminal and the additional heat transfer terminal.

10. a radiation shield thermally coupled to the first cooling stage and surrounding the second cooling stage; 10. The cryogenic device according to claim 7, wherein the radiation shield has a shield opening on the linear path.

11. 11. The cryogenic device according to claim 10, wherein the shield opening is provided with a movable shutter.

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