Cooling device and cold head replacement method

Abstract

Provided are a cooling device and a cold head replacement method that improve airtightness of a vacuum space in which an object to be cooled is disposed. The present invention comprises: a vacuum container that accommodates the object to be cooled; a refrigerator port that is provided in the vacuum container and includes a port space that accommodates a cold head of a refrigerator that cools the object to be cooled; a flange where a flow path is formed in a surface that contacts the vacuum container; and a gas pipe that communicates with the port space via the flow path.

Description

Cooling device and cold head replacement method

[0001] The present disclosure relates to a technique for cooling an object to be cooled placed in a vacuum state.

[0002] There are known cooling devices that cool an object to be cooled placed in a vacuum space (see, for example, Patent Documents 1 and 2). In the cooling devices disclosed in Patent Documents 1 and 2, when pulling out the cold head from the airtight port space while maintaining the cooling state of the object to be cooled, helium gas is introduced into the port space for the purpose of purging to atmospheric pressure and preventing air contamination.

[0003] The cooling device disclosed in Patent Document 1 is provided with a gas conduit that penetrates the wall of the vacuum vessel and reaches the port space via the vacuum space where the object to be cooled is placed. The cooling device disclosed in Patent Document 2 is provided with a supply pipe that penetrates the wall of the vacuum vessel and reaches the port space via the vacuum space where the object to be cooled is placed.

[0004] Japanese Utility Model Laid-Open No. 63-75765, Japanese Patent Laid-Open No. 2019-56519

[0005] In the cooling devices disclosed in Patent Documents 1 and 2, since the pipe for supplying helium gas is routed through the vacuum space, the area of the boundary between the vacuum space and the outside air increases, which may affect the airtightness of the vacuum space.

[0006] One object included in the present disclosure is to provide a cooling device and a cold head replacement method that improve the airtightness of the vacuum space where the object to be cooled is placed.

[0007] A cooling device according to one aspect included in the present disclosure includes: a vacuum vessel that accommodates an object to be cooled; a refrigerator port that is provided in the vacuum vessel and has a port space for accommodating a cold head of a refrigerator that cools the object to be cooled; a flange having a flow path formed on a surface in contact with the vacuum vessel; and a gas pipe that communicates with the port space via the flow path.

[0008] According to one aspect included in the present disclosure, since there is no need to route and provide the gas pipe inside the vacuum vessel, the airtightness of the vacuum space is improved.

[0009] This is a cross-sectional view showing one example configuration of the cooling device of Example 1. This is an enlarged cross-sectional view of a part of the cooling device shown in Figure 1. This is a cross-sectional view showing a modified example of the cooling device of Example 1. This is an external perspective view showing one example configuration of the flange shown in Figure 3. This is an external perspective view showing another example configuration of the flange shown in Figure 3. This is an external perspective view showing another example configuration of the flange shown in Figure 3. This is a flowchart showing the procedure for replacing the cold head in the cooling device of Example 1. This is a cross-sectional view showing one example configuration of the cooling device of Example 2. This is a cross-sectional view showing a modified example of the cooling device of Example 2. This is a cross-sectional view showing one example configuration of the cooling device of Example 3. This is a cross-sectional view showing one example configuration of the cooling device of Example 4. This is a cross-sectional view showing one example configuration of the cooling device of Example 5.

[0010] The cooling device of this embodiment has a flange that allows inert gas to flow into the port space along the outer or inner wall surface of the vacuum vessel. This eliminates the need to route gas piping into the vacuum vessel. An embodiment of the cooling device of this embodiment will be described with reference to the figures. For the sake of explanation, the three axes X, Y, and Z are shown in the referenced figures to define direction. The Z-axis arrow indicates vertically upward. Vertically downward is the direction of gravity.

[0011] The configuration of the cooling device of Example 1 will be described with reference to Figure 1. Figure 1 is a cross-sectional view showing one example of the configuration of the cooling device of Example 1. The cooling device 1 includes a vacuum container 2 for housing the object to be cooled 10, a cold head 3 of a refrigerator for cooling the object to be cooled 10, a refrigerator port 16 housing the cold head 3, a flange 4, and a gas pipe 8. The object to be cooled 10 is placed in a vacuum space 30 inside the vacuum container 2, which is maintained at a predetermined vacuum level or lower by an exhaust device (not shown in the figure).

[0012] The cold head 3 has a head 19, a columnar portion 14, a cooling stage 12, and a mounting flange 13 provided between the head 19 and the columnar portion 14. The head 19 is connected to a compressor (not shown) via refrigerant piping. The cooling stage 12 is cooled by the circulation of refrigerant between the compressor (not shown) and the cold head 3 via the refrigerant piping.

[0013] The refrigeration port 16 has a sleeve 5 and a base 6. The cold head 3 is housed in the port space 15 surrounded by the sleeve 5 and the base 6. Specifically, with the cold head 3 attached to the vacuum vessel 2, the columnar part 14 and the cooling stage 12 are housed in the port space 15. The sleeve 5 has a bellows structure. The material of the sleeve 5 is metal. The sleeve 5 covers the sides of the port space 15.

[0014] A heat transfer member 7 is provided between the base 6 and the object to be cooled 10. The cooling stage 12 is in contact with the base 6. The cooling stage 12 absorbs heat from the object to be cooled 10 via the base 6 and the heat transfer member 7. The heat transfer member 7 plays the role of transferring heat between the base 6 and the object to be cooled 10.

[0015] The gas piping 8 is connected to a gas cylinder (not shown) filled with an inert gas and an exhaust device (not shown). The inert gas is, for example, helium gas. The following explanation will assume that the inert gas is helium gas. As shown in Figure 1, a valve 9 is provided in the gas piping 8. The valve 9 is configured to be switchable by an operator to an open state that allows gas to flow through the gas piping 8, or to a closed state that stops the flow of gas through the gas piping 8. Note that the operation of opening and closing the valve 9 is not limited to the operator. The opening and closing operation of the valve 9 may be controlled by a computer (not shown in the figure).

[0016] Figure 2 is an enlarged cross-sectional view of a part of the cooling device shown in Figure 1. The flange 4 is positioned between the mounting flange 13 and the outer wall of the vacuum vessel 2. A flow path 11 is formed on the surface of the flange 4 that contacts the outer wall of the vacuum vessel 2. The port space 15 is in communication with the gas piping 8 via the flow path 11. The flow path 11 is connected to the gas piping 8 by a connection part 17. The flow path 11 serves to draw helium gas into the port space 15 via the gas piping 8 and to exhaust helium gas from the port space 15.

[0017] The cold head 3 is attached to the vacuum container 2 with the port space 15 in place by inserting screws (not shown) into pre-formed screw holes (not shown) on the mounting flange 13, flange 4, and the outer wall surface of the vacuum container 2, and tightening the screws. The space between the mounting flange 13 and flange 4, and the space between flange 4 and the vacuum container 2 are sealed with sealing members, such as O-rings. The flange 4 and the vacuum container 2 may also be connected by welding or other methods.

[0018] According to the configuration shown in Figures 1 and 2, there is no need to route the gas piping 8 inside the vacuum container 2.

[0019] (Modification 1) A modification of the cooling device 1 of Example 1 will be described. Figure 3 is a cross-sectional view showing a modification of the cooling device of Example 1. The cooling device 1a of Modification 1 has a configuration in which the flange 4 is provided inside the vacuum container 2. Specifically, the flange 4 is positioned such that a flow path 11 is formed on the surface that contacts the inner wall surface of the vacuum container 2.

[0020] As shown in Figure 3, by positioning the flange 4 inside the vacuum vessel 2, the portion of the cold head 3 protruding from the vacuum vessel 2 can be reduced by the thickness of the flange 4. In the configuration shown in Figure 3, a wider working space for inserting and removing the cold head 3 can be secured than in the configuration shown in Figure 1. The flow path 11 is connected to the gas piping 8 through an opening 18 formed in the wall of the vacuum vessel 2. The opening 18 is formed in the connection portion 17.

[0021] Next, an example of the configuration of the flange 4 will be described with reference to Figures 4 to 6. Here, the description will be given as a case where the flange 4 is attached to the cooling device 1a of Modification 1 shown in Figure 3, but the flange 4 shown in Figures 4 to 6 may also be provided in the configuration shown in Figure 1.

[0022] Figure 4 is an external perspective view showing one example configuration of the flange shown in Figure 3. The flange 4 is circular in shape, as shown in Figure 4. The flange 4 has a concentric circular opening 20 that shares its center with the outer circumference of the flange 4 in order to accommodate the cold head 3. A flow path 11 is formed on the contact surface 41 that contacts the inner wall of the vacuum vessel 2. The flow path 11 is a groove shape that extends radially from the center of the flange 4. The flow path 11 has two ends, a front end 21 and a rear end 22, and connects to the opening 18 shown in Figure 3 near the rear end 22. The front end 21 is the end closer to the center of the flange 4, and the rear end 22 is the end further from the center of the flange 4.

[0023] The effect of flange 4, as explained with reference to Figure 4, will now be described. Consider the case where an operator fills the port space 15 with helium gas, returns the port space 15 to atmospheric pressure, and withdraws the cold head 3. In this case, according to the configuration shown in Figure 4, when helium gas flows into the port space 15 via the flow path 11, it is ejected radially from the tip 21 of the flow path 11, as shown by the dashed arrow. As the helium gas continues to flow in while the operator withdraws the cold head 3, the helium gas ejected radially from the flow path 11 acts like an air curtain. Therefore, it is possible to suppress the inflow of moisture-containing air into the port space 15 from the outside.

[0024] Although Figure 4 shows the case with one groove, the number of grooves is not limited to one; there may be two or more. This is because a larger number of grooves makes it easier for the operator to align the flow path 11 with the opening 18.

[0025] Figure 5 is an external perspective view showing another example of the flange configuration shown in Figure 3. As shown in Figure 5, a flow path 11a is formed on the contact surface 41 of the flange 4. The flow path 11a has a configuration consisting of a rod-shaped groove 23 and a circumferential groove 24. Figure 5 shows the case where there are two rod-shaped grooves 23, but the number of rod-shaped grooves 23 may be three or more. The rod-shaped grooves 23 extend radially from the center of the flange 4. The shape of the rod-shaped grooves 23 is similar to the groove shape shown in Figure 4. The circumferential groove 24 is formed along the circular circumferential direction of the flange 4. The rod-shaped grooves 23 correspond to the first groove, and the circumferential groove 24 corresponds to the second groove.

[0026] The rear end 22 of the rod-shaped groove 23 is connected to the circumferential groove 24. Although not shown in Figure 5, the circumferential groove 24 is also connected to the opening 18 shown in Figure 3 at one of its circumferential positions. When helium gas flows from the gas pipe 8 through the opening 18 into the circumferential groove 24 from any point in the groove, it flows into the two rod-shaped grooves 23 arranged radially, and then flows from the two rod-shaped grooves 23 into the port space 15. As a result, as shown by the dashed arrows in Figure 5, the helium gas is ejected radially from the tips 21 of the two rod-shaped grooves 23.

[0027] The effect of flange 4, as explained with reference to Figure 5, is now described. Consider the case where an operator seals helium gas into the port space 15, returns the port space 15 to atmospheric pressure, and withdraws the cold head 3. In this case, the configuration shown in Figure 5 is more effective at suppressing the intrusion of air into the port space 15 than the configuration shown in Figure 4, because the helium gas is ejected into the port space 15 from multiple rod-shaped grooves 23.

[0028] Figure 6 is an external perspective view showing another configuration example of the flange shown in Figure 3. As shown in Figure 6, a concentric step 25 sharing the center with the outer circumference of the flange 4 is formed on the flange 4. A recess 42 is formed inside the step 25 formed on the contact surface 41. The recess 42 serves as a flow path 11. In the configuration shown in Figure 6, the opening 18 shown in Figure 3 may be connected to the recess 42 at any position within the region of the recess 42. When helium gas flows from the gas piping 8 through the opening 18 into the recess 42 from any point in the recess 42, the helium gas diffuses along the step 25 from the entire opening 20 into the port space 15, as shown by the dashed arrow in Figure 6.

[0029] The effects of flange 4, as explained with reference to Figure 6, are described below. Consider the case where an operator fills the port space 15 with helium gas, returns the port space 15 to atmospheric pressure, and withdraws the cold head 3. The configuration shown in Figure 6 provides an air curtain effect, similar to Figures 4 and 5, but also provides the following effects. Compared to the case in Figure 5 where helium gas is ejected from multiple directions, the configuration shown in Figure 6 is thought to cause helium gas to be ejected radially mainly from near the opening 18. To quickly draw in or exhaust air from the port space 15, it is desirable for the conductance of the flow path 11 to be large. The configuration shown in Figure 6 allows for a larger conductance than the configurations shown in Figures 4 and 5. In particular, when the volume of the port space 15 is large, the effect of increasing conductance with the configuration shown in Figure 6 is more pronounced.

[0030] Next, we will explain how an operator can replace the cold head 3. Figure 7 is a flowchart showing the procedure for replacing the cold head in the cooling device of Example 1.

[0031] In step S101, the worker replaces the port space 15 with helium gas in order to return it to atmospheric pressure. Specifically, the worker switches the main valve and valve 9 of the gas cylinder from the closed state to the open state, and allows helium gas to flow into the port space 15 through the gas piping 8. The port space 15 is filled with helium gas, and the port space 15 returns to atmospheric pressure.

[0032] In step S102, the operator replaces the cold head 3. Specifically, the operator loosens the screws to remove the cold head 3 from the refrigerator port 16 and installs the replacement cold head 3 into the refrigerator port 16. At this time, the operator continues to supply helium gas to the port space 15 via the flow path 11. As a result, helium gas is ejected along the wall of the vacuum container 2 toward the opening 20. While the cold head 3 is being replaced, the air curtain of the flange 4 shown in Figures 4 to 6 prevents atmospheric air from flowing into the port space 15.

[0033] In step S103, the worker exhausts the helium gas from the port space 15. Specifically, the worker switches the main valve of the gas cylinder to the closed position. Then, the worker activates the exhaust device (not shown). The exhaust device exhausts the helium gas from the port space 15 through the gas piping 8. When the pressure in the port space 15 is reduced to a predetermined level, the worker switches the valve 9 from the open position to the closed position and stops the exhaust device. This completes the cold head replacement work for the worker.

[0034] The cooling device 1 of Embodiment 1 comprises a vacuum container 2 for housing the object to be cooled 10, a refrigerator port 16, a flange 4, and a gas pipe 8. The refrigerator port 16 is provided in the vacuum container 2 and has a port space 15 for housing the cold head 3 of a refrigerator that cools the object to be cooled 10. The flange 4 has a flow path 11 formed on the surface in contact with the vacuum container 2 for drawing air into the port space 15 or exhausting air from the port space 15. The gas pipe 8 is configured to communicate with the port space 15 via the flow path 11.

[0035] According to Embodiment 1, it is not necessary to route the gas piping 8 inside the vacuum container 2. For example, the number of airtight connection points of the gas piping 8 can be minimized, such as the opening 18. Therefore, the airtightness of the vacuum space 30 can be improved. In addition, it is possible to suppress heat from entering the vacuum space 30 from the outside through the gas piping 8.

[0036] Furthermore, according to Example 1, when an operator replaces the cold head 3, helium gas is ejected radially from the flow path 11 into the port space 15, thereby suppressing the inflow of moisture-containing air into the port space 15. As a result, the freezing and formation of ice within the port space 15 is suppressed. If ice forms within the port space 15, the time required to exhaust the gas from the port space 15 becomes longer, but the cooling device 1 of Example 1 can avoid this extended gas exhaust time.

[0037] In the cooling devices disclosed in Patent Documents 1 and 2, a portion of the gas piping is located in a low-temperature area. In this case, if air enters the port space from the gas piping, the moisture contained in the air may freeze, potentially clogging the gas piping. In contrast, in the cooling device 1 of Example 1, gas flows along the inner or outer wall of the vacuum container 2 from the opening 18, which serves as the gas intake and exhaust port, and flows away from the low-temperature area. Therefore, even if moisture-containing air flows into the port space 15, freezing can be suppressed.

[0038] In the cooling device disclosed in Patent Document 2, the discharge pipe for discharging gas from the port space is formed on a flange provided on the outside of the vacuum vessel. In this case, since the discharge pipe is formed by drilling a lateral hole in the flange parallel to the flange surface, the thickness of the flange increases. The cold head protrudes into the working space by the amount of the increased flange thickness. As a result, the working space is compressed by the amount of the increased flange thickness. In contrast, according to this embodiment 1, the flow path 11 is provided on the flange 4 along the inner or outer wall surface of the vacuum vessel 2, so the flange can be made thinner than the flange disclosed in Patent Document 2. As a result, the working space for replacing the cold head can be widened.

[0039] According to Modification 1, since the flange 4 is provided inside the vacuum vessel 2, the protrusion of the cold head 3 from the vacuum vessel 2 can be minimized while enabling intake and exhaust of the port space 15. This allows for a wider working space for inserting and removing the cold head outside the refrigerator port than the cooling device disclosed in Patent Document 2.

[0040] Example 2 is a configuration in which the cooling device shown in Figure 3 is reversed. In Example 2, the same reference numerals are used for the same components as in Example 1, and their detailed descriptions are omitted.

[0041] The configuration of the cooling device of Example 2 will be described with reference to Figure 8. Figure 8 is a cross-sectional view showing one example configuration of the cooling device of Example 2. Note that the flange 4 described with reference to Figures 4 to 6 is attached to the vacuum container 2 upside down. Here, the case of the flange 4 shown in Figure 4 will be described.

[0042] The cooling device 1b is obtained by inverting the cooling device 1a shown in FIG. 3 upside down, and therefore, as shown in FIG. 8, a refrigerator port 16 is provided vertically below the object 10 to be cooled (in a direction opposite to the direction of the Z-axis arrow).

[0043] In the case of the configuration shown in FIG. 8, the following effects are obtained when an operator replaces the cold head 3. When the operator returns the pressure of the port space 15 to atmospheric pressure, the port space 15 is filled with helium gas. At this time, since the opening 20 of the port space 15 faces vertically downward, invasion of air, which has a greater mass than helium gas, into the port space 15 can be suppressed while helium gas fills the port space 15. This eliminates the need for measures to prevent air mixing using a gas bag or the like.

[0044] (Modification 2) A modification of the cooling device 1b according to Embodiment 2 will be described. FIG. 9 is a cross-sectional view showing a modification of the cooling device according to Embodiment 2. The configuration of the flange 4 corresponds to that shown in FIG. 5. Flow paths 11a and 11b are formed in the flange 4. As shown in FIG. 9, two gas pipes, a gas pipe 8a and a gas pipe 8b, are provided in the cooling device 1c. In the configuration example shown in FIG. 9, the gas pipe 8a is a supply pipe, and the gas pipe 8b is a discharge pipe. The gas pipe 8a is connected to the flow path 11a via an opening 18a, and the gas pipe 8b is connected to the flow path 11b via an opening 18b. A valve 9a is provided on the gas pipe 8a. A valve 9b is provided on the gas pipe 8b. In FIG. 9, an image of the recirculation of helium gas when returning the pressure of the port space 15 to atmospheric pressure is shown by a broken line. Note that the two gas pipes 8a and 8b shown in FIG. 9 may be provided in the configurations shown in FIG. 1 and FIG. 3 respectively.

[0045] Let's explain the effects of Modification 2. Consider the case where, after the operator replaces the cold head 3, the gas in the port space 15 is discharged to create a vacuum and reduce the pressure. Normally, when the operator vacuums the port space 15, they repeat the intake and exhaust process multiple times to purge impurities, but with the configuration shown in Figure 9, this operation becomes simpler. For example, the operator keeps valve 9a open, allowing helium gas to flow in from gas pipe 8a, and then opens valve 9b. The room-temperature helium gas flowing in from gas pipe 8a rises towards the colder area, is cooled in the port space 15, and descends, forming convection. The descending helium gas is discharged from gas pipe 8b. In other words, helium gas can be circulated in the port space 15. With this method, purging can be done simply by circulating helium gas, making the work simpler.

[0046] Example 3 is a cooling device shown in Figure 3, but with a two-stage cold head. In Example 3, the same reference numerals are used for the same components as those described in Examples 1 and 2, and their detailed descriptions are omitted.

[0047] The configuration of the cooling device of Embodiment 3 will be described with reference to the figures. Figure 10 is a cross-sectional view showing one example configuration of the cooling device of Embodiment 3. In the cooling device 1d, the refrigerator port 16 has a first sleeve 5a and a first base 6a, and a second sleeve 5b and a second base 6b. The first sleeve 5a and the first base 6a constitute the port space 15a. The first sleeve 5a covers the side surface of the port space 15a. The second sleeve 5b and the second base 6b constitute the port space 15b. The second sleeve 5b covers the side surface of the port space 15b. The cold head 3 has a head 19, a first columnar portion 14a in contact with the head 19, a first cooling stage 12a in contact with the first columnar portion 14a, a second columnar portion 14b in contact with the first cooling stage 12a, and a second cooling stage 12b in contact with the second columnar portion 14b.

[0048] The first cooling stage 12a and the first columnar portion 14a constitute the first stage, the second cooling stage 12b and the second columnar portion 14b constitute the second stage, and the head portion 19 is shared by the first stage and the second stage. The second cooling stage 12b absorbs heat from the object 10 to be cooled via the second pedestal 6b and the heat transfer member 7. A part of the periphery of the second columnar portion 14b is surrounded by the first pedestal 6a. The first pedestal 6a is in contact with the first cooling stage 12a.

[0049] A heater 32 is provided on the second pedestal 6b. The vicinity of the second pedestal 6b of the refrigerator port 16 is cooled to a helium liquefaction temperature (4.2 K) or lower. Therefore, when helium gas is introduced into the port space 15b, energizing the heater 32 raises the temperature of the port space 15b to prevent helium from liquefying. Further, a radiation shield 31 is provided to prevent radiant heat input to the object 10 to be cooled. The radiation shield 31 absorbs heat to the first cooling stage 12a via the first pedestal 6a and the heat transfer member 33, and is maintained at a low temperature.

[0050] According to Example 3, the volume of the port space 15 of a two-stage cold head is larger than that of a single-stage cold head, so the configuration of the flange 4 further exerts the effect of suppressing the inflow of atmospheric air into the port space when replacing the cold head. Note that the two-stage cold head is not limited to the configuration shown in Fig. 3, and may be applied to the configurations shown in each of Fig. 1, Fig. 8 and Fig. 9.

[0051] Example 4 has a configuration in which the cooling device shown in Fig. 10 is turned upside down and the influence of magnetism on the cold head is suppressed. In Example 4, the same constituent elements as those described in Examples 1 to 3 are denoted by the same reference numerals, and detailed description thereof is omitted.

[0052] The configuration of the cooling device of Example 4 will be described with reference to the figures. Figure 11 is a cross-sectional view showing one example configuration of the cooling device of Example 4. In the cooling device 1e shown in Figure 11, the flange 4a is made of a magnetic material. As a result, the flange 4a acts as a magnetic shield. In addition, a magnetic shield 34 is provided so as to cover the head 19. The object to be cooled 10 may be something that generates magnetism, for example, a superconducting magnet. A motor (not shown) is provided on the head 19 of the cold head 3, and it may malfunction if it is affected by magnetism. According to the configuration of Example 4, the flange 4a suppresses the influence of magnetism from the superconducting magnet on the head 19.

[0053] Let's explain another effect of Example 4. Magnetic materials used for magnetic shielding are often made of materials that are easily oxidized when exposed to the atmosphere, such as pure iron. Therefore, an anti-oxidation treatment is usually required on the surface of the magnetic material. In contrast, with the configuration shown in Figure 11, the flange 4a made of magnetic material is provided inside the vacuum container 2, so there is no need to apply an anti-oxidation treatment to the surface of the magnetic material. As a result, the effort required for preventing oxidation of the magnetic material can be reduced. Note that Example 4 may also be applied to the configurations shown in Figures 1, 3, 8, and 9, respectively.

[0054] Example 5 is a cooling device shown in Figure 11 to which an elastic mechanism has been added. In Example 5, the same reference numerals are used for the same components as those described in Examples 1 to 4, and their detailed descriptions are omitted.

[0055] The configuration of the cooling device of Example 5 will be described with reference to the figures. Figure 12 is a cross-sectional view showing one example configuration of the cooling device of Example 5. In the cooling device 1f shown in Figure 12, an elastic mechanism 35 is provided between the flange 4a and the first base 6a. The elastic mechanism 35 is composed of, for example, a columnar member and a disc spring. The columnar member is, for example, CFRP (Carbon Fiber Reinforced Plastics). The first sleeve 5a supporting the first base 6a generates a connecting force between the first base 6a and the first cooling stage 12a, and the elastic mechanism 35 plays a role in increasing that connecting force.

[0056] The effects of Example 5 will now be explained. It is desirable that the first cooling stage 12a and the second cooling stage 12b of the cold head 3 and the first base 6a and the second base 6b of the refrigerator port 16 be in close contact for heat transfer. The second cooling stage 12b is elastically supported by the second sleeve 5b, which uses a bellows with a large spring constant. On the other hand, the reaction force of the bellows of the first sleeve 5a alone may be insufficient on the first cooling stage 12a side. Therefore, by adding the elastic mechanism 35, thermal contact can be ensured.

[0057] As shown in Figure 12, in Embodiment 5 as well, since the flange 4a is provided inside the vacuum container 2, a wide workspace is secured when replacing the two-stage cold head 3, making the replacement work easier. Embodiment 5 may also be applied to the configurations shown in Figures 1, 3 and 8 to 10, respectively.

[0058] The embodiments described above are illustrative for explaining the present invention and are not intended to limit the scope of the invention to those embodiments only. Those skilled in the art can implement the present invention in various other forms without departing from the scope of the invention.

[0059] Furthermore, the embodiments described above include the following items. However, the items included in these embodiments are not limited to those listed below.

[0060] (Item 1) A cooling device comprising: a vacuum container for containing an object to be cooled; a refrigerator port provided in the vacuum container and having a port space for containing the cold head of a refrigerator for cooling the object to be cooled; a flange with a flow path formed on its surface in contact with the vacuum container; and a gas pipe communicating with the port space via the flow path.

[0061] According to this, there is no need to run gas piping inside the vacuum container.

[0062] (Item 2) A cooling device as described in Item 1, wherein the flow path is for drawing air into the port space or exhausting air from the port space. With this, it is possible to draw in an inert gas into the port space via the flow path, or to exhaust an inert gas from the port space via the flow path.

[0063] (Item 3) A cooling device according to Item 1 or 2, wherein the flange is provided inside the vacuum container and is in contact with the inner wall surface of the vacuum container.

[0064] According to this, a larger workspace can be secured when replacing the cold head.

[0065] (Item 4) A cooling device according to any one of Items 1 to 3, wherein the flange is circular in shape, and the flow path is one or more grooves provided along the radial direction of the circular shape.

[0066] According to this, because the flow path is groove-shaped, the inert gas flowing in through the gas piping flows radially toward the center of the port space.

[0067] (Item 5) A cooling device according to any one of Items 1 to 3, wherein the flange is circular in shape, the flow path has a plurality of groove-shaped first grooves provided along the radial direction of the circular shape, and a groove-shaped second groove provided along the circumferential direction of the circular shape, connected to the end of each of the plurality of first grooves that is furthest from the center of the circular shape, and the second groove is connected to the gas piping.

[0068] According to this, the inert gas flowing in through the gas piping flows circumferentially along the second groove and radiates out from multiple first grooves toward the center of the port space.

[0069] (Item 6) A cooling device according to any one of Items 1 to 3, wherein the flange is circular in shape, and the flow path is formed by a recess provided on the central side of the circular shape of a step formed in a concentric circle shape.

[0070] This allows the inert gas flowing in through the gas piping to easily diffuse along the surface of the recess toward the port space.

[0071] (Item 7) A cooling device according to any one of Items 1 to 6, wherein the refrigerator port is located vertically below the object to be cooled.

[0072] When removing a cold head while introducing an inert gas into the port space via gas piping and flow paths, helium gas, which is lighter in mass than air, is primarily used as the inert gas. In configurations where the object to be cooled is cooled from below, helium gas is filled from the top of the port space, making it easier for the air, which is heavier than helium gas, to flow out due to gravity. Therefore, it is possible to suppress the freezing of moisture contained in the air within the port space.

[0073] (Item 8) A cooling device according to any one of Items 1 to 7, wherein the cold head comprises: a head; a first columnar portion in contact with the head; a first cooling stage in contact with the first columnar portion; a second columnar portion in contact with the first cooling stage; and a second cooling stage in contact with the second columnar portion and absorbing heat from the object to be cooled. According to this, a two-stage cold head has a larger port space volume compared to a single-stage cold head, and therefore the flange configuration is more effective in suppressing the inflow of air into the port space when the cold head is replaced.

[0074] (Item 9) A cooling device described in any one of Items 1 to 8, wherein the material of the flange is a magnetic material. With this, when the object to be cooled is a superconducting magnet that generates magnetism, a magnetic shielding effect is obtained that shields the magnetism generated from the superconducting magnet.

[0075] (Item 10) In the cooling device described in Item 8, the refrigerator port has a first base that contacts the first cooling stage, a first sleeve that contacts the first base and covers a part of the side surface of the port space, a second base that contacts the second cooling stage, and a second sleeve that contacts the second base and covers the rest of the side surface of the port space, and an elastic mechanism is provided between the first base and the flange. With this, the elastic mechanism increases the connecting force between the first cooling stage and the first base.

[0076] (Item 11) A cooling device according to any one of Items 1 to 10, wherein two gas pipes are provided that are connected to the flow path. With this, by using one of the two gas pipes for gas inflow and the other for gas discharge, inert gas can be simultaneously inflowed into and discharged from the port space. In other words, inert gas can be recirculated into the port space. This makes it possible to purge impurities in the port space without repeating intake and exhaust multiple times.

[0077] 1, 1a-1f Cooling device, 2 Vacuum vessel, 3 Cold head, 4, 4a Flange, 5 Sleeve, 5a First sleeve, 5b Second sleeve, 6 Base, 6a First base, 6b Second base, 7 Heat transfer member, 8, 8a, 8b Gas piping, 9, 9a, 9b Valve, 10 Object to be cooled, 11, 11a, 11b Flow path, 12 Cooling stage, 12a First cooling stage, 12b Second cooling stage, 13 Mounting flange, 14 Columnar part, 14a First columnar part, 14b Second columnar part, 15, 15a, 15b Port space, 16 Refrigerator port, 17 Connection part, 18, 18a, 18b Opening, 19 Head, 20 Opening, 21 Tip, 22 Rear end, 23 Rod-shaped groove, 24 Circumferential groove, 25 Step, 30 Vacuum space, 31 Radiation shield, 32 Heater, 33 Heat transfer member, 34 Magnetic shield, 35 Elastic mechanism, 41 Contact surface, 42 Recess.

Claims

1. A cooling device comprising: a vacuum container for containing an object to be cooled; a refrigerator port provided in the vacuum container and having a port space for containing the cold head of a refrigerator for cooling the object to be cooled; a flange with a flow path formed on its surface in contact with the vacuum container; and a gas pipe communicating with the port space via the flow path.

2. A cooling device according to claim 1, wherein the flow path is for drawing air into the port space or exhausting air from the port space.

3. A cooling device according to claim 1, wherein the flange is provided inside the vacuum container and is in contact with the inner wall surface of the vacuum container.

4. A cooling device according to claim 1, wherein the flange is circular in shape, and the flow path is one or more grooves provided along the radial direction of the circular shape.

5. A cooling device according to claim 1, wherein the flange is circular in shape, the flow path has a plurality of first grooves in the shape of grooves provided along the radial direction of the circular shape, and a second groove in the shape of grooves provided along the circumferential direction of the circular shape, connected to the end of each of the plurality of first grooves that is furthest from the center of the circular shape, and the second groove is connected to the gas piping.

6. A cooling device according to claim 1, wherein the flange is circular in shape, and the flow path is formed by a recess provided on the central side of the circular shape of a step formed in a concentric circle shape.

7. A cooling device according to claim 1, wherein the refrigerator port is located vertically below the object to be cooled.

8. A cooling device according to claim 1, wherein the cold head comprises: a head; a first columnar portion in contact with the head; a first cooling stage in contact with the first columnar portion; a second columnar portion in contact with the first cooling stage; and a second cooling stage in contact with the second columnar portion and absorbing heat from the object to be cooled.

9. A cooling device according to claim 1, wherein the material of the flange is a magnetic material.

10. A cooling device according to claim 8, wherein the refrigerator port comprises a first base in contact with the first cooling stage, a first sleeve in contact with the first base and covering a part of the side surface of the port space, a second base in contact with the second cooling stage, and a second sleeve in contact with the second base and covering the rest of the side surface of the port space, and an elastic mechanism is provided between the first base and the flange.

11. A cooling device according to claim 1, wherein two gas pipes are provided that are connected to the flow path.

12. A method for replacing the cold head of a cooling device having a flange on which a flow path is formed on the surface in contact with the outer or inner wall of a vacuum container containing an object to be cooled, comprising: introducing an inert gas from a gas pipe connected to the flow path into a port space containing the cold head via the flow path; filling the port space with the inert gas; replacing the cold head while introducing the inert gas into the port space; and after replacing the cold head, exhausting the inert gas that has filled the port space via the gas pipe.

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