Joule-Thomson refrigerator

Abstract

A JT refrigerator (18) is provided with: a pre-cooling refrigerator (20) provided with a first pre-cooling stage (25); a stage extension member (50) attached to the first pre-cooling stage (25) and cooled by the first pre-cooling stage (25); and a first refrigerant pipe (44a) attached to the table extension member (50) so as to be capable of heat exchange with the table extension member (50). The stage extension member (50) may be attached to a second pre-cooling stage (27) of the pre-cooling refrigerator (20) and cooled by the second pre-cooling stage (27), and the second refrigerant piping (44b) may be attached to the stage extension member (50) so as to be able to exchange heat with the stage extension member (50).

Description

Technical Field

[0001] The present invention relates to a Joule - Thomson (JT) refrigerator. Background Art

[0002] Conventionally, a JT refrigerator is known which includes: a JT valve that can cool a refrigerant gas by JT expansion; and a precooling refrigerator, such as a Gifford - McMahon (GM) refrigerator, etc., that precools the refrigerant gas supplied to the JT valve.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Application Laid - Open No. 2003 - 214719 Summary of the Invention

[0006] Technical Problem to be Solved by the Invention

[0007] Generally, the refrigerant piping of a JT refrigerator is installed on the cooling table of the precooling refrigerator by direct winding or the like. The refrigerant gas flowing through the refrigerant piping is cooled to the target precooling temperature by heat exchange with the cooling table. However, when the cooling table is small and its surface area is small, the heat exchange area for installing the refrigerant piping may be insufficient, and thus the precooling of the refrigerant gas may be insufficient.

[0008] One exemplary object of an embodiment of the present invention is to be able to increase the heat exchange area of the precooling refrigerator of the JT refrigerator.

[0009] Means for Solving the Technical Problem

[0010] According to an embodiment of the present invention, a JT refrigerator includes: a precooling refrigerator having a precooling table; a table extension member installed on the precooling table and cooled by the precooling table; and a refrigerant piping installed on the table extension member so as to be able to perform heat exchange with the table extension member.

[0011] Advantageous Effects of the Invention

[0012] According to the present invention, it is possible to increase the heat exchange area of the precooling refrigerator of the JT refrigerator. Brief Description of the Drawings

[0013] Figure 1 It is a diagram schematically showing a cryogenic cooling device according to an embodiment.

[0014] Figure 2 It is a diagram schematically showing another example of the table extension member according to an embodiment. Detailed Description of the Invention

[0015] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description and drawings, the same or equivalent components, parts, and processes are denoted by the same reference numerals, and repeated descriptions are appropriately omitted. The ratios or shapes of the respective parts shown in the drawings are simply set for ease of explanation and are not construed restrictively unless otherwise specifically stated. The embodiments are examples and do not limit the scope of the present invention in any way. All features or combinations thereof described in the embodiments are not necessarily essential features or combinations of the invention.

[0016] Figure 1 is a diagram schematically showing the cryogenic cooling device 10 according to the embodiment. The cryogenic cooling device 10 includes a vacuum vessel 12, a radiation shield 14, and a JT cooler 18 for cooling the object to be cooled 16.

[0017] The vacuum vessel 12 can be, for example, a cryostat and is configured to provide a cryogenic vacuum environment inside. The vacuum vessel 12 is made of a metal material such as stainless steel or other suitable high-strength materials to withstand the surrounding pressure (for example, atmospheric pressure). Inside the vacuum vessel 12, a radiation shield 14, the cryogenic part of the JT cooler 18, and the object to be cooled 16 are arranged.

[0018] The radiation shield 14 is arranged to surround the cryogenic part of the JT cooler 18 and the object to be cooled 16 inside the vacuum vessel 12, suppressing the intrusion of radiant heat from the vacuum vessel 12 into the JT cooler 18 and the object to be cooled 16. The radiation shield 14 is made of a highly thermally conductive metal material such as copper (for example, pure copper). An insulating material such as a multi-layer insulating material can be arranged between the vacuum vessel 12 and the radiation shield 14.

[0019] The object to be cooled 16 can be, for example, a superconducting device such as a superconducting coil, a measuring device that operates better at cryogenic temperatures, or other devices used at cryogenic temperatures. Alternatively, the object to be cooled 16 can be a cryogenic fluid such as liquid helium, and the JT cooler 18 can be used for the recondensation of the vaporized cryogenic fluid.

[0020] The JT cooler 18 includes a precooling cooler 20 and a refrigerant circuit 40. The refrigerant circuit 40 includes a JT valve 30 and a final-stage heat exchanger 32. The refrigerant flowing through the refrigerant circuit 40 is precooled by the precooling cooler 20, further cooled by JT expansion in the JT valve 30, and supplied to the final-stage heat exchanger 32. The object 16 to be cooled is cooled by exchanging heat with the final-stage heat exchanger 32. The cooled refrigerant is recovered from the final-stage heat exchanger 32, boosted in pressure by a compressor described later, precooled again by the precooling cooler 20, and supplied to the JT valve 30. Thus, the refrigerant circulates in the refrigerant circuit 40. The JT cooler 18 can cool the final-stage heat exchanger 32 to a temperature range of, for example, about 4K or lower than 4K (e.g., 1K to 4K), and thus can cool the object 16 to be cooled to this temperature range.

[0021] As an example, the precooling cooler 20 is a two-stage GM cooler. The precooling cooler 20 includes a first compressor 21 and an expander 22 also called a cold head. The expander 22 includes a drive unit 23, a first cylinder block 24, a first precooling stage 25, a second cylinder block 26, and a second precooling stage 27. The first compressor 21 is disposed in the surrounding environment (e.g., room-temperature atmospheric environment), that is, outside the vacuum vessel 12. The expander 22 is disposed in the vacuum vessel 12 as follows: the drive unit 23 is disposed outside the vacuum vessel 12, and the cylinder block and the precooling stage are disposed inside the vacuum vessel 12.

[0022] The first cylinder block 24 connects the first precooling stage 25 to the drive unit 23, whereby the first precooling stage 25 is structurally supported by the drive unit 23. The second cylinder block 26 connects the second precooling stage 27 to the first precooling stage 25, whereby the second precooling stage 27 is structurally supported by the first precooling stage 25. The first cylinder block 24 and the second cylinder block 26 extend coaxially, and the drive unit 23, the first cylinder block 24, the first precooling stage 25, the second cylinder block 26, and the second precooling stage 27 are arranged in a straight line in sequence. Typically, the first precooling stage 25 and the second precooling stage 27 are made of a highly thermally conductive metal material such as copper (e.g., pure copper), and the first cylinder block 24 and the second cylinder block 26 are made of other metal materials such as stainless steel.

[0023] A first displacer and a second displacer (not shown) are disposed in the first cylinder block 24 and the second cylinder block 26, respectively, so as to be reciprocable. A first regenerator and a second regenerator (not shown) are respectively assembled on the first displacer and the second displacer. Further, the drive unit 23 has a drive mechanism (not shown) such as a motor for reciprocating the first displacer and the second displacer. The drive mechanism includes a flow path switching mechanism that switches the flow path of the refrigerant gas so as to periodically repeat the supply of the refrigerant gas into the expander 22 and the discharge thereof from the expander 22. Usually, the refrigerant gas of the precooling cooler 20 is helium, but other appropriate gases can also be used.

[0024] The first compressor 21 is configured to recover the refrigerant gas from the expander 22, boost the recovered refrigerant gas in pressure, and supply the refrigerant gas to the expander 22 again. The circulation of the refrigerant gas between the first compressor 21 and the expander 22 is carried out by a suitable combination of pressure change and volume change of the refrigerant gas in the expander 22, thereby constituting a thermodynamic cycle (for example, GM cycle) that generates cold, and the expander 22 can provide ultra-low temperature cooling.

[0025] The first pre-cooling stage 25 is cooled to the first cooling temperature, and the second pre-cooling stage 27 is cooled to the second cooling temperature lower than the first cooling temperature. The first cooling temperature can be selected from the temperature range of, for example, 50K or more and 150K or less. The second cooling temperature can be selected from the temperature range of, for example, 10K or more and 25K or less.

[0026] In this embodiment, the stage extension member 50 is mounted on the first pre-cooling stage 25. The stage extension member 50 is thermally connected to the first pre-cooling stage 25 and is cooled to the first cooling temperature by the first pre-cooling stage 25. Therefore, the stage extension member 50 can be integrated with the first pre-cooling stage 25 and function as a part of the first pre-cooling stage 25.

[0027] The stage extension member 50 is made of a metal material with a high thermal conductivity such as copper (for example, pure copper or copper alloy) or aluminum (for example, pure aluminum or aluminum alloy) or other high thermal conductivity materials. Here, the high thermal conductivity material can be, for example, a material having a higher thermal conductivity than stainless steel (for example, SUS304).

[0028] The stage extension member 50 has a cylindrical shape (for example, a cylindrical shape), one end is fixed to the first pre-cooling stage 25, and it extends toward the second pre-cooling stage 27. The second cylinder block 26 is disposed inside the stage extension member 50. The axial length of the stage extension member 50 is shorter than that of the second cylinder block 26. Therefore, the other end of the stage extension member 50 does not reach the second pre-cooling stage 27. Therefore, the stage extension member 50 does not physically contact the second pre-cooling stage 27.

[0029] The stage extension member 50 is detachably mounted on the first pre-cooling stage 25. For example, a flange formed at one end of the stage extension member 50 can be fixed to the first pre-cooling stage 25 by a fastening member such as a bolt. By removing this fastening member, the fixing of the stage extension member 50 to the first pre-cooling stage 25 can be released. In addition, the stage extension member 50 can also be mounted on the first pre-cooling stage 25 by a non-detachable method such as brazing or welding.

[0030] As Figure 1As shown, the table extension member 50 can connect the first precooling table 25 and the radiation shield 14. For example, the flange at the end of the table extension member 50 formed on the side opposite to the first precooling table 25 can be fixed to the radiation shield 14 by fastening members such as bolts. The radiation shield 14 can be thermally connected to the first precooling table 25 via the table extension member 50 and is cooled to the first cooling temperature by the first precooling table 25. The radiation shield 14 surrounds the low-temperature portions of the JT cooler 18 such as the second precooling table 27, thereby suppressing the intrusion of heat into these low-temperature portions.

[0031] In addition, the radiation shield 14 can also be directly mounted on the first precooling table 25 without passing through the table extension member 50, or can be thermally connected to the first precooling table 25 via a heat transfer member different from the table extension member 50.

[0032] In addition to the JT valve 30 and the final heat exchanger 32, the refrigerant circuit 40 further includes a second compressor 41, a heat exchanger group 42, and refrigerant supply pipes 44 and refrigerant recovery pipes 46 connecting these components. Usually, the refrigerant gas circulating in the refrigerant circuit 40 is helium, but other suitable gases can also be used. In addition, the refrigerant circuit 40 is not limited to the specific structure described here, and various typical structures can be appropriately adopted.

[0033] The second compressor 41 is configured to boost the pressure of the refrigerant gas recovered from the refrigerant recovery pipe 46 and deliver it to the refrigerant supply pipe 44. For ease of understanding, Figure 1 the direction of refrigerant flow is shown by arrows. The second compressor 41 serves as a refrigerant source for circulating the refrigerant in the refrigerant circuit 40. The second compressor 41 is arranged outside the vacuum vessel 12.

[0034] In the refrigerant circuit 40, the heat exchanger group 42 is arranged between the second compressor 41 and the final heat exchanger 32. The heat exchanger group 42 is composed of a series of countercurrent heat exchangers (42a to 42c). In this embodiment, it has a three-stage structure including a first heat exchanger 42a, a second heat exchanger 42b, and a third heat exchanger 42c. The first heat exchanger 42a is arranged between the vacuum vessel 12 and the radiation shield 14, that is, in the space inside the vacuum vessel 12 and outside the radiation shield 14. The second heat exchanger 42b, the third heat exchanger 42c, and the final heat exchanger 32 are arranged inside the radiation shield 14.

[0035] The first heat exchanger 42a cools the refrigerant gas at a high temperature (e.g., normal temperature (e.g., about 300 K)) flowing from outside the vacuum container 12 into the vacuum container 12. The second heat exchanger 42b further cools the refrigerant cooled by the first heat exchanger 42a and the first pre-cooling stage 25. The third heat exchanger 42c further cools the refrigerant cooled by the second heat exchanger 42b and the second pre-cooling stage 27.

[0036] The refrigerant supply pipe 44 connects the discharge side of the second compressor 41 to the refrigerant inlet of the final heat exchanger 32, and the refrigerant recovery pipe 46 connects the refrigerant outlet of the final heat exchanger 32 to the suction side of the second compressor 41. The refrigerant supply pipe 44 has the high-pressure side flow paths of the first heat exchanger 42a, the second heat exchanger 42b, and the third heat exchanger 42c, respectively, and the refrigerant recovery pipe 46 has the low-pressure side flow paths of the first heat exchanger 42a, the second heat exchanger 42b, and the third heat exchanger 42c, respectively. In each heat exchanger, the refrigerant flowing through the high-pressure side flow path can be cooled by heat exchange between the high-pressure side flow path and the low-pressure side flow path. The high-pressure side flow path and the low-pressure side flow path may also be referred to as the high-temperature side flow path and the low-temperature side flow path, respectively.

[0037] Moreover, the refrigerant supply pipe 44 includes a first refrigerant pipe 44a and a second refrigerant pipe 44b. These refrigerant pipes are made of a highly heat-conductive metal material such as copper (e.g., pure copper), for example.

[0038] The first refrigerant pipe 44a extends from the first heat exchanger 42a via the first pre-cooling stage 25 to the second heat exchanger 42b. The first refrigerant pipe 44a connects the high-pressure side flow path of the first heat exchanger 42a to the high-pressure side flow path of the second heat exchanger 42b. The first refrigerant pipe 44a is thermally connected to the first pre-cooling stage 25, and the refrigerant flowing through the first refrigerant pipe 44a is cooled by the first pre-cooling stage 25.

[0039] However, in this embodiment, the first refrigerant pipe 44a is installed on the stage extension member 50 instead of the first pre-cooling stage 25 so as to be able to perform heat exchange with the stage extension member 50. For example, the first refrigerant pipe 44a is fastened to the stage extension member 50 in a state of being wound around the outer peripheral surface of the stage extension member 50. The first refrigerant pipe 44a is not wound around the first pre-cooling stage 25. As described above, since the stage extension member 50 is installed on the first pre-cooling stage 25 and is thermally connected thereto, the first refrigerant pipe 44a is cooled to the first cooling temperature by the stage extension member 50 cooled by the first pre-cooling stage 25.

[0040] The second refrigerant pipe 44b extends from the second heat exchanger 42b to the third heat exchanger 42c via the second precooling stage 27. The second refrigerant pipe 44b connects the high-pressure side flow path of the second heat exchanger 42b and the high-pressure side flow path of the third heat exchanger 42c. The second refrigerant pipe 44b is thermally connected to the second precooling stage 27, and the refrigerant flowing through the second refrigerant pipe 44b is cooled by the second precooling stage 27. The second refrigerant pipe 44b can be fastened to the second precooling stage 27 in a state of being wound around the outer peripheral surface of the second precooling stage 27.

[0041] The JT valve 30 is disposed between the last heat exchanger (the third heat exchanger 42c in this example) of the heat exchanger group 42 in the refrigerant supply pipe 44 and the final heat exchanger 32. The high-pressure side flow path of the third heat exchanger 42c is connected to the refrigerant inlet of the final heat exchanger 32 via the JT valve 30. In this embodiment, the JT valve 30 is a fixed orifice. However, the JT valve 30 can also be a variable orifice capable of adjusting the opening degree.

[0042] In the steady-state operation of the JT refrigerator 18, the refrigerant flows through the refrigerant circuit 40 as follows. The high-pressure refrigerant compressed by the second compressor 41 is first supplied to the high-pressure side flow path of the first heat exchanger 42a. The high-pressure refrigerant flowing through the high-pressure side flow path of the first heat exchanger 42a exchanges heat with the returning low-pressure refrigerant flowing through the low-pressure side flow path of the first heat exchanger 42a and is cooled. The high-pressure refrigerant cooled in the first heat exchanger 42a flows into the first refrigerant pipe 44a.

[0043] The high-pressure refrigerant flowing through the first refrigerant pipe 44a is cooled by the first precooling stage 25 of the precooling refrigerator 20 and is sent to the high-pressure side flow path of the second heat exchanger 42b. The high-pressure refrigerant flowing through the high-pressure side flow path of the second heat exchanger 42b exchanges heat with the returning low-pressure refrigerant flowing through the low-pressure side flow path of the second heat exchanger 42b and is cooled. The high-pressure refrigerant cooled in the second heat exchanger 42b flows into the second refrigerant pipe 44b.

[0044] The high-pressure refrigerant flowing through the second refrigerant pipe 44b is cooled by the second precooling stage 27 of the precooling refrigerator 20 and is sent to the high-pressure side flow path of the third heat exchanger 42c. The high-pressure refrigerant flowing through the high-pressure side flow path of the third heat exchanger 42c exchanges heat with the returning low-pressure refrigerant flowing through the low-pressure side flow path of the third heat exchanger 42c and is cooled. In this way, the high-pressure refrigerant is cooled to a temperature at which the JT effect can be expected (i.e., a temperature below the inversion temperature) and is sent to the JT valve 30.

[0045] When the high-pressure refrigerant to be cooled passes through the JT valve 30, it becomes a low-pressure refrigerant in a misty gas-liquid mixed state due to the Joule-Thomson effect and generates a cooling capacity within the temperature range of the liquefied refrigerant. The misty low-pressure refrigerant is sent to the final heat exchanger 32. As described above, when the refrigerant is helium, the final heat exchanger 32 can be cooled to the liquid helium temperature range. The final heat exchanger 32 can cool the object to be cooled 16 to this temperature by exchanging heat with the object to be cooled 16.

[0046] When cooling the final heat exchanger 32, the misty low-pressure refrigerant evaporates and thus gasifies again. In the JT valve 30, the unliquefied refrigerant and the refrigerant gasified due to evaporation return to the low-pressure side flow path of the third heat exchanger 42c. The low-pressure refrigerant sequentially flows through the third heat exchanger 42c, the second heat exchanger 42b, and the first heat exchanger 42a in the refrigerant recovery pipeline 46. At this time, as described above, the low-pressure refrigerant heats up while cooling the high-pressure refrigerant in each heat exchanger (42c, 42b, 42a). In this way, the low-pressure refrigerant that has returned to room temperature leaves the vacuum container 12, is recovered to the second compressor 41, and is compressed again.

[0047] In this way, the ultra-low temperature cooling device 10 can cool the object to be cooled 16 to a temperature lower than the second cooling temperature of the precooling refrigerator 20, for example, a desired temperature of about 4K or lower than 4K (for example, 1K to 4K).

[0048] According to the embodiment, the table extension member 50 is installed on the first precooling table 25, thereby expanding the heat exchange area of the first stage of the precooling refrigerator 20. By adjusting the shape of the table extension member 50, an area sufficient for precooling the first refrigerant pipe 44a can be ensured. For example, by increasing the size of the table extension member 50, such as lengthening the axial length or increasing the diameter of the table extension member 50, its surface area can be increased. Even if the first precooling table 25 is small and has a small surface area, the shortage of the heat exchange area for the first refrigerant pipe 44a can be compensated for by the table extension member 50.

[0049] As a result, a general-purpose product can be used for the precooling refrigerator 20. For example, a commercially available GM refrigerator can be used as the precooling refrigerator 20. There is no need to specifically design the surface area of the first precooling table 25 for the precooling of the JT refrigerator 18, and the cost of the JT refrigerator 18 can be reduced.

[0050] Also, in this embodiment, the table extension member 50 is detachably mounted on the first pre-cooling table 25. The first refrigerant pipe 44a is not installed on the first pre-cooling table 25. Therefore, by releasing the fixing of the table extension member 50 to the first pre-cooling table 25, the first pre-cooling table 25 can be separated from the table extension member 50. This makes it easy to detach the pre-cooling refrigerator 20 from the JT refrigerator 18, for example, for maintaining the pre-cooling refrigerator 20, and thus it is convenient.

[0051] As described above, the present invention has been described based on the embodiments. Those skilled in the art should understand that the present invention is not limited only to the above-described embodiments, various design changes can be made and various modifications can exist, and such modifications are also within the scope of the present invention. The various features described in association with one embodiment can also be applied to other embodiments. The new embodiments generated by combination have the effects of the combined embodiments.

[0052] Figure 2 FIG. is a diagram schematically showing another example of the table extension member 50 according to the embodiment. As shown in the figure, the table extension member 50 can also be mounted on the second pre-cooling table 27 of the pre-cooling refrigerator 20. The table extension member 50 can also be thermally connected to the second pre-cooling table 27 and cooled to the second cooling temperature by the second pre-cooling table 27. The table extension member 50 can also be integrated with the second pre-cooling table 27 and function as a part of the second pre-cooling table 27. The table extension member 50 can have a cylindrical (e.g., cylindrical) shape, one end is fixed to the second pre-cooling table 27, and it extends axially from the second pre-cooling table 27 toward the side opposite to the second cylinder block 26.

[0053] The second refrigerant pipe 44b can also be installed on the table extension member 50 so as to be able to perform heat exchange with the table extension member 50. As described above, the second refrigerant pipe 44b connects the second heat exchanger 42b and the third heat exchanger 42c. The second refrigerant pipe 44b is fastened to the table extension member 50 in a state of being wound around the outer peripheral surface of the table extension member 50. In this example, the second refrigerant pipe 44b is not wound around the second pre-cooling table 27. Since the table extension member 50 is mounted on the second pre-cooling table 27 and is thermally connected thereto, the second refrigerant pipe 44b is cooled to the second cooling temperature by the table extension member 50 cooled by the second pre-cooling table 27.

[0054] In this way, the table extension member 50 can be used to expand the heat exchange area of the second stage of the pre-cooling refrigerator 20. By adjusting the shape of the table extension member 50, an area sufficient for pre-cooling the second refrigerant pipe 44b can be ensured. Even if the second pre-cooling table 27 is small and has a small surface area, the shortage of the heat exchange area for the second refrigerant pipe 44b can be compensated by the table extension member 50.

[0055] Similar to the above-described embodiment, the table extension member 50 can also be detachably mounted on the second precooling table 27. The second refrigerant pipe 44b is not mounted on the second precooling table 27. Therefore, by releasing the fixing of the table extension member 50 to the second precooling table 27, the second precooling table 27 can be separated from the table extension member 50. This makes it easy to detach the precooling refrigerator 20 from the JT refrigerator 18, for example, for the maintenance of the precooling refrigerator 20, and thus it is convenient.

[0056] Figure 2 The illustrated table extension member 50 can also be combined with the Figure 1 described embodiment. That is, the JT refrigerator 18 can include: a first table extension member 50 mounted on the first precooling table 25 and cooled by the first precooling table 25; and a second table extension member 50 different from the first table extension member 50, mounted on the second precooling table 27 and cooled by the second precooling table 27.

[0057] In addition, when it is desired to further increase the heat exchange area or the like, the first refrigerant pipe 44a can be mounted not only on the table extension member 50 but also on the first precooling table 25. Similarly, the second refrigerant pipe 44b can be mounted not only on the table extension member 50 but also on the second precooling table 27.

[0058] In Figure 1 the embodiment, the table extension member 50 extends from the first precooling table 25 toward the second precooling table 27, but the configuration of the table extension member 50 is not limited to this. The table extension member 50 can also extend from the first precooling table 25 along the first cylinder block 24. At this time, the first cylinder block 24 is disposed within the table extension member 50. The axial length of the table extension member 50 can be shorter than that of the first cylinder block 24 so that the table extension member 50 does not physically contact the vacuum vessel 12.

[0059] Similarly, in Figure 2 the embodiment, the table extension member 50 can also extend from the second precooling table 27 along the second cylinder block 26 toward the first precooling table 25. The second cylinder block 26 is disposed within the table extension member 50. The axial length of the table extension member 50 can be shorter than that of the second cylinder block 26 so that the table extension member 50 does not physically contact the first precooling table 25.

[0060] The precooling refrigerator 20 is not limited to a GM refrigerator. The precooling refrigerator 20 can also be other types of cryogenic refrigerators such as a pulse tube refrigerator or a Stirling refrigerator.

[0061] According to the embodiment, the present invention has been described using specific statements, but the embodiment only shows one aspect of the principle and application of the present invention. Without departing from the idea of the present invention defined by the claims, there can be many variations and configuration changes in the embodiment.

[0062] Industrial Applicability

[0063] The present invention can be applied to the field of Joule-Thomson refrigerators.

[0064] Symbol Explanation

[0065] 10 - Ultra-low temperature cooling device, 18 - JT refrigerator, 20 - Pre-cooling refrigerator, 25 - First pre-cooling stage, 27 - Second pre-cooling stage, 44a - First refrigerant pipe, 44b - Second refrigerant pipe, 50 - Stage extension member.

Claims

1. A Joule-Thomson refrigerator, characterized in that, Comprising: A precooling refrigerator having a precooling table; A table extension member mounted on the precooling table and cooled by the precooling table; and A refrigerant pipe mounted on the table extension member so as to be capable of heat exchange with the table extension member.

2. The Joule-Thomson refrigerator according to claim 1, wherein The table extension member is detachably mounted on the precooling table.

3. The Joule-Thomson refrigerator according to claim 2, wherein The refrigerant pipe is not mounted on the precooling table.

4. The Joule-Thomson refrigerator according to any one of claims 1 to 3, wherein The precooling refrigerator has a cylinder extending from the precooling table, The cylinder is disposed within the table extension member.

5. The Joule-Thomson refrigerator according to any one of claims 1 to 3, wherein The precooling refrigerator has a cylinder extending from the precooling table, The table extension member extends from the precooling table toward the side opposite to the cylinder.

6. The Joule-Thomson refrigerator according to claim 1, wherein The precooling refrigerator has a first precooling table and a second precooling table cooled to a temperature lower than that of the first precooling table, The table extension member is mounted on the first precooling table and cooled by the first precooling table.

7. The Joule-Thomson refrigerator according to claim 6, wherein The table extension member is detachably mounted on the first precooling table.

8. The Joule-Thomson refrigerator according to claim 7, wherein The refrigerant pipe is not mounted on the first precooling table.

9. The Joule-Thomson refrigerator according to claim 6, wherein The precooling refrigerator has a cylinder connecting the second precooling table and the first precooling table, The cylinder is disposed within the table extension member.

10. The Joule-Thomson refrigerator according to any one of claims 6 to 9, wherein The table extension member does not physically contact the second precooling table.

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