An external cold trap for a dilution refrigerator

Abstract

The application discloses an external cold trap for a dilution refrigerator and particularly relates to the field of refrigeration and cryogenics, comprising a liquid nitrogen tank, wherein a purification chamber is arranged inside the liquid nitrogen tank, and a separation unit, a purification unit and a precooling unit are sequentially arranged in the inner cavity of the purification chamber from top to bottom; a sealing top cover is arranged on the top of the purification chamber, and an air inlet pipe, an air outlet pipe and a maintenance channel are arranged on the sealing top cover. The application increases the heat exchange efficiency of airflow and reduces the cooling time by adding the precooling unit and the separation unit to the lower part and the upper part of the purification unit formed by activated carbon, so that the purification efficiency is improved; meanwhile, the self-purification device is formed by the separation unit and a copper mesh filter element, so that the self-pollution effect of the cold trap is avoided; the long-term stable operation of the throttling process and the stability of the dilution refrigerator during long-term repeated start-up are ensured, so that the maintenance period of the dilution refrigerator is greatly prolonged, and the application has a very positive significance for the practicality of the dilution refrigerator.

Description

Technical Field

[0001] This invention relates to the field of refrigeration and cryogenic engineering technology, and more specifically, to an external cold trap for a dilution refrigerator. Background Technology

[0002] Dilution refrigerators are core equipment for obtaining ultra-low temperature environments in the milliKelvin (mk) temperature range, and have important applications in cutting-edge scientific fields such as quantum computing and condensed matter physics research.

[0003] Due to their structural characteristics, dilution refrigeration units contain numerous micron-sized pores or capillary channels. During actual operation, the purity of the working gas and the stability of the throttling components directly affect the refrigeration performance and long-term operational stability of the unit. Impurities in the working gas can easily lead to pipe blockages in extremely low-temperature environments, potentially causing refrigeration cycle failure. Therefore, cold traps are often installed in dilution refrigeration systems to maximize the purification of the working gas.

[0004] However, traditional cold traps often fail to fully consider the structural characteristics of the dilution chiller itself, frequently resulting in low purification efficiency, easy clogging, or low heat exchange efficiency. Even worse, they may pose serious risks such as self-contamination, requiring frequent shutdowns for maintenance, thus affecting the continuity of the dilution chiller's operation and the overall system reliability. Therefore, developing a highly efficient, stable, and long-maintenance-cycle external cold trap to improve the overall performance and continuous operational stability of the dilution chiller is particularly necessary. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide an external cold trap for a dilution refrigerator to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an external cold trap for a dilution refrigerator, comprising a liquid nitrogen tank, wherein a purification chamber is provided inside the liquid nitrogen tank, and the inner cavity of the purification chamber comprises, from top to bottom, a separation unit, a purification unit and a precooling unit, wherein a sealed top cover is provided on the top of the purification chamber, and an air inlet pipe, an air outlet pipe and a maintenance channel are provided on the sealed top cover, wherein the air inlet pipe extends through the sealed top cover and into the inner cavity of the separation unit;

[0007] The bottom of the air outlet pipe is equipped with a clamp and a copper mesh filter.

[0008] In a preferred embodiment, the separation unit is configured as a cylindrical cavity, and the separation unit is located above the purification unit;

[0009] The precooling unit, purification unit, and separation unit together form the lower cavity of the purification chamber. The lower cavity of the purification chamber is cylindrical and is welded to the sealed top cover to form the purification chamber.

[0010] The precooling unit is a cylindrical copper sponge with multiple small cavities inside. It is placed at the bottom of the purification chamber to slow down the flow rate of the incoming gas used for precooling, prolong the heat exchange time of the incoming gas, and reduce the temperature of the incoming gas. The purification unit is a cylindrical activated carbon located above the precooling unit, which filters the incoming gas.

[0011] In a preferred embodiment, the liquid nitrogen tank, serving as a cavity for receiving liquid nitrogen, is cylindrical in shape, with an assembly port on the upper surface and an exhaust hole at the top of the assembly port.

[0012] In a preferred embodiment, a high-pressure pipe through hole is provided at the connection between the sealing top cover and the air inlet pipe, and a low-pressure pipe through hole is provided at the connection between the sealing top cover and the air outlet pipe. The high-pressure pipe through hole and the low-pressure pipe through hole are symmetrically arranged along the center of the sealing top cover.

[0013] The air inlet pipe is a high-purity circular pipe with one end close to the bottom of the lower part of the purification chamber and the other end aligned and passing through the high-pressure pipeline through hole.

[0014] The exhaust pipe is a high-cleanliness circular pipe, which is positioned inside the low-pressure pipeline through hole.

[0015] In a preferred embodiment, a clamping seat is provided at the bottom of the low-pressure pipe through hole, and the clamping seat is configured as a section of round pipe with internal threads.

[0016] In a preferred embodiment, the copper mesh filter element is assembled in the presser seat, and the copper mesh filter element is screwed into the presser seat and pressed onto the sealing top cover;

[0017] The clamping device is a section of round tube. Half of the clamping device channel has an internal hexagonal shape, and the other half is circular. The outer part of the round tube corresponding to the clamping device is threaded.

[0018] The present invention also includes a method for manufacturing an external cold trap for a dilution refrigerator, the specific steps of which are as follows:

[0019] S1: The liquid nitrogen tank is made of a material with low thermal conductivity. The lower end face is ground flat, and the upper end face has an assembly port. The diameter of the assembly port is larger than the diameter of the lower part of the purification chamber, but smaller than the diameter of the sealed top cover. The assembly port also has a semi-circular vent hole for nitrogen depressurization.

[0020] S2: The sealing top cover has a high-pressure pipe through hole and a low-pressure pipe through hole. A clamping seat is welded on the bottom surface of the sealing top cover, which is concentric with the low-pressure pipe through hole. The clamping seat is a section of round pipe with internal threads. A maintenance channel is left at the center of the sealing top cover.

[0021] S3: The lower part of the purification chamber is used to place the precooling unit. The diameter of the precooling unit is slightly larger than the inner diameter of the lower part of the purification chamber, so that the precooling unit and the purification chamber are interference fit. The precooling unit has a channel for the air inlet pipe to pass through. The lower part of the purification chamber is used to place the purification unit. The purification unit is located above the precooling unit and is made of activated carbon. After the gas is precooled, the impurities are removed after it flows through the purification unit.

[0022] S4: The last space is the separation unit, which is a cavity used to separate the fine activated carbon particles blown by the gas; the air inlet pipe is a clean pipe, which passes through the high-pressure pipeline through hole and is airtightly welded to the sealed top cover. One end of the air inlet pipe goes directly to the bottom of the lower part of the purification chamber, and the other end face leaves a gap with the upper end face of the sealed top cover.

[0023] S5: The vent pipe is welded to the through hole of the low-pressure pipeline. One end is left with a gap between it and the upper end face of the sealing top cover, and the other end does not pass through the sealing top cover. The copper mesh filter element is assembled in the clamping seat and is screwed into the clamping seat and pressed onto the sealing top cover. The clamping device is a section of round tube. Half of its channel cross-section is hexagonal and half is circular. The outer part of the round tube is threaded.

[0024] The technical effects and advantages of this invention are as follows:

[0025] 1. This invention enhances heat exchange and purification efficiency: By setting up a pre-cooling unit, the temperature of the gas entering the purification unit is effectively reduced, the adsorption efficiency and service life of activated carbon are improved, and the residence time of the gas in the purification chamber is extended, thus enhancing heat exchange.

[0026] 2. This invention can prevent self-contamination: The combined design of the separation unit and the copper mesh filter element can effectively prevent fine activated carbon particles from entering the subsequent pipeline with the airflow, thus avoiding the self-contamination problem of the cold trap.

[0027] 3. This invention can extend the maintenance cycle: The efficient purification and anti-pollution design ensures the long-term stable operation of the throttling process, reduces the risk of blockage, and thus significantly extends the maintenance cycle of the dilution chiller;

[0028] 4. The present invention has a reasonable structural design: the structure of each component is clear, and the design of the maintenance channel also provides convenience for possible maintenance. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0030] Figure 2 This is a cross-sectional schematic diagram of the overall structure of the present invention.

[0031] Figure 3 This is a schematic diagram of the combined structure of the clamping device and clamping device seat of the present invention.

[0032] Figure 4 This is a schematic diagram of the assembly structure of the purification chamber and the sealed top cover of the present invention.

[0033] Figure 5 This is a schematic diagram of the assembly structure of the vent hole and the assembly port of the present invention.

[0034] Figure 6 This is a schematic diagram of the clamping device structure of the present invention.

[0035] The attached diagram is labeled as follows: 1 Liquid nitrogen tank, 2 Purification chamber, 3 Pre-cooling unit, 4 Purification unit, 5 Separation unit, 6 Inlet pipe, 7 Outlet pipe, 8 Pressurizer, 9 Copper mesh filter element, 10 Maintenance channel, 11 Assembly port, 12 Vent hole, 13 Sealed top cover, 14 High pressure pipeline through hole, 15 Low pressure pipeline through hole, 16 Pressurizer seat, 17 Lower part of purification chamber. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] This invention provides, for example Figure 1-6 An external cold trap for a dilution refrigeration unit is shown, including a liquid nitrogen tank 1. The liquid nitrogen tank 1 has a purification chamber 2 inside. The inner cavity of the purification chamber 2 includes a separation unit 5, a purification unit 4 and a precooling unit 3 from top to bottom. The top of the purification chamber 2 is provided with a sealing top cover 13. The sealing top cover 13 is provided with an air inlet pipe 6, an air outlet pipe 7 and a maintenance channel 10. The air inlet pipe 6 penetrates the sealing top cover 13 and extends into the inner cavity of the separation unit 5.

[0038] Liquid nitrogen tank 1 is the cold source part of the cold trap. It is a cylindrical cavity used to contain liquid nitrogen. The upper end face of liquid nitrogen tank 1 is provided with an assembly port 11, which is used to connect with the purification chamber 2 or to add liquid nitrogen. The top of the assembly port 11 is provided with an exhaust port 12, which is used to discharge the nitrogen gas generated by the evaporation of liquid nitrogen and maintain the pressure balance inside the tank.

[0039] The bottom of the exhaust pipe 7 is equipped with a clamping device 8 and a copper mesh filter element 9; the precooling unit 3, the purification unit 4, and the separation unit 5 together form the cavity of the lower part 17 of the purification chamber. The lower part 17 of the purification chamber is a cylindrical cavity, and the lower part 17 of the purification chamber is welded to the sealing top cover 13 to form the purification chamber 2; the purification chamber 2 is the core part of gas purification; the upper part of the purification chamber 2 is the sealing top cover 13, which has multiple through holes: a high-pressure pipe through hole 14 is provided at a diameter of 7cm for connecting the intake pipe 6. A low-pressure pipe through hole 15 is provided at a diameter of 6cm for connecting the gas outlet pipe 7; a 10mm diameter through hole is also provided at the center of the sealing top cover 13 as a maintenance channel 10 to facilitate maintenance or replacement of the adsorbent inside the purification chamber 2; a clamping seat 16 is machined on the bottom surface of the sealing top cover 13, which is concentric with the low-pressure pipe through hole 15; the clamping seat 16 is a section of round tube with internal threads, used to install and fix the copper mesh filter element 9 and the clamping device 8;

[0040] The separation unit 5 is configured as a cylindrical cavity and is located above the purification unit 4, providing a space for settling and separation, preventing fine activated carbon particles that may be blown up during gas flow from entering the subsequent exhaust pipe 7 with the airflow.

[0041] The precooling unit 3 is a cylindrical piece of sponge copper with multiple small cavities inside. It is located at the bottom of the purification chamber 17. Sponge copper has a porous structure and good thermal conductivity. When the gas to be purified flows through this unit, it can fully exchange heat with the purification chamber wall cooled by liquid nitrogen, thus achieving precooling. At the same time, its porous structure also helps to slow down the gas flow rate, prolong the heat exchange time, improve the precooling effect, and may initially condense or adsorb some high-boiling-point impurities. The purification unit 4 is a section of cylindrical activated carbon located above the precooling unit 3. Activated carbon has a huge specific surface area and a well-developed pore structure, and is a commonly used high-efficiency adsorbent. When the precooled gas flows through the activated carbon, most of the impurities (such as air and moisture) will be adsorbed, thereby achieving the purpose of deep purification.

[0042] A high-pressure pipe through hole 14 is provided at the connection between the sealing top cover 13 and the air inlet pipe 6, and a low-pressure pipe through hole 15 is provided at the connection between the sealing top cover 13 and the air outlet pipe 7. The high-pressure pipe through hole 14 and the low-pressure pipe through hole 15 are symmetrically arranged along the center of the sealing top cover 13.

[0043] The air inlet pipe 6 is a circular pipe with electrolytic polishing to ensure the smoothness of its inner surface and low gas release rate. One end of the air inlet pipe 6 passes through the high-pressure pipe through hole 14 on the sealed top cover 13 and is sealed to it. The other end of the air inlet pipe 6 extends to the bottom of the lower part 17 of the purification chamber, that is, below the pre-cooling unit 3, to ensure that the gas can flow from bottom to top through each purification level. One end of the air inlet pipe 6 is close to the bottom of the lower part 17 of the purification chamber, and the other end of the air inlet pipe 6 is aligned and passes through the high-pressure pipe through hole 14.

[0044] The exhaust pipe 7 is also a round pipe with electrolytic polishing cleanliness, which is machined on the low-pressure pipe through hole 15 of the sealed top cover 13 and sealed to it; the inlet end of the exhaust pipe 7 is located at the top of the separation unit 5 and is used to export the purified clean gas.

[0045] The bottom of the low-pressure pipe through hole 15 is provided with a clamping seat 16, which is a section of round pipe with internal threads.

[0046] The copper mesh filter element 9 is assembled inside the presser seat 16. After being screwed into the presser seat 16, the copper mesh filter element 9 is pressed onto the sealing top cover 13. The copper mesh filter element 9 is made of fine copper mesh and is used to further filter out any small solid particles that may be present in the gas, serving as the last physical barrier.

[0047] The clamping device 8 is a section of round tube. Half of the cross-section of the clamping device 8 channel is hexagonal and the other half is round. The outer part of the round tube corresponding to the clamping device 8 is threaded. The clamping device 8 is screwed into the internal thread of the clamping device seat 16 through its external thread, thereby pressing the copper mesh filter element 9 into the corresponding position of the sealing top cover 13 to ensure the sealing and fixation of the filter element. The hexagonal shape makes it easy to use tools for tightening.

[0048] The present invention also includes a method for manufacturing an external cold trap for a dilution refrigerator, the specific steps of which are as follows:

[0049] S1: The liquid nitrogen tank 1 is made of a material with low thermal conductivity. The lower end face is ground flat and the upper end face has an assembly port 11. The diameter of the assembly port 11 is larger than the diameter of the lower part 17 of the purification chamber, but smaller than the diameter of the sealing top cover 13. The assembly port 11 has a semi-circular vent hole 12 for nitrogen depressurization.

[0050] S2: The sealing top cover 13 has a high-pressure pipe through hole 14 and a low-pressure pipe through hole 15. A clamping seat 16 is welded on the bottom surface of the sealing top cover 13, which is concentric with the low-pressure pipe through hole 15. The clamping seat 16 is a section of round pipe with internal threads. A maintenance channel 10 is left at the center of the sealing top cover 13.

[0051] S3: The lower part 17 of the purification chamber is used to place the precooling unit 3. The diameter of the precooling unit 3 is slightly larger than the inner diameter of the lower part 17 of the purification chamber, so that the precooling unit 3 and the purification chamber 2 are interference fit; the precooling unit 3 has a channel for passing through the air inlet pipe 6; the lower part 17 of the purification chamber is used to place the purification unit 4. The purification unit 4 is located above the precooling unit 3 and is made of activated carbon. After the precooled gas flows through the purification unit 4, the impurities are removed.

[0052] S4: The last space is the separation unit 5, which is a cavity used to separate the fine activated carbon particles blown by the gas; the air inlet pipe 6 is a clean pipe, which passes through the high pressure pipe through hole 14 and is airtightly welded to the sealing top cover 13. One end of the air inlet pipe 6 reaches the bottom of the lower part 17 of the purification chamber, and the other end face leaves a gap with the upper end face of the sealing top cover 13.

[0053] S5: The vent pipe 7 is welded to the low-pressure pipe through hole 15, with a gap between one end and the upper end face of the sealing top cover 13, and the other end does not pass through the sealing top cover 13; the copper mesh filter element 9 is assembled in the clamping seat 16, and is screwed into the clamping seat 16 and pressed onto the sealing top cover 13; the clamping device 8 is a section of round tube, half of its channel cross-section is hexagonal and half is circular, and the outer part of the round tube is threaded.

[0054] During operation, the gas to be purified enters through the inlet pipe 6, first passing through the pre-cooling unit 3 for cooling and deceleration, then flowing through the purification unit 4 where impurities are adsorbed by activated carbon, followed by the separation unit 5 to remove any possible particulate matter, and finally passing through the copper mesh filter element 9 for further filtration before being output as clean gas through the outlet pipe 7. The entire purification chamber 2 is cooled by the liquid nitrogen tank 1 to maintain a low-temperature environment to improve adsorption efficiency. This provides an external cold trap with optimized structure, high purification efficiency, good heat exchange performance, and effective prevention of self-contamination, used to improve the overall performance of the dilution refrigeration unit and ensure its continuous operational stability.

[0055] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change.

[0056] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other.

[0057] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An external cold trap for a dilution refrigerator, characterized in that: The system includes a liquid nitrogen tank (1), which has a purification chamber (2) inside. The purification chamber (2) includes a separation unit (5), a purification unit (4) and a precooling unit (3) from top to bottom. The purification chamber (2) has a sealed top cover (13) on top. The sealed top cover (13) has an inlet pipe (6), an outlet pipe (7) and a maintenance channel (10). The inlet pipe (6) passes through the sealed top cover (13) and extends into the cavity of the separation unit (5). The bottom of the air outlet pipe (7) is equipped with a clamp (8) and a copper mesh filter element (9). The purification unit (4) is configured as a cylindrical activated carbon, located above the precooling unit (3).

2. An external cold trap for a dilution refrigerator according to claim 1, characterized in that: The separation unit (5) is configured as a cylindrical cavity, and the separation unit (5) is located above the purification unit (4); The precooling unit (3), purification unit (4) and separation unit (5) together form the cavity of the lower part (17) of the purification chamber. The lower part (17) of the purification chamber is a cylindrical cavity. The lower part (17) of the purification chamber is welded to the sealing top cover (13) to form the purification chamber (2). The precooling unit (3) is a cylindrical sponge copper with multiple small cavities inside, and is placed at the bottom of the lower part (17) of the purification chamber.

3. An external cold trap for a dilution refrigerator according to claim 1, characterized in that: The liquid nitrogen tank (1) serves as a cavity for receiving liquid nitrogen and is cylindrical in shape. An assembly port (11) is provided on the upper surface of the liquid nitrogen tank (1), and an exhaust hole (12) is provided on the top of the assembly port (11).

4. An external cold trap for a dilution refrigerator according to claim 2, characterized in that: A high-pressure pipe through hole (14) is provided at the connection between the sealing top cover (13) and the air inlet pipe (6), and a low-pressure pipe through hole (15) is provided at the connection between the sealing top cover (13) and the air outlet pipe (7). The high-pressure pipe through hole (14) and the low-pressure pipe through hole (15) are symmetrically arranged along the center of the sealing top cover (13). The air inlet pipe (6) is a high-cleanliness circular pipe. One end of the air inlet pipe (6) is close to the bottom of the lower part (17) of the purification chamber, and the other end of the air inlet pipe (6) passes through the high-pressure pipeline through hole (14). The exhaust pipe (7) is a high-cleanliness circular pipe, which is positioned inside the low-pressure pipeline through hole (15).

5. An external cold trap for a dilution refrigerator according to claim 4, characterized in that: The bottom of the low-pressure pipe through hole (15) is provided with a clamping seat (16), and the clamping seat (16) is a section of round pipe with internal threads.

6. An external cold trap for a dilution refrigerator according to claim 5, characterized in that: The copper mesh filter element (9) is assembled inside the clamping seat (16), and the copper mesh filter element (9) is screwed into the clamping seat (16) and pressed onto the sealing top cover (13); The clamp (8) is a section of round tube. Half of the channel of the clamp (8) is hexagonal and the other half is round. The outer part of the round tube corresponding to the clamp (8) is threaded.

7. A method for manufacturing an external cold trap for a dilution refrigerator as described in any one of claims 1-6, characterized in that: The specific steps are as follows: S1: The liquid nitrogen tank (1) is made of a low thermal conductivity material, with the lower end face ground flat and the upper end face having an assembly port (11). The diameter of the assembly port (11) is larger than the diameter of the lower part (17) of the purification chamber, but smaller than the diameter of the sealing top cover (13). The assembly port (11) has a semi-circular exhaust hole (12) for nitrogen depressurization. S2: The sealing top cover (13) has a high-pressure pipe through hole (14) and a low-pressure pipe through hole (15). A clamping seat (16) is welded on the bottom surface of the sealing top cover (13) which is concentric with the low-pressure pipe through hole (15). The clamping seat (16) is a section of round pipe with internal threads. A maintenance channel (10) is left at the center of the sealing top cover (13). S3: The lower part (17) of the purification chamber is used to place the precooling unit (3). The diameter of the precooling unit (3) is larger than the inner diameter of the lower part (17) of the purification chamber, so that the precooling unit (3) and the purification chamber (2) are interference fit; the precooling unit (3) has a channel for passing through the air inlet pipe (6); the lower part (17) of the purification chamber is used to place the purification unit (4). The purification unit (4) is located above the precooling unit (3) and is made of activated carbon. After the gas is precooled, the impurities are removed after flowing through the purification unit (4); S4: The last space is the separation unit (5), which is a cavity used to separate the fine activated carbon particles blown by the gas; the air inlet pipe (6) is a clean pipe, which passes through the high pressure pipe through hole (14) and is airtightly welded to the sealing top cover (13). One end of the air inlet pipe (6) reaches the bottom of the lower part (17) of the purification chamber, and the other end face leaves a gap with the upper end face of the sealing top cover (13). S5: The vent pipe (7) is welded to the low-pressure pipe through hole (15), with a gap between one end and the upper end face of the sealing top cover (13), and the other end does not pass through the sealing top cover (13); the copper mesh filter element (9) is assembled in the clamping seat (16), and is screwed into the clamping seat (16) and pressed onto the sealing top cover (13); the clamping device (8) is a section of round tube, half of its channel cross-section is hexagonal and half is circular, and the outer part of the round tube is threaded.

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