Precooling system for dilution refrigerator

Abstract

The present invention provides a precooling system for a dilution refrigerator, which relates to the technical field of mK-level dilution refrigeration, comprising: a vacuum chamber comprising a normal temperature plate and a multi-stage cold plate, the multi-stage cold plate comprising a primary cold plate, a secondary cold plate and a tertiary cold plate, and provided in the vacuum chamber: a precooling unit arranged between the normal temperature plate and the secondary cold plate; a plurality of thermal switches respectively arranged between two adjacent cold plates between the primary cold plate and the tertiary cold plate, the plurality of thermal switches comprising a primary thermal switch and a plurality of secondary thermal switches, the primary thermal switch and the plurality of secondary thermal switches having an on state in response to the temperature of a mixing chamber being higher than different target temperatures and an off state in response to the temperature of the mixing chamber being lower than different target temperatures; the dilution refrigeration unit comprising a mixing chamber arranged on the tertiary cold plate; the primary thermal switch and the plurality of secondary thermal switches operating in an on state or an off state in response to temperature changes in the mixing chamber, so that the precooling unit is adjusted between a primary precooling mode and a secondary precooling mode.

Description

Technical Field

[0001] The present invention relates to the technical field of mK-level dilution refrigeration, and more particularly to a precooling system for a dilution refrigerator. Background Art

[0002] Dilution refrigerators are key devices in the fields of quantum computing, condensed matter physics, and detectors. In particular, in quantum computing, the core computing component, quantum computing chips, must operate at extremely low temperatures, as low as 10mK to 100mK, to enhance the quantum properties of superconducting qubits. Dilution refrigerators, due to their electromagnetic interference-free operation and high cooling capacity, are currently a widely used ultra-low temperature technology that can meet the needs of quantum computing.

[0003] A dilution refrigerator is a type of refrigerator that uses helium-3 ( 3 He) and helium-4 ( 4 In order to maintain continuous refrigeration, the dilution refrigerator separates the dilution phase entering the mixing chamber by distillation. 3 The He atoms are then extracted and circulated back into the mixing chamber, forming a continuous refrigeration cycle. By optimizing the design and operating conditions, the lowest temperature of the dilution refrigerator can reach the milliK level.

[0004] The rapid development of technologies like quantum computing has placed high demands on the cooling time of dilution refrigerators. The cooling and reheating times of dilution refrigerators directly determine the iteration speed of research in quantum computing and other fields. Currently, after a dilution refrigerator is started, the pulse tube refrigerator (PTC) at the top of the refrigerator is responsible for pre-cooling the sample from ambient temperature to a very low temperature during the pre-cooling phase. The pulse tube refrigerator consists of a primary and secondary cold head. The extremely low-temperature region (mixing chamber) of the dilution refrigerator, or the heat load, is connected to the secondary cold head. However, the secondary cold head's normal cooling power is only around 1 to 2 watts, resulting in a slow cooling rate. A single cooling cycle can take over a week, severely impacting the iteration speed of research in quantum computing and other fields. Summary of the Invention

[0005] To solve at least one of the technical problems in the prior art, an embodiment of the present invention provides a pre-cooling system for a dilution refrigerator, which can increase the cooling speed of the dilution refrigerator unit.

[0006] The present invention provides a precooling system for a dilution refrigerator, comprising: a vacuum chamber including a constant temperature plate and a multi-stage cold plate, the multi-stage cold plate including a primary cold plate, a secondary cold plate, and a tertiary cold plate arranged in sequence and spaced apart in a vertical direction; a precooling unit disposed in the vacuum chamber between the constant temperature plate and the secondary cold plate; a plurality of thermal switches disposed between two adjacent cold plates between the primary cold plate and the tertiary cold plate, the plurality of thermal switches including a primary thermal switch and a plurality of secondary thermal switches, the primary thermal switch and the plurality of secondary thermal switches respectively having an on state in response to a temperature of a mixing chamber being higher than different target temperatures and an off state in response to a temperature of the mixing chamber being lower than different target temperatures; a dilution refrigerator including the mixing chamber, the mixing chamber being disposed on the tertiary cold plate; the primary thermal switch and the plurality of secondary thermal switches operating in the on state or the off state in response to a temperature change in the mixing chamber, so that the precooling unit can be adjusted between a primary precooling mode and a secondary precooling mode, the primary precooling mode having a higher cooling power than the secondary precooling mode.

[0007] Optionally, the first-level thermal switch is arranged between the first-level cold plate and the second-level cold plate, and the first-level thermal switch has an on state in response to the temperature of the mixing chamber being higher than the first target temperature and an off state in response to the temperature of the mixing chamber being lower than the first target temperature; a plurality of second-level thermal switches are respectively arranged between two adjacent cold plates between the second-level cold plate and the third-level cold plate, and each of the second-level thermal switches has an on state in response to the temperature of the mixing chamber being higher than the second target temperature and an off state in response to the temperature of the mixing chamber being lower than the second target temperature, and the first target temperature is higher than the second target temperature.

[0008] Optionally, in response to the temperature of the mixing chamber being higher than 50K and lower than a predetermined temperature, the primary thermal switch and the plurality of secondary thermal switches are all in the on state, and the pre-cooling unit enters the primary pre-cooling mode.

[0009] Optionally, in response to the temperature of the mixing chamber being higher than 15K and lower than 50K, the first-level thermal switch is in the disconnected state, the plurality of second-level thermal switches are in the on state, and the pre-cooling unit enters the second-level pre-cooling mode.

[0010] Optionally, in response to the temperature of the mixing chamber being lower than 15K, the primary thermal switch and the plurality of secondary thermal switches are all in the disconnected state, and the pre-cooling of the pre-cooling unit ends.

[0011] Optionally, the pre-cooling unit includes: a hot end, which is arranged on the constant temperature plate; a first-level cold head, which is arranged between the constant temperature plate and the first-level cold plate; a second-level cold head, which is arranged between the first-level cold plate and the second-level cold plate, and the cooling power of the first-level cold head is higher than the cooling power of the second-level cold head; wherein, when the pre-cooling unit enters the first-level pre-cooling mode, the pre-cooling unit cools the mixing chamber through the first-level cold head; when the pre-cooling unit enters the second-level pre-cooling mode, the pre-cooling unit cools the mixing chamber through the second-level cold head.

[0012] 18. The heat dissipation controller of claim 17, wherein the bridge has an arc portion configured to disengage from the first heat dissipation controller and an arc portion configured to connect the heat dissipation controller to the first heat dissipation controller.

[0013] Optionally, a limiting boss is formed on the inner wall of the shell, for preventing the first engaging portion from moving toward the second heat conducting member under the drive of the first elastic member.

[0014] Optionally, the second heat-conducting member forms heat conduction with the first heat-conducting member at the first position, the distance between the first position and the limiting boss is a preset spacing, and the second heat-conducting member is configured to move back and forth in the vertical direction to change the size of the preset spacing, thereby adjusting the contact time between the second heat-conducting member and the first joint portion.

[0015] Optionally, the second heat conducting member includes: a second joint portion, used to press against or disengage from the first joint portion; a driving portion, one end of which is connected to the second joint portion and is configured to expand or contract in response to temperature changes of the low-temperature cold plate to drive the second joint portion to move in a vertical direction; a second adjusting portion, rotatably mounted on the shell and connected to the other end of the driving portion, for adjusting the preset spacing.

[0016] According to an embodiment of the present invention, a precooling system for a dilution refrigerator is provided, a vacuum chamber includes a constant temperature plate and a multi-stage cold plate, the multi-stage cold plate includes a primary cold plate, a secondary cold plate and a tertiary cold plate which are arranged in sequence in a vertical direction, the precooling unit is arranged between the constant temperature plate and the secondary cold plate, a plurality of thermal switches are respectively arranged between two adjacent cold plates between the primary cold plate and the tertiary cold plate, the plurality of thermal switches include a primary thermal switch and a plurality of secondary thermal switches, the primary thermal switch and the plurality of secondary thermal switches respectively have an on state in response to the temperature of the mixing chamber being higher than different target temperatures and an off state in response to the temperature of the mixing chamber being lower than different target temperatures, the dilution refrigerator includes a mixing chamber, the mixing chamber is arranged on the three-stage cold plate, the primary thermal switch and the plurality of secondary thermal switches operate in an on state or an off state in response to the temperature change of the mixing chamber, so that the precooling unit is adjusted between the primary precooling mode and the secondary precooling mode, the cooling power of the primary precooling mode is higher than the cooling power of the secondary precooling mode, and the cooling speed of the dilution refrigerator can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a side view of a precooling system for a dilution refrigerator according to an embodiment of the present invention;

[0018] Figure 2 is a perspective view of a thermal switch according to an embodiment of the present invention;

[0019] Figure 3 is a half-section view of a thermal switch according to an embodiment of the present invention, with the housing removed;

[0020] Figure 4 is a cross-sectional view of a thermal switch according to an embodiment of the present invention;

[0021] Figure 5 is a cross-sectional view of a thermal switch according to an embodiment of the present invention;

[0022] Figure 6 yes Figure 5 A partial cross-sectional view of the exemplary embodiment shown with the housing removed;

[0023] Figure 7 Schematic diagram of the working process of a thermal switch according to an embodiment of the present invention.

[0024] In the drawings, the meanings of the reference numerals are as follows:

[0025] 1. A first heat conducting member;

[0026] 11. First adjustment unit;

[0027] 111. First end cap;

[0028] 112. First sleeve;

[0029] 12. a first elastic member;

[0030] 13. a first joint;

[0031] 14. Upper limit piece;

[0032] 15. Lower limiter;

[0033] 151. Tighten the bolts;

[0034] 152. Limiting platform;

[0035] 153. Subject;

[0036] 16. Second elastic member

[0037] 2. Second heat conducting member;

[0038] 21. Second adjustment unit;

[0039] 211, second end cap;

[0040] 212, second sleeve;

[0041] 22. Driving unit;

[0042] 23. second joint;

[0043] 3. Shell;

[0044] 31. Limiting boss;

[0045] 4. Pre-cooling unit;

[0046] 41. Hot end;

[0047] 42. First-level cold head;

[0048] 43. Secondary cold head;

[0049] 5. Dilution refrigeration unit;

[0050] 51. Mixing chamber;

[0051] 6. Thermal switch;

[0052] 61. First level thermal switch;

[0053] 62. Secondary thermal switch;

[0054] 7. Vacuum chamber;

[0055] 8. Normal temperature board;

[0056] 9. First-level cold plate;

[0057] 10. Secondary cold plate;

[0058] 17. Three-stage cold plate. DETAILED DESCRIPTION

[0059] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of the concept of the present invention.

[0060] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the presence of the features, steps, operations and / or components, but do not exclude the presence or addition of one or more other features, steps, operations or components.

[0061] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0062] When expressions such as “at least one of A, B, and C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, and C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.). When expressions such as “at least one of A, B, or C, etc.” are used, they should generally be interpreted in accordance with the meaning commonly understood by those skilled in the art (for example, “a system having at least one of A, B, or C” should include but is not limited to systems having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, and C, etc.).

[0063] In order to solve the problem of slow cooling speed of the dilution refrigeration unit, according to the inventive concept of one aspect of the present invention, a vacuum chamber includes a constant temperature plate and a multi-stage cold plate, the multi-stage cold plate includes a primary cold plate, a secondary cold plate and a tertiary cold plate arranged in sequence along the vertical direction, the pre-cooling unit is arranged between the constant temperature plate and the secondary cold plate, and a plurality of thermal switches are respectively arranged between two adjacent cold plates between the primary cold plate and the tertiary cold plate, the plurality of thermal switches include a primary thermal switch and a plurality of secondary thermal switches, the primary thermal switch and the plurality of secondary thermal switches respectively have a conductive state in response to the temperature of the mixing chamber being higher than different target temperatures and a disconnected state in response to the temperature of the mixing chamber being lower than different target temperatures, the dilution refrigeration unit includes a mixing chamber, the mixing chamber is arranged on the three-stage cold plate, the primary thermal switch and the plurality of secondary thermal switches operate in a conductive state or a disconnected state in response to the temperature change of the mixing chamber, so that the pre-cooling unit is adjusted between the primary pre-cooling mode and the secondary pre-cooling mode, the cooling power of the primary pre-cooling mode is higher than the cooling power of the secondary pre-cooling mode, and the cooling speed of the dilution refrigeration unit can be improved.

[0064] Figure 1 FIG. 1 is a side view of a pre-cooling system for a dilution refrigerator according to an embodiment of the present invention.

[0065] According to an embodiment of the present invention, a precooling system for a dilution refrigerator is provided, such as Figure 1 As shown, the vacuum chamber 7 includes a constant temperature plate 8 and a multi-stage cold plate. The multi-stage cold plate includes a primary cold plate 9, a secondary cold plate 10, and a tertiary cold plate 17, which are spaced vertically in sequence. A pre-cooling unit 4, multiple thermal switches 6, and a dilution cooling unit 5 are disposed within the vacuum chamber 7. The pre-cooling unit 4 is disposed between the constant temperature plate 8 and the secondary cold plate 10. The multiple thermal switches 6 are disposed between adjacent cold plates between the primary cold plate 9 and the tertiary cold plate 17. The multiple thermal switches 6 include a primary thermal switch 61 and multiple secondary thermal switches 62. The primary thermal switch 61 and the multiple secondary thermal switches 62 each have an on state in response to the temperature of the mixing chamber 51 exceeding different target temperatures, and an off state in response to the temperature of the mixing chamber 51 falling below different target temperatures. The dilution cooling unit 5 includes a mixing chamber 51, which is disposed on the tertiary cold plate 17. The primary heat switch 61 and multiple secondary heat switches 62 operate in an on state or an off state in response to the temperature change of the mixing chamber 51, so that the precooling unit 4 is adjusted between the primary precooling mode and the secondary precooling mode, and the cooling power of the primary precooling mode is higher than the cooling power of the secondary precooling mode.

[0066] According to an embodiment of the present invention, the temperatures of the primary cold plate 9 , the secondary cold plate 10 and the tertiary cold plate 17 , which are sequentially spaced apart in the vertical direction, decrease step by step.

[0067] According to an embodiment of the present invention, the pre-cooling unit 4 may be a pulse tube refrigerator (PTC). The PTC is used to provide a low-temperature environment during the pre-cooling phase, enabling the dilution cooling unit 5 to achieve extremely low temperatures (mK level). The pre-cooling phase, serving as a pre-cooling stage for the dilution cooling unit 5, cools the mixing chamber 51 of the dilution cooling unit 5 from room temperature (approximately 300K) to a low temperature range of tens of degrees Kelvin (approximately 20K to 50K), thereby creating suitable initial conditions for the subsequent dilution cooling phase. After the pre-cooling phase, the temperature drops to a range within which the dilution cooling unit 5 can operate efficiently, reducing the heat load on the dilution cooling unit 5. The pre-cooling effect of the PTC reduces the amount of heat that the dilution cooling unit 5 must handle, enabling it to more efficiently reach extremely low temperatures (mK level). Furthermore, the stable low-temperature environment provided by the PTC ensures that the dilution cooling unit 5 operates under stable initial conditions. The PTC's design, lacking moving parts, offers high reliability and a long lifespan, reducing subsequent maintenance requirements.

[0068] According to an embodiment of the present invention, the vacuum chamber 7 includes a constant temperature plate 8 and a multi-stage cold plate, the multi-stage cold plate includes a primary cold plate 9, a secondary cold plate 10 and a tertiary cold plate 17 arranged in sequence in the vertical direction, the pre-cooling unit 4 is arranged between the constant temperature plate 8 and the secondary cold plate 10, and a plurality of thermal switches 6 are respectively arranged between two adjacent cold plates between the primary cold plate 9 and the tertiary cold plate 17, the plurality of thermal switches 6 include a primary thermal switch 61 and a plurality of secondary thermal switches 62, the primary thermal switch 61 and the plurality of secondary thermal switches 62 respectively have a function of responding to the temperature of the mixing chamber 51 being higher than that of the mixing chamber 51. The dilution refrigeration unit 5 is in an on state with different target temperatures and in an off state in response to the temperature of the mixing chamber 51 being lower than different target temperatures. The dilution refrigeration unit 5 includes a mixing chamber 51, and the mixing chamber 51 is arranged on the three-stage cold plate 17 as a heat load. The first-stage thermal switch 61 and multiple second-stage thermal switches 62 operate in an on state or an off state in response to the temperature change of the mixing chamber 51, so that the pre-cooling unit 4 is adjusted between the first-stage pre-cooling mode and the second-stage pre-cooling mode. The cooling power of the first-stage pre-cooling mode is higher than the cooling power of the second-stage pre-cooling mode, which can increase the cooling speed of the dilution refrigeration unit 5.

[0069] According to an embodiment of the present invention, a primary thermal switch 61 is disposed between the primary cold plate 9 and the secondary cold plate 10. The primary thermal switch 61 has an on state in response to the temperature of the mixing chamber 51 being higher than a first target temperature, and an off state in response to the temperature of the mixing chamber 51 being lower than the first target temperature. A plurality of secondary thermal switches 62 are disposed between two adjacent cold plates between the secondary cold plate 10 and the tertiary cold plate 17. Each secondary thermal switch 62 has an on state in response to the temperature of the mixing chamber 51 being higher than a second target temperature, and an off state in response to the temperature of the mixing chamber 51 being lower than the second target temperature. The first target temperature is higher than the second target temperature.

[0070] According to an embodiment of the present invention, the number of the secondary thermal switches 62 may be 2, 3, etc. For example, 3 secondary thermal switches 62 may be provided. Figure 1 As shown, three secondary thermal switches 62 are respectively arranged between two adjacent cold plates between the secondary cold plate 10 and the tertiary cold plate 17 in a threaded connection manner.

[0071] According to an embodiment of the present invention, in response to the temperature of the mixing chamber 51 being higher than 50K and lower than a predetermined temperature, the primary thermal switch 61 and the plurality of secondary thermal switches 62 are all in an on state, and the precooling unit 4 enters the primary precooling mode.

[0072] According to an embodiment of the present invention, the first target temperature of the primary thermal switch 61 is 50K.

[0073] According to an embodiment of the present invention, the predetermined temperature is normal temperature, which is approximately 25°C.

[0074] According to an embodiment of the present invention, in response to the temperature of the mixing chamber 51 being higher than 15K and lower than 50K, the primary thermal switch 61 is in the disconnected state, the multiple secondary thermal switches 62 are in the on state, and the precooling unit 4 enters the secondary precooling mode.

[0075] According to an embodiment of the present invention, the second target temperature of the secondary thermal switch 62 is 15K.

[0076] According to an embodiment of the present invention, in response to the temperature of the mixing chamber 51 being lower than 15K, the primary thermal switch 61 and the plurality of secondary thermal switches 62 are all in the disconnected state, and the precooling of the precooling unit 4 ends.

[0077] According to an embodiment of the present invention, the precooling unit 4 includes a hot end 41, a primary cold head 42, and a secondary cold head 43. The hot end 41 is disposed on the constant temperature plate 8. The primary cold head 42 is disposed between the constant temperature plate 8 and the primary cold head 9. The secondary cold head 43 is disposed between the primary cold plate 9 and the secondary cold plate 10. The cooling power of the primary cold head 42 is higher than that of the secondary cold head 43. When the precooling unit 4 enters the primary precooling mode, the precooling unit 4 cools the mixing chamber 51 through the primary cold head 42. When the precooling unit 4 enters the secondary precooling mode, the precooling unit 4 cools the mixing chamber 51 through the secondary cold head 43.

[0078] According to an embodiment of the present invention, the cooling power of the first-stage cold head 42 can reach up to 10W, and the temperature range of the first-stage cold head 42 is approximately 40K to 45K. The cooling power of the second-stage cold head 43 is approximately 1W to 2W, and the temperature range of the second-stage cold head 43 is approximately 3K to 4K.

[0079] According to an embodiment of the present invention, in response to the temperature of the mixing chamber 51 being higher than 50K and lower than room temperature, the primary thermal switch 61 and the plurality of secondary thermal switches 62 are both in an on state, and the pre-cooling unit 4 enters a primary pre-cooling mode. The heat in the mixing chamber 51 is transferred to the primary cold plate 9, which is then removed by the primary cold head 42. The high-power primary cold head 42 can rapidly cool the mixing chamber 51. In response to the temperature of the mixing chamber 51 being higher than 15K and lower than 50K, the primary thermal switch 61 is in an off state, and the plurality of secondary thermal switches 62 are in an on state. The pre-cooling unit 4 enters a secondary pre-cooling mode. The heat in the mixing chamber 51 is transferred to the secondary cold plate 10, which is then removed by the secondary cold head 43. The low-power secondary cold head 43 can further reduce the temperature of the mixing chamber 51. In response to the temperature of the mixing chamber 51 being lower than 15K, the primary thermal switch 61 and the secondary thermal switches 62 are all in the disconnected state, preventing the heat of the primary cold plate 9 and the secondary cold plate 10 from being transferred back to the mixing chamber 51, and the pre-cooling unit 4 ends the pre-cooling of the mixing chamber 51. After the pre-cooling unit 4 ends the pre-cooling of the mixing chamber 51, the external device transmits 3 He and 4 He mixed gas enters the vacuum chamber 7 and passes through the first-stage cold head 42 and the second-stage cold head 43. 3 He and 4 He mixed gas 4 He liquefaction ( 3 The boiling point of He is approximately 3.19K. 4 The boiling point of He is approximately 4.22K), and we get 4 He liquid, 4 The He liquid is transferred to the mixing chamber 51 under the action of gravity. 3 He and 4 He mixed gas 3 He is still in gaseous state. 3 He expands through throttling, and due to the throttling refrigeration effect, the gas after throttling 3 The temperature of He is further reduced and after condensation and liquefaction, it is obtained 3 He liquid is transferred to the mixing chamber 51, so that the temperature of the mixing chamber 51 is reduced until it reaches approximately 0.87 K. When the temperature of the mixing chamber 51 is approximately 0.87 K, 3 He liquid and 4 The He liquid phase separated and the upper layer was obtained. 3 He concentrated phase (i.e. 3 He liquid) and the lower 3 He dilution phase (i.e. 3 He and 4He mixed liquid), at this point, the dilution refrigeration unit 5 can begin the dilution refrigeration cycle. Using the primary cold head 42 to first cool the mixing chamber 51, and then switching to the secondary cold head 43 to cool the mixing chamber 51, can increase the cooling speed of the dilution refrigeration unit 5 and reduce the time of the pre-cooling stage.

[0080] According to an embodiment of the present invention, after the dilution refrigeration cycle is completed, the mixing chamber 51 of the dilution refrigeration unit 5 is gradually heated to room temperature. In response to the temperature of the mixing chamber 51 being greater than 15K and less than 50K, the primary thermal switch 61 is disconnected, the multiple secondary thermal switches 62 are connected, and the pre-cooling unit 4 heats the mixing chamber 51 via the secondary cold head 43. In response to the temperature of the mixing chamber 51 being greater than 50K and less than room temperature, both the primary thermal switch 61 and the multiple secondary thermal switches 62 are connected, and the pre-cooling unit 4 heats the mixing chamber 51 via the primary cold head 42. By first heating the mixing chamber 51 using the secondary cold head 43 and then switching to the primary cold head 42 to heat the mixing chamber 51, the dilution refrigeration unit 5 can increase the heating rate of the dilution refrigeration unit 5 and reduce the time of the heating stage.

[0081] Figure 2 is a perspective view of a thermal switch according to an embodiment of the present invention, Figure 3 is a half-section view of a thermal switch according to an embodiment of the present invention, with the housing removed. Figure 4 is a cross-sectional view of a thermal switch according to an embodiment of the present invention, Figure 5 is a cross-sectional view of a thermal switch according to an embodiment of the present invention, Figure 6 yes Figure 5 A partial cross-sectional view of the exemplary embodiment is shown with the housing removed.

[0082] According to an embodiment of the present invention, the plurality of thermal switches 6 include a primary thermal switch 61 and a plurality of secondary thermal switches 62, such as Figures 2 to 6 As shown, the first-stage thermal switch 61 or each second-stage thermal switch 62 includes a housing 3, a first heat-conducting member 1 and a second heat-conducting member 2. The housing 3 is constructed as a tubular structure with openings at both ends. The first heat-conducting member 1 contacts the cold plate with a higher temperature among the two adjacent cold plates. The first heat-conducting member 1 includes a first adjustment portion 11, a first elastic member 12 and a first joint portion 13. The first adjustment portion 11 is installed at the upper end opening of the housing 3. The first elastic member 12 is located in the housing 3 and is connected to the first adjustment portion 11. The first joint portion 13 is connected to the first adjustment portion 11 through the first elastic member 12. The second heat-conducting member 2 is installed at the lower end opening of the housing 3 and contacts the cold plate with a lower temperature among the two adjacent cold plates. The second heat-conducting member 2 has a conductive state in which the first joint portion 13 is pressed against the cold plate with a lower temperature in response to the cold plate with a lower temperature being higher than the target temperature, thereby forming a heat conduction state with the first heat-conducting member 1, and a disconnected state in which the first joint portion 13 is separated from the cold plate with a lower temperature being lower than the target temperature, thereby forming a heat isolation state with the first heat-conducting member 1.

[0083] According to an embodiment of the present invention, the first elastic member 12 is configured such that the deformation amount generated when the second heat conducting member 2 is in the conducting state can be adjusted by the first adjusting portion 11 to change the contact pressure between the second heat conducting member 2 and the first engaging portion 13 .

[0084] In such an embodiment, the first heat conductor 1 and the second heat conductor 2 are respectively installed at the openings at both ends of the shell 3 to seal the shell 3 to form a sealed cavity, and the sealed cavity is configured to be in a vacuum state. The first heat conductor 1 contacts the cold plate with a higher temperature among the two adjacent cold plates, and the second heat conductor 2 contacts the cold plate with a lower temperature among the two adjacent cold plates. When the temperature of the cold plate with a lower temperature is higher than the target temperature, the second heat conductor 2 contacts the first heat conductor 1 and presses with a certain pressure, so that the temperature of the cold plate with a lower temperature is transferred to the cold plate with a higher temperature through the second heat conductor 2 and the first heat conductor 1. When the temperature of the cold plate with a lower temperature drops below the target temperature, the second heat conductor 2 separates from the first heat conductor 1. Since the sealed cavity is in a vacuum state, heat is no longer transferred between the cold plate with a higher temperature and the cold plate with a lower temperature.

[0085] Affected by different target temperatures, the contact pressure between the second heat-conducting member 2 and the first heat-conducting member 1 will change. Since the contact surfaces of the second heat-conducting member 2 and the first heat-conducting member 1 are not ideal smooth surfaces, the change in contact pressure will affect the heat transfer efficiency. The deformation of the first elastic member 12 is adjusted by the first adjustment part 11 to achieve the adjustment of the contact pressure between the second heat-conducting member 2 and the first heat-conducting member 1 according to different target temperatures (for example, the first target temperature or the second target temperature), thereby improving the heat transfer efficiency and reducing the time required for heat transfer.

[0086] According to an embodiment of the present invention, a limiting boss 31 is formed on the inner wall of the housing 3 to prevent the first engaging portion 13 from moving toward the second heat conducting member 2 under the drive of the first elastic member 12 .

[0087] According to an embodiment of the present invention, when the second heat-conducting member 2 is in the conducting state, the first elastic member 12 is compressed, and the second heat-conducting member 2 resists the elastic force of the first elastic member 12. As the temperature of the cold plate gradually decreases, the contact pressure between the second heat-conducting member 2 and the first joint 13 gradually decreases until the limiting boss 31 resists the elastic force of the first elastic member 12. At this time, the second heat-conducting member 2 and the first joint 13 disengage, and the temperature of the cold plate drops below the target temperature.

[0088] According to an embodiment of the present invention, the second heat conducting member 2 is further configured to reciprocate in the vertical direction so that the second heat conducting member 2 switches between the on state and the off state in response to different target temperatures.

[0089] In such an embodiment, when the temperature of the high-temperature cold plate and the low-temperature cold plate changes, or the target temperature changes, the separation temperature of the thermal switch 6 is changed by adjusting the vertical position of the second heat conductor 2, thereby improving the flexibility of use of the thermal switch 6 and reducing the production cost.

[0090] Figure 7 Schematic diagram of the working process of a thermal switch according to an embodiment of the present invention.

[0091] According to an embodiment of the present invention, Figure 7 As shown, the second heat-conducting member 2 forms heat conduction with the first heat-conducting member 1 at the first position, and the distance between the first position and the limiting boss 31 is a preset spacing H. The second heat-conducting member 2 is configured to move back and forth in the vertical direction to change the size of the preset spacing H, thereby adjusting the contact time between the second heat-conducting member 2 and the first joint 13.

[0092] In this embodiment, the tubular housing 3 is arranged vertically, and the first heat conducting member 1 and the second heat conducting member 2 are also arranged vertically in sequence at both ends of the housing 3. The first adjusting portion 11, the first elastic member 12, and the first joint portion 13 of the first heat conducting member 1 are connected vertically in sequence from top to bottom. In response to the temperature of the cold plate being lower than the target temperature, the second heat conducting member 2 presses against the first joint portion 13, compressing the first elastic member 12. The pressing position, i.e., the first position, is located above the stop boss 31. As the temperature of the cold plate decreases, the compression of the first elastic member 12 decreases, and the contact pressure decreases until the stop boss 31 restricts further movement of the first joint portion 13. Subsequently, the second heat conducting member 2 disengages from the first joint portion 13. After the temperature of the cold plate stabilizes, the upper surface of the second heat conducting member 2 (i.e., the contact surface with the first joint portion 13) is located in the second position, which is located below the stop boss 31. The distance between the first position and the limiting boss 31 is a preset spacing H. For example, as the second heat-conducting member 2 moves upward and the preset spacing H increases, the time required for the second heat-conducting member 2 and the first heat-conducting member 1 to switch from heat conduction to thermal isolation becomes longer. During this period, more heat is transferred from the cold plate with a lower temperature to the cold plate with a higher temperature. When the second heat-conducting member 2 and the first heat-conducting member 1 form thermal isolation, the temperature of the cold plate with a lower temperature becomes lower, and the final isolation spacing h becomes larger. This enables the thermal switch 6 to be used in usage scenarios at different target temperatures, and the isolation temperature can be flexibly adjusted.

[0093] According to an embodiment of the present invention, the second heat conducting member 2 includes a second engaging portion 23, a driving portion 22, and a second adjusting portion 21. The second engaging portion 23 is used to press against or disengage from the first engaging portion 13. One end of the driving portion 22 is connected to the second engaging portion 23. The driving portion 22 is configured to expand or contract in response to temperature changes of the cold plate, thereby driving the second engaging portion 23 to move in a vertical direction. The second adjusting portion 21 is rotatably mounted on the housing 3 and connected to the other end of the driving portion 22. The second adjusting portion 21 is used to adjust the preset spacing H.

[0094] In such an embodiment, the second joint portion 23, the driving portion 22 and the second adjusting portion 21 of the second heat-conducting member 2 are connected in sequence from top to bottom in the vertical direction. The second joint portion 23 is roughly the same shape as the first joint portion 13, so as to have a larger contact area when pressed, thereby improving the heat transfer efficiency. The driving portion 22 can expand as the temperature of the low-temperature cold plate rises, and contract as the temperature of the low-temperature cold plate drops. It should be noted that the thermal expansion coefficient of the driving portion 22 is greater than that of the shell 3, so that when the temperature of the low-temperature cold plate drops below the target temperature, the contraction amount of the driving portion 22 is greater than the contraction amount of the shell 3, thereby separating the second joint portion 23 from the first joint portion 13. The second adjusting portion 21 is rotatably mounted on the shell 3 and can generate a vertical displacement relative to the shell 3, so that the second heat-conducting member 2 moves in the vertical direction as a whole, thereby adjusting the preset spacing H.

[0095] Exemplarily, the driving part 22 is preferably made of pure aluminum, and the shell 3 is preferably made of stainless steel. Stainless steel has higher low-temperature stability and is more reliable as the shell 3. At the same time, the expansion coefficients of stainless steel and pure aluminum are quite different whether in the room temperature range or the extremely low temperature range, which is conducive to improving the response speed of the thermal switch 6.

[0096] According to an embodiment of the present invention, Figure 6 As shown, the second adjustment portion 21 includes a second end cap 211 and a second sleeve 212. The second end cap 211 is connected to the driving portion 22. The second sleeve 212 is sleeved on the outside of the second end cap 211 and is threadedly connected to the housing 3 to drive the second end cap 211 to reciprocate in the vertical direction by rotation.

[0097] In this embodiment, the second end cap 211 is used to connect to the drive unit 22 and contact the cold plate. Therefore, it is mounted to the housing 3 via the second sleeve 212 to prevent heat from being transferred along the housing 3 and affecting the opening and closing of the thermal switch 6. The second sleeve 212 can be fixedly connected to the second end cap 211 by welding or interference fit, and then connected to the housing 3 via a simple and reliable threaded connection. By rotating the second end cap 211, the second heat-conducting member 2 can be moved vertically as a whole.

[0098] For example, when the drive portion 22 is made of pure aluminum, the second end cap 211 and the second joint portion 23 are preferably made of oxygen-free copper, which can effectively improve thermal conductivity. The second sleeve 212 is preferably made of stainless steel. On the one hand, it can form a good fit with the housing 3, reduce wear and prolong service life, and on the other hand, it can prevent heat from the second end cap 211 from leaking into the housing 3.

[0099] In some optional embodiments, the second end cap 211 and the driving portion 22 are connected by bolts, and the driving portion 22 and the second engaging portion 23 are connected in a plug-in manner.

[0100] According to an embodiment of the present invention, Figure 6 As shown, the first adjustment portion includes a first end cap and a first sleeve. The first end cap is connected to the first elastic member. The first sleeve is sleeved on the outside of the first end cap and is threadedly connected to the housing to drive the first end cap to reciprocate in the vertical direction through rotation.

[0101] In this embodiment, the first end cap 111 is used to connect to the first elastic member 12 and contact the hot cold plate. Therefore, it is mounted to the housing 3 via the first sleeve 112 to prevent heat from being transferred along the housing 3 and affecting the opening and closing of the thermal switch 6. The first sleeve 112 can be fixedly connected to the first end cap 111 by welding or interference fit, and then connected to the housing 3 via a simple and reliable threaded connection. This allows the first end cap 111 to move vertically while being rotated, thereby adjusting the deformation of the first elastic member 12.

[0102] According to an embodiment of the present invention, the first end cap 111 , the first elastic member 12 and the first joint portion 13 are made of the same material, and the thermal conductivity of the same material is greater than that of the housing 3 .

[0103] In this embodiment, heat from the cold plate (lower temperature) passes through the second heat-conducting member 2 and then needs to be transferred to the hot plate (higher temperature) via the first end cap 111, the first elastic member 12, and the first joint 13. Therefore, a material with high thermal conductivity, particularly greater than that of the housing 3, is required to achieve efficient heat transfer. Furthermore, due to the special structure of the first elastic member 12, all three are made of the same material to simplify connection.

[0104] Preferably, the first end cap 111, the first elastic member 12, and the first joint 13 are all made of oxygen-free copper. Since the first end cap 111 also needs to be configured with a first sleeve 112 and threadedly connected to the housing 3, the diameter of the first end cap 111 is limited. Therefore, the first end cap 111 and the first elastic member 12 are preferably integrally molded, and the first elastic member 12 is a generally S-shaped spring sheet made of oxygen-free copper. The diameter of the first joint 13 is not limited, so the first joint 13 and the first elastic member 12 can be integrally molded. Alternatively, a connecting seat can be provided at the lower end of the first elastic member 12 to connect to the first joint 13, or no connection is provided, so that the connecting seat and the first joint 13 are pressed against each other.

[0105] According to an embodiment of the present invention, the first end cap 111 is configured as a hollow cylindrical structure, and the first thermal conductor 1 further includes an upper stopper 14, a lower stopper 15, and a second elastic member 16. The upper stopper 14 seals the upper end of the first end cap 111, and the lower stopper 15 is disposed within the first end cap 111, extending from the lower end of the first end cap 111 and pressing against the first joint 13. The second elastic member 16 has its ends pressing against the upper stopper 14 and the lower stopper 15, respectively, and is configured to be in a compressed state to increase the contact pressure between the first joint 13 and the second thermal conductor 2.

[0106] In this embodiment, the upper limit member 14 is fixedly connected to the first end cap 111, a portion of the lower limit member 15 is located within the first end cap 111, and the other portion passes through the lower end of the first end cap 111 and the center of the first elastic member 12 to press against the first joint portion 13. When the first end cap 111 is rotated to adjust the deformation of the first elastic member 12, for example, when the first end cap 111 moves downward, the deformation of the first elastic member 12 increases, and the upper limit member 14 moves downward accordingly, while the lower limit member 15 always presses against the first joint portion 13, thereby increasing the deformation of the second elastic member 16 and increasing the pressure of the lower limit member 15 on the first joint portion 13.

[0107] In some optional embodiments, such as Figure 6 As shown, the lower limit member 15 includes a fastening bolt 151, a limit platform 152 and a main body 153. The main body 153 passes through the interior of the first end cap 111 and penetrates the first elastic member 12 to press against the first joint portion 13. The limit platform 152 is arranged on the main body 153 and is used to limit the second elastic member 16. The limit platform 152 is constructed as an annular disc. The fastening bolt 151 passes through the annular disc and is threadedly connected to the main body 153 to fix the limit platform 152 to the main body 153.

[0108] In some other embodiments, a limiting protrusion is further provided at the lower end of the first end cap 111 to limit the limiting platform 152 from falling out of the first end cap 111 .

[0109] Those skilled in the art will appreciate that various combinations and / or combinations of features described in the various embodiments and / or claims of the present invention may be made, even if such combinations and / or combinations are not explicitly described in the present invention. In particular, various combinations and / or combinations of features described in the various embodiments and / or claims of the present invention may be made, without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0110] It should also be noted that directional terms such as "upper," "lower," "front," "back," "left," and "right" mentioned in the embodiments are merely references to the directions in the accompanying drawings and are not intended to limit the scope of protection of the present invention. Throughout the drawings, identical elements are represented by identical or similar reference numerals. Conventional structures or configurations will be omitted where they may cause confusion in understanding the present invention, and the shapes and dimensions of the components in the drawings do not reflect actual size or proportion, but are merely illustrative of the contents of the embodiments of the present invention.

[0111] Unless otherwise indicated, the numerical parameters in this specification and the appended claims are approximate and can vary depending on the desired properties obtained through the teachings of the present invention. Specifically, all numbers used in the specification and claims to express composition amounts, reaction conditions, etc. should be understood to be modified by the term "about" in all cases. Generally, the meaning of the expression is to include variations of ±10% in some embodiments, ±5% in some embodiments, ±1% in some embodiments, and ±0.5% in some embodiments from the specific quantity.

[0112] The use of ordinal numbers such as "first," "second," and "third" in the specification and claims to modify corresponding elements does not in itself mean that the elements have any ordinal number, nor does it represent the order of one element relative to another or the order in the manufacturing method. The use of such ordinal numbers is only used to clearly distinguish one element with a certain name from another element with the same name.

[0113] Furthermore, unless specifically described or required to occur sequentially, the order of the steps is not limited to the order listed above and may be varied or rearranged based on desired design requirements. Furthermore, the above embodiments may be mixed and matched with each other or with other embodiments based on design and reliability considerations. That is, the technical features of different embodiments may be freely combined to form more embodiments.

[0114] The above describes embodiments of the present invention. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Although each embodiment has been described separately above, this does not mean that the measures in each embodiment cannot be advantageously used in combination. The scope of the present invention is defined by the appended claims and their equivalents. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which are intended to fall within the scope of the present invention.

Claims

1. A precooling system for a dilution refrigerator, characterized in that: include: The vacuum chamber includes a room temperature plate and a multi-stage cold plate. The multi-stage cold plate includes a primary cold plate, a secondary cold plate, and a tertiary cold plate that are sequentially spaced in the vertical direction. The vacuum chamber is provided with: A pre-cooling unit is provided between the normal temperature plate and the secondary cold plate; a plurality of thermal switches, each disposed between two adjacent cold plates between the primary cold plate and the tertiary cold plate, the plurality of thermal switches comprising a primary thermal switch and a plurality of secondary thermal switches, the primary thermal switch and the plurality of secondary thermal switches respectively having an on state in response to the temperature of the mixing chamber being higher than different target temperatures and an off state in response to the temperature of the mixing chamber being lower than different target temperatures; a dilution refrigeration unit, comprising the mixing chamber, wherein the mixing chamber is arranged on the third-stage cold plate; wherein the primary thermal switch and the plurality of secondary thermal switches operate in the on state or the off state in response to a temperature change in the mixing chamber, so that the pre-cooling unit is adjusted between a primary pre-cooling mode and a secondary pre-cooling mode, and the cooling power of the primary pre-cooling mode is higher than the cooling power of the secondary pre-cooling mode; The primary thermal switch or each of the secondary thermal switches comprises: The shell is constructed as a tubular structure with two ends open; A first heat conducting member contacts the cold plate with the higher temperature among the two adjacent cold plates, and the first heat conducting member comprises: a first adjusting portion, mounted at the upper opening of the housing; a first elastic member, located in the housing and connected to the first adjusting portion; a first engaging portion connected to the first adjusting portion via the first elastic member; The second heat-conducting member is installed at the lower end opening of the shell and contacts the cold plate with the lower temperature among the two adjacent cold plates. The second heat-conducting member has a conductive state in which it presses against the first joint portion in response to the cold plate with the lower temperature being higher than the target temperature, thereby forming heat conduction with the first heat-conducting member, and a disconnected state in which it detaches from the first joint portion in response to the cold plate with the lower temperature being lower than the target temperature, thereby forming thermal isolation with the first heat-conducting member.

2. The precooling system for a dilution refrigerator according to claim 1, characterized in that: The primary thermal switch is disposed between the primary cold plate and the secondary cold plate, the primary thermal switch having an on state in response to the temperature of the mixing chamber being higher than a first target temperature and an off state in response to the temperature of the mixing chamber being lower than the first target temperature; A plurality of secondary thermal switches are respectively arranged between two adjacent cold plates between the secondary cold plate and the tertiary cold plate, each of the secondary thermal switches having an on state in response to the temperature of the mixing chamber being higher than a second target temperature and an off state in response to the temperature of the mixing chamber being lower than the second target temperature, wherein the first target temperature is higher than the second target temperature.

3. The precooling system for a dilution refrigerator according to claim 2, characterized in that: In response to the temperature of the mixing chamber being higher than 50K and lower than a predetermined temperature, the primary thermal switch and the plurality of secondary thermal switches are all in the on state, and the pre-cooling unit enters the primary pre-cooling mode.

4. The precooling system for a dilution refrigerator according to claim 2, characterized in that: In response to the temperature of the mixing chamber being higher than 15K and lower than 50K, the primary thermal switch is in the disconnected state, the plurality of secondary thermal switches are in the on state, and the precooling unit enters the secondary precooling mode.

5. The precooling system for a dilution refrigerator according to claim 2, characterized in that: In response to the temperature of the mixing chamber being lower than 15K, the primary thermal switch and the plurality of secondary thermal switches are all in the disconnected state, and the pre-cooling of the pre-cooling unit ends.

6. The precooling system for a dilution refrigerator according to claim 1, characterized in that: The pre-cooling unit comprises: A hot end, arranged on the constant temperature plate; A primary cold head is provided between the normal temperature plate and the primary cold plate; A secondary cold head is provided between the primary cold plate and the secondary cold plate, wherein the cooling power of the primary cold head is higher than that of the secondary cold head; Wherein, when the pre-cooling unit enters the first-level pre-cooling mode, the pre-cooling unit cools the mixing chamber through the first-level cold head; When the pre-cooling unit enters the secondary pre-cooling mode, the pre-cooling unit cools the mixing chamber through the secondary cold head.

7. The precooling system for a dilution refrigerator according to claim 1, characterized in that: A limiting boss is formed on the inner wall of the shell, which is used to prevent the first engaging portion from moving toward the second heat conducting member under the drive of the first elastic member.

8. The precooling system for a dilution refrigerator according to claim 7, characterized in that: The second heat-conducting member forms heat conduction with the first heat-conducting member at a first position, the distance between the first position and the limiting boss is a preset spacing, and the second heat-conducting member is configured to move back and forth in a vertical direction to change the size of the preset spacing, thereby adjusting the contact time between the second heat-conducting member and the first joint portion.

9. The precooling system for a dilution refrigerator according to claim 8, characterized in that: The second heat conducting member comprises: a second engaging portion, used for pressing against or disengaging from the first engaging portion; a driving portion, one end of which is connected to the second joint portion and configured to expand or contract in response to a temperature change of the cold plate with a lower temperature, so as to drive the second joint portion to move in a vertical direction; The second adjusting portion is rotatably mounted on the housing and connected to the other end of the driving portion for adjusting the preset distance.

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