Air gap thermal switch and method of making same

Abstract

This application relates to an air-gap thermal switch and its fabrication method. The air-gap thermal switch includes: a hot-end conductor; a hot-end support shell coaxially connected to the hot-end conductor; a cold-end conductor opposite to the hot-end conductor and with a gap between them; a cold-end support shell coaxially connected to the cold-end conductor and coaxially connected to the hot-end support shell; and an adsorption pump, wherein the hot-end conductor, hot-end support shell, cold-end conductor, and cold-end support shell form a closed cavity, and the adsorption pump is connected to the closed cavity. The air-gap thermal switch of this application includes a hot-end support shell and a cold-end support shell, which shortens the processing length of a single support shell and reduces the processing difficulty of thin-walled and slender shells. During the fabrication process, it can detect whether the hot-end conductor and the cold-end conductor are in contact, improving the fabrication success rate. The welding and sealing of the hot-end support shell and the cold-end support shell are achieved by laser welding, resulting in a small heat-affected zone and minimal welding deformation, improving the coaxiality and gap accuracy after welding.

Description

Technical Field

[0001] This application relates to the field of quantum computing, and in particular to an air gap thermal switch and its fabrication method. Background Technology

[0002] Air-gap thermal switches have controllable and variable heat transfer capabilities and are currently widely used in cryogenic equipment such as dilution refrigerators. During the pre-cooling stage, the air-gap thermal switch remains in a "thermally closed" state, establishing a good thermal connection between the component to be cooled and the cold source, thus enabling rapid cooling. During the pre-cooling completion stage, the air-gap thermal switch remains in a "thermally open" state, achieving thermal isolation between the cooled component and the high-temperature zone, reducing heat leakage from the high-temperature zone to the low-temperature zone.

[0003] The working principle of the air gap thermal switch is as follows: When the thermal switch is closed, the gap between the hot end conductor and the cold end conductor is filled with helium as a heat-conducting medium. Helium has good thermal conductivity and can achieve an effective thermal connection between the hot end conductor and the cold end conductor. When the helium in the gap is adsorbed by the adsorption pump, the helium heat-conducting medium disappears, and the cold end conductor and the hot end conductor are only connected by the support shell with low thermal conductivity. At this time, the thermal switch is in the "thermal disconnect" state.

[0004] Existing air-gap thermal switches have thin and long supporting shells, making precision machining difficult. Ensuring that the cold and hot conductors do not touch under such a small gap is challenging. Once welding is complete, if the cold and hot conductors touch, it cannot be corrected, causing the entire air-gap thermal switch to fail. Summary of the Invention

[0005] To address the aforementioned issues, this application provides an air-gap thermal switch and its fabrication method, thereby improving the success rate of air-gap thermal switch fabrication.

[0006] In a first aspect, this application provides an air gap thermal switch, comprising: Hot-end conductor; A hot-end support shell is coaxially connected to the hot-end conductor; A cold-end conductor is disposed opposite to the hot-end conductor and has a gap between them; A cold-end support shell is coaxially connected to the cold-end conductor and is disposed opposite to and coaxially connected to the hot-end support shell; An adsorption pump is provided, wherein the hot end conductor, the hot end support shell, the cold end conductor, and the cold end support shell together form a closed cavity, and the adsorption pump is connected to the closed cavity.

[0007] According to some embodiments of this application, the air gap thermal switch further includes: A positioning structure is used for connecting and positioning the hot-end support shell and the cold-end support shell.

[0008] According to some embodiments of this application, the positioning structure includes a boss, which is disposed on the outer wall of the cold end support shell, the cold end support shell is inserted into the hot end support shell, and the end face of the hot end support shell abuts against the boss.

[0009] According to some embodiments of this application, the positioning structure further includes: The positioning groove is located on the end face of the hot end support shell; A protrusion is located on the surface of the boss, and the protrusion can enter the positioning groove.

[0010] According to some embodiments of this application, the gap between the cold end conductor and the hot end conductor is 0.1~1mm.

[0011] According to some embodiments of this application, the wall thickness of both the hot end support shell and the cold end support shell is 0.1~0.3mm.

[0012] According to some embodiments of this application, the ratio of the length of the hot end support shell to the length of the cold end support shell is 0.5 to 1.5.

[0013] According to some embodiments of this application, both the hot end support shell and the cold end support shell are made of stainless steel or titanium alloy.

[0014] Secondly, this application provides a method for fabricating the air gap thermal switch as described above, comprising: The hot end conductor and the hot end support shell are coaxially welded together to form a first assembly. The cold end conductor is coaxially welded to the cold end support shell to form a second assembly. The adsorption pump is welded to the cold end support shell; The first assembly and the second assembly are inserted and assembled to obtain an assembly; An unloaded cooling test was performed on the assembly to detect whether the hot end conductor and the cold end conductor came into contact. If a touch is detected, the first assembly and the second assembly are separated, and the first assembly and / or the second assembly are repaired. If no contact is detected, the hot end support shell and the cold end support shell are welded and sealed.

[0015] According to some embodiments of this application, the welding seal of the hot end support shell and the cold end support shell is achieved by laser welding.

[0016] The air-gap thermal switch of this application includes a hot-end support shell and a cold-end support shell, which shortens the processing length of a single support shell and reduces the processing difficulty of the thin-walled, slender shell. The hot-end conductor is pre-welded to the hot-end support shell to form a first assembly, and the cold-end conductor is pre-welded to the cold-end support shell to form a second assembly. After the two assemblies are interlocked, an unloaded cooling test can be performed to detect whether the conductors are in contact. If contact is found, the two assemblies can be separated and repaired, avoiding the problem of being unable to modify after overall welding, and improving the success rate of air-gap thermal switch fabrication. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without exceeding the scope of protection claimed by this application.

[0018] Figure 1 This is a schematic diagram of an air gap thermal switch according to an embodiment of this application; Figure 2 This is a schematic diagram of the hot-end conductor in an embodiment of this application; Figure 3 This is a schematic diagram of the hot-end support shell according to an embodiment of this application; Figure 4 This is a schematic diagram of the cold-end conductor in an embodiment of this application; Figure 5 This is a schematic diagram of the cold end support shell according to an embodiment of this application; Figure 6 This is a schematic diagram of the positioning groove and protrusion in an embodiment of this application; Figure 7 This is a schematic diagram illustrating the change in thermal conductivity of the air gap thermal switch as a function of temperature according to an embodiment of this application.

[0019] Among them, 10-air gap thermal switch; 1-Hot end conductor, 11-Hot end base, 12-Hot end column, 13-Receiving hole; 2-Hot end support shell, 21-First central hole, 211-Small diameter section, 212-Large diameter section, 22-End face of hot end support shell; 3-Cold end conductor, 31-Cold end base, 32-Cold end column; 4-Cold end support shell, 41-Second center hole; 5-Adsorption pump; 6-Gap; 7- Positioning structure, 71- Positioning groove, 72- Protrusion. Detailed Implementation

[0020] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] like Figure 1 As shown, in some embodiments, this application provides an air gap thermal switch 10, which includes: a hot end conductor 1, a hot end support shell 2, a cold end conductor 3, a cold end support shell 4, and an adsorption pump 5.

[0022] like Figure 2 As shown, the hot-end conductor 1 includes a hot-end base 11 and a hot-end pillar 12. The diameter of the hot-end base 11 is larger than the diameter of the hot-end pillar 12. The hot-end pillar 12 is disposed at one end of the hot-end base 11. Exemplarily, the hot-end pillar 12 is coaxially disposed with the base 11. A receiving hole 13 is provided at the center of the hot-end pillar 12. The hot-end base 11 and the hot-end pillar 12 can be integrally formed.

[0023] like Figure 3 As shown, the hot end support shell 2 is coaxially connected to the hot end conductor 1. For example, the hot end support shell 2 has a first central hole 21, the hot end column 12 passes through the first central hole 21 of the hot end support shell 2, and the hot end support shell 2 is connected to the end face of the hot end base 11.

[0024] like Figure 4 As shown, the cold end conductor 3 is disposed opposite to the hot end conductor 1. The cold end conductor 3 includes a cold end base 31 and a cold end column 32. The diameter of the cold end base 31 is larger than the diameter of the cold end column 32. The cold end column 32 is disposed at one end of the cold end base 31. Exemplarily, the cold end column 32 and the cold end base 31 are coaxially disposed. The cold end base 31 and the cold end column 32 can be integrally formed. The cold end column 32 can be inserted into the receiving hole 13 of the hot end conductor 1, and there is a gap 6 between the side wall of the cold end column 32 and the inner wall of the receiving hole 13.

[0025] Optionally, both the hot-end conductor 1 and the cold-end conductor 3 are made of high-purity oxygen-free copper material, which has good thermal conductivity.

[0026] like Figure 5 As shown, the cold end support shell 4 is coaxially connected to the cold end conductor 3. For example, the cold end support shell 4 has a second central hole 41 through which the cold end column 32 passes.

[0027] The cold end support shell 4 is connected to the end face of the cold end base 31. The cold end support shell 4 is also arranged opposite to and coaxially connected to the hot end support shell 2. The end of the cold end support shell 4 away from the cold end base 31 is connected to the end of the hot end support shell 2 away from the hot end base 11. The hot end conductor 1, the hot end support shell 2, the cold end conductor 3, and the cold end support shell 4 together form a closed cavity.

[0028] The adsorption pump 5 can be an existing adsorption pump. The adsorption pump 5 is connected to the cold end support shell 4 and communicates with the closed cavity formed by the hot end conductor 1, the hot end support shell 2, the cold end conductor 3 and the cold end support shell 4.

[0029] The hot-end support shell 2 and the cold-end support shell 4 are made of materials with low thermal conductivity. When the air gap thermal switch 10 is closed, the sealed cavity is filled with helium as a heat-conducting medium, and the hot-end conductor 1 and the cold-end conductor 3 are thermally connected through the helium. When the adsorption pump 5 adsorbs the helium in the sealed cavity, the hot-end conductor 1 and the cold-end conductor 3 are connected only through the hot-end support shell 2 and the cold-end support shell 4. Due to the low thermal conductivity of the support shell material, the air gap thermal switch 10 is in a thermally open state at this time.

[0030] The air gap thermal switch 10 in this embodiment includes a hot end support shell 2 and a cold end support shell 4, which shortens the processing length of a single support shell and reduces the processing difficulty of the thin-walled and slender shell.

[0031] When fabricating the air gap thermal switch 10, the hot end conductor 1 and the hot end support shell 2 are pre-welded to form a first assembly, and the cold end conductor 3 and the cold end support shell 4 are pre-welded to form a second assembly. After the two assemblies are inserted and assembled, an unloaded cooling test is conducted to detect whether the conductors are in contact. If contact is found, the two assemblies can be separated and repaired, avoiding the problem that the whole assembly cannot be modified after welding, thus improving the success rate of fabrication of the air gap thermal switch 10.

[0032] like Figure 5 As shown, in some embodiments, the air gap thermal switch 10 further includes a positioning structure 7, which is used for the connection and positioning of the hot end support shell 2 and the cold end support shell 4, thereby improving the assembly accuracy of the hot end support shell 2 and the cold end support shell 4.

[0033] like Figure 3 and Figure 5 As shown, in some embodiments, the first central hole 21 is a stepped hole, including a small-diameter portion 211 and a large-diameter portion 212 that are interconnected, with the large-diameter portion 212 being farther away from the hot-end base 11 relative to the small-diameter portion 211. The end of the cold-end support shell 4 that is away from the cold-end base 31 can be inserted into the large-diameter portion 212 of the first central hole 21. Exemplarily, the first central hole 21 and the cold-end support shell 4 are in a transition fit to improve the coaxiality accuracy of the hot-end support shell 2 and the cold-end support shell 4.

[0034] The positioning structure 7 includes a boss located on the outer wall of the cold end support shell 4. Optionally, the boss and the support shell 4 are integrally formed. The cold end support shell 4 is inserted into the large diameter portion 212 of the hot end support shell 2, and the end face 22 of the hot end support shell 2 away from the hot end base 11 abuts against the top surface of the boss.

[0035] like Figure 6 As shown, in some embodiments, the positioning structure 7 further includes a positioning groove 71 and a protrusion 72. The positioning groove 71 is located on the end face of the hot end support shell 2 away from the hot end base 11. The protrusion 72 is located on the surface of the boss and can enter the positioning groove 71.

[0036] During assembly, the cold-end support shell 4 is inserted into the hot-end support shell 2. The end face 22 of the hot-end support shell 2 away from the hot-end base 11 abuts against the top surface of the boss, and the protrusion 72 is embedded in the positioning groove 71, thereby achieving precise positioning and coaxial alignment of the hot-end support shell 2 and the cold-end support shell 4. The protrusion 72 embedded in the positioning groove 71 can effectively prevent radial displacement between the hot-end support shell 2 and the cold-end support shell 4 during assembly, ensuring uniform gap between the hot-end conductor 1 and the cold-end conductor 3.

[0037] In some embodiments, the width of the gap 6 between the sidewall of the cold end pillar 32 of the cold end conductor 3 and the inner wall of the receiving hole 13 of the hot end conductor 1 is 0.1~1mm, for example, the width of the gap 6 is 0.5mm. Heat is conducted between the hot end conductor 1 and the cold end conductor 3 through helium gas within the gap 6. If the gap 6 is too wide, the thermal resistance between the hot end conductor 1 and the cold end conductor 3 will be too high, reducing the heat transfer efficiency between them. If the gap 6 is too narrow, the assembly tolerance space will decrease, and the hot end conductor 1 and the cold end conductor 3 will easily come into contact.

[0038] In some embodiments, the wall thickness of both the hot-end support shell 2 and the cold-end support shell 4 is 0.1~0.3mm, for example, both are 0.2mm. If the wall thickness of the hot-end support shell 2 and the cold-end support shell 4 is too large, axial heat conduction of the shells will be aggravated, leading to increased heat leakage in the thermal disconnection state. If the wall thickness of the hot-end support shell 2 and the cold-end support shell 4 is too small, the thin-walled structure will lack strength, making it prone to deformation during processing and assembly.

[0039] like Figure 3 and Figure 5 As shown, in some embodiments, the ratio of the length H1 of the hot end support shell to the length H2 of the cold end support shell is 0.5 to 1.5. If the ratio is too large or too small, the length H1 of the hot end support shell or the length H2 of the cold end support shell will be too long, increasing the processing difficulty. It will also cause the gap 6 between the hot end conductor 1 and the cold end conductor 3 to be easily skewed.

[0040] In some embodiments, the hot end support shell 2 and the cold end support shell 4 are both made of stainless steel or titanium alloy.

[0041] An embodiment of this application also provides a method for preparing the above-mentioned air gap thermal switch 10, comprising: S1. The hot-end conductor 1 and the hot-end support shell 2 are coaxially welded to form the first assembly. Optionally, a vacuum brazing process is used to ensure the coaxiality and weld sealing of the hot-end conductor 1 and the hot-end support shell 2.

[0042] S2. The cold-end conductor 3 and the cold-end support shell 4 are coaxially welded to form the second assembly. Optionally, a vacuum brazing process is used to ensure the coaxiality and weld sealing of the cold-end conductor 3 and the cold-end support shell 4.

[0043] S3. Weld the adsorption pump 5 to the cold end support shell 4. Optionally, use silver brazing to weld one end of the connecting pipe to the cold end support shell 4 and the other end of the connecting pipe to the adsorption pump 5, so as to realize the connection between the adsorption pump 5 and the closed cavity.

[0044] S4. Connect and assemble the first assembly and the second assembly to obtain the assembly.

[0045] Specifically, the cold-end support shell 4 is inserted into the first central hole of the hot-end support shell 2. Simultaneously, the hot-end column 12 of the hot-end conductor 1 is inserted into the cold-end support shell 4, and the cold-end column 32 of the cold-end conductor 3 is inserted into the receiving hole 13 of the hot-end conductor 1. Optionally, the assembly of the first assembly and the second assembly is positioned by a positioning structure.

[0046] S5. Conduct an unloaded cooling test on the assembly to check whether the hot-end conductor 1 and the cold-end conductor 3 come into contact. The unloaded cooling test is an existing testing experiment.

[0047] S6. If contact is detected, separate the first assembly and the second assembly, and repair the first assembly and / or the second assembly. Repair methods include: performing minor machining on the surface of the hot end conductor 1 or the cold end conductor 3. After repair, repeat the mating assembly and no-load cooling test until no contact is detected.

[0048] S7. If no contact is detected, the hot end support shell 2 and the cold end support shell 4 shall be welded and sealed.

[0049] Traditional air gap thermal switches typically employ an integrated welding method where the cold-end conductor, hot-end conductor, and supporting housing are welded together. The final weld joint is usually made of silver brazing. Silver brazing requires heating the cold-end conductor and the hot-end conductor, which may cause structural deformation and increase the risk of the cold-end conductor and the hot-end conductor coming into contact.

[0050] In some embodiments, the final weld in this application is a weld between the hot-end support shell 2 and the cold-end support shell 4, and the weld seal between the hot-end support shell 2 and the cold-end support shell 4 is achieved by laser welding. Laser welding has a small heat-affected zone and minimal welding deformation, which can ensure the coaxiality and gap accuracy after welding.

[0051] Example 1 In this embodiment, the hot-end conductor 1 and cold-end conductor 3 are made of high-purity oxygen-free copper, and the gap 6 is set to 0.5 mm. The hot-end support shell 2 and cold-end support shell 4 are made of stainless steel with a wall thickness of 0.2 mm, and the lengths of the hot-end support shell 2 and cold-end support shell 4 are equal. The adsorption pump 5 uses an oxygen-free copper cavity encapsulated with activated carbon adsorption material; the connecting pipe between the adsorption pump 5 and the cold-end support shell 4 is made of stainless steel.

[0052] After the processing and fabrication of each component are completed, they are assembled according to the above preparation method. The prototype air gap thermal switch can achieve normal disconnection at low temperatures. By controlling the temperature of the adsorption pump 5, the switching between the closed and open states of the thermal switch can be achieved. When the temperature of the adsorption pump 5 is above approximately 20K, the thermal switch is in a fully closed state; when the temperature of the adsorption pump 5 is below approximately 13K, the thermal switch is in an open state; when the temperature of the adsorption pump 5 is between 13 and 20K, the thermal switch is in a transitional state between closed and open. Figure 7 The thermal conductivity of the air gap thermal switch at different temperatures is shown.

[0053] The embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are only for the purpose of helping to understand the technical solutions and core ideas of this application. Therefore, any changes or modifications made by those skilled in the art based on the ideas of this application, and on the specific implementation methods and application scope of this application, are all within the scope of protection of this application. In summary, the content of this specification should not be construed as a limitation of this application.

Claims

1. A gas gap thermal switch characterized in that, include: Hot-end conductor; A hot-end support shell is coaxially connected to the hot-end conductor; A cold-end conductor is disposed opposite to the hot-end conductor and has a gap between them; A cold-end support shell is coaxially connected to the cold-end conductor and is disposed opposite to and coaxially connected to the hot-end support shell; An adsorption pump is provided, wherein the hot end conductor, the hot end support shell, the cold end conductor, and the cold end support shell together form a closed cavity, and the adsorption pump is connected to the closed cavity.

2. The air gap thermal switch of claim 1, wherein, Also includes: A positioning structure is used for connecting and positioning the hot-end support shell and the cold-end support shell.

3. The air gap thermal switch of claim 2, wherein, The positioning structure includes a boss, which is disposed on the outer wall of the cold end support shell. The cold end support shell is inserted into the hot end support shell, and the end face of the hot end support shell abuts against the boss.

4. The air gap thermal switch of claim 3, wherein, The positioning structure also includes: The positioning groove is located on the end face of the hot end support shell; A protrusion is located on the surface of the boss, and the protrusion can enter the positioning groove.

5. The air gap thermal switch of claim 1, wherein, The gap between the cold end conductor and the hot end conductor is 0.1~1mm.

6. The air gap thermal switch of claim 1, wherein, The wall thickness of both the hot end support shell and the cold end support shell is 0.1~0.3mm.

7. The air gap thermal switch of claim 1, wherein, The ratio of the length of the hot end support shell to the length of the cold end support shell is 0.5 to 1.

5.

8. The air gap thermal switch of claim 1, wherein, Both the hot-end support shell and the cold-end support shell are made of stainless steel or titanium alloy.

9. A method for preparing an air gap thermal switch according to any one of claims 1 to 8, characterized in that, include: The hot end conductor and the hot end support shell are coaxially welded together to form a first assembly. The cold end conductor is coaxially welded to the cold end support shell to form a second assembly. The adsorption pump is welded to the cold end support shell; The first assembly and the second assembly are inserted and assembled to obtain an assembly; An unloaded cooling test was performed on the assembly to detect whether the hot end conductor and the cold end conductor came into contact. If a touch is detected, the first assembly and the second assembly are separated, and the first assembly and / or the second assembly are repaired. If no contact is detected, the hot end support shell and the cold end support shell are welded and sealed.

10. The preparation method according to claim 9, characterized in that, The hot-end support shell and the cold-end support shell are welded and sealed using laser welding.

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