A cryogenic interaction region device for an ultralow temperature cesium fountain clock

Abstract

The application relates to a low-temperature action zone device for an ultralow-temperature cesium atom fountain clock, which comprises the following steps: a liquid nitrogen Dewar flask is hung in a vacuum cylinder through a plurality of hanging pipes, a cold shield is arranged between the vacuum cylinder and the liquid nitrogen Dewar flask, and a microwave cavity assembly is arranged in the liquid nitrogen Dewar flask; a liquid supplementing and refrigerating device is arranged above the vacuum cylinder, and the liquid supplementing and refrigerating device is connected with the liquid nitrogen Dewar flask through a liquid nitrogen pipeline and used for filling the liquid nitrogen Dewar flask with liquid nitrogen. The hanging structure of the liquid nitrogen Dewar flask is combined with the automatic liquid supplementing system of the liquid supplementing and refrigerating device, the stability of the temperature of the low-temperature action zone is improved, and the precise control of the low-temperature environment is realized. The liquid nitrogen is automatically supplemented through the liquid supplementing and refrigerating device, temperature fluctuation caused by manual operation is avoided, and the precise tuning of the microwave cavity resonance frequency is ensured. The hanging structure is combined with the cold shield, heat exchange between the low-temperature action zone and the normal-temperature system is effectively avoided, heat loss is avoided, and the temperature stability is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of cryogenic atomic fountain clock technology, specifically relating to a cryogenic action zone device for cryogenic cesium atomic fountain clocks. Background Technology

[0002] The cryogenic cesium atomic fountain clock, as a high-precision time and frequency reference device, boasts the highest accuracy performance currently available and is used to calibrate other types of timekeeping atomic clocks. Its performance hinges on the stable environment of the cryogenic region. The cryogenic region must provide a low-temperature environment for the microwave cavity and the free-flight region of atoms to suppress the influence of blackbody radiation frequency shift on frequency uncertainty.

[0003] In existing technologies, the cryogenic zone is typically achieved through liquid nitrogen cooling combined with a vacuum insulation structure. For example, liquid nitrogen is used to lower and maintain the temperature of the cryogenic zone, and a vacuum bellows is used to insulate the microwave cavity in the cryogenic zone from the ambient temperature system below, achieving insulation and maintaining the temperature difference. However, this vacuum bellows-based contact insulation design still has significant drawbacks: First, the liquid nitrogen temperature is not adjustable and deviates from the actual operating temperature of the microwave cavity, resulting in the inability to precisely tune the microwave cavity resonant frequency. Cavity detuning causes a large pulling frequency shift, ultimately increasing the clock's frequency uncertainty. Second, during normal operation of the fountain clock, frequent manual replenishment of liquid nitrogen is usually required. Relying on manual replenishment easily leads to temperature fluctuations, and the impact force during replenishment causes significant temperature changes, resulting in a large uncertainty in the blackbody radiation frequency shift. Third, the insulation structure has significant heat loss, and heat transfer between the cryogenic zone and the ambient temperature system is difficult to block, further affecting temperature stability. Therefore, there is an urgent need for a cryogenic zone device for an ultra-low temperature cesium atomic fountain clock. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a cryogenic action zone device for an ultra-low temperature cesium atomic fountain clock. The technical problem to be solved by this invention is achieved through the following technical solution:

[0005] This invention provides a cryogenic action zone device for an ultra-low temperature cesium atomic fountain clock, comprising: a liquid nitrogen Dewar flask suspended inside a vacuum cylinder by multiple hanging pipes, a cold screen being provided between the vacuum cylinder and the liquid nitrogen Dewar flask, a microwave cavity assembly being disposed inside the liquid nitrogen Dewar flask; and a liquid replenishment and cooling device located above the vacuum cylinder, and the liquid replenishment and cooling device being connected to the liquid nitrogen Dewar flask via a liquid nitrogen pipeline for filling the liquid nitrogen Dewar flask with liquid nitrogen.

[0006] In one embodiment of the present invention, the liquid nitrogen Dewar flask includes a double-layer hollow cylinder, a perforated flange, and an annular copper base. The double-layer hollow cylinder is provided with a hollow inner cavity, and the bottom of the double-layer hollow cylinder is connected to the annular copper base through the perforated flange.

[0007] In one embodiment of the present invention, the perforated flange is provided with a plurality of through holes, the annular copper base is provided with a groove, and the hollow inner cavity is connected to the groove through the plurality of through holes.

[0008] In one embodiment of the present invention, the cold screen is provided with two layers, and each layer of the cold screen is provided with a plurality of ventilation holes, and the ventilation holes on the two layers of the cold screen are staggered.

[0009] In one embodiment of the present invention, both layers of the cold shield are connected to the upper end of the liquid nitrogen Dewar flask by screws, and a sleeve is provided outside the screws, with multiple openings provided on the side wall of the sleeve.

[0010] In one embodiment of the present invention, the microwave cavity assembly includes a microwave cavity, a microwave cavity base, a T-shaped insulating ceramic tube, an annular ceramic plate, a titanium spring washer, an internal hexagonal screw, and an external hexagonal screw. The microwave cavity is fixed to the upper end of the microwave cavity base by the internal hexagonal screw. The internal hexagonal screw is fitted with the T-shaped insulating ceramic tube, the annular ceramic plate, and the titanium spring washer. The annular ceramic plate is disposed between the lower surface of the microwave cavity and the upper surface of the microwave cavity base. The titanium spring washer is disposed between the end of the T-shaped insulating ceramic tube and the internal hexagonal screw. The lower end of the microwave cavity base is connected to the annular copper base by the external hexagonal screw.

[0011] In one embodiment of the present invention, the liquid nitrogen pipeline passes through the vacuum cylinder and the two layers of the cold shield and communicates with the hollow inner cavity.

[0012] In one embodiment of the present invention, the liquid replenishment refrigeration device includes a refrigerator, a temperature monitor, and a cryogenic controller. The refrigerator is connected to the hollow inner cavity through the liquid nitrogen pipeline, and the temperature monitor is used to monitor the liquid nitrogen temperature. The refrigerator cools the liquid nitrogen according to the liquid nitrogen temperature, and the cryogenic controller heats the liquid nitrogen according to the liquid nitrogen temperature.

[0013] In one embodiment of the present invention, multiple hanging tubes pass through the cold screen, and the upper end of the liquid nitrogen Dewar flask is suspended from the vacuum cylinder by the multiple hanging tubes, and each hanging tube has multiple openings on its side wall.

[0014] In one embodiment of the present invention, the cryogenic action zone device for an ultra-low temperature cesium atomic fountain clock further includes an exhaust pipe, which passes through the vacuum cylinder and communicates with the hollow inner cavity, and the exhaust pipe is connected to an exhaust valve.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] The cryogenic zone device for an ultra-low temperature cesium atomic fountain clock of the present invention improves the temperature stability of the cryogenic zone and achieves precise control of the cryogenic environment by combining a liquid nitrogen Dewar flask suspension structure with an automatic liquid replenishment system. The liquid nitrogen is automatically replenished by the liquid replenishment system, avoiding temperature fluctuations caused by manual operation and ensuring precise tuning of the microwave cavity resonant frequency. Furthermore, the suspension structure combined with a cold shield effectively isolates the cryogenic zone from the ambient temperature system, preventing heat loss and significantly improving temperature stability.

[0017] This invention utilizes an open flange to fill a ring-shaped copper base with liquid nitrogen, ensuring that the microwave cavity maintains the same temperature as the liquid nitrogen. A ring-shaped ceramic sheet is used to achieve insulation and heat conduction of the microwave cavity. Furthermore, the staggered layout of the ventilation holes in the double-layer cold shield and the sleeve support structure take into account both vacuum extraction and thermal radiation shielding, providing a reliable, low-noise, and highly stable operating environment for the cryogenic atomic fountain clock.

[0018] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the low-temperature action zone device for an ultra-low temperature cesium atomic fountain clock provided in an embodiment of the present invention;

[0020] Figure 2 This is a partial structural schematic diagram of the liquid nitrogen Dewar flask provided in an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the connection structure of the microwave cavity assembly provided in an embodiment of the present invention;

[0022] Figure 4 This is a schematic diagram of the hoisting structure provided in an embodiment of the present invention.

[0023] Reference numerals: 100-Vacuum cylinder; 200-Liquid nitrogen Dewar flask; 201-Double-layer hollow cylinder; 202-Opening flange; 203-Annular copper base; 300-Cold shield; 301-Sleeve; 302-Screw; 303-Nut; 400-Microwave cavity assembly; 401-Microwave cavity; 402-T-shaped insulating ceramic tube; 403-Annular ceramic plate; 404-Titanium spring washer; 405-Microwave cavity base; 406-Hex socket head cap screw; 407-Hex head cap screw; 500-Liquid replenishment cooling device; 501-Refrigeration unit; 502-Temperature monitor; 503-Cryogenic controller; 600-Liquid nitrogen pipeline; 700-Hanging pipe; 800-Exhaust pipeline; 900-Exhaust valve. Detailed Implementation

[0024] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a low-temperature action zone device for an ultra-low temperature cesium atomic fountain clock proposed according to the present invention.

[0025] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0026] Example 1

[0027] Existing cryogenic zones are typically achieved through liquid nitrogen cooling combined with a vacuum insulation structure. However, these systems still suffer from problems such as inaccurate temperature control, low liquid replenishment efficiency, uneven thermal conductivity between the microwave cavity and liquid nitrogen, and insufficient thermal stability of the cryogenic zone. Therefore, this invention provides a cryogenic zone device for an ultra-low temperature cesium atomic fountain clock, which improves the uncertainty of the ultra-low temperature atomic fountain clock by integrating automatic temperature control and efficient insulation. Figures 1 to 4 As shown, Figure 1 This is a schematic diagram of the low-temperature action zone device for an ultra-low temperature cesium atomic fountain clock provided in an embodiment of the present invention; Figure 2 This is a partial structural schematic diagram of the liquid nitrogen Dewar flask provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the connection structure of the microwave cavity assembly provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the hoisting structure provided in an embodiment of the present invention.

[0028] In this embodiment, the cryogenic action zone device for the ultra-low temperature cesium atomic fountain clock includes: a vacuum cylinder 100, a liquid nitrogen Dewar flask 200, a cold shield 300, a microwave cavity assembly 400, and a liquid replenishment and cooling device 500. The liquid nitrogen Dewar flask 200 is suspended inside the vacuum cylinder 100 by multiple hanging pipes 700. A cold shield 300 is provided between the vacuum cylinder 100 and the liquid nitrogen Dewar flask 200. The microwave cavity assembly 400 is disposed inside the liquid nitrogen Dewar flask 200. The liquid replenishment and cooling device 500 is located above the vacuum cylinder 100 and is connected to the liquid nitrogen Dewar flask 200 through a liquid nitrogen pipe 600 for filling the liquid nitrogen Dewar flask 200 with liquid nitrogen.

[0029] The principle is as follows: a vacuum is created inside the vacuum cylinder 100. Since the microwave cavity assembly 400 relies on low temperature to maintain stability, it is placed within the low-temperature zone, i.e., the internal environment of the vacuum cylinder 100 is cooled by liquid nitrogen to form the low-temperature zone. To avoid temperature loss, the low-temperature zone is physically isolated from its surrounding environment, including by using a cooling shield 300 to reduce heat radiation from outside the vacuum cylinder 100, and by suspending the liquid nitrogen Dewar flask 200 inside the vacuum cylinder 100 using multiple tubing 700. Furthermore, to avoid temperature fluctuations caused by impacts during liquid replenishment, an automatic liquid replenishment cooling device 500 is used to improve the stability of the low-temperature zone.

[0030] In one optional embodiment, the liquid nitrogen Dewar flask 200 includes a double-layer hollow cylinder 201, an open flange 202, and an annular copper base 203. The double-layer hollow cylinder 201 is provided with a hollow inner cavity, and the bottom of the double-layer hollow cylinder 201 is connected to the annular copper base 203 through the open flange 202.

[0031] In an optional embodiment, the perforated flange 202 is welded to the bottom of the double-layer hollow cylinder 201. The perforated flange 202 has multiple through holes, and the annular copper base 203 has a groove. The perforated flange 202 wraps around the annular copper base 203, and the hollow inner cavity of the double-layer hollow cylinder 201 is connected to the groove through the multiple through holes. After liquid nitrogen is poured into the hollow inner cavity through the liquid nitrogen pipe 600, it flows downward and flows into the groove of the annular copper base 203 through the multiple through holes. This increases the contact area between the double-layer hollow cylinder 201 and the annular copper base 203, ensuring the stability of the Dewar structure and facilitating direct heat conduction to the microwave cavity 401. During normal operation, the liquid nitrogen Dewar bottle 200 is filled with liquid nitrogen, providing a cryogenic environment for the internal microwave cavity 401 and the upper atomic free-flight region.

[0032] For example, the double-layer hollow cylinder 201 may be made of titanium alloy.

[0033] For example, the groove of the annular copper base 203 is annular, and multiple through holes are also arranged along the circumference. The annular copper base 203 increases the contact area through the annular groove structure, ensuring that the liquid nitrogen cooling capacity is uniformly transferred to the microwave cavity 401.

[0034] For example, the upper end of the double-layer hollow cylinder 201 is configured as a double-layer end cap structure, and the central through-hole of the double-layer end cap is used for microwave cable routing, and the two openings are sealed by welding a titanium alloy pipe.

[0035] In one optional embodiment, the cold shield 300 has two layers, each with multiple vent holes. These vent holes are staggered to ensure vacuum extraction and effectively reduce direct heat radiation from the external environment of the vacuum cylinder 100 to the cryogenic zone. Furthermore, to connect and fix the cold shield 300 to the liquid nitrogen Dewar flask 200, the two layers of cold shield 300 are connected to the upper ends of the liquid nitrogen Dewar flask 200 via screws 302. Specifically, two screws 302 are welded to the upper end of the liquid nitrogen Dewar flask 200. Openings are provided at corresponding positions on the two layers of cold shield 300, and the two screws 302 are passed through these openings and secured with nuts 303. A sleeve 301 is provided outside the screws 302. Multiple openings are provided on the side wall of the sleeve 301. The sleeve 301 is used for supporting the cold shield 300 and adjusting its distance, and also serves to maintain the temperature difference between the two layers of cold shield 300.

[0036] For example, both layers of cold screen 300 can be made of pure copper. To avoid copper oxidation and reduce heat radiation, the surfaces of both layers of cold screen 300 are plated with silver.

[0037] Furthermore, the two layers of cold screen 300 are nested together. The inner diameters of the two layers of cold screen 300 are 238mm and 268mm respectively, and the heights are 645mm and 693mm respectively. The thickness of the two layers of cold screen 300 is 2mm. The ventilation holes on the two layers of cold screen 300 are evenly spaced, such as 4 rows and 4 columns of ventilation holes. The diameter of each ventilation hole is 20mm, and the ventilation holes of the two layers of cold screen 300 are staggered during installation.

[0038] In this embodiment, the microwave cavity assembly 400 includes a microwave cavity 401, a microwave cavity base 405, a T-shaped insulating ceramic tube 402, an annular ceramic plate 403, a titanium spring washer 404, an internal hexagonal screw 406, and an external hexagonal screw 407. The lower end of the microwave cavity 401 is connected and fixed to the upper end of the microwave cavity base 405 by the internal hexagonal screw 406. The internal hexagonal screw 406 is fitted with the T-shaped insulating ceramic tube 402, the annular ceramic plate 403, and the titanium spring washer 404. The annular ceramic plate 403 is disposed between the lower surface of the microwave cavity 401 and the upper surface of the microwave cavity base 405. The titanium spring washer 404 is disposed between the end of the T-shaped insulating ceramic tube 402 and the internal hexagonal screw 406. The lower end of the microwave cavity base 405 is connected to the annular copper base 203 by the external hexagonal screw 407.

[0039] For example, the annular ceramic plate 403 can be made of aluminum nitride, and the hexagonal socket screw 406 passes through the annular ceramic plate 403. The annular ceramic plate 403 serves as insulation for the microwave cavity 401 and can rapidly conduct the liquid nitrogen temperature to the microwave cavity 401. Further, the microwave cavity 401 can be made of pure copper. Copper is significantly affected by temperature changes in the low-temperature operating region, and will undergo thermal expansion and contraction. To prevent the microwave cavity 401 from being crushed by heat, a titanium spring washer 404 is installed on the hexagonal socket screw 406 that fixes the microwave cavity 401 to allow for deformation space.

[0040] Furthermore, the lower end of the microwave cavity 401 is connected to the upper end of the microwave cavity base 405 via eight evenly spaced hexagonal socket head cap screws 406. Each hexagonal socket head cap screw 406 is fitted with a T-shaped insulating ceramic tube 402 for insulation, and each hexagonal socket head cap screw 406 is fitted with a titanium spring washer 404. Similarly, the lower end of the microwave cavity base 405 is connected to the annular copper base 203 via twelve evenly spaced external hexagonal socket head cap screws 407.

[0041] In this embodiment, the liquid replenishment cooling device 500 includes a refrigerator 501, a temperature monitor 502, and a cryogenic controller 503. The liquid nitrogen pipeline 600 passes through the vacuum cylinder 100 and two layers of cold shields 300 and is connected to the hollow inner cavity. The refrigerator 501 is connected to the hollow inner cavity through the liquid nitrogen pipeline 600. The temperature monitor 502 is used to monitor the liquid nitrogen temperature. The refrigerator 501 cools the liquid nitrogen according to the liquid nitrogen temperature, and the cryogenic controller 503 heats the liquid nitrogen according to the liquid nitrogen temperature.

[0042] For example, the temperature control of the cryogenic zone is achieved through a temperature monitor 502 and a cryogenic controller 503. The temperature monitor 502 is communicatively connected to the refrigerator 501 and the cryogenic controller 503. At the same time, the refrigerator 501, the temperature monitor 502, and the cryogenic controller 503 are all connected to an external control module. The temperature monitor 502 can be a Lake Shore 218 type temperature monitor, and the cryogenic controller 503 can be a Lake Shore 336 type cryogenic controller. Through the control of the external control module, combined with the refrigerator 501, the temperature of liquid nitrogen can be regulated in the range of 77K to 87K.

[0043] Furthermore, the cryogenic controller 503 is located below the drive piston of the refrigerator 501. The cryogenic controller 503 is equipped with an independent heater. Both the refrigerator 501 and the cryogenic controller 503 regulate the liquid nitrogen temperature based on the liquid nitrogen temperature. An external control module performs closed-loop temperature control using PID (Proportional-Integral-Derivative) control. The working process is as follows: the liquid replenishment refrigeration device 500 is connected to the hollow inner cavity of the liquid nitrogen Dewar flask 200 via a liquid nitrogen pipeline 600. The temperature monitor 502 monitors the liquid nitrogen temperature inside the liquid nitrogen Dewar flask 200 in real time and transmits the temperature signal to the refrigerator 501 and the cryogenic controller 503. When the liquid nitrogen temperature is higher than the set value, the refrigerator 501 starts, circulating refrigerant within the refrigerator 501 to cool the liquid nitrogen and lower its temperature. When the liquid nitrogen temperature is lower than the set value, the cryogenic controller 503 starts, heating the liquid nitrogen through heating elements to raise its temperature. The refrigeration unit 501 and the cryogenic controller 503 both work simultaneously or in shifts under the coordination of the external control module. They perform closed-loop temperature control based on the PID algorithm to precisely adjust the liquid nitrogen temperature within the range of 77K to 87K.

[0044] In an optional embodiment, the cryogenic action zone device for the cryogenic cesium atomic fountain clock of this embodiment further includes an exhaust pipe 800, which passes through the vacuum cylinder 100 and communicates with the hollow inner cavity, and the exhaust pipe 800 is connected to an exhaust valve 900.

[0045] The principle is as follows: the liquid nitrogen pipeline 600 serves as the input and output pipeline for liquid nitrogen, and the refrigerator 501 is a GM (Gifford-McMahon) refrigerator connected to a condenser. Utilizing the processes of liquid nitrogen evaporation, cooling, liquefaction, and reflux, the temperature of the cryogenic zone is stabilized, and the liquid nitrogen is recycled with zero evaporation, achieving automatic condensation and quasi-static replenishment. Specifically, two mounting holes are symmetrically arranged about the center on the upper outer layer of the liquid nitrogen Dewar flask 200. One mounting hole is connected to the refrigerator 501 via the liquid nitrogen pipeline 600 to inject liquid nitrogen. After the liquid nitrogen in the Dewar flask 200 vaporizes, the cryogenic nitrogen returns to the refrigerator 501 along the liquid nitrogen pipeline 600. After being refrigerated and recirculated by the refrigerator 501, it is recooled and transformed back into cryogenic liquid nitrogen. Under gravity, it re-enters the hollow inner cavity of the liquid nitrogen Dewar flask 200 through the liquid nitrogen pipeline 600, maintaining the temperature stability of the cryogenic zone and achieving the function of automatic condensation and quasi-static replenishment, with zero evaporation of liquid nitrogen for recycling. Another mounting hole of the liquid nitrogen Dewar flask 200 is connected to an exhaust valve 900 through an exhaust pipe 800 for venting gas during the initial installation process, that is, venting internal gas when liquid nitrogen is initially filled to ensure the stability of liquid nitrogen flow.

[0046] In an optional embodiment, the cold shield 300 is also provided with lifting holes, through which multiple lifting pipes 700 pass. The sidewalls of the lifting pipes 700 have multiple openings, effectively reducing direct heat radiation from the external environment of the vacuum cylinder 100 to the cryogenic zone without affecting vacuum extraction. The upper end of the liquid nitrogen Dewar flask 200 is suspended from the vacuum cylinder 100 by the multiple lifting pipes 700. Specifically, taking two lifting holes and two mounting holes (a total of four holes) and two lifting pipes 700 as an example, the two lifting pipes 700, along with the liquid nitrogen pipe 600 and the exhaust pipe 800, are all arranged vertically. The two lifting holes and two mounting holes are rectangular, with the two lifting holes and the two mounting holes diagonally positioned. The entire cryogenic zone is suspended by the liquid nitrogen pipe 600, the lifting pipes 700, and the exhaust pipe 800, preventing direct contact between the cryogenic zone and the ambient temperature physical system below, thus avoiding heat loss.

[0047] The side wall of the hanging pipe 700 has multiple openings to avoid affecting the vacuum pumping. The two hanging pipes 700, the liquid nitrogen pipe 600 and the exhaust pipe 800 are all welded to the upper outer layer of the liquid nitrogen Dewar flask 200, and are also welded to the vacuum cylinder 100. The corresponding position on the upper end of the cold screen 300 is also provided with a lifting hole to ensure that the two hanging pipes 700, the liquid nitrogen pipe 600 and the exhaust pipe 800 pass through the cold screen 300 without contact, thereby achieving both lifting and heat insulation.

[0048] It is worth noting that the cryogenic zone device for an ultra-low temperature cesium atomic fountain clock of the present invention achieves adjustable temperature of the cryogenic zone within a range of 10K, improves temperature stability, and reduces the uncertainty of blackbody radiation frequency shift. It achieves insulation of the microwave cavity 401 and direct contact between the microwave cavity 401 and liquid nitrogen, effectively reducing the traction frequency shift of the microwave cavity 401, improving the frequency uncertainty of the fountain clock, and achieving high performance of the atomic clock. Specifically, the present invention uses an automatic quasi-static liquid nitrogen replenishment method to lower and maintain the temperature of the cryogenic zone. Liquid nitrogen is filled into the annular copper base 203 using the perforated flange 202 to keep the microwave cavity 401 at the same temperature as the liquid nitrogen. Insulation and thermal conductivity of the microwave cavity 401 are achieved by combining aluminum nitride ceramic sheets and spring washers. The cryogenic zone is insulated from the ambient temperature system below by being suspended. The temperature control system based on the liquid replenishment cooling device 500 allows the temperature of the cryogenic zone to be adjusted between 77K and 87K, facilitating further tuning of the microwave cavity 401. Compared to traditional structural designs, this design avoids heat loss and the impact of manual liquid replenishment, thus improving the temperature stability of the cryogenic zone. It features non-magnetic operation, excellent thermal conductivity between the microwave cavity 401 and liquid nitrogen, controllable temperature, further tuning of the microwave cavity 401 in the cryogenic zone, and automatic quasi-static liquid replenishment.

[0049] The cryogenic zone device for an ultra-low temperature cesium atomic fountain clock of the present invention improves the temperature stability of the cryogenic zone and achieves precise control of the cryogenic environment by combining a liquid nitrogen Dewar flask suspension structure with an automatic liquid replenishment system. The liquid nitrogen is automatically replenished by the liquid replenishment system, avoiding temperature fluctuations caused by manual operation and ensuring precise tuning of the microwave cavity resonant frequency. Furthermore, the suspension structure combined with a cold shield effectively isolates the cryogenic zone from the ambient temperature system, preventing heat loss and significantly improving temperature stability.

[0050] This invention utilizes an open flange to fill a ring-shaped copper base with liquid nitrogen, ensuring that the microwave cavity maintains the same temperature as the liquid nitrogen. A ring-shaped ceramic sheet is used to achieve insulation and heat conduction of the microwave cavity. Furthermore, the staggered layout of the ventilation holes in the double-layer cold shield and the sleeve support structure take into account both vacuum extraction and thermal radiation shielding, providing a reliable, low-noise, and highly stable operating environment for the cryogenic atomic fountain clock.

[0051] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0052] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A low-temperature action zone device for an ultralow-temperature cesium fountain clock, characterized by, The application relates to a liquid nitrogen container and a microwave cavity assembly. The liquid nitrogen container is hung in a vacuum cylinder through a plurality of hanging pipes, a cold shield is arranged between the liquid nitrogen container and the vacuum cylinder, and the microwave cavity assembly is arranged in the liquid nitrogen container; A liquid supplement refrigerating device is arranged above the vacuum cylinder and is connected with the liquid nitrogen container through a liquid nitrogen pipeline to fill liquid nitrogen into the liquid nitrogen container; The liquid nitrogen container comprises a double-layer hollow cylinder, an open flange and a ring-shaped copper base, the double-layer hollow cylinder is provided with a hollow inner cavity, the bottom of the double-layer hollow cylinder is connected with the ring-shaped copper base through the open flange, the open flange is provided with a plurality of through holes, the ring-shaped copper base is provided with a groove, and the hollow inner cavity is communicated with the groove through the plurality of through holes.

2. The cold-finger apparatus for an ultralow-temperature cesium fountain clock according to claim 1, characterized by, The cold shield is provided with two layers, a plurality of air holes are arranged on the two layers of the cold shield, and the air holes on the two layers of the cold shield are arranged alternately.

3. The cold-finger device for an ultralow-temperature cesium fountain clock according to claim 2, characterized in that, The two layers of the cold shield are connected with the upper end of the liquid nitrogen container through a screw rod, a sleeve is arranged outside the screw rod, and a plurality of openings are arranged on the side wall of the sleeve.

4. The cold-finger apparatus for an ultralow-temperature cesium fountain clock of claim 1, wherein The microwave cavity assembly comprises a microwave cavity, a microwave cavity base, a T-shaped insulating ceramic pipe, a ring-shaped ceramic sheet, a titanium spring washer, an inner hexagonal screw and an outer hexagonal screw, the microwave cavity is fixed to the upper end of the microwave cavity base through the inner hexagonal screw, the inner hexagonal screw is sleeved with the T-shaped insulating ceramic pipe, the ring-shaped ceramic sheet and the titanium spring washer, the ring-shaped ceramic sheet is arranged between the lower surface of the microwave cavity and the upper surface of the microwave cavity base, the titanium spring washer is arranged between the T-shaped insulating ceramic pipe and the end of the inner hexagonal screw, and the lower end of the microwave cavity base is connected with the ring-shaped copper base through the outer hexagonal screw.

5. The cold-finger apparatus for an ultralow-temperature cesium fountain clock of claim 1, wherein The liquid nitrogen pipeline is communicated with the hollow inner cavity through the vacuum cylinder and the two layers of the cold shield.

6. The cold-finger apparatus for an ultralow-temperature cesium fountain clock of claim 5, wherein The liquid supplement refrigerating device comprises a refrigerating machine, a temperature monitor and a low-temperature controller, the refrigerating machine is communicated with the hollow inner cavity through the liquid nitrogen pipeline, the temperature monitor is used for monitoring the temperature of liquid nitrogen, the refrigerating machine refrigerates liquid nitrogen according to the temperature of liquid nitrogen, and the low-temperature controller heats liquid nitrogen according to the temperature of liquid nitrogen.

7. The cold-finger apparatus for an ultralow-temperature cesium fountain clock of claim 1, wherein A plurality of hanging pipes pass through the cold shield, the upper end of the liquid nitrogen container is hung on the vacuum cylinder through the plurality of hanging pipes, and the side wall of each hanging pipe is provided with a plurality of openings.

8. The cold-finger apparatus for an ultralow-temperature cesium fountain clock of claim 1, wherein An exhaust pipeline is further arranged, the exhaust pipeline is communicated with the hollow inner cavity through the vacuum cylinder, and the exhaust pipeline is connected with an exhaust valve.

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