A low magnetic leakage magnetic shielding device for a cold atom fountain quantum microwave clock

Abstract

The application discloses a low magnetic leakage magnetic shielding device of a cold atom fountain quantum microwave clock, which comprises a shielding cylinder, two end covers connected with two ends of the shielding cylinder respectively, wherein the end cover comprises an upper cover and a lower cover, the lower cover is connected with the shielding cylinder, the upper cover and the lower cover are coaxially provided with shaft holes, and a connecting pipe is arranged between the upper cover and the lower cover. The application takes the high magnetic permeability cylindrical permalloy material as the magnetic shielding main body of the cold atom fountain quantum microwave clock, designs the double-cover structure at the opening of the upper and lower end covers, provides a more sufficient low magnetic resistance passage for the geomagnetic field and the stray magnetic field, effectively suppresses the magnetic flux leakage at the opening, and meets the shielding requirement of the microwave clock with only three layers of magnetic shielding layers. Moreover, the distance between the atom free flight area and the opening does not need to be increased, the weight of the whole machine is reduced, and the important technical path is provided for the miniaturization of the cold atom fountain quantum microwave clock and the realization of the off-site application.

Description

Technical Field

[0001] This invention belongs to the field of shielding technology, specifically relating to a low-leakage magnetic shielding device for a cold atom fountain quantum microwave clock. Background Technology

[0002] Cold atom fountain clocks are currently the most accurate microwave atomic clocks. Cesium atomic fountain clocks are currently the reference device for reproducing the definition of the second and calibrating International Atomic Time, while also measuring the absolute frequency of optical clocks, playing a crucial role in the transformation of next-generation second-definition devices. The inherent low-frequency drift characteristics of rubidium atomic fountain clocks make them strong candidates for new types of time-keeping atomic clocks. As the requirements for time and frequency accuracy continue to increase across various fields, high-performance cold atom fountain quantum microwave clocks are moving from the laboratory to broader field applications, and their importance in off-site environments is becoming increasingly prominent.

[0003] The regions through which atomic clusters travel upwards and downwards within the microwave cavity are typically referred to as the atomic free-flight region. The microwave cavity and the atomic free-flight region are the areas where atoms interact with microwaves and evolve freely; they are the core areas of the atomic fountain clock. Since the atomic fountain clock is based on the magnetic transitions of atoms, to avoid the influence of the Earth's magnetic field and surrounding stray magnetic fields on the atomic transition frequencies, the clock transition energy levels are usually chosen to be magnon energy levels with zero magnetic angular momentum. However, the second-order response of atoms to stray magnetic fields necessitates that the microwave cavity and the atomic free-flight region typically require magnetic shielding to minimize interference from surrounding stray magnetic fields.

[0004] To achieve extremely high shielding effectiveness, the magnetic shielding of atomic fountain clocks typically employs a four-layer structure. Even when reduced to three layers, the effectiveness is ensured by keeping the free-flight zone of atoms away from the openings in the magnetic shielding cover (because the free-flight zone is a vacuum environment, the openings here are to allow the vacuum components to pass through; these openings are the main pathways for stray magnetic fields such as the Earth's magnetic field to enter the free-flight zone). However, both of these designs result in a large magnetic shielding component, severely hindering the miniaturization process of atomic fountain clocks and limiting their application in outdoor fields. Furthermore, as a component of the atomic fountain clock, the magnetic shielding device needs to coordinate with other components, such as the semi-steel cables for the microwave cavity, DC coil current lines, demagnetizing wires, and temperature measurement wires for the free-flight zone. These cables require through-holes in the magnetic shielding device. These through-holes are smaller than the openings in the vacuum components at the magnetic shielding point, but a proper design is essential to ensure the overall shielding effectiveness. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a low-leakage magnetic shielding device for a cold atom fountain quantum microwave clock. The technical problem to be solved by this invention is achieved through the following technical solution: This invention provides a low-leakage magnetic shielding device for a cold atom fountain quantum microwave clock, comprising: Shielding tube; Two end caps are respectively connected to both ends of the shielding cylinder. The end caps include an upper cap and a lower cap. The lower cap is connected to the shielding cylinder. Both the upper cap and the lower cap are coaxially provided with shaft holes. A connecting pipe is provided between the upper cap and the lower cap. One end of the connecting pipe is connected to the shaft hole of the upper cap, and the other end of the connecting pipe is connected to the shaft hole of the lower cap.

[0006] Preferably, the shielding cylinder includes: an inner shielding cylinder, a middle shielding cylinder, and an outer shielding cylinder arranged at intervals; The end cap includes: an inner end cap, a middle end cap, and an outer end cap; The inner shielding cylinder is connected to the inner end cap, the middle shielding cylinder is connected to the middle end cap, and the outer shielding cylinder is connected to the outer end cap.

[0007] Preferably, it also includes an epoxy insulation board, which comprises: an inner epoxy insulation board, a middle epoxy insulation board, and an outer epoxy insulation board; The inner epoxy insulation board is connected to the inner shielding cylinder, and the inner epoxy insulation board is connected to the inner end cap; The middle epoxy insulation board is connected to the middle shielding cylinder, the middle epoxy insulation board is connected to the middle end cap, and the middle epoxy insulation board is connected to the inner epoxy insulation board. The outer epoxy insulation board is connected to the outer shielding cylinder, the outer epoxy insulation board is connected to the outer end cap, and the outer epoxy insulation board is connected to the middle epoxy insulation board.

[0008] Preferably, one end of the outer shielding tube is provided with a plurality of first screw holes spaced apart along the circumference, and the other end of the outer shielding tube is provided with a plurality of second screw holes spaced apart along the circumference.

[0009] Preferably, the upper cover has multiple demagnetizing wire holes spaced apart circumferentially, and the lower cover has multiple third screw holes spaced apart circumferentially.

[0010] Preferably, the outer epoxy insulation board has a plurality of fourth screw holes spaced apart along the circumference.

[0011] Preferably, the upper cover has two symmetrically arranged strip holes.

[0012] Preferably, the end cap is composed of two semi-circular end caps, and the epoxy insulation board is composed of two semi-circular epoxy insulation boards.

[0013] Compared with existing technologies, the advantages of this invention are as follows: This invention uses a cylindrical permalloy material with high magnetic permeability as the magnetic shielding body of the cold atom fountain quantum microwave clock. By designing a double-cover structure at the openings in the upper and lower end caps, a more sufficient low magnetic reluctance path is provided for the geomagnetic field and stray magnetic fields, effectively suppressing magnetic flux leakage at the openings. Only three magnetic shielding layers are needed to meet the clock's shielding requirements, and there is no need to increase the distance between the free-flight region of atoms and the openings. Simultaneously, the three-layer magnetic shielding also reduces the overall weight of the device. This provides an important technical path for the miniaturization of cold atom fountain quantum microwave clocks, thereby enabling their off-site applications. Furthermore, through systematic optimization of the outward-flaring edge structure design of the magnetic shielding cylinder, the layout of the wiring holes in the upper end cap, and the installation method of the epoxy insulation board and the cylinder, the above technical solutions work synergistically to ensure that the overall performance of the magnetic shielding system reaches its optimal level.

[0014] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a low-leakage magnetic shielding device for a cold atom fountain quantum microwave clock provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the end cap of a low-leakage magnetic shielding device for a cold atom fountain quantum microwave clock provided in an embodiment of the present invention.

[0016] Figure 3 This is a schematic diagram of the inner end cap, middle end cap, and outer end cap in a low leakage magnetic shielding device for a cold atom fountain quantum microwave clock provided in an embodiment of the present invention.

[0017] Figure 4 This is a schematic diagram of the demagnetizing wire hole, the third screw hole, and the strip hole in a low leakage magnetic shielding device for a cold atom fountain quantum microwave clock provided in an embodiment of the present invention.

[0018] Figure 5 This is a schematic diagram of the outer shielding cylinder in a low-leakage magnetic shielding device for a cold atom fountain quantum microwave clock provided in an embodiment of the present invention.

[0019] Figure 6 This is a schematic diagram of the outer epoxy insulating plate in a low leakage magnetic shielding device for a cold atom fountain quantum microwave clock provided in an embodiment of the present invention.

[0020] Figure 7 This is a schematic diagram of the installation of a low-leakage magnetic shielding device for a cold atom fountain quantum microwave clock provided in an embodiment of the present invention.

[0021] Reference numerals: 1. Shielding cylinder; 2. End cap; 3. Epoxy insulation board; 4. Vacuum assembly; 5. Positioning ring; 6. C-field cylinder; 7. Microwave cavity; 8. Microwave cavity semi-steel cable; 21. Upper cover; 22. Lower cover; 23. Shaft hole; 24. Connecting pipe; 25. Demagnetizing wire hole; 26. Third screw hole; 27. Strip hole; 101. Inner shielding cylinder; 102. Middle shielding cylinder; 103. Outer shielding cylinder; 104. First screw hole; 105. Second screw hole; 201. Inner end cap; 202. Middle end cap; 203. Outer end cap; 301. Inner epoxy insulation board; 302. Middle epoxy insulation board; 303. Outer epoxy insulation board; 3031. Fourth screw hole. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0023] This invention provides a low-leakage magnetic shielding device for a cold atom fountain quantum microwave clock.

[0024] Please see Figure 1-3 , Figure 1-3 This is a schematic diagram of a low-leakage magnetic shielding device for a cold atom fountain quantum microwave clock provided in an embodiment of the present invention, comprising: Shielding cylinder 1 is made of permalloy material and has a good magnetic shielding effect; Two end caps 2 are connected to both ends of the shielding cylinder 1, respectively. The end cap 2 includes an upper cap 21 and a lower cap 22. The lower cap 22 is connected to the shielding cylinder 1. Both the upper cap 21 and the lower cap 22 are coaxially provided with shaft holes 23. A connecting pipe 24 is provided between the upper cap 21 and the lower cap 22. One end of the connecting pipe 24 is connected to the shaft hole 23 of the upper cap 21, and the other end of the connecting pipe 24 is connected to the shaft hole 23 of the lower cap 22.

[0025] The working principle and beneficial technical effects of the above technical solution: The shielding cylinder 1, made of high-permeability permalloy material, serves as the magnetic shielding body of the cold atom fountain quantum microwave clock. By creating a double-cover structure with axial holes 23 in the upper cover 21 and lower cover 22, a more sufficient low-resistivity path is provided for the geomagnetic field and stray magnetic fields, effectively suppressing magnetic flux leakage at the openings. Through the double-cover structure, a good shielding effect can be achieved without increasing the distance between the free-flight region of atoms and the openings. Only three magnetic shielding layers are needed to meet the shielding requirements of the microwave clock, and these three layers also reduce the overall weight of the device. This provides an important technical path for the miniaturization of the cold atom fountain quantum microwave clock, thereby enabling its off-site application. Furthermore, through systematic optimization of the shielding cylinder's outward-flaring edge design, the layout of the upper cover's wiring holes, and the installation method of the epoxy insulation board and the cylinder body, the above technical solutions work synergistically to ensure the optimal overall performance of the magnetic shielding system.

[0026] Specifically, in the embodiments of this application, the device utilizes the high permeability of permalloy to provide a low magnetic reluctance path for magnetic field lines, thereby achieving static magnetic shielding. When the magnetic field lines of an external magnetic field encounter the high permeability shielding cylinder 1, most of them are attracted and confined to the inside of the cylinder wall, unable to enter the internal cavity. The weakness of traditional shielding devices lies in the openings in the end caps, through which magnetic field lines can leak into the cavity. The double-layer cap structure adopted in this application includes an upper cap 21, a lower cap 22, and a connecting pipe 24. The connecting pipe 24 has a large length-to-diameter ratio, equivalent to a high magnetic reluctance pipe. When an axial magnetic field attempts to enter the interior through this pipe, because the permeability of the permalloy on the pipe wall is much higher than that of air, the magnetic field lines preferentially travel along the pipe wall and do not enter the cavity. The gap between the upper cap 21 and the lower cap 22 also allows the magnetic field lines to radially exit or close, forming multi-stage attenuation. When the single-layer cap has an opening, the magnetic field lines at the edge of the opening will bend and enter the interior. The double-layer cover structure of this application requires the magnetic leakage path to pass through the shaft hole 23 of the lower cover 22, the inner cavity of the connecting tube 24, and the shaft hole 23 of the upper cover 21 in sequence. Each step involves a sudden change in magnetic impedance, which is repeatedly attenuated, reducing end magnetic leakage and improving the magnetic shielding effect.

[0027] In one embodiment, refer to Figure 1 The shielding cylinder 1 includes: an inner shielding cylinder 101, a middle shielding cylinder 102 and an outer shielding cylinder 103 arranged at intervals of 28mm; End cap 2 includes: inner end cap 201, middle end cap 202 and outer end cap 203; The inner shielding cylinder 101 is connected to the inner end cap 201, the middle shielding cylinder 102 is connected to the middle end cap 202, and the outer shielding cylinder 103 is connected to the outer end cap 203.

[0028] The magnetic shielding effect of the cold atom fountain quantum microwave clock is improved by setting up multiple shielding cylinders and multiple end cap structures.

[0029] In one embodiment, refer to Figure 1 The low leakage magnetic shielding device for the cold atom fountain quantum microwave clock provided in this embodiment of the invention also includes an epoxy insulating plate 3, which includes an inner epoxy insulating plate 301, a middle epoxy insulating plate 302 and an outer epoxy insulating plate 303. The inner epoxy insulation board 301 is connected to the inner shielding cylinder 101, and the inner epoxy insulation board 301 is connected to the inner end cap 201. The middle epoxy insulation board 302 is connected to the middle shielding cylinder 102, the middle epoxy insulation board 302 is connected to the middle end cap 202, and the middle epoxy insulation board 302 is connected to the inner epoxy insulation board 301. The outer epoxy insulation board 303 is connected to the outer shielding cylinder 103, the outer epoxy insulation board 303 is connected to the outer end cap 203, and the outer epoxy insulation board 303 is connected to the middle epoxy insulation board 302.

[0030] The inner epoxy insulation board 301, the middle epoxy insulation board 302, and the outer epoxy insulation board 303 provide good insulation performance, preventing external electric fields from affecting the normal operation of the cold atom fountain quantum microwave clock, and also serve to fix and support the shielding cylinder and end cap.

[0031] In one embodiment, refer to Figure 5 One end of the outer shielding cylinder 103 has a plurality of first screw holes 104 spaced apart along the circumference, and the other end of the outer shielding cylinder 103 has a plurality of second screw holes 105 spaced apart along the circumference. The top and bottom of the outer shielding cylinder 103 are provided with an outward flange structure, which is divided into 12 holes, and is fixed to the corresponding magnetic shielding cover by titanium screws.

[0032] In one embodiment, refer to Figure 4 The upper cover 21 has multiple demagnetizing wire holes 25 spaced apart along the circumference for the demagnetizing wires of the cold atom fountain quantum microwave clock to pass through. The lower cover 22 has multiple third screw holes 26 spaced apart along the circumference, with 12 third screw holes 26, to achieve fixation with the corresponding magnetic shielding cylinder edge.

[0033] In one embodiment, refer to Figure 6 The outer epoxy insulation board 303 has multiple fourth screw holes 3031 spaced around the periphery and multiple rings of fourth screw holes 3031 distributed radially, which are used to install the corresponding magnetic shielding cylinder, end cap and upper epoxy insulation board respectively.

[0034] In one embodiment, refer to Figure 4Two strip holes 27 are symmetrically arranged on the upper cover 21 for the microwave cavity semi-steel cable of the cold atom fountain quantum microwave clock to pass through.

[0035] In one embodiment, refer to Figure 3 and Figure 6 End cap 2 consists of two semi-circular end caps. One semi-circular end cap has a slot, and the other semi-circular end cap has an insert, which facilitates the installation and removal of the two semi-circular end caps. Epoxy insulation board 3 consists of two semi-circular epoxy insulation boards, which also facilitates installation and removal.

[0036] Alternatively, in one implementation, refer to Figure 7 The vacuum component 4 of the cold atom fountain quantum microwave clock passes through the connecting tube 24 on the end cap 2, the demagnetizing wire passes through the demagnetizing wire hole 25, the microwave cavity semi-steel cable 8 passes through the strip hole 27, the positioning ring 5 is fixed on the vacuum component 4, the C-field cylinder 6 is installed on the positioning ring 5, the microwave cavity 7 is connected to the vacuum component 4, the free-flying atom region is located in the middle area inside the magnetic shielding device, only 3 layers of magnetic shielding are needed to meet the shielding requirements of the clock, and there is no need to increase the distance between the free-flying atom region and the opening. At the same time, the 3 layers of magnetic shielding also reduce the weight of the whole machine, realizing the miniaturization of the cold atom fountain quantum microwave clock.

[0037] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0038] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0039] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0041] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.

[0042] 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-leakage magnetic shielding device for a cold atom fountain quantum microwave clock, characterized in that, include: Shielding tube (1); Two end caps (2) are respectively connected to the two ends of the shielding cylinder (1). The end cap (2) includes an upper cap (21) and a lower cap (22). The lower cap (22) is connected to the shielding cylinder (1). The upper cap (21) and the lower cap (22) are both coaxially provided with shaft holes (23). A connecting pipe (24) is provided between the upper cap (21) and the lower cap (22). One end of the connecting pipe (24) is connected to the shaft hole (23) of the upper cap (21), and the other end of the connecting pipe (24) is connected to the shaft hole (23) of the lower cap (22).

2. The low-leakage magnetic shielding device for the cold atom fountain quantum microwave clock according to claim 1, characterized in that, The shielding cylinder (1) includes: an inner shielding cylinder (101), a middle shielding cylinder (102), and an outer shielding cylinder (103) arranged at intervals. The end cap (2) includes: an inner end cap (201), a middle end cap (202) and an outer end cap (203); The inner shielding cylinder (101) is connected to the inner end cap (201), the middle shielding cylinder (102) is connected to the middle end cap (202), and the outer shielding cylinder (103) is connected to the outer end cap (203).

3. The low-leakage magnetic shielding device for the cold atom fountain quantum microwave clock according to claim 2, characterized in that, It also includes an epoxy insulation board (3), which includes: an inner epoxy insulation board (301), a middle epoxy insulation board (302) and an outer epoxy insulation board (303). The inner epoxy insulation board (301) is connected to the inner shielding cylinder (101), and the inner epoxy insulation board (301) is connected to the inner end cap (201). The middle layer epoxy insulation board (302) is connected to the middle layer shielding cylinder (102), the middle layer epoxy insulation board (302) is connected to the middle layer end cap (202), and the middle layer epoxy insulation board (302) is connected to the inner layer epoxy insulation board (301). The outer epoxy insulation board (303) is connected to the outer shielding cylinder (103), the outer epoxy insulation board (303) is connected to the outer end cap (203), and the outer epoxy insulation board (303) is connected to the middle epoxy insulation board (302).

4. The low-leakage magnetic shielding device for the cold atom fountain quantum microwave clock according to claim 2, characterized in that, One end of the outer shielding tube (103) is provided with a plurality of first screw holes (104) spaced apart along the circumference, and the other end of the outer shielding tube (103) is provided with a plurality of second screw holes (105) spaced apart along the circumference.

5. The low-leakage magnetic shielding device for the cold atom fountain quantum microwave clock according to claim 1, characterized in that, The upper cover (21) is provided with a plurality of demagnetizing wire holes (25) spaced apart along the circumference, and the lower cover (22) is provided with a plurality of third screw holes (26) spaced apart along the circumference.

6. The low-leakage magnetic shielding device for the cold atom fountain quantum microwave clock according to claim 3, characterized in that, The outer epoxy insulation board (303) is provided with a plurality of fourth screw holes (3031) at intervals along the circumference.

7. The low-leakage magnetic shielding device for the cold atom fountain quantum microwave clock according to claim 1, characterized in that, The upper cover (21) has two symmetrical strip holes (27).

8. The low-leakage magnetic shielding device for the cold atom fountain quantum microwave clock according to claim 3, characterized in that, The end cap (2) is composed of two semi-circular end caps, and the epoxy insulation board (3) is composed of two semi-circular epoxy insulation boards.

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