Method for estimating amount of alkali metal in atomic gas chamber

Abstract

The invention relates to the field of quantum sensing, in particular to a method for estimating the amount of alkali metal in an atomic gas chamber. Comprising the following steps: placing an atomic gas chamber in a boron nitride assembly; a heating sheet and a refrigeration sheet TEC are pasted on the outer surface of the boron nitride assembly, and PT100 is pasted on the refrigeration sheet and the heating sheet for measuring the temperature; starting a heating power supply and a refrigeration power supply, controlling the heating temperature to be 120 + / -2 DEG C, controlling the refrigeration temperature to be 10 + / -1 DEG C, and because the melting points of alkali metals Rb and Cs are 38.9 and 28.4 DEG C respectively, alkali metal atoms dispersed on a heating surface can migrate to a refrigeration end to form directional migration, and when the alkali metal atoms are re-condensed at the cold end, the alkali metal atoms can form point distribution by taking a condensation nucleus as a center; the morphology of alkali metal condensation clusters in the gas chamber is reconstructed from multiple angles by using an industrial CT nondestructive testing technology; voxels occupied by the alkali metal clusters are counted, and then the volume of the alkali metal clusters is obtained through calculation; and calculating the total mass of the alkali metal according to the volume of the alkali metal cluster and the density of the alkali metal Rb and Cs.

Description

Technical Field

[0001] This invention relates to the field of quantum sensing, including atomic spin gyroscopes, atomic magnetometers, CPT atomic clocks, and Rydberg electric field measurements, and particularly to the estimation of the alkali metal content filling the atomic gas cells in these quantum measurement sensors. Background Technology

[0002] In recent years, with the continuous advancement and development of quantum measurement technology, quantum sensor devices, represented by nuclear magnetic resonance gyroscopes and atomic magnetometers, have attracted widespread attention due to their excellent detection accuracy and size advantages. The atomic gas cell, as the core sensing element of atomic spin gyroscopes, atomic magnetometers, CPT atomic clocks, and Rydberg electric field measurement systems, is typically filled with alkali metal elements Rb or Cs, as well as other gases. Taking a nuclear magnetic resonance gyroscope as an example, at operating temperature, alkali metal atoms are pumped into the optically polarized gas cell, where spin-exchange collisions polarize inert gas Xe atoms, thereby detecting carrier precession through Xe atoms. Alkali metal atoms directly affect the polarizability of the inert gas, thus affecting the gyroscope's performance. Therefore, measuring the alkali metal content of the atomic gas cell helps provide feedback for research on the precise fabrication process of the gas cell, improves the consistency of gas cell performance, and is crucial for accurately controlling the performance of the nuclear magnetic resonance gyroscope.

[0003] The gas chamber is a closed space filled with extremely small amounts of alkali metal atoms (on the order of µg), making it difficult to measure by weighing. Similarly, using differential scanning calorimetry (DSC) to calculate the heat absorbed by the alkali metal during melting to measure its mass results in significant errors due to the small change in heat. While optical absorption number density detection can calculate the number density of alkali metals within the gas chamber at a specific temperature, it still cannot calculate the total amount of alkali metals filling the chamber, which is detrimental to the control of gas chamber consistency. Alkali metals Rb and Cs exist in solid form at room temperature and are easily oxidized, making them unsuitable for measurement in atmospheric exposure. Currently, there is no effective method to accurately detect the filling amount. Therefore, this invention proposes a method based on directional deposition of alkali metals and industrial CT detection for estimating the content of alkali metals filling the gas chamber. Summary of the Invention

[0004] Purpose of the invention: This invention provides a method for estimating the alkali metal content in an atomic gas chamber, solving the problem in existing technologies where the alkali metal content filling the atomic gas chamber is difficult to calibrate. The advantage of this method is that it allows for non-destructive testing of the alkali metal content within the gas chamber without damaging its structure.

[0005] Technical solution: A method for estimating the amount of alkali metals in an atomic gas chamber includes: Step 1: Place the atomic gas chamber inside the boron nitride assembly, with the atomic gas chamber in contact with the inner wall of the boron nitride assembly, and an observation window is provided on the side of the boron nitride assembly; Step 2: Attach heating and cooling plates (TECs) to the outer surface of the boron nitride assembly, and attach PT100 to the heating and cooling plates for temperature measurement. Step 3: Turn on the heating and cooling power supplies. The heating temperature is controlled at 120±2℃ and the cooling temperature is controlled at 10±1℃. Since the melting points of alkali metals Rb and Cs are 38.9℃ and 28.4℃ respectively, the alkali metal atoms dispersed on the heating surface will migrate to the cooling end, forming a directional migration. When the alkali metal atoms recondense at the cold end, they will form a point-like distribution centered on the condensation nucleus. Step 4: Using industrial CT non-destructive testing technology, the morphology of alkali metal condensation clusters inside the gas chamber is reconstructed from multiple angles. Step 5: Statistically analyze the voxels occupied by the alkali metal clusters, and then calculate the volume of the alkali metal clusters. Step 6: Calculate the total mass of the alkali metals based on the volume of the alkali metal clusters and the densities of alkali metals Rb and Cs.

[0006] Further, in step one, the boron nitride assembly includes: a hollow cuboid, a rectangular shell, and a solid cuboid. The rectangular shell has a square cavity along its length. Observation windows are provided on the four sides of the rectangular shell. The gas chamber is placed inside the square cavity along the length of the rectangular shell, and the rectangular shell is tightly fitted to the outer wall of the gas chamber. The hollow cuboid and the solid cuboid are placed at both ends of the gas chamber. The glass nozzle at the top of the gas chamber is accommodated in the cavity of the hollow cuboid, and the bottom of the gas chamber is in contact with the solid cuboid.

[0007] Furthermore, in step one, the observation windows on the four sides of the cuboid shell are the same size and shape as the four sides of the atomic gas chamber.

[0008] Furthermore, step one also includes: After placing the atomic gas chamber into the boron nitride assembly, thermally conductive adhesive is poured between the gas chamber and the cavity cube to increase the contact area between the gas chamber and the boron nitride shell, thereby increasing the heating efficiency.

[0009] Further, in step two, specifically: heating elements are attached to the outer surfaces of the hollow cuboid and the rectangular shell, and cooling elements (TECs) are attached to the outer surface of the solid cuboid. At the same time, PT100 is attached to the cooling elements and heating elements to measure the temperature.

[0010] Furthermore, in step three, the heating and cooling time should be maintained at more than 45 minutes to ensure that the alkali metals fully migrate to the cooling surface.

[0011] Furthermore, in step three, during cooling, the heating current needs to be gradually reduced to 0, the cooling rate should not exceed 20℃ / min, and the cooling element should continue to work while cooling to prevent the alkali metal deposited at the bottom from migrating back to other sidewalls.

[0012] Furthermore, in step four, the industrial CT scan resolution is above 5µm.

[0013] Furthermore, in step five, based on the 360° two-dimensional projection data of alkali metal clusters obtained by scanning, a three-dimensional voxel matrix is ​​reconstructed through a filtered back projection algorithm. Each voxel represents a tiny cubic unit, and the volume of a single voxel is determined by the CT resolution.

[0014] Beneficial effects: The method for estimating the amount of alkali metals in an atomic gas chamber using this invention enables non-destructive testing of the alkali metal content within the chamber. This method utilizes the low melting points of alkali metals Rb and Cs. By applying a temperature difference, the alkali metals are directionally deposited onto a specific surface of the gas chamber. Since the melting and resolidification process of alkali metals resembles the solidification process of crystals, the alkali metals solidify together in a spherical shape. Subsequently, industrial CT non-destructive testing technology is used to create a three-dimensional voxel matrix model of the alkali metal clusters within the gas chamber, obtaining their volume and thus allowing the calculation of the mass of alkali metals filling the chamber. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 Schematic diagram of the air chamber structure; Figure 2 A flowchart of a method for estimating the amount of alkali metal in an atomic gas chamber according to an embodiment of the present invention; Figure 3 A schematic diagram of a boron nitride assembly used to hold the gas chamber; Figure 4 Schematic diagram of how heating and cooling elements are attached; Figure 5 This is a schematic diagram of the morphology of alkali metal clusters obtained from industrial CT scanning.

[0017] Explanation of reference numerals in the attached figures: The upper glass nozzle of the air chamber 1, the air chamber cavity 2, the glass plate 3, the cavity cuboid 11, the rectangular outer shell 12, and the solid cuboid 13. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0020] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0022] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0023] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0024] The present invention provides a method for estimating the amount of alkali metal in an atomic gas chamber. The method involves creating a temperature gradient to directionally deposit the alkali metal, then using industrial CT scanning to scan the morphology of the alkali metal condensate in the gas chamber, estimating the volume of the particles, and calculating the mass of the alkali metal.

[0025] The present invention provides a method for estimating the amount of alkali metal in an atomic gas chamber, which specifically includes the following steps: Step 1, placing the atomic gas chamber in a boron nitride assembly, wherein the inner wall of the boron nitride assembly is tightly fitted to the outer wall of the gas chamber. Boron nitride is chosen because of its high thermal conductivity and small coefficient of thermal expansion; Step 2, attaching a heating element and a cooling element (TEC) to the surface of the boron nitride assembly, and attaching PT100 to the cold source and the heat source for temperature measurement. Step 3: Simultaneously turn on the heating and cooling power supplies, controlling the heating temperature at 120±2℃ and the cooling temperature at 10±1℃. Since the melting points of alkali metals Rb and Cs are 38.9℃ and 28.4℃ respectively, the alkali metal atoms dispersed on the heating surface will migrate towards the cooling end, forming a directional migration. When the alkali metal atoms recondense at the cold end, they will form a point-like distribution centered on the condensation nucleus. Step 4: Using industrial CT non-destructive testing technology, reconstruct the morphology of the alkali metal condensation clusters inside the gas chamber from multiple angles. Step 5: Statistically analyze the voxels occupied by the alkali metal clusters, and then calculate the volume of the alkali metal clusters. Step 6: Calculate the total mass of the alkali metals.

[0026] In step one, since the gas chamber filling and exhaust branch pipe is formed by flame heating and sintering, it has an irregular conical shape and does not fit very tightly with the boron nitride assembly. Thermally conductive adhesive can be poured between the gas chamber and the boron nitride assembly to increase the bonding area between the gas chamber and the boron nitride assembly and increase the heating efficiency.

[0027] In step two, heating elements are attached to the top of the boron nitride assembly cavity cube and the four sides of the rectangular shell for heating, while cooling elements are attached to the bottom of the gas chamber to allow alkali metals to deposit at the bottom, facilitating scanning imaging.

[0028] In step three, the heating and cooling time should be maintained at more than 45 minutes to ensure that the alkali metals fully migrate to the cooling surface.

[0029] In step four, the industrial CT scan resolution should be above 5µm. The higher the resolution and the higher the number of pixels, the more accurate the volume of the alkali metal clusters read.

[0030] In step five, based on the 360° two-dimensional projection data of alkali metal clusters obtained by scanning, a three-dimensional voxel matrix is ​​reconstructed through a filtered back projection algorithm. Each voxel represents a tiny cubic unit, and the volume of a single voxel is determined by the CT resolution.

[0031] In step six, the density of Rb is 0.826 g / cm³.3 The density of Cs is 0.956 g / cm³. 3 The mass of the alkali metal filled into the gas chamber is:

[0032] Where m is the mass of the alkali metal, ρ is the density of the alkali metal, and V A It is the pixel volume of the alkali metal.

[0033] Example: The atomic gas chamber can be spherical or square. Although the collision relaxation of atoms in a spherical chamber is smaller, the spherical shape has a diverging effect on the laser, which reduces the laser's transmittance. Therefore, the atomic gas chamber is generally square in shape. Figure 1 The diagram shown is a structural schematic of a square atomic gas chamber, which consists of... Figure 1 The six glass components 3 shown are assembled together. The glass nozzle 1 at the top of the gas chamber is left when the filling and exhaust branch pipes are sealed. The gas chamber cavity 2 is a cavity filled with inert gas and alkali metal.

[0034] according to Figure 2 The procedure shown measures the alkali metal content within an atomic gas chamber. A square atomic gas chamber is inserted into a boron nitride (BN) assembly. It's important to note that the structure of the BN assembly can be adjusted according to the chamber's dimensions; the key is ensuring the inner wall of the BN assembly adheres tightly to the outer wall of the gas chamber. A temperature gradient is created outside the chamber. Heating is performed on five sides of the BN assembly to prevent alkali metal from adhering to the inner wall, while cooling is performed on the remaining side to allow the alkali metal to adhere. Subsequently, industrial CT scanning is used to construct the 3D morphology of the deposited alkali metal. The volume of the alkali metal is obtained by calculating the voxels occupied by the alkali metal clusters, thus calculating the alkali metal content.

[0035] Figure 3 The image shows a boron nitride assembly used to clamp a square gas chamber. The hollow cuboid 11 has a cylindrical perforation in the center. Figure 1 The upper glass nozzle 1 of the middle chamber is connected to the rectangular outer shell 12, which has a light window for light transmission, through which the distribution of alkali metals can be observed. The solid cuboid 13 is connected to... Figure 1 The opposing surfaces of the gas chamber glass nozzle 1 are connected. The size of the boron nitride shell can be adjusted according to the size of the gas chamber to ensure that the inner wall of the shell is tightly attached to the outer wall of the gas chamber. Any gaps where the gas chamber glass nozzle 1 component and the boron nitride shell cavity cube 11 are not tightly fitted are filled with thermally conductive adhesive before assembly.

[0036] like Figure 4As shown, heating elements are attached to the bottom surface of the hollow cuboid and the four sides of the rectangular shell, totaling five surfaces. Cooling elements are attached to the bottom surface of the solid cuboid. PT100 thermometers are also attached to the side walls and bottom surface for real-time temperature monitoring. Heating and cooling are activated simultaneously. The heating temperature is maintained at 120±2℃, and the cooling temperature at 10±1℃, for at least 45 minutes to allow the alkali metals to migrate fully to the bottom. It is important to note that during cooling, the heating current must be gradually reduced to 0, and the cooling rate should not exceed 20℃ / min. Furthermore, the cooling elements must continue operating during cooling to prevent the alkali metals deposited at the bottom from migrating back to other side walls.

[0037] like Figure 5 As shown, the alkali metals deposited at the bottom are distributed in an irregular ellipsoidal shape. The 3D morphology of the alkali metal clusters can be clearly reconstructed using industrial CT scanning. Based on the 360° two-dimensional projection data of the alkali metal clusters obtained from the scan, a three-dimensional voxel matrix is ​​reconstructed using a filtered back-projection algorithm. Each voxel represents a tiny cubic unit, and the volume of a single voxel is determined by the CT resolution.

[0038] in, This refers to the resolution of the CT scan (in µm). Volume of a single voxel (in mm) 3 ) Therefore, the volume of the entire alkali metal cluster is:

[0039] Where N is the number of voxels occupied by alkali metal clusters.

[0040] In step six, the density of Rb is 0.826 g / cm³. 3 The density of Cs is 0.956 g / cm³. 3 The mass of the alkali metal filled into the gas chamber is:

[0041] Where ρ is the density of the alkali metal.

[0042] In summary, this invention describes a non-destructive method for estimating the alkali metal content within an atomic gas chamber based on alkali metal directional deposition and industrial CT scanning technology. Compared with existing technologies, this method significantly improves the accuracy of alkali metal mass measurement.

[0043] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0044] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for estimating the amount of alkali metals in an atomic gas chamber, characterized in that, include: Step 1: Place the atomic gas chamber inside the boron nitride assembly, with the atomic gas chamber in contact with the inner wall of the boron nitride assembly, and an observation window is provided on the side of the boron nitride assembly; Step 2: Attach heating and cooling plates (TECs) to the outer surface of the boron nitride assembly, and attach PT100 to the heating and cooling plates for temperature measurement. Step 3: Turn on the heating and cooling power supplies. The heating temperature is controlled at 120±2℃ and the cooling temperature is controlled at 10±1℃. Since the melting points of alkali metals Rb and Cs are 38.9℃ and 28.4℃ respectively, the alkali metal atoms dispersed on the heating surface will migrate to the cooling end, forming a directional migration. When the alkali metal atoms recondense at the cold end, they will form a point-like distribution centered on the condensation nucleus. Step 4: Using industrial CT non-destructive testing technology, the morphology of alkali metal condensation clusters inside the gas chamber is reconstructed from multiple angles. Step 5: Statistically analyze the voxels occupied by the alkali metal clusters, and then calculate the volume of the alkali metal clusters. Step 6: Calculate the total mass of the alkali metals based on the volume of the alkali metal clusters and the densities of alkali metals Rb and Cs.

2. The method according to claim 1, characterized in that, In step one, the boron nitride assembly includes: a hollow cuboid, a rectangular shell, and a solid cuboid. The rectangular shell has a square cavity along its length. Observation windows are provided on the four sides of the rectangular shell. The gas chamber is placed in the square cavity along the length of the rectangular shell, and the rectangular shell is tightly fitted to the outer wall of the gas chamber. The hollow cuboid and the solid cuboid are placed at both ends of the gas chamber. The glass nozzle at the top of the gas chamber is accommodated in the cavity of the hollow cuboid, and the bottom of the gas chamber is in contact with the solid cuboid.

3. The method according to claim 2, characterized in that, In step one, the observation windows on the four sides of the cuboid shell are the same size and shape as the four sides of the atomic gas chamber.

4. The method according to claim 3, characterized in that, Step one also includes: After placing the atomic gas chamber into the boron nitride assembly, thermally conductive adhesive is poured between the gas chamber and the cavity cube to increase the contact area between the gas chamber and the boron nitride shell, thereby increasing the heating efficiency.

5. The method according to claim 4, characterized in that, In step two, specifically: heating elements are attached to the outer surfaces of the hollow cuboid and the rectangular shell, and cooling elements (TECs) are attached to the outer surface of the solid cuboid. At the same time, PT100 is attached to the cooling elements and heating elements to measure the temperature.

6. The method according to claim 5, characterized in that, In step three, the heating and cooling time should be maintained at more than 45 minutes to ensure that the alkali metals fully migrate to the cooling surface.

7. The method according to claim 6, characterized in that, In step three, during cooling, the heating current needs to be gradually reduced to 0, and the cooling rate should not exceed 20℃ / min. At the same time, the cooling element should continue to work to prevent the alkali metal deposited at the bottom from migrating back to other sidewalls.

8. The method according to claim 7, characterized in that, In step four, the industrial CT scan resolution is above 5µm.

9. The method according to claim 8, characterized in that, In step five, based on the 360° two-dimensional projection data of alkali metal clusters obtained by scanning, a three-dimensional voxel matrix is ​​reconstructed through a filtered back projection algorithm. Each voxel represents a tiny cubic unit, and the volume of a single voxel is determined by the CT resolution.

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