A Stable Method for Online Non-destructive Measurement of Alkali Metal Atomic Density

Abstract

This invention discloses an online non-destructive measurement and stabilization method for alkali metal atomic density, providing a feasible solution for real-time stable control of alkali metal atomic density in the atomic gas cell of a SERF magnetometer and a common magnetometer. This invention focuses on alkali metal atomic density, addressing the requirement for long-term stability of the alkali metal atomic density within the atomic gas cell. First, a loss model for optical power propagation within the atomic gas cell is established. Then, the Lambert-Beer law is used to fuse the incoming and outgoing light data to calculate the atomic density within the gas cell. Since the atomic density is related to the temperature of the atomic gas cell, density fluctuations are used as an error quantity to control the driving voltage of the heating film, thereby stabilizing the atomic density within the gas cell. The measurement method in this invention is a real-time, non-destructive method for measuring alkali metal atomic density, ensuring long-term stability and anti-interference capabilities.

Description

Technical Field

[0001] This invention relates to an online non-destructive measurement stabilization method for alkali metal atomic density, applicable to the measurement and control of atomic density stability, and applicable to the field of quantum measurement technology. Background Technology

[0002] With the development of new theories and technologies in the quantum field, various scientific instruments based on quantum effects are constantly and significantly breaking through the measurement limits of traditional instruments. Quantum instruments based on atomic spin effects, as a new generation of precision measurement instruments, have unparalleled advantages in performance indicators compared to traditional instruments, and represent an important development direction for high-precision measurement in the future.

[0003] The stability of atomic measurement signals is a prerequisite for precise measurements by atomic spin measurement devices. Fluctuations in atomic density significantly impact the performance indicators of inertial measurement devices, such as the zero-bias stability of the output signal. Temperature control schemes based on platinum resistance thermometers cannot obtain the internal temperature information of the atomic chamber, thus failing to accurately measure atomic density fluctuations. While schemes based on heterodyne interferometry and Raman spectroscopy can provide atomic density information, they are bulky and inconvenient for practical use. The solution of this invention utilizes the existing SERF (Spin-Exchange Relaxation-Free) magnetometer or covariance meter, offering advantages such as small size and real-time atomic density measurement. Summary of the Invention

[0004] This invention proposes a stable online non-destructive measurement method for alkali metal atomic density. The method calculates the atomic density within the gas chamber using the incident and emitted light power. Since the atomic density is related to the temperature of the gas chamber, the fluctuation of the atomic density is used as an error quantity. The driving voltage of the heating film is then controlled to stabilize the atomic density within the gas chamber. This method enables real-time, non-destructive measurement of alkali metal atomic density, thereby ensuring the long-term stability and anti-interference properties of alkali metal atomic density.

[0005] The technical solution of the present invention is as follows:

[0006] A method for stabilizing the online non-destructive measurement of alkali metal atomic density is characterized by the following steps: taking the alkali metal atomic density in an atomic spin measurement device as the research object, and considering the requirement for long-term stability of the alkali metal atomic density in the atomic gas chamber, an optical loss model of the gas chamber for the propagation of optical power in the atomic gas chamber is established. Then, the Lambert-Beer law is used to fuse the incident and outgoing light data of the gas chamber to calculate the alkali metal atomic density in the atomic gas chamber. The alkali metal atomic density is related to the temperature of the atomic gas chamber. The fluctuation of the alkali metal atomic density is used as an error quantity to control the driving voltage of the heating film, thereby stabilizing the atomic density in the atomic gas chamber.

[0007] The atomic spin measurement device includes a distributed feedback laser, a beam expander, a liquid crystal variable phase delayer, a half-wave plate, a polarizing beam splitter, a quarter-wave plate, an atomic gas cell, a first photodetector, and a data acquisition module connected in sequence. The control terminal of the liquid crystal variable phase delayer is connected to the data output interface of the PID module in the host computer module. The reflecting side of the polarizing beam splitter is connected to the data acquisition module through a second photodetector. The data acquisition module is connected to the data input interface of the PID module. The atomic gas cell is located inside an oven, which is located inside a triaxial magnetic field coil. The oven includes an oven support and a heating film. The heating film is connected to the data output interface of the PID module. The triaxial magnetic field coil is connected to a function generator.

[0008] The online non-destructive measurement stabilization method includes the following steps:

[0009] Step 1: The data acquisition module in the atomic spin measurement device acquires data through a photodetector, transmitting the incident light power I of the atomic gas cell. in and output light power Transmitted to the host computer module;

[0010] Step 2, the host computer module according to I in and Calculate the atomic density n of alkali metals K ;

[0011] Step 3, the host computer module according to n K The fluctuation error is obtained in real time through the PID algorithm to adjust the control voltage of the heating film.

[0012] Step 4: After the heating film heats the atomic gas chamber according to the control voltage, the cycle returns to step 1 until n. K The fluctuations end once they are suppressed or stabilized.

[0013] Step 2 includes:

[0014]

[0015] I(a)=ηI in

[0016]

[0017] Where σ p Let L be the absorption cross section, L be the inner diameter of the gas chamber, and η and These are undetermined coefficients, and α is the conversion coefficient between pump rate and pump optical power. I is the longitudinal relaxation rate of alkali metal atoms, I(a) is the light power at the incident point of the gas cell, I(b) is the light power at the exit point of the gas cell, and dI is the light power absorbed by the atoms at high temperature.

[0018] The online non-destructive measurement stabilization method includes the following steps:

[0019] Step 1: Constructing the total optical loss model of the atomic gas cell: Identify the parameters, adjust the pump laser frequency of the DFB (Distributed Feedback Laser) to the working frequency, and apply appropriate excitation to the three-dimensional magnetic compensation coil to put the system in a weak magnetic state. Considering the optical refraction, scattering, and atomic gas cell characteristics from a mechanistic perspective, construct an optical loss model containing undetermined parameters. The oven does not heat the atomic gas cell, i.e., at room temperature. Adjust the incident light power under different experimental conditions by adjusting the control voltage setting of the LCVR (Liquid Crystal Variable Retarder). Fit the parameters of the total optical loss model of the atomic gas cell based on the actual data.

[0020] Step 2: Real-time measurement of atomic density: Based on the working environment in Step 1, apply an appropriate control voltage to the heating film to heat the atomic gas chamber. Collect the optical power of the incident and exiting gas chambers through the data acquisition module. Calculate the real-time alkali metal atomic density in the gas chamber using the atomic density model based on Lambert-Beer's law and the optical loss model at room temperature.

[0021] Step 3: Using the real-time alkali metal atomic density obtained in Step 2, the error information of the alkali metal atomic density is obtained by subtracting it from the set value of the alkali metal atomic density. The control voltage of the heating film is adjusted through the PID module of the host computer to achieve the goal of stabilizing the atomic density in real time when the atomic spin system is operating.

[0022] The atomic gas cell described is a spherical atomic gas cell widely used in the field of quantum inertial measurement, considering the total optical loss model of the gas cell. Taking into account optical losses caused by the atomic gas cell walls and scattering losses caused by gas molecules, the total optical loss of the atomic gas cell is represented by ∑dI. cell This indicates that the model is constructed as ∑dI cell =I in -I in η 2 exp(-nσ s LηI in ), I in η is the power of the laser incident on the gas chamber, η is an undetermined coefficient, n is the number density of gas atoms other than alkali metal atoms, L is the length of the gas chamber, and σ is the power of the laser incident on the gas chamber. s For scattering cross section, It is the output light power at room temperature. The total optical loss model of the atomic gas cell is obtained by fitting actual data.

[0023] In step two, based on the Lambert-Beer law, the online measurement method for alkali metal atomic density utilizes data on the optical power of the incident and exit gas cells, as well as a model of the optical loss of the atomic gas cell at room temperature. The Lambert-Beer law describes the attenuation of the pump rate along the propagation direction using a differential equation; the relationship between atomic density and pump rate can be expressed as... Where R p n is the pump rate. K σ is the atomic number density of alkali metals. p For absorption cross section, It is the polarizability of the gas cell at point z. It is the longitudinal relaxation rate of the atom. Defining the left inner wall of the gas chamber as the origin and the pump light direction as the positive z-axis, then... z is the distance, R p (0) and R p (z) represents the pump rate at the origin and point z, respectively, further derived from... Atomic density can be obtained, and pump rate is obtained from optical power. Based on the relationship between pump rate and optical power, R... p (z)=αI(z), where I(z) is the optical power at point z, and α is the conversion coefficient between pump rate and pump optical power. The pump rate in the formula can be replaced with optical power, and then the atomic density can be obtained.

[0024] The technical effects of this invention are as follows: This invention discloses an online non-destructive measurement and stabilization method for alkali metal atomic density, providing a feasible solution for real-time stable control of alkali metal atomic density in the atomic gas chamber of a SERF magnetometer and a common magnetometer. This invention focuses on alkali metal atomic density, addressing the requirement for long-term stability of the alkali metal atomic density within the atomic gas chamber. First, a loss model for optical power propagation within the atomic gas chamber is established. Then, the Lambert-Beer law is used to fuse the light entering and exiting data of the gas chamber to calculate the atomic density. The atomic density is related to the temperature of the atomic gas chamber; density fluctuations are used as an error quantity to control the driving voltage of the heating film, thereby stabilizing the atomic density within the gas chamber. The measurement method in this invention is a real-time, non-destructive method for measuring alkali metal atomic density, ensuring long-term stability and anti-interference capabilities.

[0025] The advantages of this invention compared to the prior art are:

[0026] (1) First, an optical loss model is constructed, and then the density information of alkali metal atoms is obtained in real time through the power of the outgoing and incident light. It has the advantages of small size and online non-destructive measurement.

[0027] (2) Based on the real-time atomic density information, the temperature of the gas chamber is adjusted by controlling the driving voltage of the heating film to suppress atomic density fluctuations. It has the advantage of online adjustment and can effectively suppress atomic density fluctuations caused by unknown changes in the external environment. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the atomic spin measuring device used in implementing the online non-destructive measurement stabilization method for alkali metal atomic density according to the present invention.

[0029] Figure 2 This is a schematic diagram of the process for implementing an online non-destructive measurement stabilization method for alkali metal atomic density according to the present invention. Figure 2 The process includes step 1, where the data acquisition module in the atomic spin measurement device acquires data through a photodetector, transmitting the current incident light power I of the atomic gas cell. in Data and output optical power Data is transmitted to the host computer module; Step 2, the host computer module transmits data according to real-time I... in I out Calculate the atomic density n of alkali metals K Step 3, the host computer module according to n K The fluctuation error is adjusted in real time using a PID algorithm to obtain the control voltage of the heating film; in step 4, after the control voltage of the heating film heats the atomic gas chamber, the cycle returns to step 1 and repeats until n. K The fluctuations end once they are suppressed or stabilized.

[0030] Figure 3 yes Figure 1 A partial schematic diagram of the intermediate atomic gas chamber. Figure 3 It includes a spherical glass atomic gas cell, where I(a) is the light power at the incident point of the gas cell, I(b) is the light power at the exit point of the gas cell, dI is the light power absorbed by the atoms at high temperature, and ∑dI cell This is the total optical loss of the air chamber.

[0031] The reference numerals in the attached figures are explained as follows: 1-Distributed Feedback Laser (DFB); 2-Beam Expander; 3-Liquid Crystal Variable Retarder (LCVR); 4-Half-wave Plate; 5-Polarization Beam Splitter; 6-Quarter-wave Plate; 7-Oven (including oven support and heating film); 8-Atomic Gas Chamber (e.g., spherical glass atomic gas chamber); 9-Photodetector (PD); 10-Triaxial Magnetic Field Coil; 11-Data Acquisition Module; 12-Host Computer Module (with built-in PID module, PID stands for Proportional Integral Derivative, which has data input and data output interfaces); 13-Function Generator. Detailed Implementation

[0032] The following is in conjunction with the attached diagram ( Figures 1-3 The invention will be described in the following sections and examples.

[0033] Figure 1 This is a schematic diagram of the atomic spin measuring device used in implementing the online non-destructive measurement stabilization method for alkali metal atomic density according to the present invention. Figure 2 This is a schematic diagram of the process for implementing an online non-destructive measurement stabilization method for alkali metal atomic density according to the present invention. Figure 3 yes Figure 1 Partial schematic diagram of the intermediate atom gas chamber. (Reference) Figures 1 to 3As shown, an online non-destructive measurement stabilization method for alkali metal atomic density includes: taking the alkali metal atomic density in an atomic spin measurement device as the research object; establishing a gas chamber optical loss model for the propagation of optical power in the atomic gas chamber to meet the requirement of long-term stability of the alkali metal atomic density in the atomic gas chamber; then using Lambert-Beer's law to fuse the incident and outgoing light data in the gas chamber to calculate the alkali metal atomic density in the atomic gas chamber; the alkali metal atomic density is related to the temperature of the atomic gas chamber; and using the fluctuation of the alkali metal atomic density as an error quantity to control the driving voltage of the heating film, thereby stabilizing the atomic density in the atomic gas chamber. The atomic spin measurement device includes a distributed feedback laser 1, a beam expander 2, a liquid crystal variable phase delay 3, a half-wave plate 4, a polarizing beam splitter 5, a quarter-wave plate 6, an atomic gas cell 8, a first photodetector 9, and a data acquisition module 11 connected in sequence. The control terminal of the liquid crystal variable phase delay 3 is connected to the data output interface of the PID module in the host computer module 12. The reflecting side of the polarizing beam splitter 5 is connected to the data acquisition module 11 through the second photodetector 9. The data acquisition module 11 is connected to the data input interface of the PID module. The atomic gas cell 8 is located inside an oven 7, which is located inside a triaxial magnetic field coil 10. The oven 7 includes an oven support and a heating film. The heating film is connected to the data output interface of the PID module. The triaxial magnetic field coil 10 is connected to a function generator 13.

[0034] The online non-destructive measurement stabilization method includes the following steps: Step 1, the data acquisition module in the atomic spin measurement device acquires data through a photodetector, and the incident light power I of the atomic gas cell is... in and output light power Transmitted to the host computer module; Step 2, the host computer module according to I in and Calculate the atomic density n of alkali metals K Step 3, the host computer module according to n K The fluctuation error is obtained in real time through a PID algorithm to adjust the control voltage of the heating film in real time; in step 4, the heating film heats the atomic gas chamber according to the control voltage and then returns to step 1 in a loop until n. K The fluctuations end once they are suppressed or stabilized.

[0035] Step 2 includes:

[0036]

[0037] I(a)=ηI in

[0038]

[0039] Where σp Let L be the absorption cross section, L be the inner diameter of the gas chamber, and η and These are undetermined coefficients, and α is the conversion coefficient between pump rate and pump optical power. I is the longitudinal relaxation rate of alkali metal atoms, I(a) is the light power at the incident point of the gas cell, I(b) is the light power at the exit point of the gas cell, and dI is the light power absorbed by the atoms at high temperature.

[0040] The online non-destructive measurement stabilization method includes the following steps: Step 1, constructing a total optical loss model for the atomic gas cell: identifying the parameters, adjusting the pump laser frequency of the DFB to the operating frequency, and appropriately exciting the three-dimensional magnetic compensation coil to bring the system into a weak magnetic state. Considering the optical refraction, scattering, and atomic gas cell characteristics from a mechanistic perspective, constructing an optical loss model containing undetermined parameters. The oven does not heat the atomic gas cell, i.e., at room temperature. The incident light power under different experimental conditions is adjusted by adjusting the LCVR control voltage setting. The parameters of the total optical loss model of the atomic gas cell are fitted based on the actual data; Step 2, real-time measurement. Atomic density: Based on the working environment in step one, a suitable control voltage is applied to the heating film to heat the atomic gas chamber. The optical power of the incident and exit gas chambers is collected through the data acquisition module. Using the atomic density model based on Lambert-Beer's law and combined with the optical loss model at room temperature, the real-time alkali metal atomic density in the gas chamber is calculated. Step three: Using the real-time alkali metal atomic density from step two, the error information of the alkali metal atomic density is obtained by subtracting it from the set value of the alkali metal atomic density. The control voltage of the heating film is adjusted through the PID module of the host computer to achieve the goal of stabilizing the atomic density in real time during the operation of the atomic spin system.

[0041] The atomic gas cell described is a spherical atomic gas cell widely used in the field of quantum inertial measurement, considering the total optical loss model of the gas cell. Taking into account optical losses caused by the atomic gas cell walls and scattering losses caused by gas molecules, the total optical loss of the atomic gas cell is represented by ∑dI. cell This indicates that the model is constructed as ∑dI cell =I in -I in η 2 exp(-nσ s LηI in ), I in η is the power of the laser incident on the gas chamber, η is an undetermined coefficient, n is the number density of gas atoms other than alkali metal atoms, L is the length of the gas chamber, and σ is the power of the laser incident on the gas chamber. s For scattering cross section, It is the output light power at room temperature. The total optical loss model of the atomic gas cell is obtained by fitting actual data.

[0042] In step two, based on the Lambert-Beer law, the online measurement method for alkali metal atomic density utilizes data on the optical power of the incident and exit gas cells, as well as a model of the optical loss of the atomic gas cell at room temperature. The Lambert-Beer law describes the attenuation of the pump rate along the propagation direction using a differential equation; the relationship between atomic density and pump rate can be expressed as... Where R p n is the pump rate. K σ is the atomic number density of alkali metals. p For absorption cross section, It is the polarizability of the gas cell at point z. It is the longitudinal relaxation rate of the atom. Defining the left inner wall of the gas chamber as the origin and the pump light direction as the positive z-axis, then... z is the distance, R p (0) and R p (z) represents the pump rate at the origin and point z, respectively, further derived from... Atomic density can be obtained, and pump rate is obtained from optical power. Based on the relationship between pump rate and optical power, R... p (z)=αI(z), where I(z) is the optical power at point z, and α is the conversion coefficient between pump rate and pump optical power. The pump rate in the formula can be replaced with optical power, and then the atomic density can be obtained.

[0043] The technical problem solved by this invention is the online measurement of alkali metal atomic density and the stable control of atomic density inside the gas chamber of an atomic spin device.

[0044] The technical solution of this invention is: a method for measuring and stabilizing the density of alkali metal atoms inside the gas chamber of an atomic spin device, comprising the following steps:

[0045] Step 1: Construct a total optical loss model for the atomic gas cell. The optical power of the pump light at room temperature satisfies...

[0046]

[0047] in This refers to the optical power of the pump light exiting the gas cell at room temperature. By measuring the power of the incident and exiting beams, the total optical loss ∑dI of the gas cell can be obtained. cell .

[0048] Step 2: The Lambert-Beer Law has the following relationship with atomic density:

[0049]

[0050] The incident light is defined as entering the atomic gas cell from the left, with the origin being the incident light and the left inner wall of the atomic gas cell. The pump light direction is defined as the positive z-axis. The atomic polarizability at point z can be expressed as:

[0051]

[0052] Among them, R p For pump rate, The longitudinal relaxation rate of the atom is given by substituting the polarizability into Beer-Lambert law, which yields the relationship between atomic density and pump rate:

[0053]

[0054] Among them, R p (0) and R p (z) represent the pump rates at the origin and z-point, respectively. Based on the relationship between pump rate and optical power, R... p (z)=αI(z), combined with the optical loss model obtained in step one, the propagation of optical power in the air chamber is obtained.

[0055]

[0056] Where I(a) and I(b) represent the optical power at the intersection of the incident light and the left inner wall of the air chamber, and the intersection of the outgoing light and the right inner wall of the air chamber, respectively, and σ p Let L be the absorption cross section, L be the inner diameter of the gas chamber, and η and These are the coefficients of the gas cell loss model. Using the above measurement method, combined with the real-time incident and outgoing light power of the atomic gas cell, the density of alkali metal atoms in the atomic gas cell can be obtained in real time.

[0057] Step 3: The real-time incident and outgoing light power is collected by a photodetector and transmitted to the host computer's processing program. The host computer calculates the real-time atomic density fluctuation error, adjusts the control voltage of the heating film, adjusts the heating, and suppresses the atomic density fluctuation.

[0058] Figure 1 The diagram illustrates the structure of an atomic precision measurement device. The light emitted from the distributed feedback laser passes through a beam expander, a liquid crystal module, and a half-wave plate, then through a polarizing beam splitter. One beam is detected by a PD (photodetector) to determine the incident light intensity I based on the beam splitting ratio. in The other linearly polarized beam, after passing through a quarter-wave plate, becomes circularly polarized pump light and enters the atomic gas cell. The power of the emitted light is also detected by the PD to obtain I. out The incident and emitted light powers are transmitted to the host computer via a data acquisition module for data processing. The host computer calculates the fluctuations in the atomic density inside the gas chamber and adjusts the LCD control voltage using a PID controller.

[0059] Figure 2 The atomic density stabilization control process is illustrated, and a total optical loss model for the atomic gas cell is constructed. The Lambert-Beer law uses a differential equation to describe the attenuation of circularly polarized pump light along the propagation direction:

[0060]

[0061] Among them, R p n is the pump rate. K σ is the atomic number density of alkali metals. p (υ) is the absorption cross section. Let z be the polarizability of the alkali metal atom at z. Further derivation,

[0062]

[0063]

[0064]

[0065] It can be obtained

[0066]

[0067] The pump rate is proportional to the optical power I of the pump light, and can be expressed as:

[0068]

[0069] Where α is the proportionality coefficient. Taking the point of contact between the incident pump light and the atomic gas cell, i.e., point a, as the origin, R p (z) is the pump rate at point z, where c represents the speed of light in a vacuum, and r e Γ represents the classical electron radius, f represents the oscillator strength, Γ represents the pressure broadening, which is half the maximum value of the Lorentz curve and is proportional to the gas pressure in the gas chamber, A represents the effective area of ​​the incident light, h is Planck's constant, and v is the frequency of the laser.

[0070] Using the above two equations, the propagation equation of the pump light power along the direction of the gas chamber can be solved as follows:

[0071]

[0072] Where I(0) is the light intensity at the origin, the W function is the Lambertian function, which is the inverse function of the complex function f(x) = xexp(x), and I(0) = ηI in Based on the above derivation, the atomic density within the atomic chamber can be obtained:

[0073]

[0074] Where, σ p Let L be the absorption cross section, L be the inner diameter of the gas chamber, and η and These are the coefficients of the air chamber loss model.

[0075] Figure 3 The diagram illustrates a partial structure of the gas cell. At room temperature, there is no light absorption by alkali metal atoms in the atomic gas cell. Considering the refraction of the atomic gas cell wall, then...

[0076] I(a)=ηI in

[0077]

[0078] Considering the scattering of other gases inside the atomic gas chamber

[0079]

[0080] Comprehensive results

[0081]

[0082] Where η and These are undetermined coefficients, determined based on the different incident and outgoing light powers within the gas chamber at room temperature. This equation can be used to estimate the power attenuation of the laser beam as it passes through the gas chamber and to calculate the optical power transmitted through the gas chamber.

[0083] In the heated state, in addition to optical loss, the alkali metal atoms in the gas chamber also have light absorption due to being pumped by circularly polarized light. At this time, the light output power at high temperature is different from the light output power at room temperature by the light absorption power of the atoms inside the gas chamber.

[0084] dI is the optical power absorbed by atoms at high temperature. The optical power at points a and b within the atomic gas chamber can be calculated.

[0085] I(a)=ηI in

[0086]

[0087] This leads to the atomic density.

[0088] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A stable method for online non-destructive measurement of alkali metal atomic density, characterized in that, This includes studying the density of alkali metal atoms in an atomic spin measurement device. To address the requirement for long-term stability of the alkali metal atom density within the atomic gas chamber, a gas chamber optical loss model for the propagation of optical power within the atomic gas chamber is established. Then, the Lambert-Beer law is used to fuse the incident and outgoing light data within the gas chamber to calculate the alkali metal atom density within the atomic gas chamber. The alkali metal atom density is related to the temperature of the atomic gas chamber. The fluctuation of the alkali metal atom density is used as an error quantity to control the driving voltage of the heating film, thereby stabilizing the atomic density within the atomic gas chamber. The online non-destructive measurement stabilization method includes the following steps: Step 1: Constructing the total optical loss model of the atomic gas cell: Identify the parameters, adjust the pump laser frequency of the DFB to the working frequency, and apply appropriate excitation to the three-dimensional magnetic compensation coil to put the system in a weak magnetic state. Considering the optical refraction, scattering, and atomic gas cell characteristics from a mechanistic perspective, construct an optical loss model containing undetermined parameters. The oven does not heat the atomic gas cell, i.e., at room temperature. Adjust the incident light power under different experimental conditions by adjusting the LCVR control voltage setting value. Fit the parameters of the total optical loss model of the atomic gas cell based on the actual data. Step 2: Real-time measurement of atomic density: Based on the working environment in Step 1, apply an appropriate control voltage to the heating film to heat the atomic gas chamber. Collect the optical power of the incident and exiting gas chambers through the data acquisition module. Calculate the real-time alkali metal atomic density in the gas chamber using the atomic density model based on Lambert-Beer's law and the optical loss model at room temperature. Step 3: Using the real-time alkali metal atomic density obtained in Step 2, the error information of the alkali metal atomic density is obtained by subtracting it from the set value of the alkali metal atomic density. The control voltage of the heating film is adjusted through the PID module of the host computer to achieve the purpose of stabilizing the atomic density in real time when the atomic spin system is operating. The atomic gas cell described is a spherical atomic gas cell widely used in the field of quantum inertial measurement. Considering the total optical loss model of the gas cell, including optical losses caused by the atomic gas cell walls and scattering losses caused by gas molecules, the total optical loss of the atomic gas cell is... This indicates that the model is constructed as follows: , It is the power of the laser incident on the gas chamber. These are undetermined coefficients. This refers to the atomic number density of gases other than alkali metal atoms. The length of the air chamber. For scattering cross section, , It is the emitted light power at room temperature. The total optical loss model of the atomic gas cell is fitted by actual data. In step two, based on Beer-Lambert's law, the online measurement method for alkali metal atomic density utilizes data on the optical power of the incident and exit gas cells, as well as a model of the optical loss of the atomic gas cell at room temperature. Beer-Lambert's law describes the attenuation of the pump rate along the propagation direction using a differential equation. The relationship between atomic density and pump rate can be expressed as follows: ,in For pump rate, The number density of alkali metal atoms. For absorption cross section, It is the polarizability of the gas cell at point z. It is the longitudinal relaxation rate of the atom; defining the left inner wall of the gas chamber as the origin, and defining the pump light direction as the positive z-axis direction, then... , It's distance. and These are the pump rates at the origin and z-point, respectively, further derived from... Atomic density can be obtained, and pump rate is obtained from optical power. Based on the relationship between pump rate and optical power... , It is the optical power at point z. It is the conversion coefficient between pump rate and pump power. By replacing the pump rate in the formula with the optical power, the atomic density can be obtained.

2. The stable online non-destructive measurement method for alkali metal atomic density according to claim 1, characterized in that, The atomic spin measurement device includes a distributed feedback laser, a beam expander, a liquid crystal variable phase delayer, a half-wave plate, a polarizing beam splitter, a quarter-wave plate, an atomic gas cell, a first photodetector, and a data acquisition module connected in sequence. The control terminal of the liquid crystal variable phase delayer is connected to the data output interface of the PID module in the host computer module. The reflecting side of the polarizing beam splitter is connected to the data acquisition module through a second photodetector. The data acquisition module is connected to the data input interface of the PID module. The atomic gas cell is located inside an oven, which is located inside a triaxial magnetic field coil. The oven includes an oven support and a heating film. The heating film is connected to the data output interface of the PID module. The triaxial magnetic field coil is connected to a function generator.

3. The stable online non-destructive measurement method for alkali metal atomic density according to claim 1, characterized in that, The online non-destructive measurement stabilization method includes the following steps: Step 1: The data acquisition module in the atomic spin measurement device acquires data through a photodetector, transmitting the incident light power I of the atomic gas cell. in and output light power Transmitted to the host computer module; Step 2, the host computer module according to I in and Calculate the atomic density n of alkali metals K ; Step 3, the host computer module according to n K The fluctuation error is obtained in real time through the PID algorithm to adjust the control voltage of the heating film. Step 4: After the heating film heats the atomic gas chamber according to the control voltage, the cycle returns to step 1 until n. K The fluctuations end once they are suppressed or stabilized.

4. The stable online non-destructive measurement method for alkali metal atomic density according to claim 3, characterized in that, Step 2 includes: ， ， ， in For absorption cross section, It is the inner diameter of the air chamber. and These are undetermined coefficients. It is the conversion factor between pump rate and pump optical power. I is the longitudinal relaxation rate of alkali metal atoms, I(a) is the light power at the incident point of the gas cell, I(b) is the light power at the exit point of the gas cell, and dI is the light power absorbed by the atoms at high temperature.

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