A method for measuring the optimal quenching gas pressure in an alkali metal gas cell based on the atomic fluorescence effect

Abstract

The method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect belongs to the field of quantum precision measurement technology. By heating and shielding the atoms in the alkali metal gas chamber in an ultra-high sensitivity magnetic field measurement device based on atomic spin, the alkali metal atoms are pumped with circularly polarized light to achieve a SERF state. The quenching gas is used to absorb the photons spontaneously radiated by the alkali metal atoms, suppressing the frequency broadening caused by the reabsorption of the photons. At the same time, by detecting the output response of the device corresponding to gas chambers with different pressures, the maximum output signal is found, and the optimal content of the quenching gas is determined. The reduction in fluorescence intensity indicates that the quenching gas has effectively absorbed the photons. The present invention effectively improves the sensitivity and overall performance of the magnetic field measurement device by determining the optimal quenching gas pressure, reducing spin-destruction collision relaxation, and increasing the relaxation time of the system.

Description

Technical Field

[0001] The present invention relates to the field of quantum precision measurement technology, and in particular to a method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect. The method utilizes a quenching gas to absorb photons spontaneously radiated by alkali metal atoms, detects the fluorescence intensity and the device output response corresponding to gas chambers with different quenching gas pressures, reduces spin-destruction collision relaxation, and increases the relaxation time of the system, thereby determining the optimal quenching gas pressure in the alkali metal atom gas chamber in an atomic magnetic field measurement device, improving the sensitivity and overall performance of the device, and is suitable for measurement systems based on atomic spin magnetic field and inertia. Background Art

[0002] With the emergence and development of new theories and technologies in the field of quantum precision measurement, various precision measurement instruments based on quantum effects are continuously breaking through the measurement limits of traditional instruments. Among them, atomic spin magnetic field measurement devices based on the SERF effect (Spin-Exchange Relaxation-Free) have demonstrated ultra-high precision and sensitivity, playing a significant role in cutting-edge fundamental physics research and possessing significant significance for my country's scientific and technological development.

[0003] In a SERF atomic spin magnetic field measurement device, the alkali metal atom gas chamber serves as a sensitive element, and its atomic polarizability determines the sensitivity of the device. Increasing the spin coherence time of the alkali metal atoms is one of the important means to improve the sensitivity of the device. Factors affecting spin relaxation include spin exchange collision relaxation, spin destruction collision relaxation, bubble wall collision relaxation, and magnetic field gradient relaxation. Alkali metal atoms in an excited state release photons through spontaneous emission to return to the ground state. When the photons are reabsorbed by the alkali metal atoms, spin polarization is lost, thereby reducing the polarization degree of the atoms and affecting the sensitivity of the device. Adding a quenching gas to the gas chamber can absorb the photons radiated by the alkali metal atoms, thereby improving the sensitivity of the system. However, the interaction between the quenching gas and the alkali metal atoms causes spin destruction collision relaxation, which affects the relaxation rate of the system. Excessive quenching gas can reduce the sensitivity of the device. Therefore, determining the pressure of the quenching gas is a very important task. However, there is currently no method to quantitatively determine the optimal content of the quenching gas when the device is in operation. The present invention determines the optimal content of the quenching gas by detecting the fluorescence intensity and the device output response corresponding to gas chambers with different pressures. This method can also be applied to a series of atomic sensors containing alkali metals and quenching gases, such as atomic inertial measurement devices based on the SERF effect, and has broad application prospects. Summary of the Invention

[0004] In response to the deficiencies in the prior art, the present invention proposes a method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect. The method utilizes the quenching gas to absorb photons spontaneously emitted by alkali metal atoms, and detects the fluorescence intensity and the device output response corresponding to gas chambers with different quenching gas pressures. This reduces spin-destructive collision relaxation and increases the relaxation time of the system, thereby determining the optimal quenching gas pressure in the alkali metal atom gas chamber in the atomic magnetic field measurement device, thereby improving the sensitivity and overall performance of the device. The method is suitable for measurement systems based on atomic spin magnetic field and inertia.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect is characterized by comprising the following steps:

[0007] Step 1, preparing a series of alkali metal atom gas cells with different quenching gas pressures;

[0008] Step 2, selecting an alkali metal atom gas cell in step 1, placing it in an atomic magnetic field measurement and fluorescence detection device, and starting the atomic magnetic field measurement and fluorescence detection device to allow the atoms in the alkali metal atom gas cell to reach a SERF state;

[0009] Step 3, using laser to pump the alkali metal atoms to polarize them;

[0010] Step 4, using a spectrometer to detect the wavelength and intensity of fluorescence emitted by the alkali metal atom gas chamber;

[0011] Step 5, determining the magnitude of the magnetic field to be measured by detecting the change in the optical rotation angle of the light;

[0012] Step 6, determining whether the magnetic field measurement output response signal is a maximum value; if not, returning to step 1 to select the next alkali metal atom gas chamber with a different quenching gas pressure; if yes, proceeding to step 7;

[0013] Step 7: Determine the optimal quenching gas pressure of the alkali metal gas chamber.

[0014] The optimal quenching gas pressure of the alkali metal gas chamber determined in step 7 can avoid increasing spin-destruction collision relaxation due to excessive quenching gas, while avoiding reducing the polarizability of the alkali metal atoms due to insufficient quenching gas.

[0015] In step 1, the alkali metal atoms in the alkali metal atom gas chamber are pure potassium, pure rubidium or potassium-rubidium mixed atoms, and the alkali metal atom gas chamber is filled with a buffer gas helium and a quenching gas nitrogen, wherein the pressures of the buffer gas and the quenching gas are determined when the gas chamber is filled, and the quenching gas pressures of the first alkali metal atom gas chamber to the fifth alkali metal atom gas chamber are 40 Torr, 45 Torr, 50 Torr, 55 Torr and 60 Torr, respectively, and the density of alkali metal atoms in each alkali metal atom gas chamber remains consistent.

[0016] Step 4 includes: if an increase in fluorescence intensity is detected, it indicates that the quenching gas is insufficient; if a decrease in fluorescence intensity is detected, it indicates that the quenching gas has effectively absorbed photons. The quenching gas absorbs photons released by spontaneous radiation transitions of alkali metal atoms to avoid the photons being reabsorbed by the alkali metal atoms and reducing the pumping efficiency, thereby avoiding reducing the intensity of the magnetic field measurement output response signal; if no fluorescence intensity is detected, it indicates that there is an excess of quenching gas, which will increase spin-destructive collision relaxation and reduce the sensitivity of the magnetic field measurement device.

[0017] Include the following expressions:

[0018] ,

[0019] in is the spin-destruction collisional relaxation between the alkali metal atoms and the quenching gas nitrogen, is the density of quenching gas nitrogen, is the effective collision cross-sectional area of quenching gas nitrogen, is the relative thermal motion rate of the quenching gas nitrogen.

[0020] The atomic magnetic field measurement and fluorescence detection device includes a pump laser, a first reflector, a first half-wave plate, a first polarization beam splitter, a first lens beam expansion system, a first aperture, a second half-wave plate, a second polarization beam splitter, a second reflector, a first quarter-wave plate, an alkali metal atom gas chamber, an integrating sphere, a multimode optical fiber and a fluorescence spectrometer connected in sequence. The alkali metal atom gas chamber is located in an oven, the oven is located in a three-axis magnetic compensation coil, the three-axis magnetic compensation coil is located in a thermal insulation layer, and the thermal insulation layer is located in a shielding barrel.

[0021] The atomic magnetic field measurement and fluorescence detection device includes a detection laser, a third reflector, a third half-wave plate, a third polarization beam splitter, a second lens expansion system, a second aperture, a fourth half-wave plate, a fourth polarization beam splitter, a first Glan-Taylor prism, a photoelastic modulator, a second quarter-wave plate, an alkali metal atom gas chamber, a second Glan-Taylor prism, a convex lens and a photodetector, which are connected in sequence. The third polarization beam splitter is connected to a wavelength meter. The third polarization beam splitter and the wavelength meter are used to determine the wavelength of the detection light for detection of different alkali metal atoms.

[0022] Step 1 includes the following expressions:

[0023]

[0024] in is the density of nitrogen quenching gas, P is the pressure of quenching gas, k B is the Boltzmann constant, and T is the temperature of the gas chamber.

[0025] The technical effects of the present invention are as follows: The present method for measuring the optimal quenching gas pressure in an alkali metal gas chamber based on the atomic fluorescence effect utilizes a method for heating and shielding the alkali metal gas chamber atoms in an ultra-high-sensitivity magnetic field measurement device based on atomic spins, pumping the alkali metal atoms with circularly polarized light to achieve a spin-exchange relaxation-free (SERF) state. The quenching gas absorbs photons spontaneously emitted by the alkali metal atoms, suppressing the frequency broadening caused by photon reabsorption. Simultaneously, the device output response corresponding to different gas chamber pressures is monitored to find the maximum output signal and determine the optimal quenching gas content. A decrease in fluorescence intensity indicates that the quenching gas has effectively absorbed photons. Collisions between the quenching gas and the alkali metal atoms induce spin-destructive relaxation, reducing the system's relaxation time, thereby lowering signal intensity and affecting the device's sensitivity. By determining the optimal quenching gas pressure, the present invention reduces spin-destructive collisional relaxation and increases the system's relaxation time, effectively improving the sensitivity and overall performance of the magnetic field measurement device.

[0026] The advantages of the present invention over the prior art are that the optimal quenching gas pressure of the alkali metal atom gas chamber can be confirmed by the fluorescence detection method, which can reduce the spin-destruction collision relaxation caused by excessive quenching gas in the gas chamber, improve the relaxation time of the system, and avoid insufficient quenching gas that affects the polarizability of the alkali metal atoms, thereby effectively improving the sensitivity and overall performance of the magnetic field measurement device. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a schematic structural diagram of an atomic magnetic field measurement and fluorescence detection device involved in the method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect.

[0028] Figure 2 It is a schematic flow chart of the method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect of the present invention. Figure 2 The method includes step 1, selecting an alkali metal atom gas cell with different quenching gas pressures (for example, 40 Torr, 45 Torr, 50 Torr, 55 Torr, and 60 Torr respectively); step 2, placing the alkali metal gas cell in an oven inside a shielded barrel and heating it to a SERF (Spin-Exchange Relaxation-Free) state; step 3, pumping the alkali metal atoms with a laser to polarize them; step 4, using a spectrometer to detect the wavelength and intensity of fluorescence emitted by the alkali metal atom gas cell; step 5, determining the magnitude of the magnetic field to be measured by detecting the change in the optical rotation angle of the light; step 6, judging whether the magnetic field measurement output response signal is a maximum value; if not, returning to step 1 to select the next alkali metal atom gas cell with a different quenching gas pressure; if so, proceeding to step 7 to determine the optimal quenching gas pressure of the alkali metal gas cell.

[0029] Figure 3 This is a schematic diagram of the fluorescence spectrum emitted by a potassium-rubidium mixed alkali metal gas cell at 180°C. Figure 3 The horizontal axis is wavelength (nm, scale value is 400, 410,..., 430), and the vertical axis is relative intensity (dimensionless, scale value is 0, 5000,..., 30000). Figure 3 The two peaks are at wavelengths of 414.98nm and 423.22nm respectively.

[0030] Attachment Figure 1 The markings are as follows: 1-pump laser; 2-first reflector; 3-first half-wave plate; 4-first polarization beam splitter; 5-first lens beam expander; 6-first aperture; 7-second half-wave plate; 8-second polarization beam splitter; 9-second reflector; 10-first quarter-wave plate; 11-shielding barrel; 12-oven; 13-alkali metal gas chamber; 14-three-axis magnetic compensation coil; 15-insulation layer; 16-detection laser; 17-third reflector Mirror; 18-third half-wave plate; 19-third polarization beam splitter prism; 20-wavemeter; 21-second lens beam expander system; 22-second aperture; 23-fourth half-wave plate; 24-fourth polarization beam splitter prism; 25-first Glan-Taylor prism; 26-photoelastic modulator; 27-second quarter-wave plate; 28-second Glan-Taylor prism; 29-convex lens; 30-photodetector; 31-integrating sphere; 32-multimode optical fiber; 33-fluorescence spectrometer. DETAILED DESCRIPTION

[0031] Below is the attached figure ( Figure 1-Figure 3) and Examples illustrate the present invention.

[0032] Figure 1 The present invention is a schematic structural diagram of an atomic magnetic field measurement and fluorescence detection device involved in the method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect. Figure 2 It is a schematic flow chart of the method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect of the present invention. Figure 3 This is a schematic diagram of the fluorescence spectrum emitted by a potassium-rubidium mixed alkali metal gas cell at 180°C. Figure 3 The fluorescence spectrum of the potassium-rubidium mixed gas chamber (density ratio K:Rb=1:59.17, broadening of 40.98 Hz, helium pressure of 400 Torr, nitrogen pressure of 50 Torr) emitted at 180 ° C was excited by a laser with a wavelength of 770 nm. Two obvious peaks can be obtained at wavelengths of 414.98 nm and 423.22 nm. Figures 1 to 3 As shown, a method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect includes the following steps: step 1, preparing a series of alkali metal atom gas chambers with different quenching gas pressures; step 2, selecting an alkali metal atom gas chamber in step 1, placing it in an atomic magnetic field measurement and fluorescence detection device, and starting the atomic magnetic field measurement and fluorescence detection device to allow the atoms in the alkali metal atom gas chamber to reach a SERF state; step 3, pumping the alkali metal atoms with a laser to polarize them; step 4, using a spectrometer to detect the wavelength and intensity of fluorescence emitted by the alkali metal atom gas chamber; step 5, determining the size of the magnetic field to be measured by detecting the change in the optical rotation angle of light; step 6, judging whether the magnetic field measurement output response signal is a maximum value; if not, returning to step 1 to select the next alkali metal atom gas chamber with a different quenching gas pressure; if yes, proceeding to step 7; step 7, determining the optimal quenching gas pressure of the alkali metal gas chamber.

[0033] The optimal quenching gas pressure of the alkali metal gas chamber determined in step 7 can avoid increasing spin-destruction collision relaxation due to excessive quenching gas, and at the same time avoid reducing the polarizability of the alkali metal atoms due to insufficient quenching gas. The alkali metal atoms in the alkali metal atom gas chamber in step 1 are pure potassium, pure rubidium, or potassium-rubidium mixed atoms, and the alkali metal atom gas chamber is filled with a buffer gas helium and a quenching gas nitrogen, wherein the pressures of the buffer gas and the quenching gas are determined when the gas chamber is filled. The quenching gas pressures of the first alkali metal atom gas chamber to the fifth alkali metal atom gas chamber are 40 Torr, 45 Torr, 50 Torr, 55 Torr, and 60 Torr, respectively, and the density of the alkali metal atoms in each alkali metal atom gas chamber remains consistent.

[0034] Step 4 includes: if an increase in fluorescence intensity is detected, it indicates that the quenching gas is insufficient; if a decrease in fluorescence intensity is detected, it indicates that the quenching gas has effectively absorbed photons. The quenching gas absorbs photons released by spontaneous radiation transitions of alkali metal atoms to avoid the photons being reabsorbed by the alkali metal atoms and reducing the pumping efficiency, thereby avoiding reducing the intensity of the magnetic field measurement output response signal; if no fluorescence intensity is detected, it indicates that there is an excess of quenching gas, which will increase spin-destructive collision relaxation and reduce the sensitivity of the magnetic field measurement device.

[0035] Include the following expressions:

[0036] ,

[0037] in is the spin-destruction collisional relaxation between the alkali metal atoms and the quenching gas nitrogen, is the density of quenching gas nitrogen, is the effective collision cross-sectional area of quenching gas nitrogen, is the relative thermal motion rate of the quenching gas nitrogen.

[0038] The atomic magnetic field measurement and fluorescence detection device includes a pumping laser 1, a first reflector 2, a first half-wave plate 3, a first polarization beam splitter prism 4, a first lens beam expansion system 5, a first aperture 6, a second half-wave plate 7, a second polarization beam splitter prism 8, a second reflector 9, a first quarter-wave plate 10, an alkali metal gas chamber 13, an integrating sphere 31, a multimode optical fiber 32 and a fluorescence spectrometer 33 connected in sequence, the alkali metal gas chamber 13 is located in an oven 12, the oven 12 is located in a three-axis magnetic compensation coil 14, the three-axis magnetic compensation coil 14 is located in an insulation layer 15, and the insulation layer 15 is located in a shielding barrel 11. The atomic magnetic field measurement and fluorescence detection device includes a detection laser 16, a third reflector 17, a third half-wave plate 18, a third polarization beam splitter prism 19, a second lens beam expansion system 21, a second aperture 22, a fourth half-wave plate 23, a fourth polarization beam splitter prism 24, a first Glan-Taylor prism 25, a photoelastic modulator 26, a second quarter-wave plate 27, an alkali metal gas chamber 13, a second Glan-Taylor prism 28, a convex lens 29 and a photodetector 30, which are connected in sequence. The third polarization beam splitter prism 19 is connected to a wavelength meter 20. The third polarization beam splitter prism 19 and the wavelength meter 20 are used to determine the wavelength of the detection light for detection of different alkali metal atoms.

[0039] Step 1 includes the following expressions:

[0040]

[0041] in is the density of quenching gas nitrogen, P is the quenching gas pressure, kB is the Boltzmann constant, and T is the temperature of the gas chamber.

[0042] This invention discloses a method for measuring the optimal quenching gas pressure in an alkali metal gas chamber based on the atomic fluorescence effect. This method heats and shields the alkali metal gas chamber atoms in an ultra-high-sensitivity magnetic field measurement device based on atomic spins, pumping the alkali metal atoms with circularly polarized light to achieve a spin-exchange relaxation-free (SERF) state. The quenching gas absorbs photons spontaneously emitted by the alkali metal atoms, suppressing the frequency broadening caused by photon reabsorption. Simultaneously, the device output response corresponding to gas chambers at different pressures is monitored to find the maximum output signal and determine the optimal quenching gas content. A decrease in fluorescence intensity indicates that the quenching gas has effectively absorbed photons. Collisions between the quenching gas and the alkali metal atoms cause spin-destructive relaxation, reducing the system's relaxation time, thereby lowering signal intensity and affecting the device's sensitivity. By determining the optimal quenching gas pressure, the present invention reduces spin-destructive collision relaxation, increases the system's relaxation time, and effectively improves the sensitivity and overall performance of the magnetic field measurement device.

[0043] This invention addresses the shortcomings of the prior art and proposes a method for measuring the optimal quenching gas pressure in an alkali metal chamber based on the atomic fluorescence effect. After pumping light excites alkali metal atoms, they release photons through spontaneous radiation and return to their ground state. The quenching gas within the chamber absorbs the released photons. The fluorescence intensity emitted by the alkali metal atoms is measured by placing an integrating sphere outside the oven and connecting it to a spectrometer via a multimode optical fiber. By measuring the fluorescence intensity and the device output response corresponding to different pressure chambers, the maximum output signal is found, determining the optimal quenching gas content. A decrease in fluorescence intensity indicates that the quenching gas has effectively absorbed photons. This invention can effectively increase the polarizability of alkali metal atoms while avoiding increased spin-destruction collision relaxation, effectively improving the sensitivity and overall performance of magnetic field measurement devices.

[0044] refer to Figure 1 As shown, a method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect is provided. After the alkali metal atoms are excited by the pumping laser, the atoms release photons through spontaneous radiation to return to the ground state. The quenching gas in the gas chamber absorbs the photons released by the atoms. The fluorescence intensity released by the alkali metal atoms is obtained by placing an integrating sphere outside the alkali metal gas chamber oven and connecting it to a spectrometer through a multimode optical fiber. When the quenching gas is excessive, no fluorescence will appear, which will increase the destructive relaxation of the system. By detecting the output response of the device corresponding to gas chambers with different pressures, the maximum output signal is found, and the optimal content of the quenching gas is determined to avoid increasing the spin-destructive collision relaxation of the device and avoiding insufficient quenching gas that causes the polarizability of the alkali metal atoms to decrease.

[0045] The pumping system of the atomic magnetic field measurement device is that the light of the pump laser 1 passes through the first half-wave plate 3, the first polarization beam splitter prism 4, the first lens beam expansion system 5 and the first aperture 6 in sequence to obtain pumping light with appropriate power and spot size, and then passes through the second half-wave plate 7, the second polarization beam splitter prism 8 and the first quarter-wave plate 10 in sequence to convert it into circularly polarized light, which is incident on the z-axis to excite alkali metal atoms.

[0046] The alkali metal gas chamber 13 can be pure potassium, pure rubidium, or a potassium-rubidium mixture, and is filled with a buffer gas (such as helium) and a quenching gas (such as nitrogen). The gas chamber is heated in an oven 12, which is located within a triaxial magnetic compensation coil 14, which is located within a shielding barrel 11, to ensure that the atoms meet the conditions for the SERF state.

[0047] The role of the quenching gas is that excited alkali metal atoms will transition to the ground state by radiating photons. If the photons are reabsorbed by the atoms, it will reduce pumping efficiency, affect signal intensity, and cause frequency broadening. Therefore, the quenching gas is added to absorb the photons released by the radiative transition.

[0048] The device of the fluorescence detection system is to place an integrating sphere 31 at the exit of the insulation layer 15 of the oven 12 to collect the fluorescence emitted by the gas chamber. The integrating sphere 31 is connected to the spectrometer 33 through a multimode optical fiber 32 to obtain a fluorescence intensity signal. When the quenching gas is insufficient, the fluorescence released by the alkali metal atoms will be detected.

[0049] The detection system of the atomic magnetic field measurement device comprises a detection laser 16, which is amplified through a third half-wave plate 18, a third polarization beam splitter prism 19, a second lens beam expander system 21, and a second aperture 22. The linearly polarized light then passes through a fourth half-wave plate 23, a fourth polarization beam splitter prism 24, a first Glan-Taylor prism (polarizer) 25, a photoelastic modulator 26, and a second quarter-wave plate 27. The resulting linearly polarized light interacts with the alkali metal atoms at x-axis incidence. Changes in the optical rotation angle are detected using a second Glan-Taylor prism (analyzer) 28, a convex lens 29, and a photodetector 30. The wavelength of the detection light is determined using the third polarization beam splitter prism 19 and a wavelength meter 20.

[0050] refer to Figure 2As shown, we selected quenching gas chambers with pressures of 40 Torr, 45 Torr, 50 Torr, 55 Torr, and 60 Torr, respectively, and with the same alkali metal atom density. The chambers were then heated in an oven within a shielded barrel to ensure that the alkali metal atoms met the SERF state conditions. Laser pumping polarized the alkali metal atoms, and a spectrometer was used to measure the wavelength and intensity of the fluorescence emitted by the alkali metal chambers. The output response signal of the magnetic field measurement device was recorded by detecting changes in the optical rotation angle of the light. When the device's response signal reached its maximum value, the corresponding quenching gas pressure within the alkali metal chamber was the optimal gas pressure.

[0051] A method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect involves placing the alkali metal atom gas chamber in the oven of an atomic magnetic field measurement device for heating and then placing it within a shielded device. A beam of circularly polarized light is used to pump the chamber, causing the alkali metal atoms to reach a SERF state. To increase the polarizability of the alkali metal, a quenching gas is introduced into the chamber to absorb photons spontaneously emitted by the alkali metal atoms. By detecting the device output response corresponding to gas chambers at different pressures, the maximum output signal is found, and the optimal quenching gas content is determined. A decrease in fluorescence intensity indicates that the quenching gas has effectively absorbed photons. However, collisions between the quenching gas and the alkali metal atoms can cause spin-destructive relaxation, reducing the system's relaxation time, thereby reducing signal intensity and affecting the device's sensitivity. Finally, linearly polarized light is used to interact with the atoms after passing through the chamber, and the magnetic field is measured based on changes in the optical rotation angle. By determining the optimal quenching gas pressure, the present invention reduces spin-destructive collision relaxation, increases the system's relaxation time, and effectively improves the sensitivity and overall performance of the magnetic field measurement device.

[0052] The fluorescence detection system is designed to place an integrating sphere at the outlet of the oven's outer insulation layer to collect fluorescence emitted from the gas chamber. The fluorescence signal obtained by connecting it to a spectrometer via a multimode optical fiber can reflect the wavelength and intensity of the fluorescence. The wavelength is related to the type of alkali metal atom. When the quenching gas is insufficient, the fluorescence released by the alkali metal atoms will be detected. When the quenching gas is excessive, no fluorescence will appear, which will increase the destructive relaxation of the system. The relationship between spin destructive relaxation and quenching gas is expressed as follows:

[0053] ,

[0054] in, is the spin destruction relaxation between alkali metal atoms, is the spin destruction relaxation of alkali metal atoms and buffer gas (helium), is the spin destruction relaxation of the alkali metal atoms and the quenching gas (nitrogen), which is related to the density of the quenching gas and can be expressed as

[0055] ,

[0056] in is the density of the quenching gas, is the effective collision cross-sectional area, is the relative thermal motion rate. According to the ideal gas equation, the relationship between the density and pressure of the quenching gas can be obtained.

[0057] ,

[0058] Where P is the pressure of the quenching gas, k B =1.38×10 -23 J / K is the Boltzmann constant, and T is the temperature of the gas chamber. By measuring the gas chambers with different alkali metal atom quenching gas pressures, the gas chamber with the highest output response is determined. The corresponding pressure is the optimal quenching gas pressure for the device.

[0059] Any content not described in detail in this specification is prior art known to those skilled in the art. It should be noted that the above description is intended to help those skilled in the art understand the present invention, but does not limit the scope of protection of the present invention. Any equivalent substitution, modification, improvement, and / or simplification of the above description that does not depart from the essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect, characterized in that: The following steps are involved: Step 1, preparing a series of alkali metal atom gas cells with different quenching gas pressures; Step 2, selecting an alkali metal atom gas cell in step 1, placing it in an atomic magnetic field measurement and fluorescence detection device, and starting the atomic magnetic field measurement and fluorescence detection device to allow the atoms in the alkali metal atom gas cell to reach a SERF state; Step 3, using laser to pump the alkali metal atoms to polarize them; Step 4, using a spectrometer to detect the wavelength and intensity of fluorescence emitted by the alkali metal atom gas chamber; Step 5, determining the magnitude of the magnetic field to be measured by detecting the change in the optical rotation angle of the light; Step 6, determining whether the magnetic field measurement output response signal is a maximum value; if not, returning to step 1 to select the next alkali metal atom gas chamber with a different quenching gas pressure; if yes, proceeding to step 7; Step 7, determining the optimal quenching gas pressure of the alkali metal gas chamber; The atomic magnetic field measurement and fluorescence detection device includes a pump laser, a first reflector, a first half-wave plate, a first polarization beam splitter, a first lens beam expander system, a first aperture, a second half-wave plate, a second polarization beam splitter, a second reflector, a first quarter-wave plate, an alkali metal atom gas chamber, an integrating sphere, a multimode optical fiber, and a fluorescence spectrometer, which are connected in sequence. The alkali metal atom gas chamber is located in an oven, the oven is located in a three-axis magnetic compensation coil, the three-axis magnetic compensation coil is located in a thermal insulation layer, and the thermal insulation layer is located in a shielding barrel. In step 1, the alkali metal atoms in the alkali metal atom gas chamber are pure potassium, pure rubidium or potassium-rubidium mixed atoms, and the alkali metal atom gas chamber is filled with a buffer gas helium and a quenching gas nitrogen, wherein the pressures of the buffer gas and the quenching gas are determined when the gas chamber is filled, and the quenching gas pressures of the first alkali metal atom gas chamber to the fifth alkali metal atom gas chamber are 40 Torr, 45 Torr, 50 Torr, 55 Torr and 60 Torr, respectively, and the density of alkali metal atoms in each alkali metal atom gas chamber remains consistent.

2. The method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect according to claim 1, characterized in that: The optimal quenching gas pressure of the alkali metal gas chamber determined in step 7 can avoid increasing spin-destruction collision relaxation due to excessive quenching gas, while avoiding reducing the polarizability of the alkali metal atoms due to insufficient quenching gas.

3. The method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect according to claim 1, characterized in that: Step 4 includes: if an increase in fluorescence intensity is detected, it indicates that the quenching gas is insufficient; if a decrease in fluorescence intensity is detected, it indicates that the quenching gas has effectively absorbed photons. The quenching gas absorbs photons released by spontaneous radiation transitions of alkali metal atoms to avoid the photons being reabsorbed by the alkali metal atoms and reducing the pumping efficiency, thereby avoiding reducing the intensity of the magnetic field measurement output response signal; if no fluorescence intensity is detected, it indicates that there is an excess of quenching gas, which will increase spin-destructive collision relaxation and reduce the sensitivity of the magnetic field measurement device.

4. The method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect according to claim 3, characterized in that: Include the following expressions: , in is the spin-destruction collisional relaxation between the alkali metal atoms and the quenching gas nitrogen, is the density of quenching gas nitrogen, is the effective collision cross-sectional area of quenching gas nitrogen, is the relative thermal motion rate of the quenching gas nitrogen.

5. The method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect according to claim 1, characterized in that: The atomic magnetic field measurement and fluorescence detection device includes a detection laser, a third reflector, a third half-wave plate, a third polarization beam splitter, a second lens expansion system, a second aperture, a fourth half-wave plate, a fourth polarization beam splitter, a first Glan-Taylor prism, a photoelastic modulator, a second quarter-wave plate, an alkali metal gas chamber, a second Glan-Taylor prism, a convex lens and a photodetector, which are connected in sequence. The third polarization beam splitter is connected to a wavelength meter. The third polarization beam splitter and the wavelength meter are used to determine the wavelength of the detection light for detection of different alkali metal atoms.

6. The method for measuring the optimal quenching gas pressure of an alkali metal gas chamber based on the atomic fluorescence effect according to claim 1, characterized in that: Step 1 includes the following expressions: , in is the density of quenching gas nitrogen, P is the quenching gas pressure, k B is the Boltzmann constant, and T is the temperature of the gas chamber.

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