Integrated compensation method for remanent magnetization and its gradient of dual-beam SERF atomic magnetometer

Abstract

The integrated compensation method for the remanent magnetization and its gradient of the dual-beam SERF atomic magnetometer can adjust and compensate the remanent magnetization and its gradient by observing the output signal on the atomic magnetometer. Compared with the previous method of only compensating for the three-axis remanent magnetization, it adds sequential compensation for the remanent magnetization gradient, reduces gradient relaxation, and solves the problem of introducing new remanent magnetization after compensating the remanent magnetization gradient. It can achieve comprehensive integrated compensation, is simple to operate, and is easy to implement further automated magnetic compensation.

Description

Technical Field

[0001] The invention belongs to the technical field of magnetic compensation of SERF atomic magnetometers, and particularly relates to a method for integrating residual magnetism and gradient of a dual-beam SERF atomic magnetometer. Background Art

[0002] Under conditions of high atomic density, efficient polarization, and near-zero magnetic field, the atomic spin exchange rate is far greater than the Larmor precession frequency, allowing the atomic magnetometer to operate in a spin-exchange-relaxation-free (SERF) state. SERF atomic magnetometers have been proven to be among the most sensitive magnetometers in the world, with the highest sensitivity achieved in a dual-beam configuration.

[0003] For a dual-beam SERF atomic magnetometer, the smaller the ambient remanent magnetic field, the lower the Larmor precession frequency of alkali metal atoms and the smaller their transverse relaxation rate. Furthermore, the smaller the gradient of the ambient remanent magnetic field, the lower the gradient relaxation rate of the atomic ensemble. To achieve this, shim coils are used to compensate for the remanent magnetization in three directions, and gradient coils are used to compensate for the remanent magnetization gradient in three directions. This further suppresses the atomic relaxation rate and improves the sensitivity of the magnetometer.

[0004] Currently, there are only separate residual magnetization compensation methods or separate residual magnetization gradient compensation methods for dual-beam SERF atomic magnetometers. There is a lack of an integrated compensation method, which has low compensation efficiency and cannot ensure that the residual magnetization and the residual magnetization gradient are compensated to zero at the same time. Summary of the Invention

[0005] The technical problem solved by the present invention is to overcome the shortcomings of the existing technology and propose an integrated compensation method for the remanence and its gradient of a dual-beam SERF atomic magnetometer. Through this method, the remanence and remanence gradient in three axes can be compensated to zero simultaneously, thereby suppressing the influence of the atomic relaxation rate on the electron spin, improving the compensation accuracy and efficiency, and thereby improving the sensitivity of the atomic magnetometer.

[0006] The technical solutions of the present invention are as follows:

[0007] A dual-beam SERF atomic magnetometer remanence and its gradient integrated compensation method is characterized in that it includes defining the pumping light of the atomic magnetometer to propagate along the z-axis direction and the detection light to propagate along the x-axis direction. After the remanence parameters are initialized, a sinusoidal modulated magnetic field B is applied on the z-axis and the x-axis respectively. cz sinωt and B cx sinωt,B cz and B cxAll represent amplitude, ω represents frequency, and t represents time. The x-axis and z-axis residual magnetism are compensated respectively to minimize the amplitude of the magnetometer output signal Vx. After the residual magnetism of the x-axis and z-axis reaches zero field, only the sinusoidal modulated magnetic field B is applied to the y-axis. cy sinωt,B cy Represents the amplitude, compensates for the residual magnetism in the y direction, and makes the zero bias value w of the magnetometer output signal Vx x is zero; under this condition, observe the output signal Vx amplitude when the modulated magnetic field is applied on the y-axis, and adjust the y-axis gradient coil voltage to maximize the signal Vx amplitude; if the output signal zero bias value w x If the Y-axis residual magnetism changes, it is necessary to continue to compensate for the zero bias value w x zero; adjust the x-axis gradient coil voltage to maximize the amplitude of signal Vx, turn off the y-axis modulation magnetic field, and apply the z-axis modulation magnetic field. If the amplitude of the output signal Vx increases at this time, it is necessary to continue to compensate for the x-axis residual magnetism; the z-axis residual magnetism gradient compensation method is similar to that of the x-axis; after completing the above operations, the residual magnetism and its gradient of each axis can be returned to zero.

[0008] The method for integrated compensation of residual magnetism and its gradient comprises the following steps:

[0009] Step (1), adjusting the atomic magnetometer to a working state, so that the pump light enters the gas chamber from the z-axis direction and the detection light enters the gas chamber from the x-axis direction, and adjusting the optical parameters of the dual-beam SERF atomic magnetometer, including the pump light power and the detection light wavelength, so that the scale factor of the magnetometer is maximized;

[0010] Step (2): In the absence of pump light and external magnetic field, balance the two photoelectric detectors used for differential detection of optical signals, turn on the pump light, and observe the magnetometer output signal V x The zero bias value w x , and adjust to achieve the residual magnetic field B x_res (0) 、B y_res (0) 、B z_res (0) Initialization;

[0011] Step (3):

[0012]

[0013] From the above formula, we can know that a modulated magnetic field B is applied on the z-axis. cz sinωt, adjust the voltage of the x-axis magnetic compensation shim coil until the magnetometer output signal V x The amplitude is the smallest, and the compensation magnetic field at this time is recorded as B x (n) , where n is the number of compensation iterations, n=1,2,3…, B czis the modulating magnetic field amplitude, R pump is the optical pumping efficiency of the pump light, B x_res 、B y_res , and B z_res Remanence B res Remanence on the x-axis, y-axis and z-axis, γ e is the electron gyromagnetic ratio, R rel is the total relaxation rate in addition to the optical pumping rate, ω is the angular frequency of the modulating magnetic field, t represents time, and c is the output voltage signal V x and polarizability P x Similarly, a modulated magnetic field is applied to the x-axis, and the voltage of the z-axis magnetic compensation shim coil is adjusted until the magnetometer outputs a signal V x The amplitude is the smallest, and the compensation magnetic field at this time is recorded as B z (n) ; Repeat step (3) until |B x (n) -B x (n-1) |<ε and |B z (n) -B z (n-1) |<ε, where ε is the minimum resolution of magnetic field compensation, indicating that the residual magnetism of the x-axis and z-axis are compensated to zero;

[0014] Step (4):

[0015]

[0016] From the above formula, we can know that when the remanent magnetization of x and z axes is supplemented to zero field, a modulated magnetic field B is applied on the y axis. cy sin(ωt), adjust the voltage of the y-axis magnetic compensation shim coil until the output signal V x The zero bias value w x is zero, that is, satisfying |w x |<ε, indicating that the residual magnetism of the y-axis is compensated to zero; then, on this basis, adjust the voltage of the y-axis magnetic compensation gradient coil until the magnetometer output signal V x The amplitude is the largest, which means that the y-axis residual magnetic gradient is compensated to zero; if |w x |>ε, it means that the center point of the gradient coil is not aligned with the center of the detection light, thus introducing a new y-axis residual magnetism. It is necessary to further adjust the y-axis magnetic compensation shim coil so that the output signal zero bias value satisfies |w x |<ε;

[0017] Step (5):

[0018]

[0019] From the above formula, it can be seen that when the x-, y-, and z-axis residual magnetism and the y-axis residual magnetism gradient are all compensated to zero field, a modulation magnetic field is still applied to the y-axis, and the voltage of the x-axis magnetic compensation gradient coil is adjusted until the magnetometer output signal V x The amplitude is the largest, which means that the x-axis residual magnetic gradient is compensated to zero, where is the remanent magnetization gradient, R d is the sum of spin destruction relaxation, relaxation induced by detection light, and bubble-wall collision relaxation, k gx 、k gy and k gz They are the x-, y-, and z-axis remanent magnetic gradients Then remove the y-axis modulation magnetic field and apply a modulation magnetic field on the z-axis. If the output signal V x The amplitude is greater than V when step (3) is completed x The amplitude of , it means that the center point of the gradient coil is not aligned with the center of the detection light, thus introducing a new x-axis residual magnetism. It is necessary to further adjust the x-axis magnetic compensation shim coil so that the output signal V x Minimum amplitude;

[0020] Step (6): When the x-axis, y-axis, and z-axis residual magnetization and the x-axis and y-axis residual magnetization gradients are all compensated to zero field, a modulation magnetic field is applied only on the y-axis, and the voltage of the z-axis magnetic compensation gradient coil is adjusted until the magnetometer output signal V x The amplitude is the largest, which means that the z-axis residual magnetic gradient is compensated to zero; then remove the y-axis modulation magnetic field and apply a modulation magnetic field on the x-axis. If the output signal V x The amplitude is greater than V when step (3) is completed x The amplitude of , it means that the center point of the gradient coil is not aligned with the center of the detection light, thus introducing a new z-axis residual magnetism. It is necessary to further adjust the z-axis magnetic compensation shim coil so that the output signal V x Minimum amplitude;

[0021] After the above steps (1) to (6) are completed, the three-axis remanent magnetization and its gradient of the atomic magnetometer are compensated to zero.

[0022] The initialization in step (2) includes the following steps:

[0023] Step (2.1) adjusts the magnetic field in the y direction so that the output signal V x The zero bias w x Increase positively until w is satisfied x >0, that is, B is also satisfied y_res (0) >0;

[0024] Step (2.2) positively adjusts the magnetic field in the x direction: If wx continues to decrease, it means that B x_res(0) and B z_res (0) The sign is opposite, and the magnetic field in the x direction needs to be adjusted in the opposite direction; if wx continues to increase, it means that B x_res (0) and B z_res (0) The signs of are the same, which means that the requirements are met.

[0025] The dual-beam SERF atomic magnetometer includes a pumping laser system, a detection system, a magnetic shielding system composed of Permalloy and ferrite, a three-axis magnetic compensation shim coil, a three-axis magnetic compensation gradient coil, a non-magnetic electric heating system, and an atomic gas cell. Adjusting the atomic magnetometer to a working state involves placing the gas cell inside the magnetic shielding system to place it in a weak magnetic environment, and heating the gas cell containing alkali metal atoms, a quenching gas, and a buffer gas to an operating temperature using the non-magnetic electric heating system. The pumping light is circularly polarized light with a frequency locked to the D1 line of the alkali metal atom, and is incident on the gas cell along the z-axis direction to polarize the alkali metal atoms. The detection light is detuned linearly polarized light, and is incident on the gas cell along the x-axis direction. The laser light exiting the gas cell is subjected to a balanced polarization beam splitting method to measure a magneto-optical rotation angle signal on a photodetector, and the signal is then converted and amplified by a photoelectric amplifier.

[0026] The method for integrated compensation of residual magnetism and its gradient comprises the following steps:

[0027] Step 1, start parameter initialization of the residual magnetic field compensation process;

[0028] Step 2, n = 1, n is the number of iterations, and a sinusoidal AC magnetic field B is applied only in the Z direction cz sinωt, use the shim coil to compensate the DC residual magnetism in the X direction until the Vx amplitude is minimum, and record the compensation value at this time as B x (n) ;

[0029] Step 3: Apply a sinusoidal AC magnetic field B only in the X direction. cx sinωt, use the shim coil to compensate the DC residual magnetism in the Z direction until the Vx amplitude is minimum, and record the compensation value at this time as B z (n) ;

[0030] Step 4, B x (n) =B x (n-1) and B z (n) =B z (n-1) Are both true? If not, set n = n + 1 and return to step 2. If yes, go to step 5.

[0031] Step 5: Apply a sinusoidal AC magnetic field B only in the Y direction. cy sinωt, use the shim coil to compensate for the DC residual magnetism in the Y direction until the output signal is biased to w x is zero;

[0032] Step 6: Use the gradient coil to compensate for the gradient residual magnetism in the Y direction until the Vx amplitude is maximum;

[0033] Step 7: Is there a newly introduced DC magnetic field By? If yes, return to step 5; if no, go to step 8;

[0034] Step 8: Use the gradient coil to compensate for the gradient residual magnetization in the X direction until the Vx amplitude is maximum.

[0035] Step 9: Is there a newly introduced DC magnetic field Bx? If yes, return to step 2; if no, proceed to step 10.

[0036] Step 10, using the gradient coil to compensate for the gradient residual magnetization in the Z direction until the Vx amplitude is maximum;

[0037] Step 11: Is there a newly introduced DC magnetic field Bz? If yes, return to step 2; if no, proceed to step 12;

[0038] Step 12: End the integrated compensation of residual magnetism and its gradient, and both the DC and gradient residual magnetism are compensated to zero.

[0039] The dual-beam SERF atomic magnetometer includes a pumping optical path system, a detection light incident optical path system, a detection light exit detection optical path system and an atomic gas chamber. The pumping optical path system includes a pumping laser, a first half-wave plate, a first polarization beam splitter prism, a first reflector, a beam expansion and shaping combination, and a quarter-wave plate connected in sequence. The pumping light emitted from the quarter-wave plate passes through the atomic gas chamber; the detection light incident optical path system includes a detection laser, a second half-wave plate, a second polarization beam splitter prism, a second reflector, and a Glan-Taylor prism connected in sequence. The detection light emitted from the Glan-Taylor prism passes through the atomic gas chamber and then enters the atomic gas chamber. The detection light emits a third half-wave plate in the detection light path system, the third half-wave plate is connected to a third polarization beam splitter prism, the transmitted light of the third polarization beam splitter prism is input to the first channel of the dual-channel photodetector, the reflected light of the third polarization beam splitter prism is input to the second channel of the dual-channel photodetector through the third reflector, and the dual-channel photodetector is connected to the data acquisition system through a photoelectric amplifier; a non-magnetic electric heating system, a magnetic compensation coil system and a magnetic shielding system are sequentially arranged around the outer periphery of the atomic gas chamber, the magnetic compensation coil system includes a Z-direction shim coil, a Y-direction shim coil, an X-direction shim coil, a Z-direction dB z / dz gradient coil, dB in Y direction y / dy gradient coil, and dB in the X direction x / dx gradient coil, the magnetic shielding system includes a ferrite magnetic shielding barrel and a permalloy magnetic shielding barrel.

[0040] The technical effects of the present invention are as follows: the integrated compensation method for the remanence and gradient of a dual-beam SERF atomic magnetometer can adjust and compensate the remanence and gradient by observing the output signal on the atomic magnetometer. Compared with the previous method of only compensating for three-axis remanence, the method increases the sequential compensation of the remanence gradient, reduces gradient relaxation, and solves the problem of introducing new remanence after compensating the remanence gradient. It can achieve comprehensive and integrated compensation, is simple to operate, and is easy to implement further automated magnetic compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 The present invention is a schematic flow chart of a method for implementing the remanence and gradient integrated compensation method of a dual-beam SERF atomic magnetometer. Figure 1 The process includes step 1, parameter initialization of the residual magnetic field compensation process; step 2, n = 1, n is the number of iterations, and a sinusoidal AC magnetic field B is applied only in the Z direction (z-axis direction, i.e., the pumping light direction). cz sinωt,B cz The shim coil is used to compensate the DC residual magnetism in the X direction (the x-axis direction is the detection light direction) until the Vx amplitude is minimum. Vx represents the output voltage signal, and the compensation value at this time is recorded as B. x (n) ; Step 3, apply a sinusoidal AC magnetic field B only in the X direction cx sinωt,B cx Indicates the amplitude. Use the shim coil to compensate the DC residual magnetism in the Z direction until the Vx amplitude is minimum, and record the compensation value at this time as B z (n) ; Step 4, B x (n) =B x (n-1) and B z (n) =B z (n-1) Are both true? If not, set n = n + 1 and return to step 2. If yes, proceed to step 5. In step 5, apply a sinusoidal AC magnetic field B only in the Y direction. cy sinωt,B cy Indicates the amplitude, and the DC residual magnetism in the Y direction is compensated by the shim coil until the output signal is biased to w xis zero; Step 6: Use the gradient coils to compensate for the gradient residual magnetization in the Y direction until the amplitude of Vx reaches its maximum; Step 7: Is there a newly introduced DC magnetic field By? If so, return to Step 5; if not, proceed to Step 8; Step 8: Use the gradient coils to compensate for the gradient residual magnetization in the X direction until the amplitude of Vx reaches its maximum; Step 9: Is there a newly introduced DC magnetic field Bx? If so, return to Step 2; if not, proceed to Step 10; Step 10: Use the gradient coils to compensate for the gradient residual magnetization in the Z direction until the amplitude of Vx reaches its maximum; Step 11: Is there a newly introduced DC magnetic field Bz? If so, return to Step 2; if not, proceed to Step 12; Step 12: Compensate both the DC and gradient residual magnetization to zero (ending the integrated compensation of residual magnetization and its gradient).

[0042] Figure 2 The present invention is a schematic diagram of the system structure of a dual-beam SERF atomic magnetometer remanence and gradient integrated compensation method.

[0043] The reference numerals are listed as follows: 1-pumping optical path system; 11-pumping laser; 12-first half-wave plate; 13-first polarization beam splitter prism; 14-first reflector; 15-beam expansion and shaping combination; 16-1 / 4 wave plate; 2-detection light incident optical path system; 21-detection laser; 22-second half-wave plate; 23-second polarization beam splitter prism; 24-second reflector; 25-Glan-Taylor prism; 3-detection light output detection optical path system; 31-third half-wave plate; 32-third polarization beam splitter prism; 33-third reflector; 34-dual-channel photodetector; 4-photoelectric amplifier; 5-data acquisition system; 6-Permalloy magnetic shielding barrel; 7-ferrite magnetic shielding barrel; 8-atomic gas chamber; 91-Z direction shim coil; 92-Y direction shim coil; 93-X direction shim coil; 94-Z direction dB z / dz gradient coil; 95-dB in the Y direction y / dy gradient coil; 96-dB in the X direction x / dx gradient coil; 10-non-magnetic electric heating system. DETAILED DESCRIPTION

[0044] Below is the attached figure ( Figure 1-Figure 2 ) and Examples illustrate the present invention.

[0045] Figure 1 The present invention is a schematic flow chart of a method for implementing the remanence and gradient integrated compensation method of a dual-beam SERF atomic magnetometer. Figure 2 This is a schematic diagram of the system structure of the dual-beam SERF atomic magnetometer remanence and its gradient integrated compensation method implemented in the present invention. Figures 1 to 2As shown in the figure, the dual-beam SERF atomic magnetometer remanence and its gradient integrated compensation method includes defining the pumping light of the atomic magnetometer to propagate along the z-axis direction and the detection light to propagate along the x-axis direction. After the remanence parameters are initialized, a sinusoidal modulated magnetic field B is applied on the z-axis and x-axis respectively. cz sinωt and B cx sinωt,B cz and B cx All represent amplitude, ω represents frequency, and t represents time. The x-axis and z-axis residual magnetism are compensated respectively to minimize the amplitude of the magnetometer output signal Vx. After the residual magnetism of the x-axis and z-axis reaches zero field, only the sinusoidal modulated magnetic field B is applied to the y-axis. cy sinωt,B cy Represents the amplitude, compensates for the residual magnetism in the y direction, and makes the zero bias value w of the magnetometer output signal Vx x is zero; under this condition, observe the output signal Vx amplitude when the modulated magnetic field is applied on the y-axis, and adjust the y-axis gradient coil voltage to maximize the signal Vx amplitude; if the output signal zero bias value w x If the Y-axis residual magnetism changes, it is necessary to continue to compensate for the zero bias value w x zero; adjust the x-axis gradient coil voltage to maximize the amplitude of signal Vx, turn off the y-axis modulation magnetic field, and apply the z-axis modulation magnetic field. If the amplitude of the output signal Vx increases at this time, it is necessary to continue to compensate for the x-axis residual magnetism; the z-axis residual magnetism gradient compensation method is similar to that of the x-axis; after completing the above operations, the residual magnetism and its gradient of each axis can be returned to zero.

[0046] The residual magnetism and its gradient integrated compensation method comprises the following steps: Step 1, initializing the parameters of the residual magnetic field compensation process; Step 2, n=1, n is the number of iterations, applying a sinusoidal AC magnetic field B only in the Z direction cz sinωt, use the shim coil to compensate the DC residual magnetism in the X direction until the Vx amplitude is minimum, and record the compensation value at this time as B x (n) ; Step 3, apply a sinusoidal AC magnetic field B only in the X direction cx sinωt, use the shim coil to compensate the DC residual magnetism in the Z direction until the Vx amplitude is minimum, and record the compensation value at this time as B z (n) ; Step 4, B x (n) =B x (n-1) and B z (n) =B z (n-1) Are both true? If not, set n = n + 1 and return to step 2. If yes, proceed to step 5. In step 5, apply a sinusoidal AC magnetic field B only in the Y direction. cysinωt, use the shim coil to compensate for the DC residual magnetism in the Y direction until the output signal is biased to w x is zero; Step 6: Use the gradient coils to compensate for the gradient residual magnetization in the Y direction until the amplitude of Vx is maximum; Step 7: Is there a newly introduced DC magnetic field By? If yes, return to Step 5; if no, proceed to Step 8; Step 8: Use the gradient coils to compensate for the gradient residual magnetization in the X direction until the amplitude of Vx is maximum; Step 9: Is there a newly introduced DC magnetic field Bx? If yes, return to Step 2; if no, proceed to Step 10; Step 10: Use the gradient coils to compensate for the gradient residual magnetization in the Z direction until the amplitude of Vx is maximum; Step 11: Is there a newly introduced DC magnetic field Bz? If yes, return to Step 2; if no, proceed to Step 12; Step 12: End the integrated compensation of residual magnetization and its gradient, and both DC and gradient residual magnetization are compensated to zero.

[0047] The dual-beam SERF atomic magnetometer includes a pumping optical path system 1, a detection light incident optical path system 2, a detection light exit detection optical path system 3 and an atomic gas chamber 8, wherein the pumping optical path system 1 includes a pumping laser 11, a first half-wave plate 12, a first polarization beam splitter prism 13, a first reflector 14, a beam expansion and shaping assembly 15, and a quarter wave plate 16 connected in sequence, and the pumping light emitted from the quarter wave plate 16 passes through the atomic gas chamber 8; the detection light incident optical path system 2 includes a detection laser 21, a second half-wave plate 22, a second polarization beam splitter prism 23, a second reflector 24, and a Glan Taylor prism 25 connected in sequence, and the detection light emitted from the Glan Taylor prism 25 passes through the atomic gas chamber 8 and enters the atomic gas chamber 8. The detection light emits the third half-wave plate 31 in the detection light path system 3, the third half-wave plate 31 is connected to the third polarization beam splitter prism 32, the transmitted light of the third polarization beam splitter prism 32 is input to the first channel of the dual-channel photodetector 34, the reflected light of the third polarization beam splitter prism 32 is input to the second channel of the dual-channel photodetector 34 through the third reflector 33, and the dual-channel photodetector 34 is connected to the data acquisition system 5 through the photoelectric amplifier 4; the non-magnetic electric heating system 10, the magnetic compensation coil system and the magnetic shielding system are sequentially arranged around the periphery of the atomic gas chamber 8, the magnetic compensation coil system includes a Z-direction shim coil 91, a Y-direction shim coil 92, an X-direction shim coil 93, a Z-direction dB z / dz gradient coil 94, dB in Y direction y / dy gradient coil 95, and dB in the X direction x / dx gradient coil 96, the magnetic shielding system includes a ferrite magnetic shielding barrel 7 and a permalloy magnetic shielding barrel 6.

[0048] The principle of the present invention is: under the condition that the SERF atomic magnetometer works stably, according to the Bloch equation It can be seen that the polarization rate P detected by the x-axis detection light in steady state is x The signal is:

[0049]

[0050] Among them, P x 、P y 、P z are the polarizability signals along the x, y, and z directions, respectively. They are P x 、P y 、P z The differential representation of represents the unit vector along the z direction, R pump is the optical pumping rate of the pump light, γ e is the electron gyromagnetic ratio, R rel is the total relaxation rate in addition to the optical pumping rate, Q is the slowdown factor, is an intermediate variable B x 、B y 、B z are the magnetic fields in the x, y, and z directions that the gas chamber is sensitive to. Therefore, the existence of residual magnetism can be reflected by the detection light signal. rel =R d +R gr ,and where R d is the sum of spin destruction relaxation, relaxation induced by detection light, and bubble-wall collision relaxation, R gr is the gradient relaxation, k gx 、k gy and k gz They are x, y, and z gradient magnetic fields respectively Therefore, the detection of optical signals can also reflect the existence of residual magnetic gradient.

[0051] Under the condition of no pump light and external magnetic field, balance the two photodetectors used for differential detection of optical signals, turn on the pump light, and observe the output signal V of the magnetometer. x The zero bias value w x , and adjust to achieve the residual magnetic field B x_res (0) 、B y_res (0) 、B z_res (0) Initialization.

[0052] Based on B x_res (0) 、B y_res (0) and B z_res (0), perform the following operations to achieve remanence B res =[B x_res ,B y_res ,B z_res ] and remanent magnetization gradient All tend to zero.

[0053] First, the residual magnetic field in the x and z directions is compensated. An amplitude of B is applied in the z direction. cz The sinusoidal modulated magnetic field Bczsinωt, we find

[0054]

[0055] Where ω is the angular frequency of the modulated magnetic field, t represents time, and c is the output voltage signal V x and polarizability P x The ratio of V x =c*P x .

[0056] For the magnetic field in the x direction, we derive the following formula from the above formula:

[0057]

[0058] Can get When established, then

[0059] Because B x_res (0) and B z_res (0) have the same sign, so when B x_res When V approaches zero, x Take the minimum value. By adjusting the compensation magnetic field bias B x , which will make the output voltage waveform V x The minimum value is recorded as B x (1) , then the remanent magnetism in the x direction is recorded as B x_res (1) Then, an amplitude of B is applied in the x direction. cx The sinusoidal modulated magnetic field B cx sinωt, we can similarly get the output signal V x About B z_res The derivative of is expressed as:

[0060]

[0061] It can be seen that when B x_res When V approaches zero, x Take the minimum value. By adjusting the compensation magnetic field B z , which will make the output signal Vx The minimum value is recorded as B z (1) , then the remanent magnetism in the z direction is recorded as B z_res (1) Similarly, by applying a modulated magnetic field in the z direction and the x direction respectively, the compensation is made so that B x_res and B z_res Minimize, and the compensation value is updated to B z (n) and B x (n) , until |B z (n) -B z (n-1) |<ε and |B x (n) -B x (n-1) |<ε. Here, n is the number of iterations and ε is the minimum resolution of magnetic field adjustment. At this point, we consider that the residual magnetization in the x and z directions has been reset to zero.

[0062] Secondly, the residual magnetization and its gradient in the y direction are compensated. The modulated magnetic field B is applied only in the y direction. cy sinωt, we get:

[0063]

[0064] It can be seen that the output signal V x The zero bias w x It can characterize the remanence in the y direction. x When |<ε, it means that the residual magnetism in the y direction has been compensated to zero. On this basis, the following formula is used:

[0065]

[0066] It can be seen that when the remanent magnetic gradient When compensated to zero, the output signal V x The amplitude is the largest.

[0067] However, in actual operation, it is difficult to ensure that the zero point of the gradient magnetic field generated by the gradient coil for compensation is located at the center of the gas chamber, so a bias residual magnetism will be introduced again in the y direction. x |>ε, it is necessary to adjust the DC compensation magnetic field in the y direction so that |w x |<ε.

[0068] Third, follow the flowchart Figure 1 As shown, the residual magnetization gradient in the x-direction, the newly introduced residual magnetization in the x-direction, the residual magnetization gradient in the z-direction and the newly introduced residual magnetization in the z-direction are compensated in sequence.

[0069] Finally, the in-situ integrated compensation of remanent magnetization and its gradient in the SERF atomic magnetometer was completed.

[0070] A dual-beam SERF atomic magnetometer remanence and its integrated gradient compensation method is described. The pumping light of the atomic magnetometer propagates along the z-axis, and the detection light propagates along the x-axis. After the remanence parameters are initialized, a sinusoidal modulated magnetic field is first applied to the z- and x-axes to compensate for the x- and z-axis remanence, respectively, minimizing the magnetometer output signal amplitude. After the remanence in the x- and z-axes reaches zero field, a sinusoidal modulated magnetic field is applied only to the y-axis to compensate for the y-direction remanence, bringing the zero bias of the magnetometer output signal to zero. Under these conditions, the output signal amplitude is observed when the modulated magnetic field is applied to the y-axis, and the y-axis gradient coil voltage is adjusted to maximize the signal amplitude. If the output signal zero bias changes at this point, further compensation for the y-axis remanence is required to return it to zero. The x-axis gradient coil voltage is then adjusted to maximize the signal amplitude, the y-axis modulation field is turned off, and the z-axis modulation field is applied. If the output signal amplitude increases, further compensation for the x-axis remanence is required. The z-axis remanence gradient compensation method is similar to that for the x-axis. After completing the above operations, the residual magnetism and gradient of each axis can be reset to zero.

[0071] Figure 1 The present invention shows the implementation steps of the dual-beam SERF atomic magnetometer remanence and its gradient integrated compensation method. The dual-beam SERF atomic magnetometer remanence and its gradient integrated compensation method implemented by the present invention includes the following steps:

[0072] Step (1) first adjust the atomic magnetometer to a working state, so that the pump light enters the gas chamber from the z-axis direction and the detection light enters the gas chamber from the x-axis direction, and adjust the optical parameters of the dual-beam SERF atomic magnetometer, such as the pump light power and the detection light wavelength, so that the scale factor of the magnetometer is maximized;

[0073] Step (2): In the absence of pump light and external magnetic field, balance the two photoelectric detectors used for differential detection of optical signals, turn on the pump light, and observe the magnetometer output signal V x The zero bias value w x , and adjust to achieve the three-axis residual magnetic field B x_res (0) 、B y_res (0) 、B z_res (0) The specific initialization steps are as follows: 1. Adjust and increase the magnetic field in the y direction so that the output signal V x The zero bias w x Increase positively until w is satisfied x >0, that is, B is also satisfied y_res (0)>0. 2. Positive adjustment increases the magnetic field in the x direction. If w x Continue to decrease, indicating that B x_res (0) and B z_res (0) The sign is opposite, and the magnetic field in the x direction needs to be adjusted in the opposite direction; if w x Continue to increase, indicating that B x_res (0) and B z_res (0) The signs are the same, which meets our needs.

[0074] Step (3): Apply a modulated magnetic field on the z-axis and adjust the voltage of the x-axis magnetic compensation shim coil until the magnetometer outputs a signal V x The amplitude is the smallest, and the compensation magnetic field at this time is recorded as B x (n) , where n is the number of compensation iterations (n ​​= 1, 2, 3 ...); Similarly, a modulated magnetic field is applied to the x-axis and the voltage of the z-axis magnetic compensation shim coil is adjusted until the magnetometer output signal V x The amplitude is the smallest, and the compensation magnetic field at this time is recorded as B z (n) Repeat step (3) until |B x (n) -B x (n-1) |<ε and |B z (n) -B z (n-1) |<ε, where ε is the minimum resolution of magnetic field compensation, indicating that the residual magnetism of the x-axis and z-axis are compensated to zero.

[0075] Step (4): When the residual magnetization of the x-axis and z-axis is compensated to zero field, a modulated magnetic field is applied to the y-axis, and the voltage of the y-axis magnetic compensation shim coil is adjusted until the output signal V x The zero bias value w x is zero, that is, satisfying |w x |<ε, indicating that the residual magnetism of the y-axis is compensated to zero; then, on this basis, adjust the voltage of the y-axis magnetic compensation gradient coil until the magnetometer output signal V x The amplitude is the largest, which means that the y-axis residual magnetic gradient is compensated to zero. x |>ε, it means that the center point of the gradient coil is not aligned with the center of the detection light, thus introducing a new y-axis residual magnetism. It is necessary to further adjust the y-axis magnetic compensation shim coil so that the output signal zero bias value satisfies |w x |<ε.

[0076] Step (5): When the x-, y-, and z-axis residual magnetization and the y-axis residual magnetization gradient are all compensated to zero field, a modulation magnetic field is still applied to the y-axis, and the voltage of the x-axis magnetic compensation gradient coil is adjusted until the magnetometer output signal V x The amplitude is the largest, which means that the x-axis residual magnetic gradient is compensated to zero; then the y-axis modulation magnetic field is removed and a modulation magnetic field is applied to the z-axis. If the output signal V x The amplitude is greater than V when step (3) is completed x The amplitude of , it means that the center point of the gradient coil is not aligned with the center of the detection light, thus introducing a new x-axis residual magnetism. It is necessary to further adjust the x-axis magnetic compensation shim coil so that the output signal V x Minimum amplitude.

[0077] Step (6): When the x-axis, y-axis, and z-axis residual magnetization and the x-axis and y-axis residual magnetization gradients are all compensated to zero field, a modulation magnetic field is applied only on the y-axis, and the voltage of the z-axis magnetic compensation gradient coil is adjusted until the magnetometer output signal V x The amplitude is the largest, which means that the z-axis residual magnetic gradient is compensated to zero; then remove the y-axis modulation magnetic field and apply a modulation magnetic field on the x-axis. If the output signal V x The amplitude is greater than V when step (3) is completed x The amplitude of , it means that the center point of the gradient coil is not aligned with the center of the detection light, thus introducing a new z-axis residual magnetism. It is necessary to further adjust the z-axis magnetic compensation shim coil so that the output signal V x Minimum amplitude.

[0078] After the above steps are completed, the three-axis remanent magnetization and its gradient of the atomic magnetometer are compensated to zero.

[0079] Figure 2The system of the dual-beam SERF atomic magnetometer of the present invention is shown. The dual-beam SERF atomic magnetometer system includes a pumping optical system 1, a detection light incident optical system 2, a detection light exit detection optical system 3, a photoelectric amplifier 4, a data acquisition system 5, a magnetic shielding system, an atomic gas cell 8, a three-axis magnetic compensation shim coil, a three-axis magnetic compensation gradient coil, and a non-magnetic electric heating system 10. The pumping optical system 1 consists of a pump laser 11, a half-wave plate 12, a polarization beam splitter prism 13, a reflector 14, a beam expansion and shaping assembly 15, and a quarter-wave plate 16. The pumping laser light emitted by the pump laser is split into two beams by the half-wave plate and polarization beam splitter prism. One beam is used to connect to a wavemeter to observe the wavelength and lock it to the D1 line frequency. The other beam is converted into a large circular spot with a radius equivalent to the gas cell after passing through the beam expansion and shaping assembly lens. It then passes through the quarter-wave plate to become circularly polarized light and enters the gas cell, which is used to polarize the alkali metal atoms in the gas cell. The detection light incident optical path system 2 consists of a detection laser 21, a half-wave plate 22, a polarization beam splitter prism 23, a reflector 24, and a Glan-Taylor prism 25. The detection laser emitted by the detection laser can be split into two beams by passing through the half-wave plate and polarization beam splitter prism. One beam is used to connect to a wavelength meter to observe the wavelength and lock it at a frequency detuned by 100 GHz compared to the D2 line. The other beam is converted into linearly polarized light by passing through the Glan-Taylor prism and enters the gas chamber. The detection light output detection optical path system 3 consists of a half-wave plate 31, a polarization beam splitter prism 32, a reflector 33, and a dual-channel photodetector 34. The signals of the two channels of the photodetector can be subtracted through the polarization balanced beam splitting method to extract the optical rotation angle signal reflecting the magnitude of the magnetic field. The photoelectric amplifier is used to amplify the photocurrent signal into a voltage signal that can be collected by the data acquisition system. The magnetic shielding system composed of the Permalloy magnetic shielding barrel and the ferrite magnetic shielding barrel is used to provide a stable, low-noise weak magnetic environment. The atomic gas chamber is filled with alkali metal atoms (potassium, rubidium or cesium), buffer gas (usually helium) and quenching gas (usually nitrogen). The three-axis magnetic compensation shim coil includes a Z-direction shim coil 91, a Y-direction shim coil 92 and an X-direction shim coil 93. The three-axis magnetic compensation gradient coil includes a Z-direction dB z / dz gradient coil 94, dB in Y direction y / dy gradient coil 95, dB in Y direction x / dx gradient coil 96. The non-magnetic electric heating system is used to heat the atomic gas chamber to the operating temperature. According to the above mode, the atomic magnetometer is adjusted to the normal working state.

[0080] (1) Under the conditions of no pump light and external magnetic field, balance the two photodetectors used for differential detection of optical signals, turn on the pump light, and observe the magnetometer output signal V x The zero bias value w x , and adjust to achieve the residual magnetic field B x_res (0) 、By_res (0) 、B z_res (0) The specific initialization steps are as follows: 1. Adjust and increase the magnetic field in the y direction so that the output signal V x The zero bias w x Increase positively until w is satisfied x >0, that is, B is also satisfied y_res (0) >0. 2. Positive adjustment increases the magnetic field in the x direction. If w x Continue to decrease, indicating that B x_res (0) and B z_res (0) The sign is opposite, and the magnetic field in the x direction needs to be adjusted in the opposite direction; if w x Continue to increase, indicating that B x_res (0) and B z_res (0) The signs are the same, which meets our needs.

[0081] Based on B x_res (0) 、B y_res (0) and B z_res (0) , perform the following operations to achieve remanence B res =[B x_res ,B y_res ,B z_res ] and remanent magnetization gradient All tend to zero.

[0082] (2) Compensate for the residual magnetic field in the x and z directions. Apply an amplitude of B in the z direction. cz The sinusoidal modulated magnetic field B cz sinωt, we find

[0083]

[0084] where R pump is the optical pumping rate of the pump light, γ e is the electron gyromagnetic ratio, R rel is the total relaxation rate in addition to the optical pumping rate, ω is the angular frequency of the modulating magnetic field, t represents time, and c is the output voltage signal V x and polarizability P x ratio.

[0085] For the magnetic field in the x direction, we derive the following formula from the above formula:

[0086]

[0087] in

[0088] Can get When established, then

[0089] Because B x_res (0) and B z_res (0) have the same sign, so when B x_res When V approaches zero, x Take the minimum value. By adjusting the compensation magnetic field bias B x , which will make the output voltage waveform V x The minimum value is recorded as B x (1) , then the remanent magnetism in the x direction is recorded as B x_res (1) Then, an amplitude of B is applied in the x direction. cx The sinusoidal modulated magnetic field B cx sinωt, we can similarly get the output signal V x About B z_res The derivative of is:

[0090]

[0091] It can be seen that when B x_res When V approaches zero, x Take the minimum value. By adjusting the compensation magnetic field B z , which will make the output signal V x The minimum value is recorded as B z (1) , then the remanent magnetism in the z direction is recorded as B z_res (1) Similarly, by applying a modulated magnetic field in the z direction and the x direction respectively, the compensation is made so that B x_res and B z_res Minimize, and the compensation value is updated to B z (n) and B x (n) , until |B z (n) -B z (n-1) |<ε and |B x (n) -B x (n-1) |<ε. Here, n is the number of iterations and ε is the minimum resolution of magnetic field adjustment. At this point, we consider that the residual magnetization in the x and z directions has been reset to zero.

[0092] (3) Compensate for the residual magnetism and its gradient in the y direction. Apply the modulated magnetic field B only in the y direction. cy sinωt, we get:

[0093]

[0094] It can be seen that the output signal V x The zero bias w x It can characterize the remanence in the y direction. x When |<ε, it means that the residual magnetism in the y direction has been compensated to zero. On this basis, the following formula is used:

[0095]

[0096] It can be seen that when the remanent magnetic gradient When compensated to zero, the output signal V x The amplitude is the largest. gx 、k gy and k gz They are x, y, and z gradient magnetic fields respectively The weight coefficient of .

[0097] However, in actual operation, it is difficult to ensure that the zero point of the gradient magnetic field generated by the gradient coil for compensation is located at the center of the gas chamber, so a bias residual magnetism will be introduced again in the y direction. x |>ε, it is necessary to adjust the DC compensation magnetic field in the y direction so that |w x |<ε.

[0098] (4) Follow the flow chart Figure 1 As shown in the figure, the x-direction remanent magnetization gradient, the newly introduced x-direction remanent magnetization, the z-direction remanent magnetization gradient, and the newly introduced z-direction remanent magnetization are compensated in sequence. Finally, the in-situ integrated compensation of remanent magnetization and its gradient in the SERF atomic magnetometer is completed.

[0099] 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 dual-beam SERF atomic magnetometer remanence and its gradient integrated compensation method, characterized in that: The method includes defining that the pumping light of the atomic magnetometer propagates along the z-axis direction and the detection light propagates along the x-axis direction. After the residual magnetic parameters are initialized, the residual magnetic fields in the x- and z-directions are compensated. A sinusoidal modulated magnetic field Bczsinωt with an amplitude of Bcz is applied in the z-direction, and a sinusoidal modulated magnetic field Bcxsinωt with an amplitude of Bcx is applied in the x-direction, where ω represents frequency and t represents time. The x-axis and z-axis residual magnetism are compensated respectively, so that the amplitude of the magnetometer output signal Vx is minimized. The method includes: adjusting the compensation magnetic field bias Bx to record the minimum value of the output voltage waveform Vx as Bx. (1) , then the remanent magnetism in the x direction is recorded as Bx_res (1) By adjusting the compensation magnetic field Bz, the minimum value of the output signal Vx is recorded as Bz (1) , then the remanent magnetism in the z direction is recorded as Bz_res (1) ; By applying a modulated magnetic field in the z direction and the x direction respectively, the compensation is made so that Bx_res and Bz_res are minimized, and the compensation value is updated to Bz (n) and Bx (n) , until |Bz (n) -Bz (n-1) |<ε and |Bx (n) -Bx (n-1) |<ε, where n is the number of iterations and ε is the minimum resolution of magnetic field adjustment. At this point, the residual magnetization in the x and z directions is completely reset to zero. After the residual magnetization of the x and z axes reaches zero field, a sinusoidal modulated magnetic field B is applied only on the y axis. cy sinωt,B cy Represents the amplitude, compensates for the residual magnetism in the y direction, and makes the zero bias value w of the magnetometer output signal Vx x is zero; under this condition, observe the output signal Vx amplitude when the modulated magnetic field is applied on the y-axis, and adjust the y-axis gradient coil voltage to maximize the signal Vx amplitude; if the output signal zero bias value w x If the Y-axis residual magnetism changes, it is necessary to continue to compensate for the zero bias value w x is zero; Keep applying a modulated magnetic field on the y-axis, adjust the x-axis gradient coil voltage to maximize the amplitude of the signal Vx, turn off the y-axis modulated magnetic field, and apply the z-axis modulated magnetic field. If the amplitude of the output signal Vx increases at this time, it is necessary to continue compensating for the x-axis residual magnetism. Apply a modulating magnetic field only on the y-axis and adjust the voltage of the z-axis magnetic compensation gradient coil until the amplitude of the magnetometer output signal Vx is maximized. Then remove the y-axis modulating magnetic field and apply a modulating magnetic field on the x-axis. If the amplitude of the output signal Vx at this time is greater than the minimum amplitude of Vx, further adjust the z-axis magnetic compensation shim coil to minimize the amplitude of the output signal Vx. After completing the above operations, the residual magnetism and gradient of each axis can be reset to zero; The remanence parameter initialization includes: Step 1. Adjust and increase the magnetic field in the y direction so that the zero bias w of the output signal Vx x Increase positively until w is satisfied x >0 requirement, that is, it also satisfies By_res (0) >0; Step 2. Positive adjustment increases the magnetic field in the x direction. If w x Continue to decrease, indicating that Bx_res (0) and Bzères (0) The sign is opposite, and the magnetic field in the x direction needs to be adjusted in the opposite direction; if w x Continue to increase, indicating that Bx_res (0) and Bzères (0) The signs are the same.

2. The method for integrating residual magnetism and gradient compensation of a dual-beam SERF atomic magnetometer according to claim 1, characterized in that: The method for integrated compensation of residual magnetism and its gradient comprises the following steps: Step (1), adjusting the atomic magnetometer to a working state, so that the pump light enters the gas chamber from the z-axis direction and the detection light enters the gas chamber from the x-axis direction, and adjusting the optical parameters of the dual-beam SERF atomic magnetometer, including the pump light power and the detection light wavelength, so that the scale factor of the magnetometer is maximized; Step (2): In the absence of pump light and external magnetic field, balance the two photoelectric detectors used for differential detection of optical signals, turn on the pump light, and observe the magnetometer output signal V x The zero bias value w x , and adjust to achieve the residual magnetic field B x_res (0) 、B y_res (0) 、B z_res (0) Initialization; Step (3): From the above formula, we can know that a modulated magnetic field B is applied on the z-axis. cz sinωt, adjust the voltage of the x-axis magnetic compensation shim coil until the magnetometer output signal V x The amplitude is the smallest, and the compensation magnetic field at this time is recorded as B x (n) , where n is the number of compensation iterations, n=1,2,3…, B cz is the modulating magnetic field amplitude, R pump is the optical pumping efficiency of the pump light, B x_res 、B y_res , and B z_res Remanence B res Remanence on the x-axis, y-axis and z-axis, γ e is the electron gyromagnetic ratio, R rel is the total relaxation rate in addition to the optical pumping rate, ω is the angular frequency of the modulating magnetic field, t represents time, and c is the output voltage signal V x and polarizability P x Similarly, a modulated magnetic field is applied to the x-axis, and the voltage of the z-axis magnetic compensation shim coil is adjusted until the magnetometer outputs a signal V x The amplitude is the smallest, and the compensation magnetic field at this time is recorded as B z (n) ; Repeat step (3) until |B x (n) -B x (n-1) |<ε and |B z (n) -B z (n-1) |<ε, where ε is the minimum resolution of magnetic field compensation, indicating that the residual magnetism of the x-axis and z-axis are compensated to zero; Step (4): From the above formula, we can know that when the remanent magnetization of x and z axes is supplemented to zero field, a modulated magnetic field B is applied on the y axis. cy sin(ωt), adjust the voltage of the y-axis magnetic compensation shim coil until the output signal V x The zero bias value w x is zero, that is, satisfying |w x |<ε, indicating that the residual magnetism of the y-axis is compensated to zero; then, on this basis, adjust the voltage of the y-axis magnetic compensation gradient coil until the magnetometer output signal V x The amplitude is the largest, which means that the y-axis residual magnetic gradient is compensated to zero; if |w x |>ε, it means that the center point of the gradient coil is not aligned with the center of the detection light, thus introducing a new y-axis residual magnetism. It is necessary to further adjust the y-axis magnetic compensation shim coil so that the output signal zero bias value satisfies |w x |<ε; Step (5): From the above formula, it can be seen that when the x-, y-, and z-axis residual magnetism and the y-axis residual magnetism gradient are all compensated to zero field, a modulation magnetic field is still applied to the y-axis, and the voltage of the x-axis magnetic compensation gradient coil is adjusted until the magnetometer output signal V x The amplitude is the largest, which means that the x-axis residual magnetic gradient is compensated to zero, where ▽B res is the remanent magnetization gradient, R d is the sum of spin destruction relaxation, relaxation induced by detection light, and bubble-wall collision relaxation, k gx 、k gy and k gz They are the x-, y-, and z-axis remanent magnetic gradients ▽B x_res , ▽B y_res , ▽B z_res Then remove the y-axis modulation magnetic field and apply a modulation magnetic field on the z-axis. If the output signal V x The amplitude is greater than V when step (3) is completed x The amplitude of , it means that the center point of the gradient coil is not aligned with the center of the detection light, thus introducing a new x-axis residual magnetism. It is necessary to further adjust the x-axis magnetic compensation shim coil so that the output signal V x Minimum amplitude; Step (6): When the x-axis, y-axis, and z-axis residual magnetization and the x-axis and y-axis residual magnetization gradients are all compensated to zero field, a modulation magnetic field is applied only on the y-axis, and the voltage of the z-axis magnetic compensation gradient coil is adjusted until the magnetometer output signal V x The amplitude is the largest, which means that the z-axis residual magnetic gradient is compensated to zero; then remove the y-axis modulation magnetic field and apply a modulation magnetic field on the x-axis. If the output signal V x The amplitude is greater than V when step (3) is completed x The amplitude of , it means that the center point of the gradient coil is not aligned with the center of the detection light, thus introducing a new z-axis residual magnetism. It is necessary to further adjust the z-axis magnetic compensation shim coil so that the output signal V x Minimum amplitude; After the above steps (1) to (6) are completed, the three-axis remanent magnetization and its gradient of the atomic magnetometer are compensated to zero.

3. The method for integrating residual magnetism and gradient compensation of a dual-beam SERF atomic magnetometer according to claim 1, characterized in that: The dual-beam SERF atomic magnetometer includes a pumping laser system, a detection system, a magnetic shielding system composed of Permalloy and ferrite, a three-axis magnetic compensation shim coil, a three-axis magnetic compensation gradient coil, a non-magnetic electric heating system, and an atomic gas cell. Adjusting the atomic magnetometer to a working state involves placing the gas cell inside the magnetic shielding system to place it in a weak magnetic environment, and heating the gas cell containing alkali metal atoms, a quenching gas, and a buffer gas to an operating temperature using the non-magnetic electric heating system. The pumping light is circularly polarized light with a frequency locked to the D1 line of the alkali metal atom, and is incident on the gas cell along the z-axis direction to polarize the alkali metal atoms. The detection light is detuned linearly polarized light, and is incident on the gas cell along the x-axis direction. The laser light exiting the gas cell is subjected to a balanced polarization beam splitting method to measure a magneto-optical rotation angle signal on a photodetector, and the signal is then converted and amplified by a photoelectric amplifier.

4. The method for integrating residual magnetism and gradient compensation of a dual-beam SERF atomic magnetometer according to claim 1, characterized in that: The method for integrated compensation of residual magnetism and its gradient comprises the following steps: Step 1, start parameter initialization of the residual magnetic field compensation process; Step 2, n = 1, n is the number of iterations, and a sinusoidal AC magnetic field B is applied only in the Z direction cz sinωt, use the shim coil to compensate the DC residual magnetism in the X direction until the Vx amplitude is minimum, and record the compensation value at this time as B x (n) ; Step 3: Apply a sinusoidal AC magnetic field B only in the X direction. cx sinωt, use the shim coil to compensate the DC residual magnetism in the Z direction until the Vx amplitude is minimum, and record the compensation value at this time as B z (n) ; Step 4, B x (n) =B x (n-1) and B z (n) =B z (n-1) Are both true? If not, set n = n + 1 and return to step 2. If yes, go to step 5. Step 5: Apply a sinusoidal AC magnetic field B only in the Y direction. cy sinωt, use the shim coil to compensate for the DC residual magnetism in the Y direction until the output signal is biased to w x is zero; Step 6: Use the gradient coil to compensate for the gradient residual magnetism in the Y direction until the Vx amplitude is maximum; Step 7: Is there a newly introduced DC magnetic field By? If yes, return to step 5; if no, go to step 8; Step 8: Use the gradient coil to compensate for the gradient residual magnetization in the X direction until the Vx amplitude is maximum. Step 9: Is there a newly introduced DC magnetic field Bx? If yes, return to step 2; if no, proceed to step 10. Step 10, using the gradient coil to compensate for the gradient residual magnetization in the Z direction until the Vx amplitude is maximum; Step 11: Is there a newly introduced DC magnetic field Bz? If yes, return to step 2; if no, proceed to step 12; Step 12: End the integrated compensation of residual magnetism and its gradient, and both the DC and gradient residual magnetism are compensated to zero.

5. The method for integrated compensation of remanence and gradient of dual-beam SERF atomic magnetometer according to claim 1, characterized in that: The dual-beam SERF atomic magnetometer includes a pumping optical path system, a detection light incident optical path system, a detection light exit detection optical path system and an atomic gas chamber. The pumping optical path system includes a pumping laser, a first half-wave plate, a first polarization beam splitter prism, a first reflector, a beam expansion and shaping combination, and a quarter-wave plate connected in sequence. The pumping light emitted from the quarter-wave plate passes through the atomic gas chamber; the detection light incident optical path system includes a detection laser, a second half-wave plate, a second polarization beam splitter prism, a second reflector, and a Glan-Taylor prism connected in sequence. The detection light emitted from the Glan-Taylor prism passes through the atomic gas chamber and then enters the atomic gas chamber. The detection light emits a third half-wave plate in the detection light path system, the third half-wave plate is connected to a third polarization beam splitter prism, the transmitted light of the third polarization beam splitter prism is input to the first channel of the dual-channel photodetector, the reflected light of the third polarization beam splitter prism is input to the second channel of the dual-channel photodetector through the third reflector, and the dual-channel photodetector is connected to the data acquisition system through a photoelectric amplifier; a non-magnetic electric heating system, a magnetic compensation coil system and a magnetic shielding system are sequentially arranged around the outer periphery of the atomic gas chamber, the magnetic compensation coil system includes a Z-direction shim coil, a Y-direction shim coil, an X-direction shim coil, a Z-direction dB z / dz gradient coil, dB in Y direction y / dy gradient coil, and dB in the X direction x / dx gradient coil, the magnetic shielding system includes a ferrite magnetic shielding barrel and a permalloy magnetic shielding barrel.

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