Vector Measurement Method of Single-Beam Optically Pumped Atomic Magnetometer Based on Rotating Excitation Magnetic Field

Abstract

A vector measurement method for a single-beam optically pumped atomic magnetometer based on a rotating excitation magnetic field is proposed. The pump light direction is defined as the negative y-axis, and the plane of rotation of the excitation magnetic field is the xoy plane. First, an excitation magnetic field is applied along the y-axis coil, and the atomic resonance frequency is determined by frequency sweeping. Next, a rotating excitation magnetic field is applied. Based on the minimum value of the single-beam optically pumped atomic magnetometer response signal, the z-axis magnetic field is compensated, and the resonance frequency is redefined. The azimuth and polar angle ranges are determined by actively applying the magnetic field. Finally, the azimuth is measured in real time based on the phase of the modulation signal corresponding to the minimum value of the magnetometer response signal, and the polar angle and magnetic field magnitude are measured in real time based on the ratio of the minimum to maximum value of the magnetometer response signal, the z-axis compensation magnetic field, and the demodulated dispersive signal. This invention, based on the rotational excitation magnetic field controlling the atomic spin precession signal, realizes vector measurement using an optically pumped atomic magnetometer, offering advantages such as high measurement accuracy, fast response speed, and ease of integration.

Description

Technical Field

[0001] This invention relates to the field of optically pumped atomic magnetometer measurement technology, and in particular to a vector measurement method for a single-beam optically pumped atomic magnetometer based on a rotating excitation magnetic field. By rotating the excitation magnetic field and combining it with uniaxial magnetic compensation, the complete vector information of the magnetic field can be measured. This method can be widely used in fields such as geomagnetic navigation, mineral resource exploration, and life and health monitoring. Background Technology

[0002] Magnetic fields are among the most fundamental and important physical quantities, and precise measurement of magnetic fields has become a crucial technological means for humankind to understand the physical world. Optically pumped atomic magnetometers can solve the problem of precise detection of magnetic fields outside of zero-magnetic space. In recent years, with the development of laser technology and MEMS (Micro-Electro-Mechanical Systems) technology, research on optically pumped atomic magnetometers has made significant progress. However, optically pumped atomic magnetometers are scalar magnetometers and cannot measure the direction information of magnetic fields, which is particularly important in some application areas. Therefore, vector measurement methods for optically pumped atomic magnetometers have become an important research direction. However, existing vector measurement methods for optically pumped atomic magnetometers suffer from problems such as complex system structure and difficulty in rapid measurement, which require further solutions. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of existing technologies and propose a vector measurement method for a single-beam optically pumped atomic magnetometer based on a rotating excitation magnetic field. By rotating the excitation magnetic field and combining it with uniaxial magnetic compensation, complete vector information of the magnetic field can be measured. Simultaneously, the single-beam configuration facilitates miniaturization, and measurements can be performed directly in geomagnetic environments. This invention is a vector measurement method suitable for geomagnetic conditions and conducive to system integration.

[0004] The technical solution of the present invention is as follows:

[0005] A vector measurement method for a single-beam optically pumped atomic magnetometer based on a rotating excitation magnetic field is characterized by comprising the following steps:

[0006] Step 1: Start the single-beam optically pumped atomic magnetometer system, apply an excitation magnetic field along the y-axis coil, and scan the frequency of the excitation magnetic field to determine the Larmor precession resonance frequency of the atoms in the gas cell, thereby determining the vector magnitude of the magnetic field to be measured.

[0007] Step 2: Apply double-sideband amplitude-modulated voltage signals along the x-axis and y-axis coils to drive the coils and generate a rotating excitation magnetic field in the xoy plane.

[0008] Step 3: Based on the minimum response signal of the single-beam optically pumped atomic magnetometer, compensate the z-axis magnetic field and redetermine the resonance frequency, i.e., determine the magnitude of the remaining magnetic field vector after magnetic compensation.

[0009] Step 4: Determine the range of values ​​for the azimuth and polar angle of the magnetic field vector to be measured based on the actively applied magnetic field. Measure the azimuth of the magnetic field vector to be measured in real time based on the modulation signal phase corresponding to the minimum value of the response signal of the single-beam optically pumped atomic magnetometer. Measure the polar angle and magnitude of the magnetic field vector to be measured in real time based on the ratio of the minimum to maximum value of the response signal of the single-beam optically pumped atomic magnetometer, the z-axis compensation magnetic field, and the demodulated dispersive signal.

[0010] Step 1 includes: obtaining the curve of the response signal of the single-beam optically pumped atomic magnetometer as a function of the excitation magnetic field frequency by scanning the frequency of the excitation magnetic field applied along the y-axis. The frequency of the excitation magnetic field corresponding to the maximum amplitude of the curve is the Larmor precession frequency of the atom in the magnetic field, which is used as the frequency of the high-frequency carrier signal.

[0011] Step 2 includes: using a signal generator to generate two low-frequency modulation signals with a phase difference of π / 2, wherein the low-frequency modulation wave on the x-axis leads the phase, and then multiplying them with the high-frequency carrier to perform double-sideband amplitude modulation.

[0012] Step 3 includes: driving the spin precession of the atomic ensemble by rotating the excitation magnetic field, while simultaneously acquiring the response signal of the single-beam optically pumped atomic magnetometer in real time, changing the current value of the z-axis coil so that the minimum value of the response signal of the single-beam optically pumped atomic magnetometer is 0, indicating that the z-axis magnetic field is compensated.

[0013] Step 4 includes: actively applying a positive magnetic field to the y-axis, and determining the azimuth range based on the change in resonant frequency. If the resonant frequency increases, the measured magnetic field has a positive projection on the y-axis, and the azimuth range is (0, π); otherwise, it is (π, 2π). The polar angle range is determined based on the z-axis compensation current. When the z-axis compensation current generates a positive magnetic field along the z-axis, the polar angle range is... Conversely, it is

[0014] Step 4 includes:

[0015]

[0016] Where θ is the polar angle of the magnetic field vector to be measured, and B z For the z-axis compensating magnetic field magnitude, B rθ1 is the residual magnetic field magnitude after z-axis magnetic compensation, S is the magnitude of the dispersive signal, K is the slope at the resonant frequency of the dispersion curve, θ1 is the polar angle after magnetic compensation, |B| is the vector magnitude of the magnetic field to be measured, γ is the gyromagnetic ratio of the alkali metal atom, B1 is the amplitude of the excitation magnetic field, T1 is the longitudinal relaxation time, T2 is the transverse relaxation time, and R... min R is the minimum value of the response signal of a single-beam optically pumped atomic magnetometer within half a cycle of a low-frequency modulation signal. max It is the maximum value of the response signal of the single-beam optically pumped atomic magnetometer within half a cycle of the low-frequency modulation signal.

[0017] The optical path system of the single-beam optically pumped atomic magnetometer system includes a laser, a polarization-maintaining fiber with a collimator, a linear polarizer, a quarter-wave plate, a gas cell, and a photodetector connected in sequence. The photodetector is connected to the signal processing system.

[0018] The air chamber is located within a non-magnetic electric heating system, which is located within a triaxial coil.

[0019] The signal processing system includes a transimpedance voltage amplifier. The input terminal of the transimpedance voltage amplifier is connected to the photodetector. The output terminal of the transimpedance voltage amplifier is connected to the input terminal of a lock-in amplifier. The output terminal of the lock-in amplifier is connected to the first input terminal of a first multiplier and the first input terminal of a second multiplier. The second input terminal of the first multiplier is connected to the first output terminal of a signal generator. The second input terminal of the second multiplier is connected to the second output terminal of the signal generator. The output terminal of the first multiplier is connected to the x-axis coil of a triaxial coil. The output terminal of the second multiplier is connected to the y-axis coil of a triaxial coil. The z-axis coil of the triaxial coil is connected to a current source.

[0020] The technical advantages of this invention are as follows: This invention is based on a vector measurement method for a single-beam optically pumped atomic magnetometer using a rotating excitation magnetic field. The pump light direction is defined as the negative y-axis, and the plane of rotation of the excitation magnetic field is the xoy plane. First, an excitation magnetic field is applied along the y-axis coil, and the atomic resonance frequency is determined by frequency sweeping. Next, a rotating excitation magnetic field is applied. Based on the minimum value of the single-beam optically pumped atomic magnetometer response signal, the z-axis magnetic field is compensated, and the resonance frequency is redefined. The azimuth and polar angle ranges are determined by actively applying the magnetic field. Finally, the azimuth is measured in real time based on the phase of the modulation signal corresponding to the minimum value of the magnetometer response signal, and the polar angle and magnetic field magnitude are measured in real time based on the ratio of the minimum to maximum value of the magnetometer response signal, the z-axis compensation magnetic field, and the demodulated dispersion signal. This invention, based on the rotational excitation magnetic field controlling the atomic spin precession signal, realizes vector measurement using an optically pumped atomic magnetometer, offering advantages such as high measurement accuracy, fast response speed, and ease of integration.

[0021] The advantages of this invention compared to the prior art are:

[0022] (1) Vector measurement method of single-beam optical pumped atomic magnetometer based on rotating excitation magnetic field By rotating excitation magnetic field and combining single-axis magnetic compensation, the complete vector information of magnetic field can be measured directly in geomagnetic environment without the need for an additional magnetometer to search for zero magnetic field.

[0023] (2) It adopts a single-beam configuration, without complex optical paths, and has a compact structure, which is conducive to miniaturization. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the three-dimensional information of the magnetic field to be measured involved in implementing the vector measurement method of the single-beam optically pumped atomic magnetometer based on the rotating excitation magnetic field of the present invention.

[0025] Figure 2 This is a schematic flowchart illustrating the vector measurement method of a single-beam optically pumped atomic magnetometer based on a rotating excitation magnetic field, as described in this invention. Figure 2 The process includes: Step 1, frequency sweeping to determine the magnitude of the main magnetic field to be measured; Step 2, applying a rotating excitation magnetic field to the xoy plane; Step 3, compensating the z-axis magnetic field based on the minimum value of the response signal and re-sweeping the frequency to determine the magnitude of the remaining magnetic field vector after magnetic compensation; Step 4, applying a rotating excitation magnetic field to the xoy plane in combination with the z-axis compensation magnetic field to determine the magnetic field vector.

[0026] Figure 3 This is a schematic diagram of a single-beam optically pumped atomic magnetometer system involved in implementing the vector measurement method of the single-beam optically pumped atomic magnetometer based on the rotating excitation magnetic field of the present invention.

[0027] The following are explanations of the reference numerals in the attached diagram: 1 is the gas chamber; 2 is the non-magnetic electric heating system; 3 is the triaxial coil; 4 is the optical path system; 5 is the signal processing system; 41 is the laser; 42 is the polarization-maintaining fiber with a collimator; 43 is the linear polarizer; 44 is the quarter-wave plate; 45 is the photodetector; 51 is the current source; 52 is the signal generator; 53 is the first multiplier; 54 is the second multiplier; 55 is the lock-in amplifier; 56 is the transimpedance voltage amplifier; xyz - the three axes of the rectangular coordinate system (i.e., the x-axis, y-axis, and z-axis); |B| - the magnitude of the magnetic field vector to be measured; φ is... - Azimuth angle, θ - Polar angle; In - Input terminal; Out - Output terminal; Demod - Demodulation port. Detailed Implementation

[0028] The following is in conjunction with the attached diagram ( Figures 1-3 The invention will be described in the following sections and examples.

[0029] Figure 1 This is a schematic diagram of the three-dimensional information of the magnetic field to be measured involved in implementing the vector measurement method of the single-beam optically pumped atomic magnetometer based on the rotating excitation magnetic field of the present invention. Figure 2This is a schematic flowchart illustrating the vector measurement method of a single-beam optically pumped atomic magnetometer based on a rotating excitation magnetic field, as described in this invention. Figure 3 This is a schematic diagram of the single-beam optically pumped atomic magnetometer system involved in implementing the vector measurement method of the single-beam optically pumped atomic magnetometer based on the rotating excitation magnetic field of this invention. (Reference) Figures 1 to 3 As shown, the vector measurement method of a single-beam optically pumped atomic magnetometer based on a rotating excitation magnetic field includes the following steps: Step 1, start the single-beam optically pumped atomic magnetometer system, apply an excitation magnetic field along the y-axis coil, and scan the frequency of the excitation magnetic field to determine the atomic Larmor precession resonance frequency in the gas cell, thereby determining the magnitude of the magnetic field vector to be measured; Step 2, apply a double-sideband amplitude-modulated voltage signal to drive the coils along the x-axis and y-axis coils to generate a rotating excitation magnetic field in the xoy plane; Step 3, compensate the z-axis magnetic field according to the minimum value of the single-beam optically pumped atomic magnetometer response signal, and redetermine the resonance frequency, thereby determining the magnitude of the remaining magnetic field vector after magnetic compensation; Step 4, determine the range of values ​​for the azimuth angle and polar angle of the magnetic field vector to be measured according to the actively applied magnetic field, measure the azimuth angle of the magnetic field vector to be measured in real time according to the phase of the modulation signal corresponding to the minimum value of the single-beam optically pumped atomic magnetometer response signal, and measure the polar angle and magnitude of the magnetic field vector to be measured in real time according to the ratio of the minimum to maximum value of the single-beam optically pumped atomic magnetometer response signal, the z-axis compensation magnetic field, and the demodulated dispersion signal.

[0030] Step 1 includes: obtaining the curve of the single-beam optically pumped atomic magnetometer response signal as a function of the excitation magnetic field frequency by scanning the frequency of the excitation magnetic field applied along the y-axis. The frequency of the excitation magnetic field corresponding to the maximum amplitude of this curve is the Larmor precession frequency of the atom in the magnetic field, which is used as the frequency of the high-frequency carrier signal. Step 2 includes: generating two low-frequency modulation signals with a phase difference of π / 2 using a signal generator, wherein the low-frequency modulation wave on the x-axis leads the phase, and then multiplying them with the high-frequency carrier for double-sideband amplitude modulation. Step 3 includes: driving the spin precession of the atomic ensemble by rotating the excitation magnetic field, while simultaneously acquiring the single-beam optically pumped atomic magnetometer response signal in real time, changing the current value of the z-axis coil so that the minimum value of the single-beam optically pumped atomic magnetometer response signal is 0, indicating that the z-axis magnetic field is compensated.

[0031] Step 4 includes: actively applying a positive magnetic field to the y-axis, and determining the azimuth range based on the change in resonant frequency. If the resonant frequency increases, the measured magnetic field has a positive projection on the y-axis, and the azimuth range is (0, π); otherwise, it is (π, 2π). The polar angle range is determined based on the z-axis compensation current. When the z-axis compensation current generates a positive magnetic field along the z-axis, the polar angle range is... Conversely, it is

[0032] Step 4 includes:

[0033]

[0034]

[0035] Where θ is the polar angle of the magnetic field vector to be measured, and B z For the z-axis compensating magnetic field magnitude, B r θ1 is the residual magnetic field magnitude after z-axis magnetic compensation, S is the magnitude of the dispersive signal, K is the slope at the resonant frequency of the dispersion curve, θ1 is the polar angle after magnetic compensation, |B| is the vector magnitude of the magnetic field to be measured, γ is the gyromagnetic ratio of the alkali metal atom, B1 is the amplitude of the excitation magnetic field, T1 is the longitudinal relaxation time, T2 is the transverse relaxation time, and R... min R is the minimum value of the response signal of a single-beam optically pumped atomic magnetometer within half a cycle of a low-frequency modulation signal. max It is the maximum value of the response signal of the single-beam optically pumped atomic magnetometer within half a cycle of the low-frequency modulation signal.

[0036] The optical path system 4 of the single-beam optically pumped atomic magnetometer system includes, in sequence, a laser 41, a polarization-maintaining fiber 42 with a collimator, a linear polarizer 43, a quarter-wave plate 44, a gas cell 1, and a photodetector 45. The photodetector 45 is connected to a signal processing system 5. The gas cell 1 is located within a non-magnetic electric heating system 2, which is located within a triaxial coil 3. The signal processing system 5 includes a transimpedance voltage amplifier 56. The input terminal In of the transimpedance voltage amplifier 56 is connected to the photodetector 45. The output terminal Out of the transimpedance voltage amplifier 56 is connected to the input terminal In of the lock-in amplifier 55. The output terminal Out of the lock-in amplifier 55 is connected to the first input terminal of the first multiplier 53 and the first input terminal of the second multiplier 54. The second input terminal of the first multiplier 53 is connected to the first output terminal Out1 of the signal generator 52. The second input terminal of the second multiplier 54 is connected to the second output terminal Out2 of the signal generator 52. The output terminal of the first multiplier 53 is connected to the x-axis coil of the triaxial coil 3. The output terminal of the second multiplier 54 is connected to the y-axis coil of the triaxial coil 3. The z-axis coil of the triaxial coil 3 is connected to the output terminal Out of the current source 51.

[0037] A vector measurement method for a single-beam optically pumped atomic magnetometer based on a rotating excitation magnetic field is proposed. The pump light direction is defined as the negative y-axis, and the plane of rotation of the excitation magnetic field is defined as the xoy plane. First, an excitation magnetic field is applied along the y-axis coil, and the frequency of the excitation magnetic field is scanned to determine the Larmor precession resonance frequency of the atom in the external magnetic field. Second, a double-sideband amplitude-modulated voltage signal is applied along the x-axis and y-axis coils to drive the coils, generating an excitation magnetic field rotating in the xoy plane. Based on the minimum response signal of the single-beam optically pumped atomic magnetometer, the z-axis magnetic field is compensated, and the resonance frequency is redefined. The azimuth and polar angle ranges are determined by actively applying the magnetic field. Finally, the azimuth is measured in real-time based on the phase of the modulation signal corresponding to the minimum response signal of the single-beam optically pumped atomic magnetometer, and the polar angle and magnetic field magnitude are measured in real-time based on the ratio of the minimum to maximum response signal of the single-beam optically pumped atomic magnetometer, the z-axis compensated magnetic field, and the demodulated dispersive signal.

[0038] Figure 1 It represents the three-dimensional information of the magnetic field to be measured, in which, θ is the azimuth angle, θ is the polar angle, and |B| is the magnitude of the magnetic field to be measured; the vector information of the magnetic field to be measured is completely determined by the azimuth angle, polar angle, and magnitude.

[0039] like Figure 2 As shown, the vector measurement method of a single-beam optically pumped atomic magnetometer based on a rotating excitation magnetic field, implemented in this invention, includes the following steps:

[0040] Step (1): First, apply an excitation magnetic field along the y-axis coil and scan the frequency of the excitation magnetic field to determine the atomic Larmor precession resonance frequency;

[0041] Step (2): Next, apply a double-sideband amplitude-modulated voltage signal along the x-axis coil and y-axis coil to drive the coil to generate an excitation magnetic field that rotates in the xoy plane.

[0042] Step (3): Based on the minimum response signal of the single-beam optically pumped atomic magnetometer, compensate for the z-axis magnetic field and redetermine the resonance frequency;

[0043] Step (4): Determine the range of azimuth and polar angle values ​​based on the actively applied magnetic field; finally, measure the azimuth in real time based on the modulation signal phase corresponding to the minimum value of the single-beam optically pumped atomic magnetometer response signal, and measure the polar angle and magnetic field magnitude in real time based on the ratio of the minimum to the maximum value of the single-beam optically pumped atomic magnetometer response signal, the z-axis compensation magnetic field, and the demodulated dispersive signal.

[0044] like Figure 3As shown, the single-beam optically pumped atomic magnetometer system includes a sensitive gas chamber 1, a non-magnetic electric heating system 2, a triaxial coil 3, an optical path system 4, and a signal processing system 5. The sensitive gas chamber 1 is filled with an alkali metal as the sensitive medium and a buffer gas. The non-magnetic electric heating system 2 includes an oven and a heating film to provide a constant temperature for the atomic ensemble within the gas chamber. The triaxial coil 3 provides an excitation magnetic field and a compensation magnetic field. The optical path system 4 includes a laser 41, a polarization-maintaining fiber 42 with a collimator, a linear polarizer 43, a quarter-wave plate 44, and a photodetector 45, which generate circularly polarized light to polarize atoms and detect the precession signal of the atomic ensemble transmitted through the gas chamber 1. Processing system 5 includes a current source 51, a signal generator 52, a first multiplier 53, a second multiplier 54, a lock-in amplifier 55, and a transimpedance voltage amplifier 56. The transimpedance voltage amplifier 56 amplifies the output signal of the photodetector 45, and the lock-in amplifier 55 acquires the response signal of the single-beam optically pumped atomic magnetometer. After further demodulation, a dispersive signal is obtained. The signal generator 52 and the lock-in amplifier 55 generate a low-frequency modulation signal and a high-frequency carrier signal, respectively, which are then passed to the first multiplier 53 and the second multiplier 54 for double-sideband amplitude modulation. The phase of the low-frequency modulation signal entering the first multiplier 53 leads the phase of the low-frequency modulation signal entering the second multiplier 54. The modulated voltage signal is passed into the x and y coils to generate a rotating excitation magnetic field, and the z-axis magnetic field is compensated by the current source 51.

[0045] The frequency of the excitation magnetic field applied along the y-axis is scanned to obtain the curve of the response signal of the single-beam optically pumped atomic magnetometer as a function of the excitation magnetic field frequency. The frequency of the excitation magnetic field corresponding to the maximum amplitude of this curve is the Larmor precession frequency of the atom in the magnetic field, which is used as the frequency of the high-frequency carrier signal. Two channels with a phase difference of 52 are generated using signal generator 52. The low-frequency modulated signal, in which the low-frequency modulated wave on the x-axis leads the phase, is then multiplied by the high-frequency carrier to perform double-sideband amplitude modulation; the two signals are fed into the x and y axis coils respectively to achieve the rotation of the excitation magnetic field.

[0046] The atomic ensemble spin precession is driven by a rotating excitation magnetic field, and the response signal of a single-beam optically pumped atomic magnetometer is acquired in real time. The current value of the z-axis coil is changed so that the minimum value of the single-beam optically pumped atomic magnetometer response signal is 0, which indicates that the z-axis magnetic field is compensated.

[0047] By actively applying a positive magnetic field to the y-axis, the range of azimuth angle is determined based on the change in resonant frequency. If the resonant frequency increases, the measured magnetic field has a positive projection on the y-axis, and the azimuth angle range is (0, π); otherwise, it is (π, 2π). The range of polar angle is determined based on the z-axis compensation current. When the z-axis compensation current generates a positive magnetic field along the z-axis, the polar angle range is... Conversely, it is

[0048] The phase of the low-frequency modulation signal on the x-axis corresponding to the minimum response signal of the single-beam optically pumped atomic magnetometer is the azimuth angle of the magnetic field vector. Based on the real-time change of the corresponding modulation signal phase and the range of azimuth angle values, the azimuth angle is measured in real time.

[0049] After z-axis magnetic compensation, the polar angle after magnetic compensation is determined based on the ratio of the minimum to the maximum value of the response signal of the single-beam optically pumped atomic magnetometer within half a period of the low-frequency modulation signal:

[0050]

[0051] Where θ1 is the polar angle after magnetic compensation, γ is the gyromagnetic ratio of the alkali metal atom, B1 is the amplitude of the excitation magnetic field, T1 and T2 are the longitudinal relaxation time and the transverse relaxation time, respectively, and R min and R max These represent the minimum and maximum values ​​of the single-beam optically pumped atomic magnetometer response signal within half a cycle of the low-frequency modulation signal, respectively. The choice of sign in the formula is determined by observing the change in the minimum value of the single-beam optically pumped atomic magnetometer response signal within half a cycle of the low-frequency modulation signal after slightly increasing the z-axis compensation current: when the z-axis compensation current increases, the minimum value of the single-beam optically pumped atomic magnetometer response signal within half a cycle of the low-frequency modulation signal decreases, and the sign is negative; conversely, it is positive.

[0052] Combining the z-axis compensated magnetic field and the demodulated dispersive signal, the actual polar angle of the magnetic field to be measured is:

[0053]

[0054] Where θ is the actual polar angle of the magnetic field to be measured; B z B is the magnitude of the compensating magnetic field along the z-axis. r θ1 is the residual magnetic field magnitude after z-axis magnetic compensation, determined by rescanning the frequency after z-axis magnetic compensation; S is the magnitude of the dispersive signal; K is the slope at the resonant frequency of the dispersion curve; θ1 is the polar angle after magnetic compensation, determined by the ratio of the minimum to the maximum value of the response signal of the single-beam optically pumped atomic magnetometer within half a cycle of the low-frequency modulation signal.

[0055] The vector magnitude of the magnetic field under test is measured in real time based on the ratio of the minimum to maximum values ​​of the response signal of the single-beam optically pumped atomic magnetometer, the z-axis compensated magnetic field, and the demodulated dispersive signal.

[0056]

[0057] Where |B| is the magnitude of the magnetic field vector to be measured; B z B is the magnitude of the compensating magnetic field along the z-axis. rθ1 is the residual magnetic field magnitude after z-axis magnetic compensation, determined by rescanning the frequency after z-axis magnetic compensation; S is the magnitude of the dispersive signal; K is the slope at the resonant frequency of the dispersion curve; θ1 is the polar angle after magnetic compensation, determined by the ratio of the minimum to the maximum value of the response signal of the single-beam optically pumped atomic magnetometer within half a cycle of the low-frequency modulation signal.

[0058] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A vector measurement method of a single-beam optical pumping atomic magnetometer based on a rotating excitation magnetic field, characterized in that, The method comprises the following steps: Step 1, start the single-beam optical pumping atomic magnetometer system, apply an excitation magnetic field along the y-axis coil, scan the excitation magnetic field frequency to determine the atomic Larmor precession resonance frequency in the chamber, that is, to determine the modulus of the magnetic field vector to be measured; Step 2, apply a double-sideband amplitude-modulated voltage signal to the x-axis coil and the y-axis coil to drive the coil to generate a rotating excitation magnetic field in the xoy plane; Step 3, compensate the z-axis magnetic field according to the minimum value of the single-beam optical pumping atomic magnetometer response signal, and re-determine the resonance frequency, that is, to determine the modulus of the magnetic field vector remaining after magnetic compensation; Step 4, determine the azimuth angle value range and the polar angle value range of the magnetic field vector to be measured according to the actively applied magnetic field, measure the azimuth angle of the magnetic field vector to be measured in real time according to the phase of the modulation signal corresponding to the minimum value of the single-beam optical pumping atomic magnetometer response signal, measure the polar angle of the magnetic field vector to be measured in real time according to the ratio of the minimum value to the maximum value of the single-beam optical pumping atomic magnetometer response signal, the z-axis compensation magnetic field, and the demodulated dispersion signal, and measure the modulus of the magnetic field vector to be measured in real time; The step 4 comprises: judging the value range of the azimuth angle according to the change of the resonance frequency by actively applying a positive magnetic field to the y axis, if the resonance frequency increases, the magnetic field to be measured has a positive projection on the y axis, then the value range of the azimuth angle is (0, π), otherwise it is (π, 2π); judging the value range of the polar angle according to the z axis compensation current, when the z axis compensation current produces a positive magnetic field along the z axis, the value range of the polar angle is Otherwise it is Step 4 comprises: where θ is the polar angle of the magnetic field vector to be measured, B z is the z-axis compensation magnetic field modulus, B r is the z-axis magnetic compensation residual magnetic field modulus, S is the size of the dispersion signal, K is the slope at the resonance frequency of the dispersion curve, θ1 is the polar angle after magnetic compensation, |B| is the modulus of the magnetic field vector to be measured, γ is the gyromagnetic ratio of the alkali metal atom, B1 is the excitation magnetic field amplitude, T1 is the longitudinal relaxation time, T2 is the transverse relaxation time, R min is the minimum value of the single-beam optical pumping atomic magnetometer response signal in a half cycle of the low-frequency modulation signal, R max is the maximum value of the single-beam optical pumping atomic magnetometer response signal in a half cycle of the low-frequency modulation signal.

2. The single-beam optical pumping atomic magnetometer vector measurement method based on a rotating excitation magnetic field according to claim 1, characterized in that, In step 1, by scanning the excitation magnetic field frequency applied along the y-axis, the curve of the single-beam optical pumping atomic magnetometer response signal with the excitation magnetic field frequency is obtained, and the excitation magnetic field frequency corresponding to the maximum amplitude of the curve is the Larmor precession frequency of the atom in the magnetic field, which is used as the frequency of the high-frequency carrier signal.

3. The single-beam optical pumping atomic magnetometer vector measurement method based on a rotating excitation magnetic field according to claim 1, characterized in that, In step 2, two low-frequency modulation signals with a phase difference of π / 2 are generated by a signal generator, and the low-frequency modulation wave of the x-axis is phase-advanced, and then multiplied by the high-frequency carrier to perform double-sideband amplitude modulation.

4. The single-beam optical pumping atomic magnetometer vector measurement method based on a rotating excitation magnetic field according to claim 1, characterized in that, In step 3, the atomic ensemble spin precession is driven by the rotating excitation magnetic field, and the single-beam optical pumping atomic magnetometer response signal is collected in real time, and the current value of the z-axis coil is changed so that the minimum value of the single-beam optical pumping atomic magnetometer response signal is 0, indicating that the z-axis magnetic field is compensated.

5. The method of claim 1, wherein the method is a single-beam optical pumping atomic magnetometer vector measurement method based on a rotationally excited magnetic field. The optical system of the single-beam optical pumping atomic magnetometer system comprises a laser, a polarization maintaining optical fiber with a collimating head, a linear polarizer, a 1 / 4 wave plate, a chamber, and a photodetector connected in sequence.

6. The single-beam optical pumping atomic magnetometer vector measurement method based on a rotating excitation magnetic field according to claim 5, characterized in that, The chamber is located in a non-magnetic electric heating system, and the non-magnetic electric heating system is located in a three-axis coil.

7. The single-beam optical pumping atomic magnetometer vector measurement method based on a rotating excitation magnetic field according to claim 6, characterized in that, The signal processing system comprises a transimpedance voltage amplifier, an input end of the transimpedance voltage amplifier is connected to the photodetector, an output end of the transimpedance voltage amplifier is connected to an input end of a lock-in amplifier, an output end of the lock-in amplifier is connected to a first input end of a first multiplier and a first input end of a second multiplier, a second input end of the first multiplier is connected to a first output end of a signal generator, a second input end of the second multiplier is connected to a second output end of the signal generator, an output end of the first multiplier is connected to an x-axis coil in the three-axis coil, an output end of the second multiplier is connected to a y-axis coil in the three-axis coil, and a z-axis coil in the three-axis coil is connected to a current source.

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