System and method for realizing SERF atom magnetometer in-situ magnetic field compensation in geomagnetic environment

Abstract

The invention discloses a system and a method for realizing SERF atom magnetometer in-situ magnetic field compensation in a geomagnetic environment, and belongs to the technical field of quantum precision measurement. The system comprises a laser, a polarizer, a 1 / 4 wave plate, an alkali metal atom gas chamber, a heating furnace, a signal acquisition and processing system and a three-axis magnetic field coil. According to the method, a large bias magnetic field is added in the laser propagation direction, the amplitude of an absorption signal curve in the geomagnetic environment is enhanced, meanwhile, the amplitudes of absorption signals in different magnetic fields are compared, a three-axis coil in the magnetometer is driven to carry out multiple times of compensation, and in-situ compensation of the magnetic field in the geomagnetic environment is achieved; the problems that magnetic field compensation in a geomagnetic environment consumes long time, and in-situ compensation cannot be achieved can be solved.

Description

Technical Field

[0001] The invention relates to a system and method for realizing in-situ magnetic field compensation of a SERF atomic magnetometer under a geomagnetic environment, and belongs to the technical field of quantum precision measurement. Background Art

[0002] The SERF atomic magnetometer is a new type of atomic magnetometer based on the interaction between light and atoms. It works in the SERF state and greatly narrows the atomic magnetic resonance linewidth. It has the characteristics of high sensitivity, small size, and low power consumption. It has been initially used in the fields of cardio-cerebral magnetic measurement and basic physics research. In order to realize the atomic SERF state effect, two basic conditions must be met: a zero magnetic field environment and a high atomic number density. Therefore, magnetic field compensation in the geomagnetic field environment is one of the key technologies for SERF atomic magnetometers in the field of geomagnetic and space magnetic detection.

[0003] Currently, there are two main ways to achieve a zero magnetic field environment: passive shielding and active compensation. Passive shielding usually uses a magnetic shielding tube made of Permalloy, which is large in size and cannot be used for detection in geomagnetic environments. Active compensation usually uses additional sensors for magnetic field detection and performs active compensation after obtaining the magnetic field size, which increases the cost and size of the system, takes a long time, and cannot achieve in-situ compensation. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to propose a system and method for realizing in-situ magnetic field compensation of a SERF atomic magnetometer under a geomagnetic environment, to drive the internal three-axis coil of the magnetometer to perform multiple compensations, and to solve the problem that magnetic field compensation under a geomagnetic environment takes a long time and cannot be compensated in-situ.

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

[0006] An in-situ magnetic field compensation system for SERF atomic magnetometer under geomagnetic environment, comprising a laser, a polarizer, a quarter wave plate, an alkali metal atom gas chamber, a heating furnace, a signal acquisition and processing system and a three-axis magnetic field coil;

[0007] The laser emits laser light that resonates with the D1 line of alkali metal atoms;

[0008] The polarizer and the quarter wave plate are placed in sequence in the direction of laser emission and parallel to the center point of the laser to generate circularly polarized laser.

[0009] The alkali metal atom gas chamber is placed in a heating furnace, and the heating furnace is heated to make the alkali metal atom gas chamber at a target temperature;

[0010] The heating furnace is in the magnetic field generated by the three-axis magnetic field coil. The circularly polarized laser interacts with the alkali metal atom gas chamber, and the laser containing the magnetic field information enters the signal acquisition and processing system to generate an absorption signal.

[0011] The signal acquisition and processing system compares the voltage of the absorbed signal under the action of the magnetic field and feeds back the voltage to the three-axis magnetic field coil to perform in-situ compensation for the ambient magnetic field.

[0012] Furthermore, the signal acquisition and processing system compares the signal voltage under the magnetic field and uses the feedback three-axis magnetic field coil to compensate for the ambient magnetic field in situ, specifically:

[0013] Three magnetic fields of -δB0, 0, and +δB0 are applied to any one of the three-axis magnetic field coils in sequence, with a step length of δB0; the signal acquisition and processing system records the intensity of the corresponding absorption signal, which is recorded as V -1 , V0 and V +1 ; By comparison and judgment: when V -1 <V0<V +1 When V -1 >V0>V +1 When V0>V +1 And V0>V -1 When V0 is equal to V +1 , V0 and V -1 The difference between the two is less than the set signal difference δV, completing the compensation of the magnetic field of the corresponding axis.

[0014] Furthermore, in-situ compensation is to increase the bias magnetic field along the laser propagation direction to enhance the amplitude of the absorption signal curve in the geomagnetic environment.

[0015] Furthermore, the alkali metal in the alkali metal atom gas chamber is one or two of rubidium, potassium and cesium.

[0016] Furthermore, the heating furnace heats the alkali metal atom gas chamber to keep the alkali metal atom gas chamber at a target temperature.

[0017] The compensation method of the in-situ magnetic field compensation system is adopted, and the compensation method specifically includes:

[0018] S1: Set the initial step size δB0 and the signal difference δV;

[0019] S2: The three-axis magnetic field coil adds a bias magnetic field on the z-axis; the z-axis is the laser propagation direction, and the x-axis is any direction on the transverse plane perpendicular to the laser propagation direction;

[0020] S3: The x-axis coil of the three-axis magnetic field coil is applied with magnetic fields of -δB0, 0, and +δB0, respectively. The signal acquisition and processing system records the corresponding absorption signal intensities of V -1 , V0 and V +1 , through comparison and judgment: when V-1 <V0<V +1 When V -1 >V0>V +1 When V0>V +1 And V0>V -1 When the x-axis magnetic field remains unchanged, the step length δB0 is halved until V0 and V +1 , V0 and V -1 The difference between the two is less than the signal difference δV, completing the initial compensation of the x-axis magnetic field;

[0021] S4: Repeat the operation of step 3 on the y-axis coil of the three-axis magnetic field coil to complete the initial compensation of the y-axis magnetic field;

[0022] S5: cancel the bias magnetic field on the z-axis, and then increase the magnetic field of 5μT to 10μT on the x-axis;

[0023] S6: Apply magnetic fields of -δB0, 0, and +δB0 to the z-axis coil, and record the corresponding absorption signal intensities as V -1 , V0 and V +1 , through comparison and judgment: when V -1 <V0<V +1 When V -1 >V0>V +1 When V0 <V +1 And V0 <V -1 When the z-axis magnetic field remains unchanged, the step length δB0 is halved until V0 and V +1 , V0 and V -1 The difference between the two is less than the signal difference δV, completing the initial compensation of the z-axis magnetic field;

[0024] S7: cancel the magnetic field on the x-axis, and then increase the bias magnetic field of 3μT to 5μT on the z-axis; repeat steps 3 to S6, wherein the magnetic field of 0.1μT to 0.5μT is increased in the x-axis direction during z-axis compensation, and the secondary magnetic field compensation of the x-axis, y-axis and z-axis is completed;

[0025] S8: cancel the magnetic field on the x-axis, and then increase the magnetic field of 0nT on the z-axis; repeat steps S3 to S6, wherein the magnetic field of 25nT to 40nT is increased in the x-axis direction during z-axis compensation, and three magnetic field compensations of the x-axis, y-axis and z-axis are completed;

[0026] S9: The magnetic field on the x-axis is canceled, the magnetic field compensation is completed, and the signal acquisition and processing system obtains the compensated magnetic field result.

[0027] Furthermore, in step S2, the three-axis magnetic field coil adds a bias magnetic field on the z-axis, and the magnitude of the bias magnetic field is 100 μT to 200 μT.

[0028] Furthermore, in step S2, the three-axis magnetic field coil adds a bias magnetic field on the z-axis, and the bias magnetic field is preferably twice the earth's magnetic field.

[0029] Furthermore, the initial step length δB0 is set within the range of 1 to 10 μT.

[0030] Furthermore, in step S5, a magnetic field of 5 μT to 10 μT is added on the x-axis, and the magnetic field value is selected according to the principle that the magnetic field applied on the x-axis is closest to the magnetic resonance line width before z-axis compensation.

[0031] The advantages of the present invention compared with the prior art are:

[0032] The rapid in-situ compensation system and method under the geomagnetic environment provided by the present invention enhance the amplitude of the absorption signal curve under the geomagnetic environment by adding a large bias magnetic field along the laser propagation direction, and drive the internal three-axis coil of the magnetometer to perform multiple compensations by comparing the amplitudes of the absorption signals under different magnetic fields, thereby realizing in-situ compensation of the magnetic field under the geomagnetic environment, and being able to solve the problems of long time consumption of magnetic field compensation under the geomagnetic environment and inability to perform in-situ compensation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0034] Figure 1 This is a schematic diagram of the structure of a SERF atomic magnetometer according to an embodiment of the present invention;

[0035] Figure 2 This is a simulation diagram of the atomic spin polarization rate and magnetic field change in the pump light direction of an embodiment of the present invention;

[0036] Figure 3 This is a flow chart of a method for realizing rapid in-situ compensation of a SERF atomic magnetometer under a geomagnetic environment according to an embodiment of the present invention;

[0037] Figure 4 A schematic diagram of a system for verifying rapid in-situ magnetic field compensation in a geomagnetic environment according to an embodiment of the present invention;

[0038] Figure 5 This is a diagram of the optical signal response of the system for realizing rapid in-situ compensation under the geomagnetic environment of an embodiment of the present invention;

[0039] Figure 6This is a diagram of magnetic field compensation results of the system implementing rapid in-situ compensation under the geomagnetic environment of an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0041] The present invention proposes a method for realizing rapid in-situ magnetic field compensation of a SERF atomic magnetometer under a geomagnetic environment. By applying a bias magnetic field, the in-situ magnetic field compensation can be realized rapidly, thereby reducing the compensation time.

[0042] First, the Bloch equation is used to describe the dynamic process of atomic spins in the alkali metal gas chamber. Taking into account physical phenomena such as laser pump polarization, magnetic precession and atomic spin relaxation, the Bloch equation is used to describe the dynamic evolution of atomic spin polarization:

[0043]

[0044] Where P represents the atomic spin polarization rate vector, B represents the magnetic field vector, γ represents the atomic gyromagnetic ratio, and R P represents the optical pumping rate, s represents the photon polarizability vector, T1 and T2 represent the longitudinal and transverse atomic relaxation times, respectively. Solve the steady-state solution with the z axis as the pumping light direction:

[0045]

[0046] Wherein, k is the ratio of the longitudinal relaxation rate to the transverse relaxation rate, k=R1 / R2, R1 and R2 represent the longitudinal relaxation rate and the transverse relaxation rate, respectively, and ΔB is the magnetic resonance line width.

[0047] The pump light direction is along the z-axis, and the voltage signal output by the photodetector is proportional to P z When the atomic system is in the geomagnetic environment, it can be seen from the steady-state solution that P z The amplitude is small, and it is difficult to achieve magnetic field compensation by absorbing signals, such as Figure 2 As shown in the figure, P z As the magnetic field environment changes, it can be found that after applying a 2-fold bias magnetic field, the absorption signal amplitude increases significantly. Magnetic field compensation can be achieved based on the absorption signal strength. By applying a bias magnetic field, in-situ magnetic field compensation can be quickly achieved, reducing the compensation time.

[0048] Build an in-situ magnetic field compensation system for SERF atomic magnetometer in geomagnetic environment, such as Figure 1 As shown, it includes a laser 1, a polarizer 2, a quarter wave plate 3, an alkali metal atom gas chamber 4, a heating furnace 5, a signal acquisition and processing system 6 and a three-axis magnetic field coil 7. When the magnetic field is compensated in situ under the geomagnetic environment, the laser 1 emits a laser that resonates with the alkali metal atom D1 line, and the polarizer 2 and the quarter wave plate 3 are placed in the laser emission direction of the laser in sequence and are placed parallel to the common center point of the laser to generate circularly polarized laser light, which acts on the alkali metal atom gas chamber 4 to obtain a laser containing magnetic field information that enters the signal acquisition and processing system 6 to generate an absorption signal. By comparing the signal size under the action of different magnetic fields, the signal is fed back to the three-axis magnetic field coil 7 to perform in-situ compensation for the environmental magnetic field, wherein the three-axis magnetic field coil 7 needs to be able to meet the current requirement of the corresponding bias magnetic field, and the heating furnace 5 makes the alkali metal atom gas chamber 4 at the target temperature.

[0049] This method is Figure 3 As shown, the z-axis is the direction of laser propagation, and the maximum magnetic field of the geomagnetic environment is 50μT, specifically including:

[0050] S1: Set the initial step size δB0 and the signal difference δV; add a bias magnetic field of 100μT on the z-axis; δB0 is generally set in the range of 1 to 10μT.

[0051] S2: Apply magnetic fields of -δB0, 0, and +δB0 to the x-axis coil, and record the corresponding absorption signal intensities as V -1 , V0 and V +1 , through comparison and judgment: when V -1 <V0<V +1 When V -1 >V0>V +1 When V0>V +1 And V0>V -1 When the x-axis magnetic field remains unchanged, the step length δB0 is halved until V0 and V +1 , V0 and V -1 The difference between the two is less than the signal difference δV, completing the initial compensation of the x-axis magnetic field.

[0052] S3: Repeat the operation of step 2 on the y-axis coil to complete the initial compensation of the y-axis magnetic field.

[0053] S4: Canceling the bias magnetic field on the z-axis and then adding a 5μT to 10μT magnetic field on the x-axis can more quickly complete the z-axis compensation, wherein the magnetic field applied on the x-axis is generally close to the magnetic resonance line width before the z-axis compensation.

[0054] S5: Apply magnetic fields of -δB0, 0, and +δB0 to the z-axis coil, and record the corresponding absorption signal intensities as V -1 , V0 and V +1 , through comparison and judgment: when V -1 <V0<V +1 When V -1 >V0>V +1 When V0 <V +1 And V0 <V -1 When the z-axis magnetic field remains unchanged, the step length δB0 is halved until V0 and V +1 , V0 and V -1 The difference between the two is less than the signal difference δV, completing the initial compensation of the z-axis magnetic field.

[0055] S6: cancel the magnetic field on the x-axis. Since the residual magnetic field is within the range of 1.5 μT after the first magnetic field compensation, a bias magnetic field of 3 μT to 5 μT is added to the z-axis.

[0056] S7: Repeat steps 2 to 5, wherein during z-axis compensation, a bias magnetic field of 0.1 μT to 0.5 μT is added in the x-axis direction to complete secondary magnetic field compensation of the x-axis, y-axis and z-axis.

[0057] S8: Cancel the magnetic field on the x-axis. After the second compensation, the residual magnetic field is close to zero magnetic field. Add a 0nT bias magnetic field on the z-axis.

[0058] S9: repeating steps 2 to 5, wherein during z-axis compensation, the magnetic field in the x-axis direction is increased by 25nT to 40nT, completing three magnetic field compensations in the x-axis, y-axis and z-axis directions;

[0059] S10: The magnetic field on the x-axis is canceled, the magnetic field compensation is completed, and the signal acquisition and processing system obtains the compensated magnetic field result.

[0060] In order to verify the compensation method provided by the present invention, a test system was built, such as Figure 4 As shown in FIG. 1 , the system consists of a current source, a magnetic shielding tube, a three-axis magnetic field coil, a SERF atomic magnetometer, and a signal acquisition and processing system. The magnetic shielding tube shields the external magnetic field, and the current source provides current to the three-axis magnetic field coil, which can provide a stable and known geomagnetic field environment. Among them, when 39915nT is applied to the y-axis and 34560nT is applied to the z-axis (the total environmental magnetic field is 52797nT), according to the above specific steps, the bias magnetic field in the direction of the pump light is changed multiple times, and the compensation process and compensation results are shown in FIG. Figure 5 , Figure 6As shown, the compensation time is 11.2s, the compensation magnetic field is 52864nT, and the compensation error is 0.12%. From the compensation effect, it can be seen that this compensation method can realize rapid in-situ magnetic field compensation in the geomagnetic environment.

[0061] The above-described embodiments are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A SERF atomic magnetometer in-situ magnetic field compensation system under geomagnetic environment, characterized in that: It includes laser, polarizer, quarter wave plate, alkali metal atom gas chamber, heating furnace, signal acquisition and processing system and three-axis magnetic field coil; The laser emits laser light that resonates with the D1 line of alkali metal atoms; The polarizer and the quarter wave plate are placed in sequence in the direction of laser emission and parallel to the center point of the laser to generate circularly polarized laser. The alkali metal atom gas chamber is placed in a heating furnace, and the heating furnace is heated to make the alkali metal atom gas chamber at a target temperature; The heating furnace is in the magnetic field generated by the three-axis magnetic field coil. The circularly polarized laser interacts with the alkali metal atom gas chamber, and the laser containing the magnetic field information enters the signal acquisition and processing system to generate an absorption signal. The signal acquisition and processing system compares the voltage of the absorbed signal under the action of the magnetic field and feeds back the voltage to the three-axis magnetic field coil to perform in-situ compensation for the ambient magnetic field.

2. The in-situ magnetic field compensation system according to claim 1, characterized in that: The signal acquisition and processing system compares the signal voltage under the magnetic field and uses the feedback three-axis magnetic field coil to compensate for the ambient magnetic field in situ. Specifically: Three magnetic fields of -δB0, 0, and +δB0 are applied to any one of the three-axis magnetic field coils in sequence, with a step length of δB0; the signal acquisition and processing system records the intensity of the corresponding absorption signal, which is recorded as V -1 , V0 and V +1 ; By comparison and judgment: when V -1 <V0<V +1 When V -1 >V0>V +1 When V0>V +1 And V0>V -1 When V0 is equal to V +1 , V0 and V -1 The difference between the two is less than the set signal difference δV, completing the compensation of the magnetic field of the corresponding axis.

3. The in-situ magnetic field compensation system according to claim 1, characterized in that: In-situ compensation is to increase the bias magnetic field along the direction of laser propagation to enhance the amplitude of the absorption signal curve in the geomagnetic environment.

4. The in-situ magnetic field compensation system according to claim 1, characterized in that: The alkali metal in the alkali metal atom gas chamber is one or two of rubidium, potassium and cesium.

5. The in-situ magnetic field compensation system according to claim 1, characterized in that: The heating furnace heats the alkali metal atom gas chamber so that the alkali metal atom gas chamber is at a target temperature.

6. The compensation method of the in-situ magnetic field compensation system according to claim 1, characterized in that: The in-situ compensation methods specifically include: S1: Set the initial step size δB0 and the signal difference δV; S2: The three-axis magnetic field coil adds a bias magnetic field on the z-axis; the z-axis is the laser propagation direction, and the x-axis is any direction on the transverse plane perpendicular to the laser propagation direction; S3: The x-axis coil of the three-axis magnetic field coil is subjected to magnetic fields of -δB0, 0, and +δB0, respectively. The signal acquisition and processing system records the corresponding absorption signal intensities as V -1 , V0 and V +1 , through comparison and judgment: when V -1 <V0<V +1 When V -1 >V0>V +1 When V0>V +1 And V0>V -1 When the x-axis magnetic field remains unchanged, the step length δB0 is halved until V0 and V +1 , V0 and V -1 The difference between the two is less than the signal difference δV, completing the initial compensation of the x-axis magnetic field; S4: Repeat the operation of step 3 on the y-axis coil of the three-axis magnetic field coil to complete the initial compensation of the y-axis magnetic field; S5: cancel the bias magnetic field on the z-axis, and then increase the magnetic field of 5μT to 10μT on the x-axis; S6: Apply magnetic fields of -δB0, 0, and +δB0 to the z-axis coil, and record the corresponding absorption signal intensities as V -1 , V0 and V +1 , through comparison and judgment: when V -1 <V0<V +1 When V -1 >V0>V +1 When V0 <V +1 And V0 <V -1 When the z-axis magnetic field remains unchanged, the step length δB0 is halved until V0 and V +1 , V0 and V -1 The difference between the two is less than the signal difference δV, completing the initial compensation of the z-axis magnetic field; S7: cancel the magnetic field on the x-axis, and then increase the bias magnetic field of 3μT to 5μT on the z-axis; repeat steps 3 to S6, wherein the magnetic field of 0.1μT to 0.5μT is increased in the x-axis direction during z-axis compensation, and the secondary magnetic field compensation of the x-axis, y-axis and z-axis is completed; S8: cancel the magnetic field on the x-axis, and then increase the magnetic field of 0nT on the z-axis; repeat steps S3 to S6, wherein the magnetic field of 25nT to 40nT is increased in the x-axis direction during z-axis compensation, and three magnetic field compensations of the x-axis, y-axis and z-axis are completed; S9: The magnetic field on the x-axis is canceled, the magnetic field compensation is completed, and the signal acquisition and processing system obtains the compensated magnetic field result.

7. The in-situ magnetic field compensation method according to claim 6, characterized in that: In step S2, the three-axis magnetic field coil adds a bias magnetic field on the z-axis, and the magnitude of the bias magnetic field is 100 μT to 200 μT.

8. The in-situ magnetic field compensation method according to claim 7, characterized in that: In step S2, the three-axis magnetic field coil adds a bias magnetic field on the z-axis, and the bias magnetic field is preferably twice the earth's magnetic field.

9. The in-situ magnetic field compensation method according to claim 6, characterized in that: The initial step size δB0 is set in the range of 1 to 10 μT.

10. The in-situ magnetic field compensation method according to claim 6, characterized in that: In step S5, a magnetic field of 5 μT to 10 μT is added on the x-axis, and the magnetic field value is selected according to the principle that the magnetic field applied on the x-axis is closest to the magnetic resonance line width before z-axis compensation.

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