A Miniaturized Closed-Loop FID Scalar Atomic Magnetometer and Its Implementation Method

Abstract

The present invention relates to a miniaturized closed-loop FID scalar atomic magnetometer and its implementation method, belonging to the field of atomic magnetic measurement. This method uses a self-made electronics system to achieve the closed-loop working mode of the FID magnetometer. By real-time correcting the modulation frequency of the pumping light, the magnetometer can still maintain high sensitivity under a large magnetic field change rate, breaking through the performance limitation between the dynamic range and sensitivity of the open-loop FID magnetometer. The interaction between the self-made frequency meter and the timing control system is the core component of the closed-loop of this magnetometer system. The present invention can measure a magnetic field with a large change rate at high speed, with high sensitivity and high accuracy, and plays an important role in the application of on-site magnetic measurement.

Description

Technical Field

[0001] The present invention relates to the fields of atomic devices and electronics, and particularly to a miniaturized closed-loop FID (Free-Induction-Decay) scalar atomic magnetometer and a method for realizing the same. Background Art

[0002] As a precision magnetic field measurement sensor, atomic magnetometers play an important role in fields such as basic physical research, geomagnetism research, and biomedical imaging. According to the working principle, atomic magnetometers can be divided into two categories: radio frequency modulation magnetometers and all-optical magnetometers. Compared with the former, the latter does not require an additional applied modulation magnetic field, avoiding the problem of the modulation magnetic field deteriorating the system noise. The FID magnetometer belongs to the all-optical magnetometer. By separating the optical pumping stage and the optical detection stage in the time domain, it avoids the optical frequency shift effect caused by the pumping light, so the magnetic measurement accuracy is higher, and it is currently the mainstream solution in the field of atomic magnetometers.

[0003] Existing FID magnetometers adopt an open-loop working mode, in which the pumping light is modulated at the Larmor precession frequency of the atoms around the initial magnetic field to maximize the amplitude of the FID signal. However, there is a mutual restriction between the dynamic range and the sensitivity performance of the open-loop FID magnetometer. For example, for a rubidium-87 atomic magnetometer with 200 Torr nitrogen gas filled in the atomic gas cell: when the measured magnetic field changes by more than 50 nT, the frequency difference between the pumping light modulation frequency and the atomic Larmor precession frequency will be greater than 350 Hz. At this time, the amplitude of the FID signal will decrease by about 10%, resulting in a significant reduction in the sensitivity of the magnetometer system. Therefore, in practical applications, it is usually necessary to sacrifice the dynamic range to ensure the magnetic measurement sensitivity, which is obviously not the best solution. Summary of the Invention

[0004] The purpose of the present invention is to provide a miniaturized closed-loop FID scalar atomic magnetometer and a method for realizing the same.

[0005] According to a first aspect of the present invention, a miniaturized closed-loop FID scalar atomic magnetometer is provided, which is composed of a self-made miniaturized FID atomic magnetometer control circuit and a magnetic probe. The magnetic probe integrates a small-volume atomic gas cell, a first photodetector, a second photodetector, a third photodetector, and a fourth photodetector. The self-made miniaturized FID atomic magnetometer control circuit includes a pumping light source, a detection light source, a laser control unit, a pumping light modulation unit, a gas cell heating unit, and a frequency meter unit. Among them, the gas cell heating unit is used to heat the atoms in the small-volume atomic gas cell. The first photodetector and the second photodetector are respectively used to monitor the light intensities of the detection light and the pumping light. The third photodetector and the fourth photodetector are used to monitor the light intensity of the detection light after interacting with the atoms in the small-volume atomic gas cell. The laser control unit is used to provide driving currents for the pumping light source and the detection light source. The pumping light modulation unit is connected to the pumping light source and conveys the modulated pumping light to the magnetic probe through an optical fiber. The detection light output by the detection light source is conveyed to the magnetic probe. The frequency meter unit calculates the FID signal frequency in the previous detection stage and feeds it back to the pumping light modulation unit as the pumping light modulation frequency in the next cycle.

[0006] According to a second aspect of the present invention, a method for implementing an atomic magnetometer is provided, including:

[0007] The first step is to fabricate a small-volume atomic gas cell and fill the small-volume atomic gas cell with rubidium-87 atoms and nitrogen.

[0008] The second step is the assembly of the FID scalar atomic magnetometer: on the 3D-printed magnetic probe, a small-volume atomic gas cell, a gas cell heating unit, a first photodetector, a second photodetector, a third photodetector, and a fourth photodetector are integrated.

[0009] The third step is to use the gas cell heating unit to control the gas cell temperature of the small-volume atomic gas cell at 90 °C so that there are gaseous atoms with a stable atomic number density in the small-volume atomic gas cell.

[0010] The fourth step is to use the laser control unit to drive the pumping light source and the detection light source to output pumping light and detection light respectively.

[0011] The fifth step is to perform the closed-loop feedback signal processing of the FID scalar atomic magnetometer, where: the pumping light modulation unit outputs a trigger signal and frequency-modulates the pumping light intensity during the pumping stage; the frequency meter unit calculates the FID signal frequency in the previous detection stage and feeds it back to the pumping light modulation unit as the pumping light modulation frequency in the next cycle.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] 1) The closed-loop operation mode of the FID magnetometer is realized based on the proposed self-made electronics system. By real-time correcting the modulation frequency of the pumping light, it still has high sensitivity during high-dynamic-range measurements, breaking through the performance limitations of the open-loop FID magnetometer in terms of dynamic range and sensitivity, and endowing it with the ability for on-site magnetic measurement;

[0014] 2) A self-made highly integrated electronics system is used to replace the large-volume commercial instruments, realizing the miniaturization of the closed-loop FID magnetometer system;

[0015] 3) A magnetic probe is used to achieve precise positioning of the optical elements, avoiding the cumbersome optical path adjustment process, and facilitating the miniaturization integration and popularization application of the magnetometer system. Description of the Drawings

[0016] Figure 1 It is a block diagram of a miniaturized closed-loop FID scalar atomic magnetometer of the present invention;

[0017] Figure 2 It is a schematic diagram of the magnetic probe and its internal optical path in the present invention;

[0018] Figure 3 It is a closed-loop feedback signal processing flow chart and signal processing timing diagram of the FID scalar atomic magnetometer system of the present invention.

[0019] Reference Signs:

[0020] Self-made miniaturized FID atomic magnetometer control circuit 210, magnetic probe 220, small-volume atomic gas cell 221, first photodetector 222, second photodetector 223, third photodetector 224, fourth photodetector 225, pumping light source 211, detection light source 212, laser control unit 213, pumping light modulation unit 214, gas cell heating unit 215, and frequency meter unit 216, operational amplifier 217;

[0021] Clamping head 1, first polarization beam splitter 2, first 1 / 2 wave plate 3, second polarization beam splitter 4, lens 5, 1 / 4 wave plate 7, first plano-convex lens 8, collimating head 9, linear polarizer 10, beam splitter 12, second plano-convex lens 13, second 1 / 2 wave plate 14, third polarization beam splitter 15. Detailed Embodiments

[0022] In order to make the objectives, technical solutions and advantages of the present application clearer, the following further describes the present application in detail with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0023] Figure 1 It is a block diagram of a miniaturized closed-loop FID scalar atomic magnetometer of the present invention. As Figure 1As shown in the figure, the miniaturized closed-loop FID scalar atomic magnetometer consists of a self-made miniaturized FID atomic magnetometer control circuit 210 and a magnetic probe 220. The magnetic probe 220 integrates a small-volume atomic gas cell 221, a first photodetector 222, a second photodetector 223, a third photodetector 224, and a fourth photodetector 225. The self-made miniaturized FID atomic magnetometer control circuit 210 includes a pumping light source 211, a detection light source 212, a laser control unit 213, a pumping light modulation unit 214, a gas cell heating unit 215, a frequency meter unit 216, and an operational amplifier 217. Among them, the small-volume atomic gas cell 221 can contain a Herriott multi-reflection cavity and can be a container for isotope rubidium-87 atoms and buffer gas nitrogen. The gas cell heating unit 215 is used to heat the atoms in the small-volume atomic gas cell 221 and can also be used to maintain the density stability of gaseous atoms. The first photodetector 222 and the second photodetector 223 are respectively used to monitor the light intensities of the detection light and the pumping light. The third photodetector 224 and the fourth photodetector 225 are used to monitor the light intensity of the detection light after interacting with atoms in the small-volume atomic gas cell 221. The laser control unit 213 is used to provide driving currents for the pumping light source 211 and the detection light source 212 and control the pumping light source 211 and the detection light source 212. The former can output a laser with a resonance frequency of the D1 transition line of rubidium-87 atoms, and the latter can output a laser far detuned from the D1 transition line of rubidium-87 atoms. The pumping light modulation unit 214 and the pumping light source 211 can be connected by an optical fiber, used to realize the modulation of the pumping light intensity or the laser frequency, and deliver the modulated pumping light to the magnetic probe through the optical fiber. The detection light output by the detection light source 212 can be directly delivered to the magnetic probe 220 through the optical fiber. The frequency meter unit 216 calculates the frequency of the FID signal in the previous cycle of the detection stage and feeds it back to the pumping light modulation unit 214 as the pumping light modulation frequency for the next cycle. The frequency meter unit 216 is connected to an operational amplifier 217, and the operational amplifier 217 is used to convert the light intensity signals monitored by the third photodetector 224 and the fourth photodetector 225 into voltage signals and extract the corresponding FID signals.

[0024] In one embodiment, the small-volume atomic gas cell 221 is fabricated by anodic bonding. The magnetic probe 220 is fabricated by 3D printing or machining and is used for the precise positioning and assembly of the atomic gas cell and the photodetector, and should have sufficient fabrication accuracy. The laser control unit 213 provides drive currents for the pumping light source and the detection light source through a constant current source circuit, and uses a proportional-integral control circuit to achieve temperature closed-loop locking to ensure that the pumping light source and the detection light source generate pumping light and detection light with stable frequencies and constant light intensities. The pumping light modulation unit 214 modulates the light intensity or the laser frequency of the pumping light generated by the pumping light source at a frequency f (f is the Larmor precession frequency of the atom around the external magnetic field). The frequency meter unit 216 calculates the frequency of the FID signal and calculates the magnetic field strength according to the gyromagnetic ratio of rubidium 87 atoms.

[0025] In one embodiment, the gas cell heating unit 215 uses high-frequency alternating current to drive a non-magnetic heating sheet to heat the atoms in the small-volume atomic gas cell 221, and by controlling the heating temperature, the density of the gaseous atoms is stabilized. The non-magnetic heating sheet is closely attached to the lower surface of the small-volume atomic gas cell 221. The small-volume atomic gas cell 221 and the non-magnetic heating sheet are assembled together by designing a 3D printing structure inside the magnetic probe, and the assembly is wrapped with a heat-insulating material to reduce the heat exchange between the small-volume atomic gas cell 221 and the external environment, thereby reducing the heating power consumption of the magnetometer.

[0026] The internal assembly and optical path of the magnetic probe are described below.

[0027] Figure 2 This is a schematic diagram of the atomic gas cell assembly and its internal optical path of the magnetic probe in the present invention. As Figure 2As shown in the figure, the atomic gas cell assembly of the magnetic probe and its internal optical path are as follows: The pumping light is introduced into the magnetic probe through an optical fiber (fixed by the clamping head 1), and then polarized and purified by the first polarization beam splitter 2. Then, it is divided into two parts with a ratio of 12:1 by the first 1 / 2 wave plate 3 and the second polarization beam splitter 4. Among them, the light with an intensity ratio of 1 / 13 is focused on the second photodetector 223 by the lens 5 for monitoring the pumping light intensity; the light with an intensity ratio of 12 / 13 is converted into circularly polarized light by the 1 / 4 wave plate 7, and then passes through the first plano-convex lens 8 to uniformly polarize the rubidium-87 atoms in the atomic gas cell. The detection light is introduced into the magnetic probe through an optical fiber (fixed by the fiber collimator 9). The fiber collimator 9 is a special 3D printed structure with a fixed plano-convex lens inside, which is used to collimate the detection light. The collimated detection light is polarized and purified by the linear polarizer 10, and then divided into two parts with a ratio of 12:1 by the beam splitter 12. Among them, the light with an intensity ratio of 1 / 13 is received by the first photodetector 222 for monitoring the detection light intensity; the light with an intensity ratio of 12 / 13 is incident on the small-volume atomic gas cell 221, interacts with the atoms, and then exits. The exiting light is first focused by the second plano-convex lens 13, and then split into two parts with a ratio of 1:1 by the second 1 / 2 wave plate 14 and the third polarization beam splitter 15 to the third photodetector 224 and the fourth photodetector 225. Finally, the two detected light intensities are subtracted to obtain the FID signal.

[0028] So far, the optical element positioning of the main part of the magnetometer has been realized with the assistance of the magnetic probe, avoiding the cumbersome optical path adjustment link and saving a large amount of space.

[0029] Figure 3 This is the closed-loop feedback signal processing block diagram and signal processing timing diagram of the FID scalar atomic magnetometer of the present invention. Compared with the traditional open-loop FID magnetometer system, a frequency meter unit and a pumping light modulation unit are introduced to realize the closed loop of the FID magnetometer. Among them, the pumping light modulation unit outputs a trigger signal to control the pumping-detection process of the magnetometer and indicates the signal processing timing in the feedback system; the frequency meter unit calculates the FID signal frequency in the previous detection stage and feeds it back to the pumping light modulation unit as the pumping light modulation frequency in the next cycle. Taking three pumping-detection cycles ( , , ) as an example, the specific implementation steps of the above feedback system are as follows:

[0030] Step a, In the cycle, the rising edge of the trigger signal output by the pumping light modulation unit triggers the pumping light modulation unit to modulate the pumping light at the frequency , and the falling edge of the trigger signal output by the pumping light modulation unit triggers the frequency meter unit to collect the FID signal in the cycle, denoted as ;

[0031] Step b, During a period, the rising edge of the trigger signal output by the pump light modulation unit triggers the pump light modulation unit to modulate the pump light at a frequency and triggers the frequency meter unit to calculate the frequency of the signal, denoted as . The falling edge of the trigger signal output by the pump light modulation unit triggers the frequency meter unit to collect the FID signal of the period, denoted as , and transmits it to the pump light modulation unit;

[0032] Step c, During a period, the rising edge of the trigger signal output by the pump light modulation unit triggers the pump light modulation unit to modulate the pump light at a frequency and triggers the frequency meter unit to calculate the frequency of the signal, denoted as . The falling edge of the trigger signal output by the pump light modulation unit triggers the frequency meter unit to collect the FID signal of the period, denoted as , and transmits it to the pump light modulation unit;

[0033] Step d, Repeating step c can continuously realize the closed loop of the FID scalar atomic magnetometer.

[0034] In one embodiment, the high level of the trigger signal lasts for 3 milliseconds and the low level lasts for 5 milliseconds, and the magnetic field sampling rate is 125 Hz.

[0035] According to an embodiment of the present invention, there is provided a method for realizing a miniaturized closed-loop FID scalar atomic magnetometer, including:

[0036] The first step is to fabricate a small-volume atomic cell and fill the small-volume atomic cell with rubidium-87 atoms and nitrogen;

[0037] The second step is the assembly of the FID scalar atomic magnetometer: on a 3D-printed magnetic probe, integrate a small-volume atomic cell, a cell heating unit, a first photodetector, a second photodetector, a third photodetector, and a fourth photodetector. In one embodiment, the 3D-printed magnetic probe is a platform with an accuracy of 0.05 mm;

[0038] The third step is to use the cell heating unit to control the cell temperature of the small-volume atomic cell at 90 °C so that there are gaseous atoms with a stable atomic number density in the small-volume atomic cell;

[0039] The fourth step is to use the laser control unit to drive the pump light source and the detection light source to respectively output pump light (the frequency is resonant with the D1 transition line of rubidium-87 atoms) and detection light (the frequency deviates from the D1 transition line of rubidium-87 atoms by 80 GHz);

[0040] In the fifth step, perform the closed-loop feedback signal processing of the FID scalar atomic magnetometer, where: the pump light modulation unit outputs a trigger signal and frequency-modulates the intensity of the pump light during the pumping stage; the frequency meter unit calculates the frequency of the FID signal in the previous detection stage and feeds it back to the pump light modulation unit as the pump light modulation frequency for the next cycle.

[0041] For the specific implementation process of the fifth step, reference can be made to the above description of Figure 3 .

[0042] The closed-loop working mode of the FID scalar atomic magnetometer can maintain high sensitivity under a large magnetic field change rate. Compared with the open-loop mode, this mode can respond to a magnetic field change of 2600 nT / s and plays an important role in on-site magnetic measurement.

[0043] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0044] The above-described embodiments only represent several implementation manners of the present application. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A miniaturized closed-loop FID scalar atomic magnetometer, characterized in that: The invention is composed of a self-made miniaturized FID atomic magnetometer control circuit (210) and a magnetic probe (220), wherein the magnetic probe integrates a small-volume atomic gas chamber (221), a first photodetector (222), a second photodetector (223), a third photodetector (224), and a fourth photodetector (225); the self-made miniaturized FID atomic magnetometer control circuit comprises a pumping light source (211), a detection light source (212), a laser control unit (213), a pumping light modulation unit (214), a gas chamber heating unit (215), and a frequency meter unit (216); wherein the gas chamber heating unit (215) is used to heat the atoms in the small-volume atomic gas chamber (221). The first photodetector and the second photodetector are used to monitor the intensity of the detection light and the pumping light respectively; the third photodetector and the fourth photodetector are used to monitor the intensity of the detection light after the detection light interacts with atoms in the small-volume atomic gas chamber; the laser control unit is used to provide driving current for the pumping light source and the detection light source; the pumping light modulation unit (214) is connected to the pumping light source (211) and transmits the modulated pumping light to the magnetic probe through the optical fiber; the detection light output by the detection light source (212) is transmitted to the magnetic probe (220); the frequency meter unit (216) calculates the FID signal frequency of the detection stage of the previous cycle and feeds it back to the pumping light modulation unit (214) as the pumping light modulation frequency of the next cycle, The closed-loop feedback signal processing of the FID scalar atomic magnetometer includes: the pump light modulation unit outputs a trigger signal and performs frequency modulation on the pump light intensity during the pumping stage; the frequency meter unit calculates the FID signal frequency of the previous cycle detection stage and feeds it back to the pump light modulation unit as the pump light modulation frequency of the next cycle, including: Step a, first cycle The rising edge of the trigger signal output by the pump light modulation unit triggers the pump light modulation unit to generate a pulse at a frequency of Modulate the pump light, and the falling edge of the trigger signal output by the pump light modulation unit triggers the frequency meter unit to collect the first cycle The FID signal is recorded as ; Step b, second cycle The rising edge of the trigger signal output by the pump light modulation unit triggers the pump light modulation unit to generate a pulse at a frequency of Modulate the pump light and trigger the frequency counter unit to calculate The frequency of the signal is denoted by The falling edge of the trigger signal output by the pump light modulation unit triggers the frequency meter unit to collect cycle The FID signal is recorded as , and Transmitted to the pump light modulation unit; Step c, third cycle The rising edge of the trigger signal output by the pump light modulation unit triggers the pump light modulation unit to generate a pulse at a frequency of Modulate the pump light and trigger the frequency counter unit to calculate The frequency of the signal is calculated as The falling edge of the trigger signal output by the pump light modulation unit triggers the frequency meter unit to collect cycle The FID signal is recorded as , and Transmitted to the pump light modulation unit; Step d, repeating step c, thereby continuously realizing the closed loop of the FID scalar atomic magnetometer.

2. The miniaturized closed-loop FID scalar atomic magnetometer according to claim 1, characterized in that: The small-volume atomic gas chamber (221) is manufactured by an anodic bonding method, and the magnetic probe (220) is manufactured by 3D printing or machining, and is used for accurate positioning and assembly of the small-volume atomic gas chamber (221) and the first photodetector (222), the second photodetector (223), the third photodetector (224), and the fourth photodetector (225).

3. The miniaturized closed-loop FID scalar atomic magnetometer according to claim 1, characterized in that: The laser control unit (213) provides driving current for the pumping light source and the detection light source through a constant current source circuit, and uses a proportional-integral control circuit to achieve temperature closed-loop locking, thereby ensuring that the pumping light source and the detection light source generate pumping light and detection light with stable frequency and constant power.

4. The miniaturized closed-loop FID scalar atomic magnetometer according to claim 1, characterized in that: The gas chamber heating unit (215) utilizes high-frequency alternating current to drive a non-magnetic heating sheet to heat atoms in the small-volume atomic gas chamber (221), and adjusts the heating current based on the temperature of the small-volume atomic gas chamber (221) measured by a thermocouple to stabilize the density of gaseous atoms.

5. The miniaturized closed-loop FID scalar atomic magnetometer according to claim 1, characterized in that: The non-magnetic heating plate is closely attached to the lower surface of the small-volume atomic gas chamber (221), and the thermocouple is closely attached to the side of the small-volume atomic gas chamber (221). The small-volume atomic gas chamber (221), the non-magnetic heating plate and the thermocouple are assembled together by designing a 3D printing structure inside the magnetic probe to form an assembly, and the assembly is wrapped with a thermal insulation material.

6. The miniaturized closed-loop FID scalar atomic magnetometer according to claim 1, characterized in that: The internal structure of the magnetic probe is as follows: The pumping light is introduced into the magnetic probe through the optical fiber, and then polarized and purified by the first polarization beam splitter (2), and then divided into two parts with a ratio of 12:1 by the first 1 / 2 glass plate (3) and the second polarization beam splitter (4), wherein the light with a light intensity of 1 / 13 is converged on the second photodetector (223) through the lens (5) for monitoring the pumping light intensity; the light with a light intensity of 12 / 13 is converted into circularly polarized light through the 1 / 4 glass plate (7), and then passes through the first plano-convex lens (8) to uniformly polarize the rubidium 87 atoms in the atomic gas chamber; the detection light is introduced into the magnetic probe through the optical fiber, and passes through the linear polarizer (10) is polarized and purified, and then the light is divided into two parts with a ratio of 12:1 by a spectroscope (12). The light with a ratio of 1 / 13 of the light intensity is received by a first photodetector (222) for detecting light intensity monitoring. The light with a ratio of 12 / 13 of the light intensity enters the atomic gas chamber and reacts with the atoms before being emitted. The emitted light is first converged by a second plano-convex lens (13), and then split by a second 1 / 2 glass slide (14) and a third polarization spectroscope (15) with a ratio of 1:1 to a third photodetector (224) and a fourth photodetector (225). Finally, the two detected light intensities are subtracted to obtain an FID signal.

7. A method for realizing an atomic magnetometer, for realizing a miniaturized closed-loop FID scalar atomic magnetometer according to any one of claims 1 to 6, characterized in that: include: The first step is to prepare a small-volume atomic gas chamber and fill the small-volume atomic gas chamber with rubidium 87 atoms and nitrogen; The second step is to assemble the FID scalar atomic magnetometer: integrate the small-volume atomic gas chamber, the non-magnetic heating plate and thermocouple required for the gas chamber heating unit, the first photodetector, the second photodetector, the third photodetector, and the fourth photodetector on the 3D printed magnetic probe; The third step is to control the gas chamber temperature of the small-volume atomic gas chamber at 90° C. by using a gas chamber heating unit, so that gaseous atoms with a stable atomic number density exist in the small-volume atomic gas chamber; The fourth step is to use the laser control unit to drive the pumping light source and the detection light source to output the pumping light and the detection light respectively; The fifth step is to perform closed-loop feedback signal processing of the FID scalar atomic magnetometer, wherein: the pump light modulation unit outputs a trigger signal and performs frequency modulation on the pump light intensity during the pumping phase; the frequency meter unit calculates the FID signal frequency of the previous cycle detection phase and feeds it back to the pump light modulation unit as the pump light modulation frequency of the next cycle. The fifth step includes: Step a, first cycle The rising edge of the trigger signal output by the pump light modulation unit triggers the pump light modulation unit to generate a pulse at a frequency of Modulate the pump light, and the falling edge of the trigger signal output by the pump light modulation unit triggers the frequency meter unit to collect the first cycle The FID signal is recorded as ; Step b, second cycle The rising edge of the trigger signal output by the pump light modulation unit triggers the pump light modulation unit to generate a pulse at a frequency of Modulate the pump light and trigger the frequency counter unit to calculate The frequency of the signal is denoted by The falling edge of the trigger signal output by the pump light modulation unit triggers the frequency meter unit to collect cycle The FID signal is recorded as , and Transmitted to the pump light modulation unit; Step c, third cycle The rising edge of the trigger signal output by the pump light modulation unit triggers the pump light modulation unit to generate a pulse at a frequency of Modulate the pump light and trigger the frequency counter unit to calculate The frequency of the signal is calculated as The falling edge of the trigger signal output by the pump light modulation unit triggers the frequency meter unit to collect cycle The FID signal is recorded as , and Transmitted to the pump light modulation unit; Step d, repeating step c, thereby continuously realizing the closed loop of the FID scalar atomic magnetometer.

8. The method for realizing the atomic magnetometer according to claim 7, characterized in that: In the second step, the 3D printed magnetic probe is a platform with 0.05mm accuracy.

9. The method for realizing an atomic magnetometer according to claim 7, characterized in that: In the fourth step, the frequency of the pumping light resonates with the D1 transition line of the rubidium 87 atom, and the frequency of the detection light deviates from the D1 transition line of the rubidium 87 atom by 80 GHz.

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