Evaluation method and compensation method for residual magnetic field of atom magnetometer

Abstract

The embodiment of the invention discloses an evaluation method and a compensation method for a residual magnetic field of an atom magnetometer. The evaluation method comprises the following steps: after determining that an atom magnetometer performs active compensation on a preset shaft, applying a harmonic ratio coefficient of a preset modulation magnetic field; wherein the preset axis comprises at least one of an x axis, a y axis and a z axis of the atom magnetometer, and the harmonic ratio coefficient is related to a first harmonic amplitude and a second harmonic amplitude of an output signal of the atom magnetometer after the preset modulation magnetic field is applied; determining a harmonic ratio standard coefficient of the atom magnetometer; and evaluating the state of the preset axis residual magnetic field according to the harmonic ratio standard coefficient and the harmonic ratio coefficient. According to the technical scheme provided by the embodiment of the invention, the compensation effect of the residual magnetic field of each preset axis of the atom magnetometer can be accurately and independently evaluated, the independent quantitative analysis of the residual magnetic fields of the atom magnetometer in the directions of the three preset axes is realized, and the reliability and the measurement precision of the atom magnetometer in practical application are improved.

Description

Technical Field

[0001] This invention relates to the field of magnetic compensation technology for atomic magnetometers, and in particular to a method for evaluating and compensating for the residual magnetic field of an atomic magnetometer. Background Technology

[0002] In recent years, with the rapid development of quantum physics technology, the SERF atomic magnetometer (Spin-Exchange Relaxation-Free) has demonstrated outstanding advantages in the measurement of extremely weak magnetic fields. As a novel type of extremely weak magnetic field sensor that does not require a cooling environment, the SERF atomic magnetometer plays an important role in fields such as magnetic resonance imaging diagnosis of the heart and brain, and is of great significance for neuroscience research, diagnosis and treatment of brain diseases.

[0003] The SERF atomic magnetometer requires two core conditions to function properly: first, high-density polarized alkali metal atoms under high-temperature conditions; and second, an extremely low ambient magnetic field at the nT level. If there is incompletely compensated residual magnetism in the background magnetic field, it will directly disrupt the coherent evolution process of atomic spins, leading to a sharp decrease in the magnetometer's sensitivity and a significant increase in measurement error. Therefore, before starting and operating the SERF atomic magnetometer, in-situ magnetic field compensation technology must be used to eliminate the ambient magnetic field and the residual magnetism generated by the equipment itself.

[0004] However, existing in-situ magnetic compensation techniques mostly rely on the amplitude or waveform of the atomic magnetometer's output signal to indirectly determine the compensation effect. They lack a standard method to quantify the compensation effect and accurately assess the magnitude of the residual magnetic field, making independent quantitative analysis of the remanence in all three axes impossible. This severely limits the reliable application of SERF atomic magnetometers in high-precision measurement scenarios. Therefore, accurately quantifying and independently evaluating the triaxial remanence after in-situ compensation using SERF atomic magnetometers has become a key requirement for overcoming current technological limitations. Summary of the Invention

[0005] This invention provides a method for evaluating and compensating for the residual magnetic field of an atomic magnetometer, in order to solve the problem that atomic magnetometers cannot accurately quantify and independently evaluate residual magnetism.

[0006] According to one aspect of the present invention, a method for evaluating the residual magnetic field of an atomic magnetometer is provided, comprising:

[0007] After the atomic magnetometer performs active compensation on a preset axis, a harmonic ratio coefficient of a preset modulation magnetic field is applied; wherein, the preset axis includes at least one of the x-axis, y-axis, and z-axis of the atomic magnetometer, the z-axis is the pump light direction of the atomic magnetometer, the x-axis is the sensitive axis direction, and the y-axis is the non-sensitive axis direction; the harmonic ratio coefficient is related to the first harmonic amplitude and the second harmonic amplitude of the output signal of the atomic magnetometer after the preset modulation magnetic field is applied;

[0008] Determine the standard coefficients of the harmonic ratio of the atomic magnetometer;

[0009] The state of the residual magnetic field of the preset axis is evaluated based on the harmonic ratio standard coefficient and the harmonic ratio coefficient.

[0010] Optionally, determining the standard coefficients for the harmonic ratio of the atomic magnetometer includes:

[0011] Apply the preset modulation magnetic field in the x-axis direction and determine the steady-state expression of the electronic polarizability of the z-axis component after applying the preset modulation magnetic field;

[0012] The amplitudes of the first and second harmonics are determined based on the steady-state expression for electronic polarizability.

[0013] The standard coefficient of the harmonic ratio is determined based on the amplitude of the first harmonic and the amplitude of the second harmonic.

[0014] Optionally, the steady-state expression for the electronic polarizability of the z-axis component after applying the preset modulation magnetic field is:

[0015] ;

[0016] in, The electronic polarizability of the z-axis component after applying a low-frequency magnetic field in the x-axis direction. The remaining magnetic field along the x-axis. The residual magnetic field along the y-axis. The residual magnetic field along the z-axis, The low-frequency magnetic field applied along the x-axis. , , For pumping rate,

[0017] The total relaxation rate of the atomic ensemble. Electron gyromagnetic ratio;

[0018] The formula for calculating the standard coefficient of the harmonic ratio is as follows:

[0019] ;

[0020] in, The standard coefficient for harmonic ratio, The amplitude of the first harmonic. The amplitude of the second harmonic. .

[0021] Optionally, determining the harmonic ratio coefficient of the applied preset modulation magnetic field after the atomic magnetometer performs active compensation on the preset axis includes:

[0022] The atomic magnetometer undergoes a first active compensation along its x-axis, and the preset modulation magnetic field is applied.

[0023] The output signal of the atomic magnetometer is acquired to determine a time series signal, and the first harmonic amplitude and the second harmonic amplitude are determined by performing a fast Fourier transform on the time series signal.

[0024] The first harmonic ratio coefficient is determined based on the amplitude of the first harmonic and the amplitude of the second harmonic;

[0025] The residual state of the preset axis magnetic field is evaluated based on the harmonic ratio standard coefficient and the harmonic ratio coefficient, including:

[0026] When the first harmonic ratio coefficient is greater than or equal to the harmonic ratio standard coefficient, it is determined that the residual magnetic field of the atomic magnetometer along the x-axis meets the preset condition.

[0027] When the first harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it is determined that the residual magnetic field along the x-axis of the atomic magnetometer does not meet the preset condition.

[0028] Optionally, after determining the harmonic ratio coefficient of the applied preset modulation magnetic field after the atomic magnetometer performs active compensation on the preset axis, the method further includes:

[0029] A second active compensation is performed on the y-axis direction of the atomic magnetometer, and the preset modulation magnetic field is applied;

[0030] The output signal of the atomic magnetometer is acquired to determine a time series signal, and the first harmonic amplitude and the second harmonic amplitude are determined by performing a fast Fourier transform on the time series signal.

[0031] The second harmonic ratio coefficient is determined based on the amplitude of the first harmonic and the amplitude of the second harmonic;

[0032] The evaluation of the state of the residual magnetic field of the preset axis based on the harmonic ratio standard coefficient and the harmonic ratio coefficient further includes:

[0033] When the second harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient, it is determined that the residual magnetic field of the atomic magnetometer along the y-axis satisfies the preset condition.

[0034] When the second harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it is determined that the residual magnetic field of the atomic magnetometer along the y-axis does not meet the preset condition.

[0035] Optionally, after determining the harmonic ratio coefficient of the applied preset modulation magnetic field after the atomic magnetometer performs active compensation on the preset axis, the method further includes:

[0036] A third active compensation is performed on the z-axis direction of the atomic magnetometer, and the preset modulation magnetic field is applied;

[0037] The output signal of the atomic magnetometer is acquired to determine a time series signal, and the first harmonic amplitude and the second harmonic amplitude are determined by performing a fast Fourier transform on the time series signal.

[0038] The third harmonic ratio coefficient is determined based on the amplitude of the first harmonic and the amplitude of the second harmonic;

[0039] The evaluation of the state of the residual magnetic field of the preset axis based on the harmonic ratio standard coefficient and the harmonic ratio coefficient further includes:

[0040] When the third harmonic ratio coefficient is greater than or equal to the harmonic ratio standard coefficient, it is determined that the residual magnetic field of the atomic magnetometer z-axis satisfies the preset condition.

[0041] When the third harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it is determined that the residual magnetic field of the atomic magnetometer along the z-axis does not meet the preset condition.

[0042] Optionally, before performing third active compensation on the z-axis direction of the atomic magnetometer and applying the preset modulation magnetic field, the following steps are included:

[0043] A DC bias magnetic field is applied to the x-axis and y-axis of the atomic magnetometer, respectively.

[0044] Optionally, after determining the harmonic ratio coefficient of the preset modulation magnetic field after the atomic magnetometer performs active compensation on the preset axis, the process includes:

[0045] The atomic magnetometer is subjected to passive magnetic compensation to eliminate the magnetic field in the current environment;

[0046] The atomic magnetometer is heated to bring it to a spin exchange relaxation state.

[0047] According to another aspect of the present invention, a method for compensating the residual magnetic field of an atomic magnetometer is provided, comprising:

[0048] After the atomic magnetometer performs active compensation on a preset axis, a harmonic ratio coefficient of a preset modulation magnetic field is applied; wherein, the preset axis includes at least one of the x-axis, y-axis, and z-axis of the atomic magnetometer, the z-axis is the pump light direction of the atomic magnetometer, the x-axis is the sensitive axis direction, and the y-axis is the non-sensitive axis direction; the harmonic ratio coefficient is related to the first harmonic amplitude and the second harmonic amplitude of the output signal of the atomic magnetometer after the preset modulation magnetic field is applied;

[0049] Determine the standard coefficients of the harmonic ratio of the atomic magnetometer;

[0050] The state of the residual magnetic field of the preset axis is evaluated based on the harmonic ratio standard coefficient and the harmonic ratio coefficient;

[0051] Adjust the active compensation amount of the preset axis according to the state of the residual magnetic field of the preset axis, so that the residual magnetic field of the preset axis meets the preset condition.

[0052] Optionally, adjusting the active compensation amount of the preset axis according to the state of the residual magnetic field of the preset axis, so that the residual magnetic field of the preset axis meets the preset adjustment, includes:

[0053] When the harmonic ratio coefficient is greater than or equal to the harmonic ratio standard coefficient, it is determined that the residual magnetic field of the preset axis of the atomic magnetometer satisfies the preset condition;

[0054] When the harmonic ratio coefficient is less than the standard harmonic ratio coefficient, the active compensation amount of the preset axis is adjusted so that the harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient so that the residual magnetic field of the preset axis meets the preset condition.

[0055] The technical solution of this invention involves actively compensating a preset axis of an atomic magnetometer and applying a preset modulation magnetic field. The harmonic ratio coefficient after applying the preset modulation magnetic field is then determined. This harmonic ratio coefficient is related to the first and second harmonic amplitudes of the atomic magnetometer's output signal after applying the preset modulation magnetic field. Then, a standard harmonic ratio coefficient of the atomic magnetometer is determined. Based on the standard harmonic ratio coefficient and the harmonic ratio coefficient, the state of the residual magnetic field along the preset axis of the atomic magnetometer is evaluated, thereby assessing the compensation effect of the preset axis. This invention, by defining the harmonic ratio coefficient and using it as a core indicator for quantitatively evaluating the compensation effect of the atomic magnetometer, can accurately and independently evaluate the compensation effect of the residual magnetic field along each preset axis of the atomic magnetometer. It achieves independent quantitative analysis of the residual magnetic field in the three preset axis directions of the atomic magnetometer, solving the technical problem of relying on subjective judgment and being unable to accurately quantify the magnitude of the residual magnetic field in existing technologies. This significantly improves the reliability and measurement accuracy of atomic magnetometers in practical applications, providing support for the reliable application of atomic magnetometers in high-precision scenarios such as medical diagnosis.

[0056] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 A flowchart illustrating a method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention;

[0059] Figure 2 A flowchart illustrating another method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention;

[0060] Figure 3 The time-domain waveform and spectrum of the electronic polarizability of the z-axis component are given when the harmonic ratio standard coefficient is 0.25 and the residual magnetic field along the x-axis is 2nT.

[0061] Figure 4 The time-domain waveform and spectrum of the electronic polarizability of the z-axis component are given when the harmonic ratio standard coefficient is 0.88 and the residual magnetic field along the x-axis is 0.1 nT.

[0062] Figure 5 The time-domain waveform and spectrum of the electronic polarizability of the z-axis component when the harmonic ratio standard coefficient is 1 and the residual magnetic field along the x-axis is 0 nT;

[0063] Figure 6 This is a schematic diagram showing the variation of the amplitude of the first and second harmonics with the residual magnetic field along the x-axis.

[0064] Figure 7 This is a schematic diagram showing the variation of the harmonic ratio coefficient with the residual magnetic field along the x-axis.

[0065] Figure 8 A flowchart of another method for evaluating the residual magnetic field of an atomic magnetometer provided in an embodiment of the present invention;

[0066] Figure 9 A flowchart illustrating another method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention;

[0067] Figure 10 A flowchart illustrating another method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention;

[0068] Figure 11 A flowchart of another method for evaluating the residual magnetic field of an atomic magnetometer provided in an embodiment of the present invention;

[0069] Figure 12 A flowchart illustrating a method for compensating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention;

[0070] Figure 13 A flowchart illustrating another method for compensating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention;

[0071] Figure 14 A flowchart illustrating another method for compensating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention. Detailed Implementation

[0072] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0073] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0074] Figure 1 This is a flowchart illustrating a method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention. This embodiment is applicable to evaluating the residual magnetic field of an atomic magnetometer. The method can be executed by an evaluation device for the residual magnetic field of an atomic magnetometer, which can be implemented in hardware and / or software.

[0075] like Figure 1 As shown, the method for evaluating the residual magnetic field of an atomic magnetometer provided in this embodiment of the invention includes:

[0076] S110. After the atomic magnetometer performs active compensation on the preset axis, apply the harmonic ratio coefficient of the preset modulation magnetic field.

[0077] Specifically, atomic magnetometers need to operate in extremely low ambient magnetic fields during use to ensure that alkali metal atoms operate in a near-zero magnetic state, guaranteeing that the ambient magnetic field will not disrupt the coherent evolution of atomic spins. Therefore, before using the atomic magnetometer, magnetic compensation needs to be performed, and the adequacy of the magnetic compensation must be determined. This invention allows for precise evaluation and quantification of the residual magnetic field of the atomic magnetometer. After active compensation of the preset axis of the atomic magnetometer, a preset modulation magnetic field can be applied, and then the harmonic ratio coefficient of the atomic magnetometer can be determined. The harmonic ratio coefficient is related to the first and second harmonic amplitudes of the atomic magnetometer's output signal after applying the preset modulation magnetic field, and can be defined as the ratio of the second harmonic to the first harmonic of the atomic magnetometer's output signal after applying the preset modulation magnetic field. The atomic magnetometer may include three preset axes, at least one of the x-axis, y-axis, and z-axis. The z-axis can be defined as the pump light direction, the x-axis as the sensitive axis direction, and the y-axis as the non-sensitive axis direction. The x, y, and z axes satisfy a Cartesian coordinate system. After active compensation of the preset axes of the atomic magnetometer, the output signal after applying a preset modulation magnetic field to the preset axes is processed to obtain the first and second harmonic amplitudes. Then, the harmonic ratio coefficient is determined based on the first and second harmonic amplitudes. This harmonic ratio coefficient can then be used to determine the residual magnetic field of the preset axes of the atomic magnetometer, and whether active compensation of the residual magnetic field of higher preset axes is complete. The preset modulation magnetic field can be a low-frequency magnetic field; this embodiment of the invention does not specifically limit this, but for example, it can be a modulation magnetic field with an amplitude of 3 nT and a frequency of 15 Hz.

[0078] S120. Determine the standard coefficients of the harmonic ratio of the atomic magnetometer.

[0079] Specifically, after determining the preset active compensation of the atomic magnetometer and the harmonic ratio coefficient of the applied preset modulation magnetic field, it is also necessary to determine the standard harmonic ratio coefficient of the atomic magnetometer. The standard harmonic ratio coefficient can be the harmonic ratio coefficient of the atomic magnetometer's output signal when the residual magnetic field in each preset axis direction is negligible, i.e., it will not affect the measurement results; that is, the harmonic ratio coefficient when the magnetic compensation effect of the atomic magnetometer is optimal. The standard harmonic ratio coefficient can be determined through formula derivation and simulation methods.

[0080] S130. Evaluate the state of the residual magnetic field of the preset axis based on the standard harmonic ratio coefficient and harmonic ratio coefficient.

[0081] Specifically, after determining the standard harmonic ratio coefficient and the harmonic ratio coefficient after active compensation of the preset axis of the atomic magnetometer, the effect of active compensation of the preset axis by the atomic magnetometer can be determined based on the current harmonic ratio coefficient and the standard harmonic ratio coefficient. The effect of active compensation of the preset axis of the atomic magnetometer can be evaluated by the relationship between the magnitude of the harmonic ratio coefficient and the standard harmonic ratio coefficient, thus determining whether the preset axis of the atomic magnetometer has been compensated successfully. For example, when the harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it indicates that the magnetic compensation effect of the preset axis of the atomic magnetometer is not optimal; when the harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient, it indicates that the magnetic compensation effect of the preset axis of the atomic magnetometer is optimal, and the compensation effect is the best.

[0082] The method for evaluating the residual magnetic field of an atomic magnetometer provided in this embodiment involves actively compensating a preset axis of the atomic magnetometer and applying a preset modulation magnetic field. The harmonic ratio coefficient after applying the preset modulation magnetic field is determined, where the harmonic ratio coefficient is related to the first and second harmonic amplitudes of the atomic magnetometer's output signal after applying the preset modulation magnetic field. Then, the standard harmonic ratio coefficient of the atomic magnetometer is determined, and the state of the residual magnetic field along the preset axis of the atomic magnetometer is evaluated based on the standard harmonic ratio coefficient and the harmonic ratio coefficient, thereby evaluating the compensation effect of the preset axis. This embodiment of the invention defines the harmonic ratio coefficient and uses it as the core indicator for quantitatively evaluating the compensation effect of the atomic magnetometer. It can accurately and independently evaluate the compensation effect of the residual magnetic field along each preset axis of the atomic magnetometer, achieving independent quantitative analysis of the residual magnetic field in the three preset axis directions of the atomic magnetometer. This solves the technical problem of relying on subjective judgment and being unable to accurately quantify the magnitude of the residual magnetic field in existing technologies, significantly improving the reliability and measurement accuracy of atomic magnetometers in practical applications, and providing support for the reliable application of atomic magnetometers in high-precision scenarios such as medical diagnosis.

[0083] Optional, Figure 2 A flowchart illustrating another method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention. Figure 3 The time-domain waveform and spectrum of the electronic polarizability of the z-axis component are given when the harmonic ratio standard coefficient is 0.25 and the x-axis remanent magnetic field is 2nT. Figure 4 The time-domain waveform and spectrum of the electronic polarizability of the z-axis component are given when the harmonic ratio standard coefficient is 0.88 and the x-axis remanent magnetic field is 0.1 nT. Figure 5 The time-domain waveform and spectrum of the electronic polarizability of the z-axis component are given when the harmonic ratio standard coefficient is 1 and the x-axis remanent magnetic field is 0 nT. Figure 6 This is a schematic diagram showing the variation of the first and second harmonic amplitudes with the residual magnetic field along the x-axis. Figure 7 This is a schematic diagram illustrating the variation of the harmonic ratio coefficient with the residual magnetic field along the x-axis. Based on the above embodiment, see... Figure 2-7The method for evaluating the residual magnetic field of an atomic magnetometer provided in this embodiment of the invention includes:

[0084] S210. After the atomic magnetometer performs active compensation on the preset axis, apply the harmonic ratio coefficient of the preset modulation magnetic field.

[0085] S220. Apply a preset modulation magnetic field in the x-axis direction and determine the steady-state expression of the electronic polarizability of the z-axis component after applying the preset modulation magnetic field.

[0086] Specifically, when determining the standard coefficients of the harmonic ratio, the Bloch equation, which characterizes the spin evolution of atoms in an atomic magnetometer, can be solved first to determine the steady-state expression for the electronic polarizability along the z-axis. The steady-state expression for the electronic polarizability along the z-axis is:

[0087]

[0088] in, The z-axis component of the electronic polarizability of alkali metal atoms under the residual magnetic field of the environment. The remaining magnetic field along the x-axis. Residual magnetic field along the y-axis The residual magnetic field along the z-axis, , , For pumping rate, The total relaxation rate of the atomic ensemble. It is the electron gyromagnetic ratio.

[0089] Specifically, taking the x-axis as an example, after applying a preset modulation magnetic field along the x-axis, the electronic polarizability of alkali metal atoms along the z-axis will change. The steady-state expression for the electronic polarizability of the z-axis component after applying the preset modulation magnetic field along the x-axis of the atomic magnetometer is:

[0090] ;

[0091] in, The electronic polarizability of the z-axis component after applying a low-frequency magnetic field in the x-axis direction. For amplitude, for frequency, The low-frequency magnetic field applied along the x-axis. , , For time.

[0092] After expanding and simplifying the denominator, the denominator can be denoted as... Let the numerator be ? .

[0093] Therefore, after applying a preset modulation magnetic field to the x-axis of the atomic magnetometer, the steady-state expression for the electronic polarizability of the z-axis component can be simplified as follows:

[0094] ;

[0095] in, , , .

[0096] S230. Determine the amplitude of the first harmonic and the amplitude of the second harmonic based on the steady-state expression of electronic polarizability.

[0097] Specifically, after determining the steady-state expression of the electronic polarizability of the z-axis component after applying a preset modulation magnetic field to the x-axis of the atomic magnetometer, a Taylor expansion can be performed on the steady-state expression of the electronic polarizability of the z-axis component. When the modulation term is relatively small compared to the constant term, i.e. Then, the Taylor expansion of the simplified steady-state expression for electronic polarizability can be performed, where the expanded steady-state expression for electronic polarizability is:

[0098] ;

[0099] in, .

[0100] Specifically, after determining the steady-state expression for electronic polarizability after Taylor expansion, the principal terms can be retained, considering only the first three terms to determine the amplitudes of the first and second harmonics. The amplitude of the first harmonic primarily comes from the first-order terms and can be:

[0101] ;

[0102] The amplitude of the second harmonic mainly comes from the first-order and second-order terms. The amplitude of the second harmonic can be:

[0103] ;

[0104] From the formula for the amplitude of the first harmonic, it can be determined that the amplitude of the first harmonic is positively correlated with the residual magnetic field along the x-axis and the preset modulation magnetic field, while the amplitude of the second harmonic is negatively correlated with the residual magnetic field along the x-axis. The smaller the residual magnetic field along the x-axis, the smaller the amplitude of the first harmonic and the larger the amplitude of the second harmonic. In other words, the closer the residual magnetic field along the x-axis is to 0, the closer the amplitude of the first harmonic will be to 0, meaning that the x-axis compensation is better and the residual magnetic field is smaller.

[0105] S240. Determine the standard coefficient of the harmonic ratio based on the amplitude of the first harmonic and the amplitude of the second harmonic.

[0106] Specifically, after determining the amplitudes of the first and second harmonics, the standard coefficient of the harmonic ratio can be determined using these amplitudes. The formula for calculating the standard coefficient of the harmonic ratio can be defined as follows:

[0107] ;

[0108] in, The standard coefficient for harmonic ratio, The amplitude of the first harmonic. This represents the amplitude of the second harmonic.

[0109] Specifically, through simulation of the above formulas, see [link to simulation]. Figure 3-7 , Figure 3 The time-domain waveform and spectrum of the electronic polarizability of the z-axis component are given when the harmonic ratio standard coefficient is 0.25 and the residual magnetic field along the x-axis is 2nT. Figure 4 The time-domain waveform and spectrum of the electronic polarizability of the z-axis component are given when the harmonic ratio standard coefficient is 0.88 and the residual magnetic field along the x-axis is 0.1 nT. Figure 5 The time-domain waveform and spectrum of the electronic polarizability of the z-axis component are shown when the harmonic ratio standard coefficient is 1 and the x-axis remanent magnetic field is 0 nT. Simulation and the above formulas confirm that the harmonic ratio standard coefficient is greater than 0 and less than or equal to 1. The smaller the harmonic ratio standard coefficient, the larger the amplitude of the first harmonic. A larger first harmonic amplitude indicates a larger x-axis remanent magnetic field, thus indicating a poorer x-axis compensation effect. Conversely, the larger the harmonic ratio standard coefficient, the closer it is to 1, the smaller the amplitude of the first harmonic. A larger first harmonic amplitude indicates a smaller x-axis remanent magnetic field, thus indicating a poorer x-axis compensation effect. When the harmonic ratio standard coefficient is 1, such as... Figure 6 As shown, at this point, only the second harmonic amplitude is retained in the frequency band, while the first harmonic amplitude is 0, indicating that the residual magnetic field along the x-axis is 0. In this case, the atomic magnetometer is in an ideal state, achieving the best compensation effect. Simulation results of the above formula are as follows: Figure 7 As shown, the standard coefficient of the harmonic ratio can be determined to be 0.9. When the harmonic ratio coefficient is greater than 0.9, the residual magnetic field on the x-axis is close to 0 and can be ignored. At this time, the compensation effect is optimal.

[0110] S250. Evaluate the state of the residual magnetic field of the preset shaft based on the standard harmonic ratio coefficient and harmonic ratio coefficient.

[0111] Optional, Figure 8 A flowchart illustrating another method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention. Based on the above embodiments, see [link to relevant documentation]. Figure 8 The method for evaluating the residual magnetic field of an atomic magnetometer provided in this embodiment of the invention includes:

[0112] S310. Perform the first active compensation on the x-axis of the atomic magnetometer and apply a preset modulation magnetic field.

[0113] Specifically, before using an atomic magnetometer, active compensation needs to be performed on each axis of the magnetometer. Active compensation can be performed first on the x-axis, starting with a primary active compensation along the x-axis. Then, a preset modulated magnetic field is applied to the x-axis to evaluate the effectiveness of the primary active compensation. This can be achieved by using a field-programmable gate array (FPGA) to control a digital-analog circuit outputting a reference signal. This signal drives a coil along the x-axis via a current source to generate an adjustable primary active compensation magnetic field. After compensation, a preset modulated magnetic field is applied along the x-axis. This preset modulated magnetic field can be output from a function signal source, amplified, and then used to drive the coil to the center of the magnetic shielding cylinder.

[0114] S320. Acquire the output signal of the atomic magnetometer to determine the time series signal, and perform a fast Fourier transform on the time series signal to determine the amplitude of the first harmonic and the amplitude of the second harmonic.

[0115] Specifically, after performing initial active compensation on the x-axis of the atomic magnetometer and applying a preset modulation magnetic field, the output signal of the atomic magnetometer can be acquired. Then, a Fast Fourier Transform (FFT) is performed on the output signal to determine the amplitudes of the first and second harmonics. Specifically, the x-axis-compensated output signal of the atomic magnetometer can be amplified by a transimpedance amplifier, and then sampled by a sampling circuit at a preset sampling rate to obtain a time-series signal. The sampled time-series signal is then subjected to a FFT on a MATLAB or LabVIEW platform to decompose it into the amplitude signals of the first and second harmonic components, thereby determining the amplitudes of the first and second harmonics.

[0116] S330. Determine the first harmonic ratio coefficient based on the amplitude of the first harmonic and the amplitude of the second harmonic.

[0117] Specifically, after actively compensating the x-axis of the atomic magnetometer and determining the compensated first and second harmonic amplitudes, the first harmonic ratio coefficient can be determined based on these amplitudes. The first and second harmonic amplitudes can then be substituted into the aforementioned formula to calculate the first harmonic ratio coefficient under the current active compensation on the x-axis. Furthermore, the residual magnetic field on the x-axis can be determined based on the first harmonic ratio coefficient and the standard harmonic ratio coefficient, thereby evaluating the compensation status of the atomic magnetometer's x-axis.

[0118] S340. Determine the standard coefficients of the harmonic ratio of the atomic magnetometer.

[0119] S350. When the first harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient, determine that the residual magnetic field along the x-axis of the atomic magnetometer meets the preset condition.

[0120] Specifically, after determining the first harmonic ratio coefficient after the first active compensation of the atomic magnetometer's x-axis, the residual magnetic field of the atomic magnetometer's x-axis can be evaluated based on the first harmonic ratio coefficient and the standard harmonic ratio coefficient. If the first harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient, it indicates that the residual magnetic field compensation of the atomic magnetometer's x-axis is complete, the residual magnetic field of the x-axis meets the preset conditions, and will not affect the use of the atomic magnetometer. For example, when the first harmonic ratio coefficient is 0.96, which is greater than the standard harmonic ratio coefficient of 0.9, it indicates that the residual magnetic field of the atomic magnetometer's x-axis meets the preset conditions.

[0121] S360. When the first harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it is determined that the residual magnetic field of the atomic magnetometer x-axis does not meet the preset condition.

[0122] Specifically, when evaluating the residual magnetic field along the x-axis of an atomic magnetometer based on the first harmonic ratio coefficient and the standard harmonic ratio coefficient, if the first harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it indicates that the compensation effect of the residual magnetic field along the x-axis of the atomic magnetometer has not reached the preset accuracy, the residual magnetic field along the x-axis does not meet the preset conditions, and the residual magnetic field will affect the use of the atomic magnetometer. For example, when the first harmonic ratio coefficient is 0.83, which is less than the standard harmonic ratio coefficient of 0.9, it indicates that the residual magnetic field along the x-axis of the atomic magnetometer does not meet the preset conditions.

[0123] Optional, Figure 9 A flowchart illustrating another method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention. Based on the above embodiments, see [link to relevant documentation]. Figure 9 The method for evaluating the residual magnetic field of an atomic magnetometer provided in this embodiment of the invention includes:

[0124] S410. Perform a second active compensation on the y-axis of the atomic magnetometer and apply a preset modulation magnetic field.

[0125] Specifically, before using an atomic magnetometer, active compensation needs to be performed on each axis. Active compensation can be performed first on the x-axis. After the residual magnetic field in the x-axis direction meets preset conditions, a second active compensation is needed in the y-axis direction, applying a preset modulated magnetic field to evaluate the effect of the second active compensation. This can be achieved by controlling a digital-analog circuit with a reference signal via a field-programmable gate array (FPGA), which drives a coil in the y-axis direction to generate an adjustable second active compensation magnetic field. After compensation, a preset modulated magnetic field is applied in the y-axis direction. This preset modulated magnetic field can be output from a function signal source, amplified, and then applied to the center of the magnetic shielding cylinder via a power amplifier.

[0126] S420. Acquire the output signal of the atomic magnetometer to determine the time series signal, and perform a fast Fourier transform on the time series signal to determine the amplitude of the first harmonic and the amplitude of the second harmonic.

[0127] Specifically, after performing second active compensation on the y-axis of the atomic magnetometer and applying a preset modulation magnetic field, the output signal of the atomic magnetometer can be acquired. Then, a Fast Fourier Transform (FFT) is performed on the output signal to determine the amplitudes of the first and second harmonics. Specifically, the output signal of the atomic magnetometer after y-axis compensation is amplified by a transimpedance amplifier, and then sampled by a sampling circuit at a preset sampling rate to obtain a time-series signal. The sampled time-series signal is then subjected to a FFT on a MATLAB or LabVIEW platform to decompose it into the amplitude signals of the first and second harmonic components, thereby determining the amplitudes of the first and second harmonics.

[0128] S430. Determine the second harmonic ratio coefficient based on the amplitude of the first harmonic and the amplitude of the second harmonic.

[0129] Specifically, after actively compensating the y-axis of the atomic magnetometer and determining the compensated first and second harmonic amplitudes, the second harmonic ratio coefficient can be determined based on these amplitudes. The first and second harmonic amplitudes can then be substituted into the aforementioned formula to calculate the second harmonic ratio coefficient under the current active y-axis compensation. Furthermore, the residual magnetic field along the y-axis can be determined based on the second harmonic ratio coefficient and the standard harmonic ratio coefficient, thereby evaluating the compensation status of the atomic magnetometer's y-axis.

[0130] S440. Determine the standard coefficients of the harmonic ratio of the atomic magnetometer.

[0131] S450. When the second harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient, determine that the residual magnetic field of the atomic magnetometer along the y-axis meets the preset condition.

[0132] Specifically, after determining the second harmonic ratio coefficient after the first active compensation of the atomic magnetometer's y-axis, the residual magnetic field of the atomic magnetometer's y-axis can be evaluated based on the second harmonic ratio coefficient and the standard harmonic ratio coefficient. If the second harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient, it indicates that the residual magnetic field compensation of the atomic magnetometer's y-axis is complete, the residual magnetic field of the y-axis meets the preset conditions, and will not affect the use of the atomic magnetometer. For example, when the second harmonic ratio coefficient is 0.94, which is greater than the standard harmonic ratio coefficient of 0.9, it indicates that the residual magnetic field of the atomic magnetometer's y-axis meets the preset conditions.

[0133] S460. When the second harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it is determined that the residual magnetic field of the atomic magnetometer along the y-axis does not meet the preset condition.

[0134] Specifically, when evaluating the residual magnetic field along the y-axis of an atomic magnetometer based on the second harmonic ratio coefficient and the standard harmonic ratio coefficient, if the second harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it indicates that the compensation effect of the residual magnetic field along the y-axis of the atomic magnetometer has not reached the preset accuracy, the residual magnetic field along the y-axis does not meet the preset conditions, and the residual magnetic field will affect the use of the atomic magnetometer. For example, when the second harmonic ratio coefficient is 0.86, which is less than the standard harmonic ratio coefficient of 0.9, it indicates that the residual magnetic field along the y-axis of the atomic magnetometer does not meet the preset conditions.

[0135] Optional, Figure 10 A flowchart illustrating another method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention. Based on the above embodiments, see [link to relevant documentation]. Figure 10 The method for evaluating the residual magnetic field of an atomic magnetometer provided in this embodiment of the invention includes:

[0136] S510. Apply DC bias magnetic fields to the x-axis and y-axis directions of the atomic magnetometer, respectively.

[0137] Specifically, active compensation is performed on the x-axis and y-axis of the atomic magnetometer. After the residual magnetic fields in the x-axis and y-axis meet preset conditions, to avoid sensitive axis deflection and dual-axis measurement coupling errors caused by the non-orthogonality of the three axes, DC bias magnetic fields need to be applied in the two non-pumping directions of the x-axis and y-axis to correct the zero magnetic point. The DC bias magnetic field is not specifically limited in this embodiment and can be set according to actual needs. For example, the DC bias magnetic field can be ±2nT.

[0138] S520: Perform third active compensation on the z-axis direction of the atomic magnetometer and apply a preset modulation magnetic field.

[0139] Specifically, a third active compensation is needed in the z-axis direction, and a preset modulated magnetic field is applied to the z-axis to evaluate the effect of the third active compensation. This can be achieved by using a field-programmable gate array (FPGA) to control a digital-analog circuit to output a reference signal, which drives a coil in the z-axis direction via a current source to generate an adjustable third active compensation magnetic field. After compensation is completed, a preset modulated magnetic field is applied in the z-axis direction. This preset modulated magnetic field can be output from a function signal source, amplified, and then driven by a power amplifier to apply to the center of the magnetically shielded container.

[0140] S530: Acquire the output signal of the atomic magnetometer to determine the time series signal, and perform a fast Fourier transform on the time series signal to determine the amplitude of the first harmonic and the amplitude of the second harmonic.

[0141] Specifically, after performing third active compensation on the z-axis of the atomic magnetometer and applying a preset modulation magnetic field, the output signal of the atomic magnetometer can be acquired. Then, a Fast Fourier Transform (FFT) is performed on the output signal to determine the amplitudes of the first and second harmonics. Specifically, the z-axis compensated output signal of the atomic magnetometer is amplified by a transimpedance amplifier, and then sampled by a sampling circuit at a preset sampling rate to obtain a time-series signal. The sampled time-series signal is then subjected to a FFT on a MATLAB or LabVIEW platform to decompose it into the amplitude signals of the first and second harmonic components, thereby determining the amplitudes of the first and second harmonics.

[0142] S540. Determine the third harmonic ratio coefficient based on the amplitude of the first harmonic and the amplitude of the second harmonic.

[0143] Specifically, after actively compensating the z-axis of the atomic magnetometer and determining the compensated first and second harmonic amplitudes, the third harmonic ratio coefficient can be determined based on these amplitudes. The first and second harmonic amplitudes can then be substituted into the aforementioned formula to calculate the third harmonic ratio coefficient under the current active z-axis compensation. Furthermore, the residual magnetic field along the z-axis can be determined based on the third harmonic ratio coefficient and the standard harmonic ratio coefficient, thereby evaluating the compensation status of the atomic magnetometer's z-axis.

[0144] S550, Determine the standard coefficients of the harmonic ratio of the atomic magnetometer.

[0145] S560. When the third harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient, determine that the residual magnetic field of the atomic magnetometer along the z-axis meets the preset condition.

[0146] Specifically, after determining the third harmonic ratio (HMR) coefficient of the atomic magnetometer after the first active compensation on the z-axis, the residual magnetic field of the atomic magnetometer along the z-axis can be evaluated based on the HMR coefficient and the standard harmonic ratio coefficient. If the HMR coefficient is greater than or equal to the standard harmonic ratio coefficient, it indicates that the residual magnetic field compensation of the atomic magnetometer along the z-axis is complete, the residual magnetic field of the z-axis meets the preset conditions, and will not affect the use of the atomic magnetometer. For example, when the HMR coefficient is 0.95, which is greater than the standard harmonic ratio coefficient of 0.9, it indicates that the residual magnetic field of the atomic magnetometer along the z-axis meets the preset conditions.

[0147] S570. When the third harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it is determined that the residual magnetic field of the atomic magnetometer z-axis does not meet the preset condition.

[0148] Specifically, when evaluating the residual magnetic field along the z-axis of an atomic magnetometer based on the third harmonic ratio (HMR) and the standard harmonic ratio coefficient, if the HMR is less than the standard harmonic ratio coefficient, it indicates that the compensation effect of the residual magnetic field along the z-axis has not reached the preset accuracy, the residual magnetic field along the z-axis does not meet the preset conditions, and the residual magnetic field will affect the use of the atomic magnetometer. For example, if the HMR is 0.84, which is less than the standard harmonic ratio coefficient of 0.9, it means that the residual magnetic field along the z-axis of the atomic magnetometer does not meet the preset conditions.

[0149] Optional, Figure 11 A flowchart illustrating another method for evaluating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention. Based on the above embodiments, see [link to relevant documentation]. Figure 11 The method for evaluating the residual magnetic field of an atomic magnetometer provided in this embodiment of the invention includes:

[0150] S610. Perform passive magnetic compensation on the atomic magnetometer to eliminate the magnetic field in the current environment.

[0151] Specifically, before using an atomic magnetometer, passive compensation is required. This passive magnetic compensation device removes the main geomagnetic field and spatial gradient components from the experimental environment. This passive magnetic compensation is achieved using a triaxial, mutually orthogonal coil system. The coils are wound with high-conductivity copper wire and installed inside a magnetically enclosed shielding barrel consisting of four layers of permalloy and one layer of aluminum. This device effectively eliminates the geomagnetic field and spatial gradient components from the environment. Furthermore, each coil is powered by a DC steady-state source output from a lock-in amplifier, achieving a steady-state magnetic field control accuracy better than 0.5 nT.

[0152] S620: The atomic magnetometer is heated to bring it to a spin exchange relaxation state.

[0153] Specifically, the operating conditions of an atomic magnetometer require high-density polarized alkali metal atoms under high-temperature conditions. In addition to removing the main geomagnetic field and spatial gradient components from the experimental environment using a passive magnetic compensation device, the gas chamber of the atomic magnetometer also needs to be heated. The gas chamber can be made of materials containing... The isotope is housed in a glass chamber containing a buffer gas at a pressure of approximately 80 Torr. The chamber temperature can be raised to approximately 150°C using a heating module, with temperature fluctuations monitored in real-time to be less than ±0.1°C. Once the spin exchange relaxation condition is met, the system enters its highly sensitive operating region.

[0154] S630. After the atomic magnetometer performs active compensation on the preset axis, apply the harmonic ratio coefficient of the preset modulation magnetic field.

[0155] S640. Determine the standard coefficients of the harmonic ratio of the atomic magnetometer.

[0156] S650. Evaluate the state of the residual magnetic field of the preset shaft based on the standard harmonic ratio coefficient and harmonic ratio coefficient.

[0157] The residual magnetic field evaluation method for atomic magnetometers provided in this embodiment defines the harmonic ratio coefficient and determines the standard harmonic ratio coefficient. Using the harmonic ratio coefficient as the core indicator for quantitatively evaluating the compensation effect of atomic magnetometers, it can accurately and independently evaluate the compensation effect of residual magnetic field on each preset axis of atomic magnetometer. It realizes independent quantitative analysis of residual magnetic field in the three preset axis directions of atomic magnetometer, solves the technical problem of relying on subjective judgment and being unable to accurately quantify the magnitude of residual magnetic field in the prior art, significantly improves the reliability and measurement accuracy of atomic magnetometers in practical applications, and provides support for the reliable application of atomic magnetometers in high-precision scenarios such as medical diagnosis.

[0158] This invention also provides a method for compensating the residual magnetic field of an atomic magnetometer. Figure 12 This is a flowchart illustrating a method for compensating the residual magnetic field of an atomic magnetometer, provided in an embodiment of the present invention. This embodiment is applicable to the compensation of the residual magnetic field of an atomic magnetometer. The method can be executed by a compensation device for the residual magnetic field of the atomic magnetometer, which can be implemented in hardware and / or software.

[0159] like Figure 12 As shown, the method for compensating the residual magnetic field of an atomic magnetometer provided in this embodiment of the invention includes:

[0160] S710. After the atomic magnetometer performs active compensation on the preset axis, apply the harmonic ratio coefficient of the preset modulation magnetic field.

[0161] S720. Determine the standard coefficients of the harmonic ratio of the atomic magnetometer.

[0162] S730. Evaluate the state of the residual magnetic field of the preset axis based on the harmonic ratio standard coefficient and harmonic ratio coefficient.

[0163] S740. Adjust the active compensation amount of the preset shaft according to the state of the residual magnetic field of the preset shaft so that the residual magnetic field of the preset shaft meets the preset conditions.

[0164] Specifically, after determining the harmonic ratio coefficient of the preset axis of the atomic magnetometer and evaluating the state of the residual magnetic field of the current preset axis based on the harmonic ratio standard coefficient, if the residual magnetic field of the current preset axis does not meet the preset conditions, it indicates that the residual magnetic field of the preset axis is too large, and the active compensation amount needs to be adjusted to make the residual magnetic field of the preset axis meet the preset conditions. The state of the residual magnetic field of the preset axis is evaluated by the relationship between the harmonic ratio coefficient and the harmonic ratio standard coefficient, and then the active compensation amount of the preset axis is adjusted in real time until the residual magnetic field of the atomic magnetometer preset axis meets the compensation preset conditions, and the residual magnetic field will not affect the use of the atomic magnetometer.

[0165] Optional, Figure 13 A flowchart illustrating another method for compensating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention. Based on the above embodiments, see... Figure 13 The method for compensating the residual magnetic field of an atomic magnetometer provided in this embodiment of the invention includes:

[0166] S810. After the atomic magnetometer performs active compensation on the preset axis, apply the harmonic ratio coefficient of the preset modulation magnetic field.

[0167] S820. Determine the standard coefficients of the harmonic ratio of the atomic magnetometer.

[0168] S830. Evaluate the state of the residual magnetic field of the preset axis based on the standard harmonic ratio coefficient and harmonic ratio coefficient.

[0169] S840. When the harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient, determine that the residual magnetic field of the preset axis of the atomic magnetometer meets the preset condition.

[0170] Specifically, after determining the harmonic ratio coefficient of the preset axis of the atomic magnetometer and evaluating the state of the residual magnetic field of the current preset axis based on the standard harmonic ratio coefficient, if the harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient, it indicates that the residual magnetic field of the preset axis of the atomic magnetometer is relatively small. The active compensation has eliminated the residual magnetic field, and the compensation effect is good. The atomic magnetometer can be used normally and will not be affected by the residual magnetic field, or the effect is negligible.

[0171] S850. When the harmonic ratio coefficient is less than the standard harmonic ratio coefficient, adjust the active compensation amount of the preset shaft to make the harmonic ratio coefficient greater than or equal to the standard harmonic ratio coefficient so that the residual magnetic field of the preset shaft meets the preset conditions.

[0172] After determining the harmonic ratio coefficient of the preset axis of the atomic magnetometer and assessing the state of the residual magnetic field of the current preset axis based on the standard harmonic ratio coefficient, if the harmonic ratio coefficient is less than the standard harmonic ratio coefficient, it indicates that the residual magnetic field of the preset axis of the atomic magnetometer is large, and the active compensation magnetic field is small. Even after active compensation, a large residual magnetic field still remains on the preset axis. In this case, it is necessary to adjust the amount of the active compensation magnetic field according to the harmonic ratio coefficient and observe the adjusted harmonic ratio coefficient in real time. Compensation is completed once the harmonic ratio coefficient is greater than or equal to the standard harmonic ratio coefficient.

[0173] Optional, Figure 14 A flowchart illustrating another method for compensating the residual magnetic field of an atomic magnetometer, provided as an embodiment of the present invention. Based on the above embodiments, see... Figure 14 First, determine the parameters and harmonic ratio standard coefficients of the atomic magnetometer. Then, active compensation is performed on the x-axis of the atomic magnetometer. After compensation, a low-frequency modulated magnetic field signal is applied. A fast Fourier transform is then performed on the output signal of the atomic magnetometer after the low-frequency modulated magnetic field is applied to determine the amplitude of the first harmonic and the amplitude of the second harmonic, and thus determine the first harmonic ratio coefficient of the x-axis. Then determine the first harmonic ratio coefficient. Is it greater than or equal to the standard harmonic ratio coefficient? If the first harmonic ratio is less than the standard harmonic ratio coefficient. Then adjust the active compensation magnetic field along the x-axis until the first harmonic ratio coefficient is reached. Greater than or equal to the standard harmonic ratio coefficient Then, y-axis compensation is performed. After y-axis compensation, a low-frequency modulated magnetic field signal is applied to the y-axis, and the first and second harmonic amplitudes of the compensated y-axis output signal are obtained to determine the second harmonic ratio coefficient of the y-axis. Then determine the second harmonic ratio coefficient. Is it greater than or equal to the standard harmonic ratio coefficient? If the second harmonic ratio coefficient Less than the standard coefficient of harmonic ratio Then adjust the active compensation magnetic field along the y-axis until the second harmonic ratio coefficient is reached. Greater than or equal to the standard harmonic ratio coefficient Then, z-axis compensation is performed. After z-axis compensation, a low-frequency modulated magnetic field signal is applied to the z-axis, and the first and second harmonic amplitudes of the compensated z-axis output signal are obtained to determine the third harmonic ratio coefficient of the z-axis. Then determine the third harmonic ratio coefficient. Is it greater than or equal to the standard harmonic ratio coefficient? If the third harmonic ratio coefficient... If the value is less than the standard harmonic ratio coefficient, adjust the active compensation magnetic field along the z-axis until the third harmonic ratio coefficient is reached. Greater than or equal to the standard harmonic ratio coefficient This completes the compensation for the atomic magnetometer.

[0174] The technical solution of this invention evaluates the state of the residual magnetic field along a preset axis using the harmonic ratio standard coefficient and harmonic ratio coefficient. When the residual magnetic field along the preset axis does not meet the preset state, the active compensation amount is adjusted until the residual magnetic field along the preset axis meets the preset condition. This achieves independent compensation of the residual magnetic field along the three preset axes of the atomic magnetometer, allowing for accurate and independent evaluation of the compensation effect of the residual magnetic field along each preset axis. This improves the reliability and measurement accuracy of the atomic magnetometer in practical applications, providing support for the reliable application of atomic magnetometers in high-precision scenarios such as medical diagnosis.

[0175] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A method of evaluating a residual magnetic field of an atomic magnetometer, characterized by, The method comprises the following steps: determining a harmonic ratio coefficient of a preset modulation magnetic field applied after the atomic magnetometer actively compensates for a preset axis; wherein the preset axis comprises at least one of an x-axis, a y-axis and a z-axis of the atomic magnetometer, the z-axis is the direction of the pumping light of the atomic magnetometer, the x-axis is the direction of the sensitive axis, and the y-axis is the direction of the non-sensitive axis; the harmonic ratio coefficient is related to the first harmonic amplitude and the second harmonic amplitude of the output signal of the atomic magnetometer after the preset modulation magnetic field is applied; determining a harmonic ratio standard coefficient of the atomic magnetometer; evaluating the state of the residual magnetic field of the preset axis according to the harmonic ratio standard coefficient and the harmonic ratio coefficient.

2. The method of evaluating a residual magnetic field according to claim 1, characterized by, The method for determining the harmonic ratio standard coefficient of the atomic magnetometer comprises the following steps: applying the preset modulation magnetic field in the x-axis direction, and determining the steady-state expression of the electronic polarizability of the z-axis component after the preset modulation magnetic field is applied; determining the first harmonic amplitude and the second harmonic amplitude according to the steady-state expression of the electronic polarizability; determining the harmonic ratio standard coefficient according to the first harmonic amplitude and the second harmonic amplitude.

3. The method for evaluating the residual magnetic field according to claim 2, wherein the steady-state expression of the electronic polarizability of the z-axis component after the preset modulation magnetic field is applied is: the calculation formula of the harmonic ratio standard coefficient is: ； wherein, is the electronic polarizability in the z-axis component after applying a low frequency magnetic field in the x-axis direction, is the x-axis remanent magnetic field, is the y-axis remanent magnetic field, is the z-axis remanent magnetic field, is the low frequency magnetic field applied in the x-axis direction, , , is the pumping rate, is the total atomic ensemble relaxation rate, is the electronic gyromagnetic ratio; The method for determining the harmonic ratio coefficient of the preset modulation magnetic field applied after the atomic magnetometer actively compensates for the preset axis comprises the following steps: ； wherein is the harmonic ratio standard coefficient, is the first harmonic amplitude, is the second harmonic amplitude, .

4. The method of evaluating a residual magnetic field according to claim 1, characterized by, performing first active compensation on the x-axis direction of the atomic magnetometer, and applying the preset modulation magnetic field; collecting the output signal of the atomic magnetometer to determine a time sequence signal, and performing fast Fourier transform on the time sequence signal to determine the first harmonic amplitude and the second harmonic amplitude; determining a first harmonic ratio coefficient according to the first harmonic amplitude and the second harmonic amplitude; The method for evaluating the residual state of the magnetic field of the preset axis according to the harmonic ratio standard coefficient and the harmonic ratio coefficient comprises the following steps: when the first harmonic ratio coefficient is greater than or equal to the harmonic ratio standard coefficient, it is determined that the residual magnetic field of the x-axis of the atomic magnetometer meets a preset condition; when the first harmonic ratio coefficient is less than the harmonic ratio standard coefficient, it is determined that the residual magnetic field of the x-axis of the atomic magnetometer does not meet the preset condition. The method for determining the harmonic ratio coefficient of the preset modulation magnetic field applied after the atomic magnetometer actively compensates for the preset axis further comprises the following steps:

5. The method of evaluating a residual magnetic field according to claim 4, characterized in that, performing second active compensation on the y-axis direction of the atomic magnetometer, and applying the preset modulation magnetic field; collecting the output signal of the atomic magnetometer to determine a time sequence signal, and performing fast Fourier transform on the time sequence signal to determine the first harmonic amplitude and the second harmonic amplitude; determining a second harmonic ratio coefficient according to the first harmonic amplitude and the second harmonic amplitude; The method for evaluating the state of the residual magnetic field of the preset axis according to the harmonic ratio standard coefficient and the harmonic ratio coefficient further comprises the following steps: when the second harmonic ratio coefficient is greater than or equal to the harmonic ratio standard coefficient, it is determined that the residual magnetic field of the y-axis of the atomic magnetometer meets the preset condition; ​ When the third harmonic ratio coefficient is greater than or equal to the harmonic ratio standard coefficient, it is determined that the atomic magnetometer z-axis residual magnetic field meets the preset condition.

6. The method of evaluating a residual magnetic field according to claim 5, characterized by, Before determining the harmonic ratio coefficient of the atomic magnetometer after active compensation of the preset axis and application of the preset modulation magnetic field, the method further includes: performing third active compensation on the z-axis direction of the atomic magnetometer and applying the preset modulation magnetic field; collecting the output signal of the atomic magnetometer to determine a time sequence signal, and performing fast Fourier transform on the time sequence signal to determine a first harmonic amplitude and a second harmonic amplitude; determining a third harmonic ratio coefficient according to the first harmonic amplitude and the second harmonic amplitude; evaluating the state of the preset axis residual magnetic field according to the harmonic ratio standard coefficient and the harmonic ratio coefficient, and further including: When the third harmonic ratio coefficient is greater than or equal to the harmonic ratio standard coefficient, it is determined that the atomic magnetometer z-axis residual magnetic field meets the preset condition. When the third harmonic ratio coefficient is less than the harmonic ratio standard coefficient, it is determined that the atomic magnetometer z-axis residual magnetic field does not meet the preset condition.

7. The method of evaluating a residual magnetic field according to claim 6, characterized in that, Before performing third active compensation on the z-axis direction of the atomic magnetometer and applying the preset modulation magnetic field, the method includes: applying a direct current bias magnetic field to the x-axis direction and the y-axis direction of the atomic magnetometer, respectively.

8. The method of evaluating a residual magnetic field according to claim 1, characterized by, Before determining the harmonic ratio coefficient of the atomic magnetometer after active compensation of the preset axis and application of the preset modulation magnetic field, the method includes: performing passive magnetic compensation on the atomic magnetometer to eliminate the magnetic field in the current environment; heating the atomic magnetometer to make it reach a spin exchange relaxation free state.

9. A method of compensating for a residual magnetic field of an atomic magnetometer, characterized by, The method includes: determining the harmonic ratio coefficient of the atomic magnetometer after active compensation of the preset axis and application of the preset modulation magnetic field; wherein the preset axis includes at least one of the x-axis, the y-axis and the z-axis of the atomic magnetometer, the z-axis is the direction of the pumping light of the atomic magnetometer, the x-axis is the sensitive axis direction, and the y-axis is the non-sensitive axis direction; the harmonic ratio coefficient is related to the first harmonic amplitude and the second harmonic amplitude of the output signal of the atomic magnetometer after application of the preset modulation magnetic field; determining a harmonic ratio standard coefficient of the atomic magnetometer; evaluating the state of the preset axis residual magnetic field according to the harmonic ratio standard coefficient and the harmonic ratio coefficient; adjusting the active compensation amount of the preset axis according to the state of the preset axis residual magnetic field to make the preset axis residual magnetic field meet the preset condition.

10. The method of compensating for residual magnetic fields according to claim 9, wherein, Adjusting the active compensation amount of the preset axis according to the state of the preset axis residual magnetic field to make the preset axis residual magnetic field meet the preset condition includes: When the harmonic ratio coefficient is greater than or equal to the harmonic ratio standard coefficient, it is determined that the preset axis residual magnetic field of the atomic magnetometer meets the preset condition. When the harmonic ratio coefficient is less than the harmonic ratio standard coefficient, the active compensation amount of the preset axis is adjusted so that the harmonic ratio coefficient is greater than or equal to the harmonic ratio standard coefficient to make the preset axis residual magnetic field meet the preset condition.

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