Spin-exchange relaxation free atom magnetometer verification system and method

Abstract

This invention provides a calibration system and method for a spin-free exchange-relaxation atomic magnetometer, belonging to the field of precision measurement technology. The calibration system includes: a magnetic field coil configured to generate a square-wave alternating magnetic field within a preset frequency range; an atomic gas chamber configured to provide a polarizable atomic medium, wherein, when the spin-free exchange-relaxation atomic magnetometer is in an unshielded state, the atomic medium undergoes Larmor precession under the influence of the square-wave alternating magnetic field to modulate the probe light of the spin-free exchange-relaxation atomic magnetometer, obtaining an optical modulation signal; a photodetector configured to convert the optical modulation signal into an electrical signal, wherein the electrical signal is used to characterize the amplitude-frequency characteristics corresponding to the frequency range; and a calibration module configured to perform peak detection on the electrical signal and determine the operating state of the spin-free exchange-relaxation atomic magnetometer based on the peak detection result.

Description

Technical Field

[0001] This invention relates to the field of precision measurement technology, and more specifically, to a calibration system and method for a spin-free exchange-relaxation atomic magnetometer. Background Technology

[0002] An atomic magnetometer is a precision magnetic field measurement device based on the principle of light-atomic interaction. Operating in a spin-exchange relaxation-free (SERF) state, the atomic magnetometer achieves extremely high magnetic field measurement sensitivity by suppressing the relaxation effect caused by spin-exchange collisions. It has been widely used in fields such as fundamental physics research, biomedical imaging, and low-field nuclear magnetic resonance imaging.

[0003] The SERF atomic magnetometer's ability to achieve ultra-high sensitivity magnetic field measurements relies on the atomic gas chamber operating in a near-zero magnetic field environment. However, the Earth's magnetic field strength varies greatly globally, typically ranging from 25,000 nT to 65,000 nT, far exceeding the SERF vector atomic magnetometer's normal operating range. When a SERF atomic magnetometer is deployed in an unshielded outdoor environment, or moved from a magnetically shielded laboratory to an outdoor field, the excessively strong Earth's magnetic field causes rapid precession and depolarization of atomic spins, leading to saturation or disorder in the SERF atomic magnetometer's output signal. In such cases, it becomes impossible to distinguish whether the SERF atomic magnetometer itself has malfunctioned or if the environmental magnetic field is simply beyond its operating range.

[0004] Traditional solutions rely on large magnetic shielding barrels or complex active compensation systems to artificially create a near-zero field environment. However, both methods increase the complexity and deployment difficulty of the verification system, and in certain special cases, it is impossible to determine the working status of the SERF atomic magnetometer by providing a near-zero field environment.

[0005] Therefore, how to quickly and effectively verify the working status of the SERF atomic magnetometer in an unshielded geomagnetic field environment without relying on additional shielding or compensation devices has become a key technical problem to be solved. Summary of the Invention

[0006] In view of this, the present invention provides a system and method for verifying a spin-free exchange-relaxation atomic magnetometer.

[0007] One aspect of the present invention provides a verification system for a spin-free exchange-relaxation atomic magnetometer, comprising: a magnetic field coil disposed inside the probe of the spin-free exchange-relaxation atomic magnetometer, configured to generate a square wave alternating magnetic field according to a preset frequency range; an atomic gas chamber disposed in a spatial region formed by multiple magnetic field coils, configured to provide a polarizable atomic medium, wherein, when the spin-free exchange-relaxation atomic magnetometer is in an unshielded state, the atomic medium undergoes Larmor precession under the action of the square wave alternating magnetic field to modulate the probe light of the spin-free exchange-relaxation atomic magnetometer to obtain an optical modulation signal; a photodetector disposed inside the atomic gas chamber, configured to convert the optical modulation signal into an electrical signal, wherein the electrical signal is used to characterize the amplitude-frequency characteristics corresponding to the frequency range; and a verification module electrically connected to the photodetector, configured to perform peak detection on the electrical signal and determine the operating state of the spin-free exchange-relaxation atomic magnetometer based on the peak detection result.

[0008] According to an embodiment of the present invention, the above-mentioned verification module is configured as follows: based on multiple frequency points within the above-mentioned frequency range, the electrical signal is divided into multiple frequency signals, wherein each frequency signal corresponds to one of the above-mentioned frequency points; the frequency signals are divided in the time domain according to a preset time length to obtain multiple frequency sub-signals; the maximum amplitude and minimum amplitude of the frequency sub-signals in the time domain are determined, and the characteristic values ​​of the frequency sub-signals are obtained based on subtraction operations; the characteristic values ​​of the multiple frequency sub-signals are accumulated to obtain the characteristic values ​​of the frequency signal; based on the characteristic values ​​of the multiple frequency signals and multiple frequency points corresponding to the above-mentioned frequency signals, a segmented extreme value accumulated electrical signal is obtained; peak detection is performed on the segmented extreme value accumulated electrical signal, and the working state of the spin-free exchange relaxation atom magnetometer is determined based on the result of the peak detection.

[0009] According to an embodiment of the present invention, the aforementioned magnetic field coil is a triaxial Helmholtz coil including an X-axis magnetic field sub-coil, a Y-axis magnetic field sub-coil, and a Z-axis magnetic field sub-coil. The aforementioned verification module is configured to: perform peak detection on a first detection signal corresponding to a square wave alternating magnetic field generated by the aforementioned X-axis magnetic field sub-coil to obtain a first detection result; perform peak detection on a second detection signal corresponding to a square wave alternating magnetic field generated by the aforementioned Y-axis magnetic field sub-coil to obtain a second detection result; perform peak detection on a third detection signal corresponding to a square wave alternating magnetic field generated by the aforementioned Z-axis magnetic field sub-coil to obtain a third detection result; and determine the operating state of the aforementioned spin-free exchange relaxation atom magnetometer based on the aforementioned first detection result, the aforementioned second detection result, and the aforementioned third detection result.

[0010] According to an embodiment of the present invention, the above-mentioned spin-free exchange-relaxation atomic magnetometer verification system further includes: an attitude adjustment device configured to control the probe to be in a target attitude, wherein the spin-free exchange-relaxation atomic magnetometer has the highest sensitivity to changes in magnetic field under the target attitude.

[0011] According to an embodiment of the present invention, the frequency range described above covers the Larmor frequency range generated by the influence of the geomagnetic field when the above-mentioned non-spin exchange relaxation atomic magnetometer is in an unshielded state.

[0012] According to an embodiment of the present invention, the above-mentioned spin-exchange-relaxation atomic magnetometer verification system further includes: a signal conditioning device electrically connected to the photodetector and the verification module, configured to amplify and filter the electrical signal input to the photodetector to obtain a first electrical signal, and output the first electrical signal to the verification module; wherein the verification module is configured to determine the working state of the spin-exchange-relaxation atomic magnetometer based on the first electrical signal.

[0013] According to an embodiment of the present invention, the above-mentioned spin-exchange-relaxation atomic magnetometer verification system further includes: a signal conversion device electrically connected to the photodetector and the verification module, configured to perform analog-to-digital conversion processing on the electrical signal input to the photodetector based on a preset sampling rate to obtain a second electrical signal in digital encoding form, and output the second electrical signal to the verification module; wherein the verification module is configured to determine the working state of the spin-exchange-relaxation atomic magnetometer based on the second electrical signal.

[0014] According to an embodiment of the present invention, the above-mentioned non-spin exchange relaxation atom magnetometer verification system further includes: a voltage-controlled current source, electrically connected to the above-mentioned magnetic field coil, configured to generate a driving current with a preset waveform based on a preset digital scan sequence, and output the driving current to the above-mentioned magnetic field coil.

[0015] According to an embodiment of the present invention, the above-mentioned spinless exchange relaxation atomic magnetometer calibration system further includes: a temperature control module disposed on the outer surface of the atomic gas chamber and configured to adjust the temperature of the atomic gas chamber.

[0016] Another aspect of the present invention provides a method for calibrating a spin-exchange-relaxation atomic magnetometer, applied to the aforementioned spin-exchange-relaxation atomic magnetometer calibration system, comprising: generating a square wave alternating magnetic field within a preset frequency range; providing a polarizable atomic medium, wherein, when the spin-exchange-relaxation atomic magnetometer is in an unshielded state, the atomic medium undergoes Larmor precession under the action of the square wave alternating magnetic field to modulate the probe light of the spin-exchange-relaxation atomic magnetometer, thereby obtaining an optical modulation signal; converting the optical modulation signal into an electrical signal; performing peak detection on the electrical signal, and determining the operating state of the spin-exchange-relaxation atomic magnetometer based on the result of the peak detection.

[0017] According to an embodiment of the present invention, a square wave alternating magnetic field is generated by a magnetic field coil, and an electrical signal is obtained based on the square wave alternating magnetic field when the SERF atomic magnetometer is in an unshielded state. The peak value of the electrical signal is detected to determine whether the SERF atomic magnetometer is in normal working condition. This allows for rapid and effective verification of the working condition of the SERF atomic magnetometer in an unshielded geomagnetic field environment, reducing the verification cost of the SERF atomic magnetometer. Attached Figure Description

[0018] The above and other objects, features and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings.

[0019] Figure 1 A schematic diagram of a spin-free exchange-relaxation atomic magnetometer calibration system according to an embodiment of the present invention is shown.

[0020] Figure 2 A schematic diagram of the electrical signal processing flow of a spin-free exchange-relaxed atomic magnetometer verification system according to an embodiment of the present invention is shown.

[0021] Figure 3 A schematic diagram of the calibration process of a spin-free exchange-relaxation atomic magnetometer calibration system according to an embodiment of the present invention is shown.

[0022] Figure 4 A schematic diagram of a spin-free exchange-relaxed atomic magnetometer calibration system according to another embodiment of the present invention is shown.

[0023] Figure 5 A schematic diagram illustrating the determination of calibration results for a spin-free exchange-relaxation atom magnetometer calibration system according to an embodiment of the present invention is shown.

[0024] Figure 6 A flowchart of a method for verifying a spin-free exchange-relaxed atomic magnetometer according to an embodiment of the present invention is shown. Detailed Implementation

[0025] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms "comprising," "including," etc., as used herein indicate the presence of the above-described features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0027] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0028] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0029] Macroscopically polarized atomic spins will undergo Larmor precession around the direction of the magnetic field in a static magnetic field, with a precession frequency ω. L It is determined by the magnetic field strength of the static magnetic field and the gyromagnetic ratio of the atoms. In this case, if a radio frequency field with frequency ω is applied, and ω is equal to the precession frequency ω... L At this time, the atomic spin system will undergo resonant absorption, and the energy of the radio frequency field will be coupled into the spin system, causing a change in the spin polarization state. This change will be mapped onto the probe light of the atomic magnetometer through the interaction between light and atoms, resulting in a significant increase in the intensity of the transmitted light received by the photodetector of the atomic magnetometer.

[0030] When the geomagnetic field strength of the space where the SERF atomic magnetometer is located exceeds its normal range, although the atoms in the SERF atomic magnetometer have exited the SERF state, their spins will still undergo Larmor precession around the direction of the geomagnetic field. At this time, by applying an adjustable alternating magnetic field to scan the precession frequency of the atoms, if the equipment is functioning correctly, a magnetic resonance phenomenon will inevitably be observed at a certain frequency point. This manifests as a significant increase in the intensity of transmitted light received by the photodetector of the atomic magnetometer. By detecting this characteristic signal, it can be determined that the magnetometer's probe, optical path, and electronic system are functioning normally, thus completing the calibration.

[0031] Figure 1 A schematic diagram of a spin-free exchange-relaxation atomic magnetometer calibration system according to an embodiment of the present invention is shown.

[0032] like Figure 1 As shown, the spin-free exchange relaxation atomic magnetometer calibration system includes a magnetic field coil 101, an atomic gas chamber 102, a photodetector 103, and a calibration module 104.

[0033] The magnetic field coil 101 is located inside the probe of the spin-free exchange relaxation atom magnetometer and is configured to generate a square wave alternating magnetic field within a preset frequency range.

[0034] A square-wave alternating magnetic field is an alternating magnetic field in which the magnetic field strength and direction periodically change according to a square-wave pattern over time. It is generated by excitation from a square-wave alternating current and is a special waveform of alternating magnetic fields. In embodiments of the present invention, the square-wave alternating magnetic field has different frequencies in different time periods. Based on a preset frequency range, a preset sweep step size, and a preset frequency duration, a specific magnetic field can be generated for calibrating a magnetometer for atoms without spin exchange relaxation. For example, when the preset frequency range is 99 kHz to 501 kHz, the sweep step size is 2 kHz, and the frequency duration is 1 s, the square-wave alternating magnetic field in the time domain is as follows: the magnetic field frequency is 99 kHz from 0 to 1 s, 101 kHz from 1 s to 2 s, 103 kHz from 2 s to 3 s, and so on, with a magnetic field frequency of 501 kHz from 201 s to 202 s.

[0035] The atomic gas chamber 102 is located in the spatial region formed by multiple magnetic field coils 101. It is configured to provide a polarizable atomic medium. When the spin-exchange-relaxed atomic magnetometer is in an unshielded state, the atomic medium undergoes Larmor precession under the action of a square wave alternating magnetic field to modulate the probe light of the spin-exchange-relaxed atomic magnetometer and obtain an optical modulation signal.

[0036] A photodetector 103 is disposed inside an atomic gas chamber 102 and configured to convert an optical modulation signal into an electrical signal, wherein the electrical signal is used to characterize the amplitude-frequency characteristics corresponding to a frequency range.

[0037] In embodiments of the present invention, there is a formal correspondence between the electrical signal and the square wave alternating magnetic field. As mentioned above, when the square wave alternating magnetic field is characterized in the time domain as follows: the magnetic field frequency from 0 to 1 s is 99 kHz, the magnetic field frequency from 1 s to 2 s is 101 kHz, and the magnetic field frequency from 2 s to 3 s is 103 kHz, then the electrical signal is characterized as follows: the amplitude of the electrical signal from 0 to 1 s corresponds to the frequency point of 99 kHz, the amplitude of the electrical signal from 1 s to 2 s corresponds to the frequency point of 101 kHz, and the amplitude of the electrical signal from 2 s to 3 s corresponds to the frequency point of 103 kHz. Therefore, the electrical signal can be used to characterize the amplitude-frequency characteristics corresponding to each frequency point within the frequency range.

[0038] The calibration module 104 is electrically connected to the photodetector 103 and is configured to perform peak detection on the electrical signal and determine the working status of the spin-exchange-relaxation atom magnetometer based on the peak detection result.

[0039] Peak detection refers to identifying local maxima (peaks) or local minima (troughs) within a data signal. In practical applications, threshold values ​​are typically set to avoid noise interference. A peak is considered valid only when its amplitude exceeds a preset value or when the difference in amplitude between it and an adjacent trough is sufficiently large. In embodiments of this invention, peak detection can be implemented based on specific detection algorithms, including but not limited to: threshold determination methods, sliding window methods, derivative methods, and wavelet transform peak detection.

[0040] In an embodiment of the present invention, after peak detection of the electrical signal, if the peak detection result shows that the electrical signal has a peak value and the peak value is located within a time period of 2 to 3 seconds, it can be determined that the SERF atomic magnetometer has experienced magnetic resonance at a frequency of 103 kHz, and the SERF atomic magnetometer is in normal working condition.

[0041] Through the embodiments of the present invention, a square wave alternating magnetic field is generated by a magnetic field coil, and an electrical signal is obtained based on the square wave alternating magnetic field when the SERF atomic magnetometer is in an unshielded state. The peak value of the electrical signal is detected to determine whether the SERF atomic magnetometer is in normal working condition. This allows for rapid and effective verification of the working condition of the SERF atomic magnetometer in an unshielded geomagnetic field environment, reducing the verification cost of the SERF atomic magnetometer.

[0042] According to an embodiment of the present invention, the verification module is configured as follows: based on multiple frequency points within a frequency range, the electrical signal is divided into multiple frequency signals, wherein each frequency signal corresponds to a frequency point; the frequency signals are divided in the time domain according to a preset time length to obtain multiple frequency sub-signals; the maximum and minimum amplitude values ​​of the frequency sub-signals in the time domain are determined, and the characteristic values ​​of the frequency sub-signals are obtained based on subtraction operations; the characteristic values ​​of the multiple frequency sub-signals are accumulated to obtain the characteristic values ​​of the frequency signals; based on the characteristic values ​​of the multiple frequency signals and multiple frequency points corresponding to the frequency signals, a segmented extreme value accumulated electrical signal is obtained; peak detection is performed on the segmented extreme value accumulated electrical signal, and the working state of the spin-exchange relaxation atom magnetometer is determined based on the peak detection result.

[0043] Figure 2 A schematic diagram of the electrical signal processing flow of a spin-free exchange-relaxed atomic magnetometer verification system according to an embodiment of the present invention is shown.

[0044] like Figure 2 As shown, the electrical signal has multiple different frequency points. For the current frequency point f, an analog-to-digital converter (ADC) can be used to acquire the signal, obtaining a sampling sequence of N sampling points. This sampling sequence is then divided into M segments, each containing K = N / M sampling points. R(f) is used to characterize the feature value of the current frequency point. First, the maximum amplitude Max_i and minimum amplitude Min_i in the i-th sampling sequence are determined. Then, the feature value of R(f) is updated using the maximum amplitude Max_i and the minimum amplitude Min_i. This update operation based on the M sampling sequences is completed iteratively, outputting R(f) corresponding to the current frequency point. After performing the above operation on all frequency points within the frequency range, the feature value of the frequency signal corresponding to each frequency point can be obtained. By concatenating the feature values ​​of the frequency signals corresponding to all frequency points in the time domain, a piecewise extremum accumulation electrical signal can be obtained.

[0045] According to an embodiment of the present invention, the magnetic field coil is a triaxial Helmholtz coil including an X-axis magnetic field sub-coil, a Y-axis magnetic field sub-coil, and a Z-axis magnetic field sub-coil. The verification module is configured to: perform peak detection on a first detection signal corresponding to a square wave alternating magnetic field generated by the X-axis magnetic field sub-coil to obtain a first detection result; perform peak detection on a second detection signal corresponding to a square wave alternating magnetic field generated by the Y-axis magnetic field sub-coil to obtain a second detection result; perform peak detection on a third detection signal corresponding to a square wave alternating magnetic field generated by the Z-axis magnetic field sub-coil to obtain a third detection result; and determine the working state of the spin-exchange relaxation atom magnetometer based on the first detection result, the second detection result, and the third detection result.

[0046] A triaxial Helmholtz coil is a precision electromagnetic device capable of generating a directionally controllable and highly uniform three-dimensional magnetic field. A triaxial Helmholtz coil consists of three sets of mutually orthogonal (X-axis, Y-axis, Z-axis) Helmholtz coils. Each set of coils is composed of two identical, parallel, and coaxial coils connected in series, with the distance between the coils equal to their radius. This special geometry cancels out the inherent magnetic field inhomogeneities in the central region of the triaxial Helmholtz coil, thereby generating a large-scale, highly linear, uniform magnetic field region. The three axes of the triaxial Helmholtz coil can be controlled independently; by adjusting the magnitude and direction of the current in the three sets of coils, a magnetic field with any vector direction can be synthesized in three-dimensional space.

[0047] In embodiments of the present invention, multiple repeated scans can be performed on the X, Y, and Z axes respectively, and the number of scans can be preset. Multiple electrical signals obtained from the multiple scans can be superimposed and compared. If signals at similar frequencies f are detected during the multiple scans... Peak If the amplitude is significantly higher than the peak value of the adjacent frequency point at each frequency point, and the peak position is reproducible, then a stable magnetic resonance phenomenon can be confirmed.

[0048] In the embodiments of the present invention, it can be determined that no magnetic resonance phenomenon has occurred and that there is a problem with the working state of the spin-exchange relaxation atom magnetometer only when the first detection result is that the first detection signal has no signal peak, the second detection result is that the second detection signal has no signal peak, and the third detection result is that the third detection signal has no signal peak, all of which are simultaneously true.

[0049] Figure 3 A schematic diagram of the calibration process of a spin-free exchange-relaxation atomic magnetometer calibration system according to an embodiment of the present invention is shown.

[0050] like Figure 3As shown, the SERF atomic magnetometer is first activated in an unshielded state, and the probe is controlled to be in the target orientation. At this point, the SERF atomic magnetometer has the highest sensitivity to changes in the magnetic field. Then, the SERF atomic magnetometer is put into the "Geomagnetic Field Verification" working mode, a unique working mode of this invention, which can be implemented through software programming. After entering the "Geomagnetic Field Verification" working mode, the SERF atomic magnetometer can automatically execute subsequent verification procedures and output verification results. In the "Geomagnetic Field Verification" working mode, the SERF atomic magnetometer controls the X-axis magnetic field sub-coil to generate a square wave alternating magnetic field, obtaining the first detection signal; controls the Y-axis magnetic field sub-coil to generate a square wave alternating magnetic field, obtaining the second detection signal; and controls the Z-axis magnetic field sub-coil to generate a square wave alternating magnetic field, obtaining the third detection signal. By performing M repeated scans along the X, Y, and Z axes respectively, 3M electrical signals can be obtained. Finally, based on the 3M electrical signals, it is determined whether there is a peak value. If a peak value exists, the SERF atomic magnetometer is working normally; if no peak value exists, the SERF atomic magnetometer is not working normally.

[0051] According to an embodiment of the present invention, the verification system for a spin-free exchange-relaxation atomic magnetometer further includes: an attitude adjustment device configured to control the probe in a target attitude, wherein the spin-free exchange-relaxation atomic magnetometer has the highest sensitivity to changes in the magnetic field in the target attitude.

[0052] In embodiments of the present invention, the orientation of the SERF atomic magnetometer probe can be adjusted to face different directions, and the output of the SERF atomic magnetometer's photodetector can be monitored in real time until the photodetector's output value reaches its maximum. At this point, the SERF atomic magnetometer is in the detection orientation most sensitive to changes in the magnetic field, i.e., the target orientation. By setting the probe to the target orientation for subsequent square wave alternating magnetic field scanning, the amplitude of the electrical signal change during magnetic resonance can be made more significant, thereby improving the accuracy and reliability of characteristic peak identification.

[0053] According to an embodiment of the present invention, the frequency range covers the Larmor frequency range generated by the influence of the geomagnetic field when the non-spin exchange relaxation atomic magnetometer is in an unshielded state.

[0054] When the SERF atomic magnetometer is in an unshielded state, the Earth's magnetic field becomes the dominant static magnetic field of the atomic medium within the SERF. The atomic medium undergoes Larmor precession under the influence of the Earth's magnetic field. Since the intensity of the Earth's magnetic field is a range that varies from location to location, the corresponding Larmor frequency is also a range. For example, if the intensity of the Earth's magnetic field ranges from 25,000 nT to 65,000 nT, then for... 87The Rb atom has a Larmor frequency range of approximately 175 kHz to 455 kHz. To ensure that the applied square wave alternating magnetic field can resonate with the Earth's magnetic field, the frequency range of the square wave alternating magnetic field needs to cover the Larmor frequency range, that is, the lower limit of the frequency range of the square wave alternating magnetic field is less than 175 kHz, and the upper limit of the frequency range is greater than 455 kHz.

[0055] According to an embodiment of the present invention, the verification system for a spin-exchange-relaxation atomic magnetometer further includes: a signal conditioning device electrically connected to a photodetector and a verification module, configured to amplify and filter the electrical signal input to the photodetector to obtain a first electrical signal, and output the first electrical signal to the verification module; wherein the verification module is configured to determine the working state of the spin-exchange-relaxation atomic magnetometer based on the first electrical signal.

[0056] A photodetector can convert an optically modulated signal into an electrical signal, but this electrical signal is a relatively weak current signal. To facilitate subsequent analysis of the current characteristics, this weak current signal needs to be amplified and filtered. In this embodiment of the invention, the signal conditioning device can be composed of a pre-amplifier, a programmable gain amplifier unit, and an active filter module cascaded together. The pre-amplifier is electrically connected to the output of the photodetector, converting the weak current signal output by the photodetector into a voltage signal and effectively suppressing background noise. The programmable gain amplifier unit can dynamically adjust the gain through a digital interface, adaptively matching the optimal range of the subsequent analog-to-digital conversion circuit according to the input signal strength. The filter module can be implemented based on a low-pass filter, effectively filtering out high-frequency interference and power frequency noise while retaining the effective signal frequency band of the atomic magnetometer. Furthermore, the signal conditioning device can also integrate a DC bias compensation circuit and a common-mode rejection circuit to eliminate static bias errors introduced by temperature drift or light source fluctuations in the photodetector, further improving signal purity. The conditioned first electrical signal is output to the verification module for subsequent data acquisition and analysis.

[0057] According to an embodiment of the present invention, the verification system for a spin-exchange-relaxation atom magnetometer further includes: a signal conversion device electrically connected to the photodetector and the verification module, configured to perform analog-to-digital conversion processing on the electrical signal input to the photodetector based on a preset sampling rate to obtain a second electrical signal in digital encoding form, and output the second electrical signal to the verification module; wherein the verification module is configured to determine the working state of the spin-exchange-relaxation atom magnetometer based on the second electrical signal.

[0058] In embodiments of the present invention, the signal conversion device can be implemented based on an analog-to-digital converter (ADC). The electrical signal converted by the photodetector is an analog signal, which is highly susceptible to noise and electromagnetic interference during transmission or processing. Interference can be directly superimposed on the analog signal, causing irreversible distortion. Therefore, the electrical signal can be converted from analog to digital by an ADC to obtain a second electrical signal in digital encoding form. In embodiments of the present invention, the resolution of the ADC can be 18 bits, the sampling rate can be 320 kHz, the supply voltage is 2.5 V, and the reference voltage is 3.3 V. During the signal acquisition process of the ADC, 1024 consecutive sampling data points can be selected as a group of processing units. The data is accumulated, summed, and averaged. Through the above-mentioned digital filtering method of accumulation and averaging, random noise interference in the sampling data can be effectively canceled, and a digital sequence with a high signal-to-noise ratio can be output, providing a reliable data foundation for subsequent signal processing.

[0059] According to an embodiment of the present invention, the verification system for a spin-free exchange-relaxed atom magnetometer further includes: a voltage-controlled current source electrically connected to a magnetic field coil, configured to generate a driving current with a preset waveform based on a preset digital scan sequence, and output the driving current to the magnetic field coil.

[0060] In an embodiment of the present invention, the voltage-controlled current source can adopt a Howland current source structure built with an operational amplifier and be controlled by an FPGA to output the corresponding drive current. The voltage-controlled current source with this structure can output a constant current that is proportional to the input voltage and independent of the load impedance.

[0061] According to an embodiment of the present invention, the spin-free exchange relaxation atomic magnetometer calibration system further includes: a temperature control module disposed on the outer surface of the atomic gas chamber and configured to adjust the temperature of the atomic gas chamber.

[0062] In embodiments of the present invention, the temperature control module comprises a flexible heating film, a high-precision platinum resistance temperature sensor, and a temperature controller. The flexible heating film is tightly fitted to the multiple outer walls of the atomic gas chamber to ensure heating uniformity. The platinum resistance temperature sensor employs a dual-redundancy design to acquire multi-point temperature data in real time. The temperature controller is based on PID (Proportional-Integral-Derivative) control, using the temperature feedback signal acquired by the platinum resistance temperature sensor to perform closed-loop regulation of the heating power. The stable operating temperature range covers 65°C to 110°C, meeting the high-temperature, low-magnetic-field gradient operating conditions required for alkali metal rubidium atoms in the SERF state. Simultaneously, the temperature control module is equipped with an over-temperature protection circuit that automatically cuts off the heating circuit when the detected temperature exceeds a set threshold, ensuring system safety. By precisely maintaining the stability of the atomic number density and polarizability inside the atomic gas chamber, the temperature control module provides a crucial foundation for the SERF atomic magnetometer to achieve ultra-high sensitivity measurements.

[0063] Figure 4 A schematic diagram of a spin-free exchange-relaxed atomic magnetometer calibration system according to another embodiment of the present invention is shown.

[0064] like Figure 4 As shown, the coordinated operation between the sequence generator, calibration module 104, laser control module, and gas chamber heating control module can all be implemented using a Field Programmable Gate Array (FPGA). The sequence generator generates a digital scan sequence and produces a drive current based on a voltage-controlled current source to generate a square wave alternating magnetic field in the magnetic field coil. The gas chamber heating control module controls the temperature of the atomic gas chamber 102 through a heating element based on a gas chamber temperature control circuit. The laser control module controls the laser to generate laser light based on a DAC (Digital-to-Analog Converter) and an ADC constant current and constant temperature control circuit, which then acts on the atomic gas chamber 102. The photodetector 103 receives the optical modulation signal inside the probe and converts it into an electrical signal. The electrical signal is input to the calibration module 104 via a transimpedance amplifier, filter, photodetector (PD) signal conditioning circuit, and ADC signal acquisition circuit, and the calibration result of the SERF atomic magnetometer is obtained through the calibration module 104.

[0065] Figure 5 A schematic diagram illustrating the determination of calibration results for a spin-free exchange-relaxation atom magnetometer calibration system according to an embodiment of the present invention is shown.

[0066] like Figure 5As shown, the X-axis data comparison represents the processed data of the first detection signal obtained based on the X-axis magnetic field sub-coil, the Y-axis data comparison represents the processed data of the second detection signal obtained based on the Y-axis magnetic field sub-coil, and the Z-axis data comparison represents the processed data of the third detection signal obtained based on the Z-axis magnetic field sub-coil. The maximum value represents the sum of the maximum amplitude values ​​of multiple frequency sub-signals corresponding to a given frequency signal in the time domain. For example, a 99 kHz frequency signal can be divided into four frequency sub-signals in the time domain, with maximum amplitude values ​​of 2, 2.5, 3, and 3.5 respectively. Therefore, the maximum value of the 99 kHz frequency signal in the figure is 11. Similarly, the minimum value represents the sum of the minimum amplitude values ​​of multiple frequency sub-signals corresponding to a given frequency signal in the time domain. The difference represents the result of subtracting the minimum value corresponding to the given frequency signal from the maximum value, i.e., the characteristic value of the frequency signal. Figure 5 As can be seen from (e), the difference in the second detection signal at the 329 kHz frequency point is significantly greater than the difference in the adjacent frequency points, that is, the second detection signal has a peak near the 329 kHz frequency point, and the SERF atomic magnetometer has magnetic resonance. Therefore, the verification result of the SERF atomic magnetometer is that it is in normal working condition.

[0067] Figure 6 A flowchart of a method for verifying a spin-free exchange-relaxed atomic magnetometer according to an embodiment of the present invention is shown.

[0068] like Figure 6 As shown, the verification method for a spin-free exchange-relaxed atom magnetometer includes operations S610 to S640.

[0069] In operation S610, a square wave alternating magnetic field is generated according to a preset frequency range.

[0070] In operation of S620, a polarizable atomic medium is provided. When the spin-exchange-relaxed atomic magnetometer is in an unshielded state, the atomic medium undergoes Larmor precession under the action of a square wave alternating magnetic field to modulate the probe light of the spin-exchange-relaxed atomic magnetometer and obtain an optical modulation signal.

[0071] In operation of S630, the optical modulation signal is converted into an electrical signal.

[0072] In operation of S640, peak detection is performed on the electrical signal, and the working status of the spin-free exchange relaxation atomic magnetometer is determined based on the peak detection result.

[0073] Those skilled in the art will understand that the features described in the various embodiments of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0074] The embodiments of the present invention have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of the invention. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of the invention, and all such substitutions and modifications should fall within the scope of the invention.

Claims

1. A method for calibrating a spin-free exchange relaxation atomic magnetometer, applied to a calibration system for a spin-free exchange relaxation atomic magnetometer, the calibration system comprising a magnetic field coil, an atomic gas chamber, and a photodetector, wherein the magnetic field coil is disposed inside the probe of the spin-free exchange relaxation atomic magnetometer, the atomic gas chamber is disposed in a spatial region formed by multiple magnetic field coils surrounding it, and the photodetector is disposed inside the atomic gas chamber, characterized in that... The verification method includes: The magnetic field coil is controlled to generate a square wave alternating magnetic field within a preset frequency range; When the spin-exchange-relaxed atomic magnetometer is in an unshielded state, the polarizable atomic medium in the atomic gas cell is controlled to undergo Larmor precession under the action of the square wave alternating magnetic field, so as to modulate the probe light of the spin-exchange-relaxed atomic magnetometer and obtain an optical modulation signal. The optical modulation signal is converted into an electrical signal by a photodetector, wherein the electrical signal is used to characterize the amplitude-frequency characteristics corresponding to the frequency range; Peak detection is performed on the electrical signal, and the working state of the spin-free exchange-relaxation atom magnetometer is determined based on the result of the peak detection.

2. The method for calibrating a spin-free exchange-relaxation atomic magnetometer according to claim 1, characterized in that, The step of performing peak detection on the electrical signal and determining the operating state of the spin-free exchange-relaxation atom magnetometer based on the peak detection result includes: Based on multiple frequency points within the frequency range, the electrical signal is divided into multiple frequency signals, wherein each frequency signal corresponds to one of the frequency points. The frequency signal is divided in the time domain according to a preset time length to obtain multiple frequency sub-signals; Determine the maximum and minimum amplitude values ​​of the frequency sub-signal in the time domain, and obtain the characteristic values ​​of the frequency sub-signal based on subtraction operations; The feature values ​​of the multiple frequency sub-signals are accumulated to obtain the feature value of the frequency signal; Based on the feature values ​​of multiple frequency signals and multiple frequency points corresponding to the frequency signals, a piecewise extreme value accumulation electrical signal is obtained; Peak detection is performed on the segmented extreme value accumulated electrical signal, and the working state of the spin-free exchange relaxation atom magnetometer is determined based on the result of the peak detection.

3. The method for calibrating a spin-free exchange-relaxation atomic magnetometer according to claim 1, characterized in that, The magnetic field coil is a triaxial Helmholtz coil including an X-axis magnetic field sub-coil, a Y-axis magnetic field sub-coil, and a Z-axis magnetic field sub-coil. The step of peak detection of the electrical signal and determining the operating state of the spin-free exchange-relaxation atom magnetometer based on the peak detection result includes: Peak detection is performed on the first detection signal corresponding to the square wave alternating magnetic field generated by the X-axis magnetic field sub-coil to obtain the first detection result; Peak detection is performed on the second detection signal corresponding to the square wave alternating magnetic field generated by the Y-axis magnetic field sub-coil to obtain the second detection result; Peak detection is performed on the third detection signal corresponding to the square wave alternating magnetic field generated by the Z-axis magnetic field sub-coil to obtain the third detection result; Based on the first detection result, the second detection result, and the third detection result, the working state of the spin-free exchange relaxation atom magnetometer is determined.

4. The method for calibrating a spin-free exchange-relaxation atomic magnetometer according to claim 1, characterized in that, The method for verifying a spin-free exchange-relaxation atomic magnetometer also includes: The probe is controlled to be in a target attitude using an attitude adjustment device, wherein the spinless exchange relaxation atom magnetometer is most sensitive to changes in magnetic field under the target attitude.

5. The method for calibrating a spin-free exchange-relaxation atomic magnetometer according to claim 1, characterized in that, The frequency range covers the Larmor frequency range generated by the Earth's magnetic field when the spin-free exchange-relaxed atomic magnetometer is in an unshielded state.

6. The method for calibrating a spin-free exchange-relaxation atomic magnetometer according to claim 1, characterized in that, The method for verifying a spin-free exchange-relaxation atomic magnetometer also includes: The electrical signal is amplified and filtered to obtain a first electrical signal; The working state of the spinless exchange relaxation atom magnetometer is determined based on the first electrical signal.

7. The method for calibrating a spin-free exchange-relaxation atomic magnetometer according to claim 1, characterized in that, The method for verifying a spin-free exchange-relaxation atomic magnetometer also includes: The electrical signal is subjected to analog-to-digital conversion based on a preset sampling rate to obtain a second electrical signal in digital encoding form; The working state of the spinless exchange relaxation atom magnetometer is determined based on the second electrical signal.

8. The method for calibrating a spin-free exchange-relaxation atomic magnetometer according to claim 1, characterized in that, The method for verifying a spin-free exchange-relaxation atomic magnetometer also includes: A driving current with a preset waveform is generated using a voltage-controlled current source based on a preset digital scanning sequence, and the driving current is output to the magnetic field coil.

9. The method for calibrating a spin-free exchange-relaxation atomic magnetometer according to claim 1, characterized in that, The method for verifying a spin-free exchange-relaxation atomic magnetometer also includes: The temperature of the atomic gas chamber is adjusted using a temperature control module.

10. A verification system for a spin-free exchange-relaxation atomic magnetometer, applicable to the verification method for a spin-free exchange-relaxation atomic magnetometer as described in any one of claims 1-9, characterized in that, include: A magnetic field coil is placed inside the probe of a spin-free exchange-relaxation atom magnetometer and is configured to generate a square wave alternating magnetic field within a preset frequency range. An atomic gas chamber is disposed in a spatial region formed by multiple magnetic field coils and is configured to provide a polarizable atomic medium. When the spin-exchange-relaxed atomic magnetometer is in an unshielded state, the atomic medium undergoes Larmor precession under the action of the square wave alternating magnetic field to modulate the probe light of the spin-exchange-relaxed atomic magnetometer and obtain an optical modulation signal. A photodetector, disposed inside the atomic gas chamber, is configured to convert the optical modulation signal into an electrical signal, wherein the electrical signal is used to characterize the amplitude-frequency characteristics corresponding to the frequency range; The verification module is electrically connected to the photodetector and is configured to perform peak detection on the electrical signal and determine the working status of the spin-free exchange relaxation atom magnetometer based on the result of the peak detection.

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