A SERF atomic magnetometer measuring device with integrated flux guide-concentrator

Abstract

A SERF atomic magnetometer measuring device integrating a flux guide-concentrator is disclosed. Placing the flux guide-concentrator at the front end of the SERF atomic magnetometer amplifies weak magnetic fields at a distance. Guiding the amplified magnetic field through the gas cell of the SERF atomic magnetometer improves the magnetometer's response signal, thereby increasing the signal-to-noise ratio of the magnetic measurement device. Furthermore, by designing the shape of the contact magnetic field surface, flux concentration amplification of the measured magnetic field within a specific range can be achieved, thus improving spatial resolution. The device is characterized by including a flux guide-concentrator set on the magnetic field input interface of the magnetometer probe. The combination of the flux guide-concentrator and the magnetometer probe constitutes a magnetometer head with sub-millimeter spatial resolution. The magnetometer head is connected to a three-dimensional displacement stage via a connecting rod.

Description

Technical Field

[0001] This invention relates to the field of quantum precision measurement instrument technology, and in particular to a SERF atomic magnetometer measuring device with an integrated flux guide-focuser. Background Technology

[0002] Spin-Exchange-Relaxation-Free (SERF) atomic magnetometers measure magnetic fields by polarizing atoms and are the most sensitive atomic magnetometers. Miniaturized SERF atomic magnetometers offer advantages such as compact structure and high measurement sensitivity, and have great application potential in fields such as cardiac and brain magnetometry, muscle magnetometry, and magnetic imaging. However, conventional miniaturized SERF atomic magnetometer probes are only centimeter in size, limiting the spatial resolution to the centimeter level. Furthermore, the sensitive element, the atomic gas cell, is typically located at the center of the probe, a certain distance from the magnetic source being measured. This causes the magnetic field generated by the source to attenuate rapidly with the square of the distance as it travels to the atomic gas cell, weakening the measured signal. This limits the application of conventional miniaturized SERF atomic magnetometers in fields such as cardiac magnetometry, brain magnetometry, and magnetic imaging. Currently, the above problems can be solved using flux guides or flux concentrators. However, due to the geometric limitations of these devices, they can only amplify the magnetic field being measured or improve the spatial resolution of the SERF atomic magnetometer individually. This results in a tradeoff between achieving both spatial resolution and signal strength, thus limiting the application of SERF atomic magnetometers in fields such as rock measurement and magnetic material testing. The structural design of this invention comprehensively considers the geometric characteristics of improving spatial resolution and amplifying magnetic field signals, achieving simultaneous amplification of both spatial resolution and signal strength. Summary of the Invention

[0003] The problem solved by this invention is to provide a SERF atomic magnetometer measuring device with an integrated flux guide-concentrator. The invention designs a flux guide-concentrator that can focus the magnetic field to be measured. Placing the flux guide-concentrator at the front end of the SERF atomic magnetometer amplifies the weak magnetic field at a distance. Guiding the amplified magnetic field through the gas cell of the SERF atomic magnetometer improves the response signal of the atomic magnetometer, thereby increasing the signal-to-noise ratio of the magnetic measurement device. Furthermore, by designing the shape of the contact magnetic field surface, the flux concentrator can amplify the magnetic field to be measured within a specific range, thus improving spatial resolution.

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

[0005] A SERF atomic magnetometer measuring device with an integrated flux guide-focuser is characterized in that it includes a flux guide-focuser disposed on the magnetic field input interface of the magnetometer probe, the combination of the flux guide-focuser and the magnetometer probe forming a magnetometer head with sub-millimeter spatial resolution, and the magnetometer head being connected to a three-dimensional displacement stage via a connecting rod.

[0006] The flux guide-concentrator includes a magnetic field collector with its narrow end for approaching the magnetic sample to be tested, a magnetic field transmitter extending axially from the thick end of the magnetic field collector, and a magnetic field amplifier extending axially from one end face of the magnetic field transmitter and contracting radially. The narrow end of the magnetic field amplifier is attached to the magnetic field input interface of the magnetometer probe, and the end face dimensions of the narrow end of the magnetic field amplifier match the end face dimensions of the alkali metal atom gas cell in the magnetometer probe.

[0007] The flux guide-concentrator is an integrated structure formed using soft magnetic ferrite. The end face of the fine end of the magnetic field collector has a sub-millimeter scale. The magnetic field focusing and amplification effect of the flux guide-concentrator is expressed by the following expression:

[0008]

[0009] In the formula, A is the amplification factor, N is the demagnetization factor, and μ is a physical quantity related to lengths L1, L2, and L3. L1 is the length of the magnetic field amplifier, L2 is the length of the magnetic field transmitter, L3 is the length of the magnetic field collector, and μ is the length of the magnetic field acquisition device. r Φ1 is the relative permeability of the soft magnetic ferrite material, Φ3 is the diameter of the narrow end of the magnetic field amplifier, and Φ4 is the diameter of the narrow end of the magnetic field collector.

[0010] The magnetometer probe includes a housing, and a gas chamber electric heating module is disposed inside the housing, with the alkali metal atom gas chamber located inside the gas chamber electric heating module.

[0011] The magnetometer head is located inside the magnetic shielding device. The magnetometer probe is connected to the pump laser module and the detection laser module in the photoelectric measurement and control system through their respective polarization-maintaining optical fibers. The magnetometer probe is connected to the signal acquisition and processing module in the photoelectric measurement and control system through a data transmission line. The magnetometer probe is connected to the host computer.

[0012] Including the following formulas:

[0013]

[0014] Where V BThis is the magnetometer output signal from the signal acquisition and processing module. A is the amplification factor, G is the conversion coefficient of the photodetector, e is the natural constant, OD is the optical depth, c is the speed of light, r is the classical electron radius, f is the D1 line resonance intensity of the alkali metal, n is the atomic number density, l is the atomic cell length, and I... pr η represents the intensity of the detection light incident on the gas chamber, η represents the attenuation coefficient of the gas chamber glass for the intensity of the detection light, and γ represents the intensity of the detection light incident on the gas chamber. e The gyromagnetic ratio is represented by v, the laser frequency is v0, the alkali metal D1 line resonant frequency is v0, Γ is the atomic cell pressure broadening, and R is R. op R is the pumping rate. rel B is the lateral relaxation rate. z The magnitude of the magnetic field to be measured is given.

[0015] The thin end of the magnetic field amplifier is attached tightly to the magnetic field input interface of the magnetometer probe using ultraviolet adhesive.

[0016] The distance between the thin end surface of the magnetic field collector and the surface of the magnetic sample to be tested is maintained at 1 mm to 1.5 mm.

[0017] The gas chamber electric heating module heats the alkali metal atom gas chamber, so that the atomic number density of the alkali metal vapor reaches 10. 13 ~10 14 pcs / cm 3 Magnitude.

[0018] The advantages of this invention compared to the prior art are:

[0019] (1) Conventional SERF atomic magnetometers are limited by the volume of the atomic gas cell itself, and their spatial resolution is usually on the order of millimeters to centimeters. This invention improves the spatial resolution of the entire SERF atomic magnetometer magnetic measurement device to the sub-millimeter level by designing a magnetic flux guide-concentrator structure to focus the magnetic field to be measured.

[0020] (2) Conventional SERF atomic magnetometers have high sensitivity, but due to the quadratic decay of the magnetic field strength with distance, information on weak magnetic fields at distant locations is significantly lost. This invention guides the magnetic field to be measured to the vicinity of the sensitive device of the SERF atomic magnetometer through a flux guide-focuser, and amplifies the magnetic field to be measured during the guidance process.

[0021] (3) Conventional flux guide-concentrators can only achieve the effect of guiding and amplifying the magnetic field or improving spatial resolution. This invention achieves both amplification of the distant magnetic field and improvement of spatial resolution through the design of the flux guide-concentrator structure. The cross-sectional area of ​​the part of the flux guide-concentrator that contacts the magnetic field to be measured is small, which limits the range of amplified magnetic field, thereby improving spatial resolution; combined with the gas cell size in the SERF atomic magnetometer, the magnetic field to be measured is amplified by designing the size of the magnetic field output cross-section, thereby improving the signal-to-noise ratio of the distant magnetic field measurement. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the SERF atomic magnetometer measuring device that implements the present invention, which integrates a flux guide-focuser.

[0023] Figure 2 This is a schematic diagram of the overall structure of a SERF atomic magnetometer measuring device that implements an integrated flux guide-focuser according to the present invention.

[0024] Figure 3 yes Figure 2 A schematic diagram of the connection structure between the three-dimensional displacement stage and the magnetometer probe.

[0025] Figure 4 yes Figure 1 or Figure 2 Schematic diagram of the medium flux guide-concentrator structure.

[0026] The reference numerals in the attached figures are explained as follows: 1-Magnetic flux guide-concentrator; 2-Magnetic sample to be tested; 3-Magnetometer probe; 4-Gas chamber electric heating module; 5-Alkali metal atom gas chamber; 6-Polarization-maintaining fiber; 7-Data transmission line; 8-Photoelectric measurement and control system; 9-Host computer (receiving magnetometer output signal); 10-Three-dimensional displacement stage; 11-Connecting rod; 12-Magnetic shielding device; 13-Magnetic field amplifier; 14-Magnetic field transmitter; 15-Magnetic field collector; Φ1 is the diameter of the thin end of the magnetic field amplifier; Φ2 is the diameter of the thick end of the magnetic field amplifier, or the diameter of the magnetic field transmitter, or the diameter of the thick end of the magnetic field collector; Φ3 is the diameter of the thin end of the magnetic field collector; L1 is the length of the magnetic field amplifier; L2 is the length of the magnetic field transmitter; L3 is the length of the magnetic field collector. Detailed Implementation

[0027] The following is in conjunction with the attached diagram ( Figures 1-4 The invention will be described in the following sections and examples.

[0028] Figure 1 This is a schematic diagram of the SERF atomic magnetometer measuring device that implements the present invention, which integrates a flux guide-focuser. Figure 2 This is a schematic diagram of the overall structure of a SERF atomic magnetometer measuring device that implements an integrated flux guide-focuser according to the present invention. Figure 3 yes Figure 2 A schematic diagram of the connection structure between the three-dimensional displacement stage and the magnetometer probe. Figure 4 yes Figure 1 or Figure 2 Schematic diagram of the medium flux guide-concentrator structure. (Reference) Figures 1 to 4 As shown, a SERF atomic magnetometer measuring device with an integrated flux guide-focuser includes a flux guide-focuser 1 set on the magnetic field input interface of the magnetometer probe 3. The combination of the flux guide-focuser 1 and the magnetometer probe 3 constitutes a magnetometer head with sub-millimeter spatial resolution. The magnetometer head is connected to a three-dimensional displacement stage 10 via a connecting rod 11.

[0029] The flux guiding-focusing device 1 includes a magnetic field collector 15, the thin end of which is used to approach the magnetic sample 2 to be tested; a magnetic field transmitter 14 extending axially from the thicker end of the magnetic field collector 15; and a magnetic field amplifier 13 extending axially from one end face of the magnetic field transmitter 14 and contracting radially. The thin end of the magnetic field amplifier 13 is bonded to the magnetic field input interface of the magnetometer probe 3. The end face dimensions of the thin end of the magnetic field amplifier 13 match the end face dimensions of the alkali metal atom gas cell 5 in the magnetometer probe 3. The flux guiding-focusing device 1 is an integrated structure formed of soft magnetic ferrite. The end face dimensions of the thin end of the magnetic field collector 15 are on the sub-millimeter scale. The magnetic field focusing and amplification effect of the flux guiding-focusing device 1 has the following expression:

[0030]

[0031] In the formula, A is the amplification factor, N is the demagnetization factor, and μ is a physical quantity related to lengths L1, L2, and L3. L1 is the length of the magnetic field amplifier, L2 is the length of the magnetic field transmitter, L3 is the length of the magnetic field collector, and μ is the length of the magnetic field acquisition device. r Φ1 is the relative permeability of the soft magnetic ferrite material, Φ3 is the diameter of the narrow end of the magnetic field amplifier, and Φ4 is the diameter of the narrow end of the magnetic field collector.

[0032] The magnetometer probe 3 includes a housing, within which a gas chamber electric heating module 4 is disposed. The alkali metal atom gas chamber 5 is located within the gas chamber electric heating module 4. The magnetometer head is located within a magnetic shielding device 12. The magnetometer probe 3 is connected to the pump laser module and the detection laser module in the photoelectric measurement and control system 8 via their respective polarization-maintaining optical fibers 6. The magnetometer probe 3 is connected to the signal acquisition and processing module in the photoelectric measurement and control system 8 via a data transmission line 7. The magnetometer probe 3 is connected to a host computer 9.

[0033] Including the following formulas:

[0034]

[0035] Where V B This is the magnetometer output signal from the signal acquisition and processing module. A is the amplification factor, G is the conversion coefficient of the photodetector, e is the natural constant, OD is the optical depth, c is the speed of light, r is the classical electron radius, f is the D1 line resonance intensity of the alkali metal, n is the atomic number density, l is the atomic cell length, and I... pr η represents the intensity of the detection light incident on the gas chamber, η represents the attenuation coefficient of the gas chamber glass for the intensity of the detection light, and γ represents the intensity of the detection light incident on the gas chamber. e The gyromagnetic ratio is represented by v, the laser frequency is v0, the alkali metal D1 line resonant frequency is v0, Γ is the atomic cell pressure broadening, and R is R. op R is the pumping rate. rel B is the lateral relaxation rate. z The magnitude of the magnetic field to be measured is given.

[0036] The thin end of the magnetic field amplifier 13 is tightly attached to the magnetic field input interface of the magnetometer probe 3 using ultraviolet adhesive. The thin end of the magnetic field acquisition unit 15 maintains a distance of 1 mm to 1.5 mm from the surface of the magnetic sample 2 to be tested. The gas chamber electric heating module 4 heats the alkali metal atom gas chamber 5, causing the atomic number density of the alkali metal vapor to reach 10. 13 ~10 14 pcs / cm 3 Magnitude.

[0037] This invention proposes a SERF atomic magnetometer measurement device integrating a flux guide-focuser. The invention designs a flux guide-focuser structure, utilizing the properties of soft magnetic ferrite and the geometric characteristics of the designed structure to achieve ultra-high sensitivity fT-level, high resolution sub-millimeter-level measurement of weak magnetic sources. The instrument designed in this invention utilizes a specially designed geometric structure of high-permeability soft magnetic ferrite to change the distribution of the magnetic field in space, guiding and amplifying weak magnetic field signals from a distance far from the sensitive part of the SERF atomic magnetometer to the near end of the atomic source of the atomic magnetometer, thereby achieving detection of weak magnetic fields at a distance. Simultaneously, through the design of the contact cross-section with the magnetic field to be measured, the spatial resolution of the SERF atomic magnetometer is improved. Compared with conventional SERF atomic magnetometers, this invention uses a flux guide-focuser to improve the spatial resolution of the SERF atomic magnetometer from the centimeter level to the sub-millimeter level, and can simultaneously amplify the signal of the magnetic field to be measured, achieving ultra-high sensitivity fT-level, high resolution sub-millimeter-level magnetic imaging.

[0038] A SERF atomic magnetometer measuring device integrating a flux guide-focuser is provided. Its main components include: a flux guide-focuser (1), a magnetic sample to be measured (2), a magnetometer probe (3), a gas chamber electric heating module (4), an alkali metal atomic gas chamber (5), a polarization-maintaining fiber (6), a data transmission line (7), a photoelectric measurement and control system (8), a host computer (9), a three-dimensional displacement stage (10), a connecting rod (11), a magnetic shielding device (12), a magnetic field amplifier (13), a magnetic field transmitter (14), and a magnetic field collector (15). The flux guide-focuser (1) is placed on the outside of the magnetometer probe (3), and the two are bonded together using high-temperature ultraviolet glue, and the central axis of the flux guide-focuser (1) is aligned with the central axis of symmetry of the alkali metal atomic gas chamber (5). The flux guide-focuser (1) and the magnetometer probe (3) containing the gas chamber electric heating module (4) and the alkali metal atomic gas chamber (5) together form an atomic magnetometer probe with sub-millimeter spatial resolution. Two laser beams generated by the narrow linewidth laser in the photoelectric measurement and control system (8) are respectively guided into the magnetometer probe (3) through polarization-maintaining fiber (6). The pump light incident by the polarization-maintaining fiber (6) is converted into circularly polarized light in the magnetometer probe (3) after polarization state conversion, and pumps and polarizes the alkali metal atoms in the gas chamber. The detection light incident by the polarization-maintaining fiber (6) is incident through the alkali metal atom gas chamber (5). The linearly polarized light after exiting generates an optical rotation angle. The optical rotation angle is detected by differential detection technology and transmitted to the photoelectric measurement and control system (8) through the data transmission line (7). The data is preliminarily processed by the data acquisition and processing module, and the obtained magnetometer signal is transmitted to the host computer (9).

[0039] The magnetic flux guide-concentrator (1) is integrally processed from a soft magnetic material with high permeability. Its structure can be divided into: magnetic field amplifier (13), magnetic field transmitter (14), and magnetic field collector (15). The geometric features of the magnetic field amplifier (13), magnetic field transmitter (14), and magnetic field collector (15) are frustum, cylinder, and cone, respectively, with corresponding diameters of Φ1, Φ2, and Φ3, and lengths of L1, L2, and L3, respectively. They satisfy the relationship that Φ3 < Φ1 < Φ2 and that the side lengths of Φ1 and the alkali metal gas chamber (10) are equal. In addition, they should also satisfy the size condition that Φ3 is in the sub-millimeter range and Φ1 and Φ2 are in the millimeter range. The top of the magnetic field collector (15) determines the range of the magnetic field to be amplified. The diameter of the cross section at the top that contacts the magnetic field to be measured is designed to be on the sub-millimeter level. The magnetic field transmitter (14) plays the role of converging and guiding the magnetic field. The size of its end face is equal to the bottom face of the magnetic field collector (15) and the magnetic field amplifier (13). The smaller cross-sectional area of ​​the magnetic field amplifier (13) faces the magnetometer probe (3), so that the magnetic field is converged and amplified before being emitted. The diameter of the emission surface of the magnetic field amplifier (13) is similar to the size of the alkali metal gas chamber (5), so that the amplified magnetic field is completely detected.

[0040] The photoelectric measurement and control system (8) consists of a pumping narrow-linewidth laser, a detection narrow-linewidth laser, and a signal acquisition and preprocessing module. The pumping narrow-linewidth laser and the detection narrow-linewidth laser generate two laser beams for pumping atoms and detecting magnetic fields. The two laser beams enter the magnetometer probe (3) after passing through two polarization-maintaining optical fibers (6). The photoelectric measurement and control system (8) acquires magnetic field information through a data transmission line (7) and processes the signal using a data acquisition and processing module. After processing, the magnetometer output signal is transmitted to the host computer (9).

[0041] The magnetometer probe (3) contains a gas chamber electric heating module (4) and an alkali metal atom gas chamber (5). The laser incident through one of the polarization-maintaining optical fibers (6) is a pump light with a circular polarization state, which pumps and polarizes the alkali metal atoms in the alkali metal atom gas chamber (10). The laser incident through the other polarization-maintaining optical fiber (6) is a detection light with a linear polarization state.

[0042] The alkali metal atom gas chamber (5) is placed in a weak magnetic environment and inside the gas chamber electric heating module (4), which is filled with alkali metal atoms and the atomic number density reaches 10. 13 ~10 14 pcs / cm 3 The alkali metal atom gas chamber (5) is placed in the center of the gas chamber electric heating module (4), and the alkali metal atom gas chamber (5) is heated by the gas chamber electric heating module (4).

[0043] The magnetometer probe (3) and the flux guide-concentrator (1) constitute a magnetometer probe with sub-millimeter spatial resolution, which together with the photoelectric measurement and control system (8) constitute a magnetic measurement device.

[0044] The magnetometer probe (3) and the flux guide-focuser (1) constitute a magnetometer probe with sub-millimeter spatial resolution. The magnetometer probe with sub-millimeter spatial resolution is placed in a magnetic shielding device (12) so that the working environment of the magnetometer probe (3) is a near-zero magnetic environment. The flux guide-focuser (1) and the magnetometer probe (3) containing a gas chamber electric heating module (4) and an alkali metal atom gas chamber (5) together constitute an atomic magnetometer probe with sub-millimeter spatial resolution. The atomic magnetometer probe with sub-millimeter spatial resolution composed of the flux guide-focuser (1) and the magnetometer probe (3) is placed in a magnetic shielding device (12), and the photoelectric measurement and control system (8), the three-dimensional displacement stage (10), and the connecting rod (11) are placed outside the magnetic shielding device (12).

[0045] One end of the connecting rod (11) is fixed to the three-dimensional displacement stage (10), and the other end is connected to the magnetometer probe (3). By moving the platform of the three-dimensional displacement stage (10), the magnetometer probe (3) can move in the xy plane through synchronous movement, thereby realizing the measurement of the two-dimensional spatial magnetic field distribution. Movement in the z direction can realize the distance adjustment between the magnetometer probe (3) and the sample array (2) to be measured. The three-dimensional displacement stage (11) can move in the x and y directions. One end of the connecting rod (11) is fixed to the platform of the three-dimensional displacement stage (10), and the magnetometer probe (3) is fixed to the other end of the connecting rod (11). When moving the platform of the three-dimensional displacement stage (10), the magnetometer probe (3) moves synchronously, thereby realizing two-dimensional movement in the xy plane. The central axis of the flux guide-concentrator (1) is perpendicular to the plane of the magnetic sample (2) to be tested. The position between the flux guide-concentrator (1) and the magnetic sample (2) to be tested is adjusted by the three-dimensional displacement stage (10) so that the distance between them is within the range of 1 mm to 1.5 mm.

[0046] See Figure 1 This invention provides a SERF atomic magnetometer measuring device with an integrated flux guiding-focusing device. For example... Figure 1 As shown, a SERF atomic magnetometer measuring device with an integrated flux guide-concentrator includes: a flux guide-concentrator 1, a magnetic sample to be measured 2, a magnetometer probe 3, a gas chamber electric heating module 4, an alkali metal atomic gas chamber 5, a polarization-maintaining optical fiber 6, a data transmission line 7, a photoelectric measurement and control system 8, and a host computer 9 for receiving the magnetometer output signal; the central axis of the flux guide-concentrator 1 is perpendicular to the horizontal plane where the magnetic sample to be measured 2 is located.

[0047] See Figure 2 This invention provides a SERF atomic magnetometer measuring device integrating a flux guide-concentrator. The three-dimensional displacement stage 10 can realize two-dimensional motion in the xy plane. One end of the connecting rod 11 is fixed to one end of the three-dimensional displacement stage 10, and the magnetometer probe 3 is fixed to the other end of the connecting rod 11. The flux guide-concentrator 1 is fixed to the outer shell of the magnetometer probe 3 with high-temperature ultraviolet glue, so that the central axis of the flux guide-concentrator 1 is on the same straight line as the central axis of symmetry of the alkali metal atom gas chamber 5. The magnetometer probe with sub-millimeter spatial resolution, composed of the flux guide-concentrator 1 and the magnetometer probe 3, is placed in the magnetic shielding device 12. The photoelectric measurement and control system 8, the connecting rod 11, and the three-dimensional displacement stage 10 are placed outside the magnetic shielding device 12.

[0048] See Figure 3 This invention provides a motion structure for achieving three-dimensional motion. For example... Figure 3As shown, one end of the connecting rod 11 is fixed to the motion platform of the three-dimensional displacement stage 10, and the other end is connected to the magnetometer probe 3, thereby realizing the synchronous movement between the magnetometer probe 3 and the three-dimensional displacement stage 10.

[0049] See Figure 4 This invention provides a flux guiding-focusing structure. For example... Figure 3 As shown, the structure with improved spatial resolution and magnetic field guidance amplification effect comprises three parts: a magnetic field amplifier 12, a magnetic field transmitter 13, and a magnetic field collector 14. The magnetic field amplifier 12 has a cross-sectional diameter of Φ1 and a length of L1; the magnetic field transmitter 13 has a cross-sectional diameter of Φ2 and a length of L2; the amplification range of the magnetic field to be measured by the magnetic field collector 14 is determined by its cross-sectional diameter Φ3, and its length is L3; and the diameter parameters are such that Φ3 < Φ1 < Φ2, where Φ3 is in the sub-millimeter range, and Φ1 and Φ2 are in the millimeter range.

[0050] like Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, the specific implementation steps of the present invention are as follows:

[0051] (1) First, the magnetic flux guide-concentrator is fabricated. Soft magnetic ferrite with high permeability and high Curie temperature is used for processing. The cross-sectional diameter Φ3 of the magnetic field collector 15 is 0.1 mm, and the length L3 is 1 mm; the cross-sectional diameter Φ2 of the magnetic field transmitter 14 is 3 mm, and the length L2 is 1 mm; the cross-sectional diameter Φ1 of the magnetic field amplifier 13 is 1 mm, and the length L1 is 2 mm. The magnetic field converging and amplification effect of the magnetic flux guide-concentrator is related to the above-mentioned structural geometry, and the amplification factor A can be expressed as:

[0052]

[0053] In the formula, N is the demagnetization factor, which is a physical quantity related to lengths L1, L2, and L3, and μ r The relative permeability of soft magnetic ferrite materials;

[0054] (2) The flux guide-concentrator 1 is placed outside the magnetometer probe 3, and the two are tightly bonded together with UV adhesive to form a magnetometer head with sub-millimeter spatial resolution; the alkali metal atom gas chamber 5 is heated by the gas chamber electric heating module 4 to make the atomic number density of alkali metal vapor reach 10. 13 ~10 14 pcs / cm 3 Magnitude;

[0055] (3) Adjust the narrow-linewidth semiconductor laser in the photoelectric measurement and control system 8 so that the laser frequency of the pump light entering the magnetometer probe 3 through the polarization-maintaining fiber 6 is the alkali metal D1 line resonance frequency. Within the probe head, the laser undergoes polarization state conversion to become circularly polarized light, polarizing the alkali metal atoms in the alkali metal atom gas chamber 5. Adjust the narrow-linewidth semiconductor laser in the photoelectric measurement and control system 8 so that the laser frequency of the detection light entering the magnetometer probe 3 through the polarization-maintaining fiber 6 is detuned to the alkali metal D1 line resonance frequency of 5 GHz. Introduce the detection light into the alkali metal atom gas chamber 5. At this time, the linearly polarized light will rotate in polarization direction. The angle of rotation is called the optical rotation angle θ. Using differential amplification technology, the optical information containing magnetic field information is converted into electrical information. This information is collected by the photoelectric measurement and control system 8 through the output transmission line 7. After processing by the data acquisition and processing module, the magnetometer output signal V is output. B , is represented as:

[0056]

[0057] In the formula, G is the conversion coefficient of the photodetector, e is the natural constant, and I... pr Here, c is the intensity of the detection light incident on the gas cell, r is the classical electron radius, n is the atomic number density, f is the D1 line resonance intensity of the alkali metal, l is the length of the atomic gas cell, η represents the attenuation coefficient of the gas cell glass to the intensity of the detection light, v0 is the D1 line resonance frequency of the alkali metal, v is the frequency of the laser, Γ is the pressure broadening of the atomic gas cell, OD is the optical depth, and γ is the intensity of the detection light incident on the gas cell. e R represents the gyromagnetic ratio. op R is the pumping rate. rel G is the transverse relaxation rate, and B is the measurement amplification factor. z The magnitude of the magnetic field to be measured is given. Compared to the SERF atomic magnetometer magnetic measurement device without flux guide-focus 1, this invention increases the output response signal by a factor of A, achieving high-sensitivity measurement of weak magnetic fields at a distance.

[0058] (7) Place the magnetic sample 2 to be tested on the xy plane, use the three-dimensional displacement stage 10 to adjust the position of the atomic magnetometer probe with sub-millimeter spatial resolution, so that the central axis of the flux guide-concentrator 1 is perpendicular to the xy plane, and adjust the distance between the probe and the plane where the magnetic sample 2 is located, so that the distance between the two is kept within 1 mm to 1.5 mm.

[0059] (8) Using a three-dimensional displacement stage 10, the magnetometer probe 3 is moved at a constant speed in the xy plane, moving from one end of the magnetic sample 2 to the other end along the x direction. The magnetometer output signal displayed on the host computer 9 is recorded. Then, after moving 0.3 mm along the y direction, the above process is repeated at a constant speed. Using the collected magnetometer output signal, the relationship between the magnetic field and the spatial position is plotted, thereby achieving the resolution of sub-millimeter-level remote weak magnetic sources.

[0060] In summary, this invention provides a SERF atomic magnetometer measuring device with an integrated flux guide-concentrator. It constructs a flux guide-concentrator that enhances the magnitude of the magnetic field to be measured, thereby improving the spatial resolution and response signal of the SERF atomic magnetometer. The magnetic field measurement is then performed using the optical pump principle and differential detection technology within the SERF atomic magnetometer. This invention utilizes a high-permeability soft magnetic ferrite to design the flux guide-concentrator, improving the spatial resolution of the SERF atomic magnetometer measuring device and amplifying the magnetic field to be measured, enabling highly sensitive and accurate measurement of small, distant, weak magnetic fields.

[0061] Contents not described in detail in this specification are prior art known to those skilled in the art. It is hereby indicated that the above description is intended to help those skilled in the art understand this invention, but does not limit the scope of protection of this invention. Any equivalent substitutions, modifications, improvements, and / or simplifications of the above descriptions that do not depart from the essential content of this invention fall within the scope of protection of this invention.

Claims

1. A SERF atomic magnetometer measuring device integrating a flux guide-concentrator, characterized in that, The method includes setting a flux guide-concentrator on the magnetic field input interface of the magnetometer probe. The combination of the flux guide-concentrator and the magnetometer probe constitutes a magnetometer head with sub-millimeter spatial resolution. The magnetometer head is connected to a three-dimensional displacement stage via a connecting rod. The flux guide-concentrator includes a magnetic field collector with its narrow end for approaching the magnetic sample to be tested, a magnetic field transmitter extending axially from the thick end of the magnetic field collector, and a magnetic field amplifier extending axially from one end face of the magnetic field transmitter and contracting radially. The narrow end of the magnetic field amplifier is attached to the magnetic field input interface of the magnetometer probe, and the end face dimensions of the narrow end of the magnetic field amplifier match the end face dimensions of the alkali metal atom gas cell in the magnetometer probe.

2. The SERF atomic magnetometer measuring device with integrated flux guide-concentrator according to claim 1, characterized in that, The flux guide-concentrator is an integrated structure formed using soft magnetic ferrite. The end face of the fine end of the magnetic field collector has a sub-millimeter scale. The magnetic field focusing and amplification effect of the flux guide-concentrator is expressed by the following expression: In the formula, A is the amplification factor, N is the demagnetization factor, and μ is a physical quantity related to lengths L1, L2, and L3. L1 is the length of the magnetic field amplifier, L2 is the length of the magnetic field transmitter, L3 is the length of the magnetic field collector, and μ is the length of the magnetic field acquisition device. r Φ1 is the relative permeability of the soft magnetic ferrite material, Φ3 is the diameter of the narrow end of the magnetic field amplifier, and Φ4 is the diameter of the narrow end of the magnetic field collector.

3. The SERF atomic magnetometer measuring device with integrated flux guide-concentrator according to claim 1, characterized in that, The magnetometer probe includes a housing, and a gas chamber electric heating module is disposed inside the housing, with the alkali metal atom gas chamber located inside the gas chamber electric heating module.

4. The SERF atomic magnetometer measuring device with integrated flux guide-concentrator according to claim 1, characterized in that, The magnetometer head is located inside the magnetic shielding device. The magnetometer probe is connected to the pump laser module and the detection laser module in the photoelectric measurement and control system through their respective polarization-maintaining optical fibers. The magnetometer probe is connected to the signal acquisition and processing module in the photoelectric measurement and control system through a data transmission line. The magnetometer probe is connected to the host computer.

5. The SERF atomic magnetometer measuring device with integrated flux guide-concentrator according to claim 2, characterized in that, Including the following formulas: Where V B This is the magnetometer output signal from the signal acquisition and processing module. A is the amplification factor, G is the conversion coefficient of the photodetector, e is the natural constant, OD is the optical depth, c is the speed of light, r is the classical electron radius, f is the D1 line resonance intensity of the alkali metal, n is the atomic number density, l is the atomic cell length, and I... pr η represents the intensity of the detection light incident on the gas chamber, η represents the attenuation coefficient of the gas chamber glass for the intensity of the detection light, and γ represents the intensity of the detection light incident on the gas chamber. e The gyromagnetic ratio is represented by v, the laser frequency is v0, the alkali metal D1 line resonance frequency is v0, Γ is the atomic cell pressure broadening, and R is R. op R is the pumping rate. rel B is the lateral relaxation rate. z The magnitude of the magnetic field to be measured is given.

6. The SERF atomic magnetometer measuring device with integrated flux guide-concentrator according to claim 1, characterized in that, The thin end of the magnetic field amplifier is attached tightly to the magnetic field input interface of the magnetometer probe using ultraviolet adhesive.

7. The SERF atomic magnetometer measuring device with integrated flux guide-focuser according to claim 1, characterized in that, The distance between the thin end surface of the magnetic field collector and the surface of the magnetic sample to be tested is maintained at 1 mm to 1.5 mm.

8. The SERF atomic magnetometer measuring device with integrated flux guide-concentrator according to claim 3, characterized in that, The gas chamber electric heating module heats the alkali metal atom gas chamber, so that the atomic number density of the alkali metal vapor reaches 10. 13 ~10 14 pcs / cm 3 Magnitude.

Images