Device and method for measuring residual magnetic field intensity of magnetic shielding cavity

Abstract

The invention relates to the technical field of magnetic field detection, in particular to a device and method for measuring the residual magnetic field intensity of a magnetic shielding cavity, the device comprises an exploring tube, a detection system, a stabilization system and a data processing terminal, the exploring tube can stretch out, draw back and rotate, the detection system is fixedly installed on the exploring tube, the stabilization system is arranged outside the exploring tube, and the data processing terminal is connected with the data processing terminal. The data processing terminal is used for offsetting the gravitational torque of the exploring tube and feeding back the inclination state of the exploring tube in real time, and data interpolation and residual magnetic field cloud picture generation in the magnetic shielding device are achieved through the data processing terminal. According to the method, a carbon fiber probe tube is inserted, adjusted and locked through a magnetic shielding cavity cover plate, then the probe tube is stretched step by step, the probe tube is rotated after stretching of each step, magnetic field data of each point is recorded, the space coordinates of each measuring point are calculated in combination with the scale and the rotation angle of the probe tube, and a three-dimensional residual magnetic field cloud picture is generated by using a radial basis function interpolation method. And cloud picture distribution is analyzed, a shielding weak area is positioned, and structure optimization is guided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic detection, in particular to a magnetic shielding cavity residual magnetic field strength measurement device and method. BACKGROUND

[0002] Magnetic shielding cavities are widely used in quantum computing, biological magnetic measurement, high-precision inertial navigation and other fields. The accurate measurement of the internal residual magnetic field strength of the magnetic shielding cavity has an important influence on the performance of the equipment. Traditional measurement methods mainly include open cover direct measurement method, pre-embedded fixed sensor array, external excitation indirect evaluation method, mechanical arm moving measurement device and pneumatic suspension scanning platform. However, these methods have obvious limitations: (1) The open cover direct measurement method needs to repeatedly disassemble the cover, which destroys the shielding integrity, introduces external magnetic field interference, and is cumbersome and has poor repeatability; (2) The pre-embedded fixed sensor array has poor flexibility, high cost and difficult maintenance, and the demagnetization process may affect the accuracy of the sensor; (3) The external excitation indirect evaluation method cannot measure the internal inherent residual magnetism, depends on additional equipment, and is limited in application scenarios; (4) The mechanical arm moving measurement device can realize automatic scanning, but the mechanical arm itself is easy to introduce magnetic pollution, and the control is complex and requires a large aperture; (5) The positioning accuracy of the pneumatic suspension scanning platform is low, it is difficult to realize three-dimensional scanning, and the airflow disturbance affects the environmental stability.

[0003] The above methods cannot realize high-precision, high-stability and full-coverage internal residual magnetic field measurement while maintaining the integrity of the magnetic shielding cavity. Therefore, a new measurement device and method are needed to overcome the shortcomings of the prior art. SUMMARY

[0004] The main purpose of the present application is to overcome the shortcomings of the prior art, and provide a magnetic shielding cavity residual magnetic field strength measurement device and method. The technical scheme adopted by the present application to achieve its technical purpose is: a magnetic shielding cavity residual magnetic field strength measurement device, the measurement device comprises: a probe tube, which can be telescopic and rotatable; a detection system, which is fixedly installed on the probe tube and comprises a mounting frame and a fluxgate sensor, the fluxgate sensor being fixed on the probe tube through the mounting frame; a stabilizing system, which is arranged outside the probe tube and is used for counteracting the gravity moment of the probe tube and feeding back the tilt state of the probe tube in real time; a data processing terminal, which is based on MATLAB or Python algorithm and realizes data interpolation and residual magnetic field cloud map generation in the magnetic shielding device.

[0005] Preferably, the probe tube is a carbon fiber probe tube or other non-magnetic material, with an outer diameter of 28 mm, a wall thickness of 2 mm, and a magnetic susceptibility χ ≈ -1.6 × 10 -6 .

[0006] Preferably, the mounting frame is an L-shaped aluminum alloy support, and a set of three-axis orthogonal fluxgate sensors is arranged at each of the three end points, for a total of nine single-axis sensors, with a range of ±100 μT, a resolution of 0.1 nT, and covering three-dimensional magnetic field components.

[0007] Preferably, the stabilizing system includes a crank, a support sleeve, a sliding block, a pointer, a scale, a guide rail, a base support, a shaft sleeve and a cushion block, a level, and a locking wrench. The two ends of the probe tube are respectively sleeved with a support sleeve and a shaft sleeve, the shaft sleeve is fixedly installed on the base support through the cushion block, the shaft sleeve is sleeved on the outer wall of the probe tube, and the bottom of the shaft sleeve is fixedly connected to the base support through the cushion block; The support sleeve is slidingly connected to the base support through the sliding block and the guide rail, the support sleeve is rotatably connected to the probe tube, the bottom of the support sleeve is fixedly connected to the sliding block, the sliding block is slidingly connected to the guide rail, and the guide rail is fixedly installed on the base support and abuts against one side of the cushion block at one end. The crank is fixedly connected to the side wall of the probe tube at the end, the support sleeve and one end of the probe tube are slid on the sliding block by pushing the crank, the probe tube is rotated by rotating the crank, the displacement and angle of the mounting frame and the fluxgate sensors are adjusted by moving and rotating the probe tube, and the detection accuracy can be controlled.

[0008] Preferably, the outer wall of the probe tube is marked with a rotation angle scale. One side wall of the sliding block is fixedly installed with a pointer, the base support is provided with a scale corresponding to the position of the pointer, and the pointer points to the scale on the scale. When the support sleeve and one end of the probe tube slide on the sliding block, the pointer points to the scale on the scale in real time, the distance moved by the probe tube can be known in real time, the displacement of the mounting frame and the fluxgate sensors can be known in real time, and the rotation angle of the mounting frame and the fluxgate sensors can be known in real time by cooperating with the rotation angle scale marked on the outer wall of the probe tube, so that the detection accuracy can be more finely controlled.

[0009] Preferably, the other side wall of the sliding block is fixedly installed with a locking wrench, and the sliding block can be locked and fixed on the guide rail through the locking wrench.

[0010] Preferably, the base support is also fixedly installed with a level, and the level has an accuracy of ±0.1°, and the probe tube inclination state is fed back in real time through the level.

[0011] The application further provides a method for measuring the residual magnetic field intensity of a magnetic shielding cavity, which adopts the measuring device described in the above method and comprises the following steps: Step 1: insert the probe tube 1 into the 30 mm aperture on the cover plate of the magnetic shielding cavity, install the bracket inside the magnetic shielding cavity, adjust the bottom support to make the reading of the level gauge less than 0.3°, keep the balance posture, and then make the probe tube move along the central axis of the magnetic shielding cavity; Step 2: extend the probe tube step by step, rotate the probe tube after each extension, and complete the circumferential test; wherein, each measurement point is stepped by 30°, the magnetic field data of each point is recorded, and a groove is arranged at each rotation stepping point to ensure the accuracy of the test position; Step 3: scan according to the probe tube displacement and rotation angle to form a cylindrical coordinate system, calculate the spatial coordinates of each measurement point, generate all the measurement point coordinates and magnetic field vectors, and generate a three-dimensional residual magnetic cloud map by using a radial basis function interpolation method for the unmeasured area; Step 4: analyze the cloud map distribution, locate the weak shielding area, and guide the structure optimization by pasting a permalloy tape in the weak area.

[0012] Preferably, the probe tube displacement ΔL and the rotation angle θ in step 3 form a cylindrical coordinate system scan, which satisfies: ; Wherein, r is the length of the support arm, and a cylindrical surface with a radius of r is scanned.

[0013] Preferably, the interpolation method in step 3 comprises: S1, normalize the measurement point coordinates: Convert the probe tube displacement and rotation angle to the spatial coordinates of the measurement points in the rectangular coordinate system And the magnetic field vector , normalize the measurement point coordinates to make all the coordinate values fall within the interval [0, 1] to improve the stability of the interpolation, and the normalization processing is as follows: ; S2, construct a linear equation system based on the radial basis function to solve the weight coefficients: Select a basis function suitable for the magnetic field attenuation characteristics , wherein r is the distance matrix, and the Euclidean distance between the measurement points is calculated: ; The shape parameter of the control function can be selected , and the magnetic field of the unmeasured points is reconstructed based on the radial basis function: ; Wherein, the weight w i is obtained by fitting the measured points; Solve the linear equation system wherein Phi is an N x N matrix, the elements of which are , is the weight to be solved, is the measured magnetic field value; S3, using the weight coefficient and the base function to calculate the magnetic field value of the unmeasured point, to generate a cloud picture: In the radial basis function interpolation method, once the weight coefficient is determined, it will remain unchanged, and when calculating the magnetic field value of any new point, only the base function value between the point and the known point needs to be recalculated, without the need to solve the weight again. The magnetic field intensity of any point can be obtained, and then the residual magnetic field cloud picture can be obtained.

[0014] The working principle of the magnetic shielding cavity residual magnetic field strength measurement device and method is as follows: through a mechanical stability system capable of precisely controlling displacement and angle, a multi-channel magnetic field detection system is deeply scanned and measured inside a sealed magnetic shielding cavity. On the premise of not damaging the shielding integrity of the cavity, the distribution cloud picture of the three-dimensional residual magnetic field inside the cavity is reconstructed by using an algorithm. Specifically, a non-magnetic carbon fiber probe pipe is inserted into the inside through the opening on the cover plate of the magnetic shielding cavity, and the end of the probe pipe is fixed with three groups of three-axis fluxgate sensors through an L-shaped mounting bracket to form a nine-channel magnetic field detection system. The probe pipe is moved in and out along the sliding block and guide rail by pushing the support sleeve with a crank, the displacement amount is indicated by the cooperation of the pointer and the scale, the probe pipe can be rotated by rotating the crank, and the angle is indicated by the scale on the outer wall to realize accurate positioning in three-dimensional space. The inclinometer monitors the inclination in real time, and the position is fixed by the locking wrench. The sensor data is collected by the data processing terminal and the three-dimensional residual magnetic field cloud picture is generated based on the radial basis function interpolation algorithm. The whole process does not need to open the cover, and the shielding integrity is maintained.

[0015] Compared with the prior art, the magnetic shielding cavity residual magnetic field strength measurement device and method has the following advantages: The magnetic shielding cavity residual magnetic field strength measurement device and method can realize closed-state measurement, maintain the shielding integrity, insert a non-magnetic probe pipe through the limited aperture on the cover plate of the magnetic shielding cavity to realize internal measurement, do not need to open the cover, effectively avoid external magnetic field interference, and maintain the integrity and stability of the shielding structure.

[0016] The magnetic shielding cavity residual magnetic field strength measurement device and method can realize high-precision three-dimensional scanning. Through the telescopic and rotating composite motion mechanism, combined with the scale positioning and step control, three-dimensional space scanning with sub-centimeter precision is realized, and the whole domain residual magnetic field measurement is covered.

[0017] The magnetic shielding cavity residual magnetic field strength measurement device and method has high stability and anti-interference ability. The carbon fiber probe pipe and the counterweight system are designed, the probe pipe inclination angle is controlled within ±0.3°, the gravity moment is effectively offset, and mechanical vibration and magnetic pollution are avoided.

[0018] The magnetic shielding cavity residual magnetic field strength measuring device and method can realize intelligent data processing and visual processing, efficiently generate a three-dimensional residual magnetic field cloud map based on a radial basis function interpolation algorithm, intuitively display a weak shielding performance area, and provide accurate data support for structure optimization.

[0019] The magnetic shielding cavity residual magnetic field strength measuring device and method adopts an L-shaped three-axis sensor array, covers nine magnetic field components in a single measurement, greatly improves measurement efficiency, does not require external excitation equipment, reduces system complexity and cost, and has the characteristics of high efficiency and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0021] Figure 1 It is a perspective structural schematic diagram of the magnetic shielding cavity residual magnetic field strength measuring device.

[0022] Figure 2 It is Figure 1 It is a perspective structural schematic diagram of the magnetic shielding cavity residual magnetic field strength measuring device from another angle.

[0023] Figure 3 It is an operation step flow chart of the magnetic shielding cavity residual magnetic field strength measuring method.

[0024] 1, probe tube; 2, mounting frame; 3, magnetic flux gate sensor; 4, crank; 5, support sleeve; 6, sliding block; 7, pointer; 8, scale; 9, guide rail; 10, bottom plate support frame; 11, shaft sleeve; 12, pad; 13, level; 14, locking wrench. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail by means of drawings and examples. However, it should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the scope of the present application. In addition, in the following description, the description of known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present application.

[0026] In the description of the present application, it should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on another element or indirectly on the other element. When an element is referred to as "connected to" another element, it can be directly connected to another element or indirectly connected to the other element.

[0027] In the description of the present application, it should be noted that the terms "center", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly used when the product of the present application is used, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0028] In the description of the present application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "arrangement", "installation", "connection", "connection" should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0029] Example 1:

[0030] Please refer to Figures 1-2 A magnetic shielding cavity residual magnetic field strength measuring device, the measuring device comprises a probe tube 1, a detection system, a stabilizing system and a data processing terminal.

[0031] The probe tube 1 can be telescopic and rotatable, the probe tube 1 is a carbon fiber probe tube or other non-magnetic material, the outer diameter is 28mm, the wall thickness is 2mm, and the magnetic susceptibility χ≈-1.6×10 -6 .

[0032] The detection system is fixedly installed on the probe tube 1, and comprises a mounting frame 2 and a fluxgate sensor 3, the fluxgate sensor 3 is fixed on the probe tube 1 through the mounting frame 2. The mounting frame is provided as an L-shaped aluminum alloy support, and a set of three-axis orthogonal fluxgate sensors 3 are arranged at each of the three end points, a total of nine single-axis sensors, with a range of ±100μT, a resolution of 0.1nT, and covering three-dimensional magnetic field components.

[0033] The stabilizing system is arranged outside the probe tube 1, and is used for counteracting the gravity moment of the probe tube 1 and feeding back the tilt state of the probe tube in real time.

[0034] The data processing terminal realizes data interpolation and generation of a residual magnetic field cloud diagram in the magnetic shielding device based on a MATLAB or Python algorithm.

[0035] Further, in the embodiment, the stabilizing system comprises a crank 4, a supporting sleeve 5, a sliding block 6, a pointer 7, a scale 8, a guide rail 9, a bottom plate support frame 10, a shaft sleeve 11 and a pad 12, a level 13 and a locking wrench 14.

[0036] The two ends of the probe tube 1 are respectively sleeved with the supporting sleeve 5 and the shaft sleeve 11, the shaft sleeve 11 is fixedly installed on the bottom plate support frame 10 through the pad 12, the shaft sleeve 11 is sleeved on the outer wall of the probe tube 1, and the bottom of the shaft sleeve 11 is fixed on the bottom plate support frame 10 through the pad 12; the supporting sleeve 5 is slidingly connected to the bottom plate support frame 10 through the sliding block 6 and the guide rail 9, the supporting sleeve 5 is rotatably connected to the probe tube 1, the bottom of the supporting sleeve 5 is fixed to the sliding block 6, the sliding block 6 is slidingly connected to the guide rail 9, and the guide rail 9 is fixedly installed on the bottom plate support frame 10 and abuts against one side of the pad 12 at one end; the crank 4 is fixed to the side wall of the end of the probe tube 1, the supporting sleeve 5 and one end of the probe tube 1 are slid on the sliding block 6 by pushing the crank 4, the probe tube 1 is rotated by rotating the crank 4, and the displacement and angle of the mounting bracket 2 and the fluxgate sensor 3 are adjusted by the movement and rotation of the probe tube 1, so that the detection accuracy can be controlled.

[0037] The outer wall of the probe tube 1 is marked with a rotation angle scale, the side wall of the sliding block 6 is fixedly installed with the pointer 7, the scale 8 corresponding to the position of the pointer 7 is arranged on the bottom plate support frame 10, and the pointer 7 points to the scale on the scale 8; when the supporting sleeve 5 and one end of the probe tube 1 slide on the sliding block 6, the pointer 7 points to the scale on the scale 8 in real time, the distance moved by the probe tube 1 can be known in real time, the displacement of the mounting bracket 2 and the fluxgate sensor 3 can be known in real time, and the rotation angle of the mounting bracket 2 and the fluxgate sensor 3 can be known in real time by cooperating with the rotation angle scale marked on the outer wall of the probe tube 1, so that the detection accuracy can be more finely controlled.

[0038] Further, in the embodiment, the other side wall of the sliding block 6 is fixedly installed with the locking wrench 14, and the sliding block 6 can be locked and fixed on the guide rail 9 by the locking wrench 14.

[0039] Further, in the embodiment, the bottom plate support frame 10 is further fixedly installed with the level 13, the accuracy of the level 13 is ±0.1°, and the tilt state of the probe tube is fed back in real time by the level 13.

[0040] Specifically, in use, the measuring device extends the probe tube 1 through the reserved aperture on the magnetic shielding cavity cover plate into the internal sealed space, the probe tube end is fixed with three groups of three-axis orthogonal fluxgate sensors 3 through the L-shaped aluminum alloy mounting bracket 2, a magnetic field detection array of nine independent measurement channels is formed, in operation, the probe tube 1 is driven to move along the slider 6 and the guide rail 9 through the support sleeve 5 pushed by the handle 4, the pointer 7 cooperates with the high-precision scale 8 to indicate the displacement in real time, meanwhile, rotating the handle 4 can drive the probe tube 1 to rotate around the axis, the circumferential precise positioning is realized by the rotation angle scale marked on the outer wall of the probe tube, thereby the point-by-point scanning measurement of the three-dimensional space inside the cavity is realized, the level 13 monitors the probe tube inclination in real time with the accuracy of ±0.1°, the locking wrench 14 can lock the relative position of the slider 6 and the guide rail 9 at any position, the measurement posture is ensured to be stable, the measurement data is collected through the data processing terminal, and the three-dimensional distribution nephogram of the residual magnetic field inside the cavity is reconstructed based on the radial basis function interpolation algorithm, the whole measurement process is completed in the sealed state of the magnetic shielding cavity, the external magnetic field interference is effectively avoided, and the shielding integrity is maintained.

[0041] Embodiment 2:

[0042] Please refer to Figures 1-3 On the basis of the above embodiment, the embodiment of the present application further provides a measurement method for the residual magnetic field intensity of a magnetic shielding cavity, which adopts the measuring device described in embodiment 1, and comprises the following steps: Step 1: insert the probe tube 1 into the 30mm aperture on the magnetic shielding cavity cover plate, the mounting bracket 2 is located inside the magnetic shielding cavity, adjust the bottom plate support frame 10 to make the level reading less than 0.3°, keep the balance posture, and then keep the probe tube 1 moving along the central axis of the magnetic shielding cavity.

[0043] Step 2: extend the probe tube 1 step by step, rotate the probe tube 1 after each extension, and complete the circumferential test; wherein, each measurement point is stepped by 30°, the magnetic field data of each point is recorded, and a groove is set at each rotation stepping point to ensure the accuracy of the test position.

[0044] Step 3: scan according to the probe tube 1 displacement and rotation angle to form a cylindrical coordinate system, calculate the spatial coordinates of each measurement point, generate all the measurement point coordinates and magnetic field vectors, and generate a three-dimensional residual magnetic field nephogram by using the radial basis function interpolation method for the unmeasured area.

[0045] In step 3, the probe tube 1 displacement ΔL and the rotation angle θ form a cylindrical coordinate system scanning, which satisfies: ; In the formula, r is the length of the support arm, and a cylindrical surface with a radius of r is scanned.

[0046] In step 3, the interpolation method comprises: S1, normalize the coordinates of the measurement points: Convert the displacement of the probe tube 1 and the rotation angle to the spatial coordinates of the measurement points in the rectangular coordinate system and the magnetic field vector , normalize the coordinates of the measurement points to make all coordinate values fall within the interval [0, 1] to improve the stability of interpolation, and the normalization process is as follows: .

[0047] S2, construct a linear equation system based on radial basis function to solve the weight coefficient: Select a basis function that adapts to the magnetic field attenuation characteristics , where r is the distance matrix, and the Euclidean distance between the measurement points is calculated: ; The parameter of the control function can be selected to control the attenuation speed , reconstruct the magnetic field of the unmeasured points based on the radial basis function: ; where the weight w i is obtained by fitting the measured points; Solve the linear equation system , where Φ is an N × N matrix, and the elements are , is the weight to be solved, is the measured magnetic field value.

[0048] S3, calculate the magnetic field values of the unmeasured points using the weight coefficient and the basis function, and generate a cloud chart: In the radial basis function interpolation method, once the weight coefficient is determined, it will remain unchanged, and when calculating the magnetic field value of any new point, only the basis function value between the point and the known point needs to be recalculated, without the need to solve the weight again. The magnetic field intensity of any point can be obtained, and then the residual magnetic field cloud chart can be obtained.

[0049] Step 4: analyze the cloud chart distribution, locate the weak shielding area, and guide the structure optimization by increasing the paste of permalloy tape in the weak area.

[0050] Specifically, in use, first, the probe tube 1 is inserted through the 30mm aperture on the magnetic shielding cavity cover plate, the mounting frame 2 is located inside the cavity, and the bubble level reading is less than 0.3 degrees by adjusting the bottom plate support 10 to keep balance, while ensuring that the probe tube 1 moves along the magnetic shielding cavity central axis; then, the probe tube 1 is extended step by step and rotated after each extension for circumferential testing, with a 30-degree step for each measurement point and the magnetic field data of each point recorded, while the groove structure ensures the accuracy of the test position; then, according to the displacement AL of the probe tube 1 and the rotation angle θ, a cylindrical coordinate system is scanned, the spatial coordinates of each measurement point are calculated, and all measurement point coordinates and magnetic field vectors are generated, and the radial basis function interpolation method is used for interpolation processing of the unmeasured area to generate a three-dimensional residual magnetic cloud image; finally, the cloud image distribution is analyzed to locate the weak shielding area, and the structure optimization is guided by increasing the paste of the mu metal strip and the like.

[0051] The scheme in this embodiment can be selectively combined with the scheme in other embodiments.

[0052] The specific use process of the magnetic shielding cavity residual magnetic field strength measuring device and method is as follows: (1) Device installation and leveling: first, the probe tube 1 is inserted into the sealed magnetic shielding cavity through the reserved hole (such as a 30mm aperture) on the cavity cover plate, so that the mounting frame 2 and the fluxgate sensor 3 fixed at the end thereof are located inside the cavity. By adjusting the bottom plate support 10 of the entire device, observing the bubble level 13, and ensuring that the reading is less than 0.3°, the probe tube 1 is kept in a balanced posture along the central axis of the cavity.

[0053] (2) Three-dimensional space scanning measurement: the operator pushes the handle 4 to make the support sleeve 5 drive one end of the probe tube 1 to move along the guide rail 9 and the sliding block 6, and the moving distance is indicated in real time by the pointer 7 fixed on the sliding block 6 and the scale 8 installed on the bottom plate support 10. After moving to a predetermined depth, the handle 4 is turned to rotate the probe tube 1 and the sensors thereon (the outer wall of the probe tube 1 is marked with a rotation angle scale), and a circumferential scan is performed with a 30° step. At each measurement point (the accuracy can be ensured by mechanical groove positioning), the three groups of three-axis fluxgate sensors 3 (a total of nine single axes) record the three-dimensional magnetic field vector data of the point. During the scanning process, the sliding block 6 can be locked on the guide rail 9 by the locking wrench 14 to fix the position.

[0054] (3) Data processing and cloud map generation: The data processing terminal (such as a computer) collects the magnetic field data of all measurement points. Subsequently, based on the MATLAB or Python platform, the spatial coordinates of each measurement point in the rectangular coordinate system are calculated according to the displacement AL (read by the scale 8) and the rotation angle θ (read by the probe scale), and the column coordinate system scanning is constructed. For the areas not directly measured, the radial basis function interpolation algorithm is used for data interpolation, and finally the three-dimensional residual magnetic field distribution cloud map of the entire cavity internal space is generated.

[0055] (4) Result analysis and application: By analyzing the generated three-dimensional residual magnetic cloud map, the weak magnetic field shielding area in the magnetic shielding cavity can be directly located, thereby providing accurate data support for guiding the subsequent structure optimization (such as adding a permalloy strip at a specific location).

[0056] It should be noted that although the above embodiments have been described in this paper, the patent protection scope of the present application is not limited thereby. Therefore, based on the innovative idea of the present application, changes and modifications to the embodiments described herein, or equivalent structures, equivalent processes or equivalent function transformations made using the contents of the present application specification and drawings, directly or indirectly apply the above technical solutions to other related technical fields, are all included within the protection scope of the present application patent.

Claims

1. A device for measuring the residual magnetic field strength of a magnetically shielded cavity, characterized in that, The measuring device includes: The probe (1) is capable of extension, retraction, and rotation; The detection system is fixedly installed on the probe (1) and includes a mounting bracket (2) and a fluxgate sensor (3), wherein the fluxgate sensor (3) is fixed on the probe (1) by the mounting bracket (2); A stabilization system is installed outside the probe (1) to counteract the gravitational torque of the probe (1) and to provide real-time feedback on the tilt status of the probe. The data processing terminal is based on MATLAB or Python algorithms to realize data interpolation and generate residual magnetic field cloud maps within the magnetic shielding device.

2. The measuring device for the residual magnetic field strength of a magnetically shielded cavity according to claim 1, characterized in that: The probe (1) is a carbon fiber probe with an outer diameter of 28 mm, a wall thickness of 2 mm, and a magnetic susceptibility χ≈-1.6×10⁻⁶. -6 .

3. The measuring device for the residual magnetic field strength of a magnetically shielded cavity according to claim 1, characterized in that: The mounting bracket is set as an L-shaped aluminum alloy bracket, and a set of three-axis orthogonal fluxgate sensors (3) are set at each of its three ends, for a total of nine single-axis sensors with a range of ±100μT and a resolution of 0.1nT, covering three-dimensional magnetic field components.

4. The measuring device for the residual magnetic field strength of a magnetically shielded cavity according to claim 1, characterized in that: The probe (1) is fitted with a support sleeve (5) and a bushing (11) at both ends, and the bushing (11) is fixedly installed on the base plate support (10) by a pad (12); The support sleeve (5) is slidably connected to the base plate support frame (10) via a slider (6) and a guide rail (9); By setting the handle (4) to be fixed on the side wall of the end of the probe (1), pushing the handle (4) causes the support sleeve (5) and one end of the probe (1) to slide on the slider (6), and then turning the handle (4) causes the probe (1) to rotate.

5. The measuring device for the residual magnetic field strength of a magnetically shielded cavity according to claim 4, characterized in that: The outer wall of the probe (1) is marked with a rotation angle scale; A pointer (7) is fixedly installed on one side wall of the slider (6), and a scale (8) corresponding to the position of the pointer (7) is set on the base plate support (10), with the pointer (7) pointing to the scale on the scale (8).

6. The measuring device for the residual magnetic field strength of a magnetically shielded cavity according to claim 4, characterized in that: A locking wrench (14) is fixedly installed on the other side wall of the slider (6), and the slider (6) can be locked and fixed on the guide rail (9) by the locking wrench (14).

7. The measuring device for the residual magnetic field strength of a magnetically shielded cavity according to claim 4, characterized in that: A level (13) is also fixedly installed on the base plate support (10), and the level (13) has an accuracy of ±0.1°.

8. A method for measuring the residual magnetic field strength of a magnetically shielded cavity, comprising using the measuring device described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Insert the probe (1) through the 30mm hole on the cover plate of the magnetic shielding cavity. The mounting bracket (2) is located inside the magnetic shielding cavity. Adjust the base plate support (10) to make the level reading less than 0.3° and keep it in a balanced position. Then keep the probe (1) moving along the central axis of the magnetic shielding cavity. Step 2: Extend and retract the probe (1) in stages, and rotate the probe (1) after each extension and retraction to complete the circumferential test; wherein, a measurement point is moved every 30°, and the magnetic field data of each point is recorded. A groove is set at each rotation step point to ensure the accuracy of the test position; Step 3: Based on the displacement and rotation angle of the probe (1), a cylindrical coordinate system is formed for scanning. The spatial coordinates of each measuring point are calculated, and the coordinates of all measuring points and the magnetic field vector are generated. For the unmeasured area, the radial basis function interpolation method is used to generate a three-dimensional remanent cloud map. Step 4: Analyze the cloud map distribution, locate the weak shielding areas, and guide structural optimization by adding permalloy strips to the weak areas.

9. The method for measuring the residual magnetic field strength of a magnetically shielded cavity according to claim 8, characterized in that, The displacement ΔL of the probe (1) in step 3, together with the rotation angle θ, forms a cylindrical coordinate system scan, satisfying: ； Where r is the length of the support arm, enabling scanning of a cylindrical surface with radius r.

10. The method for measuring the residual magnetic field strength of a magnetically shielded cavity according to claim 8, characterized in that, The interpolation method in step 3 includes: S1. Normalize the coordinates of the measuring points: Calculate the spatial coordinates of the measuring point in the rectangular coordinate system from the displacement and rotation angle of the probe (1). and magnetic field vector The coordinates of the measurement points are normalized so that all coordinate values ​​fall within the [0,1] interval to improve interpolation stability. The normalization process is as follows: ； S2. Construct a system of linear equations based on radial basis functions to solve for the weight coefficients: Choose basis functions that adapt to the magnetic field decay characteristics. Where r is the distance matrix, the Euclidean distance between the measuring points is calculated: ； The parameters controlling the decay rate of the control function can be selected. Reconstructing the magnetic field at unmeasured points based on radial basis functions: ； Wherein, weight w i Obtained by fitting from measured points; Solve the system of linear equations , where Φ is an N×N matrix with elements of . , The weight to be determined This is the measured magnetic field value; S3. Calculate the magnetic field values ​​at unmeasured points using weighting coefficients and basis functions, and generate a contour map: In the radial basis function interpolation method, once the weight coefficients are determined, they will remain unchanged. When calculating the magnetic field value at any new point, it is only necessary to recalculate the basis function values ​​between that point and the known points, without having to resolve the weights. This allows us to obtain the magnetic field strength at any point and thus the residual magnetic field cloud map.

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