Gradient magnetic field compensation device for magnetic shielding barrel

Abstract

The invention provides a magnetic shielding barrel gradient magnetic field compensation device which comprises a plurality of magnetic compensation units, and the magnetic compensation units are designed and manufactured in a non-magnetization mode. The whole magnetic compensation unit is a flexible PCB, and the magnetic compensation unit is provided with a radial compensation surface and an axial compensation surface; the radial compensation surfaces of the plurality of magnetic compensation units are connected, so that gradient compensation can be carried out on the radial magnetic field of the magnetic shielding barrel; and the axial compensation surfaces of the plurality of magnetic compensation units are connected, so that gradient compensation can be carried out on the axial magnetic field of the magnetic shielding barrel. According to the technical scheme, the technical problems that when an existing magnetic shielding barrel has new functional requirements such as increasing radial space gradient compensation or enlarging a space uniform area, a new coil framework needs to be designed and put into production, time consumption is long, and when the production and machining precision is limited, the coil magnetic field space uniformity is limited and cannot be corrected are solved.

Description

Technical Field

[0001] This invention relates to the field of magnetic shielding barrel technology, and in particular to a gradient magnetic field compensation device for a magnetic shielding barrel. Background Technology

[0002] As a crucial component of physics, magnetic fields have long been a key research area in precision measurement, with high-performance magnetic shielding barrels providing essential testing tools. Among the various performance indicators of magnetic shielding barrels, the uniform distribution range of the spatial magnetic field is a critical factor for their use. A good uniform magnetic field region relies heavily on spatial magnetic field gradient compensation. Currently, spatial magnetic field gradient compensation is primarily limited by a pre-designed coil frame. This frame involves slotting and tightly winding wires to generate the main and compensating magnetic fields. However, once the coil frame design is finalized, it is largely unchangeable. When the magnetic field environment within the shielding barrel requires optimization, the coil frame cannot be readily modified, necessitating a redesign—a time-consuming process whose results are susceptible to manufacturing variations. Inconsistencies in manufacturing precision further limit the effectiveness of spatial magnetic field gradient compensation, making adjustments to the spatial magnetic field difficult. Introducing new types of coils, such as triaxial Helmholtz coils, into the magnetic shielding barrel would restrict the usable space within the shielding area, increasing the complexity of its use. Summary of the Invention

[0003] This invention provides a gradient magnetic field compensation device for a magnetic shielding barrel, which can solve the existing technical problems that when the magnetic shielding barrel has new functional requirements, such as adding radial spatial gradient compensation or expanding the spatial uniformity area, it is necessary to design and put into production a new coil frame, which takes a long time. Furthermore, when the production and processing accuracy is limited, the spatial uniformity of the coil magnetic field is limited and cannot be corrected.

[0004] According to one aspect of the present invention, a gradient magnetic field compensation device for a magnetic shielding barrel is provided. The magnetic shielding barrel gradient magnetic field compensation device includes multiple magnetic compensation units, which are designed and manufactured without magnetization. The magnetic compensation unit is a flexible PCB as a whole, and has a radial compensation surface and an axial compensation surface. The radial compensation surfaces of the multiple magnetic compensation units are connected to complete the gradient compensation of the radial magnetic field of the magnetic shielding barrel. The axial compensation surfaces of the multiple magnetic compensation units are connected to complete the gradient compensation of the axial magnetic field of the magnetic shielding barrel.

[0005] Furthermore, the magnetic compensation unit is manufactured from non-magnetic copper, plastic, resin, and other materials. The solder joints are copper solder joints, and the overall structure is flexible. It can fit well with the inner diameter of the curved surface of the magnetic shielding cylinder without occupying extra space inside the magnetic shielding cylinder.

[0006] Furthermore, the radial compensation surface of the magnetic compensation unit has line one, line two, solder point one, solder point two, solder point three, and solder point four. The current flow directions in line one and line two are opposite, and both include straight and curved routing positions. The straight routing positions of line one and line two form magnetic field cancellation, without generating additional magnetic field interference. The curved routing positions form a single base coil, forming a magnetic field unit. Solder point one is located at one end of line one, solder point two is located at the other end of line one, solder point four is located at one end of line two, and solder point three is located at the other end of line two. When the radial compensation surfaces of the magnetic compensation units are connected, they are connected to the adjacent magnetic compensation units through solder points one and four and solder points two and three to form a conduction. Solder points two and three of the magnetic compensation unit located at the outermost edge are short-circuited to form a closed loop.

[0007] Furthermore, the axial compensation surface of the magnetic compensation unit has line three, first branch, second branch, solder point five, solder point six, solder point seven, solder point eight, solder point nine, and solder point ten. Solder point five is located at one end of line three, solder point six is ​​located at the other end of line three, solder point seven is located at one end of the first branch, solder point eight is located at the other end of the first branch, solder point ten is located at one end of the second branch, and solder point nine is located at the other end of the second branch. Adjacent magnetic compensation units are connected by solder point five and solder point six, which conducts line three. Arranged around the inner wall of the magnetic shielding barrel, a single axial coil can be formed. Among them, the first branch, second branch, and solder points seven, eight, nine, and ten are used for the outward lead wire of the axial compensation surface.

[0008] Furthermore, when the radial compensation surfaces of the magnetic compensation units are combined, two sets of coil arrays can be formed on the left and right walls or the upper and lower walls of the magnetic shielding cylinder, respectively. By designing and arranging an asymmetrical number of coil groups, radial gradient compensation of the magnetic shielding cylinder can be achieved. Based on the thin and light characteristics of the magnetic compensation units, the coil arrays can be designed with multiple layers to enhance or suppress the magnetic gradient compensation effect. When the axial compensation surfaces of the magnetic compensation units are combined, multiple sets of axial coils can be formed on the inner wall of the magnetic shielding cylinder to complete the axial gradient compensation of the magnetic field. Multiple layers can also be stacked during combination to achieve the required compensation effect.

[0009] This invention provides a gradient magnetic field compensation device for magnetic shielding barrels. The device comprises multiple magnetic compensation units, each with a radial and axial compensation surface. Based on the radial compensation surface, multiple magnetic compensation units can be connected to form a radial gradient coil group, providing the necessary spatial magnetic field for compensating the target magnetic field gradient. Based on the axial compensation surface, multiple magnetic compensation units can be connected to form an axial compensation coil, compensating for the axial gradient magnetic field. Compared with existing technologies, the gradient magnetic field compensation device for magnetic shielding barrels provided by this invention is simple to manufacture. Axial and radial gradient compensation within the shielding barrel can be achieved through diverse combinations, significantly improving the convenience of modifying the gradient magnetic field of magnetic shielding barrels of different specifications. Its lightweight and thin design allows for direct adhesive installation inside the magnetic shielding barrel without imposing new limitations on the original usable space. This device can be flexibly combined to adapt to different specifications of shielding barrel structures, meeting the triaxial gradient magnetic field compensation capability within the magnetic shielding barrel, while maintaining low space occupancy, providing a new approach for gradient magnetic field compensation in magnetic shielding barrels. Attached Figure Description

[0010] The accompanying drawings, which form part of this specification, are provided to further illustrate embodiments of the invention and, together with the textual description, explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0011] Figure 1 A schematic diagram of the radial compensation surface of a magnetic compensation unit provided according to a specific embodiment of the present invention is shown.

[0012] Figure 2 A schematic diagram of the axial compensation surface of a magnetic compensation unit provided according to a specific embodiment of the present invention is shown.

[0013] Figure 3 and Figure 4 A schematic diagram of the current flow of a magnetic compensation unit provided according to a specific embodiment of the present invention is shown.

[0014] Figure 5 A schematic diagram of the radial compensation surface assembly of the magnetic compensation unit according to a specific embodiment of the present invention is shown, wherein the dashed lines in the figure represent the current flow.

[0015] Figure 6 A schematic diagram of the axial compensation surface assembly of the magnetic compensation unit according to a specific embodiment of the present invention is shown, with the dashed lines in the drawing representing the current flow.

[0016] Figure 7 A schematic diagram of a triaxial magnetic compensation combined explosion is shown according to a specific embodiment of the present invention.

[0017] Figure 8 A schematic diagram of an explosion of a triaxial magnetic compensation combined coil according to a specific embodiment of the present invention is shown.

[0018] Figure 9 A cross-sectional schematic diagram of a triaxial magnetic compensation assembly according to a specific embodiment of the present invention is shown.

[0019] Figure 10 A schematic cross-sectional view of a radial axis magnetic compensation assembly according to a specific embodiment of the present invention is shown.

[0020] Figure 11 A schematic cross-sectional view of an axial magnetic compensation assembly according to a specific embodiment of the present invention is shown. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0024] like Figures 1 to 11 As shown in the figure, a gradient magnetic field compensation device for a magnetic shielding barrel is provided according to a specific embodiment of the present invention. The magnetic shielding barrel gradient magnetic field compensation device includes multiple magnetic compensation units, which are designed and manufactured without magnetization. The magnetic compensation unit is a flexible PCB as a whole, and the magnetic compensation unit has a radial compensation surface and an axial compensation surface. The radial compensation surfaces of multiple magnetic compensation units are connected to complete the gradient compensation of the radial magnetic field of the magnetic shielding barrel. The axial compensation surfaces of multiple magnetic compensation units are connected to complete the gradient compensation of the axial magnetic field of the magnetic shielding barrel.

[0025] This configuration provides a gradient magnetic field compensation device for magnetic shielding barrels. The device consists of multiple magnetic compensation units, each with a radial and axial compensation surface. Based on the radial compensation surface, multiple magnetic compensation units can be connected to form a radial gradient coil group, providing the necessary spatial magnetic field for compensating the target magnetic field gradient. Based on the axial compensation surface, multiple magnetic compensation units can be connected to form an axial compensation coil, compensating for the axial gradient magnetic field. Compared with existing technologies, the gradient magnetic field compensation device for magnetic shielding barrels provided by this invention is simple to manufacture. Axial and radial gradient compensation within the shielding barrel can be achieved through diverse combinations, significantly improving the convenience of modifying the gradient magnetic field of magnetic shielding barrels of different specifications. Its lightweight and thin design allows for direct adhesive installation inside the magnetic shielding barrel without imposing new limitations on the original space. The device can be flexibly combined to adapt to different specifications of shielding barrel structures, meeting the triaxial gradient magnetic field compensation capability within the magnetic shielding barrel, while maintaining low space occupancy, providing a new approach for gradient magnetic field compensation in magnetic shielding barrels.

[0026] Furthermore, in this invention, the magnetic compensation unit is designed and manufactured without magnetization. The entire magnetic compensation unit is a flexible PCB, and the manufacturing materials of the magnetic compensation unit are non-magnetic copper, plastic, and resin foil. The solder joints are copper solder joints, and the whole structure is flexible, which can fit well with the inner diameter of the curved surface of the magnetic shielding cylinder, and does not occupy extra space inside the magnetic shielding cylinder.

[0027] like Figure 1 As shown, the radial compensation surface of the magnetic compensation unit has line one, line two, solder point one, solder point two, solder point three, and solder point four. The current flow directions in line one and line two are opposite, and both include straight and curved routing positions. The straight routing positions of line one and line two cancel each other out, without generating additional magnetic field interference. The curved routing positions form a single base coil, forming a magnetic field unit. Solder point one is located at one end of line one, solder point two is located at the other end of line one, solder point four is located at one end of line two, and solder point three is located at the other end of line two. When the radial compensation surfaces of the magnetic compensation units are connected, solder points one and four are welded to solder points two and three of adjacent magnetic compensation units to form a conductive path. Solder points two and three of the outermost magnetic compensation unit are short-circuited to form a closed loop. In this invention, the radial compensation surface and axial compensation surface of the magnetic compensation unit are located on two separate surfaces of the magnetic compensation unit.

[0028] like Figure 2 As shown, the axial compensation surface of the magnetic compensation unit has line three, first branch, second branch, solder point five, solder point six, solder point seven, solder point eight, solder point nine, and solder point ten. Solder point five is located at one end of line three, solder point six is ​​located at the other end of line three, solder point seven is located at one end of the first branch, solder point eight is located at the other end of the first branch, solder point ten is located at one end of the second branch, and solder point nine is located at the other end of the second branch. Adjacent magnetic compensation units are connected by solder point five and solder point six, which conducts line three. Arranged around the inner wall of the magnetic shielding barrel, a single axial coil can be formed. Among them, the first branch, second branch, and solder points seven, eight, nine, and ten are used for the outward lead wire of the axial compensation surface.

[0029] Specifically, in practical applications, when the radial compensation surfaces of the magnetic compensation units are combined, two sets of coil arrays can be formed on the left and right walls or the upper and lower walls of the magnetic shielding cylinder, respectively. By designing and arranging an asymmetrical number of coil groups, radial gradient compensation of the magnetic shielding cylinder can be achieved. Based on the thin and light characteristics of the magnetic compensation units, the coil arrays can be designed with multiple layers to enhance or suppress the magnetic gradient compensation effect. When the axial compensation surfaces of the magnetic compensation units are combined, multiple sets of axial coils can be formed on the inner wall of the magnetic shielding cylinder to complete the axial gradient compensation of the magnetic field. Multiple layers can also be stacked during combination to achieve the required compensation effect.

[0030] To gain a further understanding of the present invention, the following description is provided in conjunction with... Figures 1 to 11The magnetic shielding barrel gradient magnetic field compensation device provided by the present invention will be described in detail.

[0031] like Figures 1 to 11 As shown, this invention provides a gradient magnetic field compensation device and method for magnetically shielded barrels. The device and method consist of multiple magnetic compensation units, each with a radial compensation surface and an axial compensation surface. Based on the radial compensation surface, multiple magnetic compensation units can be connected to form a radial gradient coil group, providing the required spatial magnetic field for compensating the target magnetic field gradient. Based on the axial compensation surface, multiple magnetic compensation units can be connected to form an axial compensation coil, compensating for the axial gradient magnetic field. Currently, various types of magnetically shielded barrels use coil frames to control the generation of various spatial magnetic fields within the shielding barrel, including the main magnetic field coil and gradient compensation coils. Each type of coil requires slotting on the coil assembly and dense winding to generate the designed specific magnetic field. However, due to manufacturing limitations, adjustments and modifications to this type of coil after design are restricted by the coil frame, making modification difficult. When new functional requirements arise for the magnetically shielded barrel, such as adding radial spatial gradient compensation or expanding the spatial uniformity area, a new coil frame needs to be designed and produced, which is time-consuming. Furthermore, when manufacturing precision is limited, the spatial uniformity of the coil magnetic field is limited and cannot be corrected. A gradient magnetic field compensation device and method for magnetic shielding barrels are proposed. The device is simple to manufacture and can complete the axial and radial gradient compensation inside the shielding barrel through various combinations. It significantly improves the convenience of modifying the gradient magnetic field of magnetic shielding barrels of different specifications. Moreover, the lightweight and thin design can be directly pasted and installed inside the magnetic shielding barrel without causing new restrictions on the original usage space of the magnetic shielding barrel.

[0032] This invention provides a gradient magnetic field compensation device for magnetically shielded barrels, enhancing the gradient magnetic field compensation capability of existing magnetically shielded barrels and expanding their testing applicability. This invention can be flexibly combined to adapt to magnetically shielded barrels of different specifications, meeting the needs of upgrading and modifying different types of magnetically shielded barrels. Different combinations can provide targeted compensation for the radial and axial magnetic fields of the magnetically shielded barrel, covering triaxial magnetic gradient compensation requirements. Furthermore, this device almost does not encroach on the original magnetic field space of the magnetically shielded barrel, offering significant advantages during upgrades and modifications. The device consists of multiple magnetic compensation units, and different combinations of these units can meet the requirements of gradient compensation scenarios. The radial compensation surfaces of the magnetic compensation units are connected to perform radial magnetic field gradient compensation for the magnetically shielded barrel, while the axial compensation surfaces are connected to perform axial gradient compensation.

[0033] Furthermore, the magnetic compensation unit is designed and manufactured without magnetization. The entire magnetic compensation unit is a flexible PCB, and the manufacturing materials are non-magnetic copper, plastic, and resin foil. The solder joints are copper solder joints. The overall flexible structure can fit well with the curved inner diameter of the magnetic shielding cylinder without occupying extra space inside the magnetic shielding cylinder.

[0034] Furthermore, the radial compensation surface of the magnetic compensation unit contains Line 1, Line 2, Solder Point 1, Solder Point 2, Solder Point 3, and Solder Point 4. The current flows in Line 1 and Line 2 in opposite directions. Straight traces cancel out magnetic fields, preventing additional magnetic field interference, while curved traces form a single base coil, creating a magnetic field unit. When the radial compensation surfaces of the magnetic compensation units are connected, solder points 1 and 4 connect with solder points 2 and 3 of adjacent magnetic compensation units to form a conductive path. Solder points 2 and 3 of the outermost magnetic compensation unit are short-circuited to form a closed loop. This wiring design significantly reduces the number of traces required when densely arranging coil arrays on the inner wall of the shielding barrel, reduces magnetic field interference from connecting coil arrays, and effectively reduces the space occupied within the magnetic shielding barrel.

[0035] Furthermore, the axial compensation surface of the magnetic compensation unit has line three, branch, solder point five, solder point six, solder point seven, solder point eight, solder point nine, and solder point ten. Adjacent magnetic compensation units are connected by solder point five and solder point six, thus connecting line three. Arranging this line around the inner wall of the magnetic shielding barrel forms a single axial coil. The branch and solder points seven, eight, nine, and ten facilitate the outward lead-out of the axial compensation surface.

[0036] Furthermore, when the radial compensation surfaces of the magnetic compensation units are combined, two sets of coil arrays can be formed on the left and right walls or the top and bottom walls of the magnetic shielding cylinder, respectively. By designing and arranging an asymmetrical number of coil groups, radial gradient compensation of the magnetic shielding cylinder can be achieved. Based on the thin and lightweight characteristics of the magnetic compensation units, the coil arrays can be designed with multi-layer stacking to enhance or suppress the magnetic gradient compensation effect. When the axial compensation surfaces of the magnetic compensation units are combined, multiple sets of axial coils can be formed on the inner wall of the magnetic shielding cylinder to complete the axial gradient compensation of the magnetic field. Similarly, multi-layer stacking can also be used during combination to achieve the desired compensation effect.

[0037] This invention provides a gradient magnetic field compensation device for a magnetic shielding barrel. The device features an overall non-magnetized design, avoiding interference with the spatial magnetic field caused by the gradient magnetic field compensation. The device can be flexibly assembled from single components, simplifying mass production and manufacturing. Its lightweight and thin design minimizes space occupation within the magnetic shielding barrel when combined or stacked. Furthermore, different combinations of radial and axial compensation surfaces enable triaxial magnetic field gradient compensation for the magnetic shielding barrel, offering strong scalability. The modular design adapts to shielding barrels of different sizes, meeting the practical needs of upgrading various magnetic shielding barrels. It can also be directly applied to the design of magnetic shielding barrel coils, cooperating with the main magnetic field coil frame and reducing the design difficulty of the magnetic shielding barrel coil frame.

[0038] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0039] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A magnetic shielding barrel gradient magnetic field compensation device, characterized in that, The magnetic shielding barrel gradient magnetic field compensation device includes multiple magnetic compensation units, which are designed and manufactured without magnetization. The magnetic compensation unit is a flexible PCB as a whole, and it has a radial compensation surface and an axial compensation surface. The radial compensation surfaces of multiple magnetic compensation units are connected to complete the gradient compensation of the radial magnetic field of the magnetic shielding barrel. The axial compensation surfaces of multiple magnetic compensation units are connected to each other, which can complete the gradient compensation of the axial magnetic field of the magnetic shielding barrel.

2. The magnetic shielding barrel gradient magnetic field compensation device according to claim 1, characterized in that, The magnetic compensation unit is manufactured from non-magnetic copper and resin plastic foil. The solder joints are copper solder joints. The whole structure is flexible and can fit well with the inner diameter of the curved surface of the magnetic shielding cylinder without occupying extra space inside the magnetic shielding cylinder.

3. The magnetic shielding barrel gradient magnetic field compensation device according to claim 2, characterized in that, The radial compensation surface of the magnetic compensation unit has line one, line two, solder point one, solder point two, solder point three, and solder point four. The current flow direction in line one and line two is opposite, and both include straight and curved routing positions. The straight routing positions of line one and line two form magnetic field cancellation, without generating additional magnetic field interference. The curved routing positions form a single base coil, forming a magnetic field unit. Solder point one is located at one end of line one, solder point two is located at the other end of line one, solder point four is located at one end of line two, and solder point three is located at the other end of line two. When the radial compensation surfaces of the magnetic compensation units are connected, solder points one and four are welded to solder points two and three of adjacent magnetic compensation units to form a conductive path. Solder points two and three of the outermost magnetic compensation unit are short-circuited to form a closed loop.

4. The magnetic shielding barrel gradient magnetic field compensation device according to claim 3, characterized in that, The axial compensation surface of the magnetic compensation unit has line three, first branch, second branch, solder point five, solder point six, solder point seven, solder point eight, solder point nine, and solder point ten. Solder point five is located at one end of line three, solder point six is ​​located at the other end of line three, solder point seven is located at one end of the first branch, solder point eight is located at the other end of the first branch, solder point ten is located at one end of the second branch, and solder point nine is located at the other end of the second branch. Adjacent magnetic compensation units are connected by solder point five and solder point six, which conducts line three. Arranged around the inner wall of the magnetic shielding barrel, a single axial coil can be formed. The first branch, second branch, and solder points seven, eight, nine, and ten are used for the outward lead wires of the axial compensation surface.

5. The magnetic shielding barrel gradient magnetic field compensation device according to claim 4, characterized in that, When the radial compensation surfaces of the magnetic compensation units are combined, two sets of coil arrays can be formed on the left and right walls or the upper and lower walls of the magnetic shielding cylinder, respectively. By designing and arranging an asymmetrical number of coil groups, radial gradient compensation of the magnetic shielding cylinder can be achieved. Based on the thin and light characteristics of the magnetic compensation units, the coil arrays can be designed with multiple layers to improve or suppress the magnetic gradient compensation effect. When the axial compensation surfaces of the magnetic compensation units are combined, multiple sets of axial coils can be formed on the inner wall of the magnetic shielding cylinder to complete the axial gradient compensation of the magnetic field. Multiple layers can also be stacked during combination to achieve the required compensation effect.

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