Stacked Magnetic Lenses

Abstract

The present invention provides a stacked magnetic lens, comprising: an annular permanent magnet group, the annular permanent magnet group comprising a plurality of annular permanent magnets coaxially arranged in sequence along a central axis, the plurality of annular permanent magnets being used to generate a basic adjustable magnetic field, the basic adjustable magnetic field acting on a particle beam injected into an inner ring region of the annular permanent magnet group; at least one of the plurality of annular permanent magnets can be relatively displaced relative to the other annular permanent magnets in the extension direction of the central axis, so as to adjust the magnetic field distribution and size of the basic adjustable magnetic field.

Description

Technical Field

[0001] The invention relates to the technical field of magnetic lenses, and in particular to a stacked magnetic lens. Background Art

[0002] Permanent magnet lenses are widely used in various precision instruments, such as electron microscopes, electron beam processing equipment, particle accelerators, etc. In electronic optical equipment, traditional lens systems mostly use electromagnetic lenses to complete the operation of electron beams, which limits the miniaturization trend of lens systems and also introduces a series of problems such as thermal management issues and narrow application range of lens systems. Summary of the invention

[0003] In view of the above problems, the present invention provides a stacked magnetic lens.

[0004] According to a first aspect of the present invention, there is provided a stacked magnetic lens, comprising: an annular permanent magnet group, the annular permanent magnet group comprising a plurality of annular permanent magnets coaxially arranged in sequence along a central axis, the plurality of annular permanent magnets being used to generate a basic adjustable magnetic field, the basic adjustable magnetic field acting on a particle beam injected into an inner ring region of the annular permanent magnet group; at least one of the plurality of annular permanent magnets being able to perform relative displacement in the extension direction of the central axis relative to the other annular permanent magnets to adjust the magnetic field distribution and size of the basic adjustable magnetic field.

[0005] According to an embodiment of the present invention, the outer diameter of the i-th annular permanent magnet among the multiple annular permanent magnets is smaller than the inner diameter of the i+k-th annular permanent magnet among the multiple annular permanent magnets, so that the i-th annular permanent magnet can be relatively displaced relative to the i+k-th annular permanent magnet within the inner ring area of ​​the i+k-th annular permanent magnet, where i is a positive integer and k=1, 2,…

[0006] According to an embodiment of the present invention, each annular permanent magnet comprises an inner surface close to the central axis and an outer surface far from the central axis, and the inner surface and the outer surface of each annular permanent magnet have opposite polarities to each other.

[0007] According to an embodiment of the present invention, the outer surface of the i-th annular permanent magnet among the multiple annular permanent magnets and the inner surface of the i+1-th annular permanent magnet among the multiple annular permanent magnets have opposite magnetic poles, and i is a positive integer.

[0008] According to an embodiment of the present invention, the plurality of annular permanent magnets include stacked annular permanent magnets, the stacked annular permanent magnets include at least two annular permanent magnets stacked in the direction of extension of the central axis, and the at least two annular permanent magnets have the same inner diameter and the same outer diameter; wherein adjacent annular permanent magnets among the at least two annular permanent magnets are in contact based on the magnetic force applied to each other by the adjacent annular permanent magnets.

[0009] According to an embodiment of the present invention, the outer diameter of the jth group of stacked annular permanent magnets among the multiple annular permanent magnets is smaller than the inner diameter of the j+pth group of stacked annular permanent magnets among the multiple annular permanent magnets, so that the jth group of stacked annular permanent magnets can be relatively displaced relative to the j+pth group of stacked annular permanent magnets within the inner ring area of ​​the j+pth group of stacked annular permanent magnets, where j is a positive integer, and p=1, 2,…

[0010] According to an embodiment of the present invention, the outer surface of the i-th annular permanent magnet among the multiple annular permanent magnets and the inner surface of the i+1-th annular permanent magnet among the multiple annular permanent magnets have the same magnetic pole, and i is a positive integer; the multiple annular permanent magnets include stacked annular permanent magnets, and the stacked annular permanent magnets include at least two annular permanent magnets stacked in the extension direction of the central axis, and the at least two annular permanent magnets have the same inner diameter and the same outer diameter; wherein adjacent annular permanent magnets among the at least two annular permanent magnets are in contact based on an external force other than the magnetic force of the adjacent annular permanent magnets.

[0011] According to an embodiment of the present invention, there are multiple annular permanent magnet groups, and the multiple annular permanent magnet groups are arranged into an array according to a predetermined pattern in the same plane to receive a particle beam corresponding to the predetermined pattern. The particle beam corresponding to the predetermined pattern is emitted by a multi-electron source, or is obtained by splitting a particle beam emitted by a single electron source according to a predetermined pattern using a beam splitter.

[0012] According to an embodiment of the present invention, the predetermined pattern comprises a symmetrical pattern.

[0013] According to an embodiment of the present invention, the magnetic lens also includes an electromagnetic coil, a group of electromagnetic coils are wound around an annular permanent magnet along the outer surface of an annular permanent magnet; wherein the electromagnetic coil is used to generate an additional adjustable magnetic field, and the superimposed magnetic field formed by the basic adjustable magnetic field and the additional adjustable magnetic field acts on the particle beam injected into the inner ring area of ​​the annular permanent magnet group, and the magnetic field strength of the additional adjustable magnetic field changes with the change of the current size and direction of the input electromagnetic coil.

[0014] According to an embodiment of the present invention, since the multiple annular permanent magnets in the annular permanent magnet group are sequentially arranged along the same axis, the basic adjustable magnetic field formed by the superposition of the magnetic fields of the multiple annular permanent magnets is distributed radially along the central axis, reducing the stray field of the magnetic lens and improving the accuracy and stability of the magnetic lens. On this basis, by controlling the relative displacement between at least one of the multiple annular permanent magnets and other annular permanent magnet groups in the extension direction of the central axis, the magnetic field distribution and magnetic field extremes as the basic adjustable magnetic field can be flexibly adjusted from a mechanical level, without the need to use electromagnetic coils to adjust the magnetic field distribution and magnetic field extremes of the magnetic lens. Since this adjustment is a mechanical adjustment of a passive system, there is no need to consider thermal management issues. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above contents and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0016] Figure 1A Schematic diagram 1 schematically shows a stacked magnetic lens according to an embodiment of the present invention.

[0017] Figure 1B Schematic diagram of a stacked magnetic lens according to an embodiment of the present invention Figure 2 .

[0018] Figure 1C Schematic diagram of a stacked magnetic lens according to an embodiment of the present invention Figure 3 .

[0019] Figure 2 A schematic diagram schematically shows a magnetizing direction of an annular permanent magnet according to an embodiment of the present invention.

[0020] Figure 3 The schematic diagram of the structure of stacked annular permanent magnets according to an embodiment of the present invention is shown schematically.

[0021] Figure 4 The schematic diagram of the structure of two groups of stacked annular permanent magnets according to an embodiment of the present invention is shown schematically.

[0022] Figure 5 The schematic diagram of stacking annular permanent magnets according to an embodiment of the present invention is schematically shown.

[0023] Figure 6 The schematic diagram of stacking annular permanent magnets according to another embodiment of the present invention is shown schematically.

[0024] Figure 7 The schematic diagram of a magnetic lens having an electromagnetic coil and an annular permanent magnet according to an embodiment of the present invention is schematically shown.

[0025] Fig. 8A The schematic diagram of an array composed of annular permanent magnet groups according to an embodiment of the present invention is schematically shown.

[0026] Figure 8B The schematic diagram of an array composed of annular permanent magnet groups according to another embodiment of the present invention is schematically shown. DETAILED DESCRIPTION

[0027] Below, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present invention. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of embodiments of the present invention. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known structures and technologies are omitted to avoid unnecessary confusion of concepts of the present invention.

[0028] The terms used herein are only for describing specific embodiments and are not intended to limit the present invention. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0029] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0030] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0031] The present invention provides a stacked magnetic lens, which can reduce the stray field of the magnetic lens and adjust the magnetic field distribution and magnetic field extreme value of the magnetic lens without using an electromagnetic coil.

[0032] Figure 1A Schematic diagram 1 schematically shows a stacked magnetic lens according to an embodiment of the present invention.

[0033] Figure 1B Schematic diagram of a stacked magnetic lens according to an embodiment of the present invention Figure 2 .

[0034] Figure 1C Schematic diagram of a stacked magnetic lens according to an embodiment of the present invention Figure 3 .

[0035] like Figure 1A , Figure 1B and Figure 1CAs shown, the stacked magnetic lens of this embodiment includes an annular permanent magnet group. The annular permanent magnet group includes a plurality of annular permanent magnets 110_1...110_Q coaxially arranged in sequence along the central axis AX, where Q is a positive integer greater than 1. The material of the annular permanent magnet may include but is not limited to neodymium iron boron (NdFeB), samarium cobalt (SmCo), and the like. A plurality of annular permanent magnets 110_1...110_Q may be arranged in sequence from the inside to the outside in a first direction X and a second direction Y intersecting the first direction X (for example, they may be perpendicular to each other). The annular permanent magnet 110_1 is located in the inner ring area of ​​the annular permanent magnet 110_2, the annular permanent magnet 110_2 is located in the inner ring area of ​​the annular permanent magnet 110_3, and the other annular permanent magnets in the same group are similar, and are not described in detail here. It can be understood that the annular permanent magnet itself is an annular structure, and has an annular effective aperture area inside the annular permanent magnet that allows the particle beam to pass through, and this effective aperture area corresponds to the inner ring area of ​​the annular permanent magnet.

[0036] Multiple annular permanent magnets 110_1 ... 110_Q are used to generate a basic adjustable magnetic field. The basic adjustable magnetic field can be a magnetic field formed by superimposing the magnetic fields of the multiple annular permanent magnets 110_1 ... 110_Q. The basic adjustable magnetic field acts on the particle beam injected into the inner ring area IS of the annular permanent magnet group, so that the particle beam can be deflected. For example, the inner ring area IS of the annular permanent magnet group can correspond to the effective aperture area of ​​the innermost annular permanent magnet 110_1 in the annular permanent magnet group.

[0037] Since the axially magnetized magnetic ring design will produce a large residual magnetic field, the magnetization direction of the annular permanent magnet group in the present invention is designed to be expanded along the radial direction of the annular permanent magnet. The radiation magnetization of the annular permanent magnet can improve the uniformity of the magnetic field in the radial direction. In the process of designing the magnetic lens, the system aberration is minimized by optimizing the magnetic field distribution. In order to improve the uniformity of the magnetic field, the radially magnetized annular permanent magnet is easier to complete the complex magnetic field segmentation and superposition configuration.

[0038] At least one of the multiple annular permanent magnets 110_1 ... 110_Q can be relatively displaced relative to the other annular permanent magnets in the extension direction of the central axis AX to adjust the magnetic field distribution and size of the basic adjustable magnetic field. For example, at least one of the multiple annular permanent magnets 110_1 ... 110_Q can be displaced along the central axis AX, that is, displaced in a third direction Z (for example, which can be perpendicular to each other) intersecting the first direction X and the second direction Y. For example, at least one of the annular permanent magnets 110_1 ... 110_Q can be relatively displaced in the third direction relative to other annular permanent magnets in the same group, so that the relative positions between the multiple annular permanent magnets are changed, so that the magnetic field distribution and magnetic field extreme value of the basic adjustable magnetic field can be changed, thereby changing the force of the basic adjustable magnetic field on the particle beam, so that the deflection direction and deflection angle of the particle beam are changed.

[0039] According to an embodiment of the present invention, since the plurality of annular permanent magnets 110_1 ... 110_Q in the annular permanent magnet group are sequentially arranged along the same axis, the basic adjustable magnetic field formed by the superposition of the magnetic fields of the plurality of annular permanent magnets 110_1 ... 110_Q is radially distributed along the central axis AX, reducing the stray field of the magnetic lens and improving the accuracy and stability of the magnetic lens. On this basis, by controlling the relative displacement between at least one of the plurality of annular permanent magnets 110_1 ... 110_Q and other annular permanent magnet groups in the extension direction of the central axis AX, the magnetic field distribution and magnetic field extreme value as the basic adjustable magnetic field can be flexibly adjusted from a mechanical level, without using an electromagnetic coil to adjust the magnetic field distribution and magnetic field extreme value of the magnetic lens, reducing the volume of the magnetic lens, and since this adjustment is a mechanical adjustment of a passive system, there is no need to consider thermal management issues.

[0040] According to an embodiment of the present invention, the movable area of ​​the annular permanent magnet located in the inner layer is determined based on the inner ring area of ​​the annular permanent magnet located at the periphery of the annular permanent magnet. For example, the outer diameter of the i-th annular permanent magnet among the plurality of annular permanent magnets 110_1 ... 110_Q is smaller than the inner diameter of the i+k-th annular permanent magnet among the plurality of annular permanent magnets 110_1 ... 110_Q, so that the i-th annular permanent magnet is relatively displaced relative to the i+k-th annular permanent magnet in the inner ring area of ​​the i+k-th annular permanent magnet, i is a positive integer, k = 1, 2, .... i+k is less than or equal to Q. In the present invention, Q represents a quantity.

[0041] It can be understood that, since each annular permanent magnet has a width in the third direction Z, the inner ring area of ​​each annular permanent magnet can be an internal cavity surrounded by the annular structure of the annular permanent magnet. The i+kth annular permanent magnet can be the Qth annular permanent magnet 110_Q or a permanent magnet located between the i-th annular permanent magnet and the Qth annular permanent magnet 110_Q. Taking the annular permanent magnet 110_1 and the annular permanent magnet 110_Q as examples, the annular permanent magnet 110_1 is displaced only in the annular area of ​​the annular permanent magnet 110_Q along the third direction Z. In the case where the inner annular permanent magnet exceeds the outer annular permanent magnet in the third direction Z, the basic adjustable magnetic field will diverge from a position close to the third direction Z to a direction away from the third direction Z, so that the stray field is enhanced. Thus, limiting the movement of the inner annular permanent magnet in the inner ring area of ​​the outer annular permanent magnet can effectively suppress the stray field and facilitate the packaging of the annular permanent magnet group.

[0042] According to an embodiment of the present invention, each annular permanent magnet includes an inner surface close to the central axis AX and an outer surface away from the central axis AX, and the inner surface and the outer surface of each annular permanent magnet have opposite polarities to each other. Taking the Qth annular permanent magnet 110_Q as an example, the inner surface IF1_Q of the Qth annular permanent magnet 110_Q can be an N pole, and the outer surface IF2_Q can be an S pole, or the inner surface IF1_Q of the Qth annular permanent magnet 110_Q can be an S pole, and the outer surface IF2_Q can be an N pole.

[0043] According to an embodiment of the present invention, the outer surface of the i-th annular permanent magnet 110_1 ... 110_Q among the plurality of annular permanent magnets 110_1 ... 110_Q and the inner surface of the i+1-th annular permanent magnet among the plurality of annular permanent magnets 110_1 ... 110_Q have opposite magnetic poles, and i is a positive integer.

[0044] For example, the outer surface of the i-th annular permanent magnet can be an S pole, and the inner surface of the i+1-th annular permanent magnet can be an N pole. The i-th annular permanent magnet and the i+1-th annular permanent magnet can attract each other based on the magnetic force applied to each other, thereby maintaining a relatively static state. On this basis, by applying opposite forces to the i-th annular permanent magnet and the i+1-th annular permanent magnet in a third direction Z, the i-th annular permanent magnet and the i+1-th annular permanent magnet can be displaced relative to each other, thereby adjusting the basic adjustable magnetic field. For example, an opposite force can be applied to the i-th annular permanent magnet and the i+1-th annular permanent magnet in a third direction Z by a preset device, and the present invention is not limited to this.

[0045] For example, the plurality of annular permanent magnets 110_1 ... 110_Q include stacked annular permanent magnets, the stacked annular permanent magnets include at least two annular permanent magnets stacked in the direction in which the central axis AX extends, and the at least two annular permanent magnets have the same inner diameter and the same outer diameter. Adjacent annular permanent magnets among the at least two annular permanent magnets are in contact based on the magnetic force applied to each other by the adjacent annular permanent magnets.

[0046] Figure 2 The schematic diagram shows a magnetizing direction of the annular permanent magnet according to an embodiment of the present invention. It should be understood that in the present invention, the magnetizing direction can also be different from the magnetizing direction of the annular permanent magnet according to an embodiment of the present invention. Figure 2 The direction shown is opposite. Figure 3 The schematic diagram of the structure of the stacked annular permanent magnets according to the embodiment of the present invention is shown schematically. Figure 3 The magnetization directions of the stacked annular permanent magnets are opposite to each other.

[0047] Figure 4 The schematic diagram of the structure of two groups of stacked annular permanent magnets according to an embodiment of the present invention is shown schematically. Figure 4 As shown, a group of stacked annular permanent magnets located in the inner layer may include two stacked annular permanent magnets, and a group of stacked annular permanent magnets located in the outer layer may include two stacked annular permanent magnets. It should be understood that in the present invention, the stacked annular permanent magnets are not limited to two annular permanent magnets, but may also be three, four or five, etc., and the present invention is not limited to this.

[0048] Figure 5 The schematic diagram of the stacking of annular permanent magnets according to an embodiment of the present invention is shown schematically. Figure 5 N and S both represent magnetic poles.

[0049] exist Figure 5 The figure shows a stacked double-layer annular permanent magnet (a). The magnetization directions of the first layer and the second layer of the double-layer annular permanent magnet (a) are opposite, so that an alternating radiation magnetization effect can be formed. This structural design helps to enhance the uniformity of the magnetic field and improve the magnetic field distribution to a certain extent. It is suitable for application scenarios with special requirements for the magnetization direction.

[0050] exist Figure 5 The figure also shows four layers of stacked annular permanent magnets (b). The magnetization directions of two adjacent layers of the four layers of annular permanent magnets (b) are opposite. By increasing the number of stacked layers, the magnetic field density can be enhanced, and the design of multi-layer alternating magnetization can effectively reduce magnetic field interference and improve the performance stability of the magnetic ring.

[0051] exist Figure 5Also shown is a stacked six-layer annular permanent magnet (c). The magnetization directions of two adjacent layers of the six-layer annular permanent magnet (c) are opposite, so that a complex magnetic field distribution can be formed. The six-layer stacked structure can provide a strong and uniform magnetic field, which is suitable for high-precision, high-power equipment, especially in fields requiring high magnetic field stability.

[0052] It should be noted that the above is only an example, and the stacked annular permanent magnets may also be a stacked structure with other numbers, such as 3, 5, 7, 8 or 9, etc.

[0053] According to an embodiment of the present invention, the outer diameter of the jth group of stacked annular permanent magnets among the plurality of annular permanent magnets 110_1 ... 110_Q is smaller than the inner diameter of the j+pth group of stacked annular permanent magnets among the plurality of annular permanent magnets 110_1 ... 110_Q, so that the jth group of stacked annular permanent magnets can be relatively displaced relative to the j+pth group of stacked annular permanent magnets within the inner ring region of the j+pth group of stacked annular permanent magnets, where j is a positive integer, and p=1, 2, .... j+p is smaller than Q.

[0054] For example, the range of the inner ring region of the stacked annular permanent magnets can be determined based on the area of ​​the inner ring region of each of the stacked annular permanent magnets in the first direction X and the second direction Y and the width in the third direction Z, that is, the range of the inner ring region of the stacked annular permanent magnets can be the internal cavity surrounded by the annular structures of the stacked annular permanent magnets. In the case where the inner layer of the stacked annular permanent magnets exceeds the outer layer of the stacked annular permanent magnets in the third direction Z, the basic adjustable magnetic field will diverge from a position close to the third direction Z to a direction away from the third direction Z, so that the stray field is enhanced. Therefore, limiting the movement of the inner layer of the annular permanent magnets in the inner ring region of the outer layer of the annular permanent magnets can effectively suppress the stray field and facilitate the packaging of the annular permanent magnet group.

[0055] According to an embodiment of the present invention, the outer surface of the i-th annular permanent magnet 110_1…110_Q among the multiple annular permanent magnets 110_1…110_Q and the inner surface of the i+1-th annular permanent magnet among the multiple annular permanent magnets have the same magnetic poles, and i is a positive integer. The multiple annular permanent magnets 110_1…110_Q include stacked annular permanent magnets, and the stacked annular permanent magnets include at least two annular permanent magnets stacked in the extension direction of the central axis AX, and at least two annular permanent magnets have the same inner diameter and outer diameter. Adjacent annular permanent magnets among at least two annular permanent magnets are in contact based on external forces other than the magnetic force of the adjacent annular permanent magnets. For example, it can be through gluing and other fixing means to make up for the process defects of the annular permanent magnets in the ring manufacturing, such as the difficulty in manufacturing an annular structure with a height-to-diameter ratio.

[0056] Figure 6Schematically shows a schematic diagram of stacking annular permanent magnets according to another embodiment of the present invention. Figure 6 N and S both represent magnetic poles.

[0057] exist Figure 6 The figure shows a stacked double-layer annular permanent magnet (a). The magnetization directions of the first layer of annular permanent magnet and the second layer of annular permanent magnet in the double-layer annular permanent magnet (a) are the same. This structural design also helps to enhance the uniformity of the magnetic field and improve the magnetic field distribution to a certain extent, and is suitable for application scenarios with special requirements for the magnetization direction.

[0058] exist Figure 6 The figure also shows four layers of stacked annular permanent magnets (b). The magnetization directions of the annular permanent magnets in the four layers of annular permanent magnets (b) are the same. By increasing the number of stacked layers, the magnetic field density can be enhanced, and the multi-layer magnetization design can effectively reduce magnetic field interference and improve the performance stability of the magnetic ring.

[0059] exist Figure 6 Also shown is a stacked six-layer annular permanent magnet (c). The annular permanent magnets in the six-layer annular permanent magnet (c) have the same magnetization direction, so that a complex magnetic field distribution can be formed. The six-layer stacked structure can provide a strong and uniform magnetic field, which is suitable for high-precision, high-power equipment, especially in fields requiring high magnetic field stability.

[0060] It should be noted that the above is only an example, and the stacked annular permanent magnets may also be a stacked structure with other numbers, such as 3, 5, 7, 8 or 9, etc.

[0061] According to an embodiment of the present invention, the magnetic lens further comprises electromagnetic coils, and a group of electromagnetic coils are wound around an annular permanent magnet along the outer surface of the annular permanent magnet. Figure 7 The schematic diagram of a magnetic lens having an electromagnetic coil and an annular permanent magnet according to an embodiment of the present invention is schematically shown. Figure 7 As shown, the magnetic lens may include an annular permanent magnet 701 located at the outermost layer and an annular permanent magnet 702 located at the inner layer. The electromagnetic coil 703 may be wound around the annular permanent magnet 701 located at the outermost layer, and the magnetic conductive magnetic circuit 704 may conduct magnetic conduction to the magnetic field generated by the annular permanent magnet 701, the annular permanent magnet 702 and the electromagnetic coil 703. The electromagnetic coil is used to generate an additional adjustable magnetic field, and the superimposed magnetic field formed by the basic adjustable magnetic field and the additional adjustable magnetic field acts on the particle beam injected into the inner ring area of ​​the annular permanent magnet group, and the magnetic field strength of the additional adjustable magnetic field changes with the change of the current size and direction of the input electromagnetic coil. For example, the electromagnetic coil can be wound around the outer surface of the annular permanent magnet in a clockwise or counterclockwise direction. After the electromagnetic coil is energized, the additional adjustable magnetic field can enhance the basic adjustable magnetic field, or can weaken the basic adjustable magnetic field.

[0062] In the embodiment of the present invention, the permanent magnet and the electromagnetic adjustment coil together form a closed magnetic circuit, and the permanent magnet is arranged between the mold components made of high magnetic permeability materials. The total magnetic flux of the composite structure is adjusted by the electromagnetic coil, thereby fine-tuning the strength and direction of the magnetic field in the lens system, adjusting the focal length, and compensating for the deviation of the magnetic field strength and direction during operation.

[0063] Based on this, the stacked annular permanent magnets of the present invention are the first mechanical adjustment means; the electromagnetic adjustment method is used as the second electromagnetic adjustment means, which can adapt to different working conditions, create a controllable and adjustable magnetic field configuration, increase the modular control and adjustability of the magnetic lens system, and improve the applicability of the magnetic lens structure in particle beam equipment. In addition, the composite magnetic lens structure formed by the annular permanent magnet group of the present invention has a small geometric size, which is helpful for promotion and extension to multi-beam equipment.

[0064] Based on this, under the premise of ensuring that mechanical and electromagnetic adjustability can be achieved, the present invention provides a three-lens system that can be used for a universal charged particle beam device or a lens array of a multi-beam device. For example, there are multiple annular permanent magnet groups, and the multiple annular permanent magnet groups are arranged in an array in the same plane according to a predetermined pattern to receive a particle beam corresponding to the predetermined pattern. The particle beam corresponding to the predetermined pattern is emitted by a multi-electron source, or is obtained by using a beam splitter to split a particle beam emitted by a single electron source according to a predetermined pattern. For example, the predetermined pattern includes a symmetrical pattern. Fig. 8A The schematic diagram of an array composed of annular permanent magnet groups according to an embodiment of the present invention is schematically shown. Figure 8B Schematically shows a schematic diagram of an array composed of annular permanent magnet groups according to another embodiment of the present invention. For example, the array can be arranged as follows Fig. 8A The rectangle shown, or arranged as Figure 8B The circular array shown. In a rectangular array, each unit can be adjusted individually to achieve magnetic field focusing and adjustment functions in different directions. This array is suitable for applications that require uniform magnetic field distribution in a large space, such as magnetic field generation in magnetic resonance imaging (MRI) equipment. In a circular array, the circular array consists of multiple units arranged in a circular trajectory to form a uniform circular magnetic field distribution. Each unit can be electromagnetically adjusted as needed to control the intensity, shape and focusing effect of the overall magnetic field of the array. The circular array is suitable for applications that require precise concentration of the magnetic field, such as particle accelerators or specific experimental scenarios. Through different array layouts (such as rectangular arrays or circular arrays), the magnetic fields of the units interact to form a specific overall magnetic field distribution. Based on this, the effect of the array on magnetic field control and optimization has the flexibility and efficiency of magnetic field regulation in practical applications.

[0065] Based on this, the present invention provides a dual tunable permanent magnet lens structure, which integrates stacked radiation-magnetized annular permanent magnets and electromagnetic coils to achieve higher magnetic field configuration flexibility and adaptability. The system can assist in the design of lens systems for particle beam devices, and also helps in the design of miniaturized lens arrays in multi-beam devices. It can be adapted to multi-beam particle beam device arrays and provide electron beam focusing components for multi-beam particle beam devices.

[0066] In terms of design principle, the design scheme of the magnetic lens of the present invention allows the use of permanent magnets of different types and different processes to carry out composite permanent magnet lens design in the same tunable manner, so as to meet the adaptability to different magnetic field configurations and application environments. In another aspect of the present invention, a design method of a magnetic lens is also provided.

[0067] Step 1: First, select the permanent magnetic material. It is necessary to comprehensively consider the manufacturing process, magnetization direction, operating temperature range, etc. For example, according to the performance requirements of the selected material, determine the appropriate manufacturing process, such as hot pressing, sintering, bonding, additive manufacturing, etc. Different processes will affect the magnetic properties, dimensional accuracy and consistency of the permanent magnet. For example, "hot pressing process" or "additive manufacturing process" can be used to prepare annular permanent magnets to meet the requirements of higher magnetic energy product and stability. In addition, the magnetization direction suitable for the application can be selected, and the selection of magnetization direction affects the final magnetic field distribution and its stability. In addition, according to the actual use environment, permanent magnetic materials with suitable operating temperature range can be selected to ensure that the material will not demagnetize or lose magnetism in extreme environments. Typical permanent magnetic materials such as neodymium iron boron (NdFeB) and samarium cobalt (SmCo) should be appropriately selected according to the required magnetic strength, stability and working environment.

[0068] Step 2: Determine the geometric dimensions and stacking method. After selecting the permanent magnet material, the geometric dimensions of the annular permanent magnet and its stacking method need to be determined. The specific steps are as follows:

[0069] Determination of geometric dimensions: According to the design requirements, first determine the outer diameter, inner diameter, height and other dimensional parameters of each annular permanent magnet. The accuracy of the dimensions directly affects the final magnetic field distribution and application effect, so the dimensions need to be strictly controlled according to the design requirements.

[0070] Design of stacking method: In a multi-layer stacking structure, the stacking method is crucial to the magnetic field strength and uniformity. Depending on the application requirements, you can choose to stack in the same direction or in the opposite direction. The reasonable choice of stacking method helps to optimize the distribution of the overall magnetic field and reduce the uneven magnetic field or magnetic leakage.

[0071] The implementation of this step requires detailed engineering calculations and simulation analysis to ensure that the selected geometric dimensions and stacking methods can meet performance indicators such as magnetic field strength and uniformity.

[0072] Step 3: Structural parameter optimization. Further optimize the structural parameters of the magnet according to the actual working conditions and usage environment. The specific optimization contents include:

[0073] Optimize the shape of the magnetic circuit: appropriately adjust the shape of the magnetic circuit, such as changing the edge shape, surface treatment, chamfering, etc., to improve the magnetic conductivity of the magnetic circuit;

[0074] Matching of the annular permanent magnet with the magnetic circuit and lens housing structure: Determine the relative positions of the various components and other additional equipment to optimize the coupling effect of the magnetic field. Consider the interaction force between the stacked rings to avoid excessive mutual repulsion or attraction.

[0075] Step 4: Determination of tunability. To ensure that the system can flexibly adjust the magnetic field strength and direction, a certain tunable mechanism needs to be designed. The tuning mechanism can be achieved in the following ways:

[0076] Stacking method, relative position adjustment of rings: The magnetic field strength can be adjusted by changing the stacking order or relative position of multiple annular permanent magnets. For example, the ratio of stacking in the same direction and stacking in the opposite direction can be changed. At the same time, the adjustment range and accuracy of the magnetic field can be optimized by fine-tuning the position of each layer of magnetic rings. This fine-tuning can be done by high-precision mechanical devices or magnetic field sensor feedback mechanisms.

[0077] Current regulation of the peripheral electromagnetic coil assembly: The peripheral electromagnetic coil can further adjust the strength and distribution of the magnetic field by changing the current. By precisely controlling the current, the magnetic field of the composite structure can be dynamically adjusted to meet the needs of different working conditions.

[0078] Step 5: Determine the relative positions of multiple annular permanent magnets. Determine the relative positions of multiple annular permanent magnets. To this end, perform the following operations:

[0079] Numerical calculation: Based on finite element analysis (FEA) or other numerical simulation methods, calculate the influence of the relative positions of different multiple annular permanent magnets on the magnetic field distribution. Through simulation analysis, optimize the relative positions of the magnetic ring and the collar to achieve the predetermined magnetic field strength and uniformity.

[0080] Experimental test plan formulation: Based on the numerical calculation results, an experimental verification plan is designed to test the actual distribution of the magnetic field through the combination of multiple annular permanent magnets. The positions of multiple annular permanent magnets are adjusted through experimental feedback to further optimize the design plan.

[0081] During the experiment, it is necessary to build a flexible lens system test platform and use precise magnetic field measurement instruments (such as Hall probes, magnetic field probes, etc.) to monitor the magnetic field strength and distribution in real time.

[0082] The above steps are the basic implementation scheme of the technology of the present invention, covering all aspects from material selection, geometric dimension design, stacking method determination, to magnetic field tunability and stacking position optimization. Through precise design and experimental verification, this implementation scheme can effectively achieve the intensity, uniformity and regulation function of the target magnetic field to meet specific application requirements.

[0083] The following is an example of a feasible design:

[0084] A double-stacked annular permanent magnet combined with an electromagnetic coil is used to form a composite permanent magnet lens as the first-stage lens structure of the three-lens system, called the first condenser; a composite lens with the same configuration is used at a different Z-axis position as the second condenser; a magnetic lens with electromagnetic adjustment capability is used as the objective lens of the entire system and is placed at the end of the system to optimize the optical path and reduce the overall aberration of the entire system.

[0085] The theoretical design of the composite permanent magnet lens assembly is achieved by preferentially using a radiation magnetized annular permanent magnet with a relatively small stray magnetic field, combined with a magnetic circuit design with chamfered edges, based on Ampere's circuit law.

[0086] The electron optical parameters of the designed three-lens system are calculated. Under the conditions of a given electron source and observation device, the three lens assemblies are assembled in a mechanically adjustable frame to build an experimental test environment for the three-lens system.

[0087] The electron optical system is optimized by using a composite permanent magnet lens. The system includes a three-stage lens structure, which contains two condensers (as the first condenser and the second condenser, respectively) composed of a composite double-stacked annular permanent magnet and an electromagnetic coil, and a magnetic lens with electromagnetic adjustment capability as the objective lens. By precisely designing the position and adjustment mechanism of each lens component, the system aims to reduce optical distortion and improve the adjustment accuracy of the optical path.

[0088] Step 1: Select permanent magnet material and electromagnetic coil design. First, to ensure the stability and efficiency of the system, select the appropriate permanent magnet material and electromagnetic coil configuration.

[0089] Selection of permanent magnetic materials: It is preferred to select radiative magnetized annular permanent magnets with relatively small stray magnetic fields (such as neodymium iron boron or samarium cobalt materials). Such materials have high magnetic energy product and low temperature coefficient, which can ensure stable magnetic field output.

[0090] Electromagnetic coil design: Electromagnetic coils are used in combination with annular permanent magnets. The electromagnetic coils can be copper coil windings with circular or rectangular cross-sections, so that the strength and distribution of the magnetic field can be adjusted by adjusting the current. The design of the electromagnetic coils must take into account the adjustable current and the coordination with the permanent magnets. Since the electromagnetic coils involved in the present invention are only used as adjustable auxiliary magnetic field adjustment units and are not basic magnetic field generation units, the heat dissipation problem can be ignored here.

[0091] Step 2: Design a composite permanent magnet lens. The composite permanent magnet lens is composed of a double stacked annular permanent magnet and an electromagnetic coil. The specific design steps are as follows:

[0092] Stacking method: A double-stacked annular permanent magnet structure is used, with the magnetic rings stacked in the same direction or in the opposite direction. The stacking method is optimized based on the calculation results to achieve the best magnetic field distribution. The stacking method requires the spacing between the rings to be precisely designed according to the requirements of the electronic optical system.

[0093] Electromagnetic regulation mechanism: Combined with the current regulation capability of the electromagnetic coil, the magnetic field strength of the composite lens can be dynamically regulated. Based on the primary magnetic field formed by the stacked annular permanent magnets, the performance of the composite permanent magnet lens can be precisely controlled by adjusting the coil current, optimizing the electronic optical path and reducing optical distortion.

[0094] Magnetic circuit design: Adopting a magnetic circuit design with edge chamfers, using Ampere's loop law, and precisely designing the shape of the magnetic circuit and the chamfers of the edges, the influence of magnetic leakage and uneven magnetic field is reduced.

[0095] Step 3: Design a three-lens system. The three-lens system consists of three lens components: the first condenser, the second condenser, and the objective lens.

[0096] First condenser (first lens assembly): The first condenser adopts a composite permanent magnet lens design and is installed at the starting position of the system. The lens focuses the electron beam and controls the beam direction through a combination of a double-stacked annular permanent magnet and an electromagnetic coil.

[0097] Second condenser (second lens assembly): The second condenser has the same design as the first condenser, but is located in a different position. It is installed on the Z axis of the system to further optimize the focusing effect of the electron beam. By adjusting the relative position of the second condenser, the optical path of the entire optical system can be effectively calibrated.

[0098] Objective lens (third lens assembly): As the key lens of the whole system, the objective lens adopts a magnetic lens design with electromagnetic adjustment capability. The objective lens adjusts the final beam focus through the electromagnetic adjustment mechanism and reduces the aberration introduced by the two-stage condenser.

[0099] Step 4: Calculation and adjustment of electronic optical parameters. After completing the design of the three-lens system, it is necessary to calculate the electronic optical parameters to ensure the optical path accuracy and focusing effect of the entire system. The calculation includes:

[0100] Optical performance simulation: Use optical design software to simulate the designed three-lens system and calculate key parameters such as the system's focusing ability, beam distribution, and aberration.

[0101] Parameter optimization: According to the simulation results, the geometric dimensions, stacking method and current setting of each lens component are adjusted to optimize the electronic optical performance of the system. Through multiple iterative calculations and simulations, the accuracy and stability of the optical path are ensured.

[0102] Step 5: Mechanical assembly and debugging. To verify the feasibility of the theoretical design, build an experimental platform for the three-lens system and debug it. The specific steps are as follows:

[0103] Mechanical frame design: According to the design of the lens system, the mechanical frame is made to ensure that the position of each lens component can be accurately adjusted. The frame should have good stability to avoid vibration and displacement affecting system performance.

[0104] Lens assembly: The designed first condenser, second condenser and objective lens are assembled in sequence in a mechanically adjustable frame. Each lens assembly can be adjusted independently to precisely adjust the light path.

[0105] Experimental test: Build an electron source and observation window to test the system, test the focusing accuracy and electron optical parameters of the system. Adjust the electromagnetic coil current, the relative position of the stacked annular permanent magnets, and the number and stacking method of the stacked magnets to further optimize the system performance.

[0106] Step 6: Performance verification and optimization. Based on the experimental test results, verify whether the performance of the three-lens system meets the design requirements. If performance deviation is found, the design parameters need to be carefully adjusted:

[0107] Performance evaluation: Evaluate the system's optical distortion, beam focusing effect, and optical path stability to confirm whether the design goals have been achieved.

[0108] Adjustment scheme optimization: According to the test results, the adjustment range of the electromagnetic coil, the spacing and angle of the annular permanent magnet stack are optimized to further improve the optical path adjustment accuracy.

[0109] By implementing the above steps, the present invention realizes the application of the composite permanent magnet lens in the three-lens system, and effectively optimizes the focusing accuracy of the optical path and reduces optical distortion. By combining the permanent magnet material with the electromagnetic adjustment mechanism, a flexible and accurate optical adjustment scheme is provided, which is suitable for the design and application of high-precision electronic optical systems.

[0110] It will be appreciated by those skilled in the art that the features described in the various embodiments of the present invention may be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, without departing from the spirit and teachings of the present invention, the features described in the various embodiments of the present invention may be combined and / or combined in various ways. All of these combinations and / or combinations fall within the scope of the present invention.

[0111] The embodiments of the present invention are described above. However, these embodiments are only for the purpose of illustration, and are not intended to limit the scope of the present invention. Although each embodiment is described above, it does not mean that the measures in each embodiment cannot be used in combination advantageously. Without departing from the scope of the present invention, those skilled in the art may make various substitutions and modifications, which should all fall within the scope of the present invention.

Claims

1. A stacked magnetic lens, characterized in that: The stacked magnetic lens comprises: An annular permanent magnet group, the annular permanent magnet group comprising a plurality of annular permanent magnets coaxially arranged in sequence along a central axis, the plurality of annular permanent magnets being used to generate a basic adjustable magnetic field, the basic adjustable magnetic field acting on a particle beam injected into an inner ring region of the annular permanent magnet group; At least one of the plurality of annular permanent magnets can be relatively displaced relative to the other annular permanent magnets in the extension direction of the central axis to adjust the magnetic field distribution and size of the basic adjustable magnetic field.

2. The magnetic lens according to claim 1, characterized in that: The outer diameter of the i-th annular permanent magnet among the multiple annular permanent magnets is smaller than the inner diameter of the i+k-th annular permanent magnet among the multiple annular permanent magnets, so that the i-th annular permanent magnet can be relatively displaced relative to the i+k-th annular permanent magnet within the inner ring area of ​​the i+k-th annular permanent magnet, where i is a positive integer and k=1, 2,… 3. The magnetic lens according to claim 1, characterized in that: Each of the annular permanent magnets comprises an inner surface close to the central axis and an outer surface far from the central axis, and the inner surface and the outer surface of each of the annular permanent magnets have opposite polarities to each other.

4. The magnetic lens according to claim 3, characterized in that: The outer surface of the i-th annular permanent magnet among the multiple annular permanent magnets and the inner surface of the i+1-th annular permanent magnet among the multiple annular permanent magnets have opposite magnetic poles, and i is a positive integer.

5. The magnetic lens according to claim 4, characterized in that: The plurality of annular permanent magnets include stacked annular permanent magnets, wherein the stacked annular permanent magnets include at least two annular permanent magnets stacked in the direction in which the central axis extends, and the at least two annular permanent magnets have the same inner diameter and the same outer diameter; Wherein, adjacent annular permanent magnets among the at least two annular permanent magnets are in contact based on the magnetic force applied by the adjacent annular permanent magnets to each other.

6. The magnetic lens according to claim 5, characterized in that: The outer diameter of the jth group of stacked annular permanent magnets among the multiple annular permanent magnets is smaller than the inner diameter of the j+pth group of stacked annular permanent magnets among the multiple annular permanent magnets, so that the jth group of stacked annular permanent magnets can be relatively displaced relative to the j+pth group of stacked annular permanent magnets within the inner ring area of ​​the j+pth group of stacked annular permanent magnets, j is a positive integer, p=1, 2,… 7. The magnetic lens according to claim 3, characterized in that: The outer surface of the i-th annular permanent magnet among the plurality of annular permanent magnets and the inner surface of the i+1-th annular permanent magnet among the plurality of annular permanent magnets have the same magnetic pole, and i is a positive integer; The plurality of annular permanent magnets include stacked annular permanent magnets, wherein the stacked annular permanent magnets include at least two annular permanent magnets stacked in the extension direction of the central axis, and the at least two annular permanent magnets have the same inner diameter and the same outer diameter; Wherein, the adjacent annular permanent magnets among the at least two annular permanent magnets are in contact with each other based on an external force other than the magnetic force of the adjacent annular permanent magnets.

8. The magnetic lens according to claim 1, characterized in that: There are multiple annular permanent magnet groups, and the multiple annular permanent magnet groups are arranged into an array in the same plane according to a predetermined pattern so as to receive a particle beam corresponding to the predetermined pattern. The particle beam corresponding to the predetermined pattern is emitted by a multi-electron source, or is obtained by splitting a particle beam emitted by a single electron source according to the predetermined pattern using a beam splitter.

9. The magnetic lens according to claim 8, characterized in that: The predetermined pattern comprises a symmetrical pattern.

10. The magnetic lens according to claim 1, characterized in that: The magnetic lens further comprises electromagnetic coils, a group of the electromagnetic coils being wound around an annular permanent magnet along the outer surface of the annular permanent magnet; The electromagnetic coil is used to generate an additional adjustable magnetic field. The superimposed magnetic field formed by the basic adjustable magnetic field and the additional adjustable magnetic field acts on the particle beam injected into the inner ring area of ​​the annular permanent magnet group. The magnetic field strength of the additional adjustable magnetic field changes with the change of the magnitude and direction of the current input into the electromagnetic coil.

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