Hybrid excitation electron optical focusing device

Abstract

This invention discloses a hybrid excitation type electron optical focusing device, characterized by comprising: an electron beam generating device and a hybrid excitation focusing module. The electron beam generating device is used to emit an electron beam, and the hybrid excitation focusing module is coaxially arranged on one side of the electron beam emission direction of the electron beam generating device. The hybrid excitation focusing module includes a ring-shaped permanent magnet assembly composed of multiple permanent magnets arranged in a Halbach array, and an excitation coil sleeved on the outside of the ring-shaped permanent magnet assembly and not in contact with each other. The magnetic fields generated by the ring-shaped permanent magnet assembly and the excitation coil work together to focus the electron beam. This invention fully integrates the advantages of permanent magnet focusing and electromagnetic focusing, ensuring both a relatively simple structure and no high power consumption problem caused by additional continuous power supply, while achieving high-precision, wide-range dynamic focusing control.

Description

Technical Field

[0001] This utility model relates to the field of electronic vacuum device technology, and in particular to a hybrid excitation type electron optical focusing device. Background Technology

[0002] The electron optical focusing system is a core component of electron gun vacuum coating equipment, and its performance directly determines the uniformity, density, and film quality stability of the coating. In electron gun vacuum coating, the electron beam must bombard the target material in a high vacuum environment, causing the target atoms or molecules to evaporate and deposit on the substrate surface to form a thin film. During this process, the focusing accuracy, beam spot size stability, and dynamic adjustment capability of the electron beam are crucial. Poor electron beam focusing can lead to target bombardment area shift and uneven energy distribution, resulting in problems such as film thickness deviation, compositional inhomogeneity, and even localized overheating of the substrate, severely affecting the performance of the coated product.

[0003] Traditional electron beam focusing technologies are mainly divided into two categories: permanent magnet focusing and electromagnetic focusing, both of which have significant limitations in the field of electron gun vacuum coating. Permanent magnet focusing systems use permanent magnets (such as NdFeB and SmCo) to generate a constant magnetic field. While they offer advantages such as simple structure, no need for additional power supply, and no heat loss, their fixed magnetic field strength makes it difficult to dynamically adjust the beam size and focusing position according to the coating process requirements, thus limiting focusing performance, especially when it comes to wide-range energy adjustment or beam current size optimization, making it difficult to meet high-precision requirements. Electromagnetic focusing systems, on the other hand, use excitation coils to generate an adjustable magnetic field and achieve dynamic focusing control by changing the magnitude and direction of the current, offering high flexibility. However, their electromagnetic systems consume a lot of power, generate significant heat, and require complex current control circuits, increasing system cost and maintenance difficulty. Therefore, it is necessary to improve existing technologies to overcome their shortcomings. Utility Model Content

[0004] The problem to be solved by this invention is to provide a hybrid excitation type electro-optical focusing device to overcome the shortcomings of existing technologies that use a single permanent magnet focusing or electromagnetic focusing method, which cannot meet the requirements of high precision and low power consumption.

[0005] The technical solution adopted by this utility model to solve its technical problem is: a hybrid excitation type electron optical focusing device, comprising: An electron beam generator, used to emit an electron beam; The hybrid excitation focusing module is coaxially arranged on one side of the electron beam emission direction of the electron beam generator. The hybrid excitation focusing module includes a ring-shaped permanent magnet assembly composed of multiple permanent magnets in a Halbach array and an excitation coil sleeved on the outside of the ring-shaped permanent magnet assembly and not in contact with each other. The magnetic fields generated by the ring-shaped permanent magnet assembly and the excitation coil work together to focus the electron beam.

[0006] As a further improvement of this utility model, the annular permanent magnet assembly includes multiple permanent magnet rings, each composed of several permanent magnets spliced ​​together and arranged along the electron beam emission direction, with each of the multiple permanent magnet rings having a different magnetization direction.

[0007] As a further improvement of this utility model, the excitation coil is distributed outside one of the permanent magnet rings with the magnetization direction radially outward.

[0008] As a further improvement of this utility model, the annular permanent magnet assembly includes four permanent magnet rings, which are arranged sequentially along the electron beam emission direction as a first permanent magnet ring, a second permanent magnet ring, a third permanent magnet ring, and a fourth permanent magnet ring. With the electron beam emission direction defined as "front" and the opposite direction as "rear," the magnetization direction of the first permanent magnet ring is axially forward, the magnetization direction of the second permanent magnet ring is radially inward, the magnetization direction of the third permanent magnet ring is axially backward, and the magnetization direction of the fourth permanent magnet ring is radially outward. The excitation coil is sleeved on the outside of the fourth permanent magnet ring.

[0009] As a further improvement of this utility model, the outer diameter of the permanent magnet ring is 60ΔX, the inner diameter is 50ΔX, the thickness is 9ΔX, and ΔX is 1~10cm.

[0010] As a further improvement of this utility model, the two adjacent permanent magnet rings and the two adjacent permanent magnets in each permanent magnet ring are fixedly connected by adhesive.

[0011] As a further improvement of this utility model, the hybrid excitation focusing module is provided with one; Alternatively, there may be two or more hybrid excitation focusing modules, which are arranged along the electron beam emission direction.

[0012] As a further improvement of this utility model, the hybrid excitation focusing module also includes two magnetic screens, which are respectively disposed at both ends of the annular permanent magnet assembly.

[0013] As a further improvement of this utility model, the electron beam generating device includes: Cathode used for emitting electrons; A focusing electrode is used to initially focus the electrons emitted from the cathode; And an anode, located between the focusing electrode and one of the magnetic screens, for accelerating the electron beam focused by the focusing electrode.

[0014] As a further improvement of this utility model, the hybrid excitation type electron optical focusing device also includes a collecting electrode, which is disposed on one side of another magnetic screen and is used to collect the electron beam focused by the hybrid excitation focusing module.

[0015] The beneficial effects of this utility model are: 1. This utility model provides a hybrid excitation type electron optical focusing device, which adopts a Halbach array to form a ring permanent magnet assembly and an excitation coil sleeved on the outside of it without contacting each other to form a hybrid excitation focusing module. It can fully integrate the advantages of permanent magnet focusing and electromagnetic focusing. The ring permanent magnet assembly of the Halbach array can provide a basic magnetic field with good uniformity and strength. The excitation coil can realize the dynamic adjustment of the magnetic field through current adjustment. The two work together to the electron beam, which not only ensures a relatively simple structure and no high power consumption problem caused by additional continuous power supply, but also realizes high-precision and wide-range dynamic focusing control. It can be widely used in high-energy physics, precision machining and electron optical instruments and other fields. 2. This utility model distributes the excitation coil outside the permanent magnet ring with the magnetization direction radially outward. The central magnetic field generated by the excitation coil is aligned with the near-field closed region of the magnetic circuit, which can accurately match the spatial position of the excitation coil and the ring permanent magnet assembly. This can effectively compensate for the magnetic field attenuation in the radial magnetization phase of the linear Halbach array, improve the uniformity of the axial magnetic field component, and facilitate precise adjustment of the magnetic field by the excitation coil. Wide-range, high-precision dynamic focusing control can be achieved with a low current. In addition, the excitation coil and the permanent magnet ring with the magnetization direction radially outward adopt a non-contact layout, which ensures high magnetic field coupling efficiency and avoids the skin effect. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a front view of the hybrid excitation type electron optical focusing device of this utility model; Figure 2 This is a cross-sectional view of the hybrid excitation type electron optical focusing device of this utility model; Figure 3 The following are simulation diagrams of the beam current of this utility model under different coil currents; Figure 4 This is a schematic diagram of the radius of curvature of the beam trajectory under different coil currents according to this utility model; Figure 5This is a schematic diagram showing the relationship between the maximum beam envelope radius and the axial distance under different coil currents according to this utility model; Figure 6 This is a graph showing the uniformity of magnetic field strength under different axial distances of coil currents according to this invention. Figure 7 This is a simulation diagram of the beam output process of the focusing device when the excitation coil current is 0.5A.

[0018] in, Figure 2 The direction indicated by the middle arrow is the direction of electron beam emission.

[0019] Referring to the accompanying drawings, the following explanations are provided: 1. Ring-shaped permanent magnet assembly; 101. First permanent magnet ring; 102. Second permanent magnet ring; 103. Third permanent magnet ring; 104. Fourth permanent magnet ring; 2. Excitation coil; 3. Magnetic screen; 4. Cathode; 5. Focusing electrode; 6. Anode; 7. Collecting electrode. Detailed Implementation

[0020] The present application will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0021] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0023] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The illustrations only show the components related to this application and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0024] Additionally, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that practice can be carried out without these specific details.

[0025] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.

[0026] See Figures 1 to 7 This utility model provides a hybrid excitation type electron optical focusing device, including: an electron beam generating device and a hybrid excitation focusing module. The electron beam generating device is used to emit an electron beam, and the hybrid excitation focusing module is coaxially arranged on one side of the electron beam emission direction of the electron beam generating device.

[0027] The hybrid excitation focusing module includes a ring-shaped permanent magnet assembly 1 composed of multiple permanent magnets arranged in a Halbach array, and an excitation coil 2 sleeved on the outside of the ring-shaped permanent magnet assembly 1 and not in contact with each other. The electron beam generated by the electron beam generator is emitted along the axial direction of the ring-shaped permanent magnet assembly 1. At the same time, the magnetic fields generated by the ring-shaped permanent magnet assembly 1 and the excitation coil 2 work together to focus the electron beam.

[0028] This invention relates to a hybrid excitation type electron optical focusing device. It emits an electron beam by setting up an electron beam generator and combines a ring permanent magnet assembly 1 with an excitation coil 2 that is sleeved on the outside of the ring permanent magnet assembly 1 and does not contact the excitation coil 2 to form a hybrid excitation focusing module. This device can fully integrate the advantages of permanent magnet focusing and electromagnetic focusing. The ring permanent magnet assembly 1 of the Halbach array can provide a basic magnetic field with good uniformity and strength. The excitation coil 2 can dynamically adjust the magnetic field through current regulation. The two work together to focus the electron beam, which not only ensures a relatively simple structure and avoids the high power consumption problem caused by additional continuous power supply, but also achieves high-precision and wide-range dynamic focusing control. It can be widely used in fields such as high-energy physics, precision machining and electron optical instruments.

[0029] Furthermore, the annular permanent magnet assembly 1 includes multiple permanent magnet rings, each composed of several permanent magnets and arranged along the electron beam emission direction, with each permanent magnet ring having a different magnetization direction.

[0030] See Figure 1 and Figure 2In this embodiment, the annular permanent magnet assembly 1 specifically includes four permanent magnet rings, which are sequentially arranged along the electron beam emission direction as a first permanent magnet ring 101, a second permanent magnet ring 102, a third permanent magnet ring 103, and a fourth permanent magnet ring 104. Defining the electron beam emission direction as "front" and the opposite direction as "rear," the magnetization direction of the first permanent magnet ring 101 is axially forward, the magnetization direction of the second permanent magnet ring 102 is radially inward, the magnetization direction of the third permanent magnet ring 103 is axially backward, and the magnetization direction of the fourth permanent magnet ring 104 is radially outward. This invention, by employing a four-level layered assembly structure and distributing the magnetization directions of each permanent magnet ring in a specific sequence, can form a complete Halbach-enhanced magnetic field cycle, effectively optimizing the basic magnetic field distribution, improving the uniformity and intensity of the axial magnetic field, reducing local divergence or distortion during electron beam transmission, and achieving high-precision magnetic field control.

[0031] Specifically, in this embodiment, the four permanent magnet rings are precisely assembled in the circumferential direction from 16 neodymium iron boron permanent magnets with a remanence of 1.44T. Each permanent magnet has a central angle of 22.5°, achieving breakthrough maintainability and convenient magnetization. Adjacent permanent magnet rings, as well as adjacent permanent magnets within each ring, are fixedly connected by adhesive.

[0032] Furthermore, in this embodiment, the four permanent magnet rings are identical in size, with an outer diameter of 60ΔX, an inner diameter of 50ΔX, and a thickness of 9ΔX, where ΔX ranges from 1 to 10 cm. This invention employs a parametric dimensional system for the permanent magnet rings, allowing their dimensions to be flexibly adjusted according to actual application requirements, adapting to electron beam equipment of different specifications. Simultaneously, the standardized dimensional design facilitates manufacturing and assembly, improving the product's versatility and maintainability.

[0033] Continue reading Figure 1 and Figure 2 The excitation coil 2 is distributed outside a permanent magnet ring with a radially outward magnetization direction, that is, the excitation coil 2 is sleeved on the outside of the fourth permanent magnet ring 104. By distributing the excitation coil 2 outside the permanent magnet ring with a radially outward magnetization direction, this invention aligns the central magnetic field generated by the excitation coil 2 with the near-field closed region of the magnetic circuit. This allows for precise matching of the spatial position of the excitation coil 2 and the annular permanent magnet assembly 1, effectively compensating for the magnetic field attenuation in the radial magnetization phase of the linear Halbach array, improving the uniformity of the axial magnetic field component, and facilitating precise adjustment of the magnetic field by the excitation coil. Wide-range, high-precision dynamic focusing control can be achieved with a lower current.

[0034] It is worth mentioning that the excitation coil 2 and the fourth permanent magnet ring 104, which has a radially outward magnetization direction, adopt a non-contact layout. The excitation coil 2 and the fourth permanent magnet ring 104 maintain an optimal air gap of 2mm, which ensures high efficiency of magnetic field coupling and avoids the skin effect.

[0035] The excitation coil 2 adopts a multi-layer dense winding structure, specifically 1500 turns and Φ0.5mm high-temperature superconducting wire in this embodiment.

[0036] It should be noted that this utility model does not limit the number of hybrid excitation focusing modules; it can be set to only one or more.

[0037] The number of hybrid excitation focusing modules in this invention can be flexibly configured to be one or more according to the actual application scenario, possessing strong scenario adaptability and functional expandability: when a single hybrid excitation focusing module is used, relying on the uniform basic magnetic field constructed by the Halbach permanent magnet array and the efficient adjustment capability of the non-contact excitation coil 2, it can meet the basic requirements of conventional electron beam equipment for focusing accuracy, dynamic response and low power consumption. Its simplified structural design is also conducive to the miniaturization and integration of the system; when multiple hybrid excitation focusing modules are set according to the complex scenario requirements such as high-energy electron beam transmission and long-distance beam current control, two or more hybrid excitation focusing modules can be arranged and distributed along the electron beam emission direction, and each module can achieve multi-segment magnetic field superposition and step-by-step precise control through synergistic action.

[0038] The accompanying drawings in this specification Figure 1 and Figure 2 The schematic shows four hybrid excitation focusing modules. The four excitation coils 2 are powered by a four-channel independent power supply system, supporting ±1A continuously adjustable current to achieve dynamic adjustment of the axial magnetic field strength.

[0039] In addition, the hybrid excitation focusing module also includes two magnetic screens 3, which are respectively configured at both ends of the axial direction of the annular permanent magnet assembly 1. The magnetic screens 3 are made of electrical pure iron with high magnetic permeability, which can form a closed magnetic circuit and control the leakage coefficient to below 5%.

[0040] In this invention, the electron beam generating device specifically includes a cathode 4, a focusing electrode 5, and an anode 6. The cathode 4 emits electrons; the focusing electrode 5 initially focuses the electrons emitted by the cathode 4, optimizing the initial shape of the electron beam, reducing the divergence angle, and making the electron beam more concentrated, providing a stable electron beam cross-section for subsequent acceleration and transmission. The anode 6 is located between the focusing electrode 5 and one of the magnetic screens 3, and is used to accelerate the electron beam focused by the focusing electrode 5; simultaneously, the anode 6 and the magnetic screen 3 achieve zero-pitch contact, ensuring seamless coupling of the electric and magnetic fields.

[0041] In addition, the hybrid excitation type electron optical focusing device of this utility model also includes a collecting electrode 7, which is disposed on one side of another magnetic screen 3 and is used to collect the electron beam focused by the hybrid excitation focusing module.

[0042] To further verify the performance of this device, a complete simulation model including electromagnetic field-electron motion-thermodynamic coupling was established using finite element analysis software. The beam focusing characteristics of excitation coil 2 under different excitation conditions were studied in detail. The simulation settings included four typical operating conditions: (1) reference mode (I=0A current, pure permanent magnet operation); (2) reverse compensation mode (I=-1A current, used for beam period adjustment); (3) precision adjustment mode (I=0.1~1A, step 0.3A, to achieve magnetic field enhancement). This invention designed a static magnetic field simulation with excitation coil 2 and a beam dynamics simulation to verify the electromagnetic field characteristics of the electron beam emission path and the characteristics of the electron beam trajectory.

[0043] Figure 3 The diagram shows the beam current simulation of this invention under different coil currents. The parameters in the simulation are configured as follows: the remanence of the permanent magnet is 1.44T, the coercivity is 894kA / m, the number of coil turns is 1500, and ΔX is 1cm. Figure 3 Comparative analysis of the beam distribution characteristics of the four operating conditions (reference mode I=0A, reverse compensation I=-1A, enhancement I=+1A, and precision adjustment I=0.1~1A) revealed that: in reference mode, the maximum beam envelope radius is 3.75mm; in reverse compensation mode, periodic modulation is achieved by weakening the background magnetic field, and the envelope radius increases to 5.83mm, while the radius of curvature of the cathode exit (z=0mm) decreases sharply, indicating that the initial focusing effect dominated by the Lorentz force is significant; in enhancement mode, the composite magnetic field strength is enhanced, but beam oscillation is caused by the overshoot of the axial magnetic field gradient, and the envelope radius increases abnormally to 5.88mm.

[0044] Figure 4 The study revealed the variation of the electron beam trajectory radius of curvature with axial distance and compared the trends under different coil currents. It can be concluded that the beam trajectory radius of curvature increases with increasing axial distance, while the magnetic field strength continuously decreases along the axial direction. Under different coil currents, the larger the current, the smaller the beam radius of curvature, indicating that the magnetic field strength is positively correlated with the current magnitude.

[0045] Further through Figure 5Analysis of the transverse relative velocity distribution curves revealed that the beam's transverse relative velocity exhibits a Gaussian distribution. Notably, under this current condition, the total system power consumption is only 3.8W (coil resistance 0.95Ω), and the magnetic field gradient shows a strong linear correlation with the beam curvature radius. This verifies that the system still possesses excellent electromagnetic-kinematic coupling characteristics in low-current mode, providing key technical support for the long-term stable operation of high-precision electron beam processing equipment.

[0046] Figure 6 This figure illustrates the analysis of magnetic field uniformity at equiaxial distances for different coil currents. The analysis is presented as an error bar diagram, where the upper and lower limits of the error bars represent the fluctuation range of the magnetic field at that axial position. By analyzing the length of the error bars for different currents at different axial distances, the uniformity of the magnetic field can be intuitively analyzed. The figure shows that at an axial distance of 168 mm, the magnetic field is relatively uniform for all coil currents.

[0047] Figure 7 The simulation diagram of the beam output process of the focusing device when the excitation coil current is 0.5A is shown. The analysis of the diagram shows that when the excitation coil current is given as 0.5A, the beam current radius at the output port is smaller compared with other simulation cases, which is beneficial to meeting the requirements for the beam spot size of electron beam focusing under vacuum coating.

[0048] These data confirm that the system has excellent magnetic field tunability and beam current control capabilities, which greatly solves the contradiction between rapid magnetic field response and energy consumption control in high-precision electro-optical systems, and provides a precise basis for parameter optimization for practical applications.

[0049] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A hybrid excitation type electron optical focusing device, characterized by comprising: include: An electron beam generator, used to emit an electron beam; The hybrid excitation focusing module is coaxially arranged on one side of the electron beam emission direction of the electron beam generator. The hybrid excitation focusing module includes a ring permanent magnet assembly (1) composed of multiple permanent magnets in a Halbach array and an excitation coil (2) sleeved on the outside of the ring permanent magnet assembly (1) and not in contact with each other. The magnetic fields generated by the ring permanent magnet assembly (1) and the excitation coil (2) work together to focus the electron beam.

2. The hybrid excitation electronic optical focusing device according to claim 1, characterized in that: The ring-shaped permanent magnet assembly (1) includes multiple permanent magnet rings, each composed of several permanent magnets spliced ​​together and arranged along the electron beam emission direction, with each of the multiple permanent magnet rings having a different magnetization direction.

3. A hybrid excitation electron optical focusing device according to claim 2, characterized in that: The excitation coil (2) is located outside one of the permanent magnet rings, with the magnetization direction radially outward.

4. The hybrid excitation electronic optical focusing device according to claim 2, characterized in that: The annular permanent magnet assembly (1) includes four permanent magnet rings, which are arranged sequentially along the electron beam emission direction as a first permanent magnet ring (101), a second permanent magnet ring (102), a third permanent magnet ring (103), and a fourth permanent magnet ring (104). With the electron beam emission direction defined as front and the opposite direction as rear, the magnetization direction of the first permanent magnet ring (101) is axially forward, the magnetization direction of the second permanent magnet ring (102) is radially inward, the magnetization direction of the third permanent magnet ring (103) is axially backward, and the magnetization direction of the fourth permanent magnet ring (104) is radially outward. The excitation coil (2) is sleeved on the outside of the fourth permanent magnet ring (104).

5. The hybrid excitation electronic optical focusing device according to claim 2, characterized in that: The permanent magnet ring has an outer diameter of 60ΔX, an inner diameter of 50ΔX, and a thickness of 9ΔX, where ΔX is 1~10cm.

6. The hybrid excitation electronic optical focusing device according to claim 2, characterized in that: The two adjacent permanent magnet rings, as well as the two adjacent permanent magnets in each permanent magnet ring, are fixedly connected by adhesive.

7. The hybrid excitation electronic optical focusing device of claim 1, wherein: One hybrid excitation focusing module is provided; Alternatively, there may be two or more hybrid excitation focusing modules, which are arranged along the electron beam emission direction.

8. The hybrid excitation electronic optical focusing device according to claim 1, characterized in that: The hybrid excitation focusing module also includes two magnetic screens (3), which are respectively disposed at both ends of the annular permanent magnet assembly (1).

9. A hybrid excitation electronic optical focusing device according to claim 8, characterized in that: The electron beam generating device includes: Cathode (4) used to emit electrons. A focusing electrode (5) is used to initially focus the electrons emitted by the cathode (4); And an anode (6), located between the focusing electrode (5) and one of the magnetic screens (3), for accelerating the electron beam focused by the focusing electrode (5).

10. The hybrid excitation type electron optical focusing device according to claim 9, characterized in that: It also includes a collecting electrode (7), which is disposed on one side of another magnetic screen (3) for collecting the electron beam focused by the hybrid excitation focusing module.

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