Annular focus electron beam focusing device and method

Abstract

The invention discloses an annular focus electron beam focusing device and method, and belongs to the field of energy, aerospace, material analysis and high-energy physics. The annular focus electron beam focusing device comprises a cathode assembly, a focusing electrode assembly and an anode target which are sequentially arranged in the electron beam propagation direction; the cathode assembly comprises a lamp filament; the focusing electrode assembly at least comprises a focusing electrode and a focusing cover, the focusing electrode is provided with a supporting part used for fixing a filament, the supporting part is movably connected with the focusing electrode, and then the assembling height of the filament is changed; the focusing cover covers the focusing electrode in a matched mode, and the focusing electrode is provided with a positioning part used for positioning the focusing cover in the axial direction. By replacing the lamp filaments with different ring diameters and / or adjusting the assembly height of the lamp filaments, the electron beams converge on the bombardment surface of the anode target to form the annular focus with the preset size, a basis is provided for adapting to the annular focuses with different sizes, and the flexibility and the application range of equipment are greatly improved.

Description

Technical Field

[0001] This invention relates to the fields of energy, aerospace, materials analysis and high-energy physics, and in particular to a ring-shaped focal electron beam focusing device and method. Background Technology

[0002] Electron beam focusing devices, as the core components for generating X-rays, are widely used in fields such as energy, aerospace, materials analysis, and high-energy physics. Their basic working principle is that thermionic electrons emitted from a heated cathode filament are accelerated by a high-voltage electric field, and then the high-speed electron beam bombards the anode target surface, abruptly decelerating to generate X-rays. Among the performance indicators of an X-ray tube, the focal spot size is a crucial parameter. It directly determines the geometric characteristics of the X-ray source and the spatial resolution of the imaging system. Specifically: (1) Impact on image sharpness: According to the principle of optical imaging, an X-ray source can be regarded as a surface light source, and the image it produces will have penumbra blur. The larger the focal spot size, the more severe the geometric blur, and the worse the sharpness and clarity of the final perspective or photographic image. Conversely, a small focal spot with concentrated energy can significantly improve the image's detail resolution.

[0003] (2) Adaptability to different application scenarios: Although the traditional single small focal spot design is beneficial for high-resolution imaging, its power load capacity is limited because the electron energy is concentrated on a very small area of ​​the target surface, resulting in extremely high energy density and heat accumulation, which can easily lead to target melting. Therefore, a trade-off needs to be made between power (heat load) and resolution (focal size). To this end, various special-shaped focal spots have been developed, such as annular focal spots. Annular focal spots distribute electron energy within an annular area, effectively increasing the heat dissipation area and reducing the local power density of the target surface. This allows for the use of higher power while maintaining good imaging characteristics and shows advantages in specific analytical applications. In the existing technology, adjusting the focal spot size usually requires replacing the entire cathode assembly or performing complex electric field adjustments. There is a lack of simple and precise focal spot size adjustment mechanisms, which cannot quickly adapt to the needs of different application scenarios (such as high-resolution imaging and high-power elemental analysis). Summary of the Invention

[0004] The purpose of this invention is to overcome the problems of the prior art and provide an annular focal electron beam focusing device and method.

[0005] The objective of this invention is achieved through the following technical solution: an annular focal electron beam focusing device, comprising a cathode assembly, a focusing electrode assembly, and an anode target arranged sequentially along the electron beam propagation direction; The cathode assembly includes a filament; The focusing electrode assembly includes at least a focusing electrode and a focusing cover. The focusing electrode is provided with a support for fixing the filament, and the support is movably connected to the focusing electrode to change the assembly height of the filament. The focusing cover is fitted onto the focusing electrode, and the focusing electrode is provided with a positioning part for positioning the focusing cover in the axial direction. The anode target is located below the filament.

[0006] In one example, a nickel tube is provided on the support, and the filament is fixed in the nickel tube.

[0007] In one example, the positioning part is an annular flange surrounding the focusing electrode, or a plurality of circumferentially distributed protrusions.

[0008] In one example, the vertical distance from the tip of the filament to the support is defined as the first axial distance D, which is 12mm to 13mm; the vertical distance from the tip of the filament to the top of the focusing stage is defined as the second axial distance H, which is 5mm to 5.5mm; and the vertical distance from the tip of the focusing electrode to the top of the positioning part is defined as the third axial distance h, which is 1mm to 1.5mm.

[0009] In one example, the size of the annular focal point formed by the device is 12mm × 16mm or 8mm × 16mm.

[0010] It should be further noted that the technical features corresponding to the above-mentioned device examples can be combined or substituted to form new technical solutions.

[0011] The present invention also includes a method for focusing an annular focal electron beam, applied to the focusing device formed by any or a combination of the above examples, characterized by comprising the following steps: The filament is heated by passing an electric current through it, causing the filament to emit electrons; An accelerating voltage is applied between the focusing hood and the anode target to create an accelerating electric field; By confining and focusing the electron beam with a focusing electric field, a ring-shaped focal point is formed on the bombardment surface of the anode target.

[0012] In one example, the method further includes: By changing the filament to a different diameter and / or adjusting the filament mounting height, the electron beam is focused on the bombardment surface of the anode target to form a ring-shaped focal point of a predetermined size.

[0013] It should be further noted that the technical features corresponding to the above examples can be combined or replaced to form new technical solutions.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. In one example, the support is movably connected to the focusing electrode, enabling flexible adjustment of the filament assembly height. This allows the focusing characteristics of the electron beam to be changed simply by adjusting the height without replacing other components, providing a basis for adapting to annular focal points of different sizes and greatly improving the flexibility and application range of the equipment.

[0015] 2. In one example, by setting up a nickel tube, the filament is secured firmly and stably, the electron emission position is accurate, and replacement and maintenance are convenient, thus reducing maintenance costs.

[0016] 3. In one example, the positioning part design ensures the accuracy and consistency of the axial relative position between the focusing cover and the focusing electrode. Attached Figure Description

[0017] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. The accompanying drawings are provided to provide a further understanding of the present application and constitute a part of the present application. The same reference numerals are used in these drawings to denote the same or similar parts. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application.

[0018] Figure 1 A schematic diagram of the system structure is provided as an example of the present invention; Figure 2 This is an example of an annular focal point generated according to the present invention.

[0019] 101-Filament; 102-Focusing electrode; 102a-Support part; 102b-Positioning part; 103-Anode target; 104-Nickel tube. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0022] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] In one example, such as Figure 1 As shown, an annular focal electron beam focusing device for an X-ray tube is housed in a high-vacuum glass or metal-ceramic shell. A cathode assembly, a focusing electrode assembly, and an anode target 103 are arranged sequentially along the electron beam propagation direction. The focusing electrode assembly includes a focusing electrode 102 and a focusing shroud (not shown in the figure). The cathode assembly is the electron emission source, the focusing electrode assembly is used to control the shape and trajectory of the electron beam, and the anode target 103 is used to receive the high-speed electron beam and convert its kinetic energy into X-rays.

[0024] Specifically, the cathode assembly includes a filament 101, typically made of high-purity tungsten wire wound into a precise spiral shape. The filament 101 is heated to approximately 2000°C or higher by an electric current, generating thermionic emission to form a primary electron beam. The focusing electrode assembly includes a focusing electrode 102 and a focusing shield. The focusing electrode 102 is typically made of oxygen-free copper or a nickel-based alloy and has a cup-shaped structure. The focusing electrode is also made of a highly conductive metal and has a shield-shaped structure; that is, the focusing shield is fitted onto the focusing electrode 102. A support portion 102a is movably connected to the focusing electrode 102. The support portion 102a is used to fix the filament 101. By adjusting the height of the support portion 102a, the assembly height of the filament 101 can be finely adjusted. The focusing electrode 102 also has a positioning portion 102b for axially positioning the focusing shield, facilitating precise matching between the focusing shield and the focusing electrode 102. The anode target 103 is located at the bottom of the device, directly opposite the filament 101, and is typically made of high-melting-point metals such as tungsten or molybdenum, used to cut off electrons.

[0025] During operation, the filament 101 is first adjusted to a preset height via the support 102a according to the required annular focal size (e.g., 12×16mm or 8×16mm). Then, the filament 101 is energized and heated to emit electrons. At the same time, an accelerating voltage of tens of thousands to hundreds of thousands of volts is applied between the focusing electrode assembly (with negative high voltage) and the anode target 103 (grounded). Under this high voltage, a specific electrostatic electric field distribution is formed between the focusing electrode 102 and the focusing cover and the anode target 103. When the diverging electrons emitted from the filament 101 pass through this electric field, they are subjected to the electric field force. The electron trajectory is constrained and converges towards the central axis. Due to the spiral structure of the filament 101 itself and the precise shaping of the electric field, the electron beam does not converge into a solid point, but crosses in front of the target surface and finally bombards the anode target 103 to form an annular focal point.

[0026] In one example, a nickel tube 104 is provided on the support 102a for fixing the filament 101. Specifically, the support of the filament 101 is inserted into the nickel tube 104, and the nickel tube 104 is used to clamp the filament 101, thereby improving the reliability of the filament 101 under high temperature and vibration environment, ensuring the accuracy of electron emission position, and facilitating replacement and maintenance, thus reducing maintenance costs.

[0027] In one example, the positioning part 102b is an annular flange surrounding the focusing electrode 102, or a plurality of protrusions distributed circumferentially. The top surface of the annular flange or the top of the protrusion is the positioning reference surface of the focusing cover and the focusing electrode 102, thereby limiting the focusing cover to a preset axial position.

[0028] In one example, the vertical distance from the tip of the filament 101 to the support portion 102a is defined as the first axial distance D, which is 12mm to 13mm; the vertical distance from the tip of the filament 101 to the top of the focusing stage is defined as the second axial distance H, which is 5mm to 5.5mm; and the vertical distance from the tip of the focusing electrode 102 to the tip of the positioning portion 102b is defined as the third axial distance h, which is 1mm to 1.5mm. Correspondingly, the size of the annular focal spot is 12mm × 16mm or 8mm × 16mm. Through the synergistic effect of the first, second, and third axial distances, the electron beam converges on the bombardment surface of the anode target to form an annular focal spot.

[0029] The present invention also includes a method for focusing an annular focal electron beam, applied to a focusing device formed by any or a combination of the above examples, the method comprising the following steps: S1: The filament is heated by passing electricity through it, causing the filament to emit electrons; S2: An accelerating voltage is applied between the focusing hood and the anode target to form an accelerating electric field; S3: By confining and focusing the electron beam with a focusing electric field, a ring-shaped focal point is formed on the bombardment surface of the anode target.

[0030] In this example, by heating the filament with electricity to emit electrons, a strong accelerating electric field is formed under the high voltage applied between the focusing shroud and the anode target. This electric field forces the electrons to fly at high speed toward the anode target, and the electric field lines converge toward the central axis along the electron beam path. This convergent electric field distribution exerts a continuous, centripetal squeezing effect on the initially diverging electron beam from all sides, precisely constraining and converging the electron trajectory. Finally, the converged electron beam precisely bombards the anode target surface in a ring distribution pattern, thus forming a... Figure 2 The 8mm×16mm or 12mm×16mm annular focal spot shown is precisely sized and controllable.

[0031] Preferably, by changing the filament with a different diameter and / or adjusting the assembly height of the filament, the electron beam is focused on the bombardment surface of the anode target to form a ring-shaped focal point of a predetermined size.

[0032] In one implementation, the filament position is adjusted by rotating the support to make the first axial distance D 12.5 mm, the second axial distance H 5.25 mm, and the third axial distance h 1.25 mm through machining. At this time, the device is placed in a vacuum environment, and the filament is heated by applying current to emit electrons. A -100 kV high voltage is applied between the focusing cover and the anode target. The electron beam is constrained by the focusing electric field and finally forms a clear 12 mm × 16 mm annular focal spot on the anode target.

[0033] In another implementation, the filament position is adjusted by rotating the support to make the first axial distance D 12.5 mm, the second axial distance H 5.25 mm, and the third axial distance h 1.25 mm through machining. At the same time, the filament coil diameter is changed. At this time, because the coil diameter of the electron emission source (filament) is smaller, the electron beam converges into a narrower annular region under the same focusing electric field, and finally forms an 8 mm × 16 mm annular focal point on the anode target.

[0034] This invention defines the value ranges of the first axial distance D, the second axial distance H, and the third axial distance h. Based on this, by simply changing the filament diameter or fine-tuning the filament assembly height, annular focal spots of different sizes (such as 12mm×16mm and 8mm×16mm) can be accurately and stably generated. This invention transforms complex electron beam control into precise mechanical adjustment, fundamentally solving the problems of difficult and inflexible focal spot size adjustment in traditional X-ray tubes. This allows for rapid adaptation to various applications, from high-power elemental analysis to high-resolution industrial CT.

[0035] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A ring-shaped focal electron beam focusing device, characterized in that, It includes a cathode assembly, a focusing electrode assembly, and an anode target arranged sequentially along the direction of electron beam propagation; The cathode assembly includes a filament; The focusing electrode assembly includes at least a focusing electrode and a focusing cover. The focusing electrode is provided with a support for fixing the filament, and the support is movably connected to the focusing electrode to change the assembly height of the filament. The focusing cover is fitted onto the focusing electrode, and the focusing electrode is provided with a positioning part for positioning the focusing cover in the axial direction. The anode target is located below the filament.

2. The annular focal electron beam focusing device according to claim 1, characterized in that, The support is equipped with a nickel tube, and the filament is fixed in the nickel tube.

3. The annular focal electron beam focusing device according to claim 1, characterized in that, The positioning part is an annular flange surrounding the focusing electrode, or multiple protrusions distributed circumferentially.

4. The annular focal electron beam focusing device according to claim 1, characterized in that, The vertical distance from the tip of the filament to the support is defined as the first axial distance D, which is 12mm to 13mm; the vertical distance from the tip of the filament to the top of the focusing stage is defined as the second axial distance H, which is 5mm to 5.5mm; and the vertical distance from the tip of the focusing electrode to the top of the positioning part is defined as the third axial distance h, which is 1mm to 1.5mm.

5. A method for focusing an annular focal electron beam, applied to the focusing apparatus according to any one of claims 1-4, characterized in that, Includes the following steps: The filament is heated by passing an electric current through it, causing the filament to emit electrons; An accelerating voltage is applied between the focusing hood and the anode target to create an accelerating electric field; By confining and focusing the electron beam with a focusing electric field, a ring-shaped focal point is formed on the bombardment surface of the anode target.

6. The annular focal electron beam focusing device according to claim 5, characterized in that, The method further includes: By changing the filament to a different diameter and / or adjusting the filament mounting height, the electron beam is focused on the bombardment surface of the anode target to form a ring-shaped focal point of a predetermined size.

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