Microchannel plate for cathode electron self-confinement in a photocathode x-ray tube and method of use

Abstract

This invention provides a microchannel plate for cathode electron self-focusing in photocathode X-ray tubes and its usage method. Applied to the field of high-performance X-ray tube technology, the substrate is the physical base of the microchannel plate, configured as a Fresnel lens. The substrate has a planar incident surface and a deformed output surface composed of concentric rings. A gradient aperture array is distributed on the substrate, arranged on the plane of the substrate. A radial gradient material is a surface functional coating on the inner wall of the microchannel. Variable aperture channels are the three-dimensional contours of the inner wall surface of each independent microchannel constituting the gradient aperture array, defining each independent microchannel in the gradient aperture array. Different secondary electron emission materials are coated radially on the inner wall surface of each microchannel defined by the gradient aperture array. This method solves the problems of loose structure and poor performance in existing X-ray tubes.

Description

Technical Field

[0001] This invention relates to the field of high-performance X-ray tube technology, and in particular to a microchannel plate for cathode electron self-focusing in photocathode X-ray tubes and its method of use. Background Technology

[0002] Currently, high-performance X-ray tubes are core equipment in modern medical imaging, industrial non-destructive testing, safety screening, and scientific research. The growing demand for X-ray sources with higher brightness, smaller focal spots, and faster modulation speeds is directly driving innovation in X-ray tube technology. Integrating microchannel plates (MCPs) as electron multipliers into X-ray tubes is one of the key technological pathways to achieving next-generation high-performance X-ray sources, enabling extremely high electron beam currents with extremely low cathode power consumption.

[0003] Traditional glass straight-hole microchannel plates have inherent defects in long-term applications. Limited by the high-temperature reduction process, the formation of the secondary electron emission layer on the inner wall of the glass straight-hole microchannel is difficult to control precisely. Noise sources, such as impurities and defects, are introduced, leading to a decrease in the signal-to-noise ratio during the multiplication process. Furthermore, a long-standing bottleneck in existing MCP-enhanced X-ray tube technology is that the multiplied electron beam requires a complex external focusing system for shaping before it can effectively bombard the anode target. Existing focusing systems typically consist of one or more electrostatic lenses (focusing electrodes), which not only increases the manufacturing cost, assembly complexity, and physical size of the X-ray tube, limiting its final performance, but also significantly reduces the modulation speed of the X-ray pulse due to the additional capacitance introduced by the focusing electrodes, making it difficult to apply to ultrafast imaging scenarios requiring nanosecond or even picosecond responses. In addition, the electric field distortion generated by the electrodes affects the symmetry and minimum size of the focal spot, thus limiting further improvements in imaging resolution. Moreover, the focusing electrodes and their supporting structures occupy valuable space inside the X-ray tube, hindering the design of miniaturized and compact X-ray sources.

[0004] Therefore, there is an urgent need for an MCP that can focus the electron beam itself without the need for external focusing electrodes, which would fundamentally simplify the electron optical design of X-ray tubes, achieve a more compact structure, faster response speed, lower cost and better focus quality, and be of great significance to promoting the development of the entire X-ray application field. Summary of the Invention

[0005] This invention provides a microchannel plate for cathode electron self-focusing in photocathode X-ray tubes and its usage method, solving the problems of the natural divergence of the emitted electron beam in traditional MCPs, which cannot be directly used for focusing and bombarding the anode target; the necessity of external focusing electrode systems for existing MCP-enhanced X-ray tubes, resulting in system complexity and high cost; and the limitation of modulation speed and final focus quality of X-ray tubes by external focusing electrodes, making it difficult to achieve next-generation high-performance X-ray tubes with compact structure and superior performance.

[0006] According to a first aspect of the present invention, a microchannel plate is provided comprising: a substrate, a gradient aperture array, a radial gradient material, and a variable aperture channel.

[0007] The substrate is the physical base of the microchannel plate, with a Fresnel lens configuration. The substrate has a planar incident surface and an irregular output surface composed of concentric rings. A gradient aperture array is distributed on the substrate. The radial gradient material is a surface functional coating on the inner wall of the microchannel. The variable aperture channel is the three-dimensional contour of the inner wall surface of each independent microchannel that constitutes the gradient aperture array.

[0008] According to a second aspect of the present invention, a method of using a microchannel plate for cathode electron self-focusing in a photocathode X-ray tube is provided, comprising the following steps:

[0009] The initial divergent electron beam emitted from each pixel of the matrix photocathode is injected into the plane of the microchannel plate at a set tilt angle. After entering each variable aperture channel, the electrons undergo secondary electron emission under the action of the radially gradient material coated along the radial partition of the inner wall of the variable aperture channel, and are multiplied by the optimized electric field established by the gradient aperture array. At the same time, they are strongly constrained by the rapidly contracting geometry of the channel entrance. The initial divergent electron beam undergoes a multiplication process within the variable aperture channel, which is constrained by geometry, electric field gradient and material dependence, to obtain a pre-shaped electron beam. The pre-shaped electron beam is then macroscopically deflected by the electric field of the Fresnel lens to obtain a strong electron pulse pointing towards the anode target.

[0010] A strong electron pulse directed at the anode target is accelerated by the high voltage of the anode in a vacuum environment, and bombards the corresponding anode target, exciting the generation of microfocus X-rays.

[0011] Compared with existing technologies, the advantages and positive effects of this invention are:

[0012] This invention utilizes a four-in-one structure—a Fresnel lens substrate, a gradient aperture array, a radial gradient material, and a variable aperture channel—to transform the MCP into a high-performance electron optical lens, achieving self-focusing and gain homogenization of the emitted electron beam. The Fresnel lens structure, as the first fundamental surface of the electron optical lens, guides the focusing path of the electron beam through the electric field gradient of the annular zone, providing a macroscopic geometric focusing basis. The gradient aperture array creates a stronger electric field gradient in the edge region, thereby guiding electrons more effectively to the multiplication region and maintaining efficient multiplication. An alumina film is deposited on the inner wall of the channel in the central region of the radial gradient material, ensuring stable operation of the MCP under high loads; a magnesium oxide film is deposited on the inner wall of the channel in the edge region, effectively compensating for signal loss caused by lower electron flux density and edge effects. The variable aperture channel effectively avoids the problem of excessively small collision angles, allowing high-energy electrons generated at the channel end to collide with the tube wall at a more optimized angle, significantly increasing the escape probability of secondary electrons and increasing gain.

[0013] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0014] The above and other features, advantages, and aspects of the various embodiments of the present invention will become more apparent from the accompanying drawings and the following detailed description. The drawings are provided for a better understanding of the invention and are not intended to limit the invention. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein:

[0015] Figure 1 A block diagram of a microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to an embodiment of the present invention is shown;

[0016] Figure 2 A top view of a Fresnel lens ring according to an embodiment of the present invention is shown;

[0017] Figure 3 A side view of the Fresnel lens ring and a schematic diagram of the focusing principle according to an embodiment of the present invention are shown;

[0018] Figure 4 A top view of a gradient aperture array according to an embodiment of the present invention is shown;

[0019] Figure 5 A schematic diagram of a variable aperture channel according to an embodiment of the present invention is shown;

[0020] Figure 6 A perspective view of a self-focusing MCP according to an embodiment of the present invention is shown;

[0021] Figure 7 A schematic diagram of the self-focusing MCP synergistic focusing effect according to an embodiment of the present invention is shown;

[0022] Figure 8 A flowchart illustrating a method of using a microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to an embodiment of the present invention is shown. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only 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.

[0024] Furthermore, the term "and / or" in this invention is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this invention generally indicates that the preceding and following related objects have an "or" relationship.

[0025] Figure 1 A block diagram of a microchannel plate for cathode electron self-focusing in a photocathode X-ray tube, as shown in an embodiment of the present invention, is illustrated. Figure 1 As shown, the microchannel plate includes: a substrate 1, a gradient aperture array 2, and a variable aperture channel 3.

[0026] The microchannel plate is a highly integrated, multifunctional structure, an inseparable functional fusion achieved through precise design and manufacturing on the same substrate. The substrate 1 serves as the structural carrier and macroscopic optical foundation, acting as the physical base of the entire MCP. The substrate 1 is designed in the configuration of a Fresnel lens, with a planar incident surface and an aberration output surface composed of concentric rings. All other functions are built upon this foundation. A gradient aperture array 2 is distributed on the substrate 1. The gradient aperture array 2 has the characteristic that the inlet aperture size of thousands of microchannels varies according to a preset gradient law from the center to the edge (smaller at the center and larger at the edge). This is achieved by directly forming a microchannel array with different apertures during the manufacturing of the substrate 1. The radial gradient material is a surface functional coating on the inner wall of the microchannel. Through processes such as atomic layer deposition, different radial gradient materials are coated radially on the inner wall surface of each microchannel defined by the gradient aperture array 2. The central region is aluminum oxide (Al2O3), and the edge region is magnesium oxide (MgO). The functional materials are directly attached to the channel wall. The variable aperture channel 3 is the three-dimensional profile of the inner wall surface of each independent microchannel constituting the gradient aperture array 2. The three-dimensional profile of the inner wall surface defines each independent microchannel in the gradient aperture array 2. The aperture of each independent microchannel is a non-linear change curve along the channel axis, with rapid contraction at the inlet and smooth transition at the outlet. The three-dimensional profile is formed simultaneously during the manufacturing of the substrate 1 and the gradient aperture array 2. The rapid contraction at the inlet corresponds to a steep curve in the inlet focusing region, while the smooth transition at the outlet corresponds to a smooth curve in the outlet optimization region.

[0027] In this embodiment, substrate 1 serves as an integral substrate with a Fresnel lens profile, on which a microchannel array with dual geometric features of gradient aperture array 2 (planar gradient) and variable aperture channel 3 (axial curve) is fabricated. Subsequently, a radial gradient material is deposited on the inner wall of all microchannels according to their radial positions. These four components together constitute a self-focusing microchannel plate. The macroscopic focusing force provided by substrate 1, combined with the microscopic electric field optimization provided by gradient aperture array 2 and variable aperture channel 3, jointly achieves spatial self-focusing of the electron beam. Simultaneously, the electric field compensation of gradient aperture array 2, the gain control of radial gradient material, and the multiplication optimization of variable aperture channel 3 work together to ensure that the electron pulse intensity emitted from each pixel point from the center to the edge of the panel is uniform and the timing is consistent. Finally, the MCP integrating these four components can efficiently and uniformly multiply and focus the electron beam emitted from the photocathode onto the corresponding anode target point without any external focusing electrodes.

[0028] In this embodiment, the Fresnel lens substrate is structurally designed with a planar incident surface and an aberration-shaped output surface composed of concentric rings. By precisely designing the tilt angle of each ring and the overall radius of curvature, a macroscopic geometric focusing basis is provided for the electron beam, guiding the electron beam path towards the convergence point of the anode target. The gradient aperture array distribution follows a predetermined gradient pattern, with the aperture (diameter) of the microchannel varying from the center to the edge (smaller aperture in the central region and larger aperture in the edge region). This is used to actively compensate for electron optical differences caused by electric field inhomogeneity, balance electron flux density, and thus solve edge aberrations and central electron saturation problems. A radial gradient material is used, with the inner wall of the microchannel having radially partitioned secondary electron emission layers. The inner wall of the channel in the edge region is made of magnesium oxide, while the inner wall of the channel in the central region is made of aluminum oxide, to achieve active compensation and homogenization of radial gain. The variable aperture channel's curve parameter design features a non-linear aperture variation along the axial direction for each microchannel. Specifically, the inlet focusing region employs a steep parabolic or high-order exponential curve for rapid contraction to quickly establish a strong axial electric field gradient, rapidly constraining and focusing electrons. The exit optimization region transitions to a gentle exponential curve or near-straight line to optimize the collision angle of secondary electrons, improving their escape probability and overall gain. The integrated self-focusing microchannel plate structure organically integrates the Fresnel lens substrate, gradient aperture array, radial gradient material, and variable aperture channel into a single unit. Through the synergistic effect of these four components, the emitted electron beam achieves self-focusing, enabling direct and precise bombardment of the anode target, thus completely eliminating the need for an external focusing electrode system. The photocathode X-ray tube incorporating the self-focusing microchannel plate integrates the self-focusing microchannel plate directly between the cathode and anode, using it as the core electron multiplier and focusing element, thereby forming a photocathode X-ray tube that eliminates the need for an external focusing electrode system.

[0029] This embodiment fundamentally solves the radial gain non-uniformity problem of MCP by introducing radial gradient materials, achieving unprecedented performance optimization. It provides a self-focusing microchannel plate that eliminates the need for an external focusing electrode system, which can be directly applied between the cathode and anode of a photocathode X-ray tube as a core electron multiplication and focusing element. This embodiment utilizes a four-in-one structure of a Fresnel lens substrate, a gradient aperture array, a radial gradient material, and a variable aperture channel, making the MCP itself a high-performance electron optical lens, achieving self-focusing and gain uniformity of the emitted electron beam. Specifically, the Fresnel lens substrate: The MCP substrate is designed as a Fresnel lens structure, including a planar incident surface and a distorted output surface (composed of concentric rings with an inclined angle). This Fresnel lens structure serves as the first fundamental surface of the electron optical lens, guiding the focusing path of the electron beam through the electric field gradient of the rings, providing a macroscopic geometric focusing basis. Gradient aperture array: From the center to the edge of the MCP, the aperture (diameter) of the microchannels varies in a gradient; the aperture in the central region is smaller (e.g., 20). m), with larger apertures in the edge regions (e.g., 25 m). A stronger electric field gradient is formed in the edge region, thereby guiding electrons to the multiplication region more effectively and maintaining efficient multiplication. Radial gradient material: Through advanced processes such as atomic layer deposition (ALD), a radially partitioned secondary electron emission layer is formed on the inner wall of the microchannel; an alumina (Al2O3) film is deposited on the inner wall of the channel in the central region to ensure the stable operation of the MCP under high load; a magnesium oxide (MgO) film is deposited on the inner wall of the channel in the edge region to effectively compensate for signal loss caused by lower electron flux density and edge effects. Variable aperture channel: Each microchannel is designed to be curved, and the aperture of the microchannel changes linearly along the axial direction. A steeper parabola or higher-order exponential curve is used to contract in the inlet focusing region, and a gentler exponential curve, or even close to a straight line, is transitioned in the outlet optimization region. This can effectively avoid the problem of excessively small collision angle, so that the high-energy electrons generated at the end of the channel can collide with the tube wall at a more optimized angle, greatly improving the escape probability of secondary electrons and increasing the gain.

[0030] like Figure 2 and Figure 3 As shown, traditional MCPs employ a planar substrate design where the axes of all microchannel plates are parallel, resulting in a naturally divergent electron beam. The MCP substrate is designed as a Fresnel lens structure, characterized by a planar incident surface and a distorted output surface, composed of concentric ring bands. The tilt angle of these rings is precisely calculated, ensuring that after refraction by the ring structure of the distorted output surface, the electron optical paths of all rings can theoretically converge to a single point on the anode target surface, providing a macroscopic geometric focusing basis. More importantly, it provides a platform for the collaborative operation of gradient aperture and variable aperture channel designs, enabling the organic unification of the three focusing mechanisms.

[0031] like Figure 4 As shown, in the gradient aperture array, the pore size (diameter) of the microchannels changes in a gradient from the center to the edge of the MCP; the pore size is smaller in the central region (e.g., 20). m), with larger apertures in the edge regions (e.g., 25 m). (m) can form a stronger electric field gradient in the edge region, thereby guiding electrons to the multiplication region more effectively and maintaining efficient multiplication. The smaller central aperture can make electron collisions in the concentrated region more dense, which helps to improve the local electron gain efficiency.

[0032] like Figure 5 As shown, the radial gradient material abandons the traditional homogenized design of the inner wall material of the MCP channel and innovatively introduces a radial gradient material:

[0033] Outer pores (edge ​​region): Magnesium oxide is used as the secondary electron emission layer. MgO has an extremely high secondary electron emission coefficient (maximum secondary electron emission coefficient). (Up to 6.2 or higher), which can significantly improve the electronic gain in the edge region and effectively compensate for signal loss caused by low electron flux density and edge effects.

[0034] Inner layer (central region): Alumina is used as the secondary electron emission layer. Al2O3 has a moderate secondary electron emission coefficient (maximum secondary electron emission coefficient). (Approximately 3.92), but its performance is extremely stable, bombardment resistant, and has a long lifespan. When the electron flux density in the central region is extremely high, using Al2O3 can avoid electron saturation caused by excessively high gain, ensuring stable operation of the MCP under high loads.

[0035] like Figure 6 As shown, the variable aperture channel is divided into two parts. In the inlet focusing region, a steeper parabolic or higher-order exponential curve is used for contraction, transitioning to a gentler exponential curve, or even a near-straight line, in the outlet optimization region. In the first half, the channel aperture decreases rapidly, completing 80% of the total contraction, quickly establishing a strong axial electric field gradient to effectively constrain electron trajectories and rapidly focus the electron beam. In the second half, the channel diameter decreases slowly. This design effectively avoids the problem of excessively small collision angles, allowing high-energy electrons generated at the channel end to collide with the tube wall at a more optimized angle, significantly increasing the escape probability of secondary electrons and increasing gain. Taking the central region as an example, the contraction formula for the inlet focusing region is: The formula for shrinking the export optimization zone is: .

[0036] like Figure 7 and Figure 8 As shown, the Fresnel lens substrate provides the macroscopic geometric focusing basis, directing all electrons towards the anode target. The gradient aperture array and radial gradient material work together to precisely balance the electron flux density and gain level throughout the MCP working region, fundamentally solving the problem of gain unevenness. The variable aperture channel within each microchannel suppresses the initial divergence of electrons through geometric constraints. Through the synergistic effect of these four mechanisms, the electron beam emitted from the MCP is no longer divergent, but is already in a highly focused state, capable of directly and precisely bombarding the anode target to form a tiny focal spot, completely eliminating the need for an external focusing electrode system.

[0037] It should be noted that, for the sake of simplicity, the foregoing method embodiments are all described as a series of actions. However, those skilled in the art should understand that the present invention is not limited to the described order of actions, because according to the present invention, some steps can be performed in other orders or simultaneously. Furthermore, those skilled in the art should also understand that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily essential to the present invention.

[0038] The above is an introduction to the method embodiments. The following describes the solution of the present invention further through device embodiments.

[0039] Figure 8 A flowchart illustrating a method 200 for using a microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to an embodiment of the present invention is shown. Figure 2 As shown, method 200 includes:

[0040] S210: The initial divergent electron beam emitted from each pixel of the matrix photocathode is injected into the plane of the microchannel plate at a set tilt angle. After entering each variable aperture channel, the electrons undergo secondary electron emission under the action of the radial gradient material along the radial partition of the inner wall of the variable aperture channel, and are multiplied by the optimized electric field established by the gradient aperture array. At the same time, it is strongly constrained by the rapid contraction geometry of the channel entrance. The initial divergent electron beam undergoes geometric constraint, electric field gradient and material-dependent multiplication process in the variable aperture channel, resulting in an electron beam with significantly enhanced current, uniform gain and preliminary trajectory shaping.

[0041] Optionally, in some embodiments, the process of obtaining an electron beam with significantly enhanced current, uniform gain, and preliminary trajectory shaping specifically includes the following steps:

[0042] S211: The initial diverging electron beam emitted from each pixel of the matrix photocathode. When the initial diverging electron beam enters the rapid contraction zone at the entrance of the variable aperture channel, it is physically restricted and squeezed by the steep contraction geometry of the channel. After geometric constraint processing, the divergence angle is reduced and the beam tends to be collimated.

[0043] S212: While forming a collimated electron beam, electrons bombard the inner wall of the radially gradient material to excite secondary electrons. On the other hand, they are accelerated and trigger a chain avalanche under the optimized axial electric field driven by the gradient aperture array. After the synergistic multiplication process of material excitation and electric field drive, an electron beam with significantly enhanced current and uniform gain is obtained.

[0044] S213: Before the electron beam with significantly enhanced current exits from the channel outlet, its trajectory is further modulated and optimized by the transverse electric field distribution within the channel, which is determined by the gradient aperture array and the gradient change of the aperture from the center to the edge. This ultimately results in an electron beam with significantly enhanced current and a preliminary shaped trajectory.

[0045] In this embodiment of the invention, the process of further modulating and optimizing the transverse electric field distribution within the channel, determined by the gradient change in aperture from the center to the edge, specifically includes the following steps:

[0046] S2131: During the movement of the electron beam with significantly enhanced current within the microchannel, it is redistributed and guided by the non-uniform transverse electric field established by the gradient aperture array; the center aperture of the gradient aperture array is small and the edge aperture is large.

[0047] S2132: The non-uniform transverse electric field distribution determined by the gradient aperture redistributes and guides the electron beam, modulates and optimizes the final emission angle and spatial distribution of the electron beam, and finally forms an electron beam with not only strong current, but also preliminary trajectory shaping.

[0048] It should be noted that, in the embodiments, the process of modulating and optimizing the final emission angle and spatial distribution of the electron beam specifically includes the following steps:

[0049] S21321: The non-uniform transverse electric field formed by the gradient aperture exerts a lateral force on the electron. Under the action of the lateral force, the electron gains a lateral velocity component in addition to axial motion.

[0050] S21322: Since the transverse electric field strength varies depending on the location of the center and the edge, the lateral force on electrons at different radial positions is different. After radially differentiated lateral force processing, the edge electrons obtain a larger inward deflection correction amount, while the central electrons obtain a smaller correction amount.

[0051] In this embodiment of the invention, the process of radially differentiated lateral force processing specifically includes the following steps:

[0052] S213221: Based on the radial coordinates of the electron in the channel section, the system or electric field identifies and distinguishes its radial position, thereby obtaining electrons in different radial positions.

[0053] S213222: In a non-uniform transverse electric field established by a gradient aperture, electrons are subjected to lateral Coulomb forces of different magnitudes due to their different positions; after position-based differential lateral force application processing, electrons subjected to lateral forces of different magnitudes are obtained.

[0054] S213223: Within the same time period, edge electrons subjected to lateral forces greater than a set threshold generate lateral acceleration and displacement exceeding a preset acceleration threshold, while center electrons subjected to lateral forces not greater than a set threshold generate lateral acceleration and displacement not greater than a preset acceleration threshold; ultimately, the result is that edge electrons obtain an inward deflection correction greater than the effective correction threshold, and center electrons obtain a correction not greater than the effective correction threshold.

[0055] The threshold is set as the threshold that plays a role in the input of lateral force; the acceleration threshold is the threshold that plays a role in acceleration / displacement; the effective correction threshold is the core judgment threshold that plays a role in the final correction effect, and its physical meaning is the minimum correction amount to be achieved in order to achieve effective convergence; the effective correction threshold = 1 / 2 the product of the acceleration threshold and the square of the lateral force application time t.

[0056] S21323: Group-based differential correction, which integrates and optimizes the final emission angle distribution and spatial density distribution of the electron beam as a whole, ultimately forming an electron beam with a preliminary shaped trajectory.

[0057] S220: The electron beam emitted from each microchannel, after being multiplied and with its trajectory initially shaped, is subjected to the non-uniform electrostatic field introduced by the curved ring when passing through the deformed output surface with a Fresnel lens structure. The multiplied and initially shaped electron beam undergoes macroscopic deflection of the emitted electrons by this Fresnel lens electric field, resulting in a highly focused and strong electron pulse pointing towards the anode target.

[0058] S230: A highly focused and directed strong electron pulse is further accelerated by the high voltage of the anode in a vacuum environment, bombarding the corresponding anode target and exciting the generation of micro-focus X-rays, completing the conversion from electrons to information carriers.

[0059] This embodiment employs a microchannel plate in a photocathode X-ray tube to achieve cathode electron self-focusing. The initial divergent electron beam emitted from each pixel of the matrix photocathode is injected at a certain angle into the incident surface of the microchannel plate. After entering the variable aperture channel, the electrons undergo secondary emission under the influence of the radial gradient material on the inner wall. This emission is multiplied by the optimized electric field established by the gradient aperture array, while being strongly constrained by the rapidly contracting geometry of the channel entrance. Through geometric constraints, electric field gradients, and material-dependent multiplication, the electron beam current is significantly enhanced, and its trajectory is initially shaped. The multiplied and initially shaped electron beam exiting from each microchannel, upon passing through the aberrant output surface with a Fresnel lens structure, is subjected to a non-uniform electrostatic field introduced by the curved ring band. This Fresnel lens electric field macroscopically deflects the emitted electrons, causing the electron beam to highly converge and point towards the anode target, forming a strong electron pulse. This highly converged, anode-target-pointing strong electron pulse is further accelerated by the anode high voltage in a vacuum environment, bombarding the corresponding anode target and exciting the generation of micro-focused X-rays, completing the conversion from electrons to information carrier waves.

[0060] The combined use of the above-mentioned technical features enables full-process control of the electron beam from emission to bombardment of the target. Through multiplication and preliminary shaping within the microchannel plate, combined with the further convergence of the electron trajectory by the Fresnel lens electric field, the current density and spatial pointing accuracy of the electron beam are improved. Ultimately, micro-focus X-rays with high spatial coding accuracy are generated on the anode target, enhancing the spatial resolution and signal strength of the X-ray source and providing an efficient information carrier conversion basis for imaging and detection applications.

[0061] Those skilled in the art will understand that, for the sake of convenience and brevity, the specific working process of the described module can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0062] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this invention does not impose any limitations on this.

[0063] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A microchannel plate for cathode electron self-focusing in a photocathode X-ray tube, characterized in that, include: Substrate, gradient aperture array, radial gradient material, and variable aperture channel; Among them, the substrate is the physical base of the microchannel plate and has a Fresnel lens configuration; The substrate has a planar incident surface and an irregular output surface composed of concentric rings; a gradient aperture array is distributed on the substrate; the radial gradient material is a surface functional coating applied to the inner wall of the microchannel; the variable aperture channel is the three-dimensional contour of the inner wall surface of each independent microchannel constituting the gradient aperture array.

2. The microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to claim 1, characterized in that, The gradient aperture array is arranged from the center to the edge, and the gradient aperture array is composed of several microchannels. The inlet aperture size of the microchannels varies according to a preset gradient law of small at the center and large at the edge.

3. The microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to claim 1, characterized in that, The radial gradient material is prepared by atomic layer deposition and is disposed on the inner wall surface of the microchannel; the radial gradient material is coated with different secondary electron emission materials along the radial partition.

4. The microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to claim 3, characterized in that, The outer aperture of the gradient aperture array is the edge region, which uses magnesium oxide as the secondary electron emission layer; the inner aperture is the central region, which uses aluminum oxide as the secondary electron emission layer.

5. The microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to claim 1, characterized in that, The three-dimensional profile of the inner wall defines each individual microchannel in the gradient aperture array. The aperture of each individual microchannel is a non-linear curve along the microchannel axis, with rapid contraction at the inlet and smooth transition at the outlet. The three-dimensional profile is formed simultaneously during the fabrication of the substrate and the gradient aperture array.

6. A method of using a microchannel plate for cathode electron self-focusing in a photocathode X-ray tube, for implementing the microchannel plate for cathode electron self-focusing in a photocathode X-ray tube as described in any one of claims 1-5, characterized in that, Includes the following steps: The initial divergent electron beam emitted by the matrix photocathode is injected into the plane of the microchannel plate at a set tilt angle. After entering each variable aperture channel, the electrons undergo secondary electron emission under the action of the radial gradient material coated along the radial partition of the inner wall of the variable aperture channel, and are multiplied by the optimized electric field established by the gradient aperture array. The initial divergent electron beam undergoes a geometric constraint, electric field gradient and material-dependent multiplication process in the variable aperture channel to obtain a preliminarily shaped electron beam. The electron beam, after being macroscopically deflected by the electric field of the Fresnel lens, is directed towards the anode target point. A strong electron pulse directed at the anode target is accelerated by the high voltage of the anode in a vacuum environment, and bombards the corresponding anode target, exciting the generation of microfocus X-rays.

7. The method of using the microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to claim 6, characterized in that, The process of obtaining a preliminarily shaped electron beam includes the following steps: The initial diverging electron beam emitted from each pixel of the matrix photocathode is subjected to physical constraints and electric field compression by the steep contraction geometry of the variable aperture channel when it enters the rapid contraction region of the entrance. After geometric constraint processing, the divergence angle is reduced and the beam tends to be collimated. While forming a collimated electron beam, electrons bombard the inner wall of the radially gradient material to excite secondary electrons. On the other hand, they are accelerated and trigger a chain avalanche under the optimized axial electric field established by the gradient aperture array. After the synergistic multiplication process of material excitation and electric field driving, an electron beam with significantly enhanced current is obtained. Before exiting the channel, the trajectory of the electron beam with significantly enhanced current is further modulated and optimized by the transverse electric field within the channel, which is determined by the aperture gradient distribution of the gradient aperture array. This results in an electron beam with significantly enhanced current and a preliminary shaped trajectory. The aperture gradient of the gradient aperture array from the center to the edge determines the transverse electric field distribution within the channel.

8. The method of using the microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to claim 7, characterized in that, The process of further modulating and optimizing the electron beam trajectory using a gradient aperture array includes the following steps: During the movement of the electron beam with significantly enhanced current within the microchannel, it is redistributed and guided by the non-uniform transverse electric field established by the gradient aperture array; the gradient aperture array has a small central aperture and a large edge aperture. The non-uniform transverse electric field distribution determined by the gradient aperture redistributes and guides the electron beam, modulating and optimizing the final emission angle and spatial distribution of the electron beam, ultimately forming an electron beam with strong current and a preliminary shaped trajectory.

9. The method of using the microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to claim 8, characterized in that, The process of modulating and optimizing the final exit angle and spatial distribution of the electron beam includes the following steps: The non-uniform transverse electric field formed by the gradient aperture exerts a lateral force on the electron. Under the action of the lateral force, the electron gains a lateral velocity component in addition to its axial motion. Group-based differential correction integrates and optimizes the final emission angle distribution and spatial density distribution of the electron beam as a whole, ultimately forming an electron beam with a preliminary shaped trajectory.

10. The method of using the microchannel plate for cathode electron self-focusing in a photocathode X-ray tube according to claim 6, characterized in that, The process of radially differentiated lateral force treatment includes the following steps: Based on the radial coordinates of the electrons in the channel cross section, the system or electric field identifies and distinguishes their radial positions, thereby obtaining electrons at different radial positions; In a non-uniform transverse electric field established by a gradient aperture, electrons are subjected to lateral Coulomb forces of varying magnitudes depending on their position; after position-based differential lateral force application, electrons subjected to lateral forces of different magnitudes are obtained. Within the same time frame, edge electrons subjected to lateral forces greater than a set threshold generate lateral acceleration and displacement exceeding a preset acceleration threshold, while center electrons subjected to lateral forces not greater than a set threshold generate lateral acceleration and displacement not greater than a preset acceleration threshold. Ultimately, this results in edge electrons obtaining an inward deflection correction greater than the effective correction threshold, and center electrons obtaining a correction not greater than the effective correction threshold.

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