Aperiodic multi-depth fixed x-ray anode target and generative manufacturing method

Abstract

A non-periodic multi-depth fixed X-ray anode target and generative manufacturing method are disclosed, including a high-thermal-conductivity heat sink base and a bombarded target surface layer fixedly combined therewith. The target surface layer is provided with a plurality of grooves in communication with a vacuum and extending into the target, at least one of the opening width, the maximum depth and the pitch of each groove does not constitute a global repeat unit covering the entire microstructure region, and at least two grooves have different maximum depths. The structure has a complete w i 、h i 、s i The array cooperatively regulates the electron action path and the photon escape path. Under a 60 keV electron beam, a Penelope low-energy electromagnetic physics model and a representative comparison geometry, the X-ray energy conversion efficiency of the non-periodic candidate at the upstream scoring surface is about 1.36 times that of the periodic groove.

Description

Technical Field

[0001] This invention belongs to the field of X-ray tube anode target technology, and in particular relates to a non-periodic multi-depth fixed X-ray anode target and a generative manufacturing method thereof. Background Technology

[0002] Fixed anode X-ray tubes are characterized by their compact structure, high reliability, and lack of the need for a rotation mechanism, making them suitable for portable non-destructive testing and miniaturized imaging equipment. When an electron beam bombards a tungsten or tungsten alloy target, some electrons undergo backscattering, while the remaining electrons deposit energy within the target material, generating bremsstrahlung and characteristic X-rays.

[0003] To reduce electron backscattering losses, existing techniques typically incorporate regular trenches on the anode target surface, defined by a uniform trench width W, uniform trench depth H, and uniform period P. Deepening the trenches can extend the path of some electrons within the target material, but X-rays generated inside the deep trenches still need to pass through the trench opening and avoid adjacent trench walls. When the trenches are too deep, the openings too narrow, or the trench walls provide strong obstruction, photons may re-enter the target material and be absorbed.

[0004] The repeating units of periodic trenches have the same or a fixed repeating pattern in terms of trench width, depth, and spacing, making it difficult to adjust each trench individually for a finite electron beam spot, different photon generation positions, and specific emission directions. Therefore, a fixed anode target structure that does not depend on global repeating units and allows different trenches to have different widths, depths, and spacings is needed.

[0005] Problems with existing technology: (1) The geometrical degrees of freedom of periodic structures are limited: periodic trenches are formed by repeating the same set of W, H, P parameters, and there is a strict geometrical repetition relationship between each position. For a finite beam spot or a specific receiving direction, the same trench depth and the same spacing may not be able to simultaneously meet the requirements of electron energy deposition and photon escape at different positions.

[0006] (2) Competition between electron trapping and photon self-absorption: Deepening the trench can usually reduce primary electron backscattering and increase energy deposition in the target, but it also increases the probability of X-ray photons hitting the trench wall or re-entering the target. Therefore, the actual effect of the trench structure cannot be judged solely by electron trapping, backscattering rate or target energy deposition, but should also be evaluated based on the effective X-ray output that meets the receiving conditions.

[0007] (3) Fixed anode targets require continuous and stable solid boundaries: Fixed anode targets cannot rely on the rotation of the target disk to disperse the heat load. If there are sharp turns, excessively thin partitions, or excessively small local features on the sidewalls or bottom of the trench, local energy deposition and stress concentration are likely to occur. Therefore, non-periodic trenches should maintain continuous and smooth bottoms and sidewalls, and continuous target material should be retained in adjacent trenches and at the bottom of the trench. Summary of the Invention

[0008] The purpose of this invention is to provide a non-periodic multi-depth fixed X-ray anode target and a generative manufacturing method. By coordinating the width, depth and spacing of each trench, a preferred non-periodic structure with an effective X-ray energy conversion efficiency higher than that of an optimized periodic trench reference is obtained under limited working conditions.

[0009] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: A non-periodic, multi-depth fixed X-ray anode target, comprising a heat sink substrate with high thermal conductivity; It includes a bombarded target surface layer fixedly bonded to a heat sink substrate, wherein a fixed bonding interface is formed between the target surface layer and the heat sink substrate, and the target surface layer is provided with aperiodic microstructure regions; aperiodicity means that there is no repeating subsequence containing fewer than N grooves, and a complete parameter sequence can be generated by repetition.

[0010] The microstructure region includes N grooves formed on the target surface layer, where N≥3. These grooves extend laterally along the target surface layer and are arranged non-periodically along the longitudinal direction. The width w corresponds to the i-th groove. i Maximum depth h i and the net spacing s with the next trench i At least one parameter sequence does not constitute a repeating unit that can cover the entire microstructure region; At least two trenches have different maximum depths h i Alternatively, the entire microstructure region may lack a global geometric period that can repeatedly cover the entire trench depth, where the maximum trench depth h... i Less than the thickness of the target surface layer.

[0011] Furthermore, the opening profiles of the grooves can be the same or different. Corresponding to grooves with different opening profiles, multiple opening units are distributed in the transverse and longitudinal directions. Each opening unit has its own center coordinates, opening profile, and groove depth. At least one of the center distance, opening profile, and groove depth of adjacent opening units is different. Alternatively, there is no non-zero translation distance globally that completely coincides with the original structure after translation.

[0012] Furthermore, at least one trench has a continuously varying depth along its extension direction, with different depths at different locations, while the remaining trenches may have a constant depth or another continuously varying depth. Alternatively, there may be no uniform repeating unit covering the entire microstructure region between the trenches.

[0013] Furthermore, the trench sidewalls are substantially vertical or have a slope that tapers towards the bottom of the trench, and the bottom of the trench is a circular arc surface, an elliptical arc surface, or other continuous curved surface, with the trench sidewalls and the bottom of the trench forming a continuous and smooth transition surface. Continuous target material partitions are maintained between adjacent trenches, and continuous target surface material is maintained between the bottom of the trench and the bonding interface.

[0014] Furthermore, the target surface layer can be made of pure tungsten or a tungsten alloy, and the heat sink substrate can be made of oxygen-free copper or other highly thermally conductive materials. The target surface layer and the heat sink substrate are fixedly bonded together to form a fixed anode target that does not require a rotating support mechanism.

[0015] A generative manufacturing method for an aperiodic multi-depth fixed X-ray anode target, used for the preparation of an aperiodic multi-depth fixed X-ray anode target, includes the following steps: Step 1: Establish a mapping between the physical space and the processing equipment, construct the physical coordinate space, set a fixed length analysis span, and discretize the target surface depth profile within the span into a depth profile vector containing N normalized coordinate points, preferably N=128; Step 2: Physical performance verification and dataset generation. A large number of smooth depth contour vectors are randomly generated, and the X-ray conversion efficiency of each vector under a specific accelerating voltage is calculated using the electron continuous slowing approximation physical model to construct a training dataset. Step 3: Manifold dimensionality reduction and implicit regularization training. Construct a conditional variational autoencoder network to map high-dimensional depth contour vectors to low-dimensional latent space. The network learns smooth surface manifold features with physical manufacturability through joint loss function constraints, and automatically eliminates high-frequency geometric artifacts that can lead to thermal stress failure. Step 4: Non-periodic conditional sampling generation. Using the target X-ray conversion efficiency higher than the preset threshold as a conditional instruction, sampling and decoding are performed in the trained low-dimensional latent space to directly output the optimal target depth contour data containing non-uniform depth and irregular spacing. Step 5: Fix the target solid micro-nano processing, extract the target depth contour data, convert it into spatial etching commands, and control the laser ablation equipment or semiconductor etching equipment to perform directional subtractive processing on the target surface layer of the fixed anode target to prepare a solid non-periodic microstructure.

[0016] In step three, the latent space dimension of the encoder network is set and fixed at 16 dimensions to balance the expressive power of complex aperiodic geometric capacity features with the stability of the conditionally generated signal.

[0017] The present invention has the following beneficial effects: (1) The present invention adopts a solid structure in which the width, maximum depth and spacing of each trench can be varied, which can express non-repetitive geometric relationships that cannot be represented by uniform trench width, trench depth and periodic trench, thus expanding the design space of fixed anode target surface. Trenches with different depths and spacings can form different electron interaction paths and photon escape paths in the same microstructure region, providing structural freedom to adjust the balance between electron capture and trench wall self-absorption.

[0018] (2) The continuous and smooth bottom and sidewalls reduce sharp geometric changes and retain continuous target material between adjacent trenches and at the bottom of the trench, which helps to maintain the integrity of the fixed anode target surface.

[0019] (3) Under a 60 keV electron beam and the representative comparative geometry described in this specification, using the Geant4 G4EmPenelopePhysics low-energy electromagnetic physics model, simulating 50,000 primary electrons for three independent random seeds, the X-ray energy conversion efficiency of the non-periodic multi-depth trench at the upstream scoring plane of z=+2μm was 1.3567 compared to that of the periodic trench, approximately 1.36, representing an average increase of about 36%. This value is used to illustrate the significant gain achieved by the non-periodic multi-depth trench.

[0020] (4) The generative design method of the present invention maps the target surface depth profile to a low-dimensional latent space and generates candidate aperiodic structures under the constraints of physical performance and geometric manufacturability. This extends the traditional design method that relies on a small number of periodic parameters to a generative search of non-repeating depth profiles, which is beneficial to obtain aperiodic trench candidate structures that meet performance targets and processing constraints in a larger structural design space. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0022] Figure 1 Schematic diagram of the overall structure of a non-periodic, multi-depth fixed X-ray anode target.

[0023] Figure 2 : 3D schematic diagram of a non-periodic grooved target surface.

[0024] Figure 3 Schematic diagram of a non-periodic multi-depth trench cross section.

[0025] Figure 4 : Top view of the non-periodic trench target surface.

[0026] Figure 5 Schematic diagram comparing the structures of periodic trenches and non-periodic trenches.

[0027] The components represented by each number in the attached figure are listed below: heat sink substrate 110, target surface layer 120, bonding interface 160, incident electron beam 140, X-ray 150, microstructure region 130, and trench 131. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0029] like Figure 1 As shown: A non-periodic, multi-depth fixed X-ray anode target includes a high thermal conductivity heat sink substrate 110 (made of oxygen-free copper or other high thermal conductivity materials); a bombarded target surface layer 120 (made of pure tungsten or tungsten alloy) fixedly bonded to the heat sink substrate 110, forming a fixed bonding interface 160 between the target surface layer 120 and the heat sink substrate 110; the target surface layer 120 receives an incident electron beam 140 and generates emitted X-rays 150; the target surface layer 120 is provided with a non-periodic microstructure region 130; the microstructure region 130 includes N trenches formed in the target surface layer 120, all of which extend laterally along the target surface layer 120 and are arranged non-periodicly along the longitudinal direction, with the width w corresponding to the i-th trench. i Maximum depth h i and the net spacing s with the next trench i At least one parameter sequence does not constitute a repeating unit capable of covering the entire microstructure region.

[0030] like Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown: For example, groove 131 corresponds to a groove width w i Maximum depth h i and the net spacing s with the next trench i Capable of changing independently or in groups, with at least two trenches having different maximum depths h. i .

[0031] Taking five trench structures with imported data as examples: their opening widths can be 16μm, 24μm, 18μm, 22μm, and 20μm respectively; their maximum depths can be 30μm, 45μm, 35μm, 42μm, and 44.3μm respectively; and the net spacing between adjacent trenches can be 35μm, 45μm, 30μm, and 40μm respectively. The array does not form uniform repeating units; it is only used to illustrate the construction method of non-periodic structures and does not limit the scope of protection.

[0032] The opening profiles of the trenches can be the same or different. Corresponding to trenches with different opening profiles, multiple opening units are distributed in the transverse and longitudinal directions. Each opening unit has its own center coordinates, opening profile, and trench depth. At least one of the center distance, opening profile, and trench depth of adjacent opening units is different. At least one trench has a continuously varying trench depth along its extension direction, with different trench depths at different locations. The remaining trenches may have a constant depth or another continuously varying trench depth. The trench sidewalls are basically vertical or have a slope that tapers towards the trench bottom. The trench bottom is a circular arc surface, an elliptical arc surface, or other continuous curved surface. The trench sidewalls and the trench bottom form a continuous and smooth transition surface.

[0033] Calculation of X-ray energy conversion efficiency improvement for non-periodic, multi-depth fixed X-ray anode targets: Target surface coordinates and surface openings: Taking the plane containing the ungrooved target surface as z=0, the bombarded target surface layer and heat sink substrate are located on the z≤0 side, and the electron source is located on the vacuum side of z>0. The i-th groove extends from z=0 into the target to a maximum depth of z=-h. i It is connected to the vacuum at z=0.

[0034] Sample: The tungsten target area measures 300μm × 200μm × 150μm, with the ungrooved target surface having z=0. The periodic comparison structure includes five trenches with a width of 20μm, a depth of 40μm, and a period of 60μm; the aperiodic structure uses the complete w-shaped aperiodic multi-depth trenches listed in this section. i h i s i The array shows that both types of structures have a surface aperture ratio of 1 / 3, a width-weighted average depth of 40 μm, and a removal cross-sectional area of ​​4000 μm per unit trench length. 2 The electron source is located at z=+5μm, and a 60 keV monoenergetic electron beam is incident along the -z direction. The beam spot has a Gaussian distribution with a standard deviation of 5μm in both the x and y directions. The upstream scoring surface is located at z=+2μm.

[0035] Surface aperture ratio and average depth: For strip-shaped trenches extending in the same direction and of the same length, let the evaluation length of the microstructure region along the trench arrangement direction be L, and the number of trenches be N, then the one-dimensional surface aperture ratio... for:

[0036] The groove surface opening ratio is the proportion of the groove opening width to the target surface evaluation length within the evaluation area; N is the total number of grooves within the evaluation area; i is the groove number; L is the total length of the microstructure evaluation area along the groove arrangement direction, including the groove opening and the target material partition between the grooves. This is used to evaluate the sum of the opening widths of all groove surfaces within the length.

[0037] For a two-dimensional aperiodic opening, the area aperture ratio A is defined as the total area of ​​all openings. With target surface evaluation area The ratio:

[0038] in, This represents the total area of ​​all groove openings within the target surface evaluation region, in μm. 2 . This represents the total area of ​​the target evaluation region, in μm. 2The target surface evaluation area refers to a pre-determined finite region on the z=0 plane where the ungrooved target surface is located. It is used to uniformly statistically compare the microstructure's aperture ratio, average depth, amount of material removed, and related performance indicators.

[0039] When each trench has a constant depth along its extension direction, the average depth is weighted by the opening width. for:

[0040] Let be the surface opening width of the i-th groove; Let be the depth of the i-th groove extending from the target surface z=0 into the interior of the target material; This represents the area removed from the approximate cross-section of the i-th trench per unit trench length. This is the sum of the approximate cross-sectional areas of all trenches per unit length; This is the sum of the opening widths of all the trenches.

[0041] Fair Comparison Benchmark: When evaluating aperiodic structures, the periodic trench obtained after searching for trench width, trench depth, and periodic parameters under the same parameter range, constraints, and comparable search budget is preferred as the optimized periodic benchmark. Both types of structures use the same target area size, target material, heat sink material, electron beam energy, beam spot, incident direction, scoring surface, photon energy threshold, and receiving angle; and maintain the same or similar surface aperture ratio, aperture width-weighted average depth, removed material volume, and minimum remaining wall thickness within a pre-defined tolerance, depending on the comparison purpose.

[0042] Main performance indicator: The main performance indicator is the effective X-ray energy conversion efficiency that reaches the predetermined receiving area and meets the energy and orientation conditions. :

[0043] The effective X-ray energy conversion efficiency is the ratio of the total energy of X-rays that meet the receiving conditions to the total energy of the incident electrons; A is the set of received photons, which is the set of X-ray photons that simultaneously meet the conditions of the scoring surface, receiving area, energy threshold, and direction; j is the number of the received X-ray photon. Let J be the energy of the j-th received X-ray photon. This is the sum of the energies of all X-ray photons that meet the reception criteria; This represents the total number of primary electrons emitted in the Geant4 simulation; The initial kinetic energy of each primary electron; This represents the total incident energy carried by all primary electrons.

[0044] The performance ratio of the non-periodic candidate relative to the optimized periodic benchmark is defined as Q:

[0045] Where, η aperiodic Effective X-ray energy conversion efficiency of aperiodic structures. η periodic Effective X-ray energy conversion efficiency of periodic trench reference structures.

[0046] Primary electron backscattering rate, target energy deposition, and the yield of the first photon entering the vacuum from the target are used as explanatory indicators and do not directly replace [other parameters]. .

[0047] Using G4EmPenelopePhysics, the target region cutoff was 0.1 μm, and the maximum step size was 1 μm. 50,000 primary electrons were simulated for random seeds 60060, 60061, and 60062, respectively. Under the three random seeds, the mean upstream X-ray energy conversion efficiency was 0.000587472 for the periodic trench and 0.000797510 for the aperiodic multi-depth trench. The performance ratio calculated by pairing random seeds was Q = 1.3567 ± 0.133 (mean ± sample standard deviation), meaning that the principal performance of the aperiodic structure was approximately 1.36 times that of the periodic structure, with an average improvement of about 36%. This value illustrates the significant gain achieved by the aperiodic multi-depth trench.

[0048] These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can better understand and utilize the present invention.

Claims

1. A non-periodic, multi-depth fixed X-ray anode target, characterized in that: Including a heat sink substrate with high thermal conductivity (110); The bombarded target surface layer (120) is fixedly bonded to the heat sink substrate (110), and a fixed bonding interface (160) is formed between the target surface layer (120) and the heat sink substrate (110). The target surface layer (120) is provided with a non-periodic microstructure region (130). The microstructure region (130) includes N grooves formed on the target surface layer (120), where N≥3. All grooves extend laterally along the target surface layer (120) and are arranged non-periodically along the longitudinal direction. The width w of the i-th groove is... i Maximum depth h i and the net spacing s with the next trench i At least one parameter sequence does not constitute a repeating unit that can cover the entire microstructure region; At least two trenches have different maximum depths h i .

2. The non-periodic multi-depth fixed X-ray anode target according to claim 1, characterized in that: The opening profiles of the grooves may be the same or different. Corresponding to the grooves with different opening profiles, there are multiple opening units distributed in the horizontal and vertical directions. Each opening unit has its own center coordinates, opening profile and groove depth. At least one of the center distance, opening profile and groove depth of adjacent opening units is different.

3. The non-periodic multi-depth fixed X-ray anode target according to claim 1, characterized in that: At least one trench has a continuously varying depth along its extension direction, with different depths at different locations, while the remaining trenches may have a constant depth or another continuously varying depth.

4. The non-periodic multi-depth fixed X-ray anode target according to claim 1, characterized in that: The trench sidewalls are basically vertical or have a slope that tapers towards the bottom of the trench. The bottom of the trench is a circular arc surface, an elliptical arc surface, or other continuous curved surface. The trench sidewalls and the bottom of the trench form a continuous and smooth transition surface.

5. The non-periodic multi-depth fixed X-ray anode target according to claim 1, characterized in that: The target layer (120) is made of pure tungsten or tungsten alloy, and the heat sink substrate (110) is made of oxygen-free copper or other high thermal conductivity materials.

6. A method for fabricating an aperiodic multi-depth fixed X-ray anode target, used in the preparation of the aperiodic multi-depth fixed X-ray anode target as described in claim 1, characterized in that, It includes the following steps: Step 1: Establish a mapping between the physical space and the processing equipment, construct the physical coordinate space, set a fixed length analysis span, and discretize the target surface depth profile within the span into a depth profile vector containing N normalized coordinate points, preferably N=128; Step 2: Physical performance verification and dataset generation. A large number of smooth depth contour vectors are randomly generated, and the X-ray conversion efficiency of each vector under a specific accelerating voltage is calculated using the electron continuous slowing approximation physical model to construct a training dataset. Step 3: Manifold dimensionality reduction and implicit regularization training. Construct a conditional variational autoencoder network to map high-dimensional depth contour vectors to low-dimensional latent space. The network learns smooth surface manifold features with physical manufacturability through joint loss function constraints, and automatically eliminates high-frequency geometric artifacts that can lead to thermal stress failure. Step 4: Non-periodic conditional sampling generation. Using the target X-ray conversion efficiency higher than the preset threshold as a conditional instruction, sampling and decoding are performed in the trained low-dimensional latent space to directly output the optimal target depth contour data containing non-uniform depth and irregular spacing. Step 5: Fix the target solid micro-nano processing, extract the target depth contour data, convert it into spatial etching commands, and control the laser ablation equipment or semiconductor etching equipment to perform directional subtractive processing on the target surface layer of the fixed anode target to prepare a solid non-periodic microstructure.

7. The manufacturing method according to claim 6, characterized in that: In step three, the latent space dimension of the encoder network is set and fixed at 16 dimensions to balance the expressive power of complex aperiodic geometric capacity features with the stability of the conditionally generated signal.

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